JP2011029397A - Back sheet for solar cell, and method of manufacturing the same - Google Patents

Abstract

An adhesive force with a sheet body is not reduced even when exposed to a wet heat environment.
A back sheet used for a solar cell module includes a sheet main body made of a first polymer and an adhesive layer provided on a first sheet surface of the sheet main body. The adhesive layer 22 includes fine particles 25 made of an inorganic compound and a second polymer that holds the fine particles 25 and is crosslinked with an oxazoline compound. The mass ratio of the fine particles 25 to the second polymer is 100% or more. The mass ratio of the oxazoline compound to the second polymer is in the range of 10% to 50%.
[Selection] Figure 2

Description

  The present invention relates to a solar cell backsheet and a method for producing the same.

  The solar cell module has a structure in which the solar cell is protected by two sheet-like protective members, and the solar cell is sealed with a sealing material between the protective members. One protective member is a surface member disposed on the light receiving surface side that receives sunlight, and the other protective member is a so-called back sheet disposed on the back side of the solar cell. The surface member is usually made of glass, and an ethylene-vinyl acetate copolymer (EVA) is usually used as the sealing material.

  The back sheet has a function of preventing moisture from entering the inside of the module from the outside on the back side. Therefore, glass is preferable to polymer from the viewpoint of preventing moisture from entering, but from the viewpoint of low cost, in recent years, it is increasingly used as a polymer. And when it is set as a polymer, in order to raise more the adhesive force with a sealing material, the contact bonding layer has come to be provided.

  In order to increase the adhesive strength of the sheet member, it is conceivable to use a compound having an oxazoline group. A compound having an oxazoline group may be included in the coating solution in advance, and when this coating solution is applied to form a coating film, it may have a function of improving the adhesive force between the coating film and the coating object. Are known. In Patent Documents 1 and 2, a polymer having an oxazoline group is used as a component of a film made of polyester.

Japanese Patent No. 3979828 JP 2008-039803 A

  However, the methods disclosed in Patent Documents 1 and 2 have a certain effect in improving the adhesive force, but are ineffective in reducing the adhesive force in a humid heat environment.

  Further, when exposed to the outside, the backsheet may be placed not only in moisture but also in a high temperature environment or exposed to light. In such a humid heat environment, the adhesive force between the back sheet and the sealing material gradually decreases, and when an adhesive layer is provided, the adhesive force between the adhesive layer and the sheet body of the back sheet also decreases.

  Then, an object of this invention is to provide the solar cell backsheet which has strong adhesive force with a sealing material, and hold | maintains adhesive force even if exposed to a humid heat atmosphere, and its manufacturing method.

  In order to solve the above problems, the present invention provides a solar cell backsheet that seals the solar cell with a sealing material between the solar cell and a surface member that protects the light-receiving surface side of the solar cell. A sheet main body, and an adhesive layer that is provided on one sheet surface of the sheet main body and adheres the sheet main body to the sealing material. The adhesive layer holds fine particles made of an inorganic substance, the fine particles, and an oxazoline group. A polymer having a second polymer crosslinked with a compound having a mass ratio of at least 100% of the fine particles to the second polymer, and a mass ratio of the compound having an oxazoline group to the second polymer of 10% or more and 50% or less. It is comprised by the range.

  The present invention is particularly effective when the first polymer is polyester, and particularly effective when the sheet body is white by including fine particles in polyethylene terephthalate as polyester. The fine particles contained in polyethylene terephthalate are preferably titanium oxide.

  The fine particles made of an inorganic material are preferably at least one oxide of silicon, tin, zirconium, and aluminum, and the second polymer is preferably any one of polyester, polyurethane, and polyolefin.

  The compound having an oxazoline group is preferably either a monomer or an oligomer.

  The adhesive layer preferably has a coating that inhibits the removal of fine particles made of an inorganic substance, and the coating is more preferably composed of a compound having an oxazoline group and a second polymer.

  Further, the method for producing a solar cell backsheet of the present invention comprises a sheet body made of a first polymer, fine particles made of an inorganic substance, a compound having an oxazoline group, and a second polymer for holding the fine particles. A coating step of forming a coating film by applying a liquid containing, a step of heating the coating film and a drying step of drying the coating film so that the second polymer is crosslinked by the compound having an oxazoline group And the coating liquid is configured such that the mass ratio of the fine particles to the second polymer is at least 100%, and the mass ratio of the compound to the second polymer is in the range of 10% to 50%. Has been.

  According to the solar cell backsheet of the present invention, the adhesive strength with the sealing material is strong, and the adhesive strength can be maintained even when exposed to a moist heat atmosphere. According to the production method of the present invention, A solar cell backsheet can be produced.

