TWI597167B - Backsheet for solar cell with moisture absorption layer and solar cell using the same - Google Patents

Description

Back panel for solar cell with hygroscopic layer and solar cell using same

The present invention relates to a solar cell backsheet having a moisture absorbing layer, and more particularly to a solar cell backsheet comprising an inner skin layer, a moisture absorbing layer, an outer skin layer, and a barrier layer in this order. Further, the present invention relates to a solar cell using the back sheet for a solar cell.

Solar cells are attracting attention as clean energy, and the world is cooperating with solar cells. In addition to low-cost supply, the promotion of popularization requires economically balanced long-term durability. In addition, most of the solar cells are installed on the outer wall of the house, on the roof, on the roof, etc., so in the extremely harsh natural environment outside the house, high-quality standards are required.

However, the problem that the power generation cell portion and the lead portion of the solar cell element are deteriorated by moisture, and the power generation efficiency is lowered with time is known. Here, the former solar battery module has made various reviews and efforts to prevent moisture from coming into contact with the power generation battery and the lead portion. For example, Patent Document 1 discloses a solar cell including a solar cell element, a moisture proof film, and an adhesive for attaching a solar cell element and a moisture proof film. The module is a solar cell module containing an absorbent such as zeolite. However, in the solar cell module, only the moisture absorbent can be added in an amount of 30% by weight or less by weight in a small amount in the nature of the composition in which the adhesive is mixed with the moisture absorbent. When the amount of the moisture absorbent added is too large, the adhesion of the adhesive is lowered, so that the back sheet is peeled off by the solar cell element, and the power generation battery contacts the moisture or heat from the gap.

Patent Document 2 discloses a solar cell module having a space for filling a desiccant. In this configuration, a heater is provided in the space, and the moisture is evaporated by the heat of the heater to reuse the moisture-absorbing desiccant. In this invention, it is necessary to use special engineering and parts when manufacturing a solar cell module.

Patent Document 3 discloses a solar battery module having an outer moisture-proof film having a three-layer structure. The moisture-proof film has a three-layer structure of a water-repellent film, a moisture absorbing and releasing layer, and a high moisture-resistant film from the outside to the solar cell element, and a non-woven fabric containing a polyacrylate-based polymer is used as the moisture absorbing and releasing layer. However, since the polyacrylate-based polymer which absorbs and releases the wet layer as shown in Fig. 1 has low hygroscopicity in a low-humidity region, the effect is limited in such applications. In addition, the amount of the moisture absorbent cannot be used much.

Patent Document 4 discloses a solar battery module having a transparent water-repellent layer made of nylon between the back sheet and the electrode, but the nylon has limited hygroscopicity.

Patent Document 5 discloses an edge sealant composition containing inorganic substance calcium oxide as a moisture absorbent in order to prevent water from entering from the edge portion of the solar cell module. This composition, the amount of moisture absorbent added is only It can be as little as 30% by weight or less, and only absorbs moisture from the edge portion, so that it cannot absorb moisture inside.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 7-312440

[Patent Document 2] Japanese Patent Laid-Open No. Hei 9-45949

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2005-101404

[Patent Document 4] Japanese Patent Laid-Open No. Hei 7-321365

[Patent Document 5] Japanese Patent Publication No. 2013-509453

Here, an object of the present invention is to provide a solar cell backsheet which can be used without greatly changing the manufacturing process of the solar cell module, and which can provide high hygroscopicity for a long period of time, and the power generation efficiency of the use thereof is not long. And lower the solar battery.

The inventors of the present invention have found that the above problems can be solved by the following means.

[1] A back sheet for a solar cell comprising, in order, at least an inner skin layer, a moisture absorbing layer containing a binder resin and an inorganic moisture absorbent, an outer skin layer, and a barrier layer, and the inner skin layer and the outer skin layer are made of a thermoplastic resin. Composition.

[2] The back sheet for a solar cell according to [1], wherein the inorganic moisture absorbent has a moisture absorption amount of 15% by weight or more at 1 atm, a relative humidity of 20%, and 25 °C.

