| 摘要 |
PURPOSE:To obtain a substrate made of synthetic resin for a data recording medium having the surface in a radius direction formed straight or protruding in a relatively simple method by making the rear side of a cavity forming part hollow, so that the cavity forming part becomes elastically deformable by the molding pressure. CONSTITUTION:The rear side of a part where a molding cavity 15 is formed is made hollow, so that the forming part of the molding cavity 15 becomes elastically deformable by the molding pressure. Concretely, a hollow part of a very small gap is formed between mirror finished bushes 13, 14 and between cooling bushes 18, 19. The mirror finished bushes 13, 14 define the cavity forming part. The mirror finished bushes 13, 14 are made thinner at the side where they face the substrate. Therefore, when a resin is injected into the molding cavity 15, the bushes 13, 14 are elastically deformed by the injection molding pressure to the side of the hollow part. Accordingly, the substrate after it is completely molded by cooling and solidification in the molding cavity 15 has its surface projected in a radius direction after shrinkage. |
