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

Abstract

The present invention relates to a composition for an encapsulant film, which contains an ethylene / alpha-olefin copolymer and has excellent compatibility with a crosslinking additive, 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. 10-2022-0107003 filed on August 25, 2022, Korean Patent Application No. 10-2022-0112873 filed on September 6, 2022, and Korean Patent Application No. 10-2023-0043750 filed on April 3, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a composition for an encapsulant film, 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. To obtain a crystalline solar cell module during the manufacture of a 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 / alpha-olefin copolymer, which have excellent transparency, flexibility, adhesiveness, etc.

[0004] A solar cell module is a packaged product in which solar cell elements such as silicon, gallium-arsenide, or copper-indium-selenium solar cells are protected by an upper transparent protective material and a lower substrate protective material, and the solar cell elements and protective materials are fixed together with a sealant. Generally, the sealant for the solar cell elements in a solar cell module is made by extruding an ethylene / alpha-olefin copolymer containing an organic peroxide or a silane coupling agent into a sheet, and the solar cell module is manufactured by sealing the solar cell elements with the resulting sheet-shaped sealant.

[0005] In order to improve productivity during the production of the above-mentioned solar cell module, one possible method is to increase the affinity between various raw materials contained in the encapsulant film composition and the ethylene / alpha-olefin copolymer to increase the absorbency. In particular, crosslinking agents, crosslinking aids, etc., which are essential for the production of encapsulant films, are polar substances and therefore have low absorbency into non-polar ethylene / alpha-olefin copolymers, which is cited as one of the factors that leads to 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] The present invention aims to shorten the impregnation time of an ethylene / alpha-olefin copolymer in the initial stage of producing an encapsulant film, thereby reducing the migration rate of a crosslinker component impregnated into a composition for an encapsulant film. [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, which has a ratio of Si-O band integral to C-H band integral (Si-O band integral / C-H band integral) of 3 to 70 when calculated from an FT-IR spectrum.

[0010] (2) The present invention provides a composition for an encapsulant film according to (1), in which, when an encapsulant film is produced using the composition for an encapsulant film and a crosslinking agent, the migration rate of the crosslinking agent, represented by the following mathematical formula 1, is 4.5% or less: [Mathematical formula 1] Crosslinking agent migration rate (%) = [weight of crosslinking agent migrated to the surface of the encapsulant film / total weight of crosslinking agent] x 100 In the above mathematical formula 1, The weight of the crosslinking agent transferred to the surface of the film is a value measured after producing an encapsulant film using the composition for an encapsulant film and storing it at −5° C. for 1 week. The total weight of the crosslinking agent is the total weight of the crosslinking agent contained in the encapsulant film.

[0011] (3) The present invention provides a composition for an encapsulant film according to (1) or (2), wherein the ratio of the Si-O band integral to the C-H band integral (Si-O band integral / C-H band integral) is 10 to 50 when calculated from an FT-IR spectrum.

[0012] (4) The present invention provides a composition for an encapsulant film according to any one of the above (1) to (3), wherein the migration rate of the crosslinking agent is 0.1 to 4.3%.

[0013] (5) The present invention provides a composition for an encapsulant film in any one of the above (1) to (4), wherein the composition for an encapsulant film contains an ethylene / alpha-olefin copolymer and porous silica.

[0014] (6) The present invention provides the composition for a sealing material film according to (5), wherein the porous silica has an oil absorption of more than 40 mL / 100 g as measured in accordance with ASTM D1483-12(2016).

[0015] (7) The present invention provides the composition for an encapsulant film according to (5) or (6), wherein the porous silica has a —OH content of silanol groups of 1.0 wt % or more based on the total weight of the porous silica.

[0016] (8) The present invention provides a composition for an encapsulant film according to any one of (1) to (7) above, further comprising at least one selected from the group consisting of an organic peroxide, a crosslinking aid, a silane coupling agent, an unsaturated silane compound, an aminosilane compound, a light stabilizer, a UV absorber, and a heat stabilizer.

[0017] (9) The present invention provides an encapsulant film comprising the composition for an encapsulant film according to any one of (1) to (8) above.

[0018] (10) The present invention provides a solar cell module including the encapsulant film of (9). [Effects of the Invention]

[0019] When an encapsulant film is produced using the encapsulant film composition according to the present invention, the impregnation time of the ethylene / alpha-olefin copolymer can be shortened, thereby improving the economic efficiency of the encapsulant film production process. In addition, the migration of the crosslinker composition components can be delayed, thereby suppressing the slippage of the encapsulant film that may occur during the automated module manufacturing process. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will now be described in more detail to aid in understanding the present invention.

[0021] 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 inventor can appropriately define the concept of the term in order to best describe his / her invention.

[0022] <Composition for sealing film> The composition for an encapsulant film of the present invention is characterized in that the ratio of the Si-O band integral to the C-H band integral (Si-O band integral / C-H band integral) is 3 to 70 when calculated from an FT-IR spectrum.

[0023] The composition for an encapsulant film of the present invention contains an ethylene / alpha-olefin copolymer produced by copolymerizing ethylene with an alpha-olefin monomer, where the alpha-olefin, which refers to the portion of the copolymer derived from the alpha-olefin monomer, is an alpha-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, 1-eicosene, etc., and may be one of these alone or a mixture of two or more thereof.

[0024] Among others, the alpha-olefin may be 1-butene, 1-hexene or 1-octene, preferably 1-butene, 1-hexene or a combination thereof.

[0025] Furthermore, in the ethylene / alpha-olefin copolymer, the content of the alpha-olefin can be appropriately selected within a range that satisfies the above-mentioned physical property requirements, and specifically, it may be more than 0 and not more than 99 mol%, or 10 to 50 mol%, but is not limited thereto.

[0026] In the present invention, the method or route for preparing the ethylene / alpha-olefin copolymer is not limited, and a person skilled in the art can appropriately select and use the copolymer in consideration of the physical properties and purpose of the composition for the encapsulant film.

