JP5927687B2 - SOLAR CELL COVER FILM, SOLAR CELL MODULE PRODUCED USING SAME, AND METHOD FOR PRODUCING SOLAR CELL COVER FILM - Google Patents

Description

  The present invention relates to a cover film used as a protective member of a solar battery cell, and a solar battery module manufactured using the cover film.

In recent years, with increasing awareness of environmental issues such as global warming, expectations are increasing especially for photovoltaic power generation in terms of its cleanliness and non-polluting properties. The solar cell constitutes the central part of a photovoltaic power generation system that directly converts sunlight energy into electricity. In general, a plurality of solar cell elements (cells) are wired in series and in parallel as the structure, and various packaging is performed to protect the cells, thereby forming a unit. The unit built in this package is called a solar cell module, and the surface exposed to sunlight is generally covered with a transparent base material (glass / translucent solar cell sheet; front sheet) as the upper protective material, and the back surface is protected underneath. Protected by a back surface sealing sheet (back sheet) as a material, and the gap is filled with a sealing material (sealing resin layer) made of a thermoplastic (for example, ethylene-vinyl acetate copolymer). Yes.
Since these solar cell modules are mainly used outdoors, various characteristics are required for the structure and material structure thereof. Among them, the sealing material has flexibility and impact resistance for protecting the solar cell element, heat resistance when the solar cell module generates heat, and transparency for efficiently reaching the solar cell element. (Total light transmittance, etc.), durability, dimensional stability, flame retardancy, water vapor barrier properties, etc. are mainly required.
In order to prevent the rusting of internal conductors and electrodes due to the permeation of moisture or water, in addition, the required characteristics required for the surface-side transparent protective member of the solar cell are excellent durability against ultraviolet rays. In addition, excellent moisture resistance is an important requirement. For this reason, glass is widely used as a conventional surface-side transparent protective member as described above.
However, while the glass plate is excellent in weather resistance and moisture resistance, it has a drawback that it is heavy, weak against impacts and easily broken.

  On the other hand, for example, Patent Document 1 discloses a solar cell module having a film made of an acrylic resin or a fluoride polymer as a transparent surface protective film located on the outermost surface. In particular, fluoride polymers are rich in weather resistance and water repellency, and can reduce the decrease in conversion efficiency of solar cell modules due to yellowing / white turbidity due to resin deterioration or a decrease in light transmittance due to surface contamination. it can.

Currently, an ethylene-vinyl acetate copolymer (hereinafter sometimes abbreviated as EVA) is widely used as a sealing material for solar cell elements in a solar cell module from the viewpoint of flexibility, transparency, and the like. (For example, refer to Patent Document 2). In addition, crosslinking using an organic peroxide as a crosslinking agent is performed mainly for the purpose of imparting heat resistance to EVA. Therefore, a process of preparing an EVA sheet mixed with a crosslinking agent (organic peroxide) and a crosslinking aid in advance and sealing the solar cell element using the obtained sheet is employed. In the production stage of the sheet, it is necessary to form at a low temperature (usually about 80 to 100 ° C.) at which the organic peroxide is not decomposed. In the stopping stage, a process of performing air bleeding or temporary adhesion in a laminator over several minutes to ten and several minutes and a high temperature (usually about 130 to 150 ° C.) at which the organic peroxide decomposes in the oven It was necessary to go through a two-stage process consisting of a process of main bonding (crosslinking) over about 60 minutes. Therefore, man-hours and time are required for manufacturing the solar cell module, and there is a problem that the manufacturing cost is increased.
In addition, a sealing material for a solar cell element using an EVA sheet is likely to corrode solar cells due to acetic acid generated by hydrolysis of EVA or the like during long-term use. Due to the agent or the acetic acid generated, there has been a problem that peeling may occur at the interface with the solar cell element, the interface with the front sheet, or the interface with the back sheet.

For these problems, for example, Patent Document 3 discloses an amorphous α-olefin polymer and a crystalline α-olefin polymer as solar cell encapsulants that do not use an EVA sheet and can omit the crosslinking step. The solar cell sealing material which consists of a resin composition to contain is disclosed, Specifically, the resin composition which consists of a polymer which has a propylene as a main component is used.
Patent Document 4 discloses a solar cell sealing material characterized in that it is a polymer blend or polymer alloy comprising at least one polyolefin copolymer and at least one crystalline polyolefin. Specifically, a polymer blend of low melting point EVA and high melting point EVA (see Example 1), a polymer blend of ethylene-methacrylic acid copolymer and general-purpose crystalline polyethylene (see Example 2), ethylene- A polymer blend (see Example 3) of methyl acrylate copolymer and general-purpose crystalline polypropylene is used.
Furthermore, in the process of manufacturing a solar cell module by separately stacking a front sheet, a sealing material, a solar cell element, a back sheet, etc., the members at the time of stacking are diverse, and these are stacked at a predetermined position. There is a problem that the work of doing this is complicated and the number of processes is large, the productivity is inferior and the cost is high.
Therefore, Patent Document 5 is formed by laminating a filler layer containing a crosslinking agent as an essential component and further containing other additives and a front cover film, specifically, a multilayer laminated film having a weather resistant layer and a barrier layer. A solar cell cover film is disclosed.

JP-A-8-139347 JP 58-60579 A JP 2006-210905 A JP 2001-332750 A JP 2000-91611 A

  However, the surface protective film made of a fluororesin as in Patent Document 1 generally has an extremely weak adhesive force with the sealing material, and the surface protective film peels off when the solar cell module is exposed to the outdoors for a long period of time. Further, the surface of the surface protective film or the sealing material is provided with irregularities and further subjected to corona discharge treatment to improve the adhesion between the two, but this method involves steps and costs in producing a solar cell module. There were problems such as an increase.

  On the other hand, transparency (total light transmittance: 83.2% (see Examples)) was still insufficient in the resin composition comprising a polymer mainly composed of propylene used in Patent Document 3. . Moreover, the polymer which has propylene as a main component also has a problem that the embrittlement temperature is high and the low temperature characteristics are insufficient. In addition, the polymer blend used in Patent Document 4 does not necessarily have good transparency, and in particular, there is still a problem in balancing the flexibility, heat resistance, and transparency. That is, according to the knowledge disclosed in Patent Document 3 and Patent Document 4, a sealing material that satisfies all the required qualities of flexibility, heat resistance, and transparency has not been obtained.

  Further, the filler layer used in Patent Document 5 contains a crosslinking agent as an essential component, and heat resistance cannot be imparted without passing through a crosslinking step. Still had problems. Moreover, the impact resistance and durability of the obtained solar cell module were not sufficient.

  Therefore, in view of the problems of the prior art as described above, an object of the present invention is to provide a sealing resin layer that is easy to fabricate a solar cell module and excellent in flexibility, transparency, and heat resistance, and a weather resistant layer. A solar cell cover film that is excellent in handling properties by being laminated and is effective in reducing the weight, impact resistance, and durability of the solar cell module, and a solar cell module manufactured using this solar cell cover film It is to provide.

  As a result of extensive studies, the present inventors have used a weather resistant layer and a resin composition containing an ethylene-α-olefin random copolymer and an ethylene-α-olefin block copolymer having specific thermal characteristics. It has been found that the above-mentioned problems can be solved by laminating the encapsulating resin layer, and the present invention has been completed.

That is, the present invention provides a weather resistant layer, an ethylene-α-olefin random copolymer (A) that satisfies the following condition (a), and an ethylene-α-olefin block copolymer that satisfies the following condition (b): It is related with the sealing film for solar cells formed by laminating | stacking the sealing resin layer which consists of a resin composition (C) containing (B).
(A) The heat of crystal fusion measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 0 to 70 J / g.
(B) The crystal melting peak temperature measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 100 ° C. or more, and the crystal melting heat amount is 5 to 70 J / g.

  Moreover, this invention relates to the solar cell module produced using the cover film for solar cells of this invention.

  The cover film for a solar cell of the present invention has excellent handling properties by laminating a sealing resin layer excellent in flexibility, transparency, and heat resistance, and a weather resistant layer, reducing the weight and impact resistance of the solar cell module. And durability can be improved.

