Glass Substrate for Space Photovoltaic Power Generation

Abstract

To provide a glass substrate that can suppress solarization, and can also suppress resin deterioration caused by intense ultraviolet light even when the glass substrate is thinned.SOLUTION: A glass substrate for space solar power generation of the present invention has a sheet thickness of 0.2 mm or less and has a glass composition comprising, in terms of mass%, SiO2: 50-80%, Al2O3: 3-25%, B2O3: 0-20%, Li2O+Na2O+K2O: 0.01-25%, MgO: 0-20%, CaO: 0-20%, SrO: 0-20%, BaO: 0-20%, As2O3: 0-1%, Sb2O3: 0-2%, SnO2: 0.0001-2%, TiO2: 0.001-10%, and CeO2: 0.001-10%.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a glass substrate for space solar power generation.

Background Art

[0002] In recent years, the formation of communication networks using satellites has been actively carried out, and the use of solar power generation has been considered as a power supply source for these satellites. There are various types of solar cells used for this solar power generation, such as polycrystalline Si, single-crystalline Si, thin-film compounds, and GaAs. And for these solar cells, a cover glass for protecting the elements is attached to the power generation elements via a resin layer (see Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] When a solar cell is used for a long time, there arises a problem that the cover glass is discolored by ultraviolet rays, the intensity of sunlight irradiated on the solar cell element decreases, and the desired conversion efficiency cannot be obtained (hereinafter, this problem is referred to as solarization).

[0005] In addition, when strong ultraviolet rays (for example, ultraviolet rays having a wavelength of 250 nm) are irradiated during staying in space, there also arises a problem that the power generation efficiency decreases due to the deterioration of the resin used between the power generation elements. In particular, for the glass substrate, since it is launched into space, thinning is required, but the thinning increases the ultraviolet transmittance and accelerates the deterioration of the resin.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a glass substrate that can suppress deterioration of a resin due to strong ultraviolet rays while suppressing solarization and thinning the glass substrate.

Means for Solving the Problems

[0007] As a result of various studies, the inventors of the present invention have found that by introducing an appropriate amount of at least one of TiO2 and CeO2 as an essential component in the glass composition of a glass substrate for space solar power generation, the above technical problems can be solved, and the present invention is proposed.

[0008] The glass substrate for space solar power generation according to one aspect of the present invention can solve the above technical problems by introducing TiO2 as an essential component into the glass composition. That is, the glass substrate for space solar power generation according to the first invention is characterized in that the plate thickness is 0.2 mm or less, and the content of TiO2 in the glass composition is 0.001 to 10% by mass.

[0009] Further, the glass substrate for space solar power generation according to the second invention, in the first invention, the content of TiO2 in the glass composition is 0.005 to 10% by mass, and when the plate thickness is t and the content of TiO2 in the glass composition is B, it is preferable that B / t is 5% by mass / mm or more.

[0010] Further, the glass substrate for space solar power generation according to the third invention, in the first or second invention, the plate thickness is 0.2 mm or less, and as the glass composition, in mass%, SiO2 50 to 80%, Al2O3 3 to 25%, B2O3 0 to 20%, Li2O + Na2O + K2O 0 to 25%, MgO 0 to 20%, CaO 0 to 20%, SrO 0 to 20%, BaO 0 to 20%, As2O3 0 to 1%, SnO2 0.0001 to 2%, TiO2 0.005 to 10% are preferably contained.

[0011] Further, for the glass substrate for space solar power generation according to the fourth invention, in any one of the first to third inventions, it is preferable that the mass ratio SnO2 / (As2O3 + SnO2) in the glass composition is 0.90 to 1.

[0012] Further, for the glass substrate for space solar power generation according to the fifth invention, in any one of the first to fourth inventions, when the plate thickness is t and the mass ratio SnO2 / (As2O3 + SnO2) in the glass composition is A, it is preferable that A / t is 1 / mm or more.

[0013] Further, for the glass substrate for space solar power generation according to the sixth invention, in any one of the first to fifth inventions, after irradiating ultraviolet rays of 254 nm (13 mW / cm 2 ) for 23 hours, when the transmittance at a wavelength of 300 nm in terms of a thickness of 0.05 mm is t300 (%) and the transmittance at a wavelength of 300 nm in terms of a thickness of 0.05 mm before irradiating ultraviolet rays is T300 (%), it is preferable that T300 - t300 is 3% or less.

[0014] Further, for the glass substrate for space solar power generation according to the seventh invention, in any one of the first to sixth inventions, it is preferable that the transmittance at a wavelength of 250 nm in terms of a thickness of 0.05 mm is 30% or less.

[0015] Further, for the glass substrate for space solar power generation according to the eighth invention, in any one of the first to seventh inventions, it is preferable that the average transmittance at wavelengths of 400 nm to 1000 nm in terms of a thickness of 0.05 mm is 90% or more.

