JP2012054289A - Rear surface protection sheet for solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive rear surface protection film for a solar cell module which is superior in hydrolysis resistance and weatherability or the like, and most suitable for the field requiring reflection efficiency and lightweight properties.SOLUTION: The rear surface protection sheet for the solar cell module includes: a film which is made of an ethylene-vinyl acetate copolymer composition and contains a white pigment of 2.0 to 10.0 wt.%; and a polyethylene terephthalate film of which the thickness is 100 μm or more, which contains the white pigment of 2.0 to 10.0 wt.%. and in which a larger one out of thermal shrinkage factors in a longitudinal direction and a width direction after heat treatment at 150°C for 30 minutes is 0.8% or less. In the rear surface protection sheet, the intrinsic viscosity of the polyethylene terephthalate film is 0.65 dl/g or more, the amount of a terminal carboxyl group is 26 equivalent/t or less, and the content of a phosphorus element is 70 wt.ppm or less.

Description

  INDUSTRIAL APPLICABILITY The present invention is for a solar cell module that is inexpensive and excellent in environmental resistance (hydrolysis resistance, weather resistance, etc.), and is optimal for fields that require high light hiding, low shrinkage, and light weight. It is related with a back surface protection sheet.

  In recent years, solar cells have attracted attention as a next-generation energy source. The solar cell module back protective sheet used for some of the battery components is also strongly required to have durability (hydrolysis resistance and weather resistance) against the natural environment. Furthermore, the improvement of the solar light conversion efficiency of the battery is also required, and even the reflected light of the back surface protection sheet is converted. There is also a demand for lightness, strength, and battery processability.

  As a back surface protection sheet for solar cell modules, it is known to use, for example, a film of polyethylene resin or polyester resin or a fluorine film (see Patent Documents 1 and 2). In particular, back surface protection sheets using a polyethylene terephthalate film have been widely developed because low cost is required and no toxic gas is emitted when burned. However, compared with a fluorine-type film, a polyethylene terephthalate film is easy to hydrolyze and there exists a subject that a film turns yellow by UV irradiation in sunlight.

  Yellowing of the polyethylene terephthalate film by UV light can be reduced by adding a white pigment to the film. Moreover, since the white pigment reflects sunlight, the reflection efficiency to the cell side can be improved at the same time. However, in the production of a film of polyethylene terephthalate containing a white pigment, the polymer is sheared by the pigment during the extrusion process, and the polyethylene terephthalate molecule is decomposed, resulting in a decrease in hydrolysis resistance.

  Therefore, for a solar cell module having both UV resistance and hydrolysis resistance by disposing a polyethylene terephthalate film having a high concentration of white pigment on the filler side and on the outside of the transparent polyethylene terephthalate film having hydrolysis resistance. It is known that it becomes a back surface protection sheet (refer patent document 3).

  However, since the polyethylene terephthalate film having a high concentration of white pigment has no hydrolysis resistance, a polyethylene terephthalate film having a high concentration of white pigment and a transparent polyethylene terephthalate film having hydrolysis resistance are used. By providing a water vapor barrier film having high moisture resistance, hydrolysis of the polyethylene terephthalate film having a high concentration of white pigment can be reduced. Therefore, as a back surface protection sheet for a solar cell module incorporated in the solar cell module, When it is possible to maintain the degradability, but because the hydrolysis resistance of the polyethylene terephthalate film having a high concentration of white pigment is low, it is required to improve the hydrolysis resistance of the back surface protection sheet itself for solar cell modules , Hydrolysis resistance You can not foot.

  When manufacturing solar cells, if the heat shrinkage of the back protection sheet for solar cell modules is large, curling due to shrinkage of the polyester film and the ethylene vinyl acetate copolymer in the vacuum laminating process during solar cell module production The positional deviation of the sealed solar battery cells cannot be prevented.

JP-A-11-261085 JP-A-11-186575 Japanese Patent Laid-Open No. 2002-100788

  In light of the background of the prior art, the present invention is a solar cell module that is inexpensive, improves environmental resistance such as hydrolysis resistance and weather resistance, has good concealment property for sunlight, and has a low shrinkage rate. An object of the present invention is to provide a back surface protection sheet for use.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a specific polyethylene terephthalate film and having a specific layer structure, thereby completing the present invention. It was.

  That is, the gist of the present invention consists of an ethylene vinyl acetate copolymer composition, a film containing 2.0 to 10.0% by weight of a white pigment, a thickness of 100 μm or more, and a white pigment of 2.0 to A back surface protective sheet for a solar cell module containing 10.0% by weight, and having a polyethylene terephthalate film having a larger shrinkage ratio in the longitudinal direction and width direction after heat treatment at 150 ° C. for 30 minutes of 0.8% or less. The intrinsic viscosity of the polyethylene terephthalate film is 0.65 dl / g or more, the terminal carboxyl group amount is 26 equivalents / ton or less, and the phosphorus element content is 70 ppm by weight or less. It exists in the back surface protection sheet for battery modules.

  According to the present invention, since the ethylene vinyl acetate copolymer composition is excellent in hydrolysis resistance, a resin film comprising the ethylene vinyl acetate copolymer composition is laminated on the specific polyethylene terephthalate film described above. Thereby, the back surface protection sheet for solar cell modules provided with high durability by the synergistic effect of both can be obtained. Further, the white pigment can provide high light hiding and UV resistance.

  In addition, according to the present invention, the ethylene vinyl acetate copolymer composition exhibits high adhesiveness, and other members used for solar cell modules such as a solar cell module filler layer and a gas barrier film, for example. The back surface protection sheet for solar cell modules excellent in adhesiveness can be obtained. Further, by including a white pigment in the ethylene vinyl acetate copolymer film, it becomes possible to exhibit higher UV resistance.

  Furthermore, according to the present invention, since the ethylene vinyl acetate copolymer film has a low shrinkage rate, it is possible to reduce curling due to the shrinkage of the polyester film in the vacuum laminating process at the time of manufacturing the solar cell module, and the ethylene vinyl acetate copolymer. Thus, it is possible to prevent the positional deviation of the solar battery cells sealed in.

  The solar cell in the present invention refers to a system that converts sunlight into electricity and stores the electricity, and preferably has a high light transmission material, a solar cell module, a filling resin layer, and a back surface protection sheet as a basic configuration. Some are built into the roof of a house, others are used for electrical and electronic components, and some have flexible properties.

  Here, the high light-transmitting material is a material that efficiently allows sunlight to enter and protects the internal solar cell module, and glass, a high light-transmitting plastic, a film, or the like is preferably used. The solar cell module converts sunlight into electricity and stores it, and is the heart of the solar cell. For the module, a semiconductor such as silicon, cadmium-tellurium, germanium-arsenic, or the like is used. Currently, there are single crystals, polycrystalline silicon, amorphous silicon, and the like that are widely used.

  The filled resin layer is used for the purpose of fixing and protecting the solar cell module in the solar cell and for electrical insulation, and among them, ethylene vinyl acetate copolymer is preferably used in terms of performance and price.

  With the back surface protection sheet for solar cell modules referred to in the present invention, protection of the solar cell module on the back side of the solar cell is an important role. And the back surface protection sheet which has high concealment property with respect to sunlight, mechanical strength is maintained by the outdoor exposure by long-term use, and there are few changes of an appearance (color tone) is required. For general users, the change in appearance is reminiscent of product performance deterioration and failure.

  The sheet | seat of this invention is a back surface protection sheet for solar cell modules which has a plastic film which consists of a polyethylene terephthalate film and an ethylene vinyl acetate copolymer composition. Hereinafter, the plastic film which consists of a polyethylene terephthalate film and an ethylene vinyl acetate copolymer composition which are each structural member of the back surface protection sheet for solar cell modules of this invention is demonstrated in detail.

<Polyethylene terephthalate film>
The polyethylene terephthalate resin used for the polyethylene terephthalate film here is a crystal formed by polymerizing these by esterification using terephthalic acid and its derivatives as the dicarboxylic acid component and ethylene glycol as the glycol component. Thermoplastic resin. The melting point of such polyethylene terephthalate is preferably 250 ° C. or higher in view of heat resistance, and preferably 290 ° C. or lower in view of productivity.
Within this range, other dicarboxylic acid components or other glycol components may be copolymerized or other polyesters may be blended. When blending other polyesters, it is desirable that the total polyester resin be 50% by weight or less.

