JP2012015404A - Solar cell backside sheet and solar cell module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell backside sheet capable of maintaining an effect of improvement in light use efficiency over a long period of time in a solar cell module capable of improving the light use efficiency by controlling a reflection angle, and to provide the solar cell module using the solar cell backside sheet.SOLUTION: A solar cell backside sheet 14 is disposed on a back side of a solar cell module 10 disposed with a front plate 11 on a front side of a filling layer 13 in which a solar battery cell 12 is sealed. A translucent insulation layer 141, an uneven structure layer 142, a light-reflecting metal layer 144, an adhesive layer 145 and a weatherproof layer 146 are at least laminated in this order from a front side of the solar cell backside sheet 14. Also, a barrier layer 143 is laminated on the uneven structure layer 142 side or/and the weatherproof layer 146 side against the light-reflecting metal layer 144. The uneven structure layer is formed by an ultraviolet curing resin or a thermosetting resin with a glass transition temperature of 95°C or more.

Description

  The present invention relates to a solar cell back sheet disposed on the back surface of a solar cell module, and a solar cell module using the solar cell back sheet. The solar battery back sheet makes it possible to effectively utilize light that is originally incident on the back sheet but does not enter the solar battery cell.

  In recent years, the widespread use of solar panels has increased greatly, from relatively small ones mounted on small electronic devices such as calculators to large areas used for solar panels installed in houses for home use and large-scale power generation facilities The use of solar cell power generation systems and power supplies for artificial satellites has been promoted in various fields (see, for example, Patent Document 1).

  This solar cell converts incident light energy into electrical energy, and main ones of the solar cells are classified into crystalline silicon type, amorphous silicon type, organic compound type, etc., depending on the type of material used. Among these, most of those currently on the market are crystalline silicon solar cells, which are further classified into single crystal type and polycrystalline type.

The single-crystal silicon solar cell has the advantage that it is easy to increase the efficiency because the quality of the substrate is good, but has the disadvantage that the manufacturing cost of the substrate is high. On the other hand, although the polycrystalline silicon solar cell has the disadvantage that it is difficult to increase the efficiency because the quality of the substrate is inferior, it has the advantage that it can be manufactured at a low cost, and is currently the mainstream.
Various studies have been conducted on the improvement of the efficiency of such polycrystalline silicon solar cells.

  As an example, a texture structure is formed on the surface of a silicon substrate used in a solar cell, thereby reducing the reflection of sunlight on the surface of the silicon substrate and improving the conversion efficiency.

  In single crystal silicon, the reflection of sunlight is reduced by forming fine pyramids or inverted pyramids by anisotropic etching such as an alkaline solution. This anisotropic etching utilizes the fact that the etching rate of single crystal silicon differs between the Si (100) crystal orientation plane and the Si (111) crystal orientation plane. (For example, refer to Patent Document 2).

  However, when such anisotropic etching is applied to polycrystalline silicon, the etching with alkaline aqueous solution depends on the crystal plane orientation, so the pyramid structure in polycrystalline silicon cannot be formed uniformly, and the entire silicon substrate There is a problem that the reflectance cannot be effectively reduced.

  In order to solve such problems, as a method of forming a texture on a polycrystalline silicon substrate, a method of forming fine protrusions on the surface of the polycrystalline silicon substrate by reactive ion etching has been proposed. (For example, see Patent Document 3). According to this technique, the fine protrusions are uniformly formed without being influenced by the surface orientation of the irregular crystal in the polycrystalline silicon, so that the reflectance is more effective particularly in the solar cell using the polycrystalline silicon. Can be reduced.

  It is also known that the conversion efficiency can be further improved by combining a surface antireflection film. That is, since crystalline silicon has a large refractive index of 6.00 to 3.50 in the wavelength region of 400 nm to 1100 nm, there is a reflection loss of about 54% in the short wavelength region and about 34% in the long wavelength region. In order to reduce this reflection loss, a surface antireflection film can be formed from transparent materials having different refractive indexes, thereby improving the conversion efficiency.

  Further, studies have been made to increase the light receiving area by miniaturizing the electrodes formed on the silicon substrate and improve the conversion efficiency by taking in a large amount of sunlight (for example, see Patent Document 4).

  Due to the progress of the high efficiency technology as described above, conversion efficiency of about 18% has been achieved at the research level recently even in polycrystalline silicon solar cells, and the theoretical limit of conversion efficiency in polycrystalline silicon solar cells (20 ~ 30%).

  Therefore, among the sunlight incident from the front surface of the solar cell module in order to increase the light use efficiency, the sunlight incident on the back sheet without being incident on the solar cell that performs energy conversion in the solar cell module is reused. Attempts have been made.

  Here, in a general crystalline silicon solar cell module, gaps are formed between a plurality of solar cells in the solar cell module in order to reduce leakage current. Therefore, there is sunlight that does not enter the solar battery cell but enters the solar battery back sheet, and if the sunlight can be reused, the light utilization efficiency can be improved.

  Therefore, a solar battery back sheet provided with a reflective material is arranged, and the light utilization efficiency is improved by re-entering the solar battery cell by reflecting sunlight incident on the back sheet through the gap between the solar battery cells. It has been.

  As the reflecting material, it is possible to use a reflecting material that scatters and reflects light, such as a resin material mixed with a white pigment or a metal material with a matte surface treatment. Moreover, it is possible to further improve the light utilization efficiency by making the surface of the reflecting material have an uneven structure. In particular, when the surface of the reflecting material has a concavo-convex structure, it is possible to improve the light utilization efficiency by using a metal material such as aluminum (see, for example, Patent Document 5).

JP 2001-295437 A JP 62-35582 A Japanese Patent Publication No. 60-27195 JP 2000-332279 A Japanese Patent Laid-Open No. 10-284747

  A solar cell back sheet used for a solar cell is required to have long-term reliability of weather resistance, electrical insulation, and mechanical strength. That is, since it is used outdoors for a long time, it is required that there is no deterioration in weather resistance under direct sunlight, no deterioration in characteristics due to heat, and no deterioration or peeling due to moisture penetration.

  In order to confirm such long-term reliability, various resistance tests are performed. As one of them, it is necessary to conduct a high-temperature and high-humidity test at a temperature of 85 ° C. and a humidity of 85% for a minimum of 1000 hours. It was a problem.

  This invention is made | formed in view of such a subject, It is possible to improve the utilization efficiency of light, and the solar cell backsheet which is excellent in long-term reliability, and a solar cell module using the same The purpose is to provide.

In order to solve the above-mentioned problems, the invention described in claim 1 of the present invention is a solar cell module in which a translucent front plate is laminated on the front side of a filling layer in which solar cells are sealed. A solar cell back sheet disposed on the back side,
At least a translucent insulating layer, an uneven structure layer, a light-reflective metal layer supported by the uneven structure layer to form an uneven structure, an adhesive layer, and a weather resistant layer are laminated in order from the front side.
The uneven structure layer is formed of an ultraviolet curable resin or a thermosetting resin having a glass transition temperature of 95 ° C. or higher.

  According to the solar cell backsheet having such characteristics, it is possible to maintain the effect of improving the light utilization efficiency over a long period of time without deterioration or deformation of the resin even in a high temperature environment.

  Next, the invention described in claim 2 is the structure described in claim 1, wherein the light reflective metal layer is provided on at least one side of the concavo-convex structure layer side and the adhesive layer side with respect to the light reflective metal layer. A barrier layer for preventing corrosion of the layer is provided.

  According to the solar cell back sheet having such a feature, even in a high temperature and high humidity environment, the barrier layer prevents the light reflective metal layer from corroding. The effect of improving the light use efficiency by reflecting in a specific direction and re-entering the solar battery cell can be maintained for a long period of time.

Next, the invention described in claim 3 is characterized in that the barrier layer is formed in contact with the light-reflecting metal layer in the configuration described in claim 1 or claim 2. is there.
Thereby, the barrier layer can enhance the effect of preventing the light reflective metal layer from being deteriorated.

Next, the invention described in claim 4 is characterized in that, in the configuration described in any one of claims 1 to 3, the barrier layer is made of a valve metal or an alloy containing the valve metal. To do.
The valve metal refers to a metal that forms an oxide film on its surface and becomes passive. Since such a valve metal or an alloy containing the valve metal has an excellent corrosion resistance, it is possible to prevent corrosion of the light reflective metal layer for a long period of time by adopting it as a barrier layer.

Next, the invention described in claim 5 is characterized in that the barrier layer is made of an inorganic oxide with respect to the structure described in any one of claims 1 to 3.
Inorganic oxides are known to exhibit excellent water vapor barrier properties and gas barrier properties. By adopting such an inorganic oxide as a barrier layer, it becomes possible to prevent deterioration of the light reflective metal layer over a long period of time.

Next, the invention described in claim 6 is different from the configuration described in any one of claims 1 to 5 in that the concavo-convex structure has a substantially prism shape, a substantially polygonal pyramid shape, or the reverse of these shapes. Any one of the mold shapes is arranged in plural.
This makes it possible to improve the light utilization efficiency by reliably making the light incident from the front side re-enter the solar battery cell.

Next, in the invention described in claim 7, with respect to the configuration described in any one of claims 1 to 6, each top of the concavo-convex structure has a curvature, and the top of the concavo-convex structure When the pitch of Pt is Pt, the curvature radius r of the top is set in the range of 0.01 Pt or more and 0.1 Pt or less.
As a result, it is possible to prevent discharge breakdown due to charge concentration, which is likely to occur due to the presence of the metal convex portion, and to obtain sufficient electrical insulation.

