Glass for reinforcement, reinforced glass and method for producing same, and flexible cover member and electronic device using same

Abstract

Reinforced glass according to the present invention is sheet-shaped and has a compressive stress layer on a surface thereof. The reinforced glass has a glass composition in the central portion of the sheet thickness containing, in mol%, 55-80% SiO2, 4-20% Al2O3, 0-0.1% Li2O, 3-12% Na2O, 3-20% K2O, 0-10% MgO, and 0-10% CaO, wherein Na2O + K2O is 10-25%, MgO + CaO + SrO + BaO is 0-15%, and the molar ratio K2O / (Na2O + K2O) is 0.20 or more.

Description

Glass for tempering, tempered glass and its manufacturing method, flexible cover member and electronic device using the same

[0001] The present invention relates to tempered glass, tempered glass and a manufacturing method thereof, a flexible cover member, and an electronic device using the same, and particularly to tempered glass, glass to be tempered, and a flexible cover member suitable for foldable displays, foldable touch panels, and the like.

[0002] In recent years, products such as foldable displays and rollable displays have appeared on the market. These products use flexible cover members made by laminating a resin sheet and a sheet of tempered glass.

[0003] Furthermore, chemically strengthened glass that has been subjected to an ion exchange treatment is used as the strengthened glass (for example, Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2006-83045

[0005] Flexible cover members used in products such as foldable displays and rollable displays are repeatedly transformed from a folded state to an unfolded state for use. If the flexible cover member is held in the folded state for a long period of time, bending marks (deformation marks) may remain on the structural members, such as tempered glass, at the bent portion even after the flexible cover member is released and unfolded. As a result, various problems may occur at the bent portion of the flexible cover member, such as peeling between the tempered glass and other members, breakage, and deterioration of optical properties (reduced visibility of the display).

[0006] The present invention has been made in view of the above circumstances, and its technical object is to provide a tempered glass that is less likely to leave bending marks even when used as a flexible cover member.

[0007] The first aspect of the present invention is a tempered glass sheet having a compressive stress layer on the surface thereof, and the tempered glass sheet has a glass composition at the center of the sheet thickness, which is, in mol%, SiO ２ 55-80%, Al ２ O ３ 4-20%, Li ２O 0-0.1%, Na ２ O 3-12%, K ２ Contains 3-20% O, 0-10% MgO, 0-10% CaO, and Na ２ O+K ２ O is 10 to 25%, MgO + CaO + SrO + BaO is 0 to 15%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.20 or more.

[0008] Second aspect of the present invention: The tempered glass of the above aspect has a thickness of 0.20 mm or less and a bending strain measured according to JIS: K7116 of 2.0 × 10 －４ It is preferable that:

[0009] Third aspect of the present invention: The tempered glass of any of the above aspects has a glass composition at the center of the sheet thickness, which contains, in mol%, SiO ２ 55-80%, Al ２ O ３ 4-20%, Li ２ O 0-0.1%, Na ２ O 3-12%, K ２ O 3-20%, MgO 0-10%, CaO 0-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O is 10 to 21%, MgO + CaO + SrO + BaO is 1 to 15%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.20 or more, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ It is preferable that O is −20 to 30%.

[0010] Fourth aspect of the present invention: The tempered glass of any of the above aspects has a glass composition at the center of the sheet thickness, which contains, in mol%, SiO ２ 55-80%, Al ２ O ３ 4-20%, B２ O ３ 0-0.4% Li ２ O 0-0.1%, Na ２ O 3.5-12%, K ２ O 3-20%, MgO 0.5-10%, CaO 1.2-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O is 11.7 to 21%, MgO + CaO + SrO + BaO is 4 to 9.4%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.28 to 1.0, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ It is preferable that O is −10 to 20%.

[0011] Fifth aspect of the present invention: The tempered glass of any of the above aspects has a glass composition at the center of the sheet thickness, which contains, in mol%, SiO ２ 55-80%, Al ２ O ３ 4-20%, B ２ O ３ 0-0.4% Li ２ O 0-0.1%, Na ２ O 3.5-12%, K ２ O 3-20%, MgO 0.5-10%, CaO 1.2-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O is 11.8 to 21%, MgO + CaO + SrO + BaO is 4 to 9.4%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.30 to 1.0, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ It is preferable that O is −10 to 20%.

[0012] Sixth aspect of the present invention: The tempered glass of any of the above aspects has a glass composition at the center of the sheet thickness, which contains, in mol%, SiO ２ 55-80%, Al ２ O ３ 4-20%, B ２ O ３ 0-0.4% Li ２ O 0-0.1%, Na ２ O 3.5-12%, K ２ O 3-20%, MgO 0.5-6.5%, CaO 1.2-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O 11.8-21%, MgO + CaO + SrO + BaO 4-9.4%, molar ratio K ２ O / (Na ２ O+K ２ O) is 0.30 to 1.0, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ It is preferable that O is −10 to 20%.

[0013] Seventh aspect of the present invention: In the tempered glass of any one of the above aspects, it is preferable that the compressive stress value CS of the outermost surface of the compressive stress layer is 100 to 1200 MPa.

[0014] Eighth aspect of the present invention: A flexible cover member of the present invention preferably comprises the tempered glass of any of the above aspects and a resin sheet having a thickness of 0.2 mm or less laminated with the tempered glass, and is configured to be bendable.

[0015] A ninth aspect of the present invention: An electronic device of the present invention preferably comprises the flexible cover member of any of the above aspects, and a display member or an input member covered by the flexible cover member.

[0016] A tenth aspect of the present invention is a sheet-shaped glass for tempering, which has a glass composition containing, in mol %, SiO ２55-80%, Al ２ O ３ 4-20%, Li ２ O 0-0.1%, Na ２ O 3-12%, K ２ Contains 3-20% O, 0-10% MgO, 0-10% CaO, and Na ２ O+K ２ O is 10 to 25%, MgO + CaO + SrO + BaO is 0 to 15%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.20 or more.

