Flexible laminate

Abstract

The purpose of the present invention is to provide a flexible laminate having high water vapor barrier properties.　Disclosed is a flexible laminate including an adhesive resin layer and a barrier layer, wherein the barrier layer is provided on both surfaces of the adhesive resin layer, the saturated water absorption rate of the adhesive resin layer at 20°C and 60% RH measured in accordance with JIS K 7251: 2002 is 0.3% or more, and the water vapor permeability of the adhesive resin layer at 40°C and 90% RH at a thickness of 500 μm as measured in accordance with JIS Z 0208: 1976 is 15 g / m2∙24h or less.

Description

flexible laminate

[0001] This patent application claims priority under the Paris Convention to Japanese Patent Application No. 2023-198318 (filing date: November 22, 2023), the entire contents of which are incorporated herein by reference. The present invention relates to a flexible laminate and a solar cell module including the flexible laminate.

[0002] Electronic devices such as solar cells and electronic devices equipped with display devices require a light-transmitting protective member that protects their surfaces by preventing the intrusion of moisture, etc. Such protective members may be, for example, thick glass plates, barrier films, etc. Known examples of such barrier films include films having an inorganic layer and an organic layer (Patent Documents 1 and 2).

[0003] JP-T-2015-531703 A JP-A-2007-253588

[0004] In recent years, the application of flexible solar cells has been expected due to their light weight and ease of installation and portability. For such flexible solar cells, a barrier material (flexible laminate) that can suppress moisture penetration to a higher level than conventionally known barrier films is required.

[0005] Therefore, an object of the present invention is to provide a flexible laminate having high water vapor barrier properties.

[0006] The present inventors have conducted extensive research to solve the above problems, and as a result have found that the above problems can be solved, leading to the completion of the present invention. That is, the present invention includes the following preferred embodiments.

[0007] [1] A flexible laminate including an adhesive resin layer and a barrier layer, wherein the adhesive resin layer has a barrier layer on both sides thereof, the adhesive resin layer has a saturated water absorption of 0.3% or more at 20°C and 60% RH as measured in accordance with JIS K 7251:2002, and the adhesive resin layer has a water vapor transmission rate of 15 g / m or more at 40°C and 90% RH at a thickness of 500 μm as measured in accordance with JIS Z 0208:1976. ２- A flexible laminate having a shelf life of 24 hours or less. [2] The flexible laminate according to [1], wherein the barrier layer comprises at least one inorganic layer. [3] The flexible laminate according to [2], wherein the inorganic layer has a thickness of 5 nm to 4 μm. [4] The flexible laminate according to any one of [1] to [3], wherein the adhesive resin layer comprises at least one selected from the group consisting of polyvinyl alcohol resin, polyvinyl acetal resin, and ethylene-based ionomer resin. [5] The flexible laminate according to any one of [1] to [4], wherein the adhesive resin layer has a thickness of 0.3 μm to 500 μm. [6] The flexible laminate according to any one of [1] to [5], wherein the peel strength between the adhesive resin layer and the barrier layer is 0.2 N / 10 mm or more. [7] The flexible laminate according to any one of [1] to [6], wherein the barrier layer comprises at least one inorganic layer, and the adhesive resin layer and the inorganic layer are adjacent to each other. [8] The flexible laminate according to any one of [1] to [7], wherein the barrier layer comprises two or more inorganic layers. [9] The flexible laminate according to any one of [1] to [8], wherein the total light transmittance is 87% or more.

[10] A solar cell module comprising the flexible laminate according to any one of [1] to [9].

[0008] According to the present invention, a flexible laminate having high water vapor barrier properties can be provided.

[0009] Hereinafter, embodiments of the present invention will be described in detail. Note that the following description is merely illustrative of embodiments of the present invention, and is not intended to limit the present invention to the following embodiments. Note that the upper and lower limits described in this specification can be arbitrarily combined to form a suitable numerical range.

[0010] [Flexible Laminate] The flexible laminate of the present invention comprises an adhesive resin layer and a barrier layer, and is provided with barrier layers on both sides of the adhesive resin layer, wherein the adhesive resin layer has a saturated water absorption of 0.3% or more at 20°C and 60% RH as measured in accordance with JIS K 7251:2002, and the adhesive resin layer has a water vapor transmission rate of 15 g / m or more at 40°C and 90% RH at a thickness of 500 μm as measured in accordance with JIS Z 0208:1976. ２- 24 hours or less. In the present invention, "flexibility" may refer to the property of a substance to bend flexibly when subjected to an external force (for example, human force).

[0011] In the flexible laminate of the present invention, the adhesive resin layer has a barrier layer on both sides thereof. The barrier layer may be laminated directly onto the adhesive resin layer, or may be laminated via another layer, such as a substrate film such as a PET film, but a direct laminate is preferred. When laminated via another layer, the thickness of the other layer is usually preferably 0.1 to 50 μm. The barrier layers may be the same or different.

[0012] The present inventors have conducted research to improve the water vapor barrier properties of barrier materials, and have unexpectedly found that a barrier layer with a saturated water absorption rate of 0.3% or more and a water vapor permeability of 15 g / m2 when made into a film with a thickness of 500 μm has a water vapor permeability of 15 g / m2. ２ We have found that laminates containing a specific adhesive resin layer made of a resin material with a water vapor barrier property of 24 hours or less have high water vapor barrier properties. While the reason for this is unclear, it is believed that the inclusion of an adhesive resin layer with low moisture permeability in the laminate makes it difficult for water to diffuse within the laminate, and that the high water absorption rate further retards water permeation due to the desiccant effect. Furthermore, the high adhesive strength between the adhesive resin layer and the barrier layer is thought to prevent delamination at the interface, making it less likely for the water vapor barrier property to be reduced.

[0013] <Adhesive Resin Layer> In the present invention, the adhesive resin layer has a saturated water absorption at 20°C and 60% RH (hereinafter simply referred to as "saturated water absorption") of 0.3% or more, measured in accordance with JIS K 7251:2002. If the saturated water absorption is less than 0.3%, the water vapor barrier property of the flexible laminate is reduced. The saturated water absorption is preferably 0.5% or more, more preferably 1% or more, and even more preferably 2% or more. If the saturated water absorption is equal to or greater than the lower limit, the water vapor barrier property of the flexible laminate can be further improved. Since the higher the saturated water absorption, the better the desiccant effect, the upper limit of the saturated water absorption is not particularly limited, but is usually 10% or less, or 8% or less. Therefore, the saturated water absorption is preferably 0.3 to 10%, more preferably 0.5 to 10%, and even more preferably 1 to 8% or 2 to 8%. In one embodiment, the upper limit of the saturated water absorption is usually 10% or less, or 5% or less, and therefore the saturated water absorption is preferably 0.3 to 5%, more preferably 0.5 to 4%. The saturated water absorption of the adhesive resin layer can be adjusted to be equal to or greater than the lower limit by appropriately adjusting, for example, the type of resin contained in the adhesive resin layer, the molar fraction of the monomer units constituting the resin, the amount of functional groups (e.g., hydroxyl groups, carboxyl groups, etc.) contained in the resin, etc.

