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US 2014/0227561 A1Published application
Information recording medium glass substrate and information recording medium
AssigneeHoya Corporation
InventorTakeshi Endo
Life of this patent
Estimating the term…
Abstract
An information recording medium glass substrate and an information recording medium are provided in which a first roll-off variation and a second roll-off variation fall within the following ranges: 180 Å≦first roll-off variation≦990 Å (condition 1) and 650 Å≦second roll-off variation≦3700 Å (condition 2).
Claims7
A disk-shaped information recording medium glass substrate having a rotation center for use in an information recording medium of an information storage device, comprising:
- a main surface having a magnetic thin film layer formed thereon;
- and
- an outer peripheral end surface located at an edge of said information recording medium glass substrate, wherein
- in a distance in a radial direction from said outer peripheral end surface of said main surface toward said rotation center, when
- an extension of a line between a point where said distance in the radial direction from said outer peripheral end surface on said main surface is 1.2 mm and a point where said distance in the radial direction from said outer peripheral end surface is 0.75 mm is a reference position, and an amount of deviation of any selected position on said main surface from said reference position in a direction in which an axis of rotation passing through said rotation center is a roll-off value,
- said roll-off value at a first radial position where said distance in the radial direction from said outer peripheral end surface is 0.55 mm is a first roll-off value,
- said roll-off value at a second radial position where said distance in the radial direction from said outer peripheral end surface is 0.45 mm is a second roll-off value,
- said roll-off value at a third radial position where said distance in the radial direction from said outer peripheral end surface is 0.30 mm is a third roll-off value,
- a difference between said first roll-off value and said second roll-off value is a first roll-off variation, and
- a difference between said second roll-off value and said third roll-off value is a second roll-off variation,
- said first roll-off variation and said second roll-off variation satisfy the following conditions 1 and 2:
- 180 Å≦first roll-off variation≦990 Å . . . condition 1
- 650 Å≦second roll-off variation≦3700 Å . . . condition 2.
10 more elements
An information recording medium for use in an information storage device, comprising:
- a disk-shaped information recording medium glass substrate having a rotation center;
- and
- a magnetic thin film layer provided on a main surface of said information recording medium glass substrate,
- said information recording medium glass substrate including
- a main surface having said magnetic thin film layer formed thereon;
- and
- an outer peripheral end surface located at an edge of said information recording medium glass substrate, wherein
- in a distance in a radial direction from said outer peripheral end surface of said main surface toward said rotation center, when
- an extension of a line between a point where said distance in the radial direction from said outer peripheral end surface on said main surface is 1.2 mm and a point where said distance in the radial direction from said outer peripheral end surface is 0.75 mm is a reference position, and an amount of deviation of any selected position on said main surface from said reference position in a direction in which an axis of rotation passing through said rotation center is a roll-off value,
- said roll-off value at a first radial position where said distance in the radial direction from said outer peripheral end surface is 0.55 mm is a first roll-off value,
- said roll-off value at a second radial position where said distance in the radial direction from said outer peripheral end surface is 0.45 mm is a second roll-off value,
- said roll-off value at a third radial position where said distance in the radial direction from said outer peripheral end surface is 0.30 mm is a third roll-off value,
- a difference between said first roll-off value and said second roll-off value is a first roll-off variation, and
- a difference between said second roll-off value and said third roll-off value is a second roll-off variation,
- said first roll-off variation and said second roll-off variation satisfy the following conditions 1 and 2:
- 180 Å≦first roll-off variation≦990 Å . . . condition 1
- 650 Å≦second roll-off variation≦3700 Å . . . condition 2.
14 more elements
Dependencies are inferred from the claim text.