WO2011068132A1

WO2011068132A1 - Readily bondable polyester film for solar cells

Info

Publication number: WO2011068132A1
Application number: PCT/JP2010/071513
Authority: WO
Inventors: 晃侍伊藤; 寛子矢吹; 森　憲一
Original assignee: 東洋紡績株式会社
Priority date: 2009-12-02
Filing date: 2010-12-01
Publication date: 2011-06-09
Also published as: CN102639615B; KR101421360B1; CN102639615A; KR20120098786A; TW201132499A; TWI409171B

Abstract

Provided are: a readily bondable polyester film for solar cells which exhibits excellent adhesiveness; and a back sheet using the same. A polyester film which bears a coating layer on at least one surface thereof and which has a base sheet thickness of 20 to 500μm, wherein the coating layer comprises, as the main component, a urethane resin containing an aliphatic polycarbonate polyol as a constituent component, and exhibits, in the infrared spectroscopy, a ratio of absorbance in the vicinity of 1460cm^-1 to that in the vicinity of 1530cm^-1 of 0.70 to 1.60, the former absorbance being assignable to the aliphatic polycarbonate component and the latter absorbance being assignable to the urethane component.

Description

Easy-adhesive polyester film for solar cells

The present invention relates to an easily adhesive polyester film for solar cells. Specifically, it is a polyester film excellent in adhesion with a sealant even under high temperature and high humidity.

In recent years, solar cells have attracted attention as an energy alternative to petroleum energy, which causes global warming. A solar cell is a photovoltaic power generation system that directly converts sunlight energy into electricity. As solar cell elements, semiconductors such as single crystal silicon, polycrystalline silicon, and amorphous silicon, compound-based, or organic dyes are used. In general, several to several tens of solar cell elements are wired in series and in parallel, and various types of packaging are performed to protect the elements over a long period of time (about 20 years or more). A unit incorporated in this package is called a solar cell module.

The solar cell module is generally composed of a plurality of layers such as a surface that is exposed to sunlight with glass, the solar cell element is filled with a sealing material, and the back surface is called a back sheet, such as a heat-resistant, weather-resistant plastic material. The structure is protected by a protective sheet. 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. A module is produced by stacking the above glass substrate / sealing material / solar cell element / sealing material / back sheet and 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 A laminated structure such as a film (antifouling layer) has been proposed. The backsheet serves to protect 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, a polyester film that has not been subjected to a surface treatment 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).

JP 2006-152013 A JP 2006-332091 A JP 2007-48944 A JP 2007-136911 A

Solar cell modules used outdoors under harsh environmental conditions are expected to have a long service life of 20 years or more. For this reason, not only the initial adhesiveness but also the high adhesiveness of the sealing material easy-adhesive film used as a member must be maintained for a long period of time even 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 kinds of compositions 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 conventionally considered to be unavoidable, and has various sealing properties. It is an object of the present invention to provide an easily adhesive polyester film for solar cells that has good adhesion to a stopper.

As a result of intensive studies to solve the above problems, the present inventor has found that the polyester film has a coating layer on at least one surface, and the coating layer includes a urethane resin having an aliphatic polycarbonate polyol as a constituent component, In the case where the main component is a urethane resin having an aromatic polycarbonate polyol as a constituent component, the absorbance (A ₁₄₆₀ ) around 1460 cm ⁻¹ derived from the aliphatic polycarbonate component and the vicinity of 1530 cm ⁻¹ derived from the urethane component in the infrared spectrum. By using a coating layer having a ratio (A ₁₄₆₀ / A ₁₅₃₀ ) to the absorbance (A ₁₅₃₀ ) of 0.70 to 1.60, strong adhesiveness that can withstand even harsh environments can be achieved. The present inventors have found that excellent adhesiveness can be obtained even under humidity, and have reached the present invention.
Further, when the coating layer is mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component and a cross-linking agent as main components, the absorbance in the vicinity of 1460 cm ⁻¹ derived from the aliphatic polycarbonate component (A ₁₄₆₀ ) in the infrared spectrum. and 1530 cm ^-1 near the absorbance derived from urethane component by the ratio of _{_{_{(a 1530) (a 1460 /}}} a 1530) is to 0.50 to 1.55, even for various sealant, high temperature and high The present inventors have found that excellent adhesiveness can be obtained even under humidity, and have reached the present invention.

The above-described problem can be achieved by the following solution means.
(1) An easily adhesive polyester for solar cells, which is a polyester film having a substrate thickness of 20 to 500 μm having an application layer on at least one surface, and the application layer contains a urethane resin containing an aliphatic polycarbonate polyol as a constituent component the film.
(2) The coating layer is mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component, and the absorbance in the vicinity of 1460 cm ⁻¹ derived from the aliphatic polycarbonate component (A _{1460) in the} infrared spectrum of the coating layer. ) And the absorbance (A ₁₅₃₀ ) in the vicinity of 1530 cm ⁻¹ derived from the urethane component (A ₁₄₆₀ / A ₁₅₃₀ ) is 0.70 to 1.60.
(3) The coating layer is mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component and a cross-linking agent, and the absorbance around 1460 cm ⁻¹ derived from the aliphatic polycarbonate component in the infrared spectrum of the coating layer. _{(a 1460)} and 1530 cm ^-1 near the absorbance derived from urethane component ratio of _{_{_{(a 1530) (a 1460 /}}} a 1530) is 0.50 to 1.55 the sun highly adhesive polyester film for batteries.
(4) The solar cell easily adhesive polyester film, wherein the crosslinking agent is at least one crosslinking agent selected from a melamine crosslinking agent, an isocyanate crosslinking agent, a carbodiimide crosslinking agent, and an oxazoline crosslinking agent.
(5) The said easily adhesive polyester film for solar cells whose content of the said crosslinking agent in the said application layer is 5 to 90 mass% with respect to urethane resin.
(6) The said polyester film is a white polyester film, The said easily adhesive polyester film for solar cells.
(7) A solar cell backsheet in which the solar cell easy-adhesive polyester film is laminated.

