WO2014208758A1 - Protective material for solar cell - Google Patents

Abstract

　A protective material for a solar cell, said material being obtained by layering as protective material constituent layers (P) at least a weather-resistant film, a resin layer, and a moisture-proof film having an inorganic layer on at least one face of a substrate and having a moisture vapor transmission rate no greater than 0.1 g/m², wherein the resin layer is formed from a thermoplastic resin composition containing an ethylene resin, and the ratio (W_P/W_A) of the maximum width (W_P) of the protective material constituent layers (P) other than the weather-resistant film to the width (W_A) of the weather-resistant film is less than 1.

Description

Protective material for solar cells

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 capable of maintaining moisture resistance and preventing 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. A solar cell is made of an ethylene-vinyl acetate copolymer, polyethylene, polypropylene film or the like between a front protective sheet (hereinafter sometimes referred to as a front sheet) and a back protective sheet (hereinafter sometimes referred to as a back sheet). It is set as the structure which sealed the cell for solar cells with the sealing material.
Such a solar cell is usually manufactured by laminating a front protective film, a sealing material, a power generation 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 surface protection sheet or a back surface protection sheet of a solar cell, it is required to have excellent durability against ultraviolet rays. In addition, rusting of internal conductors and electrodes due to permeation of moisture and the like is required. In order to prevent this, it is extremely important to have excellent moisture resistance. Furthermore, it is desired to develop an excellent protective material that causes little deterioration in moisture resistance under long-term use or high-temperature conditions.

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, and a weather-resistant polyester film on the inorganic vapor deposition surface side. A protective material for a solar cell is prepared by laminating 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 prevention of moisture resistance deterioration is made.
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 transmission rate of 1 to 2 g / m ² / day based on a biaxially stretched polyester film, and weather resistance is provided on both sides. A protective film for solar cells is manufactured by laminating polyester films, and barrier performance and interlayer strength after a 1000 hour acceleration test at 85 ° C. and 85% humidity are evaluated, and proposals are made to prevent degradation of both characteristics.
In Patent Document 3, after a PVF film is bonded to a moisture-proof film having a water vapor transmission rate of 0.5 g / m ² / day based on a biaxially stretched polyester film, using a two-component curable polyurethane adhesive. The moisture resistance and interlayer strength before and after the pressure cooker test (PCT) (severe environmental test by high temperature and pressure, 105 ° C., 92 hours) are evaluated, and a proposal for preventing deterioration of the 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, and requires higher moisture resistance. When applied to a solar cell protective material such as a compound-based power generation element solar cell module, long-term moisture-proofing properties in harsh environments that are replaced by accelerated durability tests such as the pressure cooker test (PCT) Maintenance and prevention of delamination at the edge of the protective material could not be sufficiently performed.
As a protective material for solar cells, a material that is excellent in moisture proofing and prevention of delamination and that can maintain the moisture proof and prevention of delamination over a long period of time is desired. In the case where a film having a high moisture-proof property with a rate of less than 0.1 g / m ² / day is used, no actual proposal has been made to enable moisture-proof property and prevention of delamination for a long time. It was.

That is, the problem of the present invention is that, with respect to the protective material for solar cells including a moisture-proof film having a water vapor transmission rate of less than 0.1 g / m ² / day, the moisture-proof property does not deteriorate for a long time, and the occurrence of delamination is prevented. An object of the present invention is to provide a solar cell protective material that realizes a solar cell protective material excellent in flexibility and moisture resistance, prevents the performance of the solar cell from being lowered, and is effective in improving the durability of the solar cell.

As a result of repeated studies, the present inventors have at least a weather resistance film, a resin layer, and an inorganic layer on at least one surface of the base material, and have a water vapor transmission rate of less than 0.1 g / m ² / day. A protective material for a solar cell obtained by laminating a moisture-proof film as a protective material constituting layer P, and the maximum width W _P of the protective material constituting layer P other than the weather resistant film with respect to the width (W _A ) of the weather resistant film It was found that by using a solar cell protective material having a ratio (W _P / W _A ) of less than 1, it is possible to simultaneously satisfy the reduction in moisture resistance and the prevention of delamination after being laminated with the sealing material, The present invention has been completed.

That is, the present invention provides the following [1] to [14].
[1] At least a weather-resistant film, a resin layer, and a moisture-proof film having an inorganic layer on at least one surface of the substrate and having a water vapor transmission rate of less than 0.1 g / m ² / day, a protective material for a formed by laminating solar cell as the resin layer is formed from a thermoplastic resin composition containing the ethylene-based resin, relative to the width W _a of the weather resistant film, except weather resistant film _A protective material for solar cells in which the ratio (W _P / W _A ) of the maximum width W _P of the protective material constituting layer P is smaller than 1,
[2] At least a weather-resistant film, a resin layer, and a moisture-proof film having an inorganic layer on at least one surface of the substrate and having a water vapor transmission rate of less than 0.1 g / m ² / day, a protective member for a solar cell comprising a laminate as the resin layer is formed from a thermoplastic resin composition substantially free of cross-linking agent, to the width W _a of the weather resistant film, weather resistant film _A protective material for a solar cell in which the ratio (W _P / W _A ) of the maximum width W _P of the protective material constituting layer P other than is smaller than 1,
[3] The solar cell protective material according to [1] or [2], wherein the W _P / W _A is 0.7 to 0.98.
[4] The solar cell protective material according to [1], wherein the ethylene-based resin is an ethylene-alkyl (meth) acrylate copolymer,
[5] The solar cell protective material according to any one of [1] to [4], wherein the base material has a thickness of 25 to 250 μm.
[6] The solar cell protective material according to any one of [1] to [5], wherein the moisture-proof film is laminated with the surface on the inorganic layer side facing the weather-resistant film.

[7] The solar cell protective material according to any one of [1] to [6], wherein the layer having the maximum width among the protective material constituent layers P other than the weather resistant film is the moisture-proof film,
[8] The protective material constituting layer P further includes an adhesive layer on the moisture-proof film side, a back film having a thickness of 60 μm or more, and has the maximum width among the protective material constituting layers P other than the weather resistant film. The solar cell protective material according to any one of [1] to [6], wherein the layer having the back film and the width of the back film is larger than the width of the moisture-proof film,
[9] An encapsulant-integrated protection in which an encapsulant layer is further laminated on the side opposite to the weather-resistant film of the solar cell protector according to any one of [1] to [8] Material,
[10] width W _D of the sealing material layer, the smaller than the width W _A of the weather resistant film, and the maximum width greater than W _P of the protective material structure layer P other than the weather-resistant film, the [9] The sealing material integrated protective material according to the description,
[11] The protective material for solar cell according to any one of [1] to [8] or the protective material-integrated protective material according to any of [9] and [10] is wound. [12] The solar cell protective material according to any one of [1] to [8] or the sealing material-integrated protective material according to any one of [9] and [10] A solar cell module manufactured using

[13] Of the surface of the roll-like material according to [11], at least a part of a part corresponding to a part from which the weather-resistant film protrudes has a bending length of 70 mm or less measured under the following conditions. And a roll-like article with a cover sheet, which is covered with a cover sheet having a load dent of 0.1 or less.
[Bending length]
(1) A sample having a width of 20 mm and a length of 120 mm is taken.
(2) Place the sample on the table so that a 100 mm long portion of the sample protrudes from the table, and fix the sample by placing a weight of 5 kg on the sample.
(3) The length “x” (unit: mm) at which the end of the portion protruding from the sample hangs down from the pedestal is measured, and this value is taken as the bending length.
[Load dent]
(1) Collect a 100 mm square sample.
(2) A sample is placed on a glass plate having a thickness of 20 mm, a steel ball having a diameter of 5 mm and a weight of 0.5 g is placed on the center of the sample, and a load of 2 kg is further applied on the steel ball.
(3) The dent “d” (unit: μm) of the sample is measured, and the ratio “d / t” to the thickness “t” (unit: μm) of the sample is defined as a load-bearing dent.
[14] The roll-like product with a cover sheet according to [13], which satisfies the following conditions (a ′) and / or (b ′).
(A ′) [Bend length of cover sheet] / [Bend length of weather-resistant film] is 2 or less (b ′) [Load dent of cover sheet] / [Load dent of weather-resistant film] is 2 or less

According to the present invention, there is no decrease in moisture resistance or generation of delamination even when used under high temperature and high humidity for a long period of time, excellent flexibility and moisture resistance, preventing a decrease in the performance of solar cells, and solar It is possible to provide a highly moisture-proof solar cell protective material that is effective in improving the durability of the battery. The solar cell protective material of the present invention is excellent in flexibility and moisture resistance, in which moisture resistance and interlaminar strength do not decrease even after heat treatment in a high heat environment, that is, heat lamination conditions.

Sectional drawing which shows one Embodiment of the protective material for solar cells of this invention Sectional drawing which shows other embodiment of the protective material for solar cells of this invention Sectional drawing which shows one use example of the protective material for solar cells of this invention Sectional drawing which shows the other usage example of the protective material for solar cells of this invention The figure explaining the evaluation method of bending length The figure explaining the evaluation method of load bearing dent

Hereinafter, the present invention will be described in more detail.
The protective material for solar cells can prevent moisture from entering from the exposed surface of the film by being laminated with a moisture-proof film, but it can be used for a long time as an alternative to accelerated testing in a high-temperature, high-humidity environment. , Due to the ingress of moisture from the end face of the protective material for solar cells, the base material of the adhesive and moisture-proof film used for laminating each film gradually deteriorates, causing delamination from the edges 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 about 0.1 g / m ² / day, the influence of the moisture-proof deterioration due to the shrinkage of the film and the entry of moisture from the end is remarkable. This is because slight defects at the inside of the inorganic layer of the moisture-proof film and at the interface between the base material and the inorganic layer and deterioration due to hydrolysis of the base material have a significant influence on the moisture resistance.

From the above, the present inventors, as illustrated in FIGS. 1 and 2, have at least the solar cell protective material (10), at least the weather-resistant film (1), the resin layer (21), and the base material. A laminated body in which a moisture-proof film (3) having an inorganic layer on one surface and having a water vapor permeability of less than 0.1 g / m ² / day is laminated as a protective material constituting layer P, and further protection other than the weather-resistant film It was comprised so that the width | variety of the material structure layer P might become shorter than the width | variety of the said weather resistance film.
With this configuration, as illustrated in FIGS. 3 and 4, the width of the sealing material (20) on the solar cell (30) is shorter than the width of the weather resistant film (1) during vacuum lamination. The resin layer (21) having moisture and the moisture-proof film (3) wrap around the end face and seal the end face to achieve both the prevention of moisture-proof deterioration and the prevention of delamination from the end. I came to find it.

<Protective material for solar cells>
[Weather-resistant film]
The solar cell protective material of the present invention has hydrolysis resistance and weather resistance, and has a weather resistant film in order to impart long-term durability.
As the weather resistant film, those having hydrolysis resistance and weather resistance can be used without limitation. For example, polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene Fluororesin such as hexafluoropropylene copolymer (FEP), tetrafluoroethylene / ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF) Polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polycarbonates; acrylic resins such as polymethyl methacrylate (PMMA); films of various resins such as polyamides may be used. Kill. The weather resistant film may contain two or more of these resins, or may be a laminated film of two or more films.

