JP2008305822A - Film for solar cell module sealing sheet and solar cell module sealing sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film for a solar cell module sealing sheet which has excellent electric insulation performance and high partial discharge voltage, and to provide a solar cell module sealing sheet. <P>SOLUTION: The film for a solar cell module sealing sheet is a film forming a solar cell module sealing sheet and having a structure in which an uneven shape having a mean value of difference in height of ≥1 μm is provided on at least one surface of the film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a film used for a solar cell module sealing sheet and a solar cell module sealing sheet using the film. It is related with the film used for the solar cell module sealing sheet which has the characteristic especially excellent in electrical insulation, and the solar cell module sealing sheet using the same.

  In recent years, solar cells are rapidly spreading as clean energy. This solar cell module uses a solar cell element such as a crystalline silicon solar cell element, a surface sealing sheet layer, a filler layer, a solar cell element as a photovoltaic element, an ethylene-vinyl acetate copolymer ( (Hereinafter referred to as EVA), a filler layer, a back surface sealing sheet layer, and the like are laminated and manufactured using a vacuum suction heating lamination method or the like. Here, glass or a lightweight and strong plastic sheet is generally used as the front and back sealing sheets constituting the solar cell module. The front and back side sealing sheets using plastic sheets are excellent in mechanical strength, weather resistance, heat resistance, water resistance, light resistance, chemical resistance, and light reflectivity, and prevent entry of moisture, oxygen, etc. From the viewpoint, it is required to have excellent gas barrier properties. As a typical configuration of the back surface sealing sheet, there is a configuration in which polyester films excellent in weather resistance and gas barrier properties are laminated (Patent Documents 1 and 2).

On the other hand, with the spread of solar cells in recent years, great attention has been paid to the electrical safety of solar cells and the system voltage has been increased to improve the performance of the entire solar cell system. Since the request | requirement to set increased, the request | requirement of the electrical insulation performance with respect to a solar cell module back surface sealing sheet increased, and the proposal of the solar cell back surface sealing sheet corresponding to the solar cell system voltage 1000V is made. (Patent Document 3). In these patent documents, glass is used as the surface sealing sheet, but when a plastic film is used as the surface sealing sheet, the same electrical insulation as that of the back surface sealing sheet is required.
JP 2002-026354 A (paragraphs [0008] to [0010]) Japanese Patent Laid-Open No. 2002-100788 JP 2006-253264 A

  However, in Patent Documents 1 and 2, since electrical insulation is not particularly taken care of, it is difficult to cope with a system voltage of 1000V.

  On the other hand, Patent Document 3 defines a solar cell back surface sealing sheet that satisfies 1000 V or more as a partial discharge voltage, which is a typical characteristic of electrical insulation that can correspond to a solar cell system voltage of 1000 V, and its configuration is The barrier film was sandwiched between weather-resistant polyester resin films. However, the only way to satisfy the partial discharge voltage of 1000 V is to increase the total thickness of the sealing sheet.

  The present invention is intended to provide a film used for a solar cell module sealing sheet that is more excellent in electrical insulation and a solar cell module sealing sheet without changing the thickness of the film constituting the sealing sheet. Is.

  In order to solve the above problems, the present invention employs the following means. That is, it is a film constituting a solar cell module sealing sheet, and is a film for a solar cell module sealing sheet in which an uneven shape having an average height difference of 1 μm or more is provided on at least one surface of the film. Further, it is a solar cell module sealing sheet using at least one of these films.

  According to the present invention, a partial discharge voltage can be improved by being particularly excellent in electrical insulation, and a solar cell module encapsulating sheet corresponding to a solar cell system voltage of 1000 V can be provided.

  The solar cell module sealing sheet of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an example of a general solar cell module. The solar cell module 1 includes a surface sealing sheet 10, a filler layer 2 adjacent to the surface sealing sheet, a solar cell element 3 embedded in the filler layer 2, and the filler layer 2. The back surface sealing sheet 20 is provided.

  Since the filler layer 2 is also used on the solar light incident side of the solar cell, it needs to have transparency, and has an adhesive property with the front surface sealing sheet 10 and the rear surface sealing sheet 20. It is also necessary to have. Moreover, the function which protects a solar cell is also required. Therefore, as the filler layer 2, there are ethylene-vinyl acetate copolymer, ionomer resin, polyvinyl butyral resin, etc., but considering various characteristics such as light resistance, heat resistance and water resistance, ethylene-vinyl acetate is used. A copolymer (hereinafter referred to as EVA) or polyvinyl butyral resin is preferred.

