JPH11138423A - Slurry liquid with monocrystalline polyhedron alumina contained in it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slurry liquid which contains monocrystalline polyhedron alumina as spherical polishing material abrasive grain, is capable of obtaining the fine center-line average roughness (Ra) of a magnetic hard disc substrate and capable of texture working without causing problems including head heat. SOLUTION: Slurry liquid contains monocrystalline polyhedron alumina as spherical polishing material abrasive grain. The monocrystalline polyhedron alumina which has an average grain size of 0.1-5 μm, preferably 0.1-3 μm, is contained 0.1-5 wt.% in the slurry liquid, preferably 0.1-3 wt.%. The slurry liquid preferably contains 1-20 wt.% surface active agent. In texture working using the slurry liquid, a polishing tape is pushed against the surface of a magnetic hard disc substrate via a rubber roller while dropping the slurry liquid, into which monocrystallien polyhedron alumina and water-soluble liquid with a surface active agent contained in it are mixing stirred, and the polishing tape is moved in opposition to the rotating direction while rotating the magnetic hard disc itself.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slurry for use in precision processing of a magnetic hard disk substrate surface, and more particularly to a slurry containing single-crystal polyhedral alumina, having a fine center line average roughness (Ra) and a high grinding power. 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 abrasive grains are produced by grinding an abrasive. For example, the alumina abrasive grains are particles obtained by pulverizing electrofused alumina.

However, since it is difficult to control the size, shape, or cracking of the shards when crushing the abrasive grains, the crushed abrasive grains are not uniform. There are variations in size and shape. When texture processing is performed with a slurry liquid containing large abrasive grains, there is a problem that the large abrasive grains cut the substrate surface more deeply than necessary, and the shaved traces are raised on the substrate surface, and a projection is formed. .

[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 abrasive grains themselves may cut into the surface of the substrate and become projections.

When the recording density of the magnetic disk increases, the height of the magnetic head on the magnetic disk is reduced and the distance between the magnetic head and the magnetic disk is reduced in order to increase the signal sensitivity during recording and reproduction. However, if the protrusion is present, 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.

[0010] Furthermore, in order to reduce the center line average roughness, it is necessary to use small abrasive grains. However, since the grinding power is insufficient with small abrasive grains, coarse grinding is first performed using large abrasive grains. Then, two steps of finishing using the next smaller abrasive grains are required.

[0011] Therefore, there is a need for a slurry liquid containing abrasive abrasive grains that can obtain a fine center line average roughness without causing a problem such as a head hit and have a high grinding force.

[0012]

The slurry of the present invention comprises:
Includes single crystal polyhedral alumina which is a spherical abrasive grain. The single-crystal polyhedral alumina has a spherical surface everywhere in contact with the surface of the magnetic hard disk substrate and is substantially uniform.

Further, unlike the crushed abrasive grains, there is no corner or sharp point, so that the surface of the magnetic hard disk substrate is not deeply polished or bitten. For this reason, a protrusion that causes a head hit and a scratch that causes an error are not formed. There is no fear that the abrasive grains themselves will bite into the surface of the magnetic hard disk substrate and become projections.

Therefore, even if particles having a high grinding force and a large particle size are used, a uniform and fine center line average roughness can be obtained, and it is not necessary to use again a small particle size for finishing.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The slurry liquid of the present invention contains single-crystal polyhedral alumina which is a spherical abrasive grain.

The single-crystal polyhedral alumina suitable for use in the present invention is, for example, the Showlight series or Alfit series (both available from Showa Denko KK).

The average particle size of the single-crystal polyhedral alumina is 0.1 to
The concentration is 5 μm, preferably 0.1 to 3 μm, and the concentration in the slurry liquid is 0.1 to 5% by weight, preferably 0.1 to 2% by weight.

The slurry liquid is preferably an aqueous solution containing 1 to 20% 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, it is preferably a polyalkylene glycol.

The slurry liquid of the present invention is produced by dispersing single-crystal polyhedral alumina in a surfactant and mixing and stirring.

FIG. 1 is a view showing that a texture processing is performed using the slurry liquid of the present invention.

While the slurry liquid 10 of the present invention is dropped from the nozzle 12 on the surface of the rotating magnetic hard disk substrate 11,
The polishing tape 14 is pressed against the surface of the magnetic hard disk substrate 11 via the rubber roller 13 so that the magnetic hard disk substrate 11
The tape 14 is run in the direction opposite to the rotation direction of the tape to perform texture processing.

By using the slurry liquid of the present invention containing single-crystal polyhedral alumina, the same effect as polishing with uniform abrasive grains can be obtained, and a center line average finer than that of the conventional texture processing can be obtained. Roughness can be achieved.

Also, since there are no corners or sharp points,
Abrasive abrasive grains do not polish the magnetic hard disk substrate surface deeply to form protrusions, and abrasive abrasive grains themselves do not bite into protrusions, so head hits and errors do not occur .

Further, even if large abrasive particles having a high grinding force are used, fine center line average roughness can be obtained, so that rough grinding and finish polishing for obtaining fine center line average roughness are required. Can be performed simultaneously and is efficient.

Further, 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.

FIG. 2 shows texture processing using three types of slurry liquids each containing diamond and ground alumina, which are conventional abrasive grains, and single-crystal polyhedral alumina, which is a spherical abrasive grain of the present invention. Center line average roughness (Ra, unit (Å)), center line peak height (Rp, unit (Å)), and center line trough height (Rv, unit (Å))
Is measured and shown in a graph. All of the abrasive grains have a particle size of 8000 and an average particle size of about 1 μm.

