阅读说明：本技术 带电控制方式的喷墨打印机用油墨 (Ink for ink-jet printer with electrification control ) 是由 佐佐木洋 音羽拓也 荻野雅彦 永井启资 和田环 于 2019-02-20 设计创作，主要内容包括：本发明的目的在于：提供一种能够降低导电剂的添加率且低电阻的喷墨打印机用油墨。为了解决上述技术问题,本发明所涉及的带电控制方式的喷墨打印机用油墨的特征在于：含有树脂、颜料、导电剂和非水溶剂,导电剂为在非水溶剂中产生阴离子和阳离子的盐结构,阴离子具有三氟甲磺酰基,阳离子为季铵阳离子或者具有不饱和杂环结构。(The invention aims to: provided is an ink for an ink jet printer, which can reduce the addition rate of a conductive agent and has low resistance. In order to solve the above-described problems, an ink for an ink jet printer of a charging control system according to the present invention includes: the conductive agent is a salt structure which generates anions and cations in the non-aqueous solvent, the anions have trifluoromethanesulfonyl, and the cations are quaternary ammonium cations or have unsaturated heterocyclic structures.)

1. An ink for an ink-jet printer of a charge control system, characterized in that:

which comprises a resin, a pigment, a conductive agent and a nonaqueous solvent,

the conductive agent is a salt structure that generates anions and cations in the non-aqueous solvent,

the anion has a trifluoromethanesulfonyl group,

the cation is a quaternary ammonium cation or has an unsaturated heterocyclic structure.

2. The ink for an ink jet printer of a charging control system according to claim 1, wherein:

the anion is CF₃SO₃ ^－、(CF₃SO₂)₂N^－、(CF₃SO₂)₃C^－Any of the above.

3. The ink for an ink jet printer of a charging control system according to claim 1 or 2, wherein:

the cation has an unsaturated heterocyclic structure,

the unsaturated heterocyclic structure contains nitrogen.

4. The ink for a charging control type inkjet printer according to claim 3, wherein:

the unsaturated heterocyclic structure is a monocyclic unsaturated six-membered ring structure or a monocyclic unsaturated five-membered ring structure.

5. The ink for a charging control type inkjet printer according to claim 3, wherein:

the unsaturated heterocyclic structure is a pyridinium structure.

6. The ink for a charging control type inkjet printer according to claim 5, wherein:

a hydrocarbon group having a linear structure or a branched structure is bonded to the 1-position and the 3-position of the pyridinium structure,

the total number of carbon atoms of the hydrocarbon groups bonded to the 1-position and the 3-position is 4 to 10.

7. The ink for a charging control type inkjet printer according to claim 3, wherein:

the unsaturated heterocyclic structure is an imidazolium structure or a pyrrolium structure.

8. The ink for a charging control type inkjet printer according to claim 7, wherein:

the unsaturated heterocyclic structure is an imidazolium structure,

the 1-position and the 3-position of the imidazolium structure are bonded with hydrocarbon groups with a linear structure or a branched structure,

the total number of carbon atoms of the hydrocarbon groups bonded to the 1-position and the 3-position is 2 to 8.

9. The ink for a charging control type inkjet printer according to claim 7, wherein:

the unsaturated heterocyclic structure is a pyrrolinium structure,

2 hydrocarbon groups with a straight chain structure or a branched chain structure are bonded at the 1-position of the pyrryl structure,

the total number of carbon atoms of the 2 hydrocarbon groups bonded to the 1-position is 4 to 8.

10. The ink for a charging control type inkjet printer according to any one of claims 1 to 9, wherein:

further comprising a resin precursor and a polymerization initiator,

the resin precursor has a double bond capable of polymerization,

the ink is an ink that is cured by irradiation with ultraviolet rays.

Technical Field

The present invention relates to an ink for an ink jet printer of a charging control system.

