JP2014075508A - Sheet for solar cell back protection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back sheet for solar cell having excellent long term durability and EVA adhesion.SOLUTION: A sheet for solar cell back protection comprises: a base material layer (P1 layer) composed of polyester resin; and an easy adhesion layer (P2 layer) adjoining the P1 layer, and fully satisfies following requirements. (1) The P2 layer has an adhesion strength of 10 N/10 mm or more for both polyester resin forming the P1 layer, and ethylene-vinyl acetate copolymer resin. (2) The P2 layer has a sea-island structure, and the size of island component appearing on the surface of the P2 layer has an average diameter of 0.1-5 μm in terms of equivalent circle diameter.

Description

  The present invention relates to a sheet for protecting a back surface of a solar battery, which has good adhesion to a sealing material of a solar battery cell and has good long-term durability, partial discharge voltage, and processability.

  In recent years, solar 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 generation 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 resin sheet called a back sheet It is configured by pasting 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, the conventional solar cell back surface protection sheet has barrier properties by bonding various materials to a biaxially stretched polyethylene terephthalate (hereinafter referred to as PET), which is inexpensive and high performance, by a method such as dry lamination. And studies have been made to impart electrical characteristics. 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 addition, recently, polyester sheets (Patent Documents 1, 2, 3, and 4) that can provide 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. Yes.

JP 2006-152013 A Japanese Patent No. 4803317 JP 2012-69835 A International Publication No. 2008/069024 Pamphlet

  However, in the conventional easy-adhesion layers listed in Patent Documents 1 to 4, the adhesion to the sealing material is very weak, and during processing of solar cells, as well as while being 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, an object of the present invention is to provide a sheet for protecting the back surface of a solar cell that has good adhesion to a sealing material and good workability in view of the conventional problems.

In order to solve the above problems, the present invention has the following configuration. That is, a solar cell back surface protection sheet having a base material layer (P1 layer) made of a polyester resin and an easy adhesion layer (P2 layer) adjacent to the P1 layer, the following (1), (2) A sheet for protecting the back surface of a solar cell that satisfies the above requirements.
(1) The P2 layer has an adhesive strength of 10 N / 10 mm or more in both the polyester resin and the ethylene-vinyl acetate copolymer resin that form the P1 layer.
(2) The P2 layer has a sea-island structure, and the size of the island component appearing on the surface of the P2 layer is an average equivalent diameter of 0.1 μm or more and less than 5 μm.

  According to the present invention, compared with a laminated sheet in which an easy-adhesion layer is provided on the surface of a conventional biaxially stretched polyester film, the back surface of the solar cell has better adhesion to the sealing material, partial discharge voltage, and processing suitability. It can be suitably used as a protective sheet, 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 solar cell back surface protection sheet in the present invention is a solar cell back surface protection sheet having a base material layer (P1 layer) made of a polyester resin and an easy adhesion layer (P2 layer) adjacent to the P1 layer, It is a solar cell back surface protection sheet that satisfies the following requirements (1) and (2).
(1) The P2 layer has an adhesive strength of 10 N / 10 mm or more in both the polyester resin and the ethylene-vinyl acetate copolymer resin that form the P1 layer.
(2) The P2 layer has a sea-island structure, and the size of the island component appearing on the surface of the P2 layer is an average equivalent diameter of 0.1 μm or more and less than 5 μm.

(Base material layer (P1 layer))
First, the P1 layer of 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 Hoisofutaru 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.

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

  Next, as the diol component, aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, etc. , 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 compounds 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 selected and copolymerized one by one from the above, or a plurality of each may be selected and copolymerized.

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

  The resin constituting the P1 layer of the present invention has a polyester resin as the main constituent as described above, 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 a main constituent, if the intrinsic viscosity IV of the PET is less than 0.65 dl / g, the moisture and heat resistance of the sheet may deteriorate. Moreover, when intrinsic viscosity IV exceeds 0.8 dl / g, when manufacturing P1 layer, the extrudability of resin may be bad and sheet molding may become difficult. Furthermore, even if the intrinsic viscosity IV satisfies the above range, if the terminal carboxyl group amount is 25 equivalents / ton or more, the adhesion to the P2 layer is improved, but the moisture and heat resistance of the sheet is deteriorated, which is not preferable. 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. The lower limit of the amount of terminal carboxyl groups is not particularly limited, but it is difficult to make it substantially less than 1 equivalent / ton.

  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 18500 to 40000, more preferably 19000 to 35000, and still more preferably 20000 to 33000. When the number average molecular weight of the polyester resin constituting the P1 layer is less than 18500, long-term durability may be lowered, which is not preferable. 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, long-term durability can be improved by orientation crystallization.

  Moreover, in the solar cell back surface protection sheet of the present invention, the polyester resin constituting the P1 layer has a minute endothermic peak temperature TmetaP1 (° C.) obtained by differential scanning calorimetry (DSC) of the polyester resin constituting the P1 layer. When the melting point is TmP1 (° C.), it is preferably TmP1-90 ° C. to TmP1-40 ° C. More preferably, TmetaP1 is TmP1-80 to TmP1-50 ° C, more preferably TmetaP1 is TmP1-75 to TmP1-55 ° C. If TmetaP1 is less than TmP1-90 ° C., the residual stress during stretching may not be sufficiently eliminated. As a result, the thermal contraction of the P1 layer becomes large, and it becomes difficult to bond in the bonding process when incorporating into the solar cell. Even if the bonding can be performed, it is incorporated into the solar cell and used at a high temperature. In some cases, large warpage of the solar cell system may occur. Moreover, when TmetaP1 exceeds TmP1-40 ° C., the oriented crystallinity may be lowered and the heat and moisture resistance may be inferior. In the solar cell back surface protective sheet of the present invention, by reducing the T1 layer P1 of the P1 layer in the above-described range, it is possible to achieve both reduction in heat shrinkage and resistance to moist heat.

  Moreover, in the solar cell back surface protection sheet of this invention, since melting | fusing point TmP1 (degreeC) of the polyester resin which comprises P1 layer is 220 degreeC or more, since heat resistance becomes favorable, it is preferable. More preferably, it is 240 degreeC or more, More preferably, it is 250 degreeC. The upper limit of the melting point TmP1 (° C.) of the P1 layer is not particularly limited, but is preferably 300 ° C. or less from the viewpoint of productivity.

  For the purpose of imparting properties such as light resistance, light reflectivity, light hiding property, designability, and visibility to the P1 layer of the present invention, a method of containing particles having respective functions is also preferably used. For example, in order to improve both light 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 exhibit the effect of reducing coloration due to deterioration of the sheet over a long period of time by utilizing the ultraviolet absorbing ability and light reflectivity of the titanium oxide particles. If it is less than 1% by mass, the UV resistance may deteriorate. If it is more than 30% by mass, the adhesion between the layers may be deteriorated. A more preferable lower limit is 2% by mass or more, and further preferably 3% by mass or more. A more preferable upper limit is 25% by mass or less, and further preferably 20% by mass or less. Furthermore, it is more preferable to use rutile type titanium oxide in terms of high light reflectivity and light resistance.

  Further, in order to improve light 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 added to 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 coloration due to deterioration of the sheet over a long period of time by utilizing the ultraviolet absorbing ability and light hiding property of the carbon particles. If it is less than 0.1% by mass, the ultraviolet resistance may deteriorate. When the content is more than 5% by mass, the pressure in the furnace becomes high and the extrusion may become difficult or the adhesion between layers may deteriorate when the raw material is melt-extruded in the step of forming the P1 layer. A more preferable lower limit is 0.2% by mass or more, and further preferably 0.5% by mass or more. A more preferable upper limit is 4% by mass or less, and further preferably 3% by mass or less.

  Further, as a method of incorporating the particles into the polyester resin constituting the P1 layer, a method of melt-kneading the polyester resin and particles using a vent type biaxial 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 larger amount of added particles than the amount of particles contained in the polyester resin constituting the P1 layer is prepared and mixed with the polyester resin to dilute to obtain a predetermined P1 layer particle content. Is preferable from the viewpoint of heat and moisture resistance.

  In addition to the titanium oxide particles and carbon particles, the P1 layer in the solar cell back surface protective sheet of the present invention includes a heat resistance stabilizer and an oxidation resistance stabilizer as long as the effects of the present invention are not impaired as necessary. , 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. Add antistatic agent to improve withstand voltage, add organic / inorganic fine particles and bubbles to develop reflectivity, and add color material you want to color to add design You can also

  The P1 layer of the present invention may have a laminated structure. For example, a laminated structure of a P11 layer excellent in wet heat resistance and a layer P12 layer containing a high concentration of an ultraviolet absorber or titanium oxide particles having an ultraviolet absorbing ability is also preferably used. In the case of such a P1 layer, it is preferable from the viewpoint of light resistance that the configuration of the solar cell back surface protection sheet of the present invention is P12 layer / P11 layer // P2 layer. In this case, as the resin 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. If the thickness of the P1 layer is less than 30 μm, the partial discharge voltage is small, and dielectric breakdown may occur when used under a high voltage, which is not preferable. 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. 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.

