JP6540054B2 - Solar cell module - Google Patents

Description

  The present invention relates to a solar cell module.

  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. In general, a solar cell module has a configuration in which a transparent front substrate made of glass or the like, a solar cell element, and a back surface protection sheet are laminated via a sealing material sheet.

  The sealing material sheet is required to have adhesion to the transparent front substrate, the solar cell element and the back surface protection sheet, adhesion durability, filling property of the solar cell element, heat resistance and the like.

  The sealing material sheet is performed to improve the heat resistance of the sealing material sheet by crosslinking the resin composition. However, when the encapsulant sheet is excessively crosslinked, the embedding property of the solar cell element is deteriorated.

  Then, ionizing radiation-crosslinked resin is contained in resin which comprises a sealing material sheet as a thing which makes compatible the embedding property of a solar cell element and heat resistance at the time of manufacturing a solar cell module, and the sealing material sheet A sealant sheet having a structure in which the gel fraction is changed along the sheet thickness direction by irradiating ionizing radiation from one side has been proposed (Patent Document 1).

JP, 2011-74261, A

  Although the sealing material sheet excellent in the fillability of a solar cell element is described in patent document 1, it does not consider about the wiring which connects a photovoltaic cell. On the other hand, when laminating | stacking as a solar cell module, the wiring which takes out electricity from the solar cell element called a bus-bar is arrange | positioned between a solar cell element and a sealing material sheet. Here, when manufacturing a solar cell module, generally the lamination process of laminating a solar cell module is included, and a lamination pressure is applied to a solar cell element and a sealing material sheet in a lamination process. However, since the bus bar has a certain thickness, stress due to pressing is concentrated in the portion of the solar cell element where the bus bar overlaps. Therefore, there is a problem that a crack occurs in the portion of the solar cell element where the bus bars overlap.

  At the same time, since the sealing material sheet needs to be in close contact with the glass substrate, high adhesiveness (glass adhesion) with the glass substrate is required. Therefore, in the surface to which the solar cell element of a sealing material sheet is stuck, it has the characteristic which can control generating of a crack of the solar cell element resulting from a bus bar, and also the solar cell element of a sealing material sheet is stuck. In the surface to which the glass substrate which is the opposite side of the surface to be made to adhere, glass adhesiveness is required.

  The present invention has been made in view of the above situation, and while suppressing the generation of a crack of a solar cell element caused by a bus bar, while being a sealing material sheet for a solar cell module having sufficient heat resistance It is an object of the present invention to provide a solar cell module using a sealing material sheet that is possible and has high glass adhesion.

  The present inventors conducted sincere studies to solve the above-mentioned problems. In order to solve the problem that a crack is generated in the portion of the solar cell element in which the bus bars overlap, the surface with a low degree of crosslinking of the sealing material sheet is disposed on the bus bar side in order to improve the filling property of the bus bars It is considered good to laminate. However, it has been unexpectedly confirmed by the present inventors that the embedding property of the bus bar is improved by arranging the surface with a high degree of crosslinking of the sealing material sheet on the bus bar side. Therefore, by forming a solar cell module in which the surface having a high degree of crosslinking of the sealing material sheet is disposed on the bus bar side, the embedding property of the bus bar becomes good, and the solar cell module having high glass adhesion The present inventors have found that the present invention has been completed. More specifically, the present invention provides the following.

(1) A solar cell module in which at least a solar cell element, a bus bar which is a wire for extracting electricity from the solar cell element, and a sealing material sheet are arranged in this order, and the sealing material sheet has a density The content of polyethylene of 0.860 g / cm ³ or more and 0.970 g / cm ³ or less is 85% or more in the whole sealing material composition, and the sealing material sheet is in the thickness direction of the sealing material sheet The solar cell module in which the degree of crosslinking changes along and the surface on the side with the high degree of crosslinking of the sealing material sheet is disposed on the bus bar side.

  (2) The sealing material sheet is irradiated with ionizing radiation from only one of the front and back surfaces, or is irradiated with ionizing radiation of different intensities from the front and back (1) The solar cell module of description.

  (3) The sealing material sheet is a multilayer sheet including an intermediate layer and the outermost layers disposed on both sides thereof, and is provided on one outermost layer of the multilayer sheet opposite to the bus bar side. The solar cell module according to (1) or (2), further comprising a silane-modified polyethylene-based resin.

  (4) The solar cell module according to (3), wherein glass is disposed on the surface of the sealing material sheet opposite to the bus bar side.

  (5) The solar cell module according to any one of (1) to (4), wherein the thickness of the sealing material sheet is 300 μm to 600 μm.

  (6) The solar cell module according to any one of (1) to (5), wherein the thickness of the solar cell element is 150 μm to 300 μm, and the thickness of the bus bar is 150 μm to 300 μm.