[0017] Eleventh aspect of the present invention: The glass to be tempered of any of the above aspects has a glass composition containing, in mol%, SiO ２ 55-80%, Al ２ O ３ 4-20%, B ２ O ３ 0-0.4% Li ２ O 0-0.1%, Na ２ O 3.5-12%, K ２ O 3-20%, MgO 0.5-10%, CaO 1.2-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O is 11.8 to 21%, MgO + CaO + SrO + BaO is 4 to 9.4%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.30 to 1.0, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ It is preferable that O is −10 to 20%.

[0018] Twelfth aspect of the present invention: The glass to be tempered of any of the above aspects has a glass composition containing, in mol%, SiO ２ 55-80%, Al ２ O ３ 4-20%, B ２ O ３ 0-0.4% Li２ O 0-0.1%, Na ２ O 3.5-12%, K ２ O 3-20%, MgO 0.5-6.5%, CaO 1.2-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O is 11.8 to 21%, MgO + CaO + SrO + BaO is 4 to 9.4%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.30 to 1.0, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ It is preferable that O is −10 to 20%.

[0019] Thirteenth aspect of the present invention: The glass to be tempered according to any one of the above aspects preferably has a thickness of 0.20 mm or less.

[0020] Fourteenth aspect of the present invention: The glass to be tempered according to any one of the above aspects preferably has a strain point of 600° C. or higher.

[0021] Fifteenth aspect of the present invention: A method for producing tempered glass of the present invention comprises the steps of: ２ 55-80%, Al ２ O ３ 4-20%, Li ２ O 0-0.1%, Na ２ O 3-12%, K ２ Contains 3-20% O, 0-10% MgO, 0-10% CaO, and Na ２ O+K ２ O is 10 to 25%, MgO + CaO + SrO + BaO is 0 to 15%, and the molar ratio K ２ O / (Na ２ O+K ２ preparing a tempered glass having a thickness of 0.2 mm or less and a molten salt composition of KNO ３ 50-100% by mass, NaNO ３ +LiNO ３and a step of immersing the glass in a molten salt containing 0 to 50 mass % of ammonium hydroxide at 350 to 450°C for 80 minutes or more to obtain tempered glass.

[0022] The glass to be tempered of the present invention has a glass composition containing, in mol %, SiO ２ 55-80%, Al ２ O ３ 4-20%, Li ２ O 0-0.1%, Na ２ O 3-12%, K ２ Contains 3-20% O, 0-10% MgO, 0-10% CaO, and Na ２ O+K ２ O is 10 to 25%, MgO + CaO + SrO + BaO is 0 to 15%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.20 or more.

[0023] The tempered glass of the present invention (glass obtained by subjecting the glass to be tempered to an ion exchange treatment) has the same glass composition as the glass to be tempered at the center of the sheet thickness. That is, the tempered glass of the present invention has a glass composition of SiO at the center of the thickness. ２ 55-80%, Al ２ O ３ 4-20%, Li ２ O 0-0.1%, Na ２ O 3-12%, K ２ Contains 3-20% O, 0-10% MgO, 0-10% CaO, and Na ２ O+K ２ O is 10 to 25%, MgO + CaO + SrO + BaO is 0 to 15%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.20 or more.

[0024] The central part of the thickness of the tempered glass of the present invention typically has the glass composition of a region that has not been ion-exchanged, and preferably has the above-described glass composition at the central part of the thickness at the center position of the main surface when viewed in the thickness direction.

[0025] In the description of the contents of glass composition components in this specification, the percentages refer to mole percent unless otherwise specified.

[0026] The reasons for limiting the range of each component in the composition of the glass to be tempered and the composition of the central portion of the tempered glass sheet thickness are as follows: In the present invention, the phrase "substantially does not contain ..." means that the specified component is not actively added as a glass component, but the inclusion of impurity levels is permitted, and specifically refers to the case where the content of the specified component is less than 0.05 mol%.

[0027] SiO ２ is a component that forms the glass network. ２ If the content is too small, vitrification becomes difficult. ２ The preferred lower limit range of SiO is 55% or more, 57% or more, 59% or more, 60% or more, 61% or more, 62% or more, 63% or more, particularly 64% or more. ２ If the content of SiO is too high, the melting property and moldability tend to decrease, and the thermal expansion coefficient becomes too low, making it difficult to match the thermal expansion coefficient of the surrounding material. ２ The preferred upper limit range of is 80% or less, 75% or less, 73% or less, 71% or less, 70% or less, 69% or less, 68% or less, 67% or less, 66% or less, particularly 65% ​​or less.

[0028] Al ２ O ３ is a component that enhances ion exchange performance. ２ O ３ If the content of Al is too small, the ion exchange performance tends to decrease and bending distortion tends to increase. ２ O ３ The preferred lower limit range of Al is 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 8.5% or more, 9% or more, 9.5% or more, 10% or more, 10.5% or more, 11% or more, 11.5% or more, particularly 12% or more. ２ O ３If the content of Al is too high, devitrification crystals are likely to precipitate in the glass, making it difficult to form it into a plate by the overflow down-draw method or the like. In particular, when an alumina refractory is used as the formed refractory and the plate is formed by the overflow down-draw method, devitrification crystals such as spinel are likely to precipitate at the interface with the alumina refractory. ２ O ３ The preferred upper limit range of is 20% or less, 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, particularly 13% or less.

[0029] Alkali metal oxides are ion exchange components that reduce high-temperature viscosity and improve melting and moldability. However, if the content of alkali metal oxides is too high, bending strain increases. In addition, the thermal expansion coefficient may increase. Therefore, the total content of alkali metal oxides (Li ２ O + Na ２ O+K ２ The preferred lower limit of O) is 10% or more, 11% or more, particularly 12% or more, and the preferred upper limit is 25% or less, 24% or less, 23% or less, 22% or less, 21% or less, 20% or less, 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, particularly 13% or less. ２ O and K ２ Total amount of O (Na ２ O+K ２ The preferred lower limit range of O) is 10% or more, 11% or more, 11.7% or more, particularly 11.8% or more, and the preferred upper limit range is 25% or less, 24% or less, 23% or less, 22% or less, 21% or less, 20% or less, 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, particularly 13% or less.

