Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Patent
1997-01-21
1999-01-12
Resan, Stevan A.
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
428336, 428408, 428421, 428422, 428457, 428694TC, 428694TF, 428694TB, 428900, G11B 572
Patent
active
058585206
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a magnetic recording medium in which a ferromagnetic metal thin film and a protective layer are formed on one major surface of a non-magnetic support member, and a back-coat layer is formed on the other major surface.
BACKGROUND ART
In a magnetic recording medium used in a conventional video tape recorder (to be referred to as a "VTR" hereinafter) or the like, a magnetic layer is formed on one major surface (to be referred to as a "front surface" hereinafter) of a film-like non-magnetic support member, a protective layer is formed on the magnetic layer to protect it, and a back-coat layer for improving the characteristics of the magnetic recording medium is formed on the other major surface (to be referred to as a "rear surface" hereinafter) of the film-like non-magnetic support member.
As such a magnetic recording medium, a so-called coating type magnetic recording medium in which a magnetic coating material including a magnetic powdery material dispersed in a binder is coated on a film-like non-magnetic support member and then dried to form a magnetic layer is popularly used. In the coating type magnetic recording medium, the protective layer or the back-coat layer is formed in the same manner as that of the magnetic layer. More specifically, the protective layer or the back-coat layer is formed in such a manner that a protective layer material or a back-coat layer material including carbon dispersed in a binder is coated on a non-magnetic member and then dried. At this time, the back-coat layer is generally coated with or includes a lubricant containing a fatty acid as a main component.
In contrast to this, with a demand of high-density magnetic recording, a so-called deposition type magnetic recording medium in which a magnetic layer is formed by depositing a ferromagnetic metal material on a non-magnetic support member has attracted attention.
Such a deposition type magnetic recording medium has the following various advantages. That is, loss of a thickness in a recording/reproducing operation can be considerably decreased because the thickness of a magnetic layer in which saturation magnetization can be increased with respect to the anti-magnetic force of the magnetic layer can be remarkably decreased, and a filling density of a magnetic material can be increased because binder serving a non-magnetic material is not mixed in the magnetic layer.
As such a deposition type magnetic recording medium, the magnetic tape in which a Co.sub.80 Ni.sub.20 alloy is deposited on a film to form a magnetic layer was merchandized in 1989.
In the deposition type magnetic recording medium, as in a coating type magnetic recording medium, a back-coat layer is formed in such a manner that a back-coat layer material obtained by dispersing carbon or the like in a binder is coated on a non-magnetic support member and then dried.
However, in the deposition type magnetic recording medium, since the magnetic layer consists of a ferromagnetic metal material, when the back-coat layer is formed in a conventional manner, the following problem is posed.
That is, in the coating type magnetic recording medium, a lubricant containing a fatty acid as a main component is coated on or included in the back-coat layer to decrease a friction coefficient of the back-coat layer as described above. However, in the deposition type magnetic recording medium having the magnetic layer consisting of a ferromagnetic metal material, when a lubricant containing a fatty acid as a main component is coated on or included in the back-coat layer, the lubricant containing the fatty acid as a main component grows the rust of the ferromagnetic recording medium.
Therefore, in the deposition type magnetic recording medium, the back-coat layer cannot be coated with a lubricant containing a fatty acid as a main component, and cannot include the lubricant. For this reason, the deposition type magnetic recording medium has the following problem to be solved. That is, the friction coefficient of the back-co
REFERENCES:
patent: 5045165 (1991-09-01), Yamashita
patent: 5182132 (1993-01-01), Murai et al.
patent: 5612134 (1997-03-01), Okita et al.
patent: 5637373 (1997-06-01), Hayashi
Resan Stevan A.
Sony Corporation
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