Magnetic disk substrate and method for manufacturing the same
AssigneeKabushiki Kaisya Ohara
InventorsNaoyuki Goto, Katsuhiko Yamaguchi
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Abstract
A magnetic disk substrate is made of a glass-ceramic having crystal phases of lithium disilicate (Li.sub.2 O.2SiO.sub.2) and alpha-quartz (SiO.sub.2). The crystal phase of alpha-quartz is formed of grown crystal grains each having a globular grain structure made of aggregated particles. Each globular grain has a size within a range from 0.3 .mu.m to 3 .mu.m. Surface roughness (Ra) of a polished surface of the magnetic disk substrate is within a range from 15 .ANG. to 50 .ANG. which is an optimum range of surface roughness for the magnetic disk.
Claims22
A magnetic disk substrate made of a glass ceramic having crystal phases which consist of lithium disilicate (Li.sub.2 O.2SiO.sub.2) and alpha-quartz (SiO.sub.2) characterized in that said crystal phase of alpha-quartz is formed of grown crystal grains each having a globular grain structure made of aggregated particles, each globular grain having a size within a range from 0.3 .mu.m to 3 .mu.m and said crystal grains of alhpa-quartz being randomly scattered in the finer particles of lithium disilicate said magnetic disk substrate having a polished surface having a surface roughness (Ra) within a range of from 15 .ANG. to 50 .ANG..
A magnetic disk consisting essentially of a substrate having a coating of magnetic media formed on the surface thereof, said substrate being made of a glass-ceramic having crystal phases of lithium disilicate (Li.sub.2 O.2SiO.sub.2) and alpha-quartz (SiO.sub.2) characterized in that said crystal phase of alpha-quartz is formed of grown crystal grains each having a globular grain structure made of aggregated particles, each globular grain having a size within a range from 0.3 .mu.m to 3 .mu.m and that surface roughness (Ra) of a polished surface of the magnetic disk substrate is within a range from 15 .ANG. to 50 .ANG..
Dependencies are inferred from the claim text.