JP2011159709A - Resin sealing sheet and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin sealing sheet used in a solar cell module, capable of minimizing a decrease in generated energy, even if an incident angle of sunlight is low. <P>SOLUTION: The resin sealing sheet has a total light transmittance of ≥85% at the incident angle of zero degree, and a haze value of ≥25% at the incident angle of zero degree. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a resin sealing sheet and a solar cell module using the same.

  In recent years, due to the global warming phenomenon, awareness of the environment has increased, and a new energy system that does not generate greenhouse gases such as carbon dioxide has attracted attention. The energy generated by solar cell power generation does not generate carbon dioxide. Therefore, it has been attracting attention as clean energy, and research and development has been carried out as industrial and household energy.

  Representative examples of solar cells include those using single crystal and polycrystalline silicon cells (crystalline silicon cells), those using amorphous silicon, and compound semiconductors (thin film cells). Solar cells are often used outdoors exposed to wind and rain for a long period of time, and the power generation part is modularized by attaching a glass plate, back sheet, etc. to prevent moisture from entering from outside. We are trying to protect the parts and prevent leakage.

  As a member for protecting the power generation portion, transparent glass or transparent resin is used for the light incident side member in order to ensure light transmission necessary for power generation. As the opposite side (back side) member, a laminated sheet on which a barrier coating process such as an aluminum foil called a back sheet, a polyvinyl fluoride resin (PVF), polyethylene terephthalate (PET) or silica is used. The power generation element is sandwiched between resin sealing sheets, the outside is further covered with glass or a back sheet, and heat treatment is performed to melt the resin sealing sheet, and the whole is integrally sealed (modularized).

  The following (1) to (3) are required as characteristics of the resin-encapsulated sheet described above. That is, (1) good adhesion to glass, power generation element and back sheet, (2) flow prevention (creep resistance) of power generation element due to melting of resin-sealed sheet at high temperature, (3) sun Transparency that does not hinder the incidence of light.

  From such a viewpoint, the resin encapsulated sheet is made of an ethylene-vinyl acetate copolymer (EVA), an ultraviolet absorber as a countermeasure for ultraviolet deterioration, a coupling agent for improving adhesion to glass, and an organic material for crosslinking. Additives such as peroxide are blended to form a film by calendar molding or T-die casting. Moreover, in view of being exposed to sunlight for a long time, various additives such as a light-resistant agent are blended in order to prevent a decrease in optical properties due to deterioration of the resin.

  As a method for modularizing the solar cell with the resin-encapsulated sheet as described above, a method using a dedicated solar cell vacuum laminator can be mentioned. Specifically, glass / resin encapsulating sheet / power generation element such as crystalline silicon cell / resin encapsulating sheet / back sheet are stacked in this order, and the melting temperature of the resin or higher (temperature condition of about 150 ° C. in the case of EVA) ) And a step of preheating and a pressing step, and a method of melting and bonding the resin sealing sheet.

  In the above method, first, the resin of the resin sealing sheet is melted in the preheating process, and the member in contact with the molten resin in the pressing process is in close contact with the molten resin and vacuum laminated. In this laminating step, after (i) the crosslinking agent (for example, organic peroxide) contained in the resin sealing sheet is thermally decomposed and EVA crosslinking is promoted, (ii) the resin sealing sheet The coupling agent contained is covalently bonded to the member in contact. Thereby, the mutual adhesiveness is further improved, the flow of the power generation part due to the melting of the resin sealing sheet in a high temperature state is prevented (creep resistance), and the excellent adhesiveness of the glass, the power generation element and the back sheet is obtained. Realized.

  Patent Document 1 discloses a solar cell filling adhesive sheet made of an ethylene copolymer resin containing a coupling agent and an organic peroxide. Patent Document 2 discloses a sheet for sealing a solar cell, which is a sheet made of an ethylene vinyl acetate copolymer blended with a crosslinking agent and a silane coupling agent, and is radiation-crosslinked to a certain gel fraction. Is disclosed.

JP 58-060579 A JP-A-8-283696

  However, there is still room for improvement regarding the power generation efficiency of the solar cell module. The power generation efficiency of the solar cell module is an index indicating the rate at which received sunlight can be converted into electrical energy. One factor that improves power generation efficiency is that the amount of light reaching the power generation element in the module is large. From this point of view, a resin sealing sheet made of EVA resin is used as a sealing sheet having high transparency. However, in reality, sufficient power generation efficiency is not obtained.

  Furthermore, the power generation efficiency of the solar cell module is greatly influenced by the irradiation angle (incident angle) of sunlight. When the incident angle is 0 degree (when incident perpendicularly to the solar cell module), sunlight can be efficiently converted into electric energy, but when the incident angle is large (incident obliquely with respect to the solar cell module) Case) has a problem that sunlight cannot be efficiently converted into electric energy. Taking the case where the solar cell module is installed outdoors as an example, in the noon time zone where the sun is located just south, sunlight is irradiated from directly above the solar cell module (incidence angle 0 degree), so power generation efficiency In the morning or evening when the sun is east or west, oblique to the solar cell module (for example, the solar altitude of about 30 degrees in the case of noon on the winter solstice in Tokyo) Since the solar cell module is irradiated with sunlight from an incident angle of about 35 degrees in the case of a 25-degree inclined roof, the power generation efficiency tends to be significantly reduced.

  This invention is made | formed in view of the said situation, and provides the resin sealing sheet which can be set as the solar cell module which can suppress the fall of electric power generation amount even when the incident angle of sunlight is low. Main purpose.

