JP2009227523A - Glass substrate and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass substrate free of an extremely protrusive part at an edge face and having high mechanical strength and a method for producing the same. <P>SOLUTION: The glass substrate is obtained by etching a plate-like glass substrate to be cut-out to a desired shape and has a pair of principal surfaces and an edge face, wherein, when the cross section of the glass substrate is viewed, the relationship between the shortest length L from the most protrusive apex at the edge face to a first imaginary line connecting two edge parts composed of the respective principal surfaces and the edge face and the thickness D of the glass substrate satisfies L≤D/2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cover glass used for protecting a display screen of a mobile terminal device such as a mobile phone or a PDA (Personal Digital Assistant), a glass substrate used for a main body of a mobile device, and a manufacturing method thereof.

In mobile terminal devices such as mobile phones and PDAs, and other mobile devices, a protective plate is provided in order to prevent an impact or external force from being applied to the display (for example, Patent Document 1). 2. Description of the Related Art In recent years, a protective plate using chemically strengthened glass that has strength even if it is a thin plate has been proposed with a reduction in thickness of portable terminal devices and portable devices (for example, Patent Document 2).
JP 2004-299199 A JP 2007-99557 A

  In the conventional processing method described in Patent Document 2, the glass end surface has a rough surface roughness, and the glass end surface is chamfered to have a microcrack of about several tens μm to several hundreds μm. However, there is a problem that the mechanical strength required for the above cannot be obtained.

  In order to solve this problem, in the prior application (Japanese Patent Application No. 2007-325542), the present applicant forms a resist pattern of a desired shape on a glass substrate, and etches the glass substrate using the resist pattern as a mask. Thus, it is provided to obtain a glass substrate having a desired shape.

  However, in this method, as shown in FIG. 6, since etching proceeds isotropically from both main surfaces 61a and 61b facing the glass substrate 61, etching from the main surface 61a side and main surface 61b are performed. A top portion 61d of the end surface 61c formed by etching from the side is formed. The top portion 61d is a portion that protrudes extremely on the end surface 61c. Such a glass substrate having the top portion 61d may be broken or chipped during handling, and the portion becomes the starting point of cleaving due to breakage or chipping. There is a problem of lowering the strength.

  This invention is made | formed in view of this point, and it aims at providing the glass base material which does not have the part which protrudes extremely in an end surface, and has high mechanical strength, and its manufacturing method.

  The glass substrate of the present invention is a glass substrate that is cut into a desired shape by etching a plate-like glass substrate, and has a pair of main surfaces and end surfaces, and each main surface in a cross-sectional view. The relationship between the shortest distance L from the top of the end face that protrudes most to the first imaginary line that connects two edge portions constituted by the end face and the thickness D of the glass substrate is L ≦ D / 2 is satisfied.

  According to this configuration, in a cross-sectional view, the shortest distance L from the top portion that protrudes most at the end surface with respect to the first imaginary line that connects the two edge portions constituted by the main surface and the end surface, and the glass substrate Since the relationship with the thickness D satisfies L ≦ D / 2, there is no portion that protrudes excessively on the end face, and high mechanical strength can be exhibited.

  In the glass base material of this invention, it is preferable that the thickness of the said glass base material is 0.3 mm or more and 1.3 mm or less.

  In the glass substrate of the present invention, in the cross-sectional view, it is preferable that an angle α formed by two second imaginary lines connecting the two edge portions and the top portion is 90 ° or more and 180 ° or less. .

In the glass substrate of the present invention, the glass substrate is an aluminosilicate glass containing at least one selected from the group consisting of SiO ₂ , Al ₂ O ₃ , Li ₂ O and Na ₂ O. preferable. According to this configuration, a plate-like glass substrate can be formed by the downdraw method (fusion method), so that the main surface of the glass substrate is not scratched and has a very high smoothness on the order of nanometers. It can be a glass surface. Therefore, the mirror surface polishing process of the main surface is not required at the time of producing the glass substrate, and a glass substrate free from microcracks is obtained even on the main surface, resulting in a glass substrate having excellent mechanical strength.

  In the glass substrate of the present invention, the glass substrate is preferably glass chemically strengthened by ion exchange treatment. According to this configuration, since the compressive stress layer is formed on the main surface and end face of the glass substrate, the mechanical strength can be further increased.

