Tempered glass plates and tempered glass plates

Abstract

The tempered glass plate of the present invention is a tempered glass plate having a compressive stress layer on its surface, and is characterized by having, as a glass composition, SiO2 50-75%, Al2O3 1-20%, B2O3 5-30%, Li2O 0-15%, Na2O 1-25%, K2O 0-10%, and P2O50-15% in mol%, a molar ratio [Al2O3] / [Na2O] of 0.1-2.5, and satisfying the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-20%.

Description

Technology Field

[0001] The present invention relates to a tempered glass plate and a tempered glass plate, and in particular to a tempered glass plate and a tempered glass plate suitable for cover glass such as a foldable display. Background Technology

[0002] Recently, foldable displays have been appearing on the market, and the use of cover glass to protect the display is being considered.

[0003] For cover glass, ion-exchanged tempered glass is generally used (see Patent Documents 1 and 2, and Non-Patent Document 1). Prior art literature

[0004] Japanese Patent Publication No. 2006-83045, International Publication No. 2015 / 031188

[0005] Tetsuro Izumitani et al., *New Glass and Its Physical Properties*, First Edition, Management System Laboratory, Co., Ltd., August 20, 1984, pp. 451-498 The problem to be solved

[0006] The cover glass of a foldable display requires a low Young's modulus and a high compressive stress value on its outermost surface. A low Young's modulus reduces the tensile stress generated at the bending point of the cover glass when the flexible display is bent. Furthermore, a high compressive stress value on the outermost surface makes it easier to prevent breakage caused by tensile stress at the bending point of the cover glass when the flexible display is bent. Consequently, achieving both a low Young's modulus and a high compressive stress value on the outermost surface makes it difficult for the cover glass to break when the flexible display is bent.

[0007] In addition, the manufacturing process of flexible displays includes an acid treatment process for the cover glass; however, if the acid resistance of the cover glass is low, the cover glass becomes cloudy, resulting in reduced visibility.

[0008] The present invention has been made in consideration of the above circumstances, and its technical objective is to devise a reinforced glass plate and a glass plate for reinforcement that possess good acid resistance and can simultaneously achieve a low Young's modulus and a high compressive stress value on the outermost surface. means of solving the problem

[0009] As a result of conducting various investigations, the inventors have discovered that the above technical problem can be solved by strictly regulating the glass composition, and propose this as the present invention. That is, the tempered glass plate of the present invention is a tempered glass plate having a compressive stress layer on its surface, and is characterized by containing, in mol% as the glass composition, SiO2 50-75%, Al2O3 1-20%, B2O3 5-30%, Li2O 0-15%, Na2O 1-25%, K2O 0-10%, and P2O 50-15%, with a molar ratio [Al2O3] / [Na2O] of 0.1-2.5 and satisfying the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-20%. Here, [SiO2] represents the SiO2 content (mol%), [Al2O3] represents the Al2O3 content (mol%), [B2O3] represents the B2O3 content (mol%), [Li2O] represents the Li2O content (mol%), [Na2O] represents the Na2O content (mol%), [K2O] represents the K2O content (mol%), and [P2O5] represents the P2O5 content (mol%), respectively.

[0010] In addition, in the reinforced glass plate of the present invention, as a glass composition, it is preferable to contain SiO2 50-75%, Al2O3 11.7-13.5%, B2O3 5-30%, Li2O 0-15%, Na2O 13-16%, K2O 0-10%, and P2O 50-15% in mol%, and the molar ratio [Al2O3] / [Na2O] is 0.8-1.2, and the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-2.5% is satisfied.

[0011] In addition, in the reinforced glass plate of the present invention, as a glass composition, it is preferable to contain SiO2 62-67%, Al2O3 11.7-13.5%, B2O3 8-10%, Li2O 0-15%, Na2O 13-16%, K2O 0-10%, and P2O5 0-15% in mol%, and the molar ratio [Al2O3] / [Na2O] is 0.8-1.2, and the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-2.5% is satisfied.

[0012] In addition, in the reinforced glass plate of the present invention, it is preferable that the content of P2O5 is 0.1 to 15 mol%.

[0013] In addition, in the reinforced glass plate of the present invention, it is preferable that the content of Li2O is 0.1 to 15 mol%.

[0014] In addition, in the tempered glass plate of the present invention, it is preferable that the softening point be 950°C or lower. Here, "softening point" refers to a value measured according to the method of ASTM C338.

[0015] In addition, in the reinforced glass plate of the present invention, high temperature viscosity 10 2.5 It is preferable that the temperature in dPa·s is less than 1650℃. Here, "high temperature viscosity 10 2.5 "Temperature in dPa·s" refers to the value measured by the platinum-ball lift method.