A specific texture processing method will be described with reference to FIG.

A rubber roller is added while dropping a slurry liquid 10 obtained by mixing and stirring abrasive grains and a water-soluble liquid containing a polyalkylene glycol / fatty acid ester as a surfactant.
13 polish the polishing tape 14 through the magnetic hard disk substrate surface
While pressing the magnetic hard disk 11 itself against the 11 with a force of 1 to 1.2 kgf, running the polishing tape 14 in the direction opposite to the rotation direction, performing texture processing for 15 seconds, stylus type roughness Ra, R using a total (TENCOR P-1)
p and Rv were measured. Abrasive abrasive is one of slurry liquid
% Of the polyalkylene glycol / fatty acid ester as a surfactant was contained at a ratio of 5% by weight of the slurry liquid.

Table 1 shows the numerical values of FIG.
The number of scratches was visually measured and the number was shown.

From FIG. 2 and Table 1, it can be seen that Ra, Rp and Rv are clearly smaller than those of the prior art when texture processing is performed with the slurry containing the single-crystal polyhedral alumina of the present invention. Also, the number of scratches is clearly smaller than the conventional one.

[0031]

Table 1 Ra Rp Rv Scratch blank 22Å 90Å 133Å 10 places FP504 22Å 90Å 127Å 8 places FP404 13Å 51Å 78Å 3 places FIG. Particle size 6000, average particle size 2 μm
5 is an electron micrograph of the above, (a) is 5000 times,
(B) is magnified 10,000 times and (c) is magnified 20,000 times.

FIG. 4 is also an electron micrograph of abrasive particles of white fused alumina (WA), which is simply a crushed abrasive, having a particle size of 8000 and an average particle size of 1 μm. 5,000 times, (b) 10,000 times, and (c) 20,000 times.

According to the electron micrographs shown in FIGS. 3 and 4, the crushed abrasive particles are irregular in size, shape or cracks such as broken pieces, and have many corners and sharply pointed portions. You can see that.

FIG. 5 is an electron micrograph of a single-crystal polyhedral alumina abrasive particle of the present invention having a particle size of 6000 and an average particle size of 2 μm. As in FIG. 3, (a) is 5000
Times, (b) is 10000 times, and (c) is 20000 times.
It was enlarged twice.

FIG. 6 is also an electron micrograph of single-crystal polyhedral alumina abrasive particles of the present invention having a particle size of 8000 and an average particle size of 1 μm. As in FIG. 3, FIG.
00 times, (b) 10000 times, and (c) 200 times
It is enlarged by a factor of 00.

The electron micrographs of FIGS. 5 and 6 show that the single-crystal polyhedral alumina of the present invention is very uniform in size and shape.

[Brief description of the drawings]

FIG. 1 is a view showing that a texture processing is performed using a slurry liquid of the present invention.

FIG. 2 is a diagram showing the center line average roughness (Ra, unit (Å)) of the surface of a magnetic hard disk substrate after texture processing using a slurry liquid containing diamond, pulverized alumina, or single-crystal polyhedral alumina; Center line mountain height (R
p, unit (Å)), and center line trough height (Rv, unit (Å)).

FIG. 3 is an electron micrograph of crushed abrasive particles of white fused alumina (WA) as abrasive particles having a particle size of 6000 and an average particle size of 2 μm.
00 times, (b) 10000 times, and (c) 200 times
It is enlarged by a factor of 00.

FIG. 4 is an electron micrograph of white fused alumina (WA) abrasive particles, which are pulverized abrasive particles, having a particle size of 8000 and an average particle size of 1 μm, and (a) shows a value of 50.
00 times, (b) 10000 times, and (c) 200 times
It is enlarged by a factor of 00.

FIG. 5 is an electron micrograph of single-crystal polyhedral alumina abrasive particles, which are spherical abrasive particles of the present invention, having a particle size of 6000 and an average particle size of 2 μm.
0x, (b) 10000x, and (c) 2000x
It is enlarged to 0 times.

FIG. 6 is an electron micrograph of single-crystal polyhedral alumina abrasive particles, which are spherical abrasive particles of the present invention, having a particle size of 8000 and an average particle size of 1 μm.
0x, (b) 10000x, and (c) 2000x
It is enlarged to 0 times.

[Explanation of symbols]

 10 ... Slurry liquid 11 ... Magnetic hard disk substrate 12 ... Nozzle 13 ... Rubber roller 14 ... Abrasive tape

Claims (4)

[Claims] 1. A slurry liquid for performing texturing, comprising a spherical abrasive, wherein the spherical abrasive is a single-crystal polyhedral alumina. 2. The slurry liquid according to claim 1, wherein the single-crystal polyhedral alumina has an average particle size of 0.1 to 5 μm.
Where the slurry liquid. 3. The slurry liquid according to claim 1, comprising 0.1 to 5% by weight of the single crystal polyhedral alumina of the slurry liquid. 4. A method for producing a magnetic hard disk substrate having a textured surface using a slurry liquid containing single-crystal polyhedral alumina, wherein a polishing tape is dropped while dropping the slurry liquid containing single-crystal polyhedral alumina. The method of pressing against the surface of the magnetic hard disk substrate and rotating the magnetic hard disk substrate itself.