JP2003159639A - Clamp jig for glass substrate, buffer sheet, machining method for glass substrate, and glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for simultaneously grinding inner peripheral ends and outer peripheral ends of multiple sheets of glass substrates to be used as a magnetic recording medium or the like. <P>SOLUTION: In order to chamfer the outer end part of the glass substrate g, at first, a glass substrate block G is made by laminating a large number of annular glass substrates g while buffer sheets 5 are sandwiched inbetween. First plates 1, 1 of a clamp jig are set to both end faces of the glass substrate block G, a first fastener 3 is inserted into a central hole of the first plates 1, 1 and the glass substrate block G, the glass substrate block G is clamped from inside, and the outer end face is chamfered by a rotary grinding wheel 6. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clamp jig for stacking and holding a large number of annular glass substrates, a cushioning sheet sandwiched between the glass substrates, and grinding of inner and outer peripheral ends of a large number of annular glass substrates ( Chamfering or polishing) and a glass substrate obtained by this method.

[0002]

2. Description of the Related Art Since glass is superior to aluminum in impact resistance, rigidity, hardness and strength, it is being used as a magnetic recording medium incorporated in a hard disk drive or the like. In particular, recently, the form of a personal computer is shifting from a desktop type to a notebook type or a mobile type, and there is an increasing demand for a glass substrate excellent in flatness and high density instead of an aluminum substrate.

In order to obtain a glass substrate for a magnetic recording medium, a glass blank is cut into a disk shape (doughnut shape), and the peripheral end surfaces (inner peripheral edge and outer peripheral edge) of this disk glass substrate are, for example, disclosed in JP-A-10-154321. As disclosed in Japanese Patent Publication, lapping with a diamond grindstone and polishing with a cerium oxide suspension are performed. After that, lapping with alumina abrasive grains on the front and back recording surfaces (main surfaces) and cerium oxide suspension are performed. I try to polish it.

In the above-mentioned method, since the processing of the glass substrate is a single-wafer type and the efficiency is low, a method of simultaneously polishing a large number of glass substrates is disclosed in Japanese Patent Laid-Open No. 11-221742. In this publication, a large number of glass substrates are stacked as they are and clamped into a block shape, and a polishing brush or a polishing pad is made to face the inner hole of this block. The inner peripheral edge of the glass substrate is polished at the same time.

[0005]

The above-mentioned prior art has the following problems. First of all, for the inner peripheral edge of the glass substrate, a large number of glass substrates can be polished at the same time, but for the outer peripheral edge, the glass substrate remains contained in the substrate case, so the inner peripheral edge is polished for the outer peripheral edge. Polishing must be performed in a process completely different from the processing. That is, a large number of glass substrates are taken out from the substrate case, and the outer peripheral edge is polished by a single wafer, or it is carried to another clamper and simultaneously polished. However, if the processing is performed with a single sheet, the efficiency becomes poor, and the process of switching to another clamper not only complicates the process, but also causes a misalignment during the switching of the clamper, resulting in poor processing accuracy.

Secondly, since the glass substrates are directly laminated, the recording surface is apt to be scratched. That is, a large number of cullets (glass powder) are generated at the site of polishing work, the cullets are sandwiched between glass substrates, and when embedded on the glass substrate side by the pressure of the clamp, deep cracks (25 μm or more) are generated. As described above, the presence of cracks on the recording surface of the glass substrate hinders the formation of a uniform magnetic film, so that polishing must be performed until the cracks disappear. The thicker the polishing allowance is, the longer the polishing time is, and the glass substrate itself needs to be manufactured in consideration of the polishing allowance.

[0007]

In order to solve the above problems, a clamp jig according to the present invention is pressed against both end faces of a glass substrate block in which a large number of glass substrates are stacked and a fastener insertion hole is formed in the center. A pair of first plates, a first fastener that is inserted into the inner hole of the glass substrate block and has both ends bound to fastener insertion holes of the first plate, and is disposed outside the first plate. And a pair of second plates having an inner diameter smaller than the outer diameter of the first plate, and a second fastener for tightening the pair of second plates outside the glass substrate block. According to this clamp jig, the inner peripheral edge and the outer peripheral edge can be continuously lapped or polished without releasing the clamped state of the glass substrate block in which a large number of glass substrates are stacked.

