JP2011091346A - Solar cell back sheet and solar cell module using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a colored solar cell back sheet which is improved in the power generation efficiency of a solar cell module, excellent in design performance, and minimally suppressed in the deterioration of the long-term performance of water-vapor shielding performance, electric insulating performance, mechanical strength, adhesive properties, etc., and also the solar cell module using the back sheet. <P>SOLUTION: A light reflective polyester film, a colored resin film, and a hydrolytic-resistive and low-molecular weight analytic resistive polyester film which includes thin-film layers of a metal oxide layer are laminated in this order to form an integrated single solar cell back sheet. The solar cell module uses the solar cell back sheet. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

Detailed Description of the Invention

Industrial application fields

The present invention relates to a solar cell backsheet and a solar cell module using the backsheet, and more specifically, improves the power generation efficiency of the solar cell module, and has excellent design, water vapor barrier, electrical insulation, The present invention relates to a colored solar cell backsheet and a solar cell module using the same, which have minimized long-term performance degradation such as mechanical strength and adhesiveness.

In recent years, solar cells as a clean energy source have attracted attention due to increasing awareness of environmental problems. In general, a solar battery module manufactures, for example, a crystalline silicon solar battery cell, an amorphous silicon solar battery cell, etc., and a surface glass plate, a sealing resin, a solar battery cell, a sealing resin, and a back sheet in this order. It is manufactured by using a lamination method in which layers are stacked, vacuum sucked and heat-pressed.

In order to further promote the use of solar cells, it is necessary to reduce power generation costs, reduce the cost of solar cell modules, reduce the installation area, and so on, and to improve the power generation efficiency of solar cell modules. Yes. The light incident on the solar cell module passes through the solar cell itself or the gap between the solar cells, and the total amount does not necessarily contribute to power generation. It is known that the passing light is reflected by the back sheet and returned to the solar cell to improve the power generation efficiency of the solar cell module, and a back sheet having excellent light reflectivity is required.

Solar cell modules are used not only for industrial purposes but also for home use, and are used in various architectural fields. As the application of solar cell modules progresses, the design properties of solar cell modules that are in balance with existing buildings are gaining importance. That is, the solar cell module is required to be colored in various hues such as white, black, and blue, and for this reason, the backsheet is required to be colored in such a hue.

As a backsheet constituting the solar cell module, a plastic base material having excellent strength is currently most commonly used. Thus, the backsheet for the solar cell module is excellent in strength and has various properties such as weather resistance, heat resistance, water resistance, light resistance, chemical resistance, light reflectivity, and designability. It must be excellent. In particular, it is required to be excellent in defensive properties for preventing intrusion of moisture, oxygen, etc., extremely durable, and to have high protective ability.

In other words, it is colored to increase the power generation efficiency of the solar cell module and to have excellent design properties, minimizing long-term performance degradation such as water vapor barrier properties, electrical insulation properties, mechanical strength, adhesiveness, etc. There is a need for solar cell backsheets.

Conventionally, as a light-reflective back sheet, a structure in which a light-reflective film 121 and a vapor deposition film 122 are bonded together with an adhesive 123 as shown in FIG. 10 has been proposed (see Patent Document 1). Here, the light reflective film 121 is a white film. In FIG. 10, 1221 is a resin film, and 1222 is a vapor deposition layer. Moreover, the structure which formed the light reflective layer by the printing method on the vapor deposition film is also proposed (refer patent document 2).

Conventionally, as another example of a light-reflective backsheet, a configuration in which a white polyester film 131, a vapor deposition film 132, and a transparent polyester film 133 are bonded together with an adhesive 134 as shown in FIG. Reference 3). In FIG. 11, 1321 is a base film and 1322 is an inorganic oxide thin film layer. Moreover, the structure which bonded together the vapor deposition film and base material film which provided the light-reflective white ink layer with the adhesive agent is also proposed (refer patent document 4).

Conventionally, as another example of a light-reflective back sheet, as shown in FIG. 12, a white resin film 141, a metal oxide-adhered resin film 142, and a hydrolysis-resistant resin film 143 are bonded together with an adhesive 144. A configuration has been proposed (see Patent Document 5). In FIG. 12, 1421 is a base film, 1422 is a vapor deposition layer, and the metal oxide-coated resin film 142 is a so-called vapor deposition film. The configuration of the back sheet is basically the same as that shown in FIG.

Below, patent documents are described.
JP 2000-114564 A JP 2001-144309 A JP 2006-253264 A JP 2006-210557 A Japanese Patent Laid-Open No. 2002-100788

All of these conventional techniques have a configuration in which both are directly opposed without interposing another film between a white film or a white layer as a light reflecting film and a vapor deposition film. Here, the vapor deposition film of the prior art mainly serves as a water vapor barrier property of the back sheet, and is not intended for light reflectivity and coloring. Further, as a means for whitening, white pigments, fine foams, fine hollow cores, and the like have been proposed. However, description is not recognized about the colored back sheet, such as interposing a colored resin film, and means for coloring. That is, these conventional techniques are intended to enhance the light reflectivity of the solar cell backsheet, but are not intended to color the backsheet, that is, to improve the design of the backsheet.

Generally, a solar cell module is produced by laminating a surface glass plate, a sealing resin, a solar cell, a sealing resin, and a back sheet in this order, vacuum suction, and thermocompression bonding. At this time, the back sheet is in direct contact with the sealing resin. Thus, the sealing resin is usually an ethylene-vinyl acetate copolymer (EVA), which deteriorates over a long period of use and generates a trace amount of gas such as acetic acid. If the colored resin film, which is a constituent element of the back sheet, is in direct contact with the sealing resin, the hue and color density of the colored resin film may change. Further, the colorant in the colored resin film may move to the sealing resin and the sealing resin may be colored. That is, there is a possibility that the function and designability of the back sheet may be deteriorated or the function of the sealing resin may be deteriorated.

