Patent US3740493A successfully refreshed from Google Patents.
US5406546A
Expired / Lapsed
US
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Magneto-optical disk
Assignee: TDK Corp
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Filing: 1993-10-04
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Granted: 1995-04-11
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Expires: 2013-10-04
Abstract
Abstract In a magneto-optical disk comprising a disk-shaped substrate including a grooved region in its surface and a recording layer covering the grooved region, the groove is defined by a pair of opposed side walls and a bottom in a radial cross section of the substrate and has a depth from the substrate surface to the groove bottom. The angle θ included between tangents to the side walls is at least 120 degrees, and the groove has a half-value width of 0.90 to 1.15 μm and a depth of 600 to 900 Å. The disk produces satisfactory values of push-pull signal level, radial contrast, and C/N ratio.
Inventors
- 👤 Kenji Uchiyama
- 👤 Hirokazu Fujioka
- 👤 Masanori Shibahara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 19:26
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/0938; G11B11/00; G11B11/10; G11B11/105; G11B11/1055; G11B11/10576; G11B11/10578
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
118 words
A magneto-optical disk comprising a disk-shaped substrate having a surface including a region where a groove is formed and a recording layer in the form of a magnetic thin film covering the grooved region, wherein the groove is defined by a pair of opposed side walls and a bottom in a radial cross section of the substrate and has a depth from the substrate surface to the groove bottom, the angle θ included between tangents to the side walls at a height from the groove bottom corresponding to 50% of the groove depth is at least 120 degrees, and the groove has a half-value width of 0.90 to 1.15 μm and a depth of 600 to 900 Å.
Claim 2
Dependent Claim
118 words
A magneto-optical disk comprising a disk-shaped substrate having a surface including a region where a groove is formed and a recording layer in the form of a magnetic thin film covering the grooved region, wherein the groove is defined by a pair of opposed side walls and a bottom in a radial cross section of the substrate and has a depth from the substrate surface to the groove bottom, the angle θ included between tangents to the side walls at a height from the groove bottom corresponding to 50% of the groove depth is at least 120 degrees, and the groove has a half-value width of 0.90 to 1.15 μm and a depth of 600 to 900 Å.
Claim 3
Dependent Claim
39 words
The disk of claim 1 wherein the groove having a half-value width is separated from the adjacent groove by a land having a width in a radial direction, the groove half-value width being not smaller than the land width.
Claim 4
Dependent Claim
62 words
The disk of claim 1 wherein signals are recorded in and reproduced from the recording layer within the groove by means of an optical head having an objective lens with a numerical aperture NA of 0.40 to 0.50 using linearly polarized laser light of 600 to 900 nm in wavelength having an electric field vector in a radial direction of the substrate.
Claim 5
Dependent Claim
14 words
The disk of claim 1 wherein the angle θ is 120 to 165 degrees.
Claim 6
Dependent Claim
29 words
The disk of claim 1 wherein the reflectance through the substrate at the wavelength of recording and reproducing light is 15 to 25% in both recorded and unrecorded portions.
Claim 7
Dependent Claim
38 words
The disk of claim 1 further comprising a first protective layer on the side of the recording layer adjacent to said substrate and a second protective layer on the side of the recording layer remote from said substrate.
Claim 8
Dependent Claim
15 words
The disk of claim 6 further comprising a reflective layer on the second protective layer.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-04-10 | 1998-10-10 | 1999-04-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-04-10 | 2002-10-10 | 2003-04-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-04-10 | 2006-10-10 | 2007-04-11 | $7700.00 | Window Closed / Lapsed |