Film for securing collector wire

Abstract

Provided is a film for securing a collector wire in a busbar-less solar cell module, the film having excellent insert moldability and heat resistance.　The film for securing a collector wire in a busbar-less solar cell module contains an ethylene-based resin composition (Z) that contains an ethylene-α-olefin copolymer (A), which is a copolymer of ethylene and a C4-10 α-olefin, at a mass percentage (WA) within a range from 50 to 100 mass%, and that satisfies specific conditions (a) through (c).

Description

Current collection wire fixing film

[0001] This invention relates to a current collector wire fixing film for busbarless solar cell modules.

[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 various types of solar cell modules are currently being developed and proposed.

[0003] In a typical configuration of conventional solar cell modules, thin electrodes called fingers, which collect electricity generated by the solar cell element, and thicker electrodes called busbars, which further collect and transport the current collected by these fingers, are arranged on the surface of the solar cell element. These electrodes intersect each other perpendicularly and are electrically connected. Electrodes for current collection are an essential component of a solar cell module. However, on the other hand, there is a problem that sunlight entering the solar cell element is physically blocked in the part of the light-receiving surface covered by these wires, and this effect is particularly significant with busbars because they are wider than fingers. Against this backdrop, in recent years, solar cell modules with a so-called busbarless structure have been developed. In busbarless solar cell modules, numerous thin wires (current-collecting wires) are connected and fixed to the solar cell element by soldering or conductive adhesive. However, a problem with the above structure is that the connection reliability and structural stability of the solar cell module are insufficient due to the insufficient fixing of the current-collecting wires to the solar cell element.

[0004] To address these problems, methods have been considered for sealing and fixing the current collector wire onto a solar cell element using a resin film (for example, Patent Documents 1 and 2).

[0005] International Publication No. 2017 / 076735, Japanese Patent Publication No. 2020-13863

[0006] In the above method of fixing current collector wires onto solar cell elements using a resin film, sufficient stability of fixing the current collector wires to the solar cell elements cannot be obtained unless the resin film has sufficient properties to spread to the periphery and gaps of the current collector wires when the resin film is heated and pressed, and the film maintains a uniform film thickness without becoming locally thin (in this specification, this property is referred to as "embedding moldability"). Furthermore, since solar cell modules are expected to be used for long periods in harsh humid and hot environments, the current collector wire fixing film is required to have heat resistance that can withstand harsh operating environments in addition to the above-mentioned embedding moldability. Therefore, there is a demand for a current collector wire fixing film that achieves both good embedding moldability and heat resistance, but conventionally known current collector wire fixing films have not been able to fully satisfy these properties, and improvement is desired.

[0007] The present invention aims to provide a current collector wire fixing film for busbarless solar cell modules that has superior embedding moldability and heat resistance compared to conventionally known current collector wire fixing films.

[0008] In view of the above circumstances, the present inventors conducted diligent research and found that a current collector wire fixing film made of an ethylene-based resin composition (Z) containing an ethylene-α-olefin copolymer (A) and satisfying specific melting properties and density range exhibits excellent embedding moldability and heat resistance, thus completing the present invention. The present invention relates, for example, to the following <1> to <5>. <1> An ethylene-α-olefin copolymer (A), which is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, is used in a mass fraction (W Ａ A current collector wire fixing film for busbarless solar cell modules containing an ethylene-based resin composition (Z) that contains ) in an amount of 50% to 100% by mass and satisfies the following requirements (a) to (c): (a) Melt tension [MT(g)] at 190°C and shear viscosity [η] at 200°C and angular velocity 1.0 rad / sec. * (P)) Ratio to [MT / η * (g / P) is 0.6 × 10 －４ The above 4.0 x 10 －４ It falls within the following range: (b) Density of 880 kg / m³ ３ More than 920kg / m３ It is within the following range. (c) The melt flow rate (MFR) at a load of 2.16 kg at 190 °C is within the range of 0.1 g / 10 min or more and 100 g / 10 min or less.

[0009] <2> The current collection wire fixing film for a busbarless solar cell module according to <1>, wherein the ethylene-α-olefin copolymer (A) satisfies the following requirements (1) to (3). (1) The density is 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 within the range of 0.1 g / 10 min or more and 100 g / 10 min or less. (3) In the 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.

[0010] <3> The current collection wire fixing film for a busbarless solar cell module according to <2>, wherein the ethylene-α-olefin copolymer (A) further satisfies the following requirement (4). (4) In the cross-fractionation chromatography (CFC) measurement, 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, and the ratio (Mw Ｘ / Mw Ｔ ) is less than 1.

[0011] <4> The current collection wire fixing film for a busbarless solar cell module according to <2>, wherein the ethylene-α-olefin copolymer (A) further satisfies the following requirement (5). (5) In the elution curve obtained from the cross-fractionation chromatography (CFC) measurement, the half-width of the highest elution peak (temperature width at half of the peak height) is 5 °C or more and 35 °C or less.

[0012] <5> A busbarless solar cell module including the current collection wire fixing film for a busbarless solar cell module according to any one of <1> to <4>.

[0013] According to one embodiment of the present invention, a current collector wire fixing film is provided that has superior embedding moldability and heat resistance compared to conventionally known current collector wire fixing films.

[0014] [Ethylene-based resin composition (Z)] The ethylene-based resin composition (Z) contained in the current collector wire fixing film for busbarless solar cell modules according to the present invention (hereinafter also referred to as the current collector wire fixing film) comprises an ethylene-α-olefin copolymer (A), which is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, in a mass fraction (W Ａ ) is contained in an amount of 50% by mass or more and 100% by mass or less. The mass fraction (W) of the ethylene-α-olefin copolymer (A) Ａ The amount is preferably 55 to 100% by mass, more preferably 55 to 95% by mass.

[0015] The ethylene-based resin composition (Z) is characterized by satisfying the following requirements (a) to (c). <<Requirement (a)>> (a) 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 0.6 × 10 －４ ~4.0 x 10 －４ Preferably 0.8 × 10 －４ ~3.5 x 10 －４ , more preferably 0.9 × 10 －４ ~3.2 x 10 －４ More preferably 1.0 × 10 －４ ~3.0 x 10 －４ It is within the range of MT / η. ＊ When the value is above the lower limit of the above range, the ethylene-based resin composition (Z) exhibits excellent embedding moldability. MT / η ＊ If the value is below the upper limit of the above range, the ethylene-based resin composition (Z) exhibits excellent transparency and mechanical strength.

