Developer precursors for laser-markable compositions
阅读说明：本技术 用于可激光标记的组合物的显影剂前体 (Developer precursors for laser-markable compositions ) 是由 J.罗库费尔 于 2018-06-05 设计创作，主要内容包括：本发明涉及包含式(I)的显影剂前体的新型可激光标记的组合物。(The present invention relates to novel laser markable compositions comprising developer precursors of formula (I).)
1. A laser markable composition comprising a leuco dye and a developer precursor, characterized in that the developer precursor has the chemical structure of formula I
Formula I
Wherein the content of the first and second substances,
R1、R2and R3Selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl,
x is selected from oxygen atom, sulfur atom, -N (C = Z) R4and-NSO2R5，
Y represents a group capable of generating an acid HY having a pKa of 5 or less,
z represents an oxygen or sulfur atom,
R4selected from the group consisting of hydrogen, substituted OR unsubstituted alkyl, substituted OR unsubstituted alkenyl, substituted OR unsubstituted alkynyl, substituted OR unsubstituted alkylaryl, substituted OR unsubstituted arylalkyl, substituted OR unsubstituted aryl, substituted OR unsubstituted heteroaryl, -OR6and-NR7R8，
R5And R6Independently selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl,
R7and R8Independently selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl,
R1and R2，R1And R3，R2And R3And R7And R8Taken together may represent the necessary atoms to form a 5 to 8 membered ring.
2. The laser markable composition according to claim 1 wherein X is selected from O andNSO2R5。
3. the laser markable composition according to claim 1 or 2 wherein Y represents a group capable of generating an acid HY having a pKa of 3 or less.
4. The laser markable composition according to any of the preceding claims wherein Y is selected from o (co) R9、OSO2R10、O(PO)OR11OR12、SR13And SO2R14And wherein
R9Selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkylaryl, substituted or unsubstituted arylalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, and COR15，
R10、R11、R12And R14Independently selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl,
R13selected from substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl,
R15selected from the group consisting of hydrogen, substituted OR unsubstituted alkyl, substituted OR unsubstituted alkenyl, substituted OR unsubstituted alkynyl, substituted OR unsubstituted alkylaryl, substituted OR unsubstituted arylalkyl, substituted OR unsubstituted aryl, substituted OR unsubstituted heteroaryl, and OR16，
R16Selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl,
R11and R12May represent the necessary atoms to form a 5 to 8 membered ring.
5. Laser markable composition according to any of the preceding claims wherein Y represents-o (co) COR15Radicals or SO2R14Group, wherein R14And R15Have the same meaning as in claim 4.
6. The laser markable composition according to any of the preceding claims wherein R1Represents a substituted or unsubstituted aryl group.
7. The laser markable composition according to any of the preceding claims wherein R2And R3Independently selected from hydrogen, substituted or unsubstituted alkyl groups and substituted or unsubstituted aryl groups.
8. The laser markable composition according to any of the preceding claims further comprising a light to heat conversion agent.
9. The laser markable composition according to claim 8 wherein the light to heat conversion agent is an infrared absorbing dye.
10. A laser markable article comprising a laser markable composition as defined in any of the claims 1 to 9 provided on a support.
11. The laser markable article according to claim 10 wherein the laser markable composition is provided on a support by gravure printing, screen printing, flexographic printing, offset printing, inkjet printing or rotogravure printing.
12. The laser markable article according to claim 10 or 11 wherein the article is selected from the group consisting of packaging, foil, laminate, security document, label, decoration and RFID tag.
13. A method of making a laser marked article, the method comprising the steps of: exposing the laser markable article as defined in any of the claims 10 to 12 with an infrared laser to form a laser marked image.
14. The method of claim 13, wherein the laser marked image is selected from the group consisting of a bar code, a QR code, alphanumeric data, a picture, and a logo.
Technical Field
The present invention relates to laser-markable compositions and developer precursors for such laser-markable compositions.
Background
Laser marking, i.e. the provision of information on e.g. packaging or security documents by means of laser light, has attracted interest as an answer to the increasing demand for personalization, mass customization, security, traceability and anti-counterfeiting.
