JP2023178633A - Film for power collection sheet, power collection sheet, solar battery element with power collection sheet, and solar battery - Google Patents

Abstract

To provide a film for a power collection sheet that has a high barrier property, and to provide a power collection sheet, a solar battery element with a power collection sheet, and a solar battery using the film.SOLUTION: Provided is a film for a power collection sheet used for a power collection sheet of a solar battery and that has a transparent base material, a transparent barrier layer, an adhesive layer, and an encapsulation layer in this order.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a film for a current collector sheet, a current collector sheet, a solar cell element with a current collector sheet, and a solar cell.

In recent years, global warming caused by carbon dioxide has become a worldwide problem. In response to this problem, solar cells that utilize sunlight energy are attracting attention as an environmentally friendly and clean energy source, and active research and development is underway.

A solar cell is used, for example, in the form of a module in which a plurality of solar cell elements are connected. As a method of connecting solar cell elements to each other, for example, a method of connecting solar cell elements to each other using a strip-shaped conducting wire with a width of about 2 mm to 5 mm, which is called a buspar, has been conventionally used. In the case of the connection method using buspars, the problem is that sunlight is physically blocked in the area where the buspars are placed in the solar cell module, reducing the amount of sunlight incident on the solar electronic elements. be.

In contrast, in recent years, a method called multi-wire connection has begun to be adopted, in which solar cell elements are connected to each other using wires (thin conductive wires) having a diameter of approximately 150 μm or more and 300 μm or less, for example. In the multi-wire connection, a method for fixing the wires to the solar cell element is, for example, by embedding the wires in a thermofusible resin film to make a current collecting sheet, and then thermocompression bonding the current collecting sheet to the solar cell element. Examples include fixing methods (Patent Documents 1 and 2). The resin film used for the current collector sheet is also called a connecting film.

By the way, since solar cells are used outdoors for a long period of time, each member constituting the solar cell is required to have durability that can withstand the harsh outdoor environment for a long period of time. Among these members, the back protection sheet is required to have high weather resistance, and is also required to have high water vapor barrier properties in order to protect the solar cell element from moisture and the like.

For example, as a back protection sheet constituting a solar cell module, a back protection sheet in which metal foil such as aluminum foil is laminated on a weather-resistant base material is known (Patent Document 3). However, when a back protection sheet having metal foil is used in a solar cell module, there is a risk of electrical leakage due to its low insulation properties. In addition, although insulation treatment is performed on the end surfaces of metal foils, productivity decreases and manufacturing costs increase.

Further, as a back protection sheet, a back protection sheet having a barrier film in which an inorganic vapor-deposited film is formed on a resin film instead of a metal foil is also known. Such a back protection sheet can exhibit water vapor barrier properties without using metal foil. However, gas barrier films with high water vapor barrier properties comparable to metal foils are very expensive.

International Publication No. 2004/021455 International Publication No. 2017/076735 Japanese Patent Application Publication No. 2002-134770

Therefore, in order to improve the water vapor barrier properties of multi-wire connected solar cell modules, it is considered that not only the back protection sheet but also the resin film used in the current collector sheet described above may be provided with water vapor barrier properties. .

The present disclosure has been made in view of the above circumstances, and provides a current collector sheet film having high barrier properties, a current collector sheet using the same, a solar cell element with a current collector sheet, and a solar cell. The main purpose is

One embodiment of the present disclosure is a film for a current collector sheet used for a current collector sheet of a solar cell, which includes a transparent base material, a transparent barrier layer, an adhesive layer, and a sealing layer in this order. Provides films for current collector sheets.

Another embodiment of the present disclosure is a current collector sheet used for a solar cell, which includes the above-described current collector sheet film and a wire disposed on the side of the sealing layer of the current collector sheet film. Provided is a current collector sheet having the following.

Another embodiment of the present disclosure is a current collector comprising the above-described current collector sheet and a solar cell element disposed on the surface side of the sealing layer of the current collector sheet and electrically connected to the wire. A solar cell element with a sheet is provided.

Another embodiment of the present disclosure provides a solar cell including, in this order, a transparent substrate, a first encapsulant, the above-described solar cell element with a current collector sheet, a second encapsulant, and a back protection sheet. I will provide a.

The present disclosure can provide a film for current collector sheet having high barrier properties.

FIG. 1 is a schematic cross-sectional view illustrating a film for a current collector sheet according to the present disclosure. FIG. 1 is a schematic plan view and a cross-sectional view illustrating a current collecting sheet according to the present disclosure. FIG. 1 is a schematic perspective view and a cross-sectional view illustrating a solar cell element with a current collector sheet according to the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a film for a current collector sheet according to the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a current collector sheet in the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a solar cell element with a current collector sheet according to the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a solar cell according to the present disclosure.

Embodiments of the present disclosure will be described below with reference to the drawings and the like. However, the present disclosure can be implemented in many different ways, and should not be construed as being limited to the description of the embodiments exemplified below. Further, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual form, but this is just an example and does not limit the interpretation of the present disclosure. It's not something you do. In addition, in this specification and each figure, the same elements as those described above with respect to the previously shown figures are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

In this specification, when expressing a mode in which another member is placed on top of a certain member, when it is simply expressed as "above" or "below", unless otherwise specified, it means that the member is in contact with a certain member. This includes both cases in which another member is placed directly above or below a certain member, and cases in which another member is placed above or below a certain member via another member. In addition, in this specification, when expressing a mode in which another member is arranged on the surface of a certain member, when it is simply expressed as "on the surface" or "on the surface side", unless otherwise specified, This includes both a case in which another member is placed directly above or directly below a certain member, and a case in which another member is placed above or below a certain member via another member.

Further, in this specification, terms such as "film", "sheet", "substrate", etc. are not distinguished from each other based on the difference in designation.

Hereinafter, the film for current collector sheet, current collector sheet, solar cell element with current collector sheet, and solar cell in the present disclosure will be described in detail.

A. Film for current collector sheet The film for current collector sheet in the present disclosure is a film for current collector sheet used for a current collector sheet of a solar cell, and includes a transparent base material, a transparent barrier layer, an adhesive layer, and a sealing layer. and, in this order.

The film for a current collector sheet in the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view illustrating a film for a current collector sheet according to the present disclosure. As shown in FIG. 1, the current collector sheet film 10 includes a transparent base material 1, a transparent barrier layer 2, an adhesive layer 3, and a sealing layer 4 in this order. In the current collector sheet film 10 shown in FIG. 1, the transparent base material 1 and the transparent barrier layer 2 constitute a barrier film 5.

FIGS. 2A and 2B are a schematic plan view and a cross-sectional view illustrating a current collector sheet having a current collector sheet film according to the present disclosure. FIG. 2(b) is a cross-sectional view taken along the line AA in FIG. 2(a). As shown in FIGS. 2(a) and 2(b), the current collecting sheet 20 includes a current collecting sheet film 10 and a wire 11 disposed on the surface side of the sealing layer 4 of the current collecting sheet film 10. have In this way, the current collector sheet film 10 is used to support the wire 11. Note that FIG. 2(a) shows a schematic plan view of the current collecting sheet viewed from the sealing layer side of the film for current collecting sheet.

FIGS. 3(a) to 3(c) are a schematic perspective view and a cross-sectional view illustrating a solar cell element with a current collecting sheet including a current collecting sheet having a current collecting sheet film according to the present disclosure. FIG. 3(b) is a cross-sectional view taken along line AA in FIG. 3(a), and FIG. 3(c) is a cross-sectional view taken along line BB in FIG. 3(a). As shown in FIGS. 3(a) to 3(c), the solar cell element 30 with a current collector sheet is arranged on the surface side of the current collector sheet 10 and the sealing layer 4 of the current collector sheet 10, and is connected to the wire 11 and It has a solar cell element 31 which is connected to the solar cell element 31. In this way, the current collector sheet film 10 is used to fix the wire 11 electrically connected to the solar cell element 31. Note that FIGS. 3(a) to 3(c) show an example in which the current collecting sheet 20 has two current collecting sheet films 10, and a solar cell element 31 is arranged on each current collecting sheet film 10. It shows.

The film for current collector sheet in the present disclosure can provide barrier properties by having a transparent barrier layer. Therefore, when a current collector sheet with a current collector sheet film is used in a solar cell, the barrier properties can be improved by combining the current collector sheet film with a barrier film and the back protection sheet with a barrier film. It is possible to do so. Therefore, high barrier properties can be obtained without using a back protection sheet with metal foil or an expensive gas barrier film as the back protection sheet. Therefore, productivity can be increased and manufacturing costs can be reduced.

In addition, as mentioned above, when a current collector sheet having a current collector sheet film is used in a solar cell, high barrier properties can be obtained without using a back protective sheet with metal foil as the back protective sheet. , the insulation properties of the back protection sheet can be increased, and electrical leakage can be suppressed. Therefore, the reliability of the solar cell can be improved.

Hereinafter, each structure of the film for current collector sheet in the present disclosure will be explained.

I. Configuration of film for current collector sheet The film for current collector sheet in the present disclosure includes a transparent base material, a transparent barrier layer, an adhesive layer, and a sealing layer in this order.

