JPH01105312A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve a low friction characteristic, running stability, durability, rust preventing property, etc., by providing a Co-Ni oxide layer on a thin metallic film type magnetic recording layer provided on a magnetic base body. CONSTITUTION:The nonmagnetic base body 1 consists of a high-polymer film or glass, Al, etc. The thin metallic film type magnetic recording layer 2 is formed to 0.05-1.5mum film thickness on this base body 1. The Co-Ni oxide layer 3 is formed to 20-1,000Angstrom film thickness on the recording layer 2. The content of Ni with respect to Co in the oxide layer 3 is confined to 3-40%. The low friction characteristic, running stability, durability, rust preventing property, etc., of the magnetic recording medium are improved in such a manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium with excellent running stability and the like.

[Conventional technology]

Recently, instead of coated magnetic recording media, metal thin film magnetic recording media having high coercive force and residual magnetic flux density have been attracting attention. In particular, as a method to achieve high-density recording, a perpendicular recording method has been proposed in which signals are recorded in the thickness direction using a recording medium with an axis of easy magnetization perpendicular to the film surface of the magnetic recording medium (for example, Iwasaki et al. Perpendicular magnetic recording using anisotropic film [S, Iwasaki et al.
”Perpendicular MagneticRe
coding with a Composite
Anisotropy Film”IEEE Tran
s, Magn,, vol, MAG-15,05(19
79)]), hereinafter, as the medium (: o-Cr film,
There is active research into perpendicular magnetic recording media of cobalt alloy thin films such as Go-Ru films and CaO films.

These magnetic recording media, especially when used as magnetic tapes or magnetic disks, must have a low coefficient of friction, exhibit smooth and stable running properties, be excellent in abrasion resistance, run stably for long periods of time, and be environmentally resistant. There is a strong demand for properties such as durability and durability.

In addition to these demands, the surfaces of magnetic recording media using the above-mentioned ferromagnetic powder for high-density recording, as well as those using vapor-deposited or sputtered thin films, are becoming smoother, and the coefficient of friction is increasing. Therefore, some kind of countermeasure is required to ensure smooth and stable running. In addition, these magnetic recording media may exhibit deterioration due to rusting due to metal being exposed on the surface.

High-density recording media are required to overcome the above-mentioned problems and have even stronger requirements for running stability, running smoothness, and durability.

As a solution to these problems, it has conventionally been done to incorporate lubricants such as silicone oil and fluorine oil into the magnetic layer or to coat the surface thereof. Additionally, topcoating with a film layer tailored to a specific purpose has also been practiced.

[Problem that the invention seeks to solve]

However, the conventionally known methods are not satisfactory because it is difficult to mix or apply the lubricant uniformly, the lubricant and other effects deteriorate with use, and the lubricant is not durable. Further, when the coating 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.

The present invention was made in view of the above-mentioned shortcomings of the prior art, and aims to provide a new magnetic recording medium with improved low friction, running stability, durability, rust prevention, etc. purpose.

[Means for solving problems]

For this purpose, the present inventors have discovered that very excellent effects can be achieved by forming a Go--Ni oxide layer on the surface of the magnetic layer of a magnetic recording medium. That is,
The magnetic recording medium of the present invention has a metal thin film type magnetic recording layer on a nonmagnetic substrate, and further has CoNi oxide thereon.

The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the magnetic recording medium of the present invention. The nonmagnetic substrate 1 is a polymer film such as polyester, polyimide, polyamide acetate, or glass. The metal thin film magnetic recording layer 2 is made of Fe, Go, Ni
, Go-Ni, Go-Cr alloy, etc., using vacuum evaporation, sputtering, ion blating,
Formed using the method of Metsuki et al. The thickness of the magnetic recording layer 2 is 0.
The range of 05p to 1.5- is good.

