JP2016021431A - Method for manufacturing seal-material sheet for solar battery module use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength-conversion type seal-material sheet superior in long-term weather resistance, which includes a polyethylene-based resin as a base resin.SOLUTION: A seal-material sheet 1 for solar battery module use, which has a wavelength conversion function, comprises: an intermediate layer 11; an outermost layer 12; and as a hindered-amine based photostabilizer, a photostabilizer (A) or a photostabilizer (B) in combination with the photostabilizer (A). The photostabilizer (A) is a hindered-amine based photostabilizer having, in a monomer unit side chain, three or more piperidine rings and a molecular weight of 1000-10000. The photostabilizer (B) is a hindered-amine based photostabilizer having, in a monomer unit main chain, only one piperidine ring and a molecular weight of 1000-5000.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a sealing material sheet for a solar cell module.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. Currently, various types of solar cell modules have been developed and proposed. Generally, a solar cell module has a configuration in which a transparent front substrate made of glass or the like, a solar cell element, and a back surface protection sheet are laminated via a sealing material sheet.

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

  Here, the solar cell element generally has high spectral sensitivity to light in the wavelength region from visible light to near infrared. Therefore, by arranging a wavelength conversion layer containing a wavelength conversion agent that converts ultraviolet light into visible light in the solar cell module, it was intended to increase the utilization efficiency of sunlight in the solar cell element and improve the power generation efficiency. A solar cell module has been proposed (see Patent Document 1).

  In addition, in order to exhibit the wavelength conversion function and the original protective function of the sealing material sheet in a well-balanced manner, a multi-layer type sealing in which other functional layers such as a protective layer are laminated on both sides of the wavelength conversion layer. A stopping material sheet has also been proposed (see Patent Document 2).

Moreover, as a wavelength conversion agent used by adding to a sealing material sheet for a solar cell module, a wavelength conversion agent made of an inorganic phosphor such as MgF ₂ : Eu ²⁺ has been widely used (Patent Document 3). reference).

  However, in the case where a wavelength conversion agent is added to the above-described encapsulant sheet using the polyethylene resin as a base resin, the inorganic wavelength conversion agent as described above has poor compatibility with olefins, and the encapsulant There was a problem that the optical characteristics of the sheet were liable to be lowered. In this regard, it has become clear that it is desirable to select, for example, an organic wavelength conversion agent made of triazole or the like as the wavelength conversion agent added to the encapsulant sheet using a polyethylene resin as a base resin.

JP 2007-27271 A JP 2012-15205 A JP 2012-15205 A JP 2012-044153 A

  When adding a wavelength conversion agent to a sealing material sheet based on a polyethylene-based resin that has been growing in demand in place of the EVA sealing material in recent years, by selecting an organic wavelength conversion agent as described above, The optical characteristics in the initial stage after production can be maintained better than when an inorganic wavelength conversion agent is selected.

  However, the organic wavelength conversion agent has a problem in weather resistance at the time of long-term use in a high-temperature and high-humidity environment assumed as an actual use environment of the solar cell module, and after long-term use in the above severe environment. Further, it has been recognized as a further problem that the wavelength conversion function may be significantly deteriorated due to a decrease in the quantum yield of the wavelength conversion agent.

  Here, a radical absorbent is appropriately used for the solar cell module sealing material sheet from the viewpoint of improving weather resistance. It is presumed that the addition of a radical absorbent is also effective for the deterioration of the wavelength conversion agent. As a radical absorber, a hindered amine light stabilizer (HALS) is known. For example, Patent Document 4 describes the use of a so-called high molecular weight type hindered amine light stabilizer as HALS.

  High molecular weight type hindered amine light stabilizers with a molecular weight of 1000 or more are generally excellent in migration resistance and elution resistance. However, long-term migration differs depending on the type, resulting in haze reduction, particularly between glass. Therefore, it is important to select a HALS that can suppress the increase in haze. On the other hand, the encapsulant sheet is required to have long-term durability in terms of adhesion to the glass substrate. However, the effect of long-term glass adhesion varies depending on the type of HALS. As described above, the encapsulant sheet is required to satisfy both the haze rise suppression and the long-term glass adhesion, but the presence of HALS also causes both to decrease.

  The present invention has been made in view of the above situation, and a sealing material sheet (hereinafter referred to as “wavelength conversion type sealing”) having a wavelength conversion function using a polyethylene resin having excellent hydrolysis resistance as a base resin. It is also referred to as a “material sheet”), which can maintain good optical properties and wavelength conversion function even after long-term use in a hot and humid environment, that is, has excellent weather resistance and durability. It is an object to provide a wavelength conversion type sealing material sheet.

  As a result of intensive studies, the present inventors have made the encapsulant sheet a multilayer sheet, and by adding an organic wavelength conversion agent having a molecular weight larger than a specific value only to the intermediate layer, the wavelength conversion agent It should be possible to sufficiently prevent bleed-out associated with changes over time. Further, in such a sealing material sheet, it has been found that the above problems can be solved by selectively using HALS, which is more effective in radical absorption, and adding an appropriate amount to each layer, and to complete the present invention. It came. More specifically, the present invention provides the following.

(1) A sealing material sheet for a solar cell module, wherein the sealing material sheet is a multilayer sheet including an intermediate layer and outermost layers disposed on both surfaces thereof, and the intermediate layer and the outermost layer, the density of 0.870 g / cm ³ or more 0.970 g / cm ³ or less of low density polyethylene base resin, wherein the intermediate layer contains an organic wavelength converting material, wherein the outermost layer, the organic When the system wavelength conversion agent is included, the content ratio is smaller than the content ratio of the organic wavelength conversion agent in the intermediate layer, and the intermediate layer and the outermost layer contain a hindered amine light stabilizer. A sealing material sheet for a solar cell module in which the following light stabilizer (A) is used as the hindered amine light stabilizer.
Light stabilizer (A): A hindered amine light stabilizer having a molecular weight of 1000 or more and 10,000 or less having three or more piperidine rings in the side chain of the monomer unit.

(2) The encapsulant sheet according to (1), wherein the light stabilizer (A) and the following light stabilizer (B) are used in combination as the hindered amine light stabilizer.
Light stabilizer (B): A hindered amine light stabilizer having a molecular weight of 1,000 to 5,000 having only one piperidine ring in the main chain of the monomer unit.

  (3) The light stabilizer (A) is dibutylamine-1,3,5-triazine-N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylene It is a polycondensate of diamine-N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine, and the light stabilizer (B) contains butanedioic acid 1- [2- (4-hydroxy-2, 2,6,6-tetramethylpiperidino) ethyl], the encapsulant sheet according to (1) or (2).

(4) The encapsulant sheet according to any one of (1) to (3), wherein the contents of the light stabilizers (A) and (B) in the intermediate layer and the outermost layer are as follows.
Light stabilizer (A): 0.01% by mass or more and 1.0% by mass or less Light stabilizer (B): 0.01% by mass or more and 1.0% by mass or less (5) The organic wavelength conversion agent is The encapsulant sheet according to any one of (1) to (4), which is a wavelength conversion agent having a number average molecular weight of 100 or more and 1000 or less.

