JP2012023148A - Protective sheet for solar cell, and solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective sheet for solar cell which exhibits excellent transmittance, barrier properties, light fastness, and adhesion.SOLUTION: The protective sheet for solar cell has an inorganic layer, an organic layer, a UV-blocking layer, and a fluororesin film that are formed on a plastic film. The UV-blocking layer is a layer where inorganic particles are dispersed into a binder containing a compound having an average composition formula shown by expression (1). Refractive index of the UV-blocking layer is higher than that of a layer adjoining the UV-blocking layer on the side where the fluororesin film is provided. The fluororesin film is the outermost layer on the side where the UV-blocking layer is provided.

Description

  The present invention relates to a solar cell protective sheet and a solar cell. In particular, the present invention relates to a solar cell front sheet.

  Conventionally, a solar cell protective sheet for protecting the surface of a solar cell has been widely studied. Since solar cells are placed outdoors for many years, high barrier properties and high light resistance are required. Furthermore, about the protective sheet for solar cells which laminated | stacked the several layer, the adhesiveness of these layers is also calculated | required. In addition, when the solar cell protective sheet is used for a front sheet, high transmittance is also required. And in recent years, the thing using a plastic film as a base film of such a protection sheet is used. And in order to protect such a plastic film, the film which provided the fluororesin film | membrane on the surface is known (patent documents 1-4).

Japanese Patent Laid-Open No. 08-187825 JP 2000-138388 A JP 2010-53317 A JP 2004-168057 A

When this inventor examined the said literature, it turned out that all lack in either the high transmittance | permeability, high barrier property, high light resistance, high adhesiveness, and high wet heat resistance. In addition, a technique for providing a layer containing an organic ultraviolet absorber is known in order to enhance light resistance. However, such technique has insufficient light resistance, and may have poor barrier properties and adhesion. I found out.
The present invention is intended to solve the problems of the prior art, and an object thereof is to provide a solar cell protective sheet excellent in all of transmittance, barrier properties, light resistance and adhesion. And

As a result of intensive studies by the inventor of the present application, as a result of intensive investigation by the inventor of the present application under such circumstances, a layer having an ultraviolet absorbing ability is provided, and the refractive index of the layer is higher than that of the adjacent layer. Reached to increase.
By adopting such means, not only light resistance can be improved, but also adhesion and barrier properties can be improved. The means of the present invention is a means that can be avoided by those skilled in the art because the number of layers constituting the solar cell protective sheet increases. However, by adopting such a configuration, the present invention has a great significance in that not only the light resistance is improved but also the barrier property and the adhesion can be improved.

Specifically, the object of the present invention has been achieved by the following means.
(1) It has an inorganic layer, an organic layer, an ultraviolet blocking layer, and a fluororesin film on a plastic film, and the ultraviolet blocking layer is a compound whose average composition formula is represented by the following formula (1). It is a layer in which inorganic fine particles are dispersed in a binder, and the refractive index of the ultraviolet blocking layer is a layer adjacent to the ultraviolet blocking layer, and the refractive index of the layer on the side where the fluororesin film is provided Furthermore, the protective sheet for solar cells, wherein the fluororesin film is the outermost layer on the side where the ultraviolet blocking layer is provided.
Formula (1)
R ¹ _m Si (OR ² ) _n O _{(4-mn / 2)}
(In the formula, R ¹ is a group selected from a methyl group, an ethyl group and a phenyl group, and R ¹ may contain two or more groups, and R ² is an alkyl having 1 to 8 carbon atoms. And R ² may contain two or more kinds of alkyl groups, 0.2 ≦ m ≦ 2, n is 0.01 ≦ n ≦ 3, and m + n <4. is there.)
(2) The protective sheet for a solar cell according to (1), wherein the inorganic fine particles are an oxide containing at least one element of cerium, zinc, titanium, iron, zirconium, tagsten and strontium.
(3) The protective sheet for solar cells according to (1) or (2), wherein an inorganic layer, an organic layer, an ultraviolet blocking layer and a fluororesin film are provided on one surface of the plastic film.
(4) The solar cell protective sheet according to any one of (1) to (3), wherein the ultraviolet blocking layer and the fluororesin film are bonded together by an adhesive layer.
(5) Compound in which the inorganic fine particles contain at least one element of silicon and aluminum on the surface of the inorganic fine particles containing at least one element of cerium, zinc, titanium, iron, zirconium, tag stainless and strontium The protective sheet for solar cells according to (1), (3) or (4), which is inorganic fine particles covered with.
(6) The solar cell protective sheet according to any one of (1) to (5), wherein the inorganic layer includes at least one of silicon and aluminum and at least one of oxygen and nitrogen.
(7) The protective sheet for solar cells according to any one of (1) to (6), wherein the inorganic fine particles have an average particle size of 100 nm or less.
(8) The inorganic fine particles are covered with inorganic fine particles containing at least one element of cerium and zinc, or the surface of these inorganic fine particles is covered with a compound containing at least one element of silicon and aluminum. The protective sheet for a solar cell module according to any one of (1), (3), (4), (6), and (7), which is an inorganic fine particle.
(9) The protective sheet for solar cells according to any one of (1) to (8), wherein the thickness of the fluororesin film is 10 μm to 1000 μm.
(10) The protective sheet for solar cells according to any one of (1) to (9), wherein the organic layer is a layer formed by curing a polymerizable composition containing (meth) acrylate.
(11) The protective sheet for solar cells according to any one of (1) to (10), wherein the total light transmittance is 85% or more.
(12) The solar cell protective sheet according to any one of (4) to (10), wherein the adhesive layer includes a urethane-based adhesive.
(13) The solar cell protective sheet according to any one of (1) to (12), wherein the plastic film is a polyester resin film.
(14) The solar cell protective sheet according to any one of (1) to (13), which is for a front sheet.
(15) A solar cell element having the solar cell protective sheet according to any one of (1) to (14).

