JP2010092899A - Solar battery module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light reuse sheet for a solar battery module, having an uneven structure optimal for improving light utilization efficiency, and also to provide a solar battery module using the same. <P>SOLUTION: The solar battery module is provided with: a solar battery cell having a light receiving surface and converting the received light on the light receiving surface into electricity and outputting the electricity; and a light reuse sheet provided opposite the light receiving surface of the solar battery cell via a filling material. In the solar battery module, the light utilization efficiency of the solar battery module is improved by a light reuse sheet having a light reuse layer having a reflection surface of an uneven structure in which Gaussian curvature is 0, on the solar battery cell side of the light reuse sheet. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light reuse sheet that has a reflection surface that reflects light on one surface and can reuse light by reflecting light in a specific direction, and a solar cell module using the same.

  In recent years, the widespread use of solar cell modules has expanded greatly, from relatively small ones mounted on small electronic devices such as calculators to large areas used for solar cell modules installed in homes 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).

  In such a solar cell, the amount of power generation increases mainly in proportion to the area irradiated with light. Therefore, in order to improve the power generation efficiency, in addition to improving the manufacturing technology such as sealing technology and film forming technology, how to increase the aperture ratio of the solar cell module (the ratio of the area capable of power generation to the total area) Is an important issue.

In particular, single crystal silicon or polycrystalline silicon has a problem that the cost of the silicon is high. Also, the cost for pasting it is added.
In view of this, the amount of silicon that is a constituent member of a solar cell is small, and a thin-film silicon solar cell that can be formed by a technique such as CVD has been used.

  However, the light absorption rate of the above-mentioned is particularly low because infrared light is likely to pass through thin-film silicon solar cells. Therefore, in order to increase the light utilization efficiency, the light utilization efficiency is improved by intentionally scattering the incident light and increasing the distance through which the thin film silicon solar cells are transmitted.

  In general, there are two types of amorphous silicon solar cells. First, a transparent conductive film such as SnO2 or ITO is formed on a light-transmitting substrate such as glass, and an amorphous semiconductor (Si) p-layer, i-layer, and n-layer are stacked in this order. It is of the structure which consists of. The other is an amorphous semiconductor (Si) n-layer, i-layer, and p-layer stacked in this order on a metal substrate electrode to form a photoelectric conversion active layer, and a transparent conductive film is further formed thereon. It has a laminated structure.

  In particular, in the former structure, in order to form amorphous semiconductors in the order of pin layers, the translucent insulating substrate can also serve as a solar cell surface cover glass, and resistance to SnO 2 or the like. A plasma transparent conductive film has been developed, and an amorphous semiconductor photoelectric conversion active layer can be formed thereon by a plasma CVD method.

The amorphous semi-light-guided conversion active layer can be formed by using a plasma CVD method by glow discharge decomposition of a source gas or a vapor phase growth method by a photo-CVD method. There is also an advantage that a thin film can be formed.

  Since an amorphous Si solar cell can be formed at a relatively low temperature of about 100 ° C. to 200 ° C., it is possible to use substrates of various materials as a substrate for forming the amorphous Si solar cell. However, glass substrates and stainless steel substrates are commonly used.

  In addition, the amorphous Si solar cell has a silicon light absorption layer thickness of about 500 nm when the conversion efficiency for replacing light with an electric machine is maximized. Therefore, in order to improve the conversion efficiency of the light absorption layer, Increasing the amount of light absorption within the film thickness is an important point. Therefore, the optical path length of light in the light absorption layer is increased by forming a transparent conductive film with unevenness on the surface of the glass substrate or forming a metal film with unevenness on the surface of the stainless steel substrate. It has been performed conventionally.

  In the case of the solar cell in which the optical path length in the light absorption layer is increased by such a method, the light is compared with the case where the amorphous Si solar cell is formed on a flat substrate having no irregularities on the surface. The utilization efficiency of is significantly improved.

  By the way, as a general method for forming irregularities on the surface of a glass substrate, there is a method of forming a SnO 2 film as a transparent electrode by atmospheric pressure CVD. In addition, as a method of forming irregularities on a metal substrate such as stainless steel, a method of adjusting the formation conditions when Ag is formed by a vapor deposition method or a sputtering method, or performing a heat treatment after the formation of Ag is used. It was done.

  This thin film solar cell has a transparent conductive film, a hydrogenated amorphous silicon carbide (a-SiC: H) p layer, a hydrogenated amorphous silicon (a-Si: H) i layer, a hydrogenated film on a light-transmitting insulating substrate. An amorphous silicon (a-Si: H) n layer, a transparent conductive film, and a back electrode are sequentially formed. Then, as described above, a concavo-convex shape is formed on the surface of the transparent conductive film, whereby each layer formed on the top has a concavo-convex structure.

  Moreover, when forming semiconductor elements, such as a thin film solar cell, on a flexible substrate or a lightweight substrate, the polyimide resin with high heat resistance has been used. A method for forming irregularities in such a resin is disclosed in Patent Document 2 and the like.

  Further, Patent Document 3 discloses a patent that retroreflects light by the periodic structure of the V-groove to increase the light utilization efficiency, and that the V-groove apex angle is desirably 50 to 90 degrees. There is a description. Further, there is a description that the pitch of the period of the V groove is preferably 10 μm to 20 μm.

Further, if the arrangement interval of the solar battery cells 30 is narrowed, a leak current is generated, so that a region between adjacent solar battery cells 30 is required. As shown in FIG. 17, among the light H0 incident on the solar cell module 200, the light H1 incident on this region is reflected on the back surface material 300 by disposing the back surface material 300 on the back surface of the solar cell module 200. What is reused as H2 (Patent Document 4) is known. However, sufficient power generation efficiency has not been obtained yet.
JP 2001-295437 A Japanese Laid-Open Patent Publication No. 4-61285 JP 11-274533 A Japanese Patent Application Laid-Open No. 11-307791

  As described above, there are many requests to increase the power generation efficiency per unit area of the conventional solar cell module, but it is not yet sufficient.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a light reuse sheet having a concavo-convex structure optimal for improving the light use efficiency and a solar cell module using the same. And

  In order to achieve the above object, the present invention takes the following measures.