Further, in the method for processing a glass substrate according to the present invention, a buffer sheet is sandwiched between annular glass substrates so as not to protrude from the inner peripheral edge and the outer peripheral edge of the glass substrate, and a large number of glass substrates are sandwiched. The substrates are overlapped and clamped from the outside or inside, the outer peripheral edges of many glass substrates are ground at the same time when clamped from the inside, and the inner peripheral ends of many glass substrates are simultaneously ground when clamped from the outside. The clamped state of the glass substrate is maintained even when the grinding of the inner peripheral edge and the outer peripheral edge is switched. In the above, either of the outer peripheral edge grinding and the inner peripheral edge grinding may be performed first. For grinding, chamfering and rough polishing (lapping)
And polishing (polishing).

According to the present invention, it is possible to continuously grind the inner peripheral edge and the outer peripheral edge of a large number of glass substrates, and further it is possible to carry out polishing as it is after lapping is completed.

For chamfering in grinding, for example, a grindstone having diamond abrasive grains fixed to a base metal is brought into rotary contact. To perform lapping or polishing, for example, a polishing brush or a polishing pad is rotated while being supplied with a polishing liquid.

As the buffer sheet, it is preferable to use a resin sheet having an inner diameter larger than the inner diameter of the glass substrate and an outer diameter smaller than the outer diameter of the glass substrate and having a thickness of 0.2 mm or less. It is necessary to set the inner diameter and the outer diameter within the above ranges in order to prevent lapping failure and polishing failure, and to reduce the RC (Radial Curvature) to 40 nm or less by setting the thickness to 0.2 mm or less. You can

The buffer sheet is made of a soft material having a Rockwell hardness of 40 or less, and a soft layer and a hard layer (for example, the compressive elastic modulus is 100 MPa or more, preferably 1).
Those having a two-layer structure of 000 MPa or more) and those having a three-layer structure in which both surfaces of a hard layer are sandwiched by soft layers are suitable. The relationship between Rockwell hardness and compressive elastic modulus is shown in FIG.
4 shows. From this figure, examples of the material of the soft layer include PO (polyolefin), PU (polyurethane), PE (polyethylene), and S (suede), and examples of the material of the hard layer include PP (polypropylene) and PVC (polyvinyl chloride). ), PET (polyethylene terephthalate) and PS (polyester).

Further, as the buffer sheet, one having a convex portion on the inner peripheral edge or the outer peripheral edge is used, and the buffer sheet is superposed on the glass substrate so that the convex portion may be applied to the inner peripheral edge or the outer peripheral edge of the glass substrate. By performing grinding and leaving a portion of the inner peripheral edge or the outer peripheral edge of the glass substrate corresponding to the convex portion as an incompletely ground portion, a mark for quality control or the like can be formed on the glass substrate simultaneously with the grinding.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a procedure for manufacturing a glass substrate for a magnetic recording medium. First, a glass base plate is punched out into an annular (disc-shaped) glass substrate, and chamfering processing is performed on an outer end portion and an inner end portion of the glass substrate. Then, the outer edge and the inner edge are polished (polishing), after which the recording surface is roughly polished (lapping), then the recording surface is polished (polishing), and after scrub cleaning,
The surface is chemically strengthened, washed, and then inspected to obtain a product. The present invention is applied to chamfering of glass substrates and polishing of end faces among the above steps.

FIG. 2 is a perspective view of a clamp jig used for implementing the present invention. The clamp jig includes a pair of first plates 1 and 1, a pair of second plates 2 and 2, a first fastener 3 inserted between the pair of first plates 1 and 1, a pair of second plates 2 and 2. It consists of a second fastener 4 inserted between them.

The outer diameter of the first plate 1 is smaller than that of the glass substrate g, and the inner diameter of the first plate 1 is substantially the same as the inner diameter of the glass substrate g. The second plate 2 has an outer diameter of the glass substrate g. It has an annular shape that is larger than the diameter and smaller in inner diameter than the outer diameter of the first plate 1. Each of the first and second fasteners 3 and 4 is a combination of a bolt and a nut, and three second fasteners 4 are provided at equal intervals in the circumferential direction of the second plate 2.

