WO2015098520A1

WO2015098520A1 - Sheet for solar cell backside protection

Info

Publication number: WO2015098520A1
Application number: PCT/JP2014/082698
Authority: WO
Inventors: 規行巽; 堀江　将人; 敏弘千代; 東大路　卓司
Original assignee: 東レ株式会社
Priority date: 2013-12-27
Filing date: 2014-12-10
Publication date: 2015-07-02
Also published as: TW201535764A; JPWO2015098520A1

Abstract

The purpose of the present invention is to provide a sheet for solar cell backside protection, which exhibits excellent adhesion to a sealing material and maintains the adhesion even if placed outdoors for a long period of time (namely has excellent adhesion retention ability). A solar cell backside protection sheet (1) according to the present invention comprises: a base layer (P1 layer) that is formed of a polyester resin; and a highly adhesive layer (P2 layer) that is adjacent to at least one side of the P1 layer. The P2 layer satisfies the following conditions (A) and (B). (A) To contain three components, namely a urethane resin component, a melamine resin component and an epoxy resin component. (B) To have a contact angle with water of 74° or more.

Description

Solar cell back surface protection sheet

The present invention relates to a sheet for protecting a back surface of a solar cell, which has excellent adhesion to a sealing material for solar cells and maintains adhesion even when left outdoors for a long time (excellent retention).

In recent years, photovoltaic power generation has attracted attention as a semi-permanent and pollution-free next-generation energy source, and solar cells are rapidly spreading. In a solar cell, a power generating element is sealed with a transparent sealing material such as ethylene-vinyl acetate copolymer (hereinafter sometimes referred to as EVA), a transparent substrate such as glass, and a back sheet (for back surface protection). A resin sheet called a “sheet” is bonded together. Sunlight is introduced into the solar cell through the transparent substrate. Sunlight introduced into the solar cell is absorbed by the power generation element, and the absorbed light energy is converted into electrical energy. The converted electric energy is taken out by a lead wire connected to the power generation element and used for various electric devices.

Here, biaxially stretched polyethylene terephthalate (hereinafter sometimes referred to as PET) that is inexpensive and has high performance is widely used as a sheet for protecting the back surface of a solar cell, and various materials can be applied by a method such as dry lamination. Studies have been made to impart barrier properties and electrical characteristics by bonding. However, polyester resins such as PET have poor adhesion to the sealing material. Therefore, conventionally, it is common to laminate a polyolefin resin sheet excellent in adhesion to a sealing material on a polyester resin such as PET and use the polyolefin resin sheet as a sealing material adhesion surface of a solar cell back surface protection sheet. Met.

In recent years, polyester sheets (Patent Documents 1, 2, and 3) that are provided with an easy-adhesion layer on the surface of a biaxially stretched polyester film and can be directly bonded to a sealing material have been disclosed.

JP 2006-152013 A Japanese Patent No. 4803317 JP 2012-69835 A

However, the conventional easy-adhesion layers listed in Patent Documents 1 to 3 have very weak adhesion to the sealing material, and are not only used during the processing of solar cells but also used outdoors as solar cells. There has been a problem that it is easy to peel off at the interface with the sealing material or at the easily adhesive layer. In order to solve this problem, in the present invention, in view of the conventional problems, the solar cell is excellent in adhesion with a sealing material and maintains adhesion even when left outdoors for a long time (excellent retention property). It aims at providing the sheet | seat for back surface protection.

In order to solve the above problems, the present invention has the following configuration. That is, it has a base material layer (P1 layer) made of a polyester resin and an easy adhesion layer (P2 layer) adjacent to at least one side of the P1 layer, and the P2 layer is the following (1), (2) It is a solar cell back surface protection sheet characterized by satisfying the requirements.
(1) Contains three components, a urethane resin component, a melamine resin component, and an epoxy resin component.
(2) The contact angle of water is 74 ° or more.

According to the present invention, compared to a conventional laminated sheet in which an easy-adhesion layer is provided on the surface of a biaxially stretched polyester film, it has excellent adhesiveness with a sealing material, and even when placed outdoors for a long period of time. Can be suitably used as a sheet for protecting the back surface of a solar cell (with excellent adhesion retention), and a high-performance solar cell can be provided by using the sheet.

It is sectional drawing which shows typically an example of a structure of the solar cell using the solar cell back surface protection sheet of this invention.

The sheet for protecting the back surface of a solar cell of the present invention has a base material layer (P1 layer) made of a polyester resin and an easy adhesion layer (P2 layer) adjacent to at least one side of the P1 layer. The requirements (1) and (2) are satisfied.
(1) Contains three components, a urethane resin component, a melamine resin component, and an epoxy resin component.
(2) The contact angle of water is 74 ° or more.

(Base material layer (P1 layer))
First, the P1 layer in the present invention contains a polyester resin as a main component. Here, the main constituent component of the polyester resin means that the polyester resin is contained in an amount exceeding 50% by mass with respect to the resin constituting the P1 layer. Specific examples of the polyester resin constituting the P1 layer include polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, and polylactic acid. The polyester resin used in the present invention includes 1) polycondensation of dicarboxylic acid or an ester-forming derivative thereof (hereinafter collectively referred to as “dicarboxylic acid component”) and a diol component, and 2) carboxylic acid or carboxylic acid in one molecule. It can be obtained by a polycondensation of an acid derivative and a compound having a hydroxyl group, and 1) 2). The polymerization of the polyester resin can be performed by a conventional method.

In 1), as the dicarboxylic acid component, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalonic acid, Aliphatic dicarboxylic acids such as ethylmalonic acid, alicyclic dicarboxylic acids such as adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexane dicarboxylic acid, decalin dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 4,4′-diphenylsulfonedicarboxylic acid Acid, 5-sodium Ruhoisofutaru acid, phenyl ene boys carboxylic acid, anthracene dicarboxylic acid, phenanthrene carboxylic acid, 9,9'-bis (4-carboxyphenyl) aromatic dicarboxylic acids such as fluorene acid, or the like its ester derivatives and the like as a typical example. These may be used alone or in combination.

In addition, dicarboxyl obtained by condensing oxyacids such as l-lactide, d-lactide, and hydroxybenzoic acid, and derivatives thereof, or a combination of a plurality of such oxyacids, at least one carboxy terminus of the dicarboxylic acid component described above. Compounds can also be used.

Next, the diol component includes aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol. , Cycloaliphatic dimethanol, spiroglycol, isosorbide and other alicyclic diols, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9'-bis (4-hydroxyphenyl) fluorene, etc. Aromatic diols are typical examples. Moreover, these may be used independently or may be used in multiple types as needed. In addition, a dihydroxy compound formed by condensing a diol with at least one hydroxy terminal of the diol component described above can also be used.

In 2), examples of the compound having a carboxylic acid or a carboxylic acid derivative and a hydroxyl group in one molecule include oxyacids such as l-lactide, d-lactide and hydroxybenzoic acid, and derivatives thereof, oligomers of oxyacids, dicarboxylic acids Examples thereof include those obtained by condensing an oxyacid with one carboxyl group of the acid.

The dicarboxylic acid component and the diol component constituting the polyester resin may be copolymerized by selecting one from the above, or may be copolymerized by selecting a plurality of each.

The polyester resin constituting the P1 layer may be a single type or a blend of two or more types of polyester resins.

As described above, the resin constituting the P1 layer in the present invention is mainly a polyester resin, but the intrinsic viscosity IV is 0.65 dl / g or more and 0.80 dl / g or less, and the terminal carboxyl group amount is 25 equivalents / It is preferably less than tons. The polyester resin is preferably composed mainly of polyethylene terephthalate (PET). Here, the main component means that it is contained in excess of 50% by mass with respect to the polyester resin. When the resin constituting the P1 layer contains PET as the main constituent, the intrinsic viscosity IV of the PET is preferably 0.65 dl / g or more, more preferably 0.69 dl / g or more. When the intrinsic viscosity IV is less than 0.65 dl / g, the moisture and heat resistance of the sheet may be deteriorated. Moreover, when intrinsic viscosity IV exceeds 0.80 dl / g, when the P1 layer is manufactured, the extrudability of the resin is poor, and sheet molding may be difficult. Furthermore, even if the intrinsic viscosity IV satisfies the above range, if the terminal carboxyl group amount exceeds 25 equivalents / ton, the adhesion with the P2 layer is improved, but the moisture and heat resistance of the sheet is deteriorated, which is not preferable. There is. Therefore, when the resin constituting the P1 layer contains PET as a main constituent, by satisfying the above range, a sheet for protecting a back surface of a solar cell that is extremely excellent in moldability and long-term durability can be obtained.

In the solar cell back surface protective sheet of the present invention, the number average molecular weight of the polyester resin constituting the P1 layer is preferably 8000 to 40000, more preferably 9000 to 30000, and still more preferably 10,000 to 20000. Here, the number average molecular weight of the polyester resin constituting the P1 layer refers to the gel permeation chromatography method by separating the P2 layer from the solar cell back surface protective sheet of the present invention and dissolving it in hexafluoroisopronol (HEIP). It is a value obtained by using polyethylene terephthalate (PET-5R: Mw 55800) having a known molecular weight and dimethyl terephthalate as standard samples from values measured by a GPC method and detected by a differential refractometer. When the number average molecular weight of the polyester resin constituting the P1 layer is less than 8000, it is not preferable because the long-term durability of the sheet such as moisture and heat resistance may be deteriorated. On the other hand, if it exceeds 40,000, even if the polymerization is difficult or the polymerization can be performed, it may be difficult to extrude the resin with an extruder and film formation may be difficult. In the solar cell back surface protective sheet of the present invention, the P1 layer is preferably uniaxially or biaxially oriented. When the P1 layer is uniaxially or biaxially oriented, the long-term durability of the sheet such as moist heat resistance and heat resistance can be improved by orientation crystallization.