  (6) The encapsulant sheet according to any one of (1) to (5), wherein the organic wavelength conversion agent is any one derivative of pyrazine, pyridine, and triazole or a mixture thereof.

  (7) Any of (1) to (6), wherein the content ratio of the organic wavelength conversion agent in the outermost layer is ½ or less of the content ratio of the organic wavelength conversion agent in the intermediate layer. The sealing material sheet of crab.

  (8) The encapsulant sheet according to any one of (1) to (7), wherein the outermost layer further contains a silane-modified polyethylene resin.

  (9) A solar cell module comprising the encapsulant sheet according to any one of (1) to (8) and a solar cell element, wherein the encapsulant sheet is on the light-receiving surface side of the solar cell element The solar cell module which is arranged in.

(10) A sealing material sheet manufacturing method for a solar cell module, the sealing material for the intermediate layer to the density of 0.870 g / cm ³ or more 0.970 g / cm ³ or less of the polyethylene resin-based resin the intermediate layer comprising the composition, an outermost layer consisting of a sealing material composition for the outermost layer consisting of a density 0.870 g / cm ³ or more 0.970 g / cm ³ or less of the polyethylene resin, are laminated, multilayer sheet The intermediate layer sealing material composition includes an organic wavelength conversion agent in an amount of 0.05% by mass or more and 0.5% by mass or less, and is used for the outermost layer. The sealing material composition does not contain a wavelength converting agent, the intermediate layer and the outermost layer contain a hindered amine light stabilizer, and the hindered amine light stabilizer includes the following: Use light stabilizer (A) Sealing material sheet manufacturing method for a solar cell module.
Light stabilizer (A): A hindered amine light stabilizer having a molecular weight of 1000 or more and 10,000 or less having three or more piperidine rings in the side chain of the monomer unit.

(11) The method for producing an encapsulant sheet according to (10), wherein the light stabilizer (A) and the following light stabilizer (B) are used in combination as the hindered amine light stabilizer.
Light stabilizer (B): A hindered amine light stabilizer having a molecular weight of 1,000 to 5,000 having only one piperidine ring in the main chain of the monomer unit.

  (12) The method for producing an encapsulant sheet according to (10) or (11), wherein the organic wavelength conversion agent is a wavelength conversion agent having a number average molecular weight of 100 to 1,000.

  (13) The method for producing a sealing material sheet according to any one of (10) to (12), wherein the organic wavelength conversion agent is any one derivative of pyrazine, pyridine, and triazole, or a mixture thereof.

  (14) The method for producing a sealing material sheet according to any one of (10) to (13), further comprising: a crosslinking step in which crosslinking treatment is performed on the multilayer sheet by irradiation with ionizing radiation.

  ADVANTAGE OF THE INVENTION According to this invention, it is the sealing material sheet which used the polyethylene-type resin as the base resin, Comprising: The wavelength conversion type sealing material sheet which has the outstanding long-term weather resistance can be provided.

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

  Hereinafter, first, an encapsulant composition (hereinafter also simply referred to as “encapsulant composition”) that can be preferably used for an encapsulant sheet for a solar cell module of the present invention, an encapsulant for a solar cell module. A material sheet (hereinafter also simply referred to as “sealing material sheet”), a manufacturing method thereof, a solar cell module using the sealing material sheet of the present invention, and a manufacturing method thereof will be sequentially described. In this specification, a multilayer encapsulant sheet is an encapsulant having a multilayer structure composed of an outermost layer formed on both surfaces of the encapsulant sheet and an intermediate layer that is a layer other than the outermost layer. Say about the sheet. The intermediate layer refers to a layer other than the outermost layer, and may have a single layer structure, or the intermediate layer itself may have a multilayer structure including a plurality of layers.

<Encapsulant composition>
The encapsulant sheet of the present invention is a multilayer encapsulant sheet comprising an intermediate layer and an outermost layer. And the sealing material composition for intermediate | middle layers for forming the intermediate | middle layer of a multilayer sealing material sheet contains a wavelength conversion agent as an essential component. Moreover, although the sealing material composition for outermost layers for forming an outermost layer also uses a low density polyethylene resin as a base resin, unlike the sealing material composition for intermediate | middle layers, it does not contain a wavelength converter. And the sealing material composition for intermediate | middle layers and the sealing material composition for outermost layers make specific HALS selected by paying attention to radical absorption capability as an essential component.

[Encapsulant composition for intermediate layer]
The encapsulant composition for the intermediate layer is an encapsulant composition used for forming the intermediate layer of the multilayer encapsulant sheet of the present invention. The sealing material composition for intermediate | middle layers contains the base resin for intermediate | middle layers which consists of a polyethylene-type resin, and an organic type wavelength converter as an essential component.

(Base resin)
Examples of the polyethylene resin used as the base resin of the encapsulant composition for the intermediate layer (hereinafter also referred to as “base resin for the intermediate layer”) include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or metallocene. A linear low density polyethylene (M-LLDPE) can be preferably used.

Density polyethylene resin used as the intermediate layer base resin, 0.870 g / cm ³ or more 0.970 g / cm ³ or less, or preferably 0.870 g / cm ³ or more 0.930 g / cm ³ or less. The density of the intermediate layer base resin is preferably higher than the outermost layer base resin described in detail later. By setting the density of the base resin for the intermediate layer within the above range, it is possible to sufficiently improve the heat resistance of the encapsulant sheet while maintaining the molding characteristics and the protection performance of the solar cell element.

  Further, the base resin for the intermediate layer is preferably a polyethylene resin in which the number of full double bonds remaining in the composition stage is relatively larger than the number of full double bonds of the base resin for the outermost layer. . Further, the number of full double bonds of the base resin for the intermediate layer is preferably 0.5 or more and 4.0 or less, and more preferably 1.0 or more and 4.0 or less. By setting the total number of double bonds of the encapsulant composition for the intermediate layer within the above range, when crosslinking is performed by irradiation with ionizing radiation, the crosslinking is sufficiently advanced to increase the heat resistance of the encapsulant sheet. It can be improved sufficiently. On the other hand, even if the crosslinking of the intermediate layer by irradiation with ionizing radiation is sufficiently advanced, the total number of double bonds of the sealing material composition for the outermost layer is different from that of the sealing material composition for the intermediate layer By limiting to, the progress of crosslinking of the outermost layer is suppressed in a mode different from that of the intermediate layer, and as a result, preferable molding characteristics can be maintained as the whole sealing material sheet. In addition, the heat resistance of a sealing material sheet is not fully improved as the number of full double bonds of the sealing material composition for intermediate | middle layers is less than 0.5 piece. On the other hand, when the number exceeds 4.0, molding characteristics and adhesion are deteriorated due to excessive progress of crosslinking, which is not preferable.

Here, “the number of full double bonds” in the present specification means the sheet density d (g / cm ³ ) and sheet thickness t (cm) of the encapsulant composition in the sheet state and the absorption band of the infrared absorption spectrum. It is the value calculated | required by the following formula from the light absorbency A. In addition, about the measurement of the light absorbency A of the absorption band of an infrared absorption spectrum, it carried out by NICOLET6700 made from Thermo Scientific.
Number of terminal vinyl groups = 0.231 / (d × t) × A (910 cm ⁻¹ )
Vinylidene base = 0.271 / (d × t) × A (888 cm ⁻¹ )
Number of trans vinylene groups = 0.328 / (d × t) × A (965 cm ⁻¹ )
Total number of double bonds = number of terminal vinyl groups + number of vinylidene groups + number of transvinylene groups The total number of double bonds per 2000 carbons by the above method.

