JP2011228509A - Solar cell sealing film and solar cell employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell sealing film which contains ethylene vinyl acetate copolymer (EVA) as a main component, extremely improves an insulation property under a high temperature environment and is improved in durability of an adhesive strength, and a solar cell employing the sealing film.SOLUTION: The present invention relates to a solar cell sealing film containing an EVA, a crosslinking agent and a silane coupling agent. The crosslinking agent is comprised of 2,5-dimethyle-2,5-di(t-butylperoxy)hexane, and t-butylperoxy-2-ethylhexyl monocarbonate. The silane coupling agent is γ-methacryloxy propyl trimethoxy silane. The total content of the crosslinking agent is 1.67 to 2.05 pts.mass with respect to 100 pts.mass of the ethylene-vinyl acetate copolymer, and the content of the silane coupling agent is 0.6 to 1.0 pt.mass with respect to the 100 pts.mass of the ethylene-vinyl acetate copolymer. Further, a solar cell employing the solar cell sealing film is also disclosed.

Description

  The present invention relates to a solar cell sealing film containing an ethylene-vinyl acetate copolymer as a main component, and more particularly to a solar cell sealing film with improved insulation under a high temperature environment.

  In recent years, solar cells that directly convert sunlight into electrical energy have been widely used in terms of effective use of resources and prevention of environmental pollution, and further development has been promoted in terms of power generation efficiency and weather resistance. .

  As shown in FIG. 1, a solar cell generally has a surface side transparent protective member 11 made of a glass substrate or the like, a surface side sealing film 13A, a solar cell 14 such as a silicon crystal power generation element, a back side sealing film. 13B and the back surface side protection member (back cover) 12 are laminated in this order, and after deaeration under reduced pressure, the surface side sealing film 13A and the back surface side sealing film 13B are cross-linked and cured by heating and pressurizing, and integrated by bonding. Is manufactured.

  In solar cells, a plurality of solar cell cells 14 are connected and used in order to obtain a high electrical output. Therefore, in order to ensure the insulation of the solar cell 14, the solar cell is sealed using the insulating sealing films 13 </ b> A and 13 </ b> B.

  In addition, thin-film solar cells such as thin-film silicon-based, thin-film amorphous silicon-based solar cells, and copper indium selenide (CIS) -based solar cells are also being developed. In this case, for example, transparent substrates such as glass and polyimide substrates A power generation element layer such as a semiconductor layer is formed on the surface of the substrate by a chemical vapor deposition method or the like, and a sealing film or the like is laminated thereon and bonded and integrated.

  Conventionally, as a sealing film used in these solar cells, an ethylene-polar monomer copolymer such as an ethylene vinyl acetate copolymer (hereinafter also referred to as EVA) or an ethylene ethyl acrylate copolymer (EEA) is used. A film is used. In particular, EVA films are preferably used because they are inexpensive and have high transparency. And the EVA film for sealing films has improved the crosslinking density using crosslinking agents, such as an organic peroxide, other than EVA, in order to improve film | membrane intensity | strength and durability.

  In such a solar cell, the electricity generated by a solar cell or a thin-film solar cell power generation element (in the present invention, collectively referred to as a solar cell element) is reliably obtained using incident sunlight. It is necessary to take out. However, solar cells are often used in outdoor environments exposed to high temperatures, high humidity, and rain for a long period of several decades, and power generation performance may be reduced during use. In particular, when used in a high-temperature environment, there is a problem that insulation failure occurs and power generation performance is lowered, and solar cell sealing films have been conventionally improved.

For example, Patent Document 1 includes an ethylene polar monomer copolymer such as EVA and a cross-linking agent as a solar cell sealing film having excellent insulation under a high temperature environment, and has a volume resistivity of 1. It is specified to be 0 × 10 ^{13 to} 5.0 × 10 ¹⁴ Ω · cm. And in order to obtain the sealing film for solar cells of such volume specific resistance, the kind and compounding quantity of a crosslinking agent and a crosslinking adjuvant are mainly adjusted. Patent Document 1 includes examples of a crosslinking agent 0.6 to 1.0 part by mass, a crosslinking aid 1.0 to 2.0 parts by mass, and a silane coupling 0.5 part by mass with respect to 100 parts by mass of EVA. It is disclosed.

