Glass

Abstract

The purpose of the present invention is to provide a glass with which it is possible to suppress warpage of a solar cell and to suppress deterioration in mechanical and optical characteristics even when the glass is reduced in thickness and size. The glass has a specific gravity of 2.2-2.7, a Young's modulus of 60 GPa or more, and an average thermal expansion coefficient of 2.0-6.0 (* 10 <-6 > / K) at 50-200 DEG C, is a rectangle in which one side of the main surface is 50-300 cm, has a plate thickness of 0.01-0.5 mm, has a total content of Li2O, Na2O, and K2O of 0-3.5% in terms of mass fraction on the basis of oxides, and contains 0.1-10% of CeO2.

Description

Technical Field

[0001] This invention relates to glass, and more particularly to glass suitable for use in solar cells, ultraviolet light blocking glass, electron beam blocking glass, etc., for use in space satellites. Background Technology

[0002] Satellite constellations are a method of networking hundreds to thousands of satellites to achieve functions or services. Because building a satellite constellation requires multiple satellites, the cost of these satellites must be minimized. As a power source for these satellites, research has focused on photovoltaic power generation using solar cells. Solar cells typically use silicon, and these cells utilize cover glass to protect the components.

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

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 63-95138

[0007] Patent Document 2: International Publication No. 2023 / 022074 Summary of the Invention

[0008] Glass, especially in the application of space solar cells, demands low satellite cost. From a cost reduction perspective, this can be achieved by making the glass thinner and larger. On the other hand, due to the thinning and enlargement of the glass, it is estimated that the warping of the solar cells will be greater than in existing products due to the difference in thermal expansion coefficients between the silicon used in the solar cells and the glass. In addition, the thinning of the glass results in some deficiencies in mechanical and optical properties compared to existing products.

[0009] Therefore, the object of the present invention is to provide a glass that can suppress the warping of solar cells while suppressing the reduction of mechanical and optical properties, even when the glass is made thinner and larger.

[0010] The inventors discovered that the above-mentioned problems could be solved by making the composition of the glass within a specific range, thus completing the present invention. That is, the present invention is as follows.

[0011] 1. A glass having a specific gravity of 2.2–2.7, a Young's modulus of 60 GPa or higher, and an average coefficient of thermal expansion of 2.0–6.0 (×10⁻⁶) at 50–200 °C. －6 / K),

[0012] It is a rectangle with one side of the main surface measuring 50cm to 300cm, and the board thickness is 0.01mm to 0.5mm.

[0013] The total content of Li2O, Na2O and K2O is 0 to 3.5% by mass, expressed as an oxide basis, and contains 0.1 to 10% CeO2.

[0014] 2. The glass according to claim 1 above, wherein, expressed as a mass percentage based on oxides, it contains 0.01 to 10% TiO2.

[0015] 3. The glass according to claim 1 above, wherein, expressed as a mass percentage based on oxides, it contains 5 to 10% TiO2.

[0016] 4. A glass having a specific gravity of 2.2–2.7, a Young's modulus of 60 GPa or higher, and an average coefficient of thermal expansion of 2.0–6.0 (×10⁻⁶) at 50–200 °C. －6 / K),

[0017] It is a rectangle with one side measuring 50cm to 300cm, and a thickness of 0.01mm to 0.5mm.

[0018] It contains 5-10% TiO2, expressed as a mass percentage based on oxides.

[0019] 5. A glass, expressed as a mass percentage based on oxides, contains 50–80% SiO2, 0–25% B2O3, 0–30% Al2O3, and 0.1–10% CeO2, and the total content of Li2O, Na2O, and K2O is 0–3.5%.

[0020] It is a rectangle with one side of the main surface being 50cm to 300cm, and the thickness of the plate is 0.01mm to 0.5mm.

[0021] 6. A glass, expressed as a mass percentage based on oxides, contains 50-80% SiO2, 0-25% B2O3, 0-30% Al2O3, 5-10% TiO2, and a total content of 0-3.5% for Li2O, Na2O, and K2O.

[0022] It is a rectangle with one side of the main surface being 50cm to 300cm, and the thickness of the plate is 0.01mm to 0.5mm.

[0023] 7. A glass, expressed as a mass percentage based on oxides, contains 50–80% SiO2, 0–25% B2O3, 0–30% Al2O3, 0.01–10% TiO2, and 0.1–10% CeO2, and the total content of Li2O, Na2O, and K2O is 0–3.5%.

[0024] It is a rectangle with one side of the main surface being 50cm to 300cm, and the thickness of the plate is 0.01mm to 0.5mm.

[0025] 8. The glass according to any one of claims 5 to 7 above, wherein the average coefficient of thermal expansion at 50 to 200°C is 2.0 to 6.0 (×10⁻⁶). －6 / K).

[0026] 9. The glass according to any one of 1 to 7 above, wherein the total content of As2O3 and Sb2O3, expressed as a mass percentage based on oxides, is 0% or more and less than 0.25%.

[0027] 10. The glass according to any one of 1 to 7 above, wherein it contains SnO2 at a mass percentage of 0.01 to 0.4% based on oxides.

[0028] 11. The glass according to any one of 1 to 7 above, wherein the BaO content, expressed as a mass percentage based on oxides, is 0% to 6.5%.

[0029] 12. The glass according to any one of 1 to 7 above, wherein the average absorbance change at a wavelength of 400 to 800 nm during electron beam irradiation has a thickness of 100 μm or less.

[0030] 13. The glass according to any one of claims 1 to 7 above, wherein the fracture toughness value (K) Ic The pressure is 0.78 MPa. m 1／2 above.

[0031] 14. 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.

[0032] 15. The glass according to any one of 1 to 7 above, wherein the value E / ρ obtained by dividing the Young's modulus E (GPa) by the specific gravity ρ is 27.0 GPa or more.

[0033] 16. The glass according to any one of claims 1 to 7 above, wherein β-OH is 1.0 mm. －1 the following.

[0034] 17. The glass according to any one of claims 1 to 7, wherein at least one surface has a conductive film.

[0035] 18. The glass according to any one of claims 1 to 7 above, wherein at least one surface has an anti-reflective coating.

[0036] 19. A cover glass for a solar cell for a space satellite, using any one of the glass described in 1 to 7 above.

[0037] 20. An ultraviolet blocking glass, which uses any one of the glass described in any one of 1 to 7 above.

[0038] 21. An electron beam cutoff glass, which uses any one of the glass described in 1 to 7 above.

[0039] The glass of the first and fifth embodiments of the present invention has a glass composition with a specific range of one side of the main surface and a plate thickness, and a specific range of specific gravity, Young's modulus and thermal expansion coefficient, which can suppress the warping of solar cells and suppress the reduction of mechanical and optical properties.

[0040] The glass in embodiments 2 to 4 of the present invention has a glass composition with a specific range of one side of the main surface and a plate thickness, and is capable of suppressing the warping of solar cells while suppressing the reduction of mechanical and optical properties. Attached Figure Description

[0041] Figure 1 This is a graph showing the relationship between the average coefficient of thermal expansion and (the absolute value of the warp δ / the length of the warp direction of the glass). Detailed Implementation

[0042] The present invention will now be described in detail based on embodiments, but the present invention is not limited to the following embodiments and can be implemented by any modifications without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention (hereinafter also referred to as these embodiments) include embodiments 1 to 5 described below. In this specification, the term "~" indicating a numerical range is used to mean that the values ​​described before and after it are both lower and upper limits. Unless otherwise specified, the term "~" will also be used in the following description with the same meaning.

[0043] In this specification, "substantially does not contain" means that it does not contain any impurities other than those unavoidable contaminants introduced from raw materials, etc. That is, it indicates that it is not intentionally contained. It should be noted that, unless otherwise specified, the content of each component of the glass in this specification is expressed as a mass percentage based on oxides.

