SECRECY MAINTAINING METHOD OF OPTICAL RECORDING MEDIUM AND SECRECY MAINTENANCE TYPE OPTICAL RECORDING MEDIUM

摘要

PURPOSE:To maintain easily secrecy by providing an overcoat layer contg. an inorg. material which makes crystal-amorphous phase transfer and is made transparent by quick heating and quick cooling and is made invisible by slow heating and slow cooling on an optical recording layer and keeping the overcoat opaque except during recording and reproduction. CONSTITUTION:The optical recording layer 12 is provided on a substrate 11 and a heat insulating layer 13 is formed on the layer 12 to prevent the deterioration by a temp. increase. The overcoat layer 14 for maintaining secrecy is formed on the layer 13 by a vapor deposition method, etc. of an alloy of =1 kinds from the group of semiconductors or metals of groups, IIIA, IVA, VA, VIA and Te such as Te90Ge10 Sn10 which can make crystal-amorphous phase transfer when heated quickly and cooled quickly and can make amorphous-crystal phase transfer when heated slowly and cooled slowly. The protective layer 15 consisting of SiO2, etc. is provided on the layer 14. The layer 14 is made transparent by quick heating and quick cooling using a semiconductor laser light beam by which recording is executed. The layer 14 is made opaque by the laser beam weaker than in the recording stage. The layer 14 is made transparent by quick heating and quick cooling in the stage of reading out. The optical recording medium which can maintain secrecy is thus easily obtd.