For the purpose of imparting properties such as ultraviolet resistance, light reflectivity, light hiding property, designability, and visibility to the P1 layer in the present invention, a method of containing particles having respective functions is also preferably used. For example, in order to improve both ultraviolet resistance and light reflectivity, it is preferable to contain titanium oxide particles in the range of 1% by mass to 30% by mass with respect to the resin constituting the P1 layer. This makes it possible to reduce the coloring due to deterioration of the sheet for protecting the back surface of the solar cell over a long period by utilizing the ultraviolet absorbing ability and the light reflectivity by the titanium oxide particles, and the sun mounted with the sheet for protecting the back surface of the solar cell of the present invention. Both of the effects of increasing the power generation efficiency of the battery can be expected. If it is less than 1% by mass, the UV resistance and light reflectivity may be insufficient. If it exceeds 30% by mass, the adhesion to the P2 layer may be deteriorated. A more preferable range is 1% by mass or more and 25% by mass or less, further preferably 2% by mass or more and 25% by mass or less, and particularly preferably 3% by mass or more and 20% by mass or less. Moreover, it is more preferable to use a rutile type titanium oxide from the viewpoint of achieving both excellent ultraviolet resistance and light reflectivity.

Furthermore, in order to improve the ultraviolet resistance, light hiding property, and design, 0.1 particles (hereinafter referred to as carbon particles) made of a carbon-based material such as fullerene, carbon fiber, or carbon nanotube are used as the resin constituting the P1 layer. It is preferable to contain in the range of mass% or more and 5 mass% or less. This makes it possible to exhibit the effect of reducing coloring due to deterioration of the sheet for protecting the back surface of the solar cell over a long period of time by making use of the ultraviolet absorbing ability and light hiding property of the carbon particles. If it is less than 0.1% by mass, the UV resistance may be insufficient. If it exceeds 5% by mass, the adhesion with the P2 layer may be deteriorated. A more preferable range is 0.2% by mass or more and 4% by mass or less, and further preferably 0.5% by mass or more and 3% by mass or less.

Here, as a method of incorporating the particles into the polyester resin constituting the P1 layer, a method of melt-kneading the polyester resin and the particles using a vent type twin-screw kneading extruder or a tandem type extruder is preferably used. Here, when the polyester resin is subjected to a thermal load when the polyester resin contains particles, the polyester resin deteriorates not a little. Therefore, a high-concentration master pellet having a particle content larger than the amount of particles contained in the polyester resin constituting the P1 layer is prepared, mixed with the polyester resin and diluted to obtain a desired particle content P1 layer. It is preferable to produce it from the viewpoint of heat and humidity resistance.

In addition to the titanium oxide particles and carbon particles, the P1 layer in the solar cell back surface protection sheet of the present invention may include a heat-resistant stabilizer and an oxidation-resistant stabilizer as long as the effects of the present invention are not impaired. , UV absorbers, UV stabilizers, organic / inorganic lubricants, organic / inorganic fine particles, fillers, nucleating agents, dyes, dispersants, coupling agents, etc. It may be. For example, when an ultraviolet absorber is selected as an additive, the ultraviolet resistance of the solar cell back surface protective sheet of the present invention can be further enhanced. In addition, anti-static agents are added to improve electrical insulation, or organic or inorganic fine particles or bubbles are included to express light reflectivity, or a color material to be colored is added to create a design. Can also be given.

The P1 layer in the present invention may have a laminated structure. For example, a laminated structure of a P11 layer excellent in heat and moisture resistance and a layer P12 layer containing a high concentration of an ultraviolet absorber or titanium oxide particles having an ultraviolet absorbing ability is preferably used. In the case of such a P1 layer, the configuration of the solar cell back surface protection sheet of the present invention is preferably P12 layer / P11 layer // P2 layer from the viewpoint of coexistence of moisture and heat resistance. . In this case, as the resin and particles used for the P11 layer and the P12 layer, those exemplified for the P1 layer can be suitably used as appropriate.

In the solar cell back surface protective sheet of the present invention, the P1 layer preferably has a thickness of 30 μm or more and less than 500 μm. When the thickness of the P1 layer is less than 30 μm, the electrical insulation is insufficient, and when it is used under a high voltage, dielectric breakdown may occur, which may not be preferable as a solar cell back surface protection sheet. On the other hand, if the thickness is greater than 500 μm, the processability is poor, and when used as a solar battery back surface protection sheet, the overall thickness of the solar battery cell may become too thick, which may be undesirable. A preferable range is 38 μm or more and 400 μm or less, and more preferably 50 μm or more and 300 μm or less.

(P2 layer (hereinafter sometimes referred to as easy-adhesion layer))
The solar cell back surface protection sheet of the present invention needs to be provided with a P2 layer as an easy adhesion layer adjacent to the P1 layer. At this time, the P2 layer needs to be provided on at least one side of the P1 layer.

In the solar cell back surface protective sheet of the present invention, the P2 layer is characterized by containing three components of a urethane resin component, a melamine resin component, and an epoxy resin component. The urethane resin component mentioned here includes not only urethane resins but also components obtained by reacting urethane resins with each other or with urethane resins and other components (melamine resin or epoxy resin). The melamine resin component includes not only melamine resins but also components obtained by reacting melamine resins with each other or with melamine resins and other components (urethane resin or epoxy resin). The epoxy resin component includes not only an epoxy resin but also a component obtained by reacting an epoxy resin with each other or with an epoxy resin and another component (urethane resin or melamine resin). In addition, the term “the three components” as used herein means that the surface of the P2 layer has an X-ray photoelectron spectrometer (ESCA), a Fourier infrared spectrophotometer (FT-IR) ATR method, a time-of-flight secondary Ion mass spectrometer (TOF-SIMS) or P2 layer is dissolved and extracted with a solvent, proton nuclear magnetic resonance spectroscopy ( ¹ H-NMR), carbon nuclear magnetic resonance spectroscopy ( ¹³ C-NMR), Fourier infrared It can be confirmed by analyzing the structure with a spectrophotometer (FT-IR) and performing a qualitative analysis of the P2 layer performed by pyrolysis gas chromatography mass spectrometry (GC-MS).

The urethane resin component contained in the P2 layer of the present invention is obtained by reacting a resin containing a urethane bond obtained by a reaction between a polyol compound and a polyisocyanate compound in the main chain, and the resin and other components. Resin.

In addition, from the viewpoint of excellent adhesion retention after the acceleration test, the urethane resin component preferably includes a urethane resin having a polyester skeleton in which the polyol component is a polyester polyol (hereinafter sometimes referred to as a polyester urethane resin). Specifically, the polyester polyol preferably has a polyester structure synthesized from a dicarboxylic acid component and a diol component shown below. Dicarboxylic acid components include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalonic acid, ethylmalonic acid, etc. Aliphatic dicarboxylic acids, adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexane dicarboxylic acid, alicyclic dicarboxylic acid such as decalin dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5- Naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 4,4′-diphenylsulfonedicarboxylic acid, 5- Sodium sulfoisophthalate , Phenyl ene boys carboxylic acid, anthracene dicarboxylic acid, phenanthrene carboxylic acid, 9,9'-bis (4-carboxyphenyl) and aromatic dicarboxylic acids such as fluorene acid. Examples of the diol component include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, Arocyclic diols such as methanol, spiroglycol and isosorbide, aromatic diols such as bisphenol A, 1,3-benzenedimethanol, 1,4-benzendimethanol and 9,9'-bis (4-hydroxyphenyl) fluorene Is mentioned.

By including the polyester urethane resin, the urethane resin component contained in the P2 layer of the present invention has excellent adhesion retention with the sealing material even after the acceleration test. When mounted on a battery, the solar battery can be made more durable.

On the other hand, as the polyisocyanate component used for the urethane resin, one or a mixture of two or more known aromatic, aliphatic and alicyclic diisocyanates can be used. Specific examples of diisocyanates include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate, isophorone diisocyanate, dimaryl diisocyanate, Examples thereof include lysine diisocyanate, hydrogenated 4,4′-diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, dimerized isocyanate obtained by converting the carboxyl group of dimer acid to an isocyanate group, and adducts, biurets, and isocyanurates. Further, as the diisocyanates, trifunctional or higher functional polyisocyanates such as triphenylmethane triisocyanate and polymethylene polyphenyl isocyanate may be used.

Further, from the viewpoint of dispersibility in an aqueous medium, the urethane resin preferably has a hydrophilic group. As used herein, the hydrophilic group includes a functional group that becomes an anion in an aqueous medium such as a carboxyl group, a sulfonic acid group, a sulfuric acid group, and a phosphoric acid group. By using the polyurethane resin having the hydrophilic group, handling properties at the time of coating can be enhanced.

