Patent ID: 6846611

Claim:
A phase-change optical recording medium capable of carrying out record/readout/erase operations of information data through the reversible phase transition between amorphous and crystalline states induced by light beam irradiation in a recording layer included in said recording medium, comprising: a transparent substrate on which the light beam is incident; and contiguous layers formed on said substrate in order as follows, a lower dielectric protective layer, said recording layer, an upper dielectric protective layer, and a reflective/heat dissipating layer; wherein said upper dielectric protective layer essentially consists of a mixture of ZnS, ZrO 2 and SiO 2 , having a composition of (ZnS) x (ZrO 2 ) y (SiO 2 ) 100-x-y , where 30<x<70 and 30<y<70 (mole %).