Masterbatch, resin composition for solar cell encapsulant and method for manufacturing the same, solar cell encapsulant and solar cell module

Abstract

To provide a resin composition for solar cell encapsulants and a solar cell encapsulant that can be molded to suppress snail trail phenomena and acid-induced power degradation even after long-term use, while maintaining good transparency. [Solution] The problem is solved by a resin composition for solar cell encapsulants, characterized in that it comprises an ethylene vinyl acetate copolymer and an acid acceptor, wherein the chlorine element in the acid acceptor is 0.6% by mass or less, and the amount of the acid acceptor is 0.10 to 0.40 parts by mass per 100 parts by mass of the ethylene vinyl acetate copolymer.

Description

Technical Field

[0001] The present invention relates to a masterbatch used for forming a solar cell encapsulant and a resin composition for a solar cell encapsulant. Further, it relates to a solar cell encapsulant obtained thereby and a solar cell module provided with the solar cell encapsulant.

Background Art

[0002] In recent years, the utilization of natural energy has been promoted from the viewpoints of depletion of fossil fuels and response to global environmental conservation. Among them, solar cells are increasing in the amount of introduction worldwide due to advantages such as a decrease in introduction cost and no need for new land for installation. Since further increase in demand is expected in the future, technological development aiming at higher output and longer life of solar cells is progressing.

[0003] A solar cell has a configuration in which a plurality of solar cell modules incorporating power generation elements are incorporated. The power generation elements are sealed and protected by a solar cell encapsulant (hereinafter also referred to as an encapsulant) in order to maintain the power generation function. As the encapsulant, ethylene vinyl acetate copolymer (hereinafter also referred to as EVA) is mainly used from the viewpoints of low cost, transparency, and adhesiveness to the power generation element. However, when EVA is used as the encapsulant, there is a problem that corrosion of electrode wiring and the like are induced due to the influence of acid generated in a high temperature and high humidity environment, leading to a decrease in output.

[0004] Therefore, in Patent Document 1, a solar cell light-receiving surface side encapsulant is disclosed which suppresses the output decrease of a solar cell by blending an acid acceptor with EVA and suppressing the generation of acid.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in recent years, there has been a demand for even longer lifespans for solar cells, and long-term acid capture performance from EVA is desired. In response to this, increasing the amount of acid acceptor tends to improve long-term acid capture performance, but in that case, the transparency of the encapsulant decreases, which in turn leads to a decrease in initial output.

[0007] Furthermore, when solar cells are used for extended periods, silver ions and other metal ions generated by the oxidation of the silver electrodes react with anionic components in the encapsulating material to form metal salts. These metal salts promote the formation of black or white crack patterns on the solar cell module, known as snail trails, resulting in cosmetic defects of the solar cell module.

[0008] Therefore, the object of the present invention is to provide a resin composition for solar cell encapsulants and a solar cell encapsulant that can be molded to suppress snail trail phenomena and output degradation due to acid even when used for a long period of time, while maintaining good transparency. [Means for solving the problem]

[0009] The present invention includes, but is not limited to, the following embodiments. <1> It contains ethylene vinyl acetate copolymer and an acid acceptor, The chlorine element content in the acid acceptor is 0.6% by mass or less. A resin composition for solar cell encapsulants, wherein the content of the acid acceptor is 0.10 to 0.40 parts by mass per 100 parts by mass of the ethylene vinyl acetate copolymer. <2> The median diameter of the acid acceptor is 0.1 to 30.0 μm. <1> The resin composition for solar cell encapsulants described above. <3> The acid acceptor is a metal hydroxide. <1> or <2> The resin composition for solar cell encapsulants described above. <4> <1> ~ <3> A solar cell encapsulant molded from any of the resin compositions for solar cell encapsulants described above. <5> <4> A solar cell module equipped with the described solar cell encapsulant. <6> <1> ~ <3> A method for producing a resin composition for solar cell encapsulants as described in any of the following: The process includes melt-kneading an ethylene vinyl acetate copolymer and a masterbatch, The masterbatch comprises an ethylene vinyl acetate copolymer (X) and an acid acceptor. The content of the acid acceptor is 0.1 to 30 parts by mass per 100 parts by mass of ethylene vinyl acetate copolymer (X). A method for producing a resin composition for solar cell encapsulating materials. <7> <6> The masterbatch used in the described method. [Effects of the Invention]

[0010] The present invention provides a resin composition for solar cell encapsulants and a solar cell encapsulant that can be molded to suppress snail trail phenomena and output degradation due to acid even when used for a long period of time, while maintaining good transparency. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a cross-sectional view showing the stacking order of components used in a solar cell module. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below. Other embodiments are also included in the scope of the present invention, insofar as they are consistent with the spirit of the invention. In this specification, numerical ranges specified using "~" include the numerical values ​​before and after "~" as the lower and upper limits. Furthermore, "film" and "sheet" are synonymous and are not distinguished by thickness. In addition, unless otherwise noted, each component may be used independently or in combination of two or more. Also, the ethylene vinyl acetate copolymer used in the production of the masterbatch may be referred to as ethylene vinyl acetate copolymer (X). Furthermore, the numerical values ​​described in this specification refer to the values ​​obtained by the method described in the [Examples] section below.

