JP2012209335A - Sealing material sheet for thin film type solar cell module, and thin film type solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for suppressing infiltration of water to a boundary surface between a sealing material sheet and an outer periphery of a transparent front substrate.SOLUTION: A single-layer or multi-layer sealing material sheet is used which contains 20 to 40 mass% metallocene-based linear low-density polyethylene of 0.870 to 0.890 g/cmin density in a composition, contains a silane copolymer obtained by copolymerizing α-olefin and an ethylene modified unsaturated silane compound with a copolymer, and has a layer formed of a composition of 2,000 to 15,000 ppm in polymerized silane amount of the silane copolymer.

Description

  The present invention relates to a sealing material sheet for a thin film solar cell module, and a thin film 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, solar cell modules configured in various forms have been developed and proposed.

  For example, a general thin-film solar cell module includes a solar cell element composed of a plurality of solar cells electrically connected in series or in parallel, and includes a transparent front substrate such as glass or plastic, a solar cell. It is the structure by which the element, the sealing material sheet | seat, and the back surface protection sheet were laminated | stacked sequentially. In the thin-film solar cell module, the solar cell element is formed at the center of the transparent front substrate, and the transparent front substrate is exposed at the outer periphery for insulation. As a result, the sealing material sheet that covers the solar cell element has a structure that is disposed between the transparent front substrate and the back surface protection sheet on the outer periphery thereof (for example, see Patent Document 1). In addition, the exposed surface on the outer periphery of the transparent front substrate is formed by laser processing or sandblasting to be a rough surface (for example, see Patent Document 2).

  Here, moisture may enter from the interface between the sealing material sheet and the outer periphery of the transparent front substrate or the interface between the sealing material sheet and the outer periphery of the back surface protective sheet. Moisture that has entered is problematic because it easily conducts electricity.

  For this reason, the technique which suppresses the penetration | invasion of the water | moisture content to the interface of the sealing material sheet and the outer periphery of a transparent front substrate or the interface of a sealing material sheet and the outer periphery of a back surface protection sheet is calculated | required.

JP 2006-310680 A JP 2000-150944 A

  This invention is made | formed in order to solve the above subject, The objective is to provide the technique which suppresses the penetration | invasion of the water | moisture content to the interface of a sealing material sheet and the outer periphery of a transparent front substrate.

  Conventionally, it was not thought that the rough surface of the transparent front substrate having a surface roughness Ra of about 0.10 μm would affect the ingress of moisture into the interface between the encapsulant sheet and the transparent front substrate. The inventors paid attention to the rough surface and conducted intensive research to solve the above problems. As a result, the surface roughness Ra is 0.10 μm or more in contact with the sealing material sheet, and the rough surface on the outer periphery of the transparent front substrate affects the adhesion between the sealing material sheet and the transparent front substrate. It has been found that moisture easily enters the interface between the stopper sheet and the outer periphery of the transparent front substrate, and further, if a specific sealing material sheet is used, the interface between the sealing material sheet and the outer periphery of the transparent front substrate The present inventors have found that the intrusion of moisture can be suppressed and have completed the present invention. More specifically, the present invention provides the following.

  Note that the rough surface exists on the outer periphery of the surface of the transparent front substrate in the present invention, as illustrated in FIG. 1, from the light receiving surface side, the transparent front substrate 2, the thin-film formed solar cell element 5, the sealing In the thin-film solar cell module 1 having a configuration in which the material sheet 3 and the back surface protection sheet 4 are sequentially laminated, the transparent front substrate 2 is formed on the side where the solar cell elements 5 are formed, that is, on the element surface side, and is transparent. It means that the rough surface 6 is formed at least at one location on the outer periphery 7 so as to communicate with the solar cell element 5 from the outer peripheral end portion of the front substrate 2. Due to the presence of the rough surface 6, moisture may enter the solar cell element 5 through the rough surface 6 from the interface between the transparent front substrate 2 and the sealing material sheet 3 on the end surface of the solar cell module 1. It is a prior art.

