JPH077503B2 - Magnetic recording medium and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium having a magnetic thin film provided on a non-magnetic support, and more particularly to a highly reliable magnetic recording medium having excellent wear resistance. .

[Conventional technology]

With the increase in capacity of magnetic recording devices, magnetic recording media used therein are required to have higher recording density characteristics and higher reliability. A coating type magnetic recording medium prepared by coating a non-magnetic support with magnetic powder such as γ-Fe ₂ O ₃ dispersed in a resin binder has been generally used in the past, but in recent years, high recording density has been achieved. In response to this trend, a thin film magnetic recording medium in which a magnetic thin film is formed on a non-magnetic substrate by a vapor deposition method, a plating method, a sputtering method or the like has been receiving attention.

In this thin film magnetic recording medium, the magnetic layer can be made thin, and since the magnetic layer does not contain a non-magnetic resin binder, high magnetic flux density can be achieved, resulting in high recording density. Becomes However, in this type of magnetic recording medium, the problem that the magnetic layer is destroyed due to the sliding contact between the magnetic recording medium and the magnetic head is more likely to occur than in the coating type magnetic recording medium, and the sliding contact of the magnetic head may occur. On the other hand, it is important to treat the surface of the magnetic layer in order to provide sufficient wear resistance. For example, in a magnetic disk device, a so-called contact start stop (hereinafter referred to as CSS) method in which a magnetic head and a medium are in sliding contact at the time of starting and stopping the rotation of a magnetic disk medium has been adopted. Sufficient wear resistance is required to withstand this.

In order to secure the wear resistance of such a magnetic recording medium, conventionally, it is made of a material having a high hardness such as Al ₂ O ₃ , SiO ₂ , TiO ₂ , Si ₃ N ₄ , WC, TiC, SiC and B ₄ C. A method of forming a protective film on a magnetic layer has been proposed. (JP-B-55-39047, JP-A-53-2
1901, JP53-21902, JP58-185029, JP59-18
8835) [Problems of Prior Art] The above-mentioned protective film is usually formed on the magnetic thin film by a sputtering method. However, these protective films often do not have sufficient adhesion to the magnetic thin film, and the protective film is peeled off due to sliding contact with the magnetic head, and the peeled substance is sandwiched between the magnetic head and the protective film to protect it. The other part of the film was scraped off and the magnetic thin film was destroyed.

In addition, when the magnetic thin film is a thin film containing γ-Fe ₂ O ₃ as a main component, and a protective film is to be formed on this thin film by the sputtering method, α-Fe ₂ O ₃ or Fe ₃ O ₄ is mainly used. A film as a component is formed by the spatter method, is taken out from the spatter chamber and placed in an atmosphere furnace, and is subjected to heat treatment such as reduction and oxidation to form a thin film containing γ-Fe ₂ O ₃ as the main component. again,
A method of arranging this in a spatter chamber and forming a spatter on the protective film is adopted. However, this method complicates the process because it has to be taken in and out of the sputter chamber, which is a problem in mass production.

[Object of the Invention]

An object of the present invention is to provide a highly reliable magnetic recording medium in which a protective film is formed on a magnetic thin film with good adhesiveness, thereby having excellent wear resistance.

Another object is to provide a highly reliable magnetic recording medium having excellent wear resistance, in which a protective film made of an oxide is formed on a thin film made of a magnetic oxide by a simple method with good adhesion. That is.

[Structure of Invention]

The magnetic recording medium of the present invention is formed by forming a magnetic thin film on a non-magnetic support, and further forming an abrasion-resistant protective film on the magnetic thin film, and between the magnetic thin film and the abrasion-resistant protective film. It is characterized in that a solid solution region of both films is formed. According to this magnetic recording medium, the solid solution region is formed, so that the bonding force and the adhesiveness between the magnetic thin film and the protective film are significantly increased.
As can be seen from the CSS (contact start stop) test, abrasion resistance increases and peeling of the protective film is eliminated, and a highly reliable magnetic recording medium with a long life can be provided.

The method for producing a magnetic recording medium of the present invention comprises forming a target magnetic thin film, a precursor magnetic thin film thereof or a precursor thin film on a non-magnetic support, and an abrasion resistant film or a precursor thin film thereof thereon. Is formed and heat-treated at a predetermined temperature to form the above-mentioned films as the target magnetic thin film and wear-resistant protective film, respectively, and cause diffusion between these films to form a solid solution at the interface between them. Forming a region.

According to this method, diffusion occurs between the magnetic thin film and the protective film due to the heat treatment, and the adhesiveness between the two is enhanced, so that the excellent magnetic recording medium described above can be provided. Further, according to the method of the present invention, the target magnetic thin film, its precursor magnetic thin film or precursor thin film and the protective film or its precursor film may be sequentially formed and heat-treated,
For example, when performing vacuum deposition such as the sputtering method, the precursor oxide film of the magnetic thin film is deposited as in the conventional method, vacuum leak is performed, and the film is transferred to a heat treatment furnace to form a predetermined magnetic thin film. The troublesome procedure of loading the protective film into the sputtering device again and depositing the protective film is simplified. That is,
According to the method of the present invention, the sputtering film formation can be carried out successively without vacuum leak, and then in a heat treatment furnace, which is efficient. Nevertheless, the characteristics of the magnetic recording medium obtained by the method of the present invention as described above are superior to those of the conventional one.