(7) The sealing material sheet is obtained in a thermomechanical analysis (TMA) test under the following conditions, and a relationship between a predetermined temperature range (° C.) and a pressing depth (μm) of a needle into the sealing material sheet In the TMA curve showing the above, the needle is pushed from the surface on the side with high degree of crosslinking of the sealing material sheet, and the gradient P of the TMA curve (indentation depth (μm) / temperature in the predetermined temperature range (° C)) (° C.) is obtained, and the value of P ₈₀ which is a gradient at 80% of the film thickness of the sealing material sheet is 1 μm / ° C. or more and 10 μm / ° C. or less, and 50% of the film thickness of the sealing material sheet The solar cell module according to any one of claims 1 to 6, wherein the value of P ₅₀ which is the gradient at is 13 μm / ° C or more and 23 μm / ° C or less.
(TMA test: Set a 10 mm φ encapsulant sheet in a TMA device, set a constant pressure of 20 kPa using a φ 1 mm needle, raise the temperature from room temperature to 150 ° C. at a heating rate of 5 ° C./min. Measure the indentation depth, where P ₈₀ is the slope at 150 ° C if the indentation depth of the needle at 150 ° C is more than 50% and less than 80% of the thickness of the encapsulant sheet P _{150 ° C} Use

  According to the present invention, the degree of crosslinking of the encapsulant sheet of the solar cell module changes along the thickness direction, and the surface of the encapsulant sheet having the higher degree of crosslinking is disposed on the bus bar side The solar cell module of the present invention has excellent heat resistance and can be embedded so that it is possible to suppress the occurrence of cracks in the solar cell element due to the bus bars, and it is an excellent solar cell module having high glass adhesion. .

It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the solar cell module of this invention. In the thermomechanical analysis test (TMA) test which concerns on the sealing material sheets 1-3, it is the graph which showed the relationship of temperature (degreeC) and the pushing depth of the needle | hook to the sealing material sheet. In the thermomechanical analysis test (TMA) test according to the encapsulant sheets 1 to 3, the relationship between the temperature (° C.) and the absolute value of the gradient (indentation depth (μm) / temperature (° C.)) of the TMA curve was shown It is a graph.

  Hereinafter, the solar cell module of the present invention will be described in detail. The invention is not limited to the embodiments described below.

<Solar cell module>
An embodiment of a solar cell module of the present invention will be described. FIG. 1 is a cross-sectional view showing the layer structure of a solar cell module 10 of the present invention. In the solar cell module 10 of the present invention, 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 are sequentially stacked from the light receiving surface side of incident light. ing. Further, between the solar cell element 4 and the front surface sealing material layer 3, a bus bar 7 which is a wiring for extracting electricity from the solar cell element is disposed. In the present embodiment, the degree of crosslinking of the encapsulant sheet of the front encapsulant layer 3 changes along the thickness direction of the encapsulant sheet of the encapsulant sheet, and the degree of crosslinking of the encapsulant sheet is high. It arrange | positions so that a surface and the bus-bar 7 may contact. With such a configuration, it is possible to have sufficient heat resistance and to suppress the occurrence of cracks in the solar cell element due to the bus bars. At the same time, the surface with a low degree of crosslinking of the encapsulant sheet is disposed on the transparent front substrate side. The surface with a low degree of crosslinking of the sheet of sealing material has high adhesion to glass and the like. Therefore, it is possible to obtain an excellent solar cell module having higher adhesion to the transparent front substrate which is glass or the like.

  The transparent front substrate is not particularly limited as long as it is a material capable of transmitting sunlight and the like, but it is particularly preferable to use glass. The transparent front substrate is laminated in contact with the opposite side of the bus bar of the solar cell element, that is, the surface of the side of the sealing material sheet on the side with the low degree of crosslinking. Adhesiveness with the transparent front substrate can be made more preferable by laminating in contact with the surface of the side with a low degree of crosslinking of the encapsulant sheet.

  The thickness of the bus bar is preferably 150 μm or more and 300 μm or less. By setting it as such a range, it can have electroconductivity preferable as wiring which takes out electricity from a solar cell element.

  The thickness of the solar cell element is preferably 150 μm or more and 300 μm or less. By setting it as 150 micrometers or more, the risk of the crack generation of a solar cell element can be suppressed. Productivity can be made preferable by setting it as 300 micrometers or less.

<Sealing material sheet>
The degree of crosslinking of the encapsulant sheet used in the solar cell module of the present invention changes along the thickness direction of the encapsulant sheet. The method of crosslinking so that the degree of crosslinking of the sealant sheet changes along the thickness direction of the sealant sheet is not particularly limited. For example, a method may be used in which crosslinking is performed by irradiating ionizing radiation from only one surface side of front and back surfaces of the sealing material sheet or irradiating ionizing radiation of different intensities from the front and back surfaces. In the case of crosslinking by such a method, in order to arrange the surface on the side with a high degree of crosslinking on the bus bar side, ionizing radiation was irradiated from only one of the front and back surfaces of the sealing material sheet In this case, if the surface irradiated with ionizing radiation is irradiated with ionizing radiation of different intensities from the front and back, the bus bar of the solar cell element should be arranged on the irradiated surface irradiated with ionizing radiation of high intensity. good.

  Here, the degree of crosslinking of the encapsulating material sheet represents the rate of crosslinking of the encapsulating material sheet as specified by parameters such as gel fraction and MFR, and the smaller the degree of crosslinking, the less the crosslinking reaction occurs. It means that there are many regions of the resin component. In addition, after putting 0.1 g of a sealing material in a resin mesh and extracting it with 60 ° C toluene for 4 hours with gel fraction (%), it takes out all resin mesh and weighs after drying processing, and compares the mass before and after extraction The mass fraction of the remaining insoluble matter was measured and used as the gel fraction. Moreover, MFR (g / 10 minutes) can be calculated | required by measuring with 190 degreeC and load 2.16 kg which were measured by JIS-K6922-2.

