MOLDING METHOD FOR OPTICAL DISK BASE

摘要

PURPOSE:To mold an optical disk base whose index of birefringence is small, by controlling compression force in a releasing direction after the compression force has been applied to resin in a cavity. CONSTITUTION:When an injection compression molding device is turned ON, resin heated and melted within an injection cylinder is injected into a cavity 4 through a sprue and gate 3 and the cavity 4 is filled with the same. Hydraulic pressure is applied to the inside of a compression hydraulic cylinder 17a through an action of a servovalve 28 and the force is applied to the resin in the cavity 4 through a compression ram 18 and compression core 16. Resin pressure applied to the resin is detected by a pressure sensor 10 and controlled according to the applied resin pressure. After the lapse of a preset period of time, a mold is demolded by moving a movable mold 8A backward by a toggle type mold clamping mechanism 12 and a desired optical disc base is released through the inside of the cavity 4.