1. Transparent Barrier Layer The transparent barrier layer in the present disclosure is a member that is disposed on one surface of a transparent base material, has transparency, and has barrier properties against water vapor and oxygen. Further, the transparent barrier layer is usually a member constituting a barrier film.

Regarding the transparency of the transparent barrier layer, if the current collector sheet film has transparency, it can be said that the transparent barrier layer has transparency. Specifically, as described later, it is preferable that the light transmittance and haze of the current collector sheet film at a wavelength of 400 nm or more and 1200 nm or less are within a predetermined range.

Regarding the barrier properties of the transparent barrier layer, if the current collector sheet film has barrier properties, it can be said that the transparent barrier layer has barrier properties. Specifically, as described below, it is preferable that the water vapor permeability of the current collector sheet film is within a predetermined range.

Moreover, the transparent barrier layer has insulation properties. Thereby, the insulation properties of the current collector sheet film can be improved. Moreover, since the transparent barrier layer has insulation properties, there is no need to perform insulation treatment on the end face of the transparent barrier layer in the current collector sheet film. Therefore, productivity can be increased and manufacturing costs can be reduced.

The transparent barrier layer can be formed on one side of the transparent substrate, and is not particularly limited as long as it has barrier properties against water vapor and oxygen. Examples include inorganic hybrid membranes.

Examples of the inorganic compound contained in the inorganic compound film include inorganic oxides, inorganic oxynitrides, inorganic nitrides, inorganic oxycarbides, and inorganic oxycarbonitrides. Specifically, the inorganic compounds contained in the inorganic compound film include oxides, oxynitrides, etc. of silicon, aluminum, magnesium, calcium, potassium, tin, sodium, titanium, boron, yttrium, zirconium, cerium, zinc, etc. Examples include nitrides, oxidized carbides, oxidized carbonitrides, and the like. More specifically, silicon oxides such as _SiOx , aluminum oxides such as _AlyOz , magnesium oxides, titanium _oxides , tin oxides, silicon-zinc alloy oxides, indium alloy oxides, and silicon nitrides. , aluminum nitride, titanium nitride, silicon oxynitride, zinc silicon oxide, and the like. The inorganic compounds may be used alone or in combination of two or more.

Among these, the inorganic compound contained in the inorganic compound film is preferably an inorganic compound containing silicon, more preferably a silicon oxide such as SiO _x from the viewpoint of cost and performance.

Further, the metal element contained in the inorganic compound is preferably the same type as the metal element in the metal alkoxide used in the overcoat layer, which will be described later. When the transparent barrier layer and the overcoat layer have the same metal element, the adhesion between the transparent barrier layer and the overcoat layer can be improved. Thereby, the barrier properties of the current collector sheet film can be improved. Among these, it is preferable that both the transparent barrier layer and the overcoat layer contain silicon.

Examples of the barrier resin film include barrier resin films containing ethylene-vinyl alcohol copolymer, polyvinyl alcohol, polyvinylidene chloride, and the like.

The transparent barrier layer may be a single layer or a multilayer. In the case of multiple layers, the composition of each layer may be the same or different.

Further, the transparent barrier layer may be a vapor deposited film, or a coated film such as a coating.

The method for forming the transparent barrier layer is appropriately selected depending on the material and type of the transparent barrier layer. Examples include a vapor deposition method, a coating method, a pressure bonding method, and the like. Furthermore, when the transparent barrier layer is a barrier resin film, it may be formed by laminating the transparent base material and the transparent barrier layer by coextrusion.

The thickness of the transparent barrier layer is not particularly limited as long as desired barrier properties and transparency can be obtained, and is appropriately set depending on the type and configuration of the transparent barrier layer. For example, when the transparent barrier layer is a vapor deposited film, the thickness of the transparent barrier layer may be 5 nm or more and 200 nm or less, or 10 nm or more and 100 nm or less. Further, for example, when the transparent barrier layer is a coating film, the thickness of the transparent barrier layer may be about several μm. Further, for example, when the transparent barrier layer is a barrier resin film, the thickness of the transparent barrier layer may be about several tens of μm. If the thickness of the transparent barrier layer is too thin, sufficient barrier properties may not be obtained. Furthermore, if the transparent barrier layer is too thick, cracks and the like may easily occur.

Moreover, it is preferable that the film for current collector sheets in the present disclosure does not have a metal layer as a barrier layer. The metal layer usually has electrical conductivity. Since the current collector sheet film does not have a barrier layer having conductivity, insulation properties can be improved. The metal layer is a layer made of metal or an alloy. The metal layer may be, for example, a metal foil or a vapor deposited film. Note that the current collector sheet film usually does not have metal foil because it has transparency.

2. Transparent Substrate The transparent substrate in the present disclosure is, for example, a member that supports the transparent barrier layer.

Regarding the transparency of the transparent base material, it can be said that the transparent base material has transparency if the current collector sheet film has transparency, similar to the transparent barrier layer described above.

Moreover, it is preferable that the transparent base material has heat resistance. Specifically, the melting point of the transparent base material is
The temperature is preferably 200°C or higher, more preferably 250°C or higher.

Here, the melting point of the transparent substrate can be determined by differential scanning calorimetry (DSC) in accordance with JIS K7121 (method for measuring transition temperature of plastics). In addition, in that case, when two or more melting point peaks exist, the higher temperature can be set as the melting point.

The transparent base material is not particularly limited as long as it has transparency and heat resistance and can support the transparent barrier layer. Among these, the transparent base material is preferably a resin film containing a thermoplastic resin having the above melting point. Examples of the thermoplastic resin having the above melting point include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and the like. In particular, polyethylene terephthalate (PET) is preferred from the viewpoints of heat resistance, transparency, chemical resistance, water resistance, dimensional stability, cost, and the like.

The transparent base material can contain various additives as necessary. Examples of additives include lubricants, crosslinking agents, antioxidants, light stabilizers, fillers, lubricants, reinforcing fibers, reinforcing agents, antistatic agents, flame retardants, flame retardants, foaming agents, antifungal agents, and modifiers. Examples include resins for quality. The content of these additives is not particularly limited, and is appropriately adjusted depending on the purpose.

The transparent base material may be an unstretched resin film, or a uniaxially or biaxially stretched resin film.

The thickness of the transparent base material is not particularly limited as long as it can support the transparent barrier layer, and can be appropriately selected depending on the size and purpose of the solar cell in which the current collector sheet film is used. . Among these, as described below, the thickness of the transparent base material is preferably thinner than the thickness of the sealing layer. Specifically, the thickness of the transparent base material is preferably 12 μm or more and 38 μm or less, more preferably 12 μm or more and 25 μm or less. If the thickness of the transparent substrate is too thin, it may be difficult to support the barrier layer. Moreover, if the thickness of the transparent base material is too thick, the rigidity will become too high, and the followability of the current collector sheet film to the wire may be reduced.

When the transparent base material and the transparent barrier layer constitute a barrier film, the surface of the transparent base material on the transparent barrier layer side may be surface-treated to improve adhesion with the transparent barrier layer. good.

Furthermore, as will be described later, when a protective layer is disposed between the transparent barrier layer and the adhesive layer, the protective layer is a resin film, and the protective layer and the transparent barrier layer constitute a barrier film, for example, , a transparent substrate can be laminated on the transparent barrier layer of the barrier film via a second adhesive layer. In this case, a dry lamination method is preferably used. In the case of dry lamination, it is possible to suppress shearing of the transparent barrier layer during lamination.

3. Sealing Layer The sealing layer in the present disclosure has thermal weldability and is a member that supports the wire when the current collector sheet film is used as the current collector sheet.

(1) Material of the sealing layer The resin contained in the sealing layer is usually a resin that has thermal weldability. Further, the resin contained in the sealing layer preferably has a property of wrapping around the wire when the current collecting sheet is thermocompression bonded to the solar cell element. Hereinafter, the above-mentioned property may be referred to as wire embeddability. Examples of resins having heat-weldability and wire embedding properties include thermoplastic resins. Among them, from the viewpoint of transparency, the thermoplastic resin is preferably a polyolefin resin or an ionomer resin, and more preferably a polyolefin resin. The details of the polyolefin resin will be explained below.

(a) Polyolefin Resin The melting point of the polyolefin resin used for the sealing layer is not particularly limited as long as it can exhibit desired thermal weldability and wire embedding properties. The melting point of the polyolefin resin is, for example, 125°C or lower, may be 120°C or lower, or may be 110°C or lower. Further, the melting point of the polyolefin resin is, for example, 80° C. or higher. If the melting point of the polyolefin resin is too high, it is necessary to raise the temperature when thermocompression bonding the current collector sheet to the solar cell element, which may increase manufacturing costs or cause the solar cell element to deteriorate. There is. On the other hand, if the melting point of the polyolefin resin is too low, the sealing layer may melt in the usage environment of the solar cell, making it difficult to fix the wire.

Here, the melting point of the polyethylene resin can be determined by differential scanning calorimetry (DSC) in accordance with JIS K7121 (method for measuring transition temperature of plastics). In addition, in that case, when two or more melting point peaks exist, the higher temperature can be set as the melting point.

