JP2019021702A - Solar battery module and method for manufacturing the same - Google Patents

Abstract

To provide a solar battery module having a sealing material layer composed of a thermosetting seal-material sheet including polyethylene as a base resin, in which crosslink sufficiently progresses in the sealing material layer, and the amount of outgas present therein is adequately reduced.SOLUTION: A solar battery module 1 comprises: a surface-side protecting substrate 2; a backside protecting substrate 5; a solar battery element 4; and a sealing material layer 3 for sealing the solar battery element 4 between the surface-side protecting substrate 2 and the backside protecting substrate 5. In the solar battery module 1, the sealing material layer 3 comprises seal-material sheets 31, 32 including polyethylene of a density of 0.865 g/cmor more and 0.900 g/cmor less, as a base resin, and having a gel fraction of 65% or more and 80% or less; and the amount of outgas that presents in the sealing material layer 3 is 1.81 μg/g or less in terms of toluene.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a solar cell module and a manufacturing method thereof. More specifically, the present invention relates to a solar cell module including a sealing material made of a thermosetting polyethylene resin, which is compatible with both improvement in heat resistance and suppression of outgas generation derived from a crosslinking agent.

  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. A general solar cell module is sealed with a sealing material sheet for a solar cell module between a front surface side protective substrate such as a glass protective substrate and a back surface protection member made of a weather resistant resin sheet or the like. The solar cell element is arranged.

  Each member constituting the solar cell module, particularly the above-described sealing material sheet, is always exposed to a harsh environment such as strong ultraviolet rays, heat rays, wind and rain, and the like when used. For this reason, each said member, such as a sealing material sheet, is provided with the high durability which can endure long-term use in such a severe environment.

  For example, as a sealing material sheet having such a high durability, a sealing material comprising EVA (ethylene-vinyl acetate copolymer) as a base resin, and a resin composition containing a crosslinking agent and a crosslinking aid. A material sheet is known (see Patent Document 1). In this case, when the crosslinking reaction proceeds during extrusion molding, the above resin composition generally has an excessive load at the time of film formation, resulting in a decrease in productivity or the inability to form a film. Films are left uncrosslinked by extrusion by low-temperature heating. And after film-forming, it bridge | crosslinks by the heat processing etc. in the case of modularization.

  On the other hand, when the base resin of the encapsulant sheet is a polyethylene resin, it is known that the adhesion with the glass or the like is improved by blending the silane coupling agent, but in order to further improve the adhesion, A sealing material using a modified ethylene-based resin obtained by graft polymerization of alkoxysilane is also known (see Patent Document 2). According to this, the sealing material sheet which has durability and adhesiveness can be provided, making the bridge | crosslinking process like the case of the sealing material sheet of patent document 1 unnecessary.

JP 2009-135200 A Japanese Patent Laid-Open No. 2002-235048

  The encapsulant sheet of Patent Document 2 does not contain a crosslinking agent. That is, it is a thermoplastic resin sheet on the premise that the crosslinking treatment is not performed until the final product stage. Thus, when the base resin of the encapsulant sheet is thermoplastic polyethylene, in order to ensure the necessary and sufficient heat resistance required for the encapsulant sheet, a resin having a high density and a high melting point is used to some extent. I have to choose. In fact, in the example of Patent Document 2, the composition of the silane-modified ethylene-α-olefin copolymer (Example 2) is extruded at a high temperature of 180 ° C. It is done.

  Increasing the density of the polyethylene resin used as the base resin of the encapsulant sheet leads to a decrease in the transparency of the encapsulant sheet. However, when thermoplastic polyethylene is used as the base resin, in order to ensure sufficient heat resistance, it is necessary to accept this for a certain degree of transparency deterioration. .

  On the other hand, if a thermosetting polyethylene containing a crosslinking agent is used as a base resin, it is possible to use a low density polyethylene having a relatively low density. However, in this case, in order to provide the encapsulant sheet with sufficient heat resistance and weather resistance, it is essential to add a certain amount or more of a crosslinking agent to crosslink the polyethylene.

  In general, the crosslinking reaction of polyethylene is less likely to proceed as compared with EVA disclosed in Patent Document 1. Therefore, in order to provide sufficient heat resistance as a sealing material sheet for a solar cell module, it is necessary to add a larger amount of a crosslinking agent. However, the addition of a large amount of the crosslinking agent to the encapsulant composition generates a large amount of outgas during vacuum heating lamination for integration as a solar cell module, and also seals in the solar cell module after integration. This causes an increase in the amount of outgas inherent in the material layer. When the amount of outgas increases, the risk of inducing peeling of the encapsulant sheet due to the generation of bubbles at the interface between the encapsulant sheet and the cell increases, so in order to maintain the quality stability of the solar cell module, It is strongly desired to suppress this outgas amount to a certain amount or less.

  The present invention has been made to solve the above problems. Its purpose is to form a resin composition containing polyethylene as a base resin and contain a cross-linking agent, and then proceed with cross-linking to provide a sealing comprising a thermosetting encapsulant sheet that ensures the necessary and sufficient heat resistance. In a solar cell module provided with a material layer, it is providing the solar cell module which can make compatible improvement of heat resistance and suppression of the amount of outgas generated in a sealing material layer.

