Patent ID: 8491715

Claim:
An ink jet ink comprising a self-dispersible pigment and a salt, wherein the self-dispersible pigment is a pigment to a surface of a particle of which a functional group containing at least a group having a hydrogen bonding property and two phosphonic acid groups is bonded, counter ions of the two phosphonic acid groups containing at least one of K + and NH 4 + , wherein the salt is constituted by combining at least one cation of K + and NH 4 + 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 − , wherein a cation concentration in the ink is 0.04 mol/L or more, wherein a viscosity of a liquid obtained by evaporating 15% by mass of the ink is less than 3.5 mPa·s at 25° C., and wherein the total concentration of K + and NH 4 + in the ink is 73% or more in terms of mol based on the total concentration of alkali metal ion and ammonium ion in the ink.