[0014] In the present invention, the adhesive resin layer has a water vapor permeability at 40°C and 90% RH (hereinafter also simply referred to as "water vapor permeability") of 15 g / m or less, as measured in accordance with JIS Z 0208:1976. ２ ・24 hours or less. Water vapor permeability is 15 g / m ２ If the time exceeds 24 hours, the water vapor barrier properties of the flexible laminate will decrease. The water vapor transmission rate is preferably 13 g / m ２ 24 hours or less, more preferably 10 g / m ２ 24 hours or less, more preferably 5 g / m ２ When the water vapor transmission rate is equal to or lower than the upper limit, the water vapor barrier property of the flexible laminate can be further improved. The lower the water vapor transmission rate, the more difficult it is for water to diffuse in the adhesive resin layer. Therefore, the lower limit of the water vapor transmission rate is not particularly limited, but is usually 0.1 g / m ２ ・24 hours or more, or 0.5 g / m ２24 hours or more. Therefore, the water vapor transmission rate is preferably 0.1 to 15 g / m ２ 24 hours, more preferably 0.1 to 13 g / m ２ 24 hours, more preferably 0.5 to 10 g / m ２ ・24 hours or 0.5 to 5 g / m ２ The water vapor transmission rate of the adhesive resin layer can be adjusted to be equal to or less than the upper limit by appropriately adjusting, for example, the type of resin constituting the adhesive resin layer, the molar fraction of the monomer units constituting the resin, the amount of functional groups (e.g., hydroxyl groups, carboxyl groups, etc.) contained in the resin, etc.

[0015] In the present invention, the material constituting the adhesive resin layer is not particularly limited as long as the adhesive resin layer satisfies the above-mentioned saturated water absorption and water vapor permeability requirements. However, it is preferable that the adhesive resin layer contains at least one selected from the group consisting of polyvinyl alcohol resins, polyvinyl acetal resins, and ethylene-based ionomer resins. When the adhesive resin layer contains at least one selected from the group consisting of polyvinyl alcohol resins, polyvinyl acetal resins, and ethylene-based ionomer resins, the adhesive resin layer exhibits excellent adhesion to the barrier layer, making delamination less likely to occur, thereby improving the water vapor barrier properties of the flexible laminate of the present invention. The above compounds may be used alone or in combination of two or more. Furthermore, the same type of resin may be used, but with different number-average molecular weights and / or weight-average molecular weights, molar fractions of monomer units constituting the resin, and / or amounts of functional groups (e.g., hydroxyl groups, carboxyl groups, etc.).

[0016] In the present invention, examples of the polyvinyl alcohol resin include those obtained by saponifying a polyvinyl ester obtained by polymerizing one or more vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, and isopropenyl acetate. Among the above vinyl esters, vinyl acetate is preferred from the viewpoints of ease of production, availability, cost, etc.

[0017] The polyvinyl ester is preferably one obtained by using only one or more vinyl esters as a monomer, and more preferably one obtained by using only one vinyl ester as a monomer. However, the polyvinyl ester may be a copolymer of one or more vinyl esters with other monomers copolymerizable therewith, as long as the effects of the present invention are not impaired.

[0018] Examples of other monomers copolymerizable with the vinyl esters include α-olefins having 2 to 30 carbon atoms, such as ethylene, propylene, 1-butene, and isobutene; (meth)acrylic acid or salts thereof; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, and octadecyl (meth)acrylate; (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, diacetone(meth)acrylamide, (meth)acrylamidopropanesulfonic acid or salts thereof, and (meth)acrylamidopropyldimethylamine or salts thereof. (meth)acrylamide derivatives such as N-methylol (meth)acrylamide or derivatives thereof; N-vinylamides such as N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; vinyl cyanides such as (meth)acrylonitrile; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid or a salt, ester, or acid anhydride thereof; itaconic acid or a salt, ester, or acid anhydride thereof; vinylsilyl compounds such as vinyltrimethoxysilane; and unsaturated sulfonic acids. The polyvinyl ester may have structural units derived from one or more of the other monomers described above.

[0019] The proportion of the structural units derived from the other monomers in the polyvinyl ester is preferably 50 mol % or less, more preferably 20 mol % or less, and even more preferably 15 mol % or less, based on the number of moles of all structural units constituting the polyvinyl ester. １It can be measured using H-NMR, or can be calculated from the ratio of raw materials charged.

[0020] In the present invention, the degree of polymerization of the polyvinyl alcohol resin is preferably in the range of 200 to 8000, more preferably 400 to 2000. When the degree of polymerization is within this range, the adhesion of the adhesive resin layer containing the polyvinyl alcohol resin to the barrier layer can be improved. The degree of polymerization can be measured, for example, in accordance with the description of JIS K6726-1994.

[0021] In the present invention, the degree of saponification of the polyvinyl alcohol resin is preferably 30 to 100 mol%, more preferably 50 to 100 mol%, even more preferably 70 to 100 mol%, and even more preferably 85 to 99 mol%. When the degree of saponification is within the above range, the adhesion of the adhesive resin layer containing the polyvinyl alcohol resin to the barrier layer can be improved. The degree of saponification of the polyvinyl alcohol resin can be measured, for example, in accordance with the description of JIS K6726-1994.

[0022] In the present invention, the polyvinyl acetal resin may be one obtained by acetalizing a polyvinyl alcohol-based polymer obtained by copolymerizing polyvinyl alcohol or a vinyl ester with other monomers. The polyvinyl alcohol is not particularly limited, and one obtained by saponifying a polyvinyl ester obtained by polymerizing one or more of the vinyl esters exemplified above as those usable for producing polyvinyl alcohol can be used.

[0023] A polyvinyl acetal resin can be obtained by reacting polyvinyl alcohol with an aldehyde to form an acetal.

[0024] In a preferred embodiment of the present invention, the aldehyde used for acetalization of polyvinyl alcohol is not particularly limited, but is preferably an aldehyde having 1 to 12 carbon atoms. When the number of carbon atoms of the aldehyde is within the above range, the acetalization proceeds easily, and the synthesis of polyvinyl acetal is easy.

[0025] The aldehyde having 1 to 12 carbon atoms is not particularly limited, and examples thereof include aliphatic, aromatic, and alicyclic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, valeraldehyde, n-hexylaldehyde, 2-ethylbutyraldehyde, n-heptylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde, benzaldehyde, and cinnamaldehyde. Among these, aliphatic aldehydes having 2 to 6 carbon atoms are more preferred, and butyraldehyde is particularly preferred. The aldehydes may be used alone or in combination of two or more. Furthermore, polyfunctional aldehydes and aldehydes having other functional groups may be used in combination in an amount of 20% by mass or less relative to the mass of all aldehydes.

[0026] The acetalization method is not particularly limited. The solvent used in the acetalization reaction is not particularly limited, and for example, water, ethanol, isopropanol, or a mixture thereof can be used. The catalyst used in the acetalization reaction is also not particularly limited, and any of organic acids such as acetic acid and paratoluenesulfonic acid, and inorganic acids such as nitric acid, sulfuric acid, hydrochloric acid, and carbonic acid can be used. From the viewpoint of ease of washing the polyvinyl acetal resin after the reaction, the use of an inorganic acid is preferred.

[0027] The degree of acetalization of the polyvinyl acetal resin is preferably 30 to 90 mol%, more preferably 50 to 85 mol%, and even more preferably 55 to 80 mol%. The degree of acetalization is the amount of units forming an acetal based on a repeating unit consisting of two carbon atoms in the main chain of the polyvinyl alcohol-based polymer, which is the raw material for producing the polyvinyl acetal resin (e.g., a vinyl alcohol unit, a vinyl acetate unit, an ethylene unit, etc.). When the degree of acetalization is within the above range, the adhesion of an adhesive resin layer containing a polyvinyl acetal resin to a barrier layer can be improved. The degree of acetalization can be adjusted within the above range by appropriately adjusting the amount of aldehyde used in the acetalization reaction. When the adhesive resin layer contains two or more different polyvinyl acetal resins, it is preferable that the degree of acetalization of at least one, preferably all, of the polyvinyl acetal resins is within the above range.

