US4582623A
Expired / Lapsed
US
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Barium ferrite magnetic powder and recording medium employing the same
Assignee: Toshiba Corp
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Filing: 1984-08-31
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Granted: 1986-04-15
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Expires: 2004-08-31
Abstract
Abstract Disclosed is a barium ferrite magnetic powder comprising particles characterized by (A) a mean particle size of 0.3 mu m or smaller and (B) the presence of Sr, Ca and Si in respective amounts of 0.2 wt. % or less as SrO, 0.15 wt. % or less as CaO, and 0.3 wt. % or less as SiO2. Also disclosed is a recording medium comprising the barium ferrite magnetic powder.
Inventors
- 👤 Osamu Kubo
- 👤 Tutomu Nomura
- 👤 Tadashi Ido
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 12:32
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
52 words
A barium ferrite magnetic powder comprised of particles having a mean particle size of 0.3 μm or less, said particles containing strontium, calcium and silicon in an amount of 0.2 wt.% or less as strontium oxide, 0.15 wt.% or less as calcium oxide and 0.3 wt.% or less as silicon dioxide, respectively.
Claim 2
Dependent Claim
52 words
A barium ferrite magnetic powder comprised of particles having a mean particle size of 0.3 μm or less, said particles containing strontium, calcium and silicon in an amount of 0.2 wt.% or less as strontium oxide, 0.15 wt.% or less as calcium oxide and 0.3 wt.% or less as silicon dioxide, respectively.
Claim 3
Dependent Claim
25 words
The barium ferrite magnetic powder according to claim 1, wherein the coercive force of said barium ferrite magnetic powder ranges from 200 to 2,000 Oe.
Claim 4
Dependent Claim
22 words
The barium ferritge magnetic powder according to claim 1, wherein said barium ferrite magnetic powder is obtained by a glass crystallization method.
Claim 5
Dependent Claim
31 words
The barium ferrite magnetic powder according to claim 3, wherein the basic component of an oxide glass used in said glass crystallization method is a boric acid--barium oxide--ferric oxide base glass.
Claim 6
Dependent Claim
58 words
A recording medium comprising a barium ferrite magnetic powder, wherein said magnetic powder comprises particles having a mean particle size of 0.3 μm or smaller and containing strontium, calcium and silicon in an amount of 0.2 wt.% or less as strontium oxide, 0.15 wt.% or less as calcium oxide and 0.3 wt.% or less as silicon dioxide, respectively.
Claim 7
Dependent Claim
58 words
A recording medium comprising a barium ferrite magnetic powder, wherein said magnetic powder comprises particles having a mean particle size of 0.3 μm or smaller and containing strontium, calcium and silicon in an amount of 0.2 wt.% or less as strontium oxide, 0.15 wt.% or less as calcium oxide and 0.3 wt.% or less as silicon dioxide, respectively.
Claim 8
Dependent Claim
23 words
The recording medium according to claim 5, wherein the coercive force of said barium ferrite magnetic powder ranges from 200 to 2,000 Oe.
Claim 9
Dependent Claim
20 words
The recording medium according to claim 5, wherein said barium ferrite magnetic powder is obtained by a glass crystallization method.
Claim 10
Dependent Claim
29 words
The recording medium according to claim 3, wherein the basic component of an oxide glass used in said glass crystallization method is a boric acid--barium oxide--ferric oxide base glass.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1989-04-14 | 1989-10-14 | 1990-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-04-14 | 1993-10-14 | 1994-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-04-14 | 1997-10-14 | 1998-04-15 | $7700.00 | Window Closed / Lapsed |