JP5429684B2 - Tempered glass substrate and manufacturing method thereof - Google Patents

Description

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

Devices such as mobile phones, digital cameras, PDAs or touch panel displays are becoming increasingly popular. The glass substrate used for these applications is required to have high mechanical strength and at the same time be thin and lightweight. For these reasons, a glass substrate (so-called tempered glass substrate) chemically strengthened by ion exchange or the like is used for some devices (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 Laboratory, Inc., August 20, 1984, p. 451-498

  As described above, a substrate mounted on a portable device or the like is increasingly required to have high strength, thickness reduction, and weight reduction, and the demand for a thin tempered glass substrate is increasing. However, it has been difficult to improve the mechanical strength of the thin tempered glass substrate for the following reasons.

  In order to increase the mechanical strength of the tempered glass substrate, it is effective to increase the compressive stress value of the compressive stress layer and to form the compressive stress layer deeply. However, if it does in this way, the tensile stress equivalent to the magnitude | size of the compressive stress will be formed in the inside of a tempered glass substrate, and there exists a possibility that a tempered glass substrate may be damaged. In particular, when the thickness of the tempered glass substrate is reduced, the tendency becomes remarkable.

  Internal tensile stress is: internal tensile stress [MPa] = (compressive stress value of compressive stress layer formed on main surface [MPa] × depth of compressive stress layer formed on main surface [μm]) / (plate thickness [Μm] −represented by the relationship of the depth [μm] × 2) of the compressive stress layer formed on the main surface. As can be seen from the above relational expression, the tempered glass substrate may be self-destructed due to internal tensile stress. In particular, a thin tempered glass substrate has a high compressive stress value of the compressive stress layer formed on the main surface, and the possibility increases when the compressive stress layer becomes deep. As a result, when the thickness of the tempered glass substrate is reduced, it is difficult to increase the strength.

  In view of the above circumstances, an object of the present invention is to obtain a tempered glass substrate which is a thin plate (plate thickness is 0.7 mm or less) and has high mechanical strength.

In order to increase the strength of a thin tempered glass substrate, the present inventor has intensively studied the distribution of compressive stress strain formed inside the tempered glass substrate, and when the tempered glass substrate is damaged, the end surface is the starting point. It has been found that the probability of breakage is high and the in-plane strength of the main surface of the tempered glass substrate is higher than the end face strength. From these findings, the present inventor has found that the end surface of the tempered glass substrate has, or is easy to form, a deep flaw that leads to breakage, while the main surface hardly forms a deep flaw. It has been found that the mechanical strength of a thin tempered glass substrate can be improved by forming different stress distributions in the main surface direction and the end surface direction of the tempered glass substrate so that the internal tensile stress of the tempered glass substrate is appropriate. It is proposed as an invention. That is, the tempered glass substrate of the present invention is a tempered glass substrate having a compressive stress layer, the plate thickness is 0.7 mm or less, the internal tensile stress is 200 MPa or less, and the glass composition is SiO ₂ 45 in mass%. _{~75%, Al 2 O 3 1~30} %, Li 2 O 0~2%, Na 2 O 4.1 ~20%, K 2 O containing 0-20%, the mass ratio _{(Al 2} O 3 + _{K 2} The value of O) / Na ₂ O is 0.1 to 6.5, and the depth DT of the compressive stress layer formed on the main surface is smaller than the depth DH of the compressive stress layer formed on the end surface. It is characterized by. Here, the “main surface” refers to the surface (front surface and back surface) in the thickness direction of the tempered glass substrate, and specifically to the effective surface of the tempered glass substrate (display surface in the case of a display application). Equivalent to. The “end face” refers to a side face that constitutes the outer peripheral portion of the tempered glass substrate.

The tempered glass substrate of the present invention has an internal tensile stress of 200 MPa or less. Here, “internal tensile stress” means (compressive stress value [MPa] of compressive stress layer formed on the main surface × depth [μm] of compressive stress layer formed on the main surface) / (plate thickness [ [mu] m]-refers to a value calculated by the equation [depth [[mu] m] x 2) of the compressive stress layer formed on the main surface.

The tempered glass substrate of the present invention has a glass composition, in _{mass%, SiO 2 45~75%, Al} 2 O 3 1~30%, Li 2 O 0~2%, Na 2 O 4.1 ~20%, It is characterized by containing 0 to 20% of K ₂ O and having a mass ratio (Al ₂ O ₃ + K ₂ O) / Na ₂ O of 0.1 to 6.5.

The tempered glass substrate of the present invention is characterized in that the value of mass ratio (Al ₂ O ₃ + K ₂ O) / Na ₂ O is 0.1 to 6.5.

In the tempered glass substrate of the present invention, the compressive stress value of the compressive stress layer formed on the main surface is not less than 50 MPa, the depth of the compressive stress layer is not more than 50 μm, and the compressive stress value of the compressive stress layer formed on the end surface is Is preferably 300 MPa or more, and the depth of the compressive stress layer is preferably 10 μm or more. Here, the “compressive stress value of the compressive stress layer” and “thickness of the compressive stress layer” can be calculated by observing the number of interference fringes and their intervals with a surface stress meter.

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 67 GPa or more. Here, “Young's modulus” refers to a value measured by a bending resonance method.

