WO2019013290A1 - Solar cell module and method for manufacturing same - Google Patents

Abstract

The purpose of the present invention is to provide a solar cell module equipped with a sealing material layer comprising a heat-curable sealing material sheet having polyethylene as the base resin, wherein crosslinking of the sealing material layer is sufficiently advanced and the amount of outgas present therein is sufficiently suppressed. A solar cell module 1 including an obverse surface-side protective substrate 2, a reverse surface-side protective substrate 5, a solar cell element 4, and a sealing material layer 3 for sealing the solar cell element 4 between the obverse surface-side protective substrate 2 and the reverse surface-side protective substrate 5, wherein: the sealing material layer 3 comprises sealing material sheets 31, 32 that have a gel fraction of 65-80% and that have, as the base resin, polyethylene having a density of 0.865 g/cm3 to 0.900 g/cm3; and the amount of outgas present in the sealing material layer 3 is 1.81 μg/g or below in terms of toluene.

Description

Solar cell module and method of manufacturing the same

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

BACKGROUND OF THE INVENTION In recent years, solar cells as clean energy sources have attracted attention due to rising awareness of environmental issues. Currently, solar cell modules of various forms have been developed and proposed. A general solar cell module is sealed by a sealing material sheet for a solar cell module between a front surface side protection base material such as a glass protection substrate and a back surface protection member made of a resin sheet having weather resistance and the like. The solar cell element is disposed.

The above-described members constituting the solar cell module, in particular, the above-described sealing material sheet, are constantly exposed to severe environments such as strong ultraviolet rays, heat rays, wind and rain, etc., when used. For this reason, it is essential that the above-described members such as the sealing material sheet have high durability enough to withstand long-term use under such severe environment.

For example, as a sealing material sheet having such high durability, a sealing is made of a resin composition containing EVA (ethylene-vinyl acetate copolymer) as a base resin, and containing a crosslinking agent and a crosslinking aid. An anchor sheet is known (see Patent Document 1). In this case, when the crosslinking reaction proceeds during extrusion molding, the load of the film formation becomes excessive and the productivity decreases due to the above-mentioned resin composition, or the film formation becomes impossible. By the extrusion by the following low temperature heating, it forms into a film as non-crosslinked. Then, after the film formation, the encapsulant sheet made of the above-mentioned resin composition is crosslinked by heat treatment or the like at the time of modularization.

On the other hand, when the base resin of the sealing material sheet is a polyethylene-based resin, it is known that the adhesion with a glass etc. is improved by the blending of the silane coupling agent, but in order to further improve the adhesion, A sealing material using a modified ethylene-based resin in which alkoxysilane is graft polymerized is also known (see Patent Document 2). According to this, a sealing material sheet having durability and adhesiveness can be provided while eliminating the need for the crosslinking step as in the case of the sealing material sheet described in Patent Document 1.

JP, 2009-135200, A Japanese Patent Application Publication No. 2002-235048

The sealing material 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. As described above, when the base resin of the sealing material sheet is thermoplastic polyethylene, in order to secure the necessary and sufficient heat resistance required for the sealing material sheet, the resin having high density and high melting point is to some extent I had no choice but to choose. In fact, in the example of Patent Document 2, it is a necessary result that the composition of the silane-modified ethylene-α-olefin copolymer (Example 2) is extruded at a high temperature of 180 ° C.

Densification of the polyethylene-based resin used as the base resin of the encapsulant sheet leads to a decrease in the transparency of the encapsulant sheet. However, in the case of using thermoplastic polyethylene as a base resin, in order to ensure sufficient heat resistance, the fact that the transparency had to be deteriorated to a certain degree had to be accepted. .

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

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

The present invention has been made to solve the above problems. The purpose is to form a resin composition containing polyethylene as a base resin and containing a crosslinking agent, and then proceed with crosslinking to achieve a sealing made of a thermosetting-type sealing material sheet for securing necessary and sufficient heat resistance. In a solar cell module provided with a material layer, the present invention is to provide a solar cell module capable of achieving both improvement in heat resistance and suppression of the amount of outgas generated in a sealing material layer.

The present inventors have made the base resin of the sealing material composition which forms the sealing material sheet which comprises the sealing material layer of a solar cell module into polyethylene which consists of alpha olefin of a specific carbon number, for example, It has been found that the necessary amount of addition of the crosslinking agent can be reduced as compared to the prior art in order to advance the crosslinking to a level sufficient to secure the necessary heat resistance. And thereby, it succeeded in manufacturing a solar cell module which has a sealing material layer with a very small amount of outgases derived from a crosslinking agent, although it is a high gel fraction, and came to complete this invention. More specifically, the present invention provides the following.

(1) A sealing material for sealing the front side protection base, the back side protection base, the solar cell element, and the solar cell element between the front side protection base and the back side protection base 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 whose amount of outgassing inherent in the said sealing material layer is 1.81 microgram / g or less in toluene conversion.

