JP2012007087A - Ethylene-vinyl acetate copolymer film, and laminated glass and solar cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ethylene-vinyl acetate film that prevents blocking during storing or during use and suppresses occurrence of heat shrinkage.SOLUTION: This ethylene-vinyl acetate copolymer film includes a composition containing an ethylene-vinyl acetate copolymer and crosslinking agent, and has an embossment on at least one surface of the film. The content of vinyl acetate repeating unit of the ethylene-vinyl acetate copolymer is 26-28 mass% with reference to the mass of the ethylene-vinyl acetate copolymer. The arithmetic mean roughness Ra(JIS-B0601(2001)) of the surface having the embossment is 3.0 μm or higher and 20 μm or lower. The average length RSm(JIS-B0601(2001)) of the roughness curve element of the surface having the embossment is 300 μm or longer and shorter than 600 μm.

Description

  The present invention relates to a film having an ethylene-vinyl acetate copolymer as a main component, and particularly to a film in which blocking is prevented and shrinkage during heat curing is suppressed.

  Conventionally, a film made of a composition containing an ethylene vinyl acetate copolymer (hereinafter abbreviated as EVA) as a main component (hereinafter also referred to as an ethylene-vinyl acetate copolymer film (EVA film)) is inexpensive, Since it is excellent in insulation and has high transparency, it is used as an interlayer film for laminated glass, a sealing film for solar cells, and the like. As an interlayer film for laminated glass, for example, as shown in FIG. 1, the interlayer film 12 sandwiched between glass plates 11A and 11B exhibits functions such as penetration resistance and prevention of scattering of broken glass ( Patent Document 1). As the solar cell sealing film, for example, as shown in FIG. 2, the surface side sealing film 23A disposed between the solar cell 24 and the surface side transparent protective member 21 made of a glass substrate or the like, and As the back surface side sealing film 23B disposed between the solar cell 24 and the back surface side protection member (back cover) 22, it exhibits functions such as ensuring insulation and ensuring mechanical durability. 2). Further, in thin film solar cells such as thin film silicon-based, thin-film amorphous silicon-based solar cells, and copper indium selenide (CIS) -based solar cells, for example, chemical vapor deposition on the surface of a transparent substrate such as glass or polyimide substrate Thus, a power generation element layer such as a semiconductor layer is formed and used as a sealing film disposed between the power generation element layer and the protective member.

  In the case of producing a laminated glass or a solar battery, generally, the above-mentioned members are laminated, preliminarily pressure-bonded under reduced pressure, air remaining in each layer is degassed, and then pressure-bonded by heating and pressurizing, an EVA film ( The intermediate film 12 in FIG. 1 and the front side sealing film 23A and the back side sealing film 23B in FIG. 2 are cured and integrated. At this time, in the sealing film, the adhesiveness and durability of the sealing film can be improved by crosslinking the copolymer using a crosslinking agent such as an organic peroxide.

  The EVA film can be obtained by depositing a composition containing EVA and a crosslinking agent. Specifically, the composition can be obtained by forming a film after being put into a mixing roll or the like and melt-kneaded. As the film forming method, for example, an extrusion molding method, a calendar molding method, an injection molding method, a heating press method, or the like is used. Among these, the calender molding method is particularly useful because a sealing film having a uniform thickness can be produced at high speed. The calendar molding method is a method in which a melt-kneaded composition is put into a heating roll and rolled into a film shape.

  Such an EVA film is required not to cause a phenomenon that the films adhere to each other during storage or use (blocking), and that the heat shrinkage of the EVA film does not occur greatly when heated and pressurized. The When blocking occurs, the yield decreases and the workability deteriorates. On the other hand, if the degree of thermal shrinkage is large, the laminated glass may be misaligned, resulting in poor appearance. In addition, in solar cells, the cells for solar cells are pulled and overlapped with the sealing film (EVA film), the cells are damaged, or the back cover made of plastic film is wrinkled, resulting in poor power generation efficiency and poor appearance. It may become.

  In order to prevent blocking during storage and use as described above, an EVA film having a fine concavo-convex pattern (also referred to as embossing) on its surface has been developed (Patent Documents 3 and 4).

JP 58-79848 A Japanese Patent Laid-Open No. 06-177412 JP 2001-130931 A JP 2002-185027 A

  However, in the conventional EVA film, it cannot be said that suppression of heat shrinkage at the time of heating and pressurization is sufficient, and when used in the production of laminated glass and solar cells, the above-described defects may occur.