Among the weather resistant films described above, a fluororesin film is suitable from the viewpoint of weather resistance and transparency. Among fluororesin films, from the viewpoint of long-term durability, tetrafluoroethylene / ethylene copolymer (ETFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and polyvinylidene fluoride (PVDF) are used. One or more selected are more preferably used.
The weather resistant film preferably has a small characteristic change during vacuum lamination, temperature change, or humidity change. Accordingly, those having a low shrinkage rate by prior heat treatment are preferred. The weather resistant film is preferably subjected to an easy adhesion treatment such as a plasma treatment in order to improve the adhesion with the sealing material.

When the ratio (W _P / W _A ) of the maximum width W _P of the protective material constituting layer P other than the weather resistant film to the width W _A of the weather resistant film is 1 or more, the thickness of the sealing material that wraps around the end face Is small and easily causes delamination, W _P / W _A needs to be smaller than 1. Further, when the difference between W _A and W _P is too large, not wrap fully encapsulant to the end, also the uniformity of the thickness of the laminate after the vacuum lamination may not be maintained. Therefore, W _P / W _A is preferably 0.7 to 0.98, more preferably 0.75 to 0.95 for more stable delamination prevention, and 0.8 to 0.92 is more preferable. If W _P / W _A is smaller than 1, it is arbitrary how long W _A is to the left and right with respect to W _P , but it is preferable to lengthen W _A equally to the left and right. In the present invention, the “film width” means the length in the lateral direction with respect to the length direction of the film unwound from the roll when the protective material is provided in a roll, and is provided in a single sheet. The short side of the four sides.

In order to obtain the effect of reducing residual stress in the protective material for solar cells at the time of high temperature and high humidity, reducing the residual strain of the weather-resistant film generated during vacuum lamination in the production of the protective material for solar cells of the present invention, The weather resistant film is preferably a film having a glass transition temperature of −50 to 180 ° C. By using a weather-resistant film with a glass transition temperature within the above temperature range, the molecular and crystal orientation in the film generated by the history of force and thermal history applied in the previous process at the temperature during vacuum lamination It can be relaxed and residual strain can be reduced.

Various additives can be added to the weather resistant film as necessary. Examples of the additive include, but are not limited to, an ultraviolet absorber, a weather resistance stabilizer, an antioxidant, an antistatic agent, and an antiblocking agent.

The thickness of the weather-resistant film is generally about 20 to 200 μm, preferably 20 to 100 μm, more preferably 20 to 60 μm from the viewpoint of film handling and cost.
The heat shrinkage rate of the weather resistant film is preferably 5.0% or less, preferably at least one of the heat shrinkage rate in the width direction or the length direction of the film from the viewpoint of curling prevention. More preferably, it is more preferably 3.0% or less. Moreover, the effect is especially remarkable when the thermal contraction rate in the width direction and the length direction of the film is in the above range. In addition, the minimum of the heat shrinkage rate of a weather resistant film is about 0.3%. Thermal shrinkage weather resistant film, when the sample length after heat treatment at 30 minutes in an oven at a temperature of the sample length before heating L _0, 0.99 ° C. was _{L 1, (L 0 -L 1} ) × can be calculated from the equation 100 / L _0.

[Dampproof film]
In the present invention, the moisture-proof film has at least an inorganic layer formed on at least one surface of the substrate and the substrate, and the water vapor transmission rate is preferably less than 0.1 g / m ² / day. . Since the protective material for solar cells of the present invention 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. Accordingly, in the present invention, the moisture-proof film is less than the water vapor transmission rate of 0.1g / m ² / day, preferably not more than 0.05g / m ² / day, more preferably, 0.03 g / m ² / Day or less. The moisture-proof film is preferably transparent when the solar cell protective material is used as a front sheet used on the light-receiving surface side.
The thickness of the moisture-proof film is generally 5 to 300 μm, and preferably 25 to 250 μm, more preferably 38 from the viewpoints of curling suppression, voltage resistance, cushioning, productivity, and handleability of the solar cell protective material. It is ˜200 μm, more preferably 50 to 180 μm.

(Base material)
As the base material of the moisture-proof film, a resin film is preferable, and any material can be used without particular limitation as long as it is a resin that can be used for an ordinary solar cell material.
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 , Polyamides such as nylon 66, nylon 12 and copolymer nylon; ethylene-vinyl acetate copolymer partial hydrolyzate (EVOH), polyimide, polyetherimide, polysulfone, polyethersulfone, polyetheretherketone, polycarbonate, polyvinyl Examples include butyral, polyarylate, fluororesin, acrylic resin, biodegradable resin, and the like, and among them, a thermoplastic resin is preferable. Furthermore, polyesters, polyamides, and polyolefins are preferable from the viewpoints of film properties and costs, and polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are particularly preferable from the viewpoints of surface smoothness, film strength, heat resistance, and the like.

The elastic modulus at 23 ° C. of the base material is more preferably 2.0 to 10.0 GPa, and further preferably 2.0 to 8.0 GPa. By having an elastic modulus in the above range, deformation resistance against deformation of external force can be exhibited, and curling of the protective sheet and the laminate including the protective sheet can be sufficiently suppressed, which is preferable. Here, the elastic modulus refers to the tensile elastic modulus obtained from the slope of the linear portion of the stress-strain curve, and can be obtained by a tensile test method based on JIS K7161: 1994.

In addition, various additives can be added to the base material, the resin layer and the adhesive layer, which will be described later, as necessary. Examples of the additive include, but are not limited to, an antistatic agent, an ultraviolet absorber, a light stabilizer, a plasticizer, a lubricant, a filler, a colorant, an antiblocking agent, and an antioxidant.

Examples of ultraviolet absorbers that can be used include various types such as benzophenone-based, benzotriazole-based, triazine-based, salicylic acid ester-based, and various commercially available products can be applied.
Examples of benzophenone ultraviolet absorbers 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. In That.

Examples of the benzotriazole ultraviolet absorber include hydroxyphenyl-substituted benzotriazole compounds such as 2- (2-hydroxy-5-methylphenyl) benzotriazole and 2- (2-hydroxy-5-tert-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- ( Examples include 4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyloxy) phenol.
Examples of salicylic acid esters include phenyl salicylate and p-octylphenyl salicylate.
The content of the ultraviolet absorber in the substrate, the resin layer and the adhesive layer described later is usually about 0.01 to 2.5% by mass, preferably 0.05 to 2.0% by mass.

Hindered amine light stabilizers can be used as a weather stabilizer that imparts weather resistance in addition to the above ultraviolet absorbers. 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 hindered amine light stabilizers include dimethyl-1- (2-hydroxyethyl) succinate-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 Hydroxybenzyl) -2-n-butyl malonic acid bis (1,2,2,6,6-pentamethyl-4-piperidyl) and the like. The content of the hindered amine light stabilizer in the substrate, the resin layer described later and the adhesive layer is usually about 0.01 to 2.0% by mass, preferably 0.05 to 1.0% by mass. .

As the antioxidant, various commercial products can be used, 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. 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 Examples include '-hydroxybenzyl) -s-triazine-2,4,6- (1H, 3H, 5H) trione, tocopherol (vitamin E), and the like.
Examples of sulfur-based compounds include dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiopropionate.

Examples of phosphites 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-phos 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, etc., and it is more preferable to use a combination of both. The addition amount of the antioxidant is usually about 0.1 to 1% by mass, preferably 0.2 to 0.5% by mass in the base material, the resin layer and the adhesive layer described later.

The resin film as the substrate is formed by using the above raw materials, but may be unstretched or stretched. Further, it may be either a single layer or a multilayer.
Such a base material 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 the draw ratio can be arbitrarily set, the 150 ° C. heat shrinkage ratio is preferably 0.01 to 5%, more preferably 0.01 to 2%. Among these, from the viewpoint of film properties, biaxially stretched polyethylene terephthalate film, biaxially stretched polyethylene naphthalate film, coextruded biaxially stretched film of polyethylene terephthalate film and polyethylene naphthalate film, polyethylene terephthalate and / or polyethylene naphthalate and other A coextruded biaxially stretched film with a resin is preferred.

The thickness of the base material of the moisture-proof film is generally 5 to 300 μm, and preferably 25 to 250 μm from the viewpoint of curling suppression, voltage resistance, cushioning, and productivity and handleability of the solar cell protective material. More preferably, it is 38 to 200 μm, and still more preferably 50 to 180 μm.
When the thickness of the base material constituting the moisture-proof film is 25 μm or more, the solar cell protective material is excellent in curling suppression effect and excellent in voltage resistance, impact resistance, and cushioning properties. Moreover, when the thickness of the said base material exceeds 300 micrometers, it is unpreferable at the point of productivity or handleability.

Moreover, it is preferable that the thickness of the base material of the moisture-proof film is equal to or more than the thickness of the weather-resistant film from the viewpoint of curling suppression. Specifically, the ratio T _{A ′} / T _{B ′} of the thickness T _{A ′} of the weather resistant film to the thickness T _{B ′} of the base material of the moisture-proof film is preferably 1.0 or less. From the viewpoint of curling generation suppression, T _{A ′} / T _{B ′} is more preferably 0.07 to 0.8, and still more preferably 0.2 to 0.7.

In addition, it is preferable to form an anchor coat layer on the base material in order to improve adhesion with the inorganic layer. The anchor coat layer includes a solvent-based or water-based polyester resin; an alcoholic hydroxyl group-containing resin such as an isocyanate resin, a urethane resin, an acrylic resin, a modified vinyl resin, or a vinyl alcohol resin; a vinyl butyral resin, a nitrocellulose resin, or an oxazoline group Resins, carbodiimide group-containing resins, melamine group-containing resins, epoxy group-containing resins, modified styrene resins, modified silicone resins and the like can be used alone or in combination of two or more. Moreover, an alkyl titanate, a silane coupling agent, a titanium coupling agent, an ultraviolet absorber, a weathering stabilizer, a lubricant, an anti-blocking agent, an antioxidant and the like can be added to the anchor coat layer as necessary. . As the ultraviolet absorber, weather stabilizer and antioxidant, the same ones as those used for the aforementioned substrate can be used, and the weather stabilizer and / or ultraviolet absorber is copolymerized with the resin described above. The polymer type can also be used.

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 inorganic layer. A known coating method is appropriately adopted as the formation method. For example, 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 a resin solution. After coating, the solvent can be evaporated using a known drying method such as hot air drying at a temperature of about 80 to 200 ° C., heat drying such as hot roll drying, 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).

(Inorganic layer)
Examples of the inorganic substance constituting the inorganic layer include silicon, aluminum, magnesium, zinc, tin, nickel, titanium and the like; or their oxides, carbides, nitrides; or a mixture thereof. Among these inorganic substances, silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon oxycarbonitride, aluminum oxide, and diamond-like carbon are preferable because they are transparent. In particular, silicon oxide, silicon nitride, silicon oxynitride, and aluminum oxide are preferable because high gas barrier properties can be stably maintained.