It is a section schematic diagram of a solar cell module provided with a back sheet of the present invention. It is sectional drawing of the back seat | sheet which is 1st embodiment of this invention. It is a graph which shows the relationship between the adhesive force and the mass ratio of microparticles | fine-particles. (A) shows the relationship between the two in the conventional coating film, and (B) shows the relationship between the two in the adhesive layer of the present invention. It is sectional drawing of the back seat | sheet which is the 2nd embodiment of this invention. It is the schematic of a backsheet manufacturing equipment.

  The following embodiment is an example of the present invention and does not limit the present invention.

  As shown in FIG. 1, a solar cell module (hereinafter simply referred to as a module) 10 is provided on the surface side of the cell 11 so as to protect the solar cell (hereinafter referred to as a cell) 11 and the light receiving surface side of the cell 11. The surface member 13 is provided, a back sheet 14 as a back member protecting the back side of the cell 11, and a sealing material 15 for sealing the cell 11 between the surface member 13 and the back sheet 14. Thus, the cell 11 is held by the sealing material 15 between the surface member 13 and the back sheet 14. A plurality of modules 10 are combined and used as a solar cell panel.

  As shown in FIG. 2, the back sheet 14 according to the first embodiment of the present invention is provided on the sheet main body 21 made of the first polymer and the first sheet surface 21 a of the sheet main body 21, and seals the sheet main body 21. And an adhesive layer 22 that adheres to the material 15.

  A barrier sheet 23 that protects the sheet body 21 and the adhesive layer 22 from a high humidity and high heat environment may be provided on the second sheet surface 21 b of the sheet body 21.

[Adhesive layer]
The adhesive layer 22 is formed by applying a coating liquid containing fine particles 25 made of an inorganic substance, a compound having an oxazoline group (hereinafter referred to as an oxazoline compound), and a second polymer that holds the fine particles 25 to the first sheet surface of the sheet body 21. It is formed by applying to 21a. The mass ratio between the fine particles 25 and the second polymer and the mass ratio between the oxazoline compound and the second polymer are set in predetermined ranges as described later. By applying such a coating solution, the adhesive layer 22 reacts with the fine particles 25 having a mass ratio with respect to the second polymer within a predetermined range by reacting with the oxazoline compound with a mass ratio with respect to the second polymer within a predetermined range. And a second polymer whose chains are cross-linked.

The fine particles 25 are made of an inorganic material. The fine particles 25 made of an inorganic substance have an effect of improving the adhesive force between the sealing material 15 and the sheet main body 21, particularly the adhesive force between the sealing material 15 and the sheet main body 21 after being exposed to a wet heat atmosphere. As the inorganic substance, an inorganic compound is preferable. As the inorganic compound, silicon oxide (silica, SiO ₂ ), tin oxide SnO ₂ , zirconium oxide ZrO ₂ , aluminum oxide Al ₂ O ₃ , calcium carbonate, magnesium oxide, and magnesium carbonate are preferable, among which silicon, tin, and zirconium At least one oxide with aluminum, that is, SiO ₂ , SnO ₂ , ZrO ₂ , and Al ₂ O ₃ is more preferable. This is because, when these metal oxide fine particles 25 are used, the above effect of the present invention, that is, the effect of maintaining a strong adhesive force with the sealing material 15 for a long time can be obtained more remarkably. From the viewpoint of obtaining this effect, SiO ₂ and SnO ₂ are particularly preferable.

  The particle diameter of the fine particles 25 is preferably in the range of 10 nm to 700 nm, particularly preferably in the range of 20 nm to 300 nm. In addition, the particle diameter does not have to be uniform as shown in FIG. In FIG. 2, the fine particles 25 are greatly exaggerated. The shape of the fine particles 25 may be any of a spherical shape, an indeterminate shape, and a needle shape, and these may be mixed with each other.

  The fine particles 25 are included in the adhesive layer 22 so that the mass ratio with the second polymer is at least 100%. That is, when the mass of the second polymer is 100, the mass of the fine particles 25 is at least 100. By using the fine particles 25 at this mass ratio, the adhesive force of the adhesive layer 22 is unlikely to decrease even through a wet heat environment. The mass ratio of the fine particles 25 to the second polymer will be described in detail later using another drawing.