The easily-adhesive polyester film for solar cells of the present invention exhibits strong adhesion, and is particularly excellent in adhesion (humidity 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. Moreover, as a preferable embodiment of the present invention, when the easily adhesive polyester film for solar cell of the present invention is used as a member of a back sheet, the adhesiveness with a sealing material is good.

(Polyester film)
The polyester resin constituting the substrate in the present invention includes polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polymethylene terephthalate, and copolymerization components such as diethylene glycol, neopentyl glycol, polyalkylene glycol, etc. Polyester resins obtained by copolymerizing diol components, dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid can be used.

The polyester resin suitably used in the present invention mainly contains at least one of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate as a constituent component. Among these polyester resins, polyethylene terephthalate is most preferable from the balance between physical properties and cost. Moreover, these polyester films can improve chemical resistance, heat resistance, mechanical strength, etc. by biaxially stretching.

The polyester film of the present invention may be a single-layer polyester film or a polyester film composed of at least three layers having an outermost layer and a center layer.

In the case of the three-layer structure in the present invention, particles are contained in the outermost layer (A layer in the case of the above-mentioned two types and three layers), and particles are substantially contained in the central layer (B layer in the case of the above two types and three layers). May not be included. The reason why it is preferable to include particles in the A layer is that when the polyester film of the present invention is used as a member for a solar cell, a metal or a moisture-proof functional layer such as a metal oxide thin film layer or a coating layer, This is for improving the handling property in the post-processing step such as laminating a fouling functional layer. When particles are added to the outermost layer, sufficient handling properties suitable for processability can be obtained.

The reason why it is preferable that the B layer substantially does not contain particles is to reduce the probability of formation of protrusions due to aggregates of lubricant particles, particularly inorganic particles. Further, by adopting such a configuration, a highly transparent film can be obtained, which is suitable for a field requiring transparency, such as a see-through solar cell.

Note that “substantially free of inert particles” means, for example, in the case of inorganic particles, when the element derived from the particles is quantitatively analyzed by fluorescent X-ray analysis, it is less than 50 ppm, preferably less than 10 ppm. Preferably, the content is below the detection limit. This is because even if particles are not added positively, contaminants derived from foreign substances and raw material resin or dirt attached to the line or equipment in the film manufacturing process may be peeled off and mixed into the film. It is.

These layers can contain various additives in the polyester, if necessary. Examples of the additive include an antioxidant, a light resistance agent, an antigelling agent, an organic wetting agent, an antistatic agent, an ultraviolet absorber, and a surfactant.

The type and content of the particles contained in the outermost layer may be inorganic particles or organic particles, and are not particularly limited. Examples thereof include inorganic particles that are inert to metal oxides such as silica, titanium dioxide, talc, and kaolinite, and polyesters such as calcium carbonate, calcium phosphate, and barium sulfate. Any one of these inert inorganic particles may be used alone, or two or more thereof may be used in combination.

The above particles preferably have an average particle size of 0.1 to 3.5 μm. The lower limit of the average particle diameter is more preferably 0.5 μm, further preferably 0.8 μm, and still more preferably 1.0 μm. Further, the upper limit of the average particle is more preferably 3.0 μm, still more preferably 2.8 μm. If the average particle size is less than 0.1 μm, sufficient handling properties cannot be obtained. When it exceeds 3.5 μm, coarse protrusions are likely to be generated.

These particles are preferably porous particles, particularly porous silica. The porous particles are preferable because they are easily deformed into a flat shape when stretched in the film forming process and the decrease in transparency is small.

The content of the inorganic particles in the outermost layer is preferably 0.01 to 0.20% by mass with respect to the polyester constituting the outermost layer. The lower limit of the concentration is more preferably 0.02% by mass, and further preferably 0.03% by mass. Further, the upper limit of the concentration is more preferably 0.15% by mass, and further preferably 0.10% by mass. If it is less than 0.01% by mass, sufficient handling properties cannot be obtained. If it exceeds 0.2% by mass, the transparency is lowered, which is not preferable.

The average particle diameter of the particles can be measured by the following method.
Take a photograph of the particles with an electron microscope or an optical microscope and at a magnification such that the size of one smallest particle is 2 to 5 mm, the maximum diameter of 300 to 500 particles (in the case of porous silica, Particle diameter) is measured, and the average value is taken as the average particle diameter. Moreover, when calculating | requiring the average particle diameter of the particle | grains in the coating layer of a laminated film, the cross section of a laminated film is image | photographed by 120,000 times magnification using a transmission electron microscope (TEM), and the largest diameter of a particle | grain is calculated | required. Can do.

As a method of blending the above particles with polyester, a known method can be adopted. For example, it can be added at any stage for producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or after the end of the ester exchange reaction and before the start of the polycondensation reaction. The polycondensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a method of blending dried particles and a polyester raw material using a kneading extruder It can be carried out.

The film of the present invention preferably uses a white polyester film as a polyester film so that reflected light can be used from the viewpoint of improving the photoelectric conversion efficiency of the solar cell. In order to provide effective light reflectivity, the white polyester film should have an L value of 85.0 to 100, an a value of -10.0 to +10.0, and a b value of -10.0 to +10.0. Is preferred. If it is this range, the reflectance of light becomes high and is preferable.

As described above, it is preferable that the base material contains a white pigment and / or inorganic particles from the viewpoint of imparting whiteness or hiding property to the polyester film of the base material and improving light reflectivity.

As the white pigment used for the white polyester film, titanium oxide, barium sulfate, zinc oxide, zinc sulfide, calcium carbonate and the like can be used. The white pigment can be subjected to various organic and inorganic surface treatments for the purpose of improving dispersibility. In particular, titanium oxide is preferable among white pigments because it has a high refractive index and can exhibit high whiteness in a small amount. Further, it is preferable to use a fluorescent brightening agent in combination because the whiteness can be further improved.

