JPWO2015111524A1 - Tempered glass composition, tempered glass article and method for producing the same - Google Patents

Abstract

A tempered glass article excellent in thermal shock resistance and chemical durability is obtained. In terms of mol% based on oxide, SiO2 is 80.5 to 94 mol%, Al2O3 is 0 to 5 mol%, B2O3 is 3 to 17 mol%, and R2O (where R is a group selected from the group consisting of Na and K) 3) to 16 mol%, and the total (s + 2a) of the SiO2 content (s) and twice the Al2O3 content (a) is 83 to 94 mol%, and the number of moles of B2O3 ( A tempered glass composition and a tempered glass article, wherein the ratio (b / m) of b) to the number of moles (m) of non-crosslinked oxygen (b / m) is 0.5-2.

Description

The present invention relates to a tempered glass composition excellent in thermal shock resistance and chemical durability, a tempered glass article, and a method for producing the same.
About.

Tempered glass articles include passenger cars, trucks, buses, railways, ships, aircraft and other vehicle windows, headlights and taillights, building and residential windows, doors and show windows, partitions, desktops, bookshelves, It is used for furniture such as showcases, office appliances, home appliances such as cooking utensils. Reinforcing treatment for windows for vehicles and buildings is performed by a heat strengthening method (ie, a physical strengthening method) in which a glass plate is heated to a temperature near the yield point and air is blown onto the surface of the glass plate to rapidly cool it. .
The heat strengthening method is a method of strengthening a glass article by generating surface compressive stress using heat shrinkage caused by cooling. When the surface of the heated glass article is rapidly cooled by blowing air or the like, the surface of the glass article is cooled and hardened earlier than the inside. Thereafter, the inside contracts to cause a compressive stress on the surface of the glass article, thereby improving the strength of the glass article.
In the heat strengthening method, the glass having a larger thermal expansion coefficient tends to be strengthened. For example, Patent Document 1 discloses that the stress generated by thermal strengthening can be increased by setting the average thermal expansion coefficient of glass at 50 to 350 ° C. to 80 to 110 × 10 ⁻⁷ / ° C. On the other hand, the thermal shock resistant glass is required to have a small thermal expansion coefficient (see, for example, Patent Document 2).

JP 2003-119048 A Japanese Patent Publication No. 60-25376

Borosilicate glass with excellent thermal shock resistance and chemical durability is used for fireproof windows and physics and chemistry equipment. However, it has been difficult to heat strengthen conventional heat-resistant glass because of its low thermal expansion coefficient. In addition, the conventional heat-resistant glass has a high high temperature viscosity, so that the production efficiency is not so good.
An object of the present invention is to provide a glass composition for strengthening that is excellent in thermal shock resistance and chemical durability and that can be easily thermally strengthened. Another object of the present invention is to provide a tempered glass article excellent in thermal shock resistance and chemical durability and a method for producing the tempered glass article.

