JP5686397B2 - Film for solar cell backsheet, solar cell backsheet using the same, and solar cell - Google Patents

Description

  The present invention relates to a solar cell backsheet film that is thin but has a high partial discharge voltage, a solar cell backsheet using the same, and a solar cell using the same.

  In recent years, photovoltaic power generation, which is clean energy, has attracted attention as a semi-permanent and pollution-free next-generation energy source, and solar cells are rapidly spreading.

A typical configuration of a general solar cell is shown in FIG. In a solar cell, a power generating element 3 is sealed with a transparent filler 2 such as EVA (ethylene-vinyl acetate copolymer), and a transparent substrate 4 such as glass and a resin sheet called a back sheet 1 are bonded together. Composed. Sunlight is introduced into the solar cell through the transparent substrate 4. Sunlight introduced into the solar cell is absorbed by the power generation element 3, and the absorbed light energy is converted into electrical energy. The converted electric energy is taken out by a lead wire (not shown in FIG. 1) connected to the power generation element 3 and used for various electric devices. Here, the back sheet 1 is a sheet member that is installed on the back side of the power generation element 3 with respect to the sun and is not in direct contact with the power generation element 3. Various proposals have been made for the solar cell system and each member. For the back sheet 1, polyethylene-based, polyester-based, and fluorine-based resin films are mainly used. (See Patent Documents 1 to 3)
Here, solar cells are installed on the roofs of ordinary households and public facilities, or are installed in large sites as large-scale power generation. Moreover, since a high voltage is applied for a long time when the solar cell system is operated, it is desired that the backsheet has high electric resistance. If the electrical resistance is inferior, a discharge of minute charges inside the film called partial discharge occurs during the operation of the solar cell system, and if this continues for a long time, the chemical deterioration of the resin constituting the back sheet proceeds. If chemical degradation progresses due to a partial discharge phenomenon, even if the system has a withstand voltage sufficient to withstand lightning strikes under normal circumstances when a high voltage is momentarily applied to the system due to lightning strikes, etc. This is because there is a possibility of generating a dielectric breakdown. Therefore, the backsheet is required to increase the voltage at which the partial discharge phenomenon occurs (hereinafter referred to as “partial discharge voltage”) in order to suppress the partial discharge phenomenon even a little.

In addition, from the viewpoint of space saving and weight reduction of the solar cell system, it is desired to reduce the thickness of the back sheet.
JP-A-11-261085 JP-A-11-186575 JP 2006-270025 A

  However, no conventional film member has positively improved the partial discharge voltage. For this reason, in order to develop a high partial discharge voltage, there is only a method of increasing the film thickness. Therefore, there is a limit to thinning, and it is difficult to achieve both high partial discharge voltage and thinning.

Therefore, in view of the background of such conventional technology, the present invention provides a film for a solar battery back sheet having a high partial discharge voltage even if it is thin, a solar battery back sheet using the same, and a solar battery using the same. It is. That is, the present invention uses a film for a solar battery backsheet having a surface specific resistance R0 of 10 ⁶ Ω / □ or more and 10 ¹⁴ Ω / □ or less at least on one surface (hereinafter referred to as A surface), and the same. A solar battery back sheet and a solar battery.

  ADVANTAGE OF THE INVENTION According to this invention, the film for solar cell backsheets which has a high partial discharge voltage even if it is thin can be provided. Moreover, by using it, durability improvement of a solar cell backsheet, thickness reduction, etc. are attained, and durability improvement of a solar cell, thickness reduction, etc. are attained.

  The present invention, as a result of intensive studies on the film for solar battery backsheets having a high partial discharge voltage even if thin, solves the above problems all at once by controlling the electrical characteristics of the surface within a certain range. It has been clarified to do.

  The partial discharge phenomenon is that when a strong electric field (high voltage) is applied in the thickness direction of a solid (insulator), the electric field distribution in the insulator becomes non-uniform for some reason, and an electric field is applied to the part with poor insulation performance. This is a phenomenon in which small discharges are concentrated. In order to reduce this partial discharge phenomenon, it is effective to reduce the amount of electric field received by the solid per unit volume and to reduce the electric field concentration that causes the partial discharge phenomenon. However, conventional solar cell backsheet films have no effective means for reducing the electric field concentration, and the only method is to apparently reduce the amount of electric field received per unit volume by simply increasing the thickness of the film. There wasn't.

The film for solar battery backsheet of the present invention is characterized by having a surface A in which the surface specific resistance R0 is controlled to 10 ⁶ Ω / □ or more and 10 ¹⁴ Ω / □ or less. With this configuration, when a high voltage is applied in the thickness direction of the solar battery backsheet film, a part of the electric field received by the film can be appropriately conducted and diffused in the film surface direction. . Thereby, the amount of electric field received per unit volume in the thickness direction of the film can be reduced. As a result, even when a high voltage is applied, it is possible to suppress the concentration of the electric field on the portion with inferior insulation performance, and the occurrence of the partial discharge phenomenon can be suppressed. From the above, it is possible to increase the partial discharge voltage without increasing the film thickness, which is difficult with conventional films.

In the film for solar cell backsheet of the present invention, the surface specific resistance R0 on the A side is more preferably 10 ⁷ Ω / □ or more and 10 ¹⁴ Ω / □ or less, and further preferably 10 ⁸ Ω / □ or more and 10 ¹⁴ Ω / □ or more. □ or less, particularly preferably 10 ⁹ Ω / □ or more and 10 ¹⁴ Ω / □ or less, and most preferably 10 ⁹ Ω / □ or more and 10 ¹³ Ω / □ or less. If the surface specific resistance R0 on the A side is less than 10 ⁶ Ω / □, the film for the solar cell backsheet becomes too easy to conduct electricity and conducts in the thickness direction, and the entire A side acts as a pseudo electrode. Then, since the effect of relaxing the electric field in the plane direction is lost, the partial discharge voltage may not be improved, or when taking out electrical energy from the lead wire, the take-out efficiency may be reduced and the power generation efficiency may be lowered. This is not preferable. On the other hand, if the surface specific resistance R0 on the A plane side exceeds 10 ¹⁴ Ω / □, the conductivity is too small and the effect of relaxing the electric field in the plane direction is lost, and the partial discharge voltage may not be improved. It is not preferable. In the solar battery backsheet of the present invention, a part of the electric field applied in the film thickness direction when a high voltage is applied by controlling the surface specific resistance R0 in the range of 10 ⁶ Ω / □ or more and 10 ¹⁴ Ω / □ or less. Can be moderately conducted in the film surface direction, and the electric field concentration in the thickness direction can be relaxed, and the partial discharge voltage can be increased without increasing the film thickness. Moreover, the partial discharge characteristics and electrical resistance characteristics of the backsheet using this film can be dramatically improved.

The film for solar cell backsheet of the present invention has a surface specific resistance R1 of A surface of 10 ⁶ Ω / □ or more and 10 ¹⁴ Ω / after leaving the film for 24 hours under conditions of 125 ° C., 100% humidity and 2.5 atm. It is preferable that it is below. More preferably, it is 10 ⁷ Ω / □ or more and 10 ¹⁴ Ω / □ or less, more preferably 10 ⁸ Ω / □ or more and 10 ¹⁴ Ω / □ or less, particularly preferably 10 ⁹ Ω / □ or more and 10 ¹⁴ Ω / □ or less, most preferably Preferably, it is 10 ⁹ Ω / □ or more and 10 ¹³ Ω / □ or less. If the surface specific resistance R1 of the A surface after the treatment is less than 10 ⁶ Ω / □, the effect of relaxing the electric field in the surface direction is lost during long-term use, and the partial discharge voltage is reduced. In some cases, and the power generation efficiency of the solar cell may be reduced. On the other hand, if it exceeds 10 ¹⁴ Ω / □, the conductivity becomes too low, the effect of relaxing the electric field in the surface direction is lost, and the partial discharge voltage may be lowered. In the film for solar battery backsheet of the present invention, the surface specific resistance R1 after treatment is controlled to be in the range of 10 ⁶ Ω / □ or more and 10 ¹⁴ Ω / □ or less, thereby improving the partial discharge voltage even in long-term use. Can be maintained. As a result, it becomes possible to enhance the durability of partial discharge characteristics and electric resistance characteristics of the backsheet using the solar cell backsheet film of the present invention.

The film for solar battery backsheet of the present invention preferably has a surface specific resistance R2 of 10 ¹⁴ Ω / □ or more on the surface opposite to the A surface. As will be described later, when the film for solar cell backsheet of the present invention is incorporated into a solar cell system, the surface (6 in FIG. 1) on the opposite side of the resin layer encapsulating the power generating element may be the A surface. preferable. With such a configuration, the partial discharge voltage can be improved, and as a result, a highly durable solar cell can be obtained or the thickness of the solar cell can be reduced.

Here, if the surface specific resistance of both surfaces of the solar cell backsheet film is 10 ⁶ Ω / □ or more, the electrical resistance characteristics of the solar cell backsheet may be deteriorated, or electrical energy is taken out from the lead wire. This is because, in some cases, the take-out efficiency is lowered and the power generation efficiency is lowered.

  The film for solar battery backsheet of the present invention preferably has a breaking elongation of 50% or more. The elongation at break here is measured based on ASTM-D882 (1999) by cutting a sample into a size of 1 cm × 20 cm and pulling the sample at a distance of 5 cm between chucks and a pulling speed of 300 mm / min. More preferably, the elongation determined by the above method is 60% or more, more preferably 80% or more, particularly preferably 100% or more, and most preferably 120% or more. In the film for solar cell backsheet of the present invention, when the elongation at break is less than 50%, when an impact is applied to the solar cell from the outside when the backsheet using this is incorporated into the solar cell and used. (For example, when a load is applied during vibration during transportation or during work during transportation or construction), the backsheet may break, which is not preferable. In the film for solar cell backsheet of the present invention, by setting the elongation retention rate to 50% or more, the characteristics of the solar cell against impact can be enhanced.

Moreover, it is preferable that the film for solar cell backsheets of this invention is 50% or more of the elongation retention after leaving for 24 hours on conditions of 125 degreeC, humidity 100%, and 2.5 atm. The elongation retention referred to here is measured based on ASTM-D882 (1999), and is the condition of breaking elongation E0, 125 ° C, humidity 100%, 2.5 atm of the film before processing. This is a value obtained by the following formula (1), where E1 is the elongation at break after standing for 24 hours.
Elongation retention (%) = E1 / E0 × 100 (1)
Note that E1 is a value measured using a sample that was cut into the shape of a measurement piece and then subjected to treatment for 24 hours under conditions of 125 ° C., 100% humidity, and 2.5 atm.

  More preferably, the elongation retention determined by the above method is 55% or more, more preferably 60% or more, particularly preferably 65% or more, and most preferably 70% or more. In the film for solar cell backsheet of the present invention, if the elongation retention is less than 50%, the mechanical strength is lowered when used for a long time, and as a result, the use of the solar cell having the backsheet using the same. It is not preferable because the back sheet may break when some impact is applied to the solar cell from the outside (for example, when a falling stone hits the solar cell). In the film for solar battery backsheet of the present invention, by setting the elongation retention rate to 50% or more, durability of the mechanical strength of the backsheet during long-term use can be enhanced.

  The solar cell backsheet film of the present invention can be preferably used as long as it satisfies the above-mentioned requirements. As an example of the configuration, at least two layers including a conductive layer (A layer) and a base material layer (B layer) are used. It is preferable that it has the above laminated structure, and at least one surface thereof is composed of the A layer. By adopting this configuration, it is possible to improve the partial discharge voltage by the conductive A layer and to impart functions such as mechanical strength and electrical insulation in the film thickness direction by the base material layer (B layer). it can.

Here, the layer (A layer) having electrical conductivity of the film for solar battery backsheet of the present invention is a surface that becomes 10 ⁶ Ω / □ or more and 10 ¹⁴ Ω / □ or less when the surface specific resistance R0 is measured ( A surface). More preferably, it is 10 ⁷ Ω / □ or more and 10 ¹⁴ Ω / □ or less, more preferably 10 ⁸ Ω / □ or more and 10 ¹⁴ Ω / □ or less, particularly preferably 10 ⁹ Ω / □ or more and 10 ¹⁴ Ω / □ or less, most preferably Preferably, it is 10 ⁹ Ω / □ or more and 10 ¹³ Ω / □ or less. If the surface specific resistance R0 of the A layer is less than 10 ⁶ Ω / □, the A layer becomes too easy to conduct electricity and also conducts in the thickness direction. As a result, the entire A layer acts as a pseudo electrode, The effect of relaxing the electric field in the direction is lost, and the partial discharge voltage may not be improved. When electric energy is extracted from the lead wire, the extraction efficiency may decrease and the power generation efficiency may decrease. Further, when the surface specific resistance R0 of the A layer exceeds 10 ¹⁴ Ω / □, the conductivity is too small and the effect of relaxing the electric field in the surface direction is lost, and the partial discharge voltage may not be improved. Absent. The electric field applied in the film thickness direction when a high voltage is applied by controlling the surface specific resistance R0 of the A layer of the film for solar battery backsheet of the present invention to a range of 10 ⁶ Ω / □ to 10 ¹⁴ Ω / □. It becomes possible to moderately conduct a part of the film in the film surface direction and to reduce the concentration of the electric field in the thickness direction, and to increase the partial discharge voltage without increasing the film thickness. Moreover, the partial discharge characteristics and electrical resistance characteristics of the backsheet using this film can be dramatically improved.

The layer A in the film for solar cell backsheet of the present invention has a surface specific resistance R1 on the A surface of 10 ⁶ Ω / □ or more and 10 ¹⁴ Ω after standing for 24 hours under conditions of 125 ° C., 100% humidity, 2.5 atm. / □ or less is preferable. More preferably, it is 10 ⁷ Ω / □ or more and 10 ¹⁴ Ω / □ or less, more preferably 10 ⁸ Ω / □ or more and 10 ¹⁴ Ω / □ or less, particularly preferably 10 ⁹ Ω / □ or more and 10 ¹⁴ Ω / □ or less, most preferably Preferably, it is 10 ⁹ Ω / □ or more and 10 ¹³ Ω / □ or less. If the surface specific resistance R1 of the A surface after the treatment is less than 10 ⁶ Ω / □, the effect of relaxing the electric field in the surface direction is lost during long-term use, and the partial discharge voltage is reduced. In some cases, and the power generation efficiency of the solar cell may be reduced. On the other hand, if it exceeds 10 ¹⁴ Ω / □, the conductivity becomes too low, the effect of relaxing the electric field in the surface direction is lost, and the partial discharge voltage may be lowered. In the film for solar battery backsheet of the present invention, the partial discharge voltage is maintained even in long-term use by controlling the surface specific resistance R1 of the processed layer A to the range of 10 ⁶ Ω / □ to 10 ¹⁴ Ω / □. It is possible to maintain the improvement effect. As a result, it becomes possible to enhance the durability of partial discharge characteristics and electric resistance characteristics of the backsheet using the solar cell backsheet film of the present invention.

  Here, in the film for solar battery backsheet of the present invention, the A surface only needs to satisfy the above-mentioned characteristics, and specific examples thereof include the inclusion of a component that develops conductivity in the film and / or the A layer. It is done. Here, as the component for developing conductivity, any of organic conductive materials, inorganic conductive materials, and organic / inorganic composite conductive materials can be preferably used.

Examples of organic conductive materials include cationic conductive compounds having cationic substituents such as ammonium groups, amine bases, and quaternary ammonium groups in the molecule, sulfonate groups, phosphate groups, and carboxylate groups. Anionic conductive compounds having anionic properties such as, ionic conductive materials such as anionic substituents, amphoteric conductive compounds having both cationic substituents, polyacetylene having a conjugated polyene skeleton, poly Examples thereof include conductive polymer compounds such as paraphenylene, polyaniline, polythiophene, polyparaphenylene vinylene, and polypyrrole.
These conductive materials are introduced into the material to be a matrix constituting the film and / or the A layer by the methods 1) to 4) below, and any of them is preferably used. Thereby, it becomes possible to express film and / or A layer conductivity. That is,
1) Copolymerizing a conductive skeleton to the matrix material;
2) Add, mix, and dissolve conductive materials into the matrix material.
3) After adding and mixing the conductive material to the matrix material, the conductive material is transferred to the surface and concentrated near the surface.
4) Add and mix conductive materials into the matrix material and disperse to form a conductive network.
The film and / or layer A conductivity can be expressed by a method such as the above, and any of them is preferably used.