  The content of the base resin contained in the intermediate layer sealing material composition is preferably 10 parts by mass or more and 99 parts by mass with respect to 100 parts by mass in total of all resin components in the intermediate layer sealing material composition. It is 50 parts by mass or less, more preferably 50 parts by mass or more and 99 parts by mass or less, and still more preferably 90 parts by mass or more and 99 parts by mass or less. The sealing material composition for the intermediate layer may contain another resin within the above range. These may be used, for example, as an additive resin, or may be used for masterbatching other components described later. In the present specification, the term “all resin components” includes the other resins described above.

(Organic wavelength conversion agent)
A wavelength conversion agent contributes to the improvement of the power generation efficiency of a solar cell module by converting light in a wavelength region with low absorption sensitivity into a wavelength region with high absorption sensitivity and making it incident on a solar pond device in a solar cell element. Say things. Various wavelength conversion agents of inorganic type, organic type, or hybrid type thereof are known.

  Among these, an organic wavelength conversion agent is used for the sealing material composition for the intermediate layer of the sealing material sheet of the present invention. Of these organic wavelength conversion agents, those having a number average molecular weight of 100 or more and 1000 or less can be preferably used. By adding an organic wavelength conversion agent only to the intermediate layer in the multilayer sheet, the organic wavelength conversion agent is prevented from leaching to the outermost layer side of the sealing material sheet, and the initial stage of manufacturing the sealing material sheet The optical characteristics can be made sufficiently favorable. However, for organic wavelength converting agents, by selecting only agents having a relatively high molecular weight and a number average molecular weight of 100 or more, the organic wavelength can be changed even after a long period of use under severe conditions of high temperature and humidity. The leaching of the conversion agent to the outermost layer side is extremely well suppressed, and deterioration of the optical properties and adhesion of the encapsulant sheet due to the bleed-out of the wavelength conversion agent can be avoided.

  As the organic wavelength conversion agent, a conventionally known agent can be used without any particular limitation. However, it is more preferable to select one in the above molecular weight range. Specifically, pyrazine derivatives, pyridine derivatives, triazole derivatives, benzoxazoyl derivatives, coumarin derivatives, styrene biphenyl derivatives, pyrazolone derivatives, bis (triazinylamino) stilbene disulfonic acid derivatives, bisstyryl biphenyl derivatives, bisbenzoxazolylthiophenes Derivatives, perylene derivatives, pyrene derivatives, pentacene derivatives, fluorescene derivatives, rhodamine derivatives, acridine derivatives, benzimidazole derivatives, flavone derivatives, and the like. Among these, in particular, any one derivative of pyrazine, pyridine, and triazole or a mixture thereof can be preferably used. For example, a low-molecular-weight organic wavelength conversion agent having a number average molecular weight of less than 100, such as a wavelength conversion agent consisting of a simple substance of triazole, can be sufficiently used. It is more advantageous in long-term weather resistance in a severe environment of high temperature and humidity.

  The amount of these organic wavelength conversion agents added to the sealing material composition for the intermediate layer is 0.05% by mass or more and 0.5% by mass or less, preferably 0.1% by mass or more and 0.4% by mass. The following is sufficient. Within this range, an optimal amount may be added as appropriate depending on the light emission intensity and quantum yield of each material, the thickness of each layer of the encapsulant sheet, and the like. When the addition amount of the organic wavelength conversion agent is less than 0.05% by mass, the wavelength conversion cannot be sufficiently performed, so that the power generation efficiency of the solar cell module cannot be sufficiently increased. On the other hand, when the addition amount of the organic wavelength conversion agent is more than 0.5% by mass, the deterioration of the optical properties of the encapsulant sheet due to the leaching of the wavelength conversion agent to the outermost layer and bleed out can be sufficiently avoided. Since it may become impossible, it is not preferable.

  As described above, the organic wavelength conversion agent added to the encapsulant composition for the intermediate layer is limited to those having a molecular weight of a certain level or more, and thus, only in the composition for the intermediate layer, an appropriate amount By adding in the range, the leaching of the wavelength conversion agent from the intermediate layer to the outermost layer after the sealing material sheet is formed can be sufficiently suppressed. And the wavelength conversion-type sealing material sheet which can exhibit a preferable wavelength conversion function, preventing the deterioration of the adhesiveness by the fall of the fluidity of an outermost layer, and the deterioration of the optical characteristic by the bleed-out of a wavelength conversion agent, and can do.

(Hindered amine light stabilizer (HALS))
In the encapsulant composition for the intermediate layer of the encapsulant sheet of the present invention, the following light stabilizer (A) is used as the hindered amine light stabilizer, or the light stabilizer (A) and the following The light stabilizer (B) is used in combination. Each of the light stabilizer (A) and the light stabilizer (B) is a high molecular weight type having a molecular weight of 1000 or more. These light stabilizers ((A) and (B)) are preferably added to the sealing material composition for the outermost layer as well as the composition for the intermediate layer.
Light stabilizer (A): A hindered amine light stabilizer having a molecular weight of 1000 or more and 10,000 or less having three or more piperidine rings in the side chain of the monomer unit. Light stabilizer (B): Piperidine ring in the main chain of the monomer unit. A single hindered amine light stabilizer with a molecular weight of 1,000 to 5,000

  The light stabilizer (A) is a hindered amine light stabilizer having three or more piperidine rings in the monomer unit and having a molecular weight of 1,000 to 10,000, preferably dibutylamine-1,3,5-triazine-N, N. '-Bis (2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine-N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate This compound is commercially available as Chimassorb 2020 and is CAS No. 192268-64-7, has a molecular weight of 2600 to 3400 and a melting point of 130 ° C to 136 ° C.

  The light stabilizer (B) is a compound marketed as KEMISTAB62, butanedioic acid 1- [2- (4-hydroxy-2,2,6,6-tetramethylpiperidino) ethyl], It is a compound of CAS number 65447-77-0. It has only one piperidine ring in the main chain of the monomer unit, has a molecular weight of 3100 to 4000, has a melting point of 55 ° C to 70 ° C, and is known as HALS for polyolefin applications.

  Even if a normal HALS is a high molecular weight type, when it is blended in a large amount, it has a characteristic that the glass adhesion is inferior and the initial glass adhesion strength is lowered. For this reason, in order to improve the initial glass adhesion strength, the blending amount is considerably small, and specifically, it is necessary to be 1% or less, more preferably 0.5% or less in the encapsulant sheet. However, this compounding amount results in insufficient radical absorption ability.

  Here, among various high molecular weight types of HALS, according to the knowledge newly obtained by the present inventors, the light stabilizer (A) has three or more piperidine rings in the side chain of the monomer unit. The radical trap absorption ability is extremely excellent. Therefore, it is extremely excellent in terms of suppressing haze deterioration over time and long-term glass adhesion. Therefore, in the manufacturing method of this invention, this light stabilizer (A) is selectively used as a main light stabilizer.

