JP2017112245A - Method for laminate temperature decision in solar battery module production, and method for solar battery module production by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a method for laminate temperature decision, by which flexibility enough to prevent a solar battery element from being cracked, and fluidity enough to avoid causing the pollution on a vacuum laminator can be both achieved in a laminate process for integration into a solar battery module; and a method for solar battery module production by using the method for laminate temperature decision.SOLUTION: A method for laminate temperature decision comprises the steps of: determining, from a thermomechanical analysis (TMA) curve showing the relationship between a predetermined temperature range (°C) and the percentage (%) of a depth of a needle pushed into a seal-material sheet to a film thickness of the seal-material sheet, a temperature T(°C) when the percentage (%) of the depth of the pushed needle is 50%, and a temperature T(°C) when the percentage (%) of the depth of the pushed needle is 90%, respectively; and deciding a temperature (°C) of T(°C) to T(°C) to be an optimum laminate temperature.SELECTED DRAWING: None

Description

  The present invention relates to a method for determining a lamination temperature in manufacturing a solar cell module and a method for manufacturing a solar cell module using the same.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. Currently, various types of solar cell modules have been developed and proposed. Generally, 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.

  As a sealing material sheet used for a solar cell module, a resin sheet made of an ethylene-vinyl acetate copolymer resin (EVA resin) is most commonly used from the viewpoints of workability, workability, manufacturing cost, etc. It is used as something. However, EVA resin has a tendency to gradually decompose with long-term use, and deteriorates inside the solar cell module to decrease its strength or generate acetic acid gas that affects the solar cell element. there is a possibility. For this reason, the sealing material sheet for solar cell modules which uses polyolefin resin, such as polyethylene, instead of EVA resin is proposed (patent documents 1 and 2).

  Here, in the sealing sheet mainly composed of a polyethylene resin, transparency and flexibility can be improved by reducing the density thereof. If it is a sealing material sheet which has a softness | flexibility, a solar cell element and a sealing material sheet can be laminated | stacked, and the crack of a solar cell element can be prevented at the time of integration. However, lowering the density of the encapsulant sheet, on the other hand, causes problems such as excessive flow during heat processing and insufficient heat resistance of the base resin, leading to the risk of product deterioration during long-term use in high-temperature environments. Let

  As an adverse effect of excessive flow during the heat processing of the sealing material described above, for example, there is a problem of contamination of the vacuum laminator. That is, when laminating for integration as a solar cell module, only the sealing material flows excessively, and the facility is that the molten resin derived from the sealing material that protrudes around the back surface protection sheet contaminates the laminator. It is a problem of contamination.

  In the sealing material of patent document 1 and patent document 2, heat resistance is provided by the crosslinking agent. For example, in Patent Document 1, about 1% of a crosslinking agent is added, and in Patent Document 2, an amount of a crosslinking agent in which the gel fraction is 30% or more is added. In this case, it seems that the contamination of the laminate due to the excessive flow of only the sealing material during the lamination process can be prevented, but the flexibility required for the sealing material because the sealing material is cured by crosslinking. It is not always easy to achieve both at the same time.

JP 2000-91611 A JP 2009-10277 A

  According to the knowledge obtained by the present inventors, the laminating temperature in the thermal laminating process at the time of integrating the encapsulating material composition forming the encapsulating material sheet and the solar cell element and the encapsulating material sheet, It has been found that both the flexibility that can prevent the cracking of the solar cell element and the fluidity that does not cause the contamination of the vacuum laminator affect both characteristics. However, no attempt has been made to determine the optimum laminating temperature in the thermal laminating process from the viewpoint of achieving both of these characteristics.

  The present invention has been made in view of the above situation, and the purpose thereof is a flexibility that can prevent cracking of the solar cell element during lamination for integration as a solar cell module, It is an object of the present invention to provide a method for determining a laminate temperature that can achieve both fluidity that does not cause contamination of a vacuum laminator and a method for manufacturing a solar cell module using the method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have focused on thermomechanical analysis (TMA test) of a sealing material sheet used for manufacturing a solar cell module, and have a predetermined needle pressing depth. It was found that the above-mentioned problems can be solved by determining the optimum laminating temperature for performing the heat laminating process to be integrated from the temperature of the ratio (%). Thus, the present invention has been completed.

(1) In the production of a solar cell module, a laminating temperature determining method for determining an optimum laminating temperature for performing a heat laminating process for heating and integrating a sealing material sheet and other members. Obtained in a thermomechanical analysis (TMA) test of the conditions, and the relationship between the predetermined temperature range (° C.) and the ratio (%) of the indentation depth of the needle into the sealing material sheet relative to the film thickness of the sealing material sheet From the TMA curve showing the temperature, the temperature T _50% (° C.) when the ratio (%) of the needle pressing depth is 50% and the temperature when the ratio (%) of the needle pressing depth is 90% calculated T _90% and (℃), respectively, laminating temperature determination in the manufacture of a solar cell module that determines the _{T 50%} (℃) above the _{T 90%} (℃) temperature below the (℃) as the optimum lamination temperature Method.
(TMA test: A φ10 mm sealing material sheet is set in a TMA apparatus, the pressure is set to a constant pressure of 50 kPa by pressing into a φ1 mm needle, the temperature is raised from room temperature at a temperature rising rate of 5 ° C./min, and the needle pressing depth at that time To measure.)

  (2) The laminating temperature determining method according to (1), wherein the sealing material sheet is a multilayer sheet having a layer structure of at least 3 or more.

  (3) The lamination temperature determination method according to (2), wherein the sealing material sheet is a multilayer sheet having a three-layer structure in which a skin layer, a core layer, and a skin layer are laminated in this order.

