JP6915275B2 - A backside protective sheet with an integrated sealing material for the solar cell module, and a solar cell module using the same. - Google Patents

Description

The present invention relates to a back surface protective sheet integrated with a sealing material for a solar cell module, and a solar cell module using the same.

Conventionally, the layer structure of the solar cell module is generally the layer structure of the solar cell module 100A shown in FIG. That is, the transparent front substrate 5, the light receiving surface side sealing material sheet 4, the solar cell element 3, the non-light receiving surface side sealing material sheet 6, and the back surface protective sheet 7 are laminated in this order from the light receiving surface side.

Among the above-mentioned members constituting the solar cell module, the sealing material sheet is a resin sheet made of ethylene-vinyl acetate copolymer resin (EVA) from the viewpoint of transparency, workability, manufacturing cost, etc. It was used for general purposes. However, EVA resin tends to be gradually decomposed with long-term use, and deteriorates inside the solar cell module to reduce its strength or generate acetic acid gas that affects the solar cell element. there is a possibility. Therefore, in recent years, instead of EVA resin, a sealing material sheet for a solar cell module using a polyolefin-based resin has been proposed, and the demand for it is expanding.

On the other hand, as the back surface protective sheet arranged as a protective layer on the outermost layer of the solar cell module, a resin sheet using a fluorine-based resin or a polyester-based resin such as polyethylene terephthalate (PET) is widely used. Further, a multilayer sheet in which each member such as a resin sheet having a barrier property is laminated by a dry laminating method or the like is used.

In recent years, the encapsulant sheet and the back surface protective sheet have been formed as an integral product in advance for the purpose of reducing the thickness of the solar cell module due to design requirements and improving productivity by simplifying the manufacturing process. The development of a back surface protective sheet with an integrated sealing material is also in progress (see Patent Document 1).

This encapsulant-integrated back surface protective sheet is used by being arranged on the non-light receiving surface side of the solar cell module in the solar cell module 100, such as the encapsulant-integrated back surface protective sheet 10 in FIG. It contributes to making the battery module thinner and improving productivity.

On the other hand, the encapsulant layer 1 constituting the encapsulant integrated back surface protective sheet 10 (see FIG. 2) faces the solar cell element 3 and the back surface protective layer 2 constituting the encapsulant integrated back surface protective sheet 10. The encapsulant layer 1 is required to have adhesion between both members and adhesion durability that can withstand long-term use in a harsh environment.

Therefore, in order to improve the adhesion of the polyethylene-based sealing material sheet constituting the sealing material layer 1 to metal and glass, it is widely practiced to contain a certain amount of silane-modified polyethylene in the base resin. ing.

On the other hand, sufficient adhesion is ensured between the polyethylene-based encapsulant sheet constituting the encapsulant layer of the encapsulant-integrated back surface protective sheet and the polyester-based back surface protective sheet forming the back surface protective layer. For that purpose, it is indispensable to perform corona treatment on the back surface of the sealing material sheet on the back surface protective sheet side. However, when each layer of the encapsulant sheet contains silane-modified polyethylene as described above, there is a problem that water is generated by the corona treatment and the adhesion durability of the encapsulant sheet is lowered.

Japanese Unexamined Patent Publication No. 2012-84842

The present invention has been made in view of the above circumstances, and is an encapsulant-integrated back surface protective sheet that can contribute to reducing the thickness and manufacturing cost of the solar cell module, and is an encapsulant-integrated back surface protective sheet. Excellent adhesion durability between each layer and with other constituent members including metal members such as electrodes of solar cell elements when integrated as a solar cell module. It is an object of the present invention to provide a back surface protective sheet with an integrated sealing material that improves the long-term reliability of the solar cell module.

The present inventors have a three-layer structure of a first skin layer, a core layer, and a second skin for the sealing material layer constituting the back surface protective sheet integrated with the sealing material, and in order to improve the heat resistance of the core layer. Polypropylene is added as a high melting point component, and silane-modified polyethylene, which is an adhesive component, is added only to the first skin layer, which is the outermost layer on the encapsulant layer side, and further, the core layer and the second skin layer. By forming a layer structure in which the densities of the base resins are the same, the above-mentioned problems can be solved, and the present invention has been completed. More specifically, the present invention provides the following.

(1) An encapsulant-integrated back surface protective sheet for a solar cell module, in which a sealing material layer using a polyethylene resin as a base resin and a back surface protective layer using a polyester resin as a base resin are laminated. The encapsulant layer is a core layer using a polyethylene resin as a base resin and a polyethylene resin having a density lower than that of the base resin of the core layer as a base resin. The first skin layer arranged on the outermost surface on the sealing material layer side and the polyethylene resin having the same density as the base resin of the core layer are used as the base resin, and are arranged on the interface side with the back surface protective layer. It has a multi-layer structure including a second skin layer, the core layer contains 5% by mass or more and 40% by mass or less of polypropylene in the total resin component of the core layer, and the first skin layer is , A sealing material-integrated back surface protective sheet containing silane-modified polyethylene obtained by graft-polymerizing an ethylenically unsaturated silane compound on low-density polyethylene, and the core layer and the second skin layer not containing the silane-modified polyethylene.

(2) The encapsulant-integrated back surface protective sheet according to (1), wherein the amount of polymerized silane in the total resin components of the first skin layer is 300 ppm or more and 2000 ppm or less.

