WO2012099002A1 - Tempered glass, and tempered glass plate - Google Patents

Abstract

This tempered glass has a compressive stress layer on the surface and is characterized by containing, as the glass composition and in mol %, 50 to 75% of SiO₂, 3 to 13% of Al₂O₃, 0 to 1.5% of B₂O₃, 0 to 4% of Li₂O, 7 to 20% of Na₂O, 0.5 to 10% of K₂O, 0.5 to 13% of MgO, 0 to 6% of CaO, and 0 to 4.5% of SrO, and by substantially not containing As₂O₃, Sb₂O₃, PbO, and F.

Description

Tempered glass and tempered glass plate

The present invention relates to a tempered glass and a tempered glass plate, and in particular, a tempered glass and a tempered glass plate suitable for a mobile phone, a digital camera, a PDA (portable terminal), a solar cell cover glass, or a glass substrate of a display, particularly a touch panel display. About.

Mobile phones, digital cameras, PDAs, touch panel displays, large televisions, and contactless power supply devices are becoming increasingly popular.

For these applications, tempered glass tempered by ion exchange treatment or the like is used (see Patent Document 1 and Non-Patent Document 1).

In particular, in recent years, tempered glass has been used as a protective member for large TV displays. These protective members include (1) high mechanical strength, (2) down-draw method such as overflow down-draw method, slit down-draw method, float method, etc. in order to form large-sized glass plates in large quantities. Characteristics such as (3) having a high-temperature viscosity suitable for molding, (4) being able to perform the strengthening treatment inexpensively and efficiently, and the like are required.

JP 2006-83045 A

Tetsuro Izumiya et al., “New Glass and its Properties”, first edition, Management System Research Institute, Inc., August 20, 1984, p. 451-498

In order to increase the mechanical strength of the tempered glass, it is necessary to increase the compressive stress value of the compressive stress layer. Components such as Al ₂ O ₃ are known as components that increase the compressive stress value. However, when the content of Al ₂ O ₃ is too large, the devitrification resistance is lowered, and it is difficult to obtain a liquid phase viscosity suitable for a down draw method such as an overflow down draw method or a slit down draw method, a float method, or the like. In addition to this, the high-temperature viscosity increases, making it difficult to obtain a molding temperature suitable for the float process or the like.

In addition, when KNO ₃ molten salt is used, a large glass plate can be subjected to ion exchange treatment continuously and in large quantities. However, the use of KNO ₃ molten salt, over time KNO ₃ molten salt is degraded, there is a problem that must be replaced frequently a KNO ₃ molten salt. Since the KNO ₃ molten salt bath replacement takes time and expense, the efficiency of the ion exchange treatment is lowered, and the manufacturing cost of the tempered glass is likely to increase.

Furthermore, when a large glass plate is tempered, there is a problem that the tempered glass plate is warped due to a difference in characteristics between the front and back surfaces (opposite surfaces) of the glass plate. Further, in this case, there has been a problem that, during the tempering treatment, the glass plate is temporarily warped due to the residual stress in the plane direction, and this causes the warp of the tempered glass plate. In recent years, there is a demand for thinning the tempered glass plate. In such a case, the above problem becomes particularly significant.

Therefore, the technical problem of the present invention is that the ion exchange performance and devitrification resistance are high, and the KNO ₃ molten salt is resistant to deterioration. The idea is to create a tempered glass and a tempered glass plate that are difficult to generate.

As a result of various studies, the present inventors have found that the above technical problem can be solved by strictly regulating the glass composition, and propose the present invention. That is, the tempered glass of the present invention is a tempered glass having a compressive stress layer on the surface, and the glass composition is SiO ₂ 50 to 75%, Al ₂ O ₃ 3 to 13%, B ₂ O _{3 in} mol%. 0 to 1.5%, Li ₂ O 0 to 4%, Na ₂ O 7 to 20%, K ₂ O 0.5 to 10%, MgO 0.5 to 13%, CaO 0 to 6%, SrO 0 to It is characterized by containing 4.5% and substantially not containing As ₂ O ₃ , Sb ₂ O ₃ , PbO, and F. Here, “substantially does not contain As ₂ O ₃ ” means that it does not actively add As ₂ O ₃ as a glass component, but allows it to be mixed as an impurity. Specifically, It means that the content of As ₂ O ₃ is less than 0.05 mol%. By "substantially free of Sb ₂ O _3", but not added actively Sb ₂ O ₃ as a glass component, a purpose to allow the case to be mixed as an impurity, specifically, Sb ₂ O _It indicates that the content of ₃ is less than 0.05 mol%. “Substantially no PbO” means that PbO is not actively added as a glass component, but is allowed to be mixed as an impurity. Specifically, the PbO content is 0.05 mol. It means less than%. “Substantially no F” means that F is not actively added as a glass component but is allowed to be mixed as an impurity. Specifically, the F content is 0.05 mol. It means less than%.

As a result of various studies, the present inventors have obtained the following knowledge. When the content (or content ratio) of Al ₂ O ₃ and MgO is regulated at the same time, the ion exchange performance and devitrification resistance can be improved. When the content (or content ratio) of Al ₂ O ₃ and the alkali metal oxide is simultaneously controlled, devitrification resistance can be improved. When a predetermined amount of K ₂ O is added, the thickness of the compressive stress layer can be increased. When the contents (or content ratio) of K ₂ O and Na ₂ O are simultaneously controlled, the thickness of the compressive stress layer can be increased without reducing the compressive stress value of the compressive stress layer.

Further, when the glass composition is regulated within the above range, even when using a KNO ₃ molten salt deteriorated, the compression stress value and thickness of the compression stress layer is not extremely lowered, the frequency of replacement of KNO ₃ molten salt It can be reduced.

Secondly, the tempered glass of the present invention has a glass composition of mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 4 to 13%, B ₂ O ₃ 0 to 1.5%, Li ₂ O 0. ~ 2%, Na ₂ O 9-18%, K ₂ O 1-8%, MgO 0.5-12%, CaO 0-3.5%, SrO 0-3%, TiO ₂ 0-0.5% It is preferable to contain.

Third, the tempered glass of the present invention has a glass composition of mol%, SiO ₂ 50-75%, Al ₂ O ₃ 4-12%, B ₂ O ₃ 0-1%, Li ₂ O 0-1 %, Na ₂ O 10-17%, K ₂ O 2-7%, MgO 1.5-12%, CaO 0-3%, SrO 0-1%, TiO ₂ 0-0.5%. Is preferred.

Fourth, the tempered glass of the present invention has a glass composition of mol%, SiO ₂ 55-75%, Al ₂ O ₃ 4-11%, B ₂ O ₃ 0-1%, Li ₂ O 0-1 %, Na ₂ O 10-16%, K ₂ O 2-7%, MgO 3-12%, CaO 0-3%, SrO 0-1%, ZrO ₂ 0.5-10%, TiO ₂ 0-0 It is preferable to contain 5%.

Fifth, the tempered glass of the present invention has a glass composition of mol%, SiO ₂ 55-69%, Al ₂ O ₃ 4-11%, B ₂ O ₃ 0-1%, Li ₂ O 0-1 %, Na ₂ O 11-16%, K ₂ O 2-7%, MgO 3-9%, CaO 0-3%, SrO 0-1%, ZrO ₂ 1-9%, TiO ₂ 0-0.1 % Is preferably contained.

Sixth, it is preferable that the tempered glass of the present invention has a compressive stress value of the compressive stress layer of 300 MPa or more and a thickness (depth) of the compressive stress layer of 10 μm or more. Here, the “compressive stress value of the compressive stress layer” and the “thickness of the compressive stress layer” are observed when the sample is observed using a surface stress meter (for example, FSM-6000 manufactured by Toshiba Corporation). A value calculated from the number of interference fringes and their intervals.

Seventh, the tempered glass of the present invention preferably has a deterioration coefficient D of 0.01 to 0.6. Here, the deterioration coefficient D indicates a value calculated by the equation of (compressive stress value (new KNO ₃ molten salt) −compressive stress value (deteriorated KNO ₃ molten salt)) / compressive stress value (new KNO ₃ molten salt). . Here, “degraded KNO ₃ molten salt” refers to a KNO ₃ molten salt containing about 1500 ppm of Na ₂ O and about 20 ppm of Li ₂ O, and can be prepared by the following method, for example. SiO ₂ 58.7 _{wt%, Al} 2 O 3 12.8 _wt%, Li 2 O 0.1 _wt%, Na 2 O 14.0 _wt%, K 2 O 6.3 wt%, MgO 2.0 mass %, CaO 2.0% by mass, ZrO ₂ 4.1% by mass of glass composition is crushed, glass powder passing through a sieve opening of 300 μm and not passing through a sieve opening of 150 μm is collected, and the average particle diameter A glass powder of 225 μm is obtained. Next, 95 g of this glass powder is put into a basket made of a metal mesh having a sieve opening of 100 μm. Subsequently, the glass powder is immersed in 400 ml of KNO ₃ maintained at 440 ° C. for 60 hours (the jar is shaken up and down 10 times every 24 hours). On the other hand, "new KNO ₃ molten salt" refers to a KNO ₃ molten salt that has not been subjected to ion exchange treatment in the past, Na ₂ O content 200ppm or less, Li ₂ O content is 3ppm or less of KNO ₃ molten Refers to salt.

