JP2014240473A - Resin sealing sheet and method of producing the same, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin sealing sheet that has high productivity and a low thermal shrinkage, and satisfies physical properties required for a resin sealing sheet in a balanced manner, and a method of producing the same, and a solar cell module.SOLUTION: A resin sealing sheet comprises a first polyolefin resin having 6 g/10 min or more of Melt Index at 190°C and 2.16 kg load measured in accordance with ASTM D-1238, and also having a melting point of 90°C or less. The resin sealing sheet has 2-60% of a gel fraction and 20-100 ML of Mooney viscosity at 110°C.

Description

  The present invention relates to a resin sealing sheet, a manufacturing method thereof, and a solar cell module.

  With the recent increase in awareness of the global environment, power generation systems using natural energy such as sunlight, wind power, hydropower, and geothermal heat have attracted attention. Among these, the power generation system (solar cell) using sunlight can directly convert the energy generated by the photovoltaic effect into electric power. Therefore, research and development has been actively conducted as a clean and efficient energy system. It is attracting attention as an industrial and household energy system.

  Typical examples of the solar battery cell include a single crystal or polycrystalline crystal silicon cell, an amorphous silicon cell, and a thin film cell containing a compound semiconductor.

  By the way, solar cells are often used outdoors exposed to wind and rain for a long time, modularized by bonding a glass plate or back sheet etc. to the power generation part, preventing intrusion of moisture from the outside, The power generation part is protected and leakage is prevented. As a member to protect the power generation part, transparent glass or transparent resin is used on the light incident side in order to ensure the amount of light necessary for power generation, while an aluminum foil called a back sheet or footing is used on the opposite member. Polyvinyl resin (PVF), polyethylene terephthalate (PET), or a laminated sheet obtained by subjecting these to barrier coating with silica or the like is used. When the power generation portion is sandwiched between such resin-sealing sheets, and the outside is further covered with glass or a backsheet and subjected to heat treatment, the resin of the resin-sealing sheet is melted and the whole can be modularized.

  The above-described resin sealing sheet sandwiching the power generation portion has good adhesion to glass, the power generation element, and the back sheet, and prevents flow of the power generation element due to melting of the resin sealing sheet in a high temperature state (creep resistance). ), Transparency that does not hinder the incidence of sunlight is required as a characteristic. From these viewpoints, conventional resin-encapsulated sheets are made of an ethylene-vinyl acetate copolymer (hereinafter also referred to as “EVA”), an ultraviolet absorber for measures against ultraviolet degradation, and an improvement in adhesion to glass. An additive such as a silane coupling agent and an organic peroxide for crosslinking are blended, and the film is formed by calendar molding or T-die casting. Furthermore, in view of being exposed to sunlight for a long period of time, various additives such as a light-resistant agent are blended in order to prevent a decrease in optical properties due to deterioration of the resin. Thereby, the transparency which does not inhibit the incidence of sunlight for a long time is maintained.

  The method of modularizing a solar cell with the above-described conventional resin-encapsulated sheet is obtained by superposing glass / resin encapsulated sheet / power generation element such as crystalline silicon cell / resin encapsulated sheet / back sheet in this order, Using a dedicated solar cell vacuum laminator down, a step of preheating above the melting temperature of the resin (normally 150 ° C in the case of EVA), a pressing step of melting and bonding the resin sealing sheet, have. In the preheating process, the resin of the resin encapsulating sheet is melted, and in the pressing process, the melted resin and a member in contact with the resin are in close contact and vacuum laminated. Moreover, in these processes, the crosslinking agent (for example, organic peroxide) contained in the resin encapsulating sheet is thermally decomposed to accelerate the EVA crosslinking, and at the same time, contained in the resin encapsulating sheet. Coupling agent is covalently bonded to the member in contact. Thereby, the creep resistance of the resin-encapsulated sheet and the adhesiveness with the glass, the power generation element, and the back sheet are improved.

  However, when a resin-encapsulated sheet containing EVA is used for a long period of time, yellowing and cracking occur, and deterioration and alteration such as foaming are likely to occur, which accelerates cell corrosion and reduces power generation efficiency. It was thought to be the cause. These deteriorations and alterations include acetic acid that can be generated from EVA having a highly hydrolyzable ester structure, cross-linking aids such as organic peroxides and polyfunctional vinyl compounds used in the cross-linking reaction, residues of the cross-linking agents, It is considered that the reaction product, higher carbon at the EVA cross-linking point, and active sites such as reaction end are the cause.

  In order to solve these problems, Patent Document 1 discloses an adhesive sheet made of an alkoxysilane-modified ethylene-based resin having a melting point of 80 ° C. or higher and 120 ° C. or lower.

  Patent Document 2 discloses a sealing material containing a sealing material for an electronic device using a polyolefin copolymer and a crosslinking agent such as an organic peroxide.

  Furthermore, in patent document 3, the point which is inferior in the softness | flexibility and transparency which are the problems of a polyethylene-type sealing material is improved by setting it as the composition containing 2 or more types of polyethylene-type resin from which the density of a specific range differs. A solar cell module filler composition is disclosed.

Japanese Patent Laid-Open No. 2002-235048 JP 2010-504647 A JP 2011-37883 A

  In recent years, with the fall in the price of solar cell modules, there is an increasing demand for cost reduction for resin-encapsulated sheets, and further improvement in productivity of resin-encapsulated sheets is required. However, in patent documents 1-3, the indication regarding the improvement of the productivity of a resin sealing sheet is not made. Further, there is no disclosure of suppressing the increase in the thermal shrinkage rate of the sealing sheet in order to increase the speed of the resin sealing sheet production line and improve the productivity of the resin sealing sheet.

  The present invention has been made in view of the above problems, and has a high productivity, a low thermal shrinkage, and a resin sealing sheet that satisfies the physical properties required of the resin sealing sheet in a well-balanced manner, and a method for producing the same. An object of the present invention is to provide a solar cell module.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors include a polyolefin-based resin having a predetermined melting point and a predetermined fluidity, and having a predetermined gel fraction and a predetermined Mooney viscosity. If it was a sealing sheet, it discovered that the said subject could be solved and came to make this invention.

That is, the present invention is as follows.
[1]
Including a first polyolefin resin having a Melt Index of 6 g / 10 min or more at 190 ° C. and a load of 2.16 kg measured in accordance with ASTM D-1238, and a melting point of 90 ° C. or less;
The gel fraction is 2-60%,
Mooney viscosity is 20-100 ML at 110 ° C.,
Resin sealing sheet.
[2]
The resin-encapsulated sheet according to [1] above, wherein 0.01 to 10 parts by mass of a silane coupling agent is copolymerized with 100 parts by mass of the first polyolefin resin.
[3]
The resin sealing sheet according to [1] or [2] above, wherein the melting point of the first polyolefin resin is 50 ° C. or higher and 80 ° C. or lower.
[4]
The resin-encapsulated sheet according to any one of [1] to [3], wherein the melt index of the first polyolefin-based resin is 8 g / 10 minutes or more and 40 g / 10 minutes or less.
[5]
The resin-sealed sheet according to any one of [1] to [4], wherein the ionizing radiation treatment has been performed twice or more.
[6]
The resin-sealed sheet according to any one of [2] to [5], wherein the silane coupling agent is a compound having a vinyl group and / or a methacryloxy group.
[7]
A multilayer resin encapsulating sheet comprising the resin encapsulating sheet according to any one of [1] to [6] above and an outer layer laminated on the resin encapsulating sheet.
[8]
The outer layer includes a second polyolefin resin having a Melt Index of 6 g / 10 min or more at 190 ° C. and a load of 2.16 kg measured in accordance with ASTM D-1238 and a melting point of 90 ° C. or less. The multilayer resin encapsulating sheet according to [7] above.
[9]
The multilayer resin sealing sheet which has an inner layer and the resin sealing sheet of any one of said clause [1]-[6] laminated | stacked on the surface and back surface of this inner layer.
[10]
The inner layer includes a third polyolefin resin having a Melt Index of 6 g / 10 min or more at 190 ° C. and a load of 2.16 kg measured in accordance with ASTM D-1238, and a melting point of 90 ° C. or less. The multilayer resin encapsulating sheet according to [9] above.
[11]
100 parts by mass of a first polyolefin resin having a Melt Index of 6 g / 10 min or more at 190 ° C. under a load of 2.16 kg measured in accordance with ASTM D-1238 and a melting point of 90 ° C. or less, and a silane cup An ionizing radiation treatment step for obtaining a resin encapsulating sheet by subjecting the raw material containing 0.01 to 10 parts by mass of a ring agent and substantially not containing an organic peroxide to ionizing radiation treatment. And
The Mooney viscosity of the resin-encapsulated sheet is 20 to 100 ML at 110 ° C.
Manufacturing method of resin sealing sheet.
[12]
It has the resin sealing sheet according to any one of [1] to [6] above and / or the multilayer resin sealing sheet according to any one of [7] to [10] above as a sealing material. , Solar cell module.

  According to the present invention, it is possible to provide a resin-encapsulated sheet having high productivity, a low thermal shrinkage, and satisfying the physical properties required of the resin-encapsulated sheet in a well-balanced manner, a manufacturing method thereof, and a solar cell module. .

It is a graph which shows the relationship between the dump heat test time in Example 17, and the ratio of Pmax after a dump heat test with respect to Pmax (Pmax initial stage) before a dump heat test. In Example 17, it is a graph which shows the relationship between PID test time and the ratio of Pmax after a PID test with respect to Pmax (Pmax initial stage) before a PID test.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

[Resin sealing sheet]
The resin sealing sheet according to this embodiment is
Melt Index (hereinafter also referred to as “MI”) measured at 190 ° C. under a load of 2.16 kg measured in accordance with ASTM D-1238 is 6 g / 10 min or more, and the first melting point is 90 ° C. or less. Including polyolefin resin,
The gel fraction is 2-60%,
The Mooney viscosity is 20 to 100 ML at 110 ° C.