Several laser marking techniques coexist in the art.
Laser induced carbonization is one of the main techniques. However, laser marking based on carbonization is limited to black and white images.
As disclosed in, for example, WO2002/074548 (Datalase) or WO2008/075101 (Siltech), the use of metal oxides, such as ammonium octamolybdate or molybdenum trioxide, has been developed as an alternative method of laser marking. However, this laser marking technique is also limited to black and white images.
WO2013/014436 (Datalase) discloses a diacetylene-based technique that allows for multicolor laser marking.
Another technique for multicolour laser marking makes use of leuco dyes, as disclosed for example in EP-a 2648920 (AgfaGevaert).
Leuco dye-based technologies require the use of a developer. The developer can react with the leuco dye resulting in the formation of a colored dye.
The developer may not react, or at least not substantially react, with the leuco dye prior to laser marking to avoid background staining. Therefore, the developer and the leuco dye must be shielded from each other before laser marking.
One way to achieve shielding is to encapsulate the leuco dye and/or developer. Upon heat treatment or exposure to IR radiation, the capsules rupture and the leuco dye and developer can react with each other to form a color. Encapsulation of leuco dyes and/or developers is commonly used in aqueous laser markable compositions, as disclosed in WO2016/184881 (AgfaGevaert).
Another way to achieve this shielding is by using so-called developer precursors that do not react with the leuco dye. Upon heat treatment or infrared laser exposure, the developer precursor releases a developer that can react with the leuco dye to form a color.
Such developer precursors are typically used in solvent and uv-based laser markable compositions because the above mentioned encapsulation processes are more difficult to implement in non-aqueous compositions.
The developer precursor is typically an acid precursor. Upon heat treatment or infrared laser exposure, the acid precursor is chemically converted to an acid. The acid may then be reacted with a leuco dye.
Several acid precursors have been disclosed in the patent literature.
Acid precursors are generally derived from strong acids, as disclosed in WO2015/091688 (Agfa Gevaert) and WO2007/088104(Ciba Specialty Chemicals Holding), resulting in precursors with limited thermal and hydrolytic stability on the one hand and toxicological problems induced by their reactivity on the other hand.
Other types of thermal acid generators are based on the thermal degradation of tertiary alkyl carbonates, as disclosed in EP-A2722367 (Agfa Gevaert) and EP-A0605149 (Nippon paper industries). Acid precursors of this type generally have limited reactivity upon laser exposure and generate large amounts of gas upon thermal degradation, resulting in layer damage and ablation at the high laser power required to obtain sufficient reactivity.
Thus, there remains a need for acid precursors that have a wide range of applicability and high reactivity without forming large amounts of gas.
Summary of The Invention
It is an object of the present invention to provide novel developer precursors with which laser marking compositions having good laser marking properties can be prepared.
This object is achieved with a developer precursor as defined in claim 1.
Other objects of the present invention will become apparent from the following description.
Detailed Description
Definition of
The term "monofunctional" in, for example, monofunctional polymerizable compounds means that the polymerizable compound includes one polymerizable group.
The term "difunctional" in, for example, difunctional polymerizable compounds means that the polymerizable compound includes two polymerizable groups.
The term "multifunctional" in, for example, polyfunctional polymerizable compounds means that the polymerizable compounds include more than two polymerizable groups.
The term "alkyl" refers to all possible variations of each number of carbon atoms in an alkyl group, i.e., methyl; an ethyl group; for three carbon atoms: n-propyl and isopropyl; for four carbon atoms: n-butyl, isobutyl, and tert-butyl; for five carbon atoms: n-pentyl, 1-dimethylpropyl, 2-dimethylpropyl, and 2-methylbutyl, and the like.
Unless otherwise specified, substituted or unsubstituted alkyl is preferably C1-C6An alkyl group.
Unless otherwise specified, substituted or unsubstituted alkenyl is preferably C2-C6An alkenyl group.
Unless otherwise specified, substituted or unsubstituted alkynyl is preferably C2-C6Alkynyl.
Unless otherwise specified, a substituted or unsubstituted aralkyl group preferably includes one, two, three or more C1-C6Alkyl phenyl or naphthyl.
