Glass sheet production method

Abstract

A modification step of this glass sheet production method comprises: a first modification step in which the center MP1 of a focal line 3a of a laser beam LB is closer to a first main surface Ga of a glass sheet G than to a second main surface Gb of the glass sheet G; and a second modification step in which the center MP2 of a focal line 3b of the laser beam LB is closer to the second main surface Gb of the glass sheet G than to the first main surface Ga of the glass sheet G. The distance D4 between the center MP2 of the focal line 3b and the second main surface Gb of the glass sheet G in the second modification step is greater than the distance D1 between the center MP1 of the focal line 3a and the first main surface Ga of the glass sheet G in the first modification step.

Description

Glass plate manufacturing method

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

[0002] 2. Description of the Related Art Glass substrates used in electronic devices such as displays, such as tiling displays and bezel-less displays, and glass interposers have fine through holes (TGV: Through Glass Via) formed therein for wiring such as through electrodes.

[0003] For example, Patent Document 1 discloses a method for manufacturing a through-wiring substrate, which includes a step of forming a modified portion inside a glass substrate so as to connect at least two surfaces that constitute the glass substrate, and a step of removing the modified portion by etching and forming a microhole in the substrate (see claim 3 of the same document).

[0004] In this manufacturing method, in the step of forming a modified region inside the glass substrate, a laser beam is scanned so that the focus of the laser beam moves from one main surface (first main surface) of the glass substrate to the other main surface (second main surface), thereby forming a first modified region at the site irradiated with the laser beam (see paragraphs 0020 and 0028 and FIGS. 1 and 3 of the same document).

[0005] Then, the laser beam is scanned at a position away from the first modified region so that the focus of the laser beam moves from the second main surface toward the first main surface, thereby forming a second modified region at the site irradiated with the laser beam (see paragraphs 0024 and 0028 and FIGS. 2 and 3 of the same document).

[0006] Japanese Patent Application Laid-Open No. 2008-288577

[0007] As described above, in conventional glass substrate manufacturing methods, the scanning direction of the laser light when forming the first modified region is different from the scanning direction of the laser light when forming the second modified region. Therefore, the first modified region and the second modified region have different shapes, and the first through hole formed by etching away the first modified region and the second through hole formed by etching away the second modified region have different diameters. This makes it impossible to form multiple through holes of uniform size on a glass substrate.

[0008] The present invention has been made in view of the above circumstances, and has as its technical object to form a plurality of through holes of uniform diameter in a glass plate.

[0009] (1) The present invention has been made to solve the above-mentioned problems, and provides a method for manufacturing a glass plate having a first main surface, a second main surface, and a through hole penetrating between the first main surface and the second main surface, the method comprising: a modification step of modifying a portion where the through hole is to be formed by irradiating the portion by laser light; and an etching step of forming the through hole in the portion where the through hole is to be formed by etching, after the modification step; the laser light has a relatively high energy density and forms a focal line extending in the laser irradiation direction; the modification step involves irradiating the glass plate with the laser light from the second main surface side; and the modification step comprises a first modification step in which the center of the focal line is closer to the first main surface than to the second main surface; and a second modification step in which the center of the focal line is closer to the second main surface than to the first main surface; and the distance between the center of the focal line and the second main surface in the second modification step is greater than the distance between the center of the focal line and the first main surface in the first modification step.

[0010] According to this configuration, by differentiating the position of the focal line irradiated on the glass sheet in the first modification step from the position of the focal line irradiated on the glass sheet in the second modification step and by making the distance between the center of the focal line and the second main surface in the second modification step larger than the distance between the center of the focal line and the first main surface in the first modification step, it is possible to form a plurality of uniformly sized modified regions in the glass sheet, thereby making it possible to uniform the diameters of a plurality of through holes formed by removing the modified regions in the etching step.