(1) A metallocene linear low-density polyethylene having a density in the range of 0.870 to 0.890 g / cm ³ is contained in the composition in an amount of 20% by mass to 40% by mass. A single-layer encapsulant sheet comprising a composition comprising a silane copolymer obtained by copolymerization with a saturated silane compound as a comonomer, wherein the amount of polymerized silane of the silane copolymer is from 2000 ppm to 15000 ppm, Or a thin-film solar cell comprising a multi-layer encapsulant sheet comprising an adhesion reinforcement layer composed of the composition, wherein the adhesion reinforcement layer is provided in the outermost layer in the case of the multi-layer encapsulant sheet An encapsulant sheet for modules.

(2) The single-layer encapsulant sheet described in (1) and the element surface of the transparent front substrate on which the solar cell element is formed as a thin film are laminated, or the multilayered sheet described in (1) The surface on the adhesion reinforcing layer side in the encapsulant sheet and the element surface of the transparent front substrate are laminated,
A thin film solar cell module in which a rough surface having a surface roughness Ra of 0.10 μm or more and 10 μm or less is formed on at least a part of the outer periphery of the element surface of the transparent front substrate.

  (3) The rough surface is formed by exposing the transparent front substrate to the outer periphery by scribing a part of the solar cell element formed on the outer periphery of the transparent front substrate by laser processing or sandblasting. The thin-film solar cell module according to (2).

  According to the present invention, moisture between the transparent front substrate and the sealing material sheet, such as between the sealing material sheet and the outer periphery of the transparent front substrate, between the sealing material sheet and the outer periphery of the back surface protection sheet, or the like. Infiltration can be sufficiently suppressed.

It is the partially expanded view of the cross section which shows an example of the laminated constitution of the thin film type solar cell module of this invention.

  Hereinafter, the sealing material sheet for a thin film type solar cell module and the thin film type solar cell module of the present invention will be described in this order.

<Sealant sheet for thin-film solar cell module>
The encapsulant sheet for solar cell module of the present invention comprises a metallocene linear low-density polyethylene having a density in the range of 0.870 to 0.890 g / cm ³ , an α-olefin, an ethylene-modified unsaturated silane compound, A single-layer encapsulant sheet composed of a composition containing, as an essential component, a silane copolymer obtained by copolymerizing a silane copolymer as a comonomer, or a multilayer encapsulating provided with an adhesion reinforcing layer composed of the composition It is a stopping material sheet.

[Metallocene linear low-density polyethylene]
The metallocene linear low density polyethylene contained in the adhesion reinforcing layer (hereinafter also simply referred to as the layer of the present invention) composed of the composition of the present invention is a copolymer of ethylene and α-olefin. And the density is in the range of 0.870 to 0.890 g / cm ³ . The 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 providing flexibility to the encapsulant sheet, the adhesion between the encapsulant sheet and the transparent front substrate, the adhesion between the encapsulant sheet and the back surface protective sheet, and the like between the encapsulant sheet and the transparent front substrate Since the adhesiveness is increased, it is possible to suppress the intrusion of moisture between the sealing material sheet and the transparent front substrate.

  In addition, since the crystallinity distribution is narrow and the crystal sizes are uniform, not only a large crystal size does not exist, but also the crystallinity itself is low due to the low density. For this reason, it is excellent in transparency when processed into a sheet shape. Therefore, even if the layer of the present invention is disposed between the transparent front substrate and the solar cell element, the power generation efficiency is hardly lowered.

  As the α-olefin used for the production of the metallocene-based linear low-density polyethylene, an α-olefin having no branch is preferably used, and among these α-olefins having 6 to 8 carbon atoms. Certain 1-hexene, 1-heptene or 1-octene is particularly preferably used. When the α-olefin has 6 to 8 carbon atoms, the solar cell module sealing material sheet can be provided with good flexibility and good strength. As a result, the adhesion between the encapsulant sheet and the transparent front substrate is further increased, and the above problem of moisture intrusion can be suppressed.

The density of the metallocene linear low density polyethylene is 0.870 to 0.890 g / cm ³ , preferably 0.875 to 0.888 g / cm ³ , and 0.878 to 0.885 g / cm ^{3. 3} is more preferable. If it is this range, favorable softness | flexibility can be provided, maintaining sheet workability, and the penetration | invasion of the said water | moisture content can be suppressed.

