A (meth)acrylate copolymer obtained by copolymerization of a monomer mixture containing a monomer (A) of the general formula (I),wherein R1 is a hydrogen atom or methyl, R2 is a linear or branched alkylene group having 1 to 8 carbon atoms and Y is a single bond or an oxygen atom, a monomer (B) copolymerizable with the monomer (A) and a crosslinking monomer (C).