[0011] (2) Another aspect of the present invention is intended to solve the above-mentioned problem, and provides a method for manufacturing a glass plate having a first main surface, a second main surface, and a through hole penetrating between the first main surface and the second main surface, the method comprising: a modification step of modifying a portion where the through hole is to be formed by irradiating the portion by laser light; and an etching step of forming the through hole in the portion where the through hole is to be formed by etching, after the modification step, wherein the laser light has a relatively high energy density and forms a focal line extending in the laser irradiation direction, the modification step involves irradiating the glass plate from the second main surface side, and the modification step comprises: a first modification step of irradiating the glass plate with the laser light, the position of the focal line being set so that the center of the focal line is closer to the first main surface than to the second main surface; and a second modification step of irradiating the glass plate with the laser light, the position of the focal line being set so that the center of the focal line is closer to the second main surface than to the first main surface,

[0012] According to this configuration, by setting the position of the focal line irradiated on the glass sheet in the first modification step to be different from the position of the focal line irradiated on the glass sheet in the second modification step and setting the distance between the center of the focal line and the second main surface in the second modification step to be larger than the distance between the center of the focal line and the first main surface in the first modification step, it is possible to form a plurality of uniformly sized modified regions in the glass sheet, thereby making it possible to uniform the diameters of a plurality of through holes formed by removing the modified regions in the etching step.

[0013] (3) In the method for producing a glass plate according to the above (1) or (2), the second modification step may be carried out after the first modification step is carried out.

[0014] According to this configuration, by performing the first modification process before the second modification process, the second modification process can be performed without being affected by changes in the refractive index of the modified portion formed by the first modification process.

[0015] (4) In the method for producing a glass plate according to any one of (1) to (3) above, in the first modification step, a rear end of the focal line may be located outside the first main surface, and in the second modification step, a front end and a rear end of the focal line may be located between the first main surface and the second main surface.

[0016] According to this configuration, in the first modification step, laser light is applied so that the rear end of the focal line extends beyond the first main surface, and in the second modification step, laser light is applied so that the entire focal line is located inside the glass plate (between the first main surface and the second main surface), thereby making it possible to form a plurality of uniformly sized modified areas in the glass plate.

[0017] (5) In the method for producing a glass plate according to any one of (1) to (4) above, a rear end of the focal line in the second modification step may be located closer to the first main surface than a front end of the focal line in the first modification step.

[0018] According to this configuration, by overlapping a part of the focal line in the first modification step with a part of the focal line in the second modification step, it is possible to form a modified portion without interruption in the plate thickness direction of the glass plate.

[0019] (6) In the method for producing a glass plate according to any one of (1) to (5) above, a difference between a distance between a center of the focal line of the laser beam in the second modification step and the second main surface and a distance between a center of the focal line of the laser beam in the first modification step and the first main surface may be 30 μm or more and 100 μm or less.

[0020] (7) In the method for producing a glass plate according to any one of (1) to (6) above, the thickness of the glass plate before the etching step may be 600 μm or more and 1200 μm or less.

[0021] (8) In the method for producing a glass plate according to any one of (1) to (7) above, the length of the focal line may be 300 μm or more and 800 μm or less.

[0022] According to the present invention, a plurality of through holes having a uniform diameter can be formed in a glass plate.

[0023] FIG. 1 is a side view showing a modification step in a method for manufacturing a glass plate. FIG. 2 is a cross-sectional view showing the modification step in a method for manufacturing a glass plate. FIG. 3 is a cross-sectional view showing the modification step in a method for manufacturing a glass plate. FIG. 4 is a cross-sectional view showing the modification step in a method for manufacturing a glass plate. FIG. 5 is a cross-sectional view showing the modification step in a method for manufacturing a glass plate. FIG. 6 is a cross-sectional view showing the modification step in a method for manufacturing a glass plate. FIG. 7 is a cross-sectional view showing the modification step in a method for manufacturing a glass plate. FIG. 8 is a view for comparing a first modification step and a second modification step. FIG. 9 is a cross-sectional view showing an etching step in a method for manufacturing a glass plate. FIG. 10 is a cross-sectional view of a glass plate in which a through hole has been formed.

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for manufacturing a glass plate according to the present invention will now be described with reference to the accompanying drawings.

[0025] This method is for manufacturing a transparent glass plate having through holes. In this embodiment, an example is shown in which two through holes are formed in the glass plate, but the number of through holes formed in the glass plate is not limited to this embodiment.

[0026] The glass plate may be made of soda glass, quartz glass, alkali-free glass, borosilicate glass, aluminosilicate glass, or crystallized glass. However, when the glass plate is used as a substrate for an electronic device, quartz glass, alkali-free glass, or borosilicate glass is preferred. Here, alkali-free glass refers to glass that is substantially free of alkali components (alkali metal oxides), specifically glass with an alkali component weight ratio of 3000 ppm or less. In the present invention, the alkali component weight ratio is preferably 1000 ppm or less, more preferably 500 ppm or less, and most preferably 300 ppm or less.