Among these, the polyolefin resin is preferably a polyethylene resin or a polypropylene resin, and more preferably a polyethylene resin. This is because wire embedding is excellent.

Examples of polyethylene resins include high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene-based linear low-density polyethylene (M-LLDPE), and ultra-low density polyethylene ( VLDPE), etc. One type of polyethylene resin may be used alone, or two or more types may be used in combination. Among these, low density polyethylene (LDPE) is preferred because of its good flexibility and workability.

The density of the polyethylene resin is not particularly limited, and for example, it is preferably 0.890 g/cm ³ or more and 0.930 g/cm ³ or less, and 0.900 g/cm ³ or more and 0.925 g/cm ³ or less. is more preferable.

Here, the density of the polyethylene resin can be measured, for example, by a pycnometer method based on JIS K7112.

The sealing layer may contain only a polyolefin resin as a resin component, or may further contain a resin other than the polyolefin resin in addition to the polyolefin resin. In the latter case, the sealing layer preferably contains polyolefin resin as a main component. Note that the expression that the sealing layer contains polyolefin resin as a main component means that the proportion of polyolefin resin is the highest among all resin components.

The ratio of the polyolefin resin to all resin components in the sealing layer is, for example, 50% by mass or more, may be 60% by mass or more, or may be 70% by mass or more. Further, the proportion of the polyolefin resin may be, for example, 99% by mass or less, 95% by mass or less, or 90% by mass or less. Note that the proportion of the polyolefin resin may be 100% by mass.

(b) Adhesiveness Improver The sealing layer in the present disclosure may contain an adhesiveness improver. The adhesion improver is a component that improves the adhesion to wires and the adhesion to solar cell elements.

Examples of the adhesion improver include silane-modified resins and silane coupling agents.

(i) Silane-modified resin Examples of the silane-modified resin include silane-modified polyolefin resins. The silane-modified polyolefin resin is a copolymer of an α-olefin and an ethylenically unsaturated silane compound. The copolymer may be, for example, a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer. Among these, the copolymer is preferably a graft copolymer, and is preferably a graft copolymer in which a main chain is a polyolefin and an ethylenically unsaturated silane compound is polymerized as a side chain. In such a graft copolymer, the degree of freedom of the silanol groups that contribute to adhesion is increased, so that the adhesion to the wire and the adhesion to the solar cell element can be further improved.

Examples of the α-olefin constituting the silane-modified polyolefin resin include ethylene, propylene, 1-butene, isobutylene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, -heptene, 1-octene, 1-nonene, 1-decene, etc. One type of α-olefin may be used alone, or two or more types may be used in combination. Among them, polyethylene is preferred. That is, the silane-modified polyolefin resin is preferably a silane-modified polyethylene resin. As mentioned above, the sealing layer preferably contains polyethylene resin. In this case, the silane-modified polyethylene resin has good compatibility with the polyethylene resin contained in the sealing layer.

The silane-modified polyethylene resin is preferably a resin obtained by graft polymerizing linear low-density polyethylene (LLDPE) as a main chain and an ethylenically unsaturated silane compound as a side chain.

Examples of the ethylenically unsaturated silane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentyloxysilane, vinyltriphenoxysilane, vinyl Tribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane can be mentioned. One type of ethylenically unsaturated silane compound may be used alone, or two or more types may be used in combination.

The silane-modified polyolefin resin can be obtained, for example, by the manufacturing method described in JP-A No. 2003-46105.

The silane-modified resins may be used alone or in combination of two or more.

The ratio of the silane-modified resin to the total resin components of the sealing layer is not particularly limited, and may be, for example, 25% by mass or less.

(ii) Silane coupling agent As the silane coupling agent, a silane coupling agent used in general solar cell encapsulants can be used. The silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent in the sealing layer is not particularly limited, and may be, for example, 5% by mass or less.

(c) Other components The sealing layer may contain additives such as an antioxidant, an anti-blocking agent, and a lubricant, if necessary.

Here, the proportion of each resin component contained in each layer of the current collector sheet film is detected by, for example, differential scanning calorimetry (DSC), infrared spectroscopy (IR), or nuclear magnetic resonance (NMR). It can be analyzed from peak ratio etc.

(2) Others The thickness of the sealing layer is not particularly limited as long as it can support the wire when the current collector sheet film is used as the current collector sheet, and can be appropriately selected depending on the thickness of the wire. The thickness of the sealing layer is preferably thicker than the thickness of the transparent base material, and also preferably thicker than the thickness of the protective layer described below. Thereby, the adhesion to the wire and the embeddability of the wire can be improved. Specifically, the thickness of the sealing layer is preferably 40 μm or more and 100 μm or less, more preferably 45 μm or more and 80 μm or less. When the thickness of the sealing layer is within the above range, the adhesion to the wire and the embeddability of the wire can be improved.

The surface of the sealing layer opposite to the adhesive layer may be surface-treated. That is, the sealing layer may have a surface treatment portion on the opposite side to the adhesive layer. Thereby, the adhesion to the wire and the adhesion to the solar cell element can be improved.

The surface treatment is not particularly limited as long as it can improve adhesion to wires and solar cell elements, and examples include corona treatment, plasma treatment, ultraviolet treatment, electron beam treatment, flame treatment, etc. Can be mentioned. Among these, corona treatment is preferred from the viewpoint of processing cost and damage reduction to the sealing layer.

4. Adhesive Layer The adhesive layer in the present disclosure is a member that is disposed between the barrier film having the transparent barrier layer described above and the sealing layer and for bonding the barrier film and the sealing layer.

The adhesive used for the adhesive layer is not particularly limited as long as it is transparent and can bond the barrier film and the sealing layer. Mention may be made of the adhesives used. Examples of the adhesive include urethane adhesive, acrylic adhesive, polycarbonate adhesive, and phenol adhesive. Further, the adhesive may be, for example, an adhesive for dry lamination or an anchor coating agent for extrusion lamination.

Moreover, it is preferable that the adhesive has heat and humidity resistance. Decrease in adhesive strength due to hydrolysis can be suppressed. For example, it is preferable that the resin component constituting the adhesive does not have an ester bond. Specifically, in the case of a urethane adhesive, it is preferable that the main ingredient is a polycarbonate polyurethane resin.

The thickness of the adhesive layer is not particularly limited as long as it has transparency and can adhere the barrier film and the sealing layer, and is preferably, for example, 0.1 μm or more and 10 μm or less.

5. Protective Layer The film for current collector sheet according to the present disclosure may have a protective layer 6 between the transparent barrier layer 2 and the adhesive layer 3, as shown in FIGS. 4(a) and 4(b), for example. In this case, for example, as shown in FIG. 4(a), the transparent base material 1 and the transparent barrier layer 2 may constitute the barrier film 5, and as shown in FIG. 4(b), the protective layer 6 and the transparent The barrier layer 2 may constitute the barrier film 5. The protective layer is a member that protects the transparent barrier layer. When a barrier film having a transparent barrier layer and a sealing layer are laminated via an adhesive layer, the transparent barrier layer can be protected by the protective layer. Moreover, when manufacturing a solar cell element with a current collecting sheet or a solar cell using a current collecting sheet having a current collecting sheet film, the protective layer can suppress the wires from coming into contact with the transparent barrier layer. Thereby, it is possible to suppress the generation of cracks and the like in the transparent barrier layer due to the wire coming into contact with the transparent barrier layer, and the deterioration of the barrier properties.

In particular, when a sealing layer is laminated on the barrier film via an adhesive layer by extrusion lamination, a protective layer is preferably disposed between the transparent barrier layer and the adhesive layer. During extrusion lamination, shearing is applied to the transparent barrier layer, which may reduce the barrier properties of the transparent barrier layer. Therefore, during extrusion lamination, the transparent barrier layer can be protected by the protective layer, and deterioration of the barrier properties of the transparent barrier layer can be suppressed.

The protective layer is not particularly limited as long as it can protect the transparent barrier layer. Examples of the material for the protective layer include resin. Examples of the resin include polyolefin resin, polyester resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), poly(meth)acrylic resin, Examples include polycarbonate resin, polyvinyl alcohol resin, polyamide resin, polyimide resin, polyurethane resin, acetal resin, and cellulose resin. Examples of polyolefin resins include polyethylene and polypropylene. Examples of the polyester resin include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and the like. Examples of the polyvinyl alcohol resin include polyvinyl alcohol (PVA) resin, ethylene-vinyl alcohol copolymer (EVOH) resin, and the like. Examples of the polyamide resin include various types of nylon.

Among these, polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT) are preferred from the viewpoint of heat resistance, transparency, chemical resistance, water resistance, dimensional stability, and the like. In particular, from the viewpoint of versatility and cost, polyethylene terephthalate (PET) is preferred.

The protective layer can contain various additives as necessary. The additives may be the same as those used for the transparent base material. The content of these additives is not particularly limited, and is appropriately adjusted depending on the purpose.

The protective layer may be a resin film or may be a coating film formed by coating or the like.

