JP6741038B2 - Encapsulant sheet for solar cell module - Google Patents

Description

The present invention relates to a sealing material sheet for solar cell modules.

2. Description of the Related Art In recent years, solar cells as a clean energy source have been attracting attention due to increasing awareness of environmental issues. At present, various types of solar cell modules have been developed and proposed. Generally, a solar cell module has a structure in which a glass protective substrate, a solar cell element, and a back surface protective sheet are laminated via a sealing sheet for a solar cell module (see FIG. 1).

An encapsulant sheet for a solar cell module, which is exposed outdoors to strong sunlight for a long period of time, is required to have extremely high light resistance. An encapsulant sheet using a hindered amine light stabilizer (hereinafter also referred to as “HALS”) has been proposed as an additive for providing this light resistance. (See Patent Document 1).

Furthermore, in order to prevent the deterioration of the optical characteristics of the encapsulant sheet due to the occurrence of bleed-out due to the excessive administration of the hindered amine light stabilizer, the molecular weight is It has been disclosed that it is preferable to use 1200 or more hindered amine light stabilizers within a fixed amount range (see Patent Document 2). In the present specification, "molecular weight" refers to a molecular weight calculated by utilizing atomic weight when the structural formula/molecular formula can be specified, and in the case of a high molecular weight type in which the number of units is unknown, the weight is The average molecular weight (Mw) is referred to.

However, in recent years, conventional products such as a higher level of heat resistance and longer-term durability have been used for solar cell modules assuming a wide range of environmental conditions including deserts and tropical rainforests. It is now required to have an extremely high degree of weather resistance, which was not expected in. In order to meet such a requirement, first, it is conceivable to further increase the addition amount of the above-mentioned high molecular weight type HALS. However, although a general high molecular weight type HALS is difficult to bleed out, the compatibility with a resin is not always sufficient. In particular, when a large amount of HALS is added to the base resin in order to impart the above-described high degree of weather resistance to the encapsulant sheet, the problem that this compatibility is insufficient appears. become. However, if the low molecular weight type HALS is simply supplemented to compensate for this, the risk of occurrence of bleed-out increases as described above.

JP, 2004-214641, A JP2012-9693A

The present invention has been made in view of the above circumstances, and a sealing material for a solar cell module that can sufficiently enjoy a high light resistance improvement effect by the addition of HALS while maintaining sufficient transparency. The purpose is to provide a sheet.

In the encapsulant sheet for a solar cell module using a polyethylene resin as a base resin, the present inventors have prepared a “high molecular weight type hindered amine light stabilizer” and a “low molecular weight hindered amine light stabilizer”. It is possible to produce an encapsulant sheet having excellent transparency and high light resistance by using them together and further optimizing them by paying attention to the SP value of each HALS. The inventors have found that they can do so and have completed the present invention. Specifically, the present invention provides the following.

(1) An encapsulant sheet for a solar cell module, which comprises a polyethylene resin as a base resin and a high molecular weight hindered amine light stabilizer having a molecular weight of 1000 or more in the resin component of the encapsulant sheet. In the resin component of the encapsulant sheet, a low molecular weight type hindered amine light stabilizer containing 0.02% by mass or more and 0.20% by mass or less and having a molecular weight of less than 1000 is contained in the resin component of the encapsulant sheet in an amount of 0.02% by mass. % To 0.20% by mass, and the SP value of the high molecular weight hindered amine light stabilizer is 9.5 (cal/cm ³ ) ^1/2 or more 10.2 (cal/cm ³ ). ^1/2 or less, and the SP value of the low molecular weight type hindered amine light stabilizer is 8.6 (cal/cm ³ ) ^1/2 or more and 10.6 (cal/cm ³ ) ^1/2 or less, The absolute value of the difference in SP value between the base resin and the high molecular weight type hindered amine light stabilizer is 1.0 (cal/cm ³ ) ^1/2 or more and 1.6 (cal/cm ³ ) ^{1/ 2} or less, the absolute value of the difference in SP value between the base resin and the low molecular weight type hindered amine light stabilizer is 0.5 (cal/cm ³ ) ^1/2 or more and 2.0 (cal/ cm ³ ) ^1/2 or less, the encapsulant sheet.

(2) a hindered amine light stabilizer of the high molecular weight type, a N-CH ₃ type hindered amine light stabilizer, hindered amine light stabilizer of low molecular weight type, N-OR type hindered amine light stabilizers of The encapsulant sheet according to (1), which is an agent.

(3) The encapsulant sheet according to (1) or (2), which further contains a crosslinking agent.

(4) The encapsulant sheet according to any one of (1) to (3), which further contains a silane-modified polyethylene resin.

(5) 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, and the light-receiving-surface-side sealing material comprises (1) A solar cell module, which is the encapsulant sheet according to any one of (4) to (4).

It is possible to provide a sealing material sheet for a solar cell module, which can sufficiently enjoy a high degree of light resistance improvement effect by the addition of HALS while maintaining sufficient transparency.

It is a cross-sectional schematic diagram which shows an example of the layer structure of the solar cell module using the sealing material sheet of this invention.

