JP6098084B2 - Encapsulant composition for solar cell module and method for producing encapsulant sheet - Google Patents

Description

  The present invention relates to a polyethylene-based encapsulant composition for solar cell modules, a method for producing an encapsulant sheet, and a solar cell module encapsulant sheet.

  Conventionally, as a sealing material sheet for a solar cell module, a combination of an ethylene-vinyl acetate copolymer resin (EVA) and a crosslinking agent typified by an organic peroxide has been used. However, with the recent increase in the output of solar cells, a sealing material having a high electric resistance value is required, and the problem that the electric resistance value of EVA having a polar group becomes apparent. It has become.

  As an alternative material that can solve this electrical resistance problem, it is conceivable to use a polyethylene resin having no polar group. Here, the electrical resistance value of the polyethylene-based sealing material sheet depends on the density of the polyethylene resin used and the degree of crosslinking. The higher the density and the degree of crosslinking, the higher the electric resistance value. However, since a high-density polyethylene resin lacks transparency, it is not preferable as a material for a solar cell encapsulant. Therefore, in order to provide a preferable electrical resistance value in the polyethylene-based sealing material sheet, a crosslinking treatment to low-density polyethylene is essential.

  As such a low-density polyethylene encapsulant sheet, an appropriate amount of a cross-linking agent was added to such an encapsulant composition so that the cross-linking proceeded substantially only during vacuum lamination during integration as a solar cell module. A thermosetting polyethylene encapsulant sheet is disclosed (see Patent Document 1).

JP 2012-54521 A

  Here, for example, when a thermosetting polyethylene resin is used as the material resin of the encapsulant sheet as in the encapsulant sheet described in Patent Document 1, it is necessary to use a resin having a high MFR to some extent. . However, the thermosetting polyethylene resin has a low crosslinking rate due to the small number of double bonds, and takes a lot of time for vacuum heating and pressing (thermal lamination) in the modularization process, resulting in poor productivity. Since it is MFR and the progress of cross-linking is slow, the film thickness changes greatly during thermal lamination, and the yield is reduced.

  In order to solve the problem, development of a thermoplastic polyethylene sealing material that does not require a thermosetting treatment after film formation, such as when modularized, has been performed. After the film is formed and completed as a sealing material sheet, a thermoplastic sealing material sheet that is not subjected to thermosetting treatment (in the present specification, such a sealing material sheet is hereinafter referred to as “thermoplastic system”). Therefore, a resin having a low MFR was inevitably selected in order to provide heat resistance. Specifically, a low-density polyethylene resin having a relatively large molecular weight and low fluidity, more specifically, a melt mass flow rate (MFR) at 190 ° C. and a load of 2.16 kg measured in accordance with JIS K6922-2 (in this specification, Hereinafter, a polyethylene resin having a measured value under these measurement conditions is referred to as “MFR”) of less than 20.0 g / 10 min is used, and a low molecular weight polyethylene resin having an MFR of 20.0 g / 10 min or more is used. In the sealing material of thermoplastic resin, it was practically excluded from the choice as a material resin of the sealing material for solar cell modules.

  However, further cost reduction is required for widespread use of photovoltaic power generation. In general, high molecular weight (low MFR) polyethylene resins are relatively expensive compared to low molecular weight (high MFR) polyethylene resins. In the present situation where development of a sealing material sheet having excellent physical properties and various physical properties required for a sealing material sheet for a solar cell module is strongly desired, as a means of cost reduction, In general, there has been a demand for the development of a solar cell module sealing material sheet using a low molecular weight (high MFR) polyethylene resin available at low cost.

  The object of the present invention is to use a low molecular weight (high MFR) polyethylene resin, which has been conventionally available at a low cost, but is not suitable as a base resin for an encapsulant sheet. Another object of the present invention is to provide a thermoplastic polyethylene encapsulant sheet that is excellent in various physical properties such as insulation and processability, and can also contribute to the improvement of productivity of solar cell modules.

  The inventors of the present invention provide a sealing material composition based on a low-density polyethylene having a high MFR containing a crosslinking agent having a half-life temperature of 1 minute in a predetermined high temperature range, and a film forming step. Is carried out under predetermined film-forming conditions, so that it is inferior to a conventional thermoplastic polyethylene sealing material sheet while being a thermoplastic polyethylene sealing material sheet based on low density polyethylene of high MFR. It is found that a solar cell module encapsulant sheet having various physical properties such as electrical resistance, transparency, heat resistance, and adhesion, which is equal to or greater than or equal to, can be produced at a lower cost than conventional products. The present invention has been completed. More specifically, the present invention provides the following.

(1) A sealing material composition for a solar cell module having a density of 0.900 g / cm ³ or less and 0.01 parts by mass with respect to 100 parts by mass of the resin component in the sealing material composition. The low-density polyethylene has a MFR of 190.degree. C. and a load of 2.16 kg measured in accordance with JIS K6922-2 of 20.0 g / 10 min or more and 40.40 wt. 0 g / 10 min or less, and the cross-linking agent has a 1-minute half-life temperature of 190 ° C. or higher and 250 ° C. or lower.

