阅读说明：本技术 红外线吸收图像形成用喷墨油墨、红外线吸收图像形成方法及图像形成方法 (Inkjet ink for infrared-absorbing image formation, infrared-absorbing image formation method, and image formation method ) 是由 佐佐田美里 佐佐木大辅 原未奈子 于 2020-02-04 设计创作，主要内容包括：本发明提供一种红外线吸收图像形成用喷墨油墨及其应用,所述红外线吸收图像形成用喷墨油墨含有由式(A)表示的红外线吸收材料、水溶性有机溶剂及水,其中水溶性有机溶剂的含量为5质量％～45质量％,SP值27.5MPa～(1/2)以上的溶剂种类X在水溶性有机溶剂中所占的比例为50质量％以上。Z～(1)及Z～(2)分别独立地表示形成含氮杂环的非金属原子组,R～(1)及R～(2)分别独立地表示取代基,L～(1)表示由奇数个次甲基组成的次甲基链,a及b分别独立地表示0或1。X～(1)表示阴离子或阳离子,c表示用于取得电荷平衡所需的数量,但Cy的电荷被中和时,X～(2)不存在。(The present invention provides an ink-jet ink for infrared-absorbing image formation, which contains an infrared-absorbing compound represented by the formula (A), and an application thereofA material, a water-soluble organic solvent and water, wherein the content of the water-soluble organic solvent is 5-45 mass%, and the SP value is 27.5MPa 1/2 The proportion of the solvent species X in the water-soluble organic solvent is 50% by mass or more. Z 1 And Z 2 Each independently represents a group of non-metal atoms forming a nitrogen-containing heterocyclic ring, R 1 And R 2 Each independently represents a substituent, L 1 Represents a methine chain composed of an odd number of methines, and a and b each independently represent 0 or 1. X 1 Represents an anion or cation, c represents the amount necessary for achieving charge balance, but when the charge of Cy is neutralized, X 2 Is absent.)

1. An infrared-absorbing image-forming inkjet ink comprising an infrared-absorbing material represented by the following formula (A), a water-soluble organic solvent and water,

the content of the water-soluble organic solvent is 5 to 45% by mass based on the total amount of the infrared absorption image forming ink-jet ink,

SP value 27.5MPa^1/2The proportion of the solvent species X in the water-soluble organic solvent is 50% by mass or more,

in the formula (A), Z¹And Z²Each independently represents a group of non-metal atoms forming a 5-or 6-membered nitrogen-containing heterocyclic ring which may be condensed, R¹And R²Each independently represents an aliphatic group which may have a substituent or an aromatic group which may have a substituent, L¹Represents a methine chain composed of an odd number of methines, a and b each independently represent 0 or 1,

when the site represented by Cy in the formula (A) is a cationic moiety, X¹Denotes an anion, c denotes the amount required for achieving charge balance,

when the site represented by Cy in the formula (A) is an anion portion, X¹Denotes a cation, c denotes an amount required for achieving charge balance,

when the charge at the site represented by Cy in the formula (A) is neutralized in the molecule, X¹Is absent.

2. The inkjet ink for infrared ray absorption image formation according to claim 1, wherein,

the infrared absorbing material represented by the formula (A) is an infrared absorbing material represented by the following formula (1A),

in the formula (1A), R^1AAnd R^2AEach independently represents an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, an aralkyl group which may have a substituent or an aryl group which may have a substituent,

L^1Adenotes a methine chain consisting of an odd number of methines,

B¹and B²Each independently represents a group of atoms necessary for forming an aromatic hydrocarbon ring which may have a substituent or a group of atoms necessary for forming an aromatic heterocyclic ring which may have a substituent,

Y¹and Y²Each independently represents-S-, -O-, -NR^X1-or CR^X2R^X3-，R^X1、R^X2And R^X3Each independently represents a hydrogen atom or an alkyl group,

V^1Aand V^2AEach independently represents a halogen atom, a cyano group, a nitro group, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an aryl group, a heterocyclic group, -OR¹⁰、-COR¹¹、-COOR¹²、-OCOR¹³、-NR¹⁴R¹⁵、-NHCOR¹⁶、-CONR¹⁷R¹⁸、-NHCONR¹⁹R²⁰、-NHCOOR²¹、-SR²²、-SO₂R²³、-SO₂OR²⁴、-NHSO₂R²⁵Or SO₂NR²⁶R²⁷，R¹⁰～R²⁷Each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an aryl group or a heterocyclic group at-COOR¹²R of (A) to (B)¹²In the case of hydrogen atoms and SO₂OR²⁴R of (A) to (B)²⁴In the case of hydrogen atoms, the hydrogen atoms may be dissociated or may be in the form of a salt,

m1 and m2 each independently represent an integer of 0 to 4,

when m1 is an integer of 2 to 4, a plurality of V^1ACan be bonded to each other to form a ring, and when m2 is an integer of 2 to 4, a plurality of V^2AMay be bonded to each other to form a ring,

when the site represented by Cy in the formula (1A) is a cationic moiety, X²Denotes an anion, c denotes the amount required for achieving charge balance,

when the site represented by Cy in the formula (1A) is an anion portion, X²Denotes a cation, c denotes an amount required for achieving charge balance,

when the charge at the site represented by Cy in the formula (1A) is neutralized in the molecule, X²Is absent.

3. The inkjet ink for infrared ray absorption image formation according to claim 2, wherein,

at least 1 kind of the infrared absorbing material represented by the formula (1A) is an infrared absorbing material represented by the following formula (1B),

in the formula (1B), R^1BAnd R^2BEach independently represents an alkyl group having a sulfonate group as a substituent,

L^1Brepresents a methine chain consisting of 7 methines,

X³denotes a cation, and c denotes an amount necessary for achieving charge balance.

4. The inkjet ink for infrared ray absorption image formation according to any one of claims 1 to 3, wherein,

the content of the water-soluble organic solvent is 5 to 30% by mass based on the total amount of the infrared absorption image forming inkjet ink.

5. The inkjet ink for infrared ray absorption image formation according to any one of claims 1 to 4, further comprising resin particles.

6. The inkjet ink for infrared ray absorption image formation according to any one of claims 1 to 5, further containing a colorant.

7. The inkjet ink for infrared ray absorption image formation according to any one of claims 1 to 6, further comprising a water-soluble polymer compound.

8. The inkjet ink for infrared ray absorption image formation according to any one of claims 1 to 7, further comprising gelatin.

9. An infrared absorption image forming method includes the steps of:

the infrared ray absorption image is formed by imparting the inkjet ink for infrared ray absorption image formation according to any one of claims 1 to 8 on a substrate by an inkjet method.

10. The infrared absorbing image forming method according to claim 9,

a step of applying a treatment liquid containing a flocculant to the substrate before the step of forming the infrared absorption image,

in the step of forming the infrared absorption image, the infrared absorption image is formed by applying the infrared absorption image forming inkjet ink to at least a part of the region of the substrate to which the treatment liquid is applied by an inkjet method.

11. An image forming method, comprising:

forming an infrared absorption image by the infrared absorption image forming method according to claim 9 or claim 10; and

and a step of obtaining an image by irradiating the infrared-absorbed image with infrared light.

12. The image forming method according to claim 11,

the infrared ray has a maximum emission wavelength in a wavelength region of 700nm to 1500 nm.

Technical Field

The present invention relates to an inkjet ink for infrared-absorptive image formation, an infrared-absorptive image forming method, and an image forming method.

Background

In recent years, studies have been made on infrared-absorptive images.

For example, patent document 1 discloses a near-infrared absorbing image-forming composition containing a specific dye including a methine chain composed of 7 methine groups as a near-infrared absorbing image-forming composition having excellent spectral characteristics, and an ink composed of the near-infrared absorbing image-forming composition.

Further, patent document 2 discloses, as a stable infrared dye composition that can be used as a printing ink on an image forming element, a latex composition containing water as a continuous phase and hydrophobic polymer particles containing an infrared polymethine dye to which a phenylenediamine moiety is covalently bonded as a dispersed phase.

Patent document 1: japanese patent laid-open No. 2008-255323

Patent document 2: japanese patent laid-open publication No. 2004-1699035

Disclosure of Invention

Technical problem to be solved by the invention

In order to improve the infrared absorbability of an infrared absorption image having absorption in the infrared region, it is preferable that the proportion of molecules forming an association is large in all the molecules of the infrared absorbing material contained in the infrared absorption image.

In the present invention, a case where the ratio of molecules forming the association is large among all molecules of the infrared absorbing material contained in the infrared absorption image is referred to as excellent association formability of the infrared absorbing material contained in the infrared absorption image.

The present invention addresses the problem of providing an infrared-absorptive-image-forming inkjet ink and an infrared-absorptive-image-forming method that can form an infrared-absorptive image that has excellent association-forming properties of infrared-absorptive materials, and an image-forming method that can form an image that has excellent abrasion resistance by irradiating the infrared-absorptive image with infrared light.

Means for solving the technical problem

The means for solving the above problems include the following means.

<1> an infrared-absorbing image-forming inkjet ink comprising an infrared-absorbing material represented by the following formula (A), a water-soluble organic solvent and water,

the content of the water-soluble organic solvent relative to the total amount of the ink-jet ink for infrared absorption image formation is 5 to 45% by mass,

SP value 27.5MPa^1/2The proportion of the solvent species X in the water-soluble organic solvent is 50% by mass or more.

[ chemical formula 1]

In the formula (A), Z¹And Z²Each independently represents a group of non-metal atoms forming a 5-or 6-membered nitrogen-containing heterocyclic ring which may be condensed, R¹And R²Each independently represents an aliphatic group which may have a substituent or an aromatic group which may have a substituent, L¹Denotes a methine group consisting of an odd number of methinesAnd the chains a and b each independently represent 0 or 1.

When the site represented by Cy in the formula (A) is a cationic moiety, X¹Denotes an anion, c denotes the amount required for achieving charge balance,

when the site represented by Cy in the formula (A) is an anion portion, X¹Denotes a cation, c denotes an amount required for achieving charge balance,

when the charge at the site represented by Cy in the formula (A) is neutralized in the molecule, X¹Is absent.

<2> the inkjet ink for infrared absorption image formation according to <1>, wherein,

the infrared absorbing material represented by formula (a) is an infrared absorbing material represented by formula (1A) below.

[ chemical formula 2]

In the formula (1A), R^1AAnd R^2AEach independently represents an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, an aralkyl group which may have a substituent or an aryl group which may have a substituent,

L^1Adenotes a methine chain consisting of an odd number of methines,

B¹and B²Each independently represents a group of atoms necessary for forming an aromatic hydrocarbon ring which may have a substituent or a group of atoms necessary for forming an aromatic heterocyclic ring which may have a substituent.

Y¹And Y²Each independently represents-S-, -O-, -NR^X1-or CR^X2R^X3-，R^X1、R^X2And R^X3Each independently represents a hydrogen atom or an alkyl group.

V^1AAnd V^2AEach independently represents a halogen atom, a cyano group, a nitro group, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an aryl group, a heterocyclic group, -OR¹⁰、-COR¹¹、-COOR¹²、-OCOR¹³、-NR¹⁴R¹⁵、-NHCOR¹⁶、-CONR¹⁷R¹⁸、-NHCONR¹⁹R²⁰、-NHCOOR²¹、-SR²²、-S0₂R²³、-SO₂OR²⁴、-NHSO₂R²⁵Or SO₂NR²⁶R²⁷，R¹⁰～R²⁷Each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an aryl group or a heterocyclic group. in-COOR¹²R of (A) to (B)¹²In the case of hydrogen atoms and SO₂OR²⁴R of (A) to (B)²⁴In the case of hydrogen atoms, the hydrogen atoms may be dissociated or may be in the form of a salt.

m1 and m2 each independently represent an integer of 0 to 4.

When m1 is an integer of 2 to 4, a plurality of V^1ACan be bonded to each other to form a ring, and when m2 is an integer of 2 to 4, a plurality of V^2AMay be bonded to each other to form a ring.

When the site represented by Cy in the formula (1A) is a cationic moiety, X²Denotes an anion, c denotes the amount required for achieving charge balance,

when the site represented by Cy in the formula (1A) is an anion portion, X²Denotes a cation, c denotes an amount required for achieving charge balance,

when the charge at the site represented by Cy in the formula (1A) is neutralized in the molecule, X²Is absent.

<3> the inkjet ink for infrared absorption image formation <2>, wherein,

at least 1 kind of the infrared absorbing material represented by the formula (1A) is an infrared absorbing material represented by the following formula (1B).

[ chemical formula 3]

In the formula (1B), R^1BAnd R^2BEach independently represents a substituent having a sulfur groupThe alkyl group of the ester group is,

L^1Brepresents a methine chain consisting of 7 methines,

X³denotes a cation, and c denotes an amount necessary for achieving charge balance.

<4> the inkjet ink for infrared ray absorption image formation according to any one of <1> to <3>, wherein,

the content of the water-soluble organic solvent is 5 to 30% by mass based on the total amount of the infrared-absorptive image-forming inkjet ink.

<5> the inkjet ink for infrared absorption image formation according to any one of <1> to <4>, which further contains resin particles.

<6> the inkjet ink for infrared ray absorption image formation according to any one of <1> to <5>, which further contains a colorant.

<7> the inkjet ink for infrared absorption image formation according to any one of <1> to <6>, which further contains a water-soluble polymer compound.

<8> the inkjet ink for infrared absorption image formation according to any one of <1> to <7>, which further contains gelatin.

<9> an infrared absorption image forming method comprising the steps of:

an infrared-absorptive image is formed by imparting the inkjet ink for infrared-absorptive image formation of any one of <1> to <8> onto a substrate by an inkjet method.

<10> the image forming method according to <9>, wherein,

the method comprises a step of applying a treatment liquid containing a flocculant to the substrate before the step of forming the infrared absorption image,

in the step of forming the infrared absorption image, an infrared absorption image is formed by applying an infrared absorption image-forming inkjet ink to at least a part of the region of the substrate to which the treatment liquid has been applied by an inkjet method.

<11> an image forming method comprising:

forming an infrared absorption image on a substrate by the infrared absorption image forming method according to <9> or <10 >; and

and irradiating the infrared-absorbed image with infrared light to obtain an image.

<12> the image forming method according to <11>, wherein,

the infrared ray has a maximum emission wavelength in a wavelength region of 700nm to 1500 nm.

Effects of the invention

According to the present invention, there are provided an ink jet ink for infrared-absorbing image formation and an infrared-absorbing image forming method capable of forming an infrared-absorbing image having excellent association formability of an infrared-absorbing material, and an image forming method capable of forming an image having excellent abrasion resistance by irradiating the infrared-absorbing image with infrared light.

Drawings

Fig. 1 is a schematic view showing a state after an infrared absorption image is formed by applying ink from an ink jet head in image formation of example 12, and then, the formed infrared absorption image is subjected to infrared irradiation and warm air blowing.

Detailed Description

In the present invention, "to" is used to include numerical values before and after the "to" as a lower limit value and an upper limit value.

In the numerical ranges recited in the present invention, the upper limit or the lower limit recited in a certain numerical range may be replaced with the upper limit or the lower limit recited in another numerical range recited in a stepwise manner. In the numerical ranges described in the present invention, the upper limit or the lower limit described in a certain numerical range may be replaced with the values shown in the examples.

In the present invention, the amount of each component in the composition refers to the total amount of a plurality of substances present in the composition, when the plurality of substances corresponding to each component are present in the composition, unless otherwise specified.

In the present invention, a combination of preferred embodiments is a more preferred embodiment.

In the present invention, the term "step" includes not only an independent step but also a step that can achieve the intended purpose of the step even when the step cannot be clearly distinguished from other steps.

In the present invention, a combination of 2 or more preferred embodiments is a more preferred embodiment.

In the labeling of the group (atomic group) in the present invention, the label not labeled with substitution and non-substitution includes not only a group having no substituent but also a group having a substituent. For example, "alkyl group" includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).

The chemical structural formula in the present invention may be described by a simplified structural formula in which a hydrogen atom is omitted.

In the present invention, "(meth) acrylate" represents acrylate and methacrylate, "(meth) acrylic acid" represents acrylic acid and methacrylic acid, and "(meth) acryloyl group" represents acryloyl group and methacryloyl group.

[ Infrared-absorbing ink-jet ink for image formation ]

The inkjet ink for infrared-absorbing image formation (hereinafter, also simply referred to as "ink") of the present invention contains an infrared-absorbing material represented by the following formula (a) (hereinafter, also referred to as "specific infrared-absorbing material"), a water-soluble organic solvent and water,

the content of the water-soluble organic solvent is 5 to 45% by mass based on the total amount of the infrared absorption image forming ink-jet ink,

SP value 27.5MPa^1/2The proportion of the solvent species X in the water-soluble organic solvent is 50% by mass or more.

[ chemical formula 4]

The meaning of each symbol in the formula (A) will be explained below.

According to the ink of the present invention, an infrared-absorbing image having excellent association formability of the infrared-absorbing material contained therein can be formed.

In the present invention, the "infrared absorption image having excellent association formation properties of the contained infrared absorbing materials" means an infrared absorption image in which a large proportion of associated molecules are formed in all molecules of the infrared absorbing materials contained in the infrared absorption image.

The association referred to herein is preferably a J association.

The J association and the J associate will be explained below.

In the present invention, the ratio of the minimum reflectance α in the wavelength region of 900nm or more and the minimum reflectance β in the wavelength region of 600nm or more and 850nm or less (hereinafter also referred to as α/β ratio) is determined for the infrared absorption image, and it is determined that the smaller the α/β ratio, the more excellent the association formability of the infrared absorbing material contained in the infrared absorption image.

The α/β ratio was confirmed as follows.

Ink was applied to the substrate and dried, thereby forming a film having a thickness of 2 μm.

