JP6774614B2 - Tempered glass and tempered glass - Google Patents

Description

The present invention relates to tempered glass and tempered glass, and particularly to tempered glass and tempered glass suitable for cover glass of mobile phones, digital cameras, PDAs (mobile terminals), solar cells and the like.

Devices such as mobile phones, digital cameras, PDAs, touch panel displays, large televisions, and contactless power supplies are becoming more and more popular. Tempered glass that has been subjected to ion exchange treatment is used for these applications. For example, Patent Document 1 and Non-Patent Document 1 disclose ion-exchange-treated aluminosilicate glass.

International Publication No. 2013/076835

Tetsuro Izumitani et al., "New Glass and Its Physical Properties", First Edition, Keiei System Research Institute, Inc., August 20, 1984, p. 451-498

However, the alkaline aluminosilicate glass described in Patent Document 1 has a high high-temperature viscosity because Al ₂ O ₃ in the glass composition is excessive. Therefore, it was difficult to form a glass plate by the float method.

In detail, the float method is a method of forming into a plate shape by floating molten glass on molten tin, the viscosity of the molten glass to introduce the molten tin bath is about 10 ^{4.0 dPa} · s. Therefore, when the temperature is high in the high temperature viscosity ¹⁰ 4.0 dPa · s, it is necessary to operate the molten tin bath at a high temperature. When the molten tin bath is operated at a high temperature, the molten tin evaporates into the atmosphere in the molten kiln, and the vapor pressure of the tin compound in the atmosphere rises. After that, the vapor of the tin compound is condensed or sublimated in the low temperature region in the molten kiln, and the tin compound falls on the molten glass, so that the surface quality of the glass plate is deteriorated.

Further, when the molten tin bath is operated at a high temperature, tin diffuses from the molten tin to the molten glass, and the tin concentration on the surface layer of the molten glass increases. When the molten glass is reheated, the tin on the surface layer of the molten glass aggregates and the surface quality of the glass plate deteriorates.

Further, when the molten tin bath is operated at a high temperature, the alkaline component tends to volatilize from the molten glass. Further, when the molten tin bath is operated at a high temperature, tin is diffused from the molten tin to the molten glass, and the coefficient of thermal expansion and the alkali mobility tend to fluctuate. As a result, the amount of warpage of the tempered glass plate tends to increase after the ion exchange treatment.

The present invention has been made in view of the above circumstances, the technical problem by inventing the reinforcing glass capable of reducing the temperature in the high temperature viscosity 10 ^{4.0 dPa} · s, the surface of the tempered glass It is to reduce the amount of warpage while improving the quality.

As a result of various studies, the present inventor has found that the above technical problems can be solved by strictly regulating the glass composition of the aluminosilicate glass, and proposes the present invention. That is, the strengthening glass of the present invention has a glass composition of SiO ₂ 50 to 80%, Al ₂ O ₃ 3 to 30%, B ₂ O _{30 to} 20%, Na ₂ O 2.2 in terms of mass%. ultra _{~30%, K 2 O 0~20%} , MgO 2.2 super 20%, containing 0 to 20% CaO, the weight ratio _{Na 2 O / (Li 2 O} + Na 2 O + K 2 O + MgO + CaO + SrO + BaO) 0.50 It is characterized by being ~ 0.93. Here, "Li ₂ O + Na ₂ O + K ₂ O + MgO + CaO + SrO + BaO" refers to the total amount of Li ₂ O, Na ₂ O, K ₂ O, MgO, CaO, SrO and BaO. "Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O + MgO + CaO + SrO + BaO)" is the value obtained by dividing the content of Na ₂ O by the total amount of Li ₂ O, Na ₂ O, K ₂ O, MgO, CaO, SrO and BaO. Point to.

Secondly, the strengthening glass of the present invention has a glass composition of SiO ₂ 50 to 80%, Al ₂ O ₃ 10.5 to 30%, B ₂ O _{30 to} 20%, Li _{2 in} terms of mass%. O 0 to 2.5%, Na ₂ O over 3.3 to 30%, K ₂ O 0.1 to 20%, MgO over 2.2 to 20%, CaO over 1.0 to 20%, ZnO 0 to It contains 10% and ZrO _{20 to} 1.9%, and the mass ratio Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O + MgO + CaO + SrO + BaO) is preferably 0.50 to 0.90.

Third, the strengthening glass of the present invention has a glass composition of SiO ₂ 50 to 80%, Al ₂ O _{3 3 to} 20%, B ₂ O _{30 to} 2.5%, Li _{2 in} terms of mass%. O 0 to 2%, Na ₂ O 3.2 to 30%, K ₂ O to less than 3.3%, MgO more than 2.2 to 20%, CaO more than 1.0 to 5.9%, SrO 0 to It contains 1%, ZnO 0 to 5%, and ZrO _{20 to} 1.9%, and the mass ratio Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O + MgO + CaO + SrO + BaO) is preferably 0.50 to 0.90.