  The resin sealing sheet according to the present embodiment can be softened by a method of directly applying energy such as heat to the resin component constituting the resin sealing sheet, or a method of generating vibration inherent to the resin component to generate heat. . The object to be sealed can be sealed by bringing the resin sealing sheet in the softened state into close contact with another substance (the object to be sealed). Specific methods for softening the resin component are not particularly limited, and examples thereof include known methods such as direct heating to the resin component, indirect heat such as radiant heat, and vibrational heat generation such as ultrasonic waves.

[First polyolefin resin]
The resin sealing sheet according to the present embodiment includes a first polyolefin resin. The first polyolefin resin has an MI of 6 g / 10 min or more and a melting point of 90 ° C. or less. By using the first polyolefin-based resin, the resulting resin-encapsulated sheet has a lower thermal shrinkage rate, and the productivity can be further improved.

  Melting | fusing point of said 1st polyolefin resin is 90 degrees C or less, 50 to 80 degreeC is preferable, 60 to 80 degreeC is more preferable, 70 to 80 degreeC is further more preferable. When the melting point is 90 ° C. or less, the flexibility and transparency of the obtained resin encapsulated sheet are improved. Moreover, it exists in the tendency for the resin sealing sheet obtained to become difficult to block during storage by using polyolefin-type resin whose melting | fusing point is 50 degreeC or more. In addition, melting | fusing point can be measured by the method as described in an Example.

  The MI of the first polyolefin resin is 6 g / 10 min or more, preferably 8 g / 10 min or more and 40 g / 10 min or less, and more preferably 10 g / 10 min or more and 25 g / 10 min or less. When the MI is 6 g / 10 minutes or more, the thermal shrinkage rate of the obtained resin-encapsulated sheet is lowered, and the speed during sheet production can be increased, so that the productivity is further improved. Further, when the MI is 40 g / 10 min or less, the viscosity of the molten resin at the time of sheet molding does not tend to be too low, and the film tends to be formed easily. MI can be measured by the method described in the examples.

  Although it does not specifically limit as a 1st polyolefin resin, For example, a polyethylene resin, a polypropylene resin, and a polybutene resin are preferable.

(Polyethylene resin)
“Polyethylene resin” refers to a homopolymer of ethylene or a copolymer of ethylene and one or more other monomers. Although it does not specifically limit as a polyethylene-type resin, For example, polyethylene, an ethylene-alpha-olefin copolymer, etc. are mentioned.

  Although it does not specifically limit as said polyethylene, For example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), linear very low density polyethylene (VLDPE, ULDPE) etc. are mentioned.

  Although it does not specifically limit as said ethylene-alpha-olefin copolymer, For example, the copolymer containing ethylene and at least 1 sort (s) chosen from the group which consists of C3-C20 alpha olefin is preferable, A copolymer containing ethylene and at least one selected from the group consisting of α-olefins having 3 to 12 carbon atoms is more preferable.

  The α-olefin is not particularly limited, and examples thereof include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1 -Decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like. The α-olefin may be used alone or in combination of two or more. Among the ethylene-α-olefin copolymers, a copolymer of ethylene and at least one comonomer selected from the group consisting of propylene comonomer, butene comonomer, hexene comonomer and octene comonomer is generally easily available. Yes, it can be used suitably. The proportion of α-olefin in all monomers constituting the copolymer (based on charged monomers) is preferably 6 to 30% by mass. Further, the ethylene-α-olefin copolymer is preferably a soft copolymer, and the crystallinity by X-ray method is preferably 30% or less.

  The polyethylene resin can be polymerized using a known catalyst such as a single site catalyst or a multisite catalyst. Among these, it is preferable to perform polymerization using a single site catalyst.

The density of the polyethylene resin is preferably from 0.900 g / cm ³ or less, more preferably 0.860~0.890g / cm ^3, more preferably 0.870~0.890g / cm ^3. When the density is 0.900 g / cm ³ or less, the melting point of the resin tends to be 90 ° C. or less, and the flexibility and transparency of the obtained sealing sheet tend to be better.

  As said polyethylene-type resin, the polyethylene-type copolymer which controlled crystal / amorphous structure (morphology) by nano order can also be used.

(Polypropylene resin)
Examples of the polypropylene resin include polypropylene, propylene-α-olefin copolymer, and terpolymer of propylene, ethylene, and α-olefin.

  The propylene-α-olefin copolymer refers to a copolymer composed of at least one selected from propylene and α-olefin. The propylene-α-olefin copolymer is preferably a copolymer composed of propylene and at least one selected from ethylene and an α-olefin having 4 to 20 carbon atoms, and propylene, ethylene and 4 to 8 carbon atoms. A copolymer comprising at least one selected from α-olefins is more preferable. Examples of the α-olefin having 4 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, and 3-methyl-1-pentene. , 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like, and these can be used alone or in combination. Moreover, it is preferable that the content rate (charged monomer reference | standard) of ethylene and / or alpha-olefin in all the monomers which comprise the said propylene-alpha-olefin copolymer is 6-30 mass%. Furthermore, the propylene-α-olefin copolymer is preferably a soft copolymer, and preferably has a crystallinity of 30% or less by an X-ray method.

  As the propylene-α-olefin copolymer, a copolymer of propylene and at least one comonomer selected from ethylene comonomer, butene comonomer, hexene comonomer, and octene comonomer is generally easily available, and preferably Can be used.

The polypropylene resin can be polymerized using a known catalyst such as a single-site catalyst or a multi-site catalyst, and is preferably polymerized using a single-site catalyst. Also the polypropylene-based resin, from the viewpoint of cushioning properties, it is preferable that a density of 0.860~0.920g / cm ^3, more preferably 0.870~0.915g / cm ^3, 0. More preferably, it is 870-0.910 g / cm < ³ >. When the density is 0.920 g / cm ³ or less, the cushioning property tends to be good. If the density exceeds 0.920 g / cm ³ , the transparency may be deteriorated.

  As the polypropylene resin, a polypropylene copolymer resin having a crystal / amorphous structure (morphology) controlled in nano order can also be used.

  Examples of the polypropylene resin include copolymers of propylene and α-olefins such as ethylene, butene, hexene, and octene, or ternary compounds of propylene, ethylene and α-olefins such as butene, hexene, and octene. A copolymer etc. can be used conveniently. These copolymers may be in any form such as a block copolymer, a random copolymer, etc., preferably a random copolymer of propylene and ethylene, or a random copolymer of propylene, ethylene and butene. is there.

  The polypropylene resin is not limited to a resin polymerized with a catalyst such as a Ziegler-Natta catalyst, but may be a resin polymerized with a metallocene catalyst, for example, syndiotactic polypropylene, isotactic polypropylene, etc. it can. Moreover, it is preferable that the ratio (based on preparation monomer) of the propylene in all the monomers which comprise a polypropylene resin is 60-80 mass%. Furthermore, from the viewpoint of excellent heat shrinkability, the propylene content ratio (based on the charged monomer) in all monomers constituting the polypropylene resin is 60 to 80% by mass, and the ethylene content ratio (based on the charged monomer) is 10 to 30. A ternary copolymer having a butene content ratio (based on charged monomers) of 5 to 20% by mass is preferable.

  As the polypropylene resin, a resin obtained by uniformly finely dispersing a rubber component having a high concentration of 50% by mass or less with respect to the total amount of the polypropylene resin can be used.

  When the resin constituting the resin sealing sheet contains the polypropylene resin, properties such as hardness and heat resistance tend to be further improved.

(Polybutene resin)
The “polybutene resin” refers to a butene homopolymer or a copolymer of butene and one or more other monomers. Since the polybutene-based resin is particularly excellent in compatibility with the polypropylene-based resin, it is preferably used in combination with the polypropylene-based resin for the purpose of adjusting the hardness and stiffness of the resin sealing sheet. The polybutene-based resin is not particularly limited. For example, the polybutene-based resin is crystalline and includes a butene and at least one selected from the group consisting of ethylene, propylene, and olefinic compounds having 5 to 8 carbon atoms. In addition, a high molecular weight polybutene resin in which the content of butene in all monomers constituting the polybutene resin is 70 mol% or more can be preferably used.

[Other resins]
The resin sealing sheet according to the present embodiment may contain other resins other than the first polyolefin-based resin described above, as necessary. For example, a predetermined thermoplastic resin may be included for the purpose of newly imparting cushioning properties.

  50 mass%-100 mass% are preferable, as for content of the 1st polyolefin resin in resin which comprises the resin sealing sheet which concerns on this embodiment, 70 mass%-100 mass% are more preferable, and 90 mass%- 100 mass% is more preferable. When the content of the first polyolefin resin is within the above range, the obtained sheet tends to have more excellent transparency. Moreover, 0 mass%-50 mass% are preferable, as for content of other resin, 0 mass%-30 mass% are more preferable, and 0 mass%-10 mass% are further more preferable.

  The thermoplastic resin is not particularly limited. For example, styrene resin, vinyl chloride resin, polyurethane resin, chlorine ethylene polymer resin, polyamide resin, biodegradable resin, plant-derived raw material resin, hydrogen Addition block copolymer resin is mentioned. Among these, a hydrogenated block copolymer resin is preferable. By including the hydrogenated block copolymer resin excellent in compatibility with the crystalline polypropylene resin, the transparency of the resin-encapsulated sheet tends to be further improved.

  The hydrogenated block copolymer resin is not particularly limited, but for example, a hydrogenated block copolymer of vinyl aromatic hydrocarbon and conjugated diene is preferable.

