JP2003006837A - Magnetic disk medium having ultra-thin film protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combination of the material for a seed film and the material for a lubricant film of a magnetic disk medium, in which the recording/ reproducing characteristic, the dust resistance and the wear resistance of the magnetic disk medium having an ultra-thin film protective film can be improved. SOLUTION: In the magnetic recording medium which is made by forming a seed film, an under film, a magnetic film, and a protective film on a nonmagnetic magnetic disk medium substrate and by coating a liquid lubricant having a perfluoropolyether structure on the surface thereof, the seed film consists of a Ni alloy. The thickness of the protective film is in the range of 1.0-5.0 nm. The lubricant film on the protective film is made to contain one or more kinds of lubricant components consisting of the structure described in chemical formula (1) or chemical formula (2).

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 of a magnetic disk device, and more particularly to a protective film on the surface of the medium of several n.
About m.

[0002]

2. Description of the Related Art The recording density in a magnetic disk device has been increasing remarkably, and recently, the recording density is 10 per square inch.
Even those exceeding gigabit have been announced. In order to achieve such a high recording density, it is necessary to make the distance and the distance between the magnetic head and the magnetic recording layer of the magnetic disk medium as close as possible, and it must be smaller than 20 nm at present.

Most of this space is occupied by the protective film formed on the surface of the magnetic recording layer of the magnetic disk medium and the flying height of the magnetic head. Therefore, there is a trade-off relationship between the protective film thickness and the flying height of the magnetic head. For the magnetic disk medium, the protective film should be as thin as possible and the sliding resistance against contact with the magnetic head should be high. Required. The thickness of the protective film must be smaller than 5 nm in the future, calculated from the distance between the magnetic head and the magnetic recording layer of the magnetic disk medium.

In recent magnetic disk devices, the surface roughness of the magnetic disk medium is made as small as possible in order to make the distance as close as possible. Therefore, when the rotation of the magnetic disk medium is stopped, the magnetic head is in contact with the magnetic disk medium, and when the magnetic disk medium starts to rotate, the air flow causes the magnetic head to levitate. When the disk medium is stopped, the magnetic head is retracted from the magnetic disk medium (unloading), and when the magnetic disk medium starts rotating, the magnetic head is loaded on the magnetic disk medium. It tends to be adopted. In the latter case, the requirement for the sliding resistance is slightly relaxed, but it is necessary to withstand the impact at the time of load-on and the contact due to the abnormal posture of the magnetic head that may suddenly occur even in the normal operation.

On the other hand, in order to improve the recording / reproducing capability of the magnetic disk medium, the material search for the seed film, the base film, and the magnetic film, and the improvement of the film structure have been conducted. For example, as a material for the seed film, Japanese Patent Laid-Open No. 2000-215438 discloses CoCrZr.
The alloy is NiAl, Ni in JP-A-11-328646.
Ni alloys such as AlRu, NiCu alloys in JP-A-10-74620, and Ni alloys in JP-A-11-339239.
Al alloys are each disclosed.

In Japanese Patent Laid-Open No. 2001-56924, at least one exchange layer structure and a magnetic layer provided on the exchange layer structure are provided in order to improve the thermal stability of recorded signals and reduce medium noise. A magnetic disk media structure is disclosed. The exchange layer structure is composed of a lower ferromagnetic layer and a nonmagnetic coupling layer, and the nonmagnetic magnetic layer is made of Ru, Rh, I.
r and their alloys are disclosed.

Regarding the protective film, US Pat. No. Re3246
As disclosed in Japanese Patent No. 4 etc., carbon-based materials have been used conventionally. For example, JP-A-59-15
Addition of hydrogen as described in JP-A-4641 and JP-A-8-
As described in Japanese Patent No. 106629, it has been proposed in many cases to increase the hardness of a carbon-based protective film by adding nitrogen gas during film formation by a sputtering method and to reduce the film thickness.

In particular, a diamond-like carbon film having a high hardness among the hydrogenated carbon protective films has been attracting attention for a long time, and a hydrocarbon-based gas as described in JP-A-59-154641 mentioned above is used. Chemical vapor deposition method (hereinafter abbreviated as CVD method) in which electric discharge is generated to decompose gas and deposit it on a substrate, and thermoelectrons generated by using a heated filament are irradiated to hydrocarbon gas for ionization. Then, the ion beam is deposited by accelerating the ion beam with a bias voltage applied to the substrate and colliding it with the substrate (hereinafter referred to as IB
Abbreviated as D method. ) And various other manufacturing methods have been proposed.