  The second polymer is a so-called binder that holds the fine particles 25 in the adhesive layer 22. As the second polymer, acrylic resin, polyurethane, polyester, and polyolefin are preferable from the viewpoint of adhesiveness with the sealing material 15, and among them, the strength of the adhesive force with the sheet body 21 when crosslinked with an oxazoline compound and Polyurethane, polyester, and polyolefin are more preferable from the viewpoint of durability, and polyolefin is particularly preferable from the viewpoint that the adhesive strength does not decrease even under a moist heat environment. And what has a carboxyl group in a molecule | numerator has the effect that an adhesive force is maintained even if it passes through a moist heat environment. Therefore, a polyolefin having a carboxyl group is most preferable. In addition, the above various polymers may be used independently and multiple may be used together.

  The molecular weight of the second polymer is not particularly limited, and can be preferably used if the weight average molecular weight Mw is about several thousand to several tens of thousands, for example.

  The oxazoline compound is in a form in which the second polymer is cross-linked when the coating solution is solidified as described later to form the adhesive layer 22. That is, the oxazoline compound acts as a crosslinking agent that crosslinks the second polymer. The oxazoline compound is opened when the second polymer is crosslinked.

  The oxazoline compound is used in the range of 10% to 50% by mass with respect to the second polymer when preparing the coating solution. That is, when the mass of the second polymer is 100, the coating solution is prepared by setting the mass of the oxazoline compound in the range of 10 to 50. The mass ratio of the oxazoline compound to the second polymer is more preferably in the range of 20% to 40%.

  The oxazoline compound is preferably either a monomer or an oligomer. By including the monomer or oligomer oxazoline compound, the molecular chains of the second polymer are more closely cross-linked than when the polymer oxazoline compound is included, and as a result, the molecular network structure in the adhesive layer 22 becomes finer. This is because there is no unevenness in the adhesive force, and as a result, the adhesive force is less likely to be lowered even through a wet heat environment.

  In order to make the network structure in the adhesive layer 22 finer, the number of oxazoline groups in the molecule is more preferably 2 or more.

  As the oxazoline compound, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl -4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2,2'-bis- (2-oxazoline), 2,2'-methylene-bis- (2-oxazoline), 2,2′-ethylene-bis- (2-oxazoline), 2,2′-trimethylene-bis- (2-oxazoline), 2,2′-tetramethylene-bis- (2-oxazoline), 2, 2 ′ -Hexamethylene-bis- (2-oxazoline), 2,2'-octamethylene-bis- (2-oxazoline), 2,2'-ethylene-bis- (4,4'- Methyl-2-oxazoline), 2,2'-p-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene- Bis- (4,4′-dimethyl-2-oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, bis- (2-oxazolinylnorbornane) sulfide and the like can be used, and these compounds are polymerized. It may be an oligomer or a copolymer.

  As the oxazoline compound, there are various commercially available products. For example, Epocros K2010E, K2020E, K2030E, WS500, and WS700 (all manufactured by Nippon Shokubai Chemical Co., Ltd.) can be used.

  The thickness of the adhesive layer 22 is very thin such that it is in the range of 0.2 μm to 1 μm. This is because the adhesiveness is hardly lowered even when placed in a moist heat environment by controlling the thickness to 0.2 μm or more while keeping the cost low by setting it to 1 μm or less. A more preferable thickness of the adhesive layer 22 is in a range of 0.5 μm or more and 0.8 μm or less. The thickness of the adhesive layer 22 may be determined according to the particle diameter of the fine particles 25, and the thickness may be reduced as the fine particles 25 having a smaller particle diameter are used.

[Sheet body]
The sheet body 21 is obtained by forming the first polymer into a sheet shape by a melt film forming method or a solution film forming method. Although the 1st polymer used for the sheet | seat main body 21 is not restrict | limited in particular, A fluororesin and polyester are preferable. Among these, polyester is more preferable in terms of maintaining the adhesive force with the sealing material 15 by the adhesive layer 22 in addition to the cost and the wet heat environment.

  The polyester is a linear saturated polyester synthesized from a derivative having the property of forming an aromatic dibasic acid or ester (hereinafter referred to as ester forming property) and a diol or an ester forming derivative thereof. Specific examples of such polyester include polyethylene terephthalate (PET), polyethylene isophthalate, polybutylene terephthalate (PBT), and polyethylene-2,6-naphthalate.

  The polyester may be a homopolymer of the above-mentioned various polyesters or a copolymer. Furthermore, a small amount of other types of polymers such as polyimide may be blended with the polyester.

  Among the above polyesters, PET and polyethylene-2,6-naphthalate are particularly preferable in terms of balance between mechanical properties and cost.