Unless otherwise specified, a substituted or unsubstituted alkylaryl group is preferably C including phenyl or naphthyl7-C20An alkyl group.
Unless otherwise specified, substituted or unsubstituted aryl is preferably phenyl or naphthyl.
Unless otherwise specified, a substituted or unsubstituted heteroaryl group is preferably a five-or six-membered ring substituted with one, two or three oxygen atoms, nitrogen atoms, sulfur atoms, selenium atoms, or a combination thereof.
The term "substituted" in, for example, substituted alkyl means that the alkyl group can be substituted with atoms other than those typically present in such groups (i.e., carbon and hydrogen). For example, a substituted alkyl group may include a halogen atom or a thiol group. Unsubstituted alkyl groups contain only carbon and hydrogen atoms.
Unless otherwise indicated, substituted alkyl, substituted alkenyl, substituted alkynyl, substituted aralkyl, substituted alkaryl, substituted aryl and substituted heteroaryl groups are preferably substituted with one or more members selected from: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl and tert-butyl, esters, amides, ethers, thioethers, ketones, aldehydes, sulfoxides, sulfones, sulfonates, sulfonamides, -Cl, -Br, -I, -OH, -SH, -CN and-NO2。
Laser-markable compositions
The laser markable compositions of the present invention comprise a leuco dye and a developer precursor as disclosed below.
The laser markable composition preferably comprises a light to heat converter.
The composition may also include other ingredients, such as acid scavengers and UV absorbers.
The laser markable composition may also include dyes or pigments that enhance the contrast between the laser marked image and the background color.
Developer precursor
The developer precursors of the present invention have the chemical structure of formula I
Formula I
Wherein the content of the first and second substances,
R1、R2and R3Selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl,
x is selected from oxygen atom, sulfur atom, -N (C = Z) R4and-NSO2R5，
Y represents a group capable of generating an acid HY having a pKa of 5 or less,
z represents O or S, and Z represents O or S,
R4selected from the group consisting of hydrogen, substituted OR unsubstituted alkyl, substituted OR unsubstituted alkenyl, substituted OR unsubstituted alkynyl, substituted OR unsubstituted alkylaryl, substituted OR unsubstituted arylalkyl, substituted OR unsubstituted aryl, substituted OR unsubstituted heteroaryl, -OR6and-NR7R8，
R5And R6Independently selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl,
R7and R8Independently selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl,
R1and R2，R1And R3，R2And R3And R7And R8Taken together may represent the necessary atoms to form a 5 to 8 membered ring.
In a preferred embodiment, X is selected from O and NSO2R5。
In all of the above embodiments, Y preferably represents a group capable of generating an acid HY having a pKa of 4 or less, more preferably a pKa of 3 or less.
In all of these embodiments, Y is more preferably selected from O (CO) R9、OSO2R10、O(PO)OR11OR12、SR13And SO2R14Wherein
R9Selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkylaryl, substituted or unsubstituted arylalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, and COR15，
R10、R11、R12And R14Independently selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl,
R13selected from substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl,
R15selected from the group consisting of hydrogen, substituted OR unsubstituted alkyl, substituted OR unsubstituted alkenyl, substituted OR unsubstituted alkynyl, substituted OR unsubstituted alkylaryl, substituted OR unsubstituted arylalkyl, substituted OR unsubstituted aryl, substituted OR unsubstituted heteroaryl, and OR16，
R16Selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl,
R11and R12May represent the necessary atoms to form a 5 to 8 membered ring.
In a most preferred embodiment, Y represents-O (CO) COR15Radicals or SO2R14A group.
In another preferred embodiment, R1Represents a substituted or unsubstituted aryl group.
In yet another preferred embodiment, R2And R3Independently selected from hydrogen, substituted or unsubstituted alkyl groups and substituted or unsubstituted aryl groups.
Examples of developer precursors are given in table 1 below, but are not limited thereto.
TABLE 1
Leuco dyes
Leuco dyes are substantially colorless compounds that form colored dyes upon an intermolecular or intramolecular reaction. The intermolecular or intramolecular reaction may be triggered by heat formed during exposure with an Infrared (IR) laser.