[0028] The vinyl acetate unit content (acetyl group content) of the polyvinyl acetal resin is preferably 0.1 to 30 mol%, more preferably 0.3 to 20 mol%, and even more preferably 0.5 to 20 mol%. The vinyl acetate unit content is the amount of vinyl acetate units based on one repeating unit, where a unit consisting of two carbon atoms in the main chain of the polyvinyl alcohol-based polymer, which is the raw material for producing the polyvinyl acetal resin, (e.g., a vinyl alcohol unit, a vinyl acetate unit, an ethylene unit, etc.) is considered to be one repeating unit. When the vinyl acetate unit content is within the above range, blocking is less likely to occur during resin production, making production easier. The vinyl acetate unit content can be adjusted within the above range by appropriately adjusting the saponification degree of the raw material polyvinyl alcohol-based polymer. When the adhesive resin layer contains two or more different polyvinyl acetal resins, it is preferable that the vinyl acetate unit content of at least one, and preferably all, of the polyvinyl acetal resins is within the above range.

[0029] The vinyl alcohol unit content (hydroxyl group content) of the polyvinyl acetal resin is preferably 10 to 70 mol%, more preferably 12 to 35 mol%, and even more preferably 15 to 30 mol%. The vinyl alcohol unit content is the amount of vinyl alcohol units based on a repeating unit consisting of two carbon atoms in the main chain of the polyvinyl alcohol-based polymer, which is the raw material for producing the polyvinyl acetal resin (e.g., a vinyl alcohol unit, a vinyl acetate unit, an ethylene unit, etc.). When the vinyl alcohol unit content is within the above range, an adhesive resin layer containing the polyvinyl acetal resin can achieve low water vapor permeability while maintaining a high saturated water absorption. The vinyl alcohol unit content can be adjusted within the above range by appropriately adjusting the amount of aldehyde used in the acetalization reaction. When the adhesive resin layer contains two or more different polyvinyl acetal resins, it is preferable that the vinyl alcohol unit content of at least one, and preferably all, of the polyvinyl acetal resins be within the above range.

[0030] Polyvinyl acetal resins are generally composed of units that form acetal, vinyl alcohol units, and vinyl acetate units, and the amounts of these units can be determined, for example, according to JIS K6728 "Testing Methods for Polyvinyl Butyral" or １ It can be measured by H-NMR.

[0031] Furthermore, the polyvinyl acetal resin may be modified with one or more graft-copolymerizable monomers, as long as the effects of the present invention are not impaired. Examples of such graft-copolymerizable monomers include unsaturated carboxylic acids or derivatives thereof; unsaturated sulfonic acids or derivatives thereof; and α-olefins having 2 to 30 carbon atoms. The proportion of structural units derived from graft-copolymerizable monomers in the polyvinyl acetal resin is usually 5 mol % or less, based on the number of moles of all structural units constituting the polyvinyl acetal resin.

[0032] In the present invention, the number average molecular weight (Mn) of the polyvinyl acetal resin is preferably 10,000 to 150,000, more preferably 20,000 to 80,000. When the number average molecular weight is within this range, the water vapor barrier properties of the flexible laminate can be further improved. Furthermore, industrial handling is easy. The number average molecular weight can be determined, for example, using gel permeation chromatography (GPC) with polystyrene of known molecular weight as the standard.

[0033] In the present invention, the ethylene-based ionomer resin is not particularly limited as long as it has structural units derived from ethylene and structural units derived from an α,β-unsaturated carboxylic acid, and at least a portion of the α,β-unsaturated carboxylic acid is neutralized with a metal ion. Examples of such ethylene-based ionomer resins include those obtained by partially saponifying an ethylene-carboxylic acid ester copolymer and then demetallating at least a portion of the resulting saponified product. Such ethylene-based ionomer resins are typically composed of carboxylic acid ester units, carboxylic acid units, carboxylic acid neutralized units, and ethylene units.

[0034] Ethylene-carboxylic acid ester copolymers can be obtained, for example, by copolymerizing ethylene and a carboxylic acid ester under high temperature and high humidity. Examples of carboxylic acid esters used as raw materials include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of the carboxylic acid esters include (meth)acrylic acid esters such as pentadecyl (meth)acrylate, dodecyl (meth)acrylate, isobornyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, glycidyl (meth)acrylate, and allyl (meth)acrylate; and unsaturated carboxylic acid esters such as dimethyl itaconate, dimethyl maleate, and diethyl maleate. These carboxylic acid esters can be used alone or in combination of two or more. In this specification, "(meth)acrylic acid" is a general term for methacrylic acid and acrylic acid, and means either or both of methacrylic acid and acrylic acid.

[0035] Specific examples of the ethylene-carboxylic acid ester copolymer include ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-n-propyl acrylate copolymer, ethylene-n-propyl methacrylate copolymer, ethylene-isopropyl acrylate copolymer, ethylene-isopropyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer, ethylene-n-butyl methacrylate copolymer, ethylene-sec-butyl acrylate copolymer, and ethylene-sec-butyl methacrylate copolymer.

[0036] In the ethylene-based ionomer resin, examples of the monomer constituting the carboxylic acid ester unit include the same as the unsaturated carboxylic acid ester described above. The content of the carboxylic acid ester unit in the ethylene-based ionomer resin is preferably 0.01 to 2 mol %, preferably 0.03 to 1.5 mol %, and more preferably 0.05 to 0.8 mol %, based on the total monomer units constituting the ethylene-based ionomer resin.

[0037] In the ethylene-based ionomer resin, examples of the monomer constituting the carboxylic acid unit include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic anhydride, monomethyl maleate, and monoethyl maleate. The carboxylic acid unit content is preferably 1 to 15 mol%, more preferably 3 to 12 mol%, and even more preferably 4 to 10 mol%, based on all the monomer units constituting the ethylene-based ionomer resin. When the carboxylic acid unit content is within the above ranges, the water absorption and water vapor permeation of the adhesive resin containing the ethylene-based ionomer resin become appropriate, making it possible to achieve both good adhesion and good barrier properties.

[0038] In the ethylene-based ionomer resin, the monomer constituting the carboxylic acid neutralization unit is preferably a neutralized product of a monomer constituting the carboxylic acid unit. The carboxylic acid neutralization product is a product in which the hydrogen ion of the carboxylic acid is replaced with a metal ion. Examples of the metal ion include ions of monovalent metals such as lithium, sodium, and potassium; and ions of polyvalent metals such as magnesium, calcium, zinc, aluminum, and titanium. These metal ions can be used alone or in combination of two or more. For example, a combination of one or more monovalent metal ions and one or more divalent metal ions may be used.

[0039] The content of carboxylic acid neutralization units in the ethylene-based ionomer resin is preferably 0.1 to 5 mol %, more preferably 0.3 to 4 mol %, and even more preferably 0.65 to 3 mol %, based on all monomer units constituting the ethylene-based ionomer resin. When the content of carboxylic acid neutralization units is within this range, the water vapor barrier properties of the flexible laminate can be further improved. In addition, the ethylene-based ionomer resin achieves a good balance of mechanical properties such as tensile strength, tensile stress at break, tensile strain at break, and melt flow rate (MFR).

[0040] The ethylene unit content in the ethylene ionomer resin is preferably 90 to 94 mol%, more preferably 90.1 to 93.5 mol%, and even more preferably 90.5 to 93 mol%, based on all monomer units constituting the ethylene ionomer resin. When the ethylene unit content in the ethylene ionomer resin is within this range, the water vapor barrier property of the flexible laminate can be further improved.

[0041] The ethylene-based ionomer resin may contain other monomer units in addition to carboxylic acid ester units, carboxylic acid units, carboxylic acid neutralized unit, and ethylene units. Examples of the other monomer units include the same monomers as those copolymerizable with the vinyl esters described above. The other monomer units can be used alone or in combination of two or more. When the ethylene-based ionomer resin contains other monomer units, the content thereof is usually 5 mol % or less, preferably 3 mol % or less, based on the total monomer units constituting the ethylene-based ionomer resin.