The lower limit of the content of the white pigment in the white polyester film is preferably 5% by mass, particularly preferably 8% by mass, from the viewpoint of light reflectivity. The upper limit of the white pigment content is preferably 30% by mass, more preferably 25% by mass, and particularly preferably 20% by mass from the viewpoint of film formation stability.

In addition, in order to further increase the whiteness, when a fluorescent whitening agent is used in addition to the white pigment in the base material, if the white pigment exceeds 30% by mass, the ultraviolet absorption amount of the white pigment increases. Ultraviolet rays necessary for the whitening agent to exert its effect are reduced, the fluorescent whitening effect is remarkably inhibited, and the whiteness is lowered.

In addition, in order to impart other functions to the white polyester film, inorganic particles, heat-resistant organic particles, antioxidants, crosslinking agents, ultraviolet absorbers, plasticizers having an average particle size smaller than that of the white pigment in the base material Etc. can be contained as needed.

It is also desirable that the white polyester film contains a white pigment and at least one inorganic particle having an average particle size larger than that of the white pigment. As the inorganic particles, white pigments such as titanium oxide, barium sulfate, zinc oxide, zinc sulfide, and calcium carbonate may be used, or inorganic particles having a small difference in refractive index from polyester such as silica may be used. When two types of white pigments having different average particle diameters are used, the white pigments may be the same type or different types. In short, it is desirable from the viewpoint of light reflectivity and handling properties that two types of inorganic particles having different average particle sizes are used and the inorganic particles having a small average particle size are white pigments. As the inorganic particles having a large average particle size, silica is preferable from the viewpoints of cost and handleability.

The upper limit value of the average particle diameter of the inorganic particles contained in the white polyester film is important to be 5.0 μm from the viewpoint of appearance in post-processing, preferably 3.0 μm, particularly preferably 2.0 μm. It is. Further, the lower limit of the average particle diameter of the inorganic particles contained in the base film is preferably 0.5 μm, particularly preferably from the viewpoint of slipperiness in the film production process and the post-processing process. 7 μm.

The white polyester film may be a single layer or a multilayer. For example, when the layer containing the white pigment and / or inorganic particles is an A layer and the other layers are a B layer and a C layer, A / B / A, A / B / C, C / A / B / Layer configurations such as A, C / A / B / A / C, C / A / B, etc. can be selected. In particular, when the B / A / B layer has a two-type / three-layer structure, the B layer may not contain particles, and in order to further improve the light reflectivity, a white pigment is used in the same manner as the A layer. In addition, inorganic particles, heat-resistant organic particles, or the like may be included. Furthermore, in order to further improve the whiteness, a fluorescent whitening agent may be contained in the B layer as long as the effects of the present invention are not impaired.

In addition, the white polyester film is preferably a cavity-containing film in which a polyester resin and a thermoplastic resin incompatible with the polyester resin are contained as a cavity-forming agent and then a cavity is formed by stretching in at least one direction.

The thickness of the polyester film serving as the substrate of the present invention is 20 to 500 μm, more preferably 25 to 450 μm, and still more preferably 30 to 300 μm. When the substrate thickness is thin, the influence of heat shrinkage is large, and the adhesiveness after high temperature and high humidity treatment may be reduced. If it is thick, it cannot be wound as a roll.

(Coating layer)
The easily adhesive polyester film for solar cells of the present invention is characterized by containing a urethane resin containing an aliphatic polycarbonate polyol as a constituent component.
In particular, when a urethane resin containing an aliphatic polycarbonate polyol as a main component is used as a coating layer as a coating layer, an absorbance around 1460 cm ⁻¹ derived from an aliphatic polycarbonate component (A ₁₄₆₀ ) as measured by infrared spectroscopy. It is important that the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) of the absorbance (A ₁₅₃₀ ) near 1530 cm ⁻¹ derived from the urethane component is 0.70 to 1.60. Further, when the coating layer is mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component and a cross-linking agent as main components, the absorbance in the vicinity of 1460 cm ⁻¹ derived from the aliphatic polycarbonate component (A ₁₄₆₀ ) in the infrared spectrum. It is important that the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) between the light absorption and the absorbance (A ₁₅₃₀ ) near 1530 cm ⁻¹ derived from the urethane component is 0.50 to 1.55. 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 in the above-mentioned patent documents 1 to 4, it is desirable that the conventional technical common sense positively introduces a cross-linking structure in forming the coating layer to make the coating layer rigid and strong, in order to improve the durability of the 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 a module is packaged, thermocompression bonding is performed at a high temperature in a configuration in which a polyester film (coating layer) having a glass substrate / sealing material / 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 the present invention, a coating layer mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component, and an absorbance around 1460 cm ⁻¹ derived from an aliphatic polycarbonate component measured by infrared spectroscopy (A ₁₄₆₀ ) and the absorbance (A ₁₅₃₀ ) in the vicinity of 1530 cm ⁻¹ derived from the urethane component (A ₁₄₆₀ / A ₁₅₃₀ ) are 0.70 to 1.60, so that the above characteristics can be achieved. 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, Since heat resistance and hydrolysis resistance are maintained, it is considered that deterioration of the coating layer can be prevented.

Here, the absorbance (A ₁₄₆₀ ) in the vicinity of 1460 cm ⁻¹ is derived from the bending vibration specific to the C—H bond in the methylene group contained in the aliphatic polycarbonate component. Therefore, the absorbance (A ₁₄₆₀ ) in the vicinity of 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 around 1530 cm ⁻¹ (A ₁₅₃₀ ) originates from the variable vibration that is characteristic of the N—H bond contained in the urethane component. Therefore, the magnitude of 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 above aspect, the present invention can exhibit strong adhesiveness with the sealing material and can improve the adhesiveness (humidity heat resistance) under high temperature and high humidity. Further, the configuration of the present invention will be described in detail below.

Further, when the coating layer is mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component and a cross-linking agent, absorbance in the vicinity of 1460 cm ⁻¹ derived from the aliphatic polycarbonate component in the infrared spectrum (A ₁₄₆₀ ). When the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) of the light absorbency (A ₁₅₃₀ ) in the vicinity of 1530 cm ⁻¹ derived from the urethane component is 0.50 to 1.55, in addition to satisfying the above characteristics, various sealing It has versatility that can be widely applied to materials.

