JPH10328986A - Disk substrate intermediate, manufacture thereof, and grinding work device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the grinding amount in a next process by adjusting the flatness in each plane to be less than a specific value, and the difference of elevation of an uneven part formed by the grinding work to be less than a specific value. SOLUTION: A cup grinding wheel for machining 2 and a work surface plate 6 are relatively slid while controlling an interval between the cut grinding wheel for machining 2 and the work surface plate 6, and the speeds of rotation thereof, in such manner that a grinding face 20 as a contact part of the cut grinding wheel for machining 2, in relation to a disc substrate material 30 on the work surface plate 6, draws a constant locus of a radial curved line from a center toward an outer peripheral part, on a center of rotation P of the work surface plate 6. Whereby the irregular warp of the obtained disk substrate intermediate can be prevented. The flatness of the disc substrate intermediate is not more than 10 μm. Further the difference of elevation of the uneven part therof is less than 5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk substrate intermediate having high accuracy in flatness and surface roughness and free from defects such as pits, and particularly to a crystallized glass substrate or glass used for a hard disk. The present invention relates to a disk substrate intermediate for easily and inexpensively manufacturing an inorganic material substrate such as a substrate or a ceramic substrate, a method of manufacturing the same, and a grinding apparatus.

[0002]

2. Description of the Related Art At present, a disk substrate used for a hard disk includes an aluminum substrate obtained by plating an aluminum substrate with Ni-P (nickel-phosphorus) and a glass made of crystallized glass or glass (including tempered glass). Aluminum substrates are used as large hard disk substrates with a diameter of 5.25 inches or 3.5 inches, while glass substrates are used as small hard disk substrates with a diameter of 2.5 inches or less. It is used.

[0003] With respect to performance required for a hard disk substrate such as impact resistance (hardness) and rigidity (Young's modulus), a glass substrate is superior to an aluminum substrate, and although a good surface roughness can be obtained. However, the manufacturing cost is high due to the long processing time in the manufacturing process, and the manufacturing cost tends to increase as the size of the glass substrate increases. It is only used as a substrate for small hard disks that are listed on the market.

[0004] The surface characteristics of a glass substrate used for a hard disk are required to be high in flatness and surface roughness, and to be free from surface defects such as pits. In order to produce a glass substrate, a glass substrate material is polished, and the obtained glass substrate intermediate generally has insufficient flatness and surface roughness for required characteristics. A step of polishing the intermediate is employed.

In the polishing process, which is the final finishing step of manufacturing the glass substrate, a glass substrate intermediate is sandwiched between upper and lower surface plates, and a polishing surface (contact surface with the glass substrate intermediate) of the surface plate is made of polyurethane or glass. Polishing the glass substrate surface by applying a polishing cloth made of suede or the like and using fine cerium oxide (CeO ₂ ) abrasive grains as free abrasive grains while rotating the upper and lower platens in opposite directions while supplying a working liquid. Is what you do.

In other words, the polishing step is a step of obtaining fine and smooth surface roughness by correcting minute irregularities generated in the polishing step in the preceding step. Therefore, in the polishing processing, the flatness obtained by the polishing processing is obtained. Therefore, it is practically impossible (in terms of production efficiency) to correct the flatness in the polishing process. Therefore, in order to produce a glass substrate having a high flatness, it is necessary to have a high flatness in a polishing step.

[0007] Further, the better the surface condition of the glass substrate intermediate body after polishing, the less the load on the polishing process. That is, the time required for the polishing process is shortened, the production efficiency is improved, the consumption of the abrasive grains can be reduced, and as a result, the manufacturing cost of the glass substrate can be reduced. In other words, in the production of glass substrates, how to produce a glass substrate intermediate having good flatness and few surface defects, in other words, polishing of a glass substrate material having good flatness and less occurrence of surface defects It is important to develop a processing method.