When the protective layer is a resin film, it may be an unstretched resin film or a uniaxially or biaxially stretched resin film.

The thickness of the protective layer is not particularly limited, and can be appropriately selected depending on the size and purpose of the solar cell in which the current collector sheet film is used. As mentioned above, the thickness of the protective layer is preferably thinner than the thickness of the sealing layer. Specifically, the thickness of the protective layer is preferably 12 μm or more and 38 μm or less. If the thickness of the protective layer is too thin, it may be difficult to adequately protect the transparent barrier layer. Moreover, if the thickness of the protective layer is too thick, the rigidity will become too high, and the followability of the current collector sheet film to the wire may deteriorate.

When the protective layer is a resin film and the barrier film has a transparent base material and a transparent barrier layer, the method for disposing the protective layer on the transparent barrier layer includes, for example, applying a second adhesive on the transparent barrier layer of the barrier film. A method of laminating protective layers via layers can be mentioned. In this case, a dry lamination method is preferably used. In the case of dry lamination, it is possible to suppress shearing of the transparent barrier layer during lamination.

When the protective layer is a coating film, the method for forming the protective layer is appropriately selected depending on the material and type of the protective layer, and various coating methods can be used.

In addition, when the protective layer is a resin film and the barrier film has a protective layer and a transparent barrier layer, the surface of the protective layer on the transparent barrier layer side may be subjected to surface treatment to improve adhesion with the transparent barrier layer. may have been applied.

6. Overcoat layer The film for current collector sheet in the present disclosure may have an overcoat layer 7 between the transparent barrier layer 2 and the adhesive layer 3, as shown in FIGS. 4(c) and 4(d), for example. good. When the current collector sheet film has an overcoat layer in addition to the transparent barrier layer, barrier properties can be improved. The overcoat layer is usually a member that constitutes a barrier film together with the transparent barrier layer.

For example, as shown in FIG. 4(c), when the current collector sheet film 10 has a protective layer 6, and when the barrier film 5 has a transparent base material 1 and a transparent barrier layer 2, an overcoat layer 7 is arranged between the transparent barrier layer 2 and the protective layer 6. For example, as shown in FIG. 4(d), when the current collector sheet film 10 has the protective layer 6 and the barrier film 5 has the protective layer 6 and the transparent barrier layer 2, an overcoat Layer 7 is arranged between transparent substrate 1 and transparent barrier layer 2 .

As the material for the overcoat layer, materials commonly used as barrier coating agents and overcoating agents can be used. The overcoat layer may contain only an organic substance, or may contain a mixture of an inorganic substance and an organic substance. Among these, it is preferable that the overcoat layer contains a mixture of an inorganic substance and an organic substance. Water vapor barrier properties can be improved.

In particular, the overcoat layer preferably contains a hydrolyzed polycondensate produced from a resin composition containing a metal alkoxide and a hydrophilic group-containing resin. Water vapor barrier properties can be improved.

Examples of the metal alkoxide include one or more alkoxides represented by the following general formula.
R ¹ _n M(OR ² ) _m
(However, in the above formula, R ¹ and R ² represent an organic group having 1 or more and 8 or less carbon atoms, M represents a metal atom, n represents an integer of 0 or more, and m is 1 or more. represents an integer, and n+m represents the valence of M.)

Examples of the metal atom M of the alkoxide represented by the above formula include silicon, zirconium, titanium, and aluminum. Among them, silicon is preferred.

Further, in the above formula, it is preferable that n=0.

In the above formula, specific examples of alkoxysilanes in which the metal atom M is silicon and n=0 include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. The silicon alkoxide is preferably tetraethoxysilane (TEOS).

As the alkoxide represented by the above formula, at least one kind of partial hydrolyzate of alkoxide and hydrolyzed condensate of alkoxide can be used. Further, the partial hydrolyzate of the alkoxide is not limited to one in which all of the alkoxy groups are hydrolyzed, but may be one in which one or more alkoxy groups are hydrolyzed, or a mixture thereof. Further, as the condensate for hydrolysis, a dimer or more of partially hydrolyzed alkoxide, specifically a dimer to hexamer, may be used.

Furthermore, examples of the hydrophilic group-containing resin include resins containing hydrophilic groups. Specific examples include polyvinyl alcohol resins, ethylene-vinyl alcohol copolymers, acrylic acid resins, natural polymers such as methyl cellulose, carboxymethyl cellulose, cellulose nanofibers, and polysaccharides. Among these, polyvinyl alcohol resin is preferred.

The content of the hydrophilic group-containing resin in the resin composition is preferably, for example, 5 parts by mass or more and 20 parts by mass or less, and 7 parts by mass or more and 18 parts by mass or less, based on 100 parts by mass of the metal alkoxide. It is more preferable that

The above-mentioned hydrolyzed polycondensate can be a mixed compound containing a metal element, an oxygen element, and a hydrophilic group-containing resin, and the carbon atom (C) in the hydrophilic group-containing resin and the metal atom (M ) can have a C--O--M bond via oxygen (O). Among these, it is preferable that the hydrolyzed polycondensate is a polycondensate of tetraethoxysilane (TEOS) and a polyvinyl alcohol resin. The polycondensate of tetraethoxysilane (TEOS) and polyvinyl alcohol resin may be the same as that disclosed in, for example, Japanese Patent No. 5,568,897.

The overcoat layer may contain various additives as necessary.

The thickness of the overcoat layer is not particularly limited, but may be, for example, 100 nm or more and 4 μm or less, and may be 200 nm or more and 1 μm or less. If the thickness of the overcoat layer is within the above range, it is possible to suppress the occurrence of cracks and the like while maintaining high barrier properties.

An example of a method for forming the overcoat layer containing the hydrolyzed polycondensate is a thin film forming method using a sol-gel method. That is, this method uses a raw material liquid containing a metal alkoxide and a hydrophilic group-containing resin, which is further obtained by polycondensation using a sol-gel method. Specifically, first, a metal alkoxide or a hydrolyzate thereof is mixed with a solution in which a hydrophilic group-containing resin is dissolved in an aqueous solvent to prepare a coating liquid. As the aqueous solvent, for example, water or a mixed solvent of water and alcohol can be used. Next, the coating liquid is applied onto the transparent barrier layer, dried by heating, and subjected to heat treatment. As a result, an overcoat layer containing the above hydrolyzed polycondensate is obtained.

7. Others The thickness of the current collector sheet film in the present disclosure is not particularly limited, and can be appropriately selected depending on the thickness of the wire used in the current collector sheet. The thickness of the current collector sheet film may be, for example, 50 μm or more and 300 μm or less. If the thickness of the current collector sheet film is too thin, it may become difficult to fix the wire to the solar cell element. On the other hand, if the thickness of the current collector sheet film is too thick, transparency may decrease.

II. Physical properties of film for current collector sheet 1. Water Vapor Permeability The film for current collector sheet in the present disclosure has water vapor barrier properties by having a transparent barrier layer. The water vapor permeability of the current collector sheet film is, for example, preferably 1×10 ⁻³ g/(m ² ·day) or more and 1 g/(m ² ·day) or less, and 1×10 ⁻³ g/ (m ²・day) or more and 1×10 ⁻¹ g/(m ²・day) or less, more preferably 1×10 ⁻³ g/(m ²・day) or more and 1×10 ⁻² g /(m ² ·day) or less is more preferable.

Here, the water vapor permeability can be measured using a water vapor permeability measuring device under the conditions of a temperature of 40° C. and a relative humidity difference of 90% RH in accordance with ISO 15106-5:2015 (differential pressure method). As the water vapor permeability measuring device, for example, "DELTAPERM" manufactured by Technolox in the UK can be used. The measurement was performed so that the surface of the current collector sheet film that is located on the transparent barrier layer side with respect to the transparent base material in the thickness direction of the current collector sheet film is the high humidity side (water vapor supply side). A current collector sheet film was installed between the upper and lower chambers of the water vapor permeability measuring device, and the measurement was conducted under the above conditions with a permeation area of 50.24 cm ² (permeation area: circular 8 cm in diameter). At least three samples are measured under one condition, and the average of those measured values is taken as the water vapor permeability value under that condition.

2. Light transmittance at a wavelength of 400 nm or more and 1,200 nm or less The light transmittance of the film for a current collecting sheet in the present disclosure at a wavelength of 400 nm or more and 1,200 nm or less is a level that allows sunlight to pass through to the extent that the solar cell element can generate electricity. Not particularly limited. The light transmittance of the current collector sheet film at a wavelength of 400 nm or more and 1200 nm or less is, for example, preferably 75% or more, more preferably 80% or more, and even more preferably 85% or more. When the light transmittance is within the above range, the light utilization efficiency of the solar cell element can be increased.

Here, the light transmittance at a wavelength of 400 nm or more and 1200 nm or less is an average value of the light transmittance at a wavelength of 400 nm or more and 1200 nm or less. The light transmittance at a wavelength of 400 nm or more and 1200 nm or less can be measured in accordance with JIS K7361 1. Specifically, the light transmittance at a wavelength of 400 nm or more and 1200 nm or less can be measured using a haze meter HM150 manufactured by Murakami Color Research Institute.