[0044] <Glass>

[0045] The glass of the first embodiment is characterized by having a specific gravity of 2.2 to 2.7, a Young's modulus of 60 GPa or more, and an average coefficient of thermal expansion of 2.0 to 6.0 (×10⁻⁶) at 50 to 200°C. －6 / K), is a rectangle with one side of the main surface being 50cm to 300cm, and the plate thickness being 0.01mm to 0.5mm. It is expressed as a mass percentage based on oxides, with a total content of 0 to 3.5% of Li2O, Na2O and K2O, and contains 0.1 to 10% CeO2.

[0046] The glass of the second embodiment is characterized by containing, by mass percentage based on oxides, 50-80% SiO2, 0-25% B2O3, 0-30% Al2O3, and 0.1-10% CeO2, with a total content of 0-3.5% for Li2O, Na2O, and K2O, being a rectangle with one side of the main surface being 50cm-300cm, and having a thickness of 0.01mm-0.5mm.

[0047] The glass of the third embodiment is characterized in that, expressed as a mass percentage based on oxides, it contains 50-80% SiO2, 0-25% B2O3, 0-30% Al2O3, 5-10% TiO2, and the total content of Li2O, Na2O and K2O is 0-3.5%, it is a rectangle with one side of the main surface being 50cm-300cm, and the thickness of the plate is 0.01mm-0.5mm.

[0048] The glass of the fourth embodiment is characterized by containing, by mass percentage based on oxides, 50-80% SiO2, 0-25% B2O3, 0-30% Al2O3, 0.01-10% TiO2, and 0.1-10% CeO2, with a total content of 0-3.5% for Li2O, Na2O, and K2O, being a rectangle with one side of the main surface being 50cm-300cm, and having a thickness of 0.01mm-0.5mm.

[0049] The glass of the fifth embodiment is characterized by having a specific gravity of 2.2 to 2.7, a Young's modulus of 60 GPa or more, and an average coefficient of thermal expansion of 2.0 to 6.0 (×10⁻⁶) at 50 to 200°C. －6 / K), is a rectangle with one side of the main surface being 50cm to 300cm and a thickness of 0.01mm to 0.5mm, containing 5 to 10% TiO2 as a mass percentage based on oxides.

[0050] The specific gravity of the glass in the first and fifth embodiments is 2.2 to 2.7. The specific gravity of the glass in the first and fifth embodiments is preferably 2.21 or higher, 2.22 or higher, 2.23 or higher, 2.24 or higher, 2.25 or higher, 2.26 or higher, 2.27 or higher, 2.28 or higher, 2.29 or higher, 2.30 or higher, 2.31 or higher, 2.32 or higher, 2.33 or higher, 2.34 or higher, 2.35 or higher, 2.36 or higher, 2.37 or higher, or 2.38 or higher. The specific gravity of the glass in the first and fifth embodiments is 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.

[0051] The specific gravity of the glass in embodiments 2 to 4 is preferably 2.2 to 2.7. More preferably, the specific gravity of the glass in embodiments 2 to 4 is 2.21 or higher, 2.22 or higher, 2.23 or higher, 2.24 or higher, 2.25 or higher, 2.26 or higher, 2.27 or higher, 2.28 or higher, 2.29 or higher, 2.30 or higher, 2.31 or higher, 2.32 or higher, 2.33 or higher, 2.34 or higher, 2.35 or higher, 2.36 or higher, 2.37 or higher, or 2.38 or higher. The specific gravity of the glass in embodiments 2 to 4 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.

[0052] By setting the specific gravity to 2.2 or higher, electron and proton beams are effectively shielded, especially when used as cover glass for solar cells, which helps suppress solar cell degradation. By setting the specific gravity to 2.7 or lower, lightweight design is achieved even in large-scale applications.

[0053] Specific gravity was determined using the Archimedes method.

[0054] The Young's modulus of the glass in the first and fifth embodiments is 60 GPa or 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.

[0055] The Young's modulus of the glass in embodiments 2 to 4 is preferably 60 GPa or more, and 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.

[0056] By increasing the Young's modulus to 60 GPa or higher, the fracture toughness is improved, thereby enhancing the strength required for larger and thinner structures.

[0057] On the other hand, from the viewpoint of reducing the generation of thermal stress caused by drastic temperature differences, the Young's modulus of the glass in 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.

[0058] Young's modulus was determined using the ultrasonic pulse method (JIS R1602, 1995).

[0059] For the glass of this embodiment, the value E / ρ, obtained by dividing the Young's modulus E (GPa) by the specific gravity ρ, is preferably 27.0 to 37.0 GPa. More preferably, the value of E / ρ is 27.2 GPa or higher, 27.4 GPa or higher, 27.6 GPa or higher, 27.8 GPa or higher, 28.0 GPa or higher, 28.2 GPa or higher, 28.4 GPa or higher, 28.6 GPa or higher, 28.8 GPa or higher, or 29.0 GPa or higher. Furthermore, the value of E / ρ is more preferably 36.8 GPa or lower, 36.6 GPa or lower, 36.4 GPa or lower, 36.2 GPa or lower, 36.0 GPa or lower, 35.8 GPa or lower, 35.6 GPa or lower, 35.4 GPa or lower, 35.2 GPa or lower, or 35.0 GPa or lower. By ensuring that the value of E / ρ is 27.0 GPa or higher, the strength required for larger and thinner glass can be ensured. By keeping the E / ρ value below 37.0 GPa, it is possible to ensure lightweighting during large-scale production and achieve the strength improvements required for both large-scale and thin-scale production.

[0060] As the glass used in solar cells becomes larger and thinner, the warping of solar cells due to the difference in thermal expansion coefficients between silicon and glass has become a problem. For example... Figure 1 As shown, it is believed that the absolute value of the warpage δ is related to the average coefficient of thermal expansion. By specifying the range of the average coefficient of thermal expansion, the warpage of solar cells when used in solar cells can be effectively reduced.

[0061] The average coefficient of thermal expansion of the glass in embodiments 1 and 5 at 50–200°C is 2.0–6.0 (×10⁻⁶). －6 / K). The average coefficient of thermal expansion of the glass in embodiments 1 and 5 at 50 to 200°C is preferably 2.1 (×10⁻⁶). －6 / K) or above, 2.2 (×10 －6 / K) or above, 2.3 (×10 －6 / K) or above, 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 above, 2.8 (×10 －6 / K) or above, 2.9 (×10 －6 / K) or above, 3.0 (×10 －6 / K) or above, 3.1 (×10 －6 / K) or above, 3.2 (×10 －6 / K) or above. The average coefficient of thermal expansion of the glass in the first and fifth embodiments at 50 to 200°C is preferably 5.9 (×10) or higher. －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) and below.

[0062] The average coefficient of thermal expansion of the glass in embodiments 2 to 4 at 50 to 200°C is preferably 2.0 to 6.0 (×10⁻⁶). －6 / K). The average coefficient of thermal expansion of the glass in embodiments 2 to 4 at 50 to 200°C is more preferably 2.1 (×10). －6 / K) or above, 2.2 (×10 －6 / K) or above, 2.3 (×10 －6 / K) or above, 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 above, 2.8 (×10 －6 / K) or above, 2.9 (×10 －6 / K) or above, 3.0 (×10 －6 / K) or above, 3.1 (×10 －6 / K) or above, 3.2 (×10 －6 / K) or above. The average coefficient of thermal expansion of the glass in embodiments 2 to 4 at 50 to 200°C is preferably 5.9 (×10) or higher. －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) and below.

[0063] By setting the average coefficient of thermal expansion from 50 to 200°C within the aforementioned range, warping of the solar cell caused by the difference in thermal expansion coefficients between silicon and glass used in solar cells can be reduced, especially when used as cover glass for solar cells.

[0064] The average coefficient of thermal expansion was determined in this manual using a differential thermal dilatometer according to the method specified in JIS R3102 (1995). The measurement temperature range was 50–200 °C, and the unit was expressed as ×10⁻¹⁰. －6 / K.