  The content of the metallocene linear low-density polyethylene contained in the layer of the present invention is 20% by mass or more and 40% by mass or less. When the content of the metallocene-based linear low-density polyethylene is 20% by mass or more, good flexibility can be imparted to the solar cell module encapsulant sheet, and the encapsulant sheet, the transparent front substrate, The problem of moisture intrusion during this period can be suppressed. When the content of the metallocene linear low-density polyethylene is 40% by mass or less, processing into a sheet is facilitated. The content of the metallocene linear low-density polyethylene contained in the layer of the present invention is preferably 25% by mass or more and 35% by mass or less, and more preferably 27% by mass or more and 32% by mass or less.

  The Shore D hardness of the metallocene-based linear low-density polyethylene is preferably 15 degrees or more and 40 degrees or less, and more preferably 15 degrees or more and 35 degrees or less. When the Shore D hardness of the metallocene linear low-density polyethylene is in the above range, the flexibility of the solar cell module sealing material sheet can be maintained. The melt mass flow rate (MFR) of the metallocene linear low-density polyethylene is preferably 0.5 g / 10 min or more and 8 g / 10 min or less at 190 ° C., and preferably 2 g / 10 min or more and 5 g / 10 min or less. It is more preferable that When the MFR of the metallocene linear low-density polyethylene is in the above range, the processability during film formation is excellent.

[Silane copolymer]
A silane copolymer is a copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer, and further copolymerizing with another unsaturated monomer as necessary. Further, a modified product or a condensate of the copolymer is also included. The layer of this invention improves the adhesiveness of a sealing material sheet and a transparent front substrate by containing the said silane copolymer. In particular, when the transparent front substrate is glass, the adhesion between the encapsulant sheet and the transparent front substrate is very high.

  Moreover, a preferable physical property is provided to a sealing material sheet because the said silane copolymer is contained in a sealing material sheet. For example, a silane copolymer provides strength and durability to a sealing material sheet, and also provides weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other characteristics. To do. Furthermore, the encapsulant sheet containing the silane copolymer has an extremely excellent heat-sealability without being affected by the production conditions such as thermocompression bonding when producing the solar cell module. Solar cell modules suitable for various applications can be manufactured at low cost.

  The silane copolymer is described in, for example, JP-A-2003-46105. Usable ethylenically unsaturated silane compounds include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentyloxysilane, vinyltriphenoxysilane, vinyl Examples include tribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane. Moreover, as an alpha olefin which can be used and other unsaturated monomers, the thing similar to what is described in Unexamined-Japanese-Patent No. 2003-46105 can be illustrated.

  The content of the ethylenically unsaturated silane compound when constituting the copolymer of the α-olefin and the ethylenically unsaturated silane compound is, for example, about 0.001 to 15% by mass relative to the mass of the silane copolymer. Preferably, about 0.01 to 5% by mass, particularly preferably about 0.05 to 3% by mass is desirable. 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 adhesiveness with the glass is excellent, but the content becomes excessive. , Tend to be inferior in tensile elongation and heat-fusibility.

The production method of the silane copolymer is not particularly limited. For example, one or more α-olefins, one or more ethylenically unsaturated silane compounds such as vinylalkoxysilane, and if necessary, , to one without the other unsaturated monomer and two or more, using the desired reaction vessels, for example, a pressure 500~4000Kg / cm ^2-position, preferably, 1000~4000Kg / cm ^2-position, temperature 100 - 400 In the presence of a radical polymerization initiator and, if necessary, a chain transfer agent under conditions of about 150 ° C., preferably about 150 to 350 ° C., at the same time or in stages, and further, if necessary, The α-olefin and ethylenically unsaturated silane compound are modified by condensing or condensing a portion of the silane compound constituting the random copolymer produced by the copolymerization. It is possible to produce a copolymer, or a modified or condensate of.

  The method for producing a copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof is not particularly limited. For example, if necessary, one or more α-olefins may be used. , One or more of the other unsaturated monomers, using the desired reaction vessel, as described above, in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent, simultaneously or stepwise Then, the polyolefin polymer produced by the polymerization is graft copolymerized with one or more ethylenically unsaturated silane compounds and, if necessary, produced by the copolymer. A copolymer of α-olefin and an ethylenically unsaturated silane compound or a modified silane compound portion of the graft copolymer is modified or condensed. And it can be produced condensate.