  The polyethylene terephthalate film in the present invention has a phosphorus element amount detected by analysis using a fluorescent X-ray analyzer described later in a specific range. In the present invention, the phosphorus element in the polyethylene terephthalate film is usually derived from a phosphorus compound and is added during the production of the polyethylene terephthalate film. In the present invention, the phosphorus element amount P in the polyethylene terephthalate film needs to be in the range of 70 ppm by weight or less, preferably in the range of 50 ppm by weight or less, and more preferably in the range of 40 ppm by weight or less. Although there is no specific lower limit, in practice, about 1 ppm by weight is the lower limit in the current technology. If the amount of phosphorus element is too large, hydrolysis of the film after film formation is promoted, which is not preferable.

  Examples of phosphoric acid compounds include known ones such as phosphoric acid, phosphorous acid or ester phosphonic acid compounds, phosphinic acid compounds, phosphonous acid compounds, phosphinic acid compounds, and specific examples include regular phosphoric acid. , Dimethyl phosphate, trimethyl phosphate, diethyl phosphate, triethyl phosphate, dipropyl phosphate, tripropyl phosphate, dibutyl phosphate, tributyl phosphate, diamyl phosphate, triamyl phosphate, dihexyl phosphate, tri Examples include hexyl phosphate, diphenyl phosphate, triphenyl phosphate, and ethyl acid phosphate.

  Moreover, it is preferable not to contain as much as possible a metal compound that can act as a catalyst in order to suppress thermal decomposition and hydrolysis, but in order to reduce the volume resistivity value at the time of melting in order to improve the productivity of the polyethylene terephthalate film, Metals such as magnesium, calcium, lithium, and manganese can usually be contained in the film, except for the metal derived from the white pigment, preferably 500 ppm by weight or less, more preferably 400 ppm by weight or less.

  In order to prevent deterioration of the solar battery back surface filler due to incident light leaked from between the solar cells, the solar battery back surface filler preferably has high concealment. In this invention, a white pigment is added to the polyethylene terephthalate component which comprises the polyethylene terephthalate film of the back surface protection sheet for solar cell modules, and it is set as a white polyethylene terephthalate film. Examples of white pigments include titanium dioxide, zinc oxide, zinc sulfide, barium sulfate, and the like, preferably titanium dioxide, barium sulfate, and particularly preferably titanium dioxide.

  The average particle diameter of the white pigment is preferably 0.25 μm or more, more preferably 0.28 μm or more, and particularly preferably 0.30 μm or more. If the average particle size is less than 0.25 μm, the wavelength of light that can be efficiently scattered shifts to the lower wavelength side, and thus the reflectance in the near-infrared light region may decrease. If the average particle size of the white pigment exceeds 10 μm, the white pigment contains coarse particles depending on the particle size distribution, which may cause problems such as pinholes in the film. Therefore, the white pigment has an average particle size of 10 μm or less. It is preferable that

  The concentration WA of the white pigment in the polyethylene terephthalate film is 10.0% by weight or less, preferably 8.0% by weight or less. If the content of the white pigment is more than 10.0% by weight, the polymer chain is sheared by the white pigment during film formation, and the degradation of the polyethylene terephthalate molecule causes a decrease in intrinsic viscosity IV / an increase in the terminal carboxyl content AV. And the hydrolysis resistance of the polyethylene terephthalate film is lowered, and it becomes an unbeatable film for a biaxially stretched white polyethylene terephthalate film for a back protective film for a solar cell module. On the other hand, the lower limit of WA is 2.0, preferably 3.0% by weight or more. If the WA is less than 2.0% by weight, the film cannot have UV resistance, and the film will turn yellow when left outdoors for a long time.

  In the present invention, the thickness DA of the polyethylene terephthalate film is preferably 100 μm or more, more preferably 120 μm or more, from the viewpoint of light concealment. The upper limit of the thickness is not particularly provided, but is usually 500 μm.

  In the present invention, the polyethylene terephthalate film has a larger shrinkage ratio in the longitudinal direction and width direction after heat treatment at 150 ° C. for 30 minutes of 0.8% or less, preferably 0.6% or less, more preferably 0. .4% or less. When the shrinkage rate of the polyester film is more than 0.8%, it is reduced in curling due to shrinkage of the polyester film or sealed with an ethylene vinyl acetate copolymer in the vacuum laminating process at the time of manufacturing the solar cell module. The positional deviation of the solar battery cell cannot be prevented.

  The method for incorporating a white pigment into the polyethylene terephthalate film is not particularly limited, and conventionally known methods can be employed. For example, it can be added at any stage of producing the polyethylene terephthalate component, but it may be added preferably after the esterification stage or after the transesterification reaction to advance the polycondensation reaction. Alternatively, a white pigment slurry dispersed in ethylene glycol or water and a polyester raw material may be blended using a kneading extruder with a vent. Moreover, the method of blending the dried white pigment and the polyester raw material using a kneading extruder may be used. In addition, a so-called master batch chip containing a high concentration of white pigment is produced using a kneading extruder, and if necessary, this master batch chip may contain a polyester raw material containing no white pigment or a small amount. A polyester film having a predetermined blending amount can also be produced by mixing using a kneading extruder.

  In the present invention, in the polyethylene terephthalate film, the terminal carboxylic acid amount AV of the polyethylene terephthalate component constituting the polyethylene terephthalate film is 26 equivalent / ton or less, preferably 24 equivalent / ton or less. When the amount of terminal carboxylic acid AV exceeds 26 equivalents / ton, the hydrolysis resistance of polyethylene terephthalate is poor. On the other hand, in view of the hydrolysis resistance of the present invention, there is no lower limit of the amount of terminal carboxylic acid of polyethylene terephthalate, but it is usually about 10 equivalents / ton from the viewpoint of the efficiency of polycondensation reaction, thermal decomposition in the melt extrusion process, and the like. It is. In the present invention, the terminal carboxylic acid amount AV [equivalent / ton] means a value measured using a film by the method described in the Examples section.

  In addition, in imparting hydrolysis resistance to the polyethylene terephthalate film, in addition to setting the phosphorus element content and the terminal carboxylic acid amount within the above ranges, the intrinsic viscosity IV of the polyethylene terephthalate film is 0.65 dl / g or more, preferably It is 0.68 dl / g or more. When the intrinsic viscosity of the film is less than 0.65 dl / g, the hydrolysis resistance of the polyethylene terephthalate film is inferior, and it becomes difficult to use it in a high temperature and high humidity environment or outdoors. On the other hand, considering the hydrolysis resistance of the present invention, there is no upper limit of the intrinsic viscosity of polyethylene terephthalate, but it is usually about 0.75 dl / g from the viewpoint of thermal decomposition in the melt extrusion process. In addition, in this invention, intrinsic viscosity IV means what was measured using the film by the method described in the term of the Example.

  In the present invention, in order to make the amount of terminal carboxylic acid and intrinsic viscosity of polyethylene terephthalate within a specific range, for example, a method of shortening the residence time of polyethylene terephthalate in an extruder in an extrusion process of polyethylene terephthalate chips is used. Alternatively, a polyethylene terephthalate film having a specific amount of terminal carboxylic acid may be obtained by forming a polyethylene terephthalate chip having a low terminal carboxylic acid amount. Methods for lowering the amount of terminal carboxylic acid in polyethylene terephthalate chips include solid-phase polymerization of chips obtained by melt polymerization, methods of increasing polymerization efficiency, methods of increasing polymerization rate, methods of suppressing degradation rate, etc. A conventionally known method can be adopted. For example, it is carried out by a method of shortening the melt polymerization time, a method of increasing the amount of polymerization catalyst, a method of using a highly active polymerization catalyst, a method of lowering the polymerization temperature, or the like. In addition, in the production of polyethylene terephthalate film, the amount of terminal carboxylic acid increases when a regenerated raw material that has undergone a melting step is added. Therefore, in the present invention, it is preferable not to add such a regenerated raw material. It is preferable.

  In the polyethylene terephthalate film of the present invention, conventionally known antioxidants, heat stabilizers, lubricants, antistatic agents, fluorescent brighteners, dyes, and UV absorbers can be added as necessary. .

  Hereinafter, although the manufacturing method of the polyethylene terephthalate film of this invention is demonstrated concretely, as long as the summary of this invention is satisfied, this invention is not specifically limited to the following illustrations.

That is, dried or undried polyethylene terephthalate chips by a known method are supplied to a kneading extruder and heated to a temperature equal to or higher than the melting point of each polymer to melt.
Next, the molten polymer is extruded from a die and rapidly cooled and solidified on a rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. Even in the melt extrusion process, the amount of terminal carboxylic acid increases depending on the conditions. Therefore, in the present invention, the residence time of the polyethylene terephthalate in the extruder in the extrusion process is shortened. Dry sufficiently so that the water content is 50 ppm or less, preferably 30 ppm or less. When a twin screw extruder is used, a vent opening is provided, and 40 hectopascals, preferably 30 hectopascals, more preferably 20 hectopascals or less. A method such as maintaining a reduced pressure is employed.