The lowest reflectance α in the wavelength region of 900nm or more and the lowest reflectance β in the wavelength region of 600nm or more and 850nm or less were measured for each of the formed films. From the measurement results, a ratio of the reflectance α to the reflectance β (α/β ratio) was obtained.

The α/β ratio is preferably less than 1.2, more preferably less than 1.0, and still more preferably less than 0.8.

The reason why the above-mentioned effects are obtained by the ink of the present invention is presumed as follows.

It is considered that the ink of the present invention contains the water-soluble organic solvent in an amount of 5 to 45% by mass and has an SP value of 27.5MPa^1/2The ratio of the solvent type X in the water-soluble organic solvent is 50% by mass or more, and the ink is specified in the ink stage before the ink is applied to the substrateThe association of the infrared absorbing materials proceeds to some extent. As a result, it is considered that the association formability of the specific infrared absorbing material in the infrared absorbing image formed on the substrate is improved.

More specifically, it is considered that by limiting the content of the water-soluble organic solvent to 45 mass% or less, the intermolecular interaction between the specific infrared absorbing materials is not easily inhibited, and therefore the specific infrared absorbing materials in the ink are associated.

Further, it is considered that the SP value is 27.5MPa^1/2The ratio of the solvent species X in the water-soluble organic solvent is 50% by mass or more, and the high polarity of the liquid in the ink can be maintained, so that the specific infrared absorbing material in the ink is associated.

In the present invention, the "infrared absorption image" refers to an image having infrared absorbability.

Preferable spectral characteristics (maximum absorption wavelength, and the like) of the "infrared absorption image" are described in the section of "infrared absorption image forming method" described later.

The infrared absorption image in the present invention may be an invisible image (i.e., an image that is not easily visible) having infrared absorbability, or may be a visible image (e.g., a colored image) having infrared absorbability.

The infrared absorption image in the invisible image system can be used as an invisible image (for example, an invisible code pattern) for the purpose of, for example, forgery prevention of a commodity. For details of the invisible image, for example, the above-mentioned patent document 1 (japanese patent laid-open No. 2008-255323) can be referred to.

According to the ink of the present invention, an infrared absorption image having excellent association formability of the specific infrared absorbing material (in other words, excellent infrared absorbability) can be obtained. Therefore, when the ink of the present invention is used for forming an infrared-absorbing image of an invisible image system, an invisible image (e.g., a code pattern) excellent in readability by infrared rays can be formed.

Also, an infrared absorption image in the form of a colored image (visible image) can be used as a precursor for obtaining a colored image by infrared irradiation.

As described above, according to the ink of the present invention, an infrared absorption image excellent in association formability of a specific infrared absorbing material (in other words, excellent in infrared absorptivity) can be obtained. Therefore, when infrared rays are irradiated to an infrared ray absorption image (precursor) of a colored image system formed by the ink of the present invention, the infrared ray absorption image (precursor) absorbs infrared rays and generates heat. The infrared absorption image (precursor) itself is heated efficiently by the heat, and as a result, a colored image excellent in abrasion resistance can be obtained.

For details regarding the formation of the colored image, for example, reference can be made to the item of "image forming method" described later.

Hereinafter, each component that can be contained in the ink of the present invention will be described.

< specific Infrared-absorbing Material >

The ink of the present invention contains at least 1 specific infrared absorbing material, that is, an infrared absorbing material represented by formula (a).

[ chemical formula 5]

In the formula (A), Z¹And Z²Each independently represents a group of non-metal atoms forming a 5-or 6-membered nitrogen-containing heterocyclic ring which may be condensed, R¹And R²Each independently represents an aliphatic group which may have a substituent or an aromatic group which may have a substituent, L¹Represents a methine chain composed of an odd number of methines, and a and b each independently represent 0 or 1.

When the site represented by Cy in the formula (A) is a cationic moiety, X¹Denotes an anion, c denotes the amount required for achieving charge balance,

when the site represented by Cy in the formula (A) is an anion portion, X¹Denotes a cation, c denotes an amount required for achieving charge balance,

when the charge at the site represented by Cy in the formula (A) is neutralized in the molecule, X¹Is absent.

In the formula (A), Z¹And Z²Each independently represents a group of non-metal atoms forming a 5-or 6-membered nitrogen-containing heterocyclic ring which may be condensed.

Other heterocyclic ring, aromatic ring or aliphatic ring may be fused to the nitrogen-containing heterocyclic ring.

The nitrogen-containing heterocycle is preferably a 5-membered ring. More preferably, a benzene ring or a naphthalene ring is fused to the 5-membered nitrogen-containing heterocyclic ring.

Specific examples of the nitrogen-containing heterocycle include an oxazole ring, an isoxazole ring, a benzoxazole ring, a naphthooxazole ring, an oxazolocarbazole ring, an oxazolodibenzofurane ring, a thiazole ring, a benzothiazole ring, a naphthothiazole ring, an indolenine ring, a benzindole ring, an imidazole ring, a benzimidazole ring, a naphthoimidazole ring, a quinoline ring, a pyridine ring, a pyrrolopyridine ring, a furopyrrole ring, an indolizine ring, an imidazoquinoxaline ring, a quinoxaline ring and the like, and a quinoline ring, an indolenine ring, a benzindole ring, a benzoxazole ring, a benzothiazole ring, a benzimidazole ring are preferable, and an indolenine ring, a benzindole ring, a benzothiazole ring and a benzimidazoline ring are particularly preferable.

The nitrogen-containing heterocyclic ring and the ring condensed on the nitrogen-containing heterocyclic ring may have a substituent.

Examples of the substituent include a halogen atom, a cyano group, a nitro group, an aliphatic group, an aromatic group, a heterocyclic group and-OR¹⁰、-COR¹¹、-COOR¹²、-OCOR¹³、-NR¹⁴R¹⁵、-NHCOR¹⁶、-CONR¹⁷R¹⁸、-NHCONR¹⁹R²⁰、-NHCOOR²¹、-SR²²、-SO₂R²³、-SO₂OR²⁴、-NHSO₂R²⁵Or SO₂NR²⁶R²⁷。R¹⁰～R²⁷Each independently represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. In addition, -COOR¹²R of (A) to (B)¹²In the case of hydrogen (i.e., a carboxyl group), the hydrogen atom may be dissociated (i.e., a carboxylate group), or may be in the form of a salt. and-SO₂OR²⁴R of (A) to (B)²⁴In the case of a hydrogen atom (i.e., a sulfo group), the hydrogen atom may be dissociated (i.e., a sulfonate group) or may be in the form of a salt.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

Examples of the aliphatic group include an alkyl group, an alkenyl group, an alkynyl group, and an aralkyl group. These groups may have a substituent. Examples of the substituent include a halogen atom, a hydroxyl group, a carboxyl group, a sulfo group, an alkoxy group, an amino group, and the like, and a carboxyl group and a sulfo group are preferable, and a sulfo group is particularly preferable. In the carboxyl group and the sulfo group, a hydrogen atom may be dissociated, or may be in a salt state.

The alkyl group may be cyclic or linear. The chain alkyl group may have a branch. The number of carbon atoms of the alkyl group is preferably 1 to 20, more preferably 1 to 12, and most preferably 1 to 8. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, cyclopropyl, cyclohexyl and 2-ethylhexyl. Examples of the alkyl group having a substituent include a 2-hydroxyethyl group, a 2-carboxyethyl group, a 2-methoxyethyl group, a 2-diethylaminoethyl group, a 2-sulfoethyl group, a 3-sulfopropyl group, a 3-sulfobutyl group, a 4-sulfobutyl group and the like.

The alkenyl group may be cyclic or linear. The chain alkenyl group may have a branch. The number of carbon atoms of the alkenyl group is preferably 2 to 20, more preferably 2 to 12, and most preferably 2 to 8. Examples of the alkenyl group include vinyl, allyl, 1-propenyl, 2-butenyl, 2-pentenyl and 2-hexenyl.

The alkynyl group may be cyclic or linear. The chain alkynyl group may have a branch. The number of carbon atoms of the alkynyl group is preferably 2 to 20, more preferably 2 to 12, and most preferably 2 to 8. Examples of alkynyl groups include ethynyl and 2-propynyl.

The alkyl portion of the aralkyl group is the same as the alkyl group described above. The aryl moiety of the aralkyl group is the same as the aryl group described later. Examples of the aralkyl group include a benzyl group and a phenethyl group.

In the present invention, the aromatic group may be an aryl group. The aryl group may have a substituent. Examples of the substituent include those which the aliphatic group may have, and preferred ranges are the same.

The number of carbon atoms of the aryl group is preferably 6 to 25, more preferably 6 to 15, and most preferably 6 to 10. Examples of aryl groups include phenyl and naphthyl. Examples of the aryl group having a substituent include a 4-carboxyphenyl group, a 4-acetamidophenyl group, a 3-methanesulfonamidophenyl group, a 4-methoxyphenyl group, a 3-carboxyphenyl group, a3, 5-dicarboxyphenyl group, a 4-methanesulfonamidophenyl group and a 4-butanesulfonamidophenyl group.

In the present invention, the heterocyclic group may have a substituent. Examples of the substituent include those which the aliphatic group may have, and preferred ranges are the same.

The heterocycle of the heterocyclic group is preferably a 5-or 6-membered ring. The heterocyclic ring may be a single ring or a condensed ring. Examples of the heterocyclic ring include a pyridine ring, a piperidine ring, a furan ring, a thiophene ring, a pyrrole ring, a quinoline ring, a morpholine ring, an indole ring, an imidazole ring, a pyrazole ring, a carbazole ring, a phenothiazine ring, a phenoxazine ring, an indoline ring, a thiazole ring, a pyrazine ring, a thiadiazole ring, a benzoquinoline ring and a thiadiazole ring.

In the formula (A), R¹And R²Each independently represents an aliphatic group which may have a substituent or an aromatic group which may have a substituent.

Examples of the aliphatic group include an alkyl group, an alkenyl group, an alkynyl group, and an aralkyl group.

Examples of the aromatic group include an aryl group.

Examples of the alkyl group, alkenyl group, alkynyl group, aralkyl group and aryl group include the groups described above as substituents, and preferred ranges are the same.

The alkyl group, alkenyl group, alkynyl group, aralkyl group and aryl group may have a substituent or may be unsubstituted. Examples of the substituent include a halogen atom, a hydroxyl group, a carboxyl group, a sulfo group, an alkoxy group, an amino group, and the like, and a carboxyl group and a sulfo group are preferable, and a sulfo group is particularly preferable. In the carboxyl group and the sulfo group, a hydrogen atom may be dissociated, or may be in a salt state.

In the formula (A), L¹Represents a methine chain composed of an odd number of methines. L is¹Methine chains consisting of 3, 5 or 7 methines are preferred.

The methine group may have a substituent. The methine group having a substituent is preferably a central (meso) methine group. As specific examples of the substituent, with Z¹And Z²The nitrogen-containing heterocyclic ring of (b) may have the same substituent. Further, 2 substituents of the methine chain may be bonded to form a 5-or 6-membered ring.

In the formula (A), a and b are each independently 0 or 1. Preferably, a and b are both 0. When a and b are both 0, the formula (a) is shown below.

[ chemical formula 6]

In the formula (A), when the site represented by Cy in the formula is a cation part, X is¹Denotes an anion, and c denotes the amount required for achieving charge balance. Examples of the anion include halide ions (Cl)^-、Br^-、I^-) P-toluenesulfonate ion, ethylsulfate ion, PF₆ ^-、BF₄ ^-Or ClO₄ ^-Tris (haloalkylsulfonyl) methide anion (e.g., (CF)₃SO₂)₃C^-) Bis (haloalkylsulfonyl) imide anions (e.g., (CF)₃SO₂)₂N^-) Tetracyanoborate anions and the like.

In the formula (A), when the site represented by Cy in the formula is an anion portion, X¹Denotes a cation, and c denotes an amount necessary for achieving charge balance. As the cation, there may be mentioned an alkali metal ion (Li)⁺、Na⁺、K⁺Etc.), alkaline earth metal ions (Mg)²⁺、Ca²⁺、Ba²⁺、Sr²⁺Etc.), transition metal ions (Ag)⁺、Fe²⁺、Co²⁺、Ni²⁺、Cu²⁺、Zn²⁺Etc.), other metal ions (Al)³⁺Etc.), ammonium ion, triethylammonium ion, tributylammonium ion, pyridinium ion, tetrabutylammonium ion, guanidinium ion, tetrabutylguanidinium ion, diazaBicyclic undecaium, and the like. As the cation, Na is preferred⁺、K⁺、Mg²⁺、Ca²⁺、Zn²⁺Diazabicycloundecanium.

In the formula (A), when the charge at the site represented by Cy in the formula is neutralized in the molecule, X¹Is absent.

The compound represented by the formula (a) is more preferably a compound represented by the following formula (1A).

[ chemical formula 7]

In the formula (1A), R^1AAnd R^2AEach independently represents an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, an aralkyl group which may have a substituent or an aryl group which may have a substituent,

L^1Adenotes a methine chain consisting of an odd number of methines,

B¹and B²Each independently represents a group of atoms necessary for forming an aromatic hydrocarbon ring which may have a substituent or a group of atoms necessary for forming an aromatic heterocyclic ring which may have a substituent,

Y¹and Y²Each independently represents-S-, -O-, -NR^X1-or CR^X2R^X3-，R^X1、R^X2And R^X3Each independently represents a hydrogen atom or an alkyl group,

V^1Aand V^2AEach independently represents a halogen atom, a cyano group, a nitro group, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an aryl group, a heterocyclic group, -OR¹⁰、-COR¹¹、-COOR¹²、-OCOR¹³、-NR¹⁴R¹⁵、-NHCOR¹⁶、-CONR¹⁷R¹⁸、-NHCONR¹⁹R²⁰、-NHCOOR²¹、-SR²²、-SO₂R²³、-SO₂OR²⁴、-NHSO₂R²⁵Or SO₂NR²⁶R²⁷，R¹⁰～R²⁷Each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an aryl group or a heterocyclic group at-COOR¹²R of (A) to (B)¹²In the case of hydrogen atoms and SO₂OR²⁴R of (A) to (B)²⁴In the case of a hydrogen atom, the hydrogen atom may be dissociated or may be in the form of a salt,

m1 and m2 each independently represent an integer of 0 to 4,

when m1 is an integer of 2 to 4, a plurality of V^1ACan be bonded to each other to form a ring, and when m2 is an integer of 2 to 4, a plurality of V^2AMay be bonded to each other to form a ring,

when the site represented by Cy in the formula (1A) is a cationic moiety, X²Denotes an anion, c denotes the amount required for achieving charge balance,

when the site represented by Cy in the formula (1A) is an anion portion, X²Denotes a cation, c denotes an amount required for achieving charge balance,

when the charge at the site represented by Cy in the formula (1A) is neutralized in the molecule, X²Is absent.

In the formula (1A), as represented by R^1AAnd R^2AExamples of the substituent for each of the alkyl group which may have a substituent, the alkenyl group which may have a substituent, the alkynyl group which may have a substituent, the aralkyl group which may have a substituent, the aryl group which may have a substituent and the heterocyclic group which may have a substituent include a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like), a hydroxyl group, a carboxyl group, a sulfo group, an alkoxy group, an amino group and the like, and a carboxyl group or a sulfo group is preferable, and a sulfo group is particularly preferable. Carboxyl (-COOH group) and sulfo (-SO)₃H group), hydrogen atoms may be dissociated (i.e., may be carboxylate groups (-COO)^-Alkyl) and sulfonate (-SO)₃ ^-In the form of a group), or in the form of a salt (e.g., -COOK group, -SO)₃Form of the K group).

In the present invention, when the carboxyl group in the specific infrared absorbing material is in the form of a salt, the carboxyl group in the form of a salt may be formed from a carboxylate group (-COO)^-Radical) and from X²Of the representationAnd (4) cation formation.

In the present invention, when the sulfo group in the specific infrared absorbing material is in the form of a salt, the sulfo group in the form of a salt may be a sulfonate group (-SO)₃ ^-Radical) and from X²The cations shown are formed.

From R^1AAnd R^2AThe alkyl group which may have a substituent(s) represented by (1) may be cyclic or linear. The chain alkyl group may have a branch. The number of carbon atoms in the alkyl group (the number of carbon atoms in the portion other than the substituent when the substituent is present) is preferably 1 to 20, more preferably 1 to 12, and still more preferably 1 to 8. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, cyclopropyl, cyclohexyl and 2-ethylhexyl. Examples of the alkyl group having a substituent include a 2-hydroxyethyl group, a 2-carboxyethyl group, a 2-methoxyethyl group, a 2-diethylaminoethyl group, a 2-sulfoethyl group, a 3-sulfopropyl group, a 3-sulfobutyl group, a 4-sulfobutyl group and the like.

From R^1AAnd R^2AThe alkenyl group which may have a substituent(s) represented by (1) may be cyclic or linear. The chain alkenyl group may have a branch. The number of carbon atoms of the alkenyl group (the number of carbon atoms of the moiety other than the substituent when the substituent is present) is preferably 2 to 20, more preferably 2 to 12, and still more preferably 2 to 8. Examples of the alkenyl group include vinyl, allyl, 1-propenyl, 2-butenyl, 2-pentenyl and 2-hexenyl.

From R^1AAnd R^2AThe alkynyl group which may have a substituent(s) represented by (1) may be cyclic or linear. The chain alkynyl group may have a branch. The number of carbon atoms of the alkynyl group (the number of carbon atoms of a portion other than the substituent group when the substituent group is present) is preferably 2 to 20, more preferably 2 to 12, and still more preferably 2 to 8. Examples of alkynyl groups include ethynyl and 2-propynyl.

From R^1AAnd R^2AThe alkyl moiety of each of the aralkyl groups which may have a substituent(s) is the same as the above-mentioned alkyl group. The aryl moiety of the aralkyl group is the same as the aryl group described later. Examples of the aralkyl group include a benzyl group and a phenethyl group.

