JP2012064927A - Easily adhesive black polyester film for solar battery and back sheet using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily adhesive black polyester film for a solar battery, which is excellent in adhesiveness, and a back sheet using the same.SOLUTION: An easily adhesive black polyester film for a solar battery comprises a coating layer at least on one side, in which a substrate thickness thereof is 20-300 μm. An optical density of the film is 1.0-5.0. The coating layer is composed mainly of urethane resin composed of aliphatic polycarbonate polyol. In an infrared spectrum of the coating layer, a ratio (A/A) of an absorbance (A) around 1460 cmderived from aliphatic polycarbonate to an absorbance (A) around 1530 cmderived from urethane is 0.70-1.60.

Description

  The present invention relates to an easily adhesive black polyester film for solar cells and a backsheet using the same. Specifically, the present invention relates to a black polyester film excellent in adhesion to a sealant even under high temperature and high humidity when used on a surface of a solar cell backsheet that contacts a sealant, and a backsheet using the same.

  In recent years, solar cells have attracted attention as an energy means to replace petroleum energy that causes global warming, and the demand for solar cells has increased. A solar cell is a solar power generation system that directly converts solar energy into electricity. As a solar cell element, semiconductors such as single crystal silicon, polycrystalline silicon, and amorphous silicon, compound-based materials, and organic dyes are used. Yes. Recently, the ratio of thin-film solar cell elements in which the thickness of silicon is reduced in order to reduce raw materials, energy required for production, and costs has been increasing. In order to protect such elements over a long period of time (approximately 20 years or more), such a solar cell element is generally wired in series or in parallel with several to several tens of solar cell elements. Done and unitized. A unit incorporated in this package is called a solar cell module.

  Here, a solar cell module generally covers a surface to which sunlight is applied with glass, fills a gap with a sealing material for a solar electronic element, and has a plurality of layers such as a heat-resistant and weather-resistant plastic material called a back sheet on the back surface. It is the structure protected by the protective sheet which consists of a structure. As a sealing material filling the solar cell element, an olefin resin such as ethylene / vinyl acetate copolymer resin (hereinafter EVA) or polyvinyl butyral resin (hereinafter PVB) is used. Using these sealing materials, a module is produced by superposing the glass substrate / sealing material / solar cell element / sealing material / back sheet and then heat-pressing with a vacuum laminator or the like. The sealing material has a role of adhering and fixing the solar cell element, preventing moisture from entering from the outside, and protecting the solar cell element.

  As a solar cell backsheet, from the solar cell element side (encapsulant side) to polyester film / adhesive / polyester film (colored) / metal or metal oxide thin film layer (moisture-proof layer) / adhesive / fluorine Those having a laminated structure such as a film (antifouling layer) have been proposed. Such a back sheet has a role of protecting the solar cell element from external moisture and contamination over a long period of time. Therefore, the adhesiveness between the sealing material and the polyester film on the solar cell element side that is in direct contact with the sealing material is important. However, the surface untreated polyester film cannot obtain sufficient adhesiveness and is required to be improved. As a method for improving the adhesion of the polyester film, it has been proposed to provide an adhesive layer containing a resin or a crosslinking agent (Patent Documents 1 to 4).

  On the other hand, for the purpose of improving the photoelectric conversion efficiency, in order to reflect and efficiently absorb the light transmitted through the solar cell element (particularly, the thin film solar cell element), the solar cell element side (encapsulant side) A white polyester film may be used as the polyester film (Patent Document 5). However, depending on the solar cell element, the power generation efficiency is improved by increasing the temperature of the element during power generation, such as amorphous thin film silicon. There is a kind of thing to do. In this case, it is preferable to increase the temperature of the element by making the back sheet black and efficiently absorbing the radiant heat of sunlight (Patent Document 6).

JP 2006-152013 A JP 2006-320991 A JP 2007-48944 A JP 2007-136911 A JP 2009-182188 A JP 2007-128943 A

  Solar cell modules that are used outdoors under severe environmental conditions are expected to have a lifespan of 20 years or longer. Therefore, it was considered that not only the initial adhesiveness but also the adhesive easily adhesive film used as a member needs to maintain the adhesive property for a long period of time under high temperature and high humidity. However, the easy-adhesive polyester film for solar cells as disclosed in the above patent document still has insufficient adhesiveness, and a decrease in adhesive strength is unavoidable particularly in long-term use under high temperature and high humidity. It was a thing.

  In addition, various composition types including additives such as a crosslinking agent and an ultraviolet absorber have come to be used for the sealing material from the viewpoint of improving productivity and preventing deterioration. Therefore, there is a demand for a highly versatile and easy-to-adhere film that exhibits the same degree of adhesion to various sealing materials.

  In view of the above problems, the present invention has strong adhesiveness that can withstand harsh environments, hardly causes deterioration of adhesiveness under high temperature and high humidity, which has been considered to be unavoidable in the past, and has various sealing properties. Provided an easily-adhesive black polyester film for solar cells that has good adhesiveness to a stopper and, in addition, can efficiently absorb radiant heat by suppressing light reflection on the backsheet surface It is.

As a result of intensive studies to solve the above problems, the present inventor has found that a polyester film having a coating layer on at least one surface, the main component is a urethane resin having an aliphatic polycarbonate polyol as a constituent component, and infrared spectroscopy. In the spectrum, the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) of the absorbance (A ₁₄₆₀ ) near 1460 cm ⁻¹ derived from the aliphatic polycarbonate component to the absorbance (A ₁₅₃₀ ) near 1530 cm ⁻¹ derived from the urethane component is 0.70 to 1 The present inventors have found that by using a coating layer of .60, strong adhesiveness that can withstand harsh environments and excellent adhesiveness even under high temperature and high humidity are found, and the present invention has been achieved.

The above-described problem can be achieved by the following solution means.
(1) A black polyester film having a coating layer on at least one surface and a substrate thickness of 20 μm to 500 μm, wherein the optical density of the film is 1.0 to 5.0, and the coating layer is an aliphatic polycarbonate. The main component is a urethane resin having a polyol as a constituent component. In the infrared spectrum of the coating layer, the absorbance near 1460 cm ⁻¹ derived from the aliphatic polycarbonate component (A ₁₄₆₀ ) and the absorbance near 1530 cm ⁻¹ derived from the urethane component. _{(a 1530)} and the ratio _(a 1460 _/ a ₁₅₃₀₎ is highly adhesive black polyester film for a solar cell, which is a 0.70 to 1.60.
(2) A solar cell backsheet in which the solar cell easy-adhesive black polyester film is laminated.

  The easy-adhesion black polyester film for solar cells of the present invention exhibits strong adhesiveness, and is particularly excellent in adhesiveness (moisture heat resistance) under high temperature and high humidity. Therefore, as a preferred embodiment, the adhesiveness at the high temperature and high humidity treatment is maintained at the same level as the initial adhesiveness. As a preferred embodiment of the present invention, when the easily adhesive black polyester film for solar cells of the present invention is used as a member of a back sheet, the adhesiveness with the sealing material is good.

(Black polyester film)
The polyester used in the base material of the present invention is an aromatic dicarboxylic acid or ester such as terephthalic acid, isophthalic acid or naphthalenedicarboxylic acid and glycol such as ethylene glycol, diethylene glycol, 1,4-butanediol or neopentyl glycol. Polyester produced by polycondensation. These polyesters include (1) a method in which an aromatic dicarboxylic acid and glycol are directly reacted and then a polycondensation reaction (direct weight method), and (2) an alkyl ester of an aromatic dicarboxylic acid and glycol. It can be produced by a known method such as a method of performing an exchange reaction and then a polycondensation reaction (transesterification method), or a method of (3) polycondensation of diglycol esters of aromatic dicarboxylic acids.

