JP6798523B2 - Encapsulant sheet for electronic devices - Google Patents

Description

The present invention relates to a sealing material sheet for an electronic device. The encapsulant sheet of the present invention can be used as an encapsulant for various electronic devices. In particular, it can be preferably used for devices provided with metal wiring. As an example of a preferred embodiment of this encapsulant sheet, use as an encapsulant for a solar cell module can be mentioned.

In recent years, due to growing awareness of environmental issues, solar cells as a clean energy source have been attracting attention. Currently, solar cell modules having various forms have been developed and proposed. Generally, a solar cell module has a configuration in which a glass protective substrate, a solar cell element, and a back surface protective sheet are laminated via a sealing material sheet for the solar cell module (see FIG. 1).

Conventionally, as a sealing material sheet for a solar cell module, a resin using EVA (ethylene-vinyl acetate copolymer) having excellent transparency, adhesion and the like as a base resin has been widely used. However, in recent years, the development of a sealing material sheet based on a polyethylene resin having transparency equivalent to that of EVA and superior in hydrolysis resistance and the like as compared with EVA has been advanced.

Here, in order to provide a sealing material sheet for a solar cell module using a polyethylene-based resin as a base resin with sufficient light resistance, a hindered amine-based light-resistant stabilizer (hereinafter, also referred to as “HALS”) is usually added. Is required. (See Patent Document 1). When a hindered amine-based light-resistant stabilizer is added to the encapsulant sheet, a high-molecular-weight hindered amine-based light-resistant stabilizer having a molecular weight of 1200 or more is to be avoided in order to avoid bleed-out and deterioration of optical properties due to overdose. A finding is disclosed that it is preferable to use a stabilizer in the range of 0.01 parts by weight or more and 2.5 parts by weight or less (see Patent Document 2). In addition, in this specification, "molecular weight" shall mean "number average molecular weight (Mn)" unless otherwise specified.

On the other hand, in recent years, solar cell modules are required to have longer durability in harsher environments than before in order to cope with the increase in installation in hot and humid areas and the extension of the warranty period. ing. Solar cell modules as products are required to pass advanced durability tests such as PCT tests under harsh conditions that meet such demands.

Conventionally, the encapsulant sheet for a polyethylene-based solar cell module is different from the EVA-based encapsulant sheet in which acid gas is inevitably generated, and leads to oxidative corrosion of various metal members in the solar cell module. One of its advantages was that it did not generate acid gas. However, as a new problem, acid gas may be generated during use of some polyethylene-based encapsulant sheets in a hot and humid environment corresponding to the harshness of long-term durability conditions in recent years. It came to be recognized. Further, it was speculated that the acid gas was derived from various additives added to the base resin, such as the decomposition product of the above-mentioned hindered amine-based light-resistant stabilizer, but the details of the mechanism of its generation are not clear. There wasn't.

Japanese Unexamined Patent Publication No. 2004-214641 Japanese Unexamined Patent Publication No. 2012-9693

The present invention is a technique developed under the above circumstances, and is a polyethylene-based encapsulant sheet having sufficient weather resistance to withstand long-term use in a harsh environment of high temperature and humidity. , A seal for electronic devices suitable as a sealing material sheet for a solar cell module, which can sufficiently suppress the generation of acid gas harmful to the solar cell module and maintain power generation efficiency even in such an environment. An object is to provide a stop material sheet.

The present inventors have described "high molecular weight type hindered amine-based light-resistant stabilizers" having a specific chemical structure described in detail below in a sealing material sheet for a solar cell module using a polyethylene-based resin as a base resin. By using in combination with a "low molecular weight type hindered amine-based light-resistant stabilizer" having a specific chemical structure similar to this, high weather resistance that can withstand long-term use in harsh environments of high temperature and humidity, and such We have found that it is possible to suppress the generation of acid gas in a favorable environment, and have completed the present invention. Specifically, the present invention provides the following.

(1) An encapsulant sheet for an electronic device, in which a polyethylene resin is used as a base resin and a high molecular weight type hindered amine light-resistant stabilizer having a molecular weight of 1000 or more is added to the resin component of the encapsulant sheet. A low molecular weight type hindered amine-based light-resistant stabilizer containing 02% by mass or more and 0.20% by mass or less and having a molecular weight of less than 1000 is 0.02% by mass or more and 0.20 by mass in the resin component of the sealing material sheet. The cross-linking agent is contained in the resin component of the encapsulant sheet in a proportion of 0.2% by mass or more and 0.6% by mass or less, and the high molecular weight type hindered amine-based light-resistant stable. A sealing material sheet in which the chemical structures of the agent and the low molecular weight type hindered amine-based light-resistant stabilizer are all any of the following chemical structures (i) to (iii).
(I) Ester-free chemical structure.
(Ii) A chemical structure containing an ester, the ester having an R1-COO-R2 structure, having a molecular weight of R1 of 100 or more, and R2 containing no ester.
(Iii) A chemical structure containing an ester, the ester having an R3-OCO-R4-COO-R5 structure, having a molecular weight of R4 of 100 or more, and R3 and R5 containing no ester.

(2) The encapsulant sheet according to (1), wherein the chemical structure of the cross-linking agent is any one of the following (i), (iv) or (v).
(I) Ester-free chemical structure.
(Iv) A chemical structure containing an ester, wherein the ester has an R6-OO-COO-R7 structure, and R6 and R7 are not esterified.
(V) A chemical structure represented by the following structural formula (1), in which the molecular weight of R9 is 100 or more, and R8, R10 and R11 do not contain esters.

（１）

(1)

(3) Further, the cross-linking aid is contained in the resin component of the sealing material sheet in a proportion of 0.01% by mass or more and 1.5% by mass or less, and the chemical structure of the cross-linking aid is as follows (i). The encapsulant sheet according to (1) or (2), which has a chemical structure according to any one of (iii).
(I) Ester-free chemical structure.
(Ii) A chemical structure containing an ester, the ester having an R1-COO-R2 structure, having a molecular weight of R1 of 100 or more, and R2 containing no ester.
(Iii) A chemical structure containing an ester, the ester having an R3-OCO-R4-COO-R5 structure, having a molecular weight of R4 of 100 or more, and R3 and R5 containing no ester.

(4) The description according to any one of (1) to (3), further comprising an antioxidant, wherein the chemical structure of the antioxidant is any of the following chemical structures (i) to (iii). Encapsulant sheet.
(I) Chemical structure containing no ester (ii) A chemical structure containing an ester, the ester having an R1-COO-R2 structure, having a molecular weight of R1 of 100 or more, and R2 containing no ester.
(Iii) A chemical structure containing an ester, the ester having an R3-OCO-R4-COO-R5 structure, having a molecular weight of R4 of 100 or more, and R3 and R5 containing no ester.

(5) The encapsulant sheet according to any one of (1) to (4), further containing a silane-modified polyethylene resin.

(6) The glass protective substrate, the light receiving surface side encapsulant in close contact with the glass protective substrate, and the solar cell element are included, and the light receiving surface side encapsulant is (1). A solar cell module which is the sealing material sheet according to any one of (5) to (5).

