JPH0916955A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE: To manufacture a magnetic recording medium such as a magnetic disk in excellent appearance yield and to improve head flotation characteristics and error characteristics of the manufactured magnetic recording medium. CONSTITUTION: This manufacture of the magnetic recording medium includes a process wherein the texture of a substrate is processed concentrically and isotropically, a process wherein a base layer, a magnetic layer, and a protection layer are formed on the texture-processed substrate, and a varnishing process after the film forming process, and cleaning is performed between the film forming process and varnishing process. The cleaning is carried out by dipping the magnetic recording medium or employing scrubbing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium, particularly a magnetic disk, and more particularly to a method capable of manufacturing a magnetic disk having good head flying characteristics and error characteristics at a high yield. Is.

[0002]

2. Description of the Related Art A magnetic disk such as a hard disk is generally manufactured by the following method. First, a substrate such as aluminum, glass or carbon is textured to roughen it. This treatment is performed to prevent the magnetic head from sticking to the surface of the magnetic disk and damaging the magnetic head or the magnetic disk by making the surface of the magnetic disk to have an appropriate roughness. For example, an aluminum substrate The tape texture method of mechanically polishing and cleaning the glass substrate with a polishing tape, the method of chemically etching the glass substrate or applying the coating material containing fine particles, the method of thermally oxidizing the carbon substrate, or the substrate surface There is a method of attaching a melting point metal by vacuum vapor deposition or sputtering.

On the roughened substrate surface, an underlayer, a magnetic layer, a protective layer and the like are formed by a physical means such as sputtering using various materials. The film formation of each of these layers is usually performed continuously in a vacuum after the substrate is loaded in the sputtering apparatus, and the substrate on which each layer is formed is taken out into the atmosphere from the apparatus. Burnishing is performed on the taken-out substrate, which is for removing abnormal protrusions existing on the substrate surface to finish the surface, for example, to bring the polishing tape into contact with the substrate surface under pressure. Executed by Then, a liquid lubricant such as perfluoropolyether is applied by a dip coating method or a spin coating method to form a lubricating layer on the uppermost layer of the substrate, and a magnetic disk is obtained. For the obtained magnetic disk, glide height test (head flying characteristic), certify yield test (error characteristic), C
SS durability test, visual inspection, etc. are performed.

[0004]

The glide height tends to decrease with increasing density of magnetic recording.
It is not easy to manufacture magnetic disks satisfying the required characteristics in high yield. In addition, external damage on the surface of the magnetic disk must be avoided as much as possible.
As a result of various investigations in search of a manufacturing method satisfying these conditions, the present inventors found that the substrate surface after film formation has small foreign matter adhered during the sputtering step and from the environment before the burnishing step. It has been found that the adhered foreign matter is adhered, which is one of the factors that deteriorate the characteristics and appearance of the magnetic disk.

That is, when such minute foreign matter adheres to the substrate surface, they are mechanically pressed against the substrate surface in the burnishing process, resulting in surface damage or local peeling of the formed film. cause. As a result, in particular, the yield based on the appearance inspection is lowered, and the glide height characteristic and the error characteristic are deteriorated. Further, in the case where the texture treatment of the substrate is performed uniformly in the circumferential direction like tape texture, for example, it is difficult for the burnishing process to cause a scratch even on the appearance,
When the texture treatment is isotropically performed on the substrate surface by sputtering or powder beam,
There is a problem that the scratches generated in the circumferential direction in the burnishing process due to the minute foreign matter are likely to be clear and the appearance yield is apt to be lowered. It is an object of the present invention to provide a manufacturing method capable of solving these problems.

[0006]

According to the present invention, there are provided a step of texturing a substrate, a step of forming a magnetic layer on the textured substrate, and a burnishing step after forming the magnetic layer. In a method of manufacturing a magnetic recording medium comprising: cleaning between a film forming step of a magnetic layer and a burnishing step to remove fine foreign matters adhering to the surface of the layer formed before the burnishing step. Is proposed.

