Magnetic-disk glass substrate

Patent metadata

Field	Value
Publication number	US-2016372147-A1
Application number	US-201515122377-A
Country	US
Kind code	A1
Filing date	Mar 31, 2015
Priority date	Mar 31, 2014
Publication date	Dec 22, 2016
Grant date	—

Abstract

An edge surface of a magnetic-disk glass substrate containing an alkali metal component as a glass composition is a mirror surface, and in a bearing ratio curve of roughness cross-sectional areas obtained by measuring a surface roughness of the edge surface obtained by etching the edge surface by 2.5 μm, a roughness percentage when a bearing ratio of a roughness cross-sectional area is 50% is 40% or more.

First claim

1 . A magnetic-disk glass substrate containing an alkali metal component as a glass composition, the magnetic-disk glass substrate comprising:
an edge surface that is a mirror surface, the edge surface including 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 edge surface obtained by etching the edge surface by 2.5 μm is measured.

2 . The magnetic-disk glass substrate according to claim 1 , wherein
the roughness percentage is 60% or less.

3 . The magnetic-disk glass substrate according to claim 1 , wherein
the edge surface includes a side wall surface and a chamfered surface arranged between the side wall surface and a main surface of the magnetic-disk glass substrate, and the side wall surface and the chamfered surface include a surface with the roughness percentage that is 40% or more when the bearing ratio of the roughness cross-sectional area is 50% in the bearing ratio curve.

4 . The magnetic-disk glass substrate according to claim 1 , wherein
an arithmetic average surface roughness of the mirror surface is 0.015 μm or less.

5 . The magnetic-disk glass substrate according to claim 1 , wherein
the edge surface includes a side wall surface and a chamfered surface arranged between the side wall surface and a main surface of the magnetic-disk glass substrate, and when a measurement point is provided every 30 degrees in a circumferential direction, referenced on a center of the magnetic-disk glass substrate, and a radius of curvature of a cross-sectional shape of a portion at which the side wall surface and the chamfered surface are connected to each other at the measurement point is obtained, a difference in the radius of curvature between measurement points is 0.01 mm or less.

6 . The magnetic-disk glass substrate according to claim 1 , wherein
the glass substrate is configured to be mounted on a hard disk drive together with a magnetic head on which a head disc interface sensor is mounted and that is configured to control a protrusion amount of at least one of a recording element and a reproduction element based on a signal from the head disc interface sensor.

7 . The magnetic-disk glass substrate according to claim 1 , wherein
the glass substrate is configured for use as a magnetic disk for an energy-assisted magnetic recording method.

8 . The magnetic-disk glass substrate according to claim 2 , wherein
the edge surface includes a side wall surface and a chamfered surface arranged between the side wall surface and a main surface of the magnetic-disk glass substrate, and the side wall surface and the chamfered surface include a surface with the roughness percentage that is 40% or more when the bearing ratio of the roughness cross-sectional area is 50%, in the bearing ratio curve.

9 . The magnetic-disk glass substrate according to claim 2 , wherein
an arithmetic average surface roughness of the mirror surface is 0.015 μm or less.

10 . The magnetic-disk glass substrate according to claim 3 , wherein
an arithmetic average surface roughness of the mirror surface is 0.015 μm or less.

11 . The magnetic-disk glass substrate according to claim 2 , wherein
the edge surface includes a side wall surface and a chamfered surface arranged between the side wall surface and a main surface of the magnetic-disk glass substrate, and when a measurement point is provided every 30 degrees in a circumferential direction, referenced on a center of the magnetic-disk glass substrate, and a radius of curvature of a cross-sectional shape of a portion at which the side wall surface and the chamfered surface are connected to each other at the measurement point is obtained, a difference in the radius of curvature between measurement points is 0.01 mm or less.

12 . The magnetic-disk glass substrate according to claim 3 , wherein
the edge surface includes a side wall surface and a chamfered surface arranged between the side wall surface and a main surface of the magnetic-disk glass substrate, and when a measurement point is provided every 30 degrees in a circumferential direction, referenced on a center of the magnetic-disk glass substrate, and a radius of curvature of a cross-sectional shape of a portion at which the side wall surface and the chamfered surface are connected to each other at the measurement point is obtained, a difference in the radius of curvature between measurement points is 0.01 mm or less.

13 . The magnetic-disk glass substrate according to claim 4 , wherein
the edge surface includes a side wall surface and a chamfered surface arranged between the side wall surface and a main surface of the magnetic-disk glass substrate, and when a measurement point is provided every 30 degrees in a circumferential direction, referenced on a center of the magnetic-disk glass substrate, and a radius of curvature of a cross-sectional shape of a portion at which the side wall surface and the chamfered surface are connected to each other at the measurement point is obtained, a difference in the radius of curvature between measurement points is 0.01 mm or less.

14 . The magnetic-disk glass substrate according to claim 2 , wherein
the glass substrate is configured to be mounted on a hard disk drive together with a magnetic head on which a head disc interface sensor is mounted and that is configured to control a protrusion amount of at least one of a recording element and a reproduction element based on a signal from the head disc interface sensor.

15 . The magnetic-disk glass substrate according to claim 3 , wherein
the glass substrate is configured to be mounted on a hard disk drive together with a magnetic head on which a head disc interface sensor is mounted and that is configured to control a protrusion amount of at least one of a recording element and a reproduction element based on a signal from the head disc interface sensor.

16 . The magnetic-disk glass substrate according to claim 4 , wherein
the glass substrate is configured to be mounted on a hard disk drive together with a magnetic head on which a head disc interface sensor is mounted and that is configured to control a protrusion amount of at least one of a recording element and a reproduction element based on a signal from the head disc interface sensor.

17 . The magnetic-disk glass substrate according to claim 5 , wherein
the glass substrate is configured to be mounted on a hard disk drive together with a magnetic head on which a head disc interface sensor is mounted and that is configured to control a protrusion amount of at least one of a recording element and a reproduction element based on a signal from the head disc interface sensor.

18 . The magnetic-disk glass substrate according to claim 2 , wherein
the glass substrate is configured for use as a magnetic disk for an energy-assisted magnetic recording method.

19 . The magnetic-disk glass substrate according to claim 3 , wherein
the glass substrate is configured for use as a magnetic disk for an energy-assisted magnetic recording method.

20 . The magnetic-disk glass substrate according to claim 4 , wherein
the glass substrate is configured for use as a magnetic disk for an energy-assisted magnetic recording method.

Assignees

• Hoya Corp

Inventors

• Azuma Shuhei

Classifications

• B24B31/112

  using magnetically consolidated grinding powder, moved relatively to the workpiece under the influence of pressure · CPC title

• G11B5/82

  Disk carriers · CPC title

• C03C2214/08

  Metals · CPC title

• B24B9/107

  for glass plates while they are turning · CPC title

• B24B1/005

  using a magnetic polishing agent · CPC title