[0016] In addition, in the reinforced glass plate of the present invention, it is preferable that the plate thickness be 100 μm or less.

[0017] In addition, in the tempered glass plate of the present invention, it is preferable that the dimensions be □100 mm or more.

[0018] In addition, in the reinforced glass plate of the present invention, it is preferable that the compressive stress value of the outermost surface of the compressive stress layer is 200 to 1100 MPa.

[0019] In addition, in the reinforced glass plate of the present invention, it is preferable that the stress depth of the compressive stress layer is 10 to 15% of the plate thickness.

[0020] In addition, in the reinforced glass plate of the present invention, it is preferable to have an overflow joining surface in the center of the plate thickness direction, that is, to be formed by the overflow downdraw method.

[0021] In addition, the reinforced glass plate of the present invention is preferably used as a cover glass for a flexible display.

[0022] The reinforcing glass plate of the present invention is characterized by having, as a glass composition, SiO2 50-75%, Al2O3 1-20%, B2O3 5-30%, Li2O 0-15%, Na2O 1-25%, K2O 0-10%, and P2O50-15% in mol%, a molar ratio [Al2O3] / [Na2O] of 0.1-2.5, and satisfying the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-20%.

[0023] The reinforcing glass plate of the present invention is characterized by having, as a glass composition, SiO2 50-75%, Al2O3 1-20%, B2O3 5-30%, Na2O 1-25%, K2O 0-10%, and P2O50-15% in mol%, a molar ratio [Al2O3] / [Na2O] of 0.1-2.5, satisfying the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-20%, and having a plate thickness of less than 100㎛. Specific details for implementing the invention

[0024] The tempered glass plate (tempered glass plate) of the present invention is characterized by containing, in mol%, SiO2 50-75%, Al2O3 1-20%, B2O3 5-30%, Li2O 0-15%, Na2O 1-25%, K2O 0-10%, and P2O50-15% as the glass composition, having a molar ratio [Al2O3] / [Na2O] of 0.1-2.5 and satisfying the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-20%. The reason for limiting the content range of each component in the tempered glass plate (tempered glass plate) of the present invention is shown below. In addition, in the description of the content range of each component, % indicates mol% unless specifically mentioned otherwise.

[0025] SiO2 is a component that forms the network of glass. If the SiO2 content is too low, it becomes difficult to vitrify, and acid resistance is also prone to deterioration. Therefore, the suitable lower limit range for SiO2 is 50% or more, 52% or more, 54% or more, 55% or more, 57% or more, 59% or more, 60% or more, 61% or more, 62% or more, 63% or more, and particularly 64% or more. On the other hand, if the SiO2 content is too high, meltability or formability is prone to deterioration, and the coefficient of thermal expansion becomes too low, making it difficult to match the coefficient of thermal expansion of surrounding materials. Therefore, the suitable upper limit range for SiO2 is 75% or less, 73% or less, 71% or less, 70% or less, 69% or less, 68% or less, 67% or less, 66% or less, and particularly 65% ​​or less.

[0026] Al2O3 is a component that increases the ion exchange rate. The Al2O3 content is 10–30%. If the Al2O3 content is too low, the ion exchange rate is prone to decreasing. Therefore, the suitable lower limit range for Al2O3 is 1% 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, 11% or more, and particularly 11.7% or more. On the other hand, if the Al2O3 content is too high, devitrified crystals are prone to precipitating in the glass, making it difficult to form a plate shape using methods such as the overflow downdraw method. In particular, when using alumina refractory as the refractory material for the molded body and forming a plate shape using the overflow downdraw method, devitrified spinel crystals are prone to precipitating at the interface with the alumina refractory. Furthermore, acid resistance decreases, making it difficult to apply to acid treatment processes. Additionally, the Young's modulus becomes too high. Therefore, the suitable upper limit range for Al2O3 is 20% or less, 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 13.5% or less, 13% or less, and especially 12% or less.

[0027] B2O3 is a component that lowers Young's modulus, high-temperature viscosity, and density, while increasing permeability. However, if the content of B2O3 is too high, the ion exchange rate (especially the depth of stress) is prone to decrease. Additionally, due to ion exchange, discoloration of the glass surface known as yake may occur, or acid resistance and water resistance may decrease. Therefore, the suitable lower limit range for B2O3 is 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, and especially 10% or more. Furthermore, the suitable upper limit range for B2O3 is 30% or less, 25% or less, 22% or less, 20% or less, 18% or less, 16% or less, 13% or less, 12% or less, 11% or less, 10.5% or less, and especially 10% or less.

