JPS6243821A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To remarkably improve corrosion resistance, resistance to sliding with a head by forming a protective film consisting of boron carbide on the film surface of a magnetic recording medium. CONSTITUTION:The material of the boron carbide having the compsn. expressed by the general formula BxC1-x (where x denotes the positive number over 0.80 and 0.96 or below) is used as the protective film 3. The resistance to sliding with the head and the corrosion resistance are much improved as the size of B (boron) and C (carbon) atoms is substantially smaller than the size of ferromagnetic material atoms such as Fe, Ni and Co constituting a thin magnetic film and intrude easily into the micro-recesses of the thin magnetic film surface and the B and C atoms have high affinity to the metallic atoms of Fe, Ni and Co and are liable to attain the amorphous state by securely and tightly adhering to the thin magnetic film surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to magnetic recording media, particularly if they are corrosion resistant. ,. W
Ff 'z y)" fM 'fAfr In fl
tL t: m 'i2t Me, * * # In
Iu5 t”□ru.

[Background of the invention]

In order to achieve high-density magnetic recording, research and development of magnetic recording media using thin metal films has been actively conducted.

is being advanced. This metal thin film magnetic recording medium.

Men-V method, ion play dooring method, spatter.

Co, Fe
,.

Ferromagnetic 'I'1 metals such as N1, or these elements
A magnetic thin film made of a ferromagnetic alloy as a knee component.
This is a magnetic recording medium formed on a substrate coated with a non-magnetic material such as filtrate, aluminum, or glass. However, magnetic recording media using this metal or alloy thin film have corrosion resistance l!1. It has the disadvantages that the magnetic head etc. are easily worn out, and the recording medium itself is also easily worn out.Furthermore, the head touch is poor, which poses considerable problems when put into practical use.

To solve this problem, the magnetic thin film is made of a metal with a high oxidation resistance, such as Au or Pt.

A method of forming a protective film made of materials such as Rh, Pd, Cr, A/', and Si (Japanese Unexamined Patent Publication No. 53-4050)
5 Yumi' Publication, Japanese Unexamined Patent Application Publication No. 1765371'j)
A method of strengthening a magnetic thin film by nitriding or oxidizing the surface of the magnetic thin film
Publications), or C-based protective films made of non-metallic materials (Japanese Patent Application Laid-Open No. 1983-1999).

14320 (i-yuki publication) and r3. which is a B-based material. A method has been proposed to form a protective film of c.

However, according to the research conducted by the present inventors, in the case of the metal-based or alloy-based protective film described in 1-1, the wear resistance is not known, and the magnetic thin film can be passed through pinholes in the protective film. is gradually changing.

Corrosion resistance of 1'/1 does not always have to be reduced to 1 min.

However, although the method described in -1, in which the surface of the magnetic thin film is nitrided or oxidized, has better head sliding resistance and oxidation resistance,
Depending on the thickness of the nitride layer and oxide layer formed on the surface of the magnetic thin film, the magnetic properties of the magnetic thin film may change, or the magnetic f/l thin film may be exposed to considerably high temperatures during nitridation or oxidation. There are problems such as changes in magnetic properties. Furthermore, the C-based J(Li) film, which is a non-metallic material mentioned above, has the disadvantage of being extremely abraded during magnetic helad sliding, and the B-based B and C protective films are The drawback is that it is extremely difficult to form thin films with stoichiometric composition.

There was a point.

[Purpose of the invention]

The purpose of the present invention is to solve the problems of the prior art described above,
General formula BxC1-x (wherein, X exceeds 0.80, 09
Represents a positive number less than or equal to 6. An object of the present invention is to provide a magnetic recording medium with greatly improved corrosion resistance and head sliding resistance by forming a boron carbide-based protective film shown in ) on the film surface of the magnetic recording medium.

