JP5556947B2 - Tempered glass and method for producing the same - Google Patents

Description

The present invention relates to a tempered glass and a method for producing the same, and more particularly to a tempered glass suitable for a substrate (including both a base material and a cover glass) of a thin film compound solar cell and a method for producing the same.

  A thin film compound solar cell has a solar cell in which an electrode layer, a photoelectric conversion layer, a buffer layer, and the like are stacked on a glass substrate (base material), and the solar cell is protected by a glass substrate (cover glass). ing. In recent years, thin film compound solar cells have gradually improved photoelectric conversion efficiency, but the actual situation is that they have not yet reached the photoelectric conversion efficiency of single crystal and polycrystalline silicon solar cells.

As a thin-film compound solar cell, a CIS solar cell using a CIS-based material such as Cu (In _1-x , Ga _x ) Se ₂ is promising, and the CIS solar cell has a single crystal theoretical photoelectric conversion efficiency. It is known to be higher than silicon solar cells. Moreover, since the thickness of a photoelectric converting layer can be several micrometers in a CIS type solar cell, member cost and manufacturing cost can be reduced.

  By the way, if a CIS thin film is formed on a glass substrate by heat treatment at 500 to 550 ° C., the photoelectric conversion efficiency of the CIS solar cell can be increased.

  Generally, high mechanical strength is required for a glass substrate for a CIS solar cell. When the glass substrate is strengthened, the mechanical strength of the glass substrate can be increased.

  However, when the tempered glass is heat-treated at a high temperature, the compressive stress disappears and the mechanical strength before the heat treatment cannot be maintained. In order to prevent the disappearance of the compressive stress, it is necessary to improve the heat resistance of the tempered glass. However, when the heat resistance of the tempered glass is improved, the high temperature viscosity tends to increase and the meltability tends to decrease. Specifically, in order to chemically strengthen the glass, it is necessary to introduce an alkali metal oxide into the glass composition. However, when an alkali metal oxide is introduced, the heat resistance tends to be lowered. On the other hand, when the content of the alkali metal oxide is decreased, the heat resistance is improved, but in addition to the decrease in ion exchange performance, the meltability is easily decreased.

  Then, even if it heat-processes at high temperature, for example, 500-550 degreeC, this invention makes it a technical subject to obtain the tempered glass which can maintain high mechanical strength and was excellent in a meltability.

As a result of various studies, the inventor has been able to maintain high mechanical strength even when heat-treated at a high temperature and regulate the meltability by regulating the glass composition range of tempered glass as follows. It has been found that it can be improved, and is proposed as the present invention. That is, the tempered glass of the present invention is a tempered glass having a compressive stress layer, and has a glass composition of mol%, SiO ₂ 50-80%, Al ₂ O ₃ 7-16%, B ₂ O ₃ 0-5%. _{, Li 2 O 0~1%, Na} 2 O 7.6~20%, K 2 O 3~15%, MgO + CaO + SrO + BaO 8 ~13%, containing 0 to 3% SrO, substantially free of _as 2 _O 3, Sb ₂ O ₃ , PbO and F are not contained, the molar ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is 0.05 to ₂ , and the substrate shape is 1 mm. 0.0 mm or less.

The tempered glass of the present invention regulates the content of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , alkali metal oxide, and alkaline earth metal oxide in the glass composition within a predetermined range. If it does in this way, ion exchange performance, heat resistance, and meltability can be made compatible at a high level.

The tempered glass of the present invention regulates the value of the molar ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) to 0.05 to ₂ in the glass composition. In this way, it is possible to increase the strain point while preventing the deterioration of various characteristics.

The tempered glass of the present invention contains substantially no As ₂ O ₃ , Sb ₂ O ₃ , PbO and F in the glass composition. In this way, environmental demands in recent years can be satisfied. Here, “substantially does not contain As ₂ O ₃ ” refers to the case where the content of As ₂ O ₃ in the glass composition is 0.1% by mass or less. “Substantially no Sb ₂ O ₃ ” refers to the case where the content of Sb ₂ O ₃ in the glass composition is 0.1% by mass or less. “Substantially no PbO” refers to the case where the content of PbO in the glass composition is 0.1 mass% or less. “Substantially no F” refers to the case where the F content in the glass composition is 0.1% by mass or less.

The tempered glass of the present invention has a glass composition of mol%, SiO ₂ 55 to 70%, Al ₂ O ₃ 8 to 14%, B ₂ O ₃ 0 to 5%, Li ₂ O 0 to 1%, Na _{2. O 7.6~15%, K 2 O 3~10} %, MgO + CaO + SrO + BaO 8 ~13%, containing 0 to 3% SrO, substantially free of _{as 2 O 3, Sb 2 O} 3, PbO and F And the molar ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is 0.3 to 1.5. Here, “MgO + CaO + SrO + BaO” means the total amount of MgO, CaO, SrO, and BaO. “Li ₂ O + Na ₂ O + K ₂ O” means the total amount of Li ₂ O, Na ₂ O, and K ₂ O.

  The tempered glass of the present invention preferably has a strain point of 550 ° C. or higher. If it does in this way, the heat resistance of tempered glass will improve. Here, the “strain point” refers to a value measured based on the method of ASTM C336.