  Accordingly, an object of the present invention is to provide an EVA film in which blocking during storage or use is prevented and the occurrence of heat shrinkage is suppressed.

  Another object of the present invention is to provide a laminated glass and a solar electric ground using the EVA film.

  The EVA film is tensioned by being pulled in the film forming process, but such a sealing film generates a force to return to its original shape when it is crosslinked and cured by heating and pressurization. It is thought that thermal contraction of the film occurs.

  The present inventors pay attention to the heat shrinkage generation mechanism and tackiness to the surface of adjacent members such as glass plates so that the EVA film does not shrink (refers to the property of sticking to the adherend in a short time with a light force). I thought it was effective to increase the However, when the tackiness of the film is increased, it is considered that blocking tends to occur. Therefore, as a result of various studies to achieve both of these, the present inventors have found that the above problem can be solved by applying an emboss having a specific surface property to the film surface using EVA having a specific composition. I found it.

That is, the above object is an ethylene-vinyl acetate copolymer film comprising an ethylene-vinyl acetate copolymer and a composition containing a crosslinking agent, and having an emboss on at least one surface. The content of the vinyl acetate repeating unit is 26 to 28% by mass based on the mass of the ethylene-vinyl acetate copolymer,
Arithmetic average roughness Ra (JIS-B0601 (2001), hereinafter the same) of the surface having the emboss is 3.0 μm or more and 20 μm or less, and the average length RSm of the roughness curve element of the surface having the emboss (JIS-B0601 (2001), the same shall apply hereinafter) is achieved by an ethylene-vinyl acetate copolymer film characterized by being 300 μm or more and less than 600 μm.

Preferred embodiments of the EVA film of the present invention are as follows.
(1) Content of the said crosslinking agent is 0.5-2.5 mass parts with respect to 100 mass parts of said ethylene-vinyl acetate copolymers. Thereby, a necessary and sufficient cross-linked structure can be imparted when using the EVA film.
(2) The crosslinking agent is an organic peroxide.
(3) The average thickness of the film is 50 μm to 2 mm. Heat shrinkage can be further suppressed.
(4) An interlayer film for laminated glass or a sealing film for solar cells. These are suitable for the use of the EVA film of the present invention.

  The object of the present invention is also achieved by a laminated glass characterized in that the EVA film of the present invention is used as an interlayer film for laminated glass. Since the laminated glass of the present invention uses the EVA film of the present invention, workability due to blocking during production is not deteriorated, and poor appearance due to thermal shrinkage of the EVA film is unlikely to occur.

  Furthermore, the object of the present invention is achieved by a solar cell characterized by using the EVA film of the present invention as a solar cell sealing film. Since the solar cell of the present invention uses the EVA film of the present invention, the workability due to blocking at the time of manufacture is not deteriorated, and the power generation efficiency due to poor appearance due to thermal shrinkage of the EVA film, damage to solar cells, etc. Defects are unlikely to occur.

  The EVA film of the present invention comprises a composition containing EVA having a vinyl acetate content in the above range, and the surface properties in the above range (arithmetic surface roughness Ra, average length RSm of roughness curve elements) on the EVA film surface. Since the embossing which has this is provided, it has moderate tackiness to the adjacent member surface, and adhesion of EVA films is prevented. By these, blocking at the time of storage or use of the EVA film can be prevented, and occurrence of heat shrinkage can be suppressed.

  Therefore, by using the EVA film of the present invention, the laminated glass and the sun in which the occurrence of poor appearance and poor power generation efficiency due to thermal contraction during heating and pressurization are suppressed without causing yield reduction or workability deterioration due to blocking. A battery can be obtained.

It is a schematic sectional drawing of a common laminated glass. It is a schematic sectional drawing of a common solar cell.

  The EVA film of the present invention comprises a composition containing EVA and a crosslinking agent. Moreover, it has emboss on at least one surface of the EVA film. And the vinyl acetate repeating unit of EVA is 26-28 mass% on the basis of the mass of EVA. Further, the arithmetic average roughness Ra of the embossed surface (also referred to as an embossed surface) is 3.0 μm or more and 20 μm or less, and the average length RSm of the embossed surface roughness curve element is 300 μm or more and less than 600 μm. .

