Glass substrate for space photovoltaic power generation

Abstract

To provide a glass substrate which can suppress deterioration of a resin by strong ultraviolet even if the glass substrate is thinned, while suppressing solarization.SOLUTION: A glass substrate for space photovoltaic power generation has plate thickness of 0.2 mm or less, wherein in a glass composition, a content of TiO2+CeO2 is 0.1 to 15 mass%, a content of CeO2 is 0.1 to 10 mass%, and a content of ZnO is 0 to 5 mass%.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, the formation of communication networks using satellites has become increasingly common, and the use of solar power generation as a power supply source for these satellites is being considered. Solar cells used for solar power generation include various types such as polycrystalline Si, single-crystalline Si, thin-film compounds, and GaAs. In these solar cells, a cover glass for protecting the element is attached to the power generation element via a resin layer (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-173098 [Patent Document 2] Japanese Patent Publication No. 2022-089141 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] When solar cells are used over a long period of time, the cover glass becomes discolored due to ultraviolet rays, reducing the intensity of sunlight irradiating the solar cell element and making it impossible to achieve the desired conversion efficiency (hereinafter, this problem is referred to as solarization).

[0005] Furthermore, exposure to strong ultraviolet rays (e.g., ultraviolet rays with a wavelength of 250 nm) during space travel can cause deterioration of the resin used between the power generating element, resulting in a decrease in power generation efficiency. Glass substrates in particular must be thin because they will be launched into space, but thinner substrates increase UV transmittance, accelerating resin degradation.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a glass substrate that can suppress solarization and suppress resin deterioration due to strong ultraviolet rays even when the glass substrate is made thin. [Means for solving the problem]

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

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

[0009] Furthermore, in 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 preferably 0.005 to 10 mass %, and B / t is preferably 5 mass % / mm or more, where t is the plate thickness and B is the content of TiO2 in the glass composition.

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

[0011] Further, in the glass substrate for space solar power generation according to a 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 0.90-1.

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

[0013] The glass substrate for space solar power generation according to the sixth aspect of the present invention is any one of the first to fifth aspects of the present invention, and is characterized in that it has a wavelength of 254 nm (13 mW / cm 2 ) after 23 hours of UV irradiation, the transmittance at a wavelength of 300 nm, converted into a thickness of 0.05 mm, is defined as t300 (%), and the transmittance at a wavelength of 300 nm, converted into a thickness of 0.05 mm, before UV irradiation is defined as T300 (%). It is preferable that T300-t300 is 3% or less.

[0014] Furthermore, the glass substrate for space solar power generation according to the seventh invention is preferably any one of the first to sixth inventions, and has a transmittance of 30% or less at a wavelength of 250 nm, converted into a thickness of 0.05 mm.

[0015] Furthermore, the glass substrate for space solar power generation according to an eighth aspect of the present invention is preferably any one of the first to seventh aspects of the present invention, and has an average transmittance of 90% or more at a wavelength of 400 nm to 1000 nm, converted into a thickness of 0.05 mm.

[0016] Further, a ninth aspect of the present invention provides a glass substrate for space solar power generation according to any one of the first to eighth aspects of the present invention, wherein the density is 2.80 g / cm 3 Here, the "density" refers to a value measured by the well-known Archimedes method.

[0017] The glass substrate for space solar power generation according to the tenth aspect of the present invention is any one of the first to ninth aspects of the present invention, wherein the liquidus viscosity is 10 4.0It is preferable that the viscosity is dPa·s or more. Here, the "liquidus viscosity" refers to the viscosity of glass at the liquidus temperature.

[0018] The glass substrate for space solar power generation according to an eleventh aspect of the present invention is any one of the first to tenth aspects of the present invention, wherein the thermal expansion coefficient at 30 to 380°C is 25 × 10 -7 ~90×10 -7 / ° C. Here, the "thermal expansion coefficient" refers to the average thermal expansion coefficient measured at 30 to 380° C. using a dilatometer.

[0019] Furthermore, in the glass substrate for space solar power generation according to a twelfth aspect of the present invention, in any one of the first to eleventh aspects of the present invention, the content of Fe2O3 is preferably 500 ppm by mass or less.

[0020] Furthermore, the glass substrate for space solar power generation according to a thirteenth aspect of the present invention is preferably formed by an overflow downdraw method in any one of the first to twelfth aspects of the present invention.