[0065] The glass in this embodiment is rectangular, with one side of the main surface measuring 50cm to 300cm. By making one side of the main surface 50cm or more, the labor required for solar cell assembly can be reduced, enabling cost reduction even at large scale. Furthermore, by making one side of the main surface less than 300cm, the thin glass can be easily handled without breaking, further reducing costs. The length of one side of the main surface is preferably 60cm or more, 70cm or more, or 80cm or more, more preferably 90cm or more, 100cm or more, or 110cm or more, even more preferably 120cm or more, 130cm or more, or 140cm or more, and particularly preferably 150cm or more. Additionally, the length of one side of the main surface is more preferably 290cm or less, 280cm or less, 270cm or less, 260cm or less, 250cm or less, 240cm or less, 230cm or less, 220cm or less, 210cm or less, or 200cm or less.

[0066] The glass thickness in this embodiment is 0.01 mm to 0.5 mm. By making the thickness 0.01 mm or more, strength is ensured, and electron and proton beams can be adequately shielded. Furthermore, by making the thickness 0.5 mm or less, lightweighting is particularly feasible for space applications. Preferably, the thickness is 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. In addition, the preferred plate thickness is 0.02mm or more, 0.03mm or more, 0.04mm or more, or 0.05mm or more.

[0067] For the glass of this embodiment, the average absorbance change at wavelengths of 400–800 nm, converted to a thickness of 100 μm, 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. By ensuring that the average absorbance change is converted to a thickness of 100 μm and is 0.01 or less, coloration caused by the electron beam is suppressed, ensuring sufficient optical properties for space applications. The lower limit of this average absorbance change converted to a thickness of 100 μm is not particularly limited; for example, values ​​of 0.0001 or more can be considered.

[0068] In this specification, "conversion value for 100μm thickness" refers to the value obtained by converting the change in absorbance into the value when the glass thickness is 100μm.

[0069] The conversion value of the average absorbance change at wavelengths of 400–800 nm during electron beam irradiation to a plate thickness of 100 μm is obtained by following these steps.

[0070] (a1) Electron beam irradiation is performed by horizontally placing the glass substrate to be irradiated on a platform and irradiating it with an electron beam irradiation device (e.g., NHV Corporation, model: EPS-3000kV) at an energy of 1 MeV for 1 × 10⁻⁶ kV. 15 pcs / cm 2 The electron beam.

[0071] (a2) Transmittance of each glass substrate after electron beam irradiation was measured. Measurements were performed one week after electron beam irradiation. The absorbance before and after electron beam irradiation was calculated based on the measured transmittance and converted to absorbance at a thickness of 100 μm.

[0072] (a3) The average absorbance change at wavelengths of 400–800 nm is calculated according to the following formula.

[0073]

[0074] For 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 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. By setting the above value to 50% or more, the degradation of solar cell characteristics caused by electron beams can be effectively suppressed, especially for applications in space. There is no particular upper limit to the above value, for example, it is 95% or less.

[0075] Transmittance can be measured using a spectrophotometer (e.g., Hitachi High Technology Manufacturing Co., Ltd. U-4100).

[0076] For the glass of this embodiment, the transmittance at a wavelength of 400 nm at a thickness of 100 μm is preferably 80-93%. This transmittance is more preferably 81% or more, further preferably 82% or more, particularly preferably 83% or more, more preferably 84% or more, further preferably 85% or more, and particularly preferably 86% or more. By achieving a transmittance of 80% or more at a wavelength of 400 nm at a thickness of 100 μm, the detection characteristics of the solar cell are further improved when used as a cover glass for a solar cell.

[0077] The transmittance at a thickness of 100 μm in this specification refers to the transmittance measured at a thickness of 100 μm.

[0078] In this embodiment, the glass preferably has a transmittance of 0 to 10% at a wavelength of 300 nm at a thickness of 100 μm. This transmittance is more preferably 0.5% or more, further preferably 1% or more, particularly preferably 1.5% or more, more preferably 2% or more, further preferably 2.5% or more, and particularly preferably 3% or more. By ensuring that the transmittance at a wavelength of 300 nm at a thickness of 100 μm is 0% or more, the detection characteristics of the solar cell can be further improved when used as a cover glass for a solar cell. By ensuring that the transmittance at a wavelength of 300 nm at a thickness of 100 μm is 10% or less, the degradation of the solar cell caused by ultraviolet radiation can be suppressed.

[0079] For the glass of this embodiment, the wavelength exhibiting 50% transmittance at a thickness of 100 μm is preferably 300–370 nm. More preferably, this wavelength is 310 nm or more, further preferably 320 nm or more, and particularly preferably 330 nm or more. Furthermore, this wavelength is more preferably 360 nm or less, further preferably 355 nm or less, and particularly preferably 350 nm or less. By setting this wavelength to 300 nm or more, degradation of the solar cell caused by ultraviolet radiation can be suppressed. By setting this wavelength to 370 nm or less, the detection characteristics of the solar cell can be further improved when used as a cover glass for a solar cell.

[0080] For the glass of this embodiment, the transmittance at a wavelength of 400 nm at a thickness of 50 μm is preferably 80-94%. More preferably, this transmittance is 81% or more, further preferably 82% or more, particularly preferably 83% or more, more preferably 84% or more, further preferably 85% or more, and particularly preferably 86% or more. Furthermore, this transmittance is preferably 94% or less, more preferably 93% or less, further preferably 92% or less, particularly preferably 91% or less, and most preferably 90% or less. By achieving a transmittance of 80% or more at a wavelength of 400 nm at a thickness of 50 μm, the detection characteristics of the solar cell can be further improved when used as a cover glass for a solar cell.

[0081] In this specification, the transmittance at a thickness of 50 μm refers to the transmittance measured at a thickness of 50 μm.

[0082] For the glass of this embodiment, the transmittance at a wavelength of 300 nm at a thickness of 50 μm is preferably 0 to 25%. This transmittance is more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, more preferably 4% or more, further preferably 5% or more, and particularly preferably 7% or more. Furthermore, this transmittance is more preferably 23% or less, further preferably 20% or less, particularly preferably 15% or less, and most preferably 10% or less. By making the transmittance at a wavelength of 300 nm at a thickness of 50 μm 0% or more, the detection characteristics of the solar cell can be further improved when used as a cover glass for a solar cell. By making the transmittance at a wavelength of 300 nm at a thickness of 50 μm 25% or less, the degradation of the solar cell caused by ultraviolet radiation can be suppressed.

[0083] For the glass of this embodiment, the wavelength exhibiting 50% transmittance at a thickness of 50 μm is preferably 250–360 nm. This wavelength is more preferably 260 nm or more, further 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. Furthermore, this wavelength is more preferably 350 nm or less, more preferably 340 nm or less, further preferably 330 nm or less, particularly preferably 320 nm or less, and most preferably 310 nm or less. By setting this wavelength to 250 nm or more, degradation of the solar cell caused by ultraviolet radiation can be suppressed. By setting this wavelength to 360 nm or less, sufficient optical properties can be ensured even in large-scale applications.

[0084] The fracture toughness value K of the glass in this embodiment IC The preferred pressure is 0.78 MPa m 1／2 The above, more preferably 0.80 MPa m 1／2The above is further preferred to be 0.81 MPa. m 1／2 The above is particularly preferred, with 0.82 MPa. m 1／2 That's all. By making K IC 0.78 MPa m 1／2 This ensures sufficient strength even in large-scale applications. Fracture toughness value K IC There is no specific upper limit; for example, it can be 1.00 MPa. m 1／2 the following.

[0085] The fracture toughness value K in this specification IC This refers to the value determined using 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 provides a more accurate determination of the fracture toughness value K compared to the SEPB method. IC Therefore, the fracture toughness value K IC More preferably, the value obtained using the DC-DC method is preferred.

[0086] In this embodiment, the β-OH content of the glass is preferably 1.0 mm. －1 The following is more preferably 0.5mm －1 Hereinafter, 0.4mm is further preferred. －1 The following is particularly preferred: 0.3mm －1 The following is done by making β-OH 1.0 mm. －1 The following methods can improve ultraviolet absorption by increasing the amount of platinum dissolved in the glass from platinum crucibles, platinum stirrers, or other platinum manufacturing equipment. There is no particular limitation on the lower limit of β-OH, for example, it is 0.01 mm. －1 above.

[0087] The β-OH of the glass is determined by measuring the transmittance of the glass using FT-IR and calculated using the following formula.

