Electrolyte sheet for electrochromic device, electrochromic device, and method for producing electrolyte sheet for electrochromic device

Abstract

To provide an electrolyte sheet for an electrochromic device or the like capable of suppressing a short circuit caused by contact between electrodes of the electrochromic device even when an external pressure is applied to the electrochromic device.SOLUTION: An electrolyte sheet for an electrochromic device, comprising a crosslinked resin sheet holding an electrolyte composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrolyte sheet for an electrochromic device, an electrochromic device, and a method for manufacturing an electrolyte sheet for an electrochromic device. [Background technology]

[0002] In an electrochromic device, a voltage is applied to an electrochromic layer via a pair of electrodes, causing the device to develop a color. For example, Patent Document 1 discloses that a cured product of an electrolyte composition is used as a gel electrolyte for an electrochromic element in order to prevent optical distortion due to deformation of the gel electrolyte. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2022-139439 Summary of the Invention [Problem to be solved by the invention]

[0004] When constructing an electrochromic device as a flexible display device, it is desirable that the electrolyte layer used in the electrochromic element has excellent resistance to deformation, such as flexibility and stretchability, and is unlikely to cause short circuits due to contact between electrodes even when locally pressurized.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide an electrolyte sheet for an electrochromic device, etc., which can prevent electrodes of an electrochromic device from coming into contact with each other and causing a short circuit, even when an external pressure is applied to the electrochromic device. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that the above-mentioned problems can be solved by an electrolyte sheet for an electrochromic device, which includes a crosslinked resin sheet that holds an electrolyte composition, and have thus completed the present invention.

[0007] That is, this embodiment includes the following aspects. [1] a cross-linked resin sheet that holds an electrolyte composition; Be transparent, Electrolyte sheets for electrochromic devices. [2] The crosslinked resin sheet swells 1.5 to 7.0 times in acetone. [1] The electrolyte sheet for an electrochromic device according to [1]. [3] Tensile elongation is 50 to 2000%. The electrolyte sheet for an electrochromic device according to [1] or [2]. [4] The electrolyte composition includes an electrochromic compound. The electrolyte sheet for an electrochromic device according to any one of [1] to [3]. [5] The electrochromic compound comprises viologen, diacetylbenzene, dimethyl terephthalate, or diethyl 4,4'-biphenyldicarboxylate; [4] The electrolyte sheet for an electrochromic device according to [4]. [6] The crosslinked resin sheet contains a (meth)acrylic acid ester copolymer. The electrolyte sheet for an electrochromic device according to any one of [1] to [5]. [7] The electrolyte composition contains an ionic liquid or an inorganic salt. The electrolyte sheet for an electrochromic device according to any one of [1] to [6]. [8] The electrolyte composition contains an organic solvent. The electrolyte sheet for an electrochromic device according to any one of [1] to [7]. [9] the electrolyte composition comprises a redox compound; The electrolyte sheet for an electrochromic device according to any one of [1] to [8].

[10] The thickness of the electrolyte sheet for electrochromic devices is 75 μm or more. The electrolyte sheet for an electrochromic device according to any one of [1] to [9].

[11] An electrochromic device comprising the electrolyte sheet for an electrochromic device according to any one of [1] to

[10] .

[12] a swelling step of swelling the crosslinked resin sheet with a swelling solvent; an electrolyte composition impregnation step of impregnating the swollen crosslinked resin sheet with an electrolyte composition; and a solvent removal step of removing the swelling solvent from the crosslinked resin sheet. The method for producing an electrolyte sheet for an electrochromic device according to any one of [1] to

[10] . [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an electrolyte sheet for an electrochromic device, which can prevent electrodes of an electrochromic device from coming into contact with each other and causing a short circuit, even when an external pressure is applied to the electrochromic device. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a cross-sectional view showing an example of the configuration of a device. [Figure 2] 1 is a graph showing the results of an example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the spirit of the present invention. In the drawings, the same elements are given the same reference numerals, and redundant explanations will be omitted. Furthermore, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0011] 1. Electrolyte sheets for electrochromic devices The electrolyte sheet for an electrochromic device of this embodiment (hereinafter also simply referred to as "electrolyte sheet") includes a crosslinked resin sheet that holds an electrolyte composition. The crosslinked resin sheet is a sheet in which polymer chains are three-dimensionally crosslinked by covalent or non-covalent bonds, and voids exist between the three-dimensionally crosslinked polymer chains. Such a crosslinked resin sheet has superior flexibility and stretchability compared to simple resin films and is less likely to break when pulled horizontally or in any direction. Furthermore, the crosslinked resin sheet itself is a solid sheet and has superior mechanical strength compared to an electrolyte gel, which cannot exist without a dispersion medium. Therefore, it functions as a separator that separates electrodes even when the electrodes are brought close to each other due to external pressure in the thickness direction. By holding the electrolyte composition in such a crosslinked resin sheet, the electrolyte sheet of this embodiment has excellent deformation durability.

