JP5589498B2 - Filler composition for solar cell module and filler for solar cell module - Google Patents

Description

  The present invention relates to a filler composition for a solar cell module, a filler for a solar cell module using the same, and a solar cell module incorporating the same.

  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. In general, a solar cell module has a configuration in which a transparent front substrate, a solar cell element, and a back surface protection sheet are laminated via a filler (sealing material).

  As a filler for a solar cell module, a configuration mainly containing EVA (ethylene-vinyl acetate copolymer) from the viewpoint of transparency and fluidity and containing a crosslinking agent and a crosslinking aid is known (Patent Document). 1). In this case, the above composition is formed uncrosslinked and crosslinked by heating during modularization.

  Moreover, as a filler of another solar cell module, PBR (propylene-butene copolymer) which is a low crystalline α-olefin having a crystallinity of 40% or less, EBR (ethylene-butene copolymer), A configuration containing an EPR (ethylene-propylene copolymer) and the like, a crosslinking agent, and a crosslinking aid is known (see Patent Document 2).

  Furthermore, in applications such as electric wires, it is also known to perform crosslinking by reacting an olefin resin such as HDPE with a crosslinking agent (photoreaction initiator) and a crosslinking aid (see Patent Document 3). .

JP 2009-135200 A JP 2006-210906 A JP-A-5-4235

  The EVA of Patent Document 1 has the advantage of being excellent in transparency and fluidity, but has the basic drawback of poor water vapor barrier properties. In Patent Document 2, although the water vapor barrier property is improved by using a low crystalline olefin as a base, the elastic modulus is particularly high near room temperature and the flexibility is not sufficient.

  In addition, as in Patent Document 3, the olefin resin is cross-linked to increase the strength in the electric wire field, but as a filler for solar cells, there are many other physical properties such as transparency and flexibility. It is required to charge at the same time. And the olefin type bridge | crosslinking type solar cell module filler which satisfy | fills all these physical properties has not been obtained yet.

  The present invention has been made in order to solve the above problems, and its purpose is to have excellent water vapor barrier properties and processing such as cutting because the strength before crosslinking treatment is higher than that of EVA. The other object is to provide an olefin-based solar cell module filler that has superiority in characteristics and satisfies the required physical properties similar to those of EVA.

  The present inventors use olefin as a base resin and crosslink it with a predetermined monomer, thereby reducing the crystallinity inherent to olefin. In terms of flexibility, the inventors have found that it is possible to obtain the same physical properties as EVA, and have completed the present invention. More specifically, the present invention provides the following.

  (1) Filler composition for solar cell module comprising low density polyethylene having a density of 0.940 or less, a crosslinking agent, and a crosslinking aid comprising a polyfunctional vinyl monomer and / or a polyfunctional epoxy monomer. .

  (2) The filler composition for solar cell modules according to (1), further comprising a radical absorbent.

  (3) The filler composition for solar cell modules according to (1) or (2), wherein the low-density polyethylene has a density of 0.900 or less.

  (4) The crosslinking aid is trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate, 1,6-hexanediol diacrylate, and 1,9-nonanediol diacrylate. The filler composition for solar cell modules according to any one of (1) to (3), which is one or more selected from the above.

  (5) The solar cell module filler having a gel fraction of 80% or less after crosslinking after molding the filler composition for solar cell modules according to any one of (1) to (4). .

(6) The filler for a solar cell module according to (5), wherein the crosslinking treatment is performed when the solar cell module is assembled.
(7) A solar cell module comprising the solar cell module filler according to (5) or (6).

  According to the filler composition for a solar cell module of the present invention and the filler formed by molding the filler for a solar cell module that has been crosslinked after molding, it has excellent water vapor barrier properties and strength before crosslinking treatment Since it is higher than EVA, it has an advantage in processing characteristics such as cutting, and other performance can provide an olefin-based filler for solar cell modules that satisfies the required physical properties of the same level as EVA.

It is a graph which shows the measurement result of the Young's modulus in an Example. It is sectional drawing which shows an example of the laminated constitution of the solar cell module of this invention.

  Hereinafter, the filler composition for solar cell modules, the filler for solar cell modules, and the solar cell module of the present invention will be described in detail in this order.

<Filler composition for solar cell module>
The filler composition for solar cell modules of the present invention contains low density polyethylene having a density of 0.940 or less, a crosslinking agent, and a crosslinking aid as essential components. Hereinafter, after explaining these essential components, other resins and other components will be explained.

