WO2006035698A1

WO2006035698A1 - Sheet-like concentrator and solar cell sheet employing it

Info

Publication number: WO2006035698A1
Application number: PCT/JP2005/017608
Authority: WO
Inventors: Toshiya Nishibayashi
Original assignee: Dueller Corporation
Priority date: 2004-09-27
Filing date: 2005-09-26
Publication date: 2006-04-06
Also published as: JPWO2006035698A1; JP4155361B2; TW200614529A

Abstract

Conventional concentrating solar cell has problems of limited concentration magnification, difficulty in follow-up of solar beam, restricted installation space, and the like. A concentrating solar cell sheet suitable for the solar cell and exhibiting good productivity is developed by solving the problems. A diffuse reflection layer (14) is formed on the intermediate layer (13) of a light conducting sheet formed by sandwiching a light conducting layer (12) composed of a high refractive index substance between a light receiving layer (11) composed of a low refractive index substance and the intermediate layer (13), and a lighting part (15) is provided by partially removing the light receiving layer (11) or the intermediate layer (13). The diffuse reflection layer (14) is preferably formed of transparent resin including multiple bubbles. The diffuse reflection layer (14) is preferably formed by gas blowing extrusion. The light receiving layer (11), the light conducting layer (12), the intermediate layer (13) and the diffuse reflection layer (14) are preferably composed of thermoplastic resin and molded integrally by co-extrusion.

Description

Specification

Sheet concentrator and solar cell sheet using the same

Technical field

[0001] The present invention relates to a condensing sheet for a solar cell and a solar cell sheet using the same.

Specifically, since the present invention has a function of confining light, the multilayer plastic foam sheet that can be suitably used for condensing light rays such as sunlight, a manufacturing method thereof, a solar cell device using the multilayer sheet, and It relates to its usage.

Background art

In recent years, solar cells have attracted attention as a power generation method using renewable natural energy from the viewpoint of global environmental conservation. However, sunlight has a low energy density, is not highly efficient in converting the solar energy into electric power by solar cells, and the manufacturing cost of solar cell elements is high. Since it is not economical, it has not yet become a full-fledged practical power generation method. For this reason, in order to efficiently convert sunlight into electric power, development of solar cell elements with high power generation efficiency, examination of condensing methods for increasing energy density, and further cost reduction of solar cell elements, etc. It is being considered.

[0003] Among these, the development of solar cell elements with high power generation efficiency includes the development of single crystal silicon type, compound (Group 3-5, Group 2-6, etc.) semiconductor type solar cells, etc. As a cost reduction method, development of amorphous silicon solar cells is underway.

[0004] Further, as a condensing method for increasing the energy density, a condensing lens method, a reflecting mirror method, a prism method, and the like have been studied. For the purpose of energy conversion of the sun's rays!

[0005] This concentrating solar cell is attracting attention as a relatively low cost and energy efficient method. However, there are advantages and disadvantages depending on the concentrating method, and it has not been widely used!

[0006] As a most general condensing method, there is a method using a Furnell lens (Patent Documents 1, 2, and 3). In this method, the solar cell element is arranged at the focal position of the fullnel lens. Thus, a higher energy density can be realized. However, with this method, it is necessary to accurately track the direction of sunlight, and it is necessary to install a tracking device, so the installation location is also limited. The same limitation can be considered for systems using reflectors.

Patent Documents 4, 5, 6, and 7 disclose examples of concentrators that collect light using reflection and total reflection by a prism having a triangular cross section. However, there are restrictions on the angle of light rays that enter the prism, and there are also problems with the magnification and manufacturing cost.

[0007] On the other hand, Patent Document 8 discloses a sheet in which small prisms, semi-cylindrical or hemispherical protrusions are arranged on the surface of a sheet. Further, Patent Document 9 discloses a prism-like structure between the solar cell element and the surface sheet, and has a function of confining the reflected light of the solar cell element force in this portion. However, these condensing methods have low condensing magnification, and it is not expected to reduce the area of the solar cell element, which is a merit of the concentrating type. Further, Patent Documents 10 and 11 disclose the idea of reliably condensing light by making the prism shape a wedge shape. However, it is considered difficult to realize due to difficulties in manufacturing methods and installation methods.

[0008] Furthermore, a method of dispersing a resin having a different refractive index in a transparent resin has also been reported! (Patent Document 10), but it is expected that the concentrating efficiency of the light collecting efficiency is difficult.