The invention of claim 1 includes a front plate on which light is incident,
A filling layer that transmits light transmitted through the front plate;
Solar cells that are fixed by the filling layer and that transmit light from the filling layer are received from a light receiving surface and converted into electricity, and
A light reuse sheet having a structural layer provided on a back side of the light receiving surface of the solar battery cell and having a reflective layer that reflects light not received on the light receiving surface of the solar battery cell;
The solar cell module is characterized in that the reflective surface of the reflective layer of the light reuse sheet has a gas curvature of zero.
The invention according to claim 2 is the solar cell according to claim 1, wherein an area ratio of the reflecting surface having a Gaussian curvature of 0 is 90% or more among the reflecting surfaces of the reuse sheet. It is a module.
According to a third aspect of the present invention, the structural layer of the light reuse sheet is made of a polymer containing hollow particles and / or titanium oxide particles, and the surface of the structural layer is a reflective surface. It is a solar cell module as described in.
According to a fourth aspect of the present invention, there is provided the reflective surface, wherein an angle formed by a normal line of the front plate and a normal line of the reflective surface is 22.5 degrees or more and 30 degrees or less. It is a solar cell module.
The invention according to claim 5 is characterized in that an area ratio of the reflection surface, in which an angle formed by a normal line of the reflection surface and a normal line of the front plate is 22.5 degrees or more and 30 degrees or less, is 50% or more. The solar cell module according to claim 1.
The invention according to claim 6 is the solar cell module according to claim 1, wherein the uneven shape of the structural layer is a unit uneven structure having periodicity.
The invention according to claim 7 is the solar cell module according to claim 1, wherein a periodic pitch of the unit concavo-convex structure is 25 μm or more and 300 μm or less.
The invention according to claim 8 is the solar cell module according to claim 1, wherein a periodic pitch of the unit concavo-convex structure is 50 μm or more and 200 μm or less.

  The present invention can improve the light utilization efficiency by reusing incident light by the above-described means, and can provide a solar cell module with good power generation efficiency.

First, the solar cell module 200 according to the present invention will be described.
FIG. 1 is a cross-sectional view showing an embodiment of the solar cell module 200 of the present invention. The solar cell module 200 according to the present invention includes a front plate 22, a filling layer 21, and a light reuse sheet 20.

The front plate 22 transmits light from the light source L such as sunlight or illumination light, and protects the solar battery cell 30 from impact, dirt, moisture intrusion, and the like, and is made of a transparent material having high transmittance. Become.
The light H0 that the light from the light source L is incident on the incident surface 110 perpendicularly from the sunlight / illumination light side F is incident on the front plate 22, passes through the front plate 22, and is emitted to the filling layer 21.
The normal line NG of the incident surface 110 is a direction parallel to the normal line N of the plane P when the front plate 22 is placed on the plane P in the most stable state. The light that is perpendicularly incident on the incident surface 110 is light that is incident on the solar cell module 200 in parallel with the normal line NG.

  The material of the front plate 22 is glass such as tempered glass or sapphire glass, or a resin sheet such as PC (polycarbonate) or PEN (polyethylene naphthalate). The thickness of the front plate 22 is about 3 to 6 mm for tempered glass, and 100 μm to 3000 μm for a resin sheet.

  The light emitted from the front plate 22 enters the filling layer 21. The filling layer 21 seals the solar battery cell 30. The light H0 incident on the front plate 22 is transmitted through the filling layer 21 and becomes light H10 emitted to the solar battery cell 30, and part of the light H0 is emitted light H1 emitted on the light reuse sheet 20. A material having a high light transmittance is used to transmit the light H0 incident on the filling layer 21, and flame retardant EVA (ethylene vinyl acetate) is widely used.

Furthermore, the solar battery cell 30 has a function of converting light incident on the light receiving surface J into electricity by photoelectric effect, and is a single crystal silicon type, a polycrystalline silicon type, a thin film silicon type, CISG (Cu • In • Ga •). There are many types such as Se compound) thin film type. The solar cells 30 are used by connecting a plurality of solar cells 30 with electrodes to form a module. The light H <b> 10 that has entered the solar battery cell 30 from the filling layer 21 is converted into electricity by the solar battery cell 30.
In general, light that is incident obliquely on the incident surface 110 is reflected at the incident surface 110 more than the light H0 that is vertically incident, and light that is incident on the solar battery cell 30 is less and can be used for power generation. Less is.
Therefore, the efficiency is highest when the incident light H0 enters the incident surface 110 perpendicularly.

  The light reuse sheet 20 has a function of reflecting the light transmitted through the solar battery cell 30 itself and the light H <b> 1 incident between the solar battery cells 30 with the reflection surface 100. The reflected light H <b> 2 is reflected again at the interface such as between the front plate 22 and the atmosphere, and becomes light H <b> 3 incident on the light receiving surface J of the solar battery cell 30 and is photoelectrically converted. Thereby, compared with the structure without the light reuse sheet | seat 20, there exists an effect which light utilization efficiency improves.

  As shown in FIG. 12, the light reuse sheet 20 includes a structural layer 3, a reflective layer 4, and a base material 2.

  The traveling direction of the reflected light H2 can be controlled by the uneven structure of the reflecting surface 100 of the present invention, and a lot of light can be incident on the light receiving surface J. The uneven structure of the reflective surface 100 will be described using the normal line N0 and the Gaussian curvature Kg.

The normal line N0 is a straight line perpendicular to the tangent plane at an arbitrary point on the reflecting surface 100.
Further, from FIG. 11, the sheet normal NB is a normal normal to the flow direction (TD) and the width direction (MD) of the light reuse sheet 20. Therefore, the angle θ1 of the reflecting surface 100 is an angle formed by the normal line N0 of the reflecting surface 100 and the sheet normal line NB.

  Usually, since the sheet normal NB is arranged to be parallel to the normal NG of the incident surface 100, the incident light H1 enters in parallel to the sheet normal NB.

Next, the Gaussian curvature Kg represents the curvature of a curved surface and is generally expressed as follows. That is, assuming that the minimum curvature K1 and the maximum curvature K2 of the curve K of the cross section passing through a fixed point on the curved surface are K2, the Gaussian curvature Kg of the curved surface is the following formula 1, that is, the curvature of the curve. It is defined as the product of the maximum value and the minimum value of K.

Next, consider the case where the Gaussian curvature Kg of the reflecting surface 100 is positive, negative, or zero.
A quadric surface in three dimensions is known to have a spherical shape when it has a positive Gaussian curvature Kg, and a horseshoe shape when it has a negative curvature. It is known that when the Gaussian curvature Kg is 0, for example, it becomes a cylindrical surface or a conical surface.

  As shown in FIG. 2, when light H <b> 1 parallel to the sheet normal NB is incident on the reflective surface 100 having a positive Gaussian curvature Kg, the light H <b> 2 is scattered radially on the reflective surface 100. The light distribution of the light H2 at this time is shown in FIG.

  In addition, as shown in FIG. 3, even when the Gaussian curvature Kg is negative, similarly, the light H2 that is incident and reflected by the light H1 parallel to the sheet normal NB is scattered radially. . The light distribution of the light H2 at this time is similarly as shown in FIG.

  On the other hand, when the Gaussian curvature Kg is 0, two cases will be described. One is a case where the reflecting surface 100 has a shape obtained by cutting a part of a cone, as shown in FIG. At this time, the light distribution of the light H2 obtained by reflecting the light H1 parallel to the sheet normal NB on the reflecting surface 100 is not a radial shape but a curved shape as shown in FIG.