[0016] MT / η ＊This depends on the long-chain branching (hereinafter also referred to as "long-chain branching content") contained in the ethylene polymer (a polymer typically containing 50 mol% or more of structural units derived from ethylene, for example, ethylene-α-olefin copolymer (A)) contained in the ethylene resin composition (Z), and the higher the long-chain branching content, the greater 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 an ethylene polymer with a length greater than or equal to the inter-entanglement molecular weight (Me), and it is known that the introduction of long-chain branching significantly changes the melt properties and moldability of ethylene polymers (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 type and combination of ethylene polymers contained in the ethylene resin composition (Z). For example, if the ethylene-α-olefin copolymer (A), which is an essential component of the ethylene resin composition (Z), has long-chain branching, the ethylene-α-olefin copolymer (A) may be used alone, or it may be mixed with other thermoplastic resins to adjust the MT / η of the ethylene resin composition (Z). ＊ The MT / η of the ethylene-α-olefin copolymer (A) can be adjusted to the above range. On the other hand, even if the ethylene-α-olefin copolymer (A) does not have long-chain branching, by mixing it with another thermoplastic resin having long-chain branching, the MT / η of the ethylene-based resin composition (Z) can be adjusted. ＊ The MT / η of the ethylene polymer itself, which has abundant long-chain branching, can be adjusted. ＊ This can be adjusted by the type of catalyst used in polymerization and the polymerization method.

[0017] MT / η ＊The reason why embedding moldability is superior when the above range is above the lower limit is not entirely clear, but the presumed mechanism is as follows. When the current collector wire fixing film is heat-pressed onto the current collector wire portion and the solar cell element, high fluidity is required for the resin component of the film to flow into even narrow gaps in order for it to wrap around each current collector wire, which has a circular cross-section, without any gaps. In addition, in the above heat-pressing process, in order to form a film of uniform thickness over the uneven parts caused by the current collector wire and the flat parts of the solar cell element surface, it is necessary to suppress local thinning of the resin at locations where stress is concentrated. For this reason, it is desirable that the ethylene-based resin composition (Z) exhibits the property of increasing viscosity with increasing stress, i.e., strain-curing properties. Here, it is generally known that ethylene-based polymers with a large number of long-chain branches have excellent fluidity in the molten state and also exhibit strain-curing properties at extensional viscosity. Therefore, MT / η ＊ A current collector wire fixing film made of an ethylene-based resin composition (Z) having a value above the lower limit of the above range exhibits excellent embedding moldability because, due to its high fluidity, the resin spreads evenly around the current collector wire without gaps, and due to its strain-curing properties, thinning at stress-concentrated areas is suppressed, forming a resin layer of uniform thickness overall.

[0018] 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 stretched at a constant speed. A capillary rheometer: Capillograph 1D 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 at a time), nozzle diameter 2.095 mmφ, and nozzle length 8 mm.

[0019] Shear viscosity [η] at 200°C and angular velocity 1.0 rad / sec ＊ (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 the material 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. A sample of an ethylene-based resin composition (Z) containing an ethylene-α-olefin copolymer (A) 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.

[0020] The ethylene-based resin composition (Z) containing the ethylene-α-olefin copolymer (A) 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.

[0021] <<Requirement (b)>> (b) Density of 880 kg / m³ ３ More than 920kg / m ３ The following is true: The density of the ethylene-based resin composition (Z) is 880 kg / m³. ３ The above conditions indicate good water vapor barrier properties. Furthermore, the density is 920 kg / m³. ３ The transparency and mechanical strength are good if the following conditions are met. From the above viewpoint, the density of the ethylene resin composition (Z) is preferably 885 kg / m³. ３ More than 915kg / m ３ The following, and more preferably 890 kg / m ３ More than 915kg / m ３ The following is most preferably 895 kg / m ３ More than 915kg / m ３ It is within the following range.

[0022] The density of the ethylene-based resin composition (Z) can be adjusted, for example, by the density and quantity ratio of the ethylene-α-olefin copolymer (typically ethylene-α-olefin copolymer (A)) that constitutes the ethylene-based resin composition (Z). The density of the ethylene-α-olefin copolymer typically depends on the α-olefin content (the content of constituent units derived from α-olefins having 4 to 10 carbon atoms), 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 the ethylene-α-olefin copolymer can be determined by the composition ratio of α-olefin to ethylene in the polymerization system (α-olefin / ethylene) (for example, Walter Kaminsky, Makromol. Chem. 193, p. 606 (1992)), and by increasing or decreasing the α-olefin / ethylene ratio, an ethylene-α-olefin copolymer having a density within the above range can be obtained.

[0023] The density is measured as follows: The strand of ethylene-based resin composition (Z) obtained during melt flow rate (MFR) measurement is left at room temperature for one hour, and then measured using the density gradient tube method.

[0024] <<Requirement (c)>> (c) The melt flow rate (MFR) at a load of 2.16 kg at 190°C 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 more, 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 less, the mechanical strength of the resulting current collector wire fixing film is good. From the above viewpoint, the MFR of the ethylene-based resin composition (Z) is preferably in the range of 0.1 g / 10 min or more and 50 g / 10 min or less, more preferably 1.0 g / 10 min or more and 50 g / 10 min or less, and most preferably 1.0 g / 10 min or more and 20 g / 10 min or less.

[0025] The melt flow rate (MFR) of an ethylene-based resin composition (Z) can be adjusted, for example, by the melt flow rate (MFR) and the amount ratio of the ethylene-α-olefin copolymer contained in the ethylene-based resin composition (Z). The melt flow rate (MFR) of the ethylene-α-olefin copolymer is strongly dependent on the molecular weight; a smaller melt flow rate (MFR) tends to result in a larger molecular weight, and a larger melt flow rate (MFR) tends to result in a smaller molecular weight. Generally, the molecular weight of an ethylene-based polymer is known to be determined by the composition ratio of hydrogen to ethylene (hydrogen / ethylene) in the polymerization system (for example, Kazuo Soga et al., eds., "Catalistic Olefin Polymerization," Kodansha Scientific, 1990, p. 376). Therefore, by increasing or decreasing the hydrogen / ethylene ratio within the polymerization system when polymerizing the ethylene-α-olefin copolymer (A) contained in the ethylene-based resin composition (Z), it is possible to increase or decrease the melt flow rate (MFR) of the ethylene-α-olefin copolymer (A).

[0026] The melt flow rate (MFR) of the ethylene-based resin composition (Z) is determined by measurement under conditions of 190°C and a 2.16 kg load, in accordance with JIS K 7210.

[0027] The ethylene-α-olefin copolymer (A) contained in the ethylene-based resin composition (Z) will be described in detail below.

[0028] <Ethylene-α-olefin copolymer (A)> Ethylene-α-olefin copolymer (A) is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, preferably a random copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms. Examples of the α-olefin 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 mechanical strength and transparency of the current collector wire fixing film molded from the ethylene-based resin composition (Z), the α-olefin having 4 to 8 carbon atoms is preferred, 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.

[0029] In the ethylene-α-olefin copolymer (A), the ethylene content (content of constituent units derived from ethylene) 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 (A), the content of constituent units derived from ethylene and the content of constituent units derived from α-olefins having 4 to 10 carbon atoms are preferably 100 mol%.