  Among these compounds (conductive materials), particularly when forming a film as a solution film, or when forming a layer A by coating on a base material layer (layer B), when applying a high voltage In view of having high conductivity, an ionic conductive material is preferable, and a cationic conductive compound is more preferable in that it has an effect of improving applicability, adhesion, and partial discharge voltage over a long period of time. As these conductive compounds, it is preferable to use any of low molecular weight type conductive compounds, high molecular weight type conductive compounds, and the like. In the present invention, high molecular weight type conductive compounds are preferably used from the viewpoint of durability and the like. In addition, in the case where the film 4 and / or the A surface of the A layer is made electrically conductive by melt extrusion, when the method 4) is used, it is in a matrix like “Ilgastat” P series manufactured by Ciba Japan Co., Ltd. A polyether amide copolymer compound which is dispersed in the above and forms a conductive network is preferably used from the standpoint of excellent heat resistance and moist heat resistance on the A side.

  These organic conductive materials can be preferably used either water-soluble or water-insoluble, but the film of the solar cell backsheet film of the present invention and / or the A surface of the A layer has moisture and heat resistance characteristics. Therefore, it is preferable to use a water-insoluble conductive compound. Here, in the case of an ionic conductive material, water solubility and water insolubility are determined by the monomer species constituting these materials, and in order to achieve water insolubility, the monomer species having the functional group and the functional group The ratio of the number of moles of monomer species having the functional group to the number of moles of monomer species having no functional group (the number of moles of monomer species having the functional group). / Number of moles of monomer species having no functional group) is preferably 10/90 or more and 90/10 or more, more preferably 20/80 or more and 80/20 or less, and further preferably 30/70 or more and 70/30 or less. is there. If the ratio is smaller than 10/90, the surface specific resistance R0 of the A surface of the formed A layer becomes too high, and the partial discharge voltage improvement effect may be lost. On the other hand, when the ratio exceeds 90/10, the water solubility becomes high, so the moisture and heat resistance characteristics of the formed A-side may be inferior.

  Moreover, in the film for solar cell backsheet of the present invention, when the conductive material used for the film and / or the A layer is an organic conductive material, in order to improve the heat and moisture resistance, improve the strength of the A layer, etc. In addition to organic conductive materials, polyesters, acrylic resins, polyolefin resins, polyamide resins, polycarbonates, polystyrenes, polyethers, polyester amides can be used as the material that forms the matrix of the film and / or layer A It is also preferable to use a water-insoluble resin such as polyether ester, polyvinyl chloride, polyvinyl alcohol, and a copolymer containing these as a component. What is necessary is just to add and mix to a coating agent, when forming A layer by application | coating, and what is necessary is just to melt-knead and mix, when forming A layer by melt extrusion. In that case, even when the organic conductive material is a water-soluble conductive material, it is possible to impart moisture and heat resistance, and in the case of a water-insoluble conductive material, the moisture and heat resistance can be further improved. it can. The mixing ratio of the organic conductive material and the water-insoluble resin (weight of the organic conductive material / weight of the water-insoluble resin) is preferably 5/95 or more and 50/50 or less. More preferably, it is 10/90 or more and 40/60 or less. When the mixing ratio is less than 5/95, the surface specific resistance R0 of the A layer is increased, and the partial discharge voltage may not be improved, which is not preferable. When the mixing ratio is greater than 5/95 than 50/50, The formed layer A is not preferable because the heat-and-moisture resistance may be inferior.

  Examples of the water-insoluble resin when the film and / or the A layer are formed by melt extrusion include polyethylene terephthalate (hereinafter sometimes abbreviated as “PET”), polyethylene-2, 6-naphthalate, and polypropylene. Polyester resins such as terephthalate, polybutylene terephthalate, poly 1,4-cyclohexylene dimethylene terephthalate, polylactic acid, polyolefin resins such as polyethylene, polystyrene, polypropylene, polyisobutylene, polybutene, polymethylpentene, cycloolefin resins, Polyamide resin, polyimide resin, polyether resin, polyester amide resin, polyether ester resin, acrylic resin, polyurethane resin, polycarbonate resin, polyvinyl chloride resin Or the like can be used fluorine-based resin. Among these, because of the variety of monomer types to be copolymerized and the ease of adjustment of material properties, it is possible to use polyester resins, polyolefin resins, cycloolefin resins, polyamide resins, acrylic resins, It is preferably mainly composed of a thermoplastic resin selected from a fluororesin or a mixture thereof. Particularly preferably, the polyester resin is mainly constituted from the viewpoint of mechanical strength and cost, and further, the water-insoluble resin is uniaxially or biaxially oriented, whereby the mechanical strength is improved by orientation crystallization. In the case of a polyester resin or the like, the hydrolysis resistance of the film and / or the A layer during long-term use can be improved.

  In the case where the conductive material used for the film and / or the A layer is an organic conductive material, the moisture and heat resistance characteristics are further improved, or particularly when the substrate is applied to the base material layer (B layer) as the A layer. When the adhesion with the base material layer (B layer) is improved, especially when a film is formed as a solution film, or when the A layer is applied on the base material layer (B layer), the film is blocked. In view of the fact that it can be prevented, a crosslinking agent is preferably contained in addition to the organic conductive material and the water-insoluble resin. As the crosslinking agent, a resin or a compound that undergoes a crosslinking reaction with a functional group present in the above-described organic material and / or a resin constituting the water-insoluble resin, such as a hydroxyl group, a carboxyl group, a glycidyl group, an amide group, or the like is preferably used. Examples thereof include methylolated or alkylolated urea, melamine, acrylamide, polyamide resins and epoxy compounds, oxetane compounds, isocyanate compounds, coupling agents, aziridine compounds, oxazoline compounds, carbodiimides, etc. System compounds, acid anhydrides, carboxylic acid ester derivatives, and mixtures thereof can be used.

  The kind and content of the crosslinking agent are appropriately selected depending on the film and / or the organic conductive material constituting the A layer constituting the A layer, the water-insoluble resin, the base material layer (B layer), and the like. As a crosslinking agent in the solar battery backsheet film of the present invention, when forming a film as a solution film, or when coating a base material layer (B layer) as an A layer, an organic conductive material and / or When the water-insoluble resin has an acrylic skeleton, an oxazoline compound is used as a crosslinking agent. When the organic conductive material and / or the water-insoluble resin has a polyester-based skeleton, a melamine compound is used as a crosslinking agent. The formed A layer is more preferable in that it has better moisture and heat resistance. In the case of forming a film and / or layer A by melt extrusion, as a crosslinking agent in the case of using a polyester resin as a water-insoluble resin, an oxazoline compound, an epoxy compound, an oxetane compound, a carbodiimide compound, An acid anhydride and a carboxylic acid ester derivative are preferably used.

  The addition amount of the crosslinking agent is preferably 0.01 or more and 50 parts by weight or less, more preferably 0.2 or more and 40 parts by weight or less with respect to 100 parts by weight of the total resin component that usually constitutes the film and / or the A layer. More preferably, the range of 0.5 to 30 parts by weight is more preferable.

  Here, the crosslinking agent is also preferably used in combination with a catalyst to promote the crosslinking reaction. In addition, as a crosslinking reaction system, any of a heating system, an electromagnetic wave irradiation system, a moisture absorption system, etc. may be used, but usually a method by heating is preferably used.

  In the film for solar battery backsheet of the present invention, when the material constituting the film and / or the A layer is an organic conductive material, the surface specific resistance R0 of the A surface is the organic conductive contained in the film and / or the A layer. It depends on the type of the water-soluble material, the type and mixing ratio of the water-insoluble resin and the crosslinking agent, the mixing ratio with other materials, the film thickness, and the like. The surface specific resistance R0 increases as the ratio of the water-insoluble resin and the crosslinking agent to the organic conductive material contained in the film and / or the A layer increases, and the surface specific resistance R0 decreases as the ratio decreases. Further, as the film and / or the A layer is thicker, the surface specific resistance R0 is lower, and as the film is smaller, the surface specific resistance R0 is higher. The optimal composition, film thickness, and the like vary depending on the type of material used, the film configuration, and the like, but are formed so that the surface specific resistance R0 of the A surface satisfies the above-described requirements.

  In the solar cell backsheet film of the present invention, in the case of a laminated structure of at least two layers including a conductive layer (A layer) and a base material layer (B layer), the material constituting the A layer is inorganic. Examples of conductive materials include gold, silver, copper, platinum, silicon, boron, palladium, rhenium, vanadium, osmium, cobalt, iron, zinc, ruthenium, praseodymium, chromium, nickel, aluminum, tin, Oxidized, sub-oxidized, hypo-sub-oxidized, mainly containing inorganic groups such as zinc, titanium, tantalum, zirconium, antimony, indium, yttrium, lanthanium, magnesium, calcium, cerium, hafnium, barium, or the like, or A mixture of the inorganic substance group and the inorganic substance group oxidized, sub-oxidized and hypo-sub-oxidized (hereinafter referred to as this) Nitride, subnitride, hyponitronitride, or nitriding, subnitriding, or hyponitriding the inorganic group and the inorganic group. A mixture thereof (hereinafter referred to as “inorganic nitride”), a material mainly composed of the above-mentioned inorganic group, oxynitrided, oxynitrided, hyponitrogenated, or the above-mentioned inorganic group and inorganic group Is a mixture of oxynitrided, oxynitrided, and hypooxynitrided materials (hereinafter referred to as “inorganic oxynitrides”), and carbonized, nitrocarburized, and hypocarburized as a main component of the above inorganic group. Or a mixture of the inorganic group and the inorganic group obtained by carbonization, sub-carbonization, and hypo-sub-carbonization (hereinafter referred to as inorganic carbide), and the main component of the inorganic group as fluorinated and / Or chlorination And / or bromide and / or iodination (hereinafter referred to as halogenation), subhalogenation, hypohalogenation, the above inorganic group and the above inorganic group are halogenated, subhalogenated, hypochlorous. Mixtures with halogenated substances (hereinafter referred to as inorganic halides), or mixtures of the above inorganic substances and those obtained by sulfiding, subsulfiding or hyposulfiding the inorganic substances (hereinafter referred to as these). Inorganic sulfides), and carbon compounds such as those obtained by doping the above compounds with different elements, graphite-like carbon, diamond-like carbon, carbon fibers, carbon nanotubes, fullerenes (hereinafter referred to as carbon-based compounds), And a mixture thereof. The above material may be contained at least in the A layer, but particularly when the layer thickness of the A layer is 1 μm or less, in order to make the surface resistivity within the above range, it is more preferable to use the main component. Good. In addition, the case where it exceeds 50 weight% in this layer is defined as a main component.

  In the film for solar cell backsheet of the present invention, the material constituting the A layer is an inorganic material having a laminated structure of at least two layers including a conductive layer (A layer) and a base material layer (B layer). In the case of a conductive material, the surface specific resistance R0 of the A surface of the A layer is modified with the degree of modification (oxidation, nitridation, oxynitridation, carbonization, halogenation, sulfurization, etc.) of the inorganic group contained in the film, and with the inorganic group. It depends on the mixing ratio with the inorganic group, the mixing ratio with other materials, the film thickness, and the like. The higher the degree of modification of the inorganic group, the higher the surface specific resistance R0 of the A surface, and the lower the degree of modification, the smaller the surface specific resistance R0 of the A surface. Moreover, the surface specific resistance R0 increases as the ratio of the modified inorganic group to the inorganic group included in the A layer increases, and the surface specific resistance R0 decreases as the ratio decreases. Moreover, the surface specific resistance R0 becomes low as the film thickness increases, and the surface specific resistance R0 increases as the film thickness decreases. The optimum composition and film thickness vary depending on the metal species to be used, the modification method, etc., but the surface specific resistance R0 is formed so as to satisfy the above requirements.

  In the film for solar battery backsheet of the present invention, when the material constituting the film / and the layer A is an organic / inorganic composite conductive material (for example, i) a nonconductive water-insoluble resin as a matrix When an inorganic conductive material is used as a conductive material, ii) When an organic conductive material and an inorganic conductive material are used in combination, iii) An inorganic nonconductive material is added to the organic conductive material. Iv) When a non-conductive water-insoluble resin is dispersed in an inorganic conductive material, etc.), the above-mentioned organic conductive material, inorganic conductive material, water-insoluble resin, cross-linking In addition to the agent, an inorganic non-conductive material is appropriately combined.

  As an example in the case of i), the structure which used the water-insoluble resin as a matrix of a film and / or A layer, and disperse | distributed the inorganic type electroconductive material is mentioned. As the water-insoluble resin, those similar to those used in the case of the organic conductive material are preferably used. In addition, the shape of the inorganic conductive material dispersed in the water-insoluble resin serving as the matrix of the film and / or the A layer may be a sphere, a spheroid, a flat, a bead, a plate, a needle, or the like There is no particular limitation. Furthermore, the thing which the microparticles | fine-particles connected two-dimensionally or three-dimensionally in the water-insoluble resin is also contained. These inorganic particles may be composed of a single element or a plurality of elements.

  In the above inorganic conductive material, zinc oxide, titanium oxide, cesium oxide, antimony oxide, tin oxide, indium tin, and the like in that it can be easily dispersed in an incompatible resin serving as a film and / or layer A matrix. Metal oxides such as oxides, yttrium oxides, lanthanum oxides, zirconium oxides, aluminum oxides, and silicon oxides, and carbon-based fine particles such as carbon black, carbon fibers, carbon nanotubes, and fullerenes are preferably used. The average particle diameter of the inorganic conductive material is arbitrary, but is preferably 0.001 μm or more and 20 μm or less. More preferably, they are 0.005 micrometer or more and 10 micrometers or less, Especially preferably, they are 0.01 micrometer or more and 1 micrometer or less, More preferably, they are 0.02 micrometer or more and 0.5 micrometers or less. The particle diameter here refers to the median diameter d50. When the particle size is 0.001 μm or less, it may be difficult to disperse in the water-insoluble resin as a matrix, and when it is 20 μm or more, a uniform film and / or layer A is not preferable. It becomes difficult to form. By setting the average particle size of the inorganic conductive material to 0.001 μm or more and 20 μm or less, it is possible to achieve both conductivity and uniformity of the formed film.

  In addition, the mechanical strength and heat-and-moisture resistance are further improved, and particularly the adhesiveness with the base material layer (B layer) when coated on the base material layer (B layer) as the A layer is improved. In addition to the water-insoluble resin, it is also preferable to contain a crosslinking agent in order to prevent blocking in the case of forming a film as a film or when coating the base layer (B layer) as the A layer. Is called. As the crosslinking agent, the same ones as those used in the case of the organic conductive material are preferably used.

  In the case of ii) and iii), when an organic conductive material is used as the conductive material, in addition to the water-insoluble resin and the cross-linking agent, the improvement of the slipperiness of the A layer and the blocking resistance It is also preferable to include fine particles for application, glossiness adjustment, surface resistivity control and the like. For example, inorganic fine particles or organic fine particles can be used. Examples of the inorganic fine particles include gold, silver, copper, platinum, palladium, rhenium, vanadium, osmium, cobalt, iron, zinc, ruthenium, praseodymium, chromium, nickel, aluminum, tin, zinc, titanium, tantalum, zirconium, Fine particles of metals such as antimony, indium, yttrium, lanthanium, fine particles of carbon compounds such as graphite-like carbon and diamond-like carbon, fine particles made of inorganic conductive materials such as carbon nanotubes and fullerenes, zinc oxide, titanium oxide, cesium oxide , Antimony oxide, tin oxide, indium tin oxide, yttrium oxide, lanthanum oxide, zirconium oxide, aluminum oxide, metal oxide such as silicon oxide, lithium fluoride, magnesium fluoride, aluminum fluoride Use of metal non-conductive fine particles such as metal fluoride such as nium, cryolite, metal phosphate such as calcium phosphate, carbonate such as calcium carbonate, sulfate such as barium sulfate, talc and kaolin it can. The particle diameter (number average particle diameter) of these fine particles is preferably from 0.05 to 15 μm, and preferably from 0.1 to 10 μm. Further, the content is preferably 5 or more and 50% by weight or less, more preferably 6 or more and 30% by weight or less, and still more preferably 7 or more and 20% by weight or less with respect to all the resin components constituting the A layer. By controlling the surface specific resistance to the above range by adjusting the particle size of the contained particles to the above range, it is possible to impart surface slipperiness or adjust the surface glossiness. preferable.

