Substrate members for recording disks and process for producing same
AssigneeSumitomo Special Metals Co., Ltd.
InventorsToshiaki Wada, Yoshiaki Katsuyama
Life of this patent
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Abstract
A substrate member for recording disks comprises a sputtered film of Al.sub.2 O.sub.3, SiO.sub.2 and/or Si.sub.3 N.sub.4 on the surface of an alumina base ceramic material having therein micropores of no more than 5 microns and a relative theoretical density of no less than 96% said sputtered film having a surface roughness of no more than 80 angstroms, being substantially pore-free and strain-free on the surface, and having a thickness of 0.3 to 30 microns.
Claims17
A substrate member for recording disks comprising a sputtered film formed of at least one member selected from the group consisting of Al.sub.2 O.sub.3, SiO.sub.2, and Si.sub.3 N.sub.4 on the surface of an alumina base ceramic material having therein micropores of no more than 5 microns and a relative theoretical density of no less than 96%, said sputtered film having a surface roughness of no more than 80 angstroms, being substantially pore-free and strain-free on the surface, and having a thickness of 0.3 to 30 microns.
A process for producing substrate members for recording disks comprising the steps:
- providing a film having a thickness of 0.5 to 35 microns by sputtering at least one member selected from the group consisting of Al.sub.2 O.sub.3, SiO.sub.2, and Si.sub.3 N.sub.4 on the surface of an alumina base ceramic material having therein micropores of no more than 5 microns and a relative theoretical density of no less than 96%, and
- polishing the surface of said film under a load of 0.05 to 2 kg/cm.sup.2 with a suspension of 0.1 to 20% by weight of a fine powder of no larger than 0.1 micron of at least one of SiO.sub.2, MgO, Al.sub.2 O.sub.3, CeO.sub.2 and Fe.sub.2 O.sub.3, each of 99% purity or more in pure water, until a substantially pore-free and strain-free surface layer having a thickness of 0.3 to 30 microns and a surface roughness of no more than 80 angstroms is obtained.
Dependencies are inferred from the claim text.