MANUFACTURE OF PLASTIC BASE FOR OPTICAL DISK

摘要

PURPOSE:To manufacture the titled base improved having heat resistance and free from warpage without giving an adverse effect to the groove, etc. on the base by annealing at a specified temperature an optical disk base prepared by injection molding. CONSTITUTION:The plastic base (a polymethyl metacrylate disk) for the optical disk is annealed under the temperature circumstance 30-50 deg.C lower than the glass transition temperature. Five hours or more is suitable for the annealing time and 50-70 deg.C is most suitable for the annealing temperature. The optical disk base can be obtained in a small variation of warpage with time and in a good dimensional stability.