A polyethylene-based encapsulant sheet with sufficient weather resistance that can withstand long-term use in a harsh environment of high temperature and humidity, and acidity that is harmful to the solar cell module even in such an environment. It is possible to provide a sealing material sheet for an electronic device, which is suitable as a sealing material sheet for a solar cell module, which can sufficiently suppress the generation of gas and maintain the power generation efficiency.

It is sectional drawing which shows an example of the layer structure of the solar cell module using the sealing material sheet of this invention.

<Encapsulant sheet>
The encapsulant sheet of the present invention (hereinafter, also simply referred to as “encapsulant sheet”) uses a polyethylene-based resin as a base resin, as described in detail below, and each of them is a specific chemical whose details are described below. Two types of hindered amine-based light-resistant stabilizers that are a combination of "low-molecular-weight type hindered amine-based light-resistant stabilizers" that have the same chemical structure as "high-molecular-weight type hindered amine-based light-resistant stabilizers" that have a structure. A sealing material composition containing at least an agent and a cross-linking agent is molded into a film or sheet by a conventionally known method. In the present specification, the term "base resin" is used as a resin composition containing the base resin, which is mixed with the resin having the largest content ratio among the resin components of the resin composition and the resin. It shall refer to the same type of resin used. Details of the polyethylene-based resin and various additives that can be preferably used as the base resin will be described later as a description of the encapsulant composition used for producing the encapsulant sheet.

In the present specification, among the hindered amine-based light-resistant stabilizers (HALS), those having a molecular weight of 1000 or more are defined as "ultra-high molecular weight type hindered amine-based light-resistant stabilizers", and those having a molecular weight of less than 1000 are defined. , "Low molecular weight type hindered amine-based light-resistant stabilizer".

Further, it is preferable that the sealing material sheet is molded without being crosslinked by limiting the molding temperature to a low temperature range of 90 ° C. to 120 ° C. Then, the cross-linking treatment is performed separately after molding, or the cross-linking treatment is performed by heating at a high temperature at the time of manufacturing the solar cell module described later.

The encapsulant sheet has a gel fraction of 0% or more and 10% or less, more preferably 0%, that is, uncrosslinked in the stage after film formation and before modularization. Further, this uncrosslinked encapsulant sheet contains a predetermined amount of a cross-linking agent, and cross-linking proceeds in any process until after integration as a solar cell module, and the final product, the solar cell module. In the finished product stage, a crosslinked encapsulant sheet having a gel content of 50% or more and 90% or less is obtained.

By adjusting the composition and amount of the cross-linking agent, cross-linking aid, and other additives to a preferable range, the cross-linking reaction can be appropriately controlled so that the gel fraction is within the above range. As a result, it has a good water vapor barrier, flexibility in a low temperature region, and heat resistance at a high temperature can be obtained. Although it uses a polyethylene resin as a base resin, it can be used in a low temperature region. It is possible to obtain a sealing material sheet having excellent moldability.

Here, the "gel fraction (%)" in the present specification means that 1.0 g of a sealing material sheet is placed in a resin mesh, extracted with xylene at 110 ° C. for 12 hours, and then taken out together with the resin mesh and weighed after drying. Then, the mass before and after extraction was compared, the mass% of the residual insoluble matter was measured, and this was used as the gel fraction. The gel fraction of 0% means that the residual insoluble matter is substantially 0 and the crosslinking reaction of the encapsulant composition or the encapsulant sheet has not substantially started. More specifically, "gel fraction 0%" means that the residual insoluble matter does not exist at all, and the mass% of the residual insoluble matter measured by a precision balance is less than 0.05% by mass. Suppose to say. The residual insoluble matter does not include pigment components other than the resin component. When a mixture other than these resin components is mixed in the residual insoluble matter by the above test, for example, by separately measuring the content of these mixture in the resin component in advance, these It is possible to calculate the gel fraction that should be originally obtained for the residual insoluble matter derived from the resin component excluding the mixture.

The encapsulant sheet of the present invention may be a single-layer film, or may be a multilayer film composed of a core layer and skin layers arranged on both sides of the core layer. The multilayer film in the present specification is a film or sheet having a structure having at least one outermost layer, preferably a skin layer formed into both outermost layers, and a core layer which is a layer other than the skin layer. Say that.

When the encapsulant sheet is a multilayer film, the contents of the high molecular weight type hindered amine light-resistant stabilizer and the low molecular weight type hindered amine light-resistant stabilizer in the resin components are the resin components of all layers of the encapsulant sheet, respectively. The average content ratio in the medium may be in the range of 0.02% by mass or more and 0.20% by mass or less. Further, it is not essential that all of these hindered amine-based light-resistant stabilizers are uniformly contained in all the layers of the multilayer film at the same content ratio. However, it is preferable that the hindered amine-based light-resistant stabilizer is dispersed in all the layers of the multilayer film to the extent that at least 0.01% by mass or more of the hindered amine-based light-resistant stabilizer is contained in each layer.

When the sealing material sheet is a multilayer film, it is preferable to arrange a layer having a higher MFR as a skin layer on the outermost layer side. The encapsulant sheet of the present invention has sufficiently preferable transparency, heat resistance, and appropriate flexibility even when it is a single-layer encapsulant sheet, and thus has a relative MFR. By arranging the layer having a high value in the outermost layer, it is possible to further improve the adhesion and the molding characteristics while maintaining the above-mentioned preferable transparency and heat resistance as the sealing material sheet.

Further, when the sealing material sheet is a multilayer film, the adhesion improving component such as silane-modified polyethylene or a silane coupling agent, which will be described later, may be more inclinedly distributed to the skin layer than to the core layer. As a result, while maintaining the above-mentioned preferable transparency and heat resistance as the sealing material sheet, it is possible to further enhance the adhesion to glass and metal required when the solar cell module is integrated.

For example, in a sealing material sheet which is a multilayer film composed of three or more layers, the thickness of the outermost layer is 30 μm or more and 120 μm or less, and an intermediate layer and an outermost layer composed of all layers other than the outermost layer. The thickness ratio of the outermost layer: the intermediate layer: the outermost layer is preferably in the range of 1: 3: 1 to 1: 8: 1. By doing so, it is possible to provide preferable molding characteristics in the outermost layer while maintaining preferable heat resistance as a sealing material sheet.

<Encapsulant composition>
The encapsulant composition used for producing the encapsulant sheet of the present invention (hereinafter, also simply referred to as “encapsulant composition”) uses a low-density polyethylene-based resin as a base resin, and has a molecular weight and a specific chemical structure. It is a thermosetting resin composition containing at least a hindered amine-based light-resistant stabilizer (HALS) and a cross-linking agent, which are composed of a combination of two types selected by attention. Further, it is preferable that the encapsulant composition further contains a cross-linking aid and an antioxidant.

Further, the encapsulant composition preferably has a specific chemical structure described later with respect to the chemical structure of the cross-linking agent to be added. When the cross-linking aid and the antioxidant have been contained, it is preferable that each of them also has a specific chemical structure described later.