  In general, the lower the vinyl acetate content in EVA, the harder the EVA composition and the lower the tackiness, and the higher the vinyl acetate content, the higher the fluidity and the higher the tackiness. In the present invention, tackiness is optimized by using EVA having a vinyl acetate content in the above range. That is, when the vinyl acetate content is less than 26% by mass, the EVA film has low tackiness and heat shrinkage tends to occur, and when it is greater than 28% by mass, the EVA film has high tackiness and blocking easily occurs. Furthermore, by forming the surface texture embossing within the above range, blocking where the films adhere to each other is less likely to occur, and an EVA film that exhibits an appropriate tackiness is formed on a member adjacent to the EVA film such as a glass plate. it can. Since the EVA film adheres to an adjacent member such as a glass plate with an appropriate tackiness, the EVA film is prevented from shrinking by heating.

  When the arithmetic average roughness Ra of the embossed surface of the EVA film of the present invention is less than 3.0 μm, the tackiness of the EVA film is high and blocking tends to occur. It tends to occur. The arithmetic average roughness Ra is preferably 5 to 13 μm, and more preferably 6 to 11 μm. Further, when the average length RSm of the roughness curve element of the embossed surface is less than 300 μm, the tackiness of the EVA film is low and heat shrinkage tends to occur, and when it is 600 μm or more, the tackiness of the EVA film is high and blocking tends to occur. The average length RSm of the roughness curve element is preferably 350 to 550 μm, more preferably 400 to 500 μm.

  In the present invention, the arithmetic average roughness Ra of the surface is a value measured by a method based on JIS-B0601 (2001). That is, a predetermined length is extracted from the roughness curve in the direction of the average line, and the absolute values of deviations from the average line of the extracted portion to the measurement curve are summed and averaged.

  Further, the average length RSm of the roughness curve element is a value measured by a method based on JIS-B0601 (2001) (similar to “average interval Sm of unevenness” in JIS-B0601 (1994)). That is, a predetermined length is extracted from the roughness curve in the direction of the average line, and the length of the average line (contour curve element corresponding to one peak of the extracted portion and one valley adjacent thereto is extracted. Is the value obtained by averaging.

  Further, in the present invention, “appropriate tackiness” means that the embossed surface is brought into contact with a glass plate, a load of 500 g is applied for 90 seconds, and then peeled off at a speed of 300 mm / min (tack meter (MODEL: (Measured with DPX-SOT (manufactured by Imada)) is preferably 0.15 to 0.35N.

  The embossed uneven pattern of the EVA film of the present invention is not particularly limited as long as it has the arithmetic average roughness Ra and the average length RSm of the roughness curve elements described above. For example, the convex portions in the concavo-convex pattern can be provided as a circular shape, a semicircular shape, or a polygonal shape with a required interval, or the convex portions can be provided as a stripe shape or a mesh shape. Especially, since manufacture is easy, it is preferable that the convex part is the uneven | corrugated shape provided in stripe form.

  In the EVA film of the present invention, the embossing may be formed on at least one surface of the EVA film. For example, when using as the intermediate film 12 of the laminated glass shown in FIG. 1, the emboss may be formed only on the surface in contact with one glass plate 11A, and the emboss is formed on both surfaces in contact with the glass plates 11A and 11B. May be. It is preferable that embossing is formed on both surfaces from the viewpoint that both glass plates are in close contact with an appropriate tackiness and heat shrinkage is further suppressed.

  Moreover, also when using as the surface side sealing film 23A and the back side sealing film 23B of the solar cell shown in FIG. 2, any one of the surfaces in contact with the surface side transparent protective member 21 and the solar cell 24, Or on both surfaces (in the case of the front surface side sealing film 23A), either one or both surfaces (in the case of the back surface side sealing film 23B) of the surfaces in contact with the solar cell 24 and the back surface side protection member 22. It only has to be formed. In particular, since it is preferable that the embossed surface is in close contact with a hard surface such as a glass plate in order to suppress thermal shrinkage, at least the surface in contact with the surface side transparent protective member 21 of the surface side sealing film 23A, the back surface side sealing film It is preferable that an emboss is formed on the surface in contact with the solar battery cell 24 of 23B. It is particularly preferable that embossing is formed on both surfaces of the front surface side sealing film 23A and both surfaces of the back surface side sealing film 23B in order to adhere to each layer with appropriate tackiness.

  The average thickness of the EVA film is preferably 50 μm to 2 mm, particularly preferably 100 μm to 1.5 mm. Thereby, thermal contraction can be suppressed. In addition, with the average thickness of an EVA film, the thickness of an EVA film is measured 10 or more places using a micrometer, and it is set as the average value of the measured value.