  In the tempered glass of the present invention, the compressive stress layer preferably has a compressive stress value of 300 MPa or more, and the compressive stress layer has a thickness of 5 μm or more. The “compressive stress value of the compressive stress layer” and “thickness of the compressive stress layer” can be calculated by observing the number of interference fringes and their intervals with a surface stress meter.

  In the tempered glass of the present invention, the reduction rate of the compressive stress value of the compressive stress layer is preferably 80% or less under a heat treatment condition of 500 ° C. for 30 minutes. Here, the “decrease rate of the compressive stress value” means ([compressive stress value of compressive stress layer before heat treatment] − [compressive stress value of compressive stress layer after heat treatment]) / [compressive stress layer before heat treatment]. Compressive stress value], which is a value calculated at room temperature to 500 ° C. at a rate of 5 ° C./min, held at 500 ° C. for 30 minutes, and then cooled from 500 ° C. to room temperature at a rate of 10 ° C./min.

  The tempered glass of the present invention preferably has a compressive stress layer having a compressive stress value of 100 MPa or more and a compressive stress layer having a thickness of 5 μm or more after heat treatment at 500 ° C. for 30 minutes. In the heat treatment, the temperature is raised from room temperature to 500 ° C. at 5 ° C./minute, held at 500 ° C. for 30 minutes, and then lowered from 500 ° C. to room temperature at 10 ° C./minute.

The tempered glass of the present invention preferably has a thermal expansion coefficient (30 to 380 ° C.) of 40 to 100 × 10 ⁻⁷ / ° C. Here, “thermal expansion coefficient (30 to 380 ° C.)” refers to a value obtained by measuring an average thermal expansion coefficient in a temperature range of 30 to 380 ° C. using a dilatometer. If it does in this way, it will become easy to match the coefficient of thermal expansion of members, such as a CIS type thin film, and problems, such as film peeling, can be prevented.

  The tempered glass of the present invention preferably has a liquidus temperature of 1400 ° C. or lower. Here, “liquid phase temperature” means that glass is crushed, passed through a standard sieve 30 mesh (500 μm sieve opening), and the glass powder remaining in 50 mesh (300 μm sieve sieve) is placed in a platinum boat, and the temperature gradient The temperature at which crystals are precipitated after being kept in the furnace for 24 hours.

The tempered glass of the present invention preferably has a liquidus viscosity of 10 ^3.0 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.

  The tempered glass of the present invention has a substrate shape.

  It is preferable to use the tempered glass of this invention for the board | substrate of a solar cell.

  It is preferable to use the tempered glass of this invention for the board | substrate of a thin film compound solar cell.

  The tempered glass of the present invention is preferably used for a display substrate.

The glass of the present invention, as a glass composition, in _{mol%, SiO 2 55~70%, Al} 2 O 3 7~16%, B 2 O 3 0~5%, Li 2 O 0~1%, Na 2 O _{7.6~20%, K 2 O 3~15%} , MgO + CaO + SrO + BaO 8 ~13%, containing 0 to 3% SrO, contains substantially no _{as 2 O 3, Sb 2 O} 3, PbO and F The molar ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is 0.1 to ₂ , the substrate is shaped, and the plate thickness is 1.0 mm or less.

The method of producing glass of the present invention has a glass composition, in _{mol%, SiO 2 55~70%, Al} 2 O 3 7~16%, B 2 O 3 0~5%, Li 2 O 0~1% _{, Na 2 O 7.6~20%, K} 2 O 3~15%, MgO + CaO + SrO + BaO 8 ~13%, containing 0 to 3% SrO, substantially _{as 2 O 3, Sb 2 O} 3, PbO, F The glass raw material is melted so that the molar ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is 0.1 to ₂ , and the substrate shape has a plate thickness of 1.0 mm or less After forming into a glass, a compression stress layer is formed on the glass by performing an ion exchange treatment. The conditions for the ion exchange treatment are not particularly limited, and may be determined in consideration of the viscosity characteristics of the glass. In particular, when the K ions in the KNO ₃ molten salt and the Na component in the glass substrate are ion-exchanged, a compressive stress layer can be efficiently formed on the surface of the glass.

  The tempered glass manufacturing method of the present invention is preferably formed into a substrate shape by an overflow down draw method.

  The tempered glass of the present invention has a compressive stress layer in the vicinity of its surface. As a method for forming a compressive stress layer on glass, there are a physical strengthening method and a chemical strengthening method. The tempered glass 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 in the vicinity of the glass surface by ion exchange at a temperature below the strain point. If the compressive stress layer is formed by the chemical strengthening method, a desired mechanical strength can be obtained even if the glass substrate is thin. In addition, unlike the physical strengthening method such as the air cooling strengthening method, if the compressive stress layer is formed by the chemical strengthening method, the glass substrate is not easily damaged even if the glass substrate is cut after the strengthening treatment.

  The reason why the glass composition range is regulated as described above in the tempered glass of the present invention is shown below. In addition, in the description regarding the following glass composition,% display points out mol% unless there is particular notice.

SiO ₂ is a component forming a glass network, the content thereof is 50-80%, preferably 55-75%, more preferably 58-70%, more preferably 60% to 70%. If the content of SiO ₂ is too large, melting and molding become difficult, and in addition, the thermal expansion coefficient becomes too low, making it difficult to match the thermal expansion coefficient of the surrounding materials. On the other hand, if the content of SiO ₂ is too small, it becomes difficult to vitrify, the thermal expansion coefficient becomes too high, and the thermal shock resistance tends to be lowered.

