JP2015038024A - Method for manufacturing tempered glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing tempered glass which can optimize the compressive stress value and thickness of a compressive stress layer so that high mechanical strength can be obtained, and enables easily performing thermal processing.SOLUTION: In a method for manufacturing tempered glass, glass raw materials are mixed and melted to obtain molten glass and then the molten glass is molded into a flat plate shape by an overflow down draw method, and subsequently, after the molding, the molded glass is cooled at a cooling speed of 0.2-200°C/min, preferably 50°C/min or less in a temperature region from a slow cooling point to a strain point and then strengthening treatment is performed. The strengthening treatment is chemical strengthening treatment for forming a compressive stress layer on a glass surface, and the chemical strengthening treatment is performed so that the compressive stress value of the compressive stress layer is 50 MPa or more and the thickness of the compressive stress layer is 10 μm or more.

Description

  The present invention relates to a method for producing tempered glass, and specifically, high strength is required for a display substrate, a cover glass for a touch panel display, a cover glass for a mobile phone, a cover glass and substrate for a solar cell, an exterior component, and the like. The present invention relates to a method for producing tempered glass suitable for devices, tools, and the like.

  Mobile phones equipped with a touch panel are widely used, and glass (so-called tempered glass) tempered by ion exchange or the like is being used as a cover glass for mobile phones. Since tempered glass has higher mechanical strength than unstrengthened glass, it is suitable for this application (see Patent Document 1 and Non-Patent Document 1).

  In recent years, touch panels are being installed in applications other than mobile phones, and depending on the application, exterior parts having a specific shape, for example, a curved shape, are required. In order to apply tempered glass to these uses, it is necessary to process the tempered glass into a specific shape, for example, a curved shape. The tempered glass having a specific shape can be prepared by first forming molten glass to produce a flat plate-shaped glass, etc., and then deforming the glass into a specific shape by thermal processing, followed by a tempering treatment (Patent Document 2). 3).

  Accordingly, these tempered glasses are required to have excellent thermal workability in addition to high mechanical strength.

JP 2006-83045 A US Pat. No. 7,168,047 JP 2001-247342 A

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

  If the compressive stress value of the compressive stress layer formed on the surface is increased and the thickness (depth) of the compressive stress layer is increased, the mechanical strength of the tempered glass can be increased.

  However, it is difficult to increase the thickness of the compressive stress layer while increasing the compressive stress value of the compressive stress layer. In order to increase the thickness of the compressive stress layer, it is necessary to increase the ion exchange temperature or lengthen the ion exchange time. However, when such treatment is performed, the compressive stress value of the compressive stress layer is significantly reduced. Because it does.

Conventionally, in order to solve this problem, it has been studied to introduce a component that improves ion exchange performance such as Al ₂ O ₃ into the glass composition. However, when these components are introduced in a large amount, the viscosity of the glass increases and it becomes difficult to heat-process the glass.

  By the way, tempered glass is used for a part of the hard disk, and this tempered glass is produced by, for example, press-molding glass and then tempering it. However, once a hard disk is incorporated into a device, handling scratches do not occur, so there is no need to increase the thickness of the compressive stress layer. On the contrary, since the hard disk emphasizes the smoothness of the surface, the surface of the hard disk may be polished to remove the compressive stress layer after the strengthening treatment. Therefore, it is difficult to divert tempered glass used for a hard disk as it is to exterior parts.

  Therefore, the present invention has devised a method for producing a tempered glass that can optimize the compressive stress value and thickness of the compressive stress layer so that high mechanical strength can be obtained, and that can be easily heat-processed. Doing this is a technical issue.

  As a result of various studies, the present inventor has found that the gap in the network structure of atoms constituting the glass affects the strengthening properties. Specifically, even with the same glass composition, after thermal processing (or immediately after molding). Furthermore, it has been found that if a specific cooling process is performed in a specific temperature range, the compressive stress value and thickness of the compressive stress layer formed after the strengthening process can be optimized. That is, the method for producing tempered glass of the present invention is characterized in that a tempering treatment is performed after cooling the temperature range from the annealing point to the strain point at a cooling rate of 200 ° C./min or less. Here, “cooling” includes not only the case of cooling the glass subsequent to the forming but also the case of once heat-treating the glass once formed again to the annealing point or higher to cool it. “Annealing point” refers to a value measured based on the method of ASTM C336, and “strain point” also refers to a value measured based on the method of ASTM C336.

  In this way, the compression stress value and thickness of the compression stress layer are optimized without specifically increasing the viscosity of the glass. Specifically, the compression stress layer is compressed after securing the thickness of the compression stress layer. The stress value can be increased. As a result, the mechanical strength of the tempered glass can be increased, and a tempered glass having a specific shape, particularly a shape other than a flat plate shape, can be easily produced by thermal processing. In addition, when it heat-processes to the annealing point vicinity after performing a tempering process, most compressive-stress layers will lose | disappear and the mechanical strength of tempered glass will fall.

  2ndly, the manufacturing method of the tempered glass of this invention is characterized by cooling the temperature range from an annealing point to a strain point with the cooling rate of 50 degrees C / min or less.

  Thirdly, the method for producing tempered glass of the present invention is characterized in that the glass is cooled after being thermally processed. If it does in this way, the design property of tempered glass can be raised, raising the compression stress value of a compression stress layer.

  Fourth, the method for producing tempered glass of the present invention is a chemical tempering treatment in which the tempering treatment forms a compressive stress layer on the surface of the glass, the compressive stress layer has a compressive stress value of 50 MPa or more, and the thickness of the compressive stress layer. The chemical strengthening treatment is performed so that the thickness becomes 10 μm or more.

Fifth, the method for producing the tempered glass of the present invention is, as a glass composition, in mass%, SiO ₂ 45 to 75%, Al ₂ O ₃ 0 to 30%, Li ₂ O + Na ₂ O + K ₂ O (Li ₂ O, (Total amount of Na ₂ O, K ₂ O) After preparing glass raw materials (including cullet) so as to contain 0 to 30%, the glass raw materials are melted and the resulting molten glass is formed into glass. Features.

Sixth, the manufacturing method of the tempered glass of the present invention has a glass composition, in _{mass%, SiO 2 45~75%, Al} 2 O 3 10~22%, B 2 O 3 0~5%, Na 2 O _8-20%, to contain K 2 O 0% is characterized by formulating the glass raw materials.

  Seventh, the method for producing tempered glass of the present invention is characterized in that molten glass is formed into flat glass by an overflow downdraw method. In this way, it is possible to easily produce a glass plate that is unpolished and has good surface accuracy, and it is easy to thermally process the glass.

  Eighth, the method for producing tempered glass of the present invention is characterized in that the glass raw material is prepared so that the softening point is 860 ° C. or lower. If it does in this way, it will become easy to heat-process glass. Here, the “softening point” refers to a value measured based on the method of ASTM C338.

Ninthly, the manufacturing method of the tempered glass of this invention mix | blends a glass raw material so that a thermal expansion coefficient may be set to 60-110 * 10 < ^-7 > / degreeC. Here, the “thermal expansion coefficient” is a value measured with a dilatometer, and indicates an average value in a temperature range of 30 to 380 ° C.

  10thly, the manufacturing method of the tempered glass of this invention prepares a glass raw material so that liquidus temperature may be 1200 degrees C or less. 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. It is held for 24 hours to indicate the temperature at which crystals precipitate.

Eleventh, the method for producing a tempered glass of the present invention is characterized in that the glass raw material is prepared so that the liquid phase viscosity is 10 ^4.0 dPa · s or more. Here, “liquid phase viscosity” refers to a value obtained by measuring the viscosity of glass at the liquid phase temperature by a platinum ball pulling method.

  12thly, the manufacturing method of the tempered glass of this invention is characterized by cooling the temperature range from an annealing point to a strain point at the cooling rate of 200 degrees C / min or less, after press-molding glass.

  13thly, the tempered glass of this invention is produced by said manufacturing method, It is characterized by the above-mentioned.

  Fourteenth, the tempered glass of the present invention has a shape other than a flat plate shape, for example, a curved surface shape, an uneven shape, a corrugated shape, a stepped shape and the like.

  Fifteenth, the tempered glass of the present invention is used for a display substrate.

  Sixteenth, the tempered glass of the present invention is used for a cover glass of a touch panel display.

  Seventeenth, the tempered glass of the present invention is used for a cover glass of a mobile phone.

  Eighteenth, the tempered glass of the present invention is used for a solar cell substrate or cover glass.

  Nineteenth, the tempered glass of the present invention is used for an exterior member.

  The manufacturing method of the tempered glass of this invention has the process of cooling the temperature range from an annealing point to a strain point with the cooling rate of 200 degrees C / min or less, 100 degrees C / min or less, 50 degrees C / min or less, 10 Cooling at a cooling rate of 5 ° C / min or less, 5 ° C / min or less, 3 ° C / min or less, 2 ° C / min or less, 1 ° C / min or less, 0.5 ° C / min or less, particularly 0.2 ° C / min or less It is preferable to have the process to do. When the cooling rate is faster than 200 ° C./min, the glass structure becomes too sparse, and it is difficult to obtain a high compressive stress value even if ion exchange treatment is performed. On the other hand, when the cooling rate is slower than 0.2 ° C./min, the productivity of the tempered glass decreases. In particular, when the glass is deformed into a specific shape by thermal processing and then cooled at the cooling rate in the temperature range, a high compressive stress value can be obtained and the design of the tempered glass can be enhanced. In addition, also when it cools with the said cooling rate in the said temperature range after press-molding glass to a specific shape, while the compressive-stress value of a compressive-stress layer increases, the design property of tempered glass can be improved.

