Ink composition, and ink jet recording method and recorded matter using the same

1. An ink composition comprising at least water, a cyan dye represented by formula (II) shown below, and an aromatic compound having a carboxyl group and/or a salt thereof:

wherein R 1 to R 4 each independently represents SO 2 Z and each Z independently represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group, provided that at least one of the Z's has an ionic hydrophilic group as a substituent; and

M represents a hydrogen atom, a metal element or an oxide, hydroxide or halide thereof.

2. The ink composition as claimed in claim 1 , wherein said cyan dye is a cyan dye of formula (II) where M is a copper element and Z having an ionic hydrophilic group is a sulfoalkyl group.

3. The ink composition as claimed in claim 2 , wherein the counter cation of said sulfoalkyl group is a lithium cation.

4. The ink composition as claimed in claim 1 , wherein said aromatic compound having a carboxyl group and/or a salt thereof is an aromatic compound having one carboxyl group and/or a salt thereof.

5. The ink composition as claimed in claim 1 , wherein said aromatic compound having a carboxyl group and/or a salt thereof is a compound having a naphthalene skeleton and/or a salt thereof.

6. The ink composition as claimed in claim 5 , wherein said compound having a naphthalene skeleton and/or a salt thereof is a compound having a carboxyl group and an —OR group, wherein R is a hydrogen atom or an alkyl group having a carbon number of 1 to 6, on the naphthalene skeleton.

7. The ink composition as claimed in claim 6 , wherein said compound having a naphthalene skeleton and/or a salt thereof is a compound having one carboxyl group and one —OR group, wherein R is a hydrogen atom or an alkyl group having a carbon number of 1 to 6, on the naphthalene skeleton.

8. The ink composition as claimed in claim 5 , wherein said compound having a naphthalene skeleton and/or a salt thereof is a compound having a carboxyl group at its 2-position and/or a salt thereof.

9. The ink composition as claimed in claim 8 , wherein said compound having a carboxyl group at its 2-position and having a naphthalene skeleton and/or a salt thereof is at least one member selected from the group consisting of a 1-hydroxy-2-naphthoic acid, a 2-naphthoic acid, a 3-hydroxy-2-naphthoic acid, a 6-hydroxy-2-naphthoic acid, a 3-methoxy-2-naphthoic acid, a 6-methoxy-2-naphthoic acid, a 6-ethoxy-2-naphthoic acid, a 6-propoxy -2-naphthoic acid, and a salt thereof.

10. The ink composition as claimed in claim 1 , wherein said salt is a lithium salt.

11. The ink composition as claimed in claim 1 , which comprises said aromatic compound having a carboxyl group and/or a salt thereof in an amount of 0.1 to 10 wt % based on the entire amount of the ink composition.

12. The ink composition as claimed in claim 1 , wherein the content ratio of said cyan dye and said aromatic compound having a carboxyl group and/or a salt thereof is from 1:0.1 to 1:10 in terms of the weight ratio.

13. The ink composition as claimed in claim 1 , which further comprises a nonionic surfactant.

14. The ink composition as claimed in claim 13 , wherein said nonionic surfactant is an acetylene glycol-based surfactant.

15. The ink composition as claimed in claim 13 , which comprises said nonionic surfactant in an amount of 0.1 to 5 wt % based on the entire amount of the ink composition.

16. The ink composition as claimed in claim 1 , which further comprises a penetration accelerator.

17. The ink composition as claimed in claim 16 , wherein said penetration accelerator is a glycol ether.

18. The ink composition as claimed in claim 1 , wherein the pH of the ink composition at 20° C. is from 8.0 to 10.5.

19. An inkjet recording method that utilizes the ink composition as claimed in claim 1 .

20. The inkjet recording method as claimed in claim 19 , wherein said inkjet recording method is a recording method that utilizes an inkjet head which forms an ink droplet by mechanical deformation of an electrostrictive element.

21. An inkjet recording method comprising ejecting a liquid droplet of an ink composition, and attaching said liquid droplet onto a recording medium, thereby performing the recording, wherein the ink composition is the ink composition in claim 1 .

22. Recorded matter which is recorded with the ink composition claimed in claim 1 .

23. Recorded matter recorded by the recording method claimed in claim 21 .