Al ₂ O ₃ is a component that enhances ion exchange performance, and a component that increases the strain point and Young's modulus, and its content is 7 to 16%. When the content of Al ₂ O ₃ is too large, devitrification crystal glass is easily precipitated, it becomes difficult to mold the glass substrate. If the content of Al ₂ O ₃ is too large, the thermal expansion coefficient becomes too low, or become difficult to match the thermal expansion coefficient with those of peripheral materials becomes high viscosity at high temperature becomes difficult to melt the glass. On the other hand, when the content of Al ₂ O ₃ is too small, resulting is a possibility which can not be sufficiently exhibited ion exchange performance. The lower limit range of the Al ₂ O ₃ content is 7% or more, preferably 8% or more, 9% or more, 10% or more, 10.5% or more, 11% or more, and the upper limit range is 16% or less. , Preferably 15% or less, 14% or less, 13.5% or less, 13% or less.

Li ₂ O + Na ₂ O + K ₂ O is an ion exchange component, and is a component that lowers the high-temperature viscosity and improves meltability and moldability. If the content of Li ₂ O + Na ₂ O + K ₂ O is too large, the glass tends to devitrify, the thermal expansion coefficient becomes too high, the thermal shock resistance decreases, and the thermal expansion coefficient of the surrounding materials It becomes difficult to match. Further, when the content of _{Li 2 O + Na 2 O +} K 2 O is too large, too lowered strain point, with a high compression stress value may become difficult to obtain, the heat treatment at a high temperature, a compressive stress is liable to disappear Become. Further, when the content of _{Li 2 O + Na 2 O +} K 2 O is too large, there are cases where the viscosity is lowered in the vicinity of the liquidus temperature, it is difficult to ensure a high liquidus viscosity. Therefore, the content of Li ₂ O + Na ₂ O + K ₂ O is 25% or less, preferably 20% or less, more preferably 18% or less, still more preferably 15% or less, and particularly preferably 14% or less. On the other _hand, when the _{Li 2 O + Na 2 O +} K 2 O is too small, it decreases the ion exchange performance and meltability. Therefore, the content of Li ₂ O + Na ₂ O + K ₂ O is preferably 8% or more, more preferably 10% or more.

Li ₂ O is an ion exchange component, and is a component that lowers the high-temperature viscosity and improves meltability and moldability. Li ₂ O is a component that improves the Young's modulus. Furthermore, Li ₂ O is a component that has a high effect of increasing the compressive stress value among alkali metal oxides. However, if the content of Li ₂ O is too large, the liquid phase viscosity decreases and the glass tends to devitrify, and the thermal expansion coefficient of the glass becomes too high, resulting in a decrease in thermal shock resistance. Or it becomes difficult to match the thermal expansion coefficient of the surrounding material. Further, when the content of Li 2 _O is too large, too reduced low temperature viscosity, tends to occur stress relaxation, compression stress value conversely may deteriorate. Therefore, the content of Li ₂ O is 0 to 1%, preferably 0 to 0.5%, particularly preferably 0 to 0.1%.

Na ₂ O is an ion exchange component, is a component that lowers the high-temperature viscosity and improves meltability and moldability, and is a component that improves devitrification resistance. The lower limit range of Na ₂ O is 7.6% or more, the upper limit range is 20% or less, 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, particularly 9 % Or less is preferable. When the content of Na 2 _O is too large, the thermal expansion coefficient becomes too high, the thermal shock resistance is hardly matched to the thermal expansion coefficient of the reduced or peripheral materials. Further, when the content of Na 2 _O is too large, or too low the strain point, it is impaired balance of components glass composition, devitrification resistance conversely tends to decrease. On the other hand, if too small content of Na 2 _O, lowered the melting property, become too coefficient of thermal expansion is low, decreases the ion exchange performance.

K ₂ O is a component that promotes ion exchange, and is a component that has a high effect of increasing the thickness of the compressive stress layer among alkali metal oxides. Further, K ₂ O is a component having a high effect of reducing the high-temperature viscosity without reducing the strain point and improving the meltability and moldability among alkali metal oxides. Furthermore, K ₂ O is also a component that improves devitrification resistance. 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. If the content of K 2 _O is too large, or too low the strain point, it is impaired balance of components glass composition, devitrification resistance conversely tends to decrease. Considering the above points, the upper limit range of the content of K ₂ O is 15% or less, preferably 10% or less, 9% or less, 8% or less, 6% or less, 5% or less, and particularly preferably 4% or less. The range is preferably 3% or more, particularly preferably 3.5% or more.

MgO + CaO + SrO + BaO is a component that lowers the high-temperature viscosity without significantly reducing the strain point. However, if the content is too large, the density and thermal expansion coefficient are increased, and the devitrification resistance is likely to be decreased. , Ion exchange performance tends to decrease. Therefore, the content of MgO + CaO + SrO + BaO is 8 to 13%, preferably 8 to 12 % .

  MgO is a component that lowers the viscosity at high temperature to increase the meltability and formability, and increases the strain point and Young's modulus. Especially in alkaline earth metal oxides, the effect of improving ion exchange performance is high. It is a component, and its content is 0 to 10%, preferably 0 to 6%, more preferably 0 to 4%, still more preferably 0 to 3%, and most preferably 0 to 2%. However, when there is too much content of MgO, a density and a thermal expansion coefficient will become high, or it will become easy to devitrify glass.

