Patent US5371850A successfully refreshed from Google Patents.
US4347291A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording medium and preparation thereof
Assignee: TDK Corp
•
Filing: 1980-11-20
•
Granted: 1982-08-31
•
Expires: 2000-11-20
Abstract
Abstract A magnetic recording medium is produced by forming an alkaline aqueous slurry of an acicular hydrated iron oxide or an acicular iron oxide as a starting material; adding a water soluble silicate to said slurry; treating it by a hydrothermal reaction in a closed reactor as an autoclave at elevated temperature and pressure; dehydrating and drying said slurry to obtain a dry iron oxide containing SiO2 component; converting it into a magnetic metallic iron powder by a reduction in a reducing atmosphere as hydrogen atmosphere; and coating a magnetic composition obtained by mixing said magnetic metallic iron powder with a binder. A magnetic recording tape comprises metallic iron powder having a coercive force of 1000 Oe or more and a residual magnetic flux density of 2000 gauss or more and an orientation degree as a ratio of squareness ratio in longitudinal direction to squareness ratio in transversal direction: <IMAGE>
Inventors
- 👤 Yasumichi Tokuoka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:55
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70605; G11B5/70615; C; C21; C21B; C21B15/00; H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/065; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
175 words
A magnetic recording tape which has a coercive force of 1000 Oe or more and a residual magnetic flux density of 2000 gauss or more and an orientation degree, which is the ratio of the squareness ratio in the longitudinal direction to the squareness ratio in the transverse direction, of ##EQU5## comprising: a magnetic metallic iron powder mixed with a binder and coated on a substrate; wherein said magnetic metallic iron powder is prepared by forming an alkaline aqueous slurry of an acicular hydrated iron oxide or an acicular iron oxide having a pH in the range of 8 to 14, adding a water soluble silicate to said slurry in an amount of 0.1 to 10 mol%, as SiO 2 to Fe, treating said slurry by a hydrothermal reaction in a closed reactor at 100° to 250° C. for 5 minutes or longer, dehydrating and drying said slurry to obtain a dry iron oxide containing an SiO 2 component, and converting it into a magnetic metallic iron powder by reduction in a hydrogen reducing atmosphere.
Claim 2
Dependent Claim
175 words
A magnetic recording tape which has a coercive force of 1000 Oe or more and a residual magnetic flux density of 2000 gauss or more and an orientation degree, which is the ratio of the squareness ratio in the longitudinal direction to the squareness ratio in the transverse direction, of ##EQU5## comprising: a magnetic metallic iron powder mixed with a binder and coated on a substrate; wherein said magnetic metallic iron powder is prepared by forming an alkaline aqueous slurry of an acicular hydrated iron oxide or an acicular iron oxide having a pH in the range of 8 to 14, adding a water soluble silicate to said slurry in an amount of 0.1 to 10 mol%, as SiO 2 to Fe, treating said slurry by a hydrothermal reaction in a closed reactor at 100° to 250° C. for 5 minutes or longer, dehydrating and drying said slurry to obtain a dry iron oxide containing an SiO 2 component, and converting it into a magnetic metallic iron powder by reduction in a hydrogen reducing atmosphere.
Claim 3
Dependent Claim
123 words
A process for producing a magnetic recording medium which comprises: forming an alkaline aqueous slurry of an acicular hydrated iron oxide or an acicular iron oxide having a pH in the range of 8-14, adding a water soluble silicate to said slurry in an amount of 0.1 to 10 mol%, as SiO 2 to Fe, treating said slurry by a hydrothermal reaction in a closed reactor at 100° to 250° C. for 5 minutes or longer, dehydrating and drying said slurry to obtain a dry iron oxide containing an SiO 2 component, converting it into a magnetic metallic iron powder by reduction in a hydrogen reducing atmosphere, mixing said magnetic metallic iron powder with a binder and coating the same on a substrate.
Claim 4
Dependent Claim
123 words
A process for producing a magnetic recording medium which comprises: forming an alkaline aqueous slurry of an acicular hydrated iron oxide or an acicular iron oxide having a pH in the range of 8-14, adding a water soluble silicate to said slurry in an amount of 0.1 to 10 mol%, as SiO 2 to Fe, treating said slurry by a hydrothermal reaction in a closed reactor at 100° to 250° C. for 5 minutes or longer, dehydrating and drying said slurry to obtain a dry iron oxide containing an SiO 2 component, converting it into a magnetic metallic iron powder by reduction in a hydrogen reducing atmosphere, mixing said magnetic metallic iron powder with a binder and coating the same on a substrate.
References Cited (Backward Citations)
US3947502A
Cited
NL7600190A
Cited
US4043846A
Cited
US4169912A
Cited
US4133677A
Cited
US4178171A
Cited
US4256484A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-08-30 | 1986-03-01 | 1986-08-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-08-30 | 1990-03-01 | 1990-08-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-08-30 | 1994-03-01 | 1994-08-31 | $7700.00 | Window Closed / Lapsed |