JPH11339260A - Manufacture of information recording medium substrate and the information recording medium substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flat surface which has no protrusion on the surface caused by the residual of abrasives by conducting a finish grinding for a circular shaped substrate employing an artificial leather suede pad, while water is being supplied. SOLUTION: In the production of an information record medium substrate, a finish grinding of the substrate is conducted by an artificial leather suede pad, while water is being supplied. Thus, an information record medium substrate, in which no protrusion caused by the residual of abrasives exists on the surface and having a smooth surface (or a smooth surface having reduced number of protrusions), is realized and the amount of floating of a head is reduced. The finish grinding of the substrate is effective not only for the information record medium substrate, to which a low temperature type ion-exchange process is conducted, but also for the information record medium substrate, for which the low temperature type ion-exchange process has not been applied. A suitable PH value of the water used for the finish grinding is 4 to 10. Pure water, ion-exchanged water, and tap water can be used as the water. Buffer solution may be used with the water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a substrate for an information recording medium (for example, a magnetic disk, an optical disk, a magneto-optical disk, etc.) and a substrate for an information recording medium.

[0002]

2. Description of the Related Art There are two types of materials for substrates currently in practical use as substrates for magnetic disks, which are examples of substrates for information recording media, such as aluminum and glass. Further, the material of the glass substrate includes amorphous glass and crystallized glass. The manufacturing process of a hard disk (an example of an information recording medium) using an aluminum substrate includes, for example, the following five processes (aluminum rolling plate process, blanking process, substrate process, Ni-P plating process, media process). Is done.

[0003] First, in an aluminum rolled plate process, an aluminum raw material is melted and cast, which is hot rolled to a plate thickness of about 5 mm, and then cold rolled to finish it to a predetermined thickness. The rolled aluminum plate is coiled and transferred to a blanking process. In the blanking process, an aluminum disk made by punching an aluminum rolled plate to a predetermined inner and outer diameter is sandwiched between iron or aluminum spacers, and annealed while applying pressure to eliminate warpage, undulation and distortion of the plate I do. Then, a blank is manufactured by adjusting the dimensions of the inner and outer diameters and adjusting the shape of the inner and outer circumferences.

[0004] In the substrate process, after performing rough grinding and finish grinding on both surfaces of the blank using a sponge grindstone, an annealing process is performed to remove distortion caused by the grinding. Then, cleaning is performed to remove abrasive grains and dirt attached to the blank surface to obtain a substrate. In the Ni-P plating process, as pretreatment, degreasing (removal of oils and fats on the substrate surface with a non-erosive degreasing agent), etching (removal of a non-uniform natural protective film), and zinc substitution treatment (substitution using substitution reaction) Formation of a zinc film on the straight surface).

[0005] Next, the substrate is immersed in a plating solution, and a Ni-P plating layer is deposited on the surface of the substrate by a reduction reaction. Here, deposition is performed until the thickness of the plating layer becomes about 12 μm. Then, the disk on which the Ni-P plating layer is formed is sandwiched between polyurethane polishing cloths, and while the alumina-based abrasive is injected, the surface of the plating layer is 1-2
Finish polishing with a polishing thickness of about μm.

The polishing of the magnetic disk substrate is performed by using, for example, a double-side polishing machine having a schematic configuration shown in FIG. After the finish polishing, the substrate is washed to remove the abrasive remaining on the surface of the plating layer, thereby obtaining a magnetic disk substrate made of aluminum.

Finally, a hard disk is completed by forming a magnetic recording film and the like on the magnetic disk substrate in the media process. On the other hand, a hard disk (an example of an information recording medium) using a glass substrate is manufactured by, for example, the following steps. First, a blank called a blank is rounded to the desired outer diameter, then a hole for the inner diameter is made,
Lapping (roughing, primary lapping) of the blank surface using fine powder of silicon carbide.

