JP6040699B2 - Glass plate for thin film solar cell - Google Patents

Description

  The present invention relates to a glass plate for a thin film solar cell, and more particularly to a glass plate suitable for a CIS thin film solar cell and a CdTe thin film solar cell.

In a thin film solar cell, for example, a CIS thin film solar cell, a chalcopyrite type compound semiconductor made of Cu, In, Ga, and Se, Cu (InGa) Se ₂ is formed on a glass plate as a photoelectric conversion film.

  In order to apply Cu, In, Ga, and Se on a glass plate by a multi-source deposition method, a selenization method, or the like to obtain a chalcopyrite type compound, a heat treatment step of about 500 to 600 ° C. is required.

  Also in the CdTe thin film solar cell, a photoelectric conversion film made of Cd and Te is formed on a glass plate. Also in this case, a heat treatment step of about 500 ° C. to 600 ° C. is required.

  Conventionally, soda lime glass has been used as a glass plate in CIS thin film solar cells, CdTe thin film solar cells, and the like. However, soda-lime glass is likely to be thermally deformed or shrunk in a high-temperature heat treatment process. In order to solve this problem, increasing the strain point of a glass plate is currently under study (see Patent Document 1).

JP-A-11-135819

  By the way, in the CIS thin film solar cell and the CdTe thin film solar cell, it is considered that when the photoelectric conversion film is formed at a high temperature, the crystal quality of the photoelectric conversion film is improved and the photoelectric conversion efficiency is improved. However, since the strain point of the glass plate described in Patent Document 1 is not sufficiently high, when the film formation temperature of the photoelectric conversion film is more than 600 to 650 ° C., thermal deformation and thermal contraction are likely to occur, and the photoelectric conversion efficiency Could not be raised sufficiently.

  On the other hand, when the strain point of the glass plate is raised, the melting temperature and the molding temperature of the glass plate are likely to rise, and the production efficiency of the glass plate is likely to be lowered. Therefore, it is very difficult to achieve both high strain point and glass plate productivity.

  Furthermore, when the reflectance of a glass plate becomes high, the intensity | strength of the heat ray | wire which reaches the inside of a glass plate will fall easily in the manufacturing process of a thin film solar cell. In this case, when manufacturing a thin film solar cell, the temperature increase rate of a glass plate falls and the production efficiency of a thin film solar cell falls.

  The present invention has been made in view of the above circumstances, and its technical problem is to create a glass plate that can achieve both a high strain point and the productivity of a glass plate, and can improve the production efficiency of a thin-film solar cell. It is to be.

As a result of intensive studies, the present inventors have found that the above technical problem can be solved by regulating the glass composition and the glass characteristics to a predetermined range, and propose the present invention. That is, the glass plate for a thin-film solar cell of the present invention has a glass composition, in _{mass%, SiO 2 45~60%, Al} 2 O 3 8.0 super _{~20%, B 2 O 3 +} Li 2 O 0~4 %, Na ₂ O 4.3 to 20%, Na ₂ O + K ₂ O 4.3 to 30%, MgO + CaO + SrO + BaO 1 to 40%, and (5 × [Al ₂ O ₃ ] + 7.5 × [ZrO ₂ ] −15 × [Na ₂ O] −5 × [K ₂ O]) is −20 to 60, (0.012 × [MgO] + 0.016 × [CaO] + 0.021 × [SrO] +0 0.023 × [BaO] + 0.021 × [ZrO ₂ ] − [Fe ₂ O ₃ ]) is 0.27 to 0.52 , and the strain point is more than 580 ° C. Here, the “strain point” refers to a value measured based on ASTM C336-71. In addition, [] indicates the mass% value of the explicit component. “Fe ₂ O ₃ ” indicates a value obtained by converting the total Fe amount into the Fe ₂ O ₃ amount regardless of the valence.

