US4734810A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording medium comprising protrusion on its surface and a plasma treated substrate and recording/reproducing method therefor
Assignee: TDK Corp
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Filing: 1985-07-24
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Granted: 1988-03-29
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Expires: 2005-07-24
Abstract
Abstract A magnetic recording medium comprising a ferromagnetic metal thin film layer formed on one surface of a flexible non-magnetic substrate and primarily comprising cobalt and oxygen is improved in durability by treating the substrate with a plasma at a frequency of 10 kHz to 200 kHz, and providing the magnetic layer on the surface with protrusions having a height of 30 to 300 ANGSTROM at an average density of at least 105/a2 per square millimeter of the surface, provided that the magnetic recording medium is passed for recording/reproducing operation across a magnetic head with a gap having a distance a as expressed n mu m.
Inventors
- 👤 Masatoshi Nakayama
- 👤 Kunihiro Ueda
- 👤 Yuichi Kubota
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 13:42
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/64; G11B5/65; G11B5/658; G11B5/73; G11B5/739; G11B5/73923; G11B5/73927; G11B5/73937
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
118 words
A magnetic recording medium comprising a flexible substrate having opposed major surfaces, and a ferromagnetic metal thin film layer on one surface of the substrate primarily comprisnig cobalt, the magnetic recording medium being used in combination with a magnetic head having a gap, characterized in that said substrate is plasma treated at a frequency of 10 KHz to 200 KHz, said metal thin film layer contains oxygen, and the medium has protrusions on its surface at an average density of at least 10 5 /a 2 per square millimeter of the surface, the protrusions having a height of 30 to 300 Å, where a is the distance of the magnetic head gap and is 0.1 to 0.5 μm.
Claim 2
Dependent Claim
118 words
A magnetic recording medium comprising a flexible substrate having opposed major surfaces, and a ferromagnetic metal thin film layer on one surface of the substrate primarily comprisnig cobalt, the magnetic recording medium being used in combination with a magnetic head having a gap, characterized in that said substrate is plasma treated at a frequency of 10 KHz to 200 KHz, said metal thin film layer contains oxygen, and the medium has protrusions on its surface at an average density of at least 10 5 /a 2 per square millimeter of the surface, the protrusions having a height of 30 to 300 Å, where a is the distance of the magnetic head gap and is 0.1 to 0.5 μm.
Claim 3
Dependent Claim
21 words
A magnetic recording medium according to claim 1 wherein the plasma treatment is carried out in a treating gas containing oxygen.
Claim 4
Dependent Claim
20 words
A magnetic recording medium according to claim 2 wherein the treating gas comprises 5 to 100% by volume of oxygen.
Claim 5
Dependent Claim
48 words
A magnetic recording medium according to claim 1 wherein submicron particles having a particle size of 30 to 300 Å are placed on the substrate prior to the plasma treatment and the ferromagnetic metal thin film layer is formed on the particle-bearing, plasma treated surface of the substrate.
Claim 6
Dependent Claim
26 words
A magnetic recording medium according to claim 1 wherein the ferromagnetic metal thin film layer has a layer of ferromagnetic metal oxide on the surface thereof.
Claim 7
Dependent Claim
33 words
A magnetic recording medium according to claim 1 wherein the protrusins are distributed at an average density in the range of 2×10 6 /a 2 to 1×10 9 /a 2 per square millimeter.
Claim 8
Dependent Claim
34 words
A magnetic recording medium according to claim 1 wherein the ferromagnetic metal thin film layer consists essentially of Co and O, or Co, O and at least one element selected from Ni and Cr.
Claim 9
Dependent Claim
28 words
A magnetic recording medium according to claim 7 wherein the ferromagnetic metal thin film layer has an atomic ratio of O/Co or O/(Co+Ni) of not less than 0.5.
Claim 10
Independent Claim
125 words
A method for conducting recording/reproducing operation on a magnetic recording medium comprising a flexible substrate having opposed major surfaces, and a ferromagnetic metal thin film layer on one surface of the substrate principally comprising cobalt, by passing the medium across a magnetic head having a gap, characterized in that said ferromagnetic metla thin film layer contains oxygen and is formed on the flexible substrate which has been plasma treated at a frequency in the range of 10 to 200 kilohertz, and the medium has in average at least 10 5 /a 2 protrusions per square millimeter of the surface, the protrusions having a height of 30 to 300 Å, where a is the distance of the magnetic head gap and is 0.1 to 0.5 μm.
Claim 11
Independent Claim
125 words
A method for conducting recording/reproducing operation on a magnetic recording medium comprising a flexible substrate having opposed major surfaces, and a ferromagnetic metal thin film layer on one surface of the substrate principally comprising cobalt, by passing the medium across a magnetic head having a gap, characterized in that said ferromagnetic metla thin film layer contains oxygen and is formed on the flexible substrate which has been plasma treated at a frequency in the range of 10 to 200 kilohertz, and the medium has in average at least 10 5 /a 2 protrusions per square millimeter of the surface, the protrusions having a height of 30 to 300 Å, where a is the distance of the magnetic head gap and is 0.1 to 0.5 μm.
Claim 12
Dependent Claim
28 words
A magnetic recording/reproducing method according to claim 9 wherein at least an edge portion of the magnetic head including the gap is formed of a ferromagnetic metal material.
Claim 13
Dependent Claim
20 words
A magnetic recording/reproducing method according to claim 10 wherein the ferromagnetic metal material is a magnetic amorphous cobalt base alloy.
References Cited (Backward Citations)
JPS53116115A
Cited
JPS5742889A
Cited
JPS5868227A
Cited
US4578729A
Cited
JPS5877030A
Cited
JPS58100221A
Cited
US4575475A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-03-29 | 1991-09-28 | 1992-03-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-03-29 | 1995-09-28 | 1996-03-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-03-29 | 1999-09-28 | 2000-03-29 | $7700.00 | Window Closed / Lapsed |