Photo- and/or thermo-curable copolymer, curable resin compositions, and cured articles

ab Disclosed is a photo- and/or thermo-curable copolymer having polymerizable unsaturated groups in side chains, which is obtainable by reacting a copolymer (P) with an epoxy-containing polymerizable unsaturated compound (C), the copolymer (P) containing monomer units derived from a carboxyl-containing polymerizable unsaturated compound (A) and monomer units derived from at least one epoxy-containing polymerizable unsaturated compound (B) represented by following Formula (1) or (2), in which the epoxy group of the epoxy-containing polymerizable unsaturated compound (C) has been added to part of the carboxyl groups of the copolymer (P). In the formulae, Rs each represent hydrogen or hydroxyl-substituted or -unsubstituted alkyl having 1 to 4 carbon atoms; and Rs each represent single bond or alkylene having 1 to 18 carbon atoms which may contain heteroatom(s). The curable copolymer is highly stably synthesized and stored, has satisfactory curing properties, and permits both epoxy crosslinking and radical crosslinking.