  By this invention, it became possible to provide the protective sheet for solar cells excellent in all of the transmittance | permeability, barrier property, light resistance, adhesiveness, and wet heat resistance.

Drawing 1 is a figure showing an example of an embodiment of a protection sheet for solar cells of the present invention. FIG. 2 is a diagram showing an example of the solar cell element of the present invention.

  Hereinafter, the contents of the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

The protective sheet for solar cell of the present invention has an inorganic layer, an organic layer, an ultraviolet blocking layer, and a fluororesin film on a plastic film, and the ultraviolet blocking layer has an average composition formula of the following formula (1 ) Is a layer in which inorganic fine particles are dispersed in a binder containing a compound represented by formula (1), and the refractive index of the ultraviolet blocking layer is a layer adjacent to the ultraviolet blocking layer, and a fluororesin film is provided. It is higher than the refractive index of the layer on the side, and the fluororesin film is the outermost layer on the side where the ultraviolet blocking layer is provided.
Formula (1)
R ¹ _m Si (OR ² ) _n O _{(4-mn / 2)}
(In the formula, R ¹ is a group selected from a methyl group, an ethyl group and a phenyl group, and R ¹ may contain two or more groups, and R ² is an alkyl having 1 to 8 carbon atoms. And R ² may contain two or more kinds of alkyl groups, 0.2 ≦ m ≦ 2, n is 0.01 ≦ n ≦ 3, and m + n <4. is there.)

  By setting it as such a structure, the solar cell protective sheet excellent in all of the transmittance | permeability, barrier property, light resistance, and adhesiveness can be obtained. Various methods for improving the barrier property and adhesion of a gas barrier film in which an organic layer and an inorganic layer are laminated have been studied. For example, it is a method of adding an additive to the organic layer, devising a method for forming an organic layer or an inorganic layer, or increasing the number of stacked organic layers and inorganic layers. On the other hand, in the present invention, by providing an inorganic ultraviolet blocking layer, the barrier property of the protective sheet for solar cells to be obtained is further improved without adopting any means for further improving the performance of the gas barrier film itself. There is an advantage that you can. Of course, it goes without saying that also in the protective sheet for solar cells of the present invention, conventionally known means for enhancing the barrier property of the gas barrier film may be used in combination.

In the present invention, an ultraviolet blocking layer and a fluorine resin film are provided on one surface of the plastic film, and the refractive index of the ultraviolet blocking layer is a layer adjacent to the ultraviolet blocking layer, and the fluorine resin film is provided. It is higher than the refractive index of the layer on the side where it is formed. With such a configuration, it is possible to exhibit excellent light resistance. In the present invention, the difference in refractive index is preferably 0.01 to 0.2, more preferably 0.02 to 0.1.
Here, the layer adjacent to the ultraviolet blocking layer is usually an adhesive layer, and it is preferable that the ultraviolet blocking layer, the adhesive layer, and the fluororesin film are adjacently stacked in this order.

In the present invention, it is preferable that an inorganic layer, an organic layer, an ultraviolet blocking layer, and a fluororesin film are provided on one surface of the plastic film. FIG. 1 shows an example of a preferred embodiment of a solar cell protective sheet of the present invention, wherein 1 is a base film, 2 is an organic layer, 3 is an inorganic layer, and 4 is an ultraviolet blocking layer. 5 represents an adhesive layer, and 6 represents a fluororesin film. Usually, the organic layer 2 and the inorganic layer 3 are integrated to improve the barrier ability. Each of the organic layer 2 and the inorganic layer 3 may be one layer, or a plurality of layers may be alternately laminated.
In the present invention, in addition to the inorganic layer, the inorganic ultraviolet blocking layer also serves as a barrier layer, and synergistically improves the barrier property.
Moreover, the solar cell protective sheet of the present invention may have other constituent layers within a range not departing from the gist of the present invention.

Although the preferable layer structure of this invention is illustrated below, it cannot be overemphasized that this invention is not limited to these. In addition, although it may have another functional layer between the layers divided by /, it is preferable not to have another functional layer.
Plastic film / organic layer / inorganic layer / ultraviolet ray blocking layer / adhesive layer / fluororesin film plastic film / organic layer / inorganic layer / organic layer / ultraviolet ray blocking layer / adhesive layer / fluororesin film plastic film / organic layer / inorganic layer / Organic layer / UV blocking layer / organic layer / adhesive layer / fluororesin film plastic film / inorganic layer / organic layer / ultraviolet blocking layer / adhesive layer / fluorine resin film plastic film / inorganic layer / organic layer / inorganic layer / ultraviolet blocking layer / Adhesive layer / Fluorine resin film plastic film / Inorganic layer / Organic layer / Inorganic layer / UV blocking layer / Organic layer / Inorganic layer / Adhesive layer / Fluorine resin film plastic film / Organic layer / Inorganic layer / Adhesive layer / UV blocking layer / Fluoropolymer film Plastic film / Organic layer / Inorganic layer / Organic layer / Adhesive layer / UV blocking / Fluororesin film plastic film / inorganic layer / organic layer / adhesive layer / ultraviolet blocking layer / fluororesin film plastic film / inorganic layer / organic layer / inorganic layer / adhesive layer / ultraviolet blocking layer / fluororesin film

The protective sheet for a solar cell of the present invention is preferably configured so that the thickness of the entire sheet is 50 μm or more, and more preferably 100 μm or more. The upper limit is not particularly defined, but can be, for example, 2000 μm or less.
The solar cell protective sheet of the present invention preferably has a total light transmittance of 85% or more, and preferably 90% or more.
When measured according to the following method, the reflectance in the present invention is preferably 15% or less, more preferably 10% or less. By setting it as such a range, it exists in the tendency for the power generation conversion efficiency of a solar cell element to improve.
(Measurement method of reflectance)
Using Shimadzu UV2550, diffuse reflectance was measured using a standard white plate as barium sulfate.

