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US5486395A
Expired / Lapsed
US
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Magneto-optical disk
Assignee: Sharp Corp
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Filing: 1992-12-02
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Granted: 1996-01-23
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Expires: 2012-12-02
Abstract
Abstract A magneto optical disk comprising: a circular substrate; a recording layer, formed on the substrate, for magneto-optical recording of information; a readout layer, formed between the substrate and the recording layer, for the reproduction of information recorded on the recording layer, wherein the readout layer has a Curie temperature which is higher than the Curie temperature of the recording layer, and exhibits in-plane magnetization at room temperature and a change from in-plane magnetization to perpendicular magnetization when its temperature rises over a certain temperature as a result of the application of a light beam, and wherein the magnetic compensation temperature is set such that it increases from the peripheral edge of the magneto-optical disk toward the center thereof. When the magneto-optical disk is used with a magneto-optical recording and reproducing device using a CAV system, it achieves high-density recording and the reproduction of signals with reduced noise, without causing the light beam control system to be complicated.
Inventors
- 👤 Yoshiteru Murakami
- 👤 Naoyasu Iketani
- 👤 Akira Takahashi
- 👤 Kenji Ohta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 11:52
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10502; G11B11/10504; G11B11/10515; G11B11/10582; G11B11/10586; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
123 words
A magneto optical disk comprising: a circular substrate; a recording layer, formed on said substrate, for a recording of information; a readout layer, formed between said substrate and said recording layer, for a reproduction of information recorded on said recording layer, wherein said readout layer has a Curie temperature which is higher than a Curie temperature of said recording layer, exhibits in-plane magnetization at room temperature and a change from in-plane magnetization to perpendicular magnetization when its temperature rises as a result of an application of a light beam, and wherein a first temperature at which a change occurs from in-plane magnetization to perpendicular magnetization is set such that it increases from a peripheral edge of said magneto-optical disk toward a center thereof.
Claim 2
Dependent Claim
123 words
A magneto optical disk comprising: a circular substrate; a recording layer, formed on said substrate, for a recording of information; a readout layer, formed between said substrate and said recording layer, for a reproduction of information recorded on said recording layer, wherein said readout layer has a Curie temperature which is higher than a Curie temperature of said recording layer, exhibits in-plane magnetization at room temperature and a change from in-plane magnetization to perpendicular magnetization when its temperature rises as a result of an application of a light beam, and wherein a first temperature at which a change occurs from in-plane magnetization to perpendicular magnetization is set such that it increases from a peripheral edge of said magneto-optical disk toward a center thereof.
Claim 3
Dependent Claim
42 words
The magneto-optical disk according to claim 1, wherein a composition of said readout layer is varied along a radial direction of said magneto-optical disk such that the first temperature increases from the peripheral edge of said magneto-optical disk toward the center thereof.
Claim 4
Dependent Claim
24 words
A magneto optical disk as set forth in claim 1, wherein said first temperature is approximately the magnetic compensation temperature of the readout layer.
Claim 5
Dependent Claim
64 words
The magneto-optical disk according to claim 2, wherein the Curie temperature of said recording layer is between 150° C. and 250° C. the Curie temperature of said readout layer is between 300° C. and 400° C., and the first temperature at which there is a change from in-plane magnetization to perpendicular magnetization on said readout layer is set between 70° C. and 150° C.
Claim 6
Dependent Claim
51 words
The magneto-optical disk according to claim 2, wherein said readout layer is formed by a thin film made of an alloy of a rare earth element and a transition metal, a content of the rare earth element components increases from the peripheral edge of said magneto-optical disk toward the center thereof.
Claim 7
Dependent Claim
64 words
The magneto-optical disk according to claim 3, wherein the Curie temperature of said recording layer is between 150° C. and 250° C., the Curie temperature of said readout layer is between 300° C. and 400° C., and the first temperature at which there is a change from in-plane magnetization to perpendicular magnetization on said readout layer is set between 70° C. and 150° C.
Claim 8
Dependent Claim
51 words
The magneto-optical disk according to claim 3, wherein said readout layer is formed by a thin film made of an alloy of a rare earth element and a transition metal, a content of the rare earth element components increases from the peripheral edge of said magneto-optical disk toward the center thereof.
Claim 9
Dependent Claim
32 words
The magneto-optical disk according to claim 5 further comprising: a first transparent dielectric film between said substrate and said readout layer; and a second transparent dielectric film formed over said recording layer.
Claim 10
Dependent Claim
32 words
The magnetic disk according to claim 7 further comprising: a first transparent dielectric film between said substrate and said readout layer; and a second transparent dielectric film formed over said recording layer.
Claim 11
Dependent Claim
19 words
The magneto-optical disk according to claim 8 further comprising a reflecting film formed over said second transparent dielectric film.
Claim 12
Dependent Claim
19 words
The magneto-optical disk according to claim 9 further comprising a reflecting film formed over said second transparent dielectric film.
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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) | 1999-01-22 | 1999-07-24 | 2000-01-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-01-22 | 2003-07-24 | 2004-01-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-01-22 | 2007-07-24 | 2008-01-23 | $7700.00 | Window Closed / Lapsed |