[0042] The content of each structural unit in an ethylene-based ionomer resin can be analyzed by the following procedure: First, the structural units in the ethylene-based ionomer resin are identified by pyrolysis gas chromatography (pyrolysis GC-MS), and then the content of each unit can be evaluated using nuclear magnetic resonance spectroscopy (NMR) and elemental analysis.

[0043] When an ethylene-based ionomer resin is produced using an ethylene-carboxylic acid ester copolymer as a raw material by a method including saponification and demetallization reactions, the content of each structural unit in the ethylene ionomer resin can be adjusted by the degree of reactivity in each reaction that converts the carboxylic acid ester units in the ethylene-carboxylic acid ester copolymer into carboxylic acid units and carboxylic acid neutralized product units by the saponification reaction and the demetallization reaction, or by the ratio of ethylene units to carboxylic acid ester units in the ethylene-carboxylic acid ester copolymer used as a raw material.

[0044] In the present invention, the melt flow rate (MFR; JIS K6760, 190°C, 2.16 kg load) of the ethylene-based ionomer resin is preferably 0.1 to 20 g / 10 min, more preferably 0.2 to 18 g / 10 min, and even more preferably 0.5 to 10 g / 10 min. When the MFR of the ethylene-based ionomer resin is within the above range, the water vapor barrier property of the flexible laminate can be further improved.

[0045] The content of at least one resin selected from the group consisting of polyvinyl alcohol resins, polyvinyl acetal resins, and ethylene-based ionomer resins in the adhesive resin layer is preferably 80 to 100% by mass, more preferably 85 to 100% by mass, and even more preferably 90 to 99% by mass, in total, relative to the mass of the adhesive resin layer. When the content of at least one resin selected from the group consisting of polyvinyl alcohol resins, polyvinyl acetal resins, and ethylene-based ionomer resins is within this range, the water vapor barrier properties of the flexible laminate can be further improved, and the adhesion between the adhesive resin layer and the barrier layer can also be further improved.

[0046] The adhesive resin layer may contain additives other than at least one selected from the group consisting of polyvinyl alcohol resins, polyvinyl acetal resins, and ethylene-based ionomer resins, as long as the additives do not impair the effects of the present invention. Examples of such additives include antioxidants, ultraviolet absorbers, lubricants, colorants, preservatives, fillers, silane coupling agents, adhesion improvers, water-absorbing fillers, and plate-like fillers. The additives may be used alone or in combination of two or more.

[0047] The content of the additive is not particularly limited as long as it does not interfere with the effects of the present invention, but is, for example, about 0 to 20% by mass, preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.1 to 1% by mass, relative to the mass of the adhesive resin layer.

[0048] The thickness of the adhesive resin layer is preferably 0.3 to 500 μm, more preferably 0.5 to 480 μm, even more preferably 1 to 450 μm, even more preferably 3 to 400 μm, particularly preferably 5 to 350 μm, and extremely preferably 10 to 300 μm, for example, 15 to 250 μm or 20 to 200 μm. When the thickness of the adhesive resin layer is within the above range, the water vapor barrier properties of the flexible laminate can be further improved, and adhesion to the barrier layer can be improved. Furthermore, the flexible laminate can achieve both flexibility and mechanical strength. The thickness of the adhesive resin layer can be determined, for example, by measuring the thickness at any five or more points on the adhesive resin layer and averaging these measurements. The thickness of the adhesive resin layer can be measured by cross-sectional observation using a laser microscope, SEM (scanning electron microscope), TEM (transmission electron microscope), or the like, or by a film thickness gauge, for example, by the method described in the Examples.

[0049] The method for producing the adhesive resin layer is not particularly limited. For example, the components to be contained in the adhesive resin layer can be uniformly mixed using a mixing / stirring device or the like to form a composition, and then the composition can be produced in the form of a film. In this case, the composition can be formed into a film by a known film-forming method such as extrusion, calendaring, pressing, casting, or inflation. Alternatively, a film-shaped adhesive resin layer can be produced by press-molding pellets of the composition. The film-shaped adhesive resin layer may be stretch-molded. The film-shaped adhesive resin composition may have convex portions and / or concave portions. In this case, the composition or the film-shaped adhesive resin layer can be processed and molded using a mold having convex portions and / or concave portions.

[0050] Alternatively, the adhesive resin layer can be formed on the barrier layer by coating or painting using various types of coating or painting equipment. When forming the adhesive resin layer by coating or painting, the components contained in the adhesive resin layer may be dissolved or dispersed in a solvent and then coated and dried, or a solid composition containing the components may be coated as is and melted.

[0051] <Barrier Layer> In the present invention, the barrier layer is a layer capable of preventing moisture penetration. The barrier layer in the present invention is not particularly limited as long as it is a layer capable of preventing moisture penetration. Examples of such layers include a layer consisting solely of organic layers, a layer consisting solely of inorganic layers, and a layer containing both organic and inorganic layers. Here, a layer consisting solely of organic layers can include both an embodiment consisting of only one organic layer and an embodiment consisting of two or more organic layers. The two or more organic layers can be the same or different. Similarly, a layer consisting solely of inorganic layers can include both an embodiment consisting of only one inorganic layer and an embodiment consisting of two or more inorganic layers. The two or more inorganic layers can be the same or different. Furthermore, a layer consisting of both organic and inorganic layers can include an embodiment consisting of one organic layer and one inorganic layer, and an embodiment consisting of two or more organic layers and two or more inorganic layers. The two or more organic layers and inorganic layers can be the same or different.

[0052] The organic layer is not particularly limited, but a resin film can be used from the viewpoint of suppressing moisture penetration and having excellent physical strength. Specifically, various resin films can be used, for example, polyolefin resins such as polyethylene resins and polypropylene resins, cyclic polyolefin resins, polystyrene resins, acrylonitrile-styrene copolymers (AS resins), acrylonitrile-butadiene-styrene copolymers (ABS resins), poly(meth)acrylic resins, polycarbonate resins, polyvinyl alcohol resins, saponified ethylene-vinyl ester copolymers, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polyethylene furanoate, polyamide resins such as various nylons, polyurethane resins, acetal resins, and cellulose resins.

[0053] The thickness of the organic layer is preferably 0.3 to 1000 μm, more preferably 1 to 800 μm, even more preferably 5 to 600 μm, even more preferably 10 to 500 μm, and particularly preferably 20 to 400 μm. When the thickness of the organic layer is within this range, the flexible laminate can have high water vapor barrier properties. The thickness of the organic layer is determined, for example, by measuring the thickness at any five or more points on the organic layer and averaging these values. The thickness of the organic layer can be measured by a cross-sectional observation method using a laser microscope, SEM (scanning electron microscope), TEM (transmission electron microscope), or the like, or by a film thickness meter, for example, using the method described in the Examples. When the barrier layer can include two or more organic layers, the above ranges represent the thickness of each individual organic layer.

[0054] The inorganic layer is not particularly limited, and can be a layer containing at least one selected from the group consisting of inorganic substances, inorganic oxides, inorganic nitrides, and inorganic oxynitrides.Since it can sufficiently suppress moisture penetration even when formed thinly, specifically, tin, phosphorus, tin oxide, stainless steel, titanium, titanium oxide, indium oxide, indium tin oxide (ITO), tantalum oxide, zirconium oxide, niobium oxide, boron nitride, boron oxynitride, silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon oxycarbonitride, aluminum, aluminum oxide such as alumina, aluminum nitride, aluminum oxynitride, aluminum oxycarbide, copper, and mixtures thereof can be preferably used.

