Glass, tempered glass, and method for manufacturing tempered glass

Abstract

A glass according to the present invention is characterized by having a glass composition comprising, in % by mass, 50 to 75% of SiO2, 1 to 30% of Al2O3, 0 to 25% of B2O3, 0 to 10% of Li2O, 0.01 to 20% of Na2O, 0 to 10% of K2O, 0.0001 to 0.1% of Fe2O3, 0.00001 to 0.01% of Cr, 0.00001 to 0.01% of Ni and 0.0001 to 0.5% of TiO2.

Description

[Technical Field]

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

[0002] Cover glass is used to protect the display of a smartphone, and is generally made of tempered glass that has been ion-exchange treated.

[0003] Currently, hundreds of millions of smartphones are produced annually, and cover glass is required for each of them. At the same time, a large amount of smartphones is thought to be discarded. Therefore, it is predicted that recycling of cover glass will become an urgent issue in the future. DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] Waste glass such as cover glass, that is, waste tempered glass, can be effectively recycled by being put into a glass melting furnace again and formed into a new glass plate to be used as cover glass.

[0005] However, when waste tempered glass is remelted and then formed into a glass plate, bubbles or foreign matter may be mixed into the glass plate, the desired glass composition may not be obtained, or the transmittance of the glass plate may be reduced, which may make the glass plate unusable as a cover glass for a smartphone.

[0006] In view of the above circumstances, the technical object of the present invention is to reduce the environmental load by recycling waste tempered glass by inventing glass, tempered glass, and a method for manufacturing tempered glass that can easily use waste tempered glass as a glass raw material. [Means for solving the problem]

[0007] As a result of extensive investigations, the present inventors have found that the above technical problems can be solved by strictly controlling the glass composition, and have proposed this finding as the present invention. That is, the glass of the present invention is characterized by containing, in mass %, 50-75% SiO2, 1-30% Al2O3, 0-25% B2O3, 0-10% Li2O, 0.01-20% Na2O, 0-10% K2O, 0.0001-0.1% Fe2O3, 0.00001-0.01% Cr, 0.00001-0.01% Ni, and 0.0001-0.5% TiO2.

[0008] Furthermore, the glass of the present invention preferably contains, in mass %, as a glass composition: 50 to 75% SiO2, 1 to 30% Al2O3, 0 to 10% B2O3, 0 to 10% Li2O, 3 to 20% Na2O, 0.001 to 10% K2O, 0 to 8% ZrO2, 50 to 10% P2O, 0.0001 to 0.1% Fe2O3, 0.00001 to 0.01% Cr, 0.00001 to 0.01% Ni, and 0.0001 to 0.5% TiO2.

[0009] Furthermore, the glass of the present invention preferably contains, in mass %, as a glass composition: 60 to 75% SiO2, 1 to 15% Al2O3, 1 to 25% B2O3, 0 to 10% Li2O, 1 to 15% Na2O, 0.001 to 5% K2O, 0 to 10% CaO, 0 to 5% BaO, 0 to 5% ZnO, 0.0001 to 0.1% Fe2O3, 0.00001 to 0.01% Cr, 0.00001 to 0.01% Ni, and 0.0001 to 0.1% TiO2.

[0010] Furthermore, the glass of the present invention preferably contains, in mass %, as a glass composition: 65 to 75% SiO2, 5 to 15% Al2O3, 1 to 15% B2O3, 0 to 5% Li2O, 1 to 15% Na2O, 0.001 to 5% K2O, 0 to 10% CaO, 0 to 5% BaO, 0.0001 to 0.1% Fe2O3, 0.00001 to 0.01% Cr, 0.00001 to 0.01% Ni, and 0.0001 to 0.1% TiO2.

[0011] The glass of the present invention preferably contains 0 to 3.0 mass % of SnO2 in the glass composition.

[0012] The glass of the present invention preferably contains 0.001 to 0.3 mass % of Cl in the glass composition.

[0013] The glass of the present invention preferably contains 0 to 0.3 mass % of SO3 in the glass composition.

[0014] The glass of the present invention preferably has a plate-like, tubular or rod-like shape.

[0015] The glass of the present invention preferably has an external transmittance of 90% or more at a wavelength of 550 nm and a thickness of 0.55 mm.

[0016] Furthermore, the glass of the present invention preferably has an external transmittance of 85% or more at a wavelength of 400 nm and a thickness of 0.55 mm.

[0017] In addition, in the glass of the present invention, the chromaticity (X, Y) in the xy chromaticity coordinates (C light source, converted into a plate thickness of 1 mm) is preferably within the ranges of (0.3090 to 0.3120, 0.3150 to 0.3180).

[0018] The glass of the present invention is preferably used as any one of window glass for vehicles, cover glass for vehicle interior panels, cover glass for CMOS sensor packages, cover glass for LED packages, cover glass for wireless communication devices, glass for pharmaceutical containers, glass for physicochemical instruments, and glass for supporting semiconductors.

[0019] The tempered glass of the present invention is a tempered glass having a compressive stress layer on the surface thereof, and the glass is preferably the glass described above.

[0020] In addition, the tempered glass of the present invention preferably has a compressive stress value of the outermost surface of 200 to 1500 MPa.

[0021] In the tempered glass of the present invention, the stress depth of the compressive stress layer is preferably 5 to 100 μm.