1. Plastic Film In the present invention, a polyester film is preferably used as the base film. By using a polyester base film, the barrier performance tends to be further improved.
The type of polyester used for the polyester base film is not particularly defined, but aromatic polyester is preferable, polyethylene terephthalate (PET), polymethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN). Is more preferable, and PET or PEN is more preferable. Moreover, the mixture of 2 or more types of polyester may be sufficient.
The number average molecular weight of the polyester is preferably 13,000 to 50,000, and more preferably 15,000 to 35,000.
The thickness of the polyester base film is preferably 5 μm to 1000 μm, and more preferably 10 μm to 500 μm. That is, the film of the present invention includes both a film having a thickness of less than 250 μm and a sheet having a thickness of 250 μm or more.
By setting it as such thickness, the improvement of dimensional stability and the nick of a film become difficult to occur, and it becomes possible to supply a protective sheet for a solar cell having a stable barrier ability.

2. Organic layer The organic layer in the present invention is preferably an organic layer containing an organic polymer as a main component. Here, the main component means that the first component of the component constituting the organic layer is an organic polymer, and usually 80% by weight or more of the component constituting the organic layer is an organic polymer.
Examples of the organic polymer include polyester, acrylic resin, methacrylic resin, methacrylic acid-maleic acid copolymer, polystyrene, transparent fluororesin, polyimide, fluorinated polyimide, polyamide, polyamideimide, polyetherimide, cellulose acylate, and polyurethane. , Polyether ether ketone, polycarbonate, alicyclic polyolefin, polyarylate, polyether sulfone, polysulfone, fluorene ring modified polycarbonate, alicyclic modified polycarbonate, fluorene ring modified polyester, acryloyl compound and other thermoplastic resins, or polysiloxane, etc. Examples thereof include organosilicon polymers.
The organic layer in the present invention preferably has a glass transition temperature (Tg) of 100 ° C. or lower, and more preferably 85 ° C. or lower. The lower limit is not particularly defined, but is preferably −20 ° C. or higher.

The organic layer in the present invention is preferably formed by curing a polymerizable composition containing a polymerizable compound.
(Polymerizable compound)
The polymerizable compound is preferably a radical polymerizable compound and / or a cationic polymerizable compound having an ether group as a functional group, more preferably a compound having an ethylenically unsaturated bond at the terminal or side chain, and / or A compound having an epoxy or oxetane at the terminal or side chain. Of these, compounds having an ethylenically unsaturated bond at the terminal or side chain are preferred. Examples of compounds having an ethylenically unsaturated bond at the terminal or side chain include (meth) acrylate compounds, acrylamide compounds, styrene compounds, maleic anhydride, etc., (meth) acrylate compounds and / or Styrenic compounds are preferred, and (meth) acrylate compounds are more preferred.

As the (meth) acrylate that can be used in the present invention, (meth) acrylate, urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, and the like are preferable.
As the styrene compound, styrene, α-methylstyrene, 4-methylstyrene, divinylbenzene, 4-hydroxystyrene, 4-carboxystyrene and the like are preferable.

Specific examples of (meth) acrylate compounds that are preferably used in the present invention are shown below, but the present invention is not limited thereto.

(Polymerization initiator)
When the organic layer in the present invention is prepared by coating and curing a polymerizable composition containing a polymerizable compound, the polymerizable composition may contain a polymerization initiator. When using a photoinitiator, it is preferable that the content is 0.1 mol% or more of the total amount of the polymerizable compounds, and more preferably 0.5 to 2 mol%. By setting it as such a composition, the polymerization reaction via an active component production | generation reaction can be controlled appropriately. Examples of the photopolymerization initiator include Irgacure series (for example, Irgacure 651, Irgacure 754, Irgacure 184, Irgacure 2959, Irgacure 907, Irgacure 369, Irgacure 379, Irgacure, commercially available from Ciba Specialty Chemicals. 819), Darocure series (eg, Darocur TPO, Darocur 1173, etc.), Quantacure PDO, Ezacure series (eg, Ezacure TZM, Ezacure, commercially available from Lamberti) TZT, Ezacure KTO46, etc.).

(Formation method of organic layer)
A method for forming the organic layer is not particularly defined, but for example, it can be formed by a solution coating method or a vacuum film forming method. Examples of the solution coating method include a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method, a slide coating method, or a method described in US Pat. No. 2,681,294. It can apply | coat by the extrusion coat method which uses a hopper. Although there is no restriction | limiting in particular as a vacuum film-forming method, Film-forming methods, such as vapor deposition and plasma CVD, are preferable. In the present invention, a polymer may be applied by solution, or a hybrid coating method containing an inorganic substance as disclosed in Japanese Patent Application Laid-Open Nos. 2000-323273 and 2004-25732 may be used.

In the present invention, a composition containing a polymerizable compound is usually cured by irradiation with light, but the irradiation light is usually ultraviolet light from a high-pressure mercury lamp or a low-pressure mercury lamp. The radiation energy is preferably 0.1 J / cm ² or more, 0.5 J / cm ² or more is more preferable. When a (meth) acrylate compound is employed as the polymerizable compound, the polymerization is inhibited by oxygen in the air, and therefore it is preferable to reduce the oxygen concentration or oxygen partial pressure during polymerization. When the oxygen concentration during polymerization is lowered by the nitrogen substitution method, the oxygen concentration is preferably 2% or less, and more preferably 0.5% or less. When the oxygen partial pressure during polymerization is reduced by the decompression method, the total pressure is preferably 1000 Pa or less, and more preferably 100 Pa or less. Further, it is particularly preferable to perform ultraviolet polymerization by irradiating energy of 0.5 J / cm ² or more under a reduced pressure condition of 100 Pa or less.