Here, in order to introduce a hydrophilic group into the urethane resin, a polyol component having a carboxyl group, a sulfonic acid group, a sulfuric acid group, a phosphoric acid group or the like may be used. Examples of the polyol compound having a carboxyl group include 3,5-dihydroxybenzoic acid, 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxyethyl) propionic acid, and 2,2-bis (hydroxypropyl). Propionic acid, bis (hydroxymethyl) acetic acid, bis (4-hydroxyphenyl) acetic acid, 2,2-bis (4-hydroxyphenyl) pentanoic acid, tartaric acid, N, N-dihydroxyethylglycine, N, N-bis (2 -Hydroxyethyl) -3-carboxyl-propionamide and the like.

Further, the molecular weight of the urethane resin can be appropriately adjusted using a chain extender. Examples of the chain extender include compounds having two or more active hydrogens such as amino groups and hydroxyl groups capable of reacting with isocyanate groups. For example, diamine compounds, dihydrazide compounds, and glycols can be used.

These urethane resins can be used by obtaining commercially available resins such as, for example, Hydran series, Bondic series manufactured by DIC Corporation, and Superflex series manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

The melamine resin component contained in the P2 layer in the present invention is a resin having a triazine ring in its molecule and three amino groups around it, and a resin obtained by reacting the resin with other components. Specifically, hexamethylol melamine, hexamethoxymethyl melamine, hexaethoxymethyl melamine, hexakis- (hexatype (the number of functional groups bonded to three amino groups directly bonded to the triazine ring is 6)) Methoxymethyl) melamine, tri-type (three functional groups bonded to three amino groups directly bonded to the triazine ring) N, N ′, N ″ -trimethyl-N, N ′, N ″ -trimethylol melamine, N, N ′, N ″ -trimethylol melamine, N-methylol melamine, N, N ′-(methoxymethyl) melamine, N, N ′, N ″ -tributyl-N, N ′, N ″ -trimethylolmelamine and the like can be mentioned.

Among them, the melamine resin is preferably tri-type, and by using the tri-type melamine resin, the adhesion retention after the acceleration test can be further improved.

These melamine resins can be obtained by using commercially available resins such as, for example, Becamine series manufactured by DIC Corporation, and Nicarak series manufactured by Sanwa Chemical Co., Ltd.

The epoxy resin component contained in the P2 layer in the present invention is a resin having a glycidyl group in the molecule and a resin obtained by reacting the resin with other components. Specifically, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis (N, N-glycidylaminomethyl) cyclohexane, 1,6-hexanediol diglycidyl Ether, neopentyl glycol diglycidyl ether, etherene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, Polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid dig In addition to cisidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris (2-hydroxyethyl) isocyanurate, resorcinating glycidyl ether, bisphenol-S-diglycidyl ether, epoxy resin having two or more glycidyl groups in the molecule Etc.

Among them, the number of functional groups of the epoxy resin is preferably three or more, and by using an epoxy resin having three or more functional groups, the adhesion retention after the acceleration test can be further enhanced. Further, the upper limit of the number of functional groups of the epoxy resin is not limited to this range, but those having 4 functional groups or less are common.

These epoxy resins can be used by obtaining commercially available resins such as EPICLON series, ADDITIVE series manufactured by DIC Corporation, and Denacol series manufactured by Nagase ChemteX Corporation.

P2 layer in this invention is a layer formed from the coating composition containing a urethane resin, a melamine resin, and an epoxy resin, and 80 mass% by solid content weight in the coating composition in which urethane resin forms P2 layer It is preferable to contain 99% by mass or less. More preferably, it is 90 mass% or more. In the coating composition which forms P2 layer in P2 layer in this invention, when the urethane resin contains 80 mass% or more by solid content weight, in the solar cell back surface protection sheet | seat of this invention, it is with sealing material. Initial adhesion can be further increased. Here, the upper limit of the solid content weight of the urethane resin in the coating composition for forming the P2 layer is not limited to this range, but is 99% by mass or less from the viewpoint of adhesion retention after the acceleration test. It is preferable to do this.

The weight ratio Wm / We (weight of melamine resin / weight of epoxy resin) of the melamine resin and the epoxy resin in the coating composition forming the P2 layer in the present invention is preferably in the range of 2 to 5, More preferably, it is in the range of 2.5-4. When the weight ratio Wm / We of the melamine resin and the epoxy resin in the coating composition for forming the P2 layer in the present invention is in the range of 2 to 5, adhesion retention after the acceleration test can be further improved.

In the solar cell back surface protective sheet of the present invention, the P2 layer needs to have a water contact angle of 74 ° or more. The contact angle of water here is a contact angle with water obtained by a method defined in JIS K-6768 (1999), preferably 76 ° or more, more preferably 79 ° or more. If the contact angle of water in the P2 layer is less than 74 °, even if adhesion with the sealing material is obtained, adhesion retention after the acceleration test is insufficient.

In addition, in order to make the contact angle of water of the P2 layer in the present invention 74 ° or more, the coating composition forming the P2 layer contains three components of urethane resin, melamine resin, and epoxy resin, and the coating composition It can be obtained by setting the solid content weight ratio of the urethane resin contained therein to 70% by mass or more. In order to make the contact angle of water in the P2 layer a more preferable range, the solid content weight ratio of the urethane resin contained in the coating composition that forms the P2 layer is 80% by mass or more, and the coating material that forms the P2 layer. It can be obtained by setting the weight ratio Wm / We of the melamine resin and the epoxy resin contained in the composition in the range of 2 to 5.

In addition, the upper limit of the contact angle with water of the P2 layer is not limited, but is preferably less than 99 °. When the contact angle of the P2 layer with water is 99 ° or more, the adhesion with the P1 layer may be lowered, and as a result, the adhesion between the solar cell back surface protection sheet of the present invention and the sealing material is insufficient. There is a case.

In the solar cell back surface protective sheet of the present invention, the P2 layer contains three components of a urethane resin component, a melamine resin component, and an epoxy resin component, and the contact angle of water is set to 74 ° or more, whereby a sealing material It is possible to achieve both the adhesion and the adhesion retention after the acceleration test. When the solar cell back surface protection sheet of the present invention is mounted on a solar cell, the solar cell is excellent in durability even when placed outdoors for a long period of time. It can be a battery.

In the P2 layer in the solar cell back surface protective sheet of the present invention, a known thermal stabilizer, lubricant, antistatic agent, anti-blocking agent, dye, pigment, photosensitizer, as long as the effects of the present invention are not impaired. Various additives such as a surfactant and an ultraviolet absorber can be added.

For example, when the solar cell back surface protection sheet of the present invention is mounted on a solar cell by adding an ultraviolet absorber to the P2 layer, the solar cell back surface protection sheet and the sealing material are irradiated by ultraviolet light from the power generation cell side. It can suppress that adhesiveness falls. In this case, as the ultraviolet absorber, inorganic particles such as titanium oxide and zinc oxide, those containing an ultraviolet absorber, and a resin component copolymerized with a molecular skeleton having ultraviolet absorbing ability are preferably used and preferably contained. The amount is from 1% to 50%, more preferably from 5% to 40%, and even more preferably from 10% to 30% by weight of the solid content in the coating composition forming the P2 layer.

Furthermore, blocking at the time of winding can be prevented by adding silica particles as an anti-blocking agent to the P2 layer. Further, by adding a surfactant to the P2 layer, it is possible to increase the affinity of the coating liquid for the P1 layer and suppress coating unevenness.

The thickness of the P2 layer in the solar cell back surface protective sheet of the present invention is preferably 0.1 μm or more and 2.0 μm or less, more preferably 0.2 μm or more and 1.2 μm or less, and further preferably 0.5 μm or more and 1.0 μm. It is as follows. When the thickness of the P2 layer in the solar cell back surface protective sheet of the present invention is less than 0.1 μm, the adhesion to the sealing material may be insufficient. On the other hand, if the thickness of the P2 layer is more than 2.0 μm, the winding property may deteriorate due to insufficient drying, or the coating property may deteriorate.

The P2 layer in the present invention may have a laminated structure for the purpose of improving easy adhesion. For example, an anchor coat layer (referred to as P21 layer) having excellent adhesion with the P1 layer is provided in advance on one surface of the P1 layer, and a layer (referred to as P22 layer) that is further excellent in easy adhesion on the P21 layer. The providing method is also preferably used. In that case, the structure of the sheet is laminated in the order of P1 layer // P21 layer / P22 layer, and the thickness of the P2 layer is represented by P21 layer + P22 layer. At this time, the P21 layer has good adhesiveness with the resin constituting the P1 layer and the P22 layer, and the P22 layer is excellent in adhesiveness with the resin constituting the P21 layer and the sealing material. There is no particular limitation as long as it is compatible with the sealing material at the temperature during pressure laminating. In this case, as the resin used for the P21 layer and the P22 layer, those exemplified for the P2 layer can be suitably used as appropriate.

(Solar cell backside protection sheet)
The solar cell back surface protective sheet of the present invention is provided with a layer having other functions such as gas barrier property and ultraviolet resistance on one side surface of the P1 layer (however, the surface opposite to the surface in contact with the P2 layer). be able to. As a method of providing these layers, a method of separately preparing materials to be laminated with the P1 layer and thermocompression bonding with a heated group of rolls (thermal laminating method), a method of bonding together with an adhesive (adhesion method) ) In addition, a method of dissolving the material for forming the material to be laminated in a solvent and applying the solution onto the P1 layer prepared in advance (coating method), electromagnetic wave irradiation after applying a curable material onto the P1 layer A method of curing by heat treatment or the like, a method of depositing / sputtering a material to be laminated on the P1 layer, a method combining these, and the like can be used.