[0016] Further, for the glass substrate for space solar power generation according to the ninth invention, in any one of the first to eighth inventions, it is preferable that the density is 2.80 g / cm 3 or less. Here, the "density" refers to the value measured by the well-known Archimedes method.

[0017] Further, for the glass substrate for space solar power generation according to the tenth invention, in any one of the first to ninth inventions, the liquid-phase viscosity is 10 4.0It is preferably 0 dPa·s or more. Here, the "liquid-phase viscosity" refers to the viscosity of the glass at the liquid-phase temperature.

[0018] Moreover, the glass substrate for space solar power generation according to the 11th invention, in any one of the 1st to 10th inventions, has a thermal expansion coefficient at 30 to 380 °C of 25×10 -7 ~90×10 -7 / °C. Here, the "thermal expansion coefficient" refers to the value obtained by measuring the average thermal expansion coefficient at 30 to 380 °C using a dilatometer.

[0019] Moreover, the glass substrate for space solar power generation according to the 12th invention, in any one of the 1st to 11th inventions, preferably has a Fe2O3 content of 500 mass ppm or less.

[0020] Moreover, the glass substrate for space solar power generation according to the 13th invention, in any one of the 1st to 12th inventions, is preferably formed by the overflow down-draw method.

[0021] Moreover, the glass substrate for space solar power generation according to the 14th invention, in any one of the 1st to 13th inventions, preferably contains, as a glass composition in mass%, 50 to 80% of SiO2, 3 to 20% of Al2O3, 0 to 20% of B2O3, 5 to 20% of Li2O + Na2O + K2O, 0 to 20% of MgO, 0 to 20% of CaO, 0 to 20% of SrO, 0 to 20% of BaO, 0 to 1% of As2O3, 0.0001 to 2% of SnO2, and 2 to 10% of TiO2.

[0022] Moreover, the glass substrate for space solar power generation according to the 15th invention, in the 1st or 2nd invention, preferably contains, as a glass composition in mass%, 50 to 80% of SiO2, 3 to 25% of Al2O3, 0 to 20% of B2O3, 0.01 to 25% of Li2O + Na2O + K2O, 0 to 20% of MgO, 0 to 20% of CaO, 0 to 20% of SrO, 0 to 20% of BaO, 0 to 1% of As2O3, 0.0001 to 2% of SnO2, 0.001 to 10% of TiO2, and 0.001 to 10% of CeO2.

[0023] Furthermore, the glass substrate for space solar power generation according to another aspect of the present invention can solve the above technical problems by introducing CeO2 as an essential component into the glass composition. That is, the glass substrate for space solar power generation according to the 16th invention has a plate thickness of 0.2 mm or less, and as the glass composition, in mass %, SiO2 54 to 80%, Al2O3 4 to 25%, B2O3 0.1 to 20%, Li2O + Na2O + K2O 0 to 25%, MgO 0 to 20%, CaO 0 to 20%, SrO 0 to 20%, BaO 0 to 20%, As2O3 0 to 1%, SnO2 0.0001 to 2%, TiO2 0 to 10%, CeO2 0.001 to 10%.

Embodiments for Carrying Out the Invention

[0024] The glass substrate for space solar power generation according to one aspect of the present invention preferably contains, as the glass composition, in mass %, SiO2 50 to 80%, Al2O3 3 to 25%, B2O3 0 to 20%, Li2O + Na2O + K2O 0 to 25%, MgO 0 to 20%, CaO 0 to 20%, SrO 0 to 20%, BaO 0 to 20%, As2O3 0 to 1%, SnO2 0.0001 to 2%, TiO2 0.001 to 10%. Further, the glass substrate for space solar power generation according to another aspect of the present invention has a plate thickness of 0.2 mm or less, and as the glass composition, in mass %, SiO2 54 to 80%, Al2O3 4 to 25%, B2O3 0.1 to 20%, Li2O + Na2O + K2O 0 to 25%, MgO 0 to 20%, CaO 0 to 20%, SrO 0 to 20%, BaO 0 to 20%, As2O3 0 to 1%, SnO2 0.0001 to 2%, TiO2 0 to 10%, CeO2 0.001 to 10%. The reasons for limiting the content ranges of the respective components as described above will be explained below. In addition, the following % representation refers to mass % unless otherwise specified.

[0025] SiO2 is a component that forms a network, and its content is preferably 50 - 80%, 53 - 75%, 54 - 70%, particularly 55 - 65%. When the content of SiO2 increases, the high-temperature viscosity increases, the fusibility decreases, and devitrified crystals of cristobalite tend to precipitate easily. On the other hand, when the content of SiO2 decreases, the weather resistance decreases and it becomes difficult to vitrify.