[0055] The content of at least one selected from the group consisting of inorganic substances, inorganic oxides, inorganic nitrides, and inorganic oxynitrides in the inorganic layer is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, and even more preferably 70 to 100 mass%, 80 to 100 mass%, 85 to 99 mass%, or 90 to 98 mass%, relative to the mass of the inorganic layer. When the content of at least one selected from the group consisting of inorganic substances, inorganic oxides, inorganic nitrides, and inorganic oxynitrides in the inorganic layer is within the above range, adhesion to the barrier layer can be further improved.

[0056] The inorganic layer may be formed by any method capable of forming a thin film. For example, the inorganic layer may be formed by a known method such as physical vapor deposition (PVD) methods such as etching, printing, vacuum heating evaporation, electron beam deposition, sputtering, and ion plating, chemical vapor deposition (CVD), and coating. PVD and CVD methods may be combined with plasma assistance. Alternatively, thin film metals may be used. When the inorganic layer is made up of multiple layers, multiple methods may be used. Each method may be carried out by a method commonly used in the relevant technical field.

[0057] The thickness of the inorganic layer is preferably 5 nm to 4 μm, more preferably 10 nm to 3 μm, even more preferably 50 nm to 2 μm, even more preferably 0.1 to 1 μm, and particularly preferably 0.2 to 0.8 μm. When the thickness of the inorganic layer is within the above range, the flexible laminate can have high water vapor barrier properties. The thickness of the inorganic layer is determined, for example, by measuring the thickness at any five or more points on the inorganic layer and averaging these values. The thickness of the inorganic layer can be measured by cross-sectional observation using a laser microscope, SEM (scanning electron microscope), TEM (transmission electron microscope), or the like, or by a film thickness meter, for example, by the method described in the Examples. When the barrier layer can include two or more inorganic layers, the above ranges represent the thickness of each individual inorganic layer.

[0058] In a preferred embodiment of the present invention, the barrier layer preferably includes at least one inorganic layer. By including at least one inorganic layer in the barrier layer, the flexible laminate can have high water vapor barrier properties even when the thickness of the barrier layer is reduced. In this embodiment, the barrier layer may include only at least one inorganic layer, but preferably includes at least one inorganic layer and at least one organic layer, from the viewpoint of achieving both water vapor barrier properties and flexibility.

[0059] In another preferred embodiment of the present invention, the barrier layer preferably includes two or more inorganic layers. By including two or more inorganic layers in the barrier layer, the water vapor barrier property of the flexible laminate can be further improved. In this embodiment, the barrier layer may include only two or more inorganic layers, but preferably includes at least two or more inorganic layers and at least one organic layer, from the viewpoint of achieving both water vapor barrier property and flexibility.

[0060] When the barrier layer includes two or more inorganic layers (hereinafter sometimes referred to as "I") and at least one organic layer (hereinafter sometimes referred to as "O"), for example, when it includes two inorganic layers and one organic layer, the layer structure is not particularly limited, but possible examples are O / I / I, I / O / I, and I / I / O, from the adhesive layer side. When it includes two inorganic layers and two organic layers, possible examples are O / I / O / I, O / I / I / O / , O / O / I / I, I / O / O / I, I / O / I / O, and I / I / O / O, from the adhesive layer side. When the barrier layer includes two or more inorganic layers and at least one organic layer, it is preferable that the inorganic layers or the organic layers are not continuous with each other, from the viewpoint of flexibility. Furthermore, the more inorganic layers included in the barrier layer, the higher the water vapor barrier property can be. However, from the viewpoints of flexibility and transparency, it is preferable that the barrier layer include five or fewer inorganic layers.

[0061] In the present invention, the barrier layer may include, in addition to the organic layer and inorganic layer, layers such as an adhesive layer and a primer layer, as long as the effects of the present invention are not impaired. Furthermore, the surface of the organic layer and / or inorganic layer may be subjected to a known surface treatment such as a plasma treatment or a corona treatment.

[0062] Examples of adhesives constituting the adhesive layer include dry-hardening adhesives and chemically reactive adhesives. Examples of chemically reactive adhesives include active energy ray-curable adhesives. Such adhesives may be any known adhesives in the art.

[0063] The thickness of the adhesive layer is not particularly limited as it is determined depending on the type, adhesive strength, etc., but is usually 0.001 μm to 40 μm, and preferably 0.01 to 10 μm from the viewpoint of processability and durability.

[0064] The primer layer is not particularly limited, but may be made of a polyol, a polyisocyanate, etc. The thickness of the primer layer is, from the viewpoint of the flexibility of the flexible laminate, for example, 0.001 to 5 μm, and preferably 0.005 to 2 μm.

[0065] The thickness of the barrier layer is preferably 0.3 to 500 μm, more preferably 1 to 400 μm, even more preferably 10 to 300 μm, and even more preferably 20 to 240 μm. When the thickness of the barrier layer is within this range, adhesion to the adhesive resin layer can be improved. Furthermore, it is possible to achieve both flexibility and mechanical strength of the flexible laminate. The thickness of the barrier layer is, for example, measured at any five or more points on the barrier layer and taken as the average value. The thickness of the barrier layer can be measured using a thickness meter or the like, for example, by the method described in the Examples.

[0066] The method for producing the barrier layer is not particularly limited. For example, when the barrier layer includes an organic layer and an inorganic layer, the inorganic layer can be formed on the organic layer (e.g., a resin film) by the above-mentioned method. The barrier layer may have convex portions and / or concave portions, and in this case, the barrier layer can be produced by processing and molding using a mold having convex portions and / or concave portions.

[0067] Commercially available barrier layers can also be used as the barrier layer. Examples of commercially available barrier layers that can be used in the present invention include the oxygen / water vapor high barrier film "CLARISTA (registered trademark)" (manufactured by Kuraray Co., Ltd.), the transparent silica-deposited high gas barrier film "TECHBARIER (registered trademark)" (manufactured by Mitsubishi Chemical Corporation), the DNP transparent deposited film "IB-Film (registered trademark)" (manufactured by Dai Nippon Printing Co., Ltd.), and the transparent barrier film "GL FILM" (manufactured by TOPPAN Co., Ltd.).

[0068] The flexible laminate of the present invention has excellent water vapor barrier properties due to the high adhesion between the adhesive resin layer and the barrier layer. Therefore, in the flexible laminate of the present invention, the peel strength between the adhesive resin layer and the barrier layer is preferably 0.2 N / 10 mm or more, more preferably 0.5 N / 10 mm or more, even more preferably 1 N / 10 mm or more, and even more preferably 5 N / 10 mm or more. The stronger the adhesion between the adhesive resin layer and the barrier layer, the higher the peel strength value, ultimately leading to material failure without peeling, and therefore no upper limit for the peel strength is specifically set. The peel strength between the adhesive resin layer and the barrier layer can be adjusted to be equal to or greater than the lower limit by, for example, appropriately adjusting the type and / or amount of resin contained in the adhesive resin layer; the thickness of the adhesive resin layer; the type and / or amount of compound contained in the barrier layer; the thickness of the barrier layer; etc. The peel strength can be determined by a tensile test, for example, by the method described in the Examples below.

[0069] In the flexible laminate of the present invention, in order to further enhance the adhesion between the adhesive resin layer and the barrier layer, the adhesive resin layer is preferably adjacent to the inorganic layer in the barrier layer. In the present invention, "adjacent" means that the adhesive resin layer and the inorganic layer are directly laminated without any other layer in between. Therefore, the layer structure of the barrier layer is preferably I, I / O, I / O / I, I / O / I / O, I / O / I / O / I, I / O / I / O / I, or I / O / I / O / I / O, from the adhesive layer side.

