PURPOSE: To produce the title composition having a relaxed shrinkage strain upon radiation curing and excellent flexibility, rigidity and adhesiveness, by reacting a specified polymer with a carboxylic acid anhydride and an epoxy monomer having an ethylenically unsaturated group.

CONSTITUTION: A polymer (A) having 0.1W10 hydroxyl groups per 1,000 of MW in the molecule and having an MW ≥5,000 (e.g., phenoxy resin) is reacted with part of a carboxylic acid anhydride (B) (e.g., succinic anhydride), and the free carboxyl groups formed in this reaction are reacted with the glycidyl groups of an epoxy monomer (C) having an ethylenically unsaturated group [e.g., glycidyl (meth)acrylate] or alternately, components B and C are added to component A, and the mixture is reacted at 80W150°C in a nitrogen gas atmosphere in the presence of a catalyst (e.g., NaOH).