JP2012250902A - Glass plate for thin film solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass plate having a sufficiently high strain point, compatible with the thermal expansion coefficient of a peripheral member, and capable of forming a high-grade photoelectric conversion film.SOLUTION: This glass plate for a thin film solar cell includes as the glass composition on a mass percent basis: 45-60% SiO; >8.0 and ≤18% AlO; 0-15% (excluding 15%) BO; 1-40% MgO+CaO+SrO+BaO; and 1-30% NaO+KO; wherein the strain point thereof is >580°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 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 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 JP 2005-89286 A Japanese Patent No. 29987523

  In the CIS solar cell and the CdTe 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 glass described in Patent Document 1 does not have a sufficiently high strain point, 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. The conversion efficiency could not be increased sufficiently.

  On the other hand, Patent Document 2 discloses a glass plate having a strain point of more than 600 to 650 ° C. However, since this glass plate has a coefficient of thermal expansion that is too low, an electrode film of a thin film solar cell, a photoelectric conversion film The thermal expansion coefficient does not match, and problems such as film peeling are likely to occur. Furthermore, since this glass plate has a high temperature viscosity that is too high, the melting temperature and the molding temperature increase, and as a result, the production cost of the glass plate cannot be reduced.

Further, in the CIS solar cell, when an alkali component, particularly Na ₂ O, diffuses from the glass substrate, chalcopyrite crystals are likely to be precipitated. However, alkaline components, particularly too small content of Na 2 _O, can not be deposited photoelectric conversion film of high quality, it is not possible to increase the photoelectric conversion efficiency (see Patent Document 3).

  Accordingly, it is a technical object of the present invention to devise a glass plate that has a sufficiently high strain point, matches the thermal expansion coefficient of the peripheral member, and can form a high-quality photoelectric conversion film.

As a result of intensive studies, the present inventor has found that the above technical problem can be solved by regulating the glass composition and the glass characteristics within a predetermined range, and proposes the present invention. That is, 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 8.0-18%, B ₂ O ₃ 0-15% (however, 15%), MgO + CaO + SrO + BaO 1-40%, Na ₂ O + K ₂ O 1-30%, and the strain point is over 580 ° C. 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.

The glass plate for thin film solar cells of the present invention regulates the glass composition range as described above. If it does in this way, a strain point will rise easily and it will become easy to match with a thermal expansion coefficient of a peripheral member. ^{Furthermore, 10} 4.0 dPa · Temperature in s is less than 1200 ° C., liquidus viscosity likely to become ¹⁰ 4.0 dPa · s or more.

  Moreover, 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 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.

Second, the glass plate for a thin-film solar cell of the present invention, it is preferred weight ratio _{Na 2 O / (MgO + CaO} + SrO + BaO + Li 2 O + Na 2 O + K 2 O) is from 0.05 to 0.5. Here, “MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O” refers to the total amount of MgO, CaO, SrO, BaO, Li ₂ O, Na ₂ O, and K ₂ O.

Third, the glass plate for a thin film solar cell of the present invention has SiO ₂ —Al ₂ O ₃ of 28 to 50%, MgO + CaO + SrO + BaO of 15 to 40%, MgO + CaO of 0 to 10%, and a mass ratio of CaO / MgO of 1. It is preferable that it exceeds 0 and CaO + SrO is 0 to 30%. Here, “SiO ₂ —Al ₂ O ₃ ” refers to a value obtained by subtracting the content of Al ₂ O ₃ from the content of SiO ₂ . “MgO + CaO” refers to the total amount of MgO and CaO. “CaO + SrO” refers to the total amount of CaO and SrO.

Fourth, the glass plate for a thin-film solar cell of the present invention preferably further comprises an _Fe 2 _{O 3 0.01~1%.}

Fifth, it is preferable that the glass plate for a thin film solar cell of the present invention further contains 0.01 to 1% SO ₃ and is formed by a float process.

  Sixth, the glass plate for a thin film solar cell of the present invention preferably has a strain point of more than 600 to 650 ° C.

