JP2012160550A - Surface protection material for solar cell and solar cell module manufactured using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high moisture resistance surface protection material for solar cell including a transparent moisture-proof film having an inorganic thin film layer on one surface of a substrate and steam permeability of less than 0.1[g/m/day], and in which the moisture resistance does not deteriorate for a long term.SOLUTION: In a surface protection material for solar cell including a transparent moisture-proof film having an inorganic thin film layer on one surface of a substrate and steam permeability of less than 0.1[g/m/day], a weather-resistant film having a melting point of 130-180°C is provided on the inorganic thin film layer side of the transparent moisture-proof film, and a back film is provided on the transparent moisture-proof film on the reverse side of the inorganic thin film layer.

Description

  The present invention relates to a highly moisture-proof solar cell surface protective material having a transparent moisture-proof film including an inorganic thin film layer, an excellent solar cell surface protective material that does not deteriorate moisture resistance over a long period of time, and the solar cell surface protective material. The present invention relates to a highly durable solar cell module used.

In recent years, solar cells that directly convert sunlight into electric energy have attracted attention and are being developed from the viewpoint of effective use of resources and prevention of environmental pollution. A solar cell consists of a configuration in which a solar cell is sealed with a sealing material such as an ethylene-vinyl acetate copolymer, polyethylene, or polypropylene film between a front surface protective material and a back surface protective material on the light receiving surface side. The front protective material, the sealing material, the power generating element, the sealing material, and the back surface protective material are laminated in this order, and are manufactured by bonding and integration by heating and melting.
Solar cell front and back protection materials (hereinafter sometimes referred to as “surface protection materials”) include durability against ultraviolet rays, degradation of power generation elements due to moisture or water permeation, and the generation of internal conductors and electrodes. It is a very important requirement to have excellent moisture resistance for preventing rust.
In order to satisfy such requirements, as the surface protective material for solar cells, for example, from the exposed surface side, a weather-resistant film, a moisture-proof film having an inorganic thin film deposited surface on the exposed surface side, and adhesion such as a sealing material In addition, a laminated structure including a film having partial discharge resistance characteristics has been proposed.

For example, in the Example of patent document 1, the surface for solar cells obtained by providing a polyurethane adhesive layer on both sides of a moisture-proof film based on a biaxially stretched polyester film and laminating a weather-resistant polyester film on both sides thereof A protective material is disclosed.
Moreover, in the Example of patent document 2, the surface for solar cells which bonded the polyvinyl fluoride (PVF) film to the moisture-proof film which used the biaxially-stretched polyester film as a base material using the two-component curing type polyurethane-type adhesive agent similarly. A protective material is disclosed.
In Patent Document 3, a weather resistant resin layer having weather resistance is provided on the back surface, the weather resistant resin layer, a first vapor deposited resin layer having a metal oxide vapor deposited film on one surface, an intermediate resin layer, And a second vapor-deposited resin layer having a metal oxide vapor-deposited film on one surface, the back protective sheet for a solar cell module laminated by dry lamination, wherein the first vapor-deposited resin layer and the second vapor-deposited layer A back protective sheet for a solar cell module is disclosed in which a vapor deposition film of a resin layer is disposed on the intermediate resin layer side.
Furthermore, in Patent Document 4, there is provided a method for producing a back surface protection sheet for a solar cell module comprising a weather resistant resin layer having weather resistance on the back surface, wherein the weather resistant resin layer and a metal oxide vapor deposition film on one surface are provided. At least three vapor-deposited resin layers having a thickness of 3 are sequentially laminated by dry lamination, and the vapor-deposited resin layers each have a water vapor permeability of 0.03 to 0.5 g / m ² · day at 40 ° C. and 90% RH. The manufacturing method of the back surface protection sheet for solar cell modules characterized by these is disclosed.

JP2009-188072 JP2009-49252 JP 2010-272761 JP 2010-272762 A

  When the surface protective material is incorporated into the solar cell, the surface protective material is laminated with another member and bonded and integrated by vacuum lamination, for example, under conditions of a temperature of 130 ° C. to 180 ° C. and a time of 10 minutes to 40 minutes. This lamination temperature is much higher than the acceleration test disclosed in the above-mentioned patent document of the conventional surface protective material, and serious damage is caused to the surface protective material. This vacuum lamination is especially suitable for use in solar cell protective materials and electronic paper for compound-based power generation device solar cell modules that require high moisture-proof performance and solar cell modules that do not require glass that requires flexibility. In consideration of process influence, it is required to prevent deterioration of moisture resistance after the accelerated test.

However, in any of the above patent documents, moisture protection by using a surface protection material using a highly moisture-proof film having a water vapor transmission rate of less than 0.1 [g / m ² day] as a solar cell module through a vacuum lamination process. Disclosed is a surface protection material for solar cells that is not assumed to be inferior in performance and that maintains moisture-proof performance for a long period of time even after passing through high temperature conditions such as a temperature of 130 ° C. to 180 ° C. and a time of 10 minutes to 40 minutes. It wasn't.

That is, in the Example of Patent Document 1, only the 85 ° C., 85% humidity, 1000 hrs test was performed as the surface protection material for solar cells, and the results of evaluating the moisture resistance thereafter were shown. As the water vapor transmission rate, only 1-2 [g / m ² · day] is disclosed, and Patent Document 2 discloses a pressure cooker test (PCT) (high temperature) as a surface protection material for solar cells. Only a severe environmental test by high pressure (105 ° C., 92 hours) was conducted, and as a result of evaluating the moisture resistance, a water vapor permeability after the test of 0.5 [g / m ² · day] was disclosed. Only.
Patent Documents 3 and 4 show the results of evaluating the initial moisture resistance as a solar cell surface protective material prepared by dry lamination, but the solar cell surface protective material has a temperature of 130. Even after a high temperature condition of from 10 to 180 ° C. and from 10 to 40 minutes, it did not have sufficient moisture-proof performance.

That is, the object of the present invention is to provide a highly moisture-proof solar cell surface using a highly transparent moisture-proof film having an inorganic thin film layer on one surface of the substrate and having a water vapor transmission rate of less than 0.1 [g / m ² day]. An object of the present invention is to provide an excellent surface protection material that does not deteriorate moisture resistance over a long period of time, and to provide a solar cell module that is excellent in durability using the surface protection material for solar cells.

As a result of intensive studies, the present inventors have identified a weather-resistant film on the inorganic thin film layer side of a transparent highly moisture-proof film having an inorganic thin film layer and a water vapor transmission rate of less than 0.1 [g / m ² · day]. A film (hereinafter, referred to as “back surface”) opposite to the inorganic thin film layer of the transparent high moisture-proof film (hereinafter referred to as “back surface”) By providing a “back film” in some cases, it was found that long-term excellent moisture resistance and interlayer strength can be satisfied at the same time, thereby realizing durability of moisture resistance, and the present invention has been completed.

