JP2013077818A - Solar cell protective material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell protective material having no deterioration in moisture proofness for a long term, preventing generation of delamination, achieving a solar cell protective material excellent in flexibility and moisture proofness, preventing deterioration in solar cell performance at the same time, and further effective for an improvement of battery cell durability.SOLUTION: A solar cell protective material includes a fluorine-based resin film, an intermediate film, an adhesive layer, and a moisture proof film, in the order, the moisture proof film having a metal oxide layer on at least one surface of a base material and a steam permeability of less than 0.1 [g/(mday)]. The intermediate film has a melting point of 150°C or below, the adhesive layer has a tensile storage modulus of 5.0×10-5.0×10Pa at a temperature of 100°C, a frequency of 10 Hz and a distortion of 0.1%, and a thickness of 13 μm or more.

Description

  The present invention relates to a protective material used for solar cells and the like, and more particularly, to a protective material for solar cells that can maintain moisture resistance and prevent the occurrence of delamination.

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. The solar cell is configured such that solar cell cells are sealed with a sealing material such as an ethylene-vinyl acetate copolymer between the front surface protective film and the back surface protective film from the light receiving surface side.
Such a solar cell is usually manufactured by laminating a front protective film, a sealing material, a power generating element, a sealing material, and a back protective film in this order, and bonding and integrating them by heating and melting. As a solar cell protective material that is a front protective film and / or a back protective film of a solar cell, it is required to have excellent durability against ultraviolet rays. In order to prevent rust, excellent moisture resistance is a very important requirement. Furthermore, the development of excellent protective materials with little deterioration of moisture resistance under long-term use and high-temperature conditions has been made.

For example, in Patent Document 1, a polyester adhesive is used for a moisture-proof film having a water vapor transmission rate of 0.22 [g / (m ² · day)] based on a biaxially stretched polyester film, A solar cell protective material is prepared by laminating a weather-resistant polyester film and a polypropylene film on the back surface, and the moisture resistance after a 1000 hour test is evaluated at 85 ° C. and 85% humidity, and a proposal for preventing moisture degradation is made. ing.
Moreover, in the Example of patent document 2, a polyurethane adhesive layer is provided on both sides of a moisture-proof film having a water vapor permeability of 1 to 2 [g / (m ² · day)] based on a biaxially stretched polyester film. The surface protection material for solar cells was manufactured by laminating weather-resistant polyester films on both sides, and the barrier performance and interlayer strength after 1000 hours accelerated test at 85 ° C and 85% humidity were evaluated to prevent deterioration of both characteristics. I am making a proposal.
In Patent Document 3, a PVF film using a two-component curable polyurethane adhesive on a moisture-proof film having a water vapor transmission rate of 0.5 [g / (m ² · day)] which is also based on a biaxially stretched polyester film. After bonding, the moisture resistance and interlayer strength before and after the pressure cooker test (PCT) (severe environment test by high temperature and pressure, 105 ° C., 92 hours) are evaluated, and the proposal for preventing the deterioration of characteristics is made.

JP 2007-150084 A JP 2009-188072 A JP 2009-49252 A

However, each of the techniques disclosed in Patent Documents 1 to 3 relates to a laminate having a moisture-proof film having a water vapor transmission rate of 0.1 [g / (m ² · day)] or more. Maintaining moisture resistance after accelerated durability tests such as the pressure cooker test (PCT) when applied to solar cell surface protection materials such as compound power generation element solar cell modules that require high moisture resistance, the edge of the protective film It was not possible to sufficiently prevent the occurrence of delamination.
The protective material for solar cells is excellent in moisture resistance and prevention of delamination, and it is desired that the moisture resistance and prevention of delamination be maintained over a long period of time. In the case of using a film having a high moisture resistance of less than 0.1 [g / (m ² · day)], specific proposals have been made to enable moisture prevention and prevention of delamination for a long time. There was no actual situation.

That is, an object of the present invention is to provide a solar cell protective material including a moisture-proof film having a water vapor transmission rate of less than 0.1 [g / (m ² · day)]. Providing a solar cell protective material that prevents generation, realizes flexibility and moisture proofing, prevents solar cell performance degradation at the same time, and is effective in improving solar cell durability There is to do.

As a result of repeated studies, the present inventors have a metal oxide layer on at least one surface of the fluororesin film, the intermediate film, the pressure-sensitive adhesive layer, and the substrate, and have a water vapor transmission rate of 0.1 [g / (M ² · day)] a solar cell protective material having a moisture-proof film in this order, wherein the intermediate film has a melting point of 150 ° C. or lower, and the pressure-sensitive adhesive layer has a temperature of 100 ° C., a frequency of 10 Hz, and a strain of 0.1. The protective material for solar cells having a tensile storage elastic modulus in% of 5.0 × 10 ⁴ to 5.0 × 10 ⁵ Pa and a thickness of 13 μm or more is moisture-proof even in long-term storage in a high-temperature and high-humidity environment. It has been found that the deterioration of the property and the prevention of the occurrence of delamination can be satisfied at the same time, and the present invention has been completed.

That is, the present invention
(1) A metal oxide layer is provided on at least one surface of the fluororesin film, the intermediate film, the pressure-sensitive adhesive layer, and the base material, and the water vapor transmission rate is less than 0.1 [g / (m ² · day)]. A solar cell protective material having a moisture-proof film in this order,
The intermediate film has a melting point of 150 ° C. or lower, and the pressure-sensitive adhesive layer has a tensile storage elastic modulus of 5.0 × 10 ⁴ to 5.0 × 10 ⁵ Pa at 100 ° C., a frequency of 10 Hz, and a strain of 0.1%, The protective material for solar cells, wherein the thickness is 13 μm or more,
(2) The solar cell protective material according to (1), wherein the thickness of the intermediate film is 50 to 600 μm,
(3) The solar cell protective material according to (1) or (2), wherein the intermediate film contains a polyethylene resin as a main component.
(4) The protective material for solar cells according to any one of (1) to (3) above, which has the pressure-sensitive adhesive layer and the intermediate film on the metal oxide layer side of the moisture-proof film,
(5) The protective material for solar cells according to any one of (1) to (4), wherein the initial water vapor permeability is less than 0.1 [g / (m ² · day)],
(6) The solar cell according to any one of (1) to (5), wherein a thickness (t1) of the substrate of the moisture-proof film and a thickness (t2) of the fluororesin film satisfy the following relational expression: Protective layer,
t1 <t2
(7) A solar cell module having the solar cell protective material according to any one of (1) to (6) above,
Is to provide.

  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. It means that the maximum peak among the crystal melting peak temperatures is the melting point (Tm) (° C.). In addition, when melting | fusing point exceeds 200 degreeC and a melting peak is not observed, such as polyester, it can obtain | require by making temperature rising upper limit temperature into 300 degreeC and performing a similar measurement after that.

  According to the present invention, a solar cell protective material excellent in flexibility and moisture resistance without causing deterioration of moisture resistance and delamination over a long period of time is achieved, and the performance of the solar cell is prevented at the same time, and the durability of the solar cell is achieved. It is possible to provide a highly moisture-proof solar cell protective material that is effective in improving the property.