Background

In order to print a shelf life, a service life, a manufacturing number, and the like, an ink jet printer of a charging control system is used in a wide range of fields such as food, electronic products, and the like. The ink for a charge control type ink jet printer is mainly composed of a resin, a colorant, a conductive agent, and a solvent. Additives such as leveling agents for controlling the shape of printed dots are added.

For color development of the ink, a colorant is added. In order to hold a material such as a colorant in the print portion, a resin is added. As the leveling agent, an organic silicon-based compound is generally used.

In an ink jet printer of a charging control system, ink particles discharged from nozzles are charged, and deflected by deflection electrodes to discharge ink onto a printing surface. Therefore, it is necessary to charge the ink. In order to impart a suitable charge to the ink droplets, a conductive agent is added. Specifically, the conductive agent has a function of increasing the conductivity of the ink and reducing the resistance.

As the conductive agent, an organic substance having a salt structure is generally used.

Patent document 1 discloses an ink composition for inkjet containing an organic solvent such as acetone or propylene glycol methyl ether, a solvent-soluble binder resin, and a water-insoluble quinone dye. Further, as the conductive agent, it is disclosed that lithium trifluoromethanesulfonate can be used.

Patent document 2 discloses a composition containing an organic semiconductor, an organic solvent, and an additive for increasing conductivity as a conductive ink for preparing an organic photovoltaic cell. As the conductive additive, it is disclosed that an alkali metal salt or an organic salt of an anion formed from a Triflate (Triflate ) or a bis (trifluoromethanesulfonyl) imide may be used.

Disclosure of Invention

Technical problem to be solved by the invention

The ink for inkjet printers is mainly responsible for the abrasion resistance and adhesion of the printed matter by the resin, and may be added to an allowable viscosity for printing. When the ratio of the colorant or the conductive agent in the ink is increased, the ratio of the resin added to ensure the physical strength of printing is decreased, and therefore, the abrasion resistance and the adhesion are decreased. To ensure legibility, a colorant needs to be added. Therefore, it is difficult to reduce the content of the colorant. Therefore, it is desirable to maintain low resistance and reduce the addition rate of the conductive agent.

The conductive agent disclosed in patent document 1 has a technical problem in terms of solubility in a resin or a solvent because the cation is an inorganic substance such as an alkali metal.

The conductive compound disclosed in patent document 2 is not a resin or a colorant contained in an ink for an inkjet printer for the purpose of forming a circuit or the like. Therefore, there is no technical problem that high adhesion and high abrasion resistance are required to be obtained by adding a resin and that low resistance is obtained by adding a conductive agent.

The object of the invention is therefore: provided is an ink for an ink jet printer, which can reduce the addition rate of a conductive agent and has low resistance.

Technical solution for solving technical problem

In order to solve the above-described problems, an ink for an ink jet printer of a charging control system according to the present invention includes: the conductive agent is a salt structure which generates anions and cations in the non-aqueous solvent, the anions have trifluoromethanesulfonyl, and the cations are quaternary ammonium cations or have unsaturated heterocyclic structures.

Effects of the invention

The present invention can provide an ink for an inkjet printer, which can reduce the addition rate of a conductive agent and has a low resistance.

Drawings

Fig. 1 is a schematic diagram showing a printing process of an ink jet printer of a charging control system.

FIG. 2 is a graph showing the electrical resistance of the inks of the examples and comparative examples.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like.

1. Ink for ink-jet printer

The ink contains a resin, a colorant, a nonaqueous solvent, and a conductive agent. These are stirred by a stirring blade, an overhead stirrer, or the like to be dissolved with each other, thereby forming an ink.

< resin >

The type of the resin contained in the ink is not particularly limited as long as the resin is soluble in the solvent, and is selected in consideration of adhesion to a printing object (object to be printed), abrasion resistance, and the like. As the resin, specifically, acrylic resin, styrene acrylic resin, polyvinyl butyral resin, polyester resin, vinyl acetate containing chlorine, and a mixture of these resins can be used. The weight average molecular weight of these resins is preferably about several thousands to 2 ten thousands. The content of the resin in the ink is preferably 5% by mass or more in terms of ensuring the abrasion resistance and adhesion of the printed matter. The content of the resin in the ink is preferably 15 mass% or less in order to have a printable viscosity.