  The vinyl aromatic hydrocarbon is not particularly limited. For example, styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, Examples include vinyl anthracene, 1,1-diphenylethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene, and the like. Among these, styrene is more preferable. A vinyl aromatic hydrocarbon may be used individually by 1 type, and may use 2 or more types together.

  The conjugated diene is a diolefin having a pair of conjugated double bonds, and is not particularly limited. For example, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3- Examples thereof include dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like. A conjugated diene may be used individually by 1 type, and may use 2 or more types together.

〔Silane coupling agent〕
In the resin sealing sheet according to the present embodiment, it is preferable that 0.01 to 10 parts by mass of a silane coupling agent is copolymerized with 100 parts by mass of the first polyolefin resin. By including a silane coupling agent together with the first polyolefin-based resin, if necessary, with other thermoplastic resins, the adhesion to members such as glass, solar battery power generation cells and back sheets tends to be further improved. is there. More specifically, the silane coupling agent is efficiently introduced into the main chain of the first polyolefin-based resin by irradiating the resin sealing sheet containing the silane coupling agent with ionizing radiation (graft copolymerization). By using such a resin encapsulating sheet as an encapsulant for solar cells, the adhesive force between the resin encapsulating sheet and members such as glass, power generation cells, and back sheets, in particular, water-resistant adhesion tends to be further improved. It is in.

  The content and type of the silane coupling agent can be appropriately selected depending on the target adhesive strength and the ease of reaction of the silane coupling agent with the first polyolefin resin by ionizing radiation irradiation. The content of the silane coupling agent is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and 0.2 to 3 parts by mass with respect to 100 parts by mass of the first polyolefin resin. Is more preferable, and 0.3 to 2 parts by mass is even more preferable. When the content is 0.01 parts by mass or more, the adhesiveness tends to be superior. Moreover, by being 10 mass parts or less, it exists in the tendency which can suppress the bleed-out to the sheet | seat surface of a silane coupling agent, and can suppress the adhesive fall by bleed-out more.

  Further, the kind of the silane coupling agent may be appropriately selected in consideration of the transparency of the resin sealing sheet and the degree of dispersion, corrosion to the extruder, and the viewpoint of extrusion stability. Although it does not specifically limit as a silane coupling agent, For example, the compound etc. which have 1 type chosen from the group which consists of a vinyl group, an isocyanate group, a mercapto group, and a methacryloxy group are mentioned. Among these, a compound having a vinyl group and / or a methacryloxy group is preferable. By having a vinyl group and / or a methacryloxy group, radicals are generated at the site of the vinyl group when irradiated with an electron beam, and the silane coupling agent easily reacts with the main chain of the first polyolefin resin. As described above, the adhesiveness tends to be further improved.

  The silane coupling agent is not particularly limited. For example, γ-chloropropylmethoxysilane, vinylmethyldimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris (β-methoxyethoxy) silane, 3-isocyanate. Propyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, β- (3,4-ethoxycyclohexyl) ethyltrimethoxysilane, vinyltriacetoxysilane And compounds having an unsaturated group, such as γ-mercaptopropyltrimethoxysilane.

  The calculation method of the reaction rate of the silane coupling agent to the first polyolefin resin is as follows. The resin sealing sheet is swollen or dissolved in a good solvent, and the first polyolefin resin is reprecipitated in the poor solvent. The content of silicon atoms derived from the silane coupling agent present in the first polyolefin resin obtained by reprecipitation is determined by ICP emission analysis. From the ratio between the amount of silicon atoms and the amount of Si atoms in the silane coupling agent introduced as a raw material in the production stage of the resin encapsulating sheet, the silane coupling of the resin encapsulating sheet in the previous stage of modularization The reaction rate of the agent to the first polyolefin resin can be calculated. In the resin sealing sheet according to the present embodiment, the reaction rate is preferably 50% or more, and more preferably 70% or more.

[Ionizing radiation treatment]
The resin sealing sheet according to the present embodiment is subjected to ionizing radiation treatment. By performing the ionizing radiation treatment, the organic peroxide becomes unnecessary, the productivity of the resin-encapsulated sheet can be further improved, and the thermal shrinkage rate of the resin-encapsulated sheet tends to be lower. The ionizing radiation treatment will be described later. The number of treatments is preferably 2 or more, and more preferably 3 or more. The upper limit of the number of treatments is not particularly limited, but it is preferably 10 or less in consideration of the number of devices to be installed, the acceleration voltage of the devices, the complexity of the device for performing the treatment multiple times, and the like. When the number of treatments is within the above range, the cost tends to be better.

  A method for discriminating sheets that have not been subjected to ionizing radiation treatment is not particularly limited, and examples include a method for discriminating whether the gel fraction is 2% or more. Those not subjected to ionizing radiation treatment usually do not have a gel fraction of 2% or more, and sheets subjected to ionizing radiation treatment tend to have a gel fraction of 2% or more. In the case of a sheet containing an organic peroxide, there is a possibility that the gel fraction of the sheet not subjected to electronic radiation treatment due to heat during storage or the like may be 2% or more. Since there is a peroxide decomposition residue, it can be distinguished.

〔Additive〕
The resin-encapsulated sheet according to the present embodiment, together with the first polyolefin resin, has an ultraviolet absorber, a light stabilizer, a heat stabilizer, an antioxidant, and the like in order to improve weather resistance, light resistance, heat resistance, and the like. An agent or the like can be further included. By including these additives, the resin-encapsulated sheet tends to be excellent in yellowing prevention, crack resistance, and transparency over a long period of time. Hereinafter, the ultraviolet absorber, light stabilizer, heat stabilizer, and antioxidant will be described.

(UV absorber)
UV absorbers absorb harmful UV rays in sunlight and convert them into innocuous heat energy within the molecule. In the resin sealing sheet and the solar cell module using the resin sealing sheet, it is possible to prevent excitation of active species at the start of light degradation in the resin used for the resin sealing sheet and the back sheet.

  The content of the ultraviolet absorber is preferably 0.1 parts by mass or more and 0.3 parts by mass or less, and more preferably 0.15 parts by mass or more and 0.3 parts by mass or less with respect to 100 parts by mass of the first polyolefin resin. 0.15 parts by mass or more and 0.25 parts by mass or less is more preferable. When the content is 0.1 parts by mass or more, the light resistance tends to be superior. Moreover, there exists a tendency which can prevent yellowing by a heat | fever more because it is 0.3 mass part or less.

  Although it does not specifically limit as a ultraviolet absorber, For example, a benzophenone type compound and a benzotriazole type compound are mentioned.

  Although it does not specifically limit as a benzophenone type compound, For example, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-5-sulfobenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2 Examples include '-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone.

  Moreover, it does not specifically limit as a benzotriazole type compound, For example, 2- (2'-hydroxy-5'-methyl-phenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-). Tertiary-butylmethyl-phenyl) benzotriazole, 2- (2′-hydroxy-3′-tertiarybutyl-5′-methyl-phenyl) -5-chlorobenzotriazole, and the like.

  Of these, benzophenone compounds are preferable, and 2-hydroxy-4-n-octoxybenzophenone is more preferable. An ultraviolet absorber may be used individually by 1 type, and may use 2 or more types together.

(Light stabilizer)
The light stabilizer supplements the active species at the start of photodegradation in the first polyolefin resin and can prevent photooxidation. The content of the light stabilizer is preferably 0.05 parts by mass or more and 0.2 parts by mass or less, more preferably 0.1 parts by mass or more and 0.2 parts by mass or less, with respect to 100 parts by mass of the polyolefin resin. 1 part by mass or more and 0.15 part by mass or less are more preferable. When the content of the light stabilizer is 0.05 parts by mass or more, the light resistance tends to be superior. Moreover, when the content of the light stabilizer is 0.2 parts by mass or less, thermal yellowing and bleeding out of the light stabilizer are further suppressed, and the adhesiveness tends to be more excellent.

  Although it does not specifically limit as a light stabilizer, For example, a hindered amine type compound and a hindered piperidine type compound are mentioned.

  Although it does not specifically limit as a hindered amine type compound, For example, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) Sebacate etc. are mentioned.

  In addition, the hindered piperidine compound is not particularly limited. For example, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, dimethyl-1- (2-hydroxyethyl) -4-hydroxy succinate Examples include -2,2,6,6-tetramethylpiperidine polycondensate.

  Of these, hindered amine compounds are preferred. A light stabilizer may be used individually by 1 type and may use 2 or more types together.

  The method of adding the ultraviolet absorber and the light stabilizer to the first polyolefin resin constituting the resin sealing sheet is not particularly limited, and is a method of adding the molten resin in a liquid state directly to the target resin layer. Examples thereof include a method of kneading and adding, a method of applying after sheeting, and the like.

(Antioxidant)
The antioxidant can improve the stability of the resin encapsulating sheet at a high temperature. The content of the antioxidant is preferably 0.01 parts by mass or more and 1 part by mass or less, and more preferably 0.1 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the first polyolefin resin. When the content of the antioxidant is 0.01 parts by mass or more, the antioxidant function is more excellent, and the oxidative deterioration of the resin tends to be suppressed. Moreover, when the content of the antioxidant is 1 part by mass or less, there is a tendency that an adhesive deterioration due to bleeding out of the excessive antioxidant onto the surface of the molded product and yellowing of the molded product are suppressed.

  Although it does not specifically limit as antioxidant, For example, a monophenol antioxidant, a bisphenol antioxidant, a polymeric phenolic antioxidant, a sulfur antioxidant, and a phosphoric acid antioxidant are mentioned.