After the inner and outer diameters are processed to predetermined dimensions and shapes, the blank surface is wrapped again (secondary lapping). In addition, abrasives and stains attached to the blank are removed by ultrasonic cleaning. Next, the blank surface after the second lapping is polished on both sides with an abrasive (cerium oxide) to a predetermined flatness (3 to 5 μm).
After finishing, cleaning is performed to remove abrasives and the like remaining on the surface.

The polishing is performed using, for example, a double-side polishing machine having a schematic configuration shown in FIG. When the substrate is an amorphous glass containing sodium or the like, cleaning is performed after chemical strengthening by low-temperature ion exchange treatment. Next, a glass magnetic disk substrate (substrate) can be obtained by inspecting for surface defects.

Finally, a hard disk using a glass substrate is completed by forming a magnetic recording film and the like on the magnetic disk substrate (media process).

[0011]

On the surface of the magnetic disk substrate manufactured by the conventional manufacturing method, the abrasive used in the final polishing step remains as projections without being completely removed. In the magnetic disk substrate made of glass, in addition to the presence of the protrusions caused by the remaining abrasive used in the final polishing step, there are also protrusions on the substrate surface generated in the low-temperature ion exchange treatment step.

If the protrusions remain on the substrate surface when the magnetic recording film is formed, there is a problem that a high quality magnetic recording film cannot be obtained. Also, considering that the flying height of the head corresponding to the surface recording density of 10 Gbit / in ² is about 20 nm, the fact that the protrusions remain on the substrate surface significantly impairs the smoothness of the substrate. There is a problem because the possibility of contact between the substrate and the substrate is increased.

The present invention has been made in view of such a problem, and has a smooth surface (or a smooth surface in which the protrusions are reduced) without protrusions due to the remaining abrasive or the like on the surface.
An object of the present invention is to provide an information recording medium substrate and a method for manufacturing the same, which enable a low flying height of a head.

[0014]

Therefore, the present invention firstly provides a method for producing a substrate for an information recording medium by subjecting a disk-shaped substrate to a finish polishing process, wherein the artificial leather suede is supplied while supplying water. A method of manufacturing a substrate for an information recording medium, characterized in that the disk-shaped substrate is finish-polished by a pad (claim 1).

[0015] The present invention also provides a second aspect of the invention which comprises "at least a step of preparing a disk-shaped glass substrate, a step of performing a low-temperature ion exchange treatment on the glass substrate, and an artificial leather suede pad while supplying water. Performing a finish polishing of the substrate surface on which the ion exchange treatment has been performed, and a method of manufacturing a substrate for an information recording medium (claim 2).

[0016] The present invention is also characterized in that the third step is "at least a step of preparing a disk-shaped glass substrate, a step of performing a final polishing of the glass substrate with an artificial leather suede pad while supplying water, and a step of performing the final polishing. Subjecting the glass substrate to a low-temperature ion exchange treatment, the method for producing a substrate for an information recording medium (claim 3) ".

Further, the present invention is directed to a fourth aspect, "at least a step of preparing a disk-shaped glass substrate, a step of performing the first finish polishing of the glass substrate with an artificial leather suede pad while supplying water, and A step of performing low-temperature ion exchange treatment on the glass substrate that has been subjected to finish polishing, and a step of performing second finish polishing of the glass substrate that has been subjected to the ion exchange treatment with an artificial leather suede pad while supplying water. A method for manufacturing an information recording medium substrate (Claim 4) "is provided.

Further, the present invention provides, in a fifth aspect, an information recording medium substrate manufactured by the method according to claims 1 to 4,
The present invention provides an information recording medium substrate having a main surface having a surface roughness of not more than Rmax100 ° and not more than Ra5 ° as measured by an atomic force microscope in a measurement area of 10 μm □ (Claim 5).

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the abrasive used in the final polishing step remains on the surface of a magnetic disk substrate manufactured by a conventional manufacturing method as projections without being completely removed. . Most of the abrasive attached to the substrate surface in the polishing step can be removed by washing the substrate.