  Examples of the radical polymerization initiator and chain transfer agent that can be used for the production of the silane copolymer include those described in JP-A-2003-46105.

  Examples of the method of modifying or condensing the silane compound portion constituting the random copolymer, or the method of modifying or condensing the silane compound portion constituting the graft copolymer include, for example, tin, zinc, iron, lead, Using α-olefin and ethylenically unsaturated silane using metal carboxylate such as cobalt, organometallic compound such as titanate and chelate, organic base, inorganic acid, silanol condensation catalyst such as organic acid, etc. Modification of copolymer of α-olefin and ethylenically unsaturated silane compound by performing dehydration condensation reaction between silanols of the silane compound part constituting the random copolymer or graft copolymer with the compound The method of manufacturing a condensate is mentioned.

  As the silane copolymer used in the present invention, 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 more preferable. Since such a graft copolymer has a high degree of freedom of silanol groups that contribute to the adhesive force, the adhesion of the encapsulant sheet to the transparent front substrate in the solar cell module can be improved. When the adhesiveness of the sealing material sheet to the transparent front substrate is improved, it is preferable because moisture hardly enters from between the transparent front substrate and the sealing material sheet.

  In the present invention, the amount of polymerized silane of the silane copolymer is 2000 ppm or more and 15000 ppm or less in terms of mass ratio in the layer of the present invention. If it is 2000 ppm or more, the adhesion between the transparent front substrate and the encapsulant sheet becomes very strong, and it is used between the transparent front substrate and the encapsulant sheet by using together with the above-mentioned metallocene linear low density polyethylene. The problem of moisture intrusion can be sufficiently suppressed. The reason why it is 15000 ppm or less is that the adhesiveness between the encapsulant sheet and the transparent front substrate is not improved even if it exists more than 15,000 ppm. In addition, the amount of polymerized silane can specify the abundance in a composition by quantifying an element by ICP emission analysis etc., for example.

As the resin for addition to the silane copolymer, a resin compatible with the silane copolymer is preferable, and specific examples thereof include an unmodified polyolefin resin such as polyethylene. More specifically, a polyethylene resin is preferable, and a low-density copolymer of ethylene and an α-olefin is preferably used from the viewpoint of imparting transparency. An example of such a resin is a metallocene linear low density polyethylene. The metallocene linear low density polyethylene is synthesized using a metallocene catalyst which is a single site catalyst. Such a polyethylene resin has few side chain branches and a uniform distribution of comonomer. For this reason, it can be set as the polyethylene-type resin with narrow molecular weight distribution and a small density, and can provide a softness | flexibility to a sheet | seat. From the viewpoint of transparency, a metallocene linear low-density polyethylene having a density in the range of 0.870 to 0.915 g / cm ³ is preferable, and the α-olefin has 6 to 8 carbon atoms. preferable. The amount of the additive resin is preferably about 50 to 95% by mass with respect to the silane copolymer. The above-mentioned unmodified polyolefin resin can also be used as a resin for previously mastering a “other component” described later.

[Other resins]
The layer of the present invention can contain a resin other than the essential components. By including an inexpensive resin in the layer of the present invention, it is possible to obtain a sealing material sheet having excellent adhesion to the transparent front substrate at a low cost. Examples of the other resin include the unmodified polyolefin resin.

  The content of other resins in the layer of the present invention is not particularly limited, but is preferably about 10% by mass to 30% by mass.

[Other ingredients]
The layer of the present invention can further contain other components. For example, components such as a weather resistance masterbatch for imparting weather resistance to the sealing material sheet of the present invention, various fillers, a light stabilizer, an ultraviolet absorber, a heat stabilizer, and an antioxidant are exemplified. 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.

  A weatherproof masterbatch is a dispersion of a light stabilizer, ultraviolet absorber, heat stabilizer, antioxidant, etc., in a resin such as polyethylene, which is sealed by including the layer of the present invention. Good weather resistance can be imparted to the material sheet. The weatherproof masterbatch may be prepared and used as appropriate, or a commercially available product may be used. It does not specifically limit as resin used for a weatherproof masterbatch, Preferably unmodified polyolefin resin, such as a polyethylene-type resin, is illustrated. Since the unmodified polyolefin resin is the same as described above, the description thereof is omitted.

