SUBSTRATE FOR MAGNETIC DISK AND ITS PRODUCTION

摘要

PURPOSE:To prevent the decrease in the yield of elements occuring in substrate defects by having a coating film of specific glass on the surface of a specific alumina ceramic material. CONSTITUTION:The coating film of the glass having 10<-6>/deg relative difference in the coefft. of thermal expansion (20 deg.C- strain point) from a substrate having 0.5-200mum thickness for the purpose of maintaining an insulating characteristic from the upper film is formed on the surface of the alumina ceramic material having <=5mum (more preferably <=3mum) fine pores on the surface and 96% relative theoretical density. The thin film surface is then polished under 0.05-2kg/ cm<2> load by the suspension prepd. by suspending at least one kind of pulverous <=0.1mum powder of SiO2, MgO CeO or Al2O3. The poreless and strain-free surface layer having 0.3mum-200mum film thickness and <=80Angstrom surface roughness is thus obtd. and the improvement in the characteristic and reliability of the magnetic film deposited and formed on the substrate surface are assured.