  Further, in Patent Document 2, as a composition for sealing a solar cell that is excellent in transparency, heat resistance, adhesiveness, and the like, and silane coupling with respect to 100 parts by mass of an ethylene / polar monomer copolymer. It is specified that the agent is blended in a proportion of 0.03 to 0.3 parts by mass. Patent Document 2 discloses an example of 1.2 parts by mass of a crosslinking agent and 0.1 parts by mass of a silane coupling agent with respect to 100 parts by mass of EVA.

JP 2008-205448 A JP 2006-036875 A

  However, depending on the type and use location of the solar cell, higher insulation is required in a high-temperature environment in order to prevent a decrease in power generation efficiency, and the solar cell sealing films of Patent Documents 1 and 2 are sufficient. May not be compatible. In this case, durability of adhesive strength is also required so that the insulating property can be maintained for a long time in a high temperature environment.

  Accordingly, an object of the present invention is to provide a solar cell encapsulating material that is made of EVA that is inexpensive and highly transparent, has a significantly high insulation property in a high temperature environment, and has excellent durability in an adhesive force in a high temperature environment. It is to provide a membrane.

  Moreover, the objective of this invention is providing the solar cell using this sealing film.

  In order to achieve the above object, the present inventors have studied various kinds and blending amounts of a crosslinking agent and other additives added to EVA. As a result, two specific crosslinking agents are blended at a predetermined content, and a specific silane coupling agent is blended at a predetermined content, so that insulation in a high-temperature environment is better than a conventional sealing film. It has been found that a solar cell sealing film that is significantly improved and has improved durability of adhesive force can be obtained.

  That is, the above object is a solar cell sealing film containing an ethylene-vinyl acetate copolymer, a crosslinking agent, and a silane coupling agent, wherein the crosslinking agent is 2,5-dimethyl-2,5-disilane. It consists of (t-butylperoxy) hexane (organic peroxide A) and t-butylperoxy-2-ethylhexyl monocarbonate (organic peroxide B), and the silane coupling agent is γ-methacryloxypropyl It is trimethoxysilane, the total content of the crosslinking agent is 1.67 to 2.05 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer, and the content of the silane coupling agent The amount is achieved by a sealing film for solar cells, which is 0.6 to 1.0 part by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

The preferable aspect of the sealing film for solar cells concerning this invention is as follows.
(1) The volume specific resistance in a 60 ° C. atmosphere after crosslinking is 6.0 × 10 ¹⁴ Ω · cm or more. With such a volume resistivity, it can be said that it is a solar cell encapsulating film having a significantly high insulating property in a high temperature environment.
(2) The mass ratio of the organic peroxide B to the organic peroxide A (organic peroxide B / organic peroxide A) in the crosslinking agent is in the range of 1/99 to 9/91. The organic peroxide B is an organic peroxide having a lower half-life temperature than that of the organic peroxide A, and is a crosslinking agent capable of allowing EVA to proceed in a shorter time. However, if such an organic peroxide is used in a large amount, a bulge (foaming due to gas generation) occurs when the solar cell is used in a high temperature environment, and the power generation efficiency of the solar cell is reduced due to a decrease in transparency and insulation. May decrease. By setting the organic peroxide B / organic peroxide A within the above range, a swelling in a high temperature environment can be suppressed, and a solar cell sealing film that can maintain the power generation efficiency of the solar cell for a long period of time. be able to.
(3) Further, 0.1 to 3.0 parts by mass of a crosslinking aid is included with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. Thereby, durability of the adhesive force of a sealing film and insulation can be improved more.
(4) The crosslinking aid is triallyl isocyanurate.

  Moreover, the said objective is achieved by the solar cell characterized by using the solar cell sealing film of this invention.

  According to the present invention, for a solar cell sealing film mainly composed of an ethylene-vinyl acetate copolymer, the type and content of a crosslinking agent and a silane coupling agent to be blended are adjusted in a high temperature environment. In addition, it is possible to provide a solar cell sealing film that is remarkably high in insulation and excellent in durability of adhesive strength in a high temperature environment.