[0027] The ethylene / alpha-olefin copolymer contained in the composition for an encapsulant film of the present invention may have a density in the range of 0.850 to 0.910 g / cc, where the density may mean the density measured in accordance with ASTM D-792-20. More specifically, the density may be 0.855 g / cc or more, 0.860 g / cc or more, 0.865 g / cc or more, or 0.870 g / cc or more, and may be 0.905 g / cc or less, 0.900 g / cc or less, or 0.895 g / cc or less.

[0028] Generally, when an ethylene / alpha-olefin copolymer is used in a composition for an encapsulant film, the lower the density of the copolymer, the lower the crystallinity and the higher the optical transparency, and the shorter the impregnation time of the crosslinking agent is. However, if the density is too low, blocking between pellets may occur during pellet storage, making the pellet charging process difficult, and the pellets may easily adhere to the surface of the winding roll during sheet formation, causing blocking between sheets, which may cause problems with the sheet's payout ability and lead to various problems in the process of producing a sheet for an encapsulant film.

[0029] However, the composition for an encapsulant film of the present invention contains an ethylene / alpha-olefin copolymer having the above density, and is characterized by having improved resistance to blocking and stickiness of pellets and sheets, and by improving the problem of delayed impregnation time that has conventionally been associated with the use of ethylene / alpha-olefin copolymers.

[0030] Furthermore, due to the silanol groups and siloxane groups in the composition for sealing material films of the present invention, the composition exhibits excellent compatibility with crosslinking agents, thereby reducing the migration rate of crosslinking agent components over time and exhibiting excellent slip resistance on glass substrates.

[0031] The composition for encapsulant films of the present invention can contain porous silica. As described above, by containing porous silica, the ratio of the Si-O band integral to the C-H band integral (Si-O band integral / C-H band integral) is calculated to be 3 to 70 when the composition for encapsulant films of the present invention is used as the target for FT-IR spectrum calculation.

[0032] An FT-IR (Fourier Transformation-Infrared) instrument is one of the most basic spectroscopic instruments and is used to determine the presence or absence of most chemical functional groups. When infrared light is irradiated onto a sample, part of the irradiated light is absorbed by the sample and appears as a specific peak, and the characteristics of the sample can be determined from this specific peak.

[0033] Specific peaks are peaks that are only present for specific functional groups, and the positions of the peaks can be found in handbooks.

[0034] The Si-O band integral value is 1016 cm -1 ~1247cm -1 The C-H band integral may be an integral value of the region, and the C-H band integral may be an integral value of the region at 1975 cm -1 ~2110cm -1 It can be the integral of the region.

[0035] More specifically, the ratio of the Si—O band integral to the C—H band integral (Si—O band integral / C—H band integral) can be 3 to 70, specifically 4 to 60, or 5 to 50.

[0036] This means that in the composition for an encapsulant film of the present invention, when the Si-O component in the porous silica is at a certain content or more, there are many sites available for hydrogen bonding with the carbonyl group of the crosslinker, which can act as a factor for accelerating the impregnation rate in the impregnation reaction of the crosslinker and shortening the impregnation process time.

[0037] In addition, when an encapsulant film is produced using the composition for an encapsulant film and the crosslinking agent of the present invention, the migration rate of the crosslinking agent, represented by the following mathematical formula 1, may be 4.5% or less.

[0038] [Mathematical formula 1] Crosslinker migration rate (%) = [weight of crosslinker migrated to the film surface / total weight of crosslinker] x 100

[0039] In the above mathematical formula 1, The weight of the crosslinking agent transferred to the surface of the film is a value measured after producing an encapsulant film using the composition for an encapsulant film and storing it at −5° C. for 1 week. The total weight of the crosslinking agent is the total weight of the crosslinking agent contained in the encapsulant film.

[0040] The composition for an encapsulant film of the present invention contains porous silica, which satisfies a certain amount of silanol group -OH content and a predetermined specific surface area. The composition for an encapsulant film of the present invention contains porous silica which satisfies a certain amount of silanol group -OH content and a predetermined specific surface area, and the migration phenomenon of the crosslinker component is suppressed, thereby showing a low crosslinker migration rate.

[0041] Specifically, the migration rate of the crosslinking agent represented by the above mathematical formula 1 may be 4.5 wt % or less, specifically 0.1 to 4.3 wt %, or 0.5 to 4.3 wt %. By exhibiting such a low migration rate of the crosslinking agent, when an encapsulant film is manufactured using the same, not only can the physical properties of the encapsulant film be maintained, but also excellent slip resistance can be exhibited on a glass substrate during the manufacturing process of a solar module.

[0042] The composition for the encapsulant film of the present invention can include an ethylene / alpha-olefin copolymer and porous silica.

[0043] The porous silica may have an oil absorption of more than 40 mL / 100 g as measured in accordance with ASTM D1483-12(2016).

[0044] Specifically, the oil absorption of the porous silica is more than 40 mL / 100 g, more specifically, 60 to 500 mL / 100 g, for example, more than 40 mL / 100 g, 60 mL / 100 g or more, 70 mL / 100 g or more, 80 mL / 100 g or more, 100 mL / 100 g or more, or 130 mL / 100 g or more, and can be 500 mL / 100 g or less, 450 mL / 100 g or less, 400 mL / 100 g or less, 300 mL / 100 g or less, or 200 mL / 100 g or less.

[0045] The oil absorption of the porous silica used in the present invention falls within the above range, which means that the porous silica exhibits excellent absorption for liquid crosslinking agents. In particular, the present invention uses porous silica with a high oil absorption of more than 40 mL / 100 g, and when used in a composition for a sealing material film, the porous silica exhibits excellent oil absorption for liquid component additives, and the hydrogen bonding effect between the hydroxyl groups in the silica and the carbonyl groups in the crosslinking agent results in a shortened impregnation time for the crosslinking agent and a low migration rate of the crosslinking agent.

