Solar cell encapsulant

Abstract

We provide a solar cell encapsulant that offers an excellent balance between transparency and water vapor barrier properties. [Solution] A specific ethylene-α-olefin copolymer (A) that satisfies specific requirements (1) and (2), and a specific ethylene-α-olefin copolymer (B) that satisfies specific requirements (1') and (2'), wherein the mass fraction (W) of the ethylene-α-olefin copolymer (A) A ) is 20% by mass or more and 99% by mass or less, and the mass fraction (W) of the ethylene-α-olefin copolymer (B) B ) is 1% by mass or more and 80% by mass or less (however, W A and W B The sum of these is 100% by mass.) A solar cell encapsulant containing an ethylene-based resin composition (Z).

Description

[Technical Field]

[0001] This invention relates to a solar cell encapsulant. [Background technology]

[0002] In recent years, the use of renewable energy has been increasing from the perspective of reducing greenhouse gas emissions and protecting the environment. In particular, the amount of electricity generated by solar power has grown significantly, and currently, solar cell modules of various forms are being developed and proposed. Generally, a solar cell module has a structure in which a transparent front substrate made of glass or the like, solar cell elements, and a protective sheet on the back are laminated together with a sealing material in between.

[0003] Ethylene-vinyl acetate copolymer (EVA) film, which has high transparency and adhesive properties, has traditionally been used as a encapsulant for solar cell modules. However, EVA tends to gradually decompose with long-term use, and can generate acetic acid gas that can affect solar cell elements. For this reason, in recent years, the demand for encapsulants using polyolefins instead of EVA has been expanding. Encapsulators made primarily of polyolefin do not contain polar groups in the molecular structure of the polymer, and therefore do not produce decomposition products that affect solar cell elements, resulting in superior long-term durability compared to solar cell encapsulants made of EVA. Against this backdrop, various polyolefin-based encapsulating materials have been disclosed. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2012 / 050093 [Patent Document 2] Japanese Patent Publication No. 2013-21082 [Patent Document 3] Japanese Patent Publication No. 2016-213401 [Patent Document 4] Japanese Patent Publication No. 2012-49467 [Patent Document 5] Japanese Patent Publication No. 2017-120892 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Attempts are being made to improve the water vapor barrier properties of polyolefin-based solar cell encapsulants. While increasing the density of polyolefin improves its water vapor barrier properties, this also reduces transparency. Therefore, there is a trade-off between water vapor barrier properties and transparency, and there is a demand for improvements in both transparency and water vapor barrier properties.

[0006] The present invention aims to provide a solar cell encapsulant that offers a superior balance of transparency and water vapor barrier properties compared to conventionally known polyolefin-based solar cell encapsulants. [Means for solving the problem]

[0007] In view of the above circumstances, the inventors conducted diligent research and found that a solar cell encapsulant comprising an ethylene-α-olefin copolymer (A) having specific melting properties and density range, and an ethylene-based resin composition (Z) containing an ethylene-α-olefin copolymer (B) that is denser than ethylene-α-olefin copolymer (A) and has a specific density range, exhibits an excellent balance between transparency and water vapor barrier properties, thus completing the present invention.

[0008] The present invention, for example, includes the following: <1> ~ <4> Regarding. <1> An ethylene-α-olefin copolymer (A) is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, satisfying the following requirements (1) and (2), A copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, comprising an ethylene-α-olefin copolymer (B) that satisfies the following requirements (1') and (2'), The mass fraction (W) of the ethylene-α-olefin copolymer (A) A ) is between 20% by mass and 99% by mass, The mass fraction (W B ) of the ethylene-α-olefin copolymer (B) is 1% by mass or more and 80% by mass or less (however, the total of W A and W B is 100% by mass).) An ethylene-based resin composition (Z), A solar cell encapsulant containing the same. (1) The density is in the range of 860 kg / m 3 or more and less than 885 kg / m 3 . (2) The melt flow rate (MFR) at a load of 2.16 kg at 190 °C is in the range of 0.1 g / 10 min or more and 100.0 g / 10 min or less. (1’) The density is in the range of 885 kg / m 3 or more and 915 kg / m 3 or less. (2’) The melt flow rate (MFR) at a load of 2.16 kg at 190 °C is in the range of 0.1 g / 10 min or more and 100 g / 10 min or less.

[0009] <2> The solar cell encapsulant according to <1>, wherein the ethylene-α-olefin copolymer (B) further satisfies the following requirements (3’) and (4’). (3’) In cross-fractionation chromatography (CFC) measurement, the ratio (X) of the components eluting at 75 °C or higher is 0.5% by mass or more and 30% by mass or less. (4’) In cross-fractionation chromatography (CFC) measurement, the ratio (Mw X ) of the weight-average molecular weight of the components eluting at 75 °C or higher to the weight-average molecular weight (Mw T ) of the entire sample is less than 1. X / Mw T )

[0010] <3> The solar cell encapsulant according to <1> or <2>, wherein the ethylene-α-olefin copolymer (B) further satisfies the following requirement (5’). (5’) In the elution curve obtained from cross-fractionation chromatography (CFC) measurement, the half-width (temperature width at peak height 1 / 2) of the highest elution peak is 5 °C or more and 35 °C or less.

[0011] <4> <1> ~ <3> A solar cell module comprising a solar cell encapsulant as described in any one of the following. [Effects of the Invention]

[0012] According to one embodiment of the present invention, a solar cell encapsulant is provided that offers a superior balance between transparency and water vapor barrier properties compared to conventionally known polyolefin-based solar cell encapsulants. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a graph plotting the water vapor transmission rate and total light transmission rate of sheet samples from Examples 1-6 and Comparative Examples 1-2. [Modes for carrying out the invention]

[0014] [Ethylene-based resin composition (Z)] The ethylene-based resin composition (Z) contained in the solar cell encapsulant according to the present invention comprises an ethylene-α-olefin copolymer (A) which is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms that satisfies the following requirements (1) and (2), and an ethylene-α-olefin copolymer (B) which is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms that satisfies the following requirements (1') and (2'), The mass fraction (W) of the ethylene-α-olefin copolymer (A) A ) is 20% by mass or more and 99% by mass or less, and the mass fraction (W) of the ethylene-α-olefin copolymer (B) B ) is 1% by mass or more and 80% by mass or less (however, W A and W B (Assume the total is 100% by mass). A solar cell encapsulant containing the ethylene-based resin composition (Z) having the above configuration exhibits superior transparency and water vapor barrier properties compared to conventionally known polyolefin-based solar cell encapsulants. The reason for this superior transparency and water vapor barrier properties compared to conventionally known polyolefin-based solar cell encapsulants is not clear, but the following mechanism is hypothesized. Ethylene-α-olefin copolymer (A) is a low-density polymer with excellent transparency. On the other hand, ethylene-α-olefin copolymer (B) is slightly denser than ethylene-α-olefin copolymer (A), but the density difference is not significant enough to impair the transparency of ethylene-α-olefin copolymer (A). Furthermore, when ethylene-α-olefin copolymer (B) is mixed with ethylene-α-olefin copolymer (A), it has a density that does not significantly impair the transparency of the mixture, while still containing a moderate amount of high-melting-point components. Moreover, the weight-average molecular weight of these high-melting-point components is low compared to the weight-average molecular weight of the entire ethylene-α-olefin copolymer (B), thus effectively generating the high-melting-point components necessary for exhibiting water vapor barrier properties.

[0015] The following describes in detail the ethylene-α-olefin copolymer (A) and ethylene-α-olefin copolymer (B), which are constituent components of the ethylene-based resin composition (Z) according to the present invention.

[0016] <Ethylene-α-olefin copolymer (A)> The ethylene-α-olefin copolymer (A) is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, preferably a random copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms.

[0017] Examples of α-olefins having 3 to 10 carbon atoms include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 1-decene. From the viewpoint of having excellent strength, moldability, water vapor barrier properties, and transparency of the solar cell encapsulant molded from the resulting ethylene-based resin composition (Z), among these α-olefins having 3 to 10 carbon atoms, α-olefins having 4 to 10 carbon atoms are preferred, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 1-decene are more preferred, and 1-butene and 1-hexene are even more preferred.

[0018] The ethylene content (content of constituent units derived from ethylene) in the ethylene-α-olefin copolymer (A) is preferably 50 mol% or more, more preferably 70 mol% to 95 mol%, and even more preferably 80 mol% to 90 mol%. In the ethylene-α-olefin copolymer (A), preferably, the content of constituent units derived from ethylene and the content of constituent units derived from α-olefins having 3 to 10 carbon atoms are 100 mol%.

[0019] The ethylene-α-olefin copolymer (A) satisfies the following requirements (1) and (2). <<Requirement (1)>> (1) Density is 860 kg / m³ 3 More than 885kg / m 3 It is within the range of less than. Density is 860 kg / m³ 3 In the above case, the water vapor barrier properties of the solar cell encapsulant molded from the ethylene-based resin composition (Z) are good, and the density is 890 kg / m³. 3 If the density is less than 865 kg / m³, the transparency of the solar cell encapsulant molded from the ethylene-based resin composition (Z) is good. From the above viewpoint, the density of the ethylene-α-olefin copolymer (A) is preferably 865 kg / m³. 3 More than 885kg / m 3 Less than, more preferably 868 kg / m³ 3 More than 885kg / m 3 Less than 870 kg / m³, most preferably 870 kg / m³ 3 More than 882kg / m 3 It is within the range of less than.

