| 摘要 |
PURPOSE:To obtain an excellent substrate for a magnetic disc by forming an alumite film on the surface of an Al alloy substrate for a disc and forming an oxide film of SiO2 or the like on said film thereby relieving the thermal expansion stress between the substrate and the oxide film and improving resistance to thermal cracking. CONSTITUTION:An alumite film 4 is formed on the surface of an Al alloy substrate 5 and is polished to obtain a high-precision surface having 0.05muRmax surface roughness. An oxide film 3 consisting of at least one of SiO2, Al2O3, Ta2O5 or TiO2 is formed on the polished surface by a sputtering method, etc. The film 3 is rougher than the surface of the film 2 but the magnetic film 2 is formed on the layer 3 as it is or if necessary, after polishing. A protective film 1 is then formed on the film 2, by which the magnetic disc is obtd. Generation of cracks, etc. in the layer 3 is obviated by the presence of the layer 4 in the case of, for example, forming an Fe3O4 film on the layer 4, then subjecting the same to a heat treatment at 300 deg.C in air and forming the gamma-Fe2O3 magnetic film 2 thereon. |