Hereinafter, the present invention will be described in more detail.
Usually, in the production of a solar cell protective material, an adhesive or pressure-sensitive adhesive diluted with a solvent is applied to a plastic film to be laminated to a predetermined thickness, and the solvent is evaporated by drying in a range of 70 ° C to 140 ° C. After the adhesive layer or the pressure-sensitive adhesive layer is formed on the plastic film, the other plastic film is repeatedly bonded to the adhesive or the pressure-sensitive adhesive side, and finally it is prepared through curing at a predetermined temperature. Curing is performed 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 solar cell protective material. The produced solar cell 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 usually performed in the range of 130 ° C to 180 ° C.
Thus, the protective material for solar cells is subjected to heat treatment in the range of 130 ° C. to 180 ° C., which is a temperature much higher than the drying and curing temperature of the adhesive in the vacuum lamination process. The residual strain accumulated in the above-described lamination process acts as stress on each lamination interface during storage in a high temperature and high humidity environment. In particular, when residual strain accumulates in a plastic film, the film shrinks due to the temperature in a high-temperature and high-humidity environment, stress acts on the metal oxide layer, and serious deterioration of the metal oxide layer may occur. is there.

Moreover, the protective material for solar cells can prevent moisture from entering from the exposed surface of the film (fluorine resin film surface) by laminating a moisture-proof film, but in high-temperature and high-humidity environments. In the accelerated test, moisture and moisture penetration from the edge of the solar cell protective material gradually deteriorates the adhesive and metal oxide-free substrate used for lamination, causing delamination from the edge and moisture-proof performance. Decrease may occur.
In particular, in the case of a moisture-proof film having a high moisture-proof property of less than 0.1 [g / (m ² · day)], the moisture-proof deterioration due to the shrinkage of the film and the influence of moisture intrusion from the edge are remarkable. This is because a small amount of defects inside the metal oxide layer and between the base material and the metal oxide layer or deterioration due to hydrolysis of the base material has a significant effect on moisture resistance.

  As described above, the present inventors have provided a pressure-sensitive adhesive layer having a specific tensile storage elastic modulus on the metal oxide layer, and provided an intermediate film having a melting point of 150 ° C. or lower on the pressure-sensitive adhesive layer, thereby increasing the temperature and humidity. Reduces the stress acting on the metal oxide layer of the moisture-proof film in the environment, and the intermediate film melts in the vacuum lamination process, wraps around the edge of the protective material, and seals the end face. It has been found that it is possible to achieve both prevention of deterioration of the steel and prevention of delamination from the edge.

  Specifically, in order to reduce the transmission of stress due to shrinkage applied to the metal oxide layer resulting from residual strain in the plastic film in a high-temperature and high-humidity environment, the pressure-sensitive adhesive layer used for bonding in vacuum lamination However, it is important that the tensile elastic modulus is flexible enough to absorb stress due to deformation of the adhesive layer. That is, it is important to use an adhesive layer having a low tensile elastic modulus under a high temperature environment such as vacuum lamination. In addition, it is important that an intermediate film having a melting point of 150 ° C. or lower in the vacuum lamination process is provided on the pressure-sensitive adhesive layer so that the molten intermediate film can wrap around the end face of the solar cell protective material.

Hereinafter, the present invention will be described in detail.
The protective material for solar cells in the present invention has a metal oxide layer on at least one surface of a fluororesin film, an intermediate film, an adhesive layer, and a substrate, and has a water vapor transmission rate of 0.1 [g / (m ² · day)], and the intermediate film has a melting point of 150 ° C. or lower and the pressure-sensitive adhesive layer at 100 ° C., a frequency of 10 Hz, and a strain of 0.1%. The tensile storage elastic modulus is 5.0 × 10 ⁴ to 5.0 × 10 ⁵ Pa, and the thickness is 13 μm or more.

<Protective material for solar cells>
[Dampproof film]
In the present invention, the moisture-proof film has a metal oxide layer on at least one surface of the substrate, and its water vapor transmission rate is less than 0.1 [g / (m ² · day)]. Since the present invention relates to a solar cell protective material that is desired to maintain high moisture resistance for a long period of time, the initial moisture resistance needs to be a certain level or more. Therefore, in the present invention, the 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, it is 0.03 [g / (m ² · day)] or less. The moisture-proof film is preferably transparent when used as a solar cell protective material, particularly as a front sheet used on the light-receiving surface side. The water vapor transmission rate can be adjusted by appropriately adjusting the selection of the substrate, the selection of the metal oxide constituting the metal oxide layer, the thickness of the metal oxide layer, the oxidation number of the metal oxide, and the like.

(Base material)
As the base material of the moisture-proof film, a transparent base material is preferable. Specifically, a thermoplastic resin film is preferable, and the material is usually a resin that can be used for a solar cell member. Can be used without limitation.
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, Examples include polyvinyl butyral, polyarylate, fluororesin, acrylic 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 viewpoints of surface smoothness, film strength, heat resistance, and the like.

  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 base material is formed by using the above raw materials and the like, but may be unstretched or stretched. Further, as described later, it may be a single layer or a multilayer.
Such a substrate can be produced by a conventionally known method. For example, the raw material is melted by an extruder, extruded by an annular die or a T die, and rapidly cooled to be substantially amorphous and not oriented. A stretched film can be produced. 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 a uniaxial direction or a biaxial direction can be produced by stretching in a direction (horizontal axis) perpendicular thereto. Although a draw ratio can be set arbitrarily, the heat shrinkage rate at 100 ° C. is preferably 0.01 to 5%, and more preferably 0.01 to 2%. Further, the thermal shrinkage at 150 ° C. is more preferably 0.01 to 5%, and particularly preferably 0.01 to 2%. Among these, from the viewpoint of film properties, biaxially stretched polyethylene naphthalate film, biaxially stretched polyethylene terephthalate, polyethylene terephthalate and / or coextruded biaxially stretched film of polyethylene naphthalate and other plastics are preferable.

In addition, it is preferable to apply | coat an anchor coating agent to the said base material for the adhesive improvement with a metal oxide layer. Examples of anchor coating agents include solvent-based or aqueous polyester resins, isocyanate resins, urethane resins, acrylic resins, modified vinyl resins, vinyl alcohol resins, vinyl butyral resins, ethylene vinyl alcohol resins, nitrocellulose resins, oxazoline group-containing resins, carbodiimides. A group-containing resin, a melamine group-containing resin, an epoxy group-containing resin, a modified styrene resin, a modified silicone resin, or the like can be used alone or in combination of two or more.
Anchor coating agents contain silane coupling agents, titanium coupling agents, alkyl titanates, light blockers, UV absorbers, stabilizers, lubricants, antiblocking agents, antioxidants, etc. A material obtained by copolymerizing an agent or the like with the above resin can be contained.

  The thickness of the anchor coat layer is preferably 10 to 200 nm, and more preferably 10 to 100 nm, from the viewpoint of improving the adhesion with the metal oxide layer. A known coating method is appropriately adopted as the formation method. For example, any method such as a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, or a coating method using a spray can be used. Alternatively, the substrate may be immersed in an anchor coating agent solution. After coating, 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 production line (inline) or a method performed after the substrate production (offline).

(Metal oxide layer)
Examples of the material constituting the metal oxide layer of the moisture-proof film include silicon, aluminum, magnesium, zinc, tin, nickel, titanium and other oxides, oxide carbides, oxynitrides, oxycarbonitrides, and mixtures thereof. However, silicon oxide, silicon oxide carbide, silicon oxynitride, silicon oxycarbonitride from the point that there is no fear of leakage of current when applied to solar cells, and transparency and high moisture resistance can be stably maintained. Metal oxides such as aluminum oxide, aluminum oxide carbide and aluminum oxynitride and mixtures thereof are preferred.