  The manufacturing method of the tempered glass of this invention has the process of performing a tempering process, ie, the process of forming a compression stress layer in glass. There are a physical tempering method and a chemical tempering method as a method for forming a compressive stress layer on glass, but it is preferable that the method for producing tempered glass of the present invention forms a compressive stress layer by a chemical tempering method. The chemical strengthening method is a method in which alkali ions having a large ion radius are introduced into the surface of the glass 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, the ion exchange treatment can be performed even if the glass is thin, and a desired mechanical strength can be obtained. Furthermore, if the compressive stress layer is formed by a chemical tempering method, unlike a physical tempering method such as an air cooling tempering method, even if the tempered glass is cut after the tempering treatment, the tempered glass is not easily broken.

  In the method for producing tempered glass of the present invention, the ion exchange treatment can be performed by immersing the glass in a potassium nitrate solution at 400 to 550 ° C. for 1 to 8 hours, for example. 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.

In the method for producing tempered glass of the present invention, it is preferable to perform chemical strengthening treatment so that the compressive stress value of the compressive stress layer is 50 MPa or more, 100 MPa or more, 300 MPa or more, 500 MPa or more, 600 MPa or more, and particularly 700 MPa or more. As the compressive stress value increases, the mechanical strength of the tempered glass increases. On the other hand, when an extremely large compressive stress is formed on the surface, microcracks are likely to occur on the surface, and conversely, the mechanical strength of the tempered glass may be reduced. In addition, if an extremely large compressive stress is formed on the surface, the internal tensile stress may become extremely high. Therefore, it is preferable to perform chemical strengthening so that the compressive stress of the compressive stress layer is 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 and 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 method for producing tempered glass of the present invention, it is preferable to perform the chemical strengthening treatment so that the thickness of the compressive stress layer is 10 μm or more, 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, particularly 60 μm or more. When tempered glass is used for exterior parts, the surface of the tempered glass is often contacted directly, and the mechanical strength of the tempered glass may be significantly reduced due to handling flaws. Therefore, if the thickness of the compressive stress layer is increased, the tempered glass is hardly broken even if the tempered glass is deeply damaged. On the other hand, the thickness of the compressive stress layer is preferably 200 μm or less in order to facilitate cutting. In addition, if the content of Al ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO, ZnO in the glass composition is increased and the content of SrO, BaO is decreased, the thickness of the compressive stress layer can be increased. Furthermore, 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 method for producing tempered glass of the present invention, it is preferable to perform chemical strengthening treatment so that the internal tensile stress value calculated by the following formula 1 is 200 MPa or less, 150 MPa or less, 100 MPa or less, and particularly 50 MPa or less. The smaller the internal tensile stress value, the lower the probability that the tempered glass will break due to internal defects. However, if the internal tensile stress value is made extremely small, the compressive stress value of the compressive stress layer tends to decrease and the thickness of the compressive stress layer tends to be small, so the internal tensile stress value is 1 MPa or more and 10 MPa. Above, especially 15 MPa or more is preferable.

The method of manufacturing a tempered glass of the present invention, as a glass composition, in _{mass%, SiO 2 45~75%, Al} 2 O 3 0~30%, Li 2 O + Na 2 O + K 2 O so as to contain 0-30%, It is preferable to prepare a glass raw material. The reason why the glass composition range is regulated as described above in the method for producing tempered glass of the present invention will be described below.

SiO ₂ is a component that forms a glass network, and the content thereof is 45 to 75%, preferably 50 to 70%, more preferably 50 to 66%, still more preferably 52 to 63%, and particularly preferably 54. ~ 63%. If the content of SiO ₂ is too large, the meltability and moldability are lowered, and the thermal expansion coefficient is 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 improves ion exchange performance, and is a component that increases the strain point and Young's modulus, and its content is 0 to 30%. When Al ₂ O ₃ content is too large, devitrification crystal glass is easily precipitated, it becomes difficult to mold the glass, for example, an overflow down draw method and the like. Also, if the content of Al ₂ O ₃ is too large, the thermal expansion coefficient becomes too low, making it difficult to match the thermal expansion coefficient of the surrounding material, increasing the high temperature viscosity, making it difficult to melt the glass, Since the softening point becomes too high, the temperature at the time of heat processing / press molding becomes high, and the life of the molding die may be reduced. On the other hand, when the content of Al ₂ O ₃ is too small, there is a possibility which can not be sufficiently exhibited ion exchange performance. Judging from the above viewpoint, the upper limit range of Al ₂ O ₃ is 25% or less, 23% or less, 22% or less, 20% or less, 19% or less, 18% or less, 17% or less, particularly 16.5%. The following is preferred. Further, the lower limit range of Al ₂ O ₃ is preferably 3% or more, 5% or more, 10% or more, 12% or more, 13% or more, particularly 14% or more.

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 the meltability and moldability. If there is too much Li ₂ O + Na ₂ O + K ₂ O, in addition to the glass becoming more devitrified, the thermal expansion coefficient becomes too high, the thermal shock resistance is lowered, or the thermal expansion coefficient of the surrounding material is matched. It becomes difficult. _Further, when the _{Li 2 O + Na 2 O +} K 2 O is too large, the strain point excessively lowers, it may become difficult to increase the compression stress value of the compressive stress layer. _Further, when the _{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 30% or less, preferably 25% or less, more preferably 20% or less. On the other _hand, there is a case where the _{Li 2 O + Na 2 O +} K 2 O is too small, or decreased the ion exchange performance and meltability, softening point becomes too high. Therefore, the content of Li ₂ O + Na ₂ O + K ₂ O is preferably 0.1% or more, 8% or more, 10% or more, 13% or more, and particularly preferably 15% or more.

Li ₂ O is an ion exchange component, and is a component that lowers the high-temperature viscosity and improves the meltability and moldability. Li ₂ O is a component that increases the Young's modulus and is a component that easily increases the compressive stress value among alkali metal oxides. However, if the content of Li ₂ O is too large, the liquid phase viscosity is lowered and the glass is liable to be devitrified, the thermal expansion coefficient is too high, and the thermal shock resistance is lowered. It becomes difficult to match the thermal expansion coefficient of the surrounding material. Furthermore, if the content of Li ₂ O is too large, the low-temperature viscosity, particularly the strain point, is too low, and stress relaxation is likely to occur during ion exchange, and conversely, the compressive stress value of the compressive stress layer may be low. . Therefore, the content of Li ₂ O is 0 to 10%, 0 to 8%, 0 to 6%, 0 to 4%, 0 to 3%, 0 to 2%, 0 to 1%, particularly 0 to 0.1. % Is preferred.

Na ₂ O is an ion exchange component, is a component that lowers the high temperature viscosity of glass and improves meltability and moldability, and is a component that improves devitrification resistance, and its content is 8-20. %, 8 to 16%, 8 to 15%, 9 to 15%, 10 to 15%, 11 to 15%, particularly 12 to 15% are preferable. When the content of Na 2 _O is too large, the thermal expansion coefficient becomes too high, the thermal shock resistance becomes difficult to match or decreased, the thermal expansion coefficient with those of 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, or too high softening point, decreases the ion exchange performance.

K ₂ O is a component that improves ion exchange performance, and is a component that has a high effect of increasing the thickness of the compressive stress layer among alkali metal oxides. K ₂ O is a component that lowers the high-temperature viscosity and improves the meltability and moldability. Furthermore, K ₂ O is also a component that improves devitrification resistance. When the content of K 2 _O is too large, the thermal expansion coefficient becomes too high, the thermal shock resistance becomes difficult to match or decreased, the thermal expansion coefficient with those of peripheral 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 K ₂ O is preferably 10% or less, 8% or less, 7% or less, 6% or less, and particularly preferably 5% or less. On the other hand, in order to increase the thickness of the compressive stress layer, the lower limit range of K ₂ O is preferably 0.1% or more, 0.5% or more, 1% or more, particularly 2% or more.

  In addition to the above components, the following components may be introduced into the glass composition.

  MgO + CaO + SrO + BaO (total amount of MgO, CaO, SrO, BaO) is a component that lowers the high-temperature viscosity to increase meltability and formability, and increases the strain point and Young's modulus, and its content is 0 to 15%. 0 to 10%, 0 to 6%, particularly 0 to 5% is preferable. However, when there is too much content of MgO + CaO + SrO + BaO, there exists a tendency for a density and a thermal expansion coefficient to become high too much, devitrification resistance to fall, or ion exchange performance to fall.

  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 preferably 0 to 10%, 0 to 6%, 0 to 4%, particularly preferably 0 to 3%. However, when there is too much content of MgO, a density and a thermal expansion coefficient will become high too much, or it will become easy to devitrify glass.

  CaO is a component that lowers the high-temperature viscosity to increase meltability and moldability, and increases the strain point and Young's modulus. Further, among alkaline earth metal oxides, it is a component having a relatively high effect of improving ion exchange performance, and its content is 0 to 10%, 0 to 8%, 0 to 6%, particularly 0 to 3%. % Is preferred. However, when there is too much content of CaO, a density and a thermal expansion coefficient will become high too much, or it will become easy to devitrify glass. Moreover, the component balance of a glass composition may be impaired, and on the contrary, ion exchange performance may fall.

  SrO and BaO are components that lower the viscosity at high temperature to increase the meltability and moldability, and increase the strain point and Young's modulus, and their content is preferably 0 to 5%. When there is too much content of SrO and BaO, in addition to the tendency for ion exchange performance to fall, a density and a thermal expansion coefficient will become high too much, or it will become easy to devitrify glass. The SrO content is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly preferably 0.1% or less. The BaO content is preferably 3% or less, 2% or less, 1% or less, 0.8% or less, 0.5% or less, and particularly preferably 0.1% or less.

  If SrO + BaO (total amount of SrO and BaO) is regulated to 0 to 5%, 0 to 3%, 0 to 2.5%, 0 to 2%, 0 to 1%, particularly 0 to 0.1%, ions Exchange performance improves more effectively. As described above, SrO + BaO has an action of inhibiting the ion exchange reaction. Therefore, if SrO + BaO is excessive, it is difficult to increase the mechanical strength of the tempered glass.