[0022] The method for producing tempered glass of the present invention is characterized in that a glass batch containing waste tempered glass is melted and molded to obtain glass, and the glass is then subjected to an ion exchange treatment to obtain tempered glass. Note that "waste tempered glass" refers to waste glass consisting of glass having a compressive stress layer on its surface.

[0023] Because waste tempered glass has a compressive stress layer on its surface, there is a risk of cutting the body or fragments getting into gaps when it breaks. Therefore, waste tempered glass is not easy to break into a shape that is easy to put into a glass melting furnace. For these reasons, attempts to recycle waste tempered glass have not been actively considered until now. However, in response to the increasing need for cover glass recycling, the tempered glass manufacturing method of the present invention is characterized by using waste tempered glass as a glass raw material.

[0024] In the method for producing tempered glass of the present invention, the proportion of waste tempered glass in the glass batch is preferably 0.1 to 100 mass %.

[0025] In the method for producing tempered glass of the present invention, the waste tempered glass preferably contains, in mass %, 50 to 75% of SiO2, 1 to 30% of Al2O3, 0 to 25% of B2O3, 0 to 10% of Li2O, 0.01 to 20% of Na2O, 0 to 10% of K2O, 0 to 0.3% of Cl, and 0 to 0.3% of SO3 as a glass composition.

[0026] In the method for producing tempered glass of the present invention, the particle size D of the waste tempered glass 50 It is preferable that the thickness is 1 to 100 μm.

[0027] In the method for producing tempered glass of the present invention, it is preferable to add one or more of alkali metal sulfates, alkali metal chlorides, stannic oxide, and antimony trioxide as glass raw materials to the glass batch.

[0028] In the method for producing tempered glass of the present invention, it is preferable to add a nitrate raw material as a glass raw material to the glass batch.

[0029] In the method for producing tempered glass of the present invention, the cations of the nitrate raw material are preferably alkali metal ions or alkaline earth metal ions. The alkali metal ions are preferably one or more of lithium ions, sodium ions, and potassium ions. The alkaline earth metal ions are preferably strontium ions and / or barium ions. DETAILED DESCRIPTION OF THE INVENTION

[0030] The glass (tempered glass) of the present invention is characterized by its glass composition, which contains, in mass %, about 50 to about 75% SiO2, about 1 to about 30% Al2O3, about 0 to about 25% B2O3, about 0 to about 10% Li2O, about 0.01 to about 20% Na2O, about 0 to about 10% KO, about 0.0001 to about 0.1% Fe2O3, about 0.00001 to about 0.01% Cr, about 0.00001 to about 0.01% Ni, and about 0.0001 to about 0.5% TiO2. The reasons for limiting the content of each component are as follows. In the following description of each component, % means % by mass. Furthermore, "A%" below means about A%. For example, "5%" means about 5%.

[0031] SiO2 is a component that forms the glass network. If the SiO2 content is too low, vitrification becomes difficult, and the thermal expansion coefficient becomes too high, which tends to reduce thermal shock resistance. Therefore, the preferred lower limit range of SiO2 is 50% or more, 52% or more, 55% or more, 57% or more, 59% or more, 60% or more, 63% or more, and particularly 65% ​​or more. On the other hand, if the SiO2 content is too high, meltability and formability tend to decrease, and the thermal expansion coefficient becomes too low, making it difficult to match the thermal expansion coefficient of surrounding materials. Therefore, the preferred upper limit range of SiO2 is 75% or more, 73% or less, 71% or less, 70% or less, 68% or less, 66% or less, and particularly 65% ​​or less.

[0032] Al2O3 is a component that enhances ion exchange performance and also increases strain point, Young's modulus, fracture toughness, and Vickers hardness. Therefore, the preferred lower limit of Al2O3 is 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 12% or more, 13% or more, 14% or more, 14.4% or more, and particularly 15% or more. On the other hand, if the Al2O3 content is too high, the high-temperature viscosity increases, which tends to reduce meltability and formability. Furthermore, devitrification crystals tend to precipitate in the glass, making it difficult to form into a plate shape using the overflow downdraw method or the like. In particular, when an alumina-based refractory is used as the formed body refractory and a glass plate is formed by the overflow downdraw method, spinel devitrification crystals tend to precipitate at the interface with the alumina-based refractory. Furthermore, acid resistance also decreases, making it difficult to apply to an acid treatment process. Therefore, the preferred upper limit range of Al2O3 is 30% or less, 29% or less, 28% or less, 27% or less, 26% or less, 25% or less, 21% or less, 20.5% or less, 20% or less, 18% or less, 17% or less, 16% or less, particularly 15% or less.

[0033] B2O3 is a component that reduces the high-temperature viscosity and density, stabilizes the glass, makes crystal precipitation more difficult, and lowers the liquidus temperature. If the B2O3 content is too low, the stress depth due to ion exchange between Li ions contained in the glass and Na ions in the molten salt becomes too deep, resulting in a small compressive stress value at the outermost surface. Furthermore, the glass may become unstable, resulting in a decrease in devitrification resistance. Therefore, the preferred lower limit of B2O3 is 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, 0.9% or more, and particularly 1% or more. On the other hand, if the B2O3 content is too high, the stress depth may become shallow. In particular, the efficiency of ion exchange between Na ions contained in the glass and K ions in the molten salt may decrease, resulting in a small stress depth of the compressive stress layer. Therefore, suitable upper ranges of B2O3 are 25% or less, 10% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3.8% or less, 3.5% or less, 3.3% or less, 3.2% or less, 3.1% or less, 3% or less, 2.9% or less, 2.7% or less, 2.5% or less, 2.3% or less, 2.1% or less, 1.9% or less, and particularly 1.7% or less.

