JPH10214420A - Slurry for texturing of magnetic disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To high uniformly carry out texturing of a magnetic disk substrate and to deal with high density of magnetic recording by adding second super minute grains with a grain size smaller than abrasive grains for texturing slurry to the slurry. SOLUTION: Super minute grain diamond of material having hardness similar to the slurry and the grain size of 1-10nm is added to the texturing slurry consisting of the main abrasive grains such as diamond, alumina or silicon carbide, etc., by 10-80wt.% of main abrasive grains. Further, a solution of di- ethylene glycol mono-butyl ether is used as a dispersion medium. Thus, the super minute grain diamond lies between the main abrasive grains and a surface to be textured, and reduces rolling friction in the main abrasive grains, and shallows and narrows valleys constituting a texture, and high uniformity on a magnetic disk surface becomes possible. The addition of the second abrasive grains is easy, and a usual dispersion medium as it is used, and an excess cost isn't caused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a slurry used for texturing a magnetic disk substrate used in a fixed magnetic disk storage device.

[0002]

2. Description of the Related Art The storage density of magnetic disk devices has been increasing with the performance of computers. Only from the aspect of improving the storage density, it is necessary to make the distance between the magnetic head and the disk as small as possible, and it is ideal that the surfaces of both are as mirror as possible. However, the magnetic disk device is called a CSS (contact start / stop) system. When the magnetic disk stops, the magnetic head and the disk are in contact with each other. It is.
If the disk surface is completely a mirror surface, the coefficient of friction will be large and it will stick to the magnetic head when stopped, or it will be worn due to sliding at start-up and the magnetic layer will be destroyed. Is formed to reduce the contact area and reduce the friction coefficient.

[0003] Generally, in the case of a metal thin-film magnetic disk, the concavo-convex formation is performed by concentrically sliding the substrate surface of the magnetic disk with a buff or the like containing a tape or a slurry, and the abrasive grains held by the tape or the slurry. This is performed by texture processing to form uneven streaks. FIG. 1 is a perspective view showing a main part of the texture processing device. 1 is a substrate, 2 is a flocking buff tape, 3 is a rubber roller, and 4 is a slurry, and the substrate 1 is rotating. The processing with such abrasive grains is performed by the abrasive grains rolling on the surface of the workpiece, but the abrasive grains having a distorted shape (greater than the average grain size or larger in anisotropy than the average shape) have a low rolling resistance. And sharply cut into the surface of the workpiece to form a deep valley. In the valley portion, the clearance between the magnetic head and the magnetic head is too large, and a necessary read output cannot be obtained, resulting in an error. Further, both sides of the valley become steep peaks (burrs), which may collide with the magnetic head and degrade the flying characteristics.

[0004]

In response to the increase in the density of magnetic recording, a magnetic disk with a smaller flying height is required, and a texture processing with higher uniformity is required.
However, in the case of abrasive grains produced by crushing and classifying rough stones, conventional classification techniques cannot remove irregularly shaped abrasive grains and reduce rolling resistance, resulting in uniform texture. Processing could not be realized.

SUMMARY OF THE INVENTION An object of the present invention is to provide a textured slurry capable of performing highly uniform textured processing without forming a deep valley on a magnetic disk substrate.

[0006]

In order to achieve the above object, in a slurry for texturing a magnetic disk substrate in which abrasive grains are dispersed in a dispersion medium, a slurry having a particle diameter smaller than that of the abrasive grains is provided. It is assumed that the second abrasive has been added.
The abrasive is preferably diamond, alumina or silicon carbide, and the second abrasive is preferably ultrafine diamond.

The diameter of the ultrafine diamond is 1 to 1.
It is good to be 0 nm. The added amount of the ultrafine diamond is preferably 10 to 80% by weight of the abrasive. The dispersion medium is preferably an aqueous solution of diethylene glycol monobutyl ether.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an experiment for reducing rolling resistance using conventional abrasive grains (hereinafter referred to as main abrasive grains), the addition of ultrafine diamond as an additional component significantly improves the uniformity of texture. It is based on the finding. In the slurry for texturing of the present invention, the second abrasive grains are made of a material having the same hardness as the main abrasive grains or hardly different from the main abrasive grains (preferably higher than the main abrasive grains),
And if the grain size is smaller than the main abrasive grains, the second abrasive grains are interposed between the main abrasive grains and the surface of the workpiece, reduce the rolling friction of the main abrasive grains, and the valleys that constitute the texture as a whole are It is estimated to be shallow and the width of the valley narrow. If the hardness of the second abrasive grains is much smaller than that of the main abrasive grains, the second abrasive grains will be crushed by the main abrasive grains and will not be able to support the main abrasive grains, and the effect of addition will not be obtained.

In particular, since the ultrafine diamond has a small particle size, is uniform, and is close to a spherical shape, the above-mentioned effects are remarkable. The addition amount of the second abrasive is preferably about 50 w%, but if the addition amount is too small (several w% or less), the valley of the texture is too large (the same as in the conventional case). The grains do not hit the surface of the workpiece, and the processing efficiency is reduced.

Further, the aqueous solution of diethylene glycol monobutyl ether can maintain the friction reducing effect without agglomerating the second abrasive grains. Therefore, in the magnetic disk on which the texture is formed by using the texture processing slurry according to the present invention, the flying height is small, and improvement in density recording can be expected. The average grain size of the main abrasive grains is determined according to the required surface roughness, and is usually 1 to 3 μm. Example 1 18 g of alumina abrasive grains having a particle size of # 6000 and 2 g of ultrafine diamond having an average particle diameter of about 1 nm (manufactured by NOF Corporation) were dispersed in 1 liter of a 20 wt% solution of diethylene glycol monobutyl ether to prepare a slurry for texture processing. .

