JP7356646B2 - Back protection sheet for solar cell module and solar cell module - Google Patents

Description

The present disclosure relates to a back protection sheet for a solar cell module and a solar cell module.

In recent years, with increasing awareness of environmental issues, solar cells have been attracting attention as a clean energy source. In general, a solar cell module constituting a solar cell has a structure in which a transparent front substrate, an encapsulant, a solar cell element, an encapsulant, and a back protection sheet are laminated in this order from the light-receiving surface side, so that sunlight It has the function of generating electricity by entering the battery element.

A back protection sheet used for a solar cell module is sometimes required to have a black appearance from the viewpoint of design. In order to make the appearance of the back protective sheet black, it is also possible to use ink containing carbon black. However, since carbon black absorbs near-infrared rays contained in sunlight, it increases the temperature of the solar cell module during use, and as a result, the power generation efficiency of the solar cell module decreases. For this reason, it is not necessarily preferable to use a back protection sheet containing carbon black in a solar cell module.

Therefore, in order to suppress the heat generation in the black back protective sheet, and further improve the power generation efficiency by allowing reflected light to enter the solar cell element, a black color containing organic pigments such as oxazine pigments that have infrared transmittance is used. A back protection sheet for a solar cell module, which comprises a white resin layer having an infrared reflective property, a back protection layer having weather resistance, etc., and is manufactured by bonding these multiple layers together with an adhesive or the like. has been developed (Patent Document 1).

Japanese Patent Application Publication No. 2012-216689

As described above, a black back protection sheet is generally produced by mixing a black pigment with a resin. However, especially when perylene pigments are used as black pigments, when the solar cell module including the back protection sheet is exposed to high temperatures, a phenomenon in which part of the perylene pigments migrates to surrounding layers (migration) tends to occur. It has been found. If such migration occurs, there is a risk that the design of the back protection sheet as a whole may be impaired. Furthermore, if the migration reaches the back side encapsulant layer side, there is a possibility that the output of the solar cell module will be reduced.

The present disclosure provides a back protection sheet for a solar cell module and a solar cell module that can suppress the effects of migration.

The back protection sheet for a solar cell module according to the present embodiment is a back protection sheet for a solar cell module, and includes a first layer that reflects near infrared rays, and a near infrared rays layer that is located closer to the light-receiving surface than the first layer. and a second layer that transmits visible light, a third layer that transmits near-infrared rays and visible light and that is located closer to the light-receiving surface than the second layer, and between the first layer and the second layer, or The coloring layer is located between the second layer and the third layer, contains a perylene pigment, and transmits near infrared rays.

In the back protection sheet for a solar cell module according to this embodiment, the colored layer may be a colored adhesive layer.

In the back protection sheet for a solar cell module according to the present embodiment, the colored layer is located between the second layer and the third layer, and is located near the first layer and the second layer. A fourth layer may be located that is transparent to infrared and visible light.

In the back protection sheet for a solar cell module according to the present embodiment, the colored layer is located between the first layer and the second layer, and is located near the second layer and the third layer. A fourth layer may be located that is transparent to infrared and visible light.

In the back protection sheet for a solar cell module according to this embodiment, the fourth layer may be a transparent adhesive layer.

In the back protection sheet for a solar cell module according to the present embodiment, the colored layer is located between the second layer and the third layer, and is located near the first layer and the second layer. Additional colored layers transparent to infrared radiation may be located.

In the back protection sheet for a solar cell module according to this embodiment, the additional colored layer may be a colored adhesive layer.

The solar cell module according to this embodiment includes the solar cell module back protection sheet according to this embodiment.

According to this embodiment, the influence of migration can be suppressed.

FIG. 1 is a schematic cross-sectional view showing the layer structure of a solar cell module according to an embodiment. FIG. 2 is a schematic cross-sectional view showing the layer structure of a back protection sheet for a solar cell module according to an embodiment. FIG. 3 is a schematic cross-sectional view showing a solar cell module according to one embodiment. FIG. 4 is a schematic cross-sectional view showing a state where migration has occurred in the back protection sheet for a solar cell module. FIG. 5 is a schematic cross-sectional view showing the layer structure of a back protection sheet for a solar cell module according to a modified example. FIG. 6 is a schematic cross-sectional view showing the layer structure of a back protection sheet for a solar cell module according to a modified example.