When the value obtained by dividing MgO + CaO + SrO + BaO by Li ₂ O + Na ₂ O + K ₂ O, that is, the mass fraction (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) increases, the devitrification resistance tends to decrease. Therefore, the mass fraction (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is preferably 0.5 or less, 0.4 or less, and particularly preferably 0.3 or less.

  ZnO is a component that improves the ion exchange performance, and in particular, is a component that has a large effect of increasing the compressive stress value of the compressive stress layer, and is a component that lowers the high temperature viscosity without lowering the low temperature viscosity. Is preferably 0 to 10%, 0 to 5%, 0 to 3%, particularly preferably 0 to 1%. However, when there is too much content of ZnO, glass will phase-divide, devitrification resistance will fall, or a density will become high too much.

  If the mass fraction is regulated as follows, thermal workability (low softening point), devitrification resistance, and ion exchange performance can be achieved at a high level.

First, the mass fraction Na ₂ O / SiO ₂ is preferably 0.05 to 0.5. When the mass fraction Na ₂ O / SiO ₂ is smaller than 0.05, the softening point becomes too high, the high-temperature viscosity becomes too high, the foam quality is lowered, the liquidus temperature becomes high, or ion exchange The performance tends to decrease. On the other hand, if the mass fraction Na ₂ O / SiO ₂ is greater than 0.5, the thermal expansion coefficient and density may be too high, or the strain point may be too low, and the ion exchange performance may be reduced. The lower limit range of the mass fraction Na ₂ O / SiO ₂ is 0.1 or more, 0.15 or more, 0.2 or more, 0.22 or more, particularly preferably 0.24 or more, and the upper limit range is 0.5 or less, 0 .45 or less, 0.4 or less, 0.35 or less, 0.32 or less, and particularly preferably 0.3 or less.

Secondly, the mass fraction Al ₂ O ₃ / SiO ₂ is preferably 0.05 to 0.5. When the mass fraction Al ₂ O ₃ / SiO ₂ is smaller than 0.05, it is difficult to obtain desired ion exchange performance. Further, when the mass fraction Al 2 _O 3 _/ SiO ₂ is greater than 0.5, or too high softening point, too high temperature viscosity, or reduces the bubble quality, the liquidus temperature increases. The lower limit range of the mass fraction Al ₂ O ₃ / SiO ₂ is preferably 0.1 or more, 0.15 or more, 0.2 or more, 0.22 or more, particularly preferably 0.24 or more, and the upper limit range is 0.45 or less. 0.4 or less, 0.35 or less, 0.32 or less, 0.3 or less, 0.29 or less, 0.28 or less, and particularly 0.27 or less are preferable.

  Third, the mass fraction CaO / MgO is preferably 0 to 3, 0 to 2, particularly preferably 0 to 1. When the mass fraction CaO / MgO is larger than 3, the ion exchange performance tends to be lowered, and it is particularly difficult to increase the thickness of the compressive stress layer in a short time.

ZrO ₂ is a component that significantly 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%, 0 to 9%, 0.001 to 8%, 0.01 to 7%, 1 to 7%, 2 to 7%, 3 to 6%, particularly 3 to 5% are preferable. When the content of ZrO ₂ is too high, there are cases where the devitrification resistance is extremely lowered.

B ₂ O ₃ is a component that lowers the liquidus temperature, high-temperature viscosity, and density and increases ion exchange performance, particularly the compressive stress value of the compressive stress layer, and its content is 0 to 10%, 0 to 5%. 0 to 3%, particularly 0 to 2% is preferable. When the content of B ₂ O ₃ is too large, or occurs burnt on the surface of the glass by ion exchange treatment, or water resistance is lowered, the liquidus viscosity may be decreased. Further, when the content of B ₂ O ₃ is too large, the thickness of the compressive stress layer tends to decrease.

TiO ₂ is a component that improves the ion exchange performance and is a component that lowers the high temperature viscosity, but if its content is too large, the glass is colored or the devitrification resistance is likely to be reduced. The content is preferably 1% or less, 0.5% or less, particularly preferably 0.1% or less.

P ₂ O ₅ is a component that enhances the ion exchange performance, and is a component that is particularly effective in increasing the thickness of the compressive stress layer, and its content is 8% or less, 5% or less, 4% or less, 2% or less. 0.5% or less, particularly 0.1% or less is preferable. However, when the content of P ₂ O ₅ is too large, or glass phase separation, the water resistance tends to lower.

As a fining agent, 0 to 3% of one or more selected from the group of As ₂ O ₃ , Sb ₂ O ₃ , CeO ₂ , SnO ₂ , F, Cl, and SO ₃ can be added. However, As ₂ O ₃ , Sb ₂ O ₃ , F, particularly As ₂ O ₃ , Sb ₂ O ₃ are preferably refrained from use as much as possible from an environmental point of view, and each content is less than 0.1% Is preferred. Preferred fining agents _are SnO 2, _SO 3, Cl. The SnO ₂ content is preferably 0 to 1%, 0.01 to 0.5%, particularly preferably 0.05 to 0.4%. When the content of SnO ₂ is more than 1%, the devitrification resistance tends to decrease. The content of SO ₃ is 0 to 0.1%, 0.0001 to 0.1%, 0.0003 to 0.08%, 0.0005 to 0.05%, particularly 0.001 to 0.03%. preferable. When the content of SO ₃ is more than 0.1%, SO ₃ is reboiled at the time of melting, and the bubble quality tends to be lowered. The Cl content is preferably 0 to 0.5%, 0.005 to 0.3%, 0.01 to 0.2%, 0.01 to 0.1%, and particularly preferably 0.01 to 0.09%. . When the Cl content is more than 0.5%, the metal wiring is easily corroded when a metal wiring pattern or the like is formed on the tempered glass.

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 added in a large amount, the devitrification resistance tends to be lowered. Therefore, the rare earth oxide content is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly preferably 0.1% or less.

  Transition metal oxides such as Co and Ni are components that strongly color the glass and lower the transmittance. Therefore, it is desirable to adjust the usage amount of the glass raw material so that the content of the transition metal oxide is 0.5% or less, 0.1% or less, or 0.05% or less.

PbO and Bi ₂ O ₃ should be used as little as possible from an environmental point of view, and their content is preferably less than 0.1%.

Although the suitable content range of each component can be selected suitably and it can be set as the suitable glass composition range, the more suitable glass composition range is as follows among them.
(1) in _{mass%, SiO 2 45~75%, Al} 2 O 3 0~30%, Li 2 O + Na 2 O + K 2 O 0~30% containing,
(2) in _{mass%, SiO 2 45~75%, Al} 2 O 3 10~30%, Li 2 O + Na 2 O + K 2 O containing 0-30%, and the mass fraction _Na 2 O / SiO ₂ is 0. 05 to 0.5, mass fraction Al ₂ O ₃ / SiO ₂ is 0.05 to 0.5, mass fraction CaO / MgO is 0 to 3,
(3) _{mass%, SiO 2 45~75%, Al} 2 O 3 10~30%, Li 2 O + Na 2 O + K 2 O containing 0-30%, and the mass fraction _{Na 2} O / SiO 2 is 0. 1 to 0.4, mass fraction Al ₂ O ₃ / SiO ₂ is 0.1 to 0.4, mass fraction CaO / MgO is 0 to 2,
(4) in _{mass%, SiO 2 45~75%, Al} 2 O 3 10~30%, Li 2 O 0~10%, Na 2 O 5~20% K 2 O containing 0 to 10%, and the mass The fraction Na ₂ O / SiO ₂ is 0.2 to 0.3, the mass fraction Al ₂ O ₃ / SiO ₂ is 0.2 to 0.3, the mass fraction CaO / MgO is 0 to 1,
(5) in _{mass%, SiO 2 52~70%, Al} 2 O 3 10~25%, Li 2 O 0~6%, Na 2 O 5~20%, K 2 O containing 0-10%, and The mass fraction Na ₂ O / SiO ₂ is 0.2 to 0.3, the mass fraction Al ₂ O ₃ / SiO ₂ is 0.2 to 0.3, the mass fraction CaO / MgO is 0 to 1,
(6) _{mass%, SiO 2 52~65%, Al} 2 O 3 10~20%, Li 2 O 0~2%, Na 2 O 10~20%, K 2 O 0~5%, ZnO 0~ 1%, TiO _{2 0 to} 0.1%, and a mass fraction Na ₂ O / SiO ₂ of 0.21 to 0.28, a mass fraction of Al ₂ O ₃ / SiO ₂ of 0.21 to 0. 28, mass fraction CaO / MgO is 0-1.

In the manufacturing method of the tempered glass of this invention, it is preferable to prepare a glass raw material so that a density may be 2.7 g / cm < ³ > or less, 2.6 g / cm < ³ > or less, especially 2.55 g / cm < ³ > or less. 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.

In the method for producing tempered glass of the present invention, it is preferable to prepare the glass raw material so that the strain point is 450 ° C. or higher, 460 ° C. or higher, 480 ° C. or higher, 500 ° C. or higher, 510 ° C. or higher, particularly 520 ° C. or higher. The higher the strain point, the better the heat resistance, and the compressive stress layer is less likely to disappear even if the tempered glass is heat-treated. In addition, when the strain point is high, stress relaxation is less likely to occur in the ion exchange treatment, so that a high compressive stress value is easily obtained. In order to increase the strain point, the content of alkali metal oxide, particularly Li ₂ O in the glass composition is reduced, or the content of alkaline earth metal oxide, Al ₂ O ₃ , ZrO ₂ , P ₂ O ₅ Just increase the amount.

