Tempered glass sheet and method of manufacturing the same

Abstract

The present invention relates to a tempered glass plate having a first main surface, a second main surface facing the first main surface, and an end surface, wherein at least one of the first main surface and the second main surface has surface compressive stress formed by chemical tempering treatment and is equipped with a tempered portion in which planar compressive stress is formed along the end surface in a direction parallel to the end surface, the maximum value of the planar compressive stress of the tempered portion is 1-120 MPa, and the width of the tempered portion from the end surface in the normal direction of the end surface is 0.5 times or more the thickness of the tempered glass plate.

Description

[Technical Field]

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

[0002] Tempered glass sheets are known in which compressive stress is created on the main surfaces of the glass sheet and tensile stress is created inside the glass sheet to improve its strength. Tempered glass includes physically tempered glass, which is obtained by heating the glass sheet and then rapidly cooling it to create a temperature difference between the main surfaces and the inside, and chemically tempered glass, which is obtained by immersing the glass sheet in molten salt and performing ion exchange between ions with a small ionic radius on the main surface side and ions with a large ionic radius on the molten salt side.

[0003] Chemically strengthened glass plates have a larger compressive stress layer formed on the main surface than physically strengthened glass plates, and are therefore more resistant to sudden impacts, and have therefore been used historically as cover glass for wristwatches and more recently as cover glass for smartphones, etc. Patent Document 1 proposes chemically strengthened glass plates for use as architectural windows, exterior walls, solar cell cover glass, and vehicle windows. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2014 / 168246 Summary of the Invention [Problem to be solved by the invention]

[0005] Although a chemically strengthened glass plate is resistant to impacts on its main surfaces, it is weak against impacts on its edge surfaces and is prone to breakage if defects such as cracks occur on the edge surfaces.

[0006] The present invention provides a tempered glass sheet having high strength at both its main surfaces and edge surfaces and being resistant to breakage, and a method for producing the same. [Means for solving the problem]

[0007] The tempered glass plate of the present invention is a tempered glass plate having a first main surface, a second main surface opposite to the first main surface, and an end surface, At least one of the first main surface and the second main surface has a surface compressive stress formed by a chemical strengthening treatment, a reinforced portion in which a plane compressive stress is formed along the end surface in a direction parallel to the end surface, The maximum value of the plane compressive stress of the reinforced portion is 1 to 120 MPa, The width of the strengthened portion from the end face in the normal direction of the end face is 0.5 times or more the thickness of the strengthened glass plate.

[0008] The method for producing a tempered glass plate of the present invention is a method for producing a tempered glass plate to obtain the above-mentioned tempered glass plate, a chemical strengthening treatment step of immersing at least one main surface of a glass sheet in a molten salt to form a surface compressive stress on the main surface of the glass sheet; After the chemical strengthening treatment step, an edge strengthening step is performed to form a planar compressive stress along the edge of the glass plate in a direction parallel to the edge, In the edge surface strengthening step, the glass plate is heated so that a temperature T1 at a position on the glass plate, the position being a distance from the edge surface in a normal direction to the edge surface that is the same as the thickness of the strengthened glass plate, is equal to or higher than the strain point of the glass plate, a temperature T2 at the edge surface is lower than the softening point of the glass plate, and T1>T2. [Effects of the Invention]

[0009] The tempered glass plate of the present invention is characterized by having high strength at both the main surfaces and the edge surfaces and being resistant to breakage. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a tempered glass plate according to one embodiment of the present invention. [Figure 2] FIG. 2 shows a plan view of a tempered glass plate according to one embodiment of the present invention. [Figure 3]FIG. 3(A) is a cross-sectional view of a strengthened glass plate according to one embodiment of the present invention, FIG. 3(B) is a plan view of a strengthened glass plate according to one embodiment of the present invention, and FIG. 3(C) shows the relationship between the distance from an end face and the plane compressive stress in the parallel direction in the strengthened glass plate according to one embodiment of the present invention. [Figure 4] FIG. 4 shows a cross-sectional view of the strengthened glass sheet when irradiated with laser light in the edge strengthening step. [Figure 5] FIG. 5 shows a cross-sectional view of a tempered glass sheet according to an embodiment. [Figure 6] FIG. 6 shows the Weibull plots for Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a strengthened glass sheet according to one embodiment of the present invention will be described in detail with reference to the drawings.

[0012] Fig. 1 is a perspective view of a strengthened glass plate according to one embodiment of the present invention, Fig. 2 is a plan view of the strengthened glass plate according to one embodiment of the present invention, Fig. 3(A) is a cross-sectional view of the strengthened glass plate according to one embodiment of the present invention, Fig. 3(B) is a plan view of the strengthened glass plate according to one embodiment of the present invention, and Fig. 3(C) is a diagram showing the relationship between the distance from an end face and the plane compressive stress in the strengthened glass plate according to one embodiment of the present invention.

[0013] A tempered glass plate (10) according to one embodiment of the present invention is a tempered glass plate having a first main surface (11a), a second main surface (11b) opposite to the first main surface (11a), and an edge surface (12), wherein at least one of the first main surface (11a) and the second main surface (11b) has a surface compressive stress formed by a chemical strengthening treatment, and the tempered glass plate (30) has a planar compressive stress formed along the edge surface (12) in a direction parallel to the edge surface (12), the maximum value of the planar compressive stress of the tempered portion (30) being 1 to 120 MPa, and the width (C) of the tempered portion (30) from the edge surface (12) in the normal direction to the edge surface (12) being 0.5 times or more the thickness (T) of the tempered glass plate.

[0014] The tempered glass sheet 10 according to one embodiment of the present invention is suitable for use as, for example, architectural windows, exterior walls, handrails, solar cell cover glass, and vehicle windows. Examples of architectural windows include windows for houses, buildings, etc.

[0015] The tempered glass sheet according to one embodiment of the present invention can be used as a single sheet of glass for various applications such as architectural windows, exterior walls, handrails, solar cell cover glass, vehicle windows, etc. In another embodiment, the tempered glass sheet can be used as laminated glass in which two or more glass sheets are bonded together with an interlayer film.

[0016] In yet another embodiment, two or more glass plates can be arranged at a distance from each other and used as double glazing. In yet another embodiment, the glass plate can be used with a coating on its surface.

[0017] In the construction of laminated glass or double glazing, the tempered glass sheet of the present invention can be used for at least one sheet.

[0018] In the tempered glass plate 10 according to one embodiment of the present invention, at least one of the principal surfaces 11a and 11b is subjected to a chemical strengthening treatment to form a surface compressive stress, but it is preferable that both of the principal surfaces 11a and 11b are subjected to a chemical strengthening treatment to form a surface compressive stress. As described below, the tempered glass sheet 10 according to one embodiment of the present invention is chemically strengthened by immersing a preheated glass sheet in molten salt, such as heated potassium nitrate molten salt, to exchange ions of, for example, Na in the surface layer of the glass with K in the molten salt, thereby forming surface compressive stress on at least one of the principal surfaces 11a, 11b. Therefore, the amount of Na on the principal surfaces 11a, 11b where the surface compressive stress is formed is smaller than the amount of Na inside the tempered glass sheet 10.

[0019] In the tempered glass sheet 10 according to one embodiment of the present invention, the surface compressive stress value (hereinafter also referred to as CS) of the surface compressive stress is preferably 200 MPa or more on at least one of the first principal surface 11a and the second principal surface 11b. A CS of 200 MPa or more is preferable because the mechanical strength of the tempered glass sheet is high. CS is more preferably 250 MPa or more, even more preferably 300 MPa or more, particularly preferably 350 MPa or more, and most preferably 380 MPa or more.

