JPH05174368A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide the magnetic recording medium which has the good adhesion of a protective film to a magnetic recording layer, surface smoothness and wear resistance, has excellent corrosion resistance of the magnetic recording layer and can decrease the damage of a magnetic head. CONSTITUTION:The main parts of the magnetic recording medium are constituted of a substrate 1 consisting of an aluminum alloy, a hardening treated film 2 consisting of an Ni-P alloy, the magnetic recording layer 3 consisting of CoCrTa, and the protective film 4 consisting of amorphous carbon which is formed by a DC sputtering method set with low sputtering conditions and is disorderly arranged with amorphous graphite in amorphous diamond. A lubricating layer 5 is formed on this protective film 4. The above-mentioned amorphous carbon film constituting the protective film 3 exhibits the intermediate properties of the carbon films formed respectively by the conventional DC sputtering method and DVD method and has the excellent film characteristics, such as the above-mentioned adhesion, surface smoothness, wear resistance and corrosion resistance.

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 provided with a protective film on a magnetic recording layer, and particularly, the protective film has good adhesion to the magnetic recording layer, surface smoothness and abrasion resistance. In addition, the present invention relates to an improvement in a magnetic recording medium which is excellent in corrosion resistance of the magnetic recording layer and can reduce damage to the magnetic head due to contact.

[0002]

2. Description of the Related Art Among external storage devices in information processing systems, the CSS method (contact start and
A magnetic recording medium applied to a magnetic disk device or the like adopting a (stop system) is liable to be worn or damaged on the medium surface because the magnetic recording medium and the magnetic head surface contact each other during operation.

In addition, it is known that in a magnetic recording medium in which a metal magnetic thin film is applied to the magnetic recording layer, the magnetic recording layer is likely to be corroded depending on the installation environment and handling condition of the storage device.

Therefore, in the past, a carbon film, an S
iO ₂ film, SiN film, SiAlON film, and ZrO ₂
A protective film composed of a film or the like is formed on the magnetic recording layer to prevent abrasion or damage on the surface of the magnetic recording medium and corrosion of the magnetic recording layer. It is widely practiced to apply a fluorocarbon-based lubricant to the protective film to provide a lubricating layer for the purpose of improving wear resistance.

Among the material groups, the carbon film is widely used because it has excellent adhesion to the magnetic recording layer and absorption of lubricant as compared with other material films.
And the development is being actively done.

By the way, as a means for forming this carbon film, conventionally, a DC sputtering method has been used in which a gas pressure and a sputtering power are set to be high by using a carbon target, a mixed gas of hydrocarbon such as methane and hydrogen, and argon. A CVD (Chemical Vapor Deposition) method of forming a film using gas is applied.

[0007]

However, the carbon film formed by the DC sputtering method in which the gas pressure and the sputtering power are set to be high is 700 to 700 in Vickers hardness.
There is a drawback that the amorphous graphite structure of about 1000 is apt to occur and the hardness of the disk varies greatly, and
In many cases, protrusion-like growths were observed in the vicinity of the polishing streaks on the polished disk substrate, and the surface smoothness was poor and the compactness was poor. Therefore, there is a problem that corrosion of the magnetic recording layer easily occurs.
In the method, when the flying height of the magnetic head is set to be low, there is a problem that the head and the above-mentioned protrusion-shaped growth material are likely to collide with each other and the wear resistance thereof is rapidly deteriorated.

On the other hand, the carbon film formed by the CVD method has a Vickers hardness of usually 1500 or more, and has a good wear resistance, and the above-mentioned protrusion-shaped growth product is larger than that by the DC sputtering method. Is small and the surface smoothness is good, so that the flying height of the magnetic head can be set low. However, due to its high hardness, there is a problem that the magnetic head is easily damaged when the magnetic head slider and the carbon film come into contact with each other, and the film stress is larger than that of the carbon film formed by the DC sputtering method. Therefore, the adhesion to the magnetic recording layer is slightly inferior, and the carbon film is partially peeled off due to contact with the magnetic head, and the debris is present between the magnetic head and the magnetic recording medium, causing rapid wear of the magnetic recording medium. There was a problem that would end up.