As the method for forming the inorganic 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 all methods such as physical vapor deposition (PVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD). 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). Atomic layer deposition is performed by repeating the cycle of adsorption of raw material molecules on the surface of each monolayer on a substrate placed in a vacuum vessel, film formation by reaction, and removal of surplus molecules by purging. It is a technique to pile up one by one.

The inorganic layer may be a single layer or a multilayer. In the case of multiple layers, the same film formation method may be used, or a different film formation method may be used for each layer. From the viewpoint of sex.
In particular, the multilayer structure includes an inorganic layer formed by a vacuum deposition method, an inorganic layer formed by a chemical vapor deposition method, and an inorganic layer formed by a vacuum deposition method in this order. Is preferred.
In addition, when an inorganic layer is a multilayer, each layer may consist of the same inorganic substance, or may consist of a different inorganic substance.

The thickness of the inorganic layer is preferably 10 to 1000 nm, more preferably 20 to 800 nm, and still more preferably 20 to 600 nm, from the viewpoint of stable moisture resistance.

[Resin layer]
The resin layer as used in the field of this invention is located between a weather resistant film and a moisture-proof film. The resin layer preferably contains 50% by mass or more of the resin component, more preferably 80% by mass or more, and still more preferably 90 to 99.9% by mass.
The resin layer is a layer that is softened by heating and exhibits adhesiveness, and is distinguished from a layer containing a pressure-sensitive adhesive (pressure-sensitive adhesive) or a two-component curable adhesive.
In order to adhere the constituent members of the solar cell protective material, a method using an adhesive or an adhesive is known. The pressure-sensitive adhesive or adhesive is generally a polymer solution obtained by adding a crosslinking agent, and is dried and cured after application to form a pressure-sensitive adhesive layer or an adhesive layer. However, since the reaction rate of the crosslinking agent does not reach 100%, unreactive groups remain in the layer, which may reduce the moisture resistance of the solar cell protective material under high temperature and high humidity conditions. Further, since the pressure-sensitive adhesive and adhesive have stickiness (tack), it is necessary to wind up after laminating with another film immediately after being applied to a weather-resistant film or moisture-proof film.
On the other hand, if the above-mentioned resin layer is used, it is possible to cool in a state in which the resin layer is provided on the weather-resistant film or moisture-proof film, and to wind up as it is without laminating another film on the obtained laminate. is there. Since the resin layer is cooled, blocking can be prevented in a wound state. Moreover, since adhesiveness is expressed by heating this again, when packaging, the other layer can be easily bonded by thermal lamination.

Such a resin layer is formed from a thermoplastic resin composition containing a thermoplastic resin in order to develop adhesiveness by heating.
The thermoplastic resin composition forming the resin layer is characterized by containing an ethylene-based resin described later (first aspect) or substantially not containing a crosslinking agent (second aspect). When the thermoplastic resin composition of the first and second embodiments forms the resin layer, the melting point of the ethylene-based resin is low and the increase in the viscosity of the thermoplastic resin composition due to the influence of the crosslinking agent can be suppressed. In addition, workability in the vacuum lamination process can be improved. From the above viewpoint, it is preferable that the thermoplastic resin composition forming the resin layer contains an ethylene-based resin described later and substantially does not contain a crosslinking agent.
The thermoplastic resin is preferably contained in an amount of 50% by mass or more of the resin layer, more preferably 80% by mass or more, and further preferably 90 to 99.9% by mass. Moreover, it is preferable that content of a crosslinking agent is 0.1 mass% or less of a resin layer, it is more preferable that it is 0.01 mass% or less that it does not contain a crosslinking agent substantially, 0.001 More preferably, it is at most mass%.

Examples of the thermoplastic resin include polyester, polyurethane, polyamide, acrylic, polyethylene, polypropylene, polybutadiene, polyisobutylene, ethylene-alkyl (meth) acrylate copolymer, ethylene-vinyl acetate copolymer, vinyl chloride- Examples thereof include vinyl acetate copolymer, styrene-isoprene copolymer, and styrene-butadiene copolymer.
Among these thermoplastic resins, ethylene, such as polyethylene, ethylene-alkyl (meth) acrylate copolymer, ethylene-vinyl acetate copolymer, etc., has a relatively low melting point and allows wide processing temperature selectivity in the vacuum lamination process. System resins are preferred.

Examples of polyethylene include ethylene homopolymers and ethylene-α-olefin copolymers such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE).
In the copolymer of ethylene and α-olefin, the α-olefin copolymerized with ethylene includes propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-nonene. 1-decene, 3-methyl-butene-1, 4-methyl-pentene-1, and the like. Of these, propylene, 1-butene, 1-hexene, and 1-octene are preferably used from the viewpoints of industrial availability, various characteristics, economy, and the like. α-olefins may be used alone or in combination of two or more.
The α-olefin is usually 2 mol% or more, preferably 40 mol% or less, more preferably 3 to 30 mol%, still more preferably based on all monomer units in the copolymer with ethylene. 5 to 25 mol%. Within this range, α-olefin is copolymerized to reduce the crystallinity of the copolymer, so that transparency is improved and problems such as blocking of raw material pellets hardly occur. Among the ethylene-α-olefin copolymers, an ethylene-α-olefin random copolymer is preferably used from the viewpoint of transparency and flexibility.

Of these, the ethylene resin is preferably at least one selected from polyethylene and ethylene-alkyl (meth) acrylate copolymers. In polyethylene, 1 or more types chosen from a low density polyethylene and a linear low density polyethylene are preferable from a transparency viewpoint, and a low density polyethylene is more preferable.

When an ethylene resin is used as the thermoplastic resin, the content of the ethylene resin is preferably 5 to 100% by mass of the resin layer, more preferably 20 to 100% by mass, still more preferably 30 to 100% by mass, More preferably, it is 40 to 100% by mass.

Among ethylene-based resins, an ethylene-alkyl (meth) acrylate copolymer is preferable from the viewpoints of adhesion to a sealing material and transparency. The reason why the above effect can be obtained when the resin layer contains an ethylene-alkyl (meth) acrylate copolymer as an ethylene-based resin is considered as follows. Alkyl (meth) acrylate has polarity because it has an ester bond, and since it can be copolymerized with ethylene, it can improve the adhesion between the resin layer and the inorganic layer, and can also impart amorphous properties. High transparency can be obtained.
If the resin layer contains an acidic functional group, moisture resistance after storage under high temperature and high humidity conditions deteriorates particularly when the resin layer and the inorganic layer are in contact with each other. On the other hand, since the ethylene-alkyl (meth) acrylate copolymer does not contain an acidic functional group, it is possible to suppress deterioration of moisture resistance after storage under high temperature and high humidity conditions.
From the above viewpoint, the content of the monomer unit derived from the alkyl (meth) acrylate in the ethylene-alkyl (meth) acrylate copolymer is preferably 1 mass relative to all the monomer units in the copolymer. % Or more, more preferably 5 to 80% by mass, still more preferably 10 to 60% by mass.

The ethylene-alkyl (meth) acrylate copolymer used in the present invention means a polymer obtained by copolymerizing ethylene and one or more alkyl (meth) acrylates. ) It contains substantially no monomer units derived from monomers other than acrylate. “Substantially does not contain” means that monomer units other than ethylene and alkyl (meth) acrylate are less than 0.1 mol% among the monomer units constituting the copolymer.

The alkyl (meth) acrylate in the ethylene-alkyl (meth) acrylate copolymer preferably has 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, from the viewpoint of heat resistance and stability. More preferably, it has 1 to 4 carbon atoms. The alkyl group may be a straight chain, may have a branched structure, or may have a cyclic structure. Alkyl (meth) acrylate means alkyl acrylate or alkyl methacrylate, and alkyl acrylate is preferable from the viewpoint of adhesion.
Examples of the ethylene-alkyl (meth) acrylate copolymer used in the present invention include an ethylene-methyl (meth) acrylate copolymer, an ethylene-ethyl (meth) acrylate copolymer, and an ethylene-butyl (meth) acrylate copolymer. Ethylene-methyl (meth) acrylate-butyl (meth) acrylate copolymer, ethylene-hexyl (meth) acrylate copolymer, ethylene-pentyl (meth) acrylate copolymer, ethylene-octyl (meth) acrylate copolymer, Examples thereof include an ethylene-decyl (meth) acrylate copolymer and an ethylene-dodecyl (meth) acrylate copolymer. These may be used alone or in combination of two or more.
Among these, from the viewpoints of heat resistance and adhesiveness, one or more selected from ethylene-methyl (meth) acrylate copolymers and ethylene-butyl (meth) acrylate copolymers are preferable. Ethylene-methyl acrylate copolymers and ethylene One or more selected from -butyl acrylate copolymers is more preferred.

The ethylene-alkyl (meth) acrylate copolymer may be a block copolymer or a random copolymer. Since the structural unit derived from ethylene and the structural unit derived from alkyl (meth) acrylate have different polarities, the ethylene-alkyl (meth) acrylate copolymer is expected to have a sea-island structure in the resin layer. It is preferable that the ethylene-alkyl (meth) acrylate copolymer is a random copolymer because the island structure becomes smaller and the adhesiveness becomes uniform.

The molecular weight of the ethylene-alkyl (meth) acrylate copolymer is arbitrary, but the weight average molecular weight is preferably 5,000 to 1,000,000. When the weight average molecular weight is 5,000 or more, there is no possibility that the copolymer flows out from the layer when the resin layer containing the ethylene-alkyl (meth) acrylate copolymer is heated. If the weight average molecular weight is 1,000,000 or less, the processability is good and the thickness of the resin layer can be easily controlled. From the viewpoint of the balance between heat resistance and workability, the weight average molecular weight is more preferably from 10,000 to 100,000.

When an ethylene-alkyl (meth) acrylate copolymer is used as the thermoplastic resin, the content of the copolymer in the resin layer is preferably 5 to 100% by mass, more preferably 20 to 100% by mass, More preferably, it is 30 to 100% by mass, and still more preferably 40 to 100% by mass. If the content of the ethylene-alkyl (meth) acrylate copolymer in the resin layer is 5% by mass or more, the density of the monomer units derived from the alkyl (meth) acrylate contributing to the adhesiveness is sufficient and uniform. Therefore, it is possible to obtain a solar cell protective material having moisture resistance and adhesion even after storage under high temperature and high humidity conditions.

The preferred weight average molecular weight of the thermoplastic resin other than the ethylene-alkyl (meth) acrylate copolymer is also the same as that of the above-mentioned ethylene-alkyl (meth) acrylate copolymer.

The thermoplastic resin preferably has a melting point of 60 to 150 ° C., more preferably 60 to 120 ° C., from the viewpoint of wide processing temperature selectivity in the vacuum lamination step.
The thermoplastic resin preferably has a glass transition temperature of −20 ° C. or lower from the viewpoint of reducing the residual stress of the resin layer in the heating and cooling cycle. When the glass transition temperature is within the above range, deterioration of the barrier property of the protective material for a solar cell particularly in a low temperature region can be suppressed.