<Sealing material sheet>
The encapsulant sheet of the present invention (hereinafter, also simply referred to as “encapsulant sheet”) has a polyethylene resin as a base resin and attention is paid to a difference in SP value from the base resin, as described in detail below. Which is a combination of a "high molecular weight type hindered amine light stabilizer" and a "low molecular weight hindered amine light stabilizer", the sealing of which contains at least two hindered amine light stabilizers. The material composition is molded into a film or sheet by a conventionally known method. In the present specification, the term "base resin" refers to a resin composition containing the base resin, which has the largest content ratio among the resin components of the resin composition, and is used as a mixture with the resin. The same kind of resin that is used. Details of the polyethylene-based resin that can be preferably used as the base resin will be described later as the description of the encapsulating material composition.

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

Further, it is preferable that the encapsulant sheet is formed in an uncrosslinked state by limiting the forming temperature to a low temperature range of 90°C to 110°C. Then, it is preferable to carry out the crosslinking treatment separately after the molding, or to carry out the crosslinking treatment by heating at a high temperature at the time of manufacturing the solar cell module described later.

The encapsulant sheet of the present invention is characterized in that the base resin is adjusted such that the absolute value of the difference between the SP value and the above-mentioned two types of added HALS is within a predetermined range. To do.

In addition, the gel fraction of this encapsulating material sheet is 0% or more and 10% or less, more preferably 0%, that is, uncrosslinked, in a stage after film formation and before modularization. In addition, this uncrosslinked encapsulant sheet contains a predetermined amount of a crosslinking agent, and the crosslinking proceeds in any process until after integration as a solar cell module, and the final product is a solar cell module. In the finished product stage, it is preferred that the crosslinked encapsulant sheet has a gel fraction of 50% or more and 90% or less.

By adjusting the composition and amount of the cross-linking agent, the cross-linking aid, and other additives within the preferable ranges, the cross-linking reaction can be appropriately controlled so that the gel fraction falls within the above range. As a result, while having a good water vapor barrier, it has flexibility in the low temperature range and can also obtain heat resistance at high temperatures. Even though it uses polyethylene resin as the base resin, it can be used in the low temperature range. The encapsulant sheet having excellent moldability can be obtained.

Here, the term "gel fraction (%)" in the present specification means that 1.0 g of the encapsulating material sheet is put into a resin mesh and extracted with 110° C. xylene for 12 hours, and then the resin mesh is taken out and weighed after the drying treatment. Then, the mass ratio before and after the extraction is compared to measure the mass% of the residual insoluble matter, and this is taken as the gel fraction. The gel fraction of 0% means that the residual insoluble content 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 mass%. Shall be said. The residual insoluble matter does not include pigment components other than resin components. When the inclusions other than these resin components are present in the residual insoluble matter by the above test, for example, by separately measuring the contents of these inclusions in the resin component beforehand, 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 inclusions.

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 refers to 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 that is a layer other than the skin layer. Say that.

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

When the encapsulant sheet is a multi-layer film, it is preferable that the layer having a higher MFR be used as the skin layer and disposed on the outermost layer side. Even when the encapsulant sheet of the present invention is a single-layer encapsulant sheet, the encapsulant sheet has sufficiently preferable transparency, heat resistance, and appropriate flexibility. By arranging the layer having a high temperature as the outermost layer, the adhesiveness and the molding property can be further enhanced while maintaining the above-mentioned preferable transparency and heat resistance as the encapsulating material sheet.

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

For example, in the encapsulant sheet which is a multilayer film composed of three or more layers, the outermost layer has a thickness of 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 is preferably in the range of outermost layer:intermediate layer:outermost layer=1:3:1 to 1:8:1. By doing so, it is possible to provide preferable molding properties in the outermost layer while maintaining preferable heat resistance as the encapsulant sheet.

<Sealing material 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 resin as a base resin and focuses on the molecular weight and SP value. 2 kinds of hindered amine light stabilizers (HALS) specified by Further, this encapsulant composition is preferably a thermosetting resin composition containing an appropriate amount of a crosslinking agent.

(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 /Cm ³ or more and 0.890 g/cm ³ or less of the polyethylene resin is used as the base resin. By using such a low-density polyethylene resin as the base resin, the transparency of the encapsulant sheet can be improved. Further, according to this, the adhesion with other members constituting the solar cell module, such as the glass protective substrate, is enhanced, and the risk of cell cracking at the time of pressure bonding of each member in the laminating process can be reduced. The content of the base resin is 70% by mass or more and 100% by mass or less, and preferably 90% by mass or more and 99% by mass or less, based on all resin components of the encapsulating material composition. As long as the base resin is contained within the above range, the encapsulating material composition may contain other resins within a range that does not impair the effects of the present invention.

The melt mass flow rate (MFR) of polyethylene used as the base resin of the encapsulant composition is MFR at 190° C. and a load of 2.16 kg measured by JIS-K6922-2 (“MFR” in this specification means this measurement. The measured value depending on 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, the encapsulant sheet can be excellent in 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 the base resin is a metallocene linear chain. More preferably, it is low density polyethylene (M-LLDPE). The metallocene linear low density polyethylene is synthesized using a metallocene catalyst which is a single site catalyst. Such polyethylene has a small number of side chain branches and a uniform comonomer distribution. Therefore, the molecular weight distribution is narrow, the ultra-low density as described above can be achieved, 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 or the like is enhanced.