The present invention has been made by paying attention to such problems, and its problem is that the adhesion, surface smoothness, and abrasion resistance of the carbon protective film to the magnetic recording layer are good. Another object of the present invention is to provide a magnetic recording medium which is excellent in corrosion resistance of the magnetic recording layer and in which damage to the magnetic head due to contact can be reduced.

[0010]

That is, the invention according to claim 1 is premised on a magnetic recording medium having a magnetic recording layer and a protective film provided on the magnetic recording layer, wherein the protective film is formed by a sputtering method. And an amorphous carbon film in which amorphous graphite is randomly arranged in the amorphous diamond. The invention according to claim 2 is characterized in that Based on the invention of Item 1, the Raman spectrum of the amorphous carbon film obtained by Raman scattering spectroscopy has a Raman shift of 1
It has peaks at 550 to 1620 cm ^-1 and 1340 to 1390 cm ^-1 , and its peak intensity ratio (1340-1
390cm ^-1 / 1550~1620cm ^-1) with is 0.3 or less, the half-value width of the peak of the high frequency side 40
It is characterized by being 0 to 500 m ⁻¹ .

By such a technical means, the amorphous carbon film having the Raman spectrum specified in the invention according to claim 2 has a structure in which amorphous graphite is randomly arranged in amorphous diamond. ing.

In order to form an amorphous carbon film having such a structure, a sputtering method such as DC sputtering, RF (high frequency) sputtering or ion beam sputtering is applied, and This can be achieved by setting the gas pressure at the time of film formation to be lower than usual and also setting the sputtering power at a lower value, and further maintaining the disk substrate temperature at the time of film formation of the carbon film at about 200 to 300 ° C. That is, in the case of manufacturing a magnetic recording medium, usually, a method of preheating a disk substrate to about 300 ° C. and then sequentially laminating an underlayer, a magnetic recording layer, a protective film, etc. for adjusting magnetic characteristics is adopted. Therefore, the disk substrate temperature is slightly cooled when the protective film is formed. On the other hand, in this technical means, since the secondary heat treatment is performed again before forming the magnetic recording layer, the temperature of the disk substrate during the formation of the protective film is kept at about 200 to 300 ° C.
By setting the gas pressure and sputtering power to low values under this heat-retaining condition and performing the sputtering process, the film characteristics of amorphous graphite in which amorphous graphite is randomly arranged (adhesion to the magnetic recording layer, surface smoothness) It is possible to form an amorphous carbon film having excellent properties, abrasion resistance, and corrosion resistance).

For the disk substrate of the magnetic recording medium, the same materials as in the prior art can be applied. For example, those used as magnetic disks have a circular shape made of aluminum, aluminum alloy, ceramics, hard plastic or the like. It is possible to apply the plate material described above, or a material in which a coating film of Ni-P alloy, Ni-Cu-P alloy or the like is formed on the surface by electroless plating and the surface of the plate material is cured. As is well known, the hardened plate material is subjected to a so-called roughening process using a polishing tape or a polishing liquid to make substantially concentric scratches in the circumferential direction of the plate material. Further, as the recording material constituting the magnetic recording layer, γ-
Sputtered film made of Fe ₂ O ₃ , Co-based, Co
Ni-based, CoNiCr-based, CoPt-based, CoCrTa
A conventional material such as a sputtered film, a Fe-based sputtered film, a vapor-deposited film, a plated film can be applied, and a film such as Cr or a Cr alloy may be provided as an underlayer to adjust the magnetic characteristics. Further, as a lubricant for improving the wear resistance of the protective film, a fluorocarbon material or the like can be applied as in the conventional case.

[0014]

According to the present invention, the protective film for protecting the magnetic recording layer is formed by the sputtering method, and the amorphous graphite has a structure in which amorphous graphite is randomly arranged. It is composed of a carbon film.

The amorphous carbon protective film having such a structure includes a carbon protective film formed by DC sputtering in which gas pressure and sputtering power are set to be high and a carbon protective film formed by a CVD method. It has the intermediate characteristics of.

That is, the DC set under the above conditions
Excellent surface smoothness, abrasion resistance and compactness compared to carbon protective film formed by sputtering method, while C
Since the film hardness and the film stress are not so high as compared with the carbon protective film formed by the VD method, the head is less damaged due to contact with the magnetic head and the adhesion to the magnetic recording layer is excellent.

