glass

Abstract

The purpose of the present invention is to provide glass that makes it possible to control warping of solar cells while keeping degradation in mechanical properties and optical properties under control, even if the glass is slimmed down and made large scale. This glass is of 2.2 to 2.7 specific gravity, of 60 GPa or more Young's modulus, of 2.0 to 6.0 (x10-6 / K) average thermal expansion coefficient at 50 to 200 °C, and is a rectangle with one side of the principal surface being 50 cm to 300 cm, and furthermore is of 0.01 mm to 0.5 mm sheet thickness and contains, in mass percentage on an oxide basis, 0 to 3.5% total content of Li2O, Na2O and K2O, and 0.1 to 10% CeO2.

Description

Glass

[0001] The present invention relates to glass, and more particularly to glass suitable for use as a cover glass for solar cells used in space satellites, as a glass for blocking ultraviolet rays, and as a glass for blocking electron beams.

[0002] A satellite constellation is a method of linking several hundred to several thousand satellites to realize a function or service. Since multiple satellites are required to build a satellite constellation, there is a demand for low-cost satellites. Photovoltaic power generation using solar cells is being considered as a power supply source for satellites. Silicon is generally used for solar cells, and cover glass is used to protect the elements.

[0003] As a cover glass for space solar cells, for example, Patent Document 1 discloses a borosilicate glass composition suitable for use as a protective cover for solar cells used in artificial satellites, and Patent Document 2 discloses a glass substrate for space solar power generation.

[0004] Japanese Patent Application Laid-Open No. 63-95138 International Publication No. 2023 / 022074

[0005] When glass is used in space solar cells, in particular, low cost satellites are required. From the perspective of cost reduction, thinner and larger glass can achieve lower costs and weight. However, thinner and larger glass can cause the solar cells to warp more than conventional solar cells due to the difference in thermal expansion coefficient between the silicon used in the solar cells and the glass. Furthermore, thinner glass can cause the solar cells to have poorer mechanical and optical properties than conventional solar cells.

[0006] Therefore, an object of the present invention is to provide a glass that can suppress warping of solar cells and suppress deterioration of mechanical and optical properties even when the solar cells are made thinner and larger.

[0007] The present inventors have found that the above problems can be solved by setting the composition of glass within a specific range, and have completed the present invention. That is, the present invention is as follows.

[0008] 1. Specific gravity is 2.2 to 2.7, Young's modulus is 60 GPa or more, and the average thermal expansion coefficient at 50 to 200°C is 2.0 to 6.0 (x 10 －６ / K), one side of the main surface is a rectangle of 50 cm or more and 300 cm or less, and the plate thickness is 0.01 mm or more and 0.5 mm or less, and expressed in mass percentage based on oxides, ２ O, Na ２ O and K ２ The total content of O is 0 to 3.5%, and CeO ２ 2. Glass containing 0.1 to 10% of TiO, expressed as a mass percentage based on oxides. ２ 3. The glass according to 1 above, containing 0.01 to 10% of TiO, expressed as a mass percentage based on oxides. ２ 4. The glass according to 1 above, containing 5 to 10% of the above. 4. The glass according to 1 above, having a specific gravity of 2.2 to 2.7, a Young's modulus of 60 GPa or more, and an average thermal expansion coefficient at 50 to 200°C of 2.0 to 6.0 (×10 －６ / K), a rectangular shape with one side of the main surface being 50 cm or more and 300 cm or less, and a thickness of 0.01 mm or more and 0.5 mm or less, and expressed as a mass percentage based on oxides, ２ Glass containing 5 to 10% of SiO. 5. Mass percentage based on oxides: ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, and CeO ２ Contains 0.1 to 10% of Li ２ O, Na ２ O and K ２ 5. Glass with a total O content of 0 to 3.5%, a rectangular main surface with one side of 50 cm to 300 cm, and a thickness of 0.01 mm to 0.5 mm. 6. In terms of mass percentage based on oxides, SiO ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, TiO ２ Contains 5 to 10% of Li ２ O, Na２ O and K ２ 7. Glass with a total O content of 0 to 3.5%, a rectangular main surface with one side of 50 cm to 300 cm, and a thickness of 0.01 mm to 0.5 mm. 8. In terms of mass percentage based on oxides, SiO ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, TiO ２ 0.01 to 10% and CeO ２ Contains 0.1 to 10% of Li ２ O, Na ２ O and K ２ 8. Glass having a total O content of 0 to 3.5%, a rectangular main surface with one side of 50 cm to 300 cm, and a thickness of 0.01 mm to 0.5 mm. 9. An average thermal expansion coefficient at 50 to 200°C of 2.0 to 6.0 (×10 －６ 9. The glass according to any one of 5 to 7 above, wherein As is expressed as a mass percentage based on oxides and is: ２ O ３ and Sb ２ O ３ 10. The glass according to any one of 1 to 7 above, wherein the total content of SnO is 0% or more and less than 0.25%, expressed as a mass percentage based on oxides. ２ 11. The glass according to any one of 1 to 7 above, containing 0.01 to 0.4% or less of BaO. 12. The glass according to any one of 1 to 7 above, wherein the average absorbance change at wavelengths of 400 to 800 nm upon electron beam irradiation is 0.01 or less per 100 μm plate thickness. 13. The glass according to any one of 1 to 7 above, wherein the average absorbance change at wavelengths of 400 to 800 nm upon electron beam irradiation is 0.01 or less per 100 μm plate thickness. 14. The glass according to any one of 1 to 7 above, wherein the average absorbance change at wavelengths of 400 to 800 nm upon electron beam irradiation is 0.01 or less per 100 μm plate thickness. Ｉｃ ) is 0.78 MPa m １／２14. The glass according to any one of 1 to 7 above, wherein the value obtained by subtracting the transmittance of light at a wavelength of 300 nm from the transmittance of light at a wavelength of 400 nm is 50% or more. 15. The glass according to any one of 1 to 7 above, wherein the value E / ρ obtained by dividing Young's modulus E (GPa) by specific gravity ρ is 27.0 GPa or more. 16. The glass according to any one of 1 to 7 above, wherein β-OH is 1.0 mm －１ The glass as described in any one of 1 to 7 above, which is the following: 17. The glass as described in any one of 1 to 7 above, which has a conductive film on at least one surface. 18. The glass as described in any one of 1 to 7 above, which has an anti-reflection film on at least one surface. 19. A cover glass for a space satellite solar cell, which uses the glass as described in any one of 1 to 7 above. 20. An ultraviolet-blocking glass, which uses the glass as described in any one of 1 to 7 above. 21. An electron-beam-blocking glass, which uses the glass as described in any one of 1 to 7 above.

[0009] The glasses of the first and fifth embodiments of the present invention have a side of a main surface and a plate thickness within specific ranges, and also have specific ranges for specific gravity, Young's modulus, and thermal expansion coefficient, and have a glass composition within a specific range, so that warping of solar cells can be suppressed and deterioration of mechanical properties and optical properties can be suppressed.

[0010] The glasses of the second to fourth embodiments of the present invention have a side of a main surface and a plate thickness within specific ranges, and have glass compositions within specific ranges, and thus can suppress warping of solar cells while suppressing deterioration in mechanical properties and optical properties.

[0011] FIG. 1 is a diagram showing the correlation between the average thermal expansion coefficient and (absolute value of warpage δ / length of glass in the warpage direction).

[0012] The present invention will be described in detail below based on the embodiments, but the present invention is not limited to the following embodiments and can be implemented with any modifications within the scope of the gist of the present invention. Furthermore, the embodiments of the present invention (hereinafter also abbreviated as the present embodiments) include the first to fifth embodiments described below. In this specification, the term "to" indicating a numerical range is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit, and unless otherwise specified, "to" will be used in the same sense below.

[0013] In this specification, "substantially free" means that the glass does not contain any impurities other than those unavoidable from raw materials, etc. In other words, it means that the glass is not intentionally contained. In this specification, the content of each component of the glass is expressed as a mass percentage based on the oxide, unless otherwise specified.

[0014] <Glass> The glass of the first embodiment has a specific gravity of 2.2 to 2.7, a Young's modulus of 60 GPa or more, and an average thermal expansion coefficient of 2.0 to 6.0 (×10 －６ / K), a rectangular shape with one side of the main surface being 50 cm or more and 300 cm or less, and a plate thickness of 0.01 mm or more and 0.5 mm or less, and Li, expressed as a mass percentage based on oxides ２ O, Na ２ O and K ２ The total content of O is 0 to 3.5%, and CeO ２ The present invention is characterized in that it contains 0.1 to 10% of

[0015] The glass of the second embodiment contains, in terms of mass percentage based on oxides, SiO ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, and CeO ２ Contains 0.1 to 10% of Li ２ O, Na ２ O and K ２ The steel sheet is characterized in that the total content of O is 0 to 3.5%, the main surface is rectangular with one side of 50 cm to 300 cm, and the plate thickness is 0.01 mm to 0.5 mm.