  As a result of intensive studies to solve the above problems, the present inventors surprisingly have a total light transmittance of 85% or more at an incident angle of 0 degrees and a haze value of 25% at an incident angle of 0 degrees. By using the above resin-encapsulated sheet, it was found that even when the incident angle of sunlight is low, a decrease in the amount of power generation can be suppressed, and the present invention has been completed.

That is, the present invention is as follows.
[1]
A resin-encapsulated sheet having a total light transmittance of 85% or more at an incident angle of 0 degrees and a haze value of 25% or more at an incident angle of 0 degrees.
[2]
The resin-encapsulated sheet according to [1], having at least a resin layer containing a thermoplastic resin having a density of 0.88 to 0.91 g / cm ³ or less and a melting point of 110 ° C. or less.
[3]
The thermoplastic resin is at least one resin selected from the group consisting of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin resin, according to [2]. Resin sealing sheet.
[4]
The thermoplastic resin is the resin-encapsulated sheet according to [2] or [3], which is linear low-density polyethylene.
[5]
The resin sealing sheet according to any one of [1] to [4], which has a multilayer structure.
[6]
The resin sealing sheet according to any one of [1] to [5], which has been subjected to a crosslinking treatment.
[7]
The resin sealing sheet according to [6], wherein the crosslinking treatment is performed by electron beam irradiation.
[8]
A translucent insulating substrate;
A back insulating substrate;
A power generating element disposed between the translucent insulating substrate and the back insulating substrate;
The resin sealing sheet according to any one of [1] to [7], which seals the power generation element;
A solar cell module comprising:

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where the incident angle of sunlight is low, the resin sealing sheet which can be set as the solar cell module which can suppress the fall of electric power generation amount can be provided.

It is a side schematic diagram of one mode of a resin sealing sheet of this embodiment. It is a section schematic diagram of one mode of a solar cell module of this embodiment.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The following embodiments are exemplifications for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with appropriate modifications within the scope of the gist thereof. In the drawings, positional relationships such as up, down, left and right are based on the positional relationships shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  FIG. 1 is a schematic side view of one aspect of the resin-encapsulated sheet of the present embodiment. The resin sealing sheet 1 of the present embodiment is a resin sealing sheet having a total light transmittance of 85% or more at an incident angle of 0 degrees and a haze value of 25% or more at an incident angle of 0 degrees. Here, “incidence angle 0 degree” means a case where the incident angle α in FIG. 1 is 0 degree. The present inventors paid attention to the diffused light of sunlight as one of the elements that can improve the power generation efficiency of the solar cell module. Usually, when the haze value of the resin-encapsulated sheet is high, the surface of the sheet appears whitish and blurry, so that the transparency is poor. Therefore, it is considered that it is not preferable to use a resin sheet having a high haze value as a sealing material for solar cells. However, surprisingly, by using a resin-encapsulated sheet having transparency in which the total light transmittance at an incident angle of 0 degrees is 85% or more and the haze value at an incident angle of 0 degrees is 25% or more, Scattered light even when the incident angle is large (when sunlight enters from an angle), such as in the morning or evening hours when the sun is east or west, or during the year when the solar altitude is low such as winter. The present inventors have found that it is possible to generate power effectively. Here, the total light transmittance and the haze value can be measured by a measuring method described in Examples described later.

  For example, the range of solar altitude at noon throughout Japan is about 30 degrees for the winter solstice, about 80 degrees for the summer solstice, and about 55 degrees for the spring equinox. In such an environment, for example, in order for the solar cell module installed on the roof of a general house having an inclination angle of about 25 degrees to obtain excellent power generation efficiency throughout the year, the incident angle is in the range of about 0 to 35 degrees. It is required to reduce the variation (decrease) in power generation efficiency. In the case of a solar cell module using a conventional resin-encapsulated sheet, when the incident angle of sunlight is about 35 degrees, the power generation efficiency is significantly reduced as compared to the case where the incident angle is 0 degrees. On the other hand, if it is a solar cell module using the resin sealing sheet of this Embodiment, even if it is a case where the incident angle of sunlight is about 35 degree | times, the fall of power generation efficiency can be suppressed.

  The lower limit value of the total light transmittance at an incident angle of 0 degrees may be 85% or more, and more preferably 88% or more. The upper limit of the total light transmittance is preferably 99% or less, more preferably 95% or less, and still more preferably 90% or less. The lower limit value of the haze value at an incident angle of 0 degree may be 25% or more, more preferably 30% or more, and still more preferably 34% or more. The upper limit of the haze value is preferably 60% or less, preferably 55% or less, and more preferably 50% or less. By making the total light transmittance and the haze value within the above ranges, the effect of the present embodiment can be made more remarkable.

The resin-encapsulated sheet of the present embodiment preferably has at least a resin layer containing a thermoplastic resin having a density of 0.88 to 0.91 g / cm ³ or less and a melting point of 110 ° C. or less. Thereby, it can be set as the resin layer which was further excellent in the balance of transparency and heat laminating suitability whose total light transmittance and haze value are the said numerical range. Here, melting | fusing point is measured by the measuring method described in the Example mentioned later.

  The thermoplastic resin is more preferably at least one resin selected from the group consisting of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin resin. Among these, polyolefin resins are more preferable from the viewpoint of high total light transmittance and good sunlight transmittance.