  In the present invention, the sheet thus obtained is stretched biaxially to form a film. Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 6 times at 70 to 145 ° C. in the longitudinal direction to form a longitudinal uniaxially stretched film, and then 2 to 90 to 160 ° C. in the lateral direction. Perform ~ 6 times stretching and move to heat setting step. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary.

  The heat setting step is preferably performed at 160 ° C. to 240 ° C. for 1 second to 600 seconds, more preferably 170 ° C. to 235 ° C., and particularly preferably 200 ° C. to 230 ° C. When the heat setting temperature is less than 160 ° C., the shrinkage rate in the longitudinal direction is too high, the annealing treatment conditions become severe, and as a result, the distortion of the obtained film increases and cannot be put to practical use. On the other hand, when the heat setting temperature is 240 ° C. or higher, a polyester film having good hydrolysis resistance cannot be obtained.

The annealing treatment referred to in the present invention means that the heat-fixed biaxially stretched polyester film is heat-treated in a state where substantially no tension is applied. The heat treatment temperature during the annealing treatment is preferably in the temperature range lower by 40 ° C. or more from the glass transition temperature to the melting point of the biaxially oriented polyester film. When the annealing treatment is performed, the biaxially stretched polyester film is stretched if a large tension is applied. Therefore, it is preferable that the biaxially stretched polyester film is annealed in a state where the tension is not substantially applied. The state where substantially no tension is applied specifically means that the film tension (g / mm ² ) during the annealing treatment is 100 or less, preferably 80 or less, more preferably 60 or less.

  As for the form of annealing treatment, in-line annealing recipe that performs annealing treatment in the film manufacturing process, offline annealing recipe that treats after film production, etc. can be considered, but offline annealing is not limited by the film production speed A prescription is preferred.

  The time for annealing is not particularly limited and varies depending on the thickness of the biaxially stretched polyester film and the annealing temperature, but is generally preferably 5 seconds or more, more preferably 10 seconds to 60 minutes, and even more preferably 30 seconds to 20 minutes. is there.

  There is no particular limitation on the infrared heating furnace to which the annealing treatment is performed. For example, it is preferable that a large number of infrared heaters wider than the running film width are installed in the upper part of the furnace at regular intervals so as to cover the entire width of the running film.

  As the infrared heater, both a near-infrared heater and a far-infrared heater including a sheathed heater can be used, but a near-infrared heater is preferable in terms of heat damage to the film.

  The heat treatment of the film is performed with the furnace atmosphere at a predetermined temperature, and this temperature can be adjusted, for example, by the following method. A thermocouple temperature detection end is installed between adjacent heaters in the furnace and on the running film at a film proximity position of about 5 cm, and the ambient temperature at each position is measured. This ambient temperature can be changed by the output of each installed heater, the number of heaters, the heater installation interval, the distance between the running film and the heater, the ventilation in the furnace, etc. While adjusting in the range of 0.5 to 1.2 kW / m and appropriately performing a constant air flow ventilation, the ambient temperature in the vicinity of the film can be set to a preferable region, that is, a range of 150 to 220 ° C.

  The infrared heating furnace is characterized in that a heating effect equal to or higher than that can be obtained even if the ambient temperature in the vicinity of the running film is lower than the ambient temperature in the same position of the hot air heating furnace. For this reason, in the hot air heating furnace, it is possible to shorten the processing time and increase the efficiency that could not be achieved, and to reduce the film distortion because of the short time processing.

  For example, by performing an annealing treatment as described above on a polyester film, the heat shrinkage in the longitudinal direction after treatment at 150 ° C. for 30 minutes can be made 0.8% or less.

  In the present invention, as described above, two or three or more polyethylene terephthalate melt extruders can be used to form a laminated polyethylene terephthalate film having two layers or three or more layers by a so-called coextrusion method. As the layer structure, an A / B structure using an A raw material and a B raw material, or an A / B / A structure, and a polyethylene terephthalate film having an A / B / C structure or other structure using a C raw material can do.

  The hydrolysis resistance of a polyethylene terephthalate film is a property related to the entire polyethylene terephthalate film. In the present invention, in the case of a polyethylene terephthalate film having a laminated structure by coextrusion, the inherent property of the polyethylene terephthalate film constituting the film is unique. It is necessary that the viscosity and the amount of terminal carboxylic acid are within the above-described ranges. Similarly, in the case of a polyethylene terephthalate film having a laminated structure by coextrusion, the content of phosphorus element and the amount of white pigment must be within the above-mentioned range as the whole polyethylene terephthalate constituting the polyethylene terephthalate film. It is.

  In the present invention, a coating layer is formed on one side or both sides of the polyethylene terephthalate film in order to impart adhesiveness, antistatic property, slipperiness, releasability, etc. to the polyethylene terephthalate film in or after the stretching step. Or can be subjected to discharge treatment such as corona treatment.

<Plastic film made of ethylene vinyl acetate copolymer composition>
The plastic film which consists of an ethylene vinyl acetate copolymer composition which comprises the back surface protection sheet for solar cell modules of this invention is demonstrated. The plastic film used in the present invention is composed of an ethylene vinyl acetate copolymer composition, and is characterized by having excellent hydrolysis resistance and adhesiveness.

  As the ethylene vinyl acetate copolymer composition used in the present invention, hydrolysis resistance according to the use environment of the solar cell module using the back surface protective sheet for solar cell module of the present invention, and UV resistance, There is no particular limitation as long as it has adhesive properties and is excellent in stability over time of such properties.

  The ethylene vinyl acetate copolymer used in the present invention preferably has a vinyl acetate content of 4% by weight or more. An ethylene vinyl acetate copolymer having an excessively low vinyl acetate content has poor processability and a viscosity that is too high, and the followability to a silicon power generation element may be deteriorated when a solar cell is manufactured.

  Further, the ethylene vinyl acetate copolymer used in the present invention preferably has a melt flow rate of 0.7 to 20, particularly 1.5 to 10.

  In order to improve durability, the ethylene vinyl acetate copolymer used in the present invention has a crosslinked structure by adding a crosslinking agent. Generally, this crosslinking agent is an organic solvent that generates radicals at 100 ° C. or higher. An oxide is used, and in particular, when the stability at the time of blending is taken into consideration, a decomposition temperature of a half-life of 10 hours is preferably 70 ° C. or higher. Examples of such organic peroxides include t-butylperoxy-2-ethylhexyl carbonate, 2,5-dimethylhexane; 2,5-dihydroperoxide; 2,5-dimethyl2,5-di ( t-butylperoxy) hexane; 3-di-t-butyl peroxide; t-dicumyl peroxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne; dicumyl peroxide; α, α′-bis (t-butylperoxyisopropyl) benzene; n-butyl-4,4-bis (t-butylperoxy) butane; 2,2-bis (t-butylperoxy) butane; 1-bis (t-butylperoxy) cyclohexane; 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane; t-butylperoxybenzoate; benzo Ilperoxide or the like can be used. The compounding amount of these organic peroxides is generally 5 parts by weight or less, preferably 1 to 3 parts by weight with respect to 100 parts by weight of the ethylene vinyl acetate copolymer.

  Moreover, a silane coupling agent can be added to an ethylene vinyl acetate copolymer for the purpose of improving the adhesive force with a power generation element as a back sheet of a solar cell. Known silane coupling agents for this purpose are, for example, γ-chloropropyltrimethoxysilane; vinyltrichlorosilane; vinyltriethoxysilane; vinyl-tris- (β-methoxyethoxy) silane; γ-methacryloxy. Propyltrimethoxysilane; β- (3,4-ethoxycyclohexyl) ethyltrimethoxysilane; γ-glycidoxypropyltrimethoxysilane; vinyltriacetoxysilane; γ-mercaptopropyltrimethoxysilane; γ-aminopropyltrimethoxysilane N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane and the like can be mentioned. When using these silane coupling agents to produce a solar cell module using the back surface protective sheet for solar cell module of the present invention, when adhering to the back surface filler layer by vacuum laminating, etc., the adhesion The strength can be dramatically improved. The compounding amount of these silane coupling agents is generally 5 parts by weight or less, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the ethylene vinyl acetate copolymer.

  Furthermore, a crosslinking aid can be added to the ethylene vinyl acetate copolymer in order to improve the gel fraction of the ethylene vinyl acetate copolymer and improve the durability. Examples of the crosslinking aid provided for this purpose include triallyl isocyanates such as triallyl isocyanate; trifunctional crosslinking aids such as triallyl isocyanate, and monofunctional crosslinking aids such as NK ester. . The blending amount of these crosslinking aids is generally 10 parts by weight or less, preferably 1 to 5 parts by weight or less with respect to 100 parts by weight of the ethylene vinyl acetate copolymer.