3. Haze The transparency of the current collector sheet film in the present disclosure is not particularly limited as long as it can transmit sunlight to the extent that the solar cell element can generate electricity. The transparency of the current collector sheet film can be evaluated, for example, by haze. The haze of the current collector sheet film is, for example, 1% or more and 40% or less, may be 5% or more and 30% or less, or may be 10% or more and 20% or less.

Here, haze is measured in accordance with JIS K7136. Haze can be measured using, for example, a haze meter HM150 manufactured by Murakami Color Research Institute.

In addition, when measuring the haze of the film for current collector sheets, a measurement sample is prepared and used for measurement. The sample for measurement is prepared by the following method. First, a test piece was prepared by cutting a current collector sheet film into a size of 50 mm x 50 mm. Next, the ETFE (tetrafluoroethylene-ethylene copolymer) film, the test piece, and the ETFE film were laminated in this order, and vacuum laminated at a set temperature of 165°C, vacuuming for 2 minutes, pressing for 2.5 minutes, and pressure of 100 kPa. I do. This is to eliminate minute irregularities on the surface of the current collector sheet film during the film forming stage. Subsequently, the ETFE film is removed from both sides of the test piece to prepare a measurement sample.

III. Method for producing a film for a current collector sheet The method for producing a film for a current collector sheet in the present disclosure is such that a film for a current collector sheet having a transparent base material, a transparent barrier layer, an adhesive layer, and a sealing layer in this order can be obtained. Not particularly limited. For example, a method in which a barrier film having a transparent base material and a transparent barrier layer and a film-like sealing layer are used and the barrier film and the sealing layer are laminated via a dry laminating adhesive by a dry lamination method; Examples include a method in which a barrier film having a transparent base material and a transparent barrier layer is used, and a sealing layer is extruded onto the barrier film and laminated via an anchor coating agent for lamination by an extrusion lamination method.

Moreover, when the film for current collector sheet has a transparent base material, a transparent barrier layer, a protective layer, an adhesive layer, and a sealing layer in this order, for example, a barrier film having a transparent base material and a transparent barrier layer, A method in which a film-like protective layer and a film-like sealing layer are used, and each film is laminated via an adhesive using a dry lamination method or an extrusion lamination method, or a film-like transparent base material and a transparent barrier layer are used. Another method includes a method in which a barrier film having a protective layer and a film-like sealing layer are used, and each film is laminated via an adhesive by a dry lamination method or an extrusion lamination method.

Examples of the method for producing a barrier film include a method of using a film-like transparent base material or a protective layer and forming a transparent barrier layer on the transparent base material or the protective layer. Furthermore, in the method for producing a barrier film, an overcoat layer may be formed on the transparent barrier layer. The method for forming the transparent barrier layer and the method for forming the overcoat layer are as described above.

An example of a method for forming a film-like sealing layer is a method of preparing a resin composition for forming the sealing layer and melt-molding the resin composition. As the melt molding method, a known molding method can be used, and examples thereof include injection molding, extrusion molding, blow molding, compression molding, rotation molding, and the like. The temperature during molding is, for example, higher than the melting point of the resin composition. The upper limit of the temperature during molding is appropriately adjusted depending on the type of resin composition.

B. Current collector sheet The current collector sheet in the present disclosure is a current collector sheet used for a solar cell, and includes the above-mentioned current collector sheet film and a wire disposed on the surface side of the sealing layer of the current collector sheet film. , has.

2(a) and 2(b) are a schematic plan view and a cross-sectional view illustrating a current collecting sheet according to the present disclosure, and FIG. 2(b) is a cross-sectional view taken along the line AA in FIG. 2(a). As shown in FIGS. 2(a) and 2(b), the current collecting sheet 20 includes a current collecting sheet film 10 and a wire 11 disposed on the surface side of the sealing layer 4 of the current collecting sheet film 10. have Note that FIG. 2(a) shows a schematic plan view of the current collecting sheet viewed from the sealing layer side of the film for current collecting sheet.

In the current collector sheet according to the present disclosure, barrier properties can be imparted by having the above-described film for current collector sheet. Therefore, when the current collector sheet is used in a solar cell, barrier properties can be improved and reliability can be improved.

I. Configuration of current collector sheet The current collector sheet in the present disclosure includes a current collector sheet film and a wire.

1. Film for current collector sheet The film for current collector sheet is a member that supports the wire. Further, the current collector sheet film is a member that fixes the wire to the solar cell element.

Regarding the current collector sheet film, the content can be the same as that described in "A. Current collector sheet film", so the description here will be omitted.

As described later, when the current collecting sheet has a plurality of current collecting sheet films, at least one current collecting sheet film may be the above-mentioned current collecting sheet film. In this case, the current collecting sheet may have a current collecting sheet film other than the above-mentioned current collecting sheet film. Among these, it is preferable that all of the plurality of current collecting sheet films included in the current collecting sheet are the above-mentioned current collecting sheet films.

2. Wire The wire is arranged on the surface side of the sealing layer of the current collector sheet film. Wires are used, for example, in solar cell modules to connect solar cell elements to each other. Further, the wire is used, for example, in a single cell type solar cell to collect electricity generated in a solar cell element. The wire is usually arranged to connect with the electrode of the solar cell element.

The cross-sectional shape of the wire is typically circular, such as a perfect circle or an ellipse, but is not limited thereto.

The thickness of the wire, that is, the cross-sectional size of the wire is not particularly limited as long as it does not prevent sunlight from entering the solar cell element, and is, for example, 100 μm or more and 300 μm or less. The cross-sectional size of the wire is, for example, the diameter when the cross-section is circular, the major axis when the cross-section is elliptical, and the maximum diagonal length when the cross-section is polygonal.

The material of the wire is not particularly limited as long as it can exhibit desired conductivity, and may be the same as the material of the wire used in current collector sheets of general solar cell elements. As the material of the wire, for example, metal materials such as copper (Cu) and silver (Ag) can be used. Further, the wire may have, for example, a core portion and a skin portion disposed on the outside of the core portion. In this case, as the material of the core part, for example, the above metal materials can be used. Furthermore, solder can be used as the material for the skin portion.

The melting point of the solder is, for example, preferably 70°C or more and 140°C or less, more preferably 80°C or more and 135°C or less. If the melting point of the solder is too high, each layer of the current collector sheet film may be deteriorated when connecting wires to the solar cell element.

Examples of such solder include Sn-In-Ag-Bi-based, Sn-In-based, Bi-Sn-based, and the like.

II. Structure of Current Collecting Sheet In the current collecting sheet according to the present disclosure, at least one wire may be disposed on one current collecting sheet film. From the viewpoint of increasing the conductivity of the current collector sheet, it is preferable that a plurality of wires are arranged on one current collector sheet film.

When the current collector sheet has a plurality of wires, the arrangement of the wires in plan view is not particularly limited, and may be the same as the arrangement of the wires in known current collector sheets. For example, as shown in FIG. 2(a), the wires 11 may be arranged in a line, or, although not shown, the wires may be arranged in a grid.

Moreover, in the current collector sheet, the wire is arranged on the surface side of the sealing layer of the film for current collector sheet. For example, as shown in FIG. 2(b), the wire 11 is arranged such that a part of the wire 11 is embedded in the sealing layer 4 of the current collector sheet film 10 and a part of the wire 11 is exposed. It is preferable. Wires can be fixed well.

Further, for example, when the current collector sheet film 10 does not have a protective layer between the transparent barrier layer 2 and the adhesive layer 3, the wire 11 is attached to the transparent barrier layer 2 as shown in FIG. It is preferable that they be embedded in the sealing layer 4 so as not to contact each other.

Further, for example, when the current collector sheet film 10 has a protective layer 6 between the transparent barrier layer 2 and the adhesive layer 3, the wire 11 does not come into contact with the protective layer 6, as shown in FIG. 5(a). Alternatively, as shown in FIG. 5(b), the wire 11 may be embedded in the sealing layer 4 so as to be in contact with the protective layer 6. When the wires are embedded in the sealing layer so as to be in contact with the protective layer, the thickness of the current collector sheet can be reduced, so that the solar cell using the current collector sheet can be made thinner.

The degree of embedding of the wires, that is, the degree of exposure of the wires, is not particularly limited and depends on the material and thickness of the sealing layer, the thickness of the wires, and the form of the solar cell element in which the current collector sheet is arranged. You can choose as appropriate.

In the current collecting sheet, for example, the same wire may be arranged on a plurality of films for current collecting sheets. For example, FIG. 6 shows an example in which the same wire 11 is arranged for two current collector sheet films 10A and 10B. Further, as shown in FIG. 6, adjacent current collector sheet films 10A and 10B may be arranged such that the surfaces facing the sealing layer 4 are in opposite directions. That is, the surface of one film for current collector sheet 10A on the sealing layer 4 side and the surface of the other film for current collector sheet 10B on the transparent base material 1 side may be arranged in the same plane direction. . By having the current collector sheet having the above structure, the current collector sheet 20 can be made into a current collector sheet 20 in which two solar cell elements 31 can be arranged in series, as shown in FIG. 3(a), for example. Although not shown, adjacent films for current collector sheets may be arranged so that their surfaces on the sealing layer side are in the same surface direction.

