JPH05151556A - Magnetic disk - Google Patents

Abstract

PURPOSE:To enable stable floating of a magnetic head with a low floating quantity by specifying the height, length and number of the projecting parts of the texture of the magnetic layer. CONSTITUTION:An aluminum alloy substrate 2 is subjected to lapping and is coated thereon with an Ni-P plating film 3 at 14 to 20mum, by which a substrate 1 is formed. The substrate 1 is mirror finished by polishing and is then textured to form grooves in a circumferential direction by using a lapping tape coated with abrasive grains of alumina. A Cr substrate film 4, a Co-Ni-Cr magnetic film 5 and a carbon protective film 6 are thereafter deposited on the substrate and the surface is coated with a lubricating film 7. The difference between the max. value and min. value of the height of the projecting parts of the texture is confined to <=200Angstrom and the number of the projecting parts within a range of 50mum length toward the radial direction is specified to >=50 pieces. Consequently, the texturing is so executed that the ratio of the height of the highest projecting part and the depth of the lowest recessed part is kept within <=0.5 range, by which the generation of abnormal projections is obviated and the surface area of the surface for sliding with the magnetic disk is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk used in a magnetic disk device which is a data storage device such as a computer.

[0002]

2. Description of the Related Art In recent years, an aluminum alloy substrate, a glass substrate, a plastic substrate, or the like has been used as a substrate to be mounted on a fixed type magnetic disk device, but currently the aluminum alloy substrate is the mainstream. Generally Ni-P on aluminum alloy substrate
After the plating process, a polishing process is performed, and then a texture process for roughening the substrate surface in the circumferential direction is performed. The purpose of texture processing is to impart magnetic anisotropy to the magnetic layer provided on the substrate along the circumferential direction, and to reduce the contact area when the magnetic head and the magnetic disk come into contact by roughening the surface, resulting in frictional wear. It is to improve the characteristics and adsorption characteristics.

A general magnetic disk device adopts a contact start stop system (hereinafter abbreviated as CSS system), and the magnetic head and the magnetic disk are in contact with each other when the device is stopped. Then, when the magnetic disk device is activated, the magnetic head and the magnetic disk start to slide, and when the magnetic disk reaches a predetermined number of rotations, the magnetic head is placed on the magnetic disk with a gap of about 0.2 to 0.3 μm. To surface.

As the magnetic disk and the magnetic head slide repeatedly in this way, the friction and wear characteristics may deteriorate and the magnetic disk may be damaged. Therefore, measures are taken such as coating the surface of the magnetic disk with a solid lubricant or a liquid lubricant. However, when the lubricant is applied to the magnetic disk, the magnetic head and the magnetic disk are attracted to each other, and the motor for rotating the magnetic disk cannot be rotated at the time of starting the apparatus, and the magnetic head and the magnetic disk are damaged.

Conventionally, mechanical texture processing has been the mainstream of texture processing, and a lapping tape in which abrasive grains are fixedly held on a tape is used as a processing material. Therefore, as a processing method, a polishing tape is pressed while rotating the magnetic disk substrate. A conventional method for expressing texture-roughness is shown in FIG.
As shown in, the center line roughness Ra (where Ra is JISB
The definition defined in 0601 is used. ), The height Rp from the center line O to the maximum convex portion, the depth Rv from the center line O to the maximum concave portion, the width δh from the maximum value to the minimum value of the height of the convex portion, and in the range of 50 μm in the radial direction. There are numbers of convex parts.
As shown in FIG. 9, in the conventional texture, Ra is about 80-
100Å, Rp / Rv> 0.5, δh> 200Å, and the number of convex portions is about 100. However, in recent years, there has been a strong demand for higher density and larger capacity of magnetic disk devices, and therefore the flying height of the magnetic head has decreased, and now it is about 0.1 μm or less. Therefore, attempts have been made to develop a texture that does not attract even if the surface roughness Ra of the magnetic disk is made as small as possible.

[0006]

However, according to the prior art, the CSS is used in a low flying condition in which the flying height of the magnetic head is 0.1 μm or less.
When the test was conducted, there was a problem that the sliding time and sliding distance of the magnetic head increased, the surface of the magnetic disk was worn, and a head crash occurred. In addition, the texture-roughness Ra of the magnetic disk is made as small as possible in order to stably fly the magnetic head at a flying height of 0.1 μm or less. In the prior art, a magnetic head having a lubricating film thickness that does not deteriorate CSS characteristics is used. There is a problem that the magnetic disk is attracted and the device cannot rotate.

The present invention solves the above-mentioned problems of the prior art by providing a magnetic disk which does not deteriorate CSS characteristics even when the flying height of the magnetic head is 0.1 μm or less and which is excellent in flying characteristics and adsorption characteristics. The purpose is to provide.

