JPH0997422A - Method for texturing substrate for magnetic disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable uniform texturing and texturing in the air and to considerably enhance production efficiency by heating a carbon substrate in an oxidizing atmosphere. SOLUTION: A glassy carbon substrate used in this texturing method is a surface-polished glassy carbon substrate having 1.4-1.6g/cm<3> density. The substrate is textured by heating to 200-1,000 deg.C, preferably 400-700 deg.C in an oxidizing atmosphere. This atmosphere is obtd. by the presence of oxidizing gas and oxygen is suitable for use as the oxidizing gas. The oxidation texturing can be carried out in the air with an org. substance firing furnace.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for texturing a magnetic disk substrate. More specifically, the present invention relates to a texture method capable of subjecting a carbon substrate for a magnetic disk to a uniform texture treatment.

[0002]

2. Description of the Related Art Generally, in a magnetic recording medium such as a magnetic disk, a magnetic layer is formed on a support (substrate) by sputtering or the like, and a protective layer such as carbon or metal oxide is provided on the magnetic layer. BACKGROUND ART A fluoropolyether liquid lubricant is applied by a dip coating method or a spin coating method to form a lubricating layer.

One of the main forms of magnetic disks is a so-called hard disk drive in which a floating magnetic head is arranged. In this hard disk device, the magnetic head and the magnetic disk are in contact with each other when stopped, and the magnetic head (rotating) and the magnetic disk are not in contact with each other when started, that is, a so-called contact start stop (CS).
The S) method is the mainstream. In this method, adsorption may occur on the magnetic head levitation surface and the magnetic disk surface when the disk is stopped.To solve this, the surface of the disk substrate is polished beforehand with a polishing tape (tape polishing) so that the disk surface is appropriately roughened. The texture processing for surfaceization is generally performed.

The flying height of the magnetic head is preferably as small as possible for high density recording, and it is desirable that the height of the protrusions be reasonably uniform. However, it is difficult to accurately control the degree of surface roughening by the tape polishing method. Further, in a brittle material such as a carbon substrate or a glass substrate, a method using a polishing tape is fragile and easily causes microcracks, which in turn causes an error. There was a limit. Against this background, particularly for the purpose of improving the texture of the carbon substrate, JP-A-3-283
The carbon substrate is heat-treated as described in Japanese Patent Application Laid-Open No. 018,018, or amorphous as described in Japanese Patent Application Laid-Open Nos. 4-214225, 4-214227, and 5-94618. A method has been proposed in which a carbon substrate is subjected to a polishing process and a heating process in the presence of an oxidizing gas to perform a texture treatment.

[0005]

However, in such a hard disk drive that requires an ultra-low flying height of 1.3 micro inches or less, such texture processing alone completely solves the problem of sticking between the disk and the head. It was difficult. In addition, JP-A-3-2830
In the method disclosed in Japanese Patent No. 18, when the carbon substrate is heated in the atmosphere, roughening locally proceeds, making deep pits on the substrate surface and making it difficult to uniformly perform the texture treatment. This is presumably because the carbon substrate material used in this method is non-homogeneous and susceptible to contamination in the atmosphere. Especially, Ni and F in the atmosphere
It is considered that the transition metal such as e acts as a carbon oxidation catalyst. As described above,
According to the method disclosed in Japanese Patent No. 8, it is necessary to heat the substrate in a vacuum, but the oxidation texture in a vacuum has a slow processing speed, and in order to adjust the vacuum environment, careful attention must be paid to cleaning the inside of the system. In addition, it is necessary to prepare an expensive vacuum device, and an industrially more advantageous method is required.

[0006]

DISCLOSURE OF THE INVENTION As a result of intensive studies conducted by the present inventors in view of the above points, the density is 1.4 to 1.6 g / c.
It was found that the heat treatment in an oxidizing atmosphere using a m ³ carbon substrate allows the texture treatment to be performed uniformly, and further enables the treatment in the atmosphere, thereby significantly improving the production efficiency. It came to completion.

That is, according to the present invention, a surface-polished glassy carbon substrate for a magnetic disk having a density of 1.4 to 1.6 g / cm ³ is heat-treated at a temperature of 200 to 1000 ° C. in an oxidizing atmosphere. The present invention provides a method for texturing a magnetic disk substrate, characterized in that the surface of the substrate is roughened.