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. For example, in the case of a sealing material of standard cure type, heat treatment (for example, 30 to 50 minutes at 140 to 160 ° C.) is performed after temporary bonding by thermocompression bonding (for example, 90 to 130 ° C. for 5 to 10 minutes), and sealing is performed slowly. Adhesive conditions for curing the stop material are employed. On the other hand, in the case of a fast-cure type sealing material, an adhesive condition is employed in which heat-pressure bonding (for example, 15 to 20 minutes at 140 to 160 ° C.) is performed in a short time and the sealing material is rapidly cured. Therefore, there is a demand for a highly versatile and easy-to-adhere film that can cope with various bonding conditions as well as high versatility that exhibits the same level of adhesion to various sealing materials. On the other hand, the generation of stress accompanying thermal contraction of the film that occurs during thermocompression bonding can also vary depending on various types of sealing materials and bonding conditions. In particular, in the standard cure type that takes a high temperature for a long time, the stress change accompanying the thermal contraction becomes large. As a result, when various sealing materials are applied, the stress may not be alleviated, and adhesion with the sealing material may be reduced. In particular, in the case of high-temperature thermocompression bonding in a short time like the fast cure type, it is considered that the sealing material partially dissolved in the coating layer is eroded, and the adhesiveness with the film substrate after the high-temperature and high-humidity treatment is deteriorated. It is done. Therefore, it is desirable to make the cross-linking structure of the coating layer stronger with the cross-linking agent and to make these conflicting properties compatible.

In the present invention, it is a coating layer mainly composed of a urethane resin having a aliphatic polycarbonate polyol as a constituent component and a cross-linking agent, and has a wavelength of about 1460 cm ⁻¹ derived from the aliphatic polycarbonate component measured by infrared spectroscopy. When the ratio of the absorbance (A ₁₄₆₀ ) to the absorbance (A ₁₅₃₀ ) in the vicinity of 1530 cm ⁻¹ derived from the urethane component (A ₁₄₆₀ / A ₁₅₃₀ ) is 0.50 to 1.55, the above characteristics are compatible. . The ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is 0.50 to 1.55, and the lower limit of the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is preferably 0.60, and more preferably 0.70. The upper limit of the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is preferably 1.45, more preferably 1.35, and even more preferably 1.25. This makes it possible to relieve stress due to thermal shrinkage of the film during thermal bonding at high temperatures, so that strong adhesiveness can be obtained even under various sealing materials and bonding conditions. It is believed that the coating layer can be prevented from deteriorating because it retains heat resistance and hydrolysis resistance even in a humid environment. The reason why the preferable ratio range shifts to the crosslinking agent is considered to be due to an increase in crosslinking points by the crosslinking agent.

(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 component 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, 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. When 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 constituent of the urethane resin of the present invention include aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane. Polyaliphatic diisocyanates such as hexamethylene diisocyanate and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate, or a poly (polysiloxane) obtained by adding one or more of these compounds with trimethylolpropane or the like in advance. 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, aminoalcohols 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. From the viewpoint of imparting the flexibility of the coating layer, an aliphatic diol or diamine chain extender having a length of 4 to 10 carbon atoms in the main chain is preferred. 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 around 1530 cm ⁻¹ derived from the urethane component and to provide 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 and N-diethylethanolamine. 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.

(Additive)
In the present invention, the coating layer can contain a crosslinking agent as a main component together with the urethane resin. By including a crosslinking agent, it becomes possible to further improve the adhesiveness under high temperature and high humidity. Moreover, when making it heat-press by high temperature for a short time, the fall of the base-material adhesiveness by EVA erosion can be prevented. Therefore, highly versatile and easy-to-adhere that can be applied under various bonding conditions. As the crosslinking agent, those that react with a carboxylic acid group, a hydroxyl group, an amino group, etc. to form an amide bond, a urethane bond, or a urea bond are preferable because they are not easily deteriorated by high-temperature and high-humidity treatment. Conversely, when an ester bond or an ether bond is involved, it may be hydrolyzable, which is not preferable. Examples of the crosslinking agent suitably used in the present invention include melamine-based, isocyanate-based, carbodiimide-based, and oxazoline-based. Among these, an isocyanate type and a carbodiimide type are preferable from the viewpoint of the stability over time of the coating liquid and the effect of improving the adhesiveness under high temperature and high humidity treatment. Furthermore, it is particularly preferable to use an isocyanate-based crosslinking agent from the viewpoint that the coating layer has appropriate flexibility and suitably imparts the stress relaxation action of the coating layer. Moreover, in order to promote a crosslinking reaction, a catalyst etc. are used suitably as needed.

As content of a crosslinking agent, 5 mass% or more and 90 mass% or less are preferable with respect to urethane resin. More preferably, it is 10 mass% or more and 50 mass% or less. If the amount is small, the strength of the coating layer under high temperature and high humidity may decrease, and the adhesiveness may decrease. Adhesiveness may be reduced.

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, a catalyst etc. are used suitably as needed.

In the present invention, particles may be contained in the coating layer. 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 Inorganic particles such as soil, calcium silicate, aluminum hydroxide, hydrous halloysite, magnesium carbonate, magnesium hydroxide, (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, di Rirufutareto systems include organic particles of polyester or the like.

The particles preferably have an average particle diameter of 1 to 500 nm. The average particle size is not particularly limited, but is preferably 1 to 100 nm from the viewpoint of maintaining the transparency of the film.

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

In addition, said average particle diameter measures the maximum diameter of the 10 or more particle | grains which exist in the cross section of a coating layer by image | photographing the cross section of a laminated film at a magnification of 120,000 times using a transmission electron microscope (TEM). And can be obtained as an average value of them.

