Patent ID: 6120922
Filing Date: 2000-09-19
Classification: C03C,G11B,Y10S

Abstract:
A glass-ceramic substrate for a magnetic information storage medium having a data zone and a landing zone or adapted for a ramp loading system, said glass-ceramic substrate comprising, as predominant crystal phases, lithium disilicate (Li.sub.2 O.2SiO.sub.2) and at least one selected from the group consisting of .alpha.-quartz (.alpha.-SiO.sub.2), .alpha.-quartz solid solution (.alpha.-SiO.sub.2 solid solution), .alpha.-cristobalite (.alpha.-SiO.sub.2) and .alpha.-cristobalite solid solution (.alpha.-SiO.sub.2 solid solution) and having a coefficient of thermal expansion of +65 to +130.times.10.sup.-7 /.degree. C. at a temperature within a range from -50.degree. C. to +70.degree. C. and surface roughness (Ra) after polishing of 3 .ANG.-9 .ANG..