(2) The solar cell module according to (1), wherein the polyethylene is a copolymer of ethylene and an α-olefin, wherein the polyethylene contains an α-olefin having 3 carbon atoms in a proportion of 6 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 Forming a sealing material composition in a sheet form while maintaining the gel fraction at 10% or less, and obtaining a non-crosslinking sealing material sheet, and the non-crosslinking While making the gel fraction of the non-crosslinked sealing material sheet 65% to 80% by vacuum heating lamination, the constituent members of the solar cell module including the sealing material sheet and the solar cell element are crosslinked A module integration step of integrating, wherein the polyethylene-based resin is a copolymer of ethylene and an α-olefin, containing an α-olefin having 3 carbon atoms in a proportion of 6 mol% or more and 25 mol% or less The method for producing a solar cell module, wherein the crosslinking agent is peroxyketals, dialkyl peroxides, or peroxycarbonates.

According to the present invention, in a solar cell module provided with a thermosetting-based encapsulant layer based on polyethylene, crosslinking of the encapsulant layer is sufficiently advanced, and the outgassing inherent in the same layer. It is possible to provide a solar cell module whose amount is sufficiently suppressed.

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 configuration 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 protection 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 reception surface side of incident light. The element 4, the sealing material sheet 32 on the back surface side, and the back surface side protection base material 5 are laminated in order. The pair of sealing material sheets 31 and 32 are disposed in close contact with both surfaces of the solar cell element 4 to constitute a sealing material layer 3 for sealing them.

[Sealing material layer]
In the present specification, “the sealing material layer for sealing the solar cell element” is, as a representative example, as shown in FIG. 1, a pair of the sealing elements disposed on both sides of the solar cell element. It refers to the layer which seals this by the aspect pinched by material sheet. 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 structure in which a sealing material sheet is coated with a cell glass in which a thin film solar cell element is formed on a glass substrate, the thin film formed on the above cell glass The sealing material sheet covering the elements of the system is regarded as the “sealing material layer sealing the solar cell element” in the solar cell module.

In the solar cell module 1 of the present invention, the encapsulating material layer 3 is made of a polyethylene resin, and the encapsulating material layer 3 is sufficient to have a gel fraction of 65% or more as an index of the degree of crosslinking. Cross-linked to Usually, when the polyethylene-based resin constituting the encapsulant layer 3 is crosslinked to this extent, at least outgassing exceeding 1.81 μg / g in terms of toluene is included in the encapsulant layer 3 and The probability of becoming It is extremely difficult to stably avoid this by the manufacturing method according to the conventional knowledge, and unless the degree of crosslinking is kept below 65%, the generation of the above outgassing amount is substantially unavoidable. there were. In the solar cell module 1 of the present invention, the crosslinking of the sealing material layer 3 is sufficiently advanced to the above degree, and the amount of outgassing inherent in this layer is at least 1.81 μg in terms of toluene. It is mainly characterized in that it is suppressed to / g or less, more preferably to 1.32 μg / g or less in equivalent conversion.

Here, “gel fraction (%)” in the present specification means that 1.0 g of the sealing material is put in a resin mesh, extracted with 110 ° C. xylene for 12 hours, then taken out together with the resin mesh and weighed after drying processing. Then, mass comparison before and after extraction was performed to measure the mass% of the remaining insoluble content, and this was taken as the gel fraction. The gel fraction of 0% means that the residual insoluble content is substantially zero, and the crosslinking reaction of the encapsulant composition or the encapsulant sheet is not substantially initiated. More specifically, “gel fraction 0%” means that the above-mentioned residual insolubles are not present at all, and the above-mentioned residual insolubles measured by a precision balance have a mass% of less than 0.05% by mass. Shall be said. The above-mentioned residual insolubles do not contain pigment components other than resin components. When inclusions other than these resin components are present in the residual insolubles according to the above-mentioned test, for example, the content of these inclusions in the resin component may be separately measured in advance. The gel fraction to be originally obtained can be calculated for the residual insoluble matter derived from the resin component excluding the inclusions.

[Outgas amount inherent to the encapsulant layer]
Further, in the present specification, “the amount of outgassing included in the sealing material layer” means “the sealing material layer for sealing the solar cell element in the solar cell module in the stage of completing the crosslinking treatment and becoming a finished product. The amount of gas present in the above-mentioned “specifically” refers to the amount of gas per unit mass (μg / g) in terms of toluene. And the amount of outgassing according to this definition is determined as a specific value by sequentially performing (preparation of calibration curve), (measuring the amount of outgassing) and (calculating the amount of outgassing) by each method described below You can get it.