  These light stabilizers, ultraviolet absorbers, heat stabilizers and antioxidants can be used alone or in combination of two or more. Moreover, although content of a light stabilizer, a ultraviolet absorber, a heat stabilizer, and antioxidant changes with the particle shape, density, etc., it is 0.001-5 mass% in an adhesion reinforcement layer, respectively. It is preferable to be within the range.

  In addition to the above, other components that can be contained in the layer of the present invention include nucleating agents, crosslinking agents, dispersing agents, leveling agents, plasticizers, antifoaming agents, flame retardants, and the like.

  The encapsulant sheet for the solar cell module of the present invention (hereinafter sometimes simply referred to as “encapsulant sheet”) is a single-layer or multi-layer sheet comprising the above-described layers of the present invention. In the case of a multilayer, at least one of the outermost layers becomes an adhesion reinforcing layer. With such a layer structure, when the adhesion enhancing layer is in contact with at least one transparent front substrate, the adhesion between at least one transparent front substrate and the sealing material sheet is increased, and at least one transparent front substrate is sealed with the sealing material sheet. It is possible to suppress the intrusion of moisture from between the fixing material sheet.

  The sealing material sheet of the present invention is obtained, for example, by molding the above composition by a conventionally known method, and is, for example, a single-layer sheet or film. In addition, the sheet form in this invention means the film form, and there is no difference in both. A single layer is preferable because the entire sealing material sheet is composed of the adhesion reinforcing layer, and therefore the adhesion reinforcing layer comes into contact with both transparent front substrates. When it is necessary to reduce the amount of expensive components such as a silane copolymer used for the purpose of reducing the production cost, the concentration of the expensive components may be increased in the vicinity of the laminated surface and decreased in the interior. In addition, you may make it the density | concentration of a specific component change within a sealing material sheet not only an expensive component.

  The above composition is formed into a sheet or film by various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding, which are usually used in ordinary thermoplastic resins. Thus, by forming the composition into a sheet or film, as the sealing material sheet of the present invention, a single-layer sheet composed only of an adhesion reinforcing layer composed of the solar cell module sealing material composition, or A multilayer sheet provided with the adhesion reinforcing layer is obtained.

  The encapsulant sheet may be a single layer sheet or a multilayer sheet. In the case of a multilayer sheet, in order to improve the adhesion with the transparent front substrate, it is sufficient that an adhesion reinforcing layer is disposed at least on the outermost layer. For this reason, for example, an adhesion reinforcing layer may be arranged in only one layer with a two-layer structure of the sealing material sheet, and an adhesion reinforcing layer is arranged in at least one outermost layer as a structure of three or more layers across the core layer May be. Thereby, the usage-amount of an expensive silane copolymer etc. can be suppressed and the sealing material sheet of this invention can be manufactured at lower cost. Although the component contained in a core layer is not specifically limited, The above-mentioned silane copolymer, other resin, and another component can be contained preferably. In order to produce a sealing material sheet composed of a multilayer film as described above, for example, a conventionally known T-die multilayer coextrusion method can be used.

<Solar cell module>
The solar cell module of the present invention is a transparent front substrate made of glass or the like, in order to improve the adhesion between the thin film solar cell element and the element surface which is the side on which the rough surface is formed. The layer of this invention should just be arrange | positioned at the element surface side. Here, as described above, a rough surface having a surface roughness Ra of 0.10 μm to 10 μm is formed on the outer periphery of the transparent front substrate used in the solar cell module of the present invention. In the solar cell module of this invention, it is comprised so that the layer of this invention may be arrange | positioned on said rough surface.