That is, the present invention is a solar cell surface protective material having a transparent high moisture-proof film having an inorganic thin film layer on one surface of the substrate and having a water vapor permeability of less than 0.1 [g / m ² day], The present invention relates to a surface protective material for solar cells, comprising a weather resistant film having a melting point of 130 ° C. or higher and 180 ° C. or lower on the inorganic thin film layer side of the transparent moisture-proof film, and a back film provided on the back side of the transparent moisture-proof film. .
Moreover, this invention relates to the solar cell module produced using the said surface protection material for solar cells.

According to the present invention, a highly moisture-proof solar cell surface protective material having a transparent moisture-proof film having an inorganic thin film layer on one surface of the substrate and having a water vapor permeability of less than 0.1 [g / m ² · day]. Therefore, it is possible to provide an excellent surface protective material that does not deteriorate moisture resistance for a long period of time, and to provide a solar cell module that is excellent in durability using the solar cell surface protective material.

The present invention is described in further detail below.
Usually, the surface protection material for solar cells is produced through a lamination process by dry lamination. In dry lamination, an adhesive diluted with a solvent is applied to a weather resistant film to a predetermined thickness, and the solvent is evaporated by drying in the range of 100 ° C to 140 ° C to form an adhesive layer on the weather resistant film. The film is bonded with the inorganic thin film surface facing the adhesive side. Thereafter, an adhesive diluted with a solvent in the same manner as described above was applied to the back surface of the moisture-proof film to a predetermined thickness, and the solvent was evaporated by drying in the range of 100 ° C. to 140 ° C. to form an adhesive layer on the moisture-proof film. Then, a film is further bonded and a surface protective material is created through curing at a predetermined temperature. Curing is usually carried out in the range of 30 ° C. to 80 ° C. for 1 day to 1 week. In this lamination process, heat and bonding tension act on each film, and residual strain is accumulated in the surface protective material.

Next, the surface protective material is heated and melted by vacuum lamination together with the solar cell element and the sealing material, and is integrated into the solar cell. This vacuum lamination process is performed in the range of 130 ° C to 180 ° C.
The residual strain accumulated in the above lamination process acts as a stress on each lamination interface when the solar cell is stored in a high temperature and high humidity environment. In particular, when residual strain accumulates in the weather resistant film, the residual stress acts on the inorganic thin film layer in a high-temperature and high-humidity environment, causing serious deterioration of the inorganic thin film layer.
In particular, in the case of a moisture-proof film having a high moisture-proof property with a water vapor transmission rate of less than 0.1 [g / m ² · day], which is the subject of this application, the deterioration in moisture-proof performance due to residual stress from the weather-resistant film is significant. This is because the small amount of defects generated inside the inorganic thin film layer and between the moisture-proof film substrate, the anchor coat layer and the inorganic thin film layer has a significant influence on the high moisture-proof property.

In addition, when the adhesive force of the adhesive layer to the inorganic thin film layer is low since the production of the surface protective material, the stress propagation from the weather resistant film to the inorganic thin film layer is alleviated, and the moisture resistance performance is not deteriorated.
As described above, the present inventors reduced the stress acting on the inorganic thin film layer of the moisture-proof film in a high-temperature and high-humidity environment by reducing the residual strain in the weather-resistant film in the vacuum lamination process, and suppressed deterioration of moisture-proof performance. It came to find out to realize.

<Surface protective material>
The surface protective material for solar cells in the present invention is a surface for solar cells having a transparent high moisture-proof film having an inorganic thin film layer on one surface of the substrate and having a water vapor permeability of less than 0.1 [g / m ² · day]. A protective material having a weather resistant film having a melting point of 130 ° C. or higher and 180 ° C. or lower on the inorganic thin film layer side of the transparent moisture-proof film, and a back film on the back surface of the inorganic thin film layer of the transparent moisture-proof film. is there.
In the present invention, the “melting point of the film” means that a differential scanning calorimeter is used to heat about 10 mg of a film sample from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min according to JIS K7121. After confirming the melting peak, holding at 200 ° C. for 1 minute, the temperature was lowered to −40 ° C. at a cooling rate of 10 ° C./min, and the thermogram measured when the temperature was raised again to 200 ° C. at a heating rate of 10 ° C./min. From the crystal melting peak temperature, the maximum peak means that (Tm) (° C.) is the melting point. When the melting point exceeded 200 ° C. and no melting peak was observed, such as polyester, the temperature rise upper limit temperature was set to 300 ° C., and then the same measurement was performed.

The surface protective material for solar cells in the present invention is a weatherproof film on the exposed side for hydrolysis resistance and weather resistance, and adhesion with a sealing material, withstand voltage, etc. for a transparent moisture-proof film. Therefore, it is preferable to provide a back film on the solar cell side, and it is preferable to laminate a weather resistant film, a moisture-proof film, and a back film in this order from the exposed side. From the viewpoint of ensuring the interlayer strength of the laminate, it is preferable that the weather-resistant film and moisture-proof film, and the moisture-proof film and back film are each laminated via an adhesive.
Hereinafter, each constituent layer will be described.

(Transparent moisture-proof film)
The transparent moisture-proof film in the solar cell surface protective material of the present invention is a film having moisture resistance and transparency, and has at least one inorganic thin film layer made of an inorganic oxide on at least one surface of the base film. It is a film.
This inorganic thin film layer can protect the inner surface side of the solar cell due to moisture and water permeation, and can improve power generation efficiency in the front seat by ensuring high transparency.

  The substrate having the inorganic thin film layer is preferably a transparent thermoplastic polymer film, and any material can be used as long as it is a resin that can be used for ordinary packaging materials. Specifically, polyolefins such as homopolymers or copolymers such as ethylene, propylene and butene, amorphous polyolefins such as cyclic polyolefins, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), nylon 6 , Nylon 66, nylon 12, polyamide such as copolymer nylon, ethylene-vinyl acetate copolymer partial hydrolyzate (EVOH), polyimide, polyetherimide, polysulfone, polyethersulfone, polyetheretherketone, polycarbonate, polyvinyl Examples include butyral, polyarylate, fluororesin, acrylate resin, and biodegradable resin. Among these, polyesters, polyamides, and polyolefins are preferable from the viewpoints of film properties and cost. Among these, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are particularly preferable from the viewpoint of film properties.

In addition, the base material is a known additive such as an antistatic agent, a light blocking agent, an ultraviolet absorber, a plasticizer, a lubricant, a filler, a colorant, a stabilizer, a lubricant, a crosslinking agent, an antiblocking agent, an oxidation agent. An inhibitor or the like can be contained.
The thermoplastic polymer film as the substrate is formed by using the above raw materials, but when used as a substrate, it may be unstretched or stretched. . Moreover, you may laminate | stack with the other plastic base material.

  Such a substrate can be produced by a conventionally known method. For example, a raw material resin is melted by an extruder, extruded by an annular die or a T die, and rapidly cooled to be substantially amorphous and not oriented. An unstretched film can be manufactured. Further, by using a multilayer die, it is possible to produce a single layer film made of one kind of resin, a multilayer film made of one kind of resin, a multilayer film made of various kinds of resins, and the like.