Fourth, reinforcing glass of the present invention, as a glass composition, in weight% _{terms, SiO 2 50~80%, Al 2} O 3 5~20%, B 2 O 3 less than 0 to 2.5%, Li ₂ O 0 to 2%, Na ₂ O more than 10 to 30%, K ₂ O more than 0.1 to less than 3.3%, MgO 2.5 to 20%, CaO more than 1.0 to 5.9%, SrO It contains 0 to 1%, BaO 0 to 3%, ZnO 0 to 5%, and ZrO _{20 to} 10%, and has a mass ratio of Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O + MgO + CaO + SrO + BaO) of 0.50 to 0.89. Is preferable.

Fifth, reinforcing glass of the present invention, it is preferable that the temperature in the high temperature viscosity ¹⁰ 4.0 dPa · s is 1200 ° C. or less. Here, the "temperature in the high temperature viscosity ¹⁰ 4.0 dPa · s" refers to a value measured by a platinum ball pulling method.

Sixth, the reinforcing glass of the present invention preferably has a strain point of 480 to 550 ° C. Here, the "distortion point" refers to a value measured based on the method of ASTM C336.

Seventh, when the reinforcing glass of the present invention is immersed in KNO ₃ molten salt at 430 ° C. for 4 hours, the compressive stress value of the surface compressive stress layer is 300 MPa or more and the stress depth is 10 μm or more. Is preferable. Here, the "compressive stress value" and the "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.

Eighth, the tempered glass of the present invention is a tempered glass having a compressive stress layer on its surface, and has a glass composition of SiO ₂ 50 to 80%, Al ₂ O ₃ 3 to 30%, and B ₂ O in terms of mass%. _It contains 30 to 20%, Na ₂ O more than 2.2 to 30%, K ₂ O to 20%, MgO more than 2.2 to 20%, CaO to 20%, and a mass ratio of Na ₂ O / ( Li ₂ O + Na ₂ O + K ₂ O + MgO + CaO + SrO + BaO) is 0.50 to 0.93.

The reasons for limiting the content range of each component in the reinforcing glass of the present invention are shown below. In the description of the content range of each component,% notation indicates mass% unless otherwise specified.

SiO ₂ is a component that forms a network of glass. The content of SiO ₂ is 50 to 80%, preferably 55 to 76%, 56 to 75%, 57 to 73%, 58 to 72%, 59 to 71%, and particularly 60 to 70%. If the content of SiO ₂ is too small, it becomes difficult to vitrify, and the coefficient of thermal expansion becomes too high, so that the thermal shock resistance tends to decrease. Further, since the weather resistance is lowered, when exposed to an outdoor environment for a long time, the alkaline component may be eluted from the glass surface layer and the compressive stress value may be lowered. On the other hand, if the content of SiO ₂ is too large, the meltability and moldability tend to decrease, and the coefficient of thermal expansion becomes too low, making it difficult to match the coefficient of thermal expansion of the peripheral material.

Al ₂ O ₃ is a component that enhances ion exchange performance, strain point, and Young's modulus, and is a component that reduces the crack generation rate. The content of Al ₂ O ₃ is 3 to 30%. If the content of Al ₂ O ₃ is too small, there is a risk that the ion exchange performance cannot be fully exhibited. Therefore, the preferable lower limit content range of Al ₂ O ₃ is 3% or more, 5% or more, 9% or more, 10.5% or more, 11% or more, 11.5% or more, 12% or more, 12.5% or more. , 13% or more, 14% or more, 14.5% or more, 15% or more, especially 15.5% or more. On the other hand, if the content of Al ₂ O ₃ is too large, devitrified crystals are likely to precipitate on the glass, making it difficult to form a glass plate by a float method or the like. In addition, the coefficient of thermal expansion becomes too low, making it difficult to match the coefficient of thermal expansion of the peripheral material. In addition, acid resistance is reduced, making it difficult to apply to the acid treatment process. Further, the high-temperature viscosity becomes high, and the meltability tends to decrease. Therefore, the preferred upper limit content range of Al ₂ O ₃ is 25% or less, 20% or less, 19% or less, 18.5% or less, 18% or less, 17.5% or less, and particularly 16% or less.

B ₂ O ₃ is a component that lowers the high-temperature viscosity and density, stabilizes the glass, makes it difficult for crystals to precipitate, and lowers the liquidus temperature. However, if the content of B ₂ O ₃ is too large, it becomes difficult to obtain high strengthening characteristics, the stress depth becomes particularly small, and ion exchange causes coloring of the glass surface called discoloration. , Water resistance tends to decrease. Therefore, the content of B ₂ O ₃ is 0 to 20%, preferably 0 to 5%, 0 to 4%, 0 to 3.5%, 0 to 3%, 0 to 2.5%, 0 to 0. Less than 2.5%, 0-2%, 0-1.5%, less than 0-1%, especially 0-0.5%.

Li ₂ O is an ion exchange component, a component that lowers high-temperature viscosity, enhances meltability and moldability, and a component that enhances Young's modulus. However, in a glass system containing 7% or more of Na ₂ O, when the content of Li ₂ O becomes extremely large, the compressive stress value tends to decrease. Further, if the content of Li ₂ O is too large, the liquidus viscosity is lowered and the glass is easily devitrified. In addition, the coefficient of thermal expansion is too high and the thermal shock resistance is lowered. It becomes difficult to match with the coefficient of thermal expansion of the surrounding material. In addition, the low-temperature viscosity may decrease too much, stress relaxation may easily occur, and the compressive stress value may decrease. Further, when the ion exchange treatment using a KNO ₃ molten salt, Li ions from the glass is eluted KNO ₃ molten salt, KNO ₃ problem that the life of the molten salt is reduced occurs. Therefore, the preferred contents of Li ₂ O are 0-2.5%, 0-2%, 0-1.7%, 0-1.5%, 0-1%, less than 0-1%, 0- It is 0.5%, 0 to 0.3%, 0 to 0.1%, and particularly 0 to 0.05%.