The sealing material sheet used for the solar cell module of the present invention has a needle pushed from the surface of the sealing material sheet having a high degree of crosslinking in a thermomechanical analysis test (hereinafter sometimes referred to as a TMA test). , The predetermined temperature range (° C.) and the pushing depth (μm) of the needle into the sealing material sheet are measured, and the gradient P of the TMA curve in the predetermined temperature range (° C.) (indentation depth (μm) / temperature) (° C.)) to seek, for _{P MAX} is the maximum value of the absolute value of the slope _{P, P 1 (P 1 =} 100 × the ratio of the _{P 80} is the slope at 80% of the thickness of the sealing material sheet ( it is preferred values of _{P 80} / P _MAX)) is the sealing material sheet is 30% or less. By setting the value of P ₁ (P ₁ = 100 × (P ₈₀ / P _MAX )) to such a value, a crack of a solar cell element caused by a bus bar while being a sealant sheet having sufficient heat resistance It can be set as the sealing material sheet which can control generating of.

  Here, in the TMA test in the present invention, a sealing material sheet of φ10 mm is set in a TMA device, a pressing pressure of 20 kPa is applied to a φ1 mm needle, and a predetermined temperature range (° C.) at a heating rate of 5 ° C./min. For example, it refers to a test in which the temperature is raised from room temperature to 150 ° C., and the pushing depth of the needle at that time is measured. As a thermomechanical analysis (TMA) apparatus, TMA / SS7100 etc. by SII nanotechnology company can be used, for example.

P _MAX in the TMA test is the maximum absolute value of the gradient P (dent depth (μm) / temperature (° C)) determined by differentiating the indentation depth (μm) in the TMA curve with temperature (° C) is there. P _MAX is the maximum value of the needle penetration speed of the TMA test, and is a parameter indicating the flexibility of the sealing material sheet. An encapsulant sheet having a large P _MAX indicates that the encapsulant sheet has high flexibility in laminate pressing. Therefore, in the case of a sealing material sheet having a large P _MAX , the bus bars can be easily embedded in the laminate pressing process, and the stress of the pressing process applied to the overlapping portions of the bus bars and the solar cell element can be reduced. Can. Therefore, it is possible to suppress the occurrence of cracks in the solar cell element due to the overlapping of the bus bars. Moreover, the lamination in a lamination process is divided into an evacuation process and a press process, and setting temperature is performed at about 110 degreeC-150 degreeC. The temperature reaches 70 ° C. to 90 ° C. in the vacuum drawing step, and the temperature is raised to the set temperature in the pressing step. Therefore, since the burden on the solar cell element is generally highest at the start of the pressing step, the temperature at P _MAX is preferably 70 ° C. to 90 ° C. The value of P _MAX (indentation depth (μm) / temperature (° C.)) is preferably 10 μm / ° C. or more and 50 μm / ° C. or less, more preferably 12 μm / ° C. or more and 35 μm / ° C. or less, 15 μm / ° C. It is further more preferable to set it as (degreeC) or more and 30 micrometers / degreeC or less. By setting the value of P _MAX (indentation depth (μm) / temperature (° C.)) to 10 μm / ° C. or more, it is possible to more effectively suppress the occurrence of cracks in the solar cell element due to the overlapping of the bus bars . By setting the value of P _MAX (indentation depth (μm) / temperature (° C.)) to 50 μm / ° C. or less, a sealing material sheet having sufficient heat resistance can be obtained.

P ₈₀ in the TMA test is a gradient (indented depth (μm) / temperature (° C.)) at 80% of the film thickness of the sealing material sheet. Here, the gradient at 80% of the film thickness of the encapsulant sheet means the gradient when the indentation depth of the needle reaches 80% of the film thickness of the encapsulant sheet (indentation depth (μm ) / Temperature (° C.)). P ₈₀ is a parameter indicating the heat resistance of the sealing material sheet. As the encapsulant sheet has a smaller P _80, it means that the encapsulant sheet contains more regions with a higher degree of crosslinking. Therefore, it has a high heat resistance as small encapsulant sheet P _80. If P ₈₀ is a small encapsulant sheet, the heat resistance of the encapsulant sheet is further improved. The value of P ₈₀ (indentation depth (μm) / temperature (° C.)) is preferably 1 μm / ° C. or more and 10 μm / ° C. or less, and more preferably 2 μm / ° C. or more and 6 μm / ° C. or less. By setting the value of P ₈₀ (indentation depth (μm) / temperature (° C.)) to 10 μm / ° C. or less, a sealing material sheet having sufficient heat resistance can be obtained. By setting the value of P ₈₀ (indentation depth (μm) / temperature (° C.)) to 1 μm / ° C. or more, generation of cracks in the solar cell element due to overlapping of the bus bars can be suppressed more effectively. . In addition, when P ₈₀ is more than 50% and less than 80% of the film thickness of the sealing material sheet at a pressing depth of _{150 ° C.} , P _{150 ° C.} , which is a gradient at _{150 ° C.,} is used.

_P 1 in TMA test and _{(P 1 = 100 × (P} 80 / P MAX)) , the slope P of the TMA curve (indentation depth ([mu] m) / Temperature (° C.)) is the maximum value of the absolute value of _{P MAX} The ratio to P ₈₀ which is the slope at 80% of the film thickness of the encapsulant sheet. The encapsulating material sheet used in the solar cell module of the present invention appropriately adjusts the processing conditions by ionizing radiation, and both the flexible region excellent in laminateability and the region having a high degree of crosslinking excellent in heat resistance By setting P ₁ (P ₁ = 100 × (P ₈₀ / P _MAX )) to 30% or less, more preferably 20% or less so as to have high heat resistance and a solar cell caused by the bus bar It is possible to suppress the occurrence of cracks in the element.