Patent Document 1 Japanese Patent Application Laid-Open No. 2002-289897

Patent Document 2 JP 2002-289898 A

Patent Document 3 Japanese Unexamined Patent Application Publication No. 2004-214470

Patent Document 4 JP 54-018762 A

Patent Document 5 Japanese Patent Laid-Open No. 06-275859

Patent Document 6 Japanese Patent Application Laid-Open No. 07-122771

Patent Document 7 JP 2004-047752 A

Patent Document 8 JP 2000-031515 A

Patent Document 9 JP 2000-323734 A

Patent Document 10: Japanese Patent Laid-Open No. 10-221528

Patent Document 11: Japanese Patent Laid-Open No. 10-335689 Disclosure of the invention

Problems to be solved by the invention

[0010] As described above, the above-described conventional concentrating solar cells have problems such as the limitation of the condensing magnification, difficulty in following the sun beam, and restrictions on the installation space. There is a problem to develop a concentrating solar cell sheet that has good productivity and is suitable as a solar cell.

Means for solving the problem

[0011] The above problems are solved by the present invention described below.

That is, the sheet-like light collector for solar cell according to the present invention is an intermediate layer of a light guide sheet formed by sandwiching a light guide layer made of a high refractive index material between a light receiving layer made of a low refractive index material force and an intermediate layer. It is characterized by laminating an irregular reflection layer on the side and providing a daylighting part in part.

As shown in FIG. 1, the irregular reflection layer 14 is preferably made of a resin (transparent or translucent) containing a large number of bubbles. The irregular reflection layer 14 is preferably formed by gas foam extrusion. The light receiving layer 11, the light guide layer 12, the intermediate layer 13 and the irregular reflection layer 14 are preferably made of a thermoplastic resin and integrally formed by coextrusion.

[0013] The sheet-shaped concentrator 10 according to the present invention preferably further has the following configuration.

First, as shown in FIG. 1, it is desirable that the surface of the light receiving layer 11 has irregularities having a light confinement effect. Next, the area of the light receiving layer 11 is preferably at least twice the area of the daylighting portion 15. More preferably, it is 5 times or more. When it is less than twice, the cost advantage of the sheet-shaped concentrator cannot be obtained, so the value of using the sheet-shaped concentrator 10 is lost.

[0014] Then, it is desirable that an antifouling layer is formed on the surface of the light receiving layer 11. In this case, it is desirable that the antifouling layer has a photoactive catalyst.

[0015] By providing this sheet-shaped concentrator and a solar cell disposed so that the light receiving surface faces the daylighting portion, it can be used as a solar cell sheet.

Brief Description of Drawings FIG. 1 is a schematic explanatory view showing a solar cell sheet using a sheet-like concentrator in one embodiment of the present invention.

FIG. 2 is a schematic explanatory diagram showing light reflection at a bubble interface.

FIG. 3 is a schematic explanatory diagram of an experiment of Example 1.

FIG. 4 is a schematic explanatory diagram of the experiment of Example 2 (without black drawing paper 40).

FIG. 5 is a schematic explanatory diagram of the experiment of Example 2 (with black drawing paper 40).

Explanation of symbols

[0017] 10, 10, ... Sheet concentrator

11, 11 '… Light-receiving layer

12, 12 '... Light guiding layer

13, 13 '... middle class

14, 14 '... diffuse reflection layer

15, 15 '... Daylighting Department

16 ··· Solar cell element

20 ... Air bubbles

31 ··· Solar cell element provided facing the daylighting part of the sheet-shaped concentrator

32… Dark room solar cell element

33 ··· Aluminum foil girlfriend

34. Darkroom

35 ··· Halogen lamp

40 ... Black drawing paper

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] Inside the light guide sheet in which the light guide layer having a high refractive index material force is sandwiched between the light receiving layer and the intermediate layer having a low refractive index material force, the light that has entered the interface at a shallow angle of a predetermined critical angle or more is: Cannot go outside the light guide sheet. However, since the sunlight that first enters the light guide sheet also enters at a deep angle below this critical angle, a large amount of sunlight escapes through the light guide sheet. Even with the method of providing prism-shaped irregularities on the surface, as shown in Patent Document 8, it is difficult to confine light at all angles. It is difficult. Thus, as a result of intensive studies, the present inventor has come up with a method of providing an irregular reflection layer on the surface of the light guide sheet opposite to the side on which sunlight is incident. This irregular reflection layer changes the reflection angle of the light that has passed through the light guide sheet, thereby increasing the probability that the reflected light re-enters the light guide sheet at a shallow angle that is equal to or greater than the critical angle. As a result, all the light that is about to go out of the light guide sheet is returned to the light guide sheet, and most of the force is confined in the light guide sheet. That is, the light collection efficiency can be greatly increased.