It is a schematic sectional drawing which shows an example of embodiment of the solar cell module of this invention.

Hereinafter, the cover film for solar cells of the present invention and a solar cell module produced using the same will be described.
<Weatherproof layer>
The weather-resistant layer in the present invention is not particularly limited, as long as it has characteristics such as weather resistance normally provided in a solar cell module, but in the present invention, weather resistance, moisture resistance, transparency, A layer excellent in heat resistance and adhesiveness with a sealing resin layer described later is preferable. From this viewpoint, the weather resistant layer is mainly composed of a resin composition containing at least one resin selected from acrylic resin, polycarbonate resin, polyethylene terephthalate resin, and polyethylene naphthalate resin and an ultraviolet absorber, or a fluororesin. The layer is preferably Of these, a layer containing a fluororesin as a main component is particularly preferable because of excellent weather resistance.

  In the present specification, the term “main component” is intended to allow other components to be contained within a range that does not interfere with the action and effect of the resin constituting each layer of the solar cell encapsulant of the present invention. . Further, this term does not limit the specific content, but generally, when the total component of the resin composition is 100 parts by mass, it is 50 parts by mass or more, preferably 65 parts by mass or more, Preferably, the component occupies a range of 80 parts by mass or more and 100 parts by mass or less.

Examples of the fluororesin include polytetrafluoroethylene (PTFE), 4-fluoroethylene-perchloroalkoxy copolymer (PFA), 4-fluoroethylene-6-fluoropropylene copolymer (FEP), 2-ethylene. -4-Fluoroethylene copolymer (ETFE), poly-3-fluoroethylene chloride (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF) and the like can be preferably used.
Among these, ETFE is particularly preferably used because it has excellent weather resistance, moisture resistance, and transparency, and also has antifouling properties and flame retardancy. The ETFE used here preferably has a melting point of 150 to 270 ° C., particularly from the viewpoint of heat resistance.

  Moreover, as an acrylic resin which comprises a resin composition, a methacryl resin is generally preferably used from a viewpoint of a weather resistance and transparency. The methacrylic resin is mainly composed of a methyl methacrylate unit, specifically, a methyl methacrylate resin containing usually 50% by mass or more, preferably 70% by mass or more of a methyl methacrylate unit. It may be a 100% by mass unit methyl methacrylate homopolymer or a copolymer of methyl methacrylate and other monomers.

  Examples of other monomers copolymerizable with methyl methacrylate include ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate. Methacrylic acid esters other than methyl methacrylate, such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate Such acrylic acid esters can be mentioned. Further, styrene and substituted styrenes, for example, halogenated styrenes such as chlorostyrene and bromostyrene, alkyl styrenes such as vinyltoluene and α-methylstyrene, and the like are also included. Furthermore, unsaturated acids such as methacrylic acid and acrylic acid, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like can also be mentioned. These other monomers copolymerizable with methyl methacrylate may be used alone or in combination of two or more.

  Examples of the ultraviolet absorber added to at least one resin selected from acrylic resin, polycarbonate resin, polyethylene terephthalate resin, and polyethylene naphthalate resin include benzophenone-based, benzotriazole-based, triazine-based, and salicylic acid ester-based materials. The type can be mentioned, and various commercial products can be applied. Examples of the benzophenone-based UV absorber include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-n. -Dodecyloxybenzophenone, 2-hydroxy-4-n-octadecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-5-chlorobenzophenone, 2, , 4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, etc. Can.

The benzotriazole ultraviolet absorber is a hydroxyphenyl-substituted benzotriazole compound, for example, 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-5-t-butylphenyl) Benzotriazole, 2- (2-hydroxy-3,5-dimethylphenyl) benzotriazole, 2- (2-methyl-4-hydroxyphenyl) benzotriazole, 2- (2-hydroxy-3-methyl-5-t- Butylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-amylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, etc. be able to. Examples of triazine ultraviolet absorbers include 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol, 2- ( And 4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyloxy) phenol. Examples of salicylic acid esters include phenyl salicylate and p-octylphenyl salicylate.
It is preferable to add 0.05-10 mass parts normally with respect to 100 mass parts of resin which comprises the said weather-resistant layer for a ultraviolet absorber.

  In addition to the above ultraviolet absorbers, a weathering stabilizer that imparts weatherability can be added to the weathering layer constituting the cover film of the present invention. The weathering stabilizer includes a hindered amine light stabilizer. Are preferably used. A hindered amine light stabilizer does not absorb ultraviolet rays like an ultraviolet absorber, but exhibits a remarkable synergistic effect when used together with an ultraviolet absorber.

  Examples of hindered amine light stabilizers include dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly [{6- (1,1 , 3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {{2, 2,6,6-tetramethyl-4-piperidyl} imino}], N, N′-bis (3-aminopropyl) ethylenediamine-2,4-bis [N-butyl-N- (1,2,2, 6,6-pentamethyl-4-piperidyl) amino] -6-chloro-1,3,5-triazine condensate, bis (2,2,6,6-tetramethyl-4-piperidyl) separate, 2- (3 , 5-Di-tert-4- Mud alkoxybenzylacetic) -2-n-butyl malonic acid bis (1,2,2,6,6-pentamethyl-4-piperidyl) and the like. The hindered amine light stabilizer is preferably added in an amount of usually 0.05 to 10 parts by mass with respect to 100 parts by mass of the resin constituting the weather resistant layer.

  The thickness of the weathering layer in the present invention is not particularly limited, but is preferably in the range of 5 to 200 μm, more preferably in the range of 10 to 100 μm, from the viewpoint of cell protection.

  The weather resistance of the weather resistant layer is preferably such that there is little decrease in mechanical properties and total light transmittance in a weather resistance test conducted according to JIS K7350, and mechanical properties and total light transmittance after 5000 hours have passed. Are preferable, and those having no decrease in mechanical properties and total light transmittance after 10000 hours are particularly preferable.

Moisture-proof weathering layer, it is preferably in the range of 0.5~10g / m ² · day water vapor transmission rate measured according to JIS K7129 is in the range of 0.1~50g / m ² · day It is particularly preferred.

  The total light transmittance measured according to JIS K7105 of the weathering layer is usually 85% or more in consideration of the type of solar cell to be applied, the photoelectric conversion efficiency of the solar cell, the handling property when various members are overlaid, and the like. It is preferably 90% or more.

  The heat resistance of the weather resistant layer can be measured and evaluated in the same manner as the sealing resin layer described later, and preferably has a good state after a predetermined time.

<Sealing resin layer>
The encapsulating resin layer in the present invention is a layer excellent in flexibility, transparency, and heat resistance, suitable for encapsulating solar cell elements, and satisfies the following condition (a): ethylene-α- It is necessary to consist of a resin composition (C) containing an olefin random copolymer (A) and an ethylene-α-olefin block copolymer (B) that satisfies the following conditions (b).
(A) The heat of crystal fusion measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 0 to 70 J / g.
(B) The crystal melting peak temperature measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 100 ° C. or more, and the crystal melting heat amount is 5 to 70 J / g.

[Ethylene-α-olefin random copolymer (A)]
The ethylene-α-olefin random copolymer (A) used in the present invention is not particularly limited as long as the above condition (a) is satisfied. Usually, ethylene and an α- of 3 to 20 carbon atoms are used. A random copolymer with olefin is preferably used. Examples of the α-olefin copolymerized with ethylene include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 3-methyl-butene. -1,4-methyl-pentene-1 and the like. In the present invention, propylene, 1-butene, 1-hexene, and 1-octene are preferably used as the α-olefin copolymerized with ethylene from the viewpoints of industrial availability, various characteristics, and economical efficiency. It is done. The α-olefin copolymerized with ethylene may be used alone or in combination of two or more.

