JP2024069067A - Glass plates, bent glass, laminated glass, vehicle window glass and architectural window glass - Google Patents

Abstract

[Problem] The present invention aims to provide a glass sheet that has both excellent crack resistance and heat insulation properties. [Solution] In terms of mole % on an oxide basis, 75.0%≦SiO2≦85.0%, 1.5%≦Al2O3≦7.0%, 0.0%≦MgO≦10%, 0.0%≦CaO≦10%, 0.0%≦SrO≦0.50%, 0.0%≦BaO≦1.0%, 0.0%≦Li2O≦10%, 0.0%≦Na2O≦20%, 0.0%≦K2O≦10%, 1.0%≦RO≦10%, 8.0%≦R A glass plate containing Fe2O≦22%, 0.030%≦Fe2O3≦1.0%, and RO/R2O≦0.70 (wherein RO is at least one selected from MgO, CaO, SrO, and BaO, and R2O is at least one selected from Li2O, Na2O, and K2O), and having a solar transmittance Te defined in ISO-9050:2003 of 90% or less when converted to a thickness of 2.0 mm. [Selected Figure] None

Description

The present invention relates to glass sheets, bent glass, laminated glass, vehicle window glass, and architectural window glass.

In recent years, glass for vehicles, including automobiles, and glass for buildings are required to have heat-shielding properties in order to conserve energy. By using glass with high heat-shielding properties for vehicles, the rise in temperature inside the vehicle caused by solar radiation can be suppressed, reducing the cooling load.

Patent Document 1 discloses that by including SrO and BaO in a total content of more than 4 wt %, the absorption peak wavelength of Fe ²⁺ is shifted by about 100 nm to the longer wavelength side, thereby obtaining glass with high visible light transmittance and low thermal conductivity.

JP 2010-522686 A

However, the glass described in Patent Document 1 contains more than 4% by weight in total of SrO and BaO, which means that it has poor crack resistance and is susceptible to cracking due to flying stones when used as vehicle window glass.

In view of the above problems, the present invention aims to provide a glass plate or laminated glass that combines excellent crack resistance and heat insulation properties, and further a vehicle window glass or architectural window glass that uses the glass plate or laminated glass.

The present inventors have found that the above problems can be solved by providing a glass plate having a specific composition range, and have completed the present invention.
That is, the present invention is as follows.
[1] In mole percent based on oxide,
75.0%≦ _SiO2 ≦85.0%
1.5%≦ _{Al2O3 ≦} 7.0%
0.0%≦MgO≦10%
0.0%≦CaO≦10%
0.0%≦SrO≦0.50%
0.0%≦BaO≦1.0%
0.0%≦ _Li2O ≦10%
0.0%≦ _Na2O ≦20%
0.0%≦ _K2O ≦10%
1.0%≦RO≦10%
8.0%≦ _R2O ≦22%
0.030%≦ _{Fe2O3 ≦} 1.0%
RO/ _R2O ≦0.70
(wherein RO is at least one selected from MgO, CaO, SrO, and BaO, and R ₂ O is at least one selected from Li ₂ O, Na ₂ O, and K ₂ O).
Contains
A glass plate having a solar transmittance Te defined in ISO-9050:2003 of 90% or less when converted into a glass plate having a thickness of 2.0 mm.
[2] The glass plate according to [1], having a load of 0.25 kg or more at which a crack occurrence rate is 50%, and a fracture toughness value measured by an indentation penetration method (IF method) of 0.90 MPa·m ^0.5 or more.
[3] The glass plate according to [1], having a visible light transmittance Tv defined in ISO-9050:2003 using a D65 light source when converted to a thickness of 2.0 mm of 75% or more.
[4] The glass plate according to [1], having an ultraviolet transmittance Tuv defined in ISO-9050:2003 of 70% or less when converted into a glass plate having a thickness of 2.0 mm.
[5] The glass plate according to [1], wherein the temperature _T2 at which the glass viscosity becomes 10 ² dPa·s is 1700° C. or lower.
[6] The glass plate according to [1], wherein the temperature _T4 at which the glass viscosity becomes 10 ⁴ dPa·s is 1,200° C. or lower.
[7] The glass plate according to [1], wherein a temperature T ₁₂ at which the glass viscosity becomes 10 ¹² dPa·s is 610° C. or lower.
[8] The glass plate according to [1], having an average coefficient of linear expansion (CTE) from 50 to 350° C. of 90×10 ⁻⁷ /° C. or less.
[9] The glass plate according to [1], which contains MgO, and contains, in terms of mol % on an oxide basis, 0.0% to 3.0% of CaO and 0.0% to 3.0% of K ₂ O.
[10] The glass plate according to [9], having an average coefficient of linear expansion (CTE) from 50 to 350° C. of 85×10 ⁻⁷ /° C. or less.
[11] The glass plate according to [1], which is substantially free of B ₂ O ₃ .
[12] The glass plate according to [1], which contains MgO, and contains, in mole % on an oxide basis, 2.0% or more _{of Al2O3} , 0.0% or more and 3.0% or less of CaO, 10% or more of _Na2O , and 0.0% or more and 2.0% or less of _K2O , and is substantially free of _{B2O3 ,} has a load of 0.50 kg or more at which a crack occurrence rate is 50%, and has a fracture toughness value of 0.93 MPa·m ^or more as determined by an indentation penetration method (IF method).
[13] A bent glass comprising the glass plate according to [1].
[14] A bent glass comprising the glass plate according to [7].
[15] A glass window comprising a first glass plate, a second glass plate, and an interlayer film sandwiched between the first glass plate and the second glass plate,
At least one of the first glass plate and the second glass plate is the glass plate according to any one of [1] to [12], or the bent glass according to [13] or [14].
[16] A vehicle window glass comprising the glass plate according to any one of [1] to [12].
[17] An architectural window glass comprising the glass plate according to any one of [1] to [12].
[18] A vehicle window glass comprising the laminated glass according to [15].
[19] An architectural window glass comprising the laminated glass according to [15].

The present invention provides glass plates and laminated glass that combine excellent crack resistance and heat insulation properties, as well as vehicle window glass or architectural window glass that uses said glass plates or laminated glass.

FIG. 1 is a diagram showing the relationship between the amount of SiO ₂ and the absorption peak position of Fe ²⁺ . FIG. 2 is a graph showing the relationship between the amount of SiO ₂ and the absorption peak position of Fe ²⁺ . FIG. 3 is a graph showing the relationship between the amount of SiO ₂ and the absorption coefficient of Fe ²⁺ . FIG. 4 is a cross-sectional view of an example of a laminated glass according to an embodiment of the present invention. FIG. 5 is a conceptual diagram showing a state in which the laminated glass according to one embodiment of the present invention is used as a window glass for a vehicle. FIG. 6 is an enlarged view of a portion S in FIG. FIG. 7 is a cross-sectional view taken along line YY in FIG.

The following describes in detail an embodiment of the present invention. In addition, in the following drawings, components and parts that perform the same function may be described with the same reference numerals, and duplicate descriptions may be omitted or simplified. In addition, the embodiments shown in the drawings are schematic in order to clearly explain the present invention, and do not necessarily accurately represent the size or scale of the actual product.

<Glass composition>
The glass plate according to the embodiment of the present invention is
In mole percent based on oxide,
75.0%≦ _SiO2 ≦85.0%
1.5%≦ _{Al2O3 ≦} 7.0%
0.0%≦MgO≦10%
0.0%≦CaO≦10%
0.0%≦SrO≦0.50%
0.0%≦BaO≦1.0%
0.0%≦ _Li2O ≦10%
0.0%≦ _Na2O ≦20%
0.0%≦ _K2O ≦10%
1.0%≦RO≦10%
8.0%≦ _R2O ≦22%
0.030%≦ _{Fe2O3 ≦} 1.0%
RO/ _R2O ≦0.70
(wherein RO is at least one selected from MgO, CaO, SrO, and BaO, and R ₂ O is at least one selected from Li ₂ O, Na ₂ O, and K ₂ O).
The present invention is characterized in that it contains:

The preferred composition range of each component in the glass plate of this embodiment will be described below. The composition range of each component is expressed in mole percent based on the oxide unless otherwise specified. In addition, "substantially not contained" for each component means that it is not contained other than unavoidable impurities mixed in from raw materials, etc., that is, it is not intentionally contained.

SiO ₂ is a component constituting the network structure of glass, and is an essential component of the glass plate of this embodiment. The content of SiO ₂ is 75.0% or more and 85.0% or less. By the content of SiO ₂ being 75.0% or more, the structure of the glass becomes strong, the crack resistance is improved, and further, the absorption peak wavelength of Fe ²⁺ is shifted to a long wavelength, and the heat shielding property can be improved while maintaining the transmittance in the visible range. In addition, the Young's modulus of the glass is improved, and it is easy to ensure the strength required for vehicle applications, architectural applications, etc. In addition, it is easy to reduce the specific gravity of the glass, and further, it is possible to ensure moisture resistance and chemical durability. In addition, it is possible to suppress the average linear expansion coefficient from increasing, and to suppress thermal cracking of the glass. The content of SiO ₂ is more preferably 75.5% or more, more preferably 76.0% or more, and particularly preferably 76.5% or more.
In addition, by making the _SiO2 content 85.0% or less, the increase in viscosity during glass melting is suppressed, making glass production easier and improving the formability of architectural window glass, vehicle window glass, and particularly windshields, etc. The _SiO2 content is more preferably 83.0% or less, even more preferably 81.0% or less, particularly preferably 80.0% or less, and most preferably 79.0% or less.

Al ₂ O ₃ is an essential component of the glass plate of this embodiment. The content of Al ₂ O ₃ is 1.5% or more and 7.0% or less. By having _{Al 2} O ₃ of 1.5% or more, weather resistance, moisture resistance and chemical durability are improved. In addition, the average linear expansion coefficient does not become too large, and thermal cracking of the glass can be suppressed, and chemical strengthening treatment using ion exchange is possible. The content of Al ₂ O ₃ is preferably 1.8% or more, more preferably 1.9% or more, even more preferably 2.0% or more, particularly preferably 2.2% or more, and most preferably 2.5% or more.
Furthermore, by having Al ₂ O ₃ be 7.0% or less, an increase in viscosity during glass melting is suppressed, facilitating glass production, and improving formability for architectural window glass, vehicle window glass, particularly windshields, etc. The content of Al ₂ O ₃ is preferably 6.5% or less, more preferably 6.0% or less, further preferably 5.5% or less, and particularly preferably 5.0% or less.

MgO is a component that promotes the dissolution of glass raw materials and improves moisture resistance and Young's modulus. The content of MgO is 0.0% or more and 10% or less. By including MgO, weather resistance and Young's modulus are improved. When MgO is included in the glass plate of the present embodiment, it is preferably 0.20% or more, more preferably 0.50% or more, even more preferably 1.0% or more, particularly preferably 1.5% or more, and most preferably 2.0% or more.
In addition, if the content of MgO is 10% or less, the glass is less likely to devitrify, and the increase in viscosity during glass melting is suppressed, facilitating glass production, and improving the formability of architectural window glass, vehicle window glass, and particularly windshields. In addition, the absorption peak wavelength of Fe2 ⁺ can be shifted to a longer wavelength, and the heat shielding property can be improved while maintaining the transmittance in the visible range. The content of MgO is preferably 9.0% or less, more preferably 8.0% or less, even more preferably 7.0% or less, particularly preferably 6.5% or less, and most preferably 6.0% or less.

