Patent ID: 7361698

Claim:
A water-based pigment ink, comprising: a pigment; a hydrophilic dispersant; an aqueous medium; an alkali agent for solubilizing said hydrophilic dispersant in said aqueous medium; and a hydrophilic compound having only one structural unit of “hydrophobic molecular chain-hydrophilic molecular chain-hydrophobic molecular chain” in a structure thereof; wherein said hydrophilic compound is at least one compound selected from the group consisting of a reaction product between polyethylene glycol cetyl ether and hexamethylene diisocyanate; a reaction product between polyethylene glycol cetyl ether and tetramethylxylylene diisocyanate; a reaction product between polyethylene glycol oleyl ether and trimethyhexamethylene diisocyanate; a reaction product between polyethylene glycol oleyl ether and isocyanatoethyl 2,6-diisocyanatocaproate; a reaction product between polyethylene glycol oleyl ether and isocyanatoethyl 2,6-diisocyanatocaproate-ethylene glycol (molar ratio 2:1) urethane compound; a reaction product between a polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer and hexamethylene diisocyanate; and a reaction product between a polyoxyethylene-polyoxypropylene-ethylenediamine-polyoxypropylene-polyoxyethylene block copolymer and 1-naphthyl isocyanate.