  Therefore, by using the solar cell sealing film of the present invention, it is possible to provide a solar cell having high power generation efficiency and maintaining the power generation efficiency for a long period of time in a high temperature environment.

It is a schematic sectional drawing of a common solar cell. It is the schematic for demonstrating the 180 degree peel test method which is evaluation of adhesive force.

  The solar cell sealing film of the present invention contains at least an ethylene-vinyl acetate copolymer, a crosslinking agent, and a silane coupling agent.

  As a crosslinking agent, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (organic peroxide A) and t-butylperoxy-2-ethylhexyl monocarbonate (organic peroxide) Using 2 types of B), the sum total content is 1.67-2.05 mass parts with respect to 100 mass parts of EVA.

  Moreover, (gamma) -methacryloxypropyl trimethoxysilane is used as a silane coupling agent, and the content is 0.6-1.0 mass part with respect to 100 mass parts of EVA.

  Thereby, the sealing film for solar cells of the present invention has significantly improved insulation in a high temperature environment and improved durability of adhesive force in a high temperature environment.

In the present invention, the solar cell encapsulating film having remarkably high insulation under a high temperature environment preferably has a volume resistivity in a 60 ° C. atmosphere after crosslinking, preferably 6.0 × 10 ¹⁴ Ω · cm or more. It is preferably 8.0 × 10 ^{14 to} 1.0 × 10 ¹⁶ Ω · cm. It is useful to use volume resistivity in a 60 ° C. atmosphere after crosslinking as an index of insulating properties of the solar cell sealing film in a high temperature environment. And if it is the above volume specific resistance, it can be said that it is a sealing film for solar cells which has insulation property remarkably higher than the conventional sealing film.

  In the present invention, the volume resistivity (Ω · cm) in the atmosphere at 60 ° C. after crosslinking is obtained by crosslinking a solar cell sealing film to a gelation fraction of 90% or more, and then using a high resistivity meter (HIRESTA UP (Mitsubishi It is a value measured in a 60 ° C. atmosphere using a probe (UR-100 (manufactured by Mitsubishi Chemical))) and a probe (UR-100 (manufactured by Mitsubishi Chemical)). In general, the volume resistivity (Ω · cm) is measured at room temperature (25 ° C.), and the measured value in a 60 ° C. atmosphere is about 1/10 of the measured value in a 25 ° C. atmosphere.

  Hereinafter, the solar cell sealing film of the present invention will be described in more detail.

  Generally, it is known that when the content of the silane coupling agent is increased, the insulating property of the sealing film tends to be lowered. For example, in Patent Document 2, as an example, a composition in which 0.1 part by mass of a silane coupling agent is blended with 100 parts by mass of EVA, and as a comparative example, silane coupling with respect to 100 parts by mass of EVA. A composition in which 0.5 part by mass of the agent is blended is disclosed, and it is shown that the volume resistivity is decreased in the blend of the comparative example. As a cause of this, when the blending amount of the crosslinking agent is small as in the example of Patent Document 2 and the network density due to the crosslinking of EVA is low, the degree of freedom of the silane coupling agent contained is high, and the electron transfer In order to contribute, when there is much content of a silane coupling agent, it is thought that the electrical resistance of a sealing film falls.

On the other hand, in the present invention, an improvement in insulation is achieved by blending more silane coupling agents than in Patent Documents 1 and 2. This factor can be considered as follows. In the case of this invention, the network density of EVA is high by using 2 types of crosslinking agents and mix | blending more than the Example of patent document 1 and 2. FIG. Therefore, it is considered that the silane coupling agent is easily incorporated into the EVA network structure, and the degree of freedom is low. If it does so, a silane coupling agent will trap ion and will inhibit electron transmission. Therefore, by increasing the content of the silane coupling agent, the electrical resistance of the sealing film is improved. For example, the volume resistivity in a 60 ° C. atmosphere after crosslinking is as high as 6.0 × 10 ¹⁴ Ω · cm or more. It is considered that insulation can be obtained. Moreover, it is thought that durability with high adhesive force is acquired because there is much content of a silane coupling agent.