  As a method for forming the metal oxide layer, any method such as a vapor deposition method and a coating method can be used, but a vapor deposition method is preferable in that a uniform metal oxide layer having a high gas barrier property can be obtained. This vapor deposition method includes any method such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). Examples of physical vapor deposition include vacuum vapor deposition, ion plating, and sputtering, and chemical vapor deposition includes plasma CVD using plasma and a catalyst that thermally decomposes a material gas using a heated catalyst body. Examples include chemical vapor deposition (Cat-CVD).

The thickness of the metal oxide layer is preferably 40 to 1000 nm, more preferably 50 to 800 nm, and still more preferably 50 to 600 nm, from the viewpoint of stable moistureproof expression. The thickness of the substrate is generally about 5 to 100 μm, preferably 8 to 50 μm, more preferably 12 to 25 μm from the viewpoint of productivity and ease of handling. Therefore, the thickness of the moisture-proof film is generally about 5 to 100 μm, preferably 8 to 50 μm, more preferably 12 to 25 μm from the viewpoint of productivity and ease of handling.
In addition, the metal oxide layer can be formed into a multi-layer by using the various film formation methods mentioned above to improve moisture resistance. In that case, the same film formation method may be used, or a different film formation method may be used for each layer. However, it is effective to improve the moisture resistance and productivity by continuously performing them under reduced pressure. This is preferable.

[Intermediate film]
The intermediate film in this invention is a film directly bonded by the adhesive layer formed in the metal oxide layer surface of the said moisture-proof film. Since the intermediate film has a melting point of 150 ° C. or lower, it is melted in a vacuum lamination process and may be provided on the back side from the intermediate film by a pressure-down adhesive layer, moisture-proof film, and further from the moisture-proof film. An end face-sealing film is formed on the side surfaces, etc. to protect the pressure-sensitive adhesive layer, the base material of the moisture-proof film, etc., and prevent the moisture-proof property from being lowered and the occurrence of delamination.
From the above, it is preferable that the intermediate film is excellent in weather resistance and wet heat resistance and has good adhesion to each layer forming the solar cell protective material. From the above viewpoint, the same as the solar cell sealing material It is desirable to use a film.

From the above viewpoint, the melting point of the intermediate film is preferably 120 ° C. or less, more preferably 110 ° C. or less, and further preferably 100 ° C. or less. The lower limit is usually 50 ° C. and preferably 60 ° C. The melting point of the intermediate film is particularly preferably 60 to 110 ° C.
By using an intermediate film with a melting point within the above temperature range, it remains at the temperature at the time of vacuum lamination, relaxing the molecular and crystal orientation in the film caused by the history of the force applied in the previous process and the thermal history. The effect of reducing distortion can also be obtained.

  As the intermediate film, it is desirable that the intermediate film is highly flexible and has excellent ultraviolet and humidification durability in consideration of use as a solar cell surface protective material. Examples of the intermediate film include a film containing ethylene-vinyl acetate or polyethylene as a main component, for example, a film containing 50% by mass or more and less than 100% by mass. Furthermore, from the above viewpoint, a film containing polyethylene having a low melting point as a main component, for example, a film containing 50% by mass or more and less than 100% by mass is preferable. In particular, a resin composition obtained by kneading a UV absorber or a colorant into a resin such as low density polyethylene (LDPE) or ethylene-α-olefin copolymer is preferably used. LDPE) or an ethylene-α-olefin copolymer as a main component, for example, a film containing 50% by mass or more and less than 100% by mass is particularly preferable.

  In addition, as said ultraviolet absorber used for an intermediate | middle film, various commercial products are mention | raise | lifted, The thing of various types, such as a benzophenone series, a benzotriazole series, a triazine series, and a salicylic acid ester series, can be mentioned. 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. It is possible.

  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 blending amount of the ultraviolet absorber is usually about 0.01 to 2.0% by mass, preferably 0.05 to 0.5% by mass in the intermediate film.

  In addition to the ultraviolet absorber, a hindered amine light stabilizer is preferably used as a weather stabilizer that imparts weather resistance. 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) sebacate, 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 intermediate film.

  In the present invention, the thickness of the intermediate film is 50 μm or more from the viewpoint of easy handling of the film, preferably 100 μm or more, more preferably 200 μm or more. Preferably it is 300 micrometers or more. The upper limit is not particularly limited, but is usually 500 μm from the viewpoint of handling. The thickness of the intermediate film is preferably 100 to 500 μm from the above.

[Adhesive layer]
The protective material for solar cells of the present invention bonds the metal oxide layer surface of the moisture-proof film and the intermediate film through an adhesive layer.
In the present invention, the pressure-sensitive adhesive layer has a tensile storage elastic modulus of 5.0 × 10 ⁴ [Pa] or more and 5.0 × 10 ⁵ [Pa] or less at 100 ° C., a frequency of 10 Hz, and a strain of 0.1%. The thickness is 13 μm or more. That is, if the tensile storage elastic modulus at 100 ° C. is 5.0 × 10 ⁴ [Pa] or more, the pressure-sensitive adhesive layer does not flow during heating such as vacuum lamination, and the layer thickness can be maintained uniformly. Moreover, if it is 5.0 * 10 < ⁵ > [Pa] or less, the stress which generate | occur | produces by shrinkage | contraction of the film which opposes through this adhesive layer will be absorbed with an adhesive layer, and a damage to a metal oxide layer will be prevented. Is possible and preferable. From the above viewpoint, the tensile storage elastic modulus at 100 ° C., frequency 10 Hz, and strain 0.1% of the pressure-sensitive adhesive layer is preferably 1.0 × 10 ⁴ [Pa] to 5.0 × 10 ⁵ [Pa]. 1.0 × 10 ⁵ [Pa] to 5.0 × 10 ⁵ [Pa] is more preferable. The thickness of the pressure-sensitive adhesive layer is 13 μm or more, preferably 15 μm or more, more preferably 20 μm or more from the viewpoint of obtaining sufficient adhesive force. In addition, from the viewpoint of preventing the moisture-proof performance from deteriorating due to increased stress on the metal oxide layer surface of the resin film having a metal oxide layer due to the structural change that occurs in the pressure-sensitive adhesive layer during the high temperature and high humidity test, The thickness is 45 μm or less, preferably 30 μm or less. In particular, when the thickness of the pressure-sensitive adhesive layer exceeds 50 μm, the metal oxide layer surface acts on the thickness of the pressure-sensitive adhesive layer and the stress product generated in the pressure-sensitive adhesive layer. Accordingly, the thickness of the pressure-sensitive adhesive layer is preferably 13 to 45 μm.

In the present invention, as the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer, in order to set the tensile storage elastic modulus at 100 ° C., frequency 10 Hz, and strain 0.1% to 5 × 10 ⁵ [Pa] or less, and further From the viewpoint of exhibiting a tensile storage elastic modulus of 1 × 10 ⁶ [Pa] or more in order to maintain the adhesive strength at room temperature (20 ° C.), those containing an acrylic adhesive are preferred. More preferred are: Here, the main component is a purpose that allows other components to be included within a range that does not impede the effects of the present invention, and does not limit the specific content, but generally the configuration of the pressure-sensitive adhesive layer When the total component is 100 parts by mass, it is 50 parts by mass or more, preferably 65 parts by mass or more, more preferably 80 parts by mass or more and occupies a range of 100 parts by mass or less.