(Creation of calibration curve)
Ethyl acetate and toluene are weighed and mixed with 5.05566 g of ethyl acetate = 5.06494 ml and 0.99237 g of toluene = 1.150841 ml. Dispense 0.5 μl, 1.0 μl, 3.0 μl, 5.0 μl of the mixture into vials respectively. The content of toluene is 0.073446 μg, 0.14689 μg, 0.44068 μg, and 0.73446 μg. Next, each vial is heated at 165 ° C. for 30 minutes, 10 ml of gas is collected, a spectrum is detected by FID-GC, and the area of peak of toluene is integrated to obtain the relationship of Table 1 below. Then, from each value of Table 1, a calibration curve represented by the following linear equation is defined.
Y = (1.3488 × 10 ^-5 ) X
Y: Toluene amount (μg)
X: Area value (pA / sec)

(Measurement of outgassing amount)
200 mg of the test sample of the sealing material layer to be measured, which has been cross-linked in advance, is weighed and taken into vials. 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.

(Calculating the amount of outgassing)
The integrated value is applied to the above calibration curve to calculate the amount of outgas generation in terms of toluene from the test sample.
Toluene conversion outgas generation amount (μg / g) = (1.3488 × 10 ⁻⁵ ) ×× (1000/200) = (0.6744 × 10 ⁻⁶ ) ×
The above spectrum detection can be performed by gas chromatography analysis (qualitative / quantitative analysis) by measurement under the following conditions using the following measuring apparatus.
Device: Agilent 6890 (manufactured by Agilent Technologies)
Column: Agilent J & W GC Column “HP-5MS” (Agilent Technologies)
Column temperature: 40 ° C to 320 ° C
Gas: He
Detector: Hydrogen flame ionization detector (FID)

[Sealing material sheet]
The sealing material sheets 31 and 32 (hereinafter, also simply referred to as “sealing material sheets”) constituting the sealing material layer 3 of the solar cell module 1 are conventionally used as the sealing material compositions whose details are described below. It is molded into a film or sheet by a known method. Incidentally, the sheet-like in the present invention means that the film-like is also included, and there is no difference between the two.

In addition, the sealing material sheets 31 and 32 limit the film forming temperature to a low temperature range of 90 ° C. to 120 ° C., and form a film without being crosslinked. The crosslinking treatment is completed, for example, by 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 the .885g / cm ³ or more 0.890 g / cm ³ or less of the polyethylene resin as a base resin, 10% 0% gel fraction, more preferably is formed of a resin film of uncrosslinked 0% .

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

In addition, after completion of the cross-linking after the integration of the sealing material sheets 31 and 32 into the solar cell module 1, that is, at a stage where sufficient cross-linking in which the gel fraction of the sealing material layer 3 becomes 65% or more Also, 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 at the uncrosslinked stage after film formation is MFR at 190 ° C. and a load of 2.16 kg measured according to JIS-K6922-2 (in this specification, hereinafter, The measured value under the measurement conditions is referred to as “MFR”) is preferably 5 g / 10 minutes or more and 25 g / 10 minutes or less, and more preferably 10 g / 10 minutes or more and 20 g / 10 minutes or less. When MFR is in the range of 5 g / 10 minutes to 25 g / 10 minutes, 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 is a multilayer film which is demonstrated below, the measurement by the said process is measured in the multilayer state in which all the layers were integrally laminated, and the obtained measured value is said multilayer The MFR value of the sealant sheet of

The thickness of each of the sealing material sheets 31 and 32 may be 200 μm or more and 1000 μm or less, and preferably 300 μm or more and 600 μm or less.

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

When making a sealing material sheet into a multilayer film, it is more preferable to set it as the layer structure from which MFR differs for every layer in the range which satisfy | fills the essential component requirements of this invention, and in this case, a layer with a higher MFR It is preferable to arrange | position to the outermost layer side as a skin layer. The encapsulant sheet of the present invention, even in the case of a single-layer encapsulant sheet, has sufficiently favorable transparency, heat resistance, and appropriate flexibility, but in such a manner it is relatively MFR. By arranging the high layer as the outermost layer, it is possible to further improve the adhesion and the molding characteristics while maintaining the above-mentioned preferable transparency and heat resistance as the sealing material sheet.

For example, in a sealing material sheet which is a multilayer film consisting of three or more layers, the thickness of the outermost layer is 30 μm or more and 120 μm or less, and an intermediate layer and an outermost layer consisting of all layers other than the outermost layer It is preferable that the thickness ratio of (1) be in the range of outermost layer: intermediate layer: outmost layer = 1: 3: 1 to 1: 8: 1. By so doing, it is possible to provide the preferable molding characteristics of the outermost layer while maintaining the preferable heat resistance as the sealing material.

