A dye polymer prepared by polymerizing one or more pigment monomer represented by formula (I), or a dye polymer prepared by copolymerizing one or more pigment monomer represented by formula (I) and one or more monomer having one ethylene group.
[R1: H, chlorine atom, alkyl group, or aryl group; L1: —N(R2)C(═O)—, —OC(═O)—, —C(═O)N(R2)—, —C(═O)O—, or a group represented by formula (II), formula (III), or formula (IV); R2: H, alkyl group, aryl group, or hetero cyclic group; L2: divalent coupler for coupling L1 and Dye; n=0 or 1, m=0 or 1; Dye: pigment residue]