Seventh, the glass plate for a thin film solar cell of the present invention preferably has a thermal expansion coefficient of 70 to 100 × 10 ⁻⁷ / ° C. Here, the “thermal expansion coefficient” refers to a value obtained by measuring an average thermal expansion coefficient at 30 to 380 ° C. using a dilatometer.

Eighth, glass plate for thin-film solar cell of the present ^invention, it is preferable that the temperature at ¹⁰ 4.0 dPa · s is 1200 ° C. or less. Here, “temperature at 10 ^4.0 dPa · s” refers to a value measured by a platinum ball pulling method.

Ninth, the glass plate for a thin-film solar cell of the present invention preferably has a liquidus viscosity of 10 ^4.0 dPa · s or more. Here, “liquid phase viscosity” refers to a value obtained by measuring the viscosity of glass at the liquid phase temperature by a platinum ball pulling method. “Liquid phase temperature” is obtained by passing glass powder remaining on 50 mesh (300 μm) through a standard sieve 30 mesh (500 μm) into a platinum boat, and then holding the platinum boat in a temperature gradient furnace for 24 hours. The value at which the temperature at which crystals precipitate is measured.

Tenth, the glass plate for a thin film solar cell of the present invention has a film having a thermal expansion coefficient of 60 to 120 × 10 ⁻⁷ / ° C., and the film forming temperature is 500 to 700 ° C. Preferably there is. If it does in this way, the crystal quality of a photoelectric conversion film will be improved and it will become possible to raise the photoelectric conversion efficiency of a thin film solar cell. Furthermore, it becomes easy to match | combine the thermal expansion coefficient of a glass plate and a film | membrane.

  11thly, it is preferable that the chemical strengthening process is not performed to the glass plate for thin film solar cells of this invention.

  12thly, it is preferable to use the glass plate for thin film solar cells of this invention for a CIS type solar cell.

  13thly, it is preferable to use the glass plate for thin film solar cells of this invention for a CdTe type | system | group solar cell.

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 8.0-18%, B ₂ O ₃ 0-15% (however, 15 %)), MgO + CaO + SrO + BaO 1-40%, Na ₂ O + K ₂ O 1-30%. 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. Its content is 45-60%, preferably 45-54%, more preferably 49-52%. 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, so that the electrode film of the thin film solar cell, photoelectric 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 is more than 8.0 to 18%, preferably more than 10.0 to 15%, more preferably more than 11.0 to 14.5%, still more preferably 11.5 to 14%. When the content of Al ₂ O ₃ is too large, the high temperature viscosity becomes unduly high, meltability, moldability 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, it will become difficult to damage a glass plate in the process of removing a photoelectric converting film in patterning of a CIS type solar cell.

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B ₂ O ₃ is a component that lowers the melting temperature and the molding temperature by lowering the viscosity of the glass, but 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, B ₂ O ₃ is an optional component, and its content is 0 to less than 15%, preferably 0 to 1.5%, more preferably 0 to less than 0.1%.

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. 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. Therefore, the content of MgO + CaO + SrO + BaO is preferably 1 to 40%, 15 to 40%, more than 17.0 to 40%, 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, 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%, more than 2.9 to 8%, 3.0 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 0 to 20%, 0.1 to 15%, 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%, 0.1 to 15%, more than 2.0 to less than 14%, more than 2.0 to less than 8%, particularly preferably more than 2.0 to less than 5%. 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.

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 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 the CIS solar cell, and is an important component for increasing the photoelectric 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 photoelectric 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.

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, Li ₂ O is an optional component, and its content is preferably 0 to 10%, 0 to 2%, particularly preferably 0 to less than 0.1%.