  The pressing depth of the needle at a temperature of the melting point + 40 ° C. of the sealing material sheet in the TMA test is preferably 85% or less of the film thickness of the sealing material sheet, and more preferably 80% or less It is more preferable to make it within the limits. By setting the pressing depth of the needle in the TMA test in such a range, the heat resistance of the sealing material sheet can be made more preferable.

In addition, sealing is performed in a TMA test in which a needle is pressed from the surface of the sealing material sheet on the side with high degree of crosslinking, and a predetermined temperature range (° C.) and the pressing depth (μm) of the needle into the sealing material sheet are measured. The gradient P ₅₀ (indentation depth (μm) / temperature (° C.)) at 50% of the thickness of the material sheet is preferably 13 μm / ° C. or more and 23 μm / ° C. or less. Here, the gradient at 50% of the film thickness of the sealing material sheet means the gradient at the time when the pressing depth of the needle is 50% of the film thickness of the sealing material sheet (indentation depth (μm) / temperature ( ° C) means. P ₅₀ is a parameter indicating the property narrowing filling of the sealing material sheet. If large sealing material sheet P _50, of narrowing filled encapsulant sheet or irregularities followability is further improved. The value of P ₅₀ (indentation depth (μm) / temperature (° C.)) is preferably 13 μm / ° C. or more and 23 μm / ° C. or less, and more preferably 15 μm / ° C. or more and 20 μm / ° C. or less. By setting the value of P ₅₀ (indented depth (μm) / temperature (° C.)) to 13 μm / ° C. or more, it is possible to obtain a sealing material sheet having the embedding property of the sealing material sheet, that is, the unevenness followability. . By setting the value of P ₅₀ (indentation depth (μm) / temperature (° C.)) to 23 μm / ° C. or less, sufficient heat resistance can be obtained.

  The thickness of the sealing material sheet is more preferably 300 μm or more and 600 μm or less. By setting it as such a range, an impact can be fully relieved and it can be set as a highly productive sealing material sheet | seat.

[Sealant composition]
The encapsulant sheet contains 85% or more of a polyethylene resin having a density of 0.860 g / cm ³ or more and 0.970 g / cm ³ or less in the entire encapsulant composition. By including a polyethylene resin in such a range, decomposition of the sealing material sheet due to long-term use can be reduced, and the sealing material sheet can have transparency. As the polyethylene resin, low density polyethylene (LDPE) can be preferably used, and linear low density polyethylene (LLDPE) or metallocene linear low density polyethylene (M-LLDPE) can be particularly preferably used.

The density of the polyethylene-based resin is 0.860 g / cm ³ or more and 0.970 g / cm ³ or less, preferably 0.865 g / cm ³ or more and 0.930 g / cm ³ or less. By setting the density of the polyethylene-based resin in the above range, the transparency of the sealing material can be further improved.

  The polyethylene-based resin preferably has a melting point of 40 ° C. or more and 90 ° C. or less, and more preferably 55 ° C. or more and 80 ° C. or less.

  The sealing material sheet is preferably a multilayer sheet comprising an intermediate layer and the outermost layers disposed on both sides thereof, and further, one outermost layer of the multilayer sheet on the side opposite to the bus bar side. Preferably further contains a silane-modified polyethylene-based resin. The silane-modified polyethylene-based resin is a resin obtained by graft polymerization of an ethylenic unsaturated silane compound as a side chain on a low density polyethylene (LDPE), preferably linear low density polyethylene (LLDPE), which is a main chain. Such a graft copolymer can increase the degree of freedom of silanol groups contributing to the adhesive strength, and thus can improve the adhesion of the sealing material sheet to other members in the solar cell module. In particular, in the present invention, it is preferable that the outermost layer containing the silane-modified polyethylene-based resin be disposed on the side opposite to the bus bar side. By being arranged in this manner, adhesion to a transparent front substrate such as glass, which is arranged on the surface on the opposite side to the bus bar side, can be made more preferable.

  Although the sealing material composition for forming a sealing material sheet may contain the minimum required crosslinking agent, it is more preferable not to add a crosslinking agent. While the addition of a crosslinking agent can sufficiently promote crosslinking, the addition of a crosslinking agent such as an organic peroxide or the like requires a thermal lamination process for integration with a solar cell module. This is because the risk of problems such as foaming due to degassing is increased. When adding a crosslinking agent, a well-known thing can be used and it does not specifically limit, For example, a well-known radical polymerization initiator can be used.

  In addition, the sealing material composition for forming a sealing material sheet may contain other components such as a crosslinking assistant, a light stabilizer, an ultraviolet light absorber, a heat stabilizer and the like as necessary. . The other components are preferably in the range of 0.001% by mass to 5% by mass with respect to the total amount of the encapsulant composition.

<Method of manufacturing solar cell module>
[Sheeting process]
The sealing material sheet used for the solar cell module of this invention can be manufactured by passing through the sheeting process which melt-molds each composition and obtains a sealing material sheet, for example. The molding is carried out by a molding method usually used in a common thermoplastic resin, that is, various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, rotational molding and the like. As a method of shape | molding a sealing material sheet as a multilayer sheet, the method of shape | molding by coextrusion by 2 or more types of melt-kneading extruders is mentioned as an example.

