JPH05174372A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide the process for production of the magnetic recording medium which can improve the wear resistance of the magnetic recording medium and the attraction of a magnetic head to the surface of the magnetic recording medium. CONSTITUTION:A lubricating film 5 is formed by an applying method, such as spin coating method, for >=1 hours and within 6 hours after the end of the formation of a protective film 4 in the process for production of the magnetic recording medium having the protective film 4 for protecting a magnetic recording layer 3 on a substrate 1 and the lubricating film 5 provided thereon. The lubricating film 5 is formed under such conditions, by which the fluctuation from the correct value of the film thickness at the time of forming the lubricating film is minimized. Consequently, the wear resistance of the magnetic recording medium is improved and the attraction of the magnetic head to the magnetic recording medium surface is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a magnetic disk device or the like which has a CSS system (contact start and stop system) provided with a magnetic recording layer, a protective film and a lubricating film on a non-magnetic substrate. The present invention relates to a method for manufacturing a magnetic recording medium, and in particular, it is possible to suppress the variation of the film thickness when the lubricating film is formed from an appropriate value, and improve the wear resistance of the magnetic recording medium and the adsorption phenomenon of the magnetic head on the surface of the magnetic recording medium. The present invention relates to a method for manufacturing a magnetic recording medium.

[0002]

2. Description of the Related Art Among external storage devices in an information processing system, a magnetic recording medium applied to a magnetic disk device or the like adopting the above-mentioned CSS system (contact start and stop system) is used when it is not operated. The magnetic recording medium and the magnetic head surface are in surface contact with each other, and the magnetic recording medium and the magnetic head surface are in sliding contact with each other when the operation is started and stopped.

Therefore, the phenomenon of attraction of the magnetic head to the surface of the magnetic recording medium during non-operation is prevented, and damage to both the magnetic recording medium and the magnetic head during contact sliding is minimized to improve its durability. Therefore, conventionally, a magnetic recording medium is used in which the non-magnetic substrate is roughened and the surface of the protective film is roughened by the roughening.

That is, in order to manufacture this kind of magnetic recording medium, a series of surface treatments such as lapping, polishing and texturing are applied to the surface of the non-magnetic substrate to roughen the surface, A magnetic recording layer is formed on a roughened non-magnetic substrate, and a protective film made of carbon, SiO ₂ or the like for protecting the magnetic recording layer is formed on the magnetic recording layer. At this time, a large number of minute projections corresponding to the rough surface state of the non-magnetic substrate are formed on the surface of the protective film. Therefore, the surface is polished with a polishing tape to remove the minute projections and a cleaning tape. The surface of the protective film is subjected to a cleaning treatment by using to remove the polishing dust and the like of the fine projections scraped off by the polishing treatment.

Then, a fluorocarbon type lubricant was applied to the cleaned protective film by a coating means such as a spin coat method to form a lubricating film, and the lubricating film was formed using a burnish head. After removing dusts and other deposits adhering to the surface of the magnetic recording medium, a glide height test (head sliding characteristic test) is performed to manufacture a magnetic recording medium conforming to a predetermined standard.

[0006]

By the way, when the thickness of the lubricating film formed on the protective film is smaller than an appropriate value, the magnetic recording medium is damaged when the magnetic head slides in contact with it. It is known that it becomes easy and the wear resistance of the magnetic recording medium deteriorates.

On the other hand, if the thickness of the lubricating film becomes thicker than an appropriate value, excess lubricant easily enters between the magnetic recording medium and the magnetic head when the magnetic head is stationary on the surface of the magnetic recording medium, As a result, it is also known that the magnetic head is attracted to the surface of the magnetic recording medium, and the magnetic recording layer and the protective film of the magnetic recording medium are peeled off or the magnetic head is easily damaged when the magnetic head is activated.

Therefore, in order to ensure the durability of the magnetic recording medium, the magnetic head, etc., it is necessary to set the film thickness of the lubricating film formed on the protective film to an appropriate value and suppress the fluctuation of the film thickness as much as possible. It becomes important.

However, the relationship between the surface condition of the protective film and the film thickness of the lubricating film formed by coating on the protective film has not yet been sufficiently clarified. Since there is difficulty in setting the coating conditions when setting the above value, there is a problem that the film thickness of the lubricating film formed on the protective film is likely to largely fluctuate from its proper value.