[0013] ≪Resin composition for solar cell encapsulant≫ The resin composition for solar cell encapsulation is used to form a encapsulation material for solar cells and comprises an ethylene vinyl acetate copolymer and an acid acceptor, wherein the chlorine element content in the acid acceptor is 0.6% by mass or less, and the content of the acid acceptor is 0.10 to 0.40 parts by mass per 100 parts by mass of the ethylene vinyl acetate copolymer. Such a resin composition for solar cell encapsulants makes it possible to provide a solar cell encapsulant that maintains good transparency while suppressing snail trail phenomena and output degradation due to acid even after long-term use.

[0014] The snail trail phenomenon is a phenomenon in which black or white crack patterns appear on solar cell modules. The presence of water entering through gaps between the components of the solar cell module or cracks within the cells generates metal ions such as silver ions from the electrodes, which react with anionic components in the encapsulant to form metal salts. The presence of these metal salts is visible as black or white crack patterns, resulting in a defect in the appearance of the solar cell module.

[0015] <Ethylene vinyl acetate copolymer> The ethylene vinyl acetate copolymer (EVA) is not particularly limited, but preferably has a vinyl acetate content of 15 to 40 mol%, more preferably 25 to 35 mol%. Further, the melt flow rate (hereinafter also referred to as MFR) conforming to JIS K7210:2014 is preferably 0.1 to 60 g / 10 min, more preferably 0.5 to 45 g / 10 min.

[0016] 〈Acid acceptor〉 The acid acceptor in the present invention is an inorganic metal compound and has a function of capturing (neutralizing) the acid generated from the ethylene vinyl acetate copolymer. Specifically, metal hydroxides such as magnesium hydroxide, aluminum hydroxide, calcium hydroxide, barium hydroxide, metal oxides such as magnesium oxide, calcium oxide, and metal carbonates such as magnesium carbonate, calcium carbonate, barium carbonate, etc. can be mentioned.

[0017] Among these, from the viewpoint of transparency, metal hydroxides are preferred. Since these metal hydroxides have a refractive index close to that of EVA, the transparency is not significantly impaired even when blended. Among the metal hydroxides, magnesium hydroxide or calcium hydroxide is preferred.

[0018] Usually, the acid acceptor mainly contains chlorine elements derived from the raw materials used. In the case of magnesium hydroxide, magnesium chloride is often used as a raw material for the magnesium source, and chloride ions may be mixed at the position where hydroxide ions coordinate with magnesium. Also, when using natural products such as magnesite ore or brucite ore as raw materials, the ore contains chlorine elements as impurity components. Also, in the case of calcium hydroxide, quicklime (calcium oxide) is often used as a raw material for the calcium source, and the quicklime contains chlorine elements.

[0019] Therefore, the acid acceptor of the present invention needs to have a chlorine element content derived from such raw materials used of 0.6 mass% or less in the acid acceptor, and it can be reduced by controlling the reaction equivalent of the raw materials used and the purification process.

[0020] The chlorine element contained in the acid acceptor reacts with metal ions such as silver ions generated from the silver electrode in the encapsulant to produce metal chlorides. Depending on the proportion of chlorine element in the acid acceptor and the amount of the acid acceptor added to the encapsulant, the amount of metal chlorides produced may become significant, and the snail trail phenomenon may be observed. Increasing the amount of acid acceptor suppresses the reduction in output due to acid, but with conventional acid acceptors that contain a large amount of chlorine, the snail trail phenomenon occurs significantly. Therefore, the lower the chlorine content in the acid acceptor, the better. Specifically, it is preferable that it be 0.2% by mass or less, and more preferably 0.05% by mass or less. Within this range, the snail trail phenomenon can be suppressed more effectively. It may be 0.001% by mass or more. The amount of chlorine in the acid acceptor can be determined by automated combustion ion chromatography.