[Crosslinking step]
Although the crosslinking process of the sealing material sheet used for the solar cell module of this invention is not specifically limited, For example, with respect to the non-crosslinked sealing material sheet after a sheeting process, the crosslinking process by ionizing radiation is carried out And the like. The cross-linking step of cross-linking the non-cross-linked plug sheet by ionizing radiation after the end of the sheeting step and integrating the plug sheet with other members Do it before you start. By this crosslinking treatment, a sealing material sheet can be obtained in which the degree of crosslinking changes along the thickness direction of the sealing material sheet. The crosslinking step may be performed continuously in-line following the sheeting step or may be performed off-line.

  As for the crosslinking treatment by irradiation with ionizing radiation, the individual crosslinking conditions are not particularly limited. Although it can carry out by ionizing radiations, such as an electron beam (EB), an alpha ray, a beta ray, a gamma ray, a neutron beam, it is preferable to use an electron beam especially.

  Moreover, the method of irradiating an ionizing radiation of different intensity | strength from the surface side or front and back of only one side of a sealing material sheet can be mentioned for ionizing radiation. The degree of crosslinking can be changed along the thickness direction of the sealing material sheet by irradiating ionizing radiation of different strengths from only one side of the sealing material sheet or the front and back surfaces. By doing so, it is possible to manufacture a sealing material sheet in which the degree of crosslinking changes along the thickness direction of the sealing material sheet.

  When the ionizing radiation is irradiated by single-sided irradiation, the acceleration voltage is determined by the thickness of the sheet to be irradiated, and a thicker sheet requires a higher acceleration voltage. For example, in the sealing material sheet of 550 micrometers in thickness, it irradiates by 100 kV or more and 250 kV or less. If the acceleration voltage is less than 100 kV, crosslinking becomes insufficient, and the heat resistance of the sealing material sheet becomes insufficient. On the other hand, if the acceleration voltage exceeds 250 kV, the maximum dose peak will be inside the surface, making it difficult to produce an encapsulant sheet where the degree of crosslinking changes along the thickness direction of the encapsulant sheet. Become. The irradiation dose is in the range of 30 kGy to 50 kGy, preferably 35 kGy to 45 kGy. The irradiation may be performed in the air or in a nitrogen atmosphere.

  In addition to the irradiation with ionizing radiation by single side irradiation, ionizing radiation of different intensities may be irradiated from the front and back surfaces. In this case, the surface irradiated with strong ionizing radiation is arranged on the bus bar side. By applying ionizing radiation of different intensities from the front and back surfaces, a sealing material sheet used in the solar cell module of the present invention can be manufactured as in the case of single-side irradiation.

  When the crosslinking treatment is a general heat treatment, generally, 0.5 parts by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of all the components of the sealing material sheet is required as the content of the crosslinking agent However, in the case of crosslinking by irradiation with ionizing radiation, the content of the crosslinking agent may be 0, and even if it is contained, it is less than 0.5 parts by mass preferable. Thereby, the risk of the productivity fall by gelatinization of the sealing material composition in the sheet-forming process of a sealing material composition can be reduced.

[Lamination process]
A lamination process is a process of laminating a sealing material sheet with other members, and unifying a solar cell module. In the solar cell module, for example, members sequentially including a transparent front substrate, a front sealing material layer, a solar cell element provided with bus bars, a rear sealing material layer, and a rear surface protection sheet are sequentially laminated and then integrated by vacuum suction or the like. After that, the above-mentioned members can be manufactured by heat compression molding as an integral molding by a molding method such as a lamination method.

  In the cross-linking step, when ionizing radiation is irradiated from only one of the front and back sides of the sheet of sealing material, the surface irradiated with ionizing radiation is irradiated with ionizing radiation of different strengths from the front and back. By stacking the solar cell element so that the bus bar of the solar cell element is disposed on the irradiation surface irradiated with ionizing radiation, the solar cell module in which the surface on the side with high degree of crosslinking of the sealing material sheet is disposed on the bus bar side It can be manufactured.

  In the solar cell module of the present invention, the solar cell element and the back surface protection sheet can use conventionally known materials without particular limitation. In addition, the solar cell module of the present invention may include, for example, members other than the above members such as a heat dissipation sheet.

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

[Sealing material composition for intermediate layer for sealing material sheet]
Metallocene linear low density polyethylene (M-LLDPE): density 0.880 g / cm ³ , melting point 60 ° C., MFR at 190 ° C. 3.5 g / 10 min metallocene linear low density polyethylene 96.5 mass %, Density 0.884 g / cm ³ , MFR at 190 ° C. 1.8 g / 10 min 2.73 wt% silane-modified polyethylene resin, 0.0545 wt% light stabilizer (KEMISTAB 62), UV absorber (KEMISORB 12 ) 0.318 mass%, ultraviolet absorber (KEMISORB 79) 0.0545 mass%, ultraviolet absorber (KEMISORB 202) 0.00636 mass%, cross-linking aid (tricyclodecane dimethanol diacrylate) 0.382 mass% In order to make the inner layer sealing material sheet of the sealing material sheet of the embodiment and the comparative example. The encapsulant composition of

[Sealing material composition for outermost layer for sealing material sheet]
Metallocene linear low density polyethylene (M-LLDPE): density 0.885 g / cm ³ , melting point 66 ° C., MFR at 190 ° C. 18 g / 10 min metallocene linear low density polyethylene 86.0% by mass, 96.5 mass% of metallocene linear low density polyethylene having a MFR of 3.5 g / 10 min at 190 ° C., a density of 0.884 g / cm ³ , and a silane modification with a MFR of 1.8 g / 10 min at 190 ° C. 13.6% by mass of polyethylene resin, 0.0545% by mass of light stabilizer (KEMISTAB62), 0.318% by mass of ultraviolet absorber (KEMISORB12), 0.0545% by mass of ultraviolet absorber (KEMISORB 79), ultraviolet absorber (KEMISORB 202) It mixes so that it may become 0.00636 mass%, and the sealing material sheet for inner layers of the sealing material sheet of an Example and a comparative example Sealing composition for producing the