It is preferable that the solar cell back surface protection sheet of the present invention is excellent in moisture and heat resistance. Specifically, the elongation at break after applying the wet heat treatment to the solar cell back surface protective sheet of the present invention is preferably 10% or more, more preferably 20% or more, and further preferably 40% or more. The details of the method for measuring the elongation at break after the wet heat treatment here will be described later. In the solar cell back surface protection sheet of the present invention, when the breaking elongation after applying wet heat treatment is less than 10%, when the solar cell equipped with the solar cell back surface protection sheet of the present invention is placed outdoors for a long time In addition, cracks and the like due to deterioration may occur and the appearance of the solar cell may deteriorate. In order to improve the heat and moisture resistance in the solar cell back surface protection sheet of the present invention, polyethylene having an intrinsic viscosity IV of 0.65 dl / g or more and a terminal carboxyl group content of 25 equivalents / ton or less is used for the polyester resin constituting the P1 layer. A preferable method is to use terephthalate. By setting the intrinsic viscosity IV and the terminal carboxyl group amount of the polyester resin constituting the P1 layer within the above ranges, it is possible to improve the elongation at break after applying the wet heat treatment.

The solar cell back surface protective sheet of the present invention preferably has excellent ultraviolet resistance. Specifically, it is preferable that the color tone change Δb when the ultraviolet ray treatment test is performed using the P1 layer of the solar cell back surface protective sheet of the present invention as an incident surface is less than 10, more preferably less than 3. Details of the method for measuring the color tone change Δb when the ultraviolet treatment test is performed will be described later. In the solar cell back surface protection sheet of the present invention, when the color change Δb when the ultraviolet treatment test is performed with the P1 layer as the incident surface exceeds 10, the solar cell mounted with the solar cell back surface protection sheet of the present invention is long. When placed outdoors during the period, the appearance of the solar cell may deteriorate due to discoloration due to ultraviolet rays. Moreover, in order to make it the range which is excellent in ultraviolet-ray resistance in the solar cell back surface protection sheet of this invention, it is mentioned as a preferable method to add 3 mass% or more of titanium oxide particles with respect to the total mass of P1 layer, It is possible to reduce the color tone change Δb depending on the amount of titanium oxide particles added.

In the solar cell back surface protection sheet of the present invention, a solar cell back surface protection sheet excellent in moist heat resistance and ultraviolet resistance is used for a long time outdoors with the solar cell mounted with the solar cell back surface protection sheet of the present invention. Even if it is placed, it can be a solar cell having no appearance defect.

(Method for producing solar cell back surface protection sheet)
Next, an example is given and demonstrated about the manufacturing method of the solar cell back surface protection sheet | seat of this invention. This is an example, and the present invention should not be construed as being limited to the product obtained by such an example.

First, the manufacturing method of the raw material which comprises P1 layer can be manufactured with the following method.

The resin used as the raw material of the P1 layer of the present invention can be obtained by subjecting dicarboxylic acid or its ester derivative and diol to a transesterification reaction or an esterification reaction by a well-known method. Examples of conventionally known reaction catalysts include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and phosphorus compounds. Preferably, an antimony compound, a germanium compound, or a titanium compound is preferably added as a polymerization catalyst at an arbitrary stage before the PET production method is completed. As such a method, for example, when a germanium compound is taken as an example, it is preferable to add the germanium compound powder as it is. In order to control the number average molecular weight of the polyester resin, for example, when the number average molecular weight is 10,000 to 20,000, the polyester resin having a number average molecular weight of about 9500 is once polymerized by the above method, and then 190 ° C. A so-called solid-phase polymerization method in which heating is performed at a temperature lower than the melting point of the polyester resin under reduced pressure or a flow of an inert gas such as nitrogen gas is preferable. This method is preferably performed in that the number average molecular weight can be increased without increasing the terminal carboxyl group amount of the thermoplastic resin.

Next, when the P1 layer has a single film configuration, the P1 layer manufacturing method is a method in which the P1 layer raw material is heated and melted in an extruder and extruded from a die onto a cast drum cooled (processed into a sheet). Method). As another method, the raw material for the P1 layer is dissolved in a solvent, and the solution is extruded from a die onto a support such as a cast drum or an endless belt to form a film, and then the solvent is dried and removed from the film layer. A method of processing into a shape (solution casting method) or the like can also be used.

In addition, when the P1 layer has a laminated structure, when the material of each layer to be laminated is mainly composed of a thermoplastic resin, the two different thermoplastic resins are put into two extruders and melted to join. Thus, a method of co-extrusion onto a cast drum cooled from the die and processing it into a sheet (co-extrusion method) can be preferably used.

Further, when a uniaxial or biaxially stretched sheet base material is selected as the laminate including the P1 layer and / or the P1 layer, as a manufacturing method thereof, first, an extruder (in the case of a laminated structure, a plurality of extruders) ), Melt and extrude from the die (coextrusion in the case of a laminated structure), and cool and solidify by static electricity on a drum cooled to a surface temperature of 10 to 60 ° C. to produce an unstretched sheet .

Next, the unstretched sheet is led to a group of rolls heated to a temperature of 70 to 140 ° C., stretched 3 to 4 times in the longitudinal direction (longitudinal direction, that is, the traveling direction of the sheet), and the temperature is 20 to 50 ° C. Cool with rolls.

Subsequently, the both ends of the sheet are guided to a tenter while being gripped by clips, and stretched 3 to 4 times in a direction (width direction) perpendicular to the longitudinal direction in an atmosphere heated to a temperature of 80 to 150 ° C.

The stretching ratio is 3 to 5 times in each of the longitudinal direction and the width direction, but the area ratio (longitudinal stretching ratio × lateral stretching ratio) is preferably 9 to 15 times. When the area magnification is less than 9 times, the durability of the resulting biaxially stretched sheet is insufficient, and conversely when the area magnification exceeds 15 times, there is a tendency that tearing tends to occur during stretching.

As the biaxial stretching method, in addition to the sequential biaxial stretching method in which the stretching in the longitudinal direction and the width direction is separated as described above, the simultaneous biaxial stretching method in which the stretching in the longitudinal direction and the width direction is performed simultaneously. Either one does not matter.

The method for forming the P2 layer on the P1 layer in the sheet of the present invention is not particularly limited, but it is preferable to use a coating technique. As a coating method, a known method can be applied, and for example, a roll coating method, a dip coating method, a bar coating method, a die coating method, a gravure roll coating method, or a combination of these methods can be used. it can. Among them, the bar coating method is preferable from the viewpoint of a wide selection range of the coating agent, while the die coating method and the gravure roll coating method can be preferably selected from the viewpoint of thick film coating property when it is desired to increase the thickness of the P2 layer.

Furthermore, it is more preferable to form the P2 layer by in-line coating provided in the manufacturing process of the P1 layer from the viewpoint of simplifying the process. Specifically, in the case of the sequential biaxial stretching method, after forming an unstretched sheet or a uniaxially stretched sheet, in the case of the simultaneous biaxial stretching method, after forming the unstretched sheet, the above coating step After applying the coating composition for forming the P2 layer, the P1 layer is stretched and heat-set simultaneously with the drying step of the coating composition. At this time, the heat setting temperature of the P1 layer is preferably 150 ° C. or more and 250 ° C. or less, more preferably 170 ° C. from the viewpoint of the compatibility between the drying temperature of the coating composition, the thermal dimensional stability of the base material layer P1 and the heat and humidity resistance. It is more than 230 degreeC, More preferably, it is 180 degreeC or more and 220 degrees C or less.

Further, if necessary, from the viewpoint of improving the wettability of the coating composition to the P1 layer and improving the interlayer adhesion after the formation of the P2 layer, a corona treatment may be applied to the surface of the base material layer P1 immediately before the coating step. Good.

Examples of the solvent for the coating composition for forming the P2 layer in the sheet of the present invention include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dimethylformamide, dimethylacetamide, Methanol, ethanol, water and the like can be exemplified, and the properties of the coating liquid may be either emulsion type or dissolution type. In recent years, emphasis has been placed on environmental protection, resource saving, exhaust problems of organic solvents during production, etc., and a dissolved or emulsion type coating liquid mainly composed of water is the preferred form. The method of emulsifying the urethane resin, melamine resin, and epoxy resin contained in the coating composition for forming the P2 layer is not particularly limited, and is widely used as a solid / liquid stirring device or an emulsifier. It can be made by equipment known to the vendor.

The solar cell back surface protection sheet of the present invention can be manufactured by the above manufacturing method. The obtained sheet for protecting the back surface of the solar battery has excellent adhesion to the sealing material of the solar battery cell, maintains adhesion even when left outdoors for a long time (excellent retention), and is moisture resistant. It has the performance of being excellent in heat resistance and ultraviolet resistance.

(Solar cell)
The solar cell of the present invention is characterized by using the solar cell back surface protective sheet. By using the solar cell back surface protection sheet, it is possible to increase the durability as compared with the conventional solar cell. An example of the configuration is shown in FIG. A power generating element connected with a lead wire for taking out electricity (not shown in FIG. 1) is sealed with a transparent sealing material 2 such as EVA resin, a transparent substrate 4 such as glass, and a solar cell back surface protection Although it is configured to be bonded as the sheet 1, it is not limited to this and can be used for any configuration. In addition, in FIG. 1, although the solar cell back surface protection sheet shows an example of a single body, the solar cell back surface protection sheet should be a composite sheet in which other films are laminated according to other required characteristics. Is also possible.

