Patent ID: 8475580

Claim:
An ink jet ink comprising a self-dispersible pigment, a salt, a polyoxyethylene alkyl ether and a water-soluble organic solvent, wherein the self-dispersible pigment is a pigment to a surface of a particle of which a functional group containing at least a phosphonic acid group is bonded, the introduced amount of the functional group bonded to the self-dispersible pigment is 0.10 mmol/g or more and 0.33 mmol/g or less, wherein the salt is constituted by combining at least one cation selected from the group consisting of alkali metal ion, ammonium ion and organic ammonium ion with at least one anion selected from the group consisting of Cl − , Br − , I − , ClO − , ClO 2 − , ClO 3 − , ClO 4 − , NO 2 − , NO 3 − , SO 4 2− , CO 3 2− , HCO 3 − , HCOO − , (COO − ) 2 , COOH(COO − ), CH 3 COO − , C 2 H 4 (COO − ) 2 , C 6 H 5 COO − , C 6 H 4 (COO − ) 2 , PO 4 3− , HPO 4 2− and H 2 PO 4 − , and the value (Concentration of anion)×(Valence number of anion) of the salt in the ink is 0.005 mol/L or more and 0.06 mol/L or less, and wherein the water-soluble organic solvent includes glycerol, a content of the glycerol in the ink is 35% by mass or more and 78% by mass or less based on the total content of the water-soluble organic solvent in the ink.