  The polymerization rate of the polymerizable compound constituting the organic layer is preferably 85% or more, more preferably 88% or more, further preferably 90% or more, and particularly preferably 92% or more. . The polymerization rate here means the ratio of the reacted polymerizable group among all the polymerizable groups (for example, acryloyl group and methacryloyl group) in the polymerizable composition. The polymerization rate can be quantified by an infrared absorption method.

The organic layer in the present invention preferably has a thickness in the range of 0.3 μm to 10 μm, and more preferably in the range of 5 μm to 10 μm.
The smoothness of the organic layer is preferably less than 1 nm and more preferably less than 0.5 nm as an average roughness (Ra value) of 1 μm square. The surface of the organic layer is required to be free of foreign matters such as particles and protrusions. For this reason, it is preferable that the organic layer is formed in a clean room. The degree of cleanness is preferably class 10000 or less, more preferably class 1000 or less.
A higher hardness of the organic layer is preferable, but if it is too high, problems such as bending resistance occur. The hardness of the organic layer can be expressed as a microhardness based on the nanoindentation method. The microhardness of the organic layer is 0.03 to 0.5 GPa, and more preferably 0.03 to 0.3 Pa. By setting it as such a range, it becomes possible to improve bending resistance and to improve the scratch resistance to a level at which there is no practical problem.

3. Inorganic layer The inorganic layer in the present invention is usually a thin film layer made of a metal compound. As a method for forming the inorganic layer, any method can be used as long as it can form a target thin film. For example, there are a physical vapor deposition method (PVD) such as a vapor deposition method, a sputtering method, and an ion plating method, various chemical vapor deposition methods (CVD), and a liquid phase growth method such as plating and a sol-gel method. The component contained in the inorganic layer is not particularly limited as long as it satisfies the above-mentioned performance. For example, it is a metal oxide, metal nitride, metal carbide, metal oxynitride, or metal oxycarbide, and particularly silicon and aluminum. A compound containing at least one of the above and at least one of oxygen and nitrogen is preferred. These may contain other elements as secondary components. The inorganic layer in the present invention preferably consists essentially of these components. Here, “substantially” means, for example, that it is not included as an intentionally added component, and means that components such as impurities are not excluded. For example, it means that 99% by weight or more is composed of these components.
The smoothness of the inorganic layer formed by the present invention is preferably less than 1 nm, more preferably 0.5 nm or less, as an average roughness (Ra value) of 1 μm square. The inorganic layer is preferably formed in a clean room. The degree of cleanness is preferably class 10000 or less, more preferably class 1000 or less.

  Although it does not specifically limit regarding the thickness of an inorganic layer, It attaches to 1 layer, and is 5-500 nm normally, Preferably it is 50-400 nm, More preferably, it is 100-200 nm.

(Lamination of organic and inorganic layers)
The organic layer and the inorganic layer can be laminated by sequentially forming the organic layer and the inorganic layer in accordance with a desired layer structure. When the inorganic layer is formed by a vacuum film forming method such as a sputtering method, a vacuum vapor deposition method, an ion plating method, or a plasma CVD method, the organic layer is also preferably formed by a vacuum film forming method such as the flash vapor deposition method. . During the production of the barrier laminate, it is particularly preferable to always laminate the organic layer and the inorganic layer in a vacuum of 1000 Pa or less without returning to atmospheric pressure in the middle. The pressure is more preferably 100 Pa or less, more preferably 50 Pa or less, and further preferably 20 Pa or less.
In this invention, it is preferable to provide an organic layer or an inorganic layer on the surface of a plastic film. Moreover, it is preferable to provide an inorganic layer or an organic layer on the surface of the organic layer or the inorganic layer.
The number of stacked organic layers and inorganic layers is not particularly defined, but is usually 3 to 30 layers.

4). Ultraviolet blocking layer The ultraviolet blocking layer in the present invention is a layer in which inorganic fine particles are dispersed in a binder containing a compound having an average composition formula represented by formula (1).

(binder)
First, the binder containing the compound represented by the formula (1) will be described.
Formula (1)
R ¹ _m Si (OR ² ) _n O _{(4-mn / 2)}
(In the formula, R ¹ is a group selected from a methyl group, an ethyl group and a phenyl group, and R ¹ may contain two or more groups, and R ² is an alkyl having 1 to 8 carbon atoms. And R ² may contain two or more kinds of alkyl groups, 0.2 ≦ m ≦ 2, n is 0.01 ≦ n ≦ 3, and m + n <4. is there.)
R ¹ is a group selected from a methyl group, an ethyl group, and a phenyl group, and is preferably a methyl group and / or an ethyl group. R ² is preferably a methyl group and / or an ethyl group. Each of R ¹ and R ² may be only one type or two or more types.
Furthermore, 0.2 ≦ m ≦ 1 is preferable, and 0.1 ≦ n ≦ 2 is preferable.

Here, the average composition refers to a composition specified according to an NMR (nuclear magnetic resonance spectrum) measurement result and a GPC (gel permeation chromatography) measurement result using polystyrene as a standard substance.
The binder used in the present invention preferably has a weight average molecular weight (Mw) of 1000 to 10,000.

  By adopting such a binder, high adhesion between the plastic film and the coating layer is maintained even when irradiated with ultraviolet rays, and high transparency, high ultraviolet absorption ability, high weather resistance and flexibility are achieved. It becomes possible to do.

(Inorganic fine particles)
The inorganic fine particles used in the present invention are preferably oxides containing at least one element of cerium, zinc, titanium, iron, zirconium, tagsten and strontium, and at least one or more of cerium, titanium and zinc It is more preferable that the oxide contains these elements.
These inorganic fine particles may be so-called core-shell type inorganic fine particles whose surface is covered with a compound containing at least one element of silicon and aluminum, and are not core-shell type inorganic fine particles. However, in the present invention, core-shell type inorganic fine particles are preferable. By adopting the core-shell type inorganic fine particles, the wet heat resistance of the particles themselves can be improved, and further the deterioration of the binder can be suppressed.
The refractive index of the inorganic fine particles used in the present invention is preferably 1.5 to 3.5, and more preferably 1.7 to 3.5.