[0026] Al2O3 is a component that increases the strain point and Young's modulus and suppresses the precipitation of devitrified crystals of cristobalite, and its content is preferably 3 - 25%, 4 - 24%, 5 - 23%, 6 - 21%, 7 - 20%, 9 - 19%, 11 - 18%, particularly 13 - 17%. When the content of Al2O3 increases, the liquidus temperature rises and it tends to be difficult to form into thin sheets. On the other hand, when the content of Al2O3 decreases, the strain point and Young's modulus tend to decrease, and the high-temperature viscosity increases and the fusibility decreases.

[0027] B2O3 acts as a flux, reduces viscosity, and improves fusibility. Its content is preferably 0 - 20%, 0.1 - 18%, 0.5 - 17%, 1 - 16%, 3 - 15%, 5 - 14%, 6 - 13%, 7 - 12%, particularly 8 - 11%. When the content of B2O3 increases, the strain point and Young's modulus tend to decrease, and the weather resistance tends to decrease. On the other hand, when the content of B2O3 decreases, the liquidus temperature becomes high and it becomes difficult to form into thin sheets. Also, the high-temperature viscosity increases and the fusibility decreases. Also, the glass surface is prone to being scratched.

[0028] Li2O, Na2O, and K2O are components that adjust the coefficient of thermal expansion and reduce the high-temperature viscosity. The total content of these components (Li2O + Na2O + K2O) is preferably 0 to 25%, 0.001 to 20%, 1 to 19%, 3 to 18%, 5 to 18%, 8 to 18%, 10 to 17%, particularly 12 to 17%. When the total content of these components increases, the strain point decreases, and the heat resistance tends to decrease. Also, the coefficient of thermal expansion may become too large, potentially impairing the compatibility with surrounding components. The content of Li2O is preferably 0 to 10%, 0 to 8%, 0 to 5%, 0 to 3%, 0 to 1%, particularly 0 to 0.5%. The content of Na2O is preferably 0 to 25%, 0.1 to 24%, 1 to 22%, 3 to 21%, 5 to 20%, 8 to 18%, 10 to 17%, particularly 12 to 16%. The content of K2O is preferably 0 to 10%, 0 to 8%, 0 to 5%, 0 to 3%, 0 to 1%, particularly 0.1 to 0.5%.

[0029] MgO is a component that improves the meltability without reducing the strain point, and its content is preferably 0 to 20%, 0 to 15%, 0 to 12%, 0 to 10%, 0 to 7%, 0 to 5%, 0.1 to 3%, particularly 0.5 to 2%. When the content of MgO increases, the liquidus temperature becomes high, making it difficult to form into thin plates, the coefficient of thermal expansion becomes high, potentially impairing the compatibility with surrounding components, and the density increases. On the other hand, when the content of MgO decreases, the strain point and Young's modulus decrease, or the high-temperature viscosity increases, making it difficult to melt.

[0030] CaO is a component that improves the meltability without reducing the strain point, and its content is preferably 0 to 20%, 0.01 to 18%, 0.1 to 15%, 1 to 12%, 2 to 10%, particularly 3 to 9%. When the content of CaO increases, the liquidus temperature becomes high, making it difficult to form, the coefficient of thermal expansion becomes high, potentially impairing the compatibility with surrounding components, and the density increases. On the other hand, when the content of CaO decreases, the strain point and Young's modulus decrease, or the high-temperature viscosity increases, making it difficult to melt.

[0031] SrO is a component that improves meltability without reducing the strain point, and its content is preferably 0 to 20%, 0.001 to 15%, 0.1 to 12%, 0.3 to 9%, 0.4 to 8%, particularly 0.5 to 7%. When the content of SrO increases, the liquidus temperature becomes high and it becomes difficult to form, the coefficient of thermal expansion becomes high and the compatibility with peripheral members is impaired, or the density becomes high. On the other hand, when the content of SrO decreases, the strain point and Young's modulus decrease, or the high-temperature viscosity becomes high and it becomes difficult to melt.

[0032] BaO is a component that improves meltability by reducing the high-temperature viscosity without reducing the strain point. It is also a component that increases Young's modulus. On the other hand, when the content of BaO increases, there is a risk that the liquidus temperature becomes high and it becomes difficult to form, the coefficient of thermal expansion becomes high and the compatibility with peripheral members is impaired, or the density becomes high. Therefore, the content of BaO is preferably 0 to 20%, 0 to 15%, 0 to 10%, 0 to 8%, 0 to 5%, particularly 0 to 3%.

[0033] Alkaline earth metal oxides such as MgO, CaO, SrO, and BaO can enhance meltability and devitrification resistance when mixed and contained, but when the content of these components increases, the density tends to increase, making it difficult to reduce the weight of the glass substrate. Therefore, the total content of alkaline earth metal oxides (MgO + CaO + SrO + BaO) is preferably 0 to 30%, 0 to 25%, 0 to 20%, 0 to 18%, 0 to 15%, 0 to 12%, particularly 0 to 10%.

