KR101266885B1 - Polyester film for solar battery - Google Patents

Abstract

An object of this invention is to manufacture and provide the polyester film which improved the adhesiveness with the polyolefin resin represented by EVA used as a protective material of a solar cell at low cost.
The polyester film of this invention arrange | positioned the coating layer which has adhesiveness with polyolefin resin on at least one surface at the time of film forming of a polyester film, It is characterized by the above-mentioned. Typical examples of the polyolefin resin include ethylene vinyl acetate copolymer (EVA).

Description

Polyester film for solar battery {Polyester film for solar battery}

The present invention relates to a polyester film suitable for solar cells.

Photovoltaic power generation using solar energy that does not fall has been steadily expanded as an energy source that is clean and useful for preventing global warming, and a large amount of power generation is expected in the future. As a representative of this photovoltaic power generation, a solar cell using semiconductors such as monocrystalline silicon, polycrystalline silicon, amorphous silicon and the like can be given. The solar cell is a practical use of the principle that emits a current when sunlight is irradiated to the semiconductor. The place where solar cells are installed is a rooftop of a house, a portable power generator, a desk calculator, a clock, and the like, but all of them are places where the sun shines and are exposed to natural conditions outdoors. When moisture reaches the heart of a solar cell, its performance is remarkably deteriorated. Therefore, a solar cell is required to have a package that can withstand long periods of time in a natural environment with severe strength and water resistance. In addition, the solar cell is also required to be lighter because it is installed on the roof of a house.

As a structure of the solar cell which consists of such a durable package, the following structures are known as a typical thing. That is, the surface material and back protection film and EVA which laminated | stacked the high light-transmitting material, such as glass and a plastic, and an ethylene vinyl acetate copolymer (it abbreviates as EVA) are laminated | stacked, are connected toward EVA surface and EVA surface, It is the structure which clamps the arrange | positioned solar cell module. The role of EVA is to fix the solar cell module and to protect it from the outside world, especially from moisture.

Although water vapor barrier property is required for this back protective film and surface material, using the material which laminated | stacked the barrier material on the polyester film, and the material which apply | coated the barrier material to the polyester film is used, for example in Japan It is proposed in Unexamined-Japanese-Patent No. 9-153631, Unexamined-Japanese-Patent No. 2000-174298, 2002-26354, and 2003-60218.

As Japanese Patent Laid-Open No. 2003-60218 proposes to provide a polyester film with a layer that improves the adhesion to EVA, when the polyester film is used for the surface material or the back protective film, the adhesion with the EVA is poor. There is a need to improve the adhesion. In the method of arranging layers with a biaxially oriented film as described in Japanese Patent Laid-Open No. 2003-60218, coating is performed using an organic solvent and dried by a drying furnace to improve the operating cost of the drying furnace and the working environment. Ventilation equipment is required, and there is a problem that the cost is high.

This invention was performed in view of the said real thing, The subject to solve is providing the film excellent in adhesiveness and suitable as a film for solar cells.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining, according to the film which has a specific structure, it discovered that the said subject could be easily solved and came to complete this invention.

That is, the gist of the present invention is a polyester film for solar cells having a coating layer on at least one side, and the coating layer is formed at the time of film formation, and the heat-sealing peel strength of the surface of the ethylene vinyl acetate copolymer having the coating layer Is present in the polyester film for solar cells, characterized in that the 1.ON / 20mm width or more.

According to this invention, the film suitable for the surface material and back protection film of a solar cell can be provided, and the industrial value of this invention is high.

Hereinafter, the present invention will be described in detail.

The olefin resin referred to in the present invention is a generic term for polymers obtained by polymerizing or copolymerizing olefins such as ethylene, propylene, butadiene and isoprene or diolefins, and copolymers and ionomers of ethylene with other monomers such as vinyl acetate and acrylic acid esters. Include. Specific examples include polyethylene, polypropylene, polymethylpentene, ethylene / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, chlorinated polyethylene, chlorinated polypropylene, and the like. Among them, widely used are ethylene vinyl acetate copolymers called EVA. Although EVA may be applied as an adhesive or an adhesive, or may be used on a sheet, it is common to use EVA by thermocompression bonding on a sheet. The thickness of this sheet is typically about 0.2 mm to 5.0 mm.

