Patent ID: 7973097

Claim:
An ink jet pigment ink comprising: water; a pigment; a water-soluble organic solvent; and a graft copolymer, wherein the graft copolymer has a hydrophilic segment and a hydrophobic segment, the hydrophobic segment being obtained by copolymerizing an anionic monomer and an aromatic monomer, the hydrophilic segment being obtained by polymerizing an anionic monomer, wherein the graft copolymer has a main chain that is the hydrophobic segment and has a side chain that is the hydrophilic segment, wherein the hydrophobic segment has a copolymerization ratio of the aromatic monomer (A) to the anionic monomer (B) being from 4:1 to 16:1 in terms of monomer mass ratio A:B, wherein the side chain of the graft copolymer has a weight average molecular weight of from 300 or more to 2,000 or less, wherein the anionic monomer contained in the hydrophilic segment and in the hydrophobic segment is acrylic acid, and wherein the aromatic monomer contained in the hydrophobic segment is benzyl methacrylate.