| 摘要 |
PURPOSE:To obtain an optical card causing nearly uniform slight double refraction and having superior moisture and water resistances by incorporating a polymethylpentene film into a card-shaped optical recording medium. CONSTITUTION:A polymethylpentene film is incorporated into a card-shaped optical recording medium for optically recording, vanishing or reproducing information. When the polymethylpentene film is produced by a soln. casting method, it causes nearly uniform slight double refraction and is suitable for use as an optical material. Since the polymer is cast as a soln., high homogeneity is provided. Unlike extrusion molding the casting produces no unnecessary stress, so double refraction is suppressed. Thus, an optical card causing nearly uniform slight double refraction and having superior moisture and water resistances can be obtd. |