(3) The encapsulant-integrated back surface protective sheet according to (1) or (2), wherein the core layer contains a white pigment and the first skin layer and the second skin layer do not contain a white pigment.

(4) The encapsulant-integrated back surface protective sheet according to any one of (1) to (3), wherein the back surface protective layer includes a polyethylene terephthalate layer and / or a hydrolysis-resistant polyethylene terephthalate layer. ..

(5) The encapsulant-integrated back surface protective sheet according to any one of (1) to (4) is laminated in such a manner that the first skin layer faces the non-light receiving surface side of the solar cell element. Solar cell module.

According to the present invention, it is an encapsulant-integrated back surface protective sheet that can contribute to thinning of the solar cell module and reduction of manufacturing cost, and has adhesion durability between each layer of the encapsulant-integrated back surface protective sheet, and The solar cell module has excellent adhesion durability with other constituent members including metal members such as electrodes of the solar cell element when integrated as a solar cell module. It is possible to provide a back surface protective sheet with an integrated sealing material that improves long-term reliability.

It is sectional drawing which shows typically an example of the layer structure of the sealing material layer which comprises the sealing material integrated back surface protection sheet of this invention. It is sectional drawing which shows typically another example of the layer structure of the back surface protective sheet of the sealing material integrated type of this invention. It is sectional drawing which shows typically the outline of the layer structure of the solar cell module which comprises the back surface protection sheet integrated with the sealing material of this invention. It is sectional drawing which shows typically an example of the layer structure of the conventional general solar cell module.

Hereinafter, the details of the encapsulant-integrated back surface protective sheet of the present invention and the solar cell module using the same will be described. The present invention is not limited to the embodiments described below.

<Backside protective sheet with integrated sealing material>
As shown in FIG. 2, the encapsulant-integrated back surface protective sheet 10 for the solar cell module of the present invention mainly includes an encapsulant layer 1 that functions to protect the solar cell element from an impact from the outside of the solar cell module. This is a multi-layer sheet in which a back surface protective layer 2 having a barrier property that mainly prevents the intrusion of moisture and the like from the outside of the solar cell module is laminated and integrated. Both the sealing material layer 1 and the back surface protective layer 2 are composed of various resin sheets and the like, but since the required functions are different from each other, they are usually composed of different material resins. Then, each resin layer made of these different resins is usually laminated and integrated by a dry laminating method using an adhesive.

Then, as shown in FIG. 3, the sealing material integrated back surface protective sheet 10 integrated in advance of the integration step as the solar cell module is the non-light receiving surface of the solar cell element 3 in the solar cell module 100. It is stacked on the side to form a solar cell module. Further, the sealing material integrated back surface protective sheet 10 is arranged in the solar cell module 100 so that the sealing material layer 1 faces the non-light receiving surface side of the solar cell element 3.

The thickness of the back surface protective sheet 10 integrated with the encapsulant is preferably such that the total thickness including the encapsulant layer 1 and the back surface protective layer 2 described in detail below is 250 μm or more and 500 μm or less.

[Encapsulant layer]
As shown in FIG. 1, the sealing material layer 1 constituting the sealing material integrated back surface protective sheet 10 includes the core layer 11 and the first skin layer 12 and the second skin layer 13 arranged on both sides of the core layer 11. It has a multi-layer structure including.

As shown in FIG. 2, the first skin layer 12 is arranged on the outermost surface of the encapsulant-integrated back surface protective sheet 10 on the encapsulant layer 1 side. On the other hand, the second skin layer 13 is arranged on the interface side between the back surface protective layer 2 and the encapsulant layer 1 in the encapsulant integrated back surface protective sheet 10.

By forming the encapsulant layer 1 of the encapsulant-integrated back surface protective sheet 10 using the resin composition optimized for each layer described below, it is required for the encapsulant layer of the solar cell module. While maintaining the general required physical properties such as heat resistance and flexibility, the adhesion durability between each layer as the sealing material integrated back surface protective sheet 10 and other constituent members at the time of integration as the solar cell module 100 It is possible to improve the adhesion durability between the solar cell module and the solar cell module and contribute to the improvement of long-term reliability of the solar cell module.

The core layer of the encapsulant layer 1, the first skin layer 12, and the second skin layer 13 are each formed by an encapsulant composition using polyethylene as a base resin in a predetermined density range.

Core Core layer 11 has a density 0.890 g / cm ³ or more 0.930 g / cm ³ or less, which more preferably, a density of 0.900 g / cm ³ or more 0.920 g / cm ³ or less of the polyethylene resin as a base resin Formed by encapsulant composition for layers.

The first skin layer 12 has a density 0.880 g / cm ³ or more 0.910 g / cm less than ^3, more preferably, a is a density 0.890 g / cm ³ or more 0.900 g / cm ³ or less, besides, the core The encapsulant composition for the first skin layer is formed by using a polyethylene-based resin having a density lower than that of the base resin of the encapsulant composition for the layer as the base resin.

The second skin layer 13 has a density 0.890 g / cm ³ or more 0.930 g / cm ³ or less, more preferably, a is a density 0.900 g / cm ³ or more 0.920 g / cm ³ or less, besides, the core It is formed by a sealing material composition for a second skin layer using a polyethylene-based resin having the same density as the base resin of the sealing material composition for the layer as a base resin.