[Low density polyethylene]
In the present invention, low density polyethylene (LDPE) having a density of 0.940 or less, preferably linear low density polyethylene (LLDPE) is used. Linear low density polyethylene is a copolymer of ethylene and α- olefin, in the present invention, within the scope thereof density of 0.940 g / cm ³ or less, preferably 0.900 g / cm ³ within the following ranges More preferably, it is the range of 0.870-0.890 g / cm < ³ >. If it is this range, favorable softness | flexibility and transparency can be provided, maintaining sheet workability, and the penetration | invasion of the water | moisture content from an end surface can be suppressed.

  In the present invention, it is preferable to use a metallocene 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 filler. As a result of imparting flexibility, the adhesion between the filler and the transparent front substrate, the adhesion between the filler and the substrate, such as the adhesion between the filler and the back surface protective sheet, is increased. Intrusion of moisture into the space can be suppressed.

  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 filler comprising the filler composition 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 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 α-olefin has 6 to 8 carbon atoms, the solar cell module filler can be given good flexibility and good strength. As a result, the adhesion between the filler and the base material is further increased, and the above problem of moisture intrusion can be suppressed.

  The Shore D hardness of the low density polyethylene is preferably 80 degrees or less, 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 linear low density polyethylene is in the above range, the flexibility of the solar cell module filler can be maintained. Further, the melt mass flow rate (MFR) of the linear low density polyethylene is preferably 0.5 g / 10 min or more and 40 g / 10 min or less at 190 ° C., and preferably 2 g / 10 min or more and 40 g / 10 min or less. Is more preferable. When the MFR is in the above range, the processability during film formation is excellent.

The content of the linear low density polyethylene having a density of 0.940 g / cm ³ or less contained in the solar cell module filler composition is preferably 10% by mass or more and 99% by mass or less, more preferably in the composition. Is 50% by mass or more and 99% by mass or less, more preferably 90% by mass or more and 99% by mass or less. In other words, other resins may be contained within this range. For example, other polyethylene resins exceeding 0.940 g / cm ³ can be exemplified. These may be used, for example, as an additive resin, and can be used for masterbatching other components described later.

[Crosslinking agent]
A well-known thing can be used for a crosslinking agent, It does not specifically limit, For example, a well-known radical polymerization initiator can be used. Examples of radical polymerization initiators include hydroperoxides such as diisopropylbenzene hydroperoxide and 2,5-dimethyl-2,5-di (hydroperoxy) hexane; di-t-butyl peroxide, t-butyl Cumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-peroxy) hexyne-3, etc. Dialkyl peroxides; diacyl peroxides such as bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, benzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dichlorobenzoyl peroxide; t-butyl peroxyacetate, t-butyl pero Ci-2-ethylhexanoate, t-butyl peroxypivalate, t-butyl peroxyoctoate, t-butyl peroxyisopropyl carbonate, t-butyl peroxybenzoate, di-t-butyl peroxyphthalate, 2 , 5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexyne-3, t-butylperoxy-2-ethylhexyl carbonate Oxyesters; organic peroxides such as methyl peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, or azo compounds such as azobisisobutyronitrile and azobis (2,4-dimethylvaleronitrile), dibutyltin Diacetate, Dibutyltin dilaurate , It may be mentioned dibutyltin dioctoate, dioctyltin dilaurate, dicumyl peroxide, such a silanol condensation catalyst. As content of a crosslinking agent, it is preferable that 0.01 mass%-2 mass% are contained in a composition, More preferably, it is the range of 0.05 mass%-1.5 mass%.

[Crosslinking aid]
In the present invention, a polyfunctional vinyl-based monomer and / or a polyfunctional epoxy-based monomer is used as a crosslinking aid, thereby promoting an appropriate crosslinking reaction to a gel fraction of 80% or less. This crosslinking aid reduces the crystallinity of the linear low density polyethylene and maintains transparency. As a result, it is possible to obtain a filler that is more excellent in transparency and low-temperature flexibility, and specifically, it is possible to obtain transparency and low-temperature flexibility equivalent to those of EVA.

  Specifically, polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA) Poly (meth) acryloxy compounds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, Glycidyl methacrylate containing epoxy groups, 4-hydroxybutyl acrylate glycidyl ether and 1,6-hexanediol diglycidyl ether containing two or more epoxy groups, 1 4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and epoxy compounds such as trimethylolpropane polyglycidyl ether. These may be used alone or in combination of two or more.