  For example, since a resin-sealed sheet using EVA or the like uses a resin having a carboxylic acid group as a terminal group, there is a possibility that water vapor permeability increases and water vapor easily flows. Particularly, in EVA and the like, the side chain portion tends to be decomposed and easily detached, and the side chain portion tends to be an acidic group or a polar group, and thus tends to retain moisture. In contrast, by using at least one resin selected from the group consisting of an ethylene-aliphatic carboxylic acid ester copolymer, an ethylene copolymer containing glycidyl methacrylate, and a polyolefin resin as the thermoplastic resin. , Polarity can be suppressed, and excellent insulation can be obtained. As a result, it not only contributes to the improvement of the power generation efficiency of the solar cell module, but also has the advantages of being excellent in water vapor barrier properties and reliably sealing objects to be sealed (power generation cells, etc.) even under high temperature and high humidity. . In particular, when the crosslinking treatment is performed, these advantages become more remarkable.

  The ethylene-aliphatic carboxylic acid ester copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from an aliphatic carboxylic acid ester. The copolymerization can be performed by a known method such as a high-pressure method or a melting method, and a multisite catalyst, a single site catalyst, or the like can be used as a catalyst for the polymerization reaction. Moreover, in the said copolymer, the bond shape of each monomer is not specifically limited, The polymer which has bond shapes, such as a random bond and a block bond, can be used. From the viewpoint of optical properties, the copolymer is preferably a copolymer polymerized by random bonding using a high-pressure method.

  As the aliphatic carboxylic acid ester, for example, an ester bond of acrylic acid or methacrylic acid and an alcohol having 1 to 8 carbon atoms such as methanol or ethanol is preferably used, and copolymerization thereof with ethylene can be mentioned. These copolymers may be multi-component copolymers obtained by copolymerizing three or more monomers.

  In the ethylene-aliphatic carboxylic acid ester copolymer, the proportion of the aliphatic carboxylic acid ester in all monomers constituting the copolymer is preferably 3 to 35% by mass. MFR (190 ° C., 2.16 kg) is preferably 0.5 to 30 g / 10 min, more preferably 0.8 to 30 g / 10 min, and 1 to 25 g / 10 min. Further preferred. Here, MFR is measured by the measuring method described in the Example mentioned later.

  The ethylene copolymer containing glycidyl methacrylate refers to an ethylene copolymer and an ethylene terpolymer with glycidyl methacrylate having an epoxy group as a reaction site. For example, ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-vinyl acetate copolymer And an ethylene-glycidyl methacrylate-methyl acrylate copolymer. Since these have high reactivity of glycidyl methacrylate, they can exhibit stable adhesiveness, and they tend to have a low glass transition temperature and good flexibility.

  The polyolefin-based resin is preferably at least one selected from the group consisting of a polyethylene-based resin, a polypropylene-based resin, and a polybutene-based resin from the viewpoint of corrosivity and water vapor barrier properties, and from the viewpoint of cost, a polyethylene-based resin A resin is more preferable. Here, the polyethylene resin refers to a homopolymer of ethylene or a copolymer of ethylene and one or more other monomers. The polypropylene resin refers to a homopolymer of propylene or a copolymer of propylene and one or more other monomers. The polybutene resin refers to a homopolymer of butene or a copolymer of butene and one or more other monomers.

The resin layer preferably contains a polyethylene resin having a density of 0.88 to 0.91 g / cm ³ or less. By using a polyethylene-based resin having a density of 0.91 g / cm ³ or less, it is possible to greatly improve transparency due to high gap filling and high total light transmittance during thermal lamination. The lower limit of density, from the viewpoint of improving the ratio of diffuse light transmission, such as the haze value is high, is preferably 0.88 g / cm ³ or more, more not less 0.89 g / cm ³ or more preferable. From the viewpoint of further improving the transparency, different types of high-density polyethylene resins and the like are used for low-density polyethylene resins so that the resin layer has a density of 0.88 to 0.91 g / cm ³ . It is more preferable to use a resin in combination. More specifically, it is more preferable to add the high density polyethylene resin at a ratio of about 1 to 50% by mass with respect to the low density polyethylene resin.

  The polyethylene resin is more preferably a so-called linear low density polyethylene. By using linear low density polyethylene, the polarity can be further suppressed, and excellent insulating properties can be obtained. And it is excellent in water vapor | steam barrier property, and can seal a to-be-sealed object reliably under high temperature and high humidity. In particular, when the crosslinking treatment is performed, these advantages become more remarkable.

  The linear low-density polyethylene preferably has a melting point of 110 ° C. or lower from the viewpoint of processability of the resin-encapsulated sheet and suitability for thermal lamination, and in addition, MFR (190 ° C., 2.16 kg) is 0.5 to 30 g. / 10 minutes is more preferable, 0.8 to 30 g / 10 minutes is still more preferable, and 1.0 to 25 g / 10 minutes is still more preferable. Here, MFR is measured by the method described in the Example mentioned later.

  Linear low-density polyethylene can be polymerized using known catalysts such as single-site catalysts and multi-site catalysts, but the content of low-molecular components can be suppressed, and low-density resins can be efficiently used. From the viewpoint of synthesis, etc., it is preferable to perform polymerization using a single site catalyst. The single-site catalyst is not particularly limited, and a known one can be used. Examples thereof include metal complexes having a cyclopentacene ring. A commercial item can also be used for these.

  The resin layer preferably contains substantially no organic peroxide. Therefore, since there is no restriction on the temperature at the time of manufacturing the sheet, the sheet temperature at the time of forming the sheet or at the time of embossing described later can be increased. As a result, the film forming speed, the embossing speed, etc. can be improved, and the productivity is excellent. Examples of such organic peroxides include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, and n-butyl. Examples include -4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane, and the like.