  The method for producing a glass substrate according to the present invention includes a resist pattern formed on a main surface of a plate-shaped glass substrate as a mask and first etching the glass substrate with an etchant capable of etching the glass substrate. Cutting out into a shape to obtain a glass substrate, and second etching the glass substrate in an etchant having a flow in the thickness direction of the glass substrate.

  According to this method, since the glass substrate is subjected to the second etching in the etchant having a flow in the thickness direction of the glass substrate, there is no portion that protrudes extremely at the end face, and the glass substrate having high mechanical strength is obtained. Obtainable.

  In the method for producing a glass substrate of the present invention, it is preferable that the second etching mainly etches the most projecting apex formed on the end surface of the glass substrate by the first etching.

  In the manufacturing method of the glass base material of this invention, after cutting out to the said desired shape, it is preferable to chemically strengthen by an ion exchange process. According to this method, since the compressive stress layer is formed on the main surface and end face of the glass substrate, the mechanical strength can be further increased.

  The glass substrate of the present invention is a glass substrate that is cut into a desired shape by etching a plate-like glass substrate, and has a pair of main surfaces and end surfaces, and each main surface in a cross-sectional view. The relationship between the shortest distance L from the top of the end face that protrudes most to the first imaginary line that connects two edge portions constituted by the end face and the thickness D of the glass substrate is L ≦ D / 2 is satisfied, there is no portion that protrudes extremely on the end face, and the mechanical strength is high.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The glass substrate according to the embodiment of the present invention is obtained by first etching the glass substrate with an etchant capable of etching the glass substrate using a resist pattern formed on the main surface of the plate-like glass substrate as a mask. A glass substrate is obtained by cutting into a desired shape, and is obtained by second etching the glass substrate in an etchant having a flow in the thickness direction of the glass substrate.

  FIG. 1 is a diagram showing a part of a glass substrate obtained by etching a glass substrate and cutting it into a desired shape. A glass substrate 1 shown in FIG. 1 has a pair of opposing main surfaces 11 and 12 and an end surface 13. When a resist pattern 17 is formed on each of the main surfaces 11 and 12 of the glass substrate having a thickness D, and the glass substrate is etched (first etching) using the resist pattern 17 as a mask, the etching is performed on both the main surfaces 11 facing the glass substrate. , 12 are isotropically advanced, and a top portion 16 is formed on the end face 13 by etching from the main surface 11 side and etching from the main surface 11 side. In this etching, since the etching proceeds so as to draw a substantially circular arc from the main surface 11 side and the main surface 12 side to the inside of the glass substrate in a cross-sectional view, when the glass substrate is cut out, the glass substrate In the vicinity of the center thickness, the arcs intersect with each other, and as shown in FIG.

  The etching method for etching the glass substrate may be either wet etching (wet etching) or dry etching (dry etching). Wet etching is preferable from the viewpoint of reducing the processing cost. The etchant used for wet etching may be anything as long as it can etch a glass substrate. Preferably, an acidic solution mainly containing hydrofluoric acid or a mixed acid containing at least one acid among sulfuric acid, nitric acid, hydrochloric acid, and silicic hydrofluoric acid can be used. The etchant used for dry etching is not particularly limited as long as it can etch a glass substrate. For example, a fluorine-based gas can be used.

  The resist material used in the etching process may be any material having resistance to an etchant used when etching glass using a resist pattern as a mask. Since glass is usually etched by wet etching of an aqueous solution containing hydrofluoric acid or dry etching of a fluorine-based gas, for example, a resist material having excellent resistance to hydrofluoric acid can be used. In addition, as a stripping solution for stripping the resist material from the glass substrate, an alkaline solution such as KOH or NaOH is preferably used. Note that the types of the resist material, the etchant, and the stripping solution can be appropriately selected according to the material of the glass substrate that is the material to be etched.

  Thus, after obtaining the glass substrate 1 by the first etching, the glass substrate 1 is etched (second etching) in an etchant having a flow in the thickness direction of the glass substrate 1. In the second etching, the most projecting top portion 16 formed on the end surface 13 of the glass substrate 1 by the first etching is mainly etched.

  The second etching is performed in an etchant having a flow in the thickness direction of the glass substrate 1. For example, the glass substrate 1 after completion of the first etching is immersed in an etchant accommodated in an etching tank so that the main surface thereof is substantially parallel to the liquid surface, and the direction along the main surface of the glass substrate 1 Etching is performed by swinging in a direction substantially perpendicular to the direction (vertical direction). In this case, the glass substrate 1 is fixed to a work or the like installed in the etchant, and this work is moved up and down (oscillated) in the vertical direction. In the second etching, the glass substrate 1 may be laminated in the plate thickness direction, immersed in an etchant, and moved up and down (oscillated) in the vertical direction with respect to the direction along the main surface, or glass Without laminating the base material 1, one or a plurality of glass base materials 1 may be immersed in the etchant and moved vertically (oscillated) in the vertical direction with respect to the direction along the main surface.

  Or you may etch in the state which fixed the glass base material 1 using the apparatus shown in FIG. The apparatus shown in FIG. 3 includes an etching tank 21 having a baffle plate 22 attached to the lower portion thereof. The inner side is an etching region 24 and the outer side is an etchant storage region 23. In such an apparatus, an etchant is supplied from below the storage region 23, and an etchant is caused to flow from above the storage region 23 to the etching region 24, thereby creating a downflow of the etchant in the etching region 24. This is a flow in the thickness direction of the glass substrate 1. Thereby, the second etching can be performed on the glass substrate 1. Note that the etchant is discharged from below the etching region 24. The configuration shown in FIG. 3 is a so-called parallel down flow type configuration, but in the present invention, a parallel overflow type configuration may be used as long as a flow in the thickness direction of the glass substrate 1 can be created.

  In this second etching, the etching time is preferably 600 seconds or less, and the etchant flow rate is preferably 50 cm / second or less. Further, when the glass substrate 1 is swung up and down, the swing cycle is preferably 10 cycles / second or less. Moreover, it is preferable that the temperature of an etchant is 15 to 60 degreeC. Furthermore, in consideration of productivity, the second etching may be performed in a state where a plurality of glass substrates 1 are laminated.

  By performing such second etching (isotropic etching) on the top 16 of the end surface 13 of the glass substrate 1, an end surface shape as shown in FIG. 2 can be obtained. That is, the top 16 of the end face 13 can be obtuse (flattened) in a sectional view. The top portion 16 is preferably an edge where two layers are not cut from the surface in a sharp edge test according to UL-1439. More preferably, the top portion 16 is not cut at all layers by a sharp edge test according to UL-1439.

  In such a glass substrate 1, in the cross-sectional view of FIG. 1, from the top part 16 with respect to the first virtual line A connecting the two edge parts 14 and 15 constituted by the main surfaces 11 and 12 and the end face 13, respectively. The relationship between the shortest distance L and the thickness D of the glass substrate 1 satisfies L ≦ D / 2. Further, an angle α formed by two second virtual lines B connecting the two edge portions 14 and 15 and the top portion 16 is 90 ° or more and 180 ° or less.

  In such a glass substrate 1, since the top portion 16 has an obtuse angle, the glass substrate 1 is not damaged during handling or transportation, and chipping does not occur. In the glass substrate according to the present invention, after forming a resist pattern on the main surface of a plate-like glass substrate, the glass substrate is etched with an etchant capable of etching the glass substrate using the resist pattern as a mask. The end surface 13 of the glass substrate 1 is made of a molten glass surface, and the surface roughness (arithmetic average roughness Ra) at the end surface 13 is 10 nm or less. It has become. Thus, since the glass substrate according to the present invention forms an outer shape by etching, the end face 13 has very high smoothness, is composed of a molten glass surface, and is formed by machining. It becomes a state without microcracks that are always present on the end face, and exhibits high mechanical strength.

The mechanical strength of the glass substrate is preferably 5000 kgf / cm ² or more, more preferably 7000 kgf / cm ² or more, and most preferably 10000 kgf / cm ^{2 in} terms of three-point bending strength (three-point bending strength). The above is desirable.

  As the glass substrate 1, a glass body molded directly from a molten glass or a glass body molded to a certain thickness is cut out to a predetermined thickness, and the main surface is polished to a predetermined thickness. Things can be used. It is preferable to use what was directly molded into a sheet form from molten glass. This is because the main surface of the glass substrate molded directly from molten glass into a sheet is a hot-molded surface, and has a very high smoothness and a surface state without microcracks. Examples of a method for directly forming a sheet from molten glass include a downdraw method and a float method. Of these, the downdraw method is preferred. In addition to the effects such as high smoothness described above, when performing external processing by an etching process, using the resist pattern formed on both main surfaces of the glass substrate as a mask, when etching the glass substrate from both main surfaces, This is because etching can be performed uniformly from both main surfaces, so that the dimensional accuracy is good and the cross-sectional shape of the end face of the glass substrate is also good. The thickness of the glass substrate 1 is preferably 0.3 mm or greater and 1.3 mm or less.

Examples of the glass that can be formed into a glass plate by the downdraw method include aluminosilicate glass containing SiO ₂ , Al ₂ O ₃ , Li ₂ O and / or Na ₂ O. In particular, the aluminosilicate glass is composed of 62 wt% to 75 wt% SiO ₂ , 5 wt% to 15 wt% Al ₂ O ₃ , 4 wt% to 10 wt% Li ₂ O, 4 wt% to 12 wt%. Of Na ₂ O and 5.5 wt% to 15 wt% of ZrO ₂ , the weight ratio of Na ₂ O / ZrO ₂ is preferably 0.5 to 2.0, and Al ₂ O ₃ / weight ratio of ZrO ₂ it is preferred that the composition is 0.4 to 2.5.

SiO ₂ is a main component that forms a glass skeleton. Mobile devices, especially cover glasses for mobile phones, are used in extremely harsh environments such as touching human skin and contact with water and rainwater. It is necessary to have sex. The ratio of SiO ₂ is preferably 62% by weight to 75% by weight in consideration of the chemical durability and the melting temperature.

Al ₂ O ₃ is contained in order to improve the ion exchange performance on the glass surface. The proportion of Al ₂ O ₃ is preferably 5% by weight to 15% by weight in view of chemical durability and devitrification resistance.

Li ₂ O is an essential component for chemically strengthening glass by being ion-exchanged mainly with Na ions in the ion-exchange treatment bath at the glass surface layer. The ratio of Li ₂ O is preferably 4% by weight to 10% by weight in consideration of ion exchange performance, devitrification resistance and chemical durability.

Na ₂ O is an essential component when the glass is chemically strengthened by ion exchange with K ions in the ion exchange treatment bath at the glass surface layer. The ratio of Na ₂ O is preferably 4% by weight to 12% by weight in consideration of the mechanical strength, devitrification resistance, and chemical durability.

ZrO ₂ has the effect of increasing the mechanical strength. The ratio of ZrO ₂ is preferably 5.5% by weight to 15% by weight in consideration of chemical durability and stable production of homogeneous glass.

  Further, the above-described aluminosilicate glass can be further enhanced in mechanical strength by chemical strengthening by ion exchange treatment to form a compressive stress layer on the glass surface. Chemically strengthened glass refers to glass strengthened by replacing alkali metal ions constituting the glass with alkali metal ions having a size larger than that by ion exchange. Note that other multicomponent glass may be used instead of aluminosilicate glass. Further, crystallized glass may be used as long as the transparency necessary for the glass substrate is ensured.

In addition, as ion exchange treatment conditions, a single salt of potassium nitrate (KNO ₃ ), a single salt of sodium nitrate (NaNO ₃ ), and a mixed salt obtained by mixing potassium nitrate and sodium nitrate at an arbitrary weight ratio may be used. The temperature may be selected in the range of 350 ° C. to 450 ° C. and the time in the range of 1 hour to 20 hours.

Next, examples performed for clarifying the effects of the present invention will be described.
Example 1
First, SiO ₂ is 63.5% by weight, Al ₂ O ₃ is 8.2% by weight, Li ₂ O is 8.0% by weight, Na ₂ O is 10.4% by weight, and ZrO ₂ is 11.9% by weight. The aluminosilicate glass contained was formed into a plate-like glass substrate (sheet-like glass) having a plate thickness of 0.51 mm by the down draw method. The surface roughness (arithmetic mean roughness Ra) of the main surface of the sheet-like glass formed by this downdraw method was 0.2 nm when examined by an atomic force microscope.

Next, a negative type acid resistant resist was coated on both main surfaces of the sheet-like glass with a thickness of 32 μm, and this acid resistant resist was baked (prebaked) at 100 ° C. for 30 minutes. Next, the hydrofluoric acid resistant resist is exposed to energy of 300 mJ / cm ² from both sides through a photomask having a predetermined pattern, and the hydrofluoric acid resistant resist after the exposure is used with a developer (Na ₂ CO ₃ solution). Development was performed to form a resist pattern in which the hydrofluoric acid resistant resist remained in the region other than the region to be etched on the sheet-like glass. Further, the sheet-like glass on which the resist pattern was formed was baked (post-baked) at 250 ° C. for 30 minutes.

  Next, using a mixed acid aqueous solution (40 ° C.) of hydrofluoric acid (15% by weight) and sulfuric acid (24% by weight) as an etchant, using the resist pattern as a mask, sheet-like glass is etched from both main surface sides. One etching was performed and cut into a predetermined shape.

Next, this glass substrate is fixed to the work, and the work table which can be moved up and down is installed in an etching tank containing an etchant (a mixed acid aqueous solution (40 ° C.) of hydrofluoric acid (15 wt%) and sulfuric acid (24 wt%)). It mounted on the top and the 2nd etching was performed with respect to the glass base material by moving the work stand up and down. At this time, the work table was moved up and down so that the flow rate of the etchant was 2 cm / second, and the etching time was 240 seconds. Thereafter, the hydrofluoric acid resistant resist remaining on the glass was swollen using a NaOH solution, peeled off from the glass, and rinsed. Thus, the glass substrate of Example 1 was obtained. Further, in this molten salt, a ratio of sodium nitrate (NaNO ₃ ) and potassium nitrate (KNO ₃ ) (NaNO ₃ : KNO ₃ ) mixed at a weight ratio of 4: 6 is 380 ° C., 2 It was immersed for a period of time and subjected to ion exchange treatment for chemical strengthening.

  About the obtained glass base material, the shortest distance L from the top part 16 with respect to the 1st virtual line A which connects the two edge parts 14 and 15 in FIG. 1 was measured. In a cross-sectional view, an angle α formed by two second imaginary lines connecting the two edge portions 14 and 15 and the top portion 16 was measured. Furthermore, the bending strength measurement and the sharp edge test before and after chemical strengthening were performed. Prior to the measurement of the bending strength, the glass substrate was subjected to a cleaning treatment while applying a 40 kHz ultrasonic wave for 21 minutes (a scratch treatment). The results are shown in Table 1 below.

In addition, as shown in FIG. 4A, the bending strength measurement is performed by placing the glass substrate 1 on two supports (fulcrum points) 25 and 26 arranged at a fixed distance, and centering between the supports 25 and 26. The load was applied to one of the points via the load body 27, and the maximum bending stress at the time of failure was measured. Since the three-point bending strength depends on the distance between the fulcrums, the substrate width, and the substrate thickness, normalization was performed using the following equation.
σ = (3PL) / (2 wt ² )
Here, σ indicates the three-point bending strength (kgf / cm ² ), P indicates the maximum load (kgf) when the glass substrate breaks, and L indicates the distance (cm) between the supports 25 and 26. 4 indicates the glass substrate width (cm) as shown in FIG. 4B, and t indicates the thickness (cm) of the glass substrate as shown in FIG. 4B.

  The sharp edge test was conducted by using a sharp edge tester SET-50 manufactured by Excel Corporation and a tape kit TC-3 by a method based on UL-1439 (determination of the sharpness of the edge of the device). As shown in FIG. 5, the tape kit TC-3 is a kit having three layers of tapes 31 to 33 on the head 34 having a diameter of 12.7 mm and assuming the softness of the fingers. The tester SET-50 is a tool for pressing it against the edge to be measured with a constant load. Specifically, the tape kit TC-3 attached to the sharp edge tester SET-50 is brought into contact with the edge to be measured (the edge portion of the glass substrate) with a constant load (the arrow direction in FIG. 5: 6.67N). While maintaining the load, the tape kit TC-3 is moved back and forth 100 mm (one way 50 mm) along the edge portion.

(Example 2)
In the second etching, the glass substrate of Example 2 was obtained in the same manner as in Example 1 except that the work table was moved up and down so that the flow rate of the etchant was 6 cm / second and the etching time was 240 seconds. In addition, the glass substrate of Example 2 was chemically strengthened against the glass substrate under the same conditions as in Example 1. About the obtained glass substrate, the shortest distance L and the angle α formed by the two second imaginary lines were measured, and the bending strength measurement and the sharp edge test before and after chemical strengthening were performed. The results are also shown in Table 1 below.