First, the glassy carbon substrate used in the present invention will be described. The glassy carbon substrate used in the texturing method of the present invention has a surface-polished density of 1.4 to 1.6 g / cm ³ . If the density is less than 1.4 g / cm ³ , the error characteristics are poor,
On the other hand, if the density exceeds 1.6 g / cm ³ , the CSS characteristics will be significantly deteriorated when the texture treatment is performed in the air.

Here, the glassy carbon substrate includes a glassy carbon simple substance and a composite material containing glassy carbon as a base material. These are in the form of a molded body molded by various well-known molding methods such as casting, compression, extrusion, or a deposited body in which a glassy carbon material is directly deposited on the surface of a substrate by a sputtering method or a vapor deposition method. It is an eggplant, and specifically, it is preferable to use the materials described in JP-A-60-35333.

The glassy carbon material is a glassy carbon material obtained by carbonizing a thermosetting resin, a glassy carbon material obtained by carbonizing a resin which is modified so as to be thermoset by copolymerization or cocondensation, There are glassy carbon materials and the like obtained by remarkably hindering crystallization by chemical treatment in the course of curing or carbonization. The thermosetting resin used here is a phenol resin,
Examples thereof include epoxy resin, unsaturated polyester resin, ester resin, furan resin, urea resin, melamine resin, alkyd resin, and xylene resin. These resins are used as they are, or by blending or modifying. Preferably, it is a thermosetting resin that can contain 20% by weight or more of water in the state of an initial condensate before curing. "Initial condensate" means a resin before curing, which may contain a considerable amount of raw material monomers,
A resin composition in which viscosity has increased due to addition and / or condensation reaction to some extent. The initial condensate of the thermosetting resin referred to in the present invention can be appropriately designed depending on the type of raw material resin, blend ratio, control of polymerization degree, modification and the like. For example, a resin based on a modified phenol resin is disclosed in JP-A-60-1.
7208, JP-A-60-171209, and JP-A-60-171210. As those that can be modified into a thermosetting resin, the above-mentioned phenolic resins, thermosetting resins such as furan resin, or asphalt, materials having a naturally high carbonization yield such as pitches, lignin, cellulose, Examples include hydrophilic substances having a relatively high carbon yield such as taragacan gum, gum arabic, humic compounds and various sugars.

The composite material aggregate containing the glassy carbon material in the present invention means an aggregate of composite material containing the above-mentioned glassy carbon material and a synthetic resin and / or a carbonaceous filler. As synthetic resin, thermoplastic resin such as vinyl chloride resin, polyvinyl acetate resin, polystyrene resin, or thermosetting of phenol resin, epoxy resin, polyester resin, furan resin, urea resin, melamine resin, alkyd resin, xylene resin, etc. Resins may be mentioned. The carbon filler means a general carbon material, and examples thereof include lignin and pitch having a high residual carbon ratio.

Next, the texture method in the present invention will be described. The texture step of the present invention comprises a glassy carbon substrate having a specific density as described above,
200 to 1000 ° C., preferably 4 in an oxidizing atmosphere
It is carried out by heating to 00 to 700 ° C. The oxidizing atmosphere is obtained by the presence of an oxidizing gas, and oxygen is suitable as the oxidizing gas. Other gases such as water vapor and carbon dioxide may be used if necessary. Conditions such as heating temperature and heating time in the texture process are
It is desirable to adjust Ra (centerline average roughness) of the support to 10 to 100Å and Rp (centerline maximum height) to 50 to 500Å. Within the above range, reduction in the flying height of the head and sticking of the head can be prevented. The texture process is described in JP-A-3-283018 and JP-A-4.
-214225, JP-A-4-214227, JP-A-5-94618 and the like.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The glassy carbon substrate used in the texturing method of the present invention is obtained, for example, by the following method. First, the thermosetting resin as described above is mixed with optional components to be blended as necessary, poured into a desired mold, and cured under heating. Next, this is processed into a donut shape, further heated while raising the temperature, heated and baked in a vacuum, and then cooled. Alternatively, the raw material may be injected between glass plates to form a plate-shaped resin, which is then die-cut into a donut shape and similarly heated and baked. The density of the glassy carbon substrate before performing the texture treatment needs to have a density of 1.4 to 1.6 g / cm ³ as described above, and the material of the substrate, the heating conditions, etc., so that the density falls within this range. Is adjusted appropriately. The glassy carbon substrate is surface-polished in advance before the texture treatment. The surface polishing method is generally performed with abrasive grains having a grain size of 0.1 to 50 μm. In order to perform the texture treatment more uniformly, it is preferable that the glassy carbon substrate has a half-value width of the diffraction peak of the (002) plane by X-ray diffraction of 3 degrees or more. The number of surface defects having a size of 3 μm or more is preferably 1 / cm ² or less, and more preferably both of them are used.

