JPH0460919A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium of metal thin film type excellent in sliding resistance with good reproducibility by using a boron film containing a small hydrogen content as a protective film. CONSTITUTION:The magnetic recording medium has a boron protective film formed on a ferromagnetic metal film as a recording layer. The hydrogen con tent in the protective film is specified to <=0.2 at.%. When hydrogen intrudes into a boron film, hydrogen atoms easily couple with boron atoms even at low temp. and prevent coupling among boron atoms. This causes a region having weak coupling of boron atoms and reduces the mechanical strength of the boron film. Therefore, intrusion of hydrogen into the boron film is suppressed as much as possible so as to improve the sliding property of the film. Thus, the slinding resistance of the boron film is improved with higher reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording medium using a ferromagnetic metal thin film as a recording layer, and more particularly to a protective film thereof.

[Conventional technology]

In recent years, with the increase in recording density, vacuum evaporation methods have become popular.

2. Description of the Related Art Metal thin film magnetic recording media formed by physical film forming methods such as ion blasting and sputtering are being developed. Although such metal thin film type recording media have excellent magnetic properties and are suitable for high-density recording, their reliability in terms of sliding properties, corrosion resistance, etc. is still unsatisfactory. Among these methods, in order to improve the sliding properties, a method has been adopted in which the surface of a ferromagnetic metal thin film is coated with a thin protective film having excellent mechanical strength. Typical materials include carbon (C), silicon oxide (SiC2), and boron (B) [e.g.
Inorganic protective films such as -1 (1/13161) are known.

Among these, the boron film can be formed by vacuum evaporation, so the film formation rate is fast, and it is an excellent material from a practical point of view.

[Problem to be solved by the invention]

There was a problem in that the durability of the metal thin film type media using the above-mentioned boron storage material varied widely and the reproducibility was poor. The present invention aims to improve the sliding resistance of the boron protective film described in 1. and to further improve its reproducibility.

[Means to solve the problem]

The object described in - is achieved by controlling the hydrogen content in the boron film to Q, 2 at% or less.

[Effect]

In order to investigate the cause of the variation in durability, elemental analysis of the protective film was conducted and it was found that it contained a large amount of hydrogen atoms. Therefore, we predicted that the cause of the above variation was due to hydrogen atoms, and as a result of preparing various boron protective films with different hydrogen contents and determining the sliding strength, we found that the sliding strength depends on the hydrogen content. This discovery led to the present invention.

These hydrogen atoms are generated when water vapor remaining in the vacuum chamber of a physical film forming device such as a vacuum evaporation device, sputtering device, or ion blating device is irradiated with an electron beam or plasma and decomposed into hydrogen and oxygen atoms. It is something.

When a boron film is formed under normal thin film formation conditions, hydrogen atoms are easily incorporated into the boron film because they easily combine with boron.

The reason why the strength of the film is improved by suppressing the hydrogen content in the boron protective film is not yet clear, but it is thought to be roughly as follows.

In order to have excellent anti-sliding properties as a protective film, it is necessary that the chemical bonds between boron atoms be strong, that is, in the boron film, the atoms must be strongly connected by covalent bonds. However, when hydrogen atoms enter the boron film, hydrogen atoms easily bond with boron atoms even at low temperatures, which inhibits the bonding between boron atoms. As a result, a region where bonds between boron atoms are weak is generated, and the mechanical strength of the boron film is thought to be reduced. Therefore, in order to improve the sliding properties, it is considered important to suppress the incorporation of hydrogen atoms into the boron film as much as possible.

Hereinafter, the details of the present invention will be explained with reference to examples.

〔Example〕

A magnetic recording medium was produced using a continuous winding vapor deposition apparatus shown in FIG. As the substrate 1, a tape-shaped polyimide film with a thickness of 50 μm was used. Set the surface temperature of roller 2 to 200
'C, evaporate Co-Cr alloy from the evaporation source 3, and deposit a perpendicularly magnetized ferromagnetic metal thin film of 0.2μTn Co-20μ and %Cr on the tape surface at a deposition rate of 200nm/s. Formed. Thereafter, boron was evaporated from the evaporation source 4 to form a boron protective film with a thickness of 20 nm on the surface of the Co-Cr film at a film speed of 10 nm/s. Taking advantage of the fact that pressure decreases over time, boron was deposited under various hydrogen partial pressure conditions to create boron protective films with different hydrogen contents. Note that this hydrogen is generated when water vapor contained in the residual gas is dissociated by an electron beam, and its partial pressure was measured using a mass spectrometer.

