JP2012227280A - Solar battery sealing sheet and flexible solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell sealing sheet which is excellent in the adhesive with solar cell elements and the shape maintainability, prevents curl from occurring when the solar cell elements are sealed, and manufactures a flexible solar cell module with high efficiency, and to provide the flexible solar cell module obtained by using the solar cell sealing sheet.SOLUTION: A solar cell sealing sheet has an adhesive layer, formed by a mixed resin composed of a maleic anhydride modified olefin based resin and an olefin copolymer resin, on a fluorine based resin sheet. The content of the maleic anhydride modified olefin based resin accounts for 30 to 99% by weight of the mixed resin.

Description

The present invention is excellent in adhesion and shape maintenance with a solar cell element, and does not generate curl when sealing the solar cell element, and can manufacture a flexible solar cell module with high efficiency. The present invention relates to a flexible solar cell module obtained using the sheet and the solar cell encapsulating sheet.

As a solar cell, a rigid solar cell module based on glass and a flexible solar cell module based on a polyimide or polyester heat-resistant polymer material or a stainless thin film are known. In recent years, flexible solar cell modules have been attracting attention because of their ease of transportation and construction due to reduction in thickness and weight, and resistance to impact.

Such a flexible solar cell module is a flexible solar cell element in which a photoelectric conversion layer made of a silicon semiconductor or a compound semiconductor having a function of generating a current when irradiated with light is laminated in a thin film on a flexible substrate. The upper and lower surfaces are sealed by laminating solar cell encapsulating sheets.
The said solar cell sealing sheet is for preventing the impact from the outside, or preventing corrosion of a solar cell element.

As a method of sealing a solar cell element and manufacturing a flexible solar cell module using such a solar cell sealing sheet, a vacuum thermocompression bonding method using a laminator is generally used.
In recent years, a roll-to-roll method has been studied as a method for producing a flexible solar cell module because it is excellent in mass production (see, for example, Patent Document 1).
The roll-to-roll method uses a roll in which a film-like solar cell encapsulating sheet is wound, and the solar cell encapsulating sheet unwound from the roll is narrowed by using a pair of rolls, thereby obtaining a solar cell. In this method, the element is sealed by thermocompression bonding, and a flexible solar cell module is continuously manufactured.
According to the roll-to-roll method, it can be expected to continuously manufacture flexible solar cell modules with extremely high efficiency.

The said solar cell sealing sheet has an contact bonding layer for sealing a solar cell element on the protective layer of a transparent sheet.
A maleic anhydride-modified olefin resin is known as a material for the adhesive layer of the solar cell encapsulating sheet (see, for example, Patent Document 2). The adhesive layer made of maleic anhydride-modified olefin resin is excellent in adhesion to solar cell elements and electrodes, and is excellent in maintaining the shape at high temperatures.
However, when a solar cell encapsulating sheet having an adhesive layer made of a maleic anhydride-modified olefin resin is thermocompression bonded to the solar cell element, curling (warping) occurs and the yield of the solar cell module is extremely reduced. was there.

JP 2000-294815 A JP 2004-214641 A

In view of the present situation, the present invention is excellent in adhesiveness and shape maintenance with a solar cell element, and does not generate curl when the solar cell element is sealed, and the flexible solar cell module is highly efficient. It aims at providing the solar cell sealing sheet which can be manufactured, and the flexible solar cell module obtained using this solar cell sealing sheet.

The present invention has an adhesive layer made of a mixed resin of a maleic anhydride-modified olefin resin and an olefin copolymer resin on a fluororesin sheet, and the content of the maleic anhydride-modified olefin resin is the above mixture The solar cell encapsulating sheet is 30 to 99% by weight in the resin.
The present invention is described in detail below.

The present invention has an adhesive layer containing a specific component in a certain range and a fluororesin sheet, so that it has excellent adhesiveness and shape maintenance with a solar cell element and does not cause curling. It is a solar cell sealing sheet which can manufacture a flexible solar cell module.
When the present inventors mixed an maleic anhydride-modified olefin resin and an olefin copolymer resin to form an adhesive layer, the maleic anhydride-modified olefin-based resin even if the total amount of maleic anhydride was the same. It has been found that the shrinkage stress and storage elastic modulus of the adhesive layer are smaller than when the adhesive layer is formed of the resin alone. When the shrinkage stress is reduced, curling (warping) that occurs during thermocompression bonding of the solar cell encapsulating sheet can be prevented. However, when the storage elastic modulus is further reduced, the shape maintainability at high temperatures is lowered.
Accordingly, the present inventors have developed a maleic anhydride-modified olefin resin and an olefin copolymer which can reduce the shrinkage stress while maintaining the adhesiveness and shape maintaining property of the maleic anhydride-modified olefin resin. The optimum mixing ratio with the coalesced resin was found and the present invention was completed.

The solar cell encapsulating sheet of the present invention has an adhesive layer made of a mixed resin of a maleic anhydride-modified olefin resin and an olefin copolymer resin on a fluorine resin sheet, and the maleic anhydride-modified olefin resin Is 30 to 99% by weight in the mixed resin.
The solar cell encapsulating sheet of the present invention has an adhesive layer made of a resin in which a specific resin is mixed at a specific ratio, so that it has excellent adhesion to the solar cell element and shape maintainability, and the solar cell element. Curling can be suppressed during thermocompression bonding.

If the content of the maleic anhydride-modified olefin resin in the mixed resin is less than 30% by weight, the adhesion to the solar cell element and the shape maintenance at high temperatures may be deteriorated. If it exceeds 99% by weight, curling may occur when the solar cell element is sealed.
The content of the maleic anhydride-modified olefin resin in the mixed resin is preferably 40% by weight, more preferably 50% by weight, and 95% by weight in the mixed resin. It is preferable.
The content of the maleic anhydride-modified olefin resin in the mixed resin can be measured using HPLC (high performance liquid chromatography).

The maleic anhydride-modified olefin resin is preferably a resin obtained by graft-modifying an olefin resin with maleic anhydride.
The olefin resin may be a homopolymer composed of a single monomer or a copolymer composed of two or more kinds of monomers.
Specific examples of the homopolymer include polyethylene, polypropylene, polybutene, and the like.
Specific examples of the copolymer include α-olefin-ethylene and α-olefin-propylene copolymers.
As the olefin resin, an α-olefin-ethylene copolymer, which is a copolymer of α-olefin and ethylene, is preferable from the viewpoint of heat fusion.