  Among these, TAIC is preferably used from the viewpoint of good compatibility with low density polyethylene, lowering crystallinity by crosslinking, maintaining transparency, and imparting flexibility at low temperatures.

  The amount of the crosslinking aid used is preferably 0.01 to 3% by mass, more preferably 0.05 to 2.0 parts by mass in the composition. Within this range, an appropriate crosslinking reaction can be promoted to make the gel fraction 80% or less.

[Radical absorbent]
In the present invention, the gel fraction can be adjusted more finely by adjusting the degree of cross-linking by using the above-mentioned cross-linking auxiliary agent serving as a radical polymerization initiator in combination with the radical absorbent for quenching it. . Examples of such radical absorbers include hindered phenol-based antioxidants, hindered amine-based weather resistance stabilization, and the like. A hindered phenol-based radical absorbent having a high radical absorbing ability near the crosslinking temperature is preferred. It is preferable that the usage-amount of a radical absorber is contained in 0.01 to 3 mass% in a composition, More preferably, it is the range of 0.05 mass part-2.0 mass parts. If it exists in this range, a crosslinking reaction can be suppressed moderately and a gel fraction can be 80% or less.

[Other ingredients]
The filler composition for a solar cell module can further contain other components. For example, components such as a weather resistance masterbatch, various fillers, a light stabilizer, an ultraviolet absorber, a heat stabilizer, etc. for imparting weather resistance to the filler prepared from the filler composition for solar cell modules of the present invention Is exemplified. These contents vary depending on the particle shape, density, etc., but are preferably in the range of 0.001 to 5 mass% in the solar cell module filler composition. By including these additives, it is possible to impart, to the solar cell module filler composition, a mechanical strength that is stable over a long period of time, an effect of preventing yellowing, cracking, and the like.

  The weatherproof masterbatch is obtained by dispersing a light stabilizer, an ultraviolet absorber, a heat stabilizer and the above-mentioned antioxidant in a resin such as polyethylene, and this is used as a filler composition for solar cell modules. By adding, good weather resistance can be imparted to the solar cell module filler. The weatherproof masterbatch may be prepared and used as appropriate, or a commercially available product may be used. The resin used in the weatherproof masterbatch may be a linear low density polyethylene used in the present invention, or other resins described above.

  These light stabilizers, ultraviolet absorbers, heat stabilizers and antioxidants can be used alone or in combination of two or more.

  Further, as other components used in the solar cell module filler composition of the present invention, in addition to the above, an adhesion improver such as a silane coupling agent, a nucleating agent, a dispersing agent, a leveling agent, a plasticizer, an antifoaming agent Agents, flame retardants and the like.

<Solar cell module filler and solar cell module using the same>
Next, an example of the filler for a solar cell module of the present invention and a solar cell module using the same will be described with reference to the drawings. FIG. 2 is a cross-sectional view showing an example of the layer structure of the solar cell module of the present invention. In the solar cell module 1 of the present invention, a transparent front substrate 2, a front filler layer 3, a solar cell element 4, a back filler layer 5, and a back protective sheet 6 are laminated in order from the incident light receiving surface side. . The solar cell module 1 of the present invention uses the above solar cell module filler (hereinafter also simply referred to as “filler sheet”) for at least one of the front filler layer 3 and the back filler layer 5.

  The filler sheet of the present invention is obtained, for example, by molding and processing the above-mentioned filler composition for solar cell module by a conventionally known method, and is formed into a sheet or film. In addition, the sheet form in this invention means the film form, and there is no difference in both.

  The filler sheet is formed into a sheet 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, the filler sheet of the present invention is obtained by forming the filler composition for solar cell modules into a sheet.

  The sheet of filler material may not be a single layer. In order to improve the adhesion between the filler sheet and a member to be filled such as the transparent front substrate 2, the solar cell element 4, and the back surface protective sheet 6, the filler composition for solar cell module of the present invention is formed at the interface. It only has to be arranged. By allowing the filler composition of the present invention to be present in the vicinity of the interface, the filler sheet of the present invention can be produced at a lower cost.

  As a method for causing the filler composition of the present invention to be present in the vicinity of the interface, for example, the structure of the filler sheet is composed of three or more layers, that is, two outermost layers and the outermost layer sandwiched between them. And a method comprising a multilayer film having at least a core layer. In order to produce a filler sheet made of a multilayer film as described above, for example, a conventionally known T-die multilayer coextrusion method can be used.