  Further, the content of the α-olefin copolymerized with ethylene is not particularly limited as long as the above-described condition (a) is satisfied, but in the ethylene-α-olefin random copolymer (A) It is 2 mol% or more normally with respect to all the monomer units, Preferably it is 40 mol% or less, More preferably, it is 3-30 mol%, More preferably, it is 5-25 mol%. Within this range, the crystallinity is reduced by the copolymerization component, so that the transparency is improved and problems such as blocking of the raw material pellets are less likely to occur. In addition, the kind and content of the α-olefin copolymerized with ethylene can be qualitatively and quantitatively analyzed by a well-known method, for example, a nuclear magnetic resonance (NMR) measuring apparatus or other instrumental analyzer.

  The ethylene-α-olefin random copolymer (A) may contain monomer units based on monomers other than the α-olefin as long as the above-described condition (a) is satisfied. Examples of the monomer include cyclic olefins, vinyl aromatic compounds (such as styrene), polyene compounds, and the like. The content of the monomer unit is 20 mol% or less and 15 mol% or less when the total monomer units in the ethylene-α-olefin random copolymer (A) is 100 mol%. It is preferable. Further, the steric structure, branching, branching degree distribution and molecular weight distribution of the ethylene-α-olefin random copolymer (A) are not particularly limited as long as the above-mentioned condition (a) is satisfied. A copolymer having a long chain branch generally has good mechanical properties, and has an advantage that the melt tension (melt tension) at the time of molding a sheet is increased and the calendar moldability is improved. A copolymer having a narrow molecular weight distribution polymerized using a single site catalyst has advantages such as a low molecular weight component and a relatively low blocking of raw material pellets.

  The melt flow rate (MFR) of the ethylene-α-olefin random copolymer (A) used in the present invention is not particularly limited, but is usually MFR (JIS K7210, temperature: 190 ° C., load: 21). .18N) is about 0.5 to 100 g / 10 min, more preferably 2 to 50 g / 10 min, still more preferably 3 to 30 g / 10 min. Here, the MFR may be selected in consideration of molding processability when molding a sheet, adhesion when sealing a solar cell element (cell), a wraparound condition, and the like. For example, when calendering a sheet, the MFR is preferably relatively low, specifically about 0.5 to 5 g / 10 min from the handling property when the sheet is peeled off from the forming roll, In the case of extrusion molding using a, MFR is preferably 2 to 50 g / 10 min, more preferably 3 to 30 g / 10 min from the viewpoint of reducing the extrusion load and increasing the extrusion rate. Furthermore, MFR is preferably 2 to 50 g / 10 min, more preferably 3 to 30 g / 10 min from the viewpoint of adhesion and ease of wraparound when sealing a solar cell element (cell). Good.

  The production method of the ethylene-α-olefin random copolymer (A) used in the present invention is not particularly limited, and a known polymerization method using a known olefin polymerization catalyst can be employed. For example, slurry polymerization method, solution polymerization method, bulk polymerization method, gas phase polymerization method using multi-site catalyst represented by Ziegler-Natta type catalyst, single site catalyst represented by metallocene catalyst and post metallocene catalyst And a bulk polymerization method using a radical initiator. In the present invention, since the ethylene-α-olefin random copolymer (A) is a relatively soft resin, it has a low molecular weight from the viewpoint of easy granulation after polymerization and prevention of blocking of raw material pellets. A polymerization method using a single site catalyst capable of polymerizing a raw material with few components and a narrow molecular weight distribution is suitable.

In the ethylene-α-olefin random copolymer (A) used in the present invention, the heat of crystal fusion measured at a heating rate of 10 ° C./min in the condition (a) differential scanning calorimetry satisfies 0 to 70 J / g. It is necessary, and it is preferably 5-70 J / g, more preferably 10-65 J / g. If it is in this range, since the softness | flexibility, transparency (total light transmittance), etc. of the solar cell sealing material of this invention are ensured, it is preferable. Further, if the heat of crystal fusion is 5 J / g or more, it is preferable because problems such as blocking of raw material pellets hardly occur. Here, as reference values for the heat of crystal fusion, general-purpose high-density polyethylene (HDPE) is about 170 to 220 J / g, and low-density polyethylene resin (LDPE) and linear low-density polyethylene (LLDPE) are 100 to 160 J. / G or so.
The heat of crystal melting can be measured at a heating rate of 10 ° C./min according to JIS K7122 using a differential scanning calorimeter.

Moreover, although the crystal melting peak temperature of the ethylene-α-olefin random copolymer (A) used in the present invention is not particularly limited, it is usually less than 100 ° C and 30 to 90 ° C. There are many. Here, as reference values for the crystal melting peak temperature, general-purpose high-density polyethylene (HDPE) is about 130 to 145 ° C., and low-density polyethylene resin (LDPE) and linear low-density polyethylene (LLDPE) are 100 to 125. It is about ℃. That is, with the ethylene-α-olefin random copolymer (A) alone used in the present invention, the crystal melting peak temperature measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 100 ° C. or higher, and It is difficult to achieve a heat of crystal melting of 5 to 70 J / g.
The crystal melting peak temperature can be measured at a heating rate of 10 ° C./min according to JIS K7121 using a differential scanning calorimeter.

  Specific examples of the ethylene-α-olefin random copolymer (A) used in the present invention include trade names “Engage”, “Affinity”, and Mitsui Chemicals (Dow Chemical Co., Ltd.). Examples include trade names “TAFMER A”, “TAFMER P”, and trade names “Kernel” manufactured by Nippon Polyethylene Co., Ltd.

[Ethylene-α-olefin block copolymer (B)]
The ethylene-α-olefin block copolymer (B) used in the present invention is not particularly limited as long as the above-described condition (b) is satisfied. Usually, ethylene and α having 3 to 20 carbon atoms are used. -Block copolymers with olefins are preferably used. Examples of the α-olefin copolymerized with ethylene include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 3-methyl-butene. -1,4-methyl-pentene-1 and the like. In the present invention, propylene, 1-butene, 1-hexene, and 1-octene are preferably used as the α-olefin copolymerized with ethylene from the viewpoints of industrial availability, various characteristics, and economical efficiency. It is done. The α-olefin copolymerized with ethylene may be used alone or in combination of two or more.

  Further, the ethylene-α-olefin block copolymer (B) may contain monomer units based on monomers other than α-olefin as long as the above-described condition (b) is satisfied. Examples of the monomer include cyclic olefins, vinyl aromatic compounds (such as styrene), polyene compounds, and the like. The content of the monomer unit is 20 mol% or less and 15 mol% or less when the total monomer units in the ethylene-α-olefin block copolymer (B) is 100 mol%. It is preferable.

  The block structure of the ethylene-α-olefin block copolymer (B) used in the present invention is not particularly limited as long as the above-described condition (b) is satisfied, but flexibility, heat resistance, transparency 2 or more, preferably 3 or more segments or blocks having different comonomer contents, crystallinity, density, crystal melting peak temperature (melting point Tm), or glass transition temperature (Tg) A multi-block structure is preferable. Specific examples include a completely symmetric block, an asymmetric block, and a taper block structure (a structure in which the ratio of the block structure gradually increases in the main chain). Regarding the structure and production method of the copolymer having the multi-block structure, International Publication No. 2005/090425 (WO2005 / 090425), International Publication No. 2005/090426 (WO2005 / 090426), and International Publication No.2005. / 090427 pamphlet (WO2005 / 090427) or the like can be employed.

In the present invention, the ethylene-α-olefin block copolymer having the multi-block structure will be described in detail below.
The ethylene-α-olefin block copolymer having a multiblock structure can be suitably used in the present invention, and an ethylene-octene multiblock copolymer having 1-octene as a copolymerization component as an α-olefin is preferable. As the block copolymer, an almost non-crystalline soft segment copolymerized with a large amount of octene component (about 15 to 20 mol%) with respect to ethylene and a small amount of octene component with respect to ethylene (about 2 mol%). Less) a multiblock copolymer in which two or more highly crystalline hard segments each having a copolymerized crystal melting peak temperature of 110 to 145 ° C. are present. By controlling the chain length and ratio of these soft segments and hard segments, both flexibility and heat resistance can be achieved.
As a specific example of the copolymer having the multi-block structure, trade name “Infuse” manufactured by Dow Chemical Co., Ltd. may be mentioned.