Eighth, the tempered glass of the present invention preferably has a liquidus temperature of 1075 ° C. or lower. Here, the “liquid phase temperature” means that the glass powder that passes through the standard sieve 30 mesh (sieve opening 500 μm) and remains on the 50 mesh (mesh opening 300 μm) is placed in a platinum boat and placed in a temperature gradient furnace. It refers to the temperature at which crystals precipitate after holding for a period of time.

Ninth, the tempered glass of the present invention preferably has a liquidus viscosity of 10 ^4.0 dPa · s or more. Here, “liquid phase viscosity” refers to a value obtained by measuring the viscosity of glass at the liquid phase temperature by a platinum ball pulling method.

Tenth, the tempered glass of the present invention preferably has a temperature at 10 ^4.0 dPa · s of 1250 ° C. or lower. Here, “temperature at 10 ^4.0 dPa · s” refers to a value measured by a platinum ball pulling method.

Eleventh, the tempered glass of the present invention preferably has a density of 2.6 g / cm ³ or less. Here, the “density” can be measured by a known Archimedes method.

Twelfth, the tempered glass of the present invention preferably has a Young's modulus of 65 GPa or more. Here, the “Young's modulus” can be measured by a known resonance method or the like.

Thirteenth, the tempered glass sheet of the present invention is characterized by comprising any of the tempered glasses described above.

Fourteenth, the tempered glass plate of the present invention is preferably formed by a float process.

Fifteenth, the tempered glass plate of the present invention preferably has a surface polished by 0.5 μm or more in the thickness direction.

Sixteenthly, in the tempered glass sheet of the present invention, it is preferable that the difference ΔCS of the compressive stress values of the compressive stress layers on the opposing surfaces is 50 MPa or less. When the glass plate is formed by the float process, even if the ion exchange treatment is performed on the surface that is not in contact with the surface that is in contact with the molten tin, there is a difference in the compressive stress value of the formed compressive stress layer. In particular, warping tends to occur in the case of a large and thin tempered glass plate. Therefore, if ΔCS is within the above range, such a problem can be easily prevented.

Seventeenth, the tempered glass plate of the present invention is a tempered glass plate having a compressive stress on the surface, the length is 500 mm or more, the width is 500 mm or more, the thickness is 0.5 to 1.5 mm, and the Young's modulus is 65 GPa or more, the compressive stress value of the compressive stress layer is 200 MPa or more, the thickness of the compressive stress layer is 20 μm or more, the deterioration coefficient D is 0.6 or less, and the difference ΔCS between the compressive stress layers of the opposing surface compressive stress layers is 50 MPa or less. It is characterized by being.

Eighteenth, the tempered glass plate of the present invention is preferably used for a touch panel display.

Nineteenth, the tempered glass plate of the present invention is preferably used for a cover glass of a mobile phone.

Twenty-second, the tempered glass plate of the present invention is preferably used for a cover glass of a solar cell.

Twenty-first, the tempered glass plate of the present invention is preferably used as a protective member for a display.

Twenty-secondly, the tempered glass plate of the present invention is a tempered glass plate having a compressive stress on the surface, and has a glass composition of mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 4 to 12% , B ₂ O ₃ 0 to 1%, Li ₂ O 0 to 1%, Na ₂ O 10 to 17%, K ₂ O 2 to 7%, MgO 1.5 to 12%, CaO 0 to 3%, SrO 0 -1%, TiO ₂ 0-0.5%, molar ratio MgO / (MgO + CaO) is 0.5 or more, length is 500 mm or more, width is 500 mm or more, thickness is 0.5 to 1.5 mm, The Young's modulus is 65 GPa or more, the compressive stress value of the compressive stress layer is 400 MPa or more, the thickness of the compressive stress layer is 30 μm or more, and the degradation coefficient D is 0.4 or less.

Twenty-third, the tempered glass of the present invention is a tempered glass that is subjected to a tempering treatment, and has a glass composition of mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 3 to 13%. , B ₂ O ₃ 0 to 1.5%, Li ₂ O 0 to 4%, Na ₂ O 7 to 20%, K ₂ O 0.5 to 10%, MgO 0.5 to 13%, CaO 0 to 6 %, SrO 0 to 4.5%, and substantially free of As ₂ O ₃ , Sb ₂ O ₃ , PbO, and F.

Twenty-fourth, the strengthening glass plate of the present invention is a strengthening glass plate subjected to a strengthening process, has a thickness of 1.5 mm or less, and is a planar direction with respect to all planar portions of the strengthening glass plate. The maximum value Fmax of the residual stress is 5 MPa or less. Here, “Fmax” is a grid-like intersection position at a pitch of 10 cm on a glass plate having a dimension of 500 mm × 500 mm or more (particularly, a dimension of 1 m × 1 m) using a birefringence measuring machine: ABR-10A manufactured by UNIOPT. And the birefringence (unit: nm) in the vicinity of the outer periphery of the four sides, and the maximum value when converted into the residual stress in the plane direction. In addition, the residual stress value in the glass plate can be estimated by measuring the optical birefringence, that is, by measuring the optical path difference between orthogonal linearly polarized waves, and the deviation stress F (MPa) generated by the residual stress is , F = R / CL. “R” is the optical path difference (nm), “L” is the distance (cm) through which the polarized wave has passed, and “C” is the photoelastic constant (proportional constant). nm / cm) / (MPa). The residual stress in the plane direction includes tensile stress and compressive stress. In the above, the absolute values of both are evaluated.

Since the tempered glass of the present invention has high ion exchange performance, the compressive stress value of the compressive stress layer is increased and the compressive stress value is deeply formed even in a short time ion exchange treatment. For this reason, mechanical strength becomes high and the dispersion | variation in mechanical strength becomes small.

Further, since the tempered glass of the present invention is excellent in resistance to devitrification, it can be efficiently formed by an overflow down draw method, a float method or the like. In addition, if it is an overflow downdraw method, a float method, etc., a large sized and thin glass plate can be shape | molded in large quantities.

Further, the tempered glass of the present invention, since deterioration coefficient D is small, even if the ion-exchange treatment for a long time, the compression stress value and thickness of the compression stress layer to be formed since it is difficult to decrease the KNO ₃ molten salt It is possible to reduce the exchange frequency.

It is data which show the residual stress of the plane direction of the glass plate which concerns on [Example 3]. It is data which show the residual stress of the plane direction of the glass plate which concerns on [Example 4].

The tempered glass according to an embodiment of the present invention has a compressive stress layer on the surface and has a glass composition of mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 3 to 13%, B ₂ O ₃ 0 to 1.5%, Li ₂ O 0-4%, Na ₂ O 7-20%, K ₂ O 0.5-10%, MgO 0.5-13%, CaO 0-6%, SrO 0-4. 5% is contained, and substantially no As ₂ O ₃ , Sb ₂ O ₃ , PbO, and F are contained. In the following description, unless otherwise specified, in the description of the content range of each component, “%” indicates mol%.

There are a physical strengthening method and a chemical strengthening method as a method for forming a compressive stress layer on the surface. It is preferable that the tempered glass of this embodiment is produced by a chemical strengthening method.

The chemical strengthening method is a method of introducing alkali ions having a large ion radius to the surface of the glass by ion exchange treatment at a temperature below the strain point of the glass. If the compressive stress layer is formed by the chemical strengthening method, the compressive stress layer can be properly formed even when the glass is thin, and even if the tempered glass is cut after forming the compressive stress layer, the air cooling strengthening method is used. The tempered glass does not break easily like the physical tempering method.

In the tempered glass of the present embodiment, the reason why the content range of each component is limited as described above will be described below.

SiO ₂ is a component that forms a network of glass. The content of SiO ₂ is 50 to 75%, preferably 55 to 75%, 55 to 72%, 55 to 69%, particularly 58 to 67%. When the content of SiO ₂ is too small, it becomes difficult to vitrify. In addition, the thermal expansion coefficient becomes too high, and the thermal shock resistance tends to decrease. Furthermore, the degradation coefficient D tends to increase. On the other hand, if the content of SiO ₂ is too large, the meltability and the formability tends to decrease. In addition, the thermal expansion coefficient becomes too low, making it difficult to match the thermal expansion coefficient of the surrounding material.

Al ₂ O ₃ is a component that enhances the ion exchange performance and is the component that has the highest effect of reducing the degradation coefficient D. It is also a component that increases the strain point and Young's modulus. The content of Al ₂ O ₃ is 3 to 13%. When the content of Al ₂ O ₃ is too small, the deterioration coefficient D tends to increase, and there is a possibility that the ion exchange performance cannot be exhibited sufficiently. Therefore, the preferable lower limit range of Al ₂ O ₃ is 4% or more, 4.5% or more, 5% or more, 5.5% or more, 6% or more, 7% or more, 8.5% or more, 10% or more, In particular, it is 10.5% or more. On the other hand, when the content of Al ₂ O ₃ is too large, devitrification crystal glass becomes easy to precipitate, and it becomes difficult to mold the glass sheet by a float process and an overflow down draw method and the like. In addition, the thermal expansion coefficient becomes too low, making it difficult to match the thermal expansion coefficient of the surrounding material. Furthermore, the high-temperature viscosity becomes high and the meltability tends to be lowered. Therefore, a suitable upper limit range of Al ₂ O ₃ is 12.5% or less, particularly 12% or less.

