METHOD FOR MOLDING TRANSPARENT AND LOW BIREFRINGENCE RESIN SHEET, AND TRANSPARENT AND LOW BIREFRINGENCE RESIN SHEET

摘要

PROBLEM TO BE SOLVED: To provide a method for molding a transparent and low birefringence resin sheet by which a glass-alternative resin sheet with small optical strain can be obtained as a sheet material which is large-sized, rich in kinds of thickness and inexpensive like a glass material. SOLUTION: The transparent and low birefringence resin sheet is obtained by press heat-treating a sheet prepared by extrusion cast molding of a non- crystalline thermoplastic resin with a visible light transmittance of at least 80% so as to make frozen strain small at a temperature of at least the glass transition temperature. A non-crystalline thermoplastic resin melt is extruded on the first endless metal belt 3 and thereafter, while it is pressed by the first metal belt 3 and the second endless metal belt 4 arranged by facing to the metal belt 3 in the thickness direction of the non-crystalline thermoplastic resin melt, it is successively taken off and solidified by cooling. As the non-crystalline thermoplastic resin, cyclic polyolefins and polycarbonate are used.