[0020] The density of ethylene-α-olefin copolymer (A) typically depends on the α-olefin content (content of constituent units derived from α-olefins with 3 to 10 carbon atoms) in the ethylene-α-olefin copolymer (A), with a tendency for the density to be higher as the α-olefin content decreases and a tendency for the density to be lower as the α-olefin content increases. The α-olefin content of ethylene-α-olefin copolymer (A) can be determined by the composition ratio of α-olefin to ethylene (α-olefin / ethylene) in the polymerization system (for example, Walter Kaminsky, Makromol. Chem. 193, p.606 (1992)). Therefore, by increasing or decreasing the α-olefin / ethylene ratio, ethylene-α-olefin copolymer (A) having a density within the above range can be obtained.

[0021] The density is measured as follows: The ethylene-α-olefin copolymer (A) strands obtained during melt flow rate (MFR) measurement are left at room temperature for 1 hour and then measured using the density gradient tube method.

[0022] <<Requirement (2)>> (2) The melt flow rate (MFR) at 190°C with a 2.16 kg load is 0.1 g / 10 min or more and 100 g / 10 min or less. When the melt flow rate (MFR) is 0.1 g / 10 min or higher, the shear viscosity of the ethylene-based resin composition (Z) is not too high, and the extrusion load is good. When the melt flow rate (MFR) is 100 g / 10 min or lower, the mechanical strength of the solar cell encapsulant obtained from the ethylene-based resin composition (Z) is good. From the above viewpoint, the ethylene-α-olefin copolymer (A) is preferably in the range of 0.5 g / 10 min to 80.0 g / 10 min, and more preferably in the range of 1.0 g / 10 min to 50 g / 10 min.

[0023] The melt flow rate (MFR) of ethylene-α-olefin copolymer (A) is strongly dependent on molecular weight; a smaller melt flow rate (MFR) tends to correlate with a larger molecular weight, while a larger melt flow rate (MFR) tends to correlate with a smaller molecular weight. Generally, the molecular weight of ethylene-based polymers is known to be determined by the composition ratio of hydrogen to ethylene (hydrogen / ethylene) within the polymerization system (for example, Kazuo Soga et al., eds., "Catalytic Olefin Polymerization," Kodansha Scientific, 1990, p. 376). Therefore, by increasing or decreasing the hydrogen / ethylene ratio within the polymerization system when polymerizing ethylene-α-olefin copolymer (A), it is possible to increase or decrease the melt flow rate (MFR) of the ethylene-α-olefin copolymer (A).

[0024] The melt flow rate (MFR) of ethylene-α-olefin copolymer (A) is determined by measurement under conditions of 190°C and a 2.16 kg load, in accordance with JIS K 7210.

[0025] The above ethylene-α-olefin copolymer (A) may contain constituent units derived from biomass-derived monomers (ethylene, α-olefin). The monomers constituting the ethylene-α-olefin copolymer (A) may consist only of biomass-derived monomers, only of fossil fuel-derived monomers, or both of biomass-derived monomers and fossil fuel-derived monomers. The above biomass-derived monomers are monomers derived from any renewable natural raw materials and their residues, including fungi, yeasts, algae, and bacteria, whether plant-derived or animal-derived, and are carbon-based. 14 1 × 10¹¹ C isotopes -12 It contains a certain proportion, and the biomass carbon concentration (pMC) measured in accordance with ASTM D 6866 is about 100 (pMC). Biomass-derived monomers are obtained by conventionally known methods. It is preferable from the viewpoint of reducing environmental impact (mainly greenhouse gas reduction) that the above ethylene-α-olefin copolymer (A) contains constituent units derived from biomass-derived monomers. Even if biomass-derived monomers are included as raw material monomers for ethylene-α-olefin copolymer (A), if the polymer production conditions such as polymerization catalyst and polymerization process temperature are the same, 14 1 × 10¹¹ C isotopes -12~1 × 10 -14 Aside from the small proportions it contains, its molecular structure is equivalent to that of an ethylene-α-olefin copolymer containing only constituent units derived from fossil fuel monomers. Therefore, its performance is considered to be the same.

[0026] The above ethylene-α-olefin copolymer (A) may contain constituent units derived from chemically recycled monomers (e.g., ethylene, α-olefin, etc.). The monomers constituting the ethylene-α-olefin copolymer (A) may consist solely of chemically recycled monomers, solely of fossil fuel-derived monomers, or a mixture of chemically recycled monomers, fossil fuel-derived monomers, and / or biomass-derived monomers. Chemically recycled monomers are obtained by conventionally known methods. It is preferable for the above ethylene-α-olefin copolymer (A) to contain constituent units derived from chemically recycled monomers from the viewpoint of reducing environmental impact (mainly waste reduction). Chemical recycling-derived monomers are monomers obtained by depolymerizing polymers such as waste plastics, reducing them back to monomer units such as ethylene through thermal decomposition, etc., as well as monomers produced using such monomers as raw materials. Therefore, even if chemical recycling-derived monomers are included as raw material monomers in ethylene-α-olefin copolymer (A), if the polymer production conditions such as polymerization catalyst, polymerization process, and polymerization temperature are the same, the molecular structure will be equivalent to that of ethylene-α-olefin copolymer containing only constituent units derived from fossil fuel-derived monomers. Consequently, the performance is also considered to be unchanged.

[0027] <Method for producing ethylene-α-olefin copolymer (A)> The ethylene-α-olefin copolymer (A) can be obtained by polymerizing ethylene with an α-olefin having 3 to 10 carbon atoms. The polymerization conditions, including the polymerization catalyst used, are not particularly limited, as long as a polymer satisfying requirements (1) and (2) above, and other requirements as needed, can be obtained. For example, the ethylene-α-olefin copolymer (A) can be polymerized by polymerizing ethylene with an α-olefin having 3 to 10 carbon atoms using a single-site catalyst such as a metallocene catalyst. A co-catalyst may also be used in combination with the catalyst as needed. Polymerization can be carried out, for example, by gas-phase polymerization or solution polymerization.

[0028] Furthermore, as the ethylene-α-olefin copolymer (A), commercially available products such as linear low-density polyethylene and ethylene-α-olefin copolymers can be used. Specific examples of commercially available products include Tuffmer (registered trademark) manufactured by Mitsui Chemicals, Inc. and Kernel (registered trademark) manufactured by Nippon Polyethylene Co., Ltd., which can be used as the ethylene-α-olefin copolymer (A) if they satisfy the above requirements (1) and (2).

[0029] Furthermore, the ethylene-α-olefin copolymer (A) may be a so-called modified ethylene-α-olefin copolymer in which a part of the molecular structure of the ethylene-α-olefin copolymer has been modified by various reactions. However, an unmodified ethylene-α-olefin copolymer is preferred because it is easier to obtain a solar cell encapsulant with an excellent balance between transparency and water vapor barrier properties.

[0030] <Ethylene-α-olefin copolymer (B)> The ethylene-α-olefin copolymer (B) is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, and is preferably a random copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms. Examples of α-olefins having 4 to 10 carbon atoms include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 1-decene. From the viewpoint of having excellent strength, moldability, water vapor barrier properties, and transparency of the solar cell encapsulant molded from the resulting resin composition (Z), ethylene and α-olefins having 4 to 8 carbon atoms are preferred as the above-mentioned α-olefins having 4 to 10 carbon atoms, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene are more preferred, 1-butene, 1-hexene, and 1-octene are even more preferred, and 1-butene and 1-hexene are even more preferred.

[0031] The ethylene content (content of constituent units derived from ethylene) in the ethylene-α-olefin copolymer (B) is preferably 50 mol% or more, more preferably 80 mol% to 98 mol%, and even more preferably 90 mol% to 98 mol%. In the ethylene-α-olefin copolymer (B), preferably, the content of constituent units derived from ethylene and the content of constituent units derived from α-olefins having 3 to 10 carbon atoms are 100 mol%.

[0032] The ethylene-α-olefin copolymer (B) satisfies the following requirements (1') and (2'). <<Requirement (1')>> (1') Density 885 kg / m³ 3 More than 915kg / m 3 The following applies: The density of ethylene-α-olefin copolymer (B) is 885 kg / m³. 3 The above conditions result in good water vapor barrier properties for solar cell encapsulants molded from ethylene-based resin composition (Z). Furthermore, the density is 915 kg / m³. 3 The transparency of the solar cell encapsulant molded from the ethylene-based resin composition (Z) is good if the following conditions are met. From the above viewpoint, the density of the ethylene-α-olefin copolymer (B) is preferably 890 kg / m³. 3 More than 915kg / m 3 The following is more preferable: 892 kg / m 3 More than 912kg / m 3 The following is most preferably 892 kg / m 3 More than 908kg / m 3 It is within the following range.

[0033] The density of ethylene-α-olefin copolymer (B) typically depends on the α-olefin content (the amount of constituent units derived from α-olefins with 4 to 10 carbon atoms) in the ethylene-α-olefin copolymer (B), with a lower α-olefin content resulting in a higher density, and a higher α-olefin content resulting in a lower density. The α-olefin content of ethylene-α-olefin copolymer (B) can be determined by the composition ratio of α-olefin to ethylene (α-olefin / ethylene) in the polymerization system (for example, Walter Kaminsky, Makromol. Chem. 193, p.606 (1992)). Therefore, by increasing or decreasing the α-olefin / ethylene ratio, ethylene-α-olefin copolymer (B) having a density within the above range can be obtained.

[0034] The density is measured as follows: The ethylene-α-olefin copolymer (B) strands obtained during melt flow rate (MFR) measurement are left at room temperature for 1 hour and then measured using the density gradient tube method.