  (4) The lamination temperature determination method according to (3), wherein the core layer of the encapsulant sheet contains 5% by mass to 40% by mass of polypropylene in the total resin component of the core layer composition.

  (5) The lamination temperature determining method according to any one of (1) to (4), wherein the thickness of the sealing material sheet is 200 μm or more and 400 μm or less.

  (6) A method for manufacturing a solar cell module, wherein the thermal laminating process is performed at an optimum laminating temperature determined by the laminating temperature determining method according to any one of (1) to (5).

(7) Ratio obtained by a thermomechanical analysis (TMA) test under the following conditions, a predetermined temperature range (° C.), and a ratio of the needle pressing depth to the sealing material sheet with respect to the film thickness of the sealing material sheet (% ), The temperature T _50% (° C.) at the time when the needle pressing depth ratio (%) is 50% and the needle pressing depth ratio (%) is 90%. The temperature T _90% (° C.) at the time of the above is obtained, and the difference in temperature (° C.) between the T _50% (° C.) and the T _90% (° C.) is 20 ° C. or more. Sealing material sheet.
(TMA test: A φ10 mm sealing material sheet is set in a TMA apparatus, the pressure is set to a constant pressure of 50 kPa by pressing into a φ1 mm needle, the temperature is raised from room temperature at a temperature rising rate of 5 ° C./min, and the needle pressing depth at that time To measure.)

  The degree to which cracking of the solar cell element can be prevented in the thermal laminating process in which the sealing material sheet and the other members are heated and integrated by manufacturing the solar cell module by the lamination temperature determining method of the present invention. It is possible to achieve both the flexibility and the fluidity that does not cause contamination of the vacuum laminator.

It is a schematic diagram of the cross section which shows the laminated constitution of the sealing material sheet which can use the lamination temperature determination method of this invention. It is a schematic diagram of the cross section which shows the layer structure of the sealing material integrated back surface protection sheet which uses the sealing material sheet which can use the lamination temperature determination method of this invention. It is a schematic diagram of the cross section which shows an example of the laminated constitution of the solar cell module which uses the sealing material integrated back surface protection sheet which can use the lamination temperature determination method of this invention. It is a schematic diagram of the cross section which shows an example of the laminated constitution of the conventional common solar cell module. In the thermomechanical analysis test (TMA test) related to the sealing material integrated back surface protection sheet (sheets 1 to 4), the needle is pushed into the sealing material sheet 11 with respect to time (minutes) and the film thickness of the sealing material sheet 11 It is the graph which showed the relationship with the ratio (%) of depth. In the thermomechanical analysis test (TMA test) related to the sealing material-integrated back surface protection sheet (sheets 5 to 7), the needle is pushed into the sealing material sheet 11 with respect to the time (minutes) and the film thickness of the sealing material sheet 11 It is the graph which showed the relationship with the ratio (%) of depth.

  Hereinafter, an embodiment of a method for determining a lamination temperature of the present invention and a method for manufacturing a solar cell module using the method will be described. The present invention is not limited to the embodiments described below.

<Basic configuration of solar cell module>
First, the basic configuration of the solar cell module 10 that can be manufactured using the method for determining the laminate temperature of the present embodiment will be described with reference to FIG. The solar cell module 10 includes, from the non-light-receiving surface side, a sealing material-integrated back protective sheet 1, a solar cell element 2, a light-receiving surface-side sealing material sheet 3, and a transparent front substrate 4 disposed on the outermost layer on the light-receiving surface side. Are stacked in order.

  Further, between the solar cell element 2 and the light receiving surface side sealing material sheet 3, a current collecting wiring (not shown) that is a wiring for taking out electricity from the solar cell element 2 is arranged. The wiring for current collection is arranged on the light receiving surface side of the solar cell element 2. In addition, the number of current collecting wirings is not particularly limited, but a solar cell module arranged, for example, about 2 or 3 can be exemplified.

  Here, FIG. 4 shows a layer structure of a conventional general solar cell module (solar cell module 10A). The conventional solar cell module 10A includes a back surface protection sheet 6, a non-light receiving surface side sealing material sheet 5, a solar cell element 2, a light receiving surface side sealing material sheet 3, and an outermost layer on the light receiving surface side from the non-light receiving surface side. The transparent front substrate 4 disposed on the substrate is sequentially stacked.

  The sealing material integrated back surface protection sheet 1 is formed by integrally laminating a sealing material sheet 11 relating to the present embodiment that can be thinned while maintaining heat resistance and the like, and a back surface protection sheet 12 having a barrier property. It is a multilayer sheet (see FIG. 2). Therefore, in the solar cell module 10 using this, the solar cell module is made thinner than the conventional general solar cell module 10A in which the conventional sealing material sheets are laminated on both sides of the solar cell element 3. Can be realized. In this specification, a solar cell module using a sealing material-integrated back surface protection sheet as shown in FIG. 3 will be described as a main use example, but the lamination temperature determination in the production of the solar cell module of the present invention will be described. The method can also be used in the conventional general solar cell module shown in FIG.

  As the solar cell element 2 used in the solar cell module 10, for example, amorphous silicon type, crystalline silicon type, CdTe type, CIS type, GaAs type, and other various conventionally known solar cell elements can be used. .

  The light-receiving surface side sealing material sheet 3 is a resin sheet disposed in the solar cell module 10 so as to cover the surface of the solar cell element 2 mainly in order to protect the solar cell element 2 from external impact. As the resin base material forming the light-receiving surface side sealing material sheet 3, thermoplastic resins such as ethylene-vinyl acetate copolymer resin (EVA), ionomer, polyvinyl butyral (PVB), and polyethylene can be used as appropriate.