[3] The back sheet for a solar cell according to [1] or [2] wherein the inorganic moisture absorbent is a natural zeolite, an artificial zeolite or a synthetic zeolite.

The solar cell backsheet according to any one of the above aspects, wherein the inorganic moisture absorbent is in a range of 30% by weight or more and 80% by weight or less based on the weight of the moisture absorbing layer. Contained in the aforementioned moisture absorbing layer.

[5] The solar cell backsheet according to any one of [1], wherein the inner skin layer, the binder resin, and the outer skin layer are low density polyethylene and linear low density. Polyethylene, polypropylene, chlorinated polypropylene, saturated polyester, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ionomer A group consisting of a carboxylic acid-denatured polyethylene, a carboxylic acid-modified polypropylene, a carboxylic acid-denatured ethylene-vinyl acetate copolymer, polyvinyl chloride, polystyrene, and an inducer of these, and a mixture of these are separately selected.

[6] The solar cell backsheet according to any one of [1], wherein the barrier layer contains an aluminum foil.

[7] The back sheet for a solar cell according to any one of [1] to [6] wherein the MFR of the binder resin is measured according to an industrial standard JIS K7210 at a temperature of 190 ° C and a load of 2.16 kg. In the case of 10 g/10 minutes or more.

[8] The solar cell backsheet according to any one of [1], wherein the moisture absorption layer has a film thickness of 10 to 190 μm, and the skin layer has a film thickness of 5 to 190 μm.

[9] A solar battery module comprising: a transparent substrate, a power generation battery, a wire, a sealing resin for sealing a power generation battery and a wire, and a solar battery back according to any one of [1] to [8] board.

[10] The solar battery module according to [9], wherein the sealing resin is an ethylene vinyl acetate copolymer (EVA).

[11] The solar cell module according to [10], wherein the inner skin layer and the outer skin layer are polypropylene films having a thickness of 5 to 20 μm; the binder resin is low density polyethylene; and the inorganic moisture absorbent is zeolite. The thickness of the moisture absorbing layer is 30 to 100 μm; and the barrier film is a polyethylene terephthalate film.

The back sheet for a solar cell of the present invention can be used without significantly changing the manufacturing process of the former solar cell module, and has high adhesion to solar cell elements, and contains a large amount of strong inorganic hygroscopic agent, so even if it exists slightly The moisture in the sealing resin of the solar cell element can also be absorbed. As a result, the solar cell element can be kept low in humidity for a long period of time. Since the solar cell using the back sheet for a solar cell does not deteriorate the electrode or the like, the conversion efficiency can be maintained longer than that of the former solar cell.

1‧‧‧Transparent substrate

2‧‧‧ sealing resin

3‧‧‧Wire

4‧‧‧Power generation battery

5‧‧ ‧ barrier layer

6‧‧‧ inside cortex

7‧‧‧Moisture absorbing layer

8‧‧‧lateral cortex

10‧‧‧Solar battery components

20‧‧‧ Backplane

100‧‧‧Solar battery module

Fig. 1 is a graph showing the relationship between the amount of water absorption of sodium polyacrylate, nylon, and molecular sieve and relative humidity.

2 is a schematic view of a prior solar cell module.

Fig. 3 is a schematic view showing a solar battery module of the present invention.

<Backplane for Solar Cell of the Present Invention>

The back sheet for a solar cell of the present invention comprises at least an inner skin layer, a moisture absorbing layer containing a binder resin and an inorganic moisture absorbent, an outer skin layer, and a barrier layer. The back sheet is used on the opposite side of the incident light side of the solar cell module, and the four layers are sequentially the inner side skin layer, the moisture absorbing layer, the outer side skin layer, and the barrier layer from the incident light side. By positioning the inner skin layer and the outer skin layer, the adhesion between the sealing resin of the solar cell element and the moisture absorbing layer and the adhesion between the barrier layer and the moisture absorbing layer can be improved, respectively. Further, an adhesive may be used between the layers to improve the adhesion between the layers.

(hygroscopic layer)

In the moisture absorbing layer, an inorganic moisture absorbent is dispersed in the binder resin.