[0035] <<Requirement (2')>> (2') The melt flow rate (MFR) at 190°C with a 2.16 kg load is between 0.1 g / 10 min and 100 g / 10 min. When the melt flow rate (MFR) is 0.1 g / 10 min or higher, the shear viscosity of the ethylene-based resin composition (Z) is not too high, and the extrusion load is good. When the melt flow rate (MFR) is 100 g / 10 min or lower, the mechanical strength of the solar cell encapsulant obtained from the ethylene-based resin composition (Z) is good. From the above viewpoint, the ethylene-α-olefin copolymer (B) is preferably in the range of 0.1 g / 10 min to 50 g / 10 min, more preferably 1.0 g / 10 min to 50 g / 10 min, and most preferably 1.0 g / 10 min to 20 g / 10 min.

[0036] The melt flow rate (MFR) of ethylene-α-olefin copolymer (B) is strongly dependent on molecular weight; a smaller melt flow rate (MFR) tends to correlate with a larger molecular weight, while a larger melt flow rate (MFR) tends to correlate with a smaller molecular weight. Similar to the case of ethylene-α-olefin copolymer (A), the melt flow rate (MFR) of ethylene-α-olefin copolymer (B) can be increased or decreased by increasing or decreasing the hydrogen-to-ethylene composition ratio (hydrogen / ethylene) in the polymerization system during polymerization of ethylene-α-olefin copolymer (B).

[0037] The melt flow rate (MFR) of ethylene-α-olefin copolymer (B) is determined by measurement under conditions of 190°C and a 2.16 kg load, in accordance with JIS K 7210.

[0038] The ethylene-α-olefin copolymer (B) preferably satisfies at least one selected from the following requirements (3') and (4'), and more preferably satisfies the following requirements (3') and (4').

[0039] <<Requirement (3')>> (3') In cross-fractional chromatography (CFC) measurement, the percentage (X) of components that elute at 75°C or higher is 0.5% by mass or more and 30% by mass or less. In cross-fractional chromatography (CFC) measurements, components that elute at temperatures above 75°C are high-melting-point components with relatively thick lamellar crystals, and are considered to be components that contribute to water vapor barrier properties. In cross-fractional chromatography (CFC) measurements of the ethylene-α-olefin copolymer (B), if the proportion of components that elute at 75°C or higher (X) is above the lower limit, the water vapor barrier properties of the solar cell encapsulant obtained from the ethylene-based resin composition (Z) are good. In cross-fractional chromatography (CFC) measurements of the ethylene-α-olefin copolymer (B), if the proportion of components that elute at 75°C or higher (X) is below the upper limit, the transparency of the solar cell encapsulant obtained from the ethylene-based resin composition (Z) is good. From the above viewpoint, the proportion of components that elute at 75°C or higher (X) in cross-fractional chromatography (CFC) measurements of the ethylene-α-olefin copolymer (B) is preferably in the range of 0.5% by mass or more and 20% by mass or less, more preferably 1.0% by mass or more and 15% by mass or less, and most preferably 1.2% by mass or more and 10% by mass or less.

[0040] In cross-fractionation chromatography (CFC) measurements, the proportion of components that elute above 75°C (X) typically depends on the density and compositional distribution of the ethylene-α-olefin copolymer. The higher the density of the ethylene-α-olefin copolymer, or the broader the compositional distribution, the greater the proportion of components that elute above 75°C (X) tends to be. As mentioned above, the density of ethylene-α-olefin copolymers typically depends on the α-olefin content. Therefore, it can be adjusted by the composition ratio of α-olefin to ethylene (α-olefin / ethylene) in the polymerization system when polymerizing ethylene-α-olefin copolymer (B). However, even if the proportion of components that elute at temperatures above 75°C in cross-fractionation chromatography (CFC) measurements (X) is adjusted by the density of ethylene-α-olefin copolymer (B), the density of ethylene-α-olefin copolymer (B) must still meet the aforementioned requirement (1').

[0041] On the other hand, the compositional distribution of the ethylene-α-olefin copolymer can be adjusted by polymerization factors such as the catalyst type, polymerization process type (gas-phase polymerization, solution polymerization, etc.), and polymerization temperature. By adjusting the compositional distribution with these polymerization factors, the proportion of components that elute at temperatures above 75°C in cross-fractional chromatography (CFC) measurements (X) can be adjusted without significantly changing the density of the ethylene-α-olefin copolymer (B). In CFC measurements, temperature is expressed as an integer. For example, under the measurement conditions shown below, the elution fraction at 75°C refers to the components that eluted between 74°C and 75°C. Furthermore, components that elute above 75°C refer to components that elute at temperatures above 75°C. For example, under the measurement conditions shown below, this refers to the total of all subsequent elution fractions, including the elution fraction at 76°C (components that eluted between 75°C and 76°C).

[0042] Cross-fractionation chromatography (CFC) is performed as follows: First, the polymer sample is completely dissolved in orthodichlorobenzene (ODCB) containing 0.5 mg / mL of BHT at 145°C. This solution is then injected through the instrument's sample loop into a TREF column (a column packed with inert glass beads) maintained at 140°C, and gradually cooled to a predetermined first elution temperature to crystallize the polymer sample. After holding at the predetermined temperature for 30 minutes, the ODCB is passed through the TREF column, injecting the eluted components into the GPC section for molecular weight fractionation, and a chromatogram is obtained using an infrared detector. Meanwhile, the TREF section is heated to the next elution temperature, and after obtaining the chromatogram at the first elution temperature, the eluted components at the second elution temperature are injected into the GPC section. The same procedure is repeated thereafter to obtain chromatograms of the eluted components at each elution temperature.

[0043] The measurement conditions for CFCs are as follows: Equipment: CFC2 type cross-fraction chromatograph (Polymer Char) Detector: IR4 type infrared spectrophotometer (Polymer Char) Detection wavelength: 3.42 μm (2920 cm)-1 ) Sample concentration: 120 mg / 30 mL Injection volume: 0.5mL Cooling rate: 1℃ / min Leaching temperature: -17°C, -15~10°C (5°C intervals), 10~40°C (2°C intervals), 40~100°C (1°C intervals), 100~140°C (20°C intervals) GPC columns: Shodex HT-806M x 3 (Showa Denko) GPC column temperature: 140℃ GPC column calibration: Monodisperse polystyrene (Tosoh) Molecular weight calibration method: General-purpose calibration method (polyethylene equivalent (K = 5.06 × 10) -4 ,α=0.7)) Mobile phase: Orthodichlorobenzene (ODCB), with added BHT. Flow rate: 1.0mL / mL

[0044] From the chromatograms of the eluted components at each elution temperature obtained by measurement, the normalized elution amount (proportional to the area of ​​the chromatogram) is determined so that the sum equals 100%. Furthermore, an integral elution curve with respect to elution temperature is calculated. By differentiating this integral elution curve with respect to temperature, the differential elution curve is obtained. In addition, the molecular weight of the fractions eluted at each temperature is measured, and the PE-equivalent molecular weight is determined using a general-purpose calibration curve. Furthermore, the weight-average molecular weight of the entire sample is determined from the dissolution rate and weight-average molecular weight at each dissolution temperature.

[0045] <<Requirement (4')>> (4') In cross-fractional chromatography (CFC) measurement, the weight-average molecular weight (Mw) of the component that elutes at 75°C or higher. X ) and the weight-average molecular weight (Mw) of the entire sample. T ) ratio (Mw X / Mw T ) is less than 1. In cross-fractional chromatography (CFC) measurements, components that elute at temperatures above 75°C are high-melting-point components with relatively thick lamellar crystals, and these components contribute to water vapor barrier properties. In cross-fractional chromatography (CFC) measurement, the weight-average molecular weight (Mw) of the component that elutes at temperatures above 75°C is measured. X ) and the weight-average molecular weight (Mw) of the entire sample. T ) ratio (Mw X / Mw T The fact that ) is less than 1 means that the molecular weight of the components that elute at temperatures above 75°C (components with high melting points that contribute to heat resistance and water vapor barrier properties) is smaller than the molecular weight of the entire sample. Therefore, the above Mw X / Mw T If the value is less than 1, the components that dissolve at temperatures above 75°C have higher molecular mobility relative to other components in the polymer, resulting in the formation of more high-melting-point components during the cooling process in molding. In cross-fractional chromatography (CFC) measurement, the weight-average molecular weight (Mw) of the component that elutes at temperatures above 75°C is measured. X ) and the weight-average molecular weight (Mw) of the entire sample. T ) ratio (Mw X / Mw T If the weight-average molecular weight (Mw) of the components that elute at 75°C or higher in cross-fractionation chromatography (CFC) measurement of the ethylene-α-olefin copolymer (B) is less than 1, the water vapor barrier properties and heat resistance of the solar cell encapsulant obtained from the ethylene-based resin composition (Z) are good. From the above viewpoint, the weight-average molecular weight (Mw) of the components that elute at 75°C or higher in cross-fractionation chromatography (CFC) measurement of the ethylene-α-olefin copolymer (B) is less than 1. X ) and the weight-average molecular weight (Mw) of the entire sample. T ) ratio (Mw X / Mw T The value is preferably less than 0.9, more preferably less than 0.85, and most preferably less than 0.8.

[0046] In cross-fractional chromatography (CFC) measurements, the weight-average molecular weight (Mw) of components that elute at temperatures above 75°C. X ) and the weight-average molecular weight (Mw) of the entire sample. T ) ratio (Mw X / Mw T ) is determined from the elution ratio and weight-average molecular weight at each elution temperature obtained by the method described in Requirement (3'), and the weight-average molecular weight (Mw) of the component that elutes at 75°C or higher. X ) and the weight-average molecular weight (Mw) of the entire sample.T ) can be calculated, and from these values, it can be determined.

