Glass, glass plate for strengthening, and strengthened glass plate

Abstract

The glass according to the present invention is characterized by comprising, in mol%, 60 to 85% of SiO2, 1 to 20% of Al2O3, 0 to 5% of B2O3, 1 to 20% of Li2O + Na2O + K2O, and 0 to 5% of MgO + CaO + SrO + BaO as a glass composition.

Description

Technical Field

[0001] The present invention relates to glass having excellent chemical resistance and formability, a reinforcing glass plate, and a reinforced glass plate. In particular, it relates to a reinforced glass plate suitable as a flexible cover member for a foldable display or the like. Background Art

[0002] Heretofore, alkali aluminosilicate glass has been used for various purposes because of its excellent properties.

[0003] For example, as a reinforced glass plate, alkali aluminosilicate glass subjected to ion exchange treatment can be used (see Patent Documents 1 to 3 and Non-Patent Document 1).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-83045

[0007] Patent Document 2: International Publication No. 2015 / 031188

[0008] Patent Document 3: International Publication No. 2013 / 063275

[0009] Non-Patent Documents

[0010] Non-Patent Document 1: Tetsuro Izumitani et al., "New Glass and Its Physical Properties", First Edition, Keiei System Research Institute Co., Ltd., August 20, 1984, pp. 451-498 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] In recent years, products such as foldable displays and rollable displays that can be bent have been introduced to the market. In such products, a flexible cover member made of a laminated resin and a reinforced glass plate is used.

[0013] Although the flexible cover member is used in a bent state, when bent, minute defects present on the glass surface cause large stress to occur, and sometimes cracking occurs. Physical defects can be reduced in influence by performing ion exchange treatment, but glass that is easily chemically eroded easily generates new defects during the manufacturing process or in use, and such defects make it difficult to prevent cracks.

[0014] In addition, in recent years, the rising price of fossil fuels and the reduction of CO2 emissions have become problems. In glass manufacturing, it is necessary to melt and form glass raw materials at a high temperature, and thus it is particularly susceptible to the rising fuel price. In addition, in order to reduce CO2 emissions, it is preferable that the melting temperature and the forming temperature be as low as possible.

[0015] As a means for improving the formability of glass, addition of B2O3 and alkali metal oxides to the glass composition has been carried out. However, if B2O3 is added excessively, the ion exchange performance may decrease. In addition, if alkali metal oxides are added excessively, the chemical resistance is likely to decrease. Therefore, it is difficult to achieve high levels of chemical resistance, ion exchange performance, and formability simultaneously. Also, in this specification, hydrolysis resistance, acid resistance, and alkali resistance are collectively referred to as chemical resistance.

[0016] In view of the above circumstances, the technical problem of the present invention is to create an alkaline aluminosilicate glass that has high levels of chemical resistance, ion exchange performance, and formability.

[0017] Means for Solving the Problem

[0018] As a result of intensive research by the present inventors, it has been found that by strictly restricting the content of each glass component, the above problems can be solved, and the present invention is proposed. That is, (1) The glass of the present invention is characterized in that, as the glass composition, in terms of mol%, it contains 60 to 85% of SiO2, 1 to 20% of Al2O3, 0 to 5% of B2O3, 1 to 20% of Li2O + Na2O + K2O, and 0 to 5% of MgO + CaO + SrO + BaO. Thereby, chemical resistance, ion exchange performance, and formability can be achieved at high levels. Here, "Li2O + Na2O + K2O" refers to the total content of Li2O, Na2O, and K2O. "MgO + CaO + SrO + BaO" refers to the total content of MgO, CaO, SrO, and BaO.

[0019] (2) The glass of the present invention preferably has a content of Al2O3 of 1 to 10 mol% in the glass described in (1) above. Thereby, the formability can be improved.

[0020] (3) The glass of the present invention preferably has a content of MgO of 0 to 1 mol% and a content of CaO of 0 to 0.5 mol% in the glass described in (1) or (2) above. Thereby, the chemical resistance and ion exchange performance can be effectively improved.

[0021] (4) The glass of the present invention preferably has a content of Li2O of 3 to 8 mol%, a content of Na2O of 3 to 8 mol%, and a content of K2O of 0 to 1 mol% in the glass described in any one of (1) to (3) above. Thereby, the chemical resistance and ion exchange performance can be effectively improved.

[0022] (5) The glass of the present invention preferably has a content of SnO2 of 0.03 to 3 mol% in the glass described in any one of (1) to (4) above. Thereby, while suppressing glass coloring, the clarification can be improved.

[0023] (6) The glass of the present invention preferably has a molar ratio of (Li2O + Na2O + K2O) / (1 - K2O) of 5 to 30 in the glass described in any one of the above (1) to (5). Thereby, the ion exchange performance can be effectively improved. Here, "(Li2O + Na2O + K2O) / (1 - K2O)" means the value obtained by dividing the total content of Li2O, Na2O, and K2O by the value obtained by subtracting the K2O content from 1 (for example, when the content of K2O is 0.5 mol%, the value obtained by subtracting the K2O content from 1 is 0.5 mol%).

[0024] (7) The glass of the present invention preferably has a molar ratio of (K2O + CaO) / (Li2O + Na2O + K2O) of 0 to 0.3 in the glass described in any one of the above (1) to (6). Thereby, the ion exchange performance can be effectively improved. Here, "(K2O + CaO) / (Li2O + Na2O + K2O)" means the value obtained by dividing the total content of K2O and CaO by the total content of Li2O, Na2O, and K2O.

[0025] (8) The glass of the present invention preferably has a molar ratio of (Li2O + Na2O + K2O) / Al2O3 of 2 or more in the glass described in any one of the above (1) to (7). Thereby, the formability can be improved. Here, "(Li2O + Na2O + K2O) / Al2O3" means the value obtained by dividing the total content of Li2O, Na2O, and K2O by the content of Al2O3.

[0026] (9) The glass of the present invention preferably has a molar ratio of MoO3 / (Fe2O3 + TiO2) of 0.5 or less and a visible light transmittance of 80% or more for a thickness of 1 mm in the glass described in any one of the above (1) to (8). Thereby, while suppressing the coloring caused by MoO3, the visible light transmittance can be improved. Here, "MoO3 / (Fe2O3 + TiO2)" represents the value obtained by dividing the content of MoO3 by the total content of Fe2O3 and TiO2.

[0027] (10) The glass of the present invention preferably has a molar ratio of (10×SnO2) / (10×Fe2O3 + TiO2 + 10×SnO2 + 100×MoO3) of 0.5 to 1 and a visible light transmittance of 85% or more for a thickness of 1 mm in the glass described in any one of the above (1) to (9). Thereby, the visible light transmittance can be improved. Here, "(10×SnO2) / (10×Fe2O3 + TiO2 + 10×SnO2 + 100×MoO3)" means the value obtained by dividing 10 times the content of SnO2 by the total amount of 10 times the content of Fe2O3, TiO2, 10 times the content of SnO2, and 100 times the content of MoO3.

[0028] (11)The glass of the present invention preferably has a molar ratio ((Li2O + Na2O + K2O) / (1 - K2O)) + ((MgO + CaO + SrO + BaO) / (1 - CaO)) - Al2O3) / (SiO2 + Al2O3 + B2O3) of 0.05 to 0.15 in the glass described in any one of the above (1) to (10).

[0029] (12)The glass of the present invention is preferably subjected to ion exchange treatment in the glass described in any one of the above (1) to (11).

