Ink for ink jet recording, process for the production of ink and ink jet recording process

1. An ink for ink jet recording, comprising an aqueous medium and a phthalocyanine dye represented by the following formula (I) dissolved or dispersed in the aqueous medium,

wherein the phthalocyanine dye has an oxidation potential of more positive than 1.0 V and the ink has a conductivity of 0.01 S/m to 10 S/m:

wherein X 1 , X 2 , X 3 and X 4 each independently represent —SO-Z, —SO 2 -Z, —SO 2 NR 1 R 2 , a sulfo group, —CONR 1 R 2 or —CO 2 R 1 ; 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; R 1 and R 2 each independently represent 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; and when there are a plurality of Z's, they may be the same or different;

Y 1 , Y 2 , Y 3 and Y 4 each independently represent a monovalent substituent; and when there are a plurality of any of X 1 to X 4 and Y 1 to Y 4 , they 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 represent an integer of from 0 to 4 and are not 0 at the same time; and b 1 to b 4 each independently represent an integer of 0 to 4;

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

the phthalocyanine structure has at least one of —SO 2 -Z and —SO 2 NR 1 R 2 at a beta-position thereof.

2. The ink for ink jet recording according to claim 1 , which has a viscosity of 1 to 20 mPa·sec at 25° C.

3. The ink for ink jet recording according to claim 1 , which has a static surface tension of 25 to 50 mN/m at 25° C.

4. The ink for ink jet recording according to claim 2 ,

wherein a viscosity of the ink has a viscosity ratio of not greater than 250% from at 25° C. to at 10° C., and a static surface tension has a static surface tension ratio of not greater than 130% from at 25° C. to at 10° C.

5. The ink for ink jet recording according to claim 1 , which has a pH value of 4 to 12 at 25° C.

6. The ink for ink jet recording according to claim 1 ,

which has a dye remaining ratio of not smaller than 60% after 24 hours of storage in an atmosphere of 5 ppm ozone in a monochromatic area that is obtained by printing with a monochromatic ink in such a manner a cyan reflection density through a status A filter is from 0.9 to 1.1.

7. The ink for ink jet recording according to claim 1 ,

wherein the ink has Cu ions that are eluted with water in an amount of not greater than 20% of a total amount of the dye after 24 hours of storage in an atmosphere of 5 ppm ozone in a monochromatic area that is obtained by printing with a monochromatic ink in such a manner a cyan reflection density through a status A filter is from 0.9 to 1.1.

8. The ink for ink jet recording according to claim 1 ,

wherein the phthalocyanine dye is a water-soluble dye having an electron-withdrawing group at β-position of a benzene ring in the phthalocyanine.

9. The ink for ink jet recording according to claim 1 ,

wherein the phthalocyanine dye is a water-soluble dye that is produced by a process which doesn't pass through a sulfonation of an unsubstituted phthalocyanine.

10. The ink for ink jet recording according to claim 1 , wherein the dye represented by the formula (I) is a dye represented by the following formula (II):

wherein X 11 to X 14 and M have the same meaning as X 1 to X 4 and M in formula (I), respectively, provided that at least one of X 11 to X 14 represents —SO 2 -Z or —SO 2 NR 1 R 2 ; 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 amide group, a ureido group, a sulfonamide group, a carbamoyl group, a sulfamoyl group, an alkoxycarbonyl group, a carboxyl group or a sulfo group; when there are a plurality of X 11 to X 14 , they may be the same or different; a 11 to a 14 represent the number of substituents X 11 to X 14 , respectively, and each independently represents an integer of 1 or 2.

11. A method for ink jet recording, comprising using the ink for ink jet recording according to claim 1 .

12. A method for recording an image on an image-receiving material, comprising ejecting an ink droplet onto the image-receiving material including an image-receiving layer containing an inorganic white particulate pigment on a support according to a record signal,

wherein the ink droplet comprises the ink for ink jet recording according to claim 1 .

13. A method for producing the ink for ink jet recording according to claim 1 , which comprises at least applying an ultrasonic vibration.

14. A method for producing the ink for ink jet recording according to claim 1 ,

wherein the ink for ink jet recording prepared is filtered through a filter having pores of an effective diameter of not greater than 1 μm and defoamed before use.

15. The ink for ink jet recording according to claim 1 , wherein the ink contains the phthalocyanine dye in an amount of 0.2 to 20% by weight.

16. The ink for ink jet recording according to claim 10 , wherein X 11 to X 18 each represents a hydrogen atom.