III. Method for Manufacturing a Current Collector Sheet The method for manufacturing a current collector sheet in the present disclosure is not particularly limited as long as it is a method that can embed wires to the surface side of the sealing layer of the film for current collector sheet to the extent that they can be fixed. Known methods can be used. One example is a method in which a wire is placed on the side of the sealing layer of the current collector sheet film, and the wire is heated to melt part of the resin component in the sealing layer and embed the wire. I can do it.

C. Solar cell element with a current collector sheet The solar cell element with a current collector sheet in the present disclosure includes the above-mentioned current collector sheet, and a solar cell arranged on the surface side of the sealing layer of the current collector sheet and electrically connected to a wire. It has an element.

3(a) to 3(c) are a schematic perspective view and a cross-sectional view illustrating a solar cell element with a current collecting sheet according to the present disclosure, and FIG. 3(b) is a cross-sectional view taken along the line AA in FIG. 3(a). FIG. 3(c) is a sectional view taken along line BB in FIG. 3(a). As shown in FIGS. 3(a) to 3(c), the solar cell element 30 with a current collector sheet is arranged on the surface side of the current collector sheet 10 and the sealing layer 4 of the current collector sheet 10, and is connected to the wire 11 and It has a solar cell element 31 which is connected to the solar cell element 31. 3(a) to (c) show an example in which the current collecting sheet 20 has two current collecting sheet films 10, and a solar cell element 31 is arranged on each current collecting sheet film 10. ing.

In the solar cell element with a current collector sheet according to the present disclosure, barrier properties can be imparted by having the above-described current collector sheet. Therefore, when a solar cell element with a current collector sheet is used in a solar cell, barrier properties can be improved and reliability can be improved.

I. Configuration of solar cell element with current collector sheet The solar cell element with current collector sheet in the present disclosure includes a current collector sheet and a solar cell element.

1. Current Collector Sheet The current collector sheet can be the same as that explained in "B. Current Collector Sheet" above, so the description here will be omitted.

When the solar cell element with a current collecting sheet has a plurality of current collecting sheets, at least one current collecting sheet may be the above current collecting sheet. In this case, the solar cell element with a current collecting sheet may have a current collecting sheet other than the above-mentioned current collecting sheet. Among these, it is preferable that all the current collecting sheets are the above-mentioned current collecting sheets.

Further, when the solar cell element with a current collecting sheet is used in a solar cell, the current collecting sheet is preferably arranged so as to be located on the light-receiving surface side of the solar cell.

2. Solar Cell Element The solar cell element can be similar to elements used in general solar cells. Examples of the solar cell element include a single crystal silicon solar cell element, a polycrystalline silicon solar cell element, an amorphous silicon solar cell element, a compound semiconductor solar cell element, a dye-sensitized solar cell element, and a quantum dot solar cell element. Examples include battery elements, organic thin film type solar cell elements, and the like. The size, form, etc. of the solar cell element can be appropriately selected depending on the use of the solar cell.

II. Structure of a solar cell element with a current collector sheet A solar cell element with a current collector sheet usually has a laminated structure in which a current collector sheet and a solar cell element are laminated.

When the solar cell element with a current collector sheet is viewed from the arrangement surface of the current collector sheet of the solar cell element, for example, as shown in _FIG . The thickness of the film 10, that is, the distance from the surface of the solar cell element 31 on which the current collector sheet 20 is arranged to the surface of the current collector sheet film 10 opposite to the solar cell element 31, is determined by It is preferable that the area where the image is formed is thicker (distance is larger) than other areas. With such a laminated structure, the current collector sheet film 10 can effectively press the wire 11 toward the solar cell element 31 side, and problems such as poor contact of the wire 11 with the solar cell element 31 can be prevented.

In this case, the maximum distance y of the wire 11 in the direction D _L perpendicular to the arrangement surface, that is, the maximum distance y of the wire 11 from the surface on which the current collector sheet 20 of the solar cell element 31 is arranged, and the maximum distance y of the wire 11 in the direction D L perpendicular to the arrangement surface. The minimum distance x of the current collector sheet film 10 of _L , that is, from the surface on which the current collector sheet 20 of the solar cell element 31 is arranged to the surface of the current collector sheet film 10 opposite to the solar cell element 31. The ratio x/y of the distances to the minimum distance x is, for example, preferably 2/3 or less, more preferably 1/2 or less.

Note that the lower limit of the ratio x/y is a value that is adjusted as appropriate depending on the thickness of the sealing layer and the thickness of the wire, and is, for example, 1/20 or more. When the ratio x/y is within the above range, the wire can be well fixed to the solar cell element using the current collector sheet film.

The ratio x/y can be controlled by adjusting the wire thickness (diameter, etc.) and the thickness of the sealing layer. Further, as will be described later, the ratio x/y can also be controlled by adjusting the pressure when thermocompression bonding the current collector sheet to the solar cell element.

Further, as shown in FIG. 3C, for example, in a cross-sectional view of the solar cell element 30 with a current collector sheet, the solar cell element 31 is It is preferable that the distance from the surface on the current collector sheet 20 side to the surface of the film 10 for current collector sheet on the opposite side to the solar cell element 31 gradually decreases.

In addition, when a plurality of wires are arranged, for example, as shown in FIG. It is preferable that the distance from the surface on which the sheet 20 is placed to the surface of the current collector sheet film 10 opposite to the solar cell element 31 is located at the minimum distance. Since depressions are formed between the wires and the current collector sheet has an uneven structure, the area of the surface of the current collector sheet film opposite to the solar cell element becomes large. As a result, in a solar cell having a solar cell element with a current collecting sheet, the contact area between the current collecting sheet film and the encapsulant described later becomes large, so that the adhesion to the encapsulant can be improved.

In addition, in the solar cell element with a current collector sheet, if the film for the current collector sheet has a protective layer between the transparent barrier layer and the adhesive layer, the above-mentioned "B. Current collector sheet" section also applies. Although not shown, the wire may be embedded in the sealing layer so as to contact the protective layer. Thereby, the thickness of the solar cell element with the current collecting sheet can be reduced, so that the solar cell can be made thinner.

A solar cell element with a current collector sheet may include at least one solar cell element and a current collector sheet connected to at least one of a positive electrode and a negative electrode of the solar cell element. For example, it may be a solar cell element with a current collecting sheet that constitutes a single cell type solar cell, in which a current collecting sheet is placed on each of the positive electrode and the negative electrode of one solar cell element. For example, a solar cell element with a current collector sheet is a solar cell with a current collector sheet that constitutes a solar cell module type solar cell (solar cell module) in which multiple solar cell elements are connected in parallel or in series using a current collector sheet. It may also be a solar cell element.

III. Others The method for manufacturing a solar cell element with a current collector sheet in the present disclosure is not particularly limited as long as it is a method that can obtain a structure in which the wires of the current collector sheet are electrically connected and fixed to the solar cell element. For example, by temporarily adhering a current collector sheet to a solar cell element, and by thermocompression bonding the temporarily adhered current collector sheet to the solar cell element, the wires of the current collector sheet can be electrically connected to the solar cell element. An example of a manufacturing method includes a fixing step of physically connecting and fixing. As for the temporary bonding method and the thermocompression bonding method, known methods can be used, such as a vacuum thermal lamination method. Further, the fixing step may be performed at the same time as the unifying step of laminating and integrating each member of the solar cell, for example, as described in the section "D. Solar Cell" below.

A solar cell element with a current collector sheet is normally used as a member constituting a solar cell. In addition, when a solar cell element with a current collector sheet has, for example, one solar cell element and a current collector sheet connected to only one electrode of the positive electrode or the negative electrode of the solar cell element, the solar cell element with a current collector sheet The solar cell element can be used, for example, as a part of the above-mentioned single-cell type solar cell, or as a part of the solar cell element with a current collector sheet that constitutes the above-mentioned solar cell module.

D. Solar Cell In the solar cell according to the present disclosure, a transparent substrate, a first sealing material, the above-described solar cell element with a current collecting sheet, a second sealing material, and a back protection sheet are arranged in this order.

FIG. 7 is a schematic cross-sectional view illustrating a solar cell according to the present disclosure. As shown in FIG. 7, the solar cell 40 includes a transparent substrate 41, a first encapsulant 42, a solar cell element 30 with a current collector sheet, a second encapsulant 43, and a back protection sheet 44. .

The solar cell in the present disclosure may be a solar cell module having a plurality of solar cell elements with current collector sheets.

In the solar cell according to the present disclosure, by having the above-described solar cell element with a current collector sheet, barrier properties can be improved and reliability can be improved.

I. Configuration of Solar Cell The solar cell in the present disclosure includes, in this order, a transparent substrate, a first sealing material, a solar cell element with a current collecting sheet, a second sealing material, and a back protection sheet.