Examples of leuco dyes which can be used are disclosed in paragraphs [069] to [093] of WO2015/165854 (Agfa Gevaert).
Photothermal conversion agent
The light-to-heat converter generates heat upon absorption of radiation.
The light-to-heat converter preferably generates heat upon absorption of Infrared (IR) radiation, more preferably Near Infrared (NIR) radiation. The wavelength of the NIR radiation is between 750 and 2500 nm.
The light-to-heat converter can be an infrared absorbing dye, an infrared absorbing pigment, or a combination thereof.
The photothermal conversion agent is preferably an infrared absorbing dye, more preferably a NIR absorbing dye.
Infrared radiation absorbing pigments
Suitable examples of infrared absorbing (IR) pigments include, but are not limited to, carbon blacks such as acetylene black, channel black, furnace black, lamp black, and thermal black; oxides, hydroxides, sulfides, sulfates and phosphates of metals such as copper, bismuth, iron, nickel, tin, zinc, manganese, zirconium, tungsten, lanthanum and antimony, including lanthanum hexaboride, Indium Tin Oxide (ITO) and antimony tin oxide, titanium black and black iron oxide.
The preferred infrared absorbing pigment is carbon black.
The particle size of the pigment is preferably 0.01 to 5 μm, more preferably 0.05 to 1 μm.
The amount of infrared absorbing pigment is 10-1000 ppm, preferably 25-750 ppm, more preferably 50-500 ppm, most preferably 100-250 ppm, all relative to the total dry weight of the laser-markable layer. Amounts of infrared absorbing pigments above 1000 ppm result in a background density of the laser markable article that is too high.
The IR dyes disclosed below can also be used as IR pigments such as cyanine pigments, merocyanine pigments, and the like.
Other suitable infrared radiation absorbing pigments are disclosed in WO2005/068207, WO2007/141522, WO2009/059900 and WO 2015/015200.
Infrared radiation absorbing dyes
Infrared absorbing (IR) dyes are preferred over pigments because of their narrow absorption spectrum, enabling multicolor images to be formed.
In principle, any IR dye can be used, for example the IR Dyes disclosed in "Near-Infrared Dyes for High technology applications" (ISBN 978-0-7923) 5101-6).
An advantage of using IR dyes is that the absorption spectrum of IR dyes tends to be narrower than that of IR pigments. This allows for the creation of a multicoloured image when multiple laser markable layers are used, each containing a different IR dye and leuco dye. IR dyes having different absorption maxima wavelengths can then be addressed by an IR laser having a corresponding emission wavelength, resulting in the formation of a color only in the laser-markable layer of the addressed IR dye. Such multicoloured articles are disclosed, for example, in US 4720449, EP-A2719540 and EP-A2719541.
Preferred IR dyes are polymethine dyes due to their low absorption in the visible region and their selectivity, i.e. a narrow absorption peak in the infrared region. Particularly preferred polymethine IR dyes are cyanine IR dyes.
Preferred IR dyes having an absorption maximum of more than 1100 nm are those disclosed in paragraphs [0044] to [0083] of EP-A2722367 and paragraphs [0040] to [0051] of WO 2015/165854.
IR dyes having an absorption maximum between 1000 nm and 1100 nm are preferably selected from quinoline dyes, indolenine dyes, especially benzo [ cd ] indoline dyes. Particularly preferred IR dyes are 5- [2, 5-bis [2- [1- (1-methylbutyl) -benzo [ cd ] indol-2 (1H) -ylidene ] ethylidene ] -cyclopentylidene ] -1-butyl-3- (2-methoxy-1-methylethyl) -2,4,6(1H,3H,5H) -pyrimidinetrione (CASRN 223717-84-8) represented by the formula IR-1 or IR dyes represented by the formula IR-2:
both IR dyes IR-1 and IR-2 have a maximum absorption λ max of about 1052 nm, which makes them well suited for emitting Nd-YAG laser light with a wavelength of 1064 nm.