In order to sufficiently improve the adhesion and wear resistance intended by the present invention, the thickness of the solid solution region is 100 Å or more, preferably 200 Å or more. As a result, the CSS resistance is sufficiently improved. The thickness of the solid solution region is controlled by the heat treatment temperature and time.
The higher the heat treatment temperature and the longer the heat treatment time, the greater the thickness of the solid solution region. Normal heat treatment temperature is 100
It is performed above ℃. If it is less than this, it takes too much time to form a solid solution region having a predetermined thickness.

A typical example of a magnetic oxide forming a magnetic thin film is γ-Fe ₂ O.
₃ or an oxide mainly containing this. Such a thin film is formed by, for example, forming an α-Fe ₂ O ₃ thin film by a sputtering method, reducing the Fe ₃ O ₄ thin film in a furnace in a reducing atmosphere, and further oxidizing it in a furnace in an oxidizing atmosphere. By forming a γ-Fe ₂ O ₃ thin film. Another method is Fe ₃ O ₄
The thin film is formed by the sputtering method and is oxidized in a furnace in an oxidizing atmosphere to form a γ-Fe ₂ O ₃ thin film. In another example, the magnetic thin film is Co, Co-P,
Metals such as Co-Ni, Co-Cr, and Co-Ni-P can be used.

The conversion into the γ-Fe ₂ O ₃ thin film in one embodiment of the present invention is performed after forming a protective film or a precursor thin film thereof on the surface of the α-Fe ₂ O ₃ or Fe ₃ O ₄ thin film. . During the conversion of α-Fe ₂ O ₃ or Fe ₃ O ₄ into the γ-Fe ₂ O ₃ magnetic thin film by heat treatment, the protective film or its precursor is converted into the protective film, and both films are Will form a solid solution layer.

As the protective film or its precursor, Al ₂ O ₃ , TiO ₂ , SiO
₂ , Al, Ti, Si, etc. can be used, and these are Al ₂
It is converted to a wear-resistant protective film such as O ₃ , TiO ₂ , and SiO ₂ . The protective film must be not only sufficiently wear-resistant, but also capable of forming a solid solution region by diffusion with the magnetic thin film.

The method of the present invention can typically be carried out by the sputter method. In the present invention, Fe, α-Fe ₂ O ₃ , and F are contained in the same vacuum chamber.
A target such as e ₃ O _{4 and} a target such as Al or Al ₂ O ₃ are provided, and these are sputtered on a non-magnetic support to form a film. Then, reduction or oxidation is performed in a heat treatment furnace to change each layer into a predetermined magnetic thin film and wear-resistant oxide, and the interface between them is made into a solid solution region. As described above, this method is superior to the conventional method. Large three figures show this point. FIG. 3A shows the method of the present invention,
(B) shows a conventional method. As shown in the figure, the number of steps indicated by double frames in the conventional method is larger than that in the method of the present invention. As described above, according to the present invention, the process is simplified, so that the manufacturing time of the magnetic recording body is shortened.

Co, Cr, Co-
Magnetic metal thin films such as P, Co-Ni-P, Co-Ni, and Co-Cr can be used. In this case, a magnetic thin film and a protective thin film such as Al ₂ O ₃ are sputtered to form a spatter, which is then placed in a heat treatment furnace for heat treatment in a non-oxidizing atmosphere. As a result, a solid solution region can be formed between the protective film and the magnetic metal.

The thickness of the solid solution region can be measured by ESCA analysis, Auger analysis, RBS analysis, or the like. For example, the Auger analysis is performed by observing the profile in the thickness direction of the atoms forming the protective film and the magnetic thin film.
An example of forming an Al ₂ O ₃ protective film on a Co-Ni thin film is shown in FIG. The full width at half maximum d of the overlapping Al and Co distribution can be considered as the solid solution region, but even if there is no solid solution region, d is not zero but 20 to 100 Å because of the resolution of the Auzier analyzer. It has a value (different for each device). Therefore, the actual thickness of the solid-dissolved region is the value obtained by subtracting this value from d, that is, the half-width when there is no solid-solved region in the Aussie analyzer used by the present inventors is about 60.
Since it is Å, the actual thickness of the solid solution region is defined by d-60.

[Example 1] As a substrate, a 50 µm Ni-P plating layer was formed on an aluminum alloy and the surface was polished. The outer diameter is 13
It is a disk with a diameter of 0 mm, an inner diameter of 40 mm, and a thickness of 1.9 mm.

