Method for manufacturing glass sheet

Abstract

A method for manufacturing a glass plate comprises: an initial crack forming step, in which an initial crack (2) serving as a starting point for cutting is formed on a bent mother glass plate (1); and a laser irradiation step, in which a laser (4) is irradiated from a laser head (3) onto the mother glass plate (1), thereby causing a crack (5) to develop along a predetermined cutting line (6) starting from the initial crack (2). In the method for manufacturing a glass plate, in the laser irradiation step, a laser (4) is used to heat the surface layer and the interior of the mother glass plate (1), and under the action of the thermal shock accompanying the irradiation of the laser (4), the crack (5) is developed along the predetermined cutting line (6) and in the thickness direction of the mother glass plate (1), thereby cutting the mother glass plate (1).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a glass sheet. Background Art

[0002] As cover glass for smartphone displays, car displays, etc., a 3D-shaped glass plate that is curved vertically and horizontally is sometimes used. When manufacturing such a glass plate, as an example, it is cut out from a curved mother glass plate (a glass plate including a 3D-shaped glass plate corresponding to a plurality of surfaces) that is a raw material of the glass plate.

[0003] Here, as one of methods for cutting a glass plate, laser cutting as disclosed in Patent Document 1 is known.

[0004] In laser cutting, when cutting a glass plate along a predetermined cutting line, first, an initial crack is formed on the glass plate using a diamond cutter or the like, which serves as the starting point for cutting. Then, a carbon dioxide gas laser is irradiated from a laser head onto the glass plate, and a coolant (air, etc.) is sprayed toward the portion heated by the laser irradiation. At this time, the glass plate is cut by causing a crack to develop along the predetermined cutting line starting from the initial crack under the action of the thermal shock applied to the glass plate.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-116611 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, when the above-mentioned curved mother glass sheet is cut, when the laser cutting method of the above-mentioned method is used, the following problems to be solved occur.

[0010] That is, if the mother glass sheet is irradiated with a carbon dioxide laser, only the surface portion of the mother glass sheet (the surface portion on the laser incident surface side) is heated by the laser. In the carbon dioxide laser that can only heat the surface portion, the range of irradiation conditions that can cut the entire thickness of the mother glass sheet is extremely narrow. For example, as long as the distance between the laser head and the mother glass sheet is slightly deviated from the optimal distance, the thermal shock will be insufficient and cutting will become difficult. Therefore, from the start to the completion of the cutting of the bent mother glass sheet, it is very difficult to maintain the laser irradiation conditions to the conditions that can achieve cutting of the entire thickness. As a result of the difficulty in cutting the entire thickness as described above, additional breaking is required for cutting the mother glass sheet, and there is a problem that the properties of the cut surface of the glass sheet cut from the mother glass sheet are easily deteriorated.

[0011] The present invention has been made in view of the above circumstances and has as its technical object to improve the properties of a cut surface of a glass sheet cut out from a mother glass sheet when the bent mother glass sheet is cut by laser cleaving.

[0012] Solutions to Solve Problems

[0013] The manufacturing method of the glass plate of the present invention for solving the above-mentioned problems comprises: an initial crack forming step, in which an initial crack serving as a starting point for cutting is formed in a bent mother glass plate; and a laser irradiation step, in which a laser is irradiated from a laser head to the mother glass plate, thereby causing the crack to develop along a predetermined cutting line starting from the initial crack. The manufacturing method of the glass plate is characterized in that, in the laser irradiation step, a laser is used to heat the surface and the interior of the mother glass plate, and the crack is caused to develop along the predetermined cutting line and in the thickness direction of the mother glass plate under the action of the thermal shock accompanying the irradiation of the laser, thereby cutting the mother glass plate.

[0014] In the present method, in the laser irradiation step, a laser that heats the surface layer and the inside of the mother glass plate is used. In such a laser that can heat the inside in addition to the surface layer, a thermal shock can be applied not only to the surface layer but also to the inside, so the range of laser irradiation conditions that can cut the entire thickness of the mother glass plate is wide. As a result, from the start to the completion of the cutting of the bent mother glass plate, the laser irradiation conditions can be easily maintained to the conditions that can cut the entire thickness. Therefore, the entire thickness of the mother glass plate can be cut without difficulty in the entire section of the predetermined cutting line. As a result, the properties of the cut surface of the glass plate cut from the mother glass plate can be improved.

