US4816933A
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Magnetic recording medium of particular coercive force, filling ratio, and protrusions and recording/reproducing method therefor
Assignee: TDK Corp
•
Filing: 1985-10-21
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Granted: 1989-03-28
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Expires: 2005-10-21
Abstract
Abstract A magnetic recording medium is provided comprising a flexible substrate and a ferromagnetic metal thin film layer on the substrate primarily comprising cobalt. When coercive force is measured by changing the measuring direction in a plane defined by a longitudinal direction of the substrate and a direction normal to the major surface of the substrate, the following relationship is met: (Hc.sub.max -Hc.sub.min)/Hc(O)≦0.9 where Hc max is the maximum of the coercive force, Hc min is the minimum of the coercive force, and Hc(O) is a coercive force in the longitudinal direction of the substrate. 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 as expressed in μm of a gap in a magnetic head across which the medium is passed for recording and reproducing operation. The filling ratio of the ferromagnetic metal thin film layer is at least 0.7.
Inventors
- 👤 Toshiaki Izumi
- 👤 Kiyoshi Noguchi
- 👤 Hisae Shimizu
- 👤 Misao Kohmoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 17:27
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/64; G11B5/65; G11B5/658; G11B5/73; G11B5/739; G11B5/73923; G11B5/74; G11B5/84; G11B5/85; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 55
Claim 1
Independent Claim
144 words
A magnetic recording medium comprising a flexible substrate and a ferromagnetic metal thin film layer on one surface of the substrate primarily comprising cobalt, the improvement wherein when coercive force is measured by changing the measuring direction in a plane defined by a longitudinal direction of the substrate and a direction normal to the major surface of the substrate, the following relationship is met: (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.9 where Hc max is the maximum of the coercive force, Hc min is the minimum of the coercive force, and Hc(0) is a coercive force in the longitudinal direction of the substrate, and the filling ratio of the ferromagnetic metal thin film layer is at least 0.7, said filling ratio being ρ/ρβ wherein ρ is the average actual density of the ferromagnetic metal thin film layer and ρβ is the true density of the ferromagnetic thin film layer.
Claim 2
Dependent Claim
144 words
A magnetic recording medium comprising a flexible substrate and a ferromagnetic metal thin film layer on one surface of the substrate primarily comprising cobalt, the improvement wherein when coercive force is measured by changing the measuring direction in a plane defined by a longitudinal direction of the substrate and a direction normal to the major surface of the substrate, the following relationship is met: (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.9 where Hc max is the maximum of the coercive force, Hc min is the minimum of the coercive force, and Hc(0) is a coercive force in the longitudinal direction of the substrate, and the filling ratio of the ferromagnetic metal thin film layer is at least 0.7, said filling ratio being ρ/ρβ wherein ρ is the average actual density of the ferromagnetic metal thin film layer and ρβ is the true density of the ferromagnetic thin film layer.
Claim 3
Dependent Claim
37 words
A magnetic recording medium according to claim 1 wherein the ferromagnetic metal thin film layer consists essentially of cobalt alone or cobalt and at least one member selected from the group consisting of nickel, chromium and oxygen.
Claim 4
Dependent Claim
31 words
A magnetic recording medium according to claim 2 wherein the ferromagnetic metal thin film layer contains chromium in a weight ratio of Cr/Co or Cr/(Co+Ni) of about 0.001 to about 0.1
Claim 5
Dependent Claim
31 words
A magnetic recording medium according to claim 2 wherein the ferromagnetic metal thin film layer contains chromium in a weight ratio of Cr/Co or Cr/(Co+Ni) of about 0.001 to about 0.1.
Claim 6
Dependent Claim
31 words
A magnetic recording medium according to claim 2 wherein the ferromagnetic metal thin film layer further contains oxygen in an atomic ratio of O/Co or O/(Co+Ni) of about 0.5 or lower.