[0008]

In order to achieve this object, the difference between the maximum value and the minimum value of the heights of the convex portions of the texture is set to 1
50 Å or less and the number of protrusions in the radial direction is 50μ
The height R of the highest protrusion has 150 or more in the range of m
The ratio Rp / Rv between p and the lowest recess depth Rv is set to fall within the range of 0.5 or less.

[0009]

With this structure, no abnormal protrusion is generated and the surface area of the sliding surface with respect to the magnetic disk can be increased.

[0010]

1 is a sectional view of a magnetic disk medium according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a substrate. The substrate 1 is an aluminum alloy substrate 2 having a diameter of 3.5 inches, which is lapped, and a Ni—P plating film 3 is deposited on the substrate 15 to 20 μm.
It is a covered structure. After polishing and mirror-finishing the substrate 1, a lapping tape coated with alumina abrasive grains was used to perform texture processing for forming grooves in the circumferential direction. After that, a Cr underlayer film 4, a Co—Ni—Cr magnetic film 5, and a carbon protective film 6 were sequentially deposited by a DC magnetron sputtering method, and a lubricating film 7 was further coated.

FIG. 2 shows the texture-making apparatus of this embodiment. The texture of this embodiment is 100 to 30 for the substrate 1.
The lapping tape 8 coated with the alumina abrasive grains of each grain size is rotated at 0 rpm to 0 to 50 cm / s.
It was produced by pressing it on the disc through the contact roll 9 at a rocking speed of 0.5 to 1.5 kg / cm ² for 30 s. For the change of Ra, by changing the grain size of the lapping tape coating abrasive grain, the sample in which δh (width from the maximum value of the height of the convex portion to the minimum value) was changed, Rp / Rv The changed sample and the sample in which the number of the convex portions (with respect to the range of the radial length of 50 μm) was changed were prepared by changing the rocking speed and the rotation speed. Regarding the texture-roughness measurement, the measurement was performed by Tallystep manufactured by Rank Teller-Hobson. Stylus diameter:
0.1 × 2.5 μm, measurement length: 50 μm, cutoff frequency: 25 Hz.

First, the results of a floating test as a reliability test are shown in FIGS. As a levitation test, the contact between the head and the disk when the magnetic head is levitated on the magnetic disk with a flying height of 0.06 μm and seeks to a radius of 20 mm to 45 mm is AE (acoustic emission).
It was detected by the sensor and the number of hits was counted by the computer. The sample in FIG. 3 is a sample in which δh is changed, and FIG. 4 is a sample in which Rp / Rv is changed, and Ra is 60Å in both cases.

It can be seen from FIG. 3 that the number of hits suddenly increases when δh exceeds 150Å. This means that even if the roughness of the substrate is the same, if the variation (δh) in the texture-convex portion is small, the probability of contact between the head and the disk is low when the magnetic head is flying low, so it is possible to stably fly and seek. Because of that. Further, in FIG. 4, it can be seen that the number of AE hits sharply increases when Rp / Rv exceeds 0.5. This is because as Rp / Rv increases, abnormal projections increase and the probability of contact between the head and disk increases, so the number of AE hits also increases. For these reasons, in order to stably seek at a low flying height, it is necessary to set δh to about 150Å or less and Rp / Rv to 0.5 or less as the roughness of the texture provided on the substrate.

Next, a CSS test was conducted. The results are shown in FIGS. In the CSS test, a Winchester-monolithic microslider having a peripheral speed of 9 m / s and a width of about 0.1 μm was used, and a Patty CSS device with a radius of 25 mm, a rotation speed of 3600 rpm, a rise time of 10 s, and a fall time of 20 s was used after 20,000 times. The value of the dynamic friction coefficient μK was measured.

The sample shown in FIG. 5 is the same as the sample shown in FIG. 3, and the sample shown in FIG. 6 has a different number of protrusions in the range of 50 μm, and Ra is 60Å. It can be seen from FIG. 5 that μK becomes 0.3 or more after 20,000 times after δh exceeds about 200 Å and wear characteristics deteriorate. This means that when the magnetic head is flying low, the larger δh is, the greater the impact is when the head collides with the higher portion of the convex portion on the disk, and the head is likely to be worn and the head may crash. Therefore, if δh is about 200Å or less, there are no abnormally protruding protrusions, so the impact of the magnetic head when taking off and landing on the magnetic disk during CSS is small and wear is less likely to occur, and CSS for low flying of the magnetic head The characteristics can be satisfied. Further, in FIG. 6, it can be seen that the wear characteristics deteriorate when the number of convex portions is about 150 or less. This means that the larger the number of convex portions corresponds to the surface area of the disk, the larger the surface area. Therefore, if the surface area is large, the contact area between the head and the disk is reduced, so that the wear characteristics are improved. In order to satisfy the CSS characteristics in lowering the flying height, it is desirable that the number of protrusions is about 150 or more.