(2) A sheet forming step for thermoforming the sealing material composition according to (1), wherein the sheet forming step performs the thermoforming under the following heating conditions. Manufacturing method of sealing material sheet.
Heating condition: The average value of the resin temperature of the encapsulant composition during thermoforming is 190 ° C. or more and 260 ° C. or less, and the time during which the resin temperature during thermoforming is 190 ° C. or more is 3 minutes or more. To become a.

(3) Integration step of stacking and integrating the solar cell module sealing material sheet produced by the production method according to (1) or (2) and other solar cell module constituent members by thermocompression treatment. And performing the thermocompression bonding process under the following heating conditions.
Heating conditions: The resin temperature of the sealing material sheet during the thermocompression bonding process is 100 ° C. or higher and 170 ° C. or lower.

  According to the encapsulant composition for solar cell module and the method for producing the encapsulant sheet of the present invention, the electrical resistance value, transparency, heat resistance, and adhesion required for the encapsulant sheet for solar cell module. Thus, a thermoplastic low-density polyethylene encapsulant sheet that has various physical properties such as the above and can contribute to the improvement of the productivity of the solar cell module can be produced at a lower cost than before.

It is sectional drawing which shows an example of the laminated constitution about the solar cell module using the sealing material sheet of this invention.

  Hereinafter, it demonstrates in detail in order of the sealing material composition for solar cell modules which concerns on this invention, the sealing material sheet for solar cell modules, its manufacturing method, a solar cell module, and its manufacturing method.

<Encapsulant composition>
The encapsulant composition for a solar cell module of the present invention is based on a highly fluid low molecular weight polyethylene resin that can be produced at a relatively low cost and has a predetermined high half-life temperature of 1 minute. It contains a crosslinking agent in the temperature range. This sealing material composition can be formed into a sealing material sheet having the above-mentioned properties required for a sealing material sheet for a solar cell module by forming a film under heating conditions in a predetermined high temperature range. .

The sealing material composition used in the present invention has a density of 0.900 g / cm ³ or less, and an MFR of 20.0 g / 10 min or more at 190 ° C. and a load of 2.16 kg measured according to JIS K6922-2. Low-density polyethylene of 0.0 g / 10 min or less and a crosslinking agent having a 1 minute half-life temperature of 190 ° C. or more and 250 ° C. or less are contained as essential components. Hereinafter, after describing the essential components, other resins and other components will be described.

[Low density polyethylene]
The sealing material composition of the present invention uses low density polyethylene (LDPE) having a density of 0.900 g / cm ³ or less, preferably linear low density polyethylene (LLDPE) as a base resin. Linear low density polyethylene is a copolymer of ethylene and α- olefin, in the present invention, within the scope thereof density of 0.900 g / cm ³ or less, preferably 0.890 g / cm ³ within the following ranges , more preferably from 0.870 g / cm ³ or more 0.885 g / cm ³ or less. If it is this range, favorable softness | flexibility and transparency can be provided, maintaining sheet workability.

  The MFR of the low density polyethylene used for the sealing material composition of the present invention is 20.0 g / 10 min or more and 40.0 g / 10 min or less. Moreover, it is more preferable that they are 25.0 g / 10min or more and 35g / 10min or less.

  For example, as described in International Publication (WO2011 / 152314 A1), in the production of a low-density polyethylene-based encapsulant sheet, a limited very weak crosslinking reaction that does not involve a change in gel fraction during film formation ( It is known that a thermoplastic encapsulant sheet having preferable physical properties with respect to electrical resistance, transparency, heat resistance, adhesion, etc. can be obtained by advancing "hereinafter also referred to as" weak crosslinking "). Yes. However, in this case, if a high-MFR low-density polyethylene resin such as the encapsulant composition of the present invention is selected as the base resin, cross-linking proceeds excessively during film formation and a gel exceeding the allowable range is generated. Productivity is significantly impaired. On the other hand, if the progress of crosslinking is suppressed by shortening the heating time or decreasing the heating temperature, the heat resistance and insulation of the encapsulant sheet become insufficient. Therefore, in the thermoplastic polyethylene-based encapsulant sheet including the case where weak crosslinking is performed at the time of film formation as described above, a low MFR polyethylene resin having an MFR of less than 5.0 g / 10 min is a base resin. Has been used.

  On the other hand, the sealing material composition of the present invention uses a high MFR polyethylene resin as a base resin by optimizing the one-minute half-life temperature of the cross-linking agent and the film forming conditions within the range specific to the present invention. However, it is intended to produce a sealing material sheet excellent in heat resistance, insulation, workability, etc., by proceeding with a limited amount of weak crosslinking that does not involve a change in gel fraction during film formation. .