Furthermore, a Go-Ni oxide layer 3 is formed by reactive vacuum evaporation, reactive sputtering, or the like. The appropriate thickness of the Go-Ni oxide film is 20 to 1000. Below 20 Å,
The film peels off easily and is not durable.

If the thickness exceeds 1000 Å, the spacing becomes large and the output decreases. Furthermore, 50 to 300 people is particularly preferable.

Regarding environmental resistance, in order for the Go-Ni oxide layer 3 to have rust prevention properties, it is preferable that the Ni content with respect to Go in the Go-Ni oxide layer 3 is 3% by weight or more. However, if the Ni content exceeds 40% by weight, the durability of the film becomes weak and it becomes easy to peel off, which is a problem. Therefore, the Ni content relative to co in the Go-Ni oxide layer 3 is suitably in the range of 3 to 40% by weight. More specifically, 5 to 30% by weight is particularly preferred.

Similarly, regarding environmental resistance, in order for the CoNi oxide layer to have rust prevention properties, the oxygen content of the CoNi oxide layer 3 relative to CoNi is preferably 40 at % or more.

However, if the Ni content exceeds 80 at %, the crystal structure of the film is disturbed, the durability of the film is weakened, and it becomes easy to peel off, which is a problem. A suitable content is 40 to 80 at%, particularly preferably 50 to 75 at%.

〔Example〕

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

Example 1 Continuous sputtering film forming apparatus for wide tape (can temperature 120
℃) to form a 0.5 μm permalloy (Ni 78% by weight) film as a backing layer on the surface of a 50 μ+ thick polyimide film, and then apply G on it.

A perpendicular magnetization film of 80% by weight and 20% by weight of Cr was formed to have a thickness of 0.3 μm. Furthermore, using a Go-Ni target in which a Ni sheet (10xlOx 1 mm thick) was spot-welded on a Co target (φ5 inch), a Go-Ni oxide layer was deposited for 0.02 μs under the following film formation conditions. Formed. The Ni content relative to Co in the Go-Ni oxide layer is
It was controlled by varying the number of Ni sheets spot welded onto the Go target. With this control,
Seven types of samples 1 to 7 were prepared, each having a Ni content of 3.5, 11.22, 30.41.49% by weight. In addition, Ni
The content was analyzed by EPMA.

Target 2 Coφ5 inch target + Ni1Ox
10 x thickness 1 mm Sheet substrate and target spacing: 55 mm Pre-exhaust pressure 4 x 10-'Pa Introduced argon pressure: 0.4 Pa Introduced oxygen flow rate: 3. Occ/min sputtering power input crab 0.3KW Film formation rate: 1080 people/min Film thickness: 300 people Comparative Example 1 For comparison, the same method as Example 1 was used except that a Go-Ni oxide layer was not formed on the surface. A medium was prepared.

Comparative Example 2 A medium similar to Example 1 was produced except that a Co oxide layer was formed instead of the Go-Ni oxide layer.

(Evaluation) These samples were made into tapes, and the low friction effect as a top coat was evaluated by measuring the coefficient of dynamic friction μ. The results are shown in Table 1.

The dynamic friction coefficient μ was measured according to the method described in Kagaku Techniques R50-25 (1980). That is, as shown in FIG. 2, a magnetic tape 5 is wound around a wear ring 4 corresponding to a magnetic head with the magnetic layer side facing inside, a weight 7 is suspended from one end, and the other end is fixed to a load cell 6. Then, the friction wheel 4 was rotated, and the friction force of the magnetic tape was detected by the load cell 6.

Assuming that the frictional force is T and the weight of the weight is W, μ was determined from the following equation.

μ=(1/π)・zn('r/w) Table 1 The magnetic recording medium provided with the Go-Ni oxide layer of the present invention is:
It can be seen that the friction coefficient is less than half that of the medium without the Go-Ni oxide layer, indicating extremely low friction.