CaO is a component that improves the solubility of glass raw materials and also contributes to the average linear expansion coefficient of glass. The content of CaO is 0.0% or more and 10% or less. By including CaO, the solubility of the raw materials of the glass plate is improved, and the viscosity is further reduced, so that the formability of architectural window glass, vehicle window glass, and especially windshields is improved. When CaO is included in the glass plate of this embodiment, the content is preferably 0.20% or more, more preferably 0.50% or more, even more preferably 0.70% or more, particularly preferably 0.90% or more, and most preferably 1.0% or more.
In addition, by making the CaO content 10% or less, the increase in density of the glass can be avoided, low brittleness and strength can be maintained, and the average linear expansion coefficient can be reduced, suppressing thermal cracking of the glass. In addition, the absorption peak wavelength of Fe2 ⁺ can be shifted to a long wavelength, and the heat insulating property can be improved while maintaining the transmittance in the visible range. The CaO content is preferably 9.0% or less, more preferably 8.0% or less, even more preferably 7.0% or less, especially preferably 6.0% or less, even more preferably 5.0% or less, particularly preferably 4.0% or less, and most preferably 3.0% or less.

SrO reduces the fracture toughness value, which facilitates crack propagation and causes a decrease in crack resistance. Therefore, in this embodiment, the SrO content is 0.0% or more and 0.50% or less. The SrO content is preferably 0.20% or less, more preferably 0.10% or less, even more preferably 0.050% or less, even more preferably 0.010% or less, particularly preferably 0.0050% or less, and most preferably substantially none.

BaO reduces the fracture toughness value, which facilitates crack propagation and causes a decrease in crack resistance. Therefore, in this embodiment, the BaO content is 0.0% or more and 1.0% or less. The BaO content is preferably 0.50% or less, more preferably 0.20% or less, even more preferably 0.10% or less, even more preferably 0.050% or less, particularly preferably 0.010% or less, and most preferably substantially absent.

Li ₂ O is a component that greatly improves the solubility of glass with a small amount of addition, and also makes it easier to increase the Young's modulus and contributes to the average linear expansion coefficient of glass. Furthermore, the strength of glass can be increased by performing a chemical strengthening treatment by ion exchange with Na ions. The content of Li ₂ O is 0.0% or more and 10% or less.
The inclusion of Li ₂ O not only reduces the viscosity of the glass, suppresses an increase in specific gravity, and increases the 50% crack initiation load, but also improves the fracture toughness value, thereby improving the formability and crack resistance of architectural window glass, vehicle window glass, and particularly windshields, etc. Therefore, when Li ₂ O is contained in the glass plate of this embodiment, it is preferably 0.20% or more, more preferably 0.50% or more, even more preferably 0.80% or more, even more preferably 1.0% or more, particularly preferably 1.5% or more, and most preferably 2.0% or more.
By the content of Li ₂ O being 10% or less, the occurrence of devitrification or phase separation during glass production is suppressed, making glass production easier, and the average linear expansion coefficient can be reduced to suppress thermal cracking of glass. In addition, the absorption peak wavelength of Fe ²⁺ can be shifted to a long wavelength, and the heat shielding property can be improved while maintaining the transmittance in the visible range. Furthermore, since the lithium raw material is expensive, there is also an effect of suppressing raw material costs. The content of Li ₂ O is preferably 9.0% or less, more preferably 8.0% or less, even more preferably 7.0% or less, even more preferably 6.0% or less, especially preferably 5.0% or less, particularly preferably 4.0% or less, and most preferably 3.0% or less.

Na ₂ O is a component that improves the solubility of glass, and also makes it easier to increase the Young's modulus and contributes to the average linear expansion coefficient of glass. Furthermore, the strength of glass can be increased by performing a chemical strengthening treatment by ion exchange with K ions. The content of Na ₂ O is 0.0% or more and 20% or less.
The inclusion of Na ₂ O reduces the viscosity of the glass, improving the formability of architectural window glass and vehicle window glass, particularly windshields. The Na ₂ O content is preferably 5.0% or more, more preferably 7.0% or more, even more preferably 8.0% or more, even more preferably 9.0% or more, particularly preferably 10% or more, particularly preferably 11% or more, and most preferably 12% or more.
By making the Na ₂ O content 20% or less, the average linear expansion coefficient can be reduced and thermal cracking of the glass can be suppressed. In addition, the moisture resistance of the glass is improved, making it suitable for glass that is exposed to the atmosphere for a long period of time, such as vehicle window glass and architectural window glass. The Na ₂ O content is preferably 19% or less, more preferably 18% or less, even more preferably 17% or less, and particularly preferably 16% or less.

K ₂ O is a component that improves the melting property of glass, and also increases the Young's modulus and contributes to the average linear expansion coefficient of glass. The content of K ₂ O is 0.0% or more and 10% or less.
By including K ₂ O, the viscosity of the glass is reduced, and the moldability of architectural window glass, vehicle window glass, and especially windshield is improved. In addition, the absorption peak wavelength of Fe ²⁺ can be shifted to a longer wavelength, and the heat shielding property can be improved while maintaining the transmittance in the visible range. Therefore, when K ₂ O is included, it is preferably 0.10% or more, more preferably 0.20% or more, even more preferably 0.30% or more, particularly preferably 0.40% or more, and most preferably 0.50% or more.
On the other hand, it has the effect of increasing the average linear expansion coefficient and specific gravity compared to Li ₂ O and Na ₂ O. The content of K ₂ O is 10% or less, so that the increase in the average linear expansion coefficient and specific gravity can be suppressed. The content of K ₂ O is preferably 8.0% or less, more preferably 6.0% or less, even more preferably 5.0% or less, even more preferably 4.0% or less, particularly preferably 3.0% or less, and most preferably 2.0% or less.

In this embodiment, the total content of MgO, CaO, SrO and BaO (hereinafter sometimes referred to as RO) is 1.0% or more and 10% or less. If RO is 10% or less, the brittleness of the glass is prevented from decreasing, and the crack resistance of the glass can be improved. RO is preferably 8.0% or less, more preferably 7.5% or less, even more preferably 7.0% or less, even more preferably 6.5% or less, particularly preferably 6.0% or less, and most preferably 5.5% or less.
From the viewpoint of improving the formability of architectural window glass and vehicle window glass, particularly windshield, RO is preferably 1.5% or more, more preferably 2.0% or more, further preferably 2.5% or more, and particularly preferably 3.0% or more.

In this embodiment, the total content of _Li2O , _Na2O and _K2O (hereinafter sometimes referred to as _R2O ) is 8.0% or more and 22% or less. When _R2O is 8.0% or more, the Young's modulus is increased and the viscosity of the glass is reduced, so that the formability of architectural window glass, vehicle window glass, and especially windshield is improved. _R2O is preferably 9.0% or more, more preferably 10% or more, even more preferably 11% or more, particularly preferably 12% or more, and most preferably 13% or more.
From the viewpoint of improving moisture resistance and suppressing an increase in specific gravity and improving crack resistance, R ₂ O is 22% or less, preferably 20% or less, more preferably 19% or less, even more preferably 18% or less, particularly preferably 17% or less, and most preferably 16% or less.

_Fe2O3 is an essential component of the glass plate of this embodiment. _Fe2O3 is a component that improves the heat insulating _property of glass and also contributes to the color of glass. The content of _Fe2O3 is 0.030% or more and 1.0% or _less . The content of _Fe2O3 here refers to the total amount of _iron including FeO _, which is an oxide of divalent iron, and _{Fe2O3 ,} which is an oxide of trivalent iron.
If _Fe2O3 is not contained, it may not be usable for applications requiring heat insulation, and it may be necessary to use expensive raw materials with a low iron content for the manufacture _{of glass plate. Furthermore, if Fe2O3 is} not contained, heat radiation may reach the bottom surface of the melting furnace more than necessary during glass melting, and the melting furnace may be loaded. The content _{of Fe2O3} in the glass plate of this embodiment is preferably 0.040% or more, more preferably 0.080% or more, even more preferably 0.10% or more, even more preferably 0.12% or more, especially preferably 0.14 _% or more, particularly preferably 0.16% or more, and most preferably 0.18% or more.
On the other hand, if the content of _Fe2O3 is too high, the heat transfer by radiation during production may be hindered, and the raw material may not melt easily. Furthermore, if the content _{of Fe2O3} is too high, the light transmittance in the visible range may decrease, and _the glass may not be suitable for vehicle window glass, etc. The content of _Fe2O3 is 1.0% or less, preferably 0.80% or less, more preferably 0.70% or less, even more preferably 0.60% or less, particularly preferably 0.50% or less, _and most preferably 0.40% or less.

In the glass plate of the present embodiment, the value obtained by dividing RO by R ₂ O (RO/R ₂ O) is 0.70 or less. When RO/R ₂ O is 0.70 or less, the scratch resistance of the glass is improved. In general, when a minute scratch occurs on the surface of the glass, cracks are likely to occur when force is applied to that part. Therefore, the scratch resistance is improved, and the crack resistance is also improved. Furthermore, when RO/R ₂ O is 0.70 or less, the viscosity of the glass is reduced, and the formability of architectural window glass, vehicle window glass, and particularly windshield is improved. RO/R ₂ O is preferably 0.60 or less, more preferably 0.50 or less, even more preferably 0.45 or less, and particularly preferably 0.40 or less. In addition, the lower limit of RO/R ₂ O is preferably 0.05 or more from the viewpoint of suppressing devitrification, more preferably 0.10 or more, even more preferably 0.15 or more, and particularly preferably 0.20 or more.

The glass plate of this embodiment preferably contains 5.0% or less B ₂ O _3. By containing 5.0% or less B ₂ O ₃ , volatilization during glass melting due to reaction with R ₂ O is suppressed, veining is unlikely to occur, and deterioration of the homogeneity of the glass plate is suppressed. As a result, deterioration of crack resistance is suppressed. _{B 2} O ₃ is more preferably 3.0% or less, even more preferably 2.0% or less, even more preferably 1.0% or less, particularly preferably 0.50% or less, and most preferably substantially not contained. In this embodiment, substantially not containing B ₂ O ₃ means, for example, that the content is 0.10% or less.

In this embodiment, _SiO2 + _{Al2O3 ,} i.e., the sum of the content of _SiO2 and the content of _{Al2O3 ,} is preferably 76.5% or more. By having _{SiO2 + Al2O3} of 76.5% or more, crack resistance is improved, and the moisture resistance of the glass is further improved, and the average linear expansion coefficient of the glass can be prevented from becoming too high, so that it is suitable for window glass for vehicles and buildings. _SiO2 + _Al2O3 is more preferably 77.0% or more, even more preferably 77.5% or more, even more preferably 78.0% or more, particularly preferably 78.5% or more, _and most preferably 79.0% or more.
From the viewpoint of improving the melting property of glass raw materials and the formability of architectural window glass, vehicle window glass, and particularly windshields, etc., SiO ₂ +Al ₂ O ₃ is preferably 86.0% or less, more preferably 85.0% or less, even more preferably 83.0% or less, and particularly preferably 82.0% or less.