[0030] The ethylene-α-olefin copolymer (A) preferably satisfies at least one selected from the group consisting of the following requirements (1) to (3), and more preferably satisfies all of the following requirements (1) to (3). <<Requirement (1)>> (1) Density is 885 kg / m³ ３ More than 915kg / m ３ The following is true: The density of ethylene-α-olefin copolymer (A) is 885 kg / m³. ３ As a result, the resulting current collector wire fixing film has good water vapor barrier properties and also excellent heat resistance. Furthermore, its density is 915 kg / m³. ３ The transparency of the resulting current collector wire fixing film is good if the following conditions are met. From the above viewpoint, the density of the ethylene-α-olefin copolymer (A) 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.

[0031] The density of ethylene-α-olefin copolymer (A) typically depends on the α-olefin content (content of constituent units derived from α-olefins having 4 to 10 carbon atoms) in the ethylene-α-olefin copolymer (A). The lower the α-olefin content, the higher the density, and the higher the α-olefin content, the lower the density tends to be. 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 (e.g., Walter Kaminsky, Makromol. Chem. 193, p. 606 (1992)). By increasing or decreasing the α-olefin / ethylene ratio, ethylene-α-olefin copolymer (A) with densities within the above range can be obtained.

[0032] The density is measured as follows: The strand of ethylene-α-olefin copolymer (A) obtained during melt flow rate (MFR) measurement is left at room temperature for one hour, and then measured using the density gradient tube method.

[0033] <<Requirement (2)>> (2) The melt flow rate (MFR) at a load of 2.16 kg at 190°C 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 more, the shear viscosity is not too high and the extrusion load is good. When the melt flow rate (MFR) is 100 g / 10 min or less, the mechanical strength of the resulting current collector wire fixing film is good. From the above viewpoint, the MFR of the ethylene-α-olefin copolymer (A) is preferably in the range of 0.1 g / 10 min or more and 50 g / 10 min or less, more preferably 1.0 g / 10 min or more and 50 g / 10 min or less, and most preferably 1.0 g / 10 min or more and 20 g / 10 min or less.

[0034] The melt flow rate (MFR) of ethylene-α-olefin copolymer (A) is strongly dependent on the molecular weight; a smaller melt flow rate (MFR) tends to result in a larger molecular weight, and a larger melt flow rate (MFR) tends to result in 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) in the polymerization system (for example, Kazuo Soga et al., eds., "Catalistic Olefin Polymerization," Kodansha Scientific, 1990, p. 376). Therefore, it is possible to increase or decrease the melt flow rate (MFR) of ethylene-α-olefin copolymer (A), which is an ethylene-based polymer, by increasing or decreasing the hydrogen / ethylene ratio.

[0035] The melt flow rate (MFR) of the 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.

[0036] <<Requirement (3)>> (3) In cross-fractionation chromatography (CFC) measurement, the proportion (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-fractionation chromatography (CFC) measurement, components that elute at 75°C or higher are high-melting-point components with relatively thick lamellar crystals and are considered to be components that contribute to water vapor barrier properties and heat resistance. In cross-fractionation chromatography (CFC) measurement of ethylene-α-olefin copolymer (A), if the proportion (X) of components that elute at 75°C or higher is above the lower limit, the water vapor barrier properties of the resulting current collector wire fixing film are good. In cross-fractionation chromatography (CFC) measurement of ethylene-α-olefin copolymer (A), if the proportion (X) of components that elute at 75°C or higher is below the upper limit, the transparency of the resulting current collector wire fixing film is good. From the above viewpoint, the percentage (X) of components that elute at 75°C or higher in cross-fractional chromatography (CFC) measurement of ethylene-α-olefin copolymer (A) 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.

[0037] In cross-fractionation chromatography (CFC) measurements, the proportion of components (X) that elute above 75°C 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 wider the compositional distribution, the greater the proportion of components (X) that elute above 75°C tends to be. As mentioned above, the density of the ethylene-α-olefin copolymer typically depends on the α-olefin content. Therefore, it can be adjusted by the compositional ratio of α-olefin to ethylene (α-olefin / ethylene) in the polymerization system when polymerizing the ethylene-α-olefin copolymer (A). However, even if the proportion of components (X) that elute above 75°C in cross-fractionation chromatography (CFC) measurements is adjusted by the density of the ethylene-α-olefin copolymer (A), it is desirable that the density of the ethylene-α-olefin copolymer (A) meets the range of requirement (1) mentioned above.

[0038] On the other hand, the compositional distribution of the ethylene-α-olefin copolymer can be adjusted by the catalyst type, polymerization process type (gas-phase polymerization, solution polymerization, etc.), polymerization temperature, etc. By adjusting the compositional distribution with these polymerization factors, the proportion (X) of components that elute at 75°C or higher in cross-fractionation chromatography (CFC) measurement can be adjusted without significantly changing the density of the ethylene-α-olefin copolymer (A). All temperature indications in CFC measurement are integers. For example, in the measurement conditions shown below, the elution fraction at 75°C refers to components that eluted between 74°C and 75°C. Furthermore, components that elute at 75°C or higher refer to components that elute at temperatures of 75°C or higher. For example, in the measurement conditions shown below, this refers to the total of all elution fractions from 76°C onward, including the elution fraction at 76°C (components that eluted between 75°C and 76°C).

[0039] Cross-fractionation chromatography (CFC) measurement 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, 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.

[0040] The measurement conditions for CFCs are as follows: Apparatus: CFC2 cross-fractionation chromatograph (Polymer Char) Detector: IR4 infrared spectrophotometer (Polymer Char) Detection wavelength: 3.42 μm (2920 cm) －１Sample concentration: 120 mg / 30 mL Injection volume: 0.5 mL Cooling rate: 1 °C / min Elution temperature: -17 °C, -15 to 10 °C (5 °C intervals), 10 to 40 °C (2 °C intervals), 40 to 100 °C (1 °C intervals), 100 to 140 °C (20 °C intervals) GPC column: Shodex HT-806M x 3 (Showa Denko) GPC column temperature: 140 °C GPC column calibration: Monodisperse polystyrene (Tosoh) Molecular weight calibration method: General calibration method (polyethylene equivalent (K = 5.06 x 10) －４ α = 0.7) Mobile phase: Orthodichlorobenzene (ODCB), BHT addition flow rate: 1.0 mL / min

[0041] 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, the 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. Furthermore, the molecular weight of the fractions eluted at each temperature is measured, and the PE-equivalent molecular weight is determined using a general calibration curve. Finally, the weight-average molecular weight of the entire sample is determined from the elution ratio and weight-average molecular weight at each elution temperature.

[0042] The ethylene-α-olefin copolymer (A) preferably satisfies the following requirement (4).

