JP2014097916A - Glass plate for thin film solar cell and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high strain point glass plate which enables formation of a sulfate preventive film which has scratch preventive effect and is easy to be cleaned and removed.SOLUTION: A glass plate for thin film solar cell contains, as a glass composition, SiO45 to 60 mass%, AlOover 8.0 to 18 mass%, BO0 to less than 15.0 mass%, MgO+CaO+SrO+BaO 1 to 40 mass%, SrO 1 to 20 mass%, and NaO+KO 1 to 30 mass%, where the mass ratio SrO/BaO is 1 or more and the strain point is over 590°C.

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 solar cell and a CdTe solar cell.

In a thin film solar cell, for example, a CIS solar cell, a chalcopyrite 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 form a chalcopyrite type compound semiconductor by applying Cu, In, Ga, and Se on a glass plate by a multi-source deposition method, a selenization method, or the like, a heat treatment step of about 500 to 600 ° C. is required.

  Also in the CdTe solar cell, a photoelectric conversion film made of Cd and Te is formed on a glass substrate. 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 substrate in CIS solar cells, CdTe 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, at present, the use of high strain point glass has been studied (see Patent Document 1).

JP-A-11-135819

  By the way, if a sulfate protective film is formed on the surface of a glass plate (glass ribbon) immediately after molding, the glass plate is less likely to be damaged in subsequent steps (for example, a conveying step). However, once a sulfate protective film is formed on a conventional high strain point glass plate, it is difficult to remove the sulfate protective film by water washing or the like before product shipment. Costs are likely to rise.

  The present invention has been made in view of the above circumstances, and its technical problem is to devise a high strain point glass plate capable of forming a sulfate protective film that has a scratch-preventing effect and is easy to wash and remove. is there.

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 glass characteristics of the glass plate within 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 _~18%, B 2 O 3 less than 0 to 15.0 %, MgO + CaO + SrO + BaO 1-40%, SrO 1-20%, Na ₂ O + K ₂ O 1-30%, mass ratio SrO / BaO is 1 or more, and strain point is over 590 ° C. And Here, “MgO + CaO + SrO + BaO” refers to the total amount of MgO, CaO, SrO and BaO. “Na ₂ O + K ₂ O” refers to the total amount of Na ₂ O and K ₂ O. “Strain point” refers to a value measured based on ASTM C336-71.

  In the glass plate for a thin film solar cell of the present invention, the SrO content is regulated to 1 to 20% by mass and the mass ratio SrO / BaO is regulated to 1 or more. When SrO is introduced into the glass composition, solubility, heat resistance, and devitrification resistance can be improved.

According to the investigation of the present invention, if the mass ratio SrO / BaO is restricted to 1 or more, it becomes easy to form a sulfate protective film that has a scratch-preventing effect and is easy to clean and remove. When the content of SrO is increased as compared with BaO, when a sulfurous acid gas or the like is sprayed on the surface of the glass plate, a water-soluble SrSO ₄ is easily preferentially precipitated as a sulfate protective film, It becomes easy to remove the sulfate protection film by washing with water before shipping the product. As a result, the manufacturing cost of the glass plate can be easily reduced. On the other hand, when the content of BaO is increased as compared with SrO, when a sulfurous acid gas or the like is sprayed on the surface of the glass plate, a poorly water-soluble BaSO ₄ is preferentially precipitated as a sulfate protective film. Become.

  Moreover, in the glass plate for thin film solar cells of this invention, the strain point is controlled above 590 degreeC. If it does in this way, it will become easy to form a photoelectric converting film in high temperature, the crystal quality of a photoelectric converting film will be improved, and it will become difficult to produce thermal deformation and heat contraction to a glass plate. As a result, the photoelectric conversion efficiency of the thin film solar cell can be sufficiently increased.

  2ndly, the glass plate for thin film solar cells of this invention is a glass composition by mass%, contains SrO 3-20%, BaO 2-15%, and mass ratio SrO / BaO is 1.2 or more. It is preferable. In this way, it becomes easier to form a sulfate protective film that has an effect of preventing scratches and is easy to clean and remove.

  Thirdly, it is preferable that the glass plate for thin film solar cells of the present invention is subjected to a chemical strengthening treatment.

  Fourthly, it is preferable that the glass plate for thin film solar cells of the present invention is not subjected to chemical strengthening treatment.

