JP5875133B2 - Tempered glass substrate - Google Patents

Description

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

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

High mechanical strength is required for glass substrates used for these applications. For these applications, a glass substrate reinforced by ion exchange or the like (so-called tempered glass substrate) is used (see Patent Document 1 and Non-Patent Document 1).
JP 2006-83045 A Tetsuro Izumiya et al., “New Glass and its Properties”, first edition, Management System Research Institute, Inc., August 20, 1984, p. 451-498

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

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

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

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

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

As a result of various studies, the present inventor has found that high ion exchange performance is exhibited by including ZnO in the glass composition. Further, in the glass composition system containing ZnO, in terms of defining the proper content of _Al 2 _{O 3,} to optimize the mass ratio of _Al 2 _{O 3} and alkali metal oxides (mass fraction), and _Li 2 O By optimizing the ratio between the alkali metal oxide and the alkali metal oxide, it was found that the devitrification resistance of the glass can be improved without impairing the ion exchange performance of the glass, and the present invention has been proposed. That is, the tempered glass substrate of the present invention is a tempered glass substrate having a compressive stress layer on the surface, and the glass composition is SiO ₂ 45 to 80% by mass, Al ₂ O ₃ 12 to 21%, ZnO 0. _{01~ 2.6%, B 2 O 3} 0~ 5%, Li 2 O 0~1.9%, SrO 0~3%, BaO 0~0.2%, the 0 to 0.5% rare earth oxides contained, and a mass _{fraction, (Li 2 O + Na 2} O + K 2 O) / Al 2 value of _{O 3} is _{0.7 ~2, Li 2 O / (} Li 2 O + Na 2 O + K 2 O) values of 0 It is characterized by 0.3 .

The tempered glass substrate of the present invention preferably has a value of Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) of 0.01 or more.

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

The tempered glass substrate of the present invention preferably has an unpolished surface.

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

The tempered glass substrate of the present invention preferably has a liquidus temperature of 1100 ° C. or lower. Here, “liquid phase temperature” refers to a temperature gradient furnace in which glass is crushed, passed through a standard sieve 30 mesh (a sieve opening of 500 μm), and glass powder remaining in a 50 mesh (a sieve opening of 300 μm) is placed in a platinum boat. The temperature at which crystals are precipitated after being held for 24 hours.

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

The tempered glass substrate of the present invention preferably has a density of 2.8 g / cm ³ or less. Here, “density” refers to a value measured by the well-known Archimedes method.

The tempered glass substrate of the present invention preferably has a Young's modulus of 70 GPa or more. Here, “Young's modulus” refers to a value measured by a resonance method.

The tempered glass substrate of the present invention preferably has a thermal expansion coefficient at 30 to 380 ° C. is 70~95 × ^{10 -7} / ℃. Here, “thermal expansion coefficient” refers to a value obtained by measuring an average thermal expansion coefficient at 30 to 380 ° C. using a dilatometer.

The tempered glass substrate of the present invention preferably has a crack occurrence rate of 70% or less. Here, the “crack occurrence rate” indicates a value measured as follows. First, in a constant temperature and humidity chamber maintained at a humidity of 30% and a temperature of 25 ° C., a Vickers indenter set to a load of 500 g is driven into the glass surface (optical polishing surface) for 15 seconds, and 15 seconds later, it is generated from the four corners of the indentation. Count the number of cracks (maximum 4 per indentation). Thus, after indenting the indenter 20 times and determining the total number of cracks generated, the total number of cracks generated is calculated by the formula (total number of cracks generated / 80) × 100.

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

The glass of the present invention, as a glass composition, in _{mass%, SiO 2 45~80%, Al} 2 O 3 12~21%, ZnO 0.01~ 2.6%, B 2 O 3 0~ 5%, Li ₂ O 0 to 1.9%, SrO 0 to 3%, BaO 0 to 0.2 %, rare earth oxide 0 to 0.5%, and by mass fraction, (Li ₂ O + Na ₂ O + K ₂ O ) / _Al 2 _{O 3} value from 0.7 to _2, the value of _{Li 2 O / (Li 2 O} + Na 2 O + K 2 O) is characterized in that 0 to 0.3.