Examples of the acrylic pressure-sensitive adhesive include a main monomer component having a low glass transition point (Tg) that imparts tackiness, a comonomer component having a high Tg that imparts adhesiveness and cohesive force, and a functional group-containing monomer for improving crosslinking and adhesion. A polymer or copolymer mainly composed of components (hereinafter referred to as “acrylic (co) polymer”) is preferred.
Examples of the main monomer component of the acrylic pressure-sensitive adhesive include alkyl acrylates such as ethyl acrylate, butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, cyclohexyl acrylate, and benzyl acrylate. And alkyl methacrylates such as butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate. These may be used alone or in combination of two or more.

Examples of the comonomer component of the acrylic pressure-sensitive adhesive include methyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl acetate, styrene, acrylonitrile and the like. These may be used alone or in combination of two or more.
Examples of the functional group-containing monomer component of the acrylic pressure-sensitive adhesive include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, 2-hydroxyethyl (meth) acrylate, and 2-hydroxypropyl (meta ) Hydroxyl group-containing monomers such as acrylate and N-methylolacrylamide, acrylamide, methacrylamide, glycidyl methacrylate and the like. These may be used alone or in combination of two or more.

Examples of the initiator used for polymerization of the monomer component of the acrylic pressure-sensitive adhesive include azobisisobutylnitrile, benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, and the like. Moreover, there is no restriction | limiting in particular about the copolymerization form of the acrylic (co) polymer used as the main component of the said acrylic adhesive, Any of a random, a block, and a graft copolymer may be sufficient.
Moreover, as a molecular weight in case the said acrylic adhesive is the above-mentioned acrylic type (co) polymer, what is 300,000-1,500,000 is preferable at a mass mean molecular weight, and it is further that it is 400,000-1 million preferable. By setting the mass average molecular weight within the above range, adhesion to the adherend and adhesion durability can be secured, and floating and peeling can be suppressed.

Further, in the acrylic (co) polymer, the content of the functional group-containing monomer component unit is preferably in the range of 1 to 25% by mass. By making this content within the above range, the adhesiveness and the degree of crosslinking with the adherend are ensured, and the tensile storage elastic modulus of the pressure-sensitive adhesive layer, which is an essential condition in the present invention, is 5.0 × at 100 ° C. The value can be in the range of 10 ^{4 to} 5.0 × 10 ⁵ Pa.

  The pressure-sensitive adhesive layer in the present invention preferably contains an ultraviolet absorber. As the ultraviolet absorber that can be used, the same ultraviolet absorbers contained in the above-mentioned intermediate film can be used.

In the present invention, the pressure-sensitive adhesive layer may be formed by directly applying to the metal oxide layer of the intermediate film or moisture-proof film, or the pressure-sensitive adhesive may be applied to the release-treated surface of the release sheet subjected to the release treatment. And can be formed by bonding it to the metal oxide layer of the intermediate film or moisture-proof film. Since the metal oxide layer is protected by the pressure-sensitive adhesive layer by laminating the metal oxide layer of the moisture-proof film on the intermediate film side, the moisture-proof property is hardly deteriorated, which is preferable. Moreover, since a base material harder than a metal oxide layer becomes the element side for solar cells, since it is easy to hold | maintain a shape when it is set as a solar cell module, it is preferable.
The pressure-sensitive adhesive is preferably applied as a coating liquid, and there are organic solvent-based, emulsion-based and solvent-free coating liquids, but organic solvents are used for applications such as solar cell members where water resistance is required. A coating liquid of the system is desirable.
Examples of the organic solvent used in the organic solvent-based coating liquid include toluene, xylene, methanol, ethanol, isobutanol, n-butanol, acetone, methyl ethyl ketone, ethyl acetate, and tetrahydrofuran. These may be used alone or in combination of two or more.

For the convenience of coating, the coating liquid is preferably prepared using these organic solvents so that the solid content concentration is in the range of 10 to 50% by mass.
Coating of the coating liquid is, for example, conventionally known coating methods such as bar coating, roll coating, knife coating, roll knife coating, die coating, gravure coating, air doctor coating, doctor blade coating, etc. It can be done by a method.
After coating, the pressure-sensitive adhesive layer is usually formed by drying at a temperature of 70 to 110 ° C. for about 1 to 5 minutes.

  The thickness of the pressure-sensitive adhesive layer needs to be 13 μm or more from the viewpoint of obtaining sufficient adhesive force, preferably 15 μm or more, more preferably 18 μm or more, and further preferably 20 μm or more. Further, from the viewpoint of providing a coatable thickness, the thickness is preferably 100 μm or less, and more preferably 50 μm or less.

[Fluorine resin film]
The solar cell protective material of the present invention has hydrolysis resistance and weather resistance, and has a fluororesin film in order to impart long-term durability.
The fluororesin film preferably has weather resistance. For example, polytetrafluoroethylene (PTFE), 4-fluoroethylene-perchloroalkoxy copolymer (PFA), 4-fluoroethylene-6-fluoride From propylene copolymer (FEP), 2-ethylene-4-fluoroethylene copolymer (ETFE), poly-3-fluoroethylene chloride (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), etc. The film is preferably used.

From the viewpoint of long-term durability, 2-ethylene-4-fluoroethylene copolymer (ETFE) and 4-fluoroethylene-6-fluoropropylene copolymer (FEP) are more preferably used as the resin. It is done.
Fluorine-based resin films preferably have small changes in their characteristics even during temperature / humidity changes during vacuum lamination and at high temperatures and high humidity. A film having undergone shrinkage and the like can be used.

The thickness of the fluororesin film is generally about 20 to 200 μm, preferably 20 to 100 μm, and more preferably 20 to 50 μm from the viewpoint of film handling and cost.
Furthermore, it is preferable that the thickness (t1) of the base material and the thickness (t2) of the fluororesin film satisfy the following relational expression (1), whereby a solar cell protective material excellent in flexibility can be obtained. . When the solar cell module using such a solar cell protection material is bent, the solar cell protection material can follow the bending, and the solar cell protection material and the sealing material are delaminated. Is unlikely to occur.
t1 <t2 (1)

[Protective material for solar cells]
The solar cell protective material of the present invention has a fluorine-based resin film, an intermediate film, an adhesive layer, and a moisture-proof film in this order, and when used in a solar cell, has a fluorine-based resin film on the exposed side. is there.
The solar cell protective material of the present invention is intended to further improve physical properties (flexibility, heat resistance, transparency, adhesiveness, etc.), molding processability, economic efficiency, etc. without departing from the gist of the present invention. For example, polyolefin resins and various elastomers (olefins, styrenes, etc.), resins modified with polar groups such as carboxyl groups, amino groups, imide groups, hydroxyl groups, epoxy groups, oxazoline groups, thiol groups, silanol groups And tackifying resins and the like.

Examples of the tackifying resin include petroleum resins, terpene resins, coumarone-indene resins, rosin 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 -As the rosin resin, phenolic resins include rosin resins such as gum rosin and wood rosin, esterified rosin resins modified with glycerin, pentaerythritol, and the like. 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, in each film which comprises the protective material for solar cells, 20 mass% or less is preferable, and 10 mass% or less is still more preferable.

