Patent ID: 8690307

Claim:
An ink jet ink, comprising: a polyurethane polymer and a pigment, the polyurethane polymer having units derived from a polyisocyanate, a polyether polyol having no acid group, and a diol having an acid group, the pigment being dispersed using a polymer other than the polyurethane polymer, wherein the polyether polyol having no acid group contains at least one selected from poly(ethylene glycol), poly(propylene glycol), poly(1,2-butylene glycol), and poly(1,3-butylene glycol) and has a number-average molecular weight of 450 or more and 4,000 or less, the polyisocyanate contains a hexamethylene diisocyanate, and the percentage (% by mole) constituted by the unit(s) derived from the hexamethylene diisocyanate with respect to all the units derived from the polyisocyanate in the polyurethane polymer is 10% by mole or more and 90% by mole or less, the ratio of the percentage (% by mole) of urethane bonds in the polyurethane polymer to the percentage (% by mole) of urea bonds in the polyurethane polymer is 85.0/15.0 or more and 100.0/0 or less, and the diol having an acid group is at least one selected from dimethylolpropionic acid and dimethylolbutanoic acid, and the acid value of the polyurethane polymer resulting from the unit(s) derived from the diol having an acid group is 40 mgKOH/g or more and 140 mgKOH/g or less.