  CaO is a component that lowers the viscosity at high temperature to increase the meltability and moldability, and increases the strain point and Young's modulus, and is particularly effective in improving ion exchange performance among alkaline earth metal oxides. It is a component and also a component that improves devitrification resistance, and its content is 0 to 13%, preferably 1 to 13%, more preferably 2 to 10%, still more preferably 3 to 10%, particularly preferably. Is 4-10%. When there is too much content of CaO, a density and a thermal expansion coefficient will become high, the balance of a glass composition will be impaired, and it will become easy to devitrify glass, and also there exists a tendency for ion exchange performance to fall.

SrO is a component that lowers the high-temperature viscosity to improve meltability and moldability, and increases the strain point and Young's modulus, and its content is 0 to 3 %. If the content of SrO is too large, the ion exchange performance tends to decrease, and the density and thermal expansion coefficient increase, and the glass tends to devitrify. In particular, the content of SrO 1% or less is 0.5% or less, particularly desirably 0.2% or less under.

BaO is a component that lowers the viscosity at high temperature, improves meltability and formability, and increases the strain point and Young's modulus. In particular, it stabilizes glass in a glass composition system with a high content of Al ₂ O _3. It is a component having a high effect of improving devitrification resistance. However, if the content of BaO is too large, the ion exchange performance tends to be lowered, and the density and thermal expansion coefficient are increased, the component balance of the glass composition is impaired, and the glass is lost. It becomes easy to see through. Therefore, the lower limit range of the BaO content is preferably 0.1% or more, 0.5% or more, 0.7% or more, 1% or more, particularly preferably 1.5% or more, and the upper limit range is 10% or less, 8%. Below, 5% or less, especially 3% or less is preferred.

The present inventor, if the molar ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is regulated within a predetermined range, prevents the increase in density or the decrease in devitrification resistance, and the strain point. I found that it can be enhanced. The value of the molar ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is 0.05 to 2, preferably 0.1 to 1.8, more preferably 0.2 to 1.5, still more preferably 0.00. 3 to 1, particularly preferably 0.3 to 0.9, most preferably 0.4 to 0.8. When the molar ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is out of the above range, it is difficult to obtain the above effect.

  The tempered glass of the present invention may comprise a glass composition only with the above components, but other components may be added up to 40% within a range that does not significantly impair the properties of the glass.

B ₂ O ₃ is a component that has the effect of reducing high temperature viscosity and density, stabilizes glass, makes it difficult to precipitate crystals, and lowers the liquidus temperature, and its content is 0. -5%, preferably 0-3%, more preferably 0-2%, still more preferably 0-1%, most preferably 0-0.1%. When the content of B ₂ O ₃ is too large, or the strain point is lowered, or generated burnt on the surface of the glass by ion exchange, or water resistance is lowered, the thickness of the compressive stress layer tends to decrease .

TiO ₂ is a component that improves ion exchange performance and is a component that lowers the high-temperature viscosity. However, if the content is too large, the glass tends to be colored or devitrified. 0 to 5%, preferably 0 to 4%, more preferably 0 to 3%, still more preferably 0 to 0.5%, still more preferably 0 to 0.1%, most preferably 0 to 0.05%. is there.

ZrO ₂ is a component that remarkably improves the ion exchange performance and increases the viscosity and strain point in the vicinity of the liquid phase viscosity, and its content is 0 to 10% (preferably 0 to 8%, 0 to 3%, 0-2.6%, 0-2%, 0.1-1.7%). When the content of ZrO ₂ is too high, there are cases where the devitrification resistance is extremely lowered.

  ZnO is a component that enhances the ion exchange performance, is a component that has a particularly large effect of increasing the compressive stress value, and is a component that decreases the high temperature viscosity without decreasing the low temperature viscosity, and its content is 0-6. %, Preferably 0 to 5%, more preferably 0 to 3%, still more preferably 0 to 1%, and most preferably 0 to 0.1%. 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.

P ₂ O ₅ is a component that enhances the ion exchange performance, and is particularly a component that has a high effect of increasing the thickness of the compressive stress layer, and its content is 0 to 10% (preferably 3% or less, 1% or less, 0.5% or less, particularly 0.1% or less). However, when the content of P ₂ O ₅ is too large, glass or phase separation, the water resistance is lowered.

One or more selected from the group of SnO ₂ , CeO ₂ , Cl, SO ₃ as a fining agent is 0 to 3%, preferably 0.001 to 1%, more preferably 0.01 to 0.5%. More preferably, 0.05 to 0.4% can be added. In particular, SnO ₂ is preferable in terms of a clarification effect, and its content is preferably 0 to 1%, 0.01 to 0.5%, particularly preferably 0.05 to 0.4%.

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 if it is contained in a large amount, the devitrification resistance is lowered. Therefore, the rare earth oxide content is 3% or less, preferably 2% or less, more preferably 1% or less, still more preferably 0.5% or less, and particularly preferably 0.1% or less.

  Transition metal oxides such as Co and Ni strongly color the glass and reduce the transmittance of the glass. In particular, in the case of a touch panel display or solar battery application, if the content of the transition metal oxide is large, the visibility of the touch panel display is impaired, or the photoelectric conversion efficiency of the solar battery is lowered. Therefore, it is desirable to adjust the amount of the glass raw material used so that the content of the transition metal oxide is 0.5% or less (preferably 0.1% or less, more preferably 0.05% or less).

