JP2008115072A - Reinforced glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a glass substrate which maintains both ion exchange performance and devitrification resistance of a glass and has higher mechanical strength compared to a conventional one. <P>SOLUTION: Disclosed is a reinforced glass substrate which has a compression-stress layer on its surface, has the following glass composition (by mole): SiO<SB>2</SB>: 50 to 85%, Al<SB>2</SB>O<SB>3</SB>: 5 to 30%, Li<SB>2</SB>O: 0 to 20%, Na<SB>2</SB>O: 0 to 20%, K<SB>2</SB>O: 0 to 20%, TiO<SB>2</SB>: 0.001 to 10%, and Li<SB>2</SB>O+Na<SB>2</SB>O+K<SB>2</SB>O+Al<SB>2</SB>O<SB>3</SB>: 15 to 35%, has a [(Li<SB>2</SB>O+Na<SB>2</SB>O+K<SB>2</SB>O)/Al<SB>2</SB>O<SB>3</SB>] ratio of 0.7 to 3 by mole, and does not substantially contain As<SB>2</SB>O<SB>3</SB>or F. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tempered glass substrate, and more particularly to a tempered glass substrate suitable for a mobile phone, a digital camera, a PDA (mobile terminal), or a touch panel display.

  Devices such as mobile phones, digital cameras, PDAs or touch panel displays are becoming increasingly popular.

High mechanical strength is required for glass substrates used for these applications. Conventionally, a glass substrate reinforced by ion exchange or the like (so-called tempered glass substrate) is used for these applications (see Patent Document 1 and Non-Patent Document 1).
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

According to Non-Patent Document 1, it is described that when the Al ₂ O ₃ content in the glass composition is increased, the ion exchange performance of the glass is improved and the mechanical strength of the glass substrate can be improved.

However, if the Al ₂ O ₃ content in the glass composition is increased, the devitrification resistance of the glass deteriorates, and the glass tends to devitrify during molding, so that the production efficiency and quality of the glass substrate deteriorate. To do. In particular, when the devitrification resistance of the glass is poor, a molding method such as an overflow down draw method cannot be adopted, and the surface accuracy of the glass substrate cannot be increased. Therefore, a separate polishing process must be added after the glass substrate is formed. When the glass substrate is polished, minute defects are likely to occur on the surface of the glass substrate, and it becomes difficult to maintain the mechanical strength of the glass substrate.

  Under such circumstances, it has been difficult to achieve both ion exchange performance and devitrification resistance of glass, and it has been difficult to significantly improve the mechanical strength of the glass substrate.

  In addition, in order to reduce the weight of devices, glass substrates used in devices such as touch panel displays are becoming thinner year by year. Since a thin glass substrate is easily damaged, a technique for improving the mechanical strength of the glass substrate is becoming more and more important.

  Then, this invention makes it the technical subject to make compatible the ion exchange performance and devitrification resistance of glass, and to obtain a glass substrate whose mechanical strength is higher than before.

As a result of various studies, the present inventor has found that high ion exchange performance is exhibited by including TiO ₂ in the glass composition. In addition, after determining the appropriate content of Al ₂ O _3, the total amount of Al ₂ O ₃ and the alkali metal oxide is optimized, and the molar ratio (molar fraction) of Al ₂ O ₃ and the alkali metal oxide By optimizing the above, it was found that the devitrification resistance of the glass can be improved without impairing the ion exchange performance, and the present invention has been proposed. That is, the tempered glass substrate of the present invention has a compressive stress layer on the surface thereof, and has a glass composition of SiO ₂ 50 to 85%, Al ₂ O ₃ 5 to 30%, Li ₂ O 0 to 20% in mol%. , Na ₂ O 0-20%, K ₂ O 0-20%, TiO ₂ 0.001-10%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15-35%, and in molar fractions, a value of _{(Li 2 O + Na 2 O} + K 2 O) / Al 2 O 3 is 0.7 to 3, and wherein substantially contains no as ₂ O _3, F.

Second, the tempered glass substrate of the present invention has a glass composition of 50 to 85% SiO _{2, 5 to} 12.5% Al ₂ O ₃ , 0 to 7% B ₂ O ₃ , and Li ₂ O 0 as a glass composition. Containing 9 to 9%, Na ₂ O 7 to 20%, K ₂ O 0 to 20%, TiO ₂ 0.001 to 8%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15 to 35%, and molar fraction The value of (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is 0.7 to 2.7, and the value of (MgO + CaO) / Al ₂ O ₃ is 0 to 0.55. Is characterized by not containing As ₂ O ₃ or F.

Thirdly, the tempered glass substrate of the present invention is a tempered glass substrate having a compressive stress layer on the surface, and has a glass composition of SiO ₂ 50 to 85% by mole%, Al ₂ O ₃ 5 to 30%, B ₂ O ₃ 0-7%, Li ₂ O 0.5-20%, Na ₂ O 0-20%, K ₂ O 0-20%, TiO ₂ 0.001-10%, Li ₂ O + Na ₂ O + K ₂ O + Al It is characterized in that it contains 15-35% ₂ O ₃ and has a molar fraction of (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ of 0.7-3.

Fourth, the tempered glass substrate of the present invention has a glass composition, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~12.5%} , B 2 O 3 0~7%, Li 2 O 0 _{.5~10%, Na 2 O 0~20%} , K 2 O 0~20%, TiO 2 0.01~10%, Li 2 O + Na 2 O + K 2 O + Al 2 O 3 containing 15 to 28.5% And, in terms of mole fraction, the value of (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is characterized by 0.7 to 2.7.

  Fifth, the tempered glass substrate of the present invention is characterized in that the surface compressive stress is 100 MPa or more and the thickness of the compressive stress layer is 1 μm or more. Here, “surface compressive stress” and “compressive stress layer thickness” are the number of interference fringes observed when a sample is observed using a surface stress meter (FSM-60 manufactured by Toshiba Corporation) and The value calculated from the interval. In the calculation, the refractive index was 1.52, and the photoelastic constant was 28 [(nm / cm) / MPa] (hereinafter the same).

  Sixth, the tempered glass substrate of the present invention is characterized by having an unpolished surface.

  Seventh, the tempered glass substrate of the present invention is characterized by being formed by an overflow down draw method.

  Eighth, the tempered glass substrate of the present invention is characterized in that the liquidus temperature is 1300 ° C. or lower. Here, “liquid phase temperature” refers to a temperature gradient furnace in which glass is crushed, passed 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 placed in a platinum boat. The temperature at which crystals are precipitated after being held for 24 hours.

Ninthly, the tempered glass substrate of the present invention is characterized in that the liquid phase viscosity is 10 ^4.0 dPa · s or more. Here, “liquidus viscosity” refers to the viscosity of the glass at the liquidus temperature. In addition, it is excellent in the moldability of a glass substrate while being excellent in the devitrification resistance of glass, so that liquid phase temperature is low and liquid phase viscosity is high.