Combinations of two, three or more IR dyes may be used in the laser markable layer. This combination of IR dyes can be used to optimize the absorption spectrum of the laser markable layer. Furthermore, mixtures of IR dyes can improve the solubility of the IR dyes in the laser-markable composition for the preparation of laser-markable layers.
Ultraviolet absorber
The laser markable composition may further comprise an ultraviolet absorber. However, it is preferred that the uv absorber is present in a protective layer provided on top of the printed laser markable image.
Examples of suitable UV absorbers include 2-hydroxyphenylbenzophenone (BP), e.g., Chimassorb from BASFTM81 and ChimassorbTM90, respectively; 2- (2-hydroxyphenyl) -Benzotriazoles (BTZ), e.g. Tinuvin from BASFTM109、TinuvinTM1130、TinuvinTM171、TinuvinTM326、TinuvinTM328、TinuvinTM384-2、TinuvinTM99-2、TinuvinTM900、TinuvinTM928、TinuvinTMCarboprotectTM、TinuvinTM360、TinuvinTM1130、TinuvinTM327、TinuvinTM350、TinuvinTM234 Mixxim from FAIRMOUNTTMBB/100, Chiguard 5530 from Chitec; 2-hydroxy-phenyl-s-triazine (HPT), e.g. Tinuvin from BASFTM460、TinuvinTM400、TinuvinTM405、TinuvinTM477、TinuvinTM479、TinuvinTM1577 ED、TinuvinTM1600, 2- (2, 4-dihydroxyphenyl) -4, 6-bis- (2, 4-dimethylphenyl) -s-triazine from Capot Chemical Ltd (CASRN1668-53-7), and 4- [4, 6-bis (2-methyl-phenoxy) -1,3, 5-triazin-2-yl]-1, 3-benzenediol (CASRN 1)3413-61-1); titanium dioxide, such as Solasorb 100F from croda chemicals; zinc oxide, such as Solasorb 200F from Croda Chemicals; benzoxazines, e.g. Cyasorb UV-3638F, CYASORB from CYTECTMUV-1164; and oxamides, such as Sanduvor VSU from Clariant.
Preferred UV absorbers have an absorption maximum in the wavelength region between 300-400 nm, which is above 330 nm, more preferably above 350 nm.
Particularly preferred UV absorbers are hydroxyphenyl-benzotriazole and 2-hydroxyphenyl-s-triazine, having an absorption maximum in the wavelength region of 300-400 nm, which is above 350 nm.
Acid scavenger
The laser-markable composition may contain one or more acid scavengers.
The acid scavenger comprises an organic or inorganic base. Examples of the inorganic base include hydroxides of alkali metals or alkaline earth metals; secondary or tertiary phosphates, borates, carbonates; quinoline salts (quinolinate) and metaborate salts of alkali metals or alkaline earth metals; zinc hydroxide or zinc oxide in combination with a chelating agent (e.g., sodium picolinate); hydrotalcites, such as Hycite 713 from Clariant; ammonium hydroxide; quaternary alkylammonium hydroxides; and hydroxides of other metals. Examples of the organic base include aliphatic amines (e.g., trialkylamines, hydroxyamines, and aliphatic polyamines); aromatic amines (e.g., N-alkyl substituted aromatic amines, N-hydroxyalkyl substituted aromatic amines, and bis [ p- (dialkylamino) phenyl ] -methane), heterocyclic amines, amidines, cyclic amidines, guanidines, and cyclic guanidines.
Other preferred acid scavengers are HALS compounds. Examples of suitable HALS include Tinuvin from BASFTM292、TinuvinTM123、TinuvinTM1198、TinuvinTM1198 L、TinuvinTM144、TinuvinTM152、TinuvinTM292、TinuvinTM292 HP、TinuvinTM5100、TinuvinTM622 SF、TinuvinTM770 DF、ChimassorbTM2020 FDL、ChimassorbTM944 LD; hostavin 3051, Hostavin3050, Hostavin N30, Hostavin N321, Hostavin N from Clariant 845 PP、Hostavin PR31。
Other examples of acid scavengers are salts of weak organic acids, such as carboxylic acid salts (e.g., calcium stearate).
Preferred acid scavengers are organic bases, more preferably amines. Particularly preferred acid scavengers are organic bases having a pKb of 7 or less.
