Additives for organic conductors, organic conductor, manufacturing method thereof, and electrolytic capacitor

Abstract

To provide additives for organic conductors capable of suppressing the decrease in conductivity of organic conductors.SOLUTION: The additives for organic conductors contain a first compound. The first compound includes an anthraquinone skeleton and at least one sulfo group that attaches to the anthraquinone skeleton. The sulfate ion content of the additive is 100 ppm by mass or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an additive for an organic conductor, an organic conductor and a method for producing the same, and an electrolytic capacitor. [Background technology]

[0002] Conjugated polymers such as polythiophene or polypyrrole exhibit conductivity when doped. Conjugated polymers with dopants added are called conductive polymers or organic conductors. In recent years, self-doped organic conductors have also been developed. The performance of organic conductors can be controlled by selecting the type of conjugated polymer or the type of additive (dopant, etc.), and they are inexpensive and lightweight, making them suitable for use in a variety of electronic components. Proton-added compounds and electron-oxidized compounds are used as additive dopants.

[0003] The organic conductor includes, for example, a conjugated polymer and an aromatic sulfonic acid (additive), and is contained in the solid electrolyte of the electrolytic capacitor.

[0004] Patent Document 1 proposes "an electrolytic capacitor comprising an anode body, a dielectric layer formed on the surface of the anode body, and a solid electrolyte layer formed on the surface of the dielectric layer, wherein the solid electrolyte layer includes a conductive polymer and a first compound, the first compound including a naphthalene skeleton, at least one COOM1 group (where M1 is a hydrogen atom, a metal atom, or an onium group) bonded to the naphthalene skeleton, and at least one sulfonate group bonded to the naphthalene skeleton." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 131476 Brochure Summary of the Invention [Problem to be solved by the invention]

[0006] Aromatic sulfonic acid contains several to 10% by mass of sulfuric acid used in the manufacturing process, which tends to reduce the conductivity of organic conductors containing aromatic sulfonic acid and conjugated polymers. [Means for solving the problem]

[0007] One aspect of the present disclosure relates to an additive for an organic conductor, comprising a first compound having an anthraquinone skeleton and at least one sulfo group bonded to the anthraquinone skeleton, and having a sulfate ion content of 100 ppm by mass or less.

[0008] Another aspect of the present disclosure relates to an organic conductor comprising the above additive and a conjugated polymer.

[0009] Yet another aspect of the present disclosure relates to an electrolytic capacitor including an anode body, a dielectric layer covering at least a portion of the anode body, and a solid electrolyte covering at least a portion of the dielectric layer, wherein the solid electrolyte includes the organic conductor described above.

[0010] Yet another aspect of the present disclosure relates to a method for producing an organic conductor, the method including the steps of preparing the additive, preparing a monomer compound, and polymerizing the monomer compound in the presence of the additive to obtain an organic conductor containing the additive and a conjugated polymer. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to suppress a decrease in the conductivity of an organic conductor. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of an electrolytic capacitor. [Figure 2] FIG. 1 is a cross-sectional view schematically illustrating an example of a capacitor element. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be interpreted as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits are exemplified for numerical values ​​of specific physical properties or conditions, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. When multiple materials are exemplified, one of the materials may be selected and used alone, or two or more of the materials may be used in combination.

[0014] An additive for an organic conductor according to an embodiment of the present disclosure includes a first compound. The first compound has an anthraquinone skeleton and at least one sulfo group bonded to the anthraquinone skeleton. Hereinafter, the first compound is also referred to as an "anthraquinone sulfonic acid compound."

[0015] The sulfate ion content is 100 ppm by mass or less. Note that the "sulfate ion content" here refers to the ratio (parts per million) of the mass of sulfate ions to the total mass of the first compound and sulfate ions mixed in the first compound.

[0016] Such additives have the effect of extracting electrons from the conjugated polymer, converting it from an insulator or semiconductor to a good conductor. Therefore, additives with this effect are generally called dopants. When an organic conductor containing the above additive and a conjugated polymer is used in the solid electrolyte of an electrolytic capacitor, the equivalent series resistance (ESR) of the electrolytic capacitor can be reduced.

[0017] Organic conductors containing anthraquinone sulfonic acid compounds exhibit superior conductivity compared to organic conductors containing other aromatic sulfonic acids (naphthalene sulfonic acid compounds, benzene sulfonic acid compounds). The superior conductivity achieved with anthraquinone sulfonic acid compounds is presumed to be due to the following (i) and (ii): (i) The electron-withdrawing effect of the carbonyl group present in the anthraquinone skeleton delocalizes the charge of the sulfonate anion, facilitating the movement of positive charges on the polymer chain; (ii) The interaction of the anthraquinone sulfonic acid compounds with π-conjugated polymers, based on their highly planar structure, improves the orientation of the polymer.

[0018] In the present disclosure, it has been found that the conductivity of an organic conductor can be significantly increased by using a first compound as an additive and further reducing the sulfate ion content to 100 mass ppm or less (highly purifying the first compound).

