JP2010165873A - Rear surface protective sheet and solar battery module using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar battery rear-surface protective sheet which is superior in strength, weatherability, heat resistance, waterproofness and humidity proofness, has durability in time, is further, low cost and safe and has a thickness corresponding to a partial discharge voltage required for a voltage generated by a solar battery, and to provide a solar battery module that uses the rear-surface protective sheet. <P>SOLUTION: The solar battery module consists of a filling layer for fixing solar battery cells by at least a filling material, a surface protective sheet laminated on a solar light incident side of the filling layer and a rear surface protective sheet laminated on the other surface side. In the solar battery module, the rear-surface protective sheet has a liquid crystal polymer film 21, having a thickness of 10-150 μm, an insulating layer 22 and an easily-adhered layer 23 bonded to the filling layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a back surface protection sheet constituting a solar cell and a solar cell module using the same, and in particular, it has excellent mechanical strength, weather resistance, water resistance, moisture resistance and high durability, and is a built-in solar cell. The present invention relates to a back surface protection sheet capable of stably protecting cells and a solar cell module using the same.

  In recent years, a solar cell power generation system as a clean energy source has been spreading as one of power generation means. Since solar cells are installed outdoors, as sunlight is the source of energy, they are exposed to harmful light, particularly ultraviolet rays, and high and low temperatures throughout the year. The back surface used for the outer layer of the solar cell module so that stable power generation can be achieved for a long time without causing corrosion or deterioration of the built-in solar cell or wiring due to moisture or moisture due to exposure. The protective sheet itself is required to have high durability as well as a function that can protect the built-in solar battery cell, wiring, and the like.

  Currently, various types of solar cell modules have been developed and proposed. Generally, solar cell modules use, for example, crystalline silicon solar cells or amorphous silicon solar cells as photovoltaic elements, As shown in FIG. 3, a surface protective sheet layer, a filler layer, a photovoltaic device, a filler layer, a back surface protective sheet layer, etc. are laminated in this order, and are vacuum-sucked and manufactured by laminating by thermocompression bonding. ing. As the back surface protection sheet layer constituting the solar cell module, a plastic base material having excellent strength is generally used.

  As the back surface protection sheet layer constituting the solar cell module, strength, weather resistance, heat resistance, water resistance, light resistance, chemical resistance, light reflectivity, light diffusibility, moisture resistance, antifouling property, etc. And high durability over time is required.

The back protective sheet includes the most commonly used polyvinyl fluoride film (PVF) and metal layers such as aluminum (Al) foil, and also polyethylene terephthalate film (PET). For example, polyvinyl fluoride film / aluminum / Polyvinyl fluoride film, polyvinyl fluoride film / aluminum / polyethylene terephthalate film, polyethylene terephthalate film / aluminum / polyethylene terephthalate film, polyvinyl fluoride film / aluminum / polyethylene terephthalate film / polyvinyl fluoride film, etc. It is used as a film.
Polyvinyl fluoride film (PVF) is excellent in weather resistance, hydrolysis resistance, light reflectivity, etc., but it has poor electrical insulation, gas barrier properties and poor film processability. The film is thickened or a metal layer is provided as a gas barrier layer as described above. Furthermore, it is necessary to provide these composite films with openings (windows) through which the conductive wires pass so that the electric power generated in the solar cells is led to the junction box through the wiring, and the end faces of the openings are covered with insulating tape. Insulation treatment (insulating tape and affixing work) is required, and since there is a metal layer between the layers, the portion that contributes to the partial discharge voltage value required for the back surface protection sheet becomes thinner, so the filling inside the metal layer It is necessary to increase the thickness of the layer on the layer side, which increases the cost.

  Transparent vapor deposited barrier films (“GL Film” manufactured by Toppan Printing, “IB Film” manufactured by Dainippon Printing, “Tech Barrier” manufactured by Mitsubishi Plastics, etc.) and barrier coating films (“Ecosiale” manufactured by Toyobo, “Clarista” instead of metal layers By using “Kuraray”, the above-mentioned insulation treatment is not necessary, but it is expensive and is difficult in terms of durability under long-term high temperature and high humidity conditions required for solar cells. Thus, it is considered that the solar cell module back surface protective sheet may change with time.

