| 摘要 |
PURPOSE:To obtain a video disc in which double refraction and crown are improved and a mark of information is not missing, by using a base obtained through the forming of compound between hydrocarbon compound and specific polymethyl meth acrylate. CONSTITUTION:A polymethyl methacrylate polymer is used, which consists of (a) 80-92% methacrylic acid methyl ester and (b) and a 20-8% (metha)acrylic acid ester other than methacrylic acid methyl ester (e.g., acrylic acid methyl ester) and in which the optimum viscosity (eta) (measured value in chloroform solution) is 40-50ml/g. That is, (B) 0.01-0.1% of a hydrocarbon expressed in a formula (n is 15-25) (e.g., nonadecane and eicosane) is incorporated to (A) the said polymer, and after forming the obtained mixture and a base is formed, a video dics is formed by providing an Al vapor-deposited film on the surface. |