1. Solar cell element with current collector sheet Regarding the solar cell element with current collector sheet, the content can be the same as that explained in the above section "C. Solar cell element with current collector sheet", so the explanation here is Omitted.

2. Back Protection Sheet The back protection sheet is a member that protects the solar cell element together with the transparent substrate. The back protection sheet may or may not have transparency. When the back protection sheet has transparency, both sides of the solar cell can be used as sunlight receiving surfaces. The back protection sheet may be the same as the back protection sheet used for general solar cells.

Among these, it is preferable that the back protection sheet has an easily adhesive layer, a second barrier film, and a base material layer in this order from the second sealing material side, which will be described later.

In this specification, for convenience, the barrier film included in the back protection sheet is referred to as a second barrier film.

(1) Second barrier film The second barrier film can have a base material and a barrier layer. The second barrier film is usually arranged such that the base material is on the easily adhesive layer side and the barrier layer is on the base material layer side.

The barrier layer may or may not have transparency.

The barrier layer can be the same as the transparent barrier layer used in the film for current collector sheet, so the explanation here will be omitted.

The base material may or may not have transparency.

The base material can be the same as the transparent base material used for the above film for current collector sheet, so the explanation here will be omitted.

The second barrier film preferably has a second overcoat layer on the side of the barrier layer opposite to the base material. Barrier properties can be improved.

The second overcoat layer can be the same as the overcoat layer used for the current collector sheet film, so the description here will be omitted.

(2) Base material layer The base material layer can be similar to the base material layer that constitutes a back protection sheet used in general solar cells. As the base material layer, for example, a resin film having weather resistance can be used.

(3) Easy-adhesion layer The easy-adhesion layer is a member for increasing the adhesion between the back protection sheet and the second sealing material. The easily adhesive layer can be similar to the easily adhesive layer that constitutes a back protection sheet used in general solar cells. Examples of the easily adhesive layer include polyethylene film.

(4) Others In the back protection sheet, a third adhesive layer may be disposed between the base layer and the second gas barrier film. Further, in the back protection sheet, a fourth adhesive layer may be disposed between the second gas barrier film and the easily adhesive layer. The third adhesive layer and the fourth adhesive layer may be the same as the adhesive layer used in the current collector sheet film.

3. Transparent Substrate The transparent substrate is a member that protects the solar cell element together with the back protection sheet. Further, the transparent substrate is usually arranged on the light-receiving surface side of the solar cell, and functions as a front protection plate on the light-receiving surface side. The transparency of the transparent substrate is not particularly limited as long as it does not inhibit the power generation of the solar cell element. The transparent substrate can be the same as the transparent substrate used in general solar cells, so the explanation here will be omitted.

4. First Encapsulant and Second Encapsulant The first encapsulant and the second encapsulant are members that seal the solar cell element. The first sealing material is usually placed on the light-receiving surface side of the solar cell.

The first sealant and the second sealant contain thermoplastic resin. The thermoplastic resin used for the first encapsulant and the second encapsulant may be the same as the thermoplastic resin used for the encapsulant of general solar cells, such as polyethylene resin, ethylene resin, etc. Encapsulants containing various olefin resins such as vinyl acetate copolymer (EVA) as a main component can be used. In addition, when these resins are the main components, it means that the ratio of these resins is the largest among all resin components.

The first sealing material usually contains an ultraviolet absorber. It is possible to suppress deterioration of the transparent base material and protective layer due to ultraviolet rays, such as yellowing, cracking, and breakage.

When the back protection sheet has transparency, the second sealing material usually contains an ultraviolet absorber like the first sealing material.

The ultraviolet absorber can be the same as the ultraviolet absorber used in general solar cell encapsulants.

The thicknesses of the first encapsulant and the second encapsulant are appropriately selected depending on the type and size of the solar cell.

II. Method for Manufacturing a Solar Cell A method for manufacturing a solar cell in the present disclosure can be similar to a method for manufacturing a general solar cell. As an example, a laminate forming step of forming a laminate in which a transparent substrate, a first encapsulant, a solar cell element with a current collector sheet, a second encapsulant, and a back protection sheet are laminated in this order; An example of a manufacturing method includes an integration step of integrating the solar cells by heating and pressurizing them to form a solar cell.

The heating and pressurizing treatments are not particularly limited, and can be similar to treatments performed during the manufacture of general solar cells. For example, a vacuum thermal lamination method is preferred. The conditions for the vacuum thermal lamination method are not particularly limited, and can be appropriately selected depending on the size of the solar cell, the type of each member, etc. The lamination temperature is preferably, for example, 130°C or higher and 170°C or lower. Further, the lamination time is preferably, for example, 5 minutes or more and 30 minutes or less, and more preferably 8 minutes or more and 15 minutes or less.

III. Applications Applications of the solar cell in the present disclosure include various applications such as solar cells for electronic devices and large solar cells for outdoor installation.

Note that the present disclosure is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any embodiment that has substantially the same configuration as the technical idea stated in the claims of the present disclosure and provides similar effects is the present invention. within the technical scope of the disclosure.

Examples and Comparative Examples are shown below to further explain the present disclosure in detail.

[Example 1]
As a barrier film having a protective layer and a transparent barrier layer, a barrier film in which a 10 nm thick silicon oxide vapor deposited film was formed on one side of a 12 μm thick polyethylene terephthalate (PET) film (“Tech Barrier Tech” manufactured by Mitsubishi Chemical Corporation) was used. LX") was used. In addition, a two-component adhesive consisting of a polycarbonate base agent (KT-0035 manufactured by Rock Paint Co., Ltd.) and an isocyanate curing agent (H-039Z2 manufactured by Rock Paint Co., Ltd.) was used as the adhesive. . Moreover, low density polyethylene (LDPE) ("Sumikasen CE4009" manufactured by Sumitomo Chemical Co., Ltd.) was used as the polyethylene resin. Moreover, a polyethylene terephthalate (PET) film ("LBD" manufactured by DuPont) with a thickness of 12 μm was used as a transparent base material.

The adhesive was applied to a thickness of 5 μm on one side of the transparent substrate, and the adhesive was bonded to the silicon oxide vapor-deposited film side of the barrier film using a dry lamination method. Subsequently, aging was performed at 45° C. for 5 days to cure the adhesive. Next, the adhesive was applied as an anchor to the surface of the barrier film on the protective layer side, and polyethylene resin was extruded to a thickness of 60 μm to form a sealing layer. Further, the surface of the sealing layer opposite to the barrier film was subjected to corona treatment. Thereby, a film for a current collector sheet having a transparent base material, a second adhesive layer, a transparent barrier layer, a protective layer, an adhesive layer, and a sealing layer in this order was obtained.

[Example 2]
A current collector sheet film was produced in the same manner as in Example 1, except that the barrier film was produced as described below. Thereby, a film for a current collector sheet having a transparent base material, a second adhesive layer, an overcoat layer, a transparent barrier layer, a protective layer, an adhesive layer, and a sealing layer in this order was obtained.

As a film having a transparent base material and a transparent barrier layer, a film (manufactured by Mitsubishi Chemical Corporation) in which a 10 nm thick silicon oxide vapor deposited film (transparent barrier layer) was formed on one side of a 12 μm thick polyethylene terephthalate (PET) film was used. "Tech Barrier Tech LX") was used.

In addition, a resin composition for forming an overcoat layer was prepared. Specifically, Solution B having the following composition was added to Solution A having the following composition and stirred to obtain a resin composition for an overcoat layer by a sol-gel method.

<Liquid A: Mixed liquid>
Polyvinyl alcohol (PVA) 1.81 parts by mass Isopropyl alcohol 39.8 parts by mass Ion exchange water 2.09 parts by mass

<Liquid B: Hydrolyzed liquid>
Tetraethyl orthosilicate (TEOS) 21.49 parts by mass Isopropyl alcohol 5.03 parts by mass 0.5N aqueous hydrochloric acid solution 0.69 parts by mass Ion exchange water 29.1 parts by mass

The resin composition was applied onto the transparent barrier layer of the film, dried by heating at 150°C for 30 seconds, and then heat-treated at 200°C for 30 seconds. Thereby, a barrier film having a transparent base material, a transparent barrier layer, and an overcoat layer in this order was obtained.

[Comparative example 1]
A 12 μm thick polyethylene terephthalate (PET) film (“LBD” manufactured by DuPont) was used as the transparent base material. In addition, a two-component adhesive consisting of a polycarbonate base agent (KT-0035 manufactured by Rock Paint Co., Ltd.) and an isocyanate curing agent (H-039Z2 manufactured by Rock Paint Co., Ltd.) was used as the adhesive. . Moreover, low density polyethylene (LDPE) ("Sumikasen CE4009" manufactured by Sumitomo Chemical Co., Ltd.) was used as the polyethylene resin.

The adhesive was applied as an anchor to one side of the transparent base material, and the polyethylene resin was extruded to a thickness of 60 μm to form a sealing layer containing the polyethylene resin. Furthermore, the surface of the sealing layer opposite to the transparent base material was subjected to corona treatment. Thereby, a film for a current collector sheet having a transparent base material, an adhesive layer, and a sealing layer in this order was obtained.

