JP2019031428A - Strengthened glass sheet and strengthened glass sphere - Google Patents

Abstract

To propose a strengthened glass sheet capable of being formed in a sheet shape and hardly having surface scratch.SOLUTION: The strengthened glass sheet has a compressive stress layer on its surface, a glass composition containing, in mol%, SiO58 to 70%, AlO13.5 to 16.5%, BO0 to 3%, LiO 0 to 4%, NaO 15 to 20%, KO 0 to 2%, MgO 0 to 5%, ZrO0.1 to 3%, Vickers hardness of 800 or more, and temperature at high temperature viscosity of 10dPa s of 1660°C or less.SELECTED DRAWING: None

Description

  The present invention relates to a tempered glass plate, and more particularly to a tempered glass plate suitable for a cover glass of a touch panel display such as a mobile phone, a digital camera, and a PDA (mobile terminal). The present invention also relates to a tempered glass sphere, and more particularly to a tempered glass sphere suitable for a rolling element incorporated in a rolling device or the like.

  Mobile phones, digital cameras, PDAs (portable terminals), and the like are becoming increasingly popular. In these applications, a tempered glass plate subjected to ion exchange treatment is used as a cover glass of a touch panel display (see Patent Document 1 and Non-Patent Document 1).

JP 2006-83045 A JP-T-2006-524581 Special table 2011-510903 gazette

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

  Cover glasses, especially cover glasses used for smartphones, are often used outdoors, so light with high illuminance and parallelism makes it easier to recognize surface scratches, resulting in reduced touch panel display visibility. End up. Therefore, it is important to improve the scratch resistance of the tempered glass plate.

  As a method for improving scratch resistance, it is considered useful to increase the hardness of glass. More specifically, the conventional glass has a property that the surface is easily scratched due to silica because the hardness is much lower than that of silica (sand) that is present on the ground in large quantities. Therefore, it is considered that when the hardness of the glass is increased, the surface is hardly damaged. However, when trying to increase the hardness of the glass, the high-temperature viscosity of the glass increases, and the meltability and formability are greatly reduced. Furthermore, the balance of the glass composition is lost, and devitrification is likely to occur during molding. As a result, it becomes difficult to form a plate.

  Further, it is known that when a hard thin film is formed on the surface, the hardness of the cover glass increases (for example, see Patent Document 2). However, when a hard thin film is formed on the surface, there is a risk that the transparency of the cover glass is lowered, or the cover glass is warped due to film stress.

  In addition, since sapphire has high hardness, it seems that it is suitable for a cover member. However, sapphire is difficult to mass-produce large-sized plates.

  This invention is made | formed in view of the said situation, The technical subject is creating the tempered glass board which can be shape | molded in plate shape and is hard to have a surface damage.

As a result of various studies by the present inventors, it has been found that the above technical problem can be solved by regulating the glass composition within a predetermined range, increasing the Vickers hardness, and decreasing the high temperature viscosity. As proposed. That is, the tempered glass plate of the present invention is a tempered glass plate having a compressive stress layer on the surface, and has a glass composition of mol%, SiO ₂ 58 to 70%, Al ₂ O ₃ 13.5 to 16.5%, Contains B ₂ O ₃ 0-3%, Li ₂ O 0-4%, Na ₂ O 15-20%, K ₂ O 0-2%, MgO 0-5%, ZrO ₂ 0.1-3%. The Vickers hardness is 800 or more, and the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is 1660 ° C. or less. Here, “Vickers hardness” refers to a value measured based on a method based on JIS Z2244 with a measurement load of 100 gf. The “temperature at a high temperature viscosity of 10 ^2.5 dPa · s” can be measured by, for example, a platinum ball pulling method.

  Conventionally, the scratch resistance has been evaluated by the degree of occurrence of cracks caused by the indentation of a Vickers indenter or the degree of occurrence of lateral cracks caused by scratching of the Knoop indenter (see Patent Document 3). However, the crack generation mechanism differs between the crack generated in the above evaluation and the surface scratch recognized by light having high illuminance and parallelism. Therefore, even if the glass is less prone to crack in the conventional evaluation, surface scratches recognized by light having high illuminance and parallelism may occur, and the above technical problem may not be solved.

  According to the inventor's investigation, the degree of occurrence of surface scratches recognized by light having high illuminance and parallelism has a correlation with Vickers hardness, and when the Vickers hardness after ion exchange treatment is increased, the surface scratches are reduced. be able to. Therefore, the tempered glass plate of the present invention regulates the Vickers hardness to 800 or more to prevent the occurrence of the surface scratches.