However, since the abrasive which cannot be completely removed even by washing the substrate remains on the substrate surface, and the size of the remaining abrasive is minute, it is difficult to find it by visual observation of the substrate. . Therefore, as a result of intensive studies by the present inventors, the present inventors have performed a final polishing of a substrate with an artificial leather suede pad while supplying water, and have not been completely removed even by the above-mentioned cleaning, and have remained on the substrate surface. It has been found that the abrasive can be removed, in other words, the abrasive can be removed by rubbing the information recording medium substrate with a suede pad while supplying water.

Although the cause of the abrasive removal effect is not clear, when water is supplied to the substrate, the formation of a hydrated film on the substrate surface is promoted, and the artificial leather suede pad physically removes this water. It is expected to act on the hydrated film to remove the hydrated film and microscopic foreign matter protruding from the substrate surface in the hydrated film. Thus, according to the finish polishing according to the present invention, while minimizing the physical force acting directly on the substrate as much as possible, the removal of the soft hydrated film generated on the substrate surface and the removal of the protruding minute foreign matter are promoted, The Rmax value indicating the surface roughness of the substrate can be improved without newly damaging the substrate.

Further, in the case of a glass substrate for an information recording medium, in addition to the presence of the projections caused by the remaining abrasive used in the final polishing step, the substrate is generated in the low-temperature ion exchange processing step as described above. There are also protrusions on the substrate surface. In general, the substrate is cleaned even after the low-temperature ion exchange process, but it is extremely difficult to remove all the projections on the substrate surface generated by the low-temperature ion exchange process by cleaning.

As a result of intensive studies conducted by the present inventors,
The inventors of the present invention are able to remove projections remaining on the substrate surface that cannot be completely removed by the above-mentioned cleaning by performing final polishing of a substrate subjected to a low-temperature ion exchange treatment with an artificial leather suede pad while supplying water. Was found. Therefore, in the method of manufacturing a substrate for an information recording medium according to the present invention (claims 1 to 4), finish polishing of the substrate is performed with an artificial leather suede pad while supplying water.

According to the present invention (claims 1 to 5), the head has a smooth surface without large projections due to the remaining abrasive or the like (or a smooth surface in which the projections are reduced). An information recording medium substrate capable of reducing the flying height can be obtained. Finish polishing of the substrate according to the present invention performed by artificial leather suede pad while supplying water, not only the information recording medium substrate after subjected to low-temperature ion exchange treatment,
The present invention is also effective for an information recording medium substrate before performing the ion exchange treatment.

Further, the finish polishing of the substrate according to the present invention is also effective for a substrate for an information recording medium which is not subjected to an ion exchange treatment. Further, the PH value of the water used for the final polishing of the substrate according to the present invention is preferably 4 to 10.
As the water, pure water, ion-exchanged water, tap water and the like can be used, but a buffer solution may be used in combination. Further, an aqueous solution in which an acid, an alkali, and a salt are dissolved may be used.

The final polishing according to the present invention is intended to remove at least protrusions on the substrate surface, and the thickness removed by the final polishing is 100 mm per one side of the substrate.
The above-mentioned object can be achieved with the degree or less.
The measurement of the surface accuracy of the information recording medium substrate obtained by the manufacturing method according to the present invention (claims 1 to 4) can be performed using an atomic force microscope.

That is, if a 10 μm square area on the substrate surface is scanned using an atomic force microscope equipped with a probe having a radius of curvature smaller than several tens of nanometers, minute surface irregularities and projections can be obtained. Can be measured. The radius of curvature of the stylus in the stylus type surface roughness measurement is several hundred nm or more, and is not suitable for measurement of minute surface irregularities, protrusions, etc., and the obtained measurement value includes a considerable error. It is not preferable.