  In this specification, the gel fraction (%) refers to 0.1 g of a sealing material sheet placed in a resin mesh, extracted with 60 ° C. toluene for 4 hours, then taken out together with the resin mesh, weighed after drying, Mass comparison before and after extraction is performed to measure the mass% of the remaining insoluble matter, and this is used as the gel fraction. A gel fraction of 0% means that the residual insoluble matter is substantially 0 and that the crosslinking reaction of the encapsulant composition has not substantially started. More specifically, “gel fraction 0%” in the present invention means that the residual insoluble matter is not present at all, and the residual insoluble matter mass% measured by a precision balance is less than 0.05 mass%. Let's say the case.

  The polyethylene resin used as the base resin is more preferably 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, the polyethylene has a narrow molecular weight distribution, can be made extremely low in density as described above, and can impart flexibility to the sealing material. Moreover, as a result of providing flexibility by adopting the above polyethylene, adhesion between the sealing material and the substrate, such as adhesion between the sealing material and the transparent front substrate, adhesion between the sealing material and the back surface protective sheet, etc. Increases nature.

  In addition, the metallocene 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 due to the low density. . For this reason, it is excellent in transparency when processed into a sheet shape. Therefore, in particular, when the encapsulant sheet made of the encapsulant composition of the present invention is disposed between the transparent front substrate and the solar cell element, the solar cell module can be obtained by using the metallocene linear low density polyethylene. This can contribute to the improvement of the power generation efficiency.

  Further, as the α-olefin of the above LLDPE, an α-olefin having no branch is preferably used, and among these, 1-hexene and 1-heptene, which are α-olefins having 6 to 8 carbon atoms, are used. Or 1-octene is particularly preferably used. When the number of carbon atoms of the α-olefin is 6 or more and 8 or less, the sealing material sheet can be given good flexibility and good strength. As a result, the adhesion between the encapsulant sheet and the substrate is further enhanced.

  The low density polyethylene constituting the encapsulant composition of the present invention may further contain a silane-modified polyethylene resin. The silane-modified polyethylene resin is obtained by graft-polymerizing an ethylenically unsaturated silane compound as a side chain to linear low-density polyethylene (LLDPE) or the like as a main chain. Since such a graft copolymer has a high degree of freedom of silanol groups that contribute to the adhesive force, it can improve the adhesion of the sealing material sheet to other members in the solar cell module.

  The silane-modified polyethylene resin can be produced, for example, by the method described in JP-A-2003-46105. By using the resin as a component of a sealing material composition for a solar cell module, strength and durability can be obtained. In addition, it has excellent weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other characteristics, and is also affected by manufacturing conditions such as thermocompression bonding for manufacturing solar cell modules. Therefore, it is possible to manufacture solar cell modules that have extremely excellent heat-fusibility, are stable and low-cost, and are suitable for various applications.

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

  The graft amount, which is the content of the ethylenically unsaturated silane compound, is, for example, 0.001 to 15 masses with respect to a total of 100 mass parts of all the resin components in the sealing material composition containing other polyethylene-based resins described later. Part, preferably 0.01 to 5 parts by mass, particularly preferably 0.05 to 2 parts by mass. In the present invention, when the content of the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent. However, when the content is excessive, the tensile elongation and heat-fusibility tend to be inferior.

The content of polyethylene having a density of 0.900 g / cm ³ or less contained in the encapsulant composition is preferably 10 parts by mass with respect to a total of 100 parts by mass of all resin components in the encapsulant composition. It is 100 parts by mass or less, more preferably 50 parts by mass or more and 100 parts by mass or less, and still more preferably 90 parts by mass or more and 100 parts by mass or less. Other resin may be included as long as the melting point of the sealing material composition is within a range of less than 80 ° C. These may be used, for example, as an additive resin, or may be used for masterbatching other components described later.

[Crosslinking agent]
In the present invention, a crosslinking agent having a one-minute half-life temperature of 190 ° C. or higher and 250 ° C. or lower is used. Setting the half-life temperature for 1 minute to 190 ° C. or higher is based on a high MFR low-density polyethylene resin having a feature that there are many terminal double bonds that contribute to cross-linking and the cross-linking reaction is more likely to proceed. Also has an effect of suppressing the progress of excessive crosslinking. Moreover, the upper limit temperature of a crosslinking agent is about 250 degreeC from a viewpoint of resin oxidation degradation.

  In the case of a conventional thermosetting encapsulant sheet that is required to undergo a crosslinking treatment in the modularization process, the one-minute half-life temperature of the usable crosslinking agent is the same as that in the modularization process. Since it is restricted by the conditions of the heating temperature and the heating time, the half-life temperature for 1 minute is practically limited to the one less than about 185 ° C. In a conventional thermosetting sealing material, the crosslinking agent has a half-life temperature of less than 185 ° C. on the premise that it is not crosslinked during film formation and that it is crosslinked during thermal lamination. Is selected. That is, a crosslinking agent having a one-minute half-life temperature of 190 ° C. or higher has not been used in the past as a sealing material application for solar cells. Therefore, at least in this respect, the sealing agent of the present invention is not used. The stopping material composition is novel.