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

  Sixth, the glass plate for a thin film solar cell of the present invention is preferably used for a CdTe solar cell.

  Seventh, the glass plate for a thin film solar cell of the present invention has a strain point of over 590 ° C. and a sulfate protective film on at least one surface, and the molar ratio Sr / Ba in the sulfate protective film. Is 1 or more. Here, the “molar ratio Sr / Ba ratio” is the molar ratio of Sr atoms to Ba atoms.

  Eighth, the method for producing a glass plate for a thin-film solar cell of the present invention comprises forming a glass plate having a strain point of over 590 ° C. by a float process, and then forming a mole with respect to at least one surface of the glass plate. A sulfate protective film having a ratio Sr / Ba of 1 or more is formed, and then the sulfate protective film is removed.

  Ninth, the sulfate protective film of the present invention is a sulfate protective film for protecting the surface of a glass plate for a thin film solar cell having a strain point exceeding 590 ° C., and the molar ratio Sr in the sulfate protective film is / Ba is 1 or more.

The glass plate for a thin-film solar battery of the present invention has, as a glass composition, mass%, SiO ₂ 45-60%, Al ₂ O ₃ more than 8.0-18%, B ₂ O ₃ 0-15.0%, MgO + CaO + SrO + BaO 1~40 %, SrO 1~20%, containing _{2 O 1~30% Na 2 O +} K, at one or more mass ratio SrO / BaO. The reason why the content of each component is regulated as described above is shown below.

SiO ₂ is a component that forms a glass network. The content of SiO ₂ is preferably 45 to 60%, 45 to 54%, particularly 49 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 and also increases weather resistance and chemical durability. The content of Al ₂ O ₃ is preferably more than 8.0 to 18%, more than 10.0 to 15%, more than 11.0 to 14.5%, particularly preferably 11.5 to 14%. 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.

B ₂ O ₃ is a component that lowers the melting temperature and molding temperature by lowering the viscosity of the glass, but it is a component that lowers the strain point, and with the component volatilization at the time of melting, the furnace refractory material is changed. It is a component to be consumed. Therefore, the content of B ₂ O ₃ is preferably 0 to less than 15.0%, 0 to 1.5%, particularly preferably 0 to less than 0.10%.

  MgO + CaO + SrO + BaO is a component that lowers the high temperature viscosity without lowering the strain point. When there is too much content of MgO + CaO + SrO + BaO, devitrification resistance will fall easily and raw material cost will rise. On the other hand, when the content of MgO + CaO + SrO + BaO is too small, the high temperature viscosity becomes too high. Therefore, the content of MgO + CaO + SrO + BaO is preferably 1 to 40%, 12 to 39%, 15 to 37%, more than 17.0 to 33%, 18 to 30%, particularly 19 to 25%.

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, the content of MgO is preferably 0 to 10%, 0 to less than 3.7%, 0.01 to 3%, 0.02 to 2%, particularly 0.03 to 0.5%.

  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%, more than 2.9 to 8%, 3 to 7.5%, and particularly preferably 4.2 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.

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 1 to 20%, 3 to 18%, more than 4.0 to 15%, 5 to 14%, more than 7.0 to 13%, particularly preferably 9.2 to 12.5%. 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 content of BaO is preferably 0 to 20%, 2 to 15%, more than 2.0 to less than 14.0%, more than 2.0 to less than 8.0%, particularly preferably more than 2.0 to less than 5.0%. . 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 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.

When the mass ratio SrO / BaO is changed, the components of the sulfate protective film can be changed. The mass ratio SrO / BaO is preferably 1 or more, 1.2 or more, 1.5 or more, 2 to 10, particularly 2.2 to 8. When the mass ratio SrO / BaO is too small, BaSO _{4 that} is hardly water-soluble is easily deposited as a sulfate protective film. If the mass ratio SrO / BaO is too large, easily water-soluble SrSO ₄ is likely to precipitate as a sulfate protective film, but the raw material cost is likely to increase and the devitrification resistance is likely to be reduced.