  The average particle size of the inorganic fine particles in the present invention is preferably 100 nm or less, more preferably 5 to 50 nm, and preferably 2 to 30 nm. By setting it as such a range, while having high transparency by dispersion | distribution, it exists in the tendency for light resistance to improve more. In the case of the core-shell type, it means an average particle diameter including a shell portion.

  As for the average particle diameter of the core-shell type inorganic fine particles, the shell thickness is preferably 1.5 to 20 nm, more preferably 2 to 10 nm, and further preferably 2 to 5 nm. By setting it as such a range, it becomes possible to suppress photocatalytic ability and photolysis, without impairing transparency.

The ultraviolet blocking layer in the present invention is usually provided by applying a coating agent and drying. In the coating agent, the inorganic fine particles are preferably contained in a proportion of 10% by weight or more, and more preferably contained in a proportion of 10 to 30% by weight. By setting it as such a range, a high ultraviolet-absorbing capability is obtained, without impairing transparency.
Moreover, it is preferable that the said binder is contained in the ratio of 90 weight% or less in a coating agent, and it is more preferable that it is contained in the ratio of 90-60 weight%. By setting it as such a range, it exists in the tendency for the adhesiveness of a coating agent and another layer to become higher.
The thickness of the layer to which the coating agent is applied is not particularly defined, but is preferably 1 to 50 μm, more preferably 2 to 20 μm.

One kind of inorganic fine particles in the present invention may be contained in the coating agent, or two or more kinds thereof may be contained.
In order to accelerate the condensation reaction of the binder and cure the coating, a curing catalyst may be added. Examples of such a catalyst include alkyl titanates, tin octylate and dibutyltin dilaurate, and dioctyltin dimaleate. Metal salts of carboxylic acids; amine salts such as dibutylamine-2-hexoate, dimethylamine acetate, ethanolamine acetate; quaternary ammonium salts of carboxylic acids such as tetramethylammonium acetate; amines such as tetraethylpentamine; N- amine-based silane coupling agents such as β-aminoethyl-γ-aminopropyltrimethoxysilane and N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane; acids such as p-toluenesulfonic acid, phthalic acid and hydrochloric acid; Aluminum alkoxide, aluminum clay Aluminum compounds such as potassium hydroxide, alkali catalysts such as potassium hydroxide, titanium compounds such as tetraisopropyl titanate, tetrabutyl titanate, titanium tetraacetylacetonate, halogenated silanes such as methyltrichlorosilane, dimethyldichlorosilane, and trimethylmonochlorosilane However, other than these, there is no particular limitation as long as it is effective for the curing reaction of the binder.
Moreover, it is preferable that the addition amount of a curing catalyst is 0.001-20 weight part with respect to 100 weight part of binder components. More preferably, it is 0.005-10 weight part. When the addition amount of the curing catalyst is less than 0.001 part by weight, the curing may not be performed at room temperature, and when the addition amount of the curing catalyst exceeds 20 parts by weight, the heat resistance and weather resistance of the coating film may be deteriorated.

The adjustment method of the core-shell type inorganic fine particles in the present invention can be adjusted according to a known method, and can be adjusted, for example, according to the methods described in JP-A Nos. 2004-59421 and 2001-58821.
In the present invention, as a method of dispersing the core-shell type inorganic fine particles in the binder, a known method can be widely adopted, and it can be performed using a general mixing apparatus such as a sand mill, a ball mill, or a paint shaker. At this time, dispersion is performed using the same material as the binder component and surface treatment is performed, so that dispersion stability can be obtained even in the coating liquid, and the dispersion can be uniformly dispersed in the cured film.

  The ultraviolet blocking layer in the present invention preferably consists essentially of a binder, a curing catalyst, and inorganic fine particles. Here, “substantially” means, for example, that it is not included as an intentionally added component, and means that components such as impurities are not excluded. For example, it means that 99% by weight or more is composed of these components.

The thickness of the ultraviolet blocking layer is not particularly limited, but is usually 5 to 1500 nm, preferably 50 to 1000 nm, more preferably 200 to 500 nm per layer.
The refractive index of the ultraviolet blocking layer is preferably 1.45 to 2.5, and more preferably 1.5 to 2.0.

5. Adhesive layer In the present invention, the fluororesin film is usually adhered to an adjacent layer with an adhesive.
The adhesive layer in the present invention is not particularly defined as long as an adhesive is included, and 98% by weight or more of the layer is preferably an adhesive. In the present invention, an ultraviolet (UV) curable adhesive or a thermosetting adhesive can be preferably used, and an ultraviolet curable adhesive is more preferable. The type of the adhesive is not particularly defined, but examples of the UV curable adhesive include epoxy-based, acrylate-based, and urethane-based examples, and urethane-based adhesives are more preferable. Examples of the thermosetting adhesive include epoxy-based, acrylate-based, and urethane-based examples, and urethane-based adhesives are more preferable.
The thickness of the adhesive layer is preferably 0.1 to 20 μm, and preferably 0.5 to 5 μm.
In the present invention, an easy adhesion layer may be provided. The easy-adhesion layer is a kind of a layer called a primer layer, an undercoat layer, an undercoat layer, or the like, and is a layer provided for the purpose of adjusting the interface state between layers. By providing such a layer, there is an advantage of particularly improving the adhesion.