[0019] The irregular reflection layer may be a simple total reflection surface such as a mirror surface or a metal surface with a fine force and a scratch (scratched line), but a transparent resin layer containing many bubbles. Is also effective. As shown in Fig. 2, by utilizing the fact that the light reflected by the spherical interface of the bubble 20 is reflected at an angle different from the approach angle, it is possible to re-enter the light guide layer at a shallow angle, For this reason, it discovered that the condensing of light and accumulation | storage in a light guide layer were attained.

[0020] By using the laminated sheet of the present invention as a coextruded sheet, loss of light absorption due to an adhesive or the like on the laminated surface does not occur. Light scattered outside the system is allowed because it was reflected at an angle below the critical angle by scattering reflection at the bubble interface of the diffuse reflection layer.

[0021] The foamed sheet layer according to the present invention desirably has 80% or more of the bubbles contained in the sheet having a bubble diameter in the range of 0.1 to 50 m. As a result, good reflection characteristics can be obtained. Furthermore, it is preferable that 80% or more of the bubbles contained in the sheet have a bubble diameter in the range of 0.4 to 20 m. If the bubble diameter is too large, an optical interference effect or the like is caused, and sufficient reflection cannot be obtained. Conversely, if the bubble diameter is too large, the area that is reflected in the direction perpendicular to the sheet increases, which is not preferable.

[0022] The foamed sheet layer according to the present invention desirably has a porosity in the range of 20 to 80%. As a result, good reflection characteristics can be obtained. The porosity corresponds to the density of bubbles contained in the foamed sheet, and can be determined from the force sheet representing the gas phase occupation ratio of the sheet, the density of the resin used, and the sheet volume. The porosity of the sheet is further preferably 50 to 70%. This is because the theoretical maximum porosity is about 70% in order to maintain the spherical shape of the bubble, and if it exceeds this, the bubble collapses and good reflection characteristics can be obtained. It is not possible. On the other hand, when the porosity is too low, the density of the bubbles becomes too low and the desired reflection characteristics cannot be obtained. [0023] The light guide layer based on the high refractive index resin in the present invention and the light receiving layer and intermediate layer based on the low refractive index resin laminated on both sides thereof are the light guide layer, the light receiving layer, and the light receiving layer. Since it is possible to prevent light that has entered at the interface of the intermediate layer at an angle greater than the critical angle from leaking out from the high refractive index layer, the light can be confined in the light guide layer. The light guide layer, the light receiving layer, and the intermediate layer are more preferable because the critical angle can be reduced as the difference in refractive index increases.

In the present invention, the main thermoplastic resin constituting the diffuse reflection layer having foaming is preferably a resin having a high melt tension in order to promote fine foaming. Therefore, the melt flow rate (measured according to ASTM D1238-98) showing the fluidity in the molten state is preferably 0.5 to 44 g / 10 min. A 10 minute thermoplastic resin is more preferred. The fluidity of thermoplastic resin can be determined according to the measurement conditions (temperature, load, etc.) for various polymers described in ASTM D1238-98.

[0025] Specific examples of the thermoplastic resin that can be used in each of the irregular reflection layer, the light guide layer, the light receiving layer, and the intermediate layer in the present invention include, for example, acrylic resin, methacrylic resin, polyolefin, polyamide, and polyester. , Polycarbonate, styrene-based resin, polyetherol, polyurethane, polyphenylene sulfide, polyesteramide, polyetherester, polychlorinated butyl, modified polyphenylene ether, polyarylate, polysulfone, polyimide, polyetherimide, polyamideimide, and these The force which can mention the copolymer which makes this a main component, these mixtures, etc. is not limited to these.

[0026] In particular, when acrylic resin and Z or methacrylic resin are used as the main thermoplastic resin constituting the irregular reflection layer in the present invention, it is preferable because particularly fine foamability and moldability are obtained. As a result, since the resin itself is highly transparent, reflection at the bubble interface is also good. Furthermore, it has excellent light resistance, and raw material fats can be obtained relatively inexpensively. It is preferable to use the same resin for the light receiving layer and the intermediate layer. At this time, it is preferable to use polycarbonate resin for the light guide layer because the refractive index is higher than that of the light-receiving layer and the intermediate acrylic resin layer.