Hereinafter, one embodiment will be specifically described with reference to the drawings. Each figure shown below is shown schematically. Therefore, the size and shape of each part are appropriately exaggerated to facilitate understanding. Further, it is possible to implement the invention with appropriate changes within the scope of the technical concept. In each figure shown below, the same parts are given the same reference numerals, and some detailed explanations may be omitted. In addition, the numerical values such as dimensions and material names of each member described in this specification are examples of embodiments, and are not limited to these, and can be appropriately selected and used. In this specification, terms specifying shapes and geometrical conditions, such as terms such as parallel, perpendicular, and perpendicular, are not only meant strictly, but also include substantially the same state.

In addition, in this specification, the "light-receiving surface side" refers to the side where the surface on which sunlight enters the solar cell module is located, and specifically refers to the upper side of the paper in FIGS. 1 to 3. .

Hereinafter, the back protection sheet for a solar cell module (herein also simply referred to as "back protection sheet") according to the present embodiment will be described in detail. This embodiment is not limited to what is described below.

First, a solar cell module in which the back protection sheet for a solar cell module according to this embodiment is used will be described. FIG. 1 is a schematic cross-sectional view illustrating an example of the layer structure of a solar cell module.

As shown in FIG. 1, a solar cell module 10 constituting a solar cell includes a transparent front substrate 11, a front sealing material layer 12, and a solar cell element 13, which are laminated in order from the light-receiving surface side of incident light L1. , a back sealing material layer 14 and a back protection sheet 20. This solar cell module 10 is constructed by sequentially laminating a transparent front substrate 11, a front encapsulant layer 12, a solar cell element 13, a back encapsulant layer 14, and a back protection sheet 20, and integrating them by, for example, vacuum thermal lamination. It may also be produced by The lamination temperature at this time is preferably within the range of 130°C or higher and 190°C or lower. Moreover, the lamination time is preferably within the range of 5 minutes or more and 60 minutes or less, particularly preferably within the range of 8 minutes or more and 40 minutes or less. In this way, the solar cell module 10 can be manufactured by heating and press-molding each of the above-mentioned layers as an integral molded body. In this embodiment, a solar cell module 10 including a back protection sheet 20 in this manner is also provided.

[Overall structure of back protection sheet for solar cell module]
Next, the back protection sheet 20 according to this embodiment will be explained using FIG. 2. The back protection sheet 20 is used for the solar cell module 10 described above, and has a black appearance as a whole. Note that black includes not only colorless black but also dark gray, tinted black, and dark gray. Colored blacks and dark grays include, for example, reddish blacks and dark grays, yellowish blacks and dark grays, greenish blacks and dark grays, bluish blacks and dark grays, and purplish blacks and dark grays. , etc.

This back protection sheet 20 includes a first layer 21 that reflects near-infrared rays, a transparent second layer 22 that is located closer to the light-receiving surface than the first layer 21 and transmits near-infrared rays and visible rays, and A transparent third layer 23 is located closer to the light receiving surface than 22 and transmits near infrared rays and visible light. A transparent fourth layer 26 that transmits near infrared rays and visible light is located between the first layer 21 and the second layer 22. Further, a black layer 25 is located between the second layer 22 and the third layer 23.

In this case, the back protection sheet 20 is composed of five layers. That is, the fourth layer 26 is directly stacked on the first layer 21, and the second layer 22 is stacked directly on the fourth layer 26. Further, the black layer 25 is directly laminated on the second layer 22, and the third layer 23 is directly laminated on the black layer 25. Note that the first layer 21 is arranged on the outermost layer side (opposite the light-receiving surface) of the solar cell module 10. Further, the third layer 23 is arranged on the inner layer side of the solar cell module 10, that is, on the side of the back sealing material layer 14 (light-receiving surface side).

Next, each layer constituting the back protection sheet 20 will be explained.

[First layer]
The first layer 21 is made of, for example, a resin sheet containing a white pigment or a resin sheet on which a coating layer (a coating film or a printed film) containing a white pigment is formed, and may be a white resin layer that reflects near infrared rays. The first layer 21 may be a reflective layer that reflects near-infrared rays that have passed through the black layer 25, the second layer 22, and the fourth layer 26. The first layer 21 reflects near-infrared rays, thereby contributing to improving the power generation efficiency of the solar cell module 10. Note that white includes not only colorless white but also pale gray and tinted pale gray. In this specification, the term "resin sheet" is used as a name for a resin processed into a sheet shape, but this term is also used as a concept that also includes a resin film.