  The resin layer of the resin sealing sheet is preferably subjected to a crosslinking treatment. Thereby, good heat resistance can be imparted to the sheet without separately performing a long-time heat curing step. Furthermore, the crosslinking treatment is preferably performed by irradiating with ionizing radiation. In this embodiment, since it is not necessary to use an organic peroxide for the crosslinking treatment, gas generation due to thermal decomposition of the organic peroxide is small, and corrosion damage such as a vacuum pump and oil stains are suppressed. be able to. In the present embodiment, “crosslinking treatment” refers to a resin layer in a state where the gel fraction is preferably 3% by mass or more as a result of physical or chemical crosslinking of the polymer constituting the resin.

  In the resin-encapsulated sheet in the present embodiment, the gel fraction in the sheet thickness direction is appropriately controlled by the irradiation intensity (acceleration voltage) of ionizing radiation and the irradiation density. The irradiation intensity (acceleration voltage) indicates how deep electrons can reach in the thickness direction of the sheet, and the irradiation density indicates how many electrons are irradiated per unit area. Examples of crosslinking by irradiation with ionizing radiation include a method in which ionizing radiation such as α-ray, β-ray, γ-ray, neutron beam, and electron beam is irradiated to the resin sealing sheet for crosslinking. The acceleration voltage of ionizing radiation such as an electron beam can be appropriately adjusted according to the resin layer subjected to the crosslinking treatment. The irradiation dose of ionizing radiation varies depending on the resin used, but is generally less than 3 kGy. It tends to be difficult to uniformly cross-link the entire resin-encapsulated sheet.

  The gel fraction is preferably 3% by mass or more and 70% by mass or less, more preferably 3% by mass or more and 60% by mass or less, and further preferably 3% by mass or more and 50% by mass or less. By setting the gel fraction within the above range, it is possible to further improve the performance of sealing the level difference of the object to be sealed such as the power generation element and wiring (gap filling property) and to exhibit creep resistance. can do. In addition, even if it is a case where the resin sealing sheet has a single layer structure or a multilayer structure described later, the gel fraction is the average gel fraction of the entire resin sealing sheet (all layer gel fraction). Means the value of

The gel fraction of the resin sealing sheet can be obtained by the following formula from the ratio of the insoluble portion after extracting the resin sealing sheet in boiling p-xylene for 12 hours.
Gel fraction (mass%) = (sample weight after extraction / sample weight before extraction) × 100

  The resin layer constituting the resin sealing sheet in the present embodiment may further include an ionizing radiation-disintegrating resin. The ionizing radiation decay type resin refers to a resin having a property of decaying by irradiation with ionizing radiation such as α rays, β rays, γ rays, neutron rays, and electron beams.

  Examples of the ionizing radiation disintegrating resin include disintegrating resins in which a functional group is bonded to the α-position of the C—C bond of the main chain. Examples of the functional group include a halogen atom, a hydroxy group, a nitro group, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted amino group, and an optionally substituted group. Examples include at least one selected from the group consisting of a carboxyl group, an optionally substituted amide group, and an optionally substituted aryl group.

  Here, the alkyl group, alkoxy group, amino group, carboxyl group, amide group, and aryl group may be substituted with one or more substituents at substitutable positions. Examples of the substituent include a halogen atom (eg, fluorine atom, chlorine atom, bromine atom), an alkyl group having 1 to 6 carbon atoms (eg, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl). Group, sec-butyl group, tert-butyl group, pentyl group, hexyl group), aryl group (for example, phenyl group, naphthyl group), aralkyl group (for example, benzyl group, phenethyl group), alkoxy group (for example, methoxy group) Ethoxy group) and the like.

  Specifically, the ionizing radiation decay type resin is selected from the group consisting of polypropylene, polyisobutylene, poly α-methylstyrene, tetrafluoroethylene, polymethyl methacrylate, polyacrylamide, polymethyl glycidyl methacrylate, and cellulose. There is at least one kind.

  The resin constituting the resin sealing sheet may contain an ionizing radiation cross-linking resin having both a crosslinkable portion and a disintegratable portion. Examples of such a resin include an ethylene copolymer containing glycidyl methacrylate, an ethylene copolymer containing polypropylene, an ethylene copolymer containing methyl methacrylate, an ethylene copolymer containing glycidyl methacrylate, and an ethylene copolymer containing isoprene rubber. , Ethylene copolymers containing butadiene rubber, ethylene copolymers containing styrene-butadiene copolymer rubber, and the like.

  The ethylene copolymer containing glycidyl methacrylate refers to an ethylene copolymer and an ethylene terpolymer with glycidyl methacrylate having an epoxy group as a reaction site. For example, ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-vinyl acetate copolymer And an ethylene-glycidyl methacrylate-methyl acrylate copolymer. Since these have high reactivity of glycidyl methacrylate, they can exhibit stable adhesiveness, tend to have a low glass transition temperature and good flexibility.

  The resin sealing sheet of the present embodiment may have either a single layer structure or a multilayer structure. Hereinafter, each structure will be described. Here, when the resin sealing sheet has a multilayer structure, the surface layer of the resin sealing sheet is referred to as a “surface layer”, and the other layers are referred to as “inner layers” (in the case of three or more layers). That is, two layers forming both surfaces of the resin sealing sheet are “surface layers”. For example, in the case of a multilayer structure consisting of two layers, the structure is composed of two surface layers, but one surface layer and the other surface layer may be the same component or different components. Also good.