[Crosslinking agent]
The composition of the EVA film of the present invention contains a crosslinking agent in addition to EVA. Thereby, the crosslinked structure of EVA can be formed and the adhesive force of an EVA film can be improved.

  As the crosslinking agent, an organic peroxide is preferably used. Any organic peroxide can be used as long as it decomposes at a temperature of 100 ° C. or higher to generate radicals. The organic peroxide is generally selected in consideration of the film formation temperature, the adjustment conditions of the composition, the curing temperature, the heat resistance of the adherend, and the storage stability. In particular, those having a decomposition temperature of 70 hours or more with a half-life of 10 hours are preferred.

  As the organic peroxide, it is preferable to use a hydroperoxide compound, a dialkyl peroxide compound, and a ketone peroxide compound from the viewpoint of the processing temperature and storage stability of the resin. These may be used alone or in combination of two or more.

  Examples of the hydroperoxide compounds include P-menthane hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, and the like.

  Examples of the dialkyl peroxide compound include 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, 3-di-t-butyl peroxide, and t-butyl-α-cumyl peroxide. , Di-α-cumyl peroxide, 1,4-bis ((t-butyldioxy) isopropyl) benzene, 1,3-bis ((t-butyldioxy) isopropyl) benzene, 2,5-dimethyl-2,5-bis ((T-butylperoxy) benzene, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne, α, α′-bis (t-butylperoxyisopropyl) benzene, n-butyl- 4,4-bis (t-butylperoxy) butane, 2,2-bis (t-butylperoxy) butane, 1,1-bis (t-butylperoxy) 3 3,5-trimethyl cyclohexane and the like.

Examples of the ketone peroxide compound include methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, cyclohexanone peroxide, and methylcyclohexanone peroxide.
Among these, a dialkyl peroxide compound, particularly 2,5-dimethyl-2,5-bis (t-butylperoxy) is obtained because a cured film having excellent adhesion, heat resistance, and ultraviolet resistance can be obtained. It is preferred to use hexane.

  Content of a crosslinking agent is 0.5-5.0 mass parts normally with respect to 100 mass parts of EVA, Preferably it is 0.5-2.5 mass parts, More preferably, it is 0.65-2.5 mass. Part. If the content of the cross-linking agent is within the above range, a strong cross-linking structure can be obtained, and the amount of decomposition gas such as acetic acid gas generated during heating and pressurization can be reduced. It can be adhered.

[Crosslinking aid]
The composition of the EVA film of the present invention may further contain a crosslinking aid, if necessary. The crosslinking aid can improve the gel fraction of EVA and improve the adhesion and durability of the EVA film.

  The content of the crosslinking aid is generally 10 parts by mass or less, preferably 0.1 to 5 parts by mass, and more preferably 0.1 to 2.5 parts by mass with respect to 100 parts by mass of EVA. Thereby, the EVA film which is further excellent in adhesiveness is obtained.

  Examples of the crosslinking aid (compound having a radical polymerizable group as a functional group) include trifunctional crosslinking aids such as triallyl cyanurate and triallyl isocyanurate, and (meth) acrylic esters (eg, NK ester) ) Monofunctional or bifunctional crosslinking aids. Of these, triallyl cyanurate and triallyl isocyanurate are preferable, and triallyl isocyanurate is particularly preferable.

[Adhesion improver]
The composition of the EVA film of the present invention preferably has a further excellent adhesive force depending on the application. Therefore, an adhesion improver may be further included. As the adhesion improver, a silane coupling agent can be used. Thereby, it is possible to obtain an EVA sheet having an excellent adhesive force. Examples of the silane coupling agent include γ-chloropropylmethoxysilane, vinylethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, and γ-glycidoxypropyltrimethoxy. Silane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β Mention may be made of-(aminoethyl) -γ-aminopropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Of these, γ-methacryloxypropyltrimethoxysilane is particularly preferred.

  The content of the silane coupling agent is preferably 0.1 to 0.7 parts by mass, particularly 0.3 to 0.65 parts by mass with respect to 100 parts by mass of EVA.

[Others]
The composition of the EVA film of the present invention is optionally used for improving or adjusting various physical properties of the EVA sheet (optical properties such as mechanical strength and transparency, heat resistance, light resistance, crosslinking speed, etc.). Further, it may further contain various additives such as a plasticizer, other acryloxy group-containing compound, methacryloxy group-containing compound and / or epoxy group-containing compound other than Compound I in the present invention.