  The unstretched film is subjected to a known method such as uniaxial stretching, tenter sequential biaxial stretching, tenter simultaneous biaxial stretching, tubular simultaneous biaxial stretching, or the like. A film stretched in at least a uniaxial direction can be produced by stretching in a direction (horizontal axis) perpendicular thereto. Although a draw ratio can be set arbitrarily, it is preferable that 150 degreeC heat shrink rate is 0.01 to 5%, Furthermore, it is preferable that it is 0.01 to 2%. Among these, from the viewpoint of film properties, a biaxially stretched polyethylene naphthalate film, a polyethylene terephthalate and / or a coextruded biaxially stretched film of polyethylene naphthalate and other plastics are preferable.

  In addition, it is preferable to apply | coat an anchor coat agent and to provide an anchor coat layer in the said base material for the adhesive improvement with an inorganic thin film. As anchor coating agents, solvent-based or water-soluble polyester resins, isocyanate resins, urethane resins, acrylic resins, vinyl-modified resins, vinyl alcohol resins, vinyl butyral resins, ethylene vinyl alcohol resins, nitrocellulose resins, oxazoline group-containing resins, carbodiimides A group-containing resin, a methylene group-containing resin, an epoxy group-containing resin, a modified styrene resin, a modified silicone resin, an alkyl titanate, or the like can be used alone or in combination of two or more. Also contains silane coupling agents, titanium coupling agents, light blocking agents, ultraviolet absorbers, stabilizers, lubricants, antiblocking agents, antioxidants, etc., or they are copolymerized with the above resins Things can be used.

  As a method for forming the anchor coat layer, a known coating method is appropriately adopted. For example, any method such as a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, a spray or a coating method using a brush can be used. Alternatively, the substrate may be immersed in a resin solution. After application, the solvent can be evaporated using a known drying method such as hot drying such as hot air drying or hot roll drying at a temperature of about 80 to 200 ° C., or infrared drying. Moreover, in order to improve water resistance and durability, the crosslinking process by electron beam irradiation can also be performed. Further, the formation of the anchor coat layer may be a method performed in the middle of the substrate film production line (inline) or a method performed after the substrate film is manufactured (offline).

As the transparent moisture-proof film, a film in which a metal coating film such as aluminum is formed on the transparent base film can be used. However, when applied to a solar cell, there is no fear of leakage of current, silica, alumina. An inorganic oxide coating film such as is preferably used.
As the method for forming the inorganic thin film layer, any method such as a vapor deposition method and a coating method can be used, but the vapor deposition method is preferable in that a uniform thin film having a high gas barrier property can be obtained. This vapor deposition method includes methods such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). Examples of physical vapor deposition include vacuum deposition, ion plating, and sputtering. Examples of chemical vapor deposition include plasma CVD using plasma and a catalyst that thermally decomposes a material gas using a heated catalyst. Examples include chemical vapor deposition (Cat-CVD).

  Examples of the inorganic substance constituting the inorganic oxide coating film include silicon, aluminum, magnesium, zinc, tin, nickel, titanium, hydrogenated carbon, and the like, or oxides, carbides, nitrides, or mixtures thereof. Of these, diamond like carbon mainly composed of silicon oxide, aluminum oxide, and hydrogenated carbon is preferable. In particular, silicon oxide, silicon nitride, silicon oxynitride, and aluminum oxide are preferable in that high gas barrier properties can be stably maintained.

The thickness of the inorganic thin film layer is preferably 40 to 1000 nm, more preferably 40 to 800 nm, and still more preferably 50 to 600 nm, from the viewpoint of stable moistureproof performance and transparency. Moreover, generally the thickness of the said base film is about 5-100 micrometers, 8-50 micrometers is preferable from the point of productivity or handleability, and 12-25 micrometers is still more preferable. Therefore, the thickness of the transparent moisture-proof film is generally about 6 to 100 μm, preferably 9 to 50 μm, and more preferably 12 to 25 μm from the viewpoint of productivity and ease of handling.
In a moisture-proof film having a high moisture-proof property, the deterioration of moisture-proof performance due to residual stress from the weather-resistant film is remarkable, so that the effect of maintaining the moisture-proof property in the present invention is remarkably exhibited. Therefore, in the present invention, the transparent moisture-proof film has a water vapor transmission rate of less than 0.1 [g / m ² · day], preferably 0.05 [g / m ² · day] or less, more preferably 0.03 [g / m ² · day] or less.

(Weather-resistant film)
The surface protection material for solar cells of the present invention is provided with hydrolysis resistance and weather resistance, and a weather resistant film is laminated on the inorganic thin film layer side of the moisture proof film in order to impart long-term durability.
The weather resistant film in the present invention reduces residual strain in the weather resistant film and reduces residual stress due to shrinkage applied from the back side of the inorganic thin film layer at high temperature and high humidity. Therefore, specifically, a film having a melting point near the temperature at the time of vacuum lamination, that is, a film having a melting point of 130 ° C. or higher and 180 ° C. or lower is used.
From the above viewpoint, the lower limit of the melting point is 130 ° C., preferably 140 ° C., and more preferably 150 ° C. The upper limit of the melting point is 180 ° C, preferably 175 ° C, and more preferably 170 ° C.

  By using a weather-resistant film with a melting point within the above temperature range, the molecular / crystal orientation in the film caused by the history of force and thermal history applied in the previous process is relaxed at the temperature during vacuum lamination. Residual strain can be reduced.

  Usually, in a vacuum lamination process, a weather-resistant film flows easily with respect to pressure, and a film having a uniform thickness cannot be maintained. In this invention, the said melting | fusing point shall be 130 degreeC or more, the flow of the said back film can be suppressed, and thickness can be maintained. In addition, since the temperature rises to about 85 to 90 ° C. due to heat generated during power generation or radiant heat of sunlight, regardless of the thickness, the weather resistance film is used as the melting point is less than 80 ° C. The function of protecting the original solar cell element during softening and operation is lost.

The melting point in the present invention is determined by heating about 10 mg of a sample from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min according to JIS K7121, confirming the melting peak, and holding at 200 ° C. for 1 minute. From the thermogram measured when the temperature was lowered to −40 ° C. at a cooling rate of 10 ° C./min and again raised to 200 ° C. at a heating rate of 10 ° C./min, the melting peak (Tm) (C) is obtained using a differential scanning calorimeter. When the melting point exceeded 200 ° C. and no melting peak was observed, such as polyester, the temperature rise upper limit temperature was set to 300 ° C., and then the same measurement was performed.
The weather resistant film is not particularly limited as long as it has weather resistance and has the melting point. For example, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), and a resin such as polypropylene as a main component, What formed into a film the resin composition which knead | mixed the ultraviolet absorber to this is used preferably.