[0034] Li2O is an ion-exchange component, particularly an essential component for achieving deep stress depth by ion-exchanging Li ions contained in the glass with Na ions in the molten salt. Li2O also reduces high-temperature viscosity, improving meltability and formability, and increasing Young's modulus. Therefore, the preferred lower limit of Li2O is 0% or more, 0.001% or more, 0.003% or more, 0.004% or more, 0.005% or more, 0.006% or more, 0.007% or more, and particularly 0.008% or more. Therefore, the preferred upper limit of Li2O is 10% or less, 9.9% or less, 9% or less, 8.9% or less, 8% or less, 7.5% or less, 6.5% or less, 5% or less, 4.5% or less, 3.5% or less, 2.5% or less, 1.4% or less, 1% or less, 0.8% or less, 0.6% or less, 0.4% or less, and particularly 0.2% or less.

[0035] Na2O is an ion-exchange component and a component that reduces high-temperature viscosity and improves meltability and formability. Na2O also improves devitrification resistance, particularly suppressing devitrification caused by reaction with alumina-based refractories. Therefore, the preferred lower limit of Na2O is 0.01% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 10.6% or more, 11.4% or more, 12.5% ​​or more, 12.6% or more, 12.7% or more, 12.8% or more, 12.9% or more, 13.0% or more, 13.2% or more, and particularly 13.5% or more. On the other hand, if the Na2O content is too high, the thermal expansion coefficient becomes too high, which can lead to a decrease in thermal shock resistance. Furthermore, the component balance of the glass composition may be disrupted, which may actually reduce devitrification resistance. Therefore, the preferred upper limit range of Na2O is 20% or less, 19.5% or less, 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 14.9% or less, 14.8% or less, 14.7% or less, particularly 14.6% or less.

[0036] K2O is a component that reduces high-temperature viscosity and improves meltability and moldability. However, if the K2O content is too high, the thermal expansion coefficient becomes too high, which tends to reduce thermal shock resistance. Furthermore, the compressive stress value of the outermost surface tends to decrease. Therefore, the preferred upper limit of K2O is 10% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2.3% or less, 2.1% or less, 2.0% or less, and particularly less than 1.9%. In addition, from the perspective of deepening the stress depth, the preferred lower limit of K2O is 0% or more, 0.001% or more, 0.002% or more, 0.003% or more, 0.005% or more, 0.007% or more, 0.1% or more, 0.15% or more, 0.2% or more, 0.22% or more, 0.3% or more, 0.5% or more, and particularly 1.0% or more.

[0037] Alkali metal oxides are ion exchange components that reduce high-temperature viscosity and improve melting and molding properties. It is a component that improves the mechanical properties. If the alkali metal oxide content (Li2O + Na2O + KO) is too high, the thermal expansion coefficient may become high. Also, acid resistance may decrease. Therefore, the lower limit of the alkali metal oxide content is preferably 4% or more, 7% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, and particularly preferably 15% or more, and the upper limit is preferably 25% or less, 23% or less, 20% or less, 19% or less, and particularly preferably 18% or less.

[0038] Fe2O3 is a component that absorbs visible light, and as its content increases, visible light transmittance tends to decrease. On the other hand, if the Fe2O3 content is low, it becomes difficult to use waste tempered glass, and recyclability tends to decrease. The Fe2O3 content is preferably 0.0001 to 0.1%, 0.0005 to 0.02%, and particularly preferably 0.001 to 0.015%.

[0039] Cr is a component that absorbs visible light, and as its content increases, visible light transmittance tends to decrease. On the other hand, if the Cr content is low, it becomes difficult to use waste tempered glass, and recyclability tends to decrease. Therefore, the preferred lower limit of the Cr content is 0.00001% or more, 0.00002% or more, 0.00003% or more, 0.00004% or more, particularly 0.00005% or more, and the preferred upper limit range is 0.01% or less, 0.009% or less, 0.005% or less, 0.001% or less, 0.0009% or less, 0.0005% or less, 0.0004% or less, 0.0003% or less, 0.0002% or less, 0.0001% or less, particularly 0.00009% or less.

[0040] Ni is a component that absorbs visible light, and as its content increases, visible light transmittance tends to decrease. On the other hand, if the Ni content is low, it becomes difficult to use waste tempered glass, and recyclability tends to decrease. Therefore, the preferred lower limit of Ni content is 0.00001% or more, 0.00002% or more, 0.00003% or more, 0.00004% or more, particularly 0.00005% or more, and the preferred upper limit range is 0.01% or less, 0.009% or less, 0.005% or less, 0.001% or less, 0.0009% or less, 0.0005% or less, 0.0004% or less, 0.0003% or less, 0.0002% or less, 0.0001% or less, particularly 0.00009% or less.