In addition, since the linear low-density polyethylene has a narrow crystallinity distribution and uniform crystal sizes, not only do not have large crystal sizes, but the low density also results in low crystallinity itself. Therefore, it has excellent transparency when processed into a sheet shape as a sealing material sheet. Therefore, the encapsulant sheet made of the encapsulant composition having the base resin as the base resin, when arranged on the light-receiving surface side of the solar cell element in the solar cell module, is due to attenuation of incident light to the solar cell element. It is possible to prevent a decrease in power generation efficiency.

The "polyethylene resin" in the present specification includes 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, and modified resins obtained by grafting other chemical species to these resins.

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, It can be preferably used as a polyethylene-based resin forming a part of the base resin together with a metallocene-based linear low-density polyethylene (M-LLDPE) and the like. By adding an appropriate amount of “silane-modified polyethylene resin” to the base resin, it is possible to further improve the adhesiveness between the encapsulant sheet and another laminated member such as a glass protective substrate or a solar cell element.

The "silane-modified polyethylene resin" is described in, for example, JP-A-2003-46105. By using the copolymer as a component of the encapsulant composition of a solar cell module, it has excellent strength, durability, etc., and weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, hail resistance. , Excellent in various other properties, and further has excellent heat-sealing property without being affected by manufacturing conditions such as thermocompression bonding for manufacturing a solar cell module, which is stable, low-cost, and has various applications. A solar cell module suitable for can be manufactured.

As the silane copolymer that constitutes 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 solar cell module encapsulant to other members in the solar cell module can be significantly improved. ..

The content of the ethylenically unsaturated silane compound when forming the 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 mass of the copolymer. % 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. If so, the tensile elongation and the heat fusion property tend to be poor.

As described above, the above-mentioned polyethylene-based resin as the base resin of the encapsulating material composition has the absolute value of the SP value difference between the two types of HALS added to the encapsulating material composition, which is peculiar to the present invention. The composition of the entire encapsulant composition is adjusted so that it falls within the predetermined range. Specifically, the absolute value of the SP value of the polyethylene resin as the base resin of the encapsulant composition is 1.0 (the difference between the SP value and the "high molecular weight hindered amine light stabilizer". cal/cm ³ ) ^1/2 or more and 1.6 (cal/cm ³ ) ^1/2 or less, and preferably 1.1 (cal/cm ³ ) ^1/2 or more and 1.5 (cal/cm ³ ) ^{1 The} composition of the encapsulating material composition is adjusted so as to be ^/2 or less. The absolute value of the difference in SP value between the resin and the above-mentioned "low molecular weight type hindered amine light stabilizer" is 0.5 (cal/cm ³ ) ^1/2 or more and 2.0 (cal/cm ^{3 ).} ) ^1/2 or less, preferably 0.6 (cal/cm ³ ) ^1/2 or more and 1.9 (cal/cm ³ ) ^1/2 or less, the composition of the encapsulating material composition is adjusted. ing.

Here, in the present specification, the SP value is a value represented by the following Fedors equation (1).
SP value ^{_{(δ) = (E V /}} v) 1/2 = (ΣΔe i / ΣΔv i) 1/2 ··· formula (1)
E _V: evaporation energy v: molar volume .DELTA.e _i: evaporation energy Delta] v _i of each atom or atomic group: molar volume of each atom or atomic group

The evaporation energy and molar volume of each atom or atomic group used in the calculation of the above formula (1) are based on “RF Fedors, Polym. Eng. Sci., 14, 147 (1974)”. Further, in the present invention, when a resin obtained by copolymerizing different m (m is an integer of 2 or more) kinds of monomers is used, the SP value is calculated by the following formula.
SP value (δ)=X ₁ δ ₁ +...+X _m δ _m
X ₁ ,..., X _m are each mol% of the monomer used, and X ₁ +... X _m =100 mol %.
δ ₁ ,..., δ _m are SP values of the respective monomers and are values obtained by the above formula (1).
Furthermore, in the present invention, when different n (n is an integer of 2 or more) types of resins are used, the SP value is calculated by the following formula.
SP value (δ)=Y ₁ δ ₁ +...+Y _n δ _n
Y ₁ ,..., Y _n are each a mass% of the resin to be used, and Y ₁ +... Y _n =100 mass %.
δ ₁ ,..., δ _n are SP values of the respective resins, and are values obtained by the above formula (1).

(Hindered amine light 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 1,000 or more, and a low molecular weight hindered amine light resistance stabilizer (HALS) having a molecular weight of less than 1,000. To do. These two kinds of hindered amine light stabilizers having different molecular weights are contained in the encapsulating material composition at a ratio of 0.02 mass% or more and 0.20 mass% or less in the resin component of the encapsulating material composition. included. In addition, the total content of the hindered amine-based light stabilizer, which is a combination of these two kinds of hindered amine-based light stabilizers, is 0.1% by mass or more and 0.4% by mass or more based on all resin components in the encapsulant composition. The following is preferable.