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

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

Method for producing a tempered glass substrate of the present invention, (1) a glass substrate is a glass composition including, in _{mass%, SiO 2 45~75%, Al} 2 O 3 1~30%, Li 2 O 0~2%, _{Na 2 O 4.1 ~20%, K} 2 O containing 0-20%, so that the value of the mass ratio _{(Al 2 O 3 + K 2} O) / Na 2 O is 0.1 to 6.5, Steps for preparing glass raw materials and obtaining glass batches, (2) Steps for melting glass batches and forming the resulting molten glass into a glass substrate of 0.7 mm or less, (3) Forming a compressive stress layer on the glass substrate And (4) the depth DT of the compressive stress layer formed on the main surface so that the internal tensile stress is 200 MPa or less, and the depth DH of the compressive stress layer formed on the end face. It has the process made smaller than this, It is characterized by the above-mentioned.

The method for producing a tempered glass substrate of the present invention removes a part of the compressive stress layer formed on the main surface of the tempered glass substrate, thereby reducing the depth DT of the compressive stress layer formed on the main surface to the end surface. It is preferable to make it smaller than the depth DH of the compression stress layer to be formed.

The method for producing a tempered glass substrate according to the present invention comprises removing the entire compressive stress layer formed on the main surface of the tempered glass substrate, and further forming a compressive stress layer on the main surface of the tempered glass substrate. the depth DT of the compressive stress layer formed, is preferably smaller than the depth DH of the compressive stress layer formed on the end face.

  In the tempered glass substrate of the present invention, the plate thickness is 0.7 mm or less, preferably 0.6 mm or less, 0.5 mm or less, 0.4 mm or less, 0.3 mm or less, 0.2 mm or less, particularly preferably 0.1 mm or less. . As the plate thickness of the tempered glass substrate is smaller, the tempered glass substrate can be made lighter, and as a result, the device can be made thinner and lighter. The tempered glass substrate of the present invention has a property of high mechanical strength even if the plate thickness is small.

  The tempered glass substrate of the present invention is characterized in that the depth DT of the compressive stress layer formed on the main surface is smaller than the depth DH of the compressive stress layer formed on the end face, and the value of DT / DH is 0.00. 1-0.99, 0.1-0.7, 0.1-0.5, 0.1-0.45, 0.15-0.45, especially 0.2-0.4 are preferable. If the value of DT / DH is within the above range, the depth of the compressive stress layer can be optimized at the end face of the tempered glass substrate, and the mechanical strength of the tempered glass substrate can be increased without unduly increasing the internal tensile stress. Strength can be increased.

  In the tempered glass substrate of the present invention, the compressive stress value of the compressive stress layer formed on the main surface is preferably 100 MPa or more, 200 MPa or more, 300 MPa or more, 400 MPa or more, particularly 500 MPa or more. As the compressive stress value of the compressive stress layer increases, the mechanical strength of the tempered glass substrate increases.

  In the tempered glass substrate of the present invention, the depth DT of the compressive stress layer formed on the main surface is preferably 50 μm or less, 45 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, particularly 10 μm or less. The lower limit of the depth DT of the compressive stress layer is preferably 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, and particularly preferably 15 μm or more. If the compressive stress layer becomes too deep, the internal tensile stress becomes too high, and the tempered glass substrate may be self-destructed. On the other hand, if the compressive stress layer becomes too shallow, the tempered glass substrate tends to be damaged starting from polishing marks, handling scratches and the like formed on the tempered glass substrate. From the above points, it is necessary to determine the depth DT of the compressive stress layer formed on the main surface in consideration of the balance between the thickness of the tempered glass substrate and the required mechanical strength.

  In the tempered glass substrate of the present invention, the compressive stress value of the compressive stress layer formed on the end face is preferably 300 MPa or more, 400 MPa or more, 500 MPa or more, 600 MPa or more, 700 MPa or more, and particularly preferably 800 MPa or more. As the compressive stress value of the compressive stress layer increases, the mechanical strength of the tempered glass substrate increases.

  The depth DH of the compressive stress layer formed on the end face is preferably 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, particularly 55 μm or more. Deep scratches are likely to be formed on the end face during handling in the manufacturing process or during end face processing (chamfering). If the depth DH of the compressive stress layer is less than 10 μm, the tempered glass substrate tends to be damaged starting from these scratches, and it is practically difficult to increase the mechanical strength.

  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 75%, preferably 50% to 75%, more preferably 52-65%, more preferably 52 to 63%. When the content of SiO ₂ is less than 45%, the thermal expansion coefficient becomes too large, and the thermal shock resistance tends to be lowered, vitrification becomes difficult, and devitrification resistance tends to be lowered. On the other hand, if the content of SiO ₂ is more than 75%, it becomes difficult to melt and mold the glass, or the thermal expansion coefficient becomes too small to match the thermal expansion coefficient of the surrounding materials.

Al ₂ O ₃ is a component that increases heat resistance, ion exchange performance, and Young's modulus, and its content is 1 to 30%. When the content of Al ₂ O ₃ is less than 1%, there is a possibility that sufficient ion exchange performance cannot be exhibited. On the other hand, if the content of Al ₂ O ₃ is more than 30%, devitrified crystals are likely to precipitate on the glass, or the thermal expansion coefficient becomes too small, making it difficult to match the thermal expansion coefficient of the surrounding materials. If the content of Al ₂ O ₃ is more than 30%, the high temperature viscosity becomes higher, there is a possibility that the meltability decreases. The preferred range of Al ₂ O ₃ has an upper limit of 25% or less, 20% or less, 17% or less, 16.5% or less, 16% or less, particularly 15% or less, and a lower limit of 1.5% or more, 3 % Or more, 5% or more, 10% or more, particularly 12% or more.