  On the other hand, the light stabilizer (B) has a small content dependency of the initial glass adhesion strength, and even if the content of the sealing material sheet is about 0.5% by mass or more, the initial glass adhesion strength does not decrease. There are features. However, when the light stabilizer (B) is used alone, there is a problem that a haze increase with time is observed, and it is known that a haze increase with time occurs even if the content is lowered. This reason is considered to be due to HALS aggregation or blooming. In addition, long-term glass adhesion tends to be slightly reduced.

  As described above, the light stabilizer (B) has advantages and disadvantages, but in the present invention, by using the light stabilizer (A) and the light stabilizer (B) in combination, haze rise suppression and long-term glass adhesion are more improved. A high level of compatibility is possible. In addition, the haze in this invention means the value measured by the measuring method in an Example, and means the thing of the one side external haze inclusion measured by the state which adhered to glass.

  The preferable content of the light stabilizer (A) and the light stabilizer (B) is 0.01% by mass or more and 1.0% by mass or less, more preferably 0.1% in total in the encapsulant sheet. It is not less than 0.5% by mass. The blending ratio when both are used in combination is not particularly limited, but is preferably about 1: 1.

(Crosslinking aid)
The encapsulant composition for the intermediate layer preferably further contains a crosslinking aid. As a crosslinking aid, a polyfunctional monomer having a carbon-carbon double bond and an epoxy group can be preferably used. More preferably, a crosslinking functional agent having a polyfunctional monomer whose functional group is an allyl group, a (meth) acrylate group or a vinyl group can be used. By adding such a crosslinking aid, the crystallinity of the low-density polyethylene can be reduced, and a sealing material sheet excellent in low-temperature flexibility can be obtained.

  Specifically, polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA) , Ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, etc. ) An acryloxy compound, a glycidyl methacrylate containing a double bond and an epoxy group, 4-hydroxybutyl acrylate glycidyl ether and 1, containing two or more epoxy groups - hexanediol diglycidyl ether, and 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, an epoxy-based compounds such as trimethylolpropane polyglycidyl ether. These may be used alone or in combination of two or more.

  Among these, tricyclodecane dimethanol diacrylate, which has a particularly high effect of improving adhesion to the glass surface, has good compatibility with low density polyethylene, and can be expected to improve heat resistance, can be particularly preferably used. The content of the crosslinking aid is preferably 0.01 parts by mass or more and 3 parts by mass or less, more preferably 0 with respect to 100 parts by mass in total of all resin components of the sealing material composition for the outer layer. .05 parts by mass or more and 2.0 parts by mass or less. By providing a multilayer sheet structure in which the crosslinking aid is contained only in the intermediate layer, sufficient heat resistance is simultaneously imparted to the encapsulant sheet while maintaining the adhesion and molding characteristics of the encapsulant sheet within a preferable range. be able to.

  In addition, in the manufacturing method of this invention, it is preferable not to add the said crosslinking adjuvant to the sealing material composition for outermost layers. This is because when a crosslinking aid is added to the sealing material composition for the outermost layer, there is a high risk of lowering adhesion due to lowering of fluidity or so-called bleeding out of the crosslinking aid.

[Encapsulant composition for outermost layer]
The sealing material composition for the outermost layer is a sealing material composition used for molding the outermost layer formed on both outermost surfaces of the multilayer sealing material sheet of the present invention. The sealing material composition for the outermost layer is a base resin made of a polyethylene resin, and preferably contains an adhesive copolymer resin such as a silane-modified polyethylene resin.

(Base resin)
As the polyethylene resin used as the base resin of the sealing material composition for the outermost layer (hereinafter also referred to as “base resin for the outermost layer”), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or Metallocene linear low density polyethylene (M-LLDPE) can be suitably used as appropriate.

Density of the polyethylene resin used as the base resin for the outermost layer, 0.870 g / cm ³ or more 0.970 g / cm ³ or less, preferably 0.870 g / cm ³ or more 0.930 g / cm ³ or less. And it is preferable that the density of base resin for outermost layers is a lower density than the base resin of the sealing material composition for intermediate | middle layers. More specifically, the density of the outermost layer base resin is preferably 93% or more and 99% or less of the density of the intermediate layer base resin. By setting the density of the base resin for the outermost layer within the above range, sufficient adhesion and molding characteristics can be imparted while maintaining the protection performance of the solar cell element. From the viewpoint of imparting molding characteristics, the density of the outermost layer is preferably as low as possible. However, by maintaining the density at 93% or more of the density of the intermediate layer, an excess of the organic wavelength conversion agent from the intermediate layer to the outermost layer is achieved. Leaching can be suppressed.

  As the base resin for the outermost layer, it is preferable to use a polyethylene-based resin in which the number of full double bonds remaining in the composition stage is relatively smaller than the number of full double bonds of the base resin for the intermediate layer. The number of full double bonds of the polyethylene resin that is the base resin for the outermost layer is preferably 0 or more and 1.0 or less, and more preferably 0 or more and 0.5 or less.

(Silane-modified polyethylene resin)
It is preferable that the sealing material composition for the outermost layer contains a silane-modified polyethylene resin in addition to the base resin. The silane-modified polyethylene resin is a resin obtained by graft polymerizing low-density polyethylene as a main chain, preferably linear low-density polyethylene, with an ethylenically unsaturated silane compound as a side chain. Since such a graft copolymer has a high degree of freedom of silanol groups that contribute to the adhesive force, it can improve the adhesion of the sealing material sheet to other members in the solar cell module. The silane-modified polyethylene resin in the present specification refers to, for example, a silane-modified polyethylene resin that can be produced by the following production method, and at least a part of a linear low-density polyethylene resin that becomes a main chain. Is a concept indicating a resin obtained by graft polymerization with an ethylenically unsaturated silane compound. The resin as a main chain of the above, as with the base resin, it is preferred that the density 0.870 g / cm ³ or more 0.900 g / cm ³ or less of the polyethylene resin.

The silane-modified polyethylene resin can be produced by the following method, for example, as described in JP-A-2003-46105. For example, one or more α-olefins, one or more ethylenically unsaturated silane compounds, and, if necessary, one or more other unsaturated monomers are desired. For example, the pressure is 500 kg / cm ² or more and 4000 kg / cm ² or less, preferably 1000 kg / cm ² or more and 4000 kg / cm ² or less, temperature, 100 ° C. or more and 400 ° C. or less, preferably Random copolymerization is performed simultaneously or stepwise in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent under conditions of 150 ° C. or higher and 350 ° C. or lower, and further generated by the copolymerization. A silane-modified polyethylene resin can be produced by modifying or condensing the silane compound portion constituting the random copolymer.

  As the polyethylene-based resin of the main chain, it is preferable to use linear low-density polyethylene that is an ethylene-α-olefin copolymer, and it is more preferable to use metallocene-based linear low-density polyethylene. Metallocene linear low density polyethylene is synthesized using a metallocene catalyst which is a single site catalyst. Such polyethylene has few side chain branches and a uniform comonomer distribution. For this reason, molecular weight distribution is narrow, it is possible to make it the above ultra-low density, and a softness | flexibility can be provided with respect to a sealing material sheet. As a result of the flexibility imparted to the sealing material sheet, the adhesion between the sealing material sheet and a transparent front substrate such as glass can be enhanced.