Here, in the solar cell of the present invention, the solar cell back surface protection sheet 1 plays a role of protecting the power generation cell installed on the back surface of the sealing material 2 sealing the power generation element. Here, the solar cell back surface protection sheet is preferably arranged so that the P2 layer is in contact with the sealing material 2. By adopting this configuration, the durability of the solar cell can be enhanced by protecting the power generation cell for a long period of time even when exposed to the outdoors, taking advantage of the excellent adhesion of the present invention.

The power generating element 3 converts light energy of sunlight into electric energy, and is based on crystalline silicon, polycrystalline silicon, microcrystalline silicon, amorphous silicon, copper indium selenide, compound semiconductor, dye enhancement Arbitrary elements such as a sensitive system can be used in series or in parallel according to the desired voltage or current depending on the purpose. Since the transparent substrate 4 having translucency is located on the outermost surface layer of the solar cell, a transparent material having high weather resistance, high contamination resistance, and high mechanical strength characteristics in addition to high transmittance is used. In the solar cell of the present invention, the transparent substrate 4 having translucency can be made of any material as long as the above characteristics are satisfied. Examples thereof include glass, ethylene tetrafluoride-ethylene copolymer (ETFE), polyfluoride. Vinyl fluoride resin (PVF), polyvinylidene fluoride resin (PVDF), polytetrafluoroethylene resin (TFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polytrifluoroethylene chloride resin (CTFE) ), Fluorinated resins such as polyvinylidene fluoride resin, olefinic resins, acrylic resins, and mixtures thereof. In the case of glass, it is more preferable to use a tempered glass. Moreover, when using the resin-made translucent base material, what extended | stretched the said resin uniaxially or biaxially from a viewpoint of mechanical strength is used preferably. Moreover, in order to give these substrates the adhesiveness with EVA resin etc. which are the sealing materials of an electric power generation element, it is also preferably performed to give the surface a corona treatment, a plasma treatment, an ozone treatment, and an easy adhesion treatment. .

The sealing material 2 for sealing the power generation element covers and fixes the unevenness of the surface of the power generation element with resin, protects the power generation element from the external environment, and has a translucent base for the purpose of electrical insulation. A material having high transparency, high weather resistance, high adhesion, and high heat resistance is used in order to adhere to the material or back sheet and the power generation element. Examples thereof include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA) resin, ethylene-methacrylic acid copolymer (EMAA), Ionomer resins, polyvinyl butyral resins, and mixtures thereof are preferably used.

As described above, by incorporating the solar cell back surface protection sheet of the present invention into a solar cell system, it is possible to enhance the durability as compared with conventional solar cells. The solar cell of the present invention can be suitably used for various applications without being limited to outdoor use and indoor use such as a solar power generation system and a power source for small electronic components.
[Measurement method and evaluation method of characteristics]
(1) Component qualitative property of P2 layer The component qualitative property of the P2 layer in Examples and Comparative Examples was performed by separating the P2 layer of the solar cell back surface protection sheet and performing pyrolysis gas chromatography mass spectrometry (GC-MS). Pyrolytic device PY-2010DD (frontier lab) and gas chromatograph GC-14AF (manufactured by Shimadzu Corporation) are used for the measurement device, flame ionization detector (FID) is used for the detector, and the column is used for the column. A methylsilicone capillary column was connected for use. Further, derivatization was performed with TMAH (tetramethylammonium hydroxide) as necessary.
The presence or absence of each component was determined as follows, and in the table, the P2 layer was described as Y when each component was contained, and N when not contained.
(A) Urethane resin component When two types of diisocyanate compound and diol compound are detected from the thermal decomposition product, it is assumed that the urethane resin component is contained in the P2 layer.
(B) Melamine resin component When a melamine compound is detected from a thermal decomposition product, melamine resin component shall be contained in P2 layer.
(C) When the glycerol compound of the following chemical formula 1 is detected from the thermal decomposition product obtained by derivatization with the epoxy resin component TMAH, it is assumed that the epoxy resin component is contained in the P2 layer.
(D) Urethane resin component containing polyester urethane resin When three types of diisocyanate compound, diol compound and dicarboxylic acid compound are detected from the thermal decomposition product, the urethane resin component containing polyester urethane resin is contained in the P2 layer. Suppose that

(2) Polymer properties (2-1) Intrinsic viscosity IV
In 100 ml of orthochlorophenol, a measurement sample (polyester resin (raw material) or only the P1 layer of the solar cell back surface protection sheet separated) is dissolved (solution concentration C (measurement sample weight / solution volume) = 1.2 g / ml), and the viscosity of the solution at 25 ° C. was measured using an Ostwald viscometer. Similarly, the viscosity of the solvent was measured. [Η] was calculated by the following formula (4) using the obtained solution viscosity and solvent viscosity, and the obtained value was defined as the intrinsic viscosity (IV).
ηsp / C = [η] + K [η] ² · C (4)
(Where ηsp = (solution viscosity / solvent viscosity) −1, K is the Huggins constant (assuming 0.343))
In addition, when there existed insoluble matters, such as inorganic particles, in the solution in which the measurement sample was dissolved, the measurement was performed using the following method.
(I) A measurement sample is dissolved in 100 mL of orthochlorophenol to prepare a solution having a solution concentration higher than 1.2 mg / mL. Here, let the weight of the measurement sample used for orthochlorophenol be a measurement sample weight.
(Ii) Next, the solution containing insoluble matter is filtered, and the weight of the insoluble matter is measured and the volume of the filtrate after filtration is measured.
(Iii) Orthochlorophenol was added to the filtrate after filtration, and (measured sample weight (g) −insoluble matter weight (g)) / (volume of filtrate after filtration (mL) + added orthochlorophenol) The volume (mL) is adjusted to 1.2 g / 100 mL.
(For example, when a concentrated solution having a measurement sample weight of 2.0 g / solution volume of 100 mL was prepared, the weight of insoluble matter when the solution was filtered was 0.2 g, and the filtrate volume after filtration was 99 mL Adjusts by adding 51 mL of orthochlorophenol ((2.0 g-0.2 g) / (99 mL + 51 mL) = 1.2 g / 100 mL))
iv) Using the solution obtained in iii), the viscosity at 25 ° C. was measured using an Ostwald viscometer, and the obtained solution viscosity and solvent viscosity were used to calculate [η] according to the above equation (4). And the obtained value is taken as the intrinsic viscosity (IV).

(2-2) Amount of terminal carboxyl groups (indicated as COOH amount in the table)
The terminal carboxyl group amount was measured by the following method according to the method of Malice. (Document M. J. Malice, F. Huizinga, Anal. Chim. Acta, 22 363 (1960)).
2 g of a measurement sample (polyester resin (raw material) or solar cell back surface protection sheet P1 layer only) 2 g was dissolved in 50 ml of o-cresol / chloroform (weight ratio 7/3) at a temperature of 80 ° C. The solution was titrated with a 05N KOH / methanol solution, and the terminal carboxyl group concentration was measured and indicated by the value of equivalent / polyester 1t. In addition, the indicator at the time of titration used phenol red, and the place where it changed from yellowish green to light red was set as the end point of titration. If there is insoluble matter such as inorganic particles in the solution in which the measurement sample is dissolved, the solution is filtered to measure the weight of the insoluble matter, and the value obtained by subtracting the weight of the insoluble matter from the measurement sample weight The following correction was made.

(3) Contact angle with water Based on JIS K 6768 (1999), an average value obtained by performing the following procedure 5 times using a contact angle meter CA-D type (manufactured by Kyowa Interface Science Co., Ltd.) Was the contact angle with water.
(I) 2 μl of distilled water is dropped onto the surface on the P2 layer side of the solar cell back surface protection sheet.
(Ii) Leave for 1 minute.
(Iii) The liquid surface angle was measured.

(4) Thickness of P2 layer Using a microtome, a small piece cut in a direction perpendicular to the surface of the solar cell back surface protection sheet was prepared, and the cross section was taken as a field emission scanning electron microscope JSM-6700F (JEOL Ltd. ))) And magnified to 10,000 times. From the cross-sectional photograph, the thickness of the P2 layer was calculated from the magnification. In addition, the thickness used the cross-sectional photograph of five places arbitrarily selected from the different measurement visual field, and used the average value.

(5) Adhesion evaluation with sealing material (5-1) Adhesion with sealing material Based on JIS K 6854-2 (1999), an EVA sheet as a sealing material and a solar cell back surface protection sheet The adhesiveness was evaluated from the peel strength with the surface on the P2 layer side. The measurement test piece is a 500 μm thick EVA sheet (vinyl acetate copolymerization ratio: 28 mol%) on a semi-tempered glass having a thickness of 3 mm, and the P2 layer side of the sheet of the example and the comparative example is the EVA sheet side. A layer obtained by press treatment using a commercially available vacuum laminator under conditions of a hot platen temperature of 145 ° C., a vacuum drawing of 4 minutes, a press of 1 minute, and a holding time of 10 minutes was used. The peel strength test is performed at 180 ° peel, the width of the test piece is 10 mm, two test pieces are prepared, the place is changed for each test piece, the measurement is performed at three places, and the average value of the obtained measurement values is peeled off The initial adhesion was determined as follows using the strength value. In addition, when the sheet | seat of this invention fractured | ruptured before peeling at an interface in this measurement, the measured value at the time of the fracture | rupture was made into the value of peeling strength.
When the peel strength is 30 N / 10 mm or more: A
When the peel strength is 25 N / 10 mm or more and less than 30 N / 10 mm: B
When the peel strength is 20 N / 10 mm or more and less than 25 N / 10 mm: C
When peel strength is less than 20 N / 10 mm: D
The initial adhesion is good in A to C, and A is the best among them.