  As an example in the case of iv), a laminated structure of at least two layers including a conductive layer (A layer) and a base material layer (B layer) is used, and non-conductive in the inorganic conductive material constituting the A layer. The structure which disperse | distributed water-soluble water-soluble resin is mentioned. As the inorganic conductive material, the same materials as those used in the case of the inorganic conductive material are preferably used. In addition, the shape of the water-insoluble resin dispersed in the inorganic conductive material is not particularly limited, such as a true spherical shape, a spheroid shape, a flat shape, a bead shape, a plate shape, or a needle shape. Furthermore, the thing which the microparticles | fine-particles of the water-insoluble resin couple | bonded two-dimensionally or three-dimensionally in the inorganic type electroconductive material is also contained. These water-insoluble resins may be made of a single resin or may be made of a plurality of resins.

  As the water-insoluble resin, the same water-insoluble resin as that used in the case of the organic conductive material is preferably used, and a silicone compound, a crosslinked styrene, a crosslinked acryl, a crosslinked melamine is used. Cross-linked fine particles such as can also be used.

  Moreover, in the film for solar cell backsheet of the present invention, the film and / or the A layer contains a light stabilizer for preventing the film and / or the A layer and / or the base material layer (B layer) from being deteriorated by ultraviolet rays. It is preferable to do. Here, the light stabilizer is a compound that absorbs light such as ultraviolet rays and converts it into thermal energy, captures radicals generated by the absorption and decomposition of the film and / or layer A, and causes a decomposition chain reaction. The material to suppress is mentioned. More preferably, a compound that absorbs light such as ultraviolet rays and converts it into heat energy is used. By containing the light stabilizer in the film and / or the A layer, the effect of improving the partial discharge voltage by the A surface of the film and / or the A layer is kept high for a long time even when irradiated with long-term ultraviolet rays. It is possible to prevent color change due to ultraviolet rays, strength deterioration, and the like of the film and / or the A layer and / or the base material layer (B layer). As long as the ultraviolet absorber here is within a range in which other properties are not impaired, an organic ultraviolet absorber, an inorganic ultraviolet absorber, and a combination thereof can be preferably used without any particular limitation. It is desirable that the film has excellent moisture and heat resistance and can be uniformly and uniformly dispersed in the film and / or the A layer. Examples of such ultraviolet absorbers include, for example, in the case of organic ultraviolet absorbers, salicylic acid-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based ultraviolet absorbers, hindered amine-based ultraviolet stabilizers, etc. Is mentioned. Specifically, for example, salicylic acid-based pt-butylphenyl salicylate, p-octylphenyl salicylate, benzophenone-based 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy -5-sulfobenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane, 2- (2'-hydroxy-5) of benzotriazole series '-Methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H benzotriazol-2-yl) phenol], a cyanoacrylate-based ester 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol as a triazine-based tri-2-cyano-3,3′-diphenyl acrylate) Hindered amine bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethyl Examples of piperidine polycondensates include nickel bis (octylphenyl) sulfide and 2,4-di-t-butylphenyl-3 ′, 5′-di-t-butyl-4′-hydroxybenzoate. . Of these ultraviolet absorbers, triazine-based ultraviolet absorbers are more preferable in that they have high resistance to repeated ultraviolet absorption. These ultraviolet absorbers may be added to the film and / or layer A alone as described above, or an organic conductive material or a water-insoluble resin may be combined with a monomer having an ultraviolet absorber function. It may be introduced in a polymerized form.

  Examples of inorganic ultraviolet absorbers include metal oxides such as titanium oxide, zinc oxide, and cerium oxide, and carbon-based materials such as carbon, fullerene, carbon fiber, and carbon nanotube. In addition, these ultraviolet absorbers may be added to the film and / or the A layer as the above-mentioned ultraviolet absorber alone, or may be combined with an inorganic conductive material or function as an organic conductive material or water-insoluble. It may be introduced into the resin.

  Moreover, the said ultraviolet absorber may be individual or may be used together 2 or more types, and may use an inorganic type and an organic type compound together.

  The content of the ultraviolet absorber in the film and / or the A layer of the film for solar battery backsheet of the present invention is 0.05 with respect to the total solid components in the film and / or the A layer in the case of the organic ultraviolet absorber. The content is preferably 20% by weight or less, more preferably 0.1 or more and 15% by weight or less, and further preferably 0.15 or more and 15% by weight or less. When the content of the ultraviolet absorber is less than 0.05% by weight, the light resistance is insufficient, and the layer A is deteriorated during long-term use, and the partial discharge voltage may be lowered. If it exceeds 20%, the coloring of the A layer may increase, which is not preferable.

  In the case of an inorganic ultraviolet absorber, the total solid component of the film and / or the layer A is 1 to 50% by weight, more preferably 2 to 45% by weight, still more preferably 5 to 40% by weight, particularly Preferably they are 8 weight% or more and 35 weight% or less, Most preferably, they are 12 weight% or more and 30 weight% or less. In the case of an inorganic ultraviolet absorber, if the content of the ultraviolet absorber is less than 1% by weight, the light resistance is insufficient, and the film and / or layer A deteriorates during long-term use, resulting in a partial discharge voltage. May decrease, and if it exceeds 50% by weight, the strength of the film and / or the A layer may decrease, which is not preferable.

  The thickness of the A layer is preferably 0.001 μm or more and 50 μm or less. Among these, when the material constituting the A layer is mainly composed of an organic material and the A layer is formed by coating, it is usually preferably 0.01 μm or more and 50 μm or less, and the base material layer (B layer) is particularly uniaxial or When the A layer is formed during the production of the biaxially stretched film, it is preferably 0.01 μm or more and 1 μm or less, more preferably 0.02 μm or more from the viewpoint of the ease of forming the A layer and uniformity. 1 μm or less, more preferably 0.05 μm or more and 1 μm or less. Further, when the material constituting the A layer is mainly composed of an inorganic material, it is preferably 0.001 μm or more and 1 μm or less. In particular, when the layer is formed by a dry method such as a vapor deposition method or a sputtering method, A In view of controllability and uniformity of layer formation, the thickness is more preferably 0.005 μm to 0.8 μm, and still more preferably 0.01 μm to 0.5 μm. By controlling the thickness of the A layer within the above range, it is possible to achieve both the effect of improving the partial discharge voltage, the formability and uniformity of the A layer.

  Further, when it is desired to increase the durability against ultraviolet rays in the A layer, it is preferable to increase the thickness of the A layer. In that case, it is preferable to form the film and / or the A layer by melt extrusion. In this case, the preferable thickness of the A layer is 0.05 μm or more and 50 μm or less. More preferably, they are 1 micrometer or more and 50 micrometers or less, More preferably, they are 2 micrometers or more and 30 micrometers or less, Most preferably, they are 3 micrometers or more and 20 micrometers or less, Most preferably, they are 3 micrometers or more and 15 or less. By controlling the thickness of the A layer within the above range, durability can be imparted in addition to the effect of improving the partial discharge voltage, the formability and uniformity of the A layer.

  The base material layer (B layer) in the film for solar cell backsheet of the present invention is an organic film base material such as polyester resin, polyolefin resin, acrylic resin, polyamide resin, polyimide resin, polyether resin, polycarbonate resin, Metal base materials such as silicon, glass, stainless steel, aluminum, aluminum alloy, iron, steel, and titanium, inorganic base materials such as concrete, organic-inorganic composite base materials such as silicon-based resins, and combinations thereof are applicable. However, it is preferable to use a flexible base material containing an organic material from the viewpoint of handling and weight reduction. More preferably, the main component is made of a thermoplastic resin. Examples of thermoplastic resins include polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, polylactic acid and other polyester resins, polyethylene, polystyrene, Polyolefin resins such as polypropylene, polyisobutylene, polybutene, and polymethylpentene, cycloolefin resins, polyamide resins, polyimide resins, polyether resins, polyesteramide resins, polyetherester resins, acrylic resins, polyurethane Resin, polycarbonate resin, polyvinyl chloride resin, fluorine resin and the like can be used. Among these, because of the variety of monomer types to be copolymerized and the ease of adjustment of material properties, it is possible to use polyester resins, polyolefin resins, cycloolefin resins, polyamide resins, acrylic resins, It is preferably mainly composed of a thermoplastic resin selected from a fluororesin or a mixture thereof. Particularly preferably, the polyester resin is mainly constituted from the viewpoint of mechanical strength and cost.

  These resins may be homo-resins, copolymers or blends. However, when the resin used for the B layer is a polyester resin, the main repeating units are ethylene terephthalate, ethylene Those composed of -2,6-naphthalenedicarboxylate, propylene terephthalate, butylene terephthalate, 1,4-cyclohexylenedimethylene terephthalate, ethylene-2,6-naphthalenedicarboxylate and mixtures thereof are preferably used. Here, the main repeating unit means that the total of the above repeating units is 70 mol% or more, more preferably 80 mol% or more, more preferably 90 mol% or more of all repeating units of the polyester resin. Particularly preferred from the viewpoint of mechanical strength and heat resistance.

  Moreover, it is preferable from the point of heat resistance and mechanical strength that B layer contains the layer (B1 layer) which consists of polyester. Moreover, it is preferable to use the above-described polyester as the polyester constituting the B1 layer. Furthermore, it is preferable that the B layer comprises only the B1 layer from the viewpoints of heat resistance, mechanical strength, and easy production.

  Moreover, it is preferable that the weight average molecular weight Mw1 of polyester which comprises B1 layer is 37500 or more and 60000 or less. The weight average molecular weight here is a value obtained by gel permeation chromatography, a molecular weight calibration curve is prepared using PET-DMT (standard product), and a value obtained based on the molecular weight calibration curve. That is.

More specifically, first, a gel permeation chromatograph equipped with two Shodex HFIP 806M (manufactured by Showa Denko KK) as a column and an RI-type differential refractometer (2414 type, sensitivity 256, manufactured by WATERS) as a detector. Using GCP-244 (manufactured by WATERS), GPC measurement is performed using PET-DMT (standard product) at room temperature (23 ° C.) and a flow rate of 0.5 mL / min. Using the obtained elution volume (V) and molecular weight (M), the coefficient (A ₁ ) of the third-order approximate expression of the following formula (2) is calculated to draw a calibration curve.

Log (M) = A ₀ + A ₁ V + A ₂ V ² + A ₃ V ³ (2)
Next, using hexafluoropropanol (0.005N-sodium trifluoroacetate) as a solvent, a solution in which the B1 layer is dissolved to 0.06% by weight is prepared, and GPC measurement is performed using the solution. . In addition, although measurement conditions are arbitrary, the value is shown when the injection amount is 0.300 ml and the flow rate is 0.5 ml / min.
The obtained elution curve molecular weight curve and the molecular weight calibration curve are overlapped to obtain the molecular weight corresponding to each outflow time, and the weight average molecular weight is calculated by the following formula (3).
Weight average molecular weight (Mw) = Σ (Ni · Mi ² ) / Σ (Ni · Mi) (3)
(Here, Ni is the molar fraction, and Mi is the molecular weight of each elution position of the GPC curve obtained via the molecular weight calibration curve.)
If the B1 layer used for such measurement contains organic fine particles, inorganic fine particles, metals, metal salts, other additives and other components that are insoluble in the solvent, filter by filtration or centrifugation. This is a value obtained by preparing a solution again after removing insoluble components. If the B1 layer may contain additives such as plasticizers, surfactants, dyes, etc., after removing insoluble components, reprecipitation method, recrystallization method, chromatography method, extraction method After removing the insoluble additive in the same manner as described above, the solution was prepared again and measured.

  In the film for a solar battery backsheet of the present invention, the weight average molecular weight of the B1 layer is preferably 37500 or more and 60000 or less, more preferably 38500 or more and 58000 or less, and further preferably 40000 or more and 55000 or less. When the weight average molecular weight of the polyester resin constituting the B1 layer is less than 37500, the heat and moisture resistance is poor, hydrolysis proceeds during long-term use, and as a result, the mechanical strength may decrease, which is not preferable. On the other hand, if it exceeds 60,000, it is not preferable because polymerization becomes difficult, or even if polymerization is possible, it becomes difficult to extrude the resin with an extruder and film formation becomes difficult. In the film for solar battery backsheet of the present invention, when the weight average molecular weight of the B1 layer constituting the B layer is in the range of 37500 or more and 60000 or less, both film forming property and hydrolysis resistance can be achieved.

  In addition, when the base material layer (B layer) has a laminated structure, a value obtained by measuring using a sample in which only the B1 layer is obtained by peeling other layers or polishing the corresponding film while observing under a microscope. It is.

Moreover, it is preferable that the number average molecular weights of the polyester which comprises B1 layer are 8000-40000. The number average molecular weight here is a number average molecular weight (Mn) = ΣNiMi which is a value calculated by the following formula (4) from the molecular weight value corresponding to each outflow time obtained by the measurement of the weight average molecular weight. / ΣNi (4)
(Here, Ni is the molar fraction, and Mi is the molecular weight of each elution position of the GPC curve obtained via the molecular weight calibration curve.)
In the film for solar battery backsheet of the present invention, the number average molecular weight of the polyester of the B1 layer is more preferably 9500 or more and 40000 or less, further 10,000 or more and 40000 or less, further 10500 or more and 40000 or less, and further 11000 or more and 40000 or less. Further, it is 18500 or more and 40000 or less, further 19000 or more and 35000 or less, and particularly preferably 20000 or more and 33000 or less. When the number average molecular weight of the polyester resin constituting the B1 layer is less than 8000, the heat and moisture resistance is poor, hydrolysis proceeds during long-term use, and as a result, the mechanical strength may decrease, which is not preferable. On the other hand, if it exceeds 40,000, it is not preferable because the polymerization becomes difficult or even if the polymerization is possible, it becomes difficult to extrude the resin with an extruder and the film formation becomes difficult. In the film for solar battery backsheet of the present invention, by making the number average molecular weight of the B1 layer constituting the B layer in the range of 8000 or more and 40,000 or less, both film-forming property and hydrolysis resistance can be achieved.

  Moreover, in the film for solar cell backsheets of this invention, it is preferable that B1 layer which comprises a film and / or B layer is orientated uniaxially or biaxially. By stretching, mechanical strength can be increased by orientation crystallization, and in the case of a polyester resin, hydrolysis resistance can be improved.

  In this case, it is preferable that the minute endothermic peak temperature TmetaB1 of the B1 layer and the melting point TmB1 of the B1 layer obtained by suggestive scanning calorimetry (DSC) satisfy the following formula (5).

40 ° C. ≦ TmB1-TmetaB1 ≦ 90 ° C. (5)
The TmetaB1 and the melting point TmB1 of the B1 layer here are values in a temperature raising process (temperature raising rate: 20 ° C./min) obtained by differential scanning calorimetry (hereinafter, DSC). Specifically, by a method based on JIS K-7121 (1999), heating from 225 ° C. to 300 ° C. at a heating rate of 20 ° C./min (1st RUN), holding in that state for 5 minutes, then 25 ° C. or lower TmetaB1, with a slight endothermic peak temperature before the crystal melting peak in a differential scanning calorimetry chart of 1stRUN obtained by rapidly cooling to 300 ° C. from room temperature at a temperature rising rate of 20 ° C./min. In addition, the TmB1 of the B1 layer is set to the peak top temperature at the crystal melting peak of 2ndRun.

