Polymer film

Abstract

One embodiment of this polymer film contains: a crosslinked polymer in which a carbonyl-group-containing polymer is crosslinked by a crosslinking agent composed of a dihydrazide compound; and a composite of polyethylene dioxythiophene and polystyrenesulfonic acid. The carbonyl-group-containing polymer may have a polyvinyl alcohol skeleton.

Description

polymer membrane

[0001] The present invention relates to a polymer membrane. This application claims priority to Japanese Patent Application No. 2023-222796, filed on December 28, 2023, the contents of which are incorporated herein by reference.

[0002] A polymer film with good electrical conductivity and heat resistance can be formed by applying an aqueous dispersion of a composite of polyethylenedioxythiophene and polystyrene sulfonic acid (hereinafter sometimes referred to as "PEDOT / PSS") and then removing the water from the coating. For this reason, aqueous dispersions of PEDOT / PSS are used in a wide range of applications.

[0003] Patent Document 1 describes a solid electrolytic capacitor having a layered structure including an anode, a dielectric, a cathode, and a polymer outer layer. Patent Document 1 also describes a polymer outer layer including polystyrene sulfonic acid and poly(3,4-ethylenedioxythiophene). Patent Document 1 also describes forming the polymer outer layer by applying a crosslinker to the capacitor body, then applying a dispersion of a conjugated polymer, and removing the dispersant.

[0004] Furthermore, Patent Document 2 describes a method for producing a solid electrolytic capacitor, which sequentially includes a first step of forming a first conductive polymer layer, a second step of applying a coating solution containing at least one selected from aromatic sulfonic acids or salts thereof having both a carboxyl group and a hydroxyl group or two carboxyl groups in one molecule to the first conductive polymer layer and drying the coating solution, and a third step of forming a second conductive polymer layer.

[0005] Japanese Patent No. 5592406 International Publication No. 2014 / 087617

[0006] Although polymer films formed using conventional aqueous dispersions of PEDOT / PSS have good electrical conductivity and heat resistance, they have insufficient water resistance, which may limit the applications of such films.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a polymer film having good water resistance that can be produced using an aqueous dispersion of PEDOT / PSS.

[0008] In order to solve the above problems, the following means is provided: A polymer membrane according to one aspect of the present invention includes a crosslinked polymer in which a polymer having a carbonyl group is crosslinked with a crosslinking agent made of a dihydrazide compound, and a composite of polyethylenedioxythiophene and polystyrenesulfonic acid.

[0009] The polymer film according to one embodiment of the present invention can be produced using an aqueous dispersion of PEDOT / PSS, and has excellent electrical conductivity and heat resistance, as well as good water resistance. Therefore, the polymer film according to one embodiment of the present invention can be preferably used in a wide range of applications.

[0010] The present inventors have conducted extensive research to solve the above problems and form a polymer film with good water resistance using an aqueous dispersion of PEDOT / PSS. As a result, they have found that a polymer film containing a crosslinked polymer having a crosslinked structure can be formed using an aqueous dispersion of PEDOT / PSS and a specific crosslinking agent, and have conceived the present invention. The present invention includes the following aspects.

[0011] [1] A polymer membrane comprising: a crosslinked polymer in which a polymer having a carbonyl group is crosslinked with a crosslinking agent comprising a dihydrazide compound; and a composite of polyethylenedioxythiophene and polystyrene sulfonic acid. [2] The polymer membrane according to [1], wherein the polymer having a carbonyl group has a polyvinyl alcohol skeleton.

[0012] [3] The polymer membrane according to [1] or [2], wherein the ratio of the structural units derived from the polymer having a carbonyl group to the total mass of the structural units derived from the polymer having a carbonyl group forming the crosslinked polymer and the composite is 70 mass% or less, and the ratio of the structural units derived from the crosslinking agent to the mass of the structural units derived from the polymer having a carbonyl group is 15 mass% or less.

[0013] [4] The polymer membrane according to [1] or [2], wherein the ratio of the structural units derived from the polymer having a carbonyl group to the total mass of the structural units derived from the polymer having a carbonyl group forming the crosslinked polymer and the composite is 30 mass% or less, and the ratio of the structural units derived from the crosslinking agent to the mass of the structural units derived from the polymer having a carbonyl group is 10 mass% or less.

[0014] [5] A composite of polyethylenedioxythiophene and polystyrenesulfonic acid includes a crosslinked polymer crosslinked by a crosslinking agent, and the crosslinking agent is —NH ２ A polymer membrane comprising a salt of an amine compound containing a total of four or more of one or two types of groups selected from the group consisting of —NH— groups and —NH— groups.

[0015] [6] A polymer membrane comprising a crosslinked polymer in which a composite of polyethylenedioxythiophene and polystyrenesulfonic acid is crosslinked by a crosslinking agent, wherein the crosslinking agent is a metal salt containing a metal cation having a valence of 2 or more. [7] The polymer membrane according to [6], wherein the crosslinking agent is calcium chloride.

[0016] The polymer membrane of this embodiment will be described in detail below. The materials, numerical ranges, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate changes can be made within the scope of the present invention.