[Single layer structure]
When the resin-encapsulated sheet has a single-layer structure, from the viewpoint of ensuring good transparency, flexibility, adhesion of the adherend and handleability, an ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-fat It is preferably a layer containing at least one resin selected from the group consisting of group unsaturated carboxylic acid ester copolymers and polyolefin resins.

  When the resin layer constituting the resin encapsulating sheet contains an ethylene-vinyl acetate copolymer saponified product or an ethylene-vinyl acetate-acrylic acid ester copolymer saponified product as an adhesive resin, the degree of saponification And content can be adjusted suitably and, thereby, adhesiveness with a to-be-sealed thing can be controlled. From the viewpoint of adhesiveness and optical properties, the content of the saponified ethylene-vinyl acetate copolymer and saponified ethylene-vinyl acetate-acrylate copolymer in the resin layer is 3 to 60% by mass. Preferably, it is 3-55 mass%, More preferably, it is 5-50 mass%.

[Multilayer structure]
The resin sealing sheet of the present embodiment preferably has a multilayer structure. By setting it as a multilayer structure, the physical property of a resin sealing sheet can be improved by providing a different function for every layer. When the resin layer of the resin sealing sheet has a multilayer structure, the total light transmittance at an incident angle of 0 degrees as a whole is 85% or more, and the haze value at an incident angle of 0 degrees is 25% or more. However, among them, it is preferable that any one of the layers contains a linear low density polyethylene having a density of 0.88 to 0.91 g / cm ³ or less and is subjected to a crosslinking treatment.

  In the present embodiment, the adhesive resin is selected from the group consisting of a saponified ethylene-vinyl acetate copolymer, a saponified ethylene-vinyl acetate-acrylic ester copolymer, and a saponified ethylene-glycidyl methacrylate copolymer. It is preferable that the resin layer containing at least one kind is formed as a layer (at least one surface layer) in contact with the object to be sealed.

  The surface layer may be a layer composed only of the saponified product described above. However, from the viewpoint of ensuring good transparency, flexibility, adhesion and handling properties of the adherend, the saponified product and the ethylene-vinyl acetate copolymer are used. A layer composed of a mixed resin of at least one resin selected from the group consisting of a coalescence, an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-aliphatic unsaturated carboxylic acid ester copolymer, and a polyolefin resin. Preferably there is. Although content of adhesive resin in a surface layer is not specifically limited, From an adhesive viewpoint, 5-50 mass% is preferable, 5-40 mass% is more preferable, 5-35 mass% is further more preferable.

  The ethylene-aliphatic unsaturated carboxylic acid copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from aliphatic unsaturated carboxylic acids. Examples of the ethylene-aliphatic unsaturated carboxylic acid copolymer include an ethylene-acrylic acid copolymer (hereinafter abbreviated as “EAA”) and an ethylene-methacrylic acid copolymer (hereinafter, “EMAA”). Abbreviated).

  The ethylene-aliphatic unsaturated carboxylic acid ester copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from an aliphatic unsaturated carboxylic acid ester. Examples of the ethylene-aliphatic unsaturated carboxylic acid ester copolymer include an ethylene-acrylic acid ester copolymer and an ethylene-methacrylic acid ester copolymer. Here, as acrylic acid ester and methacrylic acid ester, ester with C1-C8 alcohols, such as methanol and ethanol, is used suitably.

  These copolymers may be multi-component copolymers obtained by copolymerizing three or more monomers. Examples of the multi-component copolymer include a copolymer obtained by copolymerizing at least three types of monomers selected from ethylene, aliphatic unsaturated carboxylic acid, and aliphatic unsaturated carboxylic acid ester.

  As the polyolefin resin, the above-described polyolefin resin can be used, and examples thereof include a polyethylene resin, a polypropylene resin, and a polybutene resin.

  Moreover, when a resin sealing sheet has a multilayer structure, it is preferable that ionizing radiation decay type resin is contained in the layer (at least 1 layer of a surface layer) which contacts a to-be-sealed thing. If the layer of the resin sealing sheet that comes into contact with the object to be sealed contains an ionizing radiation-disintegrating resin, the ability to seal a step such as a power generation element or wiring without gaps (gap filling property) is improved. There is a tendency.

  When the ionizing radiation-disintegrating resin is contained in the layer in contact with the object to be sealed, the content of the ionizing radiation-disintegrating resin in the layer in contact with the object to be sealed is preferably 5 to 80% by mass. More preferably, it is 7-70 mass%, More preferably, it is 8-60 mass%.

  When the layer in contact with the object to be sealed contains an ionizing radiation-disintegrating resin, the gel fraction of the layer (surface layer) in contact with the object to be sealed is preferably less than 3% by mass, more preferably 2% by mass. The content is 0.1% by mass or more, more preferably 1% by mass or less and 0.1% by mass or more. If the gel fraction of the layer in contact with the object to be sealed is less than 3% by mass, the gap filling property tends to be good, and if it is 0.1% by mass or more, the resin can be used even in a high temperature state such as summer. It tends to be stable without melting and the material to be sealed flowing.

The density of the surface layer in contact with the object to be sealed is preferably 0.87 g / cm ³ or more from the viewpoint of blocking, and 0.96 g / cm ³ or less from the viewpoint of cushioning and transparency. preferable. It is also effective to reduce the surface contact area by a known embossing method as a method for preventing blocking. The layer ratio of the surface layer in contact with the object to be sealed preferably has a thickness of at least 5% with respect to the total thickness of the resin sealing sheet from the viewpoint of ensuring good adhesiveness. When the thickness is 5% or more, the same adhesiveness as in the case of the single layer structure described above tends to be obtained.