Na ₂ O is an ion exchange component, a component that lowers high-temperature viscosity, enhances meltability and moldability, and is also a component that improves devitrification resistance. If the Na ₂ O content is too low, the meltability, coefficient of thermal expansion, and ion exchange performance tend to deteriorate. Therefore, the lower limit content range of Na ₂ O is more than 2.2%, preferably more than 3.2%, more than 3.3%, more than 3.6%, 5% or more, 5.1% or more, 7%. Above, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, particularly 15% or more. On the other hand, if the content of Na ₂ O is too large, the coefficient of thermal expansion becomes too high, the thermal shock resistance is lowered, and it becomes difficult to match the coefficient of thermal expansion of the peripheral material. Further, the strain point may be lowered too much, or the component balance of the glass composition may be lost, and conversely, the devitrification resistance may be lowered. Therefore, the upper limit content range of Na ₂ O is 30% or less, preferably 25% or less, 23% or less, 21% or less, 20% or less, 19.5% or less, 19% or less, 18.9% or less, It is 18.5% or less, 18.2% or less, 18% or less, 17.5% or less, and particularly 17% or less.

K ₂ O is a component that promotes ion exchange, and is a component that easily increases the stress depth, especially among alkali metal oxides. It is also a component that lowers high-temperature viscosity and enhances meltability and moldability. It is also a component that improves devitrification resistance. However, if the content of K ₂ O is too large, the coefficient of thermal expansion becomes too high, the thermal shock resistance is lowered, and it becomes difficult to match the coefficient of thermal expansion of the peripheral material. In addition, the strain point tends to decrease too much, or the component balance of the glass composition is lost, and conversely, the devitrification resistance tends to decrease. Therefore, it is _{K 2} O upper range of content below 20%, preferably 13.9% is less than 10%, 6% or less, 5% or less, 4% or less, less than 3.3%, 3% or less, 2% or less, especially less than 2%. When K ₂ O is introduced, the suitable addition amount is 0.1% or more, 0.5% or more, 1% or more, 1.5% or more, and particularly 2% or more. When the addition of K ₂ O is avoided as much as possible, the preferable upper limit content range of K ₂ O is 1% or less, less than 1%, 0.1% or less, and particularly 0.05% or less.

Na ₂ O and K ₂ O are two components that can be introduced at the lowest cost among alkaline oxides, and are components that lower the high-temperature viscosity and promote ion exchange. Suitable lower limit content range of Na ₂ O + K ₂ O (total amount of Na ₂ O and K ₂ O) is 3% or more, 5% or more, 8% or more, 10% or more, 12% or more, 15% or more, 16%. Above, especially 17% or more. However, if the amount of Na ₂ O and K ₂ O is too large, the density and the coefficient of thermal expansion tend to increase, and the chemical durability tends to decrease. Therefore, the preferred upper limit content range of Na ₂ O + K ₂ O is 40% or less, 30% or less, 25% or less, 20% or less, 19% or less, and particularly 17% or less.

MgO is a component that lowers high-temperature viscosity to improve meltability and moldability, and increases strain point and Young's modulus. Among alkaline earth metal oxides, MgO is a component that has a large effect of improving ion exchange performance. is there. Therefore, the lower limit content range of MgO is more than 2.2%, preferably 2.5% or more, 3% or more, 3.5% or more, more than 4%, and particularly 4.5% or more. However, if the content of MgO is too large, the density and the coefficient of thermal expansion tend to be high, and the glass tends to be devitrified. Therefore, the upper limit content range of MgO is 20% or less, preferably 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, and particularly 5% or less.

Compared with other components, CaO is a component that has a large effect of lowering high-temperature viscosity, improving meltability and moldability, and increasing strain point and Young's modulus without lowering devitrification resistance. is there. The CaO content is 0 to 20%, and the suitable lower limit content range is more than 1%, 1.5% or more, 2% or more, 2% or more, 2.5% or more, 3% or more, 3.5%. Above, especially 4% or more. However, if the CaO content is too high, the density and coefficient of thermal expansion become high, the component balance of the glass composition is disturbed, and conversely, the devitrification resistance tends to decrease, and the ion exchange performance deteriorates. , The ion exchange solution tends to deteriorate easily. Therefore, the preferable upper limit content range of CaO is 15% or less, 10% or less, 8% or less, 5.9% or less, and particularly 5% or less.