  In the method for producing tempered glass of the present invention, the softening point is 860 ° C. or lower, 850 ° C. or lower, 840 ° C. or lower, 830 ° C. or lower, 820 ° C. or lower, 800 ° C. or lower, 780 ° C. or lower, 770 ° C. or lower, especially 760 ° C. or lower. It is preferable to prepare the glass raw material so as to be. The lower the softening point, the easier the heat processing is possible, and the heat processing can be performed at a low temperature. Also in the case of press molding, the lower the softening point, the smaller the burden on the molding die, so the life of the molding die becomes longer and the molding cost tends to decrease.

In the method for producing tempered glass of the present invention, the glass raw material is adjusted so that the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s is 1500 ° C. or lower, 1450 ° C. or lower, 1430 ° C. or lower, 1420 ° C. or lower, particularly 1400 ° C. or lower. Is preferably prepared. The lower the temperature corresponding to a 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, resulting in glass manufacturing costs. Can be reduced. The temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s corresponds to the melting temperature, and the lower the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s, the more the glass can be melted at a low temperature. it can. To lower the temperature corresponding to 10 ^2.5 dPa · s, increase the content of alkali metal oxide, alkaline earth metal oxide, ZnO, B ₂ O ₃ , TiO _{2 in} the glass composition, or SiO ₂ , The content of Al ₂ O ₃ may be reduced.

In the method for producing tempered glass of the present invention, the glass raw material has a thermal expansion coefficient of 70 to 110 × 10 ⁻⁷ / ° C., 75 to 100 × 10 ⁻⁷ / ° C., particularly 80 to 100 × 10 ⁻⁷ / ° C. Is preferably prepared. When the thermal expansion coefficient is in the above range, it becomes easy to match the thermal expansion coefficient of a member such as a metal or an organic adhesive, and it is possible to prevent peeling of the member such as a metal or an organic adhesive. In order to increase the coefficient of thermal expansion, it is only necessary to increase the content of alkali metal oxides and alkaline earth metal oxides in the glass composition. Conversely, in order to decrease the coefficient of thermal expansion, alkali metal oxidation in the glass composition is required. And the content of alkaline earth metal oxides may be reduced.

In the method for producing tempered glass of the present invention, it is preferable to prepare the glass raw material so that the liquidus temperature is 1200 ° C. or lower, 1050 ° C. or lower, 1000 ° C. or lower, 950 ° C. or lower, 900 ° C. or lower, particularly 860 ° C. or lower. . The lower the liquidus temperature, the better the devitrification resistance, thermal processability and moldability. In particular, the lower the liquidus temperature, the more difficult it is for crystals to precipitate out of the glass, so heat processing can be performed at a relatively low temperature, and the life of the molding die can be increased accordingly. 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 the method for producing tempered glass of the present invention, the liquid phase viscosity is 10 ^4.0 dPa · s or more, 10 ^4.5 dPa · s or more, 10 ^5.0 dPa · s or more, 10 ^5.2 dPa · s or more, 10 ^5.3 dPa · s or more, 10 ^5.5 dPa · s or more, 10 ^5.7 dPa · s or more, 10 ^5.8 dPa · s or more, 10 ^6.0 dPa · s or more, 10 ^6.2. It is preferable to prepare the glass raw material so as to be dPa · s or more. The higher the liquidus viscosity, the better the devitrification resistance and moldability. 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. That's fine.

  In general, for glass, a glass raw material is charged into a continuous melting furnace, the glass raw material is heated and melted at 1500 to 1600 ° C., clarified, then supplied to a molding apparatus, and then the molten glass is formed and gradually cooled. Can be manufactured.

  In the tempered glass of the present invention, the molten glass is preferably formed into a flat glass by an overflow down draw method. By doing so, it is possible to produce a flat plate-shaped glass that is unpolished and has good surface quality. The reason is that in the case of the overflow downdraw method, the surface to be the surface of the glass 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 flat plate shape in which molten glass is overflowed from both sides of a heat-resistant bowl-shaped structure, and the molten glass overflowed is joined at the lower end of the bowl-shaped structure and stretched downward. It is a method of manufacturing the glass. The structure and material of the bowl-shaped structure are not particularly limited as long as the dimensions and surface accuracy of the glass are in a desired state and a desired quality can be realized. Further, a force may be applied to the glass by any method in order to perform downward stretching. For example, a method may be adopted in which a heat-resistant roll having a sufficiently large width is rotated and stretched in contact with glass, or a plurality of pairs of heat-resistant rolls are contacted only near the end face of the glass. It is also possible to adopt a method of stretching by stretching.

  Further, in the method for producing tempered glass of the present invention, in addition to the overflow downdraw method, various forming methods such as a downdraw method (slot down method, redraw method, etc.), a float method, a rollout method, a press method, etc. Can be adopted. In particular, if glass is formed by the press method, glass having a specific shape can be produced efficiently, and if it is cooled at the above cooling rate in the above temperature range, a high compressive stress is imparted to the glass in the subsequent strengthening treatment. Can do.

  In the method for producing tempered glass of the present invention, when used as a substrate or cover glass, in order to reduce the weight of the tempered glass, the plate thickness is 3.0 mm or less, 1.5 mm or less, 0.7 mm or less, 0.5 mm. Hereinafter, it is particularly preferably 0.3 mm or less, and when used as an exterior part, in order to maintain the mechanical strength of the tempered glass, the thickness is 0.3 mm or more, 0.5 mm or more, 0.7 mm or more, 1 It is preferably 0.0 mm or more, 1.3 mm or more, or 1.5 mm or more.

  In the method for producing tempered glass of the present invention, it is preferable to omit the polishing of the surface (excluding the cut 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 occurs on the surface of the glass in a process after molding of the molten glass, such as a polishing process. Therefore, if the polishing is omitted, the original mechanical strength is hardly lost, and the tempered glass is hardly broken. Moreover, in the manufacturing method of the tempered glass of this invention, it is preferable to shape | mold molten glass so that the average surface roughness (Ra) of the unpolished surface may be 10 or less, 5 or less, especially 2 or less. When used as an exterior component, such a surface shape can impart an appropriate gloss to the tempered glass. “Average surface roughness (Ra)” refers to a value measured by a method based on SEMI D7-97 “Measurement method of surface roughness of FPD glass substrate”. In the tempered glass of the present invention, a chamfering process or the like may be applied to the cut surface in order to prevent a situation from breaking to the cut surface.

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

  Table 1 shows the glass composition and characteristics of the glass samples used in the experiments shown in Table 2.

  The glass samples in Table 1 were produced as follows. First, after preparing a glass raw material so that it might become the glass composition shown in Table 1, the glass raw material was fuse | melted and the obtained molten glass was shape | molded by the overflow down draw method into the flat glass. About the obtained glass, the characteristic shown in Table 1 was measured. An annealer was placed at the bottom of the molded body, the temperature at the top of the annealer was set to 700 ° C., the temperature at the bottom of the annealer was set to 450 ° C., and the inside of the annealer was passed at a speed of 1200 mm / min.

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

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

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

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

  The thermal expansion coefficient is a value measured with a dilatometer, and is an average value in a temperature range of 30 to 380 ° C.

  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. Then, the temperature at which the crystal is deposited 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.

  Table 2 shows examples of the present invention, and compression of the compressive stress layer formed on the glass surface when treated under cooling conditions and ion exchange conditions in the temperature range from the annealing point to the strain point in the table. The stress value and thickness are shown. The cooling rate of 120 ° C./min exemplifies the cooling rate when passing through the annealer shown in paragraph [0082] of this specification. The cooling rate of 2 ° C./min exemplifies the cooling rate when the glass once formed is heat-treated again above the annealing point and cooled. Further, the cooling rate of 0.2 ° C./min is the cooling rate when the glass once formed is heat-treated again to the annealing point or higher, and more specifically, when so-called precision annealing is performed. The cooling rate is illustrated.

  The number of interference fringes and the distance between the interference fringes were observed using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation), and the compressive stress value on the glass surface and the thickness of the compressive stress layer were calculated. In the calculation, the refractive index of each sample was 1.52, and the optical elastic constant was 28 [(nm / cm) / MPa].

  As is clear from Table 2, even if the ion exchange treatment has the same glass composition and the same conditions, the compression stress value of the compression stress layer can be increased by lowering the cooling rate. The thickness of the compressive stress layer tends to be somewhat smaller when the cooling rate is slow. However, if the ion exchange treatment conditions are adjusted, the thickness of the compressive stress layer can be increased while increasing the compressive stress value of the compressive stress layer. Can be bigger.

  In addition, for convenience of explanation of the present invention, the flat glass formed by the overflow down draw method or the like is cooled. However, the flat glass is heat-processed and deformed into a specific shape, or the glass is in a specific shape. It is considered that the same effect can be obtained by applying the same cooling condition to the glass press-molded in the same temperature range.

  The manufacturing method of the tempered glass of this invention is suitable as a manufacturing method of the tempered glass used for cover glasses, such as a mobile telephone, a digital camera, PDA, a touch panel display. Further, the method for producing tempered glass of the present invention is suitable as a method for producing tempered glass used for exterior parts such as cellular phones, mobile PCs, pointing devices, etc. subjected to heat processing, in particular, exterior parts having a shape other than a flat plate shape. is there. Furthermore, the method for producing tempered glass of the present invention can be applied to applications requiring high mechanical strength in addition to these applications (for example, window glass, magnetic disk substrates, flat panel display substrates, solar cell substrates and It is also suitable as a method for producing tempered glass of a cover glass, a cover glass for a solid-state imaging device, and tableware.

  The present invention relates to a method for producing tempered glass, and specifically, high strength is required for a display substrate, a cover glass for a touch panel display, a cover glass for a mobile phone, a cover glass and substrate for a solar cell, an exterior component, and the like. The present invention relates to a method for producing tempered glass suitable for devices, tools, and the like.

