JPH06290452A - Carbon substrate for magnetic disk and magnetic disk medium - Google Patents

Abstract

PURPOSE:To make floating of a magnetic head lower and to surely prevent a head clash by sufficiently lowering the coefft. of friction in a contact region with the magnetic head. CONSTITUTION:The carbon of a carbon substrate for the magnetic disk subjected to surface polishing is discretely or continuously irradiated with pulse lasers and is thereby oxidized and evaporated only in the contact region where the contact with the magnetic head arises at the time of starting and stopping a magnetic disk device, thereby, plural holes 11 are formed and the contact region is provided with a hole forming region 10. The area of this hole forming region 10 is 50 to 99.9% of the area of the contact region and the cross section formed by the single pulse of the pulse lasers is 1 to 900mum<2>. Further, the depth of the holes formed by the single pulse of the pulse lasers is 10 to 3000Angstrom .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk carbon substrate which has been subjected to a texture treatment and on which a magnetic film or the like is formed to form a magnetic disk.

[0002]

2. Description of the Related Art In a fixed magnetic disk device, a magnetic head and a magnetic disk are in contact with each other when stopped, but at the time of startup, the magnetic head floats above a rotating magnetic disk.
Stop, hereinafter abbreviated as CSS) is adopted. In this method, when the fixed magnetic disk device is stopped, adsorption may occur between the magnetic head and the magnetic disk, or frictional force may increase due to contact wear between the magnetic head and the magnetic disk, which may prevent rotation of the magnetic disk. is there. In order to prevent such an increase in adsorption and frictional force, the magnetic disk substrate is subjected to surface processing for adjusting its surface to an appropriate surface roughness instead of a mirror surface. Such surface treatment is generally called texturing. The surface processed in this way is called a texture.

Conventionally, for a magnetic disk, a substrate obtained by plating an aluminum alloy with nickel phosphorus and polishing the surface has been used. As a general method for forming the texture on the magnetic disk substrate, a so-called mechanical texture forming method has been performed, in which a polishing tape is pressed against the rotated magnetic disk substrate to form striations. It was Further, recently, a method of irradiating a nickel phosphorus plating layer with a pulse laser to form irregularities on the surface has been proposed (European patent application EP 447025, USP506.
2021, USP5108781 and references: J.Appl.Phys., Vol.69, N
o.8,15, April 1991).

On the other hand, the present applicant has previously mentioned that as a method for forming a texture of a carbon substrate for a magnetic disk, the surface-polished substrate is heat-treated at a temperature of 400 ° C. to 700 ° C. in an oxidizing atmosphere. A method has been proposed in which the surface of the carbon substrate is roughened (Japanese Patent Application No. 2-83137).
issue).

This method utilizes the properties peculiar to the carbon substrate. In this texture processing method, the carbon substrate is heat-treated in an oxidizing atmosphere to utilize the oxidation reaction of C + O ₂ → CO _2. The carbon is appropriately vaporized to form fine irregularities on the surface of the magnetic disk substrate by utilizing the fact that the polishing eyes are selectively etched.

[0006]

However, in order to increase the density of the magnetic disk device, it is necessary to reduce the spacing between the magnetic head and the magnetic disk during recording / reproducing, that is, the floating gap. In order to reduce this floating gap, it is necessary to reduce the surface roughness of the substrate.

However, if the surface roughness of the substrate is made too small, the contact area between the substrate and the head increases, and there is the drawback that the frictional force increases due to adsorption. In particular, even if an attempt is made to apply a mechanical texture forming method for forming scratches that has been conventionally used to a magnetic disk that requires high recording density, it is difficult to control the density and depth of the scratches,
There is a limit to the reduction of the floating clearance.

On the other hand, in the conventional method for forming a texture of a carbon substrate for a magnetic disk in which the surface of the carbon substrate is roughened by heating in an oxidizing atmosphere, the depth of fine irregularities on the substrate surface is mechanically textured. It can be adjusted more easily than the method. It is possible to obtain an appropriate surface roughness without roughening the substrate surface more than necessary.