When the molar ratio (MgO + CaO) / Al ₂ O ₃ is increased, the high-temperature viscosity is lowered, and the meltability and moldability can be improved. Therefore, the preferred lower limit range of the molar ratio (MgO + CaO) / Al ₂ O ₃ is 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more. 1 or more, 1.20 or more, 1.3 or more, 1.4 or more, especially 1.5 or more. On the other hand, if the molar ratio (MgO + CaO) / Al ₂ O ₃ is too large, the strengthening characteristics tend to deteriorate. Therefore, the preferable upper limit range of the molar ratio (MgO + CaO) / Al ₂ O ₃ is 3.0 or less, 2.5 or less, and particularly 2.0 or less. Here, "(MgO + CaO) / Al ₂ O ₃ " refers to a value obtained by dividing the total amount of MgO and CaO by the content of Al ₂ O ₃ .

Decreasing the molar ratio (Na ₂ O + K ₂ O) / (MgO + CaO) makes it easier to increase the strain point. Therefore, the preferred upper limit range of the molar ratio (Na ₂ O + K ₂ O) / (MgO + CaO) is 3.5 or less, 3.0 or less, 2.5 or less, 2.0 or less, 1.8 or less, 1.7 or less. , Especially 1.6 or less. Here, "(Na ₂ O + K ₂ O) / (MgO + CaO)" refers to a value divided by the total amount of Na ₂ O and K ₂ O and the total amount of MgO and CaO.

SrO and BaO are components that lower the high-temperature viscosity to improve meltability and moldability, and increase the strain point and Young's modulus, but if their contents are too large, the ion exchange reaction is likely to be inhibited. In addition, the density and coefficient of thermal expansion become high, and the glass tends to be devitrified. Therefore, the suitable contents of SrO and BaO are 0 to 5%, 0 to 3%, 0 to 2%, 0 to 1.5%, 0 to 1%, 0 to 0.5%, and 0 to 0, respectively. .1%, especially less than 0-0.1%.

The lower limit range of the mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is 0.50 or more, preferably 0.51 or more, 0.52 or more, 0.53 or more, 0.54 or more, especially 0. It is .55 or more. If the mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is too small, the compressive stress value and stress depth of the compressive stress layer tend to decrease. On the other hand, if the mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is too large, the chemical durability may decrease or the temperature at high temperature viscosity may increase. Therefore, the upper limit of the mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is 0.93 or less, preferably 0.90 or less, 0.89 or less, and particularly 0.78 or less.

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

ZnO is a component that enhances the ion exchange performance, and is particularly effective in increasing the compressive stress value. It is also a component that lowers the high temperature viscosity without lowering the low temperature viscosity. However, if the ZnO content is too high, the glass tends to be phase-separated, the devitrification resistance is lowered, the density is high, and the stress depth is low. Therefore, the preferable content of ZnO is 0 to 10%, 0 to 6%, 0 to 5%, 0 to 3%, and particularly 0 to 1%.

TiO ₂ is a component that enhances ion exchange performance and a component that lowers high-temperature viscosity, but if the content is too large, the glass is easily colored or devitrified. Therefore, the content of TiO ₂ is preferably 0 to 4.5%, less than 0 to 1%, 0 to 0.5%, and particularly preferably 0 to 0.3%.

ZrO ₂ is a component that enhances ion exchange performance and also a component that enhances viscosity and strain points near the liquidus viscosity. However, if the content is too large, the devitrification resistance may be significantly reduced. There is also a risk that the density will be too high. Therefore, the suitable content of ZrO ₂ is 0 to 10%, 0 to 5%, 0 to 4%, 0 to 3%, 0 to 1.9%, particularly 0.001 to 1%.

P ₂ O ₅ is a component that enhances the ion exchange performance, and is a component that particularly increases the stress depth. However, if the content of P ₂ O ₅ is too large, the glass tends to be phase-separated and the water resistance tends to decrease. Therefore, the suitable content of P ₂ O ₅ is 0 to 20%, 0 to 3%, 0 to 1%, and particularly 0 to 0.5%.

SnO ₂ is a component that enhances ion exchange performance and is a useful component as a fining agent in the overflow downdraw method. However, if the SnO ₂ content is too high, the devitrification resistance tends to decrease. Therefore, the suitable content of SnO ₂ is 0 to 3%, 0 to 1%, 0 to 0.1%, and particularly 0 to 0.01%. When introduced as a fining agent, the SnO ₂ content is preferably 0.01% or more, particularly 0.1% or more.

SO ₃ is a useful component as a fining agent when molding by the float method. The content of SO ₃ is preferably 0 to 1%, 0 to 0.5%, 0.01 to 0.2%, and particularly 0.05 to 0.1%.

Cl is a component that acts as a fining agent. The Cl content is preferably 0 to 0.1%, 0 to 0.09%, 0 to 0.08%, and particularly 0 to 0.06%. When introduced as a fining agent, the Cl content is preferably 0.005% or more.

CeO ₂ is a component that acts as a fining agent and a decoloring agent. The content of CeO ₂ is preferably 0 to 1%, 0 to 0.5%, 0 to 0.4%, and particularly 0 to 0.1%.

Fe ₂ O ₃ is a component that acts as a fining agent, but is a component that colors glass. The content of Fe ₂ O ₃ is preferably less than 0.1%, less than 0.08%, less than 0.06%, less than 0.04%, less than 0.03%, less than 0.02%, especially 0. It is less than 015%.