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 conversion efficiency. The content of Na ₂ O + K ₂ O is preferably 1 to 30%, 2 to 20%, 4 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 adjusts the thermal expansion coefficient, and is a component that lowers the high-temperature viscosity and improves the meltability and moldability. Na 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 conversion efficiency. The content of Na ₂ O is preferably 0 to 20%, 0.1 to 15%, 4 to 12%, particularly more than 4.3 to 9%. 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 adjusts the thermal expansion coefficient, and is a component that lowers the high-temperature viscosity and improves the meltability and moldability. K ₂ O is an effective component for the growth of chalcopyrite crystals in the CIS solar cell, and is an important component for increasing the conversion efficiency. However, in a glass system containing more than 10% Al ₂ O ₃ , if the content of K ₂ O is too large, KAlSiO-based devitrified crystals are likely to precipitate. 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. Therefore, the content of K ₂ O is preferably 0 to 15%, 0.1 to 10%, particularly preferably 1 to 7%.

  Furthermore, it is preferable to have the following component content and component ratio.

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. When the content of SiO ₂ -Al ₂ O ₃ is too large, the strain point tends to decrease. On the other _hand, if the content of 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 45.0%, 32 to 43%, and particularly preferably 34 to 40%. “SiO ₂ —Al ₂ O ₃ ” refers to an amount obtained by subtracting the content of Al ₂ O ₃ from the content of SiO ₂ .

MgO + CaO, among alkaline earth metal oxides, increases the moving speed of the upward flow, downward flow, and backward flow toward the batch inlet in the glass melting furnace by reducing the high-temperature viscosity, making the glass homogeneous Is the sum of the two components to be converted. Moreover, MgO + CaO is the total of the two components that can most maintain the difficulty of breaking the glass plate and reduce the density most among the alkaline earth metal oxides. When the density is lowered, the cost of the support member of the thin film solar cell can be reduced. The content of MgO + CaO is preferably 0 to 10%, 0.1 to 10%, more than 2.9 to 10%, and more preferably more than 3.4 to less than 9.4%. When the content of MgO + CaO is too large, devitrification resistance, tends to particularly devitrification crystals ZrO ₂ system is deposited. In addition, when there is too little content of MgO + CaO, the moving speed of the molten glass in a glass melting furnace will fall, a molten glass will not be homogenized, and there exists a tendency for a meltability and a moldability to fall as a result. “MgO + CaO” refers to the total amount of MgO and CaO.

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 mass ratio CaO / MgO is more than 1.0, more than 2.0, 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 devitrifying crystals. preferable.

  The content of CaO + SrO is preferably 1 to 30%, 3 to 25%, 6.92 to 23%, 8 to 21%, particularly preferably 9 to 20%. When there is too much content of CaO + SrO, devitrification resistance will fall easily. When there is too little content of CaO + SrO, the moving speed of the molten glass in a glass melting furnace will fall, a molten glass will not be homogenized, and there exists a tendency for a meltability and a moldability to fall as a result. “CaO + SrO” refers to the total amount of CaO and SrO.

Li 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. Further, Li ₂ O is an effective component for the growth of chalcopyrite crystals in CIS solar cells in the same manner as Na ₂ O and K ₂ O. However, Li ₂ O is a component that significantly lowers the strain point in addition to the high raw material cost. Therefore, the content of Li ₂ O is preferably 0 to 10%, 0 to 2%, particularly preferably 0 to less than 0.10%.

The mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is the total amount of components (MgO, CaO, SrO, BaO, Li ₂ O, Na ₂ O, and K ₂ O that have a large effect of reducing the high-temperature viscosity. It is the ratio of the content of Na ₂ O useful for precipitation of chalcopyrite crystals in the CIS solar cell to the total amount). The mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is 0.005 to 0.5, 0.05 to 0.4, 0.1 to 0.38, 0.137 to 0.355,. 140 to 0.300, especially more than 0.158 to 0.250 are preferable. If the mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is too large, it will be difficult to maintain a high strain point, and meltability and moldability will tend to be reduced. On the other hand, if the mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is too small, the conversion efficiency of the thin-film solar cell tends to decrease. In addition, if the mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is too small, the high-temperature viscosity is lowered, so the content of Li ₂ O and K ₂ O must be increased, and as a result Raw material costs will soar. Note that when the content of K ₂ O is preferentially increased, KAlSiO-based devitrified crystals are likely to precipitate in a glass system containing more than 10% Al ₂ O ₃ . Furthermore, even if the mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is too small, it is difficult to maintain a high strain point, and devitrification resistance is lowered, and the liquid phase viscosity is likely to be lowered. .

  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%.