[0016] The glass of the third embodiment contains, in terms of mass percentage based on oxides, SiO ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, TiO ２ Contains 5 to 10% of Li ２ O, Na ２ O and K ２ The steel sheet is characterized in that the total content of O is 0 to 3.5%, the main surface is rectangular with one side of 50 cm to 300 cm, and the plate thickness is 0.01 mm to 0.5 mm.

[0017] The glass of the fourth embodiment contains, in terms of mass percentage based on oxides, SiO ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, TiO ２ 0.01 to 10% and CeO ２ Contains 0.1 to 10% of Li ２ O, Na ２ O and K ２ The steel sheet is characterized in that the total content of O is 0 to 3.5%, the main surface is rectangular with one side of 50 cm to 300 cm, and the plate thickness is 0.01 mm to 0.5 mm.

[0018] The glass of the fifth embodiment has a specific gravity of 2.2 to 2.7, a Young's modulus of 60 GPa or more, and an average thermal expansion coefficient of 2.0 to 6.0 (×10 －６ / K), a rectangular shape with one side of the main surface being 50 cm or more and 300 cm or less, and a thickness of 0.01 mm or more and 0.5 mm or less, and expressed as a mass percentage based on oxides, ２ It is characterized by containing 5 to 10% of

[0019] The glasses of the first and fifth embodiments have a specific gravity of 2.2 to 2.7. The glasses of the first and fifth embodiments preferably have a specific gravity of 2.21 or more, 2.22 or more, 2.23 or more, 2.24 or more, 2.25 or more, 2.26 or more, 2.27 or more, 2.28 or more, 2.29 or more, 2.30 or more, 2.31 or more, 2.32 or more, 2.33 or more, 2.34 or more, 2.35 or more, 2.36 or more, 2.37 or more, or 2.38 or more. The glasses of the first and fifth embodiments preferably have a specific gravity of 2.69 or less, 2.68 or less, 2.67 or less, 2.66 or less, 2.65 or less, 2.64 or less, 2.63 or less, 2.62 or less, 2.61 or less, 2.60 or less, 2.59 or less, 2.58 or less, 2.57 or less, 2.56 or less, 2.55 or less, 2.54 or less, 2.53 or less, 2.52 or less, 2.51 or less, 2.50 or less, 2.49 or less, 2.48 or less, 2.47 or less, or 2.46 or less.

[0020] The glasses of the second to fourth embodiments preferably have a specific gravity of 2.2 to 2.7. The glasses of the second to fourth embodiments more preferably have a specific gravity of 2.21 or more, 2.22 or more, 2.23 or more, 2.24 or more, 2.25 or more, 2.26 or more, 2.27 or more, 2.28 or more, 2.29 or more, 2.30 or more, 2.31 or more, 2.32 or more, 2.33 or more, 2.34 or more, 2.35 or more, 2.36 or more, 2.37 or more, or 2.38 or more. The specific gravity of the glasses of the second to fourth embodiments is more preferably 2.69 or less, 2.68 or less, 2.67 or less, 2.66 or less, 2.65 or less, 2.64 or less, 2.63 or less, 2.62 or less, 2.61 or less, 2.60 or less, 2.59 or less, 2.58 or less, 2.57 or less, 2.56 or less, 2.55 or less, 2.54 or less, 2.53 or less, 2.52 or less, 2.51 or less, 2.50 or less, 2.49 or less, 2.48 or less, 2.47 or less, or 2.46 or less.

[0021] A specific gravity of 2.2 or more effectively shields electron and proton beams, and can suppress deterioration of solar cells, particularly when used as a cover glass for solar cells. A specific gravity of 2.7 or less can reduce the weight even when the glass is large. The specific gravity is measured by the Archimedes method.

[0022] The glasses of the first and fifth embodiments have a Young's modulus of 60 GPa or more, and preferably 61 GPa or more, 62 GPa or more, 63 GPa or more, 64 GPa or more, 65 GPa or more, 66 GPa or more, 67 GPa or more, 68 GPa or more, 69 GPa or more, 70 GPa or more, 71 GPa or more, or 72 GPa or more.

[0023] The glasses of the second to fourth embodiments have a Young's modulus of preferably 60 GPa or more, more preferably 61 GPa or more, 62 GPa or more, 63 GPa or more, 64 GPa or more, 65 GPa or more, 66 GPa or more, 67 GPa or more, 68 GPa or more, 69 GPa or more, 70 GPa or more, 71 GPa or more, or 72 GPa or more.

[0024] A Young's modulus of 60 GPa or more enhances fracture toughness and improves strength, thereby ensuring the strength required for larger and thinner glass. From the viewpoint of reducing the occurrence of thermal stress due to a sudden temperature change, the Young's modulus of the glass of this embodiment is preferably 105 GPa or less, more preferably 100 GPa or less, even more preferably 95 GPa or less, and particularly preferably 90 GPa or less. The Young's modulus is measured by the ultrasonic pulse method (JIS R1602, 1995).

[0025] In the glass of this embodiment, the value E / ρ, obtained by dividing Young's modulus E (GPa) by specific gravity ρ, is preferably 27.0 to 37.0 GPa. The value of E / ρ is more preferably 27.2 GPa or more, 27.4 GPa or more, 27.6 GPa or more, 27.8 GPa or more, 28.0 GPa or more, 28.2 GPa or more, 28.4 GPa or more, 28.6 GPa or more, 28.8 GPa or more, or 29.0 GPa or more. The value of E / ρ is more preferably 36.8 GPa or less, 36.6 GPa or less, 36.4 GPa or less, 36.2 GPa or less, 36.0 GPa or less, 35.8 GPa or less, 35.6 GPa or less, 35.4 GPa or less, 35.2 GPa or less, or 35.0 GPa or less. By setting the value of E / ρ to 27.0 GPa or more, the strength required for larger and thinner products can be ensured. By setting the value of E / ρ to 37.0 GPa or less, the strength required for larger and thinner products can be improved while ensuring a lighter weight when the product is larger.

[0026] As glass used in solar cells becomes larger and thinner, warping of solar cells due to the difference in thermal expansion coefficient between the silicon and glass that make up the solar cell becomes a problem. As shown in Figure 1, the absolute value of the warpage δ is correlated with the average thermal expansion coefficient, and it is thought that by specifying the range of the average thermal expansion coefficient, warping of solar cells when used in solar cells can be effectively reduced.

[0027] The glasses of the first and fifth embodiments have an average thermal expansion coefficient of 2.0 to 6.0 (×10 －６ The glass of the first and fifth embodiments preferably has an average thermal expansion coefficient of 2.1 (×10 －６ / K) or more, 2.2(×10 －６ / K) or more, 2.3(×10 －６ / K) or more, 2.4(×10 －６ / K) or more, 2.5(×10 －６ / K) or more, 2.6(×10 －６ / K) or more, 2.7(×10 －６ / K) or more, 2.8(×10 －６ / K) or more, 2.9(×10 －６ / K) or more, 3.0(×10 －６ / K) or more, 3.1(×10 －６ / K) or more, 3.2(×10 －６ The glass of the first and fifth embodiments preferably has an average thermal expansion coefficient of 5.9 (×10 －６ / K) or less, 5.8(×10 －６ / K) or less, 5.7(×10 －６ / K) or less, 5.6(×10 －６ / K) or less, 5.5(×10 －６ / K) or less, 5.4(×10 －６ / K) or less, 5.3(×10 －６ / K) or less, 5.2(×10 －６ / K) or less, 5.1(×10 －６ / K) or less, 5.0(×10 －６ / K) or less, 4.9(×10 －６ / K) or less, 4.8(×10 －６ / K) or less, 4.7(×10 －６ / K) or less, 4.6(×10 －６ / K) or less, 4.5(×10 －６ The glass of the second to fourth embodiments preferably has an average thermal expansion coefficient of 2.0 to 6.0 (×10 －６ / K). The glass of the second to fourth embodiments preferably has an average thermal expansion coefficient of 2.1 (×10 －６ / K) or more, 2.2(×10 －６ / K) or more, 2.3(×10 －６ / K) or more, 2.4(×10 －６ / K) or more, 2.5(×10 －６ / K) or more, 2.6(×10 －６ / K) or more, 2.7(×10 －６ / K) or more, 2.8(×10 －６ / K) or more, 2.9(×10 －６ / K) or more, 3.0(×10 －６ / K) or more, 3.1(×10 －６ / K) or more, 3.2(×10 －６ The glass of the second to fourth embodiments preferably has an average thermal expansion coefficient of 5.9 (×10 －６ / K) or less, 5.8(×10 －６ / K) or less, 5.7(×10 －６ / K) or less, 5.6(×10 －６ / K) or less, 5.5(×10 －６ / K) or less, 5.4(×10 －６ / K) or less, 5.3(×10 －６ / K) or less, 5.2(×10 －６ / K) or less, 5.1(×10 －６ / K) or less, 5.0(×10 －６ / K) or less, 4.9(×10 －６ / K) or less, 4.8(×10 －６ / K) or less, 4.7(×10 －６ / K) or less, 4.6(×10 －６ / K) or less, 4.5(×10 －６ / K) or less. When the average thermal expansion coefficient at 50 to 200°C is in the above range, warping of the solar cell due to the difference in thermal expansion coefficient between the silicon and glass used in the solar cell can be reduced, particularly when used as a cover glass for the solar cell. The average thermal expansion coefficient in this specification was measured using a differential thermal dilatometer in accordance with the method specified in JIS R3102 (1995). The measurement temperature range was 50 to 200°C, and the unit was ×10 －６ / K.