[0012] The electrolyte sheet of this embodiment is used in an electrochromic device in which coloring changes depending on whether or not a voltage is applied. In a display device in which pixels are arranged on a plane, electrodes are arranged above and below the pixels, such as an electrochromic layer, in the thickness direction, and the pixels and electrolyte sheet are sandwiched between the pair of electrodes. Therefore, the electrolyte sheet is sufficiently transparent to visible light so that light emitted from the pixels can be extracted.

[0013] Furthermore, electrochromic devices in which the electrolyte sheet of the present embodiment can be used include, but are not limited to, electronic paper and light-control glass. In the case of electronic paper, when characters or the like are written on it, external pressure is applied to a specific area with a finger or a pen. Furthermore, when it is folded for use like paper, external pressure is applied to the folded area. In this way, electronic paper can be deformed by the application of external pressure. Furthermore, in the case of light-control glass, when it is used in a place where the temperature changes greatly, such as a window in a building, deformation due to temperature changes can occur. The electrolyte sheet of the present embodiment has excellent durability to deformation as described above, and is therefore suitable for use in electrochromic devices in which deformation can occur, such as these.

[0014] Furthermore, since the electrolyte sheet of this embodiment is sufficiently transparent to visible light as described above, it is also suitable for use in displays. Since the electrolyte sheet of this embodiment has excellent durability to deformation as described above, it is suitable for use in flexible displays, which, among various displays, must not lose their display function even when bent or deformed. Flexible displays are not particularly limited, but examples include electrochromic devices such as electronic paper. For example, when writing characters or the like on electronic paper, external pressure is applied to a specific area with a finger or pen. Furthermore, when electronic paper is folded for use, external pressure is applied to the folded area, just like paper.

[0015] The tensile elongation of the electrolyte sheet at room temperature is preferably 50 to 2000%, 60 to 1500%, 70 to 1000%, 80 to 750%, 90 to 500%, 100 to 300%, 100 to 200%, or 100 to 150%. Having a tensile elongation within the above range tends to enable the electrolyte sheet to be used in environments where it is more likely to be stretched. The tensile elongation is the maximum elongation when the electrolyte sheet is stretched until it breaks, and can be measured, for example, in accordance with JIS C 2151.

[0016] In this embodiment, the tensile elongation of the electrolyte sheet is measured when the electrolyte sheet is stretched until it breaks, as an index for evaluating the deformation durability of the electrolyte sheet. In this regard, it is expected that when the electrolyte sheet is actually used, the electrolyte sheet will not be stretched until it breaks. However, if the tensile elongation measured when the electrolyte sheet is stretched until it breaks falls within a predetermined range, it can be said that the electrolyte sheet tends to be usable in an environment where it is more likely to be stretched.

[0017] The tensile elongation of the electrolyte sheet of this embodiment, when stretched to breakage, can be adjusted by changing the structure or composition of the electrolyte sheet, for example, by adjusting the crosslink density of the crosslinked resin sheet.

[0018] The transmittance of the electrolyte sheet of this embodiment in the thickness direction to visible light (light with a wavelength of 400 to 800 nm) is preferably 50% or more, 50 to 100%, 60 to 100%, 70 to 100%, or 80 to 100%. When the electrolyte sheet has a visible light transmittance in the thickness direction within the above range, when the electrolyte sheet is used in an electrochromic device, the color development of the device tends to be further improved. Here, "having transparency" means, for example, that the transmittance to visible light is 50% or more.

[0019] The thickness of the electrolyte sheet of this embodiment is preferably 75 μm or more, 75 to 200 μm, 80 to 175 μm, or 85 to 150 μm. When the thickness of the electrolyte sheet is within the above range, it tends to be possible to achieve both deformation durability and transparency.

[0020] Each component of the electrolyte sheet will be described in detail below.

[0021] 1.1.Cross-linked resin sheet The crosslinked resin sheet of this embodiment can be said to be the base material of the electrolyte sheet of this embodiment, and holds an electrolyte composition, which will be described later, in the voids between the three-dimensionally crosslinked polymer chains.

[0022] The resin constituting the crosslinked resin sheet is not particularly limited, but examples thereof include (meth)acrylic acid ester copolymers. In the crosslinked resin sheet, (meth)acrylic acid ester copolymers may be bonded to each other via crosslinkable functional groups such as hydroxyl groups and epoxy groups possessed by the copolymers, or the crosslinkable functional groups possessed by the copolymers may be bonded via any curing agent. Alternatively, a three-dimensionally crosslinked (meth)acrylic acid ester copolymer may be obtained by using a monomer having a difunctional or higher polymerizable double bond that serves as a crosslinking point during the polymerization reaction.

