JPH0758543B2 - Thin film type magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thin film magnetic recording medium having a recording layer made of a magnetic thin film, and more particularly to a thin film magnetic recording medium having excellent wear resistance.

[Prior Art] In recent years, the demand for high-density recording has increased more and more, and the one using a ferromagnetic metal layer as a magnetic recording layer, and Japanese Patent Publication No. 58-
A method using a cobalt-based alloy layer having perpendicular magnetic anisotropy as disclosed in Japanese Patent No. 91 has been proposed. However, in the case of a thin film type magnetic recording medium using such a magnetic thin film as the magnetic recording layer, there is a drawback that it is easily worn or damaged due to a large frictional resistance with the magnetic recording head and lacks in durability.

For this reason, various proposals have heretofore been made in which an organic polymer, high-hardness metal, ceramics or the like is further provided as a protective layer on a ferromagnetic metal thin film.

However, the wear resistance of the thin film type magnetic recording medium, that is, the life of the magnetic recording medium when the magnetic recording medium is repeatedly run on the magnetic recording head is inferior to the conventional coating type magnetic recording medium, and is practically used. It is still in a state of not being enough.

[Object of the Invention] The present invention has been made in view of the present circumstances, and an object of the present invention is to provide a thin-film magnetic recording medium having excellent wear resistance.

[Structure / Operation of the Invention] The above-mentioned object is achieved by the present invention described below. That is, the present invention is a thin-film magnetic recording medium in which the above-mentioned recording layer is a magnetic thin film, and a protective layer made of zinc oxide or yttrium oxide is provided.

The present invention is applicable to all thin film type magnetic recording media having a known ferromagnetic thin film as a recording layer. Specifically, a thin film layer of γ-iron oxide was provided on the substrate, and a ferromagnetic metal thin film layer for in-plane recording made of a metal such as iron, cobalt, nickel, or an alloy thereof was provided. With a ferromagnetic metal thin film layer for perpendicular recording comprising a cobalt-based alloy thin film having perpendicular magnetic anisotropy, or a metal layer having high magnetic permeability such as iron, permalloy, cobalt-niobium-zircon alloy, etc. There is a known in-plane or perpendicular recording thin-film magnetic recording medium such as one in which the above-mentioned metal thin film layer for perpendicular recording is successively formed on the above. Above all, it is preferably applied to a perpendicular magnetic recording medium formed of an alloy thin film containing cobalt-chromium as a main component shown in the examples. As the substrate, a polymer film such as polyester or polyimide, a glass plate, an aluminum alloy plate or the like is used, and it is selected according to the application such as a magnetic tape, a floppy disk, a hard disk.

These magnetic recording media are manufactured by forming a magnetic thin film serving as a recording layer on a substrate. The thin film forming method includes a vacuum vapor deposition method and a sputtering method known as continuous thin film forming methods, and further, JP-A-57-100627 and 59-59.
A physical vapor deposition method such as a facing target type sputtering method, a plating method, or the like, which is known in Japanese Patent No. 193528, is used.

The protective layer of zinc oxide or yttrium oxide of the present invention is naturally provided as a continuous thin film layer on the recording layer of the magnetic recording medium. For forming this protective layer, a physical vapor deposition method or the like is used as in the case of forming the recording layer described above.

Regarding the metal oxide of zinc oxide or yttrium oxide constituting the protective layer of the present invention, the number of oxygen atoms bonded to one metal atom is unclear, but the metal oxide prepared by the above method is used. Inventive metal oxide is called.

According to the present invention, by providing the protective layer made of zinc oxide or yttrium oxide on the recording layer made of a magnetic thin film as described above, durability of several million or more passes required for a practical level is realized. It is a thing.