(Easily adhesive layer (P2 layer))
The solar cell back surface protection sheet of the present invention needs to be provided with a P2 layer that is an easily adhesive 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 easy-adhesion layer (P2 layer) has a sea-island structure, and the size of the island component appearing on the surface of the P2 layer is an equivalent circle diameter and the average diameter is 0. It is necessary to be 1 μm or more and less than 5 μm. The average diameter of the equivalent circle diameter referred to in the present invention is the diameter of a perfect circle in which the average area per island component is obtained by a measurement method described later, and the area equal to the average area per island component. Show.

  When the size of the island component appearing on the surface of the P2 layer is equivalent to a circle equivalent diameter and the average diameter is less than 0.1 μm, the shape of the island component is too small, particularly the initial adhesion with the sealing material is poor. There is a problem that it is inferior in long-term durability. In addition, in the case of 5 μm or more, since the shape of the island component is large, there may be a case where a portion having good adhesion and a portion having poor adhesion are locally formed, and it becomes difficult to impart uniform adhesion to the P2 layer. There is a problem that a gap is generated at the interface with the P1 layer, resulting in inferior initial adhesion and long-term durability. By satisfy | filling this range, when the sheet | seat of this invention and a photovoltaic cell are bonded together, the outstanding adhesive force is exhibited, Furthermore, it can be set as the solar cell back surface protection sheet excellent in long-term durability.

Moreover, it is preferable that 3 or more and less than 200 island components appear on the surface of the P2 layer per 100 μm ^{2 on the} surface of the P2 layer. When the number of island components is less than 3, the number of island components is small, so it may be difficult to impart uniform adhesion to the P2 layer, and the initial adhesion with the sealing material may deteriorate, There is a problem that initial adhesiveness with the P1 layer is deteriorated, and further, long-term durability is inferior. On the other hand, in the case of 200 or more, there are too many island components, the initial adhesion with the P1 layer is deteriorated, the initial adhesion with the sealing material is deteriorated, and the long-term durability is inferior. is there. Therefore, by making it within the scope of the present invention, it is possible to obtain a P2 layer that adheres to both the P1 layer and the sealing material in a well-balanced manner and further has excellent long-term durability. A preferable range of the number of island components existing in the P2 layer is 5 or more and less than 180 per 100 μm ² , and a more preferable range is 10 or more and less than 150.

  The method for forming the sea-island structure in the P2 layer of the present invention is not particularly limited, but there is a method for forming a sea-island structure by mixing at least two kinds of incompatible resins with each other. Preferably used. As for the resin mixing method, if the resin to be used is a thermoplastic resin, it may be kneaded in a heated and melted state, a resin dissolved in an organic solvent or a solvent such as water is mixed, or a resin emulsified in water is used. You may mix. A resin obtained by mixing resins dissolved in a solvent such as an organic solvent or water or emulsifying in water can be applied to the surface of the P1 layer and then dried to form a P2 layer having a sea-island structure.

In addition, the method of setting the island component of the present invention in the range of 0.1 to 5 μm in diameter and 3 to less than 200 per 100 μm ^{2 on the} surface of the P2 layer is not particularly limited. When the resin is a thermoplastic resin and is melt-kneaded with heat, a compatibilizer may be used to disperse the resin serving as the island component in the resin serving as the sea component so that the size is within the above range. In the case of mixing resins dissolved in a solvent such as an organic solvent or water, or mixing a resin emulsified in water, it is dispersed using a surfactant so as to have a size within the above range, or in advance You may make it disperse | distribute so that the particle diameter of an island component may become the said range.

The easy-adhesion layer (P2 layer) of the present invention is a layer having adhesion to both the polyester resin and the ethylene-vinyl acetate copolymer (EVA) resin that form the P1 layer. In the present invention, having adhesiveness means that the adhesive strength is 10 N / 10 mm or more in the measurement method described later. That is, the easy-adhesion layer (P2 layer) of the present invention must have an adhesive strength of 10 N / 10 mm or more for both the polyester resin and the ethylene-vinyl acetate copolymer (EVA) resin that form the P1 layer. is there. In the present invention, the adhesive strength between the P2 layer and the polyester resin forming the P1 layer, and the P2 layer and the ethylene-vinyl acetate copolymer (EVA) resin is based on JIS K 6854-2 (1994 edition) as follows. It is determined by the measurement method.
Adhesive strength measurement sample:
An EVA sheet (manufactured by Sanvic Co., Ltd., fast cure type (500 μm thick sheet)) is stacked on the P2 layer side of the sheet of the present invention, and a 3 mm thick semi-tempered glass is further stacked thereon to form a commercially available glass laminator. After evacuation, press treatment is performed for 15 minutes with a load of 29.4 N / cm ² under a heating condition of 135 ° C., and an adhesive strength test sample having a width of 10 mm and a length of 150 mm is produced.
Definition of measurement conditions and measurement results:
The peeling method is 180 ° peeling, and the number of measurements is n = 3. When the peel interface is the interface between the P2 layer and the P1 layer three times, the average of the three measurements is the bond strength between the P2 layer and the polyester resin forming the P1 layer, and the bond strength between the P2 layer and EVA Is more than the adhesive strength between the P2 layer and the polyester resin forming the P1 layer. If the peel interface is the interface between the P2 layer and EVA three times, the average of the three measurements is the bond strength between the P2 layer and EVA, and the bond between the P2 layer and the polyester resin that forms the P1 layer The strength is assumed to be equal to or greater than the adhesive strength between the P2 layer and EVA.

  Also, in this measurement, before the peeling at the interface occurs, when the interface that is broken and peeled off from the P1 layer, P2 layer, or EVA layer is not clear, the measured value at the time when the breaking occurs is P2 The adhesive strength between the layer and the polyester resin forming the P1 layer and the adhesive strength between the P2 layer and the EVA resin are used.

  Further, when the interface peeled in three measurements is not the same interface three times (for example, when the peel is twice at the interface between the P2 layer and the P1 layer, and the peel is once at the interface between the P2 layer and the EVA, P2 When there is one separation at the interface between the layer and the P1 layer, and two separations at the interface between the P2 layer and the EVA, there is one separation at the interface between the P2 layer and the P1 layer, and there is a separation at the interface between the P2 layer and the EVA. Once the peeled interface is not clear, etc.), the average value of the three measured values obtained is the adhesion strength between the P2 layer and the polyester resin forming the P1 layer, and the P2 layer. And the adhesive strength of EVA.

  The resin constituting the P2 layer of the present invention is not particularly limited as long as it is a resin having an adhesive strength of 10 N / 10 mm or more in both the polyester resin and EVA forming the P1 layer.

(Resin constituting the P2 layer-resin A constituting the sea component)
In the P2 layer of the present invention, the resin A constituting the sea component may be one kind of resin or a mixture of two or more kinds of resins, but has at least adhesiveness with the P1 layer. A resin is preferred. Furthermore, it is preferable that it is resin which has adhesiveness in both P1 layer and EVA by the side of a photovoltaic cell.

  For example, the resin A constituting the sea component includes a binder resin such as a polyurethane resin, a polyester resin, and an acrylic resin, a cross-linking agent including an isocyanate resin, an epoxy resin, a melamine resin, an oxazoline resin, a carbodiimide resin, and a polyolefin resin. An adhesive or the like can be used. When these adhesive resins are used for the resin A constituting the P2 layer, they may be used alone or in combination of two or more, but the adhesive strength deteriorates when used outdoors for a long time. It is necessary not to cause delamination due to this, and to prevent yellowing that leads to a decrease in light reflectance.