[0043] <<Requirement (4)>> (4) In cross-fractionation chromatography (CFC) measurement, the weight-average molecular weight (Mw) of the components that elute at 75°C or higher. Ｘ ) and the weight-average molecular weight (Mw) of the entire sample. Ｔ ) Ratio (Mw Ｘ / Mw Ｔ The weight-average molecular weight (Mw) of the components that elute at temperatures above 75°C in cross-fractionation chromatography (CFC) is less than 1. In cross-fractionation chromatography (CFC) measurements, the components that elute at temperatures above 75°C are high-melting-point components with relatively thick lamellar crystals and contribute to water vapor barrier properties and heat resistance. Ｘ ) and the weight-average molecular weight (Mw) of the entire sample. Ｔ ) Ratio (Mw Ｘ / Mw ＴThe 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 elute at temperatures above 75°C have high molecular mobility relative to other components in the polymer, and therefore more high-melting-point components are formed during the cooling process during molding. In cross-fractional chromatography (CFC) measurement, the weight-average molecular weight (Mw) of the components that elute at temperatures above 75°C is 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 component that elutes at 75°C or higher in cross-fractional chromatography (CFC) measurement of ethylene-α-olefin copolymer (A) is less than 1, the water vapor barrier properties and heat resistance are good. From the above viewpoint, the weight-average molecular weight (Mw) of the component that elutes at 75°C or higher in cross-fractional chromatography (CFC) measurement of ethylene-α-olefin copolymer (A) Ｘ ) and the ratio of the weight-average molecular weight (MwT) of the entire sample (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.

[0044] 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 item (3) of requirement (Mw) of 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.

[0045] The ethylene-α-olefin copolymer (A) preferably satisfies the following requirement (5). <<Requirement (5)>> (5) In the elution curve obtained from cross-fractionation chromatography (CFC) measurement, the full width at half maximum (temperature range at 1 / 2 of peak height) of the highest elution peak is 5°C or more and 35°C or less. In the elution curve obtained from cross-fractionation chromatography (CFC) measurement, if the full width at half maximum (temperature range at 1 / 2 of peak height) of the highest elution peak is above the lower limit, the water vapor barrier properties and heat resistance are good. If the full width at half maximum (temperature range at 1 / 2 of peak height) of the highest elution peak is below the upper limit, the transparency is good. From the above viewpoint, in the elution curve obtained from cross-fractionation chromatography (CFC) measurement of ethylene-α-olefin copolymer (A), the full width at half maximum (temperature range at 1 / 2 of peak height) of the highest elution peak is preferably in the range of 5°C or more and 30°C or less, more preferably 10°C or more and 24°C or less, and most preferably 12°C or more and 22°C or less. 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 item (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 high-temperature intersection and the low-temperature intersection closest to the elution peak are obtained by subtracting the temperature of the low-temperature intersection from the temperature of the high-temperature intersection to obtain the FWHM of the highest elution peak.

[0046] The above ethylene-α-olefin copolymer (A) may contain structural units derived from biomass-derived monomers (ethylene, α-olefin). The monomers constituting the ethylene-α-olefin copolymer (A) may contain only biomass-derived monomers, may contain only fossil fuel-derived monomers, or may contain both biomass-derived monomers and fossil fuel-derived monomers. The above biomass-derived monomers are monomers made from any renewable natural raw materials and their residues, such as plant-derived or animal-derived, including fungi, yeast, algae and bacteria, and as carbon １４ contains C isotopes at a ratio of about 1×10 －１２ , and the biomass carbon concentration (pMC) measured in accordance with ASTM D 6866 is about 100 (pMC). Biomass-derived monomers can be obtained by conventionally known methods. It is preferable from the viewpoint of reducing environmental impact (mainly reducing greenhouse gas emissions) that the above ethylene-α-olefin copolymer (A) contains structural units derived from biomass-derived monomers. Even if the raw material monomers of the ethylene-α-olefin copolymer (A) contain biomass-derived monomers, if the polymer production conditions such as the polymerization catalyst, polymerization process, and polymerization temperature are the same, １４ the molecular structure other than containing C isotopes at a ratio of 1×10 －１２ to 1×10 －１４ is equivalent to an ethylene-α-olefin copolymer containing only structural units derived from fossil fuel-derived monomers. Therefore, the performance is also said to be unchanged.

[0047] 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, returning them 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.

[0048] <Method for producing ethylene-α-olefin copolymer (A)> The ethylene-α-olefin copolymer (A) is 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. A single-site catalyst, such as a metallocene catalyst, is preferred as the polymerization catalyst because it is easier to obtain the desired ethylene-α-olefin copolymer (A). 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.

[0049] Furthermore, commercially available ethylene-α-olefin copolymers (A) can also be used. Specific examples of commercially available products include Evolu, Evolu E, and Ultzex ​​from Prime Polymer Co., Ltd., Sumikasen E, Sumikasen EP, and Excellen GMH from Sumitomo Chemical Co., Ltd., and Novatec, Kernel, and Harmolex from Nippon Polyethylene Co., Ltd.

[0050] 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, since it is easier to obtain a current collector wire fixing film for busbarless solar cell modules that has excellent embedding moldability and heat resistance, an unmodified ethylene-α-olefin copolymer (A) is preferred. The ethylene-α-olefin copolymer (A) can be used alone or in combination of two or more types.

[0051] <Other Thermoplastic Resins> The ethylene-based resin composition (Z) contained in the current collector wire fixing film for busbarless solar cell modules according to the present invention may also contain thermoplastic resins other than the ethylene-α-olefin copolymer (A) (hereinafter referred to as "other thermoplastic resins").

[0052] Other thermoplastic resins include, for example, polyolefins (excluding ethylene-α-olefin copolymer (A)), modified polyolefins (excluding ethylene-α-olefin copolymer (A)), 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.

[0053] Specific examples of the above polyolefins include ethylene polymers (excluding ethylene-α-olefin copolymer (A)), 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 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). Among these, unmodified polyolefins are preferred because they offer excellent embedding moldability and heat resistance, and are easy to use as current collector wire fixing films for busbarless solar cell modules. Unmodified ethylene polymers (excluding ethylene-α-olefin copolymer (A)) are more preferred, unmodified ethylene homopolymers are even more preferred, and low-density polyethylene, which is an unmodified ethylene homopolymer, is even more preferred.

[0054] 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.

[0055] The ethylene-based resin composition (Z) contains an ethylene-α-olefin copolymer (A) as a thermoplastic resin component. The mass fraction (W) of the ethylene-α-olefin copolymer (A) in the thermoplastic resin component of the ethylene-based resin composition (Z) is... Ａ)is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and most preferably 80% by mass or more. The mass fraction (W Ａ ), when within the above range, is excellent in the balance among transparency, water vapor barrier property, and heat resistance of the current collector wire fixing film made of the ethylene resin composition (Z). Further, from the viewpoint of easily obtaining the ethylene resin composition (Z) excellent in embedding moldability, as the ethylene-α-olefin copolymer (A), the ratio [MT / η* (g / Poise)] of the melt tension [MT (g)] at 190°C to the shear viscosity [η* (Poise)] at 200°C and an angular velocity of 1.0 rad / sec is 0.6×10 －４ or more and 4.0×10 －４ or less, preferably 0.8×10 －４ to 3.5×10 －４ , more preferably 0.9×10 －４ to 3.2×10 －４ , still more preferably 1.0×10 －４ to 3.0×10 －４ . In a preferred embodiment, the ethylene-α-olefin copolymer (A1) within the above range is contained in the ethylene-α-olefin copolymer (A) at 20 to 100% by mass, preferably 30 to 100% by mass. The melt tension [MT (g)] of the ethylene-α-olefin copolymer (A) at 190°C and the shear viscosity at 200°C and an angular velocity of 1.0 rad / sec can be measured and determined by the method described in the part of requirement (a).