[Sealant composition]
The low-density polyethylene-based sealing material composition (hereinafter, also simply referred to as “sealing material composition”) used for the production of the sealing material sheets 31 and 32 constituting the sealing material layer 3 of the solar cell module 1 It is a resin composition of a thermosetting system which uses a resin as a base resin and requires a crosslinking agent. In the present specification, the “base resin” refers to a resin having the largest content ratio in the resin component 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 A polyethylene of at least ³ cm ^{3 and not} more than 0.890 g / cm ^{3 is used} as the base resin. By using the low density polyethylene as described above as the base resin, the transparency of the sealing material sheets 31 and 32 can be improved. Moreover, according to this, adhesion with other members constituting the solar cell module 1 such as a glass substrate to be laminated as the front side protection base material 2 is enhanced, and a cell at the time of pressure bonding of each member in lamination processing The risk of cracking can also be reduced. The content of the above-mentioned base resin is 70% by mass or more and 100% by mass or less, preferably 90% by mass or more and 99% by mass or less with respect to the total resin component of the encapsulant composition. As long as the base resin is contained within the above range, the sealing material composition may contain other resins within the range not inhibiting the effects of the present invention.

The polyethylene used as a base resin of the encapsulant composition is linear low density polyethylene (LLDPE) which is a copolymer of ethylene and an α-olefin. Further, the base resin is more preferably a metallocene linear low density polyethylene (M-LLDPE). The metallocene based linear low density polyethylene is one synthesized using a metallocene catalyst which is a single site catalyst. Such polyethylene has less side chain branching and uniform comonomer distribution. For this reason, the molecular weight distribution is narrow, and the ultra-low density as described above can be achieved, and flexibility can be imparted to the sealing material. As a result of the flexibility given to the sealing material, the adhesion between the sealing material and glass, metal or the like is enhanced.

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

As the α-olefin of the linear low density polyethylene used as a base resin of the encapsulant composition, propylene having 3 carbon atoms is used at a ratio of a predetermined amount or more. Thereby, while making the gel fraction after the crosslinking treatment of the sealing material layer 3 65% or more, the amount of outgassing inherent in the same layer after such crosslinking treatment is 1.81 μg / g in terms of toluene. The following can be made. The encapsulant composition contains the α-olefin of this specific carbon number in the base resin in an amount of 18 to 25 mol%, preferably 15 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 the α-olefin of a polyethylene resin used for a sealing material sheet for a solar cell module However, by replacing this with propylene having a carbon number of 3, the sealing material layer 3 can be provided with sufficient heat resistance by the addition of a smaller amount of a crosslinking agent.

By setting the content of the α-olefin having a specific carbon number in the encapsulant composition to 18 mol% or more, even with a relatively small amount of added crosslinking agent, sufficient for the encapsulant sheets 31 and 32 It is possible to impart heat resistance, and at the same time, it is possible to suppress the deterioration of the light stabilizers contained in the sealant sheets 31 and 32. On the other hand, if the content exceeds 25 mol%, the melting point lowers and blocking tends to occur in the process of manufacturing the sealing material sheet, and therefore the content is preferably 25 mol% or less.

Although it is not essential that the α-olefins in the base resin of the encapsulant composition are all having 3 carbon atoms, it does not contain, for example, α-olefins having 8 or more carbon atoms, such as 1-octene. Is preferred.

The “content (mol%) of α-olefins of specific carbon number” of the sealing material sheets 31 and 32 and the sealing material layer 3 after crosslinking in the non-crosslinked stage after film formation is any of the following: It can be calculated by the measurement method of
'Method of measuring content (mol%) of α-olefin of specific carbon number'
The sealing material sheet or the sample for measurement of the sealing material layer after crosslinking is dissolved in ODCB / C6D6 (4/1) solvent to a concentration of 10 wt%. With the temperature of this solvent set at 130 ° C., measurement is carried out using 13 C-NMR to quantify a peak characteristic of triad (tried). After calculating the sequence fraction of the monomers (the entire sequence is normalized to 100%), the ratio of each monomer (C3 component concentration) is calculated from the sequence fraction.

Adding an appropriate amount of a silane copolymer (hereinafter also referred to as a “silane copolymer”) formed by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer to the encapsulant composition. preferable. Thereby, the adhesion between the sealing material sheets 31 and 32 and other members such as the glass substrate laminated as the front side protection base material 2 and the solar cell element 4 made of metal or ceramic can be further improved. .

The silane copolymer is, for example, one described in JP-A-2003-46105. By using the said copolymer as a component of a sealing material composition, it is excellent in intensity | strength, durability, etc., And, various things, such as weather resistance, heat resistance, water resistance, light resistance, wind resistance, falling resistance, etc. Excellent in properties, moreover, it has extremely excellent heat sealing property without being influenced by manufacturing conditions such as heat and pressure bonding for manufacturing a solar cell module, and stably, at low cost, suitable for various applications Material sheet can be manufactured.

As the silane copolymer, any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer can be preferably used, but a graft copolymer is more preferable. It is more preferable to use a graft copolymer in which polyethylene for polymerization is used as a main chain and an ethylenically unsaturated silane compound is used as a side chain. Such a graft copolymer can increase the degree of freedom of the silanol group contributing to the adhesive force, and thus can improve the adhesiveness between the sealant sheet and other members.