[0017] [First embodiment] The polymer film of the first embodiment includes a crosslinked polymer in which a polymer having a carbonyl group is crosslinked with a crosslinking agent made of a dihydrazide compound, and a composite of polyethylenedioxythiophene and polystyrenesulfonic acid (PEDOT / PSS) represented by the following formula (1):

[0018]

[0019] (Crosslinked Polymer) The crosslinked polymer contained in the polymer film of this embodiment is obtained by crosslinking the carbonyl group of a polymer having a carbonyl group with the dihydrazide group of a dihydrazide compound, which is a crosslinking agent, through a crosslinking reaction. The crosslinked polymer has a three-dimensional network structure and has excellent water resistance, and holds the PEDOT / PSS contained in the polymer film, thereby imparting water resistance to the polymer film of this embodiment. The crosslinked polymer contained in the polymer film of this embodiment may be of only one type, or may be of two or more types.

[0020] Examples of polymers having a carbonyl group (—O—C(═O)R) that can be used to form a crosslinked polymer include water-soluble polymers having a carbonyl group, such as polyvinyl alcohol resins, polyacrylamide resins, polyethylene glycol resins, and cellulose resins.

[0021] Among these, it is preferable to use a polymer having a polyvinyl alcohol skeleton as the polymer having a carbonyl group. Crosslinked polymers in which a polymer having a polyvinyl alcohol skeleton is crosslinked with a crosslinking agent made of a dihydrazide compound have good water resistance. Therefore, polymer films containing crosslinked polymers in which a polymer having a polyvinyl alcohol skeleton is crosslinked have even better water resistance. Furthermore, an aqueous solution of a polymer having a polyvinyl alcohol skeleton can be easily mixed with an aqueous dispersion of PEDOT / PSS, allowing for efficient formation of a polymer film when produced by the production method described below. In particular, it is preferable to use a modified polyvinyl alcohol represented by the following formula (2), in which a carbonyl group is bonded to a polyvinyl alcohol skeleton. This is because it has good reactivity with a crosslinking agent made of a dihydrazide compound, making it easier to obtain a polymer film with better water resistance.

[0022] (In formula (2), n and m represent the number of repeating units, and n+m is 100 to 5000. R is a monovalent substituent.)

[0023] When a modified polyvinyl alcohol represented by formula (2) is used as the polymer having a carbonyl group (—O—C(═O)R), the average degree of polymerization represented by n+m in formula (2) can be 100 to 5,000, and preferably 300 to 3,500. When the average degree of polymerization (n+m) of the modified polyvinyl alcohol represented by formula (2) is 100 or more, a crosslinked polymer having better water resistance can be obtained, and a polymer film having better water resistance can be obtained. When the average degree of polymerization of the modified polyvinyl alcohol represented by formula (2) is 5,000 or less, it becomes easily mixed with an aqueous dispersion of PEDOT / PSS, and when a polymer film is produced by the production method described below, a polymer film can be efficiently formed.

[0024] The saponification degree [[n / (n+m)]×100] of the modified polyvinyl alcohol represented by formula (2) is preferably 95% to 99%. A saponification degree of 95% or higher improves the hydrophilicity of the modified polyvinyl alcohol represented by formula (2), allowing for the formation of an aqueous solution that is more easily mixed with an aqueous dispersion of PEDOT / PSS. Furthermore, a saponification degree of 99% or lower sufficiently enhances the hydrophobicity of the modified polyvinyl alcohol represented by formula (2) due to the presence of —O—C(═O)R groups. As a result, a polymer film with better water resistance is more likely to be obtained.

[0025] The modified polyvinyl alcohol represented by formula (2) preferably has a carbonyl group (-O-C(=O)R), for example, in which the monovalent substituent represented by R in formula (2) is any one selected from alkyl groups having 1 to 5 carbon atoms. R in formula (2) is particularly preferably a methyl group because it is a functional group that has good reactivity with the dihydrazide compound that is the crosslinking agent. In the present embodiment, the polymer having a carbonyl group (-O-C(=O)R) used as a material for forming the crosslinked polymer may be of only one type, or may be of two or more types.

[0026] As the crosslinking agent made of a dihydrazide compound used in forming the crosslinked polymer, known dihydrazide compounds can be used, such as adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide, and 7,11-octadecadiene-1,18-dicarbohydrazide. Among these, as the crosslinking agent made of a dihydrazide compound, it is preferable to use adipic acid dihydrazide represented by the following formula (3) and / or 7,11-octadecadiene-1,18-dicarbohydrazide represented by the following formula (4), because they have good reactivity with polymers having carbonyl groups. In the present embodiment, the crosslinking agent made of a dihydrazide compound used as a material for forming the crosslinked polymer may be one type or two or more types.

[0027]

[0028] In this embodiment, for example, when modified polyvinyl alcohol represented by formula (2) is used as the polymer having a carbonyl group and adipic acid dihydrazide represented by formula (3) is used as the cross-linking agent made of a dihydrazide compound, a cross-linked polymer is formed as shown below. That is, a cross-linking reaction occurs between the carbonyl group of the modified polyvinyl alcohol represented by formula (2) and the dihydrazide group of the adipic acid dihydrazide represented by formula (3), and the modified polyvinyl alcohol represented by formula (2) is cross-linked by the adipic acid dihydrazide represented by formula (3), forming a cross-linked polymer containing water and a cross-linked structure represented by the following formula (5).