  When the first polymer is polyester, the sheet body 21 is formed by melt-extruding the polyester into a film and cooling and solidifying it with a casting drum to form an unstretched film. The unstretched film has a temperature of Tg or higher (Tg + 60) ° C. or lower. Biaxial stretching through a longitudinal stretching step that stretches once or more in the longitudinal direction in a range and a widthwise stretching that extends from Tg to (Tg + 60) ° C. in the width direction after the longitudinal stretching step. A film is preferred. In the longitudinal direction stretching step, stretching is performed such that the length after stretching is 3 to 6 times that before stretching, and in the width direction stretching step, the width after stretching is 3 compared to before stretching in the width direction. It is preferable that the film is stretched so as to be 5 times. Furthermore, the sheet body 21 may be previously heat treated at 180 to 230 ° C. for 1 to 60 seconds.

  The thickness of the sheet body 21 is in the range of 25 μm to 300 μm. This is because this range is more preferable in terms of the balance between mechanical strength and cost.

  The sheet body 21 preferably includes fine particles 26. This is because the sheet main body 21 includes the fine particles 26 to reflect sunlight at the interface between the fine particles 26 of the sheet main body 21 and the first polymer and guide the reflected light to the cells 11. When the first polymer is polyester, the white sheet body 21 is preferably formed by including the fine particles 26. In the case of such a sheet body 21, the adhesive force between the adhesive layer 22 and the sheet body is reduced. The effect of preventing deterioration of adhesiveness in a humid heat environment is high.

The fine particles 26 are preferably so-called inorganic fine particles made of an inorganic substance. As the inorganic substance, barium sulfate, titanium dioxide or the like can be used, and among these, titanium dioxide TiO ₂ is more preferable. When polyester is used as the first polymer and the fine particles are made of titanium dioxide, the effect of preventing the adhesiveness from decreasing in the wet and heat environment of the adhesive force between the adhesive layer 22 and the sheet body appears more remarkably. Of titanium dioxide, rutile type titanium dioxide is particularly preferable.

  The average particle size of the fine particles 26 is preferably in the range of 0.1 μm to 5.0 μm. When the average particle diameter is within this range, the detachment of the fine particles 26 from the first sheet surface 21a before and during the formation of the adhesive layer 22, and the second before and during the formation of the barrier sheet 23 are performed. This is because the problem of detachment of the fine particles 26 from the two-sheet surface 21b is less likely to occur.

  The average particle diameter of the fine particles 26 is a value measured by a transmission electron microscope method described later. This transmission electron microscopy is the following method. First, the cross section of the back sheet 14 to which the fine particles 26 are added or the cross section of the sheet body 21 is observed with a transmission electron microscope, and a photograph of this cross section is obtained. In this cross-sectional photograph, 20 fine particles 26 are arbitrarily selected, and the long diameter and short diameter of each fine particle 26 are measured. However, the major axis and minor axis are the major axis and minor axis of the ellipse obtained by approximating the cross section of each fine particle 26 with an ellipse. The average of the major axis and the minor axis is taken as the particle diameter of the fine particles 26. Then, an average value of the particle diameters of the 20 fine particles 26 is obtained, and this average value is set as the average particle diameter of the fine particles 26. A scanning electron microscope may be used instead of the transmission electron microscope.

  In addition, it is preferable that the fine particles 26 have been subjected to a purification process and a classification process in advance to adjust the particle diameter and remove coarse particles larger than the above particle diameter in advance. As industrial means of the purification process, for example, a jet mill or a ball mill can be applied as a pulverizing means, and as a classification means, for example, dry or wet centrifugation can be applied.

  The amount of the fine particles 26 is preferably 5 to 40 parts by mass, more preferably 10 to 35 parts by mass when the first polymer is 100 parts by mass. By setting the amount of the fine particles 26 to this mass ratio, it is more reliable to obtain sufficient reflection performance without the fine particles 26 being detached from the sheet main body 21 or the mechanical strength of the sheet main body 21 being lowered. become.

There is no restriction | limiting in particular in the method of including the microparticles | fine-particles 26 in the sheet | seat main body 21, For example, methods like the following (1)-(3) can be used.
(1) A method of adding the fine particles 26 before the end of the transesterification or esterification reaction at the time of polyester synthesis, or a method of adding the fine particles 26 before the start of the polycondensation reaction and forming the obtained polyester into a sheet form.
(2) A method in which the fine particles 26 are added to the polyester, and the polyester to which the fine particles 26 are added is melt-kneaded to form a sheet.
(3) A method of preparing a master pellet to which a large amount of fine particles 26 are added at the time of melt kneading of polyester, mixing this with polyester pellets not containing the fine particles 26, and melt-kneading to form a sheet.