[0070] The thickness of the flexible laminate of the present invention is preferably greater than 0.9 μm and up to 2000 μm, more preferably 10 to 1500 μm, even more preferably 20 to 1000 μm, even more preferably 50 to 800 μm, and particularly preferably 100 to 500 μm. When the thickness of the flexible laminate is within the above range, both water vapor barrier properties and flexibility can be achieved. The thickness of the flexible laminate can be adjusted to within the above range by appropriately adjusting, for example, the thickness of the adhesive resin layer; the thickness of the layers constituting the barrier layer, and / or the number of layers. The thickness of the flexible laminate can be determined, for example, by measuring the thickness at any five or more points on the flexible laminate and averaging these values. Alternatively, the thickness can be determined from the thickness of each layer constituting the flexible laminate. The thickness of the flexible laminate can be measured using a thickness meter or the like, for example, by the method described in the Examples.

[0071] The flexible laminate of the present invention also has high transparency. The total light transmittance of the flexible laminate of the present invention is preferably 87% or more, more preferably 88% or more, even more preferably 89% or more, and even more preferably 90% or more. The upper limit of the total light transmittance is 100%. The total light transmittance can be adjusted to the lower limit or more by appropriately adjusting, for example, the thickness of the flexible laminate; the type of resin constituting the adhesive resin layer; the type of compound constituting the barrier layer; etc. The total light transmittance can be measured, for example, using a haze / transmittance / reflectance meter in accordance with JIS K7105.

[0072] The flexible laminate of the present invention has high water vapor barrier properties. The water vapor transmission rate of the flexible laminate of the present invention at 40°C and 90% RH, measured in accordance with JIS Z 0208:1976, is preferably 1.0 x 10 －３ g / m ２ Less than 24 hours, more preferably 8.0 x 10 －４ g / m ２ 24 hours or less, more preferably 7.5 x 10 －４ g / m ２ 24 hours or less, and even more preferably 6.0 x 10 －４ g / m ２ 24 hours or less, particularly preferably 5.0 x 10 －４ g / m ２The lower the water vapor transmission rate, the higher the water vapor barrier property of the flexible laminate. Therefore, the lower limit of the water vapor transmission rate is not particularly limited, but is usually 1.0 × 10 －５ g / m ２ - about 24 hours or more. The water vapor transmission rate (WVTR) of the flexible laminate of the present invention to the water vapor transmission rate (WVTR) of the barrier layer alone, expressed as a WVTR ratio (flexible laminate / barrier layer) of preferably 30% or less, more preferably 25% or less, and particularly preferably 20% or less. The lower limit of the water vapor transmission rate of the flexible laminate of the present invention relative to the water vapor transmission rate of the barrier layer alone is not particularly limited, but is usually about 10%.

[0073] When the flexible laminate of the present invention is used as, for example, a front sheet of a solar cell, the required water vapor barrier property may vary depending on the type of solar cell. For example, in one embodiment in which the flexible laminate of the present invention is used as a front sheet of a perovskite solar cell, which is known to be vulnerable to moisture, the water vapor barrier property is, for example, 1.0 × 10 －３ g / m ２ ・It is preferable that it is less than 24 hours.

[0074] [Method for producing flexible laminate] The method for producing the flexible laminate of the present invention is not particularly limited, but it can be produced, for example, by a method including the steps of: laminating a barrier layer and an adhesive resin layer; and vacuum-suctioning and heat-pressing the laminate.

[0075] In the step of vacuum suction and thermocompression bonding, for example, a vacuum laminator is used. Typically, lamination is performed at a predetermined temperature under reduced pressure of 1 to 50,000 Pa. The heating temperature is preferably 80 to 200°C, more preferably 90 to 190°C, even more preferably 100 to 180°C, and still more preferably 110 to 170°C.

[0076] When a vacuum bag or vacuum ring is used, lamination is preferably carried out under a pressure of about 30,000 Pa at the above temperature.

[0077] When using nip rolls, for example, a method may be used in which the adhesive resin layer is first pre-bonded at a temperature equal to or lower than the flow initiation temperature thereof, and then pre-bonded under conditions close to the flow initiation temperature thereof. Specifically, the adhesive resin layer is heated to 30 to 100°C using an infrared heater or the like, degassed with a roll, and further heated to the above temperature, followed by pre-bonding with a roll.

[0078] The autoclave step, which is additionally performed after temporary pressure bonding, is carried out, for example, for about 2 hours at the above temperature under a pressure of about 1 to 1.5 MPa, depending on the thickness or configuration of the flexible laminate. [Uses of Flexible Laminate] The flexible laminate of the present invention has high water vapor barrier properties and is therefore suitable for use in photoelectric conversion devices, information display devices, lighting devices, and the like, where moisture penetration can be a problem. Examples of photoelectric conversion devices include various solar cells and other photoelectric conversion devices. Examples of information display devices include liquid crystal displays, organic EL displays, plasma displays, electronic paper, and other information display devices. Examples of lighting devices include LED lighting, organic EL lighting, and other lighting devices.

[0079] In particular, the flexible laminate of the present invention has high water vapor barrier properties, high transparency, and high flexibility, and can therefore be suitably used as a surface barrier material (front sheet) for solar cells, preferably as a surface barrier material for flexible solar cells. Accordingly, the present invention also encompasses a solar cell module comprising the flexible laminate of the present invention.

[0080] The solar cell module of the present invention comprises, for example, the flexible laminate of the present invention, a solar cell, a back sheet, and an encapsulant, and is produced by a known method, with the flexible laminate of the present invention being used as a front sheet.

[0081] The front sheet used in the solar cell module of the present invention may include a surface protective layer disposed on one surface of the multilayer structure. The surface protective layer is preferably a layer made of a highly transparent and scratch-resistant resin. Furthermore, the surface protective layer of a device that may be used outdoors, such as a solar cell, is preferably made of a resin with high weather resistance (e.g., light resistance). Furthermore, when protecting a surface that requires light transmission, a surface protective layer with high light transmissivity is preferred. Examples of materials for the surface protective layer (surface protective film) include acrylic resin, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, triacetyl cellulose, cycloolefin polymer, ethylene-tetrafluoroethylene copolymer (ETFE), polytetrafluoroethylene, 4-fluoroethylene-perchloroalkoxy copolymer, 4-fluoroethylene-6-fluoropropylene copolymer, 2-ethylene-4-fluoroethylene copolymer, poly-3-chlorofluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, and the like.

[0082] To enhance the durability of the surface protective layer, various additives (e.g., ultraviolet absorbers) may be added to the surface protective layer. A preferred example of a highly weather-resistant surface protective layer is an acrylic resin layer to which an ultraviolet absorber has been added. Examples of ultraviolet absorbers include, but are not limited to, benzotriazole-based, benzophenone-based, salicylate-based, cyanoacrylate-based, nickel-based, and triazine-based ultraviolet absorbers. In addition, other stabilizers, light stabilizers, antioxidants, etc. may be used in combination.

[0083] Furthermore, in order to enhance the durability of the surface protective layer, a weather-resistant coating such as a hard coat may be applied to the surface. The type of coating is not particularly limited, and known materials can be used.

