JP2011077397A - Back protective sheet for solar cell module, and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a back protective sheet for solar cell module, which is superior in adhesion, heat resistance, weatherability and durability. <P>SOLUTION: In the back protective sheet 1 for solar cell module, at least a protection layer 11, a primer layer 12, a polyester-based resin layer 13 and a substrate formed of thermoplastic resin are laminated in this order from an external side of a backside of the solar cell module. The surface protection layer 11 is formed by crosslinking and curing an ionizing radiation curing resin composition by ionizing radiation irradiation. The primer layer 12 is formed of polyurethane resin (P) formed by crosslinking and curing urethane-based prepolymer (Ppre) including urethane prepolymer (PpreH) or a diol component (OL) and urethane prepolymer (PpreC) by isocyanate-based crosslinking agent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a back surface protection sheet for a solar cell module, and a solar cell module using the back surface protection sheet.

In recent years, as interest in global environmental problems has increased, expectations for photovoltaic power generation have increased as a clean energy source to replace fossil fuels.
A solar cell element constituting the heart of a solar cell that directly converts solar energy into electricity is manufactured using a single crystal silicon substrate, a polycrystalline silicon substrate, or the like. Create a solar cell module with a structure that connects multiple solar cell elements to generate practical electrical output, covers the light-receiving surface with a transparent substrate, etc., and protects the solar cell elements with fillers etc. in the gaps It is currently being done. In general, a solar cell module uses a lamination method or the like in which a transparent front substrate, a surface filler layer, a solar cell element, a back surface filler layer, a back surface protective sheet, and the like are sequentially laminated, and these are vacuum-sucked and thermocompression bonded. Manufactured.

  In many cases, a plurality of solar cell modules are arranged side by side and installed outdoors, and therefore, high weather resistance and durability are required for members constituting the solar cell module. Especially, the back surface protection sheet used for the solar cell module mainly protects the back surface side of the solar cell element constituting the solar cell module, and thus has excellent mechanical strength, weather resistance, hydrolysis resistance, durability, etc. It is necessary to prepare. At present, as such a back surface protection sheet for a solar cell module, a plastic base material having excellent strength characteristics is most commonly used, and in addition, a metal plate or the like is also used.

Patent Document 1 discloses a base film, a barrier-type back surface protection sheet provided with a metal or metal oxide vapor-deposited film, a weather-resistant resin layer, an unsaturated group-containing acrylate-based co-polymer on the vapor-deposited film side surface. There is disclosed a back surface protection sheet for a solar cell module, in which a weatherproof outermost layer formed from a curable resin composition containing a polymer is provided in this order.
Patent Document 2 discloses a gas barrier vapor-deposited film made of a metal oxide for the purpose of improving weather resistance, moisture resistance, etc., and at least a thermoplastic resin binder and / or an acrylic oligomer made of an acrylic polyol-based resin. The back surface protection sheet for solar cells which laminated | stacked the radiation curing resin layer which becomes this is disclosed.
In an example of Patent Document 2, a solvent-free urethane acrylate radiation curable coating is applied to the surface on the vapor deposition layer side of the gas barrier vapor deposition film, and then cured by irradiation with an electron beam. Describes that a back protection sheet for solar cells was prepared by laminating a radiation-curable resin layer having a thickness of 50 μm.

  In Patent Document 3, for the purpose of improving weather resistance, moisture proofing, etc., as a colored layer on the vapor-deposited thin film layer surface of the gas barrier laminated film layer in which the vapor-deposited thin film layer of metal oxide is laminated on one side of the base material layer An uncured coating layer made of an electron beam curable acrylic ink and an uncured resin layer made of a coating agent mainly composed of an acrylic oligomer as a weather resistant resin layer, which are sequentially laminated and then cured by irradiation with an electron beam A battery back surface protective sheet is disclosed.

Japanese Patent Laid-Open No. 2002-083988 JP 2007-096210 A JP 2007-273737 A

  The back surface protection sheet for solar cell module disclosed in Patent Document 1 is provided with a weather resistant outermost layer formed from a curable resin composition containing an unsaturated group-containing acrylate copolymer. However, there has been a demand for adhesion and scratch resistance between the outermost layer and a layer adjacent to the outermost layer so as to be able to withstand artificial external stress applied during module manufacture or installation of a solar cell.

Patent Documents 2 and 3 disclose a back protective sheet for a solar cell in which a radiation curable resin layer is laminated as a protective layer on the outermost layer, and the same as described above between the radiation curable resin layer and an adjacent layer. There has been a demand for an improvement in order to suppress initial scratch resistance, peeling, cracks, and the like during long-term use in a wet and heat environment.
When a polyurethane resin that is used for a primer layer provided between the protective layer that forms the outermost layer on the back side of the back surface protective sheet for solar cells and the base material is used, the initial adhesion is improved. Resistance to deep scratches reaching the vicinity of the material was not obtained.
Moreover, in the back surface protection sheet of the solar cell, moisture and heat resistance is required from the usage environment, but when a normal polyester urethane resin having good scratch resistance is used for the primer layer adjacent to the protective layer, the moisture and heat resistance of the primer layer is Is insufficient, the urethane resin undergoes a hydrolysis reaction, the adhesiveness decreases, the holding power of the protective layer made of a radiation-cured resin layer, etc. decreases and the protective layer is detached, and the back surface for solar cells There arises a problem that the protective function of the base material surface of the protective sheet (scratch resistance, heat resistance, surface scratch resistance) is lowered.
The present invention relates to a urethane resin comprising a diol component containing at least a caprolactone-modified polyester diol, a urethane prepolymer obtained from a diisocyanate component and an isocyanate crosslinking agent, or at least a caprolactone-modified polyester diol, a polycarbonate diol, and an acrylic diol. , And a diol component (OL) containing one or more selected from polyether diol, and a primer layer containing a urethane resin composed of a urethane prepolymer obtained from diisocyanate and an isocyanate crosslinking agent, thereby providing a protective layer Back surface protection sheet for solar cell module, which has excellent adhesion and scratch resistance, excellent adhesion durability of the protective layer in a moist heat environment, and excellent weather resistance, heat resistance, abrasion resistance, and the like, and the back surface protection sheet Solar cell using And to provide a module.

  The present invention has been made against the background of the above circumstances, and an ionizing radiation curable resin layer which is the outermost layer on the back surface side of the back surface protection sheet for solar cell modules, and a polyester-based resin which becomes a base material when the resin layer is formed From a polyurethane resin mixture obtained by crosslinking and curing a prepolymer containing a diol component containing a caprolactone-modified polyester polyol and a urethane prepolymer obtained from a diisocyanate component as an inter-layer primer layer. It has been found that the above-mentioned problems can be solved by forming a layer, and the present invention has been completed.

That is, the present invention is an invention having the following (1) to (6).
(1) From the outside of the back surface of the solar cell module, at least a protective layer (A), a primer layer (B), a polyester resin layer (C), and a base material (D) formed from a thermoplastic resin are laminated in this order. The surface protective layer (A) is a layer formed by crosslinking and curing the ionizing radiation curable resin composition by ionizing radiation irradiation,
The surface protective layer (A) is a layer formed by crosslinking and curing the ionizing radiation curable resin composition by ionizing radiation irradiation,
The primer layer (B) is a urethane prepolymer (PpreH) obtained from caprolactone-modified polyester diol and diisocyanate,
Alternatively, a urethane prepolymer (OL) obtained from diisocyanate and a diol component (OL) containing at least one selected from caprolactone-modified polyester diol, polycarbonate diol, acrylic diol, and polyether diol. PpreC),
A back protective sheet for a solar cell module (hereinafter referred to as a first protective sheet), characterized in that it is a layer made of a polyurethane resin (P) formed by crosslinking and curing a urethane prepolymer (Ppre) containing an isocyanate based crosslinking agent. It may be referred to as an aspect.)
(2) The solar cell module according to (1), wherein the urethane prepolymer (Ppre) contains 50% by mass or more of a urethane prepolymer (PpreH) or (PpreC). Back surface protection sheet.
(3) The back surface for a solar cell module according to (1) or (2), wherein the diisocyanate used in obtaining the urethane prepolymer (PpreH) or (PpreC) is isophorone diisocyanate. Protective sheet.
(4) The back surface protective sheet for solar cell module according to any one of (1) to (3), wherein the primer layer (B) has a thickness of 0.5 to 7 μm.
(5) The back surface protection sheet for solar cell modules according to any one of (1) to (4), wherein the surface layer has a universal hardness of 50 N / mm ² or less.

(6) A solar cell module in which a front transparent substrate <1>, a surface filler layer <2>, a solar cell element <3>, a back surface filler layer <4>, and a back surface protection sheet <5> are arranged in this order. There,
The back surface protective sheet <5> is a base material (D) formed from at least a protective layer (A), a primer layer (B), a polyester resin layer (C), and a thermoplastic resin from the outside of the back surface of the solar cell module. ) Are laminated in this order, and the protective layer (A) is a layer formed by crosslinking and curing the ionizing radiation curable resin composition by irradiation with ionizing radiation, and is a urethane obtained from caprolactone-modified polyesterdiol and diisocyanate. Urethane-based prepolymer (PpreH) including prepolymer (PpreH1)
Alternatively, a urethane prepolymer (OL) obtained from diisocyanate and a diol component (OL) containing at least one selected from caprolactone-modified polyester diol, polycarbonate diol, acrylic diol, and polyether diol. PpreC),
A solar cell module (hereinafter sometimes referred to as a second embodiment), which is a layer made of a polyurethane resin (P) formed by crosslinking and curing with an isocyanate-based crosslinking agent.