Claim 7
Dependent Claim
23 words
A magnetic recording medium according to claim 1 wherein the ferromagnetic metal thin film layer is about 0.05 to about 0.5 μm thick.
Claim 8
Dependent Claim
37 words
A magnetic recording medium according to claim 1 wherein the ferromagnetic metal thin film layer comprises coalesced columnar crystal particles which extend at an angle with respect to the normal to the major surface of the substrate.
Claim 9
Dependent Claim
45 words
A magnetic recording medium according to claim 7 wherein the columnar crystal particle is at a larger angle with respect to the normal to the major surface of the substrate on its side adjacent to the substrate than on its side remote from the substrate.
Claim 10
Dependent Claim
11 words
A magnetic recording medium according to claim 1 wherein (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.6
Claim 11
Dependent Claim
11 words
A magnetic recording medium according to claim 9 wherein (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.4
Claim 12
Dependent Claim
23 words
A magnetic recording medium according to claim 1 wherein the filling ratio of the ferromagnetic metal thin film layer is at least 0.75.
Claim 13
Dependent Claim
35 words
A magnetic recording medium according to claim 1 wherein the ferromagnetic metal thin film layer has a higher average density on its side remote from the substrate than on its side adjacent to the substrate.
Claim 14
Dependent Claim
56 words
A magnetic recording medium according to claim 12 wherein when the ferromagnetic metal thin film layer is divided into three equal portions in a thickness direction, the average density of the upper third remote from the substrate is higher than that of the lower third adjacent to the substrate by a factor of at least 1.5.
Claim 15
Dependent Claim
76 words
The magnetic recording medium of claim 1 wherein the ferromagnetic metal thin film layer is prepared by the oblique incidence evaporation process comprising the steps of: placing an evaporation source in an evaporation apparatus to extend in a direction transverse to the feed direction of the substrate, and controlling the rates of evaporation from a plurality of transversely spaced-apart points in the evaporation source such that the resulting magnetic thin layer may meet the coercivity relationship.
Claim 16
Dependent Claim
45 words
The magnetic recording medium of claim 14 wherein at least three evaporation points are arranged in the transverse direction with one at the widthwise center of the substrate, and the rate of evaporation from the lateral points is higher than that from the central point.
Claim 17
Dependent Claim
160 words
A magnetic recording medium comprising a flexible substrate and a ferromagnetic metal thin film layer on the substrate primarily comprising cobalt, the magnetic recording medium being used in combination with a magnetic head having a gap, the improvement wherein when coercive force is measured by changing the measuring direction in a plane defined by a longitudinal direction of the substrate and a direction normal to the major surface of the substrate, the following relationship is met: (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.9 where Hc max is the maximum of the coercive force, Hc min is the minimum of the coercive force, and Hc(0) is a coercive force in the longitudinal direction of the substrate, 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 as expressed in m and is from 0.1 to 0.5 μm.
Claim 18
Dependent Claim
160 words
A magnetic recording medium comprising a flexible substrate and a ferromagnetic metal thin film layer on the substrate primarily comprising cobalt, the magnetic recording medium being used in combination with a magnetic head having a gap, the improvement wherein when coercive force is measured by changing the measuring direction in a plane defined by a longitudinal direction of the substrate and a direction normal to the major surface of the substrate, the following relationship is met: (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.9 where Hc max is the maximum of the coercive force, Hc min is the minimum of the coercive force, and Hc(0) is a coercive force in the longitudinal direction of the substrate, 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 as expressed in m and is from 0.1 to 0.5 μm.
Claim 19
Dependent Claim
37 words
A magnetic recording medium according to claim 16 wherein the ferromagnetic metal thin film layer consists essentially of cobalt alone or cobalt and at least one member selected from the group consisting of nickel, chromium and oxygen.
Claim 20
Dependent Claim
28 words
A magnetic recording medium according to claim 17 wherein the ferromagnetic metal thin film layer contains nickel in a weight ratio of Co/Ni of about 1.5 or higher.