[0021] Furthermore, when the acid acceptor is magnesium hydroxide, it is preferable from the viewpoint of transparency that the calcium element content is 0.3% by mass or less. More preferably 0.1% by mass or less, and even more preferably 0.03% by mass or less. This is because it increases transparency and, as a result, suppresses the decrease in the initial output of the solar cell.

[0022] Magnesium hydroxide contains calcium elements, primarily derived from the raw materials used. For example, when calcium hydroxide is used as an alkaline component during synthesis, calcium elements remain. Although the exact form of the calcium elements is unknown, it is presumed that calcium compounds with different refractive indices than magnesium hydroxide will coexist. By reducing the amount of these calcium elements, transparency can be improved, and the decrease in the initial output of solar cells can be suppressed.

[0023] Furthermore, when the acid acceptor is calcium hydroxide, it is preferable from the viewpoint of transparency that the magnesium content is 1.2% by mass or less. More preferably 0.9% by mass or less, and even more preferably 0.3% by mass or less. This is because it increases transparency and, as a result, suppresses the decrease in the initial output of the solar cell.

[0024] Calcium hydroxide contains magnesium elements, primarily derived from the raw materials used. For example, when quicklime is used as a raw material, magnesium elements remain. Although the exact form of the magnesium elements is unknown, it is presumed that magnesium compounds with different refractive indices than calcium hydroxide will coexist. By reducing the amount of these magnesium elements, transparency will be improved, and the decrease in the initial output of the solar cell can be suppressed.

[0025] The median diameter of the acid acceptor is preferably 0.1 to 30.0 μm, and more preferably in the range of 0.1 to 15.0 μm. This allows for a higher level of transparency. The median diameter is the particle size (D) of the cumulative 50% of the volume measured by a laser diffraction scattering particle size distribution device. 50 )

[0026] The acid acceptor content is 0.10 to 0.40 parts by mass per 100 parts by mass of ethylene vinyl acetate copolymer. Preferably, it is 0.15 to 0.30 parts by mass, and more preferably 0.15 to 0.20 parts by mass. By incorporating 0.10 to 0.40 parts by mass, good transparency is maintained and acid capture ability is enhanced while suppressing the snail trail phenomenon, even after long-term use. If the content is less than 0.10 parts by mass, the acid capture performance is insufficient, leading to a decrease in output after long-term use. In addition, the presence of uncaptured acid makes the metal contained in the electrode more susceptible to oxidation, resulting in the promotion of snail trails. On the other hand, if it exceeds 0.40 parts by mass, transparency becomes insufficient, which leads to a decrease in the initial output of the solar cell.

[0027] <Additives> The resin composition for solar cell encapsulants of the present invention may further contain, as optional components, additives such as crosslinking agents, crosslinking aids, silane coupling agents, ultraviolet absorbers, light stabilizers, antioxidants, light diffusers, wavelength converters, PID resistant agents, colorants, dispersants, and flame retardants.

[0028] Crosslinking agents are used to prevent thermal deformation of ethylene vinyl acetate copolymers under high-temperature conditions. Organic peroxides are preferred as crosslinking agents. Specifically, for example, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxy-2-ethylhexyl isopropyl carbonate, tert-butyl peroxyacetate, tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexine-3, 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane, 1,1-di(tert-hexyl peroxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-butyl peroxy)cyclohexane, 1,1-di(tert-hexyl peroxy)cyclohexane, 1,1-di(tert-amyl peroxy)cyclohexane, 2, Examples include 2-di(tert-butylperoxy)butane, methyl ethyl ketone peroxide, 2,5-dimethylhexyl-2,5-diperoxybenzoate, tert-butyl hydroperoxide, p-menthane hydroperoxide, dibenzoyl peroxide, p-chlorobenzoyl peroxide, tert-butyl peroxyisobutyrate, n-butyl-4,4-di(tert-butylperoxy)valerate, ethyl-3,3-di(tert-butylperoxy)butyrate, hydroxyheptyl peroxide, dichlorohexanone peroxide, 1,1-di(tert-butylperoxy)3,3,5-trimethylcyclohexane, n-butyl-4,4-di(tert-butylperoxy)valerate, and 2,2-di(tert-butylperoxy)butane. The crosslinking agent is preferably blended in an amount of 0.05 to 3 parts by mass per 100 parts by mass of ethylene vinyl acetate copolymer.

[0029] Crosslinking aids are used to ensure the efficient crosslinking reaction of the crosslinking agent. Unsaturated compounds such as polyallyl compounds and polyacryloxy compounds are preferred as crosslinking aids. Specifically, examples include triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate. It is preferable to blend the crosslinking aid in an amount of 0.05 to 3 parts by mass per 100 parts by mass of ethylene vinyl acetate copolymer.

