d) When the homopolymer or copolymer is a homopolymer or a copolymer of a monomer having a hydroxyl group or a carboxyl group, it is subjected to an addition reaction with a monomer having an epoxy group, a monomer having an aziridinyl group or a 1:1 adduct of a diisocyanate compound and an acrylic ester monomer having a hydroxyl group.