[0046] The —OH content of the silanol groups (Si—OH) of the porous silica may be 1.0 wt % or more, specifically 1.5 wt % or more, 2.0 wt % or more, 2.5 wt % or more, 3.0 wt % or more, 5.0 wt % or less, or 4.5 wt % or less, based on the total weight of the porous silica.

[0047] When the -OH content of the silanol group satisfies the above range, migration of the crosslinker toward the surface can be suppressed and the absorption rate of the crosslinker can be improved during long-term storage of an encapsulant film composition containing an ethylene / alpha-olefin copolymer and porous silica. If the -OH content of the silanol group is insufficient, the migration of the crosslinker may not be sufficiently suppressed. If the -OH content of the silanol group is too high, moisture in the air may be adsorbed thereto, causing side reactions when blended with a crosslinker and a silane coupling agent, resulting in a decrease in the degree of crosslinking and adhesive strength.

[0048] The specific pore volume of the porous silica is more than 0.1 mL / g, specifically 0.2 to 5.0 mL / g, for example, 0.2 mL / g or more, 0.3 mL / g or more, 0.5 mL / g or more, 0.7 mL / g or more, 5.0 mL / g or less, 3.0 mL / g or less, 2.5 mL / g or less, 2.0 mL / g or less, or 1.0 mL / g or less.

[0049] The specific pore volume of the porous silica used in the present invention falls within the above range, which means that the porous silica has excellent absorption of a liquid crosslinking agent. In particular, the present invention uses porous silica having a large specific pore volume of more than 0.1 mL / g, which effectively absorbs the crosslinking agent when used in a sealant film composition, thereby shortening the impregnation time of the crosslinking agent.

[0050] Furthermore, the porous silica of the present invention is characterized by simultaneously satisfying the above-mentioned oil absorption and specific pore volume requirements. If either one of the two does not fall within the above range, a problem of poor absorption of the liquid crosslinking agent may occur, which may act as a factor hindering the impregnation of the crosslinking agent.

[0051] In addition, when the porous silica is used, the volume resistivity also increases because the porous silica acts as an insulator, and this effect is particularly evident when porous silica having the above oil absorption and specific pore volume is used.

[0052] In the present invention, the content of the porous silica is 0.1 to 1.5% by weight, specifically 0.1 to 1.0% by weight, based on the composition for the encapsulant film.

[0053] If the content of porous silica is less than the above range, the porous silica will not efficiently absorb the liquid crosslinking agent, and the functional groups of the porous silica will not be effective in shortening the impregnation time of the crosslinking agent. If the content of porous silica is more than the above range, it may cause side effects that impair the optical transparency of the encapsulant film.

[0054] In the present invention, the porous silica may have an average particle size of 1 to 20 μm, specifically 1.0 μm or more, 1.2 μm or more, 2.0 μm or more, 15.0 μm or less, 14.0 μm or less, 10.0 μm or less, or 5.0 μm or less.

[0055] When the porous silica has the above size, it is well dispersed in the encapsulant sheet, maintaining optical transparency, and preventing sheet blocking due to low density of the ethylene / alpha-olefin copolymer during winding and storage of the encapsulant sheet. Also, it is possible to prevent the porous silica from having an average particle size that is too large, resulting in poor appearance due to unevenness on the sheet surface.

[0056] In the present invention, the porous silica has a specific surface area of ​​40 to 800 m 2 / g, specifically, 50m 2 / g or more, 100m 2 / g or more, 150m 2 / g or more, 200m 2 / g or more, 300m 2 / g or more, 400m 2 / g or more, 750m 2 / g or less, 700m 2 / g or less, 600m 2When the specific surface area of ​​the porous silica is within this range, the silanol groups (or functional groups containing OH) of the porous silica and the polar groups of the crosslinking agent are bonded efficiently, which can provide advantages such as a shorter impregnation time for the crosslinking agent.

[0057] The composition for an encapsulant film of the present invention may further contain, in addition to the above-mentioned ethylene / alpha-olefin copolymer and porous silica, one or more selected from the group consisting of known organic peroxides, crosslinking aids, silane coupling agents, unsaturated silane compounds, aminosilane compounds, light stabilizers, UV absorbers, and heat stabilizers.

[0058] The composition for encapsulant film of the present invention contains a crosslinking agent. In the preparation step of a silane-modified resin composition, the crosslinking agent serves as a radical initiator to initiate a reaction in which an unsaturated silane compound is grafted onto the resin composition. Furthermore, in the lamination step of manufacturing an optoelectronic device, the 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.

[0059] The crosslinking agent may be any crosslinking compound known in the art, as long as it is capable of initiating radical polymerization of vinyl groups or forming crosslinks. For example, one or more crosslinking agents selected from the group consisting of organic peroxides, hydroperoxides, and azo compounds may be used.

[0060] For example, 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.

[0061] Specifically, dialkyl peroxides such as t-bupyrcumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne; hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethyl-2,5-di(hydroperoxy)hexane, and t-butyl hydroperoxide; diacyl peroxides such as bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, benzoyl peroxide, o-methylbenzoyl peroxide, and 2,4-dichlorobenzoyl peroxide; t-butyl peroxyisobutyrate, t-butyl peroxyacetate, and t-butyl peroxide; Examples of the peroxyesters include peroxy-2-ethylhexyl carbonate (TBEC), t-butyl peroxy-2-ethylhexanoate, t-butyl peroxypivalate, t-butyl peroxyoctoate, t-butyl peroxyisopropyl carbonate, t-butyl peroxybenzoate, di-t-butyl peroxyphthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-di(benzoylperoxy)-3-hexyne; ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; and azo compounds such as lauryl peroxide, azobisisobutyronitrile, and azobis(2,4-dimethylvaleronitrile), but are not limited thereto.

[0062] The organic peroxide may have a one-hour half-life temperature of 120 to 135°C, for example, 120 to 130°C, 120 to 125°C, and preferably 121°C. 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 having a one-hour half-life temperature within the aforementioned range is used as a crosslinking agent, the radical initiation reaction, i.e., the crosslinking reaction, efficiently occurs at the temperature of the lamination process for manufacturing an optoelectronic device.