More preferably, it is 50 degreeC <= TmB1-TmetaB1 <= 80 degreeC, More preferably, it is 55 degreeC <= TmB1-TmetaB1 <= 75 degreeC. When TmB1-TmetaB1 exceeds 90 ° C., the residual stress at the time of stretching is not sufficiently eliminated, and as a result, the thermal shrinkage of the film becomes large, and it becomes difficult to bond in the bonding process when incorporating into a solar cell. Even if it can be pasted together, it is not preferable because warpage of the solar cell system may occur greatly when incorporated into a solar cell and used at a high temperature. Moreover, when TmB1-TmetaB1 is less than 40 degreeC, since orientation crystallinity falls and it may be inferior to hydrolysis resistance, it is unpreferable. In the film for a solar battery backsheet of the present invention, when the B1 layer constituting the B layer is 40 ° C. ≦ TmB1-TmetaB1 ≦ 90 ° C., both shrinkage reduction and hydrolysis resistance can be achieved. In the film for solar battery backsheet, TmetaB1 of the B1 layer constituting the B layer is preferably 160 ° C. or higher and TmB1-40 ° C. (however, TmB1-40 ° C.> 160 ° C.). More preferably, it is 170 ° C. or more and TmB1-50 ° C. (however, TmB1-50 ° C.> 170 ° C.), and more preferably TmetaB1 is 180 ° C. or more and TmB1-55 ° C. (however, TmB1-55 ° C.> 180 ° C.). If TmetaB1 is less than 160 ° C., the heat resistance of the film is low, and the durability as a back sheet may be lowered, which is not preferable.

  In the solar battery backsheet film of the present invention, the melting point TmB1 of the B1 layer constituting the B layer is preferably 220 ° C. or higher in view of heat resistance, more preferably 240 ° C. or higher, more preferably 250 ° C. It is. The upper limit of the melting point TmB1 of the B1 layer is not particularly limited, but is preferably 300 ° C. or less in view of productivity.

  In the film for solar cell backsheet of the present invention, the B1 layer constituting the B layer has a heat resistance stabilizer, an oxidation resistance stabilizer, an ultraviolet absorber, an ultraviolet ray as long as the effects of the present invention are not impaired as necessary. Stabilizers, organic / inorganic lubricants, organic / inorganic fine particles, fillers, nucleating agents, dyes, dispersants, coupling agents, and other additives and bubbles may be blended. For example, in order to increase the power generation efficiency of the solar cell, it is preferable to cause the B1 layer to exhibit reflectivity, in which case organic / inorganic fine particles or bubbles may be included, and design properties are imparted. Therefore, in order to color, the material of the color to be colored may be added.

  In the film for solar battery backsheet of the present invention, the base material layer (B layer) may be formed of only the B1 layer that satisfies the above-mentioned requirements, or may have a laminated structure with other layers. Moreover, 10 or more and 500 micrometers or less are preferable, and, as for the thickness of a film, 20 or more and 300 micrometers or less are more preferable. More preferably, they are 25 micrometers or more and 200 micrometers or less. When the thickness is less than 10 μm, it is difficult to ensure the flatness of the film. On the other hand, when it is thicker than 500 μm, the thickness may be too large when used in a solar cell.

  In the solar battery backsheet film of the present invention, when the base material layer (B layer) has a laminated structure including the B1 layer, the thickness of the B1 layer is 50% or more with respect to the thickness of the entire B layer. Is preferable, more preferably 60% or more, still more preferably 70% or more. If it is less than 50%, the heat and moisture resistance may be inferior.

  In the film for solar battery backsheet of the present invention, the base material layer (B layer) has an A layer, other sheet materials, and an adhesive for improving the adhesion with ethylene vinyl acetate embedding the power generation element. Layers with additional functions such as an easy-adhesion layer, a hard coat layer for improving impact resistance, an ultraviolet resistant layer for having ultraviolet resistance, and a flame retardant layer for imparting flame resistance (C layer) ) May be provided.

  Next, although an example is demonstrated about the film manufacturing method for solar cell backsheets of this invention, this invention is not limited only to this example.

  First, the manufacturing method of the raw material which comprises a base material layer (B layer) can be manufactured with the following method in the case of a polyester-type resin.

  In the method for producing a film for a solar battery backsheet of the present invention, the resin as the raw material is malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, Aliphatic dicarboxylic acids such as pimelic acid, azelaic acid, methylmalonic acid and ethylmalonic acid, adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, cyclohexanedicarboxylic acid, decalin dicarboxylic acid, terephthalic acid, isophthalic acid Acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4 ′ -Diphenyl ether dicarboxylic acid, 5- Dicarboxylic acids such as thorium sulfoisophthalic acid, phenylendanedicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, 9,9′-bis (4-carboxyphenyl) fluorenic acid or the like, or ester derivatives thereof, ethylene glycol, Aliphatic diols such as 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, cyclohexanedimethanol, spiroglycol, isosorbide, etc. Diols such as aromatic diols such as alicyclic diols, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9′-bis (4-hydroxyphenyl) fluorene Este in a well-known way It can be obtained by exchange reactions. Examples of conventionally known reaction catalysts include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and phosphorus compounds. Preferably, an antimony compound, a germanium compound, or a titanium compound is preferably added as a polymerization catalyst at an arbitrary stage before the PET production method is completed. As such a method, for example, when a germanium compound is taken as an example, it is preferable to add the germanium compound powder as it is.

  In addition, in order to control the weight average molecular weight of the polyester constituting the B1 layer to 37500 or more and 60000 or less, after polymerizing a polyester resin having a normal molecular weight of about 36000, the weight average molecular weight is 190 ° C or more. It is preferable to use as a raw material a so-called solid-phase polymerized chip that is heated at a temperature lower than the melting point under reduced pressure or an inert gas such as nitrogen gas. In addition, in order to control the number average molecular weight of the polyester constituting the B1 layer to 18500 or more and 40000 or less, after polymerizing a normal molecular weight polyester resin having a number average molecular weight of about 18000 by the above method, 190 ° C. As described above, a method of heating at a temperature lower than the melting point of the thermoplastic resin under reduced pressure or a flow of an inert gas such as nitrogen gas, that is, so-called solid phase polymerization, and extruding in a nitrogen atmosphere with a short residence time is preferable. This method is preferably performed in that the weight average molecular weight and the number average molecular weight can be increased without increasing the amount of terminal carboxyl groups of the thermoplastic resin.

  Next, the manufacturing method of the base material layer (B layer) is such that when the B layer has a single film configuration consisting of only the B1 layer, the raw material for the B1 layer is heated and melted in an extruder and extruded onto a cast drum cooled from the die. A method of processing into a sheet (melt cast method) can be used. As another method, the raw material for the B1 layer is dissolved in a solvent, and the solution is extruded from a die onto a support such as a cast drum or an endless belt to form a film, and then the solvent is dried and removed from the film layer. A method of processing into a shape (solution casting method) or the like can also be used.

  The manufacturing method in the case where the B layer has a laminated structure including the B1 layer is as follows. When the material of each layer to be laminated is mainly composed of a thermoplastic resin, two different thermoplastic resins are put into two extruders, melted and coextruded on a cast drum cooled from a die, and formed into a sheet shape. Method of processing (coextrusion method), method of laminating coating layer raw material into a sheet made of a single film into an extruder, melting extrusion and extruding from the die (melt laminating method), and material laminated with B1 layer, respectively Separately prepared, heat-pressed with a heated group of rolls (thermal laminating method), pasted via an adhesive (adhesive method), and other materials for forming the material to be laminated are dissolved in a solvent, The method (coating method) which apply | coats the solution on B1 layer produced previously, the method of combining these, etc. can be used.

  In addition, when the material to be laminated is not a thermoplastic resin, the B1 layer and the material to be laminated are separately produced and bonded together with an adhesive or the like (adhesion method), or in the case of a curable material, the B1 layer The method of hardening by electromagnetic wave irradiation, heat processing, etc. after apply | coating on can be used.

  In addition, when a uniaxial or biaxially stretched film substrate is selected as the base layer (B layer) and / or the B1 layer constituting the B layer, as a manufacturing method thereof, first, an extruder (in the case of a laminated structure) Feeds raw materials into multiple extruders), melts and extrudes from the die (co-extrusion in the case of a laminated structure), and adheres by static electricity on a cooled surface temperature of 10 ° C to 60 ° C Cool and solidify to produce an unstretched film.

  This unstretched film is led to a group of rolls heated to a temperature of 70 ° C. or higher and 140 ° C. or lower, stretched 3 to 5 times in the longitudinal direction (longitudinal direction, that is, the film traveling direction), and 20 to 50 ° C. Cool with a roll group at the following temperature.

  Subsequently, the both ends of the film are guided to a tenter while being gripped by clips, and in an atmosphere heated to a temperature of 80 ° C. or higher and 150 ° C. or lower, the direction perpendicular to the longitudinal direction (width direction) is 3 to 5 times. Stretch.

  The stretching ratio is 3 to 5 times in each of the longitudinal direction and the width direction, and the area ratio (vertical stretching ratio × lateral stretching ratio) is preferably 9 to 15 times. If the area magnification is less than 9 times, the resulting biaxially stretched laminated film has insufficient reflectivity, concealability, and film strength. Conversely, if the area magnification exceeds 15 times, the film tends to be broken during stretching. is there.

  As the biaxial stretching method, in addition to the sequential biaxial stretching method in which the stretching in the longitudinal direction and the width direction is separated as described above, the simultaneous biaxial stretching method in which the stretching in the longitudinal direction and the width direction is performed simultaneously. Either one does not matter.

  In order to complete the crystal orientation of the obtained biaxially stretched film and to impart flatness and dimensional stability, it is preferably continued for 1 second or more at a temperature below the Tg of the resin as the raw material and below the melting point in the tenter. The following heat treatment is performed for 2 seconds, and after cooling gradually, cool to room temperature. In general, when the heat treatment temperature Ts is low, the heat shrinkage of the film is large. Therefore, in order to impart high thermal dimensional stability, the heat treatment temperature is preferably higher. However, if the heat treatment temperature is too high, the oriented crystallinity is lowered, and as a result, the formed film may be inferior in hydrolysis resistance. Therefore, it is preferable that the heat processing temperature Ts of the film for solar cell backsheets of this invention shall be 40 degreeC <= TmB1-Ts <= 90 degreeC. More preferably, the heat treatment temperature Ts is 50 ° C. ≦ TmB1-Ts ≦ 80 ° C., and more preferably 55 ° C. ≦ TmB1-Ts ≦ 75 ° C. Furthermore, the solar cell backsheet film of the present invention is used as a solar cell backsheet, but since the ambient temperature may rise to about 100 ° C. during use, the heat treatment temperature Ts is 160 ° C. or higher TmB1- It is preferable that it is 40 degrees C (however, TmB1-40 degrees C> 160 degrees C) or less. More preferably, it is 170 ° C. or more and TmB1-50 ° C. (where TmB1-50 ° C.> 170 ° C.), and more preferably Ts is 180 ° C. or more and TmB1-55 ° C. (where TmB1-55 ° C.> 180 ° C.). Note that TmetaB1 can be controlled by controlling Ts.

  Moreover, in the said heat processing process, you may perform a 3-12% relaxation process in the width direction or a longitudinal direction as needed.

  Subsequently, if necessary, the substrate layer of the film for a solar battery backsheet of the present invention can be formed by performing a corona discharge treatment or the like in order to further enhance the adhesion with other materials and winding up.

  Next, as a method of forming a conductive layer (A layer) on the base material layer (B layer), a dry method such as a vapor deposition method or a sputtering method, a wet method such as a plating method, or a plurality of extruders. A method of co-extruding the raw material for the B layer and the raw material for the A layer in separate extruders and co-extruding them onto a cast drum cooled from the die (co-extrusion method), with a single film A method of laminating the raw material for the layer A into the produced base material layer (B layer) in an extruder, melt extrusion and extruding from the die (melt laminating method), the base material layer (layer B) and the layer A separately. A method of thermocompression bonding with a heated roll group (thermal laminating method), a method of pasting together with an adhesive (adhesion method), and the like. Method of coating on the base material layer (B layer) that has been prepared (co Plating method), and a method in which a combination of these can be used.

  In the case where the A layer is mainly composed of an organic material, or in the case of i) to iii) with an organic / inorganic composite conductive material, the formation of the formed A layer is among these methods described above. A co-extrusion method and a coating method, which are easy, are more preferable forming methods.

  As a method of forming the A layer on the base material layer (B layer) by the coextrusion method, a plurality of extruders are used for the B layer and / or for the B1 layer constituting the B layer, for the A layer. The raw materials are melted in different extruders and co-extruded from the die, and the B layer and / or the B layer are formed by static adhesion and solidification by static electricity on a drum cooled to a surface temperature of 10 ° C. or higher and 60 ° C. or lower. A sheet in which the A layer is formed on the B1 layer can be obtained.

  In the case of a film base material in which the base material layer (B layer) and / or the B1 layer constituting the B layer is uniaxially or biaxially stretched, the above-mentioned A layer raw material and base material layer (B layer) It can obtain by extending | stretching the sheet | seat by which the B1 layer which comprises the raw material for a material and / or B layer was laminated | stacked by the method similar to the above-mentioned method.

  In addition, as a method of forming the A layer on the base layer (B layer) and / or the B1 layer constituting the B layer by a coating method, the base layer (B layer) and / or the B1 layer constituting the B layer is used. In-line coating method to be applied during film formation, and off-line coating method to be applied to the base material layer (B layer) and / or B1 layer constituting the B layer after film formation can be used. More preferably, the base layer (B layer) and / or the B1 layer constituting the B layer can be formed simultaneously and efficiently, and the A layer base layer (B layer) and / or B layer The in-line coating method is preferably used because of its high adhesiveness to the B1 layer constituting the material. Further, when coating, corona treatment or the like may be applied to the surface of the base layer (B layer) and / or the B1 layer constituting the B layer from the viewpoint of improving the wettability of the coating solution on the support and improving the adhesive strength. Preferably done.

  As a method of forming the A layer on the base material layer (B layer) and / or the B1 layer constituting the B layer by the coating method, a coating in which the material constituting the A layer is dissolved / dispersed in a solvent is used. A means for applying and drying the liquid on the base layer (B layer) and / or the B1 layer constituting the B layer is preferably used. In this case, the solvent to be used is arbitrary, but in the in-line coating method, it is preferable to use water as a main component from the viewpoint of safety. In that case, a small amount of an organic solvent that dissolves in water may be added in order to improve applicability and solubility. Examples of such organic solvents include aliphatic or alicyclic alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, and n-butyl alcohol, diols such as ethylene glycol, propylene glycol, and diethylene glycol, methyl cellosorb, Diol derivatives such as ethyl cellosolve propylene glycol monomethyl ether, ethers such as dioxane and tetrahydrofuran, esters such as methyl acetate, ethyl acetate and amyl acetate, ketones such as acetone and methyl ethyl ketone, amides such as N-methylpyrrolidone Etc. and mixtures thereof may be used, but are not limited to these.

  In the case where the A layer is mainly composed of an inorganic material, among these methods described above, the deposition method and sputtering are easy to control the formed A layer and have excellent adhesion to the substrate and uniformity. A dry method such as a method is a more preferable forming method.

  In the method for producing a solar cell backsheet film of the present invention, the method of forming the A layer by a dry method includes resistance heating evaporation, electron beam evaporation, induction heating evaporation, and vacuum such as an assist method using plasma or ion beam. Uses vapor deposition, reactive sputtering, ion beam sputtering, sputtering such as ECR (electron cyclotron) sputtering, physical vapor deposition (PVD) such as ion plating, heat, light, plasma, etc. The chemical vapor deposition method (CVD method) etc. which were made.