Encapsulant layer 1 By adjusting the density of each layer within the above range, it is possible to obtain a multi-layer encapsulant layer having a good balance of heat resistance, flexibility, and adhesion durability.

Further, the encapsulant layer 1 contains a silane-modified polyethylene, that is, an adhesive resin component obtained by graft-polymerizing an ethylenically unsaturated silane compound on low-density polyethylene in the first skin layer 12. On the other hand, the encapsulant layer 1 does not contain silane-modified polyethylene in the core layer 11 and the second skin layer 13. That is, the encapsulant layer 1 has a skin / core / skin three-layer structure in which silane-modified polyethylene is unevenly distributed only in one skin layer (first skin layer 12).

Here, in the multi-layered resin sheet, when a layer requiring particularly enhanced adhesion is specified as one surface layer, it is conceivable to unevenly distribute the silane-modified polyethylene only on the one surface layer. However, in a multi-layer sheet having a three-layer structure of skin / core / skin, when the layer structure contains a large amount of silane-modified polyethylene in only one skin layer, the difference in layer strength between the layers increases. The research by the present inventors has clarified that cohesive fracture is likely to occur inside the layer on the side where the layer strength is weak. It is considered that this is because a layer having a weak layer strength is strongly pulled by a strong layer, so that cohesive fracture is likely to occur inside the weak layer.

Therefore, in the encapsulant layer 1 of the encapsulant-integrated back surface protective sheet 10, the densities of the base resin of the core layer 11 and the base resin of the second skin layer, which do not contain silane-modified polyethylene, are the same. Optimized for density. With such a layer structure peculiar to the present invention, in the sealing material layer 1, the adhesion component is unevenly distributed on the first skin layer 12, and the adhesion durability to other laminated members constituting the solar cell module is sufficiently improved. At the same time, the adhesion between the core layer 11 and the second skin layer is appropriately improved, and the occurrence of cohesive fracture due to the expansion of the layer strength difference between the above-mentioned layers is appropriately suppressed. .. In this way, the encapsulant-integrated back surface protective sheet 10 has adhesion durability between the back surface protective sheet 10 and other laminated members made of glass or metal, and adhesion durability between the layers of the encapsulant-integrated back surface protective sheet 10 itself. Are compatible with each other at a high level.

In the encapsulant layer 1, by unevenly distributing an appropriate amount of silane-modified polyethylene on the first skin layer 12, which is required to have adhesive durability with the solar cell element 3, the adhesiveness of the first skin layer 12 to the facing member is improved. Adhesion durability can be improved to a very preferable degree.

In addition, the second skin layer 13 in contact with the interface on the back surface protective layer side, which normally requires corona treatment, does not contain silane-modified polyethylene to prevent the generation of water caused by the corona treatment at the interface. It is also possible to avoid a decrease in adhesion durability between the second skin layer 13 and the back surface protective layer 2 at the interface. In the sealing material integrated back surface protective sheet 10, at least one of the surface of the second skin layer 13 forming the interface or the surface of the back surface protective layer 2 facing the second skin layer 13 is subjected to corona treatment. The corona treatment is a method of irradiating a resin base material with a corona discharge to introduce a polar group on the surface of the resin base material to improve the adhesion performance.

The amount of polymerized silane in the encapsulant composition for the first skin layer forming the first skin layer 12 of the encapsulant layer 1 is 300 ppm or more and 2000 ppm or less, preferably 300 ppm or more and 1500 ppm or less, more preferably 300 ppm. More than 1000 ppm or less.

The encapsulant composition forming the core layer 11 of the encapsulant layer 1, the first skin layer 12 and the second skin layer 13 is preferably made of polyethylene having a predetermined melting point range as a base resin. The encapsulant composition for the core layer preferably uses low-density polyethylene having a melting point of 100 ° C. or higher and 115 ° C. or lower as a base resin. The encapsulant composition for the first skin layer preferably uses low-density polyethylene having a melting point of 80 ° C. or higher and lower than 100 ° C. as a base resin. Further, the resin composition may be further adjusted so that the difference in melting point of the base resin of the encapsulant composition forming the core layer 11 and the first skin layer 12 is within the range of 20 ° C. or less within the above melting point range. preferable. The encapsulant composition for the second skin layer preferably uses low-density polyethylene having a melting point of 100 ° C. or higher and 115 ° C. or lower and the same melting point as the base resin of the encapsulant composition for the core layer. ..

By adjusting the melting point range of each layer to the above range, it is possible to reduce the occurrence of wrinkles caused by the difference in shrinkage stress between the layers of the encapsulant layer 1 during heat processing of the encapsulant-integrated back surface protective sheet 10. Therefore, it is possible to contribute to the improvement of the productivity and quality stability of the solar cell module 100.

In the present specification, the melting point of the resin constituting each layer of the encapsulant layer means the melting point of the resin that can be obtained by measuring by differential scanning calorimetry (DSC). When there are a plurality of valley peaks on the DSC curve, the melting point indicated by the peak having the largest peak area is referred to as the melting point of the resin.