[0030] (13)The strengthened glass plate of the present invention is characterized in that, as the glass composition, in mol%, it contains SiO2 66 to 85%, Al2O3 1 to 10%, B2O3 0 to 5%, Li2O 3 to 8%, Na2O 3 to 8%, K2O 0 to 1%, CaO 0 to 0.5%, SnO2 0.03 to 3%, the molar ratio (Li2O + Na2O + K2O) / (1 - K2O) is 5 to 30, the molar ratio (K2O + CaO) / (Li2O + Na2O + K2O) is 0 to 0.3, the molar ratio (10×SnO2) / (10×Fe2O3 + TiO2 + 10×SnO2 + 100×MoO3) is 0.5 to 1, and the molar ratio ((Li2O + Na2O + K2O) / (1 - K2O)) + ((MgO + CaO + SrO + BaO) / (1 - CaO)) - Al2O3) / (SiO2 + Al2O3 + B2O3) is 0.05 to 0.15. Here, "((Li2O + Na2O + K2O) / (1 - K2O)) + ((MgO + CaO + SrO + BaO) / (1 - CaO)) - Al2O3) / (SiO2 + Al2O3 + B2O3)" means the value obtained by dividing the sum of the values obtained by dividing the total content of Li2O, Na2O and K2O by the value obtained by subtracting the K2O content from 1, and the sum of the values obtained by dividing the total content of MgO, CaO, SrO and BaO by the value obtained by subtracting the CaO content from 1, subtracting the content of Al2O3, and then dividing the resulting value by the total content of SiO2, Al2O3 and B2O3.

[0031] (14)The strengthened glass plate of the present invention preferably has a plate thickness of 0.2 mm or less in the strengthened glass described in the above (13).

[0032] (15) The strengthened glass plate of the present invention is characterized in that, in a strengthened glass plate having a compressive stress layer on the surface, as the glass composition, in mol%, it contains 66 to 85% of SiO2, 1 to 10% of Al2O3, 0 to 5% of B2O3, 3 to 8% of Li2O, 3 to 8% of Na2O, 0 to 1% of K2O, 0 to 0.5% of CaO, 0.03 to 3% of SnO2, the molar ratio (Li2O + Na2O + K2O) / (1 - K2O) is 5 to 30, the molar ratio (K2O + CaO) / (Li2O + Na2O + K2O) is 0 to 0.3, the molar ratio (10×SnO2) / (10×Fe2O3 + TiO2 + 10×SnO2 + 100×MoO3) is 0.5 to 1, and the molar ratio ((Li2O + Na2O + K2O / (1 - K2O)) + ((MgO + CaO + SrO + BaO) / (1 - CaO)) - Al2O3) / (SiO2 + Al2O3 + B2O3) is 0.05 to 0.15. Detailed implementation mode

[0033] The glass of the present invention, as the glass composition, in mol%, contains 60 to 85% of SiO2, 1 to 20% of Al2O3, 0 to 5% of B2O3, 1 to 20% of Li2O + Na2O + K2O, and 0 to 5% of MgO + CaO + SrO + BaO. Explain the reasons for the limitation of the content range of each component. Also, in the description of the content of each component, unless otherwise specified, "%" means "mol%".

[0034] SiO2 is one of the components constituting the network structure of the glass. The lower the content of SiO2, the better the formability. However, if the content is too low, the chemical resistance is likely to decrease, and it is difficult to vitrify. In addition, the thermal expansion coefficient increases, and the thermal shock resistance is likely to decrease. On the other hand, the higher the content of SiO2, the more optimized the chemical resistance. However, if the content is too high, the viscosity of the glass increases, the formability is likely to decrease, and the liquidus temperature rises, and the glass is likely to devitrify. Therefore, the content of SiO2 is preferably 60% or more, 65% or more, 66% or more, 70% or more, 72% or more, 73% or more, 74% or more, particularly 75% or more, and preferably 85% or less, 84% or less, 83% or less, 82.5% or less, 82% or less, 81.5% or less, particularly 81% or less.

[0035] Al2O3 is one of the components that make up the network structure of glass. Additionally, it has the effect of improving chemical resistance, especially a high effect of improving hydrolysis resistance. If the content of Al2O3 is too low, the hydrolysis resistance is likely to decrease. On the other hand, if the content of Al2O3 is too high, the viscosity of the glass is likely to increase, and devitrified crystals are likely to precipitate in the glass, making it difficult to perform sheet forming by methods such as the overflow down-draw method. Especially when using alumina refractories as the forming body refractories and performing sheet forming by the overflow down-draw method, devitrified crystals of spinel are likely to precipitate at the interface with the alumina refractories. Therefore, the content of Al2O3 is preferably 1% or more, 2% or more, 2.5% or more, 3% or more, 3.5% or more, 4% or more, 4.5% or more, 4.6% or more, 4.7% or more, 4.8% or more, 4.9% or more, particularly 5% or more, and preferably 20% or less, 15% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9.5% or less, 9% or less, 8.5% or less, 8% or less, 7.5% or less, particularly 7% or less.

[0036] B2O3 has the effects of reducing the viscosity of the glass, improving meltability and formability, and reducing density and Young's modulus. However, if the content of B2O3 is too high, the ion exchange rate (especially the stress depth) is likely to decrease. Additionally, with ion exchange, coloring of the glass surface called discoloration (ヤケ) is likely to occur. Also, acid resistance and alkali resistance are likely to decrease. Therefore, the content of B2O3 is preferably 0 - 5%, 0 - 4%, 0 - 3%, 0 - 2%, 0 - 1%, 0 - 0.8%, particularly 0 - 0.5%.

[0037] As the alkali metal oxides (R2O), Li2O, Na2O, and K2O are one of the components that break the network structure of the glass and have the effects of reducing the viscosity of the glass, improving meltability and formability. The content of Li2O + Na2O + K2O is preferably 1% or more, 2% or more, 3 or more, 4% or more, 5% or more, 5.5% or more, 6% or more, 6.5% or more, 7% or more, 7.5% or more, particularly 8% or more. Also, when formability is particularly emphasized, the content of Li2O + Na2O + K2O is preferably 8.5% or more, 9% or more, 9.5% or more, 10% or more, 10.5% or more, particularly 11% or more. On the other hand, if the content of Li2O + Na2O + K2O is too high, the chemical resistance decreases, or the thermal expansion coefficient increases and the thermal shock resistance decreases. Therefore, the content of Li2O + Na2O + K2O is preferably 20% or less, 19% or less, 18.5% or less, 18% or less, 17.5% or less, 17% or less, 16.5% or less, 16% or less, 15.5% or less, particularly 15% or less.

[0038] As described above, Li2O has the effect of reducing the viscosity of glass and improving its meltability and formability. Among the alkali metal oxides, Li2O has the highest effect of reducing the glass viscosity, and the effects of Na2O and K2O follow in descending order. In addition, it is a component that can form a compressive stress layer on the glass surface through ion exchange with Na ions or K ions, and is particularly effective for obtaining a deep stress depth. However, if the content of Li2O is too high, the chemical resistance is likely to decrease, and it dissolves during the ion exchange treatment, which deteriorates the ion exchange solution. The appropriate content of Li2O varies depending on the characteristics of the glass that are emphasized. When emphasizing the formation of a large compressive stress on the glass surface through ion exchange, the content of Li2O is preferably 0 to 10%, 0 to 9%, 0 to 8%, 0 to 7%, 0 to 6%, 0 to 5%, 0 to 4%, particularly 0 to 3%. When emphasizing formability and chemical resistance, the content of Li2O is preferably 0.1 to 15%, 1 to 14.9%, 2 to 14.8%, 3 to 14.7%, 4 to 14.6%, 5 to 14.5%, 6 to 14.4%, 6.5 to 14.3%, 7 to 14.2%, 7.5 to 14.1%, particularly 8 to 14%. When emphasizing the balance of the magnitude of compressive stress, formability, and chemical resistance, the content of Li2O is preferably 1 to 14%, 1.5 to 13%, 2 to 12%, 2.5 to 11%, 2.6 to 10%, 2.7 to 9.5%, 2.8 to 9%, 2.9 to 8.5%, particularly 3 to 8%. Also, if the content of Li2O is 10% or less, devitrification is less likely to occur.