[0029]

[0030] In the polymer film of this embodiment, the ratio of the structural units derived from the polymer having a carbonyl group to the total mass of the structural units derived from the polymer having a carbonyl group forming the crosslinked polymer and PEDOT / PSS is preferably 70% by mass or less, more preferably 30% by mass or less. If the ratio of the structural units derived from the polymer having a carbonyl group is 70% by mass or less, this prevents the conductivity of the polymer film from being impaired due to an excessive proportion of structural units derived from the polymer having a carbonyl group. The ratio of the structural units derived from the polymer having a carbonyl group to the total mass is preferably 5% by mass or more, more preferably 10% by mass or more, since this ensures the content of the crosslinked polymer contained in the polymer film and makes it easier to obtain a polymer film with better water resistance.

[0031] In the polymer membrane of this embodiment, the ratio of structural units derived from the polymer having a carbonyl group to the total mass is preferably 70% by mass or less, and the ratio of structural units derived from the crosslinking agent to the mass of structural units derived from the polymer having a carbonyl group is preferably 15% by mass or less. Furthermore, it is more preferable that the ratio of structural units derived from the polymer having a carbonyl group is 30% by mass or less, and the ratio of structural units derived from the crosslinking agent is 10% by mass or less. When the ratio of structural units derived from the crosslinking agent is 15% by mass or less, the conductivity of the polymer membrane can be prevented from being impaired by the presence of many structural units derived from the crosslinking agent that do not form a crosslinked structure with the structural units derived from the polymer having a carbonyl group. The ratio of structural units derived from the crosslinking agent to the mass of structural units derived from the polymer having a carbonyl group is preferably 3% by mass or more, more preferably 5% by mass or more, since this ensures the content of crosslinked polymers contained in the polymer membrane and makes it easier to obtain a polymer membrane with better water resistance.

[0032] The content of PEDOT / PSS in the polymer film of this embodiment is preferably 30% by mass or more, and more preferably 60% by mass or more. This is because a polymer film with good conductivity is obtained when the content of PEDOT / PSS is 30% by mass or more. Furthermore, the content of PEDOT / PSS in the polymer film is preferably 85% by mass or less, and more preferably 75% by mass or less. This is because a polymer film with a sufficient amount of crosslinked polymer and good water resistance is more easily obtained when the content of PEDOT / PSS is 85% by mass or less.

[0033] The polymer membrane of this embodiment contains the crosslinked polymer described above and PEDOT / PSS represented by formula (1). In addition, one or more other components may be further contained as needed depending on the intended use of the polymer membrane. Examples of such other components include known crosslinking agents other than dihydrazide compounds, known polymers without carbonyl groups, etc. As known polymers without carbonyl groups, water-soluble or water-dispersible polymers can be preferably used, and specific examples thereof include sulfonated polyester resins.

[0034] (Method for Producing Polymer Film) The polymer film of this embodiment can be produced, for example, by the following method: A water dispersion of PEDOT / PSS, an aqueous solution of a polymer having a carbonyl group, an aqueous solution of a dihydrazide compound as a crosslinking agent, and other components as needed are mixed and stirred to produce a resin coating material.

[0035] When producing a resin paint, the order in which the aqueous dispersion of PEDOT / PSS, the aqueous solution of the polymer having a carbonyl group, and the aqueous solution of the dihydrazide compound as a cross-linking agent are mixed is not particularly limited. For example, all of the materials used in the resin paint may be mixed and stirred at the same time, or the resin paint may be produced by mixing the aqueous dispersion of PEDOT / PSS and the aqueous solution of the polymer having a carbonyl group to form a mixed liquid, and then mixing the mixed liquid with an aqueous solution of the dihydrazide compound as a cross-linking agent.

[0036] The concentrations of PEDOT / PSS in the aqueous dispersion of PEDOT / PSS used in producing the resin coating in this embodiment, the concentration of the polymer having a carbonyl group in the aqueous solution of the polymer having a carbonyl group, and the concentration of the dihydrazide compound in the aqueous solution of the dihydrazide compound are not particularly limited and can be set to concentrations that make mixing and stirring easy. The concentrations of PEDOT / PSS, the polymer having a carbonyl group, and the dihydrazide compound contained in the resin coating are set to concentrations that correspond to the proportion of PEDOT / PSS in the polymer film, the proportion of structural units derived from the polymer having a carbonyl group contained in the polymer film, and the proportion of structural units derived from the crosslinker, respectively.

[0037] The aqueous dispersion of PEDOT / PSS used in producing the resin coating can be one consisting of only PEDOT / PSS and water. The aqueous dispersion of PEDOT / PSS may contain, in addition to PEDOT / PSS and water, one or more of the other components described above. Specifically, the aqueous dispersion of PEDOT / PSS may contain PEDOT / PSS, water, and a sulfonated polyester resin, which is a polymer having no carbonyl groups.