[0015] In the above method, it is preferable that, in the laser irradiation step, the laser head and the mother glass sheet are relatively moved while keeping the inclination of the axis of the laser head constant.

[0016] As described above, the range of irradiation conditions under which the entire thickness of the mother glass sheet can be cut in the laser that heats the surface layer and the inside of the mother glass sheet is wide. Therefore, when cutting the mother glass sheet, when the laser head and the mother glass sheet are relatively moved and the curved mother glass sheet is scanned by the laser, the entire thickness can be cut even without changing the inclination of the axis of the laser head to match the bending. Therefore, the inclination of the axis can be constant, so there is no need for a mechanism for changing the inclination of the axis of the laser head, so that the equipment cost can be reduced. In addition, as there is no need to change the inclination of the axis, the time required for cutting the mother glass sheet can be shortened.

[0017] In the above method, it is preferable that, in the laser irradiation step, the laser head and the mother glass sheet are relatively moved while keeping the position of the laser head in the axial direction thereof constant.

[0018] In the above-mentioned laser, as described above, the range of irradiation conditions that can cut the entire thickness of the mother glass plate is wide. Therefore, when cutting the mother glass plate, even if the axial position of the laser head is not changed in accordance with the bending of the mother glass plate, it is possible to cut the entire thickness. Therefore, the axial position can be set to be constant, so there is no need for a mechanism for changing the axial position, so that the equipment cost can be further reduced. In addition, since there is no need to change the axial position, the time required for cutting the mother glass plate can be further shortened.

[0019] In the above method, preferably, in the laser irradiation step, a CO laser is used as the laser.

[0020] In this way, the CO laser has high output and can be stably irradiated to the mother glass sheet, so that a crack can be stably developed along the planned cutting line.

[0021] In the above method, it is preferred that the thermal stress σ of the mother glass sheet calculated according to the following [Mathematical Formula 1] T (MPa) The laser irradiation process is performed under the condition of satisfying the following [Mathematical Formula 2],

[0022] [Mathematical formula 1]

[0023]

[0024] Wherein, E is the Young's modulus of the mother glass sheet (MPa), α is the thermal expansion coefficient of the mother glass sheet ( / K), ν is the Poisson's ratio of the mother glass sheet, ΔT is the difference between the temperature at the irradiation position of the mother glass sheet by the laser (K) and the temperature at the separation position away from the irradiation position (K),

[0025] [Mathematical formula 2]

[0026] 40+60t≤σ T ≤90+60t

[0027] Wherein, t is the thickness of the mother glass sheet (mm).

[0028] In this manner, the properties of the cut surface of the glass sheet cut out from the mother glass sheet can be further improved.

[0029] In the above method, in the laser irradiation step, at least one of (1) the distance between the laser head and the mother glass sheet and (2) the incident angle of the laser beam with respect to the surface of the mother glass sheet may be changed.

[0030] In the above-mentioned laser, the range of irradiation conditions that can cut the entire thickness of the mother glass plate is wide, so even if one or both of the above-mentioned (1) and (2) are changed, cutting of the entire thickness can be performed. In other words, it is not necessary to strictly manage the above-mentioned (1) and (2) during the execution of the laser irradiation process in order to cut the entire thickness.

[0031] Effects of the Invention

[0032] According to the present invention, when a bent mother glass sheet is cut by laser cleaving, the properties of the cut surface of a glass sheet cut out from the mother glass sheet can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a perspective view showing an initial crack forming step in a method for producing a glass plate.

[0034] Figure 2 This is a perspective view showing a laser irradiation step in the method for producing a glass plate.

[0035] Figure 3 It is a cross-sectional view showing a laser irradiation step in the method for manufacturing a glass plate.

[0036] Figure 4 It is a diagram showing the irradiation conditions of the laser light in the laser irradiation step.

[0037] Figure 5 It is a cross-sectional view showing a laser irradiation step in the method for manufacturing a glass plate.

[0038] Figure 6 It is a cross-sectional view showing a laser irradiation step in the method for manufacturing a glass plate.

[0039] Figure 7 It is a graph showing the relationship between thermal stress and the thickness of a mother glass sheet. DETAILED DESCRIPTION

[0040] Hereinafter, a method for manufacturing a glass plate according to an embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that the X direction, Y direction, and Z direction shown in the accompanying drawings referred to in the description of the embodiment are mutually orthogonal directions. Furthermore, the X direction and the Y direction are horizontal directions, and the Z direction is a vertical direction.