However, since a suitable method for actively controlling and adjusting the density of the fine irregularities and the distribution pattern of the fine irregularities has not been developed, the friction coefficient for the magnetic head on the surface of the magnetic disk is made smaller. Then, it is not yet satisfactory in meeting the demand for lowering the flying height of the magnetic head for higher recording density.

Further, in a conventional method of forming a texturing by irradiating a pulsed laser on an aluminum alloy substrate plated with nickel phosphorus,
After heating and melting the nickel-phosphorus alloy film in spots,
It utilizes the fact that crater-like irregularities are formed when it cools and solidifies. In this method, the surface roughness can be controlled to some extent by adjusting the pulse interval and the laser intensity.

However, in the case of forming a so-called zone texture in which the texture is formed only on the inner peripheral portion of the disk, a head crash may occur when the head moves from the texture-unformed portion to the texture-formed portion. There is. That is, as shown in the sectional view of FIG. 3A, an Al substrate 12 plated with a nickel-phosphorus alloy is used.
Causes a step difference because the apex height of the substrate surface increases at the boundary between the texture non-formation portion and the texture formation portion,
The magnetic head and the magnetic disk are likely to come into contact with each other at this step, which may cause a head crash. Further, since the contact with the magnetic head occurs in the ring-shaped protruding portion, when controlling the contact area, there is a limit in controlling in the direction of increasing the contact area, and the magnetic disk contacts the magnetic head. May be worn out.

The present invention has been made in view of the above problems, and it is possible to sufficiently reduce the friction coefficient in the contact area with the magnetic head, and to further reduce the flying height of the magnetic head. An object of the present invention is to provide a carbon substrate for a magnetic disk and a magnetic disk medium that can reliably prevent a head crash.

[0013]

A carbon substrate for a magnetic disk according to the present invention is a carbon substrate for a magnetic disk having a surface-polished contact that causes contact between a magnetic head and a magnetic disk when the magnetic disk device is started and stopped. Only in a region including the region and the region in the vicinity thereof (hereinafter referred to as the head landing zone), carbon is oxidized and vaporized by discrete or continuous irradiation of a pulse laser to form a plurality of recesses, and a recess forming region is provided. It is characterized by that. In this recess forming region, the area of one recess formed by a single pulse of a pulse laser is 1 to 900.
μm ² or less and the depth of the depression is 10 to 3000 Å
The surface area of 50% to 99.9% is indented.

The head landing zone is usually
It is provided on the inner peripheral portion of the surface-polished carbon substrate for a magnetic disk. The head landing zone is irradiated with a pulsed laser, and the substrate is processed by utilizing the etching effect of thermal oxidation and vaporization of the substrate to form a textured surface.

[0015]

When a carbon substrate is irradiated with a pulsed laser as in the present invention, a single depression of the pulsed laser forms microscopic depressions, which is a phenomenon peculiar to the carbon substrate. With other substrates such as aluminum substrates and glass substrates, the substrate surface only melts. As described above, the contact area with the magnetic head can be controlled by continuously forming the minute depressions that can be formed by the pulse laser in the carbon substrate in an arbitrary pattern.

That is, when a pulse laser is applied to a contact area (head landing zone) of a surface-polished carbon substrate for a magnetic disk with a magnetic head, the temperature of the substrate rises, and the carbon forming the substrate is heated. Are oxidized and vaporized, and the substrate is etched. At this time, the photon energy of the laser may act directly on the carbon atoms of the substrate, causing a phenomenon of knocking out the carbon atoms. By scanning the substrate with such a pulse laser, one depression is formed for one pulse, and minute unevenness is formed in which the etched portion is a concave portion and the other portion is a convex portion.

The uneven shape, steps, density of minute unevenness and distribution pattern of minute unevenness formed on the surface of the magnetic disk carbon substrate controls the beam diameter, energy and irradiation position of the pulse laser applied to the substrate. It can be adjusted easily.