[0038] Next, the resin coating material thus prepared is applied to the surface on which the film is to be formed to form a coating film. The method for applying the resin coating material to the surface on which the film is to be formed can be a known method such as a dipping method, a method using various coaters, a method using various dispensers, or a spray method, and can be appropriately selected depending on the shape of the surface on which the film is to be formed, the viscosity of the resin coating material, etc.

[0039] Next, the coating film formed on the coating surface is dried to remove water from the coating film, which causes a reaction between the carbonyl group of the carbonyl-containing polymer and the dihydrazide group of the dihydrazide compound crosslinking agent in the coating film, forming a crosslinked polymer having a crosslinked structure, and thus forming the polymer film of this embodiment containing PEDOT / PSS and the crosslinked polymer.

[0040] As a method for removing water from the coating film, a known method such as heat treatment at a temperature of 80°C to 150°C can be used, and the method can be appropriately determined depending on the composition of the resin coating material, the thickness of the coating film, etc. In this embodiment, the polymer film obtained by removing the water from the coating film may be washed. The polymer film can be washed using, for example, water.

[0041] The polymer membrane of the present embodiment may be produced by applying the above-mentioned resin coating material to form a coating film and then removing water from the coating film, all in one step, or by repeating the above steps multiple times to form a polymer membrane having a predetermined thickness.

[0042] The polymer film of this embodiment includes a crosslinked polymer in which a polymer having a carbonyl group is crosslinked with a crosslinking agent made of a dihydrazide compound, and PEDOT / PSS. The polymer film of this embodiment can be produced using an aqueous dispersion of PEDOT / PSS, and has excellent electrical conductivity, heat resistance, and good water resistance.

[0043] [Second embodiment] The polymer film of the second embodiment contains a crosslinked polymer in which PEDOT / PSS represented by formula (1) is crosslinked by a crosslinking agent. The crosslinked polymer contained in the polymer film of this embodiment has a three-dimensional network structure resulting from the crosslinked structure between PEDOT / PSS and the crosslinking agent, and has excellent water resistance. The crosslinked polymer contained in the polymer film of this embodiment may be of only one type, or may be of two or more types.

[0044] The cross-linking agent in the polymer membrane of the second embodiment is —NH ２ The salt of the amine compound includes a salt of an amine compound containing a total of four or more groups selected from one or two types of groups selected from the group consisting of an —NH— group and an —NH— group. ２ group, and —NH— group, and contains a total of four or more groups of one or two kinds selected from the group consisting of —NH ２ group, four N resulting from -NH- groups ＋Therefore, a crosslinked structure with PEDOT / PSS can be sufficiently formed. Examples of the salt of the amine compound include hydrochlorides, phosphates, sulfonates, perchlorates, and salt-forming compounds with organic sulfonic acids such as paratoluenesulfonic acid. Hydrochlorides are preferred because they can be easily dispersed in water and have good reactivity.

[0045] Examples of such crosslinking agents include N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride, N,N'-bis(3-aminopropyl)-1,3-propanediamine tetrahydrochloride, and N,N'-bis(2-aminoethyl)-1,3-propanediamine tetrahydrochloride, which are represented by formula (6).

[0046]

[0047] Among the above crosslinking agents, N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride represented by formula (6) is preferred. This is because N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride represented by formula (6) has good reactivity with PEDOT / PSS and can form a crosslinked polymer with better water resistance. Furthermore, N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride represented by formula (6) can be easily dispersed in water. Therefore, applying an aqueous solution of the crosslinking agent to a water-soluble PEDOT / PSS film is preferred, as it can dissolve a portion of the PEDOT / PSS film and promote the crosslinking reaction with PEDOT / PSS. In the second embodiment, the crosslinking agent used to crosslink PEDOT / PSS may be one type or two or more types.

[0048] The polymer membrane of this embodiment contains the crosslinked polymer described above, and in addition to the crosslinked polymer described above, may further contain one or more other components as necessary depending on the intended use of the polymer membrane. Examples of other components include known resins other than PEDOT / PSS. Examples of resins other than PEDOT / PSS that can be preferably used include water-soluble or water-dispersible resins, and specific examples include sulfonated polyester resins.

[0049] (Method for producing polymer film) The polymer film of the second embodiment can be produced, for example, by the method shown below. First, an aqueous dispersion of PEDOT / PSS is applied to a surface on which a film is to be formed to form a coating film. If necessary, other components that will form the polymer film are mixed into the aqueous dispersion of PEDOT / PSS. In the second embodiment, the aqueous dispersion of PEDOT / PSS used to produce the coating film can be the same as the aqueous dispersion of PEDOT / PSS that can be used in the first embodiment.

[0050] The method for applying the aqueous dispersion of PEDOT / PSS onto the surface on which the film is to be formed can be any known method, such as immersing a material having a surface on which the film is to be formed in the aqueous dispersion of PEDOT / PSS, using various coaters, using various dispensers, or spraying, and can be appropriately determined depending on the shape of the surface on which the film is to be formed, the viscosity of the aqueous dispersion of PEDOT / PSS, the use of the polymer film, etc.

