Patent ID: 7160376

Claim:
An aqueous ink comprising water, at least one water-soluble organic solvent, and a colorant, wherein the colorant comprises a pigment containing a pigment particle having at least one ionic group bonded to a surface of the pigment particle directly or via another atomic group, wherein the at least one organic solvent, and any other water-soluble organic solvent in the ink, undergoes completely or substantially no solvation with the pigment and the ionic group on the surface of the pigment particle undergoes completely or substantially no ion dissociation in the at least one organic solvent, and any other water-soluble organic solvent in the ink, wherein the pigment satisfies a relationship of B−A≦10 where A represents a surface tension (mN/m) of a liquid composed of a surfactant and water and having a surfactant concentration of 2 mmol/kg, and B represents a surface tension (mN/m) of a liquid composed of the surfactant, the pigment and water, having a surfactant concentration of 2 mmol/kg and having a pigment concentration of 5% by mass, and wherein the content of the water-soluble organic solvent is twice or more as large as the content of the pigment in terms of a mass ratio.