(5-2) Adhesion retention In the same manner as in (5-1) above, a measurement test piece was prepared, and the temperature was 120 ° C. and the relative humidity was measured with a pressure cooker (manufactured by Espec Corp.). The treatment was performed for 48 hours under the condition of 100% RH. Thereafter, the peel strength after the acceleration test with the EVA sheet was measured in the same manner as in the section (5-1), and the adhesion retention was determined as follows.
When the peel strength after the acceleration test is 16 N / 10 mm or more: A
When the peel strength after the acceleration test is 13 N / 10 mm or more and less than 16 N / 10 mm: B
When the peel strength after the acceleration test is 10 N / 10 mm or more and less than 13 N / 10 mm: C
When peel strength after accelerated test is less than 10 N / 10 mm: D
The adhesion retention is good from A to C, and among them, A is the best.

(6) Moist heat resistance (measurement of elongation at break after wet heat test)
After the solar cell back surface protection sheet was cut into a measurement piece shape of 10 mm × 200 mm, it was subjected to a highly accelerated life test apparatus pressure cooker (manufactured by Espec Corp.) under the conditions of a temperature of 125 ° C. and a relative humidity of 100% RH. After 48 hours of treatment, the elongation at break was measured according to ASTM-D882 (1997). Note that the measurement was performed between the chuck 50 mm, the pulling speed 300 mm / min, the number of measurements n = 5, and after measuring for each of the longitudinal direction and the width direction of the sheet, the average value was defined as the breaking elongation after the wet heat test. . From the elongation at break after the obtained wet heat test, the wet heat resistance was determined as follows.
When the breaking elongation after the wet heat test is 40% or more of the breaking elongation before the wet heat test: A
When the breaking elongation after the wet heat test is 20% or more and less than 40% of the breaking elongation before the wet heat test: B
When the breaking elongation after the wet heat test is 10% or more and less than 20% of the breaking elongation before the wet heat test: C
When the breaking elongation after the wet heat test is less than 10% of the breaking elongation before the wet heat test: D
The wet heat resistance is good in A to C, and A is the best among them.

(7) UV resistance (color change during UV treatment test)
(7-1) Color tone (b value) measurement Based on JIS-Z-8722 (2000), a spectroscopic color difference meter SE-2000 (manufactured by Nippon Denshoku Industries Co., Ltd., light source halogen lamp 12V4A, 0 ° to −45 °) The color tone (b value) of the surface on the P1 layer side of the solar cell back surface protection sheet was measured by n = 3 by a reflection method using a post-spectral method.

(7-2) Color tone change Δb
With an i-super ultraviolet tester S-W131 (manufactured by Iwasaki Electric Co., Ltd.) so that the test light hits the surface on the P1 layer side of the solar cell back surface protection sheet, the temperature is 60 ° C., the relative humidity is 60%, and the illuminance is 100 mW / cm. ² The color tone (b value) before and after irradiation for 48 hours under the conditions of (light source: metal halide lamp, wavelength range: 295 to 450 nm, peak wavelength: 365 nm) was measured according to the above (7-1), and the following (α ) To calculate the color tone change (Δb) after UV irradiation.
Color tone change after UV irradiation (Δb) = b1−b0 (α)
b0: Color tone before UV irradiation (b value)
b1: Color tone after UV irradiation (b value)
From the color tone change (Δb) before and after the obtained ultraviolet treatment test, ultraviolet resistance was determined as follows.
When the color change (Δb) before and after the ultraviolet irradiation treatment test is less than 3: A
When the color tone change (Δb) before and after the ultraviolet irradiation treatment test is 3 or more and less than 10: B
When the color change (Δb) before and after the ultraviolet irradiation treatment test is 10 or more and less than 20: C
When the color change (Δb) before and after the ultraviolet irradiation treatment test is 20 or more: D
The UV resistance is good in A to C, and A is the best among them.

(8) Solar cell characteristics (8-1) Production of solar cell Flux H722 from HOZAN was applied to the front and back silver electrode portions of solar cell Q6LPT-G2 from Qcells with a dispenser, and silver on the front and back surfaces. As a wiring material cut to a length of 155 mm on the electrode, a copper foil SSA-SPS0.2 × 1.5 (20) manufactured by Hitachi Cable Co., Ltd. 10 mm away from one end of the cell on the front side is the back surface at the end of the wiring material. The side was placed symmetrically with the front side, and the soldering iron was contacted from the back side of the cell using a soldering iron, and the front and back sides were simultaneously soldered to produce a 1-cell module wiring.

The longitudinal direction of the wiring material protruding from the cell of the produced 1-cell module wiring and the longitudinal direction of the copper foil A-SPS 0.23 × 6.0 made by Hitachi Cable as the take-out electrode cut into 180 mm are perpendicular to each other. Then, the flux was applied to the portion where the wiring material and the take-out electrode overlapped, and solder welding was performed to produce a wire with the take-out electrode.

Next, 190 mm × 190 mm 3.2 mm thick white plate heat-treated glass for solar cells manufactured by Asahi Glass Co., Ltd., 190 mm × 190 mm 500 μm thick EVA sheet (vinyl acetate copolymerization ratio: 28 mol%), produced wiring with takeout electrode, 190 mm × A 190 mm 500 μm thick EVA sheet and a solar cell back surface protection sheet cut out to 190 mm × 190 mm are stacked in order so that the P2 layer side surface is located on the EVA side, and the glass is brought into contact with the hot platen of the vacuum laminator And laminating under the conditions of a hot platen temperature of 145 ° C., a vacuuming of 4 minutes, a press of 1 minute, and a holding time of 10 minutes to produce a solar cell. At this time, the wiring with the extraction electrode was set so that the glass surface was on the cell surface side.

(8-2) Durability of Solar Cell Ten solar cells prepared in the above section (8-1) were prepared and treated for 4000 hr in a constant temperature and humidity chamber (manufactured by ESPEC Corporation) adjusted to 85 ° C. and 85% RH. Then, it was visually confirmed whether or not peeling occurred on the laminated solar cell back surface protection sheet. The durability of the solar cell was determined by visually checking how many of the 10 solar cells had the solar cell back surface protection sheet peeled off, and determined as follows.
When peeling does not occur in all solar cells: A
When the solar cell back surface protection sheet is peeled from one or more of the produced solar cells and less than four solar cells: B
When the solar cell back surface protective sheet is peeled from 4 or more and less than 8 solar cells among the produced solar cells: C
When 8 or more of the produced solar cells are separated from the solar cell: D
The durability of the solar cell is good from A to C, and among them, A is the best.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not necessarily limited thereto.

(Polyester resin raw material)
1. PET raw material A (used in Examples 1 to 16, 18, 20 and Comparative Examples 1 to 6)
A polycondensation reaction was performed using 100 parts by mass of terephthalic acid as the dicarboxylic acid component, 100 parts by mass of ethylene glycol as the diol component, and magnesium acetate, antimony trioxide, and phosphorous acid as the catalyst. Next, the obtained polyethylene terephthalate was dried and crystallized at 160 ° C. for 6 hours, and then subjected to solid phase polymerization at 220 ° C. and a vacuum degree of 0.3 Torr for 9 hours to have a melting point of 255 ° C. and an intrinsic viscosity of 0.80 dl / g. A polyethylene terephthalate (PET-A) raw material having a terminal carboxyl group amount of 10 equivalents / ton was obtained.

2. PET raw material B (used in Example 19)
A polycondensation reaction was performed using 100 parts by mass of terephthalic acid as the dicarboxylic acid component, 100 parts by mass of ethylene glycol as the diol component, and magnesium acetate, antimony trioxide, and phosphorous acid as the catalyst. Next, the obtained polyethylene terephthalate was dried and crystallized at 160 ° C. for 6 hours to obtain a polyethylene terephthalate (PET-B) raw material having a melting point of 255 ° C., an intrinsic viscosity of 0.65 dl / g, and a terminal carboxyl group content of 25 equivalents / ton. It was.

3. Polyethylene naphthalate (hereinafter sometimes referred to as PEN) raw material (used in Example 17)
To a mixture of 100 parts by mass of dimethyl 2,6-naphthalenedicarboxylate and 60 parts by mass of ethylene glycol, 0.03 part by mass of manganese acetate tetrahydrate salt is added, and the temperature is gradually increased from 150 ° C. to 240 ° C. The transesterification was carried out while raising the temperature. In the middle, when the reaction temperature reached 170 ° C., 0.024 parts by mass of antimony trioxide was added. When the reaction temperature reached 220 ° C., 0.042 parts by mass of 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt was added. Thereafter, a transesterification reaction was carried out, and 0.023 parts by mass of trimethyl phosphoric acid was added. Next, the reaction product is transferred to a polymerization apparatus, heated to a temperature of 290 ° C., subjected to a polycondensation reaction under a high vacuum of 30 Pa, and the stirring torque of the polymerization apparatus is a predetermined value (specifically depending on the specifications of the polymerization apparatus). The value indicated by polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.65 in this polymerization apparatus was a predetermined value). Next, the obtained polyethylene naphthalate was dried and crystallized at 160 ° C. for 6 hours, and then subjected to solid phase polymerization at 220 ° C. and a vacuum degree of 0.3 Torr for 9 hours, melting point 255 ° C., intrinsic viscosity 0.70 dl / g, A PEN raw material having a terminal carboxyl group attachment amount of 25 equivalents / ton was obtained.

