JPH02137113A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the increase of coefft. of friction by incorporating an element of group 0 of periodic table at >=1 atomic% into a carbonaceous protective layer. CONSTITUTION:The element (rare gas) of the group 0 of periodic table is incorporated at >=1 atomic% into the carbonaceous protective layer of the magnetic recording medium constituted by forming a thin-film magnetic layer and the carbonaceous protective layer on a nonmagnetic substrate. The wear rate of the carbon film is high in the sliding process with a head in contact start-stop (CSS) tests if the content of the rare gas is below 1 atomic%. Worn powder is then observed and the disk is flawed after several thousand times of CSS. The magnetic layer is, therefore, damaged and the head crash is resulted. The increase of the coefft. of friction is prevented in this way and the carbonaceous protective layer is usable over a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and particularly to a thin film magnetic recording medium that has excellent durability under normal use conditions.

[Conventional technology]

Thin-film magnetic recording media are usually manufactured by depositing metals or their alloys on nonmagnetic substrates by coating, plating, vacuum evaporation, sputtering, or the like. During actual use, the magnetic head is subject to wear and tear due to physical contact, ie, sliding, between the magnetic head and the magnetic recording medium. As a result, a number of defects occur, such as an increase in torque due to an increase in the coefficient of friction and so-called squealing.

Moreover, the magnetic properties may also deteriorate.

As a method for solving the above-mentioned defects, it has been proposed and implemented to provide a protective layer on the magnetic layer. In general, wear largely depends on the applied external force and the mechanical properties of the materials that slide against each other. Conventional protective films can be roughly divided into (1) carbonaceous films, (2) modification of carbonaceous films, such as fluorination including plasma polymerization, and (3) carbonaceous films.
Examples include films other than carbonaceous films, such as oxide films, nitride films, and fertilized films.

The carbonaceous film (1) has a wide range of structures and physical properties, ranging from diamond-like thin films to amorphous thin films, and Vickers hardness ranging from several hundred to several thousand. The structure and physical properties of these films are clearly dependent on the manufacturing method. For example, in the case of diamond-like carbon films, ion beam evaporation, arc discharge, and plasma CVD are most often used. However, in view of damage to the magnetic layer during film formation, it is not preferable to apply high energy (several hundred eV or more) or to raise the temperature of the magnetic layer too much during film formation, as this will deteriorate the magnetic properties.

Furthermore, from an economic standpoint, it is not a good idea to form the protective film using a method completely different from that for forming the magnetic layer. On the other hand, an amorphous carbon film is manufactured by a plasma CVD method using hydrocarbon gas or a sputtering method using argon gas plasma using graphite as a target. Depending on the manufacturing conditions, some graphite microcrystalline phase may be observed, or s
Although the presence of a p3 structure is seen, these are basically amorphous, and strictly speaking, they are hydrogenated amorphous carbon films in the plasma CVD method. As described above, the structure and physical properties of a carbonaceous film can be changed depending on the manufacturing method and manufacturing conditions, which is one of the reasons why it is used as a protective film.

The modification of the carbonaceous film (2) is carried out by using a plasma polymerization method, a snog-vine method using a Teflon target, or surface treatment by reaction decomposition with a process gas such as CF4. There is.

The purpose of this is to obtain physical properties that cannot be obtained with ordinary carbonaceous membranes, such as improving water repellency.

There are many reports regarding (3) non-carbonaceous films, and the manufacturing methods include sintering after coating, plasma CVD, etc.
There are a wide range of methods including sputtering method, sputtering method, and reactive sputtering method. The purpose of this is to improve the adhesion with the magnetic layer even more than a carbonaceous film, to easily create a film with higher hardness than a carbonaceous film, and to improve wear by improving oxidation resistance. It is in.