< coloring agent >

As the colorant, a dye or a pigment may be used.

(dyes)

The dye is not particularly limited as long as it is a material that can be dissolved in the solvent used. Specific examples thereof include the following dyes. Examples of the black dye include oil black HBB (c.i. solvent black 3), valifastbllack 3804(c.i. solvent black 34), SPIRITBLACKSB (c.i. solvent black 5), oleosollfastblackrl (c.i. solvent black 27), aizensback 8(c.i. solvent black 7), and orasolblkcn (c.i. solvent black 28).

Examples of the red-based dye include oil red 5B (c.i. solvent red 27), VALIFASTRED1306(c.i. solvent red 109), oleosolfosalterred (c.i. solvent red 132), airzenstred 1(c.i. solvent red 24), ORASOLRED3GL (c.i. solvent red 130), and FILAMIDREDGR (c.i. solvent red 225).

Examples of the yellow dye include oil yellow 129(c.i. solvent yellow 29), oleosoldrillinitiantyellow 5G (c.i. solvent yellow 150), airnsotiyellow 1(c.i. solvent yellow 56), ORASOLYELLOW3R (c.i. solvent yellow 25), and the like.

Examples of the blue dye include oil blue 2N (c.i. solvent blue 35), valefastblue 1605(c.i. solvent blue 38), oleosollfastblueln (c.i. solvent blue 70), airtansue 1(c.i. solvent blue 25), and orasolblue (c.i. solvent blue 67).

(pigment)

In the case of black, carbon black may be used as the pigment. When white, titanium dioxide, zinc oxide, or the like can be used. For red, cadmium red, iron oxide red (iron sesquioxide), quinacridone red, or the like can be used. When yellow, chrome yellow, cadmium yellow, nickel titanium yellow, etc. may be used. For the blue color, prussian blue, copper phthalocyanine or the like can be used. For green, phthalocyanine green, chrome yellow, cyanosis blue mixture, titanium cobalt green, etc. can be used.

In addition to the white pigment, the pigment is preferably pulverized to an average particle diameter of 100nm to 1000nm and used together with an appropriate dispersant. When the white pigment is too small, the masking rate decreases, and therefore the average particle diameter is preferably 200nm or more, and this is added to the ink together with the dispersant.

< non-aqueous solvent >

The nonaqueous solvent is not particularly limited as long as it can dissolve the resin and reduce the viscosity of the ink to a level at which printing can be performed, and for example, an organic solvent such as an aromatic solvent, an ester solvent, a ketone solvent, a hydrocarbon solvent, an alcohol solvent, or a glycol solvent can be used. Wherein, in the ink-jet printer with the electrification control mode, the viscosity of the ink is controlled to be about 1 to 5 mPa.S at the temperature of 20 ℃. This is because the ink is not easily ejected from the print head when the viscosity is high.

As a solvent for ink of an ink jet printer of a charging control system, a ketone solvent such as 2-butanone (a common name is Methyl Ethyl Ketone (MEK)), acetone, methyl isopropyl ketone, or the like is generally used. These solvents are easy to dissolve the resin and have a high vapor pressure, and therefore, drying after printing is fast. Therefore, the resin and the conductive agent preferably have high solubility in ketone solvents. As the solvent, dimethoxyethane or ethanol may be used in addition to the ketone solvent.

< conductive agent >

The conductive agent has a salt structure that generates an anion and a cation in a non-aqueous solvent, and the anion has a trifluoromethanesulfonyl group (CF)₃SO₂) The cation is quaternary ammonium cation or has an unsaturated heterocyclic structure.