  Specific examples of the crosslinking agent having a 1 minute half-life temperature of 190 ° C. or more and 250 ° C. or less include, for example, 2,5-dimethyl-2,5di (t-butylperoxy) hexyne-3, diisopropylbenzene hydroperoxide, Examples thereof include p-menthane hydroperoxide, 1,1,3,3, -tetramethylbutyl hydroperoxide, and di-t-butyl peroxide.

  In the present invention, the content of a specific range in which the content of the crosslinking agent in the encapsulant composition is less than that in the case of a general thermal crosslinking treatment, with the crosslinking agent having a 1 minute half-life temperature in the above range. A cross-linking agent is used so that Content of a crosslinking agent is 0.01 mass% or more and less than 0.5 mass% in the sealing material composition for solar cell modules, Preferably an upper limit is 0.2 mass% or less, More preferably, it is 0.1. It is below mass%. By setting the content of the crosslinking agent in the encapsulant composition to less than 0.5% by mass, even when the above high MFR low density polyethylene resin is used as the base resin, Sheeting can be performed while suppressing excessive crosslinking and film-forming process load, and a sealing material sheet having particularly excellent durability can be obtained by weak crosslinking. When the content of the crosslinking agent in the sealing material composition is 0.5% by mass or more, crosslinking proceeds at the time of film formation and film formation becomes impossible. On the other hand, if the content of the crosslinking agent in the encapsulant composition is less than 0.01% by mass, even if the above-described high MFR low density polyethylene resin is used, weak crosslinking does not proceed and heat resistance is insufficient.

[Crosslinking aid]
In the sealing material composition of the present invention, the crosslinking aid is not an essential component, but can be appropriately used as necessary. Here, the crosslinking assistant is, for example, a polyfunctional vinyl monomer and / or a polyfunctional epoxy monomer, and specifically, triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fuma. Polyallyl compounds such as rate and diallyl maleate, trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6 -Poly (meth) acryloxy compounds such as hexanediol diacrylate and 1,9-nonanediol diacrylate, glycidyl methacrylate containing double bond and epoxy group, 4-hydroxybutyl acrylate glycol Epoxy compounds such as 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexane dimethanol diglycidyl ether, trimethylolpropane polyglycidyl ether and the like containing two or more diyl ethers and epoxy groups Can be mentioned.

  In the case where a crosslinking aid is used, among the above, the compatibility with low-density polyethylene is good, the crystallinity is lowered by crosslinking, the transparency is maintained, and TAIC is provided from the viewpoint of imparting flexibility at low temperature. It can be preferably used. Further, 1,6-hexanediol diacrylate can also be preferably used from the viewpoint of reactivity with the silane coupling agent. Further, addition of an appropriate amount of a crosslinking aid to the encapsulant composition can lower the crystallinity of the linear low density polyethylene and maintain higher transparency.

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

  A 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 adding this to a sealing material composition. Thereby, favorable weather resistance can be provided to the sealing material sheet for solar cell modules. 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.

  Furthermore, as other components used in the sealing material 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, a difficulty A flame retardant etc. can be mentioned.

<Sealing material sheet>
The encapsulant sheet of the present invention is obtained by subjecting the above-described encapsulant composition of the present invention to the above weak crosslinking treatment during thermoforming in the process of forming a film by the production method described in detail below. It is made into a sheet form or a film form. In addition, the sheet form in this invention means the film form, and there is no difference in both.

[Method for producing sealing material sheet]
The method for producing a sealing material sheet of the present invention is obtained by molding the above-described sealing material composition into a molding method usually used in ordinary thermoplastic resins, that is, injection molding, extrusion molding, hollow molding, compression molding, rotational molding, and the like. It is carried out by forming a film (making a sheet) by various molding methods. In addition, as an example of the sheet forming method when the encapsulant sheet is a multilayer film, a method of forming by co-extrusion using two or more types of melt-kneading extruders can be given. In addition, the sheet form in this invention means the film form, and there is no difference in both.

(Sheet making process)
In the manufacturing method of the present invention, the heat forming in the sheet forming step of the sealing material sheet is performed under the following heating conditions. That is, the resin temperature of the encapsulant composition during thermoforming exceeds the one-minute half-life temperature of the crosslinking agent used, and is in the temperature range of 190 ° C. or higher and 260 ° C. or lower, and the resin temperature Is a time within the above temperature range (this time is also referred to as “film forming time”. More specifically, the time from when the sealing material composition is charged into the molding machine until it is discharged from the molding portion. However, the heating process is adjusted so as to be 3 minutes or more, and the sheet forming step is performed. Here, the “resin temperature of the sealing material composition during heat molding” in this specification refers to the resin temperature in the molding part of the extruder. Moreover, the said shaping | molding part means the die part in a T-die extruder, for example. Such a resin temperature can be measured by attaching a temperature sensor thermocouple to the upper surface of the encapsulant sheet during heating and using a temperature / humidity data logger.