Tenth, the tempered glass substrate of the present invention is characterized in that the density is 2.8 g / cm ³ or less. Here, “density” refers to a value measured by the well-known Archimedes method.

  Eleventh, the tempered glass substrate of the present invention is characterized by a Young's modulus of 68 GPa or more. Here, “Young's modulus” refers to a value measured by a resonance method.

Twelfth, the tempered glass substrate of the present invention is characterized in that the thermal expansion coefficient at 30 to 380 ° C. is 40~95 × 10 ^-7 / ℃. Here, “thermal expansion coefficient” refers to a value obtained by measuring an average thermal expansion coefficient at 30 to 380 ° C. using a dilatometer.

  Thirteenth, the tempered glass substrate of the present invention is characterized by a crack occurrence rate of 60% or less. Here, the “crack occurrence rate” indicates a value measured as follows. First, in a constant temperature and humidity chamber maintained at a humidity of 30% and a temperature of 25 ° C., a Vickers indenter set to a load of 500 g is driven into the glass surface (optical polishing surface) for 15 seconds, and 15 seconds later, it is generated from the four corners of the indentation. Count the number of cracks (maximum 4 per indentation). Thus, after indenting the indenter 20 times and determining the total number of cracks generated, the total number of cracks generated is calculated by the formula (total number of cracks generated / 80) × 100.

  Fourteenth, the tempered glass substrate of the present invention is characterized by being used for a touch panel display.

Fifteenth, the glass of the present invention has, as a glass composition, SiO ₂ 50 to 85%, Al ₂ O ₃ 5 to 30%, Li ₂ O 0 to 20%, Na ₂ O 0 to 20% in mol%, _{K 2 O 0~20%, TiO 2} 0.001~10%, Li 2 O + Na 2 O + K 2 O + Al 2 contain O ₃ 15 to 35%, and the mole _{fraction, (Li 2 O + Na 2} O + K 2 O) / Al ₂ O _{3 has} a value of 0.7 to ₃ and is characterized by containing substantially no As ₂ O ₃ or F.

Sixteenth, the glass of the present invention has a glass composition in terms of mol% of SiO ₂ 50 to 85%, Al ₂ O ₃ 5 to 30%, B ₂ O ₃ 0 to 7%, Li ₂ O 0.5 to 0.5%. 20%, Na ₂ O 0-20%, K ₂ O 0-20%, TiO ₂ 0.001-10%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15-35%, and molar fraction And (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is characterized by a value of 0.7-3.

Seventeenth, the glass of the present invention is characterized in that the surface compressive stress is 200 MPa or more and the thickness of the compressive stress layer is 3 μm or more when ion-exchanged in KNO ₃ molten salt at 430 ° C. for 4 hours. It is done. Here, “surface compressive stress” and “compressive stress layer thickness” are the number of interference fringes observed when a sample is observed using a surface stress meter (FSM-60 manufactured by Toshiba Corporation) and The value calculated from the interval.

Eighteenth, the tempered glass of the present invention has a glass composition of 50 to 85% SiO ₂ , 5 to 30% Al ₂ O ₃ , 0 to 20% Li ₂ O, and 0 to 20% Na ₂ O as a glass composition. , K ₂ O 0-20%, TiO ₂ 0.001-10%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15-35% and in molar fraction (Li ₂ O + Na ₂ O + K ₂ O ) / Al ₂ O _{3 has} a value of 0.7 to ₃ , substantially does not contain As ₂ O ₃ and F, and is characterized in that a compressive stress layer is formed on the surface thereof.

Nineteenth, the tempered glass of the present invention has a glass composition of 50 to 85% SiO ₂ , 5 to 30% Al ₂ O ₃ , 0 to 7% B ₂ O ₃ , and 0.5% Li ₂ O as a glass composition. _{~20%, Na 2 O 0~20%} , K 2 O 0~20%, TiO 2 0.001~10%, Li 2 O + Na 2 O + K 2 O + Al 2 contain O ₃ 15 to 35%, and the molar fraction The ratio of (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is 0.7 to ₃ , and a compressive stress layer is formed on the surface.

  The tempered glass substrate of the present invention has a compressive stress layer on its surface. Methods for forming a compressive stress layer on the surface of a glass substrate include a physical strengthening method and a chemical strengthening method. The tempered glass substrate of the present invention preferably forms a compressive stress layer by a chemical tempering method. The chemical strengthening method is a method of introducing alkali ions having a large ion radius into the surface of a glass substrate by ion exchange at a temperature below the strain point of the glass. If the compressive stress layer is formed by the chemical strengthening method, even if the plate thickness of the glass substrate is thin, the strengthening treatment can be performed satisfactorily and a desired mechanical strength can be obtained. Furthermore, if the compressive stress layer is formed by the chemical strengthening method, unlike the case of the physical strengthening method such as the air cooling strengthening method, the glass substrate is not cut even if the glass substrate is cut after forming the compressive stress layer on the glass substrate. Hard to destroy.

The ion exchange conditions are not particularly limited, and may be determined in consideration of the viscosity characteristics of the glass. In particular, when K ₂ O in KNO ₃ molten salt is ion-exchanged with Li ₂ O and Na ₂ O in a glass substrate, a compressive stress layer can be efficiently formed on the surface of the glass substrate.

  The reason for limiting the glass composition to the above range in the tempered glass substrate of the present invention will be described below. In addition, the following% display points out mol% unless there is particular notice.

SiO ₂ is a component that forms a glass network, and its content is 50 to 85%, preferably 53 to 78%, more preferably 55 to 75%, and still more preferably 58 to 70%. When the content of SiO ₂ exceeds 85%, it becomes difficult to melt and mold the glass, or the thermal expansion coefficient becomes too small, and it becomes difficult to match the thermal expansion coefficient with the surrounding materials. On the other hand, if the content of SiO ₂ is less than 50%, the thermal expansion coefficient of the glass becomes too large, and the thermal shock resistance of the glass tends to decrease. Furthermore, when the content of SiO ₂ is less than 50%, it becomes difficult to vitrify or the devitrification resistance of the glass tends to deteriorate.

Al ₂ O ₃ is a component having an effect of increasing the heat resistance, ion exchange performance and Young's modulus of glass, and its content is 5 to 30%. When the content of Al ₂ O ₃ is more than 30%, devitrified crystals are likely to precipitate on the glass, or the thermal expansion coefficient of the glass becomes too small to make it difficult to match the thermal expansion coefficient with the surrounding materials. Moreover, high temperature viscosity becomes high and there exists a possibility that a meltability may deteriorate. When the content of Al ₂ O ₃ is less than 5%, there is a possibility that sufficient ion exchange performance cannot be exhibited. From the above viewpoint, the preferable range of Al ₂ O ₃ is 20% or less, 16% or less, 12.5% or less, 11% or less, 10% or less, particularly 9% or less, and the lower limit is 5.5%. % Or more, 6% or more, particularly 7% or more.