On the other hand, as shown in FIG. 5, when the normal line N0 of the reflecting surface 100 is a shape obtained by cutting a part of a cylinder, the light H2 parallel to the sheet normal line NB is reflected by the reflecting surface 100. The light distribution of is as shown in FIG.
As shown in FIG. 6, when the reflecting surface 100 is composed of a plurality of planes, the Gaussian curvature Kg in the planes 101 and 102 is naturally 0. At this time, the light distribution of the light H2 obtained by reflecting the light H1 parallel to the sheet normal NB on the reflecting surface 100 is as shown in FIG.
As another example, also in the case shown in FIG. 7, the Gaussian curvature Kg is 0 in the reflecting surfaces 101 and 102. At this time, the light distribution of the light H2 obtained by reflecting the light H1 parallel to the sheet normal NB on the reflecting surfaces 101 and 102 is shown in FIG.
That is, as shown in FIGS. 4 to 7, when the Gaussian curvature Kg of the reflecting surface 100 is 0, the reflected light H2 is not diverged and collected, but from (b) to (e) in FIG. It becomes a curve or a linear light distribution as shown in FIG.

  By the way, although photoelectric conversion is not performed in the area | region R between the adjacent photovoltaic cells 30, H1 which injects into the light reuse sheet | seat 20 irradiated to this area | region R is the light-receiving surface J side at the photovoltaic cell 30 side. The above-mentioned light H1 can be used effectively by turning it to. At this time, as shown in FIGS. 4 to 7, if the Gaussian curvature Kg of the reflecting surface 100 is 0, the reflected light H2 is reflected in a specific direction without diverging or condensing. It can inject | emitted efficiently in the direction of the photovoltaic cell 30. FIG.

  Further, the normal line N0 of the reflective surface 100 is in the direction of the solar battery cell 30 as shown in FIG. 9 or 10 so that the light H2 reflected by the reflective surface 100 goes in the direction of the solar battery cell 30. It is desirable. In this way, light can be reused more effectively.

  Note that the ratio of the surface of the reflecting surface 100 where the Gaussian curvature Kg is 0 is desirably 90% or more and 100% or less with respect to the sheet surface 105. When the ratio at which the Gaussian curvature Kg is 0 is less than 90%, the reflected light H2 cannot be emitted in the direction of the solar battery cell 30 sufficiently efficiently.

Further, if the angle formed by the incident light H1 and the reflected light H2 is increased, the reflected light H2 can be incident on the light receiving surface J of the separated solar battery cell 30, so that it is away from the solar battery cell 30. Even the light H1 incident on the light can be used, and the light incident on the light receiving surface J increases. As a result, the light use efficiency can be increased.
For this purpose, the angle θ1 of the reflecting surface 100 may be increased. If the angle of the reflected light H2 is 45 degrees or more, a sufficient effect can be obtained. That is, it is desirable that the angle θ1 of the reflecting surface 100 is 45/2 degrees = 22.5 degrees or more. When the angle θ1 of the reflecting surface 100 is smaller than 22.5 degrees, the light H1 incident perpendicularly to the region R between the adjacent solar cells 30 of the solar cell module 200 is directed in the direction of the solar cell 30. Since it cannot reflect enough, the light which injects into the light-receiving surface J cannot fully be obtained. However, when the angle θ1 is larger than 30 degrees, the reflected light H2 is multiple-reflected as shown in FIG. Multiple reflection does not occur if the angle θ1 of the reflecting surface 100 is 30 degrees or less. Therefore, the angle θ1 of the reflecting surface 100 is preferably 30 degrees or less.

  Further, in the reflecting surface 100, the ratio of the area where the angle θ1 of the reflecting surface 100 is 22.5 degrees or more and 30 degrees or less is that of the surface where the angle θ1 of the reflecting surface 100 is smaller than 22.5 degrees and larger by 30 degrees. It is desirable that it is not less than the area ratio. Of the reflecting surface 100, if the ratio of the angle θ1 of the reflecting surface 100 is 22.5 degrees or more and 30 degrees or less is smaller than the ratio of the area of other angles, sufficient light is incident on the light receiving surface J. I can't.

The reflective surface 100 also has microscopic irregularities, but it is referred to as a Mie scattering region up to about 10 times the wavelength of light, which becomes a scattering region, and the visible light region is from 460 nm to 780 nm. The normal line N0 can be obtained by performing a smoothing process so that the surface state having a roughness of 7.8 μm or less becomes smooth. As this measuring method, it is desirable to use a laser microscope. Moreover, cross-sectional measurement using an optical microscope or an electron microscope can also be used. At this time, the sheet normal NB can be regarded as a line perpendicular to the sample stage on which the light reuse sheet 20 is placed.
When measuring the Gaussian curvature Kg of the light reflecting surface 100, as in the case of the normal line N0, the curvature K is measured after the smoothing process in which the surface state with a roughness of 7.8 μm or less becomes smooth, It can be obtained by the above-mentioned formula 1. When measuring the curvatures K1 and K2, the curvature K calculated by estimating the direction of the minimum curvature K1 and the maximum curvature K2 from the shape of the reflecting surface 100 can be used. Here, when the curvature K is equal to or less than the measurement error, the Gaussian curvature Kg is considered to be zero. By the way, when the curvature K is 0, it can be said that there is no curvature K, and when the curvature K is other than 0, there is the curvature K.
Regardless of the above, it is also possible to determine whether or not the Gaussian curvature Kg is 0 by determining whether or not the curvature K is present after taking out a cross section of the sample with a microtome or the like.

  In the reflective surface 100, the normal line N0 and the Gaussian curvature Kg can be obtained at a plurality of points. In actual measurement, the reflection surface 100 is measured at a pitch of about 0.01 mm and is within the range of the present invention. It is realistic to use this as the standard. Even if the normal N0 and the Gaussian curvature Kg are measured at finer points, it is not appropriate as a measurement for examining the behavior of the reflected light H2 reflected by the reflecting surface 100. Moreover, if the measurement is performed with a rough pitch, the uneven structure of the reflecting surface 100 cannot be measured sufficiently.

In this way, the reflective surface 100 is measured from 10 points to 100 points, and the ratio of the number of surfaces having a Gaussian curvature Kg of 0 is set as the area ratio of the reflective surface 100 having a Gaussian curvature Kg of 0. it can. For example, if the point where the Gaussian curvature Kg is 0 is 92 points, it can be said that the Gaussian curvature Kg is 0 at 92% of the reflecting surface 100.
Further, the angle θ1 of the reflecting surface 100 is obtained in the same manner as described above, and the ratio of the area where the angle θ1 of the reflecting surface 100 is 22.5 degrees or more and 30 degrees or less is an area where the Gaussian curvature Kg is 0. The ratio of measurement points can be used in the same manner as when the ratio is obtained.

  As a mold for forming the reflective surface 100, a mold produced by mechanical cutting can be used. In this case, a straight surface is more preferably used as the inclined surface. Further, the tip is preferably rounded because the lens is easily damaged.

  As a method for forming a concavo-convex structure on the structure layer 3, a thermosetting resin, an ultraviolet curable resin, an electron beam curable resin, or the like is applied or injected onto the concavo-convex forming surface of a flat stamper or roll stamper, and the substrate 2 is applied thereon. And a method of releasing from the stamper after the curing process.