[0034] The total content of CaO, SrO, and BaO, that is, CaO + SrO + BaO, is preferably 0 to 10%, 0 to 7%, 0 to 8%, 0 to 5%, 0 to 3%, 0 to 2%, 0 to 1%, particularly 0 to 0.1%. When the content of these components increases, the density tends to increase, making it difficult to reduce the weight of the glass substrate.

[0035] The content of Fe2O3 is 0 to 0.05%, preferably 0.0001 to 0.05%, 0.0001 to 0.03%, 0.005 to 0.02%, particularly 0.005 to 0.015%. When the content of Fe2O3 increases, the visible light transmittance decreases too much, reducing the amount of sunlight irradiated on the solar cell element and making solarization more likely to occur. When the content of Fe2O3 decreases, the ultraviolet transmittance increases, leading to the deterioration of the resin present on the substrate and potentially shortening the lifespan of the solar cell.

[0036] As2O3 is a clarifying agent but is a component that promotes solarization. Its content is preferably 0 to 1%, 0 to 0.8%, 0 to 0.5%, 0 to 0.3%, particularly 0 to 0.005%.

[0037] SnO2 is a component that suppresses solarization. The content of SnO2 is preferably 0.0001 to 2%, 0.001 to 1.5%, 0.01 to 1%, 0.05 to 0.5%, particularly 0.05 to 0.3%. When the content of SnO2 increases, the devitrification resistance is likely to decrease. On the other hand, when the content of SnO2 decreases, it becomes difficult to enjoy the above effects. Note that SnO2 raw material may be used as the SnO2 source, but it can also be contained from trace components included in other raw materials, etc.

[0038] To reliably exhibit the solarization suppression effect, it is important to strictly regulate the mass ratio SnO2 / (As2O3 + SnO2), and the value is preferably 0.001 to 1, 0.01 to 1, 0.1 to 1, 0.3 to 1, 0.5 to 1, 0.7 to 1, 0.9 to 1, particularly 1.

[0039] TiO2 and CeO2 are components that can reduce the ultraviolet transmittance and have the effect of suppressing solrization. Therefore, in any aspect of the present invention, the glass substrate for space solar power generation contains at least one of TiO2 and CeO2 in the glass composition. Accordingly, the total amount of TiO2 and CeO2, i.e., TiO2+CeO2, is 0.001 to 20%, 0.005 to 18%, 0.01 to 15%, 0.02 to 14%, 0.1 to 13%, 0.5 to 12%, 1 to 11%, 2 to 10%, more than 2.5 to 8%, particularly more than 3 to 7%. If TiO2+CeO2 is too much, the devitrification resistance is likely to decrease.

[0040] TiO2 is a component that can reduce the ultraviolet transmittance and has the effect of suppressing solrization. The content of TiO2 is preferably 0 to 10%, 0.001 to 10%, 0.005 to 9.5%, 0.01 to 9%, 0.015 to 8.8%, 0.02 to 8.5%, 0.1 to 8%, 0.3 to 7.5%, more than 0.4 to 7%, 0.5 to 7%, 0.8 to 6.5%, 1 to 6%, 1.5 to 5.5%, 1.8 to 5%, particularly 2 to 4.5%. If the content of TiO2 increases, the devitrification resistance is likely to decrease. Also, there is a risk of reducing the transmittance in the visible range. In one aspect of the present invention, the glass substrate for space solar power generation has TiO2 as an essential component (i.e., 0.001% or more). On the other hand, in another aspect of the present invention, the glass substrate for space solar power generation contains CeO2 as an essential component in the glass composition, and in this case, TiO2 does not have to be an essential component.

[0041] CeO₂ is a component that reduces the ultraviolet transmittance and has the effect of suppressing solarization. Its content is preferably 0 to 10%, 0.001 to 9%, 0.02 to 8%, 0.1 to 7.5%, 0.3 to 7%, 0.5 to 6%, 0.8 to 6.5%, 1 to 6%, 1.5 to 5.5%, 1.8 to 5%, particularly 2 to 4.5%. When the content of CeO₂ increases, the devitrification resistance tends to decrease. Also, there is a risk of lowering the transmittance in the visible range. Note that the glass substrate for space solar power generation in one aspect of the present invention contains TiO₂ as an essential component in the glass composition, and in this case, CeO₂ does not necessarily have to be an essential component. On the other hand, the glass substrate for space solar power generation in another aspect of the present invention does not necessarily contain TiO₂ in the glass composition, and in this case, CeO₂ is an essential component (i.e., 0.001% or more).

[0042] In addition to the above components, other components can be introduced in an appropriate total amount as needed.

[0043] ZnO is a component that increases the Young's modulus and improves the meltability. Its content is preferably 0 to 10%, more preferably 0 to 5%, still more preferably 0 to 3%, particularly preferably 0 to 1%, and most preferably 0 to 0.5%. When the content of ZnO increases, the density and the coefficient of thermal expansion tend to increase. Also, the devitrification resistance and the strain point tend to decrease.