From R^1AAnd R^2AThe number of carbon atoms of the aryl group which may have a substituent (when having a substituent, the number of carbon atoms of the portion other than the substituent) represented by (1) is preferably 6 to 25, more preferably 6 to 15, and still more preferably 6 to 10. Examples of aryl groups include phenyl and naphthyl.

Examples of the aryl group having a substituent include a 4-carboxyphenyl group, a 4-acetamidophenyl group, a 3-methanesulfonamidophenyl group, a 4-methoxyphenyl group, a 3-carboxyphenyl group, a3, 5-dicarboxyphenyl group, a 4-methanesulfonamidophenyl group and a 4-butanesulfonamidophenyl group.

L^1ARepresents a methine chain composed of an odd number of methines.

L^1APreferred are methine chains consisting of 3, 5 or 7 methines, more preferred are methine chains consisting of 5 or 7 methines, and still more preferred are methine chains consisting of 7 methines.

The methine group may have a substituent. The methine group having a substituent is preferably a central (meso) methine group. Also, 2 substituents of the methine chain may be bonded to form a 5 or 6 membered ring.

Examples of the substituent which the methine group may have include a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), a cyano group, a nitro group, an aliphatic group, an aryl group, a heterocyclic group, and-OR¹⁰、-COR¹¹、-COOR¹²、-OCOR¹³、-NR¹⁴R¹⁵、-NHCOR¹⁶、-CONR¹⁷R¹⁸、-NHCONR¹⁹R²⁰、-NHCOOR²¹、-SR²²、-SO₂R²³、-SO₂OR²⁴、-NHSO₂R²⁵Or SO₂NR²⁶R²⁷。R¹⁰～R²⁷Each independently represents a hydrogen atom, an aliphatic group, an aryl group or a heterocyclic group. In addition, -COOR¹²R of (A) to (B)¹²In the case of a hydrogen atom (i.e., a carboxyl group), the hydrogen atom may be dissociated (i.e., may be a carboxylate group (-COO)^-A group)), or may be in the form of a salt (e.g., -COOK group). and-SO₂OR²⁴R of (A) to (B)²⁴In the case of a hydrogen atom (i.e. sulfo), hydrogenThe atoms may be dissociated (i.e., sulfonate groups) or may be in the form of a salt.

Among the substituents which the methine group may have, examples of the aliphatic group include an alkyl group, an alkenyl group, an alkynyl group, and an aralkyl group.

Among the substituents which the methine group may have, a preferred embodiment of the aliphatic group is represented by R^1AAnd R^2AThe preferable modes of the alkyl group which may have a substituent, the alkenyl group which may have a substituent, the alkynyl group which may have a substituent and the aralkyl group which may have a substituent are the same.

From R¹⁰～R²⁷The preferable mode of the aliphatic group represented by (1) is the same.

Among the substituents which the methine group may have, the preferred mode of aryl is represented by R^1AAnd R^2AThe preferable mode of each of the aryl groups which may have a substituent is the same.

From R¹⁰～R²⁷The preferable mode of the aryl group represented by (1) is the same.

Among the substituents which the methine group may have, the heterocycle in the heterocyclic group is preferably a 5-membered ring or a 6-membered ring. The heterocyclic ring may be a single ring or a condensed ring. Examples of the heterocyclic ring include a pyridine ring, a piperidine ring, a furan (furan) ring, a thiophene ring, a pyrrole ring, a quinoline ring, a morpholine ring, an indole ring, an imidazole ring, a pyrazole ring, a carbazole ring, a phenothiazine ring, a phenoxazine ring, an indoline ring, a thiazole ring, a pyrazine ring, a thiadiazole ring, a benzoquinoline ring and a thiadiazole ring.

From R¹⁰～R²⁷The same applies to the heterocyclic groups represented by (1).

Below, show the chemical formula consisting of^1ASpecific examples of the methine chain shown but represented by L^1AThe methine chain is not limited to the following specific examples.

In the following specific examples, a indicates a bonding site.

[ chemical formula 8]

In the context of these specific embodiments, the term "a", "b,

from the viewpoint of more effectively exhibiting the effects of the ink according to the present invention,

preferably a group L1-6 to a group L1-28,

more preferably from the group L1-12 to the group L1-28,

further preferred are the group L1-12, the group L1-15, the group L1-16, the group L1-21 or the group L1-27.

In the formula (1A), B¹And B²Each independently represents a group of atoms necessary for forming an aromatic hydrocarbon ring which may have a substituent or a group of atoms necessary for forming an aromatic heterocyclic ring which may have a substituent. From B¹And B²Each of the formed rings of (a) may have a substituent.

From B¹And B²Examples of the substituents on the aromatic hydrocarbon ring which may have a substituent(s) each formed with R^1AOr R^2AThe same applies to the substituents in the alkyl group which may have a substituent(s) and the like represented by each of (1).

As by B¹And B²Examples of the aromatic hydrocarbon ring to be formed in each of (1) include a benzene ring and a naphthalene ring.

As by B¹And B²The aromatic heterocyclic ring to be formed in each of (1) above is preferably an aromatic heterocyclic ring having at least 1 nitrogen atom, oxygen atom or sulfur atom in the ring-constituting atoms. From B¹And B²The aromatic heterocyclic ring formed by each of (a) and (b) may be fused on another ring (alicyclic ring, aromatic ring or heterocyclic ring).

As by B¹And B²The aromatic heterocyclic ring formed in each of (1) and (3) is preferably a 5-to 10-membered ring.

As by B¹And B²The aromatic heterocyclic ring to be formed in each of (a) and (b) includes a pyridine ring, a dibenzofuran ring, a carbazole ring and the like.

In the formula (1A), B is preferred¹And B²Each independently represents an aromatic hydrocarbon ring (preferably a benzene ring) which may have a substituent) A desired atom group (for example, the mode of the formula (1B) described later).

In the formula (1A), Y¹And Y²Each independently represents-S-, -O-, -NR^X1-or CR^X2R^X3-，R^X1And R^X2Each independently represents a hydrogen atom or an alkyl group.

As Y¹And Y²preferably-NR^X1-or-CR^X2R^X3-。

R^X1、R^X2And R^X3Each independently represents a hydrogen atom or an alkyl group, preferably an alkyl group. The number of carbon atoms of the alkyl group is preferably 1 to 10, more preferably 1 to 5, and still more preferably 1 to 3. The alkyl group may be linear, branched or cyclic, and is preferably linear or branched, and particularly preferably linear. As the alkyl group, a methyl group or an ethyl group is preferable, and a methyl group is particularly preferable.

V^1AAnd V^2AEach independently represents a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), a cyano group, a nitro group, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an aryl group, a heterocyclic group, -OR¹⁰、-COR¹¹、-COOR¹²、-OCOR¹³、-NR¹⁴R¹⁵、-NHCOR¹⁶、-CONR¹⁷R¹⁸、-NHCONR¹⁹R²⁰、-NHCOOR²¹、-SR²²、-SO₂R²³、-S0₂OR²⁴、-NHSO₂R²⁵Or SO₂NR²⁶R²⁷，R¹⁰～R²⁷Each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an aryl group or a heterocyclic group. -COOR¹²R of (A) to (B)¹²In the case of hydrogen atoms and SO₂OR²⁴R of (A) to (B)²⁴In the case of a hydrogen atom, the hydrogen atom may be dissociated (i.e., may be-COO^-and-SO₃ ^-A group) or a salt state (for example, each of which may be-COOK and-SO₃State of the K group).

m1 and m2 each independently represent an integer of 0 to 4.

When m1 is an integer of 2 to 4, a plurality of V^1ACan be used forA plurality of V are bonded to each other to form a ring, and m2 is an integer of 2 to 4^2AMay be bonded to each other to form a ring.

V^1AAnd V^2AThe preferable mode of each of (a) and (b) is the same as the preferable mode of the substituent which the methine group may have.

Further, as a preferable embodiment of the formula (1A), m1 and m2 are 2, 2V, respectively^1A2V, which are bonded to each other to form a benzene ring which may have a substituent^1BAnd a benzene ring which may have a substituent (for example, a mode of the formula (1B) described later) by bonding to each other.

A more preferred embodiment of formula (1A) is that m1 and m2 are 2, 2V, respectively^1AA benzene ring having a substituent (preferably a carboxylate group, a salt of a carboxyl group, a sulfonate group, or a salt of a sulfo group, particularly preferably a sulfonate group or a salt of a sulfo group) by bonding with each other (an embodiment of formula (1B) described later).

When the site represented by Cy in the formula (1A) is a cationic moiety, X²Denotes an anion, c denotes the amount required for achieving charge balance,

when the site represented by Cy in the formula (1A) is an anion portion, X²Denotes a cation, c denotes an amount required for achieving charge balance,

when the charge at the site represented by Cy in the formula (1A) is neutralized in the molecule, X²Is absent.

As a result of X²Examples of the anion include halide ions (Cl)^-、Br^-、I^-) P-toluenesulfonate ion, ethylsulfate ion, PF₆ ^-、BF₄ ^-Or ClO₄ ^-Tris (haloalkylsulfonyl) methide anion (e.g., (CF)₃SO₂)₃C^-) Bis (haloalkylsulfonyl) imide anions (e.g., (CF)₃SO₂)₂N_-) Tetracyanoborate anions and the like.

As a result of X²Examples of the anion include halide ions (Cl)^-、Br^-、I^-) P-toluenesulfonAcid radical ion, ethyl sulfate radical ion, PF₆ ^-、BF₄ ^-Or ClO₄ ^-Tris (haloalkylsulfonyl) methide anion (e.g., (CF)₃SO₂)₃C^-) Bis (haloalkylsulfonyl) imide anions (e.g., (CF)₃SO₂)₂N^-) Tetracyanoborate anions and the like.

As a result of X²As the cation, an alkali metal ion (Li) can be mentioned⁺、Na⁺、K⁺Etc.), alkaline earth metal ions (Mg)^{2 +}、Ca²⁺、Ba²⁺、Sr²⁺Etc.), transition metal ions (Ag)⁺、Fe²⁺、Co²⁺、Ni²⁺、Cu²⁺、Zn²⁺Etc.), other metal ions (Al)³⁺Etc.), ammonium ion, triethylammonium ion, tributylammonium ion, pyridinium ion, tetrabutylammonium ion, guanidinium ion, tetrabutylguanidinium ion, diazabicycloundecanium, etc. As a result of X²The cation of (A) is preferably Na⁺、K⁺、Mg²⁺、Ca²⁺、Zn²⁺Diazabicycloundecanium.

c is not particularly limited as long as it is an amount necessary for achieving charge balance. When the charge at the site represented by Cy in the formula (1A) is neutralized in the molecule, X²Is absent.

In the present invention, "the amount necessary for achieving charge balance" means the amount necessary for neutralizing the charge of the whole compound.

Examples of c include 0, 1/2, 3/2, and 3.

From the viewpoint of more effectively obtaining the effect of the ink according to the present invention, it is preferable that at least 1 kind of the specific infrared absorbing material (i.e., the infrared absorbing material represented by formula (1A)) is an infrared absorbing material represented by formula (1B) below.

In this case, the proportion of the infrared absorbing material represented by the formula (1B) in the specific infrared absorbing material is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and still more preferably 80 to 100% by mass.

[ chemical formula 9]

In the formula (1B), R^1BAnd R^2BEach independently represents an alkyl group having a sulfonate group as a substituent,

L^1Brepresents a methine chain consisting of 7 methines,

X³denotes a cation, and c denotes an amount necessary for achieving charge balance.

In the formula (1B), as R^1BAnd R^2BPreferred modes of the respective alkyl groups having a sulfonate group as a substituent are those represented by R in the formula (1A) except that the substituent is limited to the sulfonate group^1AAnd R^2AThe preferable mode of each of the alkyl groups which may have a substituent is the same.

As R^1BAnd R^2BEach of the alkyl groups having a sulfonate group as a substituent may be reacted with X³The cations shown together form a salt of a sulfo group.

And, 2 sulfonate groups (-SO) substituted with benzene ring in formula (1B)₃ ^-Groups) may be independently substituted with X³The cations shown together form a salt of a sulfo group.

In the formula (1B), from L^1BPreferred embodiments of the methine chain composed of 7 methines shown above correspond to the embodiment represented by L in the formula (1A) except that the number of methines is limited to 7^1AThe methine chains represented are the same.

As L^1B，

More preferably the group L1-12 to the group L1-28 in the above-mentioned embodiments,

further preferred are the group L1-12, the group L1-15, the group L1-16, the group L1-21 or the group L1-27.

In the formula (1B), c represents the amount necessary for achieving charge balance.

As c, 3/2 or 3 is preferable.

In the formula (1B), from X³Examples and preferred embodiments of the cation represented by the formula (1A) and X²Examples and preferred modes of the cations shown are the same.

As a result of X³The cation represented by (1) is more preferably Na⁺、K⁺、Mg²⁺、Ca²⁺、Zn²⁺Further preferably K⁺Or Mg²⁺。

Specific examples (compounds C-1 to C-69) of specific infrared absorbing materials (i.e., the infrared absorbing material represented by formula (a)) are shown below, and the specific infrared absorbing materials are not limited to the specific examples below.

In the following specific examples, Me, Et, Ph, PRS and BUS each represents a methyl group, an ethyl group, a phenyl group or a C group₃H₆SO^3-Base, C₄H₉S_O ^3-And (4) a base.

[ chemical formula 10]

[ chemical formula 11]

[ chemical formula 12]

[ chemical formula 13]

[ chemical formula 14]

[ chemical formula 15]

[ chemical formula 16]

[ chemical formula 17]

Among the specific examples of the specific infrared absorbing material, particularly preferred compounds are the compound C-36, the compound C-43, the compound C-46, the compound C-49 and the compounds C-50 to C-69, from the viewpoint of more effectively exerting the effect of the ink of the present invention.

Among them, particularly preferred compounds are the compounds C-51 to C-69,

among these, particularly preferred compounds are the compounds C-55 to C-59 and C-66 to C-69.

The content of the specific infrared absorbing material is preferably 0.01 to 5% by mass, more preferably 0.05 to 2% by mass, and still more preferably 0.1 to 1% by mass, based on the total amount of the ink.

< Water-soluble organic solvent >

The ink of the present invention contains at least 1 kind of water-soluble organic solvent.

The water-soluble organic solvent is not particularly limited, and any water-soluble organic solvent known in the field of inkjet inks can be used.

In the present invention, "water-soluble" refers to a property of dissolving 1g or more in 100g of water at 25 ℃.

The "water-soluble" in the present invention is preferably 5g or more (more preferably 10g or more) dissolved in 100g of water at 25 ℃.

The content of the water-soluble organic solvent is 5 to 45% by mass based on the total amount of the ink of the present invention.

The case where the content of the water-soluble organic solvent is 5% by mass or more contributes to improvement of the ejection property of the ink. The content of the water-soluble organic solvent is preferably 10% by mass or more, and more preferably 15% by mass or more.

The content of the water-soluble organic solvent of 45 mass% or less contributes to improvement of the association formability of the specific infrared absorbing material in the ink, and as a result, contributes to improvement of the association formability of the specific infrared absorbing material in the infrared absorbing image.

The content of the water-soluble organic solvent is more preferably 5 to 30% by mass from the viewpoint of further improving the association formability of the specific infrared absorbing material in the ink and in the infrared absorbing image.

(solvent species X)

SP value 27.5MPa^1/2The proportion of the solvent species X in the water-soluble organic solvent (i.e., in the total water-soluble organic solvent contained in the ink of the present invention) is 50% by mass or more.

This improves the association formability of the specific infrared absorbing material in the ink, and as a result, improves the association formability of the specific infrared absorbing material in the infrared-absorbing image. The reason is not clear, but it is considered that the high polarity of the solvent in the ink does not interfere with the intermolecular interaction.

The proportion of the solvent species X in the water-soluble organic solvent is preferably 70% by mass or more, and more preferably 80% by mass or more.

The ratio of the solvent type X in the water-soluble organic solvent may be 100% by mass.

The solvent species X was SP value of 27.5MPa^1/2The above water-soluble organic solvent.

In the present invention, the SP value (solubility parameter/unit: MPa)^1/2) Means a value represented by the square root of the molecular coagulation energy and calculated by the method described in R.F. Fedors, Polymer Engineering Science, 14, p 147-154 (1974).

Specific examples of the solvent type X are shown below, and the solvent type X is not limited to the following specific examples. In the following specific examples, the values in parentheses after the following examples are SP values (unit: MPa)^1/2)。

Examples of the solvent type X include propylene glycol (27.5), ethylene glycol (30.34), diethylene glycol (30.62), triethylene glycol (27.79), 2-methyl-1, 3-butanediol (28.27), 1, 2-pentanediol (28.64), 1, 5-pentanediol (28.96), 1, 6-hexanediol (27.66), glycerol (33.52), dimethylformamide (30.62), methanol (28.17), isopropanol (28.69), and triethanolamine (32.27).

(other solvent species)

The ink of the present invention may contain a water-soluble organic solvent (hereinafter, solvent type Y) other than solvent type X.

The solvent type Y is a SP value of less than 27.5MPa^1/2The water-soluble organic solvent of (1).