  The melt flow rate (MFR) of the ethylene-α-olefin block copolymer (B) used in the present invention is not particularly limited, but is usually MFR (JIS K7210, temperature: 190 ° C., load: 21). .18N) is about 0.5 to 100 g / 10 min, more preferably 1 to 50 g / 10 min, still more preferably 1 to 30 g / 10 min, and particularly preferably 1 to 10 g / 10 min.

  Here, the MFR may be selected in consideration of molding processability when molding a sheet, adhesion when sealing a solar cell element (cell), a wraparound condition, and the like. Specifically, when the sheet is calendered, the MFR is preferably relatively low, specifically about 0.5 to 5 g / 10 min from the handling property when the sheet is peeled off from the forming roll, In the case of extrusion molding using a T die, an MFR of 1 to 30 g / 10 min is preferably used from the viewpoint of reducing the extrusion load and increasing the extrusion amount. Furthermore, from the viewpoint of adhesion and ease of wraparound when sealing a solar cell element (cell), a MFR of 3 to 50 g / 10 min is preferably used.

  The ethylene-α-olefin block copolymer (B) used in the present invention has a crystal melting peak temperature of 100 ° C. or higher measured at a heating rate of 10 ° C./min in the condition (b) differential scanning calorimetry, and It is necessary that the heat of crystal fusion satisfies 5 to 70 J / g. Preferably, the crystal melting peak temperature is 105 ° C. or higher, more preferably 110 ° C. or higher, and the upper limit is usually 145 ° C. Further, the heat of crystal fusion is preferably 10 to 60 J / g, and more preferably 15 to 55 J / g. The method for measuring the crystal melting peak temperature and the crystal melting heat amount is as described above.

  Generally, a solar cell module is heated to about 85 to 90 ° C. due to heat generated during power generation or radiant heat of sunlight, etc. If the crystal melting peak temperature is 100 ° C. or higher, the heat resistance of the sealing material should be ensured. On the other hand, an upper limit temperature of 145 ° C. is preferable because it can be sealed without excessively high temperature in the sealing step of the solar cell element. Further, it is preferable that the amount of heat of crystal melting is within the above range because the sealing material has flexibility and transparency (total light transmittance) and the like, and problems such as blocking of the raw material pellets hardly occur.

[Resin composition (C)]
The resin composition (C) contains the ethylene-α-olefin random copolymer (A) and the ethylene-α-olefin block copolymer (B) described above. Here, the type of α-olefin used in each of these copolymers (A) and (B) may be the same or different, but in the present invention, The same one is preferable because the compatibility and transparency when mixed are improved, that is, the photoelectric conversion efficiency of the solar cell is improved.

  Next, the contents of the ethylene-α-olefin random copolymer (A) and the ethylene-α-olefin block copolymer (B) in the resin composition (C) are flexibility, heat resistance, transparency, etc. Are preferably 50 to 99 mass% and 1 to 50 mass%, more preferably 60 to 98 mass parts and 2 to 40 mass parts, respectively, still more preferably, They are 70-97 mass parts and 3-30 mass parts. Further, the mixing (containing) mass ratio of the ethylene-α-olefin random copolymer (A) and the ethylene-α-olefin block copolymer (B) is not particularly limited, but preferably (A). / (B) = 99-50 / 1-50, more preferably 98-60 / 2-40, more preferably 97-70 / 3-30, more preferably 97-80 / 3-20, Preferably, it is 97-90 / 3-10. However, the total of (A) and (B) is 100 parts by mass. Here, it is preferable if the mixed (containing) mass ratio is within the above range because a solar cell encapsulant having an excellent balance of flexibility, heat resistance, transparency and the like can be easily obtained.

  The resin composition (C) is described above for the purpose of further improving various physical properties (flexibility, heat resistance, transparency, adhesiveness, etc.), molding processability, economical efficiency and the like without departing from the spirit of the present invention. Resins other than the ethylene-α-olefin random copolymer (A) and the ethylene-α-olefin block copolymer (B) can be mixed. Examples of the resin include other polyolefin resins and various elastomers (olefin-based, styrene-based, etc.), polar groups such as carboxyl groups, amino groups, imide groups, hydroxyl groups, epoxy groups, oxazoline groups, thiol groups, silanol groups, and the like. And a resin modified with a tackifier resin.

Examples of the tackifying resin include petroleum resins, terpene resins, coumarone-indene resins, rosin resins, and hydrogenated derivatives thereof. Specifically, as the petroleum resin, there are an aromatic petroleum resin from alicyclic petroleum resins and C ₉ components from cyclopentadiene or dimer thereof, terpene resins and terpene from The terpene resin β- pinene -Phenol resin and rosin resin include rosin resins such as gum rosin and wood rosin, and esterified rosin resins modified with glycerin and pentaerythritol. In addition, the tackifying resin can be obtained mainly having various softening temperatures depending on the molecular weight. The ethylene-α-olefin random copolymer (A) and the ethylene-α-olefin block copolymer (B In particular, hydrogenated derivatives of alicyclic petroleum resins having a softening temperature of 100 to 150 ° C., and preferably 120 to 140 ° C., in terms of compatibility when mixed with), bleeding characteristics over time, color tone, and thermal stability. preferable. When the resins other than (A) and (B) described above are mixed, usually, when the resin composition (C) is 100% by mass, it is preferably 20% by mass or less, and more preferably 10% by mass or less.

  Various additives can be added to the resin composition (C) as necessary. Examples of the additive include a silane coupling agent, an antioxidant, an ultraviolet absorber, a weathering stabilizer, a light diffusing agent, a nucleating agent, a pigment (for example, a white pigment), a flame retardant, and a discoloration preventing agent. . In the present invention, it is preferable that at least one additive selected from a silane coupling agent, an antioxidant, an ultraviolet absorber, and a weathering stabilizer is added for reasons described later. In the present invention, a crosslinking agent and a crosslinking aid can be added to the resin composition (C). For example, when high heat resistance is required, a crosslinking agent and / or a crosslinking aid is blended. be able to.

  Silane coupling agents are useful for improving adhesion to weathering layers and solar cell elements. Examples include unsaturated groups such as vinyl groups, acryloxy groups, and methacryloxy groups, amino groups, and epoxy groups. In addition, a compound having a hydrolyzable group such as an alkoxy group can be exemplified. Specific examples of the silane coupling agent include N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, and γ-aminopropyltriethoxy. Examples include silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and the like. In the present invention, γ-glycidoxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane are preferably used because of good adhesiveness and little discoloration such as yellowing. The addition amount of this silane coupling agent is about 0.1-5 mass parts normally with respect to 100 mass parts of resin compositions (C), and it is preferable to add 0.2-3 mass parts. In addition, similar to the silane coupling agent, a coupling agent such as an organic titanate compound can be effectively used.

  As the antioxidant, various commercially available products can be applied, and various types such as monophenol type, bisphenol type, polymer type phenol type, sulfur type and phosphite type can be exemplified. Examples of monophenols include 2,6-di-tert-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-tert-butyl-4-ethylphenol, and the like. Examples of bisphenols include 2,2′-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2′-methylene-bis- (4-ethyl-6-tert-butylphenol), 4,4 '-Thiobis- (3-methyl-6-tert-butylphenol), 4,4'-butylidene-bis- (3-methyl-6-tert-butylphenol), 3,9-bis [{1,1-dimethyl- 2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} ethyl} 2,4,9,10-tetraoxaspiro] 5,5-undecane.

Examples of the high molecular phenolic group include 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3 , 5-di-tert-butyl-4-bidoxybenzyl) benzene, tetrakis- {methylene-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate} methane, bis { (3,3'-bis-4'-hydroxy-3'-tert-butylphenyl) butyric acid} glycol ester, 1,3,5-tris (3 ', 5'-di-tert-butyl-4 '-Hydroxybenzyl) -s-triazine-2,4,6- (1H, 3H, 5H) trione, triphenol (vitamin E) and the like.
Examples of sulfur-based compounds include dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiopropionate.