[0030] Li ２ O is an ion exchange component, and is particularly an effective component for obtaining a deep stress depth, and is also a component for reducing high-temperature viscosity and improving melting property and moldability. ２ O is Na ２ When present together with O, it is a component that tends to increase bending strain and is eluted during ion exchange treatment, deteriorating the ion exchange solution. Therefore, the preferred upper limit range is 0.1% or less, particularly less than 0.1%.

[0031] Na ２ O is an ion exchange component and also a component that reduces high-temperature viscosity and improves meltability and moldability. ２ O is also a component that improves devitrification resistance and reaction devitrification resistance with a refractory molded body, especially with an alumina refractory. ２ The more O there is, the higher the compressive stress that can be applied. ２ The lower limit of O is preferably 3% or more, 3.5% or more, 4% or more, and particularly preferably 5% or more. ２ If the content of O is too high, the balance of the components in the glass composition will be lost, and the devitrification resistance may be deteriorated. ２ As the proportion of O increases, bending strain increases. ２ The upper limit range of O is preferably 12% or less, 11% or less, 10% or less, 9% or less, 8.5% or less, 8% or less, 7.5% or less, 7% or less, particularly preferably 6% or less.

[0032] K ２ O is a component that reduces high-temperature viscosity and improves meltability and moldability. It also improves devitrification resistance. In addition, Na in the composition after chemical strengthening ２ O and K ２ K in the total amount of O ２ As the proportion of O increases, bending strain decreases. ２ The lower limit of O is preferably 3% or more, 4% or more, 5% or more, and particularly preferably 6% or more. ２ If the O content is too high, the balance of the components in the glass composition will be lost, and devitrification resistance may actually decrease. ２ The preferred upper limit range of O is 20% or less, 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, particularly 8% or less.

[0033] Molar ratio K ２ O / (Na ２ O+K ２ O) is a component ratio useful for reducing bending strain, and if its value is too small, bending strain will increase.２ O / (Na ２ O+K ２ The preferred lower limit range of the molar ratio K is 0.20 or more, 0.25 or more, 0.28 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, 0.50 or more, particularly 0.55 or more. ２ O / (Na ２ O+K ２ If the molar ratio K is too large, it becomes difficult to apply a suitable compressive stress when chemically strengthening with potassium nitrate. ２ O / (Na ２ O+K ２ The preferred upper limit range of K is 1.0 or less, 0.95 or less, 0.90 or less, 0.85 or less, 0.80 or less, 0.70 or less, 0.65 or less, particularly 0.60 or less. ２ O / (Na ２ O+K ２ O) is K ２ The content of O is Na ２ O and K ２ It refers to the value divided by the total amount of O.

[0034] Alkaline earth metal oxides are components that reduce high-temperature viscosity and improve meltability and moldability. On the other hand, if the total amount of alkaline earth metal oxides is too high, ion exchange performance tends to decrease. Therefore, the preferred lower limit range of alkaline earth metal oxides (MgO + CaO + SrO + BaO) is 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 7.5% or more, 8% or more, and particularly 8.5% or more. The preferred upper limit range is 15% or less, 14% or less, 13% or less, 12% or less, 11.2% or less, 10.5% or less, 10% or less, 9.8% or less, 9.6% or less, 9.4% or less, 9.2% or less, and particularly 9.0% or less. Note that (MgO + CaO + SrO + BaO) refers to the total amount of MgO, CaO, SrO, and BaO.

[0035] MgO is a component that reduces high-temperature viscosity and improves meltability and formability. Therefore, the preferred lower limit of MgO is 0% or more, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, and particularly 3.5% or more. On the other hand, if the MgO content is too high, the ion exchange performance tends to decrease and the glass tends to devitrify. In particular, when an alumina refractory is used as the refractory molding and the glass is formed into a plate shape by the overflow down-draw method, spinel devitrification crystals tend to precipitate at the interface with the alumina refractory. Therefore, if the MgO content is too high, the component balance of the glass composition may be lost, and devitrification resistance may actually decrease. Therefore, the preferred upper limit of MgO is 10% or less, 9% or less, 8% or less, 7% or less, 6.5% or less, 6% or less, 5.5% or less, 5% or less, 4.5% or less, and particularly 4% or less.

[0036] Compared to other components, CaO reduces high-temperature viscosity and improves meltability and moldability without reducing devitrification resistance. Therefore, the preferred lower limit of CaO is 0% or more, 0.1% or more, 0.5% or more, 1% or more, 1.2% or more, 2% or more, and particularly 2.5% or more. On the other hand, if the CaO content is too high, the ion exchange performance decreases and the ion exchange solution tends to deteriorate. Therefore, the preferred upper limit of CaO is 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, and particularly 3.5% or less.

[0037] SrO is a component that further reduces devitrification when contained together with other alkaline earth metal oxide components. Therefore, the preferred lower limit range of SrO is 0% or more, 0.1% or more, 0.5% or more, 1% or more, particularly 1.5% or more. On the other hand, if the SrO content is too high, devitrification deteriorates. Therefore, the preferred upper limit range of SrO is 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, particularly 2.5% or less.

[0038] Compared with other alkaline earth metal oxides, BaO is a component that reduces high-temperature viscosity and improves meltability and formability. On the other hand, if the BaO content is too high, the ion exchange rate (particularly the stress depth) tends to decrease. Therefore, the preferred BaO content is 0 to 10%, 0 to 9%, 0 to 8%, 0 to 7%, 0 to 6%, 0 to 5%, 0 to 4%, 0 to 3.5%, 0.1 to 3%, 0.1 to 2%, and particularly 0.1 to 1.5%.