A Cr thin film is formed on this substrate by a sputtering method with 3000 Å,
A Co-20 wt% Ni thin film was formed on this by 500 Å by the sputtering method. Further, a 300 Å protective film of Al ₂ O ₃ was formed. This was heat-treated in a nitrogen atmosphere at each temperature for 1 hour to complete a magnetic disk.

Table 1 shows the measurement results of the thickness (d-60) of the solid solution region and the CSS test of the completed magnetic disk by Auger analysis. The CSS test was done as follows.

CSS test A CSS test was performed using a winch ester type Mn-Zn ferrite head (load: 9.5 g). CSS was performed by repeating the cycle shown in FIG. CSS times,
The number of times until the recording / reproducing output became less than half of the initial value was performed up to 40,000 times.

Looking at the results in Table 1, it can be seen that the CSS characteristics are improved by forming the solid solution region, it is markedly improved when the thickness of the solid solution region is 100 Å or more, and it is further improved when it is 200 Å or more. .

Example 2 An aluminum alloy substrate having an alumite layer of 2 μm formed by anodic oxidation was used as the substrate. Shape is outer diameter 130 mm, inner diameter 4
It has a disk shape of 0 mm and a thickness of 1.9 mm. By using iron as a target on this substrate and sputtering in an Ar + O ₂ atmosphere (mixing ratio 50%, vacuum degree 5 × 10 ^-3 Torr), α-Fe ₂ O ₃
A film of 2000 Å was formed. Further, an Al ₂ O ₃ protective film was formed thereon by the sputtering method.

Next, the α-Fe ₂ O ₃ film was reduced in a hydrogen atmosphere furnace for 2 hours to form an Fe ₃ O ₄ film.
It was a film. At this time, the Al ₂ O ₃ film is also partially reduced and becomes a film containing Al. The reduction temperature is shown in Table 2. Further, it was oxidized in air at 310 ° C. for 1 hour to form the Fe ₃ O ₄ film as a γ-Fe ₂ O ₃ film and the protective film as an Al ₂ O ₃ film.

The above steps are summarized as a flow chart as shown in FIG. On the other hand, in the conventional method, the third method is used.
As shown in FIG. 6B, it can be seen that the process surrounded by double squares is omitted in the present invention, and the manufacturing time of the magnetic recording medium is shortened.

The thickness (d-60) of the solid solution region of the completed magnetic disk was measured by Auger analysis, and the CSS test was conducted. The results are shown in Table 2. On the other hand, when the same test was performed on the magnetic disk formed by the conventional method (FIG. 3 (b)), d-60 = 0 and CSS = 14,000 times. On the other hand, the superiority of the present invention is clear from Table 2.

[Brief description of drawings]

FIG. 1 is a diagram showing a method for measuring the thickness of a solid solution region,
FIG. 2 is a diagram showing a CSS test method, and FIG. 3 is a process comparison diagram of the method of Example 2 and the conventional method.

Claims (10)

[Claims] 1. A magnetic recording medium comprising a magnetic thin film formed on a non-magnetic support and a protective film formed on the non-magnetic support, and a region where the magnetic thin film and the protective film are solid-solved exists between the magnetic thin film and the protective film. A magnetic recording medium characterized by the above. 2. The magnetic recording medium according to claim 1, wherein the thickness of the solid solution region is 100 Å or more. 3. The magnetic recording medium according to claim 1, wherein the solid solution area is 200 liters or more. 4. A protective film is Al ₂ O _3, TiO ₂ and claims the first term of which is characterized in that a main component at least one of SiO _2, any one of the second and third terms The magnetic recording medium according to 1. 5. A first thin film comprising a magnetic thin film (B), its precursor magnetic thin film (A), or a precursor of the magnetic thin film (B) is formed on a non-magnetic support, and on this first thin film. A second thin film made of wear-resistant oxide or its precursor is formed on and heat-treated to form the first thin film as the magnetic thin film (B), and the second thin film is changed to the wear-resistant oxide film. A method of manufacturing a magnetic recording medium, comprising: 6. The first thin film is a thin film containing α-Fe ₂ O ₃ or Fe ₃ O ₄ as a main component, and the second thin film is Al or Al ₂ O.
6. The method for producing a magnetic recording medium according to claim 5, wherein the main component is at least one selected from the group consisting of ₃ , Ti, TiO ₂ , Si and SiO ₂ . 7. The magnetic thin film (B) contains γ-Fe ₂ O ₃ as a main component, and the wear-resistant oxide film contains at least one of Al ₂ O ₃ , TiO ₂ and SiO ₂ as a main component. The method of manufacturing a magnetic recording medium according to claim 5 or 6, characterized in that. 8. A solid solution region is present at the interface between the magnetic thin film (B) and the wear resistant oxide film, according to any one of claims 5, 6 and 7. A method for manufacturing the magnetic recording medium described. 9. The method for manufacturing a magnetic recording medium according to claim 8, wherein the thickness of the solid solution region is 100 Å or more. 10. The method for producing a magnetic recording medium according to claim 8, wherein the thickness of the solid solution region is 200 Å or more.