[0023] The (meth)acrylic acid ester monomer constituting the (meth)acrylic acid ester copolymer is not particularly limited, and examples thereof include alkyl (meth)acrylates having a linear or branched alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, amyl, isoamyl, hexyl, heptyl, cyclohexyl, 2-ethylhexyl, octyl, isooctyl, nonyl, isononyl, decyl, isodecyl, undecyl, lauryl, tridecyl, tetradecyl, stearyl, octadecyl, and dodecyl. These alkyl (meth)acrylates may be used alone or in combination of two or more.

[0024] Furthermore, the monomer component other than the alkyl (meth)acrylate is not particularly limited, but examples thereof include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 1-hydroxypropyl (meth)acrylate, 2 ... Examples of suitable monomers include hydroxyl group-containing monomers such as hydroxydecyl, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; sulfonic acid group-containing monomers such as styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; phosphoric acid group-containing monomers such as 2-hydroxyethylacryloylphosphate; and epoxy group-containing monomers such as glycidyl (meth)acrylate. These other monomers may be used alone or in combination of two or more.

[0025] Specific examples of the (meth)acrylic acid ester copolymer include a (meth)acrylic acid ester copolymer containing an alkyl (meth)acrylate and a carboxyl group-containing monomer, a (meth)acrylic acid ester copolymer containing an alkyl (meth)acrylate and a hydroxyl group-containing monomer, and a (meth)acrylic acid ester copolymer containing an alkyl (meth)acrylate, a hydroxyl group-containing monomer, and an epoxy group-containing monomer. In these (meth)acrylic acid ester copolymers, polymers may be crosslinked by the carboxyl group, hydroxyl group, or epoxy group.

[0026] The curing agent that bonds the crosslinkable functional groups together is not particularly limited, but examples thereof include isocyanate compounds, epoxy compounds, and amine compounds. Among these, isocyanate compounds are preferred. These curing agents may be used alone or in combination of two or more.

[0027] The isocyanate compound is not particularly limited, but examples thereof include aromatic diisocyanates such as tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, and xylylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate and methylene bis(4-cyclohexyl isocyanate); and aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate. These isocyanate compounds may be used alone or in combination of two or more. Among these, a polyfunctional isocyanate compound having two or more functionalities is preferred as the curing agent.

[0028] The content of other additives is not particularly limited, but is, for example, 0.1 to 5.0 mass % relative to the total amount of the crosslinked resin sheet. The content of curing agent is not particularly limited, but is, for example, 0.1 to 5.0 mass % relative to the total amount of the crosslinked resin sheet.

[0029] The thickness of the crosslinked resin sheet is preferably 75 μm or more, 75 to 200 μm, 80 to 175 μm, or 85 to 150 μm. When the thickness of the crosslinked resin sheet is within the above range, it tends to be possible to achieve both deformation durability and transparency.

[0030] The crosslinked resin sheet preferably swells 1.5 to 7.0 times in acetone, preferably 2.0 to 6.5 times, more preferably 2.5 to 6.0 times, and even more preferably 2.5 to 5.5 times. In one example of electrolyte sheet production, as will be described in detail later, the crosslinked resin sheet is swelled with a swelling solvent such as acetone, and then an electrolyte composition is impregnated into the crosslinked resin sheet, causing the crosslinked resin sheet to retain the electrolyte composition. The swelling solvent is then removed from the crosslinked resin sheet. In this regard, swelling the crosslinked resin sheet by 1.5 times or more in a swelling solvent such as acetone tends to facilitate the permeation of the electrolyte composition into the crosslinked resin sheet. Furthermore, if the crosslinked resin sheet swells too much in a swelling solvent such as acetone, the crosslinked structure in the crosslinked resin sheet may be destroyed, or the crosslinked resin sheet may lose its original shape. Furthermore, removing the swelling solvent from the crosslinked resin sheet may take time or require high temperatures. In this regard, when the crosslinked resin sheet is swelled by 7.0 times or less in a swelling solvent such as acetone, the above-mentioned problems associated with excessive swelling tend to be less likely to occur.

[0031] The swelling property of the crosslinked resin sheet can be changed by adjusting the composition and crosslink density of the crosslinked resin sheet. For example, by increasing the content of monomers having functional groups capable of forming crosslinks, such as hydroxyl groups, in the resin of the crosslinked resin sheet, the crosslink density increases and the swelling property decreases.

[0032] In this embodiment, unless otherwise specified, the swelling property is a value measured at room temperature (25° C.).

