Patent ID: 7276112

Claim:
An aqueous ink comprising at least water, a plurality of water-soluble organic solvents and a coloring material, wherein the coloring material is 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 plurality of water-soluble organic solvents include a good medium or good mediums for the pigment and a poor medium or poor mediums for the pigment, wherein the poor medium does not solvate perfectly or substantially the pigment, wherein the ionic group undergoes perfectly or substantially no ionic dissociation in the poor medium, wherein a water-soluble organic solvent which shows the maximum Ka value among the respective Ka values of the plurality of water-soluble organic solvents as determined by the Bristow method is the poor medium, wherein, where the total content (mass %) of the good medium in the aqueous ink is represented by X, and the total content (mass %) of the poor medium in the aqueous ink is represented by Y, the ratio of X:Y is 10:5 or more to 10:30 or less, and wherein, where the surface tension of a liquid containing a surfactant and water, and the concentration of the surfactant is 2 mmol/kg, is represented by A (mN/m) and the surface tension of a liquid containing the surfactant, a pigment, and water, and the concentration of the surfactant is 2 mmol/kg and the concentration of the pigment is 5 mass %, is represented by B, the pigment satisfies the relationship of B−A≦10.