Na ₂ O is an ion-exchange component, and is a component that lowers the high-temperature viscosity to improve meltability and moldability, and improve devitrification resistance. The content of Na ₂ O is 4.1 to 20%, preferably 7 to 20%, more preferably 7 to 18%, still more preferably 8 to 16%, and most preferably 8 to 15%. When the content of Na ₂ O is more than 20%, the thermal expansion coefficient becomes too large, the thermal shock resistance is lowered, and it becomes difficult to match the thermal expansion coefficient of the surrounding materials. Further, when the content of Na 2 _O is greater than 20%, is impaired balance of components glass composition, devitrification resistance conversely tends to decrease. Furthermore, if the content of Na ₂ O is more than 20%, the strain point may be excessively lowered, the heat resistance may be lowered, or the ion exchange performance may be lowered.

K ₂ O has an effect of promoting ion exchange, and has an effect of deeply forming a compressive stress layer among alkali metal oxides. K ₂ O is a component that lowers the high-temperature viscosity to improve meltability and moldability, reduce the crack generation rate, and improve devitrification resistance. The content of K ₂ O is 0 to 20%, preferably 0.1 to 10%, more preferably 0.5 to 8%, still more preferably 1 to 8%, particularly preferably 2 to 8%, most preferably 3-7%. When the content of K ₂ O is more than 20%, the thermal expansion coefficient becomes too large, and the thermal shock resistance is lowered or it is difficult to match the thermal expansion coefficient of the surrounding materials. Further, when the content of K 2 _O is more than 20%, is impaired balance of components glass composition, devitrification resistance conversely tends to decrease.

In the tempered glass substrate of the present invention, by removing a part of the compressive stress layer formed on the main surface of the tempered glass substrate, the depth DT of the compressive stress layer formed on the main surface is formed on the end surface. When the depth is smaller than the depth DH of the compressive stress layer, or after removing all of the compressive stress layer formed on the main surface of the tempered glass substrate, the compressive stress layer is further formed on the main surface of the tempered glass substrate. When the depth DT of the compressive stress layer formed on the main surface is made smaller than the depth DH of the compressive stress layer formed on the end surface, ion exchange is performed before removing a part or all of the compressive stress layer. It is preferable to increase the depth of the compressive stress layer, particularly the depth DH of the compressive stress layer formed on the end face, by the treatment. Therefore, the mass ratio _{(Al 2 O 3 + K 2} O) / Na 2 O values of 0.1～6.5,0.1～5,0.2～3,0.2～2.5,0. If restricted to 4 to 2, 0.7 to 1.7, and particularly 1.0 to 1.5, the depth of the compressive stress layer can be increased by the ion exchange treatment. If the value of the mass ratio (Al ₂ O ₃ + K ₂ O) / Na ₂ O is smaller than 0.1, it is difficult to increase the depth of the compressive stress layer. On the other hand, if the value of the mass ratio (Al ₂ O ₃ + K ₂ O) / Na ₂ O is larger than 6.5, the component balance of the glass composition is impaired, and the Na ₂ O component is insufficient. In addition to the decrease in the compressive stress value of the compressive stress layer, the devitrification resistance tends to decrease.

In the tempered glass substrate of the present invention, as a glass composition, in addition to the above components, components such as Li ₂ O, B ₂ O ₃ , TiO ₂ , ZnO, MgO, CaO, SrO, BaO, P ₂ O ₅ , ZrO ₂ are added. The total amount can be added up to 30%, preferably up to 20%. _{Incidentally,} components of _{Li 2 O, B 2 O 3} , TiO 2, ZnO, MgO, CaO, SrO, BaO, or the like _{P 2} O 5, ZrO 2 is an optional component.

Li ₂ O is an ion exchange component, a component that lowers the high-temperature viscosity to improve the meltability and moldability, and further improves the Young's modulus. The content of Li ₂ O is 0 to 2%, preferably 0 to 1%. If the Li ₂ O content is more than 2 %, the glass tends to be devitrified, the liquid phase viscosity is lowered, the thermal expansion coefficient is too large, the thermal shock resistance is lowered, It becomes difficult to match the thermal expansion coefficient of the material. Further, when the content of Li 2 _O is more than 2% too lowered strain point, it lowered heat resistance, rather the ion exchange performance may deteriorate.

_{Li 2 O + Na 2 O +} K 2 O (Li 2 O, Na 2 O, the total content of _{K 2} O) is too large, in addition to the glass tends to be devitrified, the thermal expansion coefficient becomes too large, heat Impact resistance is reduced, and it becomes difficult to match the thermal expansion coefficient of the surrounding material. _Further, when the _{Li 2 O + Na 2 O +} K 2 O is too large, the strain point excessively lowers, the compression stress value of the compressive stress layer is likely to excessively decrease. Therefore, Li ₂ O + Na ₂ O + K ₂ O is preferably 30% or less, 22% or less, and particularly preferably 20% or less. On the other _hand, when the _{Li 2 O + Na 2 O +} K 2 O is too small, the ion exchange performance and meltability tends to decrease. Therefore, Li ₂ O + Na ₂ O + K ₂ O is preferably 5% or more, 10% or more, 13% or more, 15% or more, and particularly preferably 17% or more.