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, ZrO ₂ is an optional component, and its content 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⁺ , and especially Fe ²⁺ has strong light absorption characteristics in the near infrared region. For this reason, Fe ^<2+> has the effect of being easy to absorb the radiant energy in a glass melting furnace, and improving a melting efficiency in a large capacity ^| capacitance glass melting furnace. Fe ³⁺ also has a clarification effect because it releases oxygen when the valence of iron changes. Furthermore, in order to reduce the manufacturing cost of the glass plate, use of a raw material containing a small amount of Fe ₂ O ₃ by limiting the use of a high-purity raw material (a raw material with a very low content of Fe ₂ O ₃ ). Is preferred. On the other hand, when the content of Fe ₂ O ₃ is too large, it becomes easy to absorb sunlight, and thus the surface temperature of the thin film solar cell is likely to rise, and as a result, the photoelectric conversion efficiency may be lowered. Further, when the content of Fe ₂ O ₃ is too large, the radiation energy of the kilns, are absorbed in the vicinity of the energy source, does not reach the central portion of the furnace, it tends to occur unevenness in the heat distribution of the glass melting furnace . Therefore, the content of Fe ₂ O ₃ is preferably 0 to 1%, particularly preferably 0.01 to 1%. Further, the preferable lower limit range of Fe ₂ O ₃ is more than 0.05%, more than 0.10%, particularly more than 0.20%. In the present invention, iron oxide is expressed in terms of “Fe ₂ O ₃ ” regardless of the valence of Fe.

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 0.1%.

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 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%.

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 cheaply, However, In this case, it is preferable to use a salt cake as a clarifier.

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%.

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%.

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%.

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%.

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 glass melt in a glass melting furnace will fall, a glass melt will not be homogenized, and there exists a tendency for a meltability and a moldability to fall as a result. is there.

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 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.

  The content of CaO + SrO is preferably 0 to 30%, 0.1 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. In addition, when there is too little content of CaO + SrO, the moving speed of the glass melt in a glass melting furnace will fall, a glass melt will not be homogenized, and there exists a tendency for a meltability and a moldability to fall as a result. is there.

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. When the mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is too large, it becomes difficult to maintain a high strain point, and the meltability and moldability tend to be lowered. On the other hand, when the mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is too small, the photoelectric conversion efficiency of the thin-film solar cell tends to be lowered. 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. .

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 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 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 more than 600 to 650 ° C, more preferably more than 605 to 650 ° C, and still more preferably more than 610 to 650 ° C. If it does in this way, it will become difficult to produce thermal contraction and a thermal deformation to a glass plate at the heat treatment process at the time of manufacturing a thin film solar cell.

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.

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.

  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 and a packing process, it will rock | fluctuate greatly and will fall, or it will become difficult to be damaged by contacting with another member. 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. However, when a glass plate is mass-produced at low cost, it is preferable to employ a 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 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 easily 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.

  Tables 1 to 6 show examples of the present invention (sample Nos. 1 to 35, 39 to 45) and comparative examples (samples No. 36 to 38).

Sample no. 1-45 were produced. First, a glass batch prepared so as to have the glass composition in the table was placed 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. About each obtained sample, thermal expansion coefficient α, density d, strain point Ps, annealing point Ta, softening point Ts, temperature at 10 ⁴ dPa · s, temperature at 10 ³ dPa · s, 10 ^2.5 dPa · s temperature at s, temperature at 10 ² dPa · s, liquid phase temperature TL, liquid phase viscosity log ₁₀ ηTL, volume resistivity ρ (150 ° C., 250 ° C., 350 ° C.), dielectric constant ε, dielectric loss tangent tan δ, Young's modulus The specific Young's modulus was evaluated. These results are shown in Tables 1-6.

  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, the annealing point Ta, and the softening point Ts are values measured based on ASTM C336-71.

The temperature at 10 ⁴ dPa · s, the temperature at 10 ³ dPa · s, and the temperature at 10 ^2.5 dPa · s are values measured by the platinum ball pulling method. The temperature at 10 ⁴ dPa · s corresponds to the molding 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 liquidus viscosity log ₁₀ ηTL is a value obtained by measuring the viscosity of the glass at the liquidus temperature TL by a platinum ball pulling method. In addition, the lower the liquidus temperature and the higher the liquidus viscosity, the better the devitrification resistance, and the more devitrified crystals are less likely to precipitate in the glass during molding, resulting in the production of a large glass plate at low cost. It becomes easy to do.