  The present inventors, for example, by setting the base resin of the encapsulant composition forming the encapsulant sheet constituting the encapsulant layer of the solar cell module to polyethylene made of an α-olefin having a specific carbon number, The present inventors have found that the necessary amount of a crosslinking agent for causing the crosslinking to progress to a level sufficient to ensure the necessary heat resistance can be reduced as compared with the conventional case. As a result, the present inventors have succeeded in producing a solar cell module having a sealing material layer with a very low gel fraction and a very small amount of outgas derived from a cross-linking agent, thereby completing the present invention. More specifically, the present invention provides the following.

(1) Front side protective substrate, back side protective substrate, solar cell element, and sealing material for sealing the solar cell element between the front side protective substrate and the back side protective substrate a solar cell module comprising a layer, wherein the sealing material layer, and a density of 0.865 g / cm ³ or more 0.900 g / cm ³ or less polyethylene base resin, gel fraction of 65% or more The solar cell module which consists of a sealing material sheet which is 80% or less, and the amount of outgass in the said sealing material layer is 1.81 microgram / g or less in conversion of toluene.

  (2) The solar cell module according to (1), wherein the polyethylene is a copolymer of ethylene and an α-olefin, containing the α-olefin having 3 carbon atoms at a ratio of 6 mol% to 25 mol%. .

  (3) The solar cell module according to (2), wherein the polyethylene is a copolymer of ethylene and an α-olefin, containing 18 mol% or more of an α-olefin having 3 carbon atoms.

(4) The method for manufacturing a solar cell module according to (1) (3), a density of 0.865 g / cm ³ or more 0.900 g / cm ³ or less of the polyethylene resin as a base resin containing a crosslinking agent The encapsulant composition is formed into a sheet shape while maintaining the gel fraction at 10% or less, and an encapsulant film forming step for obtaining an uncrosslinked encapsulant sheet; While the structural member of the solar cell module including the encapsulant sheet and the solar cell element is crosslinked by vacuum overheating lamination so that the gel fraction of the uncrosslinked encapsulant sheet is 65% or more and 80% or less. The polyethylene-based resin is a copolymer of ethylene and α-olefin, which contains the α-olefin having 3 carbon atoms at a ratio of 6 mol% to 25 mol%. Yes, the crosslinking agent is a peroxyketal, a dialkyl peroxide, or a peroxycarbonate, wherein the solar cell module is produced.

  According to the present invention, in a solar cell module including a thermosetting sealing material layer made of polyethylene as a base resin, cross-linking of the sealing material layer is sufficiently advanced, and the outgas existing in the same layer A solar cell module whose amount is sufficiently suppressed can be provided.

It is sectional drawing which shows an example of the laminated constitution of the solar cell module of this invention.

<Solar cell module>
FIG. 1 is a cross-sectional view showing an example of the layer structure of the solar cell module of the present invention. The solar cell module 1 which is an example of embodiment of this invention is the surface side protective base material 2 which consists of transparent base materials, such as a glass substrate, the sealing material sheet 31 of the surface side, and a solar cell from the light-receiving surface side of incident light. The element 4, the back surface side sealing material sheet 32, and the back surface side protective base material 5 are laminated | stacked in order. The pair of encapsulant sheets 31 and 32 are arranged in close contact with both surfaces of the solar cell element 4 to constitute an encapsulant layer 3 that seals them.

[Encapsulant layer]
In this specification, “a sealing material layer for sealing a solar cell element”, as a typical example, as shown in FIG. This refers to the layer that is sealed by the mode of being sandwiched between the material sheets. However, the aspect of “sealing the solar cell element” is not necessarily limited to this. For example, in a thin film solar cell module having a configuration in which a cell glass in which a thin film solar cell element is formed on a glass substrate is covered with a sealing material sheet, the thin film formed on the cell glass The encapsulant sheet covering the elements of the system is regarded as the “encapsulant layer for encapsulating the solar cell elements” in the solar cell module.

  In the solar cell module 1 of the present invention, the sealing material layer 3 is made of a polyethylene-based resin, and the sealing material layer 3 is sufficient so that the gel fraction as an index of the degree of crosslinking is 65% or more. It is crosslinked. Usually, when the polyethylene resin constituting the encapsulant layer 3 is crosslinked to this extent, at least an outgas exceeding 1.81 μg / g in terms of toluene is inherent in the encapsulant layer 3. The probability of becoming very high. It is extremely difficult to stably avoid this by the manufacturing method according to the range of conventional knowledge, and unless the degree of cross-linking is kept below 65%, the occurrence of the above-mentioned amount of outgas is substantially inevitable. there were. In the solar cell module 1 of the present invention, the crosslinking of the encapsulant layer 3 is sufficiently advanced to the above level, and the amount of outgas present in this layer is at least 1.81 μg in terms of toluene. The main feature is that it is suppressed to 1.32 μg / g or less, more preferably 1.32 μg / g or less in terms of equivalent.

  Here, “gel fraction (%)” in this specification means that 1.0 g of a sealing material is put into a resin mesh, extracted with 110 ° C. xylene for 12 hours, then taken out together with the resin mesh, dried and weighed. The mass ratio before and after extraction is compared to measure the mass% of the remaining insoluble matter, and this is used as the gel fraction. The gel fraction of 0% means that the residual insoluble matter is substantially 0 and the crosslinking reaction of the sealing material composition or the sealing material sheet has not substantially started. More specifically, “gel fraction 0%” means that the above-mentioned residual insoluble matter is not present at all, and that the above-mentioned residual insoluble matter mass% measured by a precision balance is less than 0.05% by mass. Shall be said. The residual insoluble matter does not include pigment components other than the resin component. When a mixture other than these resin components is mixed in the residual insoluble matter by the above test, for example, by separately measuring the content of these mixtures in the resin component beforehand, The gel fraction that should be originally obtained can be calculated for the residual insoluble matter derived from the resin component excluding the inclusions.