Further, of the above-mentioned two kinds of hindered amine light stabilizers contained in the encapsulant composition, the “high molecular weight hindered amine light stabilizer” has an SP value of 9.5 (cal/cm ³ ). ^1/2 or more and 10.2 (cal/cm ³ ) ^1/2 or less, preferably 9.6 (cal/cm ³ ) ^1/2 or more and 10.1 (cal/cm ³ ) ^1/2 or less is there. Further, the SP value of this “high molecular weight type hindered amine light stabilizer” is not only in the above SP value range, but also in the relationship with the base resin, as described above, the absolute difference between the SP values is absolute. The composition of the entire encapsulant composition is optimized so that the value falls within a predetermined range. Specifically, the absolute value of the difference in SP value between the base resin and the “high molecular weight hindered amine light stabilizer” is 1.0 (cal/cm ³ ) ^1/2 or more and 1.6 (cal/cm ^{3 ).} ) ^1/2 or less, preferably 1.1 (cal/cm ³ ) ^1/2 or more and 1.5 (cal/cm ³ ) ^1/2 or less.

On the other hand, among the above two kinds of hindered amine light stabilizers contained in the encapsulant composition, the “low molecular weight type hindered amine light stabilizer” has an SP value of 8.6 (cal/cm ³ ). ^1/2 or more and 10.6 (cal/cm ³ ) ^1/2 or less, preferably 8.7 (cal/cm ³ ) ^1/2 or more and 10.5 (cal/cm ³ ) ^1/2 or less is there. Further, the SP value of this "low molecular weight type hindered amine light stabilizer" is not only within the above SP value range, but also in the relationship with the base resin, as described above, the absolute difference between the SP values is absolute. The composition of the entire encapsulant composition is optimized so that the value falls within a predetermined range. Specifically, the absolute value of the difference in SP value between the base resin and the “low molecular weight type hindered amine light stabilizer” is 0.5 (cal/cm ³ ) ^1/2 or more and 2.0 (cal/cm ^{3 ).} ) ^1/2 or less, preferably 0.6 (cal/cm ³ ) ^1/2 or more and 1.9 (cal/cm ³ ) ^1/2 or less.

Here, the hindered amine-based light stabilizer is an NH type (hydrogen is bonded to a nitrogen atom) or an NR type (an alkyl group (R) is bonded to a nitrogen atom) depending on the binding partner of the nitrogen atom in the piperidine skeleton. , N-OR type (alkoxy group (OR) is bonded to nitrogen atom), N-CH ₃ type (methyl group (CH ₃ ) is bonded to nitrogen atom) and the like. In the encapsulant composition of the present invention, the "high molecular weight hindered amine-based light stabilizer" satisfies the above SP value requirements, and further has a chemical structure of "N-CH ₃ type". It is more preferable to use the hindered amine-based light stabilizer of "." For example, when the NH type HALS is used as the “high molecular weight type hindered amine light stabilizer”, the SP value is higher than that of the N—CH ₃ type HALS (the difference in SP value from PE). , The dispersibility is likely to deteriorate. Therefore, the optical characteristics are likely to be deteriorated or the migration to the surface of the encapsulating material sheet is likely to be excessive, and radical scavenging is difficult to function properly. On the other hand, the N-CH ₃ type HALS is more compatible with the base resin (polyethylene resin) than the N-H type HALS, and the optical characteristics are good. Further, the N-CH ₃ type HALS is converted into the N-H type HALS by heat or light, and the time until it moves to the surface of the encapsulating material sheet is secured as a certain length or more. Easy to develop long-term light resistance, not short-term. In addition, N-OR type HALS has a faster radical trap reaction rate than NHS type and N-CH ₃ type HALS, but this inhibits the crosslinking reaction during the crosslinking treatment of the encapsulant sheet. There is a risk of

In addition, in the encapsulant composition of the present invention, the "low molecular weight type hindered amine light stabilizer" satisfies the above SP value requirement, and further has a chemical structure of "N-OR". It is more preferable to use "type" hindered amine light stabilizers. The N-OR type has a faster radical capturing speed than the N-H type and the N-CH ₃ type. Furthermore, the N-OR type low molecular weight HALS that migrates to the surface faster than the high molecular weight HALS traps radicals in a shorter period of time than the NH type and N-CH ₃ type HALS, and suppresses deterioration of the sealing sheet. It is preferable in that N-OR type low-molecular-weight HALS that exhibits short-term light fastness has a function of radical scavenging that decreases when exposed to light for a long period of time, but N-CH ₃ type that exhibits long-term light fastness is exhibited. It is possible to suppress deterioration of the encapsulating sheet for a long time by using the polymer HALS in combination with.

Specific examples of the “high molecular weight type hindered amine light stabilizer” that can be preferably used in the encapsulant composition according to the present invention include:
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: "Chimassorb 119" (manufactured by BASF)), 1,2,3,4-butanetetracarboxylic acid, tetramethyl ester, reaction products with 1, 2,2,6,6-pentamethyl-4-piperidinol and β,β,β',β'-tetramethyl-2,4,8,10-tetraxaspiro [5.5] undecane-3,9-diethanol (trade name) : "LA-63P" (made by ADEKA), 1,6-hexanediamine, N,N'-bis(1,2,2,6,6-pentamethyl-4-piperidyl)-, Polymers morpholine-2, Examples thereof include 4,6-trichloro-1,3,5-triazine (trade name: "UV-3529" (manufactured by Sun Chemical Co.)).