  Furthermore, if necessary, a colorant, an ultraviolet absorber, an anti-aging agent, a discoloration preventing agent and the like can be added in addition to the above. Examples of the colorant include inorganic pigments such as metal oxides and metal powders, and organic pigments such as azo-based, phthalocyanine-based, adhesive-based, acidic or basic dye-based lakes. Examples of ultraviolet absorbers include 2-hydroxy-4-octoxybenzophenone; benzophenones such as 2-hydroxy-4-methoxy-5-sulfobenzophenone; 2- (2′-hydroxy-5-methylphenyl) benzotriazole Benzotriazoles; phenyl salsylates; hindered amines such as pt-butylphenyl salsylates. Antiaging agents include amines; phenols; bisphenyls; hindered amines, such as di-t-butyl-p-cresol; bis (2,2,6,6-tetramethyl-4- Piperazil) sebacate.

  The plastic film used in the present invention contains a white pigment. In the solar cell module using the back surface protection sheet for the solar cell module of the present invention, the white pigment is intended to be reused for power generation in the solar cell element by reflecting or diffusing sunlight on the back surface protection sheet. It is to be added. By including such a white pigment in the plastic film, it is possible to impart designability, decorativeness, and the like to the solar cell module. In addition, when the solar cell module is installed on a roof or the like, the sunlight that is reflected can be reflected or diffused. Furthermore, the durability of the back surface protective sheet for a solar cell module of the present invention can be improved by adding a white pigment having an ultraviolet absorption effect.

  Examples of such white pigments include white pigments such as basic lead carbonate, basic lead sulfate, basic lead silicate, zinc white, zinc sulfide, lithopone, antimony trioxide, anatase type titanium oxide, and rutile type titanium oxide. Can be used. Further, the white pigment used in the present invention may be only one kind, or two or more kinds may be mixed and used.

  Content WB of the white pigment in the plastic film (B) is in the range of 2.0 to 10.0% by weight and in the range of 3.0 to 8.0% by weight in the plastic film. Is preferred. When the white pigment concentration WB is 2.0% by weight or less, high light concealment and light reflectivity cannot be obtained. On the other hand, when the concentration of the white pigment is more than 10.0% by weight, the cohesive failure due to the white pigment is liable to occur with respect to the adhesiveness with the solar cell module filling layer, and sufficient adhesive strength cannot be obtained.

  The thickness of the plastic film used in the present invention is not particularly limited, and may be appropriately determined according to the application of the back surface protection sheet for the solar cell module of the present invention. Usually, it is preferably in the range of 25 μm to 300 μm, particularly A range of 50 μm to 150 μm is preferable.

  The plastic film used in the present invention preferably has a larger shrinkage ratio in the longitudinal direction and width direction after heat treatment at 150 ° C. for 30 minutes of 3.0% or less, and in particular, 1.0% or less. It is particularly preferable that the content be in the range of 0.5% to 0.3%. When the heat shrinkage rate of the plastic film is within the upper range, the back surface protection sheet for solar cell modules having an excellent appearance can be produced with low influence on the shrinkage rate of the back surface protection sheet for solar cell modules of the present invention. This is because it becomes easy. Here, the said thermal contraction rate can be measured based on the JIS C2151 electrical plastic film test method.

Next, the manufacturing method of the plastic film used for this invention is demonstrated.
The method for producing the plastic film used in the present invention is not particularly limited as long as it is a method capable of uniformly forming a film with a desired thickness. As a method for producing such a plastic film, a method in which an ethylene vinyl acetate copolymer composition is melt-kneaded and then formed into a film shape is used. For example, the ethylene vinyl acetate copolymer composition is charged into a mixing roll from a raw material supply unit such as a hopper, melt-kneaded, and then extruded into a film from an extruder, or pressed to form a film. A molding method can be used. Or the method of shape | molding in the shape of a film | membrane is also used by throwing an ethylene vinyl acetate copolymer composition into the calender roll which has a some roll, and performing melt-kneading and sheet-forming continuously. As another method, the resin composition can be obtained from a raw material supply unit such as a hopper by feeding into a kneading extruder (eg, twin screw extruder), melt kneading, and then extruding it into a film. Especially, it is preferable to form a plastic film by the method of melt-kneading an ethylene vinyl acetate copolymer composition by kneading extrusion, and extruding it into a film | membrane form.

  When producing a plastic film by such a melt film-forming method, for example, after adding the above additives to an ethylene vinyl acetate copolymer, the mixture is sufficiently kneaded to prepare an ethylene vinyl acetate copolymer composition, and then extruded. A plastic film can be produced by forming a film using a method, a T-die extrusion method, a cast molding method, an inflation method, other film molding methods, or the like.

  The temperature at the time of melt-kneading the ethylene vinyl acetate copolymer composition is preferably 50 to 90 ° C, particularly preferably 55 to 70 ° C. The melt-kneading is preferably performed for 1 to 30 minutes, particularly 5 to 15 minutes. Thereby, an ethylene vinyl acetate copolymer composition can be appropriately melted to such an extent that it does not stick to a film forming apparatus such as a roll.

  When the ethylene vinyl acetate copolymer film is produced according to the present invention, the ethylene vinyl acetate copolymer film is in the range of 70 to 75 ° C., while the ethylene vinyl acetate copolymer film is in the range of 70 to 75 ° C., for 1.0 to 2.0 minutes. Annealing treatment is performed by maintaining the vinyl copolymer film at 60 to 80 ° C.

Specifically, the annealing treatment in the present invention can be performed by heating a resin film conveyed by a conveyor having a plurality of rollers by a heating means. In this case, the roller on the entrance side of the conveyor By making the peripheral speed higher than the peripheral speed of the roller on the outlet side so that a large tension is not applied to the resin film during the annealing process, a good annealing effect can be obtained.

For example, in the conveyor, the peripheral speed of the rollers on the inlet side is about 1.05 to 1.15 times the peripheral speed of the rollers on the outlet side, and the peripheral speed of the rollers between these rollers is an intermediate peripheral speed. It is preferable that the peripheral speed of the roller gradually decreases from the inlet side toward the outlet side.

The ethylene-vinyl acetate copolymer film obtained by forming the ethylene-vinyl acetate copolymer composition of the present invention has excellent film-forming properties, and therefore has excellent surface smoothness and a uniform thickness. Furthermore, the ethylene vinyl acetate copolymer film exhibits excellent adhesion to transparent substrates such as plastic substrates and glass substrates. Therefore, the ethylene vinyl acetate copolymer film is preferably used as an adhesive film.

  Below, the back surface protection sheet for solar cell modules using a polyethylene terephthalate film and a plastic film is demonstrated.

  According to the back surface protective sheet for a solar cell module of the present invention, by using the above-described polyethylene terephthalate film, the progress of the hydrolysis reaction of the resin can be suppressed even in a high temperature and high humidity atmosphere. Moreover, since the above-mentioned plastic film does not have a hydrolyzable functional group, it is excellent in hydrolysis resistance. Therefore, since the back surface protective sheet for solar cell module of the present invention having a configuration in which the polyethylene terephthalate film and the plastic film described above are laminated can be provided with excellent hydrolysis resistance as a whole, according to the present invention, By providing the hydrolysis resistance, a solar cell module back surface protection sheet having high durability can be obtained.

  Moreover, it is preferable that the back surface protection sheet for solar cell modules of this invention has a plastic film which consists of an ethylene vinyl acetate copolymer composition in the outermost surface. Since the above-mentioned polyethylene-vinyl acetate copolymer composition has a characteristic showing adhesiveness, the back surface protective sheet for solar cell module of the present invention is used for solar cell modules such as solar cell module fillers, for example. It has the characteristic that it is excellent in adhesiveness with this member.

  In the present invention, in addition to the two layers described above, another layer may be provided according to the intended physical properties.

  The back surface protection sheet for solar cell modules of the present invention is a solar cell using the back surface protection sheet for solar cell modules of the present invention according to the manufacturing method of the back surface protection sheet for solar cell modules of the present invention. When the module is manufactured, it is preferably in a range that does not cause deformation of the solar cell module. More specifically, the heat shrinkage rate at 150 ° C. for 30 minutes is preferably 1.0% or less, and more preferably 0.5% or less, particularly 0.3% to 0.1%. % Is preferable. When the thermal shrinkage rate is larger than the above range, when producing a solar cell module using the back surface protection sheet for solar cell module of the present invention, the back surface protection sheet shrinks when performing vacuum laminating treatment, This is because the solar cell element and the lead wire (tag) connecting the elements follow the shrinkage of the back surface protection sheet, and the lead wire may be deformed or the interval between the solar cell elements may be changed. is there.