The polyester film of this invention can be used also as a surface material and a back protection film. When used as a surface material, it is necessary to be a transparent polyester film in order to improve the transmission of sunlight, and in order to prevent deterioration of the film due to sunlight, a weathering agent is blended in the polyester film or the top of the polyester film It is necessary to cope with, for example, coating it with a material that absorbs ultraviolet rays. It is also preferable to use a polyester film having high weather resistance, such as polyethylene-2,6-naphthalate. On the other hand, when used as a back protection film, although it may be transparent, a white film and a black film with high concealability may be sufficient, and it is more preferable if mix | blends a weather agent, but it does not matter.

Although the vapor barrier property is required for the protective film of a solar cell, the film of this invention and the material with a vapor barrier property can be laminated | stacked and used using an adhesive agent etc .. An aluminum foil is mentioned as a typical barrier material. As an example of the back protective film which uses an aluminum foil, aluminum foil is laminated | stacked through the adhesive agent on the opposite surface of the application surface of the film (for example, 50 micrometers in thickness) of this invention, and then a transparent polyester film is laminated | stacked through an adhesive agent. As a transparent polyester film, the range of 12 micrometers-200 micrometers is practical. As another example of a barrier material, the film which vapor-deposited silica and alumina to the biaxially stretched polyester film, and the biaxially stretched polyester film with good barrier property which apply | coated vinylidene chloride type resin, acrylic resin, etc. are mentioned. These films are used instead of aluminum foil.

As a method of providing barrier property, there exists a method of depositing or apply | coating a water vapor barrier layer in the surface opposite to the surface which contacts EVA. As a layer to vapor-deposit, the vapor deposition layer of the above silica and alumina is mentioned, for example. As an application layer, vinylidene chloride type resin, acrylic resin, etc. are mentioned, for example. As an example of the back protective film of the film of this invention which provided the vapor deposition layer, the white polyester film is laminated | stacked through the adhesive agent on the surface which arrange | positioned the silica layer of this invention film. As a white polyester film, the thing of 50 micrometers-200 micrometers thickness range is practical.

Polyester used in the polyester film of the present invention is terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4'-diphenylcarboxylic acid, 1,4-cyclohexyl dicarboxylic acid Prepared by melt polycondensation of dicarboxylic acids or esters thereof with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol Polyester. The polyester which consists of these acid components and a glycol component can be manufactured using the method currently performed arbitrarily. For example, by transesterification between lower alkyl esters and glycols of aromatic dicarboxylic acids or by direct esterification of aromatic dicarboxylic acids and glycols to form substantially bisglycol esters of aromatic dicarboxylic acids, or oligomers thereof. After adding a polymerization catalyst to this, the method of heating and polycondensing under reduced pressure can be employ | adopted. You may copolymerize an aromatic dicarboxylic acid according to the objective.

Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexane dimethylene terephthalate, and the like. Polyester which copolymerized the component may be sufficient, and may contain another component and additive as needed. These polyesters include inorganic particles such as calcium carbonate, kaolin, silica, aluminum oxide, titanium oxide, alumina and barium sulfate, organic particles such as acrylic resin and guanamine resin, and catalyst residues for the purpose of improving the running properties of the film. The granulated precipitated particles can be contained. The particle diameter and quantity of these particles can be suitably selected according to the objective. When hiding property is required, a large amount of titanium oxide, barium sulfate or carbon black may be added. Furthermore, an ultraviolet absorber, various stabilizers, lubricants, antistatic agents, etc. can be added suitably.

The polyester film of this invention can be obtained by forming the application layer excellent in adhesiveness with polyolefin resin at the time of film manufacture. It is preferable that the polyester film of this invention is a biaxially stretched polyester film. As a manufacturing method which obtains a biaxially stretched polyester film, a manufacturing method normally known may be sufficient and there is no restriction | limiting in particular. For example, the unstretched film obtained by melt-extruding from an extruder is first stretched by 2-6 times at 60-120 degreeC by the roll stretching method, and uniaxially-stretched polyester is obtained, and then 80-130 orthogonal to the previous extending | stretching direction in a tenter. The sequential biaxial stretching manufacturing method which extends | stretches 2 to 6 times at degreeC, and heat-processes for 1 to 600 second at 150-250 degreeC is preferable. Moreover, the manufacturing method of extending | stretching an unstretched film longitudinally and horizontally simultaneously, then heat-processing with a tenter and simultaneously biaxially stretching is good. The production method of the present invention may be a single layer or a multilayer film using a plurality of extruders.