The particle content is preferably 0.5% by mass or more and 20% by mass or less. When the amount is small, sufficient blocking resistance cannot be obtained. Further, scratch resistance is deteriorated. 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 adhesion to the sealing material, for example, in the range of 0.005 to 0.5 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, as a method of providing a coating layer on a polyester film, a method of coating and drying a coating solution containing a solvent, particles and a resin on the polyester film can be mentioned. Examples of the solvent include organic solvents such as toluene, water, or 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 easily adhesive polyester film for solar cells)
The method for producing an optically easy-adhesive polyester film of the present invention will be described using a polyethylene terephthalate (hereinafter abbreviated as PET) film as an example, but is not limited to this.

After sufficiently drying the PET resin in a vacuum, it is supplied to an extruder, melted and extruded at about 280 ° C. from a T-die into a rotating cooling roll into a sheet, cooled and solidified by an electrostatic application method, and unstretched PET. Get a sheet. The unstretched PET sheet may have a single layer structure or a multilayer structure by a coextrusion method.

The obtained unstretched PET sheet is stretched 2.5 to 5.0 times in the longitudinal direction with a roll heated to 80 to 120 ° C. to obtain a uniaxially stretched PET film. Further, the end of the film is gripped with a clip, led to a hot air zone heated to 70 to 140 ° C., and stretched 2.5 to 5.0 times in the width direction. Subsequently, the film is guided to a heat treatment zone of 160 to 240 ° C., and heat treatment is performed for 1 to 60 seconds to complete crystal orientation.

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

Any known method can be used as a method for applying this coating solution to the PET 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. It is done. 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 PET 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. Further, 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 , further preferably 0.01 to 0.5 g / m ² , and more. More preferably, it is 0.01 to 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 , the blocking resistance is lowered.

(Back sheet for solar cell)
The back sheet for solar cell of the present invention comprises a 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.

As an aspect of the back sheet for solar cells of the present invention, for example, a polyester film / adhesive / metal foil having a coating layer or a film / adhesive / polyvinyl fluoride film having a metal-based thin film layer or a polyester-based highly durable moisture-proof A configuration such as a film is exemplified. Further, the polyester film of the present invention may have a configuration having the coating layer on both sides. 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, each layer of the polyester film having the coating layer, the metal foil or the metal-based thin film layer, the polyvinyl fluoride film or the polyester-based high durability moisture-proof film is integrally laminated by vacuum suction or the like and heat-pressed. A solar cell backsheet can be produced by thermocompression-bonding each of the above-mentioned layers as an integral molded body using a normal molding method such as the cation method. 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, and other heat melting adhesives, solvent-based adhesives, photo-curing adhesives, etc. whose main component is a vehicle. It is done.

Here, the high durability moisture-proof film is laminated for the purpose of improving the weather resistance. Examples of the high durability moisture-proof film include polytetrafluoroethylene (PTFE), 4-fluoroethylene-perchloroalkoxy copolymer. Polymer (PFA), 4-Fluoroethylene-6-Fluoropropylene Copolymer (FEP), 2-Ethylene-4 Fluoroethylene Copolymer (ETFE), Poly-3-Fluoroethylene (PCTFE), Polyfluoride 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. In some cases, an epoxy group-containing compound is added for the purpose of promoting adhesion and curing. Examples of the epoxy group-containing compound include triglycidyl tris (2-hydroxyethyl) isocyanurate, neopentyl glycol diglycidyl ether, and 1,6-hexanediol. Epoxy group-containing compounds such as diglycidyl ether, acrylic glycidyl ether, and 2-ethylhexyl glycidyl ether are used.

Next, the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to the following examples. The evaluation method used in the present invention is as follows.

(1) Intrinsic viscosity Based on JIS K 7367-5, a mixed solvent of phenol (60% by mass) and 1,1,2,2-tetrachloroethane (40% by mass) was used as a solvent and measured at 30 ° C.

(2) Apparent density of film Four films were cut into 5 cm squares and used as samples. Four of these were overlapped, the thickness was changed with a micrometer, and arbitrary 10 locations were measured with four significant figures, and the average value of the stacked thickness was obtained. The average value was divided by 4 and rounded to 3 significant figures to obtain an average thickness per sheet (t: μm). The mass (w: g) of the four samples was measured using an automatic upper pan balance with four significant digits, and the apparent density was determined from the following equation. The apparent density was rounded to 3 significant figures.
Apparent density (g / cm ³ ) = (w × 10 ⁴ ) / (5.00 × 5.00 × 4 × t)

(3) Color tone Films were cut into 5 cm squares and overlaid so as to be 250 μm or more, and L value, a value, and b value of the Lab display system were obtained.
(Measurement condition)
Apparatus: Color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.
Measurement method: Reflected standard light: C light source Viewing angle: 2 degrees

(4) Glass transition temperature Based on JIS K7121, the glass transition start temperature was calculated | required from the DSC curve using the differential scanning calorimeter (The Seiko Instruments Inc. make, DSC6200).

(5) Absorbance measurement by infrared spectroscopy About the obtained easily adhesive polyester film for solar cells, the coating layer was scraped off and about 1 mg of a sample 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 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

(6) Adhesiveness The prepared easy-adhesive white polyester film for solar cells was prepared by cutting out a 100 mm width × 100 mm length and an EVA sheet 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, LM-30 × 30 pressurization: 1 atm 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)
Equipment: Tensilon RTM-100 manufactured by Toyo BALDWIN
Peeling speed: 200 mm / min Peeling angle: 180 degrees

(7) Moisture and heat resistance The obtained easily adhesive white 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 white 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 condenser, 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 condenser, 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 are added, and the polyurethane prepolymer solution is 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 of urethane resin containing polyester polyol as component A-7)
A water-soluble polyurethane resin solution (A) having a solid content of 35% was prepared 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 polyester diol having a number average molecular weight of 2000. -7) was obtained.

(Polymerization polymerization of polyether resin with polyether polyol A-8)
A water-soluble polyurethane resin solution (with a solid content of 35%) was prepared 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 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 resulting polyurethane resin (A-9) had a glass transition temperature of −30 ° C.

(Polymerization of urethane resin A-10 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, 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.