The α-olefin preferably has 3 to 10 carbon atoms, and more preferably 4 to 8 carbon atoms, in order to lower the melting point and improve flexibility by improving the amorphousness of the resin.
Specific examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and the like. Butene and 1-octene are preferred.
That is, the α-olefin-ethylene copolymer is preferably a butene-ethylene copolymer or an octene-ethylene copolymer.

The α-olefin-ethylene copolymer preferably has an α-olefin content of 1 to 25% by weight.
When the α-olefin content is less than 1% by weight, the flexibility of the solar cell encapsulating sheet is lowered and the melting point of the solar cell encapsulating sheet is increased. Heating is required, and curling may occur when the flexible solar cell module is manufactured. When the α-olefin content exceeds 25% by weight, the crystallinity or fluidity of the solar cell encapsulating sheet is not uniform and distortion occurs, or the melting point of the solar cell encapsulating sheet itself is too low. Therefore, it becomes difficult to maintain the shape when the solar cell element is held at a high temperature, and as a result, the adhesiveness of the solar cell sealing sheet to the solar cell element may be reduced or deformed.
The lower limit of the α-olefin content is more preferably 10% by weight, and the upper limit is more preferably 20% by weight.

The content of the α-olefin in the α-olefin-ethylene copolymer can be determined from a spectrum integrated value of ¹³ C-NMR. Specifically, for example, when 1-butene is used, a spectral integrated value derived from a 1-butene structure obtained in the vicinity of 10.9 ppm, 26.1 ppm, and 39.1 ppm in deuterated chloroform, and 26.9 ppm. , 29.7 ppm vicinity, 30.2 ppm vicinity, 33.4 ppm vicinity, it calculates using the spectrum integral value derived from the ethylene structure. For spectral attribution, known data such as a polymer analysis handbook (edited by the Analytical Society of Japan, published by Asakura Shoten, 2008) may be used.

As a method of graft-modifying the olefin resin with maleic anhydride, a known method is used. For example, a composition containing the olefin resin, maleic anhydride and a radical polymerization initiator is supplied to an extruder. Melt-kneading and then melt-modifying method in which maleic anhydride is graft-polymerized to the olefin resin, or a solution is prepared by dissolving the olefin resin in a solvent, and maleic anhydride and radical polymerization initiator are added to the solution. And a solution modification method in which maleic anhydride is graft-polymerized to the olefin resin. Especially, the said melt modification method is preferable on production at the point which can be mixed on-machine.

The radical polymerization initiator used in the above graft modification method is not particularly limited as long as it is conventionally used for radical polymerization. For example, benzoyl peroxide, cumene hydroperoxide, diisopropyl peroxydicarbonate , Cumyl peroxyneodecanoate, cumyl peroxyoctoate, azobisisobutyronitrile and the like.

The maleic anhydride-modified olefin resin preferably has a maleic anhydride modification amount of 0.1 to 3% by weight.
There exists a possibility that the adhesiveness with respect to the solar cell element of the said solar cell sealing sheet may fall that the said maleic anhydride modification amount is less than 0.1 weight%. When the maleic anhydride modification amount exceeds 3% by weight, the maleic anhydride modified olefin resin is cross-linked, and a gel is generated during the production of the solar cell encapsulating sheet, making it impossible to produce the encapsulating sheet, There exists a possibility that the extrusion moldability of the said solar cell sealing sheet may fall.
The lower limit of the amount of maleic anhydride modification is more preferably 0.15% by weight, the upper limit is more preferably 1.0% by weight, and most preferably 0.6% by weight.

The maleic anhydride-modified amount is calculated from the absorption intensity in the vicinity of 1790 cm ⁻¹ by preparing a test film using the maleic anhydride-modified olefin resin, measuring the infrared absorption spectrum of the test film. be able to. Specifically, the maleic anhydride-modified amount of the maleic anhydride-modified olefin resin is determined using, for example, FT-IR (Fourier Transform Infrared Spectrometer Nicolet 6700 FT-IR). The measurement can be performed by a known measurement method described in the association edition, published by Asakura Shoten, 2008).

Specific examples of the olefin copolymer resin include a copolymer of ethylene and an α-olefin, a copolymer of polypropylene and an α-olefin, and the like.
The α-olefin preferably has 3 to 10 carbon atoms, and more preferably 4 to 8 carbon atoms, in order to lower the melting point and improve flexibility by improving the amorphousness of the resin.
Specific examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and the like. Butene and 1-octene are preferred.
The olefin copolymer resin is preferably at least one resin selected from the group consisting of ethylene-propylene copolymers, ethylene-butene copolymers, and propylene-butene copolymers.

The maleic anhydride-modified olefin resin and olefin copolymer resin preferably have a maximum peak temperature (Tm) of an endothermic curve measured by differential scanning calorimetry of 80 to 125 ° C.
If the maximum peak temperature (Tm) of the endothermic curve is lower than 80 ° C, the heat resistance of the solar cell encapsulating sheet may be reduced. When the maximum peak temperature (Tm) of the endothermic curve is higher than 125 ° C., the heating temperature of the solar cell encapsulating sheet in the encapsulating process is increased, and the productivity of the flexible solar cell module is reduced, or the solar cell. There is a possibility that the sealing of the element becomes insufficient.
The maximum peak temperature (Tm) of the endothermic curve is more preferably 83 to 110 ° C.
In addition, the maximum peak temperature (Tm) of the endothermic curve measured by the differential scanning calorimetry can be measured according to the measurement method defined in JIS K7121.

The maleic anhydride-modified olefin resin and olefin copolymer resin preferably have a melt flow rate (MFR) of 0.5 g / 10 min to 29 g / 10 min. When the melt flow rate is less than 0.5 g / 10 min, strain remains in the encapsulating sheet during the production of the solar cell encapsulating sheet, and the module may curl after the production of the flexible solar cell module. If it exceeds 29 g / 10 minutes, it is easy to draw down during the production of the solar cell encapsulating sheet, and it is difficult to produce a sheet having a uniform thickness. It becomes easy to produce a pinhole etc. in a sheet | seat, and there exists a possibility of impairing the insulation of the said solar cell module whole.
The melt flow rate is more preferably 2 g / 10 min to 10 g / 10 min.
The melt flow rate of the maleic anhydride-modified olefin resin and olefin copolymer resin was measured at a load of 2.16 kg in accordance with ASTM D1238, which is a method for measuring the melt flow rate of polyethylene resin. Value.