[0020] On the other hand, the surface compressive stress CS of at least one of the first principal surface 11a and the second principal surface 11b is preferably 1200 MPa or less. If CS is 1200 MPa or less, the internal tensile stress is less likely to become extremely high. Furthermore, the chemical strengthening process may involve immersion in high-temperature molten salt for a short period of time, making it easy to obtain the tempered glass sheet 10. Furthermore, when cutting the tempered glass sheet 10, it becomes easy to form a score line using a wheel cutter. CS is more preferably 800 MPa or less, even more preferably 500 MPa or less, particularly preferably 480 MPa or less, and most preferably 460 MPa or less. Here, the surface compressive stress CS is a value measured at the center of gravity of the first principal surface 11a or the second principal surface 11b.

[0021] In the tempered glass sheet 10 according to one embodiment of the present invention, the depth of surface compressive stress in the sheet thickness direction (hereinafter also referred to as DOL) is preferably 5 μm or more on at least one of the first principal surface 11 a and the second principal surface 11 b. If the DOL is 5 μm or more, sufficient strength can be obtained and the glass sheet can withstand impact. The DOL is more preferably 10 μm or more, even more preferably 20 μm or more, particularly preferably 30 μm or more, and most preferably 40 μm or more.

[0022] On the other hand, the DOL of the surface compressive stress is preferably 100 μm or less. If the DOL is 100 μm or less, the immersion in the molten salt can be performed for a short period of time, making it easy to obtain the tempered glass sheet 10. The DOL is more preferably 80 μm or less, even more preferably 60 μm or less, and particularly preferably 50 μm or less. Here, the DOL of the surface compressive stress is a value measured at the center of gravity of the first main surface 11a or the second main surface 11b.

[0023] Here, CS and DOL can be measured by a surface stress meter.

[0024] The tempered glass sheet 10 according to one embodiment of the present invention may not have surface compressive stress formed on the edge surface 12 due to chemical strengthening treatment. As will be described later, a glass sheet 10 that does not have surface compressive stress formed on the edge surface 12 can be obtained by cutting a glass sheet that has been chemically strengthened. The tempered glass sheet 10 produced by such a method has good productivity because it can be produced by tempering a large glass sheet and then cutting it to the required size.

[0025] The edge surface 12 may have a chamfered portion 50 at the boundary with the first main surface 11a and at the boundary with the second main surface 11b. By providing the chamfered portion 50 on the edge surface 12, the corners of the tempered glass sheet 10 are less likely to chip when the tempered glass sheet 10 is installed in various applications such as architectural windows, exterior walls, handrails, solar cell cover glass, and vehicle windows. Examples of chamfered edge surfaces 12 include C-chamfered, R-chamfered, and a combination of R-chamfered and C-chamfered. The chamfered shape of the edge surface 12 may be linear or curved. The edge surface 12 may be polished after chamfering. Polishing can remove processing scratches caused during chamfering. The edge surface 12 may be formed by splitting the glass sheet after thermal stress scribing with a laser or gas burner to prevent microcracks from occurring when the glass sheet is cut. Furthermore, by forming the end face 12 by grinding or by cleaving after thermal stress scribing, scattering of laser light can be reduced in the end face strengthening step described later.

[0026] A tempered glass sheet 10 according to one embodiment of the present invention includes a tempered portion 30 in which a planar compressive stress is formed along an edge surface 12 in a direction parallel to the edge surface 12. A width C of the tempered portion 30 from the edge surface 12 in a direction normal to the edge surface 12 is at least 0.5 times the thickness T of the tempered glass sheet. By providing the tempered portion 30 at the edge surface 12 whose width C is at least 0.5 times the thickness T of the tempered glass sheet, the tempered glass sheet 10 is more resistant to tensile stress that occurs at the edge surface 12 when a temperature distribution occurs in the tempered glass sheet 10, and defects such as cracks are less likely to occur at the edge surface 12, making the tempered glass sheet 10 less likely to break.

[0027] The width C of the tempered portion is preferably 0.7 times or more, more preferably 1.0 times or more, even more preferably 1.5 times or more, and particularly preferably 2.0 times or more, the thickness T of the tempered glass sheet 10. There are no particular limitations on the upper limit of the width C of the tempered portion, but in order to reduce the effect of planar tensile stress generated at a position 40 of the tempered portion 30 adjacent to the end face 12 on the side opposite to the end face 12 in a direction parallel to the end face 12, the width C may be 5.0 times or less, 4.0 times or less, or 3.0 times or less the thickness T of the tempered glass sheet 10.

[0028] Here, the birefringence two-dimensional distribution evaluation device measures the deviatoric stress in the direction perpendicular to the first principal surface 11a and the second principal surface 11b. This deviatoric stress is a plane stress, and when the deviatoric stress in the direction parallel to the end surface 12 is a compressive direction, it is called a plane compressive stress, and when it is a tensile direction, it is called a plane tensile stress. Furthermore, the width C of the strengthened portion means the shortest distance from the edge of one of the principal surfaces 11a, 11b of the strengthened glass sheet 10 to the position where the measured plane compressive stress value is 0.

[0029] Furthermore, the tempered portion 30 does not have to be formed at the corner 13 where the adjacent end faces 12 meet. The distance G from the corner 13 where the adjacent end faces 12 meet to the tempered portion 30 may be 1.0 times or more and 10 times or less the thickness T of the tempered glass plate 10.

[0030] Here, when the corners 13 of the tempered glass plate 10 are chamfered and there are no corners 13, the distance from the corner where the imaginary extended surfaces of the adjacent end faces 12 meet to the tempered portion 30 may be 1.0 times or more and 10 times or less the thickness T of the tempered glass plate 10.

[0031] In the tempered glass plate 10 according to one embodiment of the present invention, the tempered portion 30 has a maximum plane compressive stress of 1 to 120 MPa. When the maximum plane compressive stress of the tempered portion 30 is 1 MPa or more, the mechanical strength of the end surface 12 is high. The maximum plane compressive stress of the tempered portion 30 is more preferably 2 MPa or more, further preferably 3 MPa or more, and particularly preferably 5 MPa or more. When the maximum plane compressive stress of the tempered portion 30 is 120 MPa or less, the plane tensile stress generated at the position 40 of the tempered portion 30 adjacent to the side opposite the end surface 12 is not too strong, and the tempered glass plate 10 is less likely to break even if the main surfaces 11a, 11b of the tempered glass plate 10 are scratched. The maximum plane compressive stress of the tempered portion 30 may be 100 MPa or less, 50 MPa or less, 30 MPa or less, or 20 MPa or less. Here, the maximum value of the planar compressive stress means the maximum value of the planar compressive stress of the strengthened portion measured on one main surface of the strengthened glass sheet 10 by a birefringence two-dimensional distribution evaluation device, and is the value shown in FIG. 3(C).

[0032] The tempered glass plate 10 according to one embodiment of the present invention preferably has no plane tensile stress in the tempered portion 30. When the tempered portion 30 has no plane tensile stress, the tempered glass plate 10 is less susceptible to thermal cracking.

[0033] The tempered glass plate 10 according to one embodiment of the present invention may have a protective layer formed on the end surface 12. Examples of the protective layer include adhesive tape, ultraviolet curable resin, and heat-melting resin.

[0034] In the tempered glass plate 10 according to one embodiment of the present invention, the areas of the first main surface 11a and the second main surface 11b are each 0.001 m 2 It is preferable that the area is 0.001 m or more. 2If the thickness is more than this, the glass can be suitably used for various applications such as architectural windows, exterior walls, solar cell cover glass, vehicle windows, etc. The areas of the first main surface 11a and the second main surface 11b are each 0.1 m 2 It may be more than 1m 2 It may be more than 2m 2 May be more than 3m 2 May be more than 5m 2 It may be more than 7m 2 May be more than 9m 2 It may be more than that.

