Process and apparatus for manufacturing substrate sheet for optical

Abstract

Optical recording mediums are prepared by extrusion molding. In the extrusion molding, a thermoplastic resin heated to a given temperature is pressed between a roll stamper and a roll opposite thereto. A gap between the roll stamper and the roll is precisely defined by belt members fixed on each side of the roll where the roll does not come into touch with the thermoplastic resin. The joints of the respective belt members are formed at positions different from each other on the periphery of the roll. Alternatively the gap may be defined by cutting the roll substrate at a part on which the stamper member is fixed, or by interposing endless belts with a given thickness between the roll stamper and the roll. The stamper member provided on the roll stamper is reduced in stress, and has a surface precision of 10 .mu.m or less.