B ₂ O ₃ is a component that lowers the high temperature viscosity and density, stabilizes the glass, makes it difficult to precipitate crystals, and lowers the liquidus temperature. However, if the content of B ₂ O ₃ is too large, coloring of the glass surface called burnt occurs due to ion exchange, water resistance is lowered, and the thickness of the compressive stress layer tends to be reduced. Therefore, the content of B ₂ O ₃ is 0 to 1.5%, preferably 0 to 1.3%, 0 to 1.1%, 0 to 1%, 0 to 0.8%, 0 to 0%. 0.5%, especially 0-0.1%.

Li ₂ O is an ion exchange component, and is a component that lowers the high-temperature viscosity to increase the meltability and moldability, and also increases the Young's modulus. Furthermore, Li ₂ O has a large effect of increasing the compressive stress value among alkali metal oxides. However, in a glass system containing 7% or more of Na ₂ O, if the Li ₂ O content is extremely increased, the compressive stress is rather increased. The value tends to decrease. Further, when the content of Li 2 _O is too large, and decreases the liquidus viscosity, in addition to the glass tends to be devitrified, the thermal expansion coefficient becomes too high, the thermal shock resistance may decrease, It becomes difficult to match the thermal expansion coefficient of the surrounding material. Furthermore, the low-temperature viscosity decreases too much, and stress relaxation is likely to occur, and the compressive stress value may decrease instead. Further, the deterioration coefficient D tends to increase. Thus, the content of Li ₂ O is 0-4%, preferably 0 to 2.5% 0-2% 0 to 1.5% 0 to 1% 0 to 0.5% in particular 0 to 0.3%.

Na ₂ O is an ion exchange component, and is a component that lowers the high temperature viscosity and improves the meltability and moldability. Na ₂ O is also a component that improves devitrification resistance. When Na 2 _O content is too small, or reduced meltability, lowered coefficient of thermal expansion tends to decrease the ion exchange performance. Therefore, the content of Na ₂ O is 7% or more, and the preferable lower limit range is 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, particularly 13% or more. On the other hand, when the content of Na ₂ O is too large, the thermal expansion coefficient becomes too high, the thermal shock resistance is lowered, and it becomes difficult to match the thermal expansion coefficient of the surrounding materials. In addition, the strain point may be excessively lowered or the component balance of the glass composition may be lost, and the devitrification resistance may be deteriorated. Furthermore, the degradation coefficient D tends to increase. Therefore, the content of Na ₂ O is 20% or less, and the preferable upper limit range is 19% or less, 17% or less, and particularly 16% or less.

K ₂ O is a component that promotes ion exchange, and among alkali metal oxides, it is a component that tends to increase the thickness of the compressive stress layer. Moreover, it is a component which reduces high temperature viscosity and improves a meltability and a moldability. Furthermore, it is also a component that improves devitrification resistance. Therefore, the content of K ₂ O is 0.5% or more, and a preferable lower limit range is 1% or more, 1.5% or more, and particularly 2% or more. However, if the content of K ₂ O is too large, the thermal expansion coefficient becomes too high, and the thermal shock resistance is lowered or it is difficult to match the thermal expansion coefficient of the surrounding materials. Moreover, there is a tendency that the strain point is excessively lowered, the component balance of the glass composition is lacking, and the devitrification resistance is lowered. Therefore, the content of K ₂ O is 10% or less, and a preferable upper limit range is 9% or less, 8% or less, 7% or less, particularly 6% or less.

The preferred content of Li ₂ O + Na ₂ O + K ₂ O is 10-25%, 13-22%, 15-20%, 16-20%, 16.5-20%, especially 18-20%. When _{Li 2 O + Na 2 O +} K content of ₂ O is too small, the ion exchange performance and meltability is liable to decrease. On the other _hand, when the content of _{Li 2 O + Na 2 O +} K 2 O is too large, the deterioration coefficient D becomes too large. Further, in addition to the glass being easily devitrified, the thermal expansion coefficient becomes too high, and the thermal shock resistance is lowered or it is difficult to match the thermal expansion coefficient of the surrounding material. In addition, the strain point may be excessively lowered, making it difficult to obtain a high compressive stress value. Furthermore, the viscosity near the liquidus temperature may decrease, making it difficult to ensure a high liquidus viscosity. “Li ₂ O + Na ₂ O + K ₂ O” is the total amount of Li ₂ O, Na ₂ O, and K ₂ O.

In the glass composition system according to the present embodiment, a factor that the content of Li ₂ O + Na ₂ O + K ₂ O affects the deterioration coefficient D will be described. In this embodiment, since the content of Li ₂ O is suppressed to 4% or less, a compressive stress layer is formed on the glass surface mainly by ion exchange of Na ions and K ions. When the content of Li ₂ O + Na ₂ O + K ₂ O decreases, the content of components to be ion-exchanged decreases, so the compressive stress value decreases, but conversely, the content of Li ₂ O + Na ₂ O + K ₂ O is too large. And, the ion exchange between Na ions and K ions (formation of compressive stress layer) is promoted, and at the same time, the ion exchange between Li ions and Na ions contained in KNO ₃ is more than the ion exchange between Na ions and K ions. Priority is likely to occur. When ion exchange between Li ions and Na ions occurs, tensile stress is formed, and it is considered that the compressive stress value decreases.

The preferred range of molar ratio (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is 1-3. If the molar ratio (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is too large, the strain point is lowered, and the ion exchange performance tends to be lowered. Permeability tends to decrease. Further, there is a possibility that the deterioration coefficient D becomes large. However, when the molar ratio _{(Li 2 O + Na 2 O} + K 2 O) / Al 2 O 3 is too small, the viscosity of the glass becomes too high, or decreases bubble quality, lack component balance of the glass composition, denitrification Permeability tends to decrease. The preferred lower limit range of the molar ratio (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is 1 or more, 1.2 or more, 1.4 or more, 1.5 or more, 1.7 or more, particularly 1.8 or more. The preferable upper limit range of the molar ratio (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is 3 or less, 2.8 or less, 2.6 or less, 2.5 or less, particularly 2.3 or less. . When importance is attached to the degradation coefficient D, the preferred lower limit range of the molar ratio (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is 1 or more, particularly 1.2 or more, and the molar ratio (Li ₂ O + Na ₂ O + K). ₂ O) / preferred upper range of _Al 2 _{O 3} is 3 or less, 2.5 or less, 2 or less, 1.8 or less, 1.5 or less, especially 1.4 or less. Further, the preferable range of the molar ratio (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is 1 to 3, 1.2 to 3, particularly 1.2 to 2.5. When the molar ratio (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ and the molar ratio Na ₂ O / Al ₂ O ₃ are regulated within the above ranges, the devitrification resistance and the degradation coefficient D can be remarkably improved. .

Suitable ranges for the molar ratio K ₂ O / Na ₂ O are 0.1 to 0.8, 0.2 to 0.8, 0.2 to 0.5, in particular 0.2 to 0.4. When the molar ratio K ₂ O / Na ₂ O decreases, the thickness of the compressive stress layer tends to decrease, and when the molar ratio K ₂ O / Na ₂ O increases, the compressive stress value decreases or the glass composition component balance is reduced. The lack of glass makes it easy to devitrify the glass.

MgO is a component that lowers the viscosity at high temperature, increases meltability and moldability, and increases the strain point and Young's modulus. Among alkaline earth metal oxides, MgO is a component that has a large effect of improving ion exchange performance. is there. Therefore, the content of MgO is 0.5% or more, and a preferable lower limit range is 1% or more, 1.5 or more, 2% or more, 3% or more, 5% or more, particularly 6% or more. However, when there is too much content of MgO, a density and a thermal expansion coefficient will become high and there exists a tendency for glass to devitrify easily. Therefore, the content of MgO is 13% or less, and a preferable upper limit range is 12% or less, 11% or less, 9% or less, 8% or less, 7% or less, particularly 6.5% or less.

When the molar ratio MgO / (MgO + Al ₂ O ₃ ) decreases, the ion exchange performance and Young's modulus are likely to decrease. Further, the degradation coefficient D tends to increase. A suitable lower limit range of the molar ratio MgO / (MgO + Al ₂ O ₃ ) is 0.05 or more, 0.1 or more, 0.15 or more, 0.2 or more, 0.25 or more, particularly 0.3 or more. On the other hand, when the molar ratio MgO / (MgO + Al ₂ O ₃ ) increases, the devitrification resistance decreases, the density increases, and the thermal expansion coefficient becomes too high. The preferable upper limit range of the molar ratio MgO / (MgO + Al ₂ O ₃ ) is 0.95 or less, 0.9 or less, 0.85 or less, 0.8 or less, 0.7 or less, 0.6 or less, particularly 0.5. It is as follows. “MgO + Al ₂ O ₃ ” is the total amount of MgO and Al ₂ O ₃ .

CaO, compared with other components, has a great effect of lowering the high-temperature viscosity without increasing devitrification resistance, improving meltability and moldability, and increasing the strain point and Young's modulus. The content of CaO is 0 to 6%. However, if the content of CaO is too large, the density and thermal expansion coefficient become high, and the balance of the composition of the glass composition is lacking. On the contrary, the glass is liable to devitrify, the ion exchange performance is lowered, and the deterioration coefficient. D tends to increase. Therefore, the preferred content of CaO is 0-5%, 0-4%, 0-3.5%, 0-3%, 0-2%, especially 0-1%.