  Next, according to an eighth aspect of the present invention, the aspect ratio of the bottom to the height of the unit structure of the concavo-convex structure is 0.15 with respect to the configuration described in any one of the first to seventh aspects. It is characterized by being set in the range of 0.35 or less.

  Here, when the aspect ratio of the unit structure of the concavo-convex structure is larger than 0.35, the moldability when forming the concavo-convex structure is lowered. On the other hand, if the aspect ratio is smaller than 0.15, the effect of improving the light utilization efficiency is weakened. Considering this point, in the present invention, since the aspect ratio is set in the above range, it is possible to improve the light utilization efficiency while maintaining the formability at the time of forming the concavo-convex structure.

  Next, in the invention described in claim 9, with respect to the configuration described in any one of claims 1 to 8, the top pitch of the concavo-convex structure is set in a range of 10 μm to 30 μm. It is characterized by being.

  When the pitch is larger than 30 μm, the height of the structure increases as the pitch increases, and therefore, problems such as easy entry of bubbles are likely to occur when pasting together via a weather resistant layer and an adhesive layer. Absent. In addition, it is necessary to increase the thickness of the adhesive layer, which makes it difficult to form and causes a high cost. On the other hand, when the pitch is less than 10 μm, diffraction of light may occur when light is reflected by the concavo-convex structure. Since the diffracted light becomes light that is spread by spectroscopy, it is difficult to control, and it is not preferable for reflection in a specific direction. Furthermore, it is not preferable because the time for cutting the mold is long, the tact is reduced, and the production efficiency is deteriorated. Based on this, in the present invention, the pitch is set in the range of 10 μm or more and 30 μm or less, so the above inconvenience can be solved.

Next, the invention described in claim 10 is characterized in that the solar cell back sheet according to any one of claims 1 to 9 is arranged on the back surface of the solar cell module. is there.
According to the solar cell module having such a feature, the resin is deteriorated and deformed even in a high temperature environment because the concavo-convex structure is formed of an ultraviolet curable resin or a thermosetting resin having a glass transition temperature of 95 ° C. or higher. Therefore, the effect of improving the light utilization efficiency can be maintained for a long time.

  Moreover, by further including a barrier layer, it is possible to prevent corrosion of the light reflective metal layer in a high temperature and high humidity environment, and reflects light incident from the front side to the solar cell back sheet toward a specific direction, The effect of improving the light utilization efficiency by re-entering the solar cell can be maintained for a long time.

According to the solar cell back sheet and the solar cell module according to the present invention, the uneven structure layer is formed of an ultraviolet curable resin or a thermosetting resin having a glass transition temperature of 95 ° C. or higher, thereby deteriorating the resin in a high temperature environment. And prevent deformation.
Moreover, the solar cell backsheet containing the light-reflective metal layer in which the concavo-convex structure is formed further prevents the light-reflective metal layer from corroding in a high-temperature and high-humidity environment by further including a barrier layer. As a result, the light incident from the front side with respect to the solar cell back sheet is reflected in a specific direction and re-entered into the solar cell, thereby improving the light use efficiency in the solar cell module and increasing the amount of power generation. The effect can be sustained over a long period of time.

It is a longitudinal cross-sectional view which shows schematic structure of the solar cell module which concerns on embodiment based on this invention. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet which concerns on embodiment based on this invention. It is a longitudinal cross-sectional view which shows schematic structure of the solar cell module containing an electrode. It is a perspective view which shows the example of an uneven structure. It is a perspective view which shows the example of an uneven structure. It is a longitudinal cross-sectional view which shows the example of the unit structure of an uneven structure. It is a figure explaining a mode when discharge arises in a cathode from a light reflective uneven structure. It is a longitudinal cross-sectional view explaining the effect | action of the back surface sheet in a solar cell module. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet which concerns on embodiment based on this invention. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet of a 1st structural example. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet of a 2nd structural example. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet of a 3rd structural example. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet of a 4th structural example. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet of a comparative example. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet which concerns on embodiment based on this invention.

Hereinafter, embodiments of a solar cell back sheet and a solar cell module according to the present invention will be described with reference to the drawings.
“First Embodiment”
(Solar cell module)
FIG. 1 is a longitudinal sectional view showing a schematic configuration of the solar cell module of the embodiment.

  As shown in FIG. 1, the solar cell module 1 of the present embodiment includes, from the light source side (front side), a front plate 11, a filling layer 13 in which solar cells 12 are sealed, and a solar cell back sheet 14 ( Hereinafter, it is also simply referred to as a back sheet 14). The solar cell module 1 generates power by receiving light from the light source L. In addition, as the light source L, the artificial illumination of the sun or a room lamp is normally employ | adopted.

  At this time, the solar cell module 1 is integrally formed by laminating the front plate 11, the filling layer 13 in which the solar cells 12 are sealed, and the back sheet 14 by heat laminating with a vacuum laminator. ing.

(Front plate)
The front plate 11 is disposed on the forefront of the solar cell module 1 and protects the solar cells 12 from impact, dirt, moisture intrusion, and the like. The front plate 11 has a plate shape made of a transparent material having a high transmittance.

  As shown in FIG. 1, among the light emitted from the light source L, the light H0 incident perpendicularly to the incident surface 110 of the front plate 11 is incident on the front plate 11 and then passes through the front plate 11 to be filled. 13 is incident. Here, the light H0 incident perpendicularly to the incident surface 110 indicates the light H0 incident on the front plate 11 in parallel with the normal line NG, that is, the light H0 incident on the solar cell module 1. Further, the normal line NG of the incident surface 110 is, for example, a direction parallel to the normal line N of the plane P in a state where the front plate 11 is placed on the plane P parallel to the horizontal plane.

  The front plate 11 is made of glass such as tempered glass or sapphire glass, or a resin sheet such as PC (polycarbonate) or PEN (polyethylene naphthalate). The front plate 11 has a thickness of about 3 to 5 mm for tempered glass and about 5 mm for a resin sheet.

(Filled bed)
The light emitted through the front plate 11 enters the filling layer 13.
The filling layer 13 has a sheet shape with a thickness of about 0.4 to 1 mm, and a plurality of solar cells 12 are sealed and fixed therein. The light H0 incident on the front plate 11 passes through the filling layer 13 and becomes light H1 incident on the solar battery cell 12, and a part of the light H1 passes through the filling layer 13 and enters the back sheet 14. It becomes.

  The filling layer 13 is made of a material having a high light transmittance in order to transmit the incident light H0, and a material having durability, such as weather resistance, high temperature resistance, high humidity resistance, weather resistance, and electrical insulation. Is preferred. As a material that satisfies this condition, for example, a thermoplastic synthetic resin material mainly composed of EVA (ethylene vinyl acetate copolymer) or PVB (polyvinyl butyral) having a vinyl acetate content of 20 to 30% is used. Is done.

(Solar cell)
The solar battery cell 12 has a function of converting light incident on the light receiving surface J into electricity by photoelectric effect. There are many types of solar cells 12 such as a single crystal silicon type, a polycrystalline silicon type, an amorphous silicon type, and a CISG (Cu • In • Ga • Se compound) thin film type. Alternatively, a description will be given using a polycrystalline silicon solar cell as an example.
A plurality of solar cells 12 are connected by electrodes (not shown in FIG. 1; see FIG. 3) to form a module.

  In the present embodiment, the light H <b> 1 that has entered the solar battery cell 12 from the filling layer 13 is converted into electricity by the solar battery cell 12. In general, light obliquely incident on the incident surface 110 has a higher ratio of reflection on the incident surface 110 and less light incident on the solar cells 12 than the vertically incident light H0. That is, there is little light available for power generation. Therefore, power generation can be performed most efficiently when the incident light H0 is perpendicularly incident on the incident surface 110.

(Back sheet)
FIG. 2 is a longitudinal sectional view illustrating a schematic configuration of the back sheet 14 of the embodiment. The back sheet 14 has a function of reflecting light transmitted through the solar battery cell 12 itself or light H <b> 1 transmitted through the filling layer 13 without entering the solar battery cell 12.
As shown in FIG. 2, the back sheet 14 has a translucent insulating layer 141, a concavo-convex structure layer 142, a barrier layer 143, a light reflective metal layer 144, an adhesive layer 145, and a weather resistant layer 146 from the front side (light source side). Are laminated.

(Translucent insulating layer)
The translucent insulating layer 141 is disposed on the front side of the back sheet 14 and is made of a material having electrical insulation.
Here, one of the important performances required for the back sheet 14 is electrical insulation. This electrical insulation is an indispensable performance for preventing a short circuit or leakage during long-term use since the solar cell module 1 includes electrodes therein. Moreover, in the solar cell module 1, it is calculated | required that especially the surface by the side of the photovoltaic cell 12 is electrically insulating.

The electrical insulation will be described below with reference to FIG.
Note that FIG. 3C illustrates an example in which the light-transmitting insulating layer 141 also serves as the uneven structure layer 142.
FIG. 3A shows a configuration example of the solar cell module 1. The solar battery cell 12 is connected to an electrode 22c for taking out the generated electric power. Usually, the solar cell 12 is located near the center of the filling layer 13 and is away from the light-reflective metal layer 144 of the back sheet 14, so that current leakage due to short-circuiting of the electrode 22c does not occur.

However, since the solar battery cell is sealed with a softened filler, the solar battery cell is disposed when the light-reflecting metal layer 144 is disposed close to the solar battery cell 12 as shown in FIG. 12 and the light-reflective metal layer 144 may come into contact with each other. In this case, the electrode 22c is short-circuited through the light reflective metal layer 144, and the current leaks.
In order to prevent this short circuit, the above-mentioned short circuit can be prevented by disposing the translucent insulating layer 141 on the front side of the light reflective metal layer 144 as shown in FIG.