[0041] TiO2 is a component that absorbs visible light, and as its content increases, visible light transmittance tends to decrease. On the other hand, if the TiO2 content is low, it becomes difficult to use waste tempered glass, and recyclability tends to decrease. Therefore, the preferred lower limit of TiO2 content is 0.0001% or more, 0.0002% or more, 0.0003% or more, 0.0004% or more, 0.0005% or more, particularly 0.001% or more, and the preferred upper limit range is 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, 0.09% or less, 0.05% or less, 0.01% or less, 0.009% or less, 0.005% or less, 0.004% or less, particularly 0.003% or less.

[0042] In addition to the above components, the following components may also be added:

[0043] MgO is a component that reduces high-temperature viscosity, improves meltability and formability, and increases strain point and Vickers hardness. Among alkaline earth metal oxides, MgO is a component that is particularly effective in improving ion exchange performance. However, if the MgO content is too high, devitrification resistance tends to decrease, and it becomes particularly difficult to suppress devitrification caused by reaction with alumina-based refractories. Therefore, the preferred MgO content is 0 to 10%, 0 to 4.9%, 0.1 to 4%, or 0.2 to 3.3%, and particularly 0.5 to less than 3%.

[0044] Compared to other components, CaO reduces high-temperature viscosity and improves meltability, moldability, strain point, and Vickers hardness without reducing devitrification resistance. However, if the CaO content is too high, there is a risk of reducing ion exchange performance or degrading the ion exchange solution during ion exchange treatment. Therefore, the preferred upper limit of CaO content is 10% or less, 6% or less, 5% or less, 4% or less, 3.5% or less, 3% or less, 2% or less, 1% or less, less than 1%, 0.5% or less, 0.3% or less, and particularly less than 0.1%.

[0045] SrO and BaO are components that reduce high-temperature viscosity and improve meltability, formability, strain point, and Young's modulus, but if their contents are too high, the ion exchange reaction is likely to be inhibited, the density and thermal expansion coefficient become unduly high, and the glass is likely to devitrify. Therefore, the preferred contents of SrO and BaO are 0 to 5%, 0 to 2%, 0 to 1.5%, 0 to 1%, 0 to 0.5%, and 0 to 0.1%, respectively, and particularly preferably 0 to less than 0.1%.

[0046] ZnO is a component that reduces high-temperature viscosity and improves meltability and formability, but if its content is too high, the glass becomes prone to devitrification. Therefore, the preferred ZnO content is 0 to 5%, 0 to 2%, 0 to 1.5%, 0 to 1%, 0 to 0.5%, or 0 to 0.1%, and particularly preferably 0 to less than 0.1%.

[0047] ZrO2 is a component that increases Vickers hardness and viscosity near the liquidus viscosity and strain point, but if its content is too high, there is a risk of significantly reducing devitrification resistance. Therefore, the preferred ZrO2 content is 0 to 8%, 0 to 4%, 0 to 2%, 0 to 1.8%, 0.001 to 1.5%, 0.002 to 1%, 0.003 to 0.1%, and particularly 0.010 to 0.050%.

[0048] P2O5 is a component that enhances ion exchange performance, particularly deepening the stress depth. It also improves acid resistance. If the P2O5 content is too low, there is a risk that the ion exchange performance will not be fully exhibited. In particular, the efficiency of ion exchange between Na ions contained in the glass and K ions in the molten salt is likely to decrease, and the stress depth of the compressive stress layer is likely to decrease. Furthermore, there is a risk that the glass will become unstable and devitrification resistance will decrease. Therefore, the preferred lower limit of P2O5 is 0% or more, 0.1% or more, 0.4% or more, 0.7% or more, 1% or more, 1.2% or more, 1.4% or more, 1.6% or more, 2% or more, 2.3% or more, 2.5% or more, and particularly 3% or more. On the other hand, if the P2O5 content is too high, the glass will easily undergo phase separation and water resistance will decrease. Therefore, the upper limit range of P2O5 is preferably 10% or less, 5% or less, 4.5% or less, 4% or less, 3% or less, 2% or less, 1% or less, particularly preferably 0.4% or less.

[0049] Oxides such as Nd2O3, La2O3, Y2O3, Nb2O5, Ta2O5, and Hf2O3 are components that increase Young's modulus. However, the raw material costs are high, and adding large amounts can easily reduce devitrification resistance. Therefore, the preferred contents of these oxides are 5% or less, 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly 0.1% or less, respectively.

[0050] SnO2 is a component that improves the clarity of glass and also improves ion exchange performance. However, if the SnO2 content is too high, devitrification resistance tends to decrease. Therefore, the preferred lower limit of SnO2 is 0% or more, 0.01% or more, 0.05% or more, 0.07% or more, 0.09% or more, particularly 0.1% or more, and the preferred upper limit is 3.0% or less, 2.0% or less, 1.0% or less, 0.9% or less, 0.8% or less, 0.6% or less, particularly 0.5% or less.

[0051] Cl is a fining agent, but if its content is too high, it can have a negative impact on the environment and equipment. Therefore, the preferred lower limit of Cl is 0.001% or more, particularly 0.01% or more, and the preferred upper limit is 0.3% or less, 0.2% or less, particularly 0.1% or less.

[0052] SO3 is a fining agent, but if its content is too high, it is a component that can have a negative impact on the environment and equipment. Therefore, the preferred lower limit range for SO3 is 0% or more, 0.001% or more, and particularly 0.01% or more, and the preferred upper limit range is 0.3% or less, 0.25% or less, 0.2% or less, 0.15% or less, 0.1% or less, 0.07% or less, and particularly 0.05% or less.