[0041] The method for manufacturing a glass plate according to the embodiment includes: an initial crack forming step ( Figure 1 ), for forming an initial crack 2 which becomes a starting point for cutting in the bent mother glass plate 1; and a laser irradiation step ( Figure 2 as well as Figure 3) is used to irradiate the mother glass plate 1 with a laser 4 from a laser head 3 so as to develop a crack 5 along a predetermined cutting line 6 starting from an initial crack 2.

[0042] In the present embodiment, the mother glass sheet 1 is cut along the predetermined cutting line 6, thereby separating the mother glass sheet 1 into the first glass sheet 7 and the second glass sheet 8. It should be noted that the predetermined cutting line 6 is located at the center of the mother glass sheet 1 in the Y direction, and the mother glass sheet 1 is formed into a symmetrical shape with respect to the predetermined cutting line 6. One end of the predetermined cutting line 6 serves as a starting point 6a for starting the cutting of the mother glass sheet 1, and the other end serves as an end point 6b for ending the cutting.

[0043] like Figure 1 As shown, the mother glass plate 1 is bent along either the X direction or the Y direction, and has a 3D shape in which the upper surface 1a of the upper and lower surfaces 1a and 1b is convex. The mother glass plate 1 is rectangular in shape when viewed from above (viewed from the Z direction). In this embodiment, the predetermined cutting line 6 extends along the X direction when viewed from above. Due to the bending of the mother glass plate 1, a height difference H (difference in height along the Z direction) is generated on the upper surface 1a along the predetermined cutting line 6. In detail, the height of the upper surface 1a is the lowest at the starting point 6a and the end point 6b of the predetermined cutting line 6, and the height of the upper surface 1a is the highest at the midpoint 6c of the predetermined cutting line 6. As for the height difference H, as an example, it is less than 20 mm, preferably less than 10 mm. In this embodiment, the height difference H is 10 mm.

[0044] The thickness of the mother glass plate 1 is, for example, 0.05 mm to 5 mm. It should be noted that in the present embodiment, a CO laser is used as the laser 4 irradiated to the mother glass plate 1, and compared with the case where a carbon dioxide gas laser is used, for example, a mother glass plate 1 with a large thickness can be cut, which will be described in detail later. Therefore, the thickness of the mother glass plate 1 is preferably greater than 0.1 mm, more preferably greater than 0.2 mm, and even more preferably greater than 0.3 mm. On the other hand, the thickness of the mother glass plate 1 is preferably less than 3 mm. In the present embodiment, the thickness of the mother glass plate 1 is 0.7 mm.

[0045] The mother glass plate 1 may be silicate glass, silica glass, borosilicate glass, soda glass, soda-lime glass, aluminosilicate glass, alkali-free glass, etc. Here, "alkali-free glass" refers to glass that does not substantially contain alkali components (alkali metal oxides), specifically, glass in which the weight ratio of alkali components is 3000ppm or less. The weight ratio of alkali components is preferably 1000ppm or less, more preferably 500ppm or less, and most preferably 300ppm or less. It should be noted that the mother glass plate 1 may be aluminosilicate glass before chemical strengthening, or a glass plate obtained by the initial crack formation process and the laser irradiation process may be subjected to chemical strengthening treatment.

[0046] exist Figure 1 In the initial crack forming step shown, first, the mother glass plate 1 is placed in a horizontal position on a support table 9 having a flat support surface 9a. Then, the initial crack 2 is formed at a portion of the upper surface 1a of the placed mother glass plate 1 where the starting point 6a of the planned cutting line 6 is located.

[0047] When forming the initial crack 2, a crack forming member 10 is used. In the present embodiment, a pointed scriber (sintered diamond tool, etc.) is used as the crack forming member 10. Of course, the present invention is not limited thereto, and a diamond pen, a carbide tool, sandpaper, etc. may also be used as the crack forming member 10. The initial crack 2 is formed by lowering the crack forming member 10 from above and contacting the upper surface 1a of the mother glass plate 1.

[0048] Here, in the present embodiment, the initial crack 2 is formed on the upper surface 1a (the convex surface) of the upper and lower surfaces 1a and 1b of the mother glass plate 1, but the present invention is not limited thereto, and the initial crack 2 may be formed on the lower surface 1b (the concave surface). In addition, the initial crack 2 may be formed on the end surface of the mother glass plate 1.