Examples and Comparative Examples FIG. 1 shows an example of the configuration of the present invention, which is a flexible double-sided perpendicular magnetic recording medium for a floppy disk.
A polyethylene terephthalate film having a diameter of 5.25 inches and a thickness of 50 μm is used as a substrate 1, and a metal thin layer 2 having a high magnetic permeability of 0.5 μm made of nickel-iron alloy and having a thickness of 0.15 μm on both sides
A perpendicular magnetic recording layer 3 made of an alloy thin film of cobalt-chromium (chromium: 20 wt%) is sequentially laminated by a facing target type sputtering method as in JP-A-57-100627, and a protective layer 4 is further formed thereon. Frequency (RF) under 100% argon gas atmosphere using zinc oxide (ZnO) powder target as
A protective layer of zinc oxide having a thickness of about 200Å was laminated by the magnetron sputtering method (Example 1). In addition, Example 1
As a protective layer 4 having the same structure as in Example 1, a sample was prepared in which a protective layer of yttrium oxide instead of zinc oxide of Example 1 was laminated in an amount of about 200Å (Example 2). Note that this protective layer was formed by the high frequency magnetron sputtering method using the oxide powder target as in Example 1.

In addition, as a comparative example, using a protective layer, tungsten oxide (Comparative Example 1), titanium oxide (Comparative Example 2), and tantalum oxide (Comparative Example 3) were used as protective layers in the same manner as in the Example. A sample was prepared by stacking to a thickness of about 200Å by the high frequency magnetron sputtering method using the powder target of the product.

Table 1 shows a commercially available floppy disk drive in which a dummy head made of alumina titanium carbide (commonly known as AlTiC) having a sliding portion (head slider portion) of a spherical surface with a radius of curvature of 50 mm is set in place of the magnetic head. The surface roughness of the sample after fixing the head on the same track with the device and rotating it for 3 million passes at a head pressing load of 18 g and a rotation speed of 1 m / Sec is shown below.

That is, for durability evaluation, the surface roughness of the sample before and after the sliding test was obtained as the center line average roughness CLA using a surface roughness meter (SURFCOM, manufactured by Tokyo Seimitsu Co., Ltd.), and the CLA value after sliding was calculated. It was determined by the relative surface roughness divided by the CLA value before sliding and the maximum depth (μm) of wear scratches formed on the medium. In Table 1, this relative surface roughness is shown as Ra increase ratio.

As is clear from the table, the examples using zinc oxide or yttrium oxide of the present invention as the protective layer show very slight wear after 3 million passes, but are very slight and in a state in which they can be sufficiently used. That is, it is understood that the present invention can provide a long-awaited thin film type magnetic recording medium having sufficiently practical sliding durability.

The present invention as described above is not limited to the floppy disk and the perpendicular magnetic recording medium shown in the embodiment in view of its gist, and as described above, the so-called hard disk or magnetic tape such as an aluminum disk subjected to alumina oxidation treatment can be used. Needless to say, can be applied. It is also clear that the above-mentioned film forming means other than the embodiment can be applied to the manufacturing method of the recording layer and the protective layer.

[Brief description of drawings]

FIG. 1 is a partial side sectional view showing the configuration of an embodiment of the present invention. 1: substrate, 2: high permeability metal thin film layer, 3: cobalt-chromium alloy thin film layer, 4: protective layer

Claims (5)

[Claims] 1. A thin film magnetic recording medium having a recording layer made of a magnetic thin film, wherein a protective layer made of zinc oxide or yttrium oxide is provided. 2. The thin-film magnetic recording medium according to claim 1, wherein the recording layer is a perpendicular recording layer. 3. The thin film magnetic recording medium according to claim 2, wherein the perpendicular recording layer is an alloy thin film containing cobalt-chromium as a main component. 4. The thin film magnetic recording medium according to claim 1, 2 or 3, wherein the protective layer made of zinc oxide or yttrium is formed by a physical vapor deposition method. 5. The thin-film magnetic recording medium according to claim 1, 2, 3, or 4, wherein the magnetic recording medium is a magnetic disk.