  In addition, when a fluorine-based resin film such as a polyvinyl fluoride resin is used for the outermost layer, although it has weather resistance, the water vapor barrier property is not high, so that the resin does not hydrolyze due to soaked moisture. A highly hydrolyzable resin, such as hydrolyzable polyethylene terephthalate, has been required. However, since it is more expensive than general polyethylene terephthalate, a member having weather resistance as well as water vapor barrier properties has been demanded.

  Based on the above, a liquid crystal polyester with excellent barrier properties (moisture resistance), heat resistance, and weather resistance is coated on the back surface, and a polyethylene terephthalate film, an acrylic film, and a polycarbonate film are laminated for the purpose of imparting mechanical strength. Has been proposed (Patent Document 1).

  In addition, as a material having a barrier property (moisture-proof property) against water vapor, it has been proposed to use a liquid crystalline polymer exhibiting optical ease when melted as a resin laminate as an outer layer of a solar cell module (Patent Document 2).

However, in the strength, weather resistance, heat resistance, water resistance, light resistance, chemical resistance, light reflectivity, light diffusibility, moisture resistance, antifouling property, etc. required for the back surface protection sheet, liquid crystal polymers alone are not suitable. It is sufficient, and there is a possibility that separation between layers between the liquid crystal polymer and another film and separation between layers due to aging may occur.
Further, recently, a back surface protection sheet having a partial discharge voltage of 1000 V or more is also demanded in response to the demand for electrical insulation capable of handling a voltage of the solar battery power generation system of 1000 V or more.

JP 2006-324478 A JP 2002-314102 A

  Therefore, the present invention is excellent in strength, weather resistance, heat resistance, water resistance, light diffusibility, moisture proofing, etc., has durability over time, and is safer at lower cost and more efficiently. An object of the present invention is to provide a back surface protection sheet capable of supporting a partial discharge voltage required for a voltage (for example, 500 to 1000 V, and recently up to 1500 V) and a solar cell module using the same. To do.

The present invention, which has been made to solve the above problems,
A solar cell module comprising: a filling layer for fixing solar cells with at least a filler; a surface protection sheet laminated on the sunlight incident side of the filling layer; and a back surface protection sheet laminated on the opposite surface side Among them, the back surface protective sheet has an easy-adhesion layer adhered to a liquid crystal polymer film having a thickness of 10 to 150 μm, an insulating layer, and a filling layer (Claim 1).

  As a result, the liquid crystal polymer film in the outermost layer of the back protective sheet has strength, weather resistance, moisture resistance, heat resistance, water resistance, light resistance, and chemical resistance, so an inexpensive polyethylene terephthalate resin or the like is used for the insulating layer. Further, by providing an adhesive layer that can be strongly bonded to the filling layer, the adhesion between the back surface protective sheet and the filling layer can be maintained, and the problem of delamination between layers over time can be reduced. Moreover, since there is no metal layer or conductive layer, the thickness corresponding to the partial discharge voltage required for the voltage generated by the solar cell can be designed for the entire back protective sheet, and the cost can be reduced.

  The liquid crystal polymer film is a thermoplastic resin having thermotropic liquid crystal properties and the heat-resistant type is classified into type I (econol type), type II (vector type), type III (X7G type). More than seeds are used as an alloy (claim 2).

  The liquid crystal polymer film has a continuous usable temperature (UL748B) of 110 ° C. or higher and / or a deflection temperature under load (DTUL) of 180 ° C. or higher (Claim 3).

  The insulating layer is made of a polyethylene terephthalate film (PET) (claim 4).

  The thickness of the insulating layer is 6 to 600 μm (Claim 5).

  The easy-adhesion layer is formed of a film of a polyethylene resin, an ethylene-vinyl acetate resin, or an acrylic resin, or a mixture thereof, or is formed by coating as a coating liquid. 6).

  When the filling layer is a cross-linked ethylene-vinyl acetate resin, the easy-adhesion layer has an ethylene-vinyl acetate resin having a vinyl acetate ratio (VA ratio) of 2 to 30% (claim 7). .