The thickness of the encapsulant layer 1 is preferably 200 μm or more and 400 μm or less, and more preferably 250 μm or more and 350 μm or less. When the thickness is 200 μm or more, the above heat resistance and other required physical properties can be sufficiently maintained. The thickness ratio of each layer in the encapsulant layer 1 having a three-layer structure in which the first skin layer 12 and the second skin layer 13 are laminated on both sides of the core layer 11 is the skin: core: skin thickness. The ratio is preferably in the range of 1: 3: 1 to 1: 30: 1.

[Core layer]
The core layer 11 mainly has a function of imparting heat resistance and appropriate rigidity to the sealing material layer 1. The core layer 11 is made of a sealing material composition for the core layer using low-density polyethylene as a base resin. And, unlike the first skin layer 12 described later, the core layer 11 does not contain silane-modified polyethylene. The encapsulant composition for the core layer contains polypropylene within a predetermined content ratio range.

As an example, the thickness of the core layer 11 is 100 μm or more and 240 μm or less, and is not particularly limited. When the thickness of the core layer 11 is 100 μm or more, good dimensional stability can be imparted to the encapsulant layer 1. Further, when the thickness of the core layer 11 is 240 μm or less, it is possible to impart the sheet transport suitability at the time of laminating to the sealing material layer 1.

(Encapsulant composition for core layer)
Encapsulant composition for the core layer to form a core layer 11, the density of 0.910 g / cm ³ or more 0.950 g / cm ³ or less of low density polyethylene resin and the base resin. The content ratio of the sealing material composition for the core layer of this low-density polyethylene resin in the total resin components may be 60% by mass or more and 95% by mass or less, preferably 75% by mass or more and 85% by mass or less. Is. The melting point of this base resin is preferably in the range of 100 ° C. or higher and 115 ° C. or lower as described above. The content ratio of each resin in the resin composition used in the present invention can be analyzed from, for example, the peak ratio detected by DSC (differential scanning calorimetry) or IR (infrared spectroscopy).

The encapsulant composition for the core layer contains polypropylene in an amount of 5% by mass or more and 40% by mass or less in terms of the content ratio in the total resin components. By adding an appropriate amount of polypropylene to the core layer 11 using low-density polyethylene as a base resin, it is possible to obtain a layer that imparts excellent heat resistance and excellent dimensional stability.

It is more preferable to use a homopolypropylene (homo-PP) resin as the polypropylene to be contained in the encapsulant composition for the core layer in the above-mentioned predetermined amount range. Homo PP is a polymer composed of polypropylene alone and has high crystallinity, and therefore has higher rigidity than block PP and random PP. By using this as an additive resin to the encapsulant composition for the core layer, the dimensional stability of the encapsulant layer 1 can be further enhanced. The MFR of homo-PP at 230 ° C. is preferably 5 g / 10 minutes or more and 125 g / 10 minutes or less. If the MFR is less than 5 g / 10 minutes, the molecular weight becomes large and the rigidity becomes too high, and the preferable sufficient flexibility of the encapsulant layer 1 depends on the physical characteristics of the first skin layer 12 and the second skin layer 13. It cannot be secured. Further, when the MFR exceeds 125 g / 10 minutes, the fluidity during heating is not sufficiently suppressed, and the encapsulant layer 1 can be sufficiently imparted with heat resistance and dimensional stability as described above. do not have. Unless otherwise specified, the term "MFR" as used herein refers to the value of MFR measured according to JIS7210 at 190 ° C. and a load of 2.16 kg (however, the same applies to polypropylene resin MFR). The value of MFR at 230 ° C. and a load of 2.16 kg).

However, polypropylene has much higher rigidity than the low-density polyethylene used as the base resin in any of the above structures. Therefore, for example, when polypropylene exceeding 40% by mass is added to the encapsulant composition for the core layer beyond the above-mentioned appropriate addition amount range, the physical characteristics of polypropylene become excessively dominant in the core layer 11. The preferable flexibility of the sealing material layer 1 as a whole cannot be ensured by the physical properties of the first skin layer 12 and the second skin layer 13. Therefore, it is preferable to add polypropylene in a limited manner within the above range also in the encapsulant composition for the core layer. By mixing polypropylene in the core layer 11 in the above content range, that is, in the range of 5% by mass or more and 40% by mass or less in terms of the content ratio in the total resin components, the encapsulant sheet is made into a thin sheet of 400 μm or less. Even in the case of, the sealing material layer 1 can be provided with good heat resistance.

The polypropylene content ratio in the total resin components of the encapsulant composition using the polyethylene-based resin as the base resin described above can also be determined by measuring the encapsulant composed of the encapsulant composition. It can be calculated and specified. As an example of the measurement / calculation method, a method of calculating from the peak intensity ratio of IR obtained by measuring by the transmission macro method (as a measuring device to be used, for example, "FT / IR-600" manufactured by JASCO Corporation) is used. Can be mentioned.

[First skin layer]
The first skin layer 12 is a surface of the solar cell element 3 on the non-light receiving surface side and a contact surface with the light receiving surface side sealing material sheet 4 in the solar cell module 100. The first skin layer 12 is a layer that mainly contributes to the improvement of adhesion durability with other members constituting the solar cell module 100, and at the same time, another configuration at the time of integration as the solar cell module. This layer contributes to the improvement of the ability to follow the unevenness of the member (hereinafter referred to as "molding characteristic").