  In the present invention, when the resin A constituting the sea component of the P2 layer contains a polyurethane resin such as a polyether urethane resin or a polyester urethane resin, the interlayer adhesion and the interlayer adhesion after the wet heat resistance test are improved. This is preferable. The polyurethane resin is a resin containing a urethane bond in the main chain, and is obtained, for example, by a reaction between a polyol compound and a polyisocyanate compound, and has an anionic group from the viewpoint of dispersibility in an aqueous medium. Those are preferred. Here, the anionic group means 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. The polyol component constituting the polyurethane-based resin is not particularly limited, and water, ethylene glycol, diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,2-propanediol, 1, 3-propanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, methyl-1,5-pentanediol, 1,8-octanediol, 2-ethyl-1,3-hexanediol , Low molecular weight glycols such as diethylene glycol, triethylene glycol and dipropylene glycol, low molecular weight polyols such as trimethylolpropane, glycerin and pentaerythritol, polyol compounds having ethylene oxide and propylene oxide units Polyether diols, high molecular weight diols such as polyester diols, bisphenols such as bisphenol A, bisphenol F, dimer diol, and the like to the carboxyl group of the dimer acid was converted to hydroxyl groups.

  On the other hand, as the polyisocyanate component, one or a mixture of two or more known aromatic, aliphatic and alicyclic diisocyanates can be used. Specific examples of the 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 include lysine diisocyanate, hydrogenated 4,4′-diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, dimerized isocyanate obtained by converting a 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.

  In order to introduce an anionic group into the polyurethane 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.

  The molecular weight of the polyurethane 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.

  The glass transition temperature Tg of the urethane resin constituting the P2 layer of the present invention is preferably 0 ° C. or higher and 40 ° C. or lower. When the glass transition temperature Tg is less than 0 ° C., the adhesion to EVA on the solar cell side is good, but it is not preferable because it may be inferior in heat and humidity resistance. Moreover, when Tg exceeds 40 degreeC, since the film forming property at the time of forming P2 layer may worsen, or adhesiveness with EVA by the side of a photovoltaic cell may be inferior, it is unpreferable. A preferable range of the glass transition temperature Tg of the urethane resin constituting the P2 layer is 0 ° C. or more and 35 ° C. or less, and a more preferable range is 5 ° C. or more and 30 ° C. or less.

  As these urethane resins, for example, commercially available resins such as “Hydran” (registered trademark) series manufactured by DIC Corporation can be obtained and used.

(Resin constituting P2 layer-resin B constituting island component)
In the P2 layer of the present invention, the resin B constituting the island component may be one type of resin or a mixture of two or more types of resins. When the resin constituting the island portion is a mixture of two or more, it is preferable that the resin is uniformly compatible. Further, the island component may be the same resin for all the island components or a plurality of types.

  For example, it is preferable that the resin B constituting the island component of the P2 layer contains a polyolefin resin because the adhesive force with the EVA resin layer of the solar battery cell is improved. The polyolefin resin is preferably a modified polyolefin resin. The modified polyolefin resin is an acid-modified polyolefin modified with an unsaturated carboxylic acid or its anhydride, or a polyolefin modified with a silane coupling agent, or other resin components such as acrylic acid ester or vinyl acetate. A resin having a polyolefin as a main component (herein, a resin having a polyolefin as a main component refers to a resin containing 50% by mass or more of polyolefin with respect to the entire resin).

  The modified polyolefin resin is an alkene such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-hexene, butadiene, isoprene, etc. Examples thereof include modified polyolefin resins such as dienes. Among them, it is an ethylene component, a propylene component or a butene component (1-butene, isobutene, etc.) in terms of ease of production of a resin, ease of aqueous formation, adhesion to various materials, blocking properties, etc. It is preferable that both can be used together.

  In the above polyolefin resin component, the form of copolymerization of each component is not limited, and examples thereof include random copolymerization and block copolymerization. From the viewpoint of ease of polymerization, random copolymerization is preferred. Moreover, what mixed 2 or more types of polyolefin resin may be used.

  The P2 layer modified polyolefin resin in the present invention is preferably a polyolefin modified with an unsaturated carboxylic acid or an anhydride thereof, or a silane coupling agent. Examples of the unsaturated carboxylic acid or its anhydride include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, itaconic acid, itaconic anhydride, or monoepoxy compounds of these derivatives and the above acids. Ester compounds, and a reaction product of a polymer having a group capable of reacting with these acids in the molecule and an acid. These metal salts can also be used. Among these, maleic anhydride, acrylic acid, and methacrylic acid are preferable, and maleic anhydride is particularly preferable from the viewpoint of easy introduction into the polyolefin resin. These unsaturated carboxylic acids or anhydrides may be copolymerized in the polyolefin resin, and the form thereof is not limited, and examples thereof include random copolymerization, block copolymerization, and graft copolymerization. Examples of the silane coupling agent include vinyltriethoxysilane, methacryloyloxytrimethoxysilane, and γ-methacryloyloxypropyltriacetyloxysilane.

  The method for introducing the unsaturated carboxylic acid into the polyolefin resin is not particularly limited. For example, in the presence of a radical generator, the reaction is performed by heating and melting the polyolefin resin and the unsaturated carboxylic acid above the melting point of the polyolefin resin. And a method in which an unsaturated carboxylic acid unit is graft-copolymerized to a polyolefin resin by a method in which the polyolefin resin is dissolved in an organic solvent and then reacted by heating and stirring in the presence of a radical generator. . The former method is preferable because the operation is simple.

  Examples of the radical generator used for graft copolymerization include di-tert-butyl peroxide, dicumyl peroxide, tert-butyl hydroperoxide, tert-butyl cumyl peroxide, benzoyl peroxide, dilauryl peroxide, Examples thereof include organic peroxides such as cumene hydroperoxide, tert-butyl peroxybenzoate, ethyl ethyl ketone peroxide, and di-tert-butyl diperphthalate, and azonitriles such as azobisisobutyronitrile. These may be appropriately selected depending on the reaction temperature.

  In addition, it is also preferable to use an ethylene-vinyl acetate copolymer (EVA) resin as the modified polyolefin resin contained in the P2 layer in terms of improving the adhesiveness with the EVA layer of the solar battery cell. The ratio of the ethylene group and the vinyl acetate group is not particularly limited, and can be suitably used as long as the adhesiveness with the EVA layer of the solar battery cell is good. Further, other components such as acrylic resin may be copolymerized mainly using EVA resin.

  In order to enhance the durability of the P2 layer of the present invention, such as adhesion, heat resistance, moisture resistance, and blocking resistance, it is preferable to use a crosslinking agent. The term "crosslinking agent" as used in the present invention refers to a resin having reactivity that links polymers and changes physical and chemical properties. The cross-linking agent used in the present invention is not particularly limited, and any cross-linking agent can be suitably used as long as it has an effect of increasing the mechanical strength of the P2 layer. For example, isocyanate resins, epoxy resins, melamine resins, oxazoline resins, carbodiimide resins, and the like are preferably used. These cross-linking agents include, for example, an isocyanate-based cross-linking agent “Elastolon” (registered trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., a melamine-based cross-linking agent “Beckamine” (registered trademark) manufactured by DIC Corporation, and an oxazoline-based cross-linking manufactured by Nippon Shokubai Co., Ltd. Commercially available cross-linking agents such as the agent “Epocross” (registered trademark), Nisshinbo Chemical Co., Ltd. carbodiimide-based cross-linking agent “Carbodilite” (registered trademark), and DIC Corporation epoxy cross-linking agent “EPICLON” (registered trademark) Can be used.

  Examples of the solvent for the coating liquid (coating liquid) for forming the P2 layer 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. In the case of a coating solution using water as a solvent, it may contain a solvent used in a structure for emulsifying the resin component, or an organic solvent as a dispersion aid, but in particular, from the viewpoint of heat and moisture resistance, a dispersant may be used. Dissolving type coating liquid not containing is preferable. In addition, the method for emulsifying the resin A and the resin B in an aqueous emulsion is not particularly limited, and the resin A and the resin B can be produced by a device widely known to those skilled in the art as a solid / liquid stirring device or an emulsifier. The P2 layer of the present invention is preferably obtained by applying and drying a coating containing the resin A, the resin B and the crosslinking agent C on the P1 layer.

  As for the thickness of P2 layer in the solar cell back surface protection sheet of this invention, 0.1 to 3 micrometer is preferable. If it is less than 0.1 μm, the adhesion with the sealing material is deteriorated, and delamination may occur. On the other hand, if it is thicker than 3 μm, it takes a long time to develop an adhesive force (accelerating the crosslinking reaction between the main agent and the curing agent), and as a result, the moisture and heat resistance of the easy-adhesive layer may be deteriorated. A more preferable lower limit is 0.15 μm or more, and further preferably 0.2 μm or more. A more preferable upper limit is 2 μm or less, and further preferably 1 μm or less. A preferred range is from 0.15 μm to 2 μm, and more preferably from 0.2 μm to 1 μm. In particular, it is preferable to provide the P2 layer by in-line coating during the formation of the P1 layer because the manufacturing process is simplified, the film-forming property of the film is good, and the thickness unevenness and coating defects are reduced.