[0051] Next, the coating film formed on the surface to be coated is dried to remove water from the coating film, thereby obtaining a PEDOT / PSS film. The method for removing water from the coating film can be a known method, such as a heat treatment at a temperature of 80°C to 150°C, and can be appropriately determined depending on the shape of the surface to be coated, the thickness of the coating film, etc.

[0052] Next, in the second embodiment, an aqueous solution of a cross-linking agent is applied onto the PEDOT / PSS film. This brings the PEDOT / PSS in the PEDOT / PSS film into contact with the cross-linking agent, and the N-type amine compound contained in the PEDOT / PSS and the cross-linking agent are cross-linked. ＋ A cross-linking reaction is initiated.

[0053] The crosslinking agent aqueous solution preferably has a crosslinking agent content in the range of 0.01 mol% to 1 mol%, and more preferably in the range of 0.03 mol% to 1 mol%. When the crosslinking agent content is 0.01 mol% or more, the effect of forming a crosslinked structure between PEDOT / PSS and the crosslinking agent can be sufficiently achieved by applying the crosslinking agent aqueous solution onto the PEDOT / PSS film and removing the water from the crosslinking agent aqueous solution. Therefore, when the crosslinking agent content is 0.01 mol% or more, a polymer film with better water resistance is likely to be obtained. Furthermore, when the crosslinking agent content is 1 mol% or less, the impact of the remaining crosslinking agent that does not form a crosslinked structure is reduced, which is preferable.

[0054] Methods for applying an aqueous solution of a crosslinking agent onto a PEDOT / PSS film include, for example, a method of immersing a material having a film-forming surface on which a PEDOT / PSS film is formed in an aqueous solution of a crosslinking agent, a method using various coaters, a method using various dispensers, a spray method, or other known methods, and can be appropriately determined depending on the shape of the film-forming surface, the viscosity of the aqueous solution of the crosslinking agent, etc.

[0055] Next, the aqueous solution of the crosslinking agent applied to the PEDOT / PSS film is dried to remove the water in the aqueous solution of the crosslinking agent, thereby removing the N-type bond between the PEDOT / PSS in the PEDOT / PSS film and the amine compound serving as the crosslinking agent. ＋ By carrying out the above steps, the polymer film of this embodiment containing a crosslinked polymer in which PEDOT / PSS is crosslinked by the crosslinking agent is obtained.

[0056] As a method for removing water from the aqueous solution of the crosslinking agent applied to the PEDOT / PSS film, a known method such as a heat treatment at a temperature of 80°C to 150°C can be used, and the method can be appropriately determined depending on the shape of the surface on which the film is to be formed, the thickness of the coating film, etc.

[0057] In this embodiment, the crosslinking reaction is initiated by applying an aqueous solution of a crosslinking agent to the PEDOT / PSS film. This promotes the crosslinking reaction near the surface of the PEDOT / PSS film. As a result, the density of the crosslinked structures contained in the polymer film of this embodiment changes continuously or stepwise in the thickness direction, presumably increasing the closer to the surface. This results in a polymer film with particularly high water resistance at the surface, effectively achieving the effect of improving the water resistance of the polymer film due to the presence of crosslinked structures. Therefore, compared to a polymer film with a substantially uniform density of crosslinked structures produced by applying an aqueous dispersion containing PEDOT / PSS and a crosslinking agent, for example, the polymer film of this embodiment can achieve sufficient water resistance even with a smaller number of crosslinked structures. Therefore, compared to a polymer film with a substantially uniform density of crosslinked structures and equivalent water resistance, the polymer film of this embodiment can have a higher PEDOT / PSS content in the polymer film, resulting in better conductivity and heat resistance.

[0058] The polymer film of this embodiment may be produced by forming the above-mentioned PEDOT / PSS film, applying an aqueous solution of a crosslinking agent thereon, and removing the water from the aqueous solution of the crosslinking agent only once, or by repeating the above steps multiple times to form a polymer film having a predetermined thickness.

[0059] The polymer membrane of this embodiment is -NH ２ The polymer film of this embodiment includes a crosslinked polymer in which PEDOT / PSS is crosslinked with a crosslinking agent containing a salt of an amine compound containing a total of four or more groups selected from one or two types of groups selected from the group consisting of —NH— groups and —NH— groups. The polymer film of this embodiment can be produced using an aqueous dispersion of PEDOT / PSS, and has excellent electrical conductivity and heat resistance as well as good water resistance.

[0060] [Third Embodiment] As in the second embodiment, the polymer film of the third embodiment includes a crosslinked polymer in which PEDOT / PSS represented by formula (1) is crosslinked by a crosslinking agent. The crosslinked polymer included in the polymer film of this embodiment has a three-dimensional network structure resulting from the crosslinked structure between PEDOT / PSS and the crosslinking agent, and has excellent water resistance. The crosslinked polymer included in the polymer film of this embodiment may be of only one type, or may be of two or more types.

[0061] The cross-linking agent in the polymer membrane of the third embodiment is made of a metal salt containing a metal cation with a valence of 2 or more. Examples of such cross-linking agents include calcium chloride, magnesium chloride, and strontium chloride.