[0063] The crosslinking agent may be contained in an amount of 0.01 to 2 parts by weight, for example, 0.05 to 1.5 parts by weight, 0.1 to 1.5 parts by weight, or 0.5 to 1.5 parts by weight, relative to 100 parts by weight of the ethylene / alpha-olefin copolymer. When the 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 also excellent, so that process constraints and deterioration of the physical properties of the encapsulant do not occur.

[0064] Crosslinking aid The composition for an encapsulant film of the present invention can contain a crosslinking aid in addition to the crosslinking agent. When the crosslinking aid is contained in the resin composition, the degree of crosslinking between the resin compositions by the crosslinking agent can be increased, thereby further improving the heat resistance and durability of the final product, for example, the encapsulant sheet.

[0065] As the crosslinking aid, various crosslinking aids known in the technical field can be used. For example, as the crosslinking aid, a compound containing at least one unsaturated group such as an allyl group or a (meth)acryloxy group can be used.

[0066] Examples of the compound containing an allyl group include polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate, and examples of the compound containing a (meth)acryloxy group include poly(meth)acryloxy compounds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate, but are not particularly limited to these.

[0067] The crosslinking aid is included in an amount of 0.01 to 0.5 parts by weight, for example, 0.01 to 0.3, 0.015 to 0.2, or 0.016 to 0.16 parts by weight, relative to 100 parts by weight of the composition for an encapsulant film. If the crosslinking aid is included in an amount of less than 0.01 part by weight, the effect of improving heat resistance is not significant. If the crosslinking aid is included in an amount of more than 0.5 part by weight, problems may arise that affect the properties of the final product, for example, the encapsulant sheet, and production costs may increase.

[0068] silane coupling agent The silane coupling agent can improve the adhesive strength between the encapsulant film and the solar cell.

[0069] 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.

[0070] The silane coupling agent may be contained in an amount of 0.1 to 0.4 parts by weight per 100 parts by weight of the composition for encapsulant film. When the content of the silane coupling agent is within the above range, excellent adhesion to glass can be achieved during the production of a solar cell module, and degradation of the long-term performance of the module due to moisture penetration can be prevented.

[0071] 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.

[0072] The unsaturated silane compound may be included in a polymerized form in the silane-modified resin composition or the aminosilane-modified resin composition by grafting onto a main chain containing a polymerized unit of a monomer of the copolymer of the present invention in the presence of a radical initiator or the like.

[0073] The unsaturated silane compound may be vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrippropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentoxysilane, vinyltriphenoxysilane, vinyltriacetoxysilane, or the like. Among these, vinyltrimethoxysilane or vinyltriethoxysilane may be used as an example, but is not limited thereto.

[0074] In addition, 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, e.g., vinyltriethoxysilane, grafted to the main chain of the ethylene / alpha-olefin copolymer into hydroxy groups during the graft modification step of the copolymer, thereby further improving the adhesive strength to the upper and lower glass substrates or backsheets made of fluororesin, etc. At the same time, the aminosilane compound also participates as a reactant in the direct copolymerization reaction, thereby providing a moiety having an amine functional group in the aminosilane-modified resin composition.

[0075] The aminosilane compound is a silane compound containing an amine group, and is not particularly limited as long as it is a primary amine or a secondary amine. For example, as the aminosilane compound, aminotrialkoxysilane, aminodialkoxysilane, etc. may be used, and 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 can be used alone or in combination.

[0076] 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.

[0077] The UV absorber can absorb ultraviolet rays from sunlight or the like and convert them into harmless thermal energy within the molecule, thereby preventing the excitation of active species that initiate photodegradation in the resin composition, depending on the intended use of the 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 titanium oxide, and ultrafine zinc oxide can be used.

[0078] 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.

[0079] 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 the range of 0.01 to 5 parts by weight per 100 parts by weight of the total solid content of the composition for encapsulant film.

[0080] <Sealing film> The present invention also provides an encapsulant film comprising the encapsulant film composition.

[0081] 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 using 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.

[0082] The thickness of the encapsulant film can 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 and workability of the device, etc., and can be changed depending on the specific application.

[0083] <Solar cell module> Furthermore, the present invention provides a solar cell module including the encapsulant film. In the present invention, the solar cell module may have a configuration in which the gaps between solar cells arranged in series or parallel are filled with the encapsulant film of the present invention, a glass surface is placed on the surface exposed to sunlight, and the back surface is protected by a backsheet, but is not limited thereto, and all of the various types and forms of solar cell modules manufactured to include an encapsulant film in the art can be applied to the present invention.

[0084] The glass surface may be made of tempered glass to protect the solar cell from external impact and prevent breakage, or may be made of low-iron tempered glass with a low iron content to prevent reflection of sunlight and increase the transmittance of sunlight, but is not limited thereto.

[0085] The backsheet is a weather-resistant film that protects the back surface of the solar cell module from the outside. Examples include fluororesin sheets, metal plates or foils such as aluminum, cyclic olefin resin sheets, polycarbonate resin sheets, poly(meth)acrylic resin sheets, polyamide resin sheets, polyester resin sheets, composite sheets obtained by laminating a weather-resistant film and a barrier film, etc., but are not limited thereto.

[0086] In addition, the solar cell module of the present invention can be manufactured without limitation by a method known in the art, except that it includes the above-mentioned encapsulant film.

[0087] The solar cell module of the present invention is manufactured using an encapsulant film having excellent volume resistivity. The encapsulant film can prevent electrons in the solar cell module from moving and current from flowing out to the outside. Therefore, it is possible to significantly suppress the PID (Potential Induced Degradation) phenomenon in which the insulation deteriorates, leakage current occurs, and the output of the module rapidly decreases.