  Moreover, as a manufacturing method of the light reuse sheet | seat 20 which consists only of the structure layer 3 without using the base material 2 like FIG. 14, the base material by the press method using a metal mold | die, the casting method, the injection molding method, etc. 2 and the method of integrally molding. In this way, the concavo-convex structure is formed simultaneously with the sheet formation.

  Moreover, the uneven structure of the reflective surface 100 may have a periodic structure. The uneven structure of the reflection surface 100 may be a prism shape, various lens / prism shapes such as a cylindrical lens, or an indeterminate shape. At this time, the pitch of the periodical structure of the reflective surface 100 is desirably 300 μm or less, and more desirably 200 μm or less. When the pitch of the period of the above-described structure is larger than 300 μm, the moldability is poor because the resin does not sufficiently enter the mold of the concave and convex shape when the reflecting surface 100 is molded. If the pitch of the period of the above-mentioned structure is 200 μm or less, even a resin having a relatively high viscosity can be molded. In addition, if the pitch of the above-described structure is too small, it becomes difficult to produce a mold. Therefore, it is preferably 25 μm or more, and more preferably 50 μm or more. If the pitch of the period of the above-mentioned structure is smaller than 25 μm, it takes a long time to cut the mold and the tact time decreases, resulting in poor production efficiency. When the pitch of the period of the above-described structure is smaller than 50 μm, the resin does not enter the groove well when the reflecting surface 100 is formed, and the shape of the concavo-convex tip portion cannot be manufactured as the mold.

  Furthermore, the thickness of the structural layer 3 is not particularly limited, but is, for example, 30 μm or more and 500 μm or less.

  The above-described production method may be appropriately selected depending on suitability for the following materials.

  In the polymer composition forming the structural layer 3, in addition to the polymer composition, for example, a scattering reflector, a curing agent, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, an antioxidant, a viscosity modifier, A lubricant, a light stabilizer and the like may be appropriately blended.

  The above-mentioned polymer composition is not particularly limited. 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, acrylonitrile- (poly) styrene copolymer (AS resin), polystyrene resin such as acrylonitrile-butadiene-styrene copolymer (ABS resin), Polyvinyl chloride resin, polycarbonate resin, polyester resin, polyamide resin, polyamideimide resin, polyaryl phthalate resin, polysulfone resin, polyphenylene sulfide resin, polyether sulfone resin, reethylene naphthalene DOO-based resins, polyether imide resins, acetal resins, cellulose resins and the like, can be used as a mixture of these polymers alone or in combination.

  Examples of the polyol that is a raw material for the polyurethane resin include a polyol obtained by polymerizing a monomer component containing a hydroxyl group-containing unsaturated monomer, a polyester polyol obtained under conditions of excess hydroxyl group, and the like. These can be used alone or in admixture of two or more.

  Examples of the hydroxyl group-containing unsaturated monomer include (a) 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, allyl alcohol, homoallyl alcohol, Keihi Hydroxyl group-containing unsaturated monomers such as alcohol and crotonyl alcohol, (b) for example ethylene glycol, ethylene oxide, propylene glycol, propylene oxide, butylene glycol, butylene oxide, 1,4-bis (hydroxymethyl) cyclohexane, phenylglycidyl Dihydric alcohols or epoxy compounds such as ether, glycidyl decanoate, Plaxel FM-1 (manufactured by Daicel Chemical Industries, Ltd.) and, for example, acrylic acid, methacrylic acid, maleic acid, fumaric acid, Tonsan, and the like hydroxyl group-containing unsaturated monomers obtained by reaction of an unsaturated carboxylic acid such as itaconic acid. One or more selected from these hydroxyl group-containing unsaturated monomers can be polymerized to produce a polyol.

  The polyols described above are ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, ethyl hexyl acrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, N-butyl methacrylate, tert-butyl methacrylate, ethyl hexyl methacrylate, glycidyl methacrylate, cyclohexyl methacrylate, styrene, vinyl toluene, 1-methylstyrene, acrylic acid, methacrylic acid, acrylonitrile, vinyl acetate, vinyl propionate, stearin Vinyl acid, allyl acetate, diallyl adipate, diallyl itaconate, diethyl maleate, vinyl chloride, vinylidene chloride, acrylamide, N-methylol acrylamide, N-butyl One or more ethylenically unsaturated monomers selected from xymethyl acrylamide, diacetone acrylamide, ethylene, propylene, isoprene and the like, and a hydroxyl group-containing non-functional group selected from the above (a) and (b) It can also be produced by polymerizing a saturated monomer.

  The number average molecular weight of a polyol obtained by polymerizing a monomer component containing a hydroxyl group-containing unsaturated monomer is from 1,000 to 500,000, preferably from 5,000 to 100,000. The hydroxyl value is 5 or more and 300 or less, preferably 10 or more and 200 or less, more preferably 20 or more and 150 or less.

  The polyester polyol obtained under the condition of excess hydroxyl group is (c), for example, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl. Glycol, hexamethylene glycol, decamethylene glycol, 2,2,4-trimethyl-1,3-pentanediol, trimethylolpropane, hexanetriol, glycerin, pentaerythritol, cyclohexanediol, hydrogenated bisphenol A, bis (hydroxymethyl) Polyhydric alcohols such as cyclohexane, hydroquinone bis (hydroxyethyl ether), tris (hydroxyethyl) isosinurate, xylylene glycol, and (d) maleic acid, for example. Polybasic acids such as fumaric acid, succinic acid, adipic acid, sebacic acid, azelaic acid, trimetic acid, terephthalic acid, phthalic acid, and isophthalic acid, and polyvalent acids such as propanediol, hexanediol, polyethylene glycol, and trimethylolpropane It can be produced by reacting under conditions where the number of hydroxyl groups in the alcohol is greater than the number of carboxyl groups of the polybasic acid.

  The number average molecular weight of the polyester polyol obtained under the above hydroxyl group-excess conditions is 500 or more and 300,000 or less, preferably 2000 or more and 100,000 or less. The hydroxyl value is 5 or more and 300 or less, preferably 10 or more and 200 or less, more preferably 20 or more and 150 or less.

  The polyol used as the polymer material of the polymer composition is obtained by polymerizing the above-described polyester polyol and a monomer component containing the above-mentioned hydroxyl group-containing unsaturated monomer, and is a (meth) acryl unit. Etc. are preferred. If such polyester polyol or acrylic polyol is used as a polymer material, the weather resistance is high, and yellowing of the structural layer 3 can be suppressed. In addition, any one of this polyester polyol and acrylic polyol may be used, and both may be used.

  The number of hydroxyl groups in the above-described polyester polyol and acrylic polyol is not particularly limited as long as it is 2 or more per molecule, but if the hydroxyl value in the solid content is 10 or less, the number of crosslinking points decreases, and the solvent resistance Film properties such as heat resistance, water resistance, heat resistance and surface hardness tend to decrease.