Therefore, if the thickness of the lubricating film is too thin than the proper value, the wear resistance of the magnetic recording medium is apt to be deteriorated as described above, and if it is too thick than the proper value, the magnetic recording medium and the magnetic head are too thick. However, there is a problem that both are easily damaged.

The present invention has been made by paying attention to such a problem, and an object thereof is to suppress the variation of the film thickness at the time of forming the lubricating film from its proper value and to improve the wear resistance of the magnetic recording medium. Another object of the present invention is to provide a method of manufacturing a magnetic recording medium that can improve the attraction phenomenon of a magnetic head.

[0012]

As a result of intensive studies conducted by the present inventors in order to solve such a problem, as a result of the above protection in order to suppress the fluctuation of the film thickness during the formation of a lubricating film from its proper value. Through various experiments, it was discovered through various experiments that the time from the completion of film formation to the formation of the lubricating film is an important parameter, and the present invention has been completed.

That is, the invention according to claim 1 is a method of manufacturing a magnetic recording medium comprising a magnetic recording layer on a non-magnetic substrate, a protective film provided on the magnetic recording layer, and a lubricating film provided on the protective film. As a premise, it is characterized in that the lubricating film is formed within 1 hour to 6 hours after the formation of the protective film.

The reason why the time for forming the lubricating film is set to be 1 hour to 6 hours after the completion of forming the protective film in such technical means is based on the following experimental results.

That is, in FIG. 2, after the protective film made of carbon is formed by the sputtering method, the time until the lubricating film is formed on the surface of the protective film by the spin coating method is appropriately from 0 to 8 hours. The conditions are set differently, and the variation widths of the film thickness (average value) of the lubricating film formed under each condition with respect to the appropriate value (reference film thickness) are plotted, and FIG. After a protective film made of is formed by the sputtering method, the time until the lubricating film is formed on the surface of the protective film by the spin coating method is set from 0 hours to 20 hours by appropriately changing the conditions. FIG. 3 is a plot of the fluctuation width of the film thickness of each lubricating film formed in (3) with respect to its appropriate value (reference film thickness).

As is clear from the results shown in FIG. 2, the film thickness (average value) of the lubricating film is 1 when it is made to correspond to the time immediately after the formation of the protective film until the formation of the lubricating film. It decreases sharply in less than time and then stabilizes. For this reason, if the time for forming the lubricating film is set to less than 1 hour after the film formation of the protective film is completed, it is difficult to suppress the fluctuation of the film thickness of the lubricating film, and it becomes thicker than an appropriate value (reference film thickness). However, the magnetic head is likely to be attracted to the surface of the obtained magnetic recording medium.

On the other hand, when the time for forming the lubricating film exceeds 6 hours after the formation of the protective film, the fluctuation range of the film thickness of the lubricating film becomes large as shown in FIG. 3, and the film thickness is proper. It can be confirmed that the value shifts to a smaller value than the value (reference film thickness). For this reason, if the lubricating film formation time is set to 6 hours or more after the completion of the formation of the protective film, the lubricating film may have a thickness smaller than an appropriate value (reference film thickness). A harmful effect that the wear resistance of the obtained magnetic recording medium deteriorates occurs.

On the basis of such technical grounds, in this technical means, the time for forming the lubricating film is set to be 1 hour to 6 hours after the completion of the formation of the protective film.

The criteria for setting the appropriate value of the film thickness of the lubricating film are as follows: the material of the applied protective film and lubricant, the roughened state of the substrate surface and the protective film surface, the bottom structure of the magnetic head, Also, the conditions are appropriately set in consideration of factors such as the head load of the magnetic head with respect to the protective film surface.

Here, when the lubricating film formation time is set to less than 1 hour after the completion of the formation of the protective film, it is difficult to suppress the fluctuation of the lubricating film thickness and the film thickness has an appropriate value (reference film thickness). The reason why the thickness of the lubricant film becomes thinner than an appropriate value (reference film thickness) when the time for forming the lubricant film is set to 6 hours or more after the completion of the formation of the protective film The inferees speculate as follows.

