Patent US4490760A successfully refreshed from Google Patents.
US4490760A
Expired / Lapsed
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Thin-film magnetic head
Assignee: Panasonic Holdings Corp
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Filing: 1982-01-18
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Granted: 1984-12-25
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Expires: 2002-01-18
Abstract
Abstract A thin-film magnetic head having a magnetic substrate made from ferrite, iron-aluminum-silicon alloy or like material, and an upper magnetic layer formed on the magnetic substrate with a lower magnetic layer and a conductive layer interposed therebetween. A portion of the upper magnetic layer is jointed to the magnetic substrate while another portion of the upper magnetic layer is jointed to the lower magnetic layer through a non-magnetic layer of SiO 2 or like material constituting a magnetic gap. The lower magnetic layer, magnetic substrate, upper magnetic layer and the non-magnetic layer in combination form a closed magnetic circuit. A groove is defined between the lower magnetic layer and the magnetic substrate, and formed in the side surface of the magnetic substrate adapted to face a magnetic recording medium. The recess is filled with a non-magnetic material such as glass. Accordingly, it is possible to realize a definite pole piece length to permit an improvement in short-wavelength reproduction characteristics.
Inventors
- 👤 Nobuyuki Kaminaka
- 👤 Kenji Kanai
- 👤 Noboru Nomura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 06:07
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/127; G11B5/31
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
136 words
A thin-film magnetic head comprising: a magnetic substrate; a lower magnetic layer formed on said magnetic substrate; an upper magnetic layer formed on said lower magnetic layer with at least one conductive layer interposed therebetween, a part of said upper magnetic layer being jointed to said magnetic substrate while another part of said upper magnetic layer is jointed to said lower magnetic layer through a non-magnetic layer constituting a magnetic gap, so that a closed magnetic circuit is formed by said lower magnetic layer, said magnetic substrate, said upper magnetic layer and said non-magnetic layer; and a non-magnetic material filling in a groove which is defined between said lower magnetic layer and said magnetic substrate and which is formed in the side surface of said magnetic substrate which is adapted to face a magnetic recording medium.
Claim 2
Dependent Claim
136 words
A thin-film magnetic head comprising: a magnetic substrate; a lower magnetic layer formed on said magnetic substrate; an upper magnetic layer formed on said lower magnetic layer with at least one conductive layer interposed therebetween, a part of said upper magnetic layer being jointed to said magnetic substrate while another part of said upper magnetic layer is jointed to said lower magnetic layer through a non-magnetic layer constituting a magnetic gap, so that a closed magnetic circuit is formed by said lower magnetic layer, said magnetic substrate, said upper magnetic layer and said non-magnetic layer; and a non-magnetic material filling in a groove which is defined between said lower magnetic layer and said magnetic substrate and which is formed in the side surface of said magnetic substrate which is adapted to face a magnetic recording medium.
Claim 3
Dependent Claim
67 words
A thin-film type magnetic head as claimed in claim 1, wherein a depth d 1 of said groove along said side surface of said magnetic substrate adapted to face said magnetic recording medium is selected in relation to a maximum wavelength λ max of a signal recorded on said magnetic recording medium in such a manner as to satisfy a condition of d 1 /λ max ≧1.
Claim 4
Dependent Claim
65 words
A thin-film magnetic head as claimed in claim 1, wherein a length l 1 of said groove as measured from said side surface of said magnetic substrate adapted to face said magnetic recording medium is selected in relation to a maximum wavelength λ max of a signal recorded on said magnetic recording medium so as to satisfy a condition of l 1 /λ max ≧0.5.
Claim 5
Dependent Claim
54 words
A thin-film magnetic head as claimed in claim 1, wherein said conductive layer between said lower magnetic layer and said upper magnetic layer comprises a coil portion, and said closed magnetic circuit constituted by said lower magnetic layer, said magnetic substrate, said upper magnetic layer and said non-magnetic layer intersects with said coil portion.
Claim 6
Dependent Claim
139 words
A thin-film magnetic head as claimed in claim 1, wherein said magnetic substrate is provided in one of the major surfaces thereof with a groove filled with a non-magnetic material and said lower magnetic layer is formed on said one of major surfaces of said substrate, said conductive layer between said lower magnetic layer and said upper magnetic layer comprising a coil portion intersecting with said closed magnetic circuit constituted by said lower magnetic layer, said magnetic substrate, said upper magnetic layer and said non-magnetic layer, a portion of said conductive layer comprising said coil portion, located near said side surface of said substrate adapted to face said recording medium rather than the portion jointed between said upper magnetic layer and said substrate, being positioned above said groove formed in said one of the major surfaces of said substrate.
Claim 7
Dependent Claim
43 words
A thin-film magnetic head as claimed in claim 1, wherein said magnetic substrate is made from ferrite or an iron-aluminum-silicon alloy, and wherein said groove formed in said side surface of said substrate adapted to face said recording medium is filled with glass.
Claim 8
Dependent Claim
45 words
A thin-film magnetic head as claimed in claim 1, wherein a width of a portion of said upper magnetic layer adjacent to said side surface of said substrate adapted to face said recording medium is substantially equal to a track width of said recording medium.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-12-25 | 1988-06-25 | 1988-12-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-12-25 | 1992-06-25 | 1992-12-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-12-25 | 1996-06-25 | 1996-12-25 | $7700.00 | Window Closed / Lapsed |