  As the back surface sealing sheet 20, a sheet made of a plurality of plastic films is generally used. The functions required for the back surface sealing sheet include water vapor barrier properties, weather resistance of the outermost layer (hydrolysis resistance), light reflectivity at the interface with the filler, electrical insulation, etc., and usually satisfy them. Laminate plastic film. That is, from the light incident side, an electrically insulating light reflecting film, a water vapor barrier film, and a weather resistant film are laminated in this order. This invention provides the film used for this backside sealing sheet, Comprising: The film which improves the partial discharge voltage of a backside sealing sheet.

  FIG. 2 is an example of the solar cell module back surface sealing sheet of the present invention. The back-side sealing sheet 20 in FIG. 2 has an electrically insulating weather resistance provided with an electrically insulating light reflecting film 23, an electrically insulating water vapor barrier film 22, and an uneven shape according to the present invention from the light incident side. It is configured by laminating a conductive film 21.

  As such an electrically insulating light reflecting film 23, the resin film 23 itself has diffuse reflectivity, and there is a method of applying a white paint on the resin film or a method of using a white resin film such as a white polyester film. Can be mentioned. Since the material cost is low and high reflectivity is obtained, it is preferable to use a white polyester film, particularly a white polyethylene terephthalate film, as the light reflecting film 23.

  Examples of the electrically insulating water vapor barrier film 22 include a structure in which an electrically insulating base film is provided with an inorganic oxide vapor deposition layer. As such an electrically insulating base film, for example, a biaxially stretched polyethylene terephthalate (PET) film is preferably used, but a polyester film such as polyethylene naphthalate, a polyolefin film such as polyethylene or polypropylene, a polystyrene film, a polyamide film, A polyvinyl chloride film, a polycarbonate film, a polyacrylonitrile film, a polyimide film, or the like may be used.

Various well-known additives and stabilizers such as an antistatic agent, an ultraviolet ray preventing agent, a plasticizer, and a lubricant may be used on the surface of the electrically insulating base film.
Although the thickness of this electrically insulating base film is not particularly limited, it is preferably 6 to 30 μm in consideration of suitability as a packaging material and workability in forming an inorganic oxide vapor deposition layer.

  Specifically, the inorganic oxide vapor deposition layer is formed by, for example, an inorganic oxide such as aluminum oxide or silicon oxide formed by a known physical vapor deposition method or chemical vapor deposition method. Moreover, after forming this inorganic oxide vapor deposition layer, you may provide the protective layer for improving a water vapor | steam barrier property further, or protecting an inorganic oxide vapor deposition layer.

  The uneven shape of the electrically insulating weather-resistant film 21 provided with the uneven shape according to the present invention is required to have an average height difference of 1 μm or more, preferably 2.5 μm or more. . Usually, the surface of the film is smooth in the film-formed state, but in the present invention, irregularities are positively formed on the film surface. By forming irregularities, the partial discharge voltage of the film can be improved. When the average value of the height difference of the unevenness is less than 1 μm, the partial discharge voltage is not improved and the solar cell system voltage 1000 V cannot be supported.

  As a method for forming such irregularities, embossing, rough polishing, sandblasting, etching, hairline processing, and the like can be used. In the present invention, embossing or rough polishing is preferable. The uneven shape may be any of a line shape, a dot shape, and a lattice shape. In the embossing, for example, the embossing roll may be used so that irregularities having a depth of about 1 mm are formed at a pitch of several mm or less. In rough polishing, the surface may be roughened by sandpaper or buffing so as to form fine irregularities on the surface. The same applies to sandblasting and etching.

  Moreover, this uneven | corrugated shape may be provided only in the single side | surface of a film, or both surfaces.

  In order to obtain excellent weather resistance, the electrically insulating weather-resistant film 21 provided with such an uneven shape has a fluororesin film or weather resistance (hydrolysis resistance) on the outermost layer on the side of the backside sealing sheet that comes into contact with the outside air. It is preferable to laminate a weather resistant film such as a biaxially stretched polyester film. Among these films, the fluororesin film has high weather resistance, but it is preferable to use a weather-resistant stretched polyester film from the viewpoint of cost.

  Moreover, it is preferable that the weather-resistant film 21 is laminated | stacked so that the surface in which the uneven | corrugated shape was provided may become the outermost surface side of a back surface sealing sheet.