B ₂ O ₃ is a component that lowers the liquidus temperature, high-temperature viscosity, and density, and its content is preferably 0 to 7%, 0 to 5%, 0 to 3%, particularly preferably 0 to 1%. If the content of B ₂ O ₃ is more than 7%, the surface may be burnt by ion exchange, the water resistance may be lowered, or the low-temperature viscosity may be reduced too much, and the compressive stress value of the compressive stress layer may be reduced. May decrease.

TiO ₂ is a component that improves the ion exchange performance and improves the mechanical strength of the glass substrate. However, if the content is too large, the glass tends to be devitrified or colored. Therefore, the content of TiO ₂ is preferably 0 to 10%, 0 to 5%, 0 to 1%, particularly preferably 0 to 0.5%, and more preferably substantially not contained. Here, “substantially does not contain TiO ₂ ” refers to the case where the content of TiO _{2 in} the glass composition is 0.1% or less.

  If an appropriate amount of ZnO is added to the glass system, the compressive stress value of the compressive stress layer is improved. ZnO also has the effect of reducing the high temperature viscosity and improving the Young's modulus. However, if the content of ZnO is more than 15%, the density and thermal expansion coefficient become too large, and the devitrification resistance tends to decrease. Therefore, the content of ZnO is preferably 0 to 15%, 0 to 10%, 0 to 2%, 0 to 0.5%, particularly preferably 0 to 0.1%.

  MgO is a component that lowers the high-temperature viscosity to increase meltability and moldability, and increase the strain point and Young's modulus. MgO has a relatively high effect of improving ion exchange performance among alkaline earth metal oxides. However, when the content of MgO increases, the density, thermal expansion coefficient and crack generation rate increase, and the glass tends to devitrify. Therefore, the MgO content is preferably 10% or less, 9% or less, 6% or less, 4% or less, and particularly preferably 3% or less.

  CaO is a component that lowers the high-temperature viscosity to increase meltability and moldability, and increases the strain point and Young's modulus. However, when the content of CaO increases, the density, thermal expansion coefficient and crack generation rate increase, and the glass tends to devitrify. Therefore, the CaO content is preferably 10% or less, 8% or less, 5% or less, and particularly preferably 3% or less.

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

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

  When MgO + CaO + SrO + BaO (total amount of MgO, CaO, SrO, BaO) increases, the density and thermal expansion coefficient increase, devitrification resistance tends to decrease, and ion exchange performance tends to decrease. Therefore, the content of MgO + CaO + SrO + BaO is preferably 0 to 16%, 0 to 10%, particularly preferably 0 to 6%.

When the value obtained by dividing (MgO + CaO + SrO + BaO) by (Li ₂ O + Na ₂ O + K ₂ O) increases, the density tends to be too high or the devitrification resistance tends to decrease. Therefore, the value of the mass ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is preferably 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, and particularly preferably 0.1 or less.

ZrO ₂ is a component that improves the strain point and Young's modulus, improves the ion exchange performance, and lowers the high temperature viscosity. Furthermore, since ZrO ₂ has the effect of increasing the viscosity near the liquid phase temperature, the liquid phase viscosity can be increased by adding an appropriate amount in the glass composition. However, when the ZrO ₂ content is increased, the devitrification resistance may be extremely lowered. Therefore, the content of ZrO ₂ is 0 to 10%, 0 to 9%, 2 to 9%, 3 to 9%, 3 to 8%, 3.5 to 7%, 3.5 to 6%, particularly 3. 5 to 5.5% is preferable.

P ₂ O ₅ is a component that enhances the ion exchange performance, and is particularly effective in increasing the thickness of the compressive stress layer. However, when the content of P ₂ O ₅ is increased, the glass is phase-separated or the water resistance is lowered. Therefore, the content of P ₂ O ₅ is preferably 8% or less, 5% or less, 4% or less, 3% or less, and particularly preferably 2% or less.

  Furthermore, in addition to the above components, other components can be added up to 20%.

It is preferable to contain 0 to 3% of one or more selected from SO ₃ , Cl, CeO ₂ , Sb ₂ O ₃ and SnO ₂ as a fining agent. As ₂ O ₃ and F also have a clarification effect, but since they may have an adverse effect on the environment, it is preferable not to use them as much as possible, and it is more preferable not to contain them substantially. Sb ₂ O ₃ is less toxic than As ₂ O ₃ , but its use may be restricted from an environmental point of view, and it may be preferable not to contain it. Further, considering the environmental standpoint and fining effect, as a refining agent, the SnO ₂ 0.01 to 3% (preferably 0.05 to 1%) is preferably contained. Here, “substantially does not contain As ₂ O ₃ ” refers to the case where the content of As ₂ O ₃ in the glass composition is 0.1% or less. “Substantially no F” refers to the case where the F content in the glass composition is 0.05% or less. “Substantially no Sb ₂ O ₃ ” refers to the case where the content of Sb ₂ O ₃ in the glass composition is 0.1% or less. On the other hand, Sb ₂ O ₃ and SO ₃ have a high effect of preventing a reduction in transmittance among the clarifiers. Therefore, when used in applications requiring high transmittance, Sb ₂ O _{3 is} used as a clarifier. It is preferable to contain + SO ₃ in an amount of 0.001 to 5%.

Rare earth oxides such as Nb ₂ O ₅ and La ₂ O ₃ are components that increase the Young's modulus. However, the raw material cost is high, and if it is contained in a large amount, the devitrification resistance is lowered. Therefore, the content of the rare earth oxide is preferably 3% or less, 2% or less, 1% or less, particularly 0.5% or less, and more preferably substantially not 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.

