JPS61271613A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled medium having excellent resistance to corrosion and wear by providing the magnetic recording layer of a ferromagnetic thin film on a nonmagnetic substrate and further furnishing a layer of the oxide film of an alloy of at least one kind of element among V, Nb and Ta and Co on the surface of the recording layer. CONSTITUTION:A nonmagnetic substrate 1 is formed with a plastic film such as polyethylene terephthalate, Al, glass, etc., having 5-100mum thickness. A magnetic recording layer 2 is formed by the vacuum deposition of a metal such as Fe, Co and Ni or the alloy contg. the elements and the thickness is regulated to 0.05-1.0mum. A protective layer 3 consists of at least one kind of metal selected from V, Nb and Ta or the oxide of the alloy of the elements and Co and the thickness is adjusted to 50-500Angstrom . At <50Angstrom , the effect as the protective and lubricating film is not exhibited and the clearance between a head and the magnetic recording layer 2 is increased and the recording and reproduction efficiency is decreased at >500Angstrom . The composition ratio of Co to V, Nb and Ta is preferably regulated to 1/9-9/1. When Co is rich, the corrosion resistance is not sufficiently improved and the effect in reducing the friction coefficient is small, when the content of Co is too small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a magnetic recording medium that has excellent corrosion resistance, abrasion resistance, and durability.

[Prior Art] In recent years, magnetic recording media in which ferromagnetic thin films containing metals such as Fe, Co, Cr, Ni, or alloys thereof are formed on a substrate by various methods have begun to be put into practical use.

A major feature of this magnetic recording medium is that the thickness of the ferromagnetic thin film can be made extremely thin, so that thickness loss can be reduced when reproducing signals recorded on the magnetic recording medium. Therefore, it can be said that reproduction at a short wavelength is advantageous.

However, ferromagnetic thin films made of the metals or alloys mentioned above suffer from the serious problem of corrosion.

An even bigger problem is that when such a metal thin film magnetic recording medium is run as a magnetic tape in a recording/playback device and comes into contact with and slides on a guide post or magnetic head, it causes damage to the magnetic tape. There is a problem that the ferromagnetic thin film wears out.

The above problems are important problems related to the reliability of magnetic recording media, but conventional methods to solve these problems have been to use fatty acid hydrocarbons, higher fatty acids, oxyfatty acids, fatty acid amides, fatty acid esters, and fatty alcohols. ,
Applying metal soap or the like to the surface has been practiced.

Problems to be solved by the invention: In the conventionally known methods, it is difficult to make the thickness of the top coat layer uniform, and the smoothness and other effects deteriorate with use, and the durability is unsatisfactory. It wasn't. Further, when the coating film becomes thick, output decreases due to spacing loss.

As described above, it has been difficult to form a thin, durable film that has a desired effect.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording medium in which the problems of corrosion and wear, which are the disadvantages of the above-mentioned conventional examples, are significantly reduced.

[Means and effects for solving the problems] The present invention has a magnetic recording layer of a ferromagnetic thin film on a nonmagnetic substrate, and further includes V on the surface of the ferromagnetic thin film.

At least one element selected from Nb and Ta and C
This is a magnetic recording medium having an alloy oxide film layer with o.

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of the medium of the present invention.

The nonmagnetic substrate 1 is a plastic film made of polyethylene terephthalate, polyimide, polycarbonate, polyamide, etc., or stainless steel, aluminum, glass, etc. with a thickness of 5 to 100 μm.

The magnetic recording layer 2 was formed of metals such as Fe, Co, and old metals, or alloys containing at least these metals, by means such as vacuum evaporation, sputtering, ion blasting, and plating. The film thickness is preferably in the range of 0.05 g to 1.0 w.

The protective film layer 3 is made of an oxide of an alloy of CO and at least one metal selected from V, Nb, and Ta, and preferably has a thickness of 50 to 500 Å. Protected when below 50A,
The effect as a lubricating film is not exhibited, and if it is 5008 or more, the gap between the head and the magnetic recording layer increases, reducing recording and reproducing efficiency. Co and V.

The composition ratio with Nb or Ta is preferably 1:9 to 9:1, and more preferably 2:8 to 8:2. If there is a large amount of Co, the effect of improving corrosion resistance will not be sufficient,
Moreover, when CO is small, the effect of reducing the friction coefficient is small.

