For obviating this drawback, plastic lenses having equal surface hardness and scratch resistance to glass lenses have been produced by applying a thermosetting resin, such as a silicone resin, a polyester resin, a melamine resin and the like or a polyfunctional monomer, such as allyl acrylate or allyl methacrylate on surfaces of a plastic lens obtained from diethylene glycol bis(allyl carbonate) a