The content of the ethylenically unsaturated silane compound when constituting a copolymer of an α-olefin and an ethylenically unsaturated silane compound is 0.001% by mass or more and 15% by mass or less based on the total mass of the copolymer The content is preferably 0.01% by mass to 5% by mass, and most preferably 0.05% by mass to 2% by mass. 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 high, the mechanical strength and the heat resistance are excellent, but the content is excessive. In such a case, it tends to be inferior in tensile elongation, heat fusion and the like.

As a crosslinking agent used for the encapsulant composition, the amount of outgassing inherent 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 crosslinker selected in is suitably selected. Specifically, in the case where the content of carbon number 3 of the α-olefin of the ethylene / α-olefin copolymer of the base resin of the sealing material 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 the base resin having the above-mentioned highly reactive composition and the crosslinking agent having an active oxygen content in the above range, the addition amount of the crosslinking agent is suppressed within an appropriate range to avoid excessive generation of outgassing. At the same time, the crosslinking can be advanced to such an extent that the gel fraction is 65% or more, and the sealing material layer 3 can be provided with sufficient heat resistance.

Moreover, it is preferable to use the thing of 125 degreeC or more and 145 degrees C or less about 1 hour half life temperature of the crosslinking agent used for a sealing material composition. This makes it possible to make the sealant composition a composition that can be melt-extruded at 120 ° C. or less.

Also, specific examples of preferable crosslinking agents satisfying the above conditions include peroxycarbonates such as t-amyl-peroxy-2-ethylhexyl carbonate, 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, etc., di-t-butyl peroxide , T-Butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-peroxy) hexyne Mentioning as a crosslinking agent which can be used by adding dialkyl peroxides such as -3 to the encapsulant composition Kill. Among them, dialkyl peroxide cross-linking agents having an active oxygen content of 9.22 or more and a one-hour half-life temperature of 140 ° C. (for example, product name “Lperox 101” (manufactured by Arkema Yoshitomi Co., Ltd.)), or A cross-linking agent of peroxyketals having an active oxygen content of 8.61 or more and a one-hour half-life temperature of 129 ° C. (for example, product name “RUPEROX 230” (manufactured by Arkema Yoshitomi Co., Ltd.)) as a sealant composition It can use especially preferably as a crosslinking agent to be used.

The content of the above-mentioned crosslinking agent in the encapsulating material composition is such that the amount of outgassing inherent in the encapsulating material layer after the crosslinking treatment is converted into toluene while performing sufficient crosslinking treatment for each of the various crosslinking agents described above Each appropriate amount range may be selected so as to be 1.81 μg / g or less. Specifically, in the case where the content of the carbon number 3 of the α-olefin 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 is 0.3 to 0.6 mass%.

More specifically, when the crosslinking agent selected in combination with the same base resin as described above is a peroxycarbonate, the content of the above-mentioned crosslinking agent in the encapsulating material composition is in the encapsulating material composition. It is preferable that content with respect to all the resin components of these 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, in the case of dialkyl peroxides, the content is preferably 0.29% by mass or more and 0.43% by mass or less.

Sufficient heat resistance can be given to the sealing material sheets 31 and 32 by adding a crosslinking agent in such an addition amount that the content of the crosslinking agent in the sealing material composition falls within the above range. Moreover, if it is the addition amount of this range, generation | occurrence | production of the outgas derived from a crosslinking agent can also be suppressed enough. In addition, the sealing material sheet concerning this invention forms into a film without advancing crosslinking substantially, and the content range of said crosslinking agent in the sealing material sheet in the sheet | seat stage after film-forming is also carried out. The range is similar to that of the composition stage.

In the encapsulant composition, a crosslinking monomer having a carbon-carbon double bond and / or an epoxy group, and more preferably, the functional group of the polyfunctional monomer is an allyl group, a (meth) acrylate group, a vinyl group It is preferable to contain an agent. In addition to promoting an appropriate crosslinking reaction by this and improving the adhesiveness with respect to the glass of a sealing agent sheet 31 and 32, or a metal, this crosslinking auxiliary agent forms the sealing agent sheet 31 and 32, the linear Decreases the crystallinity of low density polyethylene and maintains transparency. Thereby, in addition to the effect of the improvement of said adhesiveness, transparency and low temperature flexibility of the sealing material sheets 31 and 32 can be made more excellent.