Examples of the resin sheet constituting the first layer 21 include fluororesins such as PTFE (polytetrafluoroethylene) and ETFE (tetrafluoroethylene/ethylene copolymer), poly(meth)acrylic resins, and PET (polyethylene terephthalate). ) and other polyester resin sheets can be preferably used. Alternatively, as the resin sheet constituting the first layer 21, a resin sheet of polyolefin resin, PBT (polybutylene terephthalate), PPE (polyphenyl ether), PEN (polyethylene naphthalate), etc. may be used. . In this embodiment, the first layer 21 is disposed on the outermost layer side (opposite the light-receiving surface) of the solar cell module 10, and is therefore required to have high weather resistance, barrier properties, and hydrolysis resistance. From this point of view, among the above, it is particularly preferable to use polyester resins typified by PET.

The first layer 21 has a function of reflecting near-infrared rays. For this purpose, it is preferable to use a white resin layer containing a white pigment with a particle size of 0.1 μm or more and 1.5 μm or less, and a white resin layer containing a white pigment with a particle size of 0.1 μm or more and 0.6 μm or less is preferably used. is more preferable. Further, in the first layer 21, it is preferable that white pigment particles having a particle size of 0.1 μm or more and 0.6 μm or less account for 80% by mass or more of all white pigment particles. By setting the particle size and distribution ratio of the white pigment within the above range, the white resin layer efficiently reflects near-infrared rays, so that the white pigment contributes to improving the power generation efficiency of the solar cell module. Reflecting near-infrared rays means, for example, that the average reflectance is 50% or more in the wavelength range of about 750 nm or more and 1200 nm or less. Note that the "average reflectance" is the average value obtained by extracting the corresponding wavelength region from the reflectance spectrum (reflectance for each wavelength). For example, the average reflectance in the wavelength range from 750 nm to 1200 nm can be determined by "(sum of reflectances of each wavelength)/(1200-750)".

A typical example of a white pigment with a particle size of 0.1 μm or more and 1.5 μm or less is titanium oxide, and it is preferable to use titanium oxide as the white pigment in this embodiment as well. Here, titanium oxide includes surface-treated titanium oxide. For example, in the case of titanium oxide, its manufacture can be performed as follows.

Hydrous titanium oxide is used as a raw material, and an aluminum compound of 0.1% to 0.5% by mass in terms of aluminum oxide and 0.1% to 0.5% by mass in terms of potassium carbonate are added to the titanium oxide content. It can be produced by adding the following potassium compounds and zinc compounds of 0.2% by mass or more and 1.0% by mass or less in terms of zinc oxide, followed by drying and roasting.

Examples of methods for manufacturing the first layer 21 include a method of forming a coat layer containing a white pigment on a resin sheet, and a method of kneading a white pigment into a resin sheet. All of them can be manufactured by conventionally known methods without any particular limitations.

When forming a coating layer (coating film or printing film) containing a white pigment on a resin sheet, the main component is a normal paint or ink vehicle, and the white pigment is added to this, and if necessary, , an ultraviolet absorber, a crosslinking agent, and other additives are optionally added to prepare a paint or ink composition, and then coated or printed on the surface of the base film using a conventional coating method or printing method. However, a coating film or a printed film thereof can be formed.

When kneading a white pigment into a resin sheet, the resin constituting the resin sheet is used as the main component, the white pigment is added to this, and if necessary, other additives are optionally added. A sheet can be produced by adjusting the composition, producing a film or sheet by a film forming method such as an extrusion method or a T-die method, and then kneading a white pigment into the film or sheet.

The thickness of the first layer 21 is preferably, for example, 25 μm or more and 200 μm or less, and more preferably 40 μm or more and 150 μm or less. By setting the thickness of the first layer 21 to 25 μm or more, the first layer 21 can easily reflect near-infrared rays, and the first layer 21 can have high weather resistance, barrier properties, and hydrolysis resistance. can. By setting the thickness of the first layer 21 to 200 μm or less, an increase in the manufacturing cost of the back protection sheet 20 can be suppressed.

[Fourth layer]
The fourth layer 26 may be an adhesive layer that mainly adheres the first layer 21 and the second layer 22 to each other, or may be a transparent adhesive layer. In this embodiment, the fourth layer 26 is a transparent adhesive applied to the upper surface of the first layer 21 (the surface on the light-receiving surface side) or the lower surface of the second layer 22 (the surface on the opposite side to the light-receiving surface). is formed by curing after lamination.