Laser markable article
The laser-markable articles of the present invention are prepared by applying the laser-markable compositions of the present invention on a support.
The laser-markable composition may be provided on the support by co-extrusion or any conventional coating technique, such as dip coating, knife coating, extrusion coating, spin coating, spray coating, slide hopper coating and curtain coating, to form a laser-markable layer.
The laser markable composition may also be provided on the support by any printing method, such as gravure printing, screen printing, flexographic printing, offset printing, inkjet printing, rotogravure printing and the like.
When only a part or parts of the carrier have to be provided with the laser-markable composition, a printing method is preferably used.
The laser markable article may be selected from a package, a foil, a laminate, a security document, a label, an ornament or an RFID label.
Carrier
The laser-markable composition can be applied on any type of surface, for example a metal support, a glass support, a polymeric support or a paper support. Laser-markable compositions can also be applied to the textile surface.
The carrier may be provided with a primer to improve the adhesion between the carrier and the laser-markable composition.
A dye or pigment containing primer, such as a white primer, may also be provided on the support, for example to improve the contrast of the laser marked image.
The support may be a paper support, such as plain paper or resin coated paper, such as polyethylene or polypropylene coated paper.
The type of paper is not limited in practice and includes newsprint, magazine, office or wallpaper, as well as higher grammage paper, commonly referred to as board, such as white board, corrugated (fibre) board and packaging board.
Furthermore, so-called synthetic papers can be used as carriers, for example the Synaps from Agfa GevaertTMSynthetic papers which are opaque polyethylene terephthalate sheets.
Suitable polymeric carriers include cellulose acetate propionate or cellulose acetate butyrate, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyamides, polycarbonates, polyimides, polyolefins, polyvinyl chloride, polyvinyl acetals, polyethers, polysulfonamides, Polylactides (PLA) and polyimides.
The preferred polymeric support is a biaxially stretched polyethylene terephthalate foil (PET-C foil) due to its very high durability and resistance to scratches and chemicals.
The manufacture of PET-C foils and supports is well known in the art for the preparation of suitable supports for silver halide photographic films. For example, GB 811066 (ICI) teaches a method for producing biaxially oriented polyethylene terephthalate foils and supports.
The polymeric support may be a single component extrudate or a coextrusion. Examples of suitable coextrudates are PET/PETG and PET/PC.
The shape of the support is not limited. It may be a flat plate, such as paper or a polymeric film, or may be a three-dimensional object, such as a plastic coffee cup, for example.
The three-dimensional object may also be a container, like a bottle or a jerry-can, for example for containing oils, shampoos, insecticides, pesticides, solvents, paint thinners or other types of liquids.
The laser-markable compositions can also be applied on so-called shrink foils. Such foils shrink tightly on anything they cover when heat is applied.
The most commonly used shrink foils are polyolefin foils, i.e. polyethylene or polypropylene foils. However, other shrink foils include PCV foils.
Package (I)
Preferred laser markable articles are packaging.
Laser marking is commonly used to add variable data, such as lot numbers, expiration dates, addresses, etc., to packages.
Laser marking is preferably performed on-line during the packaging process.
The "image" of the laser marking on the package may comprise data, an image, a barcode, a QR code, or a combination thereof.
An advantage of using laser marking during the packaging process is that information can be marked by the packaging foil, e.g. a taste foil for cigarette packaging. In this way, variable data can be provided on the cigarette package after the protective foil has been provided.
Another preferred laser markable package is for pharmaceutical packaging. For pharmaceutical packaging, tracking and traceability requirements are becoming more and more demanding to comply with evolving regulations.
Another advantage of using laser marking instead of another printing technique, such as inkjet printing, is that no chemicals are present during the marking process. Especially for pharmaceutical and food packaging, the absence of chemicals in the packaging line is a great advantage.
By selecting an appropriate leuco dye, or mixture of leuco dyes, the package can be provided with data or images of any color.
Preferred packages are folded paperboard or corrugated board laminated with paper. Such a package is preferably used for cosmetics, pharmaceuticals, food products or electronic products.