(Encapsulant composition for the first skin layer)
The encapsulant composition for the first skin layer forming the first skin layer 12 uses ^{low-density polyethylene having a density of 0.880 g / cm 3} or more and less than 0.910 g / cm ³ as a base resin. The content ratio of the low-density polyethylene-based resin in the total resin component of the encapsulant composition for the first skin layer may be 80% by mass or more and 100% by mass or less, preferably 98% by mass or more and 100% by mass or less. It is as follows. The melting point of this base resin is preferably in the range of 80 ° C. or higher and lower than 100 ° C. as described above.

The encapsulant composition for the first skin layer is different from the encapsulant composition for the core layer described later, and does not substantially contain polypropylene, and is more than the base resin of the encapsulant composition for the core layer. Low density polyethylene with low density is used as the base resin. In the present invention, "substantially free of polypropylene" means, for example, that even if a trace amount of polypropylene derived from a resin added to the core layer is impregnated in the skin layer and this is detected, the present invention In terms of the technical idea of, it means that it is regarded as "substantially free of polypropylene". The above-mentioned extremely small amount is, for example, a content ratio in the skin layer, which is less than 0.1% by mass as a guide.

The encapsulant composition for the first skin layer contains silane-modified polyethylene in a predetermined ratio. The silane-modified polyethylene is obtained by graft-polymerizing a linear low-density polyethylene (LLDPE) or the like as a main chain with an ethylenically unsaturated silane compound as a side chain. In such a graft copolymer, the degree of freedom of the silanol group that contributes to the adhesive force is increased, so that the adhesion of the encapsulant layer 1 can be further improved.

The amount of the ethylenically unsaturated silane compound in the encapsulant composition for the first skin layer is such that the amount of polymerized silane in the encapsulant composition of the first skin layer is 300 ppm or more and 2000 ppm or less, preferably 300 ppm or more and 1500 ppm. Hereinafter, it is more preferably 300 ppm or more and 1000 ppm or less. When the amount of the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent. For example, when the amount of the ethylenically unsaturated silane compound exceeds 2000 ppm, the content becomes excessive and tension occurs. It tends to be inferior in elongation and heat fusion. The amount of polymerized silane in each layer of the encapsulant can be specified in the resin component by, for example, quantifying the elements in each layer by ICP emission spectrometry or the like.

The silane-modified polyethylene can be produced, for example, by the method described in JP-A-2003-46105, and by using the resin as a component of a sealing material composition for a solar cell module, strength, durability and the like can be obtained. Excellent in weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, haze resistance, and other characteristics, and is further affected by manufacturing conditions such as heat crimping for manufacturing solar cell modules. It is possible to manufacture a solar cell module suitable for various applications in a stable manner and at low cost, which has extremely excellent heat fusion property.

Examples of ethylenically unsaturated silane compounds graft-polymerized with straight-chain low-density polyethylene include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, and vinyltripentyroxysilane. , Vinyl triphenyloxysilane, vinyl tribenzyloxysilane, vinyl trimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, vinyltricarboxysilane be able to.

[Second skin layer]
The second skin layer 13 becomes a close contact surface between the sealing material layer 1 and the back surface protective layer 2 when the sealing material integrated back surface protective sheet 10 is formed.

(Encapsulant composition for the second skin layer)
Encapsulant composition for the second skin layer to form the second skin layer 13 is a less density 0.910 g / cm ³ or more 0.950 g / cm ^3, the sealing material composition for the core layer The base resin is low-density polyethylene with the same density as the base resin. The content ratio of the low-density polyethylene-based resin encapsulant composition for the skin layer in the total resin components may be 80% by mass or more and 100% by mass or less, preferably 98% by mass or more and 100% by mass or less. be. The melting point of this base resin is also preferably the same temperature as the base resin of the encapsulant composition for the core layer.

The encapsulant composition for the second skin layer is substantially free of polypropylene, unlike the encapsulant composition for the core layer. Further, the encapsulant composition for the second skin layer does not substantially contain silane-modified polyethylene, unlike the encapsulant composition for the first skin layer.

(Other ingredients)
The encapsulant composition for the core layer, the encapsulant composition for the first skin layer, and the encapsulant composition for the second skin layer may all contain other components. can. For example, components such as various weather resistant master batches, various fillers, light stabilizers, ultraviolet absorbers, and heat stabilizers for imparting weather resistance to the sealing material layer 1 are exemplified. These contents vary depending on the particle shape, density, etc., but are preferably in the range of 0.001% by mass or more and 5% by mass or less in the encapsulant composition. By containing these additives, it is possible to impart a long-term stable improvement in mechanical strength, an effect of preventing yellowing, cracks, and the like to the sealing material layer 1.

[Back side protective layer]
The back surface protective layer 2 constituting the encapsulant-integrated back surface protective sheet 10 can be formed as a single-layer resin layer made of a resin having a barrier property. Alternatively, the back surface protective layer 2 constituting the sealing material integrated back surface protective sheet 10 is also formed as a layer having a multi-layer structure having a barrier property, which is formed by laminating a single resin layer and other layers. You can also do it.