[0035] On the other hand, the areas of the first main surface 11a and the second main surface 11b are 12 m 2 Area of 12m or less is preferred. 2 If the thickness is less than 10 m, the tempered glass plate can be easily handled, and for example, breakage due to contact with surrounding components when the tempered glass plate is installed can be suppressed. 2 It may be the following:

[0036] The tempered glass plate 10 according to one embodiment of the present invention preferably has a rectangular first principal surface 11a and a rectangular second principal surface 11b. A rectangular shape facilitates installation as, for example, an architectural window, an exterior wall, a handrail, or a solar cell cover glass. Here, a rectangle refers to a substantially rectangular quadrilateral in which, when measuring the distance from any one side to the opposite side, the error due to the measurement position is within 0.3% for both the long and short sides, and includes shapes with curvatures or notches at the corners.

[0037] In the case where the tempered glass sheet 10 according to one embodiment of the present invention is rectangular, the length b of the long sides of the first main surface 11a and the second main surface 11b may be 50 mm or more, 100 mm or more, 300 mm or more, 500 mm or more, 1000 mm or more, 2000 mm or more, or 2500 mm or more. The length b of the long sides of the first main surface 11a and the second main surface 11b may be 5000 mm or less. Here, the length b of the long sides is the shortest distance b between the two opposing short sides shown in FIG. 2.

[0038] In the case where the tempered glass sheet 10 according to one embodiment of the present invention is rectangular, the length a of the short sides of the first main surface 11a and the second main surface 11b may be 5 mm or more, 10 mm or more, 50 mm or more, 100 mm or more, 500 mm or more, 1000 mm or more, or 2000 mm or more. The length a of the short sides of the first main surface 11a and the second main surface 11b may be 3000 mm or less. Here, the length a of the short sides is the shortest distance a between the two opposing long sides shown in FIG. 2.

[0039] The thickness of the tempered glass plate 10 according to one embodiment of the present invention may be 0.5 mm or more in terms of strength, handling, etc. The thickness may be 1 mm or more, 2 mm or more, 3 mm or more, or 5 mm or more. On the other hand, a thickness of 25 mm or less is preferable because it is lightweight. The thickness is more preferably 22 mm or less, and even more preferably 19 mm or less.

[0040] The tempered glass plate 10 according to one embodiment of the present invention preferably weighs 1000 kg or less. A weight of 1000 kg or less is preferable because it is light. A weight of 500 kg or less is more preferable. Furthermore, from the viewpoint of strength, the weight is preferably 2 kg or more. A weight of 5 kg or more is more preferable, and a weight of 10 kg or more is even more preferable.

[0041] Furthermore, the tempered glass plate 10 according to one embodiment of the present invention may have a functional film such as a heat ray reflective film or an antifouling film formed on one or both of the first main surface 11a and the second main surface 11b.

[0042] The tempered glass plate 10 according to one embodiment of the present invention preferably has a glass transition temperature Tg of 530° C. or higher, which can prevent the relaxation of surface compressive stress during ion exchange. The glass transition temperature Tg is more preferably 540° C. or higher.

[0043] The specific gravity of the strengthened glass plate 10 according to one embodiment of the present invention is preferably 2.45 to 2.55.

[0044] The symbol "to" indicating the above-mentioned numerical range is used to mean that the numerical values before and after it are included as the lower limit and upper limit, and unless otherwise specified, "to" is used in the following specification with the same meaning.

[0045] The strengthened glass sheet 10 according to one embodiment of the present invention preferably has a uniform specific gravity throughout the strengthened glass sheet 10. The uniform specific gravity throughout the strengthened glass sheet 10 means that the difference between the specific gravity of a portion of the strengthened glass sheet 10 from the end surface 12 to a depth of 1 / 10 or less of the sheet thickness and the specific gravity of a portion of the strengthened glass sheet 10 at the center from the main surfaces 11a, 11b to a depth of 1 / 10 or less of the sheet thickness is in the range of -0.50% to 0.00% of the specific gravity of the portion of the strengthened glass sheet 10 at the center from the main surfaces 11a, 11b to a depth of 1 / 10 or less of the sheet thickness. The specific gravity can be estimated by measuring the surface fictive temperature using any method, such as spectroscopic Raman spectroscopy.

[0046] The Young's modulus of the tempered glass plate 10 according to one embodiment of the present invention is preferably 65 GPa or more. This ensures sufficient rigidity and fracture strength. The Young's modulus may be 70 GPa or more. On the other hand, if the Young's modulus is 90 GPa or less, the tempered glass plate is prevented from becoming brittle, and chipping during cutting and dicing of the tempered glass plate can be suppressed. The Young's modulus may be 85 GPa or less, or even 80 GPa or less.

[0047] The tempered glass sheet 10 according to one embodiment of the present invention has an average thermal expansion coefficient of 30×10 at 50 to 350°C. -7 / ℃ or more 140×10 -7 / °C or less. The average thermal expansion coefficient at 50 to 350°C is preferably 30×10 -7 / °C or more, the tempered portion 30 can be formed even if the temperature T2 of the edge surface of the glass plate 10 is lower than the softening point of the glass plate 10 when irradiated with laser light 60 in the edge surface tempering step described below. -7 / ℃ or more is more preferable, and 80×10 -7 / ℃ or more is more preferable, and 85×10 -7 / °C or more is particularly preferred. In addition, the average thermal expansion coefficient at 50 to 350°C is 140 × 10 -7 / °C or less, the stress generated when a temperature difference occurs between the part irradiated with the laser beam 60 and the part not irradiated with the laser beam 60 during the edge strengthening step does not become too large, and the tempered glass sheet 10 is less likely to break. -7 / ℃ or less is more preferable, and 95×10 -7 / °C or less is more preferable.

[0048] Here, the tempered glass plate 10 according to one embodiment of the present invention preferably contains, expressed as mole percentages on an oxide basis, 0.003 to 1.5% Fe2O3, 56 to 75% SiO2, 0 to 20% Al2O3, 8 to 22% Na2O, 0 to 10% K2O, 0 to 14% MgO, 0 to 5% ZrO2, and 0 to 12% CaO. Hereinafter, percentages indicate the contents expressed as mole percentages on an oxide basis, unless otherwise specified.

[0049] The reasons for limiting the glass composition to the above range in the tempered glass plate 10 according to one embodiment of the present invention will be explained below.

[0050] It is preferable to add Fe2O3 when a near-infrared laser is used for edge processing, which will be described later. 2+ The ions absorb laser light with a wavelength of 1000 to 1100 nm. If the Fe2O3 content is 0.003% or more, the end surface can be efficiently heated by laser light. The Fe2O3 content is more preferably 0.005% or more, even more preferably 0.01% or more, particularly preferably 0.02% or more, and most preferably 0.05% or more. If the Fe2O3 content is 1.5% or less, the laser light is less likely to be absorbed by the glass surface and is easily focused inside the glass. The Fe2O3 content is more preferably 1.0% or less, even more preferably 0.5% or less, even more preferably 0.3% or less, particularly preferably 0.2% or less, and most preferably 0.1% or less.

[0051] When using a laser beam other than near-infrared, it is preferable to incorporate an appropriate amount of an absorbing component in the glass in accordance with the wavelength of the laser beam. Since absorption of light in the visible light region colorizes the glass, colored glass may be used for strengthening the end face with a visible light laser.

[0052] SiO2 is a component that forms a network structure in the glass microstructure and is the main component that constitutes glass. The SiO2 content is preferably 56% or more, more preferably 63% or more, even more preferably 66% or more, and particularly preferably 68% or more. The SiO2 content is preferably 75% or less, more preferably 73% or less, and even more preferably 72% or less. An SiO2 content of 56% or more is advantageous in terms of stability and weather resistance as glass. On the other hand, an SiO2 content of 75% or less is advantageous in terms of meltability and formability.

[0053] Although not essential, Al2O3 may be added because it improves ion exchange performance during chemical strengthening, particularly increasing CS. It also improves the weather resistance of the glass. When Al2O3 is added, it is preferably 0.4% or more, more preferably 0.6% or more, and even more preferably 0.8% or more. It also lowers the refractive index and reflectance. Furthermore, an Al2O3 content of 20% or less prevents a significant increase in the devitrification temperature even when the glass has high viscosity, which is advantageous in terms of melting and molding in soda-lime glass production lines. The Al2O3 content is more preferably 10% or less, even more preferably 5% or less, particularly preferably 3% or less, and most preferably 2% or less.