B ₂ O ₃ is a component that has the effect of reducing the liquidus temperature, high-temperature viscosity, and density of the glass, and is also a component that has the effect of increasing the Young's modulus and ion exchange performance of the glass. It is 7%, preferably 0 to 5%, more preferably 0 to 3%, still more preferably 0 to 1%. On the other hand, if the content of B ₂ O ₃ is more than 7%, the surface is burnt by ion exchange, the water resistance of the glass is deteriorated, the low-temperature viscosity is excessively decreased, or the liquid phase viscosity is decreased. There is a risk.

TiO ₂ enhances the ion exchange performance of a glass, a component having an effect of improving the mechanical strength of the glass substrate, is an essential component in the present invention. TiO ₂ has the effect of increasing the low temperature viscosity of the glass and decreasing the high temperature viscosity. That is, TiO ₂ is a component that shortens the viscosity of the glass and makes it easy to form a glass substrate with high surface accuracy by the overflow down draw method. Furthermore, TiO ₂ has the effect of improving the long-term stability of the molten salt used for ion exchange. However, if the content of TiO ₂ is too large, the glass tends to be devitrified or colored. Therefore, the content of TiO ₂ is 0.001 to 10%, preferably 0.01 to 8%, more preferably 0.5 to 5%, and still more preferably 1 to 5%. As TiO ₂ introduced source, may be used of TiO ₂ material, no problem also contain TiO ₂ from minor components contained in the silica sand or the like.

Li ₂ O is an ion exchange component and a component that lowers the high temperature viscosity of the glass and improves the meltability and moldability. Furthermore, Li ₂ O is a component that has the effect of improving the Young's modulus of glass and the effect of reducing the crack generation rate. The content of Li ₂ O is 0 to 20%, preferably 0 to 10%, more preferably 0.1 to 9%, and still more preferably 0.5 to 8%. When the content of Li ₂ O exceeds 20%, the glass tends to be devitrified, and in addition to the decrease in liquid phase viscosity, the thermal expansion coefficient of the glass becomes too large and the thermal shock resistance of the glass decreases. It is difficult to match the thermal expansion coefficient with the surrounding material. Further, the strain point may be excessively lowered to deteriorate the heat resistance, or the ion exchange performance may be deteriorated.

Na ₂ O is an ion exchange component and is a component that has the effect of reducing the high temperature viscosity of the glass to improve the meltability and formability, and to reduce the crack generation rate. Na ₂ O is also a component that improves the devitrification resistance of the glass. The content of Na ₂ O is 0 to 20%, preferably 7 to 20%, more preferably 7 to 18%. When the content of Na ₂ O is more than 20%, the thermal expansion coefficient of the glass becomes too large, and the thermal shock resistance of the glass is lowered, or it becomes difficult to match the thermal expansion coefficient with the surrounding materials. Further, when the content of Na ₂ O is too large, they lack the balance of the glass composition, rather tends to devitrification property of the glass deteriorates. Further, when the content of Na ₂ O is larger than 20%, the or heat resistance deteriorates strain point excessively lowers the glass, the ion exchange performance rather deteriorated.

K ₂ O is a component that not only has an effect of promoting ion exchange, but also has an effect of reducing the high temperature viscosity of the glass to improve the meltability and formability, and to reduce the crack generation rate. K ₂ O is also a component that improves devitrification resistance. The content of K ₂ O is 0 to 20%, preferably 0.5 to 10%, more preferably 0.5 to 8%, still more preferably 1 to 6%, particularly preferably 1 to 5%, most preferably 2-4%. When the content of K ₂ O is more than 20%, the thermal expansion coefficient of the glass becomes too large, and the thermal shock resistance of the glass is lowered, or it is difficult to match the thermal expansion coefficient with the surrounding materials. If the content of K ₂ O is too large, they lack the balance of the glass composition, rather devitrification resistance of the glass tends to deteriorate.

In the tempered glass substrate of the present invention, in order to achieve both high liquid phase viscosity and ion exchange performance, the content of Na ₂ O + K ₂ O + Li ₂ O + Al ₂ O ₃ , molar fraction (Li ₂ O + Na ₂ O + K ₂ O) / Al It is important to regulate the value of ₂ O ₃ . Furthermore, in the tempered glass substrate of the present invention, if the value of the molar fraction (MgO + CaO) / Al ₂ O ₃ and / or the value of Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) is regulated, at a higher level. Both liquid phase viscosity and ion exchange performance can be achieved.

If the total amount of the alkali metal component R ₂ O (R is one or more selected from Li, Na, and K, that is, R ₂ O = Li ₂ O + Na ₂ O + K ₂ O) and Al ₂ O ₃ is too large, the glass loses. In addition to being easily permeable, the thermal expansion coefficient becomes too large, and the thermal shock resistance of the glass is lowered, and it is difficult to match the thermal expansion coefficient with the surrounding materials. In addition, the strain point may be excessively lowered. Therefore, the total amount of these components is desirably 35% or less, 30% or less, 29% or less, particularly 28.5% or less. On the other hand, if the total amount of R ₂ O + Al ₂ O ₃ is too small, the ion exchange performance and meltability of the glass tend to deteriorate. Therefore, the total amount of these components is desirably 15% or more, 17% or more, 19% or more, 20% or more, particularly 22% or more.

By regulating the total amount of R ₂ O + Al ₂ O ₃ within the above range and then regulating the value of the molar fraction R ₂ O / Al ₂ O ₃ to 0.7-3, a more effective and higher liquid A glass having a phase viscosity and high ion exchange performance can be obtained. By setting the value of the molar fraction R ₂ O / Al ₂ O ₃ to 0.7 or more (preferably 1 or more, 1.5 or more, 1.7 or more, 1.8 or more, particularly 1.9 or more), The liquidus temperature is lowered and it becomes easy to obtain a glass having a high liquidus viscosity, and the meltability of the glass is improved. As a result, it becomes easy to perform molding by the overflow downdraw method. However, if the molar fraction R ₂ O / Al ₂ O ₃ is too large, the ion exchange performance of the glass tends to deteriorate. On the other hand, if the value of the molar fraction R ₂ O / Al ₂ O ₃ becomes too large, the strain point of the glass decreases and the thermal shock resistance deteriorates, the thermal expansion coefficient becomes too large, and the surrounding materials and heat Difficult to match expansion coefficients. Therefore, the value of the molar fraction R ₂ O / Al ₂ O ₃ is 3 or less, 2.8 or less, 2.7 or less, 2.5 or less, 2.4 or less, 2.3 or less, 2.2 or less, In particular, it is preferably 2.1 or less.

Moreover, it becomes easy to make ion exchange performance and devitrification resistance compatible at a higher level by defining the value of the molar fraction (MgO + CaO) / Al ₂ O ₃ in the range of 0 to 0.55. When the value of (MgO + CaO) / Al ₂ O ₃ is greater than 0.55, the density and thermal expansion coefficient tend to increase, and the devitrification resistance tends to deteriorate.