Therefore, the adhesion of the protective film to the magnetic recording layer, the surface smoothness, and the wear resistance can be improved, and the corrosion resistance of the magnetic recording layer can be dramatically improved. It is also possible to reduce damage to the magnetic head due to contact.

[0018]

EXAMPLES Examples in which the present invention is applied to a magnetic disk will be described in detail below.

As shown in FIG. 1, this magnetic disk has a substrate 1 made of an aluminum alloy (Mg: 4 parts by weight, Al: 96 parts by weight) and a film formed on the substrate 1 by electroless plating. The Ni—P alloy hardened film 2 and the CoCrTa magnetic recording layer 3 having a thickness of 300 Å formed by the DC magnetron sputtering method on the hardened film 2 via the underlayer (not shown) made of chromium. And a carbon protective film 4 formed on the magnetic recording layer 3 by a DC sputtering method, the main part of which is formed, and a lubricating layer 5 of perfluoropolyether is formed on the protective film 4. It consists of

[Example 1] Ni-P by electroless plating
A substrate 1 having a diameter of 3.5 inches and made of the above-mentioned aluminum alloy on which the alloy hardened film 2 is formed is subjected to lapping and polishing to obtain a surface roughness R _max (from the highest peak to the deepest within the reference length). A disk substrate having a surface roughness of 300 Å or less) was manufactured.

On the surface of the substrate 1 having this roughness, a polishing tape made by binding alumina abrasive grains having an average particle size of 6 μm on a polyester base film is pressed with a constant force to perform texture processing, and the surface roughness is obtained. R _tm about 550
Set to Å.

Next, the textured substrate 1 is set in a chamber of a DC sputtering apparatus, and the chamber is evacuated by a vacuum pump apparatus until the pressure in the chamber reaches about 10 ^-7 Torr. The substrate 1 was heated to 300 ° C. by the installed heater.

Then, on this substrate 1, the substrate temperature was 300 ° C. and the Ar gas pressure was 10 m by the DC sputtering method.
Torr, DC input power: thickness 50 under the condition of 5 W / cm ^2.
After forming an underlayer (not shown) for adjusting magnetic properties by depositing 0Å Cr, and heating the substrate 1 again by a heater to raise the substrate temperature to 300 ° C., the substrate 1
A bias voltage of (-150V) is applied between the sputtering target and the sputtering target, and CoCrTa with a thickness of 300Å is applied.
The magnetic recording layer 3 was formed.

Next, the substrate temperature is 200 to 300 ° C.
A magnetic disk was obtained by forming a carbon protective film 4 on the magnetic recording layer 3 by an RF sputtering method using an amorphous carbon target under the condition of being kept warm.

Regarding the sputtering conditions and the thickness of the protective film, as shown in Table 1, RF sputtering power: 0.
8 kW, argon gas pressure: 8 mTorr, film thickness: 350
It is Å.

FIG. 2 shows the Raman spectrum obtained by the Raman scattering spectroscopic analysis of the carbon protective film 4, and Table 1 shows the Raman shift of the Raman spectrum and its half-value width and peak intensity ratio data.

From these data, it was confirmed that the carbon protective film 4 had an amorphous carbon structure in which amorphous graphite was randomly arranged in amorphous diamond.

[Example 2] Except that a magnetic disk was obtained by forming a carbon protective film 4 of the same thickness shown in Table 1 under the DC sputtering conditions shown in Table 1 instead of the RF sputtering method. This is almost the same as in Example 1.

The Raman spectrum obtained by the Raman scattering spectroscopic analysis of the carbon protective film 4 is shown in FIG. 2, and the Raman shift of the Raman spectrum and the data of the half width and peak intensity ratio are shown in Table 1.

From these data, it was confirmed that the carbon protective film 4 had an amorphous carbon structure in which amorphous graphite was randomly arranged in amorphous diamond.