[0044] ZrO₂ is a component that improves the weather resistance. Its content is preferably 0 to 2%, more preferably 0 to 1%, still more preferably 0 to 0.5%, particularly preferably 0 to 0.2%, and most preferably 0.001 to 0.1%. When the content of ZrO₂ increases, devitrification nodules of zircon tend to precipitate.

[0045] Sb₂O₃ is a component that acts as a fining agent. Its content is preferably 0 to 2%, more preferably 0 to 1.5%, still more preferably 0 to 1%, and particularly preferably 0 to 0.5%. When the content of Sb₂O₃ increases, the density tends to increase.

[0046] Cl acts as a clarifying agent. Its content is preferably 0 to 1%, more preferably 0 to 0.5%. When the content of Cl increases, the volatilization from the glass melt increases, and veining is likely to occur.

[0047] Rare earth oxides such as Nb2O5 and La2O3 are components that increase the Young's modulus. However, the cost of the raw materials themselves is high, and they are also components that reduce the devitrification resistance. Therefore, the content of rare earth oxides is preferably 3% or less, 2% or less, 1% or less, particularly 0.5% or less.

[0048] In the glass substrate for space solar power generation of the present invention, the plate thickness is 0.2 mm or less, preferably 0.15 mm or less, 0.1 mm or less, 0.07 mm or less, 0.05 mm or less, particularly 0.04 mm or less. The thinner the plate thickness, the more the weight of the glass substrate can be reduced.

[0049] In the glass substrate for space solar power generation of the present invention, when the plate thickness is t and the mass ratio SnO2 / (As2O3 + SnO2) in the glass composition is A, A / t is preferably 1 / mm or more, 3 / mm or more, 5 / mm or more, 7 / mm or more, 10 / mm or more, 12 / mm or more, particularly 15 to 1000 / mm. If A / t is too small, it becomes difficult to achieve both the solarization resistance and weight reduction of the glass substrate.

[0050] In the glass substrate for space solar power generation of the present invention, when the plate thickness is t and the content of TiO2 in the glass composition is B, B / t is preferably 5 mass% / mm or more, 8 mass% / mm or more, 10 mass% / mm or more, 15 mass% / mm or more, 20 mass% / mm or more, 25 mass% / mm or more, 30 mass% / mm or more, 35 mass% / mm or more, 40 mass% / mm or more, 42 mass% / mm or more, 45 mass% / mm or more, 50 mass% / mm or more, 52 mass% / mm or more, 55 mass% / mm or more, 58 mass% / mm or more, 60 mass% / mm or more, 62 mass% / mm or more, 65 mass% / mm or more, 68 mass% / mm or more, particularly 70 to 1000 mass% / mm. If B / t is too small, it becomes difficult to obtain sufficient ultraviolet shielding properties and solarization resistance when the plate thickness of the glass substrate is reduced (for example, 0.2 mm or less).

[0051] The glass substrate for space solar power generation of the present invention preferably has an unpolished surface. Although the theoretical strength of glass is inherently very high, it often breaks even under stress much lower than the theoretical strength. This is because small defects called Griffith flaws occur on the surface of the glass substrate in processes after glass forming, such as the polishing process. If the entire surface of the glass substrate, especially both surfaces, is left unpolished, it becomes difficult to impair the original mechanical strength of the glass substrate, and the glass substrate becomes difficult to break. Also, if the surface of the glass substrate is left unpolished, the polishing process can be omitted in the manufacturing process of the glass substrate, so the manufacturing cost of the glass substrate can be reduced. Further, in order to prevent a situation where breakage occurs from the cut surface of the glass substrate, chamfering, etching, etc. may be performed on the cut surface of the glass substrate.

[0052] The glass substrate for space solar power generation of the present invention can be manufactured by charging glass raw materials prepared to have a desired glass composition into a continuous melting furnace, heating and melting the glass raw materials at 1500 to 1600 °C, clarifying them, then supplying them to a forming device and forming the molten glass into a plate shape and gradually cooling it.

[0053] The glass substrate for space solar power generation of the present invention is preferably formed by the overflow down-draw method. If the glass substrate is formed by the overflow down-draw method, a glass substrate with good surface quality without polishing can be manufactured. The reason is that in the case of the overflow down-draw method, the surface of the glass substrate that should become the surface does not come into contact with the barrel-shaped refractory and is formed in a free surface state, so that a glass substrate with good surface quality without polishing can be formed. Here, the overflow down-draw method is a method of manufacturing a glass substrate by overflowing molten glass from both sides of a heat-resistant barrel-shaped structure, merging the overflowed molten glass at the lower end of the barrel-shaped structure, and stretching and forming it downward.

[0054] As forming methods, various methods other than the overflow down-draw method can be adopted. For example, various forming methods such as the float method, slot down method, redraw method, roll out method, and press method can be adopted.