  When the thickness of the light-transmitting insulating layer 141 is insufficient, as shown in FIG. 3C, the insulating layer 141 breaks down, and a discharge d occurs between the electrode 22c and the light-reflecting metal layer 144. Current leakage occurs.

  One of the numerical standards indicating the electrical insulation is a dielectric breakdown voltage. This breakdown voltage is an index that the insulation state is broken when a voltage higher than the breakdown voltage is applied, and it can be said that a higher breakdown voltage is more electrically stable.

For example, according to Reference 1 (“Photovoltaic power generation system constituent material” (Industry Research Committee)), the approximate numerical values of dielectric breakdown voltages (kV) of various plastic films for electrical insulation (25 μm) are as follows. .
PET (polyethylene terephthalate): 6.5,
PEN (polyethylene naphthalate): 7.5,
PVC (stretched hard vinyl chloride): 4.0,
PC (polycarbonate): 5.0,
OPP (oriented polypropylene): 6.0,
PE (polyethylene): 4.0,
TAC (triacetate): 3.0
PI (polyimide): 7.0
All of these satisfy the dielectric breakdown voltage as an insulating material (reference JISC2318 / biaxially oriented polyethylene terephthalate film for electricity).

The dielectric breakdown voltage of a DuPont tedlar, which is a typical PVF (poly, fluoride, vinyl) product, is about 3.0 kV.
As one of the insulation performances of solar cell modules, it is determined that there is no abnormality such as dielectric breakdown even when a DC voltage of twice the maximum system voltage +1000 V is applied for 1 minute (reference JISC8918 / crystalline solar cell) module). The maximum system voltage is usually 600-1000V.

  From the above, it is desirable that the average value of the dielectric breakdown voltage is 3 kV or more, and the above-mentioned various materials satisfy this standard (reference JISC2151 / electric plastic film test method 17.2.2 flat plate electrode method). When the dielectric breakdown voltage is smaller than 3 kV, the possibility of short circuit or leakage due to long-term use increases.

  The translucent insulating layer 141 in the present embodiment is composed of a resin film made of any of the various materials described above. The material used for the light-transmitting insulating layer 141 is preferably a transparent or translucent material, and preferably has fewer elements that cause light scattering.

  The light incident on the back sheet 14 is reflected by the light reflective metal layer 144 after passing through the light transmissive insulating layer 141, passes through the light transmissive insulating layer 141 again, and becomes reflected light from the back sheet 14. Therefore, if the translucent insulating layer 141 is highly transparent and has few scattering elements, the efficiency when the light incident on the back sheet 14 becomes reflected light increases.

  Further, the material used for the light-transmitting insulating layer 141 is not limited to the above, and any material that satisfies the reference value of the dielectric breakdown voltage can be used as appropriate. For example, it is possible to employ a synthetic resin film mainly composed of EVA, PVB or the like. The use of these resins is preferable because the adhesion with the filling layer 13 is improved.

The light-transmitting insulating layer 141 may be a single layer or a multilayer. In the case of a single layer, any of the above materials can be selected according to the required characteristics.
As a constitution method in the case of a multilayer, for example, a method of bonding a fluororesin film such as PVF to a PET film, a method of forming a fluororesin coating film such as PVF on a PET film, and EVA or PVB as a main component on a PET film And a method of attaching a synthetic resin film to be bonded.

  A fluororesin such as PVF, and a synthetic resin mainly composed of EVA, PVB, or the like are preferable because they satisfy the electrical insulation standard and improve the adhesion to the filling layer 13. However, to obtain sufficient strength with a single layer, it is necessary to increase the thickness, which causes a high cost. Therefore, it is preferable to have a multilayer structure in combination with a base material that ensures strength. In particular, with respect to the fluororesin, a method of forming a coating film can be adopted, and this method is preferable because the process can be simplified compared to the method of laminating the fluororesin film.

Further, any of the above materials, for example, a multilayer structure in which two layers of PET films are bonded together may be used. In order to increase the insulation, it is known that the multilayer structure covers the insulation defects and has higher reliability than the single-sheet structure. Therefore, the insulating property can be further improved in the multilayer structure in which two layers are bonded to each other than the single layer of PET film.
Note that the layer structure of the light-transmitting insulating layer 141 is not limited to the above, and can be changed as appropriate according to required characteristics.

(Uneven structure layer)
The uneven structure layer 142 is made of an ultraviolet curable resin or a thermosetting resin having a glass transition temperature of 95 ° C. or higher.

  The resin used for the concavo-convex structure layer 142 is not particularly limited as long as it is an ultraviolet curable resin or a thermosetting resin having a glass transition temperature of 95 ° C. or higher. For example, poly (meth) acrylic resin, polyurethane resin, fluorine resin, silicone resin, polyimide resin, epoxy resin, polyethylene resin, polypropylene resin, methacrylic resin, polymethylpentene resin, cyclic polyolefin Resin, polystyrene resin such as acrylonitrile- (poly) styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), polyvinyl chloride resin, polycarbonate resin, polyester resin, polyamide resin Resin, Polyamideimide resin, Polyarylphthalate resin, Polysulfone resin, Polyphenylene sulfide resin, Polyethersulfone resin, Reethylene naphthalate resin, Polyetherimide resin, Acetal resin, Ce Loin resins. These resins can be used alone or in combination.

  In addition to the above resins, various additions such as scattering reflectors, curing agents, plasticizers, dispersants, various leveling agents, ultraviolet absorbers, antioxidants, viscosity modifiers, lubricants, light stabilizers, etc. An agent may be appropriately blended.

The uneven structure layer 142 has an uneven structure 421 as shown in FIGS. 4 and 5. The uneven structure 421 may have a shape with a curvature at the top. The shape of the concavo-convex structure 421 will be described later.
The uneven structure layer 142 may be a single layer or a multilayer.

(Method for forming uneven structure layer)
As a method for forming the concavo-convex structure layer 142 made of a resin material, in the case of a single layer, there are a pressing method using a mold, a casting method, an extrusion molding method, an injection molding method, and the like. In these methods, it is possible to form the concavo-convex structure 421 simultaneously with the sheet formation.

  As another method for forming the concavo-convex structure 421 made of a resin material, in the case of a multilayer, a thermosetting resin, an ultraviolet curable resin, an electron beam curable resin, or the like is applied to the concavo-convex forming surface of a flat stamper or a roll stamper. Alternatively, a method of injecting, placing the base material 422 thereon, and releasing from the stamper after the curing treatment can be mentioned. These methods have the advantage that the moldability is good because the viscosity of the resin used can be lowered. In addition, at this time, if the shape of the concave portion of the mold corresponding to the top of the concavo-convex structure 421 is sharp, it is difficult to reproduce the shape, but if the shape has a curvature, the structure can be shaped with good reproducibility, Is preferred.

  The mold to be used can be obtained by cutting a metal plate with a cutting tool, electroforming of a mother die obtained by cutting with a cutting tool, drawing or etching with an electron beam, or the like. The mold formed by such processing has an inverted structure of the concavo-convex structure 421 on the surface. For example, by cutting a metal plate with a tool having a desired shape, a mold having an inverted structure of the desired uneven structure 421 can be obtained. At this time, there is a problem that the shape reproducibility is difficult if the tip of the tool is sharp, and the tip of the tool is easily chipped. However, if the tip has a curvature, the shape is highly reproducible and the tool is not chipped. Such a problem is less likely to occur, which is preferable. The mold may be plate-shaped or roll-shaped, but is preferably a roll-shaped mold. If it is a roll-shaped metal mold | die, continuous embossing is possible and it is suitable as a preparation method of a back surface sheet which requires a large area.

  The substrate used in the above production method is not particularly limited, and PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PVC (stretched hard vinyl chloride), PC (polycarbonate), OPP (stretched polypropylene), A film made of a resin material such as PE (polyethylene), TAC (triacetate), and PI (polyimide) can be used.

In the case where the concavo-convex structure layer 142 is a multilayer, the light-transmitting insulating layer 141 can be employed as the base material 422 that supports the concavo-convex structure 421.
The metal used for the light-reflective metal layer 144 is not particularly limited as long as it has a metallic luster and any of the above forming methods is possible. For example, a simple substance or an alloy such as aluminum (Al), silver (Ag), gold (Au), copper (Cu), nickel (Ni), chromium (Cr), tin (Sn), zirconium (Zr), etc. may be mentioned. A single layer may be used, or a plurality of metals may be stacked. Among them, aluminum which is highly reflective and can form a dense metal layer relatively easily and is inexpensive is preferable.

(Barrier layer)
The barrier layer 143 is formed such that a valve metal or an alloy containing a valve metal is formed along the surface of the concavo-convex structure 421 of the concavo-convex structure layer 142, that is, a layer that follows the surface of the concavo-convex structure 421.

  The means for forming the barrier layer 143 employing a valve metal or an alloy containing the valve metal is not particularly limited as long as the metal layer can be uniformly formed without causing deterioration such as shrinkage and yellowing in the concavo-convex structure layer 142. However, (a) physical vapor deposition method (Physical Vapor Deposition method; PVD method) such as vacuum deposition method, sputtering method, ion plating method, ion cluster beam method, (b) plasma A chemical vapor deposition method (Chemical Vapor Deposition method; CVD method) such as a chemical vapor deposition method, a thermal chemical vapor deposition method, a photochemical vapor deposition method, or the like is employed. Among these, a vacuum deposition method that can form a high-quality metal layer with high productivity is preferable. Any one of an electron beam heating method, a resistance heating method, and an induction heating method may be used as appropriate as a heating means of a vacuum evaporation apparatus using a vacuum evaporation method.