[0021] Furthermore, the glass substrate for space solar power generation according to a fourteenth aspect of the present invention is preferably any of the first to thirteenth aspects of the present invention, and has a glass composition, in mass %, of SiO2 50 to 80%, Al2O3 3 to 20%, B2O3 0 to 20%, Li2O + Na2O + K2O 5 to 20%, 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%, and TiO2 2 to 10%.

[0022] Furthermore, the glass substrate for space solar power generation according to a fifteenth aspect of the present invention is preferably the glass substrate of the first or second aspect of the present invention, which contains, in mass %, 50 to 80% SiO2, 3 to 25% Al2O3, 0 to 20% B2O3, 0.01 to 25% Li2O+Na2O+K2O, 0 to 20% MgO, 0 to 20% CaO, 0 to 20% SrO, 0 to 20% BaO, 0 to 1% As2O3, 0.0001 to 2% SnO2, 0.001 to 10% TiO2, and 0.001 to 10% CeO2.

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

[0024] A glass substrate for space solar power generation in one embodiment of the present invention preferably contains, in mass %, as a glass composition 50 to 80% of SiO2, 3 to 25% of Al2O3, 0 to 20% of B2O3, 0 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, and 0.001 to 10% of TiO2. In another embodiment of the present invention, a glass substrate for space solar power generation has a thickness of 0.2 mm or less and preferably contains, in mass %, 54-80% SiO2, 4-25% Al2O3, 0.1-20% BO3, 0-25% Li2O + Na2O + KO, 0-20% MgO, 0-20% CaO, 0-20% SrO, 0-20% BaO, 0-1% As2O3, 0.0001-2% SnO2, 0-10% TiO2, and 0.001-10% CeO2. The reasons for limiting the content range of each component as described above are explained below. Note that, unless otherwise specified, the percentages below refer to mass %.

[0025] SiO2 is a component that forms a network, and its content is preferably 50 to 80%, 53 to 75%, 54 to 70%, and particularly 55 to 65%. If the SiO2 content is high, the high-temperature viscosity increases, the melting property decreases, and devitrification particles of cristobalite tend to precipitate easily. On the other hand, if the SiO2 content is low, the weather resistance decreases and vitrification becomes difficult.

[0026] Al2O3 is a component that increases the strain point and Young's modulus and suppresses the precipitation of devitrified cristobalite particles, and its content is preferably 3 to 25%, 4 to 24%, 5 to 23%, 6 to 21%, 7 to 20%, 9 to 19%, 11 to 18%, and particularly 13 to 17%. A high Al2O3 content tends to increase the liquidus temperature, making it difficult to form into a thin plate. On the other hand, a low Al2O3 content tends to decrease the strain point and Young's modulus, increase high-temperature viscosity, and reduce meltability.

[0027] B2O3 acts as a flux, lowering viscosity and improving meltability. Its content is preferably 0 to 20%, 0.1 to 18%, 0.5 to 17%, 1 to 16%, 3 to 15%, 5 to 14%, 6 to 13%, 7 to 12%, and particularly 8 to 11%. A high B2O3 content tends to lower the strain point and Young's modulus and reduce weather resistance. On the other hand, a low B2O3 content increases the liquidus temperature, making it difficult to form into a thin plate. Furthermore, high-temperature viscosity increases, tending to reduce meltability. Furthermore, the glass surface becomes more susceptible to scratches.

[0028] Li2O, Na2O, and K2O are components that adjust the thermal expansion coefficient and reduce high-temperature viscosity. The total amount 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%, and particularly 12 to 17%. If the total amount of these components is too large, the strain point decreases, and heat resistance tends to decrease. Furthermore, the thermal expansion coefficient may become too large, which may impair compatibility with surrounding components. The Li2O content is preferably 0 to 10%, 0 to 8%, 0 to 5%, 0 to 3%, 0 to 1%, and particularly 0 to 0.5%. The NaO content is preferably 0 to 25%, 0.1 to 24%, 1 to 22%, 3 to 21%, 5 to 20%, 8 to 18%, or 10 to 17%, and particularly preferably 12 to 16%. The KO content is preferably 0 to 10%, 0 to 8%, 0 to 5%, 0 to 3%, or 0 to 1%, and particularly preferably 0.1 to 0.5%.