[0030] Silane coupling agents are used to improve adhesion to surface protective glass, power generation elements, etc. Silane coupling agents are compounds having functional groups such as vinyl groups, acryloxy groups, and methacryloxy groups, as well as hydrolyzable functional groups such as alkoxy groups. Specifically, examples include vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-chloropropyltrimethoxysilane. The silane coupling agent is preferably added in an amount of 0.05 to 3 parts by mass per 100 parts by mass of ethylene vinyl acetate copolymer.

[0031] UV absorbers are used to improve weather resistance. Preferred UV absorbers include benzophenone compounds, benzotriazole compounds, triazine compounds, salicylate ester compounds, and the like. Specifically, for example, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2-hydroxy-4-n-octadecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-5-chlorobenzophenone, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-5-t -butylphenyl)benzotriazole, 2-(2-hydroxy-3,5-dimethylphenyl)benzotriazole, 2-(2-methyl-4-hydroxyphenyl)benzotriazole, 2-(2-hydroxy-3-methyl-5-t-butylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-t-butylphenyl)benzotriazole, 2-(2-hydroxy-3,5-dimethylphenyl)-5-methoxybenzotriazole, 2-(2-hydroxy-3-t-butyl-5-methylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-5-t-butylphenyl)-5-chlorobenzotriazole, 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-(octyloxy)phenol, 2-(4,6-diphenyl-1,3, Examples include 5-triazin-2-yl)-5-(hexyloxy)phenol, phenyl salicylate, and p-octylphenyl salicylate. The ultraviolet absorber is preferably added in an amount of 0.01 to 3 parts by mass per 100 parts by mass of ethylene vinyl acetate copolymer.

[0032] Light stabilizers are used to improve weather resistance, and when used in combination with UV absorbers, weather resistance is further improved. Hindered amine compounds are preferred as light stabilizers. Specifically, for example, dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate succinate, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{{2,2,6,6-tetramethyl-4-piperidyl)imino}], N,N'-bis(3-A Examples include minopropyl)ethylenediamine-2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazine condensate, bis(2,2,6,6-tetramethyl-4-piperidyl) separator, and 2-(3,5-di-tert-4-hydroxybenzyl)-2-n-butylmalonate bis(1,2,2,6,6-pentamethyl-4-piperidyl). The light stabilizer is preferably added in an amount of 0.01 to 3 parts by mass per 100 parts by mass of ethylene vinyl acetate copolymer.

[0033] Antioxidants are used to improve stability at high temperatures. Preferred antioxidants include monophenol compounds, bisphenol compounds, high molecular weight phenol compounds, sulfur compounds, and phosphoric acid compounds. Specifically, for example, 2,6-di-tert-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-tert-butyl-4-ethylphenol, 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis-(4-ethyl-6-tert-butylphenol), 4,4'-thiobis-(3-methyl-6-tert-butylphenol), and 4,4'-butyl Den-bis-(3-methyl-6-tert-butylphenol), 3,9-bis[{1,1-dimethyl-2-{β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl}2,4,8,10-tetraoxaspiro]5,5-undecane, 1,1,3-tris-(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tri (3,5-di-tert-butyl-4-hydroxybenzyl)benzene, tetrakis-{methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate}methane, bis{(3,3'-bis-4'-hydroxy-3'-tert-butylphenyl)butyric acid}glycol ester, dilaurylthiodipropionate, dimyristylthiodipropionate, distearylthiopropionate, triphenyl phosphite, diphenylisodecyl phosphite, phenyldiisodecyl phosphite, 4,4'-butylidene-bis-(3-methyl-6-tert-butylphenyl-di-tridecyl) phosphite, cyclic neopentanetetraylbis(octadecyl phosphite), trisdiphenyl phosphite, diisodecinorepentaerythritol diphosphite, 9,10-dihydro- 9-Oxa-10-phosphaphenasthrene-10-oxide, 10-(3,5-di-tert-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanshrene-10-oxide, 10-decyloxy-9,Examples include 10-dihydro-9-oxa-10-phosphaphenanthrene, cyclic neopentanetetraylbis(2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetraylbis(2,6-di-tert-methylphenyl) phosphite, and 2,2-methylenebis(4,6-tert-butylphenyl)octyl phosphite. The antioxidant is preferably added in an amount of 0.05 to 3 parts by mass per 100 parts by mass of ethylene vinyl acetate copolymer.