In the glass plate of this embodiment, the value obtained by dividing RO by _SiO2 (RO/ _SiO2 ) is preferably 0.13 or less. When RO/ _SiO2 is 0.13 or less, the specific gravity of the glass is reduced, and the crack resistance, particularly the 50% crack initiation load, is improved. Furthermore, when RO/ _SiO2 is 0.13 or less, the absorption peak wavelength of Fe2 ⁺ can be shifted to a long wavelength as described later, and high visible light transmittance and heat shielding properties can be achieved at the same time. RO/ _SiO2 is more preferably 0.11 or less, even more preferably 0.09 or less, particularly preferably 0.08 or less, and most preferably 0.07 or less. In addition, RO/ _SiO2 is preferably 0.01 or more in order to reduce the viscosity of the glass, more preferably 0.02 or more, even more preferably 0.03 or more, and particularly preferably 0.04 or more.

In the glass plate of the present embodiment, the value (RO+ _R2O )/(SiO2+ _Al2O3 ) obtained by dividing the total of the RO content and the _R2O content by the total of the _SiO2 content and the _Al2O3 content is preferably 0.15 or more and _0.31 or less. When (RO+ _R2O )/( _SiO2 + _Al2O3 ) is within the above range, the crack resistance can be improved. (RO+ _R2O )/( _{SiO2 + Al2O3} ) is more preferably _0.17 or more, even more preferably 0.19 or _more , and particularly preferably 0.21 or more. _In addition _, (RO+ _R2O )/( _SiO2 + _Al2O3 ) is more preferably 0.29 or less, even more preferably 0.28 or less, and particularly preferably 0.27 or less.

In the glass plate of the present embodiment, the mass ratio (%) of divalent iron calculated as Fe ₂ O ₃ to the total iron calculated as Fe ₂ O ₃ (hereinafter referred to as Fe-Redox) is preferably 15% or more. The value of Fe-Redox is the ratio of the Fe ²⁺ content calculated as Fe ₂ O ₃ to the total iron content calculated as Fe ₂ O ₃ .
In the glass plate of the present embodiment, since the Fe-Redox is 15% or more, the content of Fe ²⁺ having absorption in the near infrared region can be increased, and as a result, the transmittance in the near infrared region can be reduced and the heat shielding properties can be improved. Fe-Redox is more preferably 20% or more, further preferably 22% or more, and particularly preferably 24% or more. In addition, Fe-Redox is preferably 50% or less. Since Fe-Redox is 50% or less, deterioration of the melting equipment can be suppressed, and when SO ₃ is used as a fining agent, amber coloring can be suppressed and a decrease in visible light transmittance can be suppressed. Fe-Redox is more preferably 45% or less, further preferably 40% or less, and particularly preferably 38% or less.

Fe-Redox can be adjusted by the raw material composition, melting temperature, and melting atmosphere. In addition, Fe-Redox can be adjusted by controlling the degree of oxidation-reduction of the glass melt by using reducing agents such as coke or ammonium chloride as raw materials.

In addition, the glass plate of the present embodiment preferably contains MgO, 2.0% or more of Al ₂ O ₃ , 0.0% or more to 3.0% or less of CaO, 10% or more of Na ₂ O, 0.0% or more to 2.0% or less of K ₂ O, and substantially no B ₂ O ₃ , and has a load of 0.50 kg or more at which the crack occurrence rate described below is 50%, and a fracture toughness value obtained by the indentation method (IF method) of 0.93 MPa·m ^0.5 or more. By having the above-mentioned configuration of the glass plate of the present embodiment, it is possible to suppress an increase in the average linear expansion coefficient, and obtain a glass plate having excellent homogeneity, excellent crack resistance and optical properties while maintaining moisture resistance and bending formability.

The glass plate of the present embodiment may contain components other than _the above-mentioned _SiO2 , _Al2O3 , _B2O3 , _MgO , CaO, _Li2O , _Na2O , _K2O , _Fe2O3 , SrO, and BaO (hereinafter also referred to _as "other components").

Examples of other components include _TiO2 , _ZrO2 , _Y2O3 , _CeO2 , _Nd2O5 , _GaO2 , _GeO2 , _MnO2 , _NiO , _Cr2O3 , _V2O5 , _Au2O3 , _Ag2O , CuO, _CdO , _MoO3 , _SO3 , Cl, F _{, SnO2} , and _Sb2O3 , and may be metal ions or _oxides . Other components may be contained in an amount of _3.0 % or less for various purposes ( _e.g. , clarification, coloring, chemical durability, etc.). If the content of other components is 3.0% or less, clarification, glass coloring, and chemical durability can be adjusted while maintaining a 50% cracking load higher than that of conventional soda lime glass. The content of other components is preferably 2.5% or less, more preferably 2.0% or less, even more preferably 1.5% or less, particularly preferably 1.0% or less, _and most preferably 0.50% or less. In order to prevent environmental impact, the contents of _As2O3 and PbO are each preferably less than 0.0010%, and more preferably substantially absent.

The glass plate of this embodiment may contain _TiO2 . _TiO2 has absorption in the ultraviolet region, so it reduces the ultraviolet transmittance Tuv and improves UV cut performance. When the glass plate of this embodiment contains _TiO2 , its content is preferably 0.010% or more, more preferably 0.040% or more, even more preferably 0.075% or more, and particularly preferably 0.15% or more. Since _TiO2 has coloring for light in the visible region, there is a risk of a decrease in the visible light transmittance Tv and a change in the color of the glass to yellow-green or brown. When the glass plate of this embodiment contains _TiO2 , its content is preferably 2.0% or less, more preferably 1.5% or less, even more preferably 1.0% or less, particularly preferably 0.50% or less, and most preferably 0.30% or less.

The glass plate of the present embodiment may contain _ZrO2 . _ZrO2 is a component that improves chemical durability. When the glass plate of the present embodiment contains _ZrO2 , its content is preferably 0.010% or more, more preferably 0.050% or more, even more preferably 0.10% or more, and particularly preferably 0.20% or more. In addition, from the viewpoint of suppressing a decrease in the 50% crack initiation load, the content of _ZrO2 is preferably 2.0% or less, more preferably 1.5% or less, even more preferably 1.0% or less, and particularly preferably 0.50% or less.

The glass plate of the present embodiment may contain Y ₂ O _3. Y ₂ O ₃ is a component that improves Young's modulus. When the glass plate of the present embodiment contains Y ₂ O ₃ , its content is preferably 0.010% or more, more preferably 0.050% or more, even more preferably 0.10% or more, and particularly preferably 0.20% or more. In addition, from the viewpoint of suppressing the decrease in fracture toughness value and 50% crack initiation load obtained by indentation method (IF method), the content of Y ₂ O ₃ is preferably 2.0% or less, more preferably 1.5% or less, even more preferably 1.0% or less, and particularly preferably 0.50% or less.

If the glass plate of this embodiment contains NiO, the formation of NiS may cause glass breakage, so the content is preferably 0.0080% or less. The NiO content in the glass plate of this embodiment is more preferably 0.0040% or less, even more preferably 0.0020% or less, and particularly preferably substantially none.

The glass plate of this embodiment may contain _CeO2 . Since _CeO2 has absorption in the ultraviolet region, it reduces the ultraviolet transmittance Tuv and improves the UV cut performance. When the glass plate of this embodiment contains _CeO2 , its content is preferably 0.010% or more, more preferably 0.020% or more, even more preferably 0.040% or more, and particularly preferably 0.070% or more. _CeO2 absorbs light in the ultraviolet region, which may cause solarization and reduce the transmittance in the visible region. When the glass plate of this embodiment contains _CeO2 , it is preferably 0.25% or less, more preferably 0.18% or less, even more preferably 0.14% or less, and particularly preferably 0.10% or less.

The glass plate of the present embodiment may contain _Cr2O3 . _Cr2O3 acts as _an oxidizing agent to control the amount _{of Fe2+. When the glass plate of the present embodiment contains Cr2O3 ,} ^its _content is preferably 0.0020% or more, more preferably 0.0040% or more. _Cr2O3 has coloring for light in the visible range, so there is a risk of the visible light transmittance decreasing. In addition, there is a risk of the Fe2 ⁺ amount decreasing, _and the heat insulating property decreasing. Therefore, when the glass plate of the present embodiment contains _Cr2O3 , it is preferably 0.020% or _less , more preferably 0.016% or less, even more preferably 0.012% or less, and particularly preferably 0.0080% or less.

The glass plate of this embodiment may contain _SnO2 . _SnO2 acts as a reducing agent to control the amount of Fe2 ⁺ . When the glass plate of this embodiment contains _SnO2 , its content is preferably 0.010% or more, more preferably 0.040% or more, even more preferably 0.060% or more, and particularly preferably 0.080% or more. On the other hand, in order to suppress defects derived from _SnO2 during glass production, the content of _SnO2 in the glass plate of this embodiment is preferably 0.40% or less, more preferably 0.30% or less, even more preferably 0.20% or less, and particularly preferably 0.15% or less.

The glass plate of this embodiment may contain SO _3. SO ₃ acts as a fining agent to improve the bubble quality of the glass. When the glass plate of this embodiment contains SO ₃ , its content is preferably 0.0010% or more, more preferably 0.0040% or more, even more preferably 0.0070% or more, and particularly preferably 0.015% or more. When Fe-Redox is high, SO ₃ may cause amber coloring, causing the glass to turn brown, and the visible light transmittance may decrease. When the glass plate of this embodiment contains SO ₃ , it is preferably 0.070% or less, more preferably 0.060% or less, even more preferably 0.050% or less, and particularly preferably 0.040% or less.

The glass plate of the present embodiment may contain Cl. Cl acts as a fining agent to improve the bubble quality of the glass. When the glass plate of the present embodiment contains Cl, the content is preferably 0.080% or more, more preferably 0.15% or more, even more preferably 0.20% or more, particularly preferably 0.25% or more, and most preferably 0.30% or more. If the Cl content is high, _Cl2 gas volatilized from the glass melt may corrode the surrounding members. When the glass plate of the present embodiment contains Cl, the content is preferably 1.0% or less, more preferably 0.80% or less, even more preferably 0.60% or less, and particularly preferably 0.50% or less.

<Characteristics>
(Solar transmittance: Te)
The glass plate of the present embodiment has a solar radiation transmittance Te of 90% or less as specified by ISO-9050:2003 when converted to a thickness of 2.0 mm. If Te is 90% or less, the heat shielding property of the glass is excellent. Te is preferably 88% or less, more preferably 86% or less, even more preferably 84% or less, particularly preferably 82% or less, and most preferably 80% or less. The lower limit of Te is not particularly limited, but is usually 30% or more, preferably 32% or more, more preferably 34% or more, and particularly preferably 36% or more. In order to set Te within the above range, it can be achieved by adjusting the amount of Fe ₂ O ₃ to 0.030% or more.