The maleic anhydride-modified olefin resin and olefin copolymer resin preferably have a viscoelastic storage elastic modulus at 30 ° C. of 2 × 10 ⁸ Pa or less. When the viscoelastic storage elastic modulus at 30 ° C. exceeds 2 × 10 ⁸ Pa, the flexibility of the solar cell encapsulating sheet is lowered and the handleability is lowered, or the solar cell element is replaced by the solar cell encapsulating sheet. When manufacturing a solar cell module by sealing, the solar cell sealing sheet may need to be rapidly heated. If the viscoelastic storage elastic modulus at 30 ° C. is too low, the solar cell encapsulating sheet may exhibit adhesiveness at room temperature, and the handleability of the solar cell encapsulating sheet may be lowered. Is preferably 1 × 10 ⁷ Pa. The upper limit is more preferably 1.5 × 10 ⁸ Pa.

The maleic anhydride-modified olefin resin and olefin copolymer resin preferably have a viscoelastic storage elastic modulus at 100 ° C. of 5 × 10 ⁶ Pa or less. When the viscoelastic storage elastic modulus at 100 ° C. exceeds 5 × 10 ⁶ Pa, the adhesion of the solar cell encapsulating sheet to the solar cell element may be reduced.
When the viscoelastic storage elastic modulus at 100 ° C. is too low, the solar cell encapsulating sheet is pressed by a pressing force when the solar cell element is encapsulated by the solar cell encapsulating sheet to produce a solar cell module. The lower limit is preferably 1 × 10 ⁴ Pa because there is a risk that the solar cell encapsulating sheet will be greatly fluidized and the thickness of the solar cell encapsulating sheet may become uneven. The upper limit is more preferably 4 × 10 ⁶ Pa.
The viscoelastic storage elastic modulus of the maleic anhydride-modified olefin resin and the olefin copolymer resin is a value measured by a dynamic property test method based on JIS K7244.

The total maleic anhydride content of the mixed resin of the maleic anhydride-modified olefin resin and the olefin copolymer resin is preferably 0.03 to 3% by weight.
There exists a possibility that the adhesiveness with respect to the solar cell element of the said solar cell sealing sheet may fall that the total content of the said maleic anhydride is less than 0.03 weight%. If the total maleic anhydride content exceeds 3% by weight, the maleic anhydride-modified olefin resin is cross-linked and a gel is generated during the production of the solar cell encapsulating sheet, making it impossible to produce the encapsulating sheet. Or the extrudability of the solar cell encapsulating sheet may be reduced.
The lower limit of the total maleic anhydride content is more preferably 0.15% by weight, the upper limit is more preferably 1.0% by weight, and most preferably 0.6% by weight.
The total content of maleic anhydride in the mixed resin can be measured by the same method as the method for measuring the maleic anhydride-modified amount of the maleic anhydride-modified olefin resin described above.

The adhesive layer preferably further contains a silane compound having an epoxy group.
By containing the silane compound, the adhesion between the solar cell encapsulating sheet and the solar cell element surface can be improved.
The silane compound may have at least one epoxy group such as an aliphatic epoxy group or an alicyclic epoxy group in the molecule. The silane compound having an epoxy group is preferably a silane compound represented by the following general formula (I).

(In the formula, R ¹ represents a 3-glycidoxypropyl group or 2- (3,4-epoxycyclohexyl) ethyl group, R ² represents an alkyl group having 1 to 3 carbon atoms, and R ³ Represents an alkyl group having 1 to 3 carbon atoms, and n is 0 or 1.)

R ¹ represents a 3-glycidoxypropyl group represented by the following formula (II) or a 2- (3,4-epoxycyclohexyl) ethyl group represented by the following formula (III).

R ² is not particularly limited as long as it is an alkyl group having 1 to 3 carbon atoms, and examples thereof include a methyl group, an ethyl group, and a propyl group. A methyl group and an ethyl group are preferable, and a methyl group is preferable. More preferred.

The R ³ is not particularly limited as long as it is an alkyl group having 1 to 3 carbon atoms, and examples thereof include a methyl group, an ethyl group, and a propyl group, and a methyl group is preferable.

Examples of the silane compound represented by the general formula (I) include 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxysilane, Sidoxypropyltriethoxysilane, 3-glycidoxypropyltripropoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 2- ( 3,4-epoxycyclohexyl) ethyltripropoxysilane and the like.

In the general formula (I), n is preferably 0.
As the silane compound, 3-glycidoxypropyltrimethoxysilane is particularly preferable.

It is preferable that content of the said silane compound in the said contact bonding layer is 0.05-5 weight part with respect to 100 weight part of mixed resin of the said maleic anhydride modified olefin resin and olefin copolymer resin.
There exists a possibility that the adhesiveness of a solar cell sealing sheet may fall that content of the said silane compound is outside the above-mentioned range.
The lower limit of the content of the silane compound is more preferably 0.1 parts by weight and the upper limit is more preferably 1.5 parts by weight with respect to 100 parts by weight of the maleic anhydride-modified olefin resin. .

The said adhesive layer may further contain additives, such as a light stabilizer, a ultraviolet absorber, and a heat stabilizer, in the range which does not impair the physical property.

As a method for producing the adhesive layer, the maleic anhydride-modified olefin resin, the olefin copolymer resin, the silane compound added as necessary, and an additive at a predetermined weight ratio. Examples thereof include a method in which an adhesive layer is produced by supplying to an extruder, melting and kneading, and extruding into a sheet form from the extruder.

The adhesive layer preferably has a thickness of 80 to 700 μm.
If the thickness is less than 80 μm, the insulating property of the flexible solar cell module obtained using the solar cell encapsulating sheet of the present invention may not be maintained. If it exceeds 700 μm, the flame resistance of the flexible solar cell module may be adversely affected, or the weight of the flexible solar cell module may be increased, which is economically disadvantageous.
The thickness of the adhesive layer is more preferably 150 to 400 μm.