  Although it does not specifically limit as a plasticizer, Generally the ester of a polybasic acid and the ester of a polyhydric alcohol are used. Examples thereof include dioctyl phthalate, dihexyl adipate, triethylene glycol-di-2-ethylbutyrate, butyl sebacate, tetraethylene glycol diheptanoate, and triethylene glycol dipelargonate. One type of plasticizer may be used, or two or more types may be used in combination. The content of the plasticizer is preferably in the range of 5 parts by mass or less with respect to 100 parts by mass of EVA.

  The acryloxy group-containing compound and the methacryloxy group-containing compound are generally acrylic acid or methacrylic acid derivatives, and examples thereof include acrylic acid or methacrylic acid esters and amides. Examples of ester residues include linear alkyl groups such as methyl, ethyl, dodecyl, stearyl, lauryl, cyclohexyl group, tetrahydrofurfuryl group, aminoethyl group, 2-hydroxyethyl group, 3-hydroxypropyl group. Group, 3-chloro-2-hydroxypropyl group. Examples of amides include diacetone acrylamide. In addition, polyhydric alcohols such as ethylene glycol, triethylene glycol, polypropylene glycol, polyethylene glycol, trimethylolpropane, and pentaerythritol, and esters of acrylic acid or methacrylic acid can also be used.

Examples of epoxy-containing compounds include triglycidyl tris (2-hydroxyethyl) isocyanurate, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and phenol. (Ethyleneoxy) ₅ glycidyl ether, pt-butylphenyl glycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, glycidyl methacrylate, butyl glycidyl ether can be mentioned.

  The acryloxy group-containing compound, the methacryloxy group-containing compound, or the epoxy group-containing compound is generally 0.5 to 5.0 parts by mass, particularly 1.0 to 4.0 parts by mass, respectively, with respect to 100 parts by mass of EVA. It is preferable that

  Furthermore, the EVA composition according to the present invention may contain an ultraviolet absorber, a light stabilizer and an anti-aging agent. By including the ultraviolet absorber, it is possible to suppress the deterioration of the EVA due to the influence of the irradiated light and the like, and the yellowing of the EVA sheet. The ultraviolet absorber is not particularly limited, but 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxy. Preferred examples include benzophenone-based ultraviolet absorbers such as benzophenone and 2-hydroxy-4-n-octoxybenzophenone. In addition, it is preferable that the compounding quantity of the said benzophenone series ultraviolet absorber is 0.01-5 mass parts with respect to 100 mass parts of EVA.

  Moreover, it can suppress that EVA deteriorates and the EVA sheet | seat yellows by the influence of the irradiated light etc. also by including a light stabilizer. As the light stabilizer, a light stabilizer called a hindered amine type is preferably used. For example, LA-52, LA-57, LA-62, LA-63LA-63p, LA-67, LA-68 (all ADEKA), Tinuvin 744, Tinuvin 770, Tinuvin 765, Tinuvin 144, Tinuvin 622LD, CHIMASSORB 944LD (all manufactured by Ciba Specialty Chemicals Co., Ltd.), UV-3034 (BF Goodrich) Can be mentioned. In addition, the said light stabilizer may be used individually or may be used in combination of 2 or more types, and it is preferable that the compounding quantity is 0.01-5 mass parts with respect to 100 mass parts of EVA.

  Examples of the antioxidant include hindered phenolic antioxidants such as N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide], Examples thereof include phosphorus heat stabilizers, lactone heat stabilizers, vitamin E heat stabilizers, and sulfur heat stabilizers.

[Production of EVA film]
In order to produce the EVA film of the present invention, for example, (a) a step of obtaining a molded body by molding a composition containing EVA and a crosslinking agent into a sheet, and (b) embossing on at least one surface of the molded body. By the processing, a method including an embossing process in which an arithmetic average roughness Ra is 3.0 μm or more and 20 μm or less and an average length RSm of the roughness curve element is 300 μm or more and less than 600 μm is used.

  In the step (a), a conventionally known method such as extrusion molding or calendar molding (calendering) is used to form a composition containing EVA and a crosslinking agent and, if necessary, various components described above into a sheet. It is done. The composition is preferably mixed by heating and kneading at a temperature of 40 to 90 ° C, particularly 60 to 80 ° C. The heating temperature during film formation is preferably a temperature at which the crosslinking agent does not react or hardly reacts. For example, it is preferable to set it as 40-90 degreeC, especially 50-80 degreeC.