Specific examples of the solvent type Y are shown below, but the solvent type Y is not limited to the following specific examples. In the following specific examples, the values in parentheses after the following examples are SP values (unit: MPa)^1/2)。

Examples of the solvent type Y include dipropylene glycol (27.1), ethylene glycol monoethyl ether (23.47), ethylene glycol monobutyl ether (22.12), diethylene glycol monomethyl ether (22.98), diethylene glycol monoethyl ether (22.4), diethylene glycol monopropyl ether (21.9), diethylene glycol monobutyl ether (21.5), triethylene glycol monomethyl ether (22.1), triethylene glycol monoethyl ether (21.7), triethylene glycol monobutyl ether (21.1), propylene glycol monomethyl ether (23.05), propylene glycol monoethyl ether (22.34), propylene glycol monopropyl ether (21.79), propylene glycol monobutyl ether (21.35), dipropylene glycol monomethyl ether (21.3), dipropylene glycol monopropyl ether (20.69), dipropylene glycol monoethyl ether (23.69), and the likeButyl ether (20.45), dipropylene glycol tertiary-butyl ether (19.98), tripropylene glycol monomethyl ether (20.4), diethylene glycol monohexyl ether (20.91), ethylene glycol mono-2-ethylhexyl ether (20.46), diethylene glycol mono-2-ethylhexyl ether (20.26), nC₄H₉(OR²)₄-OH(R²Vinyl or propenyl; the ratio of ethenyl to propenyl is 1: 1) (20.1), and the like.

< Water >

The ink of the present invention contains water.

The water content is preferably 50% by mass or more, and more preferably 60% by mass or more, based on the total amount of the ink.

The upper limit of the content of water is not particularly limited, and may be determined according to the content of other components, and is preferably 99 mass% or less, more preferably 98 mass% or less, and further preferably 95 mass% or less.

< resin particles >

The ink of the present invention preferably contains at least 1 kind of resin particles.

Thereby, the abrasion resistance of the image is further improved. It is also presumed that the stability of the association of the specific infrared absorbing material in the image is improved, and the association formability of the specific infrared absorbing material is further improved.

The resin particles are not particularly limited as long as they are particles containing a resin, and particles composed of a resin are preferred.

The shape of the resin particles is not particularly limited, and may be irregular, polyhedral or hollow, and spherical particles are preferable from the viewpoint of ejection properties in the ink jet method.

Examples of the resin particles include particles of resins having anionic groups, such as thermoplastic, thermosetting or modified acrylic resins, epoxy resins, polyurethane resins, polyether resins, polyamide resins, unsaturated polyester resins, phenol resins, silicone resins or fluorine resins, polyethylene resins such as vinyl chloride, vinyl acetate, polyvinyl alcohol or polyvinyl butyral resins, polyester resins such as alkyd resins and phthalic resins, amino materials such as melamine resins, melamine formaldehyde resins, aminoalkyd polycondensation resins, urea resins and urea resins, and copolymers or mixtures thereof.

Among these resins, for example, anionic acrylic resins are obtained as follows: an acrylic monomer having an anionic group (an anionic group-containing acrylic monomer) and, if necessary, another monomer copolymerizable with the anionic group-containing acrylic monomer are polymerized in a solvent.

Examples of the anionic group-containing acrylic monomer include 1 or more acrylic monomers selected from the group consisting of a carboxyl group, a sulfonic acid group and a phosphonic acid group, and among them, acrylic monomers having a carboxyl group (for example, acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid and the like) are preferable, and acrylic acid or methacrylic acid is particularly preferable.

The resin particles are preferably particles of an acrylic resin, a vinyl acetate resin, a styrene-butadiene resin, a vinyl chloride resin, a urethane resin, an acrylic-styrene resin, a butadiene resin, a styrene resin, a crosslinked acrylic resin, a crosslinked styrene resin, a polyethylene resin, or the like, more preferably at least 1 selected from the group consisting of acrylic resin particles, urethane resin particles, polyethylene resin particles, and styrene-acrylic resin particles, and further preferably acrylic resin particles, from the viewpoint of abrasion resistance and dot shape.

From the viewpoint of stability (particularly dispersion stability) of the ink, the resin particles are preferably particles of a self-dispersible resin (self-dispersible resin particles).

The self-dispersible resin is a water-insoluble polymer that can be dispersed in an aqueous medium by a functional group (particularly, an acidic group or a salt thereof) of the polymer itself when the polymer is dispersed by a phase inversion emulsification method in the absence of a surfactant.

The dispersed state is defined as including both an emulsified state (emulsion) in which the water-insoluble polymer is dispersed in a liquid state in an aqueous medium and a dispersed state (suspension) in which the water-insoluble polymer is dispersed in a solid state in an aqueous medium.

In the present invention, "water-insoluble" in the water-insoluble polymer means that, when the resin is mixed in water at 25 ℃, the amount of the resin dissolved in water is 10 mass% or less in terms of mass ratio to the total amount of the resin mixed.

Examples of the self-dispersible resin particles include self-dispersible polymer particles described in paragraphs 0062 to 0076 of Japanese patent application laid-open No. 2016-188345 and paragraphs 0109 to 0140 of International publication No. 2013/180074.

As the resin in the resin particles,

more preferably an acrylic resin comprising at least 1 selected from the group consisting of benzyl (meth) acrylate units, phenoxyethyl (meth) acrylate units, and (meth) acrylate units containing a cyclic aliphatic group, and (meth) acrylic acid units,

more preferably, the acrylic resin contains at least 1 selected from the group consisting of a benzyl (meth) acrylate unit, a phenoxyethyl (meth) acrylate unit, and a (meth) acrylate unit containing a cyclic aliphatic group, a (meth) acrylic acid unit, and an alkyl (meth) acrylate unit containing an alkyl group having 1 to 4 carbon atoms.

Wherein the benzyl (meth) acrylate unit refers to a structural unit derived from benzyl (meth) acrylate, that is, a structural unit formed by polymerization of benzyl (meth) acrylate. The same applies to the other "units".

The cyclic aliphatic group-containing (meth) acrylate is preferably at least 1 selected from the group consisting of alkyl (meth) acrylates having a cycloalkyl group of 3 to 10 carbon atoms (for example, cyclohexyl (meth) acrylate), isobornyl (meth) acrylate, adamantyl (meth) acrylate, and dicyclopentanyl (meth) acrylate,

more preferably at least 1 selected from the group consisting of isobornyl (meth) acrylate, adamantyl (meth) acrylate, and dicyclopentanyl (meth) acrylate.

The total content of the benzyl (meth) acrylate unit, the phenoxyethyl (meth) acrylate unit, and the cyclic aliphatic group-containing (meth) acrylate unit in the resin particles is preferably 20 to 80% by mass, and preferably 30 to 75% by mass, based on the total amount of the resin dispersant.

The total content of the benzyl (meth) acrylate unit, the phenoxyethyl (meth) acrylate unit, the cyclic aliphatic group-containing (meth) acrylate unit, and the alkyl (meth) acrylate unit containing an alkyl group having 1 to 4 carbon atoms in the resin particles is preferably 80 to 98 mass%, preferably 85 to 97 mass%, and more preferably 90 to 95 mass% with respect to the total amount of the resin dispersant.

The content of the (meth) acrylic acid unit in the resin particles is preferably 2 to 20% by mass, preferably 3 to 15% by mass, and more preferably 5 to 10% by mass, based on the total amount of the resin dispersant.

The resin in the resin particles preferably contains neutralized acid groups.

The resin particles composed of the resin containing neutralized acid groups are obtained, for example, by synthesizing a copolymer having acid groups and neutralizing at least a part of the acid groups in the obtained copolymer.

Examples of the acid group before neutralization include a carboxyl group, and examples of the acid group to be neutralized include a salt of the carboxyl group.

The neutralization can be performed, for example, by using an alkali such as sodium hydroxide or potassium hydroxide in the production process of the water dispersion of the resin particles.

Specific examples of the resin in the resin particle include phenoxyethyl acrylate/methyl methacrylate/acrylic acid copolymer (50/45/5), phenoxyethyl acrylate/benzyl methacrylate/isobutyl methacrylate/methacrylic acid copolymer (30/35/29/6), phenoxyethyl methacrylate/isobutyl methacrylate/methacrylic acid copolymer (50/44/6), phenoxyethyl acrylate/methyl methacrylate/ethyl acrylate/acrylic acid copolymer (30/55/10/5), benzyl methacrylate/isobutyl methacrylate/methacrylic acid copolymer (35/59/6), styrene/phenoxyethyl acrylate/methyl methacrylate/acrylic acid copolymer (10/50/35 ^ ion ^ 5) Benzyl acrylate/methyl methacrylate/acrylic acid copolymer (55/40/5), phenoxyethyl methacrylate/benzyl acrylate/methacrylic acid copolymer (45/47/8), styrene/phenoxyethyl acrylate/butyl methacrylate/acrylic acid copolymer (5/48/40/7), benzyl methacrylate/isobutyl methacrylate/cyclohexyl methacrylate/methacrylic acid copolymer (35/30/30/5), phenoxyethyl acrylate/methyl methacrylate/butyl acrylate/methacrylic acid copolymer (12/50/30/8), benzyl acrylate/isobutyl methacrylate/acrylic acid copolymer (93/2/5), Methyl methacrylate/ethyl methoxyacrylate/benzyl methacrylate/acrylic acid copolymer (44/15/35/6), styrene/butyl acrylate/acrylic acid copolymer (62/35/3), methyl methacrylate/phenoxyethyl acrylate/acrylic acid copolymer (45/51/4), methyl methacrylate/isobornyl methacrylate/methacrylic acid copolymer (20/72/8), methyl methacrylate/isobornyl methacrylate/methacrylic acid copolymer (40/52/8), methyl methacrylate/isobornyl methacrylate/methacrylic acid copolymer (48/42/10), methyl methacrylate/isobornyl methacrylate/dicyclopentanyl methacrylate/methacrylic acid copolymer A copolymer (20/62/10/8), a methyl methacrylate/dicyclopentyl methacrylate/methacrylic acid copolymer (20/72/8), and the like.

In addition, the mass ratio of the copolymerization components is shown in parentheses.

Further, specific examples of the resin in the resin particles include resins obtained by neutralizing at least a part of carboxyl groups in the respective copolymers.

(acid value)

The acid value of the resin in the resin particles is preferably 25mgKOH/g to 100mgKOH/g, more preferably 30mgKOH/g to 90mgKOH/g, and still more preferably 35mgKOH/g to 80mgKOH/g, from the viewpoints of dispersion stability, cohesiveness at the time of image recording, and the like.

The acid value can be measured by the method described in JIS specification (JIS K0070: 1992).

(volume average particle diameter)

The volume average particle diameter of the resin particles is preferably 1 μm or less, more preferably 125nm or less, and still more preferably 100nm or less, from the viewpoint of improving the ink ejection property.

The volume average particle diameter of the resin particles is preferably 5nm or more, and more preferably 10nm or more, from the viewpoint of stability of the ink.

The volume average particle diameter and the particle diameter distribution of the resin particles can be measured by a dynamic light scattering method using a nanatrac particle size distribution measuring apparatus.

As the nanosrac particle size distribution measuring apparatus, for example, UPA-EX150 of Nikkiso co., ltd.

The particle size distribution of the resin particles is not particularly limited, and may be any of resin particles having a broad particle size distribution or resin particles having a monodisperse particle size distribution. Further, 2 or more kinds of resin particles may be used in combination.

(weight average molecular weight)

The weight average molecular weight of the resin in the resin particles is preferably 5000 or more, and more preferably 10000 or more.

The weight average molecular weight of the resin in the resin particles is preferably 300000 or less, and more preferably 100000 or less.

In the present invention, the number average molecular weight and the weight average molecular weight are values measured by Gel Permeation Chromatography (GPC).

Specifically, HLC-8220GPC (manufactured by Tosoh Corporation) was used as a measuring apparatus, TSKgel, Super Multipore HZ-H (4.6 mmID. times.15 cm, Tosoh Corporation) 3 pieces were used as a column, and THF (tetrahydrofuran) was used as an eluent to carry out GPC. As the measurement conditions, a differential Refractive Index (RI) detector was used, with the sample concentration being 0.45 mass%, the flow rate being 0.35ml/min, the sample injection amount being 10. mu.l, the measurement temperature being 40 ℃. And, the calibration curve was obtained from "standard sample TSK standard, polystyrene" by Tosoh Corporation: 8 samples of "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene" were prepared.

(glass transition temperature)

The glass transition temperature (Tg) of the resin in the resin particles is preferably 30 to 230 ℃, more preferably 70 to 230 ℃ from the viewpoint of abrasion resistance and ink stability.

Tg is a value measured under a conventional measurement condition using a Differential Scanning Calorimeter (DSC) EXSTAR6220 (manufactured by SII NanoTechnology inc.).

However, when it is difficult to measure the Tg by decomposition of the resin, the Tg calculated by the following calculation formula is used. The calculated Tg is calculated by the following equation (a).

1/Tg ═ Sigma (Xi/Tgi) … … equation (a)

In this case, n monomer components, i ═ 1 to n, are copolymerized in the polymer to be calculated. Xi is the mass fraction of the ith monomer (Σ Xi ═ 1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the ith monomer. However, Σ is taken as the sum of 1 to n. In addition, the value of the homopolymer glass transition temperature (Tgi) of each monomer was a value of Polymer Handbook (third edition) (j. brandrup, e.h. immergut (Wiley-Interscience, 1989)).

(content)

The ink of the present invention may contain 1 kind of resin particles alone, or may contain 2 or more kinds.

From the viewpoint of improving the abrasion resistance, the stability of the ink, and the ejection property of the ink, the content of the resin particles relative to the total amount of the ink of the present invention is preferably 1 mass% or more and 20 mass% or less, more preferably 2 mass% or more and 12 mass% or less, and preferably 3 mass% or more and 10 mass% or less.

From the viewpoint of improving the light resistance, the content of the resin particles with respect to the total content of the specific infrared absorbing material and the resin particles is preferably 60 mass% or more and 96 mass% or less.

< coloring agent >

The ink of the present invention may contain at least 1 kind of colorant (e.g., pigment, dye, etc.). The colorant is not particularly limited, and colorants known in the field of inkjet inks can be used.

When the ink of the present invention contains a colorant, a colored image having visibility (i.e., being visually recognizable) can be formed by the ink of the present invention.

The ink of the related aspect can be effectively heated by infrared irradiation when the colored image is formed by heating the ink applied to the substrate, and therefore has an advantage of excellent abrasion resistance.

The colorant includes pigments and dyes, but from the viewpoint of weather resistance, color reproducibility, and the like, pigments are preferred, and organic pigments or inorganic pigments are more preferred.

Examples of the organic pigment include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among them, azo pigments, polycyclic pigments and the like are more preferable.

Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black.

As the colorant, the colorants described in paragraphs 0096 to 0100 of Japanese patent application laid-open No. 2009-241586 are preferable.

When the ink of the present invention is a colored image forming ink, the content of the colorant is preferably 1 to 20% by mass, more preferably 1 to 15% by mass, and still more preferably 1 to 10% by mass, based on the total amount of the ink.

On the other hand, when the ink of the present invention is an ink for forming an infrared-absorbing image having invisibility (i.e., property of being difficult to see), it is preferable that the ink of the present invention contains substantially no colorant from the viewpoint of invisibility of the infrared-absorbing image.

In this case, specifically, when the ink of the present invention contains no colorant or contains a colorant, the content of the colorant is preferably less than 0.1% by mass (more preferably 0.05% by mass or less) with respect to the total amount of the ink.

(dispersing agent)

When the ink of the present invention contains a colorant, the ink of the present invention may further contain a dispersant for dispersing the colorant.

The dispersant may be either a polymer dispersant or a low-molecular surfactant type dispersant. The polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.

As the dispersant, for example, the dispersants described in paragraphs 0080 to 0096 of Japanese patent laid-open publication No. 2016-145312 are preferable.

The mixing mass ratio (p: s) of the colorant (p) and the dispersant(s) is preferably in the range of 1: 0.06 to 1: 3, more preferably in the range of 1: 0.125 to 1: 2, and further preferably in the range of 1: 0.125 to 1: 1.5.

< Water-soluble Polymer Compound >

The ink of the present invention may contain at least 1 kind of water-soluble polymer compound from the viewpoint of further improving the association formability of the specific infrared absorbing material in the ink and in the infrared absorbing image.

The water-soluble polymer compound is not particularly limited, and examples thereof include natural hydrophilic polymer compounds and synthetic hydrophilic polymer compounds described in paragraphs 0021 to 0022 of Japanese patent application laid-open No. 2010-188661.

Examples of the water-soluble polymer compound include vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl ether, polyacrylamides, polyacrylic acid or alkali metal salts thereof, acrylic resins such as water-soluble styrene acrylic resins, water-soluble styrene maleic acid resins, water-soluble vinyl naphthalene acrylic resins, water-soluble vinyl naphthalene maleic acid resins, alkali metal salts of polyvinyl pyrrolidone/polyvinyl alcohol/β -naphthalenesulfonic acid formalin condensates, and salts having a cationic functional group such as quaternary ammonium or amino group in the side chain; a water-soluble polymer compound (particularly preferably gelatin) as an amphoteric compound described later; and the like.

Among them, known water-soluble polymer compounds such as polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, polyethylene glycol, and hydroxypropylmethylcellulose are preferable.

Further, a water-soluble polymer compound (particularly, gelatin) which is an amphoteric compound described later is also preferable.

The weight average molecular weight of the water-soluble polymer compound is not particularly limited, and may be, for example, 5000 to 100000, preferably 10000 to 80000, and more preferably 10000 to 50000.

When the ink of the present invention contains a water-soluble polymer compound, the content of the water-soluble polymer compound is preferably 0.1 to 10% by mass, more preferably 0.1 to 4% by mass, even more preferably 0.1 to 2% by mass, and even more preferably 0.1 to 1% by mass, based on the total amount of the ink.

< surfactant >

The ink of the present invention may contain at least 1 kind of surfactant from the viewpoint of further improving the association formability of the specific infrared absorbing material in the ink and in the infrared absorbing image.

As the surfactant, a compound having a structure in which a hydrophilic portion and a hydrophobic portion are present in a molecule can be effectively used, and any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, and a betaine surfactant can be used.

As the surfactant, from the viewpoint of suppressing the ejection interference of the ink, an anionic surfactant or a nonionic surfactant is preferable, a nonionic surfactant is more preferable, and among them, an acetylene glycol derivative (acetylene glycol-based surfactant) is more preferable.