  When a rough surface having a surface roughness Ra of 0.10 μm or more is formed, if a conventional sealing material sheet is used, the adhesion between the transparent front substrate and the sealing material sheet is not sufficient. Water can easily enter through the space between the stop sheet. However, when the layer of the present invention is laminated on the rough surface, the adhesion between the encapsulant sheet and the transparent front substrate is greatly increased, and as a result, water enters between the transparent front substrate and the encapsulant sheet. Can be suppressed. Since the layer of the present invention contains a large amount of active silane, the adhesion due to the chemical bond between the encapsulant sheet and the transparent front substrate is increased, and the layer of the present invention has a metallocene linear low molecular weight. This is because the inclusion of the density polyethylene makes the encapsulant sheet very flexible and improves the adhesion between the encapsulant sheet and the transparent front substrate. The reason why the surface roughness of the rough surface is adjusted to 10 μm or less is that scribing such that the surface roughness is 10 μm or more is not necessary in consideration of the thickness of the transparent conductive film.

  The rough surface having a surface roughness Ra of 0.10 μm or more and 10 μm or less may be formed in any way, but in the case of a thin film type solar cell module, it is formed on the outer periphery on the transparent front substrate. When the solar cell element is scribed, a rough surface having a surface roughness Ra of 0.10 μm to 10 μm is formed. The scribing is performed by means such as sandblasting or laser processing. Therefore, when the sealing material sheet of the present invention is used for a thin film type solar cell module, the resulting thin film type solar cell module hardly receives moisture from between the transparent front substrate and the sealing material sheet.

  The method for producing the solar cell module of the present invention is not particularly limited, and a rough surface having a surface roughness Ra of 0.10 μm or more and 10 μm or less exists on the outer periphery of the transparent front substrate, and the present invention is formed on this rough surface. If the sealing material sheet of this is arrange | positioned, the solar cell module of this invention can be manufactured with the method of manufacturing a conventionally well-known thin film type solar cell module.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited to these Examples.

<Metallocene linear low density polyethylene>
It is a copolymer of ethylene and 1-hexene, and has a density of 0.880 g / cm ³ , a melt mass flow rate (MFR) at 190 ° C. of 3.4 g / 10 min, and a metallocene-based linear low with a Shore D hardness of 17 Density polyethylene was used.

<Silane copolymer>
With respect to 98 parts by mass of a metallocene linear low density polyethylene having a density of 0.898 g / cm ³ and an MFR at 190 ° C. of 2 g / 10 minutes, 2 parts by mass of vinyltrimethoxysilane and a radical generator ( Dicumyl peroxide (0.1 part by mass) as a reaction catalyst) was mixed and melted and kneaded at 200 ° C. to obtain a silane copolymer. The density of this resin was 0.901 g / cm ³ , and the MFR at 190 ° C. was 1.0. Moreover, it adjusted so that silane modification amount might be 2.1 mass% to 2.8 mass% in a silane copolymer.

<Other resins>
As another resin, a metallocene linear low density polyethylene (hereinafter referred to as “other LLDPE”) having a density of 0.901 g / cm ³ and an MFR at 190 ° C. of 2 g / 10 min was used.

<Other ingredients>
As other components, a weather-resistant masterbatch prepared by the following method was used.
With respect to 91.5 parts by mass of powder obtained by pulverizing Ziegler linear low-density polyethylene having a density of 0.924 g / cm ³ , 4.6 parts by mass of a hindered amine light stabilizer, 3.4 parts by mass of benzophenone, and phosphorous heat A weathering master batch was prepared by mixing and melting and processing 0.5 parts by mass of a stabilizer and pelletizing.

<Manufacture of sealing material sheet>
In this example, the following types of compositions were prepared in order to produce a solar cell module encapsulant sheet having a three-layer structure of outer layer / core layer / outer layer. The same composition was used for both outer layers. In all the sealing material sheets, the composition 1 was used for the core layer. In addition, if the compositions 5 and 6 are used in the compositions 1-6 mentioned later, an adhesion reinforcement layer can be manufactured.

[Outer layer 1 / core layer]
In addition, 90 parts by mass of LLDPE, 10 parts by mass of the silane copolymer, and 5 parts by mass of the weather resistant masterbatch were mixed to obtain Composition 1. This composition does not contain in the composition a metallocene-based linear low-density polyethylene having a density in the range of 0.870 to 0.890 g / cm ³ , and the amount of polymerized silane in the silane copolymer is in the composition 1200 ppm.