The adhesive layer preferably has a shrinkage stress of 0.29 MPa or less and a storage elastic modulus at 100 ° C. of 4 × 10 ⁵ Pa or more. When the shrinkage stress and the storage elastic modulus are in the above ranges, an adhesive layer having excellent shrinkage force, high-temperature shape maintainability, and adhesive force can be obtained.
The shrinkage stress is a value obtained by measurement by a stress relaxation test method using a universal material testing machine (Orientec, RTC-1310A).
The upper limit of the storage elastic modulus is preferably 5 × 10 ⁶ Pa.
The storage elastic modulus is a value obtained by measurement by a dynamic property test method based on JIS K7244.

The solar cell encapsulating sheet of the present invention is obtained by forming the adhesive layer on a fluororesin sheet.
The fluororesin sheet is not particularly limited as long as it has excellent transparency, heat resistance and flame retardancy, but is not limited to tetrafluoroethylene-ethylene copolymer (ETFE), ethylene chlorotrifluoroethylene resin (ECTFE), Polychlorotrifluoroethylene resin (PCTFE), polyvinylidene fluoride resin (PVDF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (FEP), polyvinyl fluoride resin (PVF), and tetrafluoroethylene-hexafluoropropylene It is preferable that it consists of at least 1 type of fluororesin selected from the group which consists of a copolymer (FEP).
Among these, as the fluororesin, polyvinylidene fluoride resin (PVDF), tetrafluoroethylene-ethylene copolymer (ETFE), and polyvinyl fluoride resin (PVF) are more preferable because they are superior in heat resistance and transparency. .

The fluororesin sheet preferably has a thickness of 10 to 100 μm.
If it is less than 10 μm, the insulating properties of the flexible solar cell module obtained using the solar cell encapsulating sheet of the present invention may not be ensured, or the flame retardancy may be impaired. If it exceeds 100 μm, the resulting flexible solar cell module may be heavy, which is economically disadvantageous.
The thickness of the fluororesin sheet is more preferably 15 to 80 μm.

The solar cell encapsulating sheet of the present invention can be produced by laminating and integrating the fluororesin sheet and the adhesive layer. There are no particular limitations on the method of laminating and integrating, for example, a method in which the fluororesin sheet is formed by extrusion lamination on one surface of the adhesive layer, or a coextrusion of the adhesive layer and the fluororesin sheet. And the like. Especially, the method by which the said adhesive layer and the said fluororesin sheet | seat are simultaneously formed into a film by a coextrusion process and laminated | stacked is preferable.
In the co-extrusion step, the extrusion setting temperature is preferably 30 ° C. or higher than the melting point of the fluororesin and the mixed resin and less than 30 ° C. from the decomposition temperature.
Thus, the solar cell encapsulating sheet is preferably an integral laminate in which the adhesive layer and the fluororesin sheet are simultaneously formed and laminated by a co-extrusion process.

The solar cell encapsulating sheet of the present invention preferably has an embossed shape on the surface. In particular, the solar cell encapsulating sheet preferably has an embossed shape formed on the surface of the fluororesin sheet that is on the light receiving surface side when applied to a solar cell module.
By having the said emboss shape, the reflection loss of sunlight can be reduced, glare can be prevented, and an external appearance can be improved.
The embossed shape may be a regular uneven shape or a random uneven shape.
The embossed shape may be embossed before being bonded to the solar cell element, embossed after being bonded to the solar cell element, or simultaneously molded in the step of bonding to the solar cell element. May be.
Among them, it is preferable to form by embossing before bonding to the solar cell element because there is no unevenness of emboss transfer and a uniform emboss shape can be obtained.
In particular, an adhesive layer of a solar cell encapsulating sheet and a fluororesin sheet are simultaneously formed by a co-extrusion process and embossed at the same time when the molten resin is cooled using an embossing roll as a cooling roll. Is more preferable because a uniform embossed shape can be maintained without deforming the embossed shape in the step of bonding to the solar cell element.

The solar cell sealing sheet of this invention can manufacture a flexible solar cell module by sealing a solar cell element.
In FIG. 1, the longitudinal cross-section schematic diagram of an example of the solar cell sealing sheet A of this invention which consists of the fluorine resin sheet 1 and the contact bonding layer 2 is shown.

The solar cell element is generally composed of a photoelectric conversion layer in which electrons are generated by receiving light, an electrode layer for taking out the generated electrons, and a flexible substrate.
In FIG. 2, the longitudinal cross-sectional schematic diagram of an example of the solar cell element B by which the photoelectric converting layer 3 is arrange | positioned on the flexible base material 4 is shown. Note that various arrangements of the electrode layer are possible and are omitted here.

Examples of the photoelectric conversion layer include crystal semiconductors such as single crystal silicon, single crystal germanium, polycrystalline silicon, and microcrystalline silicon, amorphous semiconductors such as amorphous silicon, GaAs, InP, AlGaAs, Cds, CdTe, and Cu _2. Examples thereof include compounds formed from compound semiconductors such as S, CuInSe ₂ and CuInS ₂ , and organic semiconductors such as phthalocyanine and polyacetylene.
The photoelectric conversion layer may be a single layer or a multilayer.
The thickness of the photoelectric conversion layer is preferably 0.5 to 10 μm.

The flexible substrate is not particularly limited as long as it is flexible and can be used for a flexible solar cell element. For example, heat-resistant resin such as polyimide, polyetheretherketone, polyethersulfone, etc. The base material which consists of can be mentioned.
The flexible substrate preferably has a thickness of 10 to 80 μm.

The electrode layer is a layer made of an electrode material.
The electrode layer may be on the photoelectric conversion layer, between the photoelectric conversion layer and the flexible base, or on the surface of the flexible base, as necessary.
Further, the solar cell element may have a plurality of the electrode layers.
Since the electrode layer on the light receiving surface side (surface) needs to be transparent, the electrode material is preferably a general transparent electrode material such as a metal oxide. Although it does not specifically limit as said transparent electrode material, ITO or ZnO etc. are used suitably.
When the transparent electrode is not used, the bus electrode and the finger electrode attached thereto may be patterned with a metal such as silver.
The electrode layer on the back side (back side) does not need to be transparent and may be made of a general electrode material, but silver is preferably used as the electrode material.