[0088] Example Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

[0089] Production Example 1: Production of Transition Metal Compound 1 <Synthesis of N-tert-butyl-1-(1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophen-3-yl)-1,1-dimethylsilanamine>

Chemical formula

[0090] 4.65 g (15.88 mmol) of chloro(1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophen-3-yl)dimethylsilane was weighed and added to a 100 ml Schlenk flask, followed by 80 ml of THF. tBuNH2 (4 eq, 6.68 ml) was added at room temperature, and the mixture was allowed to react at room temperature for 3 days. After the reaction, the THF was removed and the mixture was filtered with hexane. After drying the solvent, a yellow liquid was obtained in a yield of 4.50 g (86%).

[0091] 1 H-NMR(in CDCl3, 500 MHz): 7.99(d, 1H), 7.83(d, 1H), 7.35(dd, 1H), 7.24(dd, 1H), 3.49(s, 1H), 2.37(s, 3H), 2.17(s, 3H), 1.27(s, 9H), 0.19(s, 3H), -0.17(s, 3H).

[0092] <Production of transition metal compounds> [ka]

[0093] The ligand compound (1.06 g, 3.22 mmol / 1.0 eq) and 16.0 mL (0.2 M) of MTBE were placed in a 50 mL Schlenk flask and stirred. n-BuLi (2.64 mL, 6.60 mmol / 2.05 eq, 2.5 M in THF) was added at -40 °C and reacted overnight at room temperature. MeMgBr (2.68 mL, 8.05 mmol / 2.5 eq, 3.0 M in diethyl ether) was then slowly added dropwise at -40 °C, followed by TiCl4 (2.68 mL, 3.22 mmol / 1.0 eq, 1.0 M in toluene) and reacted overnight at room temperature. The reaction mixture was then filtered through Celite with hexane. After drying the solvent, a brown solid was obtained in a yield of 1.07 g (82%).

[0094] 11H-NMR (in CDCl3, 500 MHz): 7.99 (d, 1H), 7.68 (d, 1H), 7.40 (dd, 1H), 7.30 (dd, 1H), 3.22 (s, 1H), 2.67 (s, 3H), 2.05 (s, 3H), 1.54 (s, 9H), 0.58 (s, 3H), 0.57 (s, 3H), 0.40 (s, 3H), -0.45 (s, 3H).

[0095] Production Example 2: Production of Transition Metal Compound 2 <Synthesis of N-tert-butyl-1-(1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophen-3-yl)-1,1-(methyl)(2-methylphenyl)silaneamine>

Chemical Structure

[0096] (i) Production of chloro-1-(1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophen-3-yl)-1,1-(methyl)(2-methylphenyl)silane Into a 250 ml Schlenk flask, 2.0 g (1.0 eq, 9.985 mmol) of 1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophene and 50 ml of THF were added. 4.2 mL (1.05 eq, 10.484 mmol, 2.5 M in hexane) of n-BuLi was added dropwise at -30 °C, and then stirred at room temperature overnight. The stirred Li-complex THF solution was cannulated into a Schlenk flask containing 2.46 g (1.2 eq, 11.982 mmol) of dichloro(O-tolylmethyl)silane and 30 ml of THF at -78 °C, and then stirred at room temperature overnight. After stirring, it was dried under vacuum and then extracted with 100 ml of hexane.

[0097] (ii) Production of N-tert-butyl-1-(1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophen-3-yl)-1,1-(methyl)(2-methylphenyl)silaneamine 4.0 g (1.0 eq, 10.0 mmol) of the extracted chloro-1-(1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophen-3-yl)-1,1-(methyl)(2-methylphenyl)silane was stirred with 10 mL of hexane, and then 4.2 mL (4.0 eq, 40.0 mmol) of t-BuNH2 was added at room temperature and stirred overnight at room temperature. After stirring, the mixture was vacuum dried and extracted with 150 mL of hexane. After drying the solvent, 4.26 g (99%, dr = 1:0.83) of a viscous liquid was obtained.

[0098] 1 H-NMR (CDCl3, 500 MHz): δ 7.95(t, 2H), 7.70(d, 1H), 7.52(d, 1H), 7.47-7.44(m, 2H), 7.24-7.02(m, 9H), 6.97(t, 1H), 3.59(s, 1H), 3.58(s, 1H), 2.50(s, 3H), 2.44(s, 3H), 2.25(s, 3H), 2.16(s, 3H), 2.06(s, 3H), 1.56(s, 3H), 1.02(s, 9H), 0.95(s, 9H), -0.03(s, 3H), -0.11(s, 3H)

[0099] <Production of transition metal compounds> [ka]

[0100] In a 250 mL round-bottom flask, N-tert-butyl-1-(1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophen-3-yl)-1,1-(methyl)(2-methylphenyl)silanamine (4.26 g, 10.501 mmol) prepared above was added to 53 mL of MTBE (0.2 M) and stirred. n-BuLi (8.6 mL, 21.52 mmol, 2.05 eq, 2.5 M in hexane) was added at -40 °C and stirred overnight at room temperature.

[0101] Then, MeMgBr (8.8 ml, 26.25 mmol, 2.5 eq, 3.0 M in diethyl ether) was slowly added dropwise at -40°C, followed by TiCl (10.50 ml, 10.50 mmol), and the mixture was stirred overnight at room temperature. The reaction mixture was then filtered with hexane.

[0102] DME (3.3 ml, 31.50 mmol) was added to the filtrate, and the solution was filtered with hexane and concentrated to give 3.42 g (68%, dr=1:0.68) of a yellow solid.

