Radiation curable photochromic inks
View Patent ↗An ink that may be used in ink jet devices is a photochromic ink comprising an ink vehicle that includes at least one radiation curable component, at least one photochromic material and at least one photoinitiator. The ink is cured via exposure to radiation that cures the at least one radiation curable component of the ink. A radiation curable ink capable of exhibiting photochromatic color changes, which may be used to indicate a document's authenticity, is thus achieved.
1. A photochromic ink comprising an ink vehicle that includes at least one radiation curable component, at least one photochromic material, at least one epoxy-containing or amine-containing gelator, and at least one photoinitiator.
2. The photochromic ink according to claim 1 , wherein the at least one photochromic material has a fatigue resistance such that following curing of the photochromic ink by exposure to curing radiation, the photochromic material is able to change from a colored state to a substantially non-colored state for at least about 10 times.
3. The photochromic ink according to claim 1 , wherein the at least one photochromic material is selected from the group consisting of diarylethenes, spiropyrans, spirooxazines, fulgides, stilbenes, aromatic azo compounds, benzopyrans, naphthopyrans, bisimidazoles, spirodihydroindolizines, spirotetrahydroindolizines, spirohexahydroindolizines, quinones, perimidinespirocyclohexadienones, viologens, triarylmethanes, anils, and mixtures thereof.
4. The photochromic ink according to claim 1 , wherein the at least one photochromic material includes a diarylethene of the formula
wherein X and Y are, each independently, sulfur, nitrogen, hydrogen, or oxygen, R 1 and R 4 are, independently, an alkyl, alkoxy or aryl group having from 1 to about 30 carbon atoms, R 2 , R 3 , R 5 , and R 6 are independently hydrogen, alkyl having from 1 to about 50 carbon atoms, aryl having from about 5 to about 30 carbon atoms, arylalkyl having from about 6 to about 50 carbon atoms, silyl groups, nitro groups, sulfo groups, cyano groups, halide atoms, amine groups, hydroxy groups, alkoxy groups having from 1 to about 50 carbon atoms, aryloxy groups having from about 5 to about 30 carbon atoms, alkylthio groups or alkylsulfo groups having from 1 to about 50 carbon atoms, arylthio groups or arylsulfo groups having from about 5 to about 30 carbon atoms, aldehyde groups, ketone groups, ester groups, amide groups, carboxylic acid groups, or sulfonic acid groups, or two or more R groups can be joined together to form a ring.
5. The photochromic ink according to claim 1 , wherein the at least one photochromic material includes a diarylethene selected from the group consisting of
6. The photochromic ink according to claim 1 , wherein the at least one photochromic material includes a spirooxazine of the formula
wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 and R 13 each, independently of the others, is hydrogen, alkyl having from 1 to about 50 carbon atoms, aryl having from about 5 to about 30 carbon atoms, arylalkyl having from about 6 to about 50 carbon atoms, silyl groups, nitro groups, sulfo groups, cyano groups, halide atoms, amine groups, hydroxy groups, alkoxy groups having from 1 to about 50 carbon atoms, aryloxy groups having from about 5 to about 30 carbon atoms, alkylthio groups or alkylsulfo groups having from 1 to about 50 carbon atoms, arylthio groups or arylsulfo groups having from about 5 to about 30 carbon atoms, aldehyde groups, ketone groups, ester groups, amide groups, carboxylic acid groups, or sulfonic acid groups, or two or more R groups can be joined together to form a ring, X is O and Y is N.
7. The photochromic ink according to claim 1 , wherein the at least one photochromic material includes a spirooxazine selected from the group consisting of 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]naphth[2,1-b]-[1,4]oxazine], 1,3-dihydro-1,3,3-trimethyl-5-nitrospiro[2H-indole-2,3′-[3H]naphth[2,1-b]-[1,4]oxazine], 1,3-dihydro-1,3,3-trimethyl-5,6′-dinitro-spiro[2H-indole-2,3′-[3H]naphth[2,1-b]-[1,4]oxazine], 1,3-dihydro -1,3,3-trimethyl-5-methoxy, 5′-methoxy-spiro[2H-indole-2,3′-[3H]naphth[2,1-b]-[1,4]oxazine], and 1,3-dihydro-1-ethyl-3,3-dimethyl-5′-nitrospiro[2H-indole-2,3′-[3H]naphth[2,1-b]-[1,4]oxazine].