Furthermore, the tempered glass sheet of the present invention contains 13.5 mol% or more of Al ₂ O ₃ and 0.1 mol% or more of ZrO ₂ in the glass composition. Thereby, it becomes easy to raise Vickers hardness to 800 or more. However, when the content of Al ₂ O ₃ and ZrO ₂ increases, the high-temperature viscosity increases, and the meltability and moldability tend to decrease. Therefore, in the tempered glass sheet of the present invention, Na ₂ O is introduced in an amount of 15 mol% or more in the glass composition. This makes it easy to lower the temperature at a high temperature viscosity of 10 ^2.5 dPa · s to 1660 ° C. or lower.

Further, tempered glass of the present _invention, [ZrO 2] _- preferably satisfies [B _{2 O} 3]> 0 mole percent relationship. Here, “[ZrO ₂ ]-[B ₂ O ₃ ]” refers to an amount obtained by subtracting the mol% content of B ₂ O ₃ from the mol% content of ZrO ₂ .

Further, tempered glass of the present invention, it is preferred molar ratio _{[SiO 2] / [ZrO 2} ] is 50 to 200. Here, “molar ratio [SiO ₂ ] / [ZrO ₂ ]” refers to a value obtained by dividing the mol% content of SiO _{2 by} the mol% content of ZrO ₂ .

Further, tempered glass of the present _{invention, [Na 2 O] - [} Al 2 O 3]> preferably satisfies 2 mole percent relationship. Here, “[Na ₂ O]-[Al ₂ O ₃ ]” refers to an amount obtained by subtracting the mol% content of Al ₂ O ₃ from the mol% content of Na ₂ O.

In the tempered glass sheet of the present invention, the molar ratio [Na ₂ O] / [Al ₂ O ₃ ] is preferably 1.14 or more. Here, “molar ratio [Na ₂ O] / [Al ₂ O ₃ ]” refers to a value obtained by dividing the mol% content of Na ₂ O by the mol% content of Al ₂ O ₃ .

  Moreover, it is preferable that content of MgO is less than 1-3 mol% in the tempered glass board of this invention.

  In the tempered glass sheet of the present invention, the compressive stress layer preferably has a compressive stress value of 1200 MPa or more and a stress depth of 35 μm or more. Here, “compressive stress value” and “stress depth” refer to values calculated from the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation) and their intervals, and are calculated. At this time, the refractive index of the glass is set to 1.50, and the optical elastic constant is set to 29.4 [(nm / cm) / MPa].

  Moreover, it is preferable that the tempered glass board of this invention has an overflow merge surface in the center part of a plate | board thickness direction, ie, is shape | molded by the overflow down draw method. Here, the “overflow down draw method” is a method in which the molten glass overflows from both sides of the molded refractory, and the molten glass overflows and joins at the lower end of the molded refractory, and is stretched downward to form a glass plate. It is a manufacturing method. In the overflow down draw method, the surface to be the surface of the glass plate is not in contact with the surface of the molded refractory, but is formed into a plate shape in a free surface state. For this reason, the glass plate which is unpolished and has a good surface quality can be manufactured at low cost.

Further, the tempered glass plate of the present invention has a mean particle size of 50 μm on a surface in the range of 1 cm ² , 1 mg of silica sand, and the number of scratches when scratched with a load of 4 kg through denim fabric is ten. The following is preferable. Here, the wound test is performed under the following conditions. The damage is performed only once in one direction, and the distance to be damaged is 1 cm. The number of wound tests is 4 times, and the average value is the measured value. The wound surface is irradiated with a fiber light having an illuminance of 100,000 lux, and the number of scratches is measured visually.

  Moreover, it is preferable to use the tempered glass board of this invention for the cover glass of a touchscreen display.

The tempered glass sphere of the present invention is a tempered glass sphere having a compressive stress layer on the surface, and has a glass composition of mol%, SiO ₂ 58 to 70%, Al ₂ O ₃ 13.5 to 16.5%, Contains B ₂ O ₃ 0-3%, Li ₂ O 0-4%, Na ₂ O 15-20%, K ₂ O 0-2%, MgO 0-5%, ZrO ₂ 0.1-3%. The Vickers hardness is 800 or more, and the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is 1660 ° C. or less.

The tempered glass plate of the present invention has a glass composition of mol%, SiO ₂ 58 to 70%, Al ₂ O ₃ 13.5 to 16.5%, B ₂ O ₃ 0 to 3%, Li ₂ O 0 to 0%. _{4%, Na 2 O 15~20%} , K 2 O 0~2%, 0~5% MgO, containing ZrO 2 0.1 to 3%. The reason for limiting the content range of each component is shown below. In addition, in description of the containing range of each component,% display points out mol%, unless there is particular notice.