FIG. 7 shows the result of the adsorption test performed on the sample of FIG. The adsorption test was carried out by incorporating two magnetic disks and four magnetic heads into an actual hard disk drive. Test environment is 60 ℃, 80
The increase in static friction coefficient δμs after standing for 24 hours in a high temperature and high humidity environment of% RH was measured.

In FIG. 7, when the number of convex portions in the radial direction of 50 μm is about 100 to 150 or less, the adsorption tendency is shown, and when it is 50 or less, δμs is 0.2 or more. The motor for rotating the magnetic disk becomes difficult to rotate. This is also an improvement in the adsorption property due to the increase in the disk surface area due to the increase in the number of convex portions as in the case of CSS and the decrease in the contact area between the head and disk when the apparatus is stopped.

As described above, in this embodiment, the roughness of the texture provided on the substrate 1 is set so that δh is about 150Å or less and Rp / Rv is 0.5 or less. You can Also, δh is about 200
If it is less than or equal to Å and the number of protrusions in the radial direction of 50 μm is about 150 or more, there are no abnormally protruding protrusions, and the surface area of the magnetic disk becomes large.
When the magnetic head takes off and lands on the magnetic disk at the time of SS, the impact is small and wear is less likely to occur, so that the CSS characteristics in low flying of the magnetic head can be satisfied. Further, the width (δh) from the maximum value to the minimum value of the heights of the convex portions of the texture is set to 150 Å or less, and the number of the convex portions in the radial direction is 150 or more in the range of 50 μm, and the highest convex portion. Ratio Rp / of the height Rp of the
By setting Rv to be in the range of 0.5 or less, it is possible to simultaneously satisfy stable floating during seek and wear and adsorption characteristics (CSS characteristics).

[0019]

According to the present invention, the difference between the maximum value and the minimum value of the heights of the convex portions of the texture is set to 150 Å or less, and the number of convex portions in the radial direction of 50 μm is 150 or less. Moreover, by setting Rp / Rv to 0.5 or less, the occurrence of abnormal protrusions can be prevented and the magnetic head can be set to 0.1 μm.
Stable flying is possible with a low flying height of m or less.

Moreover, since there is no abnormal protrusion, the impact between the head and the disk during CSS is small and the density of the texture-grooves is large, so that the contact area between the head and the disk is small and the CSS characteristics and adsorption characteristics are improved. That is, it is possible to provide a highly reliable disk in which the flying height of the magnetic head is reduced.

[0021]

[Brief description of drawings]

[0022]

FIG. 1 is a sectional view showing a magnetic disk according to an embodiment of the present invention.

[0023]

FIG. 2 is a diagram showing a texture-fabrication / processing apparatus of this embodiment.

[0024]

FIG. 3 is a diagram showing the variation (δh) of convex portions and the number of AE hits.

[0025]

FIG. 4 is a diagram showing Rp / Rv and the number of AE hits.

[0026]

FIG. 5 is a diagram showing a variation (δh) of a convex portion and a dynamic friction coefficient μK after CSS 20,000 times.

[0027]

FIG. 6 is a diagram showing the number of convex portions and the coefficient of dynamic friction μK after 20,000 CSS cycles.

[0028]

FIG. 7 is a diagram showing the number of convex portions and an increase δμs in static friction coefficient after leaving for 24 hours in a high temperature and high humidity environment.

[0029]

FIG. 8 is a diagram showing a texture-roughness notation.

[0030]

FIG. 9 is a diagram showing a radial profile of a conventional texture.

[0031]

[Explanation of symbols]

 1 Substrate 2 Aluminum alloy substrate 3 Ni-P plating film 4 Cr underlayer film 5 Co-Ni-Cr magnetic film 6 Carbon protective film 7 Lubricating film 8 Lapping tape 9 Contact roll

Claims (3)

[Claims] 1. A magnetic disk in which at least a magnetic layer is provided on a textured non-magnetic substrate, and the difference between the maximum value and the minimum value of the heights of the convex portions of the texture is 200.
A magnetic disk characterized in that the number is less than or equal to Å and the number of protrusions is 50 or more within a range of 50 μm in the radial direction. 2. A magnetic disk in which at least a magnetic layer is provided on a textured non-magnetic substrate, and the difference between the maximum value and the minimum value of the heights of the convex portions of the texture is 150.
A magnetic disk, wherein the ratio Rp / Rv of the height Rp of the highest convex portion and the depth Rv of the lowest concave portion is 0.5 or less as well as Å or less. 3. A magnetic disk in which at least a magnetic layer is provided on a textured non-magnetic substrate, and the difference between the maximum and minimum heights of the convex portions of the texture is 150.
Å or less and 150 or more convex portions in a radial length range of 50 μm, and the ratio Rp / Rv of the highest convex portion height Rp and the lowest concave portion depth Rv is 0. A magnetic disk characterized by being 5 or less.