[0053] From an environmental perspective, the glass (tempered glass) of the present invention preferably contains substantially no As2O3, Sb2O3, PbO, or F in its glass composition. From an environmental perspective, it also preferably contains substantially no Bi2O3. The phrase "substantially does not contain ..." means that the specified components are not actively added as glass components, but impurity-level addition is permitted, and specifically refers to a case where the content of the specified components is less than 0.05%.

[0054] The shape of the glass of the present invention is not limited, but is preferably any of a plate, a tube, and a rod, and particularly preferably a square plate, a disk, a cylindrical tube, a rectangular tube, a hollow tube, a solid rod, etc.

[0055] In the case of a plate-like glass, the thickness is preferably 0.01 mm or more, 0.02 mm or more, 0.03 mm or more, 0.05 mm or more, 0.07 mm or more, 0.1 mm or more, 0.2 mm or more, particularly 0.3 mm or more, and is preferably 1.0 mm or less, 0.8 mm or less, 0.7 mm or less, particularly 0.6 mm or less. If the thickness is outside the above range, it becomes difficult to use the glass as a cover glass for a smartphone.

[0056] In the case of a cylindrical tube, the thickness is preferably 0.1 mm or more, 0.2 mm or more, particularly 0.3 mm or more, and preferably 1.0 mm or less, 0.8 mm or less, particularly 0.7 mm or less. The lower limit of the outer diameter is preferably 1 mm or more, 2 mm or more, 3 mm or more, 4 mm or more, 5 mm or more, 6 mm or more, 7 mm or more, 8 mm or more, 9 mm or more, particularly 10 mm or more, and preferably 50 mm or less, 45 mm or less, 40 mm or less, 35 mm or less, particularly 30 mm or less. If the thickness or outer diameter is outside the above ranges, it will be difficult to use as a pharmaceutical container.

[0057] The external transmittance at a wavelength of 550 nm and a thickness of 0.55 mm is preferably 90% or more, 90.1% or more, 90.3% or more, and particularly 90.5% or more. The external transmittance at a wavelength of 400 nm and a thickness of 0.55 mm is preferably 85% or more, 86% or more, 87% or more, and particularly 88% or more. If the external transmittance is too low, the visibility of the display is likely to decrease when used as a cover glass for a smartphone.

[0058] In the glass (tempered glass) of the present invention, x in the xy chromaticity coordinates (converted to illuminant C and plate thickness of 1 mm) is preferably 0.3090 to 0.3120, 0.3095 to 0.3115, 0.3097 to 0.3110, 0.3098 to 0.3107, and particularly 0.3100 to 0.3107. This reduces color tinge, making it possible to create a sense of luxury when the glass is used in exterior components in which part or all of the end faces are exposed to the outside.

[0059] In the xy chromaticity coordinates (converted to 1 mm plate thickness using C light source), y is preferably 0.3150 to 0.3180, 0.3155 to 0.3175, 0.3160 ​​to 0.3170, and particularly 0.3161 to 0.3167. This reduces the color tone, making it possible to create a luxurious feel when used in exterior components in which part or all of the end faces are exposed to the outside.

[0060] By subjecting the glass of the present invention to an ion exchange treatment, it is possible to obtain tempered glass having a compressive stress layer on the surface.

[0061] The compressive stress value of the outermost surface is preferably 200 MPa or more, 220 MPa or more, 250 MPa or more, 280 MPa or more, 300 MPa or more, 310 MPa or more, particularly 320 MPa or more. The higher the compressive stress value of the outermost surface, the higher the Vickers hardness. On the other hand, if an extremely large compressive stress is formed on the surface, the tensile stress inherent in the glass sheet becomes extremely high, and there is a risk of large dimensional changes before and after the ion exchange treatment. For this reason, the compressive stress value of the outermost surface is preferably 1500 MPa or less, 1400 MPa or less, 1300 MPa or less, 1200 MPa or less, particularly 1100 MPa or less. Note that the compressive stress value of the outermost surface tends to increase if the ion exchange time is shortened or the temperature of the ion exchange solution is lowered.

[0062] The stress depth is preferably 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, particularly 40 μm or more. The deeper the stress depth, the more difficult it is for protrusions on the ground to reach the tensile stress layer when the glass plate is dropped, thereby reducing the probability of breakage of the glass plate. On the other hand, if the stress depth is too deep, there is a risk of significant dimensional change before and after the ion exchange treatment. Furthermore, the compressive stress value of the outermost surface tends to decrease. Therefore, the stress depth is preferably 100 μm or less, 80 μm or less, 60 μm or less, particularly 55 μm or less. Note that the stress depth tends to increase if the ion exchange time is extended or the temperature of the ion exchange solution is increased.

[0063] The method for producing tempered glass of the present invention is characterized in that a glass batch containing waste tempered glass is melted and molded to obtain glass, and the glass is then subjected to an ion exchange treatment to obtain tempered glass. Here, the waste tempered glass is preferably recovered from commercially available smartphone cover glass or pharmaceutical container glass.

