Composition for sealing material film and sealing material film containing the same

Abstract

The present invention relates to a composition for an encapsulant film containing an ethylene / α-olefin copolymer, an encapsulant film, and a solar cell module.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 2022-0125138, filed September 30, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a composition for an encapsulant film containing an ethylene / α-olefin copolymer, an encapsulant film, and a solar cell module. [Background technology]

[0003] As global environmental and energy issues become increasingly serious, solar cells are attracting attention as a means of generating energy without the risk of environmental pollution or depletion. When solar cells are used outdoors, such as on the roof of a building, they are generally used in the form of a solar cell module. When manufacturing a solar cell module, to obtain a crystalline solar cell module, the following layers are laminated in this order: front glass / solar cell encapsulant / crystalline solar cell element / solar cell encapsulant / rear glass (or rear protective sheet). The solar cell encapsulant is generally made of an ethylene / vinyl acetate copolymer or an ethylene / α-olefin copolymer, which have excellent transparency, flexibility, adhesiveness, etc.

[0004] A solar cell module is a package in which solar cell elements such as silicon, gallium-arsenide, or copper-indium-selenium are protected with an upper transparent protective material and a lower substrate protective material, and the solar cell elements and protective material are fixed in place with a sealant. Generally, the sealant for the solar cell elements in a solar cell module is made by extruding an ethylene / α-olefin copolymer containing an organic peroxide or a silane coupling agent into a sheet, and the solar cell elements are sealed using the resulting sheet sealant to produce a solar cell module.

[0005] In order to improve productivity during the production of the above-mentioned solar cell module, one possible solution is to increase the affinity between various raw materials contained in the composition for the encapsulant film and the ethylene / α-olefin copolymer, thereby increasing the absorbency. In particular, crosslinking agents and crosslinking aids, which are essential for the production of the encapsulant film, are polar substances and have low absorbency to the non-polar ethylene / α-olefin copolymer, which is considered to be one of the factors causing reduced productivity. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-211189 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to shorten the impregnation time of an ethylene / α-olefin copolymer in the initial step during the production of an encapsulant film by using a crosslinking agent, crosslinking aid, etc. that have high affinity with the ethylene / α-olefin copolymer. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a composition for an encapsulant film, an encapsulant film, and a solar cell module.

[0009] (1) The present invention provides a composition for an encapsulant film, comprising an ethylene / α-olefin copolymer, an organic peroxide crosslinking agent, a crosslinking aid, and a silane coupling agent, wherein the crosslinking aid comprises a compound represented by the following chemical formula 1:

[0010] [ka]

[0011] n is an integer from 1 to 20.

[0012] (2) The present invention provides the composition for an encapsulant film according to (1) above, wherein n is an integer of 3 to 10 in Chemical Formula 1 above.

[0013] (3) The present invention provides the composition for a sealing material film according to (1) or (2) above, wherein the compound represented by Chemical Formula 1 is the following compound: [ka]

[0014] (4) The present invention provides the composition for a sealing material film according to any one of (1) to (3) above, wherein the crosslinking aid is present in an amount of 0.01 to 3 parts by weight based on 100 parts by weight of the composition for a sealing material film.

[0015] (5) The present invention provides the composition for an encapsulant film according to any one of (1) to (4) above, wherein the crosslinking aid further contains an allyl group-containing compound.

[0016] (6) The present invention provides the composition for an encapsulant film according to (5) above, wherein the allyl group-containing compound includes at least one compound selected from the group consisting of triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate.

[0017] (7) The present invention provides the composition for a sealant film according to (5) or (6) above, wherein the allyl group-containing compound is contained in an amount of 0.01 to 3 parts by weight based on 100 parts by weight of the composition for a sealant film.

[0018] (8) The present invention provides the composition for an encapsulant film according to any one of (5) to (7) above, wherein the molar ratio of the compound represented by Chemical Formula 1 to the allyl group-containing compound is 1:0.1 to 1:10.