Furthermore, in the tempered glass substrate of the present invention, the value of molar fraction Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O), the value of molar fraction Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O), the molar content By adjusting the value of the rate K ₂ O / (Li ₂ O + Na ₂ O + K ₂ O), the characteristics of the glass such as the coefficient of thermal expansion, Young's modulus, ion exchange performance, devitrification, crack generation rate are adjusted. Can do. In particular, the value of the molar fraction Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) has a great influence on properties such as Young's modulus, devitrification, ion exchange performance, and crack generation rate. When the value of the mole fraction _{Li 2 O / (Li 2 O} + Na 2 O + K 2 O) is increased, or the Young's modulus becomes high or it crack generation ratio tends to decrease, the devitrification resistance of the glass deteriorates Since the liquid phase viscosity is lowered, the molar fraction Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) is preferably 0.7 or less, particularly preferably 0.6 or less. In order to improve the devitrification property of the glass, the molar fraction Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) is set to 0.3 to 1, preferably 0.4 to 1, particularly 0.5. It is preferable to set to -1. Furthermore, the value of molar fraction K ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) is preferably regulated to 0 to 0.5, more preferably 0 to 0.4, and even more preferably 0 to 0.3. preferable.

In the tempered glass substrate of the present invention, components such as ZnO, MgO, CaO, SrO, BaO, P ₂ O ₅ and ZrO ₂ can be added as a glass composition in addition to the above components. In addition, components such as ZnO, MgO, CaO, SrO, BaO, P ₂ O ₅ , and ZrO ₂ are optional components.

  ZnO is a component having an effect of remarkably improving the ion exchange performance when added in an appropriate amount to the glass system according to the present invention. ZnO is a component that has the effect of reducing the high temperature viscosity of the glass or improving the Young's modulus. The content of ZnO is 0 to 15%, preferably 0 to 12%, more preferably 0 to 10%, still more preferably 0.01 to 8%, and most preferably 0.5 to 6%. When the content of ZnO exceeds 15%, in addition to the thermal expansion coefficient of the glass becoming too large, the devitrification resistance of the glass tends to deteriorate and the crack generation rate tends to increase.

  The alkaline earth metal component R′O (R ′ is one or more selected from Ca, Sr, and Ba) is a component that can be added for various purposes. However, when the alkaline earth metal component R′O is increased, the density and thermal expansion coefficient of the glass are increased and the devitrification resistance is deteriorated. In addition, the crack generation rate is increased and the ion exchange is increased. There is a tendency for performance to deteriorate. Therefore, the content of the alkaline earth metal component R′O is preferably 0 to 16%, more preferably 0 to 10%, and still more preferably 0 to 6%.

  MgO is a component that lowers the high-temperature viscosity of glass to improve meltability and formability, and increase the strain point and Young's modulus. Further, MgO has a relatively high effect of improving the ion exchange performance among alkaline earth metal oxides, so its content can be set to 0 to 10%. However, when the content of MgO increases, the density, thermal expansion coefficient and crack generation rate of the glass tend to increase, or the glass tends to devitrify. Therefore, the content is desirably 9% or less, 6% or less, and 4% or less.

  CaO is a component that lowers the high-temperature viscosity of the glass to increase the meltability and formability, and increases the strain point and Young's modulus, and its content can be 0 to 10%. However, when the content of CaO increases, the glass density, thermal expansion coefficient and crack generation rate tend to increase, or the glass tends to devitrify. Therefore, the content is desirably 8% or less, 5% or less, 3% or less, 1% or less, 0.8% or less, particularly 0.5% or less, and ideally not substantially contained. . Here, “substantially free of CaO” refers to a case where the content of CaO in the glass composition is 0.2% or less.

  SrO is a component that lowers the high-temperature viscosity of the glass to improve the meltability and formability, and increases the strain point and Young's modulus, and its content can be 0 to 10%. However, when the SrO content increases, the density, thermal expansion coefficient and crack generation rate of the glass increase, the glass tends to devitrify, and the ion exchange performance tends to deteriorate. Therefore, the content is desirably 8% or less, 5% or less, 3% or less, 1% or less, 0.8% or less, particularly 0.5% or less, and ideally not substantially contained. . Here, “substantially does not contain SrO” refers to a case where the content of SrO in the glass composition is 0.2% or less.

  BaO is a component that lowers the high temperature viscosity of the glass to improve the meltability and formability, and increases the strain point and Young's modulus, and its content can be 0 to 3%. However, when the content of BaO increases, the density, thermal expansion coefficient and crack generation rate of the glass increase, the glass tends to devitrify, and the ion exchange performance tends to deteriorate. Moreover, since the compound which is the raw material of BaO is an environmental load substance, it is preferable to refrain from using it as much as possible from an environmental viewpoint. Accordingly, the content is desirably 2.5% or less, 2% or less, 1% or less, 0.8% or less, particularly 0.5% or less, and ideally not substantially contained. Here, “substantially free of BaO” refers to a case where the content of BaO in the glass composition is 0.1% or less.

ZrO ₂ is a component that improves the strain point and Young's modulus of glass and improves the ion exchange performance, and its content can be 0 to 5%. However, when the content of ZrO ₂ increases, the devitrification resistance of the glass deteriorates. In particular, when molding is performed by the overflow downdraw method, crystals due to ZrO ₂ are precipitated at the interface with the molded body, which may reduce the productivity of the glass substrate during long-term operation. The preferred range of ZrO ₂ is 0-5% (desirably 0-3%, 0-1.5%, 0-1%, 0-0.8%, 0-0.5%, especially 0-0 .1%).

P ₂ O ₅ is a component that enhances the ion exchange performance of the glass, and in particular, since the effect of deepening the compressive stress thickness is great, its content can be 0 to 8%. However, when the content of P ₂ O ₅ is increased, the glass is phase-separated or the water resistance is deteriorated. Therefore, the content is preferably 5% or less, 4% or less, and 3% or less.