  Although it does not specifically limit as a monophenol type antioxidant, For example, 2, 6- di-tert- butyl-p-cresol, butylated hydroxyanisole, 2, 6-di-tert- butyl-4-ethyl phenol N-octadecyl- (4-hydroxy-3,5-ditertiarybutylphenyl) propionate.

  The bisphenol-based antioxidant is not particularly limited, and examples thereof include 2,2′-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2′-methylene-bis- (4-ethyl- 6-tert-butylphenol), 4,4′-thiobis- (3-methyl-6-tert-butylphenol), 4,4′-butylidene-bis- (3-methyl-6-tert-butylphenol), 3,9 -Bis [{1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} ethyl} 2,4,8,10-tetraoxaspiro] 5 5-Undecane is mentioned.

  The polymeric phenolic antioxidant is not particularly limited, and examples thereof include 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane and 1,3,5-trimethyl. -2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tetrakis- {methylene-3- (3 ', 5'-di-tert-butyl-4'-hydro Kissphenyl) propionate} methane, bis {(3,3′-bis-4′-hydroxy-3′-tert-butylphenyl) butyric acid} glycol ester, 1,3,5-tris (3 ′, 5 '-Di-tert-butyl-4'-hydroxybenzyl) -s-triazine-2,4,6- (1H, 3H, 5H) trione, triphenol (vitamin E) That.

  Although it does not specifically limit as a sulfur type antioxidant, For example, a dilauryl thiodipropionate, a dimyristyl thiodipropionate, a distearyl thiopropionate is mentioned.

  Although it does not specifically limit as a phosphoric acid type antioxidant, For example, a triphenyl phosphite, a diphenylisodecyl phosphite, a phenyl diisodecyl phosphite, 4,4'- butylidene-bis- (3-methyl-6-tert-butyl) Phenyl-di-tridecyl) phosphite, cyclic neopentanetetraylbis (octadecylphosphite), tris (mono and / or di) phenyl phosphite, diisodecylpentaerythritol diphosphite, 9,10-dihydro-9-oxa -10-phosphaphenanthrene-10-oxide, 10- (3,5-di-tert-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10 -Oxide, 10-decyloxy-9,10-di Dro-9-oxa-10-phosphaphenanthrene, cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,6-di-) tert-methylphenyl) phosphite, 2,2-methylenebis (4,6-tert-butylphenyl) octyl phosphite.

  These antioxidants may be used alone or in combination of two or more.

(Other additives)
In addition to the above additives, other additives can be added to the resin-encapsulated sheet according to the present embodiment as necessary. Examples of other additives include, but are not limited to, antifogging agents, plasticizers, surfactants, colorants, antistatic agents, crystal nucleating agents, lubricants, antiblocking agents, inorganic fillers, crosslinking regulators, and the like. Can be mentioned.

  The content of additives other than the colorant is preferably 5% by mass or less, more preferably 1% by mass or less, and still more preferably 0.5% by mass or less with respect to the total amount of the first polyolefin resin. About content of a coloring agent, 1 to 20 mass% is preferable.

[Multilayer resin encapsulated sheet]
The 1st form of the multilayer resin sealing sheet which concerns on this embodiment has the resin sealing sheet which concerns on this embodiment, and the outer layer laminated | stacked on this resin sealing sheet. By laminating another resin layer (hereinafter also referred to as “outer layer”) on the resin sealing sheet according to the present embodiment described above, a multilayer resin sealing sheet having two or more layers can be configured. In this case, the “outer layer” may have a single-layer structure or a multi-layer structure. The outer layer includes a second polyolefin resin having a Melt Index of 6 g / 10 min or more at 190 ° C. and a load of 2.16 kg measured in accordance with ASTM D-1238 and a melting point of 90 ° C. or less. preferable. Here, as the second polyolefin resin, the same one as the first polyolefin resin may be used, or a different one may be used. The resin contained in the outer layer is not limited to the second polyolefin resin, and any other resin may be used.

  A two-layer structure can be formed by forming the outer layer only on one main surface of the resin-encapsulated sheet according to the present embodiment, and a three-layer structure can be formed by forming the outer layer on both main surfaces.

  Moreover, the 2nd form of the multilayer resin sealing sheet which concerns on this embodiment has an inner layer and the resin sealing sheet which concerns on this embodiment laminated | stacked on the surface and back surface of this inner layer. By using the resin sealing sheet according to the present embodiment and sandwiching other resin layers (hereinafter referred to as inner layers) on the front and back surfaces, a multilayer resin sealing sheet having three or more layers can be configured. In this case, the “inner layer” may have a single layer structure or a multi-layer structure. The inner layer contains a third polyolefin resin having a Melt Index of 6 g / 10 min or more at 190 ° C. under a load of 2.16 kg measured in accordance with ASTM D-1238 and a melting point of 90 ° C. or less. Is preferred. Here, as the third polyolefin-based resin, the same one as the first polyolefin-based resin can be used. The resin contained in the inner layer is not limited to the third polyolefin resin, and any other resin may be used.

  Moreover, a multilayer resin sealing sheet having a three-layer structure is obtained by using a plurality of resin sealing sheets according to this embodiment and sandwiching a predetermined inner layer between these resin sealing sheets.

  When the outer layer and the inner layer are laminated on the resin sealing sheet according to the present embodiment, the outer layer and the inner layer have the above-described polyolefin-based resin, silane coupling agent, light stabilizer, and the like according to desired performance. Ultraviolet absorbers and antioxidants can be used as appropriate. Moreover, it is preferable to use a light stabilizer and an ultraviolet absorber in combination in order to develop sealing properties over a long period of time.

  In the multilayer resin sealing sheet according to the present embodiment, the thickness of the layer on the side in contact with the object to be sealed is preferably 5% or more, more preferably 10% or more, with respect to the total thickness of the multilayer structure sheet. % Or more is more preferable. The upper limit is not particularly limited but is preferably 100%. When the film thickness is within the above range, the adhesiveness tends to be more excellent.

  The resin material, additive, and the like for the inner layer and the outer layer can be appropriately selected for the purpose of imparting other functions. For example, for the purpose of newly imparting cushioning properties, the inner layer and the outer layer may contain a predetermined thermoplastic resin.

  The thermoplastic resin used in the inner layer and the outer layer is not particularly limited. For example, polyolefin resin, styrene resin, vinyl chloride resin, polyester resin, polyurethane resin, chlorine ethylene polymer resin, polyamide resin Examples thereof include biodegradable resins, plant-derived raw material resins, and hydrogenated block copolymer resins. Of these, hydrogenated block copolymer resins and propylene copolymer resins having good compatibility with propylene-based copolymer resins and crystalline polypropylene-based resins and good transparency are preferable.

  Although it does not specifically limit as said hydrogenated block copolymer resin, For example, the block copolymer of vinyl aromatic hydrocarbon and conjugated diene is preferable. The vinyl aromatic hydrocarbon is not particularly limited. For example, styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, Examples include vinyl anthracene, 1,1-diphenylethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene, and the like. Of these, styrene is preferable. These may be used alone or in combination of two or more.

  The conjugated diene is a diolefin having a pair of conjugated double bonds, and is not particularly limited. For example, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3- Examples thereof include dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like. These may be used alone or in combination of two or more.

  As the propylene-based copolymer resin, a copolymer containing propylene and ethylene or an α-olefin having 4 to 20 carbon atoms is preferable. The content of ethylene or α-olefin is preferably 6 to 30% by mass. Although it does not specifically limit as an alpha olefin, For example, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-decene, Examples include 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like.

  The propylene-based copolymer resin may be polymerized using any catalyst such as a multi-site catalyst, a single-site catalyst, and the like. Furthermore, a propylene-based copolymer resin in which the polymer morphology is controlled in nano order can also be used.

[Characteristics of resin sealing sheet]
(Mooney viscosity)
The Mooney viscosity at 110 ° C. of the resin-encapsulated sheet according to this embodiment is 20 to 100 ML, preferably 30 to 90 ML, and more preferably 40 to 80 ML. When the Mooney viscosity is 20 ML or more, the resin-encapsulated sheet is excellent in creep resistance and can effectively prevent problems such as cell displacement. Further, when the Mooney viscosity is 100 ML or less, the resin-encapsulated sheet is excellent in fluidity and gap filling properties, and can sufficiently seal gaps such as cells and wirings during module production. The Mooney viscosity can be measured by the method described in the examples.

  The Mooney viscosity at 110 ° C. of the resin encapsulated sheet before ionizing radiation treatment is preferably 15 ML or less, more preferably 10 ML or less, and even more preferably 8 ML or less. It is preferable that the Mooney viscosity is in the above range because the productivity of the resin-encapsulated sheet can be easily improved and the thermal shrinkage rate of the obtained sheet can be further reduced.

  The Mooney viscosity at 110 ° C. of the resin encapsulated sheet after the ionizing radiation treatment is preferably 30 to 90 ML, more preferably 40 to 80 ML, and further preferably 45 to 75 ML. When the Mooney viscosity is within the above range, the balance between the gap filling property (fluidity) and the creep resistance of the resin-encapsulated sheet tends to be more excellent. In addition, the measuring method of Mooney viscosity is the same as the method as described in an Example.

  In the case of the multilayer resin encapsulated sheet of the first or second form, when the average Mooney viscosity of the entire multilayer resin encapsulated sheet is measured (all layer Mooney viscosity), the Mooney viscosity is 20 ML. It is preferably 100 ML or less, more preferably 30 ML or more and 90 ML or less, and further preferably 40 ML or more and 80 ML or less.

  In addition, Mooney viscosity can be measured by the method as described in the Example mentioned later. Mooney viscosity tends to increase with increasing dose in ionizing radiation treatment and decrease with decreasing dose.