[0039] Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ O is an index of the strain point, and the larger this index, the larger the strain point, and as a result, the smaller the bending strain. ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ The preferred lower limit range of O is −20% or more, −15% or more, −10% or more, −5% or more, 0% or more, 5% or more, 8% or more, and particularly 10% or more. ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ If the amount of O becomes too large, the resistance to devitrification decreases. ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ The preferred upper limit of O is 30% or less, 25% or less, 20% or less, 15% or less, 12% or less, particularly 11% or less. ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ O is Al ２ O ３ , MgO, CaO, SrO and BaO in total amount, Li ２ O, Na ２ O and K ２ It refers to the value obtained by subtracting the total amount of O.

[0040] In addition to the above components, the following components may also be added:

[0041] ZnO is a component that enhances ion exchange performance, and is particularly effective in increasing compressive stress. It also reduces high-temperature viscosity without reducing low-temperature viscosity. Therefore, the preferred lower limit of ZnO is 0% or more, 0.1% or more, 0.5% or more, and particularly 0.8% or more. On the other hand, if the ZnO content is too high, the glass tends to undergo phase separation, reduce devitrification resistance, increase density, and reduce stress depth. Therefore, the preferred upper limit of ZnO is 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, and particularly 1.5% or less.

[0042] SnO ２ is a component that acts as a fining agent. ２ The preferred content is 0 to 3%, 0.001 to 3%, 0.05 to 1%, 0.1 to 0.5%, particularly 0.1 to 0.3%.

[0043] B ２ O ３ is a component that increases high-temperature viscosity, density, and devitrification resistance. ２ O ３ If the content of B is too high, the ion exchange rate (particularly the stress depth) tends to decrease. Furthermore, ion exchange can cause coloring of the glass surface, known as tarnish, and can easily increase bending strain, as well as decrease acid resistance and water resistance. ２ O ３ The preferred content is 0 to 10%, 0 to 9%, 0 to 8%, 0 to 7%, 0 to 6%, 0 to 5%, 0 to 4%, 0 to 3.5%, 0 to 3%, 0 to 2%, 0 to 1%, particularly 0 to 0.4%.

[0044] P ２ O ５ is a component that improves ion exchange performance while maintaining the compressive stress value. It is also a component that reduces bending strain and Young's modulus. It is also a component that reduces high-temperature viscosity and improves meltability and moldability. However, P ２ O ５If the content of P is too high, the glass may become cloudy due to phase separation, and the acid resistance may be easily reduced. ２ O ５ The preferred content is 0 to 10%, 0 to 9%, 0 to 8%, 0 to 7%, 0 to 6%, 0 to 5%, 0 to 4%, 0 to 3.5%, 0 to 3%, 0 to 2%, 0 to 0.5%, particularly 0 to 0.1%.

[0045] TiO ２ is a component that enhances ion exchange performance and also reduces high-temperature viscosity, but if its content is too high, the glass becomes colored and is prone to devitrification. ２ The preferred content is 0 to 10%, 0 to 9%, 0 to 8%, 0 to 7%, 0 to 6%, 0 to 5%, 0 to 4%, 0 to 3.5%, 0 to 3%, 0 to 2%, 0 to 0.5%, 0 to 0.3%, particularly 0 to 0.1%.

[0046] ZrO ２ is a component that significantly enhances the ion exchange performance and also increases the viscosity near the liquidus viscosity and the strain point, but if its content is too high, there is a risk that the devitrification resistance will be significantly reduced and the density will become too high. ２ The preferred content is 0 to 10%, 0 to 9%, 0 to 8%, 0 to 7%, 0 to 6%, 0 to 5%, 0 to 4%, 0 to 3.5%, 0 to 3%, 0 to 2%, 0 to 0.9%, 0 to 0.5%, particularly 0 to 0.1%.

[0047] Fe ２ O ３ is an impurity component from the raw material, but it is a component that absorbs ultraviolet light that is harmful to the human eye. ２ O ３ If the content of Fe is too high, the coloring of the glass will be intensified. ２ O ３ Suitable contents are 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, particularly less than 100 ppm.

[0048] Nd ２ O ３ , La ２ O ３These rare earth oxides are components that increase the Young's modulus. However, the raw materials themselves are expensive, and adding a large amount of them tends to reduce devitrification resistance. Therefore, the preferred content of rare earth oxides is 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly 0.1% or less.

[0049] Due to environmental considerations, the glass composition contains substantially no As. ２ O ３ , Sb ２ O ３ , PbO, F, Bi ２ O ３ It is preferable that it does not contain

[0050] <Characteristics Common to Glass to be Tempered and Tempered Glass> The glass to be tempered and the tempered glass of the present invention preferably have, for example, the following characteristics.

[0051] The strain point is preferably 480° C. or higher, 500° C. or higher, 520° C. or higher, particularly 530 to 700° C. The higher the strain point, the smaller the bending strain.

[0052] The softening point is preferably 950°C or lower, 900°C or lower, 880°C or lower, or 860°C or lower, particularly 700 to 850°C. The lower the softening point, the more improved the thermal processability and the less strain there is on glass manufacturing equipment such as thermal processing equipment. Thus, the lower the softening point, the easier it is to reduce the manufacturing costs of tempered glass.

[0053] High temperature viscosity 10 ２．５ The temperature at viscosity dPa·s is preferably less than 1650°C, 1630°C or less, 1620°C or less, particularly 1610°C or less. ２．５ The lower the temperature at dPa·s, the lower the melting temperature becomes, which reduces the burden on glass manufacturing equipment such as a melting furnace and also makes it easier to improve the bubble quality. ２．５ The lower the temperature at viscosity dPa·s, the easier it is to reduce the production cost of the glass to be tempered.