[0055] In addition, the glass substrate for space solar power generation of the present invention may be subjected to surface processing such as film coating and machining such as cutting and drilling as required. As a film that can be used for surface processing, for example, an antireflection film can be used. By using the above film, the reflection loss of the glass substrate can be reduced.

[0056] Further, since the glass substrate for space solar power generation of the present invention may have various optical properties impaired and may have a large warpage when the plate thickness is small, it is preferable not to form a compressive stress layer by ion exchange on the surface.

[0057] The glass substrate for space solar power generation of the present invention preferably satisfies the following characteristics.

[0058] T300 - t300 is a parameter related to the solarization resistance to near-ultraviolet rays (wavelength 200 - 380 nm). Here, T300 refers to the transmittance (%) of the glass substrate at a wavelength of 300 nm in terms of a thickness of 0.05 mm, and t300 is 254 nm (13 mW / cm 2) after irradiating with ultraviolet rays for 23 hours, it refers to the transmittance (%) of the glass substrate at a wavelength of 300 nm in terms of a thickness of 0.05 mm. Also, T300 - t300 refers to the value obtained by subtracting t300 from T300. T300 - t300 is preferably 3% or less, 2.5% or less, 2% or less, 1.8% or less, 1.5% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, particularly -1 to 0.3%. The smaller T300 - t300 is, the more the solarization by near-ultraviolet rays can be suppressed. Also, since the ultraviolet rays particularly near a wavelength of 250 nm are very strong, there is a risk of significantly accelerating the deterioration of the resin used between the glass substrate and the power generation element in the solar cell. Therefore, the smaller T300 - t300 is, the more the deterioration of the resin in the solar cell can be suppressed, and it becomes easier to maintain the high energy conversion efficiency of the solar cell. Note that the value of T300 - t300 does not necessarily have to be positive and can also be negative.

[0059] T300 - t’300 is a parameter related to the solarization resistance against far-ultraviolet rays (wavelength 10 - 200 nm). Here, t’300 refers to the transmittance (%) of the glass substrate at a wavelength of 300 nm in terms of a thickness of 0.05 mm after irradiating with ultraviolet rays of 185 nm (13 mW / cm 2 ) for 23 hours. Also, T300 - t’300 refers to the value obtained by subtracting t’300 from T300. T300 - t’300 is preferably 3% or less, 2.5% or less, 2% or less, 1.8% or less, 1.5% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, particularly -1 to 0.3%. The smaller T300 - t’300 is, the more the solarization by far-ultraviolet rays can be suppressed. Thus, it becomes easier to maintain the high energy conversion efficiency of the solar cell. Note that the value of T300 - t’300 does not necessarily have to be positive and can also be negative.

[0060] The transmittance T250 at a wavelength of 250 nm in terms of a thickness of 0.05 mm is a characteristic representing ultraviolet shielding property. T250 is preferably 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 8% or less, 5% or less, particularly 0 to 1%. If T250 is too high, it becomes difficult to sufficiently shield ultraviolet rays. Therefore, when strong ultraviolet rays are irradiated during staying in space, the resin used between the power generation elements is deteriorated by ultraviolet rays, and the power generation efficiency is likely to decrease.

[0061] The average transmittance at wavelengths of 400 nm to 1000 nm in terms of a thickness of 0.05 mm is 90% or more, particularly preferably 91% or more. If the average transmittance at wavelengths of 400 nm to 1000 nm in terms of a thickness of 0.05 mm is too low, the power generation efficiency is likely to decrease.

[0062] The strain point is preferably 500 °C or higher, more preferably 550 °C or higher, still more preferably 600 °C or higher, particularly preferably 630 °C or higher. The higher the strain point, the higher the heat resistance of the glass substrate, and it becomes difficult to cause deformation or the like against significant temperature changes in space.

[0063] The liquidus temperature is preferably 1200 °C or lower, 1150 °C or lower, 1120 °C or lower, 1100 °C or lower, 1090 °C or lower, particularly 1070 °C or lower. The lower the liquidus temperature, the more difficult it is for the glass to devitrify during forming by the overflow down-draw method or the like.

[0064] The liquid-phase viscosity is preferably 10 4.0 dPa·s or more, 10 4.5 dPa·s or more, 10 5.0 dPa·s or more, 10 5.3 dPa·s or more, 10 5.5 dPa·s or more, particularly 10 5.7 dPa·s or more. The higher the liquid-phase viscosity, the more difficult it is for the glass to devitrify during forming by the overflow down-draw method or the like.

[0065] In the glass substrate for space solar power generation of the present invention, when the plate thickness is t and the logarithm of the liquid-phase viscosity η of the glass is C, C / t is preferably 70 / mm or more, 75 / mm or more, 80 / mm or more, 85 / mm or more, 90 / mm or more, 95 / mm or more, particularly 100 to 150 / mm. If C / t is too small, when forming a glass substrate with a small plate thickness (for example, 0.2 mm or less) by the overflow down-draw method or the like, the glass is likely to devitrify.