(Gel fraction)
The gel fraction of the resin sealing sheet according to the present embodiment is 2% by mass or more and 60% by mass or less, preferably 3% by mass or more and 50% by mass or less, more preferably 4% by mass or more and 40% by mass or less. More preferably, it is at least 40% by mass. When the gel fraction is 2% by mass or more, the creep resistance is excellent, whereby problems such as cell displacement can be effectively prevented. Moreover, when the gel fraction is 60% by mass or less, the fluidity of the resin-encapsulated sheet is more excellent, and good gap filling properties are obtained. Thereby, it is possible to sufficiently seal gaps such as cells and wirings during module production. The gel fraction can be measured by the method described in the examples.

  In addition, a gel fraction can be measured by the method as described in the Example mentioned later. The gel fraction tends to increase when the irradiation dose in ionizing radiation treatment is increased and decrease when it is decreased.

(Heat shrinkage)
10% or less is preferable and, as for the thermal contraction rate in 70 degreeC of the resin sealing sheet which concerns on this embodiment, 5% or less is more preferable. When the heat shrinkage rate at 70 ° C. is 10% or less, it is possible to suppress the heat shrinkage of the sealing sheet at the preheating stage when the resin sealing sheet is laminated with glass, cells, and a back sheet. Thereby, position shift of a cell and contact between cells can be controlled. Moreover, it exists in the tendency which can suppress that problems, such as the resin sealing sheet shrink | contracting and the part which the resin sealing sheet was missing, generate | occur | produce. In addition, the “missing part” is a state in which the resin sealing sheet contracts and the area decreases, the area is originally smaller than the part that should be covered with resin, and the end portions of the power generation cells and the like are not covered with resin. That is, it is in an unsealed state.

  The thermal shrinkage rate of the resin-encapsulated sheet obtained is affected by the MI of the resin used, the processing temperature of the resin, the drawing speed during sheet processing, the winding speed, the cooling speed, the peelability of the sheet from the roll surface, etc. However, it was found that the high-speed film formation largely depends on the MI of the resin.

(Thickness and physical properties)
50-1500 micrometers is preferable, as for the thickness of the resin sealing sheet which concerns on this embodiment, and the multilayer resin sealing sheet of a 1st or 2nd form, 100-1000 micrometers is more preferable, 150-800 micrometers is more preferable. When the thickness is 50 μm or more, structurally sufficient cushioning properties can be obtained, and more excellent durability and strength tend to be obtained from the viewpoint of workability. On the other hand, when the thickness is 1500 μm or less, practically sufficient productivity can be ensured, and more excellent adhesion as a resin-sealed sheet tends to be obtained.

(optical properties)
The optical characteristics of the resin sealing sheet according to the present embodiment and the multilayer resin sealing sheet of the first or second form will be described. A Haze value is used as one index of optical characteristics. The Haze value is preferably 15% or less, more preferably 10% or less, and further preferably 8% or less. When the haze value is 15% or less, the object to be sealed sealed by the resin sealing sheet according to this embodiment and the multilayer resin sealing sheet of the first or second form can be confirmed on the appearance. When used as a sealing material for solar cells, a practically sufficient power generation efficiency is obtained, which is preferable. The lower limit of the Haze value is not particularly limited, and is preferably as small as possible and more preferably 0%. When the first polyolefin resin used in the resin sealing sheet according to the present embodiment has a melting point of 90 ° C. or lower, transparency tends to be good and the Haze value tends to be low. Here, the Haze value can be measured by the method described in Examples.

(Total light transmittance)
Moreover, 85% or more is preferable, as for the total light transmittance of the resin sealing sheet which concerns on this embodiment, and the multilayer resin sealing sheet of a 1st or 2nd form, 86% or more is more preferable, and 87% or more is further preferable. When the total light transmittance is within the above range, when used as a sealing material for solar cells, power generation efficiency that is practically sufficient tends to be exhibited. The upper limit of the total light transmittance is not particularly limited and is preferably as large as possible and more preferably 100%. When the first polyolefin resin used in the resin sealing sheet according to the present embodiment has a melting point of 90 ° C. or lower, transparency tends to be good and total light transmittance tends to be high. Here, the total light transmittance can be measured by the method described in Examples.

[Method for producing resin-encapsulated sheet]
The manufacturing method of the resin sealing sheet according to the present embodiment is as follows.
100 parts by mass of a first polyolefin resin having a Melt Index of 6 g / 10 min or more at 190 ° C. under a load of 2.16 kg measured in accordance with ASTM D-1238 and a melting point of 90 ° C. or less, and a silane cup An ionizing radiation treatment step for obtaining a resin encapsulating sheet by subjecting the raw material containing 0.01 to 10 parts by mass of a ring agent and substantially not containing an organic peroxide to ionizing radiation treatment. And
The Mooney viscosity of the resin sealing sheet is 20 to 100 ML at 110 ° C.

  Although the said original fabric does not have a restriction | limiting in particular, For example, it can manufacture with the following method. First, a resin composition containing the first polyolefin resin or the like is melted with an extruder, the molten resin is extruded from a die, and rapidly cooled and solidified to obtain an original fabric. As the extruder, a T die, an annular die, or the like is used, but it is preferable to use a T die because of easy thickness control and easy handling of the original fabric during high speed film formation.

  The first polyolefin resin can be the same as the first polyolefin resin.

  Further, the addition method of the silane coupling agent is not particularly limited. For example, when a raw material is produced using an extruder, a method of injecting and mixing the first polyolefin resin in the extruder, an extruder It can be added by a known addition method such as a method of mixing in a hopper and introducing it into the first polyolefin resin, or a method of making a masterbatch and mixing and adding to the first polyolefin resin.

(Organic peroxide)
Since the resin sealing sheet in this embodiment performs ionizing radiation processing, it is not necessary to contain an organic peroxide. The organic peroxide may be thermally decomposed to cause a cross-linking reaction when the processing temperature of the resin-encapsulated sheet is raised to improve productivity, and it is preferable that the organic peroxide is not substantially contained. The content of the organic peroxide before molding the sheet is preferably as small as possible, preferably 0 to 0.2 parts by mass, more preferably 0 to 0.1 parts by mass, and 0 parts by mass with respect to 100 parts by mass of the polyolefin resin. Is more preferable.

[Embossing process]
The surface of the original fabric may be embossed according to the final form of the resin sealing sheet. For example, when embossing processing is performed on both surfaces, the embossing processing can be performed by passing the original fabric between two embossing rolls. Moreover, when performing a single-sided embossing process, an embossing process can be performed by letting the said original fabric pass between the rolls which made only one side the embossing roll.

  The resin sealing sheet according to the present embodiment is preferably provided with a recess by embossing, and the total volume VH of the recess per unit area of the resin sealing sheet is multiplied by the maximum thickness. The percentage VH / VA × 100% with respect to the apparent volume VA of the resin sealing sheet is preferably 2 to 80%. The porosity P defined by VH / VA × 100% can be obtained by calculation as follows.

In the embossed resin-encapsulated sheet, the apparent volume VA (mm ³ ) of the resin-encapsulated sheet is the maximum thickness t _max (mm) of the resin-encapsulated sheet and a unit area (for example, 1 m ² = 1000 mm × 1000 mm = 1 × 10 ⁶ mm ² ) and calculated as follows.
VA (mm ³ ) = t _max × 10 ⁶

On the other hand, the actual volume V0 (mm ³ ) of the resin-encapsulated sheet of this unit area is the resin-encapsulated sheet per unit area (1 m ² ) and the specific gravity ρ (g / mm ³ ) of the resin constituting the resin-encapsulated sheet Is calculated as follows from the actual weight W (g).
V0 (mm ³ ) = W / ρ

The total volume VH (mm ³ ) of the recesses per unit area of the resin sealing sheet is calculated as a value obtained by subtracting the actual volume V0 from the apparent volume VA of the resin sealing sheet.
VH (mm ³ ) = VA−V0 = VA− (W / ρ)

Therefore, the porosity P (%) can be obtained as follows.
Porosity P (%) = VH / VA × 100
= (VA- (W / ρ)) / VA × 100
= 100-W / (ρ × VA) × 100
= 100−W / (ρ × t _max × 10 ⁶ ) × 100

  The porosity P (%) is calculated by the above-described calculation formula, and is obtained by taking a micrograph of a cross-section or an embossed surface of an actual resin sealing sheet and performing image processing. You can also.

  The porosity P (%) is preferably 2 to 80%, more preferably 3 to 50%, and further preferably 3 to 40%. When the porosity P (%) is within the above range, an appropriate cushioning property can be imparted to the resin sealing sheet when the resin sealing sheet is heat-processed in the solar cell sealing step. This tends to prevent damage to the solar cell. That is, when a pressing force is locally applied to the resin-encapsulated sheet, the convex portion to which the pressing force is applied is deformed so as to be crushed, whereby a large force is locally applied to the solar cell. Is prevented from being added.

  Moreover, at the time of the heat processing of the sealing process at the time of manufacture of a solar cell, the wide passage of air is ensured by the recessed part provided in the resin sealing sheet, and deaeration property improves. For this reason, deaeration failure is prevented and the sealing time can be shortened. In addition, during the heat processing in the sealing step when manufacturing the solar cell, the resin that has flowed flows into the recesses, so that the resin is prevented from protruding. As a result, high-quality solar cells can be manufactured with high yield.

  In addition, when the resin-encapsulated sheet is transported and stored before use, when transported and stored in a roll form, and when transported and stored in a single sheet form, the embossing described above is applied. There is also an effect of preventing adhesion and blocking between sheets during storage.

  In the present embodiment, the depth of the recess formed by embossing is preferably 2 to 70%, more preferably 3 to 50%, and further 3 to 40% with respect to the maximum thickness of 100% of the resin sealing sheet. preferable.

