JPH0823934B2 - Magnetic disk substrate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic disk substrate using a ceramic substrate as a support for the magnetic disk.

[Prior art and its problems]

A magnetic disk device plays a central role in information storage in a computer information processing system. Since magnetic recording tends to have higher density and larger capacity, research on magnetic media that can meet the demand. Development is active.

For example, it has been proposed to form α-Fe ₂ O ₃ as the magnetic medium by a thin film forming means such as sputtering, and this makes it possible to make the magnetic recording medium thinner and improve the surface accuracy.

Aluminum alloy is used for the substrate on which such a magnetic recording medium is formed.

However, the aluminum substrate has an alumite layer having a thickness of about 2 μm formed on the surface thereof, and the hardness of the substrate surface is increased by the alumite layer. On the other hand, the hard alumite layer has a small thickness and the aluminum The thermal expansion coefficients of the alloy and alumite are different, which causes substrate distortion due to heat treatment at 300 ° C or higher performed when sputtering a magnetic medium such as α-Fe ₂ O ₃ , resulting in high density magnetic field. It is blocking the record.

If a substrate made of Ni-P is applied to the surface of an aluminum substrate, it becomes magnetized at a temperature of 200 ° C. or higher, which makes it unsuitable for sputtering.

Also, when an aluminum substrate is mounted on a magnetic disk device, it is rotated at a high speed up to about 1000 to 3000 rpm,
Due to the centrifugal force applied to the substrate itself, the substrate is apt to expand, and voids are present on the surface of the substrate. Both of these reasons impede high density magnetic recording.

The present applicant has proposed a magnetic disk substrate which has already solved the above-mentioned problems in Japanese Patent Laid-Open No. 60-138730.

That is, in the case of a magnetic disk substrate in which a glaze layer is formed on the surface on which a magnetic recording medium is adhered using a ceramic substrate as a support, the thermal shock resistance and rigidity are excellent, and the void defects on the adhered surface of the magnetic medium are excellent. It has been found that can be significantly reduced.

However, α-
Phenomenon that when a thin film of Fe ₂ O ₃ etc. is formed by sputtering, when the magnetic head repeatedly aerodynamically floats and contacts the read / write on this magnetic disk, the magnetic head adheres when it rests on the plate surface It has been found that (hereinafter referred to as stick phenomenon) tends to occur.

[Object of the Invention]

The present inventors, as a result of strenuous research in view of the above circumstances, texturing the surface of the grace layer,
It was found that the stickiness can be eliminated by setting the surface roughness to a predetermined value.

Accordingly, the present invention has been completed based on the above findings, and an object thereof is to provide a magnetic disk substrate capable of suppressing the stick phenomenon by reducing the adhesion of the magnetic head to the magnetic disk plate surface. Especially.

[Means for solving problems]

According to the present invention, in a magnetic disk substrate, a glaze layer is laid on the surface of a ceramic substrate as a support, and the upper surface of the glaze layer has a center line average roughness (Ra).
The thickness of the magnetic recording medium is 0.003 to 0.04 μ, and the magnetic recording medium is deposited on the magnetic recording medium.

 Hereinafter, the present invention will be described in detail.

The magnetic disk substrate of the present invention is in line with the aluminum magnetic disk substrate in terms of forming the linear scratches in order to suppress the occurrence of the stick phenomenon, but the conventional technique of forming the scratches on the soft metal has been proposed. It was an unexpected result that the streak could be formed on the surface of the glass plate, which had a high hardness with respect to the magnetic disk substrate and cracked easily, and this streak was formed. It is important that the center line average roughness is set within a predetermined range by the above, and thereby the stick phenomenon can be eliminated.

That is, the magnetic disk substrate already proposed by the present inventors in JP-A-60-138730 has a basic structure as shown in FIG. 1 and has glass on both sides of a disk-shaped ceramic substrate 1. The glaze layer 2 is formed by coating,
By polishing the surface of the magnetic disk substrate 3, the center line average roughness (Ra) can be reduced to 0.001. As a result, a high density magnetic recording medium can be formed into a thin film by sputtering or by plating. can do.

The surface of the magnetic medium of the magnetic disk thus obtained has a remarkable surface smoothness, which tends to cause the stick phenomenon as described above. Therefore, in order to solve this problem, glaze is required. The texturing process was performed on the magnetic medium adhered surface of the layer 2.

This texturing is a method of forming an appropriate mark on the aluminum magnetic disk substrate, and this method is used for a soft metal body such as aluminum.

The inventors of the present invention applied this texturing process to a glass having a high hardness and a tendency to easily generate cracks, which, contrary to common sense, forms a proper line mark, thereby eliminating the stick phenomenon. I found that I can do it.

Further, the inventors of the present invention have formed the linear scratches so that the center line average roughness (Ra) is 0.003 to 0.04 μ, preferably 0.005.
It was also found that the stick phenomenon can be eliminated by setting the size to 0.02μ. That is, if the center line average roughness is less than 0.003μ, it is not possible to suppress the occurrence of sticking phenomenon, and if it exceeds 0.04μ, the occurrence of cracks becomes remarkable and the linear grooves are formed in the plate surface direction. The unevenness becomes conspicuous, and it becomes difficult to form a sharp linear groove, which deteriorates the magnetic characteristics of the magnetic recording medium.