[Outer layer 2]
In addition, 80 parts by mass of LLDPE, 20 parts by mass of a silane copolymer, and 5 parts by mass of a weather resistant masterbatch were mixed to obtain composition 2. This composition does not contain in the composition a metallocene-based linear low-density polyethylene having a density in the range of 0.870 to 0.890 g / cm ³ , and the amount of polymerized silane in the silane copolymer is in the composition Is 2500 ppm.

[Outer layer 3]
In addition, 50 parts by mass of LLDPE, 50 parts by mass of the silane copolymer, and 5 parts by mass of the weather resistant masterbatch were mixed to obtain a composition 3. This composition does not contain in the composition a metallocene-based linear low-density polyethylene having a density in the range of 0.870 to 0.890 g / cm ³ , and the amount of polymerized silane in the silane copolymer is in the composition 6200 ppm.

[Outer layer 4]
In addition, 30 parts by mass of LLDPE, 70 parts by mass of a silane copolymer, and 5 parts by mass of a weather resistant masterbatch were mixed to obtain a composition 4. This composition does not contain in the composition a metallocene-based linear low-density polyethylene having a density in the range of 0.870 to 0.890 g / cm ³ , and the amount of polymerized silane in the silane copolymer is in the composition 8900 ppm.

[Outer layer 5]
In addition, 50 parts by mass of LLDPE, 20 parts by mass of a silane copolymer, 30 parts by mass of a metallocene linear low-density polyethylene, and 5 parts by mass of a weather-resistant masterbatch were mixed to prepare composition 5. Obtained. This composition contains 30% by mass of a metallocene-based linear low-density polyethylene having a density in the range of 0.870 to 0.890 g / cm ^{3 in} the composition, and the amount of polymerized silane in the silane copolymer is the composition. It is 2500 ppm in the product.

[Outer layer 6]
In addition, 20 parts by mass of LLDPE, 50 parts by mass of a silane copolymer, 30 parts by mass of a metallocene linear low-density polyethylene, and 5 parts by mass of a weather resistant masterbatch were mixed, Obtained. This composition contains 30% by mass of a metallocene-based linear low-density polyethylene having a density in the range of 0.870 to 0.890 g / cm ^{3 in} the composition, and the amount of polymerized silane in the silane copolymer is the composition. It is 6200 ppm in the product.

<Evaluation 1>
For evaluation 1, a sealing material sheet for a solar cell module was prepared. The composition for the outermost layer shown in Table 1 and the composition 1 for the solar cell module for the core layer were extruded in three layers by a conventional method, and produced by a film forming machine having a T die having a width of 2 m. The film formation temperature was set to 170 to 220 ° C. from the cylinder to the T die, and the temperature of the resin composition was 230 ° C. or lower. The ratio of the thicknesses of the first layer, the second layer, and the third layer was 1: 5: 1, and the total thickness was 400 μm.

The sealing material sheet was pressure-bonded at 150 ° C. for 15 minutes with the following three types of glass plates using a vacuum laminator for manufacturing a solar cell module.
(Glass)
AED glass: Glass whose outer periphery is roughened by sandblasting (the surface roughness Ra of the rough surface is 2.85 μm).
LED glass: Glass whose outer periphery is roughened by laser processing (surface roughness Ra of the rough surface is 0.10 μm).
Blue plate glass: Commercially available product (surface roughness Ra is 0.02 μm)

  The glass on which the sealing material sheet is laminated is stored in an alkaline atmosphere (85 ° C. warm water at pH 7, 85 ° C. warm water at pH 10 and 85 ° C. warm water at pH 11) for 3 days, respectively. The change with time was confirmed. For the glass adhesion strength, peel strength (unit: N / 15 mm) at a width of 15 mm was measured according to JIS Z1707. The measurement results are shown in Table 2.

  As is clear from the results of Table 2 above, it was confirmed that a rough surface having a surface roughness Ra of about 0.10 μm affects the ingress of moisture into the interface between the transparent front substrate and the sealing material sheet. Moreover, it was confirmed that it becomes difficult for water to enter the interface between the transparent front substrate and the sealing material sheet by increasing the amount of the silane copolymer used.