[0047] The ethylene-α-olefin copolymer (B) preferably further satisfies the following requirement (5'). <<Requirement (5')>> (5') In the elution curve obtained from cross-fractional chromatography (CFC) measurement, the full width at half maximum (temperature range at half the peak height) of the highest elution peak is between 5°C and 35°C. In the elution curve obtained from cross-fractional chromatography (CFC) measurement, if the full width at half maximum (temperature range at 1 / 2 peak height) of the highest elution peak is above the lower limit, the water vapor barrier properties of the encapsulant obtained from the ethylene-based resin composition (Z) are good. If the melt flow rate (MFR) is below the upper limit, the transparency of the encapsulant obtained from the ethylene-based resin composition (Z) is good. From the above viewpoint, in the elution curve obtained from cross-fractional chromatography (CFC) measurement of the ethylene-α-olefin copolymer (B), the full width at half maximum (temperature range at 1 / 2 peak height) of the highest elution peak is preferably in the range of 5°C to 30°C, more preferably 10°C to 24°C, and most preferably 12°C to 22°C.

[0048] In the elution curve obtained from cross-fractional chromatography (CFC) measurement, the full width at half maximum (FWHM) of the highest elution peak can be determined as follows. First, based on the elution curve obtained using the method described in requirement (3'), a straight line is drawn parallel to the horizontal axis (elution temperature axis) at half the height of the highest elution peak. This line has at least two intersections with the target elution peak. Of these intersections, the FWHM of the highest elution peak can be obtained by subtracting the temperature of the low-temperature intersection from the temperature of the high-temperature intersection.

[0049] The ethylene-α-olefin copolymer (B) preferably further satisfies the following requirement (6'). <<Requirement (6')>> (6') Melt tension [MT(g)] and shear viscosity [η] at 200°C and angular velocity 1.0 rad / sec * (Poise) Ratio to [MT / η] * (g / Poise) is 1.00 × 10 -5 ~1.00×10 -4 Preferably 1.00 × 10 -5 ~8.00 x 10 -5 , comfortably 1.00 × 10 -5 ~5.00 x 10 -5 It is within the range. MT / η * When the value is above the lower limit, the ethylene-based resin composition (Z) exhibits excellent moldability. MT / η * When the value is below the upper limit, the solar cell encapsulant obtained from the ethylene-based resin composition (Z) exhibits excellent transparency and impact strength.

[0050] MT / η * This depends on the long-chain branching (hereinafter also referred to as "long-chain branching content") contained in the ethylene-α-olefin copolymer, and the higher the long-chain branching content, the higher the MT / η * The larger the value, and the lower the long-chain branching content, the MT / η * The value of becomes smaller. Long-chain branching is defined as a branched structure in ethylene-α-olefin copolymer with a length greater than or equal to the inter-entanglement molecular weight (Me). It is known that the introduction of long-chain branching significantly alters the melt properties and moldability of ethylene-α-olefin copolymers (for example, Kazuo Matsuura et al., "Polyethylene Technology Reader," Kogyo Chosakai, 2001, pp. 32, 36). MT / η * The value of can be adjusted by the polymerization conditions of the ethylene-α-olefin copolymer and the type of catalyst used for polymerization.

[0051] The melt tension [MT(g)] can be measured and determined as follows. The melt tension (MT) (unit: g) is determined by measuring the stress when the material is stretched at a constant speed. A Capillograph 1D capillary rheometer manufactured by Toyo Seiki Seisakusho Co., Ltd. is used for the measurement. The conditions are: resin temperature 190°C, melting time 6 minutes, barrel diameter 9.55 mmφ, extrusion speed 15 mm / min, winding speed 24 m / min (if the molten filament breaks, reduce the winding speed by 5 m / min increments), nozzle diameter 2.095 mmφ, and nozzle length 8 mm.

[0052] Shear viscosity at 200°C and angular velocity 1.0 rad / sec [η * Poise can be measured and determined as follows. Shear viscosity (η) * ) is the shear viscosity (η) at a measurement temperature of 200°C. * The angular velocity [ω (rad / sec)] variance of ) was measured in the range of 0.01 ≤ ω ≤ 100. An Anton Paar Physica MCR301 viscoelasticity analyzer was used for the measurement, and a 25 mmφ parallel plate was used as the sample holder. An ethylene-α-olefin copolymer (B) sample was press-molded to a thickness of approximately 2.0 mm and used for measurement. Five measurement points were set for each digit of ω. The amount of strain was appropriately selected in the range of 3 to 10% so that the torque within the measurement range could be detected without exceeding the torque limit.

[0053] The ethylene-α-olefin copolymer (B) sample used for shear viscosity measurement was prepared using a press molding machine manufactured by Shinto Metal Industries Co., Ltd., with a preheating temperature of 190°C, a preheating time of 5 minutes, a heating temperature of 190°C, a heating time of 2 minutes, and a heating pressure of 100 kgf / cm². 2 Cooling temperature 20°C, cooling time 5 minutes, cooling pressure 100 kgf / cm² 2 The measurement sample was prepared by press molding to a thickness of 2 mm under the specified conditions.

[0054] The ethylene-α-olefin copolymer (B) described above may contain constituent units derived from biomass-derived monomers (ethylene, α-olefin), similar to the ethylene-α-olefin copolymer (A), or it may contain constituent units derived from chemically recycled monomers (e.g., ethylene, α-olefin, etc.). The monomers constituting the ethylene-α-olefin copolymer (B) may consist only of biomass-derived monomers, only of chemically recycled monomers, a mixture of biomass-derived monomers and fossil fuel-derived monomers, a mixture of biomass-derived monomers and chemically recycled monomers, a mixture of chemically recycled monomers and fossil fuel-derived monomers, or a mixture of biomass-derived monomers, chemically recycled monomers, and fossil fuel-derived monomers.

[0055] <Method for producing ethylene-α-olefin copolymer (B)> The ethylene-α-olefin copolymer (B) can be obtained by polymerizing ethylene with an α-olefin having 4 to 10 carbon atoms. The polymerization conditions, including the polymerization catalyst used, are not particularly limited, as long as the copolymer satisfies requirements (1') and (2') above, and optionally any other requirements described above. A single-site catalyst, such as a metallocene catalyst, is preferred as the polymerization catalyst because it facilitates obtaining the desired ethylene-α-olefin copolymer (B). A co-catalyst may also be used in combination with the polymerization catalyst as needed. Polymerization can be carried out, for example, by gas-phase polymerization or solution polymerization.

[0056] Furthermore, commercially available ethylene-α-olefin copolymers can also be used as ethylene-α-olefin copolymer (B). Specific examples of commercially available products include Evolu® and Ultzex® manufactured by Prime Polymer Co., Ltd., and among these, those that satisfy requirements (1') and (2'), and optionally other requirements mentioned above, can be used as ethylene-α-olefin copolymer (B).

[0057] In addition, the ethylene-α-olefin copolymer (B) according to the present invention may be a so-called modified ethylene-α-olefin copolymer in which a part of the molecular structure of the ethylene-α-olefin copolymer is modified by various reactions. However, since it is easy to obtain a solar cell encapsulant having an excellent balance between transparency and water vapor barrier properties, the ethylene-α-olefin copolymer (B) is preferably an unmodified ethylene-α-olefin copolymer that has not been modified.

[0058] <Ethylene-based resin composition (Z)> The ethylene-based resin composition (Z) of the present invention contains the above ethylene-α-olefin copolymer (A) and the above ethylene-α-olefin copolymer (B), and the mass fraction (W A ) of the ethylene-α-olefin copolymer (A) is 20% by mass to 99% by mass, and the mass fraction (W B ) of the ethylene-α-olefin copolymer (B) is 1% by mass or more and 80% by mass or less (however, the total of W A and W B is 100% by mass). When the mass fraction (W A ) and the mass fraction (W B ) are within the above ranges, respectively, the solar cell encapsulant formed from the ethylene-based resin composition (Z) has an excellent balance between transparency and water vapor barrier properties. From the above viewpoints, the mass fraction (W A ) is preferably 50 to 99% by mass, more preferably 60 to 95% by mass, and most preferably 70 to 90% by mass, and the mass fraction (W B ) is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and most preferably 10 to 30% by mass (however, the total of W A and W B is 100% by mass).

[0059] In addition, the ethylene-based resin composition (Z) according to the present invention may contain a thermoplastic resin other than the ethylene-α-olefin copolymer (A) and the ethylene-α-olefin copolymer (B) (hereinafter referred to as "other thermoplastic resin") as long as the effects of the present invention are not impaired.

[0060] The mass ratio of the total of the ethylene-α-olefin copolymer (A) and the ethylene-α-olefin copolymer (B) to the "other thermoplastic resin" is preferably 99.9 / 0.1 to 0.1 / 99.9, more preferably 90 / 10 to 10 / 90, and still more preferably 70 / 30 to 30 / 70.

[0061] The ethylene-based resin composition (Z) preferably further satisfies the following requirement (a). <<Requirement (a)>> (a) The heat of crystal fusion at 120°C or higher measured at a heating rate of 10°C / min in differential scanning calorimetry is 2.5 J / g or less, preferably 2.0 J / g or less, and more preferably 1.0 J / g or less. When the heat of crystal fusion at 120°C or higher measured at a heating rate of 10°C / min in differential scanning calorimetry is below the upper limit, the ethylene-based resin composition (Z) is excellent in transparency. MT / η * The value of can be adjusted according to the polymerization conditions of the ethylene-α-olefin copolymer contained in the ethylene-based resin composition (Z) and the type of catalyst used in the polymerization.

[0062] The heat of crystal fusion at 120°C or higher measured at a heating rate of 10°C / min in differential scanning calorimetry is measured using a differential scanning calorimeter (for example, Diamond DSC manufactured by PerkinElmer was used in the examples described later) and is performed as follows. Approximately 5 mg of the sample is placed in an aluminum pan, heated to 200°C at a rate of 10°C / min, held at 200°C for 10 minutes, then cooled to -30°C at a rate of 10°C / min, and then heated again to 200°C at a rate of 10°C / min to obtain an endothermic curve. A baseline is drawn passing through the two points of 100°C and 160°C on the above endothermic curve. The heat of fusion of crystals above 120°C is calculated based on the area value of the region enclosed by the baseline and the melting curve, specifically for temperatures above 120°C.