[0054] The total content of SiO2 and Al2O3 (hereinafter also referred to as the SiO2 + Al2O3 content) is preferably 68% or more. When the SiO2 + Al2O3 content is 68% or more, crack resistance when indented is improved. In addition, the refractive index is lowered, and reflectance is reduced. The SiO2 + Al2O3 content is more preferably 70% or more. Furthermore, the SiO2 + Al2O3 content is preferably 80% or less. When the SiO2 + Al2O3 content is 80% or less, the viscosity of the glass at high temperatures is reduced, making it easier to melt. The SiO2 + Al2O3 content is more preferably 76% or less, and even more preferably 74% or less.

[0055] Na2O is a component that forms surface compressive stress through ion exchange and has the effect of deepening the DOL. It is also a component that lowers the high-temperature viscosity and devitrification temperature of glass, improving the meltability and formability of glass. The Na2O content is preferably 8% or more, more preferably 10% or more, and even more preferably 12% or more. The Na2O content is preferably 22% or less, more preferably 16% or less, and even more preferably 14% or less. When the Na2O content is 8% or more, the desired surface compressive stress is easily formed by ion exchange. On the other hand, when the Na2O content is 22% or less, sufficient weather resistance is obtained.

[0056] K2O may be added because it has the effect of increasing the ion exchange rate and deepening the DOL. On the other hand, if the amount of K2O is too much, sufficient CS cannot be obtained. When K2O is added, it is preferably 10% or less, more preferably 2% or less, and even more preferably 1% or less. When the K2O content is 10% or less, sufficient CS can be obtained.

[0057] MgO is not essential, but is a component that stabilizes the glass. When MgO is contained, it is preferably 2% or more, more preferably 4% or more, and even more preferably 6% or more. The MgO content is preferably 14% or less, more preferably 10% or less, and even more preferably 8% or less. When the MgO content is 2% or more, the chemical resistance of the glass is improved. The melting property at high temperatures is improved, and devitrification is less likely to occur. On the other hand, when the MgO content is 14% or less, the resistance to devitrification is maintained and a sufficient ion exchange rate is obtained.

[0058] ZrO2 is a component that increases the refractive index, and it is preferable that it is not substantially contained in order to lower the refractive index and reduce the reflectance. In this specification, "substantially not contained" means that it is not contained except as unavoidable impurities mixed in from raw materials, etc., that is, it is not intentionally contained. However, ZrO2 may be contained because it has the effect of increasing the CS of chemically strengthened glass. If it is contained, it is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less.

[0059] CaO is not essential, but is a component that stabilizes the glass. When CaO is contained, the CaO content is preferably 2% or more, more preferably 5% or more, and even more preferably 7% or more. The CaO content is preferably 12% or less, more preferably 10% or less, and even more preferably 9% or less. When the CaO content is 2% or more, chemical resistance is improved. When the CaO content is 12% or less, a sufficient ion exchange rate is maintained, and the desired DOL is obtained.

[0060] Although SrO is not essential, it may be contained for the purpose of lowering the high-temperature viscosity of the glass and lowering the devitrification temperature. Since SrO has the effect of lowering the ion exchange efficiency, it is preferable not to contain SrO, especially when it is desired to increase the DOL. When SrO is contained, the amount of SrO is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less.

[0061] Although BaO is not essential, it may be contained for the purpose of lowering the high-temperature viscosity of the glass and lowering the devitrification temperature. Because BaO has the effect of increasing the specific gravity of the glass, it is preferable not to contain BaO when weight reduction is intended. When BaO is contained, the amount of BaO is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less.

[0062] ZnO is preferably not substantially contained, since it is reduced in the float bath when a glass sheet is formed by the float method, causing defects in the product.

[0063] In addition, sulfates, chlorides, fluorides, etc. may be appropriately contained as a fining agent for the glass melt.

[0064] The tempered glass sheet of the present invention essentially consists of the components described above, but may contain other components within a range that does not impair the object of the present invention. When such components are contained, the total content of these components is preferably 5% or less, more preferably 3% or less, and typically 1% or less. Hereinafter, the other components will be described by way of example.

[0065] B2O3 may be contained in a range of less than 1% in order to improve the melting property at high temperatures or the glass strength. Generally, if an alkali component such as Na2O or K2O and B2O3 are contained at the same time, volatilization becomes intense and the brick is significantly corroded, so it is preferable that B2O3 is not substantially contained.

[0066] LiO is a component that lowers the strain point and makes stress relaxation more likely to occur, making it impossible to obtain a stable surface compressive stress. Therefore, it is preferable that LiO not be contained, and even if it is contained, the content is preferably 1% or less, more preferably 0.05% or less, and particularly preferably 0.01% or less.

[0067] Next, a method for manufacturing the strengthened glass plate 10 according to one embodiment of the present invention will be described.

[0068] When manufacturing the tempered glass plate 10 according to one embodiment of the present invention, a glass plate manufacturing step, a chemical tempering treatment step, and an edge tempering step are performed.

[0069] In the glass plate manufacturing process, for example, various raw materials are mixed in appropriate amounts, heated to about 1400 to 1800°C and melted, then homogenized by degassing, stirring, etc., and formed into a plate by a well-known method such as the float method, down-draw method, roll-out method, or press method. After annealing, the glass plate is cut to a desired size.

[0070] In the chemical strengthening treatment step, at least one main surface of the obtained glass sheet is immersed in molten salt to form a desired surface compressive stress on the main surface. The chemical strengthening treatment step includes a preheating step, a chemical strengthening step, and a slow cooling step.

[0071] In the preheating step, the glass plate is preheated before chemical strengthening. Preheating is performed, for example, by placing the glass plate in an electric furnace at room temperature, heating the electric furnace to the preheat temperature, and maintaining the temperature for a certain period of time. To prevent cracking due to thermal shock during the chemical strengthening step, the glass plate is preferably maintained at the preheat temperature for a certain period of time after the temperature increase is complete. This maintenance time is preferably 10 minutes or more, more preferably 20 minutes or more, even more preferably 30 minutes or more, and particularly preferably 40 minutes or more.

[0072] In the chemical strengthening treatment step, a preheated glass sheet is immersed in a molten salt, for example, heated potassium nitrate molten salt, to exchange Na on the surface of the glass with K in the molten salt. Note that in the present invention, the potassium nitrate molten salt includes KNO3, KNO2, and those containing 10 mass% or less of NaNO3.

[0073] The conditions for chemical strengthening treatment to form a desired surface compressive stress in a glass sheet vary depending on factors such as the thickness of the glass sheet, but typically involve immersing the glass sheet for 2 to 50 hours in a molten salt such as potassium nitrate molten salt at 350 to 550° C. From an economical standpoint, conditions in which the glass sheet is immersed at 350 to 500° C. for 2 to 40 hours are preferred, with an immersion time of 2 to 30 hours being more preferred.

[0074] In the annealing step, the glass sheet taken out from the molten salt is annealed. It is preferable that the glass sheet taken out from the molten salt is not annealed immediately, but is maintained at a uniform temperature for a certain period of time in order to prevent temperature distribution from occurring on the main surface of the glass sheet.

[0075] The difference between the holding temperature and the temperature of the molten salt is preferably 100° C. or less, more preferably 50° C. or less, even more preferably 20° C. or less, and particularly preferably 10° C. or less. The holding time is preferably 10 minutes or more, more preferably 20 minutes or more, and even more preferably 30 minutes or more.

[0076] The glass sheet taken out of the molten salt is preferably cooled slowly at a rate of 300°C / hour or less until the temperature of the glass sheet reaches 100°C, more preferably 200°C / hour or less, and even more preferably 100°C / hour or less.