[0084] Examples of the types of solar cells that can be used in the solar cell module of the present invention include silicon-based solar cells that use silicon-based materials such as crystalline silicon (e.g., single crystal silicon, polycrystalline silicon, microcrystalline silicon), amorphous silicon, and multi-junction or heterojunction silicon in their photoelectric conversion units; compound-based solar cells that use compound semiconductors such as those from Groups I-III-VI, I-II-IV-VI, III-V, or II-VI of the periodic table (e.g., CIGS (copper (Cu)-indium (In)-gallium (Ga)-selenium (Se))), CIS (Cu-In-Se), CZTS, gallium arsenide, and cadmium tellurium in their photoelectric conversion units; and organic-based solar cells such as dye-sensitized, organic thin-film, and organic-inorganic hybrid perovskites. Silicon-based solar cells are preferred as solar cells because of their excellent conversion efficiency, while compound-based solar cells are preferred because they can provide flexibility to the solar cells. Furthermore, the use of an organic-inorganic hybrid perovskite solar cell is more preferable because it has excellent conversion efficiency and can be made flexible.

[0085] Here, a solar cell is the smallest structural unit of a solar cell used for photovoltaic power generation, and includes at least a photoelectric conversion unit and electrodes. The electrodes are made of conductive materials, such as metals, metal compounds such as metal oxides, and carbon-based materials such as graphene and carbon nanotubes. The materials, shapes, and mounting positions of the electrodes used in a solar cell are determined appropriately depending on the materials and combinations of materials used in the photoelectric conversion unit. Depending on the type of solar cell, the solar cell may also include various components such as an anti-reflective film or a cell substrate. For example, thin-film solar cells such as amorphous silicon and CIGS typically include at least a transparent electrode layer, a photoelectric conversion unit, and a back electrode. In the case of a solar cell using amorphous silicon, the photoelectric conversion unit typically includes a p-layer amorphous silicon film, an i-layer amorphous silicon film, and an n-layer amorphous silicon film. In the case of a solar cell using CIGS, the photoelectric conversion unit typically includes CIGS. If necessary, the photoelectric conversion unit may contain other components. Examples of materials for the transparent electrode layer include inorganic oxides such as ITO, GZO, BZO, AZO, and IZO, and carbon-based materials such as carbon nanotubes.

[0086] The thin-film solar cell is preferably formed on a substrate, such as a metal foil of titanium, molybdenum, stainless steel, or the like, a ceramic sheet, or a glass substrate.

[0087] Furthermore, the material used for the backsheet constituting the solar cell module of the present invention is not particularly limited as long as it has excellent weather resistance and functions to protect the interior of the solar cell module. For example, materials made of one or more of glass, such as organic glass or inorganic glass; inorganic materials, such as metals, such as tin, aluminum, and stainless steel; acrylic resin, polycarbonate, polyester, fluorine-containing resin, polyolefin, polystyrene, polyimide, polyamide, or inorganic-vapor-deposited polyester, can be used. The use of glass, metal, acrylic resin, polycarbonate, polyester, fluorine-containing resin, polyolefin, polystyrene, polyimide, polyamide, or inorganic-vapor-deposited polyester as the backsheet is preferred in terms of weather resistance. The backsheet may be a single-layer structure made of one material, a multilayer structure made of multiple layers of different materials, or a mixture of multiple materials in one layer. Materials containing optional components other than the above materials may also be used. When barrier properties are required, it is preferable to use the flexible laminate of the present invention as the backsheet or as part of the backsheet.

[0088] The encapsulant seals and protects the solar cell, and is therefore interposed between the light-receiving surface of the solar cell and the front sheet, and between the rear surface of the solar cell and the back sheet.

[0089] The encapsulant bonds the solar cell to the front sheet and the back sheet, and also eliminates gaps around the solar cell, thereby protecting the solar cell. For this reason, suitable encapsulants include light-transmitting thermoplastic resins such as ethylene / vinyl acetate copolymer (EVA), ethylene / α-olefin copolymer, ethylene / vinyl acetate / triallyl isocyanurate (EVAT), polyvinyl butyrate (PVB), acrylic resin, urethane resin, and silicone resin.

[0090] A known manufacturing method can be used to manufacture a solar cell module, for example, a method including the steps of stacking the flexible laminate of the present invention, a solar cell, an encapsulant, and a backsheet, and then vacuum-bonding them under heat and pressure.

[0091] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0092] <Saturated Water Absorption> The resins used in the examples and comparative examples were measured in accordance with JIS K 7251:2002 under the following measurement conditions: temperature: 20°C, humidity: 60% RH

[0093] <Water vapor transmission rate of adhesive resin layer> The resins used in the examples and comparative examples were press-molded to form films with a thickness of 500 μm. The water vapor transmission rate of the films was measured by the cup method in accordance with JIS Z 0208:1976. The measurement conditions were as follows: temperature: 40° C. humidity: 90% RH

[0094] <Thickness> The flexible laminates obtained in the Examples and Comparative Examples were cut using a focused ion beam (FIB) to prepare slices for cross-sectional observation. The prepared slices were fixed to a sample base with carbon tape and subjected to platinum ion sputtering at an acceleration voltage of 30 kV for 30 seconds. The cross section of the flexible laminate was observed using a field emission transmission electron microscope, and the thickness of each layer and the thickness of the flexible laminate were calculated. The measurement conditions were as follows. The thickness was the average of the measured values ​​at five locations. Apparatus: JEM-2100F manufactured by JEOL Ltd. Acceleration voltage: 200 kV

[0095] Example 1 1. Preparation of Barrier Layer 1-1. Preparation of Coating Liquid (S) 230 parts by mass of distilled water was heated to 70°C while stirring. 88 parts by mass of triisopropoxyaluminum was added dropwise to the distilled water over 1 hour, and the liquid temperature was gradually raised to 95°C. Hydrolysis and condensation were carried out by distilling off the generated isopropanol. 4.0 parts by mass of a 60% by mass aqueous nitric acid solution was added to the resulting liquid, and the mixture was stirred at 95°C for 3 hours to deflocculate the particle aggregates of the hydrolysis and condensation product. The liquid was then concentrated to a solids concentration of 10% by mass in terms of aluminum oxide, thereby obtaining a solution. 54.29 parts by mass of distilled water and 18.80 parts by mass of methanol were added to 22.50 parts by mass of the resulting solution, and the mixture was stirred until uniform, thereby obtaining a dispersion. Subsequently, while maintaining the liquid temperature at 15°C, 4.41 parts by mass of an 85% by mass aqueous phosphoric acid solution was added dropwise to the dispersion while stirring. Further, 18.80 parts by mass of the methanol solution was added dropwise, and stirring was continued at 15°C until the viscosity reached 1,500 mPa s, to obtain the target coating solution (S). The molar ratio of aluminum atoms to phosphorus atoms in the coating solution (S) was aluminum atoms:phosphorus atoms = 1.15:1.00.

[0096] 1-2. Preparation of Coating Liquid (R) 4.8 parts by mass of PVA "Kuraray Poval (registered trademark) 48-80" and 95.2 parts by mass of water were mixed and stirred at room temperature for 5 hours to dissolve the "Kuraray Poval (registered trademark) 48-80" and obtain a PVA aqueous solution. Next, 0.8 parts by mass of polyester-based aqueous dispersion "Elitell (registered trademark) KA-5071S" (manufactured by Unitika Ltd.), 1.2 parts by mass of the PVA aqueous solution, 68.1 parts by mass of water, and 29.9 parts by mass of methanol were mixed and stirred for 1 hour to obtain Coating Liquid (R).