At present, a method of manufacturing a disk substrate intermediate made of an inorganic material such as the glass substrate intermediate, that is, a method of polishing a disk substrate material, involves minute destruction of the material constituting the disk substrate. There is a region to be used and a region to use microplastic deformation. The former is used when it is desired to increase the use of processing removal, and lapping by free abrasive grains is a typical example. On the other hand, the latter is used when processing with high surface accuracy is desired, and a typical method is grinding using a fixed grindstone.

The lapping process is a general method of polishing a disk substrate material, and is often divided into a primary lapping (rough lapping) process and a subsequent secondary lapping (fine lapping) process. In either case, set the carrier (usually a holding plate made of resin for the disk substrate material) with the disk substrate material inserted between the upper and lower lap plates made of iron, and press the disk substrate material from both planes. The upper and lower lap plates are rotated in opposite directions to each other while supplying free abrasive grains such as GC (SiC) and a working liquid therebetween, thereby removing chips and debris from the surface of the disk substrate material. Is a method of simultaneously lapping both surfaces, and is characterized by high flatness, high processing accuracy and high processing efficiency.

In the lapping process, a minute brittle fracture occurs on the surface of the disk substrate material due to the collision (sliding) of the disk substrate material and the abrasive grains, and the destruction polishes the disk substrate material surface. Processing strain is generated on the surface of the disk substrate intermediate body obtained by the brittle fracture.

Here, if a different amount of processing strain remains on the surface of the disk substrate intermediate, the disk substrate intermediate may be warped and a good flatness may not be obtained. By simultaneously processing the front and back surfaces of the material, the processing distortion generated in the disk substrate intermediate body can be made uniform and substantially the same on both the front and back surfaces.
Thus, a disk substrate having high flatness with almost no warpage can be obtained by lapping. Therefore, lapping is widely used as a method for manufacturing a disk substrate intermediate for a hard disk.

However, in lapping, uneven wear may occur on the lap surface due to long-term use, and unless the lap surface of the lap surface plate is carefully managed, plastic deformation may occur on the disk substrate intermediate. As a result, the above-mentioned good flatness may not be obtained. Further, the lapping process has a drawback that pits called "grain" due to brittle fracture processing cannot be avoided.

The pits are minute depressions which are considered to be generated by relatively large abrasive grains (secondary particles) rolling on the surface of the disk substrate material during the lapping process, and the depth of the pit generally reaches 20 to 30 μm. . For this reason, it is necessary to remove these pits in the subsequent polishing process, and a polishing time of 40 to 60 minutes is usually required for polishing both surfaces of the disk substrate intermediate. This processing time is about 8 to 10 times longer than the polishing processing time in the manufacturing process of the aluminum substrate, and the long processing time is one of the major causes for raising the cost of the disk substrate. I have.

As a method of suppressing uneven wear of the lap surface plate in such lapping, a diamond pellet surface plate has been developed, but the problem of pit generation has not been solved. Therefore, in the subsequent polishing process, it is necessary to polish the surface of the disk substrate intermediate body at least about 30 to 40 μm on both surfaces in order to remove pits. It will be equivalent.

On the other hand, grinding processing is
This is a processing method in which a so-called fixed grindstone, in which abrasive grains such as diamond, CBN, and GC are fixed with metal, resin (resin), glass, or the like, is rotated at high speed to grind the disk substrate material surface. According to this grinding process, almost no pits are generated, and even if they are generated, the depth is extremely small. Therefore, the time required for removing unevenness defects remaining on the plane of the disk substrate intermediate body in the polishing process is large. Is shortened to

However, in such grinding processing, if the processing is performed continuously, the tip of the abrasive grain is crushed and grinding cannot be performed. Therefore, it is necessary to perform dressing (sharpening) periodically. is there. further,
Since the front and back surfaces of the disk substrate material must be processed one by one, the amount or distribution of the processing strain generated on the front and back surfaces of the disk substrate material cannot be made uniform. There is a drawback that flatness is reduced due to regular warpage and twisting.