From the viewpoint of long-term durability, polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF) are more preferably used as the resin.
Further, since it is preferable that the characteristic change is small even in the temperature / humidity change at the time of vacuum lamination or high temperature and high humidity, a film which has been subjected to a low shrinkage rate by a prior heat treatment or the like is preferably used.
Considering use in solar cell protective materials, it is desirable to be a weather-resistant film that is highly flexible and has excellent heat resistance, moisture resistance, and UV durability, such as polyvinylidene fluoride (PVDF) and polyfluoride. Those mainly composed of vinyl (PVF) are preferably used.

The weather resistant film is preferably laminated to the transparent moisture-proof film directly or via an adhesive, but more preferably laminated via an adhesive.
Here, the term “main component” is intended to allow other components to be included within a range that does not impede the effects of the present invention, and is not intended to limit the specific content. When the total component is 100 parts by mass, it means 50 parts by mass or more, preferably 65 parts by mass or more, more preferably 80 parts by mass or more and a component occupying a range of 100 parts by mass or less.

As the ultraviolet absorber to be used, various commercially available products can be applied, and examples thereof include various types such as benzophenone, benzotriazole, triazine, and salicylic acid ester. Examples of the benzophenone-based UV absorber include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-n. -Dodecyloxybenzophenone, 2-hydroxy-4-n-octadecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-5-chlorobenzophenone, 2, 4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, etc. But it can.
The benzotriazole ultraviolet absorber is a hydroxyphenyl-substituted benzotriazole compound, for example, 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-5-t-butylphenyl) Benzotriazole, 2- (2-hydroxy-3,5-dimethylphenyl) benzotriazole, 2- (2-methyl-4-hydroxyphenyl) benzotriazole, 2- (2-hydroxy-3-methyl-5-t- Butylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-amylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, etc. be able to. Examples of triazine ultraviolet absorbers include 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol, 2- ( 4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyloxy) phenol and the like. Examples of salicylic acid esters include phenyl salicylate and p-octylphenyl salicylate.

The addition amount of the ultraviolet absorber is usually about 0.01 to 2.0% by mass and preferably 0.05 to 0.5% by mass in the weather resistant film.
A hindered amine light stabilizer is suitably used as a weather stabilizer that imparts weather resistance in addition to the above ultraviolet absorber. A hindered amine light stabilizer does not absorb ultraviolet rays like an ultraviolet absorber, but exhibits a remarkable synergistic effect when used together with an ultraviolet absorber.

  Examples of the hindered amine light stabilizer include dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly [{6- (1,1 3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {{2, 2,6,6-tetramethyl-4-piperidyl} imino}], N, N′-bis (3-aminopropyl) ethylenediamine-2,4-bis [N-butyl-N- (1,2,2, 6,6-pentamethyl-4-piperidyl) amino] -6-chloro-1,3,5-triazine condensate, bis (2,2,6,6-tetramethyl-4-piperidyl) separate, 2- (3 , 5-di-tert-4- Mud alkoxybenzylacetic) -2-n-butyl malonic acid bis (1,2,2,6,6-pentamethyl-4-piperidyl) and the like. The addition amount of the hindered amine light stabilizer is usually about 0.01 to 0.5% by mass, preferably 0.05 to 0.3% by mass, in the weather resistant film.

  The thickness of the weather-resistant film is generally about 20 to 100 μm, preferably 20 to 90 μm, more preferably 20 to 50 μm from the viewpoint of film handling and cost.

(Back film)
The back film in the present invention is a film bonded to the transparent moisture-proof film on the back side of the transparent moisture-proof film, preferably via an adhesive.
The back film preferably has a melting point near the vacuum lamination temperature. For example, polypropylene (PP), polylactic acid (PLA), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), cellulose butyrate (CAB) A resin composition obtained by kneading an ultraviolet absorber or a colorant in a resin such as) is preferably used, but is not limited thereto.

  Considering the use of the back film as a solar cell surface protection material, it is desirable that it is flexible and excellent in ultraviolet rays and humidification durability, and is mainly composed of polypropylene (PP) resin, polylactic acid (PLA) resin, and polyfluoride. What consists of any 1 or several resin of a vinylidene chloride (PVDF) resin is preferable, and it is preferable that these resins contain 50 weight% or more.

In addition, as said ultraviolet absorber, the thing similar to the ultraviolet absorber contained in the above-mentioned weather-resistant film can be used. Moreover, titanium oxide, calcium carbonate, etc. can be used as a coloring agent. As the resin, one of the above-listed resins can be used alone, or two or more of them can be used in combination.
The thickness of the back film is generally about 25 to 300 μm, preferably 50 to 300 μm, more preferably 50 to 250 μm, and more preferably 120 from the viewpoint of securing partial discharge of the protective material, from the viewpoint of film handling and cost. ~ 200 μm.

(Plastic film)
In the surface protection material for solar cells of this invention, it can have the said back film on the opposite side to the inorganic thin film layer of the said transparent moisture-proof film, and can also have a plastic film in this order. The plastic film is preferably laminated on the surface of the back film opposite to the transparent moisture-proof film for the purpose of improving the electric resistance performance and handling of the surface protective material. As the above, the same film as the back film may be used, but other film can be used. From the viewpoint of adhesion to the sealing material and reflectance, polypropylene or polyethylene terephthalate (PET ) Is preferably used.

  The thickness of the plastic film is preferably 10 to 100 μm, and preferably 20 to 50 μm, from the viewpoints of little influence on deterioration of moisture resistance and ensuring strength as an adhesion layer to the sealing material. It is more preferable.

(Surface protective material)
The surface protective material for a solar cell of the present invention has a transparent high moisture-proof film having a water vapor transmission rate of less than 0.1 [g / m ² day] having an inorganic thin film layer on one surface of a substrate. A material having a weather resistant film having a melting point of 130 ° C. or higher and 180 ° C. or lower on the inorganic thin film layer side of the transparent moisture-proof film and a back film on the opposite side of the transparent moisture-proof film to the inorganic thin film layer. .

  As described above, the surface protective material is not particularly limited as long as it has a specific weather-resistant film, a transparent moisture-proof film, and a back film. The weather resistant film needs to have a melting point of 130 ° C. or higher and 180 ° C. or lower. However, if the weather resistant film is within the melting point range, the component may contain only the components within the melting point range. It may contain 50 mass% or more. This is because residual stress due to shrinkage applied to the inorganic thin film layer in a high-temperature and high-humidity environment can be reduced, and moisture-proof performance can be maintained for a long time even after vacuum lamination processing.

  The surface protective material of the present invention is preferably formed by bonding a transparent moisture-proof film and the weather-resistant film through an adhesive between each film such as the weather-resistant film, transparent moisture-proof film and back film. . As the adhesive, a polyurethane-based adhesive is preferably used, and specific examples of the main agent of the adhesive include a polycarbonate polyol, a polyether polyol, an acrylic polyol, a polyurethane polyol, or a composition containing a polyester polyol. From the viewpoint of stability, humidity stability, and the like, those containing at least one of polycarbonate polyol, polyether polyol, and polyurethane polyol are more preferable.