  However, when there is too much content of a silane coupling agent, bleeding (bleeding) will arise and whitening of a sealing film may arise. Therefore, in this invention, content of a silane coupling agent is 0.6-1.0 mass part with respect to 100 mass parts of EVA, Preferably it is 0.6-0.9 mass part.

  In the present invention, γ-methacryloxypropyltrimethoxysilane is selected as a silane coupling agent because it has a high effect of improving adhesiveness and an effect of improving insulation.

  Further, as described above, two kinds of organic peroxides having different half-life temperatures, which are effective for increasing the network density by EVA crosslinking, are selected as the crosslinking agent. That is, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (organic peroxide A) having a 10-hour half-life temperature (decomposition temperature of 10-hour half-life) of 110 to 130 ° C. And t-butylperoxy-2-ethylhexyl monocarbonate (organic peroxide B) having a 10-hour half-life temperature of 80 to 100 ° C. And the total content of these organic peroxide is mix | blended in the range of 1.67-2.05 mass parts with respect to 100 mass parts of EVA, and a silane coupling agent is mix | blended with content of the said range. Thus, as described above, the insulating property of the solar cell sealing film is improved, and the durability of the adhesive force in a high-temperature environment is improved. In addition, there exists a possibility that compatibility with EVA which makes content of an organic peroxide larger than the said range may worsen.

  The total content of the crosslinking agent is preferably 1.75 to 1.95 parts by mass, more preferably 1.8 to 1.9 with respect to 100 parts by mass of EVA.

  In the present invention, the mass ratio of organic peroxide B to organic peroxide A (organic peroxide B / organic peroxide A) is not particularly limited and is usually used in the range of 1/99 to 99/1. Is done. The organic peroxide B is an essential component in the present invention because it has a low half-life temperature and can advance EVA crosslinking in a short time. However, if a large amount of organic peroxide B is used in the sealing film for solar cells, when the solar cell is used in a high-temperature environment, a bulge is considered to be caused by the decomposition product of the organic peroxide, resulting in a decrease in transparency. In some cases, the power generation efficiency of the solar cell may decrease due to a decrease in insulation. Therefore, the organic peroxide B / organic peroxide A is preferably 1/99 to 9/91, more preferably 4/95 to 9/91, and particularly preferably 7/93 to 9/91. If it is the organic peroxide B / organic peroxide A in this range, the network density of EVA can be sufficiently increased, and the swelling of the solar cell in a high temperature environment can be suppressed. Therefore, it can be set as the sealing film for solar cells which can maintain the power generation efficiency of a solar cell for a long period of time in a high temperature environment.

[Ethylene-vinyl acetate copolymer]
The content of vinyl acetate in the ethylene-vinyl acetate copolymer (EVA) used in the present invention is 20 to 35 parts by mass, more preferably 22 to 30 parts by mass, particularly 24 to 28 parts by mass with respect to 100 parts by mass of EVA. Is preferred. There exists a tendency for the sealing film obtained to become hard, so that content of the vinyl acetate unit of EVA is low. If the content of vinyl acetate is less than 20 parts by mass, the resulting sealing film may not have sufficient transparency when crosslinked and cured at high temperatures. Further, if it exceeds 35 parts by mass, the sealing film may have insufficient hardness, and further carboxylic acid, alcohol, amine, etc. are generated, and foaming is likely to occur at the interface between the sealing film and the protective member. There is a fear.

  In the solar cell encapsulating film of the present invention, in addition to EVA, an ethylene-unsaturated carboxylic acid copolymer such as an ethylene-acrylic acid copolymer and an ethylene-methacrylic acid copolymer, the ethylene-unsaturated carboxylic acid An ionomer in which part or all of the carboxyl groups of the acid copolymer are neutralized with the above metal, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene -An ethylene-unsaturated carboxylic acid ester copolymer such as an isobutyl acrylate copolymer, an ethylene-n-butyl acrylate copolymer, an ethylene-isobutyl acrylate-methacrylic acid copolymer, an ethylene-acrylic acid n- Ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid copolymer such as butyl-methacrylic acid copolymer Polymers and ethylene-polar monomer copolymers such as ethylene-vinyl ester copolymers such as ionomers in which some or all of the carboxyl groups have been neutralized with the above metals, ethylene-vinyl acetate copolymers, polyvinyl acetal series Resins (for example, polyvinyl formal, polyvinyl butyral (PVB resin), modified PVB), and vinyl chloride resin may be used as secondary agents.