  Representative examples of such polyesters include polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, or polyethylene-2,6-naphthalate. These polyesters may be homopolymers or copolymerized with a third component. In any case, in the present invention, the ethylene terephthalate unit, butylene terephthalate unit, propylene terephthalate unit, or ethylene-2,6-naphthalate unit is 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more. The polyester which is is preferable. Among these, polyethylene terephthalate is particularly preferable from the viewpoint of cost performance. Moreover, it is preferable that the intrinsic viscosity of a base film is 0.50-0.75 dl / g.

In order to improve the power generation efficiency of the solar cell element, a black polyester film that absorbs radiant heat of sunlight and easily rises in temperature is used. In order to achieve both an effective temperature rise effect and the mechanical strength of the film, the optical density (OD) of the polyester film of the present invention is preferably 1.0 to 5.0, and preferably 1.3 to 4.0. Is more preferable, and it is further more preferable that it is 2.0-3.0.
Here, the black polyester film means a film having a reflectance of less than 20%. This reflectance is more preferably less than 5% from the viewpoint of radiant heat absorption efficiency.

  Here, as a method of controlling the optical density of the polyester film within the above range, it is preferable that the polyester film is expressed by light absorption, not by light reflection or light scattering. Specifically, it is a preferred embodiment to add a light absorber such as a black pigment or a dye to the film.

  As the black pigment used in the present invention, known pigments can be used regardless of whether they are inorganic or organic. However, inorganic pigments are preferably used from the viewpoint of weather resistance, and carbon-based, titanium-based, and iron-based pigments are used. A pigment is preferably used. For example, carbon black or titanium black is used. In particular, carbon black is a preferred pigment because it can exhibit high light absorption in a small amount and can be easily obtained at low cost as an industrial material. The pigment used here can be subjected to various organic and inorganic surface treatments for the purpose of improving dispersibility.

  The addition amount of the black pigment is desirably selected as appropriate depending on the type of pigment, the optical density (light absorption) of the film, and the film thickness. For example, it is preferable that it is 0.05-10 mass% in a film, and it is more preferable that it is 0.1-3 mass%. If the amount added is less than the above range, it is difficult to obtain the required light absorption even with carbon black having a relatively high concealment property, and when the amount exceeds the above range. Is not preferable because the mechanical properties of the film are lowered or the processability is lowered due to the thixotropy of the pigment particles.

  More specifically, if a method of expressing optical density using carbon black or titanium black is used, the coefficient obtained by multiplying the addition amount (%) and the film thickness (μm) is 20 to 80% · μm. It is preferable to set it to 30 to 50% · μm. This coefficient is a parameter that represents the total amount of pigment contained in the unit volume of the film, and can be expressed as the sum of the values of each layer in the laminated film.

  In addition, in order to impart other functions to the film, the substrate may contain inorganic particles other than black pigment, organic particles, antioxidants, crosslinking agents, ultraviolet absorbers, plasticizers, etc. as necessary. it can.

  For example, the base film can be provided with slipperiness (anti-blocking property) by containing a black pigment and particles having an average particle size larger than this. The particles used here are not particularly limited, and well-known particles such as silica, titanium oxide, barium sulfate, zinc oxide, zinc sulfide, calcium carbonate, crosslinked acrylic particles, crosslinked polystyrene particles, and melamine particles can be used. However, it is a preferred embodiment to use silica particles because of its high affinity for polyester resin and close refractive index.

  Moreover, it is preferable that the average particle diameter of the particle | grains used here is 0.5-5 micrometers, and it is more preferable that it is 1-3 micrometers. When the average particle size is less than the above range, it is difficult to sufficiently exhibit slipperiness, and when it exceeds the above range, problems such as dropout of particles and poor appearance occur. In addition, said average particle diameter measured the maximum diameter of 10 or more particle | grains which existed in the cross section of a coating layer, image | photographed the cross section of a laminated film using a transmission electron microscope at 120,000 times magnification, and those It can be calculated as an average value.

  Moreover, it is preferable that the addition amount of the particle | grains used here is 200-10000 ppm, and it is more preferable that it is 500-5000 ppm. When the addition amount is less than this range, it is difficult to obtain sufficient slipperiness, and when it exceeds this range, the mechanical properties of the film are deteriorated and the appearance is unfavorable. In particular, when particles having a high refractive index such as a white pigment are used, the light reflectivity is improved with an increase in the amount of addition, and this may have an undesirable effect on the utilization of radiant heat, which is the gist of the present invention. .

The base film of the present invention may be a single layer or a multilayer. For example, it is possible to improve the appearance and cleavage strength of the film by laminating a layer A having a relatively large amount of black pigment added and a layer B having a relatively small amount in the order of B / A / B. Furthermore, it is possible to make a film with various functions by adding C layer containing other functional additives and adopting A / B / C, C / A / B / A / C, etc. It is.

  Here, the method for producing the multilayer film is not particularly limited, and a known method such as co-extrusion, extrusion lamination, and lamination by adhesion can be used, but from the viewpoint of production efficiency, it is preferable to carry out by co-extrusion. It is.

  The thickness of the polyester film used as the base material of the present invention is 20 to 300 μm, more preferably 35 to 250 μm, and still more preferably 50 to 200 μm. When the substrate layer is less than this range, it is not preferable because the strength is insufficient in protecting the solar cell module. Further, a film exceeding this range is not preferable because it not only becomes excessive quality in mechanical performance but also difficult to handle in some cases.

(Coating layer)
The easy-adhesive black polyester film for solar cells of the present invention is formed with a coating layer mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component, and the aliphatic polycarbonate is measured by infrared spectroscopy. that absorbance around 1460 cm ^-1 derived from the component ratio of _{(a 1460)} and 1530 cm ^-1 vicinity of absorbance from urethane component _{(a 1530) (a 1460 /} a 1530) is is from 0.70 to 1.60 is important. Here, the “main component” means that it is contained in an amount of 50% by mass or more, more preferably 70% by mass or more as the total solid component contained in the coating layer.

  As described in Patent Documents 1 to 4, it is desirable that the conventional technical common sense positively introduces a cross-linking structure in the formation of the coating layer in order to improve the durability of the coating layer, thereby forming a rigid and strong coating layer. It was thought. However, in the present invention, the polyurethane resin comprising an aliphatic polycarbonate polyol as a constituent component controls the absorbance by infrared spectroscopy within a certain range, thereby exhibiting strong adhesion and adhesion under high temperature and high humidity heat. As a result, the inventors have found a remarkable effect of improving the quality of the present invention and have reached the present invention. Although the mechanism of improving adhesiveness with such a configuration is not well understood, the present inventor thinks as follows.

  For example, when the module is packaged, thermocompression bonding is performed at a high temperature in a configuration in which a glass film / a sealing material / a polyester film having a coating layer (coating layer) is laminated. Under the present circumstances, stress arises between a polyester film (coating layer) and a sealing material by the thermal contraction of the polyester film at the time of high temperature adhesion. In particular, the generation of such stress can also vary depending on various kinds of sealing materials and bonding conditions. As a result, it was considered that the stress could not be alleviated and the adhesiveness with the sealing material was lowered. Furthermore, when such a laminated body is placed under high temperature and high humidity, degradation of the coating layer proceeds due to hydrolysis. As a result, it was considered that the above stress could not be endured, the sealing material was peeled off, and the adhesiveness under high temperature and high humidity was lowered. Therefore, in order to maintain high adhesion to the sealing material and high adhesiveness under high temperature and high humidity, instead of simply imparting durability by firmly crosslinking the coating layer, heat resistance, It is considered desirable to have a component that retains hydrolysis resistance and to be flexible enough to withstand the stress. However, merely having flexibility has a problem in coating strength. Therefore, it is most desirable to make these conflicting characteristics compatible.

