JPH11138424A - Slurry liquid with polycrystalline diamond fine powder contained in it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide slurry liquid, capable of obtaining the fine center-line average roughness (Ra) of a magnetic hard disc substrate and performing texture working without causing problems including head it. SOLUTION: Slurry liquid contains polycrystal diamond fine powder. The polycrystal diamond fine powder which has an average grain size of preferably 0.05-5 μm, is contained preferably 0.01-3 wt.% in the slurry liquid. In texture working for a magnetic hard disc substrate, a polishing tape is pushed against the surface of a magnetic hard disc substrate to be fed, the magnetic hard disc substrate is rotated in opposition to the moving direction of the polishing tape and the slurry liquid is supplied near a contact plane between the polishing tape and the surface of the magnetic hard disc substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slurry liquid and a polishing tape for use in precision processing of a magnetic hard disk substrate surface, and more particularly to a fine center line average roughness (Ra) containing polycrystalline diamond fine powder. The present invention relates to a slurry liquid that can be obtained and a method for producing a magnetic hard disk substrate whose surface is textured using the slurry liquid.

[0002]

2. Description of the Related Art In recent years, with the development of the so-called high-tech industry centered on the electronics industry, the capacity of magnetic disks has been increased, and the demand for precise processing and fine finishing of the magnetic hard disk substrate surface has been increasing.

However, when the magnetic head is stopped on a very fine magnetic disk, there arises a problem that the magnetic head is attracted to the magnetic disk due to moisture, lubricant or the like adsorbed on the disk.

[0004] Therefore, in order to prevent the magnetic disk from being attracted and to impart the magnetic anisotropy of the magnetic film of the magnetic disk in the circumferential direction, the magnetic disk is concentrically formed on the substrate surface in the circumferential direction of the substrate. Texture processing for forming fine irregularities is performed. For texture processing, use a processing liquid (slurry liquid) in which abrasive grains such as white fused alumina (WA) are dispersed in a liquid, or a polishing tape in which abrasive grains are applied to a backing member such as polyester Is performed.

[0005]

Conventionally used abrasives include alumina, diamond, silicon carbide, chromium oxide, CB iron oxide and cerium oxide. White fused alumina (WA), which is a particle obtained by pulverizing electrofused alumina, is a commonly used abrasive when texturing the surface of a magnetic disk substrate.

However, since it is difficult to control the size, shape, or cracking of the shards when crushing the abrasive, the crushed alumina abrasive grains are not uniform, and There is a variation in shape, shape and the like. When texture processing is performed with a slurry liquid containing large alumina abrasive grains, the large alumina abrasive grains will cut the substrate surface more deeply than necessary, and the shaved traces will swell on the substrate surface, forming protrusions There is.

[0007] Some pulverized cracks have irregular corners and some have very sharp and sharp points. Even when texture processing is performed using alumina abrasive grains having corners, the surface of the magnetic hard disk substrate is still shaved more than necessary and projections are formed as described above. Also, if a sharp pointed part breaks during texture processing, that part will pierce the magnetic hard disk substrate surface and become a protrusion, or it will deviate from the concentric direction to the broken beat, concentrically There is a possibility that scratches other than the above-mentioned groove may be formed.

Further, the alumina abrasive grains themselves may cut into the surface of the substrate to form projections.

[0009] Since diamond particles have a regular shape, they have less variation in size and shape than alumina abrasive grains. Therefore, when polishing is performed using diamond as abrasive grains, the unevenness formed on the substrate surface becomes relatively uniform and fine.

[0010] In addition to the fact that diamond has a regular particle shape, diamond also has excellent properties as abrasive grains. For example, diamond has the highest hardness as abrasive abrasive grains, so that during polishing, the diamond abrasive grains do not lose their material to be polished. Very hard materials (ultra-hard materials) that cannot be ground or polished with other substances can also be polished. In addition, because the wear is small, the polishing ability does not decrease even if it is used many times, it is possible to maintain a certain degree of polishing,
It withstands long-term use and is economical. In addition,
Although frictional heat is generated during polishing, diamond has a great resistance to this heat. Further, it has excellent oxidation resistance, does not rust even when used for a long time, and can maintain the polishing ability. Further, since it has excellent resistance to reaction with a workpiece, it can be used for polishing various substances.