Further, as shown in FIG. 3B, when the carbon substrate 13 is irradiated with the pulse laser, the peak height of the concave-convex forming portion and the surface height of the non-concave forming portion are the same. While the magnetic head rotates and floats with a predetermined gap, even if the magnetic head moves between the texture non-formation part and the texture formation part, the magnetic head and the magnetic disk come into contact with each other. Absent. Therefore, damage to the magnetic disk can be prevented.

The area ratio of the hole forming region in the head landing zone is preferably 50 to 99.9%. The reason is that if it is less than 50%, C
This is because the effect of reducing the frictional force between the magnetic head and the magnetic disk during SS is small, and if it exceeds 99.9%, the contact pressure between the magnetic head and the magnetic disk at the convex portion is large and head crushing is likely to occur.

The area of one depression formed by a single pulse of the pulse laser is preferably 1 to 900 μm ² . The reason is that if it is less than 1 μm ² , it becomes difficult to control the shape of the depression, and 900 μm
This is because if it exceeds m ² , the recess becomes almost the same as the rail width of the magnetic head, and the magnetic head and the magnetic disk are easily attracted to each other.

Further, the depth of the depression formed by the single pulse of the pulse laser is preferably 10 to 3000 Å. The reason is that if it is less than 10 Å, the surface roughness becomes almost the same as the surface roughness of the substrate, and the contact area reduction effect is small, and if it exceeds 3000 Å, the floating stability of the magnetic head is affected.

[0022]

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

First, a method for manufacturing a carbon substrate for a magnetic disk according to this embodiment will be described, and the structure of the carbon substrate for a magnetic disk according to this embodiment will be described with reference to the magnetic disk medium according to this embodiment. . For example, as a material for a carbon substrate for a magnetic disk, a phenol-formaldehyde resin, which is a thermosetting resin that becomes vitreous carbon after carbonization and firing, is selected, and this resin is hot-press molded into a magnetic disk shape, and then, for example, Preheat by heating to a temperature of 1500 ° C. in an N ₂ gas atmosphere.

Then, this is hot isostatic press (HI)
P) is used, for example, while heating to 2600 ° C., 1
An isotropic pressure of 800 atm is applied. The molded body thus obtained is subjected to predetermined end surface processing and surface polishing to prepare, for example, a carbon substrate for a magnetic disk having an outer diameter of 65 mm, an inner diameter of 20 mm and a thickness of 0.635 mm.

Next, as shown in FIG. 1, this carbon substrate 1 for magnetic disk is fixedly attached to a spindle 2 by a clamp 3, and while the substrate 1 is being rotated, a pulse laser is vertically irradiated onto the surface of the substrate 1. . That is, the light emitted from the power source and the light source 8 is guided by the light guide 7 to the Q-switch crystal 6 (optical element for converting to high-output single-pulse light), and the pulse laser 9 is emitted from the crystal 6. This pulse laser is expanded by the beam expander 5 (increasing the beam diameter), then focused by the condenser lens 4 and irradiated onto the surface of the carbon substrate 1.

In the above method, the laser irradiation system is fixed, and the pulsed laser is irradiated while rotating the carbon substrate 1 mounted on the spindle 2. Therefore, FIG. 2A and a partially enlarged view thereof are shown in FIG. As shown in (b), irregularities due to the minute holes 11 are formed in the ring-shaped region 10 on the inner peripheral portion of the substrate.

As shown in FIG. 4 which is an enlarged schematic view of the region 10, the recess 11 formed in the region 10 on the surface of the carbon substrate has a two-dimensional hole 11 having a diameter corresponding to the beam diameter of the pulse laser. They are arranged in contact with each other. In this depression forming region 10 (texture forming portion), as shown in FIG. 3B, since the carbon substrate 13 is irradiated with a pulse laser, the peak height of the unevenness forming portion and the surface of the non-unevenness forming portion. Since the height is the same, even if the magnetic head moves between the non-texture forming portion and the texture forming portion while the magnetic disk is rotating and the magnetic head is levitating with a predetermined gap. No contact occurs between the magnetic head and the magnetic disk. Therefore, damage to the magnetic disk can be prevented.