6). Fluororesin film The fluororesin film in the present invention is a resin film mainly composed of a fluororesin. Examples of the fluororesin constituting the fluororesin film include polytetrafluoroethylene (PTFE), perfluoroalkoxy resin (PFA) made of a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, tetrafluoroethylene and hexafluoropropylene, and the like. Copolymer (FEP) of tetrafluoroethylene and perfluoroalkyl vinyl ether and hexafluoropropylene (EPE), copolymer of tetrafluoroethylene and ethylene or propylene (ETFE), polychlorotrifluoroethylene resin (PCTFE), ethylene and Examples thereof include a copolymer with chlorotrifluoroethylene (ECTFE), vinylidene fluoride resin (PVDF), and vinyl fluoride resin (PVF). Among these fluororesins, polyvinyl fluoride resin (PVF) and a copolymer of tetrafluoroethylene and ethylene or propylene (ETFE) which are excellent in strength, heat resistance, weather resistance and the like are particularly preferable.

The fluororesin film of the present invention may contain a component other than the fluororesin, but it is preferable that 50% by weight or more of the component is composed of a fluororesin. Moreover, the fluororesin film of the present invention can be made to contain substantially no fine particles. Here, “substantially” means, for example, that it is not included as an intentionally added component, and means that components such as impurities are not excluded. For example, it means that 99% by weight or more is composed of these components. In the present invention, light resistance can be improved without including fine particles in the fluororesin film as described above, and therefore it can be preferably used even when scratch resistance becomes a problem.
The thickness of the fluororesin film in the present invention is preferably in the range of 10 μm to 1000 μm, and more preferably in the range of 20 μm to 500 μm.

(Solar cell)
The solar cell element of the present invention refers to a system that converts sunlight into electricity. An example of the structure is shown in FIG. That is, the front sheet layer 7, the filling adhesive resin layer 8, the solar cell element main part 9, the filling adhesive resin layer 10, and the back sheet layer 11 are the basic configuration from the side where sunlight enters. The solar cell protective sheet of the present invention is preferably used for the front sheet layer, but can also be used for the back sheet layer and the like. This solar cell element is incorporated in the roof of a house, or is installed in farm ponds, ranches, wastewater and sewage treatment facilities, volcanoes and hot spring areas, buildings and fences, and used for electronic parts. Some of the solar cell modules transmit light called daylighting type or see-through type and are used for soundproof walls such as windows, highways and railways. In this invention, it can be set as a particularly flexible type.

  The solar cell element in which the solar cell protective sheet of the present invention is preferably used is not particularly limited, but for example, a single crystal silicon solar cell element, a polycrystalline silicon solar cell element, a single junction type, or a tandem structure type Amorphous silicon-based solar cell elements composed of, etc., III-V group compound semiconductor solar cell elements such as gallium arsenide (GaAs) and indium phosphorus (InP), and II-VI group compound semiconductor solar cells such as cadmium tellurium (CdTe) I- such as element, copper / indium / selenium system (so-called CIS system), copper / indium / gallium / selenium system (so-called CIGS system), copper / indium / gallium / selenium / sulfur system (so-called CIGS system), etc. III-VI compound semiconductor solar cell elements, dye-sensitized solar cell elements, organic solar cell elements, etc. . In particular, in the present invention, the solar cell element is a copper / indium / selenium system (so-called CIS system), a copper / indium / gallium / selenium system (so-called CIGS system), copper / indium / gallium / selenium / sulfur. It is preferable to be an I-III-VI group compound semiconductor solar cell element such as a system (so-called CIGSS system).

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

(Comparative Example 1)
The following polymerizable compounds (total 14 parts by weight) and a polymerization initiator (Ciba Specialty Chemicals, IRGACURE 907, 1 part by weight) on polyethylene terephthalate having a thickness of 100 μm (Teonex Q65FA, manufactured by Teijin DuPont), 2-butanone ( 185 parts by weight) was applied with a wire bar, and cured by irradiation with an ultraviolet ray irradiation amount of 0.5 J / cm ² in an atmosphere of 100 ppm nitrogen to produce an organic layer. The film thickness of the organic layer was 500 nm. Next, Al ₂ O ₃ was formed on the surface of the organic layer by vacuum sputtering (reactive sputtering) so as to have a film thickness of 40 nm. Further, an organic layer was provided thereon in the same manner as described above to obtain a film (A).

Composition of polymerizable compound Compounds A to D shown below were used in the ratios shown below.

化合物Ｂ：ダイセルサイテック（株）製、ＴＭＰＴＡ：３０質量％

化合物Ｃ：ダイセルサイテック（株）製、ＩＲＲ＝２１４Ｋ：１０質量％

化合物Ｄ：日本化薬（株）製、ＫＡＹＡＲＡＤ、ＰＭ−２１：１０質量％

Compound A: manufactured by Kyoeisha Chemical Co., Ltd., light acrylate 1,9-ND-A: 50% by mass

Compound B: Daicel Cytec Co., Ltd., TMPTA: 30% by mass

Compound C: manufactured by Daicel Cytec Co., Ltd., IRR = 214K: 10% by mass

Compound D: Nippon Kayaku Co., Ltd., KAYARAD, PM-21: 10 mass%

An ethylene-tetrafluoroethylene copolymer film ("Neofluon ETFE film (EF-0050)" made by Daikin, which is a fluororesin film having a thickness of 50 μm on the surface of the film (A) on which the Al ₂ O ₃ layer is provided. ) Were laminated via a urethane-based adhesive to obtain a sample 101.

(Comparative Example 2)
In Comparative Example 1, Sample 102 was obtained in the same manner as Comparative Example 1, except that a benzotriazole ultraviolet absorber (manufactured by BASF, TINUVIN 328) was added to the urethane adhesive in a proportion of 25% by weight.

(Comparative Example 3)
Core-shell type zinc oxide particles (manufactured by Sakai Chemical, Nanofine, particle size: 24 nm, core: ZnO with a particle size of 20 nm, shell composition: SiO ₂ / Al ₂ O ₃ , shell thickness: 2 nm) were added to the urethane-based adhesive. Sample 103 was obtained in the same manner as in Comparative Example 1 except that.