When the value obtained by dividing the total amount of R′O by the total amount of R ₂ O is increased, the crack generation rate is increased, and the devitrification resistance of the glass tends to be deteriorated. Therefore, it is desirable to regulate the value of R′O / R ₂ O as a molar fraction to 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

Furthermore, other components can be added as long as the properties of the glass are not significantly impaired. For example, 0 to 3% of one or more selected from the group of SO ₃ , Cl, CeO ₂ , Sb ₂ O ₃ and SnO ₂ may be contained as a fining agent. As ₂ O ₃ and F also have a clarification effect, but since they may have an adverse effect on the environment, it is preferable not to use them as much as possible, and it is more preferable not to contain them substantially. Sb ₂ O ₃ is less toxic than As ₂ O ₃ , but it may be preferable to limit its use from an environmental point of view, or it may be preferable not to contain it substantially. Further, considering the environmental standpoint and fining effect, as a refining agent, the SnO ₂ 0.01 to 3% (preferably 0.05 to 1%) is preferably contained. Here, “substantially not containing As ₂ O ₃ ” refers to a case where the content of As ₂ O ₃ in the glass composition is 0.1% or less. “Substantially no F” refers to the case where the F content in the glass composition is 0.05% or less. “Substantially free of Sb ₂ O ₃ ” refers to the case where the content of Sb ₂ O ₃ in the glass composition is 0.1% or less. On the other hand, Sb ₂ O ₃ and SO ₃ have a high effect of suppressing the decrease in the transmittance of the glass among the clarifiers. Therefore, in applications where high transmittance is required, Sb ₂ O ₃ + SO ₃ is 0 as a clarifier. It is preferable to contain about 0.001 to 5%.

Rare earth oxides such as Nb ₂ O ₅ and La ₂ O ₃ are components that increase the Young's modulus of glass. However, the cost of the raw material itself is high, and if it is contained in a large amount, the devitrification resistance deteriorates. Therefore, it is desirable to limit the content thereof to 3% or less, 2% or less, 1% or less, particularly 0.5% or less, and ideally, it is desirable that the content is not substantially contained. Here, “substantially no rare earth oxide” refers to the case where the content of the rare earth oxide in the glass composition is 0.1% or less.

  In the present invention, transition metal elements such as Co and Ni that strongly color the glass are not preferable because they reduce the transmittance of the glass substrate. In particular, when used in touch panel display applications, if the content of transition metal elements is large, the visibility of the touch panel display is impaired. Specifically, it is desirable to adjust the amount of the raw material or cullet used so that it is 0.5% or less, 0.1% or less, particularly 0.05% or less. Moreover, since PbO is an environmental load substance, it is preferable not to contain PbO substantially. Here, “substantially no PbO” refers to a case where the content of PbO in the glass composition is 0.1% or less.

A suitable content range of each component can be appropriately selected to obtain a preferable glass composition range. Among these, as a more preferable glass composition range,
(1) SiO ₂ 50~85% by _{mole%, Al 2 O 3 5~12.5%} , Li 2 O 0~9%, Na 2 O 7~20%, K 2 O 0~8%, TiO 2 _{0.001~8%, B 2 O 3 0~7} %, Li 2 O + Na 2 O + K 2 O + Al 2 O 3 containing 20 to 29%, and the mole fraction _{(Li 2 O + Na 2 O} + K 2 O) / Al The value of ₂ O ₃ is 1.5 to 2.5, the value of (MgO + CaO) / Al ₂ O ₃ is 0 to 0.5, and substantially contains As ₂ O ₃ , F, PbO, BaO. SiO ₂ 55 to 75% of glass (2) mol% which does not _{contain, Al 2 O 3 6~11%,} Li 2 O 0~8%, Na 2 O 7~20%, K 2 O 0~8%, TiO _{2 0.01~5%, B 2 O 3} 0~3%, 0~10% ZnO, ZrO 2 0~5%, MgO 0~5.5%, CaO 0~5.5%, SrO 0~5 % _{P 2 O 5 0~3%, Li} 2 O + Na 2 O + K 2 O + Al 2 O 3 containing 22 to 28.5%, and the mole fraction _{(Li 2 O + Na 2 O} + K 2 O) / Al 2 O 3 value Is 1.8 to 2.4, and the value of (MgO + CaO) / Al ₂ O ₃ is 0 to 0.5, and glass containing substantially no As ₂ O ₃ , F, PbO, or BaO (3 ) SiO ₂ 55 to 75% by _{mol%, Al 2 O 3 7~9%} , Li 2 O 0~8%, Na 2 O 7~18%, K 2 O 0~7%, TiO 2 0.01~ _{5%, B 2 O 3 0~1} %, 0~6% ZnO, ZrO 2 0~5%, MgO 0~4.5%, CaO 0~4.5%, SrO 0~5%, P 2 O _{5 0~0.5%, Li 2 O +} Na 2 O + K 2 O + Al 2 O 3 containing 22 to 28.5%, and the mole fraction _{(Li 2 O + Na 2 O} + K 2 O) / Al 2 O 3 Value is 1.9~2.4, (MgO + CaO) / value of Al ₂ O ₃ is a 0 to 0.5, substantially _{As 2 O 3, F, PbO} , glass containing no BaO ( 4) SiO ₂ 50~85% by _{mole%, Al 2 O 3 5~12.5%} , B 2 O 3 0~7%, Li 2 O 0.5~10%, Na 2 O 0~15%, K ₂ O 0-10%, TiO ₂ 0.1-10%, ZnO 0-10%, ZrO ₂ 0-5%, MgO 0-10%, CaO 0-5%, SrO 0-5%, BaO 0 _{~1%, P 2 O 5 0~5} %, Li 2 O + Na 2 O + K 2 O + Al 2 O 3 containing 20 to 28.5%, and the mole fraction _{(Li 2 O + Na 2 O} + K 2 O) / Al 2 O value of ₃ is 1.5~2.5, SiO ₂ 58~70% substantially glass containing no F (5) _{mol%, Al 2 O 3 6~11%} , B 2 O ₃ 0 to 3%, Li ₂ O 3 to 10%, Na ₂ O 6 to 11%, K ₂ O 0 to 4%, TiO ₂ 0.1 to 4%, ZnO 0 to 10%, ZrO ₂ 0 to 1%, MgO 0-9%, CaO 0-3%, SrO 0-3%, BaO 0-1%, P ₂ O ₅ 0-3%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 22-28. A glass containing 5% and having a molar fraction of (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ of 1.8 to 2.3 and substantially free of F can be mentioned.

  If the glass composition is regulated within the above range, the devitrification resistance of the glass can be greatly improved, the viscosity characteristics necessary for molding by the overflow down draw method can be ensured accurately, and the ion exchange performance is remarkably improved. be able to.

  The tempered glass substrate of the present invention has the above glass composition and a compressive stress layer on the glass surface. The compressive stress of the compressive stress layer is preferably 100 MPa or more, more preferably 300 MPa or more, still more preferably 400 MPa or more, still more preferably 500 MPa or more, particularly preferably 600 MPa or more, and most preferably 700 MPa or more. As the compressive stress increases, the mechanical strength of the glass substrate increases. On the other hand, if an extremely large compressive stress is formed on the surface of the glass substrate, microcracks may be generated on the surface of the substrate, which may reduce the strength of the glass. Therefore, the magnitude of the compressive stress in the compressive stress layer is 2000 MPa. The following is preferable.

  The thickness of the compressive stress layer is preferably 1 μm or more, more preferably 3 μm or more, further preferably 5 μm or more, particularly preferably 10 μm or more, and most preferably 15 μm or more. The greater the thickness of the compressive stress layer, the more difficult it is to break even if the glass substrate is deeply scratched. On the other hand, when an extremely large compressive stress layer is formed on the surface of the glass substrate, it becomes difficult to cut the glass substrate. Therefore, the thickness of the compressive stress layer is preferably 500 μm or less.