(Polymerization of block polyisocyanate crosslinking agent)
100 parts by mass of a polyisocyanate compound having an isocyanurate structure using hexamethylene diisocyanate as a raw material (manufactured by Asahi Kasei Chemicals, Duranate TPA) in a flask equipped with a stirrer, a thermometer and a reflux condenser, 55 parts by mass of propylene glycol monomethyl ether acetate, 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 750) was charged and held at 70 ° C. for 4 hours in a nitrogen atmosphere. Thereafter, the reaction solution temperature was lowered to 50 ° C., and 47 parts by mass of methyl ethyl ketoxime was added dropwise. The infrared spectrum of the reaction solution was measured to confirm that the absorption of the isocyanate group had disappeared, and a block polyisocyanate aqueous dispersion (B) having a solid content of 75% by mass was obtained.

(Polymerization of oxazoline crosslinking agent)
A mixture of 58 parts by mass of ion-exchanged water and 58 parts by mass of isopropanol as an aqueous medium in a flask equipped with a thermometer, a nitrogen gas introduction tube, a reflux condenser, a dropping funnel, and a stirrer, and a polymerization initiator (2, 2 4 parts by mass of '-azobis (2-amidinopropane) dihydrochloride) was added. Meanwhile, in a dropping funnel, 16 parts by mass of 2-isopropenyl-2-oxazoline as a polymerizable unsaturated monomer having an oxazoline group, methoxypolyethylene glycol acrylate (average number of moles of ethylene glycol added: 9 moles, Shin Nakamura Chemical) A mixture of 32 parts by mass and 32 parts by mass of methyl methacrylate was added, and the mixture was added dropwise at 70 ° C. for 1 hour in a nitrogen atmosphere. After completion of dropping, the reaction solution was stirred for 9 hours and cooled to obtain a water-soluble resin solution (C) having an oxazoline group having a solid content concentration of 40% by mass.

(Polymerization of carbodiimide crosslinking agent)
A flask equipped with a stirrer, thermometer and reflux condenser was charged with 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (M400, average molecular weight 400), stirred at 120 ° C. for 1 hour, 26 parts by mass of 4′-dicyclohexylmethane diisocyanate and 3.8 parts by mass of 3-methyl-1-phenyl-2-phospholene-1-oxide (2% by weight based on the total isocyanate) as a carbodiimidization catalyst were added, and 185 under a nitrogen stream. Stir at 5 ° C. for a further 5 hours. An infrared spectrum of the reaction solution was measured, and it was confirmed that absorption at a wavelength of 2200 to 2300 cm ⁻¹ disappeared. It stood to cool to 60 degreeC, 567 mass parts of ion-exchange water was added, and the carbodiimide water-soluble resin solution (D) of 40 mass% of solid content was obtained.

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% by 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 easy-adhesive polyester film for solar cell A PET resin pellet (inherent viscosity is 0.62 dl / g) containing 0.03% by mass of silica particles having an average particle diameter of 2.5 μm as a film raw material polymer is 133 Pa. For 6 hours at 135 ° C. under reduced pressure. Then, it supplied to the extruder and melt | dissolved at about 285 degreeC. Each of the PET resins was filtered through a stainless steel filter medium (nominal filtration accuracy: 10 μm particle 95% cut) and melt extruded into a sheet. It was quenched and solidified on a rotating cooling metal roll maintained at a surface temperature of 30 ° C. to obtain an unstretched PET sheet.

The unstretched PET sheet was heated to 100 ° C. with a heated roll group and an infrared heater, and then stretched 3.5 times in the longitudinal direction with a roll group having a difference in peripheral speed to obtain a uniaxially stretched PET 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 stretched 4.0 times in the width direction at 120 ° C. with a tenter, and heated at 230 ° C. for 0.5 seconds with the length in the width direction fixed, and further at 100 ° C. for 10 seconds for 3 seconds. % Relaxation treatment in the width direction was performed to obtain a 250 μm easily adhesive polyester film for solar cells. The evaluation results are shown in Table 1.

Experimental example 1
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-5).

Experimental example 2
A reester film for a solar cell 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 1
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to polyurethane resin (A-7).

Comparative Example 2
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-8).

Comparative Example 3
A solar cell easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the substrate thickness of the solar cell easy-adhesive polyester film was changed to 5 μm.

Example 2
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-2).

Example 3
An easy-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-3).

Example 4
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to a silanol group-containing polyurethane resin (A-4).

Example 5
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 1 except that the substrate thickness of the easy-adhesive polyester film for solar cells was changed to 50 μm.

Example 6
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 1 except that the substrate thickness of the easy-adhesive polyester film for solar cells was changed to 100 μm.

Example 7
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 1 except that the substrate thickness of the easy-adhesive polyester film for solar cells was changed to 350 μm.

Example 8
Except having changed the coating liquid into the following, it carried out similarly to Example 1, and obtained the easily adhesive polyester film for solar cells.
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
Except having changed the coating liquid into the following, it carried out similarly to Example 1, and obtained the easily adhesive 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
(3) Manufacture of solar cell backsheet A dry laminate method with a configuration of easy-adhesive polyester film for solar cell / white polyester film (50 μm) / aluminum foil (30 μm) / polyvinyl fluoride film (38 μm) in Example 1. The solar cell back sheet was obtained by bonding.
Adhesive for dry lamination Takelac A-315 (Mitsui Chemicals) / Takenate A-10 (Mitsui Chemicals) = 9/1 (solid content ratio)

Example 11
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 12
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-10).

Example 13
(3) Manufacture of solar cell backsheet The dry-lamination method used in Example 11 was an adhesive polyester film for solar cell / white polyester film (50 μm) / aluminum foil (30 μm) / polyvinyl fluoride film (38 μm). The solar cell back sheet was obtained by bonding.
Adhesive for dry lamination Takelac A-315 (Mitsui Chemicals) / Takenate A-10 (Mitsui Chemicals) = 9/1 (solid content ratio)

About the back sheet for solar cells of Example 10 and Example 13, using an I-super UV tester SUV-W151 manufactured by Iwasaki Electric Co., Ltd. with an easily adhesive polyester film surface for solar cells as an irradiation surface, 63 ° C., 50% Rh, Continuous UV irradiation treatment was performed for 100 hours at an irradiation intensity of 100 mW / cm ² . As a result of visually confirming the solar cell backsheet after UV irradiation under a fluorescent lamp, the solar cell backsheet of Example 10 was slightly yellowed, but the solar cell backsheet of Example 13 was entirely exposed. There was no change in color, and a good appearance was maintained.