The fourth layer 26 is required to have sufficient adhesion and adhesive durability, and in addition to these characteristics, the fourth layer 26 of this embodiment is required to have a transparent appearance, that is, to resist visible light. It may also have the property of transmitting near infrared rays. In this embodiment, near-infrared rays refer to electromagnetic waves in a wavelength range of 750 nm or more and 2200 nm or less. Among these, the wavelength that particularly promotes heat storage is 1000 nm or more and 1500 nm or less. Note that "transmits near infrared rays" means that the fourth layer 26 has a total light transmittance of 80% or more at a wavelength of 750 nm or more and 1500 nm or less. Furthermore, "transmits visible light" means that the fourth layer 26 has a total light transmittance of 80% or more at a wavelength of 380 nm or more and 750 nm or less.

As the main component of the transparent adhesive composition used for the fourth layer 26, it is preferable to use a two-component type composition consisting of a main agent and a curing agent.

As the main component, for example, a urethane-based material is used, and the urethane-based material may contain carbonate or may not contain carbonate. When using one containing carbonate, the main component is preferably a polyurethane/polycarbonate diol system containing a mixture of polyurethane diol and aliphatic polycarbonate diol. The polyurethane diol and aliphatic polycarbonate diol constituting the main ingredient are both polyols having a hydroxyl group, and react with a curing agent having an isocyanate group to constitute an adhesive layer. In this embodiment, the adhesion and weather resistance of the adhesive layer are improved by using a mixture of a specific polyurethane diol and aliphatic polycarbonate diol in predetermined amounts as the main ingredient.

The curing agent has a polyisocyanate compound as its main component. A polyisocyanate compound is a compound having two or more isocyanate groups in one molecule, and this isocyanate group crosslinks the polyurethane diol compound by reacting with the hydroxyl group in the polyurethane diol compound as the main ingredient. Such a polyisocyanate compound is not particularly limited as long as it can crosslink the polyurethane diol compound as the main ingredient, but examples include polyurethane diisocyanate, hexamethylene diisocyanate (hereinafter referred to as "HDI"), Examples include isocyanurate-modified isophorone diisocyanate (hereinafter referred to as "nurate-modified IPDI"). Among these polyisocyanate compounds, a mixture of HDI and nurate-modified IPDI is preferred from the viewpoint of improving reactivity to hydroxyl groups.

It is preferable to add a solvent component to the above-mentioned transparent adhesive composition in order to obtain good applicability and handling suitability. Examples of such solvent components include, but are not limited to, carboxylic acid esters such as the above-mentioned ethyl acetate, methyl acetate, and methyl propionate. As already mentioned, the main component of the above adhesive is composed of a two-component component, the main component and the curing agent, but the solvent component used in the main component and the solvent component used in the curing agent are selected independently. , may be the same or different.

The fourth layer 26 can be formed by applying or laminating the transparent adhesive composition described above on the first layer 21 and/or the second layer 22 and drying and curing the composition. The coating method may be a roll coating method, a gravure roll coating method, a kiss coating method, or other coating methods, or a printing method. The coating amount of the transparent adhesive composition is preferably 3 g/m ² or more and 7 g/m ² or less. The thickness of the fourth layer 26 is preferably in the range of 2.0 μm or more and 10 μm or less, and more preferably in the range of 3.0 μm or more and 6.0 μm or less. By setting the thickness of the fourth layer 26 to 2.0 μm or more, the adhesive strength between the first layer 21 and the second layer 22 can be maintained. Further, by setting the thickness of the fourth layer 26 to 10 μm or less, near-infrared rays can be efficiently transmitted.

[Second layer]
The second layer 22 is interposed between the fourth layer 26 and the black layer 25. The second layer 22 has a function of increasing the strength of the back protection sheet 20, and also plays a role of alleviating the effects of migration of black pigment from the black layer 25, as will be described later. The second layer 22 may be a transparent intermediate layer that transmits near infrared rays and visible light. The second layer 22 may be transparent or translucent. From this point of view, it is preferable to use a polyolefin resin such as a polyethylene resin or a polypropylene resin, or a polyethylene terephthalate (PET) resin for the second layer 22. Among these resins, PET, which has particularly high transparency and excellent design, can be particularly preferably used. Note that "transmits near infrared rays" means that the second layer 22 has a total light transmittance of 80% or more at a wavelength of 750 nm or more and 1500 nm or less. Further, "transmits visible light" means that the second layer 22 has a total light transmittance of 80% or more at a wavelength of 380 nm or more and 750 nm or less.