[0049] exist Figure 2 as well as Figure 3 In the laser irradiation step shown, the laser light 4 is irradiated toward the initial crack 2 located at the starting point 6 a of the planned cutting line 6 , and from this state, the mother glass sheet 1 is scanned along the planned cutting line 6 by the laser light 4 .

[0050] When scanning the laser light 4, the laser head 3 is moved in the X direction while the inclination of the axis of the laser head 3 and the position of the laser head 3 in the axial direction (here, the position in the Z direction) are kept constant. It should be noted that the support table 9 on which the mother glass plate 1 is placed is stationary, and thus the mother glass plate 1 is in a stationary state. In the present embodiment, the axis of the laser head 3 extends parallel to the Z direction, and the optical axis of the laser light 4 also extends parallel to the Z direction.

[0051] Here, in the present embodiment, the laser head 3 is moved while the mother glass plate 1 is kept stationary when scanning the laser beam 4, but the present invention is not limited thereto. Conversely, the mother glass plate 1 may be moved while the laser head 3 is kept stationary. It should be noted that the mother glass plate 1 and the laser head 3 may be moved relative to each other, for example, the mother glass plate 1 and the laser head 3 may be moved while scanning the laser beam 4.

[0052] As the laser 4, a laser that heats the surface portion (the surface portion on the upper surface 1a side) and the interior of the mother glass plate 1 is used, and in this embodiment, a CO laser is used. Here, the "surface portion" means the region from the upper surface 1a to a depth of 10 μm of the mother glass plate 1. In contrast, the "interior" means the region beyond the depth of the surface portion. The wavelength of the CO laser is, for example, 5.25 μm to 5.75 μm, and in this embodiment, it is 5.5 μm. The laser 4 may be either pulsed oscillation or continuous oscillation.

[0053] Here, the laser 4 may be a laser other than a CO laser as long as it can heat the surface layer and the inside of the mother glass plate 1. For example, the laser 4 may be an Er laser (Er:YAG laser), a Ho laser (Ho:YAG laser), or an HF laser.

[0054] Hereinafter, the irradiation conditions of the laser beam 4 in the laser irradiation step will be described in detail.

[0055] The focus 4a of the laser 4 is located between the laser head 3 and the upper surface 1a of the mother glass plate 1. The shape of the laser spot 4b is not particularly limited and may be circular, elliptical, oblong, rectangular, etc., but in this embodiment, the laser spot 4b is irradiated in a circular shape.

[0056] Here, the mother glass plate 1 is curved, so when the laser head 3 moves along the X direction, the distance between the laser head 3 and the mother glass plate 1 and the incident angle of the laser 4 with respect to the upper surface 1a of the mother glass plate 1 continuously change. As a result, the diameter of the laser spot 4b (hereinafter referred to as the irradiation diameter) also changes continuously. In detail, the irradiation diameter becomes relatively larger near the starting point 6a and the end point 6b of the predetermined cutting line 6, and becomes relatively smaller near the midpoint 6c. The change in the size of the irradiation diameter is preferably within the range of 1 mm to 8 mm, and more preferably within the range of 2 mm to 6 mm.

[0057] Considering the above-mentioned change in the irradiation diameter, in this embodiment, the output of the laser 4 and the scanning speed (here, the speed at which the laser head 3 moves in the X direction) in the laser irradiation process are determined as follows. It should be noted that the following example shows a case where the size of the irradiation diameter changes within the range of 4 mm to 6 mm.

[0058] First, a glass plate having the same thickness as the bent mother glass plate 1 and formed flat (hereinafter referred to as a flat glass plate) is prepared. Next, when the flat glass plate is cut using the laser 4 (laser head 3), the output and scanning speed ranges that can be cut are calculated by setting the irradiation diameter to 4 mm. Similarly, the output and scanning speed ranges that can be cut for the flat glass plate are calculated by setting the irradiation diameter to 6 mm. Thus, Figure 4 As shown in FIG. 1 , the range 11 when the irradiation diameter is set to 4 mm and the range 12 when the irradiation diameter is set to 6 mm become clear. Finally, the range 13 (in Figure 4 The output and scanning speed within the range surrounded by the thick line in the laser irradiation step are determined as the output and scanning speed of the laser 4 in the laser irradiation step. It should be noted that in this embodiment, the output of the laser 4 is set to 38W and the scanning speed is set to 20mm / s.