[0028] Li2O is an ion exchange component, particularly effective for obtaining deep stress depths, and is also a component that lowers high-temperature viscosity to improve meltability or moldability. On the other hand, Li2O is a component that leaches out during ion exchange treatment and degrades the ion exchange solution. It is also a component that increases Young's modulus. Therefore, suitable content of Li2O is 0 to 15%, 0 to 10%, 0 to 7%, 0 to 5%, less than 0 to 3%, 0 to 2%, and particularly 0 to 1%. In addition, when Li2O is added, the suitable lower limit range of Li2O is 0.01% or more, 0.1% or more, 0.5% or more, and particularly 1% or more.

[0029] Na2O is an ion exchange component and also a component that lowers high-temperature viscosity to improve meltability and moldability. Additionally, Na2O is a component that improves devitrification resistance and devitrification resistance in reaction with molded refractories, particularly alumina refractories. If the Na2O content is too low, meltability may decrease, the coefficient of thermal expansion may decrease too low, or the ion exchange rate may decrease. Therefore, the appropriate lower limit range for Na2O is 1% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, and especially 13% or more. On the other hand, if the Na2O content is too high, Young's modulus may increase, acid resistance may decrease, or the component balance of the glass composition may be insufficient, which may actually lead to a decrease in devitrification resistance. Therefore, the suitable upper limit range for Na2O is 25% or less, 22% or less, 20% or less, 19.5% or less, 19% or less, 18% or less, 17% or less, 16.5% or less, 16% or less, 15.5% or less, and especially 15% or less.

[0030] K2O is a component that lowers high-temperature viscosity to improve meltability and moldability. It is also a component that improves permeability. However, if the content of K2O is too high, acid resistance may decrease, or the component balance of the glass composition may be insufficient, which may actually lead to a decrease in permeability. Therefore, the appropriate upper limit range is 10% or less, 8% or less, 6% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0.1% or less, and especially less than 0.1%.

[0031] P2O5 is a component that increases the ion exchange rate after maintaining the compressive stress value. It is also a component that lowers Young's modulus. It is a component that further lowers high-temperature viscosity to improve meltability and moldability. However, if the content of P2O5 is too high, cloudiness due to powdering may occur in the glass, or acid resistance may decrease. Therefore, the suitable upper limit range for P2O5 is 15% or less, 12% or less, 10% or less, 8% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly 0.1% or less. In addition, when P2O5 is added, the suitable lower limit range for P2O5 is 0.1% or more, 0.5% or more, 1% or more, 2% or more, and particularly 3% or more.

[0032] The molar ratio [Al2O3] / [Na2O] is 0.1 to 2.5, and [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5] is preferably -20% or more, -15% or more, -10% or more, -5% or more, -2.5% or more, -1% or more, and particularly 0 to 35%. When the molar ratio [Al2O3] / [Na2O] is 0.1 to 2.5 and [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5] is too large, acid resistance decreases, making it difficult to apply to acid treatment processes.

[0033] The molar ratio [Al2O3] / [Na2O] is preferably 0.1 to 2.5, 0.2 to 2.2, 0.3 to 1.8, 0.4 to 1.5, 0.5 to 1.2, 0.6 to 1.1, 0.7 to 1.0, and particularly 0.8 to 0.9. If the molar ratio [Al2O3] / [Na2O] is too large, the Young's modulus becomes too high. In addition, the internal permeability is prone to decreasing. On the other hand, if the molar ratio [Al2O3] / [Na2O] is too small, the Young's modulus becomes too high. In addition, the compressive stress value of the outermost surface is prone to decreasing.

[0034] In addition to the above ingredients, the following ingredients may be added, for example.

[0035] MgO is a component that lowers high-temperature viscosity, thereby increasing meltability and moldability. It is also a component that increases acid resistance. However, if the MgO content is too high, there is a tendency for the Young's modulus to increase, the ion exchange rate to decrease, or the glass to devitrify. In particular, when using alumina refractory as the refractory material for the molded body and forming a plate shape using the overflow downdraw method, devitrified spinel crystals are prone to precipitating at the interface with the alumina refractory. Therefore, the suitable upper limit range for MgO is 6% or less, 4.5% or less, 3% or less, 2% or less, 1% or less, and especially 0.1% or less.

[0036] Compared to other components, CaO is a component that has a significant effect of lowering high-temperature viscosity, thereby increasing meltability or moldability, or raising the deformation point, without causing a decrease in internal permeability. However, if the CaO content is too high, the Young's modulus increases, the ion exchange rate decreases, or the ion exchange solution becomes prone to deterioration. Therefore, the appropriate CaO content is 0 to 6%, 0 to 5%, 0 to 4%, 0 to 3.5%, 0 to 3%, 0 to 2%, 0 to 1%, and especially 0 to 0.5%.