  In the step (b), the embossing described above may be imparted to the sheet-like molded body using a conventionally known method such as embossing. For example, the embossing roller and embossing plate which have the reverse embossing pattern of the said surface texture predetermined embossing are heat-pressed on the predetermined surface of a molded object, and embossing can be provided. It is good also as an EVA film by which an embossing roller etc. are heat-pressed on both surfaces of a molded object, and the embossing was formed in both surfaces.

  Since the EVA film of the present invention is prevented from blocking as described above and the occurrence of heat shrinkage is suppressed, particularly high work efficiency is required at the time of production, and the occurrence of displacement and wrinkles of adjacent members due to heat shrinkage. Can be preferably used as an interlayer film for laminated glass and a sealing film for solar cells.

[Laminated glass]
The laminated glass of this invention should just use the EVA film of this invention as an intermediate film for laminated glasses. As described above, since the EVA film of the present invention is prevented from blocking and the occurrence of heat shrinkage is suppressed, the laminated glass of the present invention has high productivity and hardly causes poor appearance due to deviation of the glass plate. Laminated glass.

In order to manufacture the laminated glass of the present invention, for example, as shown in FIG. 1, the EVA film of the present invention is used as an interlayer film 12 for laminated glass, and is sandwiched between two glass plates 11A and 11B. Then, after degassing the obtained laminate, a method of pressing under heating is used. These processes are performed using, for example, a vacuum bag method, a nip roll method, or the like. Thereby, the interlayer film 12 for laminated glass is hardened, and the interlayer film 12 for laminated glass and the glass plates 11A and 11B can be bonded and integrated. As production conditions, for example, the laminate is preliminarily pressure-bonded at a temperature of 80 to 120 ° C., and EVA is crosslinked by heat treatment at 100 to 150 ° C. (particularly around 130 ° C.) for 10 minutes to 1 hour. Further, the heat treatment may be performed under pressure. At this time, it is preferable to carry out while pressing the laminate at a pressure of 1.0 × 10 ³ Pa to 5.0 × 10 ⁷ Pa. Cooling after crosslinking is generally performed at room temperature, and in particular, the faster the cooling, the better.

  The glass plate in the present invention may be a transparent substrate, for example, a glass plate such as green glass, silicate glass, inorganic glass plate, non-colored transparent glass plate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN). Alternatively, a plastic substrate or film such as polyethylene butyrate or polymethyl methacrylate (PMMA) may be used. A glass plate is preferable in terms of weather resistance, impact resistance and the like. As for the thickness of a glass plate, about 1-20 mm is common. The same glass plate may be used for each glass plate disposed on both sides of the laminated glass, or different substrates may be used in combination. The combination is determined in consideration of the strength of the base material and the use of the laminated glass.

  The laminated glass of the present invention can be used for various types of doors and walls of various devices such as window glass for buildings and vehicles (automobiles, railway vehicles, ships), electronic devices such as plasma displays, refrigerators, and heat insulation devices. Can be used for applications.

[Solar cell]
The solar cell of this invention will not be restrict | limited especially if the EVA film of this invention is used as a sealing film for solar cells. For example, between the front surface side transparent protective member and the back surface side protective member, a structure in which the EVA film of the present invention is used as a solar cell sealing film and the solar cell is sealed by cross-linking and the like. Can be mentioned. In addition, in this invention, the side (light-receiving surface side) by which the light of a photovoltaic cell is irradiated is called "front surface side", and the surface opposite to the light-receiving surface of a photovoltaic cell is called "back surface side."

  As described above, since the EVA film of the present invention is prevented from blocking and the occurrence of heat shrinkage is suppressed, the solar battery of the present invention is high in productivity, and the overlapping of solar cells and the back cover. It is a solar cell in which power generation efficiency failure and appearance failure due to wrinkles are unlikely to occur.