On the other hand, as described in Japanese Patent Application Laid-Open No. 61-126827, only by increasing the hardness of the carbon-based protective film, the sliding resistance cannot be improved, and a fluoro-based lubricant such as a perfluoropolyether structure is used. It has been clarified that they must be used together, and optimization with a lubricant is also an important factor in designing a magnetic disk medium.

As described in US Pat. No. 5,908,817, in order to improve the performance of the lubricant, it is possible to mix an additive having a phosphazene ring, and JP-A-6-2.
A lubricant having a phosphazene ring at the end of perfluoropolyether has also been proposed as described in Japanese Patent Publication No. 20077. Further, as disclosed in Japanese Patent Application No. 11-267696, a technique for attaching a phosphazene ring to the end of perfluoroether has been developed. Furthermore, JP-A-1
As described in JP-A-1-328647, it has been known that the material of the underlayer film of the magnetic recording layer also affects the sliding resistance of the magnetic disk medium.

[0011]

As described in the prior art, a magnetic film obtained by forming a seed film, a base film, a magnetic film, and a carbon protective film on a non-magnetic substrate and applying a liquid lubricant to the surface of the magnetic film. In the case of a disk medium, when the film thickness of the protective film is 5 nm or less, the reliability with respect to sliding resistance is rapidly lowered and the dust resistance is lowered. Here, the dust resistance means the strength with which the magnetic disk medium is not damaged when minute dust enters the head-disk interface.

[0012] The dust resistance against minute dust sharply decreases as the carbon protective film becomes thinner. This is because the dust has a size of several μm to several tens of nm, and when the dust enters the head disk interface, the contact stress can no longer be absorbed by the deformation of the protective film, resulting in destruction of the magnetic disk medium film. It is estimated that this is because it has reached.

Further, it is presumed that the concentration of contact stress occurs not at the surface of the protective film but at a deep position such as the seed film or the substrate. Therefore, consider the optimal combination of the layer structure of magnetic film, underlayer film, seed film, and material, and even if the protective film is thin, the magnetic film and other lower films absorb contact stress to improve dust resistance. Both have a layer structure with high recording / reproducing characteristics.
It is necessary to find a combination of materials.

Further, it is appropriate to consider that the wear resistance and the dust resistance have different characteristics in the contact stress distribution of the magnetic disk medium, and the film structure and material are improved to improve the dust resistance. Even if it does, abrasion resistance is not always improved. Therefore, it is necessary to optimally combine a film structure / material with a lubricating film / protective film that further improves wear resistance while maintaining dust resistance.

[0015]

A seed film, a base film, a magnetic film, and a protective film are formed on a non-magnetic magnetic disk medium, and the thickness of the protective film is set to 2 nm to 6 nm. A magnetic disk medium coated with a liquid lubricant having an ether structure.

As a result of examining combinations of various seed films, film structures / materials of magnetic film structures, and lubricants, the seed film was a magnetic film having an exchange layer structure using Ni alloy, and the lubricating film was represented by the chemical formula (1) or ( By using the lubricant of 2), it is possible to achieve excellent recording / reproducing characteristics and dust resistance / wear resistance by setting the thickness of the protective film to 1.0-5.0 nm. Further, as a result of the study, it was found that the above characteristics can be effectively obtained by the combination of the Ni alloy seed layer and the lubricant represented by the chemical formula (1) or (2).