  In the present invention, since the shrinkage rate is 0, it is preferable that there is no shrinkage (or movement, etc.) of the back protective sheet during vacuum lamination, but a metal foil as in the present invention is not used. The back surface protection sheet using only a plastic film is easily affected by heat. For this reason, in order to achieve the shrinkage rate of 0, it is necessary to carry out excessive heat shrinkage treatment for reducing the shrinkage rate in advance, and there is a possibility that the film or the like constituting the back surface protection sheet may be damaged. The said heat shrinkage rate can be measured based on the JIS C2151 electrical plastic film test method.

  Moreover, the back surface protection sheet for solar cell modules of this invention may have a through-hole for letting the terminal for taking out the electric power generated with the solar cell element outside after creating a solar cell module. preferable. The form of such a through-hole is not particularly limited, and the specific invention such as position, size, shape and number is the wiring of the solar cell module using the back surface protective sheet for solar cell module of the present invention. What is necessary is just to determine arbitrarily according to a form etc.

  Next, the manufacturing method of the back surface protection sheet for solar cell modules of this invention is demonstrated. As a manufacturing method of the back surface protection sheet for solar cell modules of this invention, if it is a method which can laminate | stack each structure of the back surface protection sheet for solar cell modules of this invention mentioned above with sufficient adhesiveness, it will not specifically limit. Examples of such a method include a method of dry laminating the plastic film on the polyethylene terephthalate film via an adhesive layer.

  Examples of the laminating adhesive constituting the adhesive layer include, for example, polyvinyl acetate adhesives, homopolymers such as ethyl acrylate, butyl, 2-ethylhexyl ester, and these, methyl methacrylate, acrylonitrile , Polyacrylic acid ester adhesives, cyanoacrylate adhesives, copolymers of styrene, etc., copolymers of ethylene and monomers such as vinyl acetate, ethyl acrylate, acrylic acid, methacrylic acid, etc. Ethylene copolymer adhesives, polyolefin adhesives made of polyethylene resin or polypropylene resin, cellulose adhesives, polyester adhesives, polyamide adhesives, polyimide adhesives, urea resins or melamines Amino resin adhesives made of resin, phenol resin adhesives Epoxy adhesives, polyurethane adhesives, reactive (meth) acrylic adhesives, chloroprene rubber, nitrile rubber, styrene-butadiene rubber, styrene-isoprene rubber, rubber adhesives, silicone adhesives, An adhesive such as an inorganic adhesive made of alkali metal silicate, low melting point glass, or the like can be used. Further, the composition system of these adhesives may be any composition form such as an aqueous type, a solution type, an emulsion type, and a dispersion type, and the form is a film / sheet type, powder type, solid type, etc. Further, the bonding mechanism may be any form such as a chemical reaction type, a solvent volatilization type, a heat melting type, and a hot pressure type.

  In the present invention, it is preferable to use a rubber adhesive made of styrene-butadiene rubber, styrene-isoprene rubber or the like as the adhesive. This is because the material is excellent in hydrolysis resistance and is most suitable for the high cold resistance required in this application. Moreover, in the said adhesive bond layer, it is preferable to bridge | crosslink the said adhesive agent by including a hardening | curing agent or a crosslinking agent. This is because by forming a crosslinked structure, an adhesive excellent in high heat resistance, moist heat resistance and the like can be obtained. As such a curing agent or crosslinking agent, an aliphatic or alicyclic isocyanate, or an isocyanate compound such as an aromatic isocyanate can be used. -Hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthylene diisocyanate (NDI) ), Tolidine diisocyanate (TODI), xylylene diisocyanate (XDI), and the like.

For example, the adhesive may be formed on a gas barrier film, a hydrolysis resistant film, and a resin film by a coating method such as a roll coating method, a gravure roll coating method, a kiss coating method, or the like, or a printing method. Can be coated. The coating amount is preferably in the range of 0.1 to 10 g / m ² (dry state).

  In addition, in order to prevent ultraviolet-ray deterioration etc., the above-mentioned ultraviolet absorber or light stabilizer can be added to the adhesive. As the ultraviolet absorber or light stabilizer, one or more of the aforementioned ultraviolet absorbers, or one or more of the light stabilizers can be used in the same manner. The amount used varies depending on the particle shape, density, etc., but is preferably in the range of 0.1 to 10% by weight in the adhesive.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples unless it exceeds the gist of the present invention. In addition, the measurement and evaluation method of various physical properties of a film are shown below.

<Analysis of polyethylene terephthalate resin and polyethylene terephthalate film> (1) Content of white pigment in polyethylene terephthalate / quantitative determination of catalyst-derived element Using a fluorescent X-ray analyzer (model “XRF-1500” manufactured by Shimadzu Corporation), the following Under the conditions shown in Table 1, the amount of elements in the polyethylene terephthalate film was determined by single sheet measurement. In the case of a laminated polyethylene terephthalate film, the content of the polyethylene terephthalate film as a whole was measured by melting the polyethylene terephthalate film, molding it into a disk shape, and measuring. In addition, when a white pigment is contained in the polyethylene terephthalate film, a peak derived from the white pigment is detected. Therefore, the white pigment is excluded from the whole, and the catalyst-derived element of the polyethylene terephthalate component is quantified. The white pigment content in the plastic film can be quantified in the same manner as described above.

上記表中、Ｔｉはチタン元素を、Ｐはリン元素を表す。白色顔料ＴｉＯ_２含有量φ[重量％]は、Ｔｉ由来ピークから検算する。

In the above table, Ti represents a titanium element and P represents a phosphorus element. The white pigment TiO ₂ content φ [wt%] is calculated from the Ti-derived peak.

(2) Intrinsic viscosity IV [dl / g]
A polyethylene terephthalate sample (resin or film) 0.5 g was dissolved in a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio), and a concentration of 1.0 (g / dl) was obtained using a capillary viscometer. The flow time of the solution and the flow time of the solvent alone were measured, and the intrinsic viscosity IV _appa was calculated from the time ratio using the Huggins equation. At that time, the Huggins constant was assumed to be 0.33. Intrinsic viscosity IV _resin was _determined from the IV _appa thus obtained using the following formula using the white pigment content φ [wt%].

(3) Amount of terminal carboxylic acid AV [equivalent / ton]
An apparent terminal carboxyl group amount AV _appa [equivalent / ton] was measured on a polyethylene terephthalate sample (resin or film) by a so-called titration method. After pulverizing the sample, it was dried at 140 ° C. for 15 minutes in a hot air dryer, and 0.1 g was accurately weighed from the sample cooled to room temperature in a desiccator, taken into a test tube, 3 ml of benzyl alcohol was added, The solution was dissolved at 195 ° C. for 3 minutes while blowing dry nitrogen gas, and then 5 ml of chloroform was gradually added and cooled to room temperature. Add 1-2 drops of phenol red indicator to this solution and titrate with 0.1N sodium hydroxide solution (solvent type: water / methanol / benzyl alcohol) under stirring while blowing dry nitrogen gas. It was finished when it changed to. Further, the same operation was carried out without using a sample as a blank, and the apparent terminal carboxyl group amount AV _appa [equivalent / ton] was obtained from the following formula.
AV _appa [equivalent / ton] = ( _AB ) × 0.1 × f / W
(Here, A is the amount of benzyl alcohol solution of 0.1N sodium hydroxide required for titration (μl), B is the amount of benzyl alcohol solution of 0.1N sodium hydroxide required for titration with a blank ( μl), W is the amount of sample (g), and f is the titer of 0.1N sodium hydroxide in benzyl alcohol.)
The terminal carboxyl group content AV [equivalent / ton] of the polyethylene terephthalate sample is _calculated from the apparent terminal carboxyl group content AV _appa [equivalent / ton] obtained in this way, using the white pigment content φ [wt%], the following formula: I asked for it.

The titer (f) of a 0.1 (N) caustic soda benzyl alcohol solution was obtained by collecting 5 ml of methanol in a test tube, adding 1 to 2 drops of phenol red ethanol solution as an indicator, and adding 0.1 (N ) Titration with 0.4 ml of a benzyl alcohol solution of caustic soda, and then adding 0.2 ml of 0.1 (N) aqueous hydrochloric acid solution having a known titer as a standard solution, and adding 0.1 (N) again. The solution was titrated with a benzyl alcohol solution of N) caustic soda to the color change point.
(The above operation was performed under dry nitrogen gas blowing.) The titer (f) was calculated by the following equation.