<Manufacture of encapsulant sheet for solar cell module>
Each sealing material composition is produced using a film forming machine having a φ30 mm extruder and a T-die with a width of 200 mm at an extrusion temperature of 210 ° C. and a take-up speed of 1.1 m / min. These inner layer and outer layer sealing material sheets were laminated to form a three-layer sealing material sheet for a solar cell module (Example and Comparative Example). Each of these sealing material sheets had a thickness of 550 μm, and the thickness ratio of outer layer: inner layer: outer layer was 1: 5: 1. With respect to the sheet of sealing material, electron beams are applied only to one side of the sheet of sealing material at an acceleration voltage of 195 kV and an illuminance of 40 kGy using an electron beam irradiation apparatus (manufactured by Iwasaki Electric Co., Ltd., product name EC250 / 15 / 180L) To produce a crosslinked sealant sheet 1. In addition, when the gel fraction of the sealing material sheet 1 is measured by the following method, the gel fraction of the sealing material sheet which extract | collected the part to a depth of 100 micrometers from the surface at the side of the electron beam irradiation of a sealing material sheet is It was 20%, and the gel fraction of the sealing material sheet which extract | collected the part to a depth of 100 micrometers from the surface on the opposite side seeing from the electron beam irradiation surface of a sealing material sheet was 0%. From this result, it was confirmed that the degree of crosslinking of the encapsulating material sheet 1 changes along the thickness direction of the encapsulating material sheet, and the surface on the electron beam irradiation side is a surface having a high degree of crosslinking. In addition, melting | fusing point of the sealing material sheet was 60 degreeC.

  The gel fraction is measured by collecting 0.1 g of each portion from the both sides of the encapsulant sheet 1 to a depth of 100 μm, putting it in a resin mesh, extracting it with 60 ° C. toluene for 4 hours, removing the resin mesh and drying it After weighing, the mass comparison before and after the extraction was performed to measure and measure the mass% of the remaining insoluble matter.

  Moreover, as the sealing material sheet 2, the sealing material sheet was created similarly to the sealing material sheet 1 except not irradiating an electron beam. When the gel fraction of both sides of the encapsulant sheet 2 was measured in the same manner as in the encapsulant sheet 1, the gel fraction of the portion up to 100 μm from the surface on both sides is 0%, and in the thickness direction of the encapsulant sheet It was confirmed that the degree of crosslinking did not change along.

  Furthermore, it produced similarly to the sealing material sheet 1 except having irradiated the electron beam on both surfaces of the sealing material sheet as the sealing material sheet 3. FIG. When the gel fraction of both sides of the encapsulant sheet 3 was measured in the same manner as in the encapsulant sheet 1, the gel fraction of the portion up to 100 μm from the surface on both sides is 20%, and in the thickness direction of the encapsulant sheet It was confirmed that the degree of crosslinking did not change along.

<TMA test>
The TMA test was performed on the encapsulant sheets 1 to 3 manufactured as described above. Specifically, a sealing material sheet is cut out to φ 10 mm, and set in a TMA device (TMA / SS 7100 manufactured by SII Nano Technology Co., Ltd.), and the temperature of the sealing material sheet is raised to a pressure of 20 kPa from the surface of the sealing material sheet. The needle with a diameter of 1 mm was pushed in, and the pushing depth was measured. The heating rate was 5 ° C./min, and the temperature was raised from room temperature to 150 ° C. In Table 2, the gradient of the TMA curve at 80% of the film thickness of the encapsulating material sheet is P ₈₀ (denoted as P _{80 in} Table 2), and the maximum absolute value of the gradient P of the TMA curve is P _MAX ( in Table _2, referred to as _{P MAX), 100 × (P} 80 / P MAX) P 1 ( denoted as in Table 1 _{P 1} a), FutomezaimakuAtsu at the time of 100 ° C. which is the melting point + 40 ℃ resin Shows the ratio of the pressing depth of the needle to the (in Table 1, denoted as pressing depth). In addition, Table 1 describes the pushing direction of the needle in the TMA test (in Table 1, indicated as the measurement direction), and "EB irradiated surface" means that the needle was pushed from the electron beam irradiated surface and measured. The "opposite side" means that the needle is pushed from the opposite side of the electron beam irradiation side and measured. In addition, since the sealing material sheet 2 is non-irradiated and the sealing material sheet 3 is double-sided irradiation, no particular measurement direction is described.

  The graph which represented the relationship between the temperature (degreeC) in the TMA test of the sealing material sheet in FIG. 2 and the pushing depth (micrometer) of the needle | hook of the sealing material sheets 1-3 is shown. Moreover, the graph showing the relationship between the temperature (degreeC) in the TMA test of the sealing material sheets 1-3, and the gradient (indentation depth (micrometer) / temperature (degreeC)) of a TMA curve in FIG. 3 is shown.

