US4474843A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording medium
Assignee: Fujifilm Holdings Corp
•
Filing: 1981-08-14
•
Granted: 1984-10-02
•
Expires: 2001-08-14
Abstract
Abstract A magnetic recording medium is described comprising a magnetic layer on one surface of a non-magnetic base and a back coating on the other surface of the base, said back coating being not more than 2μ thick and which contains an inorganic powder and a binder, said inorganic powder consisting of fine particles of an average size of from 0.01 to 0.1μ and coarse particles of an average size of from 0.1 to 0.8μ.
Inventors
- 👤 Takahito Miyoshi
- 👤 Toshimitu Okutu
- 👤 Masaaki Fujiyama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 03:55
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; Y10T428/24; Y10T428/24942; Y10T428/25; Y10T428/252; Y10T428/256; Y10T428/257; Y10T428/258; Y10T428/259
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
185 words
A magnetic recording medium comprising: (A) a magnetic layer on one surface of a non-magnetic base and (B) a back coating on the other surface of the base, said back coating being not more than 2μ thick and comprising (i) an inorganic powder selected from the group consisting of CaCO 3 , Al 2 O 3 , SiO 2 , Fe 2 O 3 , TiO 2 , MgO, ZnO and CaO and (ii) a binder consisting of a cellulosic resin, a thermoplastic polyurethane elastomer, a saturated polyester resin and polyisocyanate, wherein said inorganic powder consists essentially of fine particles having an average size of from 0.01 to 0.1μ and coarse particles having an average size of from 0.1 to 0.8μ, provided that the two types of particles have different average sizes, and wherein the volume ratio of the coarse particles/fine particles is 1/20 or less, and wherein the center line average roughness (Ra) of the back coating is not more than 0.024μ where the cutoff value is 0.08 mm and wherein the total thickness of the magnetic recording medium is less than about 20μ.
Claim 2
Dependent Claim
185 words
A magnetic recording medium comprising: (A) a magnetic layer on one surface of a non-magnetic base and (B) a back coating on the other surface of the base, said back coating being not more than 2μ thick and comprising (i) an inorganic powder selected from the group consisting of CaCO 3 , Al 2 O 3 , SiO 2 , Fe 2 O 3 , TiO 2 , MgO, ZnO and CaO and (ii) a binder consisting of a cellulosic resin, a thermoplastic polyurethane elastomer, a saturated polyester resin and polyisocyanate, wherein said inorganic powder consists essentially of fine particles having an average size of from 0.01 to 0.1μ and coarse particles having an average size of from 0.1 to 0.8μ, provided that the two types of particles have different average sizes, and wherein the volume ratio of the coarse particles/fine particles is 1/20 or less, and wherein the center line average roughness (Ra) of the back coating is not more than 0.024μ where the cutoff value is 0.08 mm and wherein the total thickness of the magnetic recording medium is less than about 20μ.
Claim 3
Dependent Claim
34 words
A magnetic recording medium as in claim 1, wherein the fine particles have an average size of from 0.03 to 0.08μ and the coarse particles have an average size of from 0.2 to 0.6μ.
Claim 4
Dependent Claim
34 words
A magnetic recording medium as in claim 1, wherein the fine particles have an average size of from 0.06 to 0.08μ, and the coarse particles have an average size of from 0.3 to 0.4μ.
Claim 5
Dependent Claim
27 words
A magnetic recording medium as in claim 1, wherein the particles project from the surface of the back coating to a height of not more than 0.8μ.
Claim 6
Dependent Claim
27 words
A magnetic recording medium as in claim 1, wherein the particles project from the surface of the back coating to a height of not more than 0.4μ.
Claim 7
Dependent Claim
27 words
A magnetic recording medium as in claim 1, wherein the particles project from the surface of the back coating to a height of not more than 0.2μ.
Claim 8
Dependent Claim
22 words
A magnetic recording medium as in claim 1, wherein the volume ratio of the coarse particles/fine particles is from 1/1000 to 1/50.
Claim 9
Dependent Claim
35 words
A magnetic recording medium as in claim 1, wherein the inorganic powder contains a small amount of other particulate material selected from the group consisting of carbon black powder, graphite, tungsten, disulfide, and boron nitride.
Claim 10
Dependent Claim
22 words
A magnetic recording medium as in claim 1, wherein the fine particles are made of a different material than the coarse particles.
Claim 11
Dependent Claim
28 words
A magnetic recording medium as in claim 1, wherein the coarse particles are selected from the group consisting of Al 2 O 3 , MgO, ZnO, and CaO.
Claim 12
Dependent Claim
18 words
A magnetic recording medium as in claim 1, wherein the coarse particles are Al 2 O 3 .
Claim 13
Dependent Claim
29 words
A magnetic recording medium as in claim 1, wherein the fine particles are selected from the group consisting of SiO 2 , CaCO 3 , and TiO 2 .
Claim 14
Dependent Claim
16 words
A magnetic recording medium as in claim 1, wherein the fine particles are CaCO 3 .
Claim 15
Dependent Claim
25 words
A magnetic recording medium as in claim 1, wherein the weight ratio of the inorganic powder/binder in the back coating is from 2.5/1 to 0.1/1.
Claim 16
Dependent Claim
24 words
A magnetic recording medium as in claim 1, wherein the weight ratio of the inorganic powder/binder in the back coating from 1.5/1 to 0.8/1.
Claim 17
Dependent Claim
20 words
A magnetic recording medium as in claim 1, wherein the back coating has a thickness of from 0.3 to 2μ.
Claim 18
Dependent Claim
20 words
A magnetic recording medium as in claim 1, wherein the back coating has a thickness of from 0.5 to 1μ.
Claim 19
Dependent Claim
46 words
A magnetic recording medium as in claim 1, werhein the binder contains from 20 to 80% by weight cellulosic resin, from 20 to 60% by weight thermoplastic polyurethane elastomer, from 1 to 20% by weight saturated polyester resin, and from 10 to 50% by weight polyisocyanate.
Claim 20
Dependent Claim
46 words
A magnetic recording medium as in claim 1, wherein the binder contains from 30 to 60% by weight cellulosic resin, from 30 to 50% by weight thermoplastic polyurethane elastomer, from 1 to 10% by weight saturated polyester resin, and from 20 to 40% by weight polyisocyanate.
References Cited (Backward Citations)
US4015042A
Cited
US4146031A
Cited
US4189514A
Cited
US4367261A
Cited
US4411953A
Cited
US4414270A
Cited
US4419406A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-10-02 | 1988-04-02 | 1988-10-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-10-02 | 1992-04-02 | 1992-10-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-10-02 | 1996-04-02 | 1996-10-02 | $7700.00 | Window Closed / Lapsed |