Ink and ink set for ink jet printing and method of ink jet printing

1. An ink jet recording ink composition comprising an aqueous medium and at least one dye dissolved and/or dispersed in said aqueous medium, wherein said dye is an azo dye having a chromophore represented by the formula (heterocyclic ring A)-N=N-(heterocyclic ring B), provided that the heterocyclic ring A and the heterocyclic ring B may have the same structure, and at least one betaine-type surfactant is contained in said ink composition.

2. The inkjet recording ink composition as claimed in claim 1 , wherein in a molecule of said betaine-type surfactant, a cationic moiety is a quaternary nitrogen atom and an anionic moiety is a carboxyl group or a sulfo group.

3. The inkjet recording ink composition as claimed in claim 1 , wherein said betaine-type surfactant is a compound with a N-position of imidazole being substituted by a carboxyalkyl group (compound A), or an alkylamine salt compound having an alkyl substituted by a carboxyl group or a sulfo group (compound B).

4. The inkjet recording ink composition as claimed in claim 3 , wherein said compound A is a compound represented by formula (A):

wherein R S1 and R S2 each represents an alkyl group, and R S3 represents a carboxyl or sulfo group-containing alkyl group.

5. The inkjet recording ink composition as claimed in claim 3 , wherein said compound B is a compound represented by formula (B):

wherein R S4 , R S5 and R S6 each independently represents an alkyl group, an aryl group or a heterocyclic group and may combine with each other to form a ring structure, and R S7 represents a carboxyl or sulfo group-containing alkyl group.

6. The inkiet recording ink composition as claimed in claim 5 , wherein in said compound represented by formula (B), R S4 , R S5 and R S6 each independently represents an alkyl group and a group represented by R S7 is represented by -L-COO—, in which L represents a linking group.

7. The inkiet recording ink composition as claimed in claim 6 , wherein in said compound represented by formula (B), L represents CH(R S8 ), R S8 represents a hydrogen atom or an alkyl group having 8 or more carbon atoms, and at least one of R S4 , R S5 , R S6 and R S8 is an alkyl group having 8 or more carbon atoms.

8. The inkjet recording ink composition as claimed in claim 1 , wherein said dye is an azo dye having an absorption maximum in a spectral region of 500 to 580 nm in said aqueous medium and having an oxidation potential nobler than 1.0 V (vs SCE).

9. The inkjet recording ink composition as claimed in claim 1 , wherein said azo dye is an azo dye in which an aromatic nitrogen-containing 6-membered heterocyclic ring is bonded as a coupling component directly to at least one side of an azo group.

10. The inkjet recording ink composition as claimed in claim 1 , wherein said azo dye is an azo dye having an aromatic ring amino group- or heterocyclic amino group-containing structure as an auxochrome.

11. The inkjet recording ink as claimed in claim 1 wherein said azo dye is an azo dye having a steno structure.

12. The inkjet recording ink composition as claimed in claim 1 , wherein said azo dye is a dye represented by the following formula (1):

wherein A represents a 5-membered heterocyclic group;

B 1 and B 2 each represents ═CR 1 —or —CR 2 ═ or either one of B 1 and B 2 represents a nitrogen atom and other represents ═CR 1 — or —CR 2 ═;

R 5 and R 6 each independently represents a hydrogen atom or a substituent, said substituent is an aliphatic group, an aromatic group, a heterocyclic group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, an alkylsulfonyl group, an arylsulfonyl group or a sulfamoyl group, and hydrogen atom of each substituent may be substituted;

G, R 1 and R 2 each independently represents a hydrogen atom or a substituent, said substituent is a halogen atom, an aliphatic group, an aromatic group, a heterocyclic group, a cyano group, a carboxyl group, a carbamoyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heterocyclic oxycarbonyl group, an acyl group, a hydroxy group, an alkoxy group, an aryloxy group, a heterocyclic oxy group, a silyloxy group, an acyloxy group, a carbamoyloxy group, an alkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group, an acylamino group, a ureido group, a sulfamoylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a heterocyclic sulfonylamino group, a nitro group, an alkylthio group, an arylthio group, a heterocyclic thio group, an alkylsulfonyl group, an arylsulfonyl group, a heterocyclic sulfonyl group, an alkyisulfinyl group, an arylsulfinyl group, a heterocyclic sulfinyl group, a sulfamoyl group or a sulfo group, and hydrogen atom of each substituent may be substituted; and

R 1 and R 5 , or R 5 and R 6 may combine to form a 5- or 6-membered ring.

13. The inkjet recording ink composition as claimed in claim 1 , wherein an ozone discoloration rate constant of recorded image is 5.010 −2 [hour −1 ] or less.

14. The inkjet recording ink composition as claimed in claim 1 , wherein a nonionic surfactant is contained in said ink composition.

15. The inkjet recording ink composition as claimed in claim 1 , wherein an organic solvent having a boiling point of 150° C. or more is contained in said ink composition.

16. An inkjet recording ink set comprising at least one inkjet recording ink composition claimed in any one of claims 1 to 15 .

17. An inkjet recording method comprising recording an image in an inkjet printer by using said inkjet recording ink composition claimed in claim 1 .

18. The inkjet recording method as claimed in claim 17 , comprising ejecting ink droplets according to recording signals on an image-receiving material including a support having thereon an image-receiving layer containing a white inorganic pigment particle, thereby recording an image on said image-receiving material, wherein said ink droplet comprises said inkjet recording ink composition.