OPTICAL DISK SUBSTRATE, ITS MOLDING METHOD AND OPTICAL DISK SUBSTRATE INJECTION MOLDING DEVICE

摘要

PROBLEM TO BE SOLVED: To practically reduce the sudden change in the plate thickness by inserting an insert material into the thicker portion of the plate in the optical disk substrate in which the inner peripheral section plate thickness outside an information recording region is made thicker than the plate thickness of the information recording region and to suppress the occurrence of a shrinkage failure without conducting a fine adjustment of the molding conditions such as increasing the holding pressure of the injection molding and lengthening the holding time. SOLUTION: The thick section of a clamp region 4 of an optical disk substrate 1 is constructed so that an insert material 5 is inserted into the section. Then, the optical disk substrate injection molding machine is provided with the mechanism, which is used to insert the material 5 during an injection molding and a preheating mechanism which preheats the material 5. For the case of the disk in which the plate thickness is made uniform and flat over the entire surface of the disk, the substrate 1 is provided with the material 5 having a wring shape at the boundary section between the clamp region and the information recording region.