Problems to be solved by the invention

The present invention has been made to solve the problems based on the above technical background, and enhances the power generation efficiency of the solar cell module, and has excellent design properties, water vapor barrier properties, electrical insulation properties, It is an object of the present invention to provide a colored solar cell backsheet and a solar cell module using the same, in which long-term performance deterioration such as mechanical strength and adhesiveness is minimized.

That is, the present invention laminates a hydrolysis-resistant and low-molecular weight precipitation-resistant polyester film provided with a light-reflective polyester film, a colored resin film and a thin film layer made of a metal oxide in this order. The present invention provides a back sheet for a solar cell and a solar cell module using the same.

Means for solving the problem

The present invention employs the following means in order to solve such problems.
That is,
The invention according to claim 1
A hydrolysis-resistant and low-molecular weight precipitation-resistant polyester film provided with a light-reflective polyester film, a colored resin film, and a thin film layer made of a metal oxide is laminated and integrated in this order. A solar cell backsheet.

The invention according to claim 2
2. The solar cell backsheet according to claim 1, wherein the light-reflective polyester film contains one or more selected from the group consisting of white pigments, microballoons, fine bubbles, fine particles and the like. .

The invention according to claim 3
2. The solar cell backsheet according to claim 1, wherein the light-reflective polyester film has a light-reflective layer provided on the polyester film.

The invention according to claim 4
4. The solar cell backsheet according to claim 3, wherein the light reflective layer comprises a mirror ink and / or a white pigment coating layer.

The invention according to claim 5
The said light reflective layer consists of a metal thin film and / or a dielectric thin film, The solar cell backsheet of Claim 3 characterized by the above-mentioned.

The invention according to claim 6
4. The solar cell backsheet according to claim 3, wherein the light reflective layer is at least one selected from the group consisting of a bubble-containing resin film, a microballoon-containing resin film, a fine particle-containing resin film, and the like. It is.

The invention according to claim 7 provides:
2. The solar cell backsheet according to claim 1, wherein the polyester of the light-reflective polyester film is polyethylene terephthalate.

The invention according to claim 8 provides:
2. The solar cell backsheet according to claim 1, wherein fine irregularities are provided on a light reflecting surface of the light reflecting polyester film.

The invention according to claim 9 is:
2. The solar cell backsheet according to claim 1, wherein the colored resin film is colored in a hue selected from white, black, and blue.

The invention according to claim 10 is:
The solar cell backsheet according to claim 9, wherein the colored resin film is coated and / or kneaded with a colorant selected from white, black, and blue.

The invention according to claim 11 is:
The solar cell backsheet according to claim 1, wherein the resin of the colored resin is polyester.

The invention according to claim 12
The back sheet for a solar cell according to claim 11, wherein the polyester is polyethylene terephthalate.

The invention according to claim 13 is:
2. The metal oxide is one or more metal oxides selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, zinc oxide, and tin oxide. It is a solar cell backsheet as described in.

The invention according to claim 14 is:
2. The solar cell backsheet according to claim 1, wherein the hydrolysis-resistant and low-molecular weight precipitation-resistant polyester is polyethylene terephthalate.

The invention according to claim 15 is:
The back sheet for solar cell according to claim 14, wherein the polyethylene terephthalate has an oligomer content of 0.8 wt% or less.

The invention according to claim 16 provides:
The hydrolysis-resistant and low-molecular-weight-precipitating polyester film provided with the light-reflective polyester film, the colored resin film, and the thin film layer made of the metal oxide is laminated in this order to form an adhesive. The back sheet for a solar cell according to claim 1, wherein the back sheet is integrated with a solar cell.

The invention according to claim 17 provides:
The solar cell backsheet according to claim 1, wherein an easy adhesion treatment layer is provided on the light-reflective polyester film.

The invention according to claim 18
2. The solar cell backsheet according to claim 1, wherein the elongation at break after treatment for 3000 hours is 50% or more in an environment of a temperature of 85 ° C. and a humidity of 85%.

The invention according to claim 19 is
2. The solar cell backsheet according to claim 1, wherein the alternating current withstand voltage holding ratio after treatment for 3000 hours is 50% or more in an environment of temperature 85 ° C. and humidity 85%.

The invention according to claim 20 provides
It is a solar cell module using the solar cell backsheet in any one of Claims 1-19.

The solar cell backsheet of the present invention is a hydrolysis-resistant and low-molecular weight precipitation-resistant polyester film provided with a light-reflective polyester film, a colored resin film, and a thin film layer made of a metal oxide. It is the structure which laminated | stacked and integrated in this order.

FIG. 1 is a cross-sectional view of a solar cell backsheet 1 of the present invention. 2 is a light-reflective polyester film, 3 is a colored resin film, 4 is a hydrolysis-resistant and low-molecular weight precipitation polyester film provided with a thin film layer made of a metal oxide, and laminated in this order. Then, they are integrated by the adhesive layer 5. The hydrolysis-resistant and low-molecular weight precipitation polyester film 4 provided with a thin film layer made of a metal oxide is a hydrolysis-resistant and low-molecular weight precipitation-resistant polyester film 41. The thin film layer 42 made of an oxide is provided.