[0088]

[0089] X: Glass thickness (mm)

[0090] T1: Reference wavelength 3846cm －1 Transmittance at (%)

[0091] T2: Hydroxyl absorption wavelength 3600 cm⁻¹ －1Minimum transmittance (%) in the vicinity

[0092] For the glass of this embodiment, the absolute value of the warp amount δ calculated based on the Bi-Metal warp calculation specified in the following formula is divided by the length (mm) of the glass in the warp direction, which is the value of "absolute value of warp amount δ / length of the glass in the warp direction". For example, the following are preferred (b1) to (b4).

[0093] (b1) When the length of the glass in the warp direction is 1000 mm and the glass thickness is 0.1 mm, the absolute value of the warp amount δ / the length of the glass in the warp 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 the warp amount δ / the length of the glass in the warp direction, the better. There is no particular limitation on the lower limit, for example, it is 0.001 or more.

[0094] (b2) When the length of the glass in the warp direction is 1000 mm and the glass thickness is 0.05 mm, the absolute value of the warp amount δ / the length of the 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 absolute value of the warp amount δ / the length of the glass in the warp direction, the better. There is no particular limitation on the lower limit, for example, it is 0.001 or more.

[0095] (b3) When the length of the glass in the warp direction is 500 mm and the glass thickness is 0.1 mm, the absolute value of the warp amount δ / the length of the 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 absolute value of the warp amount δ / the length of the glass in the warp direction, the better. There is no particular limitation on the lower limit, for example, it is 0.001 or more.

[0096] (b4) When the length of the glass in the warp direction is 500 mm and the glass thickness is 0.05 mm, the absolute value of the warp amount δ / the length of the 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 absolute value of the warp amount δ / the length of the glass in the warp direction, the better. There is no particular limitation on the lower limit, for example, it is 0.001 or more.

[0097] By making the absolute value of the warp amount δ / the length of the warp direction of the glass below the above upper limit, the function of the solar cell can be ensured even when the glass for solar cells is made thinner and larger.

[0098]

[0099] L: Length of the glass in the warp direction [mm]

[0100] α1: Thermal expansion coefficient of solar cell [ppm / K]

[0101] α2: Thermal expansion coefficient of glass [ppm / K]

[0102] E1: Young's modulus of the solar cell [GPa]

[0103] E2: Young's modulus of glass [GPa]

[0104] T1: Assuming the highest temperature [°C]

[0105] T2: Assuming the lowest temperature [°C]

[0106] a1: Thickness of the solar cell [mm]

[0107] a2: Glass thickness [mm]

[0108] h: a1 + a2 [mm]

[0109] m:a1 / a2

[0110] n:E1 / E2

[0111] δ: Warpage amount [mm]

[0112] The aforementioned solar cells are manufactured by Sunpower's "MAXEON" brand. TM Using “GENIII SOLAR CELLS” as a reference, it is assumed that monocrystalline silicon is used. The thermal expansion coefficient and Young's modulus of the above solar cells, assuming monocrystalline silicon, are α1 = 3.2 ppm / ℃ and E1 = 190 GPa, respectively. The thermal expansion coefficient of the glass is the average value of the coefficient of thermal expansion (ppm / ℃) from 50 to 200℃. In addition, the thickness of the above solar cells is assumed to be 0.15 mm.

[0113] For the glass of this embodiment, from the viewpoints of reducing viscosity and increasing productivity and from the viewpoints of SDGs, the temperature (T2) at which the viscosity logη is 2 (poise) is preferably 1800°C or less, more preferably 1750°C or less, and even more preferably 1700°C or less. T2 is typically 1400°C or more.

[0114] For the glass of this embodiment, from the viewpoints of reducing viscosity and improving productivity and from the viewpoints of SDGs, the temperature (T4) at which the viscosity logη is 4 (poise) is preferably 1550°C or lower, more preferably 1500°C or lower, further preferably 1450°C or lower, 1400°C or lower, 1350°C or lower, and most preferably 1300°C or lower. T4 is typically 800°C or higher.

[0115] For the glass of this embodiment, five 50mm × 50mm pieces of glass are cut from the center and near the four corners of a glass with one side greater than 50cm. The average value of the flatness (Ra) of 1μm × 1μm, measured by AFM, is preferably 2.0nm or less, more preferably 1.5nm or less, even more preferably 1.0nm or less, and even more preferably 0.8nm or less. By making the flatness 2.0nm or less, strength that is not easily broken during processing can be obtained. This flatness has a certain degree of roughness, which can reduce the static electricity between the glass and the backing paper sandwiched between the glass during processing. Therefore, the above-mentioned average value of the lower limit is preferably 0.2nm or more, more preferably 0.3nm or more, even more preferably 0.4nm or more, and even more preferably 0.5nm or more.

[0116] <<Composition>>

[0117] In embodiments 1 to 4, the content of R2O (the total content of Li2O, Na2O and K2O) is 0 to 3.5%. In embodiments 1 to 4, the R2O 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.

[0118] In the fifth embodiment, R2O is preferably 0 to 3.5%. More preferably, R2O is 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.

[0119] By reducing R2O to below 3.5%, the difference in thermal expansion coefficients between silicon and glass used in solar cells can be decreased, effectively improving solar cell warpage even in large-scale applications. Lower R2O is better; from a manufacturing standpoint, for example, above 0.01%.

[0120] Li₂O is any component that improves the Young's modulus, fracture toughness, and mechanical properties of glass. In this embodiment, when Li₂O is present, its content is preferably 0.01% or more, more preferably 0.02% or more, further preferably 0.03% or more, particularly preferably 0.04% or more, and most preferably 0.1% or more. Furthermore, from the viewpoint of reducing the difference in thermal expansion coefficients between silicon and glass, and effectively improving the warpage of solar cells even in large-scale applications, the content of Li₂O is preferably 2.0% or less, more preferably 1.5% or less, further preferably 1.0% or less, and particularly preferably 0.5% or less.

[0121] Na₂O is any component that improves the meltability of glass and may be included. In this embodiment, when Na₂O is included, its content is preferably 0.01% or more, more preferably 0.02% or more, further preferably 0.05% or more, particularly preferably 0.5% or more, and most preferably 1.0% or more. Furthermore, from the viewpoint of reducing the difference in thermal expansion coefficients between silicon and glass, and effectively improving the warpage of solar cells even in large-scale applications, the content of Na₂O is preferably 2.0% or less, more preferably 1.5% or less, further preferably 1.2% or less, and particularly preferably 1.1% or less.

[0122] K2O can be any component that improves the meltability of glass. In this embodiment, when K2O is present, its content is preferably 0.01% or more, more preferably 0.02% or more, even more preferably 0.03% or more, and particularly preferably 0.05% or more. Furthermore, from the viewpoint of reducing the difference in thermal expansion coefficients between silicon and glass, and effectively improving the warpage of solar cells even in large-scale applications, the K2O 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.

[0123] Glass tends to deteriorate and lose its transmission properties under the influence of ultraviolet rays, electron beams, proton beams, and cosmic rays (e.g., gamma rays and alpha rays). Therefore, the required properties for glass used as cover glass for solar cells in space applications include the ability to transmit light in the wavelength range of the solar cell's spectral sensitivity, while shielding against ultraviolet rays, electron beams, proton beams, and cosmic rays, and without losing its transmission properties due to these rays.

[0124] CeO2 is a component that improves the shielding effect of ultraviolet rays and inhibits staining caused by electron beams.

[0125] In embodiments 1, 2, and 4, from the viewpoint of suppressing coloration of the glass caused by electron beams and sufficiently ensuring ultraviolet shielding effect, the CeO2 content is 0.1% to 10%. In embodiments 1, 2, and 4, the CeO2 content is more preferably 0.2% or more, 0.4% or more, and 0.6% or more, more preferably 0.8% or more, 1.0% or more, and 1.2% or more, and particularly preferably 1.4% or more, 1.6% or more, and 1.8% or more, respectively. Furthermore, in embodiments 1, 2, and 4, from the viewpoint of suppressing devitrification, the CeO2 content is preferably 10% or less, more preferably 7% or less, more preferably 6% or less, particularly preferably 5% or less, and most preferably 3% or less.

