JP2866646B1 - Glass substrate manufacturing method - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To control a flatness and a warpage of a glass substrate with high precision, thereby shortening a processing step, making it possible to reduce the thickness of the glass substrate to the utmost, and reducing raw material costs, processing equipment costs, processing time, and the like. Provided is a method for manufacturing a glass substrate which enables significant savings. SOLUTION: A press forming step of press forming molten glass into a donut shape, and firing is performed by applying pressure evenly to the entire glass substrate with a pressing member from one or both surfaces of the glass substrate obtained by the press forming step. A crystallization treatment step, a chamfering step of simultaneously rotating the glass substrate and the processing grindstone obtained by the crystallization treatment step at a high speed and processing the inner and outer diameters of the glass substrate, and a glass substrate obtained by the chamfering step. A precision grinding step of performing non-dress grinding processing for sequentially and sequentially performing brittle fracture processing and plastic deformation processing on both surfaces, and a polishing step of polishing both surfaces of the glass substrate obtained in the precision grinding step are provided. This is a method for manufacturing a glass substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a glass substrate used as a substrate for a hard disk mainly used as an information recording medium for a computer, and more particularly to a method for manufacturing a glass substrate by improving the molding accuracy of the glass substrate. The present invention relates to a method for manufacturing a glass substrate capable of shortening a process.

[0002]

2. Description of the Related Art In recent years, the spread of computers has rapidly advanced, and the capacity of OS software such as an operation system which affects the operability of the computer and various kinds of program software operating on the OS tend to increase. In addition, the capacity of data created using these programs also tends to increase.

Accordingly, in the development of a hard disk as an information recording medium capable of recording / reading such a large amount of information at a high speed, hardness and smoothness have been changed in place of a conventional substrate using aluminum metal. There is an increasing movement to use glass substrates that are excellent in quality, particularly glass substrates using crystallized glass.

In general, a method for manufacturing a glass substrate is divided into a blanking process and a substrate process, as shown in a flowchart of FIG. Here, in the blanking step, first, a disk-shaped glass substrate is manufactured by pouring a melted glass material prepared to a specific composition into a press mold and press-molding.

[0005] The glass substrate thus obtained is subjected to a crystallization treatment, and thereafter, the inner hole of the glass substrate is cut to form an inner hole, and the presence or absence of a surface defect such as a chip or a crack is inspected. The donut-shaped glass substrate thus produced is called a blank.

Next, in the substrate process,
After lapping (primary lapping) the surface of the blank with an abrasive such as SiC fine powder, the inner and outer diameters are processed into a predetermined size and a predetermined shape (chamfering), and the surface is further wrapped (secondary lapping) for cleaning. The blank thus obtained is polished (polished) using cerium oxide fine powder, finished to a predetermined smoothness, subjected to ultrasonic cleaning and IPA cleaning, and finally inspected for surface defects. The blank that has gone through the above steps is called a substrate. By applying a magnetic recording film to the substrate thus obtained, a glass substrate is manufactured.

However, the above-described method for manufacturing a glass substrate attempts to correct the warpage and twist of the glass substrate caused by press molding and the warpage and twist of the glass substrate caused by shrinkage due to crystallization by thickness processing such as lapping. In this case, the glass substrate needs to have a sufficient thickness (for example, 1.5 mm) so as not to be deformed by a processing load. For this reason, in order to increase the thickness (for example, 0.7 mm) of the glass substrate (substrate) as a product, the machining allowance of the glass substrate is increased, and a long processing time is required for lapping and polishing (polishing). there were. In addition, lapping using free abrasive grains always causes local grain (pits), and therefore, in order to completely remove pits, at least 50 to 60 [mu] m of polishing allowance is required. From the above, raw material costs, processing equipment costs, and processing consumable material costs increase, and it has been difficult to reduce the price of a glass substrate (substrate) as a product.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such problems of the related art,
The purpose is to control the flatness and warpage of the glass substrate with higher precision than before so that the processing steps can be shortened and the thickness of the glass substrate (blank) can be made as thin as possible. Provision of a glass substrate manufacturing method that can significantly reduce raw material costs, processing equipment costs, processing consumable material costs, processing time, etc., and consequently contribute to significantly reducing the price of glass substrate products. Is what you do.