Example 14
(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% by 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 white polyester film for solar cells
Cavity forming agent (raw material a): 60% by mass of polymethylpentene resin, 20% by mass of polypropylene resin, and 20% by mass of polystyrene resin are mixed in pellets and supplied to a vent type twin screw extruder adjusted to 285 ° C. Manufactured.

(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).

(Titanium oxide particle-containing masterbatch c)
The above polyethylene terephthalate (raw material b) and anatase-type titanium dioxide particles (manufactured by Sakai Chemical Industry Co., Ltd.) having an average particle size of 0.2 μm are mixed at a mass ratio of 50/50, kneaded with a vent type kneading extruder, A master batch (raw material c) containing titanium particles was produced.

(Film production)
The raw material vacuum-dried under heating was continuously weighed and continuously stirred so that a / b / c = 8/82/10 (mass ratio) to obtain a raw material for the A layer. Next, this raw material was supplied to an extruder, melted and kneaded, and supplied to a feed block (co-extrusion joint) via a filter.

On the other hand, the raw material of the B layer is obtained by continuously weighing the raw material so that b / c = 80/20 (mass ratio), and is supplied to a vent type twin screw extruder and melt-kneaded, and passed through a filter. And fed to the feed block.

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, the resin discharge amount of the A layer and the B layer is controlled and supplied so that the thickness ratio of each layer before stretching is B / A / B = 10/80/10, and a cooling drum having a surface temperature of 30 ° C. Casted upward to produce an unstretched film with a thickness of 2.4 mm. At this time, 10 degreeC air was sprayed on the opposite surface of the molten polymer extruded on the cooling drum, and the molten polymer was cooled and solidified from both surfaces.

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 biaxial stretching) was adjusted so that the coating amount after drying was 0.15 g / m ² .

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. Thereafter, a 2% relaxation treatment is applied in the width direction while gradually cooling to room temperature over 40 seconds, and a void-containing laminated biaxially oriented solar cell having an apparent density of 1.10 g / cm ³ and a thickness of 250 μm. An easily adhesive white polyester film was obtained. The evaluation results are shown in Table 2.

Example 15
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 14 except that the polyurethane resin was changed to the polyurethane resin (A-2).

Example 16
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 14 except that the polyurethane resin was changed to the polyurethane resin (A-3).

Example 17
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 14 except that the polyurethane resin was changed to a silanol group-containing polyurethane resin (A-4).

Example 18
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 14 except that the polyurethane resin was changed to polyurethane resin (A-9).

Example 19
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 14 except that the polyurethane resin was changed to polyurethane resin (A-10).

Example 20
(1) Adjustment of coating liquid The following coating agent was mixed and the coating liquid was created.
Water 55.62% by mass
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 11.29% by mass
Block polyisocyanate aqueous dispersion (B) 2.26% by mass
Particles 0.71% by mass
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
0.07% by mass of particles
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

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 stretched 4.0 times in the width direction at 120 ° C. with a tenter, and heated at 230 ° C. for 0.5 seconds with the length in the width direction fixed, and further at 100 ° C. for 10 seconds for 3 seconds. % Relaxation treatment in the width direction was performed to obtain a 250 μm easily adhesive polyester film for solar cells. The evaluation results are shown in Table 3.

Experimental example 3
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the polyurethane resin was changed to the polyurethane resin (A-5).

Experimental Example 4
A reester film for a solar cell was obtained in the same manner as in Example 20 except that the polyurethane resin was changed to polyurethane resin (A-6).

Comparative Example 4
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the polyurethane resin was changed to the polyurethane resin (A-7).

Comparative Example 5
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the polyurethane resin was changed to the polyurethane resin (A-8).

Comparative Example 6
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the substrate thickness of the easy-adhesive polyester film for solar cells was changed to 5 μm.

Example 21
Except having changed the coating liquid into the following, it carried out similarly to Example 20, and obtained the easily adhesive polyester film for solar cells.
Water 58.02% by mass
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 9.47% by mass
Block polyisocyanate aqueous dispersion (B) 1.89 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)

Example 22
Except having changed the coating liquid into the following, it carried out similarly to Example 20, and obtained the easily adhesive polyester film for solar cells.
54.75% by mass of water
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 12.99% by mass
Block polyisocyanate aqueous dispersion (B) 1.52% by mass
Particles 0.71% by mass
(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 23
Except having changed the coating liquid into the following, it carried out similarly to Example 20, and obtained the easily adhesive polyester film for solar cells.
Water 57.35% by mass
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 8.12% by mass
Block polyisocyanate aqueous dispersion (B) 3.79% by mass
Particles 0.71% by mass
(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 24
Except having changed the coating liquid into the following, it carried out similarly to Example 20, and obtained the easily adhesive polyester film for solar cells.
Water 59.95% by mass
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 3.25% by mass
Block polyisocyanate aqueous dispersion (B) 6.06% by mass
Particles 0.71% by mass
(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 25
Except having changed the coating liquid into the following, it carried out similarly to Example 20, and obtained the easily adhesive polyester film for solar cells.
60.82% by mass of water
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 1.62% by mass
Block polyisocyanate aqueous dispersion (B) 6.82 mass%
Particles 0.71% by mass
(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 26
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the polyurethane resin was changed to the polyurethane resin (A-2).

Example 27
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the polyurethane resin was changed to the polyurethane resin (A-3).

Example 28
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the polyurethane resin was changed to a silanol group-containing polyurethane resin (A-4).