As the material resin for forming the back surface protective layer 2, various resins conventionally used as a back surface protective sheet for a solar cell module can be used. As the resin sheet forming the back surface protective layer 2, for example, a polyester resin such as a polycarbonate resin, polyethylene terephthalate (PET), or polyethylene naphthalate can be used. Among these, polyethylene terephthalate (PET) can be preferably used from the viewpoint of physical properties such as insulation performance, mechanical strength, cost, transparency, and economy. The melting point of the polyethylene terephthalate (PET) is about 260 ° C., and the melting point of other polyester resins is also in the range of about 220 ° C. to 280 ° C. All of them have a melting point sufficiently higher than that of the olefin resin forming the encapsulant layer 1, and are high melting points that do not melt depending on the heating temperature (150 ° C. or lower) at the time of manufacturing a general solar cell module.

Regarding the layer structure when the back surface protective layer 2 has a multi-layer structure, the inner layer facing the encapsulant layer is formed of PET from the viewpoint of improving mechanical strength and water vapor barrier property and considering economic efficiency. A structure in which the layer 22 on the outer layer side exposed to the outermost layer side is formed of hydrolysis-resistant polyethylene terephthalate (hydrolysis-resistant PET) and each of these layers is integrated via an adhesive layer is particularly preferable. It can be given as a specific example.

The thickness of the back surface protective layer 2 is not particularly limited, but is required for the back surface protective sheet 10 with an integrated sealing material as long as the physical properties such as the barrier property of water vapor required for the back surface protective layer 2 can be maintained. It may be appropriately determined in consideration of the thickness. The thickness of the back surface protective layer 2 is preferably 25 μm or more and 300 μm or less, and more preferably 25 μm or more and 250 μm or less. When the thickness of the back surface protective layer 2 is 25 μm or more, preferable durability and weather resistance can be imparted to the back surface protective sheet 10 integrated with the sealing material.

Further, as described above, a corona treatment may be performed on the surface of the back surface protective layer 2 on the interface side with the sealing material layer as a surface treatment for improving the adhesion.

[Manufacturing method of backside protective sheet with integrated sealing material]
The method for manufacturing the back surface protective sheet with an integrated sealing material of the present invention will be described. The back surface protective sheet 10 integrated with the sealing material includes a "back surface protective sheet forming step" for forming the back surface protective sheet 2 for forming the back surface protective layer 2 and a "sealing" for forming the sealing material sheet for forming the sealing material layer 1. It can be manufactured by going through a "stop material sheet forming step" and a "integration step" in which a sealing material sheet is laminated on a back surface protective layer sheet and integrated.

(Back side protective sheet forming process)
The back surface protective layer sheet is formed by forming a resin material such as PET described above by a film forming method such as an extrusion method, a cast molding method, a T die method, a cutting method, an inflation method, or another film forming method. Can be done. The back surface protective layer 2 may be made of a sheet containing other additives such as pigments in addition to the above resin material, as long as the effects of the present invention are not impaired.

(Encapsulant sheet forming process)
The encapsulant layer sheet is formed by integrally molding the encapsulant composition for the skin layer and the encapsulant composition for the core layer by a known coextrusion method to form a multilayer sheet. Can be done.

(Integration process)
An encapsulant sheet constituting the encapsulant layer 1, a back surface protective sheet constituting the back surface protective layer 2, and a sheet forming another layer formed by the same method, if necessary, are appropriately laminated. Further, by further integrating, the sealing material integrated back surface protective sheet 10 of the present invention can be obtained. The integration of each sheet can be performed by a conventionally known dry laminating method. Conventionally known laminate adhesives can be used and are not particularly limited, and a two-component curable dry laminate adhesive composed of a urethane-based or epoxy-based main agent and a curing agent can be appropriately used. In addition, this integration step can also be performed by the extrusion coat laminating method or the sandwich laminating method which is an application form thereof.

<Solar cell module>
The basic configuration of the solar cell module 100 using the back surface protective sheet 10 integrated with the sealing material of the present invention will be described with reference to FIG. The solar cell module 100 is a transparent front substrate 5 arranged on the back surface protective sheet 10 integrated with a sealing material, the solar cell element 3, the sealing material sheet 4 on the light receiving surface side, and the outermost layer on the light receiving surface side from the non-light receiving surface side. Are stacked in order. The encapsulant-integrated back surface protective sheet 10 is arranged such that the encapsulant layer 1 faces the non-light receiving surface side of the solar cell element 3.

As the solar cell element 3 used in the solar cell module 100, for example, amorphous silicon type, crystalline silicon type, CdTe type, CIS type, GaAs type, and various other conventionally known solar cell elements can be used without particular limitation. ..

As described above, the light receiving surface side sealing material sheet 4 arranged so as to cover the surface of the solar cell element 3 on the light receiving surface side is a resin sheet that mainly exhibits a function of protecting the solar cell element 3 from external impact. Further, the light receiving surface side sealing material sheet 4 is required to be a transparent sheet in order to transmit sunlight with a high transmittance. As the resin base material forming the light-receiving surface side encapsulant sheet 4, a thermoplastic resin such as ethylene-vinyl acetate copolymer resin (EVA), ionomer, polyvinyl butyral (PVB), or polyethylene-based resin such as polyethylene is used. It can be used as appropriate.

The transparent front substrate 5 is generally a glass substrate. The transparent front substrate 5 may be another member as long as it maintains the weather resistance, impact resistance, and durability of the solar cell module 100 and allows sunlight to pass through at a high transmittance. ..