[Outgas amount in the sealing material layer]
Further, in this specification, “the amount of outgas inherent in the encapsulant layer” means “the encapsulant layer for encapsulating the solar cell element” in the solar cell module at the stage where the crosslinking process has been completed to become a finished product. The amount of gas present in the graph indicates the amount of gas per unit mass (μg / g) in terms of toluene. The outgas amount according to this definition is determined as a specific value by sequentially performing (preparation of calibration curve), (measurement of outgas amount), and (calculation of outgas amount) by each method described below. Can be obtained.

(Create a calibration curve)
Ethyl acetate and toluene are weighed and mixed in an amount of 5.05566 g = 5.06494 ml of ethyl acetate and 0.99237 g = 1.50841 ml of toluene. The liquid mixture is divided into 0.5 μl, 1.0 μl, 3.0 μl, and 5.0 μl each in a vial. The content of toluene is 0.073446 μg, 0.14689 μg, 0.44068 μg, and 0.73446 μg. Next, after each vial was heated at 165 ° C. for 30 minutes, 10 ml of gas was collected, the spectrum was detected by FID-GC, and the areas of toluene peaks were integrated to obtain the relationship shown in Table 1 below. Then, a calibration curve represented by the following linear expression is defined from each value in Table 1.
Y = (1.3488 × 10 ⁻⁵ ) X
Y: Amount of toluene (μg)
X: Area value (pA / sec)

(Measurement of outgas amount)
In advance, 200 mg of the test sample of the sealing material layer subjected to the crosslinking treatment is weighed and placed in a vial. After heating at 165 ° C. for 30 minutes, 10 ml of gas is collected, a spectrum is acquired by FID-GC, and the areas of all peaks are integrated.

(Calculation of outgas amount)
This integrated value is applied to the calibration curve, and the outgas generation amount in terms of toluene from the test sample is calculated.
Toluene conversion outgas generation amount (μg / g) = (1.3488 × 10 ⁻⁵ ) X × (1000/200) = (0.6744 × 10 ⁻⁶ ) X
In addition, said spectrum detection can be performed by gas chromatography analysis (qualitative / quantitative analysis) by the measurement on the following conditions using the following measuring devices.
Apparatus: Agilent 6890 (manufactured by Agilent Technologies)
Column: Agilent J & W GC column “HP-5MS” (manufactured by Agilent Technologies)
Column temperature: 40 ° C to 320 ° C
Gas: He
Detector: Hydrogen flame ionization detector (FID)

[Encapsulant sheet]
The encapsulant sheets 31 and 32 (hereinafter also simply referred to as “encapsulant sheet”) constituting the encapsulant layer 3 of the solar cell module 1 are the same as the encapsulant composition described in detail below. The film is formed into a film or sheet by a known method. In addition, the sheet form in this invention means the film form, and there is no difference in both.

  In addition, the sealing material sheets 31 and 32 are formed in an uncrosslinked film by limiting the film forming temperature to a low temperature range of 90 ° C. to 120 ° C. The cross-linking treatment is completed by, for example, a high-temperature heat treatment at the time of manufacturing the solar cell module.

Sealing material sheet 31 and 32, density 0.865 g / cm ³ or more 0.900 g / cm ³ or less, preferably, density 0.880 g / cm ³ or more 0.895 g / cm ³ or less, more preferably, density 0 a .885g / cm ³ or more 0.890 g / cm ³ or less polyethylene resin-based resin, a gel fraction of 0% to 10% or less, more preferably formed by a resin film uncrosslinked 0% Yes.

  However, the encapsulant sheets 31 and 32 in the uncrosslinked stage after film formation contain a predetermined amount of the crosslinking agent, and in any process until after integration as a solar cell module, It is a so-called thermosetting (or cross-linking) resin film that is expected to undergo cross-linking. The gel fraction of the encapsulant sheet after completion of crosslinking after integration as the solar cell module 1, that is, the gel fraction of the encapsulant layer 3 may be 65% or more and 80% or less, and 70% or more and 80%. The following is more preferable.

  In addition, the encapsulant sheets 31 and 32 are after the completion of crosslinking after being integrated as the solar cell module 1, that is, at a stage where sufficient crosslinking has progressed so that the gel fraction of the encapsulant layer 3 is 65% or more. In addition, the amount of outgas inherent in the sealing material layer 3 is designed to be 1.81 μg / g or less in terms of toluene.

  The melt mass flow rate (MFR) of the encapsulant sheets 31 and 32 in the uncrosslinked stage after film formation is MFR at 190 ° C. and a load of 2.16 kg measured in accordance with JIS-K6922-2 (in this specification, hereinafter, The measurement value under this measurement condition is referred to as “MFR”) is preferably 5 g / 10 min or more and 25 g / 10 min or less, and more preferably 10 g / 10 min or more and 20 g / 10 min or less. When the MFR is in the above range, a sealing material having excellent adhesion to other members of the solar cell module made of glass, metal, or the like can be obtained. In addition, about MFR in case a sealing material sheet | seat is a multilayer film which is demonstrated below, the measurement by the said process is performed with the multilayer state in which all the layers were laminated | stacked integrally, and the obtained measured value is the said multilayer The MFR value of the sealing material sheet is assumed to be.

  Each thickness of the sealing material sheets 31 and 32 should just be 200 micrometers or more and 1000 micrometers or less, and it is preferable that they are 300 micrometers or more and 600 micrometers or less.