  The depth of the concave portion of the embossing in the present embodiment indicates the height difference D between the topmost portion of the convex portion and the deepest portion of the concave portion of the uneven surface of the resin sealing sheet by the embossing. Further, the maximum thickness tmax of the resin sealing sheet indicates the distance from the topmost part of the convex part to the back surface when embossed on one surface of the resin sealing sheet, and both surfaces of the resin sealing sheet In the case of embossing, the distance between the tips of the convex portions on both surfaces (the distance in the resin sealing sheet thickness direction) is shown.

  Further, as post-treatment, for example, heat setting for dimensional stabilization, corona treatment, plasma treatment, lamination with other types of resin sealing sheets, and the like may be performed.

[Ionizing radiation treatment process]
The ionizing radiation treatment step is a step of obtaining a resin encapsulating sheet by performing ionizing radiation treatment on the original fabric. By performing the ionizing radiation irradiation treatment, the first polyolefin resin is crosslinked, and the silane coupling agent is also copolymerized with the first polyolefin resin. Thereby, since a curing process becomes unnecessary, for example, when a solar cell element is protected and a solar cell is manufactured, the process can be simplified. The ionizing radiation treatment process may be performed as a pre-process or a post-process of the embossing process.

  The ionizing radiation is not particularly limited, and examples thereof include α rays, β rays, γ rays, neutron rays, and electron beams. The acceleration voltage of ionizing radiation such as an electron beam can be appropriately selected depending on the thickness of the resin encapsulating sheet, and is not particularly limited. For example, in the case of a thickness of 500 μm, when the entire resin encapsulating sheet is crosslinked, the acceleration voltage It is preferable to set it as 300 kV or more.

  By increasing the processing speed by irradiation with ionizing radiation, the productivity of the resin-sealed sheet according to this embodiment tends to be further improved. When the resin sealing sheet is irradiated with ionizing radiation, the absorbed dose is proportional to the processing current value and inversely proportional to the processing speed when processing is performed with the same irradiation apparatus. Therefore, in order to cross-link the resin-sealed sheet at a target absorbed dose at a higher speed, it is not particularly limited. For example, the method 1 increases the processing current value in proportion to the speed and the absorption is performed once. When the dose is insufficient, there is a method 2 in which processing is performed a plurality of times. In the case of the method 1, there is an upper limit on the allowable current value due to the structure of the apparatus, and the processing speed is also limited. Therefore, method 2 is preferable for further increasing the speed. By using the method 2, the target absorbed dose tends to be obtained without reducing the processing speed.

  The method of treating the ionizing radiation treatment in two or more steps is not particularly limited. For example, the resin sealing sheet to be treated is cut into single sheets, and the resin sealing sheet is processed twice or more by batch processing. There are a method I for performing the process and a method II for performing the process by passing the continuous resin-sealed sheet twice or more through the processing apparatus. Among these, the method II is preferable in view of productivity and workability.

  Moreover, as a method of passing a continuous resin-sealed sheet twice or more through a processing apparatus and processing, it is not particularly limited. For example, a method i in which a plurality of processing apparatuses are arranged in series and processed by passing a resin sheet; There are methods ii and iii that combine a method ii and a method ii that use a single device having a higher acceleration voltage and pass the sheet a plurality of times through the same processing apparatus. These methods can be appropriately selected depending on conditions such as the apparatus cost and the target processing speed.

  The acceleration voltage of ionizing radiation such as an electron beam can be appropriately adjusted according to the type of resin of the resin layer subjected to the crosslinking treatment, its thickness, and the like, and is preferably 200 kV to 1000 kV. Although the irradiation dose of ionizing radiation varies depending on the resin used, it is generally preferably 3 kGy to 200 kGy. When the irradiation dose is 3 kGy or more, the ionizing radiation cross-linking resin constituting the entire resin sealing sheet can be uniformly cross-linked.

  Moreover, the crosslinking degree by ionizing radiation can be adjusted with irradiation dose (kGy), and a crosslinking degree can be confirmed by measuring the Mooney viscosity of the resin sealing sheet after a process. Considering higher productivity and physical properties of the resulting resin encapsulated sheet, preferred ionizing radiation is obtained when the first polyolefin resin having MI (190 ° C., 2.16 kg) of 6 g / 10 min or more is used. The amount is 40 kGy to 150 kGy.

[Method for producing multilayer resin encapsulated sheet]
In addition, the method for producing the first or second form of the multilayer resin encapsulated sheet is not particularly limited. For example, a method of coextruding a target resin in each layer using a multilayer die, Before entering the single-layer die from the extruder, a feed block for multi-layering is arranged, and the resin extruded from a plurality of extruders is multi-layered in the feed block and then sheeted with a single-layer die There are methods.

[Use of resin encapsulated sheet]
The resin sealing sheet according to the present embodiment is particularly useful as a sealing material for protecting members such as elements constituting the solar cell. That is, the first polyolefin-based resin that hardly generates corrosive substances such as acetic acid by hydrolysis etc. like a sealing material using ethylene vinyl acetate copolymer (EVA) that is widely used at present. By using ionizing radiation treatment instead of using an organic peroxide, it becomes possible to produce a resin sheet at high speed, which can improve productivity and reduce costs. A resin sealing sheet that can be satisfactorily used while suppressing the heat shrinkage and that satisfies the physical properties necessary for the resin sealing sheet in a well-balanced manner can be supplied and used favorably as a sealing material for solar cells with improved durability.

[Solar cell module]
The solar cell module according to the present embodiment includes the resin sealing sheet and / or the multilayer resin sealing sheet as a sealing material. A solar cell module when used as a sealing material for a solar cell uses, for example, two resin sealing sheets according to the present embodiment, and includes a transparent substrate (transparent protective material) / resin sealing sheet / power generation element / resin sealing. It can be set as the structure laminated | stacked in order of the stop sheet / back sheet | seat (back surface protection material), and it can produce by laminating | stacking these materials and carrying out vacuum lamination.

  The resin encapsulating sheet according to the present embodiment can be used as an encapsulating sheet for solar cells, LED sealing, laminated glass and security glass interlayers, etc., plastic and glass, plastic to glass, and glass to glass adhesion. Etc. can also be used.

  Hereinafter, although a specific Example and a comparative example are given and demonstrated, this embodiment is not limited only to these Examples.

  The measuring method and evaluation method of each physical property in Examples and Comparative Examples are as follows.

[Measuring method of melting point]
According to JIS-K-7121 and 7122, the melting point of the polyolefin resin is from 0 ° C. at a nitrogen gas flow rate of 25 mL / min using a differential scanning calorimeter (DSC) manufactured by Perkin-Elmer. The temperature was raised to 200 ° C. at 10 ° C./min, and the melting point at the time of temperature rise was measured.

[Measurement method of MI]
The polyolefin resin MI (Melt Index, g / 10 min) was measured at 190 ° C. under a load of 2.16 kg according to ASTM D-1238.

[Method for measuring Mooney viscosity]
The Mooney viscosity of the resin-encapsulated sheets prepared in Examples and Comparative Examples was measured using a Mooney Viscometer (MVR) MODEL VR-1130 manufactured by Ueshima Seisakusho Co., Ltd. according to JIS K 6300-1. More specifically, using an L-shaped rotor, measurement was performed at a test temperature of 110 ° C., preheating for 1 minute, a measurement time of 9 minutes, and a rotational speed of 2 RPM. In addition, the test result rounded off the value obtained by one test result by JISZ8401, and was represented by the integer.

[Method for measuring gel fraction]
The gel fraction of the resin sealing sheets produced in Examples and Comparative Examples was measured according to JIS-K-6696. More specifically, the resin sealing sheets prepared in Examples and Comparative Examples were extracted in boiling p-xylene for 12 hours, and the proportion of the insoluble portion was calculated as the gel fraction by the following formula.
Gel fraction (mass%) = (sample weight after extraction / sample weight before extraction) × 100

[Calculation method of porosity P]
The porosity P of the resin encapsulating sheet is based on the maximum thickness t _max (mm) of the resin encapsulating sheet, the specific gravity ρ (g / mm ³ ) of the resin constituting the resin encapsulating sheet, and the unit area (1 m ² ). It calculated | required by the following formula from the actual weight W (g) of the resin sealing sheet.
Porosity P (%) = 100−W / (ρ × t _max × 10 ⁶ ) × 100

[Productivity evaluation of resin-encapsulated sheet]
The productivity of the resin encapsulating sheets produced in Examples and Comparative Examples is that the resin encapsulating sheets of Examples and Comparative Examples (thickness: 600 μm) at an allowable resin pressure of 30 MPa or less using a 250 mm width T-die described later. ) Was extruded according to the following criteria based on the amount of resin extruded per hour and the winding speed of the resin sealing sheet at that time.
A: Extrusion amount 150 kg / hour or more, winding speed 30 m / min or more.
B: Extrusion amount 100 kg / hour or more and less than 150 kg / hour, winding speed 20 m / min or more and less than 30 m / min.
C: Extrusion amount 50 kg / hour or more and less than 100 kg / hour, winding speed 10 m / min or more and less than 20 m / min.
X: Extrusion amount is less than 50 kg / hr, and winding speed is less than 10 m / min.