  The liquid crystal polymer film, the insulating layer, and the adhesive layer that adheres to each other are adhesives that are highly hydrolytic resistant polycarbonate adhesives, rubber adhesives, polyurethane adhesives, or a curing agent or a crosslinking agent. It is a two-component curing type in which an agent is used in combination (claim 8).

  The thickness of the entire back protective sheet is 100 to 300 μm for a partial discharge voltage value of 600 V, or 150 to 450 μm for a partial discharge voltage value of 1000 V, or 250 to 700 μm for a partial discharge voltage value of 1500 V. It is characterized (claim 9).

  In an environment of a temperature of 85 ° C. and a humidity of 85%, the tensile elongation retention rate after storage for 3000 hours between the liquid crystal polymer film and the insulating layer is 50 to 100% (claim 10).

In an environment of a temperature of 85 ° C. and a humidity of 85%, the laminate strength of the liquid crystal polymer film and the insulating layer after storage for 3000 hours is 2 N / 15 mm width or more, and the water vapor transmission rate is 3.0 g / m ² · 24 hr. It is the following (claim 11).

  It is a solar cell module formed by laminating | stacking the back surface protection sheet in any one of Claims 1-11 on the filling layer which fixes a photovoltaic cell with a filler (Claim 12).

  The solar cell back surface protective sheet of the present invention and a solar cell module using the same have strength, weather resistance, heat resistance, moisture resistance, water resistance, etc., and particularly excellent interlayer adhesion and durability over time, In addition, the thickness can be set to have a sufficient water vapor barrier property, and can correspond to a partial discharge voltage required for a voltage generated by a solar cell, which is safer at a lower cost.

It is sectional drawing which shows an example of the solar cell back surface protection sheet of this invention. (A), (b) is a schematic sectional drawing of the solar cell module using a solar cell back surface protection sheet.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The solar cell module 1 shown in the sectional view of FIG. 3A is represented by an ethylene-vinyl acetate copolymer (EVA) in which a plurality of silicon crystal solar cells 2 are connected by an interconnector 6 and hermetically sealed. It is a silicon crystal solar cell in which a filling layer 3, a front surface protective layer 4 and a back surface protective sheet 5 formed on both sides are laminated, so that electric power generated in the solar cell 2 is guided to the junction box 8 through the wiring 7. An opening (not shown) through which the conducting wire passes is formed in the back surface protection sheet 5. Moreover, the solar cell module 11 shown in the cross-sectional view of FIG. 3B includes a thin film solar cell 12 such as amorphous silicon, a filling layer 3 that seals the solar cell module 12, a surface protective layer 4 and a back surface that are formed on both sides. It is a thin film solar cell in which a protective sheet 5 is laminated. Similarly, an opening (not shown) through which a conductive wire passes so that the electric power generated in the solar battery cell 2 is guided to the junction box 8 through the wiring 7 is formed in the back surface protective sheet 5. Forming.

In this solar cell module 1, 11, the solar cell back surface protection sheet of the present invention satisfying various functions such as heat resistance, weather resistance and moisture resistance will be described with reference to FIG.
The back surface protective sheet 5 shown in FIG. 1 includes a liquid crystal polymer film 21, an insulating layer 22, and an easily adhesive resin layer 23 that enables strong adhesion to the filling layer 3.

The liquid crystal polymer film 21 exhibits barrier properties such as water vapor, that is, moisture resistance (the initial value of water vapor permeability is 0.5 g / m ² · 24 hr or less), and further has heat resistance (continuous usable temperature (UL748B) is 110). And those having weather resistance (high hydrolysis resistance) are preferred.
Examples of the liquid crystal polymer include wholly aromatic polyesters, polyimides, polyester amides, and the like, and resin compositions containing them. In the present invention, examples of the liquid crystal polymer include wholly aromatic polyesters, polyimides, polyester amides, and the like, and resin compositions containing them. In the present invention, the liquid crystal polymer is a thermoplastic resin having thermotropic liquid crystal properties and the heat resistance type is classified into type I (econol type), type II (vector type), type III (X7G type), These can be used alone or in combination of two or more, and can be appropriately selected.
Furthermore, the liquid crystal polymer used in the present invention includes an organic filler, an antioxidant, a heat stabilizer, a light stabilizer, a flame retardant (phosphorous flame retardant, bromine flame retardant), a lubricant, and an antistatic agent as necessary. , Inorganic colorants (pigments: carbon black, titanium oxide, barium sulfate), or organic colorants, rust inhibitors, crosslinking agents, foaming agents, fluorescent agents, surface smoothing agents, surface gloss improvers, fluororesins, etc. Various additives such as a mold release improver can be added and mixed during the production process or in subsequent processing steps.