  The metal used for the barrier layer 143 is preferably a valve metal or an alloy containing the valve metal. The valve metal refers to a metal that forms an oxide film on the surface and becomes passive. For example, aluminum (Al), chromium (Cr), titanium (Ti), zirconium (Zr), tantalum (Ta), niobium (Nb), Hafnium (Hf), zinc (Zn), tungsten (W), bismuth (Bi), antimony (Sb), and the like can be given. As the barrier layer 143, a simple substance or an alloy of these metals can be used. Further, it may be formed as a single layer, or a plurality of metals may be stacked. Among these, chromium is preferable because it exhibits excellent corrosion resistance and can form a dense metal layer relatively easily.

The barrier layer 143 may be formed using an inorganic oxide such as silicon oxide or aluminum oxide so as to follow a concavo-convex structure 421 of the concavo-convex structure layer 142.
The means for forming the barrier layer 143 employing an inorganic oxide is not particularly limited as long as the inorganic oxide layer can be formed on the concavo-convex structure layer 142 without causing deterioration such as shrinkage and yellowing. Although possible, it is generally formed by a vacuum evaporation method. Sputtering, ion plating, plasma vapor deposition (CVD), or the like can be used as means other than this vacuum vapor deposition. However, considering productivity, the vacuum deposition method is the best at present. Any one of an electron beam heating method, a resistance heating method, and an induction heating method may be appropriately used as a heating means of the vacuum evaporation apparatus by this vacuum evaporation method. In order to improve the adhesion between the barrier layer 143 and the uneven structure layer 142 and the denseness of the barrier layer 143, a plasma assist method or an ion beam assist method can be used. Further, in order to increase the transparency of the barrier layer 143, reactive vapor deposition in which oxygen gas or the like is blown may be performed during the vapor deposition.

  The inorganic oxide used for the barrier layer 143 is not particularly limited as long as it has transparency and has a gas barrier property of oxygen and water vapor and any one of the above-described forming methods is possible. For example, inorganic oxides such as silicon oxide, aluminum oxide, tin oxide, magnesium oxide, or a mixture thereof can be given. Among these, silicon oxide that can form a dense inorganic oxide layer relatively easily and has excellent long-term stability is preferable.

  The optimum thickness of the barrier layer 143 varies depending on the type and configuration of the valve metal or inorganic compound used, but is generally within the range of 5 nm or more and 300 nm or less, and the value of the barrier property is required. It is appropriately selected depending on the degree. However, if the film thickness is less than 5 nm, a uniform film may not be obtained or the film thickness may not be sufficient, and the function as a gas barrier material may not be sufficiently achieved. If the film thickness exceeds 300 nm, flexibility cannot be maintained, and there is a risk of cracking due to external factors such as bending and pulling after film formation. More preferably, it exists in the range of 10 nm or more and 150 nm or less. If the film thickness is less than 10 nm, sufficient barrier properties may not be obtained depending on the type and configuration of the valve metal and inorganic oxide. On the other hand, when the film thickness exceeds 150 nm, cracks and pinholes are likely to occur, and the barrier property may be lowered.

  In FIG. 2, the barrier layer 143 is formed on the concavo-convex structure layer 142 side with respect to the light reflective metal layer 144. The barrier layer 143 may be generated in the high temperature and high humidity environment by outgassing including an acetic acid component generated when EVA is used for the filling layer 13 or by hydrolysis of a resin material used for the uneven structure layer 142. The component which corrodes the light-reflective metal layer 144 produced on the uneven structure layer 142 side, such as carboxylic acid, is blocked, and the light-reflective metal layer 144 is prevented from corroding.

(Vapor deposition primer layer)
A vapor deposition primer layer (not shown) may be provided between the barrier layer 143 and the concavo-convex structure layer 142.

  The vapor deposition primer layer is provided on the concavo-convex structure layer 142 and has an object of improving adhesion between the concavo-convex structure layer 142 and the barrier layer 143 and preventing the occurrence of delamination. Therefore, a composite of a silane coupling agent having an organic functional group or a hydrolyzate thereof with a polyol and an isocyanate compound is preferably used as the deposition primer layer.

  Furthermore, the composite which comprises a vapor deposition primer layer is demonstrated in detail. As an example of the silane coupling agent used for the deposition primer layer, a silane coupling agent containing an organic functional group can be used. For example, vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethylsilane. A silane coupling agent such as methoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, or one or more of hydrolysates thereof may be used. it can.

  Further, among these silane coupling agents, those having a functional group that reacts with a hydroxyl group of a polyol or an isocyanate group of an isocyanate compound are particularly preferable. For example, those containing an isocyanate group such as γ-isocyanatopropyltriethoxysilane, γ-isocyanatopropyltrimethoxysilane, those containing a mercapto group such as γ-mercaptopropyltriethoxysilane, γ-aminopropyltriethoxysilane, Some include amino groups such as γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, and γ-phenylaminopropyltrimethoxysilane. Furthermore, those containing an epoxy group such as γ-glycidoxypropyltrimethoxysilane and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxyethoxy) silane, etc. A silane coupling agent such as those added with a hydroxyl group or the like may be used, and one or more of these may be used.

  These silane coupling agents have a silane cup containing a functional group in which an organic functional group present at one end exhibits an interaction in a composite composed of a polyol and an isocyanate compound, or reacts with a hydroxyl group of a polyol or an isocyanate group of an isocyanate compound. A stronger primer layer is formed by providing a covalent bond by using a ring agent. In addition, the alkoxy group at the other end or the silanol group formed by hydrolysis of the alkoxy group is highly adhered to the inorganic oxide due to strong interaction with the metal in the inorganic oxide or the highly polar hydroxyl group on the surface of the inorganic oxide. Expresses sex. As a result, the desired physical properties can be obtained. Therefore, you may use as a said vapor deposition primer layer what hydrolyzed the silane coupling agent with the metal alkoxide. In addition, the alkoxy group of the silane coupling agent may be a chloro group, an acetoxy group, etc., and if these alkoxy group, chloro group, acetoxy group, etc. are hydrolyzed to form a silanol group, this composite It can be used for things.

  The polyol used for the vapor deposition primer layer has two or more hydroxyl groups at the polymer terminal and is reacted with an isocyanate group of an isocyanate compound added later. As this polyol, an acrylic polyol which is a polyol obtained by polymerizing an acrylic acid derivative monomer or a polyol obtained by copolymerizing an acrylic acid derivative monomer and other monomers is preferable.

  Of these, acrylic polyols obtained by polymerizing acrylic acid derivative monomers such as hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate, and acrylic polyols obtained by copolymerizing the above acrylic acid derivative and other monomers such as styrene are preferably used. In consideration of the reactivity with the isocyanate compound and the compatibility with the silane coupling agent, the hydroxyl value of the acrylic polyol is preferably between 5 and 200 (mgKOH / g).

  The mixing ratio of the acrylic polyol and the silane coupling agent is preferably in the range of 1/1 to 1000/1, more preferably in the range of 2/1 to 100/1, by mass ratio. Solvents and dilution solvents include, for example, esters such as ethyl acetate and butyl acetate, alcohols such as methanol, ethanol and isopropyl alcohol, ketones such as methyl ethyl ketone, and aromatic hydrocarbons such as toluene and xylene. What was mix | blended with can be used.

However, when an aqueous solution such as hydrochloric acid is used to hydrolyze the silane coupling agent, it is preferable to use a solvent in which alcohols such as isopropyl alcohol and ethyl acetate as a polar solvent are arbitrarily mixed as a cosolvent.
The isocyanate compound used for the vapor deposition primer layer is added to increase the adhesion between the concavo-convex structure layer 142 and the barrier layer 143 by a urethane bond formed by reaction with a polyol such as acrylic polyol, and is mainly used as a crosslinking agent or a curing agent. Acts as an agent.

  Specific examples of isocyanate compounds that exhibit the above functions include aromatic tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), aliphatic xylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate ( Monomers such as IPDI), one of these polymers or derivatives, or two or more thereof can be used.

  Here, the mixing ratio of the acrylic polyol and the isocyanate compound is not particularly limited. However, if the isocyanate compound is too small, curing may be poor, and if it is too much, blocking or the like occurs and there is a problem in processing. Therefore, the blending ratio of the acrylic polyol and the insocyanate compound is preferably that the NCO group derived from the isocyanate compound is 50 times or less of the OH group derived from the acrylic polyol, and particularly preferably the NCO group and the OH group are blended in an equivalent amount. This is the case. A known method can be used as the mixing method and is not particularly limited.

  The vapor deposition primer layer is formed by preparing a composite solution in which a silane coupling agent, a polyol, and an isocyanate compound are mixed, coating the concavo-convex structure layer 142, and then drying and curing. Specifically, the primer coating agent for forming the vapor deposition primer layer is prepared by mixing a silane coupling agent and a polyol, adding a solvent and a diluent, diluting to an arbitrary concentration, and then mixing with an isocyanate compound. In addition to the above method, a silane coupling agent and a polyol are mixed in a solvent, and a silane coupling agent and a polyol previously reacted are diluted with a solvent and a diluent to an arbitrary concentration, and then added with an isocyanate compound. There are ways to do it.

  In addition to the primer coating agent, various additives such as tertiary amines, imidazole derivatives, carboxylic acid metal salt compounds, quaternary ammonium salts, quaternary phosphonium salts and other curing accelerators, phenol-based, sulfur-based, Antioxidants such as phosphites, leveling agents, flow regulators, catalysts, crosslinking reaction accelerators, fillers and the like can be added.