  A scattering reflector may be contained in the polymer composition forming the structural layer 3 in order to improve reflection performance and heat resistance performance. By including a scattering reflector in the polymer composition, the heat resistance of the structural layer 3 and thus the light reuse sheet 20 can be improved, and if the refractive index is significantly different from that of the polymer composition, light can be emitted. Can be reflected. In addition, when sufficient reflectance is obtained by this, the metal reflective layer 4 does not need to be provided as shown in FIG. The inorganic material constituting the scattering reflector agent is not particularly limited, and an inorganic oxide is preferable. As the inorganic oxide, silica or the like can be used, but a metal compound such as ZnS can also be used, but metal oxides such as TiO2, ZrO, and Al2O3 are particularly desirable. Silica hollow particles can also be used. Of these, TiO2 is preferable because of its high refractive index and easy dispersibility. The shape of the scattering reflector may be any particle shape such as a spherical shape, a needle shape, a plate shape, a scale shape, and a crushed shape, and is not particularly limited.

  The lower limit of the average particle diameter of the scattering reflector is preferably 0.1 μm, and the upper limit is preferably 30 μm. If the average particle diameter is smaller than 0.1 μm, light is not sufficiently reflected. Further, if the average particle size is larger than 30 μm, the moldability is poor.

  The lower limit of the amount of the scattering reflector to 100 parts of the polymer composition is preferably 30 parts in terms of solid content. On the other hand, the upper limit of the amount of the scattering reflector described above is preferably 100 parts. This is because when the amount of the inorganic filler is less than 30 parts, the light H1 incident on the structural layer 3 from the filler layer 21 cannot be sufficiently reflected. On the contrary, if the blending amount exceeds the above range, the moldability is poor.

  As the above-mentioned scattering reflector, one having an organic polymer fixed on its surface may be used. Thus, by using the scattering reflector fixed to the organic polymer, the dispersibility in the polymer composition and the affinity with the polymer composition can be improved. The organic polymer is not particularly limited with respect to its molecular weight, shape, composition, presence or absence of a functional group, and any organic polymer can be used. Moreover, about the shape of an organic polymer, the thing of arbitrary shapes, such as a linear form, a branched form, and a crosslinked structure, can be used.

  Specific resins constituting the above-mentioned organic polymer include, for example, (meth) acrylic resin, polystyrene, polyvinyl acetate, polyolefin such as polyethylene and polypropylene, polyester such as polyvinyl chloride, polyvinylidene chloride, polyethylene terephthalate, and the like. And a resin partially modified with a functional group such as an amino group, an epoxy group, a hydroxyl group, or a carboxyl group. Among them, those having an organic polymer containing a (meth) acryl unit such as a (meth) acrylic resin, a (meth) acrylic-styrene resin, and a (meth) acrylic-polyester resin have a film forming ability. Is preferred. On the other hand, a resin having compatibility with the above-described polymer composition is preferable, and therefore, a resin having the same composition as the polymer composition is most preferable.

  As the above-mentioned polymer composition, a polyol having a cycloalkyl group is preferable. By introducing a cycloalkyl group into the polyol as the polymer composition, the polymer composition becomes highly hydrophobic, such as water repellency and water resistance, and the structural layer 3 and thus the light reuse sheet 20 under high temperature and high humidity conditions. The bending resistance, dimensional stability, etc. are improved. In addition, the basic properties of the coating layer such as weather resistance, hardness, feeling of holding, and solvent resistance of the structural layer 3 are improved. Furthermore, the affinity with the scattering reflector having the organic polymer fixed on the surface and the dispersibility of the scattering reflector are further improved.

  Moreover, it is good to contain isocyanate as a hardening | curing agent in a polymer composition. Thus, by containing an isocyanate hardening | curing agent in a polymer composition, it becomes a much stronger crosslinked structure and the film physical property of the structural layer 3 further improves. As this isocyanate, the same substance as the above-mentioned polyfunctional isocyanate compound is used. Of these, aliphatic isocyanates that prevent yellowing of the coating are preferred.

  The scattering reflector may contain an organic polymer inside. Thereby, moderate softness and toughness can be imparted to the inorganic material that is the core of the scattering reflector.

  As the above-mentioned organic polymer, one containing an alkoxy group may be used, and the content thereof is not particularly limited, but is preferably 0.01 mmol or more and 50 mmol or less per 1 g of the scattering reflector. The alkoxy group can improve the affinity with the polymer composition and the dispersibility in the polymer composition.

  The above-described alkoxy group represents an RO group bonded to a metal element that forms a fine particle skeleton. R is an alkyl group which may be substituted, and the RO groups in the fine particles may be the same or different. Specific examples of R include methyl, ethyl, n-propyl, isopropyl, n-butyl and the like. The same metal alkoxy group as the metal constituting the scattering reflector is preferably used. When the scattering reflector is colloidal silica, it is preferable to use an alkoxy group having silicon as a metal.

  The organic polymer content of the scattering reflector to which the organic polymer is fixed is not particularly limited, but is preferably 0.5% by mass or more and 50% by mass or less based on the scattering reflector.

  When the reflective layer 4 is used in the light reuse sheet 20, surface treatment may be performed on the deposition target surface of the reflective layer 4 (the surface of the structural layer 3) in order to improve the tight adhesion and the like (not shown). ). Examples of such surface treatment include (a) corona discharge treatment, ozone treatment, low temperature plasma treatment using oxygen gas or nitrogen gas, glow discharge treatment, oxidation treatment using chemicals, and (b) primer. Examples of the coating treatment include undercoating, anchor coating, vapor deposition anchor coating, and the like. Among these surface treatments, a corona discharge treatment and an anchor coat treatment that improve adhesion strength with the reflective layer 4 and contribute to the formation of a dense and uniform reflective layer 4 are preferable.

  Examples of the anchor coating agent used in the above-described anchor coating treatment include a polyester anchor coating agent, a polyamide anchor coating agent, a polyurethane anchor coating agent, an epoxy anchor coating agent, a phenol anchor coating agent, and a (meth) acrylic anchor. Examples thereof include a coating agent, a polyvinyl acetate anchor coating agent, a polyolefin anchor coating agent such as polyethylene aly polypropylene, and a cellulose anchor coating agent. Among these anchor coating agents, polyester anchor coating agents that can further improve the adhesive strength of the reflective layer 4 are particularly preferable.

  The coating amount (in terms of solid content) of the above-described anchor coating agent is preferably 1 g / m 2 or more and 3 g / m 2 or less. When the coating amount of the anchor coating agent is less than 1 g / m 2, the adhesion improving effect of the reflective layer 4 is reduced. On the other hand, when the coating amount of the anchor coating agent is more than 3 g / m 2, the strength, durability, etc. of the light reuse sheet 20 may be lowered.

  In the above-mentioned anchor coating agent, various additives such as a silane coupling agent for improving tight adhesion, an anti-blocking agent for preventing blocking, and an ultraviolet absorber for improving weather resistance, etc. It can mix suitably. The amount of the additive to be mixed is preferably 0.1% by weight or more and 10% by weight or less from the balance between the effect expression of the additive and the function inhibition of the anchor coating agent. If the above-mentioned additive is less than 0.1% by weight, blocking cannot be sufficiently prevented and sufficient weather resistance cannot be obtained, and if it is more than 10% by weight, the function of the topcoat agent is inhibited.