Rare earth oxides such as Nd ₂ O ₃ and La ₂ O ₃ are components that increase Young's modulus. However, the cost of the raw material itself is high, and if a large amount is added, the devitrification resistance tends to decrease. Therefore, the preferable content of the rare earth oxide is 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly 0.1% or less.

From the viewpoint of the environment, the reinforcing glass of the present invention preferably contains substantially no As ₂ O ₃ , Sb ₂ O ₃ , PbO, and F as a glass composition. Further, from the viewpoint of environmental consideration, it is also preferable that Bi ₂ O ₃ is not substantially contained. "Substantially free of ~" means that although the explicit component is not positively added as the glass component, the addition of the impurity level is permitted. Specifically, the content of the explicit component is 0. Refers to the case of less than 0.05%.

The reinforcing glass of the present invention preferably has the following characteristics, for example.

The coefficient of thermal expansion is preferably 50 × ^{10-7 to} 110 × ^10-7 / ° C, 70 × ^{10-7 to} 100 × ^10-7 / ° C, 75 × ^{10-7 to} 95 × ^10-7 / ° C, particularly. It is 80 × 10 ^{-7 to} 90 × 10 ^-7 / ° C. When the coefficient of thermal expansion is out of the above range, the glass is easily damaged by thermal shock, so that the time for the preheating step before the ion exchange treatment and the slow cooling step after the ion exchange treatment can be shortened. As a result, the manufacturing cost of tempered glass can be reduced. In addition, it becomes easy to match the coefficient of thermal expansion of peripheral members such as metal and organic adhesives, and peeling of peripheral members can be prevented. If the content of the alkali metal oxide and the alkaline earth metal oxide in the glass composition is increased, the thermal expansion coefficient becomes higher, and conversely, the content of the alkali metal oxide and the alkaline earth metal oxide is reduced. Then, the thermal expansion coefficient becomes low. Here, the "coefficient of thermal expansion" refers to an average value in the temperature range of 30 to 380 ° C. using a dilatometer.

Density is preferably 2.60 g / cm ³ or less, 2.55 g / cm ³ or less, 2.50 g / cm ³ or less, 2.48 g / cm ³ or less, 2.46 g / cm ³ or less, in particular 2.45 g / It is cm ³ or less. The lower the density, the lighter the glass for strengthening. The contents of SiO ₂ , B ₂ O ₃ , and P ₂ O _{5 in} the glass composition may be increased, or the contents of alkali metal oxides, alkaline earth metal oxides, ZnO, ZrO ₂ , and TiO ₂ may be decreased. If this is done, the density tends to decrease.

The strain point is preferably 480 ° C. or higher, 490 ° C. or higher, 500 ° C. or higher, 510 ° C. or higher, 520 ° C. or higher, 530 ° C. or higher, and particularly 540 ° C. or higher. If the strain point is too low, the strengthening characteristics will vary and thermal deformation will increase after the ion exchange treatment. On the other hand, if the strain point is too high, the temperature of the ion exchange liquid, especially the KNO ₃ molten salt, must be raised in order to obtain good strengthening characteristics, and the initial investment and maintenance cost of the ion exchange equipment tend to rise. .. Therefore, the strain point is preferably 650 ° C. or lower, 600 ° C. or lower, 580 ° C. or lower, and particularly 550 ° C. or lower. If the contents of B ₂ O ₃ and alkali metal oxide in the glass composition are increased, the strain point tends to be lowered, and conversely, if the contents of SiO ₂ and Al ₂ O ₃ are increased, the strain point is lowered. It becomes easy to rise.

The temperature in the high temperature viscosity ¹⁰ 4.0 dPa · s, preferably 1250 ° C. or less, 1220 ° C. or less, 1200 ° C. or less, 1150 ° C. or less, 1100 ° C. or less, in particular 1050 ° C. or less. If the temperature at the high temperature viscosity of 10 ^4.0 dPa · s is too high, the molten tin tends to evaporate into the atmosphere in the molten tin bath when the glass plate is formed by the float method, so that the temperature in the molten tin bath is low. The tin compound falls on the molten glass in the region, and the surface quality of the glass plate tends to deteriorate. In addition, the alkaline component is likely to volatilize from the molten glass, and tin is easily diffused from the molten tin to the molten glass, so that the amount of warpage of the tempered glass plate is likely to increase after the ion exchange treatment. Further, the load on the molding equipment is reduced, and it becomes easy to extend the life of the molding equipment. The temperature at a high temperature viscosity of 10 ^4.0 dPa · s corresponds to the molding temperature. Further, alkali metal oxides, alkaline earth metal _{oxides, ZnO,} or increasing the content of _{B 2} O _3, TiO 2, if reduced the content of SiO 2, _Al 2 _{O 3,} the high temperature viscosity of 10 ⁴ The temperature at ^0.0 dPa · s tends to decrease.