[0054] The liquidus viscosity, in Log ρ, 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 liquidus viscosity is too low, devitrification resistance decreases, making it difficult to produce glass to be tempered, particularly glass to be tempered having a small thickness, by the overflow downdraw method or the like.

[0055] The Young's modulus is preferably 50 GPa or more, 60 GPa or more, or 65 GPa or more, particularly 70 to 85 GPa. The higher the Young's modulus, the smaller the amount of displacement caused by bending when attempting to bend the glass with the same stress. Furthermore, the higher the Young's modulus, the more likely it is that the bending strength and impact resistance strength will be high. The Young's modulus can be measured by the well-known resonance method.

[0056] The tempered glass and the glass to be tempered of the present invention can be in the form of a sheet (plate), and can have a rectangular shape (rectangular and square), a circular shape (perfect circle and ellipse) or the like in a plan view (viewed in the thickness direction).

[0057] The glass to be tempered and tempered glass of the present invention may have a three-dimensional shape, for example, with locally curved portions formed therein.

[0058] The sheet thickness t of the glass to be tempered and tempered glass of the present invention is preferably 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, and particularly 10 to 30 μm. The smaller the sheet thickness t, the more flexible the tempered glass is, making it easier to apply to foldable displays. In addition, the allowable radius of curvature when bending the tempered glass becomes smaller. Furthermore, it becomes easier to wind up into a roll. Note that the sheet thickness t typically refers to the average thickness.

[0059] The glass to be tempered and the tempered glass of the present invention may have portions with different thicknesses. For example, the glass to be tempered and the tempered glass of the present invention may have a shape in which portions other than the bent portions are thicker than the bent portions.

[0060] When the glass to be tempered and tempered glass of the present invention are rectangular, the dimensions of each side are 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, or 150 mm or more, particularly 200 to 2000 mm. Side dimensions within these ranges facilitate application to large flexible displays. Furthermore, multiple individual pieces can be cut from a single sheet, which tends to improve processing yield.

[0061] In the present invention, the "bending strain σ (N)" is the bending strain obtained by bending the glass to be tempered of the present invention at 430°C by KNO ３ The bending strain of glass that has been chemically strengthened in molten salt for N minutes is shown. For example, σ(0) is the bending strain of glass to be tempered that has not been chemically strengthened. The bending strain σ(80) is the bending strain of glass to be tempered of the present invention that has been chemically strengthened in molten salt for N minutes. ３ This shows the bending strain of tempered glass after chemical strengthening in molten salt for 80 minutes. The bending strain σ without parentheses indicates the bending strain of glass (tempered glass) regardless of the conditions of the ion exchange treatment. <Characteristics of tempered glass>

[0062] The bending strain σ(0) of the tempered glass is preferably 5.0 × 10 －４ Below, 4.5 x 10 －４ Below, especially 4.0 × 10 －４ If the bending strain σ(0) before tempering is too large, it may be difficult to reduce the bending strain after tempering. The lower limit of the bending strain σ(0) of the glass to be tempered is not particularly determined, but due to the properties of the glass, it is 1.0 × 10 －４ The above is realistic.

[0063] Here, the "bending strain σ" in the present invention refers to a bending strain that occurs in the bent portion of the evaluation sample after placing a fiber-like glass (evaluation sample) with a length of 150 mm and a diameter of 0.13 mm between two support plates with a distance between the plates set to 26 mm so as to maintain a U-shape, and then holding the sample at room temperature for 24 hours, removing the evaluation sample from between the support plates, releasing the holding state, and leaving the sample at room temperature for a further 5 minutes, and then calculating the bending strain according to the following formula (1) in accordance with JIS K7116: Bending strain σ=(6×St×d) / (L ２) ...(1) St: distance between the midpoint between the two base points and the tangent intersection point at each base point d: fiber diameter of the evaluation sample (0.13 mm) L: distance between the two base points The present inventors have confirmed that the value of bending strain measured on this fiber-like glass corresponds to a glass sheet formed by the overflow down-draw method and having a thickness t of 0.2 mm or less.

[0064] <Characteristics of tempered glass> The bending strain σ(80) of tempered glass is measured by the above-mentioned method and is preferably 3.0 × 10 －４ Below, 2.5 x 10 －４ Below, 2.0 x 10 －４ Below, 1.7 x 10 －４ Below, especially 1.5 × 10 －４ If the bending strain σ(80) of the tempered glass is too large, the visibility of the bent portion will decrease when the tempered glass is used in a foldable display. Although the lower limit of the bending strain σ(80) of the tempered glass is not particularly determined, due to the properties of the glass, it is 1.0 × 10 －４ The bending strain σ(80) of the tempered glass is preferably 3.0×10 －４ Below, 2.5 x 10 －４ Below, 2.0 x 10 －４ Below, 1.7 x 10 －４ Below, especially 1.5 × 10 －４ If the bending strain σ(80) of the tempered glass is too large, the visibility of the bent portion will decrease when the tempered glass is used in a foldable display. Although the lower limit of the bending strain σ(80) of the tempered glass is not particularly determined, due to the properties of the glass, it is 1.0 × 10 －４ The above is realistic.

[0065] The tempered glass of the present invention has a compressive stress layer on the surface thereof, and also has a tensile stress layer located inside the compressive stress layer.

[0066] The maximum compressive stress value CS of the surface is preferably 100 MPa or more, 200 MPa or more, 400 MPa or more, particularly 450 MPa or more. The larger the maximum compressive stress value CS, the easier it is to prevent breakage due to tensile stress generated at the bent portion of the tempered glass when the foldable display is bent. On the other hand, if extremely large compressive stress is formed on the surface, the tensile stress inherent in the tempered glass becomes extremely high, and there is a risk of large dimensional change before and after the ion exchange treatment. Therefore, the maximum compressive stress value CS is preferably 1300 MPa or less, 1100 MPa or less, 900 MPa or less, particularly 800 MPa or less. Note that, from the viewpoint of prioritizing improvement of bending strength, the maximum compressive stress value CS is preferably 600 MPa or more, 700 MPa or more, or 750 MPa or more.

