JPH0799569B2 - Magnetic recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having a ferromagnetic metal thin film suitable for high density magnetic recording as a magnetic recording layer.

2. Description of the Related Art In recent years, there has been a remarkable progress in increasing the density of magnetic recording, and it is expected that a magnetic recording medium using a ferromagnetic metal thin film as a magnetic recording layer will be put to practical use, and development is being carried out in various fields [eg, Japanese Patent Publication No. 56- twenty three
No. 208, Japanese Patent Publication No. 41-19389, Japanese Patent Publication No. 58-91, etc.]. The problem of such a magnetic recording medium is to secure the signal output-to-noise (S / N) ratio and the durability, and in the in-plane magnetized magnetism, as disclosed in JP-A-53-42010,
A method in which a ferromagnetic metal thin film to be a magnetic recording layer is formed on a polymer film directly or through an underlayer by a method of performing oblique vapor deposition with a slight amount of oxygen interposed, and a protective film and a lubricant layer are arranged The level is close to the practical level, and the development of a Co-Cr alloy film containing about 20 wt% of Cr obtained by the sputtering method in the perpendicular magnetization film is most advanced [see Japanese Patent Laid-Open Nos. 61-77126 to 77128, etc.].

FIG. 2 shows an example of a conventional magnetic recording medium, 1 is a polymer film such as polyethylene terephthalate film, 2 is a fine particle coating layer in which fine particles such as carbon and Al ₂ O ₃ are dispersed and fixed with a resin. 3 is Co-Ni (for example, containing Ni; 20 wt%) while introducing oxygen along the cylindrical can.
An oblique vapor deposition film obtained by electron beam vapor deposition of an alloy is a lubricating film such as stearic acid.

The magnetic tape of such a structure has an output of 5 at a recording wavelength of 0.75 μm, as compared with a so-called alloy powder type tape in which alloy ferromagnetic particles centering on Fe particles are fixed with resin.
(DB), S / N has an advantage of about 3 (dB), and it is expected that it will play a central role in the improvement of magnetic recording in the future from the viewpoint of high density recording characteristics. Powerful studies are being conducted in various fields for improvement. The use of an oxide film is effective for improving the durability, and it is considered that vapor deposition in oxygen as described above, surface oxidation by plasma oxidation later, or oxide formation by sputtering is performed. ing.

Problems to be Solved by the Invention However, plasma oxidation of a vapor deposition film obliquely vapor-deposited,
The protective effect of the oxide film by sputtering deposition is not sufficient, and if the durability is improved by adjusting the amount of oxygen to intervene during oblique deposition, the saturation magnetic flux density decreases and the electromagnetic conversion characteristics,
In particular, improvement was desired because the S / N was reduced.

The present invention has been made in view of the above circumstances, and provides a magnetic recording medium having a well-balanced improvement in S / N and durability.

Means for Solving the Problems In order to solve the above-mentioned problems, the magnetic recording medium of the present invention has a first structure in which a ferromagnetic alloy is obliquely deposited on a polymer film.
On the magnetic layer, a sputtered magnetic layer formed by sputtering the same ferromagnetic alloy is arranged, and the surface of the sputtered magnetic layer has an oxide layer.

Action The magnetic recording medium of the present invention has the above-mentioned configuration, and since durability can be obtained even when the amount of oxygen contained in the obliquely vapor-deposited magnetic layer is reduced, the magnetic flux density can be configured without significantly lowering the saturation magnetic flux density. In addition, since the mobility of the sputtered metal element on the surface of the columnar fine particles forming the oblique deposition layer is large, the degree of coverage is large and the adhesion strength is large.
Since the sputtered magnetic layer itself has a surface oxide layer, the durability is also good and both the S / N and the durability can be satisfied.