[0027] Specific examples of such an acrylic resin or methacrylic resin include, for example, acrylic acid ester or methacrylic acid ester homopolymer or acrylic acid ester or metatalic acid ester of 50% by weight or more. And copolymers with one or more vinyl monomers In particular, a copolymer of 50% by weight or more of a methacrylic acid ester and one or more other types of butyl monomers is preferred. Preferred is a copolymer comprising 50% by weight or less of alkyl ester and 49% by weight or less of at least one vinyl monomer copolymerizable with at least one of methacrylic acid alkyl ester and allylic acid alkyl ester. The amount of the alkyl acrylate ester contained in the copolymer is preferably 0.1% by weight to 40% by weight, more preferably 1% by weight to 15% by weight. The above acrylic resin or methacrylic resin may be used alone or in combination.

[0028] Examples of such acrylate esters include methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, acrylic acid phenyl, benzyl acrylate, and 2-ethylhexyl acrylate. And 2-hydroxyethyl acrylate and the like, and methyl acrylate and ethyl acrylate are particularly preferable. Examples of the ester of methacrylate include methyl methacrylate, ethyl acetate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and methacrylic acid 2 —Hydroxyethyl and the like can be mentioned, and in particular, methyl methacrylate and ethyl acetate are preferable. Examples of other copolymerizable butyl monomers include acrylic acid and methacrylic acid esters such as unsaturated acids such as acrylic acid and methacrylic acid, styrene, α-methylstyrene, talari-tolyl, Examples thereof include meta-tallow-tolyl, maleic anhydride, phenol maleimide, cyclohexyl maleimide and the like.

[0029] The weight average molecular weight (Mw) of the acrylic resin or methacrylic resin is preferably 40,000 to 400,000, more preferably 60,000 to 300,000. If the Mw is too small, the resulting foamed sheet layer may have insufficient mechanical strength. If the Mw is too large, the melt viscosity may increase and the extrusion performance may decrease.

[0030] Further, the above-mentioned acrylic resin or methacrylic resin may contain a rubbery polymer. By blending a rubber-like polymer with acrylic resin or methacrylic resin, the viscosity and toughness of resin can be improved, and a foam sheet with good impact resistance can be obtained.

[0031] The thermoplastic resin in the present invention includes a range that does not impair the optical characteristics of the sheet-like light collector. In a small amount, preferably in the range of 3% by weight or less, a crystallization nucleating agent, a crystallization accelerator, a cell nucleating agent, an antioxidant, a stabilizer, a processing aid, a plasticizer, an antistatic agent, Various additives such as impact aids, foaming agents, fillers, matting agents, mold release agents, flame retardants, UV absorbers, UV inhibitors, pigments, dyes, lubricants, and optical brighteners are formulated. Yo ヽ.

[0032] Of these, inorganic fine particles that function as a bubbling nucleating agent are preferably those capable of forming pores with themselves as nuclei, such as calcium carbonate, magnesium carbonate, zinc carbonate, titanium oxide (anatase type, rutile). Type), zinc oxide, barium sulfate, zinc sulfide, basic tin carbonate, titanium mica, antimony oxide, magnesium oxide, calcium phosphate, silica, alumina, my strength, talc, kaolin, and the like. Among these, it is particularly preferable to use calcium carbonate and barium sulfate, which have low absorption in the visible light range of 400 to 700 nm. If there is absorption in the visible light region, there may be a problem that the luminance decreases.

[0033] Examples of the gas dissolved in the thermoplastic resin in the extruder in order to form bubbles in the sheet include carbon dioxide, nitrogen, butane, helium, and argon. Of these, carbon dioxide and nitrogen, which have low gas permeability and are inexpensive and can be handled safely, may be used alone or in combination.

An antifouling layer can be provided on the surface of the light receiving layer of the present invention. Antifouling layer is Rf- (OC F)-

3 6 η

〇- (CF)-(CH)-0- (CH)-Si (OR) -containing perfluoropolyether group

2 m 2 1 2 s 3 3

It is also preferable that the run coupling agent power be obtained. When the antifouling layer is formed of such a material, dirt on the outermost surface of the sheet becomes difficult to adhere, and even if it adheres, it can be easily washed away.