[0027] As shown in Fig. 1, the glass sheet G has a first main surface Ga, a second main surface Gb located opposite the first main surface Ga, and an end surface Gc connecting the first main surface Ga and the second main surface Gb. The thickness T of the glass sheet G before carrying out this method is preferably 600 µm or more and 1200 µm or less. The lower limit of the thickness T of the glass sheet G is more preferably 650 µm or more, and even more preferably 700 µm or more. The upper limit of the thickness T of the glass sheet G is more preferably 1100 µm or less, and even more preferably 1000 µm or less.

[0028] This method includes a modification process in which a portion of a glass plate G where a through hole is to be formed is modified by irradiating it with laser light, and an etching process in which a through hole is formed in the portion where the through hole is to be formed after the modification process.

[0029] As shown in Fig. 1, the laser irradiation device 1 is disposed at a position away from the second main surface Gb of the glass sheet G so as to face the second main surface Gb. The laser irradiation device 1 includes a control device (not shown) and a driving device (not shown). The driving device is configured to be able to move the laser irradiation position three-dimensionally by the control device. Hereinafter, the direction from the laser irradiation device 1 toward the second main surface Gb of the glass sheet G will be referred to as the rear, and the direction from the second main surface Gb of the glass sheet G toward the laser irradiation device 1 will be referred to as the front.

[0030] The output of the laser light LB in the laser irradiation device 1 is, for example, 1 W or more and 20 W or less. The laser light LB irradiated from the laser irradiation device 1 is preferably a pulsed laser. The time required for one irradiation of the laser light LB is, for example, 0.1 ps or more and 70 ps or less. In this embodiment, the number of pulses of the laser light LB irradiated onto the glass plate G is one, but this is not limited thereto, and two or more pulses of the laser light LB may be irradiated onto the glass plate G. The spot diameter of the laser light LB is, for example, 2 μm or more and 10 μm or less.

[0031] The laser light LB may be, for example, a CO2 laser, a CO2 laser, an excimer laser, a YAG laser, a YVO4 laser, or a fiber laser. The wavelength of the laser light LB may be in the ultraviolet, visible, or infrared region, but it is preferable to use a wavelength that allows transmission through the glass plate G.

[0032] 2 , planned through-hole formation portions 2 a and 2 b are virtually set on the glass sheet G. The planned through-hole formation portions 2 a and 2 b include a first planned through-hole formation portion 2 a for forming a first through-hole in the glass sheet G and a second planned through-hole formation portion 2 b for forming a second through-hole in the glass sheet G.

[0033] As shown in FIGS. 3 to 6, the laser beam LB emitted from the laser irradiation device 1 has a relatively higher energy density than other portions and forms focal lines 3a and 3b extending in the irradiation direction.

[0034] The focal lines 3a and 3b have front ends (hereinafter referred to as "front ends") 3a1 and 3b1 and rear ends (hereinafter referred to as "rear ends") 3a2 and 3b2. The front ends 3a1 and 3b1 of the focal lines 3a and 3b are closer to the laser irradiation device 1 than the rear ends 3a2 and 3b2. Hereinafter, the intermediate position between the front ends 3a1 and 3b1 and the rear ends 3a2 and 3b2 of the focal lines 3a and 3b (the position half the length of the focal lines 3a and 3b) will be referred to as the center of the focal lines 3a and 3b.

[0035] The laser irradiation device 1 irradiates the laser beam LB so that the positions of the focal lines 3 a and 3 b of the laser beam LB are set by the control device. The positions of the focal lines 3 a and 3 b may be set based on, for example, the positions of the front ends 3 a 1 and 3 b 1 of the focal lines 3 a and 3 b, or the positions of the rear ends 3 a 2 and 3 b 2 of the focal lines 3 a and 3 b, or the center positions of the focal lines 3 a and 3 b.

[0036] The modification process includes a first modification process and a second modification process. That is, in this embodiment, each of the formation-intended portions 2 a, 2 b is irradiated with the laser light LB twice, in the first modification process and the second modification process. The number of times that each of the formation-intended portions 2 a, 2 b is irradiated with the laser light LB is not limited to this embodiment.