Since the protective layer (A) made of an ionizing radiation curable resin is provided on the outermost layer on the back side of the back surface protective sheet for a solar cell module according to the first aspect of the present invention, weather resistance, scratch resistance, Excellent heat resistance.
The urethane prepolymer (PpreH) or the urethane prepolymer (PpreC) containing the urethane prepolymer (PpreC) between the protective layer (A) which is the outermost layer of the back surface protective sheet and the polyester resin layer (C). Since the primer layer (B) containing a polyurethane resin obtained by crosslinking and curing a polymer with an isocyanate-based crosslinking agent is provided, scratch resistance is good. Moreover, since the back surface protection sheet for solar cell modules according to the first aspect of the present invention also suppresses hydrolysis resistance, the occurrence of delamination, cracks, etc. was remarkably suppressed even during long-term use between the layers. It will be a thing.
In the solar cell module according to the second aspect of the present invention, by providing the back surface protection sheet for the solar cell module according to the first aspect on the back surface protection sheet, the moisture and heat resistance, weather resistance, scratch resistance, and heat resistance are improved. Is possible.

It is a cross-sectional schematic diagram which shows an example of a layer structure about the back surface protection sheet for solar cell modules which concerns on this invention. It is a cross-sectional schematic diagram which shows the other example of a layer structure about the back surface protection sheet for solar cell modules which concerns on this invention. It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the solar cell module manufactured using the back surface protection sheet illustrated in FIG. 1 or 2 for the back surface protection sheet of a solar cell module.

  [1] The back surface protection sheet for solar cell modules (first aspect) and [3] the solar cell module (second aspect) of the present invention will be described below.

[1] Back surface protection sheet for solar cell module (first aspect)
Hereinafter, an embodiment according to a first aspect will be described with reference to the drawings. 1 and 2 are schematic cross-sectional views showing examples of the layer structure of the back surface protection sheet for a solar cell module according to the first embodiment.
A back protective sheet 1 for a solar cell module as an example of the first embodiment shown in FIG. 1 includes a protective layer (A) 11, a primer layer (B) 12, a polyester resin from the back side of the back protective sheet. The layer (C) 13, the adhesive layer 15, the base polyester layer 16, the adhesive layer 15, and the polyolefin layer 17 are laminated in this order.
The back surface protection sheet 1 for a solar cell module as another example of the first mode shown in FIG. 2 includes a protective layer (A) 11, a primer layer (B) 12, polyester from the back surface side of the back surface protection sheet. The resin layer (C) 13, the adhesive layer 15, the water vapor barrier layer 14, the adhesive layer 15, the base polyester layer 16, the adhesive layer 15, and the polyolefin layer 17 are laminated in this order.
Hereinafter, each layer which comprises the back surface protection sheet for solar cell modules is demonstrated.

(1) Protective layer (A)
The protective layer (A) is a layer provided to protect the back surface protective sheet by being laminated on the outermost layer on the back surface side of the back surface protective sheet for the solar cell module, and is a coating made of an ionizing radiation curable resin composition. It is a layer formed by crosslinking and curing by ionizing radiation irradiation after applying the working fluid. The protective layer (A) made of an ionizing radiation curable resin obtained by crosslinking and curing the ionizing radiation curable resin composition is laminated on the outermost layer on the back surface side of the solar cell module on the back surface protective sheet for the solar cell module of the present invention. Accordingly, it is excellent in weather resistance, scratch resistance, heat resistance and the like, and has an appropriate surface hardness, and can improve durability.

Hereinafter, an embodiment according to a first aspect will be described with reference to the drawings. 1 and 2 are schematic cross-sectional views showing examples of the layer structure of the back surface protection sheet for a solar cell module according to the first embodiment.
A back protective sheet 1 for a solar cell module as an example of the first embodiment shown in FIG. 1 includes a protective layer (A) 11, a primer layer (B) 12, a polyester resin from the back side of the back protective sheet. The layer (C) 13, the adhesive layer 15, the base polyester layer 16, the adhesive layer 15, and the polyolefin layer 17 are laminated in this order.
The back surface protection sheet 1 for a solar cell module as another example of the first mode shown in FIG. 2 includes a protective layer (A) 11, a primer layer (B) 12, polyester from the back surface side of the back surface protection sheet. The resin layer (C) 13, the adhesive layer 15, the water vapor barrier layer 14, the adhesive layer 15, the base polyester layer 16, the adhesive layer 15, and the polyolefin layer 17 are laminated in this order.
Hereinafter, each layer which comprises the back surface protection sheet for solar cell modules is demonstrated.

(1) Protective layer (A)
The protective layer (A) is a layer provided to protect the back surface protective sheet by being laminated on the outermost layer on the back surface side of the back surface protective sheet for the solar cell module, and is a coating made of an ionizing radiation curable resin composition. It is a layer formed by crosslinking and curing by ionizing radiation irradiation after applying the working fluid. A protective layer (A) made of an ionizing radiation curable resin obtained by crosslinking and curing an ionizing radiation curable resin composition is laminated on the outermost layer on the back surface side of the solar cell module on the back surface protective sheet for solar cell module of the present invention. By this, it is excellent in durability, such as a weather resistance and heat resistance, and also has moderate surface hardness, and it becomes possible to improve scratch resistance.

(1-1) Ionizing radiation curable resin In the present invention, the ionizing radiation curable resin has an energy quantum capable of crosslinking and polymerizing molecules in electromagnetic waves or charged particle beams, that is, ultraviolet rays, electron beams, and the like. Refers to a resin that is cross-linked and cured by irradiation. Specifically, it can be selected from polymerizable monomers and polymerizable oligomers (including prepolymers) conventionally known as components of ionizing radiation curable resins.

(A) Polymerizable monomer As a typical polymerizable monomer, a polyfunctional (meth) acrylate monomer having a radical polymerizable unsaturated group in the molecule is preferable, and among them, a polyfunctional (meth) acrylate is preferable. . Here, “(meth) acrylate” means “acrylate or methacrylate”. The polyfunctional (meth) acrylate monomer is a (meth) acrylate having two or more ethylenically unsaturated bonds in the molecule. Specifically, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) ) Acrylate, polyethylene glycol di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified diphosphate ( (Meth) acrylate, allylated cyclohexyl di (meth) acrylate, isocyanurate di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylo Propane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, tris ( Acryloxyethyl) isocyanurate, propionic acid modified dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene oxide modified dipentaerythritol hexa (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate, etc. Is mentioned. These polyfunctional (meth) acrylate monomers can be used alone or in combination of two or more.
In the present invention, a monofunctional (meth) acrylate can be used in combination with the polyfunctional (meth) acrylate within a range that does not impair the object of the present invention, for the purpose of reducing the viscosity thereof.

(B) Polymerizable oligomer As the polymerizable oligomer, an oligomer having a radical polymerizable unsaturated group in the molecule, for example, epoxy (meth) acrylate, urethane (meth) acrylate, polyester (meth) acrylate, polyether ( And a (meth) acrylate type. Here, the epoxy (meth) acrylate oligomer can be obtained by, for example, reacting (meth) acrylic acid with an oxirane ring of a relatively low molecular weight bisphenol type epoxy resin or novolak type epoxy resin and esterifying it. A carboxyl-modified epoxy (meth) acrylate oligomer obtained by partially modifying this epoxy (meth) acrylate oligomer with a dibasic carboxylic acid anhydride can also be used. The urethane (meth) acrylate oligomer can be obtained, for example, by esterifying a polyurethane oligomer obtained by the reaction of polycarbonate polyol, polyether polyol or polyester polyol and polyisocyanate with (meth) acrylic acid. As the polyester (meth) acrylate oligomer, for example, by esterifying the hydroxyl group of a polyester oligomer having a hydroxyl group at both ends obtained by a condensation reaction of a polyvalent carboxylic acid and a polyhydric alcohol with (meth) acrylic acid, or It can be obtained by esterifying the terminal hydroxyl group of an oligomer obtained by adding alkylene oxide to a polyvalent carboxylic acid with (meth) acrylic acid. The polyether (meth) acrylate oligomer can be obtained by esterifying the hydroxyl group of the polyether polyol with (meth) acrylic acid.

(1-2) Ionizing radiation curable resin composition In the present invention, when forming the protective layer (A), various additives are blended into the ionizing radiation curable resin as necessary, thereby providing a coating solution. An ionizing radiation curable resin composition can be obtained.
Examples of these additives include photopolymerization initiators, weather resistance improvers, antiblocking agents, polymerization inhibitors, crosslinking agents, fillers, viscosity modifiers, and the like.
In addition, it is preferable to use an electron beam curable resin composition as the ionizing radiation curable resin composition. When an electron beam curable resin composition is used, a photocuring initiator is not required, so that stable curing characteristics can be obtained.

When an ultraviolet curable resin composition is used as the ionizing radiation curable resin composition, it is desirable to add about 0.1 to 5 parts by weight of a photopolymerization initiator with respect to 100 parts by weight of the resin. The initiator for photopolymerization can be appropriately selected from those conventionally used.
As the weather resistance improver, known ultraviolet absorbers, light stabilizers, antioxidants and the like can be used. The ultraviolet absorber may be either inorganic or organic.

  By adding an antiblocking agent to the ionizing radiation curable resin composition, it is possible to prevent blocking when winding the back surface protection sheet for solar cell modules around a roll or the like, and to improve scratch resistance. become. In this case, an inorganic fine powder, an organic fine powder, or the like can be used as an antiblocking agent to be added. As the inorganic fine powder, silica, talc, clay, heavy calcium carbonate, light calcium carbonate, precipitated barium sulfate, calcium silicate, synthetic silicate, aluminum hydroxide, silicate fine powder, etc. can be used, Examples of the organic fine powder include heat-resistant acrylic, urethane, nylon, polyethylene, polypropylene, urea-based resin filler, styrene crosslinked filler, benzoguanamine crosslinked filler, wax and the like.

As the polymerization inhibitor, for example, hydroquinone, p-benzoquinone, hydroquinone monomethyl ether, pyrogallol, t-butylcatechol and the like can be used.
As a crosslinking agent, a polyisocyanate compound, an epoxy compound, a metal chelate compound, an aziridine compound, an oxazoline compound, etc. can be used, for example. As the filler, the above-mentioned anti-blocking agent can be used. As a viscosity modifier, the above-mentioned monofunctional (meth) acrylate and an organic solvent can be used. As the organic solvent, ethyl acetate, propyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropyl alcohol and the like can be used.