ZrO ₂ is a component that increases the strain point without increasing the high-temperature viscosity. However, if the content of ZrO ₂ is too large, the density tends to increase, the glass plate tends to break, ZrO ₂ -based devitrified crystals tend to precipitate, and it becomes difficult to form the glass plate. Therefore, the content of ZrO ₂ is preferably 0 to 15%, 0 to 10%, 0 to 7%, 0.1 to 6.5%, particularly preferably 2 to 6%.

Fe in the glass exists in the state of Fe ²⁺ or Fe ³⁺ , but both ions cause glass coloring. Therefore, the content of Fe ₂ O ₃ is preferably 0.001 to 0.07%, particularly preferably 0.005 to 0.06%. “Fe ₂ O ₃ ” refers to a value obtained by converting the total Fe amount into the Fe ₂ O ₃ amount regardless of the valence.

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 0 to less than 0.10%.

P ₂ O ₅ is a component that enhances devitrification resistance, particularly a component that suppresses precipitation of ZrO ₂ -based devitrification crystals, and a component that makes it difficult to break the glass plate. 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 0.2%, particularly preferably 0 to less than 0.10%.

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 it shape | molds by a float glass process, a glass plate can be mass-produced cheaply, However, In this case, it is preferable to use a salt cake as a clarifier.

As ₂ O ₃ is a component that acts as a fining agent, but is a component that colors glass when it is made by the float process, 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 0 to less than 0.10%.

Sb ₂ O ₃ is a component that acts as a refining agent, but is a component that colors glass when it is made by a float process, and it is a component that is concerned about the environmental burden. The content of Sb ₂ O ₃ is preferably 0 to 1%, particularly preferably 0 to less than 0.10%.

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 0.10%.

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.

  In the glass plate for a thin-film solar cell of the present invention, the strain point is preferably more than 590 ° C, more than 600 to 650 ° C, more than 605 to 645 ° C, particularly preferably more than 610 to 650 ° C. If the strain point is too low, it becomes difficult to form a photoelectric conversion film at a high temperature, and thermal deformation and thermal shrinkage tend to occur on the glass plate. As a result, it becomes difficult to increase the conversion efficiency of the thin film solar cell. If the strain point is too high, the melting temperature and the molding temperature become too high, and the manufacturing cost of the glass plate tends to increase.

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. The “thermal expansion coefficient” is a value obtained by measuring an average thermal expansion coefficient at 30 to 380 ° C. using a dilatometer.

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. The “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. The “temperature at 10 ^2.5 dPa · s” can be measured by a platinum ball pulling method.

  The glass plate for a thin film solar cell of the present invention is preferably subjected to chemical strengthening treatment, particularly ion exchange treatment. If it does in this way, after installation of a thin film solar cell, the impact resistance with respect to a hail, snowfall, etc. and pressure | voltage resistance can be improved. From the viewpoint of production cost, it is preferable that chemical strengthening treatment, particularly ion exchange treatment is not performed.

  The glass plate for a thin film solar cell of the present invention was prepared by introducing 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 then defoaming the obtained molten glass. Above, after supplying to the float bath and forming into a plate shape, a sulfate protective film is formed on the surface of the glass plate, further cooling is performed, and the sulfate protective film is removed by washing with water, etc. Can be produced.

  The method for forming the sulfate protective film is not particularly limited, and a method of spraying sulfurous acid gas on the surface of the glass plate or a method of firing after slurry coating the surface of the glass plate can be employed. In particular, the former method is preferable from the viewpoint of productivity.

  From the viewpoint of production efficiency, the sulfate protective film is preferably formed after the glass plate forming step and before the slow cooling furnace is charged.

  The sulfate protective film is preferably formed on the surface of at least one glass plate. When the sulfate protective film is formed only on one surface, the surface on which the sulfate protective film is formed may be the side in contact with the transport device or the transport device. In addition, you may form a sulfate protective film on both surfaces of a glass plate.

  The molar ratio Sr / Ba in the sulfate protective film is preferably 1 or more, more than 1.0, 1.2 or more, 1.5 or more, and particularly preferably 1.8 or more. In this way, the sulfate protective film can be easily washed and removed with water or the like while maintaining the function as the protective film.

  The method for producing a glass plate for a thin-film solar cell according to the present invention comprises forming a glass plate having a strain point of over 590 ° C. by a float process and then forming a molar ratio Sr / Ba with respect to at least one surface of the glass plate. After forming one or more sulfate protective films, the sulfate protective film is removed. The manufacturing method of the glass plate for thin film solar cells of this invention has the said technical feature in principle. Therefore, detailed description of the overlapping portion is omitted.