[0062] Among the above crosslinking agents, calcium chloride is preferably used. This is because calcium chloride is easily available, has good reactivity with PEDOT / PSS, and can form a crosslinked polymer with better water resistance. Calcium chloride can also be easily dispersed in water. For this reason, a method in which an aqueous solution of the crosslinking agent is applied to a PEDOT / PSS film, which is easily soluble in water, can dissolve part of the PEDOT / PSS film and promote the crosslinking reaction with PEDOT / PSS, which is preferable. In the third embodiment, the crosslinking agent used to crosslink PEDOT / PSS may be one type or two or more types.

[0063] The polymer membrane of this embodiment contains the crosslinked polymer described above, and in addition to the crosslinked polymer described above, may further contain one or more other components as necessary depending on the intended use of the polymer membrane. Examples of other components include known resins other than PEDOT / PSS. Examples of resins other than PEDOT / PSS that can be preferably used include water-soluble or water-dispersible resins, and specific examples include sulfonated polyester resins.

[0064] (Method for producing polymer film) The polymer film of the third embodiment can be produced, for example, by the method shown below. First, in the same manner as in the second embodiment, an aqueous dispersion of PEDOT / PSS is applied to a surface on which a film is to be formed to form a coating film. If necessary, other components that will form the polymer film are mixed into the aqueous dispersion of PEDOT / PSS. In the third embodiment, the aqueous dispersion of PEDOT / PSS used to produce the coating film can be the same as the aqueous dispersion of PEDOT / PSS that can be used in the first and second embodiments.

[0065] Next, in the third embodiment, an aqueous solution of a crosslinking agent made of a metal salt containing a metal cation with a valence of 2 or more is applied onto the PEDOT / PSS film. This brings the PEDOT / PSS in the PEDOT / PSS film into contact with the crosslinking agent, initiating a crosslinking reaction between the PEDOT / PSS and the metal cation contained in the metal salt that is the crosslinking agent.

[0066] The crosslinking agent aqueous solution preferably has a crosslinking agent content in the range of 0.01 mol% to 2 mol%, and more preferably in the range of 0.1 mol% to 1 mol%. When the crosslinking agent content is 0.01 mol% or more, applying the crosslinking agent aqueous solution onto the PEDOT / PSS film and removing the water in the crosslinking agent aqueous solution can provide the effect of forming a crosslinked structure between the PEDOT / PSS and the crosslinking agent. Therefore, when the crosslinking agent content is 0.01 mol% or more, a polymer film with good water resistance is likely to be obtained. Furthermore, when the crosslinking agent content is 2 mol% or less, the impact of the remaining crosslinking agent that does not form a crosslinked structure is reduced, which is preferable.

[0067] Methods for applying an aqueous solution of a crosslinking agent onto a PEDOT / PSS film include, for example, a method of immersing a material having a film-forming surface on which a PEDOT / PSS film is formed in an aqueous solution of a crosslinking agent, a method using various coaters, a method using various dispensers, a spray method, or other known methods, and can be appropriately determined depending on the shape of the film-forming surface, the viscosity of the aqueous solution of the crosslinking agent, etc.

[0068] Next, the aqueous solution of the crosslinking agent applied to the PEDOT / PSS film is dried to remove the water in the aqueous solution of the crosslinking agent. This further promotes the crosslinking reaction between the PEDOT / PSS in the PEDOT / PSS film and the metal cations of the metal salt crosslinking agent. By performing the above steps, the polymer film of this embodiment containing a crosslinked polymer in which the PEDOT / PSS is crosslinked by the crosslinking agent is obtained.

[0069] As a method for removing water from the aqueous solution of the crosslinking agent applied to the PEDOT / PSS film, a known method such as a heat treatment at a temperature of 80°C to 150°C can be used, and the method can be appropriately determined depending on the shape of the surface on which the film is to be formed, the thickness of the coating film, etc.

[0070] In this embodiment, as in the second embodiment, the crosslinking reaction is initiated by applying an aqueous solution of a crosslinking agent to the PEDOT / PSS film. This promotes the crosslinking reaction near the surface of the PEDOT / PSS film. As a result, the density of the crosslinked structures contained in the polymer film of this embodiment changes continuously or stepwise in the thickness direction, presumably increasing the closer to the surface. As a result, the polymer film of this embodiment has particularly high water resistance at the surface, effectively achieving the effect of improving the water resistance of the polymer film due to the presence of crosslinked structures. Therefore, compared to a polymer film produced by applying an aqueous dispersion containing PEDOT / PSS and a crosslinking agent, in which the density of crosslinked structures contained in the polymer film is approximately uniform, sufficient water resistance can be achieved even with a smaller number of crosslinked structures. Therefore, the polymer film of this embodiment can have a higher PEDOT / PSS content in the polymer film, resulting in better conductivity and heat resistance, compared to a polymer film with approximately uniform density of crosslinked structures and equivalent water resistance.

[0071] The polymer film of this embodiment may be produced by forming the above-mentioned PEDOT / PSS film, applying an aqueous solution of a crosslinking agent thereon, and removing the water from the aqueous solution of the crosslinking agent only once, or by repeating the above steps multiple times to form a polymer film having a predetermined thickness.