(1-3) Formation of Protective Layer (A) In the present invention, the above-mentioned ionizing radiation curing component polymerizable monomer, polymerizable oligomer and various additives are homogeneously mixed at a predetermined ratio, and ionizing radiation is obtained. A coating liquid comprising a curable resin composition can be obtained. The viscosity of the coating solution is not particularly limited as long as it is a viscosity capable of forming an uncured resin layer on the surface of the substrate by a coating method described later. In the case of using a high-viscosity coating liquid, the coating liquid can be heated or diluted with an organic solvent to reduce the viscosity to an appropriate viscosity.
In the present invention, a gravure coat, a bar coat, and a roll are applied so that the thickness of the protective layer (A) after curing is preferably 2 to 15 μm on the surface to which the coating liquid thus obtained is applied. It coats by well-known systems, such as a coat, reverse roll coat, comma coat, die coat, slit coat, and curtain coat, preferably a gravure coat, and forms an uncured resin layer.
When the coating liquid is composed of an ionizing radiation curable resin composition system that forms a relatively hard layer after curing, the protective layer (A) is less likely to crack when the film thickness is relatively thin, When the coating liquid is a composition system that forms a relatively soft layer after curing, cracks in the protective layer tend not to occur even when the film thickness is relatively thick.

  When the uncured resin layer formed as described above is irradiated with an electron beam to cure the uncured resin layer, the acceleration voltage can be appropriately selected according to the resin used and the thickness of the layer. Usually, the uncured resin layer is preferably cured at an acceleration voltage of about 10 to 300 kV, more preferably about 10 to 180 kV.

When the ionizing radiation curable resin composition is cured with ultraviolet rays, ultraviolet irradiation is performed with a high pressure mercury lamp, a metal halide lamp or the like. Ultraviolet light sources are more compact, safer and less expensive than electron beam sources. However, since ultraviolet rays are inferior to electron beams in their ability to transmit substances, it is necessary to pay attention to the addition of polymerization initiators and the inclusion of ultraviolet-absorbing substances. An ultraviolet absorber can be mix | blended. In the case of using a high-pressure mercury lamp, for example, the ultraviolet curable resin can be cured by irradiating about 30 to 1000 mJ / cm ² with ultraviolet rays.
It is desirable to carry out cross-linking curing by irradiation with ionizing radiation so that the reaction rate of the radically polymerizable unsaturated group in the ionizing radiation-curable resin is 60% or more. The reaction rate of the radical polymerizable unsaturated group is measured from the disappearance ratio of the characteristic peak of the radical polymerizable unsaturated group on the FT-IR chart using a Fourier transform infrared spectrophotometer (FT-IR). Can do.

(1-4) In the universal hardness and the like present invention, the protective layer (A) is the universal hardness of preferably 50 N / mm ² or less of the surface, 15~50N / mm ² is more preferable. When the universal hardness of the surface of the protective layer (A) is 50 N / mm ² or less, the thermal expansion coefficient and thermal contraction rate of the protective layer (A) and the base material (B) due to the thermal cycle during the operation of the solar cell The followability to contraction / expansion due to the difference is reduced, stress is generated, and it is possible to suppress inconveniences such as generation of fine cracks and deterioration of adhesion. On the other hand, at 15 N / mm ² or more, it is possible to effectively suppress the appearance of tackiness on the surface of the protective layer (A), and the adhesion of dust and the back surface protection sheet for solar cell modules are stored in roll form or stacked. It is possible to avoid inconveniences such as sticking the back surface protection sheets to each other.
As the number of functional groups in the monomer before curing in the ionizing radiation curable resin used in the present invention increases, the reactivity of the radical polymerizable unsaturated group tends to decrease, but the number of reactive points increases, so the crosslinking density Increases the universal hardness. In addition, the reactivity of the radical polymerizable unsaturated group tends to decrease as the molecular weight of the monomer before curing decreases, but since the distance between the reaction points (molecular weight between crosslinking points) becomes shorter, the crosslinking density becomes higher. Universal hardness tends to be high.
Moreover, when the crystallinity and rigidity of the ionizing radiation curable resin forming the protective layer (A) are increased, the universal hardness tends to be increased. Examples of such a highly rigid resin include resins having a ring structure such as an isobornyl skeleton, an adamantane skeleton, and a benzene ring. In the present invention, a preferable monomer or a combination thereof is selected in consideration of characteristics of an ionizing radiation curable resin of a resin obtained from such a monomer.
The shrinkage of curing decreases as the number of functional groups in the monomer before curing in the ionizing radiation curable resin used in the present invention decreases, and the shrinkage of curing tends to decrease as the molecular weight of the monomer before curing increases. is there.

In the present invention, the universal hardness is a value measured by using a hardness measuring device and disposing a protective layer (A) having a thickness of 10 μm on a glass plate.
Specifically, using a micro hardness tester “H-100V” (manufactured by Fisher Instrument Co., Ltd.), the test load and the indenter contacted with the object to be measured when the measurement indenter reached a depth of 2 μm. Universal hardness is calculated from the following surface area using the following formula.
Universal hardness = (test load) / (surface area of contact of the indenter with the object under test load)
Measurement conditions Measuring machine: Ultra micro hardness tester "H-100V" (Fischer Instrument Co., Ltd.)
Measurement indenter: Vickers square pyramid diamond indenter Measurement environment: 25 ° C, 50% relative humidity (RH)
Measurement data: An ionizing radiation curable resin for forming a protective layer is applied and dried on a glass plate so as to have a thickness of about 10 μm, and then irradiated with ionizing radiation to prepare a measurement sample.
Maximum pushing depth: 2μm
Load condition: A load is applied in proportion to time at a speed that reaches a test load of 300 mN in 30 seconds.
The “universal hardness” in the present invention is a hardness determined by measuring 10 points at random for each sample, and an average value of 6 points excluding 2 points above and below the universal hardness.
2-15 micrometers is preferable and, as for the thickness of a protective layer (A), 2-10 micrometers is more preferable.
When the thickness of the protective layer (A) is less than 2 μm, the weather resistance and the like are insufficient, and the function as the protective layer cannot be sufficiently exerted. On the other hand, when the thickness exceeds 15 μm, not only waste is caused in cost, Further improvement in scratch resistance, heat resistance and weather resistance cannot be expected. The thickness of the protective layer (A) can be measured with an electron microscope (for example, a scanning electron microscope) or the like in section.

(2) Primer layer (B)
The primer layer (B) is a urethane prepolymer (PpreH) obtained from caprolactone-modified polyester polyol and diisocyanate,
Alternatively, a urethane prepolymer (OL) obtained from diisocyanate and a diol component (OL) containing at least one selected from caprolactone-modified polyester diol, polycarbonate diol, acrylic diol, and polyether diol. PpreC),
It is a layer which consists of a polyurethane resin (P) formed by cross-linking and curing a urethane prepolymer (Ppre) containing an isocyanate cross-linking agent.
By using the polyurethane resin (P) for the primer layer (B), resistance to deep scratches reaching the vicinity of the polyester resin layer (C) is developed. On the other hand, compared with the case where a general polyester urethane prepolymer having an effect on scratch resistance is used, hydrolyzability in a moist heat environment is suppressed, so that the scratch resistance is less deteriorated.

The primer layer (B) is a layer made of a polyurethane resin (P), and the polyurethane resin (P) is an urethane prepolymer (Ppre) containing the urethane prepolymer (PpreH) or urethane prepolymer (PpreC). It is a layer made of a polyurethane resin (P) formed by crosslinking and curing with a system crosslinking agent.
(2-1) Urethane prepolymer (PpreH)
A diol component and a diisocyanate component used in obtaining a urethane prepolymer (PpreH) will be described.
(I) Diol component The diol component is, for example, a polyether polyol such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, 1-methylbutylene glycol; diol; neopentyl glycol, ethylene glycol, diethylene glycol, propylene glycol, 1 , 6-hexanediol, 1,4-butanediol, 1,9-nonanediol, 1,10-decanediol, 3-methylpentanediol, 2,4-diethylpentanediol, tricyclodecane dimethanol, 1,4 -Diols such as cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, cyclohexanediol, hydrogenated bisphenol A, bisphenol A,
Examples include diols obtained by reaction with lactones such as ε-caprolactone, γ-butyrolactone, γ-valerolactone, and δ-valerolactone. These diols can be used alone or in combination.
The above diols are examples, and other caprolactone-modified polyester diols capable of exhibiting the effects of the present invention are also included in the caprolactone-modified polyester diol (OLcpes) of the present application.
(B) Diisocyanate The diisocyanate component used in the production of urethane prepolymer (PpreH) (PPre-H1) includes isophorone diisocyanate, 1,6-hexamethylene diisocyanate (HDI), 1,3-trimethylene diisocyanate, 1,4. -Tetramethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 1,9-nonamethylene diisocyanate, 1,10-decamethylene diisocyanate, 1,4-cyclohexane diisocyanate, 2,2′-diethyl ether diisocyanate, methylene bis (cyclohexyl isocyanate), cyclohexane-1,3-dimethylene diisocyanate, cyclohexane-1,4 Non-yellowing or hardly yellowing diisocyanate components such as dimethylene diisocyanate, norbornane diisocyanate, hydrogenated (1,3- or 1,4-) xylylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate , Diphenylmethane-4,4′-diisocyanate, (o, m or p) -xylene diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, 3,3′-methyleneditolylene-4,4′-diisocyanate, 4, And yellowing type diisocyanate components such as aromatic diisocyanates such as 4,4'-diphenyl ether diisocyanate and tetrachlorophenylene diisocyanate. These may be used singly or in combination of two or more. Of these diisocyanate components, non-yellowing type and / or hard yellowing type diisocyanate components are preferred. Isophorone diisocyanate is preferred from the viewpoint of durability.