  Mobile phones equipped with a touch panel are widely used, and glass (so-called tempered glass) tempered by ion exchange or the like is being used as a cover glass for mobile phones. Since tempered glass has higher mechanical strength than unstrengthened glass, it is suitable for this application (see Patent Document 1 and Non-Patent Document 1).

  In recent years, touch panels are being installed in applications other than mobile phones, and depending on the application, exterior parts having a specific shape, for example, a curved shape, are required. In order to apply tempered glass to these uses, it is necessary to process the tempered glass into a specific shape, for example, a curved shape. The tempered glass having a specific shape can be prepared by first forming molten glass to produce a flat plate-shaped glass, etc., and then deforming the glass into a specific shape by thermal processing, followed by a tempering treatment (Patent Document 2). 3).

  Accordingly, these tempered glasses are required to have excellent thermal workability in addition to high mechanical strength.

JP 2006-83045 A US Pat. No. 7,168,047 JP 2001-247342 A

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

  If the compressive stress value of the compressive stress layer formed on the surface is increased and the thickness (depth) of the compressive stress layer is increased, the mechanical strength of the tempered glass can be increased.

  However, it is difficult to increase the thickness of the compressive stress layer while increasing the compressive stress value of the compressive stress layer. In order to increase the thickness of the compressive stress layer, it is necessary to increase the ion exchange temperature or lengthen the ion exchange time. However, when such treatment is performed, the compressive stress value of the compressive stress layer is significantly reduced. Because it does.

Conventionally, in order to solve this problem, it has been studied to introduce a component that improves ion exchange performance such as Al ₂ O ₃ into the glass composition. However, when these components are introduced in a large amount, the viscosity of the glass increases and it becomes difficult to heat-process the glass.

  By the way, tempered glass is used for a part of the hard disk, and this tempered glass is produced by, for example, press-molding glass and then tempering it. However, once a hard disk is incorporated into a device, handling scratches do not occur, so there is no need to increase the thickness of the compressive stress layer. On the contrary, since the hard disk emphasizes the smoothness of the surface, the surface of the hard disk may be polished to remove the compressive stress layer after the strengthening treatment. Therefore, it is difficult to divert tempered glass used for a hard disk as it is to exterior parts.

  Therefore, the present invention has devised a method for producing a tempered glass that can optimize the compressive stress value and thickness of the compressive stress layer so that high mechanical strength can be obtained, and that can be easily heat-processed. Doing this is a technical issue.

The present inventor has conducted various studies, affecting the gap reinforcing properties of networks of atoms constituting the glass, even after formation Katachijika the same glass composition in particular, the temperature range from It has been found that if a specific cooling process is performed, the compressive stress value and thickness of the compressive stress layer formed after the strengthening process can be optimized. That is, in the method for producing tempered glass of the present invention, a glass raw material is prepared and melted to obtain a molten glass, and then the molten glass is formed into a flat plate shape by an overflow down draw method, and subsequently cooled slowly after the forming. A temperature range from a point to a strain point is cooled at a cooling rate of 0.2 to 200 ° C./min , and a strengthening treatment is performed after the cooling . Here , “ annealing point” refers to a value measured based on the method of ASTM C336, and “strain point” also refers to a value measured based on the method of ASTM C336.

  In this way, the compression stress value and thickness of the compression stress layer are optimized without specifically increasing the viscosity of the glass. Specifically, the compression stress layer is compressed after securing the thickness of the compression stress layer. The stress value can be increased. As a result, the mechanical strength of the tempered glass can be increased, and a tempered glass having a specific shape, particularly a shape other than a flat plate shape, can be easily produced by thermal processing. In addition, when it heat-processes to the annealing point vicinity after performing a tempering process, most compressive-stress layers will lose | disappear and the mechanical strength of tempered glass will fall.

Method for producing a tempered glass of the present invention is to mold the molten glass by an overflow down draw method, a step of subsequently cooling the temperature range from the annealing point to strain point at 2-200 / min cooling rate molding it is preferably provided.

The method for producing tempered glass of the present invention is a chemical tempering treatment in which the tempering treatment forms a compressive stress layer on the surface of the glass, the compressive stress value of the compressive stress layer is 50 MPa or more, and the thickness of the compressive stress layer is 10 μm or more. It is preferable to perform the chemical strengthening treatment.

Method for producing a tempered glass of the present invention has a glass composition, in _{mass%, SiO 2 45~75%, Al} 2 O 3 0~30%, Li 2 O + Na 2 O + K 2 O (Li 2 O, Na 2 O, (Total amount of K ₂ O) After preparing glass raw materials (including cullet) so as to contain 0 to 30%, it is preferable to melt the glass raw materials and shape the resulting molten glass into glass.

The method of producing glass of the present invention has a glass composition, in _{mass%, SiO 2 45~75%, Al} 2 O 3 10~22%, B 2 O 3 0~5%, Na 2 O 8~20% It is preferable to prepare the glass raw material so as to contain 0 to 10% of K ₂ O.

The method for producing tempered glass of the present invention is characterized in that molten glass is formed into flat glass by an overflow downdraw method. In this way, it is possible to easily produce a glass plate that is unpolished and has good surface accuracy, and it is easy to thermally process the glass.

In the method for producing tempered glass of the present invention, the glass raw material is preferably prepared so that the softening point is 860 ° C. or lower. If it does in this way, it will become easy to heat-process glass. Here, the “softening point” refers to a value measured based on the method of ASTM C338.

In the method for producing tempered glass of the present invention, the glass raw material is preferably prepared so that the thermal expansion coefficient is 60 to 110 × 10 ⁻⁷ / ° C. Here, the “thermal expansion coefficient” is a value measured with a dilatometer, and indicates an average value in a temperature range of 30 to 380 ° C.

In the method for producing tempered glass of the present invention, the glass raw material is preferably prepared so that the liquidus temperature is 1200 ° 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. It is held for 24 hours to indicate the temperature at which crystals precipitate.

In the method for producing tempered glass of the present invention, it is preferable to prepare the glass raw material so that the liquid phase viscosity is 10 ^4.0 dPa · s or more. Here, “liquid phase viscosity” refers to a value obtained by measuring the viscosity of glass at the liquid phase temperature by a platinum ball pulling method.

It is preferable that the tempered glass of this invention is produced by said manufacturing method.

Glass of the present invention, the shape other than the plate shape, for example curved, uneven, wavy shape is preferably a stepped shape.

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

The tempered glass of the present invention is preferably used for a cover glass of a touch panel display.

The tempered glass of the present invention is preferably used for a cover glass of a mobile phone.

The tempered glass of the present invention is preferably used for a solar cell substrate or cover glass.

The tempered glass of the present invention is preferably used for an exterior member.

The method for producing tempered glass of the present invention has a step of cooling the temperature range from the annealing point to the strain point at a cooling rate of 200 ° C./min or less following molding by the overflow downdraw method , and is 100 ° C./min or less. , 50 ° C. / min or less, 10 ° C. / min or less, 5 ° C. / min or less, it is preferable to have a step of cooling at 3 ° C. / min or less cooling rate especially. When the cooling rate is faster than 200 ° C./min, the glass structure becomes too sparse, and it is difficult to obtain a high compressive stress value even if ion exchange treatment is performed. On the other hand, when the cooling rate is slower than 0.2 ° C./min, the productivity of the tempered glass decreases. In particular, when the glass is deformed into a specific shape by thermal processing and then cooled at the cooling rate in the temperature range, a high compressive stress value can be obtained and the design of the tempered glass can be enhanced. In addition, also when it cools with the said cooling rate in the said temperature range after press-molding glass to a specific shape, while the compressive-stress value of a compressive-stress layer increases, the design property of tempered glass can be improved.

  The manufacturing method of the tempered glass of this invention has the process of performing a tempering process, ie, the process of forming a compression stress layer in glass. There are a physical tempering method and a chemical tempering method as a method for forming a compressive stress layer on glass, but it is preferable that the method for producing tempered glass of the present invention forms a compressive stress layer by a chemical tempering method. The chemical strengthening method is a method in which alkali ions having a large ion radius are introduced into the surface of the glass 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, the ion exchange treatment can be performed even if the glass is thin, and a desired mechanical strength can be obtained. Furthermore, if the compressive stress layer is formed by a chemical tempering method, unlike a physical tempering method such as an air cooling tempering method, even if the tempered glass is cut after the tempering treatment, the tempered glass is not easily broken.

  In the method for producing tempered glass of the present invention, the ion exchange treatment can be performed by immersing the glass in a potassium nitrate solution at 400 to 550 ° C. for 1 to 8 hours, for example. 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.

In the method for producing tempered glass of the present invention, it is preferable to perform chemical strengthening treatment so that the compressive stress value of the compressive stress layer is 50 MPa or more, 100 MPa or more, 300 MPa or more, 500 MPa or more, 600 MPa or more, and particularly 700 MPa or more. As the compressive stress value increases, the mechanical strength of the tempered glass increases. On the other hand, when an extremely large compressive stress is formed on the surface, microcracks are likely to occur on the surface, and conversely, the mechanical strength of the tempered glass may be reduced. In addition, if an extremely large compressive stress is formed on the surface, the internal tensile stress may become extremely high. Therefore, it is preferable to perform chemical strengthening so that the compressive stress of the compressive stress layer is 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 and 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 method for producing tempered glass of the present invention, it is preferable to perform the chemical strengthening treatment so that the thickness of the compressive stress layer is 10 μm or more, 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, particularly 60 μm or more. When tempered glass is used for exterior parts, the surface of the tempered glass is often contacted directly, and the mechanical strength of the tempered glass may be significantly reduced due to handling flaws. Therefore, if the thickness of the compressive stress layer is increased, the tempered glass is hardly broken even if the tempered glass is deeply damaged. On the other hand, the thickness of the compressive stress layer is preferably 200 μm or less in order to facilitate cutting. In addition, if the content of Al ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO, ZnO in the glass composition is increased and the content of SrO, BaO is decreased, the thickness of the compressive stress layer can be increased. Furthermore, 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 method for producing tempered glass of the present invention, it is preferable to perform chemical strengthening treatment so that the internal tensile stress value calculated by the following formula 1 is 200 MPa or less, 150 MPa or less, 100 MPa or less, and particularly 50 MPa or less. The smaller the internal tensile stress value, the lower the probability that the tempered glass will break due to internal defects. However, if the internal tensile stress value is made extremely small, the compressive stress value of the compressive stress layer tends to decrease and the thickness of the compressive stress layer tends to be small, so the internal tensile stress value is 1 MPa or more and 10 MPa. Above, especially 15 MPa or more is preferable.