As described above, since such a warp or a twist cannot be removed or corrected in the polishing step, such a grinding method is used.
Heretofore, it has not been adopted as a method for producing a disk substrate intermediate for a hard disk.

[0018]

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the conventional technology,
The inventor incorporates brittle fracture processing and plastic deformation processing in the step of processing one ground surface of the disc substrate material, performs brittle fracture processing in the first grinding step, and then performs the second grinding step and spark-out (flattening). The present inventors have attempted to solve the above problems by examining means for performing plastic deformation processing in processing, and have reached the present invention.

The object of the present invention is to
In order to provide a disk substrate intermediate having a small flatness with a small load in the polishing process and a reduced level difference of the surface irregularities, the grinding resistance and the locus of fixed abrasive grains on the surface of the disk substrate material are kept constant. As a result, it is possible to prevent the occurrence of fine pits and irregular warpage of the material to be ground that occur during grinding, maintain the flatness of the disk substrate material, improve processing accuracy, improve processing efficiency, and reduce costs. An object of the present invention is to provide a method for producing a disk substrate intermediate and a grinding apparatus which can contribute.

[0020]

That is, according to the present invention, both surfaces are ground by a grindstone, the flatness of each plane is 10 μm or less, and the height difference of the uneven portion caused by the grinding is provided. Is not more than 5 μm. Also,
It is preferable that the trajectory of the grinding formed on each plane of the disk substrate intermediate be a radial curve from the center toward the outer periphery.

Further, according to the present invention, the two planes of the disk substrate material as the workpiece are ground one by one in order, and the processing strain remaining on each ground surface is made to be substantially equal, whereby the grinding is performed. A method of manufacturing a disk substrate intermediate, wherein the flatness of the processed disk substrate intermediate is maintained at 10 μm or less.

Here, in the method for manufacturing a disk substrate intermediate of the present invention, each plane of the disk substrate material is
When grinding with a rotating grindstone, in the first grinding stage, which accounts for the majority of the predetermined grinding amount, it is preferable to set the processing conditions such that the abrasive grains forming the grindstone are crushed or fall off from the grindstone. . Further, in the first grinding step of fixing the disc substrate material on the work table and rotating the work table and the grindstone together to grind each plane of the disc substrate material, the number of rotations of the worktable is set to the rotation of the grindstone. 60-80% of the number or 20-4
It is preferable to set the range to 0%.

Further, in the grinding in the second grinding step performed after the grinding in the first grinding step, it is preferable that the processing conditions are such that the abrasive grains forming the whetstone are not substantially crushed and do not fall off substantially. preferable. When the flatness of each plane of the disk substrate material is 10 μm or less, the manufacturing method of the present invention becomes more effective, and the disk substrate material is an inorganic material substrate due to a processing mechanism, and particularly, a glass substrate or a crystal substrate. It is preferably a glass substrate.

In the present invention, a disk substrate material as a workpiece is placed and fixed on a work surface plate,
A disk substrate material grinding apparatus that relatively slides a processing cup whetstone formed by solidifying abrasive grains and the work surface plate to grind each plane of the disk substrate material, The center of rotation of the work surface plate is arranged on the circumference of the processing cup grindstone, and the trajectory of the contact portion of the disk substrate material on the work surface plate with the processing cup grindstone is constant. An object of the present invention is to provide an apparatus for grinding a disk substrate material, comprising a sliding drive control mechanism for relatively sliding a cup grindstone and the work surface plate.