[0077] The chemical strengthening treatment step may be performed after the end face 12 is chamfered, or the end face 12 may be chamfered after the chemical strengthening treatment step, or the end face 12 may not be chamfered.

[0078] The chemical strengthening treatment step may be followed by a cutting step of cutting the chemically strengthened glass plate. By including the cutting step after the chemical strengthening treatment step, productivity is improved. By cutting the chemically strengthened glass plate after the chemical strengthening treatment step, a glass plate can be obtained in which surface compressive stress due to the chemical strengthening treatment is not formed on the end surface 12. In the cutting step, the glass plate may be cut by thermal stress scribing using a laser or a gas burner followed by cleaving. By cleaving the glass plate after thermal stress scribing, microcracks are less likely to occur. In addition, scattering of laser light during the edge strengthening step can be reduced.

[0079] In the edge strengthening step, a planar compressive stress is formed in a direction parallel to the edge surface along the edge surface of the glass plate on whose main surface a surface compressive stress has been formed in the chemical strengthening treatment step. FIG. 4 is a cross-sectional view of the strengthened glass sheet when irradiated with laser light in the edge strengthening step. In the end face strengthening process, for example, by irradiating the end face 12 of the glass plate 10 with the laser beam 60, the inside of the glass plate 10 is heated. Then, since the inside of the glass plate 10 is cooled more slowly than the end face 12 of the glass plate 10, tensile stress is generated inside the glass plate 10. At this time, a compressive stress region corresponding to the tensile stress region generated inside the glass plate 10 due to the stress balance is formed on the end face 12 of the glass plate, and the end face 12 can be strengthened.

[0080] In the end face strengthening process, when irradiating with the laser beam 60, the glass plate 10 is heated so that the temperature T1 at the position D, which is at the same distance from the end face in the normal direction of the end face of the glass plate 10 as the thickness of the glass plate 10, becomes equal to or higher than the strain point of the glass plate 10. If the temperature T1 at the position D is equal to or higher than the strain point of the glass plate 10, the end face 12 is sufficiently strengthened.

[0081] In the end face strengthening process, when irradiating with the laser beam 60, the temperature T2 of the end face 12 of the glass plate 10 is lower than the softening point of the glass plate 10 and T1>T2. If the temperature of the end face 12 is lower than the softening point of the glass plate 10 and T1>T2, no tensile stress will be generated on the surface of the end face 12 thereafter. If the temperature of the end face 12 is T1<T2, tensile stress may be generated on a part of the surface of the end face 12 thereafter. Also, if the temperature of the end face 12 is equal to or higher than the softening point, the end face will be deformed. When irradiating with the laser beam 60, the temperature T2 of the end face 12 of the glass plate 10 is preferably below the slow cooling point of the glass plate 10, more preferably below the strain point of the glass plate 10.

[0082] In the end face strengthening process, when irradiating with the laser beam 60, it is preferable that the temperatures of the first main surface 11a and the second main surface 11b of the glass plate 10 are 300°C or lower. If the temperatures of the first main surface 11a and the second main surface 11b of the glass plate 10 are 300°C or lower, deformation of the glass plate 10 can be suppressed. Also, diffusion of ions can be suppressed, and a decrease in the strength of the first main surface 11a and the second main surface 11b can be suppressed. When irradiating with the laser beam 60, the temperatures of the first main surface 11a and the second main surface 11b of the glass plate 10 are more preferably 200°C or lower, and even more preferably 100°C or lower.

[0083] In the edge strengthening step, by irradiating the interior of the glass plate 10 from the edge 12 of the glass plate 10 with laser light 60, the interior of the glass plate 10 can be heated over a wide range, and strengthening of the edge 12 can be promoted.

[0084] The laser beam 60 is preferably irradiated onto the end face 12 of the glass plate 10 and focused inside the glass plate 10. By arranging the focusing point 21 of the laser beam 60 inside the glass plate 10, the temperature inside the glass plate 10 becomes higher than the surface of the glass plate 10. The laser light 60 causes mainly linear absorption when irradiated onto the glass plate 10. Mainly linear absorption means that the amount of heat generated by linear absorption is greater than the amount of heat generated by nonlinear absorption. There may be almost no nonlinear absorption.

[0085] Nonlinear absorption is also called multiphoton absorption. The probability of multiphoton absorption occurring is nonlinear with respect to the photon density (power density of the laser light 60), and the higher the photon density, the greater the probability. For example, the probability of two-photon absorption occurring is proportional to the square of the photon density.

[0086] According to the findings of the present inventors, in the case of the glass plate 10, in order to generate nonlinear absorption effective for generating tensile stress inside the glass plate 10, the photon density must be 1×10 8 W / cm 2 The above is preferable.

[0087] At any point on the glass plate 10, the photon density is 1×10 8 W / cm 2 In this case, almost no nonlinear absorption occurs. Since the cross-sectional size of the laser light 60 is larger than the wavelength, the size of the focal point 21 is not zero, and the photon density at the focal point is 1×10 8 W / cm 2 It may be less than.

[0088] On the other hand, linear absorption is also called one-photon absorption. The probability of one-photon absorption occurring is proportional to the photon density. In the case of one-photon absorption, the intensity of the laser light 60 attenuates according to the Lambert-Beer's law.

[0089] If the intensity of the laser beam 60 changes from I0 to I while the laser beam 60 travels a distance E (unit: cm) through the glass plate 10, the equation I=I0×exp(-α×E) holds true. α is the absorption coefficient of the glass plate 10 (unit: cm -1 ]) and is measured using an ultraviolet-visible-near-infrared spectrophotometer or the like.

[0090] The absorption coefficient α may be, for example, smaller than 100. If the absorption coefficient α is 100 or greater, most of the laser light 60 is absorbed near the surface of the glass plate 10, making it difficult to heat the inside of the glass plate 10. The absorption coefficient α is preferably smaller than 30, and more preferably smaller than 10. The absorption coefficient α is generally larger than 0. The absorption coefficient α depends on the wavelength of the laser light 60 and the glass composition of the glass plate 10, among other factors. It is preferable to irradiate laser light having a wavelength that results in an absorption coefficient α of smaller than 100.

[0091] The wavelength of the laser light 60 may be, for example, 250 to 5000 nm, depending on the glass composition of the glass plate 10. When the wavelength of the laser light 60 is 250 to 5000 nm, the absorption coefficient α falls within an appropriate range.

[0092] Examples of light sources for the laser light 60 include near-infrared lasers such as Yb fiber laser (wavelength: 1000 to 1100 nm), Yb disk laser (wavelength: 1000 to 1100 nm), Nd:YAG laser (wavelength: 1064 nm), and high-power semiconductor laser (wavelength: 808 to 980 nm). In addition, as a light source for the laser light 60, a UV laser (wavelength: 355 nm), a green laser (wavelength: 532 nm), a Ho:YAG laser (wavelength: 2080 nm), an Er:YAG laser (2940 nm), or a laser using a mid-infrared optical parametric oscillator (wavelength: 2600 to 3450 nm) can also be used.

[0093] The light source of the laser light 60 may be a pulsed type, but is preferably a continuous wave type, which allows the interior of the glass plate 10 to be heated over a wide range.

[0094] Although the number of laser beams 60 is one in FIG. 4, it may be plural, and plural laser beams 60 may be irradiated onto the glass plate 10 simultaneously.

[0095] In the edge strengthening process, laser light 60 is irradiated onto the glass sheet 10 to primarily cause linear absorption, and the interior of the glass sheet 10 is heated to a temperature higher than that of the edge 12 of the glass sheet 10, thereby generating tensile stress and strengthening the edge 12 of the glass sheet 10. By primarily causing linear absorption, the interior of the glass sheet 10 can be heated over a wider area than when primarily causing nonlinear absorption, and strengthening of the edge 12 can be promoted. Furthermore, by heating the interior of the glass sheet 10 to a temperature higher than that of the edge 12 of the glass sheet 10, planar tensile stress is less likely to occur in the strengthened portion 30, and thermal cracking of the glass sheet 10 originating from the heated portion can be suppressed.

