As such a compound, a commonly used and known polyester (meth)acrylate, polyether (meth)acrylate, urethane (meth)acrylate, carbonate (meth)acrylate, epoxy (meth)acrylate or urethane (meth)acrylate may be employed, and specific examples thereof include hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; diacrylates of glycol such as ethylene glycol, methoxytetraethy