  The tempered glass substrate of the present invention preferably has a plate thickness of 2.0 mm or less, 1.5 mm or less, 0.7 mm or less, 0.5 mm or less, particularly 0.3 mm or less. The thinner the glass substrate, the lighter the glass substrate. Further, the tempered glass substrate of the present invention has an advantage that the glass substrate is not easily broken even if the plate thickness is reduced.

  The tempered glass substrate of the present invention preferably has an unpolished surface. The theoretical strength of glass is inherently very high, but breakage often occurs even at a stress much lower than the theoretical strength. This is because a small defect called Griffith flow is generated on the surface of the glass substrate in a step after glass molding, for example, a polishing step. Therefore, if the surface of the tempered glass substrate is unpolished, the mechanical strength of the original glass substrate is hardly impaired, and the glass substrate is hardly broken. Further, if the surface of the glass substrate is unpolished, the polishing process can be omitted in the glass substrate manufacturing process, so that the manufacturing cost of the glass substrate can be reduced. In the tempered glass substrate of the present invention, if both surfaces of the glass substrate are unpolished, the glass substrate becomes more difficult to break. Moreover, in the tempered glass substrate of this invention, in order to prevent the situation which breaks from the cut surface of a glass substrate, you may give a chamfering process etc. to the cut surface of a glass substrate.

  In the glass substrate according to the present invention, a glass raw material prepared to have a desired glass composition is charged into a continuous melting furnace, the glass raw material is heated and melted at 1500 to 1600 ° C., clarified, and then supplied to a molding apparatus. The molten glass can be produced by forming it into a plate shape and slowly cooling it.

The glass substrate according to the present invention is preferably formed by an overflow downdraw method. If the glass substrate is formed by the overflow down draw method, a glass substrate that is unpolished and has good surface quality can be produced. The reason for this is that, in the case of the overflow down draw method, the surface to be the surface of the glass substrate does not come into contact with the bowl-like refractory, and is molded in a free surface state. This is because it can be molded. Here, the overflow down draw method is to melt the molten glass from both sides of the heat-resistant bowl-like structure and draw the overflowed molten glass downward while joining at the lower end of the bowl-like structure. This is a method for producing a glass substrate. The structure and material of the bowl-shaped structure are not particularly limited as long as the dimensions and surface accuracy of the glass substrate can be set to a desired state and the quality usable for the glass substrate can be realized. Moreover, in order to perform the downward extending | stretching shaping | molding, you may apply force with what kind of method with respect to a glass substrate. For example, a method may be employed in which a heat-resistant roll having a sufficiently large width is rotated and stretched in contact with the glass substrate, or a plurality of pairs of heat-resistant rolls are only near the end face of the glass substrate. You may employ | adopt the method of making it contact and extending | stretching. The glass of the present invention is excellent in devitrification resistance and has a viscosity characteristic suitable for molding, so that molding by the overflow down draw method can be performed with high accuracy. If the liquid phase temperature is 1300 ° C. or lower and the liquid phase viscosity is 10 ^4.0 dPa · s or higher, the glass substrate can be produced by the overflow down draw method.

  In addition to the overflow down draw method, various methods can be adopted as the method for forming the tempered glass substrate of the present invention. For example, various forming methods such as a float method, a slot-down method, a redraw method, a roll-out method, and a press method can be employed. In particular, if glass is formed by a pressing method, a small glass substrate can be efficiently produced.

  As a method for producing a tempered glass substrate of the present invention, it is preferable to cut the glass substrate into a desired substrate size after the tempering treatment. Thus, a tempered glass substrate can be obtained at a low cost.

  The tempered glass substrate of the present invention preferably satisfies the following characteristics.

  In the tempered glass substrate of the present invention, the liquidus temperature of the glass is preferably 1200 ° C. or lower, 1100 ° C. or lower, 1050 ° C. or lower, 1000 ° C. or lower, 950 ° C. or lower, particularly 930 ° C. or lower. The lower the liquidus temperature of the tempered glass substrate, the more difficult it is to devitrify the glass during molding by the overflow down draw method or the like.

In the tempered glass substrate of the present invention, the liquidus viscosity of the glass, 10 ^4.0 dPa · s or more, 10 ^4.3 dPa · s or more, 10 ^4.5 dPa · s or more, 10 ^5.0 dPa · s or more, 10 ^5.3 dPa · s or more, It is preferably 10 ^5.5 dPa · s or more, particularly preferably 10 ^5.7 dPa · s or more. The higher the liquidus viscosity of the glass, the more difficult it is to devitrify during molding by the overflow downdraw method or the like.

In the tempered glass substrate of the present invention, the density of the glass, 2.8 g / cm ³ or less, 2.7 g / cm ³ or less, 2.6 g / cm ³ or less, 2.55 g / cm ³ or less, 2.5 g / cm ³ below, 2.45 g / cm ³ or less, especially 2.4 g / cm ³ or less. As the glass density is smaller, the glass substrate can be made lighter.

In the tempered glass substrate of the present invention, the thermal expansion coefficient of the glass at 30 to 380 ° C. is preferably 40 to 95 × 10 ⁻⁷ / ° C., and more preferably 70 to 95 × 10 ⁻⁷ / ° C. , more preferably from 75 to 95 × 10 ^-7 / ° C., particularly preferably from 77 to 90 × 10 ^-7 / ° C., and most preferably 80~90 × 10 ^-7 / ℃. If the thermal expansion coefficient of the glass is in the above range, it becomes easy to match the thermal expansion coefficient with a member such as a metal or an organic adhesive, and peeling of the member such as a metal or an organic adhesive can be prevented.

In the tempered glass substrate of the present invention, the temperature at a high temperature viscosity of 10 ^2.5 dPa · s of the glass is preferably 1700 ° C. or less, more preferably 1600 ° C. or less, further preferably 1550 ° C. or less, and particularly preferably 1500 ° C. or less. The lower the temperature at a glass high-temperature viscosity of 10 ^2.5 dPa · s, the smaller the burden on glass manufacturing equipment such as a melting furnace, and the higher the bubble quality of the glass substrate. That is, the glass substrate can be manufactured at a lower cost as the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is lower. The temperature at a high temperature viscosity of 10 ^2.5 dPa · s of the glass corresponds to the melting temperature of the glass. The lower the temperature at the high temperature viscosity of 10 ^2.5 dPa · s of the glass, the lower the glass can be melted.

  In the tempered glass substrate of the present invention, the Young's modulus of the glass is preferably 70 GPa or more, more preferably 71 GPa or more, and further preferably 73 GPa or more. The higher the Young's modulus of the glass, the more difficult it is to bend the glass substrate. Is less likely to occur.