[0096] In the edge strengthening step, the irradiation position of the laser beam 60 is moved along the edge 12 of the glass sheet 10, thereby forming a strengthened portion 30 on the outer edge of the glass sheet 10. The strengthened portion 30 may be formed continuously along at least a part of the outer edge of the glass sheet 10, or may be formed entirely along the outer edge of the glass sheet 10.

[0097] The position on the glass plate 10 that is irradiated with the laser beam 60 can be moved by moving the glass plate 10, the light source of the laser beam 60, or both. The position on the glass plate 10 that is irradiated with the laser beam 60 can also be moved by operating a galvanometer mirror.

[0098] The irradiation start position of the laser beam 60 is preferably such that the center of the irradiation shape of the laser beam 60 on the edge face 12 of the glass plate 10 is located more inward than the edge of the glass plate 10 on the edge face 12 of the glass plate 10. By starting the irradiation of the laser beam 60 from the position more inward than the edge of the glass plate 10, the glass plate 10 is less likely to break and the manufacturing equipment is less likely to be burned.

[0099] The irradiation shape of the laser beam 60 on the edge surface 12 of the glass plate 10 may be formed linearly along the moving direction of the laser beam 60 on the glass plate 10. In this case, the power distribution of the laser beam 60 on the glass plate 10 in the moving direction may be a top hat distribution or a Gaussian distribution. By forming the irradiation shape linearly, the temperature change of the glass plate 10 becomes gradual, and thermal cracking of the glass plate 10 in the edge surface tempering step can be suppressed.

[0100] The width Φ (see FIG. 4) in the thickness direction of the irradiation shape of the laser beam 60 on the edge face 12 of the glass plate 10 may be set to be equal to or less than the thickness of the glass plate 10. By setting the width Φ in the thickness direction of the irradiation shape of the laser beam 60 on the edge face 12 of the glass plate 10 to be equal to or less than the thickness of the glass plate 10, heating of the main faces 11a, 11b near the edge face 12 can be suppressed, and a decrease in the surface compressive stress formed by the chemical strengthening treatment on the main faces 11a, 11b near the edge face 12 can be suppressed.

[0101] The center position of the power distribution of the laser beam 60 in the thickness direction of the glass sheet 10 may coincide with the center of the thickness. By coinciding with the center of the thickness, the edge strengthening step can be carried out effectively. Furthermore, by coinciding with the center of the thickness, warping of the glass sheet 10 is less likely to occur after edge strengthening. Here, coinciding with the center of the thickness means that the center position of the power distribution of the laser beam 60 in the thickness direction may coincide completely with the center of the thickness, or may be shifted from the center of the thickness by up to ±30% of the thickness, or may be shifted by up to ±15% of the thickness. Furthermore, in order to control the center position of the power distribution of the laser beam 60 in the thickness direction to coincide with the center of the thickness, the surface of the glass sheet 10 may be measured using, for example, a distance sensor.

[0102] When irradiating the edge surface 12 of the glass plate 10 with the laser beam 60, it is preferable to restrain the main surface of the glass plate 10 with a jig or the like. By restraining the main surface of the glass plate 10, deformation is suppressed even if the glass plate 10 expands due to irradiation with the laser beam 60, and the glass plate 10 does not deviate from the irradiation position of the laser beam 60, making it possible to irradiate the laser beam 60 at a desired position on the glass plate 10. It is preferable that the entire main surface of the glass plate 10 is restrained with a jig, but part of the main surface of the glass plate 10 may also be restrained. When part of the main surface of the glass plate 10 is restrained, it is preferable that the jigs be installed on the main surface of the glass plate 10 at regular intervals, and the intervals may be 250 mm or less. Furthermore, it is preferable that the jig uses a material with low thermal conductivity in the portion that comes into contact with the glass plate 10. By using a material with low thermal conductivity, thermal stress is less likely to occur in the contact portion on the surface of the glass plate 10, and the glass plate 10 is less likely to break. Examples of materials with low thermal conductivity include MC nylon and fluororesin.

[0103] The intensity and moving speed of the laser beam 60 are preferably determined after previously measuring the absorption coefficient α of the glass plate 10. As the absorption coefficient α increases, it is preferable to set the intensity of the laser beam 60 to be weaker and the moving speed to be faster. If the intensity of the laser beam 60 is too strong, the glass plate 10 is likely to break.

[0104] In the edge strengthening step, a gas such as compressed air, a liquid such as mist, or a mixture thereof may be sprayed onto the glass sheet 10. This can suppress a temperature rise on the surface of the glass sheet 10. In addition, a temperature difference between the surface and the interior of the glass sheet 10 can be ensured, and the irradiation conditions for the laser beam 60 can be relaxed. In addition, foreign matter such as dust adhering to the surface of the glass sheet 10 can be removed. When the laser beam 60 hits a foreign matter, the foreign matter may absorb the laser beam 60.

[0105] After the end face strengthening step, a protective layer may be formed on the end face 12 .

[0106] In the tempered glass plate of the present embodiment described above, both the main surfaces and the end surfaces have high strength and are less likely to break.

[0107] The present invention is not limited to the above-described embodiment, and includes modifications and improvements within the scope of the present invention that can achieve the object of the present invention. In the above embodiment, an example has been given of a form in which the inside of the glass plate 10 is heated by irradiating the end face 12 of the glass plate with laser light 60 in the end face strengthening process, but the end face 12 may also be strengthened by heating the inside of the glass plate 10 with an infrared heater or microwaves. [Example]

[0108] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. FIG. 5 is a cross-sectional view showing a strengthened glass sheet 200 of the example. Examples 1, 3, and 5 are working examples, and Examples 2, 4, and 6 are comparative examples.

[0109] Various glass raw materials such as silica sand were mixed to obtain the glass composition shown in Table 1, and melted at a temperature of 1400 to 1500°C. The resulting molten glass was formed into a plate by the float method to have the thickness T shown in Table 2, and cut to obtain rectangular glass plates. The glass transition temperature Tg (unit: °C), specific gravity, Young's modulus (unit: GPa), and average thermal expansion coefficient (unit: 10 -7 The results are shown in Table 1.

[0110] The methods for measuring the various physical properties of the glass plate are shown below. (glass transition temperature Tg) Measurement was carried out using a differential thermal dilatometer (TMA) according to the method specified in JIS R3103-3 (2001). (specific gravity) A glass block of about 20 g containing no bubbles was measured by the Archimedes method. (Young's modulus) Measurement was carried out by the ultrasonic pulse method. (average thermal expansion coefficient) Measurement was performed using a differential thermal dilatometer (TMA) in accordance with the method specified in JIS R3102 (1995). The measurement temperature range was 50 to 350°C.

[0111] (Example 1) The obtained glass plate was cut using a wheel cutter to have a short side length a and a long side length b as shown in Table 2, and then C-chamfered. The beveled glass plate was immersed in molten potassium nitrate and chemically strengthened to obtain a tempered glass plate. The CS and DOL of the main surface of the obtained tempered glass plate were measured. CS and DOL were calculated from the number and spacing of interference fringes observed using a surface stress meter (Orihara Seisakusho: FSM-7000H). For the calculation, the refractive index of the tempered glass plate was set to 1.518, and the optical elastic constant was set to 27.1 [(nm / cm) / MPa]. The results of CS and DOL of the main surface are shown in Table 2.