The thickness of the second layer 22 is preferably, for example, 30 μm or more and 200 μm or less, and more preferably 100 μm or more and 150 μm or less. By setting the thickness of the second layer 22 to 30 μm or more, it is possible to suppress the black pigment in the black layer 25 from migrating to the first layer 21 side due to migration. By setting the thickness of the second layer 22 to 200 μm or less, near-infrared rays can be efficiently transmitted into the second layer 22.

[Black layer]
The black layer 25 may be an adhesive layer that mainly adheres the second layer 22 and the third layer 23 to each other, or may be a black adhesive layer. In this embodiment, the black layer 25 is a lamination of a black adhesive applied to the upper surface of the second layer 22 (the surface on the light-receiving surface side) or the lower surface of the third layer 23 (the surface on the opposite side to the light-receiving surface). It is formed by later curing.

The black layer 25 is required to have sufficient adhesion and adhesive durability, and in addition to these characteristics, the black layer 25 of this embodiment has a black appearance, that is, it absorbs visible light. In addition, it may have the property of transmitting near infrared rays.

As the black adhesive forming the black layer 25, an adhesive having a property of transmitting light having a wavelength of 750 nm or more and 1500 nm or less in a cured state is used. Note that "transmits light rays with a wavelength of 750 nm or more and 1500 nm or less" means that the black layer 25 transmits 15% or more of light rays with a wavelength of 750 nm or more and 1500 nm or less, preferably 50% or more, and more preferably 80% or more. means. Further, the transmittance of visible light and ultraviolet rays is not particularly specified as long as it is within the range colored black.

The black adhesive composition used for the black layer 25 preferably contains an organic black pigment as a main component, and from the viewpoint of coating properties and handling properties, the composition contains an appropriate solvent. As the main component of the black adhesive composition, it is preferable to use a two-component type consisting of a main agent and a curing agent.

As the main component and curing agent of the black adhesive composition, the same ones as the main component and curing agent of the transparent adhesive composition used for the fourth layer 26 described above can be used.

As a coloring material for making the black layer 25 black, a perylene-based black pigment is used. This is because perylene-based black pigments can easily provide a good black tint. As the perylene-based black pigment, for example, Lumogen Black K0087 (manufactured by BASF) can be used. By using a perylene-based black pigment, even if the amount of black pigment contained in the black layer 25 is suppressed, the color unevenness of the back protective sheet 20 as a whole (a phenomenon in which the black density becomes uneven within the surface) ) can be made less noticeable. Moreover, even if the amount of the black pigment contained in the black layer 25 is suppressed, the spectral transmittance in the visible light region of the back protection sheet 20 as a whole can be reduced and the blackness can be increased.

The proportion of the black pigment in the black layer 25 is preferably 5% by mass or more and less than 30% by mass, and more preferably 10% by mass or more and less than 25% by mass. By setting the proportion of the black pigment in the black layer 25 to 5% by mass or more, the color unevenness of the back protection sheet 20 as a whole can be made less noticeable, and the blackness of the back protection sheet 20 as a whole can be ensured. can do. Further, by setting the proportion of the black pigment in the black layer 25 to less than 30% by mass, the adhesive strength of the black layer 25 is less likely to decrease, and the long-term reliability of the back protection sheet 20 can be improved.

It is preferable to add a solvent component to the above-mentioned black adhesive composition in order to obtain good applicability and handling suitability. As such a solvent component, the same solvent component as that of the transparent adhesive composition used for the fourth layer 26 described above can be used.

The black layer 25 can be formed by applying or laminating the black adhesive composition described above on the first layer 21 and/or the second layer 22 and drying and curing the composition. The coating method may be a roll coating method, a gravure roll coating method, a kiss coating method, or other coating methods, or a printing method. The coating amount of the black adhesive composition is preferably 3 g/m ² or more and 7 g/m ² or less. The thickness of the black layer 25 is preferably in the range of 2.0 μm or more and 10 μm or less, and more preferably in the range of 3.0 μm or more and 6.0 μm or less. By setting the thickness of the black layer 25 to 2.0 μm or more, the adhesive strength between the first layer 21 and the second layer 22 can be maintained. Further, by setting the thickness of the black layer 25 to 10 μm or less, near-infrared rays can be efficiently transmitted.