The glass of the present invention preferably has a value of Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) of 0.01 or more.

When the glass of the present invention is subjected to ion exchange in KNO ₃ molten salt at 430 ° C. for 4 hours, the surface compressive stress is preferably 300 MPa or more and the thickness of the compressive stress layer is preferably 3 μm or more. Here, “surface compressive stress” and “compressive stress layer thickness” are the number of interference fringes observed when a sample is observed using a surface stress meter (FSM-60 manufactured by Toshiba Corporation) and A value calculated from an interval or the like.

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

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

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

SiO ₂ is a component forming a glass network, the content 45 to 80%, preferably 50% to 75%, more preferably 55 to 70%. When the content of SiO ₂ exceeds 80%, it becomes difficult to melt and mold the glass, or the thermal expansion coefficient becomes too small, and it becomes difficult to match the thermal expansion coefficient with the surrounding materials. On the other hand, if the content of SiO ₂ is less than 45%, the thermal expansion coefficient of the glass becomes too large, and the thermal shock resistance of the glass tends to decrease.

Al ₂ O ₃ is a component having an effect of increasing the heat resistance, ion exchange performance and Young's modulus of glass, and its content is 12 to 21%. When the content of Al ₂ O ₃ is more than 21%, devitrified crystals are likely to precipitate on the glass, or the thermal expansion coefficient of the glass becomes too small to make it difficult to match the thermal expansion coefficient with the surrounding materials. Moreover, the high temperature viscosity of glass becomes high and it becomes difficult to melt | dissolve. When the content of Al ₂ O ₃ is less than 12 %, there is a possibility that sufficient ion exchange performance cannot be exhibited. In view of the above, the preferred range of _Al 2 _{O 3,} and the upper limit is 18% or less, 17% or less, Ru der especially 16.5% or less.

If an appropriate amount of ZnO is added to the glass system according to the present invention, it has an effect of remarkably improving the ion exchange performance and is an essential component. ZnO is a component that has the effect of reducing the high temperature viscosity of the glass or improving the Young's modulus. The content of ZnO is 0.01 to 2.6%, preferably from 0.5 to 2.6%, the more preferably from 1 to 2.6%. And the content of ZnO is multi Kunar, in addition to the thermal expansion coefficient of the glass becomes too large, deteriorates resistance to devitrification of the glass tends to crack generation ratio increases. On the other hand, when the ZnO content is less than 0.01%, it is difficult to improve the ion exchange performance of the glass.

B ₂ O ₃ is a component that has the effect of reducing the liquidus temperature, high-temperature viscosity, and density of the glass, and is a component that has the effect of increasing the Young's modulus and ion exchange performance of the glass, and its content is 0 to 5%. On the other hand, B ₂ O ₃ content is polytene, or scorch is generated on the surface by ion exchange, or worse water resistance of the glass, the liquidus viscosity may be lowered.

Li ₂ O is an ion exchange component and a component that lowers the high temperature viscosity of the glass and improves meltability and moldability. Furthermore, Li ₂ O is a component that has the effect of improving the Young's modulus of glass and the effect of reducing the crack generation rate. Li ₂ O content of from 0 to 1.9% and preferably 0.01 to 1.9%, more preferably from 0.1 to 1.9%, preferably from 1 to 1.9% especially. If the Li ₂ O content exceeds 1.9 %, the glass tends to devitrify, the liquid phase viscosity decreases, and the thermal expansion coefficient of the glass becomes too large, resulting in the thermal shock resistance of the glass. It becomes difficult to match the thermal expansion coefficient with the surrounding material.