(Additive)
Moreover, various additives can be added to the 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 blended for the reason described later. In the present invention, for example, when high heat resistance is required, a crosslinking agent and / or a crosslinking aid may be blended.

  Examples of the silane coupling agent include compounds having a hydrolyzable group such as an alkoxy group together with an unsaturated group such as a vinyl group, an acryloxy group, and a methacryloxy group, an amino group, an epoxy group, and the like. . 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 this silane coupling agent is about 0.1-5 mass% normally in each film which comprises the protective material for solar cells, and it is preferable to add 0.2-3 mass%. In addition, similar to the silane coupling agent, a coupling agent such as an organic titanate compound can also be used effectively.

  As the antioxidant, various commercial 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 the bisphenol 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 can be mentioned.
Examples of sulfur-based compounds include dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiopropionate.

  The phosphite system includes 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-phosphine Phenanthrene, cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,6-di-tert-methylphenyl) phosphite, 2,2- And methylene bis (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 protective material for solar cell.

(Film forming method)
As a method for forming each layer excluding the pressure-sensitive adhesive layer constituting the solar cell protective material used in the present invention, a known method such as a single-screw extruder, a multi-screw extruder, a Banbury mixer, a kneader or other melt mixing equipment The extrusion casting method using a T die, a calendar method, etc. can be employed, and is not particularly limited, but in the present invention, the extrusion using a T die is considered from the viewpoint of handling properties and productivity. A casting method is 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 protective material for solar cells of the present invention is a method in which a pressure-sensitive adhesive is applied to each film formed as described above, and the pressure-sensitive adhesive layer is dried at a temperature of, for example, 70 to 140 ° C., and pasted at a temperature of 0 to 80 ° C. Can be manufactured together. From the viewpoint of sufficiently bringing the pressure-sensitive adhesive layer to the degree of saturation crosslinking, the obtained laminate is preferably cured at a temperature of 30 to 80 ° C. for 1 to 7 days.
The solar cell protective material of the present invention is excellent in flexibility and moisture resistance, in which moisture resistance and interlayer strength do not deteriorate even after heat treatment under a high heat environment, that is, heat lamination conditions.
The thickness of the solar cell protective material is not particularly limited, but is preferably 200 to 600 μm, more preferably 200 to 590 μm, more preferably 200 to 350 μm, and still more preferably 220 to 320 μm. It is used in the form of a sheet.

(Moisture resistance of solar cell protective material)
As described above, the solar cell protective material of the present invention uses the moisture-proof film having a metal oxide layer on the base material and having a water vapor permeability of less than 0.1 [g / (m ² · day)], thereby providing an initial moisture-proof material. The water vapor permeability is preferably 0.1 [g / (m ² · day)] or less, more preferably 0.05 [g / (m ² · day)] or less. it can.
The protective material for solar cell of the present invention is preferably a protective material for solar cell that is excellent in initial moisture resistance and excellent in moisture resistance and prevention of delamination even when stored in a high temperature and high humidity environment.

In addition, by using the pressure-sensitive adhesive, the moisture-proof property is the degree of deterioration due to the continuous high-temperature and high-humidity environment by the vacuum lamination and the pressure coker test (120 ° C.) according to JIS C 60068-2-66, that is, The water vapor transmission rate after the high-temperature and high-humidity environment / initial water vapor transmission rate) can be preferably within 25, more preferably within 15 and even more preferably within 10.
The “initial moisture resistance” of the protective material for solar cells in the present invention refers to moisture resistance before the member receives a history of heat, etc. in a high temperature and high humidity environment such as vacuum lameet conditions. It means the value before sex degradation occurs. Therefore, it includes changes over time from immediately after manufacture to before high-temperature and high-humidity treatment. For example, it means a moisture-proof value in a state where heat treatment such as high temperature and high humidity environment treatment at around 100 ° C. or thermal lamination treatment performed at 130 to 180 ° C. for 10 to 40 minutes is not performed. The same applies to the “initial water vapor transmission rate”.

When the protective material for solar cells is exposed to high temperature and high humidity, it is the pressure-sensitive adhesive layer that is in contact with the metal oxide layer side of the moisture-proof film, so the performance of the pressure-sensitive adhesive greatly affects the degree of moisture-proof deterioration. To do.
As a cause of the moisture-proof deterioration of the solar cell protective material, the moisture-proof deterioration of the pressure-sensitive adhesive itself can be mentioned. In this regard, it is effective to select a pressure-sensitive adhesive layer coating film that is difficult to hydrolyze. Another cause is deterioration of moisture resistance due to damage to the vapor deposition surface of the metal oxide layer.

  The inventors of the present invention designed the pressure-sensitive adhesive layer by paying attention to the fact that the metal oxide layer of the moisture-proof film was not deteriorated under high temperature and high humidity, and obtained the solar cell protective material of the present invention. When the metal oxide layer and the adhesive layer form a strong chemical bond, the deterioration of the metal oxide layer surface of the moisture-proof film is due to the change in the viscoelasticity of the adhesive layer and the decomposition and shrinkage of the adhesive layer coating film. This is considered to be due to the fact that a large stress is applied to the. On the other hand, when the adhesion between the metal oxide layer and the pressure-sensitive adhesive layer is weak, the stress due to the change in physical properties of the pressure-sensitive adhesive coating film is reduced, so that deterioration of moisture resistance is prevented. The reason why the metal oxide layer and the pressure-sensitive adhesive layer form a chemical bond is considered to be due to, for example, a reaction between a defective portion of the SiOx layer and a hydroxyl group in the pressure-sensitive adhesive layer. What is necessary is just to reduce the number of the reactive functional groups in an agent, First, restraining the number of the unreacted functional groups after application | coating of an adhesive and hardening.

Furthermore, as for the physical properties of the pressure-sensitive adhesive layer, it is desirable that the adhesive layer has a certain degree of softness and thickness and is adhered by van der Waals force from the viewpoint of protecting the metal oxide layer of the moisture-proof film and preventing the moisture-proof deterioration. If the pressure-sensitive adhesive coating film is too hard, the metal oxide layer is likely to be subjected to stress between the films due to shrinkage and the like, and the tensile storage elastic modulus at 100 ° C. is 5.0 × 10 ⁴ [Pa] or more, It is 5.0 × 10 ⁵ [Pa] or less, and the thickness of the pressure-sensitive adhesive layer is 13 μm or more.
Thus, by satisfy | filling the said moisture-proof property, deterioration of a power generating element and rusting of an internal conducting wire and an electrode can be prevented.
Each moisture-proof property in the present invention can be evaluated according to various conditions of JIS Z0222 “moisture-proof packaging container moisture permeability test method” and JIS Z0208 “moisture-proof packaging material moisture permeability test method (cup method)”.

(Interlayer strength of protective material for solar cells)
The protective material for solar cells of the present invention comprises a pressure lamination tester according to JIS C 60068-2-66 (120 ° C.) by providing the adhesive and an intermediate film having a melting point of 150 ° C. or less on a moisture-proof film. ) Can be prevented from occurring after continuous high heat treatment.