  As an adhesive used when the three films thus prepared are bonded and laminated, a known dry laminating technique may be used for bonding. In particular, an adhesive for dry lamination using a polyether polyurethane, polyester polyurethane, or polyester as a main agent and polyisocyanate as a curing agent is preferable because of its good workability.

  In addition, processing to form irregularities may be performed before or after bonding the film, but embossing is difficult to bond after processing. Preferably it is done.

  FIG. 3 is another example of the solar cell module back surface sealing sheet of the present invention. In this example, a water vapor barrier layer 32 is laminated on a single film 31 having both light reflectivity and high weather resistance provided with an uneven shape to form a back surface sealing sheet.

  For the water vapor barrier layer 32, the water vapor barrier film formed on the water vapor barrier film 22 may be directly formed on the film 31, or the water vapor barrier film 22 itself may be bonded to the film 31.

The highly weather-resistant light reflecting film 31 provided with the uneven shape may be subjected to the above-described roughening treatment on the highly weather-resistant light reflecting film. Moreover, as a highly weather-resistant light reflection film, it has a polyester resin layer which uses one or several layers whose number average molecular weights are 18500-40000, 5-40 weight% titanium dioxide in this polyester resin layer It is preferable that the polyester resin film having at least one layer containing the above-mentioned composition is formed into a shape satisfying the following four conditions by the polyester resin layer containing titanium dioxide.
1. Relative reflectance is 80% or more and 105% or less,
2. The apparent density is 1.37 to 1.65 g / cm ³ ,
3. The optical density is 0.55 to 3.50,
4). Optical density variation is within 20% of the center value.

  Next, the surface sealing sheet 10 will be described. In general, a highly transparent white plate tempered glass is often used for the surface sealing sheet 10, but a plastic film may be used for the purpose of weight reduction and flexibility. In that case, the solar cell module of the present invention is used. The partial discharge voltage can be improved by using the sealing sheet.

  An example of the solar cell module surface sealing sheet of this invention is shown in FIG. The surface sealing sheet is composed of at least a weather-light-resistant film 11 and a water vapor barrier film 12, and the weather-light-resistant film 11 has a concavo-convex shape on its light incident side surface. The unevenness may be processed in the same manner as the above-described back surface sealing sheet. The water vapor barrier film 12 may be the same as the water vapor barrier film 22 of the above-described back surface sealing sheet.

  The weather-resistant light-resistant film 11 provided with the uneven shape is required to be highly transparent and not deteriorated by long-term sunlight exposure. For example, polytetrafluoroethylene (PTFE), 4-fluoride Ethylene-perchloroalkoxy copolymer (PFA), 4-fluorinated ethylene-6-fluorinated propylene copolymer (FEP), 2-ethylene-4-fluorinated ethylene copolymer (ETFE), poly-3-fluorinated Fluorine resin film such as ethylene (PCTFE), polyvinylidene fluoride (PVDF), or polyvinyl fluoride (PVF), or polycarbonate, polymethyl methacrylate, polyacrylate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acrylic, etc. Resin composition in which UV absorber is kneaded with resin It can be used. In particular, a fluororesin film is preferable because of excellent light resistance. In addition, in order to protect the water vapor barrier film and other films to be bonded to the inside, an ultraviolet absorber is further applied to the surface to be bonded, and the surface sealing sheet is then bonded to the water vapor barrier film. Is preferred.

  In the back surface sealing sheet 20 and the front surface sealing sheet 10 described above, only one film having an uneven shape is used, but a plurality of films having an uneven shape may be used.

  First, the measurement method used in the present invention will be described.

(1) Measurement of partial discharge voltage About the film for solar cell module sealing sheets and the solar cell module sealing sheet, the partial discharge voltage was measured based on the following measuring method, and electrical insulation was evaluated.
(Measuring method)
Conformity standard: IEC60664 / A2: 2002 4.1.2.4
Test device: KPD2050 (manufactured by Kikusui Electronics)
Measurement pattern: Trapezoidal start voltage Charge threshold: 1.0 pC
Vanishing voltage charge threshold: 1.0 pC
Test time: 22.0 s.

(2) Concavity and convexity height difference The unevenness height difference of the surface on which the concavo-convex surface was formed was measured using a surface shape microscope VF-7500 manufactured by Keyence Corporation. Ten points were measured for one sample, and the average value was adopted.

(Production of weather-resistant light reflecting film)
Next, preparation of a weather-resistant light reflecting film will be described.
100 parts of dimethyl terephthalate (parts by weight: hereinafter simply referred to as parts) is mixed with 64 parts of ethylene glycol, 0.1 parts of zinc acetate and 0.03 part of antimony trioxide are added as a catalyst, and the reflux temperature of ethylene glycol is Transesterification was performed.