  Examples of the phosphite system include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl) phosphite, Crick neopentanetetrayl bis (octadecyl phosphite), tris (mono and / or di) phenyl phosphite, diisodecyl pentaerythritol diphosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10- Oxide, 10- (3,5-di-tert-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy-9,10 -Dihydro-9-oxa-10-fo Phaphenanthrene, cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,6-di-tert-methylphenyl) phosphite, 2 , 2-methylenebis (4,6-tert-butylphenyl) octyl phosphite. In the present invention, phenol-based and phosphite-based antioxidants are preferably used in view of the effect of the antioxidant, thermal stability, economy, and the like, and it is more preferable to use both in combination. The addition amount of the antioxidant is usually about 0.1 to 1 part by mass and preferably 0.2 to 0.5 parts by mass with respect to 100 parts by mass of the resin composition (C).

  As an ultraviolet absorber, the thing similar to what is used by the above-mentioned weathering layer can be mentioned. The addition amount of the ultraviolet absorber is usually about 0.01 to 2.0 parts by mass and preferably 0.05 to 0.5 parts by mass with respect to 100 parts by mass of the resin composition (C). .

As the weather stabilizer for imparting weather resistance in addition to the above ultraviolet absorber, the same ones as those used in the above-mentioned weather resistant layer can be used, and a hindered amine light stabilizer is preferably used. A hindered amine light stabilizer does not absorb ultraviolet rays like an ultraviolet absorber, but exhibits a remarkable synergistic effect when used together with an ultraviolet absorber. In addition to hindered amines, there are those that function as light stabilizers, but they are often colored and are not preferred for the sealing resin layer in the present invention.
Examples of the hindered amine light stabilizer include the same ones as those used in the aforementioned weather resistant layer. The addition amount of the hindered amine light stabilizer is usually about 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the resin composition (C), and 0.05 to 0.3 parts by mass is added. It is preferable.

[Sealing resin layer]
The thickness of the sealing resin layer in the present invention is not particularly limited, but is preferably in the range of 50 to 1000 μm, more preferably in the range of 100 to 700 μm.

  The flexibility of the sealing resin layer may be appropriately adjusted in consideration of the shape, thickness, installation location, etc. of the applied solar cell. For example, storage at a vibration frequency of 10 Hz and a temperature of 20 ° C. in dynamic viscoelasticity measurement. The elastic modulus (E ′) is preferably 1 to 2000 MPa. From the viewpoint of protection of the solar cell element, the storage elastic modulus (E ′) is preferably lower. However, in consideration of handling property when the sealing resin layer is collected in a sheet shape or the like, blocking of sheet surfaces is prevented. Then, it is more preferable that it is 3-1000 MPa, it is more preferable that it is 5-500 MPa, and it is especially preferable that it is 10-100 MPa.

  The heat resistance of the encapsulating resin layer depends on various characteristics of the ethylene-α-olefin random copolymer (A) (crystal melting peak temperature, crystal melting heat amount, MFR, molecular weight, etc.) and ethylene-α-olefin block copolymer ( Although it is influenced by various characteristics of B) (crystal melting peak temperature, crystal melting calorie, MFR, molecular weight, etc.), especially the crystal melting peak temperature of the ethylene-α-olefin block copolymer (B) is strongly influenced. In general, a solar cell module is heated to about 85 to 90 ° C. by heat generated during power generation or radiant heat of sunlight, but if the crystal melting peak temperature is 100 ° C. or higher, the heat resistance of the encapsulating resin layer is ensured. This is preferable because it can be performed. In the present invention, a seal formed by forming a sheet of 0.5 mm thickness between white plate glass (size: 75 mm length, 25 mm width) and 5 mm thickness aluminum plate (size: length 120 mm, width 60 mm). A sample is formed by stacking a resin layer and laminating and pressing at 150 ° C. for 15 minutes using a vacuum press machine, and the sample is installed at an inclination of 60 ° in a 100 ° C. thermostatic chamber and after 500 hours have elapsed. When the glass was not deviated from the initial reference position, it was evaluated as ◯, and when the glass was deviated from the initial reference position or the sheet was melted as x.

  The total light transmittance measured according to JIS K7105 of the encapsulating resin layer is applied to the type of solar cell to be applied, for example, an amorphous thin film silicon type or the like that does not block sunlight reaching the solar electronic element. May be less important, but considering the photoelectric conversion efficiency of the solar cell and handling properties when overlapping various members, it is usually preferably 85% or more, more preferably 87% or more. Preferably, it is 90% or more.

  The flexibility, heat resistance and transparency of the sealing resin layer tend to be contradictory. Specifically, when the crystallinity of the resin composition (C) used for improving flexibility is excessively lowered, the heat resistance is lowered and becomes insufficient. On the other hand, when the crystallinity of the resin composition (C) used for improving the heat resistance is excessively improved, the transparency is lowered and becomes insufficient. In the present invention, the balance is used as an index of flexibility, the vibration frequency is 10 Hz in dynamic viscoelasticity measurement, the storage elastic modulus (E ′) at a temperature of 20 ° C., and the heating rate is 10 ° C. in differential scanning calorimetry as an index of heat resistance. When the total light transmittance is used as an index of crystal melting peak temperature and transparency measured in / min, three indexes are storage elastic modulus (E ′) of 1 to 2000 MPa, and crystal melting peak temperature is 100 ° C. or higher. The total light transmittance is preferably 85% or more, the storage elastic modulus (E ′) is 5 to 500 MPa, the crystal melting peak temperature is 105 to 145 ° C., and the total light transmittance is more preferably 85% or more. It is particularly preferable that the storage elastic modulus (E ′) is 10 to 100 MPa, the crystal melting peak temperature is 110 to 145 ° C., and the total light transmittance is 90% or more.

<Solar cell cover film>
The cover film for solar cells of the present invention can be obtained by laminating the weather resistant layer and the sealing resin layer.
The method of laminating is not particularly limited.For example, after forming a weathering layer and a sealing resin layer separately, a method of laminating by a thermal lamination method, a dry lamination method, or the like, After forming the film, select a method of laminating the sealing resin layer on the weathering layer by an extrusion lamination method, extrusion coating method, calendar coating method, etc., or a method of coextrusion and lamination of the weathering layer and the sealing resin layer be able to. In the present invention, a coextrusion method or an extrusion lamination method is preferably used from the viewpoints of easy thickness control, appearance (transparency, etc.) and productivity.

  When forming the weathering layer and the sealing resin layer separately, or as a film forming method in the case of co-extrusion, a known method, for example, melting of a single screw extruder, a multi screw extruder, a Banbury mixer, a kneader, etc. Although it has a mixing facility and can adopt an extrusion cast method or a calendar method using a T die, it is not particularly limited, but in the present invention, the T die is used from the aspects of handling property and productivity. The extrusion cast method used is preferably used.

The molding temperature in the extrusion casting method using a T die is appropriately adjusted depending on the flow characteristics and film-forming properties of the resin used, but is generally 130 to 300 ° C, preferably 150 to 250 ° C. Various additives such as silane coupling agents, antioxidants, UV absorbers, and weathering stabilizers may be dry blended with the resin in advance and then supplied to the hopper. The master batch may be supplied after being prepared, or a master batch in which only the additive is previously concentrated in the resin may be prepared and supplied.
In addition, by using a method of laminating a weather resistant layer and a sealing resin layer to which various additives are added with a feed block or a multi-manifold die, etc., cooling with a chill roll, and then laminating and laminating, interlayer adhesion An excellent sheet can be obtained.

  In addition, on the surface or the back surface of the weathering layer or sealing resin layer obtained in the form of a sheet, if necessary, the sheet is used as a scroll to prevent blocking between sheets and to handle in the sealing step of the solar cell element Embossing and various irregularities (cone, pyramid shape, hemispherical shape, etc.) may be performed for the purpose of improving the performance and easiness of bleeding. Furthermore, when forming a sheet | seat, you may laminate | stack with another base film (an extending | stretching polyester film (OPET), an extending | stretching polypropylene film (OPP), etc.) and methods, such as extrusion lamination and sand lamination.