As a more preferable combination, the seed film is made of a NiTa alloy and has a film thickness of at least 20 nm, and the protective film is a diamond-like magnetic film having an exchange layer structure using Ru as a non-magnetic intermediate layer. A magnetic disk medium containing a carbon film, the lubricant film containing the lubricant of the chemical formula (1) or (2), and having an extremely thin protective film of 1.0 to 5.0 nm has excellent recording and reproducing characteristics. It can realize thermal stability, low noise, abrasion resistance, dust resistance, and corrosion resistance.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In the examination in the embodiments, a glass substrate which is commercially available for a magnetic disk medium is used as the non-magnetic magnetic disk medium substrate. Since the surface roughness of the magnetic disk medium surface reflects the surface roughness of the substrate surface, the surface roughness of the substrate surface is Ra 0.25-0.8 nm, Rp
The one having a thickness of 3.0 to 8.0 nm was prepared. Where R
a and Rp are the arithmetic average roughness and the peak line-average line distance of JIS B0601-1994, respectively. <Embodiment 1> FIG. 1 schematically shows a film structure of a magnetic disk medium of Embodiment 1. After cleaning the glass substrate 1 described above,
On top of that, a seed film (2), an undercoat film (3), a lower magnetic film (4), a non-magnetic intermediate film ( 5), the upper magnetic film (6) and the diamond-like carbon film (7) were formed. Seed film (2) is 62.5
Sputtering was performed using an at.% Ni-37.5 at.% Ta alloy target, and the film thickness was 30 nm. The film thickness of the seed film was measured and determined by a fluorescent X-ray measurement method. After forming the seed film, after heating to 260 ° C., 99 Vol% Ar-1
The sample was exposed to a Vol% oxygen mixed gas for 3.5 seconds. Then, a CrTi alloy base film (3) having a thickness of 5 nm is formed on the seed film, and a CoCrPt alloy magnetic film having a thickness of 3.5 n is used as a lower magnetic layer (4).
Further, Ru was formed to 0.5 nm as an intermediate film (5), and a CoCrPtB film was formed to 15 nm as an upper magnetic film (6). A carbon protective film (7) having a thickness of 3.5 nm was formed on the upper magnetic film by the IBD method. The film thickness of the protective film was quantified using an X-ray reflection method by forming Cr to a thickness of 5 nm on the protective film in order to improve the accuracy of film thickness measurement. The film thickness was quantified by the X-ray reflection method using SLX2000 (registered trademark) manufactured by Rigaku Denki Kogyo Co., Ltd. using X-rays of Cu Kα1. On the protective film, HFE710 manufactured by Sumitomo 3M Ltd.
The magnetic disk medium was dipped in a mixed lubricant solution containing 0 wt% of the lubricant of chemical formula (3) and 0 as a solvent to form a lubricant film. The lubricating film thickness was 2.0 nm as measured by FTIR. Example 2 A magnetic disk medium was manufactured in the same manner as in Example 1. However, in Example 2, the seed film was 70 at.%.
A Ni-20 at.% Cr-10 at.% Zr alloy target was sputtered to form a 10 nm NiCrZr film, and then a 62.5 at.% Ni-37.5 at.% Ta alloy target was sputtered to form a 30 nm film. A layer seed film was used. <Comparative Example 1> NiCr having a thickness of 10 nm shown in Example 2
60 at.% Co-30 at.% C on Zr lower seed film
An upper seed film of r-10 at.% Zr was formed to 30 nm. The other manufacturing method is the same as that of the second embodiment. <Comparative Example 2> NiCr having a film thickness of 10 nm shown in Example 2
60 at.% Co-30 at.% C on Zr lower seed film
An intermediate seed film of r-10 at.% Zr was formed to 30 nm. Then, as an upper seed film, 62.5 at.% Ni-3
A 7.5 at.% Ta film was formed to a thickness of 5 nm. The other manufacturing method is the same as that of the second embodiment. <Comparative Example 3> A magnetic disk medium having the same film structure as that of Example 1 but containing no lubricant represented by the chemical formula (2) in the lubricating film was produced.

Specific effects of the present invention will be shown by Examples 1 and 2 and Comparative Examples 1-3. First, the recording / reproducing characteristics were measured using a magnetic head having a giant magnetoresistive effect reproducing element (GMR element) and an electromagnetic induction type writing element. S /
The N ratio (ratio between reproduction signal output and medium noise), recording resolution and medium noise were measured. The results are shown in FIGS. 2 and 3. Both the resolution and the S / N ratio are as compared with Comparative Examples 1 and 2, as compared with Examples 1 and 2.
Is increasing. Further, the media noise of Examples 1 and 2 is smaller than that of Comparative Example. From this result, Ni
It can be seen that the magnetic disk medium having the seed film made of an alloy has excellent recording / reproducing ability.

Next, using the media obtained in Example 1 and Comparative Example 1, a dust introduction test was conducted. Example 1, Comparative Example 1
In both cases, a magnetic disk medium having a carbon film thickness varied from 1.0 nm to 6.0 nm was prepared and tested. The dust input test was performed as follows. With the magnetic head seeking over the magnetic disk medium, alumina particles having a diameter of 0.5 μm were sprayed onto the magnetic disk medium for 30 seconds, and then the seek was continued for 300 seconds. The time until the magnetic disk medium crashed was defined as the dust input test proof stress. The results are shown in Fig. 4.

