JP2013177508A - Resin sealing sheet and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin sealing sheet excellent in adhesion, heat resistance, light resistance, weatherability and a gap filling property.SOLUTION: A resin sealing sheet satisfying the conditions (1)-(5) is provided. (1) At least one kind of structural resins is an ionizing radiation crosslinkable resin. (2) The resin sealing sheet before being modulated is swollen or dissolved in a good solvent, and a resin polymer reprecipitates in a poor solvent, and a value of a content of a silicon atom derived from a silane coupling agent existing in the solidified resin polymer which is obtained by inductively-coupled plasma emission spectral analysis is 0.05 mass% or more and 0.2 mass% or less with respect to the whole weight of the resin sealing sheet. (3) 0.1-0.3 pt.mass of an ultraviolet absorber is contained based on 100 pts.mass of resin constituting the resin sealing sheet. (4) 0.05-0.2 pt.mass of a light stabilizer is contained based on 100 pts.mass of the resin constituting the resin sealing sheet. (5) Ionizing radiation is performed, and Mooney viscosity is 60-140 M.

Description

  The present invention relates to a resin sealing sheet and a solar cell module.

Due to the recent increase in awareness of the global environment, power generation systems using natural energy such as wind power, hydropower, and geothermal heat have attracted attention.
In particular, solar power generation systems (solar cells) are capable of directly converting energy generated by the photovoltaic effect into electric power, and are therefore actively researched and developed as clean and efficient energy systems. It is attracting attention as a household energy application.

Typical examples of solar cells include single crystal and polycrystalline silicon cells (crystalline silicon cells), amorphous silicon, and compound semiconductors (thin film cells).
By the way, the solar cell is often used outdoors for a long time by being exposed to wind and rain. It is modularized by attaching a glass plate, a back sheet, etc. to the power generation part, and prevents moisture from entering from the outside. Protecting the power generation part and preventing leakage.

In the member that protects the power generation part, transparent glass or transparent resin is used on the light incident side to secure the amount of light necessary for power generation, while the opposite member is made of an aluminum foil or a hook called a back sheet. Polyvinyl chloride resin (PVF), polyethylene terephthalate (PET), and laminated sheets obtained by subjecting these to barrier coating with silica or the like are used.
When the power generation portion is sandwiched between predetermined resin sealing sheets, and the outside is further covered with the glass or the back sheet and subjected to heat treatment, the resin of the resin sealing sheet is melted and modularized as a whole.

As described above, the following (1) to (3) are required as characteristics of the resin sealing sheet that sandwiches the power generation portion.
(1) Good adhesion to glass, power generation element and back sheet, (2) Flow prevention (creep resistance) of power generation element due to melting of resin-sealed sheet at high temperature, (3) Sunlight Transparency that does not hinder the incidence of light.
From these viewpoints, the conventional resin-encapsulated sheet is made of an ethylene-vinyl acetate copolymer (hereinafter also abbreviated as EVA), an ultraviolet absorber as a countermeasure against ultraviolet deterioration, and a silane cup for improving adhesion to glass. Additives such as organic peroxides for ring agents and cross-linking are blended to form a film by calendar molding or T-die casting.
In view of exposure to sunlight over a long period of time, various additives such as a light-resistant agent are blended in order to prevent deterioration of 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.

As described above, a method for modularizing a solar cell with a conventional resin-encapsulated sheet is formed by stacking power generating elements such as glass / resin-encapsulated sheet / crystalline silicon cell / resin-encapsulated sheet / back sheet in this order, Press with glass surface down and using a dedicated solar cell vacuum laminator to preheat above the melting temperature of the resin (typically 150 ° C in the case of EVA) and melt and bond the resin encapsulated sheet It has a process.
In the preheating step, the resin of the resin sealing sheet is melted, and in the pressing step, the resin is in close contact with a member in contact with the molten resin 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. Accordingly, the creep resistance of the resin-encapsulated sheet and the adhesiveness with the glass, the power generating element, and the back sheet are improved.

As described above, as a resin encapsulating sheet used for modularizing a solar cell, Patent Document 1 includes a sheet made of an ethylene vinyl acetate copolymer containing a crosslinking agent and a silane coupling agent, A solar cell sealing sheet characterized by radiation crosslinking to a certain gel fraction is disclosed.
Patent Document 2 discloses a resin-sealing sheet comprising a silane coupling agent and an ionizing radiation-crosslinking resin, which is radiation-crosslinked to a certain gel fraction.

JP-A-8-283696 JP 2011-74264 A

However, as in the technique described in Patent Document 1, in the case where an organic peroxide is added to the resin in order to impart heat resistance to the resin sealing sheet, the organic peroxide is decomposed. Therefore, it is necessary to carry out a long-time heat curing step for promoting the crosslinking of the resin sealing sheet, and there is a problem that the productivity is poor when used as a sealing material for a solar cell module or the like.
Further, when the resin sealing sheet contains an organic peroxide, it is necessary to perform extrusion at a low temperature so that the organic peroxide is not cleaved when the resin sealing sheet is formed. There is also a problem that it is inferior in its own productivity.
Furthermore, in patent document 1, it does not disclose about the effect | action of a light-resistant agent and a radiation, and since the resin sealing sheet will yellow when the irradiation amount of a radiation exceeds 20 kGy, it is set as the irradiation amount below 20 kGy. However, there is a problem that yellowing cannot be sufficiently prevented.

In order to solve the problems related to containing an organic peroxide as described above, as in the technique described in Patent Document 2, the resin-encapsulated sheet is cross-linked using ionizing radiation. Is valid.
However, in solar cells that are used outdoors for a long time, weather resistance and light resistance are important characteristics, and additives for improving weather resistance and light resistance are necessary. When ionizing radiation is irradiated in the presence of, the ionizing radiation causes not only the intended crosslinking reaction of the resin encapsulating sheet, but also side reactions of the resin encapsulating sheet and various reactions with additives. The resin-sealed sheet turns yellow under high temperature conditions.
Patent Document 2 discloses a crosslinking reaction of a sealing sheet by ionizing radiation in the presence of an ultraviolet absorber or a light stabilizer added for improving light resistance, and an ultraviolet absorber added to the ionizing radiation or a light stabilizer. The influence of the reaction product with the agent on the physical properties of the resin encapsulating sheet is not disclosed, and depending on the technique described in Patent Document 2, there are various side reactions and additives with the resin encapsulating sheet. And yellowing under high temperature conditions cannot be prevented.

  In the present invention, in view of the above circumstances, in a resin encapsulating sheet useful as a sealing material for solar cell modules and the like that has improved productivity by using ionizing radiation, it is used as a sealing material for solar cell modules and the like. It has excellent productivity as a resin encapsulating sheet itself, and has practically sufficient adhesion and heat resistance, and can also follow elements with excellent weather resistance, light resistance, and complex shapes. It aims at providing the resin sealing sheet which comprises various characteristics, such as outstanding gap filling property, with sufficient balance.