[Crosslinking aid]
The sealing film for solar cells of the present invention may further contain a crosslinking aid (a compound having a radical polymerizable group as a functional group) as necessary. The said crosslinking adjuvant can improve the gel fraction of an ethylene-vinyl acetate copolymer, and can improve the adhesiveness and insulation of a sealing film.

  The content of the crosslinking aid is preferably 0.1 to 3.0 parts by mass, more preferably 0.5 to 2.0 parts by mass with respect to 100 parts by mass of EVA. Thereby, the sealing film which is more excellent in adhesiveness and insulation is obtained.

  Examples of the crosslinking aid include trifunctional crosslinking aids such as triallyl cyanurate and triallyl isocyanurate, and monofunctional or bifunctional crosslinking aids such as (meth) acrylic esters (eg, NK ester). Can be mentioned. Of these, triallyl cyanurate and triallyl isocyanurate are preferable, and triallyl isocyanurate is particularly preferable.

[Others]
The sealing film for solar cell of the present invention is used as necessary for improving or adjusting various physical properties of the film (optical properties such as mechanical strength and transparency, heat resistance, light resistance, crosslinking speed, etc.). In addition, various additives such as a plasticizer, an acryloxy group-containing compound, a methacryloxy group-containing compound and / or an epoxy group-containing compound may be further included.

  Although it does not specifically limit as a plasticizer, Generally the ester of a polybasic acid and the ester of a polyhydric alcohol are used. Examples thereof include dioctyl phthalate, dihexyl adipate, triethylene glycol-di-2-ethylbutyrate, butyl sebacate, tetraethylene glycol diheptanoate, and triethylene glycol dipelargonate. One type of plasticizer may be used, or two or more types may be used in combination. The content of the plasticizer is preferably in the range of 5 parts by mass or less with respect to 100 parts by mass of the ethylene-polar monomer copolymer.

  The acryloxy group-containing compound and the methacryloxy group-containing compound are generally acrylic acid or methacrylic acid derivatives, and examples thereof include acrylic acid or methacrylic acid esters and amides. Examples of ester residues include linear alkyl groups such as methyl, ethyl, dodecyl, stearyl, lauryl, cyclohexyl group, tetrahydrofurfuryl group, aminoethyl group, 2-hydroxyethyl group, 3-hydroxypropyl group. Group, 3-chloro-2-hydroxypropyl group. Examples of amides include diacetone acrylamide. In addition, polyhydric alcohols such as ethylene glycol, triethylene glycol, polypropylene glycol, polyethylene glycol, trimethylolpropane, and pentaerythritol, and esters of acrylic acid or methacrylic acid can also be used.

Examples of epoxy-containing compounds include triglycidyl tris (2-hydroxyethyl) isocyanurate, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and phenol. (Ethyleneoxy) ₅ glycidyl ether, pt-butylphenyl glycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, glycidyl methacrylate, butyl glycidyl ether can be mentioned.

  The acryloxy group-containing compound, the methacryloxy group-containing compound, or the epoxy group-containing compound is generally 0.5 to 5.0 parts by weight, particularly 1.0, respectively, with respect to 100 parts by weight of the ethylene-polar monomer copolymer. It is preferable that -4.0 mass part is contained.

  Furthermore, the solar cell sealing film of the present invention may contain an ultraviolet absorber, a light stabilizer and an anti-aging agent. By including the ultraviolet absorber, it is possible to suppress deterioration of the ethylene-polar monomer copolymer due to the influence of irradiated light and the like, and yellowing of the solar cell sealing film. The ultraviolet absorber is not particularly limited, but 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxy. Preferred examples include benzophenone-based ultraviolet absorbers such as benzophenone and 2-hydroxy-4-n-octoxybenzophenone. In addition, it is preferable that the compounding quantity of the said benzophenone series ultraviolet absorber is 0.01-5 mass parts with respect to 100 mass parts of ethylene-polar monomer copolymers.