The disk substrate material processed by the present disk substrate material grinding apparatus is preferably glass or crystallized glass, and the abrasive used for the grindstone may be any one of diamond, CBN, and vitriafide. preferable.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION In the disk substrate intermediate according to the present invention, the flatness is good and the height difference between the uneven portions on the surface is small, so that the load in the polishing step is small, and therefore the manufacturing cost of the disk substrate is reduced. It is possible to do. Further, according to the method for producing a disk substrate intermediate of the present invention, pits and irregular warpage do not occur in the disk substrate material during grinding, and the flatness of the material to be ground can be maintained well, and the disk substrate intermediate It can contribute to the improvement of the processing accuracy and processing efficiency of the body and the reduction of the cost. Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

First, in the method for producing a disk substrate intermediate of the present invention, the abrasive grains are solidified to form a processing cup whetstone, and the rotation center of the work surface plate is on the circumference of the processing cup whetstone. The work cup grindstone and the work surface plate are relatively slid so that the locus of the contact portion of the work cup grindstone with the disk substrate material on the work surface plate is constant, and brittle fracture grinding is performed. The processing and the plastic deformation grinding are sequentially and sequentially performed, and the magnitude of the processing strain formed on the front surface and the rear surface of the disk substrate intermediate body is made substantially equal.

FIG. 1 is a schematic cross-sectional view showing an example of a disk substrate material grinding apparatus suitably used for producing the disk substrate intermediate of the present invention, and FIG. 2 is a schematic front view of FIG. FIG. FIG. 3 is a schematic front view showing another example of the disk substrate material grinding apparatus of the present invention. As shown in FIGS. 1 to 3, in the apparatus for grinding a disk substrate material 30 of the present invention, the center of rotation P of the disk-shaped work surface plate 6 is on the circumference of the disk-shaped processing cup grindstone 2. Are located in

The number of the work bases 6 is not particularly limited. However, in consideration of the necessity of interlocking the work bases 6 and the size of the disk substrate material 30 which is the material to be ground, a plurality of work bases 6 are required. It is preferable to select the number. Further, the disk substrate material 30 is placed on the work surface plate 6 by wax bonding or a method such as vacuum chuck so that the rotation center P of the work surface plate 6 and the center Q of the disk substrate material 30 coincide. .

The work cup grindstone 2 is driven to rotate by a rotating shaft 4 to which a motor (not shown) is connected.
By rotating the respective rotating shafts 8 in conjunction with each other (V belt), the grinding surface 20 (contact arc dd), which is the contact portion of the processing cup grindstone 2 with the disk substrate material 30 on the work surface plate 6. '), The processing cup grindstone 2 and the work surface plate 6 are drawn such that a locus 40 of a radial curve from the center to the outer periphery as shown in FIG. , And the rotational speeds of the processing cup grindstone 2 and the work surface plate 6 are controlled by a sliding drive control mechanism (not shown), and relatively slid.

As a result, the grinding resistance and the locus of the grinding surface of the processing cup grindstone with respect to the disk substrate material 30 on the work surface plate are kept constant as compared with the conventional rotary rotary surface grinding method using the cup grindstone. Therefore, even if the disk substrate material is ground one by one, the grinding mechanism mainly causes brittle fracture, thereby reducing the processing strain generated on each surface of the disk substrate material 30 as in the lapping process described above. It can be made substantially uniform. As a result, irregular warpage of the obtained disk substrate intermediate can be prevented, and good flatness can be maintained.

Here, in order to mainly carry out such brittle fracture, it is necessary to set processing conditions such that abrasive grains forming a grindstone used for grinding are crushed or dropped. For this purpose, in the present invention, the rotatable work surface plate 6 having the disk substrate material 30 fixed on the upper surface is used.
And the processing cup grindstone 2 to which the abrasive grains are fixed are rotated together to perform the grinding. At this time, the rotation speed of the work surface plate 6 is set to 20 to 40% of the rotation speed of the processing cup grindstone 2 or 60%. It is preferable to set the range to 80%. This makes it possible to provide a grinding mechanism mainly for brittle fracture.

As a condition for performing the brittle fracture, it is necessary to consider a speed at which the processing cup grindstone 2 is fed in the direction of the disk substrate material 30. Within the range of numbers, conditions can be easily set.