The temperature at a high temperature viscosity of 10 ^2.5 dPa · s is preferably 1600 ° C. or lower, 1550 ° C. or lower, 1500 ° C. or lower, 1450 ° C. or lower, and particularly 1400 ° C. or lower. The lower the temperature at the high temperature viscosity of 10 ^2.5 dPa · s, the lower the temperature melting becomes possible, the load on the melting equipment is reduced, and the life of the melting equipment can be easily extended. In addition, it becomes easy to improve the foam quality. As a result, the lower the temperature at the high temperature viscosity of 10 ^2.5 dPa · s, the easier it is to reduce the manufacturing cost of the tempering glass. Here, the "temperature at 10 ^2.5 dPa · s" can be measured by, for example, the platinum ball pulling method. The temperature at 10 ^2.5 dPa · s corresponds to the melting temperature. Further, if the content of alkali metal oxide, alkaline earth metal oxide, ZnO, B ₂ O ₃ and TiO _{2 in} the glass composition is increased or the content of SiO ₂ and Al ₂ O ₃ is decreased, The temperature at 10 ^2.5 dPa · s tends to decrease.

The liquidus temperature is preferably 1200 ° C. or lower, 1110 ° C. or lower, 1050 ° C. or lower, 1000 ° C. or lower, 950 ° C. or lower, particularly 900 ° C. or lower. Here, the "liquid phase temperature" is determined by passing the standard sieve 30 mesh (500 μm) and putting the glass powder remaining in 50 mesh (300 μm) into a platinum boat and holding it in a temperature gradient furnace for 24 hours, and then the platinum boat. Refers to the highest temperature at which devitrification (crystal foreign matter) was observed inside the glass by taking out the glass and observing it under a microscope. The lower the liquidus temperature, the better the devitrification resistance and moldability. Further, the content of Na ₂ O, K ₂ O, B ₂ O _{3 in} the glass composition can be increased, or the content of Al ₂ O ₃ , Li ₂ O, MgO, CaO, ZnO, TiO ₂ and ZrO ₂ can be increased. If the amount is reduced, the liquidus temperature tends to decrease.

The liquidus viscosity is preferably 10 ^4.0 dPa · s or more, 10 ^4.3 dPa · s or more, 10 ^4.8 dPa · s or more, 10 ^5.0 dPa · s or more, and 10 ^5.3 dPa · s. ^{more, 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. Here, the "liquid phase viscosity" refers to a value obtained by measuring the viscosity of glass at the liquid phase temperature by the platinum ball pulling method. The higher the liquidus viscosity, the better the devitrification resistance and moldability. Further, if the content of Na ₂ O and K ₂ O in the glass composition is increased or the content of Al ₂ O ₃ , Li ₂ O, MgO, ZnO, TiO ₂ and ZrO ₂ is decreased, the liquid phase viscosity is increased. Is likely to be high.

When the reinforcing glass of the present invention is immersed in KNO ₃ molten salt at 430 ° C. for 4 hours, the compressive stress value of the surface compressive stress layer is 300 MPa or more (preferably 400 MPa or more, 500 MPa or more, 600 MPa or more, 700 MPa or more, 800 MPa or more, 900 MPa or more, 950 MPa or more, especially 1000 MPa or more) and stress depth of 10 μm or more (preferably 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, especially 45 μm or more). preferable. In this way, the mechanical strength of the tempered glass is increased after the ion exchange treatment.

The reinforcing glass of the present invention preferably has a flat plate shape, that is, a glass plate. In this way, it becomes easy to apply to a mobile phone, a digital camera, a PDA (personal terminal), a cover glass of a solar cell, or a display, particularly a glass substrate of a touch panel display. Further, the reinforcing glass of the present invention may have a shape having a bent portion and / or a bent portion in order to enhance the design. Such a shape can be produced by thermally deforming a glass plate at a temperature equal to or higher than the softening point, or by pouring molten glass into a molding die and pressing and pressing it if necessary.

In the reinforcing glass of the present invention, the thickness (in the case of a flat plate shape, the plate thickness) is preferably 4.0 mm or less, 3.2 mm or less, 2.0 mm or less, 1.5 mm or less, 1.3 mm or less, 1.1 mm. Hereinafter, it is 1.0 mm or less, 0.8 mm or less, and particularly 0.7 mm or less. The thinner the thickness, the easier it is to reduce the weight of the glass, and the easier it is to bend the glass by heat. On the other hand, if the thickness is too thin, it becomes difficult to obtain the desired mechanical strength. Therefore, the thickness is preferably 0.1 mm or more, 0.2 mm or more, 0.3 mm or more, 0.4 mm or more, and particularly 0.5 mm or more.

The tempered glass of the present invention can be produced by subjecting the tempered glass to an ion exchange treatment.

The tempered glass of the present invention has a compressive stress layer on its surface. The compressive stress value of the compressive stress layer is preferably 300 MPa or more, 400 MPa or more, 500 MPa or more, 600 MPa or more, 700 MPa or more, 800 MPa or more, 900 MPa or more, 950 MPa or more, and particularly 1000 MPa or more. The larger the compressive stress value, the higher the mechanical strength of the tempered glass. 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 there is a possibility that the dimensional change before and after the ion exchange treatment becomes large. Therefore, the compressive stress value of the compressive stress layer is preferably 1500 MPa or less, 1400 MPa or less, 1300 MPa or less, 1200 MPa or less, and particularly 1100 MPa or less. If the contents of Al ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO, and ZnO in the glass composition are increased or the contents of SrO and BaO are decreased, the compressive stress value tends to increase. Further, if the ion exchange time is shortened or the ion exchange temperature is lowered, the compressive stress value tends to increase.