(anion)

When the content of the conductive agent in the ink is increased, the content of the resin added to ensure the physical strength of printing in the ink (during printing) is decreased, and therefore, the abrasion resistance and adhesion of printing are decreased. Therefore, it is necessary to reduce the addition rate of the conductive agent as much as possible.

As a result of the studies by the present inventors, it was found that the more acidic the acid having a proton bonded thereto as an anion in the salt structure constituting the conductive agent, the less the amount of the acid added, and the higher the conductivity. One of the parameters indicating the acid strength is the Hammett acidity function, and it is found that a substance having an acidity function of-12 or more is preferable.

In addition, it is also necessary that substances in the ink composition hardly undergo oxidation and reduction reactions. Further, it is also required that the ink composition does not exhibit oxidation to substances in the ink composition unlike strong acids such as perchloric acid and nitric acid. It is also required that even if it is an anion, it is chemically stable and shows little reducing property and nucleophilicity. That is, a strong acidic and chemically stable acid is desired. Examples of the anion corresponding thereto include those having trifluoromethanesulfonyl group (CF)₃SO₂) The anion of (4). In particular toGround is CF₃SO₃ ^－Triflate (conjugate base of triflic acid), (CF) shown₃SO₂)₂N^－The conjugate base of bis (trifluoromethanesulfonyl) imide shown as (CF)₃SO₂)₃C^－The conjugate base of the tris (trifluoromethanesulfonyl) methide shown, and the like.

(cation)

As the conductive agent, a substance that can be dissolved in a nonaqueous solvent needs to be used. In the ink, a ketone solvent such as MEK is the main stream, and therefore the conductive agent is preferably dissolved in a ketone solvent such as MEK. In the present invention, in order to improve the solubility in a solvent, an inorganic substance such as an alkali metal like Li or Na is not used as a cation, but an organic substance is used. Specifically, the cation is a quaternary ammonium cation (a cation having a quaternary ammonium salt structure) having 1 to 4 alkyl chains or a cation having an unsaturated heterocycle.

Examples of the cation having a quaternary ammonium salt structure include amines having an alkyl chain of a linear structure or a branched structure, and amines having a heterocyclic structure such as pyrrole and pyridine.

The unsaturated heterocyclic structure preferably contains nitrogen, and more preferably is a monocyclic unsaturated six-membered ring structure or a monocyclic unsaturated five-membered ring structure.

In order to reduce the rate of addition to the ink, the molecular weight of the cation is preferably small. Tetraalkylammonium salts (the cation is a tetraalkylammonium ion) which are commonly used as a conductive agent of inks, the longer the alkyl group, the higher the solubility to an organic solvent. Therefore, in the ink for an ink jet printer of the charge control system, a tetraalkylammonium ion having an alkyl group having 4 or more carbon atoms is preferably used as the cation. However, when a tetraalkylammonium ion having an alkyl group with 4 or more carbon atoms is used as the cation, the molecular weight is large. When the molecular weight of the element is calculated as an integer by rounding off the decimal point, the molecular weight is 308 when the number of carbon atoms of the alkyl group is 4; when the number of carbon atoms is 6, the molecular weight is 420; when the number of carbon atoms is 8, the molecular weight is 532; for tetraaniline, the molecular weight is also 392; in the case of a phenyl group having a fluorine group introduced thereinto for the purpose of improving the solubility in an organic solvent, the molecular weight is 464.