  Furthermore, the solar cell surface protective material of the present invention may be a sealing material / surface protective material integrated type formed by laminating a sealing material described later. By further laminating the sealing material in advance, it is possible to reduce the work of individually laminating the back surface protection sheet, the sealing material, the power generation element, the sealing material, and the front surface protection sheet in the vacuum lamination process, and the efficiency of manufacturing the solar cell module Can be achieved.

  The surface protective material for solar cells of the present invention further improves various physical properties (flexibility, heat resistance, transparency, adhesiveness, etc.), molding processability, economic efficiency, etc. without departing from the gist of the present invention. For example, modified with polar groups such as polyolefin resins and various elastomers (olefins, styrenes, etc.), carboxyl groups, amino groups, imide groups, hydroxyl groups, epoxy groups, oxazoline groups, thiol groups, silanol groups, etc. Resins and tackifying resins can be contained. In particular, the weather resistant film can contain the resin as long as it satisfies the melting point range.

Examples of the tackifying resin include petroleum resins, terpene resins, coumarone-indene resins, logistic resins, and hydrogenated derivatives thereof. Specifically, as the petroleum resin, there are an aromatic petroleum resin from alicyclic petroleum resins and C ₉ components from cyclopentadiene or dimer thereof, terpene resins and terpene from The terpene resin β- pinene -Phenol resin and rosin resin include rosin resins such as gum rosin and wood rosin, and esterified rosin resins modified with glycerin and pentaerythritol. Further, the tackifying resin can be obtained mainly having various softening temperatures depending on the molecular weight, but a hydrogenated derivative of an alicyclic petroleum resin having a softening temperature of 100 to 150 ° C, preferably 120 to 140 ° C is particularly preferable. Usually, when the resin composition forming each film constituting the surface protective material is 100% by mass, it is preferably 20% by mass or less, and more preferably 10% by mass or less.

  Moreover, various additives can be added to the surface protective material for solar cells as necessary. Examples of the additive include a silane coupling agent, an antioxidant, a weather resistance stabilizer, a light diffusing agent, a nucleating agent, a pigment (for example, a white pigment), a flame retardant, and a discoloration preventing agent. In the present invention, it is preferable that at least one additive selected from a silane coupling agent, an antioxidant, an ultraviolet absorber, and a weathering stabilizer is added. In the present invention, for example, when a high heat resistance is required, a crosslinking agent and / or a crosslinking aid may be blended.

  Examples of silane coupling agents include compounds having a hydrolyzable group such as an alkoxy group together with an unsaturated group such as a vinyl group, an acryloxy group or a methacryloxy group, an amino group or an epoxy group. . Specific examples of the silane coupling agent include N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, and γ-aminopropyltriethoxy. Examples include silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and the like. In the present invention, γ-glycidoxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane are preferably used because of good adhesiveness and little discoloration such as yellowing. The addition amount of the silane coupling agent is usually about 0.1 to 5% by mass and preferably 0.2 to 3% by mass in each film constituting the surface protective material. In addition, similar to the silane coupling agent, a coupling agent such as an organic titanate compound can be effectively used.

  As the antioxidant, various commercially available products can be applied, and various types such as monophenol type, bisphenol type, polymer type phenol type, sulfur type and phosphite type can be exemplified. Examples of monophenols include 2,6-di-tert-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-tert-butyl-4-ethylphenol, and the like. Examples of bisphenols include 2,2′-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2′-methylene-bis- (4-ethyl-6-tert-butylphenol), 4,4 '-Thiobis- (3-methyl-6-tert-butylphenol), 4,4'-butylidene-bis- (3-methyl-6-tert-butylphenol), 3,9-bis [{1,1-dimethyl- 2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} ethyl} 2,4,9,10-tetraoxaspiro] 5,5-undecane.

Examples of the high molecular phenolic group include 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3 , 5-di-tert-butyl-4-bidoxybenzyl) benzene, tetrakis- {methylene-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate} methane, bis { (3,3'-bis-4'-hydroxy-3'-tert-butylphenyl) butyric acid} glycol ester, 1,3,5-tris (3 ', 5'-di-tert-butyl-4 '-Hydroxybenzyl) -s-triazine-2,4,6- (1H, 3H, 5H) trione, triphenol (vitamin E) and the like.
Examples of sulfur-based compounds include dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiopropionate.

  Examples of the phosphite system include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl) phosphite, Crick neopentanetetrayl bis (octadecyl phosphite), tris (mono and / or di) phenyl phosphite, diisodecyl pentaerythritol diphosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10- Oxide, 10- (3,5-di-tert-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy-9,10 -Dihydro-9-oxa-10-fo Phaphenanthrene, cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,6-di-tert-methylphenyl) phosphite, 2 , 2-methylenebis (4,6-tert-butylphenyl) octyl phosphite.

  In the present invention, phenol-based and phosphite-based antioxidants are preferably used in view of the effect of the antioxidant, thermal stability, economy, and the like, and it is more preferable to use both in combination. The addition amount of the antioxidant is usually about 0.1 to 1% by mass and preferably 0.2 to 0.5% by mass in each film constituting the surface protection material for solar cell.

  As a method for forming each film constituting the surface protection material for solar cell used in the present invention, a known method, for example, a single-screw extruder, a multi-screw extruder, a Banbury mixer, a kneader or the like has melt mixing equipment. An extrusion cast method using a T die, a calendar method, or the like can be employed, and is not particularly limited. In the present invention, however, an extrusion cast method using a T die is used in terms of handling properties and productivity. Preferably used. The molding temperature in the extrusion casting method using a T-die is appropriately adjusted depending on the flow characteristics and film forming properties of the resin composition to be used, but is generally 130 to 300 ° C, preferably 150 to 250 ° C. Various additives such as silane coupling agents, antioxidants, UV absorbers, and weathering stabilizers may be dry blended with the resin in advance and then supplied to the hopper. The master batch may be supplied after being prepared, or a master batch in which only the additive is previously concentrated in the resin may be prepared and supplied.

The solar cell surface protective material of the present invention using the transparent high moisture-proof film having a water vapor transmission rate of less than 0.1 [g / m ² day] thus obtained is moisture-proof performance of the laminate before heat treatment. The initial moisture-proof performance is preferably 0.1 [g / m ² · day] or less, more preferably 0.05 [g / m ² · day] or less in terms of water vapor transmission rate. Since the surface protective material for solar cells of the present invention can be used as a surface protective material for electronic devices that require excellent moisture proof performance, by using a transparent laminated moisture proof film having excellent initial moisture proof performance. It is preferable because the effects of the present invention can be more remarkably exhibited. The moisture-proof performance is preferably such that the degree of deterioration after a pressure cooker test at 120 ° C., humidity 100%, and 32 hours is 20 or less, more preferably within 15 relative to the initial water vapor permeability of the laminate. is there.