From Table 1, the electron beam irradiated surface (surface with high degree of crosslinking) of the encapsulant sheet 1 and the surface opposite to the electron beam irradiated surface of the encapsulant sheet 1 (surface with low crosslinking degree) are both P ₁ showed 30% or less. On the other hand, the uncrosslinked sealing material sheet 2 not irradiated with the electron beam and the crosslinked sealing material sheet 3 irradiated with the electron beam from both sides showed P ₁ of more than 30%. Further, the electron beam irradiation surface of the sealing material sheet 1 (the surface of the high degree of cross-linking side) _{is, P 50} showed 13 .mu.m / ° C. or higher 23 .mu.m / ° C. or less. On the other hand, the surface opposite to the electron beam-irradiated surface of the encapsulant sheet 1 (the surface on the side with a low degree of crosslinking) and the crosslinked encapsulant sheet 3 irradiated with electron beams from both sides have a P ₅₀ of 13 μm / less than ° C., sealing material sheet 2 uncrosslinked not irradiated with the electron beam is P ₅₀ was 23 .mu.m / ° C. greater.

<Cell crack test>
The solar cell module of the example and the comparative example was produced using the sealing material sheet, and the cell crack test was done. Specifically, white plate semi-tempered glass (AGC Fabritech Co., Ltd. product: 3KWE33) having a thickness of 180 mm and a thickness of 3.2 mm, each sealing material sheet as a light receiving surface sealing material, and a bus bar having a width of 5 mm (thickness 250 μm) 5 ”single crystal solar cell element (200 μm in thickness) connected with three), each sealing material sheet as non-light-receiving side sealing material, and a back surface protection sheet (polyethylene terephthalate (PET): 188 μm in thickness) It laminated | stacked in order and laminated | stacked by vacuum pressure: 5 minutes (0 kPa), atmospheric pressure press: 7 minutes (100 kPa) at lamination temperature of 110 degreeC-150 degreeC, and the solar cell module was created. In addition, the bus-bar connected to the photovoltaic cell is arrange | positioned at the light-receiving surface side. Moreover, in Table 2, "the sealing material sheet surface in contact with the bus bar" represents the surface of the light receiving surface side sealing material in contact with the bus bar, and "EB irradiation surface" means the electron beam irradiation surface. It means that it laminated | stacked so that a bus-bar might be contacted, and "opposite side" means having laminated | stacked so that an opposite surface may be contacted to a bus-bar seeing from the electron beam irradiation surface. And the presence or absence of the crack generation of the solar cell element of a solar cell module was confirmed by EL (Elecroluminescence) test. The evaluation results are shown in Table 2 (denoted as cell crack in Table 2). The temperatures listed in Table 2 are laminating temperatures. The evaluation criteria are as follows.

[Evaluation criteria]
○: no cracks were observed in the solar cell element.
X: A crack was confirmed in the solar cell element.

  From Table 2, in the cell crack test, an example in which the electron beam irradiated surface (surface on the side with high degree of crosslinking) of the sealing material sheet is laminated in contact with the bus bar is a crack of the solar cell element under any laminating temperature conditions. Was not confirmed. However, in the cell crack test, the solar cell element under the lamination temperature condition at 110 ° C. is laminated in a cell crack test in which the opposite surface (surface on the side with low crosslinking degree) of the sealing material sheet is laminated in contact with the bus bar. The crack of was confirmed. From this, in the solar cell module according to the embodiment in which the surface with the higher degree of crosslinking of the sealing material sheet is disposed on the bus bar side, the surface with the lower crosslinking degree of the sealing material sheet is disposed with the bus bar side It can be seen that the generation of the cracks of the solar cell element due to the bus bars can be further suppressed as compared with the comparative example being carried out.

<Heat resistance test>
Electron beam-irradiated surface (surface with high degree of crosslinking) of encapsulant sheet 1, opposite surface (surface with low degree of crosslinking) viewed from electron beam-irradiated surface, encapsulant sheet 3, and encapsulant sheet The heat resistance test was conducted on No.4. Specifically, a sealing material sheet cut into 5 × 7.5 cm is placed vertically on a large glass plate on a large glass plate subjected to embossing, and left at 80 ° C. for 12 hours. The movement distance of 5 × 7.5 shibo glass after standing was measured and evaluated. The measured values were evaluated according to the following evaluation criteria. The evaluation results (expressed as heat resistance in Table 3) are shown in Table 3. The evaluation criteria are as follows.

(Evaluation criteria)
○: less than 1.5 mm △: 1.5 mm or more and less than 2 mm ×: 2 mm or more

  From Table 3, the surface of the encapsulating material sheet 1 irradiated with the electron beam (surface with high degree of crosslinking) and the opposite surface of the encapsulating material sheet 1 with the electron beam irradiated surface (surface with low degree of crosslinking) contact It can be seen that the displacement distance of the emboss glass measured facing is similar and is superior to that of the sealing material sheet 2.

[Glass adhesion test]
Glass adhesion of the electron beam irradiated surface (surface with high degree of crosslinking) of the encapsulant sheet 1 and the opposite surface (surface with low crosslinking degree) as viewed from the electron beam irradiated surface and the encapsulant sheets 2 and 3 The test was done. Electron beam-irradiated surface (surface with high degree of crosslinking) of encapsulant sheet 1, opposite surface (surface with low degree of crosslinking) viewed from electron-irradiated surface of encapsulant sheet 1, encapsulant sheet 2 , Each sealing material sheet 3 is adhered to a glass substrate (white plate float semi-tempered glass JPT 3.2 75 mm × 50 mm × 3.2 mm), heating temperature 150 ° C., vacuum heating (0 kPa) time 5 minutes, atmospheric pressure press The lamination process was performed for 7 minutes (100 kPa), and the sample for adhesive evaluation was created. Then, in this adhesion evaluation sample, the sealing material sheet in close contact with the glass substrate is cut to a width of 15 mm, and vertical peeling (50 mm / 50 mm / cm) with a peeling tester (Tensilon universal tester RTF-1150-H). min) test was performed to measure the glass adhesion strength. The measurement results are shown in Table 4 as “glass initial adhesion strength”.