According to the production method according to the present invention (claims 1 to 4), for example, the surface is 10 μm
The surface roughness of the main surface measured in the measurement area of □ is R max100Å
The following provides an information recording medium substrate having a Ra of less than 5 ° (claim 5). Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0029]

Embodiment 1 The substrate for an information recording medium of this embodiment has a main surface having a surface roughness of R max 90 ° and Ra 2.9 ° measured in a measurement area of 10 μm square by an atomic force microscope. It has a smooth surface without large projections due to residuals and the like. Further, the method for manufacturing the information recording medium substrate of the present embodiment is a method of manufacturing a disc-shaped substrate by subjecting the disk-shaped substrate to finish polishing, thereby manufacturing a substrate for the information recording medium. Finish polishing of the disk-shaped substrate is performed by a pad.

The manufacturing steps will be described below. First, an aluminum magnetic disk substrate (disc-shaped) on which a Ni-P plating layer is formed is prepared, and is sandwiched between polyurethane polishing cloths. After a final polishing of about 2 μm, cleaning was performed to remove the abrasive remaining on the surface of the plating layer.

Next, when the main surface of the washed substrate was observed in a measurement area of 10 μm square using an atomic force microscope, the surface roughness was R max 180 ° and Ra 8 °, and the main surface had protrusions. Foreign matter remained. Next, finish polishing was performed to remove protrusions (foreign matter) remaining on the main surface.

That is, a polishing pad made of artificial leather suede is attached and fixed to a cast iron upper surface plate and a lower surface plate of a double-side polishing machine, and the above-mentioned ion pad is placed between upper and lower polishing tools to which the polishing pad is fixed. The substrates subjected to the exchange treatment and the cleaning were brought into close contact with each other, and rotated and slid while supplying pure water to the pad and the substrate polishing surface, whereby both surfaces of the substrate were simultaneously finish-polished.

The suede polishing pad has grooves 5 mm wide at intervals of 10 mm (see FIG. 2). Polishing was performed at a polishing pressure of 30 to 100 g / cm ² , a lower platen rotation speed of 5 to 40 rpm, an upper platen rotation speed of 5 to 40 rpm, and a processing time of 2 to 8 minutes. The main surface of the substrate that has been subjected to finish polishing is surface 10 μm square using an atomic force microscope.
Observed in the measurement area, the surface roughness was R max90Å, R
a was 2.9Å, and the protrusions (foreign matter) remaining on the main surface after the washing were removed.

[0034]

Embodiment 2 The substrate for an information recording medium of the present embodiment has a main surface having a surface roughness R max of 41.6Å and a Ra of 2.3 測定 measured in an area of 10 μm square by an atomic force microscope, and has a polished surface. It has a smooth surface without large projections due to the residual agent. Further, the method of manufacturing the information recording medium substrate of the present embodiment includes a step of preparing a disk-shaped glass substrate, a step of performing a low-temperature ion exchange treatment on the glass substrate, and a step of supplying artificial water while supplying water. Performing a finish polishing of the substrate surface subjected to the ion exchange treatment by a suede pad.

The manufacturing process will be described below. First, a magnetic disk substrate (disc-shaped) made of aluminosilicate glass whose surface is precisely polished with a cerium oxide abrasive is prepared, washed, immersed in a molten salt of potassium nitrate, and subjected to a low-temperature ion exchange treatment. Thus, a compressive stress layer was formed on the substrate surface by ion exchange of sodium ions in the glass with potassium ions.

Next, after the substrate subjected to the ion exchange treatment was washed, the main surface was cleaned to a surface of 10 μm using an atomic force microscope.
Observed in the measurement area of □, the surface roughness was R max128
Ra, Ra3.8Å, and protrusions remained on the main surface. Next, finish polishing was performed to remove protrusions remaining on the main surface. That is, an artificial leather suede polishing pad is attached and fixed to the cast iron upper and lower platens of a double-side polishing machine, and the above-mentioned cleaning is performed between the upper and lower polishing tools to which the polishing pad is fixed. The substrate is brought into close contact and rotated while supplying pure water to the pad and substrate polishing surface.
By sliding, both surfaces of the substrate were simultaneously finished and polished.

