JPH0693476A - Production of magnetic disk - Google Patents

Abstract

PURPOSE:To provide a production method of a magnetic disk enabling to prevent an attraction phenomenon of a magnetic disk and also hardly causing head hitting, even though head floating quantity is made small. CONSTITUTION:In the production method of the magnetic disk provided with a substrate and a magnetic recording layer on it on a nonmagnetic base plate the surface of which is roughened, the surface roughness Ra (average central roughness) of the base plate is made to be 30-100Angstrom , and after electric potential of the base plate is made negative with respect to electric potential of a chamber of a sputtering device and the base plate sputtered in an inactive gas atmosphere, the substrate is formed.

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 manufacturing method of a magnetic disk applied to a magnetic disk device or the like adopting a start and stop system.

[0002]

2. Description of the Related Art Conventionally, in order to prevent the magnetic head from being attracted to the surface of a magnetic disk when the rotation of the magnetic disk is stopped, the surface of the non-magnetic substrate is roughened by lapping, polishing or texturing. The surface roughness Ra (average center roughness) of the substrate is
0 Å, then, if necessary, such as adjusting the magnetic characteristics,
It is manufactured by forming an underlayer made of Cr or a Cr alloy, and further forming a magnetic recording layer, a protective layer, and a lubricating layer on the underlayer.

However, in order to realize high-density recording, this magnetic disk is required to be able to reduce the distance from the magnetic head during magnetic recording / reproduction, that is, the so-called head flying height as much as possible.

[0004]

However, in the magnetic disk manufactured by the above method, when the flying height is greater than 0.07 μm and is intentionally reduced to 0.07 μm or less, the minute protrusions present on the surface of the disk. A so-called head hit, which is a collision between an object and a magnetic head, easily occurs, the head and the disk are damaged, and it becomes difficult to perform recording / reproducing successfully.

Therefore, if the surface roughness of the magnetic disk is made small in order to prevent a head hit from occurring, it becomes difficult to prevent the attraction phenomenon of the magnetic head. That is, the prevention of the magnetic head attraction phenomenon and the prevention of the head hit are contradictory problems.

In view of the above circumstances, an object of the present invention is to provide a method for manufacturing a magnetic disk which can prevent the magnetic head from attracting a magnetic head and is less likely to cause a head hit even when the head flying height is reduced to 0.07 μm or less. To do.

[0007]

In order to achieve the above object, the present invention provides a non-magnetic substrate having a roughened surface,
In a method of manufacturing a magnetic disk having an underlayer and a magnetic recording layer thereon, the surface roughness Ra of the substrate is 30 to 10
0 Å, the substrate is sputtered in an inert gas atmosphere so that the potential of the substrate is negative with respect to the potential of the chamber of the sputtering apparatus, and then the underlayer is formed. Is a manufacturing method.

[0008]

In the method of the present invention, as the material of the non-magnetic substrate, a non-magnetic metal having a rigidity such as a non-magnetic metal such as an aluminum alloy, glass, resin or the like is used.

Next, a hardened layer having high hardness and good machinability is formed on the entire surface of the substrate made of such a material. This hardened layer can be formed by, for example, providing an Ni-P alloy layer or a Ni-Cu-P alloy layer by an electroless plating method, or performing an alumite treatment when using an aluminum alloy.

Further, the substrate provided with the hardened layer is subjected to polishing processing for flattening the surface thereof, for example, lapping processing or polishing processing. By this flattening polishing process, the substrate surface is made a flat mirror surface.

Then, the surface of the substrate subjected to the flattening polishing process is roughened by the texture process. At this time, it is necessary to roughen the substrate so that the textured substrate surface roughness Ra is 30 to 100Å. When Ra is less than 30Å, it is difficult to prevent the magnetic head from adsorbing. On the other hand, when Ra exceeds 100Å, the flying height of the head becomes excessive.

This texturing is carried out, for example, by pressing a polishing tape having abrasive grains such as alumina bound on a film against the surface of the substrate, or an abrasive slurry in which abrasive grains such as diamond and alumina are dispersed in an aqueous solution. Is used as a processing liquid and a polishing cloth impregnated with the processing liquid is pressed against the surface of the substrate.

In the method of the present invention, such a surface-roughened non-magnetic substrate is sputtered in an inert gas atmosphere so that the potential of the substrate is negative with respect to the potential of the chamber of the sputtering apparatus. is important.

In this sputtering, neutral atoms or ionized atoms of an inert gas, which is the atmosphere, are collided with the substrate at a high speed to knock out the atoms of the hardened layer. It is possible to manufacture a magnetic disk in which head hits are unlikely to occur even if the magnetic disk size is reduced to 0.07 μm or less.

This occurs due to this bias sputtering after texturing unless this is done, and when the magnetic recording layer or the protective layer thereover is formed, it selectively grows on the magnetic recording layer and minute projections. It is speculated that this is due to the fact that the core of It is also presumed that the nuclei must be so small that the surface roughness of the substrate after texturing cannot prevent the magnetic head from sticking.

In this sputtering, (1) the potential of the substrate is 500 to 1000 V negative with respect to the potential of the chamber of the sputtering apparatus, and (2) the inert gas pressure is 0.
5-80 mTorr, (3) DC input power 0.2-5
It is preferably W / cm ² . Below these lower limits, the effect of removing the nuclei will not be sufficiently exerted, whereas above these upper limits, excessive sputtering will occur.