[0033] In this embodiment, acetone is used as the swelling solvent for measuring the swelling property of the crosslinked resin sheet. In this regard, it is also conceivable that, in some cases, an electrolyte sheet may be produced by swelling the crosslinked resin sheet using a swelling solvent other than acetone. However, even if the swelling solvent used to swell the crosslinked resin sheet is not acetone, if the swelling property measured using acetone falls within a predetermined range, it can be said that each component of the electrolyte sheet can easily penetrate into the crosslinked resin sheet and problems associated with excessive swelling are less likely to occur.

[0034] In this embodiment, 25°C is used as a reference value for measuring the swelling property of the crosslinked resin sheet. Here, 25°C is an example of the temperature at which the crosslinked resin sheet is swelled when an electrolyte sheet is actually manufactured. Depending on the environment in which the electrolyte sheet is manufactured, it is conceivable that the crosslinked resin sheet may be swelled at a temperature higher or lower than 25°C. However, even if the temperature at which the crosslinked resin sheet is swelled is not 25°C but is higher or lower than this, if the swelling property measured based on 25°C satisfies a predetermined range, it can be said that each component of the electrolyte sheet can easily penetrate into the crosslinked resin sheet and problems associated with excessive swelling are less likely to occur.

[0035] The crosslinked resin sheet preferably has a visible light transmittance in the thickness direction of 50% or more, 50 to 100%, 60 to 100%, 70 to 100%, or 80 to 100%. When the crosslinked resin sheet has a visible light transmittance in the thickness direction within the above range, the color development of an electrochromic device tends to be improved when the electrolyte sheet is used in the device.

[0036] The Young's modulus of the crosslinked resin sheet at room temperature is preferably 2.0 MPa or less, 0.0 to 2.0 MPa, 0.1 to 1.5 MPa, or 0.2 to 1.0 MPa. When the Young's modulus of the acrylic copolymer is within the above range, the deformation durability of the electrode 1 tends to be further improved. The Young's modulus can be measured, for example, in accordance with JIS K 7161.

[0037] Each component of the electrolyte composition that can be held by the crosslinked resin sheet will be described in detail below.

[0038] 1.1.1. Electrolytes The electrolyte composition of the present embodiment contains an electrolyte. This allows a voltage to be applied via electrodes in a device including an electrolyte sheet. The electrolyte is not particularly limited, but examples thereof include inorganic ion salts such as alkali metal salts and alkaline earth metal salts; and quaternary ammonium salts.

[0039] More specifically, examples of the electrolyte include alkali metal salts of Li, Na, and K such as LiClO4, LiSCN, LiBF4, LiAsF6, LiCF3SO3, LiPF6, LiI, LiBr, Li(CF3SO2)2N, NaI, NaSCN, NaClO4, NaBF4, NaAsF6, KSCN, and KCl; quaternary ammonium salts such as (CH3)4NBF4, (C2H5)4NBF4, (n-C4H9)4NBF4, (n-C4H9)4NPF6, (C2H5)4NBr, (C2H5)4NClO4, and (n-C4H9)4NClO4; and 1-butyl-3-methylimidazolium tetrafluoroborate. Examples of the electrolyte include imidazolium compounds such as 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide, pyrrolidinium compounds such as 1-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide, piperidinium compounds such as 1-butyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide, and phosphonium compounds such as methyltributylphosphonium bis(trifluoromethylsulfonyl)imide. The electrolyte may be used alone or in combination of two or more.

[0040] Alternatively, examples of the electrolyte include ionic liquids and inorganic salts. Examples of ionic liquids include quaternary ammonium salts, imidazolium compounds, pyrrolidinium compounds, pyridinium compounds, piperidinium compounds, and phosphonium compounds. Examples of inorganic salts include inorganic salts other than ionic liquids, such as alkali metal salts. Note that an ionic liquid is a salt that exists in liquid form under an environment of 1 atmosphere and 100°C or less.

[0041] The content of the electrolyte is preferably 2.0 to 10.0 mass%, 2.5 to 9.0 mass%, or 3.0 to 8.0 mass% relative to the total amount of the electrolyte composition. When the content of the electrolyte is within the above range, the conductivity of the electrolyte sheet is improved, and in a device including the electrolyte sheet, the voltage required to make the device function is reduced, tending to be excellent in energy saving. The "device functions" in the following cases, for example. That is, when a device includes an electrolyte sheet containing an electrochromic compound and electrodes, and the device changes color when a voltage is applied to the device via the electrodes, the device can be said to function.

[0042] The content of the electrolyte is preferably 60 to 99 mass%, 70 to 98 mass%, or 80 to 98 mass%, based on the total amount of the electrolyte composition excluding the organic solvent. When the content of the electrolyte is within the above range, the conductivity of the electrolyte sheet is improved, and in a device including the electrolyte sheet, the voltage required to operate the device is reduced, tending to be excellent in energy saving.