The above-mentioned "Chimassorb 119" which can be preferably used as the "high molecular weight type hindered amine light-resistant stabilizer" has a molecular weight of 2286 and an SP value of 9.87 (cal/cm ³ ) ^1/2 , and has the following general formula: It is N-CH ₃ type HALS represented by (1).

（１）

(1)

Similarly, the above-mentioned "LA-63P" which can be preferably used as the "high molecular weight type hindered amine light stabilizer" has a molecular weight of about 2000 and an SP value of 10.09 (cal/cm ³ ) ^1/2 . And is an N—CH ₃ type HALS represented by the following general formula (2).

（２）

(2)

Specific examples of the "low-molecular-weight hindered amine light stabilizers" that can be preferably used in the encapsulant composition according to the present invention include:
Bis (1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate (trade name: "Tinuvin PA 123" (manufactured by BASF)), Bis (1-undecanoxy-2,2,6,6) -Tetramethylpiperidin-4-yl)carbonate (trade name: "LA-81" (manufactured by ADEKA)), 1-(2-Hydroxy-1,1-dimethyl-ethoxy)-2,2,6,6-tetramethyl- 4-piperidinyl octadecanoate, etc. can be mentioned.

The above-mentioned "Tinuvin PA 123", which can be preferably used as the "low-molecular-weight hindered amine-based light stabilizer," has a molecular weight of 737 and an SP value of 10.47 (cal/cm ³ ) ^1/2 , and is as follows. Is an N-OR type HALS represented by the general formula (3).

（３）

(3)

Similarly, the above can be preferably used as the "low molecular weight type hindered amine light stabilizer", "LA-81" is a molecular weight of about 681, SP value: 8.77 (cal ^/ cm ^{3) 1/2} Yes, it is an N-OR type HALS represented by the following general formula (4).

（４）

(4)

[Crosslinking agent]
The cross-linking agent used in the encapsulant composition has an active oxygen amount of preferably 4.5% or more and 15.00% or less, more preferably 5.5% or more and 12.00% or less. By using a cross-linking agent having an amount of active oxygen in the range of 4.5% or more and 15.00% or less, the encapsulating material sheet can be provided with superior heat resistance, light resistance, and transparency.

Regarding the one-hour half-life temperature of the crosslinking agent used in the encapsulant composition, it is preferable to use one having a temperature of 115° C. or higher and 150° C. or lower. As a result, the encapsulant composition of the present invention can be made into a resin composition that can be melt-extruded at 110°C or lower.

Specific examples of preferable crosslinking agents satisfying the above conditions include n-butyl 4,4-di(t-butylperoxy)valerate, ethyl 3,3-di(t-butylperoxy)butyrate, 2,2- Peroxyketals such as di(t-butylperoxy)butane, di-t-butylperoxide, t-butylcumylperoxide, dicumylperoxide, 2,5-dimethyl-2,5-di(t- Butyl peroxy)hexane, dialkyl peroxides such as 2,5-dimethyl-2,5-di(t-peroxy)hexyne-3, t-butyl peroxy 2-ethylhexyl carbonate, t-amyl peroxy 2-ethylhexyl Peroxycarbonates such as carbonate can be preferably used as a crosslinking agent added to the encapsulating material composition.

The content of the cross-linking agent in the encapsulating material composition is preferably 0.2% by mass or more and 0.6% by mass or less, more preferably 0.1% by mass or less with respect to the base resin in the encapsulating material composition. It is in the range of 3 mass% or more and 0.5 mass% or less. Sufficient durability can be imparted to the encapsulant sheet by adding the crosslinking agent in this range. The encapsulant sheet of the present invention is formed into a film without substantially proceeding crosslinking, and the content of the above-mentioned cross-linking agent in the encapsulant sheet in the sheet stage after the film formation is 0. It is assumed that the range is from 2% by mass to 0.6% by mass.

[Crosslinking aid]
The encapsulant composition contains a polyfunctional monomer having a carbon-carbon double bond and/or an epoxy group, and more preferably a cross-linking promoter in which the functional group of the polyfunctional monomer is an allyl group, a (meth)acrylate group, or a vinyl group. It is preferable to include an agent. This promotes an appropriate cross-linking reaction to improve the adhesion of the encapsulant sheet to glass and metal, and in addition to this, the cross-linking aid enhances the crystallinity of the linear low-density polyethylene forming the encapsulant sheet. To maintain transparency. Thereby, in addition to the above-mentioned effect of improving the adhesiveness, the transparency and the low temperature flexibility of the encapsulant sheet can be further improved.

