Patent US4774147A successfully refreshed from Google Patents.
US4774147A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording medium
Assignee: Maxell Ltd
•
Filing: 1985-06-17
•
Granted: 1988-09-27
•
Expires: 2005-06-17
Abstract
Abstract A magnetic recording medium having an excellent electromagnetic property with low frictional magnetic layer surface which comprises a base material having a magnetic layer provided thereon, said magnetic layer comprising magnetic powder, a resinous binder and graphitized carbon black powder, and optionally, with non-graphitized carbon black powder.
Inventors
- 👤 Sadamu Kuse
- 👤 Seigi Kawarai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 10:24
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/708; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/29; Y10T428/2982; Y10T428/2991; Y10T428/30
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
76 words
A magnetic recording medium which comprises a base material having a magnetic layer provided thereon, said magnetic layer comprising magnetic powder, a resinous binder and a graphitized carbon black powder comprising essentially of particles having an average particle size of 20 to 200 mμ and each comprising an integral core portion and a graphitized surface layer around said core portion, the thickness of said graphitized surface layer being from 5 to 50% of the particle size.
Claim 2
Dependent Claim
76 words
A magnetic recording medium which comprises a base material having a magnetic layer provided thereon, said magnetic layer comprising magnetic powder, a resinous binder and a graphitized carbon black powder comprising essentially of particles having an average particle size of 20 to 200 mμ and each comprising an integral core portion and a graphitized surface layer around said core portion, the thickness of said graphitized surface layer being from 5 to 50% of the particle size.
Claim 3
Dependent Claim
39 words
The magnetic recording medium according to claim 1, wherein the graphitized carbon black powder is contained in the magnetic layer in an amount of 0.05 to 5 parts by weight to 100 parts by weight of the magnetic powder.
Claim 4
Dependent Claim
39 words
The magnetic recording medium according to claim 2, wherein the graphitized carbon black powder is contained in the magnetic layer in an amount of 0.1 to 2 parts by weight to 100 parts by weight of the magnetic powder.
Claim 5
Dependent Claim
18 words
The magnetic recording medium according to claim 1, wherein the magnetic layer further comprises dispersion-assisting carbon black powder.
Claim 6
Dependent Claim
24 words
The magnetic recording medium according to claim 4, wherein the dispersion-assisting carbon black powder has an average particle size of 20 to 100 mμ.
Claim 7
Dependent Claim
31 words
The magnetic recording medium according to claim 4, wherein the average particle size of the dispersion-assisting carbon black powder is not larger than the size of the graphitized carbon black powder.
Claim 8
Dependent Claim
26 words
The magnetic recording medium according to claim 4, wherein the dispersion-assisting carbon black powder has a DBP oil absorption of not more than 100 ml/100 g.
Claim 9
Dependent Claim
26 words
The magnetic recording medium according to claim 7, wherein the dispersion-assisting carbon black powder has a DBP oil absorption of not more than 50 ml/100 g.
Claim 10
Dependent Claim
25 words
The magnetic recording medium according to claim 4, wherein the dispersion-assisting carbon black powder has a volatile content of not less than 3% by weight.
Claim 11
Dependent Claim
35 words
The magnetic recording medium according to claim 4, wherein the dispersion-assisting carbon black powder is contained in an amount of 60 to 200% by weight based on the weight of the graphitized carbon black powder.
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) | 1991-09-27 | 1992-03-28 | 1992-09-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-09-27 | 1996-03-28 | 1996-09-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-09-27 | 2000-03-28 | 2000-09-27 | $7700.00 | Window Closed / Lapsed |