In this invention, it is a coating layer which has as a main component the urethane resin which has aliphatic polycarbonate polyol as a structural component, Comprising: The light absorbency (A of 1460cm < ^-1 > vicinity derived from the aliphatic polycarbonate component measured by infrared spectroscopy ₁₄₆₀ ) and the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) of the absorbance (A ₁₅₃₀ ) in the vicinity of 1530 cm ⁻¹ derived from the urethane component is 0.70 to 1.60, so that the above characteristics are compatible. That is, the above-mentioned characteristics can be achieved by coexisting an aliphatic polycarbonate component having hydrolysis resistance and a urethane component exhibiting toughness at a predetermined ratio. Thereby, since the stress due to thermal shrinkage of the polyester film at the time of thermal bonding at high temperature can be relieved, it is possible to obtain a strong adhesiveness with the sealing material, even in a subsequent environment of high temperature and high humidity, We believe that the coating layer can be prevented from deteriorating because it retains heat resistance and hydrolysis resistance.

Here, the absorbance in the vicinity of 1460 cm ⁻¹ (A ₁₄₆₀ ) is derived from the bending vibration specific to the C—H bond in the methylene group contained in the aliphatic polycarbonate component. Therefore, the magnitude of the absorbance (A ₁₄₆₀ ) near 1460 cm ⁻¹ depends on the amount of the aliphatic polycarbonate polyol component constituting the urethane resin present in the coating layer. On the other hand, the absorbance (A ₁₅₃₀ ) in the vicinity of 1530 cm ⁻¹ is derived from the bending vibration specific to the N—H bond contained in the urethane component. Therefore, the magnitude of the absorbance (A ₁₅₃₀ ) near 1530 cm ⁻¹ depends on the amount of the urethane component constituting the urethane resin present in the coating layer. Therefore, these absorbance ratios (A ₁₄₆₀ / A ₁₅₃₀ ) indicate that both components having different characteristics coexist in a specific ratio. In the present invention, the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is 0.70 to 1.60, but the lower limit of the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is preferably 0.75, more preferably 0.00. 80. Moreover, the upper limit of the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is preferably 1.50, more preferably 1.45, and even more preferably 1.40. When the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is less than 0.70, the amount of the hard urethane component is excessive, and the stress relaxation of the coating layer is lowered, so that the heat and moisture resistance is lowered. In addition, when the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) exceeds 1.55, the aliphatic component of the flexible aliphatic polycarbonate is excessively increased, and the strength of the coating layer is lowered, so that the coating strength and moisture and heat resistance are reduced. Decreases.

  According to the aspect described above, the present invention can exhibit strong adhesiveness with a sealing material and can improve adhesiveness (moisture heat resistance) under high temperature and high humidity. Further, the configuration of the present invention will be described in detail below.

(Urethane resin)
The urethane resin of the present invention includes at least a polyol component and a polyisocyanate component as constituent components, and further includes a chain extender as necessary. The urethane resin of the present invention is a polymer compound in which these constituent components are mainly copolymerized by urethane bonds. In this invention, it has an aliphatic polycarbonate polyol as a structural component of a urethane resin. Heat-moisture resistance can be improved by including a urethane resin containing an aliphatic polycarbonate polyol as a constituent component in the coating layer of the present invention. The components of these urethane resins can be specified by nuclear magnetic resonance analysis or the like.

  The diol component, which is a constituent component of the urethane resin of the present invention, needs to contain an aliphatic polycarbonate polyol having excellent heat resistance and hydrolysis resistance. From the viewpoint of preventing yellowing by sunlight of the present invention, it is preferable to use an aliphatic polycarbonate polyol.

Examples of the aliphatic polycarbonate polyol include aliphatic polycarbonate diols and aliphatic polycarbonate triols, and aliphatic polycarbonate diols can be preferably used. Examples of the aliphatic polycarbonate diol that is a constituent of the urethane resin of the present invention include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 3-methyl. -1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,4- Aliphatic polycarbonate diols obtained by reacting one or more diols such as cyclohexanedimethanol with carbonates such as dimethyl carbonate, diphenyl carbonate, ethylene carbonate, and phosgene. It is below. The number average molecular weight of the aliphatic polycarbonate diol is preferably 1500 to 4000, and more preferably 2000 to 3000. When the number average molecular weight of the aliphatic polycarbonate diol is small, the ratio of the aliphatic polycarbonate component constituting the urethane resin is relatively small. Therefore, in order to make the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) within the above range, it is preferable to control the number average molecular weight of the aliphatic polycarbonate diol within the above range. If the number average molecular weight of the aliphatic polycarbonate diol is large, the absorbance (A ₁₄₆₀ ) near 1460 cm ⁻¹ derived from the aliphatic polycarbonate component increases, and the aliphatic component increases. The strength after processing may be reduced. When the number average molecular weight of the aliphatic polycarbonate diol is small, a strong urethane component increases, and stress due to thermal shrinkage of the base material cannot be relieved, and adhesiveness may be lowered.

  Examples of the polyisocyanate that is a component of the urethane resin of the present invention include aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis (isocyanatomethyl) cyclohexane. Such as alicyclic diisocyanates such as hexamethylene diisocyanate and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate; Isocyanates. When aromatic isocyanate is used, there is a problem of yellowing, which may not be preferable. Moreover, since it becomes a hard coating film compared with an aliphatic type | system | group, it becomes impossible to relieve | moderate the stress by the heat shrink of a base material, and adhesiveness may fall.

Chain extenders include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol and 1,6-hexanediol, polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol, ethylenediamine Diamines such as hexamethylenediamine and piperazine, amino alcohols such as monoethanolamine and diethanolamine, thiodiglycols such as thiodiethylene glycol, and water. However, when a chain extender having a short main chain is used, the absorbance (A ₁₅₃₀ ) in the vicinity of 1530 cm ⁻¹ derived from the urethane component increases, and the flexibility of the coating layer may decrease. Therefore, a chain extender having a long main chain is preferable. Moreover, the point which provides the softness | flexibility of an application layer has preferable the chain extender of the diol and the diamine whose length of carbon number of a main chain is 4-10. From these points, 1,4-butanediol, 1,6-hexanediol, hexamethylenediamine and the like are preferable as the chain extender used in the present invention. That is, in order to prevent a decrease in absorbance in the vicinity of 1530 cm ⁻¹ derived from the urethane component and to impart flexibility, it is a straight chain such as 1,4-butanediol, 1,6-hexanediol, hexamethylenediamine, etc. and has a large molecular weight. Those are preferred.

  The coating method of the coating layer of the present invention is not particularly limited, and various off-line coating methods and in-line coating methods can be employed. However, from the viewpoint of productivity and environmental protection, the coating layer of the present invention is preferably provided by an in-line coating method described later using an aqueous coating solution. In this case, it is desirable that the urethane resin of the present invention is water-soluble. The “water-soluble” means that it dissolves in water or an aqueous solution containing less than 50% by mass of a water-soluble organic solvent.