[0009]

That is, according to the present invention, a press forming step of press forming molten glass into a donut shape, and a pressing member from one or both surfaces of the glass substrate obtained by the press forming step. A crystallization process in which the entire glass substrate is evenly pressed and baked, and the glass substrate and the processing grindstone obtained in the crystallization process are simultaneously rotated at a high speed to process the inner and outer diameters of the glass substrate. A chamfering step, a fine grinding step of performing non-dress grinding processing for sequentially performing brittle fracture processing and plastic deformation processing on both surfaces of the glass substrate obtained by the chamfering step, and And a polishing step of polishing both surfaces of the obtained glass substrate.

Further, the method for manufacturing a glass substrate of the present invention preferably has the following mode. In the crystallization process, the pressing member is a weight having a predetermined weight, the glass substrate is horizontally stacked in a firing container having an opening at the upper end, and the pressing member is placed on the glass substrate positioned at the upper end. By mounting and baking the pressing member with the opening closed, the warpage of the glass substrate can be corrected to 10 μm or less. In the chamfering process, the peripheral speeds of the inner diameter processing grindstone and the outer diameter processing grindstone are set to 1200 to 1000, respectively.
0 m / min, and the ratio between the peripheral speed of the inner diameter processing portion of the glass substrate and the peripheral speed of the inner diameter processing grindstone, and the peripheral speed of the outer diameter processing portion of the glass substrate and the outer diameter processing grindstone. Of the peripheral speeds in the range of 1/10 to 1/100. In the fine grinding step, both surfaces of the glass substrate as the workpiece are ground one by one in order, and the processing strain remaining on each ground surface is made approximately equal in amount, so that the flat surface of the glass substrate after the grinding process is performed. Degree can be maintained at 10 μm or less.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A method for producing a glass substrate of the present invention comprises a press forming step of press-forming molten glass into a donut shape, and a pressing member formed on one or both sides of the glass substrate obtained by the press forming step. A crystallization process in which the entire glass substrate is evenly pressed and baked, and the glass substrate and the processing grindstone obtained in the crystallization process are simultaneously rotated at a high speed to process the inner and outer diameters of the glass substrate. A chamfering step, a fine grinding step for non-dress grinding for sequentially performing brittle fracture processing and plastic deformation processing on both surfaces of the glass substrate obtained in the chamfering step, and a fine grinding step obtained in the fine grinding step The polishing apparatus includes a polishing step of polishing both surfaces of the glass substrate.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 8 is a flowchart showing a method for manufacturing a glass substrate of the present invention. In the method for producing a glass substrate of the present invention, first, a donut-shaped glass substrate is produced from molten glass by a press molding step. This eliminates the need to cut the inner hole portion of the glass substrate to open the inner hole, so that surface defects such as chipping and cracking of the glass substrate can be eliminated.

Next, a crystallization process of the glass substrate (blank) obtained by the press molding process is performed. Here, the crystallization process is a process in which the amorphous glass is converted into crystallized glass by reheating the amorphous glass to precipitate fine crystals in the glass. At this time, flatness, a good carbon plate of good parallelism is sandwiched on both sides of the glass substrate, and the pressing member presses the entire glass substrate evenly,
In order to make the upper and lower surfaces of the glass substrate, and the inner diameter portion and the outer diameter portion have a substantially uniform temperature, as the pressing member, in consideration of conduction, convection, and good heat propagation by radiation, which are heat transmission mechanisms,
It is preferable to use a pressing member (fin weight) provided with a large number of fins on the outer periphery. This makes it possible to reliably correct the warpage and torsion of the glass substrate caused by the warpage and shrinkage due to crystallization of the glass substrate generated in the press forming step, so that the warpage of the glass substrate is reduced to 10 μm or less, and further to 5 μm or less. Can be modified. Also,
Since the temperature in the firing container can be quickly raised and lowered, the flatness of the crystallized glass substrate can be improved. Furthermore, since the temperature distribution in the firing container can be made uniform, the variation in the flatness of the crystallized glass substrate can be reduced.

The above-mentioned crystallization process is performed, for example, by the steps shown in FIG.
As shown in FIG. 3, the pressing member is a weight 6 having a predetermined weight, and the glass substrate 2 is horizontally stacked in the firing container 1 having an opening 7 at the upper end, and the weight 6 is positioned at the upper end of the glass. It is placed on a substrate and fired with the weight 6 closing the opening 7. At this time, as shown in FIG. 1, the weight 6 extends from the columnar portion 8 whose end surface area is smaller than the area of the opening portion 7 at appropriate intervals along the axial direction of the columnar portion 8. It is preferable to use a fin weight having a shape obtained by projecting a plurality of collars 9 having the same shape as 7.