[0035] Further, as the antifouling layer, a photoactive substance having a photocatalytic action can be used on the outermost surface of the light collecting sheet of the present invention. By adopting such a configuration, the dust attached to the surface of the antifouling layer is decomposed by the action of light to destroy the adhesiveness and washed with rain and moisture! It makes it easy to keep the surface clean by pouring. Photoactive materials include TiO, ZnO, SrTiO, CdS, CaP, InP

twenty three

, GaAs, BaTiO, K TiO, K NbO, Fe O, Ta O, WO, SnO, Bi20, NiO, Cu 0, S

3 2 3 2 3 2 3 2 3 3 2 3 2 iC ゝ SiO, MoS, InPb ゝ RuO, CeO, etc., and Pt, Rh, RuO, Nb ゝ Cu ゝ Sn ゝ Ni ゝ F

2 2 2 2 2

A composition in which a metal such as e and Z or a metal oxide thereof is mixed can be used.

[0036] In the sheet-like light collector according to the present invention, an uneven pattern may be transferred to the surface of the light receiving layer. This As for the uneven pattern cake, the pattern is transferred to a thermoplastic resin sheet on a casting roll having a fine pattern formed on the surface, or a foam sheet sheeted with a plain casting roll is used. And after winding up on a roll, it can carry out by the method of transferring a pattern to a sheet | seat again using the calendar apparatus which has a fine pattern on the surface. For the fine pattern, for efficient light reflection, the cross-section is a triangle, trapezoid, semicircular shape with an inclined surface such as a triangle or trapezoid, or an array of ridges, or pyramids. It is particularly preferable to use convex or concave shapes such as a trapezoid with a truncated pyramid shape, a hemispherical shape such as a dome shape, or a hemispherical shape with a curvature. The angle (vertical angle) between the opposing slopes in the array of recesses

90 ° is preferred. Or the composite pattern etc. are mentioned.

[0037] The thickness of the entire sheet-like light collector according to the present invention is preferably 100 to 1000 m, more preferably 150 to 500 m. When the thickness is too small, it becomes difficult to ensure the flatness of the sheet, and the light collection efficiency is lowered when used as a sheet-like light collector. On the other hand, if the thickness is too large, lamination with a steel plate or the like becomes difficult.

[0038] The sheet-shaped concentrator according to the present invention may be formed by coextrusion, extrusion lamination, thermal lamination, coating, vapor deposition, or the like. Among these, a laminated sheet by coextrusion is preferable. Such a laminated sheet is formed by, for example, a polymer having a main extruder for a foam layer and a sub-extrusion machine for a non-foam layer in a feed block portion installed in a die hold portion or before entering the die. It can be formed by merging. Since this coextruded laminated sheet does not require an adhesive layer, it is advantageous for reflection characteristics and at the same time has good productivity. More preferably, by using the same main raw material composition for the intermediate layer and the irregular reflection layer, the boundary between the intermediate layer and the irregular reflection layer is less affected, for example, there is no boundary between the foamed portion of the irregular reflection layer and the non-foamed portion of the intermediate layer. This can be advantageous particularly when used as a sheet-like concentrator.

[0039] The solar cell or solar cell element in the present invention means a device that generates power using the photovoltaic effect of a semiconductor, and is a silicon (single crystal, polycrystal, amorphous) solar cell. Compound semiconductors (Groups 3-5, 2-6, etc.) solar cells, wet solar cells, dye-sensitized solar cells, organic semiconductor solar cells, and the like. [0040] In another embodiment of the present invention, a sheet-shaped concentrator and a solar cell sheet using the same may be laminated on a steel plate. The sheet-shaped concentrator laminated on this steel plate and the solar cell using the same can be used for building materials such as roofing materials and constituent materials for transportation equipment such as automobiles, buses and ships.

[0041] The sheet forming machine usable in the present invention is usually an extruder for melting the resin, a flat die for forming a sheet, a cast roll for cooling the sheet, a sheet take-up device, a sheet It consists of a take-off device. Flat dies include multi-hold types that are stacked inside the die, which is preferred by T dies, and those that have a feed block device that is stacked just before the die. Cast rolls usually have a temperature control function, and the temperature control method may be a combination of circulating cooling water, hot water, or oil, or an induction heating method. The sheet take-up device may have a roll temperature control function following the cast roll, and is equipped with a surface treatment device such as a thickness measurement device, defect detection device, antistatic device, corona treatment and frame treatment. It is also possible. The wrinkle removal device can also include a turret mechanism, a touch roll mechanism, a wrinkle changing mechanism, a tension control device, etc.