As a result of intensive studies on the above problems, the present inventors have found that the resin encapsulating sheet contains an ionizing radiation cross-linked resin grafted with a silane coupling agent, and has a specific amount of UV absorber and light stability. In addition to having a specific amount of grafted silane coupling agent and specifying Mooney viscosity, it has practically sufficient adhesion and heat resistance, as well as excellent weather resistance and light resistance. The present inventors have found that a resin-encapsulated sheet having various properties such as excellent gap filling ability capable of following a complex-shaped element in a balanced manner can be obtained, and the present invention has been completed.
That is, the present invention is as follows.

[1]
A resin-sealed sheet that is a single-layer resin-sealed sheet that softens and adheres a resin and satisfies the following conditions (1) to (5).
(1) At least one of the resins constituting the resin sealing sheet is an ionizing radiation cross-linking resin.
(2) A silicon atom derived from a silane coupling agent present in a solidified resin polymer obtained by swelling or dissolving the resin sealing sheet before modularization in a good solvent to reprecipitate the resin polymer in a poor solvent. The value obtained by inductively coupled plasma optical emission spectrometry is 0.05% by mass or more and 0.2% by mass or less with respect to the total weight of the resin-encapsulated sheet.
(3) 0.1 mass part or more and 0.3 mass part or less of an ultraviolet absorber are contained with respect to 100 mass parts of resin which comprises the said resin sealing sheet.
(4) The light stabilizer is contained in an amount of 0.05 parts by mass or more and 0.2 parts by mass or less with respect to 100 parts by mass of the resin constituting the resin sealing sheet.
(5) The resin sealing sheet has been subjected to ionizing radiation treatment and has a Mooney viscosity of 60 to 140M.
[2]
The resin sealing sheet according to [1], wherein the silane coupling agent is a compound having a vinyl group and / or a methacryloxy group.
[3]
A multilayer resin encapsulating sheet comprising at least two layers, wherein the resin encapsulating sheet according to the above [1] or [2] and other outer layers are laminated.
[4]
A multilayer resin encapsulating sheet comprising at least three layers, wherein the resin encapsulating sheet according to [1] or [2] is laminated on the front and back surfaces of other inner layers.
[5]
The solar cell module which used the resin sealing sheet as described in any one of said [1] thru | or [4] as a sealing material.

  According to the present invention, a resin seal having an excellent property balance that satisfies all of the practically sufficient adhesiveness, heat resistance, light resistance, weather resistance, and excellent gap filling ability that can follow even complex elements. A stop sheet can be provided.

  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 in this embodiment is
It is a single-layer resin sealing sheet that softens and adheres a resin, and satisfies the following conditions (1) to (5).
(1) At least one of the resins constituting the resin sealing sheet is an ionizing radiation cross-linking resin.
(2) A silicon atom derived from a silane coupling agent present in a solidified resin polymer obtained by swelling or dissolving the resin sealing sheet before modularization in a good solvent to reprecipitate the resin polymer in a poor solvent. The value obtained by inductively coupled plasma emission spectrometry (hereinafter sometimes simply referred to as ICP emission analysis) is 0.05 mass% or more and 0.0. 2% by mass or less.
(3) 0.1 mass part or more and 0.3 mass part or less of an ultraviolet absorber are contained with respect to 100 mass parts of resin which comprises the said resin sealing sheet.
(4) The light stabilizer is contained in an amount of 0.05 parts by mass or more and 0.2 parts by mass or less with respect to 100 parts by mass of the resin constituting the resin sealing sheet.
(5) The resin sealing sheet has been subjected to ionizing radiation treatment and has a Mooney viscosity of 60 to 140M.

  The resin-encapsulated sheet of the present embodiment is softened by a method of directly applying energy such as heat to the resin component constituting the resin-encapsulated sheet, or a method of applying inherent vibration to the resin component and causing the resin itself to generate heat. Moreover, when the softened state is utilized, it can seal by making it closely_contact | adhere to another substance (to-be-sealed object). As a specific method for softening the resin, known methods such as direct heating to the resin component, indirect heat such as radiant heat, vibrational heat generation such as ultrasonic waves, and the like can be used.

(resin)
The resin sealing sheet of this embodiment contains an ionizing radiation cross-linking resin as a constituent material of the resin sealing sheet.
The ionizing radiation cross-linking resin refers to a resin that is cross-linked by ionizing radiation such as α-rays, β-rays, γ-rays, neutron rays, and electron beams.
In particular, from the viewpoint of ensuring good transparency, flexibility, adhesion of an object to be adhered, and handleability, an ethylene-vinyl acetate copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-aliphatic non-polymer. Selected from the group consisting of saturated carboxylic acid ester copolymers, saponified ethylene-vinyl acetate copolymers, ethylene copolymers containing glycidyl methacrylate, saponified ethylene-vinyl acetate-acrylic acid ester copolymers, and polyolefin resins It is preferable to contain at least one kind of resin.

  The resin sealing sheet of the present embodiment may contain a resin other than the ionizing radiation cross-linking resin. This will be described later.

The ethylene-vinyl acetate copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and vinyl acetate.
The ethylene-aliphatic unsaturated carboxylic acid copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from aliphatic unsaturated carboxylic acids.
Furthermore, the ethylene-aliphatic unsaturated carboxylic acid ester copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from an aliphatic unsaturated carboxylic acid ester.

  The copolymerization can be performed by a known method such as a high-pressure method or a melting method, and a multisite catalyst, a single site catalyst, or the like can be used as a catalyst for the polymerization reaction. Moreover, in the said copolymer, the bond shape of each monomer is not specifically limited, The polymer which has bond shapes, such as a random bond and a block bond, can be used. From the viewpoint of optical properties, the copolymer is preferably a copolymer polymerized by random bonding using a high-pressure method.

In the ethylene-vinyl acetate copolymer, the ratio of vinyl acetate in all monomers constituting the copolymer is preferably 5 to 40% by mass from the viewpoint of optical properties, adhesiveness, and flexibility. More preferably, it is -35 mass%, and it is further more preferable that it is 15-30 mass%.
Further, from the viewpoint of improving the workability and productivity of the resin-encapsulated sheet, the ethylene-vinyl acetate copolymer has a melt flow rate value (hereinafter referred to as “MFR”) measured according to JIS-K-7210. Abbreviated.) (190 ^° C., 2.16 kg) is preferably 15 to 45 g / 10 min, more preferably 20 to 40 g / 10 min, and still more preferably 20 to 35 g / 10 min.
When the value of the melt flow rate is 15 g / 10 min or more, when the resin-encapsulated sheet is produced by an extruder, a sufficient amount of resin can be ensured and practically good productivity can be obtained.
Further, when film formation is performed at a high speed, the thermal shrinkage rate of the resin-encapsulated sheet can be suppressed, and it is not necessary to reduce the production speed, which is advantageous in productivity.