Na ₂ O is an ion exchange component and is a component that has the effect of reducing the high temperature viscosity of the glass to improve the meltability and formability, and to reduce the crack generation rate. Na ₂ O is also a component that improves the devitrification resistance of the glass. The content of Na ₂ O is 0 to 18%, preferably 0 to 15%, more preferably 1 to 13%, still more preferably 3 to 13%, particularly preferably 5 to 11%, and most preferably 5 to 9%. It is. When the content of Na ₂ O is more than 15%, the thermal expansion coefficient of the glass becomes too large, and the thermal shock resistance of the glass is lowered, or it is difficult to match the thermal expansion coefficient with the surrounding materials. Further, when the content of Na ₂ O is too large, they lack the balance of the glass composition, rather tends to devitrification property of the glass deteriorates.

K ₂ O is a component that not only has an effect of promoting ion exchange, but also has an effect of reducing the high temperature viscosity of the glass to improve the meltability and formability, and to reduce the crack generation rate. K ₂ O is also a component that improves devitrification resistance. The content of K ₂ O is preferably 0 to 10%, more preferably 0.5 to 9%, still more preferably 1 to 9%, and particularly preferably 2 to 8%. When the content of K ₂ O is more than 10%, the thermal expansion coefficient of the glass becomes too large, and the thermal shock resistance of the glass is lowered, or it is difficult to match the thermal expansion coefficient with the surrounding materials. If the content of K ₂ O is too large, they lack the balance of the glass composition, rather tends to devitrification property of the glass deteriorates.

If the total amount of the alkali metal component R ₂ O (R is one or more selected from Li, Na, and K) becomes too large, the glass tends to devitrify and the coefficient of thermal expansion of the glass increases. Thus, the thermal shock resistance of the glass is lowered, and it is difficult to match the thermal expansion coefficient with the surrounding material. Moreover, when the total amount of the alkali metal component R ₂ O is too large, the strain point of the glass may be excessively lowered. Therefore, the total amount of R ₂ O is desirably 30% or less, 22% or less, and particularly 20% or less. On the other hand, when the total amount of R ₂ O is too small, the ion exchange performance and meltability of the glass may be deteriorated or the crack generation rate may be increased. Therefore, the total amount of R ₂ O is desirably 1.5% or more, 6% or more, 11% or more, particularly 13% or more.

As a result of the inventor's diligent efforts, by strictly regulating the mass fractions R ₂ O / Al ₂ O ₃ and Li ₂ O / R ₂ O, the liquid phase viscosity enabling an overflow downdraw method and high It became clear that ion exchange performance can be achieved.

In the present invention, the value of R ₂ O / Al ₂ O ₃ in terms of mass fraction is 0.7 to 2, preferably 0.7 to 1.5, more preferably 0.7 to 1.4, and still more preferably 0. .8 to 1.3. If the value of R ₂ O / Al ₂ O ₃ is 0.7 or more, the devitrification resistance and meltability of the glass can be improved. On the other hand, if the value of R ₂ O / Al ₂ O ₃ is greater than 2, the balance of the glass composition is lacking, and the devitrification resistance of the glass is deteriorated or the strain point is excessively lowered. It becomes difficult to maintain a high liquid phase viscosity because the glass viscosity decreases or the glass viscosity decreases too much. Moreover, when the value of R ₂ O / Al ₂ O ₃ is larger than 2, the ion exchange performance tends to decrease. On the other hand, when the value of R ₂ O / Al ₂ O ₃ is smaller than 0.7 , the devitrification resistance and meltability of the glass deteriorate.

After adjusting the value of R ₂ O / Al ₂ O ₃ within the above range, if Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O), that is, the value of Li ₂ O / R ₂ O is optimized, The ion exchange performance can be improved while further increasing the liquid phase viscosity. The value of Li ₂ O / _{R 2} O is from 0 to 0.3, and good Mashiku mass fraction 0.01 to 0.3, more preferably from 0.05 to 0.3. If regulating the value of Li ₂ O / _{R 2} O in the range (preferably 0.01 or more values of _{Li 2 O / R 2 O)} , expressed a high ion exchange performance, at the same time a high Young's modulus of the glass In addition, it is possible to reduce the crack generation rate and the melting temperature. However, when the value of Li ₂ O / R ₂ O is greater than 0.3 , it is difficult to increase the liquid phase viscosity.