[Third layer]
The third layer 23 has a function of improving the adhesion between the back surface protective sheet 20 and the back sealing material layer 14 using polyolefin such as ethylene-vinyl acetate alcohol copolymer resin (EVA resin) or polyethylene. You may do so. Furthermore, the third layer 23 may be a transparent adhesive layer. The third layer 23 may be transparent or translucent so as to transmit the near infrared rays reflected by the first layer 21, or may be transparent or translucent so as to transmit visible light for aesthetic reasons. From this point of view, the third layer 23 is made of polyethylene resin such as low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), etc. , polyolefin resin such as polypropylene resin, polyethylene terephthalate (PET), etc. are preferably used. Among these resins, low density polyethylene (LDPE) can be particularly preferably used. Note that "transmits near infrared rays" means that the third layer 23 has a total light transmittance of 80% or more at a wavelength of 750 nm or more and 1500 nm or less. Further, "transmits visible light" means that the third layer 23 has a total light transmittance of 80% or more in the wavelength range of 380 nm or more and 750 nm or less. Note that the thickness of the third layer 23 is preferably, for example, 30 μm or more and 120 μm or less, and more preferably 40 μm or more and 80 μm or less.

[Method for manufacturing back protection sheet for solar cell module]
The back protection sheet 20 has a fourth layer 26 between the first layer 21 and the second layer 22, a black layer 25 between the second layer 22 and the third layer 23, and these layers are dry laminated. It can be manufactured by processing.

[Operation of this embodiment]
Next, the operation of this embodiment having such a configuration will be explained.

As shown in FIG. 1, in the solar cell module 10 according to the present embodiment, incident light L1 enters from the light receiving surface side, and a part of this incident light L1 is transmitted to the transparent front substrate 11 and the front sealing material layer 12. The light passes through the solar cell element 13 one after another and reaches the solar cell element 13, where the solar cell element 13 generates power.

On the other hand, a part of the incident light L1 does not directly reach the solar cell element 13. In particular, as shown in FIG. 3, sunlight (incident light L2) that has not been absorbed by the solar cell elements 13 enters the back protection sheet 20 from the third layer 23 side. Most of the near-infrared rays contained in the incident light L2 pass through the third layer 23, the black layer 25, the second layer 22, and the fourth layer 26 without being absorbed, and thus reach the first layer 21. On the other hand, since the first layer 21 reflects near-infrared rays, most of the near-infrared rays that reach the first layer 21 return to the fourth layer 26, second layer 22, black layer 25, and third layer 23. It is reflected like this. The reflected near-infrared rays pass through the fourth layer 26, the second layer 22, the black layer 25, and the third layer 23, are further reflected, and are absorbed by the solar cell element 13. Since the fourth layer 26, the second layer 22, the black layer 25, and the third layer 23 do not absorb near-infrared rays, the near-infrared rays are absorbed by the fourth layer 26, the second layer 22, the black layer 25, and the third layer 23. A rise in temperature of the solar cell module 10 is suppressed. As a result, it is possible to prevent a decrease in power generation efficiency due to a rise in temperature of the solar cell module 10. Further, by using the back protection sheet 20, the amount of near infrared rays absorbed by the solar cell element 13 increases. As a result, the power generation efficiency of the solar cell module 10 can be improved.

Here, since most of the encapsulants for the solar cell module 10 are generally transparent or semi-transparent, when the solar cell module 10 is viewed from the transparent front substrate 11 side, the gaps where the solar cell elements 13 are not placed are visible. As for the part, the color of the black layer 25 is visible through the third layer 23 and the second layer 22. Furthermore, the surface of the solar cell element 13 is often black. In particular, the surface of most products of thin-film solar cell elements, whose demand has been increasing in recent years, is black. In the back protection sheet 20 according to the present embodiment, since the black layer 25 is black, the appearance of many solar cell modules 10, especially thin-film solar cell modules 10 equipped with thin-film solar cell elements, may be affected by color unevenness. It is possible to unify the color to black without any blemishes, which is preferable in terms of design.

By the way, while using such a solar cell module 10, the solar cell module 10 may be heated by direct sunlight or the like, and the back protection sheet 20 may locally reach a high temperature (for example, 100° C. or higher). In particular, when a perylene-based black pigment is used, a phenomenon (migration) in which the black pigment contained in the black layer 25 migrates to other adjacent layers is likely to occur when the back protection sheet 20 reaches a high temperature. It has been found.

