| 摘要 |
PURPOSE:To prevent the thermal expansion of a base body and the crack of a thin recording film arising therefrom and to make possible the faithful recording and reproduction of information by laminating a thin film of a material having <=1X10<-5>/ deg.C coefft. of linear thermal expansion on the base body and forming the thin recording film on the thin film. CONSTITUTION:The thin SiO2 film 12 is formed by depositing molten silica having 4-5X10<-7>/ deg.C coefft. of linear thermal expansion by electron beam vapor deposition or sputtering on a base body 11 and the thickness of said film is preferably 0.3-1mum. Since the thin SiO2 film 12 is deposited on the polymethyl methacrylate base body 11, the heat diffusion to the base body is kept low and the expansion of the base body is prevented even if the temp. of the thin recording film in the part irradiated with a light beam increases. The film 12 expands less in spite of a temp. increase as said film has the small coefft. of linear expansion. The expansion of the thin film which has the low coefft. of linear thermal expansion and is provided between the base body and the thin recording film of the base body is suppressed low even if the bit part to be recorded with information by the irradiation of the beam shrinks owing to the amorphous-crystalline transfer of the GeTe record in said part. The generation of the crack in the thin recording film in the bit part is thus obviated and the faithful recording and reproduction of the information are made possible. |
