| abstract |
PROBLEM TO BE SOLVED: To provide a water-based ink composition excellent in printing density and the like while maintaining a pigment dispersibility equivalent to that of a conventionally known water-based ink pigment dispersant. [Solution] An unsaturated carboxylic acid and / or an unsaturated sulfonic acid in a specific ratio; Styrenes and / or (meth) acrylic acid esters which are hydrophobic monomers, A pigment dispersant for an aqueous ink comprising a polymer obtained by polymerizing a copolymerizable monomer as required, The polymer is Having at least one structure of "-S-C (= S)-" or "-S-C (= S) -S-" or "-SH"; The number average molecular weight in terms of polystyrene by gel permeation chromatography is 2000-40000, The ratio of the weight average molecular weight to the number average molecular weight is 1.8 or less, A pigment dispersant for water-based ink, wherein the sum of the number average molecular weight of less than 500 and the ratio of 200,000 or more is less than 5% of the total. [Selection figure] None |