Next, the glassy carbon substrate is subjected to a texture treatment by heating it at 200 to 1000 ° C. in an atmosphere of an oxidizing gas such as oxygen. In the present invention, the oxidation texture treatment can be carried out in the atmosphere using an organic firing furnace. Conditions such as heating temperature and heating time in the texture step are adjusted so that Ra (centerline average roughness) of the support is 10 to 100Å and Rp (centerline maximum height) is 50 to 500Å. The glassy carbon substrate that has been subjected to the texture treatment is washed according to a conventional method and is used for manufacturing a magnetic disk.

[0015]

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

Examples 1 to 5 and Comparative Examples 1 to 7 Preparation of glassy carbon substrate 500 parts by weight of furfuryl alcohol, 400 parts by weight of 92% paraformaldehyde and 30 parts by weight of water are dissolved by stirring at 85 ° C. Then phenol 520 under stirring
A mixed solution of 1 part by weight, 9.5 parts by weight of calcium hydroxide and 45 parts by weight of water was added dropwise, and the mixture was reacted at 75 ° C. for 3 hours. Thereafter, 80 parts by weight of phenol and the above-mentioned phenol / calcium hydroxide / water mixed solution were further added dropwise, and the mixture was reacted at 85 ° C. for 2 hours. After cooling to 30 ° C., the mixture was neutralized with a 30% aqueous solution of p-toluenesulfonic acid. This neutralized product is dehydrated under reduced pressure,
170 parts by weight of water are removed and furfuryl alcohol 50 is added.
0 parts by weight was added and mixed, and the insoluble matter in the resin was filtered with a membrane filter. The amount that this resin can contain was measured and found to be 35% by weight.

To 100 parts by weight of this thermosetting resin, 3.5 parts by weight of a mixed solution was added to 70% by weight of paratoluenesulfonic acid, 20% by weight of water and 10% by weight of cellosolve, and after sufficiently stirring, the thickness was 2 mm. It was poured into a disk-shaped mold and defoamed under reduced pressure. Then, it was heat-cured at 500 ° C. for 3 hours and at 80 ° C. for 2 days. Processing this thermoset into a predetermined donut shape,
Then, it is heated to 700 ° C. at a temperature rising rate of 2 to 5 ° C./hour in a nitrogen atmosphere in an organic material firing furnace, and further 0.5 mTorr.
120 at a heating rate of 5 to 20 ° C / hour in a vacuum of about r
After heating and baking to 0 ° C., holding at this temperature for 2 hours, and cooling, a glassy carbon substrate was obtained.

The glassy carbon substrate was made to have a particle size of 50 μm.
Center line roughness (Ra) by mirror polishing with ~ 0.1 μm abrasive grains
Was set to 7 to 15Å. Here, Ra was measured under the following conditions with a stylus roughness meter (TENCOR P2). Stylus diameter: 0.6 μm (needle curvature radius) Stylus pressing pressure: 7 mg Measurement length: 250 μm × 8 places Trace speed: 2.5 μm / sec Cutoff: 1.25 μm (low pass filter).

The density of this glassy carbon substrate is 1.5 g / cm ³ , and 2θ = 2 by X-ray diffraction.
The full width at half maximum of the diffraction peak of the (002) plane appearing in the vicinity of 0 to 30 ° is 3.9 °, and when observing surface defects with a polarization microscope and a differential microscope, there are no defects (voids or cracks) of 3 μm or more. Was / cm ² . In a similar way,
By changing the forming conditions, glassy carbon substrates having various densities, half widths and surface defect densities as shown in Tables 1 and 2 were produced.