[0059] Here, in order to make the thermal shock applied to the mother glass plate 1 accompanying the irradiation of the laser beam 4 significant, the periphery of the laser beam spot 4b in the mother glass plate 1 may be cooled. As a specific example, a cooling medium (air, etc.) may be blown to a portion located behind the laser beam spot 4b in the scanning direction (X direction) to cool the portion.

[0060] In addition to the above-mentioned irradiation conditions of the laser beam 4, in order to improve the properties of the cut surfaces of the first glass sheet 7 and the second glass sheet 8, in this embodiment, the thermal stress σ of the mother glass sheet 1 calculated according to the following [Mathematical Formula 3] is further calculated. T The laser irradiation step is performed under the condition that (MPa) satisfies the following [Mathematical Formula 4].

[0061] [Mathematical formula 3]

[0062]

[0063] [Formula 4]

[0064] 40+60t≤σ T ≤90+60t

[0065] In the above-mentioned [Math 3], E is the Young's modulus (MPa) of the mother glass plate 1, α is the thermal expansion coefficient ( / K) of the mother glass plate 1, ν is the Poisson's ratio of the mother glass plate 1, and ΔT is the difference between the temperature (K) at the irradiation position of the laser 4 on the mother glass plate 1 and the temperature (K) at the separation position away from the irradiation position. In addition, in the above-mentioned [Math 4], t is the thickness (mm) of the mother glass plate 1.

[0066] Here, regarding the above-mentioned ΔT, to describe in detail, the temperature of the upper surface 1a of the mother glass plate 1 is measured using a glass temperature measuring thermal imager (manufactured by Optris: PI450G7) at the irradiation position of the laser 4 and at a separation position 10 mm away from the irradiation position in the scanning direction (X direction) of the laser 4, and the temperature difference between the two positions is set to ΔT. The temperature of the mother glass plate 1 during the irradiation of the laser 4 can be changed by changing the conditions of the output and scanning speed of the above-mentioned laser 4. It should be noted that the temperature at the separation position is at the same level as the room temperature. Here, as described above, during the movement of the laser head 3, the distance between the laser head 3 and the mother glass plate 1 and the incident angle of the laser 4 with respect to the upper surface 1a of the mother glass plate 1 continuously change. As a result, the temperature at the irradiation position of the laser 4 and thus the above-mentioned ΔT also change. Therefore, it is preferable to consider these changes, and the thermal stress σ T The conditions of the above-mentioned formula [Mathematical Formula 4] are satisfied during the period from the start to the end of the cutting.

[0067] Under the conditions described above, the mother glass sheet 1 is scanned from the starting point 6a to the end point 6b of the planned cutting line 6 by the laser 4. At this time, at each position on the planned cutting line 6, a thermal shock accompanying the irradiation of the laser 4 is applied to the surface layer and the inside of the mother glass sheet 1. As a result, the crack 5 develops along the planned cutting line 6 and in the thickness direction of the mother glass sheet 1, and the entire thickness of the mother glass sheet 1 is cut.

[0068] Hereinafter, main functions and effects of the above-mentioned method for producing a glass plate will be described.

[0069] In the above-mentioned manufacturing method, the laser 4 that heats the surface layer and the inside of the mother glass plate 1 is used, and a thermal shock can be applied not only to the surface layer but also to the inside of the mother glass plate 1. Therefore, the range of the irradiation conditions of the laser 4 that can cut the entire thickness of the mother glass plate 1 becomes wider. Therefore, during the period from the start to the completion of the cutting of the bent mother glass plate 1, the irradiation conditions can be easily maintained to the conditions that can cut the entire thickness. As a result, the entire thickness of the mother glass plate 1 can be cut without difficulty in the entire section of the predetermined cutting line 6. As a result, the properties of the cut surfaces of the first glass plate 7 and the second glass plate 8 cut from the mother glass plate 1 can be improved.

[0070] Example

[0071] Next, the thermal stress σ of the present invention is T The following is an example of an embodiment.

[0072] In the same manner as in the above-mentioned embodiment, the various mother glass sheets 1 shown in the following [Table 1] were cut. And, in particular, for the case where a cut surface with excellent properties (hereinafter referred to as an excellent cut surface) was obtained, the thermal stress σ acting on the mother glass sheet 1 was calculated by the above-mentioned [Mathematical Formula 3] T (MPa) It should be noted that the quality of the properties of the cut surface was determined by visual observation.