[0126] In embodiments 3 and 5, from the viewpoint of suppressing coloration of the glass caused by electron beams and ensuring sufficient ultraviolet shielding effect, the CeO2 content is preferably 0.1% to 10%. In embodiments 3 and 5, the CeO2 content is more preferably 0.2% or more, 0.4% or more, and 0.6% or more, further preferably 0.8% or more, 1.0% or more, and 1.2% or more, and particularly preferably 1.4% or more, 1.6% or more, and 1.8% or more. Furthermore, in embodiments 3 and 5, from the viewpoint of suppressing devitrification, the CeO2 content is preferably 10% or less, more preferably 7% or less, further preferably 6% or less, particularly preferably 5% or less, and most preferably 3% or less.

[0127] In this embodiment, when the plate thickness is set as t (mm) and the CeO2 content in the glass composition is set as α (mass%), from the viewpoint of improving the ultraviolet shielding effect, α / t is preferably 0.2 to 200 mass% / mm. α / t is more preferably 5 mass% / mm or more, further 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, further preferably 120 mass% / mm or less, and particularly preferably 80 mass% / mm or less.

[0128] TiO2 is a component that inhibits solarization caused by UVC.

[0129] In the first and second embodiments, the TiO2 content is preferably 0.01 to 10%. In the first and second embodiments, from the viewpoint of further suppressing solar discoloration caused by UVC, the TiO2 content is preferably 0.30% or more, 0.50% or more, and 0.70% or more, more preferably 1.0% or more, 1.2% or more, and 1.4% or more, 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. Furthermore, in the first and second embodiments, from the viewpoint of further suppressing solar discoloration caused by UVC and preventing glass staining, the TiO2 content is more preferably 7% or less, more preferably 6% or less, and particularly preferably 5% or less.

[0130] In embodiments 3 and 5, the TiO2 content is 5-10%. In embodiments 3 and 5, from the viewpoint of further suppressing solar discoloration caused by UVC, the TiO2 content is preferably 5.5% or more, more preferably 6.0% or more, and even more preferably 7% or more. Furthermore, in embodiments 3 and 5, from the viewpoint of further suppressing solar discoloration caused by UVC and preventing glass staining, the TiO2 content 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.

[0131] In the fourth embodiment, the TiO2 content is 0.01 to 10%. In the fourth embodiment, from the viewpoint of further suppressing solar discoloration caused by UVC, the TiO2 content is preferably 0.30% or more, 0.50% or more, and 0.70% or more, more preferably 1.0% or more, 1.2% or more, and 1.4% or more, and even more preferably 1.5% or more, 2.0% or more, and 3.0% or more. Furthermore, in the fourth embodiment, from the viewpoint of further suppressing solar discoloration caused by UVC and preventing glass staining, the TiO2 content is more preferably 7.0% or less, more preferably 6.0% or less, and particularly preferably 5.0% or less.

[0132] In embodiments 1, 2, and 4, when the plate thickness is set to t (mm) and the TiO2 content in the glass composition is set to β (mass%), from the viewpoint of suppressing solar discoloration caused by UVC, β / t is preferably 0.005 to 200 mass% / mm. In embodiments 1, 2, and 4, β / t is more preferably 1 mass% / mm or more, further preferably 5 mass% / mm or more, and particularly preferably 10 mass% / mm or more. Furthermore, in embodiments 1, 2, and 4, β / t is more preferably 160 mass% / mm or less, further preferably 120 mass% / mm or less, and particularly preferably 80 mass% / mm or less.

[0133] In embodiments 3 and 5, when the plate thickness is set as t (mm) and the TiO2 content in the glass composition is set as β (mass%), from the viewpoint of suppressing solar discoloration caused by UVC, β / t is preferably 10 to 200 mass% / mm. In embodiments 3 and 5, β / t is more preferably 50 mass% / mm or more, further preferably 100 mass% / mm or more, and particularly preferably 150 mass% / mm or more. Furthermore, in embodiments 3 and 5, β / t is more preferably 190 mass% / mm or less, further preferably 180 mass% / mm or less, and particularly preferably 170 mass% / mm or less.

[0134] For the glass of this embodiment, from the viewpoint of further improving the ultraviolet shielding effect and making the wavelength with 50% transmittance in the ultraviolet region the longer wavelength side, the value of X expressed by the following formula is preferably 0.5 to 50. The value of X is more preferably 40 or less, further preferably 35 or less, and particularly preferably 30 or less. The value of X is more preferably 1 or more, further preferably 3 or more, and particularly preferably 5 or more.

[0135] (Formula) X = 5 × [CeO2] + [TiO2]

[0136] In the above formula, the brackets [ ] represent the content as a mass percentage based on oxides.

[0137] SiO2 is an essential component that forms the glass framework.

[0138] In embodiments 1 and 5, the SiO2 content is preferably 50-80%. In embodiments 1 and 5, the SiO2 content is more preferably 51% or more, further preferably 52% or more, particularly preferably 53% or more, and most preferably 55% or more. Furthermore, in embodiments 1 and 5, the SiO2 content is more preferably 75% or less, further preferably 70% or less, particularly preferably 65% ​​or less, and most preferably 60% or less. By maintaining a SiO2 content of 50% or more, chemical durability can be improved. By maintaining a SiO2 content of 80% or less, the rise in T2 or T4 is suppressed, thereby improving the meltability or formability of the glass.

[0139] In embodiments 2 to 4, the SiO2 content is 50% to 80%. In embodiments 2 to 4, the SiO2 content is preferably 51% or more, more preferably 52% or more, further preferably 53% or more, and particularly preferably 55% or more. Furthermore, in embodiments 2 to 4, the SiO2 content is preferably 75% or less, more preferably 70% or less, further preferably 65% ​​or less, and particularly preferably 60% or less. By making the SiO2 content 50% or more, chemical durability can be improved. By making the SiO2 content 80% or less, the rise of T2 or T4 is suppressed, thereby improving the meltability or formability of the glass.

[0140] B2O3 can sometimes be included to improve meltability or glass strength at high temperatures. On the other hand, high B2O3 content tends to decrease Young's modulus, fracture toughness, and strength. In addition, the glass may become more prone to phase separation, lose transparency, and become difficult to obtain homogeneous glass, thus reducing its formability.

[0141] In embodiments 1 and 5, when B2O3 is present, its content is preferably 25% or less, more preferably 20% or less, further preferably 18% or less, particularly preferably 17% or less, 16% or less, 15% or less, 14% or less, 13% or less, 12% or less, and most preferably 10% or less.

[0142] In embodiments 2 to 4, the B2O3 content is 0 to 25%. In embodiments 2 to 4, the B2O3 content is preferably 20% or less, more preferably 17% or less, further preferably 15% or less, particularly preferably 14%, 13%, 12%, 11%, 10%, and 9% or less, and most preferably 8% or less. In this embodiment, from the viewpoint of improving melt permeability or glass strength at high temperatures, the B2O3 content is preferably, for example, 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 4% or more.

[0143] Al2O3 is a component that improves the mechanical properties of glass, such as Young's modulus and fracture toughness, and enhances its durability. On the other hand, it is also a component that deteriorates devitrification resistance when added together with CeO2.

[0144] In embodiments 1 and 5, the content of Al2O3 is preferably 0 to 30%.

[0145] In embodiments 2 to 4, the content of Al2O3 is 0% to 30%.

[0146] By keeping the Al2O3 content below 30%, the meltability or formability of the glass can be improved by suppressing the rise of T2 or T4.

[0147] In embodiments 1 to 5, when Al2O3 is present, 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, and 9% or more, respectively.

[0148] In embodiments 1 and 5, the Al2O3 content is more preferably 25% or less, and even more preferably 20% or less. By keeping the Al2O3 content at 30% or less, the rise in T2 or T4 is suppressed, thereby improving the meltability or formability of the glass.

[0149] In embodiments 2 to 4, the content of Al2O3 is preferably 25% or less, more preferably 23% or less, and even more preferably 20% or less.