As described above, the tempered glass of the present invention substantially does not contain As ₂ O ₃ , Sb ₂ O ₃ , PbO and F in the glass composition from the environmental viewpoint. Further, the tempered glass of the present invention, from an environmental point of view, it is preferable to contain substantially no Bi ₂ O ₃ in the glass composition. “Substantially no Bi ₂ O ₃ ” refers to the case where the content of Bi ₂ O ₃ in the glass composition is 0.1% by mass or less.

In the tempered glass of the present invention, the strain point is preferably 550 ° C or higher, more preferably 560 ° C or higher, more preferably 570 ° C or higher, more preferably 590 ° C or higher, further preferably 600 ° C or higher, and most preferably 620 ° C or higher. . The strain point is a characteristic that becomes an index of heat resistance. The higher the strain point, the better the heat resistance, and the compressive stress hardly disappears even when the tempered glass is heat-treated. Also, the higher the strain point, the less stress relaxation occurs during ion exchange, making it easier to obtain a high compressive stress value. In order to increase the strain point, if the content of alkali metal oxide in the glass composition is reduced or the content of alkaline earth metal oxide, Al ₂ O ₃ , ZrO ₂ , P ₂ O ₅ is increased Good.

In the tempered glass of the present invention, the compressive stress value of the compressive stress layer is preferably 300 MPa or more (desirably 400 MPa or more, 500 MPa or more, 600 MPa or more, particularly 900 MPa or more). The higher the compressive stress value of the compressive stress layer, the higher the mechanical strength. On the other hand, when an extremely large compressive stress is formed in the vicinity of the surface of the glass, microcracks are generated on the surface, and there is a risk that the mechanical strength is reduced. Further, if an extremely large compressive stress is formed in the vicinity of the surface of the glass, the internal tensile stress may become extremely high. Therefore, the compressive stress value of the compressive stress layer is preferably 1300 MPa or less. In addition, 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 of the compressive stress layer can be increased. . Moreover, when the ion exchange time is shortened or the ion exchange temperature is lowered, the compressive stress value of the compressive stress layer can be increased.

In the tempered glass of the present invention, the thickness of the compressive stress layer is preferably 5 μm or more, more preferably 10 μm or more, more preferably 15 μm or more, further preferably 20 μm or more, particularly preferably 30 μm or more, and most preferably 40 μm or more. As the thickness of the compressive stress layer increases, the tempered glass is less likely to be damaged even if the tempered glass is deeply damaged. On the other hand, in order to make it easy to cut the tempered glass, the thickness of the compressive stress layer is preferably 500 μm or less. If the content of K ₂ O and P ₂ O _{5 in} the glass composition is increased and the content of SrO and BaO is decreased, the thickness of the compressive stress layer can be increased. Moreover, when the ion exchange time is lengthened or the ion exchange temperature is raised, the thickness of the compressive stress layer can be increased.

  In the tempered glass of the present invention, the reduction rate of the compressive stress value of the compressive stress layer is preferably 80% or less, 60% or less, 30% or less, particularly 10% or less under the heat treatment conditions at 500 ° C. for 30 minutes. If the reduction rate of the compressive stress value is higher than 80% under the heat treatment conditions of 500 ° C. for 30 minutes, the mechanical strength tends to be lowered by the heat treatment at 500 to 550 ° C.

  In the tempered glass of the present invention, after the heat treatment at 500 ° C. for 30 minutes, the compressive stress value of the compressive stress layer is 100 MPa or more (preferably 130 MPa or more, 300 MPa or more, 500 MPa or more, particularly 800 MPa or more), and the thickness of the compressive stress layer is It is preferable to be 5 μm or more (preferably 10 μm or more, 15 μm or more, 20 μm or more, 30 μm or more, particularly 40 μm or more). If the compressive stress value and thickness of the compressive stress layer are out of the above ranges after the heat treatment, the tempered glass tends to be damaged by mechanical impact or the like.

The tempered glass of the present invention, the density is preferably 2.7 g / cm ³ or less, more preferably 2.65 g / cm ³ or less, 2.6 g / cm ³ more preferably less, 2.55 g / cm ³ or less is particularly preferable. The smaller the density, the lighter the glass. Here, “density” refers to a value measured by the well-known Archimedes method. In order to reduce the density, the content of SiO ₂ , P ₂ O ₅ , B ₂ O _{3 in} the glass composition is increased, or alkali metal oxide, alkaline earth metal oxide, ZnO, ZrO ₂ , TiO ₂ What is necessary is just to reduce content.

The tempered glass of the present invention, the thermal expansion coefficient (30 to 380 ° C.) is preferably from 45 to 100 × ^{10 -7} / ° C., more preferably ^{75~100 × 10 -7 / ℃, 80~100} × 10 -7 / ° C is more preferable, 80 to 96 × 10 ⁻⁷ / ° C. is further preferable, and 80 to 90 × 10 ⁻⁷ / ° C. is particularly preferable. When the thermal expansion coefficient is within the above range, it becomes easy to match the thermal expansion coefficient of a member such as a CIS-based thin film, and film peeling or the like can be prevented. In order to increase the coefficient of thermal expansion, the content of alkali metal oxides and alkaline earth metal oxides in the glass composition should be increased. What is necessary is just to reduce content of an earth metal oxide.