(C) Production of urethane prepolymer (PpreH) Examples of the production of urethane prepolymer (PpreH) include, for example, a method in which the diol component and the diisocyanate component are all charged and prepolymerized, a diisocyanate component, and a part of the diol component. The method of mixing the remaining diol component after reacting the mixture, the method of reacting the polycaprolactone polyesterdiol with a part of the diisocyanate component and then mixing the remaining diol and diisocyanate to prepolymerize, etc. be able to.
When the urethane prepolymer (PpreH) is produced, the ratio of the diol component to the diisocyanate component, or, when a plurality of diol components are used, the ratio of the sum of the plurality of diol components to the diisocyanate component is the urethane prepolymer ( Since PpreH) is cross-linked and cured with an isocyanate-based cross-linking agent, the prepolymer needs to be a hydroxyl-terminated prepolymer, so that the diol component is used in a larger molar ratio of both.

In addition, the polyfunctional compound which is a compound which has 2 or more of active hydrogen which can react with an isocyanate group can also be added and used for a diol component. The polyfunctional compound may further contain a polyfunctional compound capable of introducing an acidic group, a chain extender, and the like. In addition, other diols [polyester diol and the like (not including caprolactone-modified polyester diol)] can be added within a range that does not impair the original purpose.
The urethane prepolymer (PpreH) obtained from the diol component and the polyisocyanate component is, for example, a prepolymer having a weight average molecular weight (Mw) of about 10,000 to 50,000.
(2-2) Urethane prepolymer (PpreC)
The diol component and diisocyanate component used when obtaining the urethane prepolymer (PpreC) will be described.
(I) Diol component The diol component is a diol component (OL) containing at least one selected from caprolactone-modified polyester diol, polycarbonate diol, acrylic diol, and polyether diol.
<Caprolactone-modified polyester diol> The caprolactone-modified polyester diol is the same as that described in the section "Urethane prepolymer (PpreH)".
Hereinafter, other typical diol components will be described.

<Polycarbonate diol>
Polycarbonate diol (OLpcd) can be produced, for example, by transesterification of alkylene glycol and carbonate, or reaction of phosgene or chloroformate with alkylene glycol, and has hydroxyl groups at both ends and has a carbonate skeleton (- The thing of the weight average molecular weight (Mw) of about 500-5,000 shown by General formula (1) which has (R-O-CO-O-) is mentioned.
HO (—R—O—CO—O—) _x R—OH (1)
For example, when 1,6-hexanediol as an alkylene glycol is reacted with ethylene carbonate, the following polycarbonate diol is obtained.
nHO (CH ₂ ) ₆ OH + n ethylene carbonate → mHO (CH ₂ ) ₆ OCOCH ₂ CH ₂ OH + mHO (CH ₂ ) ₆ OH
_{→ HO [(CH 2) 6} OCO] m - (CH 2) 6 OH + mHO (CH 2) 6 OH

Examples of the alkylene glycol for obtaining such a polycarbonate diol (OLpcd) include 2-ethyl-1,3-pentanediol, 2-propyl-1,3-pentanediol, 2-propyl-1,3-hexanediol, 2- Ethyl-1,3-hexanediol and the like can be used.
For example, when 2-ethyl-1,3-hexanediol is used, a flexible polyurethane resin can be obtained. Examples of the carbonic acid ester used for the transesterification include diethyl carbonate and diphenyl carbonate.
When polycarbonate diol is used, the hydrolysis resistance of the primer can be suppressed, and the deterioration of scratch resistance in a moist heat environment can be further suppressed.

<Polyetherdiol>
Examples of the polyether diol include addition reaction of alkylene oxides such as ethylene oxide and propylene oxide using a hydroxyl group-containing compound having 1 to 4 hydroxyl groups in one molecule, preferably 2 hydroxyl groups in one molecule as an initiator. And those having a weight average molecular weight (Mw) of about 200 to 5,000.
Examples of the hydroxyl group-containing compound include ethylene glycol, propanediol, butanediol, diethylene glycol, dipropylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentyl glycol, 3-methyl-1,5- Pentanediol, 1,6 hexanediol, and 1,4 cyclohexanedimethanol can be used singly or in combination of two or more. When polyether diol is used for the diol component, the effect of improving adhesion is exhibited.
The urethane made of polyether diol is preferably added to the primer layer within 50%. If it is this range, it is possible to suppress hydrolysis resistance and the stickiness of a coating film is also suppressed.

<Acrylic diol>
The acrylic diol is obtained, for example, by polymerizing an acrylic monomer (an acrylic monomer having a hydroxyl group is preferably removed) into a prepolymer by a known method, and further polymerizing an acrylic monomer having a hydroxyl group on the prepolymer. It is a prepolymer having hydroxyl groups at both ends.
Examples of the acrylic monomer include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid-n-propyl, isopropyl (meth) acrylate, and (meth) acrylic acid. Examples include (meth) acrylic acid alkyl esters such as -n-butyl and isobutyl (meth) acrylate, and these can be used alone or in combination of two or more. Also, other unsaturated bond monomers can be copolymerized as long as the intended performance is not impaired.
Examples of the acrylic monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate.
When acrylic diol is used for the diol component, the effect of improving the weather resistance is exhibited.
Examples of the acrylic diol include those having a weight average molecular weight (Mw) of about 500 to 10,000.
In addition, other diols (polyester diol and the like (excluding caprolactone-modified polyester diol)) can be added within a range that does not impair the original purpose.

(B) Diisocyanate Component The diisocyanate component is the same as the diisocyanate component described in the section “Urethane Prepolymer (PpreH)”.
(C) Production of Urethane Prepolymer (PpreC) Production of urethane prepolymer (PpreC) is basically the same as the production method described in the section “Urethane Prepolymer (PpreH)”.

(2-2) Primer layer (B) forming coating solution The primer layer (B) forming coating solution is a urethane prepolymer (Ppre) containing a urethane prepolymer (PpreH) or a urethane prepolymer (PpreC), It is obtained by adding a pigment, an isocyanate-based crosslinking agent, and, if necessary, an additive to an organic solvent.
The urethane prepolymer (Ppre) includes a urethane prepolymer (PpreH) or a urethane prepolymer (PpreC). These urethane prepolymers (PpreH) or urethane prepolymers are included in the urethane prepolymer (Ppre). It is desirable that (PpreC) is contained in an amount of 50% by mass or more. By containing 50% by mass or more of these prepolymers, the scratch resistance can be exhibited better.
In addition, in urethane type prepolymer (Ppre), urethane prepolymer and polyether obtained from polycarbonate diol and diisocyanate as an oprepolymer that can be added in addition to the urethane prepolymer (PpreH) and urethane prepolymer (PpreC). Urethane prepolymer obtained from diol and diisocyanate, urethane prepolymer obtained from polyether diol and diisocyanate), and two or more kinds of diols selected from polycarbonate diol, polyether diol, and polyether diol A urethane-based prepolymer obtained from a sulfur component and a diisocyanate,
1 type (s) or 2 or more types selected from are mentioned.

<Isocyanate-based crosslinking agent>
Examples of the isocyanate crosslinking agent include an isocyanurate type having a cyclic structure, an allophanate type having a chain structure, an adduct type, and a biuret type.
The isocyanurate-based crosslinking agent is obtained, for example, by reacting diisocyanate in the presence of an isocyanurate-forming catalyst. The allophanate-modified isocyanate is obtained, for example, by reacting a diol compound and a diisocyanate in the presence of an allophanate-forming catalyst.
The diisocyanate is preferably an aliphatic diisocyanate such as hexamethylene diisocyanate (HDI), tetramethylene diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate.
These diisocyanates can be used alone or in combination of two or more.

<Organic solvent>
Examples of the organic solvent include petroleum-based organic solvents such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; ethyl acetate, butyl acetate, 2-methoxyethyl acetate, and 2-ethoxyethyl acetate Ester organic solvents; ketone organic solvents such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, and cyclohexanone; ether organic solvents such as diethyl ether, dioxane, and tetrahydrofuran. These solvents (or dispersion media) can be used singly or in combination of two or more.
<Additive>
The purpose of the primer layer (B) forming coating solution is to improve and modify, for example, heat resistance, mechanical properties, antioxidant properties, flame retardancy, antifungal properties, electrical properties, coating suitability, etc. Thus, various plastic compounding agents and additives such as a thickener, a flame retardant, an antioxidant, and a weather resistance improver can be added. The addition amount can be arbitrarily added from a very small amount to several tens of percent depending on the purpose.

<Weather resistance improver>
As the weather resistance improver of the primer layer, an ultraviolet absorber, a light stabilizer, or an antioxidant can be used. The ultraviolet absorber may be either inorganic or organic, and as the inorganic ultraviolet absorber, titanium dioxide, cerium oxide, zinc oxide or the like having an average particle diameter of about 5 to 120 nm can be preferably used. Moreover, as an organic type ultraviolet absorber, benzotriazole type, for example, 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-tert-) is specifically mentioned. Amylphenyl) benzotriazole, 3- [3- (benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl] propionic acid ester of polyethylene glycol, and the like. Further, triazine series, specifically, 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] phenol, 1,3,5-triazine- 2,4,6 (1H, 3H, 5H) -trione, 1,3,5-tri [[3,5-bis- (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] and the like. . On the other hand, examples of the light stabilizer include hindered amines, specifically 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2′-n-butylmalonate bis (1,2,2). , 6,6-pentamethyl-4-piperidyl), bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl)- 1,2,3,4-butanetetracarboxylate and the like. As the antioxidant, it is intended to prevent photodegradation or thermal degradation of the above-mentioned polymer. For example, antioxidants such as phenols, amines, sulfurs, phosphoric acids, etc. can be used. . Depending on the purpose of use, as a UV absorber, light stabilizer, and antioxidant, a reactive UV absorber, light stabilizer, and antioxidant having a polymerizable group such as a (meth) acryloyl group in the molecule may be used. It can also be used.
The ultraviolet absorber absorbs harmful ultraviolet rays in sunlight, converts them into innocuous heat energy in the molecule, and prevents the activation of active species that initiate photodegradation in the resin. It is. Specifically, benzophenone-based, benzotriazole-based, triazine-based, salicylate-based, acrylonitrile-based, metal complex-based, ultrafine titanium oxide (particle diameter: 0.01 to 0.06 μm) or ultrafine zinc oxide ( At least one selected from the group consisting of inorganic ultraviolet absorbers such as (particle diameter: 0.01 to 0.04 μm) can be used. The light stabilizer captures radicals in the primer and / or on the primer surface and suppresses deterioration. A hindered amine system can be illustrated.