First, when the lubricating film is formed within 1 hour after the completion of the formation of the protective film, the surface of the protective layer is in a very active state, so that the phenomenon of adsorption of water and oxygen occurs on the surface. Even if the timing of forming the lubricating film is slightly deviated within the above time, the amount of water and oxygen adsorbed on the surface of the protective film is significantly different, and the state of the protective film is also different from time to time and is unstable. It is inferred that even if it is not stable, it becomes difficult to suppress the variation in the thickness of the lubricating film. Furthermore, since the surface of the protective film is in a very active state, it is inferred that the lubricant is more likely to adhere than when it is stable, and as a result, the film thickness of the lubricating film becomes thicker than an appropriate value (reference film thickness).

On the other hand, when the lubricating film is formed for more than 6 hours after the formation of the protective film, the adsorption amount of molecules existing in low concentration in the atmosphere on the surface of the protective film cannot be neglected, and the long time is required. Since the dust adheres to the protective film when left unattended, the state of the protective film becomes unstable, making it difficult to suppress the fluctuation of the thickness of the lubricating film as in the case where the lubricating film formation time is set to less than 1 hour. It is inferred that since the active state of the film surface is lowered, it becomes more difficult for the lubricant to adhere to the film compared to when it is stable, and the film thickness of the lubricating film becomes thinner than the appropriate value (reference film thickness).

On the other hand, when the time for forming the lubricating film is set to 1 hour to 6 hours after the completion of the formation of the protective film, the water and oxygen adsorbed on the surface of the protective film are saturated, and It is inferred that the variation in the thickness of the lubricating film can be suppressed because the adsorption amount of molecules existing in low concentration in the atmosphere on the surface of the protective film and the adhesion of dust can be ignored.

Next, regarding the polishing treatment and the cleaning treatment which are carried out on the surface using a polishing tape and a cleaning tape after the formation of the protective film, the steps from the completion of the formation of the protective film to the formation of the lubricating film are described. This may be done at any point in time and is optional.

However, when the above-mentioned polishing treatment or the like is performed immediately after the formation of the protective film, the protective film is in a high temperature and unstable state, and if the polishing treatment or the like is performed under this condition, scratches or the like are likely to occur on the surface of the protective film. Moreover, it is desirable to avoid it because there is no time margin in the processing step immediately after forming the protective film.

In this technical means, the same material as the conventional one can be applied to the non-magnetic substrate of the magnetic recording medium. For example, those used as magnetic disks are high-purity aluminum, aluminum alloys, ceramics and hard materials. A disk-shaped substrate made of plastic or the like can be applied. For widely used high-purity aluminum substrates, the surface is anodized and then mirror-finished, or the surface is electroless plated to form Ni-P alloy, N
After forming a film of i-Cu-P alloy or the like, mirror finishing treatment is performed. The substrate thus hardened is subjected to a so-called roughening process using a polishing tape or a polishing liquid as is well known so as to make substantially concentric scratches in the circumferential direction of the plate material.

As the recording material forming the magnetic recording layer, a sputtered film made of γ-Fe ₂ O ₃ , Co type, CoNi type, CoNiCr type, CoPt type is used.
-Based, CoCrTa-based, and Fe-based sputtering films, vapor deposition films, plating films, and other similar materials can be applied, and
A film of Cr, Cr alloy, or the like may be provided as an underlayer to adjust the magnetic characteristics. Further, as the protective film for protecting the magnetic recording layer, the sputtering method, the CV
Carbon, SiO ₂ , SiN, SiAlON, Zr formed by an appropriate film forming means such as D (chemical vapor deposition) method
An O ₂ film or the like can be applied, and a conventional material such as a fluorocarbon-based material can be applied as it is to the above-mentioned lubricant for improving the wear resistance of this protective film, and its application means is also arbitrary.

[0028]

According to the invention of claim 1, since the lubricating film is formed within 1 hour to 6 hours after the completion of the formation of the protective film, the fluctuation of the film thickness at the time of forming the lubricating film from the appropriate value is prevented. It can be minimized, and the magnetic recording medium in which the film thickness of the lubricating film is set to an appropriate value can be stably manufactured.

[0029]

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

This magnetic disk comprises a substrate 1 made of a surface-roughened aluminum alloy (Mg: 4 parts by weight, Al: 96 parts by weight) as shown in FIG.
A Ni—P alloy hardening treatment film 2 formed thereon by electroless plating, and a DC magnetron sputtering method on the hardening treatment film 2 via an underlayer (not shown) made of chromium. Of the CoCrTa magnetic recording layer 3 having a thickness of 300Å and a carbon protective film 4 formed on the magnetic recording layer 3 by the DC magnetron sputtering method. The lubricating film 5 of fluoropolyether is formed.