[0034] <Method for manufacturing resin compositions for solar cell encapsulants> The method for producing the resin composition for solar cell encapsulants of the present invention is not particularly limited, but for example, ethylene vinyl acetate copolymer, an acid acceptor, and optionally additives are put into a general high-speed shear mixer such as a Henschel mixer or super mixer and mixed, and then melt-kneaded using a two-roll, three-roll, pressure kneader, Banbury mixer, single-screw kneading extruder or twin-screw kneading extruder, and then extruded into pellets, for example. After melt-kneading, it may be processed into a sheet before being molded into pellets. Alternatively, a masterbatch may be prepared by blending a high concentration of acid acceptor into the ethylene vinyl acetate copolymer, and then mixed with additives and a diluted resin (ethylene vinyl acetate copolymer) before molding. Furthermore, using a masterbatch to manufacture the solar cell encapsulant is preferable because it improves the dispersibility of the acid acceptor and further enhances the transparency (total light transmittance / HAZE) of the encapsulant. Furthermore, a masterbatch containing an acid acceptor, a masterbatch containing other additives such as a crosslinking agent, and a main component ethylene vinyl acetate copolymer may be mixed and used as a thermoplastic resin composition.

[0035] When manufacturing a resin composition for solar cell encapsulation using a masterbatch containing an acid acceptor, the process includes a step of melt-kneading the ethylene vinyl acetate copolymer and the masterbatch. The masterbatch used in this preparation contains an ethylene vinyl acetate copolymer (X) and an acid acceptor, with the acid acceptor content being 0.1 to 30 parts by mass, preferably 1 to 20 parts by mass, per 100 parts by mass of ethylene vinyl acetate copolymer (X). This is preferable because it stabilizes the dispersion state of the acid acceptor in the masterbatch and the resin composition for solar cell encapsulation manufactured using the masterbatch, thereby maintaining better transparency in the resin composition and enhancing the effect of suppressing output degradation due to acid. The ethylene vinyl acetate polymer (X) refers to the ethylene vinyl acetate copolymer used for the production of the masterbatch, and may be the same copolymer as the ethylene vinyl acetate copolymer used as the main component of the resin composition for solar cell encapsulation materials, or it may be a different copolymer. From the viewpoint of compatibility, it is preferable that it be the same copolymer. From the viewpoint of distribution, it is desirable to blend the masterbatch containing the acid acceptor in an amount of 1 to 10 parts by mass per 100 parts by mass of ethylene vinyl acetate copolymer used as the main resin.

[0036] <<Solar Cell Encapsulating Materials>> The solar cell encapsulant is a sheet-like molded body formed using the resin composition for solar cell encapsulants of the present invention, and its intended use is to protect the cells from external factors by being positioned above and below the cells in a solar cell module. The thickness of the sealing material is preferably around 0.1 to 2 mm.

[0037] <Method for manufacturing solar cell encapsulating material> The solar cell encapsulant of the present invention can be manufactured by forming the resin composition for solar cell encapsulants into a sheet using a general molding machine such as a T-die mold or a calender mold. The solar cell encapsulant may be formed directly from the resin composition for solar cell encapsulants containing an ethylene vinyl acetate polymer, an acid acceptor, and optionally additives, or a masterbatch containing the main component, the ethylene vinyl acetate polymer, and an acid acceptor may be melt-kneaded and then formed into a sheet.

[0038] <<Solar Panel Modules>> The solar cell module comprises a encapsulant formed using the resin composition for solar cell encapsulants of the present invention. The solar cell module can have various known configurations. Figure 1 shows an example of the configuration of the solar cell module of the present invention. The solar cell module is manufactured by arranging, for example, a surface protective glass 11, a solar cell encapsulant 12A, a power generation element 13, a solar cell encapsulant 12B, and a back protective glass 14 in that order from the sun side, and then heating and pressing. The solar cell encapsulants of the present invention are used for the solar cell encapsulants 12A and 12B. For heating and pressing, for example, a vacuum laminator can be used.

[0039] The power generation element 13 can be a known solar cell power generation element. Examples include silicon-based materials such as monocrystalline silicon, polycrystalline silicon, and amorphous silicon, and III-V and II-VI group compound semiconductor materials such as gallium-arsenide, copper-indium-selenium, and cadmium-tellurium.

[0040] The solar cell module of the present invention has high power generation efficiency and is a mainstream cell in recent years, but it has poor acid resistance, so even when using N-type TOPCon cells where electrode corrosion due to acid is a problem, the output reduction can be suppressed and it can be used suitably. [Examples]

[0041] The present invention will be described in further detail by reference to examples. The present invention is not limited thereto. In the examples, "parts" means "parts by mass" and "%" means "percent mass".