The glass composition for strengthening of the present invention is expressed in mol% on the basis of oxide, and SiO ₂ is 80.5 to 94 mol%, Al ₂ O ₃ is 0 to 5 mol%, and B ₂ O ₃ is 3 to 17 mol. %, R ₂ O (where R represents one or more selected from the group consisting of Na and K), 3 to 16 mol%, SiO ₂ content (s) and Al ₂ O ₃ content ( The sum (s + 2a) of 2 times a) is 83 to 94 mol%, and the ratio (b / m) of the number of moles of B ₂ O ₃ (b) to the number of moles of non-crosslinked oxygen (m) is 0. 5 to 2.
In the glass composition for strengthening of the present invention, the ratio (b / r) of the content b of B ₂ O _{3 and} the content r of R ₂ O expressed by mol% based on the oxide is 0.5 to 2.0. It is preferable that
The glass composition for strengthening of the present invention preferably has an average coefficient of thermal expansion α of 50 × 10 ⁻⁷ / ° C. or less at 50 ° C. to 350 ° C. of the glass.
In the glass composition for strengthening of the present invention, it is preferable that the maximum value α _max of the thermal expansion coefficient between the transition point and the yield point is 200 × 10 ⁻⁷ / ° C. or more.
The glass composition for strengthening of the present invention preferably has a glass transition point of 500 to 685 ° C.
The glass composition for strengthening of the present invention preferably has a temperature T _{2 at} which the viscosity of the glass becomes 10 ² dPa · s is 1800 ° C. or lower.
The tempered glass article of the present invention is expressed in mol% on the basis of oxide, SiO ₂ is 80.5 to 94 mol%, Al ₂ O ₃ is 0 to 5 mol%, B ₂ O ₃ is 3 to 17 mol%, It contains 3 to 16 mol% of R ₂ O (wherein R represents one or more selected from the group consisting of Na and K), and contains ₂ of SiO ₂ content (s) and Al ₂ O ₃ content (a). And the total (s + 2a) is 83 to 94 mol%, and the ratio (b / m) of the number of moles of B ₂ O ₃ (b) to the number of moles of non-bridging oxygen (m) is 0.5 to 2. It consists of a certain reinforcing glass composition.
The tempered glass article of the present invention preferably has a surface compressive stress of 10 MPa or more.
The tempered glass article of the present invention preferably has an average coefficient of thermal expansion α at 50 ° C. to 350 ° C. of 60 × 10 ⁻⁷ / ° C. or less.
The manufacturing method of the tempered glass article of the present invention is expressed in mol% on the basis of oxide, SiO ₂ is 80.5 to 94 mol%, Al ₂ O ₃ is 0 to 5 mol%, and B ₂ O ₃ is 3 to 17. Mol%, R ₂ O (wherein R represents one or more selected from the group consisting of Na and K) is contained in an amount of ₃ to 16 mol%, and the SiO ₂ content (s) and Al ₂ O ₃ content (a ) Is twice the total (s + 2a) is 83 to 94 mol%, and the ratio (b / m) of the number of moles of B ₂ O ₃ (b) to the number of moles of non-bridging oxygen (m) is 0.5. It is a method of heating the glass article which is ˜2 to a temperature not lower than the transition point and not higher than the yield point, and then cooling the surface of the heated glass article by blowing air.
The term “to” indicating the numerical range described above is used to mean that the numerical values described before and after it are used as the lower limit value and the upper limit value, and unless otherwise specified, “to” is the same in the following specification. Used with meaning.

  ADVANTAGE OF THE INVENTION According to this invention, the glass composition for reinforcement | strengthening which is excellent in a thermal shock resistance and chemical durability, and can be thermally strengthened easily can be provided. Moreover, according to this invention, the tempered glass article excellent in the thermal shock resistance and chemical durability and its manufacturing method can be provided.

As used herein, components of the glass _are expressed in typical oxides such SiO _{2, B} 2 O _3, the glass composition is displayed in mole percent following oxides.
In general, in a glass structure, one O atom is covalently bonded to two Si atoms, thereby forming a glass network of —Si—O—Si— units. Such O atoms are referred to as “bridging oxygen”. When Na ₂ O or K ₂ O is contained in the glass, a positively charged Na ⁺ ion or K ⁺ exists in the network, resulting in a negatively charged structure for charge compensation. As a result, in the glass structure, while covalently bound to the Si atom and the negative charge containing charged O atoms in -Si-O ^- so that the unit occurs. The -Si-O ^- in the unit, O atoms are not covalently bonded with only one Si atom, such an oxygen atom, referred to as "non-bridging oxygen."
In the present specification, the “transition point” and “bend point” can be determined from the linear expansion curve of glass. A method for obtaining a transition point and a yield point from a linear expansion curve of glass is described in JIS R3102-1995.
“Average coefficient of thermal expansion α from 50 ° C. to 350 ° C.” (hereinafter, simply referred to as “α”) and “Maximum value α _{max of the} coefficient of thermal expansion between the transition point and the yield point” (hereinafter, “α”) , Which may be simply displayed as “α _max ”) can be measured by the method described in JIS R3102-1995.
“Temperature T _{2 at} which the viscosity is 10 ² dPa · s” (hereinafter sometimes simply referred to as “T ₂ ”) is an index representing the high-temperature viscosity of glass, and is a melting condition for producing a glass article. It can be measured using a rotational viscometer. Further, “Temperature T _{4 at} which the viscosity becomes 10 ⁴ dPa · s” (hereinafter sometimes simply referred to as “T ₄ ”) is a temperature that serves as an indication of molding conditions when manufacturing a glass article, It can be measured using a rotational viscometer. These measuring methods are described in ISO7884-2 (1987).
“Surface compressive stress” is obtained by measuring a phase difference (retardation) due to birefringence and dividing by a photoelastic constant.
The water resistance of glass can be evaluated by the weight loss per unit surface area when the glass article is immersed in pure water at 90 ° C. for 20 hours. The acid resistance of the glass can be evaluated by a change in weight per unit surface area when the glass article is immersed in hydrochloric acid (1 N) at 90 ° C. for 20 hours. Hereinafter, the water resistance and acid resistance of the glass evaluated by the above method may be collectively referred to as chemical durability.
In the present specification, the reinforcing glass composition of the present invention may be referred to as “the glass of the present invention”, and the tempered glass article of the present invention uses the reinforcing glass composition of the present invention (that is, the glass of the present invention). The glass obtained by tempering is referred to, and the glass of the present invention before the tempering treatment is referred to as “glass article”.