Example 29
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the block polyisocyanate aqueous dispersion (B) was changed to a water-soluble resin (C) having an oxazoline group.

Example 30
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the block polyisocyanate aqueous dispersion (C) was changed to the carbodiimide water-soluble resin (D).

Example 31
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the block polyisocyanate aqueous dispersion (C) was changed to imino / methylolmelamine (solid content concentration: 70% by mass).

Example 32
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the substrate thickness of the easily adhesive polyester film for solar cells was changed to 50 μm.

Example 33
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the substrate thickness of the easy-adhesive polyester film for solar cells was changed to 100 μm.

Example 34
A solar cell easy-adhesive polyester film was obtained in the same manner as in Example 20, except that the substrate thickness of the solar cell easy-adhesive polyester film was changed to 350 μm.

Example 35
Except having changed the coating liquid into the following, it carried out similarly to Example 20, and obtained the easily adhesive polyester film for solar cells.
62.82% by mass of water
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 5.67% by mass
Block polyisocyanate aqueous dispersion (B) 1.13% 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% by mass
(Silicon, solid content concentration of 100% by mass)

Example 36
Except having changed the coating liquid into the following, it carried out similarly to Example 20, and obtained the easily adhesive polyester film for solar cells.
Water 45.9 mass%
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 18.99% by mass
Block polyisocyanate aqueous dispersion (B) 3.80% by mass
1.19% 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 37
(3) Manufacture of back sheet for solar cell In the structure of Example 20 easy-adhesive polyester film for solar cell / black polyester film (50 μm) / aluminum foil (30 μm) / polyvinyl fluoride film (38 μm) by the dry laminating method. The solar cell back sheet was obtained by bonding.
Adhesive for dry lamination Takelac A-315 (Mitsui Chemicals) / Takenate A-10 (Mitsui Chemicals) = 9/1 (solid content ratio)

Example 38
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the polyurethane resin was changed to polyurethane resin (A-9).

Example 39
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 20 except that the polyurethane resin was changed to the polyurethane resin (A-10).

Example 40
(3) Manufacture of solar cell backsheet A dry laminate method with a configuration of easily adhesive polyester film for solar cell / black polyester film (50 μm) / aluminum foil (30 μm) / polyvinyl fluoride film (38 μm) of Example 38. The solar cell back sheet was obtained by bonding.
Adhesive for dry lamination Takelac A-315 (Mitsui Chemicals) / Takenate A-10 (Mitsui Chemicals) = 9/1 (solid content ratio)

About the solar cell backsheets of Example 37 and Example 40, an ISUZAWA 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 a temperature of 63 ° C, 50% Rh Continuous UV irradiation treatment was performed for 100 hours at an irradiation intensity of 100 mW / cm ² . As a result of visually confirming the solar cell backsheet after UV irradiation under a fluorescent lamp, the solar cell backsheet of Example 37 was slightly yellowed, but on the entire surface of the solar cell backsheet of Example 40. There was no change in color, and a good appearance was maintained.

Example 41
(1) Adjustment of coating liquid The following coating agent was mixed and the coating liquid was created.
Water 55.62% by mass
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 11.29% by mass
Block polyisocyanate aqueous dispersion (B) 2.26% by mass
Particles 0.71% by mass
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
0.07% by mass of particles
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

(2) Manufacture of an easily adhesive white polyester film for solar cells (cavity expressing material a)
Cavity forming agent (raw material a): 60% by mass of polymethylpentene resin, 20% by mass of polypropylene resin, and 20% by mass of polystyrene resin are mixed in pellets and supplied to a vent type twin screw extruder adjusted to 285 ° C. Manufactured.

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. Thereafter, a 2% relaxation treatment is applied in the width direction while gradually cooling to room temperature over 40 seconds, and a void-containing laminated biaxially oriented solar cell having an apparent density of 1.10 g / cm ³ and a thickness of 250 μm. An easily adhesive white polyester film was obtained. The evaluation results are shown in Table 4.

Example 42
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 41 except that the polyurethane resin was changed to the polyurethane resin (A-2).

Example 43
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 41 except that the polyurethane resin was changed to the polyurethane resin (A-3).

Example 44
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 41 except that the polyurethane resin was changed to a silanol group-containing polyurethane resin (A-4).

Example 45
An easily adhesive polyester film for solar cells was obtained in the same manner as in Example 41 except that the polyurethane resin was changed to the polyurethane resin (A-9).

Example 46
An easy-adhesive polyester film for solar cells was obtained in the same manner as in Example 41 except that the polyurethane resin was changed to polyurethane resin (A-10).

Since the easily adhesive polyester film for solar cells of the present invention is excellent in adhesiveness with a sealing material and adhesiveness (moisture and heat resistance) under high temperature and high humidity, it is used as an innermost base film of a solar cell backsheet. Is preferred.

Claims

A polyester film having a substrate thickness of 20 to 500 μm and having a coating layer on at least one surface;
The easily adhesive polyester film for solar cells, wherein the coating layer contains a urethane resin containing an aliphatic polycarbonate polyol as a constituent component.
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. The easily adhesive polyester film for a solar cell according to claim 1, wherein the) is 0.70 to 1.60.
The coating layer is mainly composed of a urethane resin and a cross-linking agent having aliphatic polycarbonate polyol as constituent components,
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. The easy-adhesive polyester film for solar cells according to claim 1, wherein) is 0.50 to 1.55.
The easily adhesive polyester for solar cells according to claim 3, wherein the crosslinking agent is at least one crosslinking agent selected from a melamine crosslinking agent, an isocyanate crosslinking agent, a carbodiimide crosslinking agent, and an oxazoline crosslinking agent. the film.
The easily adhesive polyester film for solar cells according to claim 3, wherein the content of the crosslinking agent in the coating layer is 5% by mass or more and 90% by mass or less with respect to the urethane resin.
The easily adhesive polyester film for solar cells according to any one of claims 1 to 5, wherein the polyester film is a white polyester film.
A solar cell backsheet comprising the solar cell easy-adhesive polyester film according to claim 1 laminated thereon.