[Example 1] A magnetic disk manufacturing process according to this example will be described. First, a diameter of the above-mentioned aluminum alloy on which a Ni-P alloy hardening treatment film 2 is formed by an electroless plating method. Lapping and polishing are applied to the 3.5-inch substrate 1 to obtain a surface roughness R
_max (height from the highest peak to the deepest valley bottom within the standard length)
A disk substrate having a surface roughness of less than 300Å was manufactured.

On the surface of the substrate 1 having this roughness, a polishing tape made by bonding 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. At R _tm about 600Å
Set to.

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

Then, a 500 Å-thick Cr film was formed on the substrate 1 by the DC magnetron sputtering method under the conditions of substrate temperature: 300 ° C., Ar gas pressure: 10 mTorr, and DC input power: 5 W / cm ^2. To form a base layer (not shown) for adjusting magnetic characteristics, and
After applying a bias voltage of (-150 V) between the sputtering target and the sputtering target to form a CoCrTa magnetic recording layer 3 having a thickness of 300 Å, a carbon protective film 4 is formed thereon under the same conditions as the above-mentioned underlayer. did.

Next, the substrate 1 having the carbon protective film 4 formed thereon is rotated at a high speed, and a polishing tape formed by binding alumina abrasive grains having an average particle diameter of 2 μm on a polyester base film is used as the carbon protective film 4 described above. Adheres to the top, and
After performing a polishing process using a tape polishing device to remove the fine protrusions on the surface of the carbon protective film 4, the surface of the carbon protective film 4 was cleaned using a cleaning tape made of cloth.

Then, on the surface of the protective film 4 which has been subjected to the polishing treatment and the cleaning treatment, a perfluoropolyether lubricant (product name: Krytox manufactured by DuPont) is applied by a spin coating method to form a lubricating film 5. After that, a burnishing treatment with a burnishing head was performed and a glide height test was performed to manufacture a magnetic disk.

The time from the completion of forming the carbon protective film 4 to the formation of the lubricating film 5 was 1.3 hours.

Then, ten magnetic disks were manufactured under the same conditions, the thickness of the lubricating film 5 of each magnetic disk was measured, and the fluctuation range from the proper film thickness was also calculated. Further, the surface state of the carbon protective film 4 when the polishing process and the cleaning process were performed before the formation of the lubricating film 5 was also observed, and it was examined whether or not scratches and the like were present on the surface.

The average value of these fluctuation widths and the carbon protective film 4
Table 1 shows the results of the surface state of the.

[Embodiment 2] This is substantially the same as Embodiment 1 except that the time from the completion of the formation of the carbon protective film 4 to the formation of the lubricating film 5 is 3.0 hours.

Then, as in Example 1, Table 1 shows the results of the average value of the fluctuation width of the lubricating film 5 and the surface condition of the carbon protective film 4.

[Third Embodiment] The third embodiment is substantially the same as the first embodiment except that the time from the completion of the formation of the carbon protective film 4 to the formation of the lubricating film 5 is 5.0 hours.

Then, as in Example 1, Table 1 shows the results of the average value of the fluctuation width of the lubricating film 5 and the surface condition of the carbon protective film 4.

[Comparative Example 1] This is substantially the same as Example 1 except that the time from the completion of forming the carbon protective film 4 to the formation of the lubricating film 5 is 0.8 hours.

Then, as in Example 1, Table 1 shows the results of the average value of the fluctuation width of the lubricating film 5 and the surface condition of the carbon protective film 4.

[Comparative Example 2] This is substantially the same as Example 1 except that the time from the completion of the formation of the carbon protective film 4 to the formation of the lubricating film 5 is 6.3 hours.

Then, as in Example 1, Table 1 shows the results of the average value of the fluctuation width of the lubricating film 5 and the surface condition of the carbon protective film 4.

[Comparative Example 3] This is substantially the same as Example 1 except that the time from the completion of the formation of the carbon protective film 4 to the formation of the lubricating film 5 is 21.7 hours.

Then, as in Example 1, Table 1 shows the results of the average value of the fluctuation width of the lubricating film 5 and the surface condition of the carbon protective film 4.