  Titer of aqueous solution of hydrochloric acid with titer (f) = 0.1 (N) × amount of collected aqueous solution of hydrochloric acid with 0.1 (N) (μl) / titration of benzyl alcohol solution of caustic soda with 0.1 (N) (Μl)

<Manufacture of polyethylene terephthalate resin>
Polyethylene terephthalate resin (1)
1700 parts by weight of dimethyl terephthalate and 1200 parts by weight of ethylene glycol were charged into a transesterification reactor equipped with a rectifying tower and equipped with a stirrer, and 1.39 parts by weight of magnesium acetate tetrahydrate was added as an ethylene glycol solution as a transesterification reaction catalyst. Transesterification was carried out while distilling off methanol produced by the reaction at a reaction temperature of 150 to 240 ° C. under normal pressure, and a low molecular weight polyester (oligomer, transesterification rate 99 as a transesterification product in a reaction time of 4 hours. .5%). This oligomer was transferred to a polycondensation reaction tank equipped with a stirrer and equipped with a stirrer. 0.57 parts by weight of ethyl acid phosphate having an average molecular weight of 140.01 and 0.24 parts by weight of tetrabutyl titanate were added to the transferred oligomer as an ethylene glycol solution, respectively. Further, 51 parts by weight of silica particles were added. Silica particles were dispersed in ethylene glycol and added as a slurry (silica particles: SL320 manufactured by Fuji Silysia). After adding silica particles, the pressure in the reaction vessel is gradually reduced from normal pressure to 0.2 kPa, the reaction temperature is raised from 240 ° C. to 280 ° C., and then a polycondensation reaction is performed at 280 ° C. Thereafter, the pressure was returned to normal pressure to complete the reaction, and the polycondensate was extruded in the form of a strand from the bottom of the reaction vessel, and was cut while cooling with water to obtain pellets of polyethylene terephthalate resin (1). The IV, AV and element contents of the polyethylene terephthalate resin (1) are shown below and in Table 2 below.
Intrinsic viscosity IV = 0.543 dl / g
Terminal carboxyl group amount AV = 25 equivalent / ton Titanium content = 20 ppm by weight
Magnesium content = 93 ppm by weight
Phosphorus content = 74 ppm by weight

Polyethylene terephthalate resin (2)
A slurry is prepared using a continuous polymerization apparatus comprising a slurry preparation tank, a two-stage esterification reaction tank connected in series to the slurry preparation tank, and a three-stage melt polycondensation tank connected in series to the second-stage esterification reaction tank. To the preparation tank, terephthalic acid and ethylene glycol were continuously fed at a weight ratio of 865: 485, and a 0.3 [wt%] ethylene glycol solution of ethyl acid phosphate was added per 1 ton of the resulting polyester resin. A slurry is prepared by continuously adding the amount P of phosphorus atom as 6 ppm by weight, stirring and mixing, and the slurry is 260 ° C. under a nitrogen atmosphere, relative pressure 50 kPaG, average residence time First stage esterification reactor set at 4 hours, then 260 ° C., relative pressure 5 kPaG, average residence under nitrogen atmosphere Second stage esterification reaction tank set between 1.5 hours and continuously transferred, and reacted esterification.

  In the second stage reaction tank, a 0.6 wt% ethylene glycol solution of magnesium acetate tetrahydrate is supplied through a pipe provided in the upper part of the tank, and the content M as magnesium atoms per ton of the obtained polyester resin is 6 It added continuously in the quantity used as the weight ppm.

Subsequently, when the oligomer obtained above is continuously transferred to the melt polycondensation tank, tetra-n-butyl titanate is added to the oligomer in the transfer pipe, the concentration of titanium atom is 0.15% by weight, and the water concentration is As an ethylene glycol solution containing 0.5% by weight, the content as titanium atoms per ton of the resulting polyester resin is continuously added in an amount of 4 ppm by weight, and the temperature is set to 270 ° C. and 2.6 kPa. The first stage melt polycondensation tank, then the second stage melt polycondensation tank set at 278 ° C. and pressure 0.5 kPa, then the second stage set at 280 ° C. and 0.3 kPa Continuously transferred to the melt polycondensation tank of the stage, the residence time in each polycondensation tank is adjusted and melt polycondensed so that the intrinsic viscosity IV of the resulting polyester resin is 0.650 dl / g, Continuously withdrawn into a strand from a discharge outlet provided at the bottom of the Chijimigoso, cooled with water, to produce pellets of polyethylene terephthalate resin (2) was cut with a cutter. The IV, AV and element contents of the polyethylene terephthalate resin (2) are shown below and in Table 2.
Intrinsic viscosity IV = 0.650 dl / g
Terminal carboxyl group content AV = 18 equivalent / ton Titanium content = 4 ppm by weight
Magnesium content = 6 ppm by weight
Phosphorus content = 6 ppm by weight

Polyethylene terephthalate resin (3)
After the polyethylene terephthalate resin (2) is crystallized by continuously feeding it into a stirring crystallizer maintained at about 160 ° C. in a nitrogen atmosphere so that the residence time is about 60 minutes, It was continuously supplied to a phase polycondensation apparatus, and solid phase polycondensation was performed at 210 ° C. under a nitrogen atmosphere and atmospheric pressure for a residence time of 16 hours to obtain a polyethylene terephthalate resin (3). The IV, AV and element contents of the polyethylene terephthalate resin (3) are shown below and in Table 2.
Intrinsic viscosity IV = 0.820 dl / g
Terminal carboxyl group content AV = 12 equivalents / ton Titanium content = 4 ppm by weight
Magnesium content = 6 ppm by weight
Phosphorus content = 6 ppm by weight

Polyethylene terephthalate resin (4)
In the process for producing the polyethylene terephthalate resin (2), the content P 1 of phosphorus acid as the addition amount of ethyl acid phosphate is 10 ppm by weight, the content of magnesium acetate as the magnesium atom is 15 ppm by weight, tetra-n- A polyethylene terephthalate resin (4) was obtained in the same manner as in the production method of the polyester resin (2) except that the content of butyl titanate was changed so that the content as titanium atoms was 08 ppm by weight. The IV, AV and element contents of the polyethylene terephthalate resin (4) are shown below and in Table 2.
Intrinsic viscosity IV = 0.638 dl / g
Terminal carboxyl group content AV = 28 equivalent / ton Titanium content = 8 ppm by weight
Magnesium content = 15 ppm by weight
Phosphorus content = 10 ppm by weight

Polyethylene terephthalate resin (5)
Polyethylene terephthalate resin (4) was crystallized by continuously feeding it into a stirring crystallizer maintained at about 160 ° C. in a nitrogen atmosphere so that the residence time was about 60 minutes, Polyester resin (5) was obtained by continuously feeding to a phase polycondensation device and solid phase polycondensation at 210 ° C. under a nitrogen atmosphere and atmospheric pressure for a residence time of 16 hours. The IV, AV and element contents of the polyethylene terephthalate resin (5) are shown below and in Table 2.
Intrinsic viscosity IV = 0.700 dl / g
Terminal carboxyl group content AV = 24 equivalents / ton Titanium content = 8 ppm by weight
Magnesium content = 15 ppm by weight
Phosphorus content = 10 ppm by weight

Polyethylene terephthalate resin (6)
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 0.02 part of magnesium acetate tetrahydrate as a catalyst is added to the reactor, the reaction start temperature is set to 150 ° C., and the methanol is gradually distilled off. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.03 part of ethyl acid phosphate to this reaction mixture, it moved to the polycondensation tank, added 0.04 part of antimony trioxide, and performed polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction is stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in the stirring power of the reaction vessel, the polymer is discharged under nitrogen pressure, extracted into a strand, cooled with water, and cut with a cutter. Polyethylene terephthalate resin pellets (prepolymer) were produced.