[0028] The glass of this embodiment is rectangular, with one side of the main surface being 50 cm or more and 300 cm or less. Having one side of the main surface being 50 cm or more reduces the labor required to assemble the solar cell, allowing for larger solar cells and lower costs. Having one side of the main surface being 300 cm or less makes it easier to handle thin glass without breaking, allowing for lower costs. The length of one side of the main surface is preferably 60 cm or more, 70 cm or more, or 80 cm or more, in the following order, more preferably 90 cm or more, 100 cm or more, or 110 cm or more, even more preferably 120 cm or more, 130 cm or more, or 140 cm or more, in the following order, still more preferably 150 cm or more. The length of one side of the main surface is more preferably 290 cm or less, 280 cm or less, 270 cm or less, 260 cm or less, 250 cm or less, 240 cm or less, 230 cm or less, 220 cm or less, 210 cm or less, or 200 cm or less.

[0029] The glass of this embodiment has a thickness of 0.01 mm or more and 0.5 mm or less. A thickness of 0.01 mm or more ensures strength and can sufficiently shield electron beams and proton beams. Furthermore, a thickness of 0.5 mm or less can achieve weight reduction, particularly in space applications. The thickness is preferably 0.48 mm or less, 0.46 mm or less, 0.44 mm or less, 0.42 mm or less, 0.40 mm or less, 0.38 mm or less, 0.36 mm or less, 0.34 mm or less, 0.32 mm or less, 0.30 mm or less, 0.28 mm or less, 0.26 mm or less, 0.24 mm or less, 0.22 mm or less, 0.20 mm or less, 0.18 mm or less, 0.16 mm or less, 0.14 mm or less, 0.12 mm or less, or 0.10 mm or less. The plate thickness is preferably 0.02 mm or more, 0.03 mm or more, 0.04 mm or more, or 0.05 mm or more.

[0030] In the glass of this embodiment, the average absorbance change, converted into a 100 μm plate thickness at a wavelength of 400 to 800 nm during electron beam irradiation, is preferably 0.01 or less, more preferably 0.009 or less, 0.008 or less, 0.007 or less, 0.006 or less, or 0.005 or less. When the average absorbance change converted into a 100 μm plate thickness is 0.01 or less, coloration due to electron beams is suppressed, and sufficient optical properties can be ensured for space applications. The lower limit of the average absorbance change converted into a 100 μm plate thickness is not particularly limited, but examples include 0.0001 or more. In this specification, the term "converted into a 100 μm plate thickness" refers to a value obtained by converting the absorbance change into the value when the glass plate thickness is 100 μm.

[0031] The average absorbance change amount at wavelengths of 400 to 800 nm during electron beam irradiation converted into a plate thickness of 100 μm is determined by the following procedure: (a1) For electron beam irradiation, a glass substrate to be irradiated is placed horizontally on a table, and an electron beam is irradiated onto the glass substrate at an energy dose of 1 MeV at a rate of 1×10 １５ pieces / cm ２(a2) After electron beam irradiation, the transmittance of each glass substrate is measured. The measurement is carried out within one week after electron beam irradiation. The absorbance before and after electron beam irradiation is calculated from the measured transmittance, and converted into absorbance at a plate thickness of 100 μm. (a3) ​​The average change in absorbance at wavelengths of 400 to 800 nm is calculated using the following formula:

[0032]

[0033] In the glass of this embodiment, the value obtained by subtracting the transmittance of light at a wavelength of 300 nm from the transmittance of light at a wavelength of 400 nm at a plate thickness of 100 μm is preferably 50% or more, more preferably 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, or 80% or more. A value of 50% or more can effectively suppress degradation of solar cell characteristics due to electron beams, particularly in space applications. The upper limit of this value is not particularly limited, but is, for example, 95% or less. The transmittance can be measured using a spectrophotometer (e.g., U-4100 manufactured by Hitachi High-Technologies Corporation).

[0034] The glass of this embodiment preferably has a transmittance at a wavelength of 400 nm at a plate thickness of 100 μm of 80 to 93%. The transmittance is more preferably 81% or more, even more preferably 82% or more, particularly preferably 83% or more, more preferably 84% or more, even more preferably 85% or more, and particularly preferably 86% or more. By having a transmittance at a wavelength of 400 nm at a plate thickness of 100 μm of 80% or more, the properties of solar cells can be further improved when the glass is used as a cover glass for solar cells. In this specification, the transmittance at a plate thickness of 100 μm refers to the transmittance measured at a plate thickness of 100 μm.

[0035] The glass of this embodiment preferably has a transmittance of 0 to 10% at a wavelength of 300 nm at a plate thickness of 100 μm. The transmittance is more preferably 0.5% or more, even more preferably 1% or more, particularly preferably 1.5% or more, more preferably 2% or more, even more preferably 2.5% or more, and particularly preferably 3% or more. When the glass has a transmittance of 0% or more at a wavelength of 300 nm at a plate thickness of 100 μm, the properties of the solar cell can be further improved when the glass is used as a cover glass for a solar cell. When the transmittance of 10% or less at a wavelength of 300 nm at a plate thickness of 100 μm is 10%, degradation of the solar cell due to ultraviolet light can be suppressed.

[0036] The glass of this embodiment preferably has a wavelength of 300 to 370 nm at which it exhibits 50% transmittance at a plate thickness of 100 μm. This wavelength is more preferably 310 nm or longer, even more preferably 320 nm or longer, and particularly preferably 330 nm or longer. Furthermore, this wavelength is more preferably 360 nm or shorter, even more preferably 355 nm or shorter, and particularly preferably 350 nm or shorter. Having a wavelength of 300 nm or longer can suppress deterioration of solar cells due to ultraviolet rays. Having a wavelength of 370 nm or shorter can further improve the manifestation characteristics of solar cells when used as a cover glass for solar cells.

[0037] The glass of this embodiment preferably has a transmittance of 80 to 94% at a wavelength of 400 nm at a plate thickness of 50 μm. The transmittance is more preferably 81% or higher, even more preferably 82% or higher, particularly preferably 83% or higher, more preferably 84% or higher, even more preferably 85% or higher, and particularly preferably 86% or higher. The transmittance is preferably 94% or lower, more preferably 93% or lower, even more preferably 92% or lower, particularly preferably 91% or lower, and most preferably 90% or lower. Having a transmittance of 80% or higher at a wavelength of 400 nm at a plate thickness of 50 μm allows for improved solar cell performance when used as a solar cell cover glass. In this specification, the transmittance at a plate thickness of 50 μm refers to the transmittance measured at a plate thickness of 50 μm.

[0038] The glass of this embodiment preferably has a transmittance of 0 to 25% at a wavelength of 300 nm at a plate thickness of 50 μm. The transmittance is more preferably 1% or more, even more preferably 2% or more, particularly preferably 3% or more, more preferably 4% or more, even more preferably 5% or more, and particularly preferably 7% or more. The transmittance is more preferably 23% or less, even more preferably 20% or less, particularly preferably 15% or less, and most preferably 10% or less. Having a transmittance of 0% or more at a wavelength of 300 nm at 50 μm allows for improved solar cell performance when used as a solar cell cover glass. Having a transmittance of 25% or less at a wavelength of 300 nm at 50 μm allows for suppression of solar cell degradation due to ultraviolet light.

[0039] The glass of this embodiment preferably exhibits a 50% transmittance at a plate thickness of 50 μm at a wavelength of 250 to 360 nm. The wavelength is more preferably 260 nm or more, even more preferably 270 nm or more, particularly preferably 280 nm or more, more preferably 290 nm or more, and even more preferably 300 nm or more. The wavelength is more preferably 350 nm or less, more preferably 340 nm or less, even more preferably 330 nm or less, particularly preferably 320 nm or less, and most preferably 310 nm or less. A wavelength of 250 nm or more can suppress degradation of solar cells due to ultraviolet rays. A wavelength of 360 nm or less can ensure sufficient optical properties even when the solar cell is enlarged.