[0042] The methods for measuring the MFR of the ethylene vinyl acetate copolymer, the chlorine, calcium, and magnesium content in the acid acceptor, and the average particle size are as follows. <Measurement of MFR of ethylene vinyl acetate copolymer> Measurements were taken in accordance with JIS K7210, under conditions of 190°C and a load of 2.16 kgf.

[0043] <Measurement of chlorine content of acid acceptor> A hydrogen peroxide solution was used as the adsorption solution, and the chlorine content was measured by automated combustion ion chromatography (DIONEX ICS-1100, Thermo Fisher Scientific).

[0044] <Measurement of calcium and magnesium content in acid acceptors> A solution containing an acid acceptor and an aqueous nitric acid solution was subjected to microwave decomposition. After confirming that the acid acceptor was completely dissolved, the calcium or magnesium content of the solution was measured by ICP-AES analysis (Agilent Technologies ICP-5800).

[0045] <Measurement of median diameter of acid acceptor> In the case of magnesium hydroxide, 0.5 g was placed in 50 mL of deionized water, subjected to sonication for 3 minutes, and then measured using a laser diffraction scattering particle size analyzer (Microtrac-Bel MT3300EXII). In the case of calcium hydroxide, the measurements were performed in the same manner as for magnesium hydroxide, except that ethanol was used instead of deionized water.

[0046] The raw materials used in the examples are as follows: <Ethylene vinyl acetate copolymer> (EVA1): Ethylene vinyl acetate resin (vinyl acetate content: 28 mol%, MFR: 20 g / 10 min)

[0047] <Acid saturator> Details of the acid acceptor used in this invention are shown in Table 1.

[0048] [Table 1-1]

[0049] [Table 1-2]

[0050] <Examples of acid-receiving agent manufacturing> (MH1): Magnesium hydroxide An aqueous solution containing magnesium hydroxide was prepared by mixing equal amounts of a 0.1 mol / L magnesium chloride hexahydrate aqueous solution and a 0.4 mol / L sodium hydroxide aqueous solution. The magnesium hydroxide-containing aqueous solution was placed in an autoclave and stirred for 2 hours under conditions of 150°C and 1.0 MPa. After stirring, the magnesium hydroxide-containing aqueous solution was removed, cooled to room temperature, filtered, washed with ultrapure water, and thoroughly dried to obtain MH1.

[0051] (MH2): Magnesium hydroxide MH2 was obtained by following the synthesis method of MH1, except for using a 0.15 mol / L sodium hydroxide aqueous solution.

[0052] (MH3): Magnesium hydroxide MH3 was obtained by following the synthesis method of MH1, except for using a 0.11 mol / L sodium hydroxide aqueous solution.

[0053] (MH4): Magnesium hydroxide MH4 was obtained by following the synthesis method of MH1, except that a 0.30 mol / L calcium hydroxide aqueous solution was used instead of a sodium hydroxide aqueous solution.

[0054] (MH5): Magnesium hydroxide MH4 was obtained by following the synthesis method of MH1, but using a 0.40 mol / L aqueous calcium hydroxide solution instead of an aqueous sodium hydroxide solution. Furthermore, MH5 was obtained by following the synthesis method of MH1, except that the reaction conditions were changed to 450°C, 10.0 MPa, and 3 hours.

[0055] (MH6): Magnesium hydroxide MH6 was obtained by following the synthesis method of MH1, except that the reaction conditions were changed to 300°C, 8.0 MPa, and 3 hours.

[0056] (MH7): Magnesium hydroxide MH7 was obtained by following the synthesis method of MH1, except for using a 0.105 mol / L sodium hydroxide aqueous solution.

[0057] (CH1): Calcium hydroxide A calcium hydroxide slurry was prepared by adding ultrapure water to commercially available quicklime. Nitric acid aqueous solution was added to the calcium hydroxide slurry until the pH reached 11. The resulting solution was then filtered, and the filtrate was filtered again using a UF module. A 1 mol / L sodium hydroxide aqueous solution was added to the filtrate until the pH reached 12 or higher, causing calcium hydroxide to precipitate. The solution containing the precipitated calcium hydroxide was heated to 80°C, filtered, hot-air dried, and then hammer-milled to obtain CH1.

[0058] (CH2): Calcium hydroxide CH2 was obtained by following the synthesis method for CH1, except that hydrochloric acid solution was used instead of nitric acid solution.

[0059] (CH3): Calcium hydroxide CH3 was obtained by following the synthesis method for CH1, except that an aqueous nitric acid solution was added to a calcium hydroxide slurry until the pH reached 9.5.

[0060] (CH4): Calcium hydroxide CH4 was obtained by following the synthesis method for CH1, except that an aqueous nitric acid solution was added to a calcium hydroxide slurry until the pH reached 9.0.