[0037] SrO and BaO are components that lower high-temperature viscosity to increase meltability or moldability or increase the deformation point, but if their content is too high, the Young's modulus increases, the ion exchange rate decreases, the density or coefficient of thermal expansion increases, or the glass becomes prone to devitrification. Therefore, suitable content of SrO and BaO is 0 to 2%, 0 to 1.5%, 0 to 1%, 0 to 0.5%, 0 to 0.1%, and especially less than 0 to 0.1%.

[0038] The total amount of CaO, SrO, and BaO is preferably 0 to 5%, 0 to 2.5%, 0 to 2%, 0 to 1.5%, 0 to 1%, 0 to 0.5%, 0 to 0.1%, and particularly less than 0 to 0.1%. If the total amount of CaO, SrO, and BaO is too high, the Young's modulus tends to increase, and the ion exchange rate tends to decrease.

[0039] ZnO is a component that increases the ion exchange rate and is particularly effective in increasing compressive stress values. It is also a component that reduces high-temperature viscosity without reducing low-temperature viscosity. However, if the ZnO content is too high, the glass tends to become powdery, the internal permeability decreases, the density increases, or the stress depth decreases. Therefore, the appropriate ZnO content is 0 to 6%, 0 to 3%, and especially 0 to 1%.

[0040] TiO2 is a component that increases the ion exchange rate and also lowers high-temperature viscosity, but if its content is too high, the glass becomes prone to discoloration or devitrification. Therefore, the TiO2 content is preferably 0 to 4.5%, less than 0 to 1%, 0 to 0.5%, and particularly 0 to 0.3%.

[0041] ZrO2 is a component that significantly increases the ion exchange rate and also increases the viscosity or deformation point near the liquid phase viscosity; however, if the content is too high, there is a risk that the internal permeability will significantly decrease and the density will become too high. Therefore, the appropriate content of ZrO2 is 0 to 5%, 0 to 4%, 0 to 3%, 0 to 2%, and especially less than 0 to 1%.

[0042] As a clarifying agent, it is desirable to introduce one or more selected from the group of SnO2, SO3, Cl, and CeO2 (preferably the group of SnO2, SO3, and Cl). Suitable content of SnO2+SO3+Cl is 0.01 to 3%, 0.05 to 3%, 0.1 to 3%, and particularly 0.2 to 3%. In addition, "SnO2+SO3+Cl" is the sum of SnO2, SO3, and Cl.

[0043] Fe2O3 is an impurity component from the raw materials, but it is a component that absorbs ultraviolet light that has an adverse effect on the human eye. However, if the content of Fe2O3 is too high, the coloring of the glass becomes strong. Therefore, the appropriate content of Fe2O3 is less than 1000 ppm (0.1%), less than 800 ppm, less than 600 ppm, less than 400 ppm, less than 300 ppm, less than 250 ppm, less than 200 ppm, less than 150 ppm, and especially less than 100 ppm.

[0044] Rare earth oxides such as Nd2O3 and La2O3 are components that increase Young's modulus. However, the cost of the raw materials themselves is high, and if added in large quantities, the internal permeability is prone to decreasing. Therefore, the appropriate content of rare earth oxides is 3% or less, 2% or less, 1% or less, 0.5% or less, and especially 0.1% or less.

[0045] For environmental considerations, it is desirable that the glass composition substantially does not contain As2O3, Sb2O3, PbO, F, or Bi2O3. "Substantially does not contain" means that the specified components are not actively added as glass components, but that the incorporation of impurity levels is permitted, and specifically, it refers to the case where the content of the specified components is less than 0.05%.

[0046] The tempered glass plate (tempered glass plate) of the present invention preferably has the following characteristics, for example.

[0047] The softening point is preferably 950°C or lower, 900°C or lower, 880°C or lower, 860°C or lower, and particularly 700 to 850°C. As the softening point is lower, thermal processability is improved, and the burden on glass manufacturing equipment, such as thermal processing equipment, is reduced. Therefore, as the softening point is lower, it becomes easier to reduce the manufacturing cost of tempered glass.

[0048] High temperature viscosity 10 2.5 The temperature in dPa·s is preferably less than 1650°C, 1630°C or less, 1620°C or less, and particularly 1610°C or less. High temperature viscosity 10 2.5 The lower the temperature in dPa·s, the more low-temperature melting becomes possible, reducing the burden on glass manufacturing equipment such as melting furnaces, and making it easier to improve foam quality. Therefore, high-temperature viscosity 10 2.5 The lower the temperature in dPa·s, the easier it is to lower the manufacturing cost of tempered glass.