As a method of arrange | positioning an application layer at the time of film manufacture, for example, in the sequential biaxial stretching method, after apply | coating to the film after longitudinal uniaxial stretching, it extends laterally and heat-processes, or after a biaxial stretching to a film There is a method of coating and drying. Although there is no restriction | limiting in a method, the method of apply | coating to a uniaxial stretched film, and then transversely stretching and heat-processing is preferable because there exists a characteristic of making a coating layer uniform and thin. Moreover, in the simultaneous biaxial stretching method, the method of apply | coating to the amorphous film before extending | stretching, simultaneous biaxial stretching, and heat processing after that is preferable. The film of the present invention may be a single layer or a multilayer film using a plurality of extruders.

As the coating layer of the present invention, an aqueous polymer which is dissolved, emulsified or suspended in water is preferable, and for example, a polyurethane resin, a polyacrylic resin, a polyester resin, an epoxy resin, a polyvinyl alcohol resin, or a polyvinylidene chloride resin , Polystyrene-based resin, polyvinylpyrrolidone, copolymers thereof, and the like, but are not limited to these. These compounds can be used 1 type or in mixture of 2 or more types. It is preferable to contain a polyurethane resin and polyvinylidene chloride type resin especially.

Moreover, it is preferable to use a crosslinking agent as the component for the said application layer. Examples of the crosslinking agent include methylol or alkylolated urea, melamine, guanamine, acrylamide, and amide compounds, epoxy compounds, aziridine compounds, polyisocyanurates, blocked polyisocyanates, and oxazoline group-containing water-soluble polymers. , Silane coupling agent, titanium coupling agent, zirco aluminate coupling agent and the like. Further, the coating liquid may contain inorganic or organic particles, lubricants, antistatic agents, antifoaming agents and the like within the range not impairing the effects of the present invention in order to improve the applicability.

As a coating layer of this invention, the coating layer containing an organosilane compound may be sufficient. Examples of the organosilane compound include monoalkoxysilanes, dialkoxysilanes, trialkoxysilanes, tetraalkoxysilanes, and the like, and mixtures thereof and condensation reactants may be used. In particular, the alkoxysilane which has an organic functional group in a molecule | numerator is preferable. As a typical example thereof, there are organosilane compounds represented by the following general formulas, and these are known as silane coupling agents.

XR ² Si (OR ¹ ) ₃ or (XR ² ) (YR ³ ) Si (OR ¹ ) ₂

R ¹ is a substituted alkyl group such as an alkyl group or a methoxyalkyl group represented by a methyl group or an ethyl group, R ² , R ³ are each independently an alkylene group such as a propylene group, and X and Y are each independently an organic group. It is a functional group.

In the above formula, as the organic functional groups of X and Y, an amino group, an epoxy group, a vinyl group, a hydroxyl group, a carboxyl group, an epoxycyclohexyl group, a mercapto group and a glycidyl group are preferable. In addition, the organic functional group may be substituted with a substituted amino group such as N-β- (aminoethyl) amino group and polyethyleneimine. Specific examples of the silane coupling agent having an organic functional group include γ-glycidoxypropyl trimethoxysilane, γ-glycidoxypropyl triethoxysilane, N-β- (aminoethyl) γ-aminopropyltrimethoxysilane, N -β- (aminoethyl) γ-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-mercaptopropyltrimethoxysilane and the like can be preferably exemplified. These can use 1 type, or 2 or more types, and the mixture and condensate containing the alkoxysilane which does not have a functional group as needed.

Although it is preferable to dilute and use an organosilane compound with an alcohol solvent, it is preferable that it is water-based, In this case, various surfactant can be mix | blended for the purpose of improving applicability | paintability. Moreover, you may aim to improve applicability | paintability by using together 1 type (s) or 2 or more types of the above-mentioned aqueous polymer as needed. Inorganic particles or organic particles can be added to the coating agent of the present invention for the purpose of securing the lubricity of the coated surface.