The method of manufacturing a tempered glass of the present invention, as a glass composition, in _{mass%, SiO 2 45~75%, Al} 2 O 3 0~30%, Li 2 O + Na 2 O + K 2 O so as to contain 0-30%, It is preferable to prepare a glass raw material. The reason why the glass composition range is regulated as described above in the method for producing tempered glass of the present invention will be described below.

SiO ₂ is a component that forms a glass network, and the content thereof is 45 to 75%, preferably 50 to 70%, more preferably 50 to 66%, still more preferably 52 to 63%, and particularly preferably 54. ~ 63%. If the content of SiO ₂ is too large, the meltability and moldability are lowered, and the thermal expansion coefficient is 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 improves ion exchange performance, and is a component that increases the strain point and Young's modulus, and its content is 0 to 30%. When Al ₂ O ₃ content is too large, devitrification crystal glass is easily precipitated, it becomes difficult to mold the glass, for example, an overflow down draw method and the like. Also, if the content of Al ₂ O ₃ is too large, the thermal expansion coefficient becomes too low, making it difficult to match the thermal expansion coefficient of the surrounding material, increasing the high temperature viscosity, making it difficult to melt the glass, Since the softening point becomes too high, the temperature at the time of heat processing / press molding becomes high, and the life of the molding die may be reduced. On the other hand, when the content of Al ₂ O ₃ is too small, there is a possibility which can not be sufficiently exhibited ion exchange performance. Judging from the above viewpoint, the upper limit range of Al ₂ O ₃ is 25% or less, 23% or less, 22% or less, 20% or less, 19% or less, 18% or less, 17% or less, particularly 16.5%. The following is preferred. Further, the lower limit range of Al ₂ O ₃ is preferably 3% or more, 5% or more, 10% or more, 12% or more, 13% or more, particularly 14% or more.

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 the meltability and moldability. If there is too much Li ₂ O + Na ₂ O + K ₂ O, in addition to the glass becoming more devitrified, the thermal expansion coefficient becomes too high, the thermal shock resistance is lowered, or the thermal expansion coefficient of the surrounding material is matched. It becomes difficult. _Further, when the _{Li 2 O + Na 2 O +} K 2 O is too large, the strain point excessively lowers, it may become difficult to increase the compression stress value of the compressive stress layer. _Further, when the _{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 30% or less, preferably 25% or less, more preferably 20% or less. On the other _hand, there is a case where the _{Li 2 O + Na 2 O +} K 2 O is too small, or decreased the ion exchange performance and meltability, softening point becomes too high. Therefore, the content of Li ₂ O + Na ₂ O + K ₂ O is preferably 0.1% or more, 8% or more, 10% or more, 13% or more, and particularly preferably 15% or more.

Li ₂ O is an ion exchange component, and is a component that lowers the high-temperature viscosity and improves the meltability and moldability. Li ₂ O is a component that increases the Young's modulus and is a component that easily increases the compressive stress value among alkali metal oxides. However, if the content of Li ₂ O is too large, the liquid phase viscosity is lowered and the glass is liable to be devitrified, the thermal expansion coefficient is too high, and the thermal shock resistance is lowered. It becomes difficult to match the thermal expansion coefficient of the surrounding material. Furthermore, if the content of Li ₂ O is too large, the low-temperature viscosity, particularly the strain point, is too low, and stress relaxation is likely to occur during ion exchange, and conversely, the compressive stress value of the compressive stress layer may be low. . Therefore, the content of Li ₂ O is 0 to 10%, 0 to 8%, 0 to 6%, 0 to 4%, 0 to 3%, 0 to 2%, 0 to 1%, particularly 0 to 0.1. % Is preferred.

Na ₂ O is an ion exchange component, is a component that lowers the high temperature viscosity of glass and improves meltability and moldability, and is a component that improves devitrification resistance, and its content is 8-20. %, 8 to 16%, 8 to 15%, 9 to 15%, 10 to 15%, 11 to 15%, particularly 12 to 15% are preferable. When the content of Na 2 _O is too large, the thermal expansion coefficient becomes too high, the thermal shock resistance becomes difficult to match or decreased, the thermal expansion coefficient with those of 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, or too high softening point, decreases the ion exchange performance.

K ₂ O is a component that improves ion exchange performance, and is a component that has a high effect of increasing the thickness of the compressive stress layer among alkali metal oxides. K ₂ O is a component that lowers the high-temperature viscosity and improves the meltability and moldability. Furthermore, K ₂ O is also a component that improves devitrification resistance. When the content of K 2 _O is too large, the thermal expansion coefficient becomes too high, the thermal shock resistance becomes difficult to match or decreased, the thermal expansion coefficient with those of peripheral 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 K ₂ O is preferably 10% or less, 8% or less, 7% or less, 6% or less, and particularly preferably 5% or less. On the other hand, in order to increase the thickness of the compressive stress layer, the lower limit range of K ₂ O is preferably 0.1% or more, 0.5% or more, 1% or more, particularly 2% or more.

  In addition to the above components, the following components may be introduced into the glass composition.

  MgO + CaO + SrO + BaO (total amount of MgO, CaO, SrO, BaO) is a component that lowers the high-temperature viscosity to increase meltability and formability, and increases the strain point and Young's modulus, and its content is 0 to 15%. 0 to 10%, 0 to 6%, particularly 0 to 5% is preferable. However, when there is too much content of MgO + CaO + SrO + BaO, there exists a tendency for a density and a thermal expansion coefficient to become high too much, devitrification resistance to fall, or ion exchange performance to fall.

  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 preferably 0 to 10%, 0 to 6%, 0 to 4%, particularly preferably 0 to 3%. However, when there is too much content of MgO, a density and a thermal expansion coefficient will become high too much, or it will become easy to devitrify glass.

  CaO is a component that lowers the high-temperature viscosity to increase meltability and moldability, and increases the strain point and Young's modulus. Further, among alkaline earth metal oxides, it is a component having a relatively high effect of improving ion exchange performance, and its content is 0 to 10%, 0 to 8%, 0 to 6%, particularly 0 to 3%. % Is preferred. However, when there is too much content of CaO, a density and a thermal expansion coefficient will become high too much, or it will become easy to devitrify glass. Moreover, the component balance of a glass composition may be impaired, and on the contrary, ion exchange performance may fall.

  SrO and BaO are components that lower the viscosity at high temperature to increase the meltability and moldability, and increase the strain point and Young's modulus, and their content is preferably 0 to 5%. When there is too much content of SrO and BaO, in addition to the tendency for ion exchange performance to fall, a density and a thermal expansion coefficient will become high too much, or it will become easy to devitrify glass. The SrO content is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly preferably 0.1% or less. The BaO content is preferably 3% or less, 2% or less, 1% or less, 0.8% or less, 0.5% or less, and particularly preferably 0.1% or less.

  If SrO + BaO (total amount of SrO and BaO) is regulated to 0 to 5%, 0 to 3%, 0 to 2.5%, 0 to 2%, 0 to 1%, particularly 0 to 0.1%, ions Exchange performance improves more effectively. As described above, SrO + BaO has an action of inhibiting the ion exchange reaction. Therefore, if SrO + BaO is excessive, it is difficult to increase the mechanical strength of the tempered glass.

When the value obtained by dividing MgO + CaO + SrO + BaO by Li ₂ O + Na ₂ O + K ₂ O, that is, the mass fraction (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) increases, the devitrification resistance tends to decrease. Therefore, the mass fraction (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is preferably 0.5 or less, 0.4 or less, and particularly preferably 0.3 or less.

  ZnO is a component that improves the ion exchange performance, and in particular, is a component that has a large effect of increasing the compressive stress value of the compressive stress layer, and is a component that lowers the high temperature viscosity without lowering the low temperature viscosity. Is preferably 0 to 10%, 0 to 5%, 0 to 3%, particularly preferably 0 to 1%. However, when there is too much content of ZnO, glass will phase-divide, devitrification resistance will fall, or a density will become high too much.

  If the mass fraction is regulated as follows, thermal workability (low softening point), devitrification resistance, and ion exchange performance can be achieved at a high level.

First, the mass fraction Na ₂ O / SiO ₂ is preferably 0.05 to 0.5. When the mass fraction Na ₂ O / SiO ₂ is smaller than 0.05, the softening point becomes too high, the high-temperature viscosity becomes too high, the foam quality is lowered, the liquidus temperature becomes high, or ion exchange The performance tends to decrease. On the other hand, if the mass fraction Na ₂ O / SiO ₂ is greater than 0.5, the thermal expansion coefficient and density may be too high, or the strain point may be too low, and the ion exchange performance may be reduced. The lower limit range of the mass fraction Na ₂ O / SiO ₂ is 0.1 or more, 0.15 or more, 0.2 or more, 0.22 or more, particularly preferably 0.24 or more, and the upper limit range is 0.5 or less, 0 .45 or less, 0.4 or less, 0.35 or less, 0.32 or less, and particularly preferably 0.3 or less.