  By setting the resin temperature and the film formation time within the above ranges, even when a sealing material composition using a high MFR polyethylene resin as a base resin is used, the 1-minute half-life temperature is 190 ° C. or higher. By combining with the crosslinking agent, the encapsulant composition can be weakly crosslinked in a preferred embodiment. Thereby, according to the manufacturing method of this invention, it can be set as the sealing material sheet which has the outstanding insulation and heat resistance using the sealing material composition of this invention.

  When the film forming temperature is less than 190 ° C., when the encapsulant composition of the present invention is used, the weak crosslinking does not proceed properly, and the encapsulant sheet cannot be provided with insulation or heat resistance. .

  In addition, the upper limit of the film forming temperature is excessive from the viewpoint of optimization of the progress of crosslinking, depending on the 1 minute half-life temperature of the crosslinking agent used, exceeding the limited range of weak crosslinking reaction during thermoforming. A temperature at which the crosslinking reaction does not start, that is, a temperature at which the gel fraction of the encapsulant composition can be maintained at 0%, specifically, a temperature exceeding the one-minute half-life temperature of the crosslinking agent used. And in order to suppress the excessive progress of bridge | crosslinking, the temperature difference with the 1 minute half life temperature of the crosslinking agent to be used should just be 25 degrees C or less. However, from the viewpoint of the oxidation of polyethylene, it is preferably 260 ° C. or lower in practical implementation.

  Also, when the film forming time is less than 3 minutes, when the sealing material composition of the present invention is used, the weak crosslinking does not proceed sufficiently in the above film forming temperature range, and the sealing material sheet The above insulation and heat resistance cannot be sufficiently imparted. High-temperature heating exceeding the above-mentioned film forming temperature range can advance the crosslinking in a shorter time, but is not preferable because productivity may be reduced due to the generation of gel.

The sealing material sheet of the present invention formed through the sheet forming step has a sufficient film-forming property from the viewpoint of physical properties, i) maintaining low density, and ii) improving heat resistance. There is a feature. Regarding i), the density of the sealing material sheet of the present invention does not increase at about 0.900 g / cm ³ or less, which is almost equal to the density of the low-density polyethylene resin that is the main raw material, and the resin before and after melt molding The density difference of the composition is within 0.05 g / cm ³ . For this reason, transparency is maintained.

  On the other hand, ii) heat resistance of the encapsulant sheet of the present invention is such that the MFR is 0.05 g / 10 min or more and less than 3.0 g / 10 min, and preferably the MFR difference of the encapsulant composition before and after melt molding is 20 Since it is 0.0 g / 10 min or more and 30.0 g / 10 min or less, the heat resistance is improved while being within the range of MFR capable of film formation. Normally, there is a positive correlation between the MFR and the density of the resin. In the present invention, it is possible to slightly increase the MFR within the range of the moldable MFR without changing the density.

  The result of the weak crosslinking treatment can be understood from the gel fraction. The gel fraction of the sealing material sheet of the present invention is 0%.

  The weight average molecular weight in terms of polystyrene of the encapsulant sheet of the present invention is 120,000 to 300,000, and the ratio of the weight average molecular weight of the encapsulant sheet after film formation / the polyethylene resin in the encapsulant composition Is in the range of 1.3 to 4.0. From this, it can be understood that although it is made into a macromolecule, a dense cross-linked structure is not formed and a weak cross-link is formed.

  The encapsulant sheet desirably has a heat shrinkage rate equal to or less than a predetermined value in order to keep the yield rate at the time of module manufacture sufficiently high. The thermal contraction rate of the encapsulant sheet is preferably 45% or less, more preferably 30% or less, and most preferably 20% or less. For example, under typical conditions in the production method of the present invention, such as 190 ° C., evacuation: 5 minutes, pressure: (0 kPa to 100 kPa): 1.5 minutes, pressure holding (100 kPa): 7.0 minutes, and When the laminating process is performed using a high MFR polyethylene resin having an MFR of 20.0 g / 10 min to 40.0 g / 10 min, the heat shrinkage rate can be suppressed to 45% or less.

  As mentioned above, according to the manufacturing method of the sealing material sheet of this invention, by using the polyethylene resin of high MFR as a base resin, by maintaining the gel fraction of the sealing material composition in thermoforming at 0% It is possible to reduce the load applied to the extruder or the like during film formation and increase the productivity of the encapsulant sheet. Moreover, the limited encapsulating sheet can be made into a sealing material sheet excellent in heat resistance, insulation, etc. by carrying out limited very weak bridge | crosslinking at the time of film-forming limitedly.