(2-3) Formation of primer layer (B) The primer layer (B) is obtained by applying the primer layer (B) forming coating solution onto the polyester resin layer (C), followed by drying and crosslinking by heating. To be formed.
As a method for applying the primer layer (B) forming coating liquid, gravure coating, bar coating, roll coating, reverse roll coating, comma coating, die coating so that the thickness after curing is 0.5 to 7 μm. , A known method such as slit coating or curtain coating, preferably gravure coating, to form an uncured resin layer. Next, the primer layer (B) is cured by heating.
If the thickness of the primer layer (B) is less than 0.5 μm, the adhesion to the protective layer is not sufficient, while if it exceeds 7 μm, the cost increases and economic disadvantages occur.
For the formation of the primer layer (B), it is desirable to employ the following method, in which the primer layer (B) and the protective layer (A) are applied on a substrate to be described later and cured sequentially. .
The primer layer (B) forming coating solution is applied onto the base material, and the ionizing radiation curable resin composition is applied after the layer is dried. Thereafter, the protective layer (A) made of the ionizing radiation curable resin composition is first formed by crosslinking and curing by irradiation with ionizing radiation, and then the primer layer (B) is crosslinked and cured by heating.
When the primer layer (B) is formed by crosslinking and curing, it is preferably cured by aging for about 7 days under weak heating at about 40 to 45 ° C. By adopting such a curing method, not only the primer layer (B) is surely cross-linked and cured, but also the isocyanate residue in the resin forming the primer layer (B) has a base such as a polyester resin layer. An effect of further improving the adhesion between the two layers by advancing the addition reaction between the hydroxyl group residues in the resin to be formed and the hydroxyl group residues in the resin forming the protective layer (A) is exhibited.

(3) Polyester resin layer (C)
A polyester-type resin layer (C) is a layer which has a function as a base material at the time of forming a protective layer (A) and a primer layer (B).
As the raw material dicarboxylic acid compound of the polyester resin that forms the polyester resin layer (C), for example, aromatic dicarboxylic acid, alicyclic dicarboxylic acid, aliphatic dicarboxylic acid, or the like can be used.
Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid and the like can be mentioned. Examples of the aliphatic dicarboxylic acid component include adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like.

Only one kind of the dicarboxylic acid compound may be used, or two or more kinds thereof may be used in combination, and further, a part of oxyacid such as hydroxyethoxybenzoic acid may be copolymerized.
The raw material diol compound of the polyester resin is not particularly limited as long as it can be condensed with the dicarboxylic acid to constitute the polyester resin. Examples of such diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentane. Diol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2′-bis ( 4′-β-hydroxyethoxyphenyl) propane and the like. As said diol compound, only 1 type may be used and 2 or more types may be used together.

As the polyester resin formed by condensing the dicarboxylic acid compound and the diol compound, it is preferable to use polyethylene terephthalate, polyethylene naphthalate, polyethylene-2,6-naphthalenedicarboxylate, particularly polyethylene terephthalate. It is preferable to use it.
The polyethylene terephthalate resin is suitable for use as a base material because it is excellent in toughness, rigidity, heat resistance, and the like.
The thickness of the polyester resin layer (C) is preferably about 40 to 70 μm. When the thickness of the polyester resin layer (C) is 40 μm or more, the function as a substrate can be effectively exhibited.

(4) Base material (D)
Although the base material (D) which comprises the back surface protection sheet for solar cell modules of this invention has a role as a support body in this back surface protection sheet, intensity | strength, rigidity, a water vapor | steam barrier is further used according to the intended purpose. Functions such as heat resistance, weather resistance, heat resistance, hydrolysis resistance, light reflectivity, and designability may be required.
In order for the base material (D) to function as a support or the like, at least the thermoplastic resin layer is formed of one layer or two or more layers. Further, when a water vapor barrier property is required, a water vapor barrier layer in which a metal or metal oxide vapor deposition film is provided on one side of the thermoplastic resin of one layer or two or more layers, or an aluminum foil A water vapor barrier layer can be formed.

(4-1) Thermoplastic Resin Composition Forming Substrate (D) (A) Thermoplastic Resin As a resin excellent in strength and the like that can be used for the substrate (D), for example, mechanical and chemical Or, it has excellent physical strength, weather resistance, heat resistance, light resistance, chemical resistance, moisture resistance, design, etc. It has the advantages of being limited, durable, excellent protection functionality, light weight, excellent processability, easy handling, etc. One type or two or more types can be used.
Specifically, examples of the resin include polyolefin resins such as polyethylene resins, polypropylene resins, and cyclic polyolefin resins, polystyrene resins, acrylonitrile-styrene copolymers (AS resins), and acrylonitrile-butadiene-styrene. Copolymer (ABS resin), polyvinyl chloride resin, fluorine resin, poly (meth) acrylic resin, polycarbonate resin, polyester resin such as polyethylene terephthalate or polyethylene naphthalate, polyamide resin, polyimide resin, Polyamideimide resin, polyaryl phthalate resin, silicon resin, polysulfone resin, polyphenylene sulfide resin, polyethersulfone resin, polyurethane resin, acetal resin, cellulose resin , It can be used various resins other like.

In addition, when using the said polypropylene resin, as a film or a sheet | seat, both the extending | stretching and non-stretching can be used, and when hydrolysis resistance is requested | required, as a polyester resin, It is also possible to use a hydrolysis-resistant polyester resin having an oligomer content of 0.1 to 0.6 mass% and a carboxyl end group content of about 3 to 15 equivalents / ton.
In the present invention, among the above resins, high-density polyethylene resin, polypropylene resin, cyclic polyolefin resin, or polyester resin is preferable.
In order to impart various functions to the substrate (D), the following additives can be blended in any one layer or two or more layers forming the substrate (D).

(B) Additive (b-1) White pigment As a white pigment added to any layer forming the substrate (D) in order to impart a light reflecting function to the substrate (D), the above-mentioned white layer It can be uniformly dispersed in a transparent resin, and when the back protective sheet for solar cell module of the present invention is used for a solar cell module, it efficiently reflects the light transmitted through the solar cell element included in the solar cell module. It is not particularly limited as long as it can be used.
Specifically, as such a white pigment, only one kind of metal oxides such as titanium oxide, silicon oxide, zinc oxide and aluminum oxide; inorganic compounds such as calcium carbonate and barium sulfate is used alone. Two or more types may be used in combination. In the present invention, titanium oxide, silicon oxide, zinc oxide, and calcium carbonate can be preferably used.
The particle size of the white pigment used in the present invention is not particularly limited as long as it can reflect light, but the average particle size is preferably in the range of 0.1 to 10 μm. A range of 1 to 3 μm is more preferable. Although the thickness of a white layer will not be specifically limited if it can show sufficient intensity | strength etc. when it is set as a solar cell module, 35-200 micrometers is preferable and 80-180 micrometers is more preferable.

(B-2) Black pigment A black pigment such as carbon black can be added to any layer forming the base material (D) from the viewpoint of design and the like.
(B-3) Other additives In addition, one or more of the above-mentioned various resins are used, and when forming the film, for example, film processability, heat resistance, weather resistance, mechanical properties, Various plastic compounding agents and additives are added for the purpose of improving and modifying dimensional stability, antioxidant properties, slipperiness, mold release properties, flame retardancy, antifungal properties, electrical properties, etc. be able to. The addition amount can be arbitrarily added from a very small amount to several tens of percent depending on the purpose.

(4-2) Production of Film or Sheet Forming Substrate (D) In the present invention, each film or sheet constituting the substrate (D) is, for example, one of the above-mentioned various resins. A method of forming the above-mentioned various resins independently using a film forming method such as an extrusion method, a cast molding method, a T-die method, a cutting method, an inflation method, etc. Alternatively, a method of forming a multi-layer coextrusion film using two or more kinds of resins, and a method of forming a film by mixing two or more kinds of resins before forming the film, etc. Thus, various resin films or sheets can be produced. Further, for example, various resin films or sheets formed by stretching in a uniaxial or biaxial direction using a tenter system or a tubular system can be used. In the present invention, among the resin layers constituting the substrate (D), the thickness of the layer required to function as a support is preferably 80 to 150 μm,
0-120 micrometers is more preferable.

(4-3) Water vapor barrier layer When the water vapor barrier property is required for the substrate (D), a metal or metal oxide deposited film or aluminum is formed on the surface of the film or sheet constituting the substrate (D). A foil can be laminated.
(I) Water vapor barrier layer provided with a vapor deposition film of metal or metal oxide (I-1) Base material for forming the water vapor barrier layer As the base material used when forming the water vapor barrier layer, the above-mentioned base material ( Although the thermoplastic resin which comprises D) can be used, it is desirable to use the thermoplastic resin which has a certain amount of rigidity, and as such a thermoplastic resin, a polyester-type resin can be used conveniently, for example.

(A-2) Formation of metal or metal oxide vapor deposition film on substrate The metal or metal oxide vapor deposition film formed on the substrate as the water vapor barrier layer will be described. For example, a physical vapor deposition method (PVD method), a chemical vapor deposition method (CVD method), or a combination of both, is used to form a single layer of a metal or metal oxide vapor deposition film. A multilayer film or a composite film composed of two or more layers can be manufactured and formed. Examples of the vapor deposition film of metal or metal oxide by such physical vapor deposition include metal or metal oxidation using physical vapor deposition such as vacuum deposition, sputtering, ion plating, and ion cluster beam. A vapor deposition film of an object can be formed. Specifically, a metal or metal oxide is used as a raw material, and this is heated, vaporized and vapor-deposited on a substrate film, or a metal or metal oxide is used as a raw material, if necessary Metal or metal oxide using an oxidation reaction deposition method in which oxygen gas is introduced to oxidize and deposit on a base film, and a plasma-assisted oxidation reaction deposition method in which the oxidation reaction is supported by plasma. The deposited film can be formed. As a method for heating the vapor deposition material, for example, a resistance heating method, a high frequency induction heating method, an electron beam heating method, or the like can be used.