The suede polishing pad has grooves 5 mm wide at intervals of 10 mm (see FIG. 2). Polishing was performed at a polishing pressure of 30 to 100 g / cm ² , a lower platen rotation speed of 5 to 40 rpm, an upper platen rotation speed of 5 to 40 rpm, and a processing time of 2 to 8 minutes. The main surface of the substrate that has been subjected to finish polishing is surface 10 μm square using an atomic force microscope.
Observed in the measurement area, the surface roughness was R max41.6
Ra, Ra 2.3Å, and the protrusions remaining on the main surface were removed.

[0038]

Embodiment 3 The substrate for an information recording medium of this embodiment has a main surface having a surface roughness R max of 52.3Å and a Ra of 2.9Å measured in an area of 10 μm □ by an atomic force microscope, and has a polished surface. It has a smooth surface without large projections due to the residual agent. Further, the method of manufacturing the information recording medium substrate of the present embodiment, a step of preparing a disk-shaped glass substrate, a step of finishing polishing the glass substrate with an artificial leather suede pad while supplying water, Performing a low-temperature ion exchange treatment on the glass substrate that has been subjected to the finish polishing.

The manufacturing steps will be described below. First, a magnetic disk substrate (disc-shaped) made of aluminosilicate glass whose surface is precisely polished with a cerium oxide abrasive is prepared and washed, and then the main surface of the substrate is formed with a surface of 10 μm square using an atomic force microscope. When observed in the measurement area, the surface roughness Rma
x 105 x, Ra 2.9Å, and foreign matter as projections remained on the main surface.

Next, protrusions (foreign matter) remaining on the main surface
Finish polishing was performed to remove. That is, an artificial leather suede polishing pad is attached and fixed to the cast iron upper and lower platens of a double-side polishing machine, and the above-mentioned cleaning is performed between the upper and lower polishing tools to which the polishing pad is fixed. The substrates were brought into close contact with each other, and rotated and slid while supplying pure water to the pad and the substrate polishing surface, so that both surfaces of the substrate were simultaneously finished and polished.

The above-mentioned polishing pad made of suede is provided with grooves having a width of 5 mm at intervals of 10 mm (see FIG. 2). Polishing was performed at a polishing pressure of 30 to 100 g / cm ² , a lower platen rotation speed of 5 to 40 rpm, an upper platen rotation speed of 5 to 40 rpm, and a processing time of 2 to 8 minutes. Next, the main surface of the substrate which has been subjected to the finish polishing is surface 10 using an atomic force microscope.
When observed in the μm □ measurement area, the surface roughness was R max30
Ra, Ra 2.3Å, and protrusions (foreign matter) remaining on the main surface were removed.

Here, the surface of the substrate before and after the finish polishing was analyzed by total reflection x-ray fluorescence, and the cerium detected on the substrate surface before the finish polishing was:
It was not detected on the substrate surface after the finish polishing, and it was found that the cerium oxide of the abrasive, which was a projection observed by an atomic force microscope, was removed by the finish polishing.

Next, after the substrate subjected to finish polishing is washed again, it is immersed in a molten salt of potassium nitrate and subjected to a low-temperature ion exchange treatment to exchange sodium ions in the glass with potassium ions. Then, a compressive stress layer was formed on the substrate surface. Next, after washing the substrate subjected to the ion exchange treatment, the main surface was observed in a measurement area of the surface 10 μm □ using an atomic force microscope, and the surface roughness was R max 52.3Å and Ra 2.9Å. there were.

That is, by performing the low-temperature ion exchange treatment, the surface roughness value after the treatment becomes larger than the surface roughness value before the treatment. This indicates that projections on the main surface occur. However, the surface roughness when the low-temperature ion exchange treatment was performed without subjecting the substrate to the finish polishing according to the present example was measured by using an atomic force microscope in a measurement area of the surface of 10 μm square. max128Å, Ra 3.8
Å, indicating that the finish polishing according to the present example was effective in smoothing the substrate.