[0063] <Other thermoplastic resins> Other thermoplastic resins include, for example, polyolefins (excluding ethylene-α-olefin copolymers (A) and (B)), modified polyolefins (excluding ethylene-α-olefin copolymers (A) and (B)), polyamides, polyesters, polyacetals, polystyrenes, acrylonitrile-butadiene-styrene copolymers (ABS), hydrogenated styrene-based thermoplastic elastomers (SEBS), polycarbonates, polyphenylene oxides, polyacrylates, polyvinyl chlorides, petroleum resins, terpene resins, coumarone-indene resins, rosin-based resins, and the like.

[0064] Specific examples of the polyolefins mentioned above include ethylene polymers (excluding ethylene-α-olefin copolymers (A) and (B)), propylene polymers, butene polymers, 4-methyl-1-pentene polymers, 3-methyl-1-butene polymers, hexene polymers, ethylene propylene rubber (EPR), and olefin block copolymers (OBC). Specific examples of the above-mentioned modified polyolefins include silane-modified polyolefins, acid-modified polyolefins, ethylene-vinyl acetate copolymers (EVA), ethylene-vinyl alcohol copolymers (EVOH), ethylene-methyl methacrylate copolymers (E-MMA), ethylene-ethyl acrylate copolymers (E-EAA), ethylene-glycidyl methacrylate copolymers (E-GMA), and ionomer resins (ionically crosslinkable ethylene-methacrylic acid copolymers, ionically crosslinkable ethylene-acrylic acid copolymers).

[0065] The monomers constituting the other thermoplastic resin may consist solely of biomass-derived monomers, solely of chemically recycled monomers, a mixture of biomass-derived monomers and fossil fuel-derived monomers, a mixture of biomass-derived monomers and chemically recycled monomers, a mixture of chemically recycled monomers and fossil fuel-derived monomers, or a mixture of biomass-derived monomers, chemically recycled monomers, and fossil fuel-derived monomers.

[0066] <Additives> The ethylene-based resin composition (Z) of the present invention may optionally contain additives such as silane coupling agents, crosslinking aids, organic peroxides, ultraviolet absorbers, light stabilizers, heat stabilizers, antistatic agents, anti-slip agents, anti-blocking agents, anti-fogging agents, lubricants, pigments, dyes, nucleating agents, plasticizers, anti-aging agents, hydrochloric acid absorbers, and antioxidants, as long as they do not impair the objectives of the present invention. These additives can be used individually or in combination of two or more. The total content of these additives is generally 15 parts by mass or less, preferably 10 parts by mass or less, and more preferably 8 parts by mass or less, based on 100 parts by mass of the total components other than the additives in the ethylene resin composition (Z). As an example of a preferred embodiment, an ethylene-based resin composition (Z) is used, which contains 0.1 to 5 parts by mass of a silane coupling agent such as an ethylenically unsaturated silane compound and 0.1 to 3 parts by mass of a crosslinking agent such as an organic peroxide, per 100 parts by mass of the total components other than additives of the ethylene-based resin composition (Z).

[0067] (Silane coupling agent) The silane coupling agent can be any conventionally known agent and is not particularly limited. Examples of the silane coupling agent include vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(β-methoxyethoxysilane), 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethylditriethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyl Examples include tyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-isocyanatetopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacroxypropylmethyldimethoxysilane, 3-methacroxypropyltriethoxysilane, 3-methacroxypropylmethyldiethoxysilane, and 3-acroxypropyltrimethoxysilane. Among these silane coupling agents, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, and vinyltriethoxysilane are preferred due to their good adhesion. Silane coupling agents can be used individually or in combination of two or more types.

[0068] (organic peroxide) The organic peroxide can be any conventionally known one, and there are no particular restrictions. Preferably, the organic peroxide has a 1-minute half-life temperature in the range of 100 to 170°C. Preferred organic peroxides include, for example, dilauroyl peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, dibenzoyl peroxide, t-amyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyisobutyrate, t-butyl peroxymaleic acid, 1,1-di(t-amyl peroxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-amyl peroxy)cyclohexane, t-amyl peroxyisononanoate, and t-amyl peroxy Examples include xynormal octoate, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-butylperoxy)cyclohexane, t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-amyl-peroxybenzoate, t-butylperoxyacetate, t-butylperoxyisononanoate, 2,2-di(t-butylperoxy)butane, and t-butylperoxybenzoate. Among these organic peroxides, dilauroyl peroxide, t-butylperoxyisopropyl carbonate, t-butylperoxyacetate, t-butylperoxyisononanoate, t-butylperoxy-2-ethylhexyl carbonate, and t-butylperoxybenzoate are preferred. Organic peroxides can be used individually or in combination of two or more types.

[0069] (UV absorbers, light stabilizers, heat stabilizers) Examples of the aforementioned ultraviolet absorbers include benzophenone-based ultraviolet absorbers such as 2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-4-carboxybenzophenone, and 2-hydroxy-4-N-octoxybenzophenone; benzotriazole-based ultraviolet absorbers such as 2-(2-hydroxy-3,5-di-t-butylphenyl)benzotriazole and 2-(2-hydroxy-5-methylphenyl)benzotriazole; and salicylic acid ester-based ultraviolet absorbers such as phenyl salicylate and p-octylphenyl salicylate. UV absorbers can be used individually or in combination of two or more types.

[0070] Suitable compounds for the aforementioned light stabilizer include, for example, hindered amine compounds such as bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate and poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}] and hindered piperidine compounds. Light stabilizers can be used individually or in combination of two or more types.

[0071] Examples of the heat-resistant stabilizers include phosphite-based heat-resistant 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; lactone-based heat-resistant stabilizers such as reaction products of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene; and 3,3',3”,5,5',5”-hexa-tert-butyl-a,a',a”-(methylene-2,4,6-triyl Examples of heat-resistant stabilizers include hindered phenol-based heat stabilizers such as tri-p-cresol, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenyl)benzylbenzene, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; sulfur-based heat stabilizers; and amine-based heat stabilizers. Among these heat-resistant stabilizers, phosphite-based heat stabilizers and hindered phenol-based heat stabilizers are preferred. Heat-resistant stabilizers can be used individually or in combination of two or more types.

[0072] (Cross-linking agent) The aforementioned crosslinking aid can be any conventionally known agent commonly used with olefin resins, and there are no particular restrictions. Such crosslinking aids are generally compounds having two or more double bonds in their molecule.Examples of the aforementioned crosslinking aids include monoacrylates such as t-butyl acrylate, lauryl acrylate, cetyl acrylate, stearyl acrylate, 2-methoxyethyl acrylate, ethyl carbitol acrylate, and methoxytripropylene glycol acrylate; monomethacrylates such as t-butyl methacrylate, lauryl methacrylate, cetyl methacrylate, stearyl methacrylate, methoxyethylene glycol methacrylate, and methoxypolyethylene glycol methacrylate; diacrylates such as 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, and polypropylene glycol diacrylate; and 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, and 1,9- Examples of dimethacrylates include nonanediol dimethacrylate, neopentyl glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate; triacrylates such as trimethylolpropane triacrylate, tetramethylolmethane triacrylate, and pentaerythritol triacrylate; trimethacrylates such as trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate; tetraacrylates such as pentaerythritol tetraacrylate and tetramethylolmethane tetraacrylate; divinyl aromatic compounds such as divinylbenzene and di-i-propenylbenzene; cyanurates such as triallyl cyanurate and triallyl isocyanurate; diallyl compounds such as diallyl phthalate; oximes such as p-quinone dioxime and p-p'-dibenzoylquinone dioxime; and maleimides such as phenylmaleimide.

[0073] Among these crosslinking aids, triacrylates such as diacrylate, dimethacrylate, divinyl aromatic compounds, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, and pentaerythritol triacrylate are preferred due to their excellent balance in suppressing bubble generation and crosslinking properties in the resulting solar cell encapsulant; trimethacrylates such as trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate; tetraacrylates such as pentaerythritol tetraacrylate and tetramethylolmethane tetraacrylate; cyanurates such as triallyl cyanurate and triallyl isocyanurate; and diallyl compounds such as diallyl phthalate; oximes such as p-quinone dioxime and p-p'-dibenzoylquinone dioxime; and maleimides such as phenylmaleimide are preferred, with triallyl isocyanurate being more preferred. Crosslinking agents can be used individually or in combination of two or more.

[0074] <Methene-based resin composition (Z) manufacturing method> The ethylene-based resin composition (Z) may be produced by melt-kneading the ethylene-α-olefin copolymer (A) and the ethylene-α-olefin copolymer (B), or by dry-blending granulated pellets of ethylene-α-olefin copolymer (A) and pellets of ethylene-α-olefin copolymer (B), or by separately supplying the ethylene-α-olefin copolymer (A) and the ethylene-α-olefin copolymer (B) to an extruder and melt-kneading them in the extruder. Examples of equipment used for melt mixing include single-screw extruders, twin-screw extruders, mixing rolls, Banbury mixers, and kneaders. Of these, it is preferable to use a single-screw extruder and / or a twin-screw extruder from the viewpoint of economy and processing efficiency.

[0075] When performing the above-mentioned melt kneading and dry blending, other thermoplastic resins may be added in addition to the ethylene-α-olefin copolymer (A) and the ethylene-α-olefin copolymer (B). Furthermore, the above-mentioned additives may be added in addition to, or in place of, the other thermoplastic resins.