[0049] The Young's modulus is preferably 70 GPa or less, 67 GPa or less, 65 GPa or less, 64 GPa or less, and particularly 50 to 63 GPa. If the Young's modulus is too high, the tensile stress generated in the bending portion of the cover glass increases when the flexible display is bent.

[0050] The mass loss per surface area of ​​the glass when immersed for 24 hours in a 5 mass% HCl aqueous solution heated to 80°C is preferably 30 mg / cm² or less, 25 mg / cm² or less, 20 mg / cm² or less, 15 mg / cm² or less, and particularly 10 mg / cm² or less. If the above mass loss is too large, the glass is prone to becoming cloudy during the acid treatment process.

[0051] The liquid viscosity is preferably 4.0 dPa·s or higher, 4.3 dPa·s or higher, 4.5 dPa·s or higher, 4.8 dPa·s or higher, 5.1 dPa·s or higher, 5.3 dPa·s or higher, and particularly 5.5 dPa·s or higher as Logρ. If the liquid viscosity is too low, the internal permeability decreases, making it difficult to produce reinforced glass plates, especially reinforced glass plates with a small thickness, using methods such as the overflow downdraw method.

[0052] The tempered glass plate of the present invention has a compressive stress layer on its surface. The compressive stress value of the outermost surface is preferably 200 MPa or more, 300 MPa or more, 400 MPa or more, 500 MPa or more, and particularly 600 MPa or more. The higher the compressive stress value of the outermost surface, the easier it is to prevent breakage caused by tensile stress occurring in the bending portion of the cover glass when the flexible display is bent. On the other hand, if an extremely large compressive stress is formed on the surface, the tensile stress inherent in the tempered glass plate becomes extremely high, and there is a risk that dimensional changes before and after ion exchange treatment will increase. Therefore, the compressive stress value of the outermost surface is preferably 1300 MPa or less, 1100 MPa or less, 900 MPa or less, and particularly 800 MPa or less.

[0053] The stress depth 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 also 8 to 17%, 10 to 15%, 11 to 14%, and particularly 12 to 13% of the plate thickness. The greater the stress depth, the less likely the tempered glass is to break even if it is scratched deeply, and the less the imbalance in mechanical strength becomes. On the other hand, the greater the stress depth, the more likely it is that dimensional changes will increase before and after ion exchange treatment. Therefore, the stress depth is preferably 20 μm or less, 15 μm or less, and particularly 10 μm or less.

[0054] The internal tensile stress value is preferably 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 becomes prone to self-fracture due to physical impact, etc. On the other hand, if the internal tensile stress value is too low, it becomes difficult to secure 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 can be calculated using the following Formula 1.

[0055] [Math 1]

[0056] Internal tensile stress value = (Latest surface compressive stress value × Stress depth) / (Plate thickness - 2 × Stress depth)

[0057] In the tempered glass plate (tempered glass plate) of the present invention, the plate thickness is preferably 200 μm or less, 150 μm or less, 100 μm or less, 80 μm or less, 60 μm or less, 1 to 50 μm, 5 to 40 μm, and particularly 10 to 30 μm. As the plate thickness decreases, the flexibility of the cover glass is improved, making it easier to apply to a flexible display. In addition, the allowable radius of curvature when bending the cover glass decreases. In addition, it becomes easier to wind into a roll shape.

[0058] The dimensions are preferably 100 mm or more, 120 mm or more, 150 mm or more, and particularly 200 to 2000 mm. As the dimensions increase, it becomes easier to apply to large flexible displays.

[0059] The reinforcing glass plate of the present invention is characterized by having, as a glass composition, SiO2 50-75%, Al2O3 1-20%, B2O3 5-30%, Na2O 1-25%, K2O 0-10%, and P2O50-15% in mol%, a molar ratio [Al2O3] / [Na2O] of 0.1-2.5, and satisfying the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-20%. In addition, the reinforcing glass plate of the present invention is characterized by containing, in mol%, SiO2 50-75%, Al2O3 1-20%, B2O3 5-30%, Na2O 1-25%, K2O 0-10%, and P2O 50-15% as the glass composition, having a molar ratio [Al2O3] / [Na2O] of 0.1-2.5, satisfying the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-20%, and having a plate thickness of less than 100 μm. The technical features of the reinforcing glass plate of the present invention are common to the reinforcing glass plate of the present invention, and details are omitted here.