[0043] 1.1.2. Electrochromic compounds The electrolyte composition of this embodiment may contain an electrochromic compound. Examples of the electrochromic compound include viologens such as heptyl viologen, polypyrrole, tetrathiofulvalene, pasophenanthroline complexes, polypyrrole, polyacetylene, styryl compounds, rare earth phthalocyanines, anthraquinone, pyrazoline, bipyridinium compounds such as 1,1'-diheptyl-4,4'-bipyridinium dibromide, diacetylbenzene, 4,4'-biphenyldicarboxylate diethyl, and terephthalic acid derivatives such as dimethyl terephthalate. The electrochromic compounds may be used alone or in combination.

[0044] The content of the electrochromic compound is preferably 0.10 to 5.00 mass%, 0.15 to 2.50 mass%, or 0.20 to 1.00 mass%, relative to the total amount of the electrolyte composition. When the content of the electrochromic compound is within the above range, the color development property of the electrolyte sheet tends to be improved.

[0045] The content of the electrochromic compound is preferably 1.0 to 20.0 mass%, 1.5 to 15.0 mass%, or 2.0 to 10.0 mass%, relative to the total amount of the electrolyte composition excluding the organic solvent. When the content of the electrochromic compound is within the above range, the color development property of the electrolyte sheet tends to be improved.

[0046] 1.1.3. Organic solvents The electrolyte composition of this embodiment may contain an organic solvent. Examples of organic solvents include protic solvents, such as water and alcohol, which have hydrogen atoms bonded to oxygen or nitrogen and can donate protons, and aprotic solvents, such as N,N-dimethylformamide (DMF), acetone, acetonitrile, and propylene carbonate, which do not have such hydrogen atoms and therefore do not easily donate protons. Of these, aprotic solvents are preferred. The organic solvents may be used alone or in combination of two or more.

[0047] Aprotic solvents include, but are not limited to, DMF, acetone, acetonitrile, propylene carbonate, as well as, for example, hexane, benzene, toluene, 1,4-dioxane, chloroform, diethyl ether, N-methylpyrrolidone, dichloromethane, tetrahydrofuran, ethyl acetate, and dimethyl sulfoxide (DMSO).

[0048] The content of the organic solvent relative to the total amount of the electrolyte composition is not particularly limited, but is, for example, 1.0 to 99.0 mass %, 5.0 to 97.5 mass %, or 10.0 to 95.0 mass %.

[0049] 1.1.4. Redox Compounds The electrolyte composition of this embodiment may contain a redox compound. The redox compound is a compound that promotes and stabilizes the reaction when an electrochromic compound that changes color upon application of a voltage is oxidized or reduced to change color. The redox compound is also a compound that promotes and stabilizes the reaction when the electrochromic compound is oxidized or reduced to lose its color. By including a redox compound in the electrolyte composition of this embodiment, the redox reaction for changing color in the electrochromic compound is facilitated, and the coloring of the electrolyte sheet tends to be achieved at a lower voltage, which is preferable.

[0050] The redox compound is not particularly limited, but examples thereof include oligothiophenes; phenazine compounds such as 5,10-dihydro-5,10-dimethylphenazine and 5,10-dihydro-5,10-diisopropylphenazine; pyrazoline compounds such as 1-phenyl-2-pyrazoline; ethanedione compounds; tetrazolium salts; formazan compounds; phenoxazine compounds; acridine compounds; diphenylethanedione compounds; metallocene compounds such as ferrocene, tetra-t-butylferrocene, titanocene, and cobaltocene; phenylenediamine compounds such as N,N',N,N'-tetramethyl-p-phenylenediamine; and phenothiazine compounds. The redox compounds may be used alone or in combination. Among these, metallocene compounds are preferred from the viewpoint of achieving color development of the electrolyte sheet at a lower voltage, and ferrocene compounds having Fe as the central metal are more preferred.

[0051] The ferrocene compound has a ferrocene skeleton, and the two cyclopentadienyl rings may each independently have 1 to 5 monovalent alkyl groups having 1 to 5 carbon atoms. The ferrocene compound is not particularly limited, but examples thereof include ferrocene, methylferrocene, 1,1'-dimethylferrocene, decamethylferrocene, ethylferrocene, propylferrocene, butylferrocene, and pentylferrocene.

[0052] The content of the redox compound is preferably 0.01 to 5.00 mass%, 0.02 to 2.50 mass%, or 0.03 to 1.00 mass%, relative to the total amount of the electrolyte composition. When the content of the redox compound is within the above range, coloring of the electrolyte sheet tends to be achieved at a lower voltage.

[0053] The content of the redox compound is preferably 0.1 to 10.0 mass%, 0.5 to 7.5 mass%, or 1.0 to 5.0 mass%, relative to the total amount of the electrolyte composition excluding the organic solvent. When the content of the redox compound is within the above range, coloring of the electrolyte sheet tends to be achieved at a lower voltage.

