INFORMATION RECORDING CARRIER

摘要

PURPOSE:To suppress size variation and deformation and to reduce moisture permeability by compressing polystyrene or a copolymer which contains a >=10wt% styrene component. CONSTITUTION:A copolymer which contains methyl methacrylate and styrene in 60:40 proportion (by weight) and has 14X10<4> weight average molecular weight and 8X10<4> number average molecular weight is extruded by a 40mm.phi uniaxial extruding machine at 180 deg.C cylinder temperature and at a 80rpm screw rotational frequency to obtain a biscuit of molten resin. Then, this biscuit is sandwiched between stampers held at 170 deg.C and compressed for 20sec under 70kg/cm<2>; and it is cooled down to 70 deg.C in 30sec to form a disk having 1.25mm. thickness and a 30cm diameter.