  The P2 layer of the present invention may have a laminated structure for the purpose of improving the adhesion between the P1 layer and the EVA layer of the solar battery cell. For example, a method of further providing a layer (referred to as P22 layer) that is familiar with the EVA layer on an anchor coat layer (referred to as P21 layer) provided in advance on one surface of the P1 layer is also preferably used. In that case, the configuration of the solar cell back surface protection 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 has good adhesiveness with the resin constituting the P21 layer and the EVA layer. There is no particular limitation as long as it is compatible with the EVA layer at the temperature during lamination. 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.

  Further, the method for forming the P22 layer on the P21 layer is not particularly limited, and a known coating method can be used. As the coating method, various methods can be applied. 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.

  In the P2 layer of the present invention, various additives such as known heat stabilizers, lubricants, antistatic agents, anti-blocking agents, dyes, pigments, photosensitizers, surfactants, ultraviolet absorbers, and the like are added as necessary. Can be added.

(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.

  The solar cell back surface protection sheet of the present invention preferably has a color tone change Δb of 10 or less when the P1 layer is used as an incident surface from the viewpoint of ultraviolet resistance. Here, the color change Δb is measured by the measurement method to be described later. The b value measured with the solar cell back surface protection sheet P1 layer before the ultraviolet ray treatment as the incident surface is K0, and the solar cell back surface protection sheet P1 layer after the ultraviolet ray treatment is incident. This is a value calculated as Δb = K0−K, where K is the b value measured as a surface. Preferably it is 6 or less, More preferably, it is 3 or less. In order to set the color tone change Δb to 10 or less, it is preferable to add 3% by mass or more of titanium oxide particles to the P1 layer, and the color tone change Δb is reduced according to the amount of titanium oxide particles added. It is possible.

The solar cell back surface protection sheet of the present invention preferably has a water vapor transmission rate of 0.0001 g / m ² · day or more and 10 g / m ² · day or less from the viewpoint of gas barrier properties. More preferably, it is 0.0001 g / m ² · day or more and 5 g / m ² · day or less, and most preferably 0.0001 g / m ² · day or more and 3 g / m ² · day or less. By setting it as this range, deterioration inside the solar cell due to permeation of gas from the back sheet to the sealing material can be prevented. Here, the water vapor transmission rate is a value measured according to the JIS-K7129B method (1992). The water vapor transmission rate in the present invention can be adjusted by the thickness of the P3 layer, and the water vapor transmission rate decreases as the thickness increases.

(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 an ester derivative thereof and a diol to a transesterification reaction or an esterification reaction by a 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 addition, in order to control the number average molecular weight of the polyester resin to 18500-40000, after polymerizing the polyester resin having a molecular weight of about 18000, the number average molecular weight is about 190 ° C. to a temperature below the melting point of the polyester resin. Thus, a so-called solid-phase polymerization method in which heating is performed 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, in the manufacturing method when the P1 layer has a laminated structure, when the material of each layer to be laminated is mainly composed of a thermoplastic resin, two different thermoplastic resins are put into two extruders and melted. A method of co-extrusion on a cast drum cooled from a die to process it into a sheet (co-extrusion method), a method of laminating a sheet made of a single film into an extruder, melting and extruding and extruding from the die (Melt lamination method) can be 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) ), Melted and extruded from the die (co-extrusion in the case of a laminated structure), and cooled and solidified by static electricity on a cooled drum cooled to a surface temperature of 10 to 60 ° C. Make it.

  This unstretched sheet is led to a roll group heated to a temperature of 70 to 140 ° C., stretched 3 to 4 times in the longitudinal direction (longitudinal direction, ie, the traveling direction of the sheet), and a roll group having a temperature of 20 to 50 ° C. Cooling.

  Subsequently, the both ends of the sheet are guided to a tenter while being gripped by clips, and are 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, and the area ratio (longitudinal stretching ratio x lateral stretching ratio) is preferably 9 to 15 times. When the area magnification is less than 9 times, the long-term 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.

  In addition, when forming the P2 layer by in-line coating provided in the production process of the P1 layer, in the case of the sequential biaxial stretching method, after the uniaxially stretched sheet, the unstretched sheet or the simultaneous biaxial stretching method In this case, after forming an unstretched sheet, a coating process may be provided, and a coating material as a material for the P2 layer may be applied. At this time, from the viewpoint of improving the wettability of the coating liquid onto the support and improving the adhesive force, it is also preferable to perform a corona treatment on the surface of the base material layer P1 immediately before the coating step.

  In order to complete the crystal orientation of the obtained biaxially stretched sheet and to impart flatness and dimensional stability, it is preferably continued in the tenter for 1 to 30 seconds at a temperature not lower than the melting point of the resin as a raw material and preferably lower than the melting point. The heat treatment is performed, and after cooling uniformly, cool to room temperature. In general, when the heat treatment temperature is low, the thermal shrinkage of the sheet is large. Therefore, it is preferable that the heat treatment temperature is high in order to impart high thermal dimensional stability. However, when the heat treatment temperature is too high, the orientation crystallinity is lowered, and as a result, the formed sheet may be inferior in heat and moisture resistance. Therefore, the heat treatment temperature of the P1 layer of the present invention is preferably TmP1-90 to TmP1-40 ° C. More preferably, the heat treatment temperature is TmP1-80 to TmP1-50 ° C, and more preferably TmP1-75 to TmP1-55 ° C. Since the sheet containing the P1 layer of the present invention is used as a back sheet for solar cells, the ambient temperature may rise to about 100 ° C. during use, so that the heat treatment temperature is 160 ° C. to TmP 1-40 ° C. (however, TmP1-40 ° C.> 160 ° C.) is preferable. More preferably, it is 170-TmP1-50 degreeC (however, TmP1-50 degreeC> 170 degreeC), More preferably, it is 180-TmP1-55 degreeC (however, TmP1-55 degreeC> 180 degreeC). Moreover, in the said heat processing process, you may perform a 3-12% relaxation process in the width direction or a longitudinal direction as needed.

  Subsequently, if necessary, the substrate layer of the solar cell back surface protection sheet of the present invention can be formed by performing a corona discharge treatment or the like in order to further enhance the adhesion to other materials and winding up.

  Next, as a method for forming the P2 layer on the P1 layer, a known coating technique can be used. As the coating method, various methods can be applied. 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. In addition, a method of providing an easy-adhesion layer in-line using a known coating technique during the formation of a polyester film as a substrate is also a preferable method in terms of simplifying the manufacturing process. In addition to in-line coating, using a plurality of extruders, the P1 layer raw material and the P2 layer raw material are melted in separate extruders and co-extruded on a cast drum cooled from the die to form a sheet. Processing (coextrusion method), base material layer P1 layer made of a single film, P2 layer material is put into an extruder, melt extruded and laminated while extruding from the die (melt laminating method), P1 layer And P2 layers are prepared separately, thermocompression bonding with a heated group of rolls (thermal laminating method), bonding method using an adhesive (adhesion method), and other materials for P2 layer are dissolved in a solvent Alternatively, a method of dispersing and applying the solution onto the base material layer P1 previously prepared (coating method), a method combining these, and the like can be used.

  In the present invention, a coating method in which formation of the P2 layer is easy is a more preferable method. As a method of forming the P2 layer on the base material layer P1 layer by the coating method, the in-line coating method applied during the formation of the base material layer P1 layer described above, or the base material layer P1 layer after the film formation is applied. Either of these can be used, and either can be used, but more preferably, it can be performed simultaneously with the formation of the base layer P1 and is efficient, and the adhesiveness between the P2 layer and the P1 layer is high. An in-line coating method is preferably used. Furthermore, from the viewpoint of improving the adhesion between the P1 layer and the EVA layer, the P22 layer can be provided by off-line coating on the P21 layer provided on the surface of the P1 layer by in-line coating.

  Moreover, when hardening P2 layer after coating, the hardening method can take a well-known method. For example, thermosetting, a method using active rays such as ultraviolet rays, electron beams, radiation, or a combination of these methods can be applied. In the present invention, a heat curing method using a hot air oven is preferred. Furthermore, in the curing with a hot air oven, the method of increasing the drying temperature stepwise, such as material preheating / constant rate drying / residual rate drying, is preferable because the solvent does not remain in the P2 layer. Furthermore, it is preferable to perform an aging treatment at an arbitrary temperature after the drying step in terms of promoting a crosslinking reaction between the main agent and the curing agent.