Examples Hereinafter, magnetic recording media according to examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an enlarged cross-sectional view of a magnetic recording medium according to an embodiment of the present invention. In the figure, 5 is a polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyphenylene sulfide, polyether sulfone, polyamide having a thickness of 3 μm to 15 μm. , A polymer film such as polyamide-imide or polyimide, 6 is an undercoat layer having a surface shape of earthworm-like protrusions or granular projections, alone or in combination, 7 is Co-N
i, Co-Fe, Co-Sm, Co-Ta, Co-Cr, Co-Mo, Co-Pr, Co-B,
Co-W, Co-Ti, Co-Si, Co-O, Co-Os, Co-Y, Co-La, Co-
A first magnetic layer obtained by oblique vapor deposition of Ni-O, Co-Cr-Nb, etc., 8 is a sputtered magnetic layer, and the first magnetic layer 7 has a first magnetic layer.
A sputtered film 9 of the same alloy element as that of the magnetic layer 7 is arranged, and 10 schematically shows an oxidized oxide layer of the sputtered magnetic layer.

The transition from the alloy to the oxide layer is not done as a separate layer, but by adjusting the manufacturing conditions to obtain the composition. Reference numeral 11 denotes a protective lubricant layer, which may be a fatty acid, a fatty acid ester, a fluorine compound or the like alone or may be laminated with a protective film such as an amorphous carbon film. However, the spacing loss becomes larger as the wavelength becomes shorter. The thickness of the protective lubricant layer should be up to 100Å at most and the effect should be maintained.

Next, the result of mutual comparison between an example of the present invention and a comparative example will be described.

On a polyethylene terephthalate film with a thickness of 10 μm, fine particles of Al ₂ O ₃ with a diameter of 120 Å were made with polyester resin (resin thickness was set to be 50 Å equivalent) on average 10
A subbing layer fixed to μm ² is placed, and a cylindrical can with a diameter of 1 m is placed on the undercoat layer. Co-Ni (Ni20wt%) at a minimum incident angle of 46 degrees
Was electron beam evaporated. At that time, the amount of oxygen introduced is 0.1 /
At min, the film thickness was 0.15 μm. The target was Co-Ni, and the high-frequency sputtering method was used to deposit 0.05 μm Co-Ni.
A film was formed. At that time, two gas introduction nozzles were provided, one of which was used for introducing hydrogen gas and the other was used for introducing oxygen gas so that an oxide layer was formed on the surface side. On this, perfluorobehenic acid was vacuum-deposited in a volume of 50Å to obtain a magnetic tape having a width of 8 mm. In the comparative example, Co-Ni (Ni20 wt%) was electron-beam evaporated along a cylindrical can having a diameter of 1 m at a minimum incident angle of 38 degrees. At that time, the amount of oxygen introduced was 0.38 / min, the film thickness was 0.19 μm, and perfluorobehenic acid was added to 50Å.
It is a vapor-deposited 8 mm wide magnetic tape.

The luminance signal S / N in the 8 mm video tape recorder is 2.8 (dB) better in the embodiment than in the comparative example. The initial PCM error rates were 2 × 10 ⁻⁶ and 3 × 10 ^−5, which were more than 10 times as high as those of the examples, and the PCM error rates after being left at 55 ° C. and 90% RH for 2 months were as follows. Although there is a change from 4.5 × 10 ^{−6 to} 7.3 × 10 ⁻⁶ , the comparative example is 5 × 10 ^{−5 to} 9 × 10 ⁻⁵ , and the difference between the two is still kept close to 10 times.

EFFECTS OF THE INVENTION As described above, according to the present invention, there is an excellent effect that both the S / N and durability of a magnetic recording medium in which a ferromagnetic metal thin film is magnetically recorded can be improved.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of a magnetic recording medium according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a conventional magnetic recording medium. 5 ... Polymer film, 7 ... First magnetic layer, 8 ... Sputtered magnetic layer, 10 ... Oxide layer.

Claims (1)

[Claims] 1. A sputtered magnetic layer formed by sputtering the same ferromagnetic alloy on a first magnetic layer obtained by obliquely depositing a ferromagnetic alloy on a polymer film, and the surface of the sputtered magnetic layer is an oxide layer. A magnetic recording medium comprising: