Glass plate manufacturing method

Abstract

According to the present invention, a concave line RL formed on a mother glass G comprises a protruding section 7a formed in an end section RLa in the width direction Y of the convex line RL. The protruding section 7a includes: a first base section 8a positioned on a central side in the width direction Y of the convex line RL; and a second base section 8b positioned on the opposite side to the first base section 8a. In this method for manufacturing a glass plate, a scratch is caused in at least one among the first base section 8a and the second base section 8b in an initial crack forming step S2.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a glass sheet. [Background technology]

[0002] When producing glass plates for panel displays such as liquid crystal displays and organic EL displays, for example, large mother glass formed by a forming method such as down-draw is cut to form glass plates of a predetermined size.

[0003] Patent Document 1 discloses a method for manufacturing a glass plate, which includes a recessed line forming step of forming a recessed line on the surface of mother glass by plastic deformation, an initial crack forming step of forming an internal initial crack at a position corresponding to the recessed line, a crack propagation step of propagating the internal initial crack inside the mother glass along the recessed line, and a bending and breaking step of bending and breaking the mother glass along the recessed line.

[0004] In this manufacturing method, the recessed line formed in the recessed line forming step includes a compressive stress layer formed by plastic deformation and a tensile stress layer formed closer to the interior of the mother glass than the compressive stress layer.

[0005] In the initial crack formation process, a scribe wheel is brought into contact with the surface of the mother glass and moved in a direction intersecting the concave line. This forms a scribe line intersecting the concave line on the mother glass. An internal initial crack is formed in the tensile stress layer starting from this scribe line (see paragraphs 0030, 0031 and FIG. 8 of the same document).

[0006] In the crack propagation step, a crack originating from the internal initial crack propagates in the tensile stress layer of the concave line, and then a bending step is carried out to produce a glass sheet free from lateral cracks on the edge surfaces. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-89672 Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, in conventional glass plate manufacturing methods, scribe lines are formed on the mother glass using a scribing wheel to form internal initial cracks. Because the scribe lines contain many lateral cracks, in the bending and splitting step, the portion of the mother glass where the scribe lines are formed must be separated from the glass plate and discarded.

[0009] As described above, conventional glass plate manufacturing methods require a portion of the mother glass where a scribe line is formed, and this portion must be discarded, resulting in a decrease in the yield of the glass plate.

[0010] The present invention has been made in view of the above circumstances, and has as its technical object to cut mother glass in a manner that prevents lateral cracks from occurring on the cut surface, and to improve the yield of glass plates. [Means for solving the problem]

[0011] The present invention has been made to solve the above-mentioned problems, and provides a method for manufacturing a glass plate, which includes a cutting step of cutting a mother glass, wherein the cutting step includes a recessed line forming step of forming a recessed line on the surface of the mother glass by plastic deformation, an initial crack forming step of forming an initial crack in the recessed line, and a crack propagation step of propagating the initial crack along the recessed line inside the mother glass, wherein the recessed line includes a protrusion formed at an end of the recessed line in a width direction, and the protrusion includes a first base located on the central side of the recessed line in the width direction, and a second base located on the opposite side from the first base, and the initial crack forming step includes scratching at least one of the first base and the second base.

[0012] According to the above method, in the recessed line forming step, a recessed line without lateral cracks can be formed by plastically deforming the surface of the mother glass, and in the initial crack forming step, an initial crack can be formed in the protrusion by scratching at least one of the first base and the second base of the protrusion.

[0013] Therefore, in the present invention, it is not necessary to form a scribe line that intersects with the recessed line using a scribing wheel as in the conventional method. In the crack propagation step, a crack originating from an initial crack is propagated along the recessed line, thereby making it possible to produce a glass sheet that does not have lateral cracks on the edge surface (cut surface).

[0014] In this way, in the present invention, the mother glass can be cut without forming a scribe line that intersects with the recessed line, which makes it possible to reduce the amount of glass waste in the cutting process as much as possible, thereby improving the yield of the glass plate.

[0015] In this method, the protrusion includes a first protrusion located at one end of the recessed line in the width direction and a second protrusion located at the other end of the recessed line in the width direction, and in the initial crack formation process, the scratch may be made on the first protrusion or the second protrusion.

[0016] In the initial crack forming step, the scratch may be made in the protrusion along the width direction of the recessed line, thereby making it possible to easily form an initial crack in the protrusion.

[0017] In the initial crack forming step, the scratch may be created by bringing a pointed tool into contact with at least one of the first base portion and the second base portion, thereby making it possible to reliably form an initial crack in the protrusion.

[0018] In the initial crack forming step, the tool may be vibrated, thereby making it possible to reliably form an initial crack in the protrusion. [Effects of the Invention]

[0019] According to the present invention, it is possible to cut a mother glass so as not to generate lateral cracks on the cut surface, and to improve the yield of glass plates. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a perspective view of a scribe tip. [Figure 2] FIG. 2 is a plan view of a scribe tip. [Figure 3] FIG. 2 is a side view of the scribe tip. [Figure 4] 1 is a flowchart showing a method for manufacturing a glass plate. [Figure 5] FIG. 4 is a plan view illustrating a recessed line forming step in the manufacturing method of the glass plate. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. [Figure 7] FIG. 2 is an enlarged cross-sectional view of a main part of the mother glass plate. [Figure 8] FIG. 2 is a cross-sectional view showing an initial crack formation step in the method for manufacturing a glass plate. [Figure 9] FIG. 2 is a plan view illustrating a crack propagation step in the method for manufacturing a glass plate. [Figure 10] FIG. 2 is a cross-sectional view showing a crack propagation step in the method for manufacturing a glass plate. [Figure 11] FIG. 2 is a perspective view showing a crack propagation step in the method for manufacturing a glass plate. [Figure 12] FIG. 2 is a cross-sectional view showing a bending step in the manufacturing method of a glass plate. [Figure 13] FIG. 2 is a perspective view of a manufactured glass plate. [Figure 14] FIG. 10 is a plan view of the mother glass to be cut in the cutting step. [Figure 15] FIG. 1 is a plan view of a mother glass cut by a conventional method. [Figure 16] FIG. 10 is a cross-sectional view showing another example of the initial crack formation step in the method for producing a glass plate. DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF THE INVENTION Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figures 1 to 14 show an embodiment of the method for producing a glass plate according to the present invention.

[0022] 1 to 3 show a scribe tip used to form recessed lines in a mother glass in this method. In this embodiment, a pencil-shaped scribe tip 1 is shown as an example, but the configuration of the scribe tip is not limited to this embodiment. The scribe tip 1 has a shank 2 and a tip 3 fixed to the end of the shank 2.

[0023] The shank 2 is made of metal and is configured in a cylindrical or polygonal prism shape. The shank 2 is attached to a holder H. The holder H holds the shank 2 and moves the scribe tip 1 vertically and horizontally. The holder H can also freely change the inclination angle of the shank 2 relative to the mother glass G.

[0024] The tip 3 is made of, for example, a single-crystal or polycrystalline diamond tip, but is not limited to this and may be made of PCBN, ceramic, cemented carbide, or other metals. The tip 3 is fixed to the tip of the shank 2 with an adhesive, brazing material, or the like. The tip 3 is configured in the shape of a truncated cone, and a pressing portion 4 that comes into contact with the mother glass G is formed at its end. In other words, the edge of the axial end face 3a of the tip 3 forms the pressing portion 4.

[0025] The pressing portion 4 is configured in an arc shape so as to prevent lateral cracks from occurring in the mother glass G. The pressing portion 4 presses the surface of the mother glass G to plastically deform it, and forms a recessed line RL in this plastically deformed portion. The radius (curvature radius) of the pressing portion 4 is preferably 0.001 mm to 1 mm, and more preferably 0.025 mm to 0.5 mm.

[0026] This circular pressing portion 4 can be considered to be made up of a plurality of arcs. For example, as shown in Fig. 2, the pressing portion 4 is virtually made up of three arcs 4a to 4c. In this example, the central angle θa of each of the arcs 4a to 4c is set to 120°, but is not limited to this and is preferably set to 5° to 120°. Note that although the central angle θa of each of the arcs 4a to 4c is set to be equal, these may be configured to have different angles.

[0027] As shown in FIG. 3, the mother glass G used in this method has a first principal surface Ga and a second principal surface Gb, which are opposite surfaces, and an end surface Gc connecting the first principal surface Ga and the second principal surface Gb. In the present invention, at least one of the first principal surface Ga or the second principal surface Gb is referred to as the "surface" of the mother glass G. In this embodiment, the thickness t of the mother glass G is preferably 0.01 mm to 1 mm, and more preferably 0.01 mm to 0.7 mm. The mother glass G has a side length of 1000 mm or more, but is not limited to this dimension.

[0028] The mother glass G can be formed by various known forming methods such as the float method, roll-out method, slot downdraw method, and redraw method, but is preferably formed by the overflow downdraw method. The overflow downdraw method involves pouring molten glass into an overflow groove provided at the top of a forming body having a generally wedge-shaped cross section, allowing the molten glass to overflow on both sides of the overflow groove to flow down along both sidewalls of the forming body and fuse together at the lower end of the forming body, thereby continuously forming a single ribbon-shaped glass. A rectangular mother glass G is formed by cutting a portion of the ribbon-shaped glass in the width direction.

[0029] A method for producing a glass plate will be described below. In this example, a rectangular glass plate will be produced from a rectangular mother glass G made of alkali-free glass (OA-10G manufactured by Nippon Electric Glass Co., Ltd.).

[0030] This method includes a cutting step of cutting the mother glass G. As shown in Fig. 4, the cutting step includes a recessed line forming step S1 of forming a recessed line RL by plastic deformation on the surface (e.g., the first main surface Ga) of the mother glass G using a scribe tip 1, an initial crack forming step S2 of forming an initial crack in the recessed line RL, a crack propagation step S3 of propagating the initial crack along the recessed line RL into the mother glass G, and a bending / splitting step S4 of applying a bending stress to the mother glass G.

[0031] In the recessed line forming step S1, first, the mother glass G is placed on a mounting table (not shown), and the scribe tip 1 is brought into contact with the first main surface Ga of the mother glass G. It is preferable that a resin sheet is placed on the mounting table, and the mother glass G is placed on this resin sheet. The scribe tip 1 is supported by a holder H so that the shank 2 is inclined relative to the mother glass G. When the shank 2 is inclined toward the moving direction X, the inclination angle θb (see FIG. 3) is preferably 30° to 85°, but is not limited to this range.

[0032] Thereafter, a load is applied to the scribe tip 1, and the tip 3 is slid along the moving direction X as shown in FIG. 5 while pressing the first main surface Ga of the mother glass G with the pressing portion 4 of the tip 3. The moving speed of the scribe tip 1 is preferably 50 mm / s to 1500 mm / s. The load applied to the scribe tip 1 is 0.1 N to 10 N, but is not limited to this range and is appropriately set depending on the size, thickness, material, and other conditions of the mother glass G. The pressing portion 4 (part of the arc 4a) is arranged in a direction perpendicular to the moving direction X (so that the tangent to the arc 4a is perpendicular to the moving direction X) (see FIG. 2).

[0033] A portion of the first principal surface Ga is plastically deformed by the pressure of the pressing unit 4. As shown in FIG. 5, a linear recessed line RL is formed in the plastically deformed portion of the first principal surface Ga by the movement of the pressing unit 4. Hereinafter, the direction perpendicular to the longitudinal direction (movement direction X) of the recessed line RL is referred to as the width direction Y of the recessed line RL. The width dimension W1 (see FIG. 6) of the recessed line RL in the width direction Y is preferably 10 μm to 50 μm. The depth of the recessed line RL is preferably 0.3 μm to 1.0 μm.

[0034] As shown in FIG. 6, the recessed line RL includes a compressive stress layer 5, a tensile stress layer 6, and protrusions 7a and 7b.

[0035] The compressive stress layer 5 is formed by plastic deformation of the first main surface Ga of the mother glass G. The tensile stress layer 6 is formed closer to the interior of the mother glass G than the compressive stress layer 5. The tensile stress layer 6 is covered with the compressive stress layer 5.

[0036] The protrusions 7a, 7b are formed at the ends RLa, RLb of the recessed line RL in the width direction Y. The protrusions 7a, 7b protrude from the first main surface Ga due to plastic deformation of the mother glass G. The protrusion amount (height from the first main surface Ga) h of the protrusions 7a, 7b is preferably 0.01 μm to 0.10 μm. The protrusions 7a, 7b are formed over the entire length of the recessed line RL. The protrusions 7a, 7b include a portion 5a of the compressive stress layer 5 and a portion 6a of the tensile stress layer 6.

[0037] The protrusions 7a, 7b include a first protrusion 7a formed at one end RLa of the recessed line RL in the width direction Y, and a second protrusion 7b formed at the other end RLb of the recessed line RL in the width direction Y. Each of the protrusions 7a, 7b includes a first base 8a located on the center (bottom) side of the recessed line RL in the width direction Y, and a second base 8b located on the opposite side to the first base 8a in the width direction Y. The width dimension W2 (the distance from the first base 8a to the second base 8b) of each of the protrusions 7a, 7b in the width direction Y of the recessed line RL is preferably 2 μm to 10 μm.

[0038] 7, the first base portion 8a and the second base portion 8b are relaxation layers in which compressive stress is relaxed. It is presumed that slight compressive stress or tensile stress acts on these relaxation layers, or that the compressive stress and the tensile stress are substantially cancelled out. The width dimension W3 of these relaxation layers, i.e., the width dimension of the first base portion 8a and the second base portion 8b that can be scratched, is, for example, 1 μm or less.

[0039] 8, in the initial crack formation step S2, the protrusions 7a and 7b are scratched with a pointed tool 9 so as to form initial cracks in the tensile stress layer 6a at the positions of the protrusions 7a and 7b. As the pointed tool 9, for example, a diamond tip or a cemented carbide tool can be used. More specifically, an electroplated diamond file or a cemented carbide scribing tool can be used.

[0040] In this embodiment, an example is shown in which only the first protrusion 7a is scratched, but this is not limiting, and only the second protrusion 7b, or both the first protrusion 7a and the second protrusion 7b may be scratched.

[0041] Specifically, in the initial crack formation step S2, the tip of the tool 9 is brought into contact with the first base portion 8a of the first protrusion 7a, and then moved toward the second base portion 8b along the width direction Y of the recessed line RL. In this case, the tool 9 may be rotated about its axis, or may be vibrated. From the perspective of reliably forming an initial crack, it is preferable to vibrate the tool 9. In this case, the tool 9 may be vibrated with an amplitude of 10 μm to 15 μm and a frequency of 100 Hz to 300 Hz, for example, and brought into contact with the first base portion 8a and the second base portion 8b several to several hundred times.

[0042] This movement of the tool 9 causes scratches to form in the first protrusion 7a. These scratches are formed in the first base 8a and second base 8b, which are the relaxation layers of the first protrusion 7a, but are not formed in the compressive stress layer 5a between the first base 8a and second base 8b. Hereinafter, the scratches formed in the first base 8a and second base 8b, which are the relaxation layers of the first protrusion 7a, will be referred to as initial cracks FC.

[0043] In the crack propagation step S3, a crack propagates from the initial crack FC in the tensile stress layer 6. The initial crack FC in the second base portion 8b propagates along the width direction Y of the recessed line RL, crosses the first protrusion 7a, and reaches the first base portion 8a due to the action of the stress remaining in the tensile stress layer 6, as shown by arrow A1 in Figures 9 and 10. The crack that has reached the first base portion 8a or the initial crack FC in the first base portion 8a propagates along the compressive stress layer 5a toward the center (bottom) of the width direction Y of the recessed line RL due to the action of the stress remaining in the tensile stress layer 6, as shown by arrow A2 in Figures 9 and 10.

[0044] When the crack reaches a position corresponding to the bottom of the concave line RL, it propagates along the longitudinal direction of the concave line RL as shown by arrow A3 in Figures 9 and 11. In Figures 10 and 11, the crack that has reached a position corresponding to the bottom of the concave line RL is indicated by symbol C (same in Figure 12).

[0045] In the crack propagation step S3, an external force F1 (see FIG. 11) may be applied to the mother glass G to increase the propagation speed of the crack C. This external force F1 generates bending stress in the mother glass G across the concave line RL, causing the crack C to propagate faster inside the mother glass G. The external force F1 is adjusted so that the crack C does not propagate in the thickness direction of the mother glass G.

[0046] When the crack C has finished propagating along the concave line RL, the bending / breaking step S4 is performed. As shown in Fig. 12, in the bending / breaking step S4, an external force F2 is applied to the mother glass G in order to propagate the crack C in the thickness direction of the mother glass G.

[0047] This external force F2 is set to be larger than the external force F1 applied to the mother glass G in the crack propagation step S3. The external force F2 generates a bending stress in the mother glass G across the recessed line RL.

[0048] The cracks C propagate in the thickness direction of the mother glass G due to the action of this bending stress. When the cracks C reach the first main surface Ga and the second main surface Gb, the mother glass G is divided. As a result, a glass plate G1 is formed.

[0049] As shown in FIG. 13 , the glass sheet G1 has a first main surface G1a, a second main surface G1b located on the opposite side of the first main surface G1a, and an end surface G1c connecting the first main surface G1a and the second main surface G1b. Furthermore, the glass sheet G1 has a curved surface CS and a protrusion 7 (first protrusion 7a or second protrusion 7b) that are traces of the concave line RL at the boundary B between the first main surface G1a and the end surface G1c. Because the curved surface CS and the protrusion 7 are free of lateral cracks, the glass sheet G1 has high mechanical strength even without grinding. Additionally, the glass sheet G1 has a compressive stress layer 5 formed along the curved surface CS and a tensile stress layer 6 located more inward than the compressive stress layer 5.

[0050] The effect of improving the yield by the method for manufacturing a glass plate G1 according to this embodiment will be described below with reference to Fig. 14 and Fig. 15. Fig. 14 shows a rectangular mother glass cut by the method for manufacturing a glass plate according to this embodiment. Fig. 15 shows a rectangular mother glass cut by forming a scribe line with a scribing wheel as in the conventional method.

[0051] 14 and 15, the recessed line forming step S1 forms four recessed lines RL1 to RL4 on the first main surface Ga at positions inside the edge surfaces Gc of the four sides of the mother glass G. Hereinafter, the recessed lines RL1 to RL4 will be referred to as the first recessed line RL1, the second recessed line RL2, the third recessed line RL3, and the fourth recessed line RL4, respectively. The first recessed line RL1 is parallel to the second recessed line RL2 and perpendicular to the third recessed line RL3 and the fourth recessed line RL4.

[0052] 15 illustrates an example in which an initial crack is formed in the first recessed line RL1 and the second recessed line RL2. In this case, the scribing wheel 10 contacts the first main surface Ga at a position outside the third recessed line RL3 (toward the end face Gc) and moves perpendicular to the first recessed line RL1 and the second recessed line RL2. The cutting depth of the scribing wheel 10 is set so that the scribing wheel 10 reaches the tensile stress layer of the recessed line RL.

[0053] As the scribing wheel 10 moves, a scribe line SL parallel to the third recessed line RL3 is formed on the mother glass G. This scribe line SL contains numerous lateral cracks. For this reason, the scribe line SL must be formed at a position sufficiently far from the third recessed line RL3 so that cracks originating from these lateral cracks do not propagate toward the third recessed line RL3. Therefore, in order to form the scribe line SL, the dimensions L11 and L21 of each side of the mother glass G necessarily become large.

[0054] In contrast to this, in the initial crack formation step S2 of this embodiment, the initial crack formed by the pointed tool 9 includes a lateral crack, but is mainly formed in the first base portion 8a and / or the second base portion 8b, which are the relaxation layers. Therefore, in the initial crack formation step S2, it is possible to form an initial crack in the vicinity of an intersection P (see FIG. 14) of each of the recessed lines RL1 to RL4, which becomes a corner of the glass plate G1.

[0055] Therefore, in the method for manufacturing the glass sheet G1 according to this embodiment, when manufacturing a glass sheet G1 of the same dimensions, it is possible to reduce the dimensions L1 and L2 of each side of the mother glass G compared to conventional manufacturing methods. That is, in the present invention, the amount of glass discarded in the cutting process can be reduced compared to conventional manufacturing methods. This can improve the yield of the glass sheet G1.

[0056] The present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. The present invention can be modified in various ways without departing from the spirit of the present invention.

[0057] In the above embodiment, an example has been shown in which a straight recessed line RL is formed in the mother glass G in the recessed line forming step S1, but the present invention is not limited to this. In the recessed line forming step S1, a curved recessed line or a circular recessed line may be formed in the mother glass G.