[0040] The glass of this embodiment has a fracture toughness value K ＩＣ is 0.78 MPa m １／２ It is preferably at least 0.80 MPa m １／２ More preferably, 0.81 MPa m １／２ More preferably, 0.82 MPa m １／２ That's all. ＩＣ is 0.78 MPa m １／２ By satisfying the above, sufficient strength can be ensured even when the size is increased. ＩＣ The upper limit is not particularly limited, but for example, 1.00 MPa m １／２It may be the following:

[0041] In this specification, the fracture toughness value K ＩＣ The term refers to a value measured by the DCDC (Double Cleavage Drilled Compression) method (Acta metall. mater. Vol. 43, pp. 3453-3458, 1995) or the SEPB method specified in JIS R1607 (2015). The DCDC method can more accurately measure the fracture toughness value K than the SEPB method. ＩＣ Therefore, the fracture toughness value K ＩＣ is more preferably a value determined by the DCDC method.

[0042] The glass of this embodiment has a β-OH content of 1.0 mm －１ It is preferably equal to or less than 0.5 mm, and more preferably 0.5 mm －１ Less than 0.4 mm, more preferably －１ Below 0.3 mm, particularly preferably －１ β-OH is 1.0 mm or less. －１ By ensuring that the β-OH is equal to or less than 0.01 mm, the amount of platinum eluted into the glass from a platinum crucible, a platinum stirrer, or other manufacturing equipment using platinum can be increased, thereby improving the ultraviolet absorption effect. －１ That's all.

[0043] The β-OH content of glass is determined by measuring the transmittance of the glass using FT-IR and using the following formula:

[0044]

[0045] X: Glass thickness (mm) T １ :Reference wavelength 3846cm －１ Transmittance (%) at T ２ : Hydroxyl group absorption wavelength 3600 cm －１ Minimum transmittance (%) in the vicinity

[0046] In the glass of this embodiment, the "absolute value of warpage δ / length of glass in the warpage direction," which is the value obtained by dividing the absolute value of the warpage δ calculated based on the Bi-Metal warpage calculation defined by the following formula, by the length (mm) of the glass in the warpage direction, is preferably, for example, (b1) to (b4) below. (b1) When the length of the glass in the warpage direction is 1000 mm and the glass plate thickness is 0.1 mm, (absolute value of warpage δ / length of glass in the warpage direction) is preferably 0.30 or less, more preferably 0.20 or less, even more preferably 0.15 or less, particularly preferably 0.10 or less, and most preferably 0.05 or less. The smaller the (absolute value of warpage δ / length of glass in the warpage direction), the better, and there is no particular lower limit, but it is, for example, 0.001 or more. (b2) When the length of the glass in the warp direction is 1000 mm and the thickness of the glass is 0.05 mm, the ratio (absolute value of warp amount δ / length of glass in the warp direction) is preferably 0.20 or less, more preferably 0.15 or less, even more preferably 0.10 or less, and particularly preferably 0.05 or less. The smaller the ratio (absolute value of warp amount δ / length of glass in the warp direction), the better. The lower limit is not particularly limited, but for example, it is 0.001 or more. (b3) When the length of the glass in the warp direction is 500 mm and the thickness of the glass is 0.1 mm, the ratio (absolute value of warp amount δ / length of glass in the warp direction) is preferably 0.20 or less, more preferably 0.15 or less, even more preferably 0.10 or less, and particularly preferably 0.05 or less. The smaller the ratio (absolute value of warp amount δ / length of glass in the warp direction), the better. The lower limit is not particularly limited, but for example, it is 0.001 or more. (b4) When the length of the glass in the warp direction is 500 mm and the thickness of the glass is 0.05 mm, the ratio (absolute value of warp amount δ / length of glass in the warp direction) is preferably 0.20 or less, more preferably 0.15 or less, even more preferably 0.10 or less, and particularly preferably 0.05 or less. The smaller the ratio (absolute value of warp amount δ / length of glass in the warp direction), the better, and there is no particular lower limit, but it is, for example, 0.001 or more. In the above (b1) to (b4), by having the ratio (absolute value of warp amount δ / length of glass in the warp direction) be equal to or less than the upper limit, the functionality of the solar cell can be ensured even when the glass for solar cells is made thinner and larger.

[0047]

[0048] L: Length of glass in the warping direction [mm] α １ : Thermal expansion coefficient of solar cell [ppm / K] α ２ : Thermal expansion coefficient of glass [ppm / K] E １ : Young's modulus of solar cell [GPa] E ２ : Young's modulus of glass [GPa] T １ : Expected maximum temperature [℃] T ２ : Expected minimum temperature [℃] a １ : Thickness of solar cell [mm] a ２ : Glass plate thickness [mm] h: a １ +a ２ [mm] m:a １ / a ２ n:E １ / E ２ δ: Amount of warpage [mm]

[0049] The solar cell is a Sunpower "MAXEON ＴＭ It is assumed that single crystal silicon is used, with reference to "GENIII SOLAR CELLS." The thermal expansion coefficient and Young's modulus of the solar cell are α １ =3.2ppm / ℃, E １ = 190 GPa. The thermal expansion coefficient of glass is the average thermal expansion coefficient (ppm / °C) at 50 to 200°C. The thickness of the solar cell is assumed to be 0.15 mm.

[0050] The glass of the present embodiment has a temperature (T ２ ) is preferably 1800°C or less, more preferably 1750°C or less, and even more preferably 1700°C or less. ２ is usually 1400°C or higher.

[0051] The glass of the present embodiment has a temperature (T ４) is preferably 1550°C or less, more preferably 1500°C or less, further preferably 1450°C or less, 1400°C or less, 1350°C or less, and most preferably 1300°C or less. ４ is usually 800°C or higher.

[0052] In the glass of this embodiment, five 50 mm x 50 mm pieces of glass are cut from a piece of glass measuring 50 cm or more, starting from the center and five pieces near each of the four corners. The average flatness (Ra) of each 1 μm x 1 μm measured with an AFM is preferably 2.0 nm or less, more preferably 1.5 nm or less, even more preferably 1.0 nm or less, and even more preferably 0.8 nm or less. Having a flatness of 2.0 nm or less provides strength that makes the glass less likely to break during handling. A certain degree of roughness in the flatness can reduce static electricity between the glass and the interleaf paper sandwiched between the glass pieces during handling, so the lower limit of the average value is preferably 0.2 nm or more, more preferably 0.3 nm or more, even more preferably 0.4 nm or more, and even more preferably 0.5 nm or more.

[0053] <<Composition>> In the first to fourth embodiments, R ２ O(Li ２ O, Na ２ O and K ２ The total content of R and O is 0 to 3.5%. ２ O is preferably 3.4% or less, 3.3% or less, 3.2% or less, 3.1% or less, 3.0% or less, 2.9% or less, 2.8% or less, 2.7% or less, 2.6% or less, 2.5% or less, 2.4% or less, 2.3% or less, 2.2% or less, 2.1% or less, 2.0% or less, 1.9% or less, 1.8% or less, 1.7% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 1.1% or less, 1.0% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, or 0.1% or less.

[0054] In the fifth embodiment, R ２ O is preferably 0 to 3.5%. ２O is more preferably 3.4% or less, 3.3% or less, 3.2% or less, 3.1% or less, 3.0% or less, 2.9% or less, 2.8% or less, 2.7% or less, 2.6% or less, 2.5% or less, 2.4% or less, 2.3% or less, 2.2% or less, 2.1% or less, 2.0% or less, 1.9% or less, 1.8% or less, 1.7% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 1.1% or less, 1.0% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less.

[0055] R ２ By keeping O at 3.5% or less, the difference in thermal expansion coefficient between the silicon and glass used in the solar cell can be reduced, and warpage of the solar cell can be effectively improved even when the solar cell is enlarged. ２ The smaller the O content, the better, but from the viewpoint of manufacturability, the O content is, for example, 0.01% or more.

[0056] Li ２ O is an optional component that improves the Young's modulus and fracture toughness value of the glass and improves the mechanical properties. ２ When O is contained, the content is preferably 0.01% or more, more preferably 0.02% or more, even more preferably 0.03% or more, particularly preferably 0.04% or more, and most preferably 0.1% or more. In addition, from the viewpoint of reducing the difference in thermal expansion coefficient between silicon and glass and effectively improving warpage of solar cells even when they are enlarged, Li ２ The O content is preferably 2.0% or less, more preferably 1.5% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less.

[0057] Na ２ O is an optional component that improves the meltability of the glass and may be contained. ２When O is contained, the content is preferably 0.01% or more, more preferably 0.02% or more, even more preferably 0.05% or more, particularly preferably 0.5% or more, and most preferably 1.0% or more. In addition, from the viewpoint of reducing the difference in thermal expansion coefficient between silicon and glass and effectively improving warpage of solar cells even when they are enlarged, Na ２ The O content is preferably 2.0% or less, more preferably 1.5% or less, even more preferably 1.2% or less, and particularly preferably 1.1% or less.