The glass composition for strengthening of the present invention is expressed in mol% on the basis of oxide, and SiO ₂ is 80.5 to 94 mol%, Al ₂ O ₃ is 0 to 5 mol%, and B ₂ O ₃ is 3 to 17 mol. %, R ₂ O (where R represents one or more selected from the group consisting of Na and K), 3 to 16 mol%, SiO ₂ content (s) and Al ₂ O ₃ content ( The sum (s + 2a) of 2 times a) is 83 to 94 mol%, and the ratio (b / m) of the number of moles of B ₂ O ₃ (b) to the number of moles of non-crosslinked oxygen (m) is 0. 5 to 2.

The glass of the present invention preferably has the following composition.
SiO _2: 80.5~94 mol%,
Al ₂ O _3: 0~5 mole%,
(However _{SiO 2 + 2Al 2 O 3:} 83~94 mol%),
B ₂ O _3: 3~17 mol%,
Na ₂ O: 0~12 mol%,
K ₂ O: 0~4 mol%,
(Although _{Na 2 O + K 2 O:} 3~12 mol%),
CaO + MgO: 0 to 10 mol%
(Mole number of B ₂ O ₃ ) / (Mole number of non-bridging oxygen): 0.5-2

In the glass of the present invention, SiO ₂ is an oxide (network former) that forms a network structure of glass, and is essential, and if it is less than 80.5 mol%, thermal shock resistance or chemical durability is insufficient. There is a case. The content of SiO ₂ is preferably 81 mol% or more, more preferably 82 mol% or more, and still more preferably 83 mol% or more. When the content of SiO ₂ exceeds 94 mol%, the high-temperature viscosity of the glass increases and the production efficiency decreases. The content of SiO ₂ is preferably 92 mol% or less, more preferably 90 mol% or less, and still more preferably 88 mol% or less.
In order to increase the chemical durability, the amount of SiO ₂ is preferably more than 80% by mass, more preferably 82% or more, assuming that the mass of the glass is 100% by mass.

Al ₂ O ₃ is not essential, but is a glass network former and is a component that has an effect of improving the chemical durability of glass or suppressing phase separation. The content of Al ₂ O ₃ is preferably 0.5 mol% or more, more preferably 1.0 mol% or more, and further preferably 1.5 mol% or more in order to suppress phase separation. Further, the content of Al ₂ O ₃ is 5 mol% or less, preferably 4% mol or less, more preferably 3% mol or less in order to enhance the solubility of the glass.

When the SiO ₂ content in the glass composition is s mol% and the Al ₂ O ₃ content is a mol%, the sum of s and 2 times a (s + 2a) is an indicator of the amount of network former in the glass It is. In the glass of the present invention, in order to increase the chemical durability of the glass, (s + 2a) is 83 mol% or more, more preferably 84 mol% or more, and further preferably 85 mol% or more. In order that the high temperature viscosity of the glass does not become too high, (s + 2a) is preferably 94 mol% or less, more preferably 90 mol% or less, and even more preferably 88 mol% or less.