[0056] When other thermoplastic resins are contained in addition to the ethylene-α-olefin copolymer (A), the mass fraction of each component is such that the mass fraction (W Ａ ) of the above ethylene-α-olefin copolymer (A) is preferably 50 to 99% by mass, more preferably 60 to 99% by mass, still more preferably 70 to 95% by mass, and most preferably 80 to 95% by mass, and the mass fraction (W Ｘ ) of the above other thermoplastic resin is preferably 1 to 50% by mass, more preferably 1 to 40% by mass, still more preferably 5 to 30% by mass, and most preferably 5 to 20% by mass (however, W Ａ and W Ｘ(Assume the total is 100% by mass). Mass fraction (W Ａ ) and mass fraction (W Ｘ When each of these is within the above range, the current collector wire fixing film made of ethylene resin composition (Z) has an excellent balance of transparency, water vapor barrier properties and heat resistance.

[0057] <Additives> The ethylene-based resin composition (Z) 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, to the extent that 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-α-olefin copolymer (A) and other thermoplastic resins which are optional components of the ethylene-based resin composition (Z).

[0058] (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-aminopropylmethyl Examples include dimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-isocyanatetopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-acryloxypropyltrimethoxysilane. 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. The silane coupling agents can be used individually or in combination of two or more.

[0059] (Organic Peroxides) Conventionally known organic peroxides can be used, 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, 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.

[0060] (UV absorbers, light stabilizers, heat stabilizers) Examples of the UV absorbers include benzophenone-based UV 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 UV absorbers such as 2-(2-hydroxy-3,5-di-t-butylphenyl)benzotriazole and 2-(2-hydroxy-5-methylphenyl)benzotriazole; and salicylic acid ester-based UV absorbers such as phenyl salicylate and p-octylphenyl salicylate. UV absorbers can be used individually or in combination of two or more.

[0061] Suitable compounds for the 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. The light stabilizer can be used alone or in combination of two or more.

[0062] 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 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 stabilizers, phosphite-based heat stabilizers and hindered phenol-based heat stabilizers are preferred. Heat stabilizers can be used individually or in combination of two or more.

[0063] (Crosslinking aid) The crosslinking aid can be any conventionally known agent commonly used for 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 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-nonanediol diacrylate. Dimethacrylates such as nandiol dimethacrylate, neopentyl glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and 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 are examples of these compounds.

[0064] Among these crosslinking aids, triacrylates such as diacrylate, dimethacrylate, divinyl aromatic compounds, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, and pentaerythritol triacrylate; 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; triallyl compounds: oximes such as p-quinone dioxime and p-p'-dibenzoylquinone dioxime; and maleimides such as phenylmaleimide are preferred, with triallyl isocyanurate being more preferred. The crosslinking aids can be used individually or in combination of two or more.

[0065] <Method for producing the ethylene-based resin composition (Z)> The ethylene-based resin composition (Z) contained in the current collector wire fixing film for busbarless solar cell modules according to the present invention may be produced by melt-kneading the above-mentioned ethylene-α-olefin copolymer (A) and other thermoplastic resins as optional components, or by dry-blending pellets of granulated ethylene-α-olefin copolymer (A) and pellets of other thermoplastic resins as optional components, or, if the ethylene-based resin composition (Z) contains other thermoplastic resins as optional components, the above-mentioned ethylene-α-olefin copolymer (A) and the above-mentioned other thermoplastic resins may be supplied separately to an extruder and melt-kneaded in the extruder. Examples of equipment used for melt-kneading include a single-screw extruder, a twin-screw extruder, a mixing roll, a Banbury mixer, a kneader, etc. Of these, it is preferable to use a single-screw extruder and / or a twin-screw extruder from the viewpoint of economy, processing efficiency, etc.

[0066] When performing the melt kneading and dry blending described above, the above additive may be further added in addition to, or in place of, the ethylene-α-olefin copolymer (A) and other thermoplastic resins.

[0067] 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 mixed simultaneously with one or all of the above-mentioned ethylene-α-olefin copolymer (A) and the above-mentioned other thermoplastic resins, or the above-mentioned ethylene-α-olefin copolymer (A) and the other thermoplastic resins may be kneaded together before being added.

[0068] [Current Collector Wire Fixing Film] The current collector wire fixing film for busbarless solar cell modules of the present invention is a resin film used to stably fix the connection structure when electrically connecting the current collector wire and the solar cell in a busbarless solar cell. The current collector wire fixing film of the present invention has excellent embed-molding properties and heat resistance. The current collector wire fixing film of the present invention may be a single layer film containing the ethylene-based resin composition (Z) described above, or it may be a multilayer film composited with other layers, having at least one layer containing the ethylene-based resin composition (Z). Examples of other layers besides the layer containing the ethylene-based resin composition (Z) include, if classified by purpose, hard coat layers for surface or back surface protection, adhesive layers, anti-reflective layers, gas barrier layers, anti-fouling layers, etc. If classified by material, examples include layers containing UV-curable resins, layers containing thermosetting resins, layers containing polyolefin resins, layers containing carboxylic acid-modified polyolefin resins, layers containing fluorine-containing resins, layers containing cyclic olefin (co)polymers, layers containing inorganic compounds, etc.

[0069] When the current collector wire fixing film of the present invention is a multilayer film, the positional relationship between the layer containing the ethylene resin composition (Z) and the other layers is such that the layer containing the ethylene resin composition (Z) is placed on the surface in contact with the solar cell element and the current collector wire (i.e., the innermost layer). There are no particular restrictions on the order of the layers with the other layers, and a preferred layer configuration can be appropriately selected in relation to the objectives of the present invention.

[0070] The thickness of the current collector wire fixing film of the present invention 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 0.1 to 1 mm, even more preferably 0.1 to 0.9 mm, and particularly preferably 0.1 to 0.8 mm. When the thickness is within this range, an excellent balance is achieved between the embedding moldability and heat resistance of the current collector wire fixing film.

[0071] There are no particular limitations on the method for forming the current collector wire fixing film of the present invention. Examples of known forming methods include various known forming methods such as cast molding, extruded sheet (film) molding, inflation molding, injection molding, and press molding.

[0072] The current collector wire fixing film of the present invention 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 size immediately before manufacturing the solar cell module.

[0073] When other layers are provided in the current collector wire fixing film of the present invention, there are no particular restrictions on the method of laminating the layer containing the ethylene-based resin composition (Z) with the other layers, and known manufacturing methods can be used.