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

  In the case where the encapsulant sheet is a multilayer film, it is more preferable that each layer has a different MFR within the range satisfying the essential constituent requirements of the present invention. In this case, a layer having a higher MFR is used. The skin layer is preferably disposed on the outermost layer side. Even when the encapsulant sheet of the present invention is a single-layer encapsulant sheet, the encapsulant sheet has sufficiently preferable transparency, heat resistance, and moderate flexibility. By disposing a high layer as the outermost layer, the adhesiveness and molding characteristics can be further enhanced while maintaining the above-described preferable transparency and heat resistance as the sealing material sheet.

  For example, in the encapsulant sheet which is a multilayer film composed of three or more layers, the thickness of the outermost layer is 30 μm or more and 120 μm or less, and the intermediate layer and the outermost layer composed of all layers other than the outermost layer The thickness ratio is preferably in the range of outermost layer: intermediate layer: outermost layer = 1: 3: 1 to 1: 8: 1. By doing in this way, the preferable molding characteristic in an outermost layer can be provided, maintaining the preferable heat resistance as a sealing material.

[Encapsulant composition]
The encapsulant composition used for producing the encapsulant sheets 31 and 32 constituting the encapsulant layer 3 of the solar cell module 1 (hereinafter also simply referred to as “encapsulant composition”) is a low-density polyethylene-based material. It is a thermosetting resin composition in which a resin is a base resin and a crosslinking agent is essential. In the present specification, the “base resin” refers to a resin having the largest content ratio among the resin components of the resin composition in the resin composition containing the base resin.

Sealant composition, density 0.865 g / cm ³ or more 0.900 g / cm ³ or less, preferably, density 0.880 g / cm ³ or more 0.895 g / cm ³ or less, more preferably, density 0.885g / cm ³ and more 0.890 g / cm ³ or less polyethylene base resin. By using low-density polyethylene as described above as the base resin, the transparency of the sealing material sheets 31 and 32 can be improved. In addition, according to this, adhesion to other members constituting the solar cell module 1 such as a glass substrate laminated as the surface side protective base material 2 is enhanced, and the cells at the time of pressure bonding of the respective members in the laminating process The risk of cracking can also be reduced. Content of said base resin with respect to all the resin components of a sealing material composition is 70 to 100 mass%, Preferably, it is 90 to 99 mass%. As long as this base resin is included within the above range, the sealing material composition may contain other resins within a range not impairing the effects of the present invention.

  The polyethylene used as the base resin of the sealing material composition is linear low density polyethylene (LLDPE) which is a copolymer of ethylene and α-olefin. The base resin is more preferably a metallocene linear low density polyethylene (M-LLDPE). 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. As a result of the flexibility imparted to the sealing material, the adhesion between the sealing material and glass, metal, or the like increases.

  In addition, linear low density polyethylene has a narrow crystallinity distribution and a uniform crystal size, so that not only a large crystal size does not exist, but also the crystallinity itself is low because of its low density. For this reason, it is excellent in transparency when processed into a sheet shape as the sealing material sheets 31 and 32. Therefore, when the encapsulant sheets 31 and 32 made of the encapsulant composition using this as a base resin are disposed on the light receiving surface side of the solar cell element 4 in the solar cell module 1, the solar cell element 4. It is possible to prevent a decrease in power generation efficiency due to attenuation of incident light.

  As the α-olefin of the linear low density polyethylene used as the base resin of the sealing material composition, propylene having 3 carbon atoms is used at a ratio of a predetermined amount or more. Thus, the gel fraction after the crosslinking treatment of the encapsulant layer 3 is set to 65% or more, and the amount of outgas present in the same layer after such crosslinking treatment is 1.81 μg / g in terms of toluene. It can be as follows. The sealing material composition contains the α-olefin having the specific carbon number in the base resin in an amount of 18 mol% to 25 mol%, preferably 15 mol% to 20 mol%. Conventionally, 1-hexene, 1-heptene, or 1-octene, which is an α-olefin having 6 to 8 carbon atoms, is often used as an α-olefin of a polyethylene resin used for a sealing material sheet for a solar cell module. However, by replacing this with propylene having 3 carbon atoms, the encapsulant layer 3 can be provided with sufficient heat resistance with the addition of a less cross-linking agent.

  By setting the content of the α-olefin having a specific carbon number in the encapsulant composition to 18 mol% or more, the encapsulant sheets 31 and 32 are sufficient even if the amount of the crosslinking agent added is relatively small. Heat resistance can be imparted, and at the same time, deterioration of the light-resistant stabilizer contained in the sealing material sheets 31 and 32 can be suppressed. On the other hand, when the content exceeds 25 mol%, the melting point is lowered, and blocking is likely to occur in the production process of the encapsulant sheet. Therefore, the content is preferably 25 mol% or less.

  The α-olefin in the base resin of the sealing material composition is not necessarily all having 3 carbon atoms, but does not contain an α-olefin having 8 or more carbon atoms such as 1-octene. It is preferable.

The “content of α-olefin having a specific carbon number (mol%)” of the encapsulant sheets 31 and 32 in the uncrosslinked stage after the film formation and the encapsulant layer 3 after crosslinking are both as follows: It can be calculated by the measurement method.
'Method for measuring the content (mol%) of α-olefins with specific carbon number'
The measurement sample of the sealing material sheet or the crosslinked sealing material layer is dissolved in the ODCB / C6D6 (4/1) solvent to a concentration of 10 wt%. In a state where the temperature of the solvent is 130 ° C., measurement is performed using 13 C-NMR, and a peak peculiar to triad (triplet) is quantified. After calculating the monomer sequence fraction (normalized to 100% of all sequences), each monomer ratio (C3 component concentration) is calculated from the sequence fraction.