Texture treatment The glassy carbon substrate obtained above was heated under the conditions shown in Tables 1 and 2 to perform texture treatment. Comparative Example 1 is # 6000 manufactured by Nippon Micro Coating Co., Ltd.
Using the polishing tape of No. 1, the tape was textured at a processing pressure of 1.5 kg / cm ² , a tape vibration of 300 reciprocations / minute, a work rotation speed of 50 rpm, and a processing time of 20 seconds. Tables 1 and 2 show the results of measuring Ra, Rp, and Rv (center line average height) before and after each texture treatment. In addition, Ra, R
p and Rv were measured by a stylus roughness meter by the same method as described above.

Preparation of Magnetic Disk Ar was placed on a glassy carbon substrate after texture treatment.
DC under gas pressure of 3 mTorr and substrate temperature of 200 ° C
Using a magnetron sputtering device, the underlying Cr film is 40
nm and a Co-Cr-Pt-B magnetic film were formed in order of 50 nm. Then, a carbon protective film having a thickness of 15 nm is formed on the magnetic film,
Further, 17 Å of a perfluoropolyether lubricant [Fomblin Z-03 (manufactured by Montecatini Co.)] was applied on the carbon protective film and dried.

Characteristic Evaluation The various magnetic disks obtained above were evaluated for CSS characteristics, glide height (GHT) characteristics and error characteristics by the following methods. The results are shown in Tables 1-2. * CSS characteristics; using a thin film head manufactured by Yamaha Corporation, head load 3.5g, head flying height 2.8μ inch, 4500
A cycle of operating for 5 seconds at rpm and stopping for 5 seconds was repeated, and the number of times until the static friction coefficient (μs) reached 0.6 was examined. * GHT characteristic: MG150T manufactured by PROQUIP was used, and a 50% slider head was used. The following evaluation was made based on the passing rate at a flying height of 1.5 μ inches. S: Passage rate is 90% or more A: Passage rate is 50% or more and less than 90% B: Passage rate is 30% or more and less than 50% C: Passage rate is less than 30% * Error characteristics; Error characteristics are manufactured by PROQUIP MG1
Evaluation was performed under the conditions of a recording density of 51 KFCZ using a 50T apparatus and a 70% slider head. The slice level was 70%, and the number of missing errors less than 16 bits was counted and evaluated as follows. S: 50% or more of the evaluation disks have 0 to 5 errors. A: The number of errors is 6 to 15 in 50% or more of the evaluation disks
Individual. B: The number of errors is 16 to 4 in 50% or more of the evaluation disks
There are five. C: 50% or more of the evaluation disks have 46 or more errors.

[0023]

[Table 1]

[0024]

[Table 2]

The state of the substrate surface after texture in Example 3 and Comparative Example 5 is enlarged and shown in FIG. 1 shows the substrate of Example 3, and FIG. 2 shows the substrate of Comparative Example 5. In Comparative Example 5 using a glassy carbon substrate other than the one defined in the present invention, the oxidation progressed nonuniformly and huge pits were generated. On the other hand, in Example 3, it can be seen that the oxidation proceeds uniformly.

[0026]

According to the present invention, the carbon substrate for a magnetic disk can be uniformly textured, and C
A magnetic disk having excellent SS characteristics, GHT characteristics, and error characteristics can be obtained. Moreover, since the texture method of the present invention can be performed in the atmosphere, the production efficiency is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a state of a substrate surface after being textured in Example 3;

FIG. 2 is a diagram showing a state of a substrate surface after being textured in Comparative Example 5.

Claims (3)

[Claims] 1. A surface-polished density of 1.4 to 1.6 g /
A glassy carbon substrate for a magnetic disk having a size of ³ cm ³ is heat-treated at a temperature of 200 to 1000 ° C. in an oxidizing atmosphere to roughen the surface of the substrate, and thus the texture of the magnetic disk substrate. Method. 2. The method for texturing a magnetic disk substrate according to claim 1, wherein the half-value width of the diffraction peak of the (002) plane by X-ray diffraction of the substrate is 3 degrees or more. 3. The method for texturing a magnetic disk substrate according to claim 1, wherein the number of surface defects of 3 μm or more on the substrate is 1 / cm ² or less.