[0064] The proportion of waste tempered glass in the glass batch, in mass %, is preferably less than 100.0%, 99.9% or less, 99% or less, 95% or less, 90% or less, 85% or less, 80% or less, less than 80%, 75% or less, 70% or less, 65% or less, 60% or less, and particularly 55% or less. If the proportion of waste tempered glass is too high, it becomes difficult to obtain the desired glass composition and stress characteristics. Furthermore, it becomes difficult to obtain the desired transmittance and chromaticity characteristics due to the influence of impurities (Fe2O3, Cr, Ni, TiO2, etc.) mixed in during the crushing and transportation processes of the waste tempered glass. On the other hand, the proportion of waste tempered glass, in mass %, is 0.1% or more, 0.3% or more, 0.5% or more, 1% or more, 3% or more, 5% or more, 10% or more, 20% or more, 30% or more, and particularly 40% or more. If the proportion of waste tempered glass is too small, the amount of waste tempered glass used will be small, which will hinder the recycling of waste glass. In addition, the melting property of the glass batch will decrease, which will tend to reduce the productivity of glass sheets.

[0065] The waste tempered glass preferably contains, by mass, 50-75% SiO, 1-30% AlO, 0-25% BO, 0-10% LiO, 0.01-20% NaO, 0-10% KO, 0-0.3% Cl, and 0-0.3% SO, with trace components of 0.0001-0.1% FeO, 0.00001-0.01% Cr, 0.00001-0.01% Ni, and 0.0001-0.5% TiO. Too many trace components can alter the transmittance and color of tempered glass produced using the waste tempered glass, increasing the need to use raw materials with fewer trace components, potentially increasing production costs. Furthermore, too few trace components can result in significant differences in transmittance and color from commercially available tempered glass. Furthermore, in order to adjust the content, trace components must be added to the glass batch, which may increase the manufacturing cost.

[0066] Average particle size D of waste tempered glass 50 The upper limit of the average particle size D of the waste tempered glass is preferably 100 μm or less, 80 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, particularly preferably 35 μm or less. 50If the average particle diameter D of the waste tempered glass is too large, the melting property of the glass batch decreases, and the glass batch tends to separate, which tends to reduce the uniformity of the glass composition of the molten glass. 50 The upper limit of the average particle size D of the waste tempered glass is preferably 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 10 μm or more, particularly preferably 15 μm or more. 50 If the average particle size D is too small, the dust of the waste tempered glass may fly around, causing the composition of the glass batch to fluctuate. 50 " is a value generally called the median diameter, and can be measured, for example, with a laser diffraction particle size distribution analyzer SALD-2200 manufactured by Shimadzu Corporation. In the case of large sizes that are difficult to measure with a laser diffraction particle size distribution analyzer, the average particle diameter D of the waste tempered glass 50 may be measured using a sieve of known openings.

[0067] In the method for producing tempered glass of the present invention, it is particularly preferable to analyze the glass composition of waste tempered glass (especially pulverized waste tempered glass), add a required amount of the waste tempered glass to a glass batch, and melt the glass. This makes it easier to control the amounts of components that affect transmittance and chromaticity, such as Fe2O3, Cr, Ni, and TiO2.

[0068] In the tempered glass manufacturing method of the present invention, it is preferable to add alkali metal sulfate, alkali metal chloride, stannic oxide, and antimony trioxide as glass raw materials in addition to the waste tempered glass. These components can serve as fining agents. Note that the fining agents contained in the waste tempered glass often have already lost their fining effect. Therefore, by adding new fining agents when remelting the waste tempered glass, a bubble-free glass plate can be produced again.

[0069] In the method for producing tempered glass of the present invention, it is preferable to use nitrate as part of the glass raw materials. Nitrate ions play a role in oxidizing other metal ions in the molten glass. This makes it possible to control the oxidation number of metal ions of impurities contained in the glass. As a result, it becomes possible to control the transmittance and chromaticity of the glass.

[0070] The cation of the nitrate is preferably an alkali metal ion or an alkaline earth metal ion. The cation of the alkali metal nitrate is preferably a lithium ion, a sodium ion, or a potassium ion. In this case, lithium nitrate, sodium nitrate, or potassium nitrate can be used as the glass raw material. The cation of the alkaline earth metal nitrate is preferably a strontium ion or a barium ion. In this case, strontium nitrate or barium nitrate can be used as the glass raw material.

[0071] In the method for producing tempered glass of the present invention, it is preferable to use a carbonate as part of the glass raw materials. This allows for a reduction in the cost of the glass batch. The cations of the carbonate are preferably alkali metal ions or alkaline earth metal ions. The cations of the alkali metal carbonate are preferably lithium ions, sodium ions, or potassium ions. In this case, lithium carbonate, sodium carbonate, or potassium carbonate can be used as the glass raw materials. The cations of the alkaline earth metal carbonate are preferably calcium ions, strontium ions, or barium ions. In this case, calcium carbonate, strontium carbonate, or barium carbonate can be used as the glass raw materials.

[0072] In the method for producing tempered glass of the present invention, it is preferable to use an oxide raw material as part of the glass raw materials. The oxide raw material does not generate gases such as carbon dioxide when melted, so that the environmental load during melting can be reduced. As the oxide raw material, it is preferable to use one or more of lithium oxide, sodium oxide, potassium oxide, calcium oxide, strontium oxide, and barium oxide, for example.

[0073] In the method for producing chemically strengthenable glass of the present invention, the upper limit of the mass ratio of (content of oxide raw materials in the glass batch) / (total amount of oxide raw materials and carbonate raw materials in the glass batch) is preferably 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, and particularly 0.6 or less, and the lower limit is preferably 0.01 or more, 0.05 or more, 0.1 or more, 0.2 or more, 0.25 or more, and particularly 0.3 or more. If this ratio is too low, it becomes difficult to reduce the environmental load. On the other hand, if this ratio is too high, the cost of the glass batch is likely to rise.