  In order to impart water solubility to the urethane resin, a sulfonic acid (salt) group or a carboxylic acid (salt) group can be introduced (copolymerized) into the urethane molecular skeleton. Since the sulfonic acid (salt) group is strongly acidic and it may be difficult to maintain moisture resistance due to its hygroscopic performance, it is preferable to introduce a weakly acidic carboxylic acid (salt) group. Moreover, nonionic groups, such as a polyoxyalkylene group, can also be introduced.

  In order to introduce a carboxylic acid (salt) group into a urethane resin, for example, as a polyol component, a polyol compound having a carboxylic acid group such as dimethylolpropionic acid or dimethylolbutanoic acid is introduced as a copolymer component to form a salt. Neutralize with an agent. Specific examples of the salt forming agent include trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine and tri-n-butylamine, N such as N-methylmorpholine and N-ethylmorpholine. -N-dialkylalkanolamines such as alkylmorpholines, N-dimethylethanolamine, N-diethylethanolamine and the like. These can be used alone or in combination of two or more.

  In order to impart water solubility, when a polyol compound having a carboxylic acid (salt) group is used as a copolymerization component, the composition molar ratio of the polyol compound having a carboxylic acid (salt) group in the urethane resin is the same as that of the urethane resin. When the total polyisocyanate component is 100 mol%, it is preferably 3 to 60 mol%, more preferably 5 to 40 mol%. If the composition molar ratio is less than 3 mol%, water dispersibility may be difficult. Moreover, when the said composition molar ratio exceeds 60 mol%, since water resistance falls, moist heat resistance may fall.

  The glass transition temperature of the urethane resin of the present invention is preferably less than 0 ° C, more preferably less than -5 ° C. When the glass transition temperature is less than 0 ° C., the viscosity is close to that of partially melted olefin resin such as EVA or PVB at the time of pressure bonding, contributing to the improvement of strong adhesiveness by partial mixing, From the viewpoint of stress relaxation of the coating layer, it is preferable because it is easy to achieve suitable flexibility.

  In the urethane resin of the present invention, a crosslinking group may be introduced into the resin itself in order to improve adhesion after high temperature and high humidity. A silanol group is preferred from the viewpoint of the stability over time of the coating solution and the effect of improving the crosslinking density.

  A resin other than the urethane resin of the present invention may be contained in order to improve adhesiveness. For example, a urethane resin, an acrylic resin, a polyester resin, or the like containing polyether or polyester as a constituent component can be used.

  In the present invention, a crosslinking agent may be contained in the coating layer. By including a crosslinking agent, it becomes possible to further improve the adhesiveness.

  In the present invention, two kinds of crosslinking agents may be mixed in order to improve the coating film strength. Moreover, in order to promote a crosslinking reaction, you may use a catalyst etc. suitably as needed.

  In the present invention, particles may be contained in the coating layer. The particles are (1) silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, titanium dioxide, satin white, aluminum silicate, diatomaceous earth. Soil, calcium silicate, aluminum hydroxide, hydrous halloysite, magnesium carbonate, magnesium hydroxide and other inorganic particles, (2) acrylic or methacrylic, vinyl chloride, vinyl acetate, nylon, styrene / acrylic, styrene / butadiene , Polystyrene / acrylic, polystyrene / isoprene, polystyrene / isoprene, methyl methacrylate / butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, dia Rufutareto systems include organic particles of polyester or the like.

  The particles preferably have an average particle size of 1 to 500 nm. Although an average particle diameter is not specifically limited, If it is 1-100 nm from the point which maintains the transparency of a film, it is preferable.

  The particles may contain two or more kinds of particles having different average particle diameters.

  In addition, said average particle diameter measured the maximum diameter of 10 or more particle | grains which existed in the cross section of a coating layer, image | photographed the cross section of a laminated film using a transmission electron microscope at 120,000 times magnification, and those It can be calculated as an average value.

  As content of particle | grains, 0.5 mass% or more and 20 mass% or less are preferable. When the amount is small, sufficient antiblocking properties cannot be obtained. In addition, scratch resistance deteriorates. When the amount is large, the coating film strength decreases.

  The coating layer may contain a surfactant for the purpose of improving leveling properties during coating and defoaming the coating solution. The surfactant may be any of cationic, anionic and nonionic surfactants, but is preferably a silicon-based, acetylene glycol-based or fluorine-based surfactant. These surfactants are preferably contained in a range that does not impair the adhesiveness to the sealing material, for example, in the range of 0.005 to 0.5% by mass in the coating solution.

  In order to impart other functionality to the coating layer, various additives may be contained within a range that does not impair the adhesion with the sealing material. Examples of the additive include fluorescent dyes, fluorescent brighteners, plasticizers, ultraviolet absorbers, pigment dispersants, foam suppressors, antifoaming agents, preservatives, and antistatic agents.

  In the present invention, examples of the method for providing the coating layer on the polyester film include a method in which a coating solution containing a solvent, particles and a resin is applied to the polyester film and dried. Examples of the solvent include organic solvents such as toluene, water, and a mixed system of water and a water-soluble organic solvent. Preferably, water alone or a mixture of a water-soluble organic solvent and water is used from the viewpoint of environmental problems. preferable.

(Manufacture of easy-adhesive black polyester film for solar cells)
The black polyester film of the present invention is preferably a biaxially oriented laminated polyester obtained by sequential biaxial stretching or simultaneous biaxial stretching. Hereinafter, the most widely used sequential biaxial stretching method will be described.

  After sufficiently vacuum-drying the film raw material, it is melted with an extruder and extruded into a sheet form from a T-die to obtain an unstretched film.

  At this time, the pigment and other additives are not added to the extruder and kneaded, but a masterbatch polymer is prepared in which the pigment is separately contained in the polyester resin at a high concentration in advance, and these are added to the polyester. A method of blend dilution with a resin is preferable from the viewpoint of uniform mixing. As the extruder, it is preferable to use a twin-screw extruder in order to mix various film raw materials more sufficiently and uniformly.

  In the present invention, the polyester film of the substrate may be a single layer structure or a multilayer structure, but in the case of a laminated structure, after supplying the resins of the A layer and the B layer having different compositions to separate extruders, For example, it is most preferable to adopt a co-extrusion method in which a two-layer structure of A layer / B layer is formed in a molten state, laminated in a three-layer configuration of A layer / B layer / A layer, and extruded from the same die. .

  Thereafter, the uniaxially stretched polyester film was guided to a tenter-type lateral stretching machine, heated to 80 to 180 ° C., stretched 2.5 to 5.0 times in the lateral direction, and then heat-set at 200 to 240 ° C. Then, if necessary, it is relaxed by 1 to 10% in the longitudinal direction and / or the transverse direction, and then wound up with a film winder to obtain a biaxially stretched polyester film.

  In an arbitrary stage of the film manufacturing process, a coating solution is applied to at least one surface of the film to form the coating layer. There is no particular problem even if the coating layer is formed on both sides of the film. The solid content concentration of the resin composition in the coating solution is preferably 2 to 35% by mass, particularly preferably 4 to 15% by mass.

  Any known method can be used as a method for applying the coating liquid to the film. For example, reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, etc. . These methods are applied alone or in combination.

  In the present invention, the coating layer is formed by applying the coating solution to an unstretched or uniaxially stretched film, drying it, stretching it at least in a uniaxial direction, and then performing a heat treatment. Since the adhesion between the coating layer and the polyester film substrate is further improved by the in-line coating method for forming the coating layer during film formation, it is preferable in terms of improving the adhesion with the sealing material after high temperature and high humidity.