The thickness of the liquid crystal polymer film 21 is desirably in the range of 10 to 150 μm, particularly preferably 20 to 70 μm, from the above water vapor transmission rate and flexibility. If it is less than 10 μm, it is difficult to obtain a barrier property similar to that of a metal foil, and it becomes difficult to handle. On the other hand, if it exceeds 150 μm, it becomes difficult to form a film, and the amount of resin used increases, resulting in an increase in cost.
The liquid crystal polymer film 21 is formed into a film shape by discharging a molten resin of a liquid crystal polymer from a slit of a metal die at high temperature and high pressure and cooling.

  The liquid crystal polymer film 21 has a surface treatment such as a corona discharge treatment, a plasma treatment, a flame treatment, a sputtering treatment, a solvent treatment, an ultraviolet treatment, a polishing treatment, an infrared treatment, an ozone treatment or the like in advance to improve the adhesion to the surface. Can be applied.

  The insulating layer 22 may be a resin that has insulating properties and imparts mechanical strength. Examples thereof include a polyethylene terephthalate (PET) film, an acrylic film, and a polycarbonate film. The thickness is preferably in the range of 6 to 600 μm, and if it is less than 6 μm, it is difficult to form a film, and if it exceeds 600 μm, it is not necessary if the partial discharge voltage is 2,000 V or higher.

The easy-adhesion layer 23 strongly adheres to the filling layer 3 that encloses the solar battery cells 2, and examples thereof include polyethylene resins, ethylene-vinyl acetate (EVA) resins, and acrylic resins. The mixture can be formed into a film or can be formed as a coating liquid.
In particular, when the filling layer is a cross-linked ethylene-vinyl acetate, it is preferable that the easy-adhesion layer 23 be an ethylene-vinyl acetate resin having a vinyl acetate ratio (VA ratio) of 2 to 30%. For the system packed layer, an ethylene-vinyl acetate resin or a polyethylene resin is preferable. The thickness is required to be 5 μm or more in order to obtain a sufficient adhesive strength (40 N / cm width). The upper limit is determined by the total thickness of the liquid crystal polymer film 21 and the insulating layer 22, but may be 250 μm or less in the case of a back surface protective sheet having a partial discharge voltage of 1000V. In addition, in order to raise the electric power generation efficiency of a photovoltaic cell, it is also possible to add and color a white pigment or a black pigment.

  In addition, an adhesive that can maintain a laminate strength of at least 5 N / 15 mm after 3000 hours at 85 ° C. and 85% is used between the liquid crystal polymer film 21, the insulating layer 22, and the easy adhesion layer 23. An adhesive having high hydrolysis resistance is preferable. For example, a one-component polycarbonate adhesive, a rubber adhesive, a polyurethane adhesive, or a two-component curable adhesive using a curing agent or a crosslinking agent in combination.

The back surface protection sheet 5 in which these are sequentially formed is laminated on both sides of the filling layer 3 typified by an ethylene-vinyl acetate copolymer that seals the solar cells together with the surface protection layer 4 to form solar cell modules 1 and 11. it can.
The back surface protection sheet of the present invention can be used as a back surface protection sheet for solar cells having different configurations such as organic compound solar cells, inorganic compound solar cells other than crystalline solar cells and thin film solar cells. it can.

On one side of a liquid crystal polymer film ("Bexter" Kuraray Co., Ltd.) with a thickness of 25μm formed by the Extruder method, a polyethylene terephthalate film with a thickness of 188μm and a vinyl acetate ratio (VA ratio) as an easy adhesion layer 50% of an ethylene-vinyl acetate resin film in which 2% carbon black is added to 5% ethylene-vinyl acetate resin and a two-component curable urethane adhesive (product name “main agent A511 / curing agent A50”, Mitsui Chemicals Polyurethanes, Inc. )) Was adhered at a coating amount of 5 g / m ² to obtain a back protective sheet.
Using this back surface protection sheet, as shown in FIG. 2, it is laminated on a surface protection sheet, a filling layer (EVA), a solar battery cell, and a filling layer (EVA), and laminated by vacuum heating at 150 ° C., 30 minutes, 1 torr. A solar cell module was manufactured.