(Base resin)
Sealant composition, density 0.870 g / cm ³ or more 0.900 g / cm ³ or less, preferably, density 0.875 g / cm ³ or more 0.895 g / cm ³ or less, more preferably, density 0.880g A polyethylene resin of / cm ³ or more and 0.890 g / cm ³ or less is used as the base resin. By using such a low-density polyethylene-based resin as the base resin, the transparency of the encapsulant sheet can be improved. Further, according to this, the adhesion to other members constituting the solar cell module such as a glass protective substrate is enhanced, and the risk of cell cracking at the time of crimping each member in the laminating process can be reduced. The content of the above-mentioned base resin with respect to the total resin components of the encapsulant composition is 70% by mass or more and 100% by mass or less, preferably 90% by mass or more and 99% by mass or less. As long as this base resin is contained within the above range, other resins may be contained in the encapsulant composition as long as the effects of the present invention are not impaired.

The melt mass flow rate (MFR) of polyethylene used as the base resin of the encapsulant composition is MFR measured by JIS-K6922-2 at 190 ° C. and a load of 2.16 kg (“MFR” in the present specification is this measurement. The measured value according to the conditions is preferably 5 g / 10 minutes or more and 30 g / 10 minutes or less, and more preferably 10 g / 10 minutes or more and 25 g / 10 minutes or less. When the MFR is in the above range, it is possible to obtain a sealing material sheet having excellent adhesion to other members of the solar cell module made of glass, metal or the like.

The polyethylene used as the base resin of the encapsulant composition is preferably linear low density polyethylene (LLDPE) which is a copolymer of ethylene and α-olefin, and this base resin is a metallocene linear linear chain. It is more preferably low density polyethylene (M-LLDPE). The metallocene-based linear low-density polyethylene is synthesized by using a metallocene catalyst which is a single-site catalyst. In such polyethylene, there are few side chain branches and the distribution of comonomer is uniform. Therefore, the molecular weight distribution is narrow, the density can be made ultra-low as described above, and flexibility can be imparted to the encapsulant sheet. As a result of imparting flexibility to the encapsulant sheet, the adhesion between the encapsulant sheet and glass, metal, etc. is enhanced.

Further, since the linear low-density polyethylene has a narrow crystallinity distribution and the same crystal size, not only there is no one having a large crystal size, but also the crystallinity itself is low due to the low density. Therefore, it is excellent in transparency when processed into a sheet as a sealing material sheet. Therefore, when the encapsulant sheet made of the encapsulant composition using this as a base resin is arranged on the light receiving surface side of the solar cell element in the solar cell module, it is caused by the attenuation of the incident light on the solar cell element. It is possible to prevent a decrease in power generation efficiency.

The "polyethylene-based resin" in the present specification is not only ordinary polyethylene obtained by polymerizing ethylene, but also a resin obtained by polymerizing a compound having an ethylenically unsaturated bond such as α-olefin. , Resins obtained by copolymerizing a plurality of different compounds having an ethylenically unsaturated bond, modified resins obtained by grafting another chemical species on these resins, and the like.

Among them, a resin containing a silane copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer (also referred to as “silane-modified polyethylene resin” in the present specification) is, for example, described above. It can be preferably used as a polyethylene-based resin that constitutes a part of the base resin together with a metallocene-based straight-chain low-density polyethylene (M-LLDPE) or the like. By blending an appropriate amount of "silane-modified polyethylene resin" with the base resin, the adhesiveness between the sealing material sheet and other laminated members such as a glass protective substrate and a solar cell element can be further improved.

The "silane-modified polyethylene resin" is described in, for example, Japanese Patent Application Laid-Open No. 2003-46105. By using the copolymer as a component of the encapsulant composition of the solar cell module, it is excellent in strength, durability, etc., and also has weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, and haze resistance. In addition, it has excellent heat fusion properties without being affected by manufacturing conditions such as heat crimping for manufacturing solar cell modules, and is stable, low cost, and used in various applications. It is possible to manufacture a solar cell module suitable for the above.

As the silane copolymer constituting the "silane-modified polyethylene resin", any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer can be preferably used. A graft copolymer is more preferable, and a graft copolymer obtained by polymerizing polyethylene for polymerization as a main chain and an ethylenically unsaturated silane compound as a side chain is further preferable. Since such a graft copolymer has a high degree of freedom of silanol groups that contribute to the adhesive force, the adhesiveness of the sealing material for the solar cell module to other members in the solar cell module can be remarkably improved. ..

The content of the ethylenically unsaturated silane compound when forming a copolymer of the α-olefin and the ethylenically unsaturated silane compound is, for example, 0.001% by mass or more and 15% by mass with respect to the total copolymer mass. % Or less, preferably 0.01% by mass or more and 5% by mass or less, and particularly preferably 0.05% by mass or more and 2% by mass or less. In the present invention, when the content of the ethylenically unsaturated silane compound constituting the copolymer of the α-olefin and the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent, but the content is excessive. When it becomes, it tends to be inferior in tensile elongation and heat-sealing property.

(Hindered amine-based light-resistant stabilizer)
The encapsulant composition contains, as a light resistance stabilizer, a high molecular weight type hindered amine light resistance stabilizer (HALS) having a molecular weight of 1000 or more and a low molecular weight type hindered amine type light resistance stabilizer (HALS) having a molecular weight of less than 1000. To do. Both of these two types of hindered amine-based light-resistant stabilizers having different molecular weights are used in the encapsulant composition at a ratio of 0.02% by mass or more and 0.20% by mass or less in the resin component of the encapsulant composition. included. The total content of the hindered amine-based light-resistant stabilizer, which is a combination of these two types of hindered amine-based light-resistant stabilizer, is 0.1% by mass or more and 0.4% by mass with respect to the total resin component in the encapsulant composition. The following is preferable.

The two types of "hindered amine-based light-resistant stabilizers" contained in the encapsulant composition, that is, "high-molecular-weight hindered amine-based light-resistant stabilizers" and "low-molecular-weight type hindered amine-based light-resistant stabilizers," are both. , Among the chemical structures shown in Table 1 below, it is assumed that it has any of the chemical structures (i) to (iii).

In the present specification, the “ester bond” refers to a chemical bond represented by the structural formula R-COO-R. Then, the compound having this "ester bond" is referred to as "ester".

Here, for example, as in the hindered amine light-resistant stabilizer (“Tinuvin 622” (manufactured by BASF), molecular weight: 3100-4000) represented by the following general formula (2), R3-OCO-R4-COO-R5. When the ester contains a structure and the molecular weight of R4 is less than 100 (the molecular weight of R4 in "Tinuvin622" is 18), the ester dissolves in water and has an acid dissociation constant (Pka) when hydrolyzed. ) Is small, organic acids are likely to be generated. Then, in this case, the inventors of the present application have found that acid gas, which is particularly harmful to the solar cell module, is likely to be generated, as will be shown later in Examples.

（２）

(2)

Based on this finding, in the encapsulant sheet of the present invention, as one of the means for suppressing the generation of the above-mentioned acid gas, "hindered amine-based light-resistant stability" is used as the above-mentioned chemical structure (i) containing no ester. ).