When the package is provided with a plurality of laser markable compositions, each containing a different leuco dye and a photo-thermal converting agent, multicolor and even full color images are obtained, as disclosed in EP-A2719540 (Agfa Gevaert) and EP-A2719541 (Agfa Gevaert).
Security document
The laser-markable compositions can also be used for the production of security documents, such as, for example, ID cards.
Typically, the laser markable security document is prepared by laminating a laser markable foil or laminate, optionally together with other foils or laminates, on one or both sides of the core support.
Such laser-markable security documents and their preparation have been disclosed, for example, in WO2015/091782 (AgfaGevaert).
By providing the laser-markable composition of the present invention on a support, laser-markable laminates can be prepared. The support is as described above and is preferably a transparent polymeric support.
The laser markable laminate may comprise more than one laser markable layer or may comprise further layers, such as an ink receiving layer, a UV absorbing layer, an intermediate layer or an adhesion promoting layer.
Typically, the laser markable laminate is laminated on one or both sides of the core support using elevated temperature and pressure.
Preferred core carriers are disclosed in paragraphs [0112] to [0015] of WO2014/057018 (Agfa Gevaert).
The lamination temperature depends on the type of core carrier used. For polyester cores, the lamination temperature is preferably between 120-140 deg.C, while for polycarbonate cores, the lamination temperature is preferably above 150-160 deg.C.
Laser marking
Laser marking is performed with an infrared laser.
The infrared laser may be a continuous wave or pulsed laser.
For example, CO with an emission wavelength of typically 10600 nm (10.6 microns) may be used2Laser, continuous wave, high power infrared laser.
CO2Lasers are widely available and inexpensive. However, this CO2A disadvantage of lasers is the rather long emission wavelength, which limits the resolution of the information marked by the laser.
To generate high resolution laser marked data, it is preferred to use Near Infrared (NIR) laser light emitting wavelengths between 750 and 2500 nm, preferably between 800 and 1500 nm, in the laser marking step.
A particularly preferred NIR laser is an optically pumped semiconductor laser. Optically pumped semiconductor lasers have the advantage of unique wavelength flexibility, unlike any other solid state based laser. The output wavelength may be set anywhere between about 920 nm to about 1150 nm. This allows a perfect match between the laser emission wavelength and the maximum absorption of the light-to-heat converter present in the laser-markable layer.
The preferred pulsed laser is a solid state Q-switched laser. Q-switching is a technique by which a laser can be prepared to produce a pulsed output beam. This technique allows the generation of optical pulses with very high peak power, much higher than would be generated by the same laser if operating in continuous wave (constant output) mode, Q-switching results in a much lower pulse repetition rate, much higher pulse energy, and much longer pulse duration.
Laser marking can also be performed using so-called Spatial Light Modulators (SLM), as disclosed in WO2012/044400 (VardexLaser Solutions).
Examples
Material
All materials used in the following examples are readily available from standard sources, such as ALDRICH CHEMICAL co. (belgium) and ACROS (belgium), unless otherwise noted. The water used was deionized water.
CCE is Hydran APX-101H, polyester urethane from DIC (45%).
PAR-sol is a 40 wt% aqueous solution of PAR.
PAR is a dimethyltrimethylolamine formaldehyde resin from Cyec Industries.
PEA-sol is a 10 wt% dispersion of PEA in water/ethanol (1/1).
PEA is Topearl from Momentive Performance ChemicalsTM120。
The Surfynsol is SurfynolTM420, 2.5 wt% solution.
SurfynolTM420 is a nonionic surfactant from Air Products.
DOW-sol is DowfaxTM2a1 in isopropanol.
DowfaxTM2A1 is an anionic surfactant from Pilot Chemicals C.
Infrared dye IR1 is an infrared dye according to the following structure.
The IR1 dye can be prepared according to the synthetic methods reported in EP-A2463109 (Agfa Gevaert) paragraphs [0150] to [0159 ].
Leuco dye LD1 is a magenta leuco dye according to the following structure, supplied by Connect chemical production as WINCON-RED.
PVB is polyvinyl acetal (Piolofur) BL16 supplied by Wacker-Chemie.