[0072] The polymer film of this embodiment includes a crosslinked polymer in which PEDOT / PSS is crosslinked with a crosslinking agent made of a metal salt containing a metal cation with a valence of 2 or more. The polymer film of this embodiment can be produced using an aqueous dispersion of PEDOT / PSS, and has excellent electrical conductivity and heat resistance, as well as good water resistance.

[0073] The polymer films of the first to third embodiments described above can be produced by coating a surface, and have excellent conductivity, heat resistance, and water resistance. Therefore, the polymer films of the first to third embodiments can be preferably used in a wide range of applications, such as the solid electrolyte layer of a solid electrolytic capacitor and the hole injection layer of an organic electroluminescence (EL) device.

[0074] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0075] [Test Example 1] (Example 1) A 2 mass% aqueous dispersion of PEDOT / PSS represented by formula (1) was mixed with a 5 mass% aqueous solution of modified polyvinyl alcohol represented by formula (2) (n, which indicates the degree of polymerization in formula (2), was 500, and R was a methyl group) to obtain a mixed solution. The aqueous dispersion of PEDOT / PSS was composed only of PEDOT / PSS and water. A 5 mass% aqueous solution of adipic acid dihydrazide represented by formula (3), which serves as a crosslinking agent, was mixed with the obtained mixed solution and stirred to obtain a resin coating material.

[0076] The content of PEDOT / PSS and modified polyvinyl alcohol in the resin coating was 30%:70% (PEDOT / PSS:modified polyvinyl alcohol) by mass ratio of solids. The content of the crosslinker in the resin coating was 5% by mass relative to the mass of the solids of modified polyvinyl alcohol. The resin coating thus prepared was applied to a glass plate, which was the surface on which the coating was to be formed, to form a coating film. The coating film formed on the glass plate was then dried by heat treatment at 120°C for 15 minutes to remove water from the coating film, yielding a polymer film of Example 1 having a thickness of 10 μm. The content of PEDOT / PSS in the solids of the polymer film (solids of the resin coating) is shown in Table 1.

[0077] (Examples 2 to 8, Comparative Examples 1 and 2) The polymer films of Examples 2 to 8 and Comparative Examples 1 and 2 were obtained in the same manner as Example 1, except that the type of aqueous dispersion of PEDOT / PSS, the type of aqueous solution of modified polyvinyl alcohol (modified PVA), and the type of aqueous solution of crosslinker were as shown in Table 1, and the contents (mass ratio of solids) of PEDOT / PSS and modified polyvinyl alcohol contained in the resin coating material and the content of crosslinker contained in the resin coating material (ratio to the mass of solids of modified polyvinyl alcohol) were as shown in Table 1. The content of PEDOT / PSS in the solid content of the polymer film (solid content of the resin coating material) is shown in Table 1.

[0078] The aqueous dispersions of PEDOT / PSS, aqueous solutions of modified polyvinyl alcohol, and aqueous solutions of crosslinking agents shown in Table 1 are as follows: [PEDOT / PSS aqueous dispersion] A: An aqueous dispersion consisting of only PEDOT / PSS represented by formula (1) and water, containing 2% by mass of PEDOT / PSS. [PEDOT / PSS aqueous dispersion] B: An aqueous dispersion consisting of PEDOT / PSS represented by formula (1), a sulfonated polyester resin which is a polymer having no carbonyl groups, and water, containing 2% by mass of PEDOT / PSS.

[0079] [Modified polyvinyl alcohol aqueous solution] a: An aqueous solution containing 5% by mass of modified polyvinyl alcohol represented by formula (2) (n, which indicates the degree of polymerization in formula (2), was 500, and R was a methyl group). [Modified polyvinyl alcohol aqueous solution] b: An aqueous solution containing 5% by mass of modified polyvinyl alcohol represented by formula (2) (n, which indicates the degree of polymerization in formula (2), was 2000, and R was a methyl group). [Crosslinking agent aqueous solution] I: An aqueous solution containing 5% by mass of adipic acid dihydrazide represented by formula (3). [Crosslinking agent aqueous solution] II: An aqueous solution containing 5% by mass of 7,11-octadecadiene-1,18-dicarbohydrazide represented by formula (4).

[0080] The water resistance of the polymer films obtained in Examples 1 to 8 and Comparative Examples 1 and 2 was evaluated by the following method. [Evaluation of Water Resistance] A glass plate on which a polymer film had been formed was immersed in stirred water at 80°C for 3 minutes and then removed. The state of the polymer film on the glass plate and the immersed water were then visually observed. Next, strength observation was performed by the following method. First, the surface of the wet polymer film on the glass plate removed from the water was scratched with a sharp-tipped metal rod to visually check for deformation. The polymer film was then air-dried, and the surface state was visually observed and evaluated according to the following criteria. The results are shown in Table 1.