  The sulfate protective film of the present invention is a sulfate protective film for protecting the surface of a glass plate for a thin film solar cell having a strain point exceeding 590 ° C., and the molar ratio Sr / Ba in the sulfate protective film is 1 It is the above. The sulfate protective film of the present invention has the above technical features in principle. Therefore, detailed description of the overlapping portion is omitted.

  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 shows examples (sample Nos. 1 to 3) and comparative examples (sample No. 4) of the present invention.

Sample no. 1-4 were produced. First, a glass batch prepared so as to have the glass composition in the table was melted in a melting furnace, and a 1.8 mm thick glass plate (glass ribbon) was formed with a float bath. Next, sulfurous acid gas was sprayed on the glass plate carried out from the float bath to form a sulfate protective film on one surface. Subsequently, the obtained glass plate was cut into a predetermined shape, and then predetermined processing was performed according to each measurement. About each obtained sample, coefficient of thermal expansion α, density d, strain point Ps, temperature at 10 ^4.0 dPa · s, temperature at 10 ^2.5 dPa · s, liquidus temperature TL, viscosity LogηTL at liquidus temperature The molar ratio Sr / Ba in the sulfate protective film was determined. These results are shown in Table 1.

  The thermal expansion coefficient α is a value obtained by measuring an average thermal expansion coefficient at 30 to 380 ° C. using 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 density d is a value measured by a known Archimedes method.

  The strain point Ps 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 liquid phase temperature TL passes through a standard sieve 30 mesh (500 μm), and after the glass powder remaining in 50 mesh (300 μm) is placed in a platinum boat, the platinum boat is held in a temperature gradient furnace for 24 hours to obtain a crystal It is the value which measured the temperature which deposits. The liquid phase viscosity log ηTL is a value obtained by measuring the viscosity of glass at the liquid phase temperature TL by a platinum ball pulling method.

  The molar ratio Sr / Ba in the sulfate protective film was evaluated with an XRD apparatus SmartLab manufactured by Rigaku. At the time of measurement, the X-ray incident angle was set to 0.35 degrees, and the crystal composition was identified by the In-plane method. From the identified crystal composition, the molar ratio Sr / Ba in the sulfate protective film was calculated.

  As is clear from Table 1, sample No. Nos. 1 to 3 have a large molar ratio Sr / Ba in the sulfate protective film, so that it is considered that the sulfate protective film can be easily removed by washing. On the other hand, Sample No. No. 4 is considered to be difficult to wash and remove the sulfate protective film because the molar ratio Sr / Ba in the sulfate protective film is small.

Claims (9)

As a glass composition, in _{mass%, SiO 2 45~60%, Al} 2 O 3 8.0 super _~18%, B 2 O 3 _0~15.0 less than%, MgO + CaO + SrO + BaO 1~40%, SrO 1~20% , Na ₂ O + K ₂ O 1-30%, the mass ratio SrO / BaO is 1 or more, and the strain point is higher than 590 ° C.   The glass composition contains 3 to 20% SrO and 2 to 15% BaO in terms of mass%, and the mass ratio SrO / BaO is 1.2 or more. Glass plate.   The glass plate for thin film solar cells according to claim 1 or 2, wherein chemical strengthening treatment is performed.   The glass plate for thin film solar cells according to claim 1 or 2, wherein chemical strengthening treatment is not performed.   It uses for a CIS type solar cell, The glass plate for thin film solar cells as described in any one of Claims 1-4 characterized by the above-mentioned.   It uses for a CdTe type | system | group solar cell, The glass plate for thin film solar cells as described in any one of Claims 1-4 characterized by the above-mentioned.   Thin film solar cell glass characterized by having a strain point of over 590 ° C., a sulfate protective film on at least one surface, and a molar ratio Sr / Ba in the sulfate protective film of 1 or more Board.   After forming a glass plate having a strain point of more than 590 ° C. by the float process, and forming a sulfate protective film having a molar ratio Sr / Ba of 1 or more on at least one surface of the glass plate, The manufacturing method of the glass plate for thin film solar cells characterized by removing a sulfate protective film.   A sulfate protective film for protecting the surface of a glass plate for a thin film solar cell having a strain point exceeding 590 ° C., wherein the molar ratio Sr / Ba in the sulfate protective film is 1 or more. Salt protective film.