Patent ID: 6413890
Filing Date: 2002-07-02
Classification: C03C,G11B,Y10S

Abstract:
A glass-ceramic substrate for a magnetic information storage medium comprising, as predominant crystal phases, lithium disilicate (Li2O.2SiO2) and at least one selected from a group consisting of &agr;-quartz (&agr;-SiO2), &agr;-quartz solid solution (&agr;-SiO2 solid solution), &agr;-cristobalite (&agr;-SiO2) and &agr;-cristobalite solid solution (&agr;-SiO2 solid solution) and having a coefficient of thermal expansion of +65 to +130Ã—10âˆ’7/Â° C. at a temperature within a range from âˆ’50Â° C. to +70Â° C. and surface roughness (Ra) after polishing of 3 Ã¥-9 Ã¥.