OPTICAL INFORMATION RECORDING MEDIUM, ESPECIALLY CORRELATED TO SUPPRESSING A BENDING PHENOMENON CAUSED BY ENVIRONMENTAL CHANGES AND AGING CHARACTERISTICS

摘要

PURPOSE: An optical information recording medium is provided to make coefficients of linear expansion of a thin film protective film bigger than those of a transparent substrate, thereby effectively controlling a medium bending degree not to influence a recording/reproducing property. CONSTITUTION: A transparent substrate(20) is made of polycarbonate. A single-layered or multi-layered thin film layer(40) consists of thin films such as dielectric films(41,43) formed by a sputtering process, a recording film(42), and a reflective film(44). By forming a thin film protective film(50) having resins as main components on top of the thin film layer(40), the thin film layer(40) is protected. To protect the transparent substrate(20), a substrate protective film(30) is formed on a light incident surface of the substrate(20).