[0066] The density is preferably 2.80 g / cm 3 Hereinafter, 2.70 g / cm 3 Hereinafter, 2.65 g / cm 3 Hereinafter, 2.60 g / cm 3 Hereinafter, 2.55 g / cm 3 Hereinafter, 2.50 g / cm 3 Hereinafter, particularly 2.45 g / cm 3 Hereinafter is preferable. The smaller the density, the more the weight of the glass substrate can be reduced. As a result, it becomes easier to use in space.

[0067] The thermal expansion coefficient at 30 to 380 °C is preferably 25×10 -7 ~90×10 -7 / °C, 30×10 -7 ~85×10 -7 / °C, 35×10 -7 ~83×10 -7 / °C, 40×10 -7 ~80×10 -7 / °C, 45×10 -7 ~78×10 -7 / °C, particularly 50×10 -7 ~75×10 -7 / °C. When the thermal expansion coefficient is outside the above range, it becomes difficult to match the thermal expansion coefficients with members such as metals and organic adhesives, and it becomes difficult to prevent peeling of peripheral members such as metals and organic adhesives.

[0068] The temperature at a high-temperature viscosity of 10 2.5 dPa·s is preferably 1700 °C or less, 1650 °C or less, 1600 °C or less, particularly 1550 °C or less. The temperature at a high-temperature viscosity of 10 2.5The lower the temperature in dPa·s, the smaller the burden on glass manufacturing facilities such as melting furnaces, and the higher the bubble quality of the glass substrate can be improved. That is, the higher the temperature at 10 2.5 dPa·s, the lower the cost of manufacturing the glass substrate.

[0069] The Young's modulus is preferably 68 GPa or more, 69 GPa or more, particularly 70 GPa or more. The higher the Young's modulus, the more difficult it is for the glass substrate to bend.

[0070] The specific Young's modulus is preferably 27 GPa / (g / cm 3 ) or more, 28 GPa / (g / cm 3 ) or more, 29 GPa / (g / cm 3 ) or more, particularly 30 GPa / (g / cm 3 ) or more. The higher the specific Young's modulus, the lower the deflection of the glass substrate due to its own weight.

Examples

[0071] Hereinafter, the present invention will be described based on examples.

[0072] Tables 1 to 3 show examples of the present invention (Sample Nos. 1 to 20). In the tables, A / t refers to the value obtained by dividing the value of A by the value of t when A is the mass ratio SnO2 / (As2O3 + SnO2) in the glass composition and t is the plate thickness. Also, B / t refers to the value obtained by dividing the value of B by the value of t when B is the content of TiO2 in the glass composition and t is the plate thickness. Further, C / t refers to the value obtained by dividing the value of C by the value of t when C is the logarithm of the liquid-phase viscosity η of the glass and t is the plate thickness.

[0073]

Table 1

[0074]

Table 2

[0075]

Table 3

[0076] Each sample was prepared as follows. First, glass raw materials were formulated to have the glass compositions described in Tables 1 to 3, and melted at 1600 °C for 8 hours using a platinum pot. Then, the molten glass was poured onto a carbon plate and formed into a plate shape. Various properties of the obtained glass substrates were evaluated.

[0077] The density was measured by the well-known Archimedes method.

[0078] The coefficient of thermal expansion was measured using a dilatometer to obtain the average coefficient of thermal expansion at 30 to 380 °C.

[0079] The strain point Ps and the annealing point Ta were measured based on the method of ASTM C336.

[0080] The softening point Ts was measured based on the method of ASTM C338.

[0081] The viscosity of the glass at 10 4.0 dPa·s, 10 3.0 dPa·s, 10 2.5 dPa·s was measured by the platinum ball pulling-up method.

[0082] The liquidus temperature was measured by pulverizing the glass, passing it through a standard sieve of 30 mesh (mesh opening 500 μm), putting the glass powder remaining on a 50 mesh (mesh opening 300 μm) into a platinum boat, holding it in a temperature gradient furnace for 24 hours, and measuring the temperature at which crystals precipitate. The liquidus viscosity was measured by the platinum ball pulling-up method for the viscosity of the glass at the liquidus temperature.

[0083] The transmittance is measured as follows for the values before and after irradiating with a predetermined ultraviolet ray. After precisely optically processing a 0.05 mm thick glass sample, the transmittances at wavelengths of 250 nm, 300 nm, 400 nm, 550 nm, and 1000 nm (denoted as T250, T300, T400, T550, and T1000 respectively) are measured using a UV-3100PC (manufactured by Shimadzu Corporation). Then, ultraviolet rays of 254 nm (13 mW / cm 2 ) are irradiated onto the glass sample for 23 hours. Next, after the ultraviolet irradiation, the transmittances at wavelengths of 250 nm, 300 nm, 400 nm, 550 nm, and 1000 nm (denoted as t250, t300, t400, t550, and t1000 respectively) are measured.