  The volume resistivity ρ indicates a value measured based on ASTM C657-78 at each temperature.

  The dielectric constant ε and the dielectric loss tangent tan δ are values measured under conditions of 25 ° C. and 1 MHz based on ASTM D150-87.

  The Young's modulus refers to a value measured by a resonance method. The specific Young's modulus is a value obtained by dividing Young's modulus by density.

As is apparent from Tables 1 to 6, sample No. 1 to 35 and 39 to 45 have high heat resistance because the strain point is over 600 ° C. to 650 ° C. Sample No. 1 to 35 and 39 to 45 have a thermal expansion coefficient of 70 to 100 × 10 ⁻⁷ / ° C., and therefore easily match the thermal expansion coefficients of the electrode film and the photoelectric conversion film of the thin film solar cell. Furthermore, sample no. 1-33 and 39-45 are excellent in productivity because the temperature at 10 ⁴ dPa · s is less than 1200 ° C. and the liquid phase viscosity is 10 ^4.0 dPa · s or more.

On the other hand, sample No. Although 36 has a high strain point, it does not contain an alkali component, particularly Na ₂ O, and therefore it is considered difficult to increase the photoelectric conversion efficiency of the CIS solar cell. Sample No. 36 is considered to be difficult to match with the thermal expansion coefficient of the electrode film of the thin film solar cell and the photoelectric conversion film because the thermal expansion coefficient is too low.

  Sample No. Reference numerals 37 and 38 are general-purpose glass plates. In particular, sample no. Reference numeral 38 denotes a glass plate described in Patent Document 1. Sample No. Nos. 37 and 38 have a strain point of about 580 ° C. or lower, so that the glass plate is likely to be thermally deformed or contracted in the heat treatment step, and the photoelectric conversion efficiency of the thin-film solar cell cannot be sufficiently increased.

Claims (13)

As a glass composition, in _{mass%, SiO 2 45~60%, Al} 2 O 3 8.0 super _{~18%, B 2 O 3 0~15} % ( not inclusive of 15%), MgO + CaO + SrO + BaO 1~40% , Na ₂ O + K ₂ O 1 to 30%, and a strain point is higher than 580 ° C. _{2. The} glass plate for a thin-film solar cell according to claim 1, wherein a mass ratio Na ₂ O / (MgO + CaO + SrO + BaO + Li ₂ O + Na ₂ O + K ₂ O) is 0.05 to 0.5. SiO ₂ —Al ₂ O ₃ is 28 to 50%, MgO + CaO + SrO + BaO is 15 to 40%, MgO + CaO is 0 to 10%, mass ratio CaO / MgO is more than 1.0, and CaO + SrO is 0 to 30%. The glass plate for thin film solar cells according to claim 1 or 2. Furthermore, a glass plate for a thin film solar cell according to claim 1, characterized in that it comprises an _Fe 2 _{O 3 0.01~1%.} 5. The glass plate for a thin-film solar cell according to claim 1, further comprising 0.01 to 1% SO ₃ and formed by a float process.   A strain point is 600-650 degreeC, The glass plate for thin film solar cells as described in any one of Claims 1-5 characterized by the above-mentioned. A thermal expansion coefficient is 70-100x10 < ^-7 > / degreeC, The glass plate for thin film solar cells as described in any one of Claims 1-6 characterized by the above-mentioned. 10 ^4.0 thin-film solar cell glass plate according to any one of claims 1-7, wherein the temperature in dPa · s is 1200 ° C. or less. Glass plate for thin-film solar cell according to any one of claims 1 to 8, wherein the liquidus viscosity of 10 ^{4.0 dPa} · s or more. 10. A film having a thermal expansion coefficient of 60 to 120 × 10 ⁻⁷ / ° C. is formed, and the film forming temperature of the film is 500 to 700 ° C. The glass plate for thin film solar cells as described in the paragraph.   The glass plate for thin film solar cells according to any one of claims 1 to 10, wherein a 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 1-11 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 1-11 characterized by the above-mentioned.