[Reference example 1]
A 50 μm thick white PET film (“S-PV8W” manufactured by DuPont), a 7 μm thick aluminum foil, a 250 μm thick transparent PET film (“Mylar A S6” manufactured by DuPont), and a 30 μm thick A back protection sheet A was prepared in which polyethylene films ("SE625NWT02" manufactured by Tamapori Co., Ltd., white LLDPE) were laminated in this order via an adhesive.

[Reference example 2]
A 140 μm thick transparent PET film (“AP” manufactured by DuPont), a barrier film used in Example 2, a 140 μm thick transparent PET film (“AP” manufactured by DuPont), and a barrier film used in Example 2. A barrier film is laminated in this order via an adhesive, and then a weather-resistant top coat layer based on an acrylic resin with a thickness of 5 μm is formed on the surface on the transparent PET film side. A back protection sheet B was prepared, on which an easily adhesive primer layer with a thickness of 1 μm was formed.

[Reference example 3]
Back protection in which a 152 μm thick white PET film (“BP” manufactured by DuPont) and a 30 μm thick polyethylene film (“SE625N” manufactured by Tamapori, white LLDPE) are laminated in this order via adhesive. Sheet C was prepared.

[Manufacture example 1]
As the base material layer, a polyethylene terephthalate (PET) film ("BP" manufactured by DuPont) having a thickness of 152 μm and having hydrolysis resistance was used. In addition, a 30 μm thick polyethylene film (“SE625N” manufactured by Tamapoly Co., Ltd.) was used as an easily adhesive layer. In addition, a two-component adhesive consisting of a polycarbonate base agent (KT-0035 manufactured by Rock Paint Co., Ltd.) and an isocyanate curing agent (H-039Z2 manufactured by Rock Paint Co., Ltd.) was used as the adhesive. .

A base material layer and an easily adhesive layer were laminated with an adhesive interposed therebetween by a dry lamination method. Thereby, a back protection sheet D having a base material layer, a third adhesive layer, and an easy-to-adhesion layer in this order was obtained.

[Manufacture example 2]
As the base material layer, a polyethylene terephthalate (PET) film ("BP" manufactured by DuPont) having a thickness of 152 μm and having hydrolysis resistance was used. Further, as the second barrier film, the barrier film used in Example 2 and having a transparent base material, a transparent barrier layer, and an overcoat layer in this order was used. In addition, a 30 μm thick polyethylene film (“SE625N” manufactured by Tamapoly Co., Ltd.) was used as an easily adhesive layer. In addition, a two-component adhesive consisting of a polycarbonate base agent (KT-0035 manufactured by Rock Paint Co., Ltd.) and an isocyanate curing agent (H-039Z2 manufactured by Rock Paint Co., Ltd.) was used as the adhesive. .

By a dry lamination method, the base material layer, the second barrier film, and the easy-to-adhesion layer were each laminated with an adhesive interposed therebetween. Thereby, a back protection sheet E was obtained which had a base material layer, a third adhesive layer, a second barrier film, a fourth adhesive layer, and an easily adhesive layer in this order. The second barrier film was arranged so that the transparent base material was on the easily adhesive layer side and the overcoat layer was on the base layer side.

[evaluation]
(1) Water vapor permeability The current collector sheet film and back protection sheet were measured using a water vapor permeability measuring device (“DELTAPERM” manufactured by Technolox) in accordance with ISO 15106-5:2015 (differential pressure method). Water vapor permeability was measured under conditions of a temperature of 40° C. and a relative humidity difference of 90% RH.

(2) Barrier properties First, a test solar cell module was produced using a current collector sheet film and a back protection sheet. Specifically, a 3.2 mm thick white tempered glass plate was used as the transparent substrate, and a 470 μm thick ethylene-vinyl acetate copolymer (EVA) sheet (Takiron) was used as the first and second sealing materials. Fast Cure EVA) manufactured by CI Corporation was used. Next, the transparent substrate, the first sealing material, the current collecting sheet film, the cobalt chloride paper, the current collecting sheet film, the second sealing material, and the back protection sheet are laminated in this order, Vacuum lamination was performed under the conditions of a set temperature of 150° C., evacuation for 5 minutes, press for 7.5 minutes, and pressure of 100 kPa to produce a test solar cell module. Cobalt chloride paper (manufactured by Advantech Toyo Co., Ltd.) was used after being dried in an oven at 80°C.

Next, a high temperature and high humidity test was conducted on the test solar cell module. The high temperature and high humidity test was conducted by placing the test solar cell module in an oven set at a temperature of 85°C and a humidity of 85% RH. The coloration of the paper was visually observed.

From Tables 1 and 2, it was confirmed that when the current collector sheet film had a barrier film, the barrier properties were good. In particular, when both the current collector sheet film and the back protection sheet have a barrier film (test numbers 8 and 9), when the back protection sheet has aluminum foil (test number 1), or when the back protection sheet has a barrier film, It was shown that similar high temperature and high humidity test results could be obtained as in the case of an expensive barrier film with excellent water vapor barrier properties (Test No. 2).

The present disclosure provides the following [1] to [12].
[1] A current collector sheet film used for a solar cell current collector sheet,
A film for a current collector sheet, comprising a transparent base material, a transparent barrier layer, an adhesive layer, and a sealing layer in this order.
[2] The film for a current collector sheet according to [1], which has a protective layer between the transparent barrier layer and the adhesive layer.
[3] The film for a current collector sheet according to [1] or [2], which has an overcoat layer between the transparent barrier layer and the adhesive layer.
[4] The current collector according to any one of [1] to [3], which has a water vapor permeability of 1×10 ⁻³ g/(m ² ·day) or more and 1 g/(m ² ·day) or less. Film for sheets.
[5] The film for a current collector sheet according to any one of [1] to [4], wherein the sealing layer contains a polyolefin resin.
[6] The film for a current collector sheet according to [5], wherein the polyolefin resin is a polyethylene resin.
[7] The film for a current collector sheet according to any one of [1] to [6], wherein the sealing layer has a surface-treated portion on a surface opposite to the adhesive layer.
[8] A current collector sheet used for solar cells,
The film for current collector sheet according to any one of [1] to [7],
A wire arranged on the surface side of the sealing layer of the current collector sheet film;
A current collecting sheet having.
[9] The current collector sheet according to [8],
a solar cell element arranged on the surface side of the sealing layer of the current collector sheet and electrically connected to the wire;
A solar cell element with a current collecting sheet.
[10] A solar cell comprising, in this order, a transparent substrate, a first encapsulant, the solar cell element with a current collector sheet according to [9], a second encapsulant, and a back protection sheet.
[11] The solar cell according to [10], wherein the solar cell is a solar cell module having a plurality of the solar cell elements with the current collector sheet.
[12] The solar cell according to [10] or [11], wherein the back protection sheet includes, in order from the second encapsulant side, an easily adhesive layer, a barrier film, and a base layer.

1... Transparent base material 2... Transparent barrier layer 3... Adhesive layer 4... Sealing layer 5... Barrier film 6... Protective layer 7... Overcoat layer 10, 10A, 10B... Film for current collector sheet 11... Wire 20... Current collector Sheet 30... Solar cell element with current collector sheet 31... Solar cell element 40... Solar cell 41... Transparent substrate 42... First sealing material 43... Second sealing material 44... Back protection sheet

Claims (12)

A current collector sheet film used for a solar cell current collector sheet,
A film for a current collector sheet, comprising a transparent base material, a transparent barrier layer, an adhesive layer, and a sealing layer in this order. The film for a current collector sheet according to claim 1, further comprising a protective layer between the transparent barrier layer and the adhesive layer. The film for a current collector sheet according to claim 1 or 2, further comprising an overcoat layer between the transparent barrier layer and the adhesive layer. The film for a current collector sheet according to claim 1 or 2, having a water vapor permeability of 1×10 ⁻³ g/(m ² ·day) or more and 1 g/(m ² ·day) or less. The film for a current collector sheet according to claim 1 or 2, wherein the sealing layer contains a polyolefin resin. The film for a current collector sheet according to claim 5, wherein the polyolefin resin is a polyethylene resin. The film for a current collector sheet according to claim 1 or 2, wherein the sealing layer has a surface treatment portion on a surface opposite to the adhesive layer. A current collector sheet used for solar cells,
The film for a current collector sheet according to claim 1 or 2,
a wire disposed on the surface side of the sealing layer of the current collector sheet film;
A current collecting sheet having. The current collector sheet according to claim 8,
a solar cell element disposed on the side of the sealing layer of the current collector sheet and electrically connected to the wire;
A solar cell element with a current collecting sheet. A solar cell comprising, in this order, a transparent substrate, a first encapsulant, the solar cell element with a current collector sheet according to claim 9, a second encapsulant, and a back protection sheet. The solar cell according to claim 10, wherein the solar cell is a solar cell module having a plurality of solar cell elements with a current collector sheet. The solar cell according to claim 10, wherein the back protection sheet includes, in order from the second encapsulant side, an easily adhesive layer, a barrier film, and a base layer.

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