SiO ₂ is a component that forms a network of glass. The content of SiO ₂ is 58 to 70%, preferably 59 to 68%, 60 to 66%, 61 to 65%, particularly 62 to 64%. If the content of SiO ₂ is too small, vitrification becomes difficult, and the thermal expansion coefficient becomes too high, so that the thermal shock resistance tends to decrease. On the other hand, if the content of SiO ₂ is too large, the meltability and moldability tend to be lowered, and the thermal expansion coefficient becomes too low to make it difficult to match the thermal expansion coefficient of the surrounding materials.

Al ₂ O ₃ is a component that increases Vickers hardness, and is a component that increases ion exchange performance, strain point, and Young's modulus. When Al ₂ content of O ₃ is too small, it tends to decrease. Vickers hardness, also a possibility arises which can not be sufficiently exhibited ion exchange performance. Therefore, a suitable lower limit range of Al ₂ O ₃ is 13.5% or more, preferably 14% or more, 14.4% or more, 15% or more, particularly 15.3% or more. On the other hand, when the content of Al ₂ O ₃ is too large, the high temperature viscosity rises, the melting property and formability tends to decrease. In addition, devitrified crystals are likely to precipitate on the glass, making it difficult to form a glass plate by an overflow down draw method or the like. In particular, when an alumina refractory is used as the molded refractory and a glass plate is formed by the overflow down-draw method, spinel devitrification crystals are likely to precipitate at the interface with the alumina refractory. Furthermore, acid resistance also falls and it becomes difficult to apply to an acid treatment process. The upper limit range of Al ₂ O ₃ is 16.5% or less, preferably 16% or less, particularly 15.5% or less.

B ₂ O ₃ is a component that reduces high temperature viscosity and density, stabilizes the glass, makes it difficult to precipitate crystals, and lowers the liquidus temperature. However, if the content of B ₂ O ₃ is too large, the stress depth becomes small and it becomes difficult to increase the Vickers hardness. Therefore, the content of B ₂ O ₃ is 0 to 3%, preferably 0 to 2%, 0 to 1%, 0 to 0.5%, particularly 0 to less than 0.1%.

Li ₂ O is an ion exchange component, and is a component that lowers the high-temperature viscosity to increase the meltability and moldability, and also increases the Vickers hardness. Further, Li ₂ O is generally effective in increasing the compressive stress value among alkali metal oxides, but in a glass system containing 12% or more of Na ₂ O, the content of Li ₂ O is extremely large. If it becomes, there exists a tendency for a compressive stress value to fall rather. Also the content of Li 2 _O is too large, eluting the ion exchange solution during ion-exchange treatment, there is a possibility to degrade the ion exchange solution. Therefore, the content of Li ₂ O is 0 to 4%, preferably 0 to 3%, 0 to 1.5%, 0 to less than 1%, 0 to 0.5%, 0 to 0.3%, 0 to less than 0.1%, particularly 0.01 to 0.05%.

Na ₂ O is an ion exchange component, and is a component that lowers the high temperature viscosity and improves the meltability and moldability. Na ₂ O is a component that improves devitrification resistance, particularly reaction devitrification resistance with alumina-based refractories. When Na 2 _O content is too small, the increase in high temperature viscosity, or reduces the meltability and moldability, tend to decrease the ion exchange performance. Therefore, the lower limit range of Na ₂ O is 15% or more, preferably 15.5% or more, 16% or more, 17% or more, particularly 18% or more. On the other hand, when the content of Na 2 _O is too large, the thermal expansion coefficient becomes too high, the thermal shock resistance tends to decrease. Moreover, the component balance of a glass composition may collapse | crumble and a devitrification resistance may fall on the contrary. Therefore, the upper limit range of Na ₂ O is 20% or less, preferably 19% or less, particularly 18.5% or less.

When the molar ratio [Na ₂ O] / [Al ₂ O ₃ ] is too small, the high-temperature viscosity increases, the meltability and moldability are liable to decrease, and devitrification resistance, particularly with alumina-based refractories. Reaction devitrification resistance is likely to decrease. Therefore, a preferable lower limit range of the molar ratio [Na ₂ O] / [Al ₂ O ₃ ] is 1 or more, 1.1 or more, 1.14 or more, particularly 1.2 or more. On the other hand, if the molar ratio [Na ₂ O] / [Al ₂ O ₃ ] is too large, the Vickers hardness tends to decrease. Therefore, the preferable upper limit range of the molar ratio [Na ₂ O] / [Al ₂ O ₃ ] is 2 or less, 1.5 or less, 1.4 or less, 1.35 or less, 1.3 or less, particularly 1.25 or less. It is.

[Na ₂ O]-[Al ₂ O ₃ ]> 1.5 mol%, [Na ₂ O]-[Al ₂ O ₃ ]> 2 mol%, especially [Na ₂ O]-[Al ₂ O ₃ ]> It is preferable to satisfy the relationship of 2.5 mol%. _[Na 2 O] - When _[Al 2 _{O 3]} is too small, the high temperature viscosity rises, the melting property and formability tends to decrease.

