MANUFACTURE OF SMOOTH EXTRUDED PLAIN SHEET OR FILM AND ITS DEVICE, MANUFACTURE OF EXTRUDED PRODUCT AND OPTICAL RECORDING MEDIUM

摘要

PURPOSE: To provide a method and an apparatus for manufacturing an extruded plain sheet or film of synthetic resin which has a surface quality suitable for manufacturing an optical data storage body and optical birefringence. CONSTITUTION: On the occasion when synthetic resin in a thermoplastic state is extruded to smoothing rolls from a flat die, one surface of a sheet is cooled to below a glass transition temperature, while the other surface and most of the inside of the sheet are left in the thermoplastic state, and the sheet is cooled to below the glass transition temperature under the condition of decreasing a deforming force acting on the surface of a billet.