<Solar cell module>
FIG. 1: is sectional drawing which shows an example of the layer structure about the solar cell module using the sealing material sheet of this invention. In the solar cell module 1 of the present invention, a transparent front substrate 2, a front sealing material layer 3, a solar cell element 4, a back sealing material layer 5, and a back surface protection sheet 6 are sequentially laminated from the incident light receiving surface side. ing. The solar cell module 1 of the present invention uses the above-described sealing material sheet for at least one of the front sealing material layer 3 and the back sealing material layer 5.

[Method for manufacturing solar cell module]
The solar cell module 1 is, for example, vacuum suction after sequentially laminating members composed of the transparent front substrate 2, the front sealing material layer 3, the solar cell element 4, the back sealing material layer 5, and the back surface protection sheet 6. Then, the above-mentioned members can be manufactured by thermocompression molding as an integrally molded body by a molding method such as a lamination method.

  According to the method for producing a solar cell module of the present invention, the thermocompression treatment is performed so that the resin temperature of the encapsulant sheet is in the range of 100 ° C. or more and 170 ° C. or less during the thermocompression treatment. It can be carried out. When a conventional EVA sealing material is used, heating exceeding 140 ° C. is generally essential. In addition, since a general polyethylene-based sealing material sheet has a low crosslinking rate, when it is used, for example, when laminating is performed at a temperature of 140 ° C. or lower, heating for a long time is required. There are disadvantages such as a large change in film thickness, or the need for a second heat cure after integration.

  In addition, about the resin temperature of the sealing material sheet at the time of manufacture of a solar cell module, the laminated body containing the sealing material sheet laminated | stacked by the same structure as the time of manufacture of a solar cell module is the same as the time of solar cell module manufacture. In accordance with the heating conditions, a thermal lamination treatment is performed on a trial basis. At that time, a temperature sensor thermocouple is attached to the upper surface portion of the encapsulant sheet, and measurement can be performed by using a temperature / humidity data logger. . The “resin temperature of the encapsulant sheet during the thermocompression treatment” in this specification refers to the temperature profile thus measured.

  Note that “the resin temperature of the encapsulant sheet during the thermocompression treatment” is “to be within the above temperature range” means, for example, that the encapsulant sheet is heated at a constant temperature by batch processing. Even if it is a case where the resin temperature of the encapsulant sheet being heated first reaches 100 ° C. or higher by adjusting the heating time, etc., and then heating is continued in a range that does not deviate from the above temperature range Etc. are also included.

  Also, conventionally, when a high MFR thermoplastic polyethylene resin having an MFR of 20.0 g / 10 min or more is used, there is a problem that heat resistance and molding stability are inferior. In fact, the MFR was limited to a resin having a MFR of less than 20.0 g / 10 min. However, in the production method of the present invention, since a polyethylene resin having an MFR of 20.0 g / 10 min or more can be used, the laminate process is appropriately performed even at a lower temperature, and the solar cell module is produced in a preferable mode. can do.

  It is preferable that the gel fraction after the thermocompression molding of the front sealing material layer 3 and the back sealing material layer 5 using the sealing material sheet of the present invention is 0%. By setting it as this range, the solar cell module 1 can be equipped with the sealing material layer which has high transparency, and shall have preferable heat resistance.

  And in the manufacturing method of the solar cell module of this invention, by using the sealing material sheet manufactured with the manufacturing method of the sealing material sheet of this invention, the flow of the sealing material sheet in a vacuum heating lamination is fully carried out. Can be suppressed. In addition, since there is no cross-linking step by the modularization step or the subsequent heating step, the degree of freedom of the vacuum heating laminating condition in the modularization step is increased because the cross-linking conditions need not be taken into account. Can be shortened and productivity is greatly improved. In particular, the problem of the polyethylene-based encapsulant sheet having a slower crosslinking rate than that of EVA can be solved, and the modularization time can be greatly shortened.

  In the solar cell module 1 of the present invention, the transparent front substrate 2, the solar cell element 4 and the back surface protection sheet 6 which are members other than the front sealing material layer 3 and the back sealing material layer 5 are made of conventionally known materials. It can be used without particular limitation. Moreover, the solar cell module 1 of this invention may also contain members other than the said member. In addition, the manufacturing method of the solar cell module of this invention is applicable to manufacture of not only a single crystal type but a thin film type and other solar cell modules.

  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>
The encapsulant composition having the following composition is mixed and melted, and formed into a film having a thickness of 400 μm by a conventional T-die method to obtain encapsulant sheets of Examples, Comparative Examples, and Test Examples. It was.

  The heating conditions during thermoforming during film formation were as shown in Table 1, respectively. The temperature in Table 1 refers to the “resin temperature of the encapsulant composition during heat molding” as defined above, and the time in Table 1 refers to “film formation as defined above”. Say "time".