After limiting the MgO content to the above range, the molar ratio MgO / (MgO + CaO) is 0.5 or more, 0.55 or more, 0.6 or more, 0.7 or more, 0.8 or more, particularly 0.9. It is preferable to restrict to the above. When the molar ratio MgO / (MgO + CaO) decreases, the deterioration coefficient D tends to increase and the ion exchange performance tends to decrease. In addition, when the MgO content is outside the above range, the effect of regulating the molar ratio MgO / (MgO + CaO) in addition to the lack of the component balance of the glass composition, which tends to decrease the devitrification resistance. It becomes difficult to enjoy. “MgO + CaO” is the total amount of MgO and CaO.

SrO is a component that lowers the high-temperature viscosity to improve meltability and moldability, and increase the strain point and Young's modulus. The SrO content is 0 to 6%. When there is too much content of SrO, in addition to becoming easy to inhibit an ion exchange reaction, a density and a thermal expansion coefficient will become high, or it will become easy to devitrify glass. The preferred content of SrO is 0 to 4.5%, 0 to 3%, 0 to 2%, 0 to 1.5%, 0 to 1%, 0 to 0.5%, especially 0 to 0.1%. It is.

The tempered glass of this embodiment does not substantially contain As ₂ O ₃ , Sb ₂ O ₃ , PbO, and F as a glass composition from the environmental consideration.

In addition to the above components, for example, the following components may be added.

BaO is a component that lowers the high-temperature viscosity to increase meltability and moldability, and increases the strain point and Young's modulus. When the content of BaO is too large, the ion exchange reaction is likely to be inhibited, and in addition, the density and the thermal expansion coefficient are increased, and the glass is easily devitrified. The preferred content of BaO is 0-6%, 0-3%, 0-1.5%, 0-1%, 0-0.5%, especially 0-0.1%.

If the content of SrO + BaO is regulated, the ion exchange performance can be remarkably enhanced. The preferred content of SrO + BaO is 0-6%, 0-3%, 0-2.5%, 0-2%, 0-1%, especially 0-0.2%. “SrO + BaO” is the total amount of SrO and BaO.

Preferred ranges of molar ratio (CaO + SrO + BaO) / MgO are 0-1, 0-0.9, 0-0.8, 0-0.75, especially 0-0.5. When the molar ratio (CaO + SrO + BaO) / MgO increases, the devitrification resistance decreases, the ion exchange performance decreases, the deterioration coefficient D increases, and the density and thermal expansion coefficient increase too much. “CaO + SrO + BaO” is the total amount of CaO, SrO and BaO.

The content of MgO + CaO + SrO + BaO is preferably 0.5 to 10%, 0.5 to 8%, 0.5 to 7%, 0.5 to 6%, particularly preferably 0.5 to 4%. When there is too little content of MgO + CaO + SrO + BaO, it will become difficult to improve a meltability and a moldability. On the other hand, if the content of MgO + CaO + SrO + BaO is too large, the density and thermal expansion coefficient increase and the devitrification resistance tends to decrease, and the ion exchange performance tends to decrease. “MgO + CaO + SrO + BaO” is the total amount of MgO, CaO, SrO, and BaO.

The mass ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is preferably 0.5 or less, 0.3 or less, particularly preferably 0.2 or less. When the mass ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) increases, the tendency of devitrification resistance to decrease appears.

TiO ₂ is a component that enhances ion exchange performance and a component that lowers the high-temperature viscosity. However, if its content is too large, the glass tends to be colored or devitrified. Therefore, the content of TiO ₂ is preferably 0 to 3%, 0 to 1%, 0 to 0.8%, 0 to 0.5%, particularly preferably 0 to 0.1%.

ZrO ₂ is a component that remarkably improves the ion exchange performance, and is a component that increases the viscosity and strain point near the liquid phase viscosity. However, if its content is too large, the devitrification resistance may be significantly reduced. There is also a possibility that the density becomes too high. Therefore, a suitable upper limit range of ZrO ₂ is 10% or less, 8% or less, 6% or less, 4% or less, 3% or less, particularly 1% or less. In addition, when it is desired to improve the ion exchange performance, a preferable lower limit range of ZrO ₂ is 0.01% or more, 0.1% or more, 0.5% or more, 1% or more, particularly 2% or more.

ZnO is a component that enhances ion exchange performance, and is a component that is particularly effective in increasing the compressive stress value. Moreover, it is a component which reduces high temperature viscosity, without reducing low temperature viscosity. However, when the content of ZnO is too large, the glass tends to undergo phase separation, the devitrification resistance decreases, the density increases, or the thickness of the compressive stress layer decreases. Therefore, the content of ZnO is preferably 0 to 6%, 0 to 5%, 0 to 3%, particularly preferably 0 to 1%.

P ₂ O ₅ is a component that enhances ion exchange performance, and in particular, a component that increases the thickness of the compressive stress layer. However, when the content of P ₂ O ₅ is too large, or glass phase separation, the water resistance tends to decrease. Therefore, the content of P ₂ O ₅ is preferably 0 to 10%, 0 to 3%, 0 to 1%, particularly preferably 0 to 0.5%.

As a fining agent, one or two or more selected from the group of CeO ₂ , SnO ₂ , Cl, and SO ₃ (preferably a group of SnO ₂ , Cl, and SO ₃ ) may be added in an amount of 0 to 3%. The content of SnO ₂ + SO ₃ + Cl is preferably 0 to 1%, 0.001 to 1%, 0.01 to 0.5%, particularly preferably 0.03 to 0.2%. “SnO ₂ + SO ₃ + Cl” is the total amount of SnO ₂ , Cl, and SO ₃ .

SnO ₂ has an effect of improving ion exchange performance in addition to the clarification effect. Therefore, the addition of SnO _2, it is possible to receive the effect of increasing the clarifying effect and ion exchange performance simultaneously. The SnO ₂ content is preferably 0 to 3%, 0.01 to 3%, 0.01 to 3%, particularly preferably 0.1 to 1%. On the other hand, when SnO ₂ is added, the glass may be colored. Therefore, when it is necessary to obtain a clarification effect while suppressing the coloring of the glass, it is preferable to add SO ₃ . The content of SO ₃ is 0-3%, in particular 0.001 to 3% is preferred. When SnO ₂ and SO ₃ coexist, coloring can be suppressed while improving ion exchange performance.

The Fe ₂ O ₃ content is preferably less than 1000 ppm (less than 0.1%), less than 800 ppm, less than 600 ppm, less than 400 ppm, and particularly preferably less than 300 ppm. Further, the Fe ₂ O ₃ content is regulated within the above range, and the molar ratio Fe ₂ O ₃ / (Fe ₂ O ₃ + SnO ₂ ) is regulated to 0.8 or more, 0.9 or more, particularly 0.95 or more. It is preferable to do. In this way, the transmittance (400 nm to 770 nm) of glass at a plate thickness of 1 mm can be easily improved (for example, 90% or more).

Rare earth oxides such as Nb ₂ O ₅ and La ₂ O ₃ are components that increase the Young's modulus. However, the cost of the raw material itself is high, and when it is added in a large amount, the devitrification resistance tends to be lowered. Therefore, the rare earth oxide content is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly preferably 0.1% or less.

Transition metal elements (Co, Ni, etc.) that strongly color the glass may reduce the transmittance of the glass. In particular, when used for a touch panel display, if the content of the transition metal element is too large, the visibility of the touch panel display tends to be lowered. Therefore, it is preferable to select the glass raw material (including cullet) so that the content of the transition metal oxide is 0.5% or less, 0.1% or less, particularly 0.05% or less.

The tempered glass of this embodiment preferably contains substantially no Bi ₂ O ₃ from the environmental consideration. By "substantially free of Bi ₂ O _3", but not added actively Bi ₂ O ₃ as a glass component, a purpose to allow the case to be mixed as an impurity, specifically, Bi ₂ O _It indicates that the content of ₃ is less than 0.05 mol%.