As a composite film composed of two or more deposited films of different kinds of metals or metal oxides described above, first, on a base film, a chemical vapor deposition method is used. A metal oxide vapor deposition film capable of preventing the occurrence of cracks is provided, and then a metal oxide vapor deposition film formed by physical vapor deposition is provided on the metal oxide vapor deposition film, thereby comprising two or more layers. It is desirable to form a metal oxide vapor deposition film composed of a composite film. On the other hand, a metal oxide vapor deposition film is first provided on the base film by physical vapor deposition, and then dense, flexible and relatively cracked by chemical vapor deposition. It is also possible to provide a metal oxide vapor-deposited film comprising a composite film comprising two or more layers by providing a metal oxide vapor-deposited film capable of preventing the occurrence of the above.
(B) Aluminum foil When the aluminum foil is laminated on the substrate in the water vapor barrier layer, the thickness is preferably about 20 to 40 μm. If the thickness is less than the above range, inconveniences such as generation of wrinkles at the time of lamination may occur, and the barrier function may not be sufficiently exhibited. On the other hand, if the thickness exceeds the above range, the cost increases and an economic problem occurs.

(4-4) Adhesive layer The dry laminate lamination method is adopted for the lamination between the polyester resin layer (C) and the substrate (D) and between the substrates (D) formed from a plurality of thermoplastic resin layers. In this case, as the adhesive constituting the adhesive layer for laminating, for example, polyvinyl acetate adhesive, homopolymer such as ethyl acrylate, butyl, 2-ethylhexyl ester, or these and methyl methacrylate, From polyacrylic acid ester adhesives, copolymers of acrylonitrile, copolymers with styrene, etc., cyanoacrylate adhesives, copolymers of ethylene and monomers such as vinyl acetate, ethyl acrylate, acrylic acid, methacrylic acid, etc. Ethylene copolymer adhesive, cellulose adhesive, polyester adhesive, polyamide adhesive, polyimide adhesive, Amino resin adhesives made of urea resin or melamine resin, phenol resin adhesives, epoxy adhesives, polyurethane adhesives, reactive (meth) acrylic adhesives, chloroprene rubber, nitrile rubber, styrene-butadiene rubber It is possible to use an adhesive such as a rubber adhesive, a silicon adhesive, an alkali metal silicate, a low-melting glass, or the like.

The composition system of the above-mentioned adhesive may be any composition form such as an aqueous type, a solution type, an emulsion type, and a dispersion type, and the property is any of film / sheet form, powder form, solid form, etc. Further, the bonding mechanism may be any of a chemical reaction type, a solvent volatilization type, a heat melting type, and a hot pressure type.
The adhesive can be applied, for example, by a coating method such as a roll coating method, a gravure roll coating method, a kiss coating method, or the like, or a printing method, and the coating amount is 0.1 to 10 g / m. ^A degree of ² (dry state) is desirable. In the present invention, when a resin film or sheet is used and lamination is performed by dry lamination, the surface is preliminarily subjected to surface modification pretreatment such as corona discharge treatment, ozone treatment, or plasma discharge treatment. Can be applied arbitrarily.
In the adhesive, a light stabilizer, an ultraviolet absorber and / or an antioxidant can be added in order to prevent ultraviolet degradation or the like.

(5) Layer structure of back surface protection sheet for solar cell module Basically, the back surface protection sheet for solar cell module of the present invention includes a protective layer (A), a primer layer (B), a polyester resin layer (C), and In the present invention, the layer structure of the base material (D) is a back surface protection sheet for solar cell modules, which is composed of a thermoplastic resin and one or more base materials (D). Depending on the performance required, various combinations of layers can be selected. For example, when water vapor barrier properties are required, a water vapor barrier layer can be provided in the substrate (D) layer.
The layer structure of the substrate (D), protective layer (A) / primer layer (B) / polyester resin layer (C) / substrate (D), the substrate (D) is composed of, for example, 1 to 4 layers. It can be a single layer or a multilayer.
The specific example of a structure which forms the said base material (D) is illustrated in FIG. In addition, the back surface protection sheet for solar cell modules of this invention is not limited to what was illustrated to FIG.
Specific examples of the configuration for forming the substrate (D) are illustrated in FIGS. 1 and 2, and further specific examples of the configuration for forming the substrate (D) are illustrated in [1] to [8] below. To do.
In addition, PET described below represents polyester-based resin, HDPE represents high-density polyethylene, CPP represents unstretched polypropylene-based resin, and the base material in the vapor deposition layer such as metal is hydrolysis-resistant PET.
[1] Transparent PET / White HDPE
[2] Water vapor barrier layer (metal deposition layer) / transparent PET / white HDPE
[3] Water vapor barrier layer (evaporation layer such as metal) / white CPP / transparent CPP
[4] Water vapor barrier layer (metal deposition layer) / white CPP / white HDPE
[5] Water vapor barrier layer (metal deposition layer) / transparent PET / transparent CPP
[6] Water vapor barrier layer ((evaporation layer such as metal) / black PET / transparent CPP
[7] Water vapor barrier layer (aluminum foil) / transparent PET / white HDPE
[8] Water vapor barrier layer (aluminum foil) / black PET / transparent CPP

In the back surface protection sheet for solar cell modules of the present invention, the protective layer (A) is provided on the outermost layer on the back surface side of the back surface protection sheet in order to obtain a back surface protection sheet excellent in scratch resistance, heat resistance, and weather resistance. .
Since the primer layer (B) can improve the adhesion between the protective layer (A) and the polyester resin layer (C), etc., it is a laminate even in the case where scratches have occurred up to the vicinity of the polyester resin layer (C). Occurrence of peeling or detachment in a part of the body can be suppressed.
When the water vapor barrier layer is provided on the thermoplastic resin layer constituting the base material (D), water vapor permeates the base material (D) and the thermoplastic resin layer constituting the base material (D) is subject to hydrolysis. The function to suppress can be exhibited. The water vapor barrier layer is preferably formed by vapor-depositing a metal or metal oxide on a base material made of a thermoplastic resin or laminating an aluminum foil. These metals and the like are formed of the thermoplastic resin layer. More preferably, it is laminated on the protective layer (A) side. By laminating a metal or the like on the protective layer (A) side of the substrate, the permeation of water vapor to the thermoplastic resin layer is suppressed, and the thermoplastic resin layer is prevented from being degraded by hydrolysis. be able to.
The polyester-based resin layer or the polyolefin layer having high rigidity exhibits a function as a support in the back protective sheet for solar cell module in the base material (D).
A polyolefin layer such as a high-density polyethylene layer and an unstretched polypropylene-based layer provided on the cell side of the back surface protective sheet for solar cell module of the present invention is between the back surface protective sheet and the filler constituting the base material (D). Has a function of improving adhesion. Further, the white particles can be blended in these outermost layers to impart a sunlight reflecting function.

(6) Manufacturing method of back surface protection sheet for solar cell module If the thickness of the back surface protection sheet for solar cell modules of this invention can show sufficient intensity | strength etc., when a solar cell module is formed, it will be. Although not particularly limited, it is preferably in the range of 150 to 450 μm, more preferably in the range of 200 to 350 μm.
As a manufacturing method of the back surface protection sheet for solar cell modules of this invention, after forming a primer layer (B) and a protective layer (A) on a polyester-type resin layer (C), respectively, it forms by hardening, and a base material There is no particular limitation as long as each of the layers constituting (D) can be laminated with good adhesion.

[2] Solar cell module (second embodiment)
The “solar cell module” according to the second aspect of the present invention includes a front transparent substrate <1>, a surface filler layer <2>, a solar cell element <3>, a back filler layer <4>, and a solar cell. The module back surface protection sheet <5> is a solar cell module arranged in this order,
The back surface protective sheet <5> is a base material (D) formed from at least a protective layer (A), a primer layer (B), a polyester resin layer (C), and a thermoplastic resin from the outside of the back surface of the solar cell module. ) Are laminated in this order, and the protective layer (A) is a layer formed by crosslinking and curing the ionizing radiation curable resin composition by irradiation with ionizing radiation, and the primer layer (B) is a urethane-based prepolymer made of isocyanate. It is a layer made of a polyurethane resin (P) formed by crosslinking and curing with a system crosslinking agent.

A solar cell module according to a second aspect of the present invention will be described with reference to the drawings. As illustrated in FIG. 3, the solar cell module 21 of the present invention is formed on at least a back surface protection sheet <5> 26 that is a back surface protection sheet for a solar cell module, and the back surface protection sheet <5>. Back surface filler layer <4> 25, solar cell element <3> 24 formed on back surface filler layer <4>, and surface filler layer <3> formed on solar cell element <3>2> 23 and a transparent front substrate <1> 22 formed on the surface filler layer <2>. In addition, the back surface protection sheet <5> for solar cell modules in FIG. 9 is the back surface protection sheet for solar cell modules which concerns on the 1st aspect of this invention illustrated in FIGS.
According to this invention, a back surface filler layer <4> can be laminated | stacked stably by using the back surface protection sheet <5> for solar cell modules. Moreover, it is excellent in a weather resistance, a flaw resistance, and heat resistance by providing the protective layer (A) and primer layer (B) of a 1st aspect in a back surface protection sheet <5>.
Hereinafter, each structure of the solar cell module of this invention is demonstrated.