In the above, the thermal lamination method, the dry lamination method, the extrusion lamination method, the extrusion coating method, the calendar coating method, and the coextrusion method are all known lamination methods, but will be briefly described below.
The thermal lamination method is a method in which two films previously formed into a film shape, in this case, a weather resistant layer and a sealing resin layer are stacked and heat-bonded by heating and pressing with a heating roll or the like.
In the dry lamination method, two films previously formed into a film shape, that is, a weather resistant layer and a sealing resin layer, are combined with one film using a two-component curable polyurethane adhesive or the like. For example, it is applied to the laminated surface of the weather resistant layer, the solvent component is removed by hot air drying, etc., and the other film, that is, the sealing resin layer is laminated on it with tack (adhesiveness) before curing. Are usually rolled up, stored at room temperature or at a relatively low heating temperature, and the adhesive is cured over time and bonded together.

In the extrusion lamination method, two films previously formed into a film shape, a weather resistant layer and a sealing resin layer, are melt-extruded into a film shape with a T-die or the like between them and a pressure bonding is performed. It is a method of cooling and laminating.
In the extrusion coating method, a film formed in advance, in this case, a weather resistant layer is used as a base material, and an anchor coat (a kind of primer coat) is applied to the laminated surface as necessary, and the resin composition ( C) is melt-extrusion coated in a film form with a T die or the like, and cooled and pressure-bonded with a chill roll for lamination.
In the calender coating method, for example, a thermoplastic resin, in this case, the resin composition (C) is heated with a calender and formed into a film shape, and at the same time, this is overlaid on the laminated surface of the weather resistant layer, and is subjected to pressure bonding and cooling. And laminating. Also in this case, an anchor coat can be applied to the laminated surface of the weather resistant layer as necessary.
The coextrusion method is a method in which a weather resistant layer and a sealing resin layer are laminated in a film shape with a feed block or a multi-manifold die, and are cooled and pressed with a chill roll for lamination. In some cases, an adhesive layer may be interposed between the two layers.

  By adopting the production method as described above, a wide and long weathering layer and a sealing resin layer can be continuously laminated, so that the solar cell cover film of the present invention is produced with high productivity. Can do.

The cover film for a solar cell of the present invention is not particularly limited as long as one or more weathering layers and a sealing resin layer are laminated, but the sealing resin layer is usually a solar cell. It is preferable that the structure is such that it is present in the outermost layer that is in close contact with the element, and the weather resistant layer is present in the outermost layer on the opposite surface.
For example, two types and two layers such as weathering layer / sealing resin layer, three types and three layers such as weathering layer / adhesive layer / sealing resin layer, weathering layer / sealing resin layer / weathering layer / sealing resin layer, etc. A two-kind four-layer structure is preferred.

The flexibility of the cover film for solar cells of the present invention depends on the total thickness of the cover film or the thickness composition ratio of the weathering layer and the sealing resin layer, but usually the sealing resin layer is compared with the weathering layer. Therefore, since the sealing resin layer has the flexibility described above, the flexibility of the cover film of the present invention can be evaluated.
Although the total thickness of a cover film is not specifically limited, Preferably it is the range of 55-1200 micrometers, More preferably, it is the range of 110-800 micrometers.
The thickness ratio of the weathering layer / sealing resin layer is preferably in the range of 1/200 to 1/5, more preferably in the range of 1/100 to 1/10.

  Regarding the adhesiveness between the weather resistant layer and the sealing resin layer in the solar cell cover film of the present invention, the peel peel strength between two layers measured according to JIS K6854 is preferably 10 N / cm width or more, and 20 N / Cm width or more is particularly preferable.

  The heat resistance of the cover film for solar cells of the present invention is such that two cover films (length 75 mm, width 25 mm) are aligned so that the sealing resin layers overlap each other by 25 mm in length, and a marked line is put in the overlapping portion, Using a vacuum press machine, prepare a sample that is laminated and pressed at 150 ° C. for 15 minutes, attach 10 g of weight to the lower end of the sample, hang it vertically in a 100 ° C. constant temperature bath, and leave it to stand. The state after the elapse of 500 hours was evaluated, and a mark in which the marked line provided in the overlapping part did not deviate was evaluated as ◯, and a mark deviated from the marked line provided in the overlapping part or the sheet peeled was evaluated as x.

  The total light transmittance measured according to JIS K7105 of the cover film for a solar cell of the present invention is usually preferably 85% or more and preferably 87% or more in consideration of the photoelectric conversion efficiency of the solar cell. More preferably, it is more preferably 90% or more.

As described above, the cover film for a solar cell of the present invention has excellent handling properties by laminating the sealing resin layer and the weather resistant layer, which are excellent in flexibility, transparency, and heat resistance. Can be reduced in weight, impact resistance, and durability. That is, from the thickness ratio of the weathering layer / sealing resin layer, since the sealing resin layer is usually much thicker than the weathering layer, it greatly affects the performance of the cover film that provides the properties of the sealing resin layer. To do. Therefore, since the sealing resin layer has excellent flexibility, transparency, and heat resistance, the obtained cover film for solar cells has excellent handling properties, and has excellent impact resistance and durability as a solar cell module. Have sex. Furthermore, in the present invention, the weather-resistant layer constituting the solar cell cover film is excellent in weather resistance, moisture resistance, transparency, and heat resistance, and has high adhesiveness with the sealing resin layer. This effect can be further enhanced.
As mentioned above, the said cover film for solar cells of this invention can be used suitably as an upper protective material and / or a lower protective material of a solar cell module.

<Solar cell module>
Using the solar cell cover film of the present invention (hereinafter referred to as “the cover film of the present invention”), for example, the upper part of the solar cell element is the cover film of the present invention, the sealing material which is the lower protective material, and the back surface sealing The solar cell module of the present invention can be produced by fixing with a sheet (back sheet). In addition, the transparent base material (front sheet) and the sealing material, which are the protective material of the upper part of the solar cell element, and the lower part can be fixed with the present film. The solar cell module of the invention can also be produced. Examples of such solar cell modules include various types.

  As a specific example, as shown in FIG. 1, the solar cell cover films 10 </ b> A and 10 </ b> B of the present invention are arranged in order from the sunlight receiving side (in this case, the sealing resin layer 10 </ b> B is disposed on the solar cell element side). The solar cell elements 12A and 12B, the sealing material 14, and the back surface sealing sheet 16 are laminated. Further, the junction box 18 (electric power generated from the solar cell elements) is formed on the lower surface of the back surface sealing sheet 16. The terminal box for connecting the wiring for taking out the outside is bonded. The solar cell elements 12A and 12B are connected by a wiring 20 in order to conduct the generated current to the outside. The wiring 20 is taken out to the outside through a through hole (not shown) provided in the sealing material 14 and the back surface sealing sheet 16 and connected to the junction box 18.

  Since the solar cell module deteriorates when moisture enters the inside, when attaching accessories such as a junction box, ensure sufficient sealing so that outside air does not enter the inside of the solar cell module. Although it is necessary, according to the cover film for solar cells of the present invention, since it can be bonded only by heat treatment, it is possible to easily and reliably prevent the intrusion of outside air.

  In the solar cell module of the present invention, when the sealing material is used in two or more parts, the cover film of the present invention may be used for all parts, or the sealing material made of a different resin composition. May be used. When the sealing resin layer is used for a portion requiring light transmittance, the sealing resin layer must be transparent. However, when the sealing resin layer is used as a lower protective material, the sealing resin layer may not be transparent.