For example, a high-molecular-weight hindered amine-based light-resistant stabilizer (HALS) having an ester-free chemical structure (i) is represented by the following general formula (3), N, N', 4,7-Tetrakis {4,6-bis [N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino] -1,3,5-triazine-2-yl} -4,7-Diazadecane-1,10-diamine (trade name: "Chimassorb119" (manufactured by BASF)) can be mentioned as an example. The molecular weight of this HALS is 2286.

（３）

(3)

On the other hand, as a low molecular weight type hindered amine-based light-resistant stabilizer (HALS) having a chemical structure (i) containing no ester, Bis (1-undecanoxy-) represented by the following general formula (4) is used. 2,2,6,6-tetramethylpiperidin-4-yl) carbonate (trade name: "LA-81" (manufactured by ADEKA Corporation)) can be mentioned as an example. The molecular weight of this HALS is 681.

（４）

(4)

Further, in the encapsulant sheet of the present invention, as another means for suppressing the generation of acidic gas due to the above-mentioned factors, even if the "hindered amine-based light-resistant stable" contains an ester, the ester is ". Either the ester contains an ester, the ester has an R1-COO-R2 structure, the molecular weight of R1 is 100 or more, and R2 has an ester-free chemical structure (ii), or "ester". The ester has an R3-OCO-R4-COO-R5 structure, the molecular weight of R4 is 100 or more, and R3 and R5 have an ester-free chemical structure (iii). It was decided that there was. For example, in the case of HALS having a structure in which a piperidine ring is bonded to both ends of an alkyl chain by an ester bond, the alkyl chain preferably has 6 or more carbon atoms, more preferably 6 or more and 15 or less carbon atoms, and 8 Can be most preferably used.

In the hindered amine-based photostabilizer having a chemical structure (iii), in the chemical structure (R3-OCO-R4-COO-R5) of the above (iii), R4 is CH ₂ , (CH ₂ ) ₂ , (CH ₂ ) ₃ ... (CH ₂ ) As _n increases, the organic acid generated by hydrolysis becomes less soluble in water and the acid strength becomes weaker. For example, malonic acid when n = 1, succinic acid when n = 2, glutaric acid when n = 3, adipic acid when n = 4, ... azelaic acid when n = 7, n = 8. With sebacic acid at the time, the solubility of each water is as high as 7.3, 8.3, 43, 1.4, ... 0.24, 0.10 g / 100 ml, and it becomes difficult to dissolve in water. Pka increases to 2.9, 4.2, 4.3, 4.4 ... 4.5, 4.6, and the acid strength becomes weaker. From the above, an additive having a chemical structure (iii) is preferable in that, for example, an organic acid that corrodes electrodes and the like is less likely to be generated even in a high temperature and high humidity environment.

Similarly, in the hindered amine-based photostabilizer having a chemical structure (iii), in the chemical structure (R1-COO-R2) of the above (ii), R1 is CH ₃ , CH ₃ CH ₂ , CH ₃ (CH ₂ ) ₂ When n becomes large, such as CH ₃ (CH ₂ ) _n , the organic acid generated by hydrolysis is difficult to dissolve in water and the acid strength becomes weak. For example, acetic acid when n = 0, propionic acid when n = 1, butyric acid when n = 2, valeric acid when n = 3, ... cabric acid when n = 6, n = 7. At this time, the solubility of each water of pelargonic acid is MISCIBLE, 37 g / 100 ml, MISCIBLE, 4 g / 100 ml ... 0.068 g / ml, NEGLIGIBLE, and it becomes difficult to dissolve in water. The PKa is 4.70, 4.86, 4.82, 4.84, ... 4.89, 4.96, and the acid strength becomes weak. From the above, the additive having the chemical structure (iii) is also preferable in that the organic acid that corrodes the electrodes and the like is less likely to be generated like the additive having the chemical structure (iii).

Not only hindered amine-based photostabilizers, but also other additives that have the above-mentioned chemical structures (ii) and (iii) are sealed in that the generation of organic acids due to hydrolysis can be easily suppressed. Similarly, it has a chemical structure that is advantageous as an additive to the material sheet.

For example, a high molecular weight type hindered amine-based light-resistant stabilizer (HALS) having the above-mentioned chemical structure (iii) includes 1, 2, 3, 4-represented by the following general formula (5). Examples thereof include Butanettracarboxic acid, tranquilizer, reaction products with 1,2,2,6,6-pentamethyl-4-piperidinol (trade name: "LA-63P" (manufactured by ADEKA)). The molecular weight of this HALS is about 2000.

（５）

(5)

On the other hand, as a low molecular weight type hindered amine-based light-resistant stabilizer (HALS) and having the above-mentioned chemical structure (iii), Bis (1-octyloxy-2,) represented by the following general formula (6), 2,6,6-tetramethyl-4-piperidyl) sebacate (trade name: "Tinuvin PA 123" (manufactured by BASF)) can be mentioned as an example. The molecular weight of this HALS is 737. Further, this HALS has an ester (R3-OCO-R4-COO-R5 structure) and has a molecular weight of R4 of 112.

（６）

(6)

Here, the hindered amine-based photostabilizer is NH-type (hydrogen is bonded to the nitrogen atom) or NR-type (alkyl group (R) is bonded to the nitrogen atom) depending on the bonding partner of the nitrogen atom in the piperidine skeleton. , N-OR type (alkoxy group (OR) bonded to nitrogen atom), N-CH ₃ type (methyl group (CH ₃ ) bonded to nitrogen atom) and the like can be classified into types. The "high molecular weight type hindered amine-based light-resistant stabilizer" used in the encapsulant composition of the present invention satisfies any of the above-mentioned requirements of the chemical structures (i) to (iii), and further "N-". It is more preferable that the hindered amine-based light-resistant stabilizer of "CH type ₃ " is used.

For example, when "NH type" HALS is used as the "high molecular weight type hindered amine type light resistance stabilizer", the dispersibility tends to deteriorate as compared with "N-CH type ₃ " HALS. Therefore, the optical characteristics are deteriorated, or the transfer to the surface of the encapsulant sheet is likely to be excessive, and it is difficult for radical capture to function properly. On the other hand, the HALS of "N-CH type ₃ " is more easily compatible with the base resin (polyethylene resin) and has better optical characteristics than the "N-H type". Further, the "N-CH type ₃ " HALS is changed to the "NH type" HALS by heat or light, and the time required for the HALS to move to the surface of the encapsulant sheet is longer than a certain length. As much as it is secured, it is easy to develop long-term light resistance rather than short-term. The "N-OR type" HALS has a faster radical trap reaction rate than the "NH type" and "N-CH ₃ type" HALS, but this allows cross-linking of the encapsulant sheet. There is a risk of inhibiting the cross-linking reaction during treatment.

The "Chimassorb 119" and "LA-63P" exemplified as the preferable "high molecular weight type hindered amine-based light-resistant stabilizer" in the above are both "N-CH type ₃ " HALS, and in this respect as well, the present invention It is suitable as a "high molecular weight type hindered amine-based light-resistant stabilizer" used in the encapsulant composition.

