US4594296A
Expired / Lapsed
US
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Magnetic recording medium
Assignee: TDK Corp
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Filing: 1983-12-16
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Granted: 1986-06-10
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Expires: 2003-12-16
Abstract
Abstract A magnetic recording medium which comprises a magnetic layer formed on a substrate and comprising Co, or Co and one to three elements selected from the group consisting of Ni, Cr and O, wherein, when the magnetic layer is divided equally into four portions in the direction of the thickness of the magnetic layer, the density of the portion located farthest from the substrate is greater by at least 20% than the average density of three other portions.
Inventors
- 👤 Kiyoshi Noguchi
- 👤 Kouji Kobayashi
- 👤 Suguru Takayama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 16:31
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/64; G11B5/66; G11B5/674; G11B5/68; G11B5/70; G11B5/716; Y; Y10; Y10S; Y10S428/00; Y10S428/922; Y10S428/9265; Y10S428/928; Y10T; Y10T428/00; Y10T428/12; Y10T428/12458; Y10T428/12465; Y10T428/12493; Y10T428/12771; Y10T428/12861
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
78 words
A magnetic recording medium which comprises a magnetic layer formed on a substrate and comprising Co, or Co and one to three elements selected from the group consisting of Ni, Cr and O, wherein, when the magnetic layer is divided equally into four portions in the direction of the thickness of the magnetic layer, the density of the portion located farthest from the substrate is greater by at least 20% than the average density of three other portions.
Claim 2
Dependent Claim
78 words
A magnetic recording medium which comprises a magnetic layer formed on a substrate and comprising Co, or Co and one to three elements selected from the group consisting of Ni, Cr and O, wherein, when the magnetic layer is divided equally into four portions in the direction of the thickness of the magnetic layer, the density of the portion located farthest from the substrate is greater by at least 20% than the average density of three other portions.
Claim 3
Dependent Claim
24 words
The magnetic recording medium according to claim 1, wherein the magnetic layer contains Ni, and the weight ratio of Co/Ni is at least 1.5.
Claim 4
Dependent Claim
27 words
The magnetic recording medium according to claim 1, wherein the magnetic layer contains Cr, and the weight ratio of Cr/(Co or Co+Ni) is from 0.001 to 0.1.
Claim 5
Dependent Claim
26 words
The magnetic recording medium according to claim 1, wherein the magnetic layer contains O, and the atomic ratio of O/(Co or Co+Ni) is at most 0.1.
Claim 6
Dependent Claim
21 words
The magnetic recording medium according to claim 1, wherein the magnetic layer has a thickness of from 0.05 to 0.5 μm.
Claim 7
Dependent Claim
72 words
The magnetic recording medium according to claim 1, wherein the magnetic layer comprises a first layer located adjacent to the substrate and composed of columnar crystal particles which are inclined relative to the normal line of the principal plane of the substrate and a second layer located on the first layer and composed of crystal particles which are not inclined relative to the normal line of the principal plane of the substrate.
Claim 8
Dependent Claim
21 words
The magnetic recording medium according to claim 6, wherein the second layer has a thickness of from 0.005 to 0.1 μm.
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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) | 1989-06-09 | 1989-12-09 | 1990-06-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-06-09 | 1993-12-09 | 1994-06-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-06-09 | 1997-12-09 | 1998-06-10 | $7700.00 | Window Closed / Lapsed |