Using the above clamp jig, a glass substrate g
In the case of grinding the outer end portion of the first plate 1, the first fastener 3 as described later in detail with reference to FIG.
In the case of grinding the inner end portion of the glass substrate g by using, the first plate 1, 1 and the second plate 2, 2 and the second fastener 4 are attached as described later in detail with reference to FIG. To use.

FIG. 3 shows a glass substrate block G in which a large number of glass substrates g are laminated. In the present invention, the glass substrate block G is chamfered, lapped, polished or the like. In the glass substrate block G, the buffer sheet 5 is interposed between the glass substrates g.

If foreign matter such as cullet is present between the glass substrates g directly laminated, cracks may occur on the recording surface. Therefore, the cushioning sheet 5 is interposed so that foreign matter such as cullet is embedded in the cushioning sheet 5 to prevent cracking. For such a purpose, the cushioning sheet 5
Needs to use a material softer than the glass substrate g. However, if it is too soft, the glass substrate g may be displaced during polishing even when laminated and clamped. Therefore, the preferable hardness of the buffer sheet 5 is 5 as Rockwell hardness.
That is all.

If the cushioning sheet 5 protrudes from the inner or outer end of the glass substrate during grinding, that portion cannot be ground. Therefore, the inner diameter of the cushioning sheet 5 is as shown in FIG. The inner diameter of the glass substrate g is, for example, 0.01
It is larger by mm to 5.0 mm and smaller than the outer diameter of the glass substrate g by, for example, 0.03 mm to 10.0 mm.

Further, when the buffer sheet 5 is set between the glass substrates g, in order to prevent the buffer sheet 5 from protruding from the outer periphery of the glass substrate g even if the buffer sheets 5 are set in a misaligned manner, the outer diameter of the glass substrate g and The difference in the outer diameter dimension of the cushioning sheet 5 is equal to 2 of the difference between the inner diameter dimension of the glass substrate g and the inner diameter dimension of the cushioning sheet 5.
It is preferable that the number is twice or more.

5 (a) and 5 (b) are sectional views showing another embodiment of the cushioning sheet. As the cushioning sheet 5, as shown in FIG. 5 (a), a soft layer 51 and a hard layer 52 are provided. It may have a two-layer structure or, as shown in (b), a three-layer structure in which both surfaces of the hard layer 52 are sandwiched by the soft layers 51. As the hard layer 52, a material having a compressive elastic modulus of 100 MPa or more, preferably 1000 MPa or more is used.

The relationship between the compression elastic modulus and the Rockwell hardness is as shown in FIG. 14, and as the material having the compression elastic modulus of 100 MPa or more, PP (polypropylene), PVC (polyvinyl chloride), PET (polyethylene terephthalate). And PS (polyester). In the cushioning sheet of the present invention, the relationship between the compression elastic modulus Y (Mpa) and the Rockwell hardness R of the hard layer and the soft layer is expressed by two dotted lines in FIG. 14, logY = 0.0.
22R + 0.78 and logY = 0.022R-0.4
It is composed of one of the sheets of material or a laminate thereof in the area sandwiched by two.

FIG. 6 is a graph showing the relationship between RC (Radial Curvature) and the thickness of the buffer sheet. Where R
As shown in FIG. 7, C is the radius R1 from the center of the disk-shaped glass substrate g corresponding to the position of the radius R1 separated from the center of the disk-shaped glass substrate g by a predetermined dimension distance and almost the end of the recording surface.
The RC is generally required to be 42 μm or less as a characteristic indicated by the maximum distance measured between the sagging portions AB of the glass substrate g generated in the radial direction between the two positions. To satisfy this requirement, the thickness of the cushioning sheet 5 is 0.2 mm from FIG.
It turns out that it should be:

Next, the procedure for chamfering the outer and inner ends of the glass substrate g will be described with reference to FIGS. 8 and 9. First, a large number of annular glass substrates g are laminated with a buffer sheet 5 interposed therebetween to form a glass substrate block G. Then, the first plates 1 and 1 of the clamp jig are applied to both end surfaces of the glass substrate block G, and the first fastener 3 is inserted through the central holes of the first plate 1 and 1 and the glass substrate block G. The substrate block G is clamped from the inside, and the outer end surface is chamfered with the rotary grindstone 6.

The rotary grindstone 6 has diamond abrasive grains fixed to a base metal, and the outer peripheral surface has an uneven shape corresponding to the intended chamfered shape. Then, in order to chamfer the inner end portion of the glass substrate g, while rotating the glass substrate block G, the rotary grindstone 6 is also rotated.