Conventionally, such cleaning has not been performed,
By adding a washing step before the burnishing step, glide height characteristics, error characteristics, and appearance yield can be improved. In order to remove the minute foreign matter, it is an idea to perform cleaning after the burnishing step and before forming the lubricating layer, but as described above, the present inventors
It was found that the microscopic foreign matter existing on the surface of the substrate on which the film was formed causes a problem in combination with the burnishing process,
It provides a solution of cleaning before the burnishing step.

(1) Substrate In the present invention, either a magnetic substrate or a non-magnetic substrate can be used, but a non-magnetic substrate is generally used. As such a non-magnetic substrate, for example, a substrate made of carbon such as a glassy carbon material, tempered glass, crystallized glass, aluminum and aluminum alloys, titanium and titanium alloys, ceramics, resin, or a composite material thereof is used. Among these, the glassy carbon material substrate is particularly excellent in terms of heat resistance, lightness, etc., and since it is excellent in dryness in the drying step after washing, it is difficult to cause stains and poor appearance, It can be used particularly preferably in the present invention. The "glassy carbon material" includes not only glassy carbon alone but also a composite material containing glassy carbon as a base material.

(2) Texture treatment Texture treatment includes mechanical polishing, chemical etching,
Various treatment methods can be adopted depending on the substrate to be used, such as application of fine particle-containing paint, thermal oxidation, and formation of irregularities by vapor deposition or sputtering. Since each processing method is already known, it will not be described in detail here, but the rough description of the texture processing is that a rough surface is uniformly formed in the circumferential direction of the substrate like tape texture. , Textures formed by vapor deposition or sputtering, and projections that are isotropically formed on the surface of the substrate. As described above, when the texture is evenly distributed in the circumferential direction of the substrate, the scratches caused by the minute foreign matter in the burnish are hardly noticeable in appearance, but in the case of the isotropic texture, the scratches are more noticeable. It is easy to become apparent. Therefore, the present invention is more preferable from the standpoint of improving the appearance yield, particularly when the texture treatment is isotropic.

Glass-like carbon is used as a substrate, and sputtering, vacuum deposition, and
When PVD such as ion plating is used, texture processing can be performed as follows, for example. That is, on the substrate, Si, Cr, Ta, Ti, Zr, Y,
P is a metal layer composed of one or more selected from Mo, W and V
It is provided with a thickness of 5 to 200 nm by VD, and then Al-M ₁ based alloy material (M ₁ is Si, Cr, Ta, Ti, Zr, Y, Mo, W and V
Al-M ₁ layer consisting of one or more selected from (1) or more) is formed by PVD to a thickness of 5 to 100 nm, and a non-metal amorphous layer, for example, an amorphous carbon layer is further formed thereon.
It is provided by PVD means with a thickness of 50 nm. Such a texture treatment can form isotropic unevenness with Ra = 10 to 50Å, preferably 10 to 30Å, Rp = 20 to 300Å, preferably 30 to 80Å and at the same time as the substrate. It has good familiarity and excellent durability and, in combination with the magnetic layer formed thereafter, can provide excellent electromagnetic conversion characteristics.

(3) Film Formation of Magnetic Layer Generally, the magnetic layer is formed after forming the underlayer, and it is customary to further form a protective layer on the magnetic layer. . As the underlayer, Cr, Ti, Al, or an alloy thereof can be provided by PVD means such as sputtering for the purpose of improving the orientation of the magnetic layer provided thereon. The thickness of the underlayer is preferably 10 to 100 nm. When the amorphous layer is first formed by PVD as described above, it is preferable to use Cr as the underlayer and further provide another underlayer made of Ti or Ti alloy between the amorphous layer and the amorphous layer. Its thickness is
It is about 10 to 150 nm, which can reduce noise in the magnetic recording medium.