The resin layer has a tensile storage modulus of 5 × at 100 ° C., a frequency of 10 Hz, and a strain of 0.1% in order to prevent damage to the inorganic layer by absorbing the stress generated by shrinkage of the opposing film. It is preferably 10 ⁵ Pa or less.
The resin layer preferably has a tensile storage modulus of 1 × 10 ⁷ Pa or more at 20 ° C., a frequency of 10 Hz, and a strain of 0.1% from the viewpoint of maintaining adhesive strength at normal temperature (20 ° C.).

The melt flow rate (MFR) of the resin constituting the resin layer is preferably 20 g / 10 min or less at 190 ° C. and a load of 2.16 kg. When producing a solar cell using the solar cell protective material of the present invention, since the vacuum lamination process is performed at about 150 ° C. for more than ten minutes, it is necessary that the performance of the protective material does not deteriorate in the vacuum lamination process. . If the MFR of the resin constituting the resin layer is 20 g / 10 min or less, the resin does not flow out from the interlayer in the vacuum lamination step, and the uniformity of the thickness of the resin layer can be maintained, so that the appearance is improved. The MFR of the resin constituting the resin layer is more preferably 18 g / 10 min or less at 190 ° C. and a load of 2.16 kg, and further preferably 15 g / 10 min or less. Specifically, the MFR of the resin layer can be measured by the method described in Examples.
Here, the MFR of the resin constituting the resin layer refers to an MFR of a resin obtained by mixing all the resin components contained in the resin layer.

In the present invention, the resin layer includes a thermoplastic resin composition in which components such as a thermoplastic resin, an ultraviolet absorber, and a light stabilizer constituting the resin layer are mixed with a weather resistant film or an inorganic layer of a moisture-proof film. It may be formed by directly coating the coating liquid, or the coating liquid containing the thermoplastic resin composition is applied to the release-treated surface of the release-treated release sheet, and this is a weather resistant film, Alternatively, the release sheet may be peeled off after being bonded to the inorganic layer of the moisture-proof film (coating method).
Also, without preparing a coating liquid, a thermoplastic resin composition obtained by melting and kneading a thermoplastic resin constituting the resin layer and other additives is poured onto a moisture-proof film or weather-resistant film, and cooled with a cooling roll to obtain a resin. A layer may be formed (extrusion laminating method). Or you may shape | mold the thermoplastic resin composition which melt-kneaded the thermoplastic resin which comprises a resin layer, and another additive in the shape of a film by the casting method.
In addition, when the resin layer is formed on the inorganic layer of the weather-resistant film or moisture-proof film and then the other film is laminated on the resin layer, the weather-resistant film and moisture-proof film are interposed via the resin layer. Although it is in a temporarily bonded state, it can be firmly bonded by vacuum lamination when manufacturing a solar cell module described later.

The coating liquid used in the coating method is a solution obtained by dissolving a thermoplastic resin composition in which each component such as a thermoplastic resin, an ultraviolet absorber and a light stabilizer constituting the resin layer is mixed in an organic solvent, or It is preferable to use those dissolved or dispersed in water. What was dissolved in the organic solvent is preferable for uses, such as a solar cell member in which water resistance is asked.
Examples of the organic solvent include toluene, xylene, methanol, ethanol, isobutanol, n-butanol, acetone, methyl ethyl ketone, ethyl acetate, tetrahydrofuran and the like. 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 the coating, a resin layer is formed by drying treatment usually at a temperature of 70 to 110 ° C. for about 1 to 5 minutes.

In the extrusion laminating method, a thermoplastic resin in which a thermoplastic resin constituting the resin layer and other additives are melt-kneaded is poured onto a substrate such as a weather-resistant film or a moisture-proof film, and cooled by a cooling roll, thereby being weather-resistant. A laminate of a film and a resin layer or a laminate of a moisture-proof film and a resin layer can be obtained. Two layers of the resin layer can be stacked by cooling the resin by flowing the resin again by extrusion lamination on the resin layer side of the laminate thus obtained. When the resin layers are stacked, the same resin may be used in each layer, or different resins may be used. Moreover, you may further overlap with 3 layers and 4 layers. By this method, the thickness and structure of the resin layer can be arbitrarily selected. The thickness of the resin layer provided at a time can be controlled by the discharge amount of the resin layer forming composition extruded from the die and the line speed for conveying the film. The thickness of the resin layer provided at a time is preferably selected in consideration of the temperature, spreadability, uniformity of the layer thickness, and productivity, and is usually 3 to 100 μm, and is 10 in terms of processing stability. ˜80 μm is preferred.
In addition, when producing a laminated body in which two resin layers are laminated by extrusion lamination, one resin layer is formed on a weather resistant film, the other resin layer is formed on a moisture-proof film, and then the weather resistant film. It is preferable to laminate so that the upper resin layer and the resin layer on the moisture-proof film face each other. If a resin layer is further formed on the resin layer by extrusion lamination, unevenness in thickness occurs due to heat, and the appearance after vacuum lamination deteriorates. However, by laminating as described above, the appearance after vacuum lamination is improved. can do.

In the extrusion laminating process, the resin temperature to be extruded is usually 150 to 350 ° C. If it is 150 ° C. or lower, the resin flow is poor, and if it is higher than 350 ° C., there is a concern about thermal decomposition of the resin. Furthermore, 200 to 320 ° C. is preferable and 260 to 300 ° C. is more preferable from the viewpoint of processability and prevention of thermal decomposition of the resin. The line speed can be arbitrarily selected according to the apparatus capability, but is usually about 10 to 200 m / min. From the viewpoint of processing stability, 10 to 150 m / min is preferable, and from the viewpoint of productivity, 50 to 150 m / min is preferable.
When there are a plurality of raw materials for the resin layer, they may be mixed by dry blending, put into an extrusion processing machine, or compounded in advance. It is more preferable to perform compounding in advance in order to improve the uniformity of the resin and improve the workability. In order to prevent thermal decomposition of the resin, the compound is preferably carried out at a temperature lower than the extrusion laminating temperature.
In the extrusion laminating method, films can be bonded to both sides of the resin layer at once. For example, when forming a resin layer on a moisture-proof film, the laminated body which provided the resin layer between two films can be obtained by paying out a weather resistant film from the opposite side to the moisture-proof film of a resin layer.

The thickness of the resin layer is preferably 5 to 120 μm, more preferably 10 to 100 μm, still more preferably 10 to 80 μm, and still more preferably 20 to 80 μm. If the thickness of the resin layer is 5 μm or more, a sufficient adhesive force can be obtained, and if it is 120 μm or less, it is possible to prevent the moisture-proof performance from deteriorating due to an increase in stress applied to the surface of the moisture-proof film.

Furthermore, in the solar cell protective material of the present invention, the resin layer and the inorganic layer are in contact, and when the thickness of the resin layer is a and the thickness of the inorganic layer is b, the resin layer thickness a and the resin The ratio a / b to the thickness b of the inorganic layer in contact with the layer is preferably in the range of 200 to 10,000, more preferably in the range of 250 to 9000, and still more preferably in the range of 400 to 2000. Thereby, the moisture-proof fall at the time of vacuum lamination in preparation of a solar cell protective material can be suppressed. At the time of vacuum lamination, pressure is applied in the vertical direction of the inorganic layer, and it is necessary that the moisture resistance does not deteriorate against the impact. In addition, when the thermoplastic resin contained in the resin layer melts and solidifies by cooling during the heating / cooling process during vacuum lamination, the shrinkage stress damages the inorganic layer in contact with the resin layer, reducing moisture resistance. It is necessary not to. If a / b is 200 or more, the thickness of the resin layer relative to the thickness of the inorganic layer is not too small, and there is no concern of damaging the inorganic layer due to insufficient impact resistance. On the other hand, if a / b is 10,000 or less, the shrinkage stress applied to the inorganic layer in contact with the resin layer does not become excessive, and a decrease in moisture resistance can be suppressed.
Further, when the thickness of the substrate used for the moisture-proof film is c, the ratio a / c between the thickness a of the resin layer and the thickness c of the substrate is preferably in the range of 0.1 to 8. . If a / c is 0.1 or more, the initial adhesiveness between the weather resistant film and the moisture-proof film is improved. When a / c is 8 or less, deformation of the base material due to shrinkage of the resin layer hardly occurs during thermocompression bonding (vacuum lamination) in the production of the protective material. a / c is more preferably in the range of 0.1 to 3.3, and still more preferably in the range of 0.2 to 2.0.

The resin layer may be formed of two or more layers as described above.
When two or more resin layers are used, the resin layer located on the weather resistant film side is more various than the resin layer located on the moisture proof film side, such as the ultraviolet absorber, weather stabilizer and antioxidant described above. It is preferable to contain many additives. By comprising in this way, even if an additive bleeds out in the environment of a weather resistance test or a long-term exposure test, the degree of barrier deterioration of the moisture-proof film can be reduced. Further, it is more preferable that the above-mentioned various additives are contained only in the weather-resistant film side resin layer, and the above-mentioned various additives are not contained in the moisture-proof film side resin layer.

As described above, the protective material for solar cells of the present invention prevents the occurrence of delamination by making the maximum width of the protective material constituting layer P other than the weather resistant film shorter than the width of the weather resistant film. can do.
As shown in FIG. 1, when the protective material constituting layer P is formed by laminating a weather resistant film, a resin layer and a moisture-proof film, the layer having the maximum width of the protective material constituting layer P other than the weather resistant film is moisture-proof. A film is preferred.

[Back film, adhesive layer]
In addition, as shown in FIG. 2, when the protective material constituting layer P further has an adhesive layer and a back film having a thickness of 60 μm or more on the moisture-proof film side, the protective material constituting layer P is the outermost protective material constituting layer P other than the weather resistant film. It is preferable that the layer having a large thickness is used as the back film, and the width of the back film is larger than the width of the moisture-proof film. With such a configuration, it is possible to suppress the occurrence of curling while preventing the occurrence of delamination.
As described above, in order to prevent delamination, the ratio of the maximum width W _P of the width W _A of the weather-resistant film, a protective material structure layer P other than the weather-resistant film having (W _P / W _A) is 1 It is necessary to be smaller. For Figure 2, the width of the back film corresponds to W _P. Here, in the configuration of FIG. 2, if the width of the moistureproof film was W _B, from the viewpoint of curling suppression, the ratio of the width W _B to the width _{W P (W B / W P} ) is 0.65 or more, 1. It is preferably less than 0, more preferably 0.75 or more and less than 1.0, and further preferably 0.80 or more and 0.99 or less.

The material constituting the adhesive layer includes adhesives such as pressure-sensitive adhesives such as acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, and polyester-based pressure-sensitive adhesives, thermosetting adhesives, and ionizing radiation curable adhesives. And thermoplastic resins used for the above-described resin layer. From the viewpoint of preventing curling of the solar cell protective material, it is preferable that the material constituting the adhesive layer has the same composition as the resin layer, and that the adhesive layer and the resin layer have the same thickness. It is.