  The mass ratio of the fine particles 25 to the second polymer in the adhesive layer 22 will be described with reference to FIG. The fine particles 25 are previously used in the case where the fine particles 25 are preliminarily contained in the coating solution and a coating film is formed from the coating solution. The horizontal axis of FIG. 3 is the adhesive force of the coating film to the application object, and means that the adhesive force increases as it goes upward. The horizontal axis represents the mass ratio (unit:%) of the fine particles 25 to the mass of the binder component of the coating film. In the curve (B) showing the relationship between the adhesive force in the adhesive layer 22 of the present invention and the fine particles 25, the vertical adhesive force is the adhesive force between the adhesive layer 22 and the sheet body 21, and the horizontal fine particles 25. The mass ratio of is the mass ratio of the fine particles 25 to the second polymer. In FIG. 3, the mass ratio of the fine particles 25 is 0 (zero), that is, the adhesive force when the fine particles 25 are not contained is drawn as a reference, and the reference line is denoted by reference sign BL.

  In the conventional coating film containing the fine particles 25, as shown by the curve (A), the adhesive force gradually increases as the mass ratio increases until the mass ratio of the fine particles 25 reaches about 30%. It becomes the highest at 30 to 40%, and gradually decreases when the mass ratio exceeds this. When the mass ratio is about 90%, the adhesive strength is almost the same level as that when it is not contained, and when it exceeds approximately 90%, the adhesive strength is smaller than that when it is not contained. Moreover, if it exceeds 90%, the adhesive strength further decreases as the mass ratio increases.

  On the other hand, in the adhesive layer 22 of the present invention, as shown in the curve (B), the adhesive force to the sheet main body 21 is on the reference line BL and is not contained until the mass ratio is close to 100%. does not change. However, when the mass ratio is close to 100%, the adhesive strength is greatly increased, and even if the mass ratio is further increased or exceeded 1000%, it does not decrease. As described above, in the adhesive layer 22 in which the second polymer is crosslinked with the oxazoline compound in which the mass ratio with respect to the second polymer is in the predetermined range as described above, the mass ratio of the fine particles 25 greatly exceeds the conventional common sense. As a result, the adhesive material 15 and the sheet main body 21 have a large adhesive force. Moreover, such an adhesive layer 22 also has an effect of preventing a decrease in the adhesive strength when a wet heat environment is passed. This effect is particularly remarkable in the adhesive force to the sheet body 21. The effect of preventing a decrease in adhesive strength when such a humid heat environment is passed cannot be obtained with a conventional coating film. As described above, the mass ratio of the fine particles 25 to the second polymer is preferably 100% or more, and more preferably 120% or more from the viewpoint that the effect can be surely obtained.

  In the present invention, the upper limit of the mass ratio of the fine particles 25 to the second polymer is not particularly limited as described above, from the viewpoint of preventing the adhesive force from being lowered due to the adhesive force and the moist heat environment. However, if it exceeds 1000%, there is a concern that some of the fine particles 25 are detached from the adhesive layer 22. Therefore, in consideration of prevention of detachment, the mass ratio of the fine particles 25 is preferably 1000% or less, and more preferably 900% or less.

  In addition, even when the mass ratio of the fine particles 25 is 1000% or less, when there is a concern that the fine particles 25 may be detached from the adhesive layer 22, it is effective to use an adhesive layer as in the following second embodiment.

  As shown in FIG. 4, the adhesive layer 30 is provided on the first sheet surface 21a of the sheet body 21, and adheres the sheet body 21 to the sealing material 15 (see FIG. 1). The sheet main body 21 is the same member as the sheet main body 21 of FIG. 2 and includes fine particles 26, but the illustration is omitted.

  The adhesive layer 30 is a region including the second polymer crosslinked by the reaction of the oxazoline compound and the fine particles 25 whose mass ratio with respect to the second polymer is in the same range as that of the adhesive layer 22 of FIG. (Hereinafter referred to as a high content portion) 32 and a coating 31 that covers the high content portion 32 and suppresses the detachment of the fine particles 25 from the high content portion 32. In addition, the mass ratio with respect to the 2nd polymer of the oxazoline compound in the coating liquid for forming the high content part 32 is made into the same range as the case where the contact bonding layer 22 of FIG. 2 is formed.

  By using the adhesive layer 30 provided with the coating 31, the detachment of the fine particles 25 is reliably prevented. This coating 31 is composed of a second polymer crosslinked with an oxazoline compound in the same manner as the component excluding the fine particles 25 in the high content portion 32, and the mass ratio of the used oxazoline compound to the second polymer is shown in FIG. By setting the same range as 22 times, the effect of the adhesive force with the sealing material 15 and the prevention of the decrease in the adhesive force when the wet heat environment is passed can be obtained in the same manner as the adhesive layer 22. Further, since the high content portion 32 has the same configuration as that of the adhesive layer 22, the adhesive layer 30 has a large adhesive force with the sheet main body 21 as in the case of the adhesive layer 22. There is no decrease in adhesive strength.