  As a method of forming the P2 layer on the base material layer P1 layer by the above-mentioned coating method, a coating liquid in which the material constituting the P2 layer is dissolved / dispersed in a solvent is applied on the base material layer P1 layer and dried. The means to do is used preferably. In this case, the solvent to be used is arbitrary, but in the in-line coating method, it is preferable to use water from the viewpoint of safety. In that case, a small amount of an organic solvent that dissolves in water may be added in order to improve applicability and solubility. Examples of such organic solvents include aliphatic or alicyclic alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, and n-butyl alcohol, diols such as ethylene glycol, propylene glycol, and diethylene glycol, methyl cellosorb, Diol derivatives such as ethyl cellosolve propylene glycol monomethyl ether, ethers such as dioxane and tetrahydrofuran, esters such as methyl acetate, ethyl acetate and amyl acetate, ketones such as acetone and methyl ethyl ketone, amides such as N-methylpyrrolidone Etc. and mixtures thereof may be used, but are not limited to these.

  The addition amount Wa of the resin A in the P2 layer of the present invention is preferably 1% by mass or more and 98.5% by mass or less among the resin components constituting the P2 layer. Resin A mainly improves the adhesiveness with the P1 layer, and when it is less than 1% by mass, it may be peeled off at the interface between the P1 layer and the P2 layer when bonded to the solar battery cell. Moreover, when more than 98.5 mass%, adhesiveness with the EVA layer of a photovoltaic cell may worsen. A more preferable range is 10% by mass to 95% by mass, and a most preferable range is 20% by mass to 90% by mass.

  The addition amount Wb of the resin B in the P2 layer of the present invention is preferably 0.5% by mass or more and 90% by mass or less among the resin components constituting the P2 layer. Resin B mainly enhances the adhesiveness with the EVA layer of the solar battery cell. Therefore, when it is less than 0.5% by mass, the adhesiveness between the P2 layer and the EVA layer is deteriorated when pasted to the solar battery cell. May end up. Moreover, when more than 90 mass%, it may peel at the interface of P1 layer and P2 layer. A more preferable range is 10% by mass or more and 80% by mass or less, and a most preferable range is 20% by mass or more and 60% by mass or less.

  The addition amount of the crosslinking agent C in the P2 layer of the present invention is preferably 1% by mass or more and 90% by mass or less of the resin components constituting the P2 layer. Since the crosslinking agent C functions to enhance adhesion to both the P1 layer and the EVA layer, when the addition amount Wc of the crosslinking agent C is less than 1% by mass or more than 90% by mass, the P1 layer, the P2 layer, and the EVA layer The adhesion of the may become weak. A more preferable range is 10% by mass or more and 80% by mass or less, and a most preferable range is 20% by mass or more and 70% by mass or less.

  The solar cell back surface protection sheet of the present invention obtained by the above-described method may be subjected to a processing such as heat treatment or aging as necessary within the range where the effects of the present invention are not impaired. As the upper limit of the heat treatment temperature, the glass transition temperature of the resin constituting the P1 layer is −10 ° C. or lower, more preferably the glass transition temperature −20 ° C. or lower, more preferably the glass transition temperature −30, from the flatness of the sheet. It is below ℃. The heat treatment time is 5 seconds or more and 48 hours or less. By heat-treating, the adhesion of the solar cell back surface protective sheet of the present invention can be improved. Moreover, in order to improve the adhesiveness of the solar cell back surface protection sheet | seat of this invention obtained by the said method, you may implement a corona treatment and a plasma treatment.

  The solar cell of the present invention uses the solar cell back surface protective sheet of the present invention. By using the solar cell back surface protective sheet of the present invention, it is possible to increase the durability or to make it thinner as compared to 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 the solar cell of the present invention. Although it is configured to be bonded together as the back surface protection sheet 1, it is not limited to this and can be used for any configuration. In addition, although the example in the single sheet | seat for solar cell back surface protection of this invention was shown in FIG. 1, according to the other required required characteristic, the composite sheet of the sheet | seat for solar cell back surface protection of this invention and another film It is also possible to use.

Here, in the solar cell of the present invention, the solar cell back surface protection sheet 1 described above is installed on the back surface of the sealing material 2 that seals the power generating element. Here, the solar cell back surface protective sheet of the present invention is preferably arranged so that the P2 layer is in contact with the sealing material 2. By adopting this configuration, it becomes possible to increase the resistance against the ultraviolet rays reflected from the ground, etc., and the power generation element 3 that can be made into a highly durable solar cell or can be reduced in thickness has the light energy of sunlight. Converts to electrical energy. Any element such as crystalline silicon, polycrystalline silicon, microcrystalline silicon, amorphous silicon, copper indium selenide, compound semiconductor, dye sensitization, etc. Can be used by connecting a plurality of them in series or in parallel according to the desired voltage or current. 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, tetrafluoroethylene-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 generating element covers the surface of the power generating element with resin and fixes it, protects the power generating element from the external environment, and has a light-transmitting base material for the purpose of electrical insulation. In addition, a material having high transparency, high weather resistance, high adhesion, and high heat resistance is used to adhere to the backsheet 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 protective sheet of the present invention into a solar cell system, it is possible to obtain a highly durable and / or thin solar cell system 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) Thickness of P1 layer and 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 created, and the cross section was taken as a field emission scanning electron microscope "JSM-6700F" (JEOL Co., Ltd.) was used to magnify and photograph 3000 times. From the cross-sectional photograph, the thickness of each of the P1 layer and the P2 layer was measured, and the thickness was obtained by calculating back from the magnification. In addition, the thickness used the cross-sectional photograph of five places arbitrarily selected from the mutually different measurement visual field, and used the average value.

(2) Average diameter of equivalent circle diameter of island components existing on the surface of the P2 layer The surface of the P2 layer was magnified 3000 times using a field emission scanning electron microscope “JSM-6700F” (manufactured by JEOL Ltd.). I took a picture. Using the obtained image, the sum of the areas of the island components present in the image is obtained using an image analyzer V10 manufactured by Toyobo Co., Ltd., and the total number of island components present in the image is equal to one island component. The average area was determined. The diameter of a perfect circle having the same area as the average area per island component was calculated, and the average diameter of the equivalent circle diameter of the island component was calculated.

(3) Number of island components per 100 cm ² surface of the P2 layer From the image obtained in the above item (2), the number of island components per 100 μm ^{2 of} the P2 layer surface was determined. In addition, the number was calculated | required using the surface photograph of a total of five places chosen arbitrarily from different measurement visual fields, and the average value was used.

(4) Particle content Wt1
Only the P1 layer was shaved from the solar cell back surface protective sheet, and the inorganic particle content Wt1 (mass%) of the P1 layer was determined by the following method.

The mass wt1 (g) of the shaved material was measured. Subsequently, it was made to melt | dissolve in ortho chlorophenol and the inorganic particle was fractionated among the insoluble components by centrifugation. The obtained inorganic particles were washed with orthochlorophenol and centrifuged. The washing operation was repeated until no turbidity occurred even when acetone was added to the washing solution after centrifugation. The mass wt1 ′ (g) of the obtained inorganic particles was determined, and the inorganic particle content Wt1 was measured from the following formula (1).
P1 layer inorganic particle content (% by mass) Wt1 = (wt1 ′ / wt1) × 100 (1)
(5) Adhesive strength evaluation between polyester resin and EVA resin forming P2 layer and P1 layer Adhesion between polyester resin and EVA resin forming P2 layer and P1 layer based on JIS K 6854-2 (1994 edition) The force was measured. An EVA sheet (manufactured by Sunvic Co., Ltd., fast cure type (500 μm thick sheet)) is stacked on the P2 layer side of the solar cell back surface protection sheet, and a 3 mm thick semi-tempered glass is further stacked on the sheet. After evacuation using a laminator, an evaluation sample (pseudo solar cell module sample) was produced by pressing for 15 minutes with a load of 29.4 N / cm ² under 135 ° C. heating conditions. An adhesive strength evaluation sample having a width of 10 mm and a length of 150 mm was prepared for the test piece of the adhesive strength test.
Definition of measurement conditions and measurement results:
The peeling method was 180 ° peeling, and the number of measurements was n = 3. The average value of the three measured values was determined as the adhesive strength value as follows.

  The peeling method was 180 ° peeling and the number of measurements was n = 3. When the peel interface is the interface between the P2 layer and the P1 layer three times, the average of the three measurements is the bond strength between the P2 layer and the polyester resin forming the P1 layer, and the bond strength between the P2 layer and EVA Is more than the adhesive strength between the P2 layer and the polyester resin forming the P1 layer. If the peel interface is the interface between the P2 layer and EVA three times, the average of the three measurements is the bond strength between the P2 layer and EVA, and the bond between the P2 layer and the polyester resin that forms the P1 layer The strength was assumed to be equal to or higher than the adhesive strength between the P2 layer and EVA.