  The resin constituting the inner layer is not particularly limited, and any other resin may be used in addition to the resin suitably used for the surface layer described above. For the purpose of imparting other functions to the inner layer, resin materials, mixtures, additives, and the like can be appropriately selected. For example, for the purpose of newly imparting cushioning properties, a layer containing a thermoplastic resin may be provided as the inner layer.

  Examples of the thermoplastic resin used as the inner layer include polyolefin resins, styrene resins, vinyl chloride resins, polyester resins, polyurethane resins, chlorinated ethylene polymer resins, polyamide resins, and the like. It includes those possessed and plant-derived raw materials. Among the above, a hydrogenated block copolymer resin, a propylene copolymer resin, and an ethylene copolymer resin that have good compatibility with the crystalline polypropylene resin and good transparency are preferable, and a hydrogenated block copolymer. A resin and a propylene-based copolymer resin are more preferable.

  As the hydrogenated block copolymer resin, a block copolymer of vinyl aromatic hydrocarbon and conjugated diene is preferable. Examples of vinyl aromatic hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, and 1,1-diphenyl. Examples thereof include ethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene, and styrene is particularly preferable. These may be used alone or in combination of two or more. The conjugated diene is a diolefin having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3- Examples include butadiene, 1,3-pentadiene, and 1,3-hexadiene. These may be used alone or in combination of two or more.

  As the propylene-based copolymer resin, a copolymer obtained from propylene and ethylene or an α-olefin having 4 to 20 carbon atoms is preferable. The content of the ethylene or α-olefin having 4 to 20 carbon atoms is preferably 6 to 30% by mass. Examples of the α-olefin having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-pentene and 1-decene. 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like.

  The propylene-based copolymer resin may be polymerized using a multi-site catalyst, a single-site catalyst, or any other catalyst. Further, a propylene-based copolymer in which the crystal / amorphous structure (morphology) of the polymer is controlled in nano order can be used.

  The ethylene copolymer resin may be polymerized with any of a multisite catalyst, a single site catalyst, and other catalysts. Further, an ethylene copolymer in which the crystal / amorphous structure (morphology) of the polymer is controlled in nano order can be used.

When a polyethylene resin is used as the material for the inner layer, the density of the polyethylene resin is preferably 0.88 to 0.91 g / cm ³ . From the viewpoint of transparency with a high total light transmittance, it is preferably 0.91 g / cm ³ or less, and from the viewpoint of a high ratio of haze value or diffused light transmittance, 0.88 g / cm ³ or more is preferable.

  In addition, the resin sealing sheet has a structure in which one or more layers of the same component are laminated on both sides of a central layer (layer located at the center of the multilayer structure) so as to be symmetrical with respect to the central layer. You may have. As such a resin sealing sheet, for example, a resin sealing sheet composed of two surface layers (hereinafter sometimes referred to as “skin layer”) and three inner layers, Examples thereof include a resin-encapsulated sheet in which the surface layer is composed of the same component, and two inner layers adjacent to the surface layer (hereinafter sometimes referred to as “base layer”) are composed of the same component.

  In the resin sealing sheet having the above structure, the film thickness of the surface layer is preferably 5 to 40% with respect to the film thickness of the entire resin sealing sheet, and the film thickness of the base layer is the entire resin sealing sheet. The film thickness of the inner layer sandwiched between the base layers (hereinafter sometimes referred to as “core layer”) is preferably 50 to 90% of the film thickness of the resin encapsulated sheet. It is preferable that it is 5 to 40% with respect to the thickness.

<Solar cell module>
It can be set as a solar cell module using the resin sealing sheet of this Embodiment. FIG. 2 is a schematic cross-sectional view of one aspect of the solar cell module of the present embodiment. That is, the solar cell module 2 according to the present embodiment includes a translucent insulating substrate 20, a back insulating substrate 22, and a power generation element 24 disposed between the translucent insulating substrate 20 and the back insulating substrate 22. And a resin sealing sheet 26 that seals the power generating element 24.

(Translucent insulating substrate)
There are no particular restrictions on the light-transmitting insulating substrate, but because it is located on the outermost layer of the solar cell module, long-term reliability in outdoor exposure of the solar cell module, including weather resistance, water repellency, contamination resistance, mechanical strength, etc. It is preferable to provide performance for ensuring the performance. Moreover, in order to utilize sunlight effectively, it is preferable that it is a highly transparent member with a small optical loss.

  Examples of the material of the translucent insulating substrate include a resin film made of polyester resin, fluororesin, acrylic resin, cyclic olefin (co) polymer, ethylene-vinyl acetate copolymer, and a glass substrate. A glass substrate is preferable from the viewpoint of a balance between weather resistance, impact resistance, and cost.

  Particularly suitable as the resin film is a polyester resin excellent in transparency, strength, cost and the like, particularly a polyethylene terephthalate resin.