The back surface sealing sheet constituting the solar cell module produced using the solar cell cover film of the present invention is a single-layer or multi-layer sheet such as a metal or various thermoplastic resin films, for example, tin. Examples thereof include metals such as aluminum and stainless steel, inorganic materials such as glass, single-layer or multilayer sheets such as polyester, inorganic vapor-deposited polyester, fluororesin, and polyolefin.
In addition, examples of the transparent substrate include glass, or a single layer or multilayer sheet made of acrylic resin, polycarbonate, polyester, fluorine resin, or the like. In the case of plastic, for the purpose of imparting gas barrier properties, an inorganic thin film is formed in the same manner as the gas barrier layer constituting the laminated sheet for solar cells, or heat resistance, weather resistance, mechanical strength, chargeability, For the purpose of improving dimensional stability, etc., crosslinking agents, antioxidants, light stabilizers, UV absorbers, antistatic agents, reinforcing fibers, flame retardants, preservatives, etc. are added, and various sheets are added to this. Can be stacked. The thickness of the transparent substrate can be appropriately set in view of strength, gas barrier properties, durability, and the like.

  Examples of the solar cell element include a single crystal silicon type, a polycrystalline silicon type, an amorphous silicon type, various compound semiconductor types, a dye sensitized type, and an organic thin film type.

  Although it does not specifically limit as a manufacturing method of the solar cell module at the time of using the solar cell cover film of this invention, For example, in order of the cover film of this invention, a solar cell element, a sealing material, and the sheet | seat for back surface sealing. There are a step of stacking and aligning, a step of vacuum-sucking them and thermocompression bonding them, and a step of trimming the protruding sealing resin to a predetermined dimension. Since the weather resistant layer and the sealing resin layer are laminated in advance, the film can be used for the simple lamination, alignment process, trimming process, and the like.

  The solar cell module of the present invention is suitable for various applications regardless of small solar cells, large solar cells, indoors, outdoors due to the excellent heat resistance, flexibility, transparency, and weather resistance of the cover film of the present invention. Can be used.

  In the present invention, even when referred to as “film”, “sheet” is included, and even when referred to as “sheet”, “film” is included.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In addition, the various measured values and evaluation about the sheet | seat displayed in this specification were performed as follows. Here, the flow direction of the sheet from the extruder is called the vertical direction, and the orthogonal direction is called the horizontal direction.

(1) Crystal melting peak temperature (Tm)
Using a differential scanning calorimeter manufactured by PerkinElmer, Inc., under the trade name “Pyris1 DSC”, according to JIS K7121, about 10 mg of the sample was heated from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min. After holding at 200 ° C. for 5 minutes, the temperature was lowered to −40 ° C. at a cooling rate of 10 ° C./min, and again from the thermogram measured when the temperature was raised to 200 ° C. at a heating rate of 10 ° C./min. Tm) (° C.) was determined.

(2) Heat of crystal melting (ΔHm)
Using a differential scanning calorimeter manufactured by PerkinElmer Co., Ltd., trade name “Pyris1 DSC”, according to JIS K7122, about 10 mg of the sample was heated from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min. After holding at 200 ° C. for 5 minutes, the temperature was lowered to −40 ° C. at a cooling rate of 10 ° C./min, and again from the thermogram measured when the temperature was raised to 200 ° C. at a heating rate of 10 ° C./min (ΔHm ) (J / g).

(3) Flexibility of encapsulating resin layer For a sheet-like encapsulating resin layer having a thickness of 0.5 mm, a viscoelasticity measuring device manufactured by IT Measurement Co., Ltd., trade name “Viscoelastic Spectrometer DVA-200” is used. A sample (4 mm in length, 60 mm in width) was obtained by measuring from −150 ° C. to 150 ° C. in the lateral direction at a vibration frequency of 10 Hz, a strain of 0.1%, a heating rate of 3 ° C./min, and a gap of 25 mm between the chucks. The storage elastic modulus (E ′) (MPa) at 20 ° C. was determined from the data.

(4) Heat resistance of the sealing resin layer A sheet shape having a thickness of 0.5 mm between white plate glass having a thickness of 3 mm (size: length 75 mm, width 25 mm) and an aluminum plate having a thickness of 5 mm (size: length 120 mm, width 60 mm) A sample that is laminated and pressed at 150 ° C. for 15 minutes using a vacuum press machine is prepared, and the sample is placed at an inclination of 60 ° in a 100 ° C. thermostat. The state after the lapse of time was observed and evaluated according to the following criteria.
(○) The glass did not deviate from the initial reference position (×) The glass deviated from the initial reference position or the sheet melted

(5) Total light transmittance (transparency of sealing resin layer)
A sheet-shaped sealing resin layer having a thickness of 0.5 mm is stacked between two pieces of white glass having a thickness of 3 mm (size: 75 mm length, 25 mm width), and using a vacuum press machine at 150 ° C. for 15 minutes. A sample subjected to lamination pressing was prepared, the total light transmittance was measured according to JIS K7105, the value was described, and the result evaluated according to the following criteria was also shown.
(◎) Total light transmittance is 90% or more (○) Total light transmittance is 85% or more and less than 90% (×) Total light transmittance is less than 85% or clearly cloudy (not measured) )

(Reference Example 1)
As ethylene-α-olefin random copolymer (A), ethylene-octene random copolymer (manufactured by Dow Chemical Co., Ltd., trade name: engage 8200, octene content: 7.3 mol% (24 mass%) , MFR: 5, Tm: 65 ° C., ΔHm: 53 J / g) (hereinafter abbreviated as A-1) as 95 parts by mass and an ethylene-α-olefin block copolymer (B), an ethylene-octene block copolymer Polymer (manufactured by Dow Chemical Co., Ltd., trade name: Infuse D9100.05, octene content: 12.8 mol% (37% by mass), MFR: 1, Tm: 119 ° C., ΔHm: 38 J / g) The resin composition (C) (hereinafter abbreviated as B-1) mixed at a ratio of 5 parts by mass is melt-kneaded at a set temperature of 200 ° C. using a 40 mmφ single screw extruder equipped with a T die, and 20 ° C. Cass of A sheet-like encapsulating resin layer (hereinafter simply referred to as a sheet) having a thickness of 0.5 mm was obtained by rapidly forming a film by trawling. The results of evaluation using this sheet are shown in Table 1.

(Reference Example 2)
In Reference Example 1, as shown in Table 1, the resin composition (C) (A-1) 80 parts by mass and an ethylene-octene block copolymer (manufactured by Dow Chemical Co., Ltd., trade name: Infuse D9507) .15, Octene content: 16.4 mol% (44 mass%), MFR: 5, Tm: 123 ° C., ΔHm: 21 J / g) (hereinafter abbreviated as B-2) and 20 mass parts of resin A sheet having a thickness of 0.5 mm was obtained in the same manner as in Reference Example 1 except that the composition was changed. Table 1 shows the results of evaluation using this sheet.

(Reference Example 3)
In Reference Example 1, as shown in Table 1, the resin composition (C) is an ethylene-propylene-hexene ternary random copolymer (manufactured by Nippon Polyethylene Co., Ltd., trade name: Kernel KJ640T, Propylene content: 7.4 mol% (10 mass%), hexene content: 4.4 mol% (10 mass%), MFR: 30, Tm: 53 ° C., ΔHm: 58 J / g) (hereinafter referred to as A- A sheet having a thickness of 0.5 mm was obtained in the same manner as in Reference Example 1 except that the thickness was changed to 2). Table 1 shows the results of evaluation using this sheet.

(Reference Example 4)
In Reference Example 1, as shown in Table 1, the resin composition (C) was changed to 100 parts by mass (A-1), and a sheet having a thickness of 0.5 mm was obtained in the same manner as Reference Example 1. It was. Table 1 shows the results of evaluation using this sheet.

(Reference Example 5)
In Reference Example 1, as shown in Table 1, the resin composition (C) is an ethylene-octene random copolymer (trade name, manufactured by Prime Polymer Co., Ltd.), which is a general-purpose crystalline polyethylene resin. : Moretech 0238CN, Octene content: 1 mol% (4% by mass), MFR: 2.1, Tm: 121 ° C., ΔHm: 127 J / g) (hereinafter abbreviated as P-1), In the same manner as in Reference Example 1, a sheet having a thickness of 0.5 mm was obtained. Table 1 shows the results of evaluation using this sheet.