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

  The alkaline earth metal component R′O (R ′ is one or more selected from Ca, Sr, and Ba) is a component that can be added for various purposes. However, when the alkaline earth metal component R′O is increased, the density and thermal expansion coefficient of the glass are increased and the devitrification resistance is deteriorated. In addition, the crack generation rate is increased and the ion exchange is increased. There is a tendency for performance to deteriorate. Therefore, the alkaline earth metal component R′O is preferably 0 to 10%, more preferably 0 to 8%, still more preferably 0 to 5%, and particularly preferably 0 to 3%.

  MgO is a component that lowers the high-temperature viscosity of glass to improve meltability and formability, and increase the strain point and Young's modulus. Further, MgO has a relatively high effect of improving the ion exchange performance among alkaline earth metal oxides, so its content can be set to 0 to 10%. However, when the content of MgO increases, the density, thermal expansion coefficient and crack generation rate of the glass tend to increase, or the glass tends to devitrify. Therefore, the content is desirably 8% or less, 5% or less, particularly 3% or less.

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

SrO may or enhance the meltability and the formability lowers the high temperature viscosity of the glass, Ru component der of or to enhance the strain point and the Young's modulus. The content of SrO is from 0 3%. However, when the SrO content increases, the density, thermal expansion coefficient and crack generation rate of the glass increase, the glass tends to devitrify, and the ion exchange performance tends to deteriorate. Accordingly, the content thereof is less than 3%, less than 1%, 0.8% or less, particularly preferably 0.5% or less, it is desirable that ideally substantially free. Here, “substantially does not contain SrO” refers to a case where the content of SrO in the glass composition is 0.2% or less.

BaO is or enhance the meltability and the formability lowers the high temperature viscosity of the glass is a component or to enhance the strain point and the Young's modulus, you content thereof from 0 to 0.2%. But when it comes many content BaO, density of the glass, or high coefficient of thermal expansion and crack generation ratio, or easily glass devitrified, more Ru tend to the ion exchange performance deteriorates.

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

TiO ₂ is a component that enhances the ion exchange performance of glass, and its content can be 0 to 8%. However, when the content of TiO ₂ is increased, the glass is colored or the devitrification resistance is deteriorated. Therefore, the content is preferably 5% or less and 4% or less.

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

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

Furthermore, other components can be added as long as the properties of the glass are not significantly impaired. For example, 0 to 3% (preferably 0.01 to 1%) of one or more selected from the group of SO ₃ , Sb ₂ O ₃ and SnO ₂ may be contained as a fining agent. Further, As ₂ O ₃ or the like is preferably not substantially contained in consideration of environmental considerations. Here, “substantially not containing As ₂ O ₃ ” refers to a case where the content of As ₂ O ₃ in the glass composition is 0.1% or less.

Rare earth oxides such as Nb ₂ O ₅ and La ₂ O ₃ are components that increase the Young's modulus of glass. However, the cost of the raw material itself is high, and if it is contained in a large amount, the devitrification resistance deteriorates. Therefore, their content is 0 . It is preferably 5% or less , and ideally not substantially contained. Here, “substantially no rare earth oxide” refers to the case where the content of the rare earth oxide in the glass composition is 0.1% or less.

In the present invention, transition metal elements such as Co and Ni that strongly color the glass are not preferable because they reduce the transmittance of the glass substrate. In particular, when used in touch panel display applications, if the content of transition metal elements is large, the visibility of the touch panel display is impaired. Specifically, it is desirable to adjust the amount of raw material or cullet used so that it is 0.5% or less, 0.1% or less, and particularly 0.05% or less. Further, it is preferable that PbO, Bi ₂ O _{3 and the} like are not substantially contained in consideration of environmental aspects. Here, “substantially no PbO” refers to a case where the content of PbO in the glass composition is 0.1% or less. “Substantially no Bi ₂ O ₃ ” refers to the case where the content of Bi ₂ O ₃ in the glass composition is 0.1% or less.