[0054] The ratio of the content of the redox compound to the content of the electrochromic compound (content of the redox compound / content of the electrochromic compound) is preferably 0.10 to 1.00, 0.15 to 0.75, or 0.20 to 0.50. When the ratio is within the above range, coloring of the electrolyte sheet tends to be achieved at a lower voltage.

[0055] 1.1.5. Other additives The electrolyte composition of this embodiment may or may not contain other additives. Examples of the other additives include a pH adjuster, a plasticizer, a leveling agent, a dispersant, a surfactant, and an antioxidant. When the electrolyte composition of this embodiment contains other additives, the content of the other additives is not particularly limited, but is, for example, 0.1 to 10.0 mass% relative to the total amount of the electrolyte composition.

[0056] 2. Manufacturing method of electrolyte sheet for electrochromic device The method for producing an electrolyte sheet for an electrochromic device according to this embodiment includes a swelling step of swelling a crosslinked resin sheet with a swelling solvent, an electrolyte composition impregnation step of impregnating the swollen crosslinked resin sheet with an electrolyte composition, and a solvent removal step of removing the swelling solvent from the crosslinked resin sheet. The electrolyte sheet produced by this method tends to have sufficient electrical conductivity and excellent deformation durability. Each step of the production method according to this embodiment will be described in detail below.

[0057] 2.1.Swelling process In the swelling step of this embodiment, the crosslinked resin sheet is swelled with a swelling solvent. By swelling the crosslinked resin sheet, the voids between the three-dimensionally crosslinked polymer chains become larger, so that the crosslinked resin sheet can easily retain the electrolyte composition in the electrolyte composition impregnation step described below.

[0058] The swelling solvent is not particularly limited as long as it can swell the crosslinked resin sheet, and examples thereof include acetone, water, and alcohols such as methanol. The swelling solvent may be used alone or in combination of two or more.

[0059] 2.2. Electrolyte composition impregnation process In the electrolyte composition impregnation step of this embodiment, the crosslinked resin sheet swollen in the swelling step is impregnated with the electrolyte composition. In the swollen crosslinked resin sheet, the voids between the three-dimensionally crosslinked polymer chains are large. Therefore, by impregnating the swollen crosslinked resin sheet with the electrolyte composition, the electrolyte composition can be easily retained in the voids. Furthermore, because the voids are large, a sufficient amount of the electrolyte composition can be retained.

[0060] The method for impregnating the electrolyte composition is not particularly limited, but examples thereof include a method of immersing a swollen crosslinked resin sheet in the electrolyte composition and a method of dropping the electrolyte composition onto a swollen crosslinked resin sheet.

[0061] 2.3. Solvent removal process In the solvent removal step of this embodiment, the swelling solvent is removed from the crosslinked resin sheet after the electrolyte composition impregnation step. This returns the crosslinked resin sheet to an unswollen state, reducing the voids between the three-dimensionally crosslinked polymer chains. The electrolyte composition present in the voids is then firmly held by the crosslinked resin sheet.

[0062] The method for removing the swelling solvent is not particularly limited, but examples thereof include a method of heating and drying a crosslinked resin sheet that holds an electrolyte composition and is swollen, and a method of blowing cold or hot air onto the crosslinked resin sheet to dry it.

[0063] 3. Devices The device of this embodiment includes the above-described electrolyte sheet for an electrochromic device. FIG. 1 is a cross-sectional view showing an example of the configuration of the device. As shown in FIG. 1, the device 1 may include a first electrode 10A, an electrolyte sheet for an electrochromic device 11 on the first electrode 10A, and a second electrode 10B on the electrolyte sheet for an electrochromic device 11. The first electrode 10A and the second electrode 10B are collectively referred to as electrodes 10.

[0064] The components of the device 1 other than the electrolyte sheet 11 will be described in detail below.

[0065] 3.1. Electrode When used in an electrochromic device, the electrode 10 is preferably transparent to visible light. For example, the transmittance of the electrode 10 to visible light in the thickness direction is preferably 50% or more, 50 to 100%, 60 to 100%, 70 to 100%, or 80 to 100%. Alternatively, the transmittance to light with a wavelength of 550 nm is preferably 50% or more, 50 to 100%, 60 to 100%, 70 to 100%, or 80 to 100%. The transmittance can be measured using an ultraviolet-visible spectrophotometer.

[0066] The thickness of the electrode 10 is not particularly limited, but is, for example, 10 μm or less, and is 0.05 to 10 μm.

[0067] The first electrode 10A and the second electrode 10B may have the same composition or different compositions.

[0068] The electrode 10 may contain a conductive material and a binder. Each component that the electrode 10 may contain will be described in detail below.