When using a thermoplastic resin for the adhesive layer, the same ones as exemplified for the resin layer can be used. Conventionally known adhesives such as pressure-sensitive adhesives, solution-type adhesives, thermosetting adhesives, and ionizing radiation-curable adhesives can be used.

The thickness of the adhesive layer is preferably 10 μm or more, more preferably 15 μm or more, still more preferably 18 μm or more, and most preferably 20 μm or more from the viewpoint of obtaining sufficient adhesive force. Further, from the viewpoint of production efficiency and cost effectiveness, the thickness is preferably 100 μm or less, and more preferably 50 μm or less. The width of the back adhesive layer is preferably substantially the same as the width of the moisture-proof film.

As the back film, a resin film having a thickness of 60 μm or more is used. By setting the thickness to 60 μm or more, it has an effect of suppressing deformation against shrinkage of other constituent layers, and is excellent in curling generation.
The thickness of the back film is preferably 60 to 300 μm, more preferably 75 to 250 μm, and further preferably 100 to 200 μm from the viewpoint of curling prevention, ease of handling of the film, and cost balance. preferable.
In the present invention, the shrinkage stress of the weather resistant film can be sufficiently suppressed, and from the viewpoint of handling and cost, the ratio of the thickness of the weather resistant film to the thickness of the back film (the thickness of the weather resistant film / the thickness of the back film) Thickness) is preferably 2.0 or less, more preferably 1.0 or less, further preferably 0.75 or less, and further preferably 0.20 or more and 0.75 or less. preferable.

The back film preferably has an elastic modulus at 23 ° C. of 2.0 GPa or more in order to improve the effect of suppressing deformation against shrinkage of other constituent layers. The elastic modulus at 23 ° C. of the back film is more preferably 2.0 to 10.0 GPa, and further preferably 2.0 to 8.0 GPa. Here, the elastic modulus refers to the tensile elastic modulus obtained from the slope of the linear portion of the stress-strain curve, and can be obtained by a tensile test method based on JIS K7161: 1994.

Specific examples of the material for the back film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyamides such as nylon 6, nylon 66, nylon 12 and copolymerized nylon; ethylene-vinyl acetate copolymer Combined partial hydrolyzate (EVOH), polyimide, polyetherimide, polysulfone, polyethersulfone, polyetheretherketone, polycarbonate, polyvinyl butyral, polyarylate, fluororesin, acrylate resin, biodegradable resin, and An organic or inorganic material such as a filler may be added to the resin to improve the elastic modulus reinforcing effect.

In addition, since the use temperature of solar cell modules rises to about 85-90 ° C due to heat generated during power generation and radiant heat of sunlight, the back film softens if the melting point of the back film is below the use temperature. The function of protecting the original solar cell element during operation may be lost. Therefore, as the back film, polyester such as polyethylene naphthalate and polyethylene terephthalate, or polypropylene (PP), polylactic acid (PLA), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), cellulose butyrate (CAB) It is preferable that 1 type, or 2 or more types of resin chosen from etc. are included, and it is preferable that this resin is contained 50 mass% or more. Furthermore, although what formed into a film the resin composition which mix | blended the ultraviolet absorber and the coloring agent with this resin is used preferably, it is not limited to these.

The solar cell protective material of the present invention preferably has at least the weather-resistant film, the resin layer, and the moisture-proof film in this order, and when used for a front sheet, has a weather-resistant film on the exposed side. It is preferable. Moreover, when laminating a weather-resistant film and a moisture-proof film through a resin layer, the inorganic layer at the time of storage and use of the solar cell protective material is obtained by laminating the surface of the moisture-proof film on the side of the weather-resistant film. It is preferable because it can reduce the damage to the skin.
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 spirit of the present invention. Then, other layers may be laminated.
As the other layer that can be laminated in the solar cell protective material of the present invention, any layer that can be used for the solar cell protective material can be usually used. For example, a sealing material, a light collecting material, a conductive material, Layers such as a heat transfer material and a moisture adsorbing material can be laminated.
Various additives can be added to these other layers as necessary. Examples of the additive include, but are not limited to, an antistatic agent, an ultraviolet absorber, a plasticizer, a lubricant, a filler, a colorant, a weathering stabilizer, an antiblocking agent, and an antioxidant. As the ultraviolet absorber, the weather resistance stabilizer and the antioxidant, the same materials as those used for the above-mentioned substrate can be used.

The thickness of the solar cell protective material of the present invention is not particularly limited, but is preferably 60 to 600 μm, more preferably 75 to 350 μm, from the viewpoint of curling suppression and voltage resistance. The thickness is preferably 90 to 300 μm.

(Moisture resistance of solar cell protective material)
As described above, the solar cell protective material of the present invention uses a moisture-proof film having an inorganic layer as a base material and a moisture permeability of less than 0.1 g / m ² / day. preferably not more than 0.1g / m ² / day, more preferably, to not more than 0.05g / m ² / day.
The solar cell protective material of the present invention is excellent in initial moisture resistance, and also excellent in moisture resistance and prevention of delamination even when stored in a high temperature and high humidity environment.

Further, as described above, to the width W _A of the weather resistant film, by a ratio of the maximum width W _P having the protective material structure layer P other than the weather-resistant film (W _P / W _A) 1 or less, the The moisture-proof property is the degree of decrease in moisture-proof property due to the continuous high-temperature and high-humidity environment by vacuum lamination and the pressure cooker test according to JIS C 60068-2-66, that is, (water vapor permeability after the high-temperature and high-humidity environment / initial water vapor The transmittance) can be usually 25 or less, preferably 15 or less, more preferably 10 or less, and even more preferably 2 or less.
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 resistance value in a high temperature and high humidity environment around 100 ° C., and 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. The same applies to the “initial water vapor transmission rate”.

Each moisture-proof property in the present invention can be evaluated according to various conditions of JISＪZ0222 “moisture-proof packaging container moisture permeability test method” and JIS Z0208 “moisture-proof packaging material moisture permeability test method (cup method)”.

In the solar cell protective material of the present invention, the occurrence of curling is suppressed when the moisture-proof film has a base material thickness of 25 to 250 μm or the back film has a thickness of 60 μm or more. Moreover, when the thickness of the protective material for solar cells is 90 μm or more, the voltage resistance and cushioning properties are also excellent. The withstand voltage can be evaluated, for example, by measuring a partial discharge voltage. Specifically, the withstand voltage can be evaluated by the method described in the examples.

The protective material for solar cells of the present invention preferably has a partial discharge voltage measured in accordance with IEC60664-1: 2007 Clause 6.1.3.5 of 400 V or more, more preferably 600 V or more. More preferably, it is 800 V or more.

<Sealing material integrated protective material>
The encapsulant-integrated protective material of the present invention is formed by further laminating an encapsulant layer on the side opposite to the weather resistant film of the above-described solar cell protective material of the present invention. By using a sealing material integrated protective material in which a sealing material layer is laminated in advance, each of the front sheet, the sealing material, the power generating element, the sealing material, and the back sheet in the vacuum laminating process in the solar cell module manufacturing described later. Can be reduced, and the efficiency of solar cell module manufacturing can be improved.

In the sealing material-integrated protective material of the present invention, examples of the sealing material constituting the sealing material layer include a silicone resin-based sealing material, an ethylene-vinyl acetate copolymer, and ethylene and α-olefin. A random copolymer etc. are mentioned. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 3-methyl-butene-1, 4-methyl -Those consisting of pentene-1, etc. From the viewpoint of adhesion to a resin layer or an adhesive layer, an ethylene-vinyl acetate copolymer (EVA) is preferred.

In the sealing member integral protective member, the width W _D of the sealing material layer is smaller than the width W _A of the weather-resistant film, and is larger than the maximum width W _P of protective material constituting layers other than the weather resistant film has preferable. Thereby, at the time of vacuum laminating, the end face of the protective material constituting layer other than the weather resistant film can be sealed with the sealing material layer, and the moisture-proof deterioration and delamination of the protective material can be prevented.

The thickness of the laminated sealing material layer is preferably 200 to 750 μm, more preferably 300 to 600 μm from the viewpoint of protecting the solar cell element.

As the method for laminating the sealing material layer on the solar cell protective material of the present invention, a known method can be used. For example, what is necessary is just to laminate | stack a sealing material layer on the surface on the opposite side to the weather resistance film of the protective material for solar cells through an adhesive layer as needed. As the adhesive layer used here, the same adhesive layer as exemplified above for the adhesive layer (adhesive layer between the back film and the moisture-proof film) can be used. Among these, those containing a polyurethane adhesive are preferable, and those containing a polyurethane adhesive as a main component are more preferable.

<Rolled product>
The roll-like material of the present invention is formed by winding the above-described protective material for solar cell or the protective material integrated protective material of the present invention. By making it into a roll-like product, the subsequent processability, transportability, and productivity can be improved, and the appearance can be easily protected.
The winding length is preferably 50 m or more, and more preferably 100 m or more.

<Roll with cover sheet>
The roll-like product with a cover sheet of the present invention is a roll-shaped product obtained by winding the solar cell protective material or the sealing material-integrated protective material of the present invention described above, of the surfaces of the roll-shaped product. And covering at least a part of the part corresponding to the part from which the weather resistant film protrudes with a cover sheet having a deflection length of 70 mm or less measured under the following conditions and a load dent of 0.1 or less. It will be.

[Bending length]
(1) A sample having a width of 20 mm and a length of 120 mm is taken.
(2) Place the sample on the table so that a 100 mm long portion of the sample protrudes from the table, and fix the sample by placing a weight of 5 kg on the sample.
(3) The length “x” (unit: mm) at which the end of the portion protruding from the sample hangs down from the pedestal is measured, and this value is taken as the bending length.

The bending length is an index indicating how easily the cover sheet or the like is bent.
In addition, it is preferable to measure the bending length in a state in which the numerical value is stable. Usually, the measurement is performed after 5 minutes have elapsed after fixing the sample. Moreover, it is suitable that the temperature condition of a measurement is about 23 degreeC.
Further, it is preferable that a plate having a bottom surface of 20 mm × 20 mm is first placed on the portion of the sample table, and then a 5 kg weight is placed on the plate. The height of the plate is about 5 to 15 mm, and the material is not particularly limited, and examples thereof include a glass plate and an iron plate.

[Load dent]
(1) Collect a 100 mm square sample.
(2) A sample is placed on a glass plate having a thickness of 20 mm, a steel ball having a diameter of 5 mm and a weight of 0.5 g is placed on the center of the sample, and a load of 2 kg is further applied on the steel ball.
(3) The dent “d” (unit: μm) of the sample is measured, and the ratio “d / t” to the thickness “t” (unit: μm) of the sample is defined as a load-bearing dent.

The load bearing dent is an index indicating the difficulty of the dent of the cover sheet or the like.
Note that the depth “d” of the sample measures the depth of the deepest recess.
Moreover, it is preferable to measure a load-proof dent in the state where the numerical value was stable. Usually, a steel ball is placed on a sample, and the load is applied from above the steel ball.