B ₂ O ₃ is an essential component for enhancing the thermal shock resistance of the glass and making it easier to strengthen. If the content of B ₂ O ₃ is less than 3 mol%, the effect is insufficient. The content of B ₂ O ₃ is preferably 5 mol% or more, particularly preferably 7 mol% or more. If the content of B ₂ O ₃ is more than 17 mol%, the glass tends to phase-separate and the glass tends to devitrify. The content of B ₂ O ₃ is preferably 13 mol% or less, more preferably 10 mol% or less, and still more preferably 8 mol% or less.
In the glass of the present invention, the ratio b / m of the number of moles B of B ₂ O _{3 to} the number of moles m of non-crosslinked oxygen is 0 in order to lower the high temperature viscosity, increase the thermal shock resistance of the glass, and make it easier to strengthen. 0.5 to 2, 0.7 to 1.5 is preferable, and 0.8 to 1.2 is more preferable. Based on the results of Raman scattering and NMR spectrum analysis of various glasses, the inventors of the present invention have a large change in the glass structure before and after the glass transition point by setting b / m within the above range. The coefficient of thermal expansion is thought to change significantly before and after the point.

When the glass of the present invention consists of SiO ₂ , B ₂ O ₃ and R ₂ O only, the number of moles m of the non-bridging oxygen is equal to the number of moles of R ₂ O, and the b / m is B ₂ It is equal to the ratio b / r of the mole number b of O ₃ and the mole number r of R ₂ O. When the glass of the present invention further contains Al ₂ O ₃ and an alkaline earth oxide (MgO, CaO, SrO, BaO), the number of moles m of non-crosslinked oxygen is the number of moles a of Al ₂ O ₃ , It is represented by m = r + c / 2−a with respect to the number of moles c of the alkaline earth oxide.

The glass of the present invention contains an alkali metal oxide R ₂ O. Here, R is at least one selected from the group consisting of Na and K.
The total content of R ₂ O in the glass of the present invention requires 3 mol% or more for ease of strengthening, preferably 4 mol% or more, and more preferably 6 mol% or more. In order to increase the thermal shock resistance, the total content of R ₂ O is 16 mol% or less, preferably 14 mol% or less, more preferably 12 mol% or less, and even more preferably 9% or less.

In the glass of the present invention, Na ₂ O is not essential, but is a component that increases the thermal expansion coefficient, and can be contained up to 16 mol%. When the glass of the present invention contains Na ₂ O, the content is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 5 mol% or more in terms of ease of strengthening. The Na ₂ O content is preferably 14 mol% or less, more preferably 12 mol% or less, further preferably 10 mol% or less, and particularly preferably 8 mol% or less in order to increase the thermal shock resistance.

In the glass of the present invention, K ₂ O is not essential, but is a component that increases the thermal expansion coefficient, and can be contained up to 16 mol%. When the glass of the present invention contains K ₂ O, the content is preferably 0.1 mol% or more, and more preferably 0.5 mol% or more in terms of ease of strengthening. Since K ₂ O has a large effect of increasing the thermal expansion coefficient, the content of K ₂ O is preferably 10 mol% or less, more preferably 4 mol% or less, and more preferably 2 mol% in order to increase the thermal shock resistance. % Or less is more preferable.

In the glass of the present invention, the ratio (b / r) of the content b of B ₂ O _{3 and} the content r of R ₂ O in the glass composition expressed by mol% on the basis of oxide increases the thermal shock resistance, And in order to make it easy to strengthen, 0.5-2.0 are preferable, It is more preferable that it is 0.7-1.5, 0.8-1.2 is further more preferable.

CaO, SrO, BaO and MgO are not essential, but can be contained for the purpose of increasing the stability of the glass or adjusting the thermal expansion coefficient.
In the glass of the present invention, the total content of one or more selected from the group consisting of CaO, SrO, BaO and MgO in the glass composition expressed by mol% on the basis of oxide is 10 mol% or less from the viewpoint of glass stability. Is preferable, and 5 mol% or less is more preferable. Moreover, it is more preferable to contain 10 mol% or less of one or more selected from the group consisting of CaO and MgO.