As thickness of the coating layer of this invention, 0.003-1.5 micrometers is preferable normally. When it is thin, adhesiveness cannot be exhibited and when thick, blocking of polyester films may occur.

As a method of apply | coating a coating layer to a polyester film, the application | coating technique as shown by "coating system" published by 1979 from Jinshoten by harazaki oil, can be used. Specifically, an air duct coater, a blend coater, a rod coater, a knife coater, a squeeze coater, an impregnation coater, a reverse coater, a transfer roll coater, a gravure coater, a kiss roll coater, a cast coater, a spray coater, a carton coater, a calender coater, Techniques such as extrusion coaters, bar coaters, and the like.

The heat-sealing peel strength of the ethylene vinyl acetate copolymer on the surface having the coating layer is at least 1.0 N / 20 mm wide, preferably at least 3.5 N / 20 mm wide. The measurement method of the heat sealing peel strength is shown in the Example.

As for the thickness of the polyester film of this invention, 9-200 micrometers is preferable.

As an example of manufacturing a solar cell using the film of this invention, it laminated | stacked in order of glass / EVA (sheet form) / solar cell module / EVA (sheet form) / back protection film using the film of this invention, and heated by a vacuum laminator. Examples of compression bonding can be given. At this time, the coating layer surface of this invention is arrange | positioned toward the surface which contact | connects EVA (sheet top).

According to this invention, the film suitable for the surface material and back protection film of a solar cell can be provided, and the industrial value of this invention is high.

Example

Although an Example is given to the following and this invention is demonstrated in more detail, this invention is not limited to a following example, unless the summary is exceeded. The evaluation method and the processing method of a sample in an Example and a comparative example are shown as follows. In addition, "part" in an Example and a comparative example shows a "weight part."

<Property and Evaluation Method, Evaluation Criteria>

(1) Measurement method of intrinsic viscosity [η] (dl / g) of polymer

1 g of the polymer was dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) and measured at 30 ° C. with a Uberode viscometer.

(2) measuring method of shrinkage

Heat-treat the film for 30 minutes in an oven (Tabyesvec Co., Ltd .; hot air circulation passage) set at 150 ° C. in a tension-free state by cutting the sample into a single 35 mm wide by 1000 mm long film in the longitudinal and width directions. Was carried out, the length before and after the heat treatment was measured by a straight line, and the heat shrinkage ratio was obtained by the following equation.

Thermal Shrinkage (%) = [(a-b) / a] x 100

In the formula, a denotes the length of the sample before heat treatment (mm), and b denotes the length of the sample after heat treatment (mm).

(3) Measuring method of adhesion of coating layer

Overlaid the coating layer surface of the polyester film on both sides of the EVA film ("Solaeva SC50B" manufactured by Hi-Sheet Kogyo Co., Ltd.) with a thickness of 560 µm, and was heated at a pressure of 0.16 MPa by heating the upper and lower parts at a temperature of 130 ° C. Heat sealing was performed for 60 seconds In the heat sealing, the peeling test was started while leaving the unsealed portion, and both sides of the polyester film were peeled at a speed of 0.5 m / min in the direction of 180 degrees, and the peel strength was increased. Adhesion was evaluated based on the following three steps.

Evaluation 3: Peel Strength of 3.5N / 20mm or More

Evaluation 2: Peel strength of 1.0 N / 20 mm or more and 3.5 N / 20 mm or less

Evaluation 1: Peeling Strength Less Than 1.0N / 20mm Width

Practically, evaluation 3 was judged as a range where the evaluation 2 was no problem at all, and evaluation 2 could also be used.

Example  One

By the usual melt condensation polymerization method, an polyethylene terephthalate chip having an intrinsic viscosity of 0.66 containing 0.08 parts of amorphous silica having an average particle diameter of 2.5 µm was obtained. The chip was dried, the water content was 50 ppm or less, followed by melting at 295 ° C. and melt extrusion on a cooled drum to obtain an amorphous sheet, which was then stretched 3.5 times in a longitudinal direction at 85 ° C. to 100 ° C. to monoaxially axially. A stretched film was obtained. 5 micrometers of following coating liquids A were apply | coated to this film with the gravure coater, it extended | stretched 4.0 times laterally in 90 degreeC-120 degreeC atmosphere, and then heat-processed at 235 degreeC, the biaxially stretched polyester film of 50 micrometers in film thickness Was wound into a roll. The thermal contraction rate of 30 minutes at 150 degreeC of this film was 1.0% in length, and 0.3% in width. Adhesiveness with EVA of the coating surface of this film was evaluation 3 in 4.ON / 20mm width.