  For example, the solar cell module 1 is formed by sequentially stacking the members including the transparent front substrate 2, the front filler layer 3, the solar cell element 4, the back filler layer 5, and the back protective sheet 6 and then vacuum suction or the like. Then, the above-described members can be manufactured by thermocompression molding as an integral molded body by a molding method such as a lamination method.

  Further, the solar cell module 1 has a front filler layer 3 and a rear surface on the front side and the back side of the solar cell element 4 by a molding method usually used in a normal thermoplastic resin, for example, T-die extrusion molding. The filler layer 5 is melt-laminated, the solar cell element 4 is sanded with the front filler layer 3 and the back filler layer 5, and then the transparent front substrate 2 and the back protective sheet 6 are sequentially laminated, You may manufacture by the method of integrating by vacuum suction etc. and carrying out thermocompression bonding.

  In the solar cell module 1 of the present invention, the transparent front substrate 2, the solar cell element 4, and the back protective sheet 6, which are members other than the front filler layer 3 and the back filler layer 5, are particularly limited to conventionally known materials. It can be used without. Moreover, the solar cell module 1 of this invention may also contain members other than the said member. The filler sheet of the present invention is not limited to a single crystal type, but can be applied to all other solar cell modules such as a thin film type.

  The filler sheet of the present invention may be a crosslinked sheet at the end of molding by setting the molding temperature to a high temperature of 150 to 250 ° C., and the molding temperature is a low temperature of 90 ° C. to 100 ° C., for example. By doing so, it may be uncrosslinked. In the latter case, the crosslinking is completed by heating at a high temperature at the time of manufacturing a solar cell module described later.

  The solar cell module of the present invention thus obtained is characterized in that the gel fraction after crosslinking of the filler sheet is 80% or less. As a result, high elasticity can be obtained particularly in a low temperature range from 0 ° C. to 70 ° C. while having transparency similar to that of conventional EVA. This will be described in detail in Examples. If the gel fraction is 5% or more, it is preferable because flow prevention by crosslinking can be achieved. However, if a value equal to or greater than a predetermined value is obtained as the shear stress, it may be less than 5%. That is, even if the gel fraction is zero, the shear stress can be increased by the composition of the present invention.

  The technical idea of the present invention cannot be conceived at all from the field where the transparency and flexibility need not be considered like the wire coating material of Patent Document 3. Patent Document 2 is also a simple idea of simply crosslinking to increase the gel fraction, and the present invention cannot be recalled. The present invention makes it possible to optimally adjust the degree of crosslinking by selecting the type and amount of crosslinking aid based on low density linear low density polyethylene. As a result, the desired gel fraction and elastic modulus can be obtained. This makes it possible to obtain physical properties and optical properties comparable to those of EVA while being olefin-based.

  In the solar cell module, if the water vapor permeability of the filler sheet is high, the solar cell element is adversely affected mainly by the intrusion of moisture from the end face. However, the filler sheet of the present invention is an olefin-based and water vapor permeable material. Since the degree is low, it is preferably used. In addition, as a result of increasing the adhesion between the filler sheet and the base material, it is possible to effectively suppress the intrusion of moisture from between the transparent front substrate 2 and the back protective sheet 6 and the filler sheet. Play.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.
<Manufacture of solar cell module filler>
A composition having the composition shown in Table 1 below was mixed and melted, and a film was formed by a conventional T-die method to a thickness of 400 to 480 μm to obtain an uncrosslinked filler. The film forming temperature was 90 ° C. to 100 ° C.
LLDPE: a metallocene linear low density polyethylene which is a copolymer of ethylene and 1-hexene and has a density of 0.88 g / cm ³ and a melt mass flow rate (MFR) at 190 ° C. of 8 g / 10 min.
Cross-linking agent (TBEC): t-butylperoxy-2-ethylhexyl carbonate (manufactured by Arkema Yoshitomi, trade name Luperox TBEC)
Monomer 1 (TMPT): trimethylolpropane trimethacrylate (manufactured by Statomer, trade name SR350)
Monomer 2 (TAIC): triallyl isocyanurate (manufactured by Statomer, trade name SR533)
UV absorber: Ciba Japan Co., Ltd., trade name CHMASSORB81
Weather resistance stabilizer: Ciba Japan Co., Ltd., trade name Tinuvin 770
Antioxidant: Ciba Japan Co., Ltd., trade name Irganox 1076
Silane coupling agent: Shin-Etsu Chemical Co., Ltd., trade name KBM503
In addition, the EVA filler of Comparative Example 2 is 1.5 parts by mass of a crosslinking agent (Lupersol 101) with respect to 100 parts by mass of EVA (vinyl acetate content 28%, manufactured by Mitsui DuPont Polychemical, trade name EVAFLEX / EV250 grade). , 0.2 parts by mass of an antioxidant (NAUGARD-P) and a UV absorber (0.1 parts by mass of Tinuvin 7709 and 0.3 parts by mass of Cyasorb UV-531) were used.