[0076] The order in which the above-mentioned other thermoplastic resins and additives are added is not particularly limited. For example, the above-mentioned other thermoplastic resins and additives may be blended simultaneously with one or all of the above-mentioned ethylene-α-olefin copolymer (A) and above-mentioned ethylene-α-olefin copolymer (B), or the above-mentioned ethylene-α-olefin copolymer (A) and above-mentioned ethylene-α-olefin copolymer (B) may be kneaded together before blending.

[0077] [Solar cell encapsulant] The solar cell encapsulant of the present invention offers an excellent balance between transparency and water vapor barrier properties. For this reason, it is suitably used as a solar cell encapsulant for conventionally known solar cell modules. In one preferred embodiment, the solar cell encapsulant may have a sheet-like overall shape. Furthermore, a solar cell encapsulant composited with other layers, comprising at least one sheet containing the aforementioned ethylene-based resin composition (Z), can also be suitably used. The overall thickness of the solar cell encapsulant layer is typically 0.01 to 2 mm, preferably 0.05 to 1.5 mm, more preferably 0.1 to 1.2 mm, even more preferably 0.2 to 1 mm, even more preferably 0.3 to 0.9 mm, and particularly preferably 0.3 to 0.8 mm. When the thickness is within this range, damage to glass, solar cell elements, thin-film electrodes, etc., during the lamination process when manufacturing solar cell modules can be suppressed, ensuring sufficient light transmittance allows for the acquisition of solar cell modules with high photovoltaic power generation, and enabling lamination molding of solar cell modules at low temperatures.

[0078] There are no particular restrictions on the molding method for solar cell encapsulants, as long as the solar cell encapsulant can be used to manufacture the desired solar cell module. For example, if the solar cell encapsulant is a sheet, various known molding methods can be used to mold the sheet of solar cell encapsulant (solar cell encapsulant sheet), such as casting, extrusion molding, inflation molding, injection molding, and press molding. Among these molding methods, it is particularly preferable, from the viewpoint of quality and production efficiency of the solar cell encapsulant, to prepare an ethylene-based resin composition (Z) by melt-kneading ethylene-α-olefin copolymers (A) and (B) once in an extruder, or by mixing ethylene-α-olefin copolymers (A) and (B) in a stirrer mixer, and then dry-blending this with additives, other thermoplastic resins, etc., as needed, and then putting this ethylene-based resin composition (Z) into an extrusion sheet molding hopper, performing melt-kneading while extruding to obtain a sheet-shaped solar cell encapsulant (solar cell encapsulant sheet).

[0079] When producing solar cell encapsulation sheets by extrusion sheet molding, the preferred extrusion temperature range is 100 to 130°C. Increasing the extrusion temperature above 100°C improves the productivity of solar cell encapsulation materials. Lowering the extrusion temperature below 130°C reduces the likelihood of gelation due to the crosslinking agent, even if the ethylene-based resin composition (Z) contains a crosslinking agent, when the ethylene-based resin composition (Z) is extruded to form a sheet of solar cell encapsulation material.

[0080] Furthermore, the surface of the solar cell encapsulant (typically a sheet or layer) may be embossed. Decorating the surface of the solar cell encapsulant with embossing can prevent blocking between solar cell encapsulants (solar cell encapsulant sheets) or between solar cell encapsulants (solar cell encapsulant sheets) and other sheets. In addition, since the embossing reduces the storage modulus of the solar cell encapsulant (solar cell encapsulant sheet), it can act as a cushion for the solar cell elements when laminating the solar cell encapsulant (solar cell encapsulant sheet) with the solar cell elements, thereby preventing damage to the solar cell elements. The embossing may be applied to one side or both sides of the solar cell encapsulant.

[0081] When the solar cell encapsulant of the present invention is a solar cell encapsulant sheet, the sheet may be in the form of a single sheet cut to the size of a solar cell module, or it may be in the form of a roll that can be cut to the size immediately before manufacturing the solar cell module. A preferred embodiment of the present invention, a sheet-like solar cell encapsulant (solar cell encapsulant sheet), only needs to have at least one layer containing the solar cell encapsulant. Therefore, the solar cell encapsulant sheet may be a single layer consisting only of a layer containing the ethylene-based resin composition (Z), or it may be a laminate including one layer containing the ethylene-based resin composition (Z). Alternatively, it may be a laminate including two or more layers containing the ethylene-based resin composition (Z).

[0082] When the solar cell encapsulant of the present invention is a solar cell encapsulant sheet, the solar cell encapsulant sheet may consist only of a layer containing an ethylene-based resin composition (Z), or it may have layers other than the layer containing the ethylene-based resin composition (Z) (hereinafter also referred to as "other layers"). Examples of other layers, if classified by purpose, include hard coat layers for surface or back surface protection, adhesive layers, anti-reflective layers, gas barrier layers, and anti-fouling layers. Examples of other layers, if classified by material, include layers containing UV-curable resins, layers containing thermosetting resins, layers containing polyolefin resins (however, different from layers containing the ethylene-based resin composition (Z)), layers containing carboxylic acid-modified polyolefin resins (however, different from layers containing the ethylene-based resin composition (Z)), layers containing fluorine-containing resins, layers containing cyclic olefin (co)polymers, and layers containing inorganic compounds.

[0083] In the case where the solar cell encapsulant of the present invention is a laminate comprising a layer containing an ethylene-based resin composition (Z) and other layers, there are no particular restrictions on the positional relationship between the layer containing the ethylene-based resin composition (Z) and the other layers, and a preferred layer configuration can be appropriately selected in relation to the objectives of the present invention. That is, the other layers may be provided between two or more layers containing the ethylene-based resin composition (Z), or they may be provided as the outermost layer of the solar cell encapsulant (solar cell encapsulant sheet), or they may be provided at other locations. Furthermore, the other layers may be provided on only one side of the layer containing the ethylene-based resin composition (Z), or on both sides. There are no particular restrictions on the number of other layers, and any number of other layers may be provided. In addition, the solar cell encapsulant (solar cell encapsulant sheet) may not have any other layers.

[0084] When other layers are provided on the solar cell encapsulant (solar cell encapsulant sheet), there are no particular restrictions on the method of laminating the layer containing the ethylene-based resin composition (Z) with the other layers. However, a method of obtaining a laminate by co-extrusion using a known melt extruder such as a cast molding machine, extrusion sheet molding machine, inflation molding machine, or injection molding machine is preferred; a method of obtaining a laminate by melting or heat laminating the other layer onto one of the pre-formed layers is preferred. Alternatively, lamination may be performed by a dry lamination method or a heat lamination method using a suitable adhesive (for example, maleic anhydride-modified polyolefin resin (such as "Admer" from Mitsui Chemicals, Inc. or "Modic" from Mitsubishi Chemical Corporation), low (non)crystalline soft polymers such as unsaturated polyolefins, acrylic adhesives including ethylene / acrylic acid ester / maleic anhydride ternary copolymer (such as "Bondine" from Sumika CDF Chemical Co., Ltd.), ethylene / vinyl acetate copolymer, or adhesive resin compositions containing these). As the adhesive, one with a heat resistance of approximately 120 to 150°C is preferably used, and polyester-based or polyurethane-based adhesives are examples of suitable adhesives. Furthermore, in order to improve the adhesion between the layer containing the ethylene-based resin composition (Z) and the other layers, treatments such as silane-based coupling treatment, titanium-based coupling treatment, corona treatment, and plasma treatment may be applied to each layer.

[0085] [Solar modules] The solar cell module of the present invention comprises the above-mentioned solar cell encapsulant. A solar cell module typically has a structure in which solar cell elements, formed from polycrystalline silicon or the like, are sandwiched between solar cell encapsulants (solar cell encapsulant sheets) and laminated, and both the front and back surfaces of these sheets are covered with protective sheets. That is, a typical solar cell module has the following configuration: surface protective sheet (surface protective member) / solar cell encapsulant sheet (solar cell encapsulant) / solar cell elements / solar cell encapsulant sheet (solar cell encapsulant) / backside protective sheet (backside protective member). A solar cell module, which is one of the preferred embodiments of the present invention, usually includes the above configuration, but is not limited to the above configuration. Some of the above components may be omitted, or other components (layers) may be provided, as long as the objectives of the present invention are not impaired. Examples of other components (layers) include adhesive layers, shock-absorbing layers, coating layers, anti-reflective layers, back-surface re-reflective layers, and light-diffusing layers. When these components (layers) are included in a solar cell module, they can be placed in appropriate locations on the solar cell module, taking into consideration the purpose of each component (layer) and the characteristics of each component (layer).

[0086] (Manufacturing method for solar cell modules) The solar cell module of the present invention can be obtained by any manufacturing method, such as various known manufacturing methods. The solar cell module can be obtained by, for example, the steps of: obtaining a laminate in which a back surface protective member, a solar cell encapsulant (solar cell encapsulant sheet), a plurality of solar cell elements, a solar cell encapsulant (solar cell encapsulant sheet), and a front surface protective member are laminated in this order; pressing and bonding the laminate using a laminator or the like, and simultaneously heating it as necessary; and after the above steps, further heating the laminate as necessary to cure the solar cell encapsulant.

[0087] (Solar cell module surface protection material) While there are no particular restrictions on the surface protection material used on the surface of a solar cell module (solar cell module surface protection material), it is preferable that it has properties that ensure the long-term reliability of the solar cell module when exposed to the outdoors, including weather resistance, water repellency, stain resistance, and mechanical strength, since it is located on the outermost layer of the solar cell module. Furthermore, in order to effectively utilize sunlight, it is preferable that the material (sheet) is highly transparent with low optical loss.