Examples of the ethylene-aliphatic unsaturated carboxylic acid copolymer include an ethylene-acrylic acid copolymer (hereinafter also abbreviated as “EAA”) and an ethylene-methacrylic acid copolymer (hereinafter, “EMAA”). Abbreviated as well)).
Examples of the ethylene-aliphatic unsaturated carboxylic acid ester copolymer include an ethylene-acrylic acid ester copolymer and an ethylene-methacrylic acid ester copolymer. Here, as acrylic acid ester and methacrylic acid ester, ester with C1-C8 alcohols, such as methanol and ethanol, is used suitably.

  These copolymers may be multi-component copolymers obtained by copolymerizing three or more monomers. Examples of the multi-component copolymer include a copolymer obtained by copolymerizing at least three types of monomers selected from ethylene, aliphatic unsaturated carboxylic acid, and aliphatic unsaturated carboxylic acid ester.

In the ethylene-aliphatic unsaturated carboxylic acid copolymer, the proportion of the aliphatic unsaturated carboxylic acid in all monomers constituting the copolymer is preferably 3 to 35% by mass. The ethylene-aliphatic unsaturated carboxylic acid copolymer preferably has an MFR (190 ^° C., 2.16 kg) of 15 to 45 g / 10 min, more preferably 20 to 40 g / 10 min. More preferably, it is 20-35 g / 10min.

  Examples of the saponified ethylene-vinyl acetate copolymer include a part of ethylene-vinyl acetate copolymer or a completely saponified product. Examples of the saponified ethylene-vinyl acetate-acrylic ester copolymer include, for example, a part of the ethylene-vinyl acetate-acrylic ester copolymer or a completely saponified product.

  The ratio of the hydroxyl group in each saponified product is preferably 0.1 to 15% by mass, more preferably 0.1 to 10% by mass, and still more preferably 0% in the resin constituting the resin sealing sheet. .1 to 7% by mass. When the proportion of the hydroxyl group is 0.1% by mass or more, the adhesiveness of the resin sealing sheet tends to be good, and when it is 15% by mass or less, the compatibility tends to be good and finally obtained. The risk that the resin encapsulating sheet becomes clouded can be reduced.

  The ratio of the hydroxyl group was determined based on the olefin-based polymer resin of the saponified ethylene-vinyl acetate copolymer and the saponified ethylene-vinyl acetate-acrylic acid ester copolymer, and the VA% (vinyl acetate copolymer by NMR measurement) of this resin. (Polymerization ratio), its saponification degree, and the blending ratio in the resin.

  The content of vinyl acetate in the ethylene-vinyl acetate copolymer and the ethylene-vinyl acetate-acrylic acid ester copolymer before saponification is determined from the viewpoint of obtaining good optical properties, adhesiveness, and flexibility. It is preferable that it is 10-40 mass% with respect to the whole coalescence, It is more preferable that it is 13-35 mass%, It is further more preferable that it is 15-30 mass%. The saponification degree of the saponified ethylene-vinyl acetate copolymer and the saponified ethylene-vinyl acetate-acrylic acid ester copolymer is 10 to 70% from the viewpoint of obtaining good transparency and adhesiveness. Is preferably 15 to 65%, more preferably 20 to 60%.

  Examples of the saponification method include a method of saponifying an ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate-acrylic ester copolymer pellet or powder using an alkali catalyst in a lower alcohol such as methanol, toluene, And a method of dissolving a copolymer in advance using a solvent such as xylene and hexane and then saponifying using a small amount of alcohol and an alkali catalyst. Moreover, you may graft-polymerize the monomer containing functional groups other than a hydroxyl group to the saponified copolymer.

  Since each saponified product has a hydroxyl group in the side chain, the adhesion is improved as compared with the copolymer before saponification. Moreover, transparency and adhesiveness can be controlled by adjusting the amount of hydroxyl groups (degree of saponification).

  The ethylene copolymer containing glycidyl methacrylate refers to an ethylene copolymer and an ethylene terpolymer with glycidyl methacrylate having an epoxy group as a reaction site, for example, an ethylene-glycidyl methacrylate copolymer, an ethylene-glycidyl methacrylate-vinyl acetate copolymer. Examples thereof include a polymer and an ethylene-glycidyl methacrylate-methyl acrylate copolymer. Since the above compounds have high reactivity of glycidyl methacrylate, they can exhibit stable adhesion, and have a low glass transition temperature and tend to have good flexibility.

  As the polyolefin resin, a polyethylene resin and a polybutene resin are preferable. Here, the polyethylene resin refers to a homopolymer of ethylene or a copolymer of ethylene and one or more other monomers.

Examples of the polyethylene resin include polyethylene and ethylene-α-olefin copolymers.
Examples of the polyethylene include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and linear very low density polyethylene (referred to as “VLDPE” and “ULDPE”).
The ethylene-α-olefin copolymer is preferably a copolymer composed of ethylene and at least one selected from α-olefins having 3 to 20 carbon atoms, and includes ethylene and carbon atoms having 3 to 12 carbon atoms. More preferred is a copolymer comprising at least one selected from α-olefins.
Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-decene, 1-decene, Examples include 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 ratio (based on preparation monomer) of the alpha olefin in all the monomers which comprise a copolymer is 6-30 mass%. Further, the ethylene-α-olefin copolymer is preferably a soft copolymer, and preferably has a crystallinity of 30% or less by an X-ray method.

  Further, as the ethylene-α-olefin copolymer, a copolymer of ethylene and at least one comonomer selected from propylene comonomer, butene comonomer, hexene comonomer and octene comonomer is generally easily available, It can be used suitably.

The polyethylene resin can be polymerized using a known catalyst such as a single site catalyst or a multisite catalyst, and is preferably polymerized using a single site catalyst. Also, the polyethylene resin, from the viewpoint of impact resistance, 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 to 0.910 g / cm ³ . When the density is 0.920 g / cm ³ or less, impact resistance and transparency tend to be good. When a high-density polyethylene-based resin is used, the transparency can be improved by adding a low-density polyethylene-based resin at a ratio of about 30% by mass, for example. Further, when the density is 0.860 g / cm ³ or more, the elasticity tends to be improved.

The polyethylene resin preferably has an MFR (190 ^° C., 2.16 kg) of 15 to 45 g / 10 min, more preferably 20 to 40 g / 10 min, from the viewpoint of processability of the resin-encapsulated sheet. More preferably, it is 20-35 g / 10min.

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

  In addition, since the polybutene resin is particularly excellent in compatibility with the polypropylene resin, it is preferably used in combination with the polypropylene resin for the purpose of adjusting the hardness and stiffness of the resin sealing sheet. The polybutene resin is crystalline and is a copolymer of butene and at least one selected from ethylene, propylene and an olefin compound having 5 to 8 carbon atoms, and constitutes a polybutene resin. A high molecular weight polybutene resin having a butene content of 70 mol% or more in all monomers can be suitably used.

The polybutene resin preferably has an MFR (190 ^° C., 2.16 kg) of 1 to 40 g / 10 min. Further, it is preferable that the Vicat softening point of 40 to 100 ^o C. Here, the Vicat softening point is a value measured according to JIS K 7206-1982.