Obviously, the magnetic disk medium of Example 1 is superior in the dust input test proof strength. In Comparative Example 1,
While the yield strength of the carbon protective film is sharply reduced at 5 nm or less, Example 1 has a relatively high yield strength up to 1 nm. From this, it was found that the Ni alloy seed film has the property of improving the dust resistance. In Comparative Example 1, although the lubricant of the chemical formula (2) is contained in the lubricating film, the dust resistance shows an unfavorable result, and the dust resistance cannot be improved only by improving the lubricant. It is shown that.

Further, Example 1 and Comparative Example 3 were compared in order to confirm the effect of including the lubricant of the chemical formula (2) in the lubricating film. In both Example 1 and Comparative Example 3, the carbon film thickness was 1.0.
A magnetic disk medium having a wavelength changed from nm to 6.0 nm was manufactured and tested. 4000 / for high-speed contact test
The magnetic head was slid in the direction opposite to the normal running direction at a rotation speed of min, and the time until the magnetic disk medium crashed was measured. Results are shown in FIG.

In Comparative Example 3, the carbon film thickness is 1.0-5.0n.
The high-speed contact test yield strength is remarkably small in the m range, but Example 1 has excellent yield strength. From this, it was found that by adding the lubricant represented by the chemical formula (2) to the lubricating film, the wear resistance against sliding contact with the magnetic head was significantly improved.

From the above examination results, Ni was used as the seed film.
By adding the lubricant represented by the chemical formula (2) to the lubricant film using the alloy film, the recording / reproducing characteristics, the dust resistance, and the resistance to dust of the magnetic disk medium of the ultra-thin protective film (1.0-5.0 nm) can be obtained. It has been found that it is possible to improve the abrasion resistance and to make a magnetic disk medium with high reliability and high performance.

As the material of the seed film, the same effect can be obtained as long as it is a Ni alloy such as NiAl other than NiCrZr and NiTa shown in the embodiment. In this case, a Ni concentration of 30 to 90 at% may be appropriate, but the recording / reproducing characteristics can be optimized by combining the magnetic film and the underlayer.

Further, when a Ni alloy seed film is used,
It has been revealed that there is a suitable film thickness with respect to the film thickness of the seed film. FIG. 6 shows the result of the dust injection test performed in Example 1 using the thickness of the seed film as a parameter.
The dust injection test strength tends to increase with an increase in the thickness of the seed film.
It can be seen that about nm is necessary.

Now, both Example 1 and Example 2 are magnetic disk media having a composite lubricant film in which the lubricant of the chemical formula (2) is added to the lubricant of the chemical formula (3). Even if the lubricants represented by the chemical formulas (1) and (2) alone form the lubricating film, there is no difference in their effects. At this time, each of the lubricants in the main chain portion of the lubricant represented by the chemical formulas (1) and (2) has an average molecular weight of 1500-250.
0 is preferred.

Further, a magnetic disk medium according to Example 1 was prepared by adding 10 wt% of the lubricant of the chemical formula (1) or (2) to the lubricants of the chemical formulas (4) and (5). A test was conducted and it was found that the proof stress was equal to or higher than that of Example 1.

Regarding the method of manufacturing the protective film, a magnetic disk medium according to Example 1 was prepared in which a nitrogen-added sputtered carbon film by a commonly used sputtering method was used instead of the protective film manufactured by the IBD method. And evaluated. As a result, it was found that the proof stress was equivalent to that of Example 1. In general, since the diamond-like carbon protective film is more excellent in corrosion resistance, it is preferable to use a magnetic disk medium having a diamond-like carbon film in the case of this embodiment, but the internal temperature of the actual magnetic disk device is It is economical to appropriately select the film quality of the carbon film according to the humidity environment and the usage state.

As described above, by using the material of the seed film, which is clarified in the present invention, as a Ni alloy and including the lubricant of the chemical formula (1) or the chemical formula (2) in the lubricating film, the film thickness of the protective film becomes 1 In a magnetic disk medium having an ultra-thin protective film of 0.0-5.0 nm, excellent recording / reproducing ability, dust resistance, and wear resistance can be realized. That is, FIG.
Magnetic disk medium (10) and magnetic head (9) shown in FIG.
The magnetic disk medium of the present invention has excellent recording / reproducing characteristics, dust resistance, and abrasion resistance, so that the recording / reproducing capability and reliability of the magnetic disk apparatus are greatly improved.