[0074] [Solar Cell Module] The solar cell module of the present invention comprises a current collector wire fixing film for busbarless solar cell modules. A solar cell module constructed using the current collector wire fixing film of the present invention is a so-called busbarless solar cell module that does not have busbar electrodes. The configuration of the busbarless solar cell module of the present invention is required to be such that the current collector wires arranged on the surface of the solar cell elements are fixed by the current collector wire fixing film of the present invention, but is not particularly limited to other aspects. A typical configuration of a busbarless solar cell module is, for example, a protective sheet (surface protective member) / solar cell encapsulation sheet / current collector wire fixing film / current collector wire and solar cell elements / current collector wire fixing film / solar cell encapsulation sheet / protective sheet (backside protective member). The configuration of a solar cell module, which is one of the preferred embodiments of the present invention, is not limited to the above configuration, and some of the above layers may be appropriately omitted or other layers may be appropriately provided, as long as the objective of the present invention is not impaired. Other layers include, for example, an adhesive layer, an impact absorption layer, a coating layer, a barrier sheet layer, an anti-reflective layer, a backside re-reflective layer, and a light diffusion layer. When these other layers are provided in a busbarless solar cell module, there are no particular limitations on their placement, but they can be provided in appropriate locations considering the purpose and characteristics of each layer. Furthermore, the current collector wire fixing film of the present invention can be used as a layer that serves as both a current collector wire fixing film and a solar cell encapsulation sheet, in which case the layer consisting of the solar cell encapsulation sheet with the above configuration can be omitted. In other words, the busbarless solar cell module of the present invention can also have a configuration of protective sheet (surface protective member) / current collector wire fixing film / current collector wire and solar cell element / current collector wire fixing film / protective sheet (backside protective member).

[0075] (Method for manufacturing solar cell modules) Solar cell modules can be obtained by any manufacturing method, such as various known manufacturing methods. For example, a solar cell module can be obtained by the steps of: obtaining a laminate in which a back surface protective member, a solar cell sealing sheet, a current collector wire fixing film, multiple current collector wires and solar cell elements, a current collector wire fixing film, a solar cell sealing 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 sealing material.

[0076] (Surface protection material for solar cell modules) 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), but since it is located on the outermost layer of the solar cell module, 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. In addition, in order to make effective use of sunlight, it is preferable that it be a highly transparent material (sheet) with low optical loss.

[0077] 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. It is also 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.

[0078] (Solar Cell Module Back Surface Protective Member) There are no particular restrictions on the back surface protective member used on the back surface of a solar cell module (solar cell module back surface protective member). However, 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 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 are particularly preferred. 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 are preferred.

[0079] (Solar Cell Elements) 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 and polycrystalline) solar cells, wet solar cells, and thin-film solar cell elements. Examples of thin-film solar cell elements include amorphous silicon solar cell elements, CIS solar cell elements, CIGS solar cell elements, CdTe solar cell elements, and compound-based solar cell elements such as perovskite solar cell elements.

[0080] (Solar Cell Encapsulation Sheet) While there are no particular restrictions on the solar cell encapsulation sheet used in solar cell modules, 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 vapor barrier properties, and mechanical strength. Furthermore, in order to effectively utilize sunlight, it is preferable that the sheet has low optical loss and high transparency.

[0081] Suitable materials for solar cell encapsulation sheets include ethylene-vinyl acetate copolymers, ethylene-α-olefin copolymers, and propylene polymers. Among these, ethylene-α-olefin copolymers are preferred from the viewpoint of transparency, flexibility, mechanical strength, and water vapor barrier properties. Suitable commercially available ethylene-α-olefin copolymers for use in solar cell encapsulation sheets include, for example, Tuffmer (registered trademark) manufactured by Mitsui Chemicals, Inc. and Kernel (registered trademark) manufactured by Nippon Polyethylene Co., Ltd.

[0082] (Current Collector Wire) The current collector wire is an electrode that collects the electricity generated in the solar cell element. The current collector wire can be arranged on both the front and back surfaces of the solar cell element. There are no particular restrictions on the material of the current collector wire, and it can be appropriately selected according to the purpose, but examples include metal conductors such as silver, gold, copper, tin, and nickel. In addition, SnO can be placed on these metal conductors. ２ Laminates formed by stacking transparent conductive films made of ITO, ZnO, etc., can also be used as current collector wires. There are no particular restrictions on the average width of the current collector wire, and it can be appropriately selected according to the purpose, but 20 μm to 200 μm is preferred, and 20 μm to 100 μm is more preferred because it reduces the light-shielding area. The average width of the current collector wire can be determined, for example, by measuring the width of the electrodes at any 10 points on the current collector wire and averaging the measured values. The width of the current collector wire does not have to be the same at all points, and some parts may be wider than others.

[0083] There are no particular restrictions on the method for forming the current collector wire, and it can be appropriately selected depending on the purpose. For example, one method is to print silver paste onto a crystalline solar cell so that the current collector wire forms a desired pattern shape. Examples of printing methods include screen printing.

[0084] The current collector wire fixing film for busbarless solar cell modules of the present invention, and the solar cell module equipped with such current collector wire fixing film, exhibit excellent embedding moldability and good heat resistance. Furthermore, such current collector wire fixing film and solar cell module are also expected to exhibit excellent water vapor barrier properties.

[0085] 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.

[0086] [Measurement and Evaluation of Raw Material Properties] In the following examples, the various properties of the ethylene-based resin composition (Z) and the ethylene-α-olefin copolymer (A) were measured by the method described in [Modes for Carrying Out the Invention].

[0087] [Sheet Forming and Measurement] <Sheet Forming> For ethylene-α-olefin copolymer (A) and mixtures of ethylene-α-olefin copolymer (A) with other ethylene-α-olefin copolymers (A) or with other thermoplastic resins (B), a press molding machine Fine Lab Press SAP-1 manufactured by Toyo Seiki Seisakusho Co., Ltd. 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.

[0088] <Heat Shrinkage Rate> The heat shrinkage rate of the sheet obtained above was measured at 100°C using an air oven. The closer the heat shrinkage rate is to zero and the less the sheet melts during the test, the better the heat resistance of the sealing material. The test equipment and various measurement conditions are shown below. ・Test equipment: Air oven DN600 (Yamato Scientific Co., Ltd.) ・Test temperature: 100°C ・Test piece dimensions: 10 mm x 100 mm strip (shrinkage rate is calculated in the longitudinal direction) ・Heating time: 15 minutes

[0089] <Water Vapor Permeability> The water vapor permeability (moisture transmission) of the sheet obtained above was measured using a water vapor permeability measuring device manufactured by MOCON Corporation and the MOCON method. A smaller water vapor permeability value indicates superior water vapor barrier properties of the sealing material. The test equipment and various measurement conditions are shown below. • Test equipment: PERMATRAN W3 / 31 (MOCON Corporation) • Test temperature: 40°C • Test humidity: 90%RH • Measurement area: 50 cm² ２