  When the glass of the present invention contains CaO, the content of CaO is preferably 0.5 mol% or more. For ease of strengthening, 1 mol% or more is more preferable, and 3 mol% or more is more preferable. . The CaO content of the glass of the present invention is preferably 10 mol% or less, more preferably 9 mol% or less, and even more preferably 8 mol% or less in order to suppress phase separation and stabilize the glass.

  When the glass of the present invention contains MgO, the content of MgO is preferably 0.5 mol% or more, and for ease of strengthening, 1 mol% or more is more preferable, and 3 mol% or more is more preferable. . The MgO content of the glass of the present invention is preferably 10 mol% or less, more preferably 9 mol% or less, and even more preferably 8 mol% or less in order to suppress phase separation and stabilize the glass.

The glass of the present invention consists essentially of the above components, but may contain other components as long as the object of the present invention is not impaired. Examples of the other components, for _{example, ZnO, Li 2 O, Fe} 2 O 3, ZrO 2, TiO 2, Y 2 O 3, may contain CeO ₂ and the like. Further, clarifier components such as SO ₃ , SnO ₂ , Sb ₂ O ₃ , As ₂ O ₃ , NiO, CoO, CrO, MnO, V ₂ O ₅ , SeO ₂ , AuO, Ag ₂ O, CdO, CuO, A color tone adjusting component such as the above may be contained.

Next, the physical properties of the glass of the present invention will be described.
The average thermal expansion coefficient α at 50 ° C. to 350 ° C. of the glass of the present invention is preferably 60 × 10 ⁻⁷ / ° C. or less, more preferably 50 × 10 ⁻⁷ / ° C. or less in order to increase the thermal shock resistance. Further, α of the glass of the present invention is preferably 20 × 10 ⁻⁷ / ° C. or more, more preferably 30 × 10 ⁻⁷ / ° C. or more, in that the surface compressive stress due to thermal strengthening tends to increase.

The maximum value α _max of the thermal expansion coefficient between the transition point and the yield point of the glass of the present invention is preferably 200 × 10 ⁻⁷ / ° C. or more, because the surface compressive stress due to thermal strengthening tends to increase, and is preferably 250 × 10 6. ^It is more preferably ⁻⁷ / ° C. or higher, and further preferably 300 × 10 ⁻⁷ / ° C. or higher. The α _max of the glass of the present invention is preferably 1300 × 10 ⁻⁷ / ° C. or less, more preferably 1200 × 10 ⁻⁷ / ° C. or less, so that the internal tensile stress generated by thermal strengthening does not become too large, and 1100 × 10 ^−7. / ° C. or less is more preferable.
In general, the glass having a larger average thermal expansion coefficient α at 50 ° C. to 350 ° C. has a larger maximum value α _max of the thermal expansion coefficient between the transition point and the yield point. A glass having a small average thermal expansion coefficient α from 50 ° C. to 350 ° C. and a large maximum value α _max of the thermal expansion coefficient between the transition point and the yield point is excellent in thermal shock resistance and easy to strengthen.

The temperature T _{2 at} which the viscosity of the glass of the present invention is 10 ² dPa · s is preferably 1800 ° C. or less, more preferably 1780 ° C. or less, in order to increase the productivity of the glass when a normal glass melting method is used. Preferably, 1750 degrees C or less is more preferable, and 1730 degrees C or less is especially preferable. The T ₂ of the glass of the present invention is typically 1600 ° C. or higher.

The temperature T _{4 at} which the viscosity of the glass of the present invention is 10 ⁴ dPa · s is preferably 1320 ° C. or lower, more preferably 1310 ° C. or lower, and more preferably 1300 ° C. or lower because the glass sheet is easily molded by the float process. Further preferred is 1250 ° C. or less. The T ₄ of the glass of the present invention is typically 1100 ° C. or higher.