(Base resin)
Sealed by mixing and melting 75 parts by mass of either of the following two LLDPEs (resin M1 (high MFR) or M2 (low MFR)) with different MFRs and 25 parts by mass of a silane-modified polyethylene resin (resin S) The base resin of the stopping material composition was used.
LLDPE (Resin M1)
: Polyethylene resin (LLDPE): A metallocene linear low density polyethylene which is a copolymer of ethylene and 1-hexene and has a density of 0.880 g / cm ³ and an MFR of ³⁰ g / 10 min. Number average molecular weight 55,000 in terms of polystyrene.
LLDPE (Resin M2)
: Polyethylene resin (LLDPE). A metallocene linear low density polyethylene which is a copolymer of ethylene and 1-hexene and has a density of 0.880 g / cm ³ and MFR of ³ g / 10 min. Number average molecular weight 100,000 in terms of polystyrene.
(Crosslinking agent)
The following three kinds of crosslinking agents (crosslinking agent 1 or crosslinking agent 2) were used, and the amounts (parts by mass) shown in Table 1 were added to the sealing material compositions of Examples, Comparative Examples, and Reference Examples.
2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 (crosslinking agent 1)
1 minute half-life temperature 194 ° C. Product name: “Lupelox 130”, manufactured by Arkema Yoshitomi Corporation
Di-t-butyl peroxide (crosslinking agent 2)
1 minute half-life temperature of 197 ° C. Product name: "Lupelox DI", manufactured by Arkema Yoshitomi Corporation
2,5-dimethyl-2,5-di (t-butylperoxy) hexane (crosslinking agent 3)
1 minute half-life temperature 181 ° C. Product name: “Lupelox 101” manufactured by Arkema Yoshitomi Corporation
(Adhesion improver)
A silane coupling agent was used as an adhesion improver. As the silane coupling agent, 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM503) is used, and the sealing material compositions of all Examples, Comparative Examples, and Reference Examples are 0.5. Part by mass was added.
(Other additives)
0.25 mass part of UV absorbers (Kemipro Kasei Co., Ltd., trade name KEMISORB12) were added to the sealing material compositions of all Examples, Comparative Examples, and Reference Examples.
0.2 parts by mass of a weathering stabilizer (manufactured by Ciba Japan Co., Ltd., trade name Tinuvin 770) was added to all the sealing materials of Examples, Comparative Examples, and Reference Examples.
An antioxidant (trade name: Irganox 1076, manufactured by Ciba Japan Co., Ltd.) was added to 0.05 parts by mass of the sealing material compositions of all Examples, Comparative Examples, and Reference Examples.

  The MFR of each example, comparative example, and test example and each sealing material composition was measured. In this measurement, in order to eliminate the influence of the progress of crosslinking at the time of measurement, MFR was measured for each sealing material composition in which the crosslinking agent component was excluded. The results are shown in Table 1. The definition of MFR is as described above.

  About each sealing material sheet after film forming of an Example, a comparative example, and a test example, the gel fraction was measured by the method demonstrated above. The results are shown in Table 2. The definition of the gel fraction of 0% is as described above.

<Evaluation Example 1>
The volume resistance values of the sealing material sheets of Examples, Comparative Examples, and Test Examples molded with a thickness of 400 μm were measured by the following methods to evaluate the insulating properties.
[Test method for volume resistance (Ω)]
About said sealing material sheet | seat, the volume resistance value was measured by JISC6481. The measurement was performed using a superinsulator (manufactured by Hioki Electric Co., Ltd .: model number SM-8215). The measurement results for each of the examples, comparative examples, and test examples were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 2.
A: 1.0E + 15Ω or more B: 7.0E + 14Ω or more and less than 1.0E + 15Ω C: less than 7.0E + 14Ω

<Evaluation Example 2>
The sealing material sheets of Examples, Comparative Examples, and Test Examples cut to 30 mm × 75 mm were respectively laminated on glass substrates (blue plate glass 30 mm × 75 mm × 3.2 mm), and the sealing material sheets after lamination were laminated. A vacuum heating laminator process is performed with a spacer so that the film thickness is 360 to 400 μm, and the HAZE of each encapsulant sheet after the process is measured (%) by the following test method. Transparency after integration as a module was evaluated. Lamination conditions were as follows.
(Lamination conditions) (a) Vacuum drawing: 5.0 minutes
(B) Pressurization (0 kPa to 100 kPa): 1.5 minutes
(C) Pressure holding (100 kPa): 8.0 minutes
(D) Temperature 150 ° C

[Test method for haze (%)]
According to JISK7136, it measured with Murakami Color Research Institute Co., Ltd. Haze and transmittance system HM150. The measurement results for each of the examples, comparative examples, and test examples were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 2.
A: Less than 4.0% B: 4.0% or more and less than 5.5% C: 5.5% or more