In the tempered glass of the present embodiment, it is possible to appropriately select a suitable content range of each component to obtain a suitable glass composition range. Among them, particularly preferable glass composition ranges are as follows.
(1) As a glass composition, in mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 4 to 12%, B ₂ O ₃ 0 to 1%, Li ₂ O 0 to 1%, Na ₂ O 10 to 17 %, K ₂ O 2-7%, MgO 1.5-12%, CaO 0-3%, SrO 0-1%, TiO ₂ 0-0.5%, and the molar ratio MgO / (MgO + CaO) is 0.5-1
(2) As a glass composition, mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 4 to 12%, B ₂ O ₃ 0 to 1%, Li ₂ O 0 to 1%, Na ₂ O 10 to 17 %, K ₂ O 2-7%, MgO 1.5-12%, CaO 0-3%, SrO 0-1%, TiO ₂ 0-0.5%, and the molar ratio MgO / (MgO + CaO) is 0.5 to 1, molar ratio MgO / (MgO + Al ₂ O ₃ ) is 0.2 to 0.85, molar ratio (CaO + SrO + BaO) / MgO is 0 to 0.85,
(3) As a glass composition, SiO ₂ 55 to 69%, Al ₂ O ₃ 4 to 11%, B ₂ O ₃ 0 to 1%, Li ₂ O 0 to 1%, Na ₂ O 11 to 16 in mol% %, K ₂ O 2-7%, MgO 3-9%, CaO 0-3%, SrO 0-1%, ZrO ₂ 1-9%, TiO ₂ 0-0.1%, molar ratio MgO / (MgO + CaO) is 0.5 to 1,
(4) As a glass composition, SiO ₂ 55 to 69%, Al ₂ O ₃ 4 to 11%, B ₂ O ₃ 0 to 1%, Li ₂ O 0 to 1%, Na ₂ O 11 to 16 in mol% %, K ₂ O 2-7%, MgO 3-9%, CaO 0-3%, SrO 0-1%, ZrO ₂ 1-9%, TiO ₂ 0-0.1%, molar ratio MgO / (MgO + CaO) is 0.5 to 1, molar ratio MgO / (MgO + Al ₂ O ₃ ) is 0.25 to 0.8, molar ratio (CaO + SrO + BaO) / MgO is 0 to 0.75,
(5) As a glass composition, mol%, SiO ₂ 58 to 67%, Al ₂ O ₃ 4 to 11%, B ₂ O ₃ 0 to 0.5%, Li ₂ O 0 to 0.5%, Na ₂ O 11-16%, K ₂ O 2-6%, MgO 3-6.5%, CaO 0-3%, SrO 0-0.5%, ZrO ₂ 2-6%, TiO ₂ 0-0.1 The molar ratio MgO / (MgO + CaO) is 0.5 to 1, the molar ratio MgO / (MgO + Al ₂ O ₃ ) is 0.25 to 0.8, and the molar ratio (CaO + SrO + BaO) / MgO is 0 to 0.00. 75,
(6) As a glass composition, mol%, SiO ₂ 58 to 67%, Al ₂ O ₃ 7 to 11%, B ₂ O ₃ 0 to 0.5%, Li ₂ O 0 to 0.5%, Na ₂ O 11-16%, K ₂ O 2-6%, MgO 3-6.5%, CaO 0-3%, SrO 0-0.5%, ZrO ₂ 2-6%, TiO ₂ 0-0.1 The molar ratio MgO / (MgO + CaO) is 0.5 to 1, the molar ratio MgO / (MgO + Al ₂ O ₃ ) is 0.25 to 0.8, and the molar ratio (CaO + SrO + BaO) / MgO is 0 to 0.00. 75.

Furthermore, when it is desired to obtain high ion exchange performance after reducing the density, the following glass composition ranges are preferable.
(7) As a glass composition, mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 10 to 13%, B ₂ O ₃ 0 to 1.5%, Li ₂ O 0 to 2%, Na ₂ O 12 Containing 20%, K ₂ O 0.5-9%, MgO 3-12%, CaO 0-6%, SrO 0-6%,
(8) As a glass composition, mol%, SiO ₂ 55 to 75%, Al ₂ O ₃ 10 to 13%, B ₂ O ₃ 0 to 1.5%, Li ₂ O 0 to 2%, Na ₂ O 13 -20%, K ₂ O 1-8%, MgO 6-12%, CaO 0-6%, SrO 0-6%, ZrO ₂ 0-1%, and the molar ratio MgO / (MgO + CaO) is 0. 5 to 1, molar ratio MgO / (MgO + Al ₂ O ₃ ) is 0.1 to 0.9, molar ratio (CaO + SrO + BaO) / MgO is 0 to 0.75,
(9) As a glass composition, mol%, SiO ₂ 55 to 75%, Al ₂ O ₃ 10 to 13%, B ₂ O ₃ 0 to 1.5%, Li ₂ O 0 to 2%, Na ₂ O 13 -20%, K ₂ O 1-8%, MgO 6-12%, CaO 0-6%, SrO 0-6%, ZrO ₂ 0-1%, and the molar ratio MgO / (MgO + CaO) is 0. 7 to 1, molar ratio MgO / (MgO + Al ₂ O ₃ ) is 0.25 to 0.6, molar ratio (CaO + SrO + BaO) / MgO is 0 to 0.5,
(10) As a glass composition, mol%, SiO ₂ 55 to 75%, Al ₂ O ₃ 10 to 13%, B ₂ O ₃ 0 to 1%, Li ₂ O 0 to 2%, Na ₂ O 13 to 20 %, K ₂ O 1-8%, MgO 6-12%, CaO 0-6%, SrO 0-6%, ZrO ₂ 0-1%, and a molar ratio MgO / (MgO + CaO) of 0.7- 1, molar ratio MgO / (MgO + Al ₂ O ₃ ) is 0.25 to 0.6, molar ratio (CaO + SrO + BaO) / MgO is 0 to 0.5,
(11) as a glass composition, in _{mol%, SiO 2 55 ~ 70%} , Al 2 O 3 10 ~ 13%, B 2 O 3 0 ~ 0.1%, Li 2 O 0 ~ 0.2%, Na 2 O 13-13%, K ₂ O 1-8%, MgO 6-12%, CaO 0-6%, SrO 0-6%, ZrO ₂ 0-1%, molar ratio MgO / (MgO + CaO) 0.7 to 1, the molar ratio MgO / (MgO + Al ₂ O ₃ ) is 0.25 to 0.6, and the molar ratio (CaO + SrO + BaO) / MgO is 0 to 0.5.

For example, the tempered glass of the present embodiment preferably has the following characteristics.

The tempered glass of this embodiment has a compressive stress layer on the surface. The compressive stress value of the compressive stress layer is preferably 300 MPa or more, 400 MPa or more, 500 MPa or more, 600 MPa or more, particularly 900 MPa or more. The greater the compressive stress value, the higher the mechanical strength of the tempered glass. On the other hand, when an extremely large compressive stress is formed on the surface, microcracks may be generated on the surface, which may reduce the mechanical strength of the tempered glass. Moreover, there exists a possibility that the tensile stress inherent in tempered glass may become extremely high. For this reason, the compressive stress value of the compressive stress layer is preferably 2000 MPa or less. If the content of Al ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO, ZnO in the glass composition is increased or the content of SrO, BaO is decreased, the compressive stress value tends to increase. Further, if the ion exchange time is shortened or the temperature of the ion exchange solution is lowered, the compressive stress value tends to increase.

The thickness of the compressive stress layer is preferably 10 μm or more, 15 μm or more, 20 μm or more, 30 μm or more, particularly 40 μm or more. As the thickness of the compressive stress layer increases, even if the tempered glass is deeply scratched, the tempered glass becomes difficult to break and the variation in mechanical strength becomes smaller. On the other hand, the larger the compressive stress layer is, the more difficult it is to cut the tempered glass. For this reason, the thickness of the compressive stress layer is preferably 500 μm or less. If the content of K ₂ O or P ₂ O _{5 in} the glass composition is increased or the content of SrO or BaO is decreased, the thickness of the compressive stress layer tends to increase. Moreover, if the ion exchange time is lengthened or the temperature of the ion exchange solution is increased, the thickness of the compressive stress layer tends to increase.

The tempered glass of the present embodiment, the density is 2.6 g / cm ³ or less, 2.55 g / cm ³ or less, 2.50 g / cm ³ or less, particularly preferably 2.48 g / cm ³ or less. The smaller the density, the lighter the tempered glass. In addition, the content of SiO ₂ , B ₂ O ₃ , P ₂ O _{5 in} the glass composition is increased, or the content of alkali metal oxide, alkaline earth metal oxide, ZnO, ZrO ₂ , TiO ₂ is decreased. As a result, the density tends to decrease.

In the tempered glass of this embodiment, the thermal expansion coefficient in the temperature range of 30 to 380 ° C. is 80 to 120 × 10 ⁻⁷ / ° C., 85 to 110 × 10 ⁻⁷ / ° C., 90 to 110 × 10 ⁻⁷ / ° C., In particular, 90 to 105 × 10 ⁻⁷ / ° C. is preferable. If the thermal expansion coefficient is regulated within the above range, it becomes easy to match the thermal expansion coefficient of a member such as a metal or an organic adhesive, and it becomes easy to prevent peeling of a member such as a metal or an organic adhesive. Here, “thermal expansion coefficient in a temperature range of 30 to 380 ° C.” refers to a value obtained by measuring an average thermal expansion coefficient using a dilatometer. If the content of alkali metal oxides and alkaline earth metal oxides in the glass composition is increased, the coefficient of thermal expansion tends to increase, and conversely the content of alkali metal oxides and alkaline earth metal oxides is reduced. If it decreases, the thermal expansion coefficient tends to decrease.

In the tempered glass of the present embodiment, the strain point is preferably 500 ° C. or higher, 520 ° C. or higher, 530 ° C. or higher, particularly 540 ° C. or higher. The higher the strain point, the better the heat resistance. When heat-treating tempered glass, the compressive stress layer is less likely to disappear. In addition, the higher the strain point, the less the stress relaxation occurs during the ion exchange treatment, and the easier it is to maintain the compressive stress value. If the content of alkaline earth metal oxide, Al ₂ O ₃ , ZrO ₂ , P ₂ O _{5 in} the glass composition is increased or the content of alkali metal oxide is reduced, the strain point becomes higher. easy.

In the tempered glass of the present embodiment, the temperature at 10 ^4.0 dPa · s is preferably 1250 ° C. or lower, 1230 ° C. or lower, 1200 ° C. or lower, 1180 ° C. or lower, particularly 1160 ° C. or lower. The lower the temperature at 10 ^4.0 dPa · s, the less the burden on the forming equipment, the longer the life of the forming equipment, and as a result, the manufacturing cost of tempered glass is likely to be reduced. If the content of alkali metal oxide, alkaline earth metal oxide, ZnO, B ₂ O ₃ , TiO ₂ is increased or the content of SiO ₂ , Al ₂ O ₃ is decreased, 10 ^4.0 dPa · The temperature at s tends to decrease.