The glass plate for a thin film solar cell of the present invention has a value of (5 × [Al ₂ O ₃ ] + 7.5 × [ZrO ₂ ] −15 × [Na ₂ O] −5 × [K ₂ O]) within a predetermined range. Is regulated. If it does in this way, it will become easy to make a high strain point and the productivity of a glass plate compatible. Specifically, it becomes easy to lower the melting temperature and the molding temperature while increasing the strain point.

The glass plate for a thin-film solar cell of the present invention, (0.012 × [MgO] + 0.016 × [CaO] + 0.021 × [SrO] + 0.023 × [BaO] + 0.021 × [ZrO 2] - the value of _{[Fe 2 O} 3]) is restricted to a predetermined range. If it does in this way, it will become easy to reduce a reflectance, suppressing a raise of raw material cost, and also will become easy to raise a heat ray absorption coefficient.

  Furthermore, the glass plate for thin film solar cells of this invention has a strain point exceeding 580 degreeC. If it does in this way, it will become easy to form a photoelectric converting film at high temperature, the crystal quality of a photoelectric converting film will be improved, and it will become difficult to produce a heat deformation and a heat shrink in a glass plate by a heat treatment process.

The glass plate for a thin-film solar cell of the present invention has, as a glass composition, mass%, SiO ₂ 45-60%, Al ₂ O ₃ more than 8.0-20%, B ₂ O ₃ + Li ₂ O 0-4%, Na ₂ O 4.3 super _{~20%, Na 2 O + K} 2 O 4.3 super _{~30%, MgO + CaO + SrO} + BaO 1~40%, Al 2 O 3 + ZrO 2 10.5~20%, Fe 2 O 3 0.001 It is preferable to contain -0.2%. Here, “B ₂ O ₃ + Li ₂ O” is the total amount of B ₂ O ₃ and Li ₂ O. “Na ₂ O + K ₂ O” is the total amount of Na ₂ O and K ₂ O. “MgO + CaO + SrO + BaO” is the total amount of MgO, CaO, SrO and BaO. “Al ₂ O ₃ + ZrO ₂ ” is the total amount of Al ₂ O ₃ and ZrO ₂ .

The glass plate for a thin film solar cell of the present invention preferably has a temperature at 10 ^2.5 dPa · s of 1520 ° C. or lower. Here, “temperature at 10 ^2.5 dPa · s” refers to a value measured by a platinum ball pulling method.

The glass plate for a thin film solar cell of the present invention is preferably used for a CIS thin film solar cell.

The glass plate for a thin film solar cell of the present invention is preferably used for a CdTe-based thin film solar cell.

The glass plate for a thin film solar cell of the present invention is (5 × [Al ₂ O ₃ ] + 7.5 × [ZrO ₂ ] −15 × [Na ₂ O] −5 × [K ₂ ) as a glass composition in mass%. O]) is −20 to 60, (0.012 × [MgO] + 0.016 × [CaO] + 0.021 × [SrO] + 0.023 × [BaO] + 0.021 × [ZrO ₂ ] − [ The value of Fe ₂ O ₃ ]) is 0.27 to 0.52 .

The value of (5 × [Al ₂ O ₃ ] + 7.5 × [ZrO ₂ ] −15 × [Na ₂ O] −5 × [K ₂ O]) is −20 to 60, preferably −20 to 50. Preferably it is -20-35, More preferably, it is -18-20, Most preferably, it is -15-10. If the value of (5 × [Al ₂ O ₃ ] + 7.5 × [ZrO ₂ ] −15 × [Na ₂ O] −5 × [K ₂ O]) is too large, the melting temperature and the molding temperature increase. It becomes difficult to melt and mold the glass. On the other hand, if the value of (5 × [Al ₂ O ₃ ] + 7.5 × [ZrO ₂ ] −15 × [Na ₂ O] −5 × [K ₂ O]) is too small, the strain point tends to decrease. .