  Here, when the material forming the A layer is mainly composed of inorganic oxide, inorganic nitride, inorganic oxynitride, inorganic halide, inorganic sulfide, etc., the same material as the composition of the A layer to be formed Can be directly volatilized and deposited on the surface of the base layer (B layer) and / or the B1 layer constituting the B layer, but when this method is used, the composition changes during volatilization, As a result, the formed film may not exhibit uniform characteristics. Therefore, 1) a material having the same composition as the A layer formed as a volatilization source is used, oxygen gas in the case of inorganic oxide, nitrogen gas in the case of inorganic nitride, oxygen gas and nitrogen in the case of inorganic oxynitride A method of volatilizing a mixed gas of gases by introducing a halogen-based gas in the case of an inorganic halide, and a sulfur-based gas in the case of an inorganic sulfide, while supplementarily introducing them into the system, and 2) selecting an inorganic group as a volatile source Volatilizes and vaporizes this, in the case of inorganic oxide, oxygen gas, in the case of inorganic nitride, nitrogen gas, in the case of inorganic oxynitride, mixed gas of oxygen gas and nitrogen gas, in the case of inorganic halide Introduces a halogen-based gas, and in the case of an inorganic sulfide, a sulfur-based gas is introduced into the system, and deposits on the surface of the substrate 1 while reacting the introduced gas with the inorganic material. 3) Using an inorganic group as a volatile source Volatilize this After forming the inorganic group layer, it is an oxygen gas atmosphere for inorganic oxides, a nitrogen gas atmosphere for inorganic nitrides, and a mixed gas of oxygen gas and nitrogen gas for inorganic oxynitrides. In the atmosphere, in the case of an inorganic halide, it is possible to react the introduced inorganic layer with the introduced gas by holding it in a halogen-based gas atmosphere, and in the case of an inorganic sulfide, in a sulfur-based gas atmosphere. Of these, 2) or 3) is more preferably used because it is easy to volatilize from a volatile source. Furthermore, the method 2) is more preferably used because the film quality can be easily controlled. When the A layer is an inorganic oxide, the inorganic group is used as a volatilization source, volatilized to form an inorganic group layer, and then left in the air to naturally oxidize the inorganic group. The method is also preferably used because it can be easily formed.

  Here, in the film for solar battery backsheet of the present invention, when the A layer is formed by a dry method, the surface specific resistance R0 of the A surface of the A layer can be adjusted by the degree of reaction by gas. The degree of reaction can be adjusted by the flow rate, temperature, etc. of the introduced gas. When the degree of reaction is small, the surface specific resistance R0 is low, and when the degree of reaction is large, the surface specific resistance R0 is high. The optimum conditions vary depending on the metal species used, the gas to be reacted, the apparatus, etc., but may be formed by adjusting the conditions so that the surface specific resistance R0 satisfies the above requirements.

  Moreover, when forming A layer by PVD method, when reducing pressure before volatilization, it is preferable to increase the degree of vacuum in the system. By increasing the degree of vacuum in the system, it is possible to form an A layer that is dense and has few defects, and the A layer can be formed uniformly.

  In addition, when the layer A has a laminated structure, when the inorganic group is different, an apparatus including a plurality of volatilization sources is used, and after the first layer is formed, the volatilization source is changed to form the second layer and the third layer. In the case where the same inorganic substance group is different only in the degree of reaction and / or the type of reaction gas, the flow rate of the introduced gas and / or the type of introduced gas after the first layer is formed May be changed to form the second layer, the third layer,...

  In the case where the material constituting the layer A of the solar cell backsheet film of the present invention is an organic / inorganic composite conductive material iv), the above-described production method depends on the type, composition, etc. of the material used. It can be formed by appropriately selecting from among them.

  The film for a solar battery backsheet of the present invention can be formed by the above-described process, and the obtained film is characterized by having a high partial discharge voltage even if it is thinner than a conventional film.

  The solar cell backsheet of this invention is characterized by including the above-mentioned film for solar cell backsheets. Even if the solar cell backsheet film of the present invention is thinner than a conventional film, the backsheet can be made thinner because the partial discharge voltage is high.

  The configuration of the solar cell backsheet of the present invention can be any configuration as long as the above-described solar cell backsheet is used, and adhesion with EVA that seals the power generation element on the solar cell backsheet of the present invention. EVA adhesion layer for improving the adhesion, anchor layer for increasing adhesion with the EVA adhesion layer, water vapor barrier layer, ultraviolet absorbing layer for preventing ultraviolet deterioration, light reflecting layer for enhancing power generation efficiency, and design characteristics The solar cell backsheet of the present invention is formed by forming a light absorbing layer for the purpose, an adhesive layer for adhering each layer, and the like.

  The EVA adhesion layer is a layer that improves adhesion to the EVA resin that seals the power generation element, and is disposed on the side closest to the power generation element, and contributes to adhesion between the backsheet and the system. The material is not particularly limited as long as adhesion with EVA resin is expressed. For example, EVA, EVA and ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene A mixture of butyl acrylate copolymer (EBA), ethylene-methacrylic acid copolymer (EMAA), ionomer resin, polyester resin, urethane resin, acrylic resin, polyethylene resin, polypropylene resin, polyamide resin or the like is preferably used.

  Moreover, in order to improve the adhesiveness to the back sheet | seat of an EVA contact bonding layer as needed, forming an anchor layer is also performed preferably. The material is not particularly limited as long as adhesion to the EVA adhesion layer is expressed, and for example, a mixture containing a resin as a main constituent such as an acrylic resin or a polyester resin is preferably used.

  The water vapor barrier layer is a layer for preventing water vapor from entering from the back sheet side in order to prevent water vapor deterioration of the power generation element when the solar cell is configured. It is formed by providing an oxide such as silicon oxide or aluminum oxide or a metal layer such as aluminum on the film surface by a known method such as vacuum deposition or sputtering. The thickness is preferably in the range of usually 100 to 200 angstroms.

  In this case, both the case where the gas barrier layer is directly provided on the film for solar cell backsheet of the present invention and the case where the gas barrier property is provided on another film and this film is laminated on the film surface of the present invention are preferably used. Moreover, the method of laminating | stacking metal foil (for example, aluminum foil) on the film surface can also be used. In this case, the thickness of the metal foil is preferably in the range of 10 to 50 μm from the viewpoint of workability and gas barrier properties.

  The ultraviolet absorbing layer is a layer for blocking ultraviolet rays in order to prevent ultraviolet degradation of the resin in the inner layer, and any layer can be used as long as it has a function of blocking ultraviolet rays of 380 nm or less.

  The light reflecting layer is a layer that reflects light, and by forming this layer, the inner layer resin is prevented from UV degradation, or the light that reaches the back sheet without being absorbed by the solar cell system is reflected. This layer is used to increase the power generation efficiency by returning to the system side, and is a layer containing white pigments such as titanium oxide and barium sulfate, or bubbles.

  The light absorbing layer is a layer that absorbs light, and is a layer that is used to prevent UV degradation of the resin in the inner layer or improve the design of the solar cell by forming this layer.

  The solar cell backsheet of the present invention is formed by combining the above layers and the film of the present invention. In the solar battery backsheet of the present invention, it is not necessary to form all of the above layers as independent layers, and it is also a preferred form to form a function integration layer having a plurality of functions. Moreover, when it already has a function in the film for solar cell backsheets of this invention, it is also omissible. For example, when the backsheet film of the present invention contains a white pigment or bubbles and has light reflectivity, the light reflection layer is used. When the backsheet film contains a light absorber and has light absorbency, the absorption layer is used. In the case of having an ultraviolet absorber, the ultraviolet absorbing layer may be omitted.

  As for the gas barrier layer, any of the case where the gas barrier layer is directly provided on the film of the present invention and the case where a layer having gas barrier properties is provided on another film and this film is laminated on the surface of the polyester film of the present invention are preferably used. Moreover, the method of laminating | stacking metal foil (for example, aluminum foil) on the film surface can also be used. In this case, the thickness of the metal foil is preferably in the range of 10 to 50 μm from the viewpoint of workability and gas barrier properties.

  Here, the solar cell backsheet of the present invention has a higher partial discharge voltage than that of a conventional film, and when this is used to form a backsheet, the partial discharge voltage can be increased as compared to a conventional backsheet. It becomes. In the solar cell backsheet of the present invention, both surface layers of the solar cell backsheet may be formed of layers other than the film of the present invention, or at least one surface layer may be formed of the film of the present invention. In any case, since the partial discharge voltage is higher than that of the conventional film, the safety of the solar battery backsheet can be improved and the thickness can be reduced. More preferably, it is more preferable that at least one surface of the solar cell backsheet is the polyester film for solar cell backsheet of the present invention in that the partial discharge voltage can be further increased. Furthermore, it is preferable that at least one surface is configured to be the A surface of the film for solar cell backsheet of the present invention. By adopting this configuration, the partial discharge voltage can be made higher than in the configuration having the A surface inside the back sheet, and as a result, the electric resistance characteristics of the solar cell back sheet can be increased, or the thickness of the back sheet can be increased. It is possible to make the thickness thinner.

The solar cell backsheet of the present invention has a surface specific resistance R3 of 10 ¹⁴ Ω on the surface opposite to the A surface when at least one surface is configured to be the A surface of the solar cell backsheet film described above. / □ or more is preferable. As will be described later, when the film for solar cell backsheet of the present invention is incorporated into a solar cell system, it is more durable that the surface on the opposite side of the resin layer sealing the power generating element is the A layer. Or a preferable configuration from the viewpoint that the thickness can be reduced. Here, when both side surfaces of the solar cell backsheet are A layers, the electrical resistance characteristics of the solar cell backsheet may be reduced, or when electrical energy is extracted from the lead wire, the extraction efficiency is reduced and the power generation efficiency is reduced. This is because there is a case in which the lowering may occur.

  The thickness of the solar cell backsheet of the present invention is preferably 20 μm or more and 500 μm or less, and more preferably 25 μm or more and 300 μm or less. More preferably, they are 30 micrometers or more and 200 micrometers or less. When the thickness is less than 10 μm, it is difficult to ensure the flatness of the film. On the other hand, when it is thicker than 500 μm, when it is mounted on a solar cell, the thickness of the solar cell may become too large.

  The solar cell of the present invention includes the solar cell backsheet of the present invention. The solar cell backsheet of the present invention can be made more durable or thinner than the conventional solar cell by taking advantage of the feature that the partial discharge voltage is higher than that of the conventional backsheet.

  The solar cell of this invention needs to contain the solar cell backsheet mentioned above.

  An example of the configuration is shown in FIG. A power generating element connected with a lead wire (not shown in FIG. 1) for extracting electricity is sealed with a transparent filler 2 such as EVA resin, and is called a transparent substrate 4 such as glass and a back sheet 1. Although it is configured by pasting resin sheets, it is not limited to this and can be used for any configuration.

  The power generating element 3 converts light energy of sunlight into electric energy, and is based on crystalline silicon, polycrystalline silicon, microcrystalline silicon, amorphous silicon, copper indium selenide, compound semiconductor, dye enhancement Arbitrary elements such as a sensitive system can be used in series or in parallel according to the desired voltage or current depending on the purpose.

  Since the substrate 4 having translucency is located on the outermost layer of the solar cell, a transparent material having high weather resistance, high contamination resistance, and high mechanical strength characteristics in addition to high transmittance is used. In the solar cell of the present invention, any material can be used for the light-transmitting substrate 4 as long as the above characteristics are satisfied. Examples include glass, tetrafluoroethylene-ethylene copolymer (ETFE), polyvinyl fluoride resin (PVF), polyvinylidene fluoride resin (PVDF), polytetrafluoroethylene resin (TFE), tetrafluoroethylene- Preferable examples include fluorinated resins such as hexafluoropropylene copolymer (FEP), polytrifluoroethylene chloride (CTFE), and polyvinylidene fluoride resin, olefin resins, acrylic resins, and mixtures thereof. In the case of glass, it is more preferable to use a tempered glass. In the case of fluorine-based resins, polyvinylidene fluoride resin and tetrafluoroethylene-ethylene copolymer are the main components for reasons of high weather resistance, and it is more preferable, and in terms of mechanical strength, tetrafluoroethylene-ethylene. More preferably, the copolymer is the main component. Moreover, when using the resin-made translucent base material, what extended | stretched the said resin uniaxially or biaxially from a viewpoint of mechanical strength is used preferably.

  In addition, in order to impart adhesion to the EVA resin that is a sealing material agent for the power generation element, it is preferable to subject the surface to corona treatment, plasma treatment, ozone treatment, and easy adhesion treatment. Is called.

  The resin 2 for sealing the power generation element is formed by covering and fixing the unevenness of the surface of the power generation element with resin, protecting the power generation element from the external environment, and for the purpose of electrical insulation, as well as a transparent substrate or back In order to adhere to the sheet and the power generation element, a material having high transparency, high weather resistance, high adhesion, and high heat resistance is used. Examples thereof include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA) resin, ethylene-methacrylic acid copolymer (EMAA), Ionomer resins, polyvinyl butyral resins, and mixtures thereof are preferably used. Among these resins, ethylene-vinyl acetate is more preferably used in terms of excellent balance of weather resistance, adhesiveness, filling property, heat resistance, cold resistance, and impact resistance.

  Here, in the solar cell of the present invention, the above-described solar cell backsheet 1 is installed on the back surface of the resin layer 2 encapsulating the power generation element, but is formed so as to be one side surface of the above-described solar cell backsheet. The A surface of the solar cell backsheet film 1 may be arranged so as to be on the resin layer 2 side (5 in FIG. 1), or arranged on the opposite side (6 in FIG. 1). May be. Regardless of the configuration, the solar cell backsheet of the present invention has a higher partial discharge voltage even if it is thinner than the conventional one, so that the durability of the solar cell system can be increased or the thickness can be reduced. . More preferably, it is more preferable that the A-side of the film for solar cell backsheet formed so as to be on one side surface of the above-described solar cell backsheet is the side opposite to the resin layer (6 in FIG. 1). . By adopting this configuration, it is possible to obtain a more durable solar cell or to reduce the thickness compared to the configuration in which the A surface is on the resin layer side (5 in FIG. 1).

  As described above, by incorporating the back sheet of the present invention into a solar cell system, it is possible to obtain a highly durable and / or thin solar cell system as compared with conventional solar cells.

  The solar cell of the present invention can be suitably used for various applications without being limited to outdoor use and indoor use such as a solar power generation system and a power source for small electronic components.

[Characteristic evaluation method]
A. Surface specific resistance R0, R1, R2, R3
The surface specific resistances R0 and R2 of the film and the surface specific resistance R3 on the opposite side of the A-side of the backsheet were measured with a digital ultrahigh resistance microammeter R8340 manufactured by Advantest (manufactured by Advantest). . However, when the surface specific resistance is 10 ⁵ Ω / □ or less, Lorester EP equipped with an ASP probe (manufactured by Dia Instruments Co., Ltd.). The surface resistivity R0 was determined by the average value. Further, the measurement was performed using a measurement sample that was left overnight in a room at 23 ° C. and 65% Rh.

  Further, the surface specific resistance R1 is obtained by subjecting the film to a pressure cooker manufactured by Tabai Espec Co., Ltd. for 24 hours under the conditions of 125 ° C., humidity 100%, 2.5 atm, and then the surface specific resistance R1 of the treated sample. Was measured by the same method as described above. In addition, the measurement was carried out at 10 arbitrary positions in the film plane, and the surface specific resistance R1 was determined by the average value. Moreover, after taking out from the pressure cooker after a process, the measurement sample was measured using what was left overnight in 23 degreeC and 65% Rh room | chamber interior.

B. Breaking elongation and elongation retention rate Based on ASTM-D882 (1999), breaking elongation is measured by cutting a sample into a size of 1 cm × 20 cm and pulling it at 5 cm between chucks and at a pulling speed of 300 mm / min. The degree was measured. In addition, the measurement was performed about 5 samples and it was set as the breaking elongation E0 with the average value.
In addition, the elongation retention is determined by cutting a sample into the shape of a measurement piece (1 cm × 20 cm) and then using a pressure cooker manufactured by Tabay Espec Co., Ltd. for 24 hours under conditions of 125 ° C., humidity 100%, 2.5 atm. After the treatment, the breaking elongation of the treated sample was measured based on ASTM-D882 (1999), when the elongation at break was 5 cm between chucks and pulled at a pulling speed of 300 mm / min. In addition, the measurement was performed about 5 samples and it was set as the breaking elongation E1 with the average value.
Using the obtained breaking elongations E0 and E1, the elongation retention was calculated by the following formula (1).
Elongation retention (%) = E1 / E0 × 100 (1)
The obtained elongation retention was determined as follows.
When the elongation retention is 70% or more: S
When the elongation retention is 60% or more and less than 70%: A
Elongation retention is 50% or more and less than 60%: B
Elongation retention is less than 50%: C
S or A or B is good, and S is the best.