  An appropriate amount of a silane copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer (hereinafter also referred to as “silane copolymer”) may be added to the sealing material composition. preferable. Thereby, the adhesiveness of the sealing material sheets 31 and 32 with other members, such as the glass substrate laminated | stacked as the surface side protective base material 2, the solar cell element 4 made from metal, or a ceramic, can further be improved. .

  The silane copolymer is described in, for example, JP-A-2003-46105. By using the copolymer as a component of the encapsulant composition, it is excellent in strength, durability, etc., and has weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other various properties. Excellent sealing properties, excellent heat-sealability without being affected by manufacturing conditions such as thermocompression bonding for manufacturing solar cell modules, stable, low-cost and suitable for various applications Material sheets can be produced.

  As the silane copolymer, any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer can be preferably used. However, the silane copolymer is more preferably a graft copolymer. 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 contributing to the adhesive force, it can improve the adhesion between the sealing material sheet and other members.

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

  As a crosslinking agent used for the encapsulant composition, the amount of outgas present in the encapsulant layer after the crosslinking treatment can be 1.81 μg / g or less in terms of toluene while performing sufficient crosslinking treatment. The crosslinking agent selected in (1) can be appropriately selected. Specifically, when the content of carbon number 3 of the α-olefin of the ethylene / α-olefin copolymer of the base resin of the encapsulant composition is 18 mol% or more as described above, the amount of active oxygen is A crosslinking agent of about 6% or more, more preferably 8.5% or more and 15.00% or less can be used. By using a combination of a highly reactive base resin having the above composition and a cross-linking agent having an active oxygen amount in the above range, the amount of cross-linking agent added is kept within an appropriate amount range while avoiding excessive outgas generation. At the same time, the crosslinking can be advanced to such an extent that the gel fraction becomes 65% or more, and the sealing material layer 3 can be provided with sufficient heat resistance.

  Moreover, about the 1-hour half-life temperature of the crosslinking agent used for a sealing material composition, it is preferable to use a 125 to 145 degreeC thing. Thereby, a sealing agent composition can be made into the composition which can be melt-extruded at 120 degrees C or less.

  Specific examples of preferable crosslinking agents satisfying the above conditions include peroxycarbonates such as t-amyl-peroxy-2-ethylhexyl carbonate and t-butylperoxy-2-ethylhexyl carbonate, n-butyl 4,4-di ( peroxyketals such as t-butylperoxy) valerate, ethyl 3,3-di (t-butylperoxy) butyrate, 2,2-di (t-butylperoxy) butane, di-t-butylperoxide , T-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-peroxy) hexyne -3 and other dialkyl peroxides can be mentioned as crosslinking agents that can be used by adding them to the encapsulant composition. That. Among them, a crosslinking agent of dialkyl peroxides having an active oxygen amount of 9.22 or more and a one-hour half-life temperature of 140 ° C. (for example, product name “Lupelox 101” (manufactured by Arkema Yoshitomi Corporation)), or A peroxyketal cross-linking agent having an active oxygen content of 8.61 or more and a one-hour half-life temperature of 129 ° C. (for example, product name “Lupelox 230” (manufactured by Arkema Yoshitomi Co., Ltd.)) It can use especially preferably as a crosslinking agent to be used.

  The content of the cross-linking agent in the encapsulant composition is the amount of outgas present in the encapsulant layer after the cross-linking treatment in terms of toluene while performing sufficient cross-linking treatment for each of the various cross-linking agents. Each appropriate amount range may be selected so as to be 1.81 μg / g or less. Specifically, when the content of the α-olefin having 3 carbon atoms of the ethylene / α-olefin copolymer of the base resin of the sealing material composition is 18 mol% or more as described above, the sealing material composition It is preferable that content of the crosslinking agent with respect to all the resin components in it is 0.3 mass% or more and 0.6 mass% or less.

  More specifically, the content of the crosslinking agent in the encapsulant composition is more specifically described in the encapsulant composition when the crosslinking agent selected in combination with the same base resin is a peroxycarbonate. It is preferable that content with respect to all the resin components is 0.4 mass% or more and 0.6 mass% or less. Similarly, in the case of peroxyketals, the content is preferably 0.37% by mass or more and 0.40% by mass or less. Similarly, when it is dialkyl peroxides, it is preferable that the same content is 0.29 mass% or more and 0.43 mass% or less.

  By adding a crosslinking agent in the above range, sufficient heat resistance can be imparted to the sealing material sheets 31 and 32. Moreover, if it is the addition amount of the said range, generation | occurrence | production of the outgas derived from a crosslinking agent can also be fully suppressed. The encapsulant sheet according to the present invention forms a film without proceeding with substantial cross-linking, and the content range of the cross-linking agent in the encapsulant sheet in the sheet stage after film formation is also included. This is the same range as the composition stage.

  In the encapsulant composition, a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group, more preferably a crosslinking aid in which the functional group of the polyfunctional monomer is an allyl group, a (meth) acrylate group, or a vinyl group. It is preferable to contain an agent. In addition to promoting an appropriate crosslinking reaction thereby improving the adhesion of the sealing material sheets 31 and 32 to the glass or metal, this crosslinking aid is a linear chain that forms the sealing material sheets 31 and 32. Reduces the crystallinity of low density polyethylene and maintains transparency. Thereby, in addition to the effect of improving the adhesiveness, the transparency and low-temperature flexibility of the sealing material sheets 31 and 32 can be further improved.

