| 摘要 |
PURPOSE:To relieve the strain remaining in an injection-molded disk substrate and to form the disk substrate for an information recording disk having a high CN ratio by annealing the above-mentioned disk substrate at the temp. below the thermal deformation temp. of a high-polymer material. CONSTITUTION:Metallic molds 1, 2 are integrally combined and the molten high-polymer material is injected under a high pressure into a cavity 4 from a sprue 3 formed to the mold 1. After the molten high-polymer material is thoroughly filled into the cavity 4, the molds 1, 2 are cooled to solidify the high-polymer material. The disk substrate 5 molded to the prescribed shape is then taken out. The injection-molded disk substrate 5 is housed into a heating furnace 6 and is held at the temp. slightly lower than the thermal deformation temp. of the high-polymer material forming the disk substrate 5. The disk sub strate is thereafter slowly cooled. The arrangement of the oriented molecules is rearranged again to the state having no directivity by which the disk sub strate is made optically isotropic.
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