| 摘要 |
A transparent resin composition comprising (1) 6 to 100% by weight of a nitrile graft copolymer comprising a rubber trunk polymer and a branch polymer grafted thereon, which has been obtained by graft-polymerizing onto the rubber trunk polymer a monomer mixture containing an unsaturated nitrile and a monomer copolymerizable therewith, and (2) 0 to 94% by weight of a random copolymer of an unsaturated nitrile and a monomer copolymerizable therewith, the resin components of the resin composition other than the rubber trunk polymer constituting a matrix resin, wherein (a) said rubber trunk polymer has a glass transition temperature of not higher than 0 DEG C. and constitutes 4 to 25% by weight of the resin composition, (b) the unsaturated nitrile constitutes 25 to 90% by weight of the matrix resin in the resin composition, (c) the difference in the refractive indexes between the rubber trunk polymer and the matrix resin is not more than 0.008, and (d) the resin composition, when molded into a 3 mm-thick plate, has a transmittance in diethyl phthalate of not lower than 95% with respect to the laser rays used. The above described resin composition has excellent transparency and molding fidelity and can be used for molding information signal recording discs, information pits being engraved on one side of each disc, and a metal coating being deposited thereon, the information signals recorded on the information pits being reproducible by irradiation with laser rays from the other side of said disc. |