  Specific examples of the crosslinking aid that can be used in the encapsulant composition include polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate; Methylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonane Poly (meth) acryloxy compounds such as diol diacrylate, glycidyl methacrylate containing double bond and epoxy group, 4-hydroxybutyl acrylate glycidyl ether and two or more epoxy groups 1,6-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 the above-mentioned crosslinking aids, it also contributes significantly to improving the glass adhesion of the sealing material, has good compatibility with linear low density polyethylene, reduces crystallinity by crosslinking, maintains transparency, TAIC can be preferably used from the viewpoint of imparting flexibility in the above.

  The content of the crosslinking aid in the encapsulant composition is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.05% with respect to all resin components in the encapsulant composition. The mass is not less than 2.0% by mass. If it is in this range, moderate crosslinking reaction can be promoted and the adhesiveness of the sealing material sheets 31 and 32 can be improved.

  In the encapsulant composition, a hindered amine light resistance stabilizer (HALS) is preferably used as the light resistance stabilizer. The hindered amine light stabilizers are roughly classified according to the binding partner of the nitrogen atom in the piperidine skeleton, the NH type (hydrogen is bonded to the nitrogen atom), the NR type (the alkyl group (R) is bonded to the nitrogen atom), Although there are three types of N-OR type (an alkoxy group (OR) is bonded to a nitrogen atom), among these, an NH or NR type hindered amine light stabilizer can be particularly preferably used.

  The N-OR type hindered amine light resistance stabilizer has a higher reaction speed and a higher radical trap function than the NH or NR type hindered amine light resistance stabilizer. However, in the encapsulant sheet of the type in which the cross-linking proceeds at the stage of modularization after film formation like the encapsulant sheets 31 and 32 according to the present invention, the cross-linking agent is used at the time of thermal lamination for modularization. In many cases, the light resistance cannot be sufficiently improved. By specifying the hindered amine light-resistant stabilizer as an NH type or NR type hindered amine light-resistant stabilizer, deterioration due to a crosslinking agent is avoided, and the function of capturing radicals generated by light is more stable. Can keep good.

  In general, many kinds of hindered amine light stabilizers are known, from low molecular weight compounds to high molecular weight compounds. When used in a sealing material composition for a solar cell module, bleeding out often occurs when a low molecular weight, that is, a molecular weight of less than 2000 is used. In this case, the light transmittance is low. It becomes smaller and transparency is lowered. Since a decrease in the transparency of the encapsulant leads to a decrease in power generation efficiency of the solar cell module, it is preferable to use a high molecular weight molecular weight of 2000 or more as the light resistance stabilizer used in the encapsulant composition.

  Specific examples of the hindered amine light-resistant stabilizer that can be preferably used for the encapsulant composition include N-H type and molecular weight of 2000 or more, and dibutylamine-1,3,5-triazine-N, N. Polycondensate of '-bis (2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine 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.

  Other specific examples of the hindered amine light-resistant stabilizer that can be preferably used in the encapsulant composition according to the present invention are those of N-R type and having a molecular weight of 2000 or more, butanedioic acid 1- [2- (4-hydroxy-2,2,6,6-tetramethylpiperidino) ethyl]. This compound is commercially available as KEMISTAB62 and is a compound having CAS number 65447-77-0. The molecular weight is 3100 to 4000, and the melting point is 55 ° C to 70 ° C.

  About the hindered amine light resistance stabilizer addition amount to the sealing material composition, it may be 0.1% by mass or more and 0.5% by mass or less with respect to all resin components in the sealing material composition, More preferably, it is 0.2 mass% or more and 0.4 mass% or less. By making the content 0.1% by mass or more, the effect of stabilizing light resistance can be sufficiently obtained. Further, when the content is 0.5% by mass or less, bleeding out can be suppressed, and discoloration of the resin due to excessive addition of a hindered amine light-resistant stabilizer can also be suppressed.

  The sealing material composition may further contain other components. For example, ultraviolet absorbers, heat stabilizers, adhesion improvers, nucleating agents, dispersants, leveling agents, plasticizers, antifoaming agents, flame retardants, and other various fillers can be added as appropriate. The content ratio of these additives varies depending on the particle shape, density, and the like, but is preferably in the range of 0.001% by mass to 60% by mass in the encapsulant 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 composition.

  As described above, the cross-linking reaction proceeds so that the gel fraction is in the above range by adjusting the α-olefin carbon number of the linear low density polyethylene in the base resin, the type and addition amount of the cross-linking agent to the preferable range. The outgas generation derived from the crosslinking agent can be sufficiently suppressed.

  As the solar cell element 4 constituting the solar cell module 1, various crystalline silicon type solar cell elements manufactured using a single crystal silicon substrate, a polycrystalline silicon substrate, or a tandem type silicon substrate are preferably used. it can. However, the present invention is not limited thereto, and various conventionally known solar cell elements including a thin film solar cell element (CIGS) using a chalcopyrite compound or the like can be used without particular limitation. The solar cell element 4 may be a single-sided light receiving element that can receive only light from the surface side of the solar cell module, or a double-sided light receiving element that can receive light on both sides of the element. Also good.

  Further, since the solar cell module 1 uses the sealing material sheet 32 made of a highly insulating polyethylene-based resin, a back contact type solar cell in which a plurality of electrodes having different polarities are provided on the non-light-receiving surface side. An element can also be preferably used.