  The deposition primer layer uses a primer coating agent, for example, a well-known printing method such as an offset printing method, a gravure printing method, a silk screen printing method, or a well-known coating method such as roll coating, knife edge coating, or gravure coating. Coating is performed on the concavo-convex structure layer 142, and then the coating film is dried, and the solvent is removed and cured.

  Although the thickness of a vapor deposition primer layer will not be specifically limited if a coating film can be formed uniformly, Generally it is preferable that it is the range of 0.01 micrometer or more and 2 micrometers or less. When the thickness is less than 0.01 μm, it is difficult to obtain a uniform coating film, and the adhesion may be lowered. On the other hand, when the thickness exceeds 2 μm, the coating film cannot be kept flexible because it is thick, and the coating film may be cracked due to external factors, which is not preferable. Particularly preferred is a range of 0.05 μm or more and 0.5 μm or less.

(Barrier coating layer)
In addition, a barrier coating layer (not shown) may be provided on the barrier layer 143 in order to protect the barrier layer 143 and to provide higher barrier properties.

Examples of the material for forming the barrier coating layer include a material composed of a water-soluble polymer and one or more metal alkoxides and / or a hydrolyzate thereof, and further, the metal alkoxide includes tetraethoxysilane, triisopropoxy. Examples thereof include those formed by coating a solution made of either aluminum or a mixture thereof.
Other examples of the material for forming the barrier coating layer include a material made of a water-soluble polymer and silver chloride, and a material in which the water-soluble polymer is coated with a solution made of polyvinyl alcohol.

  Specifically, the barrier coating layer is a treatment in which a water-soluble polymer and tin chloride are dissolved in an aqueous (water or water / alcohol mixed) solvent, or a metal alkoxide is directly or previously hydrolyzed in the above solution. The barrier layer 143 is coated with a mixed solution obtained by performing the above and dried by heating. Each component forming the barrier coating layer will be described in more detail.

  Specific examples of the water-soluble polymer used to form the barrier coating layer of this embodiment include polyvinyl alcohol, polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate and the like. In particular, polyvinyl alcohol (PVA) has the best gas barrier properties. The PVA here is generally obtained by saponifying polyvinyl acetate, so-called partially PVA in which only several percent of acetate groups remain from so-called partially saponified PVA in which several tens percent of acetate groups remain. It includes up to and is not particularly limited.

The tin chloride may be stannous chloride (SnCl ₂ ), stannic chloride (SnCl ₄ ), or a mixture thereof, and may be used as an anhydride or a hydrate.
Further, examples of the metal alkoxide include general formulas such as tetraethoxysilane [Si (OC ₂ H ₅ ) 4], triisopropoxy aluminum [Al (O-2′-C ₃ H ₇ ) ₃ ], M
(OR) n (M: metal such as Si, Ti, Al and Zr, R: alkyl group such as CH ₃ and C ₂ H ₅ ) can be used. Among these, tetraethoxysilane and triisopropoxyaluminum are preferable because they are relatively stable in an aqueous solvent after hydrolysis.

The barrier coating layer can be formed by coating the barrier layer 143 with a solution obtained by combining the above-described components alone or in combination, and drying by heating. Furthermore, additives such as isocyanate compounds, silane coupling agents, dispersants, stabilizers, viscosity modifiers, and colorants may be added to the barrier coating layer as long as the gas barrier properties are not impaired.
The isocyanate compound added to the barrier coating layer has two or more isocyanate groups (NCO groups) in the molecule. For example, tolylene diisocyanate (TDI), triphenylmethane triisocyanate (TTI), tetramethyl There are monomers such as xylene diisocyanate (TMXDI) and polymers or derivatives thereof.

  Conventionally known means such as a dipping method, a roll coating method, a screen printing method, and a spray method can be used as a method for applying the solution for forming the barrier coating layer. The thickness of the barrier coating layer varies depending on the type of solution forming the coating layer and the processing conditions, but the thickness after drying needs to be 0.01 μm or more, and if the thickness is 50 μm or more, the film will crack. Therefore, the range of 0.01 to 50 μm is preferable.

(Light reflective metal layer)
The light-reflective metal layer 144 follows the concavo-convex structure 421 in the same manner on the barrier layer 143 formed so that a metal such as aluminum or silver follows the concavo-convex structure 421 of the concavo-convex structure layer 142. It forms so that it may become the layered form.

  The means for forming the light-reflective metal layer 144 is not particularly limited as long as the metal layer can be uniformly formed. (A) Physical vapor such as vacuum deposition, sputtering, ion plating, ion cluster beam, etc. Phase growth method (Physical Vapor Deposition method; PVD method), (b) Chemical Vapor Deposition method such as Plasma Chemical Vapor Deposition method, Thermal Chemical Vapor Deposition method, Photochemical Vapor Deposition method (Chemical Vapor Deposition method; CVD method) ) Is adopted. Among these, a vacuum deposition method that can form a high-quality metal layer with high productivity is preferable. Any one of an electron beam heating method, a resistance heating method, and an induction heating method may be used as appropriate as a heating means of a vacuum evaporation apparatus using a vacuum evaporation method.

  The metal used for the light-reflective metal layer 144 is not particularly limited as long as it has a metallic luster and any of the above forming methods is possible. For example, a simple substance or an alloy such as aluminum (Al), silver (Ag), gold (Au), copper (Cu), nickel (Ni), chromium (Cr), tin (Sn), zirconium (Zr), etc. may be mentioned. A single layer may be used, or a plurality of metals may be stacked. Among them, aluminum which is highly reflective and can form a dense metal layer relatively easily and is inexpensive is preferable.

  The lower limit of the thickness of the light reflective metal layer 144 is preferably 10 nm, and particularly preferably 20 nm. On the other hand, the upper limit of the thickness of the light reflective metal layer 144 is preferably 200 nm, and particularly preferably 100 nm. If the thickness of the light reflective metal layer 144 is smaller than the lower limit of 10 nm, the light incident on the light reflective metal layer 144 cannot be sufficiently reflected. If the thickness is 20 nm or more, the light incident on the light-reflective metal layer 144 can be more reliably reflected. On the other hand, when the thickness of the light reflective metal layer 144 exceeds the upper limit of 200 nm, cracks that can be visually confirmed are likely to occur in the light reflective metal layer 144. Hard to occur.

The light reflective metal layer 144 is formed on the barrier layer 143 so as to follow the uneven structure 421 of the uneven structure layer 142, and the light reflective metal layer 144 has an uneven structure.
That is, the light reflecting metal layer 144 has a function of reflecting light incident on the light reflecting metal layer 144 in a predetermined direction. In order to have such a reflection function, it is desirable that the reflection surface of the light reflective metal layer 144 is a specular reflection surface.

(Weatherproof layer)
The weather resistant layer 146 is required to have long-term weather resistance such as high temperature resistance, high humidity resistance, hydrolysis resistance, and flame resistance. In order to satisfy these requirements, generally, a type of PET with improved hydrolysis resistance, such as a fluororesin film such as PVF (polyvinyl fluoride), a fluororesin coating film, or a low oligomer PET (polyethylene terephthalate) film A film or the like is used. In addition, a PEN film having excellent weather resistance may be used. The material of the weather resistant layer 146 is not limited to the above, and any material that satisfies the long-term weather resistance standard value can be used as appropriate.

  The weather resistant layer 146 may be a single layer or a multilayer. In the case of a single layer, any of the above materials can be selected according to the required characteristics. PVF is suitable because it is particularly excellent in long-term weather resistance. In addition, a hydrolysis-resistant PET film such as a low oligomer PET film is suitable because it is inexpensive and excellent in long-term weather resistance.

  Examples of this weather resistant layer 146 having a multilayer structure include a PET film bonded with a fluororesin film such as PVF (poly, fluoride, vinyl) via an adhesive layer, or a PET film such as PVF. What formed the resin coating film etc. are mentioned.

  Fluororesin such as PVF is very excellent in long-term weather resistance, and even if a single layer exhibits sufficient performance, it is necessary to increase the thickness to obtain sufficient strength with a single layer, which is a factor of high cost It becomes. Therefore, it is preferable to have a multilayer structure in combination with a base material that ensures strength.

The layer structure of the weather resistant layer 146 is not limited to the above, and can be changed as appropriate according to the required characteristics.
The weather resistant layer 146 is bonded to the light reflective metal layer 144 via the adhesive layer 145.

(Adhesive layer)
The adhesive layer 145 is required to have an adhesive strength that does not deteriorate due to outdoor use for a long period of time and does not cause delamination, and that the degree of yellowing is small. In order to satisfy these requirements, a laminating adhesive in which one or more of polyurethane, polyacrylic, polyester, epoxy, polyvinyl acetate, and cellulose resins are mixed can be used.

In addition, a deterioration inhibitor may be added to prevent deterioration of the adhesive due to long-term outdoor exposure. Examples of the deterioration preventing agent include additives such as isocyanate additives (TDI, XDI, etc.), carbodiimine, and epoxy.
Furthermore, for example, various additives such as a curing agent, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, an antioxidant, a viscosity modifier, a lubricant, and a light stabilizer may be appropriately blended. Good.

  The weather resistant layer 146 and the light reflective metal layer 144 may be bonded to each other by, for example, a dry lamination method, a non-solvent dry lamination method, a hot melt lamination method, a sandwich / extrusion lamination method using an extrusion lamination method, or the like. Known methods can be used as appropriate.