  Moreover, it can suppress that an ethylene-polar monomer copolymer deteriorates and the solar cell sealing film yellows by influence of the irradiated light etc. also by including a light stabilizer. As the light stabilizer, a light stabilizer called a hindered amine type is preferably used. For example, LA-52, LA-57, LA-62, LA-63LA-63p, LA-67, LA-68 (all ADEKA), Tinuvin 744, Tinuvin 770, Tinuvin 765, Tinuvin 144, Tinuvin 622LD, CHIMASSORB 944LD (all manufactured by Ciba Specialty Chemicals Co., Ltd.), UV-3034 (BF Goodrich) Can be mentioned. In addition, the said light stabilizer may be used individually or may be used in combination of 2 or more types, and the compounding quantity is 0.01-5 mass parts with respect to 100 mass parts of ethylene-polar monomer copolymers. It is preferable that

  Examples of the antioxidant include hindered phenolic antioxidants such as N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide], Examples thereof include phosphorus heat stabilizers, lactone heat stabilizers, vitamin E heat stabilizers, and sulfur heat stabilizers.

  What is necessary is just to perform according to a well-known method in order to form the sealing film for solar cells of this invention mentioned above. For example, a composition in which each of the above materials is mixed by a known method using a super mixer (high-speed fluid mixer), a roll mill, etc., is molded by ordinary extrusion molding, calendar molding (calendering) or the like, and then a sheet-like material It can manufacture by the method of obtaining. Alternatively, a sheet-like material can be obtained by dissolving the composition in a solvent and coating the solution on a suitable support with a suitable coating machine (coater) and drying to form a coating film. The heating temperature during film formation is preferably a temperature at which the crosslinking agent does not react or hardly reacts. For example, it is preferably 50 to 90 ° C, particularly 40 to 80 ° C. Although the thickness in particular of the sealing film for solar cells is not restrict | limited, What is necessary is just the range of 50 micrometers-2 mm.

[Solar cell]
The structure of the solar cell of the present invention is not particularly limited as long as the solar cell sealing film of the present invention is used. For example, the structure etc. which sealed the cell for solar cells by interposing the sealing film for solar cells of this invention between the surface side transparent protection member and the back surface side protection member, and making it bridge-integrate are mentioned. . In addition, in this invention, the side (light-receiving surface side) where the light of the solar cell is irradiated is referred to as “front surface side”, and the surface opposite to the light-receiving surface of the solar cell is referred to as “back surface side”.

  In the solar cell, in order to sufficiently seal the solar cell, for example, as shown in FIG. 1, the front surface side transparent protective member 11, the front surface side sealing film 13A, the solar cell cell 14, the back surface side sealing. The film 13B and the back surface side protection member 12 may be laminated, and the sealing film may be cross-linked and cured according to a conventional method such as heat and pressure.

In order to heat and pressurize, for example, the laminate is heated with a vacuum laminator at a temperature of 135 to 180 ° C., further 140 to 180 ° C., particularly 155 to 180 ° C., a degassing time of 0.1 to 5 minutes, and a press pressure of 0.1. What is necessary is just to heat-press in about 1.5 kg / cm < ² > and press time 5-15 minutes. By crosslinking the ethylene-vinyl acetate copolymer contained in the front side sealing film 13A and the back side sealing film 13B during the heating and pressurization, the front side sealing film 13A and the back side sealing film 13B are interposed. And the surface side transparent protection member 11, the back surface side transparent member 12, and the cell 14 for solar cells can be integrated, and the cell 14 for solar cells can be sealed.