After that, on the substrate satisfying the condition of Ra, C is added to adjust the magnetic characteristics of the magnetic recording layer.
An underlayer made of r, Cr alloy or the like is formed. Examples of the Cr alloy include Cr to which W, Si, and Nb are added in an amount of 0.3 to 5 atom%. The film thickness is 10 to 5
00Å will do.

A magnetic recording layer made of a predetermined ferromagnetic metal thin film is formed on the formed underlayer. Examples of the magnetic recording layer include Co-based, Co-Ni-based, Co-
There are Pt type, Co-Cr-Ta type, and Fe type.

A protective layer such as a carbon film is formed on the magnetic recording layer, and a lubricating layer such as perfluoroalkyl polyether is further formed on the protective layer, whereby a desired magnetic disk is formed. It is said that

[0020]

【Example】

Example 1 Disc-shaped aluminum alloy (Mg 4% by weight, balance Al)
After forming a Ni-P alloy layer on the substrate of the material by the electroless plating method, lapping and polishing were performed.

After that, a polishing tape made of alumina abrasive grains having an average particle size of 3 μm bonded on a polyester base film is pressed against the surfaces of these substrates to perform texture processing, and the surface roughness is concentrically formed. Ra formed fine irregularities of 63Å.

Next, after setting these textured substrates in the chamber of the DC magnetron sputtering apparatus, the pressure in the chamber is set to about 10 ^-7 T.
After evacuation to orr, bias sputtering was performed for 20 seconds at an Ar gas pressure of 30 mTorr with a substrate potential of 800 V, which is negative with respect to the chamber potential, and a DC input power of 3 W / cm ² . Surface roughness R after sputtering
a was 40Å. The result of observing this surface with a scanning tunneling microscope is shown in FIG.

Further, Cr as an underlayer is added at a substrate temperature of 3
It was formed by sputtering under the conditions of 00 ° C., Ar gas pressure of 17.6 mTorr, and DC input power of 5 W / cm ² , and the film thickness was 200 Å.

Then, a Co—Cr—Pt-based magnetic recording layer and a carbon protective layer having a thickness of 500 Å were formed on the underlayer.

After that, after a polishing treatment with a polyester polishing tape having alumina abrasive grains having an average grain size of 2 μm bonded and a cleaning treatment with a cloth tape, a perfluoropolyether type lubricating film by a spin coat method (lubrication by DuPont) is used. Agent (using trade name Krytox) was formed.

With respect to the magnetic disk thus obtained, the average number of protrusions, the head adsorption test, and the electromagnetic conversion characteristics were measured.

The average number of protrusions is measured by rotating the magnetic disk at 500 to 2000 rpm to levitate the magnetic head from the magnetic disk to a predetermined height and vibrating due to collision between the magnetic head and the magnetic disk. Is detected by the piezoelectric sensor on the surface of the magnetic disk 50,
It was performed by calculating the number of times per surface.

In the head adsorption test, the magnetic head was brought into close contact with the magnetic disk and held for 48 hours at 30 ° C. and 80% relative humidity. Was measured, and the torque was divided by the head load to calculate the head adsorption coefficient.

Example 2 A test was conducted in the same manner as in Example 1 except that the substrate temperature during bias sputtering was 300 ° C. The substrate surface roughness Ra after bias sputtering was 32Å.

Conventional Example A test was performed in the same manner as in Example 1 except that Cr was used as a base layer without performing bias sputtering on a textured substrate. The results of observing the surface of the textured substrate with a scanning tunneling microscope are shown in FIG. Table 1 shows the results obtained as described above.

[0031]

[Table 1]

In Examples 1 and 2, even if the head flying height was reduced to 0.04 μm, the average number of protrusions was less than 1, the adsorption resistance was good, and the electromagnetic conversion characteristics were the same as those of the conventional example. It is comparable to that. On the other hand, in the conventional example, although the adsorption resistance is extremely good, the head flying height is 0.08 μm.
Even if it is increased to 1, the average number of protrusions exceeds 1.

[0033]

As is apparent from the above, according to the method of the present invention, it is possible to manufacture the magnetic disk which can prevent the magnetic head from adsorbing the magnetic head and hardly cause a head hit.

[Brief description of drawings]

FIG. 1 is a result of observing the surface of a substrate after bias sputtering in Example 1 with a scanning tunneling microscope.

FIG. 2 is a result of observing a surface of a textured substrate in a conventional example with a scanning tunneling microscope.

Claims (2)

[Claims] 1. A surface roughness Ra (average center roughness) of a substrate in a method of manufacturing a magnetic disk comprising an underlayer and a magnetic recording layer on the underlayer on a surface-roughened non-magnetic substrate.
Is set to 30 to 100 Å, and the substrate is sputtered in an inert gas atmosphere so that the potential of the substrate becomes negative with respect to the potential of the chamber of the sputtering device.
A method of manufacturing a magnetic disk, comprising forming the underlayer. 2. As sputtering conditions, (1) the potential of the non-magnetic substrate is 500 to 1000 V negative with respect to the potential of the chamber of the sputtering apparatus, (2) the inert gas pressure is 0.5 to 80 mTorr, and (3) DC. Input power 0.2
The method for manufacturing a magnetic disk according to claim 1, wherein the magnetic disk has a density of about 5 W / cm ² .