| 摘要 |
PURPOSE:To enable the use of a thermoplastic resin substrate as a transparent substrate of the optical information recording medium using linearly polarized light as information reading-out light. CONSTITUTION:Molds designed to regulate the temp. of a molten high-molecular material passing an injection gate 20 to a temp. at which the viscosity of this molten high-molecular material attains 500 to 2000 poises, are used as the molds 11, 12 for injection molding of the thermoplastic resin substrate to orient the main refractive index axis in a reference direction arbitrarily set with respect to the injection direction of the molten high-molecular material or a direction perpendicular to this reference direction. The molds which are provided with cold-slug wells 21, the molds which are designed to control the injection speed of the molten high-molecular material in multiple stages and further, the molds which are regulated in the temp. distribution in the plane direction of the cavity 19 within + or -5 deg.C and are regulated in the temp. of the cavity surfaces so as to attain Tg-80<=Tc<=Tg when the glass transition temp. of the high-molecular material is designated to Tg and the temp. of the cavity surfaces as Tc are usable as the molds for injection molding. |
