JPH0271422A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a protective film having an excellent sliding characteristic by providing an amorphous carbon layer having <=30% molar concn. of the hydrogen bonded to carbon atoms in the film onto a recording layer consisting of a thin film magnetic material. CONSTITUTION:There is an underlying layer B on a substrate A and there are further, an intermediate layer C and the recording layer D thereon. The protective layer E is formed thereon. Gaseous methane is introduced into a vacuum chamber and plasma discharge is generated in the chamber by a high-frequency power source. The protective film E is deposited on the substrate cooled by cooling water. The molar concn. of the hydrogen bonded to the carbon atom in the protective film is confined to <=(25 to 30) in this case, by which the random and dense crosslinking of the carbons with each other is formed. The protective film having the excellent sliding characteristic is obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium having a protective film with excellent sliding properties, particularly wear resistance. [Prior Art] Generally, a thin metal film is used as a recording layer. In magnetic recording media that
It is said that contact with the head occurs not only when starting and stopping, but also during high-speed rotation. Therefore, magnetic recording media have sliding properties such as sufficient lubricity and wear resistance.
It must be able to withstand contact with magnetic elements.

For these reasons, research and development on carbon, especially diamond-like carbon films, with excellent sliding properties has become active in recent years. Among them, the film quality of the diamond-like carbon film, especially the hydrogen in the film and the friction coefficient, which is one of the sliding characteristics, were qualitatively discussed in the proceedings of the 34th Applied Physics Association Conference, p. 29-1. It is being Also, JP-A-62-784
8 also qualitatively discusses hydrogen in the film, focusing on its adhesion.

[Problem to be solved by the invention]

The above-mentioned conventional techniques have not yet found a film quality that exhibits optimal sliding characteristics. Therefore, there is a possibility that optimal conditions may not be found.

In the present invention, by understanding the carbon film quality from the hydrogen bonded in the film and the Raman spectrum in a constant and comprehensive manner, and linking this to the sliding properties, we are able to ensure that the carbon film quality is used as a protective film with the best sliding properties. The purpose is to obtain a magnetic recording medium having a carbon film.

[Means to solve the problem]

In order to achieve the above object, the present invention separates the molar concentration of hydrogen bonded to carbon in a film (hereinafter referred to as bonded hydrogen in the film) and the Raman spectrum of the film into two peaks. This specifies the intensity ratio of each component. It has been found that this ensures that a protective film with excellent sliding properties can be obtained.

Note that the term "hydrogen bonded in the film" as used herein refers to all hydrogen bonded to carbon atoms, and the bonding mode is not specified. The bonded hydrogen concentration [H] is C in the infrared absorption spectrum.
-H It is determined by the time formula from the integrated intensity S of the band caused by stretching vibration and the density ρ of the film.

[+11 = 100S/((1,68X 105)ρ
+0.9165) Furthermore, the intensity ratio of each component of the Raman spectrum separated into two peaks is determined as follows. That is, Ar+ laser (514,5 nm
) was used to measure the Raman spectrum of the protective film, with peak positions around 1350 am-1 and 1540 am-1
Near I-1 (each peak position shows a fluctuation of ±IO mark-1).

Furthermore, the half width of the former is separated by a Gaussian function that is approximately twice that of the latter. At this time, the range is defined as I, which is the ratio of the former intensity to the latter intensity. However, this is limited to cases where no fluorescence appears in the spectrum. - An example is shown in FIG. Further, the carbon film of the present invention can be created by the method described below. Namely, reactive sputtering involves sputtering a graphite target with a gas containing hydrogen; plasma CVD, which generates plasma using various power supplies (microwaves, radio frequency, etc.) and decomposes gas containing carbon to form a film; Alternatively, there is an ion beam deposition method in which carbon ions generated in an ion gun are drawn out by applying a voltage to form a film.