(Example 3)
In the second etching, the glass base of Example 3 was obtained in the same manner as in Example 1 except that the work table was moved up and down so that the etchant flow rate was 30 cm / second and the etching time was 240 seconds. In addition, the glass substrate of Example 3 was chemically strengthened against the glass substrate under the same conditions as in Example 1. About the obtained glass substrate, the shortest distance L and the angle α formed by the two second imaginary lines were measured, and the bending strength measurement and the sharp edge test before and after chemical strengthening were performed. The results are also shown in Table 1 below.

(Comparative example)
Without performing the second etching, the glass substrate cut out to a predetermined shape by the first etching, the hydrofluoric acid resist remaining on the glass substrate using a NaOH solution is swollen and peeled from the glass substrate, The glass substrate of the comparative example was obtained in the same manner as in Example 1 after rinsing. Further, the glass substrate of the comparative example was chemically strengthened with respect to the glass substrate under the same conditions as in Example 1. About the obtained glass substrate, the shortest distance L and the angle α formed by the two second imaginary lines were measured, and the bending strength measurement and the sharp edge test before and after chemical strengthening were performed. The results are also shown in Table 1 below.

As can be seen from Table 1, the glass substrates of Examples 1 to 3 have a short distance L, an angle α to be formed is an obtuse angle, and less than half the thickness of the glass substrate. Moreover, the three-point bending strength (three-point bending strength) was 5000 kgf / cm ² or more, and the mechanical strength was high. This is because the top part is blunted by the second etching, and there is nothing that becomes the starting point of cleaving even if the scratch treatment is performed, so it is considered that the three-point bending strength (three-point bending strength) is increased. On the other hand, the glass base material of the comparative example has a long distance L, the angle α formed is an acute angle, and exceeds half of the thickness of the glass base material, so that the top is sharp and the sharp edge test was rejected. . Also, the three-point bending strength (three-point bending strength) was far below 5000 kgf / cm ² . This is because the top portion is sharp because there is no second etching, and there are some that become the starting point of cleavage by the scratching process, so the three-point bending strength (three-point bending strength) is considered to be low.

  The present invention is not limited to the above embodiment, and can be implemented with appropriate modifications. For example, the materials, processing procedures, and the like in the above-described embodiment are merely examples, and various modifications can be made within the scope of the effects of the present invention. In addition, various modifications can be made without departing from the scope of the object of the present invention.

It is a figure which shows a part of glass base material after a 1st etching. It is a figure which shows a part of glass base material after a 2nd etching. It is a figure which shows an example of the apparatus used for the manufacturing method of the glass base material which concerns on this invention. It is a figure for demonstrating a bending strength measuring apparatus. It is a figure for demonstrating a sharp edge test. It is a figure for demonstrating the edge of a glass base material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass base material 11,12 Main surface 13 End surface 14,15 Edge part 16 Top part 17 Resist pattern 25,26 Support body 27 Load body 31-33 Tape 34 Head

Claims (8)

  A glass substrate that is cut out into a desired shape by etching a plate-like glass substrate and has a pair of main surfaces and end surfaces, and is constituted by the main surfaces and the end surfaces in a cross-sectional view. The relationship between the shortest distance L from the top portion that protrudes most on the end surface and the thickness D of the glass substrate with respect to the first imaginary line connecting two edge portions satisfies L ≦ D / 2. Glass substrate to be used.   The glass substrate according to claim 1, wherein the glass substrate has a thickness of 0.3 mm or more and 1.3 mm or less.   3. The angle α formed by two second imaginary lines connecting the two edge portions and the top portion in the cross-sectional view is 90 ° or more and 180 ° or less. 3. The glass substrate as described. The glass substrate is an aluminosilicate glass containing at least one selected from the group consisting of SiO ₂ , Al ₂ O ₃ , Li ₂ O and Na ₂ O. 4. The glass substrate according to any one of 3.   The glass substrate according to any one of claims 1 to 4, wherein the glass substrate is glass chemically strengthened by an ion exchange treatment.   Using the resist pattern formed on the main surface of the plate-like glass substrate as a mask, and first etching the glass substrate with an etchant capable of etching the glass substrate to obtain a glass substrate by cutting it into a desired shape; And a second etching process of the glass substrate in an etchant having a flow in the thickness direction of the glass substrate.   The method for producing a glass substrate according to claim 6, wherein the second etching mainly etches the most protruding top portion formed on the end surface of the glass substrate by the first etching.   The method for producing a glass substrate according to claim 6 or 7, wherein the glass substrate is chemically strengthened by ion exchange treatment after being cut into the desired shape.

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