[0090] [Materials Used] The transition metal compounds (T) and solid carriers (S) used in the examples are as follows: Transition metal complex (T-1): Dimethylsilylene (2-indenyl) (4-(3,5-di-tert-butyl-4-methoxyphenyl)-7-methoxy-1-indenyl) zirconium dichloride [Synthesized by the method described in Japanese Patent Publication No. 2019-059933] 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): Silica manufactured by Fuji Silicia Co., Ltd. (average particle size 70 μm, specific surface area 340 m²) ２ / g, pore volume 1.3cm ３ / g)

[0091] <Synthesis of Olefin Polymerization Catalyst (XP-3)> In a 270 L reactor 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 was 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 was continued at 95-100°C for 4 hours. After that, the temperature was lowered to room temperature, the supernatant was removed by decantation, and after washing twice with toluene, a total volume of 58.0 L of toluene slurry was prepared. A portion of the obtained slurry components was taken and its concentration was examined, and the slurry concentration was 248.0 g / L and the Al concentration was 1.21 mol / L. Next, 6.1 L of the toluene slurry obtained above and 21.9 L of toluene were charged into a 114 L stirrer-equipped reactor that had been thoroughly purged with nitrogen. 5.4 L of an 8 mM toluene solution of a transition metal compound (T-1) was added, and the mixture was contacted at a system temperature of 20-25°C for 1 hour. The supernatant was removed by decantation, and the mixture was washed twice with hexane to prepare a total of 30.9 L of solid catalyst slurry. While adjusting the temperature of the obtained solid catalyst slurry to 10-15°C, 3.1 L of a 0.92 M hexane solution of diisobutylaluminum hydride was added, and ethylene gas was supplied at a flow rate of 0.74 kg / h. After adding 34.3 mL of 1-hexene, the temperature was increased, and while adjusting the system temperature to 32-38°C, 34.3 mL of 1-hexene was added every hour for a total of 5 times. Six hours after the start of ethylene supply, when the ethylene supply reached 4.5 kg, the ethylene supply was stopped. Subsequently, the system was thoroughly purged with nitrogen, the supernatant was removed by decantation, and after washing four times with hexane, a total volume of 21.9 L of prepolymerization catalyst slurry was prepared. While maintaining the obtained prepolymerization catalyst slurry at 35-40°C, 6.1 L of a 10 mg / mL hexane solution of Electro Stripper® EA (manufactured by Kao Corporation) was added and the mixture was contacted for 2 hours.The entire obtained slurry was placed into a 43 L capacity evaporator with a stirrer under a nitrogen atmosphere. The pressure inside the dryer was then reduced to -68 kPaG over approximately 60 minutes, and the mixture was vacuum-dried for approximately 4.3 hours to remove hexane and volatile components from the prepolymerization catalyst. The pressure was further reduced to -100 kPaG, and the mixture was vacuum-dried for 8 hours to obtain the olefin polymerization catalyst (XP-3).

[0092] <Preparation of Catalyst for Olefin Polymerization (XP-5)> In a 270 L reactor 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 was 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 was continued at 95-100°C for 4 hours. After that, the temperature was lowered 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 portion of the obtained slurry components was taken and its concentration was examined, and the slurry concentration was 265.0 g / L and the Al concentration was 1.29 mol / L. 234.7 mL of toluene and 250.0 mL of the above toluene slurry (solid content = 66.1 g) were charged into a 2000 mL stirred reactor that had been thoroughly purged with nitrogen. 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 for 1 hour at a system temperature of 20-25°C. The supernatant was removed by decantation, and after washing twice with hexane, a total volume of 1491 mL of solid catalyst slurry was prepared. 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 at atmospheric pressure for several minutes, and then 3.1 mL of 1-hexene was added. Subsequently, ethylene was supplied 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. Six hours after the start of prepolymerization, when the ethylene supply reached 189.2 g, the ethylene supply was stopped. The supernatant was then removed by decantation, and the mixture was washed four times with hexane. Further hexane was added to bring the total volume to 1270 mL, obtaining a hexane slurry of the prepolymerization catalyst.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 (registered trademark) 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).

[0093] <Production of Ethylene-α-Olefin Copolymer (A)> [Production Example 1] (Production of Ethylene-α-Olefin Copolymer (A-1)) Ethylene-α-olefin copolymer (A-1) was produced by a gas-phase polymerization process using a fluidized bed type gas-phase polymerization reactor. 24 kg of spherical ethylene polymer particles with an average particle size of 900 μm were introduced into the reactor in advance, and nitrogen was supplied to form a fluidized bed. Then, ethylene, hydrogen, 1-hexene, olefin polymerization catalyst (XP-3), 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 a powder of ethylene-α-olefin copolymer (A-1), which is an ethylene-1-hexene random copolymer with an ethylene content of 93.7 mol%. The obtained ethylene-α-olefin copolymer (A-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. The powder was then extruded into strands and cut to obtain pellets.

[0094] [Production Examples 2-3] Except for changing the polymerization catalyst and polymerization conditions used as shown in Table 1, ethylene-α-olefin copolymers, which are ethylene-1-hexene random copolymers, were obtained in the same manner as in Production Example 1 (Production Example 2: ethylene content 94.7 mol%, Production Example 3: ethylene content 94.0 mol%).

[0095]

[0096] <Measurement of physical properties of ethylene-α-olefin copolymer> [Ethylene-α-olefin copolymer (A-1)] Physical properties were measured for the ethylene-α-olefin copolymer (A-1) pellets prepared above. The measurement results are shown in Table 2.

[0097] [Ethylene-α-olefin copolymer (A-2)] Physical properties were measured for the ethylene-α-olefin copolymer (A-2) pellets prepared as described above. The measurement results are shown in Table 2.

[0098] [Ethylene-α-olefin copolymer (A-3)] Physical properties were measured for the ethylene-α-olefin copolymer (A-3) pellets prepared as described above. The measurement results are shown in Table 2.

[0099] [Ethylene-α-olefin copolymer (A-4)] As the ethylene-α-olefin copolymer (A-4), 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%.

[0100] [Ethylene-α-olefin copolymer (A-5)] As the ethylene-α-olefin copolymer (A-5), 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%.

[0101] [Ethylene-α-olefin copolymer (A-6)] As the ethylene-α-olefin copolymer (A-6), we used an ethylene-1-hexene random copolymer obtained by high-pressure polymerization using a single-site catalyst, having the properties described in Table 2 below and an ethylene content of 92.3 mol%.

[0102] [Ethylene-based polymer (B-7)] As the ethylene-based polymer (B-7), high-pressure low-density polyethylene, an ethylene homopolymer having the properties described in Table 2 below, was used.

[0103] [Ethylene-α-olefin copolymer (A'-8)] As the ethylene-α-olefin copolymer (A'-8), 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'-9)] As the ethylene-α-olefin copolymer (A'-9), 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]

[0106] <Preparation of Ethylene-Based Resin Composition and Evaluation of Sheet Molding> [Example 1] Using 100% by mass of the ethylene-α-olefin copolymer (A-1) pellets prepared above, a sheet was prepared according to the sheet molding method described above, and the heat shrinkage rate and water vapor permeability of the obtained sheet were measured. The measurement results are shown in Table 3.