In the tempered glass of the present invention, the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is preferably 1650 ° C. or lower, 1620 ° C. or lower, 1600 ° C. or lower, 1570 ° C. or lower, 1540 ° C. or lower, 1500 ° C. or lower, particularly 1450 ° C. or lower. The temperature at the high temperature viscosity of 10 ^2.5 dPa · s corresponds to the melting temperature of the glass, and the lower the temperature at the high temperature viscosity of 10 ^2.5 dPa · s, the more the glass can be melted. In addition, the lower the temperature at a high temperature viscosity of 10 ^2.5 dPa · s, the smaller the load applied to manufacturing equipment such as a melting furnace, and the glass foam quality can be improved. Can be manufactured. In order to decrease the temperature at a high temperature viscosity of 10 ^2.5 dPa · s, the content of alkali metal oxide, alkaline earth metal oxide, ZnO, B ₂ O ₃ , TiO ₂ is increased, or SiO ₂ , Al ₂ the content of O ₃ may be reduced.

In the tempered glass of the present invention, the liquidus temperature is preferably 1400 ° C. or lower, 1300 ° C. or lower, 1200 ° C. or lower, 1150 ° C. or lower, particularly 1100 ° C. or lower. To lower the liquidus temperature, the content of Na ₂ O, K ₂ O, B ₂ O _{3 in} the glass composition is increased, or Al ₂ O ₃ , Li ₂ O, MgO, ZnO, TiO ₂ , ZrO _2. The content of can be reduced. In addition, devitrification resistance and a moldability improve, so that liquidus temperature is low.

In the tempered glass of the present invention, the liquid phase viscosity is preferably 10 ^3.0 dPa · s or more, 10 ^4.0 dPa · s or more, particularly preferably 10 ^5.0 dPa · s or more. To increase the liquid phase viscosity, increase the content of Na ₂ O, K ₂ O in the glass composition, or decrease the content of Al ₂ O ₃ , Li ₂ O, MgO, ZnO, TiO ₂ , ZrO ₂ do it. In addition, devitrification resistance and a moldability improve, so that liquid phase viscosity is high.

  When used as a glass substrate, the tempered glass of the present invention preferably has an unpolished surface, and the average surface roughness (Ra) of the unpolished surface is preferably 10 mm or less, 5 mm or less, and particularly preferably 2 mm or less. Here, “average surface roughness (Ra) of the surface” refers to a value measured by a method based on SEMI D7-97 “Measurement Method of Surface Roughness of FPD Glass Substrate”. 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 occurs on the surface of the glass substrate in a post-molding process such as a polishing process. Therefore, if the surface of the glass substrate is unpolished, the mechanical strength of the original glass substrate is hardly impaired, and the glass substrate is hardly damaged. Further, if the surface of the glass substrate is unpolished, the polishing step can be omitted, so that the manufacturing cost of the glass substrate can be reduced. In the tempered glass of the present invention, if both surfaces of the glass substrate are unpolished, the glass substrate is further hardly damaged. Furthermore, in the tempered glass of the present invention, a chamfering process or the like may be applied to the cut surface of the glass substrate in order to prevent a situation where the glass substrate is damaged. In addition, if it shape | molds by the overflow downdraw method, the glass substrate with favorable surface accuracy can be obtained without polishing.

Glass of the present invention, when used as a glass substrate, plate thickness 1.0 mm or less (preferably 0 .7Mm less, 0.5 mm or less, particularly 0.3mm or less). The thinner the glass substrate, the lighter the glass substrate. Further, the tempered glass of the present invention has an advantage that it is difficult to break even if the plate thickness is reduced. That is, the thinner the glass substrate is, the easier it is to enjoy the effects of the present invention. In addition, if it shape | molds by the overflow downdraw method, even if it abbreviate | omits grinding | polishing processing etc., a surface accuracy is favorable and a thin glass substrate can be obtained.

  The tempered glass of the present invention is suitable for a substrate of a solar cell, particularly a substrate of a thin film compound solar cell, and further a substrate of a CIS solar cell. As described above, the tempered glass of the present invention is suitable for this application because it can maintain high mechanical strength even when heat-treated at 500 to 550 ° C. and has excellent meltability. Furthermore, the tempered glass of the present invention is suitable for this application because it easily matches the thermal expansion coefficient of a member such as a CIS-based thin film and hardly causes film peeling.

  The tempered glass of the present invention is preferably used for a display substrate, particularly a cover glass for a touch panel display and a cover glass for a mobile phone. The tempered glass of the present invention is excellent in mechanical strength and productivity, and is suitable for this application.

When the glass of the present invention is ion-exchanged in KNO ₃ melt at 430 ° C., the compressive stress layer has a compressive stress value of 300 MPa or more (preferably 500 MPa or more, particularly 600 MPa or more), and the compressive stress layer has a thickness of 10 μm or more ( It is preferably 30 μm or more, particularly 40 μm or more. In order to obtain such a compressive stress layer, the temperature of KNO ₃ may be adjusted to 400 to 550 ° C. and the ion exchange time to 2 to 10 hours (preferably 4 to 8 hours).