Claim 21
Dependent Claim
31 words
A magnetic recording medium according to claim 17 wherein the ferromagnetic metal thin film layer contains chromium in a weight ratio of Cr/Co or Cr/(Co+Ni) of about 0.001 to about 0.1.
Claim 22
Dependent Claim
31 words
A magnetic recording medium according to claim 17 wherein the magnetic metal thin film layer further contains oxygen in an atomic ratio of O/Co or O/(Co+Ni) of about 0.5 or lower.
Claim 23
Dependent Claim
23 words
A magnetic recording medium according to claim 16 wherein the ferromagnetic metal thin film layer is about 0.05 to about 0.5 μm thick.
Claim 24
Dependent Claim
37 words
A magnetic recording medium according to claim 16 wherein the ferromagnetic metal thin film layer comprises coalesced columnar crystal particles which extend at an angle with respect to the normal to the major surface of the substrate.
Claim 25
Dependent Claim
45 words
A magnetic recording medium according to claim 22 wherein the columnar crystal particle is at a larger angle with respect to the normal to the major surface of the substrate on its side adjacent to the substrate than on its side remote from the substrate.
Claim 26
Dependent Claim
11 words
A magnetic recording medium according to claim 16 wherein (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.6
Claim 27
Dependent Claim
11 words
A magnetic recording medium according to claim 24 wherein (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.4
Claim 28
Dependent Claim
54 words
A magnetic recording medium according to claim 16 wherein said flexible substrate is comprised of a high polymer, submicron particles having a size of 30 to 300 Å are placed on one surface of the substrate, and the ferromagentic metal thin film layer is provided on the one substrate surface with the intervening particles.
Claim 29
Dependent Claim
76 words
The magnetic recording medium of claim 16 wherein the ferromagnetic metal thin film layer is prepared by the oblique incidence evaporation process comprising the steps of: placing an evaporation source in an evaporation apparatus to extend in a direction transverse to the feed direction of the substrate, and controlling the rates of evaporation from a plurality of transversely spaced-apart points in the evaporation source such that the resulting magnetic thin layer may meet the coercivity relationship.
Claim 30
Dependent Claim
45 words
The magnetic recording medium of claim 27 wherein at least three evaporation points are arranged in the transverse direction with one at the widthwise center of the substrate, and the rate of evaporation from the lateral points is higher than that from the central point.
Claim 31
Dependent Claim
198 words
A magnetic recording medium comprising a flexible substrate and a ferromagnetic metal thin film layer on the substrate primarily comprising cobalt, the magnetic recording medium being used in combination with a magnetic head having a gap, the improvement wherein when coercive force is measured by changing the measuring direction in a plane defined by a longitudinal direction of the substrate and a direction normal to the major surface of the substrate, the following relationship is met: (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.9 where Hc max is the maximum of the coercive force, Hc min is the minimum of the coercive force, and Hc(0) is a coercive force in the longitudinal direction of the substrate, the medium has in average at least 10 5 /a 2 protrusions per square millimeter of the surface, the protrusion having a height of 30 to 300 Å, wherein a is the distance of the magnetic head gap as expressed in μm, and the filling ratio of the ferromagnetic metal thin film layer is at least 0.7, said filling ratio being ρ/ρβ wherein ρ is the average actual density of the ferromagnetic metal thin film layer and ρβ is the true density of the ferromagnetic thin film layer.