[Problem to be solved by the invention]

When a magnetic recording medium is used, the disk is rapidly accelerated from a stopped state, and as a result, buoyancy is applied to the flying head, causing the head to float. After use, the power to the motor that rotates the magnetic recording medium is turned off, and the head and the magnetic recording medium come into physical contact. A test to check durability by frequently causing such an operation is called contact start/stop (hereinafter abbreviated as C8S). In this C8S test, with conventional magnetic recording media, the friction coefficient increases as the number of C8S cycles increases, and the drive motor stops or the head collides with the protective film within a few thousand cycles. This can cause a phenomenon called head crash that destroys the protective film.

The present invention has been made in order to solve the above-mentioned problems, and aims to prevent a significant increase in the coefficient of friction and to obtain a magnetic recording medium that can be used for many years.

[Means to solve the problem]

The gist of the present invention is to provide a magnetic recording medium comprising a thin magnetic layer and a carbonaceous protective layer formed on a non-magnetic substrate, in which the carbonaceous protective layer contains 1 atom or more of an element of Group 0 of the periodic table. A magnetic recording medium characterized by:

The present invention will be described in detail below. In the present invention, an element of group Q of the periodic table (hereinafter referred to as rare gas) is incorporated into a carbonaceous film which is a protective layer of a magnetic recording medium. Features.

Examples of rare gases include helium, neon, argon, krypton, xenon, and radon.

However, helium is a light element and has a small atomic radius, resulting in low sputtering efficiency, and radon is a radioactive element with a short half-life, making it difficult to handle. Of the remaining elements, argon is the most preferred from an industrial standpoint since it is inexpensive.

The content of rare gas needs to be 7 atoms or more in the carbonaceous film. At less than 1 atomic ratio, the carbon film wears out at a high rate during the sliding process with the head in the C8S test, and after several thousand C8S tests, wear particles were observed and the disk was scratched. This may damage the magnetic layer or cause a head crash. In addition, in order to further improve long-term durability, it is preferable to set the content of the rare gas to be at least the s-atomic ratio, preferably at least the co-atom ratio. gender tends to improve.

There are several possible methods for incorporating a rare gas into a carbonaceous film, but they can be roughly divided into (A) a method of incorporating a rare gas while forming a carbonaceous film, and (B) a method of containing a rare gas after forming a carbonaceous film. It can be divided into two methods: injecting rare gas into it. (A
) may be a plasma CVD method, a sputtering method, an evaporation method, an ion beam evaporation method, or the like. Specifically, in the case of the plasma CVD method, a rare gas is diluted in a hydrocarbon gas and simultaneously ionized in the plasma.
A method is to make the magnetic layer side electrically negative and attract positive ions of a rare gas, or a separate method is to electrically accelerate rare gas ions from an ion gaff to the carbonaceous film being formed on the magnetic layer. Examples include a method of hitting the target. In the case of sputtering, there is a method in which rare gas ions used in sputtering are actively incorporated into the carbonaceous film by intentionally lowering the potential of the carbonaceous film relative to the ions. In the case of the vapor deposition method and the ion beam evaporation method, similarly, a method of generating rare gas plasma and drawing some of the ions into the carbonaceous film, and a method of supplying the rare gas from an ion source and injecting it into the carbonaceous film. etc.

On the other hand, the method (B) includes so-called ion implantation methods and similar methods.

Here, the argon concentration in the carbonaceous film can be determined by Rutherford backscattering (R, BS) method. Specifically, by forming a carbonaceous film on a substrate of known density, such as a silicon single crystal, and comparing the edge heights of peaks derived from each atom that appear on the RBS spectrum, the atoms of each element can be determined. Calculate the density. Equation (1) gives the edge height of the peak of the RBS spectrum of element A.

HA=6hΩQN t/ cosθA − (1) where HA is the height of the peak, 0 is the scattering cross section, Ω is the solid angle of the detector, Q is the ion dose, N is the atomic density, and t is the film thickness. , θm is the backscattering angle. Further, the ratio of the atomic densities of elements A and B is expressed by the formula (II) % Formula % ([) Element B is a sample whose density is known, and the present inventors used a silicon single crystal.