Specific examples of the crosslinking aid that can be used for the sealant composition include polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate, and trilyl. 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 compound such as diol diacrylate, glycidyl methacrylate containing double bond and epoxy group, 4-hydroxybutyl acrylate glycidyl ether, and containing 2 or more epoxy groups That 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and epoxy compounds such as trimethylolpropane polyglycidyl ether. These may be independent or may combine 2 or more types. In addition, among the above-mentioned crosslinking assistants, it significantly contributes to the improvement of the glass adhesion of the encapsulating material, has good compatibility with linear low density polyethylene, reduces crystallinity by crosslinking and maintains transparency, TAIC can be preferably used from the viewpoint of imparting flexibility in

The content of the crosslinking assistant in the encapsulant composition is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.05% by mass, based on all resin components in the encapsulant composition. It is mass% or more and 2.0 mass% or less. If the content of the crosslinking assistant in the encapsulant composition is within this range, it is possible to promote appropriate crosslinking reaction and improve the adhesion of the encapsulant sheets 31 and 32.

In the sealant composition, it is preferable to use a hindered amine light stabilizer (HALS) as a light stabilizer. Hindered amine light stabilizers are roughly classified according to the bonding partner of the nitrogen atom in the piperidine skeleton into NH type (hydrogen bonded to nitrogen atom), NR type (alkyl group (R) bonded to nitrogen atom), There are three types of N-OR type (a nitrogen atom is bonded with an alkoxy group (OR)), and among them, hindered amine light stabilizers of NH type or NR type can be particularly preferably used.

The N-OR type hindered amine light stabilizer has a faster reaction speed and a higher radical trap function than the NH type or NR type hindered amine light stabilizer. However, as in the case of the encapsulant sheets 31 and 32 according to the present invention, after the film formation, in the encapsulant sheet of the type in which the crosslinking is advanced in the modularization stage, the crosslinking agent at the time of thermal lamination for modularization. As a result, it is likely to be deteriorated due to reaction with the acid, so that the light resistance can not be sufficiently improved. By specifying the hindered amine light stabilizers as the NH type or NR type hindered amine light stabilizers, the deterioration by the crosslinking agent is avoided, and the function of capturing light-generated radicals is made more stable. It can be kept good.

In general, many kinds of compounds are known as hindered amine light stabilizers, from low molecular weight ones to high molecular weight ones. In the case of using for the sealing material composition for solar cell modules, when the thing of low molecular weight, ie, the thing of molecular weight is less than 2000, bleed out will occur in many cases, and in this case, light transmittance is It becomes smaller and the transparency decreases. Since the decrease in the transparency of the sealing material leads to the decrease in the power generation efficiency of the solar cell module, it is preferable to use a high molecular weight one having a molecular weight of 2000 or more as the light resistance stabilizer used for the sealing material composition.

Specific examples of the hindered amine light stabilizers which can be preferably used for the encapsulant composition include N-H type and having a molecular weight of 2000 or more: dibutylamine-1,3,5-triazine-N, N Polycondensation of '-bis (2,2,6,6-tetramethyl-4-piperidyl) -1,6-hexamethylenediamine with N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine I can mention a thing. This compound is commercially available as Chimassor 2020 and is the compound of CAS No. 192268-64-7. Its molecular weight is between 2600 and 3400, and its melting point is between 130 ° C. and 136 ° C.

As another specific example of the hindered amine light stabilizers which can be preferably used for the sealant composition according to the present invention, butanedioic acid 1- [2- as a NR type and having a molecular weight of 2000 or more is mentioned. (4-hydroxy-2,2,6,6-tetramethylpiperidino) ethyl] can be mentioned. This compound is commercially available as KEMISTAB 62 and is a compound of CAS No. 65447-77-0. Its molecular weight is 3100 to 4000, melting point 55 ° C to 70 ° C.

The addition amount of the above-mentioned hindered amine light stabilizer to the encapsulant composition may be 0.1% by mass or more and 0.5% by mass or less based on the entire resin component in the encapsulant composition, It is more preferable that it is 0.2 mass% or more and 0.4 mass% or less. By setting the content to 0.1% by mass or more, the effect of light resistance stabilization can be sufficiently obtained. Further, by setting the content to 0.5% by mass or less, bleed out can be suppressed, and discoloration of the resin due to excessive addition of a hindered amine light stabilizer can also be suppressed.

The sealant composition can further contain other components. For example, a UV absorber, a heat stabilizer, an adhesion improver, a nucleating agent, a dispersant, a leveling agent, a plasticizer, an antifoamer, a flame retardant, and various other fillers can be appropriately added. Although the content ratio of these additives differs depending on the particle shape, density and the like, it is preferable that the content ratio of each additive is in the range of 0.001% by mass to 60% by mass in the sealing material composition. By containing these additives, the sealing material composition can be provided with stable mechanical strength over a long period of time, an effect of preventing yellowing, cracking and the like.

As described above, by adjusting the carbon number of α-olefin of linear low density polyethylene in the base resin, and the kind and addition amount of the crosslinking agent to a preferable range, crosslinking is performed to such an extent that the gel fraction is 65% or more. While proceeding, it is possible to sufficiently suppress the generation of outgassing derived from the crosslinking agent.