The inorganic moisture absorbent which can be used for the moisture absorbing layer may, for example, be a moisture absorbent such as calcium oxide, magnesium sulfate, calcium chloride, aluminum oxide, quicklime, cerium oxide gel or inorganic molecular sieve. As an inorganic molecular sieve Examples are not limited, but examples thereof include aluminosilicate minerals, clay, porous glass, fine pore activated carbon, natural zeolite, artificial zeolite, synthetic zeolite, activated carbon, or diffusion of small molecules such as water. The compound having an open structure; in particular, a molecular sieve 3A for synthesizing zeolite, molecular sieve 4A, molecular sieve 5A, and molecular sieve 13X can be mentioned. Such an inorganic moisture absorbent can obtain high hygroscopicity even in a low-humidity region, and moisture-absorbing the sealing resin of the solar cell element, particularly the water slightly contained in the ethylene vinyl acetate copolymer (EVA), can be used even in It is particularly preferable that the moisture absorbent which exhibits high hygroscopicity in an environment having a relatively low relative humidity.

Inorganic moisture absorbent, high moisture absorption from low humidity areas From the viewpoint of the properties, the atmospheric pressure, the relative humidity of 20%, and the moisture absorption amount at 25 ° C are preferably 15% by weight or more, or 20% by weight or more, based on the weight of the moisture absorbing material before moisture absorption. More preferably, it is 1 atm, the relative humidity is 10%, and the moisture absorption at 25 ° C is 15% by weight or more, or 20% by weight or more, based on the weight of the moisture absorbing material before moisture absorption. Further preferably, it is 1 atm, the relative humidity is 5%, and the moisture absorption at 25 ° C is 15% by weight or more, or 20% by weight or more, based on the weight of the moisture absorbing material before moisture absorption. 1 shows the relationship between the water absorption amount of sodium polyacrylate, nylon, and molecular sieve and the relative humidity. The molecular sieve A has a moisture absorption amount of 15% by weight or more at a relative humidity of 20%, so it is a preferred moisture absorbent. . Further, in the calculation of the moisture absorption amount, in the case of a powdery moisture absorbent, the measured moisture absorbent is stored in a predetermined storage environment (for example, 25 ° C, 20% RH), and the weight change can be calculated from the change before and after storage. Wet volume. In addition, if it is a moisture absorbent dispersed in a film, A film (for example, 10 cm × 10 cm) cut out in a predetermined area is made to absorb moisture in the same manner as described above, and the moisture absorption amount can be calculated from the change in weight before and after storage.

Inorganic moisture absorbent, from the point of view of moisture absorption capacity, relative The weight of the moisture absorbing layer can be contained in the moisture absorbing layer in a range of 10% by weight or more, 20% by weight or more, 30% by weight or more, more than 30% by weight, 50% by weight or more, 60% by weight or more, and 80% by weight or more. Further, from the viewpoint of dispersibility of the binder resin, the moisture absorbing layer can be contained in an amount of 90% by weight or less, 80% by weight or less, 70% by weight or less, or 60% by weight or less. The dispersion of the inorganic hygroscopic agent to the binder resin can be carried out by a usual kneading extruder.

The thickness of the moisture absorbing layer is determined by the viewpoint of ensuring moisture absorption capacity. It is preferable to use 10 μm or more, 20 μm or 40 μm or more. Further, from the viewpoint of preventing distortion due to the difference in heat shrinkability when bonded to the barrier layer, the thickness of the moisture absorption layer is preferably 500 μm or less, 200 μm or less, 190 μm or less, 150 μm or less, or 100 μm or less.

As a binder resin that can be used in the moisture absorbing layer, Illustrative of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), polypropylene (PP), chlorinated polypropylene, saturated polyester, ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid Co-polymer (EMAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), ionomer, carboxylic acid denatured polyethylene, carboxylic acid denatured polypropylene, carboxylic acid denaturation Ethylene vinyl acetate copolymer, polyvinyl chloride (PVC), polystyrene, and the like Conductors, and mixtures of these.

