Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Patent
1993-11-26
1996-11-05
Kiliman, Leszek
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
428694T, 428694TP, 428694TC, 428694TF, 428694TR, 428336, 428408, 4284735, 4284744, 428480, 428698, 428699, 428702, 428704, 428900, 427131, 427132, 427585, 2041922, 20419235, G11B 566, B32B 310, C23C 1400
Patent
active
055715958
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a magnetic recording medium, above all, an evaporated tape on which a thin metal film is deposited by evaporation, and a method for producing the recording medium.
BACKGROUND ART
A magnetic recording medium of a so-called magnetic metal thin film type, in which a magnetic material of metal or an alloy such as Co--Ni is directly deposited by plating or a vacuum thin film forming technique (e.g. vacuum deposition, sputtering or 1on plating) on a base film, such as a polyester film or a polyimide film, has a number of advantages, that is, it is superior in coercivity, rectangular ratio or in electromagnetic transducing characteristics for a short wavelength range, while the magnetic layer can be reduced in thickness for reducing demagnetization due to recording or thickness losses during playback. In addition, the packing density of the magnetic material may be increased because there is no necessity of mixing a non-magnetic binder into the magnetic layer.
In the magnetic metal thin film type recording medium, the magnetic layer is generally formed by vacuum deposition. For example, the magnetic layer is deposited by a so-called continuous take-up type oblique evaporation method in which an evaporated magnetic material is deposited on the base film which is caused to run in a vacuum chamber from a supply side to a take-up side so as to travel on the outer peripheral surface of a cooling can provided on the travel path of the base film.
Meanwhile, when the magnetic metal thin film type magnetic recording medium is employed in, above all, a digital video tape recorder, since the data transfer rate is extremely high, the relative velocity between the magnetic recording medium and the magnetic head during recording and playback needs to be at least twice the recording velocity for conventional analog recording. Since a considerable damage is done in this manner to the magnetic recording medium, it has become crucial to improve durability of the magnetic recording medium.
However, if oxygen be introduced during vacuum deposition for providing a protective layer, such as a Co oxide, on the surface of the magnetic layer, sufficient durability of the magnetic recording medium cannot be achieved. For this reason, it becomes additionally necessary to provide a protective film of an abrasion-resistant material. Besides, if simply the protective film is increased in thickness, there is a risk that electro-magnetic transducing characteristics be deteriorated due to spacing losses.
In view of the above-described status of the art, at is an object of the present invention to provide a magnetic recording medium which is improved in abrasion resistance without incurring deterioration of the electromagnetic transducing characteristics and which is superior in durability and reliability, and a method for producing such magnetic recording medium.
DISCLOSURE OF THE INVENTION
In its one aspect, the present invention provides magnetic recording medium in which, as shown in an enlarged schematic cross-sectional view of FIG. 1, a metal magnetic thin film 102, a layer 103 of an oxide of the metal magnetic thin film 102 and a protective layer 104 are sequentially formed on a substrate (base film) 101, the oxide layer 103 and the protective layer 104 having thicknesses t.sub.1 and t.sub.2 of 20 to 230 .ANG. and 20 to 230 .ANG., respectively, with the combined thickness T of the oxide layer 103 and the protective layer 104 being 40 to 250 .ANG..
In another aspect of the present invention, the protective layer 4 of the magnetic recording medium is formed of an inorganic material.
During deposition of the protective layer, the surface of the oxide layer may be previously bombarded for improving contact tightness of the protective film.
That is, after the magnetic metal thin film is formed on the base film within a vacuum chamber by vacuum deposition, the as-deposited magnetic metal thin film may be bombarded at a making power density of 1.6 kW/m.sup.2 or higher, and a protective film may the
REFERENCES:
patent: 4565734 (1986-01-01), Arai
patent: 4889767 (1989-12-01), Yokoyama
Arisaka Yuichi
Chiba Kazunobu
Kondo Hirofumi
Sato Ken'ichi
Yamada Yukari
Kiliman Leszek
Sony Corporation
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