Specific examples of the cross-linking aid that can be used in the encapsulating material composition include polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate; Methylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonane Poly(meth)acryloxy compounds such as diol diacrylate, glycidyl methacrylate containing a double bond and an epoxy group, 4-hydroxybutyl acrylate glycidyl ether, and 1,6-hexanediol diglycidyl ether containing two or more epoxy groups, 1 Examples of such epoxy compounds include, for example, 4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and trimethylolpropane polyglycidyl ether. These may be used alone or in combination of two or more. Further, among the above-mentioned crosslinking aids, it also contributes significantly to the glass adhesion improvement of the encapsulant sheet, has good compatibility with linear low-density polyethylene, and maintains transparency by reducing crystallinity by crosslinking, From the viewpoint of imparting flexibility at low temperature, TAIC can be preferably used.

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, more preferably 0. It is from 05% by mass to 1.0% by mass. Within this range, an appropriate crosslinking reaction can be promoted to improve the adhesion of the encapsulant sheet.

(Other additives)
The encapsulating material 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, an antifoaming agent, a flame retardant, and other various fillers can be appropriately added. The content ratio of these additives varies depending on the particle shape, density, etc., but is preferably 0.001% by mass or more and 60% by mass or less in the encapsulating material composition. By including these additives, it is possible to impart stable mechanical strength to the encapsulating material composition for a long period of time, an effect of preventing yellowing, cracking, and the like.

<Method for manufacturing encapsulant sheet>
The method for producing the encapsulant sheet of the present invention is a production method using the encapsulant composition of the present invention described in detail above, and includes a base resin selection step, a light resistance stabilizer selection step, and a material kneading step. , A sheet forming step.

[Base resin selection process]
In the base resin selection step, a polyethylene resin to be used as a base resin in the encapsulant composition is selected. Base reference of selection of resin, the base resin, the 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 is that the density 0.880 g / cm ³ or more 0.890 g / cm ³ or less of the polyethylene resin. Further, in selecting the base resin, a resin having an SP value within a range in which the absolute value of the difference between the SP values of the two hindered amine light stabilizers added to the base resin can be set within the above-mentioned specific range. Also consider that.

[Light Stabilizer Selection Process]
In the light resistance stabilizer selection step, as the light resistance stabilizer to be added to the polyethylene resin as the base resin in the encapsulating material composition, as described above, the “high molecular weight type HALS” and “high molecular weight type HALS” are selected respectively.

[Material kneading process]
In the material kneading step, the encapsulant composition is produced by adding the cross-linking agent and the above two kinds of hindered amine light stabilizers to the above base resin and kneading them.

[Sheet-making process]
In the sheet-forming step, the encapsulant composition produced in the previous step is melt-molded to produce an encapsulant sheet. The melt molding of the encapsulant composition can be carried out by a known molding method, that is, various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, rotational molding and the like. The lower limit of the molding temperature during molding may be a temperature above the melting point of the encapsulant composition. The upper limit of the molding temperature is a temperature at which crosslinking does not start during film formation, that is, a temperature at which the gel fraction of the encapsulant composition can be maintained at 0%, depending on the one-minute half-life temperature of the crosslinking 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, a glass protective substrate 2, a front surface sealing material 3, a solar cell element 4, a back surface sealing material 5, and a back surface protection sheet 6 are sequentially laminated from the light receiving surface side of 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 surface sealing material 3 and/or the back surface sealing material 5. In particular, by disposing the encapsulant sheet of the present invention having excellent transparency as the front encapsulant 3 disposed 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. ..

The solar cell module 1 is formed, for example, by sequentially stacking the above-mentioned glass protective substrate 2, front surface sealing material 3, solar cell element 4, back surface sealing material 5, and back surface protection sheet 6 and then vacuum suction or the like. It can be manufactured by integrating and then thermocompression-molding the above member as an integrally molded body by a molding method such as a lamination method. Then, at this time, the adhesion between the glass substrate and the encapsulating material sheet can be improved by stacking the front surface encapsulating material 3 on the glass protective substrate and the glass substrate. The above-mentioned thermocompression bonding can be carried out at the same time by carrying out the crosslinking treatment under heating conditions such that the temperature is 140° C. or higher and 170° C. or lower. Alternatively, the above-mentioned thermocompression bonding may be carried out at 110° C. or higher, and after the thermocompression bonding, a curing step may be carried out to promote the crosslinking reaction of polyethylene. The curing step in this case is performed under heating conditions such that the resin temperature of the encapsulant sheet is 140° C. or higher and 170° C. or lower. By any one of the above-mentioned cross-linking treatments, cross-linking of the encapsulant sheet can be appropriately progressed, and the heat resistance and light resistance of the solar cell module can be sufficiently enhanced.

Thus obtained, the solar cell module of the present invention has excellent heat resistance and light resistance, and even when exposed to harsh environments such as strong ultraviolet rays, heat rays, wind and rain, etc. The weather resistance can be maintained. Further, the excellent transparency can also contribute to the improvement of the designability 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 members, if necessary.

Although the present invention has been specifically described with reference to the exemplary embodiments, the present invention is not limited to the above-described exemplary embodiments and can be implemented 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.