(Visible light transmittance: Tv)
The glass plate of the present embodiment preferably has a visible light transmittance Tv of 75% or more, calculated by measuring the transmittance with a spectrophotometer using a D65 light source according to the provisions of ISO-9050:2003 when converted to a thickness of 2.00 mm. Since Tv is 75% or more, it has excellent transparency and is suitable for use as a windshield or door glass for a vehicle. Tv is more preferably 78% or more, more preferably 80% or more, and even more preferably 82% or more. 84% or more is particularly preferred, and 86% or more is most preferred. The upper limit of Tv is not particularly limited, but is, for example, 92% or less. In order to set Tv in the above range, it can be achieved by adjusting the glass composition, particularly SiO ₂ , Fe ₂ O ₃ , or Fe-Redox.

The glass plate of the present embodiment preferably has a low solar radiation transmittance Te and a high visible light transmittance Tv. That is, Tv/Te is preferably 1.15 or more. By having Tv/Te of 1.15 or more, the glass plate has both excellent transparency and heat shielding properties, and is more suitable as a window glass for vehicles and buildings. Tv/Te is more preferably 1.17 or more, even more preferably 1.19 or more, particularly preferably 1.20 or more, and most preferably 1.21 or more. The upper limit of Tv/Te is not particularly limited, but is, for example, 1.50 or less. In order to set Tv/Te to the above range, it can be achieved by adjusting the glass composition, particularly SiO ₂ , Fe ₂ O ₃ , or Fe-Redox.

In the glass plate of the present embodiment, it is preferable that (Tv-Te)×Tv, which is the product of the difference between the visible light transmittance Tv and the solar radiation transmittance Te and the visible light transmittance Tv, is 200% ² or more. When (Tv-Te)×Tv is 200% ² or more, it is possible to obtain glass that has both excellent visibility and heat shielding properties. (Tv-Te)×Tv is more preferably 500% ² or more, even more preferably 1000% ² or more, still more preferably 1100% ² or more, particularly preferably 1150% ² or more, particularly preferably 1200% ² or more, and most preferably 1250% ² or more.

In the glass plate of this embodiment, (Tv-Te)×Tv÷ _Fe2O3 , which is the product of the difference between the visible light transmittance Tv and the solar radiation transmittance Te and the visible light transmittance Tv _{, divided by the amount of Fe2O3 in the glass, is preferably 6000%2/mol% or more. (Tv-Te)×Tv÷Fe2O3 is an} ^index _{of the} compatibility of the visible light transmittance Tv and the solar radiation transmittance Te per unit mol%, and therefore a larger value indicates a glass composition that is more likely to achieve both excellent visibility and heat shielding properties. (Tv-Te) x Tv _{/ Fe2O3} is more preferably 6500% ² /mol% or more, even more preferably 6700% ² /mol% or more, still more preferably 6900% ² /mol% or more, particularly preferably 7100% ² /mol% or more, and most preferably 7500% ² /mol% or more.

(Ultraviolet transmittance: Tuv)
The glass plate of the present embodiment preferably has low ultraviolet transmittance, and when converted to a thickness of 2.00 mm, the ultraviolet transmittance Tuv defined in ISO-9050:2003 is preferably 70% or less. By having Tuv of 70% or less, it is possible to suppress deterioration of components such as an interlayer film and a sheet in a vehicle cabin when the glass plate of the present embodiment is used for a laminated glass. Tuv is more preferably 68% or less, even more preferably 66% or less, even more preferably 64% or less, particularly preferably 62% or less, and most preferably 60% or less. The lower limit of Tuv is, for example, 10% or more. Tuv can be set to the above range by adjusting the glass composition, particularly SiO ₂ , Fe ₂ O ₃ , TiO ₂ , CeO ₂ , or Fe-Redox.

(Fe2 ⁺ absorption peak wavelength)
In the glass plate of the present embodiment, the absorption peak wavelength of Fe ²⁺ is preferably 950 nm or more. By having the absorption peak wavelength of Fe ²⁺ of 950 nm or more, the visible light transmittance of the glass plate can be improved, making it more suitable as a window glass for vehicles and buildings. The absorption peak wavelength of Fe ²⁺ is preferably 980 nm or more, more preferably 1000 nm or more, even more preferably 1020 nm or more, even more preferably 1040 nm or more, particularly preferably 1060 nm or more, particularly preferably 1080 nm or more, and most preferably 1100 nm or more. In addition, as described below, the amount of SiO ₂ increases, and from the viewpoint of suppressing the increase in viscosity during glass melting and the viscosity increase during bending of the windshield, and from the viewpoint of suppressing the increase in the average linear expansion coefficient due to the increase in the amount of K ₂ O, the absorption peak wavelength of Fe ²⁺ is preferably 1200 nm or less, more preferably 1180 nm or less, and even more preferably 1160 nm or less.
In order to set the absorption peak wavelength of Fe2 ⁺ within the above range, the content of _SiO2 can be increased, the proportion of alkaline earth metal components with high atomic numbers in RO can be increased, or the proportion of alkali metal components with high atomic numbers in _R2O can be increased.

It is known that in glass, Fe2 ⁺ ions are influenced by the surrounding structure and take various coordination structures such as 4-coordinate, 5-coordinate, and 6-coordinate, or distorted structures, and the local structure of this Fe2 ⁺ ion determines the absorption peak wavelength of Fe2 ⁺ . Sr and Ba, which are alkaline earth metal elements with large element numbers, tend to reduce the fracture toughness value (Kc) measured by the indentation method (IF method) and reduce crack resistance as the content increases. In addition, K, which has a large element number of the alkali metal component, increases the average linear expansion coefficient significantly, so it is not preferable to contain a large amount of K.
On the other hand, since _SiO2 is a component that improves the crack resistance of glass, it is preferable to increase the content of _SiO2 . Also, since _SiO2 is a component that shifts the absorption peak wavelength of Fe2 ⁺ in glass to a longer wavelength and maintains the transmittance in the visible range, it is preferable to increase the content of _SiO2 .

The relationship between _SiO2 and the absorption peak wavelength of Fe2 ⁺ in glass will be described. Table 1 and Figure 1 show the change in the absorption peak wavelength of Fe2 ⁺ when _SiO2 is replaced with alkali metal ( _R2O ) or alkaline earth metal (RO) or both for the glass composition of Example 19 described later. Figure 2 is a graph showing the relationship between the content of _SiO2 and the absorption peak wavelength of Fe2 ⁺ in the glass described in Table 1.

1 and 2, as the amount of _SiO2 decreases, the absorption peak wavelength of Fe2 ⁺ observed at wavelengths of 950 to 1200 nm shifts to shorter wavelengths. When the absorption peak wavelength of Fe2 ⁺ shifts to shorter wavelengths, the transmittance in the visible range decreases, making it difficult to achieve both excellent visibility and heat shielding properties.
In addition, Figure 3 is a graph showing the relationship between the amount of _SiO2 and the absorption coefficient of Fe2 ⁺ in the glasses shown in Table 1. As shown in Figure 3, it can be seen that the greater the amount of _SiO2 , the greater the absorption coefficient of Fe2 ⁺ . This shows that, when comparing glasses with the same iron amount and Fe-Redox, the glass with a greater amount of _SiO2 can realize a glass with higher heat insulating properties, and that since the absorption peak wavelength of Fe2 ⁺ is located at a longer wavelength, the decrease in transmittance in the visible range can be suppressed when Fe-Redox increases. For the above reasons, it is preferable to increase the content of _SiO2 .

(50% crack occurrence load)
The glass plate according to the present embodiment preferably has a load (50% cracking load) at which the cracking rate is 50% of 0.25 kg or more. The 50% cracking load is an index of the strength of the glass, and the higher the value of the 50% cracking load, the higher the resistance to cracking. The 50% cracking load is more preferably 0.30 kg or more, even more preferably 0.50 kg or more, even more preferably 0.75 kg or more, particularly preferably 1.0 kg or more, even more preferably 1.2 kg or more, even more preferably 1.4 kg or more, particularly preferably 1.6 kg or more, and most preferably 1.8 kg or more. The 50% cracking load can be measured by the method described in the examples below.

(Fracture toughness value (Kc))
The glass plate of the present embodiment preferably has a fracture toughness value (Kc) of 0.90 MPa·m ^0.5 or more measured by the indentation method (IF method) in accordance with JIS R1607:2010. Kc is an index of glass strength, and the larger Kc is, the less likely cracks will progress and the higher the resistance to cracking is. Kc is more preferably 0.92 MPa·m ^0.5 or more, even more preferably 0.93 MPa·m ^0.5 or more, even more preferably 0.94 MPa·m ^0.5 or more, particularly preferably 0.95 MPa·m ^0.5 or more, particularly preferably 0.96 MPa·m ^0.5 or more, and particularly preferably 0.97 MPa·m ^0.5 or more.
In order to set the 50% crack initiation load and fracture toughness value in the above range, the following methods can be used: increasing the content of SiO ₂ , increasing the proportion of RO with a small element number of alkaline earth metal components, and increasing the proportion of R ₂ O with a small element number of alkali metal components. More specifically, since SiO ₂ is a component that forms a network structure, increasing the content of SiO 2 strengthens the glass structure and improves crack resistance. In addition, RO with a smaller element number of alkali metal components can suppress the increase in glass density and improve crack resistance. R ₂ O with a smaller element number of alkaline earth metal components also shows the same tendency as RO. In this embodiment, by setting these components in a specific range, a glass plate with excellent crack resistance can be obtained. As described above, by taking into consideration the absorption peak wavelength of Fe ²⁺ , Tv/Te, (Tv-Te) x Tv, and (Tv-Te) x Tv÷Fe ₂ O ₃ , the composition of the glass plate can be adjusted, whereby a glass plate having excellent crack resistance, heat insulation properties, and transparency can be obtained.

(Average linear expansion coefficient)
The average linear expansion coefficient (CTE) of the glass plate of this embodiment at 50°C to 350°C is preferably 90 x 10 ^-7 /°C or less. By having an average linear expansion coefficient of 90 x 10 ^-7 /°C or less, when used as a vehicle window glass or architectural window glass, cracks due to heat shock can be suppressed. In addition, when the glass plate of this embodiment is used as a bent glass, the thermal expansion difference due to the difference in thermal history in the plane is suppressed, and a bent glass with good dimensional and surface accuracy can be obtained. The average linear expansion coefficient of the glass plate of this embodiment at 50°C to 350°C is more preferably 88 x 10 ^-7 /°C or less, even more preferably 86 x 10 ^-7 /°C or less, even more preferably 85 x 10 ^-7 /°C or less, particularly preferably 82 x 10 ^-7 /°C or less, and most preferably 80 x 10 ^-7 /°C or less.
Furthermore, from the viewpoint of suppressing cracking of the black ceramic due to the difference in thermal expansion with the black ceramic printed on the windshield, the glass plate of the present embodiment preferably has an average linear expansion coefficient of 50×10 ^-7 /°C or more. By having an average linear expansion coefficient of 50×10 ^-7 /°C or more, the difference in thermal expansion with the black ceramic is reduced, and cracking of the black ceramic can be suppressed. The average linear expansion coefficient is more preferably 55×10 ^-7 /°C or more, even more preferably 60×10 ^-7 /°C or more, particularly preferably 65×10 ^-7 /°C or more, and most preferably 70×10 ^-7 /°C or more.
In order to set the average linear expansion coefficient within the above range, there can be mentioned a method of increasing the content of _SiO2 in the glass components and adjusting _the contents of _R2O , RO and _Al2O3 .