Secondly, the mass fraction Al ₂ O ₃ / SiO ₂ is preferably 0.05 to 0.5. When the mass fraction Al ₂ O ₃ / SiO ₂ is smaller than 0.05, it is difficult to obtain desired ion exchange performance. Further, when the mass fraction Al 2 _O 3 _/ SiO ₂ is greater than 0.5, or too high softening point, too high temperature viscosity, or reduces the bubble quality, the liquidus temperature increases. The lower limit range of the mass fraction Al ₂ O ₃ / SiO ₂ is preferably 0.1 or more, 0.15 or more, 0.2 or more, 0.22 or more, particularly preferably 0.24 or more, and the upper limit range is 0.45 or less. 0.4 or less, 0.35 or less, 0.32 or less, 0.3 or less, 0.29 or less, 0.28 or less, and particularly 0.27 or less are preferable.

  Third, the mass fraction CaO / MgO is preferably 0 to 3, 0 to 2, particularly preferably 0 to 1. When the mass fraction CaO / MgO is larger than 3, the ion exchange performance tends to be lowered, and it is particularly difficult to increase the thickness of the compressive stress layer in a short time.

ZrO ₂ is a component that significantly 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%, 0 to 9%, 0.001 to 8%, 0.01 to 7%, 1 to 7%, 2 to 7%, 3 to 6%, particularly 3 to 5% are preferable. When the content of ZrO ₂ is too high, there are cases where the devitrification resistance is extremely lowered.

B ₂ O ₃ is a component that lowers the liquidus temperature, high-temperature viscosity, and density and increases ion exchange performance, particularly the compressive stress value of the compressive stress layer, and its content is 0 to 10%, 0 to 5%. 0 to 3%, particularly 0 to 2% is preferable. When the content of B ₂ O ₃ is too large, or occurs burnt on the surface of the glass by ion exchange treatment, or water resistance is lowered, the liquidus viscosity may be decreased. Further, when the content of B ₂ O ₃ is too large, the thickness of the compressive stress layer tends to decrease.

TiO ₂ is a component that improves the ion exchange performance and is a component that lowers the high temperature viscosity, but if its content is too large, the glass is colored or the devitrification resistance is likely to be reduced. The content is preferably 1% or less, 0.5% or less, particularly preferably 0.1% or less.

P ₂ O ₅ is a component that enhances the ion exchange performance, and is a component that is particularly effective in increasing the thickness of the compressive stress layer, and its content is 8% or less, 5% or less, 4% or less, 2% or less. 0.5% or less, particularly 0.1% or less is preferable. However, when the content of P ₂ O ₅ is too large, or glass phase separation, the water resistance tends to lower.

As a fining agent, 0 to 3% of one or more selected from the group of As ₂ O ₃ , Sb ₂ O ₃ , CeO ₂ , SnO ₂ , F, Cl, and SO ₃ can be added. However, As ₂ O ₃ , Sb ₂ O ₃ , F, particularly As ₂ O ₃ , Sb ₂ O ₃ are preferably refrained from use as much as possible from an environmental point of view, and each content is less than 0.1% Is preferred. Preferred fining agents _are SnO 2, _SO 3, Cl. The SnO ₂ content is preferably 0 to 1%, 0.01 to 0.5%, particularly preferably 0.05 to 0.4%. When the content of SnO ₂ is more than 1%, the devitrification resistance tends to decrease. The content of SO ₃ is 0 to 0.1%, 0.0001 to 0.1%, 0.0003 to 0.08%, 0.0005 to 0.05%, particularly 0.001 to 0.03%. preferable. When the content of SO ₃ is more than 0.1%, SO ₃ is reboiled at the time of melting, and the bubble quality tends to be lowered. The Cl content is preferably 0 to 0.5%, 0.005 to 0.3%, 0.01 to 0.2%, 0.01 to 0.1%, and particularly preferably 0.01 to 0.09%. . When the Cl content is more than 0.5%, the metal wiring is easily corroded when a metal wiring pattern or the like is formed on the tempered glass.

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 added in a large amount, the devitrification resistance tends to be lowered. Therefore, the rare earth oxide content is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly preferably 0.1% or less.

  Transition metal oxides such as Co and Ni are components that strongly color the glass and lower the transmittance. Therefore, it is desirable to adjust the usage amount of the glass raw material so that the content of the transition metal oxide is 0.5% or less, 0.1% or less, or 0.05% or less.

PbO and Bi ₂ O ₃ should be used as little as possible from an environmental point of view, and their content is preferably less than 0.1%.

Although the suitable content range of each component can be selected suitably and it can be set as the suitable glass composition range, the more suitable glass composition range is as follows among them.
(1) in _{mass%, SiO 2 45~75%, Al} 2 O 3 0~30%, Li 2 O + Na 2 O + K 2 O 0~30% containing,
(2) in _{mass%, SiO 2 45~75%, Al} 2 O 3 10~30%, Li 2 O + Na 2 O + K 2 O containing 0-30%, and the mass fraction _Na 2 O / SiO ₂ is 0. 05 to 0.5, mass fraction Al ₂ O ₃ / SiO ₂ is 0.05 to 0.5, mass fraction CaO / MgO is 0 to 3,
(3) _{mass%, SiO 2 45~75%, Al} 2 O 3 10~30%, Li 2 O + Na 2 O + K 2 O containing 0-30%, and the mass fraction _{Na 2} O / SiO 2 is 0. 1 to 0.4, mass fraction Al ₂ O ₃ / SiO ₂ is 0.1 to 0.4, mass fraction CaO / MgO is 0 to 2,
(4) in _{mass%, SiO 2 45~75%, Al} 2 O 3 10~30%, Li 2 O 0~10%, Na 2 O 5~20% K 2 O containing 0 to 10%, and the mass The fraction Na ₂ O / SiO ₂ is 0.2 to 0.3, the mass fraction Al ₂ O ₃ / SiO ₂ is 0.2 to 0.3, the mass fraction CaO / MgO is 0 to 1,
(5) in _{mass%, SiO 2 52~70%, Al} 2 O 3 10~25%, Li 2 O 0~6%, Na 2 O 5~20%, K 2 O containing 0-10%, and The mass fraction Na ₂ O / SiO ₂ is 0.2 to 0.3, the mass fraction Al ₂ O ₃ / SiO ₂ is 0.2 to 0.3, the mass fraction CaO / MgO is 0 to 1,
(6) _{mass%, SiO 2 52~65%, Al} 2 O 3 10~20%, Li 2 O 0~2%, Na 2 O 10~20%, K 2 O 0~5%, ZnO 0~ 1%, TiO _{2 0 to} 0.1%, and a mass fraction Na ₂ O / SiO ₂ of 0.21 to 0.28, a mass fraction of Al ₂ O ₃ / SiO ₂ of 0.21 to 0. 28, mass fraction CaO / MgO is 0-1.

In the manufacturing method of the tempered glass of this invention, it is preferable to prepare a glass raw material so that a density may be 2.7 g / cm < ³ > or less, 2.6 g / cm < ³ > or less, especially 2.55 g / cm < ³ > or less. 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.

In the method for producing tempered glass of the present invention, it is preferable to prepare the glass raw material so that the strain point is 450 ° C. or higher, 460 ° C. or higher, 480 ° C. or higher, 500 ° C. or higher, 510 ° C. or higher, particularly 520 ° C. or higher. The higher the strain point, the better the heat resistance, and the compressive stress layer is less likely to disappear even if the tempered glass is heat-treated. In addition, when the strain point is high, stress relaxation is less likely to occur in the ion exchange treatment, so that a high compressive stress value is easily obtained. In order to increase the strain point, the content of alkali metal oxide, particularly Li ₂ O in the glass composition is reduced, or the content of alkaline earth metal oxide, Al ₂ O ₃ , ZrO ₂ , P ₂ O ₅ Just increase the amount.

  In the method for producing tempered glass of the present invention, the softening point is 860 ° C. or lower, 850 ° C. or lower, 840 ° C. or lower, 830 ° C. or lower, 820 ° C. or lower, 800 ° C. or lower, 780 ° C. or lower, 770 ° C. or lower, especially 760 ° C. or lower. It is preferable to prepare the glass raw material so as to be. The lower the softening point, the easier the heat processing is possible, and the heat processing can be performed at a low temperature. Also in the case of press molding, the lower the softening point, the smaller the burden on the molding die, so the life of the molding die becomes longer and the molding cost tends to decrease.

In the method for producing tempered glass of the present invention, the glass raw material is adjusted so that the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s is 1500 ° C. or lower, 1450 ° C. or lower, 1430 ° C. or lower, 1420 ° C. or lower, particularly 1400 ° C. or lower. Is preferably prepared. The lower the temperature corresponding to a 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, resulting in glass manufacturing costs. Can be reduced. The temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s corresponds to the melting temperature, and the lower the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s, the more the glass can be melted at a low temperature. it can. To lower the temperature corresponding to 10 ^2.5 dPa · s, increase the content of alkali metal oxide, alkaline earth metal oxide, ZnO, B ₂ O ₃ , TiO _{2 in} the glass composition, or SiO ₂ , The content of Al ₂ O ₃ may be reduced.

In the method for producing tempered glass of the present invention, the glass raw material has a thermal expansion coefficient of 70 to 110 × 10 ⁻⁷ / ° C., 75 to 100 × 10 ⁻⁷ / ° C., particularly 80 to 100 × 10 ⁻⁷ / ° C. Is preferably prepared. When the thermal expansion coefficient is in the above range, it becomes easy to match the thermal expansion coefficient of a member such as a metal or an organic adhesive, and it is possible to prevent peeling of the member such as a metal or an organic adhesive. In order to increase the coefficient of thermal expansion, it is only necessary to increase the content of alkali metal oxides and alkaline earth metal oxides in the glass composition. Conversely, in order to decrease the coefficient of thermal expansion, alkali metal oxidation in the glass composition is required. And the content of alkaline earth metal oxides may be reduced.