[0058] K ２ O is an optional component that improves the meltability of the glass and may be contained. ２ When O is contained, the content is preferably 0.01% or more, more preferably 0.02% or more, further preferably 0.03% or more, and particularly preferably 0.05% or more. In addition, from the viewpoint of reducing the difference in thermal expansion coefficient between silicon and glass and effectively improving warpage of solar cells even when they are enlarged, K ２ The O content is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.5% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less.

[0059] Glass tends to be deteriorated by ultraviolet rays, electron beams, proton beams, and cosmic rays (e.g., gamma rays and alpha rays), resulting in a decrease in transmission characteristics. Therefore, the properties required for glass to be used as a cover glass for solar cells in space applications include the ability to transmit the spectral sensitivity wavelength range of solar cells, while blocking ultraviolet rays, electron beams, proton beams, and cosmic rays, and not having their transmission characteristics decreased by these rays.

[0060] CeO ２ is a component that improves the ultraviolet ray blocking effect and suppresses coloring due to electron beams. In the first, second, and fourth embodiments, from the viewpoint of sufficiently ensuring the coloring of the glass due to electron beams and the ultraviolet ray blocking effect, CeO ２ In the first, second and fourth embodiments, the content of CeO ２The contents of CeO are more preferably 0.2% or more, 0.4% or more, and 0.6% or more, in the following order, further preferably 0.8% or more, 1.0% or more, and 1.2% or more, in the following order, and particularly preferably 1.4% or more, 1.6% or more, and 1.8% or more, in the following order. ２ In the third and fifth embodiments, from the viewpoint of sufficiently ensuring the coloring of the glass by an electron beam and the ultraviolet ray shielding effect, the content of CeO ２ The content of CeO is preferably 0.1 to 10%. ２ The contents of CeO are more preferably 0.2% or more, 0.4% or more, and 0.6% or more, in the following order, further preferably 0.8% or more, 1.0% or more, and 1.2% or more, in the following order, and particularly preferably 1.4% or more, 1.6% or more, and 1.8% or more, in the following order. ２ The content is preferably 10% or less, more preferably 7% or less, even more preferably 6% or less, particularly preferably 5% or less, and most preferably 3% or less.

[0061] In this embodiment, the plate thickness is t (mm), and CeO ２ When the content of is defined as α (mass %), from the viewpoint of improving the ultraviolet ray shielding effect, α / t is preferably 0.2 to 200 mass % / mm. α / t is more preferably 5 mass % / mm or more, even more preferably 10 mass % / mm or more, and particularly preferably 15 mass % / mm or more. Furthermore, in this embodiment, α / t is more preferably 160 mass % / mm or less, even more preferably 120 mass % / mm or less, and particularly preferably 80 mass % / mm or less.

[0062] TiO ２ is a component that suppresses solarization caused by UVC. In the first and second embodiments, TiO ２In the first and second embodiments, from the viewpoint of further suppressing solarization due to UVC, the content of TiO ２ The contents of TiO are preferably 0.30% or more, 0.50% or more, and 0.70% or more, in the following order, more preferably 1.0% or more, 1.2% or more, and 1.4% or more, in the following order, and even more preferably 1.5% or more, 2.0% or more, 3.0% or more, 4.0% or more, and 5.0% or more, in the following order. ２ The content of TiO is more preferably 7% or less, further preferably 6% or less, and particularly preferably 5% or less. ２ In the third and fifth embodiments, from the viewpoint of further suppressing solarization due to UVC, TiO ２ The content of TiO is preferably 5.5% or more, more preferably 6.0% or more, and even more preferably 7% or more. In the third and fifth embodiments, from the viewpoint of further suppressing UVC solarization and preventing coloring of the glass, TiO ２ The content of TiO is preferably 9.0% or less, more preferably 8.5% or less, even more preferably 8.0% or less, and particularly preferably 7.5% or less. ２ In the fourth embodiment, from the viewpoint of further suppressing solarization due to UVC, TiO ２ The contents of TiO are preferably 0.30% or more, 0.50% or more, and 0.70% or more, in the following order, more preferably 1.0% or more, 1.2% or more, and 1.4% or more, in the following order, and even more preferably 1.5% or more, 2.0% or more, and 3.0% or more, in the following order. ２ The content is more preferably 7.0% or less, further preferably 6.0% or less, and particularly preferably 5.0% or less.

[0063] In the first, second, and fourth embodiments, the plate thickness is represented by t (mm), and the TiO ２ When the content of TiO in the glass composition is defined as β (mass %), from the viewpoint of suppressing solarization by UVC, β / t is preferably 0.005 to 200 mass % / mm. In the first, second, and fourth embodiments, β / t is more preferably 1 mass % / mm or more, even more preferably 5 mass % / mm or more, and particularly preferably 10 mass % / mm or more. In the first, second, and fourth embodiments, β / t is more preferably 160 mass % / mm or less, even more preferably 120 mass % / mm or less, and particularly preferably 80 mass % / mm or less. In the third and fifth embodiments, when the plate thickness is defined as t (mm), the content of TiO in the glass composition is preferably 0.005 to 200 mass % / mm ... fourth embodiment, when the plate thickness is defined as t (mm), the content of TiO in the glass composition is preferably 0.005 to 200 mass % / mm. ２ When the content of is defined as β (mass %), from the viewpoint of suppressing solarization by UVC, β / t is preferably 10 to 200 mass % / mm. In the third and fifth embodiments, β / t is more preferably 50 mass % / mm or more, even more preferably 100 mass % / mm or more, and particularly preferably 150 mass % / mm or more. Furthermore, in the third and fifth embodiments, β / t is more preferably 190 mass % / mm or less, even more preferably 180 mass % / mm or less, and particularly preferably 170 mass % / mm or less.

[0064] In the glass of this embodiment, from the viewpoint of further enhancing the ultraviolet shielding effect and shifting the wavelength at which transmittance in the ultraviolet region reaches 50% to the longer wavelength side, the value of X represented by the following formula is preferably 0.5 or more and 50 or less. The value of X is more preferably 40 or less, even more preferably 35 or less, and particularly preferably 30 or less. The value of X is more preferably 1 or more, even more preferably 3 or more, and particularly preferably 5 or more. (Formula) X=5×[CeO ２ ]+[TiO ２ In the above formula, the brackets [ ] indicate the content expressed as a mass percentage based on the oxide.

[0065] SiO ２ is an essential component that constitutes the glass skeleton. ２In the first and fifth embodiments, the content of SiO ２ The content of SiO is more preferably 51% or more, further preferably 52% or more, particularly preferably 53% or more, and most preferably 55% or more. ２ The content of SiO is more preferably 75% or less, even more preferably 70% or less, particularly preferably 65% ​​or less, and most preferably 60% or less. ２ By making the content of SiO 50% or more, chemical durability can be improved. ２ By making the content of T 80% or less, ２ or T ４ In the second to fourth embodiments, the SiO ２ In the second to fourth embodiments, the content of SiO ２ The content of is preferably 51% or more, more preferably 52% or more, even more preferably 53% or more, and particularly preferably 55% or more. ２ The content of SiO is preferably 75% or less, more preferably 70% or less, even more preferably 65% ​​or less, and particularly preferably 60% or less. ２ By making the content of SiO 50% or more, chemical durability can be improved. ２ By making the content of T 80% or less, ２ or T ４ This can suppress an increase in the melting point of the glass and improve the melting property or formability of the glass.

[0066] B ２ O ３ may be contained in order to improve the melting property at high temperatures or the strength of the glass. ２ O ３ If the content of B is large, the Young's modulus decreases, the fracture toughness decreases, and the strength tends to decrease. In addition, the glass tends to undergo phase separation, the transparency is lost, and it becomes difficult to obtain a homogeneous glass, which may decrease the formability of the glass. ２ O ３When B is contained, its content is preferably 25% or less, more preferably 20% or less, even more preferably 18% or less, particularly preferably 17% or less, 16% or less, 15% or less, 14% or less, 13% or less, 12% or less, in the following order, and most preferably 10% or less. ２ O ３ In the second to fourth embodiments, the content of B is 0 to 25%. ２ O ３ The content of B is preferably 20% or less, more preferably 17% or less, even more preferably 15% or less, particularly preferably 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, in the following order, and most preferably 8% or less. ２ O ３ From the viewpoint of improving meltability at high temperatures or glass strength, the content is, for example, preferably 0.5% or more, more preferably 1% or more, even more preferably 2% or more, particularly preferably 3% or more, and most preferably 4% or more.