[0060] The reinforcing glass plate of the present invention can be manufactured as follows. First, glass raw materials combined to form a desired glass composition are fed into a continuous melting furnace, heated and melted at 1500 to 1700°C, and then quenched. Afterward, the molten glass is supplied to a forming device, formed into a plate shape, and then cooled. After forming the plate shape, a well-known method may be used for cutting to a predetermined size, but since the end surface becomes smooth, it is preferable to cut by laser cutting.

[0061] When forming molten glass, it is desirable to cool the temperature range between the slow cooling point and the deformation point of the molten glass at a cooling rate of 3°C / min or more and less than 1000°C / min. The cooling rate is preferably 10°C / min or more, 40°C / min or more, 60°C / min or more, and particularly 100°C / min or more; preferably less than 1000°C / min, less than 800°C / min, and particularly less than 500°C / min. If the cooling rate is too slow, it becomes difficult to reduce the thickness of the plate. On the other hand, if the cooling rate is too fast, the structure of the glass becomes rough, and the hardness of the glass is prone to decreasing.

[0062] As a method for forming molten glass into a plate shape, it is preferable to adopt the overflow downdraw method. The overflow downdraw method allows for the mass production of high-quality glass plates, as well as the easy production of thin glass plates. Furthermore, in the overflow downdraw method, alumina or zirconium oxide is used as the refractory material for the molded body; however, since the reinforcing glass plate of the present invention has good compatibility with alumina or zirconium oxide, particularly alumina, it is difficult to generate bubbles or particles by reacting with these molded bodies.

[0063] In addition to the overflow downdraw method, various forming methods can be employed. For example, forming methods such as the float method, downdraw method (slot downdraw method, lead draw method, etc.), roll-out method, and press method can be employed.

[0064] The reinforced glass plate of the present invention is manufactured by performing an ion exchange treatment on a reinforced glass plate. The conditions for the ion exchange treatment are not particularly limited, and optimal conditions may be selected by considering the viscosity characteristics of the glass, application, thickness, internal tensile stress, dimensional changes, etc. In particular, if K ions in the dissolved KNO3 salt are ion exchanged with the Na component in the glass, a compressive stress layer on the surface can be formed efficiently.

[0065] The number of ion exchange treatments is not specifically limited and may be performed once or multiple times. If the number of ion exchange treatments is reduced to one, the cost of the cover glass can be lowered. If the ion exchange treatment is performed multiple times, it is preferable to perform it twice. By doing so, the total amount of tensile stress accumulated inside the glass can be reduced while increasing the stress depth.

[0066] Example 1

[0067] The present invention will be explained below based on examples. Furthermore, the following examples are merely illustrative. The present invention is not limited in the least to the following examples.

[0068] Tables 1 to 8 show the embodiments of the present invention (samples NO. 1 to 76) and comparative examples (samples NO. 77, 78). In addition, the acid resistance index in the table is [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]. Also, NA indicates unmeasured.

[0069] Each sample in the table was prepared as follows. First, glass raw materials were combined to achieve the glass compositions in the table, and the mixture was melted at 1580°C for 8 hours using a platinum pot. Afterward, the resulting molten glass was poured onto a carbon plate, formed into a flat plate shape, and slow-cooled. Various properties were evaluated for the obtained tempered glass plates. The results are shown in Tables 1 to 8.

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078] Young's modulus refers to the value measured by the well-known resonance method.

[0079] The deformation point (Ps) and the slow cooling point (Ta) refer to values ​​measured by the well-known fiber aronation method. The softening point (Ts) refers to values ​​measured by the ASTM C338 method.

[0080] High temperature viscosity 10 2.5 The temperature in dPa·s refers to the value measured by the platinum-ball lift method.

[0081] Liquid viscosity (logη at TL) is a value obtained by measuring the viscosity of glass at the liquid temperature using the platinum ball pull method. The liquid temperature is the temperature at which crystals precipitate after glass powder that passes through a standard 30 mesh (500 μm) sieve and remains on a 50 mesh (300 μm) sieve is placed in a platinum boat and maintained in a temperature gradient for 24 hours.

[0082] The acid resistance test was evaluated by using a double-sided mirror-finished sample with dimensions of 50 mm × 10 mm × 1.0 mm as the measurement sample, thoroughly washing it with a neutral detergent and pure water, and then immersing it in a 5 mass% HCl aqueous solution heated to 80°C for 24 hours, and calculating the mass loss per unit surface area (mg / cm²) before and after immersion.