The light-reflective polyester film constituting the solar cell backsheet of the present invention contains one or more selected from the group consisting of white pigments, microballoons, fine bubbles, fine particles and the like. By whitening the film with the white pigment, microvoids are generated in the film due to microballoons and microbubbles, and the microparticles themselves become reflectors, reflecting and scattering incident light. Alternatively, the light that has been diffused and passed through the solar cell can be effectively returned to the cell.

Examples of the white pigment used in the light-reflective polyester film constituting the back sheet for solar cells of the present invention include titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, zinc sulfide, and antimony trioxide. Inorganic pigments such as kaolin, talc and lithopone, and organic pigments such as crosslinked polystyrene resin, crosslinked acrylic resin, urea resin and melamine resin. One or more of these white pigments can be used. The amount used is 0.1% to 30% by weight based on the polyester.

The white pigment is previously added to a polyester resin composition (pellet) for film formation, and formed into a film by extrusion molding or the like. Thereby, the light-reflective polyester film in which the white pigment was kneaded uniformly in the whole film can be produced. Moreover, you may extend uniaxially or biaxially as needed. An example of a polyester film whitened with a white pigment is a biaxially stretched polyethylene terephthalate film having a thickness of 100 μm in which 8% by weight of titanium oxide is kneaded.

The microballoon used for the light-reflective polyester film constituting the solar cell backsheet of the present invention is a fine hollow sphere. Examples thereof include glass balloons, silica balloons, shirasu balloons, carbon balloons, alumina balloons, inorganic balloons such as zirconia balloons, and organic balloons such as phenol balloons and polyvinylidene chloride balloons. The diameter of the microballoon is 1 μm to 30 μm, and the amount used is 0.1 wt% to 30 wt% with respect to the polyester.

The microballoon is previously added to a polyester resin composition (pellet) for film formation, and formed into a film by extrusion molding or the like. Moreover, you may extend uniaxially or biaxially as needed. Thereby, a light-reflective polyester film in which microballoons are uniformly kneaded into the entire film can be produced.

The microbubbles used in the light-reflective polyester film constituting the solar cell backsheet of the present invention are obtained by finely dispersing a resin incompatible with polyester in a polyester resin composition (pellet). This is done by molding and stretching it uniaxially or biaxially. During stretching, the incompatible resin is phase-separated, and cavities (bubbles) are formed around the incompatible resin particles, which induces a light scattering action.

Incompatible resins are polymers that are insoluble in polyester, such as poly-3-methylbutene-1, poly-4-methylpentene-1, polypropylene, polyvinyl t-butane, 1,4-trans-poly-2. , 3-dimethylbutadiene, polyvinylcyclohexane, polystyrene, polyfluorostyrene, cellulose acetate, cellulose propionate, polychlorotrifluoroethylene and the like.

The addition amount of the incompatible resin is preferably 10% by weight or more and 30% by weight or less with respect to the polyester. If it is less than 10% by weight, sufficient bubbles are not formed in the film, so that the light reflectivity is low, and if it exceeds 30% by weight, the strength of the film is lowered.

The fine particles used in the light-reflective polyester film constituting the solar cell backsheet of the present invention are substantially spherical particles. Examples of fine particles include inorganic fine particles such as silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, organic fine particles such as acrylic resin, acrylonitrile resin, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide. can give.

The average particle diameter of the fine particles is 1 μm to 50 μm. When the average particle diameter of the fine particles is less than 1 μm or more than 50 μm, the diffusibility to the reflected light may be lowered. The addition amount of the fine particles is preferably 5% by weight or more and 50% by weight or less with respect to the polyester. If it is less than 5% by weight, the light reflectivity is low, and if it exceeds 50% by weight, the film strength is lowered.

The fine particles are previously added to a polyester resin composition (pellet) for film formation, and formed into a film by extrusion molding or the like. Moreover, you may extend uniaxially or biaxially as needed. Thereby, a light-reflective polyester film in which fine particles are uniformly kneaded in the entire film can be produced.

The light-reflective polyester film of the solar cell backsheet of the present invention may be provided with a light-reflective layer on the polyester film. FIG. 2 is a cross-sectional view of the solar cell backsheet of the present invention. In the configuration of FIG. 1, the light-reflective polyester film 2 has a structure in which a light-reflective layer 22 is provided on a polyester film 21.

The light-reflective polyester film provided with the light-reflective layer of the present invention has a structure in which a mirror ink and / or a white pigment is applied to a polyester film to form a light-reflective layer.

By applying the mirror ink onto the polyester film, a metal thin film having a specular gloss is formed, and an excellent light reflective film can be obtained. The mirror ink is usually composed of scale-like or rod-like metal particles, an organic solvent varnish, an organic solvent, and the like, and is applied to a polyester film by an ordinary application method to form a light reflective layer. The metal is selected from gold, silver, platinum, palladium, rhodium, ruthenium, indium, nickel, aluminum and the like. The size of the metal particles is 100 nm or less.

Moreover, the light-reflective polyester film provided with the light-reflective layer is obtained by apply | coating the composition containing a white pigment on a polyester film. Examples of the white pigment used include inorganic pigments such as titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, zinc sulfide, antimony trioxide, kaolin, talc, and lithopone, crosslinked polystyrene resin, and crosslinked acrylic resin. Organic pigments such as urea resins and melamine resins. One or more of these white pigments can be used. A white pigment is made into a composition together with a resin, a solvent, a viscosity modifier, and the like, and is applied onto a polyester film by a known method such as solid printing to form a light reflective layer.

The light-reflective polyester film provided with the light-reflective layer of the present invention has a structure in which a light-reflective layer made of a metal thin film and / or a dielectric thin film is formed on a polyester film.