[0112] As shown in FIG. 5 , an end face 212 of the obtained tempered glass plate 200 was faced upward, and a main surface 211 of the glass plate was fixed with a jig. Laser light 260 was irradiated from above onto the end face 212 in a vertical direction so as to be focused inside the tempered glass plate 200, thereby forming a tempered portion in which planar compressive stress was formed along the end face 212. A fiber laser with a wavelength (1070 nm) that mainly causes linear absorption was used as a light source of the laser beam 260. The irradiation position of the laser beam 260 was the center in the plate thickness direction of the edge surface 212 of the strengthened glass sheet 200, and it was moved in the longitudinal direction of the strengthened glass sheet 200 at a moving speed of 10.0 mm / sec. The irradiation shape of the laser beam 260 on the edge surface 212 of the glass sheet 200 was 2 mm wide and 100 mm long. The irradiation start position of the laser beam 260 was set so that the center of the irradiation shape of the laser beam 260 on the edge surface 212 of the glass sheet 200 was located inside the edge of the glass sheet 200 on the edge surface 212 of the glass sheet 200. The depth f (see FIG. 5) of the focal point in the width direction from the end surface 212 of the strengthened glass plate 200 was 56.8 mm, and the output P (not shown) of the light source of the laser beam 260 was 1300 W. The absorption coefficient of the glass plate was 0.57 [1 / cm]. By irradiating the strengthened glass sheet 200 with the laser beam 260, the temperature of a position D, which is a distance from the end face 212 in the normal direction to the end face 212 of the strengthened glass sheet 200 that is the same as the thickness of the strengthened glass sheet 200, becomes equal to or higher than the strain point of the strengthened glass sheet 200. The temperature of the end face 212 of the glass sheet 10 was 607°C. Since the softening point of the glass sheet 10 is 730°C, the temperature of the end face 212 is lower than the softening point, and T1>T2 holds. The maximum value of the plane compressive stress of the tempered portion of the tempered glass plate 200 of Example 1 was 22.1 MPa, and the width C of the tempered portion from the end surface 212 was 2.7 mm. The width C was 0.5 times or more the thickness T of the glass plate 200. Furthermore, no plane tensile stress was formed in the tempered portion. The plane compressive stress of the tempered portion was measured using a birefringence two-dimensional distribution evaluation device (WPA-100 manufactured by Photonic Lattice, Inc.).

[0113] Fifteen tempered glass sheets 200 were produced using the above method, and the four-point bending strength of each of the 15 tempered glass sheets 200 was measured by bending the tempered glass sheets 200 convexly downward with the end surface 212 irradiated with the laser light 260 facing downward. The obtained values were averaged to determine the average breaking stress. Furthermore, a Weibull plot was performed in accordance with JIS R 1625 (1996) to determine the Weibull coefficient. The upper span was 20 mm, the lower span was 60 mm, and the head speed was 1 mm / min. The resulting average breaking stress was 346 MPa. The 0.1% fracture probability strength, calculated assuming that the logarithm of the fracture stress follows a normal distribution, was 259 MPa, and the Weibull coefficient was 12.3.

[0114] (Example 2) Eighteen tempered glass plates 200 were produced by the same method as in Example 1, except that the edge surface 212 was not irradiated with the laser light 260. A four-point bending test was conducted as in Example 1. As a result, the maximum value of the plane compressive stress in the tempered portion was 1.9 MPa, and the width C from the edge surface 212 of the tempered portion was 0.77 mm. The width C was less than 0.5 times the thickness T of the glass plate 200. The average breaking stress was 311 MPa. The 0.1% fracture probability strength, calculated by assuming that the logarithm of the breaking stress follows a normal distribution, was 122 MPa, and the Weibull coefficient was 3.6. The Weibull plots for Examples 1 and 2 are shown in Figure 6. Comparing the results of the four-point bending test for Examples 1 and 2, the average fracture stress and Weibull modulus for Example 1, in which the end surface was irradiated with laser light, were greater than those for Example 2, in which the end surface was not irradiated with laser light. In addition, the 0.1% fracture probability strength, calculated by assuming that the logarithm of the fracture stress for Example 1, in which the end surface was irradiated with laser light, follows a normal distribution, was greater than the 0.1% fracture probability strength, calculated by assuming that the logarithm of the bending strength for Example 2, in which the end surface was not irradiated with laser light, follows a normal distribution. It was found that the end surface could be strengthened by irradiating the end surface with laser light and forming a reinforced portion on the end surface.

[0115] (Example 3) The glass was formed into a plate by the float process in the same manner as in Example 1, to obtain a rectangular glass plate. The obtained glass plate was immersed in molten potassium nitrate and chemically strengthened to obtain a tempered glass plate. The obtained tempered glass plate was cut with a wheel cutter to have a short side length a and a long side length b shown in Table 2, and then C-chamfered. The CS and DOL of the beveled tempered glass plate were measured. The results are shown in Table 2. Next, the end surface was irradiated with laser light 260 in the same manner as in Example 1, but the depth f of the focal point in the width direction from the end surface 212 of the strengthened glass plate 200 (see Figure 5) was 30 mm, and the output P of the light source of the laser light 260 was 1600 W. The maximum value of the plane compressive stress in the tempered portion of the tempered glass plate 200 of Example 3 was 62.7 MPa, and the width C of the tempered portion from the end surface 212 was 3.0 mm. The width C was 0.5 times or more the thickness T of the tempered glass plate 200. In addition, no plane tensile stress was formed in the tempered portion. A four-point bending test was carried out in the same manner as in Example 1, and the average breaking stress was found to be 208 MPa. The 0.1% breaking probability strength, calculated on the assumption that the logarithmic value of the breaking stress follows a normal distribution, was 159 MPa.

[0116] (Example 4) Nineteen tempered glass plates were produced by the same method as in Example 3, except that the edge surface 212 was not irradiated with the laser light 260. A four-point bending test was conducted in the same manner as in Example 3. As a result, the maximum value of the plane compressive stress in the tempered portion was 2.1 MPa, and the width C from the edge surface 212 of the tempered portion was 0.52 mm. The width C was less than 0.5 times the thickness T of the tempered glass plate 200. The average breaking stress was 84 MPa. The 0.1% fracture probability strength, calculated by assuming that the logarithm of the breaking stress follows a normal distribution, was 66 MPa.

[0117] Comparing the results of the four-point bending test for Example 3 and Example 4, the average breaking stress of Example 3, in which the end surface was irradiated with laser light, was greater than the average breaking stress of the bending strength of Example 4, in which the end surface was not irradiated with laser light. In addition, the 0.1% fracture probability strength, calculated on the assumption that the logarithm of the fracture stress of Example 3, in which the end surface was irradiated with laser light, follows a normal distribution, was greater than the 0.1% fracture probability strength, calculated on the assumption that the logarithm of the bending strength of Example 4, in which the end surface was not irradiated with laser light, follows a normal distribution. It was found that the end surface could be strengthened by irradiating the end surface with laser light and forming a reinforced portion on the end surface.