[0019] (9) The present invention provides the composition for an encapsulant film according to any one of (1) to (8), wherein the organic peroxide crosslinking agent is at least one selected from the group consisting of t-butylperoxy 2-ethylhexyl carbonate, t-amylperoxy 2-ethylhexyl carbonate, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-butylperoxy)-cyclohexane, 2,2-di(t-amylperoxy)-butane, 2,2-di(t-butylperoxy)-butane, n-butyl-4,4-di(t-butylperoxy)valerate, polyether poly(t-butylperoxycarbonate), t-amylperoxy 3,5,5-trimethylhexanoate, t-butylperoxyacetate, and t-butylperoxybenzoate.

[0020] (10) The present invention provides the composition for an encapsulant film according to any one of (1) to (9), wherein the α-olefin comprises one or more selected from the group consisting of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene.

[0021] (11) The present invention provides an encapsulant film comprising the composition for an encapsulant film according to any one of (1) to (10) above.

[0022] (12) The present invention provides a solar cell module including the encapsulant film according to (11) above. [Effects of the Invention]

[0023] When a sealant film is produced using the composition for sealant films according to the present invention, the impregnation time of the ethylene / α-olefin copolymer can be shortened, thereby improving the economic efficiency of the sealant film production process. In addition, the composition for sealant films produced using the present invention exhibits an excellent degree of crosslinking. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will now be described in more detail so that the present invention may be more easily understood.

[0025] The terms and words used in the description of the present invention and the claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0026] <Composition for sealing film> The composition for an encapsulant film of the present invention comprises an ethylene / α-olefin copolymer, an organic peroxide crosslinking agent, a crosslinking aid, and a silane coupling agent, and the crosslinking aid comprises a compound represented by the following chemical formula 1:

[0027] Ethylene / α-olefin copolymer The composition for an encapsulant film of the present invention includes an ethylene / α-olefin copolymer, which is produced by copolymerizing ethylene with an α-olefin monomer, and the α-olefin, which refers to the portion of the copolymer derived from the α-olefin monomer, is an α-olefin having 4 to 20 carbon atoms, specifically propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, or 1-eicosene, and may be used alone or in combination of two or more thereof.

[0028] Among them, the α-olefin may be 1-butene, 1-hexene, or 1-octene, and preferably 1-butene, 1-octene, or a combination thereof.

[0029] In addition, the content of the α-olefin in the ethylene / α-olefin copolymer may be appropriately selected within a range that satisfies the above physical property requirements, and specifically, may be more than 0 and not more than 99 mol%, or 10 to 50 mol%, but is not limited thereto.

[0030] In the present invention, the method for preparing or route for obtaining the ethylene / α-olefin copolymer is not limited, and a person skilled in the art can select and use a suitable one in consideration of the physical properties and purpose of the composition for the encapsulant film.

[0031] Organic peroxide crosslinking agent The encapsulant film composition of the present invention contains an organic peroxide crosslinking agent. The organic peroxide crosslinking agent can act as a radical initiator in the preparation step of a silane-modified resin composition to initiate a reaction in which an unsaturated silane compound is grafted onto the resin composition. Furthermore, during the lamination step in the manufacture of an optoelectronic device, the organic peroxide crosslinking agent forms crosslinks between the silane-modified resin compositions or between the silane-modified resin composition and an unmodified resin composition, thereby improving the heat resistance and durability of the final product, for example, the encapsulant sheet.

[0032] In particular, the solar cell encapsulant may contain an organic peroxide as a crosslinking agent, and the organic peroxide plays a role in improving the weather resistance of the solar cell encapsulant.

[0033] The organic peroxide crosslinking agent may have a one-hour half-life temperature of 115 to 130°C.

[0034] The "one-hour half-life temperature" refers to the temperature at which the half-life of the crosslinking agent is one hour. The temperature at which a radical initiation reaction efficiently occurs varies depending on the one-hour half-life temperature. Therefore, when an organic peroxide crosslinking agent having a one-hour half-life temperature within the above range is used, the radical initiation reaction, i.e., the crosslinking reaction, can proceed effectively at the temperature of a lamination process for manufacturing an optoelectronic device.