The value of (0.012 × [MgO] + 0.016 × [CaO] + 0.021 × [SrO] + 0.023 × [BaO] + 0.021 × [ZrO ₂ ] − [Fe ₂ O ₃ ]) is 0. 27 to 0.52 , preferably 0.35 to 0.52 , more preferably 0.41 to 0.52 , and still more preferably 0.45 to 0.52 . The value of (0.012 × [MgO] + 0.016 × [CaO] + 0.021 × [SrO] + 0.023 × [BaO] + 0.021 × [ZrO ₂ ] − [Fe ₂ O ₃ ]) is too large. And, since the reflectance increases, the heat ray absorption coefficient decreases, and the strength of the heat rays that reach the inside of the glass plate is likely to decrease, the temperature increase rate of the glass plate decreases in the thin film solar cell production process. As a result, the production efficiency of the thin-film solar cell is likely to decrease. Furthermore, the raw material cost increases so that the manufacturing cost of the glass plate is likely to increase. On the other hand, the value of (0.012 × [MgO] + 0.016 × [CaO] + 0.021 × [SrO] + 0.023 × [BaO] + 0.021 × [ZrO ₂ ] − [Fe ₂ O ₃ ]) If it is too small, it will be difficult to lower the high temperature viscosity while maintaining the strain point, and the heat ray absorption coefficient will rise too much, resulting in variations in the degree of reach of the heat ray in the glass melt inside the melting furnace. It becomes easy and it becomes difficult to melt glass uniformly.

  It is preferable to limit the content of each component as follows.

SiO ₂ is a component that forms a glass network. The content is preferably 45 to 60%, 45 to 54%, and particularly preferably 48 to 52%. If the SiO ₂ content is too large, the high-temperature viscosity becomes unduly high and the meltability and moldability tend to decrease, and the thermal expansion coefficient becomes too low. It becomes difficult to match the thermal expansion coefficient of the conversion film. In the glass composition system according to the present invention, the strain point does not increase so much even when the content of SiO ₂ is increased. On the other hand, if the content of SiO ₂ is too small, devitrification resistance is liable to decrease. Furthermore, the thermal expansion coefficient becomes too high, and the thermal shock resistance of the glass plate is likely to be lowered. As a result, the glass plate is likely to be cracked in the heat treatment step when the thin film solar cell is manufactured.

Al ₂ O ₃ is a component that increases the strain point, is a component that increases the weather resistance and chemical durability, and further is a component that increases the surface hardness of the glass plate. The content of Al ₂ O ₃ is preferably more than 8.0 to 20%, 10 to 17%, more than 11.0 to 16%, particularly preferably 11.5 to 15.5%. When the content of Al ₂ O ₃ is too large, the high temperature viscosity becomes unduly high, the meltability and the formability tends to decrease. On the other hand, when the content of Al ₂ O ₃ is too small, the strain point tends to decrease. In addition, when the surface hardness of a glass plate is high, in the process of removing a photoelectric converting film in the patterning of a CIS type thin film solar cell, a glass plate becomes difficult to be damaged.

SiO ₂ —Al ₂ O ₃ is a difference between SiO _{2 as} a main component and Al ₂ O ₃ that greatly contributes to increase the strain point among components constituting the glass network. If SiO ₂ —Al ₂ O ₃ is too large, the strain point tends to decrease. On the other _hand, when the SiO 2 _-Al 2 _{O 3} is too small, devitrification resistance is liable to decrease. Therefore, the content of SiO ₂ —Al ₂ O ₃ is preferably 28 to 50%, less than 30 to 45%, 32 to 43%, particularly preferably 34 to 40%.

B ₂ O ₃ + Li ₂ O is a component that lowers the melting temperature and molding temperature by lowering the viscosity of the glass, but it is a component that extremely lowers the strain point, and along with component volatilization at the time of melting, It is a component that consumes the furnace refractory material. Therefore, B ₂ O ₃ + Li ₂ O is an optional component, and its content is preferably 0 to 4%, 0 to 2%, particularly preferably 0 to 1%.

B ₂ O ₃ is a component that lowers the high-temperature viscosity and improves the meltability and moldability, but is a component that lowers the strain point, and consumes the furnace refractory material as the component volatilizes during melting. It is an ingredient. Therefore, B ₂ O ₃ is an optional component, and its content is preferably 0 to less than 4%, 0 to 1%, particularly preferably 0 to less than 0.1%.