( _T2 )
In the glass plate of this embodiment, the temperature _T2 at which the glass viscosity η, which is a criterion for the meltability of glass, is 10 ² [dPa·s], is preferably 1700° C. or less. By setting _T2 to 1700° C. or less, consumption of fuel used in melting the glass raw material can be reduced, and the life of the brick members used in the melting furnace can be extended.
Examples of the method for setting _T2 to 1700°C or less include a method of increasing the content of _R2O and RO in the _glass plate components and reducing the content of _Al2O3 , a method of including _Li2O among _R2O , a method of reducing the content of _SiO2 , and a method of including _B2O3 within a range in which the volatilization of the raw material does not affect the equipment. In the glass plate of this embodiment, _T2 is more preferably 1675°C or less, even more preferably 1650°C or less, even more _preferably 1640°C or less, particularly preferably 1630°C or less, and most preferably 1620°C or less. In addition, from the viewpoint of maintaining the crack resistance of the glass and from the viewpoint of suppressing the average linear expansion coefficient of the glass from becoming too large, _T2 is preferably 1450°C or more, more preferably 1475°C or more, even more preferably 1500°C or more, particularly preferably 1525°C or more, and most preferably 1550°C or more.

( _T4 )
In the glass sheet of this embodiment, the temperature _T4 at which the glass viscosity η, which is a criterion for formability during float forming, is 10 ⁴ [dPa·s] is preferably 1200° C. or lower. When _T4 is 1200° C. or lower, the glass sheet is suitable for sheet forming by the float method.
Examples of the method for making T ₄ 1200° C. or less include a method of increasing the content of R ₂ O and RO in the glass plate components and reducing the content of Al ₂ O ₃ , a method of including Li ₂ O among R ₂ O, a method of reducing the content of SiO ₂ , and a method of including B ₂ O ₃ within a range in which the volatilization of the raw material does not affect the equipment. In the glass plate of this embodiment, T ₄ is more preferably 1180° C. or less, even more preferably 1170° C. or less, even more preferably 1160° C. or less, particularly preferably 1150° C. or less, and most preferably 1140° C. or less. In addition, from the viewpoint of maintaining the crack resistance of the glass and from the viewpoint of suppressing the average linear expansion coefficient of the glass from becoming too large, T ₄ is preferably 1000° C. or more, more preferably 1025° C. or more, even more preferably 1050° C. or more, and particularly preferably 1070° C. or more.

( _T12 )
In the glass sheet of this embodiment, the temperature _T12 at which the glass viscosity η, which is a criterion for bending workability, is ¹⁰¹² [dPa·s] is preferably 610° C. or lower. When _T12 is 610° C. or lower, bending forming at a low temperature becomes possible.
Examples of the method for making T ₁₂ 610°C or less include a method of increasing the content of R ₂ O and RO in the glass plate components and reducing the content of Al ₂ O ₃ , a method of including Li ₂ O among R ₂ O, a method of reducing the content of SiO ₂ , and a method of including B ₂ O ₃ within a range in which the volatilization of the raw material does not affect the equipment. In the glass plate of this embodiment, T ₁₂ is more preferably 605°C or less, even more preferably 600°C or less, even more preferably 595°C or less, especially preferably 590°C or less, particularly preferably 585°C or less, and most preferably 580°C or less. In addition, from the viewpoint of maintaining the crack resistance of the glass, from the viewpoint of suppressing the average linear expansion coefficient of the glass from becoming too large, and from the viewpoint of the firing temperature of the black ceramic printed on the windshield, T ₁₂ is preferably 540°C or more, more preferably 545°C or more, even more preferably 550°C or more, particularly preferably 555°C or more, and most preferably 560°C or more.

(specific gravity)
The specific gravity of the glass plate of the present embodiment is preferably 2.48 or less. With a specific gravity of 2.48 or less, the glass plate is more suitable as a window glass for vehicles and buildings from the viewpoint of fuel consumption and power consumption. In addition, the crack resistance can be increased. The specific gravity of the glass plate of the present embodiment is more preferably 2.47 or less, further preferably 2.46 or less, even more preferably 2.45 or less, particularly preferably 2.44 or less, particularly preferably 2.43 or less, and most preferably 2.42 or less. In addition, the specific gravity of the glass plate of the present embodiment is preferably 2.30 or more, more preferably 2.32 or more, particularly preferably 2.34 or more, and most preferably 2.36 or more, from the viewpoint of improving the sound insulation inside the vehicle.

(Young's modulus)
The Young's modulus of the glass plate of the present embodiment is preferably 65 GPa or more, more preferably 66 GPa or more, even more preferably 67 GPa or more, and particularly preferably 68 GPa or more. When the Young's modulus is in the above range, the glass plate has high rigidity and is more suitable for use as a window glass for a vehicle, etc.
On the other hand, if the Young's modulus is too high, the glass becomes difficult to deform, and there is a risk that the glass will break because it cannot absorb the energy of a flying stone hitting the glass. Therefore, the Young's modulus is preferably 80 GPa or less, more preferably 79 GPa or less, even more preferably 78 GPa or less, and particularly preferably 77 GPa or less.

( _Tg )
The glass transition temperature (T _g ) of the glass plate of this embodiment is preferably 460° C. or more and 590° C. or less. In this specification, T _g represents the glass transition point. If T _g is within this predetermined temperature range, the glass plate can be bent within the normal manufacturing condition range. By having the T _g of the glass plate of this embodiment be 460° C. or more, the alkali metal content or the alkaline earth metal content does not become too large, and the average linear expansion coefficient of the glass can be suppressed from increasing. In addition, the deterioration of the moisture resistance is suppressed, and further, the devitrification of the glass is suppressed, and the formability is improved. T _g is more preferably 480° C. or more, even more preferably 490° C. or more, and particularly preferably 500° C. or more. On the other hand, from the viewpoint of suppressing the bending temperature of the glass plate from becoming excessive and facilitating the manufacturing, T _g is preferably 590° C. or less, more preferably 585° C. or less, even more preferably 580° C. or less, particularly preferably 575° C. or less, and most preferably 570° C. or less.

The glass sheet of this embodiment is preferably float glass formed by, for example, the well-known float method. In the float method, molten glass base is floated on a molten metal such as tin, and strict temperature control is used to form glass sheets of uniform thickness and width, and large glass sheets can also be obtained.

The glass sheet of this embodiment may be a glass sheet formed by a known roll-out method or down-draw method, or may be a glass sheet with a polished surface and uniform thickness. Here, the down-draw method is broadly divided into a slot down-draw method and an overflow down-draw method (fusion method), but both are techniques in which molten glass is continuously allowed to flow down from a forming body to form a band-shaped glass ribbon.

The shape of the glass plate of the present embodiment is not particularly limited, but the area of the main surface is preferably 0.25 m ² or more, more preferably 0.45 m ² or more, and even more preferably 0.90 m ² or more. When the area of the glass plate is within the above range, it can be used for various vehicle models. In addition, if the area of the glass plate is too large, the difficulty of bending increases, such as difficulty in handling, uneven temperature distribution during heating, and poor dimensional accuracy after bending. Therefore, the area of the main surface of the glass plate of the present embodiment is preferably 10 m ² or less, more preferably 7 m ² or less, and even more preferably 5 m ² or less.

In addition, the glass plate of this embodiment preferably has a thickness of 0.50 mm or more in order to improve rigidity and strength when flying stones, vehicle keys, etc. contact the glass plate. The thickness of the glass plate is more preferably 1.00 mm or more, even more preferably 1.50 mm or more, even more preferably 1.75 mm or more, especially preferably 2.00 mm or more, even more preferably 2.25 mm or more, even more preferably 2.50 mm or more, particularly preferably 2.75 mm or more, and most preferably 3.00 mm or more. In addition, from the viewpoint of suppressing increases in fuel consumption and electricity consumption due to an increase in the weight of the glass plate, the glass plate of this embodiment preferably has a thickness of 4.00 mm or less, more preferably 3.80 mm or less, even more preferably 3.60 mm or less, particularly preferably 3.50 mm or less, and most preferably 3.40 mm or less.

The glass plate of this embodiment may be a glass plate that has been subjected to a tempering treatment such as air-cooling tempering or chemical tempering. By carrying out the above treatment, the strength of the glass plate can be increased.

Here, air-cooling tempering is a process that forms a compressive stress layer on the surface of a glass plate by thermal tempering. Specifically, a uniformly heated glass plate is rapidly cooled from a temperature near its softening point, and compressive stress is formed on the surface of the glass plate due to the temperature difference between the surface and the interior of the glass plate. The compressive stress is generated uniformly over the entire surface of the glass plate, and a compressive stress layer of uniform depth is formed over the entire surface of the glass plate. Thermal tempering is more suitable for tempering thick glass plates than chemical tempering.

Chemical strengthening is a process in which alkali metal ions (typically Li ions or Na ions) with a small ionic radius on the surface of a glass sheet are exchanged with alkali metal ions (typically Na ions or K ions) with a larger ionic radius by ion exchange at a temperature below the glass transition point, thereby forming a compressive stress layer on the surface of the glass sheet. The chemical strengthening process can be carried out by a known method, such as an ion exchange method. In the ion exchange method, a glass sheet is immersed in a treatment liquid (e.g., potassium nitrate molten salt) and ions with a small ionic radius (e.g., Na ions) contained in the glass are exchanged with ions with a large ionic radius (e.g., K ions), thereby generating compressive stress on the surface of the glass sheet.
The magnitude of the compressive stress on the surface of the glass plate (hereinafter also referred to as the surface compressive stress CS) and the depth DOL of the compressive stress layer formed on the surface of the glass plate can be adjusted by the glass composition, the chemical strengthening treatment time, and the chemical strengthening treatment temperature, respectively.

[Bent glass]
The bent glass according to the present embodiment is made of the above-mentioned glass sheet. That is, the bent glass according to the present embodiment is formed by bending the above-mentioned glass sheet. The bent glass according to the present embodiment may be bent glass obtained by forming the above-mentioned flat glass sheet into a curved shape by gravity forming, press forming, or the like.

The curved glass of this embodiment is glass that curves at a specified curvature, and may be single-curved glass that curves in only one direction, either up-down or left-right, or compound-curved glass that curves in both the up-down and left-right directions.

The bent glass of this embodiment preferably has a minimum radius of curvature of 500 mm or more and 100,000 mm or less. The radius of curvature of the bent glass is calculated by simulating the shape of the sample using a laser displacement meter (Dyvoce manufactured by Kohzu Seiki Co., Ltd.) based on the amount of warping inherent to the sample, which is determined by self-weight deflection correction in the double-sided differential mode, and the radius of curvature is determined from the shape obtained by the simulation.