[0061] (CH5): Calcium hydroxide The synthesis method for CH1 was followed, but CH5 was obtained without hammer milling.

[0062] (Example 1) <Manufacturing of masterbatches containing acid acceptors> As an ethylene vinyl acetate copolymer (X), 100 parts of EVA1 (ethylene vinyl acetate resin (vinyl acetate content: 28 mol%, MFR: 20 g / 10 min)) and 5 parts of an acid acceptor (MH1) (magnesium hydroxide with chlorine element content of 0.05% and calcium element content of 0.03%) were fed from separate feeders into a twin-screw extruder (manufactured by Nippon Placon Co., Ltd.), extruded, and cut with a pelletizer to obtain an acid acceptor-containing masterbatch (MB1).

[0063] <Manufacturing of crosslinking agent masterbatch> Separately, 100 parts of EVA1, 6 parts of crosslinking agent, 6 parts of crosslinking aid, and 4 parts of silane coupling were mixed, and the mixture was placed in an oven and left to stand at a temperature of 45°C for 5 hours to obtain a crosslinking agent masterbatch.

[0064] <Manufacturing of resin compositions for solar cell encapsulants and solar cell encapsulants> A 0.4 mm thick solar cell encapsulant was produced from a resin composition for solar cell encapsulants by mixing an acid-acid masterbatch, a crosslinking agent masterbatch, and EVA1 (the main resin) according to the following proportions, and then feeding the mixture into a T-die extruder and extruding it into a sheet at a temperature of 80°C. The content of ethylene vinyl acetate copolymer (EVA1) in the resin composition for solar cell encapsulation is the sum of the ethylene vinyl acetate copolymer (X) used in the masterbatch and the ethylene vinyl acetate copolymer of the main resin. [Formulation ratio of resin composition for solar cell encapsulant (parts by mass)] 100 parts of ethylene vinyl acetate copolymer (EVA1) Acid absorber (MH1) 0.10 part Crosslinking agent: 0.6 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane Crosslinking agent: Triaryl isocyanurate 0.6 parts Silane coupling agent: γ-methacryloxypropyltrimethoxysilane 0.4 parts

[0065] <Manufacturing of solar cell modules> The obtained solar cell encapsulant was cut to a predetermined size to prepare solar cell encapsulant 12A and solar cell encapsulant 12B. The solar cell encapsulant 12A, power generation element 13, and solar cell encapsulant 12B were stacked in that order. As shown in Figure 1, a 3 mm thick surface protective glass 11 and back protective glass 14 were used for further lamination. The stack was then placed in a vacuum laminator and heated and pressurized under vacuum at 150°C for 20 minutes to crosslink the encapsulant, thereby fabricating a solar cell module. The vacuum laminator used was the LM-50×50-S (manufactured by NPC Corporation). For the power generation element 13, an N-type TOPCON cell (manufactured by TONGWEI SOLAR Corporation) with electrodes on both sides was used.

[0066] (Examples 2-11, Comparative Examples 1-3) Acid-acid-containing masterbatches (MB2-MB13) were prepared in the same manner as in Example 1, except that the type and amount of ethylene vinyl acetate copolymer (X) and acid-acid A resin composition for solar cell encapsulation, a solar cell encapsulation, and a solar cell module were prepared in the same manner as in Example 1, except that the obtained acid-receiving masterbatch, the crosslinking agent masterbatch, and the main resin, ethylene vinyl acetate copolymer, were used in such a way that the proportions of ethylene vinyl acetate copolymer and acid-receiving agent were as shown in Table 3. The content of the crosslinking agent, crosslinking aid, and silane coupling agent in the resin composition for solar cell encapsulation, relative to 100 parts of ethylene vinyl acetate copolymer, is the same as in Example 1.

[0067] Evaluation of encapsulating materials and solar cell modules The encapsulants and solar cell modules obtained in the examples and comparative examples were evaluated using the following method. The results are shown in Table 3.

[0068] <Transparency of sealing material> The transparency of the encapsulating material was determined by HAZE evaluation and total light transmittance evaluation. To increase initial output, higher results in both evaluations are considered superior.