The resin sealing sheet of this embodiment may contain other resins other than the ionizable cross-linking resin described above.
The content of the ionizable crosslinkable resin in the resin constituting the resin sealing sheet of the present embodiment is preferably 50% by mass to 100% by mass of the ionizable crosslinkable resin, and is 70% by mass to 100% by mass. More preferably, it is more preferably 90% by mass to 100% by mass.
The other resin is preferably 0% by mass to 50% by mass, more preferably 0% by mass to 30% by mass, and still more preferably 0% by mass to 10% by mass.

  For the resin-encapsulated sheet of this embodiment, for the purpose of imparting other functions, a resin other than the above-described ionizable cross-linking resin can be selected as appropriate. For example, a predetermined thermoplastic resin may be included for the purpose of newly imparting cushioning properties.

  Examples of the thermoplastic resins include styrene resins, vinyl chloride resins, polyurethane resins, chlorinated ethylene polymer resins, polyamide resins, and the like. Is also included. Among these, a hydrogenated block copolymer resin having good compatibility with the crystalline polypropylene resin and good transparency is preferable.

  The hydrogenated block copolymer resin is preferably a block copolymer of vinyl aromatic hydrocarbon and conjugated diene. Examples of vinyl aromatic hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, and 1,1-diphenyl. Examples thereof include ethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene, and styrene is particularly 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, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3- Examples include butadiene, 1,3-pentadiene, and 1,3-hexadiene. These may be used alone or in combination of two or more.

The resin-encapsulated sheet in the present embodiment includes the ionizing radiation-crosslinking resin, and, if necessary, other thermoplastic resins, an ultraviolet absorber that improves weather resistance and light resistance, a light stabilizer that improves light resistance, And the silane coupling agent is contained in order to improve what the heat yellowing of the resin sealing sheet fell by the effect | action of the ionizing radiation with respect to these.
By containing the silane coupling agent, when the ionizing radiation for crosslinking is irradiated, the silane coupling agent is efficiently introduced into the main chain of the resin, and the resin sealing sheet is used as a solar cell sealing material. When used, the effect of improving the adhesive force between the resin sealing sheet and the glass is exhibited.
Moreover, the resin sealing sheet of this embodiment contains a ultraviolet absorber and a light stabilizer in order to improve weather resistance and light resistance. By including these additives, the composition has excellent yellowing prevention, crack resistance, adhesion and transparency over a long period of time.
Hereinafter, the ultraviolet absorber, the light stabilizer, and the silane coupling agent will be described.

(UV absorber)
The ultraviolet absorber absorbs harmful ultraviolet rays in sunlight and converts them into innocuous heat energy within the molecule. In a resin sealing sheet and a solar cell module using the resin sealing sheet, It prevents the active species at the start of photodegradation in the resin used for the stop sheet and the back sheet from being excited.
The addition amount of a ultraviolet absorber is 0.1 mass part or more and 0.3 mass part or less with respect to 100 mass parts of resin used for a resin sealing sheet.
When the amount is 0.1 part by mass or more with respect to 100 parts by mass of the resin used for the resin sealing sheet, a sufficient light resistance improvement effect is obtained. Moreover, there exists a tendency which can prevent generation | occurrence | production of yellowing by heat as it is 0.3 mass part or less.
The addition amount of the ultraviolet absorber is 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 resin used for the resin sealing sheet, and more preferably used for the resin sealing sheet. It is 0.15 mass part or more and 0.25 mass part or less with respect to 100 mass parts of resin obtained.

As the ultraviolet absorber, benzophenone compounds can be used, for example, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-5-sulfobenzophenone, 2-hydroxy-4-methoxybenzophenone, 2 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, and the like.
Moreover, as a ultraviolet absorber, a benzotriazole type compound can also be used, for example, 2- (2'-hydroxy-5'-methyl-phenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'- And di-tert-butylmethyl-phenyl) benzotriazole, 2- (2′-hydroxy-3′-tert-butyl-5′-methyl-phenyl) -5-chloro-benzotriazole, and the like.
As the ultraviolet absorber, a benzophenone-based compound is more preferable, and 2-hydroxy-4-n-octoxybenzophenone is particularly preferable.

(Light stabilizer)
A light stabilizer supplements the active species of the photodegradation start in resin used for a resin sealing sheet, and prevents photooxidation.
The addition amount of the light stabilizer is 0.05 parts by mass or more and 0.2 parts by mass or less with respect to 100 parts by mass of the resin used for the resin sealing sheet. Good light resistance is obtained when the addition amount of the light stabilizer is 0.05 parts by mass or more with respect to 100 parts by mass of the resin used in the resin sealing sheet. Moreover, by making the addition amount of the light stabilizer 0.2 parts by mass or less with respect to 100 parts by mass of the resin used for the resin sealing sheet, it is possible to prevent thermal yellowing of the resin sealing sheet itself, Moreover, there exists a tendency which can prevent the bleed-out of a light stabilizer, and can exhibit practically sufficient adhesiveness as a resin sealing sheet.
The addition amount of the light stabilizer is 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 resin used for the resin sealing sheet, and more preferably used for the resin sealing sheet. It is 0.1 mass part or more and 0.15 mass part or less with respect to 100 mass parts of resin.

  As the light stabilizer, hindered amine compounds can be used. For example, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4- And light stabilizers such as piperidyl) sebacate. Further, as the light stabilizer, hindered piperidine compounds can also be used. For example, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, dimethyl-1- (2-hydroxyethyl) -4 succinate Examples thereof include light stabilizers such as -hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, and the hindered amine system is more preferable.

The ultraviolet absorbers and light stabilizers described above may be used alone or in combination of two or more.
The method of adding the ultraviolet absorber and the light stabilizer to the resin constituting the resin encapsulating sheet is not particularly limited. The method of adding the molten resin in a liquid state, the method of kneading and adding directly to the target resin layer And a method such as coating after sheeting.

(Silane coupling agent)
The resin-encapsulated sheet of this embodiment contains a silane coupling agent in order to improve adhesion and prevent heat-resistant yellowing.
By including the silane coupling agent, the adhesiveness of the resin sealing sheet is improved.
Moreover, the fall of the heat-resistant yellowing of the resin sealing sheet by the effect | action of the ionizing radiation with respect to the ultraviolet absorber mentioned above and a light stabilizer can be prevented.