K ₂ O is a component that lowers the high-temperature viscosity and improves the meltability and moldability, but among alkali metal oxides, it reduces the compressive stress value of the compressive stress layer and increases the stress depth. Since it is a component, it is not advantageous from the viewpoint of increasing Vickers hardness. Therefore, the upper limit range of K ₂ O is 2% or less, preferably 1.5% or less, 1% or less, less than 1%, 0.5% or less, particularly less than 0.1%. Incidentally, when adding _{K 2} O, the preferred amount is 0.1% or more, 0.5% or more, particularly 1% or more.

  MgO is a component that lowers the viscosity at high temperature, increases meltability and formability, and increases the strain point and Vickers hardness. Among alkaline earth metal oxides, MgO is a component that has a large effect on improving ion exchange performance. is there. However, when there is too much content of MgO, devitrification resistance, especially the reaction devitrification resistance with an alumina-type refractory material will fall easily. Therefore, the content of MgO is 0 to 5%, preferably 0.1 to 4%, 1 to 3.5%, 1.5 to 3%, particularly less than 2 to 3%.

ZrO ₂ is a component that increases the Vickers hardness and a component that increases the viscosity and strain point in the vicinity of the liquid phase viscosity. If the content is too large, the devitrification resistance may be significantly reduced. Therefore, the content of ZrO ₂ is 0.1 to 3%, preferably 0.3 to 2.5%, 0.5 to 2%, particularly 0.8 to 1.5%.

The molar ratio [SiO ₂ ] / [ZrO ₂ ] is preferably 50 to 200, 70 to 150, particularly 80 to 140. When the molar ratio [SiO ₂ ] / [ZrO ₂ ] is too small, the devitrification resistance tends to be lowered. On the other hand, if the molar ratio [SiO ₂ ] / [ZrO ₂ ] is too large, the Vickers hardness tends to decrease.

[ZrO ₂ ]-[B ₂ O ₃ ]> 0 mol%, [ZrO ₂ ]-[B ₂ O ₃ ]> 0.5 mol%, especially [ZrO ₂ ]-[B ₂ O ₃ ]> 1 mol% It is preferable to satisfy the relationship. When [ZrO ₂ ]-[B ₂ O ₃ ] is too small, it is difficult to increase the Vickers hardness.

  In addition to the above components, for example, the following components may be added.

  CaO is a component that has a large effect of lowering high temperature viscosity, improving meltability and formability, and increasing strain point and Vickers hardness without lowering devitrification resistance compared to other components. is there. However, when there is too much content of CaO, ion exchange performance will fall or it will become easy to degrade an ion exchange solution at the time of ion exchange processing. Therefore, suitable content of CaO is 0-6%, 0-5%, 0-4%, 0-3.5%, 0-3%, 0-2%, 0-1%, especially 0-0. .5%.

  SrO and BaO are components that lower the viscosity at high temperature to increase the meltability and moldability, and increase the strain point and Young's modulus. However, if their content is excessive, the ion exchange reaction tends to be inhibited. In addition, the density and the coefficient of thermal expansion increase, and the glass tends to devitrify. Therefore, suitable content of SrO and BaO is 0 to 2%, 0 to 1.5%, 0 to 1%, 0 to 0.5%, 0 to 0.1%, particularly 0 to 0.1%, respectively. %.

  ZnO is a component that enhances the ion exchange performance, and is a component that is particularly effective in increasing the compressive stress value. Moreover, it is a component which reduces high temperature viscosity, without reducing low temperature viscosity. However, when the content of ZnO is too large, the glass tends to undergo phase separation, the devitrification resistance decreases, the density increases, or the stress depth decreases. Therefore, suitable content of ZnO is 0 to 3%, 0 to 2%, 0 to 1%, and particularly less than 0 to 1%.

TiO ₂ is a component that enhances ion exchange performance and a component that lowers the high-temperature viscosity. However, if its content is too large, transparency and devitrification resistance are likely to be lowered. Therefore, the content of TiO ₂ is preferably 0 to 4.5%, 0 to less than 1%, 0 to 0.5%, particularly preferably 0 to 0.3%.

SnO ₂ is a component that enhances the ion exchange performance, but when its content is too large, the devitrification resistance tends to be lowered. Accordingly, the preferred content of SnO ₂ is 0-3%, 0.01% to 3% 0.05 to 3% 0.1% to 3%, in particular 0.2 to 3%.

P ₂ O ₅ is a component that enhances ion exchange performance, and in particular, a component that increases the stress depth. However, when the content of P ₂ O ₅ is too large, or glass phase separation, the water resistance tends to decrease. Therefore, the suitable content of P ₂ O ₅ is 0 to 10%, 0 to 3%, 0 to 1%, particularly 0 to 0.5%.