In addition, when the adhesive is thermally decomposed under high temperature and high humidity, when using polyurethane adhesive, carboxylic acid and hydroxyl groups are generated, and these functional groups form a chemical bond with the inorganic thin film layer, causing deterioration of the inorganic thin film layer. It is thought to cause. Therefore, as the polyol contained in the main component of the polyurethane-based adhesive, polycarbonate polyol, polyether polyol, polyacryl polyol, polyurethane polyol and the like having excellent heat resistance are preferable to polyester polyol which is easily thermally decomposed.
In the present invention, the degree of deterioration of the moisture resistance (water vapor transmission rate) after the pressure cooker test is expressed as [(b−a) in the initial water vapor transmission rate (a) and the water vapor transmission rate (b) after the pressure cooker test. ) / A].

That is, the initial moisture-proof performance of the solar cell surface protective material of the present invention refers to the moisture-proof performance before the member receives a high-temperature thermal history such as vacuum lameet conditions, and the value before the moisture-proof performance is reduced due to heat. means. Therefore, it includes changes over time from immediately after production to before heat treatment. For example, it means the value of moisture-proof performance in a state where heat treatment such as thermal lamination treatment performed at 130 to 180 ° C. for 10 to 40 minutes is not performed. To do. The initial water vapor transmission rate also has the same meaning as “above”.
The moisture-proof performance can be evaluated according to the conditions of JIS Z0222 “Method of testing moisture permeability of moisture-proof packaging container” and JIS Z0208 “Method of testing moisture permeability of moisture-proof packaging material (cup method)”.

The interlayer strength of the surface protection material of the present invention is preferably 4 N / 15 mm or more after a pressure cooker test of 120 ° C., 100% humidity and 32 hours. The interlayer strength is more preferably 7.0 mm or more, further preferably 7.3 mm or more, further preferably 7.5 N / 15 mm or more, and further preferably 8 N / 15 mm or more. In particular, even after a high temperature and high humidity treatment for producing a solar cell module, it is preferably 4 N / 15 mm or more, more preferably 7.0 mm or more, still more preferably 7.3 mm or more, and 7.5 N / 15 mm or more. It is particularly preferred.
The interlayer strength can be measured using a tensile tester after cutting the laminated film into a predetermined strip shape as described later.

(Production method of surface protection material)
The solar cell surface protective material of the present invention is not particularly limited as long as it is manufactured using a back film having the above characteristics in the known surface protective material manufacturing method. The film can be produced by using a polyurethane adhesive and drying the adhesive at a temperature of 100 to 140 ° C. and bonding the film together by dry lamination at a temperature of 0 to 80 ° C. In this case, it is preferable that the obtained laminated body is cured at a temperature of 30 to 80 ° C. for 1 to 7 days from the viewpoint of sufficiently bringing the adhesive to a saturation crosslinking degree. The surface protective material of the present invention thus obtained has excellent flexibility and moisture resistance that does not deteriorate the moisture resistance and interlayer strength even after the dry laminating process.

Moreover, it is preferable that the surface protection material for solar cells of the present invention has partial discharge resistance in addition to weather resistance and moisture resistance. The partial discharge resistance test is to measure a withstand voltage until the surface protection material reaches dielectric breakdown, and preferably has a withstand voltage of 700 to 1000 V as a solar cell protection material.
In order for the surface protective material to achieve the above-mentioned electric strength characteristics, the total thickness of the surface protective material is preferably 180 to 230 μm (depending on the required withstand voltage). Therefore, the thickness of each layer is arbitrary, but the relatively expensive weather-resistant film and transparent moisture-proof film are 10 to 50 μm, the adhesive is 4 to 10 μm, respectively, and the thickness of the back film is preferably 120 to 200 μm, From the viewpoint of the productivity of the moisture-proof film and the productivity of the dry lamination process, it is more preferably 20 to 30 μm, 4 to 8 μm, and 120 to 190 μm, respectively.

The thickness of the surface protective material is not particularly limited, but is usually about 100 to 400 μm, preferably about 100 to 300 μm, more preferably about 140 to 300 μm, and still more preferably 140 to 260 μm. Used in the form of a sheet.
The thickness of the surface protective material for solar cells is not particularly limited, but is usually about 60 to 400 μm, preferably 70 to 320 μm, more preferably 90 to 280 μm, and still more preferably 180 to 230 μm. Used in sheet form.

<Solar cell module, solar cell manufacturing method>
The surface protective material can be used as a surface protective member for solar cells as it is or after being bonded to a glass plate or the like. In order to produce the solar cell module and / or the solar cell of the present invention using the surface protective material of the present invention, it may be produced by a known method.

  A solar cell module can be produced by using the surface protective material of the present invention in a layer structure of a surface protective member such as a solar cell front sheet or back sheet, and fixing the solar cell element together with a sealing material. As such a solar cell module, various types can be exemplified, and preferably, when the surface protection material of the present invention is used as a front surface protection material, a sealing material, a solar cell element, and a lower part And a solar cell module produced using a protective material. Specifically, an upper protective material (surface protective material of the present invention) / sealing material (sealing resin layer) / solar cell element / sealing material. (Sealing resin layer) / lower protective material configuration, sealing material and upper protective material (surface protective material of the present invention) are formed on the solar cell element formed on the inner peripheral surface of the lower protective material. A solar cell element formed on the inner peripheral surface of the upper protective material (surface protective material of the present invention), for example, an amorphous solar cell element produced by sputtering or the like on a fluororesin-based transparent protective material Let's form a sealing material and a lower protective material on top Or the like can be mentioned Do configuration of things. It is optional to bond a glass plate to the outside of the surface protective material of the present invention as the upper protective material. In addition, when using the above-mentioned sealing material / surface protective material integrated surface protective material, the above-mentioned sealing material may not be used.

As the solar cell element, for example, a single crystal silicon type, a polycrystalline silicon type, an amorphous silicon type, a gallium-arsenic, a copper-indium-selenium, a cadmium-tellurium, or the like III-V group or II-VI group compound semiconductor type, Examples include a dye sensitizing type and an organic thin film type.
When forming a solar cell module using the surface protective material in the present invention, the solar cell power generation element is appropriately selected according to the type of the solar cell power generation element, and is formed by laminating using a weather resistant film or the like and an adhesive. To do.

  Although it does not specifically limit about each member which comprises the solar cell module produced using the surface protection material of this invention, As an sealing material, an ethylene- vinyl acetate copolymer is mentioned, for example. Can do. The lower protective material is a single layer or multilayer sheet such as metal or various thermoplastic resin films, for example, metals such as tin, aluminum and stainless steel, inorganic materials such as glass, polyester, inorganic vapor deposition polyester, fluorine-containing resin. And a single-layer or multilayer protective material such as polyolefin. The surface of the upper and / or lower protective material can be subjected to a known surface treatment such as a primer treatment or a corona treatment in order to improve the adhesion to the sealing material or other members.

  Configuration of an upper protective material (surface protective material of the present invention) / sealing material / solar cell element / sealing material / lower protective material described above for a solar cell module produced using the surface protective material of the present invention Will be described as an example. In order from the sunlight receiving side, the surface protective material, sealing resin layer, solar cell element, sealing resin layer, and back sheet of the present invention are laminated, and a junction box (from the solar cell element) is further formed on the lower surface of the back sheet. A terminal box for connecting wiring for taking out the generated electricity to the outside is bonded. The solar cell elements are connected by wiring in order to conduct the generated current to the outside. The wiring is taken out through a through hole provided in the backsheet and connected to the junction box.