Then, a carbon substrate for a magnetic disk was actually prepared under the above-mentioned conditions, and irregularities were formed and textured by using a laser having a wavelength of 523 nm, a power of 1 W and a pulse period of 6.4 KHz. As a result, the diameter is about 4
1 μm, maximum depth 0.1 μm hemispherical hollow 1
1 was formed. In addition, the depressions 11 were formed uniformly in the region having a radius of 14 to 16.5 mm from the center of the disc with a spacing of 5 μm.

On the substrate thus formed, as a magnetic recording medium, a Cr film as a base film was 0.15 μm and a Co alloy layer was 0.03 μm as a magnetic layer by sputtering.
m, and a carbon film of 0.02 μm was continuously formed as a protective film. Further, as a lubricating film, PTFE (perfluoropolytyl ether) was formed in a thickness of 20Å by a spin coating method. FIG. 5 shows a sectional view of the magnetic disk medium formed.

When the presence or absence of adsorption between the magnetic disk thus formed and the magnetic head was investigated, no adsorption occurred.

Also, when the head is sought from the texture-unformed area to the formation area while the disk is rotating,
On the contrary, when the seek was performed from the texture formation region to the non-formation region, contact between the magnetic head and the magnetic disk was not observed.

Further, in the above-mentioned magnetic disk, the lubricant was held in the fine holes, and the reduction of the lubricating film due to the rotational scattering of the lubricating film could be prevented.

[0033]

As described above, in the carbon substrate for a magnetic disk according to the present invention, since the texture is formed by the irradiation of the pulse laser in the contact area where the magnetic head lands when the magnetic head starts and stops, the texture of the pulse laser It is possible to control the contact area between the magnetic disk medium on the carbon substrate and the magnetic head by changing the beam diameter, the output power, and the irradiation pattern. Further, in the magnetic disk medium in which the magnetic film, the protective film, and the lubricating film are formed on the surface of the carbon substrate for a magnetic disk of the present invention, adsorption of the magnetic head is less likely to occur, and a texture-unformed area and a texture-formed area are formed. Even if the head is sought in between, no contact with the magnetic disk occurs. Further, as a result of the lubricant being retained in the minute recesses, it is possible to prevent the reduction of the lubricating film due to the rotational scattering of the lubricating film.

[Brief description of drawings]

FIG. 1 is a schematic view showing a laser irradiation apparatus used for manufacturing a magnetic disk carbon substrate according to an example of the present invention.

2A and 2B are diagrams showing a depression forming region of a magnetic disk carbon substrate according to an example of the present invention, FIG. 2A is a plan view showing the entire substrate, and FIG. 2B is a partially enlarged view thereof.

FIG. 3 is a cross-sectional view showing the vicinity of a boundary between a texture forming portion and a non-forming portion, where (a) is a conventional case and (b) is the present invention.

FIG. 4 is an enlarged view schematically showing an arrangement of depressions in a texture forming area according to this embodiment.

FIG. 5 is a cross-sectional view of the magnetic disk medium of this embodiment.

[Explanation of symbols]

 1, 12, 13; Carbon substrate 2; Pulse laser 10; Dimple forming region 11; Dimple

Claims (3)

[Claims] 1. A carbon substrate for a magnetic disk having a surface-polished surface is selectively irradiated with a pulse laser to a region including a region where a magnetic head and a magnetic disk come into contact with each other at the time of starting and stopping a magnetic disk device to selectively emit carbon. The area of one depression formed by a single pulse of a pulse laser by oxidization vaporization or sputtering is 1 to 900 μm ² or less, and the depth of the depression is 10 to 3
A carbon substrate for a magnetic disk, which is 000Å and is provided with an indentation forming region having an indentation of 50% to 99.9% in surface area. 2. A magnetic disk medium, wherein a magnetic film, a protective film, and a lubricating film are sequentially formed on the carbon disk carbon substrate according to claim 1. 3. The magnetic disk medium according to claim 2, wherein an undercoat film is provided between the magnetic disk carbon substrate and the magnetic film.