In the method for producing tempered glass of the present invention, it is preferable to prepare the glass raw material so that the liquidus temperature is 1200 ° C. or lower, 1050 ° C. or lower, 1000 ° C. or lower, 950 ° C. or lower, 900 ° C. or lower, particularly 860 ° C. or lower. . The lower the liquidus temperature, the better the devitrification resistance, thermal processability and moldability. In particular, the lower the liquidus temperature, the more difficult it is for crystals to precipitate out of the glass, so heat processing can be performed at a relatively low temperature, and the life of the molding die can be increased accordingly. 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 the method for producing tempered glass of the present invention, the liquid phase viscosity is 10 ^4.0 dPa · s or more, 10 ^4.5 dPa · s or more, 10 ^5.0 dPa · s or more, 10 ^5.2 dPa · s or more, 10 ^5.3 dPa · s or more, 10 ^5.5 dPa · s or more, 10 ^5.7 dPa · s or more, 10 ^5.8 dPa · s or more, 10 ^6.0 dPa · s or more, 10 ^6.2. It is preferable to prepare the glass raw material so as to be dPa · s or more. The higher the liquidus viscosity, the better the devitrification resistance and moldability. 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. That's fine.

Generally, a glass raw material 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, and then the molten glass is flattened by an overflow down draw method. It can be manufactured by forming into a shape and slow cooling.

Glass of the present invention is molded into a glass flat plate shape by an overflow down draw method. By doing so, it is possible to produce a flat plate-shaped glass that is unpolished and has good surface quality. The reason is that in the case of the overflow downdraw method, the surface to be the surface of the glass 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 flat plate shape in which molten glass overflows from both sides of a heat-resistant bowl-shaped structure, and the overflowed molten glass is stretched downward and joined at the lower end of the bowl-shaped structure. It is a method of manufacturing the glass. The structure and material of the bowl-shaped structure are not particularly limited as long as the dimensions and surface accuracy of the glass are in a desired state and a desired quality can be realized. Further, a force may be applied to the glass by any method in order to perform downward stretching. For example, a method may be adopted in which a heat-resistant roll having a sufficiently large width is rotated and stretched in contact with glass, or a plurality of pairs of heat-resistant rolls are contacted only near the end face of the glass. It is also possible to adopt a method of stretching by stretching.

  In the method for producing tempered glass of the present invention, when used as a substrate or cover glass, in order to reduce the weight of the tempered glass, the plate thickness is 3.0 mm or less, 1.5 mm or less, 0.7 mm or less, 0.5 mm. Hereinafter, it is particularly preferably 0.3 mm or less, and when used as an exterior part, in order to maintain the mechanical strength of the tempered glass, the thickness is 0.3 mm or more, 0.5 mm or more, 0.7 mm or more, 1 It is preferably 0.0 mm or more, 1.3 mm or more, or 1.5 mm or more.

  In the method for producing tempered glass of the present invention, it is preferable to omit the polishing of the surface (excluding the cut 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 occurs on the surface of the glass in a process after molding of the molten glass, such as a polishing process. Therefore, if the polishing is omitted, the original mechanical strength is hardly lost, and the tempered glass is hardly broken. Moreover, in the manufacturing method of the tempered glass of this invention, it is preferable to shape | mold molten glass so that the average surface roughness (Ra) of the unpolished surface may be 10 or less, 5 or less, especially 2 or less. When used as an exterior component, such a surface shape can impart an appropriate gloss to the tempered glass. “Average surface roughness (Ra)” refers to a value measured by a method based on SEMI D7-97 “Measurement method of surface roughness of FPD glass substrate”. In the tempered glass of the present invention, a chamfering process or the like may be applied to the cut surface in order to prevent a situation from breaking to the cut surface.

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

  Table 1 shows the glass composition and characteristics of the glass samples used in the experiments shown in Table 2.

  The glass samples in Table 1 were produced as follows. First, after preparing a glass raw material so that it might become the glass composition shown in Table 1, the glass raw material was fuse | melted and the obtained molten glass was shape | molded by the overflow down draw method into the flat glass. About the obtained glass, the characteristic shown in Table 1 was measured. An annealer was placed at the bottom of the molded body, the temperature at the top of the annealer was set to 700 ° C., the temperature at the bottom of the annealer was set to 450 ° C., and the inside of the annealer was passed at a speed of 1200 mm / min.

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

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

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

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

  The thermal expansion coefficient is a value measured with a dilatometer, and is an average value in a temperature range of 30 to 380 ° C.

  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. Then, the temperature at which the crystal is deposited 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.

Table 2 shows examples of the present invention, and compression of the compressive stress layer formed on the glass surface when treated under cooling conditions and ion exchange conditions in the temperature range from the annealing point to the strain point in the table. The stress value and thickness are shown. The cooling rate of 120 ° C./min exemplifies the cooling rate when passing through the annealer shown in paragraph [00 79 ] of this specification. The cooling rate of 2 ° C./min exemplifies the cooling rate when the glass once formed is heat-treated again above the annealing point and cooled. Further, the cooling rate of 0.2 ° C./min is the cooling rate when the glass once formed is heat-treated again to the annealing point or higher, and more specifically, when so-called precision annealing is performed. The cooling rate is illustrated.

  The number of interference fringes and the distance between the interference fringes were observed using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation), and the compressive stress value on the glass surface and the thickness of the compressive stress layer were calculated. In the calculation, the refractive index of each sample was 1.52, and the optical elastic constant was 28 [(nm / cm) / MPa].

  As is clear from Table 2, even if the ion exchange treatment has the same glass composition and the same conditions, the compression stress value of the compression stress layer can be increased by lowering the cooling rate. The thickness of the compressive stress layer tends to be somewhat smaller when the cooling rate is slow. However, if the ion exchange treatment conditions are adjusted, the thickness of the compressive stress layer can be increased while increasing the compressive stress value of the compressive stress layer. Can be bigger.

  In addition, for convenience of explanation of the present invention, the flat glass formed by the overflow down draw method or the like is cooled. However, the flat glass is heat-processed and deformed into a specific shape, or the glass is in a specific shape. It is considered that the same effect can be obtained by applying the same cooling condition to the glass press-molded in the same temperature range.

The manufacturing method of the tempered glass of this invention is suitable as a manufacturing method of the tempered glass used for cover glasses, such as a mobile telephone, a digital camera, PDA, a touch panel display. Further, the method for producing tempered glass of the present invention is suitable as a method for producing tempered glass used for exterior parts such as cellular phones, mobile PCs, pointing devices, etc. subjected to heat processing, in particular, exterior parts having a shape other than a flat plate shape. is there. Furthermore, the method for producing tempered glass of the present invention can be applied to applications requiring high mechanical strength in addition to these applications (for example, window glass, magnetic disk substrates, flat panel display substrates, solar cell substrates and It is also suitable as a method for producing tempered glass of a cover glass, a cover glass for a solid-state imaging device, and tableware.

Claims (19)

  A method for producing a tempered glass, comprising performing a tempering treatment after cooling a temperature range from a slow cooling point to a strain point at a cooling rate of 200 ° C./min or less.   The method for producing a tempered glass according to claim 1, wherein the temperature range from the annealing point to the strain point is cooled at a cooling rate of 50 ° C / min or less.   The method for producing tempered glass according to claim 1, wherein the glass is cooled after being thermally processed.   The strengthening process is a chemical strengthening process for forming a compressive stress layer on the surface of the glass, and the chemical strengthening process is performed so that the compressive stress value of the compressive stress layer is 50 MPa or more and the thickness of the compressive stress layer is 10 μm or more. The manufacturing method of the tempered glass in any one of Claims 1-3 characterized by the above-mentioned. As a glass composition, in _{mass%, SiO 2 45~75%, Al} 2 O 3 0~30%, Li 2 O + Na 2 O + K 2 O so as to contain 0-30%, after formulating the glass raw materials, glass raw materials The method for producing tempered glass according to any one of claims 1 to 4, wherein the molten glass obtained by melting is molded into glass. As a glass composition, in _{mass%, SiO 2 45~75%, Al} 2 O 3 10~22%, B 2 O 3 0~5%, Na 2 O 8~20%, containing K 2 O 0% Thus, the manufacturing method of the tempered glass of Claim 5 characterized by preparing a glass raw material.   The method for producing tempered glass according to claim 5 or 6, wherein the molten glass is formed into a flat glass by an overflow down draw method.   The method for producing a tempered glass according to claim 5, wherein the glass raw material is prepared so that the softening point is 860 ° C. or less. The method for producing tempered glass according to any one of claims 5 to 8, wherein the glass raw material is prepared so that the thermal expansion coefficient is 60 to 110 x ^10-7 / ° C.   The method for producing tempered glass according to claim 5, wherein the glass raw material is prepared so that the liquidus temperature is 1200 ° C. or lower. The method for producing tempered glass according to any one of claims 5 to 10, wherein the glass raw material is prepared so that the liquid phase viscosity is 10 ^4.0 dPa · s or more.   2. The method for producing tempered glass according to claim 1, wherein after the glass is press-molded, the temperature range from the annealing point to the strain point is cooled at a cooling rate of 200 ° C./min or less.   A tempered glass produced by the production method according to claim 1.   The tempered glass according to claim 13, which has a shape other than a flat plate shape.   The tempered glass according to claim 13, which is used for a display substrate.   The tempered glass according to claim 13 or 14, which is used for a cover glass of a touch panel display.   The tempered glass according to claim 13, which is used for a cover glass of a mobile phone.   It uses for the board | substrate or cover glass of a solar cell, The tempered glass of Claim 13 characterized by the above-mentioned. It uses for an exterior member, The tempered glass of Claim 13 or 14 characterized by the above-mentioned.