<Evaluation 2>
A sealing material sheet of Example 1 was produced in the same manner as in Evaluation 1 except that the composition 5 was used as the composition for the outer layer. And Example 1 was laminated on AED glass and LED glass in the same manner as in Evaluation 1, and the adhesion strength between the sealing material sheet and the glass was evaluated. The evaluation results are shown in Table 3. Table 3 also shows the results of Evaluation Example 2 for reference.

  As is clear from the results in Table 3, Example 1 containing a highly flexible metallocene-based linear low-density polyethylene and a specific silane copolymer has moisture at the interface between the transparent front substrate and the encapsulant sheet. It was confirmed that it was difficult to enter.

<Evaluation 3>
A sealing material sheet of Example 2 was produced in the same manner as in Evaluation 1 except that the composition 6 was used as the composition for the outer layer. And this sealing material sheet was laminated on AED glass and LED glass by the same method as evaluation 1, and the adhesive strength of a sealing material sheet and glass was evaluated. The evaluation results are shown in Table 4. Table 4 also shows the results of Evaluation Example 3 and Example 1 for reference.

  As is clear from the results in Table 4, by increasing the amount of silane copolymer used and using a highly flexible metallocene linear low density polyethylene, the adhesion between the glass and the encapsulant sheet is improved. It becomes very high, and there is almost no problem of moisture entering between the transparent front substrate and the sealing material sheet.

<Evaluation 4>
Finally, the tensile strength, tensile elongation, water vapor permeability, volume resistivity, dielectric breakdown voltage, total light transmittance, and haze of the sealing material sheet of Example 2 were measured. The measurement method is as shown below, and Table 5 shows the results of the sealing material sheet of Example 2 and these physical property values of the sealing material sheet composed of commonly used EVA resin.

Tensile strength (MPa) and tensile elongation (%) were measured according to JIS K-7127.
The water vapor permeability (g / {(m ² · 24h) · (400 µm)}) was measured according to the JIS K-7129 B method.
The volume resistivity (Ω · cm) was measured according to JIS K6911.
The dielectric breakdown voltage (kV / mm) measured the dielectric breakdown voltage (kV) per 1 mm thickness of the sealing material sheet using a withstand voltage tester based on JIS C-2110. With regard to the dielectric breakdown voltage, when a sample having electrical insulation is sandwiched between two electrodes and then the voltage is gradually increased, the current increases rapidly, and a part of the sealing material sheet is melted and a hole is formed. It shows the voltage when it is energized by carbonization or carbonization.
The total light transmittance (%) and haze were measured according to JIS K7105.

  As is apparent from the evaluation results in Table 5, the encapsulant sheet of the present invention sufficiently satisfies the physical properties required for the encapsulant sheet for solar cell modules.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Transparent front substrate 3 Front sealing material 4 Back surface protection sheet 5 Solar cell element 6 Rough surface 7 Outer periphery

Claims (3)

A metallocene-based linear low density polyethylene having a density in the range of 0.870 to 0.890 g / cm ³ is contained in the composition in an amount of 20% by mass to 40% by mass,
A silane copolymer obtained by copolymerization of an α-olefin and an ethylene-modified unsaturated silane compound as a comonomer is contained, and the amount of polymerized silane of the silane copolymer is 2000 ppm to 15000 ppm. A multi-layer encapsulant sheet comprising a layer encapsulant sheet or an adhesion reinforcement layer composed of the composition, wherein the adhesion reinforcement layer is provided in the outermost layer in the case of the multilayer encapsulant sheet A sealing material sheet for a thin-film solar cell module. The single-layer encapsulant sheet according to claim 1 and the element surface of the transparent front substrate on which the solar cell element is formed as a thin film are laminated, or
The surface on the adhesion reinforcing layer side in the multilayer encapsulant sheet according to claim 1 and the element surface of the transparent front substrate are laminated,
A thin film solar cell module in which a rough surface having a surface roughness Ra of 0.10 μm or more and 10 μm or less is formed on at least a part of the outer periphery of the element surface of the transparent front substrate.   The rough surface is formed by exposing the transparent front substrate to the outer periphery by scribing a part of the solar cell element formed on the outer periphery of the transparent front substrate by laser processing or sandblasting. The thin film type solar cell module according to claim 2.

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