[0084] As can be seen from the above table, for Samples No. 1 to 7 and 17 to 20, T300 - t300 was as low as 0.7% or less. In particular, for Samples No. 1 to 6 and 17 to 20, T250 was 0.0%, and it was found that the glass achieved both solarization resistance and ultraviolet shielding properties. Also, since Samples No. 8 to 17 contain 1.969% or more of TiO2 + CeO2, they are considered to be glasses that similarly have low T300 - t300 and T250 and achieve both solarization resistance and ultraviolet shielding properties.

Example

[0085] First, glass raw materials were prepared to have the glass compositions described for Samples No. 1 to 20 in the table, then supplied to a glass melting furnace and melted at 1600 °C. Next, the molten glass was supplied to an overflow down-draw forming device and formed into a film-like glass substrate with a plate thickness of 0.10 mm each. After cutting the obtained glass substrate into a predetermined size, the plate thickness was thinned to 0.05 mm by surface etching to obtain a glass substrate for space solar power generation.

Claims

1. The plate thickness is 0.2 mm or less, and as the glass composition, in mass%, SiO ２ 50 to 80%, Al ２ O ３ 3 to 14.1%, B ２ O ３ 0 to 20%, Li ２ O + Na ２ O + K ２ O 0.01 to 25%, MgO 0 to 20%, CaO 0 to 20%, SrO 0 to 20%, BaO 0 to 20%, As ２ O ３ 0 to 1%, Sb ２ O ３ 0 to 2%, SnO ２ 0.0001 to 2%, TiO ２ 0.001 to 10%, CeO ２ 0.001 to 10%, and is characterized by containing 0.001 to 10% for a glass substrate for space solar power generation.

2. TiO in the glass composition ２ has a content of 0.005 to 10% by mass. When the plate thickness is t and the content of TiO ２ in the glass composition is B, the glass substrate for space solar power generation according to claim 1, characterized in that B / t is 5% by mass / mm or more.

3. The plate thickness is 0.2 mm or less, and as the glass composition, in mass %, SiO ２ 50 to 80%, Al ２ O ３ 3 to 14.1%, B ２ O ３ 0 to 20%, Li ２ O + Na ２ O + K ２ O 0.01 to 25%, MgO 0 to 20%, CaO 0 to 20%, SrO 0 to 20%, BaO 0 to 20%, As ２ O ３ 0 to 1%, Sb ２ O ３ 0 to 2%, SnO ２ 0.0001 to 2%, TiO ２ 0.005 to 10%, CeO ２ 0.001 to 10%, and the glass substrate for space solar power generation according to claim 1 or 2, characterized by containing the same.

4. The mass ratio of SnO in the glass composition ２ / (As ２ O ３ + SnO ２ ) is 0.90 to 1, and the glass substrate for space solar power generation according to claim 1 or 2, characterized in that

5. Let the plate thickness be t, and the mass ratio SnO in the glass composition ２ / (As ２ O ３ + SnO ２ ) be A. The glass substrate for space solar power generation according to claim 1 or 2, wherein A / t is 1 / mm or more.

6. After irradiating with ultraviolet rays of 254 nm (13 mW / cm ２ ), the transmittance at a wavelength of 300 nm in terms of a thickness of 0.05 mm is defined as t300 (%), When the transmittance at a wavelength of 300 nm in terms of a thickness of 0.05 mm before irradiation with the ultraviolet light is defined as T300 (%), The glass substrate for space solar power generation according to claim 1 or 2, wherein T300 - t300 is 3% or less.

7. The glass substrate for space solar power generation according to claim 1 or 2, characterized in that the transmittance at a wavelength of 250 nm in terms of a thickness of 0.05 mm is 30% or less.

8. The glass substrate for space solar power generation according to claim 1 or 2, characterized in that the average transmittance at wavelengths of 400 nm to 1000 nm in terms of a thickness of 0.05 mm is 90% or more.

9. The density is 2.80 g / cm ３ The glass substrate for space solar power generation according to claim 1 or 2, characterized in that it is as follows.

10. The liquid-phase viscosity is 10 ４．０ The glass substrate for space solar power generation according to claim 1 or 2, characterized in that it is dPa·s or more.

11. The coefficient of thermal expansion at 30 to 380 °C is 25×10 －７ to 90×10 －７ / °C, and the glass substrate for space solar power generation according to claim 1 or 2, characterized in that.

12. Fe ２ O ３ The glass substrate for space solar power generation according to claim 1 or 2, characterized in that the content of

13. The glass substrate for space solar power generation according to claim 1 or 2, characterized in that it is formed by an overflow down-draw method.

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