  As the surface-side protective base material 2 constituting the solar cell module 1, a conventionally known material such as a glass substrate having transparency required on the light receiving surface side of the solar cell module can be used without particular limitation. Since the sealing material sheet 31 on the surface side constituting the sealing material layer 3 is also excellent in glass adhesion and adhesion durability, the solar cell module 1 has a surface side made of the sealing material layer 3 and glass. A module having excellent adhesion and adhesion durability at the interface of the protective substrate 2 can be obtained.

  As the back surface side protective substrate 5 constituting the solar cell module 1, a conventionally known solar cell module such as a resin sheet such as ETFE or water resistant PET or an aluminum foil layer with a resin layer laminated on both sides is used. The back surface protection sheet can be used as appropriate.

  In addition, the layer structure of the solar cell module 1 of this invention is not restricted to said embodiment, You may further include structural members other than each member demonstrated in the above as needed.

[Method for manufacturing solar cell module]
For example, the solar cell module 1 is formed by sequentially laminating the members including the front surface side protective base material 2, the sealing material sheet 31, the solar cell element 4, the sealing material sheet 32, and the back surface side protective base material 5. It can be manufactured by integration by vacuum suction or the like, and then thermocompression-molding the above-mentioned member as an integral molded body by a molding method such as a lamination method.

(Encapsulant film forming process)
For the sealing material sheets 31 and 32 constituting the solar cell module 1, prior to the process for integration, the above-mentioned sealing material composition is held in advance with the gel fraction kept at 10% or less. It can be obtained by a step of forming a film into a sheet to obtain an uncrosslinked sealing material sheet. The melt molding can be performed by various conventionally known film formation methods such as film formation by a T-die.

(Module integration process)
As described above, each member including the uncrosslinked sealing material sheet obtained in the sealing material film forming step is thermocompression-molded as an integrally molded body by a molding method such as vacuum overheating lamination. In the process for integration, the crosslinking is advanced so that the gel fraction of the uncrosslinked sealing material sheet is 65% or more and 80% or less. If necessary according to the lamination conditions, a separate thermal crosslinking treatment may be further performed after modularization.

  The solar cell module 1 thus obtained is excellent in heat resistance and light resistance, and has extremely high durability over a long period even when exposed to harsh environments such as strong ultraviolet rays, heat rays, and wind and rain. It has become. Moreover, it can contribute also to the improvement of the power generation efficiency of a solar cell module by being excellent also in transparency.

  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]
A sealing material composition made of the following materials was melted and formed into a film having a thickness of 460 μm by a conventional T-die method to obtain an uncrosslinked single-layer sealing material sheet for a solar cell module. The film forming temperature was 90 ° C. to 100 ° C.
(Base resin)
Metallocene linear low-density polyethylene (denoted as “PE” in Table 3) having a density of 0.880 g / cm ³ and a melt mass flow rate (MFR) at 190 ° C. of 20 g / 10 minutes, and the following α -A copolymer with olefin was used as the base resin of the sealing material sheets of Examples and Comparative Examples. The type (carbon number) and content (mol%) of the α-olefin contained in each base resin are as described in Table 3, and different carbon numbers (3, 6, 8) was included in different contents.
Propylene: Carbon content 3 (indicated as “C3” in Table 3)
1-hexene: 6 carbon atoms (indicated as “C6” in Table 3)
1-octene: carbon content 8 (indicated as “C8” in Table 3)
This base resin was used in an amount of 100 parts by mass for each encapsulant composition.
(Silane-modified polyethylene)
5 parts by mass of vinyltrimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) with respect to 95 parts by mass of the metallocene linear low density polyethylene used for the base resin Were melted and kneaded at 200 ° C. to obtain a silane-modified polyethylene (silane copolymer) having a density of 0.884 g / cm ³ and an MFR at 190 ° C. of 6 g / 10 min. This silane-modified polyethylene was used in an amount of 15 parts by mass for each encapsulant composition as another additive resin for the encapsulant sheets of all Examples and Comparative Examples.
(Crosslinking agent)
About the crosslinking agent, the three types of crosslinking agents (A to C) described in Table 2 for each encapsulant composition were used properly in accordance with the formulation shown in Table 3, respectively. The content (mass%) of each crosslinking agent in the resin component for each sealing material composition was as shown in Table 3. The molecular weight, active oxygen content, and 1 hour half-life temperature of each crosslinking agent (A to C) are as shown in Table 2.
(Crosslinking aid)
The following crosslinking assistant was added to each sealing material composition. The content (mass%) of the crosslinking aid in the resin component for each sealing material composition was set to the content described in Table 3.
Crosslinking aid (TAIC): triallyl isocyanurate (product name “SR533” manufactured by Statomer)
(Hindered amine light resistance stabilizer (HASLS))
The following HASLS was added to each sealing material composition. The content (parts by mass) of each HASLS in each sealing material composition was 0.1 parts by mass in any case.
HALS: N-R type hindered amine light-resistant stabilizer having an amino group (manufactured by Adeka Co., Ltd., trade name “LA-72”)

[Evaluation Example 1: State of α-olefin]
The state (branched state) of the ethylene / α-olefin copolymer of the base resin in each encapsulant composition stage was measured by 13C-NMR as described above and as shown in Table 3. Confirmed that the condition.

