Patent ID: 8371687

Claim:
An ink composition comprising: a water-soluble organic solvent; a pigment; water; self-dispersible polymer particles; and a nonionic polymer compound as a thickener, the content of the water-soluble organic solvent being from 5 weight % to 30 weight % relative to the total amount of the ink composition, and the ratio of V high /V low , in which V high represents 25° C. viscosity (mPa·s) measured at a shear rate of 1.5×10 5 (s −1 ) and V low represents 25° C. viscosity (mPa·s) measured at a shear rate of 3.0×10 3 (s −1 ), being from 0.70 to 0.95, wherein the nonionic polymer compound comprises at least one selected from the group consisting of polyoxyethylene glycol and polyoxyethylene-polyoxypropylene block copolymer; and 70 weight % or more of the water-soluble organic solvent is a water-soluble organic solvent having a solubility parameter value of 27.5 or less.