  As a manufacturing method of the solar cell module, a known manufacturing method can be applied, and is not particularly limited, but in general, the surface protective material, the sealing resin layer, the solar cell element, the sealing resin of the present invention. A step of laminating the layers and the lower protective material in this order, and a step of vacuum-sucking them and thermocompression bonding. Also, batch type manufacturing equipment, roll-to-roll type manufacturing equipment, and the like can be applied.

  The solar cell module produced using the surface protective material of the present invention is a small solar cell represented by a mobile device, a large solar cell installed on a roof or a roof, etc., depending on the type and module shape of the applied solar cell. It can be applied to various uses, both indoors and outdoors.

  In the solar cell module and / or solar cell of the present invention, this solar cell protective sheet, encapsulant, power generation element, encapsulant, and back surface protective sheet are vacuum laminator according to a conventional method, and the temperature is preferably 130 to 180 ° C., more preferably 130 to 150 ° C., degassing time 2 to 15 minutes, press pressure 0.5 to 1 atm, press time is preferably 8 to 45 minutes, more preferably 10 to 40 minutes. Can be easily manufactured.

  EXAMPLES The present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples and comparative examples. Various physical properties were measured and evaluated as follows.

(Physical property measurement)
(1) Backside film crystal melting peak temperature (melting point, Tm)
Using a differential scanning calorimeter Q20 manufactured by T.A. Instruments Co., Ltd., according to JIS K7121, approximately 10 mg of a sample was heated from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min to be melted. After confirming the peak, holding at 200 ° C. for 1 minute, the temperature was lowered to −40 ° C. at a cooling rate of 10 ° C./min, and again from the thermogram measured when the temperature was raised to 200 ° C. at a heating rate of 10 ° C./min. The maximum peak among melting peak temperatures was determined as the melting point (Tm) (° C.). When the melting point exceeded 200 ° C. and no melting peak was observed, such as polyester, the temperature rise upper limit temperature was set to 300 ° C., and then the same measurement was performed.

(2) Pressure cooker test The surface protective material after curing was heat-treated at 150 ° C for 30 minutes, and the pressure cooker test LSK-500 manufactured by Tommy Seiko Co., Ltd. was used. Condition.

(3) Moisture-proof performance of moisture-proof film and surface protective material The moisture-proof performance of the moisture-proof film (B-1, B-2) is as follows: Measured by method. Moreover, about the surface protection material (D-1 to D-7), each constituent film is bonded and the measured value of the surface protection material after curing is used as the initial water vapor permeability, and after the curing, glass, sealing The surface after laminating materials and surface protective materials (D-1 to D-7, the back side of the moisture-proof film is the sealing material side), heat-treating at 150 ° C. for 30 minutes, and performing a pressure cooker test The water vapor transmission rate of the protective material was taken as the moisture proof value after the pressure cooker test.
Specifically, in accordance with JIS Z 0222 “moisture-proof packaging container moisture permeability test method” and JIS Z 0208 “moisture-proof packaging material moisture permeability test method (cup method)”, the following methods were used for evaluation.
Using two gas barrier film laminates each having a moisture permeable area of 10.0 cm × 10.0 cm square, a bag containing about 20 g of anhydrous calcium chloride as a hygroscopic agent and sealed on all sides was produced. Place in a 90% thermo-hygrostat and measure the mass up to about 200 days at intervals of 72 hours or more. From the slope of the regression line between the elapsed time after the 4th day and the bag weight, the water vapor transmission rate (g / m ²・ Day) was calculated. The degree of water vapor transmission rate deterioration was calculated by [(water vapor transmission rate after pressure cooker test−initial water vapor transmission rate) / initial water vapor transmission rate].

(4) Interlaminar strength measurement of surface protective material As described above, the surface protective material after curing was heat-treated at 150 ° C. for 30 minutes, and the peel strength of the surface protective material after the pressure cooker test was measured with a measurement width of 15 mm. The laminate was cut into strips, and the interlayer laminate strength (N / 15 mm) was measured at 300 mm / min using a STA-1150 manufactured by ORIENTIC.

(Structure film)

<Transparent moisture-proof film>
Moisture-proof film B-1
A 12 μm thick biaxially stretched polyethylene naphthalate film (manufactured by Teijin DuPont, “Q51C12”) was used as the base film, and the following coating solution was applied to the corona-treated surface and dried to a thickness of 0.1 μm. A layer was formed.
Next, SiO was heated and evaporated under a vacuum of 1.33 × 10 ⁻³ Pa (1 × 10 ⁻⁵ Torr) using a vacuum deposition apparatus, and SiOx (x = 1.5) having a thickness of 50 nm was formed on the coating layer. ) A moisture-proof film B-1 having an inorganic thin film layer was obtained. The moisture-proof performance of the produced moisture-proof film B-1 was 0.01 [g / m ² · day].

Coating solution “GOHSENOL” (degree of saponification: 97.0 to 98.8 mol%, degree of polymerization: 2400) manufactured by Nippon Gosei Co., Ltd. was added to 2810 g of ion-exchanged water and dissolved in an aqueous solution. While stirring at 0 ° C., 645 g of 35% hydrochloric acid was added. Subsequently, 3.6 g of butyraldehyde was added with stirring at 10 ° C., and after 5 minutes, 143 g of acetaldehyde was added dropwise with stirring to precipitate resin fine particles. Subsequently, after hold | maintaining at 60 degreeC for 2 hours, the liquid was cooled, neutralized with sodium hydrogencarbonate, washed with water, and dried, and the polyvinyl acetoacetal resin powder (acetalization degree 75 mol%) was obtained.
In addition, an isocyanate resin (“Sumijour N-3200” manufactured by Sumitomo Bayer Urethane Co., Ltd.) was used as a cross-linking agent, and mixing was performed so that the equivalent ratio of isocyanate groups to hydroxyl groups was 1: 2.

Moisture-proof film B-2
A tech barrier LX made by Mitsubishi Plastics, on which silica was deposited on a 12 μm polyethylene terephthalate resin film, was used. Further, the moisture resistance measured by the above-described method was 0.2 [g / (m ² · day)].

<Adhesive and adhesive coating solution>
Adhesive coating liquid HD1013 manufactured by Rock Paint Co., Ltd. is used as a main component containing a polyurethane polyol component, and H62 manufactured by Rock Paint Co., Ltd. is used as a curing agent containing an aliphatic hexamethylene diisocyanate component. : 1 and mixed with ethyl acetate to a solid content concentration of 30% to prepare an adhesive coating solution.

<Weather-resistant film>
The following weather resistant films C-1 to C-6 were prepared and subjected to corona discharge treatment on both sides according to a conventional method to form corona treated surfaces.

