Cyclic polyolefin optical moulding material

摘要

Provided is an optical molding material comprising a cyclic polyolefin resin having a glass transition temperature (Tg) of 120{C to 170{C, wherein the melt viscosity of the resin at 260{C is 5,000 to 50,000 poises as measured at a shear rate of 10 sec-1 and 200 to 1,000 poises at a shear rate of 10,000 sec-1, and the melt viscosity of the resin at 320{C is 500 to 5,000 poises at a shear rate of 10 sec-1 and 100 to 800 poises at a shear rate of 10,000 sec-1. An optical molding material comprising a cyclic polyolefin resin, an optical molded product and an optical disk substrate, wherein a variation range of retardation of the resin is within Ò10% of the retardation at 590 nm when the wavelength is changed from 400 nm to 830 nm, are provided. The material is molded into, for example, the optical disk substrate. A method for producing an optical disk substrate comprises injection-molding a thermoplastic resin comprising a cyclic polyolefin resin under conditions of a resin temperature of (Tg + 100){C to 400{C, a mold temperature of (Tg - 100){C to (Tg - 5){C, a shear rate of 4 x 104 to 1 x 106 sec-1 and average residence time of the resin in a molding machine of 5 to 200 seconds. The cyclic polyolefin resin is preferably composed of a norbornene derivative.