Li ₂ O is a component that promotes the growth of chalcopyrite crystals. Further, Li 2 _O is a component for adjusting the thermal expansion coefficient, also lowers the high temperature viscosity, a component for enhancing the meltability and formability. However, Li ₂ O is a component that significantly lowers the strain point in addition to the high raw material cost. Therefore, Li ₂ O is an optional component, and its content is preferably 0 to less than 4%, 0 to 1%, particularly preferably 0 to less than 0.1%.

Na ₂ O + K ₂ O is a component that adjusts the thermal expansion coefficient, and is a component that lowers the high-temperature viscosity and improves the meltability and moldability. Na ₂ O + K ₂ O is an effective component for the growth of chalcopyrite crystals in a CIS solar cell, and is an important component for increasing the photoelectric conversion efficiency. The content of Na ₂ O + K ₂ O is preferably more than 4.3 to 30%, more than 4.3 to 20%, more than 4.3 to 18%, more than 4.3 to 15%, and particularly preferably 7 to 12%. When the content of Na 2 O _{+ K} 2 _O is too large, in addition to the strain point tends to decrease, the thermal expansion coefficient becomes too high, the thermal shock resistance of the glass plate is liable to lower. As a result, in the heat treatment step when manufacturing the thin film solar cell, the glass plate is likely to be thermally contracted or thermally deformed or cracked. On the other _hand, when the content of Na 2 O + _{K 2} O is too small, it becomes difficult to enjoy the above-mentioned effects.

Na ₂ O is a component that promotes the growth of chalcopyrite crystals. Na ₂ O is a component that adjusts the thermal expansion coefficient, and is a component that lowers the high-temperature viscosity and improves the meltability and moldability. The content of Na ₂ O is 4.3 super 20%, 4.3 ultra 15%, 4.3 ultra 12%, in particular 4.3 super 9% is preferable. When the content of Na 2 _O is too large, in addition to the strain point tends to decrease, the thermal expansion coefficient becomes too high, the thermal shock resistance of the glass plate is liable to lower. As a result, in the heat treatment step when manufacturing the thin film solar cell, the glass plate is likely to be thermally contracted or thermally deformed or cracked.

K ₂ O is a component that promotes the growth of chalcopyrite crystals. K ₂ O is a component that adjusts the coefficient of thermal expansion, and is a component that lowers the high-temperature viscosity and improves meltability and moldability. The content of K ₂ O is preferably 0 to 15%, 0.1 to 10%, particularly preferably 1 to 7%. However, if the content of K ₂ O is too large, KAlSiO-based devitrified crystals tend to precipitate in a glass system containing more than 10% Al ₂ O ₃ . If the content of K 2 _O is too large, easily strain point is lowered, also too high thermal expansion coefficient, the thermal shock resistance of the glass plate is liable to lower. As a result, in the heat treatment step when manufacturing the thin film solar cell, the glass plate is likely to be thermally contracted or thermally deformed or cracked.

MgO + CaO + SrO + BaO is a component that lowers the high temperature viscosity without lowering the strain point. The content of MgO + CaO + SrO + BaO is preferably 1 to 40%, 12 to 37%, 15 to 35%, more than 17.0 to 32%, 18 to 30%, particularly 19 to 25%. When there is too much content of MgO + CaO + SrO + BaO, devitrification resistance will fall easily and raw material cost will rise. If the content of MgO + CaO + SrO + BaO is too large, the alkaline component, tend to particularly suppress the diffusion of Na ₂ O. On the other hand, when the content of MgO + CaO + SrO + BaO is too small, the high temperature viscosity becomes too high.