After simultaneously chamfering the outer edges of a large number of glass substrates g as described above, the glass substrate block G is formed.
The second plate 2, 2 of the clamp jig is applied to the outside of the first plate 1, 1 while maintaining the clamped state without breaking the plate, and the third second fastening between the second plates 2 and 2 is performed. The tool 4 is inserted and the glass substrate block G is clamped from the outside. After that, the first fastener 3 is removed, and as shown in FIG. 9, another rotary grindstone 7 is used in the central hole of the glass substrate block G to simultaneously chamfer the inner end portions of many glass substrates g.

Thereafter, as shown in FIGS. 10 and 11,
Using a polishing brush or polishing pads 8 and 9 made of nylon or the like while supplying a polishing liquid, a large number of glass substrates g are placed in a block G state, and the chamfered outer and inner ends are suspended with cerium oxide fine particles. Polishing (polishing) is performed using the polishing liquid.

In the embodiment, the outer end of the glass substrate g is processed first, and then the inner end is processed, but either may be processed first.

FIG. 12 shows another embodiment of the cushioning sheet,
The cushioning sheet 5 shown in (a) has a convex portion 5a on the outer periphery,
The cushioning sheet 5 shown in (b) has a convex portion 5b on the inner peripheral portion. In this way, the convex portions 5a, 5b are formed on the outer peripheral portion or the inner peripheral portion.
The cushioning sheet 5 having the above is overlapped so that the convex portions 5a and 5b overlap the outer end portion or the inner end portion of the glass substrate g, and lapping or polishing is performed in this state to cover the convex portions 5a and 5b. The exposed portion is not sufficiently lapped or polished, and the mark m can be positively formed at the outer end portion or the inner end portion as shown in FIG.

The mark m can be used for product management such as a product number for each lot, a production factory, a production date and time. However, since the quality is affected if the number of insufficiently polished portions is large, the size and number of the convex portions 5a and 5b are set within a range that does not affect the quality.

Next, the following table shows the experimental results obtained by polishing using various buffer sheets having different materials and layer structures. The experiment was conducted under the following conditions. The end face and chamfering of the outer and inner circumferences were bundled with a clamp jig using a 10-groove grinding wheel having an outer diameter of 80 mmφ and an outer diameter of 22 mmφ, each having 10 grooves of a predetermined cross-sectional shape. 10 sheets of glass were processed simultaneously. The grindstone used was a grindstone in which # 500 diamond grindstone was attached to a base metal in 10 grooves. At this time, buffer sheets of various materials were sandwiched between glass plates. The subsequent polishing polishing was performed while supplying a polishing liquid in which cerium oxide particles were suspended using a nylon brush roll. After that, the glass is removed from the clamp jig, the bundling of the glass is released, and the main surface (recording surface) of the glass plate has an average grain size of 0.5 to 1.7.
Using a polishing liquid containing a cerium oxide abrasive grain of μm and a polishing pad, 25 μm was polished on each side, washed and dried. Subsequently, a chemical strengthening treatment was carried out by ion exchange using a mixed molten salt of potassium nitrate and sodium nitrate, followed by washing and drying again, and the main surface was inspected for scratches. In addition, the outer peripheral end surface processing and the inner peripheral end surface processing (grinding) of a glass substrate using a diamond grindstone are performed one by one in a single-wafer type,
After that, while supplying the cerium oxide polishing liquid, a large number of glass substrates are held and fixed by bundling a number of glass substrates with a clamp for polishing the inner peripheral edge and the outer peripheral edge using a polishing pad or a polishing brush. It may be performed by a batch polishing method.