(Uneven structure)
The concavo-convex structure 421 preferably has a substantially prism shape (see FIG. 4A), a substantially polygonal pyramid shape (see FIG. 4B), or an inverted shape of these shapes. Further, as a shape of any one of a substantially prism shape having a curvature at the top (see FIG. 5A), a substantially polygonal pyramid shape having a curvature at the top (see FIG. 5B), or an inverted shape of these shapes. Also good. The substantially prism shape means that the unit structure of the concavo-convex structure is a prism shape or a shape approximate to the prism shape. The substantially polygonal pyramid shape means that the unit structure of the concavo-convex structure is a polygonal pyramid shape or a shape approximating a polygonal pyramid shape.

  Further, in these structures, it is desirable that the aspect ratio between the base X and the height Y of the unit structure as shown in FIG. 6 is 0.35 or less. When the aspect ratio of the unit structure is larger than 0.35, the resin tends to remain at the tip portion of the mold when the concavo-convex structure 421 is molded, and the moldability deteriorates. If the unit structure has an aspect ratio of 0.35 or less, the possibility that the resin remains in the mold is reduced, and the resin can be molded into a designed shape. The aspect ratio of the unit structure is desirably 0.15 or more. When the aspect ratio is smaller than 0.15, the effect of improving the light utilization efficiency is weakened. The reason for this will be described later.

  The concavo-convex structure 421 may have a periodic structure in which a plurality of convex portions constituting the concavo-convex structure 421 are arranged at a constant pitch, or may be an irregular structure in which the pitch is random.

  When the uneven structure 421 has a periodic structure, the pitch of the protrusions is desirably 30 μm or less. If the pitch is larger than 30 μm, the height of the structure increases as the pitch increases, so that bubbles are likely to enter when the weather-resistant layer 146 is bonded to the light-reflecting metal layer 144 via the adhesive layer 145. Such problems are likely to occur, which is not preferable. In addition, it is necessary to increase the thickness of the adhesive layer 145, which makes it difficult to form the adhesive layer 145, and increases the cost. In this respect, if the pitch is 30 μm or less, there is a low possibility that problems such as bubbles occur at the time of bonding, and this is preferable from the viewpoint of moldability and cost.

  Further, it is desirable that the pitch of the convex portions when the uneven structure 421 has a periodic structure is 10 μm or more. When the pitch is less than 10 μm, light can be diffracted when light is reflected by the uneven structure 421. Since the diffracted light is dispersed and spread, it is difficult to control and is not preferable for reflecting in a specific direction. Furthermore, it is not preferable because the time for cutting the mold is long, the tact is reduced, and the production efficiency is deteriorated. In this respect, if the pitch is 10 μm or more, the light can be accurately reflected in a specific direction, which is further preferable from the viewpoint of power generation efficiency.

  In addition, as another method for forming a metal layer having a concavo-convex structure such as the light-reflecting metal layer 144, for example, a method of coating a resin film having a concavo-convex structure with a resin containing metal particles or flakes, etc. However, this method is not preferable because the effect of improving the light utilization efficiency is small because the specular reflectivity is poor.

As another method for forming a metal layer having a concavo-convex structure such as the light-reflecting metal layer 144, for example, a method such as directly forming a concavo-convex structure on a metal foil can be cited. Since the thickness is large, the resistance is low, and it is not preferable because energization with an aluminum frame for fixing the module or wiring connected to the terminal BOX is likely to occur.
Here, FIG. 7 shows a state in which discharge occurs from the light reflective metal layer 144 to the cathode 22c. FIG. 7 shows an example in which the light-transmitting insulating layer 141 also serves as the concavo-convex structure layer 142.

As shown in FIG. 7A, when the light-reflective metal layer 144 is provided, the layer Ic where the equipotential lines PI are densely formed can be formed. This layer is susceptible to discharge. Therefore, in order to obtain sufficient insulation, it is necessary that a value obtained by subtracting Ic from the total thickness It of the insulating layer 141 has a sufficient thickness.
In the layer Ic where the equipotential lines PI are densely packed, the dielectric breakdown occurs at a lower voltage than the entire insulating layer 141 breaks down. Therefore, the dielectric breakdown voltage Dv of the insulating layer 141 is obtained by multiplying the total thickness It of the insulating layer 141 by the thickness Ie obtained by subtracting the layer Ic where the equipotential lines PI are densely packed and the dielectric strength Ds per unit thickness. It becomes. When the breakdown voltage Dv is expressed by an equation,

となる。

It becomes.

  It should be noted that the layer Ic where the equipotential lines PI are dense is half the pitch Pt of the top portion 144t of the light reflective metal layer 144.

  Further, if the dielectric breakdown voltage is 3 kV or more, dielectric breakdown does not occur when using a normal solar cell module. Therefore, the total thickness It of the above-described insulating layer 141 and the pitch Pt of the top portion 144t of the light reflective metal layer 144 are as follows. It is necessary to satisfy the following formula.

  Further, if the top 144t is pointed, as shown in FIG. 7A, discharge breakdown occurs from the light-reflecting metal layer 144 due to charge concentration Ec, and discharge occurs in the light-transmitting insulating layer 141. Blackening occurs in the light-transmitting insulating layer 141. When the blackening is performed, the amount of light transmitted through the light-transmitting insulating layer 141 decreases, so that light reflected by the light-reflecting metal layer 144 and incident on the solar battery cell 12 decreases. Therefore, what has a curvature as shown in FIG.7 (b) is preferable. The larger the radius r of the circle Pc inscribed in the top portion 144t, the more the charge concentration can be prevented. However, if the radius r is larger than 10% of the pitch Pt of the top portion 144t, much light is scattered and the power generation efficiency of the solar cell module 1 is reduced. End up. For this reason, the radius r is preferably 10% or less. In addition, if the radius r is too small, charge concentration occurs. Therefore, the radius r is preferably 1% or more of the pitch Pt of the top 144t.

(Other)
As described above, the back sheet 14 includes the translucent insulating layer 141, the concavo-convex structure layer 142, the barrier layer 143, the light reflective metal layer 144, the adhesive layer 145, and the weather resistant layer 146. Each layer may be bonded through an adhesive layer (not shown in FIG. 2) as necessary. As a bonding method, for example, a known method such as a dry lamination method, a non-solvent dry lamination method, a hot melt lamination method, or an extrusion lamination method using an extrusion lamination method can be appropriately used. As an adhesive to be used, it is required that the adhesive strength deteriorates after long-term outdoor use and does not cause delamination, and the degree of yellowing is small. In order to satisfy these requirements, a laminating adhesive in which one or more of polyurethane, polyacrylic, polyester, epoxy, polyvinyl acetate, and cellulose resins are mixed can be used.

In addition, a deterioration inhibitor may be added to prevent deterioration of the adhesive due to long-term outdoor exposure. Examples of the deterioration preventing agent include additives such as isocyanate additives (TDI, XDI, etc.), carbodiimine, and epoxy.
Furthermore, for example, various additives such as a curing agent, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, an antioxidant, a viscosity modifier, a lubricant, and a light stabilizer may be appropriately blended. Good.

(Effect etc.)
Next, a mechanism for improving the light utilization efficiency by the back sheet 14 will be described with reference to FIG.
FIG. 8 shows a process in which light incident on the back sheet 14 is reflected by the light reflective metal layer 144 having a concavo-convex structure and is incident on the light receiving surface J of the solar battery cell 12. In FIG. 8, a prism structure is employed as the uneven structure 421.

  As shown in FIG. 8, the back sheet 14 is provided with a light reflective metal layer 144 having an uneven structure. Of the light incident from the incident surface 110 of the solar cell module 1, the light H <b> 1 transmitted through the solar cell module 1 and incident on the back sheet 14 is reflected by the light reflective metal layer 144. The reflected light H2 is reflected again at the interface such as between the front plate 11 and the atmosphere, and becomes light H3 incident on the light receiving surface J of the solar battery cell 12, and is photoelectrically converted. Therefore, if the light H3 incident on the light receiving surface J of the solar battery cell 12 increases, the amount of photoelectric conversion increases, and the improvement of the light utilization efficiency can be expected.

In this regard, in the present embodiment, the light reflective metal layer 144 having a concavo-convex structure can reflect light incident from the front side in a specific direction. When the reflected light is incident again, the light H3 incident on the light receiving surface J of the solar battery cell 12 increases. Therefore, it is possible to improve the light utilization efficiency and increase the amount of power generation.
FIG. 8C shows the relationship between the apex angle θ and the reflection angle α (incident angle α) of the prism that constitutes the light-reflective metal layer 144 having the concavo-convex structure. As shown in FIG. 8C, when light enters perpendicularly to the incident surface 110, the following relationship is established between the apex angle θ and the reflection angle α.

The light H2 reflected by the light reflective metal layer 144 having the concavo-convex structure is reflected at the interface between the front plate 11 and the atmosphere. At this time, the incident angle of the incident light H2 is 2α.
Here, when 2α is greater than or equal to the critical angle φ, the light is totally reflected at the interface between the front plate and the atmosphere, so that the incident light H2 is very little loss and becomes reflected light H3 (see FIG. 8A).

On the other hand, when 2α is smaller than the critical angle φ, transmitted light H4 is generated in addition to the reflected light H3 (see FIG. 8B). When the transmitted light H4 is generated, the amount of the reflected light H3 is reduced and the amount of the light H3 incident on the light receiving surface J of the solar battery cell 12 is reduced. Therefore, the incident angle 2α of the incident light H2 is greater than or equal to the critical angle φ. It is desirable to become.
The critical angle φ is determined by the refractive index n1 of the front plate 11 and the refractive index n2 of the atmosphere, and the following relational expression is established.