[0073] The thermal stress σ T The results are shown in [Table 1]. Here, as described above, the irradiation diameter and ΔT of the laser 4 change due to the bending of the mother glass plate 1. The irradiation diameter and ΔT shown in [Table 1] are the irradiation diameter and ΔT when the laser 4 is irradiated to the midpoint 6c on the predetermined cutting line 6.

[0074] [Table 1]

[0075] Glass Category Alkali-free glass Alkali-free glass Borosilicate glass Soda Glass Soda Glass Young's modulus(GPa) 73 80 77 73 70 <![CDATA[Coefficient of thermal expansion (×10 -7 / K)]]> 38 45 66 90 91 Poisson's ratio 0.2 0.2 0.2 0.2 0.2 Thickness(mm) 0.5 05 0.5 0.5 0.55 Output(W) 38 38 38 38 38 Speed ​​(mm / sec) 20 40 70 90 90 Irradiation diameter(mm) 6 6 6 6 6 ΔT(K) 550 420 320 250 260 <![CDATA[σ T (MPa)]]> 95 95 102 103 104

[0076] As shown in the results in [Table 1], in order to obtain a good cut surface for a mother glass plate 1 having a thickness of about 0.5 mm, it is desirable to set the thermal stress σ to about 100 MPa during cutting regardless of the type of glass. T Act on the mother glass plate 1.

[0077] Here, it is found that the thermal stress σ for obtaining a good cut surface T The thermal stress σ for obtaining a good cut surface is different depending on the thickness of the mother glass plate 1. Therefore, the inventors conducted an experiment of cutting a plurality of mother glass plates 1 having different thicknesses (wall thicknesses) using a CO laser. T Relationship with the thickness of the mother glass plate 1. In this test, alkali-free glass, soda glass, and borosilicate glass were used as samples of the mother glass plate 1. Figure 7 The thermal stress σ in this test is shown in T Relationship with the thickness of the mother glass plate 1.

[0078] according to Figure 7 As shown in the results, the inventors found that when the mother glass sheet 1 is cut by a CO laser, in order to obtain a good cut surface, it is desirable to use the thermal stress σ of the mother glass sheet 1 calculated by the above-mentioned [Mathematical Formula 3] T The laser irradiation step is performed so that (MPa) satisfies the above-mentioned formula [Math. 4].

[0079] Here, the manufacturing method of the glass plate of this invention is not limited to the form demonstrated in the said embodiment.

[0080] For example, in the above-mentioned embodiment, the inclination of the axis of the laser head 3 and the position of the laser head 3 in the axial direction are set constant when scanning the laser beam 4, but the present invention is not limited to this. When the height difference H generated on the upper surface 1a of the mother glass plate 1 along the planned cutting line 6 is large (for example, when the height difference H exceeds 20 mm), it is also possible to adopt Figure 5 , Figure 6 As shown.

[0081] exist Figure 5 In the method shown in the figure, the inclination of the axis of the laser head 3 is changed in accordance with the bending of the mother glass plate 1. In detail, the inclination of the axis of the laser head 3 is changed for the purpose of reducing the incident angle of the laser 4 with respect to the upper surface 1a of the mother glass plate 1. In this case, the distance between the laser head 3 and the mother glass plate 1 and the incident angle of the laser 4 with respect to the upper surface 1a of the mother glass plate 1 are constant. It should be noted that the upper limit of the above-mentioned incident angle is preferably 45°. Moreover, in the method shown in the figure, in addition to changing the inclination of the axis of the laser head 3, the height position of the laser head 3 is also changed. That is, when the laser 4 is used to scan the vicinity of the starting point 6a and the end point 6b of the predetermined cutting line 6, the height position of the laser head 3 is relatively low, and when the laser 4 is used to scan the vicinity of the midpoint 6c of the predetermined cutting line 6, the height position of the laser head 3 is relatively high.

[0082] exist Figure 6 In the embodiment shown, the inclination of the axis of the laser head 3 is kept constant, while the position of the laser head 3 in the axial direction (here, the position in the Z direction) is changed in accordance with the curvature of the mother glass plate 1. Specifically, the height position of the laser head 3 is relatively low when the laser 4 is used to scan the vicinity of the starting point 6a and the end point 6b of the predetermined cutting line 6, and is relatively high when the laser 4 is used to scan the vicinity of the midpoint 6c of the predetermined cutting line 6. In this case, the distance between the laser head 3 and the mother glass plate 1 is constant, but the incident angle of the laser 4 with respect to the upper surface 1a of the mother glass plate 1 is continuously changed.

