US4146671A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic recording substance
Assignee: Fujifilm Holdings Corp
•
Filing: 1977-02-14
•
Granted: 1979-03-27
•
Expires: 1997-02-14
Abstract
Abstract In a magnetic recording substance comprising a non-magnetic support member and a magnetic recording layer provided thereon and consisting essentially of a ferromagnetic powder and a binder, the content of calcium component contained in the ferromagnetic powder is previously adjusted to 0.001% by weight or less.
Inventors
- 👤 Masaaki Fujiyama
- 👤 Hiroshi Kato
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:56
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; Y; Y10; Y10T; Y10T428/00; Y10T428/25; Y10T428/256; Y10T428/257
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
176 words
A magnetic recording substance comprising a non-magnetic support member and a magnetic recording layer provided thereon and consisting essentially of a ferromagnetic powder and a binder, the ferromagnetic powder being selected from the group consisting of γ-Fe 2 O 3 , Co-doped γ-Fe 2 O 3 , Fe 3 O 4 , Co-doped Fe 3 O 4 , Berthollide compounds of γ-Fe 2 O 3 and Fe 3 O 4 , Co-doped Berthollide compounds of γ-Fe 2 O 3 and Fe 3 O 4 , CrO 2 , Co-Ni-P alloys, Co-Ni-Fe alloys, Co-Ni-Fe-B alloys, Fe-Ni-Zn alloys, Fe-Mn-Zn alloys, Fe-Co-Ni-P alloys and Ni-Co alloys, having a particle size of about 0.2 to 1 micron in length and a length to width ratio of 1:1 to 20:1, containing at most 0.001% by weight of calcium ions and being prepared by (a) reacting calcium ion-free starting materials to prepare goethite; (b) washing said goethite with calcium ion-free water; (c) subjecting the goethite of (b) to dehydration and reduction and (d) washing the product of (c) with calcium ion-free water.
Claim 2
Dependent Claim
176 words
A magnetic recording substance comprising a non-magnetic support member and a magnetic recording layer provided thereon and consisting essentially of a ferromagnetic powder and a binder, the ferromagnetic powder being selected from the group consisting of γ-Fe 2 O 3 , Co-doped γ-Fe 2 O 3 , Fe 3 O 4 , Co-doped Fe 3 O 4 , Berthollide compounds of γ-Fe 2 O 3 and Fe 3 O 4 , Co-doped Berthollide compounds of γ-Fe 2 O 3 and Fe 3 O 4 , CrO 2 , Co-Ni-P alloys, Co-Ni-Fe alloys, Co-Ni-Fe-B alloys, Fe-Ni-Zn alloys, Fe-Mn-Zn alloys, Fe-Co-Ni-P alloys and Ni-Co alloys, having a particle size of about 0.2 to 1 micron in length and a length to width ratio of 1:1 to 20:1, containing at most 0.001% by weight of calcium ions and being prepared by (a) reacting calcium ion-free starting materials to prepare goethite; (b) washing said goethite with calcium ion-free water; (c) subjecting the goethite of (b) to dehydration and reduction and (d) washing the product of (c) with calcium ion-free water.
Claim 3
Dependent Claim
39 words
The magnetic recording substance as claimed in claim 1, wherein the content of calcium ions contained in the ferromagnetic powder is reduced by the use of reaction materials and washing water which contain sulfate ions as little as possible.
Claim 4
Dependent Claim
23 words
The magnetic recording substance as claimed in claim 1, wherein rewashing with water is carried out after the dehydration and reduction of goethite.
Claim 5
Dependent Claim
26 words
The magnetic recording substance as claimed in claim 1, wherein the binder is selected from the group consisting of thermoplastic resins, thermosetting resins and mixtures thereof.
Claim 6
Dependent Claim
30 words
The magnetic recording substance as claimed in claim 1, wherein the non-magnetic support member is of a material selected from the group consisting of polyesters, polyolefins, cellulose derivatives and polycarbonates.
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) | 1982-03-26 | 1982-09-25 | 1983-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-03-26 | 1986-09-25 | 1987-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-03-26 | 1990-09-25 | 1991-03-27 | $7700.00 | Window Closed / Lapsed |