Ink composition, image forming method and printed article

1. An ink composition comprising at least a colorant (a) and a polymer (b) which is a colorant dispersant and which contains a repeating unit represented by the following formula (1):

wherein R represents a hydrogen atom or a methyl group; J represents —CO—, —COO—, —CONR 1 —, —OCO—, a methylene group or a phenylene group; R 1 represents a hydrogen atom, an alkyl group or an aryl group; n denotes 0 or 1; W represents a single bond or a divalent connecting group; and P represents a heterocyclic moiety, wherein a hetero ring of the heterocyclic moiety is selected from the group consisting of benzimidazolone, quinoline, acridine, acridone, phthalimide, quinaldine and quinophthalone.

2. The ink composition according to claim 1 , wherein the composition further comprises a polymerizable compound (c).

3. The ink composition according to claim 1 , wherein the average particle diameter of the colorant (a) is 0.01 to 0.4 μm.

4. The ink composition according to claim 1 , wherein the colorant (a) is a pigment.

5. The ink composition according to claim 1 , wherein P in the formula (1) includes at least any one selected from benzimidazolone, quinoline, acridine and acridone.

6. The ink composition according to claim 1 , wherein the polymer (b) is a graft copolymer containing, as a copolymer unit, a polymerizable oligomer having an ethylenically unsaturated double bond at its terminal.

7. The ink composition according to claim 1 , wherein two or more of the polymer (b) are used in combination.

8. An inkjet composition comprising the ink composition of claim 1 .

9. The ink composition according to claim 1 , wherein the repeating unit represented by formula (1) is selected from the group consisting of repeating units represented by formulas M-1, M-3, M-4, M-13, M-14 and M-17:

10. The ink composition according to claim 1 , wherein J represents —CONR 1 —, —OCO—, a methylene group or a phenylene group.

11. The ink composition according to claim 1 , wherein the polymer (b) includes a repeating unit derived from a monomer selected from the group consisting of N,N-dimethylaminoethyl(meth)acrylate, N,N-dimethylaminopropyl(meth)acrylate, N,N-diethylaminoethyl(meth)acrylate, N,N-diisopropylaminoethyl(meth)acrylate, 2-(N,N-dimethylamino)ethyl(meth)acrylamide, 2-(N,N-diethylamino)ethyl(meth)acrylamide, 3-(N,N-diethylamino)propyl(meth)acrylamide and 3-(N,N-dimethylamino)propyl(meth)acrylamide.

12. The ink composition according to claim 2 , wherein a combination of at least one oxetane compound and at least one compound selected from an epoxy compound and a vinyl ether compound is used as the polymerizable compound (c).

13. The ink composition according to claim 2 , the ink composition further comprising a polymerization initiator (d).

14. The ink composition according to claim 13 , wherein the polymerizable compound (c) is a radically polymerizable compound, and the polymerization initiator (d) is a photo-radical generator.

15. The ink composition according to claim 13 , wherein the polymerizable compound (c) is a cationic polymerizable compound, and the polymerization initiator (d) is a photo-acid generator.

16. The ink composition according to claim 6 , wherein the polymerizable oligomer is an oligomer represented by the following formula (2):

wherein R 11 and R 13 each independently represent a hydrogen atom or a methyl group; R 12 represents an alkylene group having 1 to 12 carbon atoms; and Y represents a phenyl group or —COOR 14 wherein the phenyl group may be substituted by an alkyl group having 1 to 4 carbon atoms; and R 14 represents an alkyl group having 1 to 10 carbon atoms or a phenyl group.

17. The ink composition according to claim 6 , wherein the polymerizable oligomer is an oligomer represented by the following formula (3):

wherein R 21 represents a hydrogen atom or a methyl group; R 22 represents an alkylene group having 1 to 8 carbon atoms; X 21 represents —OR 23 or —OCOR 24 , wherein R 23 and R 24 each independently represent a hydrogen atom, an alkyl group or an aryl group; and n denotes a number from 2 to 200.

18. The ink composition according to claim 6 , wherein the polymer (b) is a copolymer with a monomer which further comprises a nitrogen atom-containing group.