In contrast, in this embodiment, the black layer 25 is sandwiched between the second layer 22 that transmits visible light and the third layer 23 that transmits visible light. Therefore, even if migration occurs in the black pigment of the black layer 25, the black pigment that has migrated into the second layer 22 and the third layer 23 will be inside the second layer 22 and the third layer 23. (See Figure 4). Therefore, the black pigment is prevented from reaching the back sealing material layer 14 (on the light-receiving surface side) and the first layer 21 (on the opposite side to the light-receiving surface). In this case, since the second layer 22 and the third layer 23 each transmit visible light, when viewed from the light-receiving surface side, the black pigment that has migrated not only into the black layer 25 but also into the third layer 23 and the second layer 22 The color can also be visually recognized. This suppresses changes in the black color of the appearance of the back protection sheet 20, and prevents the overall design of the back protection sheet 20 from deteriorating. Further, since the black pigment does not pass through the third layer 23 and reach the back sealing material layer 14, a decrease in the output of the solar cell module 10 due to the influence of the black pigment can be suppressed.

As explained above, according to the present embodiment, the black layer 25 containing a perylene pigment is disposed between the second layer 22 that transmits visible light and the third layer 23 that transmits visible light. There is. Thereby, even if migration occurs in the black pigment of the black layer 25, the influence of migration can be minimized, and changes in the overall color of the back protection sheet 20 can be suppressed.

Further, according to this embodiment, the black layer 25 is a black adhesive layer. Thereby, the second layer 22 and the third layer 23 can be bonded to each other using the black layer 25.

Further, according to this embodiment, the fourth layer 26 that transmits near infrared rays and visible light is located between the first layer 21 and the second layer 22. Thereby, near-infrared rays can be transmitted toward the first layer 21, and the near-infrared rays can be reflected more efficiently by the first layer 21, contributing to an improvement in the power generation efficiency of the solar cell module 10. In addition, even if the black pigment reaches the fourth layer 26 due to migration, the color of the black pigment that has migrated into the fourth layer 26 can be seen from the light-receiving surface side, so the back surface can be protected. Changes in the appearance of the sheet 20 can be suppressed.

Further, according to this embodiment, the fourth layer 26 is a transparent adhesive layer. Thereby, the first layer 21 and the second layer 22 can be bonded to each other using the fourth layer 26.

[Modified example of back protection sheet for solar cell module]
In the above, the case where the second layer 22 is directly interposed between the fourth layer 26 and the black layer 25 has been described as an example, but the present invention is not limited to this. For example, in addition to the second layer 22, another intermediate layer may be interposed between the fourth layer 26 and the black layer 25. In this case, the other intermediate layer is preferably one that transmits near infrared rays and visible light.

Further, in the above description, an example has been described in which the black layer 25 is located between the second layer 22 and the third layer 23, but the present invention is not limited to this. As shown in FIG. 5, the black layer 25 may be located between the first layer 21 and the second layer 22. In this case, the fourth layer 26 may be located between the second layer 22 and the third layer 23. In this way, by positioning the black layer 25 between the first layer 21 and the second layer 22, migration of the black pigment to the back sealing material layer 14 side due to migration can be more reliably suppressed. I can do it. Note that in FIG. 5, another intermediate layer may be interposed between the black layer 25 and the first layer 21 in order to suppress migration toward the first layer 21 side. In this case, the other intermediate layer is preferably one that transmits near infrared rays and visible light.

Further, in the above description, the case where the back protection sheet 20 includes one black layer (black layer 25) has been described as an example, but the present invention is not limited to this. The back protection sheet 20 may include two black layers. For example, as shown in FIG. 6, an additional black layer 27 may be placed between the first layer 21 and the second layer 22 instead of the fourth layer 26. In this case, the additional black layer 27 may be a black adhesive layer that adheres the first layer 21 and the second layer 22 to each other. Additionally, the additional black layer 27 may have the same configuration as the black layer 25. As described above, since the back protection sheet 20 has two black layers (the black layer 25 and the additional black layer 27), color unevenness may occur in each of the black layer 25 and the additional black layer 27. However, by overlapping two layers, the black layer 25 and the additional black layer 27, it is possible to reduce color unevenness of the back protection sheet 20 as a whole and provide a black back protection sheet 20 with good design. can. Furthermore, even when the amount of black pigment contained in each of the black layer 25 and the additional black layer 27 is kept low, a sufficiently deep black color can be achieved for the back protection sheet 20 as a whole. . When the amount of the black pigment contained in each of the black layer 25 and the additional black layer 27 is kept low, diffusion due to concentration gradient becomes less likely to occur, so migration of the black pigment can be suppressed. In addition, in FIG. 6, in order to suppress migration toward the first layer 21 side, another intermediate layer may be interposed between the additional black layer 27 and the first layer 21. In this case, the other intermediate layer is preferably one that transmits near infrared rays and visible light.