  The transparent front substrate 4 is generally a glass substrate. The transparent front substrate 4 is not particularly limited as long as it maintains the weather resistance, impact resistance, and durability of the solar cell module 10 and transmits sunlight with high transmittance.

<Lamination temperature determination method>
The laminate temperature determining method of the present embodiment determines the optimum laminate temperature for performing a thermal laminate process for heating and integrating the sealing material sheet and other members in the production of the solar cell module. It is a decision method. The laminate temperature determining method of the present embodiment is specifically a laminate temperature determining method determined by a TMA curve obtained by the following thermomechanical analysis (TMA) test.

[TMA test]
The thermomechanical analysis (TMA) test relating to the present embodiment is a test for determining the temperature of a predetermined needle indentation depth ratio (%). Specifically, a φ10 mm sealing material sheet is set in the TMA apparatus, the pressure is set to a constant pressure of 50 kPa into a φ1 mm needle, the temperature is increased from room temperature at a temperature rising rate of 5 ° C./min, and the needle pressing depth at that time This is a test to measure the thickness.

  The temperature of the ratio (%) of the predetermined needle pressing depth is, for example, the pressing of the needle into the sealing material sheet 11 with respect to the predetermined temperature range (° C.) and the film thickness of the sealing material sheet 11 as shown in FIG. It can be obtained from a TMA curve showing the relationship with the depth ratio (%).

The ratio (%) of the pressing depth of the needle into the sealing material sheet 11 with respect to the predetermined temperature range (° C.) and the film thickness of the sealing material sheet 11 is specifically the ratio of the pressing depth of the needle ( %) Is the temperature (° C.) at the time of 50% (hereinafter sometimes referred to as T _50% ) and the temperature T _90% (° C.) when the ratio of the needle indentation depth (%) is 90%. ) (Hereinafter sometimes referred to as T _90% ).

Then, to determine the lamination temperature in the thermal lamination process of integrating by heating the sealing material sheet and other members T _50% or higher T _90% or less and. When the laminating temperature is less than T _50% , the sealing material sheet and other members are integrated in a state where the sealing material sheet 11 does not have sufficient flexibility at the time of the thermal laminating process. In the integration, there is a possibility that the solar cell element is cracked. When the laminating temperature is higher than _90% , the sealing material sheet 11 is integrated with the sealing material sheet and other members while the sealing material sheet 11 has high fluidity. Only can flow excessively and contaminate the vacuum laminator.

T _50% and T ₉₀ determined by a TMA curve showing a relationship between a predetermined temperature range (° C.) and a ratio (%) of the depth of pressing of the needle into the sealing material sheet 11 with respect to the film thickness of the sealing material sheet 11. _%, It is possible to prevent cracking of the solar cell element in the thermal laminating process in which the sealing material sheet and other members are heated and integrated by determining the laminating temperature from _% and performing the thermal laminating process. And fluidity to such an extent that contamination of the vacuum laminator does not occur.

<Sealing material sheet>
The laminating temperature determination method of the present invention determines the laminating temperature from T _50% and T _90% obtained from the TMA curve. Therefore, T _{50 of the} sealing material sheet which can be used for the manufacturing method of the solar cell module which performs the thermal lamination process with the optimal lamination temperature determined by the lamination temperature determination method of this invention and the lamination temperature determination method of this invention. _% And T _90% are preferably larger. The difference between T _50% and T _90% of the encapsulant sheet is increased to prevent cracking of the solar cell element in the heat laminating process in which the encapsulant sheet and other members are heated and integrated. Therefore, the temperature range of the optimum laminating temperature that can achieve both the flexibility that can be achieved and the fluidity that does not cause contamination of the vacuum laminator becomes large.

Specifically, the encapsulant sheet is preferably an encapsulant sheet in which the difference between T _50% and T _90% is 20 ° C. or more, and the encapsulant in which the difference between T _50% and T _90% is 25 ° C. or more. More preferably, it is a sheet, more preferably a sealing material sheet in which the difference between T _50% and T _90% is 30 ° C. or more. If the difference between T _50% and T _90% is 20 ° C. or more, the temperature range of the optimum laminating temperature in the production of the solar cell module is increased, and the flexibility of the thermal laminating process in which the sealing material sheet is integrated and It becomes easier to determine the optimum laminating temperature in consideration of other requirements such as production efficiency other than fluidity.

Further, T _50% is preferably a sealing material sheet of 90 ° C. or higher and 130 ° C. or lower, and more preferably a sealing material sheet of 105 ° C. or higher and 125 ° C. or lower. Further, _{90% of} T is preferably a sealing material sheet of 130 ° C. or higher and 170 ° C. or lower, and more preferably 140 ° C. or higher and 160 ° C. or lower. Since the optimum laminating temperature in the production of a solar cell module is usually about 115 ° C. or higher and 150 ° C. or lower, if T _50% and T _90% are in the above ranges, the encapsulant sheet prevents cracking of the solar cell element. It is possible to achieve both the flexibility that can be achieved and the fluidity that does not cause contamination of the vacuum laminator.

  Next, the preferable one embodiment of the sealing material sheet which comprises the solar cell module 10 regarding this embodiment is demonstrated. The sealing material sheet which can be used for the lamination temperature determination method of the present invention is not limited to the following sealing material sheet.

[Preferred Embodiment of Sealant Sheet]
The encapsulant sheet 11 according to this embodiment is a multilayer sheet having a core layer 111 and a skin layer 112. The encapsulant sheet according to the present invention may be a single layer or may have a layer structure in which the skin layer 112 is laminated only on one surface of the core layer 111, but has at least three or more layer structures. As shown in FIG. 1, the sealing material sheet 11 is a multilayer sheet having a three-layer structure in which a skin layer, a core layer, and a skin layer are laminated in this order, as shown in FIG. Is more preferable. The encapsulant sheet 11 is composed of the resin composition components described below for each layer in an optimum composition so that the heat resistance and thermal processing suitability required for the encapsulant sheet 11 for solar cell modules can be obtained. In addition, it is possible to sufficiently meet the demand for thinning the solar cell module while maintaining various required physical properties such as flexibility and adhesion to the substrate.