  A fluororesin having particularly good weather resistance is also preferably used. Specifically, tetrafluoroethylene-ethylene copolymer (ETFE), polyvinyl fluoride resin (PVF), polyvinylidene fluoride resin (PVDF), polytetrafluoroethylene resin (TFE), tetrafluoroethylene-6 Examples thereof include a fluorinated propylene copolymer (FEP) and a poly (trifluorotrifluoroethylene resin) (CTFE). Polyvinylidene fluoride resin is preferable from the viewpoint of weather resistance, but tetrafluoroethylene-ethylene copolymer is preferable from the viewpoint of achieving both weather resistance and mechanical strength. Moreover, it is preferable to perform a corona treatment and a plasma treatment to a translucent insulated substrate for the improvement of adhesiveness with the material which comprises other layers, such as a resin sealing sheet. In order to improve mechanical strength, it is also possible to use a sheet that has been subjected to stretching treatment, for example, a biaxially stretched polypropylene sheet.

  When a glass substrate is used as the translucent insulating substrate, the total light transmittance of light having a wavelength of 350 to 1400 nm is preferably 80% or more, and more preferably 90% or more. As such a glass substrate, it is common to use white plate glass with little absorption in the infrared part, but even blue plate glass has little influence on the output characteristics of the solar cell module if the thickness is 3 mm or less. Further, tempered glass can be obtained by heat treatment to increase the mechanical strength of the glass substrate, but float plate glass without heat treatment may be used. In order to suppress reflection on the light receiving surface side of the glass substrate, an antireflection coating may be applied.

(Back insulation substrate)
Although there is no restriction | limiting in particular as a back surface insulating substrate, Since it is located in the outermost layer of a solar cell module, various characteristics, such as a weather resistance and mechanical strength, are calculated | required similarly to the above-mentioned translucent insulating substrate. Therefore, you may comprise a back surface insulating board | substrate with the material similar to a translucent insulating board | substrate. That is, the above-described various materials that can be used in the light-transmitting insulating substrate can also be used in the back insulating substrate. In particular, a polyester resin and a glass substrate can be preferably used, and among these, a polyethylene terephthalate resin (PET) is more preferable from the viewpoint of weather resistance and cost.

  Since the back insulating substrate is not premised on the passage of sunlight, the transparency (translucency) required for the translucent insulating substrate is not necessarily required. Therefore, a reinforcing plate may be attached to increase the mechanical strength of the solar cell module or to prevent distortion and warpage due to temperature change. For example, a steel plate, a plastic plate, an FRP (glass fiber reinforced plastic) plate or the like can be preferably used.

  The back insulating substrate may have a multilayer structure composed of two or more layers. Examples of the multilayer structure include a structure in which one or more layers of the same component are laminated on both sides of the central layer so as to be symmetrically arranged with respect to the central layer. As what has such a structure, PET / alumina vapor deposition PET / PET, PVF (brand name: Tedlar) / PET / PVF, PET / AL foil / PET etc. are mentioned, for example.

(Power generation element)
The power generation element is not particularly limited as long as it can generate power using the photovoltaic effect of the semiconductor. For example, silicon (single crystal system, polycrystalline system, amorphous system), compound semiconductor (3- Group 5, 2-6, etc.) can be used, and among these, polycrystalline silicon is preferred from the viewpoint of balance between power generation performance and cost.

(Method for manufacturing solar cell module)
There is no restriction | limiting in particular as a manufacturing method of the solar cell module in this Embodiment, For example, it overlaps in order of a translucent insulated substrate / resin sealing sheet a / electric power generation element / resin sealing sheet b / back surface insulating substrate, and vacuum It can be produced by vacuum lamination using a laminator at 150 ° C. for 15 minutes. In particular, the resin sealing sheet of the present embodiment is preferably used at least as the resin sealing sheet a that fills the gap between the power generation element and the translucent insulating substrate. Since sunlight reaches the power generation element through the resin sealing sheet of the present embodiment, it can contribute to the improvement of power generation efficiency effectively.

  The thickness of each member in the solar cell module is not particularly limited, but the thickness of the translucent insulating substrate is preferably 3 mm or more from the viewpoint of weather resistance and impact resistance, and the thickness of the back insulating substrate is insulating. Preferably from the viewpoint of 75 μm or more, the thickness of the power generation element is preferably 140 to 250 μm from the viewpoint of balance between power generation performance and cost, and the thickness of the resin sealing sheet is preferably from the viewpoint of cushioning and sealing properties 250 μm or more.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

The resins used in this example are as follows.
(1) Linear very low density polyethylene (VL)
VL1: affinity EG8200G, manufactured by Dow Chemical Co. (MFR = 5.0 g / 10 min, specific gravity = 0.870 g / cm ³ , melting point = 63 ° C.)
VL2: Affinity PF1140G, manufactured by Dow Chemical Company (MFR = 1.6 g / 10 min, specific gravity = 0.897 g / cm ³ , melting point = 96 ° C.)
VL3: affinity KC8852G, manufactured by Dow Chemical Co. (MFR = 3.0 g / 10 min, specific gravity = 0.875 g / cm ³ , melting point = 68 ° C.)
VL4: Affinity EG8100G, manufactured by Dow Chemical Co. (MFR = 1.0 g / 10 min, specific gravity = 0.870 g / cm ³ , melting point = 55 ° C.)
VL5: Evolue SP0510G, manufactured by Prime Polymer Co., Ltd. (MFR = 1.2 g / 10 min, specific gravity = 0.903 g / cm ³ , melting point = 98 ° C.)

