JPH10143858A - Method for texturing substrate for magnetic disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove remaining diamond abrasive grains and to obtain a substrate having excellent surface characteristics by texturing this substrate by using a polishing slurry suspended with the diamond abrasive grains, then subjecting the substrate to abrasive grain washing by using a slurry prepd. with aluminum abrasive grains. SOLUTION: Two pieces each and total four pieces of polishing tapes are pressed by contact rollers 3 to the front and rear surface of the disk-shaped substrate 1 rotating in an arrow A direction. The substrate is then subjected to slurry polishing by supplying the polishing slurry suspended with the free diamond abrasive grains from polishing liquid nozzles to the polishing surface side of the polishing tapes. The diamond abrasive grains to be used together with the polishing tapes are formed by suspending the abrasive grains of preferably 0.1 to 5μm together with a dispersant. The substrate is subjected to abrasive grain washing by using a porous tape 2A adhered with the slurry of the aluminum abrasive grains of preferably 0.5 to 2μm and a cleaning tape 10 after the texturing, by which the highly clean substrate is obtd. The production of the magnetic disk having excellent floating characteristics and wear resistance is made possible.

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 a magnetic disk has been increased, and accordingly, the distance between the magnetic disk and the magnetic head, that is, the flying height has become smaller and smaller, and recently, 0.10 μm or less has been required. 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 (polishing powder on the substrate surface and residual polishing 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. Therefore, it is required to reduce as much as possible the polishing powder adhered or embedded in the substrate surface by the texture processing.

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 greatly reduces the amount of polishing powder remaining on the surface of the substrate after texture processing, thereby greatly improving the product yield. It is intended to provide a processing method.

[0010]

According to the present invention, there is provided a method of texturing a magnetic disk substrate, comprising the steps of: texturing a magnetic disk substrate using diamond abrasive grains; Abrasive cleaning.

Immediately after the completion of the texturing using diamond abrasive grains, the abrasive grains such as diamond abrasive grains remaining on the substrate surface are efficiently removed by immediately executing abrasive cleaning using alumina abrasive grains. can do. That is, the alumina abrasive grains are excellent in the performance of removing diamond abrasive grains, and can efficiently remove diamond abrasive grains remaining after texture processing.

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.

In the method of texturing a magnetic disk substrate according to the present invention, the texturing of the magnetic disk substrate is performed by using diamond abrasive grains, and then cleaning the abrasive grains by using alumina abrasive grains. Specifically, a porous tape to which a slurry of alumina abrasive grains is adhered after the texture processing is performed by slurry grinding performed by attaching a slurry of diamond free abrasive grains to a polishing tape, and after the texturing, It is preferable to perform abrasive cleaning using a cleaning tape supplied with a cleaning liquid.

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

In the texturing process, as shown in FIG. 1, two polishing tapes 2 are pressed against the front and back surfaces of the disk-shaped substrate 1 rotating in the direction of arrow A by a total of four by a contact roller 3, A polishing slurry in which diamond 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.
The polishing tape 2 reciprocates (oscillates) in the direction of arrow C by reciprocating the contact roller 3 so that the entire surface of the substrate 1 can be polished, and at the same time, stripes formed by polishing the substrate 1 with the polishing tape 2. Crossing angle (cross angle) is 1
It is configured to have an angle of about 0 to 40 °.

The slurry grinding conditions for the above-mentioned texture processing are as follows: the abrasive slurry concentration in which diamond abrasive grains are suspended is 0.05 to 1.0% by weight; the supply amount of the polishing slurry is 5 to 30 ml / min; Rotation speed is usually 50-5
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 diamond abrasive grains is supplied between a polishing tape and a substrate, and this slurry is applied to the tape immediately before grinding. It may be used after being coated on a tape.

In the present invention, by performing the above-described 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 It is desirable to form a surface shape of a streak pattern having an intersection 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 a textured polishing tape,
For example, a porous tape such as a nonwoven fabric tape made of a material such as nylon, acrylic, cellulose, polyester, rayon, or a combination thereof is used.

As the diamond abrasive used together with the polishing tape, an abrasive having an abrasive particle diameter of 0.05 to 10 μm, preferably 0.1 to 5 μm is suitably used. Such diamond abrasive grains are used as a polishing slurry (hereinafter referred to as “diaslurry”) suspended in a liquid (water or a water-based liquid) together with a dispersant.

In the present invention, the texturing may be performed in two stages. By performing the second-stage texturing, the floating characteristics and the like can be further improved. There is no particular limitation on the processing method of this second stage texture processing, and a fixed abrasive grain type polishing tape of WA (white alumina) type, GC (green carbon) type or the like or WA
The polishing can be performed using a polishing tape or the like using free abrasive grains such as SiC, SiC and diamond.

As shown in FIG. 2, the cleaning of the abrasive grains after the texturing is performed in a first step using a porous tape 2A to which a slurry of alumina abrasive grains is adhered and a second step using a cleaning tape 10. You.

As the porous tape 2A used for the abrasive cleaning, for example, a porous tape such as a nonwoven fabric tape made of nylon, acryl, cellulose, polyester, rayon, or a combination thereof is used.

The alumina abrasive grains used together with the porous tape may have an abrasive grain diameter of 0.1 to 6 μm, preferably 0.1 to 6 μm.
A WA abrasive of 5 to 2 μm is preferably used. Such alumina abrasive grains are liquid (water or water-based liquid)
It is used as a slurry (hereinafter, referred to as “WA slurry”) suspended therein together with a dispersant.