(1) Back surface protection sheet for solar cell module <5>
The back surface protective sheet <5> used in the solar cell module of the present invention is the above-described back surface protective sheet for solar cell module according to the first aspect of the present invention, and the layer configuration and the like thereof are as described above. Is omitted.
(2) Back surface filler layer <4>
The back surface filler layer <4> used in the present invention has adhesiveness with the back surface protection sheet <5>, has thermoplasticity for maintaining the smoothness of the back surface of the solar cell element <3>, There is no particular limitation as long as it has scratch resistance and shock absorption in terms of protection of the solar cell and has weather resistance such as heat resistance, light resistance and water resistance.
Examples of the back surface filler layer <4> include fluorine resin, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acrylic acid or methacrylic acid copolymer, polyethylene resin, polypropylene resin, polyethylene, or polypropylene. Polyolefin resin such as acrylic acid, itaconic acid, maleic acid, fumaric acid, etc. 1 type, or 2 or more types of mixtures, such as a resin and others, can be used. In addition, in order to improve the weather resistance such as heat resistance, light resistance, and water resistance, the resin constituting the back surface filler layer <4> is, for example, a crosslinking agent, Additives such as antioxidants, light stabilizers, ultraviolet absorbers, photo-antioxidants, etc. can be optionally added and mixed. In addition, 200-1000 micrometers is preferable and, as for the thickness of a back surface filler layer <4>, 350-600 micrometers is more preferable.
Furthermore, the back surface filler layer <4> may have a configuration in which a plurality of sheets are laminated. Examples of the configuration in which such a plurality of sheets are laminated include a configuration in which a gas barrier sheet having an inorganic vapor deposition film is laminated, and a configuration in which tough sheets are laminated.

(3) Solar cell element <3>
As the solar cell element <3> used in the present invention, a general solar cell element can be used. Specifically, crystalline silicon solar electronic elements such as single crystal silicon type solar cell elements, polycrystalline silicon type solar cell elements, amorphous silicon solar cell elements such as single junction type or tandem structure type, gallium arsenide (GaAs), III-V compound semiconductor solar electronic devices such as indium phosphorus (InP), II-VI compound semiconductor solar electronic devices such as cadmium telluride (CdTe) and copper indium selenide (CuInSe ₂ ), organic solar cell devices, etc. are used. be able to.
As the solar cell element <3> used in the present invention, a thin film polycrystalline silicon solar cell element, a thin film microcrystalline silicon solar cell element, a hybrid element of a thin film crystalline silicon solar cell element and an amorphous silicon solar cell element, etc. Can also be used.

(4) Transparent front substrate <1>
The transparent front substrate <1> used in the present invention is not particularly limited as long as it is a substrate having sunlight permeability. For example, a glass plate, a fluororesin, a polyamide resin (various nylons), a polyester Various resin films such as resin, polyethylene resin, polypropylene resin, cyclic polyolefin resin, polystyrene resin, (meth) acrylic resin, polycarbonate resin, acetal resin, and cellulose resin can be used.
Further, the thickness of the transparent front substrate <1> is not particularly limited as long as it is within a range in which a desired strength can be realized, but usually 12 to 7000 μm is preferable, and 25 to 4000 μm is more preferable.

(5) Surface filler layer <2>
As the surface filler layer <2> used in the present invention, it has transparency to sunlight, is thermoplastic for maintaining the smoothness of the back surface of the solar cell element <3>, and in terms of protection of the solar cell. There is no particular limitation as long as it has scratch resistance and shock absorption and exhibits adhesion to the transparent front substrate <1> and the solar cell element <3>. Specific examples of the material constituting the surface filler layer <2> include, for example, a fluorine-based resin, an ethylene-vinyl acetate copolymer, an ionomer resin, an ethylene-acrylic acid or methacrylic acid copolymer, and a polyethylene-based material. Resin, Polypropylene resin, Polyolefin resin such as polyethylene or polypropylene modified with unsaturated carboxylic acid such as acrylic acid, itaconic acid, maleic acid, fumaric acid, acid-modified polyorene fin-based resin, polyvinyl butyral resin, silicon-based resin , Epoxy resins, (meth) acrylic resins, and other resins can be used.
In the present invention, in the resin constituting the surface filler layer <2>, in order to improve weather resistance such as heat resistance, light resistance, water resistance, etc. In addition, additives such as a crosslinking agent, a thermal antioxidant, a light stabilizer, an ultraviolet absorber, a photoantioxidant, and the like can be arbitrarily added and mixed. In the present invention, as the surface filler layer <2> on the sunlight incident side, in consideration of weather resistance such as light resistance, heat resistance, water resistance, etc., fluorine resin, silicon resin, ethylene-vinyl acetate System resin is a desirable material.
In addition, the thickness of the filler layer is preferably 200 to 1000 μm, and more preferably 350 to 600 μm.

  Furthermore, the surface filler layer <2> used in the present invention preferably has a total light transmittance of 70 to 100%, more preferably 80 to 100%, and still more preferably 90 to 100%. . It can suppress that the power generation efficiency of a solar cell module is impaired by the said total light transmittance being in the said range. In addition, the said total light transmittance can be measured by a normal method, for example, can be measured by Nippon Denshoku Industries Co., Ltd. make and model | form: HAZE meter NDH2000.

(6) Other Layers In the solar cell module of the present invention, other layers can be arbitrarily added and laminated for the purpose of absorbing sunlight, reinforcing, etc. . Examples of such other layers include low density polyethylene resin, medium density polyethylene resin, high density polyethylene resin, linear low density polyethylene resin, polypropylene resin, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer. Polymer, ionomer resin, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid or methacrylic acid copolymer, methyl pentene polymer, polybutene resin, polyvinyl chloride resin, polyvinyl acetate resin, polyvinylidene chloride resin , Vinyl chloride-vinylidene chloride copolymer, poly (meth) acrylic resin, polyacrylonitrile resin, polystyrene resin, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS) Resin), polyester Resins, polyamide resins, polycarbonate resins, polyvinyl alcohol resins, saponified ethylene-vinyl acetate copolymers, fluorine resins, diene resins, polyacetal resins, polyurethane resins, nitrocellulose, etc. Any resin film or sheet can be selected and used.

(7) Method for Manufacturing Solar Cell Module In the present invention, the transparent front substrate <1>, the surface filler layer <2>, the solar cell element <3>, the back surface filler layer <4>, and the back surface protective sheet <5> After laminating in order, the method of thermocompression bonding these is not particularly limited as long as the above-described components can be in close contact with each other, and generally known methods can be used. As such a method, for example, a transparent front substrate <1>, a surface filler layer <2>, a solar cell element <3>, a back surface filler layer <4>, and a back surface protection sheet <5> are laminated in this order. Then, the lamination method etc. which carry out vacuum suction and thermocompression-bonding these as integral can be illustrated. The laminating temperature when using the above lamination method is usually preferably 90 to 230 ° C, more preferably 110 to 190 ° C.
The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.
[1] Raw materials used for production of solar cell back surface protective sheet (1) Primer layer coating liquid (1-1) Monomer component of urethane prepolymer (a) Urethane prepolymer (a-1) Caprolactone modified polyester Urethane prepolymer (PCL-U)
A urethane prepolymer (weight average molecular weight (Mw) of about 10,000 to 50,000) obtained by polymerizing caprolactone-modified polyester diol and isophorone diisocyanate was used.
(I-2) Other urethane prepolymer Urethane prepolymer obtained by polymerizing polyether diol and isophorone diisocyanate [(PED-U) (weight average molecular weight (Mw) of about 10,000 to 50,000)] is used. It was.
(B) Urethane prepolymer used in the comparative example

[Comparative Example 1]
Urethane prepolymer (PES-U) having a polyester diol skeleton (not including polycaprolactone-modified polyester diol)
A urethane prepolymer obtained by reacting adipic acid, phthalic acid, polyester diol obtained from diol, and diisophorone isocyanate was used.
[Comparative Example 2]
Acrylic urethane prepolymer (PES-AU) having a polyester diol skeleton (not including polycaprolactone-modified polyester diol)
Adipic acid, phthalic acid, polyester diol obtained from diol, urethane obtained by polymerizing 2-hydroxymethacrylate at both ends of methyl methacrylate prepolymer and reacted with acrylic prepolymer having hydroxyl groups at both ends and diisophorone isocyanate A prepolymer was used. The acrylic diol is 30 parts with respect to 100 parts of the polyester diol.

[Comparative Example 3]
Urethane prepolymer having a polycarbonate diol skeleton (PCD-U)
A urethane prepolymer obtained by polymerizing polycarbonate diol obtained from polycarbonate diol derived from 1,6 hexanediol and diisophorone isocyanate was used.
[Comparative Example 4]
Acrylic urethane prepolymer having polycarbonate diol skeleton (PCD-AU)
Polycarbonate diol obtained from polycarbonate diol derived from 1,6 hexanediol, acrylic prepolymer and diisophorone having hydroxyl groups at both ends, obtained by polymerizing 2-hydroxymethacrylate at both ends of methyl methacrylate prepolymer An acrylic urethane prepolymer reacted with isocyanate was used.

(C) Isocyanate-based crosslinking agent An HDI-modified isocyanurate-based crosslinking agent was used.

(D) Primer layer coating solution The urethane prepolymer (composition and mixing ratio is shown in Tables 1 and 2) was added to MEK to prepare a MEK solution containing these solid contents.
A primer layer coating solution was prepared by mixing 17 parts by weight of a curing agent (HDI-modified isocyanurate) with 100 parts by weight of the resin content of the MEK solution.

(2) Other resin layers (A) Coating liquid for protective layer Caprolactone-modified urethane triacrylate was used as the ionizing radiation curable resin composition.
(B) A hydrolysis-resistant biaxially stretched polyester film (trade name: Lumirror X10S, manufactured by Toray Industries, Inc.) having a thickness of 50 μm was used for the hydrolysis-resistant biaxially stretched polyester layer (HR-PET).
(C) Teijin-DuPont Films Co., Ltd., Melnex S, 100 μm was used as the transparent biaxially stretched polyester film (TBO-PET) constituting the back surface protection sheet for solar cell modules.
Lumirror X30 manufactured by Toray Industries, Inc. was used for the black colored polyester film (B-PET).
The white high-density polyethylene layer (HDPE layer) has a white high-density polyethylene film having a thickness of 120 μm (as white pigment, 8% by mass of titanium oxide having an average particle size of 5 μm and 3% of titanium oxide having an average particle size of 0.3 μm). (Mixed so as to be mass%) was used.
The white unstretched polypropylene layer (W-PP layer) has a white unstretched polypropylene film having a thickness of 80 μm (as a white pigment, 8% by mass of titanium oxide having an average particle size of 5 μm and titanium oxide having an average particle size of 0.3 μm). Used in such a manner that it is 3% by mass).
A transparent unstretched polypropylene film having a thickness of 150 μm was used for the transparent unstretched PP polypropylene layer (T-PP layer).
To the water vapor barrier layer (metal vapor deposition film) (vapor deposition PET), (Mitsubishi Resin Co., Ltd., trade name: Tech Barrier LX) was bonded with the vapor deposition surface facing away from the protective layer of the laminate.
Nippon Foil Co., Ltd. Nippaku # 30 was used for the aluminum foil.