A suitable content range of each component can be appropriately selected to obtain a preferable glass composition range. Among these, as a more preferable glass composition range,
(1) _SiO 2 _45~80% by _{mass%, Al 2 O 3 12~16.5%} , ZnO 0.01~ 2.6%, Li 2 O 0~1.9%, B 2 O 3 0~ 5%, SrO 0~3%, BaO 0~ 0.2%, contains 0 to 0.5% rare earth oxide, and a mass fraction of the value of the _{Li 2} O / _R 2 O is 0 to 0.3 , the value of _R 2 _O / _Al 2 O ₃ is 0.7 to 2,
(2) _SiO 2 _55~70% by _{mass%, Al 2 O 3 12~18%} , ZnO 0.01~ 2.6%, Li 2 O 0.01~ 1.9%, Na 2 O 0~15 _{%, K 2 O 0~10%,} B 2 O 3 0~ 5%, 0~10% MgO, CaO 0~10%, SrO 0~3%, BaO 0~ 0.2%, rare earth oxide 0 Containing 0.5%, and by mass fraction, the value of Li ₂ O / R ₂ O is 0.01 to 0.3, the value of R ₂ O / Al ₂ O ₃ is 0.7 to 1.5,
(3) _SiO 2 _55~70% by _{mass%, Al 2 O 3 12~17%} , ZnO 1~ 2.6%, Li 2 O 1~ 1.9%, Na 2 O 5~11%, K 2 _{O 2~8%, B 2 O 3} 0~5%, 0~5% MgO, CaO 0~5%, SrO 0~3%, BaO 0~ 0.2%, rare earth oxide 0 to 0.5% And glass having a mass fraction of Li ₂ O / R ₂ O of 0.05 to 0.25, R ₂ O / Al ₂ O ₃ of 0.8 to 1.3, etc. It is done.

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

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

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

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

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

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

The glass substrate according to the present invention is preferably formed by an overflow downdraw method. If the glass substrate is formed by the overflow down draw method, a glass substrate that is unpolished and has good surface quality can be produced. The reason for this is that, in the case of the overflow down draw method, the surface to be the surface of the glass substrate does not come into contact with the bowl-like refractory, and is molded in a free surface state. This is because it can be molded. Here, the overflow down draw method is to melt the molten glass from both sides of the heat-resistant bowl-like structure and draw the overflowed molten glass downward while joining at the lower end of the bowl-like structure. This is a method for producing a glass substrate. The structure and material of the bowl-shaped structure are not particularly limited as long as the dimensions and surface accuracy of the glass substrate can be set to a desired state and the quality usable for the glass substrate can be realized. Moreover, in order to perform the downward extending | stretching shaping | molding, you may apply force with what kind of method with respect to a glass substrate. For example, a method may be employed in which a heat-resistant roll having a sufficiently large width is rotated and stretched in contact with the glass substrate, or a plurality of pairs of heat-resistant rolls are only near the end face of the glass substrate. You may employ | adopt the method of making it contact and extending | stretching. The glass of the present invention is excellent in devitrification resistance and has a viscosity characteristic suitable for molding, so that molding by the overflow down draw method can be performed with high accuracy. If the liquidus temperature is 1100 ° C. or less and the liquidus viscosity is 10 ^4.0 dPa · s or more, the glass substrate can be produced by the overflow downdraw method.

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

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

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

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

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

In the tempered glass substrate of the present invention, the glass density is preferably 2.8 g / cm ³ or less, more preferably 2.7 g / cm ³ or less, still more preferably 2.6 g / cm ³ or less, and 2.55 g / cm. Most preferred is ³ or less. As the glass density is smaller, the glass substrate can be made lighter.