As the metal for the metal thin film, one or more selected from the group consisting of silver, aluminum, nickel, chromium, gold, rhodium, copper and the like are used.

The dielectric thin film as the light-reflective layer is called a dielectric multilayer film, and is composed of several to tens of layers of a low refractive index film and a high refractive index film, thereby increasing the reflectance. Can do. Examples of the dielectric as the low refractive index film are silicon oxide, aluminum oxide, magnesium fluoride and the like. Examples of the dielectric as the high refractive index film are titanium oxide, thallium oxide, zinc oxide, zinc sulfide and the like.

The metal thin film or the dielectric thin film is formed on the polyester film by a known method such as a vacuum deposition method, a sputtering method, an ion plating method, a chemical vapor deposition method (CVD), a liquid phase growth method (LPD), or a plating method. Provided.

The light-reflective polyester film provided with the light-reflective layer of the present invention has a structure in which a light-reflective layer made of a bubble-containing resin film, a microballoon-containing resin film, a fine particle-containing resin film, or the like is formed on a polyester film.

The bubble-containing resin film as the light reflective layer of the present invention is a stretched film of incompatible resin, a film containing fine bubbles, or the like. These films are attached to the polyester film by a known method such as adhesion.

The stretched film of the incompatible resin is obtained by finely dispersing a resin that is incompatible with the matrix resin in a resin composition (pellet), forming a film, and stretching it uniaxially or biaxially. can get.

When the matrix resin is polyester, the incompatible resins include poly-3-methylbutene-1, poly-4-methylpentene-1, polypropylene, polyvinyl t-butane, 1,4-trans-poly-2, Examples include 3-dimethylbutadiene, polyvinylcyclohexane, polystyrene, polyfluorostyrene, cellulose acetate, cellulose propionate, and polychlorotrifluoroethylene. The addition amount of the incompatible resin is preferably 10% by weight or more and 30% by weight or less with respect to the polyester.

The resin film containing fine bubbles is obtained by adding fine bubbles to a resin film excellent in weather resistance, heat resistance, electrical insulation, water resistance and the like. Examples of the resin include polyester resins, polyolefin resins, cyclic polyolefin resins, polystyrene resins, fluorine resins, poly (meth) acrylic resins, polycarbonate resins, and the like.

The first method for containing fine bubbles is to contain a gas such as butane, pentane, hexane, carbon fluoride, carbon dioxide, or the like in the resin by an ordinary method. The second method is to foam the resin by a usual method using a foaming agent such as azodicarbonamide, dinitrosopentamethylenetetramine, p, p-oxybisbenzenesulfonylhydrazide. . The third method is to cause the resin to contain, for example, sodium hydrogen carbonate, ammonium carbonate or the like, and to heat and foam the resin. Moreover, you may uniaxially or biaxially stretch the resin film containing a fine bubble as needed.

The microballoon-containing resin film as the light-reflective layer of the present invention is a resin film excellent in weather resistance, heat resistance, electrical insulation, water resistance, etc., containing microballoons. Examples of the resin include polyester resins, polyolefin resins, cyclic polyolefin resins, polystyrene resins, fluorine resins, poly (meth) acrylic resins, polycarbonate resins, and the like.

The microballoons are fine hollow spheres, for example, glass balloons, silica balloons, shirasu balloons, carbon balloons, inorganic balloons such as alumina balloons and zirconia balloons, organic balloons such as phenol balloons and polyvinylidene chloride balloons. can give. The microballoon is previously added to a resin composition (pellet) for film formation, and formed into a film by extrusion molding or the like. Moreover, you may extend uniaxially or biaxially as needed. Thereby, it is possible to produce a resin film in which microballoons are uniformly kneaded throughout the film. The light reflective film containing the microballoon is attached to the polyester film by a known method such as adhesion.

The fine particle-containing resin film as the light-reflective layer of the present invention is obtained by adding fine particles to a resin film excellent in weather resistance, heat resistance, electrical insulation, water resistance and the like. Examples of the resin include polyester resins, polyolefin resins, cyclic polyolefin resins, polystyrene resins, fluorine resins, poly (meth) acrylic resins, polycarbonate resins, and the like.

The fine particles are substantially spherical particles, and examples thereof include inorganic fine particles such as silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, Examples thereof include organic fine particles such as polystyrene, polyacrylonitrile, and polyamide.

The fine particles are added in advance to a resin composition (pellet) for film formation, and formed into a film by extrusion molding or the like. Moreover, you may extend uniaxially or biaxially as needed. Thereby, a light-reflective resin film in which fine particles are uniformly kneaded in the entire film can be produced. The light reflecting film containing the fine particles is attached to the polyester film by a known method such as adhesion.

The polyester used in the light-reflective polyester film of the present invention is a polyester resin that is a polycondensate of a dicarboxylic acid derivative and a diol derivative. For example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2, 6-naphthalate and the like.

Among these polyesters, polyethylene terephthalate is particularly preferred as the polyester used in the light-reflective polyester film of the present invention because it has excellent mechanical properties, thermal properties, electrical properties, and the like. A slipping agent, a colorant, an antistatic agent, a density reducing agent, and the like may be added as long as there is no problem in terms of various characteristics and productivity.

The thickness of the light-reflective polyester film, particularly the polyethylene terephthalate film constituting the solar cell backsheet of the present invention is required to be 50 μm or more. By making the thickness of the polyethylene terephthalate film 50 μm or more, the electrical insulation is improved, and the partial discharge voltage, which is a typical characteristic of electrical insulation that can correspond to the system voltage 1000 V of the solar battery, is used for a solar battery that satisfies 1000 VDC or more. A backsheet is obtained.