[0035] Specifically, the organic peroxide crosslinking agent may be one or more selected from the group consisting of t-butylperoxy 2-ethylhexyl carbonate (TBEC), t-amylperoxy 2-ethylhexyl carbonate (TAEC), 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-butylperoxy)-cyclohexane, 2,2-di(t-amylperoxy)-butane, 2,2-di(t-butylperoxy)-butane, n-butyl-4,4-di(t-butylperoxy)valerate, polyether poly(t-butylperoxycarbonate), t-amylperoxy 3,5,5-trimethylhexanoate, t-butylperoxyacetate, and t-butylperoxybenzoate, but is not limited thereto.

[0036] When the 1-hour half-life temperature of the organic peroxide crosslinking agent is within the above range, the radical decomposition rate of the crosslinking agent is not faster than the crosslinking rate of the ethylene / α-olefin copolymer during the crosslinking process, thereby achieving the desired degree of crosslinking. Furthermore, under normal crosslinking conditions (140 to 150°C), the slow radical decomposition rate of the crosslinking agent can be prevented from slowing down the crosslinking rate.

[0037] The organic peroxide crosslinking agent may be contained in an amount of 0.1 to 3.0 parts by weight, 0.1 to 2.0 parts by weight, or 0.5 to 1.5 parts by weight, based on 100 parts by weight of the ethylene / α-olefin copolymer. When the organic peroxide crosslinking agent is contained in the above range, the effect of improving heat resistance is sufficiently exhibited, and the formability of the encapsulant film is excellent, so that process restrictions and deterioration of the physical properties of the encapsulant do not occur.

[0038] Crosslinking aid The composition for an encapsulant film of the present invention contains a crosslinking aid, and the crosslinking aid contains a compound represented by the following Chemical Formula 1.

[0039] [ka]

[0040] n is an integer from 1 to 20.

[0041] Specifically, in Chemical Formula 1, n may be 3 or more, for example, an integer of 3 to 10, an integer of 3 to 8, an integer of 3 to 6, or an integer of 4 to 6.

[0042] In particular, substances in which n is 2 or less include biotoxic substances, and therefore are not used as crosslinking aids in the present invention. For example, diallyl malate, diallyl fumarate, diallyl dicarbonate, etc. are so harmful that their SDS lists acute toxicity, oral / acute toxicity, percutaneous / skin corrosion / skin irritation / severe eye damage / eye irritation / skin hypersensitivity, etc., among the harmfulness / hazard classifications, and therefore are not suitable for use as crosslinking aids in compositions for encapsulant films.

[0043] In addition, the compound represented by Chemical Formula 1 has a structure that does not contain other substituents in the alkylene chain that links the functional groups, which is to adjust the polarity level of the compound and increase its absorbency for non-polar ethylene / α-olefin copolymers. As confirmed in the present invention, when the compound represented by Chemical Formula 1 contains other polar substituents in the alkylene chain that links the functional groups, the effect of improving the impregnation time is not achieved.

[0044] Specifically, the compound represented by Chemical Formula 1 may be the following compound:

[0045] [ka]

[0046] The crosslinking aid used in the present invention is different from conventionally used crosslinking aids such as triallyl isocyanurate in that it is non-polar and has excellent affinity with the ethylene / α-olefin copolymer, allowing for rapid impregnation.

[0047] In addition, when the crosslinking aid is used in an amount of 0.01 to 3 parts by weight based on 100 parts by weight of the composition for encapsulant film, it is possible to achieve a crosslinking degree of 60% or more, which is generally required in the solar encapsulant industry. 16 It is possible to ensure a volume resistivity of Ω·cm or more and a light transmittance of 90% or more.

[0048] In this way, by including the crosslinking aid in the composition for a sealant film, the absorption rate of the crosslinking agent and crosslinking aid into the composition for a sealant film is significantly improved, and the degree of crosslinking is further increased, thereby maintaining the heat resistance and durability of final products such as sealant films and significantly improving production economy.

[0049] In the present invention, the composition for an encapsulant film may further contain an allyl group-containing compound as a crosslinking aid.