[0074] Although various forming methods can be adopted as a method for shaping molten glass, it is preferable to adopt the overflow downdraw method as a method for shaping molten glass into a sheet. The overflow downdraw method is a method that can mass-produce high-quality glass sheets and can easily produce large glass sheets. Furthermore, in the overflow downdraw method, alumina or zirconia is used as the refractory formed body, but the glass of the present invention has good compatibility with alumina and zirconia, particularly alumina, and is therefore unlikely to react with these formed bodies to generate bubbles, pimples, etc.

[0075] The tempered glass of the present invention is produced by subjecting glass to an ion exchange treatment. The conditions for the ion exchange treatment are not particularly limited, and optimal conditions may be selected taking into consideration the viscosity characteristics, intended use, thickness, internal tensile stress, dimensional change, etc. of the glass. In particular, ion exchange of K ions in a KNO molten salt with Na components in the glass can efficiently form a compressive stress layer on the surface.

[0076] The number of times of ion exchange treatment is not particularly limited, and may be performed once or multiple times. When the ion exchange treatment is performed multiple times, the number of times of ion exchange treatment is preferably two. In this way, the total amount of tensile stress accumulated inside the glass can be reduced while increasing the stress depth.

[0077] As described above, the method for producing tempered glass of the present invention involves melting and forming a glass batch containing waste tempered glass to obtain glass, but it is also preferable to use waste glass made of ion-exchangeable glass instead of the waste tempered glass. Here, the waste glass made of ion-exchangeable glass is preferably waste glass generated during glass forming, processing, or inspection, and is also preferably waste glass generated after cutting into individual pieces and before being introduced into an ion exchange tank.

[0078] In the method for producing tempered glass of the present invention, it is also preferable to melt and mold a glass batch containing waste tempered glass to obtain glass, then crystallize the glass, and then subject the obtained crystallized glass to ion exchange treatment to obtain tempered glass. [Example]

[0079] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0080] Tables 1 and 2 show examples of the present invention (samples No. 1 to 24). Samples No. 1 to 23 were obtained by melting and molding a glass batch containing waste tempered glass to obtain glass, which was then subjected to ion exchange treatment. Sample No. 24 was obtained by melting and molding a glass batch containing waste tempered glass to obtain glass, which was then crystallized, and the resulting crystallized glass was then subjected to ion exchange treatment. Tables 3 and 4 show the glass compositions of the waste tempered glass used in these examples. These were waste tempered glass (samples No. 25 to 49) recovered from commercially available smartphone cover glass, ampoule tubes, building glass, and image sensor cover glass.

[0081] [Table 1]

[0082] [Table 2]

[0083] [Table 3]

[0084] [Table 4]

[0085] The samples listed in Tables 1 and 2 were prepared as follows. First, waste tempered glass was roughly crushed to a size of 5 mm or less, and then crushed to a predetermined particle size using a commercially available glass crushing device such as a ball mill or a jet mill to prepare powdered waste tempered glass. The average particle size D of each powder was 50 was measured using a commercially available laser diffraction particle size distribution analyzer or a sieve with a known mesh size. The composition of the pulverized waste tempered glass was then analyzed, and the waste glass, oxide raw materials, nitrate raw materials, and carbonate raw materials shown in the table were mixed to produce a glass batch. The glass batch was then melted in a continuous melting furnace, and the resulting molten glass was formed into a glass plate. The resulting glass plate was then cut to a size of 200 mm x 200 mm x 0.55 mm.

[0086] The glass composition, transmittance, and chromaticity of each sample were evaluated.

[0087] The external transmittance was measured at an optical path length of 0.55 mm using a UV-3100PC manufactured by Shimadzu Corporation.

[0088] The chromaticity is a value calculated from a transmittance curve measured using a UV-3100PC manufactured by Shimadzu Corporation in accordance with JIS Z8722:2009.

[0089] Next, both surfaces of the glass plate were optically polished, and then ion-exchange treatment was performed by immersing them in molten KNO3 salt at 430°C for 4 hours. After the ion-exchange treatment, the surface of each sample was washed.

[0090] The compressive stress value (outermost surface) and stress depth of the compressive stress layer on the surface were then calculated from the number and spacing of interference fringes observed using a surface stress meter (Orihara Manufacturing Co., Ltd. FSM-6000). For the calculations, the refractive index of each sample was set to 1.50 and the optical elastic constant to 30 [(nm / cm) / MPa]. The compressive stress value (outermost surface) and stress depth of the compressive stress layer on the surface were also calculated using the same method for the samples listed in Tables 3 and 4.

[0091] As is clear from Tables 1 and 2, samples Nos. 1 to 24 contain waste tempered glass in the glass batch, but the resulting glass sheets have high transmittance, which is believed to promote the recycling of waste tempered glass. [Industrial Applicability]

[0092] The glass and tempered glass of the present invention can be used for vehicle window glass, cover glass for vehicle interior panels, cover glass for CMOS sensor packages, cover glass for LED packages, cover glass for wireless communication devices, glass for pharmaceutical containers, glass for physicochemical instruments, glass for semiconductor supports, etc.