In the above-described grinding method, since the number of ground surfaces per unit time is small, the grinding resistance can be reduced, the generation of grinding heat can be suppressed, and the disk substrate material 30 can be ground at high speed. it can. However, with such a grinding method mainly based on brittle fracture, an extremely high flatness can be obtained. However, with only brittle fracture processing, the height difference of the uneven portion of the ground surface may reach up to about 8 μm. As a method of improving the difference in height of the portion, it is preferable to add a process by plastic deformation subsequent to the brittle fracture process.

Here, if plastic deformation occurs in the grinding process, the processing strain may increase significantly. Therefore, in order to suppress the generation of the processing strain, the grinding amount due to the plastic deformation is suppressed to at most 5 μm. Is preferred. Therefore, as a method for preventing the flatness of the disk substrate material 30 from being reduced by the plastic deformation processing, the grinding locus remaining on the ground surface of the obtained disk substrate intermediate body is moved from the center as shown in FIG. It is preferable that a radial curve spread toward.

In the grinding step, plastic deformation can be mainly performed by reducing the feed speed of the processing cup grindstone 2, and the above-described brittle fracture processing and plastic deformation processing are performed. By the combination, the flatness is high and the height difference of the uneven portion can be suppressed to 5 μm or less. That is, according to the grinding apparatus for the disk substrate material 30 of the present invention, the brittle fracture grinding is first performed reliably, whereby the clogging of the grindstone of the processing cup grindstone 2 is suppressed, and the subsequent plastic deformation grinding is performed. Can be performed efficiently.

Now, as the sliding drive control mechanism (not shown) in the grinding apparatus of the present invention, the distance between the processing cup grindstone and the work surface plate, the number of rotations of the processing cup grindstone and the work surface plate, and the like are described. It is preferable to perform closed loop control in which measurement is performed and the result is fed back to a sliding drive unit (not shown).

On the other hand, the strain remaining on the disk substrate intermediate due to the state of the chuck on the work surface plate and the grinding heat greatly affects the processing accuracy. In order to obtain a disk substrate intermediate, it is necessary to pay close attention to the management of the installation state of the disk substrate material and the method of removing the grinding heat.

For this reason, the grinding process is usually performed by a wet method, and equipment such as a nozzle for supplying a grinding liquid to the grinding portion and a circulation pipe is provided. In addition, the grinding fluid varies depending on the type of abrasive grains forming the processing cup whetstone,
For example, in the case of a diamond grindstone or a vitrified grindstone, a water-soluble grinding fluid having good cooling properties is preferable, and a CBN grindstone is preferably a water-insoluble grinding fluid.

Here, the processing cup grindstone used in the present invention preferably has high rigidity in order to highly accurately grind a disk substrate material having a normal grinding resistance much larger than a tangential grinding resistance. For this reason, it is preferable that the abrasive grains forming the processing cup grindstone are any of diamond, CBN, and vitrified, and it is more preferable to use both vitrified and diamond. In addition,
It is preferable that the processing cup grindstone used in the present invention is porous, pellets, or segments in order to eliminate chips and facilitate supply of the grinding fluid to the grinding point.

In this way, in the disk substrate intermediate having the grinding locus of the radial curve 40 on the surface produced by using the grinding apparatus of the present invention, the generation of pits on the grinding surface is prevented, and the height difference of the uneven portion is reduced. Since the depth is as small as 5 μm or less, the polishing amount in the polishing process in the next step can be suppressed to about 10 μm on both surfaces.

Accordingly, since the polishing amount in the polishing process can be reduced, the polishing process can be performed at low cost without causing roll-off or scratch while maintaining the flatness of the disk substrate intermediate. It can be carried out. Thus, for example, a disk substrate intermediate made of ground glass or crystallized glass is suitably used as a precursor of a disk substrate having a diameter of 3 inches or more for a hard disk.