For example, when glass such as tempered glass is used for the front plate 11, the refractive index n1 is about 1.5 and the atmospheric refractive index n2 is about 1.0, so the critical angle φ is about 42 °. .
From the above, in order to effectively use the reflected light H2 from the light reflective metal layer 144 having the concavo-convex structure, 2α needs to be equal to or greater than the critical angle φ, and the critical angle φ is 42 ° as described above. In some cases, the reflection angle α at the light-reflecting metal layer 144 having the concavo-convex structure is required to be 21 ° or more.

  Here, when the concavo-convex structure 421 is a prism structure, the apex angle θ with respect to the aspect ratio between the base X and the height Y of the prism and the value of the reflection angle α at the light-reflecting metal layer 144 forming the concavo-convex structure are shown in the following table. It is shown in 1. As described above, in order to effectively use the reflected light H2 from the light-reflecting metal layer 144 having the concavo-convex structure, the reflection angle α needs to be 21 ° or more. It is necessary to set to 2 or more.

  In the above, the case where the incident angle to the incident surface 110 of the front plate 11 is 0 ° has been considered, but actually, the incident angle of incident light is various. Therefore, if the aspect ratio is 0.15 or more, that is, the difference between the incident angle 2α and the critical angle φ of the light H2 incident on the interface between the front plate 11 and the atmosphere is within about 10 °, the incident angle of the light is different. Finally, light incident on the light receiving surface J is generated. However, when the aspect ratio is less than 0.15, the incident angle 2α of the light H2 incident on the interface between the front plate 11 and the atmosphere becomes nearly 10 ° smaller than the critical angle φ, and the total reflected light is reduced. Therefore, the aspect ratio is preferably at least 0.15 or more. Thereby, the utilization efficiency of light can be kept large.

  As described above, when the aspect ratio of the prism is 0.35 or more, the moldability deteriorates. Therefore, the aspect ratio is desirably 0.35 or less. Therefore, the aspect ratio in this embodiment is 0. .15 or more and 0.35 or less.

  And according to the solar cell back sheet and solar cell module of this embodiment, the uneven structure layer is formed of an ultraviolet curable resin or a thermosetting resin having a glass transition temperature of 95 ° C. or higher, so that the resin in a high temperature environment It is possible to prevent deterioration and deformation.

  Moreover, the solar cell backsheet containing the light-reflective metal layer in which the concavo-convex structure is formed further prevents the light-reflective metal layer from corroding in a high-temperature and high-humidity environment by further including a barrier layer. As a result, the light incident from the front side with respect to the solar cell back sheet is reflected in a specific direction and re-entered into the solar cell, thereby improving the light use efficiency in the solar cell module and increasing the amount of power generation. The effect can be sustained over a long period of time.

“Second Embodiment”
Next, a second embodiment of the present invention will be described with reference to the drawings.
(Back sheet)
FIG. 9 is a longitudinal sectional view showing a schematic configuration of the back sheet 15 of the second embodiment.

The back sheet 15 has a function of reflecting light transmitted through the solar battery cell 12 itself or light H1 transmitted through the filling layer 13 without being incident on the solar battery cell 12.
The back sheet 15 of this embodiment includes a light-transmitting insulating layer 141, a concavo-convex structure layer 142, a light-reflecting metal layer 144, a barrier layer 143, an adhesive layer 145, and a weathering layer 146 in order from the front side (light source side). It is configured by stacking. That is, the basic configuration is the same as in the first embodiment. However, the arrangement location of the barrier layer 143 is different.

  Regarding the materials used and the manufacturing method, the same materials can be used except that the barrier layer 143 is formed on the weather resistant layer 146 side with respect to the light-reflecting metal layer 144, and the same manufacturing method is adopted. It is possible.

(Barrier layer)
Here, the barrier layer 143 is formed on the weather resistant layer 146 side with respect to the light reflective metal layer 144. This barrier layer 143 is water vapor that may enter from the weather-resistant layer 146 side in a high-temperature and high-humidity environment, carboxylic acid that may be generated by hydrolysis of the resin material used for the adhesive layer 145, etc. The component which corrodes the light reflective metal layer 144 generated on the weather resistant layer 146 side is blocked, and the light reflective metal layer 144 is prevented from corroding.

  Moreover, you may provide the barrier layer 143 in both the uneven | corrugated structure layer 142 side and the weather-resistant layer 146 side with respect to the light reflective metal layer 144 (not shown). At this time, a component that may occur on the uneven structure layer 142 side and the weather resistant layer 146 side, which corrodes the light reflective metal layer 144, can be blocked from both sides, which is preferable.

  The embodiments based on the present invention have been described above. However, the present invention is not limited to these embodiments, and some design changes can be made without departing from the technical idea of the present invention.

(Modification)
For example, the back sheet 20 of the first configuration example may have a layer configuration shown in FIG.
In the back sheet 20, a PET film is used as the translucent insulating layer 141. A concavo-convex structure layer 142, a barrier layer 143, and a light-reflective metal layer 144 are laminated on the back surface side of the light-transmitting insulating layer 141, and further from a hydrolysis-resistant PET film via an adhesive layer 145. A weathering layer 146 is disposed. At this time, the concavo-convex structure layer 142 has a multilayer structure, and the light-transmitting insulating layer 141 also serves as the base material 422 that supports the concavo-convex structure 421.

Further, the back sheet 30 of the second configuration example may have a layer configuration shown in FIG.
In the back sheet 30, an EVA film is used as the translucent insulating layer 141. On the back surface side of the translucent insulating layer 141, a concavo-convex structure layer 142 composed of a concavo-convex structure 421 and a base material 422, a barrier layer 143, and a light-reflecting metal layer 144 are laminated, and further through an adhesive layer 145. A weathering layer 146 made of hydrolysis resistant PET film is disposed. At this time, the light-transmitting insulating layer 141 and the base material 422 constituting the concavo-convex structure layer 142 are bonded to each other with the adhesive layer 147 interposed therebetween.

Further, the back sheet 40 of the third configuration example may have a layer configuration shown in FIG.
In this back sheet 40, a PET film is used as the light-transmitting insulating layer 141 and a light-reflective metal layer 144 is laminated, and a weather-resistant layer 146 composed of a PET film 461 and a PVF film 462 via an adhesive layer 145. Is arranged. At this time, the PET film 461 and the PVF 462 constituting the weather resistant layer 146 are bonded together via the adhesive layer 463. The light-transmitting insulating layer 141 and the concavo-convex structure layer 142 are attached to each other with an adhesive layer 147 interposed therebetween.

And the thing of the layer structure shown in FIG. 13 may be sufficient as the back surface sheet 50 of a 4th structural example.
In the back sheet 50, an EVA film is used as the translucent insulating layer 141. On the back surface side of the translucent insulating layer 141, a concavo-convex structure layer 142 composed of a concavo-convex structure 421 and a base material 422, a barrier layer 143, and a light-reflecting metal layer 144 are laminated, and further through an adhesive layer 145. A weathering layer 146 made of a PET film 461 and a PVF film 462 is disposed. At this time, the PET film 461 and the PVF 462 constituting the weather resistant layer 146 are bonded together via the adhesive layer 463. Further, the base material 422 constituting the light-transmitting insulating layer 141 and the concavo-convex structure layer 142 is bonded through an adhesive layer 147.

  Since the back sheet 20, 30, 40, 50 of the first to fourth configuration examples includes the light reflective metal layer 144 similarly to the back sheet 14 of the first embodiment, the light is directed toward the front side. It can be reflected efficiently. Therefore, it is possible to increase the power generation amount by improving the light use efficiency of the solar cell module 1.

  In addition, in the back sheet 14, 20, 30, 40, 50 of the above-described embodiment and the first to fourth configuration examples, when a prism structure is employed as the uneven structure 421, the longitudinal direction of the prism that is a unit structure is the solar cell. If it inclines with respect to 12, it can improve light utilization efficiency more and is preferable.

  In addition, when the prism structure is employed as the concave-convex structure 421 in the back sheet 14, 20, 30, 40, 50 of the above-described embodiment and the first to fourth configuration examples, the longitudinal direction of the prism that is a unit structure is the solar cell. If it arrange | positions in parallel with each 12 end surface, light utilization efficiency can be improved more and it is preferable.

  Furthermore, the backsheets 14, 20, 30, 40, 50 are not limited to use in the solar cell module 1, and it is desirable to improve the light utilization efficiency such as the light utilization efficiency of light emitting elements such as LED lighting and EL elements. Can be diverted to optical elements and display members.

Next, examples based on the above embodiment will be described.
(Comparative Example 1)
As Comparative Example 1 for comparison, the back sheet 60 shown in FIG. 14, that is, a translucent insulating layer 141 made of a PET film, an uneven structure layer 142, a light reflective metal layer 144, an adhesive layer 145, hydrolysis resistance, The back sheet 60 which laminated | stacked in order of the weather resistant layer 146 which consists of a property PET film was produced.

Evaluation was carried out using the sample 1 for evaluation produced by laminating the back sheet 60, the EVA film, and the tempered glass in this order, and performing thermal lamination with a vacuum laminator.
The evaluation sample 1 has the same configuration as that of the solar battery module 1 except that the solar battery cell 12 is omitted.

The back sheet 60 has the same configuration as the back sheet 20 except that the barrier layer 143 is omitted. Here, aluminum is used as the light reflective metal layer 144.
Further, as the concavo-convex structure layer 142, a resin J which is an ultraviolet curable resin having a glass transition temperature of 101 ° C. was employed.