  The reflective layer 4 reflects light incident on the light reuse sheet 20. When the reflective layer 4 is formed, the reflective layer 4 is formed by vapor-depositing a metal along the surface on which the concavo-convex structure of the structural layer 3 is formed. The means for depositing the reflective layer 4 is not particularly limited as long as a metal can be deposited without causing deterioration of the structural layer 3 such as shrinkage and yellowing. (A) Vacuum deposition method, sputtering method, ion plate Chemical vapor deposition methods (Physical Vapor Deposition method; PVD method), (b) Plasma chemical vapor deposition method, thermal chemical vapor deposition method, photochemical vapor deposition method, etc. A phase growth method (Chemical Vapor Deposition method; CVD method) is employed. Among these vapor deposition methods, a vacuum vapor deposition method and an ion plating method that can form a high-quality reflective layer 4 with high productivity are preferable.

  The metal used for the reflective layer 4 is not particularly limited as long as it has a metallic luster and can be deposited. For example, aluminum (Al), silver (Ag) nickel (Ni), tin (Sn), Zirconium (Zr) etc. are mentioned. Among these, aluminum is preferable because it is highly reflective and the dense reflective layer 4 can be formed relatively easily.

  The reflective layer 4 may have a single layer structure or a multilayer structure of two or more layers. Thus, by making the reflective layer 4 into a multi-layer structure, the deterioration of the structural layer 3 is reduced by reducing the thermal burden during vapor deposition, and the adhesion between the structural layer 3 and the reflective layer 4 is further improved. Can do. At this time, a metal oxide layer may be provided on the metal film. The vapor deposition conditions in the physical vapor deposition method and the chemical vapor deposition method are appropriately designed according to the resin type of the structural layer 3 and the base material 2, the thickness of the reflective layer 4, and the like.

  As a minimum of the thickness of the reflection layer 4, 10 nm is preferable and 20 nm is especially preferable. On the other hand, the upper limit of the thickness of the reflective layer 4 is preferably 200 nm, and particularly preferably 100 nm. If the thickness of the reflective layer 4 is smaller than the lower limit of 10 nm, the light incident on the reflective layer 4 from the filling layer 21 cannot be sufficiently reflected. Further, even if the thickness is 20 nm or more, the light reflected by the reflection layer 4 does not increase. On the other hand, if the thickness of the reflective layer 4 exceeds the upper limit of 200 nm, cracks that can be visually confirmed occur in the reflective layer 4, and cracks that cannot be visually confirmed occur if the thickness is 100 nm or less.

  Further, the outer surface of the reflective layer 4 is preferably subjected to a top coat treatment (not shown). By performing the top coat treatment on the outer surface of the reflective layer 4 in this manner, the reflective layer 4 is sealed and protected, and as a result, the handleability of the light reuse sheet 20 is improved. Moreover, the aged deterioration of the reflective layer 4 is also suppressed.

  Examples of the topcoat agent used in the above-described topcoat treatment include a polyester topcoat agent, a polyamide topcoat agent, a polyurethane topcoat agent, an epoxy topcoat agent, a phenol topcoat agent, and a (meth) acrylic top. Examples thereof include a coating agent, a polyvinyl acetate top coating agent, a polyolefin top coating agent such as polyethylene aly polypropylene, and a cellulose top coating agent. Among such topcoat agents, a polyester-based topcoat agent that has high adhesive strength with the reflective layer 4 and contributes to surface protection of the reflective layer 4, sealing of defects, and the like is particularly preferable.

  The coating amount (in terms of solid content) of the above-mentioned top coat agent is preferably 3 g / m 2 or more and 7 g / m 2 or less. When the coating amount of the top coat agent is smaller than 3 g / m 2, the effect of sealing and protecting the reflective layer 4 may be reduced. On the other hand, even if the coating amount of the top coat agent exceeds 7 g / m 2 above, the sealing and protecting effect of the reflective layer 4 does not increase so much, and the thickness of the light reuse sheet 20 increases instead. .

  In addition, in the above-mentioned top coat agent, various additives such as a silane coupling agent for improving tight adhesion, an ultraviolet absorber for improving weather resistance and the like, an inorganic filler for improving heat resistance and the like Can be mixed as appropriate. The amount of the additive to be mixed is preferably 0.1% by weight or more and 10% by weight or less from the balance between the effect expression of the additive and the function inhibition of the topcoat agent. If the above-mentioned additive is less than 0.1% by weight, close adhesion, weather resistance and heat resistance cannot be sufficiently obtained, and if it is more than 10% by weight, the function of the topcoat agent is inhibited.

The base material 2 constituting the light reuse sheet 20 is formed by sheet molding using a synthetic resin as a material. As the synthetic resin used for the base material 2, in view of being installed outdoors, it is desirable to have water resistance, weather resistance such as durability against ultraviolet rays, for example, polyethylene terephthalate resin (PET resin), etc. Polyethylene resin, polypropylene resin, methacrylic resin, polymethylpentene resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile- (poly) styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), polyvinyl chloride resin, fluorine resin, poly (meth) acrylic resin, polycarbonate resin, polyester resin, polyamide resin, polyimide resin, polyamideimide resin, polyarylphthalate resin, Silicone resin, polysulfo System resin, polyphenylene sulfide resins, polyether sulfone resins, triethylene naphthalate resins, polyether imide resins, Epokishin resins, polyurethane resins, acetal resins, cellulose resins and the like.
Among the above resins, polyimide resins, polycarbonate resins, polyester resins, fluorine resins, polylactic acid resins are those having high heat resistance, strength, weather resistance, durability, gas barrier properties against water vapor and the like. preferable.

  Examples of the polyester-based resin include polyethylene terephthalate and polyethylene naphthalate. Among these polyester-based resins, polyethylene terephthalate is particularly preferable because it has a good balance between various functions such as heat resistance and weather resistance, and price.

  Examples of the fluororesin include polytetrafluoroethylene (PTFE), perfluoroalkoxy resin (PFA) made of a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, and a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP). ), Copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether and hexafluoropropylene (EPE), copolymer of tetrafluoroethylene and ethylene or propylene (ETFE), polychlorotrifluoroethylene resin (PCTFE), ethylene and chlorotrifluoroethylene Copolymer (ECTFE), vinylidene fluoride resin (PVDF), vinyl fluoride resin (PVF), and the like. Among these fluororesins, polyvinyl fluoride resin (PVF) and a copolymer of tetrafluoroethylene and ethylene or propylene (ETFE) which are excellent in strength, heat resistance, weather resistance and the like are particularly preferable.

  Examples of the above-mentioned cyclic polyolefin-based resin include polymerizing cyclic dienes such as a) cyclopentadiene (and derivatives thereof), dicyclopentadiene (and derivatives thereof), cyclohexadiene (and derivatives thereof), norbornadiene (and derivatives thereof), and the like. And b) a copolymer obtained by copolymerizing the cyclic diene with one or more olefinic monomers such as ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, and isoprene. It is done. Among these cyclic polyolefin resins, cyclopentadiene (and derivatives thereof), dicyclopentadiene (and derivatives thereof) or norbornadiene (and derivatives thereof) such as polymers having excellent strength, heat resistance, and weather resistance are particularly preferred. preferable.