Claim 32
Dependent Claim
198 words
A magnetic recording medium comprising a flexible substrate and a ferromagnetic metal thin film layer on the substrate primarily comprising cobalt, the magnetic recording medium being used in combination with a magnetic head having a gap, the improvement wherein when coercive force is measured by changing the measuring direction in a plane defined by a longitudinal direction of the substrate and a direction normal to the major surface of the substrate, the following relationship is met: (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.9 where Hc max is the maximum of the coercive force, Hc min is the minimum of the coercive force, and Hc(0) is a coercive force in the longitudinal direction of the substrate, the medium has in average at least 10 5 /a 2 protrusions per square millimeter of the surface, the protrusion having a height of 30 to 300 Å, wherein a is the distance of the magnetic head gap as expressed in μm, and the filling ratio of the ferromagnetic metal thin film layer is at least 0.7, said filling ratio being ρ/ρβ wherein ρ is the average actual density of the ferromagnetic metal thin film layer and ρβ is the true density of the ferromagnetic thin film layer.
Claim 33
Dependent Claim
36 words
A magnetic recording medium according to claim 29 wherein the ferromagnetic metal thin film layer consists essentially of cobalt alone or cobalt and at least one selected from the group consisting of nickel, chromium and oxygen.
Claim 34
Dependent Claim
28 words
A magnetic recording medium according to claim 30 wherein the ferromagnetic metal thin film layer contains nickel in a weight ratio of Co/Ni of about 1.5 or higher.
Claim 35
Dependent Claim
31 words
A magnetic recording medium according to claim 30 wherein the ferromagnetic metal thin film layer contains chromium in a weight ratio of Cr/Co or Cr/(Co+Ni) of about 0.001 to about 0.1.
Claim 36
Dependent Claim
31 words
A magnetic recording medium according to claim 30 wherein the magnetic metal thin film layer further contains oxygen in an atomic ratio of 0/Co or 0/(Co+Ni) of about 0.5 or lower.
Claim 37
Dependent Claim
23 words
A magnetic recording medium according to claim 29 wherein the ferromagnetic metal thin film layer is about 0.05 to about 0.5 μm thick.
Claim 38
Dependent Claim
37 words
A magnetic recording medium according to claim 29 wherein the ferromagnetic metal thin film layer comprises coalesced columnar crystal particles which extend at an angle with respect to the normal to the major surface of the substrate.
Claim 39
Dependent Claim
45 words
A magnetic recording medium according to claim 35 wherein the columnar crystal particle is at a larger angle with respect to the normal to the major surface of the substrate on its side adjacent to the substrate than on its side remote from the substrate.
Claim 40
Dependent Claim
11 words
A magnetic recording medium according to claim 29 wherein (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.6.
Claim 41
Dependent Claim
11 words
A magnetic recording medium according to claim 37 wherein (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.4.
Claim 42
Dependent Claim
23 words
A magnetic recording medium according to claim 29 wherein the filling ratio of the ferromagnetic metal thin film layer is at least 0.75.
Claim 43
Dependent Claim
35 words
A magnetic recording medium according to claim 29 wherein the ferromagnetic metal thin film layer has a higher average density on its side remote from the substrate than on its side adjacent to the substrate.
Claim 44
Dependent Claim
55 words
A magnetic recording medium according to claim 40 wherein the ferromagnetic metal thin film layer is divided into three equal portions in a thickness direction, the average density of the upper third remote from the substrate is higher than that of the lower third adjacent to the substrate by a factor of at least 1.5.
Claim 45
Dependent Claim
54 words
A magnetic recording medium according to claim 29 wherein said flexible substrate is comprised of a high polymer, submicron particles having a size of 30 to 300 Å are placed on one surface of the substrate, and the ferromagnetic metal thin film layer is provided on the one substrate surface with the intervening particles.
Claim 46
Dependent Claim
76 words
The magnetic recording medium of claim 29 wherein the ferromagnetic metal thin film layer is prepared by the oblique incidence evaporation process comprising the steps of: placing an evaporation source in an evaporation apparatus to extend in a direction transverse to the feed direction of the substrate, and controlling the rates of evaporation from a plurality of transversely spaced-apart points in the evaporation source such that the resulting magnetic thin layer may meet the coercivity relationship.
Claim 47
Dependent Claim
45 words
The magnetic recording medium of claim 43 wherein at least three evaporation points are arranged in the transverse direction with one at the widthwise center of the substrate, and the rate of evaporation from the lateral points is higher than that from the central point.