Another method is to use fluorescent X-ray analysis to compare the X-ray intensity of an unknown sample and a standard argon sample (injected with a fixed amount of argon ions using an ion implantation device) to determine the absolute amount of argon in the film. The argon concentration can also be determined from this value and the density of the film. Both results agree well.

Further, in the present invention, the hardness of the carbonaceous film is iooθK
The zero hardness is preferably greater than or equal to y f /-.
If it is less than OoKqf /mA, the head tends to be easily scratched, the wear rate increases, and the wear resistance tends to decrease.

Furthermore, the carbonaceous film is required not only to have wear resistance in order to function as a protective layer, but also to have corrosion resistance in order to protect the magnetic layer from oxidation. A low-density carbon film has poor corrosion resistance, and in order to block gases such as water vapor that oxidize the magnetic layer, it is desirable that the carbon film be dense and dense. In the present invention, the density of the carbonaceous film is preferably equal to or higher than qzt/air. If the density is less than qrv/aA, deterioration of the magnetic layer may occur.

In the present invention, as the non-magnetic substrate, for example, non-magnetic metals such as aluminum alloys and magnesium alloys, synthetic resins such as polysulfone, ceramics, glass, etc., which are commonly used as substrates for magnetic recording media, can be used.

Although a thin magnetic layer is formed on these nonmagnetic substrates, a thin film of a nonmagnetic metal such as nickel phosphide may be formed prior to this.

The thin film magnetic layer is formed by depositing a ferromagnetic metal such as a cobalt alloy or an iron alloy onto a substrate by a known method such as electroless plating or sputtering.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited by the Examples unless the gist thereof is exceeded.

A graphite target was used on a magnetic disk with a diameter of 3.3 inches on which a magnetic thin film was formed, in an argon atmosphere, at a film-forming pressure of &mTorr, and at a power density of 3.7 W/crA applied to the target, and the negative potential applied to the substrate side was set to 0.
Thicknesses with different argon contents were formed by direct magnetron sputtering by varying the range from -1sov to θnm.
A carbonaceous protective layer was formed.

Using the obtained magnetic disk, cssf-'<p was performed. The C8S cycle rotates the disc by 360 Orp.
The friction coefficient between the head and disk exceeds l, or the friction coefficient between the head and disk exceeds l, or the head or disk We investigated the number of C8S cycles until scratches or dirt appeared on the surface. A thin film head with a slider of Al2O, .TiC was used, and the pressing test was conducted at a load/jg. In addition, no lubricant was applied on the protective film.The results are shown in Table 1. For example, if the argon content in the carbonaceous protective layer is 0.2 atoms, the C8S cycle is 5ooo
The friction coefficient exceeded 1 after 100 times, and the head crashed after 100 times.

Example S - A magnetic disk having a carbonaceous protective film with a different argon concentration by increasing or decreasing the negative potential applied to the substrate side by high-frequency magnetron sputtering on a magnetic disk on which the same cobalt alloy thin film as in Example 1 was formed. was prepared and a C8S test was conducted.

Negative potential range from -20 to -10OV, film forming pressure &mT
orr, power density applied to the target 2, 3 W
/crtl, and the other conditions were the same as in Example 1. The results are shown in Table 2.

Examples g to 10 and Comparative Example D A carbonaceous protective film with a different argon concentration was formed on a magnetic disk on which the same cobalt alloy thin film as in Example 1 was formed by applying high frequency power to the substrate side using a DC magnetron method. A magnetic disk having the following characteristics was prepared and a C8S test was conducted.The conditions of high frequency power ranged from 3 to SOW, film thickness, film forming pressure, power density applied to the target, etc. were as in Example 1.
I did it in the same way. The results are shown in Table 3.0 Example// Argon ions were implanted by ion implantation into a protective film formed in the same manner as in Example/ with an incident energy of II OkeV and an implantation amount of 1xior' ions/-. I typed it in. The argon content in the film was about λ atoms. A C8S test was conducted using the obtained magnetic disk. This membrane withstood up to 20,000 C8S cycles.Example/2 and Comparative Examples 3-6 Except that the atmosphere was xenon instead of argon and the negative potential range was from -20 to -gov. conducted a C8S test on a magnetic disk having a carbonaceous protective film manufactured by the same method as in Example 1. The results are shown in Table 4.