[0069] (HAZE evaluation, average light transmittance) The HAZE and average light transmittance of the obtained solar cell encapsulant (0.4 mm thick) were measured. HAZE was measured using a HAZE meter (HZ-V3, manufactured by Suga Test Instruments Co., Ltd.), and average light transmittance was measured using a UV-Vis-Near-Infrared spectrophotometer (UV-1800, manufactured by Shimadzu Corporation) in the wavelength range of 380 to 1100 nm. "HAZE evaluation" [Evaluation Criteria] A: 10 or less B: Over 10 and under 13 C: Over 13 and under 17 (the minimum level that is practically acceptable) D: Exceeds 17 (a level that is not practically acceptable) "Average light transmittance evaluation" [Evaluation Criteria] A: 91.4% or more B: 91.2% or more and less than 91.4% C: 90.9% or higher and less than 91.2% (the minimum level that is practically acceptable) D: Less than 90.9% (a level that is not practically acceptable)

[0070] <Snail Trail Evaluation> After applying a mechanical load using pneumatic methods to the solar cell module for 1000 cycles (a sealed space is created at the bottom of the solar cell module, and the air pressure in this space is depressurized and pressurized, with one cycle defined as the air pressure changing from +1000 Pa to -1000 Pa), the module is left to stand for a predetermined time in an 85°C, 85% RH environment, and then 1000 W / m² is applied to the removed module. 2 After light irradiation, the presence or absence of snail trails on the module's exterior was visually confirmed. This evaluation method intentionally applies mechanical load to create gaps between components and cracks within cells, thereby increasing the entry points for water from the outside and promoting the formation of snail trails. Furthermore, light irradiation promotes the generation of silver ions, thereby accelerating the formation of snail trails. The appearance of the solar cell modules after testing was evaluated on a four-point scale based on the area percentage of ST (snail trails) on the module surface, as follows. A lower ST area percentage indicates a better appearance. [Evaluation Criteria] 3+: The area ratio of ST is 5% or less 2+: The area ratio of ST is greater than 5% but less than or equal to 10%. 1+: The area ratio of ST is greater than 10% but less than or equal to 15% (the minimum level that is practically acceptable). NG: The area ratio of ST exceeds 15% (a level that is not practically acceptable).

[0071] <Power retention rate of solar cell modules after DH testing> Using the obtained solar cell modules, a DH (Damp Heat) test was conducted in accordance with IEC 61215:2021. In the DH test, the solar cell modules are left to stand under high temperature and high humidity conditions, accelerating the hydrolysis of the EVA encapsulating resin and the generation of acetic acid. The electrodes of the solar cell modules are corroded by the acid, increasing their resistivity, resulting in a decrease in the output of the solar cell modules. In other words, the DH test allows for the evaluation of output reduction due to acid. The test conditions for this experiment were a temperature of 85°C and a humidity of 85%, and a test duration of 2000 hours (equivalent to 10-20 years of outdoor exposure). After the test, the solar cell modules were removed, and power generation characteristics were measured (IV measurement). The output retention rate was calculated based on the output value before the test, and the output degradation due to acid was evaluated. For practical purposes, an output retention rate of 95% or higher is preferable, and 97% or higher is even more preferable.

[0072] [Table 2-1]

[0073] [Table 2-2]

[0074] [Table 3-1]

[0075] [Table 3-2]

[0076] The results in Table 3 confirm that by using the masterbatch and resin composition for solar cell encapsulation materials of the present invention, it is possible to create solar cell encapsulation materials and solar cell modules that maintain good transparency while suppressing snail trail phenomena and output degradation due to acid even after long-term use. [Explanation of Symbols]

[0077] 11: Surface protective glass 12A: Solar cell encapsulant 12B: Solar cell encapsulant 13: Power generation element 14: Back protective glass

Claims

1. It contains ethylene vinyl acetate copolymer and an acid acceptor, The chlorine element content in the acid acceptor is 0.6% by mass or less. A resin composition for solar cell encapsulating material, wherein the content of the acid acceptor is 0.10 to 0.40 parts by mass per 100 parts by mass of the ethylene vinyl acetate copolymer.

2. The resin composition for solar cell encapsulant according to claim 1, wherein the median diameter of the acid acceptor is 0.1 to 30.0 μm.

3. The resin composition for solar cell encapsulant according to claim 1, wherein the acid acceptor is a metal hydroxide.

4. A solar cell encapsulant molded from a resin composition for solar cell encapsulants according to any one of claims 1 to 3.

5. A solar cell module comprising the solar cell encapsulant described in claim 4.

6. A method for producing a resin composition for solar cell encapsulants according to any one of claims 1 to 3, The process includes melt-kneading an ethylene vinyl acetate copolymer and a masterbatch, The masterbatch comprises an ethylene vinyl acetate copolymer (X) and an acid acceptor. The content of the acid acceptor is 0.1 to 30 parts by mass per 100 parts by mass of ethylene vinyl acetate copolymer (X). A method for producing a resin composition for solar cell encapsulating materials.

7. A masterbatch used in the method described in claim 6.

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