Patent ID: 7026392

Claim:
Water-based pigment dispersion which comprises a pigment dispersing resin, pigment and aqueous medium, said resin being a copolymer of: A) polymerizable unsaturated monomer containing at least one quaternary ammonium salt group; B) nonionic polymerizable unsaturated monomer having polyoxyethylene chain; and C) other ethylenically unsaturated monomer, wherein the copolymer is produced by the copolymerization of 1 to 15% by weight of quaternary ammonium salt group-containing polymerizable unsaturated monomer (A), 5 to 40% by weight of nonionic polymerizable unsaturated monomer (B) and 45 to 94% by weight of other ethylenically unsaturated monomer (C) on the basis of the total weight of monomers (A), (B) and (C).