[Comparative Example 1] The substrate after the above underlayer was formed was not reheated (that is, the substrate temperature was 200 to 3).
Under the sputtering conditions (DC sputtering power: 7.0 kW, argon gas pressure: 15 mTorr) shown in Table 1 (without heating at 00 ° C.), the film thickness (3
70 Å) A carbon protective film was formed to obtain a magnetic disk, which is substantially the same as the embodiment.

The Raman spectrum obtained by the Raman scattering spectroscopic analysis of this carbon protective film is shown in FIG. 2, and the Raman shift of this Raman spectrum and the data of its half width and peak intensity ratio are shown in Table 1.

[Comparative Example 2] The CVD method was applied instead of the DC sputtering method as the film forming method, and the substrate was not reheated after the underlayer was formed (that is, the substrate temperature was 200 to 300 ° C). This example is substantially the same as the example except that a magnetic disk was obtained by forming a carbon protective film having the same film thickness as shown in Table 1 under the applicable gas and condition shown in Table 1 (without heating).

The Raman spectrum obtained by the Raman scattering spectroscopic analysis of this carbon protective film is shown in FIG. 2, and the Raman shift of the Raman spectrum and its half value width and peak intensity ratio data are shown in Table 1.

[Comparative Example 3] A SiO ₂ target was applied instead of the carbon target, and the substrate was not reheated after the underlayer was formed (that is, the substrate temperature was not kept at 200 to 300 ° C.). Under the sputtering conditions shown in Table 1, SiO ₂ having the same film thickness shown in Table 1
The procedure is substantially the same as that of the example except that a magnetic disk is obtained by forming a protective film.

Raman scattering spectroscopy analysis has not been performed on this SiO ₂ protective film.

[0037]

[Table 1] "Comparison Test" Next, various comparison tests as described below were performed on the magnetic disks according to the examples and the comparison examples.

(1) Dynamic friction coefficient test A protective layer of each magnetic disk was coated with 25 Å of perfluoropolyether (trade name, manufactured by Craytox, DuPont) by a spin coating method to form a lubricating layer, and this was applied to a rotary spindle. A thin film magnetic head (slider material: Al ₂ O ₃ .TiC, slider size: length 3.20) is set at a position with a radius of 20 mm on this magnetic disk.
mm, width: 2.66 mm, load: 7.2 g weight),
The magnetic disk was rotated at 1 rpm, and the dynamic friction coefficient of one revolution of each magnetic disk was evaluated.

The results are shown in Table 2.

(2) CSS Test Using the above thin film magnetic head, 0 rpm (that is, the thin film magnetic head is in contact with the magnetic disk surface)
→ 3600 rpm (that is, the thin film magnetic head is floating above the magnetic disk surface. In this test, the flying height is:
0.13 μm) → 0 rpm (that is, the thin film magnetic head returns from the flying state to the contact state again) in a cycle of 30 seconds to perform a CSS test (contact start and stop), and after starting Friction coefficient after 5000 times, friction coefficient after 20000 times, and 2000
After 0 times, the friction coefficient after standing for 48 hours was measured. The results are also shown in Table 2.

(3) Adsorption test Further, with the thin film magnetic head in contact with the surface of each magnetic disk, the temperature is 30 ° C. and the humidity is 80% RH.
After standing for 8 hours, the magnetic disk was rotated and the friction coefficient at the time of starting the magnetic disk, so-called adsorption force was measured.

The results are also shown in Table 2.

(4) Corrosion resistance test Similarly, each magnetic disk was tested at a temperature of 30 ° C. and a humidity of 80% RH.
After being left for 48 hours under the above environment, magnetic disk appearance inspection and signal error inspection (however, two magnetic disks according to each Example and Comparative Example were used, and the average number of signal errors per disk surface was measured. And the corrosion resistance of each magnetic disk was tested.

[0044]

[Table 2] "Evaluation" (1) Dynamic friction coefficient test As is clear from the results shown in Table 2, the magnetic disk according to each example has a small dynamic friction coefficient of 0.22 or less as compared with the magnetic disk according to Comparative Example 3. It was confirmed that the wear resistance of the protective film after the formation of the lubricating layer was good.

The dynamic friction coefficient of the magnetic disks according to Comparative Examples 1 and 2 is 0.18 to 0.22, which is substantially the same as that of Examples 1 and 2, but from the results of the CSS test described below. As is apparent, it can be confirmed that the friction coefficient increases with time and the deterioration with time is severe.