Further, in the encapsulant composition of the present invention, the "low molecular weight type hindered amine light resistant stabilizer" used in combination with the "high molecular weight type hindered amine light resistant stabilizer" has the above-mentioned chemical structures (i) to (iii). It is more preferable that the hindered amine-based light-resistant stabilizer of "N-OR type" satisfies any of the above requirements. The N-OR type hindered amine-based light-resistant stabilizer captures radicals faster than the NH type and N-CH ₃ type. Furthermore low-molecular HALS of N-OR type having transferred to the faster surface than polymeric HALS is short term supplemented radicals than N-H-type or N-CH ₃ type HALS, suppress the deterioration of the sealing sheet In that respect, it is preferable. N-OR type low molecular weight HALS that exhibits short-term light resistance is N-CH type ₃ that exhibits long-term light resistance, although the function of radical capture is reduced when exposed to light for a long period of time. By using the above polymer HALS in combination, it is possible to suppress the deterioration of the sealing sheet for a long time.

The "Tinuvin PA 123" and "LA-81" exemplified as the preferable "low molecular weight type hindered amine-based light-resistant stabilizer" in the above are both "N-OR type" HALS, and in this respect as well, the present invention It is suitable as a "low molecular weight type hindered amine-based light-resistant stabilizer" used in the encapsulant composition of. In addition, 1- (2-Hydroxy-1,1-dimethyl-ethoxy) -2,2,6,6-tetramethyl-4-piperidinyl octadecanate is also given as a suitable example of "low molecular weight type hindered amine-based light-resistant stabilizer". be able to.

[Crosslinking agent]
In the encapsulant composition of the present invention, it is preferable to sufficiently suppress the generation of acid gas derived from the cross-linking agent. Therefore, the cross-linking agent contained in the encapsulant composition may have any of the chemical structures (i), (iv), or (v) among the chemical structures shown in Table 2 below. preferable.

As described above, in the present specification, the compound having an "ester bond" is referred to as "ester", and the reaction for producing this "ester" (dehydration reaction) is referred to as "esterification".

Here, for example, the cross-linking agent n-butyl 4,4 di (t-butyl peroxy) barrate (trade name: "Luperox 230" (manufactured by Alchema Yoshitomi)) represented by the following general formula (7) is described above. The inventors of the present application have found that the molecular weight of R9 in the structural formula (1) is 29, and that the product after thermal decomposition is likely to generate an acidic gas harmful to the solar cell module.

（７）

(7)

As a specific example of a preferable cross-linking agent satisfying the requirements for the chemical structure shown in Table 2, a cross-linking agent for dialkyl peroxides having a chemical structure represented by the following general formula (8) is “2,5-”. Dimethyl-2,5-di (t-bulperoxy) hexane "(trade name" Luperox 101 "(manufactured by Alchema Yoshitomi)) and di-t-butyl peroxide (trade name" Luperox DI "(manufactured by Alchema Yoshitomi)" ), Dikmyl peroxide (trade name "Luperox DC" (manufactured by Alchema Yoshitomi Co., Ltd.)) and the like. All of these cross-linking agents have an ester-free chemical structure (i).

（８）

(8)

Further, as another specific example of a preferable cross-linking agent satisfying the requirements for the chemical structure shown in Table 2, a cross-linking agent for peroxycarbonates having a chemical structure represented by the following general formula (9) is used. "t-butylperoxy2-ethylhexyl carbonate" (trade name "Luperox TBEC" (manufactured by Alchema Yoshitomi)), "t-amylperoxy2-ethylhexyl carbonate" (trade name "Luperox TAEC" (manufactured by Alchema Yoshitomi)) And so on. These cross-linking agents have a chemical structure (iv).

（９）

(9)

The cross-linking agent used in the encapsulant composition preferably has an active oxygen amount of 4.5% or more and 15.00% or less, and more preferably 5.5% or more and 12.00% or less. By using a cross-linking agent having an active oxygen amount in the above range, the sealing material sheet can be provided with excellent heat resistance, light resistance, and transparency. The 1-hour half-life temperature of the cross-linking agent used in the encapsulant composition is preferably 115 ° C. or higher and 150 ° C. or lower. Thereby, the encapsulant composition of the present invention can be made into a resin composition capable of melt extrusion molding at 110 ° C. or lower. As specific examples of preferable cross-linking agents, the above-mentioned "2,5-dimethyl-2,5-di (t-bulperoxy) hexane" and "t-butylperoxy2-ethylhexyl carbonate" can be used in this respect as well. It is suitable as a cross-linking agent used in a stop material composition.

The content of the above-mentioned cross-linking agent in the encapsulant composition is preferably 0.2% by mass or more and 0.6% by mass or less with respect to the base resin in the encapsulant composition, and more preferably 0. It is in the range of 3% by mass or more and 0.5% by mass or less. By adding a cross-linking agent in this range, sufficient durability can be imparted to the sealing material sheet. The encapsulant sheet of the present invention is formed without substantially advancing cross-linking, and the content of the above-mentioned cross-linking agent in the encapsulant sheet at the sheet stage after film formation is also 0. It is assumed that the range is 2% by mass or more and 0.6% by mass or less.

[Crossing aid]
In the encapsulant composition of the present invention, it is preferable to sufficiently suppress the generation of acid gas derived from the cross-linking aid. Therefore, it is preferable that the cross-linking aid contained in the encapsulant composition has any of the chemical structures (i) to (iii) among the chemical structures shown in Table 3 below.

Here, for example, the cross-linking aid (“A-9300” (manufactured by Shin-Nakamura Chemical Co., Ltd.)) represented by the following general formula (10) has an ester (R1-COO-R2 structure) and has a molecular weight of R1. Is 27. The inventor of the present application has stated that when such a cross-linking aid is used, the unreacted material remaining after the cross-linking treatment of the encapsulant sheet is easily hydrolyzed to generate acid gas harmful to the solar cell module. Have come to find out.

（１０）

(10)

As a specific example of a preferable cross-linking aid that satisfies the requirements for the chemical structure shown in Table 3 above, "Triallyl Isocyanurate (TAIC)" having a chemical structure represented by the following general formula (11) (Nihon Kasei Co., Ltd.) (Manufactured by) and "trimetharyl isocyanurate (TMAIC)" having a chemical structure represented by the following general formula (12). All of these cross-linking aids have an ester-free chemical structure (i).

（１１）

(11)

（１２）

(12)

Further, the cross-linking aid contained in the encapsulant composition further comprises a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group, and more preferably the functional group of the polyfunctional monomer is an allyl group. It is preferably a cross-linking aid having a meta) acrylate group or a vinyl group. This promotes an appropriate cross-linking reaction to improve the adhesion of the encapsulant sheet to glass and metal, and in addition, this cross-linking aid is the crystallinity of the linear low-density polyethylene forming the encapsulant sheet. To maintain transparency. As a result, in addition to the above-mentioned effect of improving the adhesiveness, the transparency and low-temperature flexibility of the encapsulant sheet can be made more excellent.