Claim 48
Independent Claim
169 words
A method for conducting recording/reproducing operation on a magnetic recording medium comprising a flexible substrate 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 when coercive force is measured by changing the measuring direction in a plane defined by a longitudinal direction of the substrate and a direction normal to the major surface of the substrate, the magnetic recording medium meets the following relationship: (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.9 where Hc max is the maximum of the coercive force, Hc min is the minimum of the coercive force, and Hc(0) is a coercive force in the longitudinal direction of the substrate 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 ○, wherein a is the distance of the magnetic head gap as expressed in μm and is from 0.1 to 0.5 μm.
Claim 49
Independent Claim
169 words
A method for conducting recording/reproducing operation on a magnetic recording medium comprising a flexible substrate 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 when coercive force is measured by changing the measuring direction in a plane defined by a longitudinal direction of the substrate and a direction normal to the major surface of the substrate, the magnetic recording medium meets the following relationship: (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.9 where Hc max is the maximum of the coercive force, Hc min is the minimum of the coercive force, and Hc(0) is a coercive force in the longitudinal direction of the substrate 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 ○, wherein a is the distance of the magnetic head gap as expressed in μm and is from 0.1 to 0.5 μm.
Claim 50
Dependent Claim
28 words
A magnetic recording/reproducing method according to claim 45 wherein at least an edge portion of the magnetic head including the gap is formed of a ferromagnetic metal material.
Claim 51
Dependent Claim
20 words
A magnetic recording/reproducing method according to claim 46 wherein the ferromagnetic metal material is a magnetic amorphous cobalt base alloy.
Claim 52
Independent Claim
213 words
A method for conducting recording/reproducing operation on a magnetic recording medium comprising a flexible substrate 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 when coercive force is measured by changing the measuring direction in a plane defined by a longitudinal direction of the substrate and a direction normal to the major surface of the substrate, the magnetic recording medium meets the following relationship: (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.9 where Hc max is the maximum of the coercive force, Hc min is the minimum of the coercive force, and Hc(0) is a coercive force in the longitudinal direction of the substrate, 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 as expressed in μm and is from 0.1 to 0.5 μm, and the filling ratio of the ferromagnetic metal thin film layer is at least 0.7, said filling ratio being wherein μ is the average actual density of the ferromagnetic metal thin film layer and μ is the true density of the ferromagnetic thin film layer.
Claim 53
Independent Claim
213 words
A method for conducting recording/reproducing operation on a magnetic recording medium comprising a flexible substrate 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 when coercive force is measured by changing the measuring direction in a plane defined by a longitudinal direction of the substrate and a direction normal to the major surface of the substrate, the magnetic recording medium meets the following relationship: (Hc.sub.max -Hc.sub.min)/Hc(0)≦0.9 where Hc max is the maximum of the coercive force, Hc min is the minimum of the coercive force, and Hc(0) is a coercive force in the longitudinal direction of the substrate, 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 as expressed in μm and is from 0.1 to 0.5 μm, and the filling ratio of the ferromagnetic metal thin film layer is at least 0.7, said filling ratio being wherein μ is the average actual density of the ferromagnetic metal thin film layer and μ is the true density of the ferromagnetic thin film layer.
Claim 54
Dependent Claim
28 words
A magnetic recording/reproducing method according to claim 48 wherein at least an edge portion of the magnetic head including the gap is formed of a ferromagnetic metal material.
Claim 55
Dependent Claim
20 words
A magnetic recording/reproducing method according to claim 49 wherein the ferromagnetic metal material is a magnetic amorphous cobalt base alloy.
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) | 1992-03-27 | 1992-09-26 | 1993-03-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-03-27 | 1996-09-26 | 1997-03-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-03-27 | 2000-09-26 | 2001-03-28 | $7700.00 | Window Closed / Lapsed |