Claims

1. The glass composition is, in mass%, SiO ２ 50-75%, Al ２ O ３ 1-30%, B ２ O ３ 0-10%, Li ２ O 0-10%, Na ２ O 3-20%, K ２ O 0.001-10%, ZrO 2 0-8%, P 2 O 5 0-10%, Fe ２ O ３ 0.009-0.1%, Cr 0.00001-0.01%, Ni 0.00001-0.01%, TiO ２ A glass characterized by containing 0.0001 to 0.5% of Cr.

2. The glass composition is, in mass%, SiO ２ 60-75%, Al ２ O ３ 1-15%, B ２ O ３ 1-10%, Li ２ O 0-10%, Na ２ O 3-15%, K ２ O 0.001-5%, ZrO 2 0-8%, P 2 O 5 0-10%, CaO 0-10%, BaO 0-5%, ZnO 0-5%, Fe ２ O ３ 0.009-0.1%, Cr 0.00001-0.01%, Ni 0.00001-0.01%, TiO ２ 2. The glass according to claim 1, wherein the content is 0.0001 to 0.1%.

3. The glass composition is, in mass%, SiO ２ 65-75%, Al ２ O ３ 5-15%, B ２ O ３ 1-10%, Li ２ O 0-5%, Na ２ O 3-15%, K ２ O 0.001-5%, ZrO 2 0-8%, P 2 O 5 0-10%, CaO 0-10%, BaO 0-5%, Fe ２ O ３ 0.009-0.1%, Cr 0.00001-0.01%, Ni 0.00001-0.01%, TiO ２ 2. The glass according to claim 1, wherein the content is 0.0001 to 0.1%.

4. SnO in the glass composition ２ The glass according to any one of claims 1 to 3, characterized in that it contains 0 to 3.0 mass % of

5. 5. The glass according to claim 1, wherein the glass composition contains 0.001 to 0.3 mass % of Cl.

6. SO in the glass composition ３ 6. The glass according to claim 1, further comprising 0 to 0.3 mass % of

7. 7. The glass according to claim 1, which has a shape of a plate, a tube, or a rod.

8. 8. The glass according to claim 1, wherein the external transmittance at a wavelength of 550 nm and a thickness of 0.55 mm is 90% or more.

9. 9. The glass according to claim 1, wherein the glass has an external transmittance of 85% or more at a wavelength of 400 nm and a thickness of 0.55 mm.

10. 10. The glass according to claim 1, wherein chromaticity (X, Y) in xy chromaticity coordinates (C light source, converted into a plate thickness of 1 mm) is within the ranges of (0.3090 to 0.3120, 0.3150 to 0.3180).

11. The glass according to any one of claims 1 to 10, which is used for any one of window glass for vehicles, cover glass for vehicle interior panels, cover glass for CMOS sensor packages, cover glass for LED packages, cover glass for wireless communication devices, glass for pharmaceutical containers, glass for physical and chemical instruments, and glass for supporting conductors.

12. Tempered glass having a compressive stress layer on the surface, characterized in that the glass is the glass according to any one of claims 1 to 11.

13. The tempered glass according to claim 12, wherein the compressive stress value of the outermost surface is 200 to 1500 MPa.

14. 14. The tempered glass according to claim 12, wherein the compressive stress layer has a stress depth of 5 to 100 μm.

15. A glass batch containing waste tempered glass is melted and molded to obtain glass, and then the glass is subjected to an ion exchange treatment to obtain tempered glass, and the tempered glass contains, as a glass composition, in mass %: SiO ２ 50-75%, Al ２ O ３ 1-30%, B ２ O ３ 0-25%, Li ２ O 0-10%, Na ２ O 0.01-20%, K ２ O 0-10%, Fe ２ O ３ 0.009-0.1%, Cr 0.00001-0.01%, Ni 0.00001-0.01%, TiO ２ A method for producing tempered glass, characterized in that it contains 0.0001 to 0.5%.

16. The method for producing tempered glass according to claim 15, wherein the proportion of waste tempered glass in the glass batch is 0.1 to 100 mass%.

17. The waste tempered glass has a glass composition, in mass%, of SiO ２ 50-75%, Al ２ O ３ 1-30%, B ２ O ３ 0-25%, Li ２ O 0-10%, Na ２ O 0.01-20%, K ２ O 0-10%, Cl 0-0.3%, SO ３ The method for producing tempered glass according to claim 15 or 16, characterized in that it contains 0 to 0.3% of Cr.

18. Grain size D of waste tempered glass ５０ The method for producing tempered glass according to any one of claims 15 to 17, characterized in that the thickness is 1 to 100 µm.

19. 19. The method for producing tempered glass according to any one of claims 15 to 18, wherein one or more of alkali metal sulfate, alkali metal chloride, stannic oxide, and antimony trioxide are added to the glass batch as glass raw materials.

20. 20. The method for producing tempered glass according to claim 15, wherein a nitrate raw material is added as a glass raw material to the glass batch.

21. 21. The method for producing tempered glass according to claim 20, wherein the cations of the nitrate raw material are alkali metal ions or alkaline earth metal ions.

22. 22. The method for producing tempered glass according to claim 21, wherein the alkali metal ions are one or more of lithium ions, sodium ions, and potassium ions.

23. 22. The method for producing tempered glass according to claim 21, wherein the alkaline earth metal ions are strontium ions and / or barium ions.

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