Table 1 Reference Example On a silicon wafer (100) with a diameter of 3.0 inches,
In an argon atmosphere, using a graphite target at a film formation pressure and a power density of 3.7 W/crtl applied to the mTorr target, the negative potential applied to the substrate side was varied in the range of -20 to -100 V, and the argon was sputtered by direct current magnetron sputtering. Carbon films with different contents were formed.

Table 3 shows the measurement results of the Knoop hardness, internal stress, and density of the obtained carbonaceous film.

Knoop hardness is JIS Z except that the load is 2f.
It was measured based on the microhardness test method of 22r/.

The internal stress was determined by measuring the warpage at the center of the silicon wafer before and after forming the carbonaceous film using a wafer stress gauge manufactured by Ionic Systems, and from the amount of displacement using the following formula.

(In the formula, Σ is the internal stress (dyn/ca), d is the displacement at the center of the silicon wafer, r is the silicon wafer radius NE, E8 is the Young's modulus of silicon, υ is Poisson's ratio of silicon, and Ts is the silicon wafer's Thickness, Tf
O) indicates the thickness of the carbonaceous film.If the argon content in the carbonaceous film is less than /atom, the hardness is insufficient, and if the argon content is more than latom, the inside of the carbonaceous film will be damaged. It can be seen that the stress increases and the density also increases. The reason for this is unknown, but it is thought to be as follows.

Argon atoms with high energy collide with the carbonaceous film being formed, which densifies the film that is being formed. Compressive stress in the film also increases due to the intrusion of argon into the film and the reduction in the distance between carbon atoms due to densification. It is recognized that bulk materials become harder as compressive stress increases, and this sample also seems to have become harder as compressive stress increases. It is generally recognized that hardening is effective in improving wear resistance, and hardening the carbon film is considered to be one of the reasons why the present invention is effective.

〔Effect of the invention〕

The problems to be solved by the present invention can also be solved by other methods. For example, there is a method of roughening the surface of a magnetic recording medium.However, considering higher recording density, it is desirable to lower the flying distance between the flying head and the magnetic recording medium, and the method of roughening the surface of the magnetic recording medium is This is not desirable as it goes against this direction. Another method is to apply a suitable lubricant over the protective film. However, depending on the lubricant,
On the contrary, it may accelerate the increase in the coefficient of friction.Even if a good lubricant is selected, the life of the lubricant also depends on the protective film, and a high-quality protective film is still desired. 0 According to the present invention, it is possible to prevent a significant increase in the coefficient of friction. A small increase in the coefficient of friction means that there are fewer physical and chemical changes due to sliding between the head and magnetic recording medium, which improves not only wear durability but also
This means that the durability against the environment is also good, and the present invention can provide a highly reliable magnetic recording medium.

Procedural amendment (voluntary) September 2, 1999 1 Case indication 1986 patent W! i No. 290850 2 Name of the invention Magnetic recording medium 3 Amendment applicant Applicant (596) Mitsubishi Kasei Corporation 4th generation
Director 2-5-2-5 Marunouchi, Chiyoda-ku, Tokyo 100 Column 6 of “Detailed Description of the Invention” of the specification to be amended Contents of the amendment

Claims (1)

[Claims] (1) In a magnetic recording medium formed by forming a thin film magnetic layer and a carbonaceous protective layer on a nonmagnetic substrate, the carbonaceous protective layer contains 1 atomic % or more of an element of Group 0 of the periodic table. A magnetic recording medium characterized by: