Abstract: A curable composition comprising (A) a modified copolymer which is a partial ester of a styrene-carboxylic anhydride copolymer, a hydroxyalkyl (meth)acrylate and, if required, a monovalent alcohol; (B) at least one diluent for the modified copolymer; (C) at least one multifunctional epoxy; and (D) a photoinitiator or a system capable of initiating photopolymerisation; and being characterised in that it further includes (E) at least one catalyst for the reaction between carboxylic acid functions and epoxy functions. The composition is useful for coating substrates by heat and radiation curing.