As the solar cell element 4 constituting the solar cell module 1, it is preferable to preferably use various crystalline silicon solar cell elements manufactured using a single crystal silicon substrate, a polycrystalline silicon substrate, or a tandem type silicon substrate. it can. However, the present invention is not limited thereto, and various conventionally known solar cell elements including thin film solar cell elements (CIGS) and the like using, for example, chalcopyrite-based compounds and the like can be used without particular limitation. In addition, the solar cell element 4 may be a single-sided light receiving type element capable of receiving only light from the surface side of the solar cell module, or a double sided light receiving type element capable of receiving light on both sides of the element It is also good.

In addition, 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 used preferably.

As the surface side protection base material 2 which comprises the solar cell module 1, conventionally well-known materials, such as a glass substrate which has transparency calculated | required by the light-receiving surface side of a solar cell module, can be used without a restriction | limiting especially. The surface-side sealing material sheet 31 constituting the sealing material layer 3 is excellent in glass adhesion and adhesion durability, so the solar cell module 1 has the surface side formed 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 protection base material 5 which constitutes the solar cell module 1, a resin sheet such as ETFE, water resistant PET etc. or a resin layer laminated on both sides with an aluminum foil layer as a core layer, etc. The back surface protection sheet of can be used suitably.

In addition, the layer configuration of the solar cell module 1 of the present invention is not limited to the above embodiment, and may further include constituent members other than the members described above as necessary.

[Method of manufacturing a solar cell module]
For example, the solar cell module 1 sequentially stacks the members including the front side protection base material 2, the sealing material sheet 31, the solar cell element 4, the sealing material sheet 32, and the back side protection base material 5 described above It can be integrated by vacuum suction or the like, and then manufactured by heat compression molding the above-described members as an integral molded body by a molding method such as a lamination method.

(Sealing material deposition process)
About the sealing material sheets 31 and 32 which comprise the solar cell module 1, the above-mentioned sealing material composition is hold | maintained previously by 10% or less of gel fraction prior to the process for unification. It can form into a sheet form and can be obtained by the process of obtaining the non-crosslinked sealing material sheet. Melt forming can be carried out by various known film forming methods such as film forming using a T-die.

(Module integration process)
As described above, the respective members including the non-crosslinked sealing material sheet obtained in the sealing material film forming step are thermocompression-bonded as an integral molding by a molding method such as vacuum heating lamination. In the process for this integration, crosslinking is advanced so that the gel fraction of the uncrosslinked sealing material sheet is 65% or more and 80% or less. Incidentally, if necessary depending on the lamination conditions, a separate thermal crosslinking treatment may be performed after modularization.

The solar cell module 1 thus obtained is excellent in heat resistance and light resistance, and is extremely durable over a long period even when exposed to severe environments such as strong ultraviolet rays, heat rays, wind and rain, etc. It has become. In addition, the excellent transparency also contributes to the improvement of the power generation efficiency of the solar cell module.

Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited to the following examples.

[Manufacture of encapsulant sheet for solar cell module]
The sealing material composition consisting of the following materials was melted and formed into a film to a thickness of 460 μm by a conventional T-die method to obtain a non-crosslinked single layer sealing material sheet for a solar cell module. The deposition temperature was 90 ° C. to 100 ° C.
(Base resin)
A metallocene-based 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 min, and the following α -A copolymer with an olefin was used as a base resin of the encapsulant sheet 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 the carbon number (3, 6 The thing of 8) was made to be contained by different content.
Propylene: Carbon 3 (denoted as "C3" in Table 3)
1-hexene: carbon amount 6 (denoted as "C6" in Table 3)
1-octene: carbon amount 8 (denoted as "C8" in Table 3)
This base resin was used 100 parts by mass for each encapsulant composition.
(Silane modified polyethylene)
5 parts by mass of vinyltrimethoxysilane and 0.1 parts 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 mixed and melted at 200 ° C., and kneaded to obtain a density of 0.884 g ^/ cm 3, MFR at 190 ° C. is 6 g / 10 min silane-modified polyethylene (silane copolymer). This silane-modified polyethylene was used in each plug composition at 15 parts by mass as another additive resin of the plug sheets of all the Examples and Comparative Examples.
(Crosslinking agent)
As for the crosslinking agent, the three types of crosslinking agents (A to C) described in Table 2 were used properly according to the formulation described in Table 3 for each sealing material composition. The content (% by mass) of each crosslinking agent in the resin component for each sealing material composition was as described in Table 3. The molecular weight, active oxygen content and 1 hour half-life temperature of each crosslinking agent (AC) are as described in Table 2.
(Crosslinking assistant)
The following crosslinking assistants were added to each encapsulant composition. The content (% by mass) of this crosslinking assistant in the resin component for each sealing material composition was made to be the content described in Table 3.
Crosslinking auxiliary (TAIC): triallyl isocyanurate (manufactured by Statomer, trade name "SR 533")
(Hindered amine light stabilizers (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 part by mass in all cases.
HASLS: NR-type hindered amine light stabilizer having an amino group (Adeka Co., Ltd., trade name "LA-72")

[Evaluation Example 1: State of α-Olefin]
The α-olefin state (branched state) of the ethylene / α-olefin copolymer of the base resin in each plugging material composition stage is as described in Table 3 as measured by 13 C-NMR as described above. It confirmed that it was a state.