[0039] Similar to Li₂O, Na₂O has the effect of reducing the viscosity of glass, improving the meltability and formability. In addition, it is also a component that improves the devitrification resistance and the reaction devitrification with the refractory of the formed body, especially alumina refractory. Furthermore, if Na₂O is introduced, a compressive stress layer can be formed on the glass surface through ion exchange with K ions. If the content of Na₂O is too low, the devitrification resistance is likely to decrease. On the other hand, if the content of Na₂O is too high, the chemical resistance is likely to decrease. The appropriate content of Na₂O varies depending on the characteristics of the glass that are emphasized. When emphasizing the formation of a large compressive stress on the glass surface through ion exchange, the content of Na₂O is preferably 0.1 - 15%, 1 - 14.9%, 2 - 14.8%, 3 - 14.7%, 4 - 14.6%, 5 - 14.5%, 6 - 14.4%, 6.5 - 14.3%, 7 - 14.2%, 7.5 - 14.1%, especially 8 - 14%. When emphasizing formability and chemical resistance, the content of Na₂O is preferably 0 - 10%, 0 - 9%, 0 - 8%, 0 - 7%, 0 - 6%, 0 - 5%, 0 - 4%, especially 0 - 3%. When emphasizing the balance of the magnitude of the compressive stress, formability, and chemical resistance, the content of Na₂O is preferably 1 - 14%, 1.5 - 13%, 2 - 12%, 2.5 - 11%, 2.6 - 10%, 2.7 - 9.5%, 2.8 - 9%, 2.9 - 8.5%, especially 3 - 8%.

[0040] The effect of K₂O is not as good as that of Li₂O and Na₂O, but it has the effect of reducing the viscosity of glass, improving the meltability and formability. If the content of K₂O is too low, the devitrification resistance decreases. On the other hand, if the content of K₂O is too high, the hydrolysis resistance is likely to decrease. In addition, it is difficult to form a compressive stress in the ion exchange with Na ions or K ions. Therefore, the content of K₂O is preferably 0 - 15%, 0 - 5%, 0 - 4%, 0 - 3.5%, 0 - 3%, 0 - 2.5%, 0 - 2%, 0 - 1.5%, 0 - 1.3%, 0 - 1%, especially 0 - less than 1%.

[0041] Among the alkali metal oxides (R₂O), the effect of reducing the viscosity of glass is the highest for Li₂O, and then in descending order of effect are Na₂O and K₂O. Therefore, from the perspective of reducing the viscosity of glass, the relationship of the content of alkali metal oxides is preferably Li₂O≥Na₂O≥K₂O, Li₂O≥Na₂O>K₂O or Li₂O>Na₂O≥K₂O, especially Li₂O>Na₂O>K₂O. In addition, if the proportion of K₂O among the alkali metal oxides is too high, it is difficult to balance the chemical resistance and formability, and it is also difficult to form a compressive stress in the ion exchange with Na ions or K ions. Therefore, it is particularly preferred that Na₂O>K₂O.

[0042] As described above, alkali metal oxides are components that reduce the chemical resistance while lowering the glass viscosity, and are necessary components for forming compressive stress on a glass plate through ion exchange. In order to form compressive stress on a glass plate, larger ions need to be introduced into the glass interior. Generally, as the ions introduced into the glass through ion exchange, Na ions or K ions are mostly used. Therefore, if the content of K2O in the glass is high, the difference in the size of the exchanged ions becomes smaller, making it difficult to form compressive stress. Based on this, from the perspective of emphasizing ion exchange performance, especially the formation of compressive stress, it is preferable that the proportion of the content of K2O in the total content of alkali metal oxides is small. Therefore, the molar ratio (Li2O + Na2O + K2O) / (5 - K2O) is preferably -10 to 150, 0.2 to 150, 0.2 to 100, 0.2 to 70, 0.2 to 50, 0.2 to 40, 0.2 to 35, 0.2 to 32, 0.2 to 30, 0.2 to 27, particularly 0.2 to 25. Here, "(Li2O + Na2O + K2O) / (5 - K2O)" means dividing the total content of Li2O, Na2O, and K2O by the value obtained by subtracting the K2O content from 5.

[0043] When emphasizing the coexistence of chemical resistance, formability, and ion exchange performance, it is preferable to strictly limit the content of K2O. In this case, the molar ratio (Li2O + Na2O + K2O) / (1 - K2O) is preferably -15 to 150, 1 to 150, 1.5 to 100, 2 to 70, 2.5 to 50, 3 to 30, 3.5 to 27, 4 to 25, 4.5 to 23, particularly 5 to 20.

[0044] As described above, alkali metal oxides are components that reduce the chemical resistance while lowering the glass viscosity because they break the network structure of the glass. However, Al2O3 forms the network structure of the glass together with alkali metal oxides in the glass. Therefore, if Al2O3 is introduced into the glass composition, the function of a part of the alkali metal oxides can be changed from breaking the network structure to forming the network structure. Based on this, from the perspective of emphasizing chemical resistance, it is preferable that all Al2O3 forms bonds with alkali metal oxides in a stoichiometric ratio, which is the state when the value of the molar ratio (Li2O + Na2O + K2O) / Al2O3 is 1 or more. Therefore, the closer the value of the molar ratio (Li2O + Na2O + K2O) / Al2O3 is to 1, the more the network structure increases, and thus the chemical resistance is optimized. On the other hand, in this state, the breakage of the network structure becomes less, so the formability decreases. Therefore, from the perspective of balancing chemical resistance and formability, the molar ratio (Li2O + Na2O + K2O) / Al2O3 is preferably 1 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2 or more, particularly higher than 2. On the other hand, if the molar ratio (Li2O + Na2O + K2O) / Al2O3 is too large, the formability improves, but the chemical resistance is likely to decrease. Therefore, the molar ratio (Li2O + Na2O + K2O) / Al2O3 is preferably 5 or less, 4 or less, 3.5 or less, 3.4 or less, 3.3 or less, 3.2 or less, 3.1 or less, particularly 3 or less.

[0045] MgO, CaO, SrO, and BaO as alkaline earth metal oxides (R’O), like alkali metal oxides, are components that break the network structure of the glass and also have the effect of reducing the glass viscosity. They are also components that affect chemical resistance. If the content of MgO + CaO + SrO + BaO is too high, not only is the chemical resistance likely to decrease, but the devitrification resistance is also likely to decrease. Therefore, the content of MgO + CaO + SrO + BaO is preferably 0 - 5%, 0 - 4%, 0 - 3.7%, 0 - 3%, 0 - 2%, 0 - 1%, 0 - 0.9%, 0 - 0.8%, 0 - 0.7%, 0 - 0.6%, 0 - 0.5%, 0 - 0.4%, 0 - 0.3%, 0 - 0.2%, particularly 0 - 0.1%.

[0046] MgO, as described above, like the alkali metal oxides, is one of the components that break the network structure of the glass, lower the high-temperature viscosity, and improve the meltability and formability. It is also a component that affects chemical resistance. If the content of MgO is too high, the chemical resistance is likely to decrease, and there is also a tendency for the ion exchange performance to decrease or for the glass to devitrify. In particular, when using an alumina refractory as the forming body refractory and performing sheet forming by the overflow down-draw method, devitrified crystals of spinel are likely to precipitate at the interface with the alumina refractory. Therefore, the content of MgO is preferably 0 to 5%, 0 to 3%, 0 to 1%, 0 to 0.9%, 0 to 0.8%, 0 to 0.7%, 0 to 0.6%, 0 to 0.5%, 0 to 0.4%, 0 to 0.3%, 0 to 0.2%, 0 to 0.1%, 0 to 0.05%, 0 to 0.03%, 0 to less than 0.03%, 0 to 0.01%, 0 to less than 0.01%, especially 0 to less than 0.001%.

[0047] CaO, as described above, like the alkali metal oxides, is one of the components that break the network structure of the glass, lower the high-temperature viscosity, and improve the meltability and formability. It is also a component that affects chemical resistance. If the content of CaO is too high, the chemical resistance may decrease. In addition, CaO is also a component that is likely to cause a decrease in ion exchange performance and deterioration of the ion exchange solution. Therefore, the content of CaO is preferably 0 to 5%, 0 to 4%, 0 to 3%, 0 to 2%, 0 to 1%, 0 to 0.9%, 0 to 0.8%, 0 to 0.7%, 0 to 0.6%, 0 to 0.5%, 0 to 0.4%, 0 to 0.3%, 0 to 0.2%, 0 to 0.1%, 0 to 0.05%, 0 to 0.03%, 0 to less than 0.03%, 0 to 0.01%, 0 to less than 0.01%, especially 0 to less than 0.001%.