[Manufacture of encapsulant sheet]
An encapsulant composition containing the following base resin, hindered amine light stabilizer, cross-linking agent, and cross-linking aid was melted to produce encapsulant sheets of Examples and Comparative Examples. The encapsulant sheet was manufactured by a conventional T-die method so as to form a film having a thickness of 600 μm, thereby obtaining an uncrosslinked single-layer encapsulant sheet. The film forming temperature was 90°C to 100°C. The content (mass %) of each hindered amine light stabilizer in each sealing material composition with respect to all resin components was as shown in Table 1. Further, the absolute values of the difference in SP value between each hindered amine light stabilizer and the base resin are also listed in Table 1.

(Base resin)
: 85 parts by mass of metallocene-based linear low-density polyethylene (M-LLDPE) having a density of 0.880 g/cm ³ and an MFR at 190° C. of 20 g/10 min, and the following silane-modified polyethylene resin (density 0.884 g/ cm ³ )15 parts by mass of the mixed resin was used as the “base resin” of the encapsulant sheets 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 vinyltrimethoxysilane with respect to 98 parts by mass of a metallocene-based linear low-density polyethylene (M-LLDPE) having a density of 0.881 g/cm ³ and an MFR at 190° C. of 30 g/10 min. 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 stabilizer 1 (referred to as "polymer HALS1" in Table 1))
The above-mentioned "Chimassorb 119" was used. This HALS is N-CH ₃ type HALS represented by the above general formula (1), and has a molecular weight of 2286 and an SP value of 9.87 (cal/cm ³ ) ^1/2 .

(High molecular weight type hindered amine light stabilizer 2 (referred to as "polymer HALS2" in Table 1))
The above-mentioned "LA-63P" was used. This HALS is an N—CH ₃ type HALS represented by the above general formula (2), and has a molecular weight of about 2000 and an SP value of 10.09 (cal/cm ³ ) ^1/2 . ..

(High molecular weight type hindered amine light stabilizer 3 (referred to as "polymer HALS3" in Table 1))
"XJ100H (manufactured by Nippon Polyethylene Co., Ltd.)" was used. This HALS is a light-resistant stabilizer which is a copolymer of a cyclic aminovinyl compound represented by the following general formula (5) and ethylene, and is an NH type HALS, having a molecular weight of 35,000 and an SP value. Is 8.55 (cal/cm ³ ) ^1/2 .

（５）
（式（５）中、Ｒ１及びＲ２は水素原子又はメチル基を示し、Ｒ３は水素原子を示す。）

(5)
(In the formula (5), R1 and R2 represent a hydrogen atom or a methyl group, and R3 represents a hydrogen atom.)

(High molecular weight type hindered amine light stabilizer 4 (referred to as "polymer HALS4" in Table 1))
"LA-68 (made by ADEKA)" was used. This HALS is an NH type HALS represented by the following general formula (6), and has a molecular weight of about 1900 and an SP value of 10.54 (cal/cm ³ ) ^1/2 .

（６）

(6)

(Low molecular weight hindered amine light-resistant stabilizer 1 (referred to as "low molecular weight HALS1" in Table 1))
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 (3), and has a molecular weight of 737 and an SP value of 10.47 (cal/cm ³ ) ^1/2 .

(Low molecular weight hindered amine light stabilizer 2 (referred to as "low polymer HALS2" in Table 1))
The above-mentioned "LA-81 (made by ADEKA)" was used. This HALS is an N-OR type HALS represented by the above general formula (4), and has a molecular weight of 681 and an SP value of 8.77 (cal/cm ³ ) ^1/2 .

(Low molecular weight hindered amine light stabilizer 3 (referred to as "low molecular weight HALS3" in Table 1))
"Uvinal 4050 (manufactured by BASF)" was used. This HALS is an NH type HALS represented by the following general formula (7), and has a molecular weight of 450 and an SP value of 12.15 (cal/cm ³ ) ^1/2 .

（７）

(7)

(Crosslinking agent)
The amount of "Luperox 101 (manufactured by Arkema Yoshitomi Co., Ltd.)" was adjusted so that the content (% by mass) of the encapsulating material composition with respect to the base resin was 0.4% by mass.

(Crosslinking aid)
The amount of "TAIC (manufactured by Nippon Kasei)" was adjusted so that the content (% by mass) of the encapsulating material composition with respect to the base resin was 0.6% by mass.

[Evaluation Example 1: Transparency]
The uncrosslinked encapsulant sheets of Examples and Comparative Examples produced as described above were sandwiched by ETFE films and subjected to a crosslinking treatment at the same time when integrated by vacuum heating lamination. Was used as a sample for evaluating a sealing material sheet. The vacuum heating laminate strip was as follows.
(Vacuum heating laminating condition) (a) Vacuuming: 6 minutes
(B) Pressurization: (0 kPa to 50 kPa): 10 seconds
(C) Pressure retention: (50 kPa): 11 minutes
(D) Temperature: 165°C
After peeling off the ETFE of each of the above-mentioned sealing material sheet evaluation samples, the transparency (HAZE) (measured by JIS K7136, Murakami Color Research Laboratory, haze/transmittance system HM150) was measured. The evaluation criteria are as follows. The evaluation results are shown in Table 1 "Transparency".
(Evaluation criteria)
A: less than 8.0% haze B: more than 8.0% haze 10.0% or less C: more than 10.0% haze