[0033]

[Table 1]

In the above (Table), each of Examples 1 to 6 is an example in which a buffer sheet composed of a single layer having a Rockwell hardness of 40 MPa or less is used, and the occurrence of scratches on the glass main surface is suppressed, and 500 W is obtained. In the visual inspection method of irradiating with the illumination lamp of No. 2, a high numerical value of 92% or more was obtained as the yield when passing the condition that no flaw was recognized.
Of these, in Example 1, the total thickness of the buffer sheet was 0.27.
5mm thickest, with 1 radial carvecher
The value was as large as 78 nm. On the other hand, Example 2
Since the buffer sheets of ~ 7 had a thin thickness of 0.2 mm or less, the radial curve betcha obtained a small characteristic of 45 nm or less. Comparative Examples 1 to 3 are single-layer buffer sheets made of a hard material, in which scratches were observed on the main surface, and the scratch yield was a low value of 78% or less. Among the three Comparative Examples, Comparative Example 2 having a large thickness has a large radial curve, and it is found that it is not suitable for manufacturing a magnetic recording medium substrate. In addition, the workability of the cushioning sheet depends on the thickness of the sheet, the adhesion to the glass in the wet state due to the material, the strength of the waist, etc., the ease of setting on the glass surface, the wet glass surface It is considered that the workability evaluation points were different when they were removed.

[0035]

As described above, according to the present invention,
When lapping or polishing the inner peripheral edge and outer peripheral edge of a glass substrate used as a magnetic recording medium,
Since a large number of sheets can be processed at the same time, a significant cost reduction can be achieved.

In addition, when lapping or polishing the outer peripheral edge subsequent to the lapping or polishing of the inner peripheral edge, it is possible to maintain the clamped state of a large number of glass substrates without releasing the clamped state. There is no gap between the edges.

Since a buffer sheet is sandwiched between the glass substrates when a large number of glass substrates are laminated, even if foreign matter such as cullet is sandwiched between the glass substrates, it is embedded in the buffer sheets. However, cracks and the like do not occur on the recording surface of the glass substrate.

Further, according to the buffer sheet of the present invention used for stacking a large number of glass substrates, since the Rockwell hardness thereof has a predetermined value, scratches may occur on the main surface (recording surface) of the glass substrate. Suppressed. Further, by using a buffer sheet having a multilayer structure with the soft layer, lateral displacement of the glass substrate can be further suppressed, and chamfering of the end face and polishing can be made into a perfect circular shape.

Further, a convex portion is provided on a part of the buffer sheet, and lapping or polishing is performed so that the convex portion may be applied to the inner end portion or the outer end portion of the glass substrate, so that the quality and the like can be easily controlled. Marks can be formed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a manufacturing procedure of a glass substrate for a magnetic recording medium.

FIG. 2 is a perspective view of a clamp jig.

FIG. 3 is a side view of a glass substrate block in which many glass substrates are stacked.

FIG. 4 is a plan view showing a state in which a buffer sheet is stacked on a glass substrate.

5A and 5B are cross-sectional views showing another embodiment of the cushioning sheet.

FIG. 6 is a graph showing the relationship between RC (Radial Curvature) and the thickness of the buffer sheet.

[Figure 7] Conceptual diagram of RC (Radial Curvature)

FIG. 8 is a side view showing a state where the outer edge of the glass substrate is chamfered.

FIG. 9 is a side view showing a state where the inner end portion of the glass substrate is chamfered.

FIG. 10 is a side view showing a state where the outer end portion of the glass substrate is being polished.

FIG. 11 is a side view showing a state where the inner end portion of the glass substrate is being polished.

12A is a plan view of a cushioning sheet having a convex portion on an outer peripheral portion, and FIG. 12B is a plan view of a cushioning sheet having a convex portion on an inner peripheral portion.

FIG. 13 is a diagram showing a glass substrate manufactured using a buffer sheet having a convex portion.

FIG. 14 is a diagram showing the relationship between elastic compressibility and Rockwell hardness.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st plate of a clamp jig, 2 ... 2nd plate of a clamp jig, 3 ... 1st fastener of a clamp jig, 4 ...
Second fastener of clamp jig, 5 ... Buffer sheet, 5a,
5b ... Convex part, 51 ... Soft layer, 52 ... Hard layer, 6,7 ... Rotating grindstone, 8,9 ... Polishing brush or polishing pad, g ... Glass substrate, G ... Glass substrate block, m ... Mark.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kensuke Matsuno             7-28 Kitahama 4-28, Chuo-ku, Osaka City, Osaka Prefecture             Within Nippon Sheet Glass Co., Ltd. (72) Inventor Takeo Watanabe             7-28 Kitahama 4-28, Chuo-ku, Osaka City, Osaka Prefecture             Within Nippon Sheet Glass Co., Ltd. F term (reference) 3C043 BB05 CC03 DD05                 3C049 AA18 AB04 AB08 CA01 CA06                 4G059 AA08 AB19 AC03