In the solar cell backsheet of the present invention, by providing fine irregularities on the light reflecting surface of the light-reflective polyester film, it is possible to impart good diffusibility to the reflected light, and light is more effective for the solar cells. It is possible to effectively improve the power generation efficiency.

FIG. 3 shows an embodiment thereof, which is a configuration in which fine irregularities 23 are provided on the surface of the light-reflective polyester film 2 in the configuration of FIG. Fine irregularities can be formed by, for example, embossing, polishing, or striating a light-reflective polyester film. It can also be formed by applying a composition containing fine particles and the like. The size (depth) of the unevenness is 1 μm to 50 μm. When the thickness is less than 1 μm or more than 50 μm, the diffusibility to the reflected light may be lowered.

FIG. 4 shows another embodiment of the present invention. In the configuration shown in FIG. 2, the light-reflective layer 22 of the light-reflective polyester film 2 is provided with fine irregularities 24. The formation of fine irregularities on the light reflecting layer includes, for example, embossing, polishing, filament processing, and fine particles on the surface of the polyester film on which the light reflecting layer is formed before the light reflecting layer is formed. It can also be realized by forming fine irregularities in advance by applying the composition or the like.

In the solar cell backsheet of the present invention, it is also effective to incline the light reflecting surface of the light-reflective polyester film with respect to incident light. Since light does not enter at 90 degrees with respect to the reflecting surface, the reflected light is reflected in an oblique direction without regular reflection with respect to the light-reflective polyester film. As a result, more reflected light returns to the solar battery cell, and the power generation efficiency can be further increased.

FIG. 5 shows an embodiment thereof. In the configuration of FIG. 1, the surface S1 of the light-reflective polyester film 2 is inclined with respect to incident light. This structure is realizable by producing the light-reflective polyester film from which thickness differs in the width direction of a film, for example.

FIG. 6 shows another embodiment. In the configuration of FIG. 2, the surface S2 of the light reflective layer 22 of the light reflective polyester film 2 is inclined with respect to the incident light. This structure is realizable by providing a light-reflective layer on the inclined surface side of the polyester film from which thickness differs in the width direction of a film, for example. Moreover, it is realizable also by providing the light-reflective layer from which thickness differs in the width direction on a polyester film.

In the solar cell backsheet of the present invention, the colored resin film is colored in a hue selected from white, black, and blue. The hue varies depending on the purpose and is white when the reflection / reuse of incident light is important. Moreover, it is black or blue when importance is attached to designability, decoration, etc. as a roofing material.

The resin used for the colored resin film of the present invention is preferably excellent in strength and excellent in weather resistance, heat resistance, water resistance, light resistance, electrical insulation, and the like. For example, polyester resins, polyolefin resins, cyclic polyolefin resins, polystyrene resins, fluorine resins, poly (meth) acrylic resins, polycarbonate resins, and the like.

Among these resins, polyester is suitable as the resin used for the colored resin film. Here, the polyester is a polyester resin that is a polycondensate of a dicarboxylic acid derivative and a diol derivative, and examples thereof include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate.

Among these polyesters, polyethylene terephthalate is particularly preferred as the polyester used in the colored resin film of the present invention because it has excellent mechanical properties, thermal properties, electrical properties, and the like. A slipping agent, a colorant, an antistatic agent, a density reducing agent, and the like may be added as long as there is no problem in terms of various characteristics and productivity.

By adding a colorant to a resin composition (pellet) for film formation in advance and forming a film by extrusion or the like, a colored resin film in which the colorant is uniformly kneaded into the entire film can be produced. it can. Moreover, you may extend uniaxially or biaxially as needed.

The colored resin film can also be produced by applying a colorant on the resin film to form a colored layer. In FIG. 7, the colored resin film 3 has a configuration in which a colored layer 32 is provided on the resin film 31. The colorant is a composition including a resin, a solvent, a viscosity modifier, and the like, and a colored layer is formed on one side of the resin film by solid printing. As the solid printing means, any known roll coating method, screen printing method, gravure printing method, die coating method, dipping method, spray method or the like may be used.

White pigments used in white resin films include inorganic pigments such as titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, and talc, crosslinked polystyrene resins, crosslinked acrylic resins, urea resins, and melamine resins. There are organic pigments.

Examples of the black pigment used for the black resin film include carbon black (channel or furnace), black iron oxide, and other black pigments. In the present invention, the black resin film may have a blackish color such as brown or brownish black or grayish black.

Examples of the blue pigment used for the blue resin film include ultramarine, cobalt blue, Prussian blue, turquoise blue, manganese blue, and phthalocyanine blue. Further, in order to adjust the hue, pigments of other hues may be used in combination.

The usage-amount of the white, black, and blue coloring agent used for a colored resin film is 0.1 weight part-15 weight part with respect to 100 weight part of resin.

The hydrolysis resistant and low molecular weight precipitation polyester film provided with a thin film layer made of a metal oxide constituting the solar cell backsheet of the present invention is resistant to hydrolysis and low resistance. A thin film layer of a metal oxide is provided on the surface of a molecular weight-precipitating polyester film, and particularly exhibits a water vapor blocking effect on a solar cell module. The metal oxide has an insulating property, is chemically stable, and does not react with moisture. Therefore, when used in a solar cell module, there is no risk of current leakage, and a material having a high withstand voltage can be used as a building material.