Next, these media were made into magnetic disks with a diameter of 47 mm, and the environmental resistance effect was evaluated by measuring the number of dropouts under high temperature and high humidity conditions. Specifically, the evaluation was carried out using a recording and reproducing device dedicated to vertical recording media, and a disk on which images were recorded at 3600 rpm and a sampling frequency (luminance signal) of 7.16 MHz was placed in a high temperature and high humidity tank at 50°C and 70%. 24
This was done by allowing the test to stand for a period of time and checking the number of dropouts in the reproduced image using the recording/reproducing device.

The results of the number of samples of Examples and Comparative Examples are shown in FIG. The broken line is the initial number of dropouts before leaving in the high temperature and high humidity tank. As shown in FIG. 3, the number of dropouts increases four times in the Go oxide film that does not contain Ni. N
When the Ni content is 3% by weight or more, the increase in the number of dropouts is 1.5 times or less, and a magnetic recording medium with high environmental resistance and commercial value can be obtained.
When it exceeds 0% by weight, the number of dropouts gradually increases, and at 49% by weight, it increases to more than 8 times the initial number of dropouts.

From this, it can be seen that Ni for Go in the Go-Ni oxide layer
It has been revealed that when the content is in the range of 3 to 40% by weight, the magnetic recording properties of the magnetic layer can be fully exhibited and a magnetic recording medium with excellent environmental resistance can be obtained.

Example 2 A perpendicularly magnetized film of 80% by weight of Go and 20% by weight of R was formed in 0.3 scales on the surface of a 10u thick polyimide film by sputtering using a continuous film forming apparatus for magnetic tape, and Example 1 Go78wt%-Ni2 under the same film formation conditions as
A 2% by weight oxide layer was formed. Thus, Go-Ni
Six types of samples were prepared with oxide layer thicknesses of 30, 50, 100, 300, 500, and 700.

Comparative Example 3 A magnetic recording medium was produced in the same manner as in Example 2, except that the formation of the Go-Ni oxide layer on the surface layer of the magnetic layer was omitted.

(Evaluation) For six samples obtained in Example, the output of the magnetic recording medium obtained in Comparative Example 2 was OdB, and 4.5 MH
The relative power of z was measured. In addition, commercially available VH3 type VTR
The steel life was measured using the following method and a wear resistance test was conducted.

Table 2 shows the results. As shown in Comparative Example 2, when the Go-Ni oxide layer is not provided on the surface of the magnetic layer, the steel life is as short as 5 minutes and the wear resistance is poor. When the thickness of the C0-Ni oxide layer becomes 50 Å or more, the steel life becomes longer and a magnetic recording medium with high wear resistance and commercial value can be obtained. However, when the thickness of the oxide layer becomes 300 Å or more, The relative output gradually decreases, and for 500 people, the output decreases to one-half of the original output. From this, it has become clear that when the thickness of the oxide layer is in the range of 50 to 300 mm, it is possible to fully demonstrate the performance of magnetic recording properties and obtain a magnetic recording medium with excellent wear resistance. .

〔Effect of the invention〕

As explained above, Go-
By forming the Ni oxide layer as a top coat layer, it has become possible to provide a magnetic recording medium with improved low friction, environmental resistance, and wear resistance, and excellent running performance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the magnetic recording medium of the present invention, FIG. 2 is a schematic diagram of a friction coefficient measuring device, and FIG. 3 is a diagram showing the number of dropouts in Examples and Comparative Examples. 1: Nonmagnetic substrate 2: Metal thin film type magnetic recording layer 3: Go-Ni oxide layer 4: Wear ring (drum) 5
: Tape 6: Tension detector 7: Weight Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1) A magnetic recording medium comprising a metal thin film type magnetic recording layer on a nonmagnetic substrate, and further having a Co--Ni oxide layer thereon. 2) The magnetic recording medium according to claim 1, wherein the content of Ni relative to Co in the Co-Ni oxide layer is 3 to 40% by weight.