In the present invention, examples of the magnetic layer provided on the underlayer include a metal thin film type magnetic layer formed by PVD means. Examples of materials for forming the metal thin film type magnetic layer include CoCr, CoNi, and CoCr.
X, CoCrPtX, CoNiX, CoWX, CoSm, CoSmX (X is T
a, Pt, Au, Ti, V, Cr, Ni, W, La, Ce, Pr, Nd, P
m, Sm, Eu, Li, Si, B, Ca, As, Y, Zr, Nb, Mo, R
Examples thereof include Co-based magnetic alloys containing Co as a main component, such as one or more selected from the group consisting of u, Rh, Ag, Sb, and Hf. Among these, CoCr and CoCrPt type are preferably used. The film thickness of the magnetic layer is about 300 to 1000Å.

When a protective layer is provided on the magnetic layer, such a protective layer preferably has high hardness from the viewpoint of abrasion resistance. For example, Al, Si, Ti, Cr, Zr, Nb, Mo,
Examples thereof include oxides, nitrides, and carbides of metals such as Ta and W, carbon, boron nitride, and the like. Among them, preferred are carbon, silicon carbide, tungsten carbide, silicon oxide, zirconium oxide, boron nitride, and composites of these materials. Particularly preferred is carbon, especially diamond-like carbon.
The protective layer preferably has a thickness of 5 to 25 nm. The protective layer is also P
It can be formed by VD means.

(4) Cleaning According to the present invention, after the magnetic layer is formed, that is, when the underlayer and the protective layer are provided, after forming the recording medium constituting layer including them, the burnishing step is performed. Cleaning is done before. As a result, the minute foreign matter that adheres during the film formation of the magnetic layer and the minute foreign matter that adheres from the environment when exposed to the atmosphere after the film formation is eliminated. To be done. Washing can be performed by immersion in pure water, preferably 60-80
It is carried out by appropriately repeating immersion for 10 to 60 seconds in warm pure water at about ℃. At this time, it is more preferable to use ultrasonic waves of 20 kHz to 1 MHz together. When a strong ultrasonic wave is applied to the NiP / Al substrate, dimples are generated, which causes a problem, but since the carbon substrate is a hard substrate, such a problem does not occur.
It is preferable because the cleaning is enhanced. More preferably, scrub cleaning, that is, cleaning is performed by mechanically rubbing in the presence of a cleaning liquid. The cleaning liquid is preferably an aqueous surfactant solution because the cleaning power is improved, and is more preferably an aqueous solution of a nonionic surfactant. Furthermore, it is more preferable to use a warm pure aqueous solution of a surfactant or the like. After cleaning, the disk substrate is dried by spin drying or the like.

When the texture treatment is performed by sputtering or vacuum deposition as described above, the texture treatment and the film formation of the magnetic layer can be continuously performed on the same vacuum line, but for some reason, When the atmosphere is opened between the texture treatment and the magnetic layer formation, it is preferable to perform washing after the texture treatment and before the formation of the magnetic layer (underlayer). This cleaning can also be performed by the same cleaning method as just described.

(5) Burnishing Process The burnishing process is performed to remove abnormal protrusions existing on the disk surface after film formation and finish the surface. In the burnishing process using a polishing tape, the polishing tape, which is made by placing abrasive grains such as alumina and diamond on a flexible support with an organic binder, is brought into contact with the surface of the disk by applying an appropriate pressure, and the disk is polished. This is done by running the tape. As such a burnishing process, for example, there is one disclosed in JP-A-59-148134.

A lubricating layer may be formed after the burnishing step in order to improve runnability. The lubricating layer has a thickness of about 5 to 40 liters, and as the lubricant, a lubricant having a polar group or a lubricant having no polar group is used alone or in combination. For example, after applying a solution of a lubricant having a polar group, a solution of a lubricant having no polar group at the end is applied, or a mixed solution of a lubricant having a polar group and a lubricant having no polar group is applied. A lubricant having a polar group can be present on the lower layer side and a lubricant having no polar group can be present on the upper layer side. As the lubricant having a polar group, there are perfluoropolyether type lubricants having a molecular weight of 2000 to 4000, and those having an aromatic ring at the terminal are particularly preferable. As a lubricant without polar groups, the molecular weight is 20
A perfluoropolyether type of 100 to 10,000 is preferable.