  The thickness of the sealing material sheet 11 is, for example, in the range of 200 μm or more and 400 μm or less. Even when the thickness is 250 μm or less, various required physical properties other than the above heat resistance can be sufficiently retained. In the case of a multilayer sheet having a three-layer structure in which the skin layer, the core layer, and the skin layer are laminated in this order, as in the sealing material sheet 11 of the present embodiment, Their thickness ratio is preferably in the range of 1: 3: 1 to 1: 30: 1 in the skin layer: core layer: skin layer thickness ratio.

Examples of the core layer 111 and the skin layer 112 include a material in which low density polyethylene having a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less is contained in an amount of 60% by mass or more in the total resin components of each layer composition. Can do. When the low-density polyethylene is contained in the sealing material sheet 11 in such a range, the sealing material sheet 11 having transparency and flexibility can be obtained. In the total resin component of each layer composition, the core layer 111 means the whole resin component of the core layer 111 composition, and the skin layer 112 means the whole resin component of the skin layer 112 composition. .

(Core layer)
The core layer 111 mainly has a function of imparting heat resistance and appropriate rigidity to the encapsulant sheet 11. Examples of the core layer 111 include a material in which low density polyethylene having a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less is contained in an amount of 60% by mass or more in the total resin components of the core layer composition. From the viewpoint of preventing laminator contamination caused by melting of the resin derived from the sealing material at the time of laminating, a heat-resistant resin (hereinafter simply referred to as a heat-resistant resin) having higher heat resistance than low-density polyethylene may be used. ) Is further preferably contained. Examples of such a heat resistant resin include high density polyethylene and polypropylene having a density of 0.940 g / cm ³ or more.

  An example of the thickness of the core layer 111 is 40 μm or more and 240 μm or less, and is not particularly limited. When the thickness of the core layer 111 is 40 μm or more, good dimensional stability can be imparted to the encapsulant sheet 11. In addition, when the thickness of the core layer 111 is 240 μm or less, the encapsulating sheet 11 can be given sheet transportability at the time of lamination.

(Core layer composition)
The core layer composition that can form the core layer 111 is not particularly limited. For example, a low-density polyethylene having a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less is a total resin of the core layer composition. The thing contained 60 mass% or more in a component can be mentioned. The low density polyethylene contained in the core layer 111 is preferably a low density polyethylene having a density of 0.910 g / cm ³ or more and 0.940 g / cm ³ or less. The low density polyethylene is preferably 60% by mass or more and 95% by mass or less, more preferably 75% by mass or more and 85% by mass or less, based on the total resin component of the core layer composition. The core layer composition preferably further contains a heat resistant resin, and among the heat resistant resins, it is preferred that polypropylene is contained. 5 mass% or more and 40 mass% or less are preferable in the total resin component of a core layer composition, and, more preferably, polypropylene is 10 mass% or more and 30 mass% or less. In addition, content ratio of each resin in the resin composition used for this invention can be analyzed from the peak ratio etc. which are detected by DSC (differential scanning calorimetry) or IR (infrared spectroscopy) etc., for example.

  As the polypropylene that can be contained in the core layer composition in the above predetermined amount range, it is more preferable to use a homopolypropylene (homo PP) resin. Homo PP is a polymer composed only of polypropylene and has high crystallinity, and therefore has higher rigidity than block PP and random PP. By using this as an additive resin to the core layer composition, the dimensional stability of the encapsulant sheet 11 can be further enhanced. Moreover, it is preferable that MFR in 230 degreeC of homo PP is 5 g / 10min or more and 125 g / 10min or less. When the MFR is less than 5 g / 10 minutes, the molecular weight increases and the rigidity becomes too high, and the preferable and sufficient flexibility of the encapsulant sheet 11 cannot be secured even by the physical properties of the skin layer 112. If the MFR exceeds 125 g / 10 minutes, the fluidity during heating is not sufficiently suppressed, and the sealing material sheet 11 can be sufficiently provided with heat resistance and dimensional stability as described above. Absent. In addition, unless otherwise specified, “MFR” in the present specification is the value of MFR at 190 ° C. and a load of 2.16 kg measured according to JIS7210 (however, the same applies to the MFR of polypropylene resin) MFR value at 230 ° C. and a load of 2.16 kg).

However, polypropylene has a rigidity much higher than that of low-density polyethylene having a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less in any of the above structures. Therefore, for example, when polypropylene exceeding 40% by mass is added to the core layer composition exceeding the appropriate addition amount range, the physical properties of polypropylene in the core layer 111 become excessively superior, and the encapsulant sheet The preferable flexibility as a whole cannot be secured even by the physical properties of the skin layer 112.

  By mixing a heat-resistant resin such as polypropylene within the above content range, even when the encapsulant sheet 11 is a thin sheet of 400 μm or less, the encapsulant sheet 11 can have good heat resistance. Therefore, it is preferable. Moreover, by giving sufficient heat resistance to the sealing material sheet | seat 11, generation | occurrence | production of the sealing material sheet | seat 11 curl deformation | transformation which becomes a problem especially at the time of the vacuum lamination process in manufacture of a solar cell module can also be suppressed.