[0050]

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

(1) CSS Test The magnetic disks according to the example and the comparative example on which the lubricating film 5 is formed are set on a rotary spindle, and the thin film magnetic head (slider material: Al ₂ O ₃ · TiC, slider dimensions: length 3.
After applying 20 mm, width: 2.66 mm, load: 7.2 g weight, 0 rpm (that is, the state where the thin film magnetic head is in contact with the magnetic disk surface) → 3600 rpm (that is, the thin film magnetic head floats from the magnetic disk surface) The state of doing.
In this test, the flying height: 0.13 μm) → 0 rpm (that is, the thin film magnetic head returns from the floating state to the contact state) at a cycle of 30 seconds to perform a CSS test (contact start and stop). Was carried out, and the friction coefficient before the start, the friction coefficient after 5,000 times from the start, and the friction coefficient after 20,000 times were measured.

The results are shown in Table 2.

(2) Adsorption test Next, the thin-film magnetic head was brought into contact with the surface of each magnetic disk, and was placed in an environment of temperature 30 ° C. and humidity 80% RH for 4 hours.
After standing for 8 hours, the magnetic disk was rotated to measure the friction coefficient at the time of starting the magnetic disk, so-called adsorption force.

The results are also shown in Table 2.

[0055]

[Table 2] “Evaluation” In the magnetic disks according to Examples 1 to 3,
The average value of the fluctuation range of the film thickness of the lubricating film from the proper film thickness is suppressed to 2Å or less as shown in Table 1, and the surface state of the carbon protective film after the polishing process and the cleaning process is performed. Was also good. For this reason,
As shown in Table 2, the friction coefficient in the CSS test and the friction coefficient in the adsorption test are less than 0.5, and the wear resistance of the magnetic disk and the adsorption characteristic of the magnetic head on the surface of the magnetic disk. Was confirmed to have been improved.

On the other hand, in Comparative Example 1, the time from the formation of the carbon protective film to the formation of the lubricating film was as short as 0.8 hours,
As a result, as shown in Table 1, the thickness of the lubricating film is 4 Å thicker than the above-mentioned appropriate film thickness, the average value of the fluctuation width is also large at about 5 Å, and the surface of the carbon protective film is large. There were many scratches on the surface. Therefore, as shown in Table 2, the coefficient of friction in the CSS test and the coefficient of friction in the adsorption test have larger values than those of the magnetic disks according to the examples, and the obtained magnetic disks have wear resistance. It was confirmed that the magnetic head had poor adsorption properties on the magnetic disk surface.

Next, in Comparative Examples 2 to 3, the time from the formation of the carbon protective film to the formation of the lubricating film was as long as 6 hours or more, and as a result, as shown in Table 1, the film thickness of the lubricating film was Is thinner than the above-mentioned appropriate film thickness by 4 to 5Å at the maximum, and the average value of the fluctuation range is as large as 3.8 to 5.6Å. Further, the surface state of the carbon protective film after the polishing treatment and the cleaning treatment was good, and as shown in Table 2, there was no problem in the friction coefficient in the adsorption test, but the friction coefficient in the CSS test was It was confirmed that the wear resistance was inferior because the value was considerably larger than that of the magnetic disk according to the example.

[0058]

According to the invention of claim 1, it is possible to minimize the fluctuation of the film thickness when the lubricating film is formed from the proper value, and the film thickness of the lubricating film is set to the proper value. It is possible to stably manufacture the magnetic recording medium.

Therefore, it has the effect of improving the wear resistance of the magnetic recording medium and the phenomenon of attraction of the magnetic head to the surface of the magnetic recording medium.

[Brief description of drawings]

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

FIG. 2 is a graph showing the relationship between the time from the formation of the protective film to the formation of the lubricating film and the fluctuation range of the film thickness (average value) of the lubricating film formed under each condition with respect to its appropriate value. Fig.

FIG. 3 is a graph showing the relationship between the time from the formation of the protective film to the formation of the lubricating film and the fluctuation range of the film thickness of each lubricating film formed under each condition with respect to its proper value.

[Explanation of symbols]

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

Claims (1)

[Claims] 1. A method of manufacturing a magnetic recording medium comprising a magnetic recording layer, a protective film provided on the magnetic recording layer, and a lubricating film provided on the protective film on a non-magnetic substrate. A method of manufacturing a magnetic recording medium, characterized in that the lubricating film is formed within 1 hour to 6 hours after the end.