(2) CSS Test As is clear from the results shown in Table 2, in the magnetic disks according to the respective examples, the friction coefficient after 20,000 times was as small as 0.56 and the friction after 48 hours. The coefficient is as small as 0.45 or less. Therefore, it can be confirmed that the deterioration of the protective film with time is small.

On the other hand, in the magnetic disk according to Comparative Example 1, the half-value width of the peak value on the high wavenumber side of the Raman shift is small, and the peak intensity ratio [strength (1340-1.
390 cm ^-1 ) / strength (1550 to 1620 cm ^-1 )]
Is as large as 0.33, which seems to have an amorphous graphite structure unlike the carbon film of the example. Therefore, the dynamic friction coefficient is not so different from that of the embodiment, but the CSS
It was confirmed that the friction coefficient in the test increased as the number of CSSs increased and the wear resistance was inferior. Also, in the magnetic disk according to Comparative Example 2, the half-value width of the peak value on the high wave number side of the Raman shift is small, and the peak intensity ratio [strength (1340 to 1390 cm ^-1 ) / strength (1550
.About.1620 cm ⁻¹ )] also exceeds 0.3, and it can be confirmed that the structure is different from the carbon film of each example. For this reason, the coefficient of dynamic friction is superior to the examples, but the coefficient of friction in the CSS test is 20,000 when the CSS count is 20,000.
It was confirmed that the protective film was peeled off over time due to a large rise after exceeding the number of times and partial scratches were generated on the magnetic disk, resulting in poor adhesion. For the magnetic disk according to Comparative Example 3, the dynamic friction coefficient and CS
The friction coefficient in the S test was also large at 0.52 to 0.92, and it was confirmed that the wear resistance was inferior.

(3) Adsorption Test As is clear from the results shown in Table 2 in the magnetic disks according to the respective examples, the friction coefficient thereof is as small as 0.45 or less, while in the magnetic disks according to the comparative example. Except for Comparative Example 2, it shows a larger value than this, especially SiO ₂
In the magnetic disk according to Comparative Example 3 to which the protective film of No. 2 is applied, the friction coefficient thereof is as large as 1.42.

Therefore, the magnetic disk according to the example is also excellent in the adsorption test.

(4) Corrosion resistance test No signal error due to corrosion of the magnetic recording layer was observed in the magnetic disks according to the examples, and it was confirmed that the magnetic recording layer had excellent corrosion resistance.

On the other hand, in the magnetic disks of Comparative Examples except Comparative Example 2, it was confirmed that the number of signal errors increased with time and the corrosion resistance thereof was inferior to that of the Examples.

[0052]

According to the first and second aspects of the present invention, the adhesion of the protective film to the magnetic recording layer, the surface smoothness, and the abrasion resistance can be improved, and the corrosion resistance of the magnetic recording layer can be improved. It is possible to remarkably improve the magnetic field and reduce damage to the magnetic head due to contact.

Therefore, the life of the magnetic head can be extended and the recorded information can be stably stored for a long period of time.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic disk according to an embodiment.

FIG. 2 is a Raman spectrum diagram of carbon protective films according to examples and comparative examples.

[Explanation of symbols]

 1 substrate 2 hardening treatment film 3 magnetic recording layer 4 protective film 5 lubrication layer

Claims (2)

[Claims] 1. A magnetic recording medium comprising a magnetic recording layer and a protective film provided on the magnetic recording layer, wherein the protective film is formed by sputtering to form amorphous graphite in amorphous diamond. The magnetic recording medium is characterized by being composed of an amorphous carbon film in which are randomly arranged. 2. Raman shifts of Raman spectra obtained by Raman scattering spectroscopy of the amorphous carbon film are 1550 to 1620 cm ⁻¹ and 1340 to 1390c.
It has a peak at m ^-1 and its peak intensity ratio (134
0~1390cm ^-1 / 1550~1620cm ^-1) with is 0.3 or less, the magnetic recording according to claim 1, wherein the half-value width of the peak of the high frequency side is characterized in that it is a 400～500M ^-1 Medium.