Examples of the acetylene glycol surfactant include 2, 4, 7, 9-tetramethyl-5-decyne-4, 7-diol and alkylene oxide adducts of 2, 4, 7, 9-tetramethyl-5-decyne-4, 7-diol, and preferably at least 1 selected from these.

Commercially available acetylene glycol surfactants include Surfynol series such as Nissin Chemical Industry co., Surfynol 104PG manufactured by ltd, and E series such as Nissin Chemical Industry co., olfin E1010 manufactured by ltd.

As the surfactant other than the acetylene glycol-based surfactant, a fluorine-based surfactant is preferable. Examples of the fluorine-based surfactant include an anionic surfactant, a nonionic surfactant, and a betaine-based surfactant, and among them, an anionic surfactant is more preferable. Examples of the anionic surfactant include Capscone FS-63, Capscone FS-61 (manufactured by Dupont), Ftergent 100, Ftergent 110, Ftergent 150 (manufactured by Neos), CHEMGUARD S-760P (manufactured by Chemguard Inc.).

< Water-soluble organic Compound X1>

From the viewpoint of further improving the association formability of the specific infrared absorbing material in the ink and in the infrared absorbing image, the ink of the present invention may contain at least 1 water-soluble organic compound X1 having a melting point of 50 ℃ or higher and a molecular weight of less than 3000.

The melting point of the water-soluble organic compound X1 is 50 ℃ or higher.

The water-soluble organic compound X1 is different from the above-mentioned water-soluble organic solvents in this respect.

The water-soluble organic compound X1 is soluble in the ink because of its water solubility. This can adjust the viscosity of the ink to a range suitable for the head, or help to suppress drying and curing near the nozzles, thereby improving the ejection performance.

The molecular weight of the water-soluble organic compound X1 is less than 3000.

When the water-soluble organic compound X1 has a molecular weight distribution, the above molecular weight means a number average molecular weight. The number average molecular weight means a value measured by GPC. The detailed conditions of GPC are as described above.

The molecular weight of the water-soluble organic compound X1 of less than 3000 contributes to improvement of the ejection property of the ink. When the molecular weight of the water-soluble organic compound X1 is less than 3000, the formation or dispersibility of J associations in the ink is not easily hindered. Therefore, the molecular weight of the water-soluble organic compound X1 of less than 3000 also contributes to improvement of infrared absorptivity of an image.

The molecular weight of the water-soluble organic compound X1 is preferably 400 or less, more preferably 200 or less, and further preferably 100 or less.

The lower limit of the molecular weight of the water-soluble organic compound X1 is, for example, 50.

The water-soluble organic compound X1 is not particularly limited as long as it is a compound having water solubility, a melting point of 50 ℃ or higher, and a molecular weight of less than 3000.

Examples of the water-soluble organic compound X1 include polyols having a melting point of 50 ℃ or higher, urea derivatives, saccharides, saccharide derivatives, and hyaluronic acids.

Examples of the polyhydric alcohol having a melting point of 50 ℃ or higher include trimethylolpropane, xylitol, sorbitol and the like.

Examples of the urea derivative include a compound in which a hydrogen atom directly bonded to a nitrogen atom in the structure of urea is substituted with a substituent, thiourea, a compound in which a hydrogen atom directly bonded to a nitrogen atom in the structure of urea is substituted with a substituent, and the like.

Specific examples of the urea derivative include N, N-dimethylurea, thiourea, ethyleneurea, hydroxyethylurea, hydroxybutylurea, ethylenethiourea, diethylthiourea, phenylurea, benzylurea, N-ethyl-N '-phenylurea, ethoxyphenylurea, N' -diphenylurea, N-diphenylurea, tetraphenylurea, and N-benzoylurea.

Examples of the saccharides include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), and polysaccharides.

Specific examples of the saccharide include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, and maltotriose.

The polysaccharide is a sugar in a broad sense, and includes substances widely present in nature, such as alginic acid, α -cyclodextrin, and cellulose.

Examples of the saccharide derivative include reducing sugars (e.g., sugar alcohols) and oxidized sugars (e.g., aldonic acids, uronic acids, amino acids, and thiosugars) of saccharides.

Examples of the sugar alcohol include maltitol, sorbitol, xylitol and the like.

Examples of the hyaluronic acid include a hyaluronate salt.

When the ink contains the hyaluronate, a commercially available sodium hyaluronate 1% aqueous solution (molecular weight of 350000) can be used as a raw material.

The water-soluble organic compound X1 preferably contains at least one of urea and trimethylolpropane. This further improves the abrasion resistance and infrared absorbability of the infrared absorbing material.

When the water-soluble organic compound X1 contains at least one of urea and trimethylolpropane, the total content of urea and trimethylolpropane is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, even more preferably 60 to 100% by mass, and even more preferably 80 to 100% by mass, based on the total content of all the water-soluble organic compounds X1 contained in the ink.

The content (total content when 2 or more are contained) of the water-soluble organic compound X1 with respect to the total amount of the ink is preferably 1 mass% or more and 8 mass% or less.

When the content of the water-soluble organic compound X1 is 1% by mass or more, the effect based on the water-soluble organic compound X1 (that is, improvement of the ejection property of the ink) is exhibited. The content of the water-soluble organic compound X1 is preferably 2% by mass or more, and more preferably 3% by mass or more.

When the content of the water-soluble organic compound X1 is 8% by mass or less, the high polarity of the solvent of the ink can be maintained, and therefore, the J-association formation in the ink is facilitated. Therefore, the content of the water-soluble organic compound X1 of 8 mass% or less contributes to improvement of infrared absorptivity of an image. The content of the water-soluble organic compound X1 is preferably 6% by mass or less.

< other ingredients >

Examples of other components in the ink include additives such as discoloration inhibitors, emulsion stabilizers, permeation enhancers, ultraviolet absorbers, preservatives, antifungal agents, pH adjusters, surface tension adjusters, antifoaming agents, viscosity adjusters, dispersants, dispersion stabilizers, rust inhibitors, and chelating agents. As the above-mentioned components, compounds described in paragraphs 0044 to 0050 of Japanese patent application laid-open No. 2008-144004 can be used.

< surface tension of ink >

The ink of the present invention has a surface tension at 25 ℃ of preferably 60mN/m or less, more preferably 20mN/m to 50mN/m, and still more preferably 25mN/m to 45 mN/m. When the surface tension of the ink is within the above range, the occurrence of curling in the substrate can be suppressed. The Surface tension was measured by the plate method using an Automatic Surface Tensiometer CBVP-Z (Kyowa Interface Science Co., Ltd.).

The Surface tension of the ink of the present invention at 25 ℃ is a value measured by a plate method at 25 ℃ using a Surface tension measuring apparatus (for example, Automatic Surface tensometer CBVP-Z (Kyowa Interface Science Co., Ltd.).

< viscosity >

The viscosity of the ink of the present invention is preferably 0.5 mPas to 30 mPas, more preferably 2 mPas to 20 mPas, preferably 2 mPas to 15 mPas, and still more preferably 2 mPas to 10 mPas.

The viscosity is measured at 30 ℃ by using a VISCOMETER (for example, VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD)).

< maximum absorption wavelength >

The maximum absorption wavelength of the ink of the present invention when used as a dried product is preferably in the range of 700nm to 1200 nm.

From the viewpoint of invisibility of the obtained recorded matter, the maximum absorption wavelength is more preferably in the range of 710nm to 1200nm, still more preferably in the range of 760nm to 1200nm, and particularly preferably in the range of 800nm to 1200 nm.

When the maximum absorption wavelength in the case of a dried product is in the range of 700nm to 1200nm, the obtained infrared absorption image is more excellent in invisibility and readability by a detector using infrared light.

In the present invention, the dried product of the ink is obtained as follows: printing the ink on OK coated Paper (Oji Paper Co., Ltd.) at a dot percentage of 1-100% under the conditions of 7-10 pL and 600dpi, and heating and drying the ink for 1 minute by using warm air at 100 ℃.

The maximum absorption wavelength as a dried product was determined by measuring the reflectance spectrum using a spectrophotometer UV-3100PC (manufactured by Shimadzu Corporation) equipped with a 150mm phi large integrating sphere attachment LISR-3100 (manufactured by Shimadzu Corporation).

From the viewpoint of invisibility and readability of the obtained infrared absorption image, it is preferable that the maximum absorption wavelength of the ink of the present invention in the range of 400nm to 1200nm exists in the range of 700nm to 1200nm when the ink is used as a dried product.

The value of the maximum absorption wavelength can be measured by measuring the optical density in the range of 400nm to 1200nm by the same method as the measurement of the maximum absorption wavelength in the case of the dried product.

The optical concentration was measured by using a spectrophotometer UV-3100PC (manufactured by Shimadzu Corporation) equipped with a 150mm phi large integrating sphere attachment LISR-3100 (manufactured by Shimadzu Corporation).

< J associate >

In the ink of the present invention, it is preferable that at least a part of the infrared absorbing material represented by the formula (1) forms a J-association in a dried product from the viewpoint of invisibility of the obtained infrared absorbing image.

In general, a state in which compounds are fixed to each other by a bonding force such as a covalent bond, a coordinate bond, an intermolecular force (for example, a hydrogen bond, a van der waals force, a coulomb force, or the like) in a specific steric configuration is referred to as an associated (or aggregated) state. From the viewpoint of the absorption wavelength of the associate, an associate whose absorption is shifted to a short wavelength with respect to the absorption of the monomer is referred to as an H-associate (particularly, a dimer), and an associate shifted to a long wavelength is referred to as a J-associate.

The specific infrared absorbing material in the J-associated state shows a sharp absorption spectrum peak because of the formation of a so-called J band. The association and J band of specific infrared absorbing materials are described in detail in the literature (for example, Photographic Science and Engineering Vol 18, No 323-335 (1974)).

The maximum absorption wavelength of the specific infrared absorbing material in the J-associated state is shifted to the long-wavelength side more than the maximum absorption wavelength of the specific infrared absorbing material in the solution state. Therefore, whether the specific infrared absorbing material is in the J-associated state or in the unassociated state can be determined by measuring the maximum absorption wavelength at 400nm to 1200 nm.

In the present invention, when the difference between the maximum absorption wavelength in the range of 700nm to 1200nm in the dried product and the maximum absorption wavelength of a solution in which the specific infrared absorbing material contained in the ink is dissolved in N, N-Dimethylformamide (DMF) is 30nm or more, it is determined that the specific infrared absorbing material in the dried product forms a J-association.

From the viewpoint of improving the invisibility of the obtained infrared absorption image, the difference is preferably 50nm or more, more preferably 70nm or more, and further preferably 100nm or more.

The specific infrared absorbing material may form J-associations in the ink, or may form J-associations in the infrared absorbing image without forming J-associations in the ink during or after the droplets reach the substrate.

Further, it is not necessary that all the specific infrared absorbing materials form J associations on the base material, and the specific infrared absorbing materials forming J associations and the specific infrared absorbing materials in a molecularly dispersed state may be present in a mixture.

As described above, at least a part of the specific infrared absorbing material in the ink of the present invention preferably forms a J-association. This further improves the association formability of the specific infrared absorbing material in the infrared absorption image.

The specific infrared absorbing material preferably forms an association only when dissolved in water, but in order to promote the formation of an association in the ink or in the infrared absorbing image, the ink may contain an amphoteric compound (including a high molecular compound such as gelatin, low molecular collagen, oligopeptide, polyacrylic acid (TOAGOSEI co., ltd. jurymet 410, etc.), amino acid, etc.) in the range of the above-mentioned water-soluble high molecular compound);

salts (for example, alkaline earth metal salts such as barium chloride, strontium chloride, calcium chloride, and magnesium chloride, alkali metal salts such as potassium chloride and sodium chloride, group 13 metal salts such as magnesium chloride, organic salts such as ammonium acetate, and salts containing organic intramolecular salts, organic polycations, and polyanions such as betaine);

acids (inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid, p-toluenesulfonic acid and citric acid);

inorganic bases such as potassium carbonate and sodium hydroxide;

organic bases such as trialkylamine and pyridine; and the like.

These components may be contained in 1 kind alone, or may be contained in 2 or more kinds.

Among the above components, amphoteric compounds are preferable, and gelatin is more preferable.

The content of the amphoteric compound is preferably 10 to 50000ppm (5% by mass), more preferably 30 to 20000ppm (2% by mass), based on the total amount of the ink.

The content of the salt is preferably 10 to 50000ppm (5% by mass), more preferably 30 to 20000ppm (2% by mass), based on the total amount of the ink.

The respective contents of the acid and the base are preferably 10ppm to 50000ppm (5% by mass), more preferably 30ppm to 20000ppm (2% by mass), based on the total amount of the ink.

In the present invention, ppm means ppm on a mass basis (i.e., mass ppm).

< 2-valent alkali metal element and 3-valent group 13 metal element >

The ink of the present invention preferably contains 10ppm to 50000ppm of at least 1 of the 2-valent alkaline earth metal element and the 3-valent group 13 metal element with respect to the total amount of the ink.

Examples of the 2-valent alkaline earth metal include magnesium, calcium, strontium, barium, and radium.

Examples of the group 13 metal element having a valence of 3 include aluminum, gallium, indium and thallium.

The above-mentioned alkaline earth metal element having a valence of 2 or the above-mentioned group 13 metal element having a valence of 3 is preferably an element derived from the above-mentioned alkaline earth metal salt or the above-mentioned group 13 metal salt, respectively.

From the viewpoint of dispersion stability and ejection property of the ink, the content of the alkali metal element having a valence of 2 and the group 13 metal element having a valence of 3 is preferably 10ppm to 50000ppm (5% by mass), more preferably 10ppm to 10000ppm (1% by mass), still more preferably 10ppm to 1000ppm (0.1% by mass), and particularly preferably 10ppm to 100ppm (0.01% by mass), based on the total amount of the ink.

The content of the alkali metal element having a valence of 2 or the group 13 metal element having a valence of 3 is preferably 0.01 equivalent to 1 equivalent, more preferably 0.1 equivalent to 0.8 equivalent, and still more preferably 0.15 equivalent to 0.6 equivalent, as a molar ratio to the specific infrared absorbing material.

The content of the above-mentioned alkali metal element having a valence of 2 or the above-mentioned group 13 metal element having a molar ratio of 0.01 equivalent to the specific infrared absorbing material means that the molar amount of the alkali metal element having a valence of 2 or the above-mentioned group 13 metal element having a valence of 3 per molar amount of the specific infrared absorbing material is 0.01.

The above-mentioned alkali metal element having a valence of 2 and the above-mentioned group 13 metal element having a valence of 3 may contain 1 kind alone, or may contain 2 or more kinds.

When 2 or more types of the alkali metal element having a valence of 2 and the group 13 metal element having a valence of 3 are contained, the content is a total content of 2 or more types.

The content was determined by analyzing a solution in which the ink was diluted with N-methylpyrrolidone and the specific infrared absorbing material was completely dissolved, using a plasma emission spectrometer (OPTIMA 7300DV Perkin Elmer Co., Ltd.).

It is presumed that when the contents of the alkali metal element having a valence of 2 and the group 13 metal element having a valence of 3 are within the above ranges, the metal ions having a valence of 2 or 3 are bonded to the plurality of specific infrared absorbing materials having negative charges to form a bridge structure locally between the specific infrared absorbing materials, thereby further improving the dispersion stability of the ink.

It is also presumed that when the contents of the alkali metal element having a valence of 2 and the group 13 metal element having a valence of 3 are within the above ranges, the formation amount of the bridging structure becomes appropriate, and excessive aggregation of the specific infrared absorbing materials can be suppressed, so that the ink ejection property is maintained.

< method for producing ink >

The method for producing the ink of the present invention is not particularly limited, and the ink can be produced (prepared) by a known ink production method (preparation method).

For example, the ink can be produced by the ink production methods described in each of Japanese patent application laid-open Nos. 5-148436, 5-295312, 7-97541, 7-82515, 7-118584, 11-286637, and 11-286637.

In addition, a preferred embodiment of the method for producing an ink of the present invention is an embodiment including a step of obtaining a composition containing the specific infrared absorbing material and water by dispersing or dissolving the specific infrared absorbing material in water, and a step of mixing the obtained composition with other components of the ink.

Procedure for obtaining the composition

The step of obtaining the composition is a step of obtaining a composition containing the specific infrared absorbing material and water by dispersing or dissolving the specific infrared absorbing material in water.

The content of the specific infrared absorbing material in the composition is preferably 0.1 to 10% by mass, and more preferably 0.1 to 5% by mass, based on the total mass of the composition.

In addition, the composition may further contain a water-soluble polymer compound serving as a surfactant or a dispersant, or an ionic compound including the amphoteric compound, in order to improve dispersibility or association formation.

Examples of the surfactant include surfactants contained in the above-mentioned inks.

The content of the surfactant, the dispersant, and the ionic compound in the water dispersion is preferably 0.1 to 5% by mass based on the total mass of the water dispersion.

The dispersing or dissolving method may be any known dispersing or mixing method without particular limitation, and examples thereof include stirring with a Three-one-motor stirrer or dissolver, dispersion in a medium using a medium such as beads, and a dispersing method using ultrasonic waves.

-a mixing procedure-

The mixing step is a step of mixing the composition obtained in the step of obtaining the above-mentioned composition with other components of the ink (for example, water, a dispersant, resin particles, a surfactant, a dispersant, and the like).

The ink of the present invention can be obtained by the mixing step.

The ink of the present invention may be obtained by filtering the obtained mixed liquid with a filter after the mixing step.

In the mixing step, the content of the specific infrared absorbing material is preferably 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, based on the total amount of the ink.

As a mixing method in the mixing step, a known mixing method can be used without particular limitation, and as an example, a method of stirring the respective components in a container may be mentioned.

