| 摘要 |
PURPOSE:To prevent the thermal deformation of a substrate and the crack of a thin recording film arising from the deformation and to execute the faithful recording and reproduction of information by laminating a thin film of a mate rial which is specified in the upper limit of the coefft. of linear thermal expan sion and the lower limit of the m.p. and making the film thickness to >=100nm. CONSTITUTION:Molten silica 13 are deposited on the thin recording film 12 on the substrate 11 of polymethyl methacrylate. A thin GeTe film 12 exhibits the phase transfer from the amorphous to crystalline state in a 1,750 deg.C+ or -5 deg.C and the optical constants of the refractive index and absorption coefft. change accordingly. A difference in the reflectivity and transmittance thereof arises when a light beam is irradiated to said film. The m.p. of the material to be deposited on the thin recording film is made >=725 deg.C to suppress the deformation of the substrate and thin recording film and to prevent the crack from generat ing in the recording film. The effect of preventing the crack of the thin record ing film is high with the material having <=2X10<-5>/ deg.C coeff. of linear thermal expansion. The thin recording film is not cracked and the faithful recording of signals is made possible even if the information is recorded thereto by the recording light beam when the thickness of the thin SiO2 film is >=100nm. |