  Transition metal elements having a coloring action such as Co, Ni, Cu, etc. are not preferable because they reduce the transmittance of the tempered glass substrate. In particular, when used for display applications, if the content of the transition metal oxide is large, the visibility of the display is impaired. Therefore, the transition metal oxide content is preferably 0.5% or less, 0.1% or less, and particularly preferably 0.05% or less.

  Since PbO is an environmental load substance, it is preferable not to contain PbO substantially. Here, “substantially no PbO” refers to a case where the content of PbO in the glass composition is 0.1% or less.

A suitable content range of each component can be appropriately selected to obtain a preferable glass composition range.
Among these, as a more preferable glass composition range,
(1) in _mass%, it contains _{SiO 2 45~75%, Al 2 O} 3 1~25%, Li 2 O 0~ 2%, Na 2 O 7~20%, the K 2 O 0 to 8%, Substantially free of As ₂ O ₃ , F, PbO,
(2) in _mass%, it contains _{SiO 2 45~75%, Al 2 O} 3 3~25%, Li 2 O 0~ 2%, Na 2 O 7~20%, the K 2 O 0 to 7%, The value of mass ratio (Al ₂ O ₃ + K ₂ O) / Na ₂ O is 0.1 to 3, and substantially does not contain As ₂ O ₃ , F, or PbO.
(3) _mass%, contains _{SiO 2 45~70%, Al 2 O} 3 10~20%, Li 2 O 0~ 2%, Na 2 O 7~20%, the K 2 O 0 to 7%, The mass ratio (Al ₂ O ₃ + K ₂ O) / Na ₂ O has a value of 0.5 to 2 and substantially does not contain As ₂ O ₃ , F, or PbO.
(4) in _{mass%, SiO 2 45~65%, Al} 2 O 3 10~20%, Li 2 O 0~ 2%, Na 2 O 7~16%, K 2 O 0~7%, MgO + CaO + SrO + BaO 0~ 10% is contained, the value of mass ratio (Al ₂ O ₃ + K ₂ O) / Na ₂ O is 0.3 to 1.8, and substantially no As ₂ O ₃ , F, or PbO is contained.
(5) in _{mass%, SiO 2 45~65%, Al} 2 O 3 11~20%, Li 2 O 0~ 2%, Na 2 O 7~16%, K 2 O 0~7%, MgO 0~ 3%, MgO + CaO + SrO + BaO 0 to 9%, and the mass ratio of (Al ₂ O ₃ + K ₂ O) / Na ₂ O is 1 to 1.5, substantially As ₂ O ₃ , F, PbO. Does not contain.
(6) _{mass%, SiO 2 50~63%, Al} 2 O 3 11~18%, Li 2 O 0~2%, Na 2 O 8~15.5%, K 2 O 0~6%, MgO 0 to 3%, MgO + CaO + SrO + BaO 0 to 8%, and the mass ratio of (Al ₂ O ₃ + K ₂ O) / Na ₂ O is 1 to 1.5, substantially As ₂ O ₃ , F Does not contain PbO,
(7) in _{mass%, SiO 2 50~63%, Al} 2 O 3 11~16%, Li 2 O 0~1%, Na 2 O 8~15%, K 2 O 0.1~5%, MgO 0 to 2.5%, MgO + CaO + SrO + BaO 0 to 6%, the mass ratio of (Al ₂ O ₃ + K ₂ O) / Na ₂ O is 1 to 1.5, substantially As ₂ O ₃ , F, and PbO are not included.

In the tempered glass substrate of the present invention, the density is 2.8 g / cm ³ or less, 2.7 g / cm ³ or less, 2.6 g / cm ³ or less, 2.57 g / cm ³ or less, 2.55 g / cm ³ or less, 2.5 g / cm ³ or less, 2.45 g / cm ³ or less, especially 2.4 g / cm ³ or less. The smaller the density, the lighter the tempered glass substrate.

  In the tempered glass substrate of the present invention, the Young's modulus is preferably 67 GPa or more, 68 GPa or more, 70 GPa or more, 71 GPa or more, particularly 73 GPa or more. The higher the Young's modulus, the more difficult it is for the tempered glass substrate to bend, and when the display is pressed with a pen or the like in a device such as a touch panel display, the liquid crystal elements inside the device are less likely to be pressed, and display defects are unlikely to occur on the display. Become. On the other hand, if the Young's modulus is too high, when the tempered glass substrate is deformed by being pushed with a pen or the like, the stress generated by the deformation tends to be high. In particular, in the case of a thin tempered glass substrate, since it has a property of being easily deformed and easily broken, the Young's modulus is 100 GPa or less, 95 GPa or less, 90 GPa or less, 85 GPa or less, 80 GPa or less, so that the stress value due to deformation does not increase. In particular, it is preferably 78 GPa or less.

In the tempered glass substrate of the present invention, the specific Young's modulus is 27 GPa / (g / cm ³ ) or more, 28 GPa / (g / cm ³ ) or more, 29 GPa / (g / cm ³ ) or more, particularly 30 GPa / (g / cm ³ ) or more is preferable. The higher the specific Young's modulus, the more difficult the tempered glass substrate bends due to its own weight. As a result, when storing tempered glass substrates in cassettes, etc., it becomes possible to narrow the clearance between tempered glass substrates and store tempered glass substrates, improving the productivity of tempered glass substrates and the productivity of devices. To do.

