JPH07320259A - Magnetic disk and its production - Google Patents

Abstract

PURPOSE:To improve CSS characteristics by specifying the average spacings of texture grooves on the surface of a magnetic disk to a specific value. CONSTITUTION:The average spacings of the texture grooves on the magnetic disk surface of this magnetic disk are 0.1 to 7mum. The magnetic disk is formed by subjecting the substrate surface to texturing by using a pad composed of fibers having a diameter 1 to 25mum in a slurry type texturing method of bringing the pad into contact with the substrate for the magnetic disk under a suitable pressure and discretely rotating the pad and the substrate while properly supplying a slurry contg. abrasive grains therebetween. The roughness curves on the magnetic surface are measured by using a needle of a radius 0.5mum and by a stylus type roughness meter DEKTAK8000 under conditions of a scanning length 200mum and sampling interval 13.3mum. The half the number of intersected points of the central curves of the roughness curves and the roughness curves is defined as the number of grooves of the texture groove groups and the scanning length 200mum/the number of the grooves is defined as an average inter- groove spacing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk for horizontal magnetic recording or vertical magnetic recording used in video recording, audio recording, computers and the like. In particular, it relates to improvements in the shape of the magnetic disk surface and the method of forming the same.

[0002]

2. Description of the Related Art In recent years, magnetic disks for computers have been required to have smaller diameters, higher recording density, and larger capacities.
Therefore, when the magnetic recording device is used, the flying height of the magnetic head with respect to the magnetic disk is decreasing year by year.
The momentum is from 0.075 μm to 0.05 μm or less. Due to such a smaller diameter of the magnetic disk and a lower flying height of the magnetic head, a higher CSS for the magnetic disk is obtained.
Characteristics are required. The CSS characteristic is a contact start / stop characteristic and represents the sliding characteristic of the magnetic disk with respect to the magnetic head. For example, the magnetic characteristic when the magnetic head is CSS-driven 10,000 times on the magnetic disk. It is expressed by the frictional force acting on the disc. Conventionally, in order to satisfy this CSS characteristic, for example, after non-magnetic Ni-P plating on an aluminum substrate, the surface of the substrate (Ni-P / Al substrate) is textured to roughen the substrate surface, A Cr underlayer, a Co magnetic film, and a carbon protective film are sequentially formed, and then a lubricant is applied to manufacture a thin film magnetic disk. As another example, a glass substrate having an appropriate surface roughness is used as the non-magnetic substrate, and a silicon oxide coating film is used as the protective film.

[0003]

As described above, the flying height of the head has drastically decreased in recent years, from 0.075 μm.
It is a momentum that is going to be less than 0.05 μm. Therefore, C
SS characteristics are, for example, at 35 ° C under normal temperature and humidity atmosphere.
Good CS even in a high temperature and high humidity environment such as 80% RH
S characteristics are required. With the recent decrease in the flying height of the head, it has become a problem in the conventional magnetic disk that the head sticks to the magnetic disk (stiction) particularly in a high temperature and high humidity atmosphere. Further, the conventional magnetic disk using the carbon protective film has a drawback that the scratch due to the sliding of the magnetic head is likely to appear on the surface of the magnetic disk in a relatively fast CSS test, and the reliability is poor.

The object of the present invention is to remedy these drawbacks,
It is to provide a new magnetic disk having excellent CSS characteristics.

[0005]

SUMMARY OF THE INVENTION The present invention is a magnetic disk characterized by having an average texture-groove interval on the surface of the magnetic disk of 0.1 to 7 .mu.m or less, and a method for producing the same. In addition, the pad is brought into contact with the surface of the magnetic disk substrate with an appropriate pressure,
In a slurry-type texture processing method in which a pad and a substrate are individually rotated while appropriately supplying a slurry containing abrasive grains,
The present invention provides a magnetic disk characterized in that a substrate surface is texture-processed using a pad composed of fibers having a diameter of 1 to 25 μm, and a method for producing the same. In the present invention,
The roughness curve of the magnetic disk surface was measured with a probe type roughness meter DEKTAK8000 under the conditions of a scanning length of 200 μm and a sampling interval of 13.3 μm using a needle with a radius of 0.5 μm, and the center curve and the roughness curve of this roughness curve were measured. The half of the number of intersection points was defined as the “groove number” of the texture-groove group, and the “scan length 200 μm / groove number” was defined as the average groove interval.

Further, in order to clarify the attraction phenomenon of the magnetic head, the friction coefficient between the magnetic head and the magnetic disk immediately after the start of rotation of the magnetic disk was evaluated in detail. When the rotational speed of the disk is raised from 0 rpm, which is a stopped state, to 3600 rpm, the friction coefficient between the head and the disk changes as shown in FIG. The peak value of the friction coefficient shown as (a) in the figure represents the magnitude of the attraction force between the head and the disk when the disk starts to rotate and the head begins to slide (hereinafter, the absorption coefficient μs Called). After that, the coefficient of friction decreased sharply and then increased again, and after showing the peak value (b), decreased again.
It becomes 0 when the head is completely lifted. This peak value
(b) is what has been conventionally measured.
It is called friction coefficient μf. When the head is attracted during CSS, the attraction coefficient μs between the head and the disk measured at the start of rotation of the disk becomes large and may exceed 1.0. Remarkably, the torque required for rotation becomes too large, and It turned out that the disc may not rotate.

[0007]

[Function] Texture of magnetic disk surface-Average groove spacing is 0.1
By setting the thickness to 7 μm or less, a hard disk drive (HDD) composed of a magnetic head and a magnetic disk is CS.
The contact area per contact point between the head and the disk becomes small when the S drive is performed, and both the adsorption coefficient μs and the friction coefficient μf between the head and the disk can be decreased, and as described later, good CSS characteristics can be obtained. can get. Further, the present invention has discovered that the groove spacing after texture processing is determined by the particle size distribution of the texture pad and slurry used during processing, and is composed of fibers having a diameter of 1 to 25 μm. By texture-processing the substrate surface using a pad, it is possible to form texture-groove groups having an average groove interval of 0.1 to 7 μm on the substrate surface.

If the groove interval of the texture is set to 7 μm or more, the contact area between the head and the disk per contact becomes large, and the friction coefficient becomes large, so that the surface of the disk is worn and scratched at the initial stage of the CSS test. In addition, the contact area of the water adsorbed between the head and the disk becomes large in a high temperature and high humidity atmosphere, and a large torque is required to rotate the disk during CSS driving, which significantly hinders the disk rotation. There are drawbacks. Further, in order to improve the CSS characteristics, it is necessary to make the groove depth (Rmax) of the texture deeper than necessary, which causes a drawback that the write characteristics of the magnetic disk deteriorate, and a hard disk drive using this disk occurs. When the magnetic disk is driven, a defect occurs in which the head collides with the protrusion of the magnetic disk. At present, the flying height of the head is lowered from 0.075 μm to 0.05 μm in order to improve the magnetic recording density, and it is fatal that the write characteristic is deteriorated.

As described above, the texture of the magnetic disk surface
Strict CS by setting the average groove spacing to 7 μm or less
It is possible to realize a magnetic disk satisfying both the S characteristic and the bright characteristic. If the groove interval of the texture is set to 0.1 μm or less, the depth of the groove becomes too shallow, the adsorption coefficient μs and the friction coefficient μf both increase, and it becomes unsuitable for a magnetic disk.

When texture processing is performed using a pad and abrasive grains, the surface shape of the processed product is basically a dynamic transfer of the shape of the pad surface used for the texture. Has been found to depend mainly on the diameter of the fibers that make up the pad. As a result of the experiment, by using a pad and a slurry composed of fibers having a diameter of 1 to 25 μm, the surface of the substrate is textured so that the average distance between the grooves is 0.1 to 7 μm.
It was found that the texture-grooves of m or less were formed. When the diameter of the fiber is 1 μm or less, the strength of the fiber itself is weak, and a large amount of resin is required to bundle the fibers and maintain the strength, which is not suitable for a texture pad. When a pad made of fibers with a diameter of 25 μm or more is used, the groove spacing of the texture-processed product is 7
More than μm.

According to the present invention, a texture-groove group having an average interval of 0.1 to 7 μm can be formed on the surface of the magnetic disk, and the friction coefficient between the head and the disk generated during CSS driving is small,
At the same time, a magnetic disk having a small adsorption coefficient and a weak adsorption force can be manufactured.

[0012]

EXAMPLES The present invention will be specifically described with reference to the following examples. Example 1 Ni-P plating on an aluminum substrate, diameter 95 mm, thickness 1.2
A slurry of 40 μm diameter pads made by impregnating polyester polymer fibers of 25 μm diameter with polyurethane on both surfaces of a 7 mm non-magnetic substrate was pressed with a pressure of ² kg / cm ² to disperse diamond abrasive grains of 2 μm in diameter. The surface of the substrate was texture-processed by rotating the substrate and the pad while appropriately supplying-between the substrate and the pad. After that, after cleaning the substrate surface, a Cr film having a thickness of 70 nm and a CoCrTa magnetic film having a thickness of 60 nm are continuously formed at a substrate temperature of 280 ° C. by a sputtering method.
A carbon protective film having a thickness of 25 nm was formed by a sputtering method at a substrate temperature of 200 ° C. After that, a lubricant perfluoropolyether was applied to a thickness of 3 nm to prepare a thin film magnetic disk.

The roughness curve on the surface of the magnetic disk of the present invention was evaluated by a stylus type roughness meter DEKTAK8000 under the conditions of a scanning length of 200 μm and a sampling interval of 13.3 μm using a needle having a radius of 0.5 μm. A roughness curve was obtained. 1 / the number of intersections between the center curve connecting the upper and lower envelopes of this roughness curve and the roughness curve
The number of grooves in the texture-groove group was obtained from 2, and the average groove spacing of 7.0 μm was obtained from “scan length 200 μm / number of grooves”. As a result of evaluating the bright characteristics of the manufactured magnetic disk, the number of protrusions of 0.075 μm was two over the entire effective area of the substrate. The CSS characteristics were evaluated using a composite head having a flying height of 0.075 μm at an evaluation position of a disk rotation speed of 3600 rpm and a radius of 20 mm.

The CSS characteristics of the product of the present invention were measured at 25 ° C., 60% RH and
The results of evaluation under an atmosphere of 35 ° C. and 80% RH are shown in (a) of FIGS. 3 and 4. As shown in FIG. 3 (a), the product of the present invention has a friction coefficient μf of the head at the start of the CSS test.
Is 0.19, and then the number of CSSs is 5k, 10k, 15
The friction coefficient μf gradually increases with increasing k, 20k, 25k, and 30k times, but is 0.20,
Only 0.20, 0.21, 0.21, 0.22, 0.22, it can be seen that the CSS characteristics are excellent. As a result of observing the surface of the magnetic disk with an optical microscope after the CSS test, wear scratches due to the head were not observed.

Further, as shown in FIG. 4A, at 35 ° C.,
Even in a high temperature and high humidity environment such as 80% RH, the friction coefficient μf of the head is 0.38, 0.38, 0.38, 0.39, 0.39, 0.
It was good at 40,0.40. FIG. 5A shows the measurement result of the adsorption coefficient μs between the head and the disk, which was measured at the same time as FIG. 3A. As shown in Fig. 5 (a), μs is 0.38, 0.38, 0.39, 0.39, 0.39, 0.40, 0.40 under normal temperature and normal humidity.
And was good. FIG. 6 (a) shows the evaluation result of the adsorption coefficient μs under the high temperature and high humidity atmosphere of 35 ° C. and 80% RH.
μs is as small as 0.65, 0.65, 0.66, 0.66, 0.67, 0.67, 0.68,
In addition, the result of observing the surface of the magnetic disk with an optical microscope after the CSS test did not show wear scratches due to the head. The product of the present invention, even in a high temperature and high humidity atmosphere,
This shows that the adsorption force between the disks is small and the CSS characteristics are good.

(Comparative Example 1) The same nonmagnetic substrate as in Example 1 was formed on both surfaces with a texture pad formed of polymer fibers having a diameter of 30 μm and a diamond abrasive grain having a diameter of 2 μm.
After processing, the same film formation and lubricant application as in Example 1 were performed to manufacture a thin film magnetic disk. The roughness curve of the magnetic disk surface of this comparative product was measured by the same method as in Example 1, and the average groove spacing was evaluated to obtain 8.0 μm. As a result of evaluating the bright characteristics of the manufactured magnetic disk, the height was 0.
The number of protrusions of 075 μm was detected as many as 52 per disk. The results of evaluating the CSS characteristics of this comparative product under the same conditions as in Example 1 are shown in (b) of FIGS. 3, 4 and 5, 6.

As shown in FIG. 3 (b), the comparative disk was subjected to a normal temperature and normal humidity atmosphere of 25 ° C. and 60% RH.
At the start of the CSS test, the friction coefficient μf of the head is 0.25, and after that, the number of CSS increases to 5k, 10k, and 15k times, and the friction coefficient μf becomes 0.27, 0.28, and 0.29, respectively.
When the number of CSSs reaches 17k, wear scratches are generated on the disk surface and the disk cannot be used as a magnetic recording disk. In addition, as shown in FIG. 4 (b), in an atmosphere of high temperature and high humidity such as 35 ° C. and 80% RH, the number of times of CSS is 0 to 5k, 10k, 1
The friction coefficient μf of the head increased to 0.45, 0.48, 0.49, and 0.50, respectively, as it increased to 5 k times, and wear scratches due to the head occurred on the disk surface at 20 k times.
It can be seen that the CSS characteristics are inferior to the invention product.

In FIG. 5 (b), the head / head measured at the same time as FIG. 3 (b) using a comparative disk was used as in Example 1.
The change result of the adsorption coefficient μs between the disks is shown. Figure 5
As shown in (b), μs is
The adsorption coefficient μs is large at 0.76, 0.77, 0.79 and 0.79, and it can be seen that the comparative disk is inferior in CSS characteristics to the product of the present invention.
FIG. 6B shows the evaluation result of the adsorption coefficient μs under the high temperature and high humidity atmosphere of 35 ° C. and 80% RH. μs is 1.14,1.1
5,1.16,1.18 and the adsorption coefficient μs are larger than 1.0, and the adsorption force between the head and the disk is very large, which is inferior to the product of the present invention. Currently, disks with an adsorption coefficient μs of 1.0 cannot be mounted in the drive.

(Embodiment 2) The same non-magnetic substrate as in Embodiment 1 is formed on both surfaces with a texture pad formed of polymer fibers having a diameter of 1 μm and a diamond grit having a diameter of 0.5 μm.
-Processing was performed, and thereafter, the same film formation and lubricant application as in Example 1 were performed to manufacture a thin film magnetic disk. The roughness curve of the surface of the magnetic disk of the present invention was measured by the same method as in Example 1 and the average groove spacing was evaluated to obtain 0.1 μm. As a result of evaluating the bright characteristics of the manufactured magnetic disk, the height was
The number of protrusions of 0.05 μm was measured once per disk. The CSS characteristics of the product of the present invention were evaluated in the same manner as in Example 1 using a composite head having a flying height of 0.05 μm at an evaluation position of a rotation speed of 3600 rpm and a radius of 20 mm.

The CSS characteristics of the product of the present invention were measured at 25 ° C., 60% RH and
The CSS test results evaluated in an atmosphere of 35 ° C. and 80% RH are shown in (a) of FIGS. 7 and 8 and FIGS. Figure 7
As shown in (a) of the present invention, the friction coefficient μf of the head of the present invention is 0.37 at the start of the CSS test, and then C
Although the friction coefficient μf gradually increases as the number of SSs increases to 5k, 10k, 15k, 20k, 25k and 30k times, 0.38, 0.38, 0.39, 0.39, 0.40, 0.4 respectively.
It can be seen that the CSS characteristics are excellent, with the value remaining at 0. CS
As a result of observing the surface of the magnetic disk with an optical microscope after the S test, no abrasion damage due to the head was observed.

Further, as shown in FIG.
Even in an environment of high temperature and high humidity such as ℃ and 80% RH, the friction coefficient μf of the head is 0.58, 0.61, 0.61, 0.62, respectively.
It was good with 0.62, 0.63, and 0.63. FIG. 9A shows FIG.
(A) shows the measurement results of the adsorption coefficient μs between the head and the disk measured at the same time. As shown in Fig. 9 (a), μs is 0.52, 0.58, 0.61, 0.61, 0.62, under normal temperature and normal humidity.
It was good at 0.62 and 0.63. 8A to FIG.
(A) shows the results of evaluation of the adsorption coefficient μs under the high temperature and high humidity atmosphere of 35 ° C. and 80% RH, which was measured at the same time. μs
Was 0.80, 0.89, 0.91, 0.91, 0.92, 0.93, 0.94, which was smaller than 1, and no abrasion scratch was observed on the disk surface. It can be seen that the product of the present invention has a small adsorption force between the head and the disk even in a high temperature and high humidity atmosphere and has good CSS characteristics.

(Comparative Example 2) The same nonmagnetic substrate as in Example 2 was formed on both surfaces with a texture pad made of polymer fibers having a diameter of 0.5 μm and a diamond abrasive grain having a diameter of 0.5 μm. After processing, the same film formation and lubricant application as in Example 2 were performed to manufacture a thin film magnetic disk. When the surface of the magnetic disk of this comparative product was observed with an optical microscope, many deep scratches were observed and it was not uniformly textured. The average groove distance was measured by the same method as in Example 2 and the average groove distance was evaluated.
3.0 μm was obtained. As a result of evaluating the bright characteristics of the manufactured magnetic disk, the number of protrusions having a height of 0.075 μm was detected to be 126, which was a large number per disk. The results of evaluating the CSS characteristics of this comparative product under the same conditions as in Example 2 are shown in (b) of FIGS. 7, 8 and 9, 10.