MgO is a component that increases the meltability and moldability by reducing the high-temperature viscosity. Moreover, MgO is a component with a large effect which makes a glass plate hard to break among alkaline-earth oxides. However, when MgO coexists with ZrO ₂ , it is a component that remarkably lowers the liquid phase viscosity by precipitating ZrO ₂ -based devitrified crystals. Further, when coexisting with CaO, it is a component that easily deposits a CaMgSiO-based devitrified crystal. Therefore, MgO is an optional component, and its content is 0 to 10%, 0 to less than 3.7%, 0.01 to 3%, 0.02 to 2%, particularly 0.03 to 0.5%. preferable.

  CaO is a component that increases the meltability and moldability by reducing the high-temperature viscosity. Moreover, CaO is a component with a large effect which makes a glass plate hard to break among alkaline-earth oxides. The content of CaO is preferably 0 to 10%, 0.1 to 9%, 1 to 8%, 2 to 7.5%, particularly 3 to 6%. When there is too much content of CaO, devitrification resistance will fall easily and it will become difficult to shape | mold into a glass plate.

The mass ratio CaO / MgO is a ratio of MgO and CaO having a large effect of reducing the high temperature viscosity among the alkaline earth oxides. From the point of view of resistance to devitrification, against easy MgO especially to generate devitrification crystals ZrO ₂ system, which is the ratio of hard CaO which caused the devitrification crystals ZrO ₂ system as compared with MgO. The value of the mass ratio CaO / MgO is preferably more than 1, more than 2, more than 2.5, particularly more than 3.4 in order to reduce the high temperature viscosity while suppressing the precipitation of ZrO ₂ -based devitrified crystals.

SrO is a component that increases the meltability and moldability by reducing the high-temperature viscosity. Also, SrO, when coexisting with ZrO _2, is a component that hardly deposited devitrification crystals ZrO ₂ system. The content of SrO is preferably 0 to 20%, 0.1 to 17%, more than 4.0 to 16%, 5 to 15%, more than 7.0 to 14%, particularly preferably 9.2 to 13.5%. If the content of SrO is too large, feldspar group devitrified crystals are likely to precipitate, and the raw material cost increases.

  BaO is a component that lowers the high-temperature viscosity and improves the meltability and moldability. The BaO content is preferably 0 to 20%, 0.1 to 15%, more than 2.0 to less than 14%, more than 2.0 to less than 10%, particularly preferably more than 2.0 to less than 8%. When there is too much content of BaO, the devitrification crystal | crystallization of a barium feldspar group will become easy to precipitate, and raw material cost will rise. Furthermore, the density increases, and the cost of the support member for the thin-film solar cell is likely to increase. In addition, when there is too little content of BaO, high temperature viscosity will become high and there exists a tendency for a meltability and a moldability to fall.

Al ₂ O ₃ + ZrO ₂ is a component that increases the strain point. The content is preferably 5 to 20%, 10.5 to 20%, more than 13.0 to 20%, particularly preferably 17.4 to 20%. When the content of Al ₂ O ₃ + ZrO ₂ is too high, devitrification resistance is liable to lower, it becomes difficult to mold the glass sheet. On the other _hand, when the content of Al ₂ O 3 + ZrO ₂ is too small, the strain point tends to decrease.

ZrO ₂ is a component that increases the strain point without increasing the high-temperature viscosity. The content of ZrO ₂ is preferably 0.1 to 10%, 0.5 to 8%, 1 to 6.5%, particularly 2 to 6%. If the content of ZrO ₂ is too large, the density tends to be high, the glass plate is easily broken, and ZrO ₂ -based devitrified crystals are likely to precipitate, making it difficult to form the glass plate. On the other hand, when the content of ZrO ₂ is too small, the strain point tends to decrease.

Fe ₂ O ₃ is a component that increases the heat ray absorption coefficient. The content of Fe ₂ O ₃ is preferably 0.001 to 0.2%, 0.015 to 0.15%, particularly preferably 0.03 to less than 0.1%. When the content of Fe ₂ O ₃ is too large, the melting furnace the glass melt, it tends to occur variation in the heat ray achievement, difficult to uniformly melt the glass. On the other hand, when the content of Fe ₂ O ₃ is too small, it is necessary to use expensive high purity source, the production cost of the glass plate increases. Moreover, since the heat ray absorption coefficient becomes small and the strength of the heat ray that reaches the inside of the glass plate is likely to decrease, the temperature increase rate of the glass plate decreases in the production process of the thin film solar cell, and the production efficiency of the thin film solar cell Tends to decrease.