  In the tempered glass substrate of the present invention, the liquidus temperature is preferably 1200 ° C. or lower, 1100 ° C. or lower, 1050 ° C. or lower, 1000 ° C. or lower, 930 ° C. or lower, 900 ° C. or lower, particularly 880 ° C. or lower. The lower the liquidus temperature, the more difficult it is to devitrify the glass when molding by the overflow downdraw method or the like. 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 and refers to a value obtained by measuring the temperature at which crystals precipitate.

In the tempered glass substrate of the present invention, the liquid phase viscosity is 10 ^4.0 dPa · s or more, 10 ^4.3 dPa · s or more, 10 ^4.5 dPa · s or more, 10 ^5.0 dPa · s or more, 10 ^{5 0.5} dPa · s or more, 10 ^5.7 dPa · s or more, 10 ^5.9 dPa · s or more, and particularly preferably 10 ^6.0 dPa · s or more. The higher the liquidus viscosity, the more difficult it is to devitrify the glass when forming by the overflow downdraw method or the like. 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.

In the tempered glass substrate of the present invention, the thermal expansion coefficient of ^{40~110 × 10 -7 / ℃, 70~105} × 10 -7 / ℃, 75~100 × 10 -7 / ℃, 80~100 × 10 -7 / C., particularly 80 to 90.times.10.sup.- ⁷ / .degree. C. is preferred. When the thermal expansion coefficient is within the above range, the thermal expansion coefficient can be easily matched 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. Here, the “thermal expansion coefficient” refers to a value obtained by measuring an average value in a temperature range of 30 to 380 ° C. using a dilatometer.

In the tempered glass substrate of the present invention, the strain point is preferably 500 ° C. or more, 510 ° C. or more, and particularly preferably 520 ° C. or more. When the strain point is high, it is difficult for stress relaxation to occur during the ion exchange treatment, and the compressive stress value of the compressive stress layer is easily increased. Here, the “strain point” refers to a value measured based on the method of ASTM C336. In addition, if the content of the alkaline earth metal oxide, Al ₂ O ₃ , ZrO ₂ , and P ₂ O _{5 in} the glass composition is increased or the content of the alkali metal oxide is decreased, the strain point is increased.

In the tempered glass substrate of the present invention, the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is preferably 1700 ° C. or lower, 1600 ° C. or lower, 1560 ° C. or lower, 1500 ° C. or lower, 1450 ° C. or lower, 1420 ° C. or lower, particularly 1400 ° C. or lower. . The lower the temperature at 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 substrate. That is, the lower the temperature at a high temperature viscosity of 10 ^2.5 dPa · s, the lower the production cost of the glass substrate. Here, “temperature at a high temperature viscosity of 10 ^2.5 dPa · s” refers to a value measured by a platinum ball pulling method. The temperature at a high temperature viscosity of 10 ^2.5 dPa · s corresponds to the melting temperature of the glass. The lower the temperature at the high temperature viscosity of 10 ^2.5 dPa · s, the more the glass can be melted.

Method for producing a tempered glass substrate of the present invention, (1) a glass substrate is a glass composition including, in _{mass%, SiO 2 45~75%, Al} 2 O 3 1~30%, Li 2 O 0~2%, _{Na 2 O 4.1 ~20%, K} 2 O containing 0-20%, so that the value of the mass ratio _{(Al 2 O 3 + K 2} O) / Na 2 O is 0.1 to 6.5, Steps for preparing glass raw materials and obtaining glass batches, (2) Steps for melting glass batches and forming the resulting molten glass into a glass substrate of 0.7 mm or less, (3) Forming a compressive stress layer on the glass substrate And (4) the depth DT of the compressive stress layer formed on the main surface so that the internal tensile stress is 200 MPa or less, and the depth DH of the compressive stress layer formed on the end face. It has the process made smaller than this, It is characterized by the above-mentioned. In the method for producing a tempered glass substrate of the present invention, suitable compositions and characteristics of the tempered glass substrate are as described in the description of the tempered glass substrate of the present invention, and the description thereof is omitted here.

In the manufacturing method of the tempered glass substrate of the present invention, it is preferred to form into a glass substrate of 0.7 mm or less by the overflow down draw method. In the case of the overflow downdraw method, a thin glass substrate can be easily produced. Here, the overflow down draw method is a method in which molten glass is overflowed from both sides of a heat-resistant bowl-shaped structure, and the overflowed molten glass is stretched and formed downward while joining at the lower end of the bowl-shaped structure. This is a method of molding. The structure and material of the bowl-shaped structure are not particularly limited as long as desired dimensions and surface quality can be realized. Moreover, the method of applying force to the glass when stretched downward is not particularly limited. 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 the glass, or a plurality of pairs of heat-resistant rolls are provided only near the edge of the glass. You may employ | adopt the method of making it contact and extending | stretching. If the liquidus temperature is 1200 ° C. or less and the liquidus viscosity is 10 ^4.0 dPa · s or more, a thin glass substrate can be produced by the overflow down draw method.

  In the manufacturing method of the tempered glass substrate of the present invention, various forming methods such as a float method, a slot down method, a redraw method, a roll-out method, a press method and the like are adopted in addition to the overflow down draw method. can do.