The method for producing the solar cell element is not particularly limited as long as it is a known method. For example, it may be formed by a known method in which the photoelectric conversion layer or the electrode layer is disposed on the flexible substrate.
The solar cell element may have a long shape wound in a roll shape or a rectangular sheet shape.

As a method of manufacturing the flexible solar cell module by sealing the solar cell element using the solar cell sealing sheet of the present invention, the solar cell sealing sheet is formed on at least the light receiving surface of the solar cell element. Can be confined using a pair of heat rolls and thermocompression-bonded.
The light-receiving surface of the solar cell element is a surface that can receive light and is a surface on the side where the photoelectric conversion layer is disposed with respect to the flexible substrate.
In the method for producing the flexible solar cell module, the surface of the solar cell element on which the photoelectric conversion layer is disposed and the adhesive layer surface of the solar cell encapsulating sheet of the invention face each other. A method of laminating solar cell encapsulating sheets, constricting them using a pair of heat rolls, and thermocompression bonding is preferable.

It is preferable that the temperature of the said heat roll at the time of constricting using said pair of heat roll is 70-160 degreeC. If it is less than 70 ° C., adhesion failure may occur. If it exceeds 160 ° C., curling tends to occur during thermocompression bonding. The temperature of the heat roll is more preferably 80 to 110 ° C.

The rotational speed of the hot roll is preferably 0.1 to 10 m / min. If it is less than 0.1 m / min, curling tends to occur after thermocompression bonding. If it exceeds 10 m / min, adhesion failure may occur. The rotation speed of the heat roll is more preferably 0.3 to 5 m / min.

An example of a method for producing a flexible solar cell module using the solar cell encapsulating sheet of the present invention will be specifically described with reference to FIG.
As shown in FIG. 3, the solar cell encapsulating sheet A and the solar cell element B are long, and are each wound in a roll shape. First, the roll of the solar cell encapsulating sheet A and the solar cell element B is unwound, and the light receiving surface (photoelectric conversion layer surface) of the solar cell element B and the adhesive layer surface of the solar cell encapsulating sheet A are arranged to face each other. Then, both are laminated to form a laminated sheet C.
Next, the laminated sheet C is supplied between a pair of rolls D and D heated to a predetermined temperature, and the laminated sheet C is heated and thermocompression bonded while pressing in the thickness direction, so that the solar cell element B and the solar cell. The sealing sheet A is bonded and integrated. Thereby, the said solar cell element is sealed with the said solar cell sealing sheet, and the flexible solar cell module E can be manufactured.

Moreover, when sealing a solar cell element using the solar cell sealing sheet of this invention, you may seal only the photoelectric conversion layer side surface (light-receiving surface) of a solar cell element, or photoelectric conversion of a solar cell element. You may seal both a layer side surface and a flexible base material side surface. By sealing both surfaces of the solar cell element with the solar cell encapsulating sheet, the solar cell element can be better sealed, and a flexible solar cell module that can stably generate power over a long period of time can be obtained.

Moreover, when sealing the flexible base material side surface of a solar cell element, since light transmittance is not required, even if it uses the sheet | seat which consists of an adhesive layer and a metal plate instead of the solar cell sealing sheet of this invention. Good.
It is preferable that the said adhesive layer is a layer which consists of a component similar to the adhesive layer of the solar cell sealing sheet of this invention.
Examples of the metal plate include a plate made of stainless steel, aluminum, or the like.
The thickness of the metal plate is preferably 25 to 800 μm.

As a method of sealing the flexible substrate side surface (back surface), for example, the solar cell sealing sheet of the present invention is bonded to the flexible substrate side surface (back surface) of the solar cell element in the same manner as described above. May be disposed so as to face the flexible base material, and may be thermocompression bonded by narrowing using a pair of heat rolls.
Moreover, when sealing the flexible base material side surface (back surface) of a solar cell element with the said adhesive layer and a metal plate, for example, the sheet | seat which consists of the said adhesive layer and a metal plate is formed first, Then, Similarly, the flexible substrate and the adhesive layer may be thermocompression bonded to the side surface (back surface) of the flexible substrate of the solar cell element using a sheet made of the adhesive layer and the metal plate.
The step of thermocompression bonding the solar cell encapsulating sheet or the sheet made of the adhesive layer and the metal plate to the flexible substrate side surface (rear surface) of the solar cell element is performed on the light receiving surface of the solar cell element described above. It may be performed before the step of thermocompression bonding the solar cell encapsulating sheet, may be performed simultaneously, or may be performed later.

Using the solar cell encapsulating sheet of the present invention, for example, a method for producing a flexible solar cell module by simultaneously encapsulating a photoelectric conversion layer side surface (front surface) and a flexible base material side surface (back surface) of a solar cell element. An example will be described with reference to FIG.
Specifically, while preparing a long solar cell element wound in a roll shape, two long solar cell encapsulating sheets wound in a roll shape are prepared. And as shown in FIG. 4, while unwinding the elongate solar cell sealing sheets A and A, respectively, unwind the elongate solar cell element B, and the adhesive layer of two solar cell encapsulating sheets is In a state of facing each other, the solar cell sealing sheets A and A are overlapped with each other through the solar cell element B to obtain a laminated sheet C. And by supplying the laminated sheet C between a pair of rolls D, D heated to a predetermined temperature, and heating the laminated sheet C while pressing it in the thickness direction, the solar cell encapsulating sheets A, A together The solar cell element B is sealed by the solar cell sealing sheets A and A, and the flexible solar cell module F is continuously manufactured.
In the manufacturing method of the flexible solar cell module, the solar cell encapsulating sheets A and A are overlapped with each other via the solar cell element B to form the laminated sheet C, and at the same time, while pressing the laminated sheet C in the thickness direction. You may heat.