As a fining agent, _Cl, SO 3, CeO ₂ group (preferably Cl, SO group ₃₎ one member selected from or two or more may be added 0.001 to 1%.

Suitable content of Fe ₂ O ₃ is less than 1000 ppm (less than 0.1%), less than 800 ppm, less than 600 ppm, less than 400 ppm, especially less than 300 ppm. Further, the Fe ₂ O ₃ content is regulated within the above range, and the molar ratio SnO ₂ / (Fe ₂ O ₃ + SnO ₂ ) is regulated to 0.8 or more, 0.9 or more, and particularly 0.95 or more. It is preferable. If it does in this way, it will become easy to improve the total light transmittance in wavelength 400-770 nm and thickness 1mm.

Rare earth oxides such as Nd ₂ O ₃ and La ₂ O ₃ are components that increase Vickers hardness. However, the cost of the raw material itself is high, and when it is added in a large amount, the devitrification resistance tends to be lowered. Therefore, the preferable content of the rare earth oxide is 3% or less, 2% or less, 1% or less, 0.5% or less, particularly 0.1% or less.

The tempered glass plate of the present invention preferably contains substantially no As ₂ O ₃ , Sb ₂ O ₃ , PbO, and F as a glass composition from the environmental consideration. Moreover, environmental considerations, it is also preferable to contain substantially no Bi ₂ O _3. “Substantially free of” means that an explicit component is not actively added as a glass component, but the addition of an impurity level is allowed. Specifically, the content of the explicit component is 0. Indicates the case of less than 05%.

  In the tempered glass sheet of the present invention, the Vickers hardness is 800 or more, preferably 820 or more, 830 or more, 840 or more, 850 or more, particularly 860 to 910. If the Vickers hardness is too low, surface scratches that are recognized by light having high illuminance and parallelism tend to be attached.

In the tempered glass sheet of the present invention, the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is 1660 ° C. or less, preferably 1650 ° C. or less, particularly preferably 1550 to 1640 ° C. When the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is too high, the meltability and formability are lowered, making it difficult to form the molten glass into a plate shape.

  The tempered glass sheet of the present invention preferably has the following characteristics in addition to the above characteristics.

The number of scratches is preferably 10 or less, particularly 8 or less, especially when wound with a load of 4 kg through denim fabric on a surface of 1 cm ² with an average particle size of 50 μm and 1 mg of silica sand. 7 or less. When the number of scratches increases, surface scratches recognized by light having high illuminance and parallelism are likely to be attached.

Density is preferably 2.60 g / cm ³ or less, 2.55 g / cm ³ or less, 2.50 g / cm ³ or less, 2.49 g / cm ³ or less, is particularly in 2.40~2.47g / cm ³ . The smaller the density, the lighter the tempered glass. In addition, the content of SiO ₂ , B ₂ O ₃ , P ₂ O _{5 in} the glass composition is increased, or the content of alkali metal oxide, alkaline earth metal oxide, ZnO, ZrO ₂ , TiO ₂ is decreased. As a result, the density tends to decrease.

Liquidus viscosity, preferably of ¹⁰ 4.0 dPa · s or ^{more, 10} 4.4 dPa · s or ^{more, 10} 4.8 dPa · s or ^{more, 10} 5.0 dPa · s or ^more, 10 5.3 dPa · s Above, 10 ^5.5 dPa · s or more, 10 ^5.7 dPa · s or more, 10 ^5.8 dPa · s or more, particularly 10 ^6.0 dPa · s or more. In addition, devitrification resistance improves so that a liquid phase viscosity is high, and it becomes difficult to generate | occur | produce devitrification flaws at the time of molding. Here, “liquid phase viscosity” refers to a value obtained by measuring the viscosity at the liquid phase temperature by a platinum ball pulling method. “Liquid phase temperature” means that the glass powder that passes through 30 mesh (500 μm) of standard sieve and remains on 50 mesh (300 μm) is put into a platinum boat and kept in a temperature gradient furnace for 24 hours, and then the platinum boat is taken out. The highest temperature at which devitrification (devitrification) was observed inside the glass by microscopic observation.

  The tempered glass sheet of the present invention has a compressive stress layer on the surface. The compressive stress value of the compressive stress layer is preferably 1000 MPa or more, 1200 MPa or more, 1250 MPa or more, 1300 MPa or more, 1350 MPa or more, 1400 MPa or more, particularly 1430 MPa or more. The larger the compressive stress value, the higher the Vickers hardness. On the other hand, when an extremely large compressive stress is formed on the surface, the tensile stress inherent in the tempered glass becomes extremely high, and the dimensional change before and after the ion exchange treatment may increase. For this reason, the compressive stress value of the compressive stress layer is preferably 1800 MPa or less, 1650 MPa or less, and particularly preferably 1500 MPa or less. If the ion exchange time is shortened or the temperature of the ion exchange solution is lowered, the compressive stress value tends to increase.