[0029] MgO is a component that improves meltability without lowering 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%, and particularly 0.5 to 2%. If the MgO content is too high, the liquidus temperature will be high, making it difficult to mold into a thin plate, the thermal expansion coefficient will be high, impairing compatibility with surrounding components, and the density will be high. On the other hand, if the MgO content is too low, the strain point and Young's modulus will be low, and the high-temperature viscosity will be high, making it difficult to melt.

[0030] CaO is a component that improves meltability without lowering 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%, and particularly 3 to 9%. If the CaO content is too high, the liquidus temperature will be high, making molding difficult, the thermal expansion coefficient will be high, impairing compatibility with surrounding components, and the density will be high. On the other hand, if the CaO content is too low, the strain point and Young's modulus will be low, and high-temperature viscosity will be high, making melting difficult.

[0031] SrO is a component that improves meltability without lowering 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%, and particularly 0.5 to 7%. If the SrO content is too high, the liquidus temperature will be high, making molding difficult, the thermal expansion coefficient will be high, impairing compatibility with surrounding components, and the density will be high. On the other hand, if the SrO content is too low, the strain point and Young's modulus will be low, and high-temperature viscosity will be high, making melting difficult.

[0032] BaO is a component that reduces high-temperature viscosity without lowering the strain point, thereby improving meltability. It is also a component that increases Young's modulus. On the other hand, if the BaO content is too high, the liquidus temperature may become high, making molding difficult, the thermal expansion coefficient may become high, which may impair compatibility with surrounding components, or the density may become high. Therefore, the BaO content is preferably 0 to 20%, 0 to 15%, 0 to 10%, 0 to 8%, 0 to 5%, and particularly 0 to 3%.

[0033] Although the inclusion of a mixture of alkaline earth metal oxides, MgO, CaO, SrO, and BaO, can improve melting properties and devitrification resistance, increasing the content of these components tends to increase density, 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%, and particularly preferably 0 to 10%.

[0034] The total amount of CaO, SrO, and BaO, i.e., 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%, and particularly preferably 0 to 0.1%. If the amount of these components is too large, the density tends to increase, making it difficult to reduce the weight of the glass substrate.

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

[0036] As2O3 is a fining agent, but is also 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 preferably 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%, and particularly 0.05 to 0.3%. If the SnO2 content is too high, the devitrification resistance is likely to decrease. On the other hand, if the SnO2 content is too low, it becomes difficult to obtain the above effects. Note that although a SnO2 raw material may be used as the SnO2 source, it is also acceptable to incorporate SnO2 from trace components contained in other raw materials.

[0038] To ensure the solarization suppression effect, it is important to strictly control 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, and particularly 1.

[0039] TiO2 and CeO2 are components that reduce ultraviolet transmittance and suppress solarization. Therefore, in any embodiment of the present invention, the glass substrate for space solar power generation contains at least one of TiO2 and CeO2 in the glass composition. Therefore, the total amount of TiO2 and CeO2, 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%, and particularly more than 3 to 7%. Note that if the amount of TiO2 + CeO2 is too high, devitrification resistance is likely to decrease.

[0040] TiO2 is a component that reduces ultraviolet transmittance and inhibits solarization. The TiO2 content 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%, greater 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%, and particularly 2 to 4.5%. A high TiO2 content tends to reduce devitrification resistance. It may also reduce transmittance in the visible range. In one embodiment of the present invention, the glass substrate for space solar power generation contains TiO2 as an essential component (i.e., 0.001% or more). On the other hand, a glass substrate for space solar power generation in another embodiment of the present invention contains CeO2 as an essential component in the glass composition, and in this case TiO2 may not be an essential component.

[0041] CeO2 is a component that reduces ultraviolet transmittance and suppresses 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%, and particularly 2 to 4.5%. A high CeO2 content tends to reduce devitrification resistance. It may also reduce transmittance in the visible range. Note that a glass substrate for space solar power generation in one embodiment of the present invention contains TiO2 as an essential component in the glass composition, but in this case, CeO2 may not be an essential component. Meanwhile, a glass substrate for space solar power generation in another embodiment of the present invention does not necessarily contain TiO2 in the glass composition, but in this case, CeO2 is an essential component (i.e., 0.001% or more).

[0042] In addition to the above components, other components may be incorporated in a total amount as needed.

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

[0044] ZrO2 is a component that improves weather resistance. Its content is preferably 0 to 2%, more preferably 0 to 1%, even more preferably 0 to 0.5%, particularly preferably 0 to 0.2%, and most preferably 0.001 to 0.1%. If the ZrO2 content is high, devitrified particles 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%, even more preferably 0 to 1%, and particularly preferably 0 to 0.5%. As the Sb2O3 content increases, the density tends to increase.

