JPH064858A - Continuous thin film medium - Google Patents

Abstract

PURPOSE:To form a protective film having satisfactory durability in practical use on a magnetic recording layer. CONSTITUTION:A magnetic recording layer is formed as a continuous thin film by plating, ion plating, sputtering or other method and a protective film is formed on the recording layer to obtain a continuous thin film medium. When the protective film is made of SiO2, it is liable to adhere to FeNi or Fe-Al-Si used frequently as the material of a magnetic pole of a magnetic head. When the protective film is made of Al2O3, it is liable to adhere to Al2O3 or TiC used frequently as a slider material. The SiO2 or Al2O3, film cannot ensure satisfactory durability in practical use. When the protective film is made of an SiO2-Al2O3, mixture contg. 10-90wt.% Al2O3, it has satisfactory durabililty in practical use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium whose magnetic recording layer is a continuous thin film.

[0002]

2. Description of the Related Art With the recent progress of magnetic recording media, research and development of continuous thin film media in which the magnetic recording layer is composed of only a ferromagnetic material has been actively conducted, and hard disk plating methods
It has been put to practical use as a large-capacity storage medium formed by the sputtering method. Further, an 8 mm video tape formed by vapor deposition is commercially available for a small video tape with high image quality.

Also for floppy disks, continuous thin film media have been studied in order to exhibit the characteristics of high density, small size and light weight. Typical composition ratios of these continuous thin film media are polyethylene terephthalate (PET),
A magnetic recording layer is formed on a polymer film such as polyethylene naphthalate (PEN) or polyimide (PI) or a substrate such as an aluminum compound or glass by a vapor deposition method, a sputtering method, an ion plating method or the like.

The structure of this magnetic recording layer differs depending on the use. The structure of the magnetic recording layer is composed of only a single magnetic thin film layer such as 8 mm video tape, and in a hard disk, the coercive force (Hc) of the magnetic thin film is provided between the magnetic thin film layer and the substrate. In some cases, a layer for improving the above is formed. Here, in any of the continuous thin film media, in order to improve durability against friction and wear due to contact with the magnetic head, a carbon thin film, a silicon oxide (SiO ₂ ) thin film, or a surface of the magnetic recording layer is formed on the magnetic recording layer. A protective layer composed of an oxide layer formed by oxidation is provided.

[0005]

The composition ratio of the coating type magnetic recording medium that has been used conventionally includes, in addition to the magnetic powder for magnetic recording, abrasive particles and a lubricant for improving durability. It is composed of a binder called a binder, and in addition to running durability at room temperature and humidity, it also secures environmental durability in various environments.

On the other hand, in the case of the continuous thin film medium, since the protective layer is formed on the magnetic thin film as described above,
It is difficult to retain the lubricant, and the protective layer is required to have strict mechanical and chemical properties.

For example, a 3.5-inch floppy disk (hereinafter referred to as MFD), which is one of the commonly used magnetic recording media, is defined in the JIS standard as shown in Table 1.

[0008]

[Table 1]

The judgment conditions in the durability test are as follows:
When the average signal amplitude after 300 passes is A ₀ and the average signal amplitude after the durability test is A ₁ , A ₁ / A ₀ is 0.7 or more.

On the other hand, normally commercially available MFDs have cleared the number of running times about 10 times as much as this standard, and continuous thin film media are also required to have durability about 10 times as high as the JIS standard.

However, commercially available coating type M has been used in all durability tests at high temperature, normal temperature and low temperature.
None of them showed durability as good as FD, which was an obstacle to practical use.

This tendency is also present in magnetic recording media other than MFD, and it must be able to be used for a long period without problems in any environment used as a product in terms of durability.

However, among the continuous thin film media, hard disks which have been put to practical use and are commercially available, and 8
The millivideo tape is a state in which the magnetic recording medium and the magnetic head are slightly apart from each other when the magnetic head for recording / reproducing or the magnetic recording medium is running, and friction and wear between the continuous thin film medium and the magnetic head. Are limited to systems that are designed to prevent damage to continuous thin film media or magnetic heads. Further, it is desirable that the distance between the continuous thin film medium and the magnetic head at the time of recording / reproducing is as small as possible in view of recording / reproducing characteristics. By reducing this distance, a magnetic recording medium having a larger capacity or higher image quality can be obtained. it can.

Therefore, there is a demand for a continuous thin film medium having further improved durability in the hard disk and the 8 mm video tape which have been practically used so far, and in other magnetic recording media which have not been practically used yet.

[0015]

Means for Solving the Problems As a result of earnest studies on such a problem, the present inventor has made a thin film of silicon oxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) a protective layer. In practice, a continuous thin film medium having sufficient durability can be obtained.

That is, the present invention is as follows. In a continuous thin film medium in which a magnetic recording layer is formed by a continuous thin film by a plating method, a vacuum deposition method, an ion plating method, a sputtering method, etc., silicon oxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) are used as protective layers. It is a continuous thin film medium characterized by being a mixture of 2. The composition ratio of aluminum oxide (Al ₂ O ₃ ) according to claim 1 is 10 wt.
% Or more and 90 wt% or less, a continuous thin film medium is formed.