  The stress depth is preferably 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, and particularly 52 μm or more. As the stress depth increases, even if the tempered glass plate is deeply scratched, the tempered glass becomes difficult to break and the variation in mechanical strength becomes smaller. On the other hand, the greater the stress depth, the more difficult it is to cut the tempered glass plate. In addition, the tensile stress inherent in the tempered glass plate becomes extremely high, and the dimensional change may increase before and after the ion exchange treatment. For this reason, the stress depth is preferably 80 μm or less, 70 μm or less, and particularly 60 μm or less. Note that if the ion exchange time is lengthened or the temperature of the ion exchange solution is increased, the stress depth tends to increase.

  The internal tensile stress value is preferably 150 MPa or less, 140 MPa or less, 130 MPa or less, 120 Pma or less, 110 MPa or less, 100 MPa or less, 90 MPa or less, 80 MPa or less, particularly 70 MPa or less. If the internal tensile stress value is too high, the tempered glass sheet tends to self-break due to physical point collision. On the other hand, if the internal tensile stress value is too low, it becomes difficult to ensure the mechanical strength of the tempered glass sheet. The internal tensile stress value is preferably 25 MPa or more, 35 MPa or more, 45 MPa or more, particularly 50 MPa or more. The internal tensile stress can be calculated by the following formula 1.

[Equation 1]
Internal tensile stress value = (compressive stress value × stress depth) / (plate thickness−2 × stress depth)

  In the tempered glass plate of the present invention, the plate thickness is preferably 2.0 mm or less, 1.5 mm or less, 1.3 mm or less, 1.1 mm or less, 1.0 mm or less, particularly 0.9 mm or less. The smaller the plate thickness, the lower the mass of the tempered glass plate. On the other hand, if the plate thickness is too thin, it is difficult to obtain a desired mechanical strength. Therefore, the plate thickness is preferably 0.3 mm or more, 0.4 mm or more, 0.5 mm or more, 0.6 mm or more, particularly 0.7 mm or more.

  The method for producing the tempered glass sheet of the present invention is as follows, for example. First, a glass raw material prepared to have a desired glass composition is put into a continuous melting furnace, heated and melted at 1550 to 1700 ° C., clarified, and then supplied to a molding apparatus and molded into a plate shape. It is preferable to cool. A well-known method can be adopted as a method of cutting into a predetermined dimension after forming into a plate shape.

  As a method for forming molten glass into a plate shape, it is preferable to employ an overflow down draw method. The overflow downdraw method is a method capable of producing a large number of high-quality glass plates and easily producing a large glass plate. Further, in the overflow down draw method, an alumina refractory or a zirconia refractory is used as the molded refractory. The tempered glass sheet of the present invention has good compatibility with alumina refractories and zirconia refractories (especially alumina refractories), and reacts with these refractories to generate bubbles and blisters. It has a difficult property.

  In addition to the overflow downdraw method, various molding methods can be employed. For example, a forming method such as a float method, a downdraw method (slot downdraw method, redraw method, etc.), a rollout method, a press method, or the like can be employed.

  When forming the molten glass, it is preferable to cool the temperature range between the annealing point and the strain point of the molten glass at a cooling rate of 3 ° C./min or more and less than 1000 ° C./min, and the cooling rate is preferably 10 ° C / min or more, 20 ° C / min or more, 30 ° C / min or more, particularly 50 ° C / min or more, preferably less than 1000 ° C / min, less than 500 ° C / min, particularly less than 300 ° C / min. If the cooling rate is too high, the glass structure becomes rough and it becomes difficult to increase the Vickers hardness after the ion exchange treatment. On the other hand, when the cooling rate is too slow, the production efficiency of the glass plate is lowered.

In the method for producing a tempered glass sheet of the present invention, the conditions for the ion exchange treatment are not particularly limited, and the optimum conditions should be selected in consideration of the viscosity characteristics, application, thickness, internal tensile stress, dimensional change, etc. That's fine. In particular, when K ions in the KNO ₃ molten salt are ion-exchanged with Na components in the glass, the compressive stress layer can be efficiently formed. In the ion exchange treatment, the temperature of the ion exchange solution is preferably 400 to 450 ° C., and the ion exchange time is preferably 2 to 6 hours. In this way, the compressive stress layer can be efficiently formed on the surface.