[0069] 3.1.1.Conductive Materials The conductive material that may be contained in the electrode 10 of this embodiment is not particularly limited, but examples thereof include metals such as copper, silver, gold, and aluminum; transparent inorganic conductors such as fluorine-doped tin oxide (FTO), indium tin oxide (ITO), antimony-doped tin oxide (ATO), indium zinc oxide (IZO), indium oxide, and tin oxide; and organic conductors such as molecular conductors containing tetrathiafulvalene as a constituent component, and composites containing poly(3,4-ethylenedioxythiophene) and polystyrenesulfonic acid.

[0070] The content of the conductive material is preferably 60 to 100 mass %, 70 to 100 mass %, or 80 to 100 mass % relative to the total amount of electrode 10. When the content of the conductive material is within the above range, the conductivity of electrode 10 tends to be improved.

[0071] Binder The electrode 10 may or may not contain a binder. The binder is not particularly limited as long as it is a material that has sufficient transparency to visible light, and examples thereof include matrix resins. The matrix resin is not particularly limited, and examples thereof include epoxy copolymers, urethane copolymers, and nylon copolymers.

[0072] The content of the binder is not particularly limited, but is, for example, 1 to 10 mass % relative to the total amount of the electrode 10. [Example]

[0073] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited to the following examples. The experiments in the examples and comparative examples were carried out at room temperature (25°C) under 1 atmosphere unless otherwise specified.

[0074] 1. Electrolyte Sheet Fabrication [Example 1] A crosslinked resin sheet made of a (meth)acrylic acid ester copolymer (manufactured by Osaka Organic Chemical Industry Ltd., product name SUAVE-15F100) with a thickness, length, and width of 0.1 mm, 20 mm, and 20 mm, respectively, was immersed in 10 mL of acetone for 10 minutes to obtain a swollen crosslinked resin sheet.

[0075] An electrolyte composition was obtained by dissolving and dispersing 15 mg of heptyl viologen, 5 mg of dimethylferrocene, and 300 mg of 1-butyl-3-methylimidazolium tetrafluoroborate in 5 mL of propylene carbonate. A swollen crosslinked resin sheet was immersed in the electrolyte composition for 10 minutes, allowing the electrolyte composition to penetrate the swollen crosslinked resin sheet and replace it with acetone. The crosslinked resin sheet was then dried at room temperature for 30 minutes to volatilize the acetone, thereby obtaining the electrolyte sheet of Example 1.

[0076] [Comparative Example 1] A mixture was obtained by mixing and stirring 50 mg of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) (manufactured by Sigma-Aldrich, product name 427160), 15 mg of heptyl viologen, 5 mg of dimethylferrocene, 300 mg of 1-butyl-3-methylimidazolium tetrafluoroborate, and 10 mL of acetone. This mixture was molded on a glass plate so that the length and width were 20 mm and 20 mm, respectively, to obtain an electrolyte sheet of Comparative Example 1. Note that in this electrolyte sheet, the PVDF-HFP was not crosslinked.

[0077] Comparative Example 2 An electrolyte sheet of Comparative Example 2 was obtained in the same manner as Comparative Example 1, except that methyl methacrylate polymer (PMMA) (product name M0088, manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of PVDF-HFP and 5 mL of propylene carbonate was added. Note that in this electrolyte sheet, the PMMA was not crosslinked.

[0078] The materials used in each example are as follows: Heptyl viologen: Tokyo Chemical Industry Co., Ltd., D1593 (product name) Dimethylferrocene: Tokyo Chemical Industry Co., Ltd., D1273 (product name) 1-Butyl-3-methylimidazolium tetrafluoroborate: B2195 (product name), manufactured by Tokyo Chemical Industry Co., Ltd. Propylene carbonate: Tokyo Chemical Industry Co., Ltd., P0525 (product name) Acetone: Kanto Chemical Co., Ltd., 01026-80 (product name)

[0079] [Transparency measurement] The electrolyte sheet of each example was sandwiched between ITO glass sheets to prepare a sample for transparency measurement. First, as a baseline measurement, the transmittance in the stacking direction (thickness direction) of a control sample made by stacking two sheets of ITO glass identical to the above ITO glass sheets was measured using a UV-visible spectrophotometer (Shimadzu Corporation, product name UV-1900i). Next, the transmittance in the stacking direction (thickness direction) of a sample made by sandwiching the electrolyte sheet of each example between ITO glass sheets was measured using the same UV-visible spectrophotometer. The transmittance of the electrolyte sheet of each example was then calculated from the transmittance of the sample and the transmittance of the control sample. Figure 2 shows the transmittance of the electrolyte sheet of each example.

[0080] [Color measurement] The electrolyte sheet of each example was sandwiched between ITO glass sheets, and a voltage of 1.0 V was applied to evaluate whether or not coloration occurred. As a result, the electrolyte sheets of each example were visually colored. In other words, all of them showed good coloration.

