Patent US4612244A successfully refreshed from Google Patents.
US4612244A
Expired / Lapsed
US
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Magnetic recording medium
Assignee: Sony Corp
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Filing: 1984-10-01
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Granted: 1986-09-16
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Expires: 2004-10-01
Abstract
Abstract A magnetic recording medium is disclosed, in which a magnetic layer is formed on one surface of the non-magnetizable substrate and a back coating layer consisting essentially of a binder and a non-magnetizable pigment is formed on the other surface of the substrate. In the back coating layer, more than 80 weight percent of the binder is a polyurethane resin or a polyester resin having hydrophilic polar groups. The back coating layer also contains carbon black for preventing electrostatic charging and pigments with Mohs hardness higher than 5 for improving durability. The carbon black to the pigments weight ratio is set to be in the range of 95:5 to 60:40.
Inventors
- 👤 Koji Kaneda
- 👤 Masayoshi Sugiyama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 17:50
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/73; G11B5/735; G11B5/7356; G11B5/7358; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/30; Y10T428/31504; Y10T428/31551; Y10T428/31565; Y10T428/31598; Y10T428/31609; Y10T428/31786
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
174 words
A magnetic recording medium comprising a non-magnetizable substrate, a magnetic layer formed on one surface of said non-magnetizable substrate and a back coating layer composed of a binder and non-magnetizable pigment formed on the other surface of said non-magnetizable substrate, said binder being composed of at least one of a polyester resin having hydrophilic groups and a polyurethane resin having hydrophilic groups, in an amount of at least 80% by weight of said binder, said hydrophilic groups being selected from the group consisting of groups having the general formulas: ##STR7## wherein M is hydrogen, lithium, sodium, or potassium; and M 1 and M 2 are hydrogen, lithium, sodium, potassium or alkyl groups, said hydrophilic groups being present in said resin in an amount between 0.01 and 2.0 mg equivalents/g and said non-magnetizable pigment being composed of carbon black having a mean particle diameter between 0.02 and 0.1 micron, and non-magnetizable pigment having Mohs hardness not less than 5, the weight ratio of said carbon black to said non-magnetizable pigment being from 60:40 to 95:5.
Claim 2
Dependent Claim
174 words
A magnetic recording medium comprising a non-magnetizable substrate, a magnetic layer formed on one surface of said non-magnetizable substrate and a back coating layer composed of a binder and non-magnetizable pigment formed on the other surface of said non-magnetizable substrate, said binder being composed of at least one of a polyester resin having hydrophilic groups and a polyurethane resin having hydrophilic groups, in an amount of at least 80% by weight of said binder, said hydrophilic groups being selected from the group consisting of groups having the general formulas: ##STR7## wherein M is hydrogen, lithium, sodium, or potassium; and M 1 and M 2 are hydrogen, lithium, sodium, potassium or alkyl groups, said hydrophilic groups being present in said resin in an amount between 0.01 and 2.0 mg equivalents/g and said non-magnetizable pigment being composed of carbon black having a mean particle diameter between 0.02 and 0.1 micron, and non-magnetizable pigment having Mohs hardness not less than 5, the weight ratio of said carbon black to said non-magnetizable pigment being from 60:40 to 95:5.
Claim 3
Dependent Claim
32 words
A magnetic recording medium according to claim 1, in which the amount of said non-magnetizable pigment is from 100 to 300 parts by weight per 100 parts by weight of said binder.
Claim 4
Dependent Claim
24 words
A magnetic recording medium according to claim 1, in which the mean particle diameter of said carbon black is from 0.04 to 0.08 μm.
Claim 5
Dependent Claim
30 words
A magnetic recording medium according to claim 1 in which the particle diameter of said non-magnetizable pigment having Mohs hardness not less than 5 is from 0.2 to 0.3 μm.
Claim 6
Dependent Claim
22 words
A magnetic recording medium according to claim 1, in which the Mohs hardness of said non-magnetizable pigment is from 5 to 8.
Claim 7
Dependent Claim
24 words
A magnetic recording medium according to claim 1, in which said non-magnetizable pigment having Mohs hardness not less than 5 is an inorganic pigment.
Claim 8
Dependent Claim
25 words
A magnetic recording medium according to claim 1, in which the shape of said non-magnetizable pigment having Mohs hardness not less than 5 is spherical.
References Cited (Backward Citations)
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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) | 1989-09-15 | 1990-03-17 | 1990-09-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-09-15 | 1994-03-17 | 1994-09-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-09-15 | 1998-03-17 | 1998-09-16 | $7700.00 | Window Closed / Lapsed |