US5156922A
Expired / Lapsed
US
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Acicular magnetic iron based alloy particles for magnetic recording and method of producing the same
Assignee: Toda Kogyo Corp
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Filing: 1991-07-08
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Granted: 1992-10-20
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Expires: 2011-07-08
Abstract
Abstract Disclosed herein are acicular magnetic iron based alloy particles for magnetic recording, containing 1.5 to 10 mol % of B based on Fe (calculated as B) and 1.5 to 10 mol % of Co based on Fe (calculated as Co) in the vicinity of the surfaces of said particles and having a saturation magnetization of not less than 125 emu/g and an S.F.D. value of not more than 0.50, and a process for producing the same.
Inventors
- 👤 Akio Mishima
- 👤 Mamoru Tanihara
- 👤 Yasutaka Ota
- 👤 Hirofumi Kawasaki
- 👤 Kenji Okinaka
- 👤 Kunio Ikemoto
- 👤 Kousaku Tamari
- 👤 Kohji Mori
- 👤 Norimichi Nagai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-10 01:31
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70605; G11B5/70615; Y; Y10; Y10T; Y10T428/00; Y10T428/12; Y10T428/12181
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
97 words
Acicular magnetic iron based alloy particles for magnetic recording, each having 1.5 to 10 mol % of B based on Fe and 1.5 to 10 mol % of Co based on Fe close to the particle surfaces, and having a saturation magnetization of not less than 125 emu/g, an S.F.D. value of not more than 0.50 and a coercive force of not less than 1450 Oe, a change of saturation magnetization (Δσs/σs) of not more than 15%, and a particle length of 0.1 to 0.4 μm and an aspect ratio (major axis:minor axis) of 5:1 to 15:1.
Claim 2
Dependent Claim
97 words
Acicular magnetic iron based alloy particles for magnetic recording, each having 1.5 to 10 mol % of B based on Fe and 1.5 to 10 mol % of Co based on Fe close to the particle surfaces, and having a saturation magnetization of not less than 125 emu/g, an S.F.D. value of not more than 0.50 and a coercive force of not less than 1450 Oe, a change of saturation magnetization (Δσs/σs) of not more than 15%, and a particle length of 0.1 to 0.4 μm and an aspect ratio (major axis:minor axis) of 5:1 to 15:1.
Claim 3
Dependent Claim
31 words
Acicular magnetic iron based alloy particles for magnetic recording according to claim 1 which additionally have 1.0 to 10 mol % of Al based on Fe close to the particle surfaces.
Claim 4
Dependent Claim
31 words
Acicular magnetic iron based alloy particles for magnetic recording according to claim 1, which additionally have 0.4 to 10 mol % of Ni based on Fe close to the particle surfaces.
Claim 5
Dependent Claim
43 words
Acicular magnetic iron based alloy particles for magnetic recording according to claim 1 which additionally have each 1.0 to 10 mol % of Al based on Fe and 0.3 to 10 mol % of Ni based on Fe close to the particle surfaces.
Claim 6
Dependent Claim
36 words
Acicular magnetic iron based alloy particles for magnetic recording according to claim 1, which additionally have 1.0 to 10 mol % of Si based on Fe (calculated as SiO 2 ) close to the particle surfaces.
Claim 7
Dependent Claim
47 words
Acicular magnetic iron based alloy particles for magnetic recording according to claim 1, which additionally have 1.0 to 10 mol % of Si based on Fe (calculated as SiO 2 ) and 1.0 to 10 mol % of Al based on Fe close to the particle surfaces.
Claim 8
Dependent Claim
45 words
Acicular magnetic iron based alloy particles for magnetic recording according to claim 2, 3 or 4, which have a gloss of not less than 100% at a dispersion time of 50% and a gloss of not less than 120% at a dispersion time of 100%.
Claim 9
Dependent Claim
39 words
Acicular magnetic iron based alloy particles for magnetic recording according to claim 2, 3 or 4, which have a resin adsorption of not less than 1.1 g based on 20 g of the acicular magnetic iron based alloy particles.
Claim 10
Dependent Claim
29 words
Acicular magnetic iron based alloy particles for magnetic recording according to claim 5 or 6, which have a specific surface area of not less than 45 m 2 /g.
Claim 11
Dependent Claim
83 words
Acicular magnetic iron based alloy particles for magnetic recording according to claim 1, which are produced by: (a) coating the surfaces of acicular goethite particles with a boron compound and a cobalt compound; (b) heat-treating said particles at a temperature in the range of 300° to 600° C. to obtain acicular hematite coated with a boron oxide and a cobalt oxide; and (c) heat-treating said acicular hematite particles at a temperature in the range of 300° to 500° C. in a reducing atmosphere.
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