Since the protective material for solar cells or the protective material integrated protective material of the present invention described above has a wide weather-resistant film, as shown in FIGS. 1 and 2, the film protrudes from the other protective material constituting layers. A protrusion 11 is provided. Therefore, the roll-shaped object which wound up the protective material for solar cells of this invention mentioned above or the sealing material integrated protective material also has such a protrusion part. And the roll-shaped thing which has such a protrusion may bend | fold and a wrinkle may arise when a load is applied to a protrusion part at the time of transportation.
In the roll-like product with a cover sheet of the present invention, at least a part of the surface of the roll-like material corresponding to the location where the weather-resistant film protrudes is covered with the cover sheet, so that the protruding portion is bent during transportation. Or wrinkles are prevented.

The cover sheet may cover at least a part corresponding to a part where the weather resistant film protrudes, but it is preferable to cover 50% or more of the part, and it is more preferable to cover the whole part. Moreover, a still more preferable aspect is to cover the entire surface of the roll-shaped material.
The ratio ([W _K ] / [W _A ]) of the width W _{k of the} cover sheet to the width W _A of the weather resistant film is preferably 1 or more, more preferably 1.05 or more. More preferably, it is 15 or more. Further, from the viewpoint of handling properties, [W _K ] / [W _A ] is preferably 1.5 or less, and more preferably 1.3 or less.
In addition, since the bending and wrinkles of the protrusion are mainly loads from the up and down direction of the roll-shaped object, the object of the present invention can be achieved by covering the surface of the roll-shaped object with the cover sheet. Furthermore, in consideration of the load from the left-right direction of the roll-shaped object, the side surface of the roll-shaped object may be covered with a cover sheet.

The bending length is preferably 60 mm or less, more preferably 50 mm or less, and further preferably 40 mm or less. The load bearing dent is preferably 0.05 or less, and more preferably 0.03 or less.
In addition, from the viewpoint of handling when covering the surface of the roll-shaped object with the cover sheet and fixing the lengthwise end of the cover sheet, the bending length is 5 mm or more, and the load dent is 0.01 or more. It is preferable that the bending length is 10 mm or more, and the load bearing dent is more preferably 0.02 or more.

Cover sheets include polyolefins such as homopolymers or copolymers of ethylene, propylene, butene, etc .; amorphous polyolefins such as cyclic polyolefin (Cyclo-Olefin-Polymer: COP); polyethylene terephthalate (PET), polyethylene naphthalate Polyester such as (PEN); polyamide such as nylon 6, nylon 66, nylon 12, copolymer nylon; polyimide, triacetyl cellulose (TAC), cellulose diacetate, cellulose acetate butyrate, polyether sulfone, polysulfone, polymethyl Use plastic sheets such as pentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, polymethyl methacrylate, polycarbonate, polyurethane, etc. It can be.
The thickness of the cover sheet is preferably 50 μm to 2 mm, more preferably 100 μm to 1 mm.

Also, the cover sheet may cause blocking with the roll. In particular, the cover sheet positioned below the roll-shaped object is likely to cause blocking between the roll-shaped object and the cover sheet due to the weight of the roll-shaped object. For this reason, the cover sheet preferably has a predetermined surface roughness, and specifically, a cover sheet having an arithmetic average roughness Ra of JIS B 0601 of 50 nm or more is suitable.

The cover sheet preferably has a cushioning property while having a predetermined strength. For this reason, the foamed plastic film based on the plastic sheet illustrated above is suitable.
In addition, since a foamed plastic film is opaque, it is suitable also in the point which is easy to distinguish when the transparency of a laminated body is high, the point which is excellent in blocking prevention property, and the point which is excellent also in handling property since it is lightweight.

In the present invention, the cover sheet only needs to be configured to cover the surface of the roll-shaped object, but the cover sheet and the roll-shaped object are used with a tape or an adhesive so that the state does not collapse during transportation. It is preferable to partially stick together. Moreover, when the cover sheet covers the entire surface of the roll-shaped object, it is preferable to fix both end portions in the length direction of the cover sheet with a tape or an adhesive.

In the present invention, the cover sheet and the weather resistant film preferably satisfy the following conditions (a ′) and / or (b ′).
(A ′) [Bend length of cover sheet] / [Bend length of weather-resistant film] is 2 or less (b ′) [Load dent of cover sheet] / [Load dent of weather-resistant film] is 2 or less By satisfying the condition (a ′) or (b ′), it is possible to easily prevent the protrusion from being bent or wrinkled. By satisfying the conditions (a ′) and (b ′), the protrusion from being bent Wrinkles can be more easily prevented.

Further, (a ′) [the bending length of the cover sheet] / [the bending length of the weather resistant film] is preferably 1 or less, and more preferably 0.1 to 0.6. Further, (b ′) [Load dent of cover sheet] / [Load dent of weather resistant film] is more preferably 1 or less, further preferably 0.5 or less, and 0.01 to 0 .2 is even more preferable.

<Solar cell module, solar cell manufacturing method>
The solar cell protective material of the present invention can be used as a solar cell surface protective material as it is, or further bonded to a glass plate or the like.
A solar cell module can be manufactured by using the solar cell protective material of the present invention in a layer structure of a surface protective material such as a front sheet and a back sheet, and fixing the solar cell element.

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 sheet, a solar cell module produced using a sealing material, a solar cell element, and a back sheet can be mentioned. Specifically, front sheet (protective material for solar cell of the present invention) / sealing material (sealing resin layer) / solar cell element / sealing material (sealing resin layer) / back sheet; A structure in which a sealing material and a front sheet (protective material for solar cell of the present invention) are formed on a solar cell element formed on the inner peripheral surface of the sheet; front sheet (protection for solar cell of the present invention) A solar cell element formed on the inner peripheral surface of the material), for example, a structure in which an encapsulant and a back sheet are formed on an amorphous solar cell element formed on a weather resistant film by sputtering or the like Can be mentioned.

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, III-V group and II -VI group compound semiconductor type, dye sensitized type, organic thin film type, and the like.
When a solar cell module is formed using the solar cell protective material in the present invention, a moisture-proof film having a moisture vapor transmission rate of less than about 0.1 g / m ² / day is used depending on the type of the solar cell power generation element. A film or a highly moisture-proof film of less than about 0.01 g / m ² / day is appropriately selected and laminated with another member such as a weather-resistant film through the above-described resin layer or adhesive layer.

The other members constituting the solar cell module manufactured using the solar cell protective material of the present invention are not particularly limited. Further, the solar cell protective material of the present invention may be used for both the front sheet and the back sheet. On the other hand, a single layer or a multilayer such as a sheet made of an inorganic material such as metal or glass or various thermoplastic resin films is used. These sheets may be used. Examples of the metal include tin, aluminum, and stainless steel, and examples of the thermoplastic resin film include single-layer or multilayer sheets of polyester, fluorine-containing resin, polyolefin, and the like. The surface of the front sheet and / or the back sheet can be subjected to a known surface treatment such as a primer treatment or a corona treatment in order to improve the adhesion with a sealing material or other members.

The solar cell module produced using the solar cell protective material of the present invention is a front sheet (solar cell protective material of the present invention) / sealing material / solar cell element / sealing material / back sheet as described above. The configuration will be described as an example. 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 it is not particularly limited, but in general, the solar cell protective material, sealing material, solar cell element, sealing of the present invention. A step of laminating materials and a back sheet in that order, and a step of vacuum-sucking them and thermocompression bonding them. 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 0. .1 MPa, pressing time is preferably 8 to 45 minutes, 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 produced using the solar cell protective material of the present invention is installed on a small solar cell represented by a mobile device, a roof or a roof, regardless of the type and module shape of the applied solar cell. It can be applied to various uses such as large solar cells, both indoors and outdoors. In particular, among electronic devices, it is suitably used as a protective material for solar cells for a flexible solar cell module such as a compound power generation element solar cell module or an amorphous silicon type.

Hereinafter, 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) Evaluation of the end face sealing state The weather resistant film exposes the glass, the sealing material, and the protective materials E-1 to E-7 for solar cells which were left to stand at 40 ° C. for 4 days and then cured. The layers were sequentially laminated so as to be on the side, vacuum lamination was performed under the conditions of 150 ° C. × 11 minutes and a pressure of 0.1 MPa, the state was observed, and the following criteria were evaluated.
(A) The sealing material reaches the end face of the weather resistant film width, and no extreme thinning occurs.
(C) The sealing material does not extend to the end face of the weather resistant film width, or the thickness of the reaching sealing material is small, and the end portion is thinned.

(2) Pressure cooker (PC) test After the production, the solar cell protective materials (E-1 to E-7) which were allowed to stand at 40 ° C for 4 days and then cured were vacuum-laminated by the above method, and then Tommy Seiko Using a pressure cooker test LSK-500 manufactured by the company, a water vapor transmission rate was measured after performing a pressure cooker test under the test (PC48) conditions of 105 ° C., 100% humidity and 48 hours.

(3) Delamination time The solar cell protective materials (E-1 to E-7) cured after standing for 4 days at 40 ° C after production were subjected to vacuum lamination by the above method, and then pressure produced by Tommy Seiko Co., Ltd. Using the cooker test LSK-500, the test time until the occurrence of delamination could be visually confirmed at the end face portion of the protective material for solar cell was measured under the test conditions of 105 ° C. and 100% humidity. Those in which the occurrence of delamination could not be confirmed in 90 hours were over 90 hours (> 90).

(4) Water vapor transmission rate The water vapor transmission rate of the moisture-proof film was measured by the following method as the water vapor transmission rate after the moisture-proof film was prepared and after curing at 40 ° C for one week.
For solar cell protective materials (E-1 to E-7), the measured value after curing at 40 ° C. for 4 days is the initial water vapor transmission rate, and after the curing, glass, solar cell protective material (weather resistance) The measured value of each protective material for solar cells after performing the pressure cooker test under the condition of (2) above is subjected to a heat treatment at 150 ° C. for 30 minutes. The water vapor transmission rate after the test was used.
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 protective materials for each solar cell with a moisture permeable area of 10.0 cm x 10.0 cm square, a bag with about 20 g of anhydrous calcium chloride added as a hygroscopic agent and sealed on all sides was produced, and the bag was heated to 40 ° C relative humidity Place in a 90% thermo-hygrostat and measure the mass until about 200 days at intervals of 72 hours or more. From the slope of the regression line between the elapsed time after the fourth day and the bag weight, the water vapor transmission rate g / m ² / The day was calculated. The degree of decrease in moisture resistance was calculated by [water vapor permeability after pressure cooker test (PC48) / initial water vapor permeability].

(5) Unevenness of thickness of resin layer and appearance after vacuum lamination Regarding the protective materials E-5 and E-6 for solar cells, the thickness unevenness of the resin layer and the appearance after vacuum lamination were visually observed. “A” when the thickness of the resin layer is uniform and there is no wrinkle after vacuum lamination and the appearance is good, and when the thickness of the resin layer is non-uniform and wrinkles occur after vacuum lamination and the appearance is poor “C”.

(6) MFR
The MFR of the resin constituting the resin layer was measured at a temperature of 190 ° C. and a load of 2.16 kg according to JIS K7210.