  Similar to the adhesive layer 22 in the first embodiment, the thickness of the adhesive layer 30 is very thin, such as in the range of 0.2 μm to 1 μm. The thickness of the adhesive layer 22 may be determined according to the particle diameter of the fine particles 25, and the thickness may be reduced as the fine particles 25 having a smaller particle diameter are used. The ratio of the thickness T31 of the coating 31 to the thickness T32 of the high content portion 32, that is, T31 / T32 is preferably in the range of about 1/5 to 1/1. By making this ratio in a range of 1/1 or less, that is, by making the coating 31 thinner than the high content portion 32, the adhesiveness when placed in a humid heat environment is further improved and 1/5. This is because the desorption of the fine particles 25 can be prevented more reliably by the above.

  The above backsheet 14 can be manufactured by the manufacturing apparatus 41 shown in FIG. The manufacturing apparatus 41 manufactures a back sheet provided with the adhesive layer 30 on the sheet main body 21. The back sheet manufacturing apparatus 41 includes a sheet main body manufacturing unit 42 that manufactures the sheet main body 21, a first coating liquid manufacturing unit 46 that prepares a first coating liquid 43 that forms the high content rate unit 32, and a high content rate unit 32. A second coating solution production unit 48 for producing a second coating solution 48 that is applied to the coating film 31 and an adhesive layer forming unit 41 that forms the adhesion layer 30 on the sheet body 21, and a barrier sheet 23. Is further provided, a barrier sheet forming portion (not shown) is provided downstream of the adhesive layer forming portion 41. The adhesive layer forming unit 41 and the barrier sheet forming unit may not be a continuous so-called online system. The sheet main body 21 on which the adhesive layer 30 is formed is wound up in a roll shape and pulled out from this roll to form a barrier. It may be a so-called offline system that guides the sheet forming unit.

  The sheet main body manufacturing unit 42 introduces, for example, a pellet-shaped first polymer 56 that is a raw material of the sheet main body 21 into a dryer 57 and then dries the pellet, and then guides the pellet to the melt extruder 58. Extrude into film shape with machine 58. Hereinafter, the polymer compound having the film shape is referred to as a base material 61. The base material 61 is guided to the stretching machine 63.

  The stretching machine 63 is provided with a temperature adjuster (not shown) that adjusts the base material 61 to a predetermined temperature. With this temperature adjuster, the base material 61 is heated or lowered so as to reach a predetermined temperature at a predetermined timing while being conveyed.

  The stretching machine 63 performs a stretching process of applying tension in a predetermined direction while conveying the base material 61. The stretching process is performed after the longitudinal stretching process for stretching the base material 61 in the longitudinal direction, the stretching process in the width direction for stretching the base material 61 in the width direction and expanding the width, and after the stretching process in the width direction. A heating step of heating is performed. The base material 61 becomes the sheet main body 21 by the above-described steps in the stretching machine 63.

  The first coating solution 43 manufactured by the first coating solution manufacturing unit 46 is sent to the high content portion forming device 66 of the adhesive layer forming unit 51.

  The sheet main body 21 obtained by film formation in the sheet main body manufacturing unit 42 is continuously guided to the high content portion forming device 66 of the adhesive layer forming portion 51 to form the high content portion 32. The high content portion forming apparatus 66 includes a coating machine 71 that coats the first coating liquid 43 on the sheet main body 21 and a dryer 72 that dries the first coating liquid 43 on the sheet main body 21. With this high content portion forming device 66, a coating film of the first coating solution 43 is formed on the sheet main body 21 being conveyed, and this coating film is dried with a dryer 72 to form the high content portion 32. .

  The sheet body 21 on which the high content portion 32 is formed is continuously guided to the coating forming portion 67. The coating forming unit 67 includes a coating machine 75 that applies the second coating solution 47 manufactured by the second coating solution manufacturing unit 48 to the high content portion 32 formed in the sheet main body 21, and the second coating solution 47. And a heater 76 that heats and dries. The coating forming unit 67 applies the second coating liquid 47 to the conveyed sheet body 21, and the coating film is dried by heating with a heater 76 to form the coating 31.

  Due to the heating of the heater 72 and the heater 76, the oxazoline compound reacts with the second polymer to crosslink the second polymer. That is, both the heating process for heating the coating film and the drying process for the coating film are performed by the dryers 72 and 76. Note that when the adhesive layer 22 is formed instead of the adhesive layer 30, the coating forming portion 67 is not necessary.