(2) Ethylene-vinyl acetate copolymer (EVA)
EVA1: Ultrasen 751, manufactured by Tosoh Corporation (MFR = 0.8 g / 10 min, specific gravity = 0.950 g / cm ³ , melting point = 85 ° C., VA = 20 mass%)

(3) Ethylene-vinyl acetate-glycidyl methacrylate copolymer (EVA-GMA copolymer)
BF: Bond First 7B, manufactured by Sumitomo Chemical Co., Ltd. (MFR = 7.0 g / 10 min, specific gravity = 0.950 g / cm ³ , melting point = 95 ° C., GMA = 12 mass%, VA = 5 mass%)

<Preparation of resin encapsulated sheet>
Using the resins shown in the table, the resin was melted using three extruders, the resin was melt-extruded into a tube shape from an annular die connected to the extruder, and the tube formed by melt extrusion was directed upward A film was formed by the direct inflation method, and the molten resin sheet was cooled and solidified using cold air to obtain a resin sheet.
Next, the cooled and solidified resin sheet was subjected to embossing by passing the resin sheet softened by main heating with an infrared heater between a backup roll and an embossing roll. The obtained resin-encapsulated sheet (embossed sheet) was subjected to a crosslinking treatment using an EPS-800 electron beam irradiation apparatus (manufactured by Nisshin High Voltage). Electron beam processing was performed.

<Production of solar cell module>
Using the obtained resin encapsulating sheet, AGC-made white plate glass with embossment for solar cell as a transparent protective material (thickness 3.2 mm × width 700 mm × length 1000 mm, sealing material surface has 150 μm emboss), power generation element As a backside protective material (back sheet), PVF (40 μm thickness) / PET (250 μm thickness) / PVF (40 μm) manufactured by Mitsubishi Aluminum Packaging Co., Ltd. (Thickness) was used to produce a solar cell module. Six 6-inch polycrystalline cells are arranged in 16 sheets (4 rows x 4 sheets), transparent substrate (transparent protective material) / resin sealing sheet (a) / power generation element (250 μm) / resin sealing sheet (b) / back A solar cell module is manufactured by stacking sheets (back surface protective materials) in this order and vacuum laminating using a LM type vacuum laminating apparatus (NPC) under laminating conditions of 150 ° C. residual heat for 5 minutes and pressing for 5 minutes. A test was conducted.

<Total light transmittance and haze value>
Based on ASTM D-1003, it measured with Nippon Denshoku Industries haze meter (turbidity meter) NDH2000. As a sample for evaluation, a glass plate for solar cells (white glass 5 cm × 10 cm square by AGC, thickness: 3 mm) / resin sealing sheet / glass plate for solar cells was laminated in this order, and an LM type vacuum laminator (NPC) ) Was used for vacuum lamination. In general, measurement is performed with the sample placed upright so that it is perpendicular to the light source of the haze meter (with the incident light angle at the power generation element being 0 degrees), but in addition, the incident light on the sample is tilted. The optical properties were measured even when the angle was 35 degrees.
Total light transmittance Tt (= Td + Tp)
Diffuse light transmittance Td (Dfs)
Parallel light transmittance Tp (Pt)
Haze value (haze): Scattered light transmittance [= (total light transmittance−parallel light transmittance) / total light transmittance]

The melting point was measured according to JIS-K-7121.
The density was measured according to JIS-K-7112.
The melt flow rate (MFR; 190 ° C., 2.16 kg) was measured according to JIS-K-7210.

<Power generation>
With a module tester NMS-300R (NPC), 16 power generation elements connected in series before module manufacture and power generation performance after module manufacture were measured. Normally, the module is placed upright and perpendicular to the light source of the module tester (the incident light angle to the power generation element is 0 degrees) to measure the power generation performance. In addition, the module or power generation element is tilted. Thus, the power generation performance was measured even when the incident light angle to the power generation element was 23 degrees and 35 degrees.

  According to the table, it was confirmed that the increase rate of the power generation amount (Pmax) at the incident light angle of 35 degrees was large in each example. Further, even when compared with the prior art of Comparative Example 1, it was confirmed that the power generation amount was greatly improved in each Example. From the above, it was confirmed that the resin-encapsulated sheet of this example can be a solar cell module that can suppress a decrease in the amount of power generation even when the incident angle of sunlight is low.

  The resin sealing sheet according to the present invention has industrial applicability as a sealing material for sealing various members such as elements constituting a solar cell.

1,26 Resin encapsulating sheet 2 Solar cell module 20 Translucent insulating substrate 22 Back insulating substrate 24 Power generation element α Incident angle

Claims (8)

  A resin-encapsulated sheet having a total light transmittance of 85% or more at an incident angle of 0 degrees and a haze value of 25% or more at an incident angle of 0 degrees. The resin-encapsulated sheet according to claim 1, which has at least a resin layer containing a thermoplastic resin having a density of 0.88 to 0.91 g / cm ³ or less and a melting point of 110 ° C. or less.   The said thermoplastic resin is at least 1 sort (s) of resin selected from the group which consists of ethylene-aliphatic carboxylic acid ester copolymer, ethylene copolymer containing glycidyl methacrylate, and polyolefin resin. Resin sealing sheet.   The resin-sealed sheet according to claim 2 or 3, wherein the thermoplastic resin is linear low-density polyethylene.   It is a multilayer structure, The resin sealing sheet as described in any one of Claims 1-4.   The resin sealing sheet as described in any one of Claims 1-5 in which the crosslinking process was given.   The resin sealing sheet according to claim 6, wherein the crosslinking treatment is performed by electron beam irradiation. A translucent insulating substrate;
A back insulating substrate;
A power generating element disposed between the translucent insulating substrate and the back insulating substrate;
The resin sealing sheet according to any one of claims 1 to 7, which seals the power generation element,
A solar cell module comprising:

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