[0150] As2O3 is a component that promotes discoloration from sunlight and can be any component. In this embodiment, from the viewpoint of inhibiting discoloration from sunlight and from the viewpoint of SDGs, the content of As2O3 is preferably 0.25% or less, more preferably 0.10% or less, and even more preferably 0.05% or less. There is no particular limitation on the lower limit of the content of As2O3, but from the viewpoint of clarification, it is preferably 0.001% or more when it is present.

[0151] Sb₂O₃ is the component that functions as a clarifying agent. In this embodiment, from the viewpoint of SDGs, the content of Sb₂O₃ is preferably 0.25% or less, more preferably 0.2% or less, and even more preferably 0.1% or less. There is no particular limitation on the lower limit of the content of Sb₂O₃, but from the viewpoint of clarification, it is preferable to contain 0.001% or more.

[0152] In this embodiment, from the viewpoint of SDGs, the total content of As2O3 and Sb2O3 is preferably 0% or more and less than 0.25%, more preferably 0% to 0.2%, further preferably 0% to 0.1%, and particularly preferably 0% to 0.05%.

[0153] SnO2 is the component that inhibits discoloration under sunlight. In this embodiment, the content of SnO2 is preferably 0.01% to 0.4%. From the viewpoint of further inhibiting discoloration under sunlight, in this embodiment, the content of SnO2 is more preferably 0.02% or more, more preferably 0.05% or more, and particularly preferably 0.1% or more. Furthermore, from the viewpoint of inhibiting the decrease in resistance to devitrification, the content of SnO2 is more preferably 0.3% or less, and more preferably 0.2% or less.

[0154] Fe2O3 can be any component, and it can be included from the viewpoint of improving the shielding effect of ultraviolet light and suppressing coloration caused by electron beams. On the other hand, it is also a component that reduces the transmittance from the visible light region to the near-infrared region, thereby reducing power generation efficiency. In this embodiment, the content of Fe2O3 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, or 0.01% or less. In addition, there is no particular limitation on the lower limit of the content, but from the viewpoint of improving the shielding effect of ultraviolet light and suppressing coloration caused by electron beams, it is preferably 0.001% or more, more preferably 0.002% or more, 0.003% or more, or 0.004% or more when it is included. By ensuring the Fe2O3 content is above 0.001%, the shielding effect against ultraviolet light can be guaranteed, and coloration caused by electron beams can be further suppressed. By ensuring the Fe2O3 content is below 3%, the visible light transmittance can be improved.

[0155] For the glass of this embodiment, when it contains CeO2, the ultraviolet shielding effect is further improved. From the viewpoint of controlling the redox state of Ce, the value of Y expressed by the following formula is preferably 0 to 1300. The value of Y is more preferably 1200 or less, more preferably 1000 or less, and particularly preferably 800 or less. The value of Y is more preferably 100 or more, more preferably 300 or more, and particularly preferably 500 or more.

[0156] (Formula) Y=[CeO2] / [Fe2O3]

[0157] In the above formula, the brackets [ ] represent the content as a mass percentage based on oxides.

[0158] MgO is any component that can suppress the decrease in strength or improve the meltability. In this embodiment, when MgO is present, its content is preferably 0.5% or more, more preferably 1.0% or more, further preferably 1.5% or more, and particularly preferably 2.0% or more. In this embodiment, the content of MgO is preferably 13% or less, more preferably 12.5% ​​or less, further 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.

[0159] BaO is a component that improves melt permeability at high temperatures or reduces the likelihood of devitrification, and may be included. In this embodiment, the content of BaO is preferably 0% to 6.5%. When BaO is included, its content is more preferably 0.5% or more, further preferably 1.0% or more, and particularly preferably 1.5% or more. From the viewpoint of suppressing the increase in specific gravity, the content of BaO is more preferably 5.0% or less, further preferably 4.0% or less, and particularly preferably 3.0% or less.

[0160] CaO can be included because it improves meltability at high temperatures or makes devitrification less likely. In this embodiment, when CaO is included, its content is preferably 0.5% or more, more preferably 1.0% or more, further preferably 1.5% or more, and particularly preferably 2.0% or more. In this embodiment, the content of CaO is preferably 13% or less, more preferably 12.5% ​​or less, further 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.

[0161] SrO can be included because it improves melt permeability at high temperatures or makes devitrification less likely. In this embodiment, when SrO is included, its content is more preferably 0.5% or more, further preferably 1.0% or more, and particularly preferably 1.5% or more. From the viewpoint of suppressing the increase in specific gravity, the content of SrO is preferably 8% or less, more preferably 6% or less, further preferably 4% or less, particularly preferably 2% or less, and most preferably 0.1% or less.

[0162] In this embodiment, when it contains any one or more of BaO, CaO and SrO, 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.

[0163] From the viewpoint of improving the power generation efficiency of solar cells by increasing the transmittance at wavelengths of 300–1100 nm, it is preferable that the solar cells do not contain NiO substantially. In this embodiment, when NiO is present, its content is preferably 1% or less, more preferably 0.5% or less, even more preferably 0.1% or less, and even more preferably 0.08% or less.

[0164] ZrO2 is not an essential component. It can be included as long as it is in the range of 1.6% or less, as it can reduce viscosity at high temperatures or improve chemical durability. In this embodiment, by keeping the ZrO2 content at 1.6% or less, strength reduction can be suppressed. The ZrO2 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.

[0165] ZnO can be contained in glass because it improves the glass's melting point at high temperatures. In this case, the content is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.25% or less. When manufacturing using the float glass process, the ZnO content is preferably 0.5% or less, more preferably 0.25% or less, even more preferably substantially absent, and most preferably 0%. By keeping the ZnO content to 1% or less, reduction during float glass forming is suppressed, thus preventing product defects.

[0166] V₂O₅ can be included to improve ultraviolet shielding effectiveness. From the viewpoint of further improving ultraviolet shielding effectiveness, when V₂O₅ is included, 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. On the other hand, from the viewpoint of suppressing coloration, when V₂O₅ is included, its content is preferably 1.0% or less, more preferably 0.8% or less, even more preferably 0.6% or less, and particularly preferably 0.4% or less.

[0167] As a clarifying agent during glass melting, SO3, chlorides, fluorides, etc., may be appropriately contained. However, in order to improve the power generation efficiency of solar cells when used as cover glass for solar cells, it is preferable to minimize the inclusion of components such as Cr2O3, which have absorption in the wavelength region of 300 to 1100 nm, as impurities in the raw materials. When contained, it is preferably 0.15% or less, more preferably 0.1% or less, and particularly preferably 0.05% or less.

[0168] As one type of glass in the first embodiment, the following methods (1a) to (1c) can be cited.

[0169] Method (1a): The total content of Li2O, Na2O and K2O is 0 to 3.5% as a mass percentage based on oxides, and contains 0.1 to 10% CeO2.

[0170] Method (1b): The total content of Li2O, Na2O and K2O is 0 to 3.5% as a mass percentage based on oxides, and contains 0.1 to 10% CeO2 and 5 to 10% TiO2.

[0171] Method (1c): The total content of Li2O, Na2O and K2O is 0 to 3.5%, and it contains 0.1 to 10% CeO2 and 0.01 to 10% TiO2.

[0172] Examples of specific components of the glass in this embodiment include the following.

[0173] (1) Glass containing 50-80% SiO2, 0-25% B2O3, 0-30% Al2O3, 0.1-10% CeO2 and 0-3.5% R2O, expressed as a mass percentage based on oxides.

[0174] (2) Glass containing 50-80% SiO2, 0-25% B2O3, 0-30% Al2O3, 5-10% TiO2 and R2O of 0-3.5% by mass percentage based on oxides.

[0175] (3) Glass containing 50-80% SiO2, 0-25% B2O3, 0-30% Al2O3, 0.01-10% TiO2, 0.1-10% CeO2 and R2O of 0-3.5% as a mass percentage based on oxides.

[0176] <Methods of Glass Manufacturing>

[0177] The glass of this embodiment can be manufactured using conventional methods. For example, the raw materials for the various components of the glass are mixed and melted using a glass melting furnace. Then, the glass is homogenized using known methods, shaped into a desired shape such as a glass sheet, and slowly cooled.