[0083] Of course, a method may be adopted in which both the inclination of the axis of the laser head 3 and the position of the laser head 3 in the axial direction are changed when scanning the laser 4. For example, a method may be adopted in which the distance between the laser head 3 and the mother glass plate 1 is continuously changed and the incident angle of the laser 4 with respect to the upper surface 1a of the mother glass plate 1 is kept constant. This method, Figure 5 , Figure 6 The illustrated method can be realized using a robot (a combination of a multi-joint robot and a single-axis robot, etc.), a linear actuator, a rotation mechanism, etc.

[0084] In the above-mentioned embodiment, the mother glass plate 1 is cut on the basis of setting the convex surface of the bent mother glass plate 1 as the upper surface 1a, but the present invention is not limited to this. The front and back of the mother glass plate 1 may be reversed and the mother glass plate 1 may be cut on the basis of setting the concave surface as the upper surface 1a. In this case, the surface where the initial crack 2 is formed may be the upper surface 1a (the concave surface), the lower surface 1b (the convex surface), or the end surface. Furthermore, in the above-mentioned embodiment, the mother glass plate 1 is cut in a horizontal posture, but the present invention is not limited to this. The mother glass plate 1 set in a vertical posture or an inclined posture by a holding member or the like may also be cut.

[0085] In the above embodiment, the planned cutting line 6 extends in the X direction in plan view, but the present invention is not limited thereto. The planned cutting line 6 may be a meandering line or a closed loop line (for example, a line that describes a circle in plan view).

[0086] In the above-described embodiment, the mother glass sheet 1 curved in both the X direction and the Y direction is cut, but the present invention is not limited thereto and can be applied to the case of cutting the mother glass sheet 1 curved in only one direction.

[0087] Description of Reference Numerals

[0088] 1 Mother glass plate

[0089] 1a Upper surface of the mother glass plate

[0090] 2 Initial crack

[0091] 3 Laser head

[0092] 4 Laser

[0093] 5 Crack

[0094] 6 Cut the predetermined line.

Claims

1. A method for manufacturing a glass plate, comprising: An initial crack forming step of forming an initial crack, which will serve as a starting point for cutting, in the bent mother glass sheet; as well as a laser irradiation step of irradiating the mother glass sheet with laser light from a laser head so that cracks are propagated along a predetermined cutting line starting from the initial cracks; The method for manufacturing the glass plate is characterized in that: In the laser irradiation step, the laser is used to heat the surface layer and the interior of the mother glass sheet, and the crack is developed along the planned cutting line and in the thickness direction of the mother glass sheet due to the thermal shock caused by the laser irradiation, thereby cutting the mother glass sheet. In the laser irradiation step, the laser head and the mother glass sheet are relatively moved while the inclination of the axis of the laser head is kept constant, and the mother glass sheet is cut only by irradiation of the laser. The shape of the laser spot formed on the mother glass plate accompanying the irradiation of the laser is circular. The thermal stress σ of the mother glass sheet calculated according to the following [Mathematical Formula 1] T The laser irradiation process is performed under the condition that the following [Mathematical Formula 2] is satisfied: [Mathematical formula 1] Wherein, E is the Young's modulus of the mother glass sheet, α is the thermal expansion coefficient of the mother glass sheet, ν is the Poisson's ratio of the mother glass sheet, ΔT is the difference between the temperature at the irradiation position of the laser on the mother glass sheet and the temperature at the separation position away from the irradiation position, [Mathematical formula 2] Wherein, t is the thickness of the mother glass plate, σ T The unit of is MPa, the unit of E is MPa, the unit of α is / K, the unit of the temperature at the irradiation position of the laser on the mother glass plate is K, the unit of the temperature at the separation position away from the irradiation position is K, and the unit of t is mm.

2. The method for manufacturing a glass plate according to claim 1, wherein: In the laser irradiation step, the laser head and the mother glass sheet are relatively moved while the position of the laser head in the axial direction is kept constant.

3. The method for manufacturing a glass plate according to claim 1 or 2, characterized in that: In the laser irradiation step, CO laser is used as the laser.

4. The method for manufacturing a glass plate according to claim 1 or 2, characterized in that: In the laser irradiation step, at least one of (1) a distance between the laser head and the mother glass sheet and (2) an incident angle of the laser beam with respect to a surface of the mother glass sheet is changed.

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