[ Infrared-absorbing image forming method ]

The infrared absorption image forming method of the present invention includes a step of applying the ink of the present invention to a substrate by an ink jet method to form an infrared absorption image (hereinafter, also referred to as "infrared absorption image forming step").

The infrared absorption image forming method of the present invention may include other steps as necessary.

< substrate >

The substrate on which the infrared absorption image is formed is not particularly limited as long as it can form the infrared absorption image, and examples thereof include paper, cloth, wood, metal plate, and plastic film.

The paper is not particularly limited, and so-called high-quality paper used for general offset printing or the like, general printing paper mainly composed of cellulose such as coated paper and copperplate paper, ink jet recording paper, or the like can be used without particular limitation.

Further, as the base material, an impermeable base material can also be used. When the non-permeable substrate is used as the substrate, it is preferable to include a step of applying a treatment liquid to the substrate, which will be described later, from the viewpoint of image formability.

The term "non-permeable" of the non-permeable substrate used in the present invention means that water contained in the ink is absorbed little or not, and specifically means that the absorption amount of water is 10.0g/m²The following properties are provided.

The non-permeable substrate used in the present invention is not particularly limited, and examples thereof include a sheet-like substrate and a film-like substrate.

The impermeable base material used in the present invention is preferably an impermeable base material that can be formed into a roll by winding a sheet-like or film-like impermeable base material from the viewpoint of the productivity of printed matter.

Examples of the impermeable substrate include a metal (e.g., aluminum foil), a plastic film (e.g., polyvinyl chloride resin, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal), a plastic, and glass.

Among them, a substrate containing a thermoplastic resin such as polyvinyl chloride, polyethylene terephthalate, or polypropylene is preferable.

The impermeable substrate may be provided with a surface treatment.

Examples of the surface treatment include, but are not limited to, corona plasma treatment, flame treatment, heat treatment, abrasion treatment, light irradiation treatment (UV treatment), flame treatment, and the like. For example, if the surface of the non-permeable substrate is subjected to corona treatment in advance before the ink recorded image is imparted, the surface energy of the non-permeable substrate increases, and wetting of the surface of the non-permeable substrate and adhesion of the ink to the non-permeable substrate are promoted. The Corona treatment can be performed using, for example, a Corona Master (Shinko Electric & Instrumentation co., ltd., PS-10S) or the like. The conditions for the corona treatment may be appropriately selected depending on the kind of the impermeable base material, the composition of the ink, and the like. For example, the following process conditions may be set.

Processing voltage: 10-15.6 kV

Processing speed: 30 to 100mm/s

The visible image may be formed on the substrate by an ink jet method or other known methods.

The visible image may be a visible image formed in a step of forming a visible image described later, or a substrate on which a visible image is formed in the infrared absorption image forming method of the present invention may be used.

< Infrared-ray-absorbing image Forming Process >

The infrared absorption image forming step is a step of applying the ink of the present invention to a substrate by an ink jet method to form an infrared absorption image.

According to this step, ink can be selectively applied to the substrate, and a desired infrared absorption image can be formed.

(Infrared absorption image)

The infrared absorption image formed in this step is not particularly limited, and may be an infrared absorption image composed of a single pattern (e.g., a dot pattern, a line pattern, a solid pattern, or the like), and preferably an infrared absorption image composed of a plurality of element patterns (e.g., a dot pattern, a line pattern, or the like), in other words, an infrared absorption image that is a set of a plurality of element patterns.

The dot pattern preferably has a diameter of 25 μm to 70 μm, more preferably 30 μm to 60 μm.

The maximum absorption wavelength of the infrared absorption image is preferably in the range of 700nm to 1200nm, more preferably in the range of 710hm to 1200nm, still more preferably in the range of 760nm to 1200nm, and particularly preferably in the range of 800nm to 1200 nm.

The maximum absorption wavelength is measured by the same method as that for the ink of the present invention when it is dried.

In addition, from the viewpoint of invisibility of the infrared absorption image and readability by infrared rays, the maximum absorption wavelength in the range of 400nm to 1200nm in the infrared absorption image is preferably in the range of 700nm to 1200 nm.

The maximum absorption wavelength is measured by the same method as that for the ink of the present invention as a dried product.

From the viewpoint of invisibility of the infrared absorption image, in the infrared absorption image in the recorded matter of the present invention, the Optical Density (OD) at 450nm is preferably 1/7 or less of the optical density at the maximum absorption wavelength. The optical density is more preferably 1/8 or less of the optical density at the maximum absorption wavelength, and still more preferably 1/9 or less of the optical density at the maximum absorption wavelength.

From the viewpoint of readability, the optical density at the maximum absorption wavelength of the infrared absorption image is preferably 0.1 or more, more preferably 0.3 or more, and still more preferably 0.5 or more.

The optical density is measured by the same method as that for measuring the optical density when the ink of the present invention is used as a dried product.

In the infrared ray absorption image, the content per unit area of the specific infrared ray absorbing material is preferably 0.0001g/m²～1.0g/m²More preferably 0.0001g/m²～0.5g/m²。

The method of the ink Jet method in the infrared absorption image forming step is not particularly limited, and any known method may be used, for example, a charge control method in which ink is ejected by an electrostatic induction force, a demand ink Jet method (pressure pulse method) in which an ink is irradiated with an electric signal converted into an acoustic beam and the ink is ejected by an irradiation pressure, and a thermal ink Jet method (Bubble Jet (registered trademark)) in which bubbles are formed by heating the ink and the pressure generated is used.

As the ink jet method, the following ink jet methods can be effectively used in particular: in the method described in jp 54-59936 a, a rapid volume change occurs in the ink subjected to the thermal energy, and the ink is ejected from the nozzle by the urging force generated by the state change.

Further, as for the ink jet method, the method described in paragraphs 0093 to 0105 of Japanese patent application laid-open No. 2003-306623 can be also referred to.

As an ink jet head used in the ink jet method, there are a reciprocating type in which recording is performed while scanning the head in the width direction of the substrate using a short, line head, and a line head in which recording elements are arranged over the entire area corresponding to one side of the substrate.

In the line system, by scanning the base material in a direction intersecting the array direction of the recording elements, a pattern can be formed over the entire surface of the base material, and a transport system such as a carriage for scanning a short nozzle is not required.

Further, since only the base material is moved without performing complicated scanning control of the movement of the carriage and the base material, the recording speed can be increased as compared with the reciprocating system.

The image forming method of the present embodiment can be applied to any of these, and the line method is preferred.

The amount of the ink droplets discharged from the ink jet head is preferably 1pL (picoliter, the same applies hereinafter) to 20pL, and more preferably 1.5pL to 10pL, from the viewpoint of obtaining a high-definition pattern.

The amount of the specific infrared absorbing material to be applied per unit area in the infrared absorbing image formed in the present step is preferably 0.0001g/m²～1.0g/m²More preferably 0.0001g/m²～0.5g/m²。

The step (infrared absorption image forming step) may include a step of heating the ink applied to the substrate.

That is, the infrared absorption image forming step may be a step of: the ink of the present invention is applied to a substrate by an ink jet method and the applied ink is heated, thereby forming an infrared absorption image.

When the infrared absorption image forming step includes the heating step, it is considered that the coating film formed of the resin particles is more effectively formed in the infrared absorption image. This further improves the abrasion resistance of the infrared absorption image.

Examples of the mechanism for heating the ink on the substrate include a known heating mechanism such as a heater, a known air blowing mechanism such as a dryer, and a combination thereof.

Examples of the method for heating the ink include a method of heating the substrate from the side opposite to the image forming surface by a heater or the like, a method of blowing hot air or warm air to the image forming surface of the substrate, a method of heating the substrate from the image forming surface or the side opposite to the image forming surface by an infrared heater, and a method of combining a plurality of these.

The heating temperature when heating the ink on the substrate is preferably 60 ℃ or higher, more preferably 65 ℃ or higher, and particularly preferably 70 ℃ or higher.

The upper limit of the heating temperature is not particularly limited, but is preferably 150 ℃ or lower, for example.

The heating time when the ink on the substrate is heated is not particularly limited, but is preferably 1 second to 300 seconds, more preferably 1 second to 30 seconds.

< Process for applying treatment liquid to substrate (treatment liquid applying Process) >

The infrared absorption image forming method of the present invention may include a step of applying a treatment liquid containing a flocculant onto the substrate (hereinafter, also referred to as "treatment liquid applying step") before the infrared absorption image forming step.

Preferred modes of treating the liquid will be described below.

When the infrared absorption image forming method of the present invention includes the treatment liquid applying step, in the infrared absorption image forming step, an ink is applied to at least a part of a region of the substrate to which the treatment liquid is applied, thereby forming an infrared absorption image.

When the infrared absorption image forming method of the present invention includes the treatment liquid applying step, the components in the ink can be aggregated in the infrared absorption image forming step, and therefore an infrared absorption image having more excellent image quality can be formed.

When the infrared absorption image forming method of the present invention in which a non-permeable substrate is used as a substrate includes a treatment liquid applying step, bleeding of the infrared absorption image can be further suppressed.

The infrared absorption image forming method of the present invention including the treatment liquid applying step is also advantageous in that the association formability of the specific infrared absorbing material in the infrared absorption image is improved.

The treatment liquid can be applied to the substrate by applying a known method such as a coating method, an ink jet method, or a dipping method.

Examples of the coating method include known coating methods using a bar coater (e.g., a wire bar coater), an extrusion die coater, an air knife coater, a bar coater, a knife coater, a squeeze coater, a reverse roll coater, a gravure coater, a flexographic coater, and the like.

The details of the ink jet method are the same as those of the ink jet method applicable to the infrared absorption image forming step.

In the treatment liquid application step, the treatment liquid is preferably applied to the substrate in a pattern image by an ink jet method.

In the treatment liquid application step, the substrate may be heated before the treatment liquid is applied.

The heating temperature is preferably 20 to 50 ℃ and more preferably 25 to 40 ℃ for the base material.

In the treatment liquid application step, the treatment liquid may be heated and dried after the treatment liquid is applied and before the infrared absorption image forming step.

Examples of the means for heating and drying the treatment liquid include known heating means such as a heater, known air blowing means such as a dryer, and a combination thereof.

Examples of the method for heating and drying the treatment liquid include a method of heating the substrate from the side opposite to the side to which the treatment liquid is applied by a heater or the like, a method of blowing warm air or hot air to the side to which the treatment liquid is applied of the substrate, a method of heating the substrate from the side to which the treatment liquid is applied or the side opposite to the side to which the treatment liquid is applied by an infrared heater, and a method of combining a plurality of these.

The heating temperature at the time of heating and drying the treatment liquid is preferably 35 ℃ or higher, more preferably 40 ℃ or higher.

The upper limit of the heating temperature is not particularly limited, but is preferably 100 ℃, more preferably 90 ℃, and still more preferably 70 ℃.

The time for the heat drying is not particularly limited, but is preferably 0.5 to 60 seconds, more preferably 0.5 to 20 seconds, and particularly preferably 0.5 to 10 seconds.

(treatment solution)

Coagulant(s) -

The treatment liquid contains a coagulant.

The flocculant is preferably at least 1 selected from the group consisting of polyvalent metal salts, organic acids, inorganic acids, cationic compounds and metal complexes.

Details regarding each component will be described below.

When the processing liquid contains the aggregating agent, the ink aggregates and an image having excellent image quality can be easily obtained.

Organic acids-

Examples of the organic acid include organic compounds having an acidic group.

Examples of the acidic group include a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, and a carboxyl group. The acidic group is preferably a phosphoric group or a carboxyl group, and more preferably a carboxyl group, from the viewpoint of the coagulation rate of the ink.

At least a part of the acidic groups are preferably dissociated in the treatment solution.

The organic compound having a carboxyl group is preferably polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid (preferably DL-malic acid), maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, phthalic acid, 4-methylphthalic acid, lactic acid, sulfonic acid, orthophosphoric acid, pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, or a derivative of these compounds or a salt of these compounds, and the like. These compounds may be used in 1 kind, or 2 or more kinds may be used simultaneously.

As the organic compound having a carboxyl group, a carboxylic acid having a valence of 2 or more (hereinafter, also referred to as a polycarboxylic acid) is preferable from the viewpoint of the coagulation rate of the ink.

As the polycarboxylic acid, malonic acid, malic acid, maleic acid, succinic acid, glutaric acid, fumaric acid, tartaric acid, 4-methylphthalic acid or citric acid is more preferable, and malonic acid, malic acid, glutaric acid, tartaric acid or citric acid is preferable.

The organic acid preferably has a low pKa (e.g., 1.0 to 5.0).

Thus, the surface charge of particles such as pigments and polymer particles in an ink, which are stably dispersed by a weakly acidic functional group such as a carboxyl group, is reduced by contacting with an organic acidic compound having a lower pKa, and the dispersion stability can be lowered.

The organic acid contained in the treatment liquid preferably has a low pKa, a high solubility in water, and a valence of 2 or more, and more preferably is a 2-or 3-valent acidic substance having a high buffering capacity in a pH region having a pKa lower than a functional group (for example, a carboxyl group or the like) that stabilizes the dispersion of particles in the ink.

When an organic acid is used as the flocculant, the content of the organic acid is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and still more preferably 5 to 10% by mass, based on the total amount of the treatment liquid.

Inorganic acid-

The inorganic acid may include a compound such as sulfuric acid, hydrochloric acid, nitric acid, or phosphoric acid.

When an inorganic acid is used as the coagulant, the content of the inorganic acid is preferably 1 to 40% by mass, more preferably 2 to 30% by mass, and still more preferably 5 to 20% by mass, based on the total amount of the treatment liquid.

Polyvalent metal salts

The polyvalent metal salt is composed of a polyvalent metal ion having a valence of 2 or more and an anion bonded to the polyvalent metal ion. Also, the polyvalent metal salt is preferably water-soluble.

Specific examples of the polyvalent metal ion include Ca²⁺、Cu²⁺、Ni²⁺、Mg²⁺、Zn²⁺、Ba²⁺Isovalent 2 metal ion, Al³⁺、Fe³⁺、Cr³⁺And 3 valence metal ions are added. Examples of the anion include Cl^-、NO₃ ^-、I^-、Br^-、ClO₃ ^-、SO₄ ^2-Carboxylate ions, and the like.

The polyvalent metal salt is preferably constituted to contain Ca from the viewpoint of the quality of the obtained infrared absorption image²⁺Or Mg²⁺A salt.

Further, as the polyvalent metal salt, sulfate ion (SO) is preferable₄ ^2-) Nitrate ion (NO)₃ ^-) Or carboxylate ions (RCOO)^-And R represents an alkyl group having 1 or more carbon atoms).

Among them, the carboxylate ions are preferably derived from a saturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms or a carbocyclic monocarboxylic acid having 7 to 11 carbon atoms. Preferred examples of the saturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, and hexanoic acid. Formic acid and acetic acid are particularly preferable.

When a polyvalent metal salt is used as the coagulant, the content of the polyvalent metal salt is preferably 1 to 40% by mass, more preferably 2 to 25% by mass, and still more preferably 5 to 20% by mass, based on the total amount of the treatment liquid of the present invention.

Cationic compounds

The cationic compound is preferably a primary amine salt type compound, a secondary amine salt type compound, or a tertiary amine salt type compound, for example. Examples of the amine salt type compound include compounds such as hydrochloride and acetate (for example, laurylamine, cocoamine, stearylamine, and pinorethylamine), quaternary ammonium salt type compounds (for example, lauryltrimethylammonium chloride, cetyltrimethylammonium chloride, lauryldimethylbenzylammonium chloride, benzyltributylammonium chloride, benzalkonium chloride, etc.), pyridinium salt type compounds (for example, cetylpyridinium chloride, cetylpyridinium bromide, etc.), imidazoline type cationic compounds (for example, 2-heptadecyl-hydroxyethylimidazoline, etc.), and ethylene oxide adducts of higher alkylamines (for example, dihydroxybenzylethylstearylamine, etc.). Also, polyallylamines can be used.

The polyallylamine or polyallylamine derivative is not particularly limited, and known materials can be appropriately selected and used, and examples thereof include polyallylamine hydrochloride, polyallylamine amide sulfate, allylamine hydrochloride/diallylamine hydrochloride copolymer, allylamine acetate/diallylamine acetate copolymer, allylamine hydrochloride/dimethylallylamine hydrochloride copolymer, allylamine/dimethylallylamine copolymer, polydiallylamine hydrochloride, polydiallylamine/dimethylallylamine hydrochloride, polydiallylamine amide sulfate, polydiallylamine acetate, polydiallyldimethylammonium chloride, diallylamine acetate/sulfur dioxide copolymer, diallylmethylammonium ethylsulfanate/sulfur dioxide copolymer, polyallylamine hydrochloride/diallyl amine acetate copolymer, polyallylamine sulfate/sulfur dioxide copolymer, polyallylamine sulfate, polyallylamine sulfate, polyallylamine, or polyallylamine derivatives, and polyallylamine derivatives, and the like, Methyl diallyl amine hydrochloride/sulfur dioxide copolymer, diallyl dimethyl ammonium chloride/acrylamide copolymer, and the like.

When the cationic compound is a polymer, a water-soluble polymer is preferable.

As such polyallylamine or polyallylamine derivatives, commercially available products can be used, for example, "PAA-HCL-01", "PAA-HCL-03", "PAA-HCL-05", "PAA-HCL-3L", "PAA-HCL-10L", "PAA-H-HCL", "PAA-SA", "PAA-01", "PAA-03", "PAA-05", "PAA-08", "PAA-15C", "PAA-25", "PAA-H-10C", "PAA-D11-HCL", "PAA-D41-HCL", "PAA-D19-HCL", "PAS-21 CL", "PAS-M-1L", "PAS-M-1", "PAS-22 SA "PAS-M-1A", "PAS-H-1L", "PAS-H-5L", "PAS-H-10L", "PAS-92A", "PAS-J-81L", "PAS-J-81" (trade name, NITTOBO MEDICAL CO., LTD.), "Himo Neo-600", "Himoloc Q-101", "Himoloc Q-311", "Himoloc Q-501", "Himax SC-505" (trade name, HYMO CORPORATION), and the like.