[Summary of the invention]

The necessary conditions for the protective film of the magnetic recording medium in the present invention are that it has corrosion resistance and protects the magnetic thin film layer of the medium, that it has slipperiness against the magnetic head, and that it is protected to prevent deterioration of electromagnetic conversion characteristics. Basically, the film should be as thin as possible, with a thickness of 1000 A or less. Since the surface of a magnetic thin film formed on a non-magnetic substrate has microscopic undulations, the protective film not only satisfies the above conditions but also firmly adheres to these microscopic undulations. This is necessary, and it is desirable that the L microscopic undulations be flattened in the formation of the protective film. The microscopic undulations on the surface of a magnetic thin film are greatest in the case of a perpendicularly magnetized film in which the microcrystalline grains constituting the magnetic thin film are composed of vertically oriented village crystals. Then, the surface has a period of 200 to 500 A.
, there are undulations with a depth of 50-200A. Further, in the portion where the interface of the microcrystalline particle is exposed on the surface, pores with a depth of atomic scale (IOA or less) also exist. Therefore, it is necessary for the protective film to be formed so as to wrap around every corner of the microscopic undulations on the surface of the magnetic thin film and to firmly adhere thereto.

As a result of various researches, the present inventors found that as a protective film,
General formula BXC1-x (wherein, X exceeds 0.80 and 0.
Represents a positive number of 96 or less. ) The present invention was completed based on the finding that head sliding resistance and corrosion resistance are further improved by using a boron carbide material having the composition shown in (a). That is, B (boron).

The size of the C (carbon) atom makes up the magnetic thin film,
Compared to the size of ferromagnetic atoms such as Ni and Go.

It is small enough to fit into the microscopic depressions on the surface of the magnetic thin film.

and B and C atoms.

has a high affinity with metal atoms such as Fe, Ni, and Co.

This is because it adheres tightly to the surface of the magnetic thin film and tends to become amorphous. This amorphous protective film.

The feature is that there are few chemically active points, so it is corrosion resistant.

In contrast, in a crystalline protective film, grain boundaries and defective areas within the crystal grains tend to become chemically active sites. Chemical reactions proceed preferentially, causing corrosion resistance deterioration. Furthermore, in a crystalline protective film, the stress of the load of the magnetic head concentrates on the crystal grain boundaries, which deteriorates the mechanical strength.

General formula of the present invention Bx C+ -x (0,80(x (
The boron carbide-based amorphous protective film with the composition shown by 0.96) has higher hardness than the C protective film, so it has less wear when the head slides, and when producing the protective film, Use B and a mixture of B and C as a deposition source, or use the above mixture as a target.

The protective film of the present invention can be formed relatively easily by

can be made.

General formula of the boron carbide-based protective film of the present invention.

The range of X in the composition represented by BxCl-X is shown in Figure 2.

The resistance at (, B single protective film (X = 1.0 >) is shown.

Carbonization shows a value larger than the head sliding strength (times).

Boron-based protective film composition, that is, X = 0.96,
.

Boron carbide without 84C protective film composition (x-0,80).

system protective film composition, i.e., X) shown between 0.80,
.

A BxC1-x protective film having a composition range of Therefore, the range of X in the BXCl-X composition is greater than 0.80 and less than or equal to 0.96 (0.80<X<0.96)
It is. and.

From the viewpoint of higher head sliding resistance and its reproducibility, from the characteristic curve shown in FIG. 2, the -1 preferred range of X is 0.81 to 0.91.

Bx C1-x of the present invention (0,80<X<0.9
The protective film having the composition shown in 6) is formed by vacuum evaporation method or sputtering method.

On a magnetic thin film formed by a so-called dry method, which is a physical vapor deposition method such as ion blating method.

・　7　・ The protective film of the present invention provides particularly strong adhesion.

can get. Moreover, BxC1□(0,80<X<
.

0.96) on the surface of the magnetic thin film,
.

By the dry method described above, a film thickness of 50 to 1000 A is formed.

When formed, microscopic undulations appear on the surface of the magnetic thin film.

Flattened.

Bx C+ −x (0,80<x<0
．． 96) Te is shown.

If the thickness of the protective film with the composition is less than 50A, the effect as a protective film will be small, and if it exceeds 1000A, the magnetic recording and reproducing characteristics will deteriorate. The thickness range is 100-800A, and the most preferable film thickness range is 150-300A.

[Embodiments of the invention]

Embodiments of the present invention will be described below in more detail with reference to the drawings.

(Example 1) A magnetic recording medium having the structure shown in FIG. 1 was manufactured by vacuum evaporation using a polyimide film as a substrate. After the sample chamber of the vacuum evaporation apparatus was evacuated to I.times.10' Torr8.times., the temperature of the substrate 1 was set to 150.degree.

A magnetic thin film having a composition of Go-20 wt% Cr.