[0067] Al ２ O ３ is a component that improves the mechanical properties of glass, such as Young's modulus and fracture toughness, and improves weather resistance. ２ When added together with Al, it is also a component that deteriorates devitrification resistance. ２ O ３ The content of Al is preferably 0 to 30%. ２ O ３ The content of Al is 0 to 30%. ２ O ３ By making it 30% or less, T ２ or T ４ In the first to fifth embodiments, the Al ２ O ３When it contains Al, it is preferably 1% or more, more preferably 2% or more, even more preferably 4% or more, and particularly preferably 5% or more, 5.5% or more, 6% or more, 6.5% or more, 7% or more, 7.5% or more, 8% or more, 9% or more in the following order. ２ O ３ The content of Al is more preferably 25% or less, and further preferably 20% or less. ２ O ３ By making it 30% or less, T ２ or T ４ In the second to fourth embodiments, the Al ２ O ３ The content is preferably 25% or less, more preferably 23% or less, and even more preferably 20% or less.

[0068] As ２ O ３ is a component that promotes solarization and is an optional component. In this embodiment, from the viewpoint of suppressing solarization and from the viewpoint of SDGs, As ２ O ３ The As content is preferably 0.25% or less, more preferably 0.10% or less, and further preferably 0.05% or less. ２ O ３ Although there is no particular lower limit for the content, from the viewpoint of fining, when contained, it is preferably 0.001% or more.

[0069] Sb ２ O ３ is a component that functions as a fining agent. In this embodiment, from the viewpoint of SDGs, Sb ２ O ３ The content of Sb is preferably 0.25% or less, more preferably 0.2% or less, and further preferably 0.1% or less. ２ O ３ Although there is no particular lower limit for the content, from the viewpoint of fining, when contained, it is preferably 0.001% or more.

[0070] In this embodiment, from the perspective of SDGs, ２ O３ and Sb ２ O ３ The total content is preferably 0% or more and less than 0.25%, more preferably 0% or more and 0.2% or less, even more preferably 0% or more and 0.1% or less, and particularly preferably 0% or more and 0.05% or less.

[0071] SnO ２ is a component that suppresses solarization. ２ The content of SnO is preferably 0.01% or more and 0.4% or less. ２ The content of SnO is more preferably 0.02% or more, further preferably 0.05% or more, and particularly preferably 0.1% or more. ２ The content is more preferably 0.3% or less, and further preferably 0.2% or less.

[0072] Fe ２ O ３ is an optional component, but may be contained from the viewpoint of enhancing the ultraviolet ray shielding effect and suppressing coloration due to electron beams. On the other hand, it is also a component that reduces the transmittance in the visible to near-infrared range and reduces the power generation efficiency. ２ O ３ The content of is preferably 3% or less, more preferably 2% or less, 1.5% or less, 1% or less, 0.8% or less, 0.6% or less, 0.4% or less, 0.2% or less, 0.1% or less, 0.09% or less, 0.08% or less, 0.07% or less, 0.06% or less, 0.05% or less, 0.04% or less, 0.03% or less, 0.02% or less, 0.01% or less. There is no particular lower limit on the content, but from the viewpoint of the ultraviolet ray shielding effect and suppression of coloring due to electron beams, when contained, it is preferably 0.001% or more, more preferably 0.002% or more, 0.003% or more, 0.004% or more. Fe ２ O ３ By setting the content of Fe to 0.001% or more, it is possible to ensure the ultraviolet ray blocking effect and further suppress coloring due to electron beams. ２ O ３By setting the content to 3% or less, the visible light transmittance can be increased.

[0073] The glass of this embodiment contains CeO ２ When the compound contains CeO, the value of Y represented by the following formula is preferably 0 or more and 1300 or less, from the viewpoint of further enhancing the ultraviolet ray shielding effect and controlling the redox state of Ce. The value of Y is more preferably 1200 or less, even more preferably 1000 or less, and particularly preferably 800 or less. The value of Y is more preferably 100 or more, even more preferably 300 or more, and particularly preferably 500 or more. (Formula) Y=[CeO ２ ] / [Fe ２ O ３ In the above formula, the brackets [ ] indicate the content expressed as a mass percentage based on the oxide.

[0074] MgO is an optional component that suppresses a decrease in strength or improves meltability. In this embodiment, when MgO is contained, its content is preferably 0.5% or more, more preferably 1.0% or more, even more preferably 1.5% or more, and particularly preferably 2.0% or more. In this embodiment, the MgO content is preferably 13% or less, more preferably 12.5% ​​or less, even more preferably 12% or less, and particularly preferably 11.5% or less, 11% or less, 10.5% or less, 10% or less, 9.5% or less, 9% or less, 8.5% or less, 8% or less, 7.5% or less, and 7% or less, in that order.

[0075] BaO is a component that improves meltability at high temperatures or makes devitrification less likely to occur, and may be contained. In this embodiment, the content of BaO is preferably 0% or more and 6.5% or less. When BaO is contained, its content is more preferably 0.5% or more, even more preferably 1.0% or more, and particularly preferably 1.5% or more. From the viewpoint of suppressing an increase in specific gravity, the content of BaO is more preferably 5.0% or less, even more preferably 4.0% or less, and particularly preferably 3.0% or less.

[0076] CaO may be contained to improve meltability at high temperatures or to make devitrification less likely to occur. In this embodiment, when CaO is contained, its content is preferably 0.5% or more, more preferably 1.0% or more, even more preferably 1.5% or more, and particularly preferably 2.0% or more. In this embodiment, the CaO content is preferably 13% or less, more preferably 12.5% ​​or less, even more preferably 12% or less, and particularly preferably 11.5% or less, 11% or less, 10.5% or less, 10% or less, 9.5% or less, 9% or less, 8.5% or less, 8% or less, 7.5% or less, and 7% or less, in that order.

[0077] SrO may be contained to improve meltability at high temperatures or to make devitrification less likely to occur. In this embodiment, when SrO is contained, its content is more preferably 0.5% or more, even more preferably 1.0% or more, and particularly preferably 1.5% or more. From the viewpoint of suppressing an increase in specific gravity, the SrO content is preferably 8% or less, more preferably 6% or less, even more preferably 4% or less, particularly preferably 2% or less, and most preferably 0.1% or less.

[0078] In the present embodiment, when one or more of BaO, CaO, and SrO are contained, the total content of these three components is preferably 10% or less, more preferably 8% or less, 6% or less, 4% or less, or 2% or less.

[0079] From the viewpoint of increasing the transmittance in the wavelength range of 300 to 1100 nm and improving the power generation efficiency of the solar cell, it is preferable that NiO is substantially not contained. In this embodiment, when NiO is contained, the content thereof is preferably 1% or less, more preferably 0.5% or less, even more preferably 0.1% or less, and still more preferably 0.08% or less.

[0080] ZrO ２ is not an essential component, but may be contained in an amount of 1.6% or less in order to reduce viscosity at high temperatures, improve chemical durability, etc. ２ When the content of ZrO is 1.6% or less, a decrease in strength can be suppressed. ２The content is more preferably 1.5% or less, further preferably 1.4% or less, particularly preferably 1.3% or less, and most preferably 1.1% or less.

[0081] ZnO may be contained to improve the meltability of the glass at high temperatures, but in that case, the content is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.25% or less. When produced by the float process, the ZnO content is preferably 0.5% or less, more preferably 0.25% or less, and even more preferably substantially no ZnO is contained, and most preferably 0%. By keeping the ZnO content at 1% or less, reduction during float forming can be suppressed, and the occurrence of product defects can be prevented.

[0082] V ２ O ５ may be contained in order to improve the ultraviolet ray shielding effect. ２ O ５ When V is contained, its content is preferably 0.01% or more, more preferably 0.05% or more, even more preferably 0.1% or more, and particularly preferably 0.2% or more. ２ O ５ When it is contained, the content is preferably 1.0% or less, more preferably 0.8% or less, further preferably 0.6% or less, and particularly preferably 0.4% or less.

[0083] SO 4 is used as a fining agent when melting glass. ３ However, in order to improve the power generation efficiency of solar cells when used as a cover glass for solar cells, Cr, which has absorption in the wavelength range of 300 to 1100 nm, may be contained. ２ O ３ It is preferable to reduce the amount of such components that are mixed in as impurities in the raw materials as much as possible, and if they are contained, it is preferable that the amount is 0.15% or less, more preferably 0.1% or less, and particularly preferably 0.05% or less.

[0084] Examples of the glass of the first embodiment include the following (1a) to (1c): (1a) In terms of mass percentage based on oxides, Li ２ O, Na ２ O and K ２ The total content of O is 0 to 3.5%, and CeO ２ (1b) In terms of mass percentage based on oxides, Li ２ O, Na ２ O and K ２ The total content of O is 0 to 3.5%, and CeO ２ 0.1 to 10%, TiO ２ (1c) An embodiment containing 5 to 10% of Li ２ O, Na ２ O and K ２ The total content of O is 0 to 3.5%, and CeO ２ 0.1 to 10%, TiO ２ An embodiment containing 0.01 to 10%.