[Evaluation Example 2: Gel fraction]
In order to evaluate the degree of crosslinking of the encapsulant layer in a state integrated as a solar cell module, that is, heat resistance, each encapsulant sheet is sandwiched between ETFE films, and the following vacuum heating laminate (Condition 1: In Table 3, “high”) or by vacuum heating lamination and subsequent curing treatment (condition 2: described as “low” in Table 3), the gel was measured by the above-described measurement method. The fraction was measured. The results are shown as “gel fraction” in Table 3. The evaluation criteria for “heat resistance” based on the numerical values of the gel fractions were as follows. In addition, after film formation, in the state before the crosslinking treatment, it is also confirmed that the gel fraction is 0% for any sealing material sheet.
(Condition 1: (High))
Vacuum heating lamination conditions Vacuum drawing: 6 minutes / pressurization: (0 kPa to 50 kPa): 10 seconds / pressure holding: (50 kPa): 11 minutes / temperature: 165 ° C.
(Condition 2: (Low))
Vacuum heating lamination conditions Vacuum drawing: 4 minutes / pressurization: (0 kPa to 50 kPa): 10 seconds / pressure holding: (50 kPa): 7 minutes / temperature: 110 ° C.
Cure conditions Time 40 minutes, temperature 150 ° C
(Evaluation criteria) A: Gel fraction is 70% or more.
B: The gel fraction is 65% or more and less than 70%.
C: The gel fraction is less than 65%.

[Evaluation Example 3: Outgas amount]
About each sealing material sheet which performed the crosslinking process similar to the measurement of the gel fraction of the evaluation example 2 in order to evaluate the amount of outgas inherent in each sealing material layer in the state integrated as a solar cell module The outgas amount was measured by the method of performing (preparation of calibration curve), (measurement of outgas amount), and (calculation of outgas amount) described in paragraphs <0024> to <0026> of this specification. The results are shown in Table 3 as “Outgas amount”.

[Evaluation Example 4: Generation of bubbles]
The solar cell module evaluation sample of an Example and a comparative example was created using each said sealing material sheet | seat and the following transparent front substrate, back surface protection sheet, and solar cell element. Each of the above members is laminated along the general layer structure shown in FIG. 1, and is subjected to a vacuum heating laminating process under the same vacuum heating laminating conditions as in Evaluation Example 2 above. A battery module evaluation sample was obtained.
(Transparent front substrate): White plate semi-tempered glass (JPT3.2 75 mm × 50 mm × 3.2 mm)
(Back surface protection sheet): Polyethylene terephthalate (PET) base material: Thickness 188 μm (“Lumirror S10”, manufactured by Toray Industries, Inc.)
Was used.
(Solar cell element): A crystalline silicon solar cell element produced using a polycrystalline silicon substrate. (Motech, IM156B3)
And about each solar cell module evaluation sample of an Example and a comparative example, after storing for 6 hours at 190 degreeC, the presence or absence of the bubble generation | occurrence | production at the interface of a sealing material sheet and another member was observed visually. The results are shown in Table 3 as “bubble generation”. The evaluation criteria were as follows.
(Evaluation criteria) A: Generation | occurrence | production of the bubble was confirmed visually.
C: It was confirmed by visual observation that no bubbles were generated.

  From Table 3, the solar cell module of the present invention is a thermosetting system that ensures a necessary and sufficient heat resistance by forming a resin composition containing polyethylene as a base resin and containing a crosslinking agent, and then proceeding with crosslinking. It is a solar cell module provided with the sealing material layer which consists of a sealing material sheet, Comprising: It turns out that heat resistance improvement and suppression of the outgas amount which exists in a sealing material layer can be made compatible.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Front surface side protective base material 3 Sealing material layer 31, 32 Sealing material sheet 4 Solar cell element 5 Back surface side protective base material

Claims (4)

A surface-side protective substrate, a back-side protective substrate, a solar cell element, and a sealing material layer that seals the solar cell element between the front-side protective substrate and the back-side protective substrate; A solar cell module comprising:
The sealing material layer, and a density of 0.865 g / cm ³ or more 0.900 g / cm ³ or less polyethylene base resin consists encapsulant sheet a gel fraction of 80% or less than 65%
The solar cell module whose outgas amount which exists in the said sealing material layer is 1.81 microgram / g or less in conversion of toluene.   2. The polyethylene is a copolymer of ethylene and an α-olefin, containing an α-olefin having 3 carbon atoms in a proportion of 6 mol% to 25 mol% and not containing an α olefin having 8 or more carbon atoms. The solar cell module according to.   The solar cell module according to claim 2, wherein the polyethylene is a copolymer of ethylene and an α-olefin, containing 18 mol% or more of an α-olefin having 3 carbon atoms. It is a manufacturing method of the solar cell module according to claim 1,
Density 0.865 g / cm ³ or more 0.900 g / cm ³ or less of the polyethylene resin as a base resin and then sealing material composition comprising a crosslinking agent, while the sheet-like holding the gel fraction to 10% or less A sealing material film forming step for obtaining an uncrosslinked sealing material sheet,
The component of the solar cell module including the uncrosslinked encapsulant sheet and the solar cell element is subjected to vacuum overheating lamination so that the gel fraction of the uncrosslinked encapsulant sheet is 65% or more and 80% or less. Including a module integration step of integrating while cross-linking to
The polyethylene-based resin is a copolymer of ethylene and an α-olefin, containing an α-olefin having 3 carbon atoms at a ratio of 6 mol% to 25 mol%.
The crosslinking agent is peroxyketals, dialkyl peroxides, or peroxycarbonates.
Manufacturing method of solar cell module.

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