In the tempered glass of the present embodiment, the temperature at 10 ^2.5 dPa · s is preferably 1600 ° C. or lower, 1550 ° C. or lower, 1530 ° C. or lower, 1500 ° C. or lower, particularly 1450 ° C. or lower. The lower the temperature at 10 ^2.5 dPa · s, the lower the temperature melting becomes possible, and the burden on glass production equipment such as a melting kiln is reduced, and the bubble quality is easily improved. That is, the lower the temperature at 10 ^2.5 dPa · s, the easier it is to reduce the manufacturing cost of tempered glass. The temperature at 10 ^2.5 dPa · s corresponds to the melting temperature. Also, if the content of alkali metal oxide, alkaline earth metal oxide, ZnO, B ₂ O ₃ , TiO _{2 in} the glass composition is increased or the content of SiO ₂ , Al ₂ O ₃ is reduced, The temperature at 10 ^2.5 dPa · s tends to decrease.

In the tempered glass of the present embodiment, the liquidus temperature is preferably 1075 ° C. or lower, 1050 ° C. or lower, 1030 ° C. or lower, 1010 ° C. or lower, 1000 ° C. or lower, 950 ° C. or lower, 900 ° C. or lower, particularly 870 ° C. or lower. In addition, devitrification resistance and a moldability improve, so that liquidus temperature is low. Also, increase the content of Na ₂ O, K ₂ O, B ₂ O _{3 in} the glass composition or reduce the content of Al ₂ O ₃ , Li ₂ O, MgO, ZnO, TiO ₂ , ZrO _2. In this case, the liquidus temperature tends to decrease.

In the tempered glass of this embodiment, the liquid phase viscosity is 10 ^4.0 dPa · s or more, 10 ^4.4 dPa · s or more, 10 ^4.8 dPa · s or more, 10 ^5.0 dPa · s or more, 10 ^{5 3} dPa · s or more, 10 ^5.5 dPa · s or more, 10 ^5.7 dPa · s or more, 10 ^5.8 dPa · s or more, and particularly preferably 10 ^6.0 dPa · s or more. In addition, devitrification resistance and a moldability improve, so that liquid phase viscosity is high. Also, if the content of Na ₂ O, K ₂ O in the glass composition is increased or the content of Al ₂ O ₃ , Li ₂ O, MgO, ZnO, TiO ₂ , ZrO ₂ is reduced, the liquidus viscosity Tends to be high.

In the tempered glass of the present embodiment, the Young's modulus is preferably 65 GPa or more, 69 GPa or more, 71 GPa or more, 75 GPa or more, particularly 77 GPa or more. The higher the Young's modulus, the harder the tempered glass bends. When used for a touch panel display, etc., even if the surface of the tempered glass is strongly pressed with a pen or the like, the amount of deformation of the tempered glass is reduced, and as a result, the liquid crystal element located on the back surface It becomes easy to prevent a situation in which a display defect occurs due to contact with.

In the tempered glass of the present embodiment, the deterioration coefficient D is preferably 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, 0.1 or less, particularly 0.05 or less. The smaller the degradation coefficient D, the lower the compression stress value obtained even when ion exchange treatment is performed in an aged KNO ₃ molten salt. As a result, the production cost of tempered glass can be easily reduced.

The tempered glass plate according to the embodiment of the present invention is characterized by comprising the tempered glass of the above-described embodiment. Therefore, the technical characteristics and suitable range of the tempered glass sheet of the present embodiment are the same as the technical characteristics of the tempered glass of the present embodiment. Here, the description is omitted for convenience.

In the tempered glass plate of the present embodiment, the difference ΔCS of the compressive stress values of the compressive stress layers on the opposing surfaces is preferably 50 MPa or less, 30 MPa or less, 20 MPa or less, 10 MPa or less, particularly 5 MPa or less. When ΔCS becomes large, the tempered glass plate is likely to warp after the ion exchange treatment of the large glass plate. In order to make ΔCS within the above range, it is preferable to polish the opposite surfaces of the glass plate by 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, 1 μm or more, 3 μm or more, particularly 5 μm or more. .

In the tempered glass plate of the present embodiment, the average surface roughness (Ra) of the surface is preferably 10 mm or less, 8 mm or less, 6 mm or less, 4 mm or less, 3 mm or less, particularly 2 mm or less. There exists a tendency for the mechanical strength of a tempered glass board to fall, so that average surface roughness (Ra) is large. Here, the average surface roughness (Ra) refers to a value measured by a method based on SEMI D7-97 “Measurement method of surface roughness of FPD glass substrate”.

In the tempered glass plate of this embodiment, the length is preferably 500 mm or more, 700 mm or more, particularly 1000 mm or more, and the width is preferably 500 mm or more, 700 mm or more, particularly 1000 mm or more. When the tempered glass plate is enlarged, it can be suitably used as a cover glass for a display unit of a large TV or the like.

In the tempered glass plate of this embodiment, the plate thickness is 3.0 mm or less, 2.0 mm or less, 1.5 mm or less, 1.3 mm or less, 1.1 mm or less, 1.0 mm or less, 0.8 mm or less, 7 mm or less is preferable. On the other hand, if the plate thickness is too thin, it is difficult to obtain a desired mechanical strength. Therefore, the plate thickness is preferably 0.1 mm or more, 0.2 mm or more, 0.3 mm or more, 0.4 mm or more, particularly 0.5 mm or more.

The tempered glass according to the embodiment of the present invention is a tempered glass subjected to an ion exchange treatment, and has a glass composition of mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 3 to 13%, B ₂ O ₃ 0 to 1.5%, Li ₂ O 0 to 4%, Na ₂ O 7 to 20%, K ₂ O 0.5 to 10%, MgO 0.5 to 13%, CaO 0 to 6% , SrO 0 to 4.5%, and substantially free of As ₂ O ₃ , Sb ₂ O ₃ , PbO, and F. The technical features of the tempered glass of the present embodiment are the same as the technical features of the tempered glass and tempered glass plate of the present embodiment. Here, the description is omitted for convenience.

When the glass for strengthening of this embodiment is ion-exchanged in KNO ₃ molten salt at 430 ° C., the compressive stress value of the surface compressive stress layer may be 300 MPa or more and the thickness of the compressive stress layer may be 10 μm or more. Preferably, the surface compressive stress is 600 MPa or more and the thickness of the compressive stress layer is 50 μm or more, and the surface compressive stress is 700 MPa or more and the thickness of the compressive stress layer is preferably 50 μm or more.

In the ion exchange treatment, the temperature of the KNO ₃ molten salt is preferably 360 to 550 ° C., and the ion exchange time is preferably 2 to 10 hours, particularly 4 to 8 hours. If it does in this way, it will become easy to form a compressive stress layer appropriately. Incidentally, the reinforcing glass of the present embodiment has a glass composition described above, without using a mixture of KNO ₃ molten salt and NaNO ₃ molten salt, to increase the compressive stress value and thickness of the compression stress layer It becomes possible. Further, even when a deteriorated KNO ₃ molten salt is used, the compressive stress value and thickness of the compressive stress layer are not extremely reduced.

In the tempered glass plate of the present embodiment, the maximum value Fmax of the residual stress in the plane direction with respect to the entire plane portion of the glass plate is preferably 5 MPa or less, 3 MPa or less, 1 MPa or less, 0.5 MPa or less, particularly preferably 0.1 MPa or less. When the maximum value Fmax of the residual stress is large, the warp of the tempered glass plate may increase when the large glass plate is tempered.

Reinforcing glass plate of the present embodiment, _SiO 2, TiO ₂ on the surface, NESA, ITO, it is preferable formed by forming a film of the AR and the like. If it does in this way, even if it does not grind | polish, the curvature of a tempered glass board can be reduced. Examples of the film forming method include CVD, sputtering, and spin coating. When the film is formed by sputtering, the film thickness is preferably 1 nm or more, 5 nm or more, 10 nm or more, 30 nm or more, particularly 50 nm or more. On the other hand, if the film thickness is too thick, the compressive stress value of the compressive stress layer on the film surface may be too low. Therefore, a preferable upper limit range of the film thickness is 1000 nm or less, 800 nm or less, 500 nm or less, and particularly 300 nm or less. Note that it is preferable to form a film in a portion where warpage is likely to occur after the strengthening treatment. The tempered glass plate of the present embodiment is preferably formed by forming a film of SiO ₂ , TiO ₂ , Nesa, ITO, AR, etc. on the surface before the tempering treatment.

As described below, the tempering glass, tempered glass, and tempered glass plate of this embodiment can be produced.

First, the glass raw material prepared so as to have the above glass composition is put into a continuous melting furnace, heated and melted at 1500 to 1600 ° C., clarified, fed into a molding apparatus, shaped into a plate shape, etc. By cooling, a plate-like glass can be produced.

It is preferable to employ a float method as a method of forming into a plate shape. The float method is a method that can produce a glass plate in a large amount at a low cost, and is a method that can easily produce a large glass plate.