On the other hand, the molecular weight can be reduced by making the cation a monocyclic unsaturated heterocycle. For example, when no alkyl group is present in the molecule, the molecular weights of the imidazolium structure and the pyrrolium structure having a monocyclic unsaturated five-membered ring structure are as low as 69 and 72, respectively. When no alkyl group is present in the molecule, the molecular weight of the pyridinium structure having a monocyclic unsaturated six-membered ring structure is as low as 80. In these structures, solubility in an organic solvent can be ensured by introducing 1 or 2 alkyl groups into nitrogen in the molecule. However, if the alkyl group is too long, the solubility in an alcohol solvent such as ethanol is also lowered. Therefore, when the unsaturated heterocyclic structure is a pyridinium structure, the total number of carbon atoms of the hydrocarbon group having a linear structure or a branched structure bonded to the nitrogen of the pyridinium structure is preferably 4 to 10. When the unsaturated heterocyclic structure is an imidazolium structure, the total number of carbon atoms of the hydrocarbon group having a linear structure or a branched structure bonded to the nitrogen of the imidazolium structure is preferably 2 to 8. When the unsaturated heterocyclic structure is a pyrrolinium structure, the total number of carbon atoms of the hydrocarbon group having a linear structure or a branched structure bonded to the nitrogen of the pyrrolinium structure is preferably 4 to 8.

By using the cation, the solubility in a nonaqueous solvent which is generally used for an ink for an inkjet printer is improved.

Further, by forming the cation into a nitrogen-containing unsaturated heteromonocyclic ring, a conductive agent having a small molecular weight and a trifluoromethanesulfonyl acid salt structure can be obtained.

Next, the introduction site of the alkyl group will be described. The nitrogen at the 1-position is quaternized, and therefore, the hydrophilicity is high. In other words, since the hydrophobicity is low, it is preferable to introduce a hydrophobic alkyl group into the nitrogen at the 1-position in order to improve the solubility of the nitrogen site in a hydrophobic organic solvent such as MEK.

Further, the site other than the 1-position to which the alkyl group is introduced is preferably a site distant from nitrogen. The number of bits is preferably 3 or 4 as compared with 2. This is because the anion is easily accessible to the vicinity of nitrogen, thereby improving the thermal stability of the salt structure. When an alkyl group is present at the 2-position, steric hindrance is generated to prevent the approach of an anion to nitrogen, and thus the thermal stability of the salt tends to be lowered. In the vicinity of a portion where heat is generated by a pump or the like inside an ink jet printer, the ink may be heated to several tens of degrees, and therefore it is important to ensure thermal stability. Therefore, in order to ensure thermal stability, the site of introduction of an alkyl group other than the 1-position is preferably a site distant from nitrogen, such as the 3-position or the 4-position.

As described above, when the unsaturated heterocyclic structure is a pyridinium structure, as shown in chemical formula 1, a hydrocarbon group having a linear structure or a branched structure is preferably bonded to the 1-position and the 3-position of the pyridinium structure, and the total number of carbon atoms of the hydrocarbon groups bonded to the 1-position and the 3-position is preferably 4 to 10.

In chemical formula 1, R1 and R2 are each independently an alkyl group, and the total number of carbon atoms of R1 and R2 is 4 to 10. In addition, when the unsaturated heterocyclic structure is an imidazolium structure, as shown in chemical formula 2, the alkyl group having a linear structure or a branched structure is preferably bonded to the 1-position and the 3-position of the imidazolium structure, and the total number of carbon atoms of the alkyl groups bonded to the 1-position and the 3-position is preferably 2 to 8.

In chemical formula 2, R1 and R2 are each independently an alkyl group, and the total number of carbon atoms of R1 and R2 is 2 to 8.

When the unsaturated heterocyclic structure is a pyrrolinium structure, it is preferable that 2 hydrocarbon groups having a linear structure or a branched structure are bonded to the 1-position of the pyrrolinium structure represented by chemical formula 3, and the total carbon number of the 2 hydrocarbon groups bonded to the 1-position is preferably 4 to 8.

In chemical formula 3, R1 and R2 are each independently an alkyl group, and the total carbon number of R1 and R2 is 4 to 8.

Therefore, as the conductive agent, compounds represented by compound group 1, compound group 2, and compound group 3 described below are preferable.