If further smoothing of the substrate surface is required, the above-mentioned finish polishing may be performed again after the low-temperature ion exchange treatment step. In addition, the use of a polishing machine used for precisely polishing the surface of a magnetic disk substrate made of aluminosilicate glass with a cerium oxide abrasive and a polishing machine used in the finish polishing process can be performed more smoothly. Is preferable for obtaining a good substrate.

However, since it is difficult to switch the polishing machine in consideration of mass productivity, the supply of the polishing liquid mixed with the polishing agent is stopped in the same polishing machine after the step of precision polishing with the cerium oxide polishing agent is completed. However, instead of supplying only water to the polishing machine, the same effect can be obtained even if a method of performing final polishing of the substrate is employed.

[0047]

As described above, the present invention (Claim 1)
According to 5), information recording which has a smooth surface without large projections due to residual abrasive or the like (or a smooth surface with reduced projections) on the surface and enables a low flying height of the head. A medium substrate is obtained. The present invention (claims 1 to 4)
According to the manufacturing method described above, for example, a substrate for an information recording medium in which the surface roughness of the main surface measured by an atomic force microscope in a measurement area of the surface of 10 μm □ is R max100 ° or less and Ra 5 ° or less (claim 5) ) Is obtained.

If the substrate having a smooth surface according to the present invention is used as a substrate for an information recording medium and the recording medium is formed on the substrate, the flying height of the head can be suppressed to a low level, so It can respond to density increase. That is, according to the present invention, the flying height of the head (for example, a magnetic head) can be reduced, and the density of an information recording medium (for example, a magnetic disk) can be increased (particularly, the linear recording density can be increased).

Further, the density of an information recording medium (for example, a magnetic disk) can be increased, and a disk device (a hard disk drive device, for example, a magnetic disk drive device)
It is possible to reduce the number of disks to be mounted on the disk and to reduce the size of the disk diameter, and to reduce the size of the apparatus. In particular, if the performance of the hard disk drive is improved, the size is reduced, and the space is saved, the performance of a personal computer or the like on which the hard disk drive is mounted can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a double-side polishing machine.

FIG. 2 is a top view of the polishing pad according to the present invention.

[Explanation of symbols]

 1. Magnetic disk substrate 2. Polishing liquid 3. Upper surface plate 4. Lower surface plate

Claims (5)

[Claims] Claims: 1. A disc-shaped substrate is subjected to finish polishing,
A method for manufacturing a substrate for an information recording medium, comprising: finishing polishing the disc-shaped substrate with an artificial leather suede pad while supplying water. 2. At least a step of preparing a disk-shaped glass substrate, a step of performing a low-temperature ion exchange treatment on the glass substrate, and the ion exchange treatment by an artificial leather suede pad while supplying water. Performing a finish polishing of the substrate surface. 3. At least a step of preparing a disk-shaped glass substrate, a step of performing finish polishing of the glass substrate with an artificial leather suede pad while supplying water, and a low-temperature mold for the glass substrate having been subjected to the finish polishing. Performing an ion exchange treatment. 4. At least a step of preparing a disk-shaped glass substrate, a step of performing primary finish polishing of the glass substrate with an artificial leather suede pad while supplying water, and a glass substrate having been subjected to the finish polishing Manufacturing a substrate for an information recording medium, comprising: performing a low-temperature ion exchange treatment on the glass substrate; and performing a second finish polishing of the glass substrate subjected to the ion exchange treatment by an artificial leather suede pad while supplying water. Method. 5. A substrate for an information recording medium manufactured by the method according to claim 1, wherein the main surface has a surface roughness R m measured in an area of 10 μm square by an atomic force microscope.
An information recording medium substrate with an ax of 100 mm or less and a Ra of 5 mm or less.