US4420408A
Expired / Lapsed
US
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Magnetic recording medium
Assignee: TDK Corp
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Filing: 1981-05-20
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Granted: 1983-12-13
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Expires: 2001-05-20
Abstract
Abstract A magnetic recording medium comprises a combination of two or more kinds of fine abrasive powders having different true specific gravities in a magnetic layer containing a magnetic powder.
Inventors
- 👤 Norifumi Kajimoto
- 👤 Kinji Sasaki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 04:07
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/708; G11B5/7085; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/31504; Y10T428/31551; Y10T428/31609
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
63 words
A magnetic recording medium which comprises an admixture consisting of at least two fine abrasive powders having different true specific gravities differing by more than 1.0, each of said powders being of a Moh's hardness of at least 7, in a magnetic layer containing a magnetic powder, the ratio of the two fine abrasive powders being in the range of 2:8 to 8:2.
Claim 2
Dependent Claim
63 words
A magnetic recording medium which comprises an admixture consisting of at least two fine abrasive powders having different true specific gravities differing by more than 1.0, each of said powders being of a Moh's hardness of at least 7, in a magnetic layer containing a magnetic powder, the ratio of the two fine abrasive powders being in the range of 2:8 to 8:2.
Claim 3
Dependent Claim
27 words
The magnetic recording medium according to claim 1 wherein said abrasive powders are incorporated at a ratio of up to 20 wt.% based on said magnetic powder.
Claim 4
Dependent Claim
23 words
The magnetic recording medium according to claim 1 wherein said fine abrasive powders are alumina and chromium oxide having different true specific gravities.
Claim 5
Dependent Claim
45 words
The magnetic recording medium according to claim 1 wherein said abrasive powders and true specific gravities are selected from the group consisting of Al 2 O 3 (3.9), Cr 2 O 3 (5.2), ZrO 2 (5.7), SiC (3.2), SiO 2 (2.7), and TiO 2 (4.2).
Claim 6
Dependent Claim
18 words
The magnetic recording medium according to claim 1 wherein the magnetic power is Co-adsorbed iron oxide magnetic powder.
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) | 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 |