[0042] The casting apparatus usable in the present invention may include a vacuum chamber apparatus having a cross section along the curvature of the roll above the roll in the take-up apparatus following the cast roll or the cast roll. . This vacuum chamber apparatus is a box-shaped apparatus having a width matched to the sheet, and can be depressurized by exhausting air inside the chamber by a vacuum pump provided outside. The chamber box has a sealing mechanism for maintaining a vacuum, and is composed of a plurality of rooms as required. Such a vacuum chamber apparatus is preferably capable of reducing the pressure inside the chamber to 30 kPa or less in order to obtain a desired foamed sheet.

[0043] The seal mechanism attached to the chamber apparatus usable in the present invention includes an inlet seal on the inlet side, an outlet seal on the outlet side, and side seals arranged on both sides with respect to the flow direction of the sheet. As the inlet seal and outlet seal, a labyrinth seal type, a contact roller type seal type, or the like can be adopted. As the side seal, labyrinth seal type, contact guide type, etc. can be adopted. it can.

[0044] Preferred examples of the sheet-shaped collector according to the present invention and a method for producing a solar cell sheet using the same will be described below, but the present invention is not limited to these specific examples. Absent.

[0045] First, if necessary, a thermoplastic resin chip as a raw material that has been heated and Z or dried is subjected to foaming and extruding main extruder (A) for foaming and extruding, and foaming, respectively. Supplied to the sub-extruder (B) used for the light-receiving layer and intermediate layer not to be used, and further to the sub-extruder (C) for the light guide layer. The main extruder (A) is supplied with gas, preferably under supercritical conditions, by a gas supply device placed outside the apparatus. Inside the main extruder (A), the molten thermoplastic resin and gas are sufficiently mixed, and the gas is dissolved in the thermoplastic resin and extruded.

[0046] Main extruder (A) Feed the extruded polymer (a) and sub-extruder (B) Extruded polymer (b) and polymer (c) extruded from the sub-extruder (C) The blocks are merged to form four layers (b), ( _C ), (b), and ( _a ), then supplied to the T-die and discharged into a sheet. At this time, the gas supply amount is adjusted so that the polymer (a) is in a non-foamed sheet state in which the gas is dissolved.

[0047] The sheet discharged from the T-die is landed on a casting roll and cooled. At this time, the sheet is usually a transparent uniform sheet. After cooling to a predetermined temperature on the casting roll, the sheet is introduced into the take-up roll following the casting roll. Next, the sheet is exposed to a vacuum state by a vacuum chamber provided on the take-up roll. Then, the sheet generates fine foam and changes to a pure white sheet. Then, this sheet is wound up into a roll shape by a winder.

[0048] The laminated sheet according to the present invention can be produced by a method including a step of foaming by extruding a thermoplastic resin in which a gas is dissolved. In this case, a non-foamed or foamed sheet that is foamed without using the vacuum chamber may be passed through the vacuum chamber.

[0049] In one embodiment, the present invention provides a step of sheeting a molten polymer of thermoplastic resin in which a gas is dissolved in an unfoamed state, by exposing the sheet to a vacuum under a temperature condition of 50 to 200 ° C, thereby causing bubbles. A method for producing a foam sheet. Such manufacturing method The method is suitable for the production of the foamed sheet or laminated sheet according to the present invention, and the above steps are preferably continuous. Here, the temperature condition is more preferably 70 to 120 ° C.

In the present invention, “sheeting in a non-foamed state” means that the gas is dissolved in the molten resin polymer, but the sheet is formed in a state without foaming when discharged from the die portion. This can be done by reducing the amount of gas to be dissolved and controlling the Z or discharge conditions. Since the non-foamed sheet has a gas dissolved in the polymer, it can be easily foamed by applying a stimulus such as reduced pressure to the sheet.

[0051] According to the post-foaming method after sheeting, the bubble generation state can be easily controlled by adjusting the conditions such as the temperature and reduced pressure of the sheet, so that the bubble size and the number of bubbles can be easily optimized. Liked in terms of.

[0052] Thus, the foamed sheet of the present invention can be obtained by using a sheeting device and a vacuum chamber device following gas supply extrusion. Therefore, it is possible to produce a sheet excellent in reflection characteristics, workability, and surface smoothness in-line with high productivity.

[0053] The laminated sheet according to the present invention can be suitably used as a sheet-shaped concentrator and a solar cell sheet using the same.

