Patent US4636448A successfully refreshed from Google Patents.
US4636448A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording medium
Assignee: TDK Corp
•
Filing: 1985-01-16
•
Granted: 1987-01-13
•
Expires: 2005-01-16
Abstract
Abstract In a magnetic recording medium particularly for perpendicular magnetization comprising a non-magnetic substrate and a magnetic thin film formed on the surface thereof and including at least two layers, a lower layer with low coercive force and high permeability, for example, of permalloy is sputtered on the substrate and an upper layer for perpendicular recording, for example, of cobalt-chromium alloy is sputtered on the lower layer, and the average grain diameter of the lower layer is less than one half of that of the upper layer.
Inventors
- 👤 Haruyuki Morita
- 👤 Jiro Yoshinari
- 👤 Kazumasa Fukuda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 20:18
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/64; G11B5/66; G11B5/674; G11B5/672; Y; Y10; Y10S; Y10S428/00; Y10S428/922; Y10S428/9265; Y10S428/928; Y10T; Y10T428/00; Y10T428/12; Y10T428/12431; Y10T428/12438; Y10T428/12465; Y10T428/12493; Y10T428/12535; Y10T428/12556; Y10T428/12562; Y10T428/12569; Y10T428/12597; Y10T428/12736; Y10T428/1275; Y10T428/12771; Y10T428/12861; Y10T428/12931; Y10T428/12986
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
84 words
A magnetic recording medium comprising a non-magnetic substrate and a magnetic thin film formed on the surface thereof said magnetic film comprising two layers, an upper layer having an average grain diameter A and a lower layer having an average grain diameter B, wherein the lower layer is contiguous to said upper layer and closer to the non-magnetic substrate, and the average grain diameter B of the lower layer is less than one half of the average grain diameter A of said upper layer.
Claim 2
Dependent Claim
84 words
A magnetic recording medium comprising a non-magnetic substrate and a magnetic thin film formed on the surface thereof said magnetic film comprising two layers, an upper layer having an average grain diameter A and a lower layer having an average grain diameter B, wherein the lower layer is contiguous to said upper layer and closer to the non-magnetic substrate, and the average grain diameter B of the lower layer is less than one half of the average grain diameter A of said upper layer.
Claim 3
Dependent Claim
22 words
The magnetic recording medium according to claim 1, wherein the average grain diameter of B is less than one-fifth that of A.
Claim 4
Dependent Claim
32 words
The magnetic recording medium according to claim 1, wherein the upper magnetic layer is a perpendicular magnetizable film and the lower magnetic layer is a low coercive force, high permeability magnetic film.
Claim 5
Dependent Claim
27 words
The magnetic recording medium according to claim 1, wherein the upper magnetic layer is of a cobalt-chromium alloy and the lower magnetic layer is of a permalloy.
Claim 6
Dependent Claim
36 words
The magnetic recording medium according to claim 4, wheein the average grain diameter of the upper magnetic layer is from 200-800 Å and the average grain diameter of the lower magnetic layer is from 70-400 Å.
Claim 7
Dependent Claim
18 words
The magnetic recording medium according to claim 1, wherein said thin film is not more than 10 μm.
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) | 1990-01-12 | 1990-07-14 | 1991-01-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-01-12 | 1994-07-14 | 1995-01-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-01-12 | 1998-07-14 | 1999-01-13 | $7700.00 | Window Closed / Lapsed |