Subsequently, a chamfering step of the glass substrate obtained in the crystallization processing step is performed. In the above-described chamfering step, for example, as shown in FIG.
2. An inner diameter grinding wheel 13 and an outer diameter grinding wheel 14 for chamfering the glass substrate 11 are respectively arranged at predetermined positions, and the glass substrate 11, the inner diameter grinding wheel 13 and the outer diameter grinding wheel 14 are simultaneously placed. The inner and outer diameters of the glass substrate 11 are processed by rotating the glass substrate 11 at a high speed.

At this time, the peripheral speeds of the inner diameter processing grindstone and the outer diameter processing grindstone are each within a range of 1200 to 10000 m / min, and the peripheral speed of the inner diameter processing portion of the glass substrate and the peripheral speed of the inner diameter processing grindstone are set. The ratio of the speed, and the ratio of the peripheral speed of the outer diameter processing portion of the glass substrate and the peripheral speed of the outer diameter processing whetstone,
In any case, it is important to set them within the range of 1/10 to 1/100. By setting such processing conditions, the load and thermal shock applied to the grindstones 13 and 14 can be reduced, and uneven wear can be prevented. Further, since the load applied to the glass substrate 11 is also reduced, the depth of the generated chipping (see FIG. 4) can be reduced to about 25 μm or less, which is 1/2 to 1/4 or less of the conventional one, without reducing the processing speed. Therefore, the amount of double-side polishing after chamfering can be reduced, the shape of the formed chamfer is constant, and the time required for polishing and the cost of equipment and consumables can be reduced.

Further, as shown in FIG. 3, the glass substrate 1
1 and the grinding wheel 13 for inner diameter machining are respectively rotated in the same direction,
The grindstone 14 for outer diameter processing is rotated in a direction opposite to that of the glass substrate 11, that is, the chamfering is performed such that the grindstones 13 and 14 have a so-called circling relationship with respect to the rotation direction of the glass substrate 11. Setting the processing conditions
This is preferable for preventing chipping of the glass substrate 11 from occurring.

Next, a fine grinding step of the glass substrate obtained by the chamfering step is performed. In the fine grinding step, for example, as shown in FIGS. 5 and 6, the rotation center P of the disk-shaped work surface plate 26 is
And the glass substrate 40 is positioned between the rotation center P of the work surface plate 26 and the glass substrate 30.
Are mounted so that their centers Q coincide with each other, and the grinding surface 42 (contact arc dd ′) which is a contact portion of the processing cup grindstone 32 with the glass substrate 30 on the work surface plate 26 is The processing cup grindstone 2 is arranged such that a radial locus 44 as shown in FIG.
2 and the work surface plate 26 and the processing cup grindstone 22
By performing relative sliding while controlling the respective rotation speeds of the work surface plate 26, non-dress grinding is performed, in which brittle fracture processing and plastic deformation processing are sequentially and continuously performed on both surfaces of the glass substrate 40. Things.

The reason for performing such a grinding process is to eliminate the disadvantage of the grinding method by brittle fracture processing that can obtain an extremely high flatness, and to increase the height difference of the uneven portion of the ground surface. This is because it has been found that it is effective to appropriately add plastic deformation processing subsequent to brittle fracture processing.

Here, if plastic deformation occurs during the grinding, 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 glass substrate 40 from being lowered by the plastic deformation processing, the grinding locus 44 remaining on the ground surface of the obtained glass substrate 40 is moved from the center as shown in FIG. It is preferred that the curve be a radial curve that widens.

The number of rotations of the work surface plate 26 is set to 20 to 40% of the number of rotations of the
It is preferred to be in the range of 80%. This is because, under the above conditions, the grinding mechanism mainly performs brittle fracture processing, and brittle fracture processing and plastic deformation processing can be performed sequentially and sequentially, and the processing precision is the highest.