This abrasive grain cleaning removes the polishing powder remaining in the texturing process, and does not substantially change the average roughness Ra or the cross angle of the surface shape formed in the texturing process. It is preferable that protrusions such as burrs and burrs are selectively removed by polishing so that the maximum protrusion height Rp of the surface is desirably about 50 to 250 °.

As the cleaning tape, acrylic,
It is preferable to use a nonwoven fabric tape, a woven fabric tape, or a flocking tape made of cellulose, rayon, polyester, nylon, or a combination thereof. The cleaning liquid supplied to the cleaning tape includes polyethylene oxide, phenolamine-based nonionic surfactant, triethanolamine, sodium tripolyphosphate and methylbenzenesulfonate anionic surfactant, alkylphenol ethylene oxide, nonionic surfactant. Activator, sodium pyrophosphate, P-based builder, silicate, E
DTA or the like can be used.

As an apparatus for cleaning the abrasive grains, an apparatus similar to that used for texture processing is usually used. In the first step and the second step, the porous tape 2A and the cleaning tape 10 Abrasive cleaning is performed by reciprocating (vibrating) in the direction of arrow C by reciprocating motion.

The abrasive cleaning conditions are not particularly limited, and usually the following conditions are employed.

First step : The number of rotations of the substrate: 50 to 300 rpm The concentration of abrasive grains in the WA slurry: 0.1 to 10% by weight The supply amount of the WA slurry: 5 to 30 ml / min The number of reciprocations of the porous tape (oscillation frequency) ): 5
0 to 400 times / minute Cylinder pressing pressure of porous tape: 1.0 to 3.0 kg
/ Cm ² Porous tape feeding speed: 0.5 to 10.0 mm / sec Processing time: 2 to 10 seconds Second step substrate rotation speed: 50 to 300 rpm Reciprocating number of cleaning tape (oscillation frequency): 30 -300 times / min. Pressure of the cleaning tape on the cylinder: 0.5-2.
Feeding speed of 0 kg / cm ² cleaning tape: 0.5 to 10.0 mm
/ Sec. Cleaning solution supply amount: 200 to 1000 ml / min. Processing time: 2 to 10 seconds After such abrasive cleaning, cleaning and drying are performed according to a conventional method to form an underlayer, a magnetic layer, and a protective layer. Manufacture magnetic disks.

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.

Examples 1 and 2 After a Ni—P alloy plating layer was formed on the surface of an aluminum alloy substrate, the polished magnetic disk substrate (diameter: 95 mm) was subjected to texture processing and abrasive grain cleaning in accordance with the present invention. went. The processing conditions for texture processing and abrasive cleaning are as follows.

The textured substrate rotational speed: 1200 times / min Diameter Slurry: 0.3 wt% of diamond abrasive grains having an average particle size shown in Table 1 water slurry die slurry supply amount: 1.2 ml / min Polishing Tape Material: Nylon Nonwoven fabric tape composed of fiber and polyester fiber 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 Abrasive grain cleaning [ First step] Substrate rotation speed: 300 times / minute WA slurry: 3% by weight of WA-based abrasive grains having an average particle diameter of 1 μm
Water slurry WA slurry supply amount: 10 ml / min Porous tape material: Cellulose Porous tape feed speed: 5.0 mm / sec Oscillation frequency of porous tape: 70 times / min Cylinder pressing pressure: 1.5 kg / cm ² Processing time: 5 seconds [Second step] Substrate rotation speed: 300 times / minute Cleaning tape material: Cellulose Cleaning tape feed speed: 5.0 mm / second Cleaning tape oscillation frequency: 70 times / minute
Min Cylinder pressing pressure: 1.0 kg / cm ² Cleaning liquid: methylbenzenesulfonate surfactant Cleaning liquid supply: 500 ml / min Processing time: 4 seconds The above texture processing forms a streak pattern with a cross angle of 5 ° The substrate has a surface roughness (Ra) of 15 ° and a maximum projection height of Rp180 °. The abrasive cleaning removes the diamond abrasive remaining in the texturing process and substantially reduces the Ra and the cross angle. Rp 150 ° without any change.

A glide test was performed on the substrate after the texture processing and the abrasive grain cleaning, and the foreign substance adhesion rate (the adhesion rate of the diaslurry and the grinding pieces) was determined. The results are shown in Table 1.

Comparative Examples 1 and 2 In Examples 1 and 2, texturing was carried out in the same manner as in Examples 1 and 2 except that the abrasive grains were not washed, and a foreign matter adhesion rate was similarly examined by glide inspection. The results are shown in Table 1. .

[0045]

[Table 1]

As is evident from the above results, by performing abrasive grain cleaning using alumina abrasive grains after texturing with diamond abrasive grains, polishing powder such as diamond abrasive grains remaining on the substrate due to texture processing is removed. It can be effectively removed, thereby greatly improving the yield.

[0047]

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]

FIGS. 1A and 1B are diagrams illustrating an embodiment of texture processing according to the present invention, wherein FIG. 1A is a plan view and FIG. 1B is a side view.

FIG. 2 is a plan view illustrating an embodiment of abrasive grain cleaning according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Polishing tape 2A Porous 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, comprising: performing texturing using diamond abrasive grains; and then performing abrasive cleaning using alumina abrasive grains. Processing method.