C. Weight average molecular weight (Mw), number average molecular weight (Mn)
Two columns, Shodex HFIP 806M (manufactured by Showa Denko KK), and a gel permeation chromatograph GCP-244 (manufactured by WATERS) equipped with RI type (2414 type, sensitivity 256, manufactured by WATERS) as a detector are used. Then, GPC measurement was performed using PET-DMT (standard product) at room temperature (23 ° C.) and a flow rate of 0.5 mL / min. Using the obtained elution volume (V) and molecular weight (M), the coefficient (A ₁ ) of the third-order approximate expression of the following formula (2) was calculated to draw a calibration curve.
Log (M) = A ₀ + A ₁ V + A ₂ V ² + A ₃ V ³ (2)
Next, using hexafluoropropanol (0.005N-sodium trifluoroacetate) as a solvent, a solution in which the B1 layer is dissolved to 0.06% by weight is prepared, and GPC measurement is performed using the solution. It was. In addition, although measurement conditions are arbitrary, in this measurement, the injection amount was 0.300 ml and the flow rate was 0.5 ml / min.
The obtained elution curve molecular weight curve and the molecular weight calibration curve were superposed to determine the molecular weight corresponding to each outflow time, and the weight average molecular weight was determined from the value calculated by the following formula (3).
Weight average molecular weight (Mw) = Σ (Ni · Mi ² ) / Σ (Ni · Mi) (3)
Moreover, the number average molecular weight was calculated | required with the value computed by following formula (4).
Number average molecular weight (Mn) = ΣNiMi / ΣNi (4)
(Here, Ni is the molar fraction, and Mi is the molecular weight of each elution position of the GPC curve obtained via the molecular weight calibration curve.)
In addition, when the base material layer (B layer) has a laminated structure, the measurement was performed using a sample in which only the B1 layer was formed by peeling other layers or polishing the corresponding film while observing under a microscope. D . Slight endothermic peak temperature TmetaB1, melting point TmB1
The minute endothermic peak temperature TmetaB1 and melting point TmB1 of the B1 layer were measured by using a differential scanning calorimeter “Robot DSC-RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. according to JIS K7122 (1999). Measurements were performed using / 5200 ". The B1 layer is weighed 5 mg each in a sample pan, and the resin is heated at a heating rate of 20 ° C./min from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min 1st RUN. The measurement was carried out by rapidly cooling to below ℃ and then raising the temperature from room temperature to 300 ℃ at a rate of temperature increase of 20 ℃ / min. In the obtained differential scanning calorimetry chart of 1stRUN, TmetaB1 was the endothermic peak temperature before the crystal melting peak, and TmB1 of the B1 layer was the peak top temperature in the 2ndRun crystal melting peak.

G. Partial discharge voltage The partial discharge voltage was determined using a partial discharge tester KPD2050 (manufactured by Kikusui Electronics Co., Ltd.). The test conditions are as follows.
The output voltage application pattern on the output sheet is a pattern in which the first stage simply increases the voltage from 0 V to a predetermined test voltage, the second stage is a pattern that maintains a predetermined test voltage, and the third stage is a predetermined test A pattern composed of three stages of patterns in which the voltage is simply dropped from 0 to 0 V is selected.
・ The frequency is 50 Hz. The test voltage is 1 kV.
The first stage time T1 is 10 sec, the second stage time T2 is 2 sec, and the third stage time T3 is 10 sec.
• The counting method on the pulse count sheet is “+” (plus), and the detection level is 50%.
-The amount of charge in the range sheet is in the range 1000 pc.
・ In the protection sheet, enter 2 kV after checking the voltage check box. The pulse count is 100,000.
In the measurement mode, the start voltage is 1.0 pc and the extinction voltage is 1.0 pc.
In addition, the measurement is performed when the A side is the upper electrode side, and when the A side is the lower electrode side, the measurement is performed at any 10 points in the film plane for each, and the average value is obtained, The partial discharge voltage V0 was determined by the higher value of the average values of the above. The measurement was performed using a measurement sample that was left overnight in a room at 23 ° C. and 65% Rh.

  The partial discharge voltage V1 after the wet heat treatment was processed for 24 hours under the conditions of 125 ° C., 100% humidity and 2.5 atm using a pressure cooker manufactured by Tabai Espec Co., Ltd. The voltage V1 was measured. In addition, the measurement is performed when the A side is the upper electrode side, and when the A side is the lower electrode side, the measurement is performed at any 10 points in the film plane for each, and the average value is obtained, The partial discharge voltage V <b> 1 was determined by the higher value of the average values. Moreover, after taking out from the pressure cooker after a process, the measurement sample was measured using what was left overnight in 23 degreeC and 65% Rh room | chamber interior.

Further, by using a light (UV) portion after the test discharge voltage V2 is eye ultraviolet degradation accelerated tester film Super UV Tester SUV-W131 (manufactured by Iwasaki Electric Co.), light 24 hours (illuminance: 100 mW / cm ² , Temperature and humidity: 60 ° C. × 50% RH) was subjected to an ultraviolet irradiation test for 4 hours, and the partial discharge voltage V2 after the treatment was measured. In addition, the measurement is performed at 10 arbitrary locations in the film plane, and the measurement sample is taken out from the ultraviolet ray accelerating tester after processing and then left overnight in a room at 23 ° C. and 65% Rh. Measurements were performed. Further, when the A surface side is set as the upper electrode side and the B surface side is set as the upper electrode side, the above measurement is carried out for each, and the partial discharge voltage V2 is obtained with the higher value of the respective average values. It was.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not necessarily limited to these.

(Example 1-1)
Polyethylene terephthalate (melting point TmB1 = 255 ° C.) having an intrinsic viscosity of 0.81 is vacuum-dried at a temperature of 180 ° C. for 3 hours and then supplied to an extruder, and melted at a temperature of 280 ° C. in a nitrogen atmosphere. Introduced.

  Next, the molten single layer sheet is extruded from the inside of the T die die into a molten single layer sheet, and the molten single layer sheet is closely cooled and solidified by an electrostatic application method on a drum maintained at a surface temperature of 25 ° C. A layer film was obtained. Subsequently, the unstretched single layer film was preheated with a roll group heated to a temperature of 90 ° C., and then stretched 3.3 times in the longitudinal direction (longitudinal direction) using a heating roll having a temperature of 95 ° C. A uniaxially stretched film was obtained by cooling with a roll group at a temperature of ° C.

  After the uniaxially stretched film was subjected to corona treatment, the following coating agent 1-1 was applied with a # 6 metering bar.

<Coating agent 1-1>
・ Water dispersion of water-insoluble cationic conductive material: “BONDEIP-PM (registered trademark)” main agent (manufactured by Konishi Oil & Fat Co., Ltd., solid content 30%) 18 parts by weight ・ Acrylic resin water dispersion: methyl methacrylate / Ethyl acrylate / acrylic acid / N-methylolacrylamide = 62/35/2/1 (weight ratio) copolymer acrylic resin (glass transition temperature: 42 ° C.) dispersed in water at a solid content of 10% . 3 parts by weight-Oxazoline group-containing compound aqueous dispersion: "Epocross (registered trademark)" WS-500 (manufactured by Nippon Shokubai Co., Ltd., solid content 40%) 0.75 parts by weight-acetylenediol surfactant: "Orphine (Registered trademark) “EXP4051F (manufactured by Nissin Chemical Industry Co., Ltd.)” 0.1 part by weight, water 78.15 parts by weight.

  While holding both ends of the obtained uniaxially stretched film with clips, it is guided to a preheating zone at a temperature of 95 ° C. in the tenter, and continuously in a heating zone at a temperature of 105 ° C. in a direction perpendicular to the longitudinal direction (width direction). The film was stretched 3.5 times. Subsequently, heat treatment was performed for 20 seconds at a predetermined temperature in the heat treatment zone in the tenter, and after further relaxation treatment in the 4% width direction at a temperature of 180 ° C., further in the 3% width direction at a temperature of 140 ° C. A relaxation treatment was performed. Subsequently, the film was gradually cooled and wound up to obtain a biaxially stretched film having a thickness of 50 μm and having an A layer formed on the surface with a film thickness of 0.15 μm. B1 layer weight average molecular weight, number average molecular weight, surface specific resistance of surface A, surface specific resistance of surface opposite to surface A, elongation at break, partial discharge voltage, heat shrinkage, wet heat treatment The surface specific resistance, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that each characteristic was excellent.

Next, using this film as the first layer, as an adhesive layer, 90 parts by weight of “Takelac (registered trademark)” A310 (manufactured by Mitsui Takeda Chemical Co., Ltd.), “Takenate (registered trademark)” A3 (Mitsui Takeda Chemical Co., Ltd.) The second layer is 125 μm thick biaxially stretched polyester film “Lumirror (registered trademark)” S10 (manufactured by Toray Industries, Inc., surface resistivity is 4.5 × 10 ¹⁵ Ω / both on both sides) □). Next, the above-mentioned adhesive layer is applied onto the second layer, and a 12 μm-thick barrier locks “HGTS” (alumina-deposited PET film manufactured by Toray Film Processing Co., Ltd.) is placed on the opposite side of the second layer. And a back sheet having a thickness of 188 μm was formed. In addition, about the case where it bonded so that A surface might become inner side (opposite a 2nd layer) about the 1st layer, and the case where it bonded together so that it might become an outer side (opposite side to a 2nd layer), it produced both.

  The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. All showed high partial discharge voltage, and it turned out that a higher partial discharge voltage is shown especially when A surface is formed in the outer side.

(Examples 1-2 to 1-3)
As the coating agent for forming the A layer, except that the following coating agent 1-2 and coating agent 1-3 were used, respectively, the A layer had a film thickness of 0.15 μm on the surface in the same manner as in Example 1-1. A formed biaxially stretched film having a thickness of 50 μm was obtained.

<Coating agent 1-2>
-Water dispersion of water-insoluble cationic conductive material: "BONDEIP-PM (registered trademark)" (manufactured by Konishi Yushi Co., Ltd., solid content 30%) 16 parts by weight-Acrylic resin water dispersion: methyl methacrylate / Ethyl acrylate / acrylic acid / N-methylolacrylamide = 62/35/2/1 (weight ratio) Copolymerized acrylic resin (glass transition temperature: 42 ° C.) dispersed in water at a solid content of 10%. 6 parts by weight-Oxazoline group-containing compound aqueous dispersion: "Epocross (registered trademark)" WS-500 (manufactured by Nippon Shokubai Co., Ltd., solid content 40%) 1.25 parts by weight-acetylenediol surfactant: "Orphine (Registered trademark) "EXP4051F (manufactured by Nissin Chemical Industry Co., Ltd.)" 0.1 parts by weight; water, 76.65 parts by weight.

<Coating agent 1-3>
-Water dispersion of water-insoluble cationic conductive material: "BONDEIP-PM (registered trademark)" main agent (Konishi Yushi Co., Ltd., solid content 30%) 12 parts by weight-Acrylic resin water dispersion: methyl methacrylate / Ethyl acrylate / acrylic acid / N-methylolacrylamide = 62/35/2/1 (weight ratio) copolymer acrylic resin (glass transition temperature: 42 ° C.) dispersed in water at a solid content of 10% . 12 parts by weight-Oxazoline group-containing compound aqueous dispersion: "Epocross (registered trademark)" WS-500 (manufactured by Nippon Shokubai Co., Ltd., solid content 40%) 2.5 parts by weight-Acetylenediol surfactant: "Orphine (Registered trademark) “EXP4051F (manufactured by Nissin Chemical Industry Co., Ltd.)” 0.1 part by weight, 73.4 parts by weight of water.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It turned out that it is excellent in each characteristic like Example 1-1.

  Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1. The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, all showed a high partial discharge voltage, and in particular, when the A surface was formed outside, it was found that a higher partial discharge voltage was exhibited.

(Examples 1-4 and 1-5)
As the coating agent for forming the A layer, except that the following coating agent 1-4 and coating agent 1-5 were used, respectively, the A layer on the surface had a film thickness of 0.15 μm in the same manner as in Example 1-1. A biaxially stretched film having a thickness of 50 μm and a thickness of 0.03 μm was obtained.

<Coating agent 1-4>
-Water dispersion of water-insoluble cationic conductive material: "BONDEIP-PM (registered trademark)" main agent (Konishi Yushi Co., Ltd., solid content 30%) 10 parts by weight-Acrylic resin water dispersion: methyl methacrylate / Ethyl acrylate / acrylic acid / N-methylolacrylamide = 62/35/2/1 (weight ratio) copolymer acrylic resin (glass transition temperature: 42 ° C.) dispersed in water at a solid content of 10% . 15 parts by weight of oxazoline group-containing compound aqueous dispersion: “Epocross (registered trademark)” WS-500 (manufactured by Nippon Shokubai Co., Ltd., solid content 40%) 3.75 parts by weight of acetylenediol surfactant: “Orphine (Registered trademark) "EXP4051F (manufactured by Nissin Chemical Industry Co., Ltd.)" 71.15 parts by weight.

<Coating 1-5>
Water-insoluble polythiophene-based conductive polymer aqueous dispersion: “Baytron (registered trademark)” P (manufactured by Bayer / HC Stark (Germany), solid content 1.2%) 41.6 parts by weight Water-insoluble polyester resin: copolymerized with terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalate = 60/30/10 as the acid component and ethylene glycol / diethylene glycol / polyethylene glycol = 95/3/2 as the diol component 2.5 parts by weight of a polyester resin (glass transition temperature 48 ° C.) dispersed at a concentration of 10% by weight. Epoxy crosslinking agent: polyglycerol polyglycidyl ether epoxy crosslinking agent EX-512 (molecular weight about 630) ( Nagase ChemteX Corp.) 0.25 parts by weight Acetylenediol surfactant: Rufin (registered trademark) "EXP4051F 0.1 parts by weight, water 32.1 parts by weight.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Although it was inferior to Examples 1-1 to 1-3, it showed that it showed a high partial discharge voltage and was excellent in each characteristic.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that all of them showed a high partial discharge voltage, although inferior to Examples 1-1 to 1-3, and in particular, when the A surface was formed on the outside, a higher partial discharge voltage was shown.

(Example 1-6)
Biaxial stretching with a thickness of 50 μm in which the A layer was formed on the surface with a thickness of 0.03 μm by the same method as in Example 1-1, except that the following coating agent 1-6 was used as the coating agent for forming the A layer. A film was obtained.

<Coating 1-6>
Water-insoluble polythiophene-based conductive polymer aqueous dispersion: “Baytron (registered trademark)” P (manufactured by Bayer / HC Stark (Germany), solid content 1.2%) 50 parts by weight Water-soluble polyester resin: polyester obtained by copolymerizing terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalate = 60/30/10 as an acid component and ethylene glycol / diethylene glycol / polyethylene glycol = 95/3/2 as a diol component 2 parts by weight of resin (glass transition temperature 48 ° C.) dispersed at a concentration of 10% by weight. Epoxy crosslinking agent: polyglycerol polyglycidyl ether epoxy crosslinking agent EX-512 (molecular weight about 630) (Nagase Chemtex ( 0.2 parts by weight / acetylene diol surfactant: “Orphine” (Registered trademark) "EXP4051F 0.1 parts by weight and water 47.7 parts by weight.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Although it was inferior to Examples 1-4 and 1-5, it showed a high partial discharge voltage and was found to be excellent in each characteristic.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. Both were inferior to Examples 1-4 and 1-5, but showed a high partial discharge voltage. In particular, when the A surface was formed on the outside, it was found that a higher partial discharge voltage was exhibited.

(Example 1-7)
50 μm thick biaxially formed on the surface with a thickness of 0.03 μm by the same method as Example 1-1, except that the following coating agent 1-7 was used as the coating agent for forming the A layer A stretched film was obtained.