The transition point of the glass of the present invention is preferably 685 ° C. or lower, more preferably 650 ° C. or lower, and further preferably 620 ° C. or lower because the temperature of the tempering treatment can be lowered. When the temperature of the tempering treatment is low, the lifetime of a jig or the like used for the tempering treatment of the glass article is extended, or an inexpensive member can be used. The transition point is preferably 500 ° C. or higher, more preferably 550 ° C. or higher, and further preferably 580 ° C. or higher because surface compressive stress due to thermal strengthening tends to increase.
The yield point is higher than the transition point. The yield point is preferably 640 ° C. or higher and more preferably 660 ° C. or higher because the surface compressive stress due to strengthening tends to increase. Further, the yield point is preferably 750 ° C. or lower, more preferably 700 ° C. or lower because the temperature of the strengthening treatment can be lowered.

The glass of the present invention is excellent in chemical durability.
Weight loss per unit surface area before and after immersion for 20 hours glass in pure water at 90 ° C. of the present invention is preferably from 0.025 mg / cm ² or less, more preferably 0.020 mg / cm ² or less, 0.010 mg / More preferably, it is cm ² or less.
Weight loss per unit surface area before and after immersion for 20 hours in 1 N dilute hydrochloric acid in glass 90 ° C. of the present invention is preferably from 0.015 mg / cm ² or less, more preferably 0.010 mg / cm ² or less, 0. More preferably, it is 008 mg / cm ² or less.

Next, the tempered glass article of the present invention will be described.
The tempered glass article of the present invention is a glass article made of the glass of the present invention. The glass article is preferably a glass plate, but the glass article may be in the form of a glass tube, a glass container, tableware or the like.
When the tempered glass article of the present invention is a glass plate, the thickness of the glass plate is preferably 1.0 mm or more, more preferably 1.4 mm or more, and even more preferably 1.8 mm or more, because the strength is increased. On the other hand, for weight reduction, 15 mm or less is preferable, 9 mm or less is more preferable, and 6 mm or less is more preferable.

The surface compressive stress of the tempered glass article of the present invention is preferably 10 MPa or more, more preferably 15 MPa or more, and further preferably 20 MPa or more. When the surface compressive stress is small, the tempered glass article is easily broken, and the fragments generated when it is broken are likely to be large.
The surface compressive stress of the tempered glass article of the present invention is typically 200 MPa or less.
The tempered glass article of the present invention, especially the tempered glass plate, is used for passenger cars, trucks, buses, railways, ships, aircraft and other vehicle windows, headlights and taillights, building and residential windows, doors and show windows, as well as partitions. It can be used for furniture such as desktops, bookshelves, and showcases, and home appliances such as office supplies and cooking utensils.

Next, the manufacturing method of the tempered glass article of this invention is demonstrated.
In the method for producing a tempered glass article of the present invention, the glass article of the present invention is heated to a temperature not lower than the transition point and not higher than the yield point, and then cooled by blowing air onto the surface of the heated glass article.
In the manufacturing method of the tempered glass article of the present invention, the manufacturing method of the glass article is not particularly limited. The production of the glass article can be performed by melting, forming, and slowly cooling the glass raw material by a usual method. When the glass article is a glass plate, the glass article can be produced by any method such as a float method, a fusion method, a downdraw method, and a rollout method. The float method is easy to mass-produce plate glass of 1.3 mm or more in a large area, and easily reduces the plate thickness deviation. A glass plate having a small thickness deviation is preferable because it can be strengthened uniformly.

In the method for producing a tempered glass article of the present invention, the glass article is heated to a temperature not lower than its transition point and not higher than a yield point for the tempering treatment. If the temperature of the strengthening treatment is lower than the transition point, it is difficult to strengthen, and if it exceeds the yield point, the glass article may be deformed. The temperature of the tempering treatment is preferably 640 to 690 ° C., more preferably 650 to 680 ° C. in terms of easy use of a normal air-cooling strengthening device.
Cooling from the temperature of the tempering treatment is performed by blowing air onto the surface of the glass article. For example, when the glass article is a glass plate, a tempered glass plate can be obtained by blowing air from both sides to the surface of the heated glass plate and cooling it. The wind pressure of the air used for cooling is preferably 30 kPa or less, and more preferably 25 kPa or less, because it is given by a general wind-cooling strengthening apparatus and can effectively impart surface compressive stress. The wind pressure is preferably 15 kPa or more, and more preferably 20 kPa or more in order to sufficiently apply the surface compressive stress. As the air-cooling strengthening device, a general air-cooling strengthening device that has been conventionally used can be used.

EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to these Examples.
<Manufacture of glass composition for strengthening>
The glass raw material for 500 g of glass was weighed and mixed so as to have the composition shown in mol% in Table 1. The resulting mixture was placed in a platinum crucible and melted at 1650 ° C. for 1 hour. The obtained molten glass was poured into a mold, immersed in water together with the mold, and crushed into pieces of 15 mm or less. Next, this piece was put again in a platinum crucible and melted at 1650 ° C. for 2 hours, and then poured out onto a mold.
The obtained glass was held at a temperature about 30 ° C. higher than the transition point for 1 hour, and then slowly cooled to room temperature at a cooling rate of 1 ° C. per minute to obtain slowly cooled glass. Examples 1 to 3 are examples, and examples 4 to 6 are comparative examples.

<Evaluation>
The annealed glass was processed to produce a glass rod having a diameter of 5 mm and a length of 20 mm. Using a thermal dilatometer (manufactured by Bruker AXS, TD5010SA), applying a weight of 10 g to a glass rod, measuring a linear expansion curve at a heating rate of 5 ° C / min, a transition point (unit: ° C), The yield point (unit: ° C.), the average coefficient of thermal expansion α (unit: x 10 ⁻⁷ / ° C.) from 50 ° C. to 350 ° C., and the maximum value α _max of the thermal expansion coefficient between the transition point and the yield point (unit: x 10 ⁻⁷ / ° C.).
The high temperature viscosity of glass is determined to be that the higher the glass spreads under its own weight when the glass is poured onto the mold, the lower the high temperature viscosity. Relative evaluation was made in 4 stages.
For Examples 1-5, using a rotary viscometer measuring the viscosity of the glass, the temperature _{T 2} (unit: ° C.) at which the viscosity becomes ¹⁰ 2 dPa · s temperature _T 4 which and a viscosity of ¹⁰ 4 dPa · s ( Unit: ° C) was determined.
For Examples 1, 4, and 5, a glass disc having a diameter of 20 mm, a thickness of 5 mm, and a mirror surface was prepared from the obtained slowly cooled glass, and the ease of strengthening was evaluated by the following method. .
First, the photoelastic constant was determined by a disk compression method. Subsequently, the glass disks were suspended one by one in a platinum crucible using a platinum wire and held at a temperature 125 ° C. higher than the transition point for 10 minutes. The platinum crucible used at this time was a cylinder having a diameter of about 6 cm and a height of about 10 cm, and the glass disk was positioned substantially at the center inside the crucible. After heating, the glass disk was taken out together with the crucible, and the glass disk was quenched by cooling the crucible in the air. The retardation of the rapidly cooled glass disk was measured with a strain inspection machine (manufactured by Toshiba), and the retardation value was divided by the photoelastic constant to determine the generated surface compressive stress (unit: MPa).
The water resistance is 30 mm × 30 mm from a slow-cooled glass, the thickness is 1.8 mm, and the entire surface is a mirror surface. The weight loss before and after being immersed in pure water at 90 ° C. for 20 hours is the surface area of the glass plate. The value divided by (unit: mg / cm ² ) was evaluated.
The acid resistance was evaluated by a value (unit: mg / cm ² ) obtained by dividing the weight loss before and after immersing a similar glass plate in dilute hydrochloric acid having a concentration of 1 mol / liter at 90 ° C. for 20 hours by the surface area of the glass plate.
The obtained results are shown in Table 1.

Example 4 is an example of a glass composition conventionally used as a glass excellent in thermal shock resistance and chemical durability. Comparing Example 4 and Examples 1 to 3, Example 4 has a large (b / m), and the maximum value α _max of the thermal expansion coefficient between the transition point and the yield point is small, so that it is difficult to reinforce, and the surface due to heat strengthening Small compressive stress. Moreover, T2 is high and the fluidity | liquidity at high temperature is inferior.
Example 5 is an example of a glass composition conventionally used as a glass for heat strengthening. Comparing Example 5 and Examples 1 to ₃ , Example 5 containing no B ₂ O ₃ has a large average thermal expansion coefficient α at 50 ° C. to 350 ° C. and insufficient thermal shock resistance. Moreover, water resistance and acid resistance are inferior.
In Example 6, compared with Examples 1 to 3, the SiO ₂ content and (s + 2a) are small, and the water resistance and acid resistance are inferior.