Weather resistant films C-1 and C-2
To isotactic polypropylene resin, titanium oxide (8 wt%) as a whitening agent and ultrafine titanium oxide (particle diameter, 0.01 to 0.06 μm, 3 wt%) as an ultraviolet absorber are added, In addition, a necessary additive is added and sufficiently kneaded to prepare a polypropylene resin composition, and then the polypropylene resin composition is extruded with an extruder to give an unstretched polypropylene (PP) resin film having a thickness of 50 μm ( C-1) and 90 μm thick unstretched polypropylene (PP) resin film (C-2) were produced.

Weather resistant film C-3
Polyvinylidene fluoride (PVDF) film Kynar 302-PGM-TR (thickness: 30 μm) manufactured by Arkema was used.

Weather resistant film C-4
As the hydrolysis-resistant polyester film, a hydrolysis-resistant polyethylene terephthalate (PET) film manufactured by Mitsubishi Plastics, P100 (thickness: 50 μm) was used as C-3.

Weather resistant film C-5
Asahi Glass Co., Ltd. Ethylene-tetrafluoroethylene copolymer (ETFE) Aflex 50N 1250NT 50 μm was used as C-5.

Weather resistant film C-6
A biaxially stretched polyethylene naphthalate (PEN) film (“Q51C25”) made by Teijin DuPont with a thickness of 25 μm was used as C-6.

The composition, thickness, and melting point values of C-1 to C-6 are summarized in Table 1 above.

<Back film>
Weather resistant film C-1 was used.

Example 1
The adhesive coating liquid was applied and dried on the weather resistant film so as to have a solid content of 6 g / m ^2, and the inorganic thin film layer of the moisture-proof film B-1 was bonded to the adhesive surface by a dry laminate with a tension of about 80 N / m.
Thereafter, the adhesive coating solution was applied and dried on the opposite surface of the inorganic thin film film so that the solid content was 6 g / m ^2, and the corona surface of the back film C-1 was bonded, followed by curing at 40 ° C. for 5 days, and a thickness of 164 μm. Surface protective material D-1 was prepared. Laminated in the order of glass, encapsulant, surface protective material D-1 (encapsulant side is the back film), vacuum laminated at 150 ° C for 15 minutes, and then a pressure cooker test was conducted to determine the interlayer strength and moisture resistance. Sex was measured. The results are shown in Table 2.

Example 2
A surface protective material D-2 having a thickness of 204 μm was prepared in the same manner as in Example 1 except that the weather resistant film C-1 in Example 1 was changed to C-2, and after vacuum lamination, a pressure cooker test was conducted. Strength and moisture resistance were measured. The results are shown in Table 2.

Example 3
A surface protective material D-3 having a thickness of 144 μm was prepared in the same manner as in Example 1 except that the weather-resistant film C-1 in Example 1 was changed to C-3, and after vacuum lamination, a pressure cooker test was conducted. Strength and moisture resistance were measured. The results are shown in Table 2.

Comparative Example 1
A surface protective material D-4 having a thickness of 164 μm was prepared in the same manner as in Example 1 except that the weather resistant film C-1 in Example 1 was changed to C-4, and after vacuum lamination, a pressure cooker test was conducted. Strength and moisture resistance were measured. The results are shown in Table 2.

Comparative Example 2
A surface protective material D-5 having a thickness of 164 μm was prepared in the same manner as in Example 1 except that the weather resistant film C-1 in Example 1 was changed to C-5, and after vacuum lamination, a pressure cooker test was conducted. Strength and moisture resistance were measured. Comparative Example 3 whose results are shown in Table 2
A surface protective material D-6 having a thickness of 139 μm was prepared in the same manner as in Example 1 except that the weather-resistant film C-1 in Example 1 was changed to C-6, and after vacuum lamination, a pressure cooker test was conducted. Strength and moisture resistance were measured. The results are shown in Table 2.

Reference example 1
A surface protective material D-7 having a thickness of 164 μm was prepared in the same manner as in Comparative Example 2 except that the moisture-proof film B-1 was changed to B-2. After vacuum lamination, a pressure cooker test was conducted to obtain interlayer strength and moisture resistance. It was measured. The results are shown in Table 2.

Thus, it is a highly moisture-proof surface protection material for solar cells having a transparent moisture-proof film having an inorganic thin film layer on one surface of the substrate and having a water vapor permeability of less than 0.1 [g / m ² day]. The surface protective materials of Examples 1 to 3 having a weather-resistant film having a melting point within a specific range on the inorganic thin film layer side of the transparent moisture-proof film retains moisture-proof performance for a long time even after heat treatment in a vacuum lamination process. It became clear from the evaluation by the pressure cooker test. Moreover, it turned out that the surface protection material of Examples 1-3 has sufficient interlayer intensity | strength for a long term even if the said heat processing is made | formed.
On the other hand, for Comparative Examples 1 to 3 in which a film having a melting point outside the above specified range is disposed on the inorganic thin film layer side of the transparent moisture-proof film, it becomes clear that the long-term moisture-proof performance after the heat treatment in the vacuum lamination process is remarkably lowered. It was. In addition, Reference Example 1 having a low initial moisture-proof performance shows that the degree of deterioration of the moisture-proof performance is small, and the degree of deterioration of the moisture-proof performance becomes larger as the initial moisture-proof performance is higher than in the examples.
Thus, it became clear that the highly moisture-proof surface protection material for solar cells in the present invention has a remarkable effect of maintaining moisture resistance in a highly moisture-proof film that is particularly susceptible to deterioration in moisture-proof performance. Therefore, by using this for a solar cell module, it is possible to remarkably improve the durability of the solar cell module because it significantly suppresses the arrival of water vapor to the solar cell and the deterioration of the surface protection material itself. It is.

Claims (7)

A surface protective material for a solar cell having an inorganic thin film layer on one surface of a substrate and having a transparent moisture-proof film having a water vapor transmission rate of less than 0.1 [g / m ² · day],
A solar cell having a weather resistant film having a melting point of 130 ° C. or higher and 180 ° C. or lower on the inorganic thin film layer side of the transparent moisture-proof film and a back film on the opposite side of the transparent moisture-proof film to the inorganic thin film layer. Surface protective material.   The surface protection material for solar cells according to claim 1, wherein the weather-resistant film contains at least one resin selected from polyvinylidene fluoride resin, polyvinyl fluoride, and polypropylene resin as a main component.   The solar cell surface protective material according to claim 1 or 2, wherein the weather-resistant film has a thickness of 20 to 100 µm.   The surface protection material for solar cells in any one of Claims 1-3 which has an adhesive bond layer between the said transparent moisture-proof film and the said weather resistance film.   The surface protection material for solar cells in any one of Claims 1-4 which have the said back film and a plastic film in this order on the opposite side to the inorganic thin film layer of the said transparent moisture-proof film.   Furthermore, the surface protection material for solar cells in any one of Claims 1-5 which have a sealing material laminated | stacked.   The solar cell module produced using the surface protection material for solar cells in any one of Claims 1-6.