  As the α-olefin of the linear low density polyethylene, an α-olefin having no branch is preferably used. Among these, 1-hexene and 1-heptene which are α-olefins having 6 to 8 carbon atoms are preferable. Or 1-octene is particularly preferably used. When the number of carbon atoms of the α-olefin is 6 or more and 8 or less, the sealing material sheet can be given good flexibility and good strength. As a result, the adhesion between the encapsulant sheet and a transparent front substrate such as glass is further enhanced.

  Examples of ethylenically unsaturated silane compounds to be graft polymerized with linear low density polyethylene include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, and vinyltripentyloxysilane. , One or more selected from vinyltriphenoxysilane, vinyltribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane be able to.

  The graft amount, which is the content of the ethylenically unsaturated silane compound in the silane-modified polyethylene resin, is 0.001% by mass or more and 15% by mass or less, preferably 0.01% by content in the base resin of the silane-modified polyethylene resin. What is necessary is just to adjust suitably so that it may become 0.05 mass% or more and 2 mass% or less especially preferably 5 mass% or more. In the present invention, when the content of the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent. However, when the content is excessive, the tensile elongation and heat-fusibility tend to be inferior.

  Content in the sealing material composition for outermost layers of the silane modified polyethylene resin used for the sealing material composition for outermost layers of the sealing material sheet of this invention is 8 mass% or more and 45 mass% or less. Is preferred. In the present invention, if the content of the silane-modified polyethylene resin is 8% by mass or more, it is excellent in mechanical strength and heat resistance, but if the content is excessive, it tends to be inferior in tensile elongation and heat-fusibility. It is in.

  By using the silane-modified polyethylene resin described above as a component of the encapsulant composition for the outermost layer among the encapsulant composition for the solar cell module, it has excellent adhesion, strength, durability, etc. And it can be set as the sealing material sheet which is excellent in a weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other various characteristics. Various effects can be obtained in this way by using a silane-modified polyethylene-based resin, but in particular, it is extremely effective for a sealing material sheet without being affected by manufacturing conditions such as thermocompression bonding for manufacturing a solar cell module. As a general advantage, excellent heat-fusibility, that is, excellent adhesion to a glass substrate constituting a solar cell module can be given.

  Moreover, according to the addition of the silane-modified polyethylene resin to the outermost layer of the sealing material sheet of the present invention, not only the above general advantages, but also (bleed out) of the wavelength conversion agent is further suppressed. The effects specific to the present invention are also exhibited. This suppression of bleed-out is not caused by the silane-modified polyethylene resin staying inside the outermost layer but aggregating at the interface with the glass or solar cell element constituting the transparent front substrate to form Si—O—Si bonds. Thus, it is presumed that the wavelength conversion agent is an effect due to the delay of shifting to the surface of the encapsulant sheet. Also from the viewpoint of the effect specific to the present invention, addition of the silane-modified polyethylene resin to the outermost layer is preferable.

(Hindered amine light stabilizer (HALS))
In addition to the base resin, the hindered amine light stabilizer, the light stabilizer (A) alone, or the light stabilizer (A) and the light stabilizer (B) is also included in the sealing material composition for the outermost layer. In combination, it is preferable to contain them in the same formulation as when added to the intermediate layer.

[Other additives]
Any of the encapsulant compositions for the intermediate layer and the outermost layer may contain the following additives as necessary, as necessary.

(Crosslinking agent)
Each sealing material composition for the intermediate layer and the outermost layer may contain a necessary minimum amount of a crosslinking agent, but it is more preferable that the crosslinking agent is not added to any layer. While addition of a crosslinking aid to the intermediate layer described above allows adequate crosslinking to proceed sufficiently, a separate addition of a crosslinking agent such as an organic peroxide would result in integration with the solar cell module. This is because there is an increased risk of problems such as foaming due to degas during the heat laminating process. When adding a crosslinking agent, a well-known thing can be used and it does not specifically limit, For example, a well-known radical polymerization initiator can be used.

  When the crosslinking agent is added, the content thereof is preferably 0 to 0.5% by mass, more preferably 0 to the sealing material composition for the intermediate layer and the outermost layer. The range is 0.02 mass% or more and 0.5 mass% or less. When the addition amount of the crosslinking agent exceeds 0.5% by mass, the progress of crosslinking in the crosslinking process becomes excessive, and molding characteristics are insufficient, which is not preferable.

(Adhesion improver)
In each of the encapsulant compositions for the intermediate layer and the outermost layer, the adhesion durability with other base materials can be further enhanced by appropriately adding an adhesion improver. As the adhesion improver, a known silane coupling agent can be used. The silane coupling agent is not particularly limited. For example, vinyl-based silane coupling agents such as vinyltrichlorosilane, vinyltrimethoxysilane, and vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyldiethoxy. A methacryloxy-based silane coupling agent such as silane or 3-methacryloxypropyltriethoxysilane can be preferably used. In addition, these can also be used individually or in mixture of 2 or more types.

  When a silane coupling agent is added as an adhesion improver, the content thereof is 0.1% by mass or more and 10.0% by mass or less in the sealing material composition, and the upper limit is preferably 5.0% by mass. It is as follows. When the content of the silane coupling agent is in the above range, and the polyolefin resin constituting the encapsulant composition contains an appropriate amount of the ethylenically unsaturated silane compound, the adhesion is more preferable. And improve. In addition, when this range is exceeded, the film-forming property is lowered, and the silane coupling agent may bleed out, which is not preferable.

(Other ingredients)
Each sealing material composition for intermediate layer and outermost layer may further contain other components. For example, components such as various fillers, ultraviolet absorbers and heat stabilizers are exemplified. These contents vary depending on the particle shape, density, and the like, but are preferably in the range of 0.001% by mass to 5% by mass with respect to each sealing material composition. By including these additives, it is possible to impart a mechanical strength that is stable over a long period of time, an effect of preventing yellowing, cracking, and the like to the encapsulant sheet.

<Sealing material sheet>
The sealing material sheet of this invention is a multilayer sealing material sheet comprised by the intermediate | middle layer and the outermost layer arrange | positioned on both surfaces of an intermediate | middle layer. Then, the above-mentioned organic wavelength conversion agent, preferably in the specific molecular weight range, is added only to the intermediate layer, and the specific one or two types of HALS are selected as the intermediate layer and the outermost layer, and each layer is selected. It was produced by adding an appropriate amount.

  In addition, the content ratio of the wavelength conversion agent in the outermost layer after film formation is smaller than the content ratio of the wavelength conversion agent in the intermediate layer, and at least immediately after film formation, the content of the wavelength conversion agent in the intermediate layer. It is suppressed to ½ or less of the content ratio. More specifically, the content of the wavelength conversion agent in the intermediate layer in the encapsulant sheet after film formation is in the range of 0.05% by mass or more and 0.5% by mass or less, and the wavelength conversion in the outermost layer is performed. The content of the agent is in the range of 0% by mass to 0.25% by mass.

