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Patent US4725482A successfully refreshed from Google Patents.
US4725482A
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Perpendicular magnetic recording medium
Assignee: Sharp Corp
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Filing: 1984-12-24
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Granted: 1988-02-16
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Expires: 2004-12-24
Abstract
Abstract A Co-Cr perpendicular magnetic recording medium includes a chromium oxide film formed on a Co-Cr perpendicular magnetization film, and a SiO 2 protective film formed on the chromium oxide film. The chromium oxide film is formed by conducting a heating treatment to the surface of the Co-Cr perpendicular magnetization film in an oxygen atmosphere of about 10 -4 to 10 -3 Torr, at a temperature of about 300° C. to 400° C. for about two hours. The chromium oxide film has a thickness of about 20 to 200 Å. The SiO 2 protective film has a thickness greater than 50 Å, but the total thickness of the chromium oxide film and the SiO 2 protective film is selected between 70 and 300 Å.
Inventors
- 👤 Tomohisa Komoda
- 👤 Mamoru Ishizuka
- 👤 Shuhei Tsuchimoto
- 👤 Mitsuhiko Yoshikawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 20:46
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/64; G11B5/65; G11B5/656; G11B5/72; G11B5/726; G11B5/7262; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/24; Y10T428/24942; Y10T428/2495; Y10T428/24967; Y10T428/24975; Y10T428/26; Y10T428/263; Y10T428/264; Y10T428/265
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
126 words
A perpendicular magnetic recording medium having improved recording and reproducing characteristics and durability, which comprises: a substrate; a Co-Cr perpendicular magnetization film formed on said substrate; a chromium oxide film formed on said Co-Cr perpendicular magnetization film; and a protective layer film selected from SiO 2 , SiO or Si 3 N 4 having a minimal thickness formed on said chromium oxide film to protect said Co-Cr perpendicular magnetization film from being damaged and to ensure stable operation and impart an increase in physical strength to the perpendicular magnetic recording medium; wherein the minimal thickness of the protective layer film is greater than 50 Å, but the total thickness of the chromium oxide film and the protective layer film is between 70 Å and 300 Å.
Claim 2
Dependent Claim
126 words
A perpendicular magnetic recording medium having improved recording and reproducing characteristics and durability, which comprises: a substrate; a Co-Cr perpendicular magnetization film formed on said substrate; a chromium oxide film formed on said Co-Cr perpendicular magnetization film; and a protective layer film selected from SiO 2 , SiO or Si 3 N 4 having a minimal thickness formed on said chromium oxide film to protect said Co-Cr perpendicular magnetization film from being damaged and to ensure stable operation and impart an increase in physical strength to the perpendicular magnetic recording medium; wherein the minimal thickness of the protective layer film is greater than 50 Å, but the total thickness of the chromium oxide film and the protective layer film is between 70 Å and 300 Å.
Claim 3
Dependent Claim
32 words
The perpendicular magnetic recording medium of claim 1, wherein said chromium oxide film is formed on said Co-Cr perpendicular magnetic film by performing a heat treatment to said Co-Cr perpendicular magnetic film.
Claim 4
Dependent Claim
41 words
The perpendicular magnetic recording medium of claim 2, wherein said heat treatment is performed in an oxygen atmosphere of between 10 -4 Torr and 10 -3 Torr, and at a temperature between 300° C. and 400° C., for about two hours.
Claim 5
Dependent Claim
22 words
The perpendicular magnetic recording medium of claim 2, wherein said chromium oxide film has a thickness between 20 Å and 200 Å.
Claim 6
Dependent Claim
19 words
The perpendicular magnetic recording medium of claim 1, wherein said protective layer film is Si 3 N 4 .
Claim 7
Dependent Claim
23 words
The perpendicular magnetic recording medium of claim 1, wherein said Co-Cr perpendicular magnetization film is formed on said substrate by an RF-sputtering method.
Claim 8
Dependent Claim
128 words
A perpendicular magnetic recording medium having improved recording and reproducing characteristics and durability, which comprises: a substrate; a Co-Cr perpendicular magnetization film formed on said substrate; a chromium oxide film formed on said Co-Cr perpendicular magnetization film; and a SiO 2 protective layer film having a minimal thickness formed on said chromium oxide film which functions in combination with said chromium oxide film to protect the Co-Cr perpendicular magnetization film from being damaged and to ensure stable operation and impart an increase in physical strength to the perpendicular magnetic recording medium; wherein the minimal thickness of the SiO 2 protective layer film is greater than 50 Å, but the total thickness of the chromium oxide film and the protective layer film is between 70 Å and 300 Å.
Claim 9
Dependent Claim
128 words
A perpendicular magnetic recording medium having improved recording and reproducing characteristics and durability, which comprises: a substrate; a Co-Cr perpendicular magnetization film formed on said substrate; a chromium oxide film formed on said Co-Cr perpendicular magnetization film; and a SiO 2 protective layer film having a minimal thickness formed on said chromium oxide film which functions in combination with said chromium oxide film to protect the Co-Cr perpendicular magnetization film from being damaged and to ensure stable operation and impart an increase in physical strength to the perpendicular magnetic recording medium; wherein the minimal thickness of the SiO 2 protective layer film is greater than 50 Å, but the total thickness of the chromium oxide film and the protective layer film is between 70 Å and 300 Å.
Claim 10
Dependent Claim
22 words
The perpendicular magnetic recording medium of claim 7, wherein said chromium oxide film has a thickness between 20 Å and 200 Å.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1991-02-15 | 1991-08-17 | 1992-02-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-02-15 | 1995-08-17 | 1996-02-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-02-15 | 1999-08-17 | 2000-02-16 | $7700.00 | Window Closed / Lapsed |