  The core layer 111 can further contain an inorganic filler. Thereby, the rigidity of the core layer 111 is increased and the occurrence of undesirable curl deformation of the encapsulant sheet 11 can be suppressed. Such inorganic fillers include talc (hydrous magnesium silicate) or titanium oxide, and others such as calcium carbonate, carbon black, titanium black, Cu—Mn based composite oxide, Cu—Cr—Mn based composite oxide, Alternatively, zinc oxide, aluminum oxide, iron oxide, silicon oxide, barium sulfate, calcium carbonate, titanium yellow, chrome green, ultramarine, aluminum powder, mica, barium carbonate, or the like can be used. The inclusion of the inorganic filler in the core layer composition forming the core layer 111 is not essential, and the content thereof may be in the range of 0% by mass to 30% by mass in the total resin components of the core layer composition. .

  In addition, when it is calculated | required that the back surface protection sheet 12 has a colored external appearance, it is excellent in a weather resistance among said inorganic fillers, and it is easy to obtain including price and easy to obtain. Therefore, the white pigment may further include titanium oxide and the like, and the black pigment may further include carbon black and the like. The inclusion of these colored pigments is preferable in that it can improve the power generation efficiency due to re-reflection of sunlight or meet the demands on the design.

(Skin layer)
The skin layer 112 is a layer mainly disposed in the outermost layer of the sealing material sheet 11. In the solar cell module 10, the skin layer 112 is in close contact with the surface on the non-light receiving surface side of the solar cell element 2 and the light receiving surface side sealing material sheet 3, or in close contact with the back surface protective sheet 12 as necessary. It becomes. In particular, in the former case, to improve the adhesion of the encapsulant sheet 11 and the follow-up to the unevenness of other members during lamination for integration as a solar cell module (hereinafter referred to as “molding characteristics”). Contribute.

  The thickness of the skin layer 112 may be appropriately determined in consideration of the thickness (thinness) required for the sealing material sheet 11. As an example, when the skin layer 112 has a layer configuration in which the skin layer 112 is laminated on one surface of the core layer 111, a preferable thickness of the skin layer 112 is 3 μm or more and 150 μm or less. When the thickness of the skin layer 112 is 3 μm or more, sufficient adhesion and molding characteristics can be imparted to the encapsulant sheet 11.

  When the skin layer 112 is formed on both surfaces of the core layer 111, a colored pigment can be contained in any one of the two layers. In this case, it is preferable that at least the outermost surface of the other skin layer 112 preferably contains no colored pigment over substantially the entire other skin layer. The encapsulant sheet 11 having such a layer structure is preferably disposed in the solar cell module 10 so that one skin layer 112 containing a colored pigment faces the back surface protective sheet 12. Thereby, in the solar cell module 10, the sealing material sheet 11 can exhibit the light reflection function on the non-light-receiving surface side of the solar cell element 2, and can contribute to the improvement of the power generation rate of the solar cell module 10. At this time, if it is assumed that the other skin layer 112 does not contain a colored pigment, the load derived from the pigment on the solar cell element is reduced in the laminating step when integrating as a solar cell module, and the solar cell The occurrence of cracking of the element can be suppressed. In addition, it is possible to avoid the wraparound of the white pigment to the light receiving surface side of the solar cell element, which causes a decrease in power generation efficiency in the laminating step. Therefore, it is preferable that the other skin layer 112 does not contain a colored pigment.

(Skin layer composition)
The skin layer composition that can form the skin layer 112 is not particularly limited. For example, low density polyethylene having a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less is included in all the resin components of the skin layer composition. The thing contained 60 mass% or more can be mentioned. The low density polyethylene contained in the skin layer 112 is preferably a low density polyethylene having a density of 0.880 g / cm ³ or more and less than 0.910 g / cm ³ . The low density polyethylene is preferably 80% by mass or more and 100% by mass or less, more preferably 98% by mass or more and 100% by mass or less, based on the total resin component of the skin layer composition. And unlike a core layer composition, it is preferable that a skin layer composition does not contain heat resistant resins, such as a polypropylene. As described above, the skin layer 112 is preferably a layer mainly composed of low-density polyethylene having a lower density than the base resin of the core layer composition, from the viewpoint of imparting molding characteristics and adhesion to the skin layer.

  For the skin layer composition, low density polyethylene (LDPE) in the above density range, more preferably a copolymer of ethylene and α-olefin, and linear low density polyethylene (LLDPE) in the above density range is used. be able to. By setting the type, density range, and content ratio of the adhesion component to the composition range described above, preferable flexibility can be imparted to the sealing material sheet 11 having the skin layer 112.

  The skin layer composition preferably contains silane-modified polyethylene at a predetermined ratio. The silane-modified polyethylene resin is obtained by graft-polymerizing an ethylenically unsaturated silane compound as a side chain to linear low-density polyethylene (LLDPE) or the like as a main chain. Such a graft copolymer can further improve the adhesion of the encapsulant sheet 11 because the degree of freedom of silanol groups contributing to the adhesive force is increased.

  The amount of grafting that is the content of the ethylenically unsaturated silane compound is such that the amount of grafting of the ethylenically unsaturated silane compound with respect to 100 parts by mass of the polyethylene resin forming the skin layer is, for example, 0.001 part by mass or more and 15 parts by mass or less. Preferably, it may be appropriately adjusted so that it is 0.05 parts by mass or less, more preferably 0.1 parts by mass or more and 1.0 part by mass or less. When the content of the ethylenically unsaturated silane compound is large, the mechanical strength and the heat resistance are excellent. However, when the content is excessive, the tensile elongation and the heat fusion property tend to be inferior.