[0048] From the perspective of emphasizing the ion exchange performance with Na ions or K ions, it is preferable to strictly limit the content of K2O, which easily reduces the compressive stress imparted to the glass plate, and the content of CaO, which reduces the ion exchange performance. In particular, it is preferably strictly limited based on the relationship with the proportion in the total amount of alkali metal oxides contributing to ion exchange. Therefore, the molar ratio (K2O + CaO) / (Li2O + Na2O + K2O) is preferably 0 to 0.3, 0 to 0.25, 0 to 0.2, 0 to 0.17, 0 to 0.15, 0 to 0.14, 0 to 0.13, 0 to 0.12, 0 to 0.11, especially 0 to 0.1.

[0049] The content of SrO is preferably 0 to 1%, 0 to 0.9%, 0 to 0.8%, 0 to 0.7%, 0 to 0.6%, 0 to 0.5%, 0 to 0.4%, 0 to 0.3%, 0 to 0.2%, 0 to 0.1%, 0 to 0.01%, 0 to less than 0.01%, especially 0 to 0.001%. If the content of SrO is too much, the chemical resistance is likely to decrease.

[0050] The content of BaO is preferably 0 to 1%, 0 to 0.9%, 0 to 0.8%, 0 to 0.7%, 0 to 0.6%, 0 to 0.5%, 0 to 0.4%, 0 to 0.3%, 0 to 0.2%, 0 to 0.1%, 0 to 0.01%, 0 to less than 0.01%, especially 0 to 0.001%. If the content of BaO is too much, the chemical resistance is likely to decrease.

[0051] As described above, CaO is a component that reduces the ion exchange performance. When attaching importance to forming a compressive stress layer by ion exchange, it is preferable to strictly limit the proportion of CaO in the total amount of alkaline earth metal oxides. The molar ratio (MgO + CaO + SrO + BaO / (1 - CaO)) is preferably 0 to 10, 0 to 5, 0 to 4, 0 to 3.7, 0 to 3, 0 to 2, 0 to 1, 0 to 0.9, 0 to 0.8, 0 to 0.7, 0 to 0.6, 0 to 0.5, 0 to 0.4, 0 to 0.3, 0 to 0.2, especially 0 to 0.1.

[0052] The molar ratio (Li2O + Na2O + K2O + MgO + CaO + SrO + BaO - Al2O3) / (SiO2 + Al2O3 + B2O3) means the ratio of the components that break the network structure in the cut glass to the components that form the network structure in the glass. Alkali metal oxides and alkaline earth metal oxides, as described above, have the effect of breaking the network structure in the glass. However, Al2O3 forms the network structure in the glass together with the alkali metal oxides. Therefore, the alkali metal oxides in an amount equal to the content of Al2O3 do not have the effect of breaking the network. In addition, SiO2, Al2O3, and B2O3 are the components that form the network structure in the glass. In other words, the smaller the molar ratio (Li2O + Na2O + K2O + MgO + CaO + SrO + BaO - Al2O3) / (SiO2 + Al2O3 + B2O3), the fewer the components that break the network structure relative to the components that form the network structure, and the chemical resistance, especially hydrolysis resistance, is optimized. However, if it is too small, the formability is likely to decrease. Therefore, the molar ratio (Li2O + Na2O + K2O + MgO + CaO + SrO + BaO - Al2O3) / (SiO2 + Al2O3 + B2O3) is preferably 0 to 0.2, 0.01 to 0.19, 0.02 to 0.18, 0.03 to 0.17, 0.04 to 0.16, 0.041 to 0.159, 0.042 to 0.158, 0.043 to 0.157, 0.044 to 0.156, 0.045 to 0.155, 0.046 to 0.154, 0.047 to 0.153, 0.048 to 0.152, 0.049 to 0.151, especially 0.05 to 0.15. Also, "(Li2O + Na2O + K2O + MgO + CaO + SrO + BaO - Al2O3) / (SiO2 + Al2O3 + B2O3)" refers to the value obtained by dividing the value obtained by subtracting the content of Al2O3 from the total content of Li2O, Na2O, K2O, MgO, CaO, SrO, and BaO by the total content of SiO2, Al2O3, and B2O3.

[0053] When attaching importance to both ion exchange performance and chemical resistance, the molar ratio ((Li2O + Na2O + K2O / (1 - K2O)) + ((MgO + CaO + SrO + BaO) / (1 - CaO)) - Al2O3) / (SiO2 + Al2O3 + B2O3) means the ratio of the components that break the network structure in the glass to the components that form the network structure in the glass, on the basis of strictly restricting the components that reduce the ion exchange performance. Alkali metal oxides and alkaline earth metal oxides, as described above, have the effect of breaking the network structure in the glass. However, Al2O3 forms the network structure in the glass together with the alkali metal oxides. Therefore, the alkali metal oxides equivalent to the content of Al2O3 do not have the effect of breaking the network. In addition, SiO2, Al2O3, and B2O3 are the components that form the network structure in the glass. In other words, the smaller the molar ratio ((Li2O + Na2O + K2O / (1 - K2O)) + ((MgO + CaO + SrO + BaO) / (1 - CaO)) - Al2O3) / (SiO2 + Al2O3 + B2O3), the fewer the components that break the network structure relative to the components that form the network structure. Therefore, the chemical resistance, especially the hydrolysis resistance, is optimized. However, if it is too small, the formability is likely to decrease. Therefore, the molar ratio ((Li2O + Na2O + K2O / (1 - K2O)) + ((MgO + CaO + SrO + BaO) / (1 - CaO)) - Al2O3) / (SiO2 + Al2O3 + B2O3) is preferably 0 to 0.2, 0.01 to 0.19, 0.02 to 0.18, 0.03 to 0.17, 0.04 to 0.16, 0.041 to 0.159, 0.042 to 0.158, 0.043 to 0.157, 0.044 to 0.156, 0.045 to 0.155, 0.046 to 0.154, 0.047 to 0.153, 0.048 to 0.152, 0.049 to 0.151, especially 0.05 to 0.15.

[0054] In addition to the above components, other components may also be introduced.

[0055] Fe2O3 is a component mixed as an impurity from the glass raw materials and manufacturing equipment. If the content of Fe2O3 is too high, the glass will be colored and the transmittance of visible light will decrease. Therefore, the content of Fe2O3 is preferably 0 to 0.5%, 0 to 0.3%, 0 to 0.1%, 0 to 0.05%, 0 to 0.04%, 0 to 0.03%, 0 to 0.02%, especially 0 to 0.01%.

[0056] Similar to Fe2O3, TiO2 is a component that is mixed as an impurity from glass raw materials and manufacturing equipment. If the content of TiO2 is too high, the glass will be colored black and the transmittance of visible light will decrease. Therefore, the content of TiO2 is preferably 0 - 0.5%, 0 - 0.3%, 0 - 0.1%, 0 - 0.05%, 0 - 0.04%, particularly 0 - 0.03%.

[0057] In the electrofusion of glass, Mo is sometimes used as the electrode material. The electrofusion of glass can suppress the energy unit to a lower level compared to the fusion using a burner, so it is an effective fusion method for issues such as the soaring price of fossil fuels and the reduction of CO2 emissions. On the other hand, during fusion, MoO3 may be mixed into the glass from the electrode surface. If too much MoO3 is mixed into the glass, the glass will be colored black and the transmittance of visible light will decrease. MoO3 is the most likely component among those that can be mixed into the glass from manufacturing equipment to color the glass, and its content needs to be strictly restricted. Therefore, the content of MoO3 is preferably 0 - 0.1%, 0.00001 - 0.03%, 0.00002 - 0.01%, particularly 0.00003 - 0.0005%.