[0067] The maximum stress depth DOL of the compressive stress layer is preferably 1 μm or more, 3 μm or more, 5 μm or more, and 5 to 30%, 6 to 25%, or 7 to 20% of the plate thickness. The greater the stress depth, the less likely the tempered glass is to break even if deep scratches are made on the tempered glass, and the smaller the variation in mechanical strength. On the other hand, the greater the stress depth, the greater the dimensional change before and after the ion exchange treatment. Therefore, the stress depth is preferably 20 μm or less.

[0068] The maximum tensile stress value CT of the tensile stress layer is preferably 400 MPa or less, 350 MPa or less, or 300 MPa or less. If the internal tensile stress value is too high, the tempered glass is more likely to self-destruct due to physical impact, etc. On the other hand, if the internal tensile stress value is too low, it becomes difficult to ensure the mechanical strength of the tempered glass. The internal tensile stress value is preferably 60 MPa or more. The maximum tensile stress value CT can be calculated using the following formula (2): CT = (CS x DOL) / (t - 2 x DOL) ... (2)

[0069] <Method for manufacturing glass to be tempered> The glass to be tempered of the present invention can be produced as follows. First, glass raw materials prepared to obtain a desired glass composition are charged into a continuous melting furnace, and the raw materials are heated and melted at 1500 to 1700°C. After clarification, the molten glass is preferably supplied to a forming device, formed into a plate, and cooled. After forming into a plate, known methods can be used to cut the glass to a predetermined size, but laser cutting is preferred because it results in smooth edge surfaces.

[0070] When forming the molten glass, it is preferable to cool the temperature range between the annealing point and the strain point of the molten glass at a cooling rate of 2 ° C. / min or more and less than 2500 ° C. / min. The 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 becomes difficult to reduce the plate thickness. On the other hand, if the cooling rate is too fast, the glass structure becomes coarse and the hardness of the glass to be tempered tends to decrease.

[0071] As a method for forming molten glass, it is preferable to employ the overflow down-draw method. The overflow down-draw method is a method that can mass-produce high-quality glass sheets and can easily produce thin glass sheets. Furthermore, in the overflow down-draw method, alumina or zirconia is used as the refractory formed body, but the glass to be tempered of the present invention has good compatibility with alumina in particular, and therefore is less likely to generate bubbles, bumps, etc. during forming.

[0072] In addition to the overflow down-draw method, various other forming methods can be used, such as the float method, the down-draw method (slot down-draw method, re-draw method, etc.), the roll-out method, and the press method.

[0073] <Method for producing tempered glass> The tempered glass of the present invention is produced by subjecting glass to tempering to an ion exchange treatment. The glass to be tempered is subjected to the ion exchange treatment, for example, by immersing it in a molten salt for the ion exchange treatment.

[0074] The molten salt is a salt containing a component that can be ion-exchanged with the component in the tempered glass, and is typically an alkali metal nitrate. Examples of alkali metal nitrates include NaNO ３ , KNO ３ , LiNO ３ These can be used alone (100% by mass) or in combination. ３ When a plurality of kinds of alkali metal nitrates are mixed, the mixing ratio may be determined arbitrarily. For example, ３ 5-95%, KNO ３ 5 to 95%, preferably NaNO ３ 30-80%, KNO ３ 20 to 70%, more preferably NaNO ３ 50-70%, KNO ３ It can be 30 to 50%.

[0075] The temperature of the molten salt is, for example, 350° C. to 500° C., preferably 355° C. to 470° C., 360° C. to 450° C., 365° C. to 430° C., or 370° C. to 410° C. The immersion time is, for example, 3 to 500 minutes, preferably 5 to 120 minutes, or 7 to 100 minutes.

[0076] The conditions such as the composition of the molten salt, the temperature, and the immersion time can be appropriately changed depending on the glass within a range that allows the above-mentioned stress characteristics to be obtained.

[0077] The glass to be tempered and tempered glass of the present invention may be subjected to chemical etching using an acidic solution such as hydrofluoric acid or a basic solution. Etching the glass to be tempered before ion exchange treatment can reduce the plate thickness and suppress a decrease in strength due to scratches. Etching the tempered glass after ion exchange treatment can reduce the effects of scratches, surface roughness, and the like, caused during the ion exchange treatment.

[0078] <Flexible Cover Member> The tempered glass can be used as a constituent material for a flexible cover member. A flexible cover member is a foldable laminate structure typically used as a cover component for a flexible display device. The flexible cover member of the present invention comprises, for example, the sheet-like tempered glass of the present invention and a resin sheet. The resin sheet is, for example, a foldable resin sheet having a thickness of 0.2 mm or less. The resin sheet can be made of synthetic resins such as polyimide, polyethylene terephthalate, and acrylic resins. The flexible cover member may comprise multiple synthetic resin layers. The flexible cover member may also further comprise a metal layer. The metal layer can be made of, for example, a stainless steel alloy, aluminum, or an aluminum alloy having a thickness of 0.2 mm or less.

[0079] <Electronic Device> The flexible cover member can be used as a constituent member of an electronic device. Typical electronic devices are foldable displays, foldable smartphones, foldable tablet computers, foldable touch panels, rollable displays, rollable smartphones, rollable tablet computers, and rollable touch panels. The electronic device of the present invention comprises the flexible cover member of the present invention and, typically, a display member, an input member, a central processing unit, a battery, input / output terminals, a radio wave transmitter / receiver, a housing member, and other members necessary to constitute the electronic device.

[0080] The tempered glass of the present invention may be disposed as the outermost layer of a flexible cover member and an electronic device. Tempered glass has high strength, weather resistance, and excellent texture, making it suitable for the outermost layer of a flexible cover member and an electronic device. On the other hand, the tempered glass of the present invention does not necessarily have to be disposed as the outermost layer of a flexible cover member and an electronic device. That is, the tempered glass of the present invention may be disposed as an internal layer located inside any other cover member in a flexible cover member and an electronic device.