(Application of protective material for solar cells)
The solar cell protective material of the present invention is particularly used for a surface protection member for a solar cell of a compound-based power generation element solar cell module or a flexible solar cell module. And the rusting of the electrodes can be prevented, and the retention of the electromotive force over a long period can be achieved.

The solar cell protective material for solar cells is composed of the solar cell protective material, in particular, by attaching the specific intermediate film to the metal oxide layer of the moisture-proof film via the specific adhesive layer. Realize solar cell protective materials with excellent moisture resistance and moisture resistance that does not deteriorate the moisture resistance, interlayer strength for a long time even under conditions, and prevent the performance deterioration of solar cells, etc., and durability of solar cells, etc. It is possible to provide a surface protective material for highly moisture-proof solar cells and electronic paper that is effective in improving the temperature.
The solar cell surface protective material may be a sealing material / surface protective material integrated type formed by laminating a sealing material. 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 generating 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.

<Solar cell module, solar cell manufacturing method>
The solar cell protective material can be used as a solar cell surface protective member as it is or by being bonded to a glass plate or the like. What is necessary is just to produce by the well-known method, in order to manufacture the solar cell module and / or solar cell of this invention using the protective material for solar cells of this invention.

  A solar cell module can be produced by using the solar cell 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. Preferably, when the solar cell protective material of the present invention is used as a front surface protective material, a sealing material, a solar cell element, And a solar cell module produced using a back surface protective material, specifically, a front surface protective material (protective material for solar cell of the present invention) / sealing material (sealing resin layer) / solar cell element. / Encapsulant (encapsulating resin layer) / back surface protective material, encapsulant and front surface protective material (for solar cell of the present invention) on a solar cell element formed on the inner peripheral surface of the back surface protective material A solar cell element formed on the inner peripheral surface of a front protective material (protective material for solar cell of the present invention), for example, an amorphous solar cell on a fluororesin-based transparent protective material Sealing material on top of the device made by sputtering etc. And the like can be mentioned configuration, such as to form a surface protective material. It is optional to attach a glass plate to the outside of the solar cell protective material of the present invention as the front 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.

Examples of solar cell elements include single crystal silicon type, polycrystalline silicon type, amorphous silicon type, gallium-arsenic, copper-indium-selenium, copper-indium-gallium-selenium, cadmium-tellurium, etc. II-VI group compound semiconductor type, dye-sensitized type, organic thin film type and the like can be mentioned.
When a solar cell module is formed using the solar cell protective material of the present invention, the moisture resistance is less than 0.1 [g / (m ² · day)] in terms of water vapor transmission rate depending on the type of the solar cell power generation element. From a low moisture-proof film of a degree to a high moisture-proof film of less than 0.01 [g / (m ² · day)], which is appropriately selected according to the type of the element, an intermediate film having a melting point of 150 ° C. or less and a specific tensile storage A pressure-sensitive adhesive having a modulus of elasticity and a thickness is used for lamination.

  Although it does not specifically limit about each other member which comprises the solar cell module produced using the protective material for solar cells of this invention, For example, as a sealing material, ethylene-vinyl acetate copolymer weight Coalescence can be mentioned. The back surface protection material is a single layer or multilayer sheet such as metal or various thermoplastic resin films, for example, metals such as tin, aluminum, 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 protective material on the front surface and / or the back surface 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.

  Front surface protective material (protective material for solar cell of the present invention) / sealing material / solar cell element / sealing material / back surface protective material described above for a solar cell module produced using the solar cell protective material of the present invention An example of such a configuration will be described. The solar cell protective material, sealing material, solar cell element, sealing material, and back sheet are laminated in order from the solar light receiving side, 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 solar cell protective material, the sealing resin layer, the solar cell element, the sealing of the present invention. It has the process of laminating | stacking a stop resin layer and a back surface protective material in order, and the process of vacuum-sucking them and carrying out thermocompression bonding. The step of vacuum suction and thermocompression bonding is, for example, a vacuum laminator, the temperature is preferably 130 to 180 ° C, more preferably 130 to 150 ° C, the degassing time is 2 to 15 minutes, and the press pressure is 0.05 to 1 MPa. The pressing time is preferably 8 to 45 minutes, and more preferably 10 to 40 minutes.
Also, batch type manufacturing equipment, roll-to-roll type manufacturing equipment, and the like can be applied.

  The solar cell module manufactured using the solar cell 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, depending on the type and module shape of the applied solar cell. The battery can be applied to various uses regardless of whether it is indoors or outdoors. In particular, among electronic devices, high moisture resistance is required for use as a protective material for solar cells for flexible solar cell modules such as compound-based power generation element solar cell modules and amorphous silicon, and for use in electronic paper. Therefore, it is effectively used as a protective material for solar cells in consideration of this continuous high heat treatment. Therefore, the solar cell module manufactured using the solar cell protective material of the present invention is particularly preferably used as the surface protective material of the electronic device.

  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) Tensile storage elastic modulus of the pressure-sensitive adhesive layer or the adhesive layer The pressure-sensitive adhesive used on the silicone release PET film is applied to 25 g / m ² (the thickness after drying is 25 μm), and at 40 ° C. It was cured for 4 days and then maintained at 150 ° C. for 30 minutes to form a pressure-sensitive adhesive layer or an adhesive layer. Thereafter, only the pressure-sensitive adhesive layer or adhesive layer was taken out, and a plurality of the pressure-sensitive adhesive layers or adhesive layers were stacked to prepare a sample (length 4 mm, width 60 mm, thickness 200 μm). Using the viscoelasticity measuring device (trade name “Viscoelasticity Spectrometer DVA-200”) manufactured by IT Measurement Co., Ltd. The stress with respect to the strain applied to the sample was measured from −100 ° C. to 180 ° C. in the transverse direction with 25 mm between the chucks and the tensile storage elastic modulus at 100 ° C. was obtained from the obtained data. In addition, the tensile storage elastic modulus was set to 0 when the measurement at 100 degreeC was difficult from the sample shape change at the time of temperature rising.

(2) Crystal melting peak temperature of the intermediate film (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 and 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 (° C.). When the melting point exceeded 200 ° C. and no melting peak was observed, such as polyester, the upper limit temperature rise was set to 300 ° C., and then the same measurement was performed to obtain the melting point.

(3) Pressure cooker (PC) test Each solar cell protective material is cut into a 150 mm × 150 mm square, and this is used as a surface protective material. Glass, sealing material, surface protective material (fluorine resin film is on the outside) The layers were laminated in the order of, and vacuum lamination was performed using a vacuum laminator (manufactured by NPC, “LM30 × 30”) under the conditions of 150 ° C., 15 minutes, and a pressure of 0.1 MPa. Next, a pressure cooker test was performed using a pressure cooker test LSK-500 manufactured by Tommy Seiko Co., Ltd. under the test (PC48) conditions of 105 ° C., 100% humidity, and 48 hours.

(4) Pressure cooker (PC) delamination test Each solar cell protective material is cut into a 150 mm × 150 mm square, and this is used as a surface protective material. Glass, sealing material, surface protective material (fluorine-based resin film on the outside) Were laminated in order, and vacuum lamination was performed using a vacuum laminator (manufactured by NPC, “LM30 × 30”) under the conditions of 150 ° C., 15 minutes, pressure 0.1 MPa. . Next, using a pressure cooker test LSK-500 manufactured by Tommy Seiko Co., Ltd., a test until a pressure cooker test is performed at 105 ° C. and a humidity of 100%, and the occurrence of delamination can be visually confirmed at the end face of the surface protective material. Time was measured. Those in which the occurrence of delamination could not be confirmed in 90 hours were over 90 hours (> 90).