  In addition to the above components, for example, the following components may be added. In addition, the addition amount of the following components is preferably 10% or less, 5% or less, and particularly preferably 2% or less.

P ₂ O ₅ is a component that enhances devitrification resistance, in particular, a component that suppresses precipitation of ZrO ₂ -based devitrification crystals, and a component that makes the glass plate difficult to break. However, when the content of P ₂ O ₅ is too large, easily glass phase separation milky. Therefore, the content of P ₂ O ₅ is preferably 0 to 10%, 0 to 0.5%, particularly preferably less than 0 to 0.1%.

  ZnO is a component that lowers the high temperature viscosity. When there is too much content of ZnO, devitrification resistance will fall easily. Therefore, the content of ZnO is preferably 0 to 10%, particularly preferably 0 to 5%.

TiO ₂ is a component that prevents coloring by ultraviolet rays and enhances weather resistance. However, when the content of TiO ₂ is too large, or glass is devitrified, glass tends colored brown. Therefore, the content of TiO ₂ is preferably 0 to 10%, particularly preferably less than 0 to 1%.

SO ₃ is a component that acts as a fining agent, and its content is preferably 0 to 1%, particularly preferably 0.01 to 1%. In addition, when a glass plate is shape | molded by the float glass process, a glass plate can be mass-produced. However, in this case, it is preferable to use mirabilite as a clarifier.

As ₂ O ₃ is a component that acts as a fining agent. However, when a glass plate is formed by the float process, it is a component that colors the glass and is a component that is concerned about the environmental burden. The content of As ₂ O ₃ is preferably 0 to 1%, particularly preferably less than 0 to 0.1%.

Sb ₂ O ₃ is a component that acts as a fining agent. However, when a glass plate is formed by the float process, Sb ₂ O ₃ is a component that colors the glass and is a component that is concerned about the environmental burden. The content of Sb ₂ O ₃ is preferably 0 to 1%, particularly preferably less than 0 to 0.1%.

SnO ₂ is a component that acts as a fining agent, but is a component that reduces devitrification resistance. The SnO ₂ content is preferably 0 to 1%, particularly preferably 0 to less than 0.1%.

In addition to the above components, F, Cl, and CeO ₂ may be added up to 1% in total in order to enhance solubility, clarity, and moldability. In order to increase chemical durability, Nb ₂ O ₅ , HfO ₂ , Ta ₂ O ₅ , Y ₂ O ₃ , and La ₂ O ₃ may be added up to 3% each. Furthermore, in order to adjust the color tone, a rare earth oxide or transition metal oxide other than the above may be added up to 2% in total.

In the glass plate for a thin film solar cell of the present invention, the density is preferably 2.90 g / cm ³ or less, particularly preferably 2.85 g / cm ³ or less. If it does in this way, it will become easy to reduce the cost of the support member of a thin film solar cell. The “density” can be measured by a known Archimedes method.

  In the glass plate for a thin-film solar cell of the present invention, the strain point is more than 580 ° C, preferably 600 ° C or more, more than 600 to 660 ° C, more preferably more than 605 to 650 ° C, still more preferably more than 610 to 645 ° C. is there. If it does in this way, it will become easy to form a photoelectric converting film at high temperature, the crystal quality of a photoelectric converting film will be improved, and it will become difficult to produce a heat deformation and a heat shrink in a glass plate by a heat treatment process.

In the glass plate for a thin-film solar cell of the present invention, the temperature at 10 ^4.0 dPa · s is preferably 1200 ° C. or less, particularly preferably 1180 ° C. or less. If it does in this way, it will become easy to shape | mold a glass plate at low temperature. Here, “temperature at 10 ^4.0 dPa · s” can be measured by a platinum ball pulling method.