Moreover, an example of the manufacturing point of the flexible solar cell module at the time of using a rectangular thing as a solar cell element is shown in FIG.
Specifically, a rectangular sheet-like solar cell element B having a predetermined size is prepared instead of the long solar cell element wound in a roll shape. And as shown in FIG. 5, the long solar cell sealing sheet A and A currently wound by roll shape were each unwound, and the solar cell sealing sheet which made the state which each adhesive layer was made to oppose A solar cell element B is supplied between A and A at predetermined time intervals, and the solar cell encapsulating sheets A and A are overlapped via the solar cell element B to obtain a laminated sheet C. And by supplying the laminated sheet C between a pair of rolls D, D heated to a predetermined temperature, and heating the laminated sheet C while pressing it in the thickness direction, the solar cell encapsulating sheets A, A together The solar cell element B is sealed by the solar cell sealing sheets A and A, and the flexible solar cell module F is continuously manufactured.
In the production of the flexible solar cell module, simultaneously with the formation of the laminated sheet C, the laminated sheet C may be heated while being pressed in the thickness direction.

Moreover, as another method of sealing the said solar cell element using the solar cell sealing sheet of this invention, and manufacturing a flexible solar cell module, for example, the solar cell of this invention cut | disconnected to the desired shape A solar cell encapsulating sheet and a solar cell element are prepared, and the solar cell encapsulating sheet is in a state where the adhesive layer of the solar cell encapsulating sheet and the photoelectric conversion layer side surface or both surfaces of the solar cell element face each other. And the solar cell element are laminated, and the obtained laminate is heated in a stationary state under reduced pressure while applying a pressing force in the thickness direction, so that the solar cell element is covered with the solar cell encapsulating sheet. The method of sealing is mentioned.

The step of heating the laminate while applying a pressing force in the thickness direction under reduced pressure is preferably performed in a reduced pressure atmosphere of 1000 Pa or less, and more preferably in a reduced pressure atmosphere of 80 to 1000 Pa.
In the heating step, the laminate is preferably heated to 100 to 150 ° C, more preferably 100 to 120 ° C. The heating time is preferably 1 to 15 minutes, and more preferably 2 to 5 minutes.
The step of heating the laminate while applying a pressing force in the thickness direction under reduced pressure can be performed using a conventionally known apparatus such as a vacuum laminator.

Even when the solar cell encapsulating sheet of the present invention is applied to any of the above-described production methods, the time for the crosslinking step can be shortened, and curling does not occur. A flexible solar cell module excellent in adhesiveness with the battery element can be suitably manufactured.

The longitudinal cross-sectional schematic diagram of an example of the flexible solar cell module obtained by the above-mentioned manufacturing method using the solar cell sealing sheet of this invention is shown to FIGS.
FIG. 6 is a schematic vertical cross-sectional view of an example of a flexible solar cell module obtained by sealing the photoelectric conversion layer side surface of the solar cell element with the solar cell sealing sheet of the present invention.
The flexible solar cell module of FIG. 6 is obtained by laminating and integrating the solar electronic sealing sheet of the present invention and a solar cell element in which a photoelectric conversion layer is disposed on the above-described flexible substrate.
FIG. 7 is a schematic longitudinal sectional view of an example of a flexible solar cell module obtained by sealing both surfaces of a solar cell element with the solar cell sealing sheet of the present invention.
The flexible solar cell module of FIG. 7 includes the solar cell encapsulating sheet of the present invention, the solar cell element in which the photoelectric conversion layer is disposed on the above-described flexible substrate, and the solar cell encapsulating sheet of the present invention in order. It is an integrated stack.
FIG. 8 shows a flexible solar cell obtained by sealing the photoelectric conversion layer side surface of the solar cell element with the solar cell encapsulating sheet of the present invention and encapsulating the flexible substrate side surface with a sheet made of an adhesive layer and a metal plate. It is a longitudinal cross-sectional schematic diagram of an example of a module.
The flexible solar cell module of FIG. 8 includes a solar cell encapsulating sheet of the present invention, a solar cell element in which a photoelectric conversion layer is disposed on the flexible substrate, a maleic anhydride-modified olefin resin, and an olefin copolymer. An adhesive layer made of resin and a metal plate are sequentially laminated and integrated.
Such a flexible solar cell module manufactured using the solar cell encapsulating sheet of the present invention is free from curling, has an adhesive property between the solar cell encapsulating sheet and the solar cell element, and maintains shape. Excellent.
Such a flexible solar cell module is also one aspect of the present invention.

Thus, the solar cell encapsulating sheet of the present invention has an adhesive layer made of a specific component on the fluororesin sheet, so that the solar cell element and the solar cell encapsulating sheet are not curled. A flexible solar cell module excellent in adhesiveness and shape maintainability can be efficiently produced.

Since the solar cell encapsulating sheet of the present invention has the above-described configuration, the solar cell encapsulating sheet is excellent in adhesiveness and shape maintenance with the solar cell element, and curl is generated when the solar cell element is encapsulated. Therefore, a flexible solar cell module can be manufactured with high efficiency. For this reason, the solar cell sealing sheet of this invention can be applied suitably for manufacture of a flexible solar cell module.

It is the longitudinal cross-sectional schematic diagram which showed an example of the solar cell sealing sheet of this invention. It is the longitudinal cross-sectional schematic diagram which showed an example of the solar cell element. It is the schematic diagram which showed an example of the manufacturing point of the flexible solar cell module using the solar cell sealing sheet of this invention. It is the schematic diagram which showed an example of the manufacturing point of the flexible solar cell module using the solar cell sealing sheet of this invention. It is the schematic diagram which showed an example of the manufacturing point of the flexible solar cell module using the solar cell sealing sheet of this invention. It is the longitudinal cross-sectional schematic diagram which showed an example of the flexible solar cell module manufactured using the solar cell sealing sheet of this invention. It is the longitudinal cross-sectional schematic diagram which showed an example of the flexible solar cell module manufactured using the solar cell sealing sheet of this invention. It is the longitudinal cross-sectional schematic diagram which showed an example of the flexible solar cell module manufactured using the solar cell sealing sheet of this invention. It is the graph which showed the contraction stress with respect to the maleic anhydride total content of the contact bonding layer which consists of modified butene-type resin, and the contact bonding layer which consists of mixed resin. It is the graph which showed the storage elastic modulus with respect to the maleic anhydride total content of the contact bonding layer which consists of modified butene-type resin, and the contact bonding layer which consists of mixed resin.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.