The stress depth 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, and particularly 40 μm or more. The larger the stress depth, the more difficult it is for the tempered glass to break even if the tempered glass is deeply scratched, and the less the variation in mechanical strength becomes. On the other hand, the larger the stress depth, the more difficult it is to cut the tempered glass. Further, the tensile stress inherent in the tempered glass becomes extremely high, and there is a possibility that the dimensional change becomes large before and after the ion exchange treatment. Therefore, the stress depth is preferably 70 μm or less, 60 μm or less, and particularly 50 μm or less. If the content of K ₂ O and P ₂ O _{5 in} the glass composition is increased or the content of SrO and BaO is decreased, the stress depth tends to increase. Further, if the ion exchange time is lengthened or the ion exchange temperature is raised, the stress depth tends to increase.

The internal tensile stress values are 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, and particularly 70 MPa or less. If the internal tensile stress value is too high, the tempered glass is likely to self-destruct when it collides with a sharp object. On the other hand, if the internal tensile stress value is too low, it becomes difficult to secure the mechanical strength of the tempered glass. Therefore, the internal tensile stress value is preferably 1 MPa or more, 5 MPa or more, 7 MPa or more, and particularly 10 MPa or more. The internal tensile stress can be calculated by the following mathematical formula 1.

The tempered glass and tempered glass of the present invention can be produced as follows.

First, the glass raw material prepared to have the above glass composition is put into a continuous melting furnace, melted by heating at 1500 to 1700 ° C., clarified, supplied to a molding apparatus, molded into a flat plate shape, etc. By cooling, strengthening glass can be produced.

It is preferable to adopt the float method as a method for forming into a flat plate shape. The float method is a method capable of producing a large glass plate at low cost.

In addition to the float method, various molding methods can be adopted. For example, a molding method such as an overflow down draw method, a down draw method (slot down method, redraw method, etc.), a rollout method, a press method, etc. can be adopted.

Next, the tempered glass can be produced by subjecting the obtained tempered glass to an ion exchange treatment. The time for cutting the tempered glass to a predetermined size may be before the ion exchange treatment or after the ion exchange treatment.

During the ion exchange treatment, the temperature of the ion exchange solution (KNO ₃ molten salt), that is, the ion exchange temperature is preferably 350 to 550 ° C, particularly 400 to 460 ° C, and the ion exchange time is 0.5 to 10 hours, particularly 1 to 1. 8 hours is preferred. By doing so, it becomes easy to properly form the compressive stress layer while increasing the production efficiency of the tempered glass. Since the reinforcing glass of the present invention has the above glass composition, the compressive stress value and stress depth of the compressive stress layer can be increased without using a mixture of KNO ₃ molten salt and NaNO ₃ molten salt. can do.

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

Table 1 shows examples (Sample Nos. 1 to 14) of the present invention. In addition, "Na / (Li + Na + K + Mg + Ca + Sr + Ba)" in the table represents mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O).

Each sample in the table was prepared as follows. First, the glass raw materials were prepared so as to have the glass composition shown in the table, and melted at 1550 to 1600 ° C. for 3 hours using a platinum pot. Then, the obtained molten glass was poured onto a carbon plate and formed into a flat plate shape. Various characteristics of the obtained glass plate were evaluated.

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

The strain point Ps and the slow cooling 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 is a value measured by the platinum ball pulling method.

The coefficient of thermal expansion α is an average value in the temperature range of 30 to 380 ° C. using a dilatometer.

The liquidus temperature TL passes through a standard sieve of 30 mesh (500 μm), the glass powder remaining in 50 mesh (300 μm) is placed in a platinum boat, held in a temperature gradient furnace for 24 hours, then the platinum boat is taken out and a microscope is used. By observation, the temperature was set to the highest temperature at which devitrification (crystal foreign matter) was observed inside the glass.

The liquidus viscosity logη _TL is a value obtained by measuring the viscosity of glass at the liquidus temperature by the platinum ball pulling method.

As is clear from Table 1, the sample No. Since the densities of 1 to 14 are 2.58 g / cm ³ or less, the tempered glass can be reduced in weight, and since the strain point is 490 ° C to 561 ° C, the tempered characteristics vary and thermal deformation occurs after the ion exchange treatment. It can be reduced. In addition, sample No. 1 to 14 have a liquidus viscosity of 10 ^4.4 dPa · s or more, so that they can be easily formed into a glass plate by the float method, and the temperature at 10 ^4.0 dPa · s is 1208 ° C. or less. It is possible to reduce the amount of warpage after the ion exchange treatment while improving the quality. Furthermore, the sample No. Since the temperatures of 1 to 14 at a high temperature viscosity of 10 ^2.5 dPa · s are 1549 ° C. or lower, it is considered that a large amount of glass plates can be produced at low cost.

Subsequently, both surfaces of each sample were optically polished and then immersed in a KNO ₃ molten salt at 430 ° C. for 4 hours to perform an ion exchange treatment. The surface of each sample was washed after the ion exchange treatment. Subsequently, the compressive stress value CS and the stress depth DOL of the surface compressive stress layer were calculated from the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation) and their intervals. In the calculation, the refractive index of each sample was 1.50, and the optical elastic constant was 30 [(nm / cm) / MPa]. Although the glass composition of the surface layer is microscopically different before and after the ion exchange treatment, the glass composition is not substantially different when viewed as a whole glass.

