Patent ID: 7691193

Claim:
A method of producing a water-based pigment dispersion for ink-jet ink, comprising: a kneading process for kneading a mixture containing a styrene-based resin, a quinacridone-based pigment, a phthalimidomethylated quinacridone-based compound, an alkali metal hydroxide and a humectant to produce a solid and colored kneaded mixture; and a dispersing process for dispersing the solid and colored kneaded mixture in an aqueous medium, wherein the styrene-based resin has 60% by mass or more of a styrene-based monomer unit based on all monomer components, a monomer unit containing an unsaturated aliphatic carboxylic acid having a radical polymerizable double bond, an acid value of 50 to 300 and a weight-average molecular weight of 7500 to 40000; and the solid content of the kneaded mixture containing the styrene-based resin, the quinacridone-based pigment and the phthalimidomethylated quinacridone-based compound during kneading is from 50 to 80% by mass.