(Experimental example)
As maleic anhydride-modified olefin resin, butene-ethylene copolymer (butene component 25% by weight) is graft-modified with maleic anhydride, and the maleic anhydride modification amount is 0.15% by weight, 0.3% by weight. A modified butene resin was prepared.
Further, a butene-ethylene copolymer (butene component 25% by weight) was prepared as an olefin copolymer resin.
The modified butene resin and the butene-ethylene copolymer are mixed as appropriate so that the total maleic anhydride content is 0.08 wt%, 0.12 wt%, 0.15 wt%, 0.21 wt%. %, 0.27% by weight, 0.29% by weight, and 0.3% by weight of mixed resin were prepared.
The obtained 7 points of the above mixed resin and 2 points of modified butene resin (maleic anhydride modified amounts of 0.15% by weight, 0.3% by weight) were respectively supplied to an extruder at 250 to 290 ° C. After melt-kneading and extruding from a T die into a sheet, adhesive layers each having a thickness of 0.25 mm were formed. The obtained adhesive layer was measured for shrinkage stress and storage elastic modulus at 100 ° C. and shown in FIGS.
In addition, the said shrinkage stress was measured by the stress relaxation test method of the universal material testing machine (Orientec make, RTC-1310A). Moreover, the storage elastic modulus at 100 ° C. was measured by a tensile mode of a dynamic viscoelastic device (DVA-200, manufactured by IT Measurement Control Co., Ltd.).
As shown in FIGS. 9 and 10, even when the total maleic anhydride content is the same, the adhesive layer formed of the mixed resin has a shrinkage stress rather than the adhesive layer formed of the maleic anhydride-modified butene resin alone. The storage elastic modulus was low.

(Examples 1-10, Comparative Examples 1-9)
A composition for an adhesive layer comprising a total of 100 parts by weight of the resins having the compositions shown in Tables 1 and 2 and a silane compound was supplied to the first extruder and melt-kneaded at 250 ° C.
On the other hand, the predetermined fluororesins shown in Tables 1 and 2 were supplied to the second extruder and melt kneaded at the extrusion set temperatures shown in Tables 1 and 2.
Then, the joining layer composition and the fluororesin are supplied and joined to a joining die that connects the first extruder and the second extruder together, and T is connected to the joining die. Extruded into a sheet form from a die, a long and constant width obtained by laminating and integrating a 0.3 mm thick adhesive layer made of the above adhesive layer composition and a 0.03 mm thick fluororesin layer. A solar cell encapsulating sheet was obtained.
The modified butene resins in the table are modified butene resins obtained by graft-modifying a butene-ethylene copolymer containing a predetermined amount of butene component and ethylene component with maleic anhydride.
Examples of the fluororesin include polyvinylidene fluoride (PVDF) (manufactured by Arkema, trade name “Kyner 720”) or tetrafluoroethylene-ethylene copolymer (ETFE) (trade name, Fluon ETFE “C”, manufactured by Asahi Glass Co., Ltd.). -55AP ").
Examples of the silane compound include 3-glycidoxypropyltrimethoxysilane (trade name “Z-6040” manufactured by Toray Dow Corning), or 3-acryloxypropyltrimethoxysilane (trade name “manufactured by Shin-Etsu Chemical Co., Ltd.)” KBM-5103 ") was used.
Also, the melt flow rate (MFR) of the modified butene resin used, the maximum peak temperature (Tm) of the endothermic curve measured by differential scanning calorimetry, the maleic anhydride modification amount, the content in the mixed resin, and the butene-ethylene Tables 1 and 2 show the MFR and Tm of the copolymer and the total maleic anhydride content of the mixed resin.

The adhesive layer shrinkage stress and storage elastic modulus of the solar cell encapsulating sheet obtained above were measured by the following methods and are shown in Tables 1 and 2.
<Adhesive layer shrinkage stress>
It measured by the stress relaxation test of the universal material testing machine (Orientec RTC-1310A).

<Adhesive layer storage modulus>
The storage elastic modulus at 100 ° C. of the adhesive layer was measured by a tensile mode of a dynamic viscoelastic device (DVA-200, manufactured by IT Measurement Control Co., Ltd.).

Subsequently, the flexible solar cell module was produced in the following ways using the solar cell sealing sheet of the Example and comparative example obtained above. First, two solar cell sealing sheets in which the solar cell sealing sheet obtained above was wound in a roll shape and a solar cell element wound in a roll shape were prepared. The solar cell element has a photoelectric conversion layer made of a thin film-like amorphous silicon on one surface of a flexible base material made of a flexible polyimide film, and an ITO transparent electrode on the photoelectric conversion layer. It is formed and a metal electrode is formed on the other surface.

Next, as shown in FIG. 5, the long solar cell sealing sheets A and A wound in a roll shape are unwound and the solar cell seals in which the respective adhesive layers are opposed to each other. A solar cell element B was supplied between the stop sheets A and A, and the solar cell sealing sheets A and A were overlapped with each other via the solar cell element B to obtain a laminated sheet C. Then, the laminated sheet C is supplied between a pair of rolls D and D heated to the temperatures shown in Table 3, and pressed while heating the laminated sheet C in the thickness direction, and the solar cell encapsulating sheet A, A was bonded and integrated, and both surfaces of the solar cell element B were sealed to produce a flexible solar cell module F.

The obtained flexible solar cell module was evaluated for the following items, and the results are shown in Table 3.
<Occurrence of curls>
The flexible solar cell module having a size of 500 mm × 500 mm was placed on a flat plane, the height of the lift from the horizontal plane at the end was measured, and evaluated according to the following criteria. Note that Comparative Example 9 was not evaluated due to adhesion to the roll.
◎: Less than 15 mm ○: 15 mm or more and less than 20 mm Δ: 20 mm or more and less than 30 mm x: 30 mm or more

<High temperature shape maintainability>
The obtained flexible solar cell module was placed on a step and allowed to stand in an environment of 100 ° C. for 1000 hours, and the presence or absence of deformation was visually observed. Comparative Examples 8 and 9 were not evaluated because the solar cell encapsulating sheet was peeled off.
○: No deformation ×: Deformation

<Battery cell peel strength>
The peel strength when the solar cell sealing sheet on the transparent electrode surface of the solar cell element was peeled from the obtained flexible solar cell module was measured according to JIS K6854.

