Patent US4794047A successfully refreshed from Google Patents.
US4794047A
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Method of manufacturing magnetic recording medium
Assignee: Hitachi Ltd
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Filing: 1987-07-20
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Granted: 1988-12-27
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Expires: 2007-07-20
Abstract
Abstract The method of manufacturing a magnetic recording medium according to the present invention comprises a first step in which a ferromagnetic metal layer of a predetermined thickness is formed on a substrate, and a second step contiguous to said first step and in which another ferromagnetic metal layer is formed by applying a bias voltage to the substrate. Since the ferromagnetic metal layer formed at the second step is excellent in corrosion resistance, even if a protective layer such as a carbon layer incurs a pit defect when the medium is being produced or even when the protective layer is separated, the ferromagnetic metal layer in consideration will not be corroded, thus preventing any error from occurring in data recording or reproduction.
Inventors
- 👤 Susumu Funamoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 09:59
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/84; G11B5/851; G11B5/85; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10S428/922; Y10S428/9265; Y10S428/928; Y10T; Y10T428/00; Y10T428/12; Y10T428/12465; Y10T428/12493; Y10T428/12736; Y10T428/1275; Y10T428/12771; Y10T428/12806; Y10T428/12826; Y10T428/12847; Y10T428/12854; Y10T428/12861; Y10T428/12931; Y10T428/30
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
84 words
A method of manufacturing a magnetic recording medium, comprising a step of forming on a substrate a ferromagnetic metal layer containing Co metal or Co-alloy by sputtering or evaporation, said step comprising: a first process in which said ferromagnetic metal layer is formed on said substrate to a predetermined thickness without applying a bias voltage to said substrate, and a second process contiguous to said first process and in which another ferromagnetic metal layer is formed by applying a bias voltage to said substrate.
Claim 2
Independent Claim
84 words
A method of manufacturing a magnetic recording medium, comprising a step of forming on a substrate a ferromagnetic metal layer containing Co metal or Co-alloy by sputtering or evaporation, said step comprising: a first process in which said ferromagnetic metal layer is formed on said substrate to a predetermined thickness without applying a bias voltage to said substrate, and a second process contiguous to said first process and in which another ferromagnetic metal layer is formed by applying a bias voltage to said substrate.
Claim 3
Dependent Claim
27 words
A method according to claim 2, wherein said second process comprising a step in which the biasing is done by applying a high-frequency power to said substrate.
Claim 4
Dependent Claim
12 words
A magnetic recording medium manufactured by the method according to claim 1.
Claim 5
Dependent Claim
12 words
A magnetic recording medium manufactured by the method according to claim 2.
Claim 6
Dependent Claim
31 words
A method according to claim 1, wherein said ferromagnetic metal layer formed by said first process and said another ferromagnetic metal layer formed by said second process have the same composition.
Claim 7
Dependent Claim
14 words
A method according to claim 2, wherein said high frequency power is about 200W.
Claim 8
Dependent Claim
20 words
A method according to claim 1, wherein each of said first process and said second process is a sputtering process.
Claim 9
Dependent Claim
39 words
A method according to claim 1, wherein said substrate comprises an aluminum-alloy having a NiP layer provided thereon and a Cr layer provided on said NiP layer, and wherein said ferromagnetic metal layer is provided on said Cr layer.
Claim 10
Dependent Claim
18 words
A method according to claim 8, further comprising forming a carbon layer over said another ferromagnetic metal layer.
Claim 11
Dependent Claim
38 words
A method according to claim 1, wherein said bias voltage is applied to said substrate so as to form said another ferromagnetic metal layer with corrosion resistance superior to said ferromagnetic metal layer formed by said first process.
Claim 12
Dependent Claim
12 words
A magnetic recording medium manufactured by the method according to claim 10.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-12-27 | 1992-06-27 | 1992-12-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-12-27 | 1996-06-27 | 1996-12-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-12-27 | 2000-06-27 | 2000-12-27 | $7700.00 | Window Closed / Lapsed |