[2] Evaluation method (1) Initial scratch resistance It was carried out according to JIS K 5600 5-5 (Clemens needle scratch test).
The laminate sample was fixed on the test stand, and the test was carried out at a speed of 30 mm / min and a stroke length of 15 mm.
If the test is carried out from a light load, and the scratches do not enter the primer layer, the load is increased and the test is performed again, and the test is stopped at a load where the primer layer is damaged during the stroke length of 15 mm. The load before the primer layer was damaged was recorded.
The evaluation criteria are as follows.
○: Load of 120 g or more, x: Load of less than 120 g Load of 120 g or more was considered acceptable.
(2) Adhesion test A cellophane tape (manufactured by Nichiban Co., Ltd., trade name: cellotape (registered trademark) CT405AP-24) is applied to the protective layer and adhered to the protective layer, and then peeled off at an angle of 45 ° C. After performing the operation twice, it was confirmed whether or not the protective layer was detached.
The evaluation criteria were as follows, and only in the case of ○, it was considered acceptable.
○: no desorption, Δ: partial desorption, x: total desorption

(3) Moisture and heat resistance after dump heat test (DH2000h) Hydrolysis resistance after a dump heat test (stored at 85 ° C. and 85% relative humidity for 2000 hours) was evaluated.
On the stretched polypropylene film (OPP), a coating film was prepared with an applicator so that the thickness of the coating solution for the primer layer after curing was 15 μm, and dried and cured at 42 ° C. for 7 days after coating.
The coating film was peeled off from OPP, and only the coating film was stored at 85 ° C. and 85 RH% for 2000 hours, and the hydrolysis resistance was visually evaluated.
○: It can be confirmed that the film is maintained.
X: Cracks were generated as a whole and could not be maintained as a film, or hydrolysis degradation progressed and dissolved and the film could not be maintained.
○ was accepted.
[Example 1]
(1) Preparation of back surface protection sheet Corona treatment was performed on one surface of the polyester film. The primer layer coating solution having the composition shown in Table 1 was applied to the corona-treated surface so as to have a thickness of 4 μm after drying.
After the protective layer coating solution was dried, the protective layer coating solution was applied so that the thickness after curing was 5 μm.
<Formation of protective layer>
A protective layer was formed under the following conditions.
Using caprolactone-modified urethane triacrylate, the viscosity of the resin was adjusted with ethyl acetate to prepare a coating solution, and the thickness after curing was adjusted to 5 μm. The curing conditions are as follows.
Using Iwasaki Electric Co., Ltd., ionizing radiation irradiation (model: electro curtain EC250 / 150 / 180L), curing is performed under irradiation conditions: 125 kV-50 kGy, 10 m / min in a nitrogen atmosphere with an oxygen concentration of 100 ppm or less, A protective layer was formed. After the formation of the protective layer, a primer layer was formed by curing at 42 ° C. for 7 days.
In addition, after preparing a coating solution for protective layer in which the viscosity of caprolactone-modified urethane triacrylate was adjusted with ethyl acetate on a glass plate and coating the cured protective layer to a thickness of 10 μm, the above irradiation conditions were satisfied. The universal hardness of the protective layer (A) cross-linked and cured was 39.3 N / mm ² .
Next, the back surface protection sheet was produced using the laminated body which formed the primer layer and the protective layer on the polyester film.
On the opposite side of the protective layer, apply 5μm of 2-component urethane adhesive, then paste Melinex S 100μm (Teijin / DuPont Film), and then apply 5μm of 2-component urethane urethane adhesive. Then, 120 μm of white HDPE was laminated. This was cured for 7 days under heating at 40 ° C. to obtain a back sheet for a solar cell module.
(2) Evaluation and evaluation results Initial adhesion, initial scratch resistance, and hydrolysis resistance were evaluated. The results are shown in Table 1.

[Example 2]
A back protective sheet was prepared in the same manner as described in Example 1 except that the diol composition of the primer layer coating solution shown in Table 1 was used.
About the obtained back surface protection sheet, initial adhesiveness and initial scratch resistance were evaluated. The results are shown in Table 1.
[Examples 3 to 10]
A back protective sheet was produced in the same manner as described in Example 1 except that the substrate (D) shown in Table 2 was used. About the obtained back surface protection sheet, initial adhesiveness, initial scratch resistance, and hydrolysis resistance were evaluated. The results are shown in Table 2.
[Example 11]
Using the back surface protective sheet prepared in Example 4, the protective sheet / back surface filler (ethylene vinyl acetate copolymer: EVA 400 μm) / solar cell element / surface filler layer (EVA 400 μm) / glass (3. 5 mm), and vacuum lamination was performed at 150 ° C. and 100 kPa at a holding time of 7 minutes, followed by curing by heating at 150 ° C. for 30 minutes to produce a solar cell module.
In addition, the solar cell element used the polycrystalline cell by Neo solar.

[Comparative Example 1-4]
(1) Production of Back Protective Sheet A back protective sheet was produced in the same manner as described in Example 1 except that the urethane prepolymer shown in Table 1 used for the primer layer coating solution was used.
(2) Evaluation and evaluation result About the obtained back surface protection sheet, initial adhesiveness, initial scratch resistance, and hydrolysis resistance were evaluated. The results are shown in Table 1.

[Summary of evaluation]
The backside protective sheet obtained in Example 1 has good initial adhesion and uses caprolactone-modified polyurethane, so that it has good scratch resistance, good wet heat resistance, and good resistance to Clemens test scratch resistance of 120 g or more. Showed sex.
The back surface protective sheet obtained in Example 2 has good initial adhesion and uses caprolactone-modified polyurethane and polyether urethane, so that the scratch resistance is better, the moisture and heat resistance is better, and the Clemens test scratch resistance is better. Good scratch resistance of 120 g or more was exhibited.
The back surface protection sheets obtained in Examples 3 to 10 showed the same results as in Examples 1 and 2.
Since the back surface protection sheets obtained in Comparative Examples 1 and 2 contained polyester diol, the scratch resistance was good, but the hydrolysis reaction proceeded in a moist heat environment, and the presence of the film could be confirmed visually. There wasn't.
In Comparative Examples 3 and 4, since general urethane was used, the scratch resistance was below the standard.

DESCRIPTION OF SYMBOLS 1 Back surface protection sheet for solar cell modules 11 Protective layer (A)
12 Primer layer (B)
14 Polyester resin layer (C)
16 Water vapor barrier layer 17 Adhesive layer 18 Base polyester layer 19 Polyolefin layer 21 Solar cell module 22 Transparent front substrate <1>
23 Surface filler layer <2>
24 Solar cell element <3>
25 Back surface filler layer <4>
26 Back side protection sheet <5>

Claims (6)

From the outside of the back surface of the solar cell module, at least a protective layer (A), a primer layer (B), a polyester resin layer (C), and a base material (D) formed from a thermoplastic resin are laminated in this order, The surface protective layer (A) is a layer formed by crosslinking and curing the ionizing radiation curable resin composition by ionizing radiation irradiation,
The primer layer (B) is a urethane prepolymer (PpreH) obtained from caprolactone-modified polyester diol and diisocyanate,
Alternatively, a urethane prepolymer (OL) obtained from diisocyanate and a diol component (OL) containing at least one selected from caprolactone-modified polyester diol, polycarbonate diol, acrylic diol, and polyether diol. PpreC),
A back protective sheet for a solar cell module, which is a layer made of a polyurethane resin (P) formed by crosslinking and curing a urethane prepolymer (Ppre) containing an isocyanate based crosslinking agent.   The back protective sheet for a solar cell module according to claim 1, wherein the urethane prepolymer (Ppre) contains 50% by mass or more of the urethane prepolymer (PpreH) or (PpreC). .   The back protective sheet for a solar cell module according to claim 1 or 2, wherein the diisocyanate used in obtaining the urethane prepolymer (PpreH) or (PpreC) is isophorone diisocyanate.   The thickness of the said primer layer (B) is 0.5-7 micrometers, The back surface protection sheet for solar cell modules of any one of Claim 1 thru | or 3 characterized by the above-mentioned. The back surface protection sheet for solar cell modules of any one of Claims 1 thru | or 4 whose universal hardness of the surface of the said protective layer (A) is 50 N / mm < ² > or less. A solar cell module in which a front transparent substrate <1>, a surface filler layer <2>, a solar cell element <3>, a back surface filler layer <4>, and a back surface protection sheet <5> are arranged in this order,
The back surface protective sheet <5> is a base material (D) formed from at least a protective layer (A), a primer layer (B), a polyester resin layer (C), and a thermoplastic resin from the outside of the back surface of the solar cell module. ) Are stacked in this order,
The protective layer (A) is a layer formed by crosslinking and curing the ionizing radiation curable resin composition by ionizing radiation irradiation,
A urethane prepolymer (PpreH) in which the primer layer (B) is obtained from caprolactone-modified polyester polyol and diisocyanate,
Alternatively, a urethane prepolymer (OL) obtained from diisocyanate and a diol component (OL) containing at least one selected from caprolactone-modified polyester diol, polycarbonate diol, acrylic diol, and polyether diol. PpreC),
A solar cell module comprising a polyurethane resin (P) formed by crosslinking and curing a urethane-based prepolymer (Ppre) containing an isocyanate-based crosslinking agent.

Images