The tempered glass composition excellent in thermal shock resistance and chemical durability can be obtained by the tempered glass composition of the present invention. The tempered glass article of the present invention includes a tempered glass article, a tempered glass plate for vehicles such as passenger cars, trucks, buses, railways, ships, and aircrafts, a tempered glass plate for architectural windows, and various furniture. It is useful as a tempered glass plate for products and household appliances.
The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2014-011442 filed on January 24, 2014 are incorporated herein as the disclosure of the present invention. .

Claims (10)

Represented by mol% based on oxides, the SiO ₂ from 80.5 to 94 mol%, the _Al 2 _{O 3} 0 to 5 _mol%, the B 2 _{O 3} 3 to 17 _{mol%, R} 2 O (wherein, R is 1 or more selected from the group consisting of Na and K.) 3 to 16 mol%,
The sum (s + 2a) of SiO ₂ content (s) and twice Al ₂ O ₃ content (a) is 83 to 94 mol%,
B ₂ ratio of O ₃ molar number (b) and the number of moles of non-bridging oxygen (m) (b / m) is 0.5 to 2, reinforced glass composition. The strengthening according to claim 1, wherein the ratio (b / r) of the content b of B ₂ O _{3 and} the content r of R ₂ O (b / r) expressed in mol% on the oxide basis is 0.5 to 2.0. Glass composition. The glass composition for reinforcement | strengthening of Claim 1 or 2 whose average thermal expansion coefficient (alpha) in 50 to 350 degreeC of the said glass composition for reinforcement | strengthening is 60x10 < ^-7 > / degrees C or less. The maximum value α _{max of the} coefficient of thermal expansion between the transition point and the yield point of the glass composition for strengthening is 200 × 10 ⁻⁷ / ° C. or more, for strengthening according to claim 1. Glass composition.   The glass composition for reinforcement | strengthening of any one of Claims 1-4 whose transition point of the said glass composition for reinforcement | strengthening is 500-685 degreeC. The reinforcing glass composition has a viscosity ¹⁰ 2 dPa · s and comprising temperature _{T 2} is 1800 ° C. or less, reinforced glass composition according to any one of claims 1 to 5. Represented by mol% based on oxides, the SiO ₂ from 80.5 to 94 mol%, the _Al 2 _{O 3} 0 to 5 _mol%, B 2 _{O 3} and 3 to 17 _{mol%, R} 2 O (wherein R is Na And at least one selected from the group consisting of K.) 3-16 mol%,
The sum (s + 2a) of SiO ₂ content (s) and twice Al ₂ O ₃ content (a) is 83 to 94 mol%,
A tempered glass article, wherein the ratio (b / m) of the number of moles of B ₂ O ₃ (b) to the number of moles of non-crosslinked oxygen (m) is 0.5-2.   The tempered glass article according to claim 7 whose surface compressive stress is 10 or more MPa. The tempered glass article according to claim 7 or 8, wherein the tempered glass article has an average coefficient of thermal expansion α at 50 ° C to 350 ° C of 60 × 10 ^-7 / ° C or less. Represented by mol% based on oxides, the SiO ₂ from 80.5 to 94 mol%, the _Al 2 _{O 3} 0 to 5 _mol%, the B 2 _{O 3} 3 to 17 _{mol%, R} 2 O (wherein, R is 1 or more selected from the group consisting of Na and K.) 3 to 16 mol%,
The sum (s + 2a) of SiO ₂ content (s) and twice Al ₂ O ₃ content (a) is 83 to 94 mol%,
A glass article in which the ratio (b / m) of the number of moles of B ₂ O ₃ (b) to the number of moles of non-crosslinked oxygen (m) (b / m) is 0.5 to 2 is heated to a temperature not lower than the transition point and not higher than the yield point. ,
Next, a method for producing a tempered glass article, wherein air is blown onto the surface of the heated glass article to cool it.