[0017]

The following three characteristics are considered to be necessary as a protective film for a continuous thin film medium. Bending strength / Young's modulus is high and hardness is high. Chemically stable and corrosion resistant. It is hard to cause adhesion with the magnetic head and slider. Here, oxide is a typical candidate for satisfying This is the main reason why the silicon oxide (SiO ₂ ) film and the aluminum oxide (Al ₂ O ₃ ) film have been studied as protective films so far. However, the protective film composed of the silicon oxide (SiO ₂ ) film and the aluminum oxide (Al ₂ O ₃ ) film has a very problematic problem, and sufficient characteristics have not been obtained so far.

That is, permalloy (FeNi) and sendust (Fe-Al) which are often used as magnetic poles of magnetic heads.
-Si) tends to cause adhesion of a silicon oxide (SiO ₂ ) protective film, and is often used as a slider material for Al ₂ O ₃ .TiC and aluminum oxide (Al).
₂ O ₃₎ aluminum oxide (Al ₂ O ₃₎ liable protective film is adhesion with respect, silicon oxide (SiO ₂₎ film or aluminum oxide (Al ₂ O ₃₎ protection film layer is practically sufficient It was not possible to obtain durability.

The inventor of the present invention solves this problem by using a thin film made of silicon oxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) as a protective film, so that it has practically sufficient durability. A thin film medium was obtained.

[0020]

[Embodiment 1] The present invention will be described in detail below. Cobalt chrome (CoCr) thin films of 0.2 μm each were formed on both sides of a 45 μm thick polyimide film by a sputtering method. The sputter target at this time was a 6-inch magnetron target, and the sputter power was RF5.
The pressure was set to 00 [W] and the sputtering pressure was set to 0.1 [Pa]. After that, silicon oxide (SiO ₂ ) pellets (10 × 10 mm) are placed on an aluminum oxide (Al ₂ O ₃ ) target.
A protective film was formed with a composite target placed on the substrate so as to have a thickness of 20 [nm]. The composition ratio of the formed protective film is such that silicon oxide (SiO ₂ ) is 0, 5, 10, 50, 9
Six kinds of 0.95 [wt%], and the rest is aluminum oxide (Al ₂ O ₃ ). The composition ratio was measured by forming the protective film and then adjusting the number of silicon oxide (SiO ₂ ) pellets so that the composition was set by quantitative analysis by EPMA. The sputtering gas here is a mixed gas of argon (Ar) and oxygen (O ₂ ), and argon (Ar); 14 [c
c / min], oxygen (O ₂ ); 6 [cc / min].

[0021] The original fabric having protective films formed on both sides is punched out into a 3.5-inch size to obtain a 3.5-inch MFD, and then 2
Normal-temperature, high-temperature, and low-temperature durability tests were conducted with a floppy disk driver for HD.

The test conditions were set in accordance with JIS X6223, and the judgment conditions were evaluated by setting the number of traveling paths to 10 times the JIS standard. The experimental results are shown in Table 2.

[0023]

[Table 2]

Here, the case where the ratio of the average signal amplitude after 300 passes after the start of the experiment and after the end of the experiment is 0.7 or more is designated as ◯,
The case of less than 0.7 was marked with x.

[0025]

Example 2 In Example 1, a polyimide film having a thickness of 25 μm was punched into a 2-inch size to form a 2-inch still video floppy disk. Here, the method of forming the magnetic thin film and the protective film was the same as in Example 1. Also, for the environmental durability test, JIS for 2 inch still video floppy
Since there is no standard, the test was conducted according to the standard of 3.5-inch floppy disk. The experimental results are shown in Table 3.

[0026]

[Table 3]

In Examples 1 and 2, the composition ratio of the protective film was aluminum oxide (Al ₂ O ₃ ): 10 to 90.
When [wt%] and the balance is silicon oxide (SiO ₂ ), sufficient environmental durability was obtained at low temperature / normal temperature / high temperature.

[0028]

As described above, according to the present invention, practical continuous environmental durability was obtained in the continuous thin film medium. In the embodiments of the present invention, the 3.5-inch and 2-inch cobalt chrome (CoCr) floppy disks have been described, but the invention can be applied to hard disks and tapes, and the size and shape of the magnetic thin film medium and the composition of the magnetic layer are described below. The invention is not limited to the embodiments. Further, the method of forming the protective film has been described by the sputtering method in the embodiments of the present invention, but it is obvious that the same effect can be obtained by the vacuum vapor deposition method, the ion plating method, etc. Not limited to examples.

Claims (2)

[Claims] 1. A continuous thin film medium in which a magnetic recording layer is formed by a continuous thin film by a plating method, a vacuum deposition method, an ion plating method, a sputtering method or the like, and silicon oxide (SiO ₂ ) and aluminum oxide ( A continuous thin film medium characterized by being a mixture of Al ₂ O ₃ ). 2. The continuous thin film medium according to claim 1, wherein a protective film having a composition ratio of aluminum oxide (Al ₂ O ₃ ) of 10 wt% or more and 90 wt% or less is formed.