The addition amount and type of the silane coupling agent can be appropriately selected depending on the effect of improving the heat yellowing of the resin sealing sheet and the ease of reaction of the silane coupling agent with the resin polymer by irradiation with ionizing radiation.
First, as an addition amount of a silane coupling agent, 0.45 mass part or more and 2 mass parts or less are preferable with respect to 100 mass parts of resin of the resin sealing sheet which adds a silane coupling agent.
In particular, the content of silicon atoms derived from a silane coupling agent present in a solidified resin polymer obtained by reprecipitating a resin polymer obtained by swelling or dissolving a resin encapsulating sheet before modularization into a poor solvent. The value obtained by inductively coupled plasma optical emission spectrometry (ICP emission analysis) is 0.05% by mass or more and 0.2% by mass or less with respect to the weight of the entire resin sealing sheet. If the value obtained by ICP emission analysis of the silicon atom content is 0.05% by mass or more based on the total weight of the resin-encapsulated sheet, a sufficient effect of improving thermal yellowing can be obtained.
In addition, when the value obtained by ICP emission analysis of the silicon atom content is 0.2% by mass or less with respect to the total weight of the resin sealing sheet, the reaction of the silane coupling agent to the resin polymer The resin-sealed sheet that is sufficiently performed and finally obtained can prevent bleeding out of the silane coupling agent, and can exhibit practically sufficient adhesiveness.
Preferably, the content of silicon atoms derived from the silane coupling agent present in the solidified resin polymer by reprecipitating the resin polymer obtained by swelling or dissolving the resin encapsulating sheet before modularization into a poor solvent The value obtained by ICP emission analysis is 0.05% by mass or more and 0.15% by mass or less, more preferably 0.05% by mass or more and 0.1% by mass with respect to the total weight of the resin sealing sheet. It is as follows.
Specifically, it can measure by the method described in the Example mentioned later.
These silane coupling agents are prepared by injecting and mixing the resin-encapsulated sheet of the present embodiment into the resin in the extruder, and mixing and introducing it into the extruder hopper. It can be added by a known addition method such as a method of adding a mixture by mixing into a master batch.

  Further, the type of the silane coupling agent may be appropriately selected in consideration of the transparency and dispersion condition of the resin-encapsulated sheet, corrosion to the extruder, and the viewpoint of extrusion stability. , A compound having one type selected from the group consisting of an isocyanate group, a mercapto group, and a methacryloxy group. In particular, when an electron beam is irradiated, radicals are generated at the vinyl group site, the silane coupling agent easily reacts with the main chain, and the adhesion tends to be improved. Therefore, the vinyl group and / or methacryloxy Compounds having a group are preferred.

  Examples of the silane coupling agent include γ-chloropropylmethoxysilane, vinylmethyldimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris (β-methoxyethoxy) silane, 3-isocyanatopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, β- (3,4-ethoxycyclohexyl) ethyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyl Examples thereof include compounds having an unsaturated group, such as trimethoxysilane.

In the resin sealing sheet in this embodiment, it is estimated that the silane coupling agent in resin is grafted to the resin polymer by ionizing radiation irradiation.
As described above, the content of silicon atoms derived from the silane coupling agent present in the resin polymer when the resin polymer obtained by swelling or dissolving the resin sealing sheet in a good solvent is reprecipitated in a poor solvent and solidified. From the ratio of the amount of Si atoms when obtained by ICP emission analysis and the amount of Si atoms in the silane coupling agent introduced as a raw material in the resin sealing sheet production stage, The reaction rate of the resin sealing sheet to the resin polymer of the silane coupling agent can be calculated. In the resin sealing sheet of the present embodiment, the reaction rate is preferably 50% or more, and 70 % Or more is more preferable.

(Other additives)
In the resin-encapsulated sheet of the present embodiment, in addition to the above-mentioned additives, antioxidants and other additives, for example, antifogging agents, plasticizers, surfactants, colorants, as long as the properties are not impaired. An antistatic agent, a crystal nucleating agent, a lubricant, an antiblocking agent, an inorganic filler, a crosslinking regulator, and the like may be added.
The additive amount of these additives is preferably 5% by mass or less, and preferably 1% by mass or less, based on the total amount of the resin to be added, excluding pigments added for the purpose of coloring the resin sealing sheet. Is more preferably 0.5% by mass or less. About the pigment for coloring of a resin sealing sheet, 1 mass% or more and 20 mass% or less are preferable.

[Multilayer resin encapsulated sheet]
By laminating another resin layer (hereinafter referred to as an outer layer) on the resin sealing sheet of the present embodiment described above, a multilayer resin sealing sheet having two or more layers can be formed. In this case, the “outer layer” may have a single-layer structure or a multi-layer structure.
In addition, by using the resin sealing sheet of 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.
A two-layer structure can be formed by forming the outer layer only on one main surface of the resin-encapsulated sheet of the present embodiment, and a three-layer structure can be formed by forming the outer layer on both main surfaces.
Moreover, a multilayer resin sealing sheet having a three-layer structure is obtained by using a plurality of the resin sealing sheets of 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-encapsulated sheet of the present embodiment, the outer layer and the inner layer have the above-mentioned ionizing radiation cross-linking resin, silane coupling agent, and light stable depending on the desired performance. An agent, an ultraviolet absorber, and an antioxidant can be used as appropriate. Moreover, in order to express the sealing characteristic over a long term, it is preferable to use together a light stabilizer and a ultraviolet absorber with respect to the layer to add.

  The layer ratio of the layer in contact with the object to be sealed, that is, the layer ratio of the resin sealing sheet, is preferably at least 5% or more based on the total thickness of the multilayer structure sheet from the viewpoint of ensuring good adhesion. .

As resin which comprises the inner layer and outer layer which are laminated | stacked with the said resin sealing sheet, it is not limited to ionizing radiation bridge | crosslinking type resin, You may use any other resin.
Resin materials, mixtures, additives, and the like can be appropriately selected for the purpose of imparting other functions to the inner layer and the outer layer. For example, for the purpose of newly imparting cushioning properties, a layer containing a predetermined thermoplastic resin may be provided as the inner layer and the outer layer.

Examples of the thermoplastic resin used for the inner layer and the outer layer include polyolefin resins, styrene resins, vinyl chloride resins, polyester resins, polyurethane resins, chlorinated ethylene polymer resins, polyamide resins, and the like. In addition, those having biodegradability and plant-derived materials are also included.
Among the above thermoplastic resins, hydrogenated block copolymer resins and propylene copolymer resins having good compatibility with propylene copolymer resins and crystalline polypropylene resins and good transparency are preferable, and hydrogenated block copolymers are preferable. A polymer resin and a propylene-based copolymer resin are more preferable.

The hydrogenated block copolymer resin is preferably a block copolymer of vinyl aromatic hydrocarbon and conjugated diene. Examples of the vinyl aromatic hydrocarbon include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, 1, Examples thereof include 1-diphenylethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene, and styrene is particularly 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 such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-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.

  The propylene-based copolymer resin is preferably a copolymer obtained from propylene and ethylene or an α-olefin having 4 to 20 carbon atoms. The content of the ethylene or α-olefin having 4 to 20 carbon atoms is preferably 6 to 30% by mass. Examples of the α-olefin having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-pentene and 1-decene. 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 in which the polymer morphology is controlled in nano order can be used.

  In the multilayer resin sealing sheet described above, the inner layer and the outer layer may be a resin layer that satisfies the requirements of the resin sealing sheet of the present embodiment, and have the same configuration as the laminated resin sealing sheets. You may have.