4). PET raw material A-based titanium oxide master (used in Examples 1 to 15, 20 and Comparative Examples 1 to 6)
Above 1. 100 parts by mass of the PET resin (PET-A) obtained according to the above and 100 parts by mass of rutile-type titanium oxide particles having an average particle diameter of 210 nm are melt-kneaded in a vented 290 ° C. extruder to obtain a titanium oxide raw material (PETa- TiO ₂ ) was prepared.

5. PET raw material B base titanium oxide master (used in Example 19)
2. 100 parts by mass of the PET resin (PET-B) obtained according to the above and 100 parts by mass of rutile-type titanium oxide particles having an average particle diameter of 210 nm are melt-kneaded in a vented 290 ° C. extruder to obtain a titanium oxide raw material (PETb- TiO ₂ ) was prepared.

6). PEN raw material-based titanium oxide master (used in Example 17)
4. above. 100 parts by mass of the PEN resin obtained according to the above and 100 parts by mass of rutile-type titanium oxide particles having an average particle diameter of 210 nm are melt-kneaded in a vented 300 ° C. extruder to produce a titanium oxide raw material (PEN-TiO ₂ ). did.

7). PET raw material A base carbon particle master (used in Example 18)
Above 1. 100 parts by mass of the PET resin (PET-A) obtained according to the above and 100 parts by mass of carbon particles having an average particle diameter of 40 nm were melt-kneaded in a vented 290 ° C. extruder to obtain a carbon particle raw material (PETa-CB). Produced.

(Preparation of easy adhesive layer coating)
After preparing coating agents A to S using the coating agents described in the following section using pure water as a diluent solvent, acetylene diol surfactant Orphine EXP4051F manufactured by Nissin Chemical Co., Ltd. It mix | blended so that it might become a ratio of 0.25 mass% with respect to mass. The blending amounts of the coating agents described in the following items are all solid content ratios.

1. Coating agents A to I (used in Examples 1 to 9 and 16 to 20)
DIC Corporation polyester urethane resin coating “Hydran” (registered trademark) AP-201 as urethane resin and DIC Corporation tri-type melamine resin coating “Beckamine” (registered trademark) PM-80 as epoxy resin, as epoxy resin After mixing the epoxy resin coating ADDITIVE EP-10 manufactured by DIC Corporation so as to have the solid content weight ratio shown in Tables 1 and 2, it is diluted with pure water so that the solid content concentration becomes 17% by mass. ~ I was obtained.

2. Coating agent J (used in Example 10)
A coating agent J was obtained in the same manner as coating agent A, except that a polyether urethane resin coating agent “HYDRAN” (registered trademark) WLS-202 manufactured by DIC Corporation was used as the urethane resin.

3. Coating agent K (used in Example 11)
A coating K was obtained in the same manner as coating A except that the polycarbonate urethane resin coating “HYDRAN” (registered trademark) WLS-213 manufactured by DIC Corporation was used as the urethane resin.

4). Coating agent L (used in Examples 12 and 13)
Coating agent L was obtained in the same manner as coating agent A, except that dilution with pure water was performed so that the solid content concentration was 6% by mass.

5. Coating agent M (used in Examples 14 and 15)
Coating agent M was obtained in the same manner as coating agent A, except that the solid content concentration was 23% by mass with dilution with pure water.

6). Coating agent N (used in Example 21)
A coating agent N was obtained in the same manner as coating agent A, except that a hexa-type melamine resin coating agent “Beckamine” (registered trademark) J-101 manufactured by DIC Corporation was used as the melamine resin.

7). Coating agent O (used in Comparative Example 1)
DIC Corporation Polyester Urethane Resin “Hydran” (Registered Trademark) AP-201 was used alone as the urethane resin to dilute with pure water to a solid content concentration of 17% by mass to obtain Coating O .

8). Coating agent P (used in Comparative Example 2)
DIC Corporation polyester urethane resin coating “Hydran” (registered trademark) AP-201 as urethane resin and DIC Corporation tri-type melamine resin coating “Beccamin” (registered trademark) PM-80 as melamine resin in Table 3 After mixing at a solid content weight ratio, the mixture was diluted with pure water so that the solid content concentration was 17% by mass, and a coating agent P was obtained.

9. Coating Q (used in Comparative Example 3)
DIC Corporation polyester urethane resin coating “Hydran” (registered trademark) AP-201 as urethane resin and DIC Corporation epoxy resin coating ADDITIVE EP-10 as epoxy resin so that the solid content weight ratio of Table 3 becomes After mixing, the coating material Q was obtained by diluting with pure water so that the solid content concentration was 17% by mass.

10. Coating agent R (used in Comparative Example 4)
DIC Corporation polyester urethane resin coating “Hydran” (registered trademark) AP-201 as urethane resin and DIC Corporation tri-type melamine resin coating “Beckamine” (registered trademark) PM-80 as epoxy resin, as epoxy resin After mixing the epoxy resin coating ADDITIVE EP-10 manufactured by DIC Corporation so as to have the solid content weight ratio shown in Table 3, it is diluted with pure water so that the solid content concentration is 17% by mass to obtain the coating material R. It was.

11. Coating agent S (used in Comparative Example 5)
A coating S was obtained in the same manner as the coating A except that an acrylic resin-based coating “Nicazole” (registered trademark) RX7013ED manufactured by Nippon Carbide Industries Co., Ltd. was used instead of the urethane resin.

12 Coating agent T (used in Comparative Example 6)
A coating agent T was obtained in the same manner as the coating agent A except that a polyester resin-based coating material Pes Resin TR620K manufactured by Takamatsu Yushi Co., Ltd. was used instead of the urethane resin.

(Examples 1 to 11)
PET raw material A (PET-A) vacuum-dried at 180 ° C. for 2 hours and PET raw material A-based titanium oxide master (PETa-TiO ₂ ) were blended so that the amount of particles was the concentration shown in Table 1, and inside the extruder at 280 ° C. And kneaded and introduced into a T die die. Subsequently, it was melt-extruded into a sheet form from a T-die die and adhered and cooled and solidified by an electrostatic application method on a drum maintained at a surface temperature of 25 ° C. to obtain an unstretched sheet. Subsequently, after preheating the unstretched sheet with a roll group heated to a temperature of 80 ° C., a three-fold speed difference is created between the roll heated to a temperature of 88 ° C. and the roll adjusted to a temperature of 25 ° C. After stretching 3 times in the longitudinal direction (longitudinal direction), it was cooled with a roll group at a temperature of 25 ° C. to obtain a uniaxially stretched sheet. After the uniaxially stretched sheet was subjected to corona treatment, a coating agent corresponding to the example numbers shown in Table 1 was applied with a # 8 metering bar.

While holding both ends of the obtained uniaxially stretched sheet with a clip, the tenter is guided to a preheating zone at a temperature of 80 ° C. in the tenter, and then continuously heated at 90 ° C. in a direction perpendicular to the longitudinal direction (width direction). The film was stretched 3.5 times. Subsequently, heat treatment was performed at 220 ° C. for 20 seconds in a heat treatment zone in the tenter, and further relaxation treatment was performed in the 4% width direction at 220 ° C. Then, it was gradually cooled gradually to form a sheet having a total thickness of 125 μm. When the P1 layer was separated from the obtained sheet and the polymer characteristics were measured, the intrinsic viscosity IV and the amount of terminal carboxyl groups were as shown in Table 1. Further, when the characteristics of the P2 layer were evaluated, the contact angle with water and the thickness were as shown in Table 1.

About the obtained sheet | seat, the qualitative analysis of P2 layer and the evaluation of the solar cell back surface protection sheet were performed. As a result, as shown in Table 4, the P2 layer contains three components of a urethane resin component, a melamine resin component, and an epoxy resin component. Except for Examples 10 and 11, the urethane resin component contains a polyester urethane resin. It was confirmed to be a urethane resin component. In addition, the solar cell back surface protection sheet has good initial adhesion and adhesion retention with the sealing material, and in particular, the example in which the contact angle with water of the P2 layer is in a preferable range (76 ° or more) is sealed. An example in which the contact angle with the water of the P2 layer is in a more preferable range (79 ° or more) is excellent in the close contact retention with the material. It turned out that it is a sheet for use. It was also found that all the solar cell back surface protection sheets obtained were excellent in heat and moisture resistance and UV resistance.
Furthermore, the solar cell carrying the obtained solar cell back surface protection sheet was produced, and the durability of the solar cell was evaluated. As a result, as shown in Table 4, it was found that the solar cell on which the sheet for protecting the back surface of the solar cell, which was very excellent in adhesion and retention with the sealing material, had very excellent durability.