The texturing used in manufacturing the magnetic disk substrate of the present invention is as shown in FIGS. 2 and 3, and FIG. 3 is a view as seen from the direction of arrow A in FIG.

That is, the magnetic disk substrate 3 is mounted on the spindle 4, the central axis of the spindle 4 is located at the center of the substrate 3, and the substrate 3 is rotationally driven by the spindle 4. Then, the polishing tape 5 having polishing particles made of white alundum, silicon carbide, diamond or the like adhered to the tape is pressed against the semi-circumferential surface of the contact roll 6 made of urethane rubber, and the contact roll 6 is rotated. The polishing tape 5 is moved by a separately provided drive source (not shown) as shown in the arrow B direction. Further, a center rod 7 is provided so as to penetrate the center axis of the contact roll 6, and pressing rods 8 are attached to both ends of the center rod 7 so that the pushing rod 8 presses the substrate. In this way the substrate 3
Is rotated and the polishing tape 5 moves, which causes the polishing tape 5 to slide on the surface of the substrate, resulting in the fourth tape.
As shown in the figure, linear scratches are formed concentrically on the surface of the glaze layer. Incidentally, in FIG. 3, a part of the spindle 4 and the polishing tape 5 are omitted.

〔Example〕

 Next, examples of the present invention will be described.

(Manufacturing method of substrate for texturing) A sintering additive is added to alumina powder and press-formed to 1200
Baking at a temperature of ℃ or more, a polycrystalline alumina substrate with a thickness of 1.85 mm is made with a hollow disk with an outer diameter of 210 mm and an inner diameter of 100 mm, and then this substrate is flattened with a diamond grindstone to a flatness of 15μ.
After polishing to the following, both surfaces of this substrate were coated with high melting point glass (softening point: 500 ° C. or higher), glass was melted at 600 ° C. or higher, and glaze was formed to a thickness of 100 μm. After that,
Polishing the surface of this glaze layer, center line average roughness (Ra)
Was set to a size of 0.001μ and used as a substrate for texturing.

(Texturing and Evaluation) When the substrate for texturing was subjected to texturing for 20 seconds with a diamond abrasive or a silicon carbide abrasive according to FIGS. 2 and 3 described above,
The results are shown in Table 1.

According to this processing, the size of the linear scratches can be changed depending on the type of the abrasive and the grain size of the abrasive, and this size is represented by the center line average roughness.

The evaluations in Table 1 are classified into ⊚, ∘ and × marks according to the visual observation with a scanning electron microscope and the presence or absence of stick phenomenon. The ⊚ and ∘ marks have linear stripe marks as shown in FIG. It is formed and stick phenomenon is unlikely to occur, especially ◎
The mark indicates the case where the stick phenomenon did not occur at all, whereas the mark x indicates the case where the unevenness was conspicuous in the plate surface direction of the linear scratches as shown in FIG. 6 and the stick phenomenon was likely to occur.

As is clear from Table 1, samples No. 2 to No. 6 of the present invention
According to the above, the occurrence of stick phenomenon was suppressed, and particularly in Samples No. 3 and No. 4, it did not occur at all. However,
In sample No. 1, the stick phenomenon has occurred.
In No. 7, the linear streaks were uneven and the magnetic properties were degraded.

[Comparative example]

In this example, when the conventional aluminum magnetic disk substrate was textured in the same manner as in this example,
By visually observing the state of the grooves of the filaments with a scanning electron microscope, it became as shown in FIG. 7 or FIG.

According to FIG. 7, both sides of the groove are raised,
In FIG. 8, the cut layer does not fall off and remains as a projection on the substrate surface, and both of them require polishing (called a cleaning step) to remove these defective portions.

〔The invention's effect〕

As described above, according to the magnetic disk substrate of the present invention,
The adhesion force of the magnetic head to the magnetic medium formed on this substrate by the thin film forming technique is remarkably reduced, so that the stick phenomenon does not occur, and as a result, a magnetic disk of high performance and high reliability can be obtained. A magnetic disk substrate is provided.

Further, according to the magnetic disk substrate of the present invention, a magnetic disk substrate that does not undergo any plastic deformation during the texturing process and thus does not require a cleaning step is provided.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of a magnetic disk substrate of the present invention, FIGS. 2 and 3 are explanatory views showing a texturing process, and FIG. 4 is a plan view showing a disk substrate surface after the texturing process. FIG. 5 is an enlarged view showing the linear grooves formed in the glaze layer of the magnetic disk substrate of the present invention, FIG.
The figure is an enlarged view showing the linear grooves formed in the glaze layer of the comparative example, and FIGS. 7 and 8 are enlarged views showing the linear grooves formed on the aluminum magnetic disk substrate after texturing. is there. 1 ... Ceramic substrate 2 ... Glaze layer

Claims (1)

[Claims] 1. A glaze layer is laid on the surface of a ceramic substrate as a support, and the upper surface of the glaze layer has a center line average roughness (Ra) of 0.003 to 0.04 μ, and a magnetic recording medium is deposited thereon. Magnetic disk substrate.