<Coating 1-7>
Water-insoluble polythiophene-based conductive polymer aqueous dispersion: “Baytron (registered trademark)” P (manufactured by Bayer / HC Stark (Germany), solid content 1.2%) 66.7 parts by weight Water-insoluble polyester resin: copolymerized with terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalate = 60/30/10 as the acid component and ethylene glycol / diethylene glycol / polyethylene glycol = 95/3/2 as the diol component 1 part by weight of a dispersed polyester resin (glass transition temperature 48 ° C.) at a concentration of 10% by weight. Epoxy crosslinking agent: polyglycerol polyglycidyl ether epoxy crosslinking agent EX-512 (molecular weight about 630) (Nagase Chem) Manufactured by Tex Co., Ltd.) 0.1 parts by weight, acetylenic diol-based surfactant: “Orphy (Registered trademark) EXP4051F 0.1 parts by weight, water 32.1 parts by weight.
The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Although it is inferior to Example 1-6, it showed a high partial discharge voltage and was found to be excellent in each characteristic.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that all showed a high partial discharge voltage although inferior to Example 1-6, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 1-8)
A biaxially stretched film having a thickness of 50 μm was obtained in the same manner as in Example 1-1 except that the film thickness was 125 μm. The surface specific resistance of the obtained film, the surface specific resistance R2 of the surface opposite to the A surface, the breaking elongation, the partial discharge voltage, the heat shrinkage rate, the surface specific resistance after wet heat treatment, the breaking elongation, the partial discharge voltage It was measured. The results are shown in Tables 1 and 2. It was found that each characteristic was excellent.

  Using the obtained film, a backsheet was prepared in the same manner as in Example 1-1 except that a 50 μm thick biaxially stretched polyester film “Lumirror (registered trademark)” S10 (manufactured by Toray Industries, Inc.) was used as the second layer. Formed.

  The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. Although all showed the high partial discharge voltage although it was inferior to Example 1-1, when the A surface was formed in the outer side, it turned out that a higher partial discharge voltage is shown.

(Example 1-9)
A biaxially stretched film having a thickness of 50 μm in which an A layer was formed on the surface with a film thickness of 0.15 μm was obtained in the same manner as in Example 1-1 except that the film thickness was 188 μm. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that each characteristic was excellent.

As the obtained first film layer, this film was set in an electron beam vapor deposition apparatus, alumina was used as a volatilization source, the degree of vacuum was 3.4 × 10 ⁻⁵ Pa, the vapor deposition rate was 10 Å / sec, the vapor deposition source-base material Under the condition of a distance of 25 cm, alumina was electron beam evaporated from the normal direction of the film surface to form a second layer made of alumina having a film thickness of 0.2 μm. In addition, about the case where it vapor-deposited so that A surface might become inner side (opposite a 2nd layer) about the 1st layer, and the case where it vapor-deposited so that it might become an outer side (opposite side to a 2nd layer).

  The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, all showed a high partial discharge voltage, and in particular, when the A surface was formed outside, it was found that a higher partial discharge voltage was exhibited.

(Example 1-10)
A 50 μm thick biaxially stretched film in which the A layer was formed on the surface in a thickness of 0.15 μm by the same method as in Example 1-1 except that the following coating agent 1-10 was used as the coating agent for forming the A layer. Got.

<Coating 1-10>
・ Water dispersion of water-insoluble cationic conductive material: “BONDEIP-PM (registered trademark)” main agent (manufactured by Konishi Oil & Fat Co., Ltd., solid content 30%) 18 parts by weight ・ Acrylic resin water dispersion: methyl methacrylate / Ethyl acrylate / acrylic acid / N-methylolacrylamide = 62/35/2/1 (weight ratio) copolymer acrylic resin (glass transition temperature: 42 ° C.) dispersed in water at a solid content of 10% . 6 parts by weight-Acetylenediol-based surfactant: "Orphine" EXP4051F (manufactured by Nissin Chemical Industry Co., Ltd.) 0.1 part by weight, 75.9 parts by weight of water.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It turned out that it is excellent in each characteristic like Example 1-1.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 1-11)
Biaxial stretching with a thickness of 50 μm in which the A layer was formed on the surface with a thickness of 0.15 μm by the same method as in Example 1-1, except that the following coating agent 1-11 was used as the coating agent for forming the A layer. A film was obtained.

<Coating 1-11>
-Water dispersion of water-insoluble cationic conductive material: 12 parts by weight of "BONDEIP-PM (registered trademark)" main ingredient (manufactured by Konishi Yushi Co., Ltd., solid content 30%)-Acetylenediol-based surfactant: "Orphine "EXP4051F (manufactured by Nissin Chemical Industry Co., Ltd.) 0.1 parts by weight, water 87.9 parts by weight.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Compared to Example 1-1, it was found that each characteristic was excellent although it was in the partial discharge voltage after the moisture-resistant heat treatment.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 1-12)
Biaxial stretching with a thickness of 50 μm in which the A layer was formed to a thickness of 0.15 μm on the surface in the same manner as in Example 1-1, except that the following coating agent 1-12 was used as the coating agent for forming the A layer. A film was obtained.

<Coating 1-12>
Water-soluble cationic material: polystyrene sulfonate ammonium salt (weight average molecular weight: 65000) 1.5 parts by weight Water-insoluble acrylic resin: methyl methacrylate / ethyl acrylate / acrylic acid / N-methylol acrylamide = 62/35 / 2/1 (weight ratio) copolymer acrylic resin (glass transition temperature: 42 ° C.) dispersed in water at a solid content of 10% in the form of particles. 35 parts by weight of oxazoline group-containing compound aqueous dispersion: “Epocross (registered trademark)” WS-500 (manufactured by Nippon Shokubai Co., Ltd., solid content 40%) 4.2 parts by weight of acetylenic diol surfactant: “Orphine (Registered trademark) "EXP4051F (Nisshin Chemical Industry Co., Ltd. 0.1 part by weight, water 59.2 parts by weight.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It turned out that it is excellent in each characteristic like Example 1-1.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 1-13)
Biaxial stretching with a thickness of 50 μm in which the A layer was formed to a thickness of 0.15 μm on the surface in the same manner as in Example 1-1 except that the following coating agent 1-13 was used as the coating agent for forming the A layer. A film was obtained.

<Coating 1-13>
Water-soluble cationic material: polystyrene sulfonate ammonium salt (weight average molecular weight: 65000) 1.5 parts by weight Water-insoluble acrylic resin: methyl methacrylate / ethyl acrylate / acrylic acid / N-methylol acrylamide = 62/35 / 2/1 (weight ratio) copolymer acrylic resin (glass transition temperature: 42 ° C.) dispersed in water at a solid content of 10% in the form of particles. 45 parts by weight acetylene diol surfactant: “Orphine (registered trademark)” EXP4051F 0.1 part by weight / water 53.4 parts by weight The weight average molecular weight, number average molecular weight of the B1 layer of the obtained film, The surface specific resistance, the surface specific resistance R2 on the surface opposite to the A surface, the breaking elongation, the partial discharge voltage, the thermal contraction rate, the surface specific resistance after wet heat treatment, the breaking elongation, and the partial discharge voltage were measured. The results are shown in Tables 1 and 2. Although the partial discharge voltage after moisture-resistant heat treatment was low compared with the case of Example 1-10 using a water-insoluble cationic conductive material, it was found that each characteristic was excellent.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 1-14)
Biaxial stretching with a thickness of 50 μm in which the A layer was formed on the surface with a film thickness of 0.15 μm by the same method as in Example 1-12 except that the following coating agent 1-14 was used as the coating agent for forming the A layer. A film was obtained.

<Coating 1-14>
Water-soluble cationic material: polystyrene sulfonate ammonium salt (weight average molecular weight: 65000) 6 parts by weight Acetylene diol surfactant: "Olfin (registered trademark) EXP4051F 0.1 part by weight Water 93.9 parts by weight .

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Unlike Example 1-10 using a water-insoluble cationic conductive material, the partial discharge voltage was not improved after wet heat treatment, but other characteristics were excellent.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Examples 1-15 to 17)
In the same manner as in Example 1-1, except that polyethylene terephthalate having intrinsic viscosities of 0.74, 0.70, and 0.66 were used and the longitudinal stretching temperatures were 95 ° C, 90 ° C, and 85 ° C, respectively. A biaxially stretched film having a thickness of 50 μm, in which an A layer was formed to a thickness of 0.15 μm on the surface, was obtained. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Although the breaking elongation after the wet heat treatment was inferior to that of Example 1-1, it was found that various properties were excellent.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Examples 1-18 and 1-19)
A biaxially stretched film having a thickness of 50 μm having an A layer formed on the surface with a thickness of 0.15 μm was obtained in the same manner as in Example 1-1 except that the heat treatment temperatures were 210 ° C. and 160 ° C., respectively. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Although the breaking elongation after the wet heat treatment was inferior to that of Example 1-1, it was found that various properties were excellent.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 1-20)
Example 1 except that polyethylene naphthalate (melting point TmB1 = 270 ° C.) having an intrinsic viscosity of 0.82 was used as the raw material for the B1 layer, the extrusion temperature was 290 ° C., the longitudinal stretching temperature was 140 ° C., and the transverse stretching temperature was 150 ° C. In the same manner as in 1-1, a biaxially stretched film having a thickness of 50 μm having an A layer formed on the surface with a thickness of 0.15 μm was obtained. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Similar to Example 1-1, it was found that various characteristics were excellent. In particular, it was found that the breaking elongation after the wet heat treatment was higher than that of Example 1-1.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Examples 1-21 to 23)
A layer was formed on the surface in the same manner as in Example 1-1 except that polyethylene terephthalate having an intrinsic viscosity of 0.90, 1.0, 1.2 was used and the longitudinal stretching temperature was 95 ° C. A biaxially stretched film with a thickness of 50 μm formed with a thickness of 0.15 μm was obtained. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that the elongation at break after the wet heat treatment was superior to that of Example 1-1, and various characteristics were excellent.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 1-24)
50 μm thick biaxially formed on the surface with a thickness of 0.03 μm by the same method as Example 1-1, except that the following coating agent 1-16 was used as the coating agent for forming the A layer A stretched film was obtained.

<Coating 1-16>
-Carbon nanotube aqueous dispersion (double-layer CNT (Science Laboratories, purity 95%) 0.85 part by weight and 97 parts by weight of pure water, 2 parts by weight of polyvinylpyrrolidone were added, and ultrasonic crusher (Tokyo Science Equipment) (CX-502 manufactured by Co., Ltd., output 250W, direct irradiation) and obtained by ultrasonic treatment for 30 minutes) 5 parts by weight / water-insoluble acrylic resin: methyl methacrylate / ethyl acrylate / acrylic acid / N- Methylolacrylamide = 62/35/2/1 (weight ratio) copolymer acrylic resin (glass transition temperature: 42 ° C.) dispersed in water at a solid content of 10% in the form of particles. 2.5 parts by weight / water 92.5 parts by weight.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that each characteristic was excellent as in Example 1-1, and the partial discharge voltage after UV irradiation was improved as compared with Example 1-1.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Examples 1-25, 26, 27)
As the coating agent for forming the A layer, the following coating agents 1-17, 1-18, and 1-19 were used, respectively, in the same manner as in Example 1-1, and the A layer had a film thickness of 0.15 μm on the surface. A biaxially stretched film having a thickness of 50 μm was obtained.

<Coating 1-17>
・ Water dispersion of water-insoluble cationic conductive material: “BONDEIP-PM (registered trademark)” main agent (manufactured by Konishi Oil & Fat Co., Ltd., solid content 30%) 18 parts by weight ・ Acrylic resin water dispersion: methyl methacrylate / Ethyl acrylate / acrylic acid / N-methylolacrylamide = 62/35/2/1 (weight ratio) copolymer acrylic resin (glass transition temperature: 42 ° C.) dispersed in water at a solid content of 10% . 3 parts by weight-Oxazoline group-containing compound aqueous dispersion: "Epocross (registered trademark)" WS-500 (manufactured by Nippon Shokubai Co., Ltd., solid content 40%) 0.75 parts by weight-acetylenediol surfactant: "Orphine (Registered trademark) "EXP4051F (manufactured by Nissin Chemical Industry Co., Ltd.)" 0.1 parts by weight, titanium oxide aqueous dispersion: "Nanotech" (registered trademark) RTIW15WT% G0 (manufactured by CII Kasei Co., Ltd. 20-30 nm, concentration 15% by weight) 5 parts by weight, water 73.15 parts by weight.
(Contains 11% by weight of titanium oxide as a light stabilizer in the A layer)
<Coating 1-18>
・ Water dispersion of water-insoluble cationic conductive material: “BONDEIP-PM (registered trademark)” main agent (manufactured by Konishi Oil & Fat Co., Ltd., solid content 30%) 18 parts by weight ・ Acrylic resin water dispersion: methyl methacrylate / Ethyl acrylate / acrylic acid / N-methylolacrylamide = 62/35/2/1 (weight ratio) copolymer acrylic resin (glass transition temperature: 42 ° C.) dispersed in water at a solid content of 10% . 3 parts by weight-Oxazoline group-containing compound aqueous dispersion: "Epocross (registered trademark)" WS-500 (manufactured by Nippon Shokubai Co., Ltd., solid content 40%) 0.75 parts by weight-acetylenediol surfactant: "Orphine (Registered trademark) "EXP4051F (manufactured by Nissin Chemical Industry Co., Ltd.)" 0.1 parts by weight, titanium oxide aqueous dispersion: "Nanotech" (registered trademark) RTIW15WT% G0 (manufactured by CII Kasei Co., Ltd. 20-30 nm, concentration 15% by weight) 10 parts by weight, water 68.15 parts by weight.
(Contains 20% by weight of titanium oxide as a light stabilizer in the A layer)
<Coating 1-19>
・ Water dispersion of water-insoluble cationic conductive material: “BONDEIP-PM (registered trademark)” main agent (manufactured by Konishi Oil & Fat Co., Ltd., solid content 30%) 18 parts by weight ・ Acrylic resin water dispersion: methyl methacrylate / Ethyl acrylate / acrylic acid / N-methylolacrylamide = 62/35/2/1 (weight ratio) copolymer acrylic resin (glass transition temperature: 42 ° C.) dispersed in water at a solid content of 10% . 3 parts by weight-Oxazoline group-containing compound aqueous dispersion: "Epocross (registered trademark)" WS-500 (manufactured by Nippon Shokubai Co., Ltd., solid content 40%) 0.75 parts by weight-acetylenediol surfactant: "Orphine (Registered trademark) "EXP4051F (manufactured by Nissin Chemical Industry Co., Ltd.) 0.1 parts by weight. Zinc oxide aqueous dispersion: GZOW15WT% -E05 (manufactured by CII Kasei Co., Ltd., zinc oxide particle size 20-30 nm, concentration 15) (% By weight) 10 parts by weight and 73.15 parts by weight of water.
(Contains 20% by weight of zinc oxide as a light stabilizer in the A layer)
The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that each characteristic was excellent as in Example 1-1, and the partial discharge voltage after UV irradiation was improved as compared with Example 1-1.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 2-1)
A biaxially stretched film having a thickness of 50 μm was produced in the same manner as in Example 1-1 except that the A layer was not formed.

The obtained film was set in an electron beam vapor deposition apparatus, aluminum having a purity of 99.999% was used as a volatilization source, the degree of vacuum was 3.4 × 10 ⁻⁵ Pa, the vapor deposition rate was 10 Å / sec, and between the vapor deposition source and the substrate. Under conditions of a distance of 25 cm, aluminum was electron beam evaporated while introducing 350 sccm of oxygen gas from the normal direction of the film surface to form an A layer made of aluminum oxide having a thickness of 0.15 μm.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Similar to Example 1-1, it was found that various characteristics were excellent.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 1-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Examples 2-2 and 2-3)
An A layer having a thickness of 0.15 μm was formed on a biaxially stretched film having a thickness of 50 μm by the same method as in Example 2-1, except that the oxygen supply amounts were 400 sccm and 500 sccm, respectively. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It turned out that it is excellent in various characteristics like Example 2-1.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. As in Example 2-1, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Examples 2-4 and 2-5)
A layer A was formed in a thickness of 0.15 μm on a biaxially stretched film having a thickness of 50 μm by the same method as in Example 2-1, except that the oxygen supply amounts were 600 sccm and 330 sccm, respectively. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Although it was inferior to Examples 2-1 to 2-3, the high partial discharge voltage was shown and it turned out that it is excellent in each characteristic.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. Although it was inferior to Examples 2-1 to 2-3, it was found that a high partial discharge voltage was exhibited, and in particular, when the A surface was formed on the outside, a higher partial discharge voltage was exhibited.