Claims (17)

[Claims] 1. A clamp jig for stacking and holding a large number of annular glass substrates, wherein the clamp jig is pressed against both end faces of a glass substrate block in which a large number of glass substrates are stacked, and a fastener insertion hole is formed in the center. A pair of first plates formed with the first plate, a first fastener that is inserted into the inner hole of the glass substrate block, and both ends thereof are bound to fastener insertion holes of the first plate; A glass substrate clamping jig including a pair of second plates arranged outside and having an inner diameter smaller than the outer diameter of the first plate, and a second fastener for tightening the pair of second plates outside the glass substrate block. . 2. A buffer sheet sandwiched between annular glass substrates, wherein the buffer sheet is made of a soft material having a Rockwell hardness of 40 or less. 3. A buffer sheet sandwiched between annular glass substrates, the buffer sheet having a two-layer structure of a soft layer and a hard layer. 4. A buffer sheet sandwiched between annular glass substrates, wherein the buffer sheet has a three-layer structure in which both sides of a hard layer are sandwiched by soft layers. 5. The buffer sheet according to claim 3 or 4, wherein the hard layer has a compression elastic modulus of 100 MPa or more. 6. The cushioning sheet according to any one of claims 2 to 5, wherein the cushioning sheet has a thickness of 0.2 mm or less. 7. The cushioning sheet according to claim 2, wherein the cushioning sheet is formed such that the inner diameter is larger than the inner diameter of the glass substrate and the outer diameter is smaller than the outer diameter of the glass substrate. Cushioning sheet. 8. A plurality of annular glass substrates are stacked by sandwiching the buffer sheet according to any one of claims 2 to 7 between the glass substrates, and the glass substrates are placed on an outer peripheral side or an inner peripheral side. The method for processing a glass substrate is characterized in that the glass substrate is clamped from the glass substrate and the non-clamped side is ground. 9. A buffer sheet is sandwiched between annular glass substrates so as not to protrude from the inner and outer peripheral edges of the glass substrates, and a large number of glass substrates are stacked and clamped from the outside or inside. , The outer peripheral edges of many glass substrates are ground at the same time when clamped from the inside, and the inner peripheral edges of many glass substrates are simultaneously ground when clamped from the outside, and the grinding is switched between the inner peripheral edge and the outer peripheral edge. A method of processing a glass substrate, characterized in that the clamped state of the glass substrate is maintained even in the case of. 10. The method for processing a glass substrate according to claim 9, wherein the grinding of the outer peripheral edge and the inner peripheral edge is chamfering performed by bringing a grindstone having diamond abrasive grains fixed to an alloy into rotational contact. And a method of processing a glass substrate. 11. The method for processing a glass substrate according to claim 9, wherein the grinding of the outer peripheral edge and the inner peripheral edge is polishing performed by rotating a polishing brush or a polishing pad while supplying a polishing liquid. And a method of processing a glass substrate. 12. After the grinding according to claim 9, while continuously holding the clamped state of the glass substrate without releasing it, the polishing brush or polishing pad is rotated and brought into contact with the outer peripheral edge while supplying the polishing liquid. A method for processing a glass substrate, which comprises polishing the inner peripheral edge. 13. The method of processing a glass substrate according to claim 9, wherein the cushioning sheet is formed according to claim 2.
A method of processing a glass substrate, wherein the glass substrate according to claim 7 is used. 14. The glass substrate processing method according to claim 9, wherein the buffer sheet has a convex portion on an inner peripheral edge or an outer peripheral edge, and the convex portion is an inner peripheral surface of the glass substrate. It is characterized in that a cushioning sheet is superposed on a glass substrate so as to be overlapped with an edge or an outer peripheral edge and is ground, and a portion corresponding to the convex portion of the inner peripheral edge or the outer peripheral edge of the glass substrate is left as an incompletely ground portion. Glass substrate processing method. 15. A glass substrate obtained by the processing method according to claim 8. 16. A glass substrate obtained by the method for processing a glass substrate according to claim 13. 17. A glass substrate obtained by the method for processing a glass substrate according to claim 14, wherein the inner peripheral edge and / or the outer peripheral edge have marks formed by incomplete grinding. Glass substrate.