The manufacturing method of the tempered glass substrate of this invention has the process of forming a compressive-stress layer in a glass substrate and obtaining a tempered glass substrate. As a method for forming a compressive stress layer on a glass substrate, there are 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 in which ion exchange is performed at a temperature equal to or lower than the strain point of glass to introduce alkali ions having a large ion radius on the glass surface. The ion exchange conditions are not particularly limited, and may be determined in consideration of the viscosity characteristics of the glass. In particular, when the Na component in the glass composition is ion-exchanged with K ions in the KNO ₃ molten salt, the compressive stress layer can be efficiently formed. Unlike the physical strengthening method such as the air cooling strengthening method, the chemical strengthening method has an advantage that even if the strengthened glass substrate is cut after the chemical strengthening, the strengthened glass substrate is not easily broken.

In the method for producing a tempered glass substrate of the present invention, it is preferable to form a compressive stress layer on the glass substrate by immersing the glass substrate in KNO ₃ molten salt at 350 to 500 ° C. for 2 to 24 hours. If it does in this way, a compressive-stress layer can be efficiently formed in a glass substrate.

  In the method for producing a tempered glass substrate of the present invention, it is preferable to remove a part of the compressive stress layer formed on the main surface of the tempered glass substrate, and it is more preferable to remove a part of the compressive stress layer by etching or polishing. preferable. This makes it easier to make the depth DT of the compressive stress layer formed on the main surface smaller than the depth DH of the compressive stress layer formed on the end surface.

  In the method for producing a tempered glass substrate of the present invention, it is preferable to form a compressive stress layer on the main surface of the tempered glass substrate after removing all of the compressive stress layer formed on the main surface of the tempered glass substrate, etching. Or after removing all the compressive-stress layers by grinding | polishing, it is more preferable to form a compressive-stress layer in the main surface of a tempered glass board | substrate further. In this way, once the compressive stress strain exists only on the end surface of the tempered glass substrate, when removing the compressive stress layer on the main surface, the stress difference between the front surface and the back surface of the main surface While it becomes easy to prevent the curvature to generate | occur | produce, it becomes easy to make depth DT of the compressive-stress layer formed in a main surface smaller than depth DH of the compressive-stress layer formed in an end surface. The second strengthening treatment uses the same chemical solution as the first strengthening treatment, lowers the temperature (ion exchange temperature) when strengthening than the first strengthening treatment, or the time of the strengthening treatment (ion exchange time). It is preferable to take measures such as shortening the length so that an extremely deep compressive stress layer is not formed on the main surface of the tempered glass substrate.

  In the method for producing a tempered glass substrate of the present invention, after forming a compressive stress layer on the end surface of the glass substrate in a state where the main surface of the glass substrate is masked, the masking is removed, and a compressive stress layer is further formed on the main surface of the tempered glass substrate. By forming, the depth DT of the compressive stress layer formed on the main surface is preferably smaller than the depth DH of the compressive stress layer formed on the end surface. In this way, once the compressive stress strain is present only on the end surface of the tempered glass substrate, it becomes easier to prevent warpage caused by the stress difference between the front surface and the back surface of the main surface, and the main surface. It becomes easy to make depth DT of the compressive-stress layer formed in (1) smaller than depth DH of the compressive-stress layer formed in an end surface.

Hereinafter, the present invention will be described based on examples. Tables 1 and 2 show examples of the present invention (Sample Nos. 4 to 14). Sample No. 1-3 are reference examples.

  Each sample was produced as follows. First, glass raw materials were prepared so as to have the glass compositions shown in Tables 1 and 2, and a glass batch was prepared. Then, the glass batch was put into a platinum pot and melted at 1600 ° C. for 8 hours to obtain a molten glass. Next, the molten glass was poured out on the carbon plate and formed into a glass substrate. Various characteristics were evaluated about the obtained glass substrate.

  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 at a high temperature viscosity of 10 ^4.0 dPa · s, 10 ^3.0 dPa · s, and 10 ^2.5 dPa · s was measured by a well-known platinum ball pulling method.

  Thermal expansion coefficient (alpha) is the value which measured the average thermal expansion coefficient in 30-380 degreeC using the dilatometer.

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

  The Young's modulus is a value measured by a resonance method.

As apparent from Tables 1 and 2, Sample No. 1 to 14 had a density of 2.57 g / cm ³ or less, a Young's modulus of 67 GPa or more, and a thermal expansion coefficient of 58 to 100 × 10 ⁻⁷ / ° C. Furthermore, sample no. 1 to 14 had a liquidus viscosity of 10 ^4.4 dPa · s or higher and a temperature at a high temperature viscosity of 10 ^2.5 dPa · s of 1650 ° C. or lower.

  In addition, although an unstrengthened glass substrate and a tempered glass substrate differ microscopically in a glass composition in a surface layer, the glass composition does not differ substantially as a whole. Therefore, properties such as density, viscosity, Young's modulus and the like are not substantially different between the untempered glass substrate and the tempered glass substrate.

Subsequently, the main surface of each sample was subjected to optical polishing and then subjected to ion exchange treatment. Ion exchange was performed by immersing in KNO ₃ molten salt at 410 ° C. for 4 hours or in KNO ₃ molten salt at 440 ° C. for 6 hours. Next, after cleaning the surface of each sample after the ion exchange treatment, the compression stress layer is compressed from the number of interference fringes to be observed and the distance between them using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation). Stress values and thicknesses were calculated. In the measurement, the refractive index was 1.52, and the photoelastic constant was 28 [(nm / cm) / MPa].

  As apparent from Tables 1 and 2, Sample No. In Nos. 1 to 14, the compressive stress value of the compressive stress layer was 300 MPa or more, and the thickness was 15 μm or more.