  The content of the wavelength conversion agent in the outermost layer may be 0%, or a part of the organic wavelength conversion agent leached from the intermediate layer may be included as long as it is within the above range. If it is content in the said range, even if the wavelength conversion agent has penetrate | invaded in the outermost layer, the initial optical characteristic and adhesiveness of a sealing material sheet can be fully hold | maintained in the preferable range. Hereinafter, as a preferred embodiment of the present invention, a sealing material sheet 1 having a three-layer structure in which a total of two outermost layers are laminated on the front and back of an intermediate layer that is a single layer will be described with reference to FIG. To do.

  The sealing material sheet 1 has an intermediate layer 11, and the outermost layer 12 is disposed on both surfaces of the intermediate layer 11. However, even if the intermediate layer itself has a multilayer structure and the sealing material sheet has other functional layers disposed in the intermediate layer, the intermediate layer includes the intermediate layer and the outermost layer having the configuration requirements of the present invention, and As long as it is a sealing material sheet having other constituent elements of the present invention, it is within the scope of the present invention.

  The intermediate layer 11 is a layer constituting a main part as a substrate layer in the encapsulant sheet 1. Furthermore, the intermediate layer 11 is also a wavelength conversion layer that imparts a wavelength conversion function to the encapsulant sheet 1 by containing a wavelength conversion agent. In addition, it is preferable that the intermediate | middle layer 11 is what the crosslinking process for the purpose of heat resistance improvement, such as the process which combined the appropriate amount addition of the crosslinking adjuvant, and irradiation of ionizing radiation, is performed. Thereby, the weather resistance and durability of the solar cell module can be further improved.

  The outermost layer 12 is a layer that is disposed on the outermost surface of the sealing material sheet in the sealing material sheet 1 and constitutes a subordinate portion as a surface material. The outermost layer 12 is a layer that mainly exhibits the effect of improving the adhesion as a solar cell module and the molding characteristics during the integration process.

  The encapsulant sheet 1 is also a multilayer sheet obtained by laminating resin sheets for each layer having different advantageous physical properties and special functions in an optimal arrangement. It is a wavelength conversion type sealing material sheet that is made of a polyethylene-based resin having a high water vapor barrier property and has an excellent balance of heat resistance, adhesion, and molding characteristics.

  The total thickness of the sealing material sheet 1 including the intermediate layer 11 and the outermost layer 12 is preferably 100 μm or more and 1000 μm or less, and more preferably 200 μm or more and 600 μm or less. If it is less than 100 μm, the impact cannot be sufficiently mitigated, and if it exceeds 1000 μm, no further effect can be obtained and it is uneconomical. In addition, the encapsulant sheet of the present invention has a flexibility in the outermost layer and heat resistance in the intermediate layer, thereby suppressing flow out and film thickness change during the laminating process. Even when the film is thinned, it is possible to provide sufficiently preferable molding properties, heat resistance, and solar cell element protection performance.

  About the ratio of the thickness of each layer in the sealing material sheet 1, the thickness ratio of the outermost layer 12: the intermediate layer 11: the outermost layer 12 may be in the range of 1: 2: 1 to 1: 30: 1. preferable. By setting the thickness ratio of each layer within this range, the heat resistance and molding characteristics of the sealing material sheet 1 can be maintained within a favorable range.

<Method for producing sealing material sheet>
[Sheet making process]
The melt molding of each composition for the intermediate layer and the outermost layer, each of which has been described in detail above, is a molding method usually used in ordinary thermoplastic resins, that is, injection molding, extrusion molding, hollow molding, compression molding, It is performed by various molding methods such as rotational molding. As an example of the forming method as the multilayer sheet, a method of forming by co-extrusion with two or more melt-kneading extruders can be given.

  The lower limit of the molding temperature at the time of molding may be a temperature exceeding the melting point of each sealing material composition. The upper limit of the molding temperature is, when a crosslinking agent is used, the temperature at which crosslinking does not start during film formation, that is, the gel fraction of the encapsulant composition, depending on the 1 minute half-life temperature of the crosslinking agent used. The temperature may be any temperature that can be maintained at 0%. Here, in the method for producing a sealing material sheet of the present invention, a crosslinking agent is not essential in the sealing material composition, and even when a crosslinking agent is added, its content is less than 0.5% by mass. It is limited to. For this reason, under a normal low density polyethylene resin molding temperature, for example, a heating condition of about 120 ° C., the gel fraction does not change, and the crosslinking that substantially affects the physical properties of the resin does not proceed. In addition, when the crosslinking treatment is performed by irradiation with ionizing radiation, a crosslinking agent having a half-life temperature higher than that of the conventional one can be used, which is freed from the restriction of heating conditions in the modularization process. In this case, the gel fraction of the encapsulant composition can be maintained at 0% even when the molding temperature is set higher than before. According to the manufacturing method that maintains the gel fraction of the encapsulant composition during film formation at 0%, it is possible to reduce the load on the extruder during film formation and increase the productivity of the encapsulant sheet. It is.

[Crosslinking process]
A cross-linking step of performing a cross-linking process by ionizing radiation on the uncross-linked encapsulant sheet after the sheet forming step is integrated with the other members after the completion of the sheet forming step. It is preferably performed before the start of the solar cell module integration step. By this crosslinking treatment, a sealing material sheet having a gel fraction of 2% to 80% is obtained.

  Regarding the crosslinking treatment by irradiation with ionizing radiation, the individual crosslinking conditions are not particularly limited. As a rough standard of specific irradiation amount, it may be appropriately set so that the gel fraction of the intermediate layer after the crosslinking treatment is in a range of about 10% or more. Specifically, it can be performed by ionizing radiation such as electron beam (EB), α-ray, β-ray, γ-ray, neutron beam, etc. Among them, it is preferable to use an electron beam. Further, the ionizing radiation may be irradiated from either one side or both sides. From the viewpoint of improving productivity, single-sided irradiation that is irradiation only from one outermost layer side is preferable.

  When ionizing radiation is applied by single-sided irradiation, the acceleration voltage is determined by the thickness of the sheet that is the object to be irradiated, and a thicker sheet requires a larger acceleration voltage. For example, in the case of a sheet having a thickness of 0.6 mm, irradiation is performed at 200 kV to 1000 kV, preferably 250 kV to 1000 kV. When the acceleration voltage is less than 200 kV, electrons do not pass through to the outermost layer on the non-irradiated surface side, and the heat resistance of the encapsulant sheet 1 becomes insufficient. On the other hand, when the acceleration voltage exceeds 1000 kV, electrons are uniformly transmitted through all the layers of the multilayer sheet, and it becomes impossible to form a storage elastic gradient structure which is a characteristic structure of the present invention. The irradiation dose is in the range of 5 kGy to 800 kGy, preferably 100 kGy to 500 kGy. Irradiation may be in an air atmosphere or a nitrogen atmosphere.

  Here, the gel fraction (%) means that 0.1 g of a sealing material sheet is put in a resin mesh, extracted with 60 ° C. toluene for 4 hours, taken out together with the resin mesh, weighed after drying, and mass before and after extraction. Comparison is made and the mass% of the remaining insoluble matter is measured, and this is used as the gel fraction.

