Injection compression molding method for optically molded products

摘要

A method of producing an optically molded product of a thermoplastic resin by injection compression molding, the method comprising the steps of:(1) expanding the volume of a cavity more than the volume of the optically molded product of interest;(2) injecting a molten thermoplastic resin into the cavity through an injection cylinder;(3) compressing the expanded cavity to a prescribed thickness of the molded product;(4) returning an excess of the thermoplastic resin produced by the compression into the injection cylinder; and(5) keeping the molten thermoplastic resin in the cavity until the molded product of interest is formed.The present invention makes it possible to produce an optically molded product (for example, a spectacle lens) free from a weld line and excellent in surface accuracy using a metal mold having a simple structure industrially advantageously.