  Also, in this measurement, before the peeling at the interface occurs, when the interface that is broken and peeled off from the P1 layer, P2 layer, or EVA layer is not clear, the measured value at the time when the breaking occurs is P2 The adhesive strength between the layer and the polyester resin forming the P1 layer and the adhesive strength between the P2 layer and the EVA resin were used.

  Further, when the interface peeled in three measurements is not the same interface three times (for example, when the peel is twice at the interface between the P2 layer and the P1 layer, and the peel is once at the interface between the P2 layer and the EVA, P2 When there is one separation at the interface between the layer and the P1 layer, and two separations at the interface between the P2 layer and the EVA, there is one separation at the interface between the P2 layer and the P1 layer, and at the interface between the P2 layer and the EVA Once the peeled interface is not clear, etc.), the average value of the three measured values obtained is the adhesion strength between the P2 layer and the polyester resin forming the P1 layer, and the P2 layer. And EVA.

In measurement evaluation, when peeling occurred at the interface between the P2 layer and EVA and the adhesive strength between the P2 layer and EVA was determined, the adhesive strength between the P2 layer and EVA was evaluated as follows.
When the adhesive strength is 40 N / 10 mm or more: SS
When the adhesive strength is 30 N / 10 mm or more: S
When the adhesive strength is 20 N / 10 mm or more and less than 30 N / 10 mm: A
When the adhesive strength is 10 N / 10 mm or more and less than 20 N / 10 mm: B
When the adhesive strength is less than 10 N / 10 mm: C
SS to B are good, and SS is the best among them.

(6) Adhesive strength with sealing material (EVA) after moisture and heat resistance test In the same manner as in the above (5), an evaluation sample (pseudo solar cell module sample) is prepared and applied to a pressure cooker manufactured by Tabay Espec Co., Ltd. Then, the treatment was performed for 48 hours under the conditions of a temperature of 120 ° C. and a relative humidity of 100% RH. Then, according to the said (5) term, the adhesive force with the EVA sheet | seat after a wet heat test was measured, and it determined as follows.
When the adhesive strength is 40 N / 10 mm or more: SS
When the adhesive strength is 30 N / 10 mm or more and less than 40 N / 10 mm: S
When the adhesive strength is 20 N / 10 mm or more and less than 30 N / 10 mm: A
When the adhesive strength is 10 N / 10 mm or more and less than 20 N / 10 mm: B
When the adhesive strength is less than 10 N / 10 mm: C
Cannot measure adhesive strength due to sheet breakage: D
SS to B are good, and SS is the best among them.

(7) Elongation retention after wet heat resistance test After the solar cell back surface protection sheet was cut into the shape of a measurement piece (1 cm × 20 cm), a temperature cooker manufactured by Tabay Espec Co., Ltd., temperature 125 ° C., relative humidity The treatment was performed under the condition of 100% RH, and then the elongation at break was measured based on ASTM-D882 (1997). In addition, the measurement was made into n = 5, and after measuring about each of the longitudinal direction of the sheet | seat, and the width direction, the average value was made into elongation at break E1.

Further, the solar cell back surface protection sheet before the treatment was cut into a size of 1 cm × 20 cm, and the elongation at break E0 was measured when pulled between chucks at 5 cm and a pulling speed of 300 mm / min. Using the obtained breaking elongations E0 and E1, the elongation retention was calculated by the following equation (2), and the treatment time at which the elongation retention was 50% was defined as the elongation half-life.
Elongation retention (%) = E1 / E0 × 100 (2)
About the obtained elongation half life, it determined as follows.
When elongation half-life is 60 hours or more: S
When the elongation half-life is 40 hours or more and less than 60 hours: A
When the elongation half-life is 30 hours or more and less than 40 hours: B
When elongation half-life is less than 30 hours: C
S to B are good, and S is the best among them.

(8) Average relative reflectance Using a spectrophotometer U-3410 (manufactured by Hitachi, Ltd.), the spectral reflectance in the range of 400 to 700 nm is measured at 10 nm intervals, and the average value is taken as the average relative reflectance. did. The number of samples was n = 5, each average relative reflectance was measured, and the average value was calculated. The measuring unit used an integrating sphere (model number 130-0632) with a diameter of 60 mm, and a 10 ° inclined spacer was attached. Moreover, aluminum oxide (model number 210-0740) was used for the standard white plate. In addition, a measurement is measured from the P1 layer side of this invention.
When the average relative reflectance is 80% or more: S
When the average relative reflectance is 60% or more and less than 80%: A
When the average relative reflectance is 30% or more and less than 60%: B
When the average relative reflectance is less than 30%: C
S to B are good, and S is the best among them.

(9) UV resistance When the b value measured from the P1 layer side of the solar cell back surface protection sheet before ultraviolet treatment is K0, and the b value measured from the P1 layer side of the sheet after ultraviolet treatment is K, the following ( 3) The value obtained from the equation was defined as the color change Δb on the P1 layer side, and the ultraviolet resistance of the sheet was evaluated from this value.
Δb = K−K0 (3)
Ultraviolet treatment is performed under the conditions of a temperature of 65 ° C., a relative humidity of 50% RH, and an intensity of 60 W / m ² (light source: xenon lamp, wavelength range: 290 to 400 nm) using a Xenon weather meter SC750 manufactured by Suga Test Instruments Co., Ltd. The P1 layer side was irradiated for 1000 hours. The method for obtaining the b value is as follows.
Using a spectroscopic color difference meter SE-2000 type (manufactured by Nippon Denshoku Industries Co., Ltd.), the b value was measured from the P1 layer side according to JIS Z-8722 (2000). The light source is C / 2, and the measurement mode is selected when the relative reflectance of the sheet for protecting the back surface of the solar cell obtained by the above item (8) is 40% or more, and when the relative reflectance is less than 40%. The transmission mode was set.

The number of samples was n = 5, the sample measurement diameter was 30 mmφ, each b value was measured, and the average value was calculated. From the obtained color tone change Δb, the ultraviolet resistance of the laminated sheet was determined as follows.
When the color change Δb is 3 or less: S
When the color change Δb is greater than 3 and less than or equal to 6: A
When the color change Δb is greater than 6 and 10 or less: B
When the color change Δb is greater than 10: C
S to B are good, and S is the best among them.

(10) Glass transition temperature Tg of P2 layer
Only the P2 layer is cut out, and the temperature is increased at a rate of temperature increase of 20 ° C./min from −20 ° C. to 200 ° C. in differential scanning calorimetry (hereinafter DSC) by a method based on JIS K-7121 (1999). The glass transition temperature Tg in the differential scanning calorimetry chart obtained at this time was determined.

(11) Intrinsic viscosity IV
The P1 layer was dissolved in 100 ml of orthochlorophenol (solution concentration C = 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 used 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))
(12) Amount of terminal carboxyl groups (in the table, described as COOH amount)
The amount of terminal carboxyl groups of the P1 layer was measured by the method of Malice. (Document M. J. Malice, F. Huizinga, Anal. Chim. Acta, 22 363 (1960)).

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not necessarily limited to these.

(Polyester resin raw material)
1. PET raw material A (used in Examples 1 to 12, Example 14, Example 16, and Comparative Examples 1 to 5)
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 15)
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. PEN raw material (used in Example 13)
To a mixture of 100 parts by mass of dimethyl 2,6-naphthalenedicarboxylate and 60 parts by mass of ethylene glycol, 0.03 parts by mass of manganese acetate tetrahydrate salt is added and gradually increased from a temperature of 150 ° C. to a temperature of 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). Although this value was different, 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 terephthalate was dried and crystallized at 160 ° C. for 6 hours, followed by 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 polyethylene naphthalate (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 1-11, 16 and Comparative Examples 1-5)
Above 1. 100 parts by mass of the PET resin obtained according to the above and 100 parts by mass of rutile titanium oxide particles having an average particle diameter of 210 nm are melt-kneaded in a vented 290 ° C. extruder to produce a titanium oxide raw material (PETa-TiO ₂ ). did.

5. PET raw material B base titanium oxide master (used in Example 15)
2. 100 parts by mass of the PET resin obtained according to the above and 100 parts by mass of rutile titanium oxide particles having an average particle diameter of 210 nm are melt-kneaded in a vented 290 ° C. extruder to produce a titanium oxide raw material (PETb—TiO ₂ ). did.

6). PEN raw material-based titanium oxide master (used in Example 13)
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 size 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 14)
Above 1. 100 parts by mass of the PET resin 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 prepare a carbon particle raw material (PETa-CB).