[0046] Cl is a component that acts as a fining agent. Its content is preferably 0 to 1%, more preferably 0 to 0.5%. If the Cl content is high, more Cl is evaporated from the glass melt, making striae more likely to occur.

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

[0048] The glass substrate for space solar power generation of the present invention has a thickness of 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 thickness, the lighter the glass substrate can be.

[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, and particularly 15 to 1000 / mm. If A / t is too small, it becomes difficult to achieve both solarization resistance and weight reduction in the glass substrate.

[0050] In the glass substrate for space solar power generation of the present invention, where t is the plate thickness and B is the TiO content in the glass composition, B / t is preferably 5% by mass / mm or more, 8% by mass / mm or more, 10% by mass / mm or more, 15% by mass / mm or more, 20% by mass / mm or more, 25% by mass / mm or more, 30% by mass / mm or more, 35% by mass / mm or more, 40% by mass / mm or more, 42% by mass / mm or more, 45% by mass / mm or more, 50% by mass / mm or more, 52% by mass / mm or more, 55% by mass / mm or more, 58% by mass / mm or more, 60% by mass / mm or more, 62% by mass / mm or more, 65% by mass / mm or more, 68% by mass / mm or more, and particularly 70 to 1000% by mass / mm. If B / t is too small, it becomes difficult to obtain sufficient UV-shielding properties and solarization resistance when the glass substrate is made thinner (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 at stresses far lower than the theoretical strength. This is because small defects called Griffith flows occur on the surface of the glass substrate during processes after glass molding, such as a polishing process. Leaving the surface of the glass substrate, particularly both surfaces entirely unpolished, makes it difficult for the original mechanical strength of the glass substrate to be impaired, making the glass substrate less susceptible to breakage. Furthermore, leaving the surface of the glass substrate unpolished allows the polishing step to be omitted in the glass substrate manufacturing process, thereby reducing the manufacturing cost of the glass substrate. Furthermore, to prevent breakage from occurring at the cut surface of the glass substrate, the cut surface of the glass substrate may be subjected to chamfering, etching, or the like.

[0052] The glass substrate for space solar power generation of the present invention can be produced 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, fining the glass raw materials, supplying the glass raw materials to a forming device, forming the molten glass into a plate shape, and slowly cooling the glass raw materials.

[0053] The glass substrate for space solar power generation of the present invention is preferably formed by the overflow downdraw method. Forming a glass substrate by the overflow downdraw method allows the production of a glass substrate that is unpolished and has good surface quality. This is because, in the overflow downdraw method, the surface that will become the glass substrate does not come into contact with the tub-shaped refractory and is formed in a free surface state, allowing the production of a glass substrate that is unpolished and has good surface quality. Here, the overflow downdraw method is a method for producing a glass substrate by overflowing molten glass from both sides of a heat-resistant tub-shaped structure, and stretching the overflowed molten glass downward while joining at the bottom of the tub-shaped structure.

[0054] As a forming method, various methods other than the overflow downdraw method can be used, such as a float method, a slot down method, a redraw method, a roll out method, a press method, etc.

[0055] The glass substrate for space solar power generation of the present invention may be subjected to surface processing such as film deposition, or mechanical processing such as cutting and drilling, as necessary. An example of a film that can be used for surface processing is an anti-reflection film. The use of such a film can reduce the reflection loss of the glass substrate.

[0056] Furthermore, it is preferable that the glass substrate for space solar power generation of the present invention does not have a compressive stress layer formed on the surface by ion exchange, since there is a risk that various optical properties will be impaired and that warping will increase if the plate thickness is small.

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

[0058] T300 - t300 is a parameter related to solarization resistance to near-ultraviolet rays (wavelengths of 200 to 380 nm). Here, T300 refers to the transmittance (%) of a glass substrate at a wavelength of 300 nm, converted into a thickness of 0.05 mm, and t300 refers to the transmittance (%) of a glass substrate at a wavelength of 254 nm (13 mW / cm 2(T300-t300) refers to the transmittance (%) of a glass substrate at a wavelength of 300 nm, converted into a value for a thickness of 0.05 mm, after 23 hours of irradiation with ultraviolet light of 100 nm. Furthermore, 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, or 0.5% or less, particularly -1 to 0.3%. The smaller T300-t300, the more effectively solarization caused by near-ultraviolet rays can be suppressed. Furthermore, ultraviolet rays, particularly those with a wavelength around 250 nm, are very strong, which may significantly accelerate the degradation of the resin used between the glass substrate and the power generation element in a solar cell. Therefore, the smaller T300-t300, the more effectively the degradation of the resin in the solar cell can be suppressed, making it easier to maintain the high energy conversion efficiency of the solar cell. Note that the value of T300-t300 is not necessarily positive and can be negative.

