abstract |
(57) [Summary] [PROBLEMS] While providing reliable printing performance, In particular, the present invention provides a pigment-dispersed aqueous ink composition capable of obtaining an excellent quality image on plain paper. SOLUTION: An ink composition is prepared using a polyamino acid derivative in which a hydrophobic polymer is covalently bonded to a terminal amino group of a polyamino acid as a pigment dispersant, and the ink composition is used. The polyamino acid is composed of aspartic acid or glutamic acid or a mixture thereof. |