[0019] Anthraquinone sulfonic acid compounds have low solubility in organic solvents, making it difficult to separate sulfuric acid by separation operations, which are common methods for removing sulfuric acid. Furthermore, due to their low solubility, low crystallinity, and strong intermolecular interactions, purification by chromatography, recrystallization, sublimation, and the like is difficult to employ. For high purification, it is necessary to use purification methods and conditions suitable for anthraquinone sulfonic acid compounds. For high purification of anthraquinone sulfonic acid compounds, it is preferable to use the high purification process described below.

[0020] When the sulfate ion content is 100 ppm by mass or less, the decrease in the conductivity of the organic conductor due to an increase in the amount of sulfate ions mixed in is significantly suppressed. Furthermore, the decrease in the film quality of the organic conductor due to a large amount of sulfate ions mixed in is also suppressed. From the viewpoint of improving the conductivity of the organic conductor, the sulfate ion content may be 50 ppm by mass or less, 30 ppm by mass or less, or even 0 ppm by mass. Note that "0 ppm by mass" here means below the detection limit in analysis such as ion chromatography.

[0021] The content of sulfate ions in the first compound containing sulfate ions can be determined by ion chromatography, capillary electrophoresis, or the like.

[0022] When the solid electrolyte of the electrolytic capacitor contains an organic conductor, the content of sulfate ions can be determined as follows. First, the electrolytic capacitor is disassembled, the capacitor element is removed, and a portion of the solid electrolyte is removed from the capacitor element by scraping or the like. The obtained solid electrolyte (sample) is immersed in ion-exchanged water in a beaker and heated to boil the ion-exchanged water for 10 minutes. The sample is then removed from the beaker, and the ion-exchanged water is analyzed by ion chromatography to measure the sulfate ion concentration and the first compound (anion) concentration. The sulfate ion content is calculated from the measured sulfate ion concentration and the first compound concentration.

[0023] (additives) The additive for the organic conductor contains a first compound (anthraquinone sulfonic acid compound). From the viewpoint of improving the conductivity of the organic conductor and reducing the ESR of the electrolytic capacitor, it is preferable that all of the additives are the first compound. The additive may further contain an aromatic sulfonic acid compound other than the first compound (hereinafter referred to as the second compound). However, in order to fully obtain the effect of the first compound, the content of the first compound relative to the total of the first compound and the second compound is desirably 95 mass% or more.

[0024] (1st compound) The first compound has an anthraquinone skeleton and at least one sulfo group bonded to the anthraquinone skeleton. One type of the first compound may be used alone, or two or more types may be used in combination.

[0025] The sulfo group includes salts or esters of the sulfo group in addition to the SO3H group. Examples of the salts include metal salts and onium salts. Examples of the metal salts include alkali metal salts such as sodium salts. Examples of the onium salts include ammonium salts, sulfonium salts, and phosphonium salts. In the solid electrolyte, the sulfo group forms an anion (-SO3 - ), -SO3H, salts or esters.

[0026] The position of the sulfo group bonded to the anthraquinone skeleton is not particularly limited. The number of sulfo groups is preferably 3 or less. When the number of sulfo groups is 3 or less, decomposition of the first compound is easily suppressed. The number of sulfo groups may be 1.

[0027] The first compound may have at least one substituent bonded to the anthraquinone skeleton, and may further have at least one substituent selected from the group consisting of a nitro group, a hydroxy group, a hydrocarbon group, a methoxy group, and a carboxy group.

[0028] The first compound may have one or more carboxy groups, which enhances the interaction between the conjugated polymer and the first compound and makes it easier to suppress undoping. When the first compound has one carboxy group, the sulfo group and the carboxy group are preferably located at meta positions. When the first compound has two carboxy groups, the sulfo group and each carboxy group are preferably located at meta positions.

[0029] The hydroxy group includes not only an OH group but also an ester of a hydroxy group. In a solid electrolyte, the hydroxy group forms an anion (-O - ), -OH, or ester form. The carboxy group includes not only the COOH group but also salts or esters of the carboxy group. Examples of salts include metal salts (alkali metal salts, etc.) such as sodium salts, ammonium salts, sulfonium salts, and phosphonium salts. In the solid electrolyte, the carboxy group is present in the form of an anion (-COO -), -COOH, salts or esters.

[0030] The hydrocarbon group is preferably a chain aliphatic hydrocarbon group, since it is easy to dope the conjugated polymer in the pits (concave portions) of the anode body. The chain aliphatic hydrocarbon group is, for example, -(CH2) n It may be a saturated or unsaturated hydrocarbon group represented by H (n is an integer of 1 to 20). The aliphatic hydrocarbon group may have a substituent such as a hydroxyl group or an alkoxy group.

[0031] Among these, from the viewpoints of improving the conductivity of the organic conductor, ease of availability, ease of handling, chemical stability, etc., the first compound preferably contains at least one selected from the group consisting of anthraquinone-2-sulfonic acid, anthraquinone-1-sulfonic acid, anthraquinone-1,5-disulfonic acid, anthraquinone-1,4-disulfonic acid, anthraquinone-1,6-disulfonic acid, anthraquinone-2,6-disulfonic acid, and anthraquinone-2,7-disulfonic acid, with anthraquinone-2-sulfonic acid being more preferred.