The content of the cross-linking aid in the encapsulant composition is preferably 0.01% by mass or more and 1.5% by mass or less with respect to the base resin in the encapsulant composition, and more preferably 0. It is 05% by mass or more and 1.0% by mass or less. Within this range, an appropriate cross-linking reaction can be promoted to improve the adhesion of the encapsulant sheet.

[Antioxidant]
In the encapsulant composition of the present invention, it is preferable to sufficiently suppress the generation of acid gas derived from the antioxidant. Therefore, it is preferable that the antioxidant used in the encapsulant composition has any of the chemical structures (i) to (iii) among the chemical structures shown in Table 4 below.

Specific examples of preferable antioxidants that satisfy the requirements for the chemical structure shown in Table 4 above are those having a chemical structure (i) containing no ester, and specific examples are represented by the following general formula (13). Examples thereof include "Iragafos 168 (manufactured by BASF)" having a chemical structure. Further, as a specific example of the one satisfying the requirement of (ii) in Table 4, "Iraganox 1076 (manufactured by BASF)" having a chemical structure represented by the following general formula (14) can be mentioned.

（１３）

(13)

（１４）

(14)

The content of the antioxidant in the encapsulant composition is preferably 0.005% by mass or more and 0.2% by mass or less with respect to the base resin in the encapsulant composition, and more preferably 0. It is 01% by mass or more and 0.1% by mass or less. Within this range, oxidative deterioration due to heat during film formation and deterioration due to heat of the encapsulant when hot spots are generated in the solar cell module are unlikely to occur. Furthermore, bleeding of additives is less likely to occur in the encapsulant, and good transparency is maintained.

(Other additives)
The encapsulant composition may further contain other components. For example, an ultraviolet absorber, a heat stabilizer, an adhesion improver, a nucleating agent, a dispersant, a leveling agent, a plasticizer, a defoaming agent, a flame retardant, and various other fillers can be appropriately added. The content ratio of these additives varies depending on the particle shape, density, etc., but is preferably in the range of 0.001% by mass or more and 60% by mass or less in the encapsulant composition. By including these additives, it is possible to impart stable mechanical strength over a long period of time and an effect of preventing yellowing, cracking, etc. to the encapsulant composition.

<Manufacturing method of sealing material sheet>
The method for producing a sealing material sheet of the present invention is a manufacturing method using the sealing material composition of the present invention, the details of which have been described above, and includes an additive selection step, a material kneading step, and a sheeting step. It is a process that includes.

[Additive selection process]
In the additive selection process, among the additives added to the polyethylene-based resin used as the base resin in the encapsulant composition, the light-resistant stabilizers are high-molecular-weight hindered amine light-resistant stabilizers and low-molecular-weight type hin. A combination of dartamine light-resistant stabilizers will be used, and at least these hindered amine light-resistant stabilizers will be selected as essential requirements for the above-mentioned chemical structure. Further, as for the cross-linking agent which is an essential additive, and the cross-linking aid and the antioxidant which are added as necessary, an additive which satisfies the above-mentioned chemical structure requirements is selected as much as possible. ..

[Material kneading process]
In the material kneading step, various additives including the above two types of hindered amine-based light-resistant stabilizers selected in the above-mentioned additive selection step and a cross-linking agent are added to the base resin (polyethylene-based resin) and mixed. The encapsulant composition is produced by smelting.

[Sheet process]
In the sheet forming step, the sealing material composition produced in the previous step is melt-molded to produce a sealing material sheet. The melt molding of the encapsulant composition can be performed by a known molding method, that is, various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotary molding. The lower limit of the molding temperature at the time of molding may be a temperature exceeding the melting point of the encapsulant composition. The upper limit of the molding temperature is the temperature at which cross-linking does not start during film formation, that is, the temperature at which the gel fraction of the encapsulant composition can be maintained at 0%, depending on the 1-minute half-life temperature of the cross-linking agent used. Good.

<Solar cell module>
FIG. 1 is a cross-sectional view showing an example of the layer structure of the solar cell module of the present invention. In the solar cell module 1 of the present invention, the glass protective substrate 2, the front sealing material 3, the solar cell element 4, the back sealing material 5, and the back surface protective sheet 6 are laminated in this order from the light receiving surface side of the incident light. .. In the solar cell module 1 according to the present invention, the sealing material sheet of the present invention can be preferably used as the front sealing material 3 and / or the back sealing material 5. In particular, by arranging the sealing material sheet of the present invention having excellent transparency as the front sealing material 3 arranged on the light receiving surface side of the solar cell element 4, it is possible to effectively contribute to the improvement of power generation efficiency. ..

In the solar cell module 1, for example, a member composed of the above-mentioned glass protective substrate 2, front sealing material 3, solar cell element 4, back sealing material 5, and back surface protective sheet 6 is sequentially laminated, and then vacuum suction is performed. After being integrated, it can be manufactured by heat-pressing molding the above-mentioned member as an integrally molded body by a molding method such as a lamination method. At this time, the adhesion between the glass substrate and the encapsulant sheet can be improved by laminating the front encapsulant 3 glass protective substrate and the glass substrate. The above heat crimping can be carried out at the same time by performing the cross-linking treatment under heating conditions such that the temperature is 140 ° C. or higher and 170 ° C. or lower. Alternatively, the above heat crimping may be carried out at 110 ° C. or higher, and after the heat crimping, a curing step may be carried out to promote the cross-linking reaction of polyethylene. The curing step in this case is performed under heating conditions such that the resin temperature of the sealing material sheet is 140 ° C. or higher and 170 ° C. or lower. By any of the above-mentioned cross-linking treatments, the cross-linking of the sealing material sheet can be appropriately advanced, and the heat resistance and light resistance of the solar cell module can be sufficiently enhanced.

The solar cell module of the present invention thus obtained has excellent heat resistance and light resistance, and is highly advanced for a long period of time even when exposed to harsh environments such as strong ultraviolet rays, heat rays, wind and rain, etc. It is possible to maintain the weather resistance of. In addition, it is also excellent in transparency, which can contribute to the improvement of the design and power generation efficiency of the solar cell module.

In the solar cell module 1 of the present invention, conventionally known materials can be used for the glass protective substrate 2, the solar cell element 4, and the back surface protective sheet 6 other than the sealing material sheet without particular limitation. Further, the solar cell module 1 of the present invention may further include members other than the above-mentioned members, if necessary.

Although the present invention has been specifically described above by showing embodiments, the present invention is not limited to the above-described embodiments, and can be carried out with appropriate modifications within the scope of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

[Manufacturing of encapsulant sheet]
The encapsulant composition containing the following base resin, hindered amine-based light-resistant stabilizer, cross-linking agent, cross-linking aid, and antioxidant was melted to produce encapsulant sheets of Examples and Comparative Examples. This encapsulant sheet was produced by a conventional T-die method so as to have a thickness of 600 μm, thereby forming an uncrosslinked single-layer encapsulant sheet. The film formation temperature was 90 ° C to 100 ° C. The content (mass%) of each hindered amine-based light-resistant stabilizer in each encapsulant composition with respect to the total resin components is as shown in Table 1. If each of the hindered amine-based light-resistant stabilizers, cross-linking agents, and cross-linking aids corresponds to any of the chemical structures (i) to (v) described above, the corresponding numbers ((i) to (i) to Any of (v)) is added to the column of "Chemical structure" in Table 1. Those that do not correspond to any of the above chemical structures (i) to (v) are marked with "-".