[0037] In the first modification step, the laser beam LB is irradiated so that the position of the focal line 3 a of the laser beam LB (hereinafter referred to as the “first focal line”) is closer to the first main surface Ga of the glass sheet G. In the second modification step, the laser beam LB is irradiated so that the position of the focal line 3 b of the laser beam LB (hereinafter referred to as the “second focal line”) is closer to the second main surface Gb of the glass sheet G.

[0038] Each focal line 3a, 3b has a predetermined length L1, L2 along the thickness direction of the glass sheet G. The lengths L1, L2 of the focal lines 3a, 3b are smaller than the thickness T of the glass sheet G (L1<T, L2<T) and larger than half the thickness T of the glass sheet G (L1>T / 2, L2>T / 2). The relationship between the lengths L1, L2 of the focal lines 3a, 3b and the thickness T of the glass sheet G is not limited to this embodiment. The lengths L1, L2 of the focal lines 3a, 3b are preferably 300 μm or more and 800 μm or less. The lower limit of the lengths L1, L2 of the focal lines 3a, 3b is more preferably 400 μm or more, and even more preferably 500 μm or more. The upper limit of the lengths L1, L2 of the focal lines 3a, 3b is more preferably 700 μm or less, and even more preferably 600 μm or less. In this embodiment, the length L1 of the first focal line 3a is set to be equal to the length L2 of the second focal line 3b, but may be different from the length L2 of the second focal line 3b.

[0039] The output of the laser irradiation device 1 in the second modification step is desirably smaller than the output of the laser irradiation device 1 in the first modification step. The output of the laser irradiation device 1 in the second modification step is preferably 90% or less, and more preferably 80% or less, of the output of the laser irradiation device 1 in the first modification step.

[0040] In this embodiment, an example is shown in which the second reforming step is performed after the first reforming step is performed, but the order in which the reforming steps are performed is not limited to this embodiment.

[0041] 3 and 4 , in the first modification step, the first planned formation portion 2 a is irradiated with the laser beam LB, and then the second planned formation portion 2 b is irradiated with the laser beam LB. At this time, the laser beam LB is irradiated so that the first focal line 3 a overlaps the first main surface Ga of the glass sheet G. More specifically, the first focal line 3 a of the laser beam LB is irradiated so that the rear end 3 a 2 is located outside the first main surface Ga of the glass sheet G and the front end 3 a 1 is located between the first main surface Ga and the second main surface Gb of the glass sheet G, i.e., inside the first main surface Ga.

[0042] As shown in Fig. 4, a partial modified region 4a is formed at a location in the first planned formation portion 2a where the laser beam LB is irradiated. The modified region 4a is a portion where a change in refractive index, transmittance, etc. occurs due to the irradiation with the laser beam LB. Similarly, as shown in Fig. 5, a partial modified region 4b is formed at a location in the second planned formation portion 2b where the laser beam LB is irradiated. These modified regions 4a, 4b are formed in a range from the first main surface Ga of the glass sheet G to a midpoint in the thickness direction of the glass sheet G.

[0043] As shown in Fig. 5, in the second modification step, the second focal line 3b of the laser beam LB is irradiated so as to overlap with the partially modified portion 4a formed in the first predetermined formation portion 2a. In Fig. 5, the overlapping portion between the laser beam LB and the partially modified portion 4a is depicted by cross-hatching (the same applies to Fig. 6).

[0044] Furthermore, the second focal line 3b of the laser beam LB is irradiated so as to be located inside the glass sheet G. That is, the front end 3b1 and the rear end 3b2 of the second focal line 3b are irradiated so as to be located between the first main surface Ga and the second main surface Gb of the glass sheet G. At this time, the rear end 3b2 of the second focal line 3b is located in a middle portion of the partially modified region 4a formed in the glass sheet G. In other words, the rear end 3b2 of the second focal line 3b is irradiated at a position closer to the first main surface Ga than the front end 3a1 of the first focal line 3a, which was irradiated earlier in the first modification step.

[0045] By irradiating the laser beam LB, a modified region 5a is formed in the first formation target region 2a of the glass plate G over almost the entire range from the first main surface Ga to the second main surface Gb (see FIG. 6).