In order to manufacture the solar cell of the present invention, for example, as shown in FIG. 2, the surface side transparent protective member 21, the surface side sealing film 23A (EVA film of the present invention), the solar cell 24, the back side sealing. The film 23B (EVA film of the present invention) and the back surface side protective member 22 are laminated, and the sealing films 23A and 23B may be cross-linked and cured according to a conventional method such as heating and pressurization. In order to heat and pressurize, for example, the laminate is heated with a vacuum laminator at a temperature of 135 to 180 ° C., further 140 to 180 ° C., particularly 155 to 180 ° C., a degassing time of 0.1 to 5 minutes, and a press pressure of 0.1. What is necessary is just to heat-press in about 1.5 kg / cm < ² > and press time 5-15 minutes. At the time of heating and pressing, the EVA contained in the front surface side sealing film 23A and the rear surface side sealing film 23B is cross-linked, whereby the front surface side transparent film is protected via the front surface side sealing film 23A and the back surface side sealing film 23B. The member 21, the back surface side transparent member 22, and the solar cell 24 can be integrated to seal the solar cell 24.

  The solar cell sealing film of the present invention is not limited to a solar cell using a single crystal or polycrystalline silicon crystal solar cell as shown in FIG. It can also be used for sealing films of thin film solar cells such as solar cells and copper indium selenide (CIS) solar cells. In this case, for example, on a thin film solar cell element layer formed by a chemical vapor deposition method or the like on the surface of a surface side transparent protective member such as a glass substrate, a polyimide substrate, or a fluororesin-based transparent substrate, a solar cell seal is formed. On the solar cell element formed on the surface of the stop film (EVA film of the present invention), the back surface side protective member laminated and bonded and integrated, and the back surface side protective member surface EVA film of the invention), a structure in which a surface-side transparent protective member is laminated and bonded and integrated, or a surface-side transparent protective member, a surface-side sealing film (EVA film of the invention), a thin-film solar cell element, a back-side sealed The structure etc. which laminated | stacked the stop film (EVA film of this invention), and the back surface side protection member in this order, and were united and integrated are mentioned.

  The surface side transparent protective member 11 used in the solar cell of the present invention is usually a glass substrate such as silicate glass. As for the thickness of a glass substrate, 0.1-10 mm is common, and 0.3-5 mm is preferable. The glass substrate may generally be chemically or thermally strengthened.

  The back surface side protective member 12 used in the present invention is preferably a plastic film such as polyethylene terephthalate (PET). Further, a film obtained by laminating a fluorinated polyethylene film, particularly a fluorinated polyethylene film / Al / fluorinated polyethylene film in this order in consideration of heat resistance and wet heat resistance may be used.

  In addition, the solar cell (including a thin film solar cell) of the present invention is characterized by the EVA film used on the front surface side and / or the back surface side as described above. Therefore, the members other than the sealing film such as the front-side transparent protective member, the back-side protective member, and the solar cell need only have the same configuration as the conventionally known solar cell, and are not particularly limited. .

  Hereinafter, the present invention will be described with reference to examples.

[Examples 1-6, Comparative Examples 1-4]
1. Preparation of EVA Film Sample A sheet-like molded body (thickness: 1.0 mm) was obtained by a calendar molding method using the compositions of the following Formulation 1 and Formulation 2 as raw materials. The composition was kneaded at 80 ° C. for 15 minutes, the calender roll temperature was 80 ° C., and the processing speed was 5 m / min. Then, Examples 1-6 of the surface properties (arithmetic average roughness Ra, average length RSm of roughness curve elements) shown in Table 1 by embossing the compact using a mini embossing roll, and Each EVA film sample (thickness 0.5 mm, width 100 mm, length 305 mm) of Comparative Examples 1 to 4 was obtained.
(Formulation 1)
EVA (vinyl acetate content 26% by mass in EVA): 100 parts by mass,
Cross-linking agent (2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane): 1.0 part by mass,
Cross-linking aid (triallyl isocyanurate): 2.0 parts by mass (formulation 2)
EVA (vinyl acetate content 28% by mass in EVA): 100 parts by mass,
Cross-linking agent (2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane): 1.0 part by mass,
Crosslinking aid (triallyl isocyanurate): 2.0 parts by mass

2. Surface texture measurement method The arithmetic average roughness Ra of the embossed surface of the EVA film sample and the average length RSm of the roughness curve element were measured according to JIS-B0601 (2001) by a surface roughness measuring machine (Rank Taylor Hobson). Measured using Surtronic 3+). Moreover, the measurement was performed 10 places and the average value of the measured value was calculated | required. The measurement conditions were: measurement distance: 7.5 cm, measurement speed: 1 mm / s, cutoff wavelength: 2.5 μm, long wavelength reference length λc: 2.5 mm, short wavelength reference length λs: 0.0025 mm.