[0178] Examples of glass forming methods include float glass, pressing glass, overflow drawing glass, and slot drawing glass. Float glass, which is particularly suitable for mass production, is especially preferred. Continuous forming methods other than float glass, namely overflow drawing glass and slot drawing glass, are also preferred.

[0179] Then, the shaped glass is subjected to grinding, polishing, and etching processes to form a glass substrate. The thickness of the glass substrate can be adjusted to a desired thickness depending on the processing conditions. Specifically, as etching, for example, a method of polishing the glass surface by immersing the glass substrate in a solution containing hydrofluoric acid or the like can be cited.

[0180] In this embodiment, the glass preferably has a conductive film on at least one surface. Examples of components for the conductive film include In₂O₃, SnO₂, and ZnO. 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, or 100 nm or less. The lower limit of the film thickness is not particularly limited, but for example, it is 1 nm or more, more preferably 5 nm or more or 10 nm or more.

[0181] In this embodiment, the glass preferably has an anti-reflective film on at least one surface. Examples of components for the anti-reflective film include MgF2, CrNi, Ag, and SiO2. X TiO X Ta2O5, Al2O3, etc.

[0182] Furthermore, the antireflective film is not limited to a single layer, but can also be a multilayer film combining multiple components. The thickness of the antireflective 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 limited; for example, it can be 1 nm or more, more preferably 5 nm or more, or 10 nm or more.

[0183] <Uses>

[0184] The glass of this embodiment is suitable for use as cover glass for solar cells (e.g., cover glass for solar cells in space satellites), electron beam blocking glass, and ultraviolet light blocking glass. The glass of this embodiment is more suitable as cover glass for solar cells requiring these properties because it has superior electron beam resistance and ultraviolet light shielding compared to conventional glass, as well as superior strength and can be manufactured in larger sizes.

[0185] Example

[0186] The present invention will be specifically described below with examples, but the present invention is not limited thereto.

[0187] (Glass making)

[0188] For the glasses shown in Tables 1-6, commonly used glass raw materials such as oxides, hydroxides, carbonates, or nitrates are appropriately selected in a manner that uses the mass percentage of oxides as a reference in the tables for each glass composition. These raw materials are placed in a platinum crucible and heated to a high temperature above 1550-1650°C using an electric furnace to melt them. The molten glass is then poured onto a carbonaceous mold frame and held at Tg+50°C for 1 hour, followed by cooling at 1.0°C / min to obtain a glass block. The obtained glass block is cut, ground, and polished to produce glass samples of specified dimensions for property evaluation.

[0189] (Evaluation of characteristics)

[0190] The characteristics of the obtained glass substrate are evaluated according to the following steps.

[0191] [proportion]

[0192] Specific gravity was determined using the Archimedes method.

[0193] Young's modulus

[0194] Young's modulus was determined using the ultrasonic pulse method (JIS R1602, 1995). A glass substrate with dimensions of 30 mm in length × 30 mm in width × 1 mm in thickness was used in the measurement.

[0195] [Average coefficient of thermal expansion CTE (50-200) [ppm / K]]

[0196] The measurements were performed using a differential thermal dilatometer, following the method specified in JIS R3102 (1995). The measurement temperature range was 50–200 °C, and the units were expressed as "×10⁻¹⁰". －6 / K”. A glass substrate with dimensions of 25mm in length × 6mm in width × 0.8mm in thickness was used in the measurement.

[0197] [β-OH]

[0198] For glass samples, the transmittance of the glass was determined using FT-IR and calculated using the following formula. A glass substrate with dimensions of 30 mm in length × 30 mm in width × 1 mm in thickness was used in the measurement.

[0199]

[0200] X: Glass wall thickness (mm)

[0201] T1: Reference wavelength 3846cm －1 Transmittance (%)

[0202] T2: Hydroxyl absorption wavelength 3600 cm⁻¹ －1 Minimum transmittance (%) in the vicinity

[0203] [K] IC ]

[0204] The fracture toughness value was determined using the DCDC method (Acta metall.mater.Vol.43,pp.3453-3458,1995).

[0205] [Transmittance]

[0206] Transmittance was measured using a spectrophotometer (trade name U-4100) manufactured by Hitachi High Technology Co., Ltd. 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 in the measurement.

[0207] [Average absorbance change at wavelengths of 400–800 nm during electron beam irradiation (converted to a plate thickness of 100 μm)]

[0208] Electron beam irradiation is performed by horizontally placing the glass substrate to be irradiated on a platform and irradiating it with an electron beam irradiation device (manufactured by NHV Corporation, model: EPS-3000kV) at an energy of 1 MeV for 1 × 10⁻¹⁰ times. 15 pcs / cm 2 An electron beam was used for the measurements. Glass substrates with dimensions of 20 mm (length) × 20 mm (width) × 0.5 mm (thickness) were used. Transmittance was measured before electron beam irradiation and again after each substrate was irradiated. Measurements were performed within one week of electron beam irradiation. The absorbance before and after electron beam irradiation was calculated based on the measured transmittance, converted to absorbance at a thickness of 100 μm, and then the average change in absorbance from 400 to 800 nm was calculated using the following formula.

[0209]

[0210] [Warp]

[0211] For each example of glass, the warpage is calculated based on the Bi-Metal warpage calculation specified in the following formula. Specifically, the absolute value of the warpage δ is calculated by the following formula.

[0212]

[0213] L: Length of the glass in the warp direction [mm]

[0214] α1: Thermal expansion coefficient of solar cell [ppm / K]

[0215] α2: Thermal expansion coefficient of glass [ppm / K]

[0216] E1: Young's modulus of the solar cell [GPa]

[0217] E2: Young's modulus of glass [GPa]

[0218] T1: Assuming the highest temperature [°C]

[0219] T2: Assuming the lowest temperature [°C]

[0220] a1: Thickness of the solar cell [mm]

[0221] a2: Glass thickness [mm]

[0222] h: a1 + a2 [mm]

[0223] m:a1 / a2

[0224] n:E1 / E2

[0225] δ: Warpage amount [mm]

[0226] The aforementioned solar cells are manufactured by Sunpower's "MAXEON" brand. TM Using “GENIII SOLAR CELLS” as a reference, it is assumed that monocrystalline silicon is used. Therefore, the thermal expansion coefficient and Young's modulus of the above solar cells, assuming monocrystalline silicon, are α1 = 3.2 ppm / ℃ and E1 = 190 GPa, respectively. The thermal expansion coefficient of the glass is the average coefficient of thermal expansion (ppm / ℃) from 50 to 200℃. In addition, the thickness of the above solar cells is assumed to be 0.15 mm.

[0227] Tables 1-6 show the results of evaluating the glass composition and properties as a mass percentage based on oxides. Additionally, Figure 1 This is a graph showing the relationship between the average coefficient of thermal expansion and (the absolute value of the warp δ / the length of the warp direction of the glass).

[0228] In Tables 1-6, Examples 1-39 are exemplary cases, and Examples 40-42 are comparative cases. In Tables 1-6, italics indicate calculated values, and "-" indicates no evaluation.

[0229] When studying the transmittance at 50 μm based on the transmittance at 100 μm, it can be considered as a state where the light-absorbing element is halved, and the result is obtained according to the Lambert-Beer law.

[0230]

[0231]

[0232]

[0233]

[0234]

[0235]

[0236] As shown in Tables 1-6, Examples 1-39, as embodiments, have similar specific gravity and Young's modulus to Comparative Examples 40-42, and exhibit smaller changes in average absorbance at wavelengths of 400-800 nm during electron beam irradiation, as well as lower values ​​for (absolute value of warp amount δ / length of the warp direction of the glass). These results indicate that the glass according to this embodiment can effectively suppress warping of solar cells when used in large-scale and thin-film solar cells.

[0237] As stated above, the following matters are disclosed in this specification.