Membrane 2 was vacuum deposited to a thickness of 0.2 μm. Next, try it.

A mixture of B, B, and C can be used as the evaporation source without breaking the vacuum in the chamber.

A protective film 3 having a thickness of 200A was formed under the same conditions as above. In this case, B is the vapor deposition source.

By changing the mixing ratio of 84C, a set of protective film 3 was obtained.

BXCl, which is composed of
It was possible to freely prepare within the range of . In addition, the protective film 3
The composition was determined by Auger electron spectroscopy.

As comparative examples, a sample without a protective film and a sample with B alone as a protective film were prepared.

Each of the above samples was tested for head sliding resistance and corrosion resistance as shown below.

The head sliding resistance test was performed by cutting out a disk sample from each sample, setting it on a disk rotation device, and then applying a load of 18
The disk was continuously rotated at a speed of 2 m/s with the head of No. g in contact with the disk, and the head sliding strength (number of times) was determined based on the number of rotations until scratches appeared on the sample magnetic recording medium. In addition, the corrosion resistance test was carried out by leaving each sample in an environment of relative humidity 9) C) and temperature 6 °C for a month, and then observing its surface with an optical microscope to determine its corrosion resistance. I judged it.

♀11 of the durability and sliding test. The king is shown in Figure 2.

, as is clear from 1 to 1, the composition of the protective film is
-1', xC, -8 is ('1.80 < X < 0.
It shows that there is a head sliding resistance +'l of 96, where the value is B l
It body protection:'! Membrane (X-' 1.0) lco'J3
Kel 1)
．． The lower limit value of 96'; c, ): is 1 (excluding the C protective film (x,, 080) < BxC, the X value of the y composition, that is, X>080).

In addition, Table 1f1) of samples with B, C+-X (0,80 < When observed under a microscope and compared, it was found that the surface of the sample on which the protective film was formed had fewer undulations and was smoother. Regarding the results of the corrosion resistance 1f1 test, discoloration was observed only in the samples in the comparative example without a protective film, while in the samples with a protective film, there was no discoloration and no corrosion was observed at all. 2) Also, the protection 71 in this embodiment has a large thickness.

Head, head sliding resistance P (face direction) tilt 11 but 12. First of all, the distance between magnetic recording media and magnetism has increased.

Electromagnetic conversion to! 1, the electromagnetic transmissibility 14F does not deteriorate, and the film thickness range with good resistance to -\, 1, The most desirable color range was 100-800A, and the most desirable range was 151-300A.

Furthermore, in this example, a method was described in which a protective film was formed continuously within the same device (?1) after forming a magnetic film. It is also possible to form a protective film after transferring the sample to the apparatus. However, in order to form a protective film with high contact 7 strength, it is necessary to In this case, it is desirable to form the protective film in one continuous manner as shown in this embodiment.

In addition, in this Example 1, 1: [, a Co-Cr alloy adhesive thin film was used, but other Cn-based alloys were used]
When a c-based 11. alloy or an N+-based alloy is used as a magnetic thin film, I3x C1-x (0,80<X<0.
96) Composition.

By providing a protective film of this type, it was possible to improve head sliding resistance and corrosion resistance. .

(Example 2) A magnetic recording medium having the structure shown in FIG. 3 was fabricated by a bicarbonate sputtering method using an aluminum foil substrate.
rr wait”°! After airing, introduce Ar scum and
Adjust the r pressure to 5 × river-・' Torr, and
, the temperature of the substrate 4 was set to 120' (:, by the 4-frequency sputtering method, ]!1wt% Fc-N
A high magnetic permeability thin film 5 having a composition of i was formed to a thickness of 0571 m. Then, in the same sample chamber (Jl) (plate 4, 11.'1 degree is 100'C,
A magnetic i'l thin film 6 having a composition of 0.5 mm was sputtered to a thickness of 0.27 nm.

Protection 1 and 7 were formed to a thickness of 200 mm at a substrate temperature ε]OT using a target with B4C placed on 11+ or a target with B placed on B4C. This place 1? By changing the (7 ratio of B, etc.) that constitutes the target, BXCl, , -X (0,80<
A protective film 7 having a composition <(i, 9'''i) can be obtained.

As a comparative example, a sample without a protective film and a sample with an I3 shell as a protective film were prepared, and a corrosion resistance test and a heat resistance test were conducted in the same manner as in Example-1. However, the vacuum evaporation shield method of Example 1 was used.