(Base resin)
: 85 parts by mass of metallocene linear low density polyethylene (M-LLDPE) with a density of 0.880 g / cm ³ and an MFR of 20 g / 10 minutes at 190 ° C. and the following silane-modified polyethylene resin (density 0.884 g /). cm ³ ) The mixed resin with 15 parts by mass was used as the "base resin" of the encapsulant sheet of all Examples and Comparative Examples. The density of this base resin is 0.881 g / cm ³ . The SP value of this "base resin" is 8.6.
(Silane-modified polyethylene resin)
: 2 parts by mass of vinyl trimethoxysilane with respect to 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ³ and an MFR of 30 g / 10 minutes at 190 ° C. A silane-modified polyethylene resin obtained by mixing 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst), melting and kneading at 200 ° C. The density of this silane-modified polyethylene resin is 0.884 g / cm ³ , and the MFR at 190 ° C. is 18 g / 10 minutes.

(High molecular weight type hindered amine light resistant stabilizer 1)
In Table 1, it is referred to as "polymer HALS1".
The above-mentioned "Chimassorb 119" (manufactured by BASF) was used. The HALS is N-CH ₃ type HALS represented by the above general formula (3), having a chemical structure that does not contain ester (i). The molecular weight is 2286.

(High molecular weight type hindered amine light-resistant stabilizer 2)
In Table 1, it is referred to as "polymer HALS2".
The above-mentioned "LA-63P" (manufactured by ADEKA Corporation) was used. The HALS is N-CH ₃ type HALS represented by the above general formula (5), has an ester (R3-OCO-R4-COO -R5 structures), the molecular weight of R4 is located at 100 or more , R3 and R5 have an ester-free chemical structure (iii). The molecular weight is about 2000.

(High molecular weight type hindered amine light resistant stabilizer 3)
In Table 1, it is referred to as "polymer HALS3".
"Thinuvin 622" (manufactured by BASF) was used. This HALS is a HALS represented by the above general formula (2), has an ester (R3-OCO-R4-COO-R5 structure), and has a chemical structure having a molecular weight of R4 of 28. .. The molecular weight is 3100-4000.

(Low molecular weight hindered amine-based light-resistant stabilizer 1)
In Table 1, it is referred to as "small molecule HALS1".
The above-mentioned "Tinuvin PA 123" (manufactured by BASF) was used. This HALS is an N-OR type HALS represented by the above general formula (6), has an ester (R3-OCO-R4-COO-R5 structure), has a molecular weight of R4 of 112, and has a molecular weight of R3. And R5 have an ester-free chemical structure (iii). The molecular weight is 737.

(Low molecular weight hindered amine-based light-resistant stabilizer 2)
In Table 1, it is referred to as "low polymer HALS2".
The above-mentioned "LA-81" (manufactured by ADEKA Corporation) was used. This HALS is an N-OR type HALS represented by the above general formula (4), and has an ester-free chemical structure (i). The molecular weight is about 681.

(Crosslinking agent 1)
In Table 1, it is referred to as “crosslink 1”.
"Luperox 101" (manufactured by Arkema Yoshitomi Co., Ltd.) having a chemical structure represented by the above general formula (8) was used. The addition amount was adjusted so that the content (mass%) of the encapsulant composition with respect to the base resin was 0.4% by mass.

(Crosslinking agent 2)
In Table 1, it is referred to as “crosslink 2”.
"Luperox TBEC" (manufactured by Arkema Yoshitomi Co., Ltd.) having a chemical structure represented by the above general formula (9) was used. The addition amount was adjusted so that the content (mass%) of the encapsulant composition with respect to the base resin was 0.4% by mass.

(Crosslinking agent 3)
In Table 1, it is referred to as “crosslink 3”.
"Luperox 230" (manufactured by Arkema Yoshitomi Co., Ltd.) having a chemical structure represented by the above general formula (7) was used. The addition amount was adjusted so that the content (mass%) of the encapsulant composition with respect to the base resin was 0.4% by mass.

(Crosslinking aid 1)
In Table 1, it is referred to as "auxiliary agent 1".
"TAIC (manufactured by Nihon Kasei Co., Ltd.)" having a chemical structure represented by the above general formula (11) was used. The addition amount was adjusted so that the content (mass%) of the encapsulant composition with respect to the base resin was 0.6% by mass.

(Crosslinking aid 2)
In Table 1, it is referred to as "auxiliary agent 2".
The content (mass%) of the encapsulant composition with respect to the base resin of "TMAIC (manufactured by Nihon Kasei Co., Ltd.)" having the chemical structure represented by the above general formula (12) is 0.6% by mass. The amount of addition was adjusted so as to.

(Crosslinking aid 3)
In Table 1, it is referred to as "auxiliary agent 3".
"A-9300 (manufactured by Shin-Nakamura Chemical Co., Ltd.)" having a chemical structure represented by the above general formula (10) was used. The addition amount was adjusted so that the content (mass%) of the encapsulant composition with respect to the base resin was 0.6% by mass.

(Crosslinking aid 4)
In Table 1, it is referred to as "auxiliary agent 4".
"TMPTMA (manufactured by Nihon Kasei Co., Ltd.)" having a chemical structure represented by the following general formula (15) was used. This cross-linking aid has an ester (R1-COO-R2 structure) and has a molecular weight of R1 of 41. The addition amount was adjusted so that the content (mass%) of the encapsulant composition with respect to the base resin was 0.6% by mass.

（１５）

(15)

(Antioxidant)
Regarding the antioxidant, in both Examples and Comparative Examples, "Iragafos 168 (manufactured by BASF)" having a chemical structure represented by the above general formula (13) and the above general formula (14) are used. It was used in combination with "Iraganox 1076 (manufactured by BASF)" having the chemical structure to be used. The content (mass%) of the encapsulant composition with respect to the base resin is 0.02% by mass for "Iragafos 168 (manufactured by BASF)" and 0.04% by mass for "Iraganox 1076 (manufactured by BASF)". , The amount of each addition was adjusted.