19. The ink composition according to claim 18 , wherein the monomer having a nitrogen atom-containing group and an ethylenically unsaturated double bond is represented by the following formula (4):

wherein R 1 represents a hydrogen atom or a methyl group; R 2 represents an alkylene group having 1 to 12 carbon atoms; X′ represents —N(R 3 )(R 4 ), —R 5 —N(R 6 )(R 7 ) or a basic heterocyclic group containing nitrogen; R 3 , R 4 , R 6 and R 7 each independently represent a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or an aryl group having 6 to 18 carbon atoms; R 5 represents an alkylene group having 1 to 12 carbon atoms; and m and n each independently denote 1 or 0.

20. The ink composition according to claim 9 , wherein the repeating unit represented by formula (1) is a repeating unit represented by formula M-4 or M-13:

21. An image forming method comprising: applying an ink composition comprising at least a colorant (a) and a polymer (b) on a recording medium by printing, and irradiating the applied ink composition with an active energy ray to cure the composition,

wherein the polymer (b) is a colorant dispersant and contains a repeating unit represented by the following formula (1):

wherein R represents a hydrogen atom or a methyl group; J represents —CO—, —COO—, —CONR 1 —, —OCO—, a methylene group or a phenylene group; R 1 represents a hydrogen atom, an alkyl group or an aryl group; n denotes 0 or 1; W represents a single bond or a divalent connecting group; and P represents a heterocyclic moiety, wherein a hetero ring of the heterocyclic moiety is selected from the group consisting of benzimidazolone, quinoline, acridine, acridone, phthalimide, quinaldine and quinophthalone.

22. The image forming method according to claim 21 , wherein the repeating unit represented by formula (1) is selected from the group consisting of repeating units represented by formulas M-1, M-3, M-4, M-13, M-14 and M-17:

23. The image forming method according to claim 21 , wherein J represents —CONR 1 —, —OCO—, a methylene group or a phenylene group.

24. The image forming method according to claim 21 , wherein the polymer (b) includes a repeating unit derived from a monomer selected from the group consisting of N,N-dimethylaminoethyl(meth)acrylate, N,N-dimethylaminopropyl(meth)acrylate, N,N-diethylaminoethyl(meth)acrylate, N,N-diisopropylaminoethyl(meth)acrylate, 2-(N,N-dimethylamino)ethyl(meth)acrylamide, 2-(N,N-diethylamino)ethyl(meth)acrylamide, 3-(N,N-diethylamino)propyl(meth)acrylamide and 3-(N,N-dimethylamino)propyl(meth)acrylamide.

25. The image forming method according to claim 22 , wherein the repeating unit represented by formula (1) is a repeating unit represented by formula M-4 or M-13:

26. A printed article obtained by curing an ink composition comprising at least a colorant (a) and a polymer (b),

wherein the polymer (b) is a colorant dispersant and contains a repeating unit represented by the following formula (1):

wherein R represents a hydrogen atom or a methyl group; J represents —CO—, —COO—, —CONR 1 —, —OCO—, a methylene group or a phenylene group; R 1 represents a hydrogen atom, an alkyl group or an aryl group; n denotes 0 or 1; W represents a single bond or a divalent connecting group; and P represents a heterocyclic moiety, wherein a hetero ring of the heterocyclic moiety is selected from the group consisting of benzimidazolone, quinoline, acridine, acridone, phthalimide, quinaldine and quinophthalone.

27. The printed article according to claim 26 , wherein the printed article is obtained by applying the ink composition to a recording medium by printing using an inkjet printer and then irradiating the ink composition with an active energy ray to cure the ink composition.

28. The printed article according to claim 26 , wherein the repeating unit represented by formula (1) is selected from the group consisting of repeating units represented by formulas M-1, M-3, M-4, M-13, M-14 and M-17:

29. The printed article according to claim 26 , wherein J represents —CONR 1 —, —OCO—, a methylene group or a phenylene group.

30. The printed article according to claim 26 , wherein the polymer (b) includes a repeating unit derived from a monomer selected from the group consisting of N,N-dimethylaminoethyl(meth)acrylate, N,N-dimethylaminopropyl(meth)acrylate, N,N-diethylaminoethyl(meth)acrylate, N,N-diisopropylaminoethyl(meth)acrylate, 2-(N,N-dimethylamino)ethyl(meth)acrylamide, 2-(N,N-diethylamino)ethyl(meth)acrylamide, 3-(N,N-diethylamino)propyl(meth)acrylamide and 3-(N,N-dimethylamino)propyl(meth)acrylamide.

31. The printed article according to claim 28 , wherein the repeating unit represented by formula (1) is a repeating unit represented by formula M-4 or M-13: