JPH07169220A - Magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk hard to be scratched even in the case of a small height of levitation of a magnetic head from the magnetic disk. CONSTITUTION:A magnetic recording layer is formed on a nonmagnetic substrate with minute grooves almost circularly formed on the surface to obtain the objective magnetic disk. The grooves have <=3 deg. parallelism to the circumferential direction, <=50Angstrom surface roughness Ra in the radial direction and <=20nm average radius of curvature in the radial direction at the peaks.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a CSS (contact
The present invention relates to a magnetic disk applied to a magnetic disk device or the like adopting a start / stop system.

[0002]

2. Description of the Related Art As the above magnetic disk, a magnetic recording layer is formed on a non-magnetic substrate having a finely machined groove formed on its surface by subjecting it to a surface treatment such as lapping, polishing or texturing. It is known that a protective layer made of carbon, SiO ₂ or the like for protecting the magnetic recording layer is formed on the magnetic recording layer, and a lubricating layer is further formed on the protective layer.

By the way, in recent years, with the increase in density of magnetic disks, the distance between the magnetic disk and the magnetic head tends to become narrower. Therefore, in order to set the flying height of the magnetic head lower than that of the magnetic disk, the roughness of the processed groove must be lowered. Then, the contact area between the magnetic disk and the magnetic head increases and the sliding of this portion increases, so that the magnetic disk is easily scratched and cannot be used for a long period of time.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a magnetic disk which is not easily scratched even when the flying height of the magnetic head from the magnetic disk surface is set low. is there.

[0005]

In order to achieve the above object, the present invention provides a magnetic disk in which the machined groove has a degree of parallelism with the circumferential direction of 3 ° or less and a surface roughness Ra in the radial direction. The magnetic disk is characterized in that the average radius of curvature in the radial direction is 500 nm or less and the tip of the peak portion is 20 nm or less.

[0006]

In the magnetic disk of the present invention, the non-magnetic substrate has high hardness over its entire surface and excellent machinability as compared with a substrate having rigidity such as non-magnetic metal such as aluminum alloy, glass and resin. The cured layer is formed. A non-magnetic substrate provided with such a hardened layer is subjected to flattening and polishing, and then roughening of the surface is performed by texture processing, so that finely processed grooves are formed in a substantially circular shape on the surface. It is formed.

In the present invention, the machined grooves formed at this time have a parallelism with respect to the circumferential direction of 3 ° or less, a surface roughness Ra (center line average roughness) of 500 nm or less in the radial direction, and the tip of the crest portion. 20n average radius of curvature in the radial direction
It is set to m or less.

If the parallelism with respect to the circumferential direction exceeds 3 °, abnormal cutting marks are likely to occur in the vicinity of the intersections of the machining grooves, and the head hit characteristics deteriorate. Also, Ra is 500
When the thickness exceeds nm, a minute waviness in the radial direction becomes large, and the head hit characteristic also deteriorates. Furthermore, when the average radius of curvature in the radial direction at the tip of the crest exceeds 20 nm, the contact area with the magnetic head becomes large and CS
The durability by the S test decreases.

To form a machined groove in such a state,
For example, do as follows. That is, a slurry in which abrasive grains of diamond, alumina, silicon carbide or chromium oxide having a particle size of 4 μm or less are dispersed in an aqueous solution is used as a working fluid, and a polishing cloth impregnated with the working fluid is applied to the surface of a hardened layer of a rotating substrate. Press on. At this time, the number of rotations of the substrate, the pressing force on the surface of the cured layer, the winding speed of the polishing cloth,
The period of vibration for slightly swinging the polishing cloth in the radial direction of the substrate is appropriately adjusted.

The non-magnetic substrate having the above-mentioned processed grooves is
If necessary, C may be used to adjust the magnetic characteristics of the magnetic recording layer.
After the underlayer made of r, Cr alloy or the like is formed, a magnetic recording layer of, for example, Co-based, Co-Ni-based, or Co-Cr-Ta-based is formed. Next, a protective layer made of carbon, SiO ₂ or the like for protecting the magnetic recording layer is formed on the magnetic recording layer, and a lubricating layer is further formed on the protective layer to form the desired magnetic disk. To be done.