As the metal oxide, one or more selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, zinc oxide, and tin oxide can be used. These metal oxides may be a simple substance or a complex oxide. Silicon oxide and / or aluminum oxide is preferably used from the viewpoint of easy formation of the thin film layer, water vapor blocking performance and the like.

The thickness of the metal oxide thin film layer varies depending on the type and configuration of the metal oxide to be used, but is generally preferably in the range of 5 nm to 300 nm. If the film thickness is less than 5 nm, a uniform film may not be obtained or the film thickness may not be sufficient, and the water vapor blocking effect may not be sufficiently achieved. In addition, when the film thickness exceeds 300 nm, the metal oxide thin film layer cannot be kept flexible, and the metal oxide thin film layer may be cracked due to external factors such as bending and pulling after film formation. There is.

In order to form a metal oxide thin film layer on a hydrolysis resistant and low molecular weight precipitation resistant polyester film, a known method such as a vacuum deposition method, a sputtering method, an ion plating method, various CVD methods, Any of plating methods and the like can be used, but a vacuum deposition method, a sputtering method, a CVD method and the like are preferably used.

In order to form a metal oxide thin film layer on a polyester film that is resistant to hydrolysis and precipitates low molecular weight, it is composed of a water-soluble polymer and one or more metal alkoxides and / or hydrolysates thereof. A solution may be formed by coating. As the metal alkoxide, tetraethoxysilane, triisopropoxyaluminum, or a mixture thereof may be preferably used.

As a method for applying the solution, conventionally known means such as a roll coating method, a screen printing method, a gravure printing method, a die coating method, a dipping method, and a spray method can be used.

In the hydrolysis-resistant and low-molecular-weight precipitate-resistant resin of the present invention, the hydrolysis resistance means that the resin itself is hardly subject to hydrolysis during long-term use. In addition, the low molecular weight resistance to precipitation is such that low molecular weight substances that may be contained in the resin during long-term use are difficult to precipitate from the resin and / or only a very small amount of low molecular weight substances may be precipitated. It means not included.

When the resin is hydrolyzed, the molecular weight of the resin is usually lowered, and as a result, mechanical properties such as breaking strength and breaking elongation, heat resistance, moisture resistance and the like are lowered. In addition, a functional group is generated, and the water resistance, weather resistance, electrical characteristics and the like are lowered. When a low molecular weight substance is precipitated from the resin, spots are generated, appearance is deteriorated due to yellowing or the like, transparency is lowered, adhesive strength is lowered, and electrical characteristics are lowered. These are undesirable phenomena for solar cell backsheets and solar cell modules using the same.

The hydrolysis resistant and low molecular weight precipitation resistant resin of the present invention is polyester. The polyester in the present invention includes a polyester resin that is a polycondensate of a dicarboxylic acid derivative and a diol derivative. For example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, and the like can be used.

Among these polyesters, in particular, polyethylene terephthalate is excellent in mechanical properties, thermal properties, electrical properties, etc., so that it is a hydrolysis resistant and low molecular weight precipitation resistant resin of the present invention. , Preferably used. In addition, a slip agent, a colorant, an antistatic agent, a low density agent, and the like may be added as long as there are no problems in terms of various characteristics and productivity.

Polyethylene terephthalate is a so-called polymer obtained by condensation polymerization of ethylene glycol and terephthalic acid, and usually 1.6% by weight to 2% by weight of an oligomer which is an intermediate between the monomer and the polymer. Here, the oligomer is a low polymer having a number of repeating structural units (degree of polymerization) of about 2 to 20. The content of the oligomer can be known using means such as a nuclear magnetic resonance method and a xylene extraction method.

In contrast, the hydrolysis-resistant and low-molecular weight precipitation-resistant resin used in the present invention is polyethylene terephthalate having a highly advanced polymerization reaction and an oligomer content of 0.8% by weight or less. If the polymerization reaction proceeds and the oligomer content is as low as 0.8% by weight or less, the hydrolysis resistance is excellent, that is, mechanical properties, thermal properties, electrical properties, etc. A stable and excellent resin sheet can be obtained. In addition, in the long-term use, low-molecular weight substances, that is, oligomers are very little precipitated, and there is no adverse effect on the performance and appearance because the transparency is not lowered and spots are not generated.

A hydrolysis-resistant and low-molecular weight precipitation-resistant polyester film provided with a light-reflective polyester film, a colored resin film, and a thin film layer made of a metal oxide is laminated in this order to form an adhesive. And integrated into a solar cell backsheet. In FIG. 1 which showed the structure of the solar cell backsheet 1 of the present invention, it is hydrolysis resistant and provided with a light-reflective polyester film 2, a colored resin film 3 and a thin film layer made of a metal oxide. The low molecular weight precipitateable polyester film 4 is bonded and integrated by the adhesive layer 5.

As a method of adhesion / integration, a method of applying an adhesive to each film constituting the back sheet of the present invention and bonding them under superposition, pressurization, or heating can be used.

Typical adhesives include acrylic resins, urethane resins, epoxy resins, polyester resins, polyamides, phenols, polyolefins, ionomers, ethylene-vinyl acetate copolymers, polyvinyl acetals, etc., but are not necessarily limited to these. It's not trivial.

As the adhesive, a two-component curable polyurethane resin composed of a solvent solution of a polyol component and an isocyanate component is usually used. In this case, alkyd resin, acrylic resin, polyvinyl alcohol or the like is used as the polyol component, and various isocyanate resins or the like are used as the isocyanate component.

The thickness of the adhesive is preferably 1 μm to 10 μm in terms of adhesive strength, water vapor barrier properties, and the like. In applying the adhesive, conventionally known means such as a roll coating method, a screen printing method, a gravure printing method, a die coating method, a dipping method, and a spray method can be used.