When a large amount of inorganic hygroscopic agent is added, it will cause a decrease. From the viewpoint of ensuring the formability of the moisture absorbing layer, the melt flow rate (MFR) of the binder resin is measured at a temperature of 190 ° C and a load of 2.16 kg, according to the industrial standard JIS K7210. It is 3 g/10 minutes or more, 5 g/10 minutes or more, 8 g/10 minutes or more, 10 g/10 minutes or more, 12 g/10 minutes or more, 15 g/10 minutes or more, or 20 g/10 minutes or more.

(medial cortex and lateral cortex)

Since the moisture absorbing layer has low surface smoothness, the adhesion to the sealing resin of the solar cell element cannot be improved by only this layer. However, by using the inner skin layer, the adhesion between the moisture absorbing layer and the sealing resin can be improved. The resin to be used for the inner skin layer is not particularly limited as long as it is a thermoplastic resin which can be well adhered to the sealing resin and the moisture absorbing layer. As the thermoplastic resin which can be used, the same resin as the binder of the above-mentioned moisture absorbing layer can be mentioned.

Using the outer skin layer, the barrier layer and the moisture absorbing layer can be improved. Adhesion. The resin to be used for the outer skin layer is not particularly limited as long as it is a thermoplastic resin which can be well adhered to the barrier layer and the moisture absorbing layer. As the thermoplastic resin which can be used, the same resin as the above-mentioned moisture absorbing layer and the binder can be mentioned.

The thickness of the inner cortex and the outer cortex is ensured and hygroscopic From the viewpoint of adhesion of the layer, it is preferably 3 μm or more, 5 μm or more, or 7 μm or more, and is prevented from being heat-shrinkable when bonded to the barrier layer. From the viewpoint of the distortion caused by the difference, and the inner skin layer ensuring the moisture permeability to the moisture absorbing layer, it is preferably 100 μm or less, 50 μm or less, 30 μm or less, or 20 μm or less. When the surface roughness Ra of the inner skin layer and the outer skin layer is measured by the industrial standard JIS B0601-1994, it is 1.50 μm or less, preferably 1.30 μm or less, more preferably. It is 1.00 μm or less.

(barrier layer)

As the barrier layer used in the present invention, a fluorine-based resin film, a polyester film such as polyethylene terephthalate (PET), or the like, and a laminate of these can be used. In the case of a laminate, each layer can be followed by an adhesive or the like. Further, a metal layer such as an aluminum foil and a copper foil, and/or a metal oxide layer such as a hafnium oxide layer and an aluminum oxide layer may be laminated, and the lamination may be performed by dry lamination, vapor deposition, or the like. In addition, the solar cell backsheet used previously can be used directly. For example, Reprea PKT HD (trademark), Reprea TFB MD (trademark) (both manufactured by Lintec), and Tedlar (trademark) film (manufactured by DuPont) can be cited.

The thickness of the barrier layer is from 12 μm to 600 μm, preferably from 20 μm to 400 μm, from the viewpoint of the build-up workability.

(adhesive)

As an adhesive which can be used in the production of the barrier layer, and also The adhesive which can be used for the sealing resin and the inner skin layer and the outer skin layer and the barrier layer may, for example, be an urethane-based adhesive, an olefin-based resin adhesive, a butyl rubber-based adhesive, an acrylic resin-based adhesive, or a poly An ester resin-based adhesive, an epoxy resin-based adhesive, a polyoxymethylene-based adhesive, or the like.

<Solar battery module of the present invention>

The solar cell module of the present invention comprises a solar cell element and the aforementioned back sheet for a solar cell. The solar cell element includes a transparent substrate, a power generation battery, a wire, and a sealing resin for sealing the power generation battery and the wire. The transparent substrate is a glass substrate for a solar cell which is conventionally known, and examples of the power generation battery include a conventional single crystal type, polycrystalline type, amorphous type, and compound semiconductor type battery. As the sealing resin, ethylene vinyl acetate copolymer (EVA), thermoplastic polyurethane, polyvinyl butyral or the like can be used, and in particular, EVA can be used.