Corona treatment is applied to both sides of a 25 μm thick liquid crystal polymer film (“BEXTER” Kuraray Co., Ltd.) formed by the Extruder method, and a 250 μm thick polyethylene terephthalate film (and , A two-component curable urethane adhesive (product name "Main Agent A511 / Curing Agent A50" Mitsui Chemical Polyurethanes Co., Ltd.) is applied at an application amount of 5 g / m ² , and an acrylic emulsion resin as an easy adhesion layer on the insulating layer side (Easily adhesive coating agent) was applied after drying so that the coating amount was 10 g / m ² , to obtain a back surface protective sheet.
Using this back surface protection sheet, a solar cell module was produced in the same manner as in Example 1.

<Comparative Example 1>
A 25-μm-thick polyvinyl fluoride resin film (product name: PV2111 DuPont), a 20-μm-thick aluminum foil, and a 250-μm-thick polyethylene terephthalate film are each a two-component curable urethane-based adhesive (product name: “main agent A511 / curing agent”. A50 "Mitsui Chemicals Polyurethane Co., Ltd.) was adhered at a coating amount of 5 g / m ² , and an acrylic easy-adhesive coating agent 10 g / m ² was further applied to the polyethylene terephthalate film surface to obtain a back surface protective sheet.
Using this back surface protection sheet, a solar cell module was produced in the same manner as in Example 1.

<Comparative example 2>
A 25-μm-thick polyvinyl fluoride resin film (product name: PV2111 DuPont) and a 250-μm-thick polyethylene terephthalate film are each a two-component curable urethane adhesive (product name “main agent A511 / curing agent A50”, Mitsui Chemicals Polyurethanes) ) Was applied at a coating amount of 5 g / m ² , and an acrylic easy-adhesion coating agent 10 g / m ² was further applied to the polyethylene terephthalate film surface to obtain a back surface protective sheet.
Using this back surface protection sheet, a solar cell module was produced in the same manner as in Example 1.

<Comparative Example 3>
25 μm thick polyvinyl fluoride resin film (product name: PV2111 DuPont),
A polyethylene terephthalate film having a thickness of 12 μm with a vapor deposition layer of alumina deposited to a thickness of 4000 nm, a polyethylene terephthalate film with a thickness of 188 μm, and an ethylene-vinyl having an vinyl acetate ratio (VA ratio) of 5% as an easy adhesion layer An ethylene-vinyl acetate resin film 50 μm in which 2% carbon black is added to acetate resin is applied to each two-component curing type urethane adhesive (product name “main agent A511 / curing agent A50”, Mitsui Chemicals Polyurethane Co., Ltd.) Adhering at 5 g / m ² , a back protective sheet was obtained.
Using this back surface protection sheet, a solar cell module was produced in the same manner as in Example 1.

<Evaluation>
The back surface protection sheets obtained in Example 1, Example 2 and Comparative Examples 1 to 3 had predetermined partial discharge voltage values, strength (interlaminar laminate strength), moisture resistance (water vapor barrier property), and tensile elongation retention rate, respectively. Evaluation is performed by an evaluation method, and the cost of insulation processing, materials, and the like is further evaluated. Table 1 shows the evaluation results.
<Evaluation method>
(1) Partial discharge voltage: Measured in accordance with IEC60664-1: 2007 Clause 6.1.3.5 V
(2) Interlaminar laminate strength: Measure the interlaminar laminate strength at the initial stage and after storage for 3000 hours in an environment of 85 ° C. and 85% RH at a measurement width of 15 mm and a measurement speed of 300 mm / min. N / 15 mm
(3) water vapor barrier property: 40 ℃ · 90% RH environment at 3000 hours MOCON method of back protective sheet after storage - measuring the water vapor transmission in infrared sensor g / ^{m 2}
(4) Tensile elongation maintenance ratio: measured in the MD direction (parallel to the molding direction) with a measurement width of 15 mm and a measurement speed of 300 mm / min. N / 15 mm
In addition, when the solar cell module using the back surface protection sheet obtained in Example 1, Example 2 and Comparative Examples 1 to 3 was irradiated with sunlight and subjected to an output test, good output results were obtained in all cases. It was.