Example 1

[0054] Optical acrylic resin (Sumitomo Chemical Co., Ltd. Sumipex MGSS) heated in advance at 120 ° C for 4 hours is used as a raw material, and this is the first stage with 35mm and L / D of 34. Single-screw extruder, 50mm for the second stage, L / D 28 is supplied to the tandem extruder of the single-screw extruder, and supercritical conditions from the high-pressure gas supply device installed outside the extruder The carbon dioxide gas was supplied to the nozzle provided in the cylinder part of the melt-compression part of the first stage extruder at 38 ° C and 15 MPa, which was dissolved and mixed in the resin. At this time, the carbon dioxide gas was supplied at a rate of 0.03 kg / h with respect to the discharge rate of the extruder of 14.3 kg / h. The extrusion temperature at this time was 240 ° C for the first stage and 200 ° C for the second stage.

[0055] When this was discharged from a die having a slit width of 150 mm and a slit gap of 0.8 mm to form a sheet, a transparent smooth sheet was obtained. When this sheet was heated to 90 ° C. and placed in a desiccator (vacuum vessel) and depressurized to 28 kPa, it foamed and became cloudy. This resulting white sea A (average thickness: 205 m) was cut with a microtome without crushing the film cross section, and the cut cross section was magnified 500 times using a scanning electron microscope S-2100A type (manufactured by Hitachi, Ltd.). As a result, the bubble diameter was 10 μm at the center, and more than 85% of the bubbles had a bubble diameter in the range of 20 μm or less.

[0056] Using the same extruder, the same foamed resin (Sumitomo Chemical Co., Ltd. Sumipex MGSS) was extruded at a discharge rate of 8.5kg / h without supplying carbon dioxide, and sheeted, averaged. A transparent sheet B having a thickness of 122 m was obtained.

[0057] Further, using the same extruder, different polycarbonate resins (Gariba No. 301-10 manufactured by Sumitomo Dow Co., Ltd.) were extruded at a discharge rate of 12.5 kg / h without supplying carbon dioxide, and sheeted. Transparent sheet C having an average thickness of 180 m was obtained.

[0058] Transparent sheet B cut to 80 mm width x 80 mm as light receiving layer 11, transparent sheet C cut to 80 mm width x 120 mm length as light guide layer 12, transparent sheet B as intermediate layer 13 Prepare 80mm width x 120mm length cut white sheet A as diffuse reflection layer 14 cut to 80mm width x 120mm length.

[0059] As shown in FIG. 3, the four sheets are removed in the order of the light receiving layer 11, the light guide layer 12, the intermediate layer 13, and the irregular reflection layer 14 while moistening them with a small amount of water to eliminate the air between them. The sheet-shaped concentrator 10 is produced by superimposing as described above. Cover both ends with aluminum foil 33, and fix with a clip. Due to the difference in length between the light receiving layer 11 and the light guide layer 12, a portion of the light guide layer 12 is covered with the light receiving layer 11. This portion becomes a daylighting part 15 for taking out light from the light guide layer 12.

As shown in FIG. 3, the sheet-shaped concentrator 10 thus manufactured has the light receiving layer 11 on the upper side, a part including the daylighting part 15 projects outside the dark room 34, and the remaining part is in the dark room 34. Arrange them as follows. Illuminate the dark room 34 with Rogen Light 35. At this time, a solar cell element (NIPPON TETECH Solar Panel SPM01 Single Crystal Silicon Type 33mm X 62mm) 32 is placed in the dark room 34 at the same height as the sheet.

On the daylighting unit 15, a solar cell element 31 of the same type as that in the dark room 34 is arranged so that its light receiving surface faces the daylighting unit 15. In this state, the halogen lamp 35 is turned on, and the short-circuit current and the open-circuit voltage of the solar cell element 32 in the dark room 34 and the solar cell element 31 outside the dark room 34 are displayed. To calculate the power.

As a result, it was confirmed that the electric power obtained by the solar cell element 31 outside the dark room was 155% of the electric power obtained by the solar cell element 32 inside the dark room 34.

Example 2

[0063] In the same manner as in Example 1, white sheet A, transparent sheet B, and transparent sheet C were obtained.

Transparent layer B cut to 80mm width x 120mm length as light receiving layer 11 ', transparent sheet C cut to 80mm width x 120mm length as light guide layer 12', transparent layer 13 'as transparent layer 13' Prepare light sheet B cut to 80mm width x 80mm length, and white sheet A cut to 80mm width x 80mm length as diffuse reflection layer 14 '.