In the solar cell backsheet of the present invention, an easy adhesion treatment layer may be provided on the light-reflective polyester film. By providing the easy adhesion treatment layer, the adhesiveness between the back sheet and the sealing resin (usually ethylene-vinyl acetate copolymer) is remarkably improved, and as a result, the reliability of the solar cell module is improved. FIG. 8 is a cross-sectional view of a solar cell backsheet provided with an easy adhesion treatment layer, and the easy adhesion treatment layer 6 is provided on one side of the light-reflective polyester film 2.

The easy-adhesion treatment agent preferably contains a thermoplastic resin such as polyurethane, polyester or acrylic as a main component. These have almost no tackiness at room temperature, and may have any tackiness at the time of heating. Accordingly, the glass transition point is preferably in the range of 20 ° C to 100 ° C. When the glass transition point is less than 20 ° C., the easy adhesion treatment layer tends to have tackiness at room temperature, and may adhere when the easy adhesion treatment layer and the easy adhesion treatment layer are overlapped. Cause problems with sex. If the temperature exceeds 100 ° C., the adhesiveness may be reduced, or the easy-adhesion treatment layer may become brittle and the adhesion may not be maintained.

The thickness of the easy adhesion treatment layer is preferably 0.1 μm to 1 μm. If it is less than 0.1 μm, the adhesive force between the back sheet provided with the easy-adhesion treatment layer and the sealing resin may be insufficient. If it exceeds 1 μm, Newton rings may be easily generated, and the light transmittance may be reduced.

Conventionally known means such as a roll coating method, a screen printing method, a gravure printing method, a die coating method, a dipping method, and a spray method can be used for forming the easy adhesion treatment layer.

A low density polyethylene film can also be used as the easy adhesion treatment layer. Low density polyethylene has excellent mechanical strength such as pulling, tearing, impact, folding resistance, etc., and also has excellent weldability with the sealing resin, so the adhesion between the backsheet and the sealing resin is significantly improved. . Low density polyethylene is polyethylene having a density of 0.91 or more and less than 0.93.

The low-density polyethylene is a film having a thickness of 5 μm to 100 μm and is bonded to one side of the light-reflective polyester film with, for example, a urethane adhesive or directly welded.

In the solar cell backsheet of the present invention, it is desirable that the breaking elongation retention after treatment for 3000 hours is 50% or more in an environment of a temperature of 85 ° C. and a humidity of 85%. Aging for 3,000 hours in an environment of a temperature of 85 ° C. and a humidity of 85% is one of tests for inspecting durability corresponding to 20 years in an outdoor exposure state as a back sheet for a solar cell. If the breaking elongation retention when tested under these conditions is less than 50%, the backsheet is remarkably deteriorated and does not serve as a backsheet for solar cells.

In the back sheet for a solar cell of the present invention, it is desirable that the alternating current withstand voltage holding ratio after treatment for 3000 hours is 50% or more in an environment of a temperature of 85 ° C. and a humidity of 85%. If the alternating voltage withstand voltage holding ratio when tested under these conditions is less than 50%, the electrical insulation property of the backsheet is significantly lowered and does not serve as a backsheet for a solar cell module. Usually, as a back sheet for a solar cell, in order to maintain sufficient electrical insulation, the alternating current withstand voltage of 2000 V / mil or more is required.

Embodiments of the back sheet for a solar cell of the present invention are shown in FIGS. 1, 2, 3, 4, 5, 6, 6, 7 and 8. The solar cell using the back sheet for a solar cell of the present invention is shown in FIG. An embodiment of the module is shown in FIG. Moreover, the embodiment of the conventional solar cell backsheet is shown in FIG.10, FIG11 and FIG.12.

FIG. 9 is a cross-sectional view of a solar cell module 7 using the solar cell backsheet 1 of the present invention. After sequentially laminating the glass plate 8, which is a surface protection plate, the sealing resin 9, the solar battery cell 11 in which the wiring 10 has been previously disposed, and the solar cell backsheet 1 of the present invention, and integrating them by vacuum suction or the like, Integrally molded by thermocompression molding. Sunlight L that has passed through the solar cells or passed through the gap between the solar cells is reflected by the backsheet 1 of the present invention, returns to the solar cells again, and is used for power generation. As a result, power generation efficiency is improved.

The invention's effect

According to the present invention, in the back sheet, by effectively arranging the light-reflective polyester film, incident light can be effectively returned to the solar battery cell. As a result, the power generation efficiency is improved. A solar cell module can be provided.

According to the present invention, by using a polyester film film on the side of the back sheet that comes into contact with the sealing resin layer, deterioration in long-term use can be prevented, so that the long-term reliability of the back sheet and thus the solar cell module is remarkably high. improves. Further, it is possible to prevent the hue and color density of the backsheet from changing over a long period of use. Furthermore, it can prevent that the coloring agent in a colored resin film transfers to a sealing resin layer, and a sealing resin layer colors.

According to the present invention, the outermost layer that is in direct contact with the outside air of the backsheet uses a polyester film that is resistant to hydrolysis and precipitates low molecular weight substances, thereby reducing deterioration of the backsheet and unnecessary low molecular weight. Precipitation of the body is suppressed. As a result, it is possible to provide an excellent back sheet and solar cell module that have stable mechanical properties, thermal properties, electrical properties, and the like for long-term use.