In the present invention, the thickness of the finally obtained coating layer is preferably 10 to 3000 nm, more preferably 10 to 1000 nm, still more preferably 10 to 500 nm, and still more preferably 10 to 400 nm. The coating amount after drying of the coating layer is preferably 0.01 to 3 g / ^{m 2,} more preferably 0.01 to 1 g / ^{m 2,} more preferably 0.01 to 0.5 g / ^{m 2,} more More preferably, it is 0.01-0.4 g / m < ² >. When the coating amount of the coating layer is less than 0.01 g / m ² , the effect on adhesiveness is almost lost. On the other hand, when the coating amount exceeds 3 g / m ² , haze increases.

(Back sheet for solar cell)
The solar cell backsheet of the present invention comprises a black polyester film having the coating layer as a constituent member. In particular, it is preferably used for the outermost layer that is in direct contact with the sealing material. With such a configuration, the solar cell backsheet of the present invention can exhibit strong adhesion to the encapsulant, and can exhibit good adhesion even under harsh environments over a long period of time. Therefore, it can contribute to moisture proof maintenance and barrier property improvement of the solar cell element. Furthermore, since the solar cell backsheet of the present invention exhibits good light absorptivity, it is suitable for improving the photoelectric conversion efficiency.

  As an aspect of the solar cell backsheet of the present invention, for example, a black polyester film having the coating layer / adhesive / metal foil or a film having a metal thin film layer / adhesive / polyvinyl fluoride film or polyester high durability A configuration such as a moisture-proof film is exemplified. Moreover, the structure which has the said coating layer on both surfaces may be sufficient as the black polyester film of this invention. The coating layer of the present invention can exhibit good adhesiveness with configurations other than the sealing material. Here, as the film having a metal foil or a metal thin film layer, a film having a water vapor barrier property can be suitably used.

  Examples of the metal include aluminum, tin, magnesium, silver, and stainless steel. Among them, aluminum and silver are preferable because they have a relatively high reflectance and are easily available industrially. The metal layer may be used as a metal foil, or may be laminated as a thin film on a polyester film or the like. As a method of laminating these metals as a thin film, a vacuum deposition method, a sputtering method, an ion plating method, a plasma vapor deposition method (CVD), or the like can be used.

  In the present invention, the respective layers of the black polyester film having the coating layer, the metal foil or the film having the metal thin film layer, the polyvinyl fluoride film, or the polyester high durability moisture-proof film are integrated by vacuum suction or the like and subjected to thermocompression bonding. A solar cell backsheet can be produced by using a conventional molding method such as a lamination method and thermocompression-molding each of the above layers as an integral molded body. In the above, in order to improve the adhesiveness etc. between each film, it is preferable to laminate | stack via an adhesive agent. Examples of the adhesive include (meth) acrylic resins, olefinic resins, vinyl resins, heat-melt adhesives having a resin as a main component of a vehicle, solvent adhesives, and photocurable adhesives.

  Here, the high durability moisture-proof film is laminated for the purpose of improving weather resistance, and examples of the high durability moisture-proof film include polytetrafluoroethylene (PTFE), 4-fluoroethylene-perchloroalkoxy copolymer. Copolymer (PFA), 4-fluorinated ethylene-6-fluorinated propylene copolymer (FEP), 2-ethylene-4-fluorinated ethylene copolymer (ETFE), poly-3-fluorinated ethylene (PCTFE), polyfluorinated Fluorine resin film such as vinylidene (PVDF) or polyfuca vinyl (PVF), or UV absorber for resin such as polycarbonate, polymethyl methacrylate, polyacrylate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acrylic A film made of a kneaded resin composition It is.

(Solar cell module)
The solar cell module uses, for example, a glass substrate, a solar cell element as a photovoltaic element provided with wiring, a sealing material interposed so as to sandwich the solar cell element, and the solar cell backsheet of the present invention. Configured. As the sealant, an olefin resin such as an ethylene / vinyl acetate copolymer or a polyvinyl butyral resin is preferably used. In particular, since the coating layer of the present invention has such flexibility, it can exhibit good adhesiveness with a sealing material such as an ethylene / vinyl acetate copolymer or a polyvinyl butyral resin.

  Sealing materials are classified into a standard cure type that cures by a curing process in an oven provided in a separate line after thermocompression bonding in the laminating process, and a fast cure type that cures inside the laminator in the laminating process. However, either can be applied. As the main component of the sealing material, an olefin resin such as an ethylene / vinyl acetate copolymer or a polyvinyl butyral resin is used. Here, the “main component” means that 50% by mass or more, more preferably 70% by mass or more of the sealant is contained. For example, a crosslinking agent or a reaction initiator for causing the crosslinking reaction to proceed is added. For example, when thermal crosslinking is performed, 2,5-dimethylhexane-2,5-dihydroxyperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, di-t Organic peroxides such as -butyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane are used. When photocuring is performed, a photosensitizer such as benzophenone, methyl orthobenzoylbenzoate or benzoin ether is used. Furthermore, a silane coupling agent may be blended in consideration of adhesion to the glass substrate. It may be blended for the purpose of accelerating adhesion and curing. Examples of the epoxy group-containing compound include triglycidyl tris (2-hydroxyethyl) isocyanurate, neopentyl glycol diglycidyl ether, 1,6-hexanediol. Epoxy group-containing compounds such as diglycidyl ether, acrylic glycidyl ether, and 2-ethylhexyl glycidyl ether are used.

  EXAMPLES Next, although this invention is demonstrated in detail using an Example and a comparative example, naturally this invention is not limited to a following example. The evaluation method used in the present invention is as follows.

(1) Intrinsic viscosity of resin It measured at 30 degreeC using the mixed solvent of phenol (60 mass%) and 1,1,2,2-tetrachloroethane (40 mass%) based on JISK7367-5.

(2) Melting point of resin and glass transition temperature DSC measurement was performed according to “Method for measuring plastic transition temperature” described in JIS K7121. As the sample, about 10 mg of a small piece obtained by cutting a thermal adhesive layer from a film using a microtome with a magnifying glass, sealed in an aluminum pan, melted at 300 ° C. for 3 minutes, and quenched with liquid nitrogen was used. A differential scanning calorimeter (manufactured by Seiko Instruments Inc., EXSTAR 6200DSC) was used as a measuring instrument, and the measurement was performed under a dry nitrogen atmosphere. After heating from room temperature at a rate of 10 ° C./min to determine the midpoint glass transition temperature, the melting peak temperature (melting point) was determined.

(3) Film thickness It measured by "the foamed plastic-film and sheet-thickness measuring method" described in JIS K7130. The measuring instrument used was an electronic micrometer (manufactured by Marl, Millitron 1240). Four 5 cm square samples were cut from arbitrary four locations of the film to be measured, and 5 points (20 points in total) were measured per sheet, and the average value was taken as the thickness.

(4) Lamination thickness of film Small pieces were cut out from arbitrary three locations of the film to be measured. The small piece was cut using a microtome to create a film cross section perpendicular to the film surface. A platinum-palladium alloy was sputtered onto the cross section to obtain a sample, and the cross section was examined using a scanning electron microscope (S2500, manufactured by Hitachi, Ltd.). The total thickness of the film was observed at an appropriate magnification included in one field of view, and the thickness of each layer was measured. The measurement was performed at three places for each field of view, and the average value of a total of nine places was used as the laminate thickness.

(5) Optical density of film The optical density in white light was measured using a black and white transmission densitometer (manufactured by Ihara Electronics Co., Ltd., Ihac-T5). The measurement was carried out in a room where external light was shielded. Measurement was performed on five 50 mm square samples cut out from five arbitrary locations of the sample to be measured, and the average value was obtained as the optical density.