[Manufacturing method of solar cell module]
In the solar cell module 100, for example, a member composed of the transparent front substrate 5, the light receiving surface side encapsulant sheet 4, the solar cell element 3, and the encapsulant integrated back surface protective sheet 10 are sequentially laminated and then vacuum suctioned. After that, the above-mentioned members can be heat-bonded and molded as an integrally molded body by a molding method such as a lamination method. For example, in the case of vacuum heat laminating processing, the laminating temperature is preferably in the range of 130 ° C. to 180 ° C. The laminating time is preferably in the range of 5 to 20 minutes, particularly preferably in the range of 8 to 15 minutes. In this way, the solar cell module 100 can be manufactured by heat-pressing molding each of the above layers as an integrally molded body.

Although the present invention has been specifically described above with reference to embodiments, the present invention is not limited to the above-described embodiments, and can be carried out with appropriate modifications within the scope of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the following examples.

<Manufacturing of encapsulant sheet>
Using the following materials, the encapsulant forming the encapsulant layer of the encapsulant-integrated back surface protective sheet of Examples and Comparative Examples by the manufacturing method described in the above (Encapsulant sheet forming step) column. I made a sheet.

A mixture of the following materials having the compositions (parts by mass) shown in Table 1 was used as the encapsulant composition for the core layer and the skin layer of the encapsulant sheet of each Example and Comparative Example. Then, these encapsulant compositions are sheet-molded at an extrusion temperature of 210 ° C. and a take-up speed of 1.1 m / min using a φ30 mm extruder and a sheet molding machine having a T-die having a width of 200 mm, and skin / min. A core / skin three-layered encapsulant sheet was used. The total thickness of each encapsulant sheet and the thickness of each layer were set to 50 μm for each skin layer, 200 μm for the core layer, and 300 μm for each encapsulant sheet.

The following raw materials were used as the material of the encapsulant sheet.
Linear low density polyethylene 1 (LLDPE, indicated as "PE1" in the table): ^{A resin having a density of 0.898 g / cm 3} and a melting point of 90 ° C. was used as the low density base resin.
Low-density polyethylene 2 (denoted as "PE2" in the table): ^{Silane-modified polyethylene using a resin having a density of 0.919 g / cm 3} and a melting point of 105 ° C. as a high-density base resin (denoted as "PESi" in the table): With respect to 98 parts by mass of metallocene-based linear low-density polyethylene (M-LLDPE) having a density of 0.900 g / cm ³ and MFR of 1.1 g / 10 minutes, 2 parts by mass of vinyltrimethoxysilane and a radical generator (reaction catalyst). ), 0.1 part by mass of dicumyl peroxide, melted and kneaded at 200 ° C., and ^{a silane-modified polyethylene with a density of 0.900 g / cm 3} is added to the base resin as an adhesion component. Using.
Polypropylene (PP, indicated as "PP" in the table): Homopolypropylene, density 0.900 g / cm ³ , melting point 155 ° C, MFR 8.5 g / 10 minutes (230 ° C) resin is added as a heat-resistant component to the base resin. Using.
Weather-resistant stabilizer: manufactured by BASF Corporation, trade name Tinuvin622SF. 0.2 parts by mass was added to each of the encapsulant compositions for the core layer and the skin layer of all Examples and Comparative Examples.
Antioxidant: manufactured by Ciba Japan Co., Ltd., trade name Irganox 1076. 0.05 parts by mass was added to each of the encapsulant compositions for the core layer and the skin layer of all Examples and Comparative Examples.

The amount of graft (part by mass) of the ethylenically unsaturated silane compound with respect to 100 parts by mass of the polyethylene-based resin in each layer of each encapsulant sheet of the above Examples and Comparative Examples is shown in Table 2 as "Si graft amount". rice field.

<Manufacturing of backside protective sheet with integrated sealing material>
The encapsulant sheet of each of the above Examples and Comparative Examples and a PET film having a corona treatment on the surface (“Melinex S” manufactured by Teijin DuPont, 125 μm in thickness) are laminated by a conventionally known dry laminating method. Then, a back surface protective sheet integrated with a sealing material of each Example and Comparative Example was obtained. However, in Comparative Example 5, the PET film was laminated without corona treatment.

<Evaluation example 1: Evaluation of metal adhesion of the first skin layer>
[Metal adhesion test]
The encapsulant layer of the encapsulant-integrated back surface protective sheet of Examples and Comparative Examples cut to a width of 15 mm was brought into close contact with the first skin layer on a copper foil (75 mm × 50 mm × 0.035 mm), and the following vacuum was applied. Vacuum heating laminator treatment was performed under the heat laminating conditions (a) to (d), and samples for metal adhesion evaluation were obtained for each of Examples and Comparative Examples. For each of these metal adhesion evaluation samples, the adhesion strength was measured by the following measuring method to evaluate the metal adhesion. The measurement was performed by vertically peeling (50 mm / min) the encapsulant sheet in close contact with the copper foil in the above metal adhesion evaluation sample with a peeling tester (Tencilon universal testing machine RTF-1150-H). The test was conducted. The results are shown in Table 1 as "made of metal contact". The evaluation criteria are as follows.
(Vacuum heating laminating conditions) (a) Evacuation: 6.0 minutes
(B) Pressurization (0 kPa to 70 kPa): 1.5 minutes
(C) Pressure retention (70 kPa): 10.0 minutes
(D) Temperature 165 ° C
(Evaluation criteria) A: 15.0N / 15mm or more
B: 10.0N / 15mm or more and less than 15.0N / 15mm
C: 10.0N / less than 15mm