[Evaluation example 1: Weather resistance (light resistance of sealing material sheet)]
The uncrosslinked encapsulant sheets of Examples and Comparative Examples manufactured as described above were sandwiched between ETFE films and crosslinked at the same time as integration by vacuum heating lamination. Weather resistance of Examples and Comparative Examples It was used as a sample for evaluating the sealing material sheet for evaluating (light resistance at high temperature). The vacuum heating laminate strips are as follows.
(Vacuum heating laminating conditions) (a) Evacuation: 6 minutes
(B) Pressurization: (0 kPa to 50 kPa): 10 seconds
(C) Pressure retention: (50 kPa): 11 minutes
(D) Temperature: 165 ° C
The following light resistance test was carried out on the above-mentioned encapsulant sheet evaluation sample, and then the following tensile stress test was carried out to evaluate the light resistance of each encapsulant sheet in a high temperature environment.
(Light resistance test)
: Each evaluation sample was subjected to an irradiation test for 1000 hours using Toyo Seiki Seisakusho Atlas Weatherometer Ci4000 under the conditions of irradiance of 180 W / m ² , black panel temperature (BPT) of 110 ° C., and humidity of 50%.
(Tensile stress test method)
: A sealing material sheet cut to a length of 50 mm and a width of 10 mm is pressed by a jig 10 mm above and below the peeling tester (Tencilon universal tester RTF-1150-H), the distance between chucks is 30 mm, and the tensile speed is 50 mm. A tensile test of / min was performed, and the tensile stress of the encapsulant sheet was measured.
(Evaluation criteria)
A: The tensile stress is 3.0 MPa or more B: The tensile stress is 1.0 MPa or more and less than 3.0 MPa C: The tensile stress is less than 1.0 MPa

[Evaluation example 2: Weather resistance (maintenance rate of power generation efficiency of solar cell module)]
Each of the following members is laminated in the order of glass substrate / sealing material sheet / solar cell element / sealing material sheet / back surface protective sheet, and vacuum heating laminating treatment is performed under the following laminating conditions to create a moist heat environment. A sample for evaluating the solar cell module was manufactured to evaluate the maintenance rate of the power generation efficiency of the solar cell module below.
(Element)
Glass substrate: (white plate semi-tempered glass (JPT3.2))
Encapsulant sheet: Each uncrosslinked encapsulant sheet of Examples and Comparative Examples manufactured as described above Solar cell element: T-SEC single crystal p-type PERC TSS63TN
Backside protective sheet: SiOx-PET resin film (vacuum heating lamination conditions) (a) Vacuuming: 6 minutes
(B) Pressurization: (0 kPa to 50 kPa): 10 seconds
(C) Pressure retention: (50 kPa): 11 minutes
(D) Temperature: 155 ° C
The following durability test was carried out on the above-mentioned solar cell module evaluation sample, and then the following power generation efficiency long-term maintenance rate test was carried out, and the solar cell module made of each encapsulant sheet was subjected to a moist heat environment. The power generation efficiency maintenance rate was evaluated. The heating temperature at the time of modularization was set to the above temperature so that the cross-linking agent and the cross-linking aid did not completely complete the reaction during the laminating process.
(An endurance test)
: Each evaluation sample was set to 121 ° C., 100% RH, and 2 atm with a pressure cooker tester (manufactured by Hirayama Seisakusho: HASTEST), and each of the above evaluation samples was charged. After 800 hours, it was left at room temperature for several hours.
(Power generation efficiency long-term maintenance rate test)
For each solar cell module evaluation sample, the Pmax values before and after the above durability test were measured, the maintenance rate of power generation efficiency was calculated, and the long-term maintenance rate of power generation efficiency was evaluated based on the following evaluation criterion 1. The Pmax value is the maximum output value at the operating point where the output of the solar cell is maximum. Using a solar simulator (XES-155S1 manufactured by Sannaga Electric Mfg. Co., Ltd.), the Pmax value of each evaluation sample was measured under the conditions of a cell back surface temperature of 25 ° C. and an illuminance of 100 mW / cm ² .
(Evaluation criteria)
A: The power generation efficiency maintenance rate is 80% or more.
B: The power generation efficiency maintenance rate is 60% or more and less than 80%.
C: The power generation efficiency maintenance rate is less than 60%.

From Tables 5 and 6, the encapsulant sheet for the solar cell module of the present invention is a polyethylene-based encapsulant sheet having sufficient weather resistance to withstand long-term use in a harsh environment of high temperature and humidity. Moreover, even in such an environment, it is possible to configure a solar cell module that can sufficiently suppress the generation of acid gas harmful to the solar cell module and maintain good power generation efficiency. It turns out that it is a thing.

1 Solar cell module 2 Glass protective substrate 3 Front sealing material 4 Solar cell element 5 Back sealing material 6 Back back protective sheet

Claims (5)

Encapsulant sheet for electronic devices
Using polyethylene resin as the base resin
A high molecular weight type hindered amine-based light-resistant stabilizer having a molecular weight of 1000 or more is contained in the resin component of the encapsulant sheet in a proportion of 0.02% by mass or more and 0.20% by mass or less.
A low molecular weight type hindered amine-based light-resistant stabilizer having a molecular weight of less than 1000 is contained in the resin component of the encapsulant sheet in a proportion of 0.02% by mass or more and 0.20% by mass or less.
The cross-linking agent is contained in the resin component of the sealing material sheet in a proportion of 0.2% by mass or more and 0.6% by mass or less.
The chemical structure of the hindered amine light stabilizer and the low molecular weight type hindered amine light stabilizer of the high molecular weight type, Ri any chemical structure der of any of the following (i) (iii),
The chemical structure of the cross-linking agent is any of the following (i), (iv) or (v).
The gel fraction is 0%,
Encapsulant sheet.
(I) Ester-free chemical structure.
(Ii) A chemical structure containing an ester, the ester having an R1-COO-R2 structure, having a molecular weight of R1 of 100 or more, and R2 containing no ester.
(Iii) A chemical structure containing an ester, the ester having an R3-OCO-R4-COO-R5 structure, having a molecular weight of R4 of 100 or more, and R3 and R5 containing no ester.
(Iv) A chemical structure containing an ester, wherein the ester has an R6-OO-COO-R7 structure, and R6 and R7 are not esterified.
(V) A chemical structure represented by the following structural formula (1), in which the molecular weight of R9 is 100 or more, and R8, R10 and R11 do not contain esters.

(1) Further, the cross-linking aid is contained in the resin component of the sealing material sheet in a proportion of 0.01% by mass or more and 1.5% by mass or less.
The encapsulant sheet according to claim 1 , wherein the chemical structure of the cross-linking aid is any of the following chemical structures (i) to (iii).
(I) Ester-free chemical structure.
(Ii) A chemical structure containing an ester, the ester having an R1-COO-R2 structure, having a molecular weight of R1 of 100 or more, and R2 containing no ester.
(Iii) A chemical structure containing an ester, the ester having an R3-OCO-R4-COO-R5 structure, having a molecular weight of R4 of 100 or more, and R3 and R5 containing no ester. It also contains antioxidants
The encapsulant sheet according to claim 1 or 2, wherein the chemical structure of the antioxidant is any of the following chemical structures (i) to (iii).
(I) Chemical structure containing no ester (ii) A chemical structure containing an ester, the ester having an R1-COO-R2 structure, having a molecular weight of R1 of 100 or more, and R2 containing no ester.
(Iii) A chemical structure containing an ester, the ester having an R3-OCO-R4-COO-R5 structure, having a molecular weight of R4 of 100 or more, and R3 and R5 containing no ester. The encapsulant sheet according to any one of claims 1 to 3 , further comprising a silane-modified polyethylene resin. It is composed of a glass protective substrate, a light receiving surface side sealing material that is in close contact with the glass protective substrate, and a solar cell element.
A solar cell module in which the light receiving surface side sealing material is the sealing material sheet according to any one of claims 1 to 4 .

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