(5) Moisture-proof The moisture-proof property of the moisture-proof films (D-1, D-2) is determined by JIS Z 0222 “Moisture-proof packaging container's permeability as the water vapor transmission rate after storage at 40 ° C. for one week after the preparation of the moisture-proof film. In accordance with various conditions of “humidity test method” and JIS Z 0208 “moisture-proof packaging material moisture permeability test method (cup method)”, measurement was performed by the following method.
Moreover, about the moisture resistance of the protective material for solar cells (E-1 to E-8), the measured value of the water vapor transmission rate measured by the following method was used as the initial water vapor transmission rate. Next, after performing a pressure cooker test after vacuum lamination under the condition (3) above, JIS Z 0222 “moisture-proof packaging container moisture permeability test method”, JIS Z 0208 “moisture-proof packaging material moisture permeability test method (cup method) The measured value of the water vapor transmission rate of each solar cell protective material measured by the following method was taken as the water vapor transmission rate after the pressure cooker test.

(Water vapor permeability of moisture-proof film)
Apply urethane adhesive (containing Toyo Morton Co., Ltd. AD900 and CAT-RT85 in a ratio of 10: 1.5) on the surface of a stretched polypropylene film (P1146 manufactured by Toyobo Co., Ltd.) having a thickness of 60 μm. Then, an adhesive layer having a thickness of about 3 μm was formed. On the adhesive layer, the metal oxide layer side of the moisture-proof film after storage at 40 ° C. for one week was laminated on the adhesive layer to obtain a laminate.
Next, using two laminates each having a moisture permeable area of 10.0 cm × 10.0 cm square made of the laminate, with the stretched polypropylene film on the inside, about 20 g of anhydrous calcium chloride is added as a hygroscopic agent, and the four sides are A sealed bag is prepared, and the bag is put into a constant temperature and humidity device at a temperature of 40 ° C. and a relative humidity of 90%. The mass is measured until about 200 days at intervals of 72 hours or more, and the elapsed time and the bag mass after the fourth day. The water vapor permeability [g / (m ² · day)] was calculated from the slope of the regression line.

(Water vapor permeability and moisture-proof deterioration degree of protective materials for solar cells)
Apply urethane adhesive (containing Toyo Morton Co., Ltd. AD900 and CAT-RT85 in a ratio of 10: 1.5) on the surface of a stretched polypropylene film (P1146 manufactured by Toyobo Co., Ltd.) having a thickness of 60 μm. Then, an adhesive layer having a thickness of about 3 μm was formed, and the substrate surface side of the moisture-proof film of the solar cell protective material was laminated on the adhesive layer to obtain a laminate.
Next, using two laminates each having a moisture permeable area of 10.0 cm × 10.0 cm square made of the laminate, with the stretched polypropylene film on the inside, about 20 g of anhydrous calcium chloride is added as a hygroscopic agent, and the four sides are A sealed bag is prepared, and the bag is put into a constant temperature and humidity device at a temperature of 40 ° C. and a relative humidity of 90%. The mass is measured until about 200 days at intervals of 72 hours or more, and the elapsed time and the bag mass after the fourth day. The water vapor transmission rate [g / (m ² · day)] was calculated from the slope of the regression line and the initial water vapor transmission rate of the solar cell protective material. For the moisture proof evaluation after the pressure cooker test, a laminate was prepared in the same manner as described above using the solar cell protective material after the test, and a laminate having a moisture permeable area of 10.0 cm × 10.0 cm square made of the laminate. Evaluation was performed in the same manner as described above using two of each body.
Using the obtained water vapor transmission rate, the degree of moisture proof deterioration was determined by the following equation.
Degree of moisture proof deterioration = (water vapor transmission rate of protective material for solar cell after pressure cooker test) / (initial water vapor transmission rate of protective material for solar cell)

<Structure film>
(Fluorine resin film)
A tetrafluoroethylene-ethylene copolymer (ETFE) film (manufactured by Asahi Glass Co., Ltd., trade name: Aflex 50 MW 1250 DCS, thickness 50 μm) was used as the fluorine resin film.

(Intermediate film)
B-1: An ethylene-vinyl acetate sealing material (trade name: EVASKY S11 (thickness: 500 μm, melting point: 69.6 ° C.)) manufactured by Bridgestone Corporation was used as an intermediate film.

B-2: Add necessary additives to low-density polyethylene resin, and knead well to prepare low-density polyethylene resin, and then extrude the low-density polyethylene resin with an extruder, unstretched with a thickness of 140 μm An intermediate film made of low density polyethylene resin was produced. The melting point was 109 ° C.

B-3: Layer thickness ratio of homopolypropylene resin composition and ethylene-propylene random copolymer resin with an extruder 0.1: 0.8: 0.1 (homopolypropylene resin layer is the central layer, ethylene-propylene random A copolymer resin was multilayer extruded with both outer layers) to produce a 190 μm thick unstretched polypropylene resin film, which was used as an intermediate film. The melting point measured by the above method was 162.3 ° C.

(Adhesive coating solution)
C-1: Using a reactor equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas introduction tube, 90 parts by mass of butyl acrylate, 10 parts by mass of acrylic acid, 75 parts by mass of ethyl acetate, and 75 parts by mass of toluene 0.3 parts by mass of azobisisobutyronitrile was added to the mixed solution, and polymerization was performed at 80 ° C. for 8 hours in a nitrogen gas atmosphere. After completion of the reaction, the solid content was adjusted to 30% by mass with toluene to obtain a resin having a mass average molecular weight of 500,000. To 100 parts by mass of the obtained resin, 1 part by mass of Coronate L (trade name: Nippon Polyurethane Industry Co., Ltd., solid content: 75% by mass) is added as an isocyanate-based crosslinking agent to prepare a pressure-sensitive adhesive coating solution. did. Table 1 shows the results of measuring the tensile storage elastic modulus at 100 ° C., frequency 10 Hz, and strain 0.1% by the method described above.

C-2: Using a reactor equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas inlet tube, 70 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of methyl acrylate, 5 parts by mass of acrylic acid, ethyl acetate To a mixed solution of 20 parts by mass and 20 parts by mass of toluene, 0.3 part by mass of azobisisobutyronitrile was added, and polymerization was performed at 80 ° C. for 8 hours in a nitrogen gas atmosphere. After completion of the reaction, the solid content was adjusted to 30% by mass with toluene to obtain a resin having a mass average molecular weight of 500,000. To 100 parts by mass of the obtained resin, 1 part by mass of Coronate L (trade name: Nippon Polyurethane Industry Co., Ltd., solid content: 75% by mass) is added as an isocyanate-based crosslinking agent to prepare a pressure-sensitive adhesive coating solution. did. Table 1 shows the results of measuring the tensile storage elastic modulus at 100 ° C., frequency 10 Hz, and strain 0.1% by the method described above.

