| 摘要 |
PROBLEM TO BE SOLVED: To provide a molding method optimum for molding a thin data recording disk substrate low in double diffraction and excellent in mechanical characteristics, and a mold therefor. SOLUTION: A cylindrical sleeve 40 advancing and retreating with respect to a cavity 20a is provided to a movable mold 31. The cylindrical sleeve 40 is allowed to advance toward a fixed mold before or during injection to protrude the end part of the cylindrical sleeve 40 into the cavity 20a. By this constitution, the flow of a molten resin into the cavity 20a is controlled. After injection, the cylindrical sleeve 40 is allowed to retreat to cool the resin charged in the cavity 20a. The substrate molded by this method is reduced in the double refraction caused by the generation of stress in the substrate and has excellent mechanical characteristics.
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