[0081] The present invention will be described below based on examples. Note that the following examples are merely illustrative and are not intended to limit the present invention in any way.

[0082] Tables 1 to 4 show examples of the present invention (samples Nos. 1 to 43) and a comparative example (sample No. 44).

[0083] Each sample in the table was prepared as follows. First, glass raw materials were mixed to obtain the glass composition shown in the table, and melted in a platinum pot at 1600°C for 8 hours. The resulting molten glass was then poured onto a carbon plate, formed into a flat plate, and slowly cooled. Various properties of the resulting tempered glass were evaluated. The results are shown in Tables 1 to 4.

[0084]

[0085]

[0086]

[0087]

[0088] Next, the obtained tempering glass was ground to obtain a cylindrical glass of 6 mm in diameter, and then redrawn to obtain a fiber-like pre-tempered fiber sample of 150 mm in length and 0.13 mm in diameter. Furthermore, this pre-tempered fiber sample was subjected to KNO at 430°C. ３ A chemical strengthening treatment was carried out in molten salt for 80 minutes to obtain a reinforced fiber sample.

[0089] The bending strain σ(0) of the pre-reinforced fiber sample obtained as described above was measured and evaluated by the method described above. The bending strain σ(80) of the reinforced fiber sample obtained as described above was also measured and evaluated by the method described above. The inventors have confirmed that the bending strain measured on this glass fiber corresponds to a glass sheet having a thickness t of 0.2 mm or less formed by the overflow down-draw method.

[0090] The strain point Ps and the annealing point Ta are values ​​measured by the well-known fiber elongation method, and the softening point Ts is a value measured by the method of ASTM C338.

[0091] High temperature viscosity 10 ２．５ The temperature at dPa·s refers to a value measured by the platinum sphere pull-up method.

[0092] The Young's modulus E is a value measured by the well-known resonance method for the glass to be tempered. Although the Young's modulus of the surface layer of the glass differs microscopically before and after the ion exchange treatment, there is essentially no difference when viewed as the glass as a whole because the Young's modulus is measured as an average value by the resonance method. In other words, the tempered glasses obtained by ion-exchanging the glasses to be tempered in each Example have the same Young's modulus E.

[0093] Further, the tempered glass obtained as described above was subjected to optical polishing on both surfaces, and the thickness of the tempered glass was reduced to 0.7 mm. Then, the tempered glass was heated at 430° C. with KNO. ３ Ion exchange treatment was performed by immersing in molten salt for 4 hours. After the ion exchange treatment, the surface of each sample was cleaned. Subsequently, the compressive stress value CS and stress depth DOL of the outermost surface were calculated from the number and spacing of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Orihara Seisakusho Co., Ltd.). In the calculation, the refractive index of each sample was set to 1.50 and the optical elastic constant was set to 29.5 [(nm / cm) / MPa]. Note that although the glass composition in the surface layer of the glass is microscopically different before and after the ion exchange treatment, when viewed as a whole, the glass composition is not substantially different.

[0094] As is clear from the table, Samples Nos. 1 to 43, which are examples, have smaller bending strain σ(80) than Comparative Example Sample No. 44. Therefore, it is thought that when made into tempered glass, bending marks are less likely to remain.

[0095] Glass batches having the glass compositions of Samples No. 1 to 43 shown in the table were melted in a test melting furnace to obtain molten glass, which was then formed and cut by the overflow down-draw method to form glass sheets to be tempered having a thickness of 50 μm. Note that, when forming the glass sheets, the speed of the tension rollers, the speed of the cooling rollers, the temperature distribution of the heating device, the temperature of the molten glass, the flow rate of the molten glass, and the sheet drawing speed were appropriately adjusted.

[0096] Tempered glass having a compressive stress layer was produced by subjecting the obtained glasses to be tempered Nos. 1 to 43 to an ion exchange treatment. Then, by appropriately changing the conditions of the ion exchange treatment, the compressive stress value of the outermost surface of the compressive stress layer was adjusted to 500 to 700 MPa, and the stress depth was adjusted to 8 to 12 μm.

[0097] For Samples Nos. 1 to 43 before the ion exchange treatment, when they were held in a bent state for a certain period of time and then released, the visibility of the bent portion of the glass sheet was unlikely to decrease. Furthermore, for Samples Nos. 1 to 43 after the ion exchange treatment, when they were held in a bent state for a certain period of time and then released, the visibility of the bent portion of the glass sheet was unlikely to decrease.

[0098] Tempered glass sheets A and B for strength tests were produced by treating tempered glass Nos. 38 and 39 having a sheet thickness of 32 μm under the conditions described in Table 5. That is, tempered glass A and B were produced by subjecting the tempered glass to a thinning step, a chemical strengthening step, and a surface etching step in this order.

[0099] The thinning step was carried out by immersing the glass to be tempered in an aqueous HF solution.

[0100] The chemical strengthening process was carried out by subjecting the tempering glass to KNO under the conditions of temperature and time shown in Table 5. ３ The test was carried out by immersion in 100% molten salt.

[0101] The surface etching step was performed by immersing the tempered glass in an aqueous HF solution.

[0102]

[0103] The two-point bending strength was measured by the following strength test. First, the obtained tempered glasses A and B (50 mm × 50 mm in plan view) were placed in an Autograph AG-IS 10kN (Shimadzu Corporation) with a plate spacing of 20 mm. The plate spacing was narrowed at a rate of 5 mm / min, and the bending radius at break and the fracture strength were determined from the plate spacing at break and the Young's modulus of the sample.

[0104] The tempered glass of the present invention is suitable for flexible cover members used in electronic devices such as foldable displays and foldable touch panels.

