JPH1049866A - Texture working method for substrate for magnetic disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a texture working method which prevents a polishing powder from being left after a texture was worked, which cleans a disk-shaped substrate, and which enhances the surface characteristic of the substrate by pressing four polishing tapes by contact rollers so as to be run on both the surface and the rear of the substrate which is being turned. SOLUTION: Two each of polishing tapes 2 in a total of four tapes are pressed by contact rollers 3 and via roller suppression cylinders 4 onto the surface and the rear of a disk-shaped substrate 1 which is being turned in the direction of an arrow A. At the same time, a polishing slurry in which isolated polishing particles are suspended is supplied by a polishing-liquid nozzle 5 to the polishing side of every polishing tape 2, and a slurry polishing operation is performed. The polishing tapes 2 are run in the direction of an arrow B, they are moved back and forth in the direction of an arrow C by the back-and-forth movement of the contact rollers 3, and the front face of the substrate 1 is polished. Thereby, stripe traces which are polished and formed on the substrate 1 are formed at their angle of crossing of 10 to 40 deg.. Thereby, it is possible to prevent a polishing powder from being left on the surface of the substrate after a texture is worked, and a magnetic disk which is highly clean and which is excellent in a surface characteristic can be manufactured at a good yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for texturing a substrate for a magnetic disk, and more particularly to a method for preventing polishing powder from remaining on the surface of a substrate after texturing to dramatically improve the product yield.

[0002]

2. Description of the Related Art Generally, a magnetic disk used as an external storage device of a computer or the like is formed by subjecting an aluminum alloy substrate to a non-magnetic plating treatment such as alumite treatment or Ni-P plating and then forming an underlayer such as Cr. Then, a magnetic layer of a Co-based alloy is formed, and a carbonaceous protective layer is further formed.

In recent years, the density of such magnetic disks has been increased, and as a result, the distance between the magnetic disk and the magnetic head, that is, the flying height, has become smaller and smaller. I have. As described above, since the flying height of the magnetic head is extremely small, if there is a projection on the magnetic disk surface, a head crash may be caused, and the disk surface may be damaged. Further, even a minute protrusion that does not lead to a head crash tends to cause various errors when reading and writing information. For this reason, in the manufacture of a magnetic disk, it is important to reduce surface defects due to the attachment of foreign matter (particles) such as dust to a substrate.

On the other hand, the size of magnetic disks has been reduced in parallel with the increase in capacity and density, and motors for rotating spindles and the like have become smaller. For this reason, a phenomenon in which the torque of the motor is insufficient and the magnetic head does not fly while being fixed to the magnetic disk surface is likely to occur. As means for preventing the sticking of the magnetic head by reducing the contact between the magnetic head and the surface of the magnetic disk, a process of forming a fine groove on the substrate surface of the magnetic disk and performing surface processing called texture processing is performed. Have been done.

Conventionally, as a method of texturing a substrate, for example, tape grinding using a fixed abrasive type polishing tape (Japanese Patent Laid-Open No. 1-86320) or a slurry of free abrasive particles is adhered to the surface of the polishing tape. Slurry grinding (Japanese Patent Laid-Open No. 3-147518) and the like are known.

[0006] By performing such texture processing, polishing powder (fine abrasive grains) remains on the substrate surface. Therefore, in order to remove the polishing powder, the substrate after the texture processing is subjected to cleaning processing such as scrub cleaning and ultrasonic cleaning.

[0007]

As described above, as the density of a magnetic disk increases, it is necessary to reduce foreign matter such as dust on the substrate surface as much as possible in order to reduce defects on the substrate surface.

However, in the conventional texture processing method, since a large amount of polishing powder remains on the substrate surface after processing, the polishing powder cannot be efficiently removed in a subsequent cleaning step. Even if the amount of the polishing powder that cannot be removed in the cleaning step is very small, it causes a final product defect, which causes a decrease in product yield.

The present invention solves the above-mentioned conventional problems and prevents the polishing powder from remaining on the surface of the substrate after texture processing.
It is an object of the present invention to provide a method of texturing a magnetic disk substrate that can dramatically improve product yield.

[0010]

A method of texturing a magnetic disk substrate according to the present invention is a method of texturing a magnetic disk substrate, wherein the surface of the magnetic disk substrate is polished using a polishing tape and a cleaning tape. Wherein the cleaning tape is reciprocated in a radial direction of the substrate.