[0011]

【Example】

Examples 1 to 4 and Comparative Examples 1 to 6 A substrate has an outer diameter of 95 mm, an inner diameter of 25 mm, and a thickness of 1.27 mm.
Aluminum alloy material is used to form Ni—P alloy layers on both surfaces of the aluminum alloy material by a known electroless plating method to a thickness of 15 μm, and then Ra and La are processed by lapping and polishing.
Was a 5 nm mirror surface.

Then, the mirror-finished substrate is subjected to 500r.
While rotating at pm, the working liquid was dropped and supplied from the nozzle to the polishing cloth, and the polishing cloth was pressed against the substrate by a roll to perform texture processing. The working liquid is prepared by adjusting a diamond abrasive grain having a particle size of 90% by weight in the range of 1 to 3 μm and a diamond abrasive grain having a particle size of 90% by weight in the range of 3 to 7 μm into a slurry. did. Further, the above-mentioned texture processing was performed by changing the parallelism of the processed grooves, Ra and the average radius of curvature in the radial direction at the tip of the crest portion variously.

For the various substrates thus obtained, the parallelism with respect to the circumferential direction and the surface roughness Ra in the radial direction are obtained.
The average radius of curvature in the radial direction at the tip of the processed groove crest was measured by a scanning electron tunneling microscope. The results are shown in Table 1.

Then, a Cr underlayer film was formed on these substrates by the DC magnetron sputtering method, and then a CoCrTa magnetic recording layer was formed on this underlayer film by the above method. Further, a carbon protective film was formed on this magnetic recording layer under the same conditions as the formation of the Cr underlayer film, and a lubricating layer was formed thereon by spin coating. The various magnetic disks thus obtained were evaluated for head hit characteristics, durability by a CSS test, and adsorption characteristics.

For the head hit characteristic, the magnetic head equipped with a vibration sensor is levitated and the number of contact between the magnetic disk and the magnetic head is measured for 10 sheets (20 sides). The flying height of the magnetic head is 0.05 μm or more. No head hits were produced, and those in which the flying height of the magnetic head was 0.09 μm or more, 0.07 μm or more and less than 0.09 μm, and 0.05 μm or more and less than 0.07 μm were produced. They were marked with x, Δ, and ◯, respectively.

The durability of the CSS test is 0 rpm → 3600 r after the magnetic head is placed on the magnetic disk.
The process of pm → 0 rpm was performed in a cycle of 30 seconds. 10,
The process was interrupted every 000 times, and the presence or absence of sliding scratches on the surfaces of four (8) magnetic disks was observed. If no sliding scratch was observed, the test was continued, and if observed, the test was stopped.

Further, the adsorption characteristic is that the magnetic head is placed on a magnetic disk and the magnetic head is 100 at an environment of 30 ° C. and a relative humidity of 80%.
The ratio of the static friction coefficient between the magnetic head and the magnetic disk after being left for a period of time and the static friction coefficient between the magnetic head and the magnetic disk before being left was determined for four sheets (8 surfaces). Those having a ratio of less than 1.2, 1.2 or more and less than 3 and 3 or more were marked as ⊚, ◯ and ×, respectively. The above results are shown in Table 1.

[0018]

[Table 1]

[0019]

The present invention can provide a magnetic disk that is not easily scratched even when the flying height of the magnetic head from the magnetic disk is set as low as about 0.05 μm.

Claims (1)

[Claims] 1. A magnetic disk in which a magnetic recording layer is formed on a non-magnetic substrate on the surface of which fine processed grooves are formed in a substantially circular shape, and the processed grooves have a parallelism in the circumferential direction. Surface roughness Ra in the radial direction of 3 ° or less, 500 nm
A magnetic disk characterized in that the average radius of curvature in the radial direction below and at the tip of the peak is 20 nm or less.