[0238] 1. A glass having a specific gravity of 2.2–2.7, a Young's modulus of 60 GPa or higher, and an average coefficient of thermal expansion of 2.0–6.0 (×10⁻⁶) at 50–200 °C. -6 / K),

[0239] It is a rectangle with one side of the main surface measuring 50cm to 300cm, and the board thickness is 0.01mm to 0.5mm.

[0240] The total content of Li2O, Na2O and K2O is 0 to 3.5% by mass, expressed as an oxide basis, and contains 0.1 to 10% CeO2.

[0241] 2. The glass according to claim 1 above, wherein it contains 0.01 to 10% TiO2, expressed as a mass percentage based on oxides.

[0242] 3. The glass according to 1 or 2 above, wherein it contains 5 to 10% TiO2, expressed as a mass percentage based on oxides.

[0243] 4. A glass having a specific gravity of 2.2–2.7, a Young's modulus of 60 GPa or higher, and an average coefficient of thermal expansion of 2.0–6.0 (×10⁻⁶) at 50–200 °C. -6 / K),

[0244] It is a rectangle with one side measuring 50cm to 300cm, and a thickness of 0.01mm to 0.5mm.

[0245] It contains 5-10% TiO2, expressed as a mass percentage based on oxides.

[0246] 5. A glass, expressed as a mass percentage based on oxides, containing 50–80% SiO2, 0–25% B2O3, 0–30% Al2O3, and 0.1–10% CeO2, with a total content of 0–3.5% Li2O, Na2O, and K2O.

[0247] It is a rectangle with one side of the main surface being 50cm to 300cm, and the thickness of the plate is 0.01mm to 0.5mm.

[0248] 6. Glass, expressed as a mass percentage based on oxides, containing 50–80% SiO2, 0–25% B2O3, 0–30% Al2O3, 5–10% TiO2, and a total content of 0–3.5% Li2O, Na2O, and K2O.

[0249] It is a rectangle with one side of the main surface being 50cm to 300cm, and the thickness of the plate is 0.01mm to 0.5mm.

[0250] 7. A glass, expressed as a mass percentage based on oxides, containing 50–80% SiO2, 0–25% B2O3, 0–30% Al2O3, 0.01–10% TiO2, and 0.1–10% CeO2, with a total content of 0–3.5% for Li2O, Na2O, and K2O.

[0251] It is a rectangle with one side of the main surface being 50cm to 300cm, and the thickness of the plate is 0.01mm to 0.5mm.

[0252] 8. The glass according to any one of claims 5 to 7 above, wherein the average coefficient of thermal expansion at 50 to 200°C is 2.0 to 6.0 (×10⁻⁶). －6 / K).

[0253] 9. The glass according to any one of 1 to 8 above, wherein the total content of As2O3 and Sb2O3, expressed as a mass percentage based on oxides, is 0% or more and less than 0.25%.

[0254] 10. The glass according to any one of 1 to 9 above contains SnO2 at a mass percentage of 0.01 to 0.4% based on oxides.

[0255] 11. The glass according to any one of 1 to 10 above, wherein the BaO content, expressed as a mass percentage based on oxides, is 0% to 6.5%.

[0256] 12. The glass according to any one of 1 to 11 above, wherein the average absorbance change at a wavelength of 400 to 800 nm during electron beam irradiation has a thickness of 100 μm or less.

[0257] 13. The glass according to any one of 1 to 12 above, wherein the fracture toughness value (K) Ic The pressure is 0.78 MPa. m 1／2 above.

[0258] 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.

[0259] 15. The glass according to any one of 1 to 14 above, wherein the value E / ρ obtained by dividing the Young's modulus E (GPa) by the specific gravity ρ is 27.0 GPa or more.

[0260] 16. The glass according to any one of claims 1 to 15 above, wherein β-OH is 1.0 mm. －1 the following.

[0261] 17. The glass according to any one of claims 1 to 16 above, wherein at least one surface has a conductive film.

[0262] 18. The glass according to any one of claims 1 to 17 above, wherein at least one surface has an anti-reflective coating.

[0263] 19. A cover glass for a solar cell for a space satellite, using any one of the glass described in 1 to 18 above.

[0264] 20. An ultraviolet blocking glass, using any one of the glass described in any one of 1 to 18 above.

[0265] 21. An electron beam cutoff glass, using any one of the glass described in 1 to 18 above.

[0266] It should be noted that this application is based on Japanese Patent Application 2023-152237 filed on September 20, 2023, the contents of which are incorporated herein by reference.

Claims

1. A glass having a specific gravity of 2.2 to 2.7, a Young's modulus of 60 GPa or more, and an average coefficient of thermal expansion of 2.0 x 10"7 / K to 6.0 x 10"7 / K in the range of 50 to 200°C. －6 －6 ​​ It is a rectangle with one side measuring 50cm to 300cm, and the board thickness is 0.01mm to 0.5mm. The total content of Li2O, Na2O and K2O is 0 to 3.5% by mass, expressed as an oxide basis, and contains 0.1 to 10% CeO2.

2. The glass according to claim 1, wherein, It contains 0.01 to 10% TiO2, expressed as a mass percentage based on oxides.

3. The glass according to claim 1, wherein, It contains 5-10% TiO2, expressed as a mass percentage based on oxides.

4. A glass having a specific gravity of 2.2–2.7, a Young's modulus of 60 GPa or higher, and an average coefficient of thermal expansion of 2.0 × 10⁻⁶ at 50–200 °C. －6 / K~6.0×10 －6 / K, It is a rectangle with one side measuring 50cm to 300cm, and a thickness of 0.01mm to 0.5mm. It contains 5-10% TiO2, expressed as a mass percentage based on oxides.

5. A glass, expressed as a mass percentage based on oxides, contains 50–80% SiO2, 0–25% B2O3, 0–30% Al2O3, and 0.1–10% CeO2, and the total content of Li2O, Na2O, and K2O is 0–3.5%. It is a rectangle with one side of the main surface being 50cm to 300cm, and the thickness of the plate is 0.01mm to 0.5mm.

6. A glass, expressed as a mass percentage based on oxides, contains 50-80% SiO2, 0-25% B2O3, 0-30% Al2O3, 5-10% TiO2, and a total content of 0-3.5% for Li2O, Na2O, and K2O. It is a rectangle with one side of the main surface being 50cm to 300cm, and the thickness of the plate is 0.01mm to 0.5mm.

7. A glass, expressed as a mass percentage based on oxides, contains 50–80% SiO2, 0–25% B2O3, 0–30% Al2O3, 0.01–10% TiO2 and 0.1–10% CeO2, and the total content of Li2O, Na2O and K2O is 0–3.5%. It is a rectangle with one side of the main surface being 50cm to 300cm, and the thickness of the plate is 0.01mm to 0.5mm.

8. The glass according to any one of claims 5 to 7, wherein, The average coefficient of thermal expansion between 50 and 200℃ is 2.0 × 10⁻⁶. －6 / K~6.0×10 －6 / K.

9. The glass according to any one of claims 1 to 7, wherein, The total content of As2O3 and Sb2O3, expressed as a mass percentage based on oxides, is greater than 0% and less than 0.25%.

10. The glass according to any one of claims 1 to 7, wherein, Expressed as a mass percentage based on oxides, it contains SnO2 in the range of 0.01 to 0.4%.

11. The glass according to any one of claims 1 to 7, wherein, The content of BaO, expressed as a mass percentage based on oxides, ranges from 0% to 6.5%.

12. The glass according to any one of claims 1 to 7, wherein, The average absorbance change at wavelengths of 400–800 nm during electron beam irradiation is less than 0.01 when the plate thickness is 100 μm.

13. The glass according to any one of claims 1 to 7, wherein, Fracture toughness value K Ic 0.78 MPa m 1／2 above.

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

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

16. The glass according to any one of claims 1 to 7, wherein, β-OH is 1.0 mm －1 the following.

17. The glass according to any one of claims 1 to 7, wherein, At least one surface has a conductive film.

18. The glass according to any one of claims 1 to 7, wherein, At least one surface has an anti-reflective coating.

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

20. An ultraviolet blocking glass, using the glass according to any one of claims 1 to 7.

21. An electron beam cutoff glass, using the glass according to any one of claims 1 to 7.

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