The tempered glass sphere of the present invention is a tempered glass sphere having a compressive stress layer on the surface, and has a glass composition of mol%, SiO ₂ 58 to 70%, Al ₂ O ₃ 13.5 to 16.5%, Contains B ₂ O ₃ 0-3%, Li ₂ O 0-4%, Na ₂ O 15-20%, K ₂ O 0-2%, MgO 0-5%, ZrO ₂ 0.1-3%. The Vickers hardness is 800 or more, and the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is 1660 ° C. or less. The suitable glass composition and glass characteristics of the tempered glass sphere of the present invention are the same as those of the tempered glass plate of the present invention. Here, detailed description thereof is omitted.

  In the tempered glass sphere of the present invention, the diameter is preferably 15 mm or less, 10 mm or less, particularly 5 mm or less, and preferably 1 mm or more. When the diameter is out of the above range, it becomes difficult to use the rolling element such as a rolling device.

  The surface roughness Ra of the surface of the tempered glass sphere is preferably 10 nm or less, 5 nm or less, particularly 3 nm or less. If the surface roughness Ra of the surface of the tempered glass sphere is too large, the tempered glass sphere tends to be damaged under severe conditions such as high-speed rotation, high friction, and high load. Here, the “surface roughness Ra” can be measured by a method based on JIS B0601: 2001 in a state where a glass sphere is fixed with a jig or the like.

  In the tempered glass sphere of the present invention, the dimensional tolerance of the diameter is preferably within 0.015%, within 0.010%, and particularly within 0.005%. The difference in diameter is preferably 1.5 μm or less, 1.0 μm or less, 0.5 μm or less, particularly 0.1 μm or less. If the dimensional tolerance and the unequal diameter are too large, the driving stability tends to be lowered. In addition, "diameter unequal" refers to the difference between the maximum value and the minimum value when the diameter of a sphere is measured at 10 locations with a contact type or non-contact type length measuring device (for example, Mitutoyo Lightmatic VL-50).

  The tempered glass sphere of the present invention can be produced, for example, as follows. First, the prepared glass batch is put into a continuous melting furnace, heated and melted at 1500 to 1600 ° C. to obtain molten glass, and then supplied to a forming container via a clarification container and a stirring container, and then into a spherical shape. Mold and cool slowly.

  As a method for forming and processing the glass sphere, a method in which glass cut into a plate shape or a bulk shape is ground into a spherical shape, and lapping polishing or polishing polishing is preferable. Also preferred is a method of lapping polishing and polishing glass formed by the droplet forming method. In the latter method, the dimensional accuracy of the glass sphere can be improved and the polishing amount of the surface can be reduced.

  When the glass sphere is subjected to ion exchange treatment, a tempered glass sphere can be obtained. The conditions for the ion exchange treatment are the same as in the case of the tempered glass plate. The “compressive stress value and stress depth of the compressive stress layer of the tempered glass sphere” refers to a glass plate for strengthening having the same glass composition and thermal history as a reference sample at the time of ion exchange treatment of the glass sphere. Then, the compressive stress value and stress depth of the compressive stress layer of the tempered glass plate obtained are measured by the above method, and the values are treated as the compressive stress value and stress depth of the compressive stress layer of the tempered glass sphere. To do.

  Hereinafter, the present invention will be described based on examples. The following examples are merely illustrative. The present invention is not limited to the following examples.

  Tables 1 and 2 show the glass compositions and glass characteristics of Examples (Sample Nos. 1 to 18) and Comparative Examples (Sample No. 19) of the present invention.

  Each sample in the table was prepared as follows. First, glass raw materials were prepared so as to have the glass composition in the table, and were melted at 1650 ° C. for 21 hours using a platinum pot. Subsequently, the molten glass obtained was poured onto a carbon plate and formed into a flat plate shape, and then the temperature range from the annealing point to the strain point was cooled at 3 ° C./min to obtain a glass plate. . About the obtained glass plate, the surface was optically polished so that plate thickness t = 0.8 mm, and then various characteristics were evaluated.

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

The temperature at a high temperature viscosity of 10 ^2.5 dPa · s is a value measured by a platinum ball pulling method.

  The liquid phase viscosity is a value obtained by measuring the viscosity at the liquid phase temperature by a platinum ball pulling method. The liquid phase temperature passes through a standard sieve 30 mesh (500 μm), puts the glass powder remaining on 50 mesh (300 μm) into a platinum boat, holds it in a temperature gradient furnace for 24 hours, then removes the platinum boat and observes it with a microscope. Thus, the highest temperature at which devitrification (devitrification) was observed inside the glass was set.

The compatibility with alumina refractories was evaluated as follows. After each sample was kept in contact with the alumina refractory at a temperature of 10 ^4.5 dPa · s at a high temperature viscosity for 48 hours, the contact interface between each sample and the alumina refractory was observed, and the number density of devitrified bumps ( pieces / mm ²⁾ was measured to evaluate the case where the number density thereof is less than 0.5 pieces / mm ² as "○", "×" in the case of 0.5 number / mm ² or more.