In the tempered glass substrate of the present invention, specific Young's modulus of the glass is preferably 27GPa / (g / cm ³⁾ or ^{more, 28GPa / (g / cm 3} ) or more is more ^{preferable, 29GPa / (g / cm 3} ) or higher More preferred is 30 GPa / (g / cm ³ ) or more. As the specific Young's modulus of the glass is higher, the deflection of the glass substrate due to its own weight is reduced. As a result, when the glass substrate is stored in a cassette or the like in the manufacturing process, the clearance between the substrates can be narrowed and stored, thereby improving productivity.

  In the tempered glass substrate of the present invention, the glass crack generation rate is preferably 60% or less, more preferably 50% or less, further preferably 40% or less, and more preferably 30% or less. Is particularly preferable, and is most preferably 20% or less. The smaller the glass crack generation rate, the harder it is to generate cracks in the glass substrate.

The glass of the present invention, a glass composition, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~30%} , Li 2 O 0~20%, Na 2 O 0~20%, K 2 O 0~ 20%, TiO ₂ 0.001-10%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15-35% and in molar fraction (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ The value of is 0.7 to ₃ , and is substantially free of As ₂ O ₃ and F. The glass of the present invention has a glass composition, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~30%} , B 2 O 3 0~7%, Li 2 O 0.5~20%, Containing Na ₂ O 0-20%, K ₂ O 0-20%, TiO ₂ 0.001-10%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15-35%, and in molar fractions ( the value of _{li 2 O + Na 2 O +} K 2 O) / Al 2 O 3 is characterized in that 0.7 to 3. In the glass of the present invention, the reason why the glass composition is limited to the above range and the preferable range are the same as those of the tempered glass substrate described above, and thus the description thereof is omitted here. Furthermore, the glass of the present invention can naturally have both the characteristics and effects of the tempered glass substrate described above.

The glass of the present invention preferably has a surface compressive stress of 200 MPa or more and a compressive stress layer thickness of 3 μm or more when ion-exchanged in KNO ₃ molten salt at 430 ° C. for 4 hours. Since the glass composition of the present invention is regulated within the above range, the ion exchange performance is good, the surface compressive stress can be easily 200 MPa or more, and the thickness of the compressive stress layer can be 3 μm or more. .

The tempered glass of the present invention is SiO ₂ 50-85%, Al ₂ O ₃ 5-30%, Li ₂ O 0-20%, Na ₂ O 0-20%, K ₂ O 0-20% in mol%, TiO ₂ 0.001-10%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15-35%, and in terms of mole fraction, the value of (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is a 0.7 to 3, substantially contains no as ₂ O _3, F, compressive stress layer is formed on the surface. Further, the tempered glass of the present invention, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~30%} , B 2 O 3 0~7%, Li 2 O 0.5~20%, Na 2 O _{0~20%, K 2 O 0~20%} , TiO 2 0.001~10%, Li 2 O + Na 2 O + K 2 O + Al 2 contain O ₃ 15 to 35%, and the mole fraction, (Li ₂ O + Na _{The value of 2} O + K ₂ O) / Al ₂ O ₃ is 0.7 to ₃ , and a compressive stress layer is formed on the surface. In the tempered glass of the present invention, the reason why the glass composition is limited to the above range, the preferred range, and the reason for forming the compressive stress layer are the same as those of the tempered glass substrate described above, and therefore the description thereof is omitted here. Furthermore, the tempered glass of the present invention can naturally have both the characteristics and effects of the tempered glass substrate described above.

  The touch panel display is mounted on a mobile phone, a digital camera, a PDA or the like. In the touch panel display for mobile use, there is a strong demand for weight reduction, thinning, and high strength, and a thin and high mechanical strength glass substrate is required. In that respect, the tempered glass substrate of the present invention can be suitably used for this application because it has sufficient mechanical strength for practical use even if the plate thickness is reduced. It can also be used as a cover glass for protecting LCDs mounted on mobile phones and digital cameras.

  Hereinafter, the present invention will be described based on examples.

  Tables 1 to 7 show examples of the present invention (sample Nos. 1 to 46) and comparative examples (samples No. 47 and 48) of the present invention.

  Each sample was produced as follows. First, the glass raw material was prepared so that it might become a glass composition of Tables 1-7, and it melted at 1600 degreeC for 8 hours using the platinum pot. Thereafter, the molten glass was poured onto a carbon plate and formed into a plate shape. Various characteristics were evaluated about the obtained glass substrate.

  The density was measured by the well-known Archimedes method.

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

  The softening point Ts was measured based on the method of ASTM C338.

The glass viscosity of 10 ^4.0 dPa · s, 10 ^3.0 dPa · s, and 10 ^2.5 dPa · s were measured by the platinum ball pulling method.

  The thermal expansion coefficient α is an average thermal expansion coefficient measured at 30 to 380 ° C. using a dilatometer.

  The liquid phase temperature is obtained by crushing glass, passing through a standard sieve 30 mesh (a sieve opening of 500 μm), putting the glass powder remaining in 50 mesh (a sieve opening of 300 μm) into a platinum boat, and keeping it in a temperature gradient furnace for 24 hours. Then, the temperature at which the crystals are deposited is measured.

  The crack occurrence rate was measured as follows. First, in a constant temperature and humidity chamber maintained at a humidity of 30% and a temperature of 25 ° C., a Vickers indenter set to a load of 500 g is driven into the glass surface (optical polishing surface) for 15 seconds, and 15 seconds later, it is generated from the four corners of the indentation. Count the number of cracks (maximum 4 per indentation). Thus, after indenting 20 times and calculating | requiring the total number of crack generation, it calculated | required by the formula of (total number of crack generation / 80) x100.

  Young's modulus was measured by the resonance method.

As a result, no. The glass substrates 1 to 46 have a density of 2.6 g / cm ³ or less, a Young's modulus of 71 GPa or more, and a specific Young's modulus of 29.5 GPa / (g / cm ³ ) or more, and are lightweight and hardly deflected. No. The glass substrate 1 to 46 has a thermal expansion coefficient of 43 to 95 × 10 ⁻⁷ / ° C., the thermal expansion coefficient is consistent with that of the surrounding material, the crack generation rate is 30% or less, and the glass is cracked. Hateful. Furthermore, no. Glass 1-46 are moldable at liquidus viscosity ^of 10 ^4.0 dPa · s or more and higher overflow down draw method, moreover 10 ^2.5 low temperature is 1700 ° C. or less in dPa · s, inexpensively mass of the glass substrate Can be supplied. In addition, although a glass composition differs microscopically in the surface layer of a glass substrate, a glass composition does not differ substantially as the whole glass substrate. Therefore, the characteristic values such as density, viscosity, Young's modulus, etc. are not substantially different between the untempered glass substrate and the tempered glass substrate. In addition, since the crack occurrence rate is affected by the composition of the glass surface layer, the characteristic value may differ between the untempered glass substrate and the tempered glass substrate, but the crack occurrence rate tends to be lower in the tempered glass substrate. In the present invention, it is not a factor for reducing the strength.