  The formation method in particular of the high content part 32 and the coating | cover 31 is not restrict | limited, What is necessary is just to select suitably according to the objective and apply | coat. For example, the application | coating by a spin coater, a roll coater, a bar coater, and a curtain coater is mentioned.

  In the heat drying of the applied first coating solution 43 and second coating solution 47, the temperature of each coating film is at least 100 ° C., that is, a temperature of 100 ° C. or higher, more preferably a temperature of 130 ° C. or higher. As described above, heating is performed by the heaters 72 and 76.

  Using the back sheet manufacturing apparatus 41 described above, 17 types of back sheets 14 were manufactured in each of Experiments 1 to 17. In this example, the barrier sheet 23 was not provided.

  The first polymer of the sheet body 21 is polyester, and the type is shown in Table 1. Titanium oxide was used as the fine particles 26. The type of oxazoline compound in the adhesive layer 22, the amount used in the first coating solution 43, and the amount of tin oxide as the fine particles 25 are respectively "type" column, "content" column, and "content" column of "Oxazoline compound" in Table 1. It is shown in the “content” column of “fine particles”. The type of the second polymer is shown in the “Polymer” column of “Adhesive layer” in Table 1. In this “polymer” column, “S75N” is a polyolefin polymer Chemipearl S75N manufactured by Mitsui Chemicals, and “S120” is a polyolefin polymer Chemipearl S120 manufactured by Mitsui Chemicals.

  The obtained back sheet 14 was evaluated for adhesive strength and evaluation of the degree of desorption of the fine particles 25. The evaluation of the adhesive strength is performed for each of those not subjected to the wet heat environment and those subjected to the wet heat environment, and the results are shown in the “1” column of Table 1 for the former and the “2” column for the latter. Here, “having a moist heat environment” means that the back sheet 14 was exposed to an atmosphere of 105 ° C. and a relative humidity of 100% RH for 144 hours.

  The evaluation of adhesive strength was performed by the following method. First, from each backsheet 14 obtained, two samples having a length of 120 mm and a width of 50 mm were cut out. The sample cut out in this way is hereinafter referred to as a backsheet sample. The sheet main body 21 of the two backsheet samples is exposed to the outside, and EVA (ethylene-vinyl acetate co-polymer) having a length of 80 mm, a width of 20 mm, and a thickness of 500 μm is provided between the two backsheet samples. The union, ethylene: vinyl acetate = 70: 30 (weight ratio) was sandwiched, and EVA and two backsheet samples were pressed and adhered at 130 ° C. for 3 minutes. The pressure load is 3 kgf (= 3 × 9.8 N). Thereafter, heat treatment is performed at 150 ° C. for 30 minutes to completely adhere the two backsheet samples and EVA. Thus, what adhered two backsheet samples and EVA is called an EVA laminated sample in the following description.

  The EVA laminated sample was cut into a width of 8 mm. Then, the cut EVA laminated sample is pulled in the vertical direction at a rate of 100 mm / min, with the upper and lower two backsheet samples so that the thickness direction is the vertical direction, and a known T-shaped peel test is performed. At this time, the peel force was continuously measured, and the maximum value was obtained from the continuously measured values. This test was performed on three EVA laminated samples, and the maximum value was measured for each. And the average value of the three measured maximum values was made into the adhesive force of the backsheet 14 and EVA.

Based on the obtained adhesive strength, “adhesiveness” was evaluated according to the following evaluation criteria. Those practically acceptable are those classified into levels 3 to 5.
5; Sample breaks without interface peeling 4; Peeling force is 50N or more 3; Peeling force is 20N or more and less than 50N 2; Peeling force is 5N or more and less than 20N 1; Less than 5N and peeling occurred during wet heat environment test

  Further, the degree of desorption of the fine particles 25 was evaluated by the following method. A 5 cm × 5 cm sample was cut out from the obtained backsheet 14. The exposed surface of the adhesive layer 22 of the cut back sheet sample was turned down, and the back sheet sample was stacked on the black paper so that the exposed surface was in contact with the black paper. Then, a load of 5 kgf (= 5 × 9.8 N) was applied from above. In this state, the back sheet sample was slid on the black paper at a speed of 1 cm / second. The black paper after the distance of 20 cm was reciprocated five times and the surface of the adhesive layer 22 of the back sheet sample were visually observed. The test was performed three times on the same backsheet, that is, three backsheet samples were cut out from one backsheet, and these three backsheets were used. The average value of these three tests was determined.