As shown in FIG. 7 (b), the comparative disk was subjected to a normal temperature and normal humidity atmosphere of 25 ° C. and 60% RH.
The friction coefficient μf of the head was 0.46 at the start of the CSS test, and then the number of CSS cycles was 5k, 10k, 15k, 20.
friction coefficient μ with increasing k, 25k and 30k times
f gradually increases to 0.48,0.49,0.50,0.51,0.5, respectively.
2, 0.52, and as shown in FIG.
In a high temperature and high humidity atmosphere such as 80% RH, the coefficient of friction μf of the head becomes 0.69, 0.72, 0.78, respectively, and C
When the number of SSs exceeded 1200, the rotation of the disk stopped and the subsequent measurement was stopped as described later. C compared to the invention
It can be seen that the SS characteristics are inferior.

In FIG. 9B, the head / head measured at the same time as FIG.
The change result of the adsorption coefficient μs between the disks is shown. Figure 9
As shown in (b), μs is
1.09,1.16,1.17,1.18,1.18,1.19,1.19 have a large adsorption coefficient μs, and it can be seen that the comparative disk has inferior CSS characteristics to the product of the present invention. In addition, as shown in FIG.
Adsorption coefficient μ under high temperature and high humidity atmosphere of ℃ and 80% RH
s are 1.52, 1.74, and 1.95, respectively, and the CSS count is 120.
At the stage of exceeding 0 times, the torque during the rotation of the disk became too large and the rotation of the disk stopped, and further CSS evaluation was stopped. It can be seen that the comparative disk has inferior CSS characteristics to the product of the present invention.

[0025]

According to the present invention, the reliability characteristics of a magnetic disk, which has been insufficient in the past, particularly the CSS characteristics are greatly improved, and a hard disk drive incorporating this magnetic disk is driven by CSS. At times, the head has a low frictional force on the surface of the magnetic disk, and the attraction force in a high temperature and high humidity atmosphere is small, so that the disk surface is less likely to be damaged, and a highly reliable thin film magnetic disk can be manufactured.

[Brief description of drawings]

FIG. 1 is a diagram showing a roughness curve of a first embodiment of a magnetic disk according to the present invention.

FIG. 2 is a diagram showing an example of evaluation of CSS characteristics used for evaluation of products of the present invention and comparative products.

FIG. 3 is a diagram showing the evaluation results of the coefficient of friction of the magnetic disks of Example 1 of the present invention and Comparative Example 1 during a CSS test at room temperature and humidity.

FIG. 4 is a diagram showing the evaluation results of the friction coefficient of the magnetic disks of Example 1 of the present invention and Comparative Example 1 in a CSS test at high temperature and high humidity.

FIG. 5 is a diagram showing evaluation results of adsorption coefficients of the magnetic disks of Example 1 of the present invention and Comparative Example 1 during a CSS test at room temperature and normal humidity.

FIG. 6 is a diagram showing evaluation results of adsorption coefficients of the magnetic disks of Example 1 of the present invention and Comparative Example 1 in a CSS test at high temperature and high humidity.

FIG. 7 is a diagram showing the evaluation results of the coefficient of friction of the magnetic disks of Example 2 of the present invention and Comparative Example 2 during a CSS test at room temperature and normal humidity.

FIG. 8 is a diagram showing the evaluation results of the coefficient of friction of the magnetic disks of Example 2 of the present invention and Comparative Example 2 during the CSS test at high temperature and high humidity.

FIG. 9 is a diagram showing evaluation results of adsorption coefficients of magnetic disks of Example 2 of the present invention and Comparative Example 2 during a CSS test at room temperature and normal humidity.

FIG. 10 is a diagram showing the evaluation results of the adsorption coefficient of the magnetic disks of Example 2 of the present invention and Comparative Example 2 during a CSS test at high temperature and high humidity.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kohei Ito 5200 Mikashiri, Kumagaya-shi, Saitama Hitachi Metals Co., Ltd.

Claims (2)

[Claims] 1. In a magnetic disk having a textured surface, the radius of the roughness curve of the surface of the magnetic disk is
Scanning length is 200μm using 0.5μm needle, sampling interval is 1
Measured with a stylus type roughness meter under the condition of 3.3 μm, 1/2 of the number of intersections of this roughness curve and its center line is defined as the “groove number” of the texture-groove group, and “scan length 200 μm A magnetic disk characterized in that the average groove interval of texture grooves on the surface of the magnetic disk is 0.1 to 7 μm when "/ number of grooves" is defined as the average groove interval. 2. The magnetic disk according to claim 1, wherein the surface of the substrate is textured by using a pad made of fibers having a diameter of 1 to 25 μm by a texture processing using a pad and a slurry.