(Evaluation criteria)
○: 40 N / 15 mm or more Δ: 30 N / 15 mm or more 40 N / 15 mm or less ×: 30 N / 15 mm or less

Next, the glass adhesion strength maintenance factor after the following dump heat (D.H.) test was measured about each above-mentioned sample for adhesive evaluation. D. H. According to JIS C8917, the test was conducted for 500 hours on the durability test of the evaluation sample under the conditions of a temperature of 85 ° C. and a humidity of 85%. About the sample for evaluation after a test, glass adhesion strength was remeasured by the same test method as the above, and the maintenance factor (%) of adhesion strength with respect to initial stage glass adhesion strength was computed. The results are shown in Table 4 as "Glass adhesion strength retention rate".
(Evaluation criteria)
○: 80% or more Δ: 70% or more and less than 80% ×: less than 70%

  The glass adhesion on the opposite surface of the encapsulant sheet 1 to the electron beam irradiated surface (the surface on the side having a low degree of crosslinking) is higher than that on the electron beam irradiated surface of the encapsulant sheet 1 (the surface on the side having a high degree of crosslinking) It has become. From this, in the solar cell module in which the surface with the high degree of crosslinking of the sealing sheet 1 is disposed on the bus bar side, the surface with the low crosslinking degree of the sealing sheet is disposed on the bus bar side It turns out that it is a module for solar cells in which adhesiveness with the transparent front substrate (glass) arrange | positioned on the opposite side to the bus-bar side compared with a solar cell module is favorable.

  From Tables 2 to 4, in the sealing material sheet in which the degree of crosslinking changes along the thickness direction of the sealing material sheet, the surface on the side with the high degree of crosslinking of the sealing material sheet is disposed on the bus bar side of the solar cell element The solar cell module having the same degree of heat resistance as the solar cell module in which the surface having the lower degree of crosslinking is disposed on the bus bar side of the solar cell element and has the same or more embeddability. It can be seen that the solar cell module is a solar cell module capable of suppressing the generation of cracks in the solar cell element due to the bus bars, and yet it is an excellent solar cell module having high adhesion to the glass used for the transparent front substrate.

10 solar cell module 2 transparent front substrate 3 front sealing material layer 4 solar battery element 5 back sealing material layer 6 back protective sheet 7 bus bar

Claims (7)

A solar cell module in which at least a solar cell element, a bus bar which is a wiring for extracting electricity from the solar cell element, and a sealing material sheet are disposed in this order,
In the sealing material sheet, the content of polyethylene having a density of 0.860 g / cm ³ or more and 0.970 g / cm ³ or less is 85% or more in the entire sealing material composition,
In the sealing material sheet, the degree of crosslinking changes along the thickness direction in such a manner that the degree of crosslinking gradually or gradually decreases from one surface of the sealing material sheet to the other surface ,
Higher side surfaces, a solar cell module which is disposed on the bus bar side of the cross-linking degree of the sealing material both surfaces of the sheet.   The solar cell according to claim 1, wherein the sealing material sheet is irradiated with ionizing radiation from only one of the front and back surfaces, or is irradiated with ionizing radiation of different intensities from the front and back surfaces. Battery module. The encapsulant sheet is a multilayer sheet comprising an intermediate layer and outermost layers disposed on both sides thereof,
The solar cell module according to claim 1, wherein a silane-modified polyethylene-based resin is further contained in one outermost layer of the multilayer sheet opposite to the bus bar side.   The solar cell module according to claim 3, wherein glass is disposed on the surface of the sealing material sheet opposite to the bus bar side.   The thickness of the said sealing material sheet is 300 micrometers or more and 600 micrometers or less, The solar cell module in any one of Claim 1 to 4. The thickness of the solar cell element is 150 μm or more and 300 μm or less,
The thickness of the said bus-bar is 150 micrometers or more and 300 micrometers or less, The solar cell module in any one of Claim 1 to 5. The sealing material sheet is
In a TMA curve obtained in a thermomechanical analysis (TMA) test under the following conditions, showing a relationship between a predetermined temperature range (° C.) and a pressing depth (μm) of a needle into the sealing material sheet,
The needle is pushed from the surface on the side with the high degree of cross-linking of the sealing material sheet, and the slope P (pushing depth (μm) / temperature (° C)) of the TMA curve in the predetermined temperature range (° C) is determined. ,
The value of P80 which is a gradient at 80% of the film thickness of the sealing material sheet is 1 μm / ° C. or more and 10 μm / ° C. or less,
The solar cell module according to any one of claims 1 to 6, wherein a value of P50 which is a gradient at 50% of a film thickness of the sealing material sheet is 13 μm / ° C or more and 23 μm / ° C or less.
(TMA test: Set a 10 mm φ encapsulant sheet in a TMA device, set a constant pressure of 20 kPa using a φ 1 mm needle, raise the temperature from room temperature to 150 ° C. at a heating rate of 5 ° C./min. Measure the indentation depth, but use P150 ° C, which is the gradient at 150 ° C, if P80 is more than 50% and less than 80% of the film thickness of the encapsulant sheet at 150 ° C. .)

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