(Evaluation of heat shrinkage)
The resin sealing sheets produced in the examples and comparative examples were cut into squares of 10 cm in the MD direction and 10 cm in the TD direction before and after irradiation with the electron beam to obtain test pieces. The length of the test piece in the MD direction of the obtained test piece was measured, immersed in warm water of 70 ° C. for 5 minutes, and the length of the test piece in the MD direction after immersion for 5 minutes was measured. Based on the following formula, the thermal contraction rate before and after the electron beam irradiation was calculated from the obtained length of the test piece after immersion and the length of the test piece before immersion. As shown in Table 2, it was found that the shrinkage rate hardly changed before and after the electron beam irradiation treatment.
Thermal contraction rate (%) = (length of test piece before immersion−length of test piece after immersion) / length of test piece before immersion × 100

The 70 degreeC thermal contraction rate of the resin sealing sheet after electron beam irradiation was evaluated on the following references | standards.
A: Thermal contraction rate is 5% or less B: Thermal contraction rate is greater than 5% and 10% or less X: Thermal contraction rate is greater than 10%

[Blocking evaluation]
In order to evaluate the blocking property due to adhesion between sheets when the resin sealing sheets prepared in Examples and Comparative Examples are stored in a roll shape and in a single sheet shape, the resin sealing sheets are made into 10 cm × 10 cm square sheets. Cut and emboss three surfaces so that the embossed surface is the upper surface and the non-embossed surface is the lower surface. Place a weight of 50 cm ² and a weight of 2000 g on it, and place it in a thermostatic chamber at 50 ° C. for one week. The peelability of the sheet after being held was evaluated according to the following criteria.
A: Resin-encapsulated sheets peel off naturally even when little force is applied, and there is almost no blocking.
B: The resin-encapsulated sheets are not naturally peeled off, but are peeled off when a weak force of less than 0.5 N / cm is applied, and are weakly blocked.
C: Resin-sealed sheets are peeled off when a force of 0.5 N / cm or more and less than 1.0 N / cm is applied and blocking is seen, but the sheet can be peeled without deformation.
X: The sheet | seats between resin sealing sheets cannot be peeled off if the force of 1.0 N / cm or more is not applied, and cannot peel without the sheet | seat deform | transforming in the state blocked strongly.

[Evaluation of gap filling in power generation part]
Glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) / resin encapsulated sheet (thickness 600 μm) prepared in examples and comparative examples / power generation part / prepared in examples and comparative examples Laminated in the order of the resin-sealed sheet / solar cell glass plate (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm), and vacuum laminated at 150 ° C. using an LM50 type vacuum laminator (NPC). did.

  The power generation portion has a structure in which two tab wires (thickness: 300 μm) are wired on each side of a single crystal silicon cell (thickness: 200 μm). As a result, the power generation portion has a shape in which convex portions of 300 μm exist on part of both surfaces of the 200 μm thick single crystal silicon cell, and the entire power generation portion has a thickness of 200 to 800 μm.

The gap filling performance of the power generation portion was evaluated visually according to the following criteria.
A: The contact portions of the single crystal silicon cell, the tab wire, and the resin encapsulating sheet as the power generation portion were all good, and there was no gap.
X: A gap occurred in the contact portion between the single crystal silicon cell, which is a power generation portion, the tab wire, and the resin sealing sheet. Or when the sealing sheet was made into heat flow at the time of lamination, it protruded from the edge part of the glass plate for solar cells, and the external appearance defect was confirmed.

[Creep resistance evaluation]
Glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) / resin encapsulated sheet produced in Examples and Comparative Examples / power generation part (single crystal silicon cell (thickness 250 μm) / Example And a resin-encapsulated sheet / solar cell glass plate (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) prepared in the order of comparison and 150 using an LM50 type vacuum laminator (NPC). A solar cell was obtained by vacuum lamination at 0 ° C. One glass plate of the obtained solar cell was fixed to the wall of a thermostatic bath set at 85 ° C. and left for 24 hours, and the deviation from the other glass plate was Measured and evaluated according to the following criteria.
A: The deviation of the glass plate is less than 2 mm.
B: The deviation of the glass plate is 2 mm or more and less than 3 mm.
C: The deviation of the glass plate is 3 mm or more and less than 4 mm.
X: The shift | offset | difference of a glass plate is 4 mm or more.

[Total light transmittance evaluation and Haze evaluation]
The total light transmittance evaluation and the Haze evaluation of the resin sealing sheets prepared in Examples and Comparative Examples were performed based on values measured in accordance with ASTM D-1003. As a sample for measurement, a glass plate for solar cell (white glass made by AGC, 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet prepared in Examples and Comparative Examples / glass plate for solar cell are stacked in this order, and LM50 type vacuum laminate What was vacuum-laminated at 150 degreeC using the apparatus (NPC company) was prepared. The evaluation criteria are shown below.
(Total light transmittance)
A: Total light transmittance is 85% or more.
X: Total light transmittance is less than 85%.
(Haze)
A: Haze is less than 15%.
X: Haze is 15% or more.

[Evaluation of initial bond strength with glass and evaluation of water-resistant adhesion with glass]
Laminated glass glass for solar cells (AGC white plate glass 10 cm x 5 cm square, thickness 3 mm) / resin encapsulated sheet / back sheet (Toyo Aluminum Co., Ltd. manufactured by Toyo Aluminum Co., Ltd.) Using a LM50 type vacuum laminator (NPC), the sample was degassed at 150 ° C. for 5 minutes and then vacuum laminated for 10 minutes to prepare a sample for measurement with glass.

The initial bond strength between the measurement sample and the glass was measured using a “Tensilon UMT-II-500 type” manufactured by Toyo Bald Inn Co., Ltd. under conditions of a temperature of 23 ° C. and a relative humidity of 55%. Evaluation was performed according to the following evaluation criteria. The tensile speed was 200 mm / min, the peel angle was 180 degrees, and the value when the strength reached a steady state was taken as the value of the adhesive strength.
A: Adhesive strength is 30 N / cm or more, indicating good adhesion.
B: Adhesive strength is 15 N / cm or more and less than 30 N / cm, indicating relatively good adhesion.
C: Adhesive strength is 5 N / cm or more and less than 15 N / cm and there is only a minimum level of adhesion.
X: Adhesive strength is less than 5 N / cm, and adhesiveness is inferior.

In addition, the water resistance of the measurement sample to the glass is that the adhesion strength is the same as the initial adhesion strength after holding the measurement sample in a constant temperature and humidity chamber at 85 ° C. and a relative humidity of 85% for 500 hours. Was measured and evaluated according to the following evaluation criteria.
A: Adhesive strength is 30 N / cm or more, indicating good adhesion.
B: Adhesive strength is 15 N / cm or more and less than 30 N / cm, indicating relatively good adhesion.
C: Adhesive strength is 5 N / cm or more and less than 15 N / cm and there is only a minimum level of adhesion.
X: Adhesive strength is less than 5 N / cm, and adhesiveness is inferior.

[Bleed-out resistance evaluation]
The resin sealing sheets prepared in Examples and Comparative Examples were cut into 100 mm squares to make evaluation samples, which were kept for 24 hours in a constant temperature bath at 50 ° C. Thereafter, the surface of the sample for evaluation was visually observed in a state of normal temperature, and bleed out was evaluated according to the following evaluation criteria.
A: The bleedout of the additive is not observed on the sheet surface, and is in a good state.
X: State in which presence of powder and liquid of additive is observed on sheet surface.

[Evaluation of power generation characteristics]
The evaluation of the power generation characteristics of the 40 straight solar cell module produced in Example 17 was performed based on the maximum power measured using a solar cell module tester DSKMT-1220 manufactured by Denken at a temperature of 25 ° C.

〔Comprehensive evaluation〕
1) Sheet productivity, 2) 70 ° C. thermal shrinkage after irradiation with electron beam (EB), 3) blocking, 4) gap filling, 5) creep resistance, 6) total light transmittance, 7) Evaluation was performed on 7 items of Haze, and comprehensive evaluation was performed according to the following criteria.
A: The best resin-encapsulated sheet having excellent sheet productivity in all seven evaluation items, with A evaluation.
B: One or more of the above seven evaluation items are B evaluations, and the rest are all A evaluations.
C: A practically acceptable minimum resin-encapsulated sheet in which one or more of the above seven evaluation items is C evaluation, and the rest are all A evaluation or B evaluation.
X: A resin-encapsulated sheet in which one or more of the above seven evaluation items are evaluated as x, and the productivity is inferior or the physical properties are insufficient in practice.
The materials used in the examples and comparative examples are as follows.

[Polyolefin resin]
As the polyolefin resin, as shown in Table 1, ethylene-octene copolymers manufactured by The Dow Chemicals Company were used as PE1 to PE4 and PE6 to PE9. For PE5, 60 parts by mass of PE9 and 40 parts by mass of PE4 were dry blended, kneaded with a twin screw extruder and pelletized. Table 1 shows melting points and MI of PE1 to PE9.

〔Silane coupling agent〕
As the silane coupling agent, KBM503 (trade name) manufactured by Shin-Etsu Chemical Co., Ltd., substance name: 3-methacryloxypropyltrimethoxysilane was used.

[Additive Masterbatch]
The additive masterbatch was prepared by adding 90 parts by mass of the polyolefin-based resin PE1, 5 parts by mass of the following ultraviolet absorber, 2.5 parts by mass of the following light stabilizer, and 2.5 parts by mass of the following antioxidant, a twin-screw extruder. The kneaded and pelletized material was used.
[Ultraviolet absorber]
As an ultraviolet absorber, Adeka stab 1413 (trade name) manufactured by ADEKA Corporation, substance name: 2-hydroxy-4-n-octoxybenzophenone was used.
(Light stabilizer)
As the light stabilizer, hindered amine light stabilizer: Adekastab LA-77Y (trade name) manufactured by Adeka Corporation, and substance name: bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate were used.
〔Antioxidant〕
As the antioxidant, Adeka Stab AO-50 (trade name) manufactured by Adeka Company, Inc., substance name: n-octadecyl-3- (3,5-di-t-butyl-4-hydroxy-phenyl) propionate was used.