In the glass plate for a thin film solar cell of the present invention, the temperature at 10 ^2.5 dPa · s is preferably 1520 ° C. or less, particularly preferably 1460 ° C. or less. If it does in this way, it will become easy to melt | dissolve a glass raw material at low temperature.

In the glass plate for a thin film solar cell of the present invention, the thermal expansion coefficient is preferably 70 to 100 × 10 ⁻⁷ / ° C., particularly preferably 80 to 90 × 10 ⁻⁷ / ° C. If it does in this way, it will become easy to match with the thermal expansion coefficient of the electrode film of a thin film solar cell, and a photoelectric conversion film. If the thermal expansion coefficient is too high, the thermal shock resistance of the glass plate tends to be lowered, and as a result, the glass plate is likely to be cracked in the heat treatment step when manufacturing the thin film solar cell.

  In the glass plate for a thin film solar cell of the present invention, the liquidus temperature is preferably 1160 ° C. or less, particularly preferably 1100 ° C. or less. When the liquidus temperature rises, the glass tends to devitrify during molding, and the moldability tends to decrease.

In the glass plate for a thin-film solar cell of the present invention, the liquid phase viscosity is preferably 10 ^4.0 dPa · s or more, particularly preferably 10 ^4.3 dPa · s or more. When the liquid phase viscosity is lowered, the glass is easily devitrified during molding, and the moldability is easily lowered.

In the glass plate for a thin film solar cell of the present invention, the Young's modulus is preferably 78 GPa or more, particularly preferably 80 GPa or more. The specific Young's modulus is preferably 27.5 GPa / (g / cm ³ ) or more, and particularly preferably 28 GPa / (g / cm ³ ) or more. If it does in this way, since it will become difficult to bend a glass plate, at the time of handling in a conveyance process or a packing process, it will become difficult to rock a glass plate. Here, “Young's modulus” refers to a value measured by a resonance method. “Specific Young's modulus” is a value obtained by dividing Young's modulus by density.

  The glass plate for a thin-film solar cell of the present invention is prepared by putting the prepared glass raw material into a continuous melting furnace so as to be in the above glass composition range, heating and melting the glass raw material, and defoaming the obtained glass melt Then, it can be produced by supplying it to a molding apparatus, molding it into a plate shape, and slowly cooling it.

  Examples of the glass plate forming method include a float method, a slot down draw method, an overflow down draw method, a redraw method, and the like, but when a glass plate is mass-produced, it is preferable to employ the float method.

  The glass plate for a thin film solar cell of the present invention is preferably not subjected to chemical strengthening treatment, particularly ion exchange treatment. A thin film solar cell has a high-temperature heat treatment step. In the high-temperature heat treatment process, the strengthening layer (compressive stress layer) disappears, and the actual benefit of performing the chemical strengthening treatment becomes poor. Further, for the same reason as described above, it is preferable that physical strengthening processing such as wind cooling strengthening is not performed.

  In particular, in the case of a CIS-based thin film solar cell, when the glass plate is subjected to ion exchange treatment, Na ions on the glass surface are reduced, and the photoelectric conversion efficiency is likely to be lowered. In this case, it is preferable to adopt a method of separately forming a Na supply film on a glass plate.

  Hereinafter, based on an Example, this invention is demonstrated in detail. The following examples are merely illustrative. The present invention is not limited to the following examples.

Table 1, specimen No. 1 to 10 are shown.

Sample no. 1-10 were produced. First, a glass batch prepared so as to have the glass composition in the table was put in a platinum crucible and melted at 1550 ° C. for 2 hours. Next, the obtained molten glass was poured out on a carbon plate, formed into a flat plate shape, and then gradually cooled. Thereafter, predetermined processing was performed according to each measurement. For each sample obtained, the strain ^point, the temperature at ¹⁰ 4.0 dPa · ^s, the temperature at ¹⁰ 2.5 dPa · s, the thermal expansion coefficient was measured Atsushi Nobori performance. These results are shown in Table 1. The parameter a in the table indicates a value of (5 × [Al ₂ O ₃ ] + 7.5 × [ZrO ₂ ] −15 × [Na ₂ O] −5 × [K ₂ O]), The parameter b is (0.012 × [MgO] + 0.016 × [CaO] + 0.021 × [SrO] + 0.023 × [BaO] + 0.021 × [ZrO ₂ ] − [Fe ₂ O ₃ ]) Points to the value.