[0107] [Example 2] Using 100% by mass of ethylene-α-olefin copolymer (A-2) pellets, a sheet was prepared according to the sheet molding method described above, and the heat shrinkage rate and water vapor permeability of the obtained sheet were measured. The measurement results are shown in Table 3.

[0108] [Example 3] 90% by mass of ethylene-α-olefin copolymer (A-5) pellets and 10% by mass of ethylene-based polymer (B-7) pellets were stirred and mixed, and the resulting mixture was melt-kneaded under the following conditions using a twin-screw extruder (KZW15TW) manufactured by Technovel Co., Ltd. to obtain strands.

[0109] Model: KZW15TW-45MG-NH (15mm twin-screw extruder) L / D: 45 Screw rotation speed: 200 rpm Set temperature: 190℃

[0110] The obtained strands were water-cooled and then cut in a pelletizer to obtain pellets of an ethylene-based resin composition. Sheets were prepared from the obtained ethylene-based resin composition pellets according to the sheet molding method described above, and the heat shrinkage rate and water vapor permeability of the obtained sheets were measured. The measurement results are shown in Table 3.

[0111] [Example 4] 60% by mass of the ethylene-α-olefin copolymer (A-1) pellets prepared above and 40% by mass of the ethylene-α-olefin copolymer (A-3) pellets prepared above were stirred and mixed. The resulting mixture was melt-kneaded in the same manner as in Example 3, and the resulting strand was water-cooled and then cut in a pelletizer to obtain pellets of an ethylene-based resin composition. Sheets were prepared from the obtained ethylene-based resin composition pellets according to the sheet molding method described above, and the heat shrinkage rate and water vapor permeability of the obtained sheets were measured. The measurement results are shown in Table 3.

[0112] [Example 5] 70% by mass of ethylene-α-olefin copolymer (A-4) pellets and 30% by mass of ethylene-α-olefin copolymer (A-1) pellets prepared above were stirred and mixed. The resulting mixture was melt-kneaded in the same manner as in Example 3, and the resulting strand was water-cooled and then cut in a pelletizer to obtain pellets of an ethylene-based resin composition. Sheets were prepared from the obtained ethylene-based resin composition pellets according to the sheet molding method described above, and the heat shrinkage rate and water vapor permeability of the obtained sheets were measured. The measurement results are shown in Table 3.

[0113] [Example 6] 85% by mass of the ethylene-α-olefin copolymer (A-1) pellets prepared above and 15% by mass of the ethylene-α-olefin copolymer (A'-9) pellets were stirred and mixed. The resulting mixture was melt-kneaded in the same manner as in Example 3, and the resulting strand was water-cooled and then cut in a pelletizer to obtain pellets of an ethylene-based resin composition. The heat shrinkage rate and measurement results are shown in Table 3.

[0114] [Comparative Example 1] Using 100% by mass of the ethylene-α-olefin copolymer (A-3) pellets prepared above, a sheet was prepared according to the sheet molding method described above, and the heat shrinkage rate and water vapor permeability of the obtained sheet were measured. The measurement results are shown in Table 3.

[0115] [Comparative Example 2] Using 100% by mass of ethylene-α-olefin copolymer (A-4) pellets, a sheet was prepared according to the sheet molding method described above, and the heat shrinkage rate and water vapor permeability of the obtained sheet were measured. The measurement results are shown in Table 3.

[0116] [Comparative Example 3] Using 100% by mass of ethylene-α-olefin copolymer (A-5) pellets, a sheet was prepared according to the sheet molding method described above, and the heat shrinkage rate and water vapor permeability of the obtained sheet were measured. The measurement results are shown in Table 3.

[0117] [Comparative Example 4] 80% by mass of ethylene-α-olefin copolymer (A-3) pellets and 20% by mass of ethylene-α-olefin copolymer (A'-9) pellets prepared above were stirred and mixed. The resulting mixture was melt-kneaded in the same manner as in Example 3, and the resulting strand was water-cooled and then cut in a pelletizer to obtain pellets of an ethylene-based resin composition. Sheets were prepared from the obtained ethylene-based resin composition pellets according to the sheet molding method described above, and the heat shrinkage rate and water vapor permeability of the obtained sheets were measured. The measurement results are shown in Table 3.

[0118] [Comparative Example 5] Using 100% by mass of ethylene-α-olefin copolymer (A-6) pellets, a sheet was prepared according to the sheet molding method described above, and the heat shrinkage rate and water vapor permeability of the obtained sheet were measured. The measurement results are shown in Table 3.

[0119] [Comparative Example 6] Using 100% by mass of ethylene-α-olefin copolymer (A'-8) pellets, a sheet was prepared according to the sheet molding method described above, and the heat shrinkage rate and water vapor permeability of the obtained sheet were measured. The measurement results are shown in Table 3.

[0120]

[0121] Table 3 shows the MT / η ratio of the ethylene resin composition (Z). ＊ 0.6 × 10 －４ Examples 1 to 6 described above are expected to exhibit excellent embedding moldability. Furthermore, the sheet samples of Examples 1 to 6 do not melt and have low heat shrinkage rates, indicating good heat resistance. Therefore, the sheet samples of Examples 1 to 6 have excellent embedding moldability and heat resistance. In addition, although not the main focus of this invention, the sheet samples of Examples 1 to 6 also exhibit excellent water vapor barrier properties.

Claims

1. Ethylene-α-olefin copolymer (A), which is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, is divided by mass fraction (W Ａ A current collector wire fixing film for busbarless solar cell modules containing an ethylene-based resin composition (Z) that contains ) in an amount of 50% to 100% by mass and satisfies the following requirements (a) to (c): (a) Melt tension [MT(g)] at 190°C and shear viscosity [η] at 200°C and angular velocity 1.0 rad / sec. * (P)) Ratio to [MT / η * (g / P) is 0.6 × 10 －４ The above 4.0 x 10 －４ It falls within the following range: (b) Density of 880 kg / m³ ３ More than 920kg / m ３ The following ranges apply: (c) 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 g / 10 min.

2. The current collecting wire fixing film for a busbarless solar cell module according to claim 1, wherein the ethylene-α-olefin copolymer (A) satisfies the following requirements (1) to (3). (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. (3) In the 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.

3. The current collector wire fixing film for a busbarless solar cell module according to claim 2, wherein the ethylene-α-olefin copolymer (A) further satisfies the following requirement (4). (4) The weight-average molecular weight (Mw) of the component that elutes at 75°C or higher in cross-fractional chromatography (CFC) measurement. Ｘ ) and the weight-average molecular weight (Mw) of the entire sample. Ｔ ) Ratio (Mw Ｘ / Mw Ｔ ) is less than 1.

4. The current collector wire fixing film for a busbarless solar cell module according to claim 2, wherein the ethylene-α-olefin copolymer (A) 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 5°C or more and 35°C or less.

5. A busbarless solar cell module comprising a current collector wire fixing film for a busbarless solar cell module according to any one of claims 1 to 4.

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