[0050] The allyl group-containing compound may include one or more selected from the group consisting of triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl malate.

[0051] Here, the molar ratio of the compound represented by Chemical Formula 1 to the allyl group-containing compound may be 1:0.1 to 1:10, specifically 1:0.2 to 1:7, more specifically 1:0.3 to 1:5, or 1:0.3 to 1:4.

[0052] When the content is within the above range, the impregnation time of the ethylene / α-olefin copolymer can be shortened and the degree of crosslinking of the composition for an encapsulant film can be increased.

[0053] The allyl group-containing compound may be contained in an amount of 0.01 to 3 parts by weight, specifically 0.1 to 2.0 parts by weight, 0.1 to 1.50 parts by weight, or 0.1 to 1.00 parts by weight, based on 100 parts by weight of the composition for the encapsulant film.

[0054] In the present invention, the crosslinking coagent may be contained in an amount of 0.01 to 3 parts by weight, specifically 0.1 to 2.0 parts by weight, or 0.20 to 1.50 parts by weight, based on 100 parts by weight of the ethylene / α-olefin copolymer.

[0055] By including the crosslinking aid in the above range, the degree of crosslinking of the composition for an encapsulant film can be maintained high, and the impregnation time of the ethylene / α-olefin copolymer can be shortened.

[0056] silane coupling agent The composition for an encapsulant film of the present invention contains a silane coupling agent, which can improve the adhesive strength between the encapsulant film and the solar cell.

[0057] The silane coupling agent may be, for example, one or more selected from the group consisting of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane (MEMO), but is not limited thereto.

[0058] The silane coupling agent may be included in an amount of 0.1 to 1.0 parts by weight or 0.1 to 0.4 parts by weight based on 100 parts by weight of the ethylene / α-olefin copolymer. When the content of the silane coupling agent is within the above range, excellent adhesion to glass can be achieved during fabrication of a solar cell module, and degradation of the module's long-term performance due to moisture penetration can be prevented.

[0059] The composition for an encapsulant film of the present invention may further contain one or more selected from the group consisting of an unsaturated silane compound, an aminosilane compound, a light stabilizer, a UV absorber, and a heat stabilizer.

[0060] The unsaturated silane compound may be grafted to a main chain containing polymerized units of the monomer of the copolymer of the present invention in the presence of a radical initiator, etc., and may be included in a polymerized form in the silane-modified resin composition or the aminosilane-modified resin composition.

[0061] The unsaturated silane compound may be vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrippropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentoxysilane, vinyltriphenoxysilane, or vinyltriacetoxysilane, and examples thereof include, but are not limited to, vinyltrimethoxysilane or vinyltriethoxysilane.

[0062] Furthermore, the aminosilane compound acts as a catalyst to promote the hydrolysis reaction that converts reactive functional groups, such as alkoxy groups of unsaturated silane compounds grafted to the main chain of the copolymer during the graft modification step of the ethylene / α-olefin copolymer, into hydroxy groups, thereby further improving the adhesive strength with the upper and lower glass substrates or backsheets made of fluororesin, etc. In addition, the aminosilane compound directly participates in the copolymerization reaction as a reactant, thereby providing a moiety having an amine functional group in the aminosilane-modified resin composition.

[0063] The aminosilane compound is not particularly limited as long as it is a silane compound containing an amine group and is a primary amine or a secondary amine. For example, aminotrialkoxysilane, aminodialkoxysilane, etc. can be used as the aminosilane compound. Examples thereof include 3-aminopropyltrimethoxysilane (APTMS), 3-aminopropyltriethoxysilane (APTES), bis[(3-triethoxysilyl)propyl]amine, bis[(3-trimethoxysilyl)propyl]amine, 3-aminopropylmethyldiethoxysilane, 3-aminopropylmethyldimethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine (DAS), aminoethylaminopropyltriethoxysilane, aminoethylaminopropylmethyldimethoxysilane, aminoethylaminopropylmethyldiethoxysilane, Examples of suitable aminosilane compounds include at least one selected from the group consisting of silane, aminoethylaminomethyltriethoxysilane, aminoethylaminomethylmethyldiethoxysilane, diethylenetriaminopropyltrimethoxysilane, diethylenetriaminopropyltriethoxysilane, diethylenetriaminopropylmethyldimethoxysilane, diethyleneaminomethylmethyldiethoxysilane, (N-phenylamino)methyltrimethoxysilane, (N-phenylamino)methyltriethoxysilane, (N-phenylamino)methylmethyldimethoxysilane, (N-phenylamino)methylmethyldiethoxysilane, 3-(N-phenylamino)propyltrimethoxysilane, 3-(N-phenylamino)propyltriethoxysilane, 3-(N-phenylamino)propylmethyldimethoxysilane, 3-(N-phenylamino)propylmethyldiethoxysilane, and N-(N-butyl)-3-aminopropyltrimethoxysilane. The aminosilane compounds may be used alone or in combination.