(6) Absorbance measurement by infrared spectroscopy The coating layer about the film was scraped off with a normal razor blade, and a sample of about 1 mg was collected. A pressure was applied to the collected sample to prepare a coating layer sample piece (size: about 50 μm × about 50 μm) molded into a film having a thickness of about 1 μm. Further, a sample piece (blank sample piece) was prepared in the same manner as described above for a PET resin having the same quality as the base film as a film surface layer blank sample.
The prepared sample piece was placed on a KBr plate, and an infrared absorption spectrum was measured by a microscopic transmission method under the following conditions. The infrared spectrum of the coating layer was determined as the difference spectrum between the infrared spectrum obtained from the coating layer sample piece and the spectrum of the blank sample piece.
Absorbance around 1460 cm ^-1 derived from an aliphatic polycarbonate component _{(A 1460)} is 1460 and the value of the absorption peak height having an absorption maximum in the region of ± 10 cm ^-1, the absorbance in the vicinity of 1530 cm ^-1 derived from urethane component (A ₁₅₃₀ ) is the value of the absorption peak height having an absorption maximum in the region of 1530 ± 10 cm ⁻¹ . The baseline was a line connecting the hems on both sides of each maximum absorption peak. The absorbance ratio was determined from the obtained absorbance by the following formula.
(Absorbance ratio) = A ₁₄₆₀ / A ₁₅₃₀

(Measurement condition)
Apparatus: FT-IR analyzer SPECTRA TECH IRμs / SIRM
Detector: MCT
Resolution: 4cm ^-1
Integration count: 128 times

(7) An integrating sphere was attached to a reflectance spectrophotometer (manufactured by Hitachi, Ltd., Spectrophotometer U-3500), and the baseline was corrected so that the reflectance of the white alumina plate (manufactured by Hitachi Instruments Service) was 100%. The film sample was fixed through the mirror surface measurement jig (tilt angle 10 degrees) attached to the apparatus. The reflectance was measured in 1 nm increments in the wavelength range of 950 to 1050 nm, and the measured values of 995 to 1005 nm (11 points in total) were averaged to measure the reflectance of the film. This reflectance was ranked according to the following criteria.
◎: 0% or more, less than 5% ○: 5% or more, less than 20% ×: 20% or more

(8) Adhesiveness The prepared easy-adhesive black polyester film for solar cells was cut into 100 mm width × 100 mm length, and the EVA sheet was cut into 70 mm width × 90 mm length, and the film (coating layer surface) / EVA / (Coating layer surface) A sample was prepared by stacking with a film structure and heat-pressing with a vacuum laminator under the bonding conditions described below. The prepared sample was cut out into a width of 20 mm and a length of 100 mm, attached to a SUS plate, and the peel strength between the film layer and the EVA layer was measured with a tensile tester under the conditions described below. The peel strength was determined as the average value of the portions that peeled stably after exceeding the maximum point. The ranking was based on the following criteria.
◎: 100 N / 20 mm or more, or film breakage of film ○: 75 N / 20 mm or more, less than 100 N / 20 mm Δ: 50 N / 20 mm or more, less than 75 N / 20 mm ×: less than 50 N / 20 mm

(Sample creation conditions)
Apparatus: Vacuum laminator NP-30 type LM-30x30 pressurization: 1 atmosphere EVA:
A. Standard cure type Sunvik Ultra Pearl PV (0.4μm)
Lamination process: 100 ° C. (vacuum 5 minutes, vacuum pressurization 5 minutes)
Cure process: Heat treatment 150 ° C (normal pressure 45 minutes)
II. Mitsui Fabro Solar EVA SC4 (0.4μm)
Lamination process: 130 ° C (vacuum 5 minutes, vacuum pressurization 5 minutes)
Cure process: 150 ° C (45 minutes at normal pressure)
B. Fast cure type Sunvik Ultra Pearl PV (0.45μm)
Lamination process: 135 ° C (vacuum 5 minutes, vacuum pressure 15 minutes)
II. Mitsui Fabro Solar Eva RC02B (0.45μm)
Lamination process: 150 ° C. (vacuum 5 minutes, vacuum pressure 15 minutes)

(Measurement condition)
Apparatus: Tensilon RTM-100 manufactured by Toyo BALDWIN
Peeling speed: 200 mm / min Peeling angle: 180 degrees

(7) Moisture and heat resistance The resulting easily adhesive black polyester film for solar cells was left in an environment of 85 ° C. and 85% RH for 1000 hours in a high-temperature and high-humidity tank. Subsequently, the easily adhesive black polyester film for solar cells was taken out and allowed to stand at room temperature and humidity for 24 hours. Thereafter, the peel strength was measured by the same method as in (4) above, and ranked according to the following criteria.
◎: 100 N / 20 mm or more, or film breakage of film ○: 75 N / 20 mm or more, less than 100 N / 20 mm Δ: 50 N / 20 mm or more, less than 75 N / 20 mm ×: less than 50 N / 20 mm

(Polymerization of urethane resin A-1 containing aliphatic polycarbonate polyol)
In a four-necked flask equipped with a stirrer, Dimroth cooler, nitrogen inlet tube, silica gel drying tube, and thermometer, 43.75 parts by mass of 4,4-diphenylmethane diisocyanate, 12.85 parts by mass of dimethylolbutanoic acid, several 153.41 parts by mass of polyhexamethylene carbonate diol having an average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were added and stirred at 75 ° C. for 3 hours in a nitrogen atmosphere. It was confirmed that had reached the predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring and adjusted to 25 ° C., while stirring and mixing at 2000 min ⁻¹ , the polyurethane prepolymer solution was added and dispersed in water. . Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble polyurethane resin solution (A-1) having a solid content of 35%. The obtained polyurethane resin (A-1) had a glass transition temperature of -30 ° C.

(Polymerization of urethane resin A-2 containing aliphatic polycarbonate polyol)
In a four-necked flask equipped with a stirrer, a Dimroth cooler, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 29.14 parts by mass of 4,4-diphenylmethane diisocyanate, 7.57 parts by mass of dimethylolbutanoic acid, several An average molecular weight of 3000 polyhexamethylene carbonate diol 173.29 parts by mass, dibutyltin dilaurate 0.03 parts by mass, and 84.00 parts by mass of acetone as a solvent were added, and the mixture was stirred at 75 ° C. for 3 hours in a nitrogen atmosphere. It was confirmed that had reached the predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 5.17 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring and adjusted to 25 ° C., while stirring and mixing at 2000 min ⁻¹ , the polyurethane prepolymer solution was added and dispersed in water. . Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble polyurethane resin solution (A-2) having a solid content of 35%.

(Polymerization of urethane resin A-3 containing aliphatic polycarbonate polyol as a constituent)
In a four-necked flask equipped with a stirrer, Dimroth cooler, nitrogen inlet tube, silica gel drying tube, and thermometer, 43.75 parts by mass of 4,4-diphenylmethane diisocyanate, 11.12 parts by mass of dimethylolbutanoic acid, hexane 1.97 parts by mass of diol, 143.40 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were added, and 75 ° C. in a nitrogen atmosphere. The mixture was stirred for 3 hours to confirm that the reaction solution reached a predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring and adjusted to 25 ° C., while stirring and mixing at 2000 min ⁻¹ , the polyurethane prepolymer solution was added and dispersed in water. . Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble polyurethane resin solution (A-3) having a solid content of 35%.

