Optical recording medium and substrate for use therein

摘要

An optical recording medium for recording and reproducing information utilizing the change of a physical property of a recording layer caused by the irradiation with light, which comprises a substrate, characterized in that the substrate comprises a hydrogenated styrene polymer having a content of nucleus-hydrogenated styrene units of 80 wt % or more, has a glass transition temperature of 110° C. or higher, has a light transmittance of 88% or more at 400 nm, and exhibits an absolute value of retardation of 30 nm or less at 0° and 30° from the normal direction of the plane thereof. The optical recording medium suitable for use in the high density optical recording capable of responding to a greater number of openings and the use of a light having a shorter wave length in an optical head.