As is clear from Table 1, the sample No. Since CS of 1 to 14 is 656 MPa or more and DOL is 17 μm or more, it is considered that the mechanical strength is high.

The tempered glass and tempered glass of the present invention are suitable as a cover glass for mobile phones, digital cameras, PDAs, etc., or a glass substrate for touch panel displays, etc. In addition to these applications, the tempered glass and tempered glass of the present invention are used for applications requiring high mechanical strength, such as window glass, magnetic disk substrate, flat panel display substrate, and solar cell cover glass. , Glass substrate for solar cells, cover glass for solid-state imaging elements, and tableware.

Claims (8)

As the glass composition, in terms of mass%, SiO ₂ 50 to 80%, Al ₂ O ₃ 3 to 30%, B ₂ O _{30 to} 20%, Na ₂ O 2.2 or more to 30%, K ₂ O 0 to 0 It contains 20%, MgO more than 2.2% to 20%, CaO 3.5 to 20%, SO ₃ 0.01 to 0.2%, Fe ₂ O _{30 to} less than 0.04 %, and mass ratio Na ₂ A strengthening glass characterized in that O / (Li ₂ O + Na ₂ O + K ₂ O + MgO + CaO + SrO + BaO) is 0.50 to 0.93 and the molar ratio (MgO + CaO) / Al ₂ O ₃ is 1.58 to 2.5. As the glass composition, SiO ₂ 50 to 80%, Al ₂ O ₃ 10.5 to 30%, B ₂ O _{30 to} 20%, Li ₂ O 0 to 2.5%, Na ₂ O 3 in terms of mass%. .3 super _{~30%, K 2 O 0.1~20%} , MgO 2.2 super ~20%, CaO 3.5~20%, 0~10 % ZnO, ZrO 2 0~1.9%, SO ₃ 0.01 to 0.2%, Fe ₂ O _{30 to} less than 0.04 %, mass ratio Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O + MgO + CaO + SrO + BaO) 0.50 to 0.90, mol The strengthening glass according to claim 1, wherein the ratio (MgO + CaO) / Al ₂ O ₃ is 1.58 to 2.5. As the glass composition, SiO ₂ 50 to 80%, Al ₂ O _{3 3 to} 20%, B ₂ O _{30 to} 2.5%, Li ₂ O 0 to 2%, Na ₂ O 3.2 in terms of mass%. to _30%, K less than 2 O 0~3.3%, MgO 2.2 super ~20%, CaO 3.5~5.9%, SrO 0~1%, 0~5% ZnO, ZrO 2 0~ It contains 1.9%, SO ₃ 0.01 to 0.2%, Fe ₂ O _{30 to} less than 0.04 %, and has a mass ratio of Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O + MgO + CaO + SrO + BaO) of 0.50. The tempering glass according to claim 1, wherein the temperature is ~ 0.90 and the molar ratio (MgO + CaO) / Al ₂ O ₃ is 1.58 to 2.5. As the glass composition, SiO ₂ 50 to 80%, Al ₂ O _{3 to} 20%, B ₂ O _{30 to} less than 2.5%, Li ₂ O 0 to 2%, Na ₂ O 10 or more in terms of mass%. ~ 30%, K ₂ O over 0.1 ~ less than 3.3%, MgO 2.5 to 20%, CaO 3.5 to 5.9%, SrO 0 to 1%, BaO 0 to 3%, ZnO 0 _{~5%, ZrO 2 0~10%,} SO 3 0.01~0.2%, contains _Fe 2 O 3 0 to less than 0.04%, the weight ratio _{Na 2 O / (Li 2 O} + Na 2 O + K 2 The reinforcing glass according to claim 1, wherein O + MgO + CaO + SrO + BaO) is 0.50 to 0.89, and the molar ratio (MgO + CaO) / Al ₂ O ₃ is 1.58 to 2.5. The tempering glass according to any one of claims 1 to 4, wherein the temperature at a high temperature viscosity of 10 ^4.0 dPa · s is 1200 ° C. or lower. The reinforcing glass according to any one of claims 1 to 5, wherein the strain point is 480 to 550 ° C. Any of claims 1 to 6, wherein the compressive stress value of the surface compressive stress layer becomes 300 MPa or more and the stress depth becomes 10 μm or more when immersed in KNO ₃ molten salt at 430 ° C. for 4 hours. The strengthening glass according to item 1. In tempered glass having a compressive stress layer on the surface, the glass composition is SiO ₂ 50 to 80%, Al ₂ O ₃ 3 to 30%, B ₂ O _{30 to} 20%, Na ₂ O 2. Over 2 to 30%, K ₂ O 0 to 20%, MgO Over 2.2 to 20%, CaO 3.5 to 20%, SO ₃ 0.01 to 0.2%, Fe ₂ O _{30 to} 0. Containing less than 04 %, mass ratio Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O + MgO + CaO + SrO + BaO) is 0.50 to 0.93, and molar ratio (MgO + CaO) / Al ₂ O ₃ is 1.58 to 2.5. Tempered glass characterized by being.