When a cationic compound is used as the flocculant, the content of the cationic compound is preferably 1 to 40% by mass, more preferably 2 to 25% by mass, and still more preferably 5 to 20% by mass, based on the total amount of the treatment liquid.

Metal complexes

The metal complex is a compound in which a ligand is coordinated to a metal ion such as a zirconium ion, a titanium ion, or an aluminum ion.

As the metal complex, various commercially available metal complexes can be used.

Also, various polydentate ligands capable of forming various organic ligands, particularly metal chelate catalysts, are commercially available. Therefore, as the metal complex, a metal complex prepared by combining a commercially available organic ligand and a metal can be used.

Examples of the metal complex include zirconium tetraacetylacetonate (e.g., "ORGATIX ZC-150" of Matsumoto Fine Chemical co., ltd.), zirconium monoacetylacetonate (e.g., "ORGATIX ZC-540" of Matsumoto Fine Chemical co., ltd.), zirconium bisacetylacetonate (e.g., "ORGATIX ZC-550" of Matsumoto Fine Chemical co., ltd.), zirconium monoethylacetoacetate (e.g., "ORGATIX ZC-560" of Matsumoto Fine Chemical co., ltd.), zirconium acetate (e.g., "ORGATIX ZC-115" of Matsumoto Fine Chemical co., ltd.), titanium diisopropoxybis (e.g., "ORGATIX ZC-100" of Matsumoto Chemical co., ltd.), titanium tetraacetylacetonate (e.g., "ORGATIX TC"), titanium tetraacetylacetonate (e.g., titanium dioctoate (e.g., "ORGATIX ZC-401" of Matsumoto Fine Chemical co., ltd. "ORGATIX TC-200" of ltd., diisopropoxybis (ethylacetoacetate) titanium (e.g., "ORGATIX TC-750" of Matsumoto Fine Chemical co., ltd.), zirconium tetraacetylacetonate (e.g., "ORGATIX ZC-700" of Matsumoto Fine Chemical co., ltd.), zirconium tributoxydonoacetylacetonate (e.g., "ORGATIX ZC-540" of Matsumoto Fine Chemical co., ltd., zirconium monobutoxyacetylacetonate) (e.g., "ORGATIX-570" of Matsumoto Fine Chemical co., ltd.), zirconium dibutoxybis (ethylacetoacetate) (e.g., "ORGATIX-580" of Matsumoto Fine Chemical co., ltd., titanium acetate-300 "of Matsumoto co., ltd., titanium lactate-300" of Matsumoto Chemical co., ltd., titanium lactate (Matsumoto Fine Chemical co., ltd. "ORGATIX TC-310, 315"), titanium triethanolamine (Matsumoto Fine Chemical co., ltd. "ORGATIX TC-400"), a zirconium dichloride compound (Matsumoto Fine Chemical co., ltd. "ORGATIX ZC-126").

Among them, preferred are titanium ammonium lactate (Matsumoto Fine Chemical co., ltd. "ORGATIX TC-300"), titanium lactate (Matsumoto Fine Chemical co., ltd. "ORGATIX TC-310, 315"), titanium triethanolamine (Matsumoto Fine Chemical co., ltd. "ORGATIX TC-400"), and zirconium chloride compound (Matsumoto Fine Chemical co., ltd. "ORGATIX ZC-126").

Water-

The treatment liquid preferably contains water.

The content of water is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass or more, based on the total amount of the treatment liquid.

The upper limit of the water content relative to the total amount of the treatment liquid is appropriately determined depending on the amount of other components such as a flocculant. The upper limit of the water content relative to the total amount of the treatment liquid is preferably 95% by mass or less, more preferably 90% by mass or less, and still more preferably 85% by mass or less.

Water-soluble organic solvent

The treatment liquid may contain at least 1 kind of water-soluble organic solvent.

As the water-soluble organic solvent, a known water-soluble organic solvent can be used without particular limitation.

Examples of the water-soluble organic solvent include glycols such as glycerin, 1, 2, 6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentanediol, and dipropylene glycol; polyhydric alcohols such as alkanediols such as 2-butene-1, 4-diol, 2-ethyl-1, 3-hexanediol, 2-methyl-2, 4-pentanediol, 1, 2-octanediol, 1, 2-hexanediol, 1, 2-pentanediol, and 4-methyl-1, 2-pentanediol; saccharides or sugar alcohols, hyaluronic acids, alkyl alcohols having 1 to 4 carbon atoms, glycol ethers, 2-pyrrolidone, N-methyl-2-pyrrolidone, and the like described in section 0116 of Japanese patent application laid-open No. 2011-42150.

Among them, from the viewpoint of suppressing image peeling, polyalkylene glycol or a derivative thereof is preferable, and at least 1 selected from the group consisting of diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, dipropylene glycol, tripropylene glycol monoalkyl ether, polyoxypropylene glycerol ether, and polyoxyethylene polyoxypropylene glycol is more preferable.

When the treatment liquid contains a water-soluble organic solvent, the content of the water-soluble organic solvent is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, based on the total amount of the treatment liquid, from the viewpoint of coatability and the like.

Surfactants-

The treatment liquid may contain at least 1 surfactant.

Surfactants can be used as surface tension modifiers or defoamers.

Examples of the surface tension adjusting agent and the defoaming agent include nonionic surfactants, cationic surfactants, anionic surfactants, and betaine surfactants. Among them, anionic surfactants are preferable from the viewpoint of the coagulation rate of the ink.

The anionic surfactant can be appropriately selected from known anionic surfactants, and examples thereof include sulfate ester salts, sulfonates, phosphates, fatty acid salts, formalin condensates, and the like. Examples of the cation forming the salt include an ammonium ion, a triethanolamine ion, and a metal cation. Among these cations, the metal cation having a valence of 1 is more preferable, and sodium ion or potassium ion is particularly preferable.

As the surfactant, there may be mentioned those exemplified as surfactants in Japanese patent application laid-open No. Sho 59-157636, pages 37 to 38 and Research Disclosure No.308119 (1989). Further, fluorine (fluorinated alkyl) surfactants and silicone surfactants described in each of Japanese patent application laid-open Nos. 2003-322926, 2004-325707, and 2004-309806 can be cited.

The content of the surfactant may be adjusted as appropriate so that the surface tension of the treatment liquid falls within the range described below.

Other additives

The treatment liquid may contain other components than those described above as necessary.

Examples of the other components that can be contained in the treatment liquid include known additives such as a solid wetting agent, colloidal silica, an inorganic salt, a discoloration inhibitor, an emulsion stabilizer, a penetration enhancer, an ultraviolet absorber, a preservative, an antifungal agent, a pH adjuster, a viscosity adjuster, an antirust agent, and a chelating agent.

Physical Properties of the treatment liquid

From the viewpoint of the coagulation rate of the ink, the pH of the treatment liquid at 25 ℃ is preferably 0.1 to 3.5.

When the pH of the treatment liquid is 0.1 or more, the roughness of the base material can be further reduced, and the adhesion of the image portion can be further improved.

When the pH of the treatment liquid is 3.5 or less, the coagulation rate is further increased, and the coalescence of dots (ink dots) caused by the ink on the substrate can be further suppressed, whereby the roughness of the image can be further reduced.

The pH (25 ℃) of the treatment liquid is more preferably 0.2 to 2.0.

From the viewpoint of the aggregation speed of the ink, the viscosity of the treatment liquid is preferably in the range of 0.5 to 30 mPas, more preferably in the range of 1 to 20 mPas, even more preferably in the range of 2 to 15 mPas, and still more preferably in the range of 2 to 10 mPas.

The viscosity of the treatment solution was measured at 25 ℃ using VISCOMETER TV-22(TOKI SANGYO co., LTD.).

The surface tension of the treatment liquid at 25 ℃ is preferably 60mN/m or less, more preferably 20mN/m to 50mN/m, and still more preferably 30mN/m to 45 mN/m.

When the surface tension of the treatment liquid is within the range, the adhesion between the substrate and the treatment liquid is improved.

The Surface tension of the treatment solution was measured by a plate method using an Automatic Surface densitometer CBVP-Z (Kyowa Interface Science Co., Ltd.).

< Process for Forming visible image >

The infrared absorption image forming method of the present invention may further include a step of forming a visible image.

In the present invention, the visible image is an image which can be visually recognized, and is preferably an image formed with an ink other than the ink of the present invention (for example, a coloring ink containing a colorant).

The step of forming a visible image is not particularly limited, and examples thereof include a step of forming an image by a known printing method such as printing by an ink jet method, screen printing, gravure printing, flexo printing, and the like.

In the infrared absorption image forming method of the present invention, the step of forming the visible image may be included before the step of forming the infrared absorption image or may be included after the step of forming the infrared absorption image.

< step of Forming overcoat layer >

The infrared absorption image forming method of the present invention may further include a step of forming an overcoat layer after the step of forming the infrared absorption image.

As a method for forming the overcoat layer, for example, a method in which an overcoat composition containing the same resin particles as those contained in the ink of the present invention is applied to an image formed in a step of forming an infrared-absorbing image and heated can be given.

(composition for external application)

The overcoat composition preferably contains the same resin particles as those contained in the ink of the present invention and/or a polymer compound other than those contained in the ink of the present invention.

The overcoat composition preferably contains the same water-soluble organic solvent, surfactant, and water as the resin particles contained in the ink of the present invention. The composition for external application preferably contains additives such as a fading inhibitor, an emulsion stabilizer, a penetration enhancer, an ultraviolet absorber, a preservative, an antifungal agent, a pH adjuster, a surface tension adjuster, an antifoaming agent, a viscosity adjuster, a dispersant, a dispersion stabilizer, a rust inhibitor, and a chelating agent as other components.

The components contained in the overcoat composition have the same meanings as those contained in the ink of the present invention, and the preferable modes are also the same.

(method of applying composition for external coating)

The method of applying the composition for external coating is not particularly limited, and examples thereof include methods such as spray coating, coating with an application roll or the like, applying by an ink jet method, and dipping, and the ink jet method is preferable.

The application of the external coating composition by the ink jet method can be performed by the same method as the ink jet method in the step of forming the infrared absorption image.

(heating method)

The overcoat layer is formed by heating the overcoat composition formed on the infrared-absorbing image, for example, to form a coating film based on resin particles in the overcoat composition. Upon heating, drying may be performed.

The heating method in the step of forming the overcoat layer can be performed by the same method as the heating method for the ink.

< Process for Forming protective film >

The infrared absorption image forming method of the present invention may further include a method of forming a protective film after the step of forming the infrared absorption image.

The protective film is not particularly limited, and preferably has a transmittance of 50% or more at the maximum absorption wavelength of an infrared absorption image at a wavelength of 700nm to 1200 nm.

Examples of the material of the protective film include resin and glass.

The method for forming the protective film is not particularly limited, and examples thereof include a method of disposing a protective film on an infrared absorption image, a method of adhering a protective film by a known adhesion method, and the like. Examples of the known adhesion method include a method using an adhesive and a lamination method.

[ image Forming method ]

The image forming method of the present invention includes a step of forming an infrared absorption image on a substrate by the above-described infrared absorption image forming method of the present invention (hereinafter, also referred to as "infrared absorption image forming step") and a step of obtaining an image by irradiating the infrared absorption image with infrared light (hereinafter, also referred to as "infrared irradiation step").

The image forming method of the present invention may include other processes as necessary.

In the image forming method of the present invention, the specific infrared absorbing material of the infrared absorbing image formed in the infrared absorbing image forming step is excellent in association formability (in other words, excellent in infrared absorbability).

In the image forming method of the present invention, the infrared absorption image having excellent infrared absorbability is used as a precursor, and the precursor is irradiated with infrared rays in the infrared irradiation step to obtain an image. By this irradiation with infrared rays, the infrared-ray-absorbing image (precursor) absorbs infrared rays to generate heat, and the precursor itself is efficiently heated by this heat, so that an image excellent in abrasion resistance can be obtained.

The image forming method of the present invention is suitable for forming a visible image (e.g., a colored image).

When a colored image is obtained by the image forming method of the present invention, it is preferable to use an ink containing a colorant as the ink of the present invention, and form an infrared-absorbing image of the colored image in the infrared-absorbing image forming step.

In the infrared irradiation step, infrared rays are irradiated onto the infrared absorption image of the coloring image system, thereby efficiently heating the infrared absorption image of the coloring image system. Therefore, a colored image excellent in abrasion resistance can be obtained.

In the obtained colored image, the infrared absorbability (i.e., the association of the specific infrared absorbing materials) may or may not remain.

< Infrared-ray-absorbing image Forming Process >

The infrared absorption image forming step is a step of forming an infrared absorption image (precursor) on a substrate by the above-described infrared absorption image forming method of the present invention.

As for the infrared absorption image forming step, reference can be made to the above-described one of the infrared absorption image forming methods of the present invention.

However, in the infrared absorption image forming step, heating of the ink after the ink is applied to the substrate may be omitted.

< Infrared irradiation step >

The infrared irradiation step is a step of irradiating an infrared absorption image (precursor) with infrared rays to obtain an image.

In this step, the infrared-ray-absorbed image (precursor) is irradiated with infrared rays, and the infrared-ray-absorbed image (precursor) absorbs the infrared rays, thereby generating heat. The infrared absorption image (precursor) itself is effectively heated by the generated heat.

The infrared absorbability may or may not remain in the precursor after the infrared absorption.

The infrared ray is preferably an infrared ray having a maximum emission wavelength in a wavelength region of 700nm to 1500nm, more preferably an infrared ray having a maximum emission wavelength in a wavelength region of 780nm to 1500nm, and still more preferably an infrared ray having a maximum emission wavelength in a wavelength region of 800nm to 1500 nm.

In the infrared irradiation step, an image can be obtained as follows: not only the infrared ray absorption image (precursor) is irradiated with infrared rays, but also the infrared ray absorption image (precursor) is actively heated by the heating mechanism.

As the heating conditions in this case, the preferable heating conditions in the infrared absorption image forming method of the present invention can be applied.

< other Process >

The image forming method of the present invention may include other processes.

As for the other steps, other steps (a step of forming a visible image, a step of forming an overcoat layer, a step of forming a protective film, and the like) in the infrared absorption image forming method of the present invention can be applied to the image forming method of the present invention.

Examples

Examples of the present invention will be described below, but the present invention is not limited to the following examples.

In the following, unless otherwise specified, "part" and "%" represent "part by mass" and "% by mass", respectively.

Hereinafter, ultrapure water is used as water.

[ example 1-1 ]

< preparation of ink >

Compound C-36 as a specific infrared absorbing material was added to water and dispersed for 3 hours with a bead mill, and then propylene glycol as a water-soluble organic solvent (solvent type X) and the following surfactant were added thereto and stirred for 60 minutes. The obtained composition was filtered with a filter having a pore size of 5 μm, thereby obtaining an ink having the following composition.

Composition of the ink

Compound C-36 (specific infrared absorbing Material) … … 0.5.5% by mass

Propylene glycol (manufactured by FUJIFILM Wako Pure Chemical Corporation) [ water-soluble organic solvent; solvent type X … … 20 wt%

OLFINE E1010(Nissin Chemical Industry C0., Ltd.) [ acetylene surfactant ] … … 0.5.5% by mass

The remaining amount of water … … as a whole being 100 mass%

< evaluation >

Using the above ink, the following evaluations were carried out.

The results are shown in Table 1.

(Association Forming Property of specific Infrared absorbing Material in Infrared absorbing image)

The ink was filled in an ink cartridge attached to an ink jet recording apparatus (FUJIFILM DMP-2831), applied to a coated paper (OK TopKOTE) in a solid image form at a dot percentage of 100% under conditions of 600dpi × 600dpi (dots per inch) and a dropping amount of 10pL, and then dried with warm air at 100 ℃ for 1 minute. Thereby, an infrared absorption image (solid image) was formed on the coated paper.

The obtained film was measured for the lowest reflectance α in the wavelength region of 900nm or more and the lowest reflectance β in the wavelength region of 600nm or more and less than 850nm, respectively, using an integrating sphere unit of ultraviolet-visible near-infrared spectrophotometer "V-570" manufactured by JASCO Corporation.

The ratio of the reflectance α to the reflectance β (hereinafter also referred to as α/β ratio) was obtained, and the association formability of the specific infrared absorbing material in the infrared absorption image was evaluated based on the obtained α/β ratio according to the following evaluation criteria.

In the evaluation criteria described below, the grade "a" is the most excellent in the association formability of the specific infrared absorbing material in the infrared absorption image.

Evaluation criteria for association formability of specific infrared absorbing material in infrared absorption image-

A: the alpha/beta ratio is less than 0.8.

B: the alpha/beta ratio is 0.8 or more and less than 1.1.

C: the alpha/beta ratio is 1.1 or more and less than 1.5.

D: the alpha/beta ratio is 1.5 or more and less than 2.0.

E: the α I β ratio is 2.0 or more.

[ examples 1-2 to 8-7 and comparative examples 1-1 to 7-3 ]

The same operations as in example 1-1 were carried out except that the ink compositions were changed as shown in tables 1 to 3.

The results are shown in tables 1 to 3.

Description of tables 1 to 3

The numerical values shown in the column of the respective components indicate the content (mass%) of the ink relative to the total amount of the ink.

The blank column indicates that the corresponding component is not contained.

The SP value has units of MPa^1/2。

The "remaining amount" as the amount of water means a remaining amount for making the entire ink 100 mass%.

The abbreviations and components in tables 1 to 3 are as follows.