[0088] Examples of materials for the surface protection member of a solar cell module include resin sheets containing resins such as polyester resin, fluororesin, acrylic resin, cyclic olefin (co)polymer, and ethylene-vinyl acetate copolymer; and glass substrates. From the viewpoint of transparency, strength, and cost, polyester resin, particularly polyethylene terephthalate resin, is preferred as the resin for the resin sheet, while fluororesin is preferred from the viewpoint of weather resistance. Examples of fluororesins include tetrafluoroethylene-ethylene copolymer (ETFE), polyvinyl fluoride resin (PVF), polyvinylidene fluoride resin, polytetrafluoroethylene resin (TFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and polytrifluoroethylene chloride resin (CTFE). Among these fluororesins, polyvinylidene fluoride resin is preferred for its superior weather resistance, while tetrafluoroethylene-ethylene copolymer is preferred for its excellent balance of weather resistance and mechanical strength. Furthermore, to improve adhesion with materials constituting other layers, such as the solar cell encapsulation layer (solar cell encapsulation sheet layer), it is desirable to perform surface treatments such as corona treatment or plasma treatment on the solar cell module surface protection member. In addition, it is possible to use a sheet that has been stretched to improve mechanical strength, such as a biaxially oriented polypropylene sheet, as the solar cell module surface protection member.

[0089] (Protective material for the back surface of solar cell modules) The back surface protective member used on the back of a solar cell module (solar cell module back surface protective member) is not particularly limited, but since it is located on the outermost layer of the solar cell module, it is required to have various properties such as weather resistance and mechanical strength, similar to the solar cell module surface protective member described above. Therefore, the solar cell module back surface protective member may be made of the same material as the solar cell module surface protective member. In other words, the various materials described above that are used as surface protective members (resin sheets, glass substrates, etc.) can also be used as solar cell module back surface protective members. Polyester resin and glass can be used in particular. Furthermore, since the solar cell module back surface protective member is not intended to allow sunlight to pass through, the transparency required for the solar cell module surface protective member is not necessarily required. Therefore, in order to increase the mechanical strength of the solar cell module or to prevent distortion and warping due to temperature changes, a reinforcing plate may be attached to the solar cell module back surface protective member. As the reinforcing plate, for example, steel plates, plastic plates, FRP (glass fiber reinforced plastic) plates can be used in particular.

[0090] Furthermore, the solar cell encapsulant of the present invention may be integrated with the back surface protection member of the solar cell module. By integrating the solar cell encapsulant and the back surface protection member of the solar cell module, the process of cutting the solar cell encapsulant and the back surface protection member of the solar cell module to module size during solar cell module assembly can be shortened. In addition, the process of laminating the solar cell encapsulant and the back surface protection member of the solar cell module separately can be shortened or omitted by laminating them as an integrated sheet. When the solar cell encapsulant and the back surface protection member of the solar cell module are integrated, the method of laminating the solar cell encapsulant and the back surface protection member of the solar cell module is not particularly limited. Preferred lamination methods include obtaining a laminate by co-extrusion using a known melt extruder such as a cast molding machine, an extrusion sheet molding machine, an inflation molding machine, or an injection molding machine; or obtaining a laminate by melting or heat laminating one layer onto one layer that has been pre-formed.

[0091] (Solar cell element) There are no particular restrictions on the solar cell elements used in solar cell modules, as long as they can generate electricity using the photovoltaic effect of semiconductors. Examples of solar cell elements include silicon (monocrystalline, polycrystalline, amorphous) solar cells, compound semiconductor (Group III-III, Group II-VI, etc.) solar cells, wet solar cells, and organic semiconductor solar cells. Among these, polycrystalline silicon solar cells are preferred from the viewpoint of balancing power generation performance and cost.

[0092] (Collector electrode) Solar cell elements typically have current-collecting electrodes to extract the generated electricity. Examples of current-collecting electrodes include busbar electrodes and finger electrodes. Generally, current-collecting electrodes have a structure where they are placed on both the front and back surfaces of the solar cell element. The composition and materials of current collector electrodes used in solar cell modules are not particularly limited, but a specific example is a laminated structure of a transparent conductive film and a metal film. The transparent conductive film is formed from materials such as SnO2, ITO, and ZnO. The metal film is formed from metals such as silver, gold, copper, tin, aluminum, cadmium, zinc, mercury, chromium, molybdenum, tungsten, nickel, and vanadium. These metal films may be used individually or as composite alloys. The transparent conductive film and the metal film are formed by methods such as CVD, sputtering, and vapor deposition.

[0093] Among solar cell elements, silicon solar cell elements and compound semiconductor solar cell elements, in particular, possess excellent properties as solar cell elements, but are known to be susceptible to damage from external stress and impact. The solar cell encapsulant of the present invention has excellent flexibility, and is highly effective in absorbing stress and impact on the solar cell elements, thereby preventing damage to the solar cell elements. To further enhance this effect, it is desirable that the layer of the solar cell encapsulant of the present invention be directly bonded to the solar cell elements in the solar cell module of the present invention. Furthermore, if the solar cell encapsulant is thermoplastic, the solar cell elements can be removed relatively easily even after the solar cell module has been manufactured, thus offering excellent recyclability. The ethylene-based resin composition (Z) constituting the solar cell encapsulant of the present invention is preferably thermoplastic. Therefore, the entire solar cell encapsulant is also preferably thermoplastic, which is superior from the viewpoint of recyclability. [Examples]

[0094] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples.

[0095] [Measurement and evaluation of the physical properties of raw materials] In the following examples, the various physical properties of ethylene-α-olefin copolymer (A) and ethylene-α-olefin copolymer (B) were measured by the method described in [Modes for Carrying Out the Invention].

[0096] [Sheet forming and measurement] <Sheet molding> For the ethylene-based resin composition (Z), a press molding machine manufactured by Toyo Seiki Seisakusho Co., Ltd., Fine Lab Press SAP-1, was used with a preheating temperature of 190°C, a preheating time of 6 minutes, a heating temperature of 190°C, a heating time of 4 minutes, and a heating pressure of 100 kgf / cm². 2 Cooling temperature 20°C, cooling time 5 minutes, cooling pressure 100 kgf / cm² 2 A press sheet with a thickness of 500 μm was fabricated under these conditions.

[0097] <Total light transmittance> The sheets obtained above were placed in cells filled with cyclohexanol and measured in accordance with JIS K7361 (light source: D65). The higher the total light transmittance value, the better the transparency of the sealing material.

[0098] <Water vapor transmission rate> The water vapor transmission rate (moisture permeability) of the sheets obtained above was measured using a water vapor transmission rate measuring device manufactured by MOCON Corporation, according to the MOCON method. The lower the water vapor permeability value, the better the water vapor barrier performance of the sealing material. The test models and various measurement conditions are shown below. • Test model: PERMATRAN W3 / 31 (MOCON Corporation) • Test temperature: 40°C • Test humidity: 90%RH ·Measurement area: 50cm 2

[0099] [Raw materials used] The transition metal compounds (T) and solid carriers (S) used in the examples are as follows. Transition metal complex (T-2): (1,3-dimethylcyclopentadienyl)(1-n-butyl-3-methylcyclopentadienyl)zirconium dichloride [synthesized by the same method as described in Japanese Patent Publication No. 2000-514494] Solid carrier (S-3): P-10 manufactured by Fuji Silicia Co., Ltd. (average particle size 70 μm, specific surface area 340 m²) 2 / g, pore volume 1.3cm 3 / g)

[0100] <Preparation of olefin polymerization catalyst (XP-5)> In a 270 L reactor equipped with a stirrer, 10 kg of solid support (S-3) was suspended in 77 L of toluene under a nitrogen atmosphere, and then cooled to 0-5°C. 20.4 L of a toluene solution of methylaluminoxane (3.5 mol / L in terms of Al atoms) was added dropwise to this suspension over 30 minutes. During this time, the temperature in the system was maintained at 0-5°C. The reaction continued at 0-5°C for 30 minutes, then the temperature was raised to 95-100°C over approximately 1.5 hours, and the reaction continued at 95-100°C for 4 hours. After cooling to room temperature, the supernatant was removed by decantation, and the mixture was washed twice with toluene to prepare a total volume of 58.0 L of toluene slurry. A sample of the obtained slurry components was taken and its concentration was examined, revealing a slurry concentration of 265.0 g / L and an Al concentration of 1.29 mol / L. 234.7 mL of toluene and 250.0 mL of the above-mentioned toluene slurry (solid content = 66.1 g) were charged into a 2000 mL stirred reactor with a sufficient nitrogen purging. Next, 250.0 mL of a 0.010 mol / L toluene solution of the transition metal complex (T-2) was added, and the mixture was contacted at a system temperature of 20-25°C for 1 hour. After removing the supernatant by decantation, the mixture was washed twice with hexane to prepare a total volume of 1491 mL of solid catalyst slurry. The prepared solid catalyst slurry was cooled to 10°C under a nitrogen atmosphere, and 125.3 mL of a 1.0 mol / L diisobutylaluminum hydride hexane solution was added. While maintaining the system temperature at 10-15°C, ethylene was continuously supplied to the system under atmospheric pressure for several minutes, followed by the addition of 3.1 mL of 1-hexene. Then, ethylene supply was started at 31.5 g / h, and prepolymerization was carried out at a system temperature of 32-37°C. 3.1 mL of 1-hexene was added every hour for a total of five times from the start of prepolymerization, and the ethylene supply was stopped when it reached 189.2 g after 6 hours from the start of prepolymerization. The supernatant was then removed by decantation and washed four times with hexane. Further hexane was added to bring the total volume to 1270 mL, obtaining the prepolymerization catalyst hexane slurry. The prepared prepolymerization catalyst hexane slurry was heated to 35°C under a nitrogen atmosphere, and 268.4 mL of a 10 mg / mL hexane solution of Electro Stripper® EA (manufactured by Kao Corporation) was added. The mixture was then contacted at 32-37°C for 2 hours. Next, it was transferred to a 1000 mL glass filter that had been thoroughly purged with nitrogen, and the pressure was reduced to -68 kPaG over approximately 1 hour. Once -68 kPaG was reached, it was vacuum-dried for approximately 2 hours to obtain the olefin polymerization catalyst (XP-5).