  On the other hand, Comparative Example No. The sample No. 47 has a liquidus temperature of 1350 ° C. or higher and a low liquidus viscosity, so it is considered difficult to mold by the overflow downdraw method.

Subsequently, after both surfaces of each glass substrate were optically polished, ion exchange treatment was performed. Ion exchange was performed by immersing each sample in KNO ₃ molten salt at 430 ° C. for 4 hours. After the surface of each sample after the treatment was cleaned, the surface compressive stress value and the thickness of the compressive stress layer were determined from the number of interference fringes observed using a surface stress meter (FSM-60 manufactured by Toshiba Corporation) and the interval between the interference fringes. Was calculated.

  As a result, No. 1 as an example of the present invention. In each of the samples 1 to 46, a compressive stress of 200 MPa or more was generated on the surface, and the thickness was 9 μm or more.

  On the other hand, Comparative Example No. In each of the samples 47 and 48, the presence of a compressive stress layer could not be confirmed even after the ion exchange treatment.

  In the above examples, for convenience of explanation of the present invention, glass was melted and cast by casting, and then optically polished before ion exchange treatment. When implemented on an industrial scale, it is desirable to form a glass substrate by an overflow down draw method or the like, and to perform ion exchange treatment in a state where both surfaces of the glass substrate are unpolished.

  The tempered glass substrate of the present invention is suitable as a glass substrate for a mobile phone, a digital camera, a cover glass such as a PDA, or a touch panel display. In addition to these uses, the tempered glass substrate of the present invention is used for applications requiring high mechanical strength, such as window glass, magnetic disk substrates, flat panel display substrates, solar cell cover glasses, solid-state imaging. Application to cover glass for elements and tableware can be expected.

Claims (19)

A tempered glass substrate having a compressive stress layer on its surface,
A glass composition, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~30%} , Li 2 O 0~20%, Na 2 O 0~20%, K 2 O 0~20%, TiO 2 0 0.001-10%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15-35%, and in terms of mole fraction, the value of (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is 0.7 a to 3, tempered glass substrate, wherein substantially contains no as ₂ O _3, F. A glass composition, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~12.5%} , B 2 O 3 0~7%, Li 2 O 0~9%, Na 2 O 7~20%, Contains K ₂ O 0-8%, TiO ₂ 0.001-8%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15-35%, and in molar fraction (Li ₂ O + Na ₂ O + K ₂ O) The value of / Al ₂ O ₃ is 0.7 to 2.7, the value of (MgO + CaO) / Al ₂ O ₃ is 0 to 0.55, and substantially no As ₂ O ₃ or F is contained. The tempered glass substrate according to claim 1. A tempered glass substrate having a compressive stress layer on its surface,
A glass composition, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~30%} , B 2 O 3 0~7%, Li 2 O 0.5~20%, Na 2 O 0~20%, _{K 2 O 0~20%, TiO 2} 0.001~10%, Li 2 O + Na 2 O + K 2 O + Al 2 contain O ₃ 15 to 35%, and the mole _{fraction, (Li 2 O + Na 2} O + K 2 O) / Al ₂ O _{3 has} a value of 0.7 to ₃ , a tempered glass substrate. A glass composition, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~12.5%} , B 2 O 3 0~7%, Li 2 O 0.5~10%, Na 2 O 0~20 %, K ₂ O 0-20%, TiO ₂ 0.01-10%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15-28.5% and in molar fractions (Li ₂ O + Na ₂ The tempered glass substrate according to claim ₃ , wherein the value of O + K ₂ O) / Al ₂ O ₃ is 0.7 to 2.7.   The tempered glass substrate according to claim 1, wherein the surface has a compressive stress of 100 MPa or more and a thickness of the compressive stress layer of 1 μm or more.   The tempered glass substrate according to claim 1, which has an unpolished surface.   The tempered glass substrate according to claim 1, wherein the tempered glass substrate is molded by an overflow downdraw method.   Liquid phase temperature is 1300 degrees C or less, The tempered glass substrate in any one of Claims 1-7 characterized by the above-mentioned. The tempered glass substrate according to any one of claims 1 to 8 liquidus viscosity, characterized in that of 10 ^4.0 dPa · s or more. The tempered glass substrate according to claim 1, wherein the density is 2.8 g / cm ³ or less.   The tempered glass substrate according to claim 1, wherein Young's modulus is 68 GPa or more. The thermal expansion coefficient in 30-380 degreeC is 40-95 * 10 < ^-7 > / degreeC, The tempered glass substrate in any one of Claims 1-11 characterized by the above-mentioned.   The tempered glass substrate according to any one of claims 1 to 12, wherein a crack generation rate is 60% or less.   It uses for a touch panel display, The tempered glass substrate in any one of Claims 1-13 characterized by the above-mentioned. A glass composition, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~30%} , Li 2 O 0~20%, Na 2 O 0~20%, K 2 O 0~20%, TiO 2 0 0.001-10%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15-35%, and in terms of mole fraction, the value of (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is 0.7 a to 3, glass characterized by substantially contains no as ₂ O _3, F. A glass composition, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~30%} , B 2 O 3 0~7%, Li 2 O 0.5~20%, Na 2 O 0~20%, _{K 2 O 0~20%, TiO 2} 0.001~10%, Li 2 O + Na 2 O + K 2 O + Al 2 contain O ₃ 15 to 35%, and the mole _{fraction, (Li 2 O + Na 2} O + K 2 O) / Al ₂ O _{3 has} a value of 0.7-3. The glass according to claim 15 or 16, wherein when ion exchange is performed in KNO ₃ molten salt at 430 ° C for 4 hours, the compressive stress of the surface is 200 MPa or more and the thickness of the compressive stress layer is 3 µm or more. A glass composition, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~30%} , Li 2 O 0~20%, Na 2 O 0~20%, K 2 O 0~20%, TiO 2 0 0.001-10%, Li ₂ O + Na ₂ O + K ₂ O + Al ₂ O ₃ 15-35%, and in terms of mole fraction, the value of (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ is 0.7 a to 3, substantially free of as ₂ O _3, not containing F, tempered glass, wherein a compressive stress layer formed on the surface. A glass composition, SiO ₂ 50 to 85% by _{mol%, Al 2 O 3 5~30%} , B 2 O 3 0~7%, Li 2 O 0.5~20%, Na 2 O 0~20%, _{K 2 O 0~20%, TiO 2} 0.001~10%, Li 2 O + Na 2 O + K 2 O + Al 2 contain O ₃ 15 to 35%, and the mole _{fraction, (Li 2 O + Na 2} O + K 2 O) A tempered glass having a value of / Al ₂ O ₃ of 0.7 to ₃ and a compressive stress layer formed on the surface.