Inkjet recording ink and method of inkjet recording

1. An inkjet recording ink comprising an aqueous medium having dissolved therein a phthalocyanine dye, wherein said phthalocyanine dye has an ionic hydrophilic group and is a water-soluble dye having an oxidation potential more positive than 1.0 V (vs SCE) and the ink comprises a water-miscible organic solvent having a vapor pressure of 2,000 Pa or less at 20° C.

wherein said phthalocyanine dye is represented by the following formula (I):

wherein X 1 , X 2 , X 3 and X 4 each independently represents —SO-Z, —SO 2 -Z, —SO 2 NR1R2, a sulfo group, —CONR1R2 or —CO 2 R1, and at least one of X 1 , X 2 , X 3 and X 4 represents —SO 2 -Z or —SO 2 NR1R2;

Z 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, and R1 and R2 each independently represents a hydrogen atom, 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 when a plurality of Zs are present, these may be the same or different,

Y 1 , Y 2 , Y 3 and Y 4 each independently represents a monovalent substituent,

provided that when a plurality of X 1 s, X 2 s, X 3 s, X 4 s, Y 1 s, Y 2 s, Y 3 s or Y 4 s are present, these may be the same or different,

a 1 to a 4 and b 1 to b 4 represent the number of substituents X 1 to X 4 and Y 1 to Y 4 , respectively, a 1 to a 4 each independently represents an integer of 0 to 4 but all are not 0 at the same time, b 1 to b 4 each independently represents an integer of 0 to 4, and

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

2. The inkjet recording ink as claimed in claim 1 , which comprises at least one organic solvent having a boiling point of 150° C. or more as the water-miscible organic solvent.

3. The inkjet recording ink as claimed in claim 2 , wherein the at least one organic solvent having a boiling point of 150° C. or more is an alcohol derivative.

4. The inkjet recording ink as claimed in claim 1 , which comprises at least one organic solvent having a boiling point of less than 150° C. as the water-miscible organic solvent.

5. The inkjet recording ink as claimed in claim 4 , wherein the at least one organic solvent having a boiling point of less than 150° C. is an alcohol derivative.

6. The inkjet recording ink as claimed in claim 1 , which comprises a polyhydric alcohol and/or a derivative thereof as the water-miscible organic solvent.

7. The inkjet recording ink as claimed in claim 6 , which comprises a mixture of two or more members containing the polyhydric alcohol and/or a derivative thereof.

8. The inkjet recording ink as claimed in claim 6 or 7 , which comprises the polyhydric alcohol and/or a derivative thereof at a concentration of 10 to 60 (mass/volume) %.

9. The inkjet recording ink as claimed in claim 1 , which comprises an organic solvent, in which the phthalocyanine dye has a solubility of 10 (g/100 g-solvent) or more at 250° C., as the water-miscible organic solvent.

10. The inkjet recording ink as claimed in claim 9 , which comprises a water-miscible organic solvent, in which the phthalocyanine dye has a solubility of 10 (g/100 g-solvent) or more at 250° C., in an amount of 10 mass % or less in the ink.

11. The inkjet recording ink as claimed in claim 1 , which comprises an organic solvent, which is liquid at ordinary temperature and does not contain a heteroatom other than an oxygen atom, as the water-miscible organic solvent.

12. The inkjet recording ink as claimed in claim 11 , wherein the organic solvent has a boiling point of 150° C. or more.

13. The inkjet recording ink as claimed in claim 1 , wherein the organic solvent is an alcohol derivative and is selected from a monool, a diol and a triol.

14. The inkjet recording ink as claimed in claim 1 , wherein the water content is from 40 to 80 mass % based on the ink solution.

15. The inkjet recording ink as claimed in claim 1 , wherein when the monochromatic moiety printed by using a single (cyan) color of the ink so as to give a cyan reflection density of 0.9 to 1.1 in a Status A filter is stored in an ozone environment of 5 ppm for 24 hours, a dye residual ratio (density after color fading/initial density×100) is 60% (preferably 80%) or more.

16. The inkjet recording ink as claimed in claim 1 , wherein after color fading with ozone under the conditions of claim 15 , the amount of Cu ion flowed out into water is 20% or less of all dyes.

17. The inkjet recording ink as claimed in claim 1 , wherein the phthalocyanine dye is a water-soluble dye having an electron-withdrawing group at the β-position of a benzene ring of said phthalocyanine.

18. The inkjet recording ink as claimed in claim 1 , wherein said phthalocyanine dye is a water-soluble phthalocyanine dye produced by a process not passing through sulfonation of an unsubstituted phthalocyanine.

19. The inkjet recording ink as claimed in claim 1 , wherein the dye represented by formula (I) is a dye represented by the following formula (II):

wherein X 11 to X 14 , and M 1 have the same meanings as X 1 to X 4 , and M in formula (I), respectively, provided that when a plurality of X 11 s to X 14 s are present, a plurality of substituents X 11 , X 12 , X 13 or X 14 may be the same or different;

Y 11 to Y 18 each represents a hydrogen atom or monovalent group;

a 11 to a 14 represent the number of substituents X 11 to X 14 and each independently represents an integer of 1 or 2.

20. An inkjet recording method comprising using the inkjet recording ink claimed in claims 1 .

21. An inkjet recording method comprising ejecting ink droplets according to recording signals on an image-receiving material comprising a support having thereon an image-receiving layer containing a white inorganic pigment particle, thereby recording an image on the image-receiving material, wherein said ink droplet comprises the inkjet recording ink claimed in claim 1 .

22. The inkjet recording ink as claimed in claim 19 , wherein Y 11 to Y 18 each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a cyano group, an alkoxy group, an amido group, a ureido group, a sulfonamido group, a carbamoyl group, a sulfamoyl group, an alkoxycarbonyl group, a carboxyl group, or a sulfo group.

23. The inkjet recording ink as claimed in claim 1 , wherein the water-miscible organic solvent is present in an amount of from 10 to 50 mass % of the inkjet recording ink.