The protective film layer 3 is formed by vacuum evaporation or ion blating of the alloy in an oxidizing gas atmosphere such as oxygen or ozone. Alternatively, it is formed by sputtering the alloy in an inert gas containing an oxidizing gas. The partial pressure range of the oxidizing gas depends on the size of the equipment used, the distance between the evaporation source and the magnetic medium to be deposited, and the film formation rate, but in vacuum evaporation and ion blating methods, it is usually l0-4. ~10-2 Torr, and in the sputtering method, it is several % or more with respect to the total sputtering gas.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A ferromagnetic thin film having a composition of Cog, aria, 2 was formed on a 12 pm thick polyethylene terephthalate by an oblique evaporation method, and Co-V was further coated on the surface.
100 oxide layers were formed by sputtering.

Co--V oxide was sputtered in Ar gas containing 10% oxygen gas using CO and V dual source targets simultaneously. The target area ratio of co and ■ is 1+1.

Comparative Example 1 For comparison, a magnetic tape with only a Co-old magnetic layer without forming a Ca-V oxide layer was produced.

After cutting the above media into 1-inch pieces and playing still images on a VHS video deck for 20 minutes, we examined the amount of wear on the magnetic layer.1 The magnetic tape of the present invention showed almost no wear and no change in playback output. On the other hand, the magnetic layer of the tape of Comparative Example 1 was scratched off in 10 seconds.

Furthermore, the magnetic tape of the present invention and Comparative Example 1 were placed in a constant temperature and humidity environment with a temperature of 70°C and a humidity of 90% for about 100 hours.
When the magnetic tape of Comparative Example 1 was inserted, there were scattered areas of corrosion, but no corrosion was detected in the magnetic tape of the present invention.

In addition, the coefficient of dynamic friction with respect to the SUS post (4φ, surface roughness 0.2S) was 0.48 for the magnetic tape of Comparative Example 1, while the coefficient of kinetic friction for the magnetic tape of the present invention was 0.30.
The coefficient of friction was significantly reduced.

Example 2 Co 80at$-Nb 20at$ alloy was deposited on the same base film and magnetic recording layer magnetic tape as in Example 1. C is evaporated on the magnetic recording layer by electron beam heating vacuum evaporation in an oxygen partial pressure of OX 10-4 Torr.
The abrasion resistance, corrosion resistance, and coefficient of dynamic friction of the magnetic tape of this example in which an o-Nb oxide layer of 20 OA was formed was measured in the same manner as in Example 1.

As a result, no decrease in playback output or occurrence of scratches was observed after 20 minutes of still playback, and no rust was observed during the high-temperature, high-humidity test. Also, the coefficient of dynamic friction is 0.29
This was significantly lower than the magnetic tape of Comparative Example 1.

Example 3 Old 80 wt$ on polyimide film with a thickness of 40 l
-Fe 20at$ film with 0.5 p-m, Co
80at$ -Cr 20at$ perpendicular magnetization film with 0.
It was formed by a three-layer sputtering method. Furthermore, using CO and Ta targets by sputtering method, 1
A Co--Ta oxide film layer of 20 OA was formed in an oxygen partial pressure of 2%. At this time, the target area ratio of CO and Ta was 2:1. Durability tests were conducted on the vertical double-layer floppy disk A of the present invention manufactured in this manner and the vertical double-layer floppy disk B without a Co-Talli film for comparison.

As a result, as shown in Fig. 2, the playback output of disk B without the Co-Ta oxide film decreased by 6 dB after 90,000 buses, whereas the output of disk A of the present invention decreased even after 1 million buses. No scratches occur when running the head, and it is extremely durable.

Example 4 The same base film and magnetic recording layer as in Example 3 were used on the magnetic disk H by sputtering using targets of CO, V, and Nb, and Co-V in a 0% oxygen partial pressure.
-A 20OA Nb # film layer was formed.

At this time, the area ratio of CO and V:Nb targets is 4:1.
:l. A durability test was conducted on the vertical double-layer floppy disk C of the present invention produced in this way, and the disk showed extremely excellent durability, with no decrease in output or scratches during head running even after 1.2 million passes.

[Effects of the Invention] As explained above, according to the present invention, a magnetic recording medium with excellent corrosion resistance and ITFt abrasion resistance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the magnetic recording medium of the present invention. FIG. 2 is a diagram showing the durability test results of a vertical double layer floppy disk. l...Nonmagnetic substrate 2...Magnetic recording layer 3...Protective film layer

Claims (1)

[Claims] It has a magnetic recording layer made of a ferromagnetic thin film on a nonmagnetic substrate,
A magnetic recording medium further comprising an alloy oxide film layer of Co and at least one element selected from V, Nb, and Ta on its surface.