According to the present invention, a solar cell backsheet that is lightweight, has excellent water resistance and voltage resistance, has excellent design properties, and is inexpensive. Therefore, when the solar cell module using the backsheet of the present invention is integrated with a general residential or industrial roofing material to form a solar cell module, it is excellent in design, lightweight and excellent in durability, And it can be set as an inexpensive solar cell module with high power conversion efficiency.

According to the present invention, the power generation efficiency of the solar cell module is increased, and the long-term performance deterioration such as water vapor barrier property, electrical insulation property, mechanical strength, adhesiveness, etc., which is excellent in design, is minimized. A colored solar cell backsheet and a solar cell module using the same can be provided.

It is sectional drawing which shows an example of the solar cell backsheet of this invention. It is sectional drawing which shows another example of the solar cell backsheet of this invention. It is sectional drawing which shows another example of the solar cell backsheet of this invention. It is sectional drawing which shows another example of the solar cell backsheet of this invention. It is sectional drawing which shows another example of the solar cell backsheet of this invention. It is sectional drawing which shows another example of the solar cell backsheet of this invention. It is sectional drawing which shows another example of the solar cell backsheet of this invention. It is sectional drawing which shows another example of the solar cell backsheet of this invention. It is sectional drawing of the solar cell module using the solar cell backsheet of this invention. It is sectional drawing which shows an example of the conventional solar cell backsheet. It is sectional drawing which shows another example of the conventional solar cell backsheet. It is sectional drawing which shows another example of the conventional solar cell backsheet.

DESCRIPTION OF SYMBOLS 1 Back sheet 2 Light-reflective polyester film 21 Polyester film 22 Light-reflective layer 23 Fine unevenness | corrugation provided in the light-reflective polyester film 24 Fine unevenness | corrugation provided in the light-reflective layer 3 Colored resin film 31 Resin Film 32 Colored layer 4 Polyester film 41 having hydrolysis resistance and low molecular weight precipitation resistance provided with a thin film layer made of a metal oxide 41 Polyester film having hydrolysis resistance and low molecular weight precipitation resistance 42 Thin film layer 5 made of metal oxide Adhesive layer 6 Easy adhesion treatment layer 7 Solar cell module 8 Glass plate 9 Sealing resin 10 Wiring 11 Solar cell 12 Conventional solar cell backsheet 121 Light reflective film 122 Vapor deposition film 1221 Resin film 1222 Vapor deposition layer 123 Adhesive 13 Other conventional back cover for solar cell G 131 White polyester film 132 Vapor deposition film 1321 Base film 1322 Inorganic oxide thin film layer 133 Transparent polyester film 134 Adhesive 14 Other conventional solar cell backsheet 141 White resin film 142 Metal oxide coated resin film 1421 Base Film 1422 Metal oxide layer 143 Hydrolysis resistant resin film 144 Adhesive

Claims (20)

A hydrolysis-resistant and low-molecular weight precipitation-resistant polyester film provided with a light-reflective polyester film, a colored resin film, and a thin film layer made of a metal oxide is laminated and integrated in this order. A solar cell backsheet. The solar cell backsheet according to claim 1, wherein the light-reflective polyester film contains one or more selected from the group consisting of white pigments, microballoons, fine bubbles, fine particles, and the like. The solar cell backsheet according to claim 1, wherein the light-reflective polyester film is provided with a light-reflective layer on the polyester film. The solar cell backsheet according to claim 3, wherein the light-reflective layer comprises a coating layer of mirror ink and / or white pigment. The solar cell backsheet according to claim 3, wherein the light reflective layer comprises a metal thin film and / or a dielectric thin film. 4. The solar cell backsheet according to claim 3, wherein the light reflective layer is at least one selected from the group consisting of a bubble-containing resin film, a microballoon-containing resin film, a fine particle-containing resin film, and the like. . 2. The solar cell backsheet according to claim 1, wherein the polyester of the light-reflective polyester film is polyethylene terephthalate. The solar cell backsheet according to claim 1, wherein fine irregularities are provided on a light reflecting surface of the light reflecting polyester film. The solar cell backsheet according to claim 1, wherein the colored resin film is colored in a hue selected from white, black, and blue. The solar cell backsheet according to claim 9, wherein the colored resin film is coated and / or kneaded with a colorant selected from white, black, and blue. The solar cell backsheet according to claim 1, wherein the resin of the colored resin is polyester. The back sheet for a solar cell according to claim 11, wherein the polyester is polyethylene terephthalate. 2. The metal oxide is one or more metal oxides selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, zinc oxide, and tin oxide. The back sheet for solar cells as described in 2. 2. The solar cell backsheet according to claim 1, wherein the hydrolysis-resistant and low-molecular weight precipitation-resistant polyester is polyethylene terephthalate. The solar cell backsheet according to claim 14, wherein the polyethylene terephthalate has an oligomer content of 0.8 wt% or less. A hydrolysis-resistant and low-molecular-weight-precipitating polyester film provided with a light-reflective polyester film, a colored resin film, and a thin film layer made of a metal oxide is laminated in this order to form an adhesive. The solar cell backsheet according to claim 1, wherein the backsheet for solar cells is integrated. The solar cell backsheet according to claim 1, wherein an easy adhesion treatment layer is provided on the light-reflective polyester film. 2. The solar cell backsheet according to claim 1, wherein the elongation at break after treatment for 3000 hours is 50% or more in an environment of a temperature of 85 ° C. and a humidity of 85%. The back sheet for a solar cell according to claim 1, wherein the alternating voltage withstand voltage holding ratio after treatment for 3000 hours is 50% or more in an environment of a temperature of 85 ° C and a humidity of 85%. A solar cell module comprising the solar cell backsheet according to claim 1.

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