C-3: Using a reactor equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas introduction tube, 40 parts by mass of butyl acrylate, 10 parts by mass of isobutyl acrylate, 40 parts by mass of methyl acrylate, 10 parts by mass of acrylic acid 10 0.3 parts by mass of azobisisobutyronitrile was added to a mixed solution of parts by mass, 75 parts by mass of ethyl acetate and 75 parts by mass of toluene, and polymerized at 80 ° C. for 8 hours in a nitrogen gas atmosphere. After completion of the reaction, the solid content was adjusted to 30% by mass with toluene to obtain a resin having a mass average molecular weight of 500,000. To 100 parts by mass of the obtained resin, 1 part by mass of Coronate L (trade name: Nippon Polyurethane Industry Co., Ltd., solid content: 75% by mass) is added as an isocyanate-based crosslinking agent to prepare a pressure-sensitive adhesive coating solution. did. Table 1 shows the results of measuring the tensile storage elastic modulus at 100 ° C., frequency 10 Hz, and strain 0.1% by the method described above.

(Adhesive coating solution)
C-4: HD1013 manufactured by Rock Paint Co., Ltd. is used as the main component containing the polyurethane polyol component, and H62 manufactured by Rock Paint Co., Ltd. is used as the curing agent containing the aliphatic hexamethylene diisocyanate component, and the weight ratio is 10 The mixture was mixed so that the solid content concentration was 30% by mass, and diluted with ethyl acetate to prepare an adhesive coating solution. Table 1 shows the results of measuring the tensile storage elastic modulus at 100 ° C., frequency 10 Hz, and strain 0.1% by the method described above.

(Dampproof film)
D-1: A biaxially stretched polyethylene naphthalate film (made by Teijin DuPont, “Q51C12”) having a thickness of 12 μm was used as a substrate, and the following coating solution was applied to the corona-treated surface and dried to a thickness of 0.1 μm. A coat 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 on the coating layer. A moisture-proof film D-1 having a metal oxide layer was obtained. The moisture-proof property of the produced moisture-proof film D-1 was 0.01 [g / (m ² · day)].

Coating solution “GOHSENOL” manufactured by Nihon Gosei Co., Ltd. (saponification degree: 97.0 to 98.8 mol%, polymerization degree: 2400) was added to 2810 g of ion-exchanged water and 20% of the aqueous solution was dissolved by heating. 645 g of 35 mol% hydrochloric acid was added with stirring at ° C. Next, 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.

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

(Encapsulant)
Intermediate film B-1 was used as a sealing material.

(Glass)
AGC Fabrytec solar cell cover glass TCB09331, size 150 × 150 × 3.2 mm was used.

Example 1
An adhesive coating liquid C-1 was applied to a 38 μm silicone release PET film so that the thickness after drying was 20 μm, and dried to form an adhesive surface. The moisture-proof film D-1 was bonded to the formed adhesive surface, and then the silicone release PET film was peeled off, and the intermediate film B-1 was bonded to the other adhesive surface, followed by curing at 40 ° C. for 4 days. Furthermore, the fluororesin film was overlapped with the intermediate film B-1 surface of the produced laminate, and adhered by hot pressing at 90 ° C. for 30 seconds. Thereafter, it was cured at 40 ° C. for 5 days to produce a protective material E-1 for solar cells of 582 μm. Various physical property measurements and evaluations were performed using the obtained solar cell protective material. The results are shown in Table 1.

Example 2
A protective material E-2 for a solar cell having a thickness of 222 μm was produced in the same manner as in Example 1 except that the intermediate film was changed to B-2. Various physical property measurements and evaluations were performed using the obtained solar cell protective material. The results are shown in Table 1.

Example 3
A protective material E-3 for solar cell with a thickness of 582 μm was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive coating solution was C-2. Various physical property measurements and evaluations were performed using the obtained solar cell protective material. The results are shown in Table 1.

Example 4
A protective material E-4 for a solar cell having a thickness of 222 μm was produced in the same manner as in Example 2 except that the pressure-sensitive adhesive coating solution was changed to C-2. Various physical property measurements and evaluations were performed using the obtained solar cell protective material. The results are shown in Table 1.

Comparative Example 1
A solar cell protective material E-5 having a thickness of 582 μm was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive coating liquid C-1 of Example 1 was changed to C-3. Various physical property measurements and evaluations were performed using the obtained solar cell protective material. The results are shown in Table 1.

Comparative Example 2
A solar cell protective material E-6 having a thickness of 272 μm was produced in the same manner as in Example 1 except that the intermediate film B-1 of Example 1 was changed to B-3. Various physical property measurements and evaluations were performed using the obtained solar cell protective material. The results are shown in Table 1.

Comparative Example 3
A solar cell protective material E-7 having a thickness of 582 μm was produced in the same manner as in Example 1 except that the moisture-proof film D-1 in Example 1 was changed to D-2. Various physical property measurements and evaluations were performed using the obtained solar cell protective material. The results are shown in Table 1.

Comparative Example 4
Except that the adhesive coating liquid C-1 of Example 1 was changed to the adhesive coating liquid C-4, and the thickness after drying of the adhesive layer was 6 μm, the same as in Example 1. A solar cell protective material E-8 having a thickness of 568 μm was produced. Various physical property measurements and evaluations were performed using the obtained solar cell protective material. The results are shown in Table 1.

From Table 1, all of Examples 1 to 4 having the configuration of the present invention were not deteriorated in moisture resistance for a long time, and the occurrence of delamination was prevented. Further, Comparative Example 2 using an intermediate film having a melting point exceeding the range of the present invention is inferior in moisture resistance with time and insufficient in preventing the occurrence of delamination, and the tensile elastic modulus is within the range of the present invention. Comparative Example 1 using a deviating pressure-sensitive adhesive layer is inferior in moisture resistance over time, and Comparative Example 4 using an adhesive layer in place of the pressure-sensitive adhesive layer is inferior in moisture resistance over time, and delamination It was inferior in prevention of occurrence. Incidentally, Comparative Example 3 using a moisture-proof film having a moisture-proof film having a water vapor transmission rate higher than 0.1 [g / (m ² · day)] is not inferior in the degree of deterioration of the water vapor transmission rate. The water vapor transmission rate was high, which was not preferable for practical use.

Claims (7)

A moisture-proof film having a metal oxide layer on at least one surface of a fluororesin film, an intermediate film, an adhesive layer, and a substrate and having a water vapor transmission rate of less than 0.1 [g / (m ² · day)] A solar cell protective material in this order,
The intermediate film has a melting point of 150 ° C. or lower, and the pressure-sensitive adhesive layer has a tensile storage elastic modulus of 5.0 × 10 ⁴ to 5.0 × 10 ⁵ Pa at 100 ° C., a frequency of 10 Hz, and a strain of 0.1%, The protective material for solar cells, wherein the thickness is 13 μm or more.   The protective material for solar cells according to claim 1, wherein the intermediate film has a thickness of 50 to 600 μm.   The protective material for solar cells according to claim 1 or 2, wherein the intermediate film contains a polyethylene resin as a main component.   The protective material for solar cells in any one of Claims 1-3 which has the said adhesive layer and intermediate | middle film in the metal oxide layer side of the said moisture-proof film. The protective material for solar cells according to any one of claims 1 to 4, wherein the initial water vapor permeability is less than 0.1 [g / (m ² · day)]. The solar cell protective material according to any one of claims 1 to 5, wherein a thickness (t1) of the substrate of the moisture-proof film and a thickness (t2) of the fluororesin film satisfy the following relational expression.
t1 <t2   The module for solar cells which has the protective material for solar cells in any one of Claims 1-6.