[0081] (Criteria) A (excellent): No detachment of the polymer film from the glass plate was confirmed by visual observation. Furthermore, the wet polymer film was not deformed when scratched with a metal rod. B (good): No detachment of the polymer film from the glass plate was confirmed by visual observation. Furthermore, the wet polymer film was deformed when scratched with a metal rod, but returned to its original shape after drying at 80°C for 10 minutes. C (fair): It was confirmed by visual observation that a portion of the polymer film had detached from the glass plate and that the detached polymer film was floating in the water in which it was immersed. D (poor): It was confirmed by visual observation that the entire polymer film had detached from the glass plate and that the detached polymer film was floating in the water in which it was immersed, or that the detached polymer film was dissolved in the water in which it was immersed.

[0082] The sheet resistance of the polymer films of Examples 2 to 8 and Comparative Examples 1 and 2 was measured using a low resistivity meter in accordance with JIS K7194. The results are shown in Table 1.

[0083]

[0084] As shown in Table 1, the polymer films of Examples 1 to 8 contain PEDOT / PSS and a crosslinked polymer in which modified polyvinyl alcohol (modified PVA) is crosslinked with a crosslinking agent made of a dihydrazide compound. It was confirmed that the polymer films of Examples 1 to 8 have better water resistance than the polymer films of Comparative Examples 1 and 2, which do not contain a crosslinked polymer. Furthermore, as shown in Table 1, the polymer films of Examples 1 to 8 had sufficiently low sheet resistance.

[0085] [Test Example 2] (Examples 11 to 20) A glass plate was immersed in an aqueous dispersion containing only PEDOT / PSS represented by formula (1) and water, and containing 2% by mass of PEDOT / PSS, to form a coating film on the glass plate. The glass plate on which the coating film was formed was then heat-treated at 120°C for 15 minutes to dry the coating film and remove the water in the coating film, thereby obtaining a PEDOT / PSS film with a thickness of 10 µm.

[0086] Next, the glass plate on which the PEDOT / PSS film was formed was immersed for 3 minutes in an aqueous solution of the crosslinking agent containing the crosslinking agent shown in Table 2 in the amount shown in Table 2. Next, the aqueous solution of the crosslinking agent applied to the PEDOT / PSS film formed on the glass plate was dried by heat treatment at 80°C for 5 minutes to remove water from the aqueous solution of the crosslinking agent, and the polymer films of Examples 11 to 20 were obtained.

[0087] Comparative Example 11 The PEDOT / PSS film formed when producing the polymer film of Example 11 was used as the polymer film of Comparative Example 11.

[0088] The crosslinking agents shown in Table 2 are as follows: [Crosslinking agent] A: N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride represented by formula (6). [Crosslinking agent] B: Calcium chloride.

[0089] The water resistance of the polymer membranes of Examples 11 to 20 and Comparative Example 11 thus obtained was evaluated by the same method and criteria as in Example 1.

[0090] The sheet resistance of the polymer films of Examples 11 to 20 and Comparative Example 11 was measured using a low resistivity meter in accordance with JIS K7194. The results are shown in Table 2.

[0091]

[0092] As shown in Table 2, the polymer films of Examples 11 to 20 contain crosslinked polymers in which PEDOT / PSS is crosslinked with a crosslinking agent. It was confirmed that the polymer films of Examples 11 to 20 have better water resistance than Comparative Example 11, which is a non-crosslinked PEDOT / PSS film. Furthermore, as shown in Table 2, the polymer films of Examples 12 to 15 and Examples 18 to 19 had sufficiently low sheet resistance.

[0093] The polymer film of this embodiment is suitable for a wide range of applications, such as a solid electrolyte layer in a solid electrolytic capacitor and a hole injection layer in an organic electroluminescence (EL) element.

Claims

1. A polymer film comprising a crosslinked polymer in which a polymer having a carbonyl group is crosslinked with a crosslinking agent composed of a dihydrazide compound, and a composite of polyethylene dioxythiophene and polystyrene sulfonic acid.

2. The polymer film according to claim 1, wherein the polymer having a carbonyl group has a polyvinyl alcohol backbone.

3. The polymer film according to claim 1, wherein the ratio of the structural unit derived from the polymer having a carbonyl group to the total mass of the structural unit derived from the polymer having a carbonyl group and the composite is 70% by mass or less, and the ratio of the structural unit derived from the crosslinking agent to the mass of the structural unit derived from the polymer having a carbonyl group is 15% by mass or less.

4. The polymer film according to claim 1, wherein the ratio of the structural unit derived from the polymer having a carbonyl group to the total mass of the structural unit derived from the polymer having a carbonyl group and the composite is 30% by mass or less, and the ratio of the structural unit derived from the crosslinking agent to the mass of the structural unit derived from the polymer having a carbonyl group is 10% by mass or less.

5. The composite of polyethylene dioxythiophene and polystyrene sulfonic acid contains a crosslinked polymer crosslinked by a crosslinking agent, and the crosslinking agent contains a salt of an amine compound containing a total of four or more of one or two groups selected from -NH ２ groups and -NH- groups, a polymer membrane.

6. A polymer film in which the composite of polyethylene dioxythiophene and polystyrene sulfonic acid contains a crosslinked polymer crosslinked with a crosslinking agent, and the crosslinking agent is a metal salt containing a metal cation having a valence of 2 or more.

7. The polymer film according to claim 6, wherein the crosslinking agent is calcium chloride.

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