However, conventionally used diamonds are single crystal diamonds, and they have corners even though they are smaller than alumina abrasive grains. As described above, diamond has the highest hardness as abrasive abrasive grains, and therefore has excellent machinability, but such corners easily damage the material to be polished. In addition, the above-mentioned protrusion may be formed.

As the recording density of the magnetic disk increases, the height of the magnetic head on the magnetic disk is reduced to reduce the distance between the magnetic head and the magnetic disk in order to increase the signal sensitivity during recording and reproduction. However, if there is a protrusion as described above, the magnetic head collides with the protrusion when the height of the magnetic head is lowered (head hit). However, if the texture processing is performed only lightly so as not to cause protrusions, the smoothness of the magnetic disk is too high, and the head is attracted as described above.

Therefore, there is a need for a slurry liquid containing abrasive grains capable of obtaining a fine center line average roughness without causing a problem such as a head hit.

[0014]

The slurry of the present invention comprises:
Contains polycrystalline diamond fines. Polycrystalline diamond has a rounder shape than single crystal diamond. Therefore, the portion in contact with the surface of the magnetic hard disk substrate is spherical and substantially uniform. Therefore, when polishing is performed with a slurry liquid containing polycrystalline diamond fine powder, a very uniform and fine center line average roughness can be obtained.

Further, unlike a single crystal diamond, since there are no corners, the surface of the magnetic hard disk substrate is not polished deeply or bitten. For this reason,
There are no protrusions that cause head hits and no scratches that cause errors. There is no fear that the abrasive grains themselves will bite into the surface of the magnetic hard disk substrate and become projections.

Further, since it is diamond, it has the same advantages as a single crystal diamond, such as abrasion resistance, heat resistance, oxidation resistance and reaction resistance.

[0017]

DETAILED DESCRIPTION OF THE INVENTION The slurry liquid of the present invention contains fine powder of polycrystalline diamond.

The fine polycrystalline diamond powder of the present invention preferably has an average particle size d50 of 0.05 to 5 μm and a concentration in the slurry liquid of preferably 0.01 to 3% by weight.

The slurry liquid is preferably an aqueous solution containing 0.5 to 30% by weight of a surfactant. This is because the surfactant acts to uniformly disperse the abrasive grains and prevent the abrasive grains from settling. Although a well-known surfactant can be used, polyoxyethylene alkyl ether sulfate is preferred. The slurry liquid of the present invention is produced by dispersing polycrystalline diamond fine powder in a water-soluble liquid containing a surfactant, and mixing and stirring.

The texture processing of the magnetic hard disk substrate is performed by pressing the polishing tape against the surface of the magnetic hard disk substrate, feeding the polishing tape, and rotating the magnetic hard disk substrate in the opposite direction to the polishing tape, so that the polishing tape and the surface of the magnetic hard disk substrate are rotated. This is performed by supplying a slurry liquid in the vicinity of the contact surface with the slurry.

By using the slurry liquid of the present invention containing fine powder of polycrystalline diamond, the same effect as polishing with uniform abrasive grains can be obtained, and the center line average is finer than the conventional texture processing. Roughness can be achieved.

Further, since there are no corners, the magnetic hard disk substrate surface is not polished deeply with abrasive grains to form projections, and the abrasive grains themselves do not bite into projections. No head hits or errors occur.

Furthermore, since the slurry liquid of the present invention can be easily washed with water, similarly to the conventional slurry liquid, the treatment after polishing is simple.

[0024]

FIG. 1 shows a conventional single crystal diamond fine powder,
2 containing the polycrystalline diamond fine powder of the present invention.
FIG. 4 is a graph showing the relationship between the particle size (μm) of diamond abrasive grains and the center line average roughness (Ra, unit (テ ク ス チ ャ)) after texture processing for various types of slurry liquids. The method of measuring the values in FIG. 1 will be described with reference to FIG.

FIG. 2 is a view showing a state in which texture processing using a slurry liquid is performed.

The magnetic hard disk substrate used for texture processing is obtained by subjecting an aluminum plate to Ni-P plating and polished.

