Pigment dispersion for ink jet ink, ink jet ink, and printed matter

1 . A pigment dispersion for ink jet ink, comprising a binder (A), a pigment (B), and an aqueous medium (C),

wherein the binder (A) is a binder containing a urethane resin (A1) that is a reaction product of polyol (a1), containing polyol (a1-1) having an acid group selected from the group consist of a carboxyl group and a sulfonate group, and polyester polyol (a1-2) other than the polyol (a1-1), with polyisocyanate (a2) containing polyisocyanate (a2-1) having an aromatic ring structure;

the acid groups possessed by the urethane resin (Al) are partially or entirely neutralized;

the glass transition temperature of the urethane resin (A1) is 70° C. or less,

the urethane resin (A1) having a mass-average molecular weight within a range of 35,000 to 100,000; and

wherein the reaction of the polyol (a1) with the polyisocyanate (a2) is performed so that the equivalent ratio of isocyanate groups of the polyisocyanate (a2) to hydroxyl groups of the polyol (a1) is within a range of 0.8 to 2.5.

2 . The pigment dispersion for inkjet according to claim 1 , wherein the acid value of the urethane resin (A1) is 10 to 40 mgKOH/g.

3 . The pigment dispersion for ink jet ink according to claim 1 , wherein the content of the binder (A) is 5% to 30% by mass in the total amount of the pigment dispersion.

4 . The pigment dispersion for ink jet ink according to claim 1 , the pigment dispersion being used for printing on a plastic substrate.

5 . An ink jet ink comprising the pigment dispersion for ink jet ink according to claim 1 .

6 . A printed matter printed with the ink jet ink according to claim 5 .

7 . The pigment dispersion for ink jet ink according to claim 2 , wherein the minimum film-forming temperature (MFT) of the urethane resin (A1) is 40° C. or less.

8 . The pigment dispersion for ink jet ink according to claim 7 , wherein the urethane resin (A1) contains a ring structure in an amount of 500 to 5,000 mmol/kg based on the entire urethane resin (A1).

9 . The pigment dispersion for ink jet ink according to claim 1 , wherein the carboxyl group is selected from the group consisting of 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid and 2,2-dimethylolvaleric acid.

10 . The pigment dispersion for ink jet ink according to claim 1 , wherein the sulfonate group is selected from the group consisting of 5-sulfoisophthalic acid, sulfoterephthalic acid, 4-sulfophthalic acid and 5-(4-sulfophenoxy) isophthalic acid.

11 . The pigment dispersion for ink jet ink according to claim 1 , wherein the polyester polyol (a1-2) comprises a structural unit derived from a polyvalent carboxylic acid and a structural unit derived from a polyhydric alcohol,

the polyvalent carboxylic acid is selected from the group consisting of phthalic acid, isophthalic acid, terephthalic acid, adipic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dimer acid, trimellitic acid, benzene tetracarboxylic acid, benzene pentacarboxylic acid and benzene hexacarboxylic acid: and

the polyhydric alcohol is selected from the group consisting of ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexane dimethanol, and the like; glycols having a branched structure, such as 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,2-butanediol, 1,3-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 2-isopropyl-1,4-butanediol, 2,4-dimethyl-1, 5-pentanediol, 2, 4-diethyl-1,5-pentanediol, 2-ethyl-1, 3-hexaneddiol, 2-ethyl-1,6-hexanediol, 3,5-heptanediol, 2-methyl-1, 8-octanediol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol and sorbitol.

12 . The pigment dispersion for ink jet ink according to claim 1 , wherein the polyisocyanate (a2-1) having an aromatic ring structure is selected from the group consisting of 4,4-diphenylmethane diisocyanate, 2,4 1-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude diphenylmethane diisocyanate, phenylene diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate and tetramethylxylylene diisocyanate.