  In addition, as a formation material of the base material 2, the above-mentioned synthetic resin can be used 1 type or in mixture of 2 or more types. In addition, various additives and the like can be mixed in the forming material of the base material 2 for the purpose of improving and modifying processability, heat resistance, weather resistance, mechanical properties, dimensional stability, and the like. Examples of the additive include a lubricant, a crosslinking agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a filler, a reinforcing fiber, a reinforcing agent, an antistatic agent, a flame retardant, a flame retardant, a foaming agent, and an antifungal agent. And pigments. The method for forming the substrate 2 is not particularly limited, and known methods such as an extrusion method, a cast forming method, a T-die method, a cutting method, and an inflation method are employed.

  When the substrate 2 is used, the thickness is preferably 25 μm or more and 500 μm or less, and particularly preferably 250 μm. When the thickness of the substrate 2 is less than 25 μm, curling occurs during the coating process of the structural layer 3 due to the influence of curing shrinkage of an ultraviolet curable resin or the like, and a problem occurs when it is incorporated into the solar cell module 200. Conversely, if the thickness of the substrate 2 exceeds 500 μm, the film weight increases and the weight of the solar cell module 200 also increases. If it is 250 micrometers or less, the lighter-weight solar cell module 200 is realizable.

  Further, the base material 2, the structural layer 3, and the base material 2 may contain an ultraviolet stabilizer or a polymer in which an ultraviolet stabilizing group is bonded to a molecular chain. By this ultraviolet stabilizer or ultraviolet stabilizer, radicals generated by ultraviolet rays, active oxygen, etc. are inactivated, and the ultraviolet stability, weather resistance, etc. of the light reuse sheet 20 can be improved. As the UV stabilizer or UV stabilizer, a hindered amine UV stabilizer or a hindered amine UV stabilizer having high stability to UV is preferably used.

  According to the solar cell module 200 using the light reuse sheet 20 having such characteristics, the light incident on the region R between the adjacent solar cells 30 is reflected by the reflection surface 100 of the light reuse sheet 20, The light can enter the solar battery cell 30. Thereby, the light incident on the region R between the adjacent solar cells 30 can also be used, and the power generation efficiency of the solar cell module 200 can be improved.

  The light reuse sheet 20 can also be disposed with the back surface of the reflection surface 100 of the light reuse sheet 20 facing the filling layer side 21 as shown in FIG.

  Further, as shown in FIG. 16, the light reuse sheet 20 having a barrier layer made of an aluminum layer of 10 μm to 30 μm and a silica layer of 10 nm to 100 nm can be used. Moreover, in order to raise durability, you may make it protect a solar cell module by apply | coating PVF (polyvinyl fluoride resin) or bonding together the film which has a polyvinyl fluoride resin. By doing in this way, the solar cell module 200 can also be used as a back sheet.

Example 1
As Example 1, a polycarbonate resin, which is a thermoplastic resin, was heated to about 300 ° C. and formed into a 0.3 mm thick film while being stretched along a roll, and then the shape of the first concavo-convex structure was cut. Using a cylinder mold, the heated film is cooled while being pressurized (cylinder mold itself is 80 ° C.), and then the film having the shape of the first concavo-convex structure is completely cured before the film is completely cured. 2 is further heated by pressurizing with a cylinder mold in which the shape of the concavo-convex structure is cut (the temperature of the cylinder mold in which the shape of the second lens array 5 is cut is 10 ° C. with a water-cooled roll). The viscosity of the plastic resin was lowered and completely cured. The light reuse sheet 20 produced by this method has a first concavo-convex structure in the form of a lenticular lens having a portion of the reflective surface 100 having a pitch of 120 μm and an angle of 30 degrees, and the longitudinal direction of the concavo-convex structure. The shape of the light reuse sheet 20 having the second concavo-convex structure in the form of a triangular prism having a rounded apex so that the pitch is 30 μm and the angle of the reflection surface 100 is 30 degrees is orthogonal to did.
Thus, by producing a mold roll having the shape of the first concavo-convex structure and the second first concavo-convex structure on the cooling roll, the extrusion is once performed by roll-to-roll (film feed speed 1 m / min). It was possible to produce the structural layer 3.
When the surface shape of this light reuse sheet 20 was measured with a scanning confocal laser microscope OLS1100 at 100 points at a pitch of 15 μm, the Gaussian curvature Kg was 0 at all points, and the reflection surface 100 was at 62 points. The angle was changed from 22.5 degrees to 30 degrees.
Further, the reflective layer 4 was formed thereon by vapor deposition so that aluminum was about 20 nm.
Further, when the light reuse sheet 20 produced in this way was measured with an easy contrast (viewing angle measuring device), it was possible to obtain almost the same light distribution as in FIG.

(Example 2)
As Example 2, a polycarbonate resin, which is a thermoplastic resin, was heated to about 300 ° C., formed into a film while being stretched along a roll, and then a cylinder mold cut into the shape of the light reuse sheet 20 was used. By cooling the heated film while applying pressure (the cylinder mold cut into the shape of the light reuse sheet 20 is set to 80 ° C. with a water-cooled roll), the viscosity of the thermoplastic resin is lowered, It hardened | cured in the state which maintained the shape of the utilization sheet | seat 20. FIG.
The light reuse sheet 20 produced by this method has a first concavo-convex structure in the form of a lenticular lens having a portion of the reflective surface 100 having a pitch of 80 μm and an angle of 30 degrees, and a first concavo-convex structure. The shape of the light reuse sheet 20 having the second concavo-convex structure of the triangular prism shape such that the angle of the reflection surface 100 with a pitch of 40 μm is 30 degrees is formed so as to be orthogonal to the longitudinal direction.
Thus, it was possible to produce the light reuse sheet 20 at a time by extrusion molding using a roll-to-roll (film feed rate of 1.5 m / min) with one lens mold roll.
When the surface shape of this light reuse sheet 20 was measured with a scanning confocal laser microscope OLS1100 at 100 points at a pitch of 20 μm, the Gaussian curvature Kg was 0 at 93 points, and the reflective surface 100 was at 65 points. The angle was changed from 22.5 degrees to 30 degrees.
Further, the reflective layer 4 was formed thereon by vapor deposition so that aluminum was about 20 nm.
Further, when the light reuse sheet 20 produced in this way was measured with an easy contrast (viewing angle measuring device) manufactured by ELDIM, it was possible to obtain almost the same light distribution as in FIG.

  Here, in the manufacturing method of Example 1, the shape of the light reuse sheet 20 can be easily deformed by replacing one of the two cooling rolls with a lens having a different shape, whereas the method of Example 2 Then, like Example 1, there exists an advantage that it is easy because there is little effort which sets the cooling temperature of two cooling rolls, and the optimization of pressurization conditions.