[0031]

According to the present invention, the thickness of the protective film is 1.0-5.
In a magnetic disk medium having a 0 nm ultrathin protective film, excellent recording / reproducing capability, dust resistance, and abrasion resistance can be realized.

[0032]

[Chemical 1]

[Chemical 2]

[Chemical 3]

[Chemical 4]

[Chemical 5]

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a cross-sectional structure of a magnetic disk medium of Example 1.

FIG. 2 is a diagram showing a comparison of recording and reproducing characteristics between an example and a comparative example.

FIG. 3 is a diagram showing a comparison of recording and reproducing characteristics between an example and a comparative example.

FIG. 4 is a diagram showing a comparison of dust input test strengths of Examples and Comparative Examples.

FIG. 5 is a diagram showing a comparison of high-speed contact sliding test strength between an example and a comparative example.

FIG. 6 is a diagram showing the relationship of the seed film thickness dependency of the dust injection test strength.

FIG. 7 is a diagram showing an outline of a magnetic disk device.

[Explanation of symbols]

1 --- non-magnetic substrate, 2 --- seed film, 3 ----
Underlayer film, 4--lower magnetic film, 5--non-magnetic intermediate layer, 6 --- upper magnetic film, 7 --- protective film,
8--Lubrication film, 9 --- Magnetic head, 10 ---- Magnetic disk medium.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoko Ogawa             2880 Kozu, Odawara City, Kanagawa Stock Association             Company Hitachi Ltd. Storage Division (72) Inventor Yoshifumi Matsuda             2880 Kozu, Odawara City, Kanagawa Stock Association             Company Hitachi Ltd. Storage Division (72) Inventor Minori Ozaki             2880 Kozu, Odawara City, Kanagawa Stock Association             Company Hitachi Ltd. Storage Division (72) Inventor Tetsuya Kambe             2880 Kozu, Odawara City, Kanagawa Stock Association             Company Hitachi Ltd. Storage Division (72) Inventor Mitsuhiro Masada             2880 Kozu, Odawara City, Kanagawa Stock Association             Company Hitachi Ltd. Storage Division (72) Inventor Koji Sakamoto             2880 Kozu, Odawara City, Kanagawa Stock Association             Company Hitachi Ltd. Storage Division (72) Inventor Yakuo             2880 Kozu, Odawara City, Kanagawa Stock Association             Company Hitachi Ltd. Storage Division (72) Inventor Koji Sonoda             2880 Kozu, Odawara City, Kanagawa Stock Association             Company Hitachi Ltd. Storage Division F-term (reference) 5D006 AA01 AA06 BB07 CA01 DA03                       EA03 FA02

Claims (6)

[Claims] 1. A magnetic recording medium in which a seed film, a base film, a magnetic film, and a protective film are formed on a non-magnetic magnetic disk medium substrate and a liquid lubricant having a perfluoropolyether structure is applied to the surface thereof. , The seed film is made of Ni alloy, the thickness of the protective film is in the range of 1.0 nm to 5.0 nm, and the lubricating film on the protective film has a structure according to the chemical formula (1) or the chemical formula (2). An ultra-thin protective film magnetic disk medium containing the following lubricant component. Where p
Is a natural number of 5 to 36, q is 4 to 30, and x is a natural number of 1 to 5. 2. An ultra-thin protective film magnetic disk medium according to claim 1, wherein the seed film is made of an alloy containing Ni and Ta. 3. An ultra-thin protective film magnetic disk medium according to claim 1 or 2, wherein the magnetic film has a non-magnetic intermediate layer containing Ru. 4. The ultra-thin protective film magnetic disk medium according to claim 1, wherein the protective film is a protective film containing a diamond-like carbon film. . 5. The ultra-thin protective film magnetic disk medium according to any one of claims 1 to 4, wherein the seed film has a thickness of at least 20 nm. 6. The ultra-thin protective film magnetic disk medium according to any one of claims 1 to 5, wherein the lubricating film contains one of the lubricants represented by chemical formulas (3) to (5). An ultra-thin protective film magnetic disk medium characterized by the above. Here, p, q, and s are natural numbers.