PURPOSE: To obtain the titled compound, having a nitrogen-containing aromatic heterocyclic ring residue conjugated with a double bond in the side chain, soluble in solvents, and having high sensitivity, by copolymerizing a specific vinyl monomer with a copolymerizable monomer by the radical polymerization method, etc.

CONSTITUTION: (A) A vinyl monomer expressed by formulaI(R1 is O, NH or bifunctional organic group; R2 is H or alkoxyl; R3 is H or CH3; Z is an atomic group forming an aromatic heterocyclic ring) is copolymerized with (B) a copolymerizable monomer, e.g. (meth)acrylonitrile to give preferably 2W10mol% introduction ratio of a residue expressed by formula II by the radical, ion or coordination polymerization according to the conventional method and afford the aimed compound having preferably 3000W300000 molecular weight.

EFFECT: A small amount of photosensitive groups is introduced, and no photosensitizer is required.