The polyester resin pellet (prepolymer) was used as a starting material, and solid phase polymerization was performed at 220 ° C. under vacuum to obtain a polyester resin (6). The IV, AV and element contents of the polyethylene terephthalate resin (6) are shown below and in Table 2.
Intrinsic viscosity IV = 0.850 dl / g
Terminal carboxyl group content AV = 34 equivalents / ton Titanium content = 0 ppm by weight
Magnesium content = 32 ppm by weight
Phosphorus content = 66 ppm by weight

Polyethylene terephthalate resin (7)
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 441 ppm by weight of magnesium acetate tetrahydrate as a catalyst is added to the reactor, the reaction start temperature is set to 150 ° C., and the methanol is gradually distilled off. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. This reaction mixture was transferred to a polycondensation tank and orthophosphoric acid was added so that the amount of phosphorus was 1000 ppm by weight, and then germanium dioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.62 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain polyethylene terephthalate (7). The IV, AV and element contents of the polyethylene terephthalate resin (7) are shown below and in Table 2.
Intrinsic viscosity IV = 0.620 dl / g
Terminal carboxyl group content AV = 45 equivalent / ton Titanium content = 0 ppm by weight
Magnesium content = 69 ppm by weight
Phosphorus content = 1000 ppm by weight

Polyethylene terephthalate resin (8)
50 parts by weight of the polyethylene terephthalate resin (2) and 50 parts by weight of titanium dioxide particles having an average particle size of 0.45 μm were melt-mixed at 290 ° C. in an extruder according to a conventional method to obtain a polyethylene terephthalate resin (8). The IV, AV and element contents of the polyethylene terephthalate resin (8) are shown below and in Table 2.
Intrinsic viscosity IV = 0.510 dl / g
Terminal carboxyl group content AV = 84 equivalent / ton Titanium dioxide content = 50 [wt%]
Phosphorus content = 6 ppm by weight

<Manufacture of polyethylene terephthalate film>
Polyethylene terephthalate film (1) to (6)
Polyethylene terephthalate resin pellets were mixed in the proportions shown in Table 3 below, melted and extruded at 290 ° C. with a vented twin screw extruder, and the electrostatic application adhesion method was performed on a cooling roll set at a surface temperature of 40 ° C. Application and casting gave an unstretched sheet. Next, the film was stretched 3.7 times in the longitudinal direction at 88 ° C., then led to a tenter, stretched 3.9 times in the transverse direction at 120 ° C., and further heat-treated at 225 ° C., and a polyester film having a thickness DA of 125 μm Got. The obtained film was passed through an infrared heater direct heating furnace, treated at an ambient temperature of 150 to 210 ° C. for a treatment time of 9 seconds, and treated at a film tension of 400 mN / mm ² for annealing. Table 3 shows the thickness DA, white pigment-containing concentrations WA, IV, AV, and phosphorus element content P of the obtained polyethylene terephthalate film.

Polyethylene terephthalate film (7)
Polyethylene terephthalate resin pellets were mixed in the proportions shown in Table 3, and melted and extruded at 290 ° C with a vented twin-screw extruder, and the electrostatic application adhesion method was applied to a cooling roll set at a surface temperature of 40 ° C. And an unstretched sheet was obtained by casting. Next, the film was stretched 3.7 times in the longitudinal direction at 88 ° C., then led to a tenter, stretched 3.9 times in the transverse direction at 115 ° C., and further subjected to heat treatment at 230 ° C., and the thickness DA [μm] was 115 μm. A polyester film was obtained. The obtained film was passed through an infrared heater direct heating furnace, treated at an ambient temperature of 150 to 210 ° C. for a treatment time of 9 seconds, and treated at a film tension of 400 mN / mm ² for annealing. Table 3 shows the thickness DA, white pigment-containing concentrations WA, IV, AV, and phosphorus element content P of the obtained polyethylene terephthalate film.

Polyethylene terephthalate film (8)
Polyethylene terephthalate resin pellets were mixed in the proportions shown in Table 4 below, melted and extruded at 290 ° C. by a twin screw extruder with a vent, and the electrostatic application adhesion method was applied to a cooling roll whose surface temperature was set to 40 ° C. Application and casting gave an unstretched sheet. Next, the film was stretched 3.7 times in the longitudinal direction at 88 ° C., then led to a tenter, stretched 3.9 times in the transverse direction at 110 ° C., and further heat treated at 235 ° C., and a polyethylene terephthalate having a thickness DA of 75 μm. A film was obtained. The obtained film was passed through an infrared heater direct heating furnace, treated at an ambient temperature of 150 to 210 ° C. for a treatment time of 9 seconds, and treated at a film tension of 400 mN / mm ² for annealing. Table 4 shows the thickness DA, white pigment-containing concentrations WA, IV, AV, and phosphorus element content P of the obtained polyethylene terephthalate film.

Polyethylene terephthalate film (9) to (13)
Polyethylene terephthalate resin pellets were mixed in the proportions shown in Table 4, and melted and extruded at 290 ° C with a vented twin screw extruder, and the electrostatic application adhesion method was applied to a cooling roll set at a surface temperature of 40 ° C. And an unstretched sheet was obtained by casting. Next, the film was stretched 3.7 times in the longitudinal direction at 88 ° C., then led to a tenter, stretched 3.9 times in the transverse direction at 120 ° C., and further subjected to heat treatment at 230 ° C., and a polyethylene terephthalate having a thickness DA of 125 μm. A film was obtained. The obtained film was passed through an infrared heater direct heating furnace, treated at an ambient temperature of 150 to 210 ° C. for a treatment time of 9 seconds, and treated at a film tension of 400 mN / mm ² for annealing. Table 4 shows the thickness DA, white pigment-containing concentrations WA, IV, AV, and phosphorus element content P of the obtained polyethylene terephthalate film.

Polyethylene terephthalate film (14) to (19)
Polyethylene terephthalate resin pellets were mixed in the proportions shown in Table 5 below, melted and extruded at 290 ° C. with a vented twin screw extruder, and the electrostatic application adhesion method was applied on a cooling roll set at a surface temperature of 40 ° C. Application and casting gave an unstretched sheet. Next, the film was stretched 3.7 times in the longitudinal direction at 88 ° C., then led to a tenter, stretched 3.9 times in the transverse direction at 120 ° C., and further heat-treated at 225 ° C., and a polyester film having a thickness DA of 125 μm Got. Table 5 shows the thickness DA, white pigment-containing concentrations WA, IV, AV, and phosphorus element content P of the obtained polyethylene terephthalate film.

Polyethylene terephthalate film (20)
Polyethylene terephthalate resin pellets were mixed in the proportions shown in Table 5, and melted and extruded at 290 ° C with a vented twin screw extruder, and the electrostatic application adhesion method was applied to a cooling roll set at a surface temperature of 40 ° C. And an unstretched sheet was obtained by casting. Next, the film is stretched 3.7 times in the longitudinal direction at 88 ° C., then led to a tenter, stretched 3.9 times in the transverse direction at 115 ° C., and further heat-treated at 230 ° C. to obtain a polyester film having a thickness DA of 115 μm. Got. Table 5 shows the thickness DA, white pigment-containing concentrations WA, IV, AV, and phosphorus element content P of the obtained polyethylene terephthalate film.

<Creation of plastic film>
Plastic film (1)
100 parts by weight of an ethylene vinyl acetate copolymer (96 parts by weight of ethylene vinyl acetate copolymer, 4 parts by weight of vinyl acetate), titanium dioxide particles having an average particle diameter of 0.45 μm (8 [wt%]), a crosslinking agent ( 3 parts by weight of t-butylperoxy-2-ethylhexyl carbonate), 2 parts by weight of a crosslinking aid (triallyl isocyanate) and 0.5 parts by weight of a silane coupling agent (γ-methacryloxypropyltrimethoxysilane) are added. Kneaded sufficiently to prepare an ethylene vinyl acetate copolymer composition, and then the ethylene vinyl acetate copolymer composition was melt-extruded with a T-die extruder to obtain an ethylene vinyl acetate copolymer film. An annealing treatment was performed while the temperature was 75 ° C. or higher to produce an ethylene vinyl acetate copolymer film having a thickness of 100 μm. On both sides of the sulfonyl copolymer film, according to a conventional method, to form the corona-treated surface is subjected to corona discharge treatment.

  As the conveyor, a roller having 12 rollers arranged in parallel is used. When the peripheral speed of the last roller on the outlet side is 100, the peripheral speed of the first roller on the inlet side is 110, followed by 2-3. The peripheral speeds of the individual rollers are 106 to 107, and the peripheral speeds of the three to four rollers following these rollers are 102 to 103. The peripheral speed of the rollers gradually decreases from the inlet side to the outlet side. The peripheral speed was set so that And the ethylene vinyl acetate copolymer film currently conveyed with this conveyance conveyor was kept at 70 degreeC or more by heating with a heater. This annealing treatment was performed for 1.0 minute.

  The ethylene vinyl acetate copolymer film after the annealing treatment was cooled with a cooling roll and wound up with a winder.

Plastic film (2)
In the production of the plastic film (1), the plastic film (2) was produced by the same production method as the plastic film (1) except that the titanium dioxide particles were not added.

Plastic film (3)
In the production of the plastic film (1), the plastic film (3) was produced by the same production method as the plastic film (1) except that the titanium dioxide particle concentration WB was 18% by weight.

Plastic film (4)
In the production of the plastic film (1), the plastic film (4) was produced by the same production method as that for the plastic film (1) except that the annealing treatment was not performed.

Examples 1-7:
A polyester-based adhesive is used on one of the corona-treated surfaces of the polyethylene terephthalate films (1) to (7) produced by the above method, and this is coated with a film thickness of 5.0 g / m ² (dry) by a gravure roll coating method. After coating and drying, an adhesive layer for laminating was formed.