Further, in the above description, the fourth layer 26, the black layer 25, and the additional black layer 27 are each an adhesive layer, but the present invention is not limited to this. At least one of the fourth layer 26, the black layer 25, and the additional black layer 27 may be a non-adhesive layer that is not an adhesive layer. In this case, the non-adhesive layer may include, for example, a film of polyolefin resin such as polyethylene resin or polypropylene resin, or polyethylene terephthalate (PET) resin. When the black layer 25 or the additional black layer 27 is a non-adhesive layer, the black layer 25 or the additional black layer 27 may be a black resin layer obtained by impregnating the above film with a black pigment. Further, in the above description, a black layer in which a black pigment is mixed has been described as an example, but the present invention is not limited to this. One or more types of pigments of colors other than black may be used to obtain black or any color other than black.

Further, in the above description, the case where a black layer (the black layer 25 and the additional black layer 27) is used has been described as an example, but the present invention is not limited to this. A colored layer may be used instead of the black layer. As this colored layer, a colored adhesive layer (colored adhesive layer) may be used. The colored layer is not limited to black, and may be, for example, a dark color close to black. The dark color close to black may be, for example, bluish-purple, reddish-purple, or gray. Alternatively, the colored layer is not limited to a dark color, and may be colored in any desired color to impart design to the back protection sheet 20.

[Example]
Next, specific examples of this embodiment will be described.

(Creation of back protection sheet)
Back protection sheets of Examples and Comparative Examples were each produced as follows.

(Example)
A back protection sheet having the configuration shown in FIG. 2 was produced. In this case, first, a first layer, a second layer, and a third layer were prepared. As the first layer, a hydrolysis-resistant white PET film containing titanium oxide and having a thickness of 50 μm was used. A transparent PET film with a thickness of 125 μm was used as the second layer. Further, as the third layer, a transparent LDPE film with a thickness of 60 μm was used. Next, a transparent fourth layer is provided between the first layer and the second layer, a black layer is provided between the second layer and the third layer, and these layers are dry laminated to form the back side. A protective sheet was made. The black layer used was made of a urethane-based resin containing a perylene-based black pigment. The proportion of the perylene black pigment in the black layer was 20% by mass. The fourth layer used was the same as the black layer except that the black pigment was removed from the black layer. The thickness of the fourth layer and the black layer was each 4.5 μm.

(Comparative example)
A back protection sheet of a comparative example was produced in the same manner as in the example except that the second layer and the fourth layer were not provided. That is, the back protection sheet of the comparative example had a three-layer structure including a first layer, a black layer on the first layer, and a third layer on the black layer.

Next, the back protection sheets of Examples and Comparative Examples were each heated at 150° C. for 48 hours to cause migration in the black pigment contained in the black layer.

Thereafter, the first layer was observed from the opposite direction to the light-receiving surface. As a result, it was observed that the first layer of the back protection sheet of the example maintained its original color (white). On the other hand, in the back protection sheet of the comparative example, the black pigment moved into the first layer due to migration, so the first layer was discolored to light purple.

It is also possible to appropriately combine the plurality of components disclosed in the above embodiments and modifications as necessary. Alternatively, some components may be deleted from all the components shown in the above embodiments and modifications.

10 Solar cell module 11 Transparent front substrate 12 Front encapsulant layer 13 Solar cell element 14 Rear encapsulant layer 20 Back protection sheet 21 First layer 22 Second layer 23 Third layer 25 Black layer 26 Fourth layer 27 Additional black layer

Claims (4)

A back protection sheet for a solar cell module,
a first layer that is a white resin layer that reflects near-infrared rays;
a second layer that is located closer to the light-receiving surface than the first layer and transmits near-infrared rays and visible light;
a third layer that is located closer to the light-receiving surface than the second layer and transmits near-infrared rays and visible light;
a colored layer located between the second layer and the third layer, containing a perylene pigment and transmitting near infrared rays;
a fourth layer located between the first layer and the second layer and transmitting near infrared rays and visible light ;
The fourth layer is a back protection sheet for a solar cell module, which is formed directly on the first layer . The back protection sheet for a solar cell module according to claim 1, wherein the colored layer is a colored adhesive layer. The back protection sheet for a solar cell module according to claim 1 or 2, wherein the fourth layer is a transparent adhesive layer. A solar cell module comprising the back protection sheet for a solar cell module according to any one of claims 1 to 3.