  The silane-modified polyethylene resin can be produced, for example, by the method described in JP-A-2003-46105. By using the resin as a component of a sealing material composition for a solar cell module, strength and durability can be increased. In addition, it has excellent weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other characteristics, and also affects manufacturing conditions such as thermocompression bonding for manufacturing solar cell modules. It is possible to manufacture solar cell modules that have extremely excellent heat-sealability without being received, that are stable, low-cost, and suitable for various applications.

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

(Other ingredients)
The skin layer composition and the core layer composition may further contain other components. For example, components such as various weather resistance master batches, various fillers, light stabilizers, ultraviolet absorbers, heat stabilizers and the like for imparting weather resistance to the encapsulant sheet 11 are exemplified. These contents vary depending on the particle shape, density and the like, but are preferably in the range of 0.001% by mass or more and 5% by mass or less in the total resin composition of the sealing material sheet 11, respectively. . By including these additives, the sealing material sheet 11 of the sealing material-integrated back surface protection sheet 1 is provided with a long-term improvement in mechanical strength, an effect of preventing yellowing, cracking, and the like. Can do.

[Back protection sheet]
As the back surface protection sheet 12, various resin sheets that have been conventionally used as back surface protection sheets for solar cell modules can be used. Examples of the resin sheet forming the back protective sheet 12 include polyethylene resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride resin, poly (Meth) acrylic resins, polycarbonate resins, polyethylene terephthalate (PET), polyester resins such as polyethylene naphthalate, polyamide resins such as various nylons, polyimide resins, polyamideimide resins, polyarylphthalate resins, Various resin sheets such as silicone resins, polysulfone resins, polyphenylene sulfide resins, polyether sulfone resins, polyurethane resins, acetal resins, and cellulose resins can be used. Among these, polyethylene terephthalate (PET) can be preferably used from the viewpoints of physical properties such as insulation performance, mechanical strength, cost, transparency, and economy. In addition, from the viewpoint of further improving mechanical strength and water vapor barrier properties, a multilayer sheet obtained by further laminating hydrolysis resistant PET in the outermost layer in addition to the above PET can be particularly preferably used as the back surface protective sheet 12. .

  The thickness of the back surface protective sheet 12 is not particularly limited, but may be appropriately determined within a range in which physical properties such as water vapor barrier properties required for the back surface protective sheet 12 can be maintained. The thickness of the back surface protective sheet 12 is preferably 50 μm or more and 300 μm or less, and more preferably 50 μm or more and 200 μm or less. When the thickness of the back surface protection sheet 12 is 50 μm or more, preferable durability and weather resistance can be imparted to the solar cell module 10.

  In addition, the back surface protection sheet 12 can also be preferably used in which a weathering layer (not shown) is further laminated on one surface assumed to be the outermost layer side when integrated with the solar cell module 10. . As the weather resistant layer, a layer excellent in weather resistance, heat resistance, light resistance and the like is used. As the base material for forming the weather resistant layer, hydrolysis resistant polyethylene terephthalate (hydrolysis resistant PET), PCTFE (polychlorotrifluoroethylene), PFA (tetrafluoroethylene perfluoroalkyl vinyl ester copolymer), PTFE Preferred examples include resin sheets such as fluorine-based resins such as (polytetrafluoroethylene), ETFE (tetrafluoroethylene / ethylene copolymer), PVDF (polyvinylidene fluoride), and aluminum sheets. Among the above, hydrolysis resistant PET can be particularly preferably used. Hydrolysis-resistant PET refers to polyethylene terephthalate having excellent hydrolysis resistance described in JP2012-62380A. This hydrolysis-resistant PET is polyethylene terephthalate containing an alkali metal element in an amount of 2 ppm to 100 ppm and a phosphorus element in an amount of 10 ppm to 250 ppm. This resin contains 2 parts by mass or more and 20 parts by mass or less of oxyalkylene glycol. Hydrolysis-resistant PET is excellent in hydrolysis resistance, and also in heat resistance and durability required for a protective sheet disposed on the back side of the solar cell module. Moreover, since it is excellent in workability and is relatively inexpensive, it can be used very preferably as a material for forming the weather resistant layer of the back surface protective sheet 12.

  In addition, the weather-resistant layer of the back surface protection sheet 12 may be obtained by forming a weather-resistant coating layer on the surface of the base material layer by surface processing such as fluorine coating, EB coating, or silica deposition. Furthermore, the above-mentioned weather-resistant resin sheet or the like having a required strength by a predetermined thickness or processing can be used as the back surface protection sheet 12.

<Encapsulant integrated back protection sheet>
The sealing material integrated back surface protection sheet 1 obtained by integrating the sealing material sheet 11 and the back surface protection sheet 12 can also be used as a member for a solar cell module. The sealing material sheet 11 and the back surface protection sheet 12 in the sealing material integrated back surface protection sheet 1 are preferably integrated by a dry laminating method performed via an adhesive layer (not shown). However, as long as it can maintain desired adhesion and durability, it may be integrated by other conventionally known means. For example, by the extrusion coat laminating method in which the resin composition that becomes the encapsulating material sheet 11 is directly extruded onto the surface of the back surface protective sheet 12 by an extruder to form the encapsulating material sheet 11, and the sandwich lamination method that is an application form thereof. Alternatively, the sealing material sheet 11 and the back surface protection sheet can be integrated to form the sealing material integrated back surface protection sheet 1.

(Back surface protection sheet forming process)
The back surface protection sheet 12 is formed by depositing a resin material such as PET described above by an extrusion method, a cast molding method, a T-die method, a cutting method, an inflation method, other film forming methods, or the like. Can do. In addition, the back surface protection sheet 12 may contain other additives, such as a pigment other than the said resin material, in the range which does not impair the effect of this invention.

(Encapsulant sheet forming process)
The encapsulant sheet 11 can be obtained by integrally forming the above-described skin layer composition and core layer composition by a known coextrusion method to form a multilayer sheet.