<Metal electrode peel strength>
The peel strength when the solar cell sealing sheet on the metal electrode surface of the solar cell element was peeled from the obtained flexible solar cell module was measured according to JIS K6854, and evaluated according to the following criteria.
○: 50 N / cm or more Δ: 10 N / cm or more and less than 50 N / cm x: less than 10 N / cm

<High temperature and high humidity durability (adhesion)>
The obtained flexible solar cell module was allowed to stand in an environment of 85 ° C. and a relative humidity of 85% described in JIC C8991, and peeling of the solar cell encapsulating sheet from the solar cell element was started. And observed every 500 hours, and the time when peeling was confirmed was measured.
In JIC C8991, which defines the authentication conditions for solar cell modules, durability of 1000 hours or more is required in terms of power generation efficiency, and it is determined that an object whose peeling has been confirmed in less than 1000 hours is insufficient in adhesiveness.
“-” In Comparative Examples 8 and 9 means that peeling was confirmed in less than 1000 hours.

<High temperature and high humidity durability (power generation characteristics)>
The obtained flexible solar cell module was allowed to stand in an environment of 85 ° C. and 85% relative humidity described in JIC C8990, and the amount of change in the maximum output Pmax was measured using 1116N manufactured by Nissin Tor Co., Ltd. In addition, about what peeling was confirmed in less than 1000 hours, it did not implement. Moreover, the evaluation result of Table 3 means the following.
> 3000H: Maintaining 95% output after 3000 hours.
2000H: Maintain 95% output until 2000 hours.
1000H: Maintains 95% output until lapse of 1000 hours (JIS-C8991 standard).
X: Output cannot be maintained at 95% after 1000 hours.
-: Measurement is not possible due to peeling before 1000 hours.

Moreover, the flexible solar cell module was produced in the following ways using the solar cell sealing sheet of the Example and comparative example which were obtained above.
Two solar cell encapsulating sheets (50 × 50 cm) of the present invention and a solar cell element (40 × 40 cm) cut into a predetermined shape are prepared, an adhesive layer of the solar cell encapsulating sheet, and the sun The solar cell encapsulating sheet and the solar cell element are laminated in a state where the photoelectric conversion layer side surface of the battery element and the flexible substrate side surface are opposed to each other, and the obtained laminate is made into a vacuum laminator (manufactured by SPIRE). Using SPI-LAMINATOR 350), after deaeration by heating at 80 ° C. for 2.5 minutes, both sides of the solar cell element are sealed with the solar cell by heating at the temperature and time described in Table 4 A flexible solar cell module sealed with a sheet was obtained.
The solar cell element used has the same configuration as the solar cell element used above.

Regarding the obtained flexible solar cell module, the occurrence of curling, high temperature shape maintainability, battery cell peel strength, metal electrode peel strength, high temperature and high humidity durability (adhesion) and high temperature and high humidity durability (power generation characteristics) are described above. Evaluation was made in the same manner, and the results are shown in Table 4.
In Comparative Example 9, since the solar cell encapsulating sheet peeled from the solar cell element, the occurrence of curling was not evaluated.

The solar cell sealing sheet of this invention can be applied suitably for manufacture of a flexible solar cell module.

A Solar cell encapsulating sheet B Solar cell element C Laminated sheet D Rolls E, F, G Flexible solar cell module 1 Fluorine resin sheet 2 Adhesive layer 3 Photoelectric conversion layer 4 Flexible substrate 5 Metal plate

Claims (9)

On the fluorine resin sheet, it has an adhesive layer made of a mixed resin of maleic anhydride-modified olefin resin and olefin copolymer resin,
Content of the said maleic anhydride modified olefin resin is 30 to 99 weight% in the said mixed resin, The solar cell sealing sheet characterized by the above-mentioned. The maleic anhydride-modified olefin resin is a resin obtained by graft-modifying an α-olefin-ethylene copolymer having an α-olefin content of 1 to 25% by weight with maleic anhydride, and the amount of maleic anhydride modification The solar cell encapsulating sheet according to claim 1, wherein is 0.1 to 3 wt%. 3. The sun according to claim 1, wherein the olefin copolymer resin comprises at least one resin selected from the group consisting of an ethylene-propylene copolymer, an ethylene-butene copolymer, and a propylene-butene copolymer. Battery sealing sheet. Fluorine-based resin sheets include tetrafluoroethylene-ethylene copolymer, ethylene chlorotrifluoroethylene resin, polychlorotrifluoroethylene resin, polyvinylidene fluoride resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinyl fluoride The solar cell encapsulating sheet according to claim 1, 2 or 3, comprising at least one fluororesin selected from the group consisting of a resin and a tetrafluoroethylene-hexafluoropropylene copolymer. The adhesive layer further contains 0.05 to 5 parts by weight of the silane compound represented by the general formula (I) with respect to 100 parts by weight of the mixed resin of maleic anhydride-modified olefin resin and olefin copolymer resin. Item 5. A solar cell encapsulating sheet according to item 1, 2, 3 or 4.

(In the formula, R ¹ represents a 3-glycidoxypropyl group or 2- (3,4-epoxycyclohexyl) ethyl group, R ² represents an alkyl group having 1 to 3 carbon atoms, and R ³ Represents an alkyl group having 1 to 3 carbon atoms, and n is 0 or 1.) The solar cell encapsulating sheet according to claim 1, 2, 3, 4, or 5, wherein an embossed shape is formed on the surface of the fluororesin sheet. The solar cell encapsulating sheet according to claim 1, and a solar cell element in which a photoelectric conversion layer is disposed on a flexible substrate are laminated and integrated. Flexible solar cell module. The solar cell encapsulating sheet according to claim 1, 2, 3, 4, 5 or 6, a solar cell element in which a photoelectric conversion layer is disposed on a flexible substrate, and claims 1, 2, 3, 4, 5 Or the solar cell sealing sheet of 6 is laminated | stacked and integrated in order, The flexible solar cell module characterized by the above-mentioned. The solar cell encapsulating sheet according to claim 1, a solar cell element in which a photoelectric conversion layer is disposed on a flexible substrate, a maleic anhydride-modified olefin resin, and an olefin copolymer A flexible solar cell module, wherein an adhesive layer made of a coalesced resin and a metal plate are sequentially laminated and integrated.

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