[0064] As shown in FIG. 4, the four sheets are respectively wetted with a small amount of water in the order of the light receiving layer 11 ', the light guiding layer 12', the intermediate layer 13 ', and the reflection layer 14'. The collector 10 'is made by overlapping so as to exclude the air between the two. Cover both ends with aluminum foil 33, and fix with a clip. Due to the difference in length between the light guide layer 12 ′ and the intermediate layer 13 ′, a part of the light guide layer 12 ′ is not covered with the intermediate layer 13 ′. This part becomes the daylighting part 15 ′. A solar cell element 31 of the same type as that used in Example 1 is arranged so that its light receiving surface faces the daylighting portion 15 ′. Place the sheet concentrator 10 'so that the light-receiving layer 11' is on top, measure the short-circuit current and open-circuit voltage of the solar cell element, and calculate the power.

In addition, as shown in Fig. 5, cover the light receiving layer 11 'with black drawing paper 40 cut to 80mm width x 80mm length (Dao Paper Recycled Color Paper Basis Weight 122.1g / m ² ) and diffuse reflection layer In a state in which the sunlight is not incident on 14 ', that is, in a state where the action of the present invention does not occur, the short-circuit current and the open-circuit voltage of the solar cell element are measured to calculate the power.

[0065] The above measurements were taken outdoors (Kyoto city, north latitude 34 ° 59 ', east longitude 135 ° 46')

I went at midnight on March 15, 2005. As a result, the electric power obtained when the black paper 40 was not covered was 147% of the electric power when the black paper 40 was not covered.

In addition, the same measurement was performed at midnight on a clear day (March 21, 2005). As a result, the power obtained when the black paper 40 was not covered was 140% of the power when the black paper 40 was not covered.

[0066] These measurement results were obtained in the sheet form of this example both in fine weather and in cloudy weather. This shows that the light condensing efficiency to the solar cell element is increased by using the concentrator 10 '.

Industrial applicability

The sheet-shaped concentrator of the present invention and the solar cell sheet using the same are because of its light condensing property, caloric property, low cost, etc. It can be applied to solar cell building materials, solar cell transport equipment, etc., but the scope of application is not limited to these! /.

Claims

The scope of the claims

[I] A diffused reflection layer is laminated on the intermediate layer side of a light guide sheet formed by sandwiching a light guide layer made of a high refractive index material between a light receiving layer made of a low refractive index material and an intermediate layer, and a daylighting part A sheet-shaped concentrator characterized by having a.

[2] The sheet-like concentrator according to [1], wherein the irregular reflection layer is made of a resin containing a large number of bubbles.

[3] The sheet-shaped concentrator according to claim 2, wherein the irregular reflection layer is formed by gas foam extrusion.

[4] The light-receiving layer, the light-guiding layer, the intermediate layer, and the irregular reflection layer are made of thermoplastic resin and are integrally formed by coextrusion. Sheet-shaped collector.

[5] The sheet-shaped concentrator according to any one of claims 1 to 4, wherein unevenness having a light confinement effect is formed on the surface of the light receiving layer.

[6] The sheet-shaped concentrator according to any one of [1] to [5], wherein the area of the light receiving layer is at least twice the area of the daylighting portion.

[7] The sheet-like concentrator according to any one of [1] to [6], wherein an antifouling layer is formed on the surface of the light receiving layer.

[8] The sheet-like concentrator according to [7], wherein the antifouling layer has a photoactive catalyst.

[9] A diffused reflection layer is laminated on the intermediate layer side of the light guide sheet formed by sandwiching a light guide layer made of a high refractive index material between a light receiving layer made of a low refractive index material and an intermediate layer, and a daylighting part A sheet-shaped concentrator with

A solar cell disposed such that a light-receiving surface faces the daylighting unit;

A solar cell sheet comprising:

10. The solar cell sheet according to claim 9, wherein the irregular reflection layer is made of a resin containing a large number of bubbles.

[II] The solar cell sheet according to claim 10, wherein the irregular reflection layer is formed by gas foam extrusion.

[12] The light-receiving layer, the light-guiding layer, the intermediate layer, and the irregular reflection layer are made of thermoplastic resin and are coextruded. The solar cell sheet according to any one of claims 9 to 11, wherein the solar cell sheet is integrally formed.

[13] The solar cell sheet according to any one of claims 9 to 4, wherein unevenness having a light confinement effect is formed on the surface of the light receiving layer.

[14] The solar cell sheet according to any one of [9] to [13], wherein the area of the light receiving layer is at least twice the area of the daylighting portion.

[15] The solar cell sheet according to any one of [9] to [14], wherein an antifouling layer is formed on the surface of the light receiving layer.

16. The solar cell sheet according to claim 15, wherein the antifouling layer has a photoactive catalyst.