PG … … propylene glycol (manufactured by FUJIFILM Wako Pure Chemical Corporation) [ solvent type X ]

DPG … … dipropylene glycol (manufactured by FUJIFILM Wako Pure Chemical Corporation)

DEGmBE … … diethylene glycol monobutyl ether (manufactured by FUJIFILM Wako Pure Chemical Corporation)

E1010 … … OLFINE E1010(Nissin Chemical Industry CO., Ltd.)

[ acetylene surfactant ]

Gelatin … … Nitta Gelatin Inc

As shown in tables 1 to 3, the infrared absorbing material used herein contains a specific infrared absorbing material, a water-soluble organic solvent and water, and the content of the water-soluble organic solvent is 5 to 45% by massSP value 27.5MPa^1/2In each example (for example, example 1-1) of the ink in which the ratio of the solvent type X in the water-soluble organic solvent is 50 mass% or more, the specific infrared absorbing material in the infrared absorbing image is excellent in the association formability.

On the other hand, in each of the comparative examples (for example, comparative example 1-1) in which the ratio of the solvent type X in the water-soluble organic solvent was less than 50 mass% and each of the comparative examples (for example, comparative example 1-3) in which the content of the water-soluble organic solvent exceeded 45 mass%, the association formability of the specific infrared absorbing material in the infrared absorption image was lowered.

For example, from the comparison between examples 1-1 and 1-2, it is understood that when the content of the water-soluble organic solvent is 5 to 30% by mass (example 1-1), the association formability of the specific infrared absorbing material in the infrared absorption image is further improved.

[ example 9-1 ]

< preparation of ink >

The ink of example 7-1 was prepared.

< preparation of treating solution >

The following components were mixed to obtain a treatment solution having the following composition.

Composition of the treatment liquid

Diethylene glycol monoethyl ether … … 4 mass%

Tripropylene glycol monomethyl ether … … 4 mass%

… … 2.6.6% by mass of 1, 2, 3-propanetricarboxylic acid

Malonic acid … … 7.3.3% by mass

Malic acid … … 7.3.3% by mass

Phosphoric acid … … 4.3.3% by mass

The following water-soluble polymer 1 … … 2.5.5% by mass

Benzotriazole … … 1 mass%

Anionic surfactant (sodium dodecylbenzenesulfonate) … … 0.5.5% by mass

Silicone emulsion (solid content 15 mass%) … … 0.1.1 mass%

The remaining amount of water … … as a whole being 100 mass%

[ chemical formula 18]

Water-soluble Polymer 1

(Mw＝45000)

The ratio of each structural unit (the lower right number of each structural unit) in the water-soluble polymer 1 is a mass ratio.

Water-soluble polymer 1 was synthesized as follows.

30.0g of isopropyl alcohol was added to a 200ml three-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet, and the temperature was raised to 65 ℃ under a nitrogen atmosphere.

Next, 30.0g of methyl methacrylate, 6.5g of ethyl acrylate, 13.5g of 2-acrylamido-2-methylpropanesulfonic acid, 30g of isopropyl alcohol, 15g of water, and 2.97g ((0.0129 mol); polymerization initiator manufactured by FUJIFILM Wako Pure Chemical Corporation) of "V-601" ("3 mol") were added dropwise at the same rate over 2 hours.

After completion of the dropwise addition, the mixture was stirred for 2 hours, and then 1.48g (1.5 mol% based on the total moles of the monomers) of "V-601" and 3.0g of isopropyl alcohol were added thereto, followed by stirring for 2 hours.

The obtained polymer solution was neutralized with an aqueous solution of sodium hydroxide in an amount equal to the number of moles of the above 2-acrylamido-2-methylpropanesulfonic acid, isopropanol was distilled off by concentration under reduced pressure, and water was added until the total amount of the polymer solution became 310g, thereby obtaining an aqueous polymer solution containing 16 mass% of the water-soluble polymer 1.

The weight average molecular weight (Mw) of the obtained water-soluble polymer was 45000.

< evaluation >

The following evaluations were carried out using the above ink and the above treatment liquid.

(evaluation of invisibility of image)

The treatment liquid was applied to a coated Paper (Oji Paper co., ltd., manufactured by okkote) as a substrate with a #0 bar (MATSUO SANGYO co., ltd., manufactured by ltd.).

The ink was filled in an ink cartridge attached to an ink jet recording apparatus (FUJIFILM DMP-2831), and applied to the surface of the coated paper coated with the treatment liquid at a dot percentage of 5% under conditions of 600dpi × 600dpi (dots per inch) and a dropping amount of 10 pL. The ink thus applied was dried with warm air at 100 ℃ for 1 minute, whereby an infrared absorption image was obtained.

The obtained infrared absorption image was visually observed, and the invisibility of the infrared absorption image was evaluated according to the following evaluation criteria.

As a result, the result of the invisibility evaluation was "a" (i.e., the invisibility of the image was excellent).

Evaluation criteria for invisibility of images-

A: the dots of the infrared absorption image are hardly visible, and the image is excellent in invisibility.

B: when the point of the infrared absorption image is observed, the point is at a level that can be visually detected, and the invisibility of the image is within the allowable range for practical use.

C: the level of dots of the infrared absorption image can be easily detected, and the invisibility of the image is poor.

[ example 9-2 ]

The same operation as in example 9-1 was carried out except that the ink of example 7-1 was changed to the ink of example 7-2.

As a result, the result of the invisibility evaluation was "a" (i.e., the invisibility of the image was excellent).

[ example 9-3 ]

The same evaluation as in example 9-1 was carried out except that the treatment liquid was not applied and a dot image was directly formed on the substrate using the ink of example 7-1.

As a result, the invisibility evaluation result was "B".

[ examples 9 to 4]

The same evaluation as in example 9-2 was carried out except that the treatment liquid was not applied and a dot image was directly formed on the substrate using the ink of example 7-2.

As a result, the invisibility evaluation result was "B".

[ examples 10-1 to 10-7 ]

Each of the inks of examples 1-1, 2-1, 3-1, 4-1, 5-1, 6-1 and 7-1 was added with an aqueous dispersion of the following resin particles A-1 (acrylic resin particles) so that the content of the resin particles A-1 (solid content) was 3% by mass based on the total amount of the ink, thereby producing 10-1 to 10-7 inks. In this case, the contents of the components other than the contents of the resin particles A-1 and water in each ink were adjusted to be constant.

(preparation of resin particle A-1)

Methyl ethyl ketone (540.0g) was added to a 2L three-necked flask equipped with a mechanical stirrer, a thermometer, a reflux condenser and a nitrogen inlet, and the temperature was raised to 75 ℃. While the temperature in the reaction vessel was kept at 75 ℃, a mixed solution composed of methyl methacrylate (108g), isobornyl methacrylate (388.8g), methacrylic acid (43.2g), methyl ethyl ketone (108g) and "V-601" (manufactured by FUJIFILM Wako Pure Chemical Corporation) (2.1g) was added dropwise at a constant rate over 2 hours. After the end of the dropwise addition, a solution composed of "V-601" (1.15g) and methyl ethyl ketone (15.0g) was added and stirred at 75 ℃ for 2 hours. Further, a solution composed of "V-601" (0.54g) and methyl ethyl ketone (15.0g) was added, and stirred at 75 ℃ for 2 hours. After that, the temperature was raised to 85 ℃, and the stirring was continued for 2 hours, thereby obtaining a resin solution of a methyl methacrylate/isobornyl methacrylate/methacrylic acid (═ 20/72/8[ mass ratio ]) copolymer.

The obtained copolymer had a weight average Molecular Weight (MW) of 60000, an acid value of 54.2mgKOH/g and a glass transition temperature of 124 ℃.

Subsequently, the resin solution (588.2g) was weighed, isopropanol (165g) and a1 mol/L aqueous solution of sodium hydroxide (120.8ml) were added thereto, and the temperature in the reaction vessel was raised to 80 ℃. Then, distilled water (718g) was added dropwise at a rate of 20ml/min to disperse water. Thereafter, the temperature in the reaction vessel was maintained at 80 ℃ for 2 hours, 85 ℃ for 2 hours and 90 ℃ for 2 hours under atmospheric pressure, and the solvent was distilled off. Then, the pressure in the reaction vessel was reduced, and isopropyl alcohol, methyl ethyl ketone, and distilled water were distilled off, thereby obtaining an aqueous dispersion of resin particles a-1 (solid content: 25.0 mass%).

(abrasion resistance of image)

Using the inks, the abrasion resistance of the image was evaluated as follows.

The ink was filled in an ink cartridge attached to an ink jet recording apparatus (FUJIFILM DMP-2831), an image of 100% dot percentage was applied to a coated paper (OK TopKOTE) under conditions of 600dpi (dots per inch) and 10pl at 1 dot, and then dried with warm air at 100 ℃ for 1 minute.

The image formed on the coated paper was paperweight obtained by winding the coated paper at 55g/cm²After the rubbing operation was performed 2 times with a heavy weight and slowly rubbed back and forth, the image after the rubbing operation was visually observed and observed by an IR microscope (a hand-held digital microscope having a color measuring function, HandyScope, manufactured by Spectra Co-op., wavelength of an IR light source is 783 nm). From the observation results, the abrasion resistance of the infrared absorption image was evaluated according to the following evaluation criteria.

Evaluation criteria for abrasion resistance of images-

A: after the rubbing operation, the surface of the image was hardly scratched.

B: after the rubbing operation, the surface of the image was slightly scratched, and the image was scraped off to see that the area of the substrate was less than 30% of the entire area.

C: after the rubbing operation, there is an area where the image is scraped off to see the substrate, and the area is 30% or more with respect to the entire image.

The abrasion resistance of the images obtained using the inks (containing resin particles) of examples 10-1 to 10-7 was all evaluated as "B".

The abrasion resistance of the image was evaluated in the same manner as in examples 10-1 to 10-7 except that the inks of examples 1-1, 2-1, 3-1, 4-1, 5-1, 6-1 and 7-1 (containing no resin particles) were used in place of the inks of examples 10-1 to 10-7 (containing resin particles).

As a result, the abrasion resistance of the image was evaluated as "C".

It was thus confirmed that the abrasion resistance of the image was improved by including the resin particles in the ink.

[ example 11]

The ink of example 11 was prepared by adding a water dispersion of a magenta pigment (c.i. pigment red 122; hereinafter, also referred to as "PR 122") (hereinafter, magenta pigment dispersion M1) to the ink of example 6-1 so that the content of PR122 based on the total amount of the ink was 3 mass%. In this case, the contents of components other than the contents of PR122, the resin dispersant and water in the ink were adjusted to be constant.

(preparation of magenta pigment Dispersion M1)

Synthesis of the Water-soluble Polymer dispersant Q-1

A monomer supply composition was prepared by mixing methacrylic acid (172.0 parts by mass), benzyl methacrylate (828.0 parts by mass), and isopropyl alcohol (375.0 parts by mass). Also, an initiator supplying composition was prepared by mixing 2, 2-azobis (2-methylbutyronitrile) (22.1 parts by mass) and isopropanol (187.5 parts by mass). Subsequently, a mixture of the monomer supply composition and the initiator supply composition was added dropwise to isopropyl alcohol (187.5 parts by mass) heated to 80 ℃ under a nitrogen atmosphere over 2 hours. After the completion of the dropwise addition, the mixture was further held at 80 ℃ for 4 hours, and then cooled to 25 ℃ and then the solvent was removed under reduced pressure, whereby a water-soluble polymer dispersant Q-1 (water-soluble polymer) having a weight average molecular weight of about 30,000 and an acid value of 112mgKOH/g was obtained.

Preparation of the magenta pigment Dispersion M1

An aqueous solution of a water-soluble polymer dispersant was obtained by neutralizing 0.8 equivalents of methacrylic acid in the water-soluble polymer dispersant Q-1(150.0 parts by mass) obtained above with an aqueous potassium hydroxide solution, and then further adding ion-exchanged water to adjust the concentration of the water-soluble polymer dispersant to 25.0% by mass.

This aqueous solution of the water-soluble polymer dispersant (216.0 parts by mass), PR122(120.0 parts by mass), and pure water (464.0 parts by mass) were mixed, and dispersed with a bead mill (bead diameter: 0.1 mm. phi., zirconia beads) until a desired volume average particle diameter was obtained, whereby a dispersion of polymer-coated magenta pigment particles (uncrosslinked dispersion DM1) having a pigment concentration of 15.0% by mass was obtained.

To the above uncrosslinked dispersion DM1(136.0 parts by mass), Denacol EX-521 (crosslinking agent manufactured by Nagase ChemteX Corporation) (0.3 parts by mass) and an aqueous boric acid solution (boric acid concentration: 4.0 mass%) (13.7 parts by mass) were added, and after allowing to react at 70 ℃ for 6 hours, they were cooled to 25 ℃, thereby obtaining a crosslinked dispersion.

Subsequently, the obtained crosslinked dispersion was ultrafiltered by passing through a Polyethersulfone (PESU) membrane (pore size: 0.1 μm) mounted on an ultrafiltration apparatus (crossflow UF, manufactured by Sartorius) at a flow rate of 600ml for 1 minute at an ambient temperature of 25 ℃. The ultrafiltration was performed 10 times with 1 time of the volume ratio of the added liquid. Then, pure water was added to the crosslinked dispersion after ultrafiltration until the pigment concentration became 12.0 mass%, whereby magenta pigment dispersion M1 was obtained.

The magenta pigment dispersion liquid M1 contains a polymer-coated pigment (encapsulated pigment) having a structure in which the surface of a magenta pigment (PR122) is coated with a water-soluble polymer dispersant Q-1 (crosslinked polymer) crosslinked by a crosslinking agent.

(Density of image)

Using the ink of example 11 described above, the density of the image was evaluated as follows.

The ink was filled in an ink cartridge attached to an ink jet recording apparatus (FUJIFILM DMP-2831), dots were printed on a coated paper (OK TopKOTE) at a dot percentage of 5% under conditions of 600dpi × 600dpi (dots per inch) and a dropping amount of 10pL, and then dried with warm air at 100 ℃ for 1 minute.

When the image (dot) was observed with a hand-held digital microscope hand Scope (manufactured by Spectra Co-op.) having a color measurement function, a sufficient density was obtained in the near infrared region so as to be distinguishable without affecting the magenta hue.

[ example 12]

An image forming method including a treatment liquid applying step, an infrared absorption image forming step, and an infrared irradiation step is performed.

The image forming method is carried out by the same method as that described in paragraphs 0216 to 0219 of Japanese patent laid-open No. 2016-.

The treatment liquid used in example 9-1 was used as the treatment liquid, and the inks used in examples 10-1 to 10-7 were used as the inks.

Hereinafter, details are shown.

< treating liquid applying step and Infrared-absorbing image Forming step >

A sheet of paper (recording paper) cut into 150mm square was fixed on a table capable of moving in a predetermined linear direction at 500 mm/sec, and the table temperature was maintained at 30 ℃. On the retained recording paper, the treatment liquid prepared in example 9-1 was applied by a bar coater to a thickness of 1.2 μm (1.5 g/m)²) Immediately after the coating, the coating was dried at 50 ℃ for 2 seconds (treatment liquid application step).

Next, while the recording paper coated with the treatment liquid was moved at a constant speed, the ink of any of examples 10-1 to 10-7 was ejected from the nozzle of the inkjet head and applied to the area of the recording paper coated with the treatment liquid, thereby forming a solid infrared absorption image (image precursor) (infrared absorption image forming step).

The ink ejection conditions were set to 5.0pL of ink droplets, an ejection frequency of 25.5kHz, and a resolution of 1200dpi × 1200 dpi.

< Infrared irradiation step >

While the recording sheet on which the infrared absorption image is formed is moved at a constant speed, the infrared absorption image is subjected to infrared irradiation and warm air blowing by an infrared heater and a warm air blower disposed downstream of the inkjet head (infrared irradiation step).

Fig. 1 is a schematic view showing a state after an infrared absorption image is formed by applying ink from an ink jet head in image formation of example 12, and then, the formed infrared absorption image is subjected to infrared irradiation and warm air blowing. In fig. 1, the portions of the recording paper before the treatment liquid is applied thereto are not shown.

As shown in fig. 1, an infrared heater IR1, a heater HA1, an infrared heater IR2, a heater HA2, an infrared heater IR3, and a heater HA3 are disposed in this order on the downstream side of the head 1.

In this embodiment, the infrared ray irradiation and the warm air blowing are performed on the infrared ray absorption image 3 times by the infrared ray heater IR1, the warm air blower HA1, the infrared ray heater IR2, the warm air blower HA2, the infrared ray heater IR3, and the warm air blower HA3 in this order.

Short-wavelength infrared heaters ZKG2400/340G (a halogen lamp having a maximum energy wavelength of 1.3 μm, an output of 2400W, and a light emission length of 340 mm) manufactured by Heraeus k.k. were used as the infrared heater IR1, the infrared heater IR2, and the infrared heater IR3, respectively.

Fans blowing warm air at 60 ℃ and 5m/s were used as the fan heaters HA1, HA2, and HA 3.

(abrasion resistance of image)

The solid images after infrared irradiation and warm air blowing were evaluated for wear resistance according to the same evaluation method and evaluation criteria as those of the wear resistance in example 10-1.

As a result, the abrasion resistance of the image was all "A" when any of the inks of examples 10-1 to 10-7 was used.

Next, with respect to an image in which only warm air blowing was performed on the infrared ray absorption image without performing infrared ray irradiation, the abrasion resistance was evaluated in the same manner as described above.

As a result, when any of the inks of examples 10-1 to 10-7 was used, the abrasion resistance of the image was "B".

The invention of japanese patent application No. 2019-068257, filed 3/29 in 2019, is incorporated by reference in its entirety into the present specification.

All documents, patent applications, and technical standards cited in the present specification are incorporated by reference into the present specification to the same extent as if each document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.