OPTICAL BLANK MATERIAL MADE OF PLASTICS

PURPOSE:To improve the scratch resistance and lightness of an optical blank material by mixing a silane coupling agent and a metallic alkoxide compd., coating the mixture on a synthetic resin substrate to provide a hardened film layer and vapor depositing an oxide film, etc. thereon by a vacuum deposition method. CONSTITUTION:A silane coupling agent and a metallic alkoxide compd. are mixed, and after the mixture is controlled so as to have the same refractive index as the refractive index of synthetic resins, the mixture is coated on a transparent synthetic resin substrate such as methyl methacrylate, by a dipping method or the like, and is dried, whereby a hardened film layer is formed. Thereafter, oxide such as SiO2, fluoride such as MgF2 or a mixture thereof is vapor deposited thereon by using a vacuum deposition method, whereby multilayered films are formed. Thus, scratch resistance is improved and the optical blank material made of lightweight plastics is obtained by forming the multilayered films on the transparent synthetic substrates in the above-mentioned way.