The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples.

[0019]

【Example】

Examples 1 to ³ glassy carbon substrates having a diameter of 1.8 inches, a thickness of 25 mils and a specific gravity of 1.5 g / cm ³ were prepared. A Ti layer having a thickness of 100 nm was formed on this carbon substrate by DC magnetron sputtering under the conditions of Ar gas pressure of 2 mTorr and substrate temperature of 250 ° C. Then, under the conditions of Ar gas pressure of 2 mTorr and substrate temperature of 260 ° C., an Al—Si alloy layer (Al: Si = 10: 90 / wt%) having a thickness of 20 nm was formed on the Ti layer by DC magnetron sputtering. After that, under the conditions of Ar gas pressure of 2 mTorr and substrate temperature of 260 ° C., Al− was formed by DC magnetron sputtering.
A 25 nm thick amorphous carbon (diamond-like carbon) layer was formed on the Si alloy layer.

After performing the texture treatment in this way, Ar gas pressure of 2 mTorr, in the same vacuum line,
Under the condition of the substrate temperature of 200 ° C., a Ti layer with a thickness of 100 nm is formed on the amorphous carbon layer by using a DC magnetron sputtering device, and then a C layer with a thickness of 40 nm is formed on this Ti layer.
The r layer is provided. Furthermore, Ar gas pressure 2mTorr, substrate temperature 260 ℃
Under the conditions of DC magnetron sputtering, Cr
A 400 nm-thick CoCrPt-based alloy magnetic layer was provided on the layer. Then, using a facing target type sputtering apparatus equipped with a glassy carbon target, Ar gas pressure 2 mTo
Under the condition of rr, a protective layer made of amorphous carbon (diamond-like carbon) having a thickness of 20 nm was provided on the magnetic layer.

After forming the film in this way, the substrate was washed as follows. Example 1: The operation of immersing in pure water at 60 ° C. for 15 seconds was repeated 3 times, further immersing in pure water at 60 ° C. for 15 seconds, and then pulled up at a speed of 70 mm / s (method 1). Example 2: The same procedure as in Example 1 was carried out except that ultrasonic waves of 950 kHz were used together. Example 3: The operation of rubbing a polyvinyl alcohol scrub pad at a contact pressure of 0.5 kg / cm ² for 15 seconds while applying pure water at 60 ° C. was repeated 3 times, and then the disk was applied while applying pure water at 60 ° C. It was spun at 50 rpm for 5 seconds and then the disk was spun at 5000 rpm for 10 seconds without pure water (method 2). Example 4: 10 of normal temperature Triton X (manufactured by Rohm & Haas Co.)
% Aqueous solution, rubbing a polyvinyl alcohol scrub pad at a contact pressure of 0.5 kg / cm ² for 15 seconds is repeated 3 times, and then the disk is rotated at 50 rpm for 5 seconds while applying pure water at 60 ° C. The disk was then spun at 5000 rpm for 10 seconds without pure water (method 3).

After the washing step was completed, burnishing was performed by pressing a polishing tape of WA # 10000 against the rotating disk at a relative speed of 100 m / sec for 1 second with a rubber roll. The roll hardness was a Shore hardness of 25, and the roll pressing pressure was 0.8 kgf.

After that, a solution of a perfluoropolyether lubricant (Fomblin AM2001 manufactured by Montecatini Co., Ltd.) was applied so that the thickness after drying was 17Å to form a lubricant layer on the protective layer to form a magnetic disk. Got

Example 5 A magnetic disk was obtained in the same manner as in Example 4, except that the NiP-plated aluminum substrate was used as the substrate of Example 4.