[0043]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that these Examples do not limit the present invention.

As a disk substrate material to be ground, a donut-shaped glass substrate (diameter: 65 mm, wall thickness:
0.83 mm) by using a crystallized glass substrate material crystallized by heat treatment at 750 ° C. for 2 hours (hereinafter referred to as “rotating rotary flat slab”) of the type shown in FIG. (Examples 1 and 2), lapping method using fixed abrasive grains (also known as pellet grinding) (Comparative Example 1), lapping method using free abrasive grains (also known as G)
Polishing was performed under the polishing processing conditions shown in Table 1 using (C wrap) (Comparative Example 2).

[0045]

[Table 1]

Next, the glass substrate intermediate obtained after polishing by each method was subjected to polishing (mirror polishing) using cerium oxide abrasive grains. Table 2 shows the polishing amount required to completely remove the surface defects of the glass substrate intermediate at this time.

[0047]

[Table 2]

Table 1 also shows the flatness of the glass substrate intermediate obtained before and after the polishing and the state of the polished surface (whether or not pits and warpage occurred). From the results in Table 1, the polishing method using a conventional diamond pellet surface plate (Comparative Example 1)
In the lapping method using free abrasive grains (Comparative Example 2), although warpage can be prevented, pits cannot be prevented. On the other hand, when the rotary rotary flat grinding method (Examples 1 and 2), which is the method for manufacturing a disk substrate of the present invention, is used, it is apparent that pits and warpage generated during grinding can be simultaneously prevented. Was.

Further, from Table 2, in all of Examples 1 and 2 and Comparative Examples 1 and 2, the flatness after polishing was suppressed to 4 μm or less. For example, the quality required of a disk substrate for a hard disk is that the flatness (warpage) is 5 μm or less. Therefore, it is considered that these polishing methods yield good results in terms of flatness. I can say.

Therefore, from the viewpoint of increasing the size of the disk substrate and reducing the cost, a disk substrate intermediate in which the amount of polishing is reduced as much as possible is desired. However, from Table 2, in Examples 1 and 2, pits are not generated. Therefore, while the polishing amount required for the polishing process is suppressed to 8 to 15 μm, in Comparative Examples 1 and 2, a polishing amount of 30 to 50 μm is required in order to delete the generated pits. I understood. Therefore, it can be said that the rotary rotary flat grinding according to the present invention has the least load on the polishing process and is an excellent grinding method.

Next, in the disk substrate manufacturing method of the present invention of the type shown in FIG. 2, the ratio of the number of rotations of the processing cup whetstone and the work surface plate is changed to be different from that used in the above-described first embodiment and the like. The same crystallized glass substrate material was ground. Table 3 shows the results.

[0052]

[Table 3]

As shown in Table 3, the brittle fracture process and the plasticity were performed under the condition that the work table rotation speed ratio (= work table rotation speed / processing cup grinding wheel rotation speed × 100) was 20 to 40% or 60 to 80%. Deformation processing can be performed continuously and repeatedly, and it has been clarified that the conditions are excellent in processing accuracy.

[0054]

As described above, according to the disk substrate intermediate of the present invention, the amount of polishing in the next step is small, and therefore the time required for the polishing process can be greatly reduced. It has an excellent effect on cost reduction. Further, a large substrate of 2.5 inches or more, which has not been conventionally provided, can be provided at low cost. Further, according to the disk substrate intermediate manufacturing method and the grinding apparatus of the present invention, the grinding resistance and the fixed abrasive trajectory with respect to the surface of the disk substrate material to be ground are kept constant, thereby enabling Since the occurrence of pits and the occurrence of irregular warpage are prevented, a disk substrate intermediate having good flatness is obtained, and the processing accuracy and processing efficiency are improved and the processing cost is reduced. It works. In addition, this reduces the amount of polishing in the polishing step of the disk substrate intermediate, thereby reducing the load on the polishing step and reducing costs, and consequently reducing the cost of the disk substrate. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a disk substrate grinding apparatus according to the present invention.