Further, the present invention relates to a method of producing a solar cell backsheet by combining the inner skin layer, the moisture absorbing layer, and the outer skin layer with the barrier layer described above. Further, the present invention relates to a method of manufacturing a solar battery module by combining the solar battery back sheet with the solar battery element.

Fig. 2 is a schematic view showing a solar battery module constructed in the past. The solar battery module 100 includes a solar cell element 10 including a glass 1 for sealing a transparent substrate, a sealing resin 3 for sealing the wires 3 and the power generation cell 4, and a barrier layer 5, which is provided on the incident light side. Backboard 20. Although not shown, the solar cell element 10 and the backing plate 20 are usually followed by an adhesive.

Figure 3 shows an overview of the solar cell module of the present invention. To map. The solar cell module 100 includes a solar cell element 10 including a glass 1 for sealing a transparent substrate, and a sealing resin 2 for sealing the lead 3 and the power generation cell 4, and an inner skin layer 6 and a suction layer from the incident light side. The wet layer 7, the outer skin layer 8, and the backing plate 20 of the barrier layer 5.

[Examples]

Hereinafter, the production methods, evaluation methods, and evaluation results of the evaluation samples of Examples 1 to 3 and Comparative Example 1 are shown.

[Example 1]

A laminate of the absorbent layer, the inner skin layer, and the outer skin layer is formed using an expansion film forming mechanism. Here, the moisture absorbing layer was 60 μm, and the inner skin layer and the outer skin layer were each 10 μm. The moisture absorbing layer was prepared by mixing 50 wt% of the zeolite with 50 wt% of the binder resin. On the outer skin layer of the laminate, a 200 μm white PET film having a laminated barrier layer was dried using an adhesive to obtain a back sheet. Further, vacuum pressure bonding was performed using a vacuum laminator at 130 ° C for 10 minutes to form a panel of the solar cell element. Here, the thickness of the glass substrate was 5 mm, and the thickness of the sealing resin including the power generation cell and the lead wire was 600 μm.

[Embodiment 2]

In addition to the white PET instead of the barrier layer, a 12 μm PET film and a 9 μm aluminum foil were used for the outer skin layer, and the aluminum foil was used as the adhesion surface to dry the laminate. The solar cell module was obtained in the same manner as in Example 1 except that it was laminated.

[Example 3]

In addition to the white PET instead of the barrier layer, the two-layer transparent vapor-deposited PET film (GX-P-F12μm/GX-P-F12μm) is in the order of PET film, vapor-deposited surface, PET film, vapor-deposited surface/outer skin layer. A solar cell module was obtained in the same manner as in Example 1 except that the laminate was dried and laminated.

[Comparative Example 1]

A solar cell module was obtained in the same manner as in Example 1 except that the laminate of the moisture absorbing layer, the inner skin layer, and the outer skin layer was not used. That is, a 200 μm white PET film was used as a backing plate, which was panelized with a solar cell element.

The details of each of the foregoing samples are shown in the table below. Further, the four solar battery modules having the above configuration were stored under the conditions of a temperature of 85 ° C and a relative humidity of 85% for 3,000 hours according to the industrial standard JIS C8917-1998, and the conversion efficiency before and after storage was measured. The results are shown in the table below.

Embodiments 1 to 3 incorporated in the back sheet for solar cells of the present invention In the solar battery module, even after 3,000 hours at a temperature of 85 ° C and a relative humidity of 85%, the conversion efficiency can be maintained at 90% or more in the initial stage. On the other hand, the comparative example of the solar battery back sheet of the present invention is not used. The conversion efficiency was reduced to the initial 76.1%.

Further, the glass, the single crystal germanium type power generation battery, and the white PET of the barrier layer are used in a commercially available product used in a general solar battery module. Moreover, this white PET has a water vapor transmission rate of 0.2 g/m ² ‧ days or less. The model (trademark), source, etc. of other materials, and the details of the machine used in the production are as follows.

EVA: Solar EVA (manufactured by Mitsui Chemicals East Cello Co., Ltd.)