[0085] Specific examples of the composition of the glass according to this embodiment include the following: (1) In terms of mass percentage based on oxides, SiO ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, CeO ２ Contains 0.1 to 10% of R ２ (2) Glass containing 0 to 3.5% of O. In terms of mass percentage based on oxides, SiO ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, TiO ２ Contains 5 to 10% of R ２ (3) Glass containing 0 to 3.5% of O. In terms of mass percentage based on oxides, SiO ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, TiO ２ 0.01 to 10%, CeO２ Contains 0.1 to 10% of R ２ A glass containing 0 to 3.5% O.

[0086] <Glass Manufacturing Method> The glass of this embodiment can be manufactured by a conventional method. For example, raw materials for the glass components are blended and heated and melted in a glass melting furnace. The glass is then homogenized by a known method, formed into a desired shape such as a glass plate, and slowly cooled.

[0087] Examples of glass sheet forming methods include the float method, press method, fusion method, and down-draw method. In particular, the float method, which is suitable for mass production, is preferred. Continuous forming methods other than the float method, i.e., the fusion method and down-draw method, are also preferred.

[0088] The molded glass is then subjected to grinding, polishing, and etching to form a glass substrate. The thickness of the glass substrate can be adjusted to a desired thickness by adjusting the conditions of the treatments. Specific examples of etching include a method in which the glass substrate is immersed in a solution containing hydrofluoric acid or the like to etch the glass substrate, thereby polishing the glass surface.

[0089] The glass of this embodiment preferably has a conductive film on at least one surface. The conductive film may contain, for example, In. ２ O ３ , SnO ２ , ZnO, etc. The thickness of the conductive film is preferably 10,000 nm or less, more preferably 80,000 nm or less, 50,000 nm or less, 10,000 nm or less, 5,000 nm or less, 1,000 nm or less, 500 nm or less, 100 nm or less. The lower limit of the film thickness is not particularly specified, but is, for example, 1 nm or more, more preferably 5 nm or more, 10 nm or more.

[0090] The glass of this embodiment preferably has an anti-reflection film on at least one surface. Examples of the components of the anti-reflection film include MgF ２ , CrNi, Ag, SiO Ｘ , TiO Ｘ , Ta ２ O ５ , Al ２ O３ Examples include:

[0091] The antireflection film is not limited to a single layer, but may be a multi-layer film made up of a combination of multiple components. The thickness of the antireflection film is preferably 10,000 nm or less, more preferably 80,000 nm or less, 50,000 nm or less, 10,000 nm or less, 5,000 nm or less, 1,000 nm or less, 500 nm or less, or 100 nm or less. The lower limit of the film thickness is not particularly specified, but is, for example, 1 nm or more, more preferably 5 nm or more, or 10 nm or more.

[0092] <Uses> The glass of this embodiment is suitable for use as a cover glass for solar cells (for example, a cover glass for solar cells on a space satellite), an electron beam blocking glass, or an ultraviolet ray blocking glass. The glass of this embodiment is superior to conventional glasses in electron beam resistance and ultraviolet ray blocking effect, and also has excellent strength and can be made large, making it particularly suitable as a cover glass for solar cells, which require these properties.

[0093] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0094] (Glass Preparation) Commonly used glass raw materials such as oxides, hydroxides, carbonates, or nitrates were appropriately selected to obtain the glass compositions shown in Tables 1 to 6, expressed in mass percentages based on oxides, and placed in a platinum crucible. The mixture was melted by heating to a high temperature of 1550 to 1650°C or higher in an electric furnace, and the molten glass was then poured onto a carbon mold and held at Tg + 50°C for 1 hour, followed by cooling at a rate of 1.0°C / min to obtain a glass block. The obtained glass block was cut, ground, and polished to prepare glass samples of predetermined sizes, and their physical properties were evaluated.

[0095] (Evaluation of Characteristics) The properties of the obtained glass substrates were evaluated by the following procedures.

[0096] [Specific Gravity] The specific gravity was measured by the Archimedes method.

[0097] [Young's Modulus] Young's modulus was measured by an ultrasonic pulse method (JIS R1602, 1995) using a glass substrate measuring 30 mm length x 30 mm width x 1 mm thickness.

[0098] [Average coefficient of thermal expansion CTE (50-200) [ppm / K]] Measured using a differential thermal dilatometer in accordance with the method specified in JIS R3102 (1995). The measurement temperature range was 50 to 200°C, and the unit was "×10 －６ The measurement was carried out using a glass substrate having a size of 25 mm length x 6 mm width x 0.8 mm thickness.

[0099] [β-OH] The transmittance of the glass sample was measured using FT-IR and calculated using the following formula: For the measurement, a glass substrate measuring 30 mm length x 30 mm width x 1 mm thickness was used.

[0100]

[0101] X: Glass thickness (mm) T １ :Reference wavelength 3846cm －１ Transmittance (%) at T ２ : Hydroxyl group absorption wavelength 3600 cm －１ Minimum transmittance (%) in the vicinity

[0102] [K ＩＣ The fracture toughness value was measured using the DCDC method (Acta metall. mater. Vol. 43, pp. 3453-3458, 1995).

[0103] [Transmittance] The transmittance was measured using a spectrophotometer (product name U-4100) manufactured by Hitachi High-Tech Corp. For the measurement, glass substrates with dimensions of 25 mm length × 25 mm width × 100 μm thickness and 25 mm length × 25 mm width × 50 μm thickness were used.

[0104] [Average absorbance change at wavelengths of 400 to 800 nm upon electron beam irradiation (value converted to plate thickness of 100 μm)] Electron beam irradiation was performed by placing a glass substrate to be irradiated horizontally on a table, and using an electron beam irradiation device (manufactured by NHV Corporation, model number: EPS-3000 kV), irradiating the glass substrate with an electron beam at an energy of 1 MeV at a rate of 1×10 １５pieces / cm ２ The measurement was carried out by irradiating an electron beam of 100 μm in thickness onto a glass substrate measuring 20 mm in length, 20 mm in width, and 0.5 mm in thickness. The transmittance was measured before electron beam irradiation, and then the transmittance was measured again after electron beam irradiation for each glass substrate. The measurement was carried out within one week of electron beam irradiation. The absorbance before and after electron beam irradiation was calculated from the measured transmittance and converted to absorbance at a plate thickness of 100 μm. The average change in absorbance at wavelengths of 400 to 800 nm was then calculated using the following formula:

[0105]

[0106] [Amount of Warpage] For each glass example, the amount of warpage was calculated based on the Bi-Metal warpage calculation defined by the following formula. Specifically, the absolute value of the amount of warpage δ was calculated using the following formula.

[0107]

[0108] L: Length of glass in the warping direction [mm] α １ : Thermal expansion coefficient of solar cell [ppm / K] α ２ : Thermal expansion coefficient of glass [ppm / K] E １ : Young's modulus of solar cell [GPa] E ２ : Young's modulus of glass [GPa] T １ : Expected maximum temperature [℃] T ２ : Expected minimum temperature [℃] a １ : Thickness of solar cell [mm] a ２ : Glass plate thickness [mm] h: a １ +a ２ [mm] m:a １ / a ２ n:E １ / E ２ δ: Amount of warpage [mm]

[0109] The solar cell is a Sunpower "MAXEON ＴＭ It was assumed that single crystal silicon was used, with reference to "GENIII SOLAR CELLS." Therefore, the thermal expansion coefficient and Young's modulus of the solar cell were set to α １ =3.2ppm / ℃, E １= 190 GPa. The thermal expansion coefficient of glass was the average thermal expansion coefficient (ppm / °C) at 50 to 200°C. The thickness of the solar cell was assumed to be 0.15 mm.

[0110] Tables 1 to 6 show the results of evaluating the glass compositions and properties in terms of mass percentage based on oxides. Figure 1 shows the correlation between the average thermal expansion coefficient and (absolute value of warpage δ / length of glass in the warpage direction).

[0111] In Tables 1 to 6, Examples 1 to 39 are working examples, and Examples 40 to 42 are comparative examples. In Tables 1 to 6, italics indicate calculated values, and "-" indicates unevaluated values.

[0112] When considering the transmittance at 50 μm from the transmittance at 100 μm, the transmittance can be calculated according to the Beer-Lambert law by assuming that the amount of light-absorbing elements is halved.

[0113]

[0114]

[0115]

[0116]

[0117]

[0118]

[0119] As shown in Tables 1 to 6, Examples 1 to 39, which are working examples, had similar specific gravities and Young's moduli to Comparative Examples 40 to 42, and also had smaller changes in average absorbance at wavelengths of 400 to 800 nm during electron beam irradiation, and lower values ​​of (absolute value of warpage δ / length of glass in the warpage direction). These results demonstrate that the glass of the present embodiment can effectively suppress warpage of solar cells, even when the glass is made larger and thinner and used in solar cells.