[0058] When emphasizing the transparency of the glass, it is necessary to strictly control the amount of MoO3 mixed in. The order of influence on transparency is MoO3 > Fe2O3 > TiO2, and it is preferred that the amount of MoO3 mixed in is less than that of Fe2O3 and TiO2. Therefore, the molar ratio MoO3 / (Fe2O3 + TiO2) is preferably 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, particularly 0.2 or less.

[0059] ZrO2 is a component that improves alkali resistance. However, if the content of ZrO2 is too high, the viscosity of the glass will increase and the devitrification resistance will be easily reduced. Therefore, the content of ZrO2 is preferably 0 - 3%, 0 - 2.5%, 0 - 2%, 0 - 1.5%, 0.1 - 0.8%, particularly 0.2 - 0.6%.

[0060] SnO2 is a component that functions as a fining agent for molten glass. Additionally, in the electro-fusion of glass, since Sn is used as an electrode, it is a component that may be mixed as an impurity from the electrode surface. If the content of SnO2 is too low, the time required for defoaming becomes longer, and moreover, the amount of glass containing bubble defects may increase. On the other hand, if the content of SnO2 is too high, the glass becomes brown-colored and the transmittance of visible light decreases. Therefore, the content of SnO2 is preferably 0 to 3%, 0.001 to 2%, 0.01 to 1%, 0.02 to 0.8%, 0.03 to 0.7%, 0.04 to 0.6%, 0.05 to 0.5%, 0.06 to 0.45%, 0.07 to 0.4%, 0.08 to 0.35%, 0.09 to 0.33%, particularly 0.1 to 0.3%.

[0061] During the electro-fusion of glass, Fe2O3, TiO2, SnO2, and MoO3 may be mixed as components that color the glass. When adding SnO2 as a fining agent, it is preferably as free as possible from impurities other than SnO2 that affect coloring. The influence of these components on the transmittance is MoO3 > Fe2O3 ≒ SnO2 > TiO2. Therefore, from the perspective of emphasizing transmittance, the molar ratio (10×SnO2) / (10×Fe2O3 + TiO2 + 10×SnO2 + 100×MoO3) is preferably 0.4 to 1, 0.5 to 1, 0.55 to 1, 0.6 to 1, 0.65 to 1, 0.7 to 1, 0.75 to 1, particularly 0.8 to 1.

[0062] In addition to SnO2, one or more of F, Cl, Sb2O3, SO3, etc. can also be introduced as fining agents. The total content and individual content of these fining agents are preferably 5% or less, 3% or less, 1% or less, 0.8% or less, 0.5% or less, 0.3% or less, 0.1% or less, particularly 0 to 0.05%.

[0063] ZnO is a component that improves the ion exchange performance, especially a component that has a significant effect on increasing the compressive stress value. It is also a component that reduces the high-temperature viscosity without reducing the low-temperature viscosity. However, if the content of ZnO is too high, there are problems such as a decrease in hydrolysis resistance, glass phase separation, a decrease in devitrification resistance, an increase in density, and a decrease in stress depth. Therefore, the content of ZnO is preferably 0 to 4%, 0 to 1%, particularly 0 to 0.01%.

[0064] P2O5 is a component that maintains the compressive stress value and improves the ion exchange performance. Additionally, it is a component that reduces the Young's modulus. Moreover, it is also a component that decreases the high-temperature viscosity and improves the meltability and formability. However, if the content of P2O5 is too high, the glass is prone to cloudiness due to phase separation and a decrease in acid resistance. Therefore, the content of P2O5 is preferably 0 to 5%, 0 to 4%, 0 to 3.5%, particularly 0 to 3%.

[0065] In order to improve chemical resistance, high-temperature viscosity, etc., Cr2O3, PbO, La2O3, WO3, Nb2O3, Y2O3, etc. can also be introduced in the ranges of 3% or less, 2% or less, 1% or less, less than 1%, especially 0.5% or less, respectively.

[0066] As impurities, components such as H2, CO2, CO, H2O, He, Ne, Ar, N2, etc. can also be introduced up to 0.1%. In addition, the mixing amount of noble metal elements such as Pt, Rh, Au, etc. is preferably 0.05% or less, and more preferably 0.03% or less, respectively.

[0067] The glass of the present invention preferably has the following characteristics.

[0068] According to the grade of the hydrolysis resistance test (acetone cleaning) of ISO720, it is preferably at least HGA2, and particularly preferably HGA1. Here, the so-called "hydrolysis resistance test (acetone cleaning) according to ISO720" refers to the following test.

[0069] (1) Crush the glass sample with an alumina mortar and classify it into 300 - 425 μm with a sieve.

[0070] (2) Clean the obtained powder sample with acetone and dry it in an oven at 140 °C.

[0071] (3) Put 10 g of the dried powder sample into a quartz flask, add 50 mL of distilled water, cover it, and perform the treatment in an autoclave. The treatment is carried out according to the following treatment conditions: heat from 100 °C to 121 °C at 1 °C / minute, then maintain at 121 °C for 30 minutes, and cool to 100 °C at 0.5 °C / minute.

[0072] (4) After the autoclave treatment, transfer the solution in the quartz flask to another beaker, and wash the inside of the quartz flask 3 times with 15 mL of distilled water. This washing solution is also added to the beaker.

[0073] (5) Add methyl red indicator to the beaker and titrate with 0.02 mol / L hydrochloric acid aqueous solution.

[0074] (6) Convert 1 mL of 0.02 mol / L hydrochloric acid aqueous solution into the alkali dissolution amount per 1 g of glass, which is equivalent to 620 μg of Na2O.

[0075] Also, the so-called "grade in the hydrolysis resistance test (acetone cleaning) according to ISO720 is at least HGA2" means that the alkali dissolution amount per 1 g of glass in terms of Na2O obtained by the above test is 527 μg / g or less.

[0076] The alkali dissolution amount in terms of Na2O conversion in the hydrolysis resistance test (acetone cleaning) according to ISO720 is preferably less than 527 μg / g, 200 μg / g or less, 100 μg / g or less, 90 μg / g or less, 80 μg / g or less, 70 μg / g or less, less than 62 μg / g, 60 μg / g or less, 57 μg / g or less, 55 μg / g or less, 53 μg / g or less, especially 50 μg / g or less. If the alkali dissolution amount is too large, when the glass is processed into a flexible cover member, the alkaline components dissolve out from the glass and fine defects are generated on the surface. When the glass is bent or collides with an object, the glass is likely to crack.

[0077] The alkali resistance in the test according to ISO695 is preferably at least grade 2. Here, the "alkali resistance test according to ISO695" refers to the following test.

[0078] (1)Prepare a sample with a surface area of A cm 2 (where A is 10 - 15 cm 2 ) that has been mirror-finished on the entire surface. First, as a pretreatment, prepare a solution by mixing hydrofluoric acid (40% by mass) and hydrochloric acid (2 mol / L) in a volume ratio of 1:9. Immerse the sample in this solution and stir with a magnetic stirrer for 10 minutes. Take out the sample, perform ultrasonic cleaning with distilled water 3 times for 2 minutes each time, and perform ultrasonic cleaning with ethanol 2 times for 1 minute each time.

[0079] (2)Subsequently, dry the sample in an oven at 110°C for 1 hour and cool it in a desiccator for 30 minutes.

[0080] (3)Measure the mass m1 of the sample to an accuracy of ±0.1 mg and record it.

[0081] (4)Prepare 800 mL of a solution by mixing an aqueous sodium hydroxide solution (1 mol / L) and an aqueous sodium carbonate solution (0.5 mol / L) in a volume ratio of 1:1. Add this solution to a stainless-steel container and bring it to a boil using a mantle heater. Then, suspend the sample with a platinum wire, keep it for 3 hours, take out the sample, perform ultrasonic cleaning with distilled water 3 times for 2 minutes each time, and perform ultrasonic cleaning with ethanol 2 times for 1 minute each time. After that, dry the sample in an oven at 110°C for 1 hour and cool it in a desiccator for 30 minutes.