[0101] <Production of ethylene-α-olefin copolymer (B)> [Manufacturing Example 1] (Production of ethylene-α-olefin copolymer (B-1)) Ethylene-α-olefin copolymer (B-1) was produced by a gas-phase polymerization process using a fluidized bed gas-phase polymerization reactor. 24 kg of spherical ethylene polymer particles with an average particle size of 900 μm were introduced into the reactor, and nitrogen was supplied to form a fluidized bed. Ethylene, hydrogen, 1-hexene, olefin polymerization catalyst (XP-5), and electrostripper (registered trademark) EA (manufactured by Kao Corporation) were continuously supplied to maintain a steady state under the polymerization conditions shown in Table 1. The polymerization reaction product was continuously withdrawn from the reactor and dried in a drying apparatus to obtain ethylene-α-olefin copolymer (B-1) powder, which is an ethylene-1-hexene random copolymer with an ethylene content of 94.0 mol%. The obtained ethylene-α-olefin copolymer (B-1) powder was melt-kneaded using a twin-screw coaxial 46 mmφ extruder manufactured by Ikegai Co., Ltd., under conditions of a set temperature of 200°C and a screw rotation speed of 300 rpm. After that, it was extruded into strands and cut to obtain pellets.

[0102] [Table 1]

[0103] <Measurement of physical properties of ethylene-α-olefin copolymers> [Ethylene-α-olefin copolymer (A-1)] As the ethylene-α-olefin copolymer (A-1), we used an ethylene-1-butene random copolymer obtained by solution polymerization using a metallocene catalyst, having the properties described in Table 2 below and an ethylene content of 85.4 mol%.

[0104] [Ethylene-α-olefin copolymer (A-2)] As the ethylene-α-olefin copolymer (A-2), we used an ethylene-1-butene random copolymer obtained by solution polymerization using a metallocene catalyst, having the properties described in Table 2 below and an ethylene content of 85.9 mol%.

[0105] [Ethylene-α-olefin copolymer (B-1)] Physical properties were measured for the ethylene-α-olefin copolymer (B-1) pellets prepared as described above. The measurement results are shown in Table 2.

[0106] [Ethylene-α-olefin copolymer (B-2)] As the ethylene-α-olefin copolymer (B-2), we used an ethylene-1-hexene random copolymer obtained by gas-phase polymerization using a metallocene catalyst, having the properties described in Table 2 below and an ethylene content of 93.5 mol%.

[0107] [Ethylene-α-olefin copolymer (B-3)] As the ethylene-α-olefin copolymer (B-3), we used an ethylene-1-hexene random copolymer obtained by gas-phase polymerization using a metallocene catalyst, having the properties described in Table 2 below and an ethylene content of 92.5 mol%.

[0108] [Ethylene-α-olefin copolymer (B-4)] As the ethylene-α-olefin copolymer (B-4), we used an ethylene-1-octene random copolymer obtained by solution polymerization using a single-site catalyst, having the properties described in Table 2 below and an ethylene content of 94.1 mol%.

[0109] [Ethylene-α-olefin copolymer (B-5)] As the ethylene-α-olefin copolymer (B-5), we used an ethylene-1-butene random copolymer obtained by gas-phase polymerization using a single-site catalyst, having the properties described in Table 2 below and an ethylene content of 92.6 mol%.

[0110] [Table 2]

[0111] <Ethylene-based resin composition (Z) manufacturing and sheet molding evaluation> [Example 1] 80% by mass of ethylene-α-olefin copolymer (A-1) pellets and 20% by mass of ethylene-α-olefin copolymer (B-1) pellets prepared above were stirred and mixed. The resulting mixture was melt-kneaded under the following conditions using a twin-screw extruder (KZW15TW) manufactured by Technovel Co., Ltd. to obtain strands.

[0112] Model: KZW15TW-45MG-NH (15mm twin-screw extruder) L / D: 45 Screw rotation speed: 200 rpm Set temperature: 190℃

[0113] The obtained strands were water-cooled and then cut in a pelletizer to obtain pellets of the ethylene-based resin composition (Z). Sheets were prepared from the obtained ethylene-based resin composition (Z) pellets according to the sheet molding method described above, and the total light transmittance and water vapor transmittance of the obtained sheets were measured. The measurement results are shown in Table 3.

[0114] [Example 2] 80% by mass of ethylene-α-olefin copolymer (A-1) pellets and 20% by mass of ethylene-α-olefin copolymer (B-2) pellets were stirred and mixed. Pelletization and sheet molding were performed on the obtained mixture in the same manner as in Example 1, and the total light transmittance and water vapor transmittance of the obtained sheets were measured. The measurement results are shown in Table 3.

[0115] [Example 3] 80% by mass of ethylene-α-olefin copolymer (A-2) pellets and 20% by mass of ethylene-α-olefin copolymer (B-3) pellets were stirred and mixed. Pelletization and sheet molding were performed on the resulting mixture in the same manner as in Example 1, and the total light transmittance and water vapor transmittance of the resulting sheets were measured. The measurement results are shown in Table 3.

[0116] [Example 4] 80% by mass of ethylene-α-olefin copolymer (A-2) pellets and 20% by mass of ethylene-α-olefin copolymer (B-1) pellets were stirred and mixed. Pelletization and sheet molding were performed on the obtained mixture in the same manner as in Example 1, and the total light transmittance and water vapor transmittance of the obtained sheets were measured. The measurement results are shown in Table 3.

[0117] [Example 5] 80% by mass of ethylene-α-olefin copolymer (A-1) pellets and 20% by mass of ethylene-α-olefin copolymer (B-4) pellets were stirred and mixed. Pelletization and sheet molding were performed on the obtained mixture in the same manner as in Example 1, and the total light transmittance and water vapor transmittance of the obtained sheets were measured. The measurement results are shown in Table 3.

[0118] [Example 6] 80% by mass of ethylene-α-olefin copolymer (A-1) pellets and 20% by mass of ethylene-α-olefin copolymer (B-5) pellets were stirred and mixed. Pelletization and sheet molding were performed on the obtained mixture in the same manner as in Example 1, and the total light transmittance and water vapor transmittance of the obtained sheets were measured. The measurement results are shown in Table 3.

[0119] [Comparative Example 1] Using 100% by mass of ethylene-α-olefin copolymer (A-1) pellets, sheets were prepared according to the sheet molding method described above, and the total light transmittance and water vapor transmittance of the obtained sheets were measured. The measurement results are shown in Table 3.

[0120] [Comparative Example 2] Using 100% by mass of ethylene-α-olefin copolymer (A-2) pellets, sheets were prepared according to the sheet molding method described above, and the total light transmittance and water vapor transmittance of the obtained sheets were measured. The measurement results are shown in Table 3.

[0121] [Table 3]

[0122] Figure 1 is a graph plotting the water vapor transmittance and total light transmittance of the sheet samples from Examples 1 to 6 and Comparative Examples 1 to 2. As shown in Figure 1, water vapor transmittance and total light transmittance basically have a linear correlation (the higher the water vapor transmittance, the higher the total light transmittance tends to be), but in the examples of the present invention, this approximate line is located higher and to the left compared to the comparative examples. In other words, the examples are positioned with lower water vapor transmittance and higher total light transmittance compared to the comparative examples, and can be said to have an excellent balance between water vapor barrier properties and transparency.

Claims

1. An ethylene-α-olefin copolymer (A) is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, satisfying the following requirements (1) and (2), A copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, comprising an ethylene-α-olefin copolymer (B) that satisfies the following requirements (1') and (2'), The mass fraction (W) of the ethylene-α-olefin copolymer (A) Ａ ) is 20% by mass or more and 99% by mass or less, The mass fraction (W) of the ethylene-α-olefin copolymer (B) Ｂ ) is 1% by mass or more and 80% by mass or less (however, W Ａ and W Ｂ The sum of these shall be 100% by mass.) Ethylene resin composition (Z), Solar cell encapsulant containing [this material]. (1) Density is 860 kg / m³ ３ More than 885kg / m ３ It is within the range of less than. (2) The melt flow rate (MFR) at a load of 2.16 kg at 190°C is in the range of 0.1 g / 10 min to 100.0 g / 10 min. (1') Density is 885 kg / m³ ３ More than 915kg / m ３ It is within the following range. (2') The melt flow rate (MFR) at 190°C with a 2.16 kg load is in the range of 0.1 g / 10 min to 100 g / 10 min.

2. The solar cell encapsulant according to claim 1, wherein the ethylene-α-olefin copolymer (B) further satisfies the following requirements (3') and (4'). (3') In cross-fractional chromatography (CFC) measurement, the percentage (X) of components that elute at 75°C or higher is 0.5% by mass or more and 30% by mass or less. In the measurement of (4') cross-fractionation chromatography (CFC), the weight-average molecular weight (Mw Ｘ ) of the components eluting at 75 °C or higher, and the weight-average molecular weight (Mw Ｔ ) of the entire sample, the ratio (Mw Ｘ / Mw Ｔ ) is less than 1.

3. The solar cell encapsulant according to claim 2, wherein the ethylene-α-olefin copolymer (B) further satisfies the following requirement (5'). (5') In the elution curve obtained from cross-fractional chromatography (CFC) measurement, the full width at half maximum (temperature range at half peak height) of the highest elution peak is between 5°C and 35°C.

4. A solar cell module comprising the solar cell encapsulant described in any one of claims 1 to 3.

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