  This crosslinking treatment may be performed continuously in-line following the sheet forming step, or may be performed off-line. Further, when the crosslinking treatment is a general heat treatment, generally, the content of the crosslinking agent is 0.5 parts by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of all components of the sealing material sheet. However, in the sealing material sheet of the present invention, the content of the crosslinking agent may be 0, and even if it is contained, it is preferably less than 0.5 parts by mass. Thereby, the risk of the productivity fall by gelatinization of the sealing material composition in the sheeting process of a sealing material composition can be reduced.

<Solar cell module>
Next, a preferred embodiment of the solar cell module of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view showing an example of the layer structure of the solar cell module 10 in which the sealing material sheet 1 of the present invention having a wavelength conversion function is arranged on the light receiving surface side of the solar cell element 3. The solar cell module 10 includes, from the light receiving surface side of incident light, the transparent front substrate 4, the sealing material sheet 1 for the light receiving surface side, the solar cell element 3, the sealing material sheet 2 for the non-light receiving surface side, and the back surface protection. Sheets 5 are laminated in order.

  In the solar cell module 10, the sealing material sheet 1 disposed on the light receiving surface side exhibits the wavelength conversion function and improves the power generation efficiency of the solar cell module 10 by being disposed on the light receiving surface side of the solar cell element. Let Further, due to the excellent molding characteristics of the outermost layer, it is possible to firmly adhere to uneven surfaces such as electrodes of the solar cell element 3.

  In the solar cell module 10, the encapsulant sheet 2 disposed on the non-light-receiving surface side may be the same sheet as the encapsulant sheet 1, but other polyethylene-based encapsulant having no wavelength conversion function. A sheet can be appropriately selected.

  As the encapsulant sheet 2 disposed on the non-light-receiving surface side, a polyethylene-based white encapsulant sheet obtained by adding a white colorant to a polyethylene resin as a base resin and coloring it white is particularly preferably used. it can. As a coloring agent for making the sealing material sheet 2 into a white sealing material sheet, a white coloring agent made of an inorganic compound can be preferably used. When the white sealing material sheet containing such a white colorant is arranged as the sealing material sheet 2 on the non-light-receiving surface side in the solar cell module 10, of the incident light to the solar cell module 10. By further introducing the sunlight that has not entered the solar cell element 3 and reached the non-light-receiving surface side to the light-receiving surface side of the solar cell element 3, the power generation efficiency of the solar cell module 10 can be further improved. it can.

  Although it does not specifically limit as said white colorant, For example, white pigments, such as a calcium carbonate, barium sulfate, a zinc oxide, and a titanium oxide, can be used preferably. Among these, titanium oxide can be particularly preferably used from the viewpoint of versatility.

  The white pigment preferably has a particle size of 0.5 μm to 1.5 μm. If the particle size of the white pigment is in the above range, the white layer formed from it effectively reflects near infrared rays in addition to the visible light region, so that the particles that can further contribute to the power generation efficiency improvement of the solar cell module. A typical example of a white pigment having a diameter of 0.5 μm or more and 1.5 μm or less is titanium oxide, and it is preferable to use titanium oxide as the white pigment in order to improve the reflection performance of sunlight.

  In addition, about the point of such power generation efficiency improvement, although it is desirable to whiten the sealing material layer by the side of the non-light-receiving surface in a solar cell module as mentioned above, light reflectivity other than white is obtained. If it is such a color tone, for example, it may be colored yellow, green, light blue or the like.

  Moreover, when the sealing material sheet 2 is a multilayer sheet similar to the sealing material sheet 1, it is more preferable that the coloring material is contained only in the intermediate layer. By setting it as such a structure, it can avoid that the adhesiveness of outermost layer falls by the influence of a coloring material.

  The layer configuration of the solar cell module of the present invention is not limited to the above embodiment. Since the sealing material sheet 1 of the present invention has adhesiveness to both glass and metal, taking advantage of its characteristics, the solar cell module of various configurations including a glass substrate and a metallic solar cell module can be used. Can be used for general purposes. For example, in a solar cell module, the encapsulant sheet of the present invention is preferably used even when one surface of the encapsulant sheet faces the metal surface and the other surface opposes the glass layer. be able to.

  The solar cell module 10 is formed by sequentially laminating the above-described module constituent members including the sealing material sheets 1 and 2 and the solar cell elements 3 and the like, and then integrating them by vacuum suction or the like, and then by a molding method such as a lamination method, These members can be manufactured by thermocompression molding as an integral molded body.

  In addition, in the solar cell module 10 of the present invention, conventionally known materials can be used for the transparent front substrate 4, the solar cell element 3, and the back surface protection sheet 5, which are members other than the sealing material sheet 1, without any particular limitation. . Moreover, the solar cell module 10 of this invention may also contain members other than the said member.

  While the present invention has been specifically described with reference to the embodiment, the present invention is not limited to the above embodiment, and can be implemented with appropriate modifications within the scope of the present invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

<Manufacture of sealing material sheet for solar cell module>
The raw materials of the encapsulant composition described below are mixed so that the contents in the encapsulant composition are in the ratios shown in Table 1 below, and the encapsulants of Examples, Comparative Examples, and Reference Examples, respectively. It was set as the sealing material composition for producing the sealing material sheet for inner layers and outer layers of a sheet | seat. Each sealing material composition is produced by using a φ30 mm extruder and a film forming machine having a 200 mm wide T die at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min to produce an inner layer and an outer layer sealing material sheet. These inner layer and outer layer encapsulant sheets were laminated to form a single or three-layer encapsulant sheet for solar cell modules (Examples, Comparative Examples and Reference Examples). Each of these encapsulant sheets had a thickness of 600 μm, and the outer layer: inner layer: outer layer thickness ratio was 1: 5: 1. In addition, as a raw material of a sealing material composition, the following raw materials were used.

[Polyethylene resin]
Metallocene linear low density polyethylene (M-LLDPE): Metallocene linear low density polyethylene having a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.5 g / 10 min was used as a base resin (Table 1 and described as “PE”).

[Silane-modified polyethylene resin]
Silane crosslinkable resin: vinyl trimethoxy 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 at 190 ° C. of 2 g / 10 min. A silane crosslinkable resin composed of 2 parts by mass of silane and 0.1 parts by mass of dicumyl peroxide as a radical generator (reaction catalyst) was used as a silane-modified polyethylene resin mixed with the base resin. The density of this resin is 0.884 g / cm ³ and the MFR at 190 ° C. is 1.8 g / 10 minutes (described as “S-PE” in Table 1).

[Light stabilizer A]
As a hindered amine light stabilizer, 2.28 parts by mass of a hindered amine light stabilizer (manufactured by BASF: Chimassorb 2020) with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ^3. Were mixed, melted, processed, and pelletized master batches were prepared. (Described as “HALS1” in Table 1)

[Light stabilizer B]
1. As a hindered amine light stabilizer, 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ³ , hindered amine light stabilizer (Kemipro Kasei Co., Ltd .: KEMISTAB62) 28 parts by mass were mixed, melted, processed, and pelletized master batch was prepared. (Described as “HALS2” in Table 1)

[Wavelength conversion agent]
As a wavelength converting agent, 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ³ is mixed with 1 part by mass of a triazole derivative (number average molecular weight: 3233) to be melted and processed. A pelletized master batch (MB) was prepared.