[Evaluation Example 2: Light resistance to glass adhesion]
For each of the above-mentioned samples for evaluation of the encapsulant sheet, a test relating to glass adhesion light resistance was conducted. The uncrosslinked encapsulant sheets of Examples and Comparative Examples produced as described above were brought into close contact with a glass substrate (white plate semi-tempered glass (JPT 3.2 75 mm x 50 mm x 3.2 mm)), and the following vacuum was applied. Vacuum heating and laminating is performed under heating and laminating conditions, and after lamination, two parallel pieces are placed at 15 mm intervals from the surface side of the encapsulating material sheet to the glass plate so that the encapsulating material sheet portion becomes a strip shape with a width of 15 mm. Samples for evaluating the glass adhesion light resistance of each Example and Comparative Example were obtained. Then, with respect to each of these samples, the adhesion after the following light resistance test was carried out was measured by the following peel test method, and the glass adhesion light resistance of each encapsulant sheet was evaluated.
(Vacuum heating laminating condition) (a) Vacuuming: 6 minutes
(B) Pressurization: (0 kPa to 50 kPa): 10 seconds
(C) Pressure retention: (50 kPa): 11 minutes
(D) Temperature: 165°C
(Light resistance test)
: For each evaluation sample, "Suga Test Instruments Co., Ltd. Super Xenon Weather Meter SX-75" was used for irradiation for 1333 hours under the conditions of irradiance of 180 W/m ² , black panel temperature (BPT) 65° C. and humidity of 50% The test was conducted.
(Peeling test method)
The sealant sheet (each strip-shaped portion) adhered to the glass plate is subjected to a vertical peeling (50 mm/min) test with a peeling tester (Tensilon universal testing machine RTF-1150-H), and the glass is adhered. The strength was measured and the average value of three measurements was adopted. The evaluation criteria are as follows. The evaluation results are shown in Table 1 "Glass adhesion".
(Evaluation criteria)
A: Glass adhesion strength is 20 N/15 mm or more B: Glass adhesion strength is 10 N/15 mm or more and less than 20 N/15 mm C: Glass adhesion strength is less than 10 N/15 mm

[Evaluation Example 3: Light resistance at high temperature]
The encapsulant sheet evaluation sample used for evaluation of transparency used in Evaluation Example 1 was also used as a material for evaluating light resistance at high temperature. Each of these samples was subjected to an irradiation test for 1000 hours under the conditions of an irradiance of 180 W/m ² , a black panel temperature (BPT) of 110° C. and a humidity of 50%, using an Atlas Weatherometer Ci4000 manufactured by Toyo Seiki Seisakusho. The light resistance test conducted in Evaluation Example 2 above was carried out, and then the following tensile stress test was carried out to evaluate the light resistance of each encapsulant sheet at high temperatures.
(Tensile stress test method)
: A sheet of encapsulant cut into a length of 50 mm and a width of 10 mm was pressed with a jig at an upper and lower 10 mm of a peeling tester (Tensilon universal tester RTF-1150-H), a chuck distance of 30 mm, and a pulling speed of 50 mm/ A tensile test of min was performed to measure the tensile stress of the encapsulant sheet. The evaluation criteria are as follows. The evaluation results are shown in Table 1 "Light resistance".
(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

From Table 1, it can be seen that the encapsulant sheet of the present invention is a encapsulant sheet for a solar cell module, which has polyethylene as a base resin and has excellent transparency and extremely high light resistance.

1 Solar Cell Module 2 Glass Protective Substrate 3 Front Sealing Material 4 Solar Cell Element 5 Back Sealing Material 6 Backside Protection Sheet

Claims (5)

A sealing material sheet for a solar cell module,
With polyethylene resin as the base resin,
A high molecular weight type hindered amine light 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 hindered amine light 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 high molecular weight hindered amine light stabilizer has an SP value of 9.5 (cal/cm ³ ) ^1/2 or more and 10.2 (cal/cm ³ ) ^1/2 or less,
The SP value of the low molecular weight hindered amine light stabilizer is 8.6 (cal/cm ³ ) ^1/2 or more and 10.6 (cal/cm ³ ) ^1/2 or less,
The absolute value of the difference in SP value between the base resin and the high molecular weight type hindered amine light stabilizer is 1.0 (cal/cm ³ ) ^1/2 or more and 1.6 (cal/cm ³ ) ^{1/ 2} or less,
The absolute value of the difference in SP value between the base resin and the low molecular weight hindered amine light stabilizer is 0.5 (cal/cm ³ ) ^1/2 or more and 2.0 (cal/cm ³ ) ^{1/ An} encapsulant sheet of ² or less. The high molecular weight type hindered amine light stabilizer is an N—CH ₃ type hindered amine light stabilizer,
The encapsulant sheet according to claim 1, wherein the low molecular weight hindered amine light stabilizer is an N-OR type hindered amine light stabilizer. The encapsulant sheet according to claim 1, further comprising a crosslinking agent. The encapsulant sheet according to claim 1, further comprising a silane-modified polyethylene resin. 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, wherein the light-receiving surface-side encapsulant is the encapsulant sheet according to any one of claims 1 to 4.

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