[0059] T300-t'300 is a parameter related to solarization resistance against far ultraviolet rays (wavelength 10-200 nm). Here, t'300 is 185 nm (13 mW / cm 2 (t'300) refers to the transmittance (%) of a glass substrate at a wavelength of 300 nm, converted into a value of 0.05 mm thick, after 23 hours of irradiation with ultraviolet light of 1000 nm. Furthermore, 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, or 0.5% or less, particularly -1 to 0.3%. The smaller T300-t'300, the more effectively solarization caused by far ultraviolet light can be suppressed. This makes it easier to maintain high energy conversion efficiency of solar cells. Note that the value of T300-t'300 is not necessarily positive; it can also be negative.

[0060] The transmittance T250 at a wavelength of 250 nm, converted into a thickness of 0.05 mm, is a characteristic that indicates ultraviolet ray blocking ability. T250 is preferably 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 8% or less, 5% or less, and particularly 0 to 1%. If T250 is too high, it becomes difficult to sufficiently block ultraviolet rays. Therefore, when exposed to strong ultraviolet rays while in space, the resin used between the power generating element and the film is deteriorated by the ultraviolet rays, which can easily reduce power generation efficiency.

[0061] The average transmittance at wavelengths of 400 nm to 1000 nm, converted into a plate thickness of 0.05 mm, is preferably 90% or more, and particularly preferably 91% or more. If the average transmittance at wavelengths of 400 nm to 1000 nm, converted into a plate 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, and particularly preferably 630° C. or higher. The higher the strain point, the higher the heat resistance of the glass substrate, making it less likely to deform due to the significant temperature changes in outer 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 preferably 1070° C. The lower the liquidus temperature, the more unlikely the glass is to devitrify during forming by an overflow downdraw method or the like.

[0064] The liquidus 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, especially 10 5.7 The higher the liquidus viscosity, the less likely the glass is to devitrify during molding using the overflow downdraw method, etc.

[0065] In the glass substrate for space solar power generation of the present invention, when the plate thickness is t and log η, which is the logarithm of the liquidus 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, and particularly 100 to 150 / mm. If C / t is too small, the glass is likely to devitrify when a thin glass substrate (for example, 0.2 mm or less) is formed by the overflow downdraw method or the like.

[0066] The density is preferably 2.80 g / cm 3 Below 2.70g / cm 3 Below 2.65g / cm 3 Below, 2.60g / cm 3 Below 2.55g / cm 3 Below 2.50g / cm 3 Below, especially 2.45g / cm 3 The following are preferable: The lower the density, the lighter the glass substrate can be, making it easier to use in space.

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

[0068] High temperature viscosity 10 2.5 The temperature at dPa·s is preferably 1700°C or less, 1650°C or less, 1600°C or less, particularly 1550°C or less. 2.5The lower the temperature at dPa·s, the less strain is placed on glass manufacturing equipment such as melting furnaces, and the higher the bubble quality of the glass substrate. 2.5 The lower the temperature in dPa·s, the more inexpensively the glass substrate can be manufactured.

[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 less likely the glass substrate is to bend.

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

[0071] The present invention will be described below based on examples.

[0072] Tables 1 to 3 show examples (samples No. 1 to 20) of the present invention. In the tables, A / t refers to the value of A divided by the value of t, where 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 of B divided by the value of t, where B is the content of TiO2 in the glass composition and t is the plate thickness. Furthermore, C / t refers to the value of C divided by the value of t, where C is the logarithm of the liquidus viscosity η of the glass, logη, 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 mixed to obtain the glass compositions shown in Tables 1 to 3, and melted in a platinum pot at 1600°C for 8 hours. The molten glass was then poured onto a carbon plate and formed into a plate. Various properties of the obtained glass substrate were evaluated.

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

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

[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] Glass viscosity 10 4.0 dPa·s, 10 3.0 dPa·s, 10 2.5 The temperature in dPa·s was measured by the platinum sphere pulling method.