[0097] 1-3. Preparation of multilayer structure (barrier layer) A PET substrate ("Lumirror #25-S105", manufactured by Toray Industries, Inc.) was used as the substrate (X). ２One surface of the substrate was subjected to a surface treatment at a strength of 100000000000000. The coating liquid (R) was applied to one surface of the surface-treated substrate using a bar coater so that the thickness after drying would be 10 nm. The coated substrate was dried at 140 ° C. for 1 minute to form a layer (I) on one surface of the substrate. The coating liquid (S) was applied to one surface of the substrate on which the layer (I) was formed using a bar coater so that the thickness after drying would be 0.4 μm. The coated substrate was dried at 120 ° C. for 3 minutes and then heat-treated at 180 ° C. for 1 minute to form a precursor layer of the inorganic layer (Y) on the substrate. Next, the other surface was surface-treated in the same manner, and then the layer (I) and a precursor layer of the inorganic layer (Y) were formed. The obtained film having the precursor layer of inorganic layer (Y) formed thereon was heat-treated at 210°C for 1 minute to obtain a multilayer structure A (barrier layer) having a structure of inorganic layer (Y) (0.4 µm) / layer (I) (10 nm) / substrate (X) (23 µm) / layer (I) (10 nm) / inorganic layer (Y) (0.4 µm).

[0098] 2. Preparation of Flexible Laminate Using a polyvinyl butyral (PVB) film (MOWITAL (registered trademark) Thin Film, manufactured by Kuraray Co., Ltd., thickness 25 μm) as the adhesive resin layer, a flexible laminate of multilayer structure A (barrier layer) / adhesive resin layer / multilayer structure A (barrier layer) was laminated using a vacuum laminator. The lamination conditions were as follows: hot plate temperature: 150°C, evacuation: 12 minutes, pressure: 30 kPa, pressing time: 18 minutes

[0099] Example 2 A laminate was produced in the same manner as in Example 1, except that a PVB film (MOWITAL (registered trademark) Thin Film, manufactured by Kuraray Co., Ltd., thickness 250 μm) was used as the adhesive resin layer.

[0100] Example 3 A laminate was produced in the same manner as in Example 1, except that an ethylene-based ionomer (IO) film (Sentryglass (registered trademark): thickness 100 μm) was used as the adhesive resin layer.

[0101] Example 4 Polyvinyl alcohol "Kuraray Poval (registered trademark) 5-74" is used as the adhesive resin layer. An aqueous solution of polyvinyl alcohol resin is prepared, and then coated onto multilayer structure A using a bar coater so that the dry film thickness is 25 μm, followed by drying. Next, a flexible laminate of multilayer structure A (barrier layer) / adhesive resin layer / multilayer structure A (barrier layer) is laminated using a vacuum laminator. The lamination conditions are as follows: hot plate temperature: 180°C, evacuation: 12 minutes, pressure: 30 kPa, press time: 18 minutes

[0102] Comparative Example 1 A laminate was prepared in the same manner as in Example 1, except that an ethylene-vinyl acetate (EVA) film (thickness: 100 μm) was used as the adhesive resin layer.

[0103] Comparative Example 2 A laminate was prepared in the same manner as in Example 1, except that an ethylene-vinyl acetate (EVA) film (thickness: 200 μm) was used as the adhesive resin layer.

[0104] Comparative Example 3 A laminate was prepared in the same manner as in Example 1, except that a polyolefin elastomer (POE) film (thickness: 150 μm) was used as the adhesive resin layer.

[0105] Comparative Example 4 A laminate was prepared in the same manner as in Example 1, except that an olefin-based thermoplastic elastomer (TPO) film (thickness: 180 μm) was used as the adhesive resin layer.

[0106] Comparative Example 5 Only the multilayer structure A was used.

[0107] Table 1 shows the evaluation results of each layer in the examples and comparative examples.

[0108] <Total Light Transmittance> Measured using a haze / transmittance / reflectance meter "HR-100" in accordance with JIS K7105.

[0109] <Water vapor transmission rate of flexible laminate> The flexible laminates obtained in the examples and comparative examples were attached to a water vapor transmission rate measuring device, and the water vapor transmission rate was measured by a differential pressure method in accordance with JIS Z 0208: 1976. The measurement conditions were as follows: First, the flexible laminate was subjected to a pressure test at a temperature of 70°C and a pressure of 5 x 10 -３The sample was heated at 4000 Torr for 4,000 minutes to remove moisture from inside the sample. Thereafter, the temperature was lowered to 40°C, and water vapor at 90% RH was introduced into the water vapor supply side. The measured value 50 hours after the introduction of water vapor was evaluated. Next, a value was calculated by subtracting the measured value (background value) immediately before the introduction of water vapor from the measured value when the pressure sensor on the water vapor supply side reached the upper limit of 1.1 Torr. It was determined that the lower the water vapor permeability, the better the water vapor barrier property. Apparatus: DELTAPERM manufactured by TECHNOLOX Corporation Temperature: 40°C Humidity on water vapor supply side: 90% RH

[0110] <Peel Strength> The flexible laminates prepared in the Examples and Comparative Examples were left to stand at 23°C and 50% RH for 24 hours, and then cut into 10 mm wide samples for peel strength measurement. Using an autograph (manufactured by Shimadzu Corporation), the peel strength was measured when the interface between the barrier layer and the adhesive resin layer contained in the flexible laminate was T-peeled at 250 mm / min. Three to five samples for peel strength measurement were measured, and the average value was taken as the peel strength of the flexible laminate.

[0111] The results obtained are shown in Table 2.

[0112]

[0113] As shown in Table 2, the flexible laminates obtained in Comparative Examples 1 to 5 had high water vapor permeability and did not have sufficient water vapor barrier properties, whereas the flexible laminates obtained in Examples 1 to 3 were found to have high water vapor barrier properties.

[0114] Example 4: The barrier layer was made of GX-PF (manufactured by TOPPAN Corporation, PET substrate, water vapor permeability 0.05 g / m ２ A laminate was produced in the same manner as in Example 1, except that a laminate was produced using a test piece (JIS K7129 method, 40°C, 90% RH) and the barrier coat layer of GX-PF was laminated in a direction that adhered to the adhesive resin layer.

[0115] Comparative Example 6 A laminate was produced in the same manner as in Example 4, except that a polyolefin elastomer (POE) film (thickness: 150 μm) was used as the adhesive resin layer. The results of Example 4 and Comparative Example 6 are shown in Table 3.

[0116]

[0117] The flexible laminate of the present invention has high water vapor barrier properties and can therefore be suitably used in photoelectric conversion devices, information display devices, lighting devices, and the like, and can be particularly suitably used as a surface barrier material (front sheet) for solar cells, preferably a surface barrier material for flexible solar cells.

Claims

1. A flexible laminate comprising an adhesive resin layer and a barrier layer, the adhesive resin layer having a barrier layer on both sides thereof, the adhesive resin layer having a saturated water absorption of 0.3% or more at 20°C and 60% RH measured in accordance with JIS K 7251:2002, and the adhesive resin layer having a water vapor transmission rate of 15 g / m or less at 40°C and 90% RH at a thickness of 500 μm measured in accordance with JIS Z 0208:1976. ２ A flexible laminate having a life of 24 hours or less.

2. The flexible laminate of claim 1, wherein said barrier layer comprises at least one inorganic layer.

3. The flexible laminate according to claim 2, wherein the inorganic layer has a thickness of 5 nm to 4 μm.

4. The flexible laminate according to claim 1, wherein the adhesive resin layer comprises at least one selected from the group consisting of polyvinyl alcohol resin, polyvinyl acetal resin and ethylene-based ionomer resin.

5. The flexible laminate according to claim 1, wherein the adhesive resin layer has a thickness of 0.3 μm to 500 μm.

6. The flexible laminate according to claim 1, wherein the peel strength between the adhesive resin layer and the barrier layer is 0.2 N / 10 mm or more.

7. The flexible laminate according to claim 6, wherein said barrier layer comprises at least one inorganic layer, and said adhesive resin layer and said inorganic layer are adjacent to each other.

8. The flexible laminate of claim 1, wherein said barrier layer comprises two or more inorganic layers.

9. The flexible laminate according to claim 1, having a total light transmittance of 87% or more.

10. A solar cell module comprising the flexible laminate of claim 1.

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