8. The photochromic ink according to claim 1 , wherein the at least one photochromic material includes a fulgide of the formula:
wherein one, two, three or more substituents may be optionally present at the 1, 2, 4, 5 and 6 positions, wherein X is O or NR, and wherein R is hydrogen, alkyl having from 1 to about 50 carbon atoms, aryl having from about 5 to about 30 carbon atoms, arylalkyl having from about 6 to about 50 carbon atoms, silyl groups, nitro groups, sulfo groups, cyano groups, halide atoms, amine groups, hydroxy groups, alkoxy groups having from 1 to about 50 carbon atoms, aryloxy groups having from about 5 to about 30 carbon atoms, alkylthio groups or alkylsulfo groups having from 1 to about 50 carbon atoms, arylthio groups or arylsulfo groups having from about 5 to about 30 carbon atoms, aldehyde groups, ketone groups, ester groups, amide groups, carboxylic acid groups, or sulfonic acid groups.
9. The photochromic ink according to claim 1 , wherein the at least one photochromic material includes a fulgide selected from the group consisting of 1-(p-methoxyphenyl)-ethylidene (isopropylidene) succinic anhydride, 2-[1-(2,5-dimethyl-3-furyl)-2-methylpropylidene]-3-isopropylidene succinic anhydride, and (1,2-dimethyl-4-isopropyl-5-phenyl)-3-pyrryl ethylidene (isopropylidene) succinic anhydride.
10. The photochromic ink according to claim 1 , wherein the photochromic material comprises from about 1% to about 10% by weight of the photochromic ink.
11. The photochromic ink according to claim 1 , wherein the at least one radiation curable component is a cycloaliphatic epoxide, a multifunctional vinyl ether, an acrylate or methacrylate monomer or oligomer, or includes the following:
where X is O or NH, and C* is any of
12. The photochromic ink according to claim 1 , wherein the radiation curable component comprises from about 5% to about 95% by weight of the photochromic ink.
13. The photochromic ink according to claim 1 , wherein the ink forms a gel state having a viscosity of at least 10 2.5 cps at temperatures between about 30° C. to about 60° C.
14. The photochromic ink according to claim 1 , wherein the ink has a viscosity of about 1 to about 20 cps at temperatures of from about 50° C. to about 150° C.
15. The photochromic ink according to claim 1 , wherein the gelator comprises from about 1% to about 50% by weight of the ink.
16. The photochromic ink according to claim 1 , wherein the at least one photoinitiator comprises from about 0.5% to about 15% by weight of the ink.
17. The photochromic ink according to claim 1 , wherein the ink further comprises at least one colorant.
18. The photochromic ink according to claim 1 , wherein the ink further comprises at least one thermal solvent selected from among polyols, sulfonamides, urea, ethyl urea, ethylene carbonate, tetrahydro-thiophene-1,1-dioxide, methyl anisate, bifunctional fatty alcohols, pyridine N-oxide, acetamide, acrylamide, sulfamide, maleimide, pyrazole or imidazole.
19. The photochromic ink according to claim 1 , wherein the at least one photoinitiator is selected from the group consisting of benzophenones, benzoin ethers, benzilketals, α-hydroxyalkylphenones, α-aminoalkylphenones, acylphosphines, titanocenes, isopropylthioxanthone, 1-hydroxy-cyclohexylphenylketone, benzophenone, 2,4,6-trimethylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzoylphenylphosphinic acid ethyl ester, oligo(2-hydroxy-2-methy-1-(4-(1-methylvinyl)phenyl) propanone), 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzyl-dimethylketal, ethyl-4-dimethylaminobenzoate, 2-ethylhexyl1-4-dimethylaminobenzoate, sulfonium salts, sulfoxonium salts, iodonium salts, sensitized acids and mixtures thereof.
20. An image forming process, comprising
providing a photochromic ink comprising an ink vehicle that includes at least one radiation curable component, at least one photochromic material, at least one epoxy-containing or amine-containing gelator, and at least one photoinitiator,
forming an image on an image receiving substrate with the photochromic ink, and
curing the photochromic ink by exposure to radiation for curing the at least one radiation curable component.
21. The image forming process according to claim 20 , wherein the image is formed by jetting the photochromic ink at a temperature of from about 50° C. to about 130° C. onto the image receiving substrate.
22. The image forming process according to claim 20 , wherein the process further comprises permitting the ink to form a gel state during formation of the image on the image receiving substrate.
23. A process for authenticating a document, comprising forming an image on the document with a photochromic ink comprising an ink vehicle that includes at least one radiation curable component, at least one photochromic material, at least one epoxy-containing or amine-containing gelator, and at least one photoinitiator,
curing the photochromic ink by exposure to radiation for curing the at least one radiation curable component, which curing effects a color change in the at least one photochromic material, and subsequently exposing the cured ink to visible light to render the photochromic material substantially colorless, and
exposing the document to activating radiation to generate a color change in the photochromic ink, the color change indicating the authenticity of the document.
24. A process according to claim 23 , wherein the wavelength of the activating radiation is from about 200 to about 400 nm.