[0046] Thereafter, as shown in Fig. 6, the second focal line 3b of the laser beam LB is irradiated onto the second planned formation portion 2b. Similar to the irradiation of the first planned formation portion 2a, the second focal line 3b of the laser beam LB is irradiated so as to overlap with the partially modified portion 4b formed in the second planned formation portion 2b. As a result, as shown in Fig. 7, an entire modified portion 5b is formed in the second planned formation portion 2b of the glass sheet G over almost the entire range from the first main surface Ga to the second main surface Gb. Each modified portion 5a, 5b is configured in a cylindrical shape so as to correspond to the shape of each focal line 3a, 3b of the laser beam LB.

[0047] 8 is a virtual diagram for comparing the irradiation position of the first focal line 3 a in the first modification step with the irradiation position of the second focal line 3 b in the second modification step. The first focal line 3 a and the second focal line 3 b are irradiated coaxially as described above, but are depicted at separate positions in FIG. 8 for comparison.

[0048] 8 , the center MP1 of the first focal line 3a irradiated onto the glass sheet G in the first modifying step is located closer to the first main surface Ga than to the second main surface Gb of the glass sheet G. That is, the distance D1 from the first main surface Ga of the glass sheet G to the center MP1 of the first focal line 3a is smaller than the distance D2 from the second main surface Gb of the glass sheet G to the center MP1 of the first focal line 3a (D1<D2).

[0049] Furthermore, the center MP2 of the second focal line 3b irradiated onto the glass sheet G in the second modification step is located closer to the second principal surface Gb than to the first principal surface Ga. That is, the distance D3 from the first principal surface Ga of the glass sheet G to the center MP2 of the second focal line 3b is greater than the distance D4 from the second principal surface Gb of the glass sheet G to the center MP2 of the second focal line 3b (D3>D4).

[0050] The distance D4 between the center MP2 of the second focal line 3b and the second main surface Gb of the glass sheet G in the second modification step is greater than the distance D1 between the center MP1 of the first focal line 3a and the first main surface Ga of the glass sheet G in the first modification step (D4>D1). The difference (D4-D1) between the distance D4 between the center MP2 of the second focal line 3b and the second main surface Gb and the distance D1 between the center MP1 of the first focal line 3a and the first main surface Ga of the glass sheet G is preferably 30 μm or more and 100 μm or less. The lower limit of the difference (D4-D1) between the distance D4 and the distance D1 is more preferably 40 μm or more, and even more preferably 50 μm or more. The upper limit of the difference (D4-D1) between the distance D4 and the distance D1 is more preferably 90 μm or less, and even more preferably 80 μm or less.

[0051] The distance D7 between the front end 3a1 of the first focal line 3a and the second main surface Gb of the glass sheet G in the first modification step is preferably 200 μm or more and 500 μm or less. The distance D8 between the rear end 3a2 of the first focal line 3a and the first main surface Ga of the glass sheet G in the first modification step is preferably 100 μm or more and 300 μm or less. The distance D5 between the front end 3b1 of the second focal line 3b and the second main surface Gb of the glass sheet G in the second modification step is preferably 0 μm or more and 30 μm or less. This distance D5 is smaller than the distance D6 between the rear end 3b2 of the second focal line 3b and the first main surface Ga of the glass sheet G (D5<D6). The length D9 of the overlapping portion of the first focal line 3a and the second focal line 3b is preferably 30 μm or more and 200 μm or less.

[0052] In the etching step, the glass sheet G that has undergone the modification step is immersed in an etching solution to remove the modified portions 5 a, 5 b. The etching solution is preferably an alkaline aqueous solution, such as a sodium hydroxide (NaOH) aqueous solution or a potassium hydroxide (KOH) aqueous solution. The alkaline etching solution has a lower etching rate than the acidic etching solution, and is therefore suitable for forming straight through-holes.

[0053] In the etching step, portions of the first principal surface Ga, the second principal surface Gb, and the end surface Gc of the glass sheet G are gradually removed by etching. Furthermore, as shown in Fig. 9, recesses 6a, 6b are formed by contacting the modified regions 4a, 4b with the etching solution. The recesses 6a, 6b include a first recess 6a formed on the first principal surface Ga and a second recess 6b formed on the second principal surface Gb.

[0054] In the etching process, the modified regions 5a, 5b are removed by the etching solution over time, increasing the depth of the recesses 6a, 6b. When the bottoms of the recesses 6a, 6b reach the middle of the glass sheet G in the thickness direction, the first recess 6a and the second recess 6b merge. As a result, as shown in FIG. 10 , a first through hole 7a and a second through hole 7b are formed that penetrate between the first main surface Ga and the second main surface Gb of the glass sheet G. Each through hole 7a, 7b has a circular first opening 8a formed in the first main surface Ga of the glass sheet G and a circular second opening 8b formed in the second main surface Gb of the glass sheet G. The thickness of the glass sheet G after the etching process is preferably 500 μm or more and 1150 μm or less.