[0120] As explained above, the present specification discloses the following: 1. A specific gravity of 2.2 to 2.7, a Young's modulus of 60 GPa or more, and an average thermal expansion coefficient of 2.0 to 6.0 (×10 －６ / K), one side of the main surface is a rectangle of 50 cm or more and 300 cm or less, and the plate thickness is 0.01 mm or more and 0.5 mm or less, and expressed in mass percentage based on oxides, ２ O, Na ２ O and K ２ The total content of O is 0 to 3.5%, and CeO ２ 2. Glass containing 0.1 to 10% of TiO, expressed as a mass percentage based on oxides. ２ 3. The glass according to 1 above, containing 0.01 to 10% of TiO, expressed as a mass percentage based on oxides. ２ 4. The glass according to 1 or 2 above, containing 5 to 10% of the above. 4. The glass according to 1 or 2 above, having a specific gravity of 2.2 to 2.7, a Young's modulus of 60 GPa or more, and an average thermal expansion coefficient at 50 to 200°C of 2.0 to 6.0 (×10 －６ / K), a rectangular shape with one side of the main surface being 50 cm or more and 300 cm or less, and a thickness of 0.01 mm or more and 0.5 mm or less, and expressed as a mass percentage based on oxides, ２ Glass containing 5 to 10% of SiO. 5. Mass percentage based on oxides: ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, and CeO ２ Contains 0.1 to 10% of Li ２ O, Na ２ O and K ２ 5. Glass with a total O content of 0 to 3.5%, a rectangular main surface with one side of 50 cm to 300 cm, and a thickness of 0.01 mm to 0.5 mm. 6. In terms of mass percentage based on oxides, SiO ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, TiO ２ Contains 5 to 10% of Li ２ O, Na ２ O and K ２7. Glass with a total O content of 0 to 3.5%, a rectangular main surface with one side of 50 cm to 300 cm, and a thickness of 0.01 mm to 0.5 mm. 8. In terms of mass percentage based on oxides, SiO ２ 50-80% of B ２ O ３ 0 to 25%, Al ２ O ３ 0 to 30%, TiO ２ 0.01 to 10% and CeO ２ Contains 0.1 to 10% of Li ２ O, Na ２ O and K ２ 8. Glass having a total O content of 0 to 3.5%, a rectangular main surface with one side of 50 cm to 300 cm, and a thickness of 0.01 mm to 0.5 mm. 9. An average thermal expansion coefficient at 50 to 200°C of 2.0 to 6.0 (×10 －６ 9. The glass according to any one of 5 to 7 above, wherein As is expressed as a mass percentage based on oxides and is: ２ O ３ and Sb ２ O ３ 9. The glass according to any one of 1 to 8 above, wherein the total content of SnO is 0% or more and less than 0.25%, expressed as a mass percentage based on oxides. ２ 11. The glass according to any one of 1 to 9 above, containing 0.01 to 0.4% or less of BaO. 12. The glass according to any one of 1 to 11 above, wherein the average absorbance change at wavelengths of 400 to 800 nm upon electron beam irradiation is converted into a plate thickness of 100 μm of 0.01 or less. 13. The glass according to any one of 1 to 11 above, wherein the average absorbance change at wavelengths of 400 to 800 nm upon electron beam irradiation is converted into a plate thickness of 100 μm of 0.01 or less. 14. The glass according to any one of 1 to 9 above, wherein the average absorbance change at wavelengths of 400 to 800 nm upon electron beam irradiation is converted into a plate thickness of 100 μm of 0.01 or less. Ｉｃ ) is 0.78 MPa m １／２ 14. The glass according to any one of 1 to 13 above, wherein the value obtained by subtracting the transmittance of light at a wavelength of 300 nm from the transmittance of light at a wavelength of 400 nm is 50% or more. 15. The glass according to any one of 1 to 14 above, wherein the value E / ρ obtained by dividing Young's modulus E (GPa) by specific gravity ρ is 27.0 GPa or more. 16. The glass according to any one of 1 to 14 above, wherein β-OH is 1.0 mm－１ The glass as described in any one of 1 to 15 above, which is the following: 17. The glass as described in any one of 1 to 16 above, which has a conductive film on at least one surface. 18. The glass as described in any one of 1 to 17 above, which has an anti-reflection film on at least one surface. 19. A cover glass for a space satellite solar cell, which uses the glass as described in any one of 1 to 18 above. 20. An ultraviolet-blocking glass, which uses the glass as described in any one of 1 to 18 above. 21. An electron-beam-blocking glass, which uses the glass as described in any one of 1 to 18 above.

[0121] This application is based on Japanese Patent Application No. 2023-152237 filed on September 20, 2023, the contents of which are incorporated herein by reference.

Claims

1. Specific gravity is 2.2 to 2.7, Young's modulus is 60 GPa or more, and the average thermal expansion coefficient at 50 to 200°C is 2.0 to 6.0 (x10 －６ / K), one side of the main surface is a rectangle of 50 cm to 300 cm, and the plate thickness is 0.01 mm to 0.5 mm, and expressed as a mass percentage based on oxide, ２ O, Na ２ O and K ２ The total content of O is 0 to 3.5%, and CeO ２ A glass containing 0.1 to 10% of 2. Mass percentage based on oxide: TiO ２ The glass according to claim 1, containing 0.01 to 10%.

3. Mass percentage based on oxide: TiO ２ The glass according to claim 1, containing 5 to 10%.

4. Specific gravity is 2.2 to 2.7, Young's modulus is 60 GPa or more, and the average thermal expansion coefficient at 50 to 200°C is 2.0 to 6.0 (x10 －６ / K), one side of the main surface is a rectangle of 50 cm to 300 cm, and the thickness is 0.01 mm to 0.5 mm, and expressed as a mass percentage based on oxides, ２ Glass containing 5 to 10%.

5. Mass percentage based on oxide: SiO ２ 50-80% B ２ O ３ 0 to 25% Al ２ O ３ 0 to 30%, and CeO ２ Contains 0.1 to 10% Li ２ O, Na ２ O and K ２ A glass having a total O content of 0 to 3.5%, a principal surface of which is rectangular with one side of 50 cm or more and 300 cm or less, and a plate thickness of 0.01 mm or more and 0.5 mm or less.

6. Mass percentage based on oxide: SiO ２ 50-80% B ２ O ３ 0 to 25% Al ２ O ３ 0 to 30%, TiO ２ Contains 5 to 10% Li ２ O, Na ２ O and K ２ A glass having a total O content of 0 to 3.5%, a principal surface of which is rectangular with one side of 50 cm or more and 300 cm or less, and a plate thickness of 0.01 mm or more and 0.5 mm or less.

7. Mass percentage based on oxide: SiO ２ 50-80% B ２ O ３ 0 to 25% Al ２ O ３ 0 to 30%, TiO ２ 0.01 to 10% and CeO ２ Contains 0.1 to 10% of Li ２ O, Na ２ O and K ２ A glass having a total O content of 0 to 3.5%, a principal surface of which is rectangular with one side of 50 cm or more and 300 cm or less, and a plate thickness of 0.01 mm or more and 0.5 mm or less.

8. The average thermal expansion coefficient at 50 to 200°C is 2.0 to 6.0 (x10 －６ / K).

9. As expressed as mass percentage based on oxide ２ O ３ and Sb ２ O ３ The glass according to any one of claims 1 to 7, wherein the total content of is 0% or more and less than 0.25%.

10. Mass percentage based on oxide: SnO ２ The glass according to any one of claims 1 to 7, comprising 0.01 to 0.4% or less of 11. The glass according to any one of claims 1 to 7, wherein the content of BaO is 0% or more and 6.5% or less, expressed as a mass percentage based on oxides.

12. The glass according to any one of claims 1 to 7, wherein the average change in absorbance at wavelengths of 400 to 800 nm upon irradiation with electron beams is 0.01 or less in terms of a plate thickness of 100 µm.

13. Fracture toughness value (K Ｉｃ ) is 0.78MPa m １／２ The glass according to any one of claims 1 to 7.

14. The glass according to any one of claims 1 to 7, wherein the value obtained by subtracting the transmittance of light at a wavelength of 300 nm from the transmittance of light at a wavelength of 400 nm is 50% or more.

15. The glass according to any one of claims 1 to 7, wherein the value E / ρ obtained by dividing Young's modulus E (GPa) by specific gravity ρ is 27.0 GPa or more.

16. β-OH is 1.0 mm －１ 8. The glass according to claim 1 , wherein:

17. The glass according to any one of claims 1 to 7, having a conductive film on at least one surface.

18. The glass according to any one of claims 1 to 7, having an anti-reflective coating on at least one surface.

19. A cover glass for a solar cell of a space satellite, which uses the glass according to any one of claims 1 to 7.

20. An ultraviolet ray blocking glass comprising the glass according to any one of claims 1 to 7.

21. An electron beam blocking glass comprising the glass according to any one of claims 1 to 7.

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