From the above, in the fine grinding step, the generation of pits and irregular irregularities in the grinding process are performed by maintaining the grinding resistance and the fixed abrasive trajectory with respect to the surface of the glass substrate as the workpiece to be ground. Since the occurrence of warpage can be suppressed, a glass substrate having a flatness of 10 μm or less can be obtained, and processing accuracy and processing efficiency can be improved, and processing costs can be reduced.

In addition, since the height difference of the uneven portion on the ground surface of the glass substrate obtained by the fine grinding step can be made as small as 5 μm or less, the polishing amount in the next polishing step is suppressed to about 10 μm on both sides. be able to. Thus, the burden on the polishing step is reduced, the processing cost can be reduced, and as a result, the cost of the glass substrate can be reduced.

Finally, the glass substrate obtained in the fine grinding step is subjected to a polishing step of polishing (fine polishing) both surfaces of the glass substrate so as to satisfy the glass substrate characteristics required for a product. A glass substrate (substrate) as a product is manufactured. In the polishing step, although not particularly limited, for example, it is preferable to polish the glass substrate on a pad of SUBA-800 (trade name) using cerium oxide abrasive grains (0.6 μm).

FIG. 8 is a flowchart showing the above-described method for manufacturing a glass substrate of the present invention. The steps up to the completion of a glass substrate (substrate) as a product are as follows.
This is extremely reduced as compared with the conventional method (see FIG. 9).
In addition, the processing time is the longest during the manufacturing process of the glass substrate, and the lapping process which increases the equipment cost can be omitted, so that the processing equipment cost and the processing time can be greatly reduced. Furthermore, since the flatness and warpage of the glass substrate are controlled with higher precision than before, the stock removal in each process can be reduced, so that the thickness of the glass substrate (blank) can be made as thin as possible. As a result, it is possible to significantly reduce raw material costs, processing consumable material costs, and the like. From the above, it is possible to significantly reduce the price of a glass substrate (substrate) as a product.

[0026]

EXAMPLES Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto. (Examples 1 and 2) A glass substrate (substrate) as a product was manufactured under the conditions shown in Table 1 based on the flowchart shown in FIG. The results are shown in Tables 4 and 5.

[0027]

[Table 1]

(Comparative Examples 1 and 2) A glass substrate (substrate) as a product was manufactured under the conditions shown in Tables 2 and 3, based on the flowchart shown in FIG. Table 4 shows the results.
Are shown in FIGS.

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Table 5]

(Discussion: Examples 1-2, Comparative Examples 1-2)
As shown in Table 4, the method for manufacturing a glass substrate of the present invention (Examples 1 and 2) is different from the conventional method for manufacturing a glass substrate (Comparative Examples 1 and 2) in that glass obtained by press molding is used. Even if the thickness of the substrate (blank) is close to the thickness of the glass substrate (substrate) as a product (for example, 0.72 mm), by performing the crystallization process, it can be used during press molding or crystallization. It has been found that the generated warpage can be corrected to 5 μm or less. This eliminates the necessity of performing a lapping step, which was mainly performed to eliminate warpage (flatness), and reduces the thickness of a glass substrate (blank) obtained by press molding to a product glass substrate (substrate). )
(For example, 0.72 mm), so that the cost of expensive glass substrate materials can be reduced by 40%.

In the method for manufacturing a glass substrate of the present invention (Examples 1 and 2), the occurrence of pits and warpage during grinding can be prevented by performing fine grinding instead of lapping. Compared with the conventional method for manufacturing a glass substrate (Comparative Examples 1 and 2), the removal amount of the glass substrate during polishing could be reduced to about 1/5 to 1/6.

As shown in Table 5, the method for manufacturing a glass substrate of the present invention (Examples 1 and 2) was compared with the conventional method for manufacturing a glass substrate (Comparative Examples 1 and 2). The removal of the substrate and the production time could be greatly reduced, and the quality of the glass substrate (substrate) as the product was good. The surface roughness (Ra) is J
It is the same as the arithmetic average roughness (Ra) described in IS B0601 “Surface Roughness—Definition and Display”.

Further, Examples 1 and 2 and Comparative Example 2 in Table 5
The production time (all steps) of the glass substrate at 25 yen /
Table 6 shows the conversion in one minute. As can be clearly seen from Table 6, according to the example, the cost was significantly reduced as compared with the comparative example.