[0064] The light stabilizer may act to capture active species that initiate photodegradation of the resin and prevent photooxidation depending on the application of the composition. The type of light stabilizer that can be used is not particularly limited, and known compounds such as hindered amine compounds or hindered piperidine compounds can be used.

[0065] The UV absorber can absorb ultraviolet rays from sunlight or the like depending on the intended use of the composition, convert them into harmless thermal energy within the molecule, and prevent the excitation of active species that initiate photodegradation in the resin composition. The specific type of UV absorber that can be used is not particularly limited, and for example, one or a mixture of two or more inorganic UV absorbers such as benzophenone-based, benzotriazole-based, acrylonitrile-based, metal complex salt-based, hindered amine-based, ultrafine particle titanium oxide, or ultrafine particle zinc oxide can be used.

[0066] Examples of the heat stabilizer include phosphorus-based heat stabilizers such as tris(2,4-di-tert-butylphenyl)phosphite, bis[2,4-bis(1,1-dimethylethyl)-6-methylphenyl]ethyl ester phosphorous acid, tetrakis(2,4-di-tert-butylphenyl)[1,1-biphenyl]-4,4′-diylbisphosphonate, and bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite; and lactone-based heat stabilizers such as a reaction product of 8-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene, and one or more of the above may be used.

[0067] The contents of the light stabilizer, UV absorber, and heat stabilizer are not particularly limited. That is, the contents of the additives can be appropriately selected in consideration of the use of the resin composition, the shape and density of the additive, etc., and can usually be appropriately adjusted within a range of 0.01 to 5 parts by weight based on 100 parts by weight of the total solid content of the composition for encapsulant film.

[0068] <Sealing film> The present invention also provides an encapsulant film comprising the encapsulant film composition.

[0069] The encapsulant film of the present invention can be produced by molding the composition for encapsulant films into a film or sheet. The molding method is not particularly limited, and the composition can be produced by, for example, forming the composition into a sheet or film by a conventional process such as a T-die process or extrusion. For example, the encapsulant film can be produced in situ using an apparatus in which the process for producing a modified resin composition using the composition for encapsulant films and the process for forming the film or sheet are connected to each other.

[0070] The thickness of the encapsulant film may be adjusted to about 10 to 2,000 μm or about 100 to 1,250 μm, taking into consideration the support efficiency and breakage risk of elements in an optoelectronic device, weight reduction of the device, workability, etc., and may vary depending on the specific application.

[0071] <Solar cell module> The present invention also provides a solar cell module including the encapsulant film. In the present invention, the solar cell module may have a configuration in which the encapsulant film of the present invention fills the gaps between solar cells arranged in series or parallel, a glass surface is placed on the surface exposed to sunlight, and the back surface is protected by a backsheet. However, the present invention is not limited thereto, and various types and shapes of solar cell modules manufactured using encapsulant films in the art are all applicable to the present invention.

[0072] The glass surface may be made of tempered glass to protect the solar cell from external impact and prevent breakage, and may be made of low-iron tempered glass having a low iron content to prevent reflection of sunlight and increase the transmittance of sunlight, but is not limited thereto.