(Integration process)
The sealing material sheet 11, the back surface protection sheet 12, and a sheet for forming other layers formed by the same method as necessary are appropriately laminated and further integrated, whereby the sealing of this embodiment is performed. The stop material-integrated back protective sheet 1 can be obtained. The integration of the sheets can be performed by a conventionally known dry laminating method. Conventionally known laminating adhesives can be used and are not particularly limited. A two-component curable dry laminating adhesive composed of a main agent such as urethane or epoxy and a curing agent can be used as appropriate. In addition, this integration process can also be based on the extrusion coat lamination method and the sandwich lamination method which is the application form.

<Method for manufacturing solar cell module>
The solar cell module 10 is, for example, vacuum-sucked after sequentially laminating the members including the transparent front substrate 4, the light-receiving surface side sealing material sheet 3, the solar cell element 2, and the sealing material integrated back surface protection sheet 1. Then, the above-mentioned members can be manufactured by thermocompression molding as an integrally molded body by a molding method such as a lamination method. The lamination temperature can be determined from T _50% (° C.) and T _90% (° C.) obtained from the TMA curve obtained by the TMA test. By performing the thermal laminating process with the optimum laminating temperature determined by the laminating temperature determining method of the present invention, the flexibility that can prevent the solar cell element from cracking and the flow that does not cause contamination of the vacuum laminator It is possible to achieve both sex.

  The laminating time is preferably in the range of 5 minutes to 20 minutes, particularly preferably in the range of 8 minutes to 15 minutes. In this way, the solar cell module 10 can be manufactured by thermocompression-bonding each of the above layers as an integrally formed body. The laminating process is preferably performed by vacuum heat laminating.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

<Manufacture of sealing material sheet>
Each encapsulant sheet was created by the following method according to the above-described “manufacturing method of encapsulant sheet”.

  Each of the following materials mixed in the composition shown in Table 1 was used separately as a blend for the core layer and skin layer of each encapsulant sheet. Each of these blends was formed into a sheet at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a φ30 mm extruder and a sheet molding machine having a 200 mm wide T die, and these were formed into a skin layer, a core It was set as the sealing material sheet by which the layer and the skin layer were laminated | stacked in this order. The total thickness of each encapsulant sheet and the thickness of each layer were 50 μm for each skin layer, 300 μm for the core layer, and 400 μm for the total thickness for any encapsulant sheet. In addition, the sheet | seat 1 in Table 1 similarly shape | molded the sealing material sheet | seat with a total thickness of 400 micrometers as a single layer for the core layer and a skin layer.

The following raw materials were used as the material for the encapsulant sheet.
Low density polyethylene (LDPE, expressed as “LD1” in the table): density 0.920 g / cm ³ , melting point 123 ° C.
Low density polyethylene (LDPE, indicated as “LD2” in the table): density 0.920 g / cm ³ , melting point 105 ° C.
Linear low-density polyethylene (LLDPE, indicated as “LLD” in the table): density 0.898 g / cm ³ , melting point 97 ° C.
Polypropylene (PP, indicated as “PP” in the table): homopolypropylene. Density 0.900 g / cm ³ , melting point 155 ° C., MFR 8.5 g / 10 min (230 ° C.).
EVA rapid cross-linking type (shown as “EVA” in the table)
White pigment: Titanium oxide having an average particle size of 0.2 μm. 7 parts by mass per 100 parts by mass of the resin component is added only to the core layer of all the encapsulant sheets.
UV absorber: manufactured by Chemipro Kasei Co., Ltd., trade name KEMISORB12. All 0.3 parts by mass are added to each of the encapsulant compositions for the core layer and skin layer of all Examples and Comparative Examples.
Weathering stabilizer: BASF Corporation, trade name Tinuvin 622SF. 0.2 parts by mass are added to each of the sealing material compositions for the core layer and skin layer of all Examples and Comparative Examples.
Antioxidant: Ciba Japan Co., Ltd., trade name Irganox 1076. 0.05 parts by mass are added to each encapsulant composition for the core layer and skin layer or single layer of all Examples and Comparative Examples.

<Manufacture of sealing material-integrated back surface protection sheet>
Each sealing material is laminated by a conventionally known dry laminating method by laminating the above sealing material sheet and a PET film (“Melinex S”, manufactured by Teijin DuPont, thickness 125 μm) whose surface has been subjected to corona treatment. An integrated back protection sheet was obtained.

<Thermomechanical analysis (TMA) test>
A TMA test was performed on each sealing material-integrated back protective sheet. Specifically, the sealing material integrated back surface protection sheet is cut out to φ10 mm, set in a TMA apparatus (TMA / SS7100 manufactured by SII Nanotechnology), the temperature of the sealing material integrated back surface protection sheet is raised, and the sealing material integrated type A φ1 mm needle was pushed in at a pressure of 50 kPa from the surface of the sealing material sheet of the back surface protective sheet, and the indentation depth was measured. The heating rate was 5 ° C./min, and the temperature was raised from room temperature to 166 ° C. FIG. 5 is a graph showing the relationship between the temperature (° C.) in the TMA test of each sealing material-integrated back protective sheet and the depth (%) of pushing the needle into the sealing material sheet with respect to the thickness of the sealing material sheet. Indicates. Table 1 also shows the temperature (° C.) when the ratio (%) of the needle indentation depth is 50% (indicated as T _50% in Tables 1 and 2) and the ratio of the needle indentation depth ( %) Represents a temperature T _90% (° C.) at _90% (indicated as T _90% in Tables 1 and 2). In Table 1, the sheet 6, at the time of 166 ° C., for needle penetration depth into the sealing member seat to the thickness of the sealing material sheet (%) was 70%, the T _{90 ° C.} It was estimated to be 166 ° C or higher.