<Evaluation Example 3>
About the sealing material sheet | seat after film forming of an Example, a comparative example, and a test example, the heat resistance creep was measured with the following method, respectively, and it was set as the index value of heat resistance evaluation.
[Test method for heat-resistant creep test (mm)]
The sealing material sheet after film formation of Examples, Comparative Examples, and Test Examples cut to 7.5 × 5.0 cm is placed on a glass substrate (white plate float semi-tempered glass JPT3.2 150 mm × 150 mm × 3.2 mm). Two glass plates are placed on top of each other, and a glass substrate (white plate float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) is placed on top of each other, and vacuum heating laminator treatment is performed under the same heat laminating conditions as in Evaluation Example 2, Samples for solar cell module evaluation were obtained for Examples, Comparative Examples, and Test Examples. These solar cell module evaluation samples were subjected to a heat-resistant creep test under the following test conditions to evaluate heat resistance.
The solar cell module evaluation sample was placed vertically and allowed to stand at 140 ° C. for 12 hours, and the moving distance of the glass substrate (white plate semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) after being left was measured and evaluated. . About the sealing material sheet after film forming of each Example, a comparative example, and a test example, the measurement result was evaluated by the following evaluation criteria. The evaluation results are shown in Table 2.
A: Less than 4.0 mm B: 4.0 mm or more and less than 6.0 mm C: 6.0 mm or more

<Evaluation Example 4>
Evaluation Example 1 The sealing material sheets of Examples, Comparative Examples, and Test Examples cut to a width of 15 mm were adhered to a glass substrate (white plate semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm), respectively. Under the same heat laminating conditions, a vacuum heating laminator treatment was performed, and solar cell module evaluation samples were obtained for the respective examples and comparative examples. About these solar cell module evaluation samples, the glass adhesion strength under the following test conditions was measured to evaluate the glass adhesion.
[Test method for glass adhesion strength (N / 15 mm)]
Peeling test method: In the above solar cell module evaluation sample, the sealing material sheet in close contact with the glass substrate was vertically peeled (50 mm / min) with a peeling tester (Tensilon Universal Tester RTF-1150-H). A test was conducted to measure the glass adhesion strength. The measurement results for each Example and Comparative Example were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 2.
A: 30 N / 15 mm or more B: 25 N / 15 mm or more and less than 30 N / 15 mm C: Less than 25 N / 15 mm

  From Table 2, the manufacturing method of the sealing material sheet using the sealing material composition of the present invention using a high MFR resin as a base resin is a method of forming a film while maintaining the gel fraction at 0%. Therefore, it turns out that it is an excellent method from the viewpoint of productivity in the sheeting process. In addition, regarding heat resistance, which has been a conventional problem when using a resin with high fluidity as a base resin, the physical properties comparable to those of conventional products using low MFR resins (Comparative Examples 1 and 2) are sealed. It can be seen that it can be applied to the stop sheet.

  Also, from Table 2, according to the production method of the present invention, the transparency and insulation superior to those of the conventional products can be imparted to the encapsulant sheet by appropriately advancing the weak crosslinking specific to the present invention. Can be.

  Moreover, it can be seen from Table 2 that according to the manufacturing method of the present invention, it is possible to manufacture a sealing material sheet having sufficient adhesion to glass, which is the main material of the constituent members of the solar cell module. In addition, as for the adhesion to other substrates, the adhesion can be improved by appropriately adjusting the film forming conditions and the type and amount of additives to the sealing material composition for each substrate to be laminated. It is thought that.

  From Tables 1-2, the manufacturing method of the sealing material sheet | seat of this invention restricts the kind and content of a crosslinking agent, and film forming conditions to the range unique to this invention, respectively, processability, heat resistance. It can be seen that this is a production method capable of producing a sealing material sheet excellent in all adhesion at a lower cost than in the past.

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

Claims (2)

A low density polyethylene having a density of 0.900 g / cm ³ or less and an MFR of 20.0 g / 10 min or more and 40.0 g / 10 min or less at 190 ° C. and a load of 2.16 kg measured according to JIS K6922-2; A sealing material composition including a crosslinking agent having an initial temperature of 190 ° C. or more and 250 ° C. or less and contained in an amount of 0.01 parts by mass or more and less than 0.5 parts by mass with respect to 100 parts by mass of the resin component Equipped with a sheeting process,
The sheet forming step performs the thermoforming under the following heating conditions,
The gel fraction of the encapsulant sheet after the sheeting step is 0%,
The manufacturing method of the sealing material sheet | seat for solar cell modules.
Heating condition: The resin temperature of the encapsulant composition during thermoforming exceeds the 1 minute half-life temperature of the cross-linking agent and is in a temperature range of 190 ° C. or higher and 260 ° C. or lower, and the resin temperature is The time within the temperature range is 3 minutes or more. The solar cell module sealing material sheet manufactured by the manufacturing method according to claim 1 and another solar cell module component are provided with an integration step of stacking and integrating by thermocompression bonding,
The manufacturing method of the solar cell module characterized by performing the said thermocompression-bonding process on the following heating conditions.
Heating conditions: The resin temperature of the sealing material sheet during the thermocompression bonding process is 100 ° C. or higher and 170 ° C. or lower.

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