  As shown in Table 1, the back surface protective sheet of the present invention has strength, weather resistance, moisture resistance, etc., particularly excellent interlayer adhesion and durability over time, and has sufficient water vapor barrier properties, The thickness can correspond to a partial discharge voltage required for a voltage generated by a solar cell, which is cheaper and safer. Furthermore, a solar cell module excellent in strength, weather resistance, moisture resistance and the like can also be obtained by using this back surface protective sheet.

DESCRIPTION OF SYMBOLS 1 ... Solar cell module 2 ... Solar cell 3 ... Filling layer 4 ... Surface protective layer 5 ... Back surface protection sheet 6 ... Interconnector 7 ... Wiring 8 ... Junction box 11 ... Solar cell module 12 ... Solar cell 21 ... Liquid crystal polymer film 22 ... Insulating layer 23 ... Adhesive layer

Claims (12)

  A solar cell module comprising: a filling layer for fixing solar cells with at least a filler; a surface protection sheet laminated on the sunlight incident side of the filling layer; and a back surface protection sheet laminated on the opposite surface side Among these, the back surface protection sheet comprises a liquid crystal polymer film having a thickness of 10 to 150 μm, an insulating layer, and an easy adhesion layer adhered to the filling layer.   The liquid crystal polymer film is a thermoplastic resin having thermotropic liquid crystal properties and heat resistance types classified into type I (econol type), type II (vector type), type III (X7G type), and these can be used alone Alternatively, the back surface protective sheet according to claim 1, wherein two or more types are used as an alloy.   3. The back protective sheet according to claim 1, wherein the liquid crystal polymer film has a continuous usable temperature (UL748B) of 110 ° C. or higher and / or a deflection temperature under load (DTUL) of 180 ° C. or higher.   The solar cell back surface protective sheet according to claim 1, wherein the insulating layer is made of a polyethylene terephthalate film (PET).   The thickness of the said insulating layer is 6-600 micrometers, The solar cell back surface protection sheet of Claim 1 or 4 characterized by the above-mentioned.   The easy-adhesion layer is formed by forming a film of a polyethylene resin, an ethylene-vinyl acetate resin, or an acrylic resin, or a mixture thereof, or by coating as a coating liquid. The solar cell back surface protection sheet of 1.   7. The adhesive layer according to claim 6, wherein when the filling layer is a cross-linked ethylene-vinyl acetate resin, the easy adhesion layer includes an ethylene-vinyl acetate resin having a vinyl acetate ratio (VA ratio) of 2 to 30%. The solar cell back surface protection sheet of description.   The adhesive that bonds the liquid crystal polymer film, the insulating layer, and the easy-adhesion layer is a one-component liquid or a curing agent of a polycarbonate-based adhesive, a rubber-based adhesive, a polyurethane-based adhesive having high hydrolysis resistance, or The solar cell back surface protective sheet according to claim 1, wherein the solar cell back surface protective sheet is a two-component curable type in which a crosslinking agent is used in combination.   The thickness of the entire back protective sheet is 100 to 300 µm for a partial discharge voltage value of 600 V, or 150 to 450 µm for 1000 V, or 250 to 700 µm for 1500 V. The back surface protection sheet as described.   2. The tensile elongation retention ratio after storage for 3000 hours between the liquid crystal polymer film and the insulating layer in an environment of a temperature of 85 ° C. and a humidity of 85% is 50 to 100%. Solar cell back surface protection sheet. In an environment of a temperature of 85 ° C. and a humidity of 85%, the laminate strength of the liquid crystal polymer film and the insulating layer after storage for 3000 hours is 2 N / 15 mm width or more and the water vapor transmission rate is 3.0 g / m ² · 24 hr or less. The solar cell back surface protective sheet according to claim 1, wherein the solar cell back surface protective sheet is provided.     A solar battery module comprising the back surface protection sheet according to claim 1, which is laminated on a filling layer for fixing a solar battery cell with a filler.

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