  About each said sealing material integrated type back surface protection sheet, based on the following test method and evaluation criteria, it measured and evaluated about the laminator contamination presence and cell protection performance at the time of a lamination process. The results are shown in Table 2.

<Evaluation of laminator contamination during laminating>
White plate semi-tempered glass, solar cell element (manufactured by Q-CELLS, cell Q6LTT-200 / 152 156 mm) (2 × 2), sealing sheet for light-receiving surface side, `` Protective sheet '', respectively, a glass sheet, a sealing material sheet for the light-receiving surface side, a solar cell element, a sealing material integrated back protection sheet, and a glass sheet are laminated in this order, Under the laminating conditions, vacuum heating laminating treatment was performed, and solar cell module evaluation samples were obtained for the respective examples and comparative examples.
Immediately after taking this sample out of the laminator, the glass sheet portion was visually observed to evaluate the presence or absence of laminator contamination during lamination. The evaluation results are shown in Table 2 as “Excess”.

(Lamination condition) Vacuum drawing: 5.0 minutes
Pressurization (100 kPa): 10.0 minutes
Temperature: Indicated in Table 2

(Laminator contamination assessment criteria)
○: No resin stains.
(Triangle | delta): There is a resin stain | pollution | contamination of the grade which can be removed by stroke | battering once with the brush attached to a laminator.
X: Resin stains such that removal with the brush is impossible.

<Evaluation of solar cell element protection performance during laminating>
About each said solar cell module evaluation sample, it measured with the EL light emission tester, and evaluated the protective performance of the solar cell element at the time of a lamination process. The evaluation results are shown in Table 2 as “cell cracks”.

(Cell protection performance evaluation criteria)
○: There is no crack on the entire surface of all the solar cell elements. Δ: There is a crack on a part of the surface of the solar cell element, but the light emission can be confirmed.

From Table 2, the solar cell module evaluation sample integrated by heat laminating at a temperature (° C.) of T _50% (° C.) or more and T _90% (° C.) or less is a laminator contamination evaluation test and a solar cell. In each element protection performance evaluation test, the evaluation is “◯”. From the results of this test, the solar cell module was manufactured by the method for determining the lamination temperature of the present invention, so that the solar cell element was cracked in the thermal laminating process in which the sealing material sheet and other members were integrated by heating. It can be seen that both the flexibility that can be prevented and the fluidity that does not cause contamination of the vacuum laminator can be achieved.

DESCRIPTION OF SYMBOLS 1 Sealing material integrated back surface protection sheet 11 Sealing material sheet 111 Core layer 112 Skin layer 12 Back surface protection sheet 2 Solar cell element 3 Light-receiving surface side sealing material sheet 4 Transparent front substrate 5 Non-light-receiving surface side sealing material sheet 6 Back surface protection sheet 10 Solar cell module 10A Solar cell module

Claims (7)

In the production of a solar cell module, a laminating temperature determining method for determining an optimum laminating temperature for performing a heat laminating process for heating and integrating a sealing material sheet and other members,
It is obtained in the thermomechanical analysis (TMA) test under the following conditions, and shows the relationship between the temperature (° C.) and the ratio (%) of the indentation depth of the needle to the sealing material sheet with respect to the film thickness of the sealing material sheet. From the TMA curve
The temperature T _50% (° C.) when the needle pressing depth ratio (%) is 50% and the temperature T _90% (° C.) when the needle pressing depth ratio (%) is 90%. And
A method for determining a lamination temperature in manufacturing a solar cell module, wherein a temperature (° C.) between T _50% (° C.) and T _90% (° C.) is determined as an optimum lamination temperature.
(TMA test: A φ10 mm encapsulant sheet is set in a TMA apparatus, the pressure is set to a constant pressure of 50 kPa into a φ1 mm needle, the temperature is raised from room temperature at a temperature rising rate of 5 ° C./min, and the needle push-in depth is To measure.)   The lamination temperature determination method according to claim 1, wherein the sealing material sheet is a multilayer sheet having a layer structure of at least three.   The lamination temperature determination method according to claim 2, wherein the sealing material sheet is a multilayer sheet having a three-layer structure in which a skin layer, a core layer, and a skin layer are laminated in this order.   The lamination temperature determination method according to claim 3, wherein the core layer of the encapsulant sheet contains 5% by mass to 40% by mass of polypropylene in the total resin component of the core layer composition.   The lamination temperature determination method according to any one of claims 1 to 4, wherein a thickness of the sealing material sheet is 200 µm or more and 400 µm or less.   The manufacturing method of the solar cell module which performs the said thermal lamination process at the optimal lamination temperature determined by the lamination temperature determination method in any one of Claim 1 to 5. Obtained in a thermomechanical analysis (TMA) test under the following conditions, a predetermined temperature range (° C.) and a ratio (%) of the depth of pressing of the needle into the sealing material sheet with respect to the film thickness of the sealing material sheet From the TMA curve showing the relationship,
The temperature T _50% (° C.) when the needle pressing depth ratio (%) is 50% and the temperature T _90% (° C.) when the needle pressing depth ratio (%) is 90%. And
The sealing material sheet for solar cell modules whose difference of temperature (degreeC) with said T50 _% (degreeC) and said _T90% (degreeC) is 20 degreeC or more.
(TMA test: A φ10 mm encapsulant sheet is set in a TMA apparatus, the pressure is set to a constant pressure of 50 kPa into a φ1 mm needle, the temperature is raised from room temperature at a temperature rising rate of 5 ° C./min, and the needle push-in depth is To measure.)

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