As the apparatus, a texture processing apparatus manufactured by Nippon Micro Coating Co., Ltd. was used.

As shown in FIG. 2, this texture processing apparatus has a rubber roller 4 rotatable with respect to a bearing shaft 3 and a nozzle whose ejection port is directed to the vicinity of the contact surface between the polishing tape 7 and the surface of the magnetic hard disk substrate 8. 2, the pressure of the polishing tape 7 on the surface of the magnetic hard disk substrate 8 is adjusted by the inner pressure 5 and the outer pressure 6 applied to the bearing shaft 3.

The texture processing was performed under the following conditions.

The rotation speed of the magnetic hard disk substrate 8 is
It was 95 rpm.

The pressing pressure is 1.0 kg (inside pressure 5) and 1.2 kg (outside pressure 6) via a rubber roller 4 having a hardness of 50 degrees.
The polishing tape 7 is pressed against the surface of the magnetic hard disk substrate 8 with a vibration of 150 times / minute (that is, in the radial direction of the magnetic hard disk substrate 8) with an amplitude of 3 mm at a running speed of 150 mm / minute. The substrate 8 was run in a direction opposite to the rotation direction of the substrate 8 to perform texture processing. Here, the polishing tape is swung in the radial direction of the magnetic hard disk substrate in order to secure a floating distance of the magnetic head from the surface of the magnetic hard disk substrate in order to avoid an extreme change in the surface roughness of the substrate. .

The slurry liquid 1 was dropped from the nozzle 2 onto the magnetic hard disk substrate 8. The drop amount was 4 cc per minute.

Two types of slurry liquid 1 are produced, one containing single-crystal diamond fine powder, which is a conventional abrasive, and the other containing polycrystalline diamond fine, which is the abrasive of the present invention. Was. Specifically, 0.1% by weight of the slurry liquid is a single crystal diamond fine powder having an average particle diameter of 0.5 μm, and a water-soluble liquid containing 5% by weight of the slurry liquid such as polyoxyethylene alkyl ether sulfate as a surfactant. 0.1% by weight of the slurry liquid of the mixed and stirred polycrystalline diamond fine powder having an average particle diameter of 0.5 μm, and a water-soluble liquid containing 5% by weight of the slurry liquid such as polyoxyethylene alkyl ether sulfate as a surfactant. Was stirred and produced.

From FIG. 1, it can be seen that the center line average roughness is clearly smaller when texture processing is performed with the slurry liquid containing polycrystalline diamond fine powder of the present invention than with the conventional slurry liquid containing single crystal diamond fine powder. I understand.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing two types of slurries containing a single crystal diamond fine powder and a polycrystalline diamond fine powder, the particle diameter (μm) of diamond fine powder abrasive grains, and the center line after texture processing. It shows the relationship with the average roughness (Ra, unit (Å)).

FIG. 2 is a diagram showing a state where a texture processing using a slurry liquid is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Slurry liquid 2 ... Nozzle 3 ... Bearing shaft 4 ... Rubber roller 5 ... Inner pressure 6 ... Outer pressure 7 ... Abrasive tape 8 ... Magnetic hard disk substrate

Claims (5)

[Claims] 1. A slurry liquid for texturing the surface of a magnetic hard disk substrate, the slurry liquid containing polycrystalline diamond fine powder. 2. The slurry liquid according to claim 1, wherein the polycrystalline diamond fine powder has an average particle size d50 of 0.05 to 0.05.
The slurry liquid, which is 5 μm. 3. The slurry liquid according to claim 1, wherein the slurry liquid contains 0.01 to 3% by weight of the polycrystalline diamond fine powder of the slurry liquid. 4. The slurry liquid according to claim 1, comprising 0.5 to 30% by weight of the slurry liquid of a surfactant.
Slurry liquid. 5. A method for producing a magnetic hard disk substrate having a textured surface using a slurry liquid containing polycrystalline diamond fine powder, wherein a polishing tape is formed while dropping the slurry liquid containing polycrystalline diamond fine powder. The method of pressing against the surface of the magnetic hard disk substrate and rotating the magnetic hard disk substrate itself.