The glass of the present invention, as a glass composition, in _{mol%, SiO 2 55~70%, Al} 2 O 3 7~16%, B 2 O 3 0~5%, Li 2 O 0~1%, Na 2 O _{7.6~20%, K 2 O 3~15%} , MgO + CaO + SrO + BaO 8 ~13%, containing 0 to 3% SrO, contains substantially no _{as 2 O 3, Sb 2 O} 3, PbO and F The molar ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is 0.1 to ₂ , the substrate is shaped, and the plate thickness is 1.0 mm or less. The technical features (preferable numerical ranges, preferred embodiments, etc.) of the glass of the present invention are as already described in the description of the tempered glass of the present invention. For example, the description of the tempered glass of the present invention in paragraphs [0029] to [0051], [0056], and [0064] of this specification can be read as the description of the glass of the present invention.

  In the tempered glass of the present invention, a glass raw material prepared to have a predetermined glass composition is put 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. It can be produced by forming molten glass and slowly cooling it.

The method of producing glass of the present invention has a glass composition, in _{mol%, SiO 2 55~70%, Al} 2 O 3 7~16%, B 2 O 3 0~5%, Li 2 O 0~1% _{, Na 2 O 7.6~20%, K} 2 O 3~15%, MgO + CaO + SrO + BaO 8 ~13%, containing 0 to 3% SrO, substantially _{as 2 O 3, Sb 2 O} 3, PbO, F The glass raw material is melted so that the molar ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is 0.1 to ₂ , and the substrate shape has a plate thickness of 1.0 mm or less After forming into a glass, a compression stress layer is formed on the glass by performing an ion exchange treatment. The technical characteristics (preferable numerical range, preferable aspect, etc.) of the method for producing tempered glass of the present invention are as described above or described later, and the description thereof is omitted here for convenience.

  The tempered glass manufacturing method of the present invention is preferably formed into a substrate shape by an overflow down draw method. In this way, a glass substrate that is unpolished and has good surface quality can be produced. The reason is that, in the case of the overflow downdraw method, the surface to be the surface of the glass substrate is not in contact with the bowl-like refractory and is molded in a free surface state. Here, the overflow down draw method is a method in which molten glass is overflowed from both sides of a heat-resistant bowl-shaped structure, and the overflowed molten glass is stretched and formed downward while joining at the lower end of the bowl-shaped structure. It is a method of manufacturing. 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 tempered glass of the present invention is excellent in devitrification resistance and has a viscosity characteristic suitable for molding, and therefore has a property of easily molding a glass substrate by an overflow downdraw method.

  In addition to the overflow downdraw method, various molding methods can be employed. For example, a molding method such as a downdraw method (slot down method, redraw method, etc.), a float method, a rollout method, or a press method can be employed. For example, if a glass substrate is formed by a pressing method, a small glass substrate can be efficiently produced.

In the method for producing tempered glass of the present invention, the tempering treatment is performed by ion exchange treatment. The ion exchange treatment can be performed, for example, by immersing the glass in KNO ₃ molten salt at 400 to 550 ° C. for 1 to 8 hours. What is necessary is just to select optimal conditions for the ion exchange conditions in consideration of the viscosity characteristics of glass, application, plate thickness, internal tensile stress, and the like.

  Although the glass may be cut before the tempering treatment, it is preferable to cut the tempered glass after the tempering treatment from the viewpoint of manufacturing cost.

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

  Tables 1-3 show sample No. 1 to 12 are shown. In addition, the display of “not yet” in the table means that the characteristic is not measured.

  Each sample of Tables 1-3 was produced as follows. First, the glass raw material was prepared so that it might become the glass composition in a table | surface, and it melted at 1580 degreeC for 8 hours using the platinum pot. Thereafter, the molten glass was poured out on the carbon plate and formed into a substrate shape. Various characteristics were evaluated about the obtained glass substrate.

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

  A thermal expansion coefficient is the value which measured the average thermal expansion coefficient in the temperature range of 30-380 degreeC using the dilatometer.

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

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

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

  In addition, although the glass composition differs microscopically in the surface layer of glass, the glass composition as a whole is not substantially different between untempered glass and tempered glass. Therefore, characteristic values such as density and viscosity are not substantially different between untempered glass and tempered glass.

Sample No. After subjecting both surfaces 1 to 12 to optical polishing, ion exchange treatment was performed. The ion exchange treatment is performed using sample no. 1 for 455 ° C. for 2 hours, sample no. 2 to 5, 11 and 12, 410 ° C. for 4 hours, sample No. Under the condition of 440 ° C. -6 hours for 6-10, it was performed by immersing each sample in a KNO ₃ molten salt. Next, after cleaning the surface of each sample, the number of interference fringes and their spacing were observed with a surface stress meter (FSM-6000 manufactured by Toshiba Corporation), and the compressive stress value and compressive stress of the compressive stress layer in the vicinity of the glass surface. The layer thickness was calculated. In the calculation, the refractive index of each sample was 1.52, and the optical elastic constant was 28 [(nm / cm) / MPa].

  After the heat treatment, the compressive stress value and thickness of the compressive stress layer near the glass surface were calculated by the above method. In the heat treatment, the temperature was raised from room temperature to 500 ° C. at 5 ° C./minute, held at 500 ° C. for 30 minutes, and then lowered from 500 ° C. to room temperature at 10 ° C./minute.