[Characteristics of resin sealing sheet]
<Mooney viscosity>
The Mooney viscosity of the resin sealing sheet of this embodiment is 60M or more and 140M or less.
When the Mooney viscosity is 60 M or more, excellent creep resistance can be obtained, and problems such as cell displacement can be effectively prevented. Moreover, the fluidity | liquidity of the resin sealing sheet | seat which was excellent by being 140 M or less is obtained, favorable gap filling property is obtained, and gaps, such as a cell at the time of module manufacture, and wiring, can fully be sealed.
The Mooney viscosity is preferably 70M or more and 120M or less, more preferably 80M or more and 110M or less.
In addition, when further comprising the outer layer and the inner layer described above to constitute a multilayer resin encapsulated sheet as a whole, when measuring the average Mooney viscosity of the entire multilayer resin encapsulated sheet (all layer Mooney viscosity), The Mooney viscosity is preferably from 60 M to 140 M, more preferably from 70 M to 120 M, and even more preferably from 80 M to 110 M.
The Mooney viscosity can be measured according to JIS K 6300-1.
Specifically, it can measure by the method as described in the Example mentioned later.

<Processability>
Next, the viewpoint of resin-encapsulated sheet processability is examined.
The MFR (190 ^° C., 2.16 kg) of the resin constituting the resin sealing sheet of the present embodiment and the multilayer resin sealing sheet in the case where the outer layer and the inner layer described above are provided is from the viewpoint of ensuring good processability. It is preferably 15 to 45 g / 10 min, more preferably 20 to 40 g / 10 min, still more preferably 20 to 35 g / 10 min.
When the inner layer and the outer layer described above are laminated on the resin sealing sheet and have a multilayer structure as a whole, the MFR of the resin constituting the inner layer is that of the resin sealing sheet that is the surface layer from the viewpoint of resin sealing sheet processability. Preferably it is lower than MFR.

<Thickness and physical properties>
When the resin sealing sheet of this embodiment and the multilayer resin sealing sheet having the outer layer and the inner layer described above are included, the thickness is preferably 50 to 1500 μm, more preferably 100 to 1000 μm, and more preferably 150 to More preferably, it is 800 μm.
When the thickness is 50 μm or more, structurally sufficient cushioning properties can be obtained, and excellent durability and strength can be obtained from the viewpoint of workability. On the other hand, when the thickness is 1500 μm or less, practically sufficient productivity can be secured, and excellent adhesion as a resin-encapsulated sheet can be obtained.

<Optical characteristics>
The optical characteristics of the multilayer resin encapsulating sheet when the resin encapsulating sheet of the present embodiment and the above-described outer layer and inner layer are provided will be described.
A haze value is used as an index of optical characteristics. When the haze value is 10.0% or less, it is possible to confirm the appearance of the object sealed with the resin sealing sheet of this embodiment and the multilayer resin sealing sheet in the case where the outer layer or the inner layer described above is provided. At the same time, when used as a sealing material for solar cells, practically sufficient power generation efficiency is obtained, which is preferable. From the above viewpoint, the haze value is preferably 9.5% or less, and more preferably 9.0% or less. Here, the haze value can be measured according to ASTM D-1003.

<Total light transmittance>
Further, the resin encapsulating sheet of the present embodiment and the multilayer resin encapsulating sheet in the case where the outer layer and the inner layer described above are provided are used to ensure practically sufficient power generation efficiency when used as a solar cell encapsulant. Further, the total light transmittance is preferably 85% or more, more preferably 87% or more, and still more preferably 88% or more. Here, the total light transmittance can be measured in accordance with ASTM D-1003.

[Method for producing resin-encapsulated sheet]
Although there is no restriction | limiting in particular as a manufacturing method of a resin sealing sheet, For example, the following methods are mentioned.
First, the resin is melted by 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 a T die is preferable because of easy thickness control.

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 sides, between the two embossing rolls, when performing single-sided embossing processing, by passing the original fabric between the rolls where only one side is embossing roll, Embossing treatment can be performed.
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.

A crosslinking treatment for the resin constituting the resin sealing sheet, that is, an ionizing radiation irradiation treatment is performed on the original fabric.
Thereby, since the ionizing radiation cross-linking resin described above is cross-linked and a curing process is unnecessary, for example, when a solar cell element is protected and a solar cell is manufactured, the process can be simplified.
Depending on each case, it can be selected whether to perform the pre-process or post-process of the embossing process. It can also be selected whether to perform the pre-process or post-process of the post-processing.

  Examples of the crosslinking by irradiation with ionizing radiation include a method of irradiating the resin encapsulating sheet with ionizing radiation such as α rays, β rays, γ rays, neutron rays, electron beams and the like. The acceleration voltage of ionizing radiation such as an electron beam may be selected according to the thickness of the resin sealing sheet. For example, when the thickness is 500 μm, when the entire resin sealing sheet is crosslinked, the acceleration voltage is 300 kV or more. preferable.

The acceleration voltage of ionizing radiation such as an electron beam can be appropriately adjusted according to the resin layer subjected to the crosslinking treatment, 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 150 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 bridge | crosslinking by ionizing radiation can adjust the Mooney viscosity of a resin sealing sheet with irradiation intensity | strength (acceleration voltage) and irradiation density. The irradiation intensity (acceleration voltage) indicates how deep electrons can reach in the thickness direction of the sheet, and the irradiation density indicates how many electrons are irradiated per unit area. In view of higher productivity and physical properties of the resulting resin-encapsulated sheet, a preferred example is an ethylene vinyl acetate copolymer having an MFR (190 ° C., 2.16 kg) of 15 to 45 g / 10 min (vinyl acetate content 25 to 25). When 30 mass%) is used, the preferable ionizing radiation dose is 55 kGy to 85 kGy.

  In addition, as a method for producing a multilayer resin encapsulated sheet, a method of co-extruding a target resin in each layer using a multilayer die, and for multilayering before the resin enters a single-layer die from an extruder There is a method in which a feed block is arranged, a resin extruded from a plurality of extruders is multilayered in the feed block, and then formed into a sheet with a single layer die.

[Use of resin encapsulated sheet]
The resin sealing sheet of this embodiment is particularly useful as a sealing material for protecting members such as elements constituting the solar cell. That is, it is excellent in weather resistance and light resistance, is less colored due to thermal yellowing, has little decrease in power generation efficiency due to ultraviolet rays, sunlight, and heat, and also has good adhesion to an object to be sealed. By using the resin sealing sheet, the durability of the solar cell can be improved and the power generation efficiency can be kept high.
The solar cell module when used as a solar cell encapsulant, for example, uses two resin encapsulating sheets of this embodiment, transparent substrate (transparent protective material) / resin encapsulating sheet / power generation element / resin encapsulating It can be set as the structure laminated | stacked in order of the sheet | seat / back sheet | seat (back surface protective material), and it can produce by laminating | stacking these materials and carrying out vacuum lamination.
Moreover, the resin encapsulating sheet of this embodiment can be used as an encapsulating sheet for solar cells, LED sealing, interlayer films of laminated glass and security glass, etc., plastic and glass, plastics, adhesion between glasses, etc. Can also be used.