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

[0083] The transmittance was measured before and after irradiation with a specified ultraviolet ray as follows. After precision optical processing on a glass sample with a thickness of 0.05 mm, the transmittance at wavelengths of 250 nm, 300 nm, 400 nm, 550 nm, and 1000 nm (referred to as T250, T300, T400, T550, and T1000, respectively) was measured using a UV-3100PC (manufactured by Shimadzu Corporation). After that, the transmittance was measured at 254 nm (13 mW / cm 2 The glass sample is irradiated with ultraviolet light of 250 nm, 300 nm, 400 nm, 550 nm, and 1000 nm (t250, t300, t400, t550, and t1000, respectively) for 23 hours.

[0084] As can be seen from the table above, samples Nos. 1 to 7 and 17 to 20 had low T300-t300 values ​​of 0.7% or less. In particular, samples Nos. 1 to 6 and 17 to 20 had T250 values ​​of 0.0%, demonstrating that these glasses combine solarization resistance and UV blocking properties. Furthermore, samples Nos. 8 to 17 contained 1.969% or more of TiO2 + CeO2, and therefore similarly had low T300-t300 and T250 values, and are considered to be glasses that combine solarization resistance and UV blocking properties. [Example]

[0085] First, glass raw materials were prepared to obtain the glass compositions shown in Samples No. 1 to 20 in the table, then fed into a glass melting furnace and melted at 1600°C. The molten glass was then fed into an overflow downdraw forming device and formed into a sheet thickness of 0.10 mm to obtain a film-like glass substrate. The obtained glass substrate was cut to a predetermined size and then slimmed to a thickness of 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 TiO in the glass composition ２ + CeO ２ The content of is 0.1 to 15 mass %, CeO ２ % by mass and ZnO content is 0 to 5% by mass.

2. TiO in the glass composition ２ The content of is 0.005 to 10 mass %, the plate thickness is t, and the TiO ２ 2. The glass substrate for space solar power generation according to claim 1, wherein, when the content of said element is defined as B, B / t is 5 mass % / mm or more.

3. The plate thickness is 0.2 mm or less, and the glass composition is, in mass%, SiO ２ 50-80%, Al ２ O ３ 3-25%, B ２ O ３ 0-20%, Li ２ O + Na ２ O+K ２ O 5-25%, MgO 0-20%, CaO 0-20%, SrO 0-20%, BaO 0-20%, ZnO 0-5%, As ２ O ３ 0-1% SnO ２ 0.0001-2%, TiO ２ 0.005-10%, CeO ２ 3. The glass substrate for space solar power generation according to claim 1, wherein the content is 0.5 to 10%.

4. Mass ratio of SnO in glass composition ２ / (As ２ O ３ + SnO ２ 3. The glass substrate for space solar power generation according to claim 1, wherein the value of (a) is 0.90 to 1.

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

6. 254nm (13mW / cm ２ ) after 23 hours of irradiation with ultraviolet light, the transmittance at a wavelength of 300 nm, converted into a thickness of 0.05 mm, is defined as t300 (%), When the transmittance at a wavelength of 300 nm converted into a thickness of 0.05 mm before the ultraviolet light irradiation is T300 (%), 3. The glass substrate for space solar power generation according to claim 1, wherein T300-t300 is 3% or less.

7. 3. The glass substrate for space solar power generation according to claim 1, wherein the transmittance at a wavelength of 250 nm, converted into a thickness of 0.05 mm, is 30% or less.

8. 3. The glass substrate for space solar power generation according to claim 1, wherein the glass substrate has an average transmittance of 90% or more at wavelengths of 400 nm to 1000 nm, converted into a thickness of 0.05 mm.

9. Density is 2.80 g / cm ３ 3. The glass substrate for space solar power generation according to claim 1, wherein the glass substrate is:

10. Liquidus viscosity is 10 ４．０ 3. The glass substrate for space solar power generation according to claim 1, wherein the viscosity is dPa·s or more.

11. Thermal expansion coefficient at 30 to 380°C is 25 x 10 －７ ~90 x 10 －７ 3. The glass substrate for space solar power generation according to claim 1, wherein the temperature is 100°C.

12. Fe ２ O ３ 3. The glass substrate for space solar power generation according to claim 1, wherein the content of is 500 mass ppm or less.

13. 3. The glass substrate for space solar power generation according to claim 1, which is formed by an overflow downdraw method.

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