By using a cleaning tape together with the polishing tape and performing texture processing while reciprocating the cleaning tape in the radial direction of the substrate, fine polishing powder generated from abrasive grains can be efficiently removed by the cleaning tape. Can be removed.

Therefore, the amount of polishing powder remaining on the surface of the substrate after the texture processing is greatly reduced, and a highly clean substrate with almost no adhesion of foreign matter in the cleaning processing after the texture processing can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for texturing a magnetic disk substrate according to the present invention will be described below.

A substrate made of an aluminum alloy is generally used as the magnetic disk substrate in the present invention.
Usually, after processing the aluminum alloy substrate to a predetermined thickness, the surface thereof is mirror-finished, and then a nonmagnetic metal, for example, a Ni-P alloy or a Ni-Cu-P alloy is electroless-plated on the substrate surface. For example, a film having a thickness of about 5 to 20 μm to form a surface layer is used. In general, this substrate is polished on its surface layer and then textured to form specific irregularities and streak patterns.

The polishing is carried out, for example, by sandwiching a substrate between polishing pads having free abrasive grains attached to and impregnated on the surface thereof, and replenishing a polishing liquid such as a surfactant aqueous solution. In a normal case, the surface layer of the substrate is polished by about 2 to 5 μm by such a polishing process, and the surface thereof has an average roughness Ra of 50 ° or less, preferably 30 ° or less.
鏡 Mirror finish below.

The method for texturing a magnetic disk substrate of the present invention uses a polishing tape and a cleaning tape for texturing the magnetic disk substrate, and reciprocates the cleaning tape in the radial direction of the substrate. Specifically, the first-stage texture processing is performed by slurry grinding performed by attaching a slurry of loose abrasive grains to a polishing tape, and the second-stage texture processing is performed as a finishing process after the first-stage texture processing. Processing and
Of these, it is preferable to perform the second-stage texture processing using a polishing tape and a cleaning tape.

Hereinafter, such an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1A is a plan view for explaining the first-stage texture processing, and FIG. 1B is a side view of the same.
FIG. 2 is a plan view for explaining the second-stage texture processing. In FIGS. 1 and 2, members having the same function are denoted by the same reference numerals.

In the first stage of the texture processing, as shown in FIG. 1, a total of four polishing tapes 2, two on each of the front and back surfaces of a disk-shaped substrate 1 rotating in the direction of arrow A, And a polishing slurry in which free abrasive grains are suspended is supplied from the polishing liquid nozzle 5 to the polishing surface side of the polishing tape 2 to perform slurry grinding. The contact roller 3 presses the polishing tape 2 against the surface of the substrate 1 with a predetermined force by a roller pressing cylinder 4. The polishing tape 2 runs in the direction of arrow B, and is polished in such a manner that a new tape surface always contacts the surface of the substrate 1. Also,
The polishing tape 2 can reciprocate (vibrate) in the direction of arrow C by reciprocation of the contact roller 3 to polish the entire surface of the substrate 1 and, at the same time, the intersection of the traces formed by polishing the substrate 1 with the polishing tape 2 Angle (cross angle) is 10-4
It is configured to have an angle of about 0 °.

The conditions for slurry grinding in the first stage of texturing are as follows: the polishing slurry in which free abrasive grains are suspended has an abrasive concentration of 0.05 to 1.0% by weight, and the supply amount of the polishing slurry is 5 to 30 ml. / Min, the number of rotations of the substrate is usually 50 to 5
00 times / minute, preferably 100 to 300 times / minute, the number of reciprocating movements (oscillation frequency) of the polishing tape in the radial direction of the substrate is 50 times / minute or more, preferably 100 to 5000 times / minute. Pressing pressure is 1.0 to 3.0 kg / cm
^{2. The} polishing time is 5 to 30 seconds and the tape feeding speed is 1 to 1.
Within the range of 0 mm / sec.

In the method shown in FIG. 1, a slurry containing free abrasive grains is supplied between a polishing tape and a substrate, and this slurry is applied to the tape just before grinding, but the slurry is prepared in advance. It may be used after being coated on a tape.

In the present invention, by performing the first-stage texture processing, irregularities having an average roughness Ra of the substrate surface of 50 ° or less and a maximum projection height Rp of 400 ° or less are formed and formed. It is desirable to form a surface pattern of a streak pattern having a crossing angle (cross angle) of 10 to 40 °, preferably 10 to 35 ° on the substrate surface. Here, the definition of the surface shape of the substrate is defined by JIS surface roughness (B0601).