As apparent from Tables 1 and 2, Sample No. In Nos. 1 to 10, the compressive stress value of the compressive stress layer before the heat treatment was 300 MPa or more, and the thickness of the compressive stress layer was 10 μm or more. Sample No. Nos. 1 to 10 have a high strain point of 571 ° C. or higher, so that even when heat-treated, the compressive stress value of the compressive stress layer is difficult to decrease, and the compressive stress is not easily lost when a substrate such as a CIS solar cell is manufactured. it is conceivable that. Furthermore, sample no. Nos. 1 to 10 have excellent meltability because the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is 1650 ° C. or lower.

On the other hand, sample No. Although No. 11 had a high strain point, the melt viscosity was inferior because the temperature at a high temperature viscosity of 10 ^2.5 dPa · s was 1747 ° C. Sample No. Since No. 12 has a strain point of 460 ° C., it is considered that compressive stress easily disappears after heat treatment.

  As is clear from the above description, the tempered glass of the present invention is suitable for a substrate of a solar cell, particularly a substrate of a thin film compound solar cell, and further a substrate of a CIS solar cell. Moreover, the tempered glass of this invention is suitable for cover glasses, such as a mobile telephone, a digital camera, a portable terminal (PDA), a touch panel display, besides these uses. Furthermore, the tempered glass of the present invention can be expected to be applied to applications requiring high mechanical strength, for example, window glass, magnetic disk substrates, flat panel display substrates, cover glass for solid-state image sensors, and tableware.

Claims (16)

In tempered glass having a compressive stress layer,
As a glass composition, in _{mol%, SiO 2 50~80%, Al} 2 O 3 7~16%, B 2 O 3 0~5%, Li 2 O 0~1%, Na 2 O 7.6~20% _{, K 2 O 3~15%, MgO} + CaO + SrO + BaO 8 ~13%, containing 0 to 3% SrO, contains substantially no _{as 2 O 3, Sb 2 O} 3, PbO and F, the molar ratio (MgO + CaO + SrO + BaO ) / (Li ₂ O + Na ₂ O + K ₂ O) is a tempered glass characterized by having a substrate shape and a plate thickness of 1.0 mm or less while having a value of 0.05-2. Molar ratio _{(MgO + CaO + SrO + BaO} ) / tempered glass according to claim 1, the value of _{(Li 2 O + Na 2 O} + K 2 O) is characterized in that it is a from 0.3 to 0.9.   The tempered glass according to claim 1 or 2, wherein a strain point is 550 ° C or more.   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 5 μm or more.   The tempered glass according to any one of claims 1 to 4, wherein a reduction rate of the compressive stress value of the compressive stress layer is 80% or less under a heat treatment condition of 500 ° C for 30 minutes.   6. The tempered glass according to claim 1, wherein after the heat treatment at 500 ° C. for 30 minutes, the compression stress value of the compression stress layer is 100 MPa or more and the thickness of the compression stress layer is 5 μm or more. A thermal expansion coefficient (30-380 degreeC) is 40-100 * 10 < ^-7 > / degreeC, The tempered glass in any one of Claims 1-6 characterized by the above-mentioned.   Liquid phase temperature is 1400 degrees C or less, Tempered glass in any one of Claims 1-7 characterized by the above-mentioned. Liquid phase viscosity is 10 < ^3.0 > dPa * s or more, Tempered glass in any one of Claims 1-8 characterized by the above-mentioned.   Plate thickness is 0.5 mm or less, Tempered glass in any one of Claims 1-9 characterized by the above-mentioned.   It uses for the board | substrate of a solar cell, The tempered glass of Claim 10 characterized by the above-mentioned.   It uses for the board | substrate of a thin film compound solar cell, Tempered glass of Claim 10 characterized by the above-mentioned.   It uses for the board | substrate of a display, Tempered glass of Claim 10 characterized by the above-mentioned. As a glass composition, in _{mol%, SiO 2 55~70%, Al} 2 O 3 7~16%, B 2 O 3 0~5%, Li 2 O 0~1%, Na 2 O 7.6~20% _{, K 2 O 3~15%, MgO} + CaO + SrO + BaO 8 ~13%, containing 0 to 3% SrO, contains substantially no _{as 2 O 3, Sb 2 O} 3, PbO and F, the molar ratio (MgO + CaO + SrO + BaO ) / (Li ₂ O + Na ₂ O + K ₂ O) has a value of 0.1 to ₂ , a substrate shape, and a plate thickness of 1.0 mm or less. As a glass composition, in _{mol%, SiO 2 55~70%, Al} 2 O 3 7~16%, B 2 O 3 0~5%, Li 2 O 0~1%, Na 2 O 7.6~20% _{, K 2 O 3~15%, MgO} + CaO + SrO + BaO 8 ~13%, containing 0 to 3% SrO, substantially contains no _{as 2 O 3, Sb 2 O} 3, PbO, F, and the molar ratio (MgO + CaO + SrO + BaO ) / (Li ₂ O + Na ₂ O + K ₂ O) is melted so that the glass raw material has a value of 0.1 to ₂ , and after forming into a substrate shape having a plate thickness of 1.0 mm or less, an ion exchange treatment is performed. A method for producing tempered glass, characterized in that a compressive stress layer is formed on the glass.   The method for producing tempered glass according to claim 15, wherein the glass is formed into a substrate shape by a float process.