[Method of manufacturing curved glass]
In the method for producing bent glass according to this embodiment, the glass sheet is heated and bent to form bent glass.
An example of a method for forming curved glass is a method in which a heated glass sheet is placed on a forming die and pressed from above by a press means to bend the glass sheet.
Another method is to place a flat glass sheet on a mold having a bending surface corresponding to a desired curved surface, and then to carry the mold into a heating furnace in this state, where the glass sheet is heated to a temperature close to the glass softening point. According to this forming method, the glass sheet is curved by its own weight along the bending surface of the mold as it softens, and thus a bent glass sheet having a desired curved surface is produced.

In this embodiment, bending using the press means is preferred from the viewpoint of improving productivity and surface accuracy after forming. The bending method using the press means is not particularly limited, and for example, the method described in International Publication No. 2016/093031 can be appropriately adopted. The bending method using the press means is described below as an example.

First, the glass sheet of this embodiment is transported to a press area by a transport conveyor, etc. Next, in the press area, the glass sheet is heated to a temperature at which it can be bent and softened.
Here, the temperature at which bending is possible is, for example, equal to or higher than the temperature _T12 at which the glass viscosity is 10 ¹² [dPa·s]. The heating may be performed by a heater or the like in a heating furnace during the process of transporting the glass to the pressing area on a transport conveyor or the like.
Moreover, the bending time under the condition that the heating temperature (≧T ₁₂ ) is maintained can be set to, for example, 1 second or more.

A lower press die (female die) and an upper press die (male die) are arranged at predetermined positions in the press area, and the upper surface shape of the female die and the lower surface shape of the male die correspond to the curved shape of the glass sheet to be bent in the conveying direction and/or the perpendicular direction. The female die can be raised and lowered between a waiting position below the conveyor and a press position above it, and after the glass sheet is transferred from the conveyor, the female die rises from a predetermined raised position to a press position above the conveyor with the glass sheet placed on it, thereby press-forming the glass sheet.

Next, the press-formed glass sheet is transported to the cooling area using a transport shuttle or similar device. In the cooling area, the glass sheet is cooled by blowing cold air onto it, for example.

The above steps result in bent glass. Although the above describes bending of glass sheets in this embodiment, the above bending may also be performed on laminated glass, as described below.

[Laminated glass]
The laminated glass according to this embodiment includes a first glass plate, a second glass plate, and an interlayer film sandwiched between the first glass plate and the second glass plate, and the first glass plate is the above-mentioned glass plate or the above-mentioned bent glass plate.

Figure 4 is a diagram showing an example of laminated glass 10 according to this embodiment. The laminated glass 10 has a first glass plate 11, a second glass plate 12, and an intermediate film 13 sandwiched between the first glass plate 11 and the second glass plate 12. The laminated glass 10 according to this embodiment is not limited to the embodiment shown in Figure 4, and can be modified within the scope of the present invention. For example, the intermediate film 13 may be formed in one layer as shown in Figure 4, or in two or more layers. The laminated glass 10 according to this embodiment may have three or more glass plates, and in that case, an organic resin or the like may be interposed between the adjacent glass plates. Hereinafter, the laminated glass 10 according to this embodiment will be described as having only two glass plates, the first glass plate 11 and the second glass plate 12, and sandwiching the intermediate film 13.

In the laminated glass of this embodiment, from the viewpoint of bending formability, it is preferable that the second glass sheet 12 is the above-mentioned glass sheet or the above-mentioned bent glass. When the first glass sheet 11 and the second glass sheet 12 are the above-mentioned glass or the above-mentioned bent glass, the first glass sheet 11 and the second glass sheet 12 may be glass sheets of the same composition or glass sheets of different compositions.

When the second glass plate 12 is not one of the above glass plates, the type of the glass plate is not particularly limited, and any conventionally known glass plate used for vehicle window glass, etc. can be used. Specific examples include alkali aluminosilicate glass, alkali aluminoborosilicate glass, and soda lime glass. These glass plates may or may not be colored to the extent that transparency is not impaired.

In the laminated glass of the present embodiment, the second glass sheet 12 may be alkali aluminosilicate glass containing 1.0% or more of Al ₂ O ₃ , or alkali aluminoborosilicate glass containing 1.0% or more of Al ₂ O ₃ and 1.0% or more of B ₂ O _3. By using the alkali aluminosilicate glass or alkali aluminoborosilicate glass as the second glass sheet 12, chemical strengthening is possible as described below, and strength can be increased.

From the viewpoint of improving weather resistance, moisture resistance, and chemical strengthening properties, the above-mentioned alkali aluminosilicate glass and alkali aluminoborosilicate glass preferably have an _Al2O3 content of 5.0% or more, more preferably 8.0% or more, and particularly preferably 10% or more. In order to reduce the viscosity of the glass and facilitate production, _{the Al2O3 content} is preferably 18% or less, _and more preferably 15% or less.

From the viewpoint of chemical strengthening, the alkali aluminosilicate glass and alkali aluminoborosilicate glass preferably have an R ₂ O content of 10% or more, more preferably 12% or more, and even more preferably 13% or more. From the viewpoint of improving moisture resistance, the R ₂ O content is preferably 22% or less, more preferably 20% or less, and even more preferably 18% or less.

The alkali aluminoborosilicate glass preferably has a B ₂ O ₃ content of 2.0% or more, more preferably 3.0% or more, and even more preferably 4.0% or more in order to increase the strength when the glass comes into contact with flying stones, vehicle keys, etc. In addition, in the alkali aluminoborosilicate glass, from the viewpoint of improving chemical durability and weather resistance, the B ₂ O ₃ content is preferably 9.0% or less, more preferably 8.0% or less, and even more preferably 7.0% or less.

Specific examples of the alkali aluminosilicate glass include glasses having the following compositions, in which each component is expressed in mole percentage on an oxide basis.
61%≦ _SiO2 ≦75%
1.0%≦ _{Al2O3 ≦} 20%
0.0%≦MgO≦15%
0.0%≦CaO≦10%
0.0%≦SrO≦1.0%
0.0%≦BaO≦1.0%
0.0%≦ _Li2O ≦15%
2.0%≦ _Na2O ≦15%
0.0%≦ _K2O ≦6.0%
0.0%≦ _ZrO2 ≦4.0%
0.0%≦ _TiO2 ≦1.0%
0.0%≦ _{Y2O3 ≦} 2.0%
10%≦ _R2O ≦25%
0.0%≦RO≦20%
(R ₂ O represents the total content of Li ₂ O, Na ₂ O and K ₂ O, and RO represents the total content of MgO, CaO, SrO and BaO.)

Specific examples of the alkali aluminoborosilicate glass include glasses having the following compositions, in which each component is expressed in mole percentage on an oxide basis.
61%≦ _SiO2 ≦75%
1.0%≦ _{Al2O3 ≦} 20%
1.0%≦ _{B2O3 ≦} 10%
0.0%≦MgO≦15%
0.0%≦CaO≦10%
0.0%≦SrO≦1.0%
0.0%≦BaO≦1.0%
0.0%≦ _Li2O ≦15%
2.0%≦ _Na2O ≦15%
0.0%≦ _K2O ≦6.0%
0.0%≦ _ZrO2 ≦4.0%
0.0%≦ _TiO2 ≦1.0%
0.0%≦ _{Y2O3 ≦} 2.0%
10%≦ _R2O ≦25%
0.0%≦RO≦20%
(R ₂ O represents the total content of Li ₂ O, Na ₂ O and K ₂ O, and RO represents the total content of MgO, CaO, SrO and BaO.)

In the laminated glass of this embodiment, the second glass sheet 12 may be soda-lime glass. _The soda-lime glass may contain less than 1.0% _Al2O3 . Specifically, examples of the soda-lime glass include glasses having the following compositions. Each component is expressed in mole percentage based on the oxide.
60%≦ _SiO2 ≦75%
0.0% _{≦ Al2O3} <1.0%
2.0%≦MgO≦11%
2.0%≦CaO≦10%
0.0%≦SrO≦3.0%
0.0%≦BaO≦3.0%
10%≦ _Na2O ≦18%
0.0%≦ _K2O ≦8.0%
0.0%≦ _ZrO2 ≦4.0%
0.0010%≦ _{Fe2O3 ≦} 5.0%

The lower limit of the thickness of the first glass plate 11 or the second glass plate 12 is preferably 0.50 mm or more, more preferably 0.70 mm or more, even more preferably 1.00 mm or more, particularly preferably 1.20 mm or more, and most preferably 1.50 mm or more. A thickness of 0.50 mm or more for the first glass plate 11 or the second glass plate 12 is preferable from the viewpoint of impact resistance.

The upper limit of the thickness of the first glass sheet 11 or the second glass sheet 12 is preferably 4.00 mm or less, more preferably 3.80 mm or less, even more preferably 3.60 mm or less, particularly preferably 3.50 mm or less, and most preferably 3.40 mm or less. If the thickness of the first glass sheet 11 or the second glass sheet 12 is 4.00 mm or less, the weight of the laminated glass 10 does not become too large, which is preferable in terms of improving fuel efficiency when used in a vehicle.
Furthermore, the first glass plate 11 and the second glass plate 12 may have the same thickness or may have different thicknesses.

In the laminated glass 10 of this embodiment, the total thickness of the first glass sheet 11, the second glass sheet 12, and the intermediate film 13 is preferably 2.30 mm or more. A total thickness of 2.30 mm or more provides sufficient strength. The total thickness is more preferably 2.50 mm or more, even more preferably 2.70 mm or more, even more preferably 3.00 mm or more, particularly preferably 3.50 mm or more, and most preferably 4.00 mm or more. From the viewpoint of weight reduction, the total thickness may be 5.00 mm or less, preferably 4.90 mm or less, more preferably 4.85 mm or less, and even more preferably 4.80 mm or less.

In the laminated glass 10 of this embodiment, the thickness of the first glass sheet 11 and the second glass sheet 12 may be constant over the entire surface, or may vary from place to place as necessary, such as forming a wedge shape in which the thickness of one or both of the first glass sheet 11 and the second glass sheet 12 gradually decreases.

One of the first glass plate 11 and the second glass plate 12 may be chemically strengthened glass that has been subjected to glass strengthening to improve its strength. The method of chemical strengthening is the same as the chemical strengthening treatment of the glass plate described above. Examples of chemically strengthened glass include the above-mentioned alkali aluminosilicate glass and the above-mentioned alkali aluminoborosilicate glass that have been subjected to chemical strengthening treatment.

The first glass sheet 11 and the second glass sheet 12 may have a flat shape or a curved shape having a curvature on the entire surface or a part thereof. When the first glass sheet 11 and the second glass sheet 12 are curved, they may have a single curved shape that is curved only in one of the vertical direction or the horizontal direction, or a compound curved shape that is curved in both the vertical direction and the horizontal direction. When the first glass sheet 11 and the second glass sheet 12 are curved, the radius of curvature in the vertical direction and the horizontal direction may be the same or different. When the first glass sheet 11 and the second glass sheet 12 are curved, the radius of curvature in the vertical direction and/or the horizontal direction is preferably 1000 mm or more. The shape of the main surface of the first glass sheet 11 and the second glass sheet 12 is made to fit the window opening of the vehicle in which they are installed.