(Reference Example 6)
In Reference Example 1, as shown in Table 1, the resin composition (C) was changed to 100 parts by mass of (P-1), and a sheet having a thickness of 0.5 mm was obtained in the same manner as Reference Example 1. It was. Table 1 shows the results of evaluation using this sheet.

(6) Adhesiveness (peel peel strength) of the cover film of the present invention
A weather resistant layer and a sealing resin layer film (length 75 mm, width 15 mm) are stacked, a Teflon (trade name) sheet (length 30 mm, width 25 mm, thickness 300 μm) is sandwiched between the two layers, and a vacuum press is used. A sample that was laminated and pressed at 150 ° C. for 15 minutes was prepared. In accordance with JIS K6854, peel peel strength was evaluated at a test speed of 50 mm / min.
(○) 10 N / cm width or more (×) less than 10 N / cm width

(7) Heat resistance of the cover film of the present invention The two cover films (75 mm in length, 25 mm in width) in which the weathering layer and the sealing resin layer are laminated are matched so that the sealing resin layers overlap each other by 25 mm in length. A marked line was put in the overlapping part. Using a vacuum press machine, prepare a sample that is laminated and pressed at 150 ° C. for 15 minutes, attach 10 g of weight to the lower end of the sample, hang it vertically in a 100 ° C. constant temperature bath, and leave it to stand. The state after the lapse of 500 hours was observed and evaluated according to the following criteria.
(○) The marked line provided in the overlapping part did not deviate. (×) The standard line provided in the overlapping part deviated or the sheet peeled off.

(8) Total light transmittance (transparency of cover film)
For a cover film (75 mm long, 25 mm wide) in which a weather resistant layer and a sealing resin layer are laminated, the total light transmittance is measured according to JIS K7105, the value is described, and the results evaluated according to the following criteria Also written.
(◎) Total light transmittance is 90% or more (○) Total light transmittance is 85% or more and less than 90% (×) Total light transmittance is less than 85% or clearly cloudy (not measured) )

Example 1
Γ-methacryloxypropyltrimethoxysilane (trade name: KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) using 100 parts by mass of the resin composition (C) of the sealing resin layer described in Reference Example 1 and a silane coupling agent ETFE film (manufactured by Asahi Glass Co., Ltd., manufactured by Asahi Glass Co., Ltd.), melt-kneaded at a set temperature of 200 ° C. using a 40 mmφ single-screw extruder equipped with a T die. Name: Aflex ETFE, thickness 25 μm, water vapor transmission rate: 7 μg / cm ² · day) at a thickness of 100 μm, pressure-bonded with a rubber roll, and rapidly cooled with a 20 ° C. cast roll to form a sheet having a thickness of 0.525 mm A cover film for a solar cell was obtained by an extrusion laminating method. The results of evaluation using this cover film are shown in Table 2.

(Example 2)
In Example 1, except that the resin composition (C) was changed to that used in Reference Example 2, a cover film for a solar cell was obtained by an extrusion laminating method in the same manner as in Example 1. Table 2 shows the results of evaluation using this cover film.

(Example 3)
In Example 1, except that the resin composition (C) was changed to that used in Reference Example 3, a cover film for a solar cell was obtained by an extrusion laminating method in the same manner as in Example 1. Table 2 shows the results of evaluation using this cover film.

Example 4
Modified ETFE resin (adhesive ETFE resin) as a weather-resistant layer (manufactured by Daikin Co., Ltd., trade name: NEOFLON EFEP RP-4020), 100 resin composition (C) used in Reference Example 1 as a sealing resin layer A mixture in which 0.5 part by mass of 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane (trade name: KBM-303, manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent is mixed at a ratio of 0.5 part by mass. Using a feed block and a T-die, a cover film for solar cells is laminated by coextrusion so that the thickness of the weather resistant layer is 0.025 mm and the thickness of the sealing resin layer is 0.5 mm at a die temperature of 200 ° C. Obtained by coextrusion. Table 2 shows the results of evaluation using this cover film.

(Comparative Example 1)
In Example 1, except that the resin composition (C) was changed to that used in Reference Example 4, a cover film for a solar cell was obtained by an extrusion laminating method in the same manner as in Example 1. Table 2 shows the results of evaluation using this cover film.

(Comparative Example 2)
In Example 1, except that the resin composition (C) was changed to that used in Reference Example 5, a cover film for a solar cell was obtained by an extrusion laminating method in the same manner as in Example 1. Table 2 shows the results of evaluation using this cover film.

(Comparative Example 3)
A solar cell cover film was obtained in the same manner as in Example 1, except that the resin composition (C) was changed to that used in Reference Example 6 in Example 1. Table 2 shows the results of evaluation using this cover film.

  From Tables 1 and 2, the solar cell cover film in which the weathering layer and the sealing resin layer of the present invention are laminated is excellent in flexibility, heat resistance, transparency (total light transmittance), and adhesiveness is also good. It can confirm that there exists (Examples 1-4 and Reference Examples 1-3). On the other hand, what does not contain the block copolymer (B) in this invention in the sealing resin layer is one or more characteristics of a softness | flexibility, heat resistance, and transparency (total light transmittance). Can be confirmed to be insufficient (Comparative Examples 1 to 3 and Reference Examples 4 to 6). Specifically, if the heat resistance is insufficient (Comparative Example 1) or the heat resistance of Comparative Example 1 is to be improved with a general-purpose crystalline polyethylene resin, the heat resistance is good, but the transparency ( It can be confirmed that the total light transmittance is insufficient (Comparative Example 2).

10A: Weather-resistant layer 10B of cover film ... Sealing resin layers 12A, 12B of cover film ... Solar cell element 14 ... Sealing material 16 ... Sheet 18 for back surface sealing ... Junction Box 20 ... Wiring

Claims (7)

50-99% by mass of the weather resistant layer, ethylene-α-olefin random copolymer (A) satisfying the following condition (a), and ethylene-α-olefin block copolymer satisfying the following condition (b) The cover film for solar cells formed by laminating | stacking the sealing resin layer which consists of a resin composition (C) containing 1-50 mass% of unification | combination (B).
(A) The heat of crystal fusion measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 0 to 70 J / g.
(B) The crystal melting peak temperature measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 100 ° C. or more, and the crystal melting heat amount is 5 to 70 J / g.   The weather resistant layer is mainly composed of a resin composition containing at least one resin selected from the group consisting of acrylic resin, polycarbonate resin, polyethylene terephthalate resin, and polyethylene naphthalate resin and an ultraviolet absorber, or a fluororesin. The solar cell cover film according to claim 1, wherein:   The fluororesin is polytetrafluoroethylene, 4-fluoroethylene-perchloroalkoxy copolymer, 4-fluoroethylene-6-fluoropropylene copolymer, 2-ethylene-4-fluoroethylene copolymer. The solar cell cover film according to claim 2, wherein the cover film is at least one resin selected from the group consisting of poly (3-fluoroethylene chloride), polyvinylidene fluoride, and polyvinyl fluoride.   The cover film for solar cells according to any one of claims 1 to 3, wherein the ethylene-α-olefin block copolymer (B) is an ethylene-octene multiblock copolymer.   The type of α-olefin constituting each of the ethylene-α-olefin random copolymer (A) and the ethylene-α-olefin block copolymer (B) is the same, characterized in that: The solar cell cover film according to any one of the above. 50-99% by mass of the weather resistant layer, ethylene-α-olefin random copolymer (A) satisfying the following condition (a), and ethylene-α-olefin block copolymer satisfying the following condition (b) A cover film for a solar cell, wherein a sealing resin layer made of a resin composition (C) containing 1 to 50% by mass of the union (B) is laminated using a co-extrusion method or an extrusion lamination method. Manufacturing method .
(A) The heat of crystal fusion measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 0 to 70 J / g.
(B) The crystal melting peak temperature measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 100 ° C. or more, and the crystal melting heat amount is 5 to 70 J / g. The solar cell module which fixes a solar cell element with an upper protective material and a lower protective material, The said upper protective material and / or the said lower protective material are the cover for solar cells of any one of Claims 1-5. A solar cell module that is a film .

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