<Structure film>
(Weather-resistant film)
The following weather resistant films (fluorinated resin films) A-1 to A-3 were prepared.
A-1 ETFE film (Asahi Glass Co., Ltd., trade name: Aflex 50 MW 1250 DCS, thickness 50 μm) cut to a width of 200 mm.
A-2 The ETFE film cut to 230 mm in width.
A-3 The ETFE film cut into a width of 180 mm.

(Dampproof film)
As a base material, a biaxially stretched polyethylene naphthalate film (made by Teijin DuPont, “Q51C12”) having a thickness of 12 μm is used, and the following coating solution is applied to the corona-treated surface and dried to form an anchor coat having 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 a 50 nm thick SiO _x (x = 1) was formed on the anchor coat layer. .5) A moisture-proof film having a thin film was obtained, cut into a width of 180 mm and used. The produced moisture-proof film B-1 had a water vapor transmission rate of 0.01 g / m ² / day.

(Coating solution)
To an aqueous solution in which 220 g of polyvinyl alcohol resin of “GOHSENOL” manufactured by Nippon Gosei Co., Ltd. (degree of saponification: 97.0 to 98.8 mol%, degree of polymerization: 2400) was added to 2810 g of ion-exchanged water and dissolved at 20 ° C. While stirring, 645 g of 35 mol% 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.
Further, an isocyanate resin (“Sumidule N-3200” manufactured by Sumitomo Bayer Urethane Co., Ltd.) was used as a cross-linking agent and mixed so that the equivalent ratio of isocyanate groups to hydroxyl groups was 1: 2.

(Method for forming resin layer)
Resin layers R-1 to R-3 were formed on a substrate (weather-resistant film or moisture-proof film) by the following method.
R-1: ethylene-methyl acrylate copolymer as a thermoplastic resin (manufactured by Nippon Polyethylene Co., Ltd., trade name: Lexpearl EB240H, MFR: 7.0 g / 10 min, mass ratio of ethylene-methyl acrylate copolymer 80/20) A thermoplastic composition obtained by mixing an ultraviolet absorbent (BASF Tinuvin 1600) with 1.5% by mass of the resin and a light stabilizer (BASF Chimassorb2020FDL) with 0.5% by mass of the resin. It melt-kneaded at 170 degreeC using the T-die extrusion molding machine by a Soken company. The melt-kneaded thermoplastic composition was poured onto a substrate and cooled with a cooling roll to form a resin layer having a thickness of 30 μm and a width of 180 mm.
R-2: An ethylene-methyl acrylate copolymer, an ethylene-butyl acrylate copolymer (manufactured by Arkema, LOTRYL 35BA40, ethylene-butyl acrylate copolymer mass ratio 65/35), and an ethylene-butyl acrylate copolymer (Made by Arkema, LOTRYL 30BA02, ethylene-butyl acrylate copolymer mass ratio 70/30) and blended at 3: 2 (MFR of mixed resin: 12.1 g / 10 min) In the same manner as in -1, a resin layer having a thickness of 30 μm and a width of 180 mm was formed on the substrate.
R-3: Except for changing the ethylene-methyl acrylate copolymer to low density polyethylene (manufactured by Nippon Polyethylene Co., Ltd., trade name: Kernel (registered trademark) KC452T, MFR: 6.5 g / 10 min) Similarly to R-1, a resin layer having a thickness of 30 μm and a width of 180 mm was formed on the substrate.
R-4: R-4 was formed on the substrate in the same manner as the resin layer R-1 except that the thickness of the resin layer was changed to 20 μm.

(Encapsulant)
Brand name: EVASKY S11 (thickness 500 μm, melting point 69.6 ° C.) manufactured by Bridgestone Corporation was used.

(Glass)
A cover glass TCB09331 (3.2 mm thickness) manufactured by AGC Fabritech Co., Ltd. was used, and the glass was cut into the same size as the weather resistant film used in each of the examples and comparative examples.

Example 1
A resin layer R-1 was formed on the SiO _x surface of the moisture-proof film B-1, and a weather resistant film A-1 was further laminated thereon. Vacuum lamination was performed at 150 ° C. for 11 minutes under a pressure of 0.1 MPa to produce a solar cell protective material E-1 having a thickness of 92 μm. In addition, the length of each layer is substantially the same.
Using the solar cell protective material E-1, the end face sealing state was evaluated, and then a pressure cooker test and a delamination test were performed, and a water vapor transmission rate and a delamination generation time were measured.

Example 2
A solar cell protective material E-2 having a thickness of 92 μm was prepared in the same manner as in Example 1 except that A-2 was used as the weather resistant film. Thereafter, in the same manner as in Example 1, the end face sealing state, the water vapor transmission rate, and the delamination generation time were evaluated.

Example 3
A solar cell protective material E-3 having a thickness of 92 μm was prepared in the same manner as in Example 1 except that R-2 was used as the resin layer. Thereafter, in the same manner as in Example 1, the end face sealing state, the water vapor transmission rate, and the delamination generation time were evaluated.

Example 4
A solar cell protective material E-4 having a thickness of 92 μm was prepared in the same manner as in Example 1 except that R-3 was used as the resin layer. Thereafter, in the same manner as in Example 1, the end face sealing state, the water vapor transmission rate, and the delamination generation time were evaluated.

Example 5
A resin layer R-4 was formed on the SiO _x surface of the moisture-proof film B-1. Next, a resin layer R-4 was formed on the weather resistant film A-1. A moisture-proof film and a weather-resistant film are laminated so that the resin layer R-4 and the resin layer R-4 face each other, and vacuum lamination is performed under the conditions of 150 ° C. × 11 minutes and a pressure of 0.1 MPa. A battery protective material E-5 was produced. Thereafter, in the same manner as in Example 1, the end face sealing state, the water vapor transmission rate, and the delamination generation time were evaluated. Further, the thickness unevenness of the resin layer of the solar cell protective material E-5 and the appearance after vacuum lamination were visually observed.

Reference example 1
A resin layer R-4 was formed on the SiO _x surface of the moisture-proof film B-1. Next, the resin layer having the same composition as that of the resin layer R-4 is subjected to the same formation conditions (a thermoplastic resin composition melt-kneaded at 170 ° C. is poured onto the resin layer R-4 to be cooled and solidified). Formed directly on layer R-4. Next, a weather resistant film was laminated on the second resin layer, and vacuum lamination was performed at 150 ° C. for 11 minutes and under a pressure of 0.1 MPa to prepare a protective material E-6 for solar cells having a thickness of 102 μm. Thereafter, in the same manner as in Example 1, the end face sealing state, the water vapor transmission rate, and the delamination generation time were evaluated. Further, Table 1 shows the results of visual observation of the thickness unevenness of the resin layer of the solar cell protective material E-6 and the appearance after vacuum lamination. Further, the thickness unevenness of the resin layer of the protective material for solar cell E-6 and the appearance after vacuum lamination were visually observed.

Comparative Example 1
A solar cell protective material E-7 having a thickness of 92 μm was produced in the same manner as in Example 1 except that the weather-resistant film A-1 in Example 1 was changed to A-3. Thereafter, in the same manner as in Example 1, the end face sealing state, the water vapor transmission rate, and the delamination generation time were evaluated. The results are shown in Table 1.

As is apparent from the results in Table 1, Examples 1 to 5 and Reference Example 1 within the scope of the present invention are all excellent in moisture resistance and prevention of delamination, while forming a solar cell protective material. Comparative Example 1 in which the width of each layer to be performed was not within the specified range of the present invention was inferior in delamination prevention performance. Further, the solar cell protective material (protective material E-5) of Example 5 is a laminate of two resin layers, and the resin layer has a uniform thickness and a good appearance after vacuum lamination. Met.

(Adhesive 1)
Using a reactor equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas inlet tube, a mixed solution of 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, 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: manufactured by Nippon Polyurethane Industry Co., Ltd., solid content: 75% by mass) was added as an isocyanate-based crosslinking agent to prepare an adhesive 1.

Example 6
The pressure-sensitive adhesive 1 was applied to the moisture-proof film side surface of the solar cell protective material E-1 produced in Example 1 so as to have a thickness of 5 μm, and dried to form an adhesive layer made of the pressure-sensitive adhesive 1. A sealing material D-1 having a width of 190 mm was laminated on the adhesive surface of the formed layer and cured at 40 ° C. for 4 days to produce a sealing material integrated protective material F-1 having a thickness of 597 μm.
The obtained sealing material-integrated protective material F-1 had good adhesion between the solar cell protective material E-1 and the sealing material layer. Further, when the sealing material integrated protective material F-1 was evaluated for the PC delamination time and the end surface sealing state, the same evaluation as in Example 1 was obtained while being superior in workability to Example 1. It was.

(Moisture-proof film B-2 to B-4)
The moisture-proof film B-2 is the same as the moisture-proof film B-1, except that the base material of the moisture-proof film B-1 is changed to a biaxially stretched polyethylene naphthalate film (Mitsubishi Resin, T100) with a thickness of 125 μm. Produced. The produced moisture-proof film B-2 had a water vapor transmission rate of 0.01 g / m ² / day.
The moisture-proof film B-3 is the same as the moisture-proof film B-1, except that the base material of the moisture-proof film B-1 is changed to a biaxially stretched polyethylene naphthalate film (manufactured by Mitsubishi Plastics, T100) with a thickness of 100 μm. Produced. The produced moisture-proof film B-3 had a water vapor transmission rate of 0.01 g / m ² / day.
The moisture-proof film B-4 is the same as the moisture-proof film B-1, except that the base material of the moisture-proof film B-1 is changed to a biaxially stretched polyethylene naphthalate film (Mitsubishi Resin, T100) with a thickness of 50 μm. Produced. The produced moisture-proof film B-4 had a water vapor transmission rate of 0.01 g / m ² / day.

(7) Curling Evaluation The solar cell protective materials E-8 to E-10 were placed flat in an oven maintained at 150 ° C. and allowed to stand for 5 minutes. Then, the height of the four corners of the protective material was measured with a micro caliper, and the average value of the measured values at the four corners was taken as the curl value. The marked line was the surface where the base and the protective material contacted when the protective material was placed on a horizontal base so that the weather-resistant film faced upward.

(8) Partial discharge voltage The partial discharge voltage of the solar cell protective materials E-8 to E-10 was measured according to IEC60664-1: 2007 Clause 6.1.3.5. The measurement was performed in a measurement room in which the environment was controlled at a temperature of 23 ± 5 ° C. and a relative humidity of 40 ± 10%.

Example 7
A solar cell protective material E-8 having a thickness of 205 μm was prepared in the same manner as in Example 1 except that B-2 was used as the moisture-proof film.

Example 8
A solar cell protective material E-9 having a thickness of 180 μm was prepared in the same manner as in Example 1 except that B-3 was used as the moisture-proof film.

Example 9
A solar cell protective material E-10 having a thickness of 130 μm was prepared in the same manner as in Example 1 except that B-4 was used as the moisture-proof film.

As shown in Table 2, the solar cell protective materials of Examples 7 to 9 were excellent in curling suppression effect and withstand voltage. For the solar cell protective materials of Examples 7 to 9, when the end face sealing state, water vapor transmission rate, and delamination generation time were evaluated in the same manner as in Example 1, the same results as in Example 1 were obtained. It was.