Example 1
As Example 1, the back sheet 20 of the first configuration example shown in FIG. 10, that is, the light-transmissive insulating layer 141 made of a PET film, the concavo-convex structure layer 142, the barrier layer 143, the light-reflective metal layer 144, and the adhesive The back sheet 20 which laminated | stacked in order of the layer 145 and the weathering layer 146 which consists of a hydrolysis-resistant PET film was produced.

Evaluation was carried out using the sample 2 for evaluation produced by laminating the back sheet 20, EVA film, and tempered glass in this order, and performing thermal lamination with a vacuum laminator.
The evaluation sample 2 has the same configuration as that of the solar cell module 1 except that the solar cells 12 are omitted. The back sheet 20 is made of aluminum as the light reflective metal layer 144 in the same manner as the back sheet 60 of Comparative Example 1. Adopted.

Further, as the concavo-convex structure layer 142, a resin A which is an ultraviolet curable resin having a glass transition temperature of 73 ° C, a resin B which is a thermosetting resin at 77 ° C, a resin C which is an ultraviolet curable resin at 81 ° C, and an ultraviolet curable resin at 84 ° C. Resin D, resin E which is thermosetting resin at 88 ° C., resin F which is thermosetting resin at 91 ° C., resin G which is UV curable resin at 93 ° C., resin H which is UV curable resin at 95 ° C. Resin I, a thermosetting resin at 97 ° C., Resin J, an ultraviolet curable resin at 101 ° C., Resin K, a thermosetting resin at 104 ° C., Resin L, a thermosetting resin at 107 ° C., 110 ° C. 15 types of resin M, which is an ultraviolet curable resin, resin N which is a thermosetting resin at 113 ° C., and resin O which is an ultraviolet curable resin at 118 ° C.
At this time, chromium was adopted as the barrier layer 143.

(Example 2)
As Example 2, the back sheet 20 of the first configuration example shown in FIG. 10, that is, the light-transmissive insulating layer 141 made of a PET film, the concavo-convex structure layer 142, the barrier layer 143, the light-reflective metal layer 144, the adhesive The back sheet 20 which laminated | stacked in order of the layer 145 and the weathering layer 146 which consists of a hydrolysis-resistant PET film was produced.

Evaluation was carried out using the evaluation sample 3, which was prepared by laminating the back sheet 20, the EVA film, and the tempered glass in this order and performing thermal lamination with a vacuum laminator.
The evaluation sample 3 has the same configuration as that of the solar battery module 1 except that the solar battery cell 12 is omitted.
Similar to the back sheet 60 of Comparative Example 1, the back sheet 20 employs aluminum as the light reflective metal layer 144.

  Further, a resin K, which is a thermosetting resin having a glass transition temperature of 104 ° C., is used as the uneven structure layer 142, and silicon oxide is used as the barrier layer 143.

(Example 3)
As Example 3, the back sheet 70 shown in FIG. 15, that is, the translucent insulating layer 141 made of PET film, the concavo-convex structure layer 142, the light reflective metal layer 144, the barrier layer 143, the adhesive layer 145, hydrolysis resistance The back sheet 70 which laminated | stacked in order of the weathering layer 146 which consists of a property PET film was produced.

Evaluation was carried out using the evaluation sample 4 produced by laminating the back sheet 70, the EVA film, and the tempered glass in this order and performing thermal lamination with a vacuum laminator.
The evaluation sample 4 has the same configuration as that of the solar battery module 1 except that the solar battery cell 12 is omitted.

  The back sheet 70 has the same configuration as that of the back sheet 20 except that the barrier layer 143 is disposed on the weather resistant layer 146 side of the light reflective metal layer 144, and, similarly to the back sheet 60 of Comparative Example 1, it reflects light. Aluminum was used as the conductive metal layer 144.

  Further, a resin L which is a thermosetting resin having a glass transition temperature of 107 ° C. is used as the uneven structure layer 142, and chromium is used as the barrier layer 143.

(Implementation of high temperature and high humidity test)
In Comparative Sample 1 and Evaluation Samples 1 to 4 of Examples 1 to 3, a high temperature and high humidity test (1000 hours in an environment of 85 ° C. and 85% temperature) was performed in order to evaluate long-term weather resistance (reference) JISC 8990 / ground-mounted crystalline silicon solar cell (PV) module-10.13 high temperature and high humidity test for design qualification and type certification requirements).

(Evaluation of uneven structure shape)
In the evaluation sample 2 (resins A to O) of Example 1, the shape of the concavo-convex structure 421 before and after the high temperature and high humidity test was evaluated. For shape evaluation, a cross-section was observed using a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation) after cutting out a cross-section using a microtome (manufactured by LEICA).

  As a result of observing the cross-sectional shape and comparing the shape before and after the high-temperature and high-humidity test, deformation of the concavo-convex structure 421 was observed in the resins A, B, and C. In resins D, E, F, and G, slight deformation was observed. In the resins H, I, J, K, L, M, N, and O, deformation of the concavo-convex structure 421 was not recognized.

(Interlayer adhesion evaluation)
Evaluation sample 2 (resins A to O) of Example 1 was subjected to interlayer adhesion evaluation before and after the high temperature and high humidity test. Interlaminar adhesion evaluation was performed using Tensilon (manufactured by A & D Co., Ltd.) to measure the peel strength of the weathering layer 146 (reference ASTM D-1876 / Standard Test Method for Resistance of Adhesives (T-Peel)). Test)).

  As a result of measuring the peel strength and comparing the peel strength before and after the high temperature and high humidity test, first, the peel strength was about 8 N / cm before the test. After the test, in the resins A, B, and C, the peel strength was 1 N / cm or less. For resins D, E, F, and G, the peel strength was about 1 to 5 N / cm. For resins H, I, J, K, L, M, N, and O, the peel strength was 5 N / cm or more. Note that the peeling site was the interface between the uneven structure layer 142 and the barrier layer 143.

  Table 2 shows the results of the shape evaluation of the uneven structure 421 and the interlayer adhesion evaluation. From Table 2, if the glass transition temperature of the resin material forming the concavo-convex structure layer 142 is 95 ° C. or higher, the shape change after the high-temperature and high-humidity test can be prevented, and the decrease in interlayer adhesion can be prevented. It could be confirmed.

(Evaluation of corrosion resistance of light reflective metal layer)
Evaluation samples 1 to 4 were evaluated for corrosion resistance before and after the high temperature and high humidity test. The corrosion resistance was evaluated by measuring transmittance from the tempered glass side using a spectrophotometer (manufactured by Shimadzu Corporation).

  Table 3 shows the measurement results of transmittance (measurement wavelength: 900 nm). In the transmittance of 900 nm, the transmittance after the test of the evaluation sample 1 of Comparative Example 1 is increased by 38% compared to the transmittance before the test, whereas the evaluation sample 2 of Examples 1 to 3 It was confirmed that the transmittance after the test of -4 was suppressed to an increase of 1% or less compared to the transmittance before the test.

  From this result, it was confirmed that the presence of the barrier layer 143 can prevent an increase in transmittance, that is, it is possible to prevent corrosion of the light reflective metal layer 144.

DESCRIPTION OF SYMBOLS 1 Solar cell module 10 Solar cell module 11 Front plate 12 Solar cell 13 Packing layer 14,15,20,30,40,50,60,70 Back surface sheet (solar cell back surface sheet)
141 Translucent insulating layer 142 Uneven structure layer 143 Barrier layer 144 Light reflective metal layer 144t Top 145 Adhesive layer 146 Weather resistant layer 147 Adhesive layer 421 Uneven structure 422 Base material 461 Film 462 Film 463 Adhesive layer Pt Pitch r Curvature radius

Claims (10)

A solar battery back sheet disposed on the back side of a solar cell module in which a translucent front plate is laminated on the front side of a filling layer in which solar cells are sealed,
At least a translucent insulating layer, an uneven structure layer, a light-reflective metal layer supported by the uneven structure layer to form an uneven structure, an adhesive layer, and a weather resistant layer are laminated in order from the front side.
The solar cell backsheet, wherein the concavo-convex structure layer is formed of an ultraviolet curable resin or a thermosetting resin having a glass transition temperature of 95 ° C or higher.   The barrier layer for preventing corrosion of the light reflective metal layer is provided on at least one side of the concavo-convex structure layer side and the adhesive layer side with respect to the light reflective metal layer. Solar cell back sheet.   The solar cell backsheet according to claim 1 or 2, wherein the barrier layer is formed in contact with the light-reflective metal layer.   The solar cell backsheet according to any one of claims 1 to 3, wherein the barrier layer is made of a valve metal or an alloy containing the valve metal.   The solar cell backsheet according to any one of claims 1 to 3, wherein the barrier layer is made of an inorganic oxide.   6. The uneven structure according to any one of claims 1 to 5, wherein the concavo-convex structure is formed by arranging a plurality of substantially prism shapes, substantially polygonal pyramid shapes, or inverted shapes of these shapes. Solar cell back sheet.   Each top of the concavo-convex structure has a curvature, and when the pitch of the top of the concavo-convex structure is Pt, the radius of curvature r of the top is set in a range of 0.01 Pt or more and 0.1 Pt or less. The solar cell back surface sheet of any one of Claims 1-6 characterized by the above-mentioned.   8. The aspect ratio between the base and height of the unit structure of the concavo-convex structure is set in a range of 0.15 or more and 0.35 or less. Solar cell back sheet.   The solar cell backsheet according to any one of claims 1 to 8, wherein the pitch of the top of the concavo-convex structure is set in a range of 10 µm to 30 µm.   A solar cell module comprising the solar cell back sheet according to any one of claims 1 to 9 arranged on a back surface of the solar cell module.

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