Next, these uncrosslinked fillers were treated with a vacuum heating laminator at 120 ° C., and then heated and crosslinked in a 150 ° C. oven for 30 minutes to obtain post-crosslinking fillers for the respective examples and comparative examples. The post-crosslinking filler was evaluated for gel fraction, physical properties, optical properties, and water vapor permeability. The results are summarized in Table 2. Each test condition is as shown below, and-in the table is not measured. Further, the change in elastic modulus (Young's modulus) with temperature was measured for Example 3, Reference Example 1, and Comparative Example 2. The result is shown in FIG.
Gel fraction (%): 1 g of filler after cross-linking is weighed and placed in an 80 mesh wire mesh bag. Next, a sample with the wire mesh is put into a Soxhlet extractor, and xylene is refluxed at the boiling point. After 10 hours of continuous extraction, the sample was taken out together with the wire mesh, weighed after the drying treatment, and the weight percentage before and after extraction was compared to measure the mass% of the remaining insoluble matter, which was taken as the gel fraction.
Gap stress (Pa): Two sheets of filler cut out to 5 × 7.5 cm are placed on a large glass plate that has been subjected to graining, and then 5 × 7.5 grain glass is placed on top of it to perform a crosslinking treatment. It was. Thereafter, the large-sized glass is placed at an angle of 45 ° so that the 5 × 7.5 cm grain glass is on the lower surface, and left at 150 ° C. for 12 hours. The moving distance of 5 × 7.5 grain glass after being left was measured and evaluated.
Young's modulus (Pa): A test piece after cross-linking was cut into 5 × 20 mm and measured with a UBM Rheogel E-4000.
Haze (%): Measured with Murakami Color Research Laboratory Haze / Transmissivity HM150.
Total light transmittance (%): Measured with Murakami Color Research Laboratory Haze / Transmissivity HM150.
Yellowness (Yi): Measured with SM Color Computer, Suga Test Instruments Co., Ltd.
Water vapor transmission rate (g / m ² · day): Measured by JISK7129B method, 40 ° C. × 90% RH.

  As can be seen from Table 2, the filler of the present invention has a low crosslinking degree with a gel fraction of 80% or less. As can be seen from FIG. 1, Example 3 has a lower elasticity than that of Comparative Examples 1 and 2 in the region of 70 ° C. or lower, and has the flexibility higher than EVA. On the other hand, the water vapor permeability has the physical properties of olefins, and the optical physical properties are comparable to those of EVA. That is, from this result, it can be understood that in the present invention, physical properties similar to EVA are obtained in terms of transparency and flexibility while having an olefin water vapor barrier.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Transparent front substrate 3 Front filler layer 4 Solar cell element 5 Back filler layer 6 Back surface protection sheet

Claims (5)

A solar cell module filler sheet made of only low density polyethylene having a density of 0.940 g / cm ³ or less as a resin,
Crosslinking comprising the resin, 0.05% by mass to 1.5% by mass of a crosslinking agent, and 0.05% by mass to 2.0% by mass of a polyfunctional vinyl monomer and / or a polyfunctional epoxy monomer. After forming an auxiliary agent and a solar cell module filler composition containing 0.05% by mass or more and 0.1% by mass or less of a hindered phenol-based radical absorbent, it is crosslinked by heating,
A solar cell module filler sheet having a gel fraction after crosslinking of 5% to 80%. The filler sheet for a solar cell module according to claim 1, wherein the low-density polyethylene has a density of 0.870 g / cm ³ or more and 0.900 g / cm ³ or less.   The cross-linking aid is selected from trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate, 1,6-hexanediol diacrylate relate, and 1,9-nonanediol diacrylate The filler sheet for solar cell modules according to claim 1, wherein the filler sheet is one or more kinds.   The filler sheet for a solar cell module according to any one of claims 1 to 3, wherein the crosslinking treatment is performed when the solar cell module is assembled.   A solar cell module provided with the filler sheet for solar cell modules in any one of Claim 1 to 4.

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