[0073] The backsheet is a weather-resistant film that protects the back surface of the solar cell module from the outside, and examples thereof include, but are not limited to, a fluorine-based resin sheet, a metal plate or foil such as aluminum, a cyclic olefin-based resin sheet, a polycarbonate-based resin sheet, a poly(meth)acrylic-based resin sheet, a polyamide-based resin sheet, a polyester-based resin sheet, and a composite sheet obtained by laminating a weather-resistant film and a barrier film.

[0074] In addition, the solar cell module of the present invention can be produced by any method known in the art, without any limitations, except that it contains the above-mentioned encapsulant film.

[0075] The solar cell module of the present invention is manufactured using an encapsulant film with excellent volume resistivity, and the encapsulant film can prevent electrons in the solar cell module from moving and causing current to leak out, thereby significantly suppressing the PID (Potential Induced Degradation) phenomenon, in which insulation deteriorates, causing leakage current and resulting in a sudden drop in module output.

[0076] Example The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0077] Example 1 As the ethylene / α-olefin copolymer, LF675 (ethylene / 1-butene copolymer, density 0.877 g / cc, MI 14.0) manufactured by LG Chemical was used.

[0078] Ethylene / α-olefin copolymer pellet resin was mixed with TBEC (t-butylperoxy 2-ethylhexyl carbonate) as a crosslinking agent, 0.25 phr of diallyl adipate as a crosslinking aid, and MEMO (3-(trimethoxysilyl)propyl methacrylate) as a silane coupling agent, and then impregnated.

[0079] A Haake mixer was used for the impregnation process. The torque value was monitored over time while stirring at 40 rpm at a temperature of 41.5°C, and the impregnation was completed when the torque value increased sharply. Before the crosslinker was absorbed into the ethylene / α-olefin copolymer, it acted as a lubricant, maintaining a low torque value. However, once the crosslinker was completely absorbed, the torque value increased. Therefore, the time when the torque value suddenly increased was defined as the impregnation completion time.

[0080] Examples 2 to 5, Comparative Examples 1 to 3 The sealing material film was produced in the same manner as in Example 1, except that the type and content of the crosslinking aid were changed as shown in Table 1 below.

[0081] [Table 1] [ka]

[0082] Experimental Example 1 (1) Impregnation completion time As described above in Example 1, the time when the torque value suddenly increased was taken as the time when the impregnation was completed, and the time from the start of stirring to the completion of impregnation was measured and shown in Table 2 below.

[0083] (2) MDR torque (MH-ML, Nm) To evaluate the degree of crosslinking, the MDR torque value of each sample was measured using an Alpha Technologies Production MDR (Moving Die Rheometer).

[0084] Specifically, the 550 μm films of the encapsulating material prepared in the examples and comparative examples were cut into 1 g pieces, and four pieces were stacked to prepare a total of 4 g of samples, which were then subjected to measurement at 150° C. for 20 minutes. H Value and M L The measured M H Value to M L By subtracting the value, the MDR torque (M H -M L ) was calculated, where M H is the maximum vulcanizing torque, and M L is the minimum vulcanizing torque.

[0085] (3) Crosslinking degree (%) The degree of crosslinking was evaluated based on the CPIA (China Photovoltaic Industry Association) standard and ASTM D 2765. The encapsulant film prepared above was cut into a 10 cm x 10 cm piece, and then vacuum laminated at 150°C for 20 minutes (5 minutes vacuum / 1 minute pressure / 14 minutes pressure), to obtain a crosslinked test piece.

[0086] The crosslinked test specimens were cut into 2mm x 2mm pieces, weighed at 0.5g each, and placed in a 200-mesh iron cage. They were then dissolved in refluxing xylene for 5 hours. The test specimens were then dried in a vacuum oven, and the weights before and after reflux were compared to determine the degree of crosslinking for each specimen.

[0087] [Table 2]

[0088] As shown in Table 2, Examples 1 to 5, which used the composition for an encapsulant film of the present invention, showed a fast impregnation rate, a shortened impregnation completion time, and an excellent level of crosslinking. On the other hand, Comparative Example 1, which used TAIC as a crosslinking aid, and Comparative Examples 2 and 3, which used a crosslinking aid other than that of Chemical Formula 1, showed a slow impregnation rate and a significantly longer impregnation completion time than the Examples.