(Comparative Example 4)
A sample 104 was obtained in the same manner as in Comparative Example 1 except that CeO ₂ fine particles (Nydral U-15 manufactured by Taki Chemical Co., Ltd.) were added to the urethane-based adhesive.

Example 1
(Adjustment of binder composition)
100 parts by weight of an alkoxy silicone oligomer (Shin-Etsu Chemical Co., Ltd., X-40-925 0) as a siloxane binder, 5 parts by weight of a titanium-based curing catalyst (Shin-Etsu Chemical Co., Ltd., D-20), 100 parts by weight of butanol Were mixed and adjusted.

(Preparation of butanol dispersion containing core-shell type zinc oxide particles)
Core shell type zinc oxide particles (manufactured by Sakai Chemical, Nanofine, average particle size: 24 nm, core: ZnO with an average particle size of 20 nm, shell composition: SiO ₂ / Al ₂ O ₃ , shell thickness: 2 nm) 10 parts by weight of butanol 100 parts by weight And 50 parts by weight of X-40-9250 were added and dispersed with a planetary ball mill to obtain a butanol dispersion containing core-shell type zinc oxide particles.

(Coating agent adjustment)
In the coating agent, add butanol dispersion containing core-shell type zinc oxide particles to the binder composition so that the content of core-shell type zinc oxide particles of the core-shell type zinc oxide particle composition is 20% by weight, and stir. The coating agent was adjusted.

(Application)
After producing a film (A) in the same manner as in Comparative Example 1, the coating agent was applied onto the film (A) by a wire bar coat so that the dry film thickness was 5 μm, and dried at room temperature for 6 hours. Then, an ultraviolet ray fault was formed to obtain a film (B).
An ethylene-tetrafluoroethylene copolymer film ("Neofluon ETFE film (EF-0050)" manufactured by Daikin), which is a fluororesin film having a thickness of 50 μm, is applied to the surface of the film (B) on which the coating agent is applied. A sample 105 was obtained by laminating with a urethane adhesive.

(Example 2)
(Preparation of CeO ₂ fine particle-containing butanol dispersion)
CeO ₂ fine particles (Nidral U-15 manufactured by Taki Chemical Co., Ltd.) were subjected to solvent substitution with butanol solvent. 100 parts by weight of butanol and 50 parts by weight of X-40-9250 were added to 10 parts by weight of the obtained dispersion and dispersed with a planetary ball mill to obtain a butanol dispersion containing CeO ₂ fine particles.
Sample 106 was obtained in the same manner as in Example 1, except that the butanol dispersion containing core-shell type zinc oxide particles was changed to the butanol dispersion containing CeO ₂ fine particles prepared above.

(Example 3)
80 parts by weight of X-40-9250 and 20 parts by weight of KR-500 (manufactured by Shin-Etsu Chemical Co., Ltd.) instead of the siloxane-based binder X-40-9250 in (Adjustment of binder composition) of Example 1 Sample 107 was obtained in the same manner except that the mixture consisting of

Example 4
80 parts by weight of X-40-9250 and 10 weights of X-40-9225 (manufactured by Shin-Etsu Chemical Co., Ltd.) are used instead of the siloxane-based binder X-40-9250 in (Adjustment of binder composition) of Example 1. A sample 108 was obtained in the same manner except that a mixture consisting of 10 parts by weight and KR-500 was used.

(Example 5)
A sample 109 was obtained in the same manner as in Example 1 except that the adhesive was changed to an acrylic adhesive.

(Comparative Example 5)
SiO ₂ fine particles (Nissan Chemical, Snowtech 20) were solvent-substituted with a butanol solvent to obtain a butanol dispersion of SiO ₂ fine particles. 100 parts by weight of butanol and 50 parts by weight of X-40-9250 are added to 10 parts by weight of the obtained SiO ₂ butanol dispersion, and dispersed in a planetary ball mill to obtain a butanol dispersion containing SiO ₂ fine particles. It was.
A sample 110 was obtained in the same manner as in Example 1 except that the butanol dispersion containing core-shell type zinc oxide particles was changed to the SiO ₂ butanol dispersion.

(Comparative Example 6)
Sample 111 was obtained in the same manner as in Example 1 except that the core-shell type zinc oxide particles of the core-shell type zinc oxide particle composition in the coating agent were not added.

(Comparative Example 7)
Core-shell type zinc oxide particles (manufactured by Sakai Chemical, Nanofine, particle size: 24 nm, core: ZnO with a particle size of 20 nm, shell composition: SiO ₂ / Al ₂ O ₃ , shell thickness: 2 nm) were added to the urethane-based adhesive. Sample 112 was obtained in the same manner as in Comparative Example 5 except for the above.

  The following evaluation was performed about the obtained sample.

[Barrier performance]
The water vapor permeability (g / m 2 / day) was measured using the method described in G. NISATO, PCPBOUTEN, PJSLIKKERVEER et al. SID Conference Record of the International Display Research Conference, pages 1435-1438. The temperature at this time was 40 ° C. and the relative humidity was 90%. The obtained results were evaluated as follows, and the results are shown in the following table.
(Evaluation)
×: 0.005 g / m ² / day or more ○: 0.001 g / m ² / day or more 0.005 g / m less than ² / day ◎: 0.001 g / m less than ² / day

[Light resistance]
Using a metalling vertical weather meter (MV 3000 manufactured by Suga Test Instruments Co., Ltd.), 0.53 kW / m ² (wavelength: 300 to 400 nm), black panel temperature 63 ° C., chamber humidity 50%, 2000 hours, ultraviolet rays for test sample An exposure test was conducted. The UV-vis of the sample before and after UV irradiation was measured with a Hitachi spectrophotometer (U-3200), the Abs. At a wavelength of 330 nm was measured, and the ratio of Abs. Before and after irradiation was T (abs.). did. The obtained results were evaluated as follows, and the results are shown in the following table.
T (Abs.) = Abs. After UV irradiation (330 nm) / Abs. Before UV irradiation (330 nm)
(Evaluation)
×: T (Abs.)> 25
Δ: 25 ≧ T (Abs.) ≧ 13
○: 13 ≧ T (Abs.) ≧ 6
◎: 6> T (Abs.)