Table 1 summarizes the characteristics of the samples prepared in this way. Sample 1 has a hydrogen partial pressure of 1 X i 0-RTorr, Sample 2 has a hydrogen partial pressure of 2 X 10-9 Torr, and Sample 3 has a hydrogen partial pressure of 5 X 10 Torr.
- It was produced under the condition of 0 Torr. When the amount of hydrogen contained in these boron films was investigated using an IMA (ion microanalyzer), it was found to be 0.5 at% in atomic ratio for sample ]-, and 0.287% for sample 2.
It was found that Sample 3 contained 0 and 1 at%.

Next, sample 1. ．． Cut out 2.3 and make 3.5
A floppy disk of No. n was prepared, and the disk was run on a commercially available live device, and the number of times the disk was slid until the initial playback output value decreased by 2 dB was determined. The results are shown in Table 1. As is clear from this table, it can be seen that as the amount of hydrogen contained in the boron film decreases, the number of times of sliding increases, and the life of the Co--Cr film is extended. Especially when the hydrogen content is Q, 2a
It can be seen that when it is less than t%, the sliding strength is 2700 kpass, and characteristics without any practical problems can be obtained.

Table 1 Relationship between hydrogen content and sliding strength Furthermore, the amount of hydrogen atoms contained in a boron film can be controlled by the substrate temperature during vapor deposition, as described in the blowing example. be.

[Example 2] A magnetic recording medium was produced in the same manner as in Example 1, except that the hydrogen partial pressure during coboron evaporation was 8 x 10-'Torr and the substrate temperature was varied. At this time, in order to arbitrarily adjust the substrate temperature during boron vapor deposition, an infrared lamp 6 was irradiated toward the vapor deposition surface. By changing the irradiation power of the lamp, boron films were formed at various deposition temperatures.

Sample 4 was irradiated with an infrared lamp of 100 W and a temperature of 270°C.
For sample 5, a boron film was deposited at 200 W at 320° C., and for comparison, sample 6 was deposited at 200° C. without irradiation with an infrared lamp. The advantage of this method is that the temperature drops only at the moment of vapor deposition, which reduces the thermal burden on the organic polymer film that is the substrate.

The amount of hydrogen contained in the boron films of Samples 4 and 5.6 and the anti-sliding properties were investigated using the same method as in Example 1, and the results are shown in Table 2.

Table 2 Relationship between hydrogen content and sliding strength As can be seen from Table 2, even under conditions where the hydrogen partial pressure during boron evaporation is relatively high at 8X10-', the hydrogen content can be reduced by increasing the substrate temperature. It is possible to improve the sliding strength.

Using the results of Examples 1 and 2, the relationship between the hydrogen content in the boron film and the sliding strength is summarized in FIG.

Regardless of the boron film fabrication conditions, the hydrogen content is 0.2at.
% or less, it has been shown that excellent sliding strength exceeding 3000 kpass can be obtained.

The above examples have shown that the sliding strength can be significantly improved by reducing the hydrogen content in the boron film. In addition, the metal thin film serving as the recording layer may be a Co--based vapor deposited film, a Co-Nj sputtered film for in-plane recording, or a Go-Pt film.
It has also been confirmed that in the case of a sputtered film, a similar effect can be obtained by covering the surface with the protective film.

〔Effect of the invention〕

As is clear from the above examples, by using a boron film with a low hydrogen content as a protective film, it is possible to obtain a metal thin film type medium with excellent anti-sliding characteristics with good reproducibility. In particular, by reducing the hydrogen content to 0.2 atomic% or less, there is no problem in practical use.3, OO0k
It is possible to obtain sliding strength greater than pass.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the continuous vapor deposition apparatus used in the present invention, and FIG.
The figure shows the relationship between hydrogen content in a boron film and sliding strength. 1...Substrate, 2...Rotating roller, 3...Co-C
r evaporation source, 4...■3 evaporation source, 5...electron gun, 6.
...Infrared lamp.

Claims (1)

[Claims] 1. A magnetic recording medium having a boron protective film on a ferromagnetic metal film serving as a recording layer, characterized in that the concentration of hydrogen atoms contained in the protective film is 0.2 atomic % or less. .