  The strain point is a value measured based on ASTM C336-71.

Temperature at 10 ^4.0 dPa · ^s, temperature at ¹⁰ 2.5 dPa · s is a value measured by a platinum ball pulling method. The temperature at 10 ^4.0 dPa · s corresponds to the molding temperature, and the temperature at 10 ^2.5 dPa · s corresponds to the melting temperature.

  The thermal expansion coefficient is an average thermal expansion coefficient at 30 to 380 ° C., and is a value measured with a dilatometer. A cylindrical sample having a diameter of 5.0 mm and a length of 20 mm was used as a measurement sample.

  The temperature rise property was evaluated as follows. First, two glass plates (plate thickness of 1.8 mm) were used as samples, and the samples were placed in a roof shape inside an electric furnace with superkanthal heating elements on both sides. Furthermore, a thermocouple was installed inside the roof. Next, the temperature of the electric furnace was increased at 10 ° C./min, and when the temperature was increased to 600 ° C., the temperature was measured with a thermocouple inside the roof. Finally, the difference between 600 ° C. and the measured temperature inside the roof was evaluated as the temperature rise property.

As is clear from Table 1, sample No. 1 to 9 have high heat resistance because the strain point is 613 ° C. or higher. Sample No. ^{1-9 10} 4.0 temperature of 1192 ° C. or less in dPa · ^s, the temperature at ¹⁰ 2.5 dPa · s of 1460 ° C. or less, is excellent in productivity of the glass plate. Furthermore, sample no. 1 to 9 were good in evaluation of temperature rise.

  On the other hand, sample No. No. 10 is considered to be difficult to achieve both high strain point and productivity of the glass sheet because the glass composition is outside the predetermined range. Furthermore, sample no. No. 10 was poor in evaluation of temperature rise.

Claims (5)

As a glass composition, in _{mass%, SiO 2 45~60%, Al} 2 O 3 8.0 super _{~20%, B 2 O 3 +} Li 2 O 0~4%, Na 2 O 4.3 super 20%, Contains Na ₂ O + K ₂ O 4.3 to 30%, MgO + CaO + SrO + BaO 1-40%, (5 × [Al ₂ O ₃ ] + 7.5 × [ZrO ₂ ] −15 × [Na ₂ O] −5 × _[K 2 O] value of) the -20 ~60, (0.012 × [MgO ] + 0.016 × [CaO] + 0.021 × [SrO] + 0.023 × [BaO] + 0.021 × [ZrO 2 ]-[Fe ₂ O ₃ ]) is 0.27 to 0.52 , and the strain point is higher than 580 ° C. As a glass composition, in _{mass%, SiO 2 45~60%, Al} 2 O 3 8.0 super _{~20%, B 2 O 3 +} Li 2 O 0~4%, Na 2 O 4.3 super 20%, It contains Na ₂ O + K ₂ O 4.3 to 30%, MgO + CaO + SrO + BaO 1-40%, Al ₂ O ₃ + ZrO ₂ 10.5-20%, Fe ₂ O ₃ 0.001-0.2%. The glass plate for thin film solar cells according to claim 1. The glass plate for a thin-film solar cell according to claim 1 or 2, wherein the temperature at 10 ^2.5 dPa · s is 1520 ° C or lower.   It uses for a CIS type thin film solar cell, The glass plate for thin film solar cells as described in any one of Claims 1-3 characterized by the above-mentioned.   It uses for a CdTe type | system | group thin film solar cell, The glass plate for thin film solar cells as described in any one of Claims 1-3 characterized by the above-mentioned.