[0089] In particular, the impregnation completion time was longer in Comparative Examples 2 and 3 than in Comparative Example 1. This is because the cross-linking coagent used in Comparative Example 2 has a structure containing three allyl groups and a benzene ring, and therefore has greater polarity than TAIC, while the cross-linking coagent used in Comparative Example 3 has a structure containing three allyl groups and a hydroxyl group, and therefore has increased polarity, resulting in lower affinity with the non-polar ethylene / α-olefin copolymer.

[0090] In this way, when the composition for an encapsulant film according to the present invention is used, it has the effect of shortening the impregnation time while exhibiting an appropriate level of crosslinking degree.

[0091] Experimental Example 2 The sealing material film (15 cm x 15 cm) produced in the above Examples and Comparative Examples was placed between two release films (thickness: approximately 100 μm), and the film was laminated and crosslinked in a vacuum laminator at a process temperature of 150°C for a process time of 20 minutes.

[0092] (1) Volume resistance Measurements were performed based on ASTM D257. Specifically, the sample was placed in a Keithley 8009 test fixture at a temperature of 23±1°C and a humidity of 50±3%, and a voltage of 1000V was applied for 600 seconds using a Keithley 6517B electrometer connected to the fixture.

[0093] (2) Light transmittance In addition, the light transmittance at 550 nm was measured using a Shimadzu UV-3600 spectrophotometer (measurement mode: transmittance, wavelength interval: 1 nm, measurement speed: medium).

[0094] [Table 3]

[0095] As shown in Table 3, it was confirmed that when the composition for an encapsulant film according to the present invention was used, excellent levels of volume resistance and light transmittance were achieved.

Claims

1. The composition comprises an ethylene / α-olefin copolymer, an organic peroxide crosslinking agent, a crosslinking aid, and a silane coupling agent, The crosslinking aid comprises a compound represented by the following Chemical Formula 1: 【Chemical 1】 (n is an integer from 1 to 20.)

2. In the above Chemical Formula 1, 2. The composition for a sealing material film according to claim 1, wherein n is an integer of 3 to 10.

3. The composition for a sealant film according to claim 1 , wherein the compound represented by Chemical Formula 1 is the following compound: 【Chemistry 2】

4. The composition for a sealing material film according to claim 1, wherein the crosslinking aid is contained in an amount of 0.01 to 3 parts by weight based on 100 parts by weight of the composition for a sealing material film.

5. The composition for a sealant film according to claim 1 , wherein the crosslinking aid further comprises an allyl group-containing compound.

6. The composition for a sealing material film according to claim 5, wherein the allyl group-containing compound comprises at least one compound selected from the group consisting of triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate.

7. The composition for a sealing material film according to claim 5, wherein the allyl group-containing compound is contained in an amount of 0.01 to 3 parts by weight based on 100 parts by weight of the composition for a sealing material film.

8. The composition for a sealing material film according to claim 5, wherein the molar ratio of the compound represented by Chemical Formula 1 to the allyl group-containing compound is 1:0.1 to 1:

10.

9. 2. The composition for a sealant film according to claim 1, wherein the organic peroxide crosslinking agent is at least one selected from the group consisting of t-butylperoxy 2-ethylhexyl carbonate, t-amylperoxy 2-ethylhexyl carbonate, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-butylperoxy)-cyclohexane, 2,2-di(t-amylperoxy)-butane, 2,2-di(t-butylperoxy)-butane, n-butyl-4,4-di(t-butylperoxy)valerate, polyether poly(t-butylperoxycarbonate), t-amylperoxy 3,5,5-trimethylhexanoate, t-butylperoxyacetate, and t-butylperoxybenzoate.

10. The composition for a sealant film according to claim 1, wherein the α-olefin comprises at least one selected from the group consisting of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene.

11. An encapsulant film comprising the composition for encapsulant films according to claim 1 .

12. A solar cell module comprising the encapsulant film of claim 11.

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