| 摘要 |
PURPOSE:To obtain an optical disk substrate excellent in transparency, heat resistance and toughness and reduced in optical strain by subjected a polyvinyl cyclohexane resin specified in its MW and the nuclear hydrogenation rate of an aromatic ring to injection molding under a specific condition. CONSTITUTION:A polyvinyl cyclohexane resin having a number average MW of 40,000-300,000 and a nucleus hydrogenation rate of 90% or more obtained by hydrogenating the aromatic ring of a styrenic resin is subjected to injection molding under such a condition that the temp. of the resin is 270-350 deg.C and that of a mold is 30-120 deg.C to prepare an optical disk substrate. It is necessary that the number average MW is large than 4,000 from the aspect of toughness and, when said MW exceeds 300,000, no good moldability is obtained. When the nucleus hydrogenation rate is below 90%, the heat resistance of the resin is lowered and double diffraction is increased. When the temp. of the resin exceeds 350 deg.C, coloration and a silver streak are generated and toughness is lowered and, when said temp. is below 270 deg.C, the flowability of the resin is lowered and a group transfer property becomes inferior and optical strain is increased. When the temp. of the mold exceeds 120 deg.C, deformation becomes large and, when said temp. is below 30 deg.C, a molded product reduced in optical strain is not obtained. |