  Hereinafter, although a specific Example and a comparative example are given and demonstrated, this invention 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.
<Content (mass%) of Si atom in resin sealing sheet>
As pretreatment, 1.5 g of resin-encapsulated sheet samples of Examples and Comparative Examples described later are dissolved or swollen in 50 mL of a good solvent (chloroform), and then reprecipitated in 150 mL of a poor solvent (methanol). The content of Si (silicon) atoms is removed by filtering to remove UV absorbers, light stabilizers, antioxidants, silane coupling agents not grafted in the resin polymer, and other additives in the resin. A sample for measurement was obtained.
Next, using the sample obtained by pretreatment as described above, inductively coupled plasma optical emission spectrometry (ICP emission analysis) is performed, and the weight of the original resin-encapsulated sheet sample before pretreatment is 100. The content (mass%) of Si atoms contained in the sample was determined as mass%.
The measurement was carried out using an inductively coupled plasma emission spectrometer (ICP-AES) model iCAP 6300 Duo manufactured by Thermo Fisher Scientific Co., Ltd.

<Mooney viscosity>
Based on JIS K 6300-1, it measured with the Mooney viscometer (MVR) MODEL VR-1130 by the Ueshima Seisakusho company.
The rotor shape was measured using a rotor having an L shape at a test temperature of 100 ^° C., a preheating of 1 minute, a measurement time of 4 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.

<Evaluation of gap filling ability of power generation part>
Glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet (thickness 600 μm) / power generation part / resin sealing sheet / glass plate for solar cell (manufactured by AGC, White sheet glass 5 cm × 10 cm square: thickness 3 mm) and laminated in a vacuum at 150 ^° C. using a LM50 type vacuum laminator (NPC), The contact state of was confirmed visually.
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.
Judgment of the contact state of the power generation part was made visually according to the following criteria.
A: The contact portions of the single crystal silicon cell, the tab wire, and the resin sealing sheet as the power generation portion were all good, and there were no gaps.
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 / power generation part (single crystal silicon cell (thickness 250 μm) / resin encapsulated sheet / solar cell glass plate (AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) are laminated in this order, vacuum laminated using an LM50 type vacuum laminator (NPC), and one glass plate of the laminated solar cell is 85 ^° C. It was fixed to the wall surface of the thermostat set to, and allowed to stand for 24 hours, and the deviation from the other glass plate was measured and evaluated.
A: The deviation of the glass plate is less than 3 mm.
X: The shift | offset | difference of a glass plate is 3 mm or more.

<Color difference>
The b value was measured using a color difference meter Z-300A manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS Z 8722, a color measurement method.
[Color difference (b value) of laminate after light resistance test]
Laminate in order of glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet / back sheet (manufactured by Toyo Aluminum Co., Ltd., using Toyal Solar as the back surface protective material) Using an LM type vacuum laminator (NPC), deaeration was performed at 150 ° C. for 5 minutes, and then vacuum lamination was performed for 10 minutes to prepare an evaluation sample.
In the light resistance test, UV irradiation was performed for 96 hours at 60 mW / cm ² at 68 ° C. and a relative humidity of 50% using an I-Super UV tester manufactured by Iwasaki Electric.
The color difference (b value) before and after the light resistance test of the sample for evaluation was evaluated according to the following criteria.
In this method, the yellowing of the resin sealing sheet and the back sheet due to the ultraviolet rays that passed through the glass plate and the resin sealing sheet was mainly evaluated.
A: The increase in the b value after the test is less than 2 compared with that before the test, which is the best light resistance.
B: The increase in b value after the test is 2 or more and less than 4 compared to before the test, which is relatively good light resistance.
C: The increase in b value after the test is 4 or more and less than 10 compared to before the test, which is the minimum light resistance.
X: The increase in b value after the test was 10 or more compared to before the test, and the yellowing was severe.

[Color difference (b value) of sealing sheet after light resistance test]
Glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet / glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) The samples were laminated, degassed at 150 ° C. for 5 minutes using a LM vacuum laminator (NPC), and then vacuum laminated for 10 minutes to prepare a sample for evaluation.
In the light resistance test of the resin-encapsulated sheet, irradiation was performed for 500 hours at 45 mW / cm ² as UV irradiation conditions using a small UV irradiation device Handy UV-300 manufactured by Oak Manufacturing Co., Ltd.
In the color difference (b value) measurement, an evaluation sample was placed on the same white plate before and after the light resistance test, and the change in the b value before and after was measured.
The color difference (b value) before and after the light resistance test of the sample for evaluation was evaluated according to the following criteria.
In this method, yellowing due to UV of the resin sealing sheet itself was evaluated.
A: The increase in the b value after the test is less than 2 compared with that before the test, which is the best light resistance.
B: The increase in b value after the test is 2 or more and less than 4 compared to before the test, which is relatively good light resistance.
C: The increase in b value after the test is 4 or more and less than 10 compared to before the test, which is the minimum light resistance.
X: The increase in b value after the test was 10 or more compared to before the test, and the yellowing was severe.

[Color difference after thermal yellowing test (b value)]
Glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet / glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) The samples were laminated, degassed at 150 ° C. for 5 minutes using a LM vacuum laminator (NPC), and then vacuum laminated for 10 minutes to prepare a sample for evaluation.
In the thermal yellowing test of the resin-encapsulated sheet, the sample for evaluation was held in an oven at 120 ° C. for 500 hours, and the color difference (b value) was measured before and after the test.
In the color difference (b value) measurement, an evaluation sample was placed on the same white plate before and after the thermal yellowing test, and the change in the b value before and after was measured.
In this method, yellowing due to heat of the resin sealing sheet itself was mainly evaluated.
A: The increase in the b value after the test is less than 2 compared with that before the test, which is the best light resistance.
B: The increase in b value after the test is 2 or more and less than 4 compared to before the test, which is relatively good light resistance.
C: The increase in b value after the test is 4 or more and less than 10 compared to before the test, which is the minimum light resistance.
X: The increase in b value after the test was 10 or more compared to before the test, and the yellowing was severe.

<Adhesive strength with glass>
Laminate LM50 type vacuum laminator (NPC) in the order of glass plate for solar cell (white glass 10cm x 5cm square, thickness 3mm) / resin sealing sheet / back sheet (Toyo Aluminum Co., Ltd., manufactured by Toyo Aluminum Co., Ltd.) Was used for deaeration at 150 ^° C. for 5 minutes, followed by vacuum lamination for 10 minutes to prepare a sample for measuring adhesive strength with glass.
The initial adhesive strength with glass was measured using the “Tensilon UMT-II-500 type” manufactured by Toyo Bald Inn Co., Ltd. under the conditions of a temperature of 23 ^° C. and a relative humidity of 55%.
Moreover, regarding water-resistant adhesiveness with glass, after holding the measurement sample for 500 hours in a constant temperature and humidity chamber at 85 ° C. and a relative humidity of 85%, the adhesive strength was measured under the same conditions.
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. The adhesive strength was evaluated according to the following 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 evaluation>
A resin encapsulated sheet cut into a 100 mm square is used as an evaluation sample, held in a thermostatic bath at 50 ° C. for 24 hours, then taken out, and the evaluation sample surface is visually observed in a state of normal temperature. The bleed-out was evaluated.
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.