[0037]

[Table 6]

[0038]

As described above, according to the method for manufacturing a glass substrate of the present invention, the degree of flatness and warpage of the glass substrate are controlled with higher precision than in the conventional method, thereby shortening the processing steps and reducing the glass substrate. Material thickness, processing equipment cost, processing consumable material cost,
It is possible to greatly reduce processing time and the like, and as a result, it is possible to contribute to significantly reducing the product price of the glass substrate.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a crystallization process in a method for manufacturing a glass substrate of the present invention.

FIG. 2 is a schematic cross-sectional view showing one example of a chamfering step in the method for manufacturing a glass substrate of the present invention.

FIG. 3 is an explanatory diagram showing a rotation direction of a glass substrate and a grindstone in a chamfering step in the method for manufacturing a glass substrate of the present invention.

FIG. 4 is an explanatory diagram showing chipping that occurs in a glass substrate chamfering step.

FIG. 5 is a schematic sectional view showing an example of a fine grinding step in the method for manufacturing a glass substrate of the present invention.

FIG. 6 is a schematic front view of FIG.

FIG. 7 shows a positional relationship between a work surface plate and a work surface plate (disk substrate) in the fine grinding step in the method of manufacturing a disk substrate of the present invention, wherein (a) is a schematic explanatory view, (b) is an image diagram showing a trajectory of a ground surface of a processing surface plate on a disk substrate.

FIG. 8 is a flowchart showing a method for manufacturing a glass substrate of the present invention.

FIG. 9 is a flowchart showing a conventional method for manufacturing a glass substrate.

[Explanation of symbols]

1 ... firing container, 2 ... glass substrate, 3 ... disk-shaped weight,
Reference numeral 4: honeycomb plate, 5: SUS weight, 6: weight (fin weight), 7: opening, 8: columnar portion, 9: collar, 11: glass substrate, 12: work table, 13 ...
Whetstone for inner diameter processing, 14 ... Whetstone for outer diameter processing, 15 ... Spindle, 16 ... Groove, 17 ... Chamfer processing part, 18
... Glass substrate, 19 ... Chipping, 22 ... Cup grinding wheel for processing, 24 ... Rotary axis (Cup grinding wheel for processing), 26 ... Work surface plate, 28 ... Rotation shaft (for work surface plate), 30 ... Belt pulley (V belt) ), 32 ... motor (for work surface plate),
Reference numeral 40 denotes a disk substrate, 42 denotes a grinding surface of a processing cup grindstone, and 44 denotes a locus of a radial curve.

Claims (4)

(57) [Claims] 1. A press forming step of press forming molten glass into a donut shape, and applying pressure evenly to the entire glass substrate by a pressing member from one or both surfaces of the glass substrate obtained by the press forming step. A crystallization treatment step of firing; a chamfering step of simultaneously rotating the glass substrate and the processing grindstone obtained in the crystallization treatment step at a high speed to process the inner and outer diameters of the glass substrate; A fine grinding step for sequentially and continuously performing brittle fracture processing and plastic deformation processing on both surfaces of the glass substrate, and polishing for polishing both surfaces of the glass substrate obtained in the fine grinding step. And a step of manufacturing a glass substrate. 2. In the crystallization step, the pressing member is a weight having a predetermined weight, and the glass substrates are horizontally stacked in a firing container having an opening at an upper end, and the pressing member is moved to the upper end. 2. The method for manufacturing a glass substrate according to claim 1, wherein the glass substrate is placed on the glass substrate, and the pressing member closes the opening so as to perform baking so that the warpage of the glass substrate can be corrected to 10 μm or less. . 3. In the chamfering step, the peripheral speeds of the inner diameter machining grindstone and the outer diameter machining grindstone are set to 1 respectively.
200 to 10000 m / min, and the ratio of the peripheral speed of the inner diameter processing portion of the glass substrate to the peripheral speed of the inner diameter processing grindstone, and the peripheral speed of the outer diameter processing portion of the glass substrate and the outer diameter processing The ratio of the peripheral speed of the whetstone is 1/10 to 10
The method for producing a glass substrate according to claim 1, wherein the ratio is within 1/100. 4. In the fine grinding step, both surfaces of a glass substrate as a workpiece are ground one by one in order, and the processing distortion remaining on each ground surface is made to be substantially the same amount. The method for manufacturing a glass substrate according to claim 1, wherein the flatness of the subsequent glass substrate can be maintained at 10 µm or less.