The intermediate film 13 according to this embodiment is sandwiched between the first glass sheet 11 and the second glass sheet 12. By including the intermediate film 13, the laminated glass 10 according to this embodiment can firmly bond the first glass sheet 11 and the second glass sheet 12 together and can reduce the impact force when flying fragments collide with the glass sheets.

As the intermediate film 13, various organic resins that are generally used in laminated glass used as laminated glass for conventional vehicles can be used. Examples of organic resins include polyethylene (PE), ethylene vinyl acetate copolymer (EVA), polypropylene (PP), polystyrene (PS), methacrylic resin (PMA), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), cellulose acetate (CA), diallyl phthalate resin (DAP), urea resin (UP), melamine resin (MF), unsaturated polyester (UP), polyvinyl butyral (PVB), polyvinyl hol, etc. Marl (PVF), polyvinyl alcohol (PVAL), vinyl acetate resin (PVAc), ionomer (IO), polymethylpentene (TPX), vinylidene chloride (PVDC), polysulfone (PSF), polyvinylidene fluoride (PVDF), methacrylic-styrene copolymer resin (MS), polyarene (PAR), polyarylsulfone (PASF), polybutadiene (BR), polyethersulfone (PESF), or polyetheretherketone (PEEK) can be used. Among these, EVA and PVB are preferred from the viewpoint of transparency and adhesion, and PVB is particularly preferred because it can provide sound insulation.

From the viewpoint of impact force mitigation and sound insulation, the thickness of the intermediate film 13 is preferably 0.300 mm or more, more preferably 0.500 mm or more, and even more preferably 0.700 mm or more. From the viewpoint of suppressing a decrease in visible light transmittance, the thickness of the intermediate film 13 is preferably 1.00 mm or less, more preferably 0.900 mm or less, and even more preferably 0.800 mm or less. The thickness of the intermediate film 13 is preferably in the range of 0.300 mm to 1.00 mm, and more preferably in the range of 0.700 mm to 0.800 mm.

The thickness of the intermediate film 13 may be constant over the entire surface, or may vary from place to place as necessary.

If the difference in linear expansion coefficient between the interlayer 13 and the first glass sheet 11 or the second glass sheet 12 is large, the laminated glass 10 may crack or warp when the laminated glass 10 is produced through a heating process described below, which may result in poor appearance. Therefore, it is preferable that the difference in linear expansion coefficient between the interlayer 13 and the first glass sheet 11 or the second glass sheet 12 is as small as possible. The difference in linear expansion coefficient between the interlayer 13 and the first glass sheet 11 or the second glass sheet 12 may be expressed as the difference between the average linear expansion coefficients in a specified temperature range.

In particular, since the resin constituting the intermediate film 13 has a low glass transition point, a predetermined average linear expansion coefficient difference may be set in a temperature range below the glass transition point of the resin material. The difference in linear expansion coefficient between the first glass sheet 11 or the second glass sheet 12 and the resin material may be set at a predetermined temperature below the glass transition point of the resin material.

The intermediate film 13 may be an adhesive layer containing an adhesive. The adhesive is not particularly limited, but for example, an acrylic adhesive or a silicone adhesive can be used.
When the interlayer 13 is an adhesive layer, there is no need to go through a heating step in the process of joining the first glass plate 11 and the second glass plate 12, and therefore there is little risk of the above-mentioned cracking or warping occurring.

[Other layers]
The laminated glass 10 of the present embodiment may include layers (hereinafter also referred to as "other layers") other than the first glass plate 11, the second glass plate 12, and the interlayer film 13, provided such layers do not impair the effects of the present invention. For example, the laminated glass 10 may include a coating layer that imparts a water-repellent function, a hydrophilic function, an anti-fogging function, or the like, an infrared reflective film, or the like.

The positions at which the other layers are provided are not particularly limited, and they may be provided on the surface of the laminated glass 10, or may be provided so as to be sandwiched between the first glass sheet 11, the second glass sheet 12, or the intermediate film 13. The laminated glass 10 of this embodiment may also be provided with a black ceramic layer or the like arranged in a strip shape on part or all of the peripheral portion for the purpose of concealing the attachment portion to the frame or the wiring conductors.

The laminated glass 10 of this embodiment can be manufactured in the same manner as conventionally known laminated glass. For example, a first glass sheet 11, an intermediate film 13, and a second glass sheet 12 are laminated in this order, and a process of heating and pressing is performed to obtain a laminated glass 10 in which the first glass sheet 11 and the second glass sheet 12 are bonded together via the intermediate film 13.

The manufacturing method of the laminated glass 10 according to this embodiment may, for example, include a process of heating and shaping the first glass sheet 11 and the second glass sheet 12, followed by a process of inserting the intermediate film 13 between the first glass sheet 11 and the second glass sheet 12 and heating and pressurizing the sheet. By going through such processes, the laminated glass 10 may be formed in which the first glass sheet 11 and the second glass sheet 12 are joined together via the intermediate film 13.

The laminated glass 10 of this embodiment preferably has a visible light transmittance Tv defined in ISO-9050:2003 using a D65 light source of 70% or more. Tv is more preferably 71% or more, and even more preferably 72% or more. In addition, Tv is, for example, 90% or less.

The laminated glass 10 according to this embodiment preferably has a total solar transmittance Tts of 70% or less, as defined in ISO-13837:2008 convention A and measured at a wind speed of 4 m/s. When the total solar transmittance Tts of the laminated glass 10 according to this embodiment is 70% or less, sufficient heat shielding properties are obtained. Tts is more preferably 68% or less, and even more preferably 66% or less. In addition, Tts is, for example, 55% or more.

[Vehicle window glass, architectural window glass]
The vehicle window glass and architectural window glass of the present embodiment have the above-mentioned glass plate. Moreover, the vehicle window glass and architectural window glass of the present embodiment may be made of the above-mentioned laminated glass.

Hereinafter, an example of the case where the laminated glass 10 of this embodiment is used as a vehicle window glass will be described with reference to the drawings.
5 is a conceptual diagram showing a state in which the laminated glass 10 of this embodiment is attached to an opening 110 formed in the front of an automobile 100 and used as an automobile window glass. The laminated glass 10 used as an automobile window glass may have a housing (case) 120 that houses an information device or the like attached to its surface on the inside of the vehicle to ensure the traveling safety of the vehicle.

The information device housed in the housing is a device that uses a camera, radar, etc. to prevent rear-end collisions with vehicles ahead, pedestrians, obstacles, etc., and to notify the driver of dangers. For example, it is an information receiving device and/or an information transmitting device, etc., and includes a millimeter wave radar, a stereo camera, an infrared laser, etc., and transmits and receives signals.
The "signal" in question refers to electromagnetic waves including millimeter waves, visible light, infrared light, and the like.

Figure 6 is an enlarged view of part S in Figure 5, and is a perspective view showing the portion of the laminated glass 10 of this embodiment where the housing 120 is attached. The housing 120 houses a millimeter wave radar 201 and a stereo camera 202 as information devices. The housing 120 that houses the information devices is usually attached on the outer side of the vehicle than the rearview mirror 150 and on the inner side of the vehicle than the laminated glass 10, but may be attached to other portions.

Figure 7 is a cross-sectional view taken along line Y-Y in Figure 6 and perpendicular to the horizontal line. It is preferable that the first glass sheet 11 of the laminated glass 10 is disposed on the exterior side of the vehicle. With the above configuration, a lightweight windshield with high resistance to flying stones and high rigidity can be realized.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these.

<Preparation of Glass Plates of Examples 1 to 23>
Raw materials were charged into a platinum crucible and melted at a temperature of 1600°C to 1650°C for 3 hours to obtain molten glass so as to obtain the glass composition (unit: mol%) shown in Tables 2 and 3. The molten glass was poured onto a carbon plate and slowly cooled. Both sides of the obtained plate-like glass were polished to obtain a glass plate having a thickness of 2.00 mm. Examples 1 to 19 are working examples, and Examples 20 to 23 are comparative examples.

The glass plates obtained above were subjected to the following evaluations, and the results are shown in Tables 2 and 3. Note that blank spaces in the tables indicate that no measurements were taken.

(1) Specific gravity:
A bubble-free glass block of about 20 g cut from the glass plate was measured by the Archimedes method.

(2) Glass transition temperature (T _g ):
This value was measured using TMA and was determined according to the standard JIS R3103-3 (2001).

(3) Average coefficient of linear expansion from 50 ° C. to 350 ° C. (CTE _50-350 ):
The measurement was carried out using a thermal expansion meter (TMA) and was determined in accordance with the standard of JIS R3102 (1995).

(4) Young's modulus:
Measurement was performed at 25° C. using an ultrasonic pulse method (Olympus, DL35).

(5) Fracture toughness value (Kc)
For the glass plate obtained above, an indentation was made with a Vickers hardness tester using a Vickers indenter at an indentation load of 2.0 kgf and a holding time of 15 seconds based on the IF method in accordance with JIS R1607:2010, and then the Vickers indenter was removed. After waiting for 15 seconds, the diagonal length of the indentation and the crack length were measured using a microscope attached to the testing machine. This was repeated 10 times, and the results were calculated using the following formula.
Kc = 0.026 × (E × P) 1/2 × a × c - 3/2
Here, E is the Young's modulus of the glass plate (Pa), P is the indentation load (N), a is half the average diagonal length of the indentation (m), and c is half the average crack length (m).

(6) 50% crack generation load In a thermohygrostat maintained at a humidity of 40% and a temperature of 23°C, a Vickers indenter set to loads of 0.1 kg, 0.2 kg, 0.3 kg, 0.5 kg, 1.0 kg, and 2.0 kg was driven into the glass surface (optically polished surface) for 15 seconds, and the number of cracks generated from the four corners of the indentation after 15 seconds was counted (maximum 4 per indentation). This was repeated 20 times at each load (i.e., the indenter was driven 20 times), the total number of cracks was counted, and the crack generation rate was calculated by dividing the total number of cracks generated by 80. The obtained crack generation rate was plotted against the load, and the load at which the crack generation rate was 50% when the sigmoid function was fitted by the least squares method was defined as the 0% crack generation load (kg).

(7) Fe-Redox:
The crushed glass plate was decomposed at room temperature with a mixture of hydrofluoric acid and hydrochloric acid, and a certain amount of the decomposition solution was dispensed into a plastic container, and a hydroxylammonium chloride solution was added to reduce Fe ³⁺ in the sample solution to Fe ²⁺ . Then, a 2,2'-dipyridyl solution and an ammonium acetate buffer solution were added to color Fe ²⁺ . The color-developing solution was adjusted to a certain amount with ion-exchanged water, and the absorbance at a wavelength of 522 nm was measured with an absorptiometer. The concentration was then calculated from a calibration curve prepared using the standard solution to determine the amount of Fe ²⁺ . Since Fe ³⁺ in the sample solution was reduced to Fe ²⁺ , this amount of Fe ²⁺ means "[Fe ²⁺ ] + [Fe ³⁺ ]" in the sample.
Next, the crushed glass plate was decomposed at room temperature with a mixture of hydrofluoric acid and hydrochloric acid, and a certain amount of the decomposition solution was dispensed into a plastic container, and a 2,2'-dipyridyl solution and an ammonium acetate buffer solution were quickly added to cause only Fe2 ⁺ to develop color. The color-developing solution was adjusted to a certain amount with ion-exchanged water, and the absorbance at a wavelength of 522 nm was measured using a spectrophotometer (U-4100, manufactured by Hitachi, Ltd.). The concentration was then calculated from a calibration curve prepared using the standard solution, and the amount of Fe2 ⁺ was calculated. This amount of Fe2 ⁺ means the [Fe2 ⁺ ] in the sample.
Then, Fe-Redox: [Fe ²⁺ ]/([Fe ²⁺ ]+[Fe ³⁺ ]) was calculated from the [Fe ²⁺ ] and [Fe ²⁺ ]+[Fe ³⁺ ] determined above.