The materials used in the examples and comparative examples are as follows.
<Resin>
Ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA): EVA RF7830 manufactured by Asahi Kasei Chemicals Corporation was used. This resin has a vinyl acetate content of 28%, MFR (Code D) of 30 g / 10 min, and a melting point of 71 ° C.
In addition, in the evaluation of the productivity of the resin-encapsulated sheet described later, in addition to the EVA RF7830 manufactured by Asahi Kasei Chemicals Corporation, ethylene-vinyl acetate copolymer: EVA Ultrasen 751 manufactured by Tosoh Corporation (vinyl acetate content 28%, MFR 5.7). , Melting point 72 ° C.) and Ultracene 710 (vinyl acetate content 28%, MFR 18, melting point 71 ° C.).
<Silane coupling agent>
As the silane coupling agent, KBM503 (trade name) manufactured by Shin-Etsu Chemical Co., Ltd., substance name: 3-methacryloxypropyltrimethoxysilane 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.

[Examples 1-20], [Comparative Examples 1-19]
Prior to the production of the resin-encapsulated sheets of Examples and Comparative Examples, evaluation of the productivity of the resin-encapsulated sheets was performed using Asahi Kasei Chemicals EVA: RF7830 and Tosoh EVA: Ultrasen 751 and 710. .
In addition, in the evaluation of productivity, the resin sheet was extruded using only the resin as a material, and the evaluation was performed by regarding the productivity as the resin-encapsulated sheet.
Using an extruder (single shaft, caliber = 65 mm, L / D = 29), the resin temperature at the die outlet is set to 130 ° C., and the resin is extruded from an 800 mm wide T-die. Sheet productivity was evaluated.
As a result, with RF7830 with MFR = 30, the resin pressure at the die inlet at a resin extrusion rate of 100 kg / hour is 20 Mpa or less, and a resin sheet can be obtained stably. Even with Ultrasen 710 with MFR = 18, the resin extrusion rate is 100 kg. Resin pressure at the die inlet at 25 MPa / hour was stably obtained at 25 MPa, but with Ultrasen 751 with MFR = 5.7, the resin pressure at the die inlet was 50 kg / hour of resin extrusion rate. It became 30 MPa, and the amount of extrusion beyond that could not be increased.
From the above results, regarding the productivity of the resin-encapsulated sheet, RF7830 is the best, Ultrasen 710 is also excellent, and Ultrasen 751 is inferior. Using RF7830, the resin sealing of the following Examples and Comparative Examples A stop sheet was produced.
Hereafter, the resin sealing sheet | seat of Examples 1-20 and Comparative Examples 1-19 was manufactured according to the composition ratio (a unit is a mass part) shown in the following Table 1 and Table 2.
The resin and various additives are melt-kneaded using an extruder, the resin is melt-extruded from a T-die connected to the extruder into a cast roll with an emboss, cooled by a cast roll, and a plurality of It cooled with the roll and finally wound up in roll shape and obtained the resin sealing sheet.
Using the EPS-800 electron beam irradiation apparatus (manufactured by Nissin High Voltage), an electron beam with an irradiation dose described in Tables 1 and 2 was applied to the obtained resin-encapsulated sheet (sheet with emboss) at an acceleration voltage of 800 kV. Was subjected to crosslinking treatment. This obtained the resin sealing sheet of Examples 1-20 and Comparative Examples 1-19.

For the obtained resin-encapsulated sheets of Examples 1 to 20 and Comparative Examples 1 to 19, Mooney viscosity, gap filling property, creep resistance, color difference (b value) of laminated product after light resistance test, light resistance test The color difference (b value) of the subsequent sealing sheet, the color difference (b value) after the thermal yellowing test, initial adhesion strength to glass, water-resistant adhesion to glass, and bleed-out evaluation were evaluated. A comprehensive evaluation was conducted. The results are shown in Tables 1 and 2.
<Comprehensive evaluation>
A: The above 8 items (gap filling property, creep resistance, color difference (b value) of laminate after light resistance test, light resistance, color difference (b value) of sealing sheet after test, color difference after thermal yellowing test (B value), initial adhesion strength to glass, water-resistant adhesion to glass, bleed-out property), and the best resin-encapsulated sheet by A evaluation.
B: A practically good resin-sealed sheet in which one or more of the above 8 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 eight items is C evaluation and the rest are all A evaluation or B evaluation.
X: One or more of the above 8 items is x evaluation, and the resin-encapsulated sheet is practically insufficient.

  As can be seen from the results in Tables 1 and 2, the resin-encapsulated sheets of Examples 1 to 20 are excellent in light resistance and heat yellowing resistance, filling gaps, creep resistance, adhesion to glass, and bleed-out resistance. It was found that all the properties of the material are good and the balance of properties is excellent.

  The present invention has industrial applicability as a sealing material for protecting the solar cell member of the present invention.

Claims (5)

A resin-sealed sheet that is a single-layer resin-sealed sheet that softens and adheres a resin and satisfies the following conditions (1) to (5).
(1) At least one of the resins constituting the resin sealing sheet is an ionizing radiation cross-linking resin.
(2) A silicon atom derived from a silane coupling agent present in a solidified resin polymer obtained by swelling or dissolving the resin sealing sheet before modularization in a good solvent to reprecipitate the resin polymer in a poor solvent. The value obtained by inductively coupled plasma optical emission spectrometry is 0.05% by mass or more and 0.2% by mass or less with respect to the total weight of the resin-encapsulated sheet.
(3) 0.1 mass part or more and 0.3 mass part or less of an ultraviolet absorber are contained with respect to 100 mass parts of resin which comprises the said resin sealing sheet.
(4) The light stabilizer is contained in an amount of 0.05 parts by mass or more and 0.2 parts by mass or less with respect to 100 parts by mass of the resin constituting the resin sealing sheet.
(5) The resin sealing sheet has been subjected to ionizing radiation treatment and has a Mooney viscosity of 60 to 140M.   The resin sealing sheet according to claim 1, wherein the silane coupling agent is a compound having a vinyl group and / or a methacryloxy group.   A multilayer resin encapsulating sheet comprising at least two layers, wherein the resin encapsulating sheet according to claim 1 and other outer layers are laminated.   The multilayer resin sealing sheet which consists of at least 3 layers by which the resin sealing sheet of Claim 1 or 2 was laminated | stacked on the front and back of the other inner layer.   The solar cell module using the resin sealing sheet as described in any one of Claims 1 thru | or 4 as a sealing material.