| 摘要 |
PURPOSE:To obtain the substrate having high heat resistance, transparency and low hygroscopicity and further extremely low double refractions by using a material essentially consisting of thermoplastic arom. polyester contg. a specific structural unit. CONSTITUTION:The extremely low double refractive optical disk substrate which is improved in the heat resistance, transparency and low hygroscopicity and has <60nm double refractions of perpendicular incident single pulse in the same manner as in case of using a polycarbonate material if the optical disk substrate is produced by executing the injection molding using the material essentially consisting of the thermoplastic arom. polyester contg. the structural unit expressed by formula I. Exact recording and reproducing are then possible. |
