US4529661A
Expired / Lapsed
US
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Magnetic recording medium
Assignee: Sony Corp
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Filing: 1983-07-01
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Granted: 1985-07-16
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Expires: 2003-07-01
Abstract
Abstract PCT No. PCT/JP83/00210 Sec. 371 Date Mar. 1, 1984 Sec. 102(e) Date Mar. 1, 1984 PCT Filed Jul. 1, 1983 PCT Pub. No. WO84/00240 PCT Pub. Date Jan. 19, 1984.A magnetic recording medium has, on a nonmagnetic support, a magnetic layer consisting mainly of an acicular iron oxide magnetic powder and a binder. In order to improve the S/N ratio, a fine magnetic powder having a specific surface area as determined by the BET method, of not less than 35 m2/g is used. In order to improve the dispersibility of the magnetic powder and to improve the squareness ratio and durability thereof, the binder contains a resin which has a molecular weight of not more than 50,000 and has at least one polar group selected from the group consisting of polar groups having the general formulas: <IMAGE> (wherein M is hydrogen, lithium, sodium or potassium; and M1 and M2 are hydrogen, lithium, sodium, potassium or alkyl groups.
Inventors
- 👤 Yoshinobu Ninomiya
- 👤 Akira Hashimoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 21:04
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/702; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257; Y10T428/31504; Y10T428/31551; Y10T428/31609
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
116 words
A magnetic recording medium having on a nonmagnetic support a magnetic recording layer consisting mainly of an acicular iron oxide magnetic powder and a binder, characterized in that said iron oxide magnetic powder has a specific surface area as determined by the BET method, of not less than 45 m 2 /g, and said binder contains not less than 30% by weight of a resin which has a molecular weight of not more than 50,000 and at least one polar group selected from the group consisting of polar groups having the general formulas: ##STR5## (wherein M is hydrogen, lithium, sodium, or potassium; and M 1 and M 2 are hydrogen, lithium, sodium, potassium or alkyl groups).
Claim 2
Dependent Claim
116 words
A magnetic recording medium having on a nonmagnetic support a magnetic recording layer consisting mainly of an acicular iron oxide magnetic powder and a binder, characterized in that said iron oxide magnetic powder has a specific surface area as determined by the BET method, of not less than 45 m 2 /g, and said binder contains not less than 30% by weight of a resin which has a molecular weight of not more than 50,000 and at least one polar group selected from the group consisting of polar groups having the general formulas: ##STR5## (wherein M is hydrogen, lithium, sodium, or potassium; and M 1 and M 2 are hydrogen, lithium, sodium, potassium or alkyl groups).
Claim 3
Dependent Claim
20 words
A magnetic recording medium according to claim 1, characterized in that the alkyl group has up to 23 carbon atoms.
Claim 4
Dependent Claim
46 words
A magnetic recording medium according to claim 1, characterized in that said iron oxide magnetic powder is γ-Fe 2 O 3 , a weakly reduced γ-Fe 2 O 3 , a Co-Coated γ-Fe 2 O 3 or a weakly reduced Co-coated γ-Fe 2 O 3 .
Claim 5
Dependent Claim
30 words
A magnetic recording medium according to claim 1, characterized in that a main chain of said resin having the polar group is a polyester, polyurethane or a vinyl chloride-based copolymer.
Claim 6
Dependent Claim
25 words
A magnetic recording medium according to claim 1, characterized in that the molecular weight of said resin having the polar group is 2,000 to 50,000.
Claim 7
Dependent Claim
25 words
A magnetic recording medium according to claim 1, characterized in that the molecular weight of said resin having the polar group is 10,000 to 50,000.
Claim 8
Dependent Claim
28 words
A magnetic recording medium according to claim 1, characterized in that said reisn having the polar group has a molecular weight of 2,000 to 50,000 per polar group.
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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) | 1988-07-15 | 1989-01-14 | 1989-07-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-07-15 | 1993-01-14 | 1993-07-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-07-15 | 1997-01-14 | 1997-07-16 | $7700.00 | Window Closed / Lapsed |