(Preparation of easy adhesive layer coating)
After preparing coating agents A to O having a solid content concentration of 15% by mass using water as a diluent solvent and coating materials described in the following section, an acetylene diol surfactant, “Olfin” manufactured by Nisshin Chemical Co., Ltd. ( (Registered trademark) EXP4051F was blended in an amount of 0.5 mass% with respect to each coating agent. The blending amounts of the paints described in the following items are all solid content ratios.

1. Coating agent A (used in Examples 1 and 12 to 16)
-Aqueous polyurethane resin paint, 60% by mass of "Hydran" (registered trademark) AP-201 manufactured by DIC Corporation
-20% by mass of ethylene vinyl acetate (EVA) copolymer resin aqueous dispersion, "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
-Melamine cross-linking agent, 20% by mass of “Becamine” (registered trademark) PM-80 manufactured by DIC Corporation
2. Coating agent B (Example 2)
-50% by mass of water-based polyurethane resin paint, DIC Corporation "Hydran" (registered trademark) AP-201
-20% by mass of ethylene vinyl acetate (EVA) copolymer resin aqueous dispersion, "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
・ Melamine crosslinking agent, 30% by mass of “Becamine” (registered trademark) PM-80 manufactured by DIC Corporation
3. Coating agent C (used in Example 3)
-Aqueous polyurethane resin paint, 70% by mass of “Hydran” (registered trademark) AP-201 manufactured by DIC Corporation
-20% by mass of ethylene vinyl acetate (EVA) copolymer resin aqueous dispersion, "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
・ Melamine cross-linking agent, 10% by mass of “Beckamine” (registered trademark) PM-80 manufactured by DIC Corporation
4). Coating agent D (used in Example 4)
Water-based polyurethane resin paint, 71% by mass of “Hydran” (registered trademark) AP-201 manufactured by DIC Corporation
-Ethylene vinyl acetate (EVA) copolymer resin aqueous dispersion, 5% by mass of "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
・ Melamine crosslinking agent, 24% by mass of “Becamine” (registered trademark) PM-80 manufactured by DIC Corporation
5. Coating agent E (used in Example 5)
Water-based polyurethane resin paint, 37.5% by mass of “Hydran” (registered trademark) AP-201 manufactured by DIC Corporation
-Ethylene vinyl acetate (EVA) copolymer resin water dispersion, 50% by mass of "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
Melamine cross-linking agent, 12.5% by mass of “Becamine” (registered trademark) PM-80 manufactured by DIC Corporation
6). Coating agent F (used in Example 6)
-Aqueous polyurethane resin paint, 60% by mass of "Hydran" (registered trademark) AP-201 manufactured by DIC Corporation
-20% by mass of ethylene vinyl acetate (EVA) copolymer resin aqueous dispersion, "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
・ Melamine cross-linking agent, 10% by mass of “Beckamine” (registered trademark) PM-80 manufactured by DIC Corporation
-10% by mass of epoxy crosslinking agent, CR-5L manufactured by DIC Corporation
7). Coating agent G (used in Example 7)
・ Water-based polyester resin paint, TP-620K manufactured by Takamatsu Yushi Co., Ltd. is 60% by mass.
-20% by mass of ethylene vinyl acetate (EVA) copolymer resin aqueous dispersion, "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
-Melamine cross-linking agent, 20% by mass of “Becamine” (registered trademark) PM-80 manufactured by DIC Corporation
8). Coating agent H (used in Example 8)
-Aqueous acrylic resin paint, DIC Corporation "Dicknal" FP-2D is 60% by mass
-20% by mass of ethylene vinyl acetate (EVA) copolymer resin aqueous dispersion, "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
-Melamine cross-linking agent, 20% by mass of “Becamine” (registered trademark) PM-80 manufactured by DIC Corporation
9. Coating agent I (used in Example 9)
-Aqueous polyurethane resin paint, DIC Corporation "Hydran" (registered trademark) WLS-201 60% by mass
-20% by mass of ethylene vinyl acetate (EVA) copolymer resin aqueous dispersion, "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
-Melamine cross-linking agent, 20% by mass of “Becamine” (registered trademark) PM-80 manufactured by DIC Corporation
10. Coating agent J (used in Example 10)
-Aqueous polyurethane resin paint, 60% by mass of "Hydran" (registered trademark) AP-201 manufactured by DIC Corporation
-Acid-modified polypropylene (acid-modified PP) copolymer resin aqueous dispersion, 20% by mass of “Chemical” (registered trademark) EP-310H manufactured by Mitsui Chemicals, Inc.
-Melamine cross-linking agent, 20% by mass of “Beckamine” (registered trademark) PM-80 manufactured by DIC Corporation
11. Coating agent K (used in Example 11)
-Aqueous polyurethane resin paint, DIC Corporation "Hydran" (registered trademark) AP-201 is 80% by mass
-20% by mass of ethylene vinyl acetate (EVA) copolymer resin aqueous dispersion, "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
12 Coating agent L (used in Comparative Example 2)
-100% by mass of water-based polyurethane resin paint, DIC Corporation "Hydran" (registered trademark) AP-201
13. Coating agent M (used in Comparative Example 3)
-Aqueous polyurethane resin paint, 10% by mass of “Hydran” (registered trademark) AP-201 manufactured by DIC Corporation
-80% by mass of ethylene vinyl acetate (EVA) copolymer resin aqueous dispersion, "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
・ Melamine cross-linking agent, 10% by mass of “Beckamine” (registered trademark) PM-80 manufactured by DIC Corporation
14 Coating agent N (used in Comparative Example 4)
-Ethylene vinyl acetate (EVA) copolymer resin aqueous dispersion, 100% by mass of "Aquatex" (registered trademark) HA-1100 manufactured by Chuo Rika Kogyo Co., Ltd.
15. Coating agent O (used in Comparative Example 5)
-90% by mass of water-based polyurethane resin paint, DIC Corporation "Hydran" (registered trademark) AP-201
・ Melamine cross-linking agent, 10% by mass of “Beckamine” (registered trademark) PM-80 manufactured by DIC Corporation
Example 1
The PET raw material A and the PET-based titanium oxide master A described in the section (Polyester-based resin raw material) that were vacuum-dried at 180 ° C. for 2 hours were prepared so that the amount of particles was the concentration shown in Table 1, and in an extruder at 290 ° C. It was melt-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, the unstretched sheet is preheated with a roll group heated to a temperature of 80 ° C., and then stretched 2.8 times in the longitudinal direction (longitudinal direction) using a heating roll having a temperature of 85 ° C. It cooled with the roll group of temperature, and obtained the uniaxially stretched sheet. After the corona treatment is applied to the uniaxially stretched sheet, the coating corresponding to the numbers in Examples and Comparative Examples is applied to the 8-mesh metalling bar. Was applied.

  While holding both ends of the obtained uniaxially stretched sheet with a clip, it is guided to a preheating zone at a temperature of 90 ° C. in the tenter, and is continuously heated at 100 ° C. in a direction perpendicular to the longitudinal direction (width direction). The film was stretched 3.2 times. Subsequently, heat treatment was performed at 200 ° C. for 20 seconds in a heat treatment zone in the tenter, and further relaxation treatment was performed in the 4% width direction at 210 ° C. Then, it was gradually cooled gradually to obtain a biaxially stretched sheet. Table 1 shows the sheet thickness of the P1 layer, the intrinsic viscosity IV, the amount of terminal carboxyl groups, and the easily adhesive layer thickness of the P2 layer.

  The resulting sheet was evaluated for characteristics. As a result, as shown in Table 2, it was found that the sheet is excellent in various properties such as moisture and heat resistance, ultraviolet resistance, and EVA adhesion, and has characteristics suitable for use as a solar cell back surface protection sheet. .

(Examples 2 to 12, Comparative Examples 2 to 5)
A biaxially stretched sheet was obtained in the same manner as in Example 1, except that the type of P1 layer material and the type of coating material were changed to the materials and coating materials described in Table 1.

  In Example 2, since the melamine crosslinking agent component in the P2 layer was large, the EVA adhesion after the moist heat test was good.

  Since Example 3 had few melamine crosslinking agent components in P2 layer, it was the characteristic in which EVA adhesiveness after a moist heat test was a little inferior.

  In Example 4, since the number of island components on the surface of the P2 layer was small, EVA adhesion was slightly inferior.

  In Example 5, since the number of island components on the surface of the P2 layer was large, EVA adhesion was slightly inferior.

  In Example 6, since the melamine crosslinking agent and the epoxy crosslinking agent were used in combination in the P2 layer, the EVA adhesion after the moist heat resistance test was good.