(Polymerization of silanol group-containing urethane resin A-4 containing aliphatic polycarbonate polyol as a constituent)
In a four-necked flask equipped with a stirrer, a Dimroth cooler, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 38.41 parts by mass of isophorone diisocyanate, 6.95 parts by mass of dimethylolpropanoic acid, and a number average molecular weight of 2000 Polyhexamethylene carbonate diol 158.999 parts by mass, dibutyltin dilaurate 0.03 parts by mass, and acetone 84.00 parts by mass as a solvent were added and stirred at 75 ° C. for 3 hours in a nitrogen atmosphere. It was confirmed that the equivalent amount was reached. Next, after cooling this reaction liquid to 40 degreeC, 4.37 mass parts of triethylamine was added, and the polyurethane prepolymer solution was obtained. Next, 3.84 parts by mass of γ- (aminoethyl) aminopropyltriethoxysilane, 1.80 parts by mass of 2-[(2-aminoethyl) amino] ethanol and 450 g of water were added, and the polyurethane prepolymer solution was dropped. And dispersed in water. Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble silanol group-containing polyurethane resin solution (A-4) having a solid content of 30%.

(Polymerization of urethane resin A-5 containing aliphatic polycarbonate polyol as a constituent)
A water-soluble polyurethane resin having a solid content of 35% was obtained in the same manner except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 in the water-soluble polyurethane resin (A-1) was changed to a polyhexamethylene carbonate diol having a number average molecular weight of 1000. A solution (A-5) was obtained.

(Polymerization of urethane resin A-6 containing aliphatic polycarbonate polyol as a constituent)
A water-soluble polyurethane resin having a solid content of 35% was obtained in the same manner except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 in the water-soluble polyurethane resin (A-1) was changed to a polyhexamethylene carbonate diol having a number average molecular weight of 5000. A solution (A-6) was obtained.

(Polymerization A-7 of Polyurethane Resin Containing Polyester Polyol)
A water-soluble polyurethane resin solution (A) having a solid content of 35% was obtained in the same manner except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 of the water-soluble polyurethane resin (A-1) was changed to a polyester diol having a number average molecular weight of 2000. -7) was obtained.

(Polymerization A-8 of Polyurethane Resin Containing Polyether Polyol)
A water-soluble polyurethane resin solution having a solid content of 35% (with a solid content of 35%), except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 in the water-soluble polyurethane resin (A-1) was changed to a polyether diol having a number average molecular weight of 2000. A-8) was obtained.

(Polymerization of urethane resin A-9 containing aliphatic polycarbonate polyol as a constituent)
In a four-necked flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 32.39 parts by mass of 1,3 bis- (isocyanatomethyl) cyclohexane, dimethylolbutanoic acid 13. 09 parts by mass, 156.74 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 80.89 parts by mass of acetone as a solvent, and 3 hours at 75 ° C. in a nitrogen atmosphere The mixture was stirred and it was confirmed that the reaction solution reached a predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring and adjusted to 25 ° C., while stirring and mixing at 2000 min ⁻¹ , the polyurethane prepolymer solution was added and dispersed in water. . Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble polyurethane resin solution (A-9) having a solid content of 35%. The obtained polyurethane resin (A-9) had a glass transition temperature of -30 ° C.

(Polymerization of urethane resin A-10 containing aliphatic polycarbonate polyol)
In a four-necked flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 45.93 parts by mass of 4,4-dicyclohexyl diisocyanate, 13.09 parts by mass of dimethylolbutanoic acid, several An average molecular weight of 3000 polyhexamethylene carbonate diol (235.11 parts by mass), dibutyltin dilaurate (0.03 parts by mass), and acetone (117.66 parts by mass) as a solvent were added, and the mixture was stirred at 75 ° C. for 3 hours in a nitrogen atmosphere. It was confirmed that had reached the predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring and adjusted to 25 ° C., while stirring and mixing at 2000 min ⁻¹ , the polyurethane prepolymer solution was added and dispersed in water. . Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble polyurethane resin solution (A-10) having a solid content of 35%. The obtained polyurethane resin (A-10) had a glass transition temperature of -40 ° C.

Example 1
(1) Adjustment of coating liquid The following coating agent was mixed and the coating liquid was created.
Water 55.86% by mass
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 13.52 mass%
0.59% by mass of particles
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
Surfactant 0.03 mass%
(Silicon, solid content concentration of 100% by mass)

(2) Manufacture of easily adhesive black polyester film for solar cells (Polyester a)
After the polyethylene terephthalate resin was polymerized by a conventional method, solid phase polymerization was performed by a conventional method to produce a polyethylene terephthalate resin (raw material a) having an intrinsic viscosity of 0.69 dl / g and an acid value of 8 (eq / ton).

(Polyester b)
Silica particle-containing polyethylene terephthalate resin was polymerized by a conventional method to produce polyethylene terephthalate (raw material b) having an intrinsic viscosity of 0.62 dl / g and containing 500 ppm of agglomerated silica particles (average particle diameter of 2.0 μm). This was subjected to solid phase polymerization treatment by a conventional method to produce a polyethylene terephthalate resin (raw material b) having an intrinsic viscosity of 0.65 dl / g and an acid value of 11 (eq / ton).

(Carbon black containing masterbatch c)
After mixing raw material a and carbon black at 95 to 5 (mass ratio), 280 ° C.
The mixture was fed to a twin screw extruder adjusted to a high temperature and kneaded to produce a carbon black-containing masterbatch (raw material c).

(Carbon black-containing masterbatch d)
The raw material a and carbon black were mixed at 99 to 1 (mass ratio), and then supplied to a twin-screw extruder adjusted to 280 ° C. and kneaded to produce a carbon black-containing masterbatch (raw material d).

(Carbon black containing masterbatch e)
The raw material a and carbon black were mixed at 80 to 20 (mass ratio), then supplied to a twin screw extruder adjusted to 280 ° C. and kneaded to produce a carbon black-containing masterbatch (raw material e).

(Titanium black-containing masterbatch f)
Raw material a and titanium black (Mitsubishi Materials Co., Ltd., 13M) were mixed at 95: 5 (mass ratio), then supplied to a twin screw extruder temperature-controlled at 280 ° C. and kneaded to obtain a titanium black-containing masterbatch (raw material f ) Was manufactured.

(Titanium oxide-containing masterbatch g)
The raw material a and titanium oxide were mixed at 50:50 (mass ratio), and then supplied to a twin screw extruder adjusted to 280 ° C. and kneaded to produce a titanium oxide-containing master batch (raw material g).

(Barium sulfate-containing masterbatch h)
The raw material a and titanium oxide were mixed at 99: 1 (mass ratio), and then supplied to a twin screw extruder adjusted to 280 ° C. and kneaded to produce a barium sulfate-containing master batch (raw material h).

(Film production)
The raw material vacuum-dried under heating is supplied to the extruder as the raw material of layer A while continuously weighing and continuously stirring so that a / c = 90/10 (mass ratio). Via a feed block (co-extrusion joint).

  On the other hand, as the raw material for the B layer, the raw material that has been dried in the same manner is continuously weighed so that b / c = 96/4 (mass ratio), and is supplied to a vent type twin screw extruder and melted. The mixture was kneaded and supplied to the feed block via a filter.

  In the feed block, the B layer was bonded to both sides of the A layer so as to have the same thickness. At this time, a cooling drum having a surface temperature of 30 ° C. is supplied by controlling the resin discharge amount of the A layer and the B layer so that the thickness ratio of each layer before stretching is B / A / B = 5/90/5 Casted upward to produce an unstretched film with a thickness of 2.4 mm.