In the tempered glass substrate of the present invention, the thermal expansion coefficient of the glass at 30 to 380 ° C. is preferably 70~95 × 10 ^-7 / ℃, more preferably from 75~95 × 10 ^-7 / ℃ , more preferably from 75 to 90 × 10 ^-7 / ° C., particularly preferably from 77~88 × 10 ^-7 / ℃, and most preferably 80~88 × 10 ^-7 / ℃. If the thermal expansion coefficient of the glass is in the above range, it becomes easy to match the thermal expansion coefficient with a member such as a metal or an organic adhesive, and peeling of the member such as a metal or an organic adhesive can be prevented.

In the tempered glass substrate of the present invention, the temperature at a high temperature viscosity of 10 ^2.5 dPa · s of the glass is preferably 1600 ° C. or less, more preferably 1550 ° C. or less, and further preferably 1530 ° C. or less. The lower the temperature at a glass high-temperature viscosity of 10 ^2.5 dPa · s, the smaller the burden on glass manufacturing equipment such as a melting furnace, and the higher the bubble quality of the glass substrate. That is, the glass substrate can be manufactured at a lower cost as the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is lower. The temperature at a high temperature viscosity of 10 ^2.5 dPa · s of the glass corresponds to the melting temperature of the glass. The lower the temperature at the high temperature viscosity of 10 ^2.5 dPa · s of the glass, the lower the glass can be melted.

  In the tempered glass substrate of the present invention, the Young's modulus of the glass is preferably 70 GPa or more, more preferably 71 GPa or more, and further preferably 73 GPa or more. The higher the Young's modulus of the glass, the more difficult it is to bend the glass substrate. As a result, in devices such as touch panel displays, when the display is pressed with a pen or the like, the liquid crystal elements inside the device are less likely to be pressed and the display Defects are less likely to occur.

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

  In the tempered glass substrate of the present invention, the crack occurrence rate of the glass is preferably 70% or less, more preferably 50% or less, further preferably 40% or less, and 30% or less. Is particularly preferable, and is most preferably 20% or less. The smaller the glass crack generation rate, the harder it is to generate cracks in the glass substrate.

The glass of the present invention, as a glass composition, in _{mass%, SiO 2 45~80%, Al} 2 O 3 12~21%, ZnO 0.01~ 2.6%, B 2 O 3 0~ 5%, Li ₂ O 0 to 1.9%, SrO 0 to 3%, BaO 0 to 0.2 %, rare earth oxide 0 to 0.5%, and by mass fraction, (Li ₂ O + Na ₂ O + K ₂ O ) / Al ₂ O _{3 has} a value of 0.7 to 2, and Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) has a value of 0 to 0.3. In the glass of the present invention, the reason why the glass composition is limited to the above range and the preferable range are the same as those of the tempered glass substrate described above, and thus the description thereof is omitted here. Furthermore, the glass of the present invention can naturally have both the characteristics and effects of the tempered glass substrate described above.

When the glass of the present invention is ion-exchanged in KNO ₃ molten salt at 430 ° C. for 4 hours, the surface compressive stress is preferably 300 MPa or more and the thickness of the compressive stress layer is preferably 3 μm or more. Since the glass composition of the present invention regulates the glass composition within the above range, the ion exchange performance is good, the surface compressive stress can be easily set to 300 MPa or more, and the thickness of the compressive stress layer can be set to 3 μm or more. .

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

Hereinafter, the present invention will be described based on examples. Table 1-5, specimen No. 1 that shows the 24.

  Each sample was produced as follows. First, the glass raw material was prepared so that it might become the glass composition of Tables 1-5, and it melted at 1600 degreeC for 8 hours using the platinum pot. Thereafter, the molten glass was poured onto a carbon plate and formed into a plate shape. Various characteristics were evaluated about the obtained glass substrate.

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

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

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

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

  The thermal expansion coefficient is obtained by measuring an average thermal expansion coefficient at 30 to 380 ° C. using a dilatometer.

  The liquid phase temperature is obtained by crushing glass, passing through a standard sieve 30 mesh (a sieve opening of 500 μm), putting the glass powder remaining 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 crystals are deposited is measured.

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

  Young's modulus was measured by the resonance method.