Based on the average value obtained as described above, the degree of desorption was evaluated according to the following evaluation criteria. Those practically acceptable are those classified into levels 3 to 5. The evaluation results are shown in the “Degree of powder fall” column of Table 1. Note that the scratches on the adhesive layer 22 in the following evaluation criteria are formed by the fine particles 25 detached from the adhesive layer 22, and are related to the degree of desorption of the fine particles 25.
5: No change is observed on the black paper or the surface of the adhesive layer 22.
4; No change is seen in the black paper, but the adhesive layer 22 is slightly scratched on the surface.
3: Very few fine particles 25 detached on the black paper are seen, and slight scratches are also confirmed on the surface of the adhesive layer 22.
2; Fine particles 25 detached on the black paper are seen, and scratches are confirmed on the surface of the adhesive layer 22.
1; Fine particles detached on the black paper are clearly confirmed, and clear scratches are also confirmed on the surface of the adhesive layer 22.

[Comparative example]
As comparative examples for the present invention, Comparative Experiments 1 to 6 shown in Table 1 were performed. Other conditions were the same as in Example 1, and the barrier sheet 23 was not provided as in Example 1.

  Each of the backsheets obtained in Comparative Experiments 1 to 6 was evaluated in the same manner as in Example 1. Each evaluation result is shown in Table 1. Since the back sheet obtained in Comparative Experiment 6 was unacceptable as a back sheet due to severe coating unevenness of the applied layer, the degree of adhesion and the degree of detachment of fine particles were evaluated. There wasn't. For this reason, in the columns of “Adhesiveness” and “Degree of powder fall” in Table 1, “Surface defect” is described.

  The back sheet 14 provided with the adhesive layer 30 was manufactured using the back sheet manufacturing apparatus 41 with a barrier sheet forming part added thereto. Experiments according to the present invention are referred to as “experiments”, and those not included in the present invention are referred to as “comparative experiments”. In Example 2, the barrier sheet 23 was not provided. The composition of the first coating solution 43 that forms the high content portion 32 and the second coating solution 47 that forms the coating 31 are shown in Table 2.

  Each backsheet obtained was evaluated in the same manner as in Example 1 for adhesiveness and the degree of desorption of the fine particles 25. The evaluation results are shown in Table 2.

DESCRIPTION OF SYMBOLS 10 Solar cell module 11 Cell 13 Surface member 14 Back sheet 15 Sealing material 21 Sheet body 22, 30 Adhesive layer 31 Coating 32 High content rate part

Claims (10)

In the solar cell backsheet for sealing the solar cell with a sealing material between the surface member protecting the light receiving surface side of the solar cell,
A sheet body made of a first polymer;
Provided on one sheet surface of the sheet body, and an adhesive layer for bonding the sheet body to the sealing material,
The adhesive layer includes fine particles made of an inorganic substance and a second polymer that holds the fine particles and is crosslinked with a compound having an oxazoline group,
The mass ratio of the fine particles to the second polymer is at least 100%, and the mass ratio of the compound having an oxazoline group to the second polymer is in the range of 10% to 50%. Back sheet.   The solar cell backsheet according to claim 1, wherein the first polymer is polyester.   The solar cell backsheet according to claim 2, wherein the sheet main body is white by including fine particles in polyethylene terephthalate as the polyester.   The solar cell backsheet according to claim 3, wherein the fine particles contained in the polyethylene terephthalate are titanium oxide.   The solar cell backsheet according to any one of claims 1 to 4, wherein the inorganic fine particles are at least one oxide of silicon, tin, zirconium, and aluminum.   The solar cell backsheet according to any one of claims 1 to 5, wherein the second polymer is any one of polyester, polyurethane, and polyolefin.   The solar cell backsheet according to any one of claims 1 to 6, wherein the compound having an oxazoline group is any one of a monomer and an oligomer.   The solar cell backsheet according to any one of claims 1 to 7, wherein the adhesive layer has a film that suppresses detachment of the fine particles made of the inorganic substance.   9. The solar cell backsheet according to claim 8, wherein the coating film comprises the compound having the oxazoline group and the second polymer. An application step of forming a coating film by applying a liquid containing fine particles made of an inorganic substance, a compound having an oxazoline group, and a second polymer for holding the fine particles to a sheet body made of a first polymer; ,
Heating the coating film so that the second polymer is crosslinked by the compound having the oxazoline group;
A drying step of drying the coating film,
The coating solution is characterized in that the mass ratio of the fine particles to the second polymer is at least 100%, and the mass ratio of the compound to the second polymer is in the range of 10% to 50%. A method for producing a solar cell backsheet.

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