[0103] 1 H NMR(CDCl3, 500 MHz): δ 7.83(d, 1H), 7.80(d, 1H), 7.74(d, 1H), 7.71(d, 1H), 7.68(d, 1H), 7.37(d, 1H), 7.31-6.90(m, 9H), 6.84(t, 1H), 2.54(s, 3H), 2.47(s, 3H), 2.31(s, 3H), 2.20(s, 3H), 1.65(s, 9H), 1.63(s, 9H), 1.34(s, 3H), 1.00(s, 3H), 0.98(s, 3H), 0.81(s, 3H), 0.79(s, 3H), 0.68(s, 3H), 0.14(s, 3H), -0.03(s, 3H)

[0104] Production Example 3: Production of ethylene / alpha-olefin copolymer A 1.5 L continuous reactor was preheated to 150°C while being charged with 7 kg / h of hexane solvent and 1.05 kg / h of 1-butene. A triisobutylaluminum compound (0.05 mmol / min), a mixture of transition metal compound 1 obtained in Preparation Example 1 and transition metal compound 2 obtained in Preparation Example 2 in a 2.3:1 molar ratio, and dimethylanilinium tetrakis(pentafluorophenyl)borate cocatalyst (1.5 μmol / min) were simultaneously charged to the reactor in an equivalent ratio of 1:1.2. Ethylene (0.87 kg / h), butene (1.05 kg / h), and hydrogen gas (20 cc / min) were then charged to the reactor. A copolymerization reaction was carried out at 135.0°C in a continuous process under a pressure of 89 bar for at least 60 minutes, yielding a copolymer. The copolymer was then dried in a vacuum oven for at least 12 hours and its physical properties were measured.

[0105] The following Table 1 shows the physical properties of the ethylene / alpha-olefin copolymer produced in Production Example 3. The physical properties of the copolymer were measured as follows.

[0106] 1) Density Measurement was carried out in accordance with ASTM D-792-20.

[0107] 2) Melt index (MI) and melt flow rate ratio (MFRR) ASTM D-1238-04 [Condition E, MI 10 (190℃, 10kg load), MI 2.16 (190°C, 2.16 kg load)] 10 and M.I. 2.16 Measure MI 2.16 The melt index was then calculated. 10 MI 2.16 The melt flow rate ratio (MFRR) was calculated by dividing the melt flow rate by the melt flow rate.

[0108] [Table 1]

[0109] Example 1 A mixture of 99.9% by weight of the ethylene / alpha-olefin copolymer obtained in Preparation Example 3 and 0.1% by weight of porous silica (oil absorption 149 mL / 100 g, specific pore volume 0.82 mL / g, average particle size D 50 2.13μm, specific surface area 554m 2 The resulting sample was extrusion blended with 500 g of tert-butyl 1-(2-ethylhexyl) monoperoxycarbonate (TBEC) at 1.3 phr (parts per hundred rubber), triallyl isocyanurate (TAIC) at 0.65 phr, and methacryloxypropyltrimethoxysilane (MEMO) at 0.26 phr. The pellets were then impregnated with the additives while stirring at 40 rpm.

[0110] Thereafter, an encapsulant film having an average thickness of 550 μm was produced using a T-die extruder at a low temperature (extruder barrel temperature of 100° C. or less) that would not cause high-temperature crosslinking.

[0111] The crosslinking agent was impregnated using a planetary mixer manufactured by Thermo Electron (Karlsruhe) GmbH. 500 g of ethylene / alpha-olefin copolymer was mixed with 0.5 phr of triallyl isocyanurate (TAIC) and 0.2 phr of methacryloxypropyltrimethoxysilane (MEMO), and the mixture was stirred at 40 rpm at 40°C for a sufficient time to allow the crosslinking additive to be absorbed into the ethylene / alpha-olefin copolymer. The torque change over time was monitored, and the impregnation was terminated after a sudden increase in torque.

[0112] Example 2 A mixture of 99.7% by weight of the ethylene / alpha-olefin copolymer obtained in Preparation Example 3 and 0.3% by weight of porous silica (oil absorption 152 mL / 100 g, specific pore volume 0.78 mL / g, average particle size D 50 2.10μm, specific surface area 552m 2 An encapsulant film was produced in the same manner as in Example 1, except that a cellulose acylate film (1 / g) was used.

[0113] Example 3 A mixture of 99.5% by weight of the ethylene / alpha-olefin copolymer obtained in Preparation Example 3 and 0.5% by weight of porous silica (oil absorption 148 mL / 100 g, specific pore volume 0.83 mL / g, average particle size D 50 2.16μm, specific surface area 556m 2 An encapsulant film was produced in the same manner as in Example 1, except that a cellulose acylate film (1 / g) was used.

[0114] Example 4 A mixture of 99.3 wt % of the ethylene / alpha-olefin copolymer obtained in Preparation Example 3 and 0.7 wt % of porous silica (oil absorption 146 mL / 100 g, specific pore volume 0.84 mL / g, average particle size D 50 2.11μm, specific surface area 557m 2 An encapsulant film was produced in the same manner as in Example 1, except that a cellulose acylate film (1 / g) was used.

[0115] Example 5 A mixture of 99.0% by weight of the ethylene / alpha-olefin copolymer obtained in Preparation Example 3 and 1.0% by weight of porous silica (oil absorption 150 mL / 100 g, specific pore volume 0.79 mL / g, average particle size D 50 2.06μm, specific surface area 549m 2 An encapsulant film was produced in the same manner as in Example 1, except that a cellulose acylate film (1 / g) was used.

[0116] Comparative Example 1 An encapsulant film was produced in the same manner as in Example 1, except that 100% by weight of the ethylene / alpha-olefin copolymer obtained in Production Example 3 was used.

[0117] Comparative Example 2 A mixture of 98.0% by weight of the ethylene / alpha-olefin copolymer obtained in Preparation Example 3 and 2.0% by weight of porous silica (oil absorption 145 mL / 100 g, specific pore volume 0.85 mL / g, average particle size D 50 2.07μm, specific surface area 552m 2 An encapsulant film was produced in the same manner as in Example 1, except that a cellulose acylate film (1 / g) was used.

[0118] Comparative Example 3 A mixture of 95.0% by weight of the ethylene / alpha-olefin copolymer obtained in Preparation Example 3 and 5.0% by weight of porous silica (oil absorption 141 mL / 100 g, specific pore volume 0.85 mL / g, average particle size D 50 2.14μm, specific surface area 556m 2 An encapsulant film was produced in the same manner as in Example 1, except that a cellulose acylate film (1 / g) was used.