  In Examples 7 to 9, since the binder component in the P2 layer was changed and the equivalent circle diameter and the number of island components on the surface of the P2 layer were changed, the EVA adhesion after the wet heat resistance test was slightly inferior.

  In Example 10, the olefin resin component in the P2 layer was changed, and the equivalent circle diameter and the number of island components on the surface of the P2 layer were changed, but the properties were excellent in wet heat resistance, ultraviolet resistance, and EVA adhesion. It was.

  Since Example 11 did not use a crosslinking agent in the P2 layer, the EVA adhesion after the moist heat resistance test was slightly inferior.

  In Example 12, since the P1 layer did not contain titanium oxide, the heat and moisture resistance of the sheet was very excellent, but the relative reflectance and the ultraviolet resistance were inferior.

  In Comparative Example 2, the P2 layer was formed from a single resin, and no island component was present on the surface. Therefore, the characteristics were inferior in EVA adhesion after the wet heat resistance test.

  Since Comparative Example 3 had a large equivalent-circle diameter and a small number of island components on the surface of the P2 layer, it was inferior in EVA adhesion after the wet heat resistance test.

In Comparative Example 4, since the P2 layer was formed from a single resin and no island component was present on the surface, the properties were inferior in EVA adhesion after the wet heat resistance test.
In Comparative Example 5, the two component resins constituting the P2 layer were compatible, so that no island component was present on the surface of the P2 layer, and the EVA adhesion after the wet heat resistance test was inferior.

(Example 13)
The PEN raw material and the PEN-based titanium oxide master described in the section of (Polyester resin raw material), which were vacuum-dried at 180 ° C. for 2 hours, were mixed so as to have the concentrations shown in Table 1, and melt-kneaded in an extruder at 300 ° C. Introduced into the base. 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, the unstretched sheet was preheated with a roll group heated to a temperature of 130 ° C., and then stretched 3.0 times in the longitudinal direction (longitudinal direction) using a heating roll having a temperature of 145 ° C. It cooled with the roll group of temperature, and obtained the uniaxially stretched sheet. After the corona treatment was applied to the uniaxially stretched sheet, the coating A was applied with an 8 mesh metering bar.

  While holding both ends of the obtained uniaxially stretched sheet with a clip, the tenter is led to a preheating zone at a temperature of 135 ° C. in the tenter, and is then continuously heated at 145 ° C. in a direction perpendicular to the longitudinal direction (width direction). The film was stretched 3.2 times. Subsequently, heat treatment was performed at 200 ° C. for 20 seconds in a heat treatment zone in the tenter, and further relaxation treatment was performed in the 4% width direction at 210 ° C. Then, it was gradually cooled gradually to obtain a biaxially stretched sheet. When the characteristics of the obtained sheet were evaluated, as shown in Table 2, the sheet was excellent in various characteristics such as moisture and heat resistance, ultraviolet resistance, and EVA adhesion, and suitable for use as a solar cell back surface protection sheet. It was found to have characteristics.

(Example 14)
In the process of the P1 layer, except that the PET raw material A and the PET base carbon particle master described in the section (Polyester resin raw material) vacuum-dried at 180 ° C. for 2 hours were prepared so as to have the concentrations shown in Table 1. In the same manner as in Example 1, a biaxially stretched sheet was obtained. When the characteristics of the obtained sheet were evaluated, as shown in Table 2, the sheet was excellent in various characteristics such as moisture and heat resistance, ultraviolet resistance, and EVA adhesion, and suitable for use as a solar cell back surface protection sheet. It was found to have characteristics.

(Example 15)
In the process of the P1 layer, except that the PET raw material B and the PET-based titanium oxide master B described in the section of (polyester resin raw material) vacuum-dried at 180 ° C. for 2 hours were prepared so as to have the concentrations in Table 1, A biaxially stretched sheet having the structure shown in Table 1 was prepared in the same manner as in Example 1. When the characteristics of the obtained laminated sheet were evaluated, as shown in Table 2, since the intrinsic viscosity IV and the terminal carboxyl group amount of the PET raw material constituting the P1 layer were changed, the mechanical strength of the P1 layer was lowered, and the heat and moisture resistance In the adhesive strength test after the test, the P1 layer was broken three times. Therefore, the bond strength between the P2 layer and the EVA layer was determined as B when the strength at the time when the P1 layer was broken was used.

(Example 16)
The PET raw material A and the PET-based titanium oxide master A described in the section (Polyester-based resin raw material) that were vacuum-dried at 180 ° C. for 2 hours were prepared so that the amount of particles was the concentration shown in Table 1, and in an extruder at 290 ° C. It was melt-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 a 300 μm unstretched sheet. On one side of the sheet obtained above, coating agent A was applied using a gravure coater under the following coating conditions to provide an easy adhesion layer.
Coating conditions: dry film thickness 0.5μm, drying oven set temperature 120 ° C
Aging: After coating and winding, the sheet was aged for 2 days in a room at 40 ° C. The characteristics of the obtained sheet were evaluated. As a result, as shown in Table 2, it was found that the sheet is excellent in various properties such as moisture and heat resistance, ultraviolet resistance, and EVA adhesion, and has characteristics suitable for use as a solar cell back surface protection sheet. .

(Comparative Example 1)
The PET raw material A described in the section (Polyester resin raw material), which was vacuum-dried at 180 ° C. for 2 hours, was melt-kneaded in an extruder at 290 ° C. 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, the unstretched sheet is preheated with a roll group heated to a temperature of 80 ° C., and then stretched 2.8 times in the longitudinal direction (longitudinal direction) using a heating roll having a temperature of 85 ° C. It cooled with the roll group of temperature, and obtained the uniaxially stretched sheet. While holding both ends of the obtained uniaxially stretched sheet with a clip, it is guided to a preheating zone at a temperature of 90 ° C. in the tenter, and is continuously heated at 100 ° C. in a direction perpendicular to the longitudinal direction (width direction). The film was stretched 3.2 times. Subsequently, heat treatment was performed at 200 ° C. for 20 seconds in a heat treatment zone in the tenter, and further relaxation treatment was performed in the 4% width direction at 210 ° C. Then, it was gradually cooled gradually to obtain a biaxially stretched sheet having a sheet thickness of 250 μm. When the characteristics of the obtained sheet were evaluated, as shown in Table 2, it was found that the sheet was inferior in initial EVA adhesion.

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 adhesive sheet in applications where adhesion with an ethylene-vinyl acetate copolymer resin is required.

1: Back sheet 2: Sealing material 3: Power generation element 4: Transparent substrate 5: Surface on the sealing material 2 side of the solar cell backsheet 6: Surface on the opposite side of the sealing material 2 of the solar cell backsheet

Claims (10)

A solar cell back surface protection sheet having a base material layer (P1 layer) made of a polyester resin and an easy-adhesion layer (P2 layer) adjacent to the P1 layer, and satisfying the following requirements (1) and (2) A sheet for protecting the back side of the solar cell to be filled.
(1) The P2 layer has an adhesive strength of 10 N / 10 mm or more in both the polyester resin and the ethylene-vinyl acetate copolymer resin that form the P1 layer.
(2) The P2 layer has a sea-island structure, and the size of the island component appearing on the surface of the P2 layer is an average equivalent diameter of 0.1 μm or more and less than 5 μm. The solar cell back surface protection sheet according to claim 1, wherein 3 or more and less than 200 island components appearing on the surface of the P2 layer are present per 100 µm ^{2 on the} surface of the P2 layer. The P2 layer includes a resin A constituting a sea component, a resin B constituting an island component, the resin A containing a urethane resin, and the resin B containing an olefin resin. Or the solar cell back surface protection sheet of 2. The solar cell back surface protection sheet according to claim 3, wherein the urethane resin has a glass transition temperature Tg of 0 ° C. or more and 40 ° C. or less. The solar cell back surface protection sheet according to claim 3 or 4, wherein the olefin resin is a modified polyolefin resin. The solar cell back surface protection sheet according to claim 5, wherein the modified polyolefin resin is an ethylene-vinyl acetate copolymer resin. The said P2 layer is obtained by apply | coating the coating agent containing the said resin A, the said resin B, and the crosslinking agent C to a P1 layer, and drying, The sun in any one of Claims 3-6 characterized by the above-mentioned. Battery back protection sheet. The thickness of the said P2 layer is 0.1 micrometer or more and less than 3 micrometers, The solar cell back surface protection sheet in any one of Claims 1-7 characterized by the above-mentioned. The 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 1. The solar cell using the solar cell back surface protection sheet described in any one of Claims 1-9.

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