[0081] [Swelling measurement] The electrolyte sheet of each example was immersed in acetone for 5 minutes, and then the volume change rate was measured. The measurement results were evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1. The volume change rate was calculated as follows: The volume change rate of the electrolyte sheet of Example 1 was 450%. Volume change rate (%) = (volume after immersion - volume before immersion) / volume before immersion x 100 [Evaluation criteria] A: The electrolyte sheet swells and does not dissolve. B: The electrolyte sheet dissolves.

[0082] [Tensile elongation measurement] Next, the electrolyte sheet of each example was stretched laterally until the sheet broke. The tensile elongation at the time of breakage was then measured. Specifically, one end of the electrolyte sheet of each example was fixed onto a glass plate with cellophane tape. The other end of the electrolyte sheet of each example was then stretched until it broke. The tensile elongation was then determined. The measurement results are shown in Table 1. The tensile elongation can be calculated using the following formula. The electrolyte sheet of Comparative Example 2 was in a gel state, and the tensile elongation could not be measured. Tensile elongation (%) = (length from one end to the other end (in the horizontal direction) of the electrolyte sheet just before it broke - original length of the electrolyte sheet in the horizontal direction) / original length of the electrolyte sheet in the horizontal direction × 100

[0083] [Table 1]

[0084] 2. Evaluation 2.1.Distortion resistance For each example of electrolyte sheet, the tensile elongation at the time of sheet breakage was evaluated based on the following evaluation criteria. The evaluation results are shown in Table 2. Electrolyte sheets with an evaluation of A can be said to be usable even in environments where the electrolyte sheet is significantly deformed. [Evaluation criteria] A: The tensile elongation at the time of sheet breakage is 100% or more. B: The tensile elongation at the time when the sheet broke was 50% or more and less than 100%. C: The tensile elongation at the time of sheet breakage was less than 50%, or the sheet was in a gel or liquid state, making it impossible to measure the tensile elongation.

[0085] [Table 2]

[0086] 2.2. Crush test The ITO-coated side of the ITOPET was attached to both sides of the electrolyte sheet to fabricate a device. The ITOPET is a polyethylene terephthalate substrate on which an ITO film is formed. First, the resistance of each device was measured without a weight placed on it.

[0087] Then, a weight of 10g, 20g, 300g, or 1000g was placed on each device. The resistance of the device was measured in this state. The resistance of the device without the weight was set to 100%, and the percentage of the resistance of the device with the weight placed was calculated. The calculation results are shown in Table 3. A decrease in resistance indicates a short circuit within the device.

[0088] [Table 3]

[0089] A device was fabricated using the electrolyte sheet of Comparative Example 1 in the same manner as in Example 1, and a crushing test was carried out. As a result, the resistance value became less than 100% when a 10 g weight was placed on it. [Explanation of symbols]

[0090] 1...Device, 10...Electrode, 11...Electrolyte sheet for electrochromic device

Claims

1. a cross-linked resin sheet that holds an electrolyte composition; Be transparent, Electrolyte sheets for electrochromic devices.

2. The crosslinked resin sheet swells 1.5 to 7.0 times in acetone.

2. The electrolyte sheet for an electrochromic device according to claim 1.

3. Tensile elongation is 50 to 2000%.

2. The electrolyte sheet for an electrochromic device according to claim 1.

4. The electrolyte composition includes an electrochromic compound.

2. The electrolyte sheet for an electrochromic device according to claim 1.

5. The electrochromic compound comprises viologen, diacetylbenzene, dimethyl terephthalate, or diethyl 4,4'-biphenyldicarboxylate; The electrolyte sheet for an electrochromic device according to claim 4 .

6. The crosslinked resin sheet contains a (meth)acrylic acid ester copolymer.

2. The electrolyte sheet for an electrochromic device according to claim 1.

7. The electrolyte composition contains an ionic liquid or an inorganic salt.

2. The electrolyte sheet for an electrochromic device according to claim 1.

8. The electrolyte composition contains an organic solvent.

2. The electrolyte sheet for an electrochromic device according to claim 1.

9. the electrolyte composition comprises a redox compound; 2. The electrolyte sheet for an electrochromic device according to claim 1.

10. The thickness of the electrolyte sheet for electrochromic devices is 75 μm or more.

2. The electrolyte sheet for an electrochromic device according to claim 1.

11. An electrochromic device comprising the electrolyte sheet for an electrochromic device according to any one of claims 1 to 10.

12. a swelling step of swelling the crosslinked resin sheet with a swelling solvent; an electrolyte composition impregnation step of impregnating the swollen crosslinked resin sheet with an electrolyte composition; and a solvent removal step of removing the swelling solvent from the crosslinked resin sheet. A method for producing the electrolyte sheet for an electrochromic device according to any one of claims 1 to 10.

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