  The solar cell sealing film of the present invention is not limited to a solar cell using a single crystal or polycrystalline silicon crystal solar cell as shown in FIG. It can also be used for sealing films of thin film solar cells such as solar cells and copper indium selenide (CIS) solar cells. In this case, for example, the solar cell of the present invention is formed on a thin film solar cell element layer formed by a chemical vapor deposition method or the like on the surface of a surface side transparent protective member such as a glass substrate, a polyimide substrate, or a fluororesin transparent substrate. On the solar cell element formed on the surface of the back surface side protective member, the structure for laminating the battery sealing film and the back surface side protective member and adhering and integrating them, the front surface side Laminated transparent protective member, bonded and integrated structure, or front side transparent protective member, front side sealing film, thin film solar cell element, back side sealing film, and back side protective member are laminated in this order, For example, a structure that is bonded and integrated.

  The solar cell sealing film of the present invention has high insulation under a high temperature environment and has excellent durability of the adhesive strength under a high temperature environment, so that high power generation efficiency is maintained for a long time under a high temperature environment. Solar cells can be provided.

  The surface side transparent protective member 11 used in the solar cell of the present invention is usually a glass substrate such as silicate glass. As for the thickness of a glass substrate, 0.1-10 mm is common, and 0.3-5 mm is preferable. The glass substrate may generally be chemically or thermally strengthened.

  The back surface side protective member 12 used in the present invention is preferably a plastic film such as polyethylene terephthalate (PET). Further, a film obtained by laminating a fluorinated polyethylene film, particularly a fluorinated polyethylene film / Al / fluorinated polyethylene film in this order in consideration of heat resistance and wet heat resistance may be used.

  In addition, the solar cell (including a thin film solar cell) of the present invention is characterized by a sealing film used on the front surface side and / or the back surface side as described above. Therefore, the members other than the sealing film such as the front-side transparent protective member, the back-side protective member, and the solar cell need only have the same configuration as the conventionally known solar cell, and are not particularly limited. .

  Hereinafter, the present invention will be described with reference to examples.

(Examples 1-5, Comparative Examples 1-6)
Each material was supplied to a roll mill with the formulation shown in Tables 1 and 2, and kneaded at 70 ° C. to prepare a sealing film composition for a solar cell. The solar cell sealing film composition was calendered at 70 ° C., allowed to cool, and then a solar cell sealing film (thickness 0.6 mm) was produced.

(Evaluation methods)
(1) Volume specific resistance A sample having a size of 100 mm × 100 mm of each of the solar cell sealing films prepared above was prepared, and after temporarily press-bonding at 90 ° C. with a vacuum laminator, the sample was heated to have a gelation fraction of 90% or more. Until crosslinked.
About each produced sample, volume resistivity ((ohm)) in 25 degreeC and 60 degreeC atmosphere using a high resistivity meter (Hiresta UP (made by Mitsubishi Chemical Corporation)) and a probe (UR-100 (made by Mitsubishi Chemical Corporation)). Cm) was measured. A volume resistivity of 60 × 10 ¹⁴ Ω · cm or more in a 60 ° C. atmosphere was regarded as acceptable.

(2) Durability of glass adhesion strength Adhesion strength was evaluated by a 180 ° peel test (JIS K 6854, 1994). Specifically, the 180 ° peel test was performed according to the following procedure as shown in FIG.

Glass substrate 21 (thickness 3 mm) / each solar cell sealing film 23 / release PET (thickness 0.75 mm) was laminated in this order, and the resulting laminate was vacuum deaerated with a vacuum laminator. After pre-pressing at 100 ° C. for 10 minutes, it was further placed in an oven and crosslinked at a temperature of 150 ° C. for 30 minutes. A part between the glass substrate 21 and the solar cell sealing film 23 is peeled off, and the solar cell sealing film 23 is folded back 180 ° to obtain a tensile tester (manufactured by Shimadzu Corporation, Autograph). The peeling force at a pulling speed of 100 mm / min was measured and used as the glass adhesive force (initial) [N / cm].
In addition, in order to investigate the durability of the adhesive strength, the sample after cross-linking was allowed to stand for 2000 hours in an environment of a temperature of 85 ° C. and a humidity of 85% RH. After) was measured. From the initial adhesive strength, if the adhesive strength after the durability test was reduced by 20% or less, the test was accepted.