● Composition of Coating Liquid A

The coating liquid (concentration 10%) which uses water which makes solid content of following compounds (1)-(4) become a lower part as a medium was prepared.

(1) HIBLAN AP-40 (brand name) which is polyurethane manufactured by Nippon Ink Chemical Co., Ltd.

60 copies

(2) Ten parts of permanent ring UA310 (brand name) which is polyurethane manufactured by Sanyou Kasei

(3) 20 parts of Finetex ES-670 made of polyester manufactured by Nippon Ink Chemical Co., Ltd.

(4) 10 parts of alkylolmelamine.

Example  2

By the usual polymerization method, the chip A of the polyethylene terephthalate of the intrinsic viscosity 0.70 which does not contain any particle | grains was obtained. 40 parts of anatase titanium oxides having a particle size of 0.3 µm were blended with respect to 60 parts of the chips, and kneaded well by a kneading apparatus, and extruded to obtain a chip B. 65 parts of chips A and 35 parts of chips B were blended, and the white biaxially stretched polyester film having a thickness of 50 µm in which the coating liquid A was disposed in the same manner as in Example 1 was wound in a roll. The thermal contraction rate of 30 minutes at 150 degreeC of this film was 1.0% of the length, and 0.3% of the width. EVA and adhesiveness of the coating surface of this film were extremely evaluation 3 in 4.0N / 20mm width.

Example  3

A biaxially stretched polyester film was obtained in the same manner as in Example 2 except that the coating solution of Example 2 was changed to an 8% ethanol solution of N-β (aminoethyl) γ-aminopropyltrimethoxysilane. Adhesiveness with EVA of the coating surface of this film was evaluation 2 in 1.ON / 20mm width.

Comparative example  One

Except not having provided a coating layer in Example 1, it carried out similarly and obtained the biaxially stretched polyester film. The adhesiveness of this film with EVA was evaluation 1 at 0.3 N / 20 mm width.

Comparative example  2

A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the coating layer was changed to the following coating solution B in Example 1. The adhesiveness of this film with EVA was evaluation 1 at 0.3 N / 20 mm width.

Coating liquid B: The coating liquid (concentration 10%) which used water as a medium was manufactured so that solid content of following compounds (1) and (2) might become the following part.

(1) 70 parts of dulymer M-918 which is polyacryl manufactured by Nippon Junyakusha

(2) 30 parts of Finetex ES-670 made of polyester manufactured by Nippon Ink Chemical Co., Ltd.

Claims (4)

At least one surface has a coating layer formed at the time of film forming, and the coating layer is a polyurethane resin, a polyacrylic resin, a polyester resin, an epoxy resin, a polyvinyl alcohol resin, a polyvinylidene chloride resin, a polystyrene resin , At least one aqueous polymer selected from polyvinylpyrrolidone and copolymers thereof, or a silane coupling agent represented by the following general formula (1) as an organic silane compound, or a combination thereof Ethylene vinyl acetate copolymer on the sheet is heated and pressed to contact the coating layer surface, and the heat-sealing peel strength between the coating layer surface and the ethylene vinyl acetate copolymer sheet is 1.ON / 20mm width or more. Polyester film for solar cell:
XR ² Si (OR ¹ ) ₃ or (XR ² ) (YR ³ ) Si (OR ¹ ) ₂ (1)
Wherein R ¹ is an alkyl group or a substituted alkyl group, R ² , R ³ are each independently an alkylene group, and X and Y are each independently an organic functional group. The polyester film for solar cells of Claim 1 in which an application layer contains the aqueous resin of polyurethane-type resin. After apply | coating a coating liquid to a polyester film, it extends | stretches in at least 1 direction, and forms a coating layer by heat-processing at 150-250 degreeC, The polyester film for solar cells of Claim 1 or 2 characterized by the above-mentioned. Method of preparation. The manufacturing method of the polyester film for solar cells of Claim 3 in which a coating liquid contains an aqueous polymer and a crosslinking agent.