[0082] (5)Measure the mass m2 of the sample to an accuracy of ±0.1 mg and record it.

[0083] (6)Based on the masses m1, m2 (mg) before and after being put into the boiling alkali solution and the surface area A (cm 2 ) of the sample, calculate the mass reduction per unit area through the following formula as the measured value of the alkali resistance test.

[0084] (Mass reduction per unit area) = 100 × (m1 - m2) / A

[0085] In addition, the so-called "alkali resistance in the test according to ISO695 is Grade 2" means that the mass reduction per unit area obtained as described above is 175 mg / dm 2 or less. In addition, if the mass reduction per unit area obtained as described above is 75 mg / dm 2 or less, then it is "alkali resistance in the test according to ISO695 is Grade 1". For the glass of the present invention, the mass reduction per unit area is preferably 130 mg / dm 2 or less, particularly 75 mg / dm 2 or less. If this mass reduction is large, when the glass is processed into a flexible cover member, alkaline components dissolve out from the glass and fine defects are generated on the surface, and when the glass is bent or collided with an object, the glass is likely to crack.

[0086] In the acid resistance test according to YBB00342004, the mass reduction per unit area is preferably 1.5 mg / dm 2 or less, particularly 0.7 mg / dm 2 or less. If this mass reduction is large, when the glass is processed into a flexible cover member, alkaline components dissolve out from the glass and fine defects are generated on the surface, and when the glass is bent or collided with an object, the glass is likely to crack.

[0087] The so-called "acid resistance test according to YBB00342004" refers to the following test.

[0088] (1) Prepare a sample with a surface area of A cm 2 (where A is 100 ± 5 cm 2 ) that has been mirror-finished on the entire surface. First, as a pretreatment, prepare a solution in which hydrofluoric acid (40% by mass) and hydrochloric acid (2 mol / L) are mixed in a volume ratio of 1:9. Immerse the sample in this solution and stir with a magnetic stirrer for 10 minutes. Take out the sample, perform ultrasonic cleaning with distilled water 3 times for 2 minutes each, and perform ultrasonic cleaning with ethanol 2 times for 1 minute each.

[0089] (2) Then, dry the sample in an oven at 110°C for 1 hour and let it cool in a desiccator for 30 minutes.

[0090] (3) Measure the mass m1 of the sample to an accuracy of ±0.1 mg and record it.

[0091] (4) Prepare 800 mL of hydrochloric acid solution (6 mol / L). Add this hydrochloric acid solution to a container made of silica glass and heat it to boiling using an electric heater. Suspend the sample with a platinum wire and maintain for 6 hours. Take out the sample, perform ultrasonic cleaning with distilled water three times for 2 minutes each time, and perform ultrasonic cleaning with ethanol twice for 1 minute each time. Thereafter, dry the sample in an oven at 110 °C for 1 hour and cool it in a desiccator for 30 minutes.

[0092] (5) Measure the mass m2 of the sample to an accuracy of ±0.1 mg and record it.

[0093] (6) Based on the masses m1 and m2 (mg) before and after adding to the boiling acid solution and the surface area A (cm 2 ) of the sample, calculate one-half of the mass reduction per unit area as the measurement value for the acid resistance test using the following formula.

[0094] (Mass reduction per unit area) = 1 / 2 × 100 × (m1 - m2) / A

[0095] The transmittance of visible light (wavelength 380 - 760 nm) at a thickness of 1 mm is preferably 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, particularly 90% or more. If the transmittance of visible light at a thickness of 1 mm is high, when used as the cover glass of a display, the display clarity of the display is likely to be improved.

[0096] Working point (temperature at 10 4.0 dPa·s) is preferably 1350 °C or lower, 1300 °C or lower, 1260 °C or lower, particularly 1250 °C or lower. If the working point increases, the forming temperature of the molten glass becomes higher, so the life of the forming equipment is likely to be shortened.

[0097] 10 2.5 The temperature at 10 2.5 dPa·s is preferably 1700 °C or lower, 1650 °C or lower, 1640 °C or lower, 1630 °C or lower, 1620 °C or lower, 1610 °C or lower, particularly 1600 °C or lower. The lower the temperature at 10 2.5 dPa·s, the lower the melting temperature can be, the easier it is to reduce the burden on glass manufacturing equipment such as melting furnaces, and the easier it is to improve the bubble quality. Therefore, the lower the temperature at 10 2.5 dPa·s, the easier it is to lower the manufacturing cost of the strengthened glass plate and the strengthened glass plate for strengthening. On the other hand, if the temperature at 10

[0098] The liquid-phase viscosity Logρ is preferably 4.0 dPa·s or more, 4.3 dPa·s or more, 4.5 dPa·s or more, 4.8 dPa·s or more, 5.1 dPa·s or more, 5.3 dPa·s or more, particularly 5.5 dPa·s or more. If the liquid-phase viscosity is too low, the devitrification resistance decreases, and it is difficult to form sheet glass by the overflow down-draw method or the like.

[0099] The glass of the present invention is preferably sheet-shaped (including film-shaped). Thus, it is easily applicable to a cover member, particularly a flexible cover member. In this case, the plate thickness is preferably 0.2 mm or less, that is, 200 μm or less, 150 μm or less, 100 μm or less, less than 100 μm, 80 μm or less, 60 μm or less, 1 to 50 μm, 5 to 40 μm, particularly 10 to 30 μm. The smaller the plate thickness, the higher the flexibility, and the more easily it is applicable to a foldable cover member. In addition, the smaller the plate thickness, the smaller the allowable radius of curvature when bending the glass plate, and the more easily it can be wound into a roll shape.

[0100] The size of the glass plate is preferably □50 mm or more, □60 mm or more, □70 mm or more, □80 mm or more, □90 mm or more, □100 mm or more, □120 mm or more, □150 mm or more, particularly □200 to 2000 mm. If the size increases, it is more easily applicable to a large flexible display.

[0101] The strengthened glass plate of the present invention has been subjected to ion exchange treatment on the strengthened glass plate and has a compressive stress layer on the surface. The compressive stress value at the outermost surface is preferably 100 MPa or more, 200 MPa or more, 400 MPa or more, 500 MPa or more, 600 MPa or more, particularly 700 MPa or more. The larger the compressive stress value at the outermost surface, the more easily it is to prevent breakage caused by tensile stress occurring at the bent portion of the strengthened glass plate when bending a foldable display. On the other hand, if an extremely large compressive stress is formed on the surface, the tensile stress inherent in the strengthened glass plate will increase extremely, and the dimensional change before and after the ion exchange treatment may increase. Therefore, the compressive stress value at the outermost surface is preferably 1300 MPa or less, 1100 MPa or less, 900 MPa or less, particularly preferably 800 MPa or less.

[0102] The depth of compressive stress is preferably 1 μm or more, 3 μm or more, 5 μm or more, 7 μm or more, 8 μm or more, 9 μm or more, and particularly 10 μm or more, and is 5 to 30%, 6 to 25%, 7 to 20%, 8 to 17%, 10 to 15%, 11 to 14%, and particularly 12 to 13% of the plate thickness. The greater the stress depth, the more difficult it is for the tempered glass plate to break, even if there is a flaw deep in the tempered glass plate, and the deviation in mechanical strength is reduced. On the other hand, the greater the stress depth, the more likely it is that the dimensional change before and after the ion exchange treatment increases. Therefore, the stress depth is preferably 20 μm or less, 15 μm or less, and particularly 10 μm or less.

[0103] The internal tensile stress value of the tempered glass plate is preferably 400 MPa or less, 350 MPa or less, 300 MPa or less, 250 MPa or less, 220 MPa or less, 200 MPa or less, 180 MPa or less, and particularly 170 MPa or less. If the internal tensile stress value is too high, the tempered glass plate is likely to explode due to physical collision or the like. On the other hand, if the internal tensile stress value is too low, it is difficult to ensure the mechanical strength of the tempered glass plate. The internal tensile stress value is preferably 60 MPa or more, 80 MPa or more, 100 MPa or more, 125 MPa or more, 140 MPa or more, and particularly 150 MPa or more. In addition, the internal tensile stress value can be calculated by the following formula 2.