(Example 2-6)
A layer A having a thickness of 0.15 μm was formed on a biaxially stretched film having a thickness of 50 μm by the same method as in Example 2-1, except that the oxygen supply amount was 320 sccm. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Although it was inferior to Examples 2-4 and 2-5, the high partial discharge voltage was shown and it turned out that it is excellent in each characteristic.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. Although it was inferior to Examples 2-4 and 2-5, a high partial discharge voltage was exhibited, and it was found that a higher partial discharge voltage was exhibited particularly when the A surface was formed outside.

(Example 2-7)
A layer A having a thickness of 0.15 μm was formed on a biaxially stretched film having a thickness of 50 μm by the same method as in Example 2-1, except that the oxygen supply amount was 310 sccm. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Although it was inferior to Example 2-6, the high partial discharge voltage was shown and it turned out that it is excellent in each characteristic.

  Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.

  The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. Although it was inferior to Example 2-6, the high partial discharge voltage was shown, and it turned out that a higher partial discharge voltage is shown especially when A surface is formed in the outer side.

(Example 3-1)
Polyethylene terephthalate (melting point TmB1 = 255 ° C.) having an intrinsic viscosity of 0.81 was vacuum-dried at a temperature of 180 ° C. for 3 hours and then supplied to the main extruder. In addition, a sub-extruder was used separately from the main extruder, and the sub-extruder was vacuum-dried at a temperature of 180 wt. C. for 85 wt.% PET (melting point TA: 265 ° C.) with an intrinsic viscosity of 0.81 for 3 hours. 85 parts by weight of 0.81 polyethylene terephthalate and 15 parts by weight of polyetheramide-based conductive polymer material “IRGASTAT” P18 (manufactured by Ciba Japan Co., Ltd.) vacuum-dried at 100 ° C. for 6 hours were supplied to the sub-extruder. . Each of the component layers supplied to the sub-extruder is melted at a temperature of 280 ° C. in a nitrogen atmosphere, and then supplied to the sub-extruder on both sides of the component layer supplied to the main extruder. Combined so that component layer = 9: 1, melted two-layer lamination co-extrusion from the inside of the T die die, made into a laminated sheet, and cooled closely by electrostatic application on a drum maintained at a surface temperature of 20 ° C Solidified to obtain an unoriented (unstretched) laminated sheet.

  Using the obtained unstretched sheet, a biaxially stretched film having a thickness of 50 μm and having a layer A formed on the surface with a thickness of 5 μm in the same manner as in Example 1-1, except that corona treatment and coating were not performed after longitudinal stretching. Got.

  B1 layer weight average molecular weight, number average molecular weight, surface specific resistance of surface A, breaking elongation, partial discharge voltage, thermal shrinkage rate, surface specific resistance after wet heat treatment, surface opposite to surface A of the obtained film The surface specific resistance R2, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Each characteristic was found to be excellent.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that a high partial discharge voltage was exhibited in the same manner as in Example 1-1, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 3-2)
The raw material to be supplied to the sub-extruder is 90 parts by weight of polyethylene terephthalate (melting point TmB1 = 255 ° C.) having an intrinsic viscosity of 0.81, 20 parts by weight of sodium dodecylbenzenesulfonate and polyethylene terephthalate having an intrinsic viscosity of 0.81. A layer A was formed on the surface in the same manner as in Example 3-1, except that 10 parts by weight of a pellet containing 400% polyethylene glycol was mixed and vacuum-dried at 180 ° C. for 3 hours. A biaxially stretched film having a thickness of 5 μm and a thickness of 50 μm was obtained.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Although the partial discharge voltage was not improved after the wet heat treatment, other characteristics were found to be excellent.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that a high partial discharge voltage was exhibited in the same manner as in Example 1-1, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 3-3)
The raw material to be supplied to the sub-extruder is 65 parts by weight of polyethylene terephthalate (PET) having an intrinsic viscosity of 0.81 vacuum-dried at 180 ° C. for 3 hours, and rutile having an average particle size of 230 nm vacuum-dried at 180 ° C. for 3 hours. Type Titanium Oxide-containing PET (produced by kneading PET / titanium oxide with intrinsic viscosity of 0.81 and a twin screw extruder with a vent so that PET / titanium oxide = 1/1 by weight) 20% by weight, 100 ° C. 15 parts by weight of a polyetheramide-based conductive polymer material “IRGASTAT” P18 (manufactured by Ciba Japan Co., Ltd.) that was vacuum-dried for 6 hours (with titanium oxide as a light stabilizer in the A layer to the A layer) A biaxially stretched film having a thickness of 50 μm in which the A layer was formed on the surface with a film thickness of 5 μm was obtained in the same manner as in Example 3-1, except that the content was 10 wt%.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that each characteristic was excellent, and in particular, the partial discharge voltage after UV irradiation was improved as compared with Example 1-1.

  Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1. The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that a high partial discharge voltage was exhibited in the same manner as in Example 1-1, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 3-4)
The raw material to be supplied to the sub-extruder is 65 parts by weight of PET having an intrinsic viscosity of 0.81 vacuum-dried at 180 ° C. for 3 hours, and a rutile-type titanium oxide-containing PET having an average particle size of 230 nm vacuum-dried at 180 ° C. for 3 hours. (Produced by kneading PET / titanium oxide with an intrinsic viscosity of 0.81 and a twin screw extruder with a vent so that PET / titanium oxide = 1/1 by weight) 40% by weight, vacuum dried at 100 ° C. for 6 hours 15 parts by weight of the polyetheramide conductive polymer material “IRGASTAT” P18 (manufactured by Ciba Japan Co., Ltd.) was used (containing 20% by weight of titanium oxide as a light stabilizer in the A layer relative to the A layer) ) Was obtained in the same manner as in Example 3-1, to obtain a biaxially stretched film having a thickness of 50 μm in which an A layer was formed on the surface with a thickness of 5 μm.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that each characteristic was excellent, and in particular, the partial discharge voltage after UV irradiation was improved as compared with Example 3-3.

  Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.

  The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that a high partial discharge voltage was exhibited in the same manner as in Example 1-1, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 3-5)
The raw material to be supplied to the sub-extruder was 35 parts by weight of PET having an intrinsic viscosity of 0.81 vacuum-dried at 180 ° C. for 3 hours, and zinc oxide-containing PET having an average particle size of 30 nm vacuum-dried at 180 ° C. for 3 hours (inherent PET prepared with a viscosity of 0.81 and titanium oxide, kneaded with a vented twin screw extruder so that the weight ratio of PET / zinc oxide is 8/2)) 50% by weight, vacuum dried at 100 ° C. for 6 hours Other than using 15 parts by weight of etheramide based conductive polymer material “IRGASTAT” P18 (manufactured by Ciba Japan Co., Ltd.) (containing 10% by weight of zinc oxide as a light stabilizer in layer A with respect to layer A) Was the same method as in Example 3-1, to obtain a biaxially stretched film having a thickness of 50 μm and an A layer having a thickness of 5 μm formed on the surface.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that each characteristic was excellent, and in particular, the partial discharge voltage after UV irradiation was improved as compared with Example 3-3.

  Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.

  The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that a high partial discharge voltage was exhibited in the same manner as in Example 1-1, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Example 3-6, Example 3-7)
The raw material to be supplied to the sub-extruder is 65 parts by weight of PET having an intrinsic viscosity of 0.81 vacuum-dried at 180 ° C. for 3 hours, and rutile-type titanium oxide-containing PET having an average particle size of 230 nm vacuum-dried at 180 ° C. for 3 hours. (Produced by kneading PET / titanium oxide with an intrinsic viscosity of 0.81 and a twin screw extruder with a vent so that PET / titanium oxide = 1/1 by weight) 40% by weight, vacuum dried at 100 ° C. for 6 hours 15 parts by weight of the polyetheramide conductive polymer material “IRGASTAT” P18 (manufactured by Ciba Japan Co., Ltd.) is used (containing 20% by weight of titanium oxide as a light stabilizer in the A layer) That is, the component layers supplied to the sub-extruder on the surface layers on both sides of the component layer supplied to the main extruder are in a thickness ratio, respectively, the component layer of the main extruder: the component layer of the sub-extruder = 24: 1, 48: 1 Join together A biaxially stretched film with a thickness of 50 μm in which the A layer is formed on the surface with a thickness of 2 μm and 1 μm, respectively, except that the melted two-layer laminated co-extrusion was made from the inside of the T die die. Got.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that each characteristic was excellent, and in particular, the partial discharge voltage after UV irradiation was higher than Example 3-1 although it was inferior to Example 3-5.

  Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.

  The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that a high partial discharge voltage was exhibited in the same manner as in Example 1-1, and in particular, when the A surface was formed outside, a higher partial discharge voltage was exhibited.

(Comparative Example 1-1)
A biaxially stretched film having a thickness of 50 μm was produced in the same manner as in Example 1-1 except that the A layer was not formed. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that the partial discharge voltage was lower than when the A layer was not formed.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that the partial discharge voltage was lower than when the A layer was not formed.

(Comparative Example 1-2)
A 125 μm-thick biaxially stretched film was produced in the same manner as in Example 1-1, except that the A layer was not formed. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, breaking elongation, partial discharge voltage, thermal shrinkage, surface specific resistance after wet heat treatment, breaking elongation, partial discharge voltage of the B1 layer of the obtained film Was measured. The results are shown in Tables 1 and 2. It was found that the partial discharge voltage was lower than when the A layer was not formed.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-8.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that the partial discharge voltage was lower than when the A layer was not formed.

(Comparative Example 1-3)
A biaxially stretched film having a thickness of 188 μm was produced in the same manner as in Example 1-1, except that the A layer was not formed. The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that the partial discharge voltage was lower than when the A layer was not formed.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-9.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that the partial discharge voltage was lower than when the A layer was not formed.

(Comparative Example 1-4)
A 50 μm-thick biaxially stretched film having a thickness of 0.03 μm formed by the same method as Example 1-1, except that the following coating agent 1-15 was used as the coating agent for forming the A layer. did.

<Coating 1-15>
Water-insoluble polythiophene-based conductive polymer water dispersion: “Baytron (registered trademark)” P (manufactured by Bayer / HC Stark (Germany), solid content 1.2%) 83 parts by weight Acetylene Diol-based surfactant: “Orphine (registered trademark)” EXP4051F (manufactured by Nissin Chemical Industry Co., Ltd.) 0.1 part by weight / water 16.9 parts by weight The weight average molecular weight and number average of the B1 layer of the obtained film The molecular weight, the surface specific resistance of the A surface, the surface specific resistance R2 of the surface opposite to the A surface, breaking elongation, partial discharge voltage, thermal shrinkage, surface specific resistance after wet heat treatment, breaking elongation, partial discharge voltage. It was measured. The results are shown in Tables 1 and 2. Although the surface specific resistance was a low value compared with the Example, it turned out that the partial discharge voltage is low compared with the Example.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that the partial discharge voltage was lower than that of the example.

(Comparative Example 2-1)
A layer A having a thickness of 0.15 μm was formed on a biaxially stretched film having a thickness of 50 μm by the same method as in Example 2-1, except that the oxygen supply amount was 300 sccm. B1 layer weight average molecular weight, number average molecular weight, surface specific resistance of surface A, surface specific resistance of surface opposite to surface A, elongation at break, partial discharge voltage, heat shrinkage, wet heat treatment The surface specific resistance, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. Although the surface specific resistance was a low value compared with the Example, it turned out that the partial discharge voltage is low compared with the Example.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that the partial discharge voltage was lower than that of the example.

(Comparative Example 2-2)
A layer A having a thickness of 0.15 μm was formed on a biaxially stretched film having a thickness of 50 μm by the same method as in Example 2-1, except that alumina was used as the vapor deposition source.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that the surface specific resistance was higher than that of the example and the partial discharge voltage was low.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that the partial discharge voltage was lower than that of the example.

(Comparative Examples 3-1, 3-2)
The raw material supplied to the sub-extruder was PET having an intrinsic viscosity of 0.81 that was vacuum dried at 180 ° C. for 3 hours, and a rutile titanium oxide-containing PET having an average particle size of 230 nm that was vacuum dried at 180 ° C. for 3 hours. PET / titanium oxide-containing PET = 8 by weight ratio PET / titanium oxide kneaded by a twin screw extruder with a vent so that PET / titanium oxide = 1/1 by weight ratio / 2, 6/4 (except that titanium oxide is contained in the A layer as a light stabilizer in an amount of 10% by weight and 20% by weight with respect to the A layer, respectively). A biaxially stretched film with a thickness of 50 μm in which the A layer was formed with a thickness of 5 μm was obtained.

  The weight average molecular weight, number average molecular weight, surface specific resistance of the A surface, surface specific resistance R2 of the surface opposite to the A surface, elongation at break, partial discharge voltage, thermal contraction rate, wet heat treatment Subsequent surface resistivity, breaking elongation, and partial discharge voltage were measured. The results are shown in Tables 1 and 2. It was found that the surface specific resistance was higher than that of the example and the partial discharge voltage was low.

Moreover, about each obtained film, the back sheet was formed similarly to Example 1-1.
The partial discharge voltage of the obtained back sheet was measured. The results are shown in Table 3. It was found that the partial discharge voltage was lower than that of the example.

  The solar cell back surface sealing film of the present invention can be suitably used not only for solar cells used as roofing materials, but also for flexible solar cells and electronic components.

It is sectional drawing which shows an example of a structure of a solar cell typically.

Explanation of symbols

1: Solar cell back sheet 2: Transparent filler 3: Power generation element 4: Transparent substrate 5: Surface on the resin layer 2 side of the solar cell back sheet 6: Surface on the opposite side of the resin layer 2 of the solar cell back sheet

Claims (13)

A film for a solar battery backsheet having a surface (hereinafter referred to as A surface) having a surface specific resistance R0 of 10 ⁶ Ω / □ or more and 10 ¹⁴ Ω / □ or less, wherein the film is 125 ° C., humidity 100%, 2 The surface specific resistance R1 of the A surface after standing for 24 hours under the condition of 0.5 atm is 10 ⁶ Ω / □ or more and 10 ¹⁴ Ω / □ or less,
It has a laminated structure of at least two layers including a conductive layer (A layer) and a base material layer (B layer), and at least one side surface is an A surface composed of an A layer,
The material that forms the matrix constituting the A layer contains an organic conductive material, a water-insoluble resin, and a crosslinking agent,
A film for a solar battery back sheet, wherein the thickness of the A layer is 0.15 μm or more and 1 μm or less.   The film for solar cell backsheet according to claim 1, wherein the elongation retention after standing for 24 hours under conditions of 125 ° C, 100% humidity and 2.5 atm is 50% or more.   The film for solar battery backsheet according to claim 1 or 2, wherein the B layer includes a layer made of polyester (B1 layer), and the number average molecular weight of the polyester is 18500 or more and 40000 or less. The B1 layer is biaxially oriented, and the minute endothermic peak temperature TmetaB1 of the B layer obtained by differential scanning calorimetry (DSC) satisfies the following formula (5) with respect to the melting point TmB1 of the B layer. The film for solar cell backsheet of description.
40 ° C. ≦ TmB1-TmetaB1 ≦ 90 ° C. (5)   The film for solar battery backsheet according to any one of claims 1 to 4, wherein the organic conductive material is a water-insoluble organic conductive compound.   The film for solar battery backsheet according to any one of claims 1 to 4, wherein the organic conductive material is a cationic conductive compound having a cationic substituent.   The film for solar cell backsheet according to any one of claims 1 to 4, wherein the organic conductive material is an ionic conductive material having both an anionic substituent and a cationic substituent.   The film for a solar battery back sheet according to any one of claims 1 to 4, wherein the organic conductive material is a polyetheramide copolymer compound.   The film for solar battery backsheet according to any one of claims 1 to 8, wherein the water-insoluble resin has a polyester skeleton, and the crosslinking agent is a melamine compound. The solar cell backsheet formed by bonding the film for solar cell backsheets in any one of Claims 1-9 on the resin sheet.   The solar cell backsheet according to claim 10, wherein the surface on at least one side is the A surface of the film for solar cell backsheet according to any one of claims 1 to 9.   The solar cell which uses the solar cell backsheet of Claim 10 or 11.   The solar cell according to claim 12, wherein a power generation element is formed on a surface opposite to the A surface.

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