US4649073A
Expired / Lapsed
US
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Magnetic recording medium
Assignee: Toshiba Corp
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Filing: 1985-03-06
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Granted: 1987-03-10
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Expires: 2005-03-06
Abstract
Abstract In a magnetic recording disk of a double-sided recording type according to a perpendicular magnetic recording technique of the invention, recording layers having different film thicknesses are formed on two surfaces of a base layer. The film thickness of one magnetic recording layer is set to be larger than the film thickness of the other magnetic recording layer. Thus, a curl phenomenon can be prevented. In addition, a coercive force of the thicker recording layer is set to be higher than that of the thinner recording layer. A difference in a perpendicular recording density between the two recording layers due to a difference in the film thickness thereof can be compensated for.
Inventors
- 👤 Toshiyuki Suzuki
- 👤 Reiji Nishikawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 07:01
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/64; G11B5/68; G11B5/70; G11B5/716; G11B5/718; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/24; Y10T428/24942; Y10T428/2495; Y10T428/24967; Y10T428/24975; Y10T428/31504; Y10T428/31678
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
147 words
A disk-shaped magnetic recording medium which can record data on two surfaces thereof in accordance with a perpendicular magnetic recording technique, comprising: a flexible base layer; and magnetic recording layers which sandwich said base layer therebetween and are formed to have different film thicknesses whose ratio is set so as to prevent a curl phenomenon from occurring in said magnetic recording medium, wherein a first recording layer is, thicker than a second recording layer, and has a perpendicular coercive force which is higher than that of said second recording layer so as to compensate for a decrease in a perpendicular recording density of said first recording layer due to the enlargement in thickness thereof, whereby the amount of a curl occurring in said recording medium may be minimized, and any non-coincidence between perpendicular recording densities of said first and second recording layers may be simultaneously compensated for.
Claim 2
Dependent Claim
147 words
A disk-shaped magnetic recording medium which can record data on two surfaces thereof in accordance with a perpendicular magnetic recording technique, comprising: a flexible base layer; and magnetic recording layers which sandwich said base layer therebetween and are formed to have different film thicknesses whose ratio is set so as to prevent a curl phenomenon from occurring in said magnetic recording medium, wherein a first recording layer is, thicker than a second recording layer, and has a perpendicular coercive force which is higher than that of said second recording layer so as to compensate for a decrease in a perpendicular recording density of said first recording layer due to the enlargement in thickness thereof, whereby the amount of a curl occurring in said recording medium may be minimized, and any non-coincidence between perpendicular recording densities of said first and second recording layers may be simultaneously compensated for.
Claim 3
Dependent Claim
23 words
The disk-shaped magnetic recording medium according to claim 1, wherein said first and second magnetic recording layers comprise alloy films containing metal cobalt.
Claim 4
Dependent Claim
42 words
The disk-shaped magnetic recording medium according to claim 1, wherein said first and second recording layers comprise alloy films containing metal cobalt, and wherein the thickness ratio is set to substantially be 3:2, whereby the amount of a curl can be minimized.
Claim 5
Dependent Claim
37 words
The disk-shaped magnetic recording medium according to claim 3, wherein the thickness of said first recording layer is set to be 0.6 micrometers, and the thickness of said second recording layer is set to be 0.4 micrometers.
References Cited (Backward Citations)
GB1530911A
Cited
US4410583A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-03-09 | 1990-09-08 | 1991-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-03-09 | 1994-09-08 | 1995-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-03-09 | 1998-09-08 | 1999-03-10 | $7700.00 | Window Closed / Lapsed |