Other than the float method, various molding methods can be employed. For example, an overflow downdraw method, a downdraw method (slot down method, redraw method, etc.), a rollout method, a press method, or the like can be employed.

Next, tempered glass can be produced by tempering the obtained glass. The time when the tempered glass is cut into a predetermined dimension may be before the tempering treatment, but it is advantageous from the viewpoint of cost to carry out after the tempering treatment.

As the reinforcing treatment, an ion exchange treatment is preferable. The conditions for the ion exchange treatment are not particularly limited, and the optimum conditions may be selected in consideration of the viscosity characteristics, application, thickness, internal tensile stress, and the like of the glass. For example, the ion exchange treatment can be performed by immersing the glass in KNO ₃ molten salt at 400 to 550 ° C. for 1 to 8 hours. In particular, when K ions in the KNO ₃ molten salt are ion-exchanged with Na components in the glass, a compressive stress layer can be efficiently formed on the surface of the glass.

Hereinafter, examples of the present invention will be described. The following examples are merely illustrative. The present invention is not limited to the following examples.

Tables 1 to 5 show examples of the present invention (sample Nos. 1 to 24). In the table, “not yet” means unmeasured.

Each sample in the table was prepared as follows. First, glass raw materials were prepared so as to have the glass composition in the table, and were melted at 1580 ° C. for 8 hours using a platinum pot. Thereafter, the obtained molten glass was poured out on a carbon plate and formed into a plate shape. Various characteristics were evaluated about the obtained glass plate.

The density ρ is a value measured by the well-known Archimedes method.

The thermal expansion coefficient α is a value obtained by measuring an average thermal expansion coefficient in a temperature range of 30 to 380 ° C. using a dilatometer.

The strain point Ps and the annealing point Ta are values measured based on the method of ASTM C336.

The softening point Ts is a value measured based on the method of ASTM C338.

The temperature at a high temperature viscosity of 10 ^4.0 dPa · s, 10 ^3.0 dPa · s, and 10 ^2.5 dPa · s is a value measured by a platinum ball pulling method.

The liquid phase temperature TL passes through a standard sieve 30 mesh (a sieve opening of 500 μm), and glass powder remaining in a 50 mesh (a sieve opening of 300 μm) is put in a platinum boat, and then held in a temperature gradient furnace for 24 hours. This is a value obtained by measuring the temperature at which crystals are deposited.

Liquid phase viscosity is a value obtained by measuring the viscosity of glass at the liquid phase temperature by a platinum ball pulling method.

As is clear from Tables 1 to 5, sample No. Nos. 1 to 24 had a density of 2.54 g / cm ³ or less and a thermal expansion coefficient of 87 to 107 × 10 ⁻⁷ / ° C., and were suitable as a tempered glass material, that is, a tempered glass. Further, since the liquid phase viscosity is 10 ^4.5 dPa · s or more, it can be formed into a plate shape by a float process, and the temperature at 10 ^2.5 dPa · s is 1622 ° C. or less, so that productivity is high. It is considered that a large amount of glass plates can be produced at low cost. In addition, although the glass composition in the surface layer of glass differs microscopically before and after the tempering treatment, the glass composition is not substantially different when viewed as the whole glass.

Next, after both surfaces of each sample were subjected to optical polishing, ion exchange treatment was performed by immersing in KNO ₃ molten salt (new KNO ₃ molten salt) at 440 ° C. for 6 hours. The surface of each sample was washed after the ion exchange treatment. Subsequently, the compressive stress value and thickness of the compressive stress layer on the surface were calculated from the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation) and the distance between the interference fringes. In the calculation, the refractive index of each sample was 1.52, and the optical elastic constant was 28 [(nm / cm) / MPa].

The deterioration coefficient D was calculated as follows. First, SiO ₂ 58.7 mass%, Al ₂ O ₃ 12.8 mass%, Li ₂ O 0.1 mass%, Na ₂ O 14.0 mass%, K ₂ O 6.3 mass%, MgO 2.0 A glass having a glass composition of mass%, CaO 2.0 mass%, and ZrO ₂ 4.1 mass% was produced. Next, this glass was pulverized, and glass powder that passed through a sieve opening of 300 μm and did not pass through a sieve opening of 150 μm was collected to obtain a glass powder having an average particle diameter of 225 μm. Subsequently, the glass powder was immersed in 400 ml of KNO ₃ maintained at 440 ° C. for 60 hours (the jar was shaken up and down 10 times every 24 hours) to simulate the deteriorated KNO ₃ molten salt. Incidentally, Na ₂ O contained in the deterioration KNO ₃ molten salt prepared in this condition was 1000 ppm (mol) or more.

Ion exchange treatment was performed by immersing each sample in a deteriorated KNO ₃ molten salt produced under these conditions at 440 ° C. for 6 hours. Thereafter, the compressive stress value and thickness of the compressive stress layer on the surface were determined in the same manner as described above. From the compression stress values thus obtained (new KNO ₃ molten salt, deteriorated KNO ₃ molten salt), the deterioration coefficient D = (compressive stress value (new KNO ₃ molten salt) −compressive stress value (deteriorated KNO ₃ molten salt). )) / Compressive stress value (new KNO ₃ molten salt) was calculated.

As is clear from Tables 1 to 5, sample No. When 1 to 24 were ion-exchanged with new KNO ₃ molten salt, the compressive stress value of the compressive stress layer on the surface was 730 MPa or more and the thickness was 43 μm or more. Further, when ion exchange treatment was performed with the deteriorated KNO ₃ molten salt, the compressive stress value of the compressive stress layer on the surface was 625 MPa or more, the thickness was 43 μm or more, and the deterioration coefficient D was 0.22 or less.

Sample No. After preparing the glass raw material so that it might become the glass composition of 1, it melt | dissolved the obtained glass batch, Then, the glass plate was shape | molded by the float glass process. Next, ion exchange treatment was performed by immersing the obtained glass plate in KNO ₃ molten salt (new KNO ₃ molten salt) at 440 ° C. for 6 hours. Subsequently, for the glass plate, the compression stress value and thickness of the compression stress layer on the surface were calculated from the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation) and the interval between the interference fringes. Further, after polishing both surfaces of the glass plate by 0.2 μm, the compressive stress value of the compressive stress layer on the surface is determined from the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation) and the distance between them. And the thickness was calculated. Further, after polishing both surfaces of the glass plate by 10 μm, the compressive stress value and thickness of the compressive stress layer on the surface are determined from the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation) and the distance between them. Was calculated. In the calculation, the refractive index of the glass plate was 1.52, and the optical elastic constant was 28 [(nm / cm) / MPa]. As a result, when unpolished, the difference ΔCS between the compressive stress values of the compressive stress layer on the front surface (front surface) and the back surface is 40 MPa, and when both surfaces are polished by 0.2 μm, the surface (front surface) The difference ΔCS between the compression stress values of the compression stress layer on the back surface and the back surface is 20 MPa. When both surfaces are polished by 10 μm, the difference ΔCS between the compression stress values on the surface (front surface) and the compression stress layer on the back surface is not recognized. It was.

Next, sample No. A glass raw material was prepared so that the glass composition described in 1 was obtained. After the obtained glass batch was melted, a glass plate having a thickness of 1 mm was formed by a float process. At that time, the temperature was set so that the temperature near the entrance of the tin bath was 1200 ° C and the temperature near the exit was about 700 ° C. Subsequently, the glass plate exiting the tin bath was passed through the slow cooling furnace. The temperature is set so that the temperature near the inlet of the slow cooling furnace is about 700 ° C and the temperature near the outlet is about 100 ° C. The temperature distribution in the plate width direction is ± 2% or less, and the temperature difference between the front and back surfaces of the glass plate in the slow cooling furnace Was gradually cooled while controlling the temperature so that the value became ± 1% or less. A 1 m × 1 m glass plate was cut out from the obtained glass plate, and the glass plate was used with a birefringence measuring machine manufactured by UNIOPT Co., Ltd .: ABR-10A. Residual stress values were measured. The data is shown in FIG. As a result, the maximum value Fmax of the residual stress in the plane direction of the glass plate was 0.25 MPa. Furthermore, when this glass plate was immersed in 440 ° C. KNO ₃ molten salt (new KNO ₃ molten salt) for 6 hours to perform ion exchange treatment, the warped amount of the tempered glass plate was 0.1%. there were. From this result, it can be seen that if the distribution of residual stress in the plane direction is regulated, the amount of warpage of the tempered glass plate can be reduced without polishing. In addition, the curvature amount of a tempered glass board is the value which measured the straightness per long side dimension using the laser interferometer.

Sample No. A glass raw material was prepared so that the glass composition described in 1 was obtained. After the obtained glass batch was melted, a glass plate having a thickness of 1 mm was formed by a float process. At that time, the temperature was set so that the temperature near the entrance of the tin bath was 1200 ° C and the temperature near the exit was about 700 ° C. Subsequently, the glass plate exiting the tin bath was passed through the slow cooling furnace. The temperature is set so that the temperature near the inlet of the slow cooling furnace is about 700 ° C and the temperature near the outlet is about 100 ° C. The temperature distribution in the width direction of the plate is ± 2% or less. Was gradually cooled while controlling the temperature so that the value became ± 1% or less. [Example 3] and [Example 4] have different slow cooling rates. A 1 m × 1 m glass plate was cut out from the obtained glass plate, and the glass plate was used with a birefringence measuring machine manufactured by UNIOPT Co., Ltd .: ABR-10A. Residual stress values were measured. The data is shown in FIG. As a result, the maximum value Fmax of the residual stress in the plane direction of the glass plate was 0.80 MPa. Furthermore, when this glass plate was immersed in 440 ° C. KNO ₃ molten salt (new KNO ₃ molten salt) for 6 hours to perform ion exchange treatment, the warped amount of the tempered glass plate was 0.1%. there were. From this result, it can be seen that if the distribution of residual stress in the plane direction is regulated, the amount of warpage of the tempered glass plate can be reduced without polishing. In addition, the curvature amount of a tempered glass board is the value which measured the straightness per long side dimension using the laser interferometer.