FIG. 2 is a schematic front view showing an example of a disk substrate grinding apparatus according to the present invention.

FIG. 3 is a schematic front view showing another example of the disk substrate grinding apparatus of the present invention.

FIG. 4 shows a positional relationship between a processing cup grindstone and a work surface plate (disk substrate) according to the disk substrate manufacturing method of the present invention, wherein (a) is a schematic explanatory view and (b)
FIG. 4 is an image diagram showing a trajectory of a grinding surface of a processing cup grindstone on a disk substrate.

[Description of Signs] 2 ... Cup grinding wheel for processing, 4 ... Rotary axis (for grinding wheel for processing), 6 ... Work surface plate, 8 ... Rotary shaft (for work surface plate),
Reference numeral 10: Belt pulley (V belt), 12: Motor (for work surface plate), 20: Grinding surface of processing cup grindstone, 30:
Disc substrate material, 40: grinding locus of radial curve.

Claims (12)

[Claims] 1. A disk substrate characterized in that both surfaces are ground by a grindstone, the flatness in each plane is 10 μm or less, and the height difference of the uneven portion caused by the grinding is 5 μm or less. Intermediate. 2. The disk substrate according to claim 1, wherein the trajectory of the grinding formed on each plane of the disk substrate intermediate is a radial curve extending from the center of each plane to the outer peripheral direction. Intermediate. 3. Grinding both planes of a disk substrate material as a workpiece in order, one by one, so that the processing strain remaining on each ground surface is substantially equal, whereby the disk substrate intermediate after the grinding is processed. A method for producing a disk substrate intermediate, wherein the flatness of the body is maintained at 10 μm or less. 4. When grinding each plane of the disk substrate material with a rotating grindstone, abrasive grains forming the grindstone are crushed in a first grinding stage occupying most of a predetermined grinding amount. 4. The method for producing a disk substrate intermediate according to claim 3, wherein the processing conditions are set such that the processing conditions drop off from the whetstone. 5. In the first grinding step of fixing the disk substrate material on a work table and rotating the work table and the grindstone together to grind each plane of the disk substrate material, the work table The rotation speed of 60 to 80% of the rotation speed of the whetstone or 20 to 4
The method for producing a disk substrate intermediate according to claim 3 or 4, wherein the range is 0%. 6. In a grinding process in a second grinding stage performed after the grinding process in the first grinding stage, the processing conditions are such that abrasive grains forming a whetstone are not substantially crushed and do not fall off substantially. The method for producing a disk substrate intermediate according to any one of claims 3 to 5, characterized in that: 7. The method for producing a disk substrate intermediate according to claim 3, wherein the flatness of each plane of the disk substrate material is 10 μm or less. 8. The method according to claim 3, wherein the disk substrate material is an inorganic substrate. 9. The method for producing a disk substrate intermediate according to claim 8, wherein said inorganic material substrate is a glass substrate or a crystallized glass substrate. 10. A disk substrate material, which is a workpiece, is placed and fixed on a work surface plate, and a work cup whetstone formed by solidifying abrasive grains and the work surface plate relatively slide. And a grinding machine for a disk substrate material for grinding each plane of the disk substrate material, wherein a rotation center of the work surface plate is arranged on a circumference of the processing cup grindstone, Having a sliding drive control mechanism for relatively sliding the cup grindstone and the work surface plate such that the trajectory of the contact portion of the disc substrate material with the processing cup grindstone is constant. Grinding equipment for disk substrate material. 11. The apparatus for grinding a disk substrate material according to claim 10, wherein said disk substrate material is glass or crystallized glass. 12. The method according to claim 1, wherein the abrasive grains are diamond, CBN,
12. The disk substrate material grinding apparatus according to claim 10, wherein the disk substrate material is any of vitrifide.