To this was added 0.08 part of trimethyl phosphate, and the temperature was gradually raised and reduced, and polymerization was carried out at a temperature of 271 ° C. for 5 hours. The intrinsic viscosity of the obtained polyethylene terephthalate was 0.55. The polymer was cut into a chip having a length of 4 mm, and the chip shape of PET (polyethylene terephthalate) was a cylindrical shape. Length: 5.95 to 8.05 mm, width: 3.20 to 4.80 mm, high The height was 1.70-2.30 mm, and the specific gravity was 1.3 g / cm ³ . This PET was put into a rotary vacuum apparatus (rotary vacuum dryer) having a high polymerization temperature of 190 to 230 ° C. and a vacuum degree of 0.5 mmHg, and heated with stirring for 10 to 23 hours to obtain a PET polymer.

In the polymerization of PET used for the compound and the base, the high polymerization temperature is adjusted to 190 to 230 ° C., the high polymerization time is adjusted to 10 to 23 hours, and the intrinsic viscosity of the PET polymer is 0.71. Got. This PET polymer and titanium dioxide fine particles were compounded to obtain a master chip containing 50% by weight of titanium dioxide. Since this master chip had a specific gravity of 2.5 g / cm ³ , the chip shape of the master chip was length: 2.40 to 4.60 mm, width: 3.20 to 4.80 mm, and height: 1.70. It was made into the chip | tip shape where classification | category does not occur easily as a cylinder shape of-2.30 mm.

40% by weight of a titanium dioxide master chip was added to adjust the titanium dioxide concentration to 20% by weight with respect to the base polyester. These polymers were laminated through a laminating apparatus so as to be B layer / A layer / B layer, and formed into a sheet form from a T-die. The stacked configuration is a composite three-layer configuration. Here, a resin having an intrinsic viscosity of 0.71 and a number average molecular weight of 21,000 and no titanium dioxide was used for the A layer, and a resin having an intrinsic viscosity of 0.71 and a number average molecular weight of 21,000 and a titanium dioxide particle concentration of 20% by weight was used for the B layer. . An unstretched sheet obtained by cooling and solidifying the sheet-like molded product discharged from the T die with a cooling drum having a surface temperature of 25 ° C. is led to a roll group heated to 85 to 98 ° C., and stretched 3.3 times in the longitudinal direction. It cooled with the roll group of 25 degreeC. Subsequently, the film was stretched by 3.6 times in the direction perpendicular to the longitudinal direction in an atmosphere heated to 130 ° C. while being guided to a tenter while holding both ends of the longitudinally stretched film with clips. Thereafter, heat setting was performed at 220 ° C. in a tenter, and after uniform cooling, the film was cooled to room temperature to obtain a film having a winding thickness of 125 μm. This weather-resistant light reflecting film is referred to as film A. This film A has an apparent density of 1.41 g / cm ³ , an optical density of 0.85, an optical density variation of 9.5%, a relative reflectance of 90%, a UV transmittance of 0.09%, and hydrolysis resistance. The evaluation was 55%, and the UV resistance was an evaluation pass with a b-value increase rate of 4, and the heat resistance (elongation retention) was 63%.

Example 1
On one side of the weather-resistant light reflecting film A (thickness 250 μm), a square shape with a bottom of 2 mm on one side and a square pyramid with a height of 1 mm was formed by embossing. The average value of the height difference of the unevenness was 1 mm. When the partial discharge voltage of this film was evaluated, it was 1057V.

(Example 2)
On one surface of the weather-resistant light reflecting film A (thickness 250 μm), rough polishing was performed 20 times with # 400 sandpaper to form irregularities on the surface. The average value of the height difference of the unevenness was 2.8 μm. When the partial discharge voltage of this film was evaluated, it was 1010V.

(Example 3)
On one side of the weather-resistant light reflecting film A (thickness 250 μm), rough polishing was performed 80 times with # 400 sandpaper to form irregularities on the surface. The average height difference of the unevenness was 3.0 μm. When the partial discharge voltage of this film was evaluated, it was 1067V.

Example 4
On one side of the weather-resistant light reflecting film A (thickness 250 μm), rough polishing was carried out 20 times with # 1000 sandpaper to form irregularities on the surface. The average height difference of the irregularities was 1.4 μm. When the partial discharge voltage of this film was evaluated, it was 923V.