(Example 3)
As Example 3, an ultraviolet curable resin (urethane manufactured by Nippon Kayaku Co., Ltd.) containing urethane acrylate as a main component for forming a pattern of the light reuse sheet 20 on an optically biaxially stretchable easy-adhesive PET film (film thickness 125 μm). UV light while transporting a film coated with UV curable resin using a cylinder mold coated with acrylate resin (refractive index 1.51) and cut into the shape of the reflective surface 100 of the light reuse sheet 20 Was exposed from the PET film side to cure the ultraviolet curable resin to form the structural layer 3. After curing, by releasing the mold from the PET film, a first concavo-convex structure in the form of a lenticular lens having a portion of the reflection surface 100 having a pitch of 100 μm and an angle of 30 degrees, and further a first concavo-convex structure The shape of the light reuse sheet 20 having the second concavo-convex structure of the triangular prism shape in which the angle of the reflection surface 100 having a pitch of 75 μm and the angle of 30 degrees is formed so as to be orthogonal to the longitudinal direction is formed.
When the surface shape of this light reuse sheet 20 was measured with a scanning confocal laser microscope OLS1100 at 100 points at a pitch of 25 μm, the Gaussian curvature Kg was 0 at all points, and the reflection surface 100 was 75 points. The angle was changed from 22.5 degrees to 30 degrees.
Moreover, when the light reuse sheet | seat 20 produced in this way was measured by easy contrast (viewing angle measuring apparatus), the waste port distribution of the substantially same shape as FIG.8 (c) was able to be obtained.

Example 4
In Example 4, a prism-like concavo-convex structure in which the angle of the reflective surface 100 having a pitch of 150 μm and a pitch of 150 μm is formed as a structural layer 3 on a 250 μm PET film as the base material 2 is formed as the structural layer 3. Then, a 20 nm aluminum layer was formed as the metal reflective layer 4 by vapor deposition to obtain a light reuse sheet 20. Using this, a solar cell module 200 was produced. The front plate 22 is a glass plate having a thickness of about 2 mm, and the filling layer 21 is formed by filling EVA with a thickness of about 1.5 mm so that the solar battery cell 30 is positioned 1.0 mm from the front plate 22. . The polycrystalline cell type was used as the solar battery cell 30, and the power generation efficiency was measured using the solar battery cell 30 whose peripheral part margin was about 10% with respect to the total area of the solar battery module 200. Table 1 shows the results of the power generation efficiency.

(Example 5)
As Example 5, the configuration of Example 4 described above was changed, an acrylic resin in which 30% of titanium oxide was mixed into the constituent layer 21 was used, the reflective layer 4 was not provided, and the substrate 2 was similarly 250 μm PET. The light reuse sheet 20 using a film was produced and the same measurement was performed. The measurement results are shown in Example 5 in Table 1.

(Comparative Example 1)
As Comparative Example 1, the same measurement was performed on the solar cell module 200 having the conventional configuration, and the power generation efficiency was compared. The measurement results are shown in Comparative Example 1 in Table 1. In the conventional configuration, instead of the light reuse sheet 20, 250 μm white PET is arranged on the back surface.

From the results of Table 1, it can be seen that the power generation efficiency of the solar cell is improved by using the light reuse sheet 20 as in the present invention.

Sectional drawing which shows an example of the solar cell module of this invention. The perspective view which shows an example of a reflective surface. The perspective view which shows an example of a reflective surface. The perspective view which shows an example of the reflective surface of the light reuse sheet | seat of this invention. The perspective view which shows an example of the reflective surface of the light reuse sheet | seat of this invention. The perspective view which shows an example of the reflective surface of the light reuse sheet | seat of this invention. The perspective view which shows an example of the reflective surface of the light reuse sheet | seat of this invention. The figure which shows the example of the light distribution of reflected light. The front view which shows an example of the solar cell module of this invention. The front view which shows an example of the solar cell module of this invention. Sectional drawing which shows an example of the light reuse sheet | seat of this invention. Sectional drawing which shows an example of the light reuse sheet | seat of this invention. Sectional drawing which shows an example of the light reuse sheet | seat of this invention. Sectional drawing which shows an example of the light reuse sheet | seat of this invention. Sectional drawing which shows an example of the solar cell module of this invention. Sectional drawing which shows an example of the solar cell module of this invention. Sectional drawing which shows the solar cell module using the conventional back material

Explanation of symbols

F ... Light source direction, 2 ... Base material, 3 ... Structural layer, 4 ... Reflective layer, 20 ... Light reuse sheet, 21 ... Filling layer, 30 ... Solar cell, 22 ... Front plate, 200 ... Solar cell module, 300 ... Back surface material, 301 ... Reflected light distribution, 100, 101, 102 ... Reflecting surface, 105 ... Sheet surface, 110 ... Incident surface, 120 ... Edge line of reflecting surface, J ... Light receiving surface, Kg ... Gaussian curvature, K ... Curvature , K1 ... Minimum curvature, K2 ... Maximum curvature, TD ... Sheet flow direction, MD ... Sheet width direction, N ... Normal, N0, N1, N2 ... Reflection surface normal, NB ... Sheet normal, NG ... Front plate 22 normal line, θ1: angle of reflection surface, H0: light perpendicularly incident on solar cell module, H1: light incident on reflection surface, H2: reflected light, H3: light to be reused, 40: protective layer・ Protective film, L ... light source

Claims (8)

A front plate for incident light;
A filling layer that transmits light transmitted through the front plate;
Solar cells that are fixed by the filling layer and that transmit light from the filling layer are received from a light receiving surface and converted into electricity, and
A light reuse sheet having a structural layer provided on a back side of the light receiving surface of the solar battery cell and having a reflective layer that reflects light not received on the light receiving surface of the solar battery cell;
A solar cell module comprising: a reflective surface of the reflective layer of the light reuse sheet having a gas curvature of zero. 2. The solar cell module according to claim 1, wherein an area ratio of the reflecting surface having a Gaussian curvature of 0 out of the reflecting surfaces of the reuse sheet is 90% or more. The solar cell module according to claim 1, wherein the structural layer of the light reuse sheet is made of a polymer containing hollow particles and / or titanium oxide particles, and the surface of the structural layer is a reflective surface. 2. The solar cell module according to claim 1, wherein the reflection surface has an angle formed by a normal line of the front plate of the previous period and a normal line of the reflection surface of 22.5 degrees or more and 30 degrees or less. 2. The area ratio of the reflection surface, in which an angle formed between a normal line of the reflection surface and a normal line of the front plate is 22.5 degrees or more and 30 degrees or less, is 50% or more. Solar cell module. 2. The solar cell module according to claim 1, wherein the uneven shape of the structural layer is a unit uneven structure having periodicity. 2. The solar cell module according to claim 1, wherein a periodic pitch of the unit concavo-convex structure is 25 μm or more and 300 μm or less. 2. The solar cell module according to claim 1, wherein a periodic pitch of the unit concavo-convex structure is 50 μm or more and 200 μm or less.

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