(3) Presence / absence of whitening after endurance test The samples in (2) above, which were left for 2000 hours in an environment of temperature 85 ° C. and humidity 85% RH, were visually observed for the presence or absence of whitening of the solar cell sealing film. The case where whitening was not recognized was set as the pass.

(Evaluation results)
The evaluation results of each sample are shown in Tables 1 and 2. In Examples 1-5, 1.67-2.05 mass parts (Organic peroxide B / organic peroxide A is 8 / 92-9) combining 2 types of crosslinking agents with respect to 100 mass parts of EVA. / 91) and a solar cell sealing film containing 0.6 to 1.0 parts by mass of a silane coupling agent. As a result, in all Examples, the 60 ° C. volume specific resistance, the durability of the glass adhesive force, and the presence or absence of whitening after the durability test were all acceptable. Here, when Example 1 and Example 4 were compared, when the silane coupling agent was increased from 0.6 parts by mass to 0.9 parts by mass, a further increase in volume resistivity was observed, and the above-mentioned It was thought that the result suggested the consideration of the effect of the present invention.

  On the other hand, in Comparative Examples 1, 2, and 4 in which the blending amount of the crosslinking agent and the silane coupling agent was small, both the volume resistivity and the durability of the adhesive force were rejected. In Comparative Example 3, when the compounding amount of the silane coupling agent was increased as compared with Comparative Example 2, the durability of the adhesive force was improved, but as is generally known, the volume resistivity was further reduced.

  In Comparative Example 5, the crosslinking agent was blended in the same manner as in Example 1, and the blending amount of the silane coupling agent was 0.3 parts by mass. there were. In Comparative Example 6, the crosslinking agent was the same as in Example 1, and the blending amount of the silane coupling agent was 1.2 parts by mass. The durability of volume resistivity and adhesive strength was acceptable, but the durability was Whitening was observed after the test and it was rejected.

As described above, for the first time by the blending of the present invention, the volume resistivity in a 60 ° C. atmosphere after crosslinking is 6.0 × 10 ¹⁴ Ω · cm or more and has a remarkably high insulating property, and durability of the adhesive strength in a high temperature environment It was shown that the sealing film for solar cells excellent in property was obtained.
In addition, this invention is not limited to the structure and Example of said embodiment, A various deformation | transformation is possible within the range of the summary of invention.

  The present invention can provide a solar cell in which high power generation efficiency is maintained for a long time under a high temperature environment.

DESCRIPTION OF SYMBOLS 11 Surface side transparent protective member 12 Back surface side protective member 13A Surface side sealing film 13B Back surface side sealing film 14 Cell for solar cells 21 Glass substrate 23 Sealing film for solar cells

Claims (6)

A solar cell encapsulating film comprising an ethylene-vinyl acetate copolymer, a crosslinking agent, and a silane coupling agent,
The cross-linking agent is 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (organic peroxide A) and t-butylperoxy-2-ethylhexyl monocarbonate (organic peroxide B). )
The silane coupling agent is γ-methacryloxypropyltrimethoxysilane;
The total content of the crosslinking agent is 1.67 to 2.05 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer, and the content of the silane coupling agent is the ethylene- The sealing film for solar cells, which is 0.6 to 1.0 part by mass with respect to 100 parts by mass of the vinyl acetate copolymer. 2. The solar cell sealing film according to claim 1, wherein the volume resistivity in a 60 ° C. atmosphere after crosslinking is 6.0 × 10 ¹⁴ Ω · cm or more.   The mass ratio of the organic peroxide B to the organic peroxide A (organic peroxide B / organic peroxide A) in the crosslinking agent is in the range of 1/99 to 9/91. The sealing film for solar cells as described in any one of.   Furthermore, the sealing for solar cells of any one of Claims 1-3 which contain 0.1-3.0 mass parts of crosslinking adjuvant with respect to 100 mass parts of said ethylene-vinyl acetate copolymers. film.   The solar cell sealing film according to claim 4, wherein the crosslinking aid is triallyl isocyanurate.   A solar cell using the solar cell sealing film according to any one of claims 1 to 5.

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