<Evaluation example 2: Evaluation of adhesiveness of the second skin layer>
The second skin layer of the encapsulant sheet of Examples and Comparative Examples cut to a width of 15 mm is directed onto the PET film (75 mm × 50 mm × 0.035 mm) for the back surface protective layer, and dried with an acrylic adhesive. I tried to bond by lamination. Only Comparative Example 5 in which the corona treatment was not performed was unable to adhere at a level that could withstand practical use.

<Evaluation example 3: Durability evaluation of encapsulant layer>
[Durability test]
In order to evaluate the light resistance of the encapsulant sheet of the present invention, each sample of the encapsulant-integrated back surface protective sheet used in Evaluation Example 1 conforms to JIS C8917, and has a test chamber temperature of 85 ° C. and a humidity of 85%. A "dump heat test" was carried out under the above conditions, and the durability was evaluated by the time until a visually visible peeling occurred between the encapsulant layer and the back surface protective layer. The results are shown in Table 1 as "durability". The evaluation criteria are as follows.
(Evaluation criteria) A: No peeling occurred after 2000 hours
B: The time until the peeling occurs is 1000 hours or more and less than 2000 hours.
C: The time until the peeling occurs is less than 1000 hours.

<Evaluation example 4: Evaluation of curl deformation suppression of encapsulant integrated back surface protective sheet>
[Heat deformation test]
In order to evaluate the suppression of curl deformation of the encapsulant sheet of the present invention, the encapsulant-integrated back surface protective sheet used in Evaluation Example 1 is diagonally 13 cm square at the center of a test piece cut out to 16 cm square. The cut was made in the container and stored in a 60 ° C. C oven for 24 hours, and the height of the tip of the cut after taking out was measured to evaluate the superiority or inferiority of curl deformation suppression of the encapsulant-integrated back surface protective sheet. The results are shown in Table 1 as "curl suppression". The evaluation criteria are as follows.
(Evaluation criteria) A: The height of the notch is less than 27 mm
B: The height of the notch is 27 mm or more and less than 31 mm.
C: The height of the notch is 31 mm or more

From Table 1, the encapsulant-integrated back surface protective sheet of the present invention is an encapsulant-integrated back surface protective sheet that can contribute to reducing the thickness and manufacturing cost of the solar cell module, and is suitable for productivity and quality stability. It can be seen that it is an encapsulant-integrated back surface protective sheet that can contribute to the improvement of long-term reliability of the solar cell module by exhibiting excellent adhesion durability when integrated as a solar cell module.

1 Encapsulant layer 11 Core layer 12 1st skin layer 13 2nd skin layer 2, 7 Back surface protective layer 3 Solar cell element 4 Light receiving surface side encapsulant sheet 5 Transparent front substrate 6 Non-light receiving surface side encapsulant sheet 10 Encapsulant integrated backside protective sheet 100, 100A Solar cell module

Claims (5)

An encapsulant-integrated back surface protective sheet for a solar cell module, in which a sealing material layer using a polyethylene resin as a base resin and a back surface protective layer using a polyester resin as a base resin are laminated.
The encapsulant layer includes a core layer using a polyethylene resin as a base resin and
A polyethylene-based resin having a density lower than that of the base resin of the core layer is used as the base resin, and the first skin layer arranged on the outermost surface of the encapsulant-integrated back surface protective sheet on the encapsulant layer side is used.
It has a multilayer structure in which a polyethylene-based resin having the same density as the base resin of the core layer is used as the base resin and includes a second skin layer arranged on the interface side with the back surface protective layer.
Corona treatment is applied to at least one surface of the second skin layer on the back surface protective layer side or the surface of the back surface protective layer on the second skin layer side.
The core layer contains 5% by mass or more and 40% by mass or less of polypropylene in the total resin component of the core layer.
The first skin layer contains silane-modified polyethylene obtained by graft-polymerizing an ethylenically unsaturated silane compound on low-density polyethylene.
The core layer and the second skin layer do not contain the silane-modified polyethylene, and the core layer and the second skin layer do not contain the silane-modified polyethylene.
The first skin layer and the second skin layer are substantially free of polypropylene.
Encapsulant integrated backside protective sheet. The encapsulant-integrated back surface protective sheet according to claim 1, wherein the amount of polymerized silane in all the resin components of the first skin layer is 300 ppm or more and 2000 ppm or less. The encapsulant-integrated back surface protective sheet according to claim 1 or 2, wherein the core layer contains a white pigment, and the first skin layer and the second skin layer do not contain a white pigment. The encapsulant-integrated back surface protective sheet according to any one of claims 1 to 3, wherein the back surface protective layer includes a polyethylene terephthalate layer and / or a hydrolysis-resistant polyethylene terephthalate layer. A solar cell module in which the encapsulant-integrated back surface protective sheet according to any one of claims 1 to 4 is laminated so that the first skin layer faces the non-light receiving surface side of the solar cell element.

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