(Examples 12 to 15)
The coating agent corresponding to the number of the example in the coating agent described in Table 2 in the P2 layer is the same as that in Example 1 except that the count of the metering bar is adjusted so as to be the thickness of the P2 layer shown in Table 2. Similarly, a sheet was obtained. When the characteristics of the P2 layer of the obtained sheet were evaluated, the contact angle with water and the thickness were as shown in Table 2.

About the obtained sheet | seat, the qualitative analysis of P2 layer and the evaluation of the solar cell back surface protection sheet were performed. As a result, as shown in Table 4, the P2 layer contained three components, a urethane resin component, a melamine resin component, and an epoxy resin component, and the thickness of the P2 layer was thinner than that of Example 1. Nos. 12 and 13 were found to be solar cell back surface protection sheets in a range that is inferior in initial adhesion to the sealing material and in close contact retention but no problem. On the other hand, although Examples 14 and 15 in which the thickness of the P2 layer was thicker than Example 1 had initial adhesion and adhesion retention with a very excellent sealing material equivalent to Example 1, As for No. 15, application stripes were confirmed visually.

Furthermore, the solar cell on which the obtained solar cell back surface protection sheets of Examples 14 and 15 are mounted has extremely excellent durability, and the solar cell back surface protection sheets of Examples 12 and 13 are mounted. The solar cell was found to be in a range where there is no problem although it is inferior in durability.

(Example 16)
A sheet was obtained in the same manner as in Example 1 except that only PET raw material A (PET-A) was used for the P1 layer. When the P1 layer was separated from the obtained sheet and the polymer characteristics were measured, the intrinsic viscosity IV and the amount of terminal carboxyl groups were as shown in Table 2.

As shown in Table 4, the obtained sheet has initial adhesion and adhesion retention with a very excellent sealing material equivalent to that in Example 1, and is slightly inferior in UV resistance, but very excellent moisture and heat resistance. It turned out that it is a solar cell back surface protection sheet which has. Furthermore, it turned out that the solar cell carrying the obtained sheet | seat for solar cell back surface protection has very outstanding durability.

(Example 17)
A sheet was obtained in the same manner as in Example 1 except that the PEN material (PEN) and the PEN-based titanium oxide master (PEN-TiO ₂ ) were used for the P1 layer. When the P1 layer was separated from the obtained sheet and the polymer characteristics were measured, the intrinsic viscosity IV and the amount of terminal carboxyl groups were as shown in Table 2.

As shown in Table 4, the obtained sheet is inferior to Example 1 but has excellent initial adhesiveness and adhesiveness retention with a sealing material, and has a very excellent moisture and heat resistance sheet. I found out that Furthermore, although the solar cell carrying the obtained sheet | seat for solar cell back surface protection was inferior compared with Example 1, it turned out that it has the outstanding durability.

(Example 18)
A sheet was obtained in the same manner as in Example 1 except that PET raw material A (PET-A) and PET raw material A-based CB master (PETa-CB) were used for the P1 layer. When the P1 layer was separated from the obtained sheet and the polymer characteristics were measured, the intrinsic viscosity IV and the amount of terminal carboxyl groups were as shown in Table 2.

As shown in Table 4, the obtained sheet has initial adhesion and adhesion retention with a very excellent sealing material equivalent to that of Example 1, and has a very excellent ultraviolet resistance for protecting the back surface of a solar cell. It turned out to be a sheet. Furthermore, it turned out that the solar cell carrying the obtained sheet | seat for solar cell back surface protection has very outstanding durability.

(Example 19)
A sheet was obtained in the same manner as in Example 1 except that PET raw material B (PET-B) and PET raw material B-based titanium oxide master (PETb-TiO ₂ ) were used for the P1 layer. When the P1 layer was separated from the obtained sheet and the polymer characteristics were measured, the intrinsic viscosity IV and the amount of terminal carboxyl groups were as shown in Table 2.

As shown in Table 4, the obtained sheet has initial adhesiveness and adhesion retention with a very excellent sealing material equivalent to that of Example 1, and has no problem although moisture and heat resistance is inferior to that of Example 1. It turned out that it is a solar cell back surface protection sheet. Furthermore, although the solar cell carrying the obtained sheet | seat for solar cell back surface protection was inferior compared with Example 1, it turned out that it has the outstanding durability.

(Example 20)
In the P1 layer, the PET raw material A (PET-A) and the PET raw material A-based titanium oxide master (PETa-TiO ₂ ) were mixed separately so that the P11 layer and the P12 layer had the particle amounts shown in Table 2. The raw materials were melted and kneaded separately by two extruders, introduced into a T-die die through feed blocks from the two extruders to obtain a laminated sheet of P11 / P12. Obtained. At this time, the screw rotation speeds of the two extruders were adjusted so that the stacking ratio of P11 / P12 was 7/1. When the P1 layer was separated from the obtained sheet and the polymer characteristics were measured, the intrinsic viscosity IV and the amount of terminal carboxyl groups were as shown in Table 2.

As shown in Table 4, the obtained sheet was found to be a sheet for protecting the back surface of a solar cell having very excellent easy adhesion equivalent to that of Example 1, and having very excellent moist heat resistance and ultraviolet resistance. It was. Furthermore, it turned out that the solar cell carrying the obtained sheet | seat for solar cell back surface protection has very outstanding durability.

(Example 21)
As described in Table 2, a sheet was obtained in the same manner as in Example 1 except that the coating agent N was applied to the P2 layer. When the characteristics of the P2 layer of the obtained sheet were evaluated, the contact angle with water and the thickness were as shown in Table 2.

As shown in Table 4, the obtained sheet was found to be a sheet for protecting the back surface of a solar cell, which was inferior to that of Example 1 but had excellent initial adhesion and adhesion retention with an excellent sealing material. Furthermore, although the solar cell carrying the obtained sheet | seat for solar cell back surface protection was inferior compared with Example 1, it turned out that it has the outstanding durability.

(Comparative Examples 1 to 6)
As shown in Table 3, coating material O obtained only from urethane resin, coating material P or Q not containing any of melamine resin or epoxy resin, coating material obtained from coating composition containing urethane resin and melamine resin, epoxy resin A sheet was obtained in the same manner as in Example 1 except that coating agents S and T using acrylic resin or polyester resin instead of R and urethane resin were applied. When the characteristics of the P2 layer of the obtained sheet were evaluated, the contact angle with water and the thickness were as shown in Table 2.

About the obtained sheet | seat, the qualitative analysis of P2 layer and the evaluation of the solar cell back surface protection sheet were performed. As a result, as shown in Table 4, only the comparative example 4 contained the three components of the urethane resin component, the melamine resin component, and the epoxy resin component in the P2 layer. As for the solar cell back surface protection sheet, Comparative Examples 1 to 3 were excellent in initial adhesion to the encapsulant, but all Comparative Examples were found to have poor adhesion retention with the encapsulant. Furthermore, it turned out that durability is inferior also about the solar cell carrying the obtained solar cell back surface protection sheet.

The solar cell back surface protection sheet of the present invention can be suitably used as a back surface protection sheet of a solar cell module. In addition, it can be suitably used as an easy-adhesive sheet in applications that require adhesion with an ethylene-vinyl acetate copolymer resin.

1: Solar cell back surface protection sheet 2: Sealing material 3: Power generation element 4: Transparent substrate 5: Surface of solar cell back surface protection sheet on sealing material 2 side 6: Solar cell back surface protection sheet sealing material 2 Opposite side

Claims

It has a base material layer (P1 layer) made of polyester resin and an easy adhesion layer (P2 layer) adjacent to at least one side of the P1 layer, and the P2 layer satisfies the following requirements (1) and (2) A sheet for protecting the back surface of a solar cell, characterized by satisfying.
(1) Contains three components, a urethane resin component, a melamine resin component, and an epoxy resin component.
(2) The contact angle of water is 74 ° or more.
The P2 layer is a layer formed from a coating composition containing a urethane resin, a melamine resin, and an epoxy resin, and the urethane resin forms 80% by mass or more by solid content in the coating composition forming the P2 layer. The solar cell back surface protection sheet according to claim 1, further comprising:% by mass or less.
3. The weight ratio Wm / We (weight of melamine resin / weight of epoxy resin) of the melamine resin and the epoxy resin in the coating composition forming the P2 layer is in the range of 2 to 5. The solar cell back surface protection sheet according to 1.
The solar cell back surface protective sheet according to any one of claims 1 to 3, wherein the urethane resin component contained in the P2 layer has a polyester skeleton.
The solar cell back surface protection sheet according to any one of claims 1 to 4, wherein the polyester resin constituting the P1 layer contains 1% by mass or more and 25% by mass or less of titanium oxide particles.
The polyester resin constituting the P1 layer is polyethylene terephthalate having an intrinsic viscosity IV of 0.65 dl / g or more and 0.80 dl / g or less and a terminal carboxyl group amount of 25 equivalents / ton or less. The solar cell back surface protection sheet according to any one of 5.
A solar cell using the solar cell back surface protective sheet according to any one of claims 1 to 6.
An easy-adhesion layer (P2 layer) adjacent to at least one side of a base material layer (P1 layer) made of a polyester resin is provided, and the P2 layer satisfies (3) and (4). Sheet manufacturing method.
(3) It is a layer formed from the coating composition containing 3 components of a urethane resin, a melamine resin, and an epoxy resin.
(4) The contact angle of water is 74 ° or more.
The method for producing a solar cell back surface protection sheet according to claim 8, wherein the urethane resin contained in the coating composition is a tri-type melamine resin.