The surface average roughness Ra and the maximum projection height Rp are determined by the above-mentioned slurry grinding conditions, particularly, the abrasive grain size, the substrate rotation speed, the tape feed speed, the reciprocating number of the polishing tape (oscillation frequency), This can be achieved by appropriately adjusting the pressing pressure of the cylinder and the polishing time within the above ranges.

On the other hand, the angle at which the texture streaks intersect (cross angle) can be achieved by adjusting the number of rotations of the substrate and the number of reciprocating movements of the polishing tape (oscillation frequency) in the above range. .

As the first-stage textured polishing tape, for example, a non-woven fabric tape made of a material such as nylon, acrylic, cellulose, polyester, rayon, or a combination thereof is used.

Examples of the free abrasive used together with the polishing tape include WA (white alumina), SiC
A (silicon carbide) type, a diamond type, or the like can be used, and abrasive grains having an abrasive particle diameter of 0.1 to 10 μm are preferably used. Such loose abrasives are used as a polishing slurry suspended in a liquid (water or water-based liquid) with a dispersant.

The texturing of the second stage after the texturing of the first stage is performed to further improve the floating characteristics and the like. This second stage of texturing is
As shown in FIG. 2, the first step using the polishing tape 2 and the second step using the cleaning tape 10 are performed.

As the polishing tape 2 used in the second-stage texture processing, a polishing tape using free abrasive grains such as a WA-based, SiC-based, or diamond is used.
A-type, GC (green carbon) -based fixed abrasive grain type polishing tape may be used.

This second-stage texturing is performed without substantially changing the average roughness Ra or the cross angle of the surface shape formed in the first-stage texturing, and is effective in removing burrs and burrs on the substrate surface. The protrusions are selectively removed by polishing, and the maximum protrusion height Rp of the surface is preferably 5
It is preferable to perform the heating so as to be about 0 to 250 °.

In the second stage of texturing, particularly when free abrasive grains and a polishing tape are used, a nonwoven fabric tape such as cellulose, nylon, rayon or the like is suitably used as the polishing tape. Also, as the loose abrasive, for example,
WA-based, SiC-based, diamond-based abrasive grains having an abrasive grain diameter of 0.1 to 6 μm are used, and the free abrasive grains are used as a polishing slurry suspended in a water-based liquid together with a dispersant. .

On the other hand, it is preferable to use acrylic, cellulose, rayon, polyester, nylon or the like as the cleaning tape.

As the second-stage texture processing apparatus, the same apparatus as that used in the first-stage texture processing is used. In the first and second steps, the polishing tape 2 and the cleaning tape 10 are used, respectively.
Is reciprocated (oscillated) in the direction of arrow C by the reciprocating motion of the contact roller 3 to perform texture processing.

The texture processing conditions in the second stage include:
There is no particular limitation, and the following conditions are usually employed.

First step Substrate rotation speed: 50-300 rpm Abrasive grain concentration of polishing slurry: 0.1-10% by weight Supply amount of polishing slurry: 5-30 ml / min Reciprocating number of polishing tape (oscillation frequency) : 50
Up to 400 times / min Cylinder pressing pressure of polishing tape: 1.0 to 3.0 kg /
Feed speed of cm ² polishing tape: 0.5 to 10.0 mm / sec Polishing time: 2 to 10 seconds Second step substrate rotation speed: 50 to 300 rpm Reciprocating number of cleaning tape (oscillation frequency): 30 to 300 Times / minute Cylinder pressing pressure of cleaning tape: 0.5-2.
Feeding speed of 0 kg / cm ² cleaning tape: 0.5 to 10.0 mm
/ Sec Cleaning time: 2 to 10 seconds The reciprocating width (moving distance) of the cleaning tape is
38-60 mm width for 65-95 mm diameter substrate
When the cleaning tape is used, the thickness is preferably about 1 to 10 mm.

After performing such a texture processing, the magnetic disk is manufactured by washing and drying according to a conventional method to form an underlayer, a magnetic layer and a protective layer.

The underlayer is usually formed by sputtering Cr. The thickness of the Cr underlayer is usually 50 to
The range is 2000 mm.

As the magnetic layer, Co—Cr, Co—N
i, or Co-Cr-X, Co-Ni-X, Co-
A thin film layer of a Co-based alloy represented by WX or the like is preferable. Here, X is Li, Si, Ca, T
i, V, Cr, Ni, As, Y, Zr, Nb, Mo, R
u, Rh, Ag, Sb, Hf, Ta, W, Re, Os,
Ir, Pt, Au, La, Ce, Pr, Nd, Pm, S
m and one or more elements selected from the group consisting of Eu.