In the case of [1], the corrosion resistance showed excellent values in all the magnetic recording media protected by the protective film, and the head sliding resistance f1 was the same when the protective film composition was 13yCl-, y was 0.
In the range of more than 80 and less than 0.96, it showed a value superior to that of the comparative example B protective film.

In addition, a protective film can be formed using the ion blating method.
Even in the case of e-formation, excellent effects similar to those of this example could be observed.

(Example 3) A magnetic recording medium having the structure shown in FIG. 4 was fabricated by magnetron sputtering using an N1-P/Al radical as a substrate.
After vacuuming to 1O-6To+"r, Ar gas was introduced to make the Ar pressure 5 x 1O-3Torr, and N1-P/M! was deposited on the N1-P/M! substrate 8 at a substrate temperature of 120°C by magnetron sputtering. Cr is used as the intermediate layer 9.

The film thickness was 500A. Then, a 25 wt % Co--Ni alloy was formed thereon as a magnetic thin film 10 to a thickness of 0.2 μm at a substrate temperature of 100'C. Protective film 11
゜ is the target with 84C placed on B or B4
Using a target with B placed on C, the substrate temperature is 90
The film was formed to a thickness of 200 Å at a temperature of 200° C. by the same magnetron sputtering method as above.

The magnetic recording medium produced according to this example exhibited excellent corrosion resistance and head sliding resistance equivalent to those of the above-mentioned examples] and 2.

〔Effect of the invention〕

As explained in detail above, the general formula BxC according to the present invention
An amorphous boron carbide-based protective film with a composition expressed by 1-x (0,80<x<0.96) easily adheres firmly to the surface of a magnetic thin film, and has few chemically active sites. Since it has good corrosion resistance and is homogeneous, it has high mechanical strength, so magnetic recording media using it as a protective film have excellent corrosion resistance.

Of course, the head sliding resistance is especially high.

Extremely durable for high-density magnetic recording and reproduction.

A long recording medium can be obtained.

The boron carbide-based protective film of the present invention is a dry method.

It can be easily formed by physical vapor deposition method.

It has extremely great industrial value.

stomach.

[Brief explanation of drawings]

FIG. 1 shows a magnetic recording medium in Example 1 of the present invention. FIG. 2 is a graph showing the relationship between the composition range of the protective film BxC1-X and the bending resistance against sliding strength of the protective film BxC1-X according to the present invention, and FIG. FIG. 4 is a sectional view showing the structure of a magnetic recording medium in Example 3 of the present invention. 1... Polyimide substrate 2... Magnetic thin film 3... Protective film 4... A/substrate 15. 5... High magnetic permeability thin film 6... Magnetic thin film 7... Protective film 8. ...N1-P/kI! Substrate 9...Intermediate thin film 10...Magnetic thin film 11...Protective film Junnosuke Nakamura, patent attorney.・16・′(

Claims (1)

[Claims] 1. In a magnetic recording medium in which a magnetic thin film layer is provided on a substrate, the general formula B_xC_1_-_x(
In the formula, x represents a positive number greater than 0.80 and less than or equal to 0.96. ) A magnetic recording medium characterized by forming a boron carbide-based protective film having a composition represented by: 2. The magnetic recording medium according to claim 1, characterized in that in the boron carbide-based protective film having a composition represented by the general formula B_xC_1_-_x, x is in the range of 0.81 to 0.91. . 3. The magnetic recording medium according to claim 1 or 2, wherein the boron carbide-based protective film having a composition represented by the general formula B_xC_1_-_x is amorphous. 4. Any one of claims 1 to 3, characterized in that the thickness of the boron carbide-based protective film having the composition represented by the general formula B_xC_1_-_x is in the range of 50 to 1000 Å. The magnetic recording medium described in . 5. According to any one of claims 1 to 3, the boron carbide protective film having a composition represented by the general formula B_xC_1_-_x has a thickness of 100 to 800 Å. magnetic recording media. 6. According to any one of claims 1 to 3, the boron carbide protective film having a composition represented by the general formula B_xC_1_-_x has a thickness of 150 to 300 Å. magnetic recording media. 7. The boron carbide-based protective film having the composition represented by the general formula B_xC_1_-_x is formed by a physical vapor deposition method, according to any one of claims 1 to 6. magnetic recording medium.