[Effect]

When the molar degree of hydrogen bonded to carbon atoms in the film according to the present invention is 25% or less and no fluorescence is observed in the Raman spectrum (by argon laser excitation), the Raman spectrum is converted to 2 by Gaussian function. When separated into two peaks, the experimental results show that excellent sliding properties can be obtained in an amorphous carbon film where the ratio of the intensity of the component around 1350an-' to the intensity of the component around 1540an-1 is 55% or less. I found out. On the other hand, when the hydrogen concentration is higher than 25%, the film becomes organic, and the degree of cross-linking between carbon atoms is considered to be low, resulting in a mechanically weak film. According to the experimental results (FIG. 3), the critical value of bound hydrogen in the film was 25-30% when the relative wear amount did not exceed 8.

In addition, Raman spectra are used as a means to understand the state of the skeletal structure between carbons, which is difficult to understand from hydrogen concentration alone, and it is known that as the intensity ratio of the two peaks increases, the structure approaches that of graphite. . In this case as well, experiments have shown that the critical value of the strength ratio at which the relative wear amount does not exceed 8 is 55-60% (see FIG. 3). For the above reasons, carbon films outside the specified range of the present invention have poor sliding properties. In contrast, in the protective film of the present invention, excellent sliding properties are obtained due to random and dense cross-linking between carbon atoms.

On the other hand, if the thickness of the protective film is less than 50, there is a high probability that the film will not be formed in an island shape and will be discontinuous, and the effect will be small. On the other hand, if it is thicker than 1,000 mm, the distance between the magnetic head and the recording layer increases, which deteriorates the electromagnetic conversion characteristics, which is not preferable. For these reasons, the thickness of the protective layer is preferably in the range of 50 to 1000 layers.

〔Example〕

Examples and comparative examples of the present invention will be described below. In each case, a carbon film was formed on a metal thin film magnetic disk having a similar structure, and evaluation was performed using the following method.

That is, the amount of wear and coefficient of dynamic friction were measured by a pin-on-disk test in which the sample was rotated at a circumferential speed of 4 m/sec.
top) The sliding characteristics were evaluated by a test. The molar degree of hydrogen bonded to carbon was determined from FT-IR (Fourier transform infrared absorption spectrum) measurement. In addition, 411 Raman spectra were determined.

Example 1 FIG. 1 is a schematic diagram showing a cut surface of a magnetic disk. As shown in the figure, there is a base layer NB on top of the substrate A, and further thereon there is a middle layer 7flC. There is a recording layer on top of C/Lf, and a protective layer E is formed on this.

The substrate A is made of aluminum, the base MB is made of nickel-phosphorus, the intermediate layer C is made of chromium, and the recording layer is made of cobalt-nickel. However, layers A to D may be made of different materials.

The protective film was created by high frequency plasma CVD method. The creation method will be described below. First, the inside of the vacuum chamber is evacuated to LXIO-'Torr using a vacuum pump. Next, methane gas is introduced and the internal pressure of the vacuum chamber is adjusted to 60 m Torr. and 13
．． A 56 MHz high frequency power supply supplies 500 W to generate plasma discharge within the chamber. At this time, a protective film is deposited on the substrate cooled by the cooling water. When the film quality was evaluated using FT-IR and Raman spectra, the FT-IR showed that the concentration of bonded hydrogen in the film was 15%, and the Raman spectrum showed a separated peak near 1540 Cm-', which is the intensity of the separated peak near 1350 CIl+'. The ratio of this to the strength was 45%. In addition, C8s of this film
When I tested it, it crashed at 35 times and pinned.
Relative on-disc wear was 5.

Example 2 A carbon film was formed on the same magnetic disk as in Example 1 by the ion beam deposition method. After evacuating the inside of the vacuum chamber to 5 x 10-7 Torr, a mixed gas of methane and hydrogen is introduced, and the gas pressure is set to 1 mTorr. Next, a plasma discharge is generated inside the ion gun, and 3
A film was formed by applying an extraction voltage of 0.00 V to extract ions. When the film quality was evaluated using FT-IR and Raman spectra in the same manner as in Example 1, the bonded hydrogen concentration in the film was 1.
At 0%, the intensity of the separated peak near 135°■-1 is 15%
The ratio of the separated peak near 40 an-'' to the intensity was 40%.