[0055] According to the method for manufacturing a glass sheet G according to the present embodiment described above, the irradiation position of the first focal line 3a in the first modification step and the irradiation position of the second focal line 3b in the second modification step are made different from each other, and the distance D4 between the center MP2 of the second focal line 3b in the second modification step and the second main surface Gb is made larger than the distance D1 between the center MP1 of the first focal line 3a in the first modification step and the first main surface Ga, thereby making it possible to form a plurality of uniformly sized modified regions 5a, 5b in the glass sheet G. This makes it possible to make uniform the diameters of a plurality of through holes 7a, 7b formed by removing the modified regions 5a, 5b in the etching step.

[0056] Furthermore, in the first modification step, the partially modified regions 4a, 4b formed by irradiating the transparent glass plate G with the laser beam LB may have a different refractive index than unmodified glass. Therefore, if a position farther from the laser irradiation device 1 than the partially modified regions 4a, 4b is modified after the partially modified regions 4a, 4b are formed, the modified position may be shifted. By performing the second modification step after the first modification step, as in this embodiment, the modified position can be accurately controlled, and the diameter of the through holes 7a, 7b can be made uniform.

[0057] 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.

[0058] In the above embodiment, the modification step is exemplified in which the first formation-intended portion 2 a of the glass sheet G is irradiated with the laser beam LB, and then the second formation-intended portion 2 b of the glass sheet G is irradiated with the laser beam LB. However, the present invention is not limited to this configuration. In the modification step, the formation-intended portions 2 a, 2 b may be simultaneously irradiated with the laser beam LB by a plurality of laser irradiation devices 1.

[0059] In the above embodiment, in the second modification step, the front end 3b1 of the second focal line 3b is located between the first principal surface Ga and the second principal surface Gb of the glass sheet G. However, the present invention is not limited to this embodiment. For example, the second focal line 3b may be irradiated so that the front end 3b1 coincides with the second principal surface Gb of the glass sheet G. Alternatively, the second focal line 3b may be irradiated so that the front end 3b1 is located outside the second principal surface Gb of the glass sheet G.

[0060] In the above embodiment, an alkaline aqueous solution is used as the etching solution, but the present invention is not limited to this configuration. A hydrofluoric acid-based etching solution may be used instead of an alkaline aqueous solution. When a hydrofluoric acid-based etching solution is used, it may be a mixed acid of hydrochloric acid, nitric acid, sulfuric acid, or a combination thereof. This dissolves and removes poorly soluble salts produced by etching, thereby improving the uniformity of the through holes.

[0061] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0062] The present inventors conducted a test to confirm the effects of the present invention. In this test, four square glass plates (OA-11 manufactured by Nippon Electric Glass Co., Ltd.) with a thickness of 0.7 mm and a side length of 50 mm were prepared. Each glass plate was subjected to a modification process and an etching process to form through holes. In this way, two glass plates according to the example and two glass plates according to the comparative example were produced.

[0063] In the modification step, as in the above embodiment, the first modification step was performed and then the second modification step was performed.

[0064] That is, in the first modification step, a focal line (first focal line) of laser light was irradiated so as to overlap with a main surface (first main surface) of the glass plate located far from the laser irradiation device, thereby forming a partially modified area. Thereafter, in the second modification step, a focal line (second focal line) of laser light was irradiated so as to overlap with this modified area, thereby forming an overall modified area on the glass plate.

[0065] The second focal line in the second modification step was irradiated at a position closer to the second principal surface (the principal surface closer to the laser irradiation device) than the first focal line. The above modification step was performed 25 times on one glass plate, resulting in 25 modified areas on each glass plate. The positions of the focal lines in the thickness direction of the glass plate differed between the examples and comparative examples. The length of each focal line was 0.5 mm.

[0066] In the subsequent etching step, the glass plate was immersed in an alkaline etching solution (18 mol / L aqueous sodium hydroxide solution) to remove the modified portions formed on the glass plate. The temperature of the etching solution was 90°C, and the etching time was 1800 minutes. In this manner, glass plates according to the examples and comparative examples having 25 through holes were manufactured.