The texture processing was performed using an apparatus (FIG. 1) for pressing a flocking buff tape while dropping a slurry for texturing on a rotating substrate. A NiP-plated Al alloy substrate was used as the substrate of the magnetic disk. The surface roughness of the substrate was Rmin ≦ 3 nm and Rmax ≦ 50 nm. Texture processing conditions are: rotation speed = 100 RPM, processing time 30 se
c, the amount of drop was 3.0 ml / min. After the texturing, precision cleaning was performed so that powder and the like did not remain, followed by drying. After that, a Cr underlayer, Co-Cr-Ta magnetic layer, DLC (diamond-like carbon) protective layer were formed by sputtering, and a lubricating layer was formed by dip coating.
It was a magnetic disk. Example 2 4 g of silicon carbide abrasive grains having an average particle size of 2 μm (corresponding to a particle size of # 6000) and ultrafine diamond particles having an average particle size of ≒ 1 nm (Nippon Oil & Fat)
(Manufactured by Co., Ltd.) was dispersed in 1 liter of a 20% by weight solution of diethylene glycol monobutyl ether to prepare a slurry for texture processing.

Texture processing was performed under the same substrate and processing conditions as in Example 1, and a magnetic layer and a lubricating layer were similarly formed to obtain a magnetic disk. Example 3 4 g of single crystal diamond abrasive grains having an average particle size of 2 μm (corresponding to a particle size of # 6000) and 1 g of ultrafine diamond (manufactured by Nippon Oil & Fats Co., Ltd.) having an average particle size of ≒ 1 nm were added to 1 liter of a 20 wt% solution of diethylene glycol monobutyl ether. Dispersed and prepared a slurry for texturing.

Texture processing was performed under the same substrate and processing conditions as in Example 1, and a magnetic layer and a lubricating layer were similarly formed to obtain a magnetic disk. Comparative Example 1 A slurry for texturing was prepared by dispersing only 20 g of alumina abrasive grains having a particle size of # 6000 in 1 liter of a 20 wt% solution of diethylene glycol monobutyl ether.

Texture processing was performed under the same substrate and processing conditions as in Example 1, and a magnetic layer and a lubricating layer were similarly formed to obtain a magnetic disk. Comparative Example 2 Only 4 g of single-crystal diamond abrasive grains having an average particle size of 2 μm (corresponding to a particle size of # 6000) were dispersed in 1 liter of a 20 wt% solution of diethylene glycol monobutyl ether to prepare a slurry for texture processing.

The texture processing was performed under the same substrate and processing conditions as in Example 1, and a magnetic layer and a lubricating layer were similarly formed to obtain a magnetic disk. With respect to the magnetic disks manufactured in the above Examples and Comparative Examples, the surface roughness, the minimum magnetic head flying height, and the read error characteristics were evaluated. The depth of the valley (the distance from the center line of the valley to the bottom of the valley) was measured with a surface roughness meter (Surfcoder ET-30K, manufactured by Kosaka Laboratory Co., Ltd.), stylus diameter = 0.5 μm, measurement length = 0. The measurement was performed at 24 points per magnetic disk.

Table 1 shows the surface roughness, minimum magnetic head flying height (GH), and read error characteristics of the manufactured magnetic disk. The pass / fail judgment was made based on the number of read errors per surface of the magnetic disk. 0 was evaluated as ◎, 1 to 5 was evaluated as Δ, and 6 or more was evaluated as x (defective).

[0017]

[Table 1] From Table 1, it can be seen that the magnetic disks manufactured in the examples have a smaller valley depth and a relatively shallower valley than the comparative example. It can be seen that the flying height of the magnetic head is small and the number of reading errors is small.

[0018]

According to the present invention, in a slurry for texture processing in which abrasive grains are dispersed in a dispersion medium, the second abrasive grains having the particle diameter of the abrasive grains are added. Interposed between the abrasive grains and the surface of the workpiece, the rolling friction of the main abrasive grains is reduced, and the valleys constituting the texture are shallow and the widths of the valleys are narrow. Therefore, the flying height of the magnetic head is reduced, and high-density magnetic recording can be realized.

The addition of the second abrasive grains is easy, the conventional dispersion medium can be used as it is, and the cost does not increase.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of a texture processing device.

[Explanation of symbols]

 Reference Signs List 1 magnetic disk 2 flocking buff tape 3 rubber roller 4 texture processing slurry

Claims (5)

[Claims] 1. A textured slurry for a magnetic disk substrate in which abrasive grains are dispersed in a dispersion medium, wherein a second abrasive grain having a particle diameter smaller than that of the abrasive grains is added. For texture processing of magnetic disk substrates. 2. A slurry for texturing a magnetic disk substrate according to claim 1, wherein said abrasive grains are diamond, alumina or silicon carbide, and said second abrasive grains are ultrafine diamond. . 3. The ultrafine diamond particle size is 1 to 1
3. The slurry for texturing a magnetic disk substrate according to claim 1, wherein the slurry has a thickness of 0 nm. 4. The slurry for texturing a substrate for a magnetic disk according to claim 1, wherein the amount of said ultrafine diamond is 10 to 80% by weight of said abrasive grains. 5. The method according to claim 1, wherein the dispersion medium is an aqueous solution of diethylene glycol monobutyl ether.
A slurry for texturing a substrate for a magnetic disk according to any one of claims 1 to 4.