[0119] Experimental Example 1: Method for measuring the physical properties of silica The physical properties of the silica used in the examples and comparative examples were measured by the following methods before use.

[0120] (1) Oil absorption amount (mL / 100g) The oil absorption of the porous silica was measured by a method according to JIS K5101.21.

[0121] (2) Specific pore volume (mL / g) The BET specific surface area was measured using a BELSORP-mini II (model name) manufactured by BEL Japan. To remove moisture, a load and filter were attached to an empty sample cell, which was then vacuum-treated at 150°C and cooled to room temperature. The weight of the sample cell (a) was measured. At least 0.05 g of sample was placed in the cell, and the load and filter were attached. The weight was measured, followed by vacuum treatment at 150°C for 1 hour. After purging at room temperature and atmospheric pressure, the weight of the sample cell containing the sample (b) was measured. The accurate sample weight (ba) obtained in the previous step was entered, and measurements were performed under the following conditions: Ads Temp (77 K), Sat. Vapor Pressure (Actual Measure), Adsorptive (n2), sample cell diameter (7.0 mm), Molecular Diameter (0.364 nm), Glass Rod D (6.0 mm), and Ads. P / P0 upper limit (0.3). After the measurement, the amount of nitrogen gas adsorption was determined, and the results of nitrogen gas adsorption / desorption (P / P0, range of 0.1 to 0.99) were calculated by a predetermined method to calculate the specific pore volume.

[0122] (3) Average particle size (μm) Measurements were performed using a SYMPA TEC HELOS KR VIBRI RODOS M (model name). The R4 lens, which can measure particle sizes in the 0.5 to 350 μm range, was used to select the appropriate trigger condition for the sample. First, a reference measurement was performed without adding a sample to adjust the instrument's zero point, and then 0.1 to 0.3 g of sample was placed in the funnel and measurement began. When the measurement was completed, D 50 Gets the value and span value.

[0123] (4) Specific surface area (m 2 / g) The BET specific surface area was measured using a BELSORP-mini II (model name) manufactured by BEL Japan. To remove moisture, a load and filter were attached to an empty sample cell, which was then vacuum-treated at 150°C and cooled to room temperature, and the weight of the sample cell (a) was measured. At least 0.05 g of sample was placed in the cell, and the load and filter were attached. The weight was measured, and the cell was vacuum-treated at 150°C for 1 hour. After purging at room temperature and atmospheric pressure, the weight of the sample cell containing the sample (b) was measured. The accurate sample weight (ba) obtained in the previous step was entered, and measurements were performed under the following conditions: Ads Temp (77 K), Sat. vapor pressure (actual measure), Adsorptive (N2), sample cell diameter (7.0 mm), Molecular Diameter (0.364 nm), Glass rod D (6.0 mm), and Ads. P / P0 upper limit (0.3). After the measurement, the amount of nitrogen gas adsorption was determined and the BET specific surface area was calculated.

[0124] (5) Silanol group -OH content (wt%) Measurements were performed using a Mettler Toledo TGA. A pan was placed in the autosampler, the tare function was activated to zero the instrument, and 4-6 mg of sample was weighed and placed in the pan. Measurements were performed under N2 gas flow at 50 mL / min, starting from an initial stabilization temperature of 30°C and increasing the temperature by 30°C per minute to 150°C. The temperature was maintained at 150°C for 30 minutes, and after completely removing any remaining moisture, it was increased by 30°C per minute to 950°C.

[0125] The weight (c) of silica excluding water other than the weight (b) that decreased from 30°C to 150°C from the total weight (a) of silica was calculated. The weight (d) that decreased from 150°C to 950°C was divided by the weight (c) of silica excluding water to measure the -OH group content of silanol groups in the silica.

[0126] [Table 2]

[0127] Experimental Example 2: Si-O band integral value / CH band integral value The ethylene / alpha-olefin copolymers used in the examples and comparative examples were prepared into sheets of approximately 0.5 mm thickness by T-die molding without the use of a crosslinking agent, and then analyzed in transmission mode using an Invenio S (Bruker) FT-IR. The sample was placed in a 10 mm aperture and then irradiated with 4 cm -1 Resolution, 32 average, wavenumber 400cm -1 From 4000cm -1 The infrared absorptivity of the region was measured. After determining the silica characteristic peak area for each sample, the normalized Si-O band area was calculated by dividing it by the reference peak area corresponding to the C-H band to correct for thickness deviation.

[0128] Here, the integration method is as follows: Si-O band has a wavenumber of 1247 cm -1 From 1016cm -1 The area is integrated and the CH band is at 2110 cm -1 From 1975cm -1 The area was integrated.

[0129] [Table 3]

[0130] As shown in Table 3, Examples 1 to 5 are compositions for encapsulant films having an integral ratio of 3 to 70, while Comparative Examples 1 to 3 are outside this range.

[0131] Experimental Example 3 (1) Crosslinking agent migration rate The encapsulant films (10 cm x 10 cm) prepared in the examples and comparative examples were left in a chamber at -5°C for one week to promote migration of the crosslinker. The encapsulant films were washed with cold MeOH, and the additives migrated to the surface of the encapsulant films were washed with MeOH.

[0132] The MeOH used to wash the encapsulant film was vacuum distilled to evaporate the solvent, and the residue, the transferred crosslinker, was obtained. The weight of the crosslinker was measured and divided by the weight of the crosslinker added in the Examples and Comparative Examples to calculate the transferred ratio (Equation 1 below).

[0133] [Mathematical formula 1] Crosslinking agent migration rate (%) = [weight of crosslinking agent migrated to the surface of the encapsulant film / total weight of crosslinking agent] x 100

[0134] In the above mathematical formula 1, The weight of the crosslinking agent transferred to the surface of the film is a value measured after preparing an encapsulant film using the composition for an encapsulant film, storing the encapsulant film at −5° C. for 1 week, and The total weight of the crosslinking agent is the total weight of the crosslinking agent contained in the encapsulant film.