[Resin encapsulating sheets: Examples 1 to 11 and Comparative Examples 1 to 6]
The resin sealing sheets of Examples 1 to 11 and Comparative Examples 1 to 6 were prepared as follows using the composition shown in Table 2 and a polyolefin resin, a silane coupling agent, and an additive master batch. Two extruders (biaxial, caliber = 45 mm, L / D = 35, L: distance from raw material supply port to discharge port (m), D: inner diameter of extruder (m), the same applies hereinafter). Using a polyolefin resin and various additives by melt-kneading, using a feed block to form a single layer, a sheet-shaped resin composition from a T-die having a width of 250 mm and a lip opening of 1.2 mm connected to an extruder It was melt-extruded into a cast roll with emboss, cooled with a cast roll, and further cooled with a plurality of rolls to finally obtain a rolled resin encapsulated sheet in a roll shape. At this time, the resin temperature at the die outlet was set to the temperature shown in Table 2, and the film forming speed was adjusted so that the sheet thickness was 600 μm. The embossing was performed using a cast roll having a trapezoidal gravure cup pattern embossing with a depth of 40 μm so that the porosity P was about 5%.

  As a result, as shown in Table 2, in Examples 1 to 11, the resin was extruded at a resin temperature of 180 to 200 ° C., the resin pressure at the die inlet was 30 MPa or less of the equipment pressure resistance, and the resin extrusion rate was 80 to 160 kg / hour. Can be extruded. On the other hand, in Comparative Examples 1 to 4, the resin pressure at the die inlet at the resin extrusion rate of 50 kg / hour exceeded the equipment pressure resistance of 30 MPa in the same resin temperature range using the same equipment. It turned out that it was inferior to productivity.

  The resin-encapsulated sheet (sheet with embossing) obtained as described above is irradiated with radiation doses listed in Table 2 at an acceleration voltage of 800 kV using an electron beam irradiation apparatus (manufactured by Nissin High Voltage) of EPS-800. The crosslinking treatment was performed by irradiating with an electron beam. At this time, in order to cope with the increase in speed, the resin sealing sheet was folded back and irradiated three times. Thereby, the resin sealing sheets of Examples 1 to 11 and Comparative Examples 1 to 6 were obtained.

  For the resin-encapsulated sheets obtained in Examples 1 to 11 and Comparative Examples 1 to 6, physical property measurements and evaluation shown in Table 2 were performed, 1) sheet productivity, and 2) electron beam (EB) irradiation. The post-sheet 70 ° C. heat shrinkage rate, 3) blocking property, 4) gap filling property, 5) creep resistance, 6) total light transmittance, and 7) haze were evaluated. A comprehensive evaluation was conducted. The results are shown in Table 2.

[Multilayer resin encapsulated sheet: Examples 12 to 16, Comparative Example 7]
The resin sealing sheets of Examples 12 to 16 and Comparative Example 7 use the resin, silane coupling agent, and additive master batch shown in Table 3 so as to have the composition shown in the table, and the layer configuration shown in Table 3 is used. It was multilayered so as to be manufactured as follows. Using two inner layer extruders (biaxial, caliber = 45 mm, L / D = 35) and one outer layer extruder (biaxial, caliber = 32 mm, L / D = 35) Except having melt-kneaded various additives and laminated | stacked so that it might become 2 types and 3 layers using a feed block, operation similar to Examples 1-11 was performed, and the resin sealing sheet was obtained. The resin temperature at the die outlet was set to the temperature shown in Table 3.

  The resin-encapsulated sheet (sheet with embossing) obtained as described above was irradiated with an electron beam so that the irradiation dose shown in Table 3 was obtained in the same manner as in Examples 1 to 11, and Examples 12 to 16 were performed. And the multilayer resin sealing sheet of the comparative example 7 was obtained.

  For the resin-encapsulated sheets obtained in Examples 12 to 16 and Comparative Example 7, physical property measurements and evaluations shown in Table 3 were performed. 1) Sheet productivity, 2) Electron beam (EB) post-irradiation sheet 70) heat shrinkage rate, 3) blocking property, 4) gap filling property, 5) creep resistance, 6) total light transmittance, and 7) haze, and finally, comprehensively based on the above criteria. Evaluation was performed. The results are shown in Table 3.

  The outer layers 1 and 2 of Example 13 had a Mooney viscosity (ML) of 62 and a gel fraction (%) of 36. The Mooney viscosity (ML) of the inner layers of Examples 13 and 15 was 51, and the gel fraction (%) was 19. Furthermore, the Mooney viscosity (ML) of the inner layer of Example 14 was 60, and the gel fraction (%) was 35. Moreover, the Mooney viscosity (ML) of the inner layer of Example 16 was 50, and the gel fraction (%) was 23.

  As can be seen from the results in Tables 2 and 3, the resin-encapsulated sheets of Examples 1 to 16 are excellent in sheet productivity, and the 70 ° C. heat shrinkage rate and blocking resistance of the sheets after electron beam (EB) irradiation. It was found that the gap filling property, creep resistance and optical properties were good and the balance of properties was excellent.

[Solar cell module: Example 17]
Glass plate for solar cell (white plate glass manufactured by AGC) / resin sealing sheet obtained in Example 12 / single crystal silicon cell (manufactured by E-TON Solar Tech.) / Resin sealing obtained in Example 12 Sheet / back sheet (Toyo Aluminum Co., Ltd., TOYAL SOLAR) are laminated in this order and vacuum laminated at 170 ° C using a PVL1016S type vacuum laminator (Nisshinbo Mechatronics Co., Ltd.) to produce a 40 straight solar cell module. did. A so-called dump heat test was performed in which the 40 straight solar cell module was allowed to stand in a constant temperature and humidity chamber having a temperature of 85 ° C. and a humidity of 85%, and the relationship between the standing time and power generation characteristics was confirmed. According to the above [Evaluation of power generation characteristics], the power generation characteristics of the 40 direct solar cell module were evaluated by the maximum power (Pmax). FIG. 1 shows the relationship between the dump heat test time and the ratio of Pmax after the dump heat test to Pmax before the dump heat test (initial Pmax). From FIG. 1, the 40 straight solar cell module using the resin-encapsulated sheet obtained in Example 12 has a power generation characteristic of 95% or more compared to before the dump heat test even after 4000 hours after the dump heat test. It was found that it was maintained.

  Next, a potential induced degradation test (PID test) according to IEC 1131-3 was performed using the obtained 40 straight solar cell module. The test conditions were: temperature: 60 ° C., humidity: 85%, applied voltage: −1000 V, glass surface treatment: water filling. FIG. 2 shows the relationship between the PID test time and the ratio of Pmax after the PID test to Pmax before the PID test (initial Pmax). From FIG. 2, it was found that the power generation characteristics of the solar cell module using the resin-encapsulated sheet obtained in Example 12 hardly deteriorated compared to before the PID test even after 96 hours of the PID test.

  There is industrial applicability as a resin sealing sheet for protecting the members of the solar cell of the present invention.

Claims (12)

Including a first polyolefin resin having a Melt Index of 6 g / 10 min or more at 190 ° C. and a load of 2.16 kg measured in accordance with ASTM D-1238, and a melting point of 90 ° C. or less;
The gel fraction is 2-60%,
Mooney viscosity is 20-100 ML at 110 ° C.,
Resin sealing sheet.   The resin sealing sheet according to claim 1, wherein 0.01 to 10 parts by mass of a silane coupling agent is copolymerized with 100 parts by mass of the first polyolefin resin.   The resin sealing sheet according to claim 1 or 2, wherein the melting point of the first polyolefin-based resin is 50 ° C or higher and 80 ° C or lower.   The resin-encapsulated sheet according to any one of claims 1 to 3, wherein the Melt Index of the first polyolefin-based resin is 8 g / 10 min or more and 40 g / 10 min or less.   The resin-encapsulated sheet according to any one of claims 1 to 4, which has been subjected to ionizing radiation treatment twice or more.   The resin sealing sheet according to any one of claims 2 to 5, wherein the silane coupling agent is a compound having a vinyl group and / or a methacryloxy group.   The multilayer resin sealing sheet which has the resin sealing sheet of any one of Claims 1-6, and the outer layer laminated | stacked on this resin sealing sheet.   The outer layer includes a second polyolefin resin having a Melt Index of 6 g / 10 min or more at 190 ° C. and a load of 2.16 kg measured in accordance with ASTM D-1238 and a melting point of 90 ° C. or less. The multilayer resin encapsulating sheet according to claim 7.   The multilayer resin sealing sheet which has an inner layer and the resin sealing sheet of any one of Claims 1-6 laminated | stacked on the surface and back surface of this inner layer.   The inner layer includes a third polyolefin resin having a Melt Index of 6 g / 10 min or more at 190 ° C. and a load of 2.16 kg measured in accordance with ASTM D-1238, and a melting point of 90 ° C. or less. The multilayer resin sealing sheet according to claim 9. 100 parts by mass of a first polyolefin resin having a Melt Index of 6 g / 10 min or more at 190 ° C. under a load of 2.16 kg measured in accordance with ASTM D-1238 and a melting point of 90 ° C. or less, and a silane cup An ionizing radiation treatment step for obtaining a resin encapsulating sheet by subjecting the raw material containing 0.01 to 10 parts by mass of a ring agent and substantially not containing an organic peroxide to ionizing radiation treatment. And
The Mooney viscosity of the resin-encapsulated sheet is 20 to 100 ML at 110 ° C.
Manufacturing method of resin sealing sheet.   The solar cell module which has the resin sealing sheet of any one of Claims 1-6 and / or the multilayer resin sealing sheet of any one of Claims 7-10 as a sealing material.