Optical information recording medium

Abstract

An optical information recording medium comprising a substrate provided with periodically wobbling guide grooves with a track pitch of 1.6.+-.0.1 .mu.m, and a lower protective layer, a phase-change type recording layer, an upper protective layer and a reflective layer formed in this sequence on the substrate, for recording, retrieving and erasing amorphous marks in the guide grooves by modulation of light intensity of at least two levels by means of a focused light having a wavelength of 780.+-.30 nm applied from the side of the substrate opposite to the recording layer side so that a crystalline state with a reflectance of from 15 to 25% is an unrecorded state, and an amorphous state with a reflectance of less than 10% is a recorded state, wherein the recording layer is a thin film of an alloy of My.sub.y (Sb.sub.x Te.sub.1-x).sub.1-y where 0.ltoreq.y<0.3, 0.5<x<0.9, and My is at least one member selected from the group consisting of In, Ga, Zn, Ge, Sn, Si, Cu, Au, Ag, Pd, Pt, V, Nb, Ta, Pb, Cr, Co, O, S and Se, and its thickness is from 15 to 30 .mu.m, the thickness of the lower protective layer is at least 70 nm and less than 150 nm and thicker by more than 0 nm and not more than 30 nm than the thickness where the reflectance in the crystalline state becomes minimum, and the grooves have a depth of from 25 to 45 nm and a width of from 0.4 to 0.6 .mu.m.