Magnetic-disk glass substrate
AssigneeHoya Corporation
InventorShuhei Azuma
Life of this patent
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Abstract
A magnetic-disk glass substrate containing an alkali metal component as a glass composition includes a pair of main surfaces and an outer circumferential side edge surface that is a mirror surface. The outer circumferential side edge surface includes a surface with a roughness percentage that is 40% or more when a bearing ratio of a roughness cross-sectional area is 50%, in a bearing ratio curve of roughness cross-sectional areas obtained when a surface roughness of the outer circumferential side edge surface obtained by etching the outer circumferential side edge surface by 2.5 μm is measured.
Claims20
A magnetic-disk glass substrate containing an alkali metal component as a glass composition, the magnetic-disk glass substrate comprising:
- a pair of main surfaces;
- and
- an outer circumferential side edge surface including an outer side wall surface and outer chamfered surfaces arranged between the outer side wall surface and the main surfaces, the outer side wall surface being a mirror surface,
- the outer side wall surface including a surface with a roughness percentage that is 40% or more and 67% or less when a bearing ratio of a roughness cross-sectional area is 50%, in a bearing ratio curve of roughness cross-sectional areas obtained when a surface roughness of the outer side wall surface obtained by etching the outer side wall surface by 2.5 μm is measured.
A glass substrate for a magnetic-disk glass substrate containing an alkali metal component as a glass composition, the glass substrate comprising:
- a pair of main surfaces;
- and
- an outer circumferential side edge surface including an outer side wall surface and outer chamfered surfaces arranged between the outer side wall surface and the main surfaces, the outer side wall surface being a mirror surface,
- the outer side wall surface including a surface with a roughness percentage that is 40% or more and 67% or less when a bearing ratio of a roughness cross-sectional area is 50%, in a bearing ratio curve of roughness cross-sectional areas obtained when a surface roughness of the outer side wall surface obtained by etching the outer side wall surface by 2.5 μm is measured.
Dependencies are inferred from the claim text.