Further, when this film was subjected to a C8S test, it crashed in 40 cycles, and the relative wear amount due to pin-on-disk was 3. In addition, although only magnetic disks were described in the examples, flexible disks, magnetic tapes,
It is clear that magnetic cards have a similar effect.

Comparative Example 1 A carbon film was formed on the same magnetic disk as in Examples 1 and 2 except for the carbon layer by high-frequency plasma CVD. Almost the same as Example 1, except that the RF high output was 50W.
A film was formed after drying. When the film quality was evaluated in the same manner as in Examples 1 and 2, the bonded hydrogen concentration in the film was 30%, 1350a.
The ratio of the intensity of the separated peak near 1540an-1 to the intensity of the separated peak near 1540an-1 was 35%.

Further, when this film was subjected to a CSS test, it crashed in 13 cycles, and the relative wear amount due to pin-on-disk was 15.

Comparative Example 2 D was placed on the same magnetic disk as in Examples 1 and 2 except for the carbon layer.
A carbon film was created by C-macnetron sputtering.

First, the inside of the vacuum chamber was evacuated to I×10 −' Torr, then argon gas of 20 mTorr was introduced therein, IKW was turned on using a DC power source to generate plasma, and a graphite target was sputtered to form a film. When the membrane quality was evaluated in the same manner as in Examples 1 and 2, the concentration of bound hydrogen in the membrane was 3%, and the ratio of the intensity of the separated peak near 1350 ゛ to the intensity of the separated peak near 1540 ゛ was 85%. It became. In addition, C8S of this film
When we tested it, it crashed after 8 turns, and the bin-on-disc crash occurred, and the amount of wear was ill.
! I couldn't get it fixed.

Margin Table Below [Effects of the Invention] According to the present invention, as is clear from the above results, a magnetic recording medium having excellent sliding properties, particularly excellent wear resistance, can be obtained.

In addition, feedback on film formation conditions can be provided through non-destructive evaluation.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of the magnetic recording medium of the present invention. FIG. 2 is an example of peak separation of a Raman spectrum of an amorphous carbon film. No. 31A shows the relationship between film quality (concentration of bonded hydrogen in the film, intensity ratio of separated peaks in the Raman spectrum) and the amount of wear. A...Substrate, B...Underlayer. C...Intermediate layer, D...Recording layer, E...
protective layer. % ■ Figure

Claims (1)

[Claims] 1. An amorphous carbon layer in which the molar concentration of hydrogen bonded to carbon atoms in the film is 30% or less is provided on the recording layer made of a thin magnetic material. magnetic recording medium. 2. On the recording layer made of thin film magnetic material, 1000 to 200
When no fluorescence is seen in the Raman spectrum (due to argon laser excitation) around 0 cm^-^1, when the Raman spectrum is separated into two peaks using a Gaussian function,
1540cm^1 of the intensity of the component near 1350cm^1
1. A magnetic recording medium comprising a filmy amorphous carbon layer having a ratio of intensity to nearby components of 60% or less. 3. A magnetic recording medium characterized in that an amorphous carbon layer having a film quality that satisfies the characteristics of claims 1 and 2 at the same time is provided on a recording layer made of a thin film magnetic material. 4. The magnetic recording medium according to claim 1, 2, or 3, wherein the thickness of the carbon protective film is 50 Å or more and 1000 Å or less. 5. Claims 1, 2, 3, on the recording layer made of a thin film magnetic material.
Or the method of creating an amorphous carbon layer according to 4 by an ion beam deposition method. 6. Claims 1, 2, 3, on the recording layer made of a thin film magnetic material.
Or the method of creating the amorphous carbon layer according to 4 by a reactive sputtering method. 7. Claims 1, 2, 3, on the recording layer made of a thin film magnetic material.
Or the method of creating the amorphous carbon layer according to 4 by plasma CVD method. 8. A magnetic recording medium in which an amorphous carbon film is formed by the method according to claim 5, 6, or 7. 9. A magnetic disk device comprising the magnetic disk according to claim 1, 2, 3, or 4. 10. A hard protective film comprising the amorphous carbon layer according to claim 1, 2, or 3.