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US4002546A Expired / Lapsed US ⏱️ 0.0 years remaining

Method for producing a magnetic recording medium

Assignee: Fujifilm Holdings Corp
•
Filing: 1975-12-10
•
Granted: 1977-01-11
•
Expires: 1995-12-10
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Abstract

Abstract An improved method of making a magnetic recording medium with excellent coercive force and rectangular ratio is provided by means of an ion plating technique. A support and an evaporation source of a magnetic Co-Si alloy are placed in an ion plating apparatus which is filled with an inert gas and kept at low vacuum. High voltage is then applied between the support and the evaporation source such that the former has a negative polarity and the latter a positive polarity, thereby causing a glow discharge zone in the apparatus. The magnetic alloy is evaporated into the glow discharge zone from the source to form a magnetic thin film on the support. Such a magnetic thin film can have a coercive force of 750 Oe or more and a rectangular ratio of 0.80 or more and can be used as a magnetic recording medium.

Inventors

  • 👤 Ryuji Shirahata
  • 👤 Tatsuji Kitamoto
  • 👤 Masaaki Suzuki

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-23 01:31
CPC Classifications
C; C23; C23C; C23C14/00; C23C14/06; C23C14/14; H; H01; H01F; H01F41/00; H01F41/14; Y; Y10; Y10T; Y10T428/00; Y10T428/31504; Y10T428/31678

Claims Analysis

Total Claims: 7
Claim 1
Independent Claim 76 words
In the method of forming a magnetic recording medium comprising a support carrying a magnetic thin film thereon which comprises ion plating a magnetic alloy from an evaporation source onto a support, the polarities of said evaporation source and said support being positive and negative, respectively, in an inert gas atmosphere by applying a high tension voltage between said evaporation source and said support, the improvement wherein said magnetic alloy consists essentially of Co and Si.
Claim 2
Dependent Claim 76 words
In the method of forming a magnetic recording medium comprising a support carrying a magnetic thin film thereon which comprises ion plating a magnetic alloy from an evaporation source onto a support, the polarities of said evaporation source and said support being positive and negative, respectively, in an inert gas atmosphere by applying a high tension voltage between said evaporation source and said support, the improvement wherein said magnetic alloy consists essentially of Co and Si.
Claim 3
Dependent Claim 27 words
A method of making a magnetic recording medium as claimed in claim 1, wherein said magnetic alloy contains from about 2 to about 25 wt% of Si.
Claim 4
Dependent Claim 25 words
A method of making a magnetic recording medium as claimed in claim 2, wherein said magnetic alloy contains from 5 to 20 wt% of Si.
Claim 5
Dependent Claim 29 words
A method of making a magnetic recording medium as claimed in claim 3, wherein said magnetic alloy further comprises Ni, and the Co/Ni weight ratio is > about 50/50.
Claim 6
Dependent Claim 29 words
A method of making a magnetic recording medium as claimed in claim 3, wherein said magnetic alloy further contains Fe, and the Co/Fe weight ratio is > about 80/20.
Claim 7
Dependent Claim 46 words
A method of making a magnetic recording medium as claimed in claim 3, wherein said magnetic alloy further contains Fe and Ni, and the composition thereof is defined by the area bounded by points A, B, C and D in FIG. 3 of the attached drawings.

References Cited (Backward Citations)

US3772174A Cited
US3898952A Cited
US3929604A Cited
US3928159A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1980-01-11 1980-07-12 1981-01-11 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1984-01-11 1984-07-12 1985-01-11 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1988-01-11 1988-07-12 1989-01-11 $7700.00 Window Closed / Lapsed

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