Subsequently, both surfaces of each sample were optically polished so as to have the plate thickness in the table. Thereafter, the KNO ₃ molten salt of 430 ° C., by dipping each sample 4 hours, subjected to ion exchange treatment to obtain a tempered glass plate. Furthermore, after cleaning the surface of each tempered glass plate, the compressive stress value of the surface compressive stress layer (from the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation) and its spacing ( CS) and stress depth (DOL) were calculated. In the calculation, the refractive index of each sample was 1.50, and the optical elastic constant was 29.4 [(nm / cm) / MPa].

  The Vickers hardness Hv is a value measured for each sample after the ion exchange treatment based on a method based on JIS Z2244 with a measurement load of 100 gf.

The scratch resistance test was conducted as follows. First, an average particle diameter of 50 μm and 1 mg of silica sand were uniformly spread on the surface of each sample in a range of 1 cm ² , and were injured with a load of 4 kg through a commercially available denim fabric. The scratch was performed only once in one direction, and the distance to be scratched was 1 cm. After scratching the surface of each sample, the scratches were observed with a fiber light having an illuminance of 100,000 lux, and the number of scratches that could be visually confirmed was counted. The test was performed four times, and the average value of the four times was taken as the measured value.

As is apparent from the table, sample No. Nos. 1 to 18 have a Vickers hardness of 816 or higher, and therefore have good scratch resistance evaluation. Further, the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is 1652 ° C. or lower and the liquid phase viscosity is 10 ^4.28 dPa · s. Since it is s or more, it is considered that it can be formed into a plate shape. On the other hand, sample No. No. 19 had a Vickers hardness of 600, and the scratch resistance evaluation was poor.

  The tempered glass sheet of the present invention is suitable as a cover glass for touch panel displays such as mobile phones, digital cameras, and PDAs (mobile terminals). Moreover, the tempered glass plate of the present invention is used for applications requiring high mechanical strength in addition to these applications, such as window glass, magnetic disk substrates, flat panel display substrates, solar cell cover glasses, solid-state imaging. Application to cover glass for devices is expected.

Claims (11)

In the tempered glass plate having a compressive stress layer on the surface, the glass composition is SiO ₂ 58 to 70%, Al ₂ O ₃ 13.5 to 16.5%, B ₂ O ₃ 0 to 3%, Li, as a glass composition. ₂ O 0-4%, Na ₂ O 15-20%, K ₂ O 0-2%, MgO 0-5%, ZrO ₂ 0.1-3%, Vickers hardness is 800 or more, and A tempered glass sheet having a temperature at a high temperature viscosity of 10 ^2.5 dPa · s of 1660 ° C. or lower. The tempered glass sheet according to claim 1, wherein a relationship of [ZrO ₂ ]-[B ₂ O ₃ ]> 0 mol% is satisfied. Molar ratio _[SiO 2] / tempered glass sheet according to claim 1 or 2 [ZrO _2] is characterized in that 50 to 200. The tempered glass sheet according to claim 1, wherein a relationship of [Na ₂ O] − [Al ₂ O ₃ ]> 2 mol% is satisfied. Molar ratio _{[Na 2 O] / [Al} 2 O 3] is tempered glass plate as claimed in any one of claims 1 to 4, characterized in that at 1.14 or more.   Content of MgO is less than 1-3 mol%, The tempered glass board as described in any one of Claims 1-5 characterized by the above-mentioned.   The tempered glass sheet according to any one of claims 1 to 6, wherein the compressive stress layer has a compressive stress value of 1200 MPa or more and a stress depth of 35 µm or more.   The tempered glass sheet according to any one of claims 1 to 7, wherein the tempered glass sheet has an overflow merging surface at a central portion in a plate thickness direction. An average particle diameter of 50 μm and 1 mg of silica sand are sprinkled on a surface in a range of 1 cm ² , and the number of scratches when wound with a load of 4 kg through denim fabric is 10 or less. The tempered glass board as described in any one of 1-8.   It uses for the cover glass of a touchscreen display, The manufacturing method of the chemically strengthened glass plate as described in any one of Claims 1-9 characterized by the above-mentioned. It is a chemically strengthened glass sphere having a compressive stress layer on the surface, and the glass composition is SiO ₂ 58 to 70%, Al ₂ O ₃ 13.5 to 16.5%, B ₂ O ₃ 0 to 3 as a glass composition. %, Li ₂ O 0-4%, Na ₂ O 15-20%, K ₂ O 0-2%, MgO 0-5%, ZrO ₂ 0.1-3%, and Vickers hardness is 800 or more. A chemically strengthened glass sphere having a high temperature viscosity of 10 ^2.5 dPa · s and a temperature of 1660 ° C. or lower.