[0067] Thereafter, the diameters of 25 through holes in each example and comparative example were measured. The hole diameters were measured at two locations: the first opening on the first main surface side of the glass plate, and the second opening on the second main surface side. The average hole diameter was calculated for each example and comparative example. The quality of the hole diameter was determined based on this average hole diameter.

[0068] The test results are shown in Table 1. In Table 1, the "center distance of the first focal line" refers to the distance between the center of the first focal line and the first main surface of the glass plate (distance D1 in the above embodiment). In Table 1, the "center distance of the second focal line" refers to the distance between the center of the second focal line and the second main surface of the glass plate (distance D4 in the above embodiment). In Table 1, the difference between the maximum and minimum diameters of the first opening and second opening of the 25 through holes formed in each glass plate is referred to as the "hole diameter variation." In Table 1, the "hole diameter evaluation" is rated as "○" (good) when the hole diameter variation is 15 μm or less, and as "×" (poor) when the hole diameter variation exceeds 15 μm.

[0069] As shown in Table 1, in Examples 1 and 2, it was confirmed that by making the center-to-center distance D4 of the second focal line larger than the center-to-center distance D1 of the first focal line (D4>D1), a glass plate having through holes with a uniform diameter could be produced.

[0070] 2a First planned formation portion 2b Second planned formation portion 3a First focal line 3a1 Front end of first focal line 3a2 Rear end of second focal line 3b Second focal line 3b1 Front end of second focal line 3b2 Rear end of second focal line 7 Through hole D1 Distance between center of first focal line and first main surface D4 Distance between center of second focal line and second main surface G Glass plate Ga First main surface Gb Second main surface L1 Length of first focal line L2 Length of second focal line LB Laser light MP1 Center of first focal line MP2 Center of second focal line

Claims

1. A method for manufacturing a glass plate having a first main surface, a second main surface, and a through hole penetrating between the first main surface and the second main surface, comprising: a modification step of modifying an area where the through hole is to be formed by irradiating the area with laser light; and an etching step of forming the through hole in the area where the through hole is to be formed by etching after the modification step, the laser light has a relatively high energy density and forms a focal line extending in the laser irradiation direction, the laser light is irradiated from the second main surface side in the modification step, the modification step comprises a first modification step in which the center of the focal line is closer to the first main surface than to the second main surface, and a second modification step in which the center of the focal line is closer to the second main surface than to the first main surface, and the distance between the center of the focal line and the second main surface in the second modification step is greater than the distance between the center of the focal line and the first main surface in the first modification step.

2. A method for manufacturing a glass plate having a first main surface, a second main surface, and a through hole penetrating between the first main surface and the second main surface, comprising: a modification step of modifying an area where the through hole is to be formed by irradiating the area with laser light; and an etching step of forming the through hole in the area where the through hole is to be formed by etching after the modification step, the laser light has a relatively high energy density and forms a focal line extending in a direction of laser irradiation, the modification step involves irradiating the laser light from the second main surface side, the modification step comprising: a first modification step of irradiating the laser light by setting a position of the focal line so that the center of the focal line is closer to the first main surface than to the second main surface, and a second modification step of irradiating the laser light by setting the position of the focal line so that the center of the focal line is closer to the second main surface than to the first main surface, 3. The method for producing a glass sheet according to claim 1 or 2, wherein the second modification step is carried out after the first modification step is carried out.

4. A method for manufacturing a glass plate according to claim 1 or 2, wherein in the first modification step, a rear end of the focal line is located outside the first main surface, and in the second modification step, a front end and a rear end of the focal line are located between the first main surface and the second main surface.

5. The method for manufacturing a glass plate according to claim 1 or 2, wherein a rear end of the focal line in the second modification step is located closer to the first main surface than a front end of the focal line in the first modification step.

6. The method for manufacturing a glass plate according to claim 1 or 2, wherein a difference between a distance between a center of the focal line of the laser light in the second modification step and the second main surface and a distance between a center of the focal line of the laser light in the first modification step and the first main surface is 30 μm or more and 100 μm or less.

7. A method for manufacturing a glass plate according to claim 1 or 2, wherein the thickness of the glass plate before the etching step is 600 μm or more and 1200 μm or less.

8. The method for manufacturing a glass plate according to claim 1 or 2, wherein the length of the focal line is 300 μm or more and 800 μm or less.

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