[0083] Next, optical polishing was performed on both surfaces of each sample to achieve a plate thickness of 1.5 mm, and then ion exchange treatment was performed by immersing the samples in a dissolved KNO3 salt solution at 430°C for 4 hours. After the ion exchange treatment, the surface of each sample was cleaned. Subsequently, the compressive stress value and stress depth of the outermost surface were calculated from the number and spacing of the observed interference fringes using a surface stress meter (FSM-6000 manufactured by Orihara Manufacturing Co., Ltd.). For the calculation, the refractive index of each sample was set to 1.51 and the optical elastic constant to 37.2 [(nm / cm) / MPa]. Furthermore, although the glass composition in the surface layer of the glass differs microscopically before and after the ion exchange treatment, the glass composition does not differ substantially when viewed as a whole glass.

[0084] As is evident from the table, samples NO. 1–76 had low Young's modulus and high acid resistance. On the other hand, sample NO. 77 had a high Al2O3 content, a large molar ratio of Al2O3 / Na2O, and a low acid resistance index; consequently, it had a high Young's modulus, low acid resistance, and low liquid-phase viscosity. Sample NO. 78 had a low molar ratio of Al2O3 / Na2O, so it had a high Young's modulus and low compressive stress values.

[0085] Example 2

[0086] A glass batch having the glass composition of Sample NO. 41 listed in the table was melted in a test melting furnace to obtain molten glass, and then a reinforced glass plate with a thickness of 50 μm was formed using the overflow downdraw method. Additionally, during the forming of the reinforced glass plate, the plate thickness of the reinforced glass plate was adjusted by appropriately adjusting the speed of the tension roller, the speed of the cooling roller, the temperature distribution of the heating device, the temperature of the molten glass, the flow rate of the molten glass, the plate pulling speed, and the rotation speed of the stirring stirrer. Next, after cutting the obtained reinforced glass plate into a predetermined size, an ion exchange treatment was performed by immersing it in a dissolved KNO3 salt at 430°C for 4 hours or in a dissolved KNO3 salt at 390°C for 2.5 hours to obtain the reinforced glass plate.

[0087] Example 3

[0088] A glass batch having the glass composition of Sample NO. 41 listed in the table was melted in a test melting furnace to obtain molten glass, and then a reinforced glass plate with a thickness of 100 μm was formed using the overflow downdraw method. In addition, during the forming of the reinforced glass plate, the plate thickness of the reinforced glass plate was adjusted by appropriately adjusting the speed of the tension roller, the speed of the cooling roller, the temperature distribution of the heating device, the temperature of the molten glass, the flow rate of the molten glass, the plate pulling speed, and the rotation speed of the stirring stirrer. Next, after cutting the obtained reinforced glass plate into a predetermined size, an ion exchange treatment was performed by immersing it in a dissolved KNO3 salt at 430°C for 4 hours or in a dissolved KNO3 salt at 390°C for 2.5 hours to obtain the reinforced glass plate.

[0089] Example 4

[0090] A glass batch having the glass composition of Sample NO. 41 listed in the table was melted in a test melting furnace to obtain molten glass, and then a reinforced glass plate with a thickness of 30 μm was formed using the overflow downdraw method. Additionally, during the forming of the reinforced glass plate, the plate thickness of the reinforced glass plate was adjusted by appropriately adjusting the speed of the tension roller, the speed of the cooling roller, the temperature distribution of the heating device, the temperature of the molten glass, the flow rate of the molten glass, the plate pulling speed, and the rotation speed of the stirring stirrer. Next, after cutting the obtained reinforced glass plate into a predetermined size, an ion exchange treatment was performed by immersing it in a dissolved KNO3 salt at 430°C for 4 hours or in a dissolved KNO3 salt at 390°C for 2.5 hours to obtain the reinforced glass plate.

[0091] Example 5

[0092] Glass raw materials were combined to obtain the glass composition of Sample NO. 41 listed in the table, and melted at 1580°C for 8 hours using a platinum pot. Afterward, the obtained molten glass was poured onto a carbon plate, formed into a flat plate shape, and slow-cooled. From the obtained flat glass, a plate-shaped glass with a thickness of 0.5 mm was obtained through grinding and polishing, and then a reinforced glass plate with a thickness of 75 μm was obtained through slimming via an etching process using hydrofluoric acid. Next, the obtained reinforced glass plate was cut to a predetermined size and subjected to ion exchange treatment by immersing it in a dissolved KNO3 salt at 390°C for 2.5 hours to obtain a reinforced glass plate. The compressive stress value was 763 MPa, and the compressive stress layer depth was 15.6 μm. When a strength test was performed using a two-point bending test, fracture occurred at a bending radius (R) of 2.3 mm. In the two-point bending test, a sample of size 20×130 mm was used as the measurement sample, and bending deformation was applied in the long axis direction to reduce the bending radius (R) until failure. Measurement results for 15 samples were recorded, and their average value was used as the evaluation result.