[Adhesion evaluation]
The adhesion of the protective film was evaluated by a cross-cut test based on JIS K5400. On the surface of the protective film, cuts of 90 ° with respect to the film surface were made with a cutter knife at intervals of 1 mm, and 100 grids with intervals of 1 mm were produced. A 2 cm wide Mylar tape [manufactured by Nitto Denko, polyester tape (No. 31B)] was applied thereto, and the tape attached using a tape peeling tester was peeled off. Of the 100 grids on the protective film, the number of cells remaining without peeling (n) was counted.
Regarding the adhesion evaluation, 0.53 kW / m ² (wavelength: 300 to 400 nm), black panel temperature of 63 ° C., humidity in the tank using a metallizing vertical weather meter (MV 3000 manufactured by Suga Test Instruments) Evaluation was performed after an ultraviolet exposure test was performed on the test sample at 50% for 2000 hours. The results are shown in the table below.
Number of remaining N = n / 100
(Evaluation)
×: N <0.2
Δ: 0.2 ≦ N ≦ 0.5
○: 0.51 ≦ N ≦ 0.8
: 0.81 <N

[Total light transmittance]
According to JIS K7361-1, the total light transmittance was measured using a haze meter (NDH 5000 manufactured by Nippon Denshoku Industries Co., Ltd.).

[Refractive index]
Using a visible spectroscopic ellipsometer (made by HORIBA), the refractive index of each layer is derived, the difference between the refractive index of the adhesive layer and the refractive index of the adjacent ultraviolet shielding layer is calculated, and the refractive index na of the adhesive layer is adjacent. Difference Δn = nu−na from the refractive index nu of the UV shielding layer was determined. Δn is defined as follows and summarized in Table 1.
Δn <−0.1: −−
Δn = 0 to −0.1: −
Δn = 0 to +0.1: +
Δn> +0.1: ++

(Example 5) Production of solar cell Using ethylene vinyl acetate (EVA) resin film as an adhesive, samples 105 to 108 having the structure of the above example were used as a front sheet, and in Example 1 of JP2009-99973A A solar cell was prepared by pasting on the surface of the CIS film of the CIS-based thin film solar cell described. It was confirmed to operate as a solar cell.

DESCRIPTION OF SYMBOLS 1 Plastic film 2 Organic layer 3 Inorganic layer 4 Ultraviolet ray blocking layer 5 Adhesive layer 6 Fluoro resin film 7 Front sheet layer 8 Filling adhesive resin layer 9 Solar cell element principal part 10 Filling adhesive resin layer 11 Back sheet layer

Claims (15)

In a binder containing an inorganic layer, an organic layer, an ultraviolet blocking layer, and a fluororesin film on a plastic film, and the ultraviolet blocking layer includes a compound having an average composition formula represented by the following formula (1) And the refractive index of the ultraviolet blocking layer is a layer adjacent to the ultraviolet blocking layer and higher than the refractive index of the layer on which the fluororesin film is provided, Furthermore, the protective sheet for solar cells, wherein the fluororesin film is the outermost layer on the side where the ultraviolet blocking layer is provided.
Formula (1)
R ¹ _m Si (OR ² ) _n O _{(4-mn / 2)}
(In the formula, R ¹ is a group selected from a methyl group, an ethyl group and a phenyl group, and R ¹ may contain two or more groups, and R ² is an alkyl having 1 to 8 carbon atoms. And R ² may contain two or more kinds of alkyl groups, 0.2 ≦ m ≦ 2, n is 0.01 ≦ n ≦ 3, and m + n <4. is there.) The protective sheet for solar cells according to claim 1, wherein the inorganic fine particles are an oxide containing at least one element of cerium, zinc, titanium, iron, zirconium, tagsten and strontium. The protective sheet for solar cells according to claim 1 or 2, wherein an inorganic layer, an organic layer, an ultraviolet blocking layer and a fluororesin film are provided on one surface of the plastic film. The protective sheet for solar cells according to any one of claims 1 to 3, wherein the ultraviolet blocking layer and the fluororesin film are bonded together by an adhesive layer. The surface of the inorganic fine particles containing at least one element of cerium, zinc, titanium, iron, zirconium, tag stainless and strontium is covered with a compound containing at least one element of silicon and aluminum. The protective sheet for solar cells according to claim 1, 3 or 4, which is an inorganic fine particle. The solar cell protective sheet according to any one of claims 1 to 5, wherein the inorganic layer contains at least one of silicon and aluminum and at least one of oxygen and nitrogen. The average particle diameter of the said inorganic fine particle is 100 nm or less, The protective sheet for solar cells of any one of Claims 1-6 characterized by the above-mentioned. Inorganic fine particles in which the inorganic fine particles contain at least one element of cerium and zinc, or the surface of these inorganic fine particles is covered with a compound containing at least one element of silicon and aluminum The protective sheet for a solar cell module according to any one of claims 1, 3, 4, 6, and 7. The protective sheet for solar cells of any one of Claims 1-8 whose thickness of a fluororesin film is 10 micrometers-1000 micrometers. The protective sheet for solar cells according to any one of claims 1 to 9, wherein the organic layer is a layer formed by curing a polymerizable composition containing (meth) acrylate. The protective sheet for solar cells of any one of Claims 1-10 whose total light transmittance is 85% or more. The solar cell protective sheet according to any one of claims 4 to 10, wherein the adhesive layer contains a urethane-based adhesive. The protective sheet for solar cells of any one of Claims 1-12 whose plastic film is a polyester resin film. The solar cell protective sheet according to claim 1, which is for a front sheet. The solar cell element which has a protection sheet for solar cells of any one of Claims 1-14.

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