Example 6 A magnetic disk was obtained in the same manner as in Example 4, except that the glass substrate was used as the substrate in Example 4.

Example 7 In Example 4, after the texturing, the disk was taken out of the vacuum line, exposed to the atmosphere, cleaned by the above-mentioned method 3 and again transferred into the vacuum line.
An underlayer, a magnetic layer, and a protective layer were formed according to Example 4.
After that, the same operation as in Example 4 was carried out to obtain a magnetic disk.

Example 8 The same glassy carbon substrate as in Examples 1 to 4 was subjected to tape texture treatment in the atmosphere. The conditions for this tape texture processing are # 600 manufactured by Japan Micro Coating Co., Ltd.
Using 0 polishing tape, processing pressure 1.5kg / cm ² , tape vibration 3
It was 00 reciprocations / minute, the number of revolutions of the workpiece was 50 rpm, and the processing time was 20 seconds. After the texture treatment, washing was performed according to the above method 3. Thereafter, the same operations as in Example 4 were carried out to form a film and the like to obtain a magnetic disk.

Comparative Example 1 A magnetic disk was obtained in the same manner as in Example 4, but the cleaning by Method 3 was carried out not after the burnishing step but after the burnishing step and before the formation of the lubricating layer.

Comparative Example 2 A magnetic disk was obtained in the same manner as in Example 4, but the cleaning according to Method 3 was not performed.

The following characteristic evaluations were conducted on the magnetic disks obtained in the examples and comparative examples. Table 1 shows the results. (1) Appearance inspection Visual inspection under a halogen light was performed to check for scratches and the like, and a product having an appearance of a degree that practically caused no problems was passed. (2) It was carried out by using a MG150T device manufactured by GHT Proquip and using a 50% slider head. The pass / fail was judged by the flying height of 1.5 μ inch. (3) MCF (Error Characteristic) The error characteristic was evaluated by using MG150T device manufactured by Proquip, 70% slider head, and recording density of 5 kBPI. 16 or more errors were rejected with MP75% and EP20%.

[0031]

[Table 1]

As can be understood from these results, the magnetic recording medium according to the manufacturing method of the present invention is excellent in the appearance yield because the fine foreign matters are removed by washing during film formation and from the environment, and the head flying height is increased. The characteristics and error characteristics are also good.

[0033]

According to the manufacturing method of the present invention, it is possible to effectively remove minute foreign substances adhering to the surface of the substrate during the manufacturing process of the magnetic recording medium, and particularly when the texture treatment is isotropic. In addition, the defective appearance is remarkably reduced, and the certify (error) yield and the glide height yield are also improved.

Claims (8)

[Claims] 1. A method of manufacturing a magnetic recording medium, comprising: a step of texturing a substrate; a step of forming a magnetic layer on the textured substrate; and a burnishing step after forming the magnetic layer. A method of manufacturing a magnetic recording medium, comprising: performing cleaning between a film forming step of a magnetic layer and a burnishing step. 2. The method for manufacturing a magnetic recording medium according to claim 1, wherein the cleaning is performed by scrub cleaning, and the cleaning liquid is pure water or a surfactant aqueous solution. 3. The method for manufacturing a magnetic recording medium according to claim 2, wherein the cleaning is performed by immersion in warm pure water. 4. The method for manufacturing a magnetic recording medium according to claim 1, wherein the texture treatment is isotropically performed on the substrate surface. 5. The method for manufacturing a magnetic recording medium according to claim 4, wherein the texture treatment is performed by sputtering. 6. The method of manufacturing a magnetic recording medium according to claim 4, further comprising a cleaning step between the texture processing step and the magnetic layer forming step. 7. The method of manufacturing a magnetic recording medium according to claim 6, wherein the cleaning step is performed by scrub cleaning, and the cleaning liquid is pure water or a surfactant aqueous solution. 8. The method for manufacturing a magnetic recording medium according to claim 6, wherein the cleaning step is performed by immersion in warm pure water.