Here, as the glass exiting the tin bath is not damage by subsequent roller conveyor, near the exit of the tin bath, preferably by blowing SO ₂ gas from above and below. When SO ₂ gas adheres to the glass, it has an effect of eluting Na in the glass. On the other hand, if a compositional imbalance occurs on the upper and lower surfaces of the glass, it can cause warping. Thus, SO ₂ gas, becomes constant at the upper and lower glass, and it is preferred to be constant even in the upper and lower respectively in the width direction. Therefore, a slit-like gas outlet extending in the width direction is provided on each of the upper and lower sides of the glass, and a slit-like gas exhaust outlet extending in the width direction is provided immediately behind the gas outlet to supply SO ₂ gas. It is preferable. The flow rate of the SO ₂ gas is set to 1 liter / min, for example.

Next, sample No. A glass raw material was prepared so that the glass composition described in 1 was obtained. After the obtained glass batch was melted, a glass plate having a thickness of 1 mm was formed by a float process. At that time, the temperature was set so that the temperature near the entrance of the tin bath was 1200 ° C and the temperature near the exit was about 700 ° C. Subsequently, the glass plate exiting the tin bath was passed through the slow cooling furnace. The temperature is set so that the temperature near the inlet of the slow cooling furnace is about 700 ° C. and the temperature near the outlet is about 100 ° C., the temperature distribution in the width direction of the plate is controlled to ± 2% or less, and the glass plate in the slow cooling furnace Was slowly cooled while controlling the temperature so that the temperature difference between the front and back surfaces (over ± 2% ± 10% or less) was large. When the obtained glass plate is immersed in KNO ₃ (new KNO ₃ molten salt) at 440 ° C. for 6 hours, the tempered glass plate warps convexly by about 1% in the top surface direction (direction not in contact with the tin bath). . At that time, the compressive stress value of the compressive stress layer on the top surface side was 15 MPa higher than the bottom surface (tin bath contact surface) side. The thickness of the compressive stress layer was the same on the top surface and the bottom surface. Therefore, the obtained glass plate where, after forming a SiO ₂ film having a thickness of 100nm on top surface by sputtering, was immersed for 6 hours in 440 ° C. KNO ₃ (new KNO ₃ molten salt), top The difference in compressive stress value between the surface and the bottom surface was about 1 MPa or less, and the amount of warpage was reduced to 0.1%.

The tempered glass and the tempered glass plate of the present invention are suitable as a glass substrate for a mobile phone, a digital camera, a cover glass such as a PDA, or a touch panel display. Further, the tempered glass and the tempered glass plate of the present invention are used for applications requiring high mechanical strength in addition to these uses, such as window glass, substrates for magnetic disks, substrates for flat panel displays, and cover glasses for solar cells. Application to cover glass for solid-state imaging devices and tableware can be expected.

Claims (24)

It is a tempered glass having a compressive stress layer on its surface, and has a glass composition of mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 3 to 13%, B ₂ O ₃ 0 to 1.5%, Li ₂ O 0-4%, Na ₂ O 7-20%, K ₂ O 0.5-10%, MgO 0.5-13%, CaO 0-6%, SrO 0-4.5% Tempered glass characterized by not containing As ₂ O ₃ , Sb ₂ O ₃ , PbO, and F. As a glass composition, SiO ₂ 50 to 75%, Al ₂ O ₃ 4 to 13%, B ₂ O ₃ 0 to 1.5%, Li ₂ O 0 to 2%, Na ₂ O 9 to 18% in mol%. _2. K ₂ O 1-8%, MgO 0.5-12%, CaO 0-3.5%, SrO 0-3%, TiO ₂ 0-0.5%. Tempered glass as described in 2. The glass composition is, as mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 4 to 12%, B ₂ O ₃ 0 to 1%, Li ₂ O 0 to 1%, Na ₂ O 10 to 17%, K _{3. 2} O 2-7%, MgO 1.5-12%, CaO 0-3%, SrO 0-1%, TiO ₂ 0-0.5%. Tempered glass. As a glass composition, in _{mol%, SiO 2 55 ~ 75%} , Al 2 O 3 4 ~ 11%, B 2 O 3 0 ~ 1%, Li 2 O 0 ~ 1%, Na 2 O 10 ~ 16%, K _{2 O 2 ~ 7%, MgO} 3 ~ 12%, CaO 0 ~ 3%, SrO 0 ~ 1%, ZrO 2 0.5 ~ 10%, characterized by containing TiO 2 0 ~ 0.5% The tempered glass according to any one of claims 1 to 3. As a glass composition, SiO ₂ 55 to 69%, Al ₂ O ₃ 4 to 11%, B ₂ O ₃ 0 to 1%, Li ₂ O 0 to 1%, Na ₂ O 11 to 16%, K in mol% ₂ O 2-7%, MgO 3-9%, CaO 0-3%, SrO 0-1%, ZrO ₂ 1-9%, TiO ₂ 0-0.1%. The tempered glass according to any one of 1 to 4. 6. The tempered glass according to claim 1, wherein the compressive stress layer has a compressive stress value of 300 MPa or more, and the compressive stress layer has a thickness of 10 μm or more. The tempered glass according to any one of claims 1 to 6, wherein the deterioration coefficient D is 0.01 to 0.6. The tempered glass according to any one of claims 1 to 7, wherein the liquidus temperature is 1075 ° C or lower. The tempered glass according to any one of claims 1 to 8, which has a liquidus viscosity of 10 ^4.0 dPa · s or more. The tempered glass according to any one of claims 1 to 9, wherein the temperature at 10 ^4.0 dPa · s is 1250 ° C or lower. The tempered glass according to any one of claims 1 to 10, wherein the density is 2.6 g / cm ³ or less. The tempered glass according to any one of claims 1 to 11, wherein the Young's modulus is 65 GPa or more. A tempered glass sheet comprising the tempered glass according to any one of claims 1 to 12. The tempered glass sheet according to claim 13, which is formed by a float process. The tempered glass sheet according to claim 13 or 14, wherein the tempered glass sheet has a surface polished in the thickness direction by 0.5 μm or more. The tempered glass sheet according to any one of claims 13 to 15, wherein a difference ΔCS in compressive stress values of the compressive stress layers on the opposing surfaces is 50 MPa or less. A tempered glass plate having a compressive stress on its surface, having a length of 500 mm or more, a width of 500 mm or more, a thickness of 0.5 to 1.5 mm, a Young's modulus of 65 GPa or more, and a compressive stress value of the compressive stress layer of 200 MPa or more A tempered glass sheet, wherein the thickness of the compressive stress layer is 20 μm or more, the degradation coefficient D is 0.6 or less, and the difference ΔCS of the compressive stress values of the compressive stress layers on the opposite surfaces is 50 MPa or less. The tempered glass sheet according to any one of claims 13 to 17, which is used for a touch panel display. The tempered glass sheet according to any one of claims 13 to 17, which is used for a cover glass of a mobile phone. The tempered glass sheet according to any one of claims 13 to 17, which is used for a cover glass of a solar cell. The tempered glass sheet according to any one of claims 13 to 17, wherein the tempered glass sheet is used as a protective member for a display. A tempered glass plate having a compressive stress on the surface, and having a glass composition of mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 4 to 12%, B ₂ O ₃ 0 to 1%, Li ₂ O 0 Contains 1 to 1%, Na ₂ O 10 to 17%, K ₂ O 2 to 7%, MgO 1.5 to 12%, CaO 0 to 3%, SrO 0 to 1%, TiO ₂ 0 to 0.5% The molar ratio MgO / (MgO + CaO) is 0.5 or more, the length is 500 mm or more, the width is 500 mm or more, the thickness is 0.5 to 1.5 mm, the Young's modulus is 65 GPa or more, and the compressive stress value of the compressive stress layer is A tempered glass sheet characterized by 400 MPa or more, a compressive stress layer thickness of 30 μm or more, and a degradation coefficient D of 0.4 or less. A tempered glass to be subjected to a tempering treatment, and has a glass composition of mol%, SiO ₂ 50 to 75%, Al ₂ O ₃ 3 to 13%, B ₂ O ₃ 0 to 1.5%, Li ₂ O 0-4%, Na ₂ O 7-20%, K ₂ O 0.5-10%, MgO 0.5-13%, CaO 0-6%, SrO 0-4.5% A glass for strengthening characterized by not containing As ₂ O ₃ , Sb ₂ O ₃ , PbO, and F. A tempered glass to be subjected to a tempering process, characterized in that the plate thickness is 1.5 mm or less, and the maximum value Fmax of the residual stress in the planar direction with respect to all the planar portions of the tempered glass plate is 5 MPa or less. Glass plate for strengthening.

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