[0093] Example 6

[0094] Glass raw materials were combined to achieve the glass composition of Sample NO. 76 listed in the table, and melted at 1580°C for 8 hours using a platinum pot. Afterward, the obtained molten glass was poured onto a carbon plate, formed into a flat plate shape, and slow-cooled. From the obtained flat glass, a plate-shaped glass with a thickness of 0.5 mm was obtained through grinding and polishing, and then a reinforced glass plate with a thickness of 55 μm was obtained through slimming via an etching process using hydrofluoric acid. Next, the obtained reinforced glass plate was cut to a predetermined size and subjected to ion exchange treatment by immersing it in a dissolved KNO3 salt at 390°C for 15 minutes to obtain a reinforced glass plate. The compressive stress value was 832 MPa, and the compressive stress layer depth was 10.3 μm. When a strength test was performed using a two-point bending test, fracture occurred at a bending radius (R) of 1.8 mm. In the two-point bending test, a sample of size 20×130 mm was used as the measurement sample, and bending deformation was applied in the direction of the major axis to reduce the bending radius (R) until failure. Measurement results for 15 samples were recorded, and their average value was used as the evaluation result. Industrial applicability

[0095] The tempered glass plate and tempered glass plate of the present invention are preferred for cover glass of foldable displays, etc., but are also preferred as cover glass of mobile phones, digital cameras, PDAs, etc., or as glass substrates of touch panel displays, etc.

Claims

Claim 1 A reinforced glass plate having a compressive stress layer on its surface, characterized in that, as a glass composition, it contains SiO2 50-75%, Al2O3 1-20%, B2O3 5-30%, Li2O 0-15%, Na2O 1-25%, K2O 0-10%, and P2O 50-15% in mol%, the molar ratio [Al2O3] / [Na2O] is 0.1-2.5, and the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-20% is satisfied, the plate thickness is 80㎛ or less, the stress depth of the compressive stress layer is 15㎛ or less, and the internal tensile stress value is 60MPa or more. Claim 2 A reinforced glass plate according to claim 1, having a compressive stress layer on its surface, characterized in that, as a glass composition, it contains SiO2 50-67%, Al2O3 11.7-13.5%, B2O3 5-25%, Li2O 0-15%, Na2O 13-16%, K2O 0-10%, and P2O 50-15% in mol%, the molar ratio [Al2O3] / [Na2O] is 0.8-1.2, and the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-2.5%. Claim 3 A reinforced glass plate according to claim 1 or 2, wherein the reinforced glass plate having a compressive stress layer on its surface, the glass composition comprises, in mol%, SiO2 62-67%, Al2O3 11.7-13.5%, B2O3 8-10%, Li2O 0-5%, Na2O 13-16%, K2O 0-4%, and P2O5 0-5%, the molar ratio [Al2O3] / [Na2O] is 0.8-1.2, and the relationship [SiO2]-3×[Al2O3]-[B2O3]-2×[Li2O]-1.5×[Na2O]-[K2O]+1.2×[P2O5]≥-2.5%. Claim 4 A reinforced glass plate according to claim 1 or 2, characterized in that the P2O5 content is 0.1 to 15 mol%. Claim 5 A reinforced glass plate according to claim 1 or 2, characterized in that the Li2O content is 0.1 to 15 mol%. Claim 6 A reinforced glass plate according to claim 1 or 2, characterized in that its softening point is 950℃ or lower. Claim 7 In claim 1 or 2, high temperature viscosity 10 2.5 A reinforced glass plate characterized by a temperature of less than 1650℃ in dPa·s. Claim 8 A reinforced glass plate according to claim 1 or 2, characterized in that the plate thickness is 60㎛ or less. Claim 9 A tempered glass plate according to claim 1 or 2, characterized in that the dimensions are □100 mm or more. Claim 10 A reinforced glass plate according to claim 1 or 2, characterized in that the compressive stress value of the outermost surface of the compressive stress layer is 200 to 1100 MPa. Claim 11 A reinforced glass plate according to claim 1 or 2, characterized in that the stress depth of the compressive stress layer is 10 to 15% of the plate thickness. Claim 12 A reinforced glass plate according to claim 1 or 2, characterized by having an overflow joining surface in the center of the plate thickness direction. Claim 13 A tempered glass plate characterized by being used for the cover glass of a flexible display in claim 1 or 2. Claim 14 delete Claim 15 delete

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