Claims

1. A sheet-shaped tempered glass having a compressive stress layer on the surface, in which the glass composition at the center of the sheet thickness is SiO ２ 55-80%, Al ２ O ３ 4-20%, Li ２ O 0-0.1%, Na ２ O 3-12%, K ２ O 3-20%, MgO 0-10%, CaO 0-10%, Na ２ O+K ２ O is 10 to 25%, MgO + CaO + SrO + BaO is 0 to 15%, and the molar ratio K ２ O / (Na ２ O+K ２ Tempered glass characterized in that the tensile strength (Tb) of the tempered glass is 0.20 or more.

2. The thickness is 0.20 mm or less, and the bending strain measured using JIS: K7116 is 2.0 x 10 －４ 2. The tempered glass according to claim 1, wherein:

3. The glass composition at the center of the sheet thickness is SiO ２ 55-80%, Al ２ O ３ 4-20%, Li ２ O 0-0.1%, Na ２ O 3-12%, K ２ O 3-20%, MgO 0-10%, CaO 0-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O is 10 to 21%, MgO + CaO + SrO + BaO is 1 to 15%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.20 or more, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ The tempered glass according to claim 1 or 2, wherein O is −20 to 30%.

4. The glass composition at the center of the sheet thickness is SiO ２ 55-80%, Al ２ O ３ 4-20%, B ２ O ３ 0-0.4% Li ２ O 0-0.1%, Na ２ O 3.5-12%, K ２ O 3-20%, MgO 0.5-10%, CaO 1.2-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O is 11.7 to 21%, MgO + CaO + SrO + BaO is 4 to 9.4%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.28 to 1.0, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ The tempered glass according to claim 3, wherein O is −10 to 20%.

5. The glass composition at the center of the sheet thickness is SiO ２ 55-80%, Al ２ O ３ 4-20%, B ２ O ３ 0-0.4% Li ２ O 0-0.1%, Na ２ O 3.5-12%, K ２ O 3-20%, MgO 0.5-10%, CaO 1.2-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O is 11.8 to 21%, MgO + CaO + SrO + BaO is 4 to 9.4%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.30 to 1.0, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ The tempered glass according to claim 4, wherein O is −10 to 20%.

6. The glass composition at the center of the sheet thickness is SiO ２ 55-80%, Al ２ O ３ 4-20%, B ２ O ３ 0-0.4% Li ２ O 0-0.1%, Na ２ O 3.5-12%, K ２ O 3-20%, MgO 0.5-6.5%, CaO 1.2-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O 11.8-21%, MgO + CaO + SrO + BaO 4-9.4%, molar ratio K ２ O / (Na ２ O+K ２ O) is 0.30 to 1.0, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ The tempered glass according to claim 5, wherein O is −10 to 20%.

7. The tempered glass according to claim 6, wherein the compressive stress value CS of the outermost surface of the compressive stress layer is 100 to 1200 MPa.

8. A flexible cover member comprising the tempered glass of claim 1 and a resin sheet having a thickness of 0.2 mm or less laminated with the tempered glass, said flexible cover member being configured to be bendable.

9. An electronic device comprising the flexible cover member according to claim 8 and a display member or an input member covered by said flexible cover member.

10. Sheet-shaped tempered glass, the glass composition of which is, in mole percent, SiO ２ 55-80%, Al ２ O ３ 4-20%, Li ２ O 0-0.1%, Na ２ O 3-12%, K ２ Contains 3-20% O, 0-10% MgO, 0-10% CaO, and Na ２ O+K ２ O is 10 to 25%, MgO + CaO + SrO + BaO is 0 to 15%, and the molar ratio K ２ O / (Na ２ O+K ２ 0) is 0.20 or more.

11. The glass composition is, in mole percent, SiO ２ 55-80%, Al ２ O ３ 4-20%, B ２ O ３ 0-0.4% Li ２ O 0-0.1%, Na ２ O 3.5-12%, K ２ O 3-20%, MgO 0.5-10%, CaO 1.2-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O is 11.8 to 21%, MgO + CaO + SrO + BaO is 4 to 9.4%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.30 to 1.0, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ The glass to be tempered according to claim 10, wherein O is −10 to 20%.

12. The glass composition is, in mole percent, SiO ２ 55-80%, Al ２ O ３ 4-20%, B ２ O ３ 0-0.4% Li ２ O 0-0.1%, Na ２ O 3.5-12%, K ２ O 3-20%, MgO 0.5-6.5%, CaO 1.2-10%, ZrO ２ 0-0.9%, TiO ２ Contains 0 to 0.3% Na ２ O+K ２ O is 11.8 to 21%, MgO + CaO + SrO + BaO is 4 to 9.4%, and the molar ratio K ２ O / (Na ２ O+K ２ O) is 0.30 to 1.0, Al ２ O ３ +MgO+CaO+SrO+BaO-Li ２ O-Na ２ OK ２ The glass to be tempered according to claim 11, wherein O is −10 to 20%.

13. The glass to be tempered according to claim 12, characterized in that the thickness is 0.20 mm or less.

14. The glass to be tempered according to claim 12 or 13, characterized in that it has a strain point of 600°C or higher.

15. The glass composition is, in mole percent, SiO ２ 55-80%, Al ２ O ３ 4-20%, Li ２ O 0-0.1%, Na ２ O 3-12%, K ２ Contains 3-20% O, 0-10% MgO, 0-10% CaO, and Na ２ O+K ２ O is 10 to 25%, MgO + CaO + SrO + BaO is 0 to 15%, and the molar ratio K ２ O / (Na ２ O+K ２ preparing a sheet-shaped tempered glass having a thickness of 0.2 mm or less and a molten salt composition of KNO ３ 50-100% by mass, NaNO ３ +LiNO ３ and immersing the glass in a molten salt at 350 to 450°C containing 0 to 50 mass% of molten aluminum for 80 minutes or more to obtain tempered glass.

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