As a result, no. The glass substrate of 1 to 20 has a density of 2.55 g / cm ³ or less, a thermal expansion coefficient of 76 to 91 × 10 ⁻⁷ / ° C., a crack generation rate of 30% or less, a Young's modulus of 70 GPa or more, tempered glass It was suitable as a material. No. The glass substrate of 1 to 20 has a liquid phase viscosity as high as 10 ^5.0 dPa · s or more and can be overflow downdraw molded, and the temperature at 10 ^2.5 dPa · s is as low as 1600 ° C. It is considered that a large amount of glass substrate can be supplied. In addition, although the glass composition differs microscopically in the surface layer of a glass substrate, the glass composition is not substantially different as the whole glass substrate. Therefore, characteristic values such as density, viscosity, Young's modulus and the like are not substantially different between the untempered glass substrate and the tempered glass substrate. In addition, since the crack occurrence rate is affected by the composition of the glass surface layer, the characteristic value may differ between the untempered glass substrate and the tempered glass substrate, but the crack occurrence rate tends to be lower in the tempered glass substrate. It is not a factor that decreases the strength.

  On the other hand, no. Since the glass substrate No. 21 has a high liquidus temperature of 1280 ° C. and a low liquidus viscosity, it is difficult to form by the overflow downdraw method. No. The glass substrate of 23 has a high crack generation rate. Therefore, cracks are likely to occur in the glass, and it is difficult to obtain high strength even if ion strengthening is performed. Furthermore, no. The glass substrate No. 24 has a high liquidus temperature of 1350 ° C. or higher and a low liquidus viscosity, so that it is difficult to form by the overflow downdraw method. Moreover, since the high temperature viscosity is as high as 1647 ° C., it is difficult to melt the glass.

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

  As a result, No. 1 as an example of the present invention. Each of the glass substrates 1 to 20 had a compressive stress of 519 MPa or more on its surface, and its thickness was as deep as 15 μm or more.

  On the other hand, no. 22 and no. In the 24 glass substrate, no compressive stress layer was observed even after the ion exchange treatment. As described above, Comparative Example No. The glass substrates 21 to 24 do not have both high devitrification resistance and ion exchange performance at a high level and have a low crack generation rate.

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

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

Claims (11)

A tempered glass substrate having a compressive stress layer on its surface,
A glass composition, _SiO 2 45 to _80% by _{mass%, Al 2 O 3 12~21%} , ZnO 0.01~ 2.6%, B 2 O 3 0~ 5%, Li 2 O 0~1.9 %, SrO 0-3%, BaO 0-0.2%, rare earth oxide 0-0.5%, and by mass fraction, (Li ₂ O + Na ₂ O + K ₂ O) / Al ₂ O ₃ A tempered glass substrate having a value of 0.7 to 2 and a value of Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) of 0 to 0.3 . The tempered glass substrate according to claim 1, wherein a value of Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) is 0.01 or more. Compressive stress of the surface at least 100 MPa, and tempered glass substrate according to claim 1 or 2 thickness of the compression stress layer is characterized in that at 1μm or more. The tempered glass substrate according to any one of claims 1 to 3, characterized in that has an unpolished surface. The tempered glass substrate according to any one of claims 1 to 4, wherein the substantially contains no As ₂ O _3. The tempered glass substrate according to any one of claims 1 to 5, liquidus viscosity, characterized in that of ¹⁰ 4.0 dPa · s or more. The tempered glass substrate according to any one of claims 1 to 6 density is equal to or is 2.8 g / cm ³ or less. The Young's modulus is 70 GPa or more, The tempered glass substrate according to any one of claims 1 to 7 . The tempered glass substrate according to any one of claims 1 to 8, the thermal expansion coefficient is equal to or is 70~95 × ^{10 -7} / ℃ at 30 to 380 ° C.. The tempered glass substrate according to any one of claims 1 to 9, wherein a crack generation rate is 70% or less. It uses for a touch panel display, The tempered glass substrate in any one of Claims 1-10 characterized by the above-mentioned.