  Next, one side of the corona-treated surface of the plastic film (1) produced above is opposed to the surface of the laminating adhesive layer formed as described above, and then both are laminated by dry lamination. Thus, a back surface protection sheet for a solar cell module according to the present invention was produced.

Comparative Examples 1-6:
A polyester-based adhesive is used on one of the corona-treated surfaces of the polyethylene terephthalate films (8) to (13) produced by the above method, and this is coated with a film thickness of 5.0 g / m ² (dry) by a gravure roll coating method. After coating and drying, an adhesive layer for laminating was formed.

  Next, the surface of the laminating adhesive layer formed above is overlaid with one of the corona-treated surfaces of the plastic film produced above facing each other, and then both are laminated by dry lamination. The back surface protection sheet for solar cell modules concerning invention was manufactured.

Comparative Examples 7 to 13:
A polyester adhesive is used on one of the corona-treated surfaces of the polyethylene terephthalate films (1) to (7) so that the film thickness becomes 5.0 g / m ² (in a dry state) by a gravure roll coating method. After coating and drying, an adhesive layer for laminating was formed.

  Next, one side of the corona-treated surface of the plastic film (2) produced above is opposed to the surface of the laminating adhesive layer formed as described above, and then both are laminated by dry lamination. Thus, a back surface protection sheet for a solar cell module according to the present invention was produced.

Comparative Examples 14-20:
A polyester adhesive is used on one of the corona-treated surfaces of the polyethylene terephthalate films (1) to (7) so that the film thickness becomes 5.0 g / m ² (in a dry state) by a gravure roll coating method. After coating and drying, an adhesive layer for laminating was formed.

  Next, one side of the corona-treated surface of the plastic film (3) produced above is opposed to the surface of the laminating adhesive layer formed as described above, and then both are laminated by dry lamination. Thus, a back surface protection sheet for a solar cell module according to the present invention was produced.

Comparative Examples 21 to 27:
A polyester-based adhesive is used on one of the corona-treated surfaces of the polyethylene terephthalate films (1) to (7) produced by the above method, and this is coated with a film thickness of 5.0 g / m ² (dry) by a gravure roll coating method. After coating and drying, an adhesive layer for laminating was formed.

  Next, one side of the corona-treated surface of the plastic film (4) produced above is opposed to the surface of the laminating adhesive layer formed as described above, and then both are laminated by dry lamination. Thus, a back surface protection sheet for a solar cell module according to the present invention was produced.

Comparative Examples 28-34:
Polyester adhesive is used on one of the corona-treated surfaces of the polyethylene terephthalate films (14) to (20) produced by the above method, and this is coated with a film thickness of 5.0 g / m ² (dry) by a gravure roll coating method. After coating and drying, an adhesive layer for laminating was formed.

  Next, one side of the corona-treated surface of the plastic film (1) produced above is opposed to the surface of the laminating adhesive layer formed as described above, and then both are laminated by dry lamination. Thus, the back surface protection sheet for the solar cell module according to the present invention was manufactured.

Comparative Examples 35-41:
Polyester adhesive is used on one corona-treated surface of the polyethylene terephthalate film (14) -polyethylene terephthalate film (20) produced by the above method, and this is coated with a gravure roll coat method to give a film thickness of 5.0 g / m. ² After coating and drying, a laminating adhesive layer was formed.

  Next, one side of the corona-treated surface of the plastic film (4) produced above is opposed to the surface of the laminating adhesive layer formed as described above, and then both are laminated by dry lamination. Thus, the back surface protection sheet for the solar cell module according to the present invention was manufactured.

  About the back surface protection sheet for solar cell modules, (1) hydrolysis resistance, (2) UV resistance, (3) transmission density, and (4) adhesive strength to filler were evaluated. About said polyethylene terephthalate film and a plastic film, (5) Shrinkage was evaluated. Examples 1-7 go to Table 5, Comparative Examples 1-6 go to Table 6, Comparative Examples 7-13 go to Table 7, Comparative Examples 14-20 go to Table 8, Comparative Examples 21-27 go to Table 9. Comparative examples 28 to 34 show the evaluation results in Table 10, and Comparative Examples 35 to 41 show the evaluation results in Table 11.

(1) Evaluation of hydrolysis resistance A solar cell back surface-filled sheet was treated for 2000 hours in an atmosphere of 85 ° C. to 85% RH, and the elongation at break was measured as the mechanical properties of the film. The retention rate (%) of elongation at break before and after the treatment was calculated by the following formula and judged according to the following criteria.
Breaking elongation retention rate = breaking elongation after treatment ÷ breaking elongation before treatment × 100
○: Retention rate is 20% or more △: Retention rate is 6-20%
X: Retention rate is less than 6%

(2) Evaluation of UV resistance A) Accelerated weather resistance test A light irradiation test was performed on the surface of the back protective sheet for solar cell modules with the polyethylene terephthalate film under the following conditions.
Equipment: Metal Weather Testing Machine (Model / Manufacturer: KW-R5TP / Daipura Wintes Co., Ltd.)
Irradiance 100 mW / cm ²
Irradiation condition BP63 ℃ Humidity 50%
Filter: KF-2
Processing time: 12 hours

B) Evaluation method of weather resistance The color (L ^* , a ^* , b ^* ) before and after the weather resistance test of the polyethylene terephthalate film was measured by a reflection method using a spectrophotometer CM-3730d manufactured by Konica Minolta. The UV resistance was evaluated based on the color difference (ΔEab).
Colors before the weather resistance test L ^* ₁ , a ^* ₁ , b ^* ₁
Color after weathering test L ^* ₂ , a ^* ₂ , b ^* ₂

○：１０未満
△：１０以上−１２未満
×：１２以上

○: Less than 10 Δ: 10 or more and less than −12 ×: 12 or more

(3) Evaluation of transmission density Using a Macbeth densitometer TD-904 type, a single back sheet for solar cell module was measured. Reading was performed after the displayed value stabilized. The obtained physical property values were judged according to the following criteria.
◎: Transmission density is 1.5 or more ○: Transmission density is 1.3 or more to less than 1.5 △: Transmission density is 1.1 or more to less than 1.3 ×: Transmission density is less than 1.1

(4) Evaluation of Solar Cell Module Filler Adhesive Strength Maintenance Rate A fast cure type ethylene vinyl acetate copolymer was prepared as a solar cell module filler. In a heat sealer where the plastic film surface of the back surface protection sheet for solar cell modules manufactured in Examples and Comparative Examples and the ethylene vinyl acetate copolymer are in contact with each other and heated at a temperature of 130 ° C., at a pressure of 0.16 MPa And heat sealed for 60 seconds. In the heat sealing, the part where the heat sealing was not performed was left, and the part where the peeling test was started was used.
Based on JIS standard C8917-1989, an environmental test (temperature 85 ° C., humidity 85%, 1000 hr) of the back protective sheet laminate for a solar cell module was performed, and the filler adhesive strength for the solar cell module after the environmental test was performed. The solar cell module is slit to a width of 15 mm, and using a tensile tester [Model name Tensilon, manufactured by A & D Co., Ltd.], the back surface protection sheet for the solar cell module and the solar cell The adhesive strength with the module filler was measured. The obtained physical property values were judged according to the following criteria.
○: Maintenance rate is 60% or more ×: Maintenance rate is less than 60%

(5) Shrinkage The polyethylene terephthalate film was heat-treated for 30 minutes in a 150 ° C. atmosphere in each of the longitudinal direction and the width direction in a tensionless state, and the length of the sample before and after that was measured to calculate the following formula.
Shrinkage rate S (%) = (L1-L0) / L0 × 100
(In the above formula, L1 (mm) is the sample length before heat treatment, and L0 (mm) is the sample length after heat treatment)
○: The larger shrinkage ratio S ≦ 0.8% of the longitudinal direction and the width direction
×: Shrinkage ratio S> 0.8% of the longer one in the longitudinal direction and the width direction
The shrinkage rate of the plastic film was also measured by the same method.

  The sheet | seat of this invention can be utilized suitably as a back surface protection sheet for solar cell modules, for example.

Claims (1)

A film comprising an ethylene vinyl acetate copolymer composition, containing 2.0 to 10.0% by weight of a white pigment, a thickness of 100 μm or more, and containing 2.0 to 10.0% by weight of a white pigment. A back protective sheet for a solar cell module having a polyethylene terephthalate film having a larger shrinkage ratio in the longitudinal direction and width direction after heat treatment at 150 ° C. for 30 minutes of 0.8% or less, wherein the polyethylene terephthalate film A back protective sheet for a solar cell module, having an intrinsic viscosity of 0.65 dl / g or more, a terminal carboxyl group content of 26 equivalents / ton or less, and a phosphorus element content of 70 ppm by weight or less.