[0104] Internal tensile stress value = (compressive stress value on the outermost surface × stress depth) / (plate thickness - 2 × stress depth) ···Formula 2

[0105] In the tempered glass plate of the present invention, the pen drop strength is preferably 5 mm or more, 6 mm or more, 7 mm or more, 8 mm or more, 9 mm or more, 10 mm or more, 11 mm or more, 12 mm or more, 13 mm or more, 14 mm or more, 15 mm or more, and particularly 16 mm or more. The higher the pen drop strength, the less likely the tempered glass plate is to be broken by an external force, and the durability of the foldable display is improved. In addition, the "pen drop strength" can be measured by the method shown below.

[0106] The glass, tempered glass plate, and tempered glass plate of the present invention can be produced by the following method. First, glass raw materials prepared according to the desired glass composition are put into a continuous melting furnace, heated at 1500 to 1700°C to melt and clarify, and then the molten glass is supplied to a forming device, and then formed into a plate shape and cooled. After forming into a plate shape, the method of cutting into a predetermined size can adopt a well-known method, but in order to make the end surface smooth, it is preferably cut by laser melting.

[0107] When forming molten glass, in the temperature range from the annealing point to the strain point of the molten glass, it is preferably cooled at a cooling rate of 2 °C / min or more and less than 2500 °C / min. This cooling rate is preferably 5 °C / min or more, 10 °C / min or more, 40 °C / min or more, 60 °C / min or more, particularly 100 °C / min or more, and preferably less than 2500 °C / min, less than 2000 °C / min, less than 1800 °C / min, less than 1500 °C / min, less than 1300 °C / min, less than 1000 °C / min, less than 800 °C / min, particularly less than 500 °C / min. If the cooling rate is too slow, it is difficult to reduce the plate thickness. On the other hand, if the cooling rate is too fast, the glass structure becomes rough and the hardness of the strengthened glass plate is likely to decrease.

[0108] As a method for forming molten glass, the overflow down-draw method is preferably used. The overflow down-draw method is a method capable of mass-producing high-quality glass plates and can also easily manufacture thin glass plates. In addition, in the overflow down-draw method, alumina or zirconia is used as the forming refractory, but since the glass of the present invention has particularly good compatibility with alumina, it is difficult for bubbles or foreign substances to occur during forming.

[0109] In addition to the overflow down-draw method, various forming methods can also be used. For example, forming methods such as the float method, the down-draw method (slot down-draw method, redraw method, etc.), the rolling method, and the pressing method.

[0110] The strengthened glass plate of the present invention is produced by subjecting the strengthened glass plate to ion exchange treatment. The conditions of the ion exchange treatment are not particularly limited, and the optimal conditions can be selected considering the viscosity characteristics of the glass, its use, plate thickness, internal tensile stress, dimensional changes, etc. In particular, if the K ions in the KNO3 molten salt are ion-exchanged with the Na component in the glass, a surface compressive stress layer can be efficiently formed.

[0111] The number of times of ion exchange treatment is not particularly limited and can be carried out once or multiple times. If the number of times of ion exchange treatment is once, the cost of the strengthened glass plate can be reduced. When performing multiple ion exchange treatments, the number of times of ion exchange treatment is preferably 2 times. In this case, the total amount of tensile stress accumulated inside the glass can be reduced while increasing the stress depth.

[0112] The strengthened glass plate and the strengthened glass plate of the present invention can be etched with an acidic solution such as hydrofluoric acid or a basic solution such as sodium hydroxide, and in particular, the end face can be etched. If the etching treatment is carried out before the ion exchange treatment, the plate thickness can be thinned or the strength reduction caused by defects can be suppressed. If the etching treatment is carried out after the ion exchange treatment, the influence of defects or surface roughness generated during the ion exchange treatment can be reduced.

[0113] Example

[0114] Hereinafter, the present invention will be described based on examples. In addition, the following examples are merely illustrative. The present invention is not limited by any of the following examples.

[0115] Tables 1 to 4 show the examples of the invention (Sample Nos. 1 to 48). In the tables, R2O / Al2O3 means (Li2O + Na2O + K2O) / Al2O3. R2O / (5 - K2O) means the molar ratio (Li2O + Na2O + K2O) / (5 - K2O). R2O / (1 - K2O) means the molar ratio (Li2O + Na2O + K2O) / (1 - K2O). R’O / (1 - CaO) means the molar ratio (MgO + CaO + SrO + BaO / (1 - CaO). (K2O + CaO) / R2O means the molar ratio (K2O + CaO) / (Li2O + Na2O + K2O). 10SnO2 / (10Fe2O3 + TiO2 + 10SnO2 + 100MoO3) means the molar ratio (10×SnO2) / (10×Fe2O3 + TiO2 + 10×SnO2 + 100×MoO3). (R2O + R’O - Al2O3) / (SiO2 + Al2O3 + B2O3) means the molar ratio (Li2O + Na2O + K2O + MgO + CaO + SrO + BaO - Al2O3) / (SiO2 + Al2O3 + B2O3). ((R2O / (1 - K2O)) + (R’O / (1 - CaO)) - Al2O3) / (SiO2 + Al2O3 + B2O3) means the molar ratio (((Li2O + Na2O + K2O / (1 - K2O)) + ((MgO + CaO + SrO + BaO) / (1 - CaO))) - Al2O3) / (SiO2 + Al2O3 + B2O3).

[0116] [Table 1]

[0117]

[0118] [Table 2]

[0119]

[0120] [Table 3]

[0121]

[0122] [Table 4]

[0123]

[0124] Each sample in the table was prepared as follows. First, a 550 g batch was blended according to the glass composition shown in the table, and melted in a platinum crucible at 1600 °C for 18 hours. Also, to improve the homogeneity of the molten glass, stirring was performed twice during the melting process. In addition, to reduce the bubbles in the glass, it was melted at 1650 °C for 2 hours. Second, the glass was rapidly cooled using a metal roller to produce a plate with a thickness of approximately 5 mm, and processed into the shape required for measurement for various evaluations. The results are shown in the table.

[0125] The transparency was judged visually for a plate-shaped sample with a thickness of approximately 5 mm, based on two levels: transparent and colored. Specifically, when the text was clearly visible when viewed through the sample, it was judged as transparent; when the text was unclear, it was judged as colored.

[0126] The transmittance was measured using a spectrophotometer (V-670 manufactured by JASCO Corporation) with a plate-shaped sample processed into 30×30×1 mm and its surface processed into a mirror surface as the measurement sample. The measurement wavelength range was 380 - 760 nm, the band width was 5 nm, the response was Medium, the scanning speed was 200 nm, and the data import interval was 1 nm. The table shows the lowest transmittance value in the wavelength range of 380 - 760 nm.

[0127] The strain point Ps was obtained by the fiber elongation method based on ASTM C336. The annealing point Ta and the softening point Ts were obtained by the fiber elongation method based on ASTM C388.

[0128] The working point (the temperature at which the viscosity of the glass is 10 4.0 dPa·s) and the temperature at which the viscosity of the glass is 10 2.5 dPa·s were obtained by the platinum ball pulling method.

[0129] The acid resistance test was carried out in accordance with the acid resistance test following YBB00342004, and the alkali resistance test was carried out in accordance with the test following ISO695.

[0130] The hydrolysis resistance test was carried out in accordance with the hydrolysis resistance test following ISO720 (acetone cleaning) and the alkali resistance test following ISO695. Also, the detailed test procedure was as described above.

[0131] The liquidus temperature was determined by filling a platinum dish of approximately 120×20×10 mm with crushed glass, putting it into an electric furnace with a linear temperature gradient for 24 hours, observing the precipitation position of specific crystals through a microscope, and specifying the temperature corresponding to the precipitation position of the specific crystals according to the temperature gradient diagram of the electric furnace.