(Adhesive layer)
Adhesive layers R-5 to R-7 were formed on the substrate (back film) by the following method.
R-5: An adhesive layer R-5 was formed in the same manner as the resin layer R-1 except that the width of the resin layer was changed to 190 mm.
R-6: An adhesive layer R-6 was formed in the same manner as the resin layer R-2 except that the width of the resin layer was changed to 190 mm.
R-7: An adhesive layer R-7 was produced in the same manner as the resin layer R-3 except that the width of the resin layer was changed to 190 mm.

Example 10
An adhesive layer R-5 was formed on the back film (biaxially stretched polyester film, thickness 125 μm, width 190 mm, elastic modulus 4.0 GPa). Next, a resin layer R-1 was formed on the weather resistant film A-1. Next, the film was laminated in the order of back film-adhesive layer-moisture-proof film B-1-resin layer-weather-resistant film A-1, and vacuum lamination was performed at 150 ° C. for 11 minutes for a solar cell with a thickness of 247 μm A protective material E-11 was produced. In addition, the length of each layer which comprises a protective material is substantially the same. Further, moisture-proof film, the surface of the SiO _X side is disposed such that the weather resistant film side.

Example 11
The back film was changed to a biaxially stretched polyester film having a thickness of 75 μm, a width of 190 mm, and an elastic modulus of 4.0 GPa, the adhesive layer R-5 was changed to the adhesive layer R-6, and the resin layer R-1 was changed to the resin layer R-- A solar cell protective material E-12 having a thickness of 197 μm was produced in the same manner as in Example 10 except that the thickness was changed to 2.

Example 12
The back film was changed to a biaxially stretched polyester film having a thickness of 50 μm, a width of 190 mm, and an elastic modulus of 4.0 GPa, the adhesive layer R-5 was changed to the adhesive layer R-7, and the resin layer R-1 was changed to the resin layer R-- A solar cell protective material E-13 having a thickness of 172 μm was produced in the same manner as in Example 10 except that the thickness was changed to 3.

As shown in Table 3, the solar cell protective materials of Examples 10 to 12 were excellent in curling suppression effect. For the solar cell protective materials of Examples 10 to 12, as in Example 1, when the end face sealing state, water vapor transmission rate, and delamination occurrence time were evaluated, the same results as in Example 1 were obtained. It was.

(Cover sheets K-1 to K-4)
The following was prepared as a cover sheet.
K-1: Foamed polyethylene sheet (made by Pollen Chemical Industry Co., Ltd., Polene sheet, thickness 700 μm, width 250 mm)
K-2: Polypropylene film (manufactured by KOKUGO, polypropylene sheet (product code: 07-175-02), thickness 500 μm, width 250 mm)
K-3: Transparent polyester film (Mitsubishi Resin, Diafoil T100, thickness 380 μm, width 250 mm)
K-4: Polyethylene film (manufactured by TGK, product code: 125-18-18-01, thickness 30 μm, width 250 mm)

(9) Deflection length As shown in FIG. 5, the cover sheet and the weather resistant film A-1 were cut into a strip shape having a width of 20 mm and a length of 120 mm to prepare a measurement sample S of the cover sheet and the weather resistant film. . Next, the sample S is placed on a table 71 having a height of 100 mm or more so that a portion of the sample S having a width of 20 mm and a length of 100 mm protrudes from the table, and the bottom surface of the sample S on the table is 20 mm × 20 mm. Then, an iron plate having a height of 10 mm was placed thereon, and a weight 72 having a weight of 5 kg was placed thereon. The length “x” (unit: mm) at which the end portion of the sample S projecting from the platform hangs down from the platform 71 was measured, and this value was taken as the deflection length.
The measurement was carried out after 5 minutes had passed after fixing the sample, and the temperature condition during the measurement was 23 ° C. The results are shown in Table 4.

(10) Load-proof dent As shown in FIG. 6, the cover sheet and the weather-resistant film A-1 were cut into 100 mm squares to produce a measurement sample S of the cover sheet and the weather-resistant film. Next, the sample S was placed on a glass plate 81 having a thickness of 20 mm, a steel ball 82 having a diameter of 5 mm and a weight of 0.5 g was placed on the center of the sample, and a load of 2 kg was applied from above the steel ball 82. The depth “d” (unit: μm) of the deepest recessed portion of the sample S after 24 hours at 23 ° C. is measured, and the ratio to the thickness “t” (unit: μm) of the sample S “D / t” was defined as a load-bearing dent. The results are shown in Table 4.

(11) Bending resistance of the protruding portion For the roll-like material with the cover sheet obtained in Examples 13 to 15 and Reference Example 2, a load of 5 kg was applied to the portion corresponding to the protruding portion from the top of the cover sheet for 24 hours. The state of the weather resistant film was visually observed and evaluated according to the following criteria. The results are shown in Table 4.
(A): The part which protrudes from the moisture-proof film of a weather-resistant film is not bent (C): The part which protrudes from the moisture-proof film of a weather-resistant film is bent

(12) Fixing of cover sheet edge (handling)
The rolls with cover sheets obtained in Examples 13 to 15 and Reference Example 2 were evaluated according to the following criteria. The results are shown in Table 4.
(A): The cover sheet was fixed with tape for 3 days or more (B): The cover sheet was not fixed with tape for 3 days

Example 13
The solar cell protective material E-1 produced in Example 1 was wound on a core having an outer diameter of 172.4 mm to obtain a 200-m roll-up product. Next, the entire surface of the roll was covered with the cover sheet K-1, and the end was fixed with one piece of tape (diapertex Piolan tape cut to 50 mm width x 100 mm length), Example 13 A roll-like product with a cover sheet was obtained.

Example 14
A roll with a cover sheet of Example 14 was obtained in the same manner as in Example 13 except that K-2 was used as the cover sheet.

Example 15
A roll with a cover sheet of Example 15 was obtained in the same manner as in Example 13 except that K-3 was used as the cover sheet.

Reference example 2
A roll with a cover sheet of Reference Example 2 was obtained in the same manner as in Example 13 except that K-4 was used as the cover sheet.

As shown in Table 4, the rolls with cover sheets of Examples 13 to 15 were excellent in bending resistance and handling properties.

According to the present invention, there is no decrease in moisture resistance or generation of delamination even when used under high temperature and high humidity for a long period of time, excellent flexibility and moisture resistance, preventing a decrease in the performance of solar cells, and solar It is possible to provide a highly moisture-proof solar cell protective material that is effective in improving the durability of the battery. The solar cell protective material of the present invention is excellent in flexibility and moisture resistance, in which moisture resistance and interlaminar strength do not decrease even after heat treatment in a high heat environment, that is, heat lamination conditions.

1: Weather-resistant film 21: Resin layer 22: Adhesive layer 3: Moisture-proof film 4: Back film 10: Solar cell protective material 11: Protrusion 20: Sealing material 30: Solar cell

Claims (14)

At least a weather-resistant film, a resin layer, and a moisture-proof film having an inorganic layer on at least one surface of the substrate and having a water vapor transmission rate of less than 0.1 g / m ² / day are laminated as a protective material constituting layer P. comprising a protective member for a solar cell Te, the resin layer is formed from a thermoplastic resin composition containing the ethylene-based resin, relative to the width W _a of the weather resistant film, protective material structures other than weatherproof film The protective material for solar cells in which the ratio (W _P / W _A ) of the maximum width W _P of the layer P is smaller than 1. At least a weather-resistant film, a resin layer, and a moisture-proof film having an inorganic layer on at least one surface of the substrate and having a water vapor transmission rate of less than 0.1 g / m ² / day are laminated as a protective material constituting layer P. comprising a protective member for a solar cell Te, the resin layer is formed from a thermoplastic resin composition substantially free of cross-linking agent, to the width W _a of the weather resistant film, a protective non-weather-resistant film The protective material for solar cells in which the ratio (W _P / W _A ) of the maximum width W _P of the material constituent layer P is smaller than 1. The solar cell protective material according to claim 1 or 2, wherein the W _P / W _A is 0.7 to 0.98. The solar cell protective material according to claim 1, wherein the ethylene-based resin is an ethylene-alkyl (meth) acrylate copolymer. The solar cell protective material according to any one of claims 1 to 4, wherein the base material has a thickness of 25 to 250 µm. The solar cell protective material according to any one of claims 1 to 5, wherein the moisture-proof film is laminated so that the surface on the inorganic layer side is the weather-resistant film side. The solar cell protective material according to any one of claims 1 to 6, wherein a layer having the maximum width among the protective material constituting layers P other than the weather resistant film is the moisture-proof film. As the protective material constituting layer P, there is an adhesive layer on the moisture-proof film side, a back film having a thickness of 60 μm or more, and a layer having the maximum width among the protective material constituting layers P other than the weather resistant film. The protective material for a solar cell according to any one of claims 1 to 6, which is the back film, and the width of the back film is larger than the width of the moisture-proof film. A sealing material-integrated protective material, wherein a sealing material layer is further laminated on the side opposite to the weather-resistant film of the solar cell protective material according to any one of claims 1 to 8. Sealing according to the width W _D of the sealing material layer, the smaller than the width W _A of the weather resistant film, and the maximum width greater than W _P of the protective material structure layer P other than the weather-resistant film, according to claim 9 Integrated material protective material. A roll-shaped product obtained by winding the solar cell protective material according to any one of claims 1 to 8 or the encapsulating material-integrated protective material according to any one of claims 9 and 10. A solar cell module manufactured using the solar cell protective material according to any one of claims 1 to 8 or the encapsulant-integrated protective material according to any one of claims 9 and 10. The surface of the roll-shaped article according to claim 11, wherein at least a part of the part corresponding to the part from which the weather resistant film protrudes has a bending length of 70 mm or less measured under the following conditions, and the load resistance. A roll-like product with a cover sheet, which is covered with a cover sheet having a dent of 0.1 or less.
[Bending length]
(1) A sample having a width of 20 mm and a length of 120 mm is taken.
(2) Place the sample on the table so that a 100 mm long portion of the sample protrudes from the table, and fix the sample by placing a weight of 5 kg on the sample.
(3) The length “x” (unit: mm) at which the end of the portion protruding from the sample hangs down from the pedestal is measured, and this value is taken as the bending length.
[Load dent]
(1) Collect a 100 mm square sample.
(2) A sample is placed on a glass plate having a thickness of 20 mm, a steel ball having a diameter of 5 mm and a weight of 0.5 g is placed on the center of the sample, and a load of 2 kg is further applied on the steel ball.
(3) The dent “d” (unit: μm) of the sample is measured, and the ratio “d / t” to the thickness “t” (unit: μm) of the sample is defined as a load-bearing dent. The roll-like article with a cover sheet according to claim 13, which satisfies the following conditions (a ') and / or (b').
(A ′) [Bend length of cover sheet] / [Bend length of weather-resistant film] is 2 or less (b ′) [Load dent of cover sheet] / [Load dent of weather-resistant film] is 2 or less

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