[0135] (2) Slip resistance The encapsulant films (10 cm x 10 cm) prepared in the examples and comparative examples were left in a chamber at -5°C for one week to promote migration of the additives. The encapsulant films were then removed from the chamber and placed on a glass substrate (3.2T embossed low-iron glass) tilted at a 45° angle. The distance traveled in one minute was measured and shown in Table 5 below. The migrated crosslinker composition accelerates the slippage of the encapsulant film, so the more the migrated crosslinker, the greater the migration distance of the encapsulant film.

[0136] (3) Impregnation time When ethylene / alpha-olefin copolymer pellets and three liquid crosslinking agent components are mixed in a planetary mixer, the crosslinking agent acts as a lubricant before it is completely absorbed into the pellets, and the torque value (Nm) applied to the mixing blade remains constant over the soaking time. After that, when the crosslinking agent is completely absorbed into the pellets, the lubricating effect of the crosslinking agent disappears and the torque value applied to the mixing blade rises sharply; the inflection point at this point was defined as the impregnation completion time.

[0137] Here, after soaking was performed until the impregnation completion time, the impregnation rate was calculated and confirmed to be 99% or more, thereby cross-validating whether the impregnation completion time was measured appropriately.

[0138] [Formula 1] Impregnation rate (%) = {1-(W2-W3) / W1} x 100

[0139] W1 (g) = total weight of the crosslinker composition charged W2 (g) = weight of the dust-free cloth used to wipe the mixing bowl, mixing blade, and soaked pellets after the impregnation experiment is completed W3 (g) = weight of the dust-free cloth before starting the impregnation experiment and before wiping the mixing bowl, mixing blade, and soaked pellets

[0140] [Table 4]

[0141] As shown in Table 4 above, it was found that the composition for an encapsulant film of Comparative Example 1 had a high migration rate of the crosslinking agent and a long slip migration distance.

[0142] Experimental Example 4 (1) Lamination process After crosslinking the encapsulant film, a lamination process was carried out to measure the optical properties and volume resistivity. Specifically, the process was continued at a temperature of 150°C for a total of 20 minutes (vacuum 5 minutes / pressure 1 minute / pressure sustained 14 minutes) to obtain a laminated sheet.

[0143] (2) Light transmittance The light transmittance of the laminated sheet in the visible light region (380 to 1,100 nm) was measured using a Shimadzu UV-3600 spectrophotometer (measurement mode: transmittance, wavelength interval: 1 nm, measurement speed: medium).

[0144] (3) Haze According to the American Society for Testing and Materials standard ASTM D1003-21, the degree of light refraction (%) when light was projected onto the laminated sheet at 1T (1 mm) was measured. Haze was measured as the transparency of the test piece by Td (refracted light) / Tt (transmitted light) × 100 (%).

[0145] (4) Volume resistivity According to the American Society for Testing and Materials standard ASTM D257-07, the laminated sheet 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 test fixture.

[0146] (5) Crosslinking properties Crosslinking properties were measured using an Alpha Technologies Premier MDR in accordance with ASTM D5289-19A. The test was conducted at 150°C for 20 minutes, and a torque curve was obtained over time. Here, 150°C corresponds to the lamination temperature, and 20 minutes corresponds to the lamination time. Furthermore, the difference between the maximum torque (MH) and minimum torque (ML) applied by the MDR during that time was used to compare the crosslinking properties of the samples.

[0147] [Table 5]

[0148] As shown in Table 5, the compositions for encapsulant films of Comparative Examples 2 and 3 had low light transmittance and high haze, making them unsuitable for use as encapsulant films, and also showed poor crosslinking properties. In addition, the compositions for encapsulant films of Examples 1 to 5 according to the present invention exhibited superior volume resistivity compared to Comparative Example 1.

Claims

1. A composition for an encapsulant film, which has a ratio of Si—O band integral to C—H band integral (Si—O band integral / C—H band integral) of 3 to 70 when calculated from an FT-IR spectrum.

2. 2. The composition for an encapsulant film according to claim 1, wherein when an encapsulant film is produced using the composition for an encapsulant film and the crosslinking agent, the crosslinking agent has a migration rate of 4.5% or less, as represented by the following mathematical formula 1: [Mathematical formula 1] Transfer rate of crosslinking agent (%) = [weight of crosslinking agent transferred to the surface of the sealing material film / total weight of crosslinking agent] x 100 In the above mathematical formula 1, The weight of the crosslinking agent transferred to the surface of the film is a value measured after producing an encapsulant film using the composition for an encapsulant film and storing it at −5° C. for 1 week. The total weight of the crosslinking agent is the total weight of the crosslinking agent contained in the encapsulant film.

3. 2. The composition for sealing material films according to claim 1, wherein the ratio of Si—O band integral to C—H band integral (Si—O band integral / C—H band integral) is 4 to 60 when calculated from an FT-IR spectrum.

4. The composition for sealing material films according to claim 1, wherein the migration rate of the crosslinking agent is 0.1 to 4.3%.

5. The composition for a sealant film according to claim 1, comprising an ethylene / alpha-olefin copolymer and porous silica.

6. The composition for sealing material films according to claim 5, wherein the porous silica has an oil absorption of more than 40 mL / 100 g as measured in accordance with ASTM D1483-12 (2016).

7. The composition for a sealing material film according to claim 5, wherein the porous silica has a —OH content of silanol groups of 1.0 wt % or more based on the total weight of the porous silica.

8. 2. The composition for an encapsulant film according to claim 1, further comprising one or more selected from the group consisting of an organic peroxide, a crosslinking aid, a silane coupling agent, an unsaturated silane compound, an aminosilane compound, a light stabilizer, a UV absorber, and a heat stabilizer.

9. A sealant film comprising the sealant film composition according to any one of claims 1 to 8.

10. A solar cell module comprising the encapsulant film of claim 9.