Patent US4420537A successfully refreshed from Google Patents.
US4420537A
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Magnetic recording medium having cobalt adsorbed iron oxide layer
Assignee: TDK Corp
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Filing: 1980-11-25
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Granted: 1983-12-13
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Expires: 2000-11-25
Abstract
Abstract A magnetic recording medium comprises a substrate coated with a magnetic composition comprising a cobalt adsorbed iron oxide powder with a phosphoric ester type anionic surfactant at a ratio of 2 wt. % or more and a binder at a ratio of said iron oxide powder to said binder of 4 or more. A magnetic recording medium has a coercive force Hc of 950 to 1200 Oe and a residual magnetic flux phi r of 0.35 to 0.6 maxwell.
Inventors
- 👤 Masashi Hayama
- 👤 Hiroto Saguchi
- 👤 Kenji Hirabayashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 16:07
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/702; G11B5/7028; G11B5/706; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/29; Y10T428/2982; Y10T428/2991
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
84 words
A magnetic recording medium having a coercive force Hc of 950 to 1200 Oe and a residual magnetic flux φr of 0.35 to 0.6 maxwell which comprises a substrate coated with a magnetic composition comprising a cobalt adsorbed iron oxide powder, a phosphoric ester type anionic surfactant as a dispersing agent at a ratio of 2 wt.% to 5 wt.% based on said iron oxide powder, and a binder at a ratio of said iron oxide powder to said binder of 4 to 7.
Claim 2
Dependent Claim
84 words
A magnetic recording medium having a coercive force Hc of 950 to 1200 Oe and a residual magnetic flux φr of 0.35 to 0.6 maxwell which comprises a substrate coated with a magnetic composition comprising a cobalt adsorbed iron oxide powder, a phosphoric ester type anionic surfactant as a dispersing agent at a ratio of 2 wt.% to 5 wt.% based on said iron oxide powder, and a binder at a ratio of said iron oxide powder to said binder of 4 to 7.
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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) | 1986-12-12 | 1987-06-13 | 1987-12-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-12-12 | 1991-06-13 | 1991-12-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-12-12 | 1995-06-13 | 1995-12-13 | $7700.00 | Window Closed / Lapsed |