The magnetic layer made of such a Co-based alloy is
Usually, it is formed on the base layer of the substrate by means such as sputtering.
範 囲 range.

As the protective layer formed on the magnetic layer, a carbonaceous film is preferable. The carbonaceous protective layer is usually formed by depositing carbon in an atmosphere of a rare gas such as argon or He or in the presence of a small amount of hydrogen. A target is formed by sputtering as an amorphous carbon film or a hydrogenated carbon film. The thickness of the protective layer is usually 50 to 50.
0 ° range. Note that a lubricating film may be further formed on the protective layer in order to reduce the coefficient of friction.

[0040]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 After a Ni-P alloy plating layer was formed on the surface of an aluminum alloy substrate, a polished magnetic disk substrate (diameter: 95 mm) was textured according to the present invention. The processing conditions for the first-stage texture processing and the second-stage texture processing are as follows.

First stage textured substrate rotation speed: 300 / min. Polishing slurry: 0.3% by weight of water-based slurry of diamond-based abrasive grains having an average particle diameter of 2.0 μm. Polishing slurry supply amount: 1.2 ml / min. Material: Nylon pile Polishing tape feed speed: 2.0 mm / sec Oscillation frequency of polishing tape: 2000 times / min Cylinder pressing pressure: 2.0 kg / cm ² Polishing time: 10 seconds Second stage texture processing [No. 1 step] Substrate rotation speed: 300 times / minute Polishing slurry: 3% by weight of WA-based abrasive grains having an average particle diameter of 1 μm
Water slurry Abrasive slurry supply amount: 10 ml / min Abrasive tape material: Cellulose Abrasive tape feed speed: 5.0 mm / sec Oscillation frequency of abrasive tape: 70 times / min Cylinder pressing pressure: 1.5 kg / cm ² Polishing time : 5 seconds [2nd step] Substrate rotation speed: 300 times / minute Cleaning tape material: Cellulose Cleaning tape width: 45 mm Cleaning tape feed speed: 5.0 mm / sec Cleaning tape oscillation frequency: 70 times / minute
Min Cylinder pressing pressure: 1.0 kg / cm ² Cleaning time: 4 seconds Cleaning tape reciprocating width: ± 1 mm (In FIG. 2, the distance in which the longitudinal center line of the cleaning tape reciprocates right and left in the C direction is 1 mm each. In the texturing, the first-stage texturing forms a streak pattern with a cross angle of 30 °, the surface roughness (Ra) of the substrate is 50 °, and the maximum protrusion height Rp250 °.
Rp is set to 200 ° without substantially changing the Ra and the cross angle by the second-stage texture processing.

A glide test was performed on the substrate after the texture processing, and the yield was determined. As a result, 3
The average value measured 7 times was 75.8%.

Comparative Example 1 In Example 1, except that the cleaning tape for the second stage of texturing was not reciprocated, texturing was performed in the same manner, and the yield of glide inspection was similarly calculated (average value of three measurements). Was 35.2%.

As is evident from the above results, the polishing tape and the cleaning tape are used in the second stage of texturing, and the cleaning tape is reciprocated in the radial direction of the substrate. The remaining diamond-based abrasive grains can be effectively removed by the second-stage texture processing, thereby greatly improving the yield.

[0046]

As described in detail above, according to the method for texturing a magnetic disk substrate of the present invention, a highly clean magnetic disk substrate can be obtained by preventing polishing powder from remaining on the substrate surface after texturing. Can be provided. For this reason, according to the magnetic disk substrate textured according to the present invention, it is possible to manufacture a magnetic disk having excellent surface characteristics, and therefore, excellent flying characteristics and wear resistance with a high product yield.

[Brief description of the drawings]

FIG. 1 is a view for explaining an embodiment of a first-stage texture processing according to the present invention, wherein FIG.
(B) The figure is a side view.

FIG. 2 is a plan view illustrating an embodiment of a second-stage texture processing according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Polishing tape 3 Contact roller 4 Roller holding cylinder 5 Polishing liquid nozzle 10 Cleaning tape

Claims (1)

[Claims] 1. A method for texturing a magnetic disk substrate, the method comprising texturing the surface of the magnetic disk substrate using a polishing tape and a cleaning tape, wherein the cleaning tape has a diameter equal to the diameter of the substrate. A texture processing method for a magnetic disk substrate characterized by reciprocating in a direction.