[0058] In the above embodiment, the initial crack FC is formed by moving the pointed tool 9 from the first base 8a to the second base 8b of the first protrusion 7a in the initial crack formation step S2, but the present invention is not limited to this. As shown in Fig. 16, the initial crack formation step S2 may also be performed by bringing the tool 9 into contact with two locations, the first protrusion 7a and the second protrusion 7b, to form multiple initial cracks FC. Alternatively, the initial crack FC may be formed by moving the tool 9 from the second base 8b of the protrusion 7 toward the first base 8a.

[0059] Furthermore, in the initial crack formation step S2, the initial crack FC may be formed only in the first base portion 8a, or may be formed only in the second base portion 8b. That is, in the initial crack formation step S2, it is sufficient to scratch at least one of the first base portion 8a and the second base portion 8b. From the viewpoint of improving manufacturing efficiency, it is preferable to scratch at least one of the first base portion 8a and the second base portion 8b. Note that when forming the initial crack FC only in the first base portion 8a, scratches may be formed on the first main surface Ga in the periphery of the first base portion 8a (for example, within 50 μm from the first base portion 8a, preferably within 30 μm from the first base portion 8a, and more preferably within 20 μm from the first base portion 8a). From the viewpoint of preventing scratches from being formed on the first main surface Ga, it is preferable to form the initial crack FC only in the first base portion 8a.

[0060] In the above embodiment, an example of cutting a single layer of mother glass G is shown, but this is not limited to this, and the present method can also be applied to cutting a glass laminate made by stacking multiple mother glasses, or a glass resin laminate made by stacking mother glass and a resin plate.

[0061] In the initial crack formation step S2 in the above embodiment, the tip of the tool 9 is brought into contact with the first base 8a of the first protrusion 7a and then moved toward the second base 8b along the width direction Y of the recessed line RL, vibrating the tool 9 during this process. However, the tool 9 does not necessarily have to be moved or vibrated. For example, the tool 9 may be positioned above the first base 8a or the second base 8b of the first protrusion 7a, and then dropped to bring the tip of the tool 9 into contact with the first base 8a or the second base 8b of the first protrusion 7a, thereby forming the initial crack FC. In this case, the kinetic energy of the tip of the tool 9 when it comes into contact with the first protrusion 7a or the like is preferably, for example, 0.013 J or more. [Explanation of symbols]

[0062] 7a First protrusion 7b Second protrusion 8a First base 8b Second base 9 Pointed tools FC initial crack G Mother Glass G1 glass plate RLa Width direction edge of concave line RLb Width direction end of concave line S1 Concave line forming process S2 Initial crack formation process S3 Crack propagation process Y Width direction of concave line

Claims

1. A method for manufacturing a glass plate, comprising a cutting step of cutting a mother glass, the cutting step includes a recessed line forming step of forming a recessed line on the surface of the mother glass by plastic deformation, an initial crack forming step of forming an initial crack on the recessed line, and a crack propagation step of propagating the initial crack inside the mother glass along the recessed line, the recessed line includes a protrusion formed at an end of the recessed line in a width direction, the protrusion includes a first base portion located on a central side of the recessed line in the width direction, and a second base portion located on an opposite side to the first base portion, the first base portion and the second base portion are relaxation layers in which compressive stress is relaxed, A method for manufacturing a glass plate, characterized in that in the initial crack formation process, a pointed tool is brought into contact with at least one of the first base portion and the second base portion, thereby scratching at least one of the first base portion and the second base portion.

2. the protrusion includes a first protrusion located at one end of the recessed line in the width direction and a second protrusion located at the other end of the recessed line in the width direction, The method for manufacturing a glass plate according to claim 1 , wherein in the initial crack formation step, the scratch is formed on the first protrusion or the second protrusion.

3. The method for manufacturing a glass plate according to claim 1 or 2, wherein in the initial crack forming step, the scratch along the width direction of the recessed line is formed on the protrusion.

4. The method for manufacturing a glass plate according to claim 1 , wherein the initial crack forming step includes vibrating the tool.

5. A method for manufacturing a glass plate described in any one of claims 1 to 4, wherein in the initial crack formation process, the scratch is not formed in the compressive stress layer between the first base and the second base.

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