(Example 5)
The weather-resistant light-reflecting film A (thickness 250 μm) and an alumina transparent vapor deposition film (Toray Film Processing Co., Ltd., Barrox (registered trademark), 12 μm thickness) as a gas barrier film are commercially available as a polyester adhesive main agent LX703VL. And a polyisocyanate curing agent KR90 (both manufactured by Dainippon Ink & Chemicals, Inc.) in an admixture (dry weight 4 g / m ² ) mixed at a weight ratio of 15: 1. Dry lamination was performed so as to face film A. Thereafter, embossing was performed in the same manner as in Example 1 from the alumina transparent vapor-deposited film side to obtain a solar cell module back surface protective sheet of the present invention in which the apex side of the quadrangular pyramid was formed on the film A side surface. The average value of the height difference of the unevenness was 1 mm. When the partial discharge voltage of this film was evaluated, it was 1065V.

(Examples 6 to 8)
An alumina transparent vapor deposition film, which is a gas barrier film, was dry-laminated in the same manner as in Example 5 on the surface side of the films of Examples 2 to 4 where the uneven shape was not provided, thereby obtaining the solar cell module back surface protective sheet of the present invention.

  It was 1020V when the partial discharge voltage of the back surface protection sheet of Example 6 which carried out the dry lamination to the film of Example 2 was evaluated.

  It was 1057V when the partial discharge voltage of the back surface protection sheet of Example 7 which carried out the dry lamination to the film of Example 3 was evaluated.

  It was 932 V when the partial discharge voltage of the back surface protection sheet of Example 8 which carried out the dry lamination to the film of Example 4 was evaluated.

(Comparative Example 1)
The partial discharge voltage of the weather-resistant light reflecting film A (thickness 250 μm, maximum unevenness difference 0.3 μm) was evaluated as it was, and it was 913 V.

(Comparative Example 2)
An alumina transparent vapor deposition film, which is a gas barrier film, was dry laminated in the same manner as in Example 5 on the weather-resistant light reflecting film A (thickness: 250 μm). The partial discharge voltage of this film was evaluated and found to be 920V.

[Comparison between Examples 1 to 4 and Comparative Example 1]
It can be seen that the partial discharge voltage is improved by providing the uneven shape on the film of Comparative Example 1, and the uneven shape contributes to the improvement of the partial discharge voltage. However, Example 4 shows that the amount of improvement is smaller than that of Comparative Example 1, and the uneven height difference is not sufficient.

[Comparison between Examples 5 to 8 and Comparative Example 2]
Both film structures are bonded to 250 μm and 12 μm, but the partial discharge voltage is improved compared to Comparative Example 2, and the use of a film provided with an uneven shape for the back surface protective sheet improves the partial discharge voltage. Is effective. However, Example 8 shows that the amount of improvement is smaller than that of Comparative Example 2, and the uneven height difference is not sufficient.

It is a cross-sectional schematic diagram of a general solar cell module. An example of the solar cell module surface sealing sheet of this invention is shown. An example of the solar cell module back surface sealing sheet of this invention is shown. The 2nd example of the solar cell module back surface sealing sheet of this invention is shown. Indicates.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Filler 3 Solar cell element 4 Lead wire 10 Solar cell module surface sealing sheet 20 Solar cell module back surface sealing sheet 11 Uneven weatherproof light-resistant film 12, 22 Electrically insulating water vapor barrier film 13, 24 Concavity and convexity surface 21 Weatherproof film provided with concavity and convexity 23 Electrical insulating light reflection film 31 Weatherproof light reflection film provided with concavity and convexity 32 Water vapor barrier layer

Claims (6)

  A film for forming a solar cell module sealing sheet, wherein the film for a solar cell module sealing sheet is provided with an uneven shape having an average height difference of 1 μm or more on at least one surface of the film.   The film for solar cell module sealing sheet according to claim 1, wherein the partial discharge voltage is 1000 V or more.   The film for solar cell module sealing sheets according to claim 1 or 2, wherein the uneven shape is provided by embossing.   The film for solar cell module sealing sheets according to claim 1 or 2, wherein the uneven shape is provided by a polishing treatment using an abrasive.   The solar cell module sealing sheet which used at least one film for solar cell module sealing sheets in any one of Claims 1-4.   The solar cell module sealing sheet of Claim 5 comprised so that the uneven | corrugated surface of the said film for solar cell module sealing sheets may become the outermost surface of a solar cell module sealing sheet.

Images