3. Evaluation Method (1) Heat Shrinkability on Glass Plate The EVA film sample prepared above is placed on a glass plate (size: 305 mm × 305 mm, thickness: 3 mm) with the embossed surface facing the glass plate. It was put into an oven heated to ° C. After 3 minutes, the sealing film was taken out and left in the air for 10 minutes. Then, the length A ₁ (305 mm) in the long side direction before heating of the sealing film and the length A ₂ (mm) in the long side direction after heating are measured, and the formula [(A ₁ −A ₂ ) / a calculated heat shrinkage rate (%) by ₁ × 100]. 0.8% or less was accepted.
(2) Evaluation of tackiness (blocking property) The adhesive force when the embossed surface of the EVA film sample produced above is brought into contact with a glass plate, a load of 500 g is applied for 90 seconds, and then peeled off at a speed of 300 mm / min. Was measured with a tack meter (MODEL: DPX-SOT (manufactured by Imada)). An adhesion strength of 0.15 to 0.35 N was determined to be acceptable as an appropriate tackiness.

4). Evaluation results Table 1 shows the evaluation results.

  As shown in Table 1, EVA has a vinyl acetate content of 26 to 28% by mass, the arithmetic average roughness Ra of the embossed surface is 3.0 μm or more and 20 μm or less, and the average length RSm of the roughness curve element is 300 μm or more. The EVA films of Examples 1 to 6 having a size of less than 600 μm had a small heat shrinkage rate on the glass plate and also passed the tackiness. Therefore, it is shown that these EVA films are EVA films that are less likely to cause slippage of glass plates and solar cell cells due to heat shrinkage and back cover wrinkles, and that blocking is prevented and there is no problem in workability. It was.

  On the other hand, Comparative Examples 1 and 3, in which the average length RSm of the roughness curve elements was smaller than 300 μm, had a large heat shrinkage rate on the glass plate and were rejected. In these EVA films, defects such as misalignment of glass plates and solar cell cells are likely to occur. Further, Comparative Examples 2 and 4 in which the average length RSm of the roughness curve elements was 600 μm or more were rejected because the thermal shrinkage rate on the glass plate was small, but the tack property (blocking property) was too large. In these EVA films, blocking is likely to occur, causing a problem in workability.

From the above, it was shown that the EVA film of the present invention was one in which blocking was prevented and the occurrence of heat shrinkage was suppressed.
In addition, this invention is not limited to the structure and Example of said embodiment, A various deformation | transformation is possible within the range of the summary of invention.

According to the present invention, it is possible to provide, with high productivity, a laminated glass that does not easily cause an appearance defect, and a solar cell that does not easily cause a power generation efficiency defect or an appearance defect.

11A, 11B Glass plate 12 Intermediate film 21 Front-side transparent protective member 22 Back-side protective member 23A Front-side sealing film 23B Back-side sealing film 24 Solar cell

Claims (7)

An ethylene-vinyl acetate copolymer film comprising an ethylene-vinyl acetate copolymer and a crosslinking agent, and having an emboss on at least one surface of the film,
The content of the vinyl acetate repeating unit in the ethylene-vinyl acetate copolymer is 26 to 28% by mass based on the mass of the ethylene-vinyl acetate copolymer,
The arithmetic average roughness Ra (JIS-B0601 (2001)) of the surface having the emboss is 3.0 μm or more and 20 μm or less, and the average length RSm (JIS-B0601) of the roughness curve element of the surface having the emboss (2001)) is 300 μm or more and less than 600 μm, an ethylene-vinyl acetate copolymer film.   The ethylene-vinyl acetate copolymer film according to claim 1, wherein the crosslinking agent is an organic peroxide.   The ethylene-vinyl acetate copolymer film according to claim 1 or 2, wherein a content of the crosslinking agent is 0.5 to 2.5 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. .   The average thickness of a film is 50 micrometers-2 mm, The ethylene-vinyl acetate copolymer film of any one of Claims 1-3.   The ethylene-vinyl acetate copolymer film according to any one of claims 1 to 4, which is an interlayer film for laminated glass or a sealing film for solar cell.   Laminated glass, wherein the ethylene-vinyl acetate copolymer film according to any one of claims 1 to 4 is used as an interlayer film for laminated glass.   A solar cell, wherein the ethylene-vinyl acetate copolymer film according to claim 1 is used as a solar cell sealing film.

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