[Evaluation Example 2: Gel Fraction]
In order to evaluate the degree of crosslinking of the encapsulating material layer in the integrated state as a solar cell module, that is, the heat resistance, the above-mentioned encapsulating material sheets are sandwiched by ETFE films, and the following vacuum heating laminate (conditions 1: Gels obtained by the above-mentioned measurement method for those that have been cross-linked by “high” described in Table 3) or vacuum heating lamination and subsequent curing (described as “low” in Condition 2: Table 3) The fraction was measured. The results are shown in Table 3 as "gel fraction". Moreover, the evaluation criteria of "heat resistance" based on the numerical value of each gel fraction were as follows. In addition, in the state before the said crosslinking process after film-forming, it is also collectively confirmed that a gel fraction is 0% also about any sealing material sheet.
(Condition 1: (High))
Vacuum heating laminating conditions Vacuuming: 6 minutes / pressurizing: (0 kPa to 50 kPa): 10 seconds / pressure holding: (50 kPa): 11 minutes / temperature: 165 ° C.
(Condition 2: (Low))
Vacuum heating laminating conditions Vacuuming: 4 minutes / pressure: (0 kPa to 50 kPa): 10 seconds / pressure holding: (50 kPa): 7 minutes / temperature: 110 ° C.
Cure conditions 40 minutes, temperature 150 ° C
(Evaluation criteria) A: Gel fraction is 70% or more.
B: Gel fraction is 65% or more and less than 70%.
C: Gel fraction less than 65%.

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

[Evaluation example 4: bubble generation]
The solar cell module evaluation samples of Examples and Comparative Examples were prepared using the above-described sealing material sheets, and the following transparent front substrate, back surface protection sheet, and solar cell element. The above respective members are laminated along the general layer structure shown in FIG. 1, and vacuum heating lamination is performed under the same vacuum heating laminating conditions as in the above-mentioned evaluation example 2, and the solar examples for the respective examples and comparative examples A sample for battery module evaluation was obtained.
(Transparent front substrate): White board semi-tempered glass (JPT 3.2 75 mm x 50 mm x 3.2 mm)
(Back surface protection sheet): Polyethylene terephthalate (PET) base material: 188 μm thick ("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, the presence or absence of generation | occurrence | production of the bubble in the interface of a sealing material sheet and other members was observed visually after storage for 6 hours at 190 degreeC. The results are shown in Table 3 as "bubble generation". Evaluation criteria were as follows.
(Evaluation criteria) A: Generation | occurrence | production of air bubbles was confirmed visually.
C: It was confirmed visually that no bubbles were generated.

From Table 3, the solar cell module of the present invention is a thermosetting system in which a resin composition containing polyethylene as a base resin and containing a crosslinking agent is formed into a film, and then crosslinking is advanced to ensure necessary and sufficient heat resistance. It is understood that the solar cell module is provided with a sealing material layer formed of a sealing material sheet, and it is possible to achieve both improvement in heat resistance and suppression of the amount of outgassing included in the sealing material layer.

DESCRIPTION OF SYMBOLS 1 solar cell module 2 surface side protection base material 3 sealing material layer 31, 32 sealing material sheet 4 solar cell element 5 back surface protection base material

Claims (4)

A front surface side protection base material, a back side protection base material, a solar cell element, and a sealing material layer for sealing the solar cell element between the front side protection base material and the back side protection base material; 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 in which the amount of outgassing inherent in the sealing material layer is 1.81 μg / g or less in terms of toluene. The polyethylene is a copolymer of ethylene and an α-olefin, which contains an α-olefin having 3 carbon atoms in a proportion of 6 to 25 mol% and contains no 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. The method of manufacturing a solar cell module according to any one of claims 1 to 3,
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 film forming step of forming an uncrosslinked sealing material sheet by
The gel fraction of the non-crosslinked sealing material sheet is 65% to 80% or less by vacuum superheating lamination of the constituent members of the solar cell module including the non-crosslinked sealing material sheet and the solar cell element And integrating the module while integrating the
The polyethylene-based resin is a copolymer of ethylene and an α-olefin, containing an α-olefin having 3 carbon atoms in a ratio of 6 mol% or more and 25 mol% or less,
The crosslinker is peroxyketals, dialkyl peroxides, or peroxycarbonates.
Method of manufacturing a solar cell module

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