  Next, the unstretched film obtained by the above method was heated to 65 ° C. using a heating roll, and then stretched 3.2 times between rolls having different peripheral speeds. At this time, a condensing infrared heater was installed in the middle of the low-speed roll and the high-speed roll at a position facing each other across the film, and a sufficient amount of heat necessary to uniformly stretch the film was given evenly from both sides of the film. .

Subsequently, after apply | coating the said coating liquid on the single side | surface of PET film by the roll coat method, it dried at 80 degreeC for 20 second. The final coating amount after drying (after biaxial stretching) was adjusted to 0.15 g / m ² (the coating layer thickness after drying was 150 nm).

  Subsequently, the film was introduced into a tenter, and stretched 3.9 times in the width direction while heating from 120 ° C to 150 ° C. Further, heat treatment was performed by blowing hot air of 220 ° C. for 30 seconds in the tenter. Then, 2% relaxation treatment was applied in the width direction while gradually cooling to room temperature over 40 seconds to obtain an easily adhesive black polyester film for solar cells having a thickness of 100 μm. The evaluation results are shown in Table 1.

Comparative Example 1
An easy-adhesive black polyester film for solar cells was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to the polyurethane resin (A-5).

Comparative Example 2
A solar cell reester film was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to the polyurethane resin (A-6).

Comparative Example 3
The raw material of layer A is continuously weighed so that the raw material a / d = 95/5 (mass ratio) and the raw material of layer B is the raw material b / d = 95/5 (mass ratio) Was used. Moreover, the polyurethane resin was changed to the polyurethane resin (A-7). Other than this was carried out similarly to Example 1, and obtained the easily adhesive black polyester film for solar cells.

Comparative Example 4
The raw material of B layer used what measured continuously so that it might become said raw material b / d / g = 65/5/30 (mass ratio). Moreover, the polyurethane resin was changed to the polyurethane resin (A-8). Other than this was carried out similarly to Example 1, and obtained the easily adhesive black polyester film for solar cells.

Comparative Example 5
The raw material of layer A is continuously weighed so that the raw material a / g = 70/30 (mass ratio) and the raw material of layer B is the raw material b / g = 70/30 (mass ratio) Was used. Moreover, the easily adhesive black polyester film for solar cells was obtained like Example 1 except having changed the base material thickness of the easily adhesive black polyester film for solar cells into 18 micrometers.

Example 2
The raw material of layer A is continuously weighed so that the raw material a / c = 92/8 (mass ratio) and the raw material of layer B is the raw material b / c = 98/2 (mass ratio) Was used. Moreover, the easily adhesive black polyester film for solar cells was obtained like Example 1 except having changed the polyurethane resin into the polyurethane resin (A-2).

Example 3
The resin discharge amount of the A layer and the B layer was changed so that the thickness ratio of each layer before stretching was B / A / B = 10/80/10. Moreover, the easily adhesive black polyester film for solar cells was obtained like Example 1 except having changed the polyurethane resin into the polyurethane resin (A-3).

Example 4
The resin discharge amounts of the A layer and the B layer were changed so that the thickness ratio of each layer before stretching was B / A / B = 3/94/3. Moreover, the easily adhesive black polyester film for solar cells was obtained like Example 1 except having changed the polyurethane resin into the silanol group containing polyurethane resin (A-4).

Example 5
Easy-adhesive black polyester for solar cells in the same manner as in Example 1 except that the raw material of layer B was continuously weighed so that the raw material b / c / h = 90/5/5 (mass ratio). A film was obtained.

Example 6
Example 1 except that the raw material of the layer A was continuously weighed so that the raw material a / c = 92/8 (mass ratio), and an unstretched film was produced as a single layer without laminating the layer B In the same manner as above, an easily adhesive black polyester film for solar cells was obtained.

Example 7
The raw material of the A layer is continuously weighed so that the raw material a / f = 92/8 (mass ratio) and the raw material of the B layer is the raw material b / f = 98/2 (mass ratio). Was used. Moreover, the resin discharge amount of A layer and B layer was changed so that the thickness ratio of each layer before extending | stretching might become B / A / B = 10/80/10. Except this, it carried out similarly to Example 1, and obtained the easily adhesive black polyester film for solar cells.

Example 8
The resin discharge amount of the A layer and the B layer was changed so that the thickness ratio of each layer before stretching was B / A / B = 5/40/5, and the substrate thickness was changed to 50 μm. Moreover, the easily adhesive black polyester film for solar cells was obtained like Example 1 except having changed the coating liquid into the following.
61.51% by mass of water
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 8.11% by mass
0.35% by mass of particles
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
Surfactant 0.03 mass%
(Silicon, solid content concentration of 100% by mass)

Example 9
The raw material of layer A is continuously weighed so that the raw material a / f = 70/30 (mass ratio) and the raw material of layer B is the raw material b / f = 90/10 (mass ratio) Was used. Moreover, the coating liquid was changed into the following. Except this, it carried out similarly to Example 8, and obtained the easily adhesive black polyester film for solar cells.
Water 41.71% by mass
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 27.05% by mass
1.18% by mass of particles
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
Surfactant 0.06% by mass
(Silicon, solid content concentration of 100% by mass)

Example 10
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to the polyurethane resin (A-9).

Example 11
Except having changed the polyurethane resin into the polyurethane resin (A-10), it carried out similarly to Example 1, and obtained the easily adhesive polyester film for solar cells.

(3) Manufacturing Examples 12 and 13 of Back Sheet for Solar Cell
Adhesive polyester film for solar cell of Example 1 and Example 11 / Black polyester film (50 μm) / Aluminum foil (30 μm) / Polyvinyl fluoride film (38 μm) A backsheet was obtained.
Adhesive for dry laminate Takelac A-315 (Mitsui Chemicals) / Takenate A-10 (Mitsui Chemicals) = 9/1 (solid content ratio)

Examples 14 and 15
In Example 12 and Example 13, a solar cell back sheet was prepared in the same manner except that a white polyester film (50 μm) was used instead of the black polyester film (50 μm). Example 14 using the easily adhesive polyester film for solar cells of Example 14 and Example 11 using the conductive polyester film was produced. About the obtained back sheet for solar cells, an I-super UV tester SUV-W151 manufactured by Iwasaki Electric Co., Ltd. was used with the easily adhesive polyester film surface for solar cells as an irradiation surface, and 63 ° C., 50% Rh, irradiation intensity 100 mW / cm ^2. And 100 hours of continuous UV irradiation treatment. As a result of visually confirming the solar cell backsheet after the UV irradiation under a fluorescent lamp, the solar cell backsheet of Example 14 was slightly yellowed, but the solar cell backsheet of Example 15 was entirely covered. There was no change in color, and a good appearance was maintained.

  The easy-adhesive black polyester film for solar cells of the present invention is excellent in adhesiveness with a sealing material and adhesiveness under high temperature and high humidity (moisture and heat resistance). It is suitable as.

Claims (2)

A base material thickness having a coating layer on at least one side is a black polyester film having a thickness of 20 to 300 μm,
The optical density of the film is 1.0 to 5.0,
The coating layer is mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component,
The ratio (A ₁₄₆₀ / A ₁₅₃₀ ) of the absorbance (A ₁₄₆₀ ) near 1460 cm ⁻¹ derived from the aliphatic polycarbonate component and the absorbance (A ₁₅₃₀ ) near 1530 cm ⁻¹ derived from the urethane component in the infrared spectrum of the coating layer. ) Is 0.70 to 1.60, an easily adhesive black polyester film for solar cells.   The solar cell backsheet which laminated | stacked the easily-adhesive black polyester film for solar cells of Claim 1.