(8) Absorption peak wavelength of Fe2 ⁺ :
The glass plate obtained above was measured using a spectrophotometer (LAMBDA950 spectrophotometer manufactured by Perkinelmer) to measure the maximum absorption wavelength of the peak present in the wavelength range of 950 to 1200 nm.

(9) Visible light transmittance (Tv):
Tv, calculated based on a thickness of 2.00 mm, was measured using a D65 light source according to the method defined in ISO-9050: 2003. Note that Tv was measured using a Perkinelmer LAMBDA 950 spectrophotometer.

(10) Solar transmittance (Te):
The solar transmittance Te is a solar transmittance calculated by measuring the transmittance using a spectrophotometer LAMBDA950 manufactured by Perkinelmer in accordance with the provisions of ISO-9050:2003.

(11) Ultraviolet transmittance (Tuv):
Tuv, calculated based on a thickness of 2.00 mm, was measured by the method defined in ISO-9050: 2003. Note that Tuv was measured using a spectrophotometer LAMBDA950 manufactured by Perkinelmer.

(12) Viscosity:
The temperature _T2 at which the viscosity η, which is a criterion for the solubility of the glass, is ¹⁰² dPa·s and the temperature _T4 at which the viscosity η, which is a criterion for the formability during float forming, is ¹⁰⁴ dPa·s were measured using a rotational viscometer. The temperature _T12 at which the viscosity η, which is a criterion for the bending workability, is ¹⁰¹² dPa·s was measured using a beam bending method.

The glass plates of Examples 1 to 19, which are working examples, have a larger 50% crack initiation load and a larger fracture toughness value determined by the indentation penetration method (IF method) than the glass plates of Examples 20 to 23, which are comparative examples, and therefore are found to have excellent crack resistance. In addition, the glass plates have a Te of 90% or less and are found to have excellent heat insulation properties.
On the other hand, Example 20, which is a comparative example, has excellent heat insulation properties, but since _SiO2 is less than 75% and RO is more than 10%, the 50% crack initiation load is low at 0.10 kg, and the crack resistance is poor. Example 21 has excellent heat insulation properties, but BaO is more than 1.0%, and the fracture toughness value obtained by the indentation method (IF method) is low at 0.84 MPa·m ^0.5 , and the crack resistance is poor. Example 22 has excellent heat insulation properties, but SrO is more than 0.50%, and the fracture toughness value obtained by the indentation method (IF method) is low at 0.87 _MPa ·m ^0.5 , and the crack resistance is poor. Moreover, Example 23, which is a comparative example, has excellent crack resistance, but _Fe2O3 is less than 0.030%, and the heat insulation properties are poor.

As described above, the present specification discloses the following configurations.
[1] In mole percent based on oxide,
75.0%≦ _SiO2 ≦85.0%
1.5%≦ _{Al2O3 ≦} 7.0%
0.0%≦MgO≦10%
0.0%≦CaO≦10%
0.0%≦SrO≦0.50%
0.0%≦BaO≦1.0%
0.0%≦ _Li2O ≦10%
0.0%≦ _Na2O ≦20%
0.0%≦ _K2O ≦10%
1.0%≦RO≦10%
8.0%≦ _R2O ≦22%
0.030%≦ _{Fe2O3 ≦} 1.0%
RO/ _R2O ≦0.70
(wherein RO is at least one selected from MgO, CaO, SrO, and BaO, and R ₂ O is at least one selected from Li ₂ O, Na ₂ O, and K ₂ O).
Contains
A glass plate having a solar transmittance Te defined in ISO-9050:2003 of 90% or less when converted into a glass plate having a thickness of 2.0 mm.
[2] The glass plate according to [1], having a load of 0.25 kg or more at which a crack occurrence rate is 50%, and a fracture toughness value measured by an indentation penetration method (IF method) of 0.90 MPa·m ^0.5 or more.
[3] The glass plate according to [1] or [2], which has a visible light transmittance Tv defined in ISO-9050:2003 using a D65 light source when converted to a thickness of 2.0 mm of 75% or more.
[4] The glass plate according to any one of [1] to [3], having an ultraviolet transmittance Tuv defined in ISO-9050:2003 of 70% or less when converted into a glass plate having a thickness of 2.0 mm.
[5] The glass plate according to any one of [1] to [4], wherein the temperature _T2 at which the glass viscosity becomes 10 ² dPa·s is 1700° C. or lower.
[6] The glass plate according to any one of [1] to [5], wherein the temperature T ₄ at which the glass viscosity becomes 10 ⁴ dPa·s is 1,200° C. or lower.
[7] The glass plate according to any one of [1] to [6], wherein a temperature T ₁₂ at which the glass viscosity becomes 10 ¹² dPa·s is 610° C. or lower.
[8] The glass plate according to any one of [1] to [7], which has an average coefficient of linear expansion (CTE) of 90×10 ^-7 /° C. or less from 50 to 350° C.
[9] The glass plate according to any one of [1] to [8], which contains MgO, and contains, in terms of mol % on an oxide basis, 0.0% to 3.0% of CaO and 0.0% to 3.0% of K ₂ O.
[10] The glass plate according to [9], having an average coefficient of linear expansion (CTE) from 50 to 350° C. of 85×10 ⁻⁷ /° C. or less.
[11] The glass plate according to any one of [1] to [10], which is substantially free of B ₂ O ₃ .
[12] The glass plate according to [1], which contains MgO, and contains, in mole % on an oxide basis, 2.0% or more _{of Al2O3} , 0.0% or more and 3.0% or less of CaO, 10% or more of _Na2O , and 0.0% or more and 2.0% or less of _K2O , and is substantially free of _{B2O3 ,} has a load of 0.50 kg or more at which a crack occurrence rate is 50%, and has a fracture toughness value of 0.93 MPa·m ^or more as determined by an indentation penetration method (IF method).
[13] A bent glass comprising the glass plate according to any one of [1] to [12].
[14] A bent glass comprising the glass plate according to [7].
[15] A glass window comprising a first glass plate, a second glass plate, and an interlayer film sandwiched between the first glass plate and the second glass plate,
At least one of the first glass plate and the second glass plate is the glass plate according to any one of [1] to [12], or the bent glass according to [13] or [14].
[16] A vehicle window glass comprising the glass plate according to any one of [1] to [12].
[17] An architectural window glass comprising the glass plate according to any one of [1] to [12].
[18] A vehicle window glass comprising the laminated glass according to [15].
[19] An architectural window glass comprising the laminated glass according to [15].

Reference Signs List 10 Laminated glass 11 First glass sheet 12 Second glass sheet 13 Interlayer film 100 Automobile 110 Opening 120 Housing 150 Rearview mirror 201 Millimeter wave radar 202 Stereo camera 300 Radio wave

Claims (19)

In mole percent based on oxide,
75.0%≦ _SiO2 ≦85.0%
1.5%≦ _{Al2O3 ≦} 7.0%
0.0%≦MgO≦10%
0.0%≦CaO≦10%
0.0%≦SrO≦0.50%
0.0%≦BaO≦1.0%
0.0%≦ _Li2O ≦10%
0.0%≦ _Na2O ≦20%
0.0%≦ _K2O ≦10%
1.0%≦RO≦10%
8.0%≦ _R2O ≦22%
0.030%≦ _{Fe2O3 ≦} 1.0%
RO/ _R2O ≦0.70
(wherein RO is at least one selected from MgO, CaO, SrO, and BaO, and R ₂ O is at least one selected from Li ₂ O, Na ₂ O, and K ₂ O).
Contains
A glass plate having a solar transmittance Te defined in ISO-9050:2003 of 90% or less when converted into a glass plate having a thickness of 2.0 mm. 2. The glass plate according to claim 1, wherein the load at which a crack occurrence rate reaches 50% is 0.25 kg or more and the fracture toughness value determined by the indentation penetration method (IF method) is 0.90 MPa·m ^0.5 or more. The glass plate according to claim 1, which has a visible light transmittance Tv of 75% or more as defined in ISO-9050:2003 using a D65 light source when converted to a thickness of 2.0 mm. The glass plate according to claim 1, having an ultraviolet transmittance Tuv defined in ISO-9050:2003 of 70% or less when converted to a thickness of 2.0 mm. The glass plate according to claim 1 , wherein the temperature T ₂ at which the glass viscosity becomes 10 ² dPa·s is 1700° C. or lower. The glass plate according to claim 1 , wherein a temperature T ₄ at which the glass viscosity becomes 10 ⁴ dPa·s is 1,200° C. or lower. The glass plate according to claim 1 , wherein the temperature T ₁₂ at which the glass viscosity becomes 10 ¹² dPa·s is 610° C. or lower. 2. The glass plate according to claim 1, having an average coefficient of linear expansion (CTE) from 50 to 350° C. of 90×10 ⁻⁷ /° C. or less. The glass plate according to claim 1, which contains MgO, and further contains, in mole percent on an oxide basis, 0.0% to 3.0% of CaO and 0.0% to 3.0% of K ₂ O. 10. The glass plate according to claim 9, having an average coefficient of linear expansion (CTE) from 50 to 350° C. of 85×10 ⁻⁷ /° C. or less. 2. The glass sheet according to claim 1, _which is substantially free of _B2O3 . 2. The glass plate according to claim 1, which contains MgO, and contains, in terms of mole % on an oxide basis, 2.0% or more _{of Al2O3} , 0.0% or more and 3.0% or less of CaO, 10% or more of _Na2O , and 0.0% or more and 2.0% or less of _K2O , and is substantially free of _{B2O3 ,} has a load of 0.50 kg or more at which a crack occurrence rate is 50%, and has a fracture toughness value of 0.93 MPa·m ^or more as determined by an indentation penetration method (IF method). Bent glass made from the glass sheet according to claim 1. Bent glass made from the glass sheet according to claim 7. A glass window pane comprising a first glass sheet, a second glass sheet, and an interlayer sandwiched between the first glass sheet and the second glass sheet,
A laminated glass, wherein at least one of the first glass plate and the second glass plate is the glass plate according to any one of claims 1 to 12 or the bent glass according to claim 13 or 14. A vehicle window glass comprising a glass plate according to any one of claims 1 to 12. Architectural window glass comprising a glass sheet according to any one of claims 1 to 12. A vehicle window glass comprising the laminated glass according to claim 15. Architectural window glass comprising the laminated glass according to claim 15.

Images