[0132] The liquid-phase viscosity logη at TL is obtained by calculating the viscosity curve of the glass based on the strain point Ps, annealing point Ta, softening point Ts, working point, and the viscosity calculation formula of Fulcher, and then calculating the viscosity of the glass at the liquid-phase temperature according to this viscosity curve.

[0133] The linear thermal expansion coefficient is measured using a dilatometer in the temperature range of 20 to 300 °C with a glass rod formed into a shape of approximately 5 mm φ × 20 mm as the measurement sample.

[0134] The Young's modulus is a value measured by the well-known resonance method. Also, before and after the ion exchange treatment, although the Young's modulus of the glass surface layer is microscopically different, when considering the glass as a whole, since it is measured as an average value by the resonance method, there is no substantial difference in essence.

[0135] In addition, optical grinding is performed on the two surfaces of the obtained plate-shaped sample. After the plate thickness reaches 0.7 mm, it is immersed in molten KNO3 salt at 430 °C for 4 hours to perform ion exchange treatment. After the ion exchange treatment, the surfaces of each sample are cleaned. Then, using a surface stress meter (FSM-6000 manufactured by Oriehara Seisakusho), the surface compressive stress value CS and the stress depth DOL are calculated based on the number and interval of the observed interference fringes. When calculating, the refractive index of each sample is set to 1.50, and the photoelastic constant is 29.5 [(nm / cm) / MPa]. Also, before and after the ion exchange treatment, although the glass composition of the glass surface layer is microscopically different, when considering the glass as a whole, the glass composition is not substantially different.

[0136] The pen-down impact strength is measured according to the following steps. After obtaining a plate-shaped sample with a thickness of 0.5 mm by grinding, it is etched with hydrofluoric acid to make the plate thickness reach 53 μm, obtaining a glass plate for strengthening. The concentration of hydrofluoric acid is not particularly limited, but in this experiment, a hydrofluoric acid solution with a concentration of 0.25 mol / L is used. Next, the obtained glass plate for strengthening is cut into a size of approximately 50×50 mm and immersed in a KNO3 molten salt at 380 °C for ion exchange treatment. The immersion time is appropriately adjusted so that the depth of the compressive stress reaches about 10 μm, obtaining a strengthened glass plate. Next, the strengthened glass plate is etched with a hydrofluoric acid solution having the same concentration as that for etching to obtain a strengthened glass plate with a thickness of 50 μm. A polyethylene sheet (245 μm thick) having an adhesive layer (5 μm thick) is pasted on the bottom surface of the obtained strengthened glass plate (50 μm thick) as a laminate. Next, this laminate is placed on a platform (granite) with the polyethylene sheet side facing down, and a ballpoint pen is vertically dropped onto the glass sample surface of the laminate for testing. Also, as the ballpoint pen, a ballpoint pen (manufactured by BIC Corporation, Orange EG0.7) with a ball diameter of 0.7 mm and a mass of 1.1 g is used. The height of the pen tip before dropping is used as the dropping height, and its initial value is set to 5 mm and dropped. When the glass does not break due to the pen-down, the height is increased by 5 mm and dropped again. Such attempts of raising and dropping the height are repeated until the glass breaks, and the dropping height at which the glass sample breaks is obtained as the pen-down impact breaking height. This measurement is performed 5 times, and the average value of the 5 test results is used as the pen-down impact strength of the sample. Also, each time, the place where the pen drops is changed so that the pen does not drop on the place where it has dropped before.

[0137] As can be seen from the table, for Samples No. 1 to 48, since the glass composition is restricted within a specified range, it can be considered that they have high levels of chemical resistance, ion exchange performance, and formability.

Claims

1. A glass, characterized in that, As a glass composition, in terms of mol%, it contains 60% - 85% of SiO2, 1% - 20% of Al2O3, 0% - 5% of B2O3, 0% - 5% of MgO + CaO + SrO + BaO, and 1% - 20% of Li2O + Na2O + K2O.

2. The glass according to claim 1, wherein The content of Al2O3 is 1 mol% - 10 mol%.

3. The glass according to claim 1 or 2, characterized in that, The content of MgO is 0 mol% - 1 mol%, and the content of CaO is 0 mol% - 0.5 mol%.

4. The glass according to claim 1 or 2, characterized in that, The content of Li2O is 3 mol% - 8 mol%, the content of Na2O is 3 mol% - 8 mol%, and the content of K2O is 0 mol% - 1 mol%.

5. The glass according to claim 1 or 2, characterized in that, The content of SnO2 is 0.03 mol% - 3 mol%.

6. The glass according to claim 1 or 2, characterized in that, The molar ratio (Li2O + Na2O + K2O) / (1 - K2O) is 5 - 30.

7. The glass according to claim 1 or 2, characterized in that, The molar ratio (K2O + CaO) / (Li2O + Na2O + K2O) is 0 - 0.

3.

8. The glass according to claim 1 or 2, characterized in that, The molar ratio (Li2O + Na2O + K2O) / Al2O3 is 2 or more.

9. The glass according to claim 1 or 2, characterized in that, The molar ratio MoO3 / (Fe2O3 + TiO2) is 0.5 or less, and the visible light transmittance at a thickness of 1 mm is 80% or more.

10. The glass according to claim 1 or 2, characterized in that, The molar ratio (10×SnO2) / (10×Fe2O3 + TiO2 + 10×SnO2 + 100×MoO3) is 0.5 - 1, and the visible light transmittance at a thickness of 1 mm is 85% or more.

11. The glass according to claim 1 or 2, characterized in that, The molar ratio (((Li2O + Na2O + K2O) / (1 - K2O)) + ((MgO + CaO + SrO + BaO) / (1 - CaO)) - Al2O3) / (SiO2 + Al2O3 + B2O3) is 0.05 - 0.

15.

12. The glass according to claim 1 or 2, characterized in that, For ion exchange treatment.

13. A glass plate for strengthening, characterized in that, As a glass composition, in terms of mol%, it contains 66% - 85% of SiO2, 1% - 10% of Al2O3, 0% - 5% of B2O3, 3% - 8% of Li2O, 3% - 8% of Na2O, 0% - 1% of K2O, 0% - 0.5% of CaO, 0.03% - 3% of SnO2, the molar ratio (Li2O + Na2O + K2O) / (1 - K2O) is 5 - 30, the molar ratio (K2O + CaO) / (Li2O + Na2O + K2O) is 0 - 0.3, the molar ratio (10×SnO2) / (10×Fe2O3 + TiO2 + 10×SnO2 + 100×MoO3) is 0.5 - 1, and the molar ratio (((Li2O + Na2O + K2O) / (1 - K2O)) + ((MgO + CaO + SrO + BaO) / (1 - CaO)) - Al2O3) / (SiO2 + Al2O3 + B2O3) is 0.05 - 0.

15.

14. The strengthened glass plate according to claim 12, wherein The plate thickness is 0.2 mm or less.

15. A tempered glass plate is a tempered glass plate having a compressive stress layer on its surface, characterized in that, As a glass composition, in mol%, it contains 66% - 85% of SiO2, 1% - 10% of Al2O3, 0% - 5% of B2O3, 3% - 8% of Li2O, 3% - 8% of Na2O, 0% - 1% of K2O, 0% - 0.5% of CaO, 0.03% - 3% of SnO2, the molar ratio (Li2O + Na2O + K2O) / (1 - K2O) is 5 - 30, the molar ratio (K2O + CaO) / (Li2O + Na2O + K2O) is 0 - 0.3, the molar ratio (10×SnO2) / (10×Fe2O3 + TiO2 + 10×SnO2 + 100×MoO3) is 0.5 - 1, and the molar ratio (((Li2O + Na2O + K2O) / (1 - K2O)) + ((MgO + CaO + SrO + BaO) / (1 - CaO)) - Al2O3) / (SiO2 + Al2O3 + B2O3) is 0.05 - 0.15.

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