Polypropylene: F-704NP (manufactured by Prime Polymer)

Zeolite: Zeolite 4A (manufactured by Union Showa)

LDPE: Petrocen 202 (made by Tosoh)

PET: E5102 (manufactured by Toyobo Co., Ltd....Example 2

Aluminum foil: Bespa (manufactured by Light Aluminum Foil Co., Ltd.)...Example 2

Transparent vapor-deposited PET film: GX-P-F (manufactured by Convex Printing Co., Ltd.) Example 3

A urethane-based adhesive: a mixture of LIS-073-50 and CR-001 (manufactured by Toyo Ink Co., Ltd.)

Expansion film making machine: multi-layer expansion film making machine 3SOIB (manufactured by Placo)

Vacuum laminating machine: cypress vacuum packaging machine (manufactured by NPC)

[Industrial use possibility]

Since the back sheet for a solar cell of the present invention has high adhesion to a solar cell element and can contain a large amount of an inorganic moisture absorbent, it is useful for keeping the solar cell element low in humidity for a long period of time. Since the solar cell using the back sheet for a solar cell does not deteriorate the electrode or the like, it is useful because the conversion efficiency can be maintained for a longer period of time than the former solar cell.

1‧‧‧Transparent substrate

2‧‧‧ sealing resin

3‧‧‧Wire

4‧‧‧Power generation battery

5‧‧ ‧ barrier layer

6‧‧‧ inside cortex

7‧‧‧Moisture absorbing layer

8‧‧‧lateral cortex

10‧‧‧Solar battery components

20‧‧‧ Backplane

100‧‧‧Solar battery module

Claims (11)

A back sheet for a solar cell, characterized in that it comprises at least an inner skin layer, a moisture absorbing layer containing a binder resin and an inorganic moisture absorbent, an outer skin layer, and a barrier layer, and the inner skin layer and the outer skin layer are made of a thermoplastic resin. Composition. The back sheet for a solar cell according to the first aspect of the invention, wherein the inorganic moisture absorbent has a moisture absorption amount of 15% by weight or more at 1 atm, a relative humidity of 20%, and 25 °C. The back sheet for a solar cell according to claim 1 or 2, wherein the inorganic moisture absorbent is a natural zeolite, an artificial zeolite or a synthetic zeolite. The back sheet for a solar cell according to the first or second aspect of the invention, wherein the inorganic moisture absorbent is contained in the moisture absorbing layer in a range of 30% by weight or more and 80% by weight or less based on the weight of the moisture absorbing layer. The back sheet for a solar cell according to claim 1 or 2, wherein the inner skin layer, the binder resin, and the outer skin layer are made of low density polyethylene, linear low density polyethylene, polypropylene, and chlorine. Polypropylene, saturated polyester, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ionomer, carboxylic acid modified polyethylene A group consisting of a carboxylic acid-denatured polypropylene, a carboxylic acid-denatured ethylene-vinyl acetate copolymer, polyvinyl chloride, polystyrene, and an inducer of these, and a mixture of these are separately selected. For example, the backsheet for solar cells of claim 1 or 2, Wherein the barrier layer comprises aluminum foil. The solar cell back sheet according to claim 1 or 2, wherein the MFR of the binder resin is 10 g/10 min under the condition of a temperature of 190 ° C and a load of 2.16 kg, measured according to the industrial standard JIS K7210. the above. The solar cell backsheet according to claim 1 or 2, wherein the moisture absorption layer has a film thickness of 10 to 190 μm, and the skin layer has a film thickness of 5 to 100 μm. A solar cell module comprising: a transparent substrate, a power generation battery, a wire, a sealing resin for sealing a power generation battery and a wire, and a solar battery back plate according to any one of claims 1 to 8. . The solar cell module of claim 9, wherein the sealing resin is an ethylene vinyl acetate copolymer (EVA). The solar cell module according to claim 10, wherein the inner skin layer and the outer skin layer are polypropylene films having a thickness of 5 to 20 μm; the binder resin is low density polyethylene; and the inorganic moisture absorbent is zeolite; The thickness of the moisture absorbing layer is 30 to 100 μm; and the barrier layer is a polyethylene terephthalate film.