[0118] (Example 5) A tempered glass plate was obtained in the same manner as in Example 1. The obtained tempered glass plate was thermally stress scribed with a laser and then cleaved to have a short side length a and a long side length b shown in Table 2, thereby obtaining 10 mirror-finished, C-chamfered tempered glass plates. An edge surface 212 of the obtained tempered glass plate was faced upward, and a main surface 211 of the glass plate was fixed with a jig. A laser beam 260 was irradiated perpendicularly from above onto the edge surface 212, thereby forming a tempered portion in which planar compressive stress was formed on the edge surface 212. A fiber laser with a wavelength (1070 nm) that mainly causes linear absorption was used as the light source of the laser beam 260. The irradiation position of the laser beam 260 was the center in the plate thickness direction of the edge surface 212 of the glass plate 200, and it was moved in the longitudinal direction of the glass plate 200 at a moving speed of 10.0 mm / sec. The irradiation shape of the laser beam 260 on the edge surface 212 of the strengthened glass plate 200 was 2 mm wide and 100 mm long. The irradiation start position of the laser beam 260 was set so that the center of the irradiation shape of the laser beam 260 on the edge surface 12 of the glass plate 10 was located inside the edge of the glass plate 10 on the edge surface 12 of the glass plate 10. The depth f (see FIG. 5) of the focal point in the width direction from the end surface 212 of the strengthened glass plate 200 was 30 mm, and the output P (not shown) of the light source of the laser beam 260 was 1550 W. The absorption coefficient of the glass plate was 0.57 [1 / cm]. By irradiating the strengthened glass sheet 200 with the laser beam 260, the temperature of a position D, which is a distance from the end face 212 in the normal direction to the end face 212 of the strengthened glass sheet 200 that is the same as the thickness of the glass sheet 200, becomes equal to or higher than the strain point of the strengthened glass sheet 200. The temperature of the end face 212 of the strengthened glass sheet 200 was 532°C. Since the softening point of the glass sheet 10 is 730°C, this temperature is lower than the softening point, and T1>T2 holds. The maximum value of the plane compressive stress in the tempered portion of the tempered glass plate 200 of Example 5 was 2.8 MPa, and the thickness C from the end surface 212 of the tempered portion was 8 mm, which was 2.85 times the thickness T (2.8 mm) of the glass plate 200. No plane tensile stress was formed in the tempered portion. The plane compressive stress in the tempered portion was measured using a birefringence two-dimensional distribution evaluation device (WPA-100 manufactured by Photonic Lattice, Inc.). After irradiation with the laser beam 260, a transparent adhesive tape (J6150 manufactured by Nitoms Corporation) was applied as a protective layer to the end surface 212 irradiated with the laser beam 260, and then a four-point bending test was performed in which the glass plate 200 was bent downward in a convex shape. The upper span was 300 mm, the lower span was 900 mm, and the head speed was 1 mm / min. The resulting average breaking stress was 458 MPa. The 0.1% fracture probability strength, calculated by assuming that the logarithm of the breaking stress follows a normal distribution, was 329 MPa, and the Weibull coefficient was 20.65.

[0119] (Example 6) Sixteen tempered glass plates were produced by the same method as in Example 5, except that the edge surface 212 was not irradiated with the laser light 260. A four-point bending test was conducted as in Example 5. As a result, the average breaking stress was 324 MPa. In addition, the 0.1% fracture probability strength, calculated by assuming that the logarithm of the breaking stress follows a normal distribution, was 46.9 MPa, and the Weibull coefficient was 2.63.

[0120] Comparing the results of the four-point bending test for Example 5 and Example 6, the average fracture stress and Weibull modulus of the bending strength for Example 5, in which the end surface was irradiated with laser light, were greater than the average fracture stress and Weibull modulus of the bending strength for Example 6, in which the end surface was not irradiated with laser light. In addition, the 0.1% fracture probability strength, calculated on the assumption that the logarithm of the fracture stress for Example 5, in which the end surface was irradiated with laser light, followed a normal distribution, was greater than the 0.1% fracture probability strength, calculated on the assumption that the logarithm of the bending strength for Example 6, in which the end surface was not irradiated with laser light, followed a normal distribution. It was found that the end surface could be strengthened by irradiating the end surface with laser light and forming a reinforced portion on the end surface.

[0121] From the above results, it was found that the edge of a glass plate can be strengthened by irradiating the edge with laser light and forming a strengthened area along the edge. The detailed reason why the breaking stress is improved by forming a strengthened area on the edge is not clear, but it is thought that the strength is increased not only by the improvement in strength due to stress, but also by healing the scratches that had occurred on the edge of the glass plate.

[0122] [Table 1]

[0123] [Table 2]

[0124] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2019-120489) filed on June 27, 2019, the contents of which are incorporated herein by reference. [Industrial Applicability]

[0125] The tempered glass sheet of the present invention is suitably used for, for example, architectural windows, exterior walls, handrail materials, solar cell cover glass, and vehicle windows. [Explanation of symbols]

[0126] 10 Tempered glass plate 11a first principal surface 11b second principal surface 12 End face 30 Strengthening section

Claims

1. A tempered glass plate having a first main surface, a second main surface opposite to the first main surface, and an end surface, At least one of the first main surface and the second main surface has a surface compressive stress formed by a chemical strengthening treatment, a reinforced portion in which a plane compressive stress is formed along the end surface in a direction parallel to the end surface, The maximum value of the plane compressive stress of the reinforced portion is 2 to 120 MPa, a width of the strengthened portion from the end surface in a normal direction of the end surface is 2.0 times or more the thickness of the strengthened glass plate, The thickness of the tempered glass plate is 0.5 mm or more. Tempered glass plate.

2. The tempered glass sheet according to claim 1 , wherein the surface compressive stress CS is 200 MPa or more.

3. The tempered glass plate according to claim 1 or 2, wherein the DOL of the surface compressive stress is 5 μm or more.

4. The tempered glass plate according to any one of claims 1 to 3, wherein no surface compressive stress is formed on the end surface provided with the tempered portion due to a chemical tempering treatment.

5. The tempered glass plate according to any one of claims 1 to 4, wherein the tempered portion has no plane tensile stress.

6. The tempered glass plate according to any one of claims 1 to 5, further comprising a protective layer on the end surface on which the tempered portion is provided.

7. In terms of mole percentage based on oxide, Fe ２ O ３ 0.003 to 1.5%, SiO ２ 56 to 75%, Al ２ O ３ 0-20%, Na ２ O 8-22%, K ２ O 0-10%, MgO 0-14%, ZrO ２ The tempered glass sheet according to any one of claims 1 to 6, containing 0 to 5% of ZnO and 0 to 12% of CaO.

8. The tempered glass plate according to any one of claims 1 to 7, wherein the tempered portion is formed on the end face at a position away from a corner where the adjacent end faces meet, the position being 1.0 to 10 times the thickness of the tempered glass plate.

9. The tempered glass plate according to any one of claims 1 to 8, wherein a planar tensile stress is formed in a direction parallel to the end face at a position of the tempered portion adjacent to the end face on the opposite side of the tempered portion.

10. The tempered glass sheet according to any one of claims 1 to 9, wherein the entire tempered glass sheet has a uniform specific gravity.

11. The strengthened glass plate according to any one of claims 1 to 10, wherein the end surface has a chamfered portion at a boundary with the first main surface and a boundary with the second main surface.

12. A method for producing a tempered glass plate according to any one of claims 1 to 11, a chemical strengthening treatment step of immersing at least one main surface of a glass sheet in a molten salt to form a surface compressive stress on the main surface of the glass sheet; After the chemical strengthening treatment step, an edge strengthening step is performed to form a planar compressive stress along the edge of the glass plate in a direction parallel to the edge, the edge surface tempering step comprises heating the glass plate such that a temperature T1 at a position on the glass plate, the position being a distance from the edge surface in a normal direction to the edge surface that is the same as a thickness of the tempered glass plate, is equal to or higher than a strain point of the glass plate, a temperature T2 at the edge surface is lower than a softening point of the glass plate, and T1 > T2.

13. The method for producing a strengthened glass plate according to claim 12 , wherein in the edge surface strengthening step, a planar compressive stress is formed on the edge surface of the glass plate by irradiating the edge surface with laser light.

14. In the end face strengthening step, the absorption coefficient α of the glass plate is 100 [cm －１ 14. The method for producing a strengthened glass sheet according to claim 13, wherein the laser beam has a wavelength shorter than the wavelength of the laser beam.

15. The method for manufacturing a strengthened glass plate according to claim 13 or 14, wherein in the edge strengthening step, the laser light has a wavelength of 250 nm to 5000 nm.

16. The method for manufacturing a tempered glass plate according to any one of claims 12 to 15, further comprising, after the chemical strengthening treatment step, a cutting step of cutting the chemically strengthened glass plate.

17. The method for producing a tempered glass plate according to claim 16, wherein in the cutting step, the glass plate is cut by a method using a thermal stress scribe.

18. The method for manufacturing a tempered glass plate according to any one of claims 12 to 17, further comprising forming a protective layer on the edge surface after the edge surface tempering step.

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