<Evaluation Example 1>
About the sealing material sheet | seat of an Example and a comparative example, a storage stability test (temperature 40 degreeC, humidity 90% RH, for three months) is performed, and the optical characteristic (HAZE) before and behind a storage stability test (JIS K7136, Murakami Color Research Co., Ltd.) And measured with a haze / transmittance system HM150) and glass adhesion. Regarding the optical characteristics, a haze of 5.0% or less was “◯”, and a haze of over 5.0% was “x”. The glass adhesion is 23 ° C. under a peeling condition of 50 mm / min at 180 ° peel using a peeling test apparatus (trade name “TENSILON RTA-1150-H” manufactured by A & D Co., Ltd.). In the peeling, 30 N / 15 mm was set as “◎”, 20 N / 15 mm or more as “◯”, and less than 20 N / 15 mm as “X”. The results are shown in Table 2.

<Evaluation Example 2>
On the glass substrate (white plate semi-tempered glass JPT3.2 75 mm x 50 mm x 3.2 mm), the sealing material sheets of Examples and Comparative Examples cut to a width of 15 mm were laminated, and heated in vacuum at 150 ° C for 18 minutes. It processed with the laminator and the solar cell module evaluation sample was obtained about each.

About the sealing material sheet | seat of an Example and a comparative example, 165 hours on the conditions of irradiance 180W / m < ² >, black panel temperature (BPT) 63 degreeC, and humidity 50% using the super xenon weather meter by Suga Test Instruments Co., Ltd. An irradiation test was performed. The quantum yield of the sealing sheet before and after the test was measured. Compared with the initial stage, those having a quantum yield maintenance ratio of more than 50% were indicated as “◯”, those having a quantum yield of 20% or more and 50% or less as “Δ”, and those having 20% or less as “X”. The results are shown in Table 2.

  From Table 2, it can be seen that, in the examples of the present invention, the optical properties, the glass adhesion, and the wavelength conversion function are all maintained within the preferable ranges even after the storage stability test. From the above, the wavelength conversion type sealing material sheet of the present invention is a sealing material sheet having excellent weather resistance and durability related to optical properties, glass adhesion, wavelength conversion function, and their physical properties and functions. I understand that.

DESCRIPTION OF SYMBOLS 1 Sealing material sheet 11 Intermediate layer 12 Outermost layer 2 Non-light-receiving surface side sealing material sheet 3 Solar cell element 4 Transparent front substrate 5 Back surface protection sheet 10 Solar cell module

Claims (14)

A sealing material sheet for a solar cell module,
The sealing material sheet is a multilayer sheet comprising an intermediate layer and an outermost layer disposed on both sides thereof,
Said intermediate layer and said outermost layer, and a density of 0.870 g / cm ³ or more 0.970 g / cm ³ or less of low density polyethylene-based resin,
The intermediate layer contains an organic wavelength conversion agent,
When the outermost layer includes the organic wavelength conversion agent, the content ratio thereof is smaller than the content ratio of the organic wavelength conversion agent in the intermediate layer,
The intermediate layer and the outermost layer contain a hindered amine light stabilizer,
As the hindered amine light stabilizer,
The sealing material sheet for solar cell modules in which the following light stabilizer (A) is used.
Light stabilizer (A): A hindered amine light stabilizer having a molecular weight of 1000 or more and 10,000 or less having three or more piperidine rings in the side chain of the monomer unit. The encapsulant sheet according to claim 1, wherein the light stabilizer (A) and the following light stabilizer (B) are used in combination as the hindered amine light stabilizer.
Light stabilizer (B): A hindered amine light stabilizer having a molecular weight of 1,000 to 5,000 having only one piperidine ring in the main chain of the monomer unit. The light stabilizer (A) is dibutylamine-1,3,5-triazine-N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine-N -(2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate,
The sealing according to claim 1 or 2, wherein the light stabilizer (B) is butanedioic acid 1- [2- (4-hydroxy-2,2,6,6-tetramethylpiperidino) ethyl]. Material sheet. The encapsulant sheet according to any one of claims 1 to 3, wherein the contents of the light stabilizers (A) and (B) in the intermediate layer and the outermost layer are as follows.
Light stabilizer (A): 0.01% by mass or more and 1.0% by mass or less Light stabilizer (B): 0.01% by mass or more and 1.0% by mass or less   The encapsulant sheet according to any one of claims 1 to 4, wherein the organic wavelength conversion agent is a wavelength conversion agent having a number average molecular weight of 100 to 1,000.   The encapsulant sheet according to any one of claims 1 to 5, wherein the organic wavelength converting agent is any one derivative of pyrazine, pyridine, and triazole, or a mixture thereof.   The sealing according to any one of claims 1 to 6, wherein a content ratio of the organic wavelength conversion agent in the outermost layer is ½ or less of a content ratio of the organic wavelength conversion agent in the intermediate layer. Stop sheet.   The sealing material sheet according to claim 1, wherein the outermost layer further contains a silane-modified polyethylene resin. A solar cell module comprising the encapsulant sheet according to any one of claims 1 to 8 and a solar cell element,
The solar cell module in which the said sealing material sheet is arrange | positioned at the light-receiving surface side of the said solar cell element. A method for producing a sealing material sheet for a solar cell module,
An intermediate layer made of a sealing material composition for the intermediate layer and the density 0.870 g / cm ³ or more 0.970 g / cm ³ or less of the polyethylene resin as a base resin, density 0.870 g / cm ³ or more 0.970 g A sheet forming step of forming a multilayer sheet by laminating an outermost layer made of a sealing material composition for an outermost layer made of polyethylene resin of / cm ³ or less,
In the sealing material composition for the intermediate layer, an organic wavelength conversion agent is contained in an amount of 0.05% by mass or more and 0.5% by mass or less,
The sealing material composition for the outermost layer does not contain a wavelength converting agent,
The intermediate layer and the outermost layer contain a hindered amine light stabilizer,
The manufacturing method of the sealing material sheet for solar cell modules which uses the following light stabilizer (A) as said hindered amine light stabilizer.
Light stabilizer (A): A hindered amine light stabilizer having a molecular weight of 1000 or more and 10,000 or less having three or more piperidine rings in the side chain of the monomer unit. The method for producing a sealing material sheet according to claim 10, wherein the light stabilizer (A) and the following light stabilizer (B) are used in combination as the hindered amine light stabilizer.
Light stabilizer (B): A hindered amine light stabilizer having a molecular weight of 1,000 to 5,000 having only one piperidine ring in the main chain of the monomer unit.   The method for producing an encapsulant sheet according to claim 10 or 11, wherein the organic wavelength conversion agent is a wavelength conversion agent having a number average molecular weight of 100 to 1,000.   The method for producing a sealing material sheet according to any one of claims 10 to 12, wherein the organic wavelength converting agent is any one derivative of pyrazine, pyridine, and triazole, or a mixture thereof.   The method for producing a sealing material sheet according to any one of claims 10 to 13, further comprising a crosslinking step of performing a crosslinking treatment on the multilayer sheet by irradiation with ionizing radiation.

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