In the compound group 1, R1 and R2 are each independently an alkyl group, and the total carbon number of R1 and R2 is 2 to 8. n is an integer of 1 to 3, X is oxygen when n is 1, X is nitrogen when n is 2, and X is carbon when n is 3.

In the compound group 2, R1 and R2 are each independently an alkyl group, and the total carbon number of R1 and R2 is 4 to 8. n is 1 to 3, X is oxygen when n is 1, X is nitrogen when n is 2, and X is carbon when n is 3.

In compound group 3, R1 and R2 are each independently an alkyl group, and the total carbon number of R1 and R2 is 4 or more and 10 or less. n is 1 to 3, X is oxygen when n is 1, X is nitrogen when n is 2, and X is carbon when n is 3.

When the molecular weights of compound group 1, compound group 2 and compound group 3 are compared, the molecular weight of compound group 1 is 97 to 181, the molecular weight of compound group 2 is 180 to 292 and the molecular weight of compound group 3 is 136 to 220. Therefore, from the viewpoint of solubility in a solvent, the compound group 1 is particularly preferably used as the conductive agent.

As the ink for an ink jet printer, a photocurable ink which is cured by irradiation with light such as ultraviolet light can be used. The photocurable ink contains a solvent, a resin, a colorant, a conductive agent, a resin precursor, a polymerization initiator, and the like. The solvent, resin, colorant, and conductive agent may be the same compounds as those used in the above-described ink.

The resin precursor has a double bond capable of polymerization. The resin precursor is irradiated with light such as ultraviolet rays in the presence of a polymerization initiator to form a polymer, which is then cured.

As the resin precursor, an acrylic monomer or a methacrylic monomer can be cited. As the acrylic monomer, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate, stearyl acrylate, isopropyl acrylate, isobutyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, cyclooctyl acrylate, cyclodecyl acrylate, methoxypolyethylene glycol acrylate, phenoxypolyethylene glycol acrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, 1, 6-hexanediol diacrylate, 1, 8-octanediol diacrylate, 1, 10-decanediol diacrylate, 1, 12-dodecanediol diacrylate, trimethylolpropane triacrylate, etc. can be used. Examples of the methacrylate ester monomer include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, stearyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, 2-ethylbutyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, cyclooctyl methacrylate, cyclodecyl methacrylate, methoxypolyethylene glycol methacrylate, phenoxyethylene glycol methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1, 6-hexanediol dimethacrylate, 1-dimethacrylic acid, 8-octanediol ester, 1, 10-decanediol dimethacrylate, glyceryl dimethacrylate, polytrimethylene dimethacrylate, and the like.

The polymerization initiator is selected depending on the kind of polymerization reaction. The initiator has a peroxide-based, alkylbenzene-based, oxime ester-based structure, and the like. Examples of the peroxides include azobisisobutyronitrile, benzoyl peroxide, di-t-butyl peroxide; as the alkyl-phenone series, 2-dimethoxy-1, 2-diphenylpropan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide; as the oxime ester, 1, 2-octanedione, 1- [ 4- (phenylthio) -2- (o-benzoyloxime) ] and the like can be used.

2. Ink-jet printer

The ink described above can be incorporated into an ink jet printer to provide desired printing.

Fig. 1 shows a printing process in which ink is ejected from a charge control type ink jet printer until the ink is applied. The ink droplets 2 discharged from the nozzles 1 are charged by the charging electrodes 3, and then are applied to the printing substrate 5 while controlling the direction by the deflection electrodes 4. The ink not printed is collected in the collection tank 6 and returned to the ink cartridge (not shown in fig. 1).

The dot size of the printed ink is about 300 to 400 μm. When the substrate to be printed is a resin surface such as polypropylene (PP) or Polyethylene (PE), the dot size is as small as about 300 to 350 μm because of the high hydrophobicity of the substrate to be printed. On the other hand, when printing is performed on the surface of an aluminum can or a glass bottle having high hydrophilicity, the dot size is about 350 to 400 μm.