  In the experiment of the examples, for convenience of explanation of the present invention, molten glass was poured out, a glass substrate was formed, and then optical polishing was performed before ion exchange treatment. From the viewpoint of production efficiency, when producing a tempered glass substrate on an industrial scale, it is desirable to ion-treat the unpolished glass substrate after forming the glass substrate by an overflow downdraw method or the like.

Sample No. About 1-14, the glass substrate of 40 mmx80mmx0.5mm and 40mmx80mmx0.52mm was produced by the overflow downdraw method. Next, the glass substrate was subjected to ion exchange treatment at 440 ° C. for 6 hours in KNO ₃ molten salt to obtain a tempered glass substrate. For the tempered glass substrate having a plate thickness of 0.52 mm, the main surfaces (front surface and back surface) were optically polished by 10 μm to obtain a tempered glass substrate having a plate thickness of 0.5 mm. Each tempered glass substrate was subjected to a four-point bending test using AG-10kNIS (manufactured by Shimadzu Corporation). During the test, the support span was 50 mm and the load jig span was 25 mm. As a result, the strength value of the tempered glass substrate whose main surface was polished was almost equal to the strength value of the tempered glass substrate whose both main surfaces were not polished.

  The tempered glass substrate of the present invention is suitable as a substrate for a mobile phone, a digital camera, a cover glass for 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 strength, for example, window glass, magnetic disk substrates, flat panel display substrates, solar cell cover glasses, and solid-state imaging devices. Application to cover glass and tableware can be expected.

Claims (16)

In a tempered glass substrate having a compressive stress layer,
The plate thickness is 0.7 mm or less,
The internal tensile stress is 200 MPa or less,
As a glass composition, in _{mass%, SiO 2 45~75%, Al} 2 O 3 1~30%, Li 2 O 0~2%, Na 2 O 4.1 ~20%, K 2 O 0~20% content And the value of mass ratio (Al ₂ O ₃ + K ₂ O) / Na ₂ O is 0.1-6.5,
And the depth DT of the compressive-stress layer formed in a main surface is smaller than the depth DH of the compressive-stress layer formed in an end surface, The tempered glass substrate characterized by the above-mentioned. The tempered glass substrate according to claim 1, comprising 12% by mass or more of Al ₂ O ₃ .   The tempered glass substrate according to claim 1, wherein the tempered glass substrate is formed by an overflow downdraw method.   The tempered glass substrate according to any one of claims 1 to 3, wherein a depth DT of a compressive stress layer formed on the main surface is reduced by etching.   The compression stress value of the compression stress layer formed on the main surface is 50 MPa or more, the depth of the compression stress layer is 50 μm or less, and the compression stress value of the compression stress layer formed on the end surface is 300 MPa or more. The tempered glass substrate according to claim 1, wherein the depth is 10 μm or more. The tempered glass substrate according to claim 1, a SnO ₂ containing 0.01 to 3 wt%, and wherein the substantially contains no _{As 2 O 3, Sb 2 O} 3.   The tempered glass substrate according to claim 1, wherein Young's modulus is 67 GPa or more.   It uses for a display, The tempered glass substrate in any one of Claims 1-7 characterized by the above-mentioned.   The tempered glass substrate according to claim 1, wherein the tempered glass substrate is used for a touch panel display. (1) a glass substrate is a glass composition including, in _{mass%, SiO 2 45~75%, Al} 2 O 3 1~30%, Li 2 O 0~2%, Na 2 O 4.1 ~20%, K _A step of preparing a glass batch by preparing a glass raw material so that the content of ₂ O is 0 to 20% and the mass ratio (Al ₂ O ₃ + K ₂ O) / Na ₂ O is 0.1 to 6.5. (2) A step of melting a glass batch and forming the obtained molten glass into a glass substrate of 0.7 mm or less, (3) A step of forming a compression stress layer on the glass substrate to obtain a tempered glass substrate, (4 ) Having a step of making the depth DT of the compressive stress layer formed on the main surface smaller than the depth DH of the compressive stress layer formed on the end surface so that the internal tensile stress becomes 200 MPa or less. A method for manufacturing a tempered glass substrate.   By removing a part of the compressive stress layer formed on the main surface of the tempered glass substrate, the depth DT of the compressive stress layer formed on the main surface is made larger than the depth DH of the compressive stress layer formed on the end surface. The method for producing a tempered glass substrate according to claim 10, wherein the tempered glass substrate is also made smaller.   After removing all of the compressive stress layer formed on the main surface of the tempered glass substrate, the depth DT of the compressive stress layer formed on the main surface is further formed by forming the compressive stress layer on the main surface of the tempered glass substrate. Is made smaller than the depth DH of the compressive stress layer formed on the end face, The manufacturing method of the tempered glass substrate according to claim 10 characterized by things. Glass substrate, as a glass composition, the Al ₂ O ₃ so as to contain more than 12 wt%, the manufacturing method of the tempered glass substrate according to any one of claims 10 to 12, characterized in that formulating a glass raw material.   The method for producing a tempered glass substrate according to claim 10, wherein the glass substrate is formed by an overflow downdraw method.   The depth DT of the compressive stress layer formed on the main surface is made smaller by etching than the depth DH of the compressive stress layer formed on the end surface. A method for producing a tempered glass substrate. The glass raw material is prepared such that the glass substrate contains 0.01 to 3% by mass of SnO ₂ as a glass composition and does not substantially contain As ₂ O ₃ or Sb ₂ O _3. Item 16. A method for producing a tempered glass substrate according to any one of Items 10 to 15.