[0032] (Second compound) The second compound may be a monomolecular anion or a polymeric anion. Specific examples of monomolecular anions include aromatic sulfonic acids such as benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfone, and butylnaphthalenesulfonic acid, and alkylsulfonic acids such as dodecanesulfonic acid. Specific examples of polymeric anions include polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylicsulfonic acid, polymethacrylicsulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprenesulfonic acid, and polyacrylic acid. These may be used alone or in combination of two or more. Furthermore, these may be polymers of a single monomer or copolymers of two or more monomers.

[0033] [Organic conductors] An organic conductor according to an embodiment of the present disclosure includes the additive described above and a conjugated polymer. The additive has excellent electron acceptor properties and can function as a dopant for the conjugated polymer. By using the additive described above, an organic conductor with high conductivity can be obtained. Such an organic conductor has excellent conductivity and can be used in various electronic devices. It is particularly suitable for use as a solid electrolyte in an electrolytic capacitor.

[0034] From the viewpoint of reducing the ESR of the electrolytic capacitor, the conductivity of the organic conductor is preferably 190 S / cm or more, more preferably 200 S / cm or more. The conductivity of the organic conductor can be increased to 190 S / cm or more by the additive (highly purified first compound).

[0035] The conductivity of the organic conductor can be determined as follows. The conductivity of a sample film of an organic conductor (e.g., 20 to 40 μm thick) is measured under room temperature. The sample film of the organic conductor may be prepared by electropolymerization using a polymerization solution containing a monomer compound and an additive. The measurement device used may be a Loresta-GP (MCP-T610 type, four-point in-line probe) manufactured by Nitto Seiko Analytech Co., Ltd.

[0036] When the solid electrolyte of the electrolytic capacitor contains an organic conductor, the conductivity of the organic conductor can be determined by the following method. The electrolytic capacitor is disassembled, the capacitor element is removed, and the solid electrolyte is analyzed. When the solid electrolyte is formed using a treatment solution containing an organic conductor, the treatment solution may also be analyzed. Examples of analytical methods that can be used include ion chromatography, TEM (transmission electron microscope)-EELS (electron energy loss spectroscopy), NMR (nuclear magnetic resonance spectroscopy), and Raman spectroscopy. Based on the analysis results, a sample film (e.g., 20 to 40 μm thick) containing the same components as the solid electrolyte is prepared, and its conductivity is measured.

[0037] (conjugated polymers) The conjugated polymer may be any polymer that becomes a good conductor when acted upon by an additive, and examples thereof include π-conjugated polymers and σ-conjugated polymers. The organic conductor may contain one or more of the above-mentioned additives. The organic conductor may contain one or more of the conjugated polymers.

[0038] Conjugated polymers include polymers with a basic skeleton such as polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, or polythiophene vinylene. These polymers include homopolymers, copolymers of two or more monomers, and derivatives thereof (e.g., substituted products having substituents). For example, polythiophenes include poly(3,4-ethylenedioxythiophene).

[0039] Among conjugated polymers, those containing a monomer unit corresponding to a pyrrole compound are preferred. Combining such a conjugated polymer with the additives mentioned above tends to achieve higher bonding strength. Examples of pyrrole compounds include pyrrole, compounds in which an aliphatic ring or heterocycle is condensed with pyrrole, and substituted versions of these (compounds having a substituent). Examples of the substituent include alkyl groups (including aminoalkyl groups and hydroxyalkyl groups), amino groups, substituted amino groups, alkoxy groups, hydroxy groups, mercapto groups, and halogen atoms. Pyrrole or the condensed compound may contain one or more of these substituents. The conjugated polymer preferably has a repeating structure of a monomer unit corresponding to the pyrrole compound.

[0040] The weight average molecular weight (Mw) of the conjugated polymer is not particularly limited, but is, for example, 1,000 or more and 1,000,000 or less.

[0041] In this specification, the weight-average molecular weight (Mw) is a value calculated as polystyrene measured by gel permeation chromatography (GPC), which is usually performed using a polystyrene gel column and water / methanol (volume ratio 8 / 2) as the mobile phase.

[0042] The amount of the additive is, for example, 0.1 parts by mass or more and 400 parts by mass or less, or may be 1 part by mass or more and 350 parts by mass or less, or may be 10 parts by mass or more and 300 parts by mass or less, relative to 100 parts by mass of the conjugated polymer.

[0043] [Method for manufacturing organic conductors] The method includes the steps of preparing the additive, preparing a monomer compound, and polymerizing the monomer compound in the presence of the additive to obtain an organic conductor containing the additive and a conjugated polymer. The polymerization is preferably electrolytic polymerization, but may also be chemical polymerization.

[0044] (Additive preparation process) The first compound may be a commercially available product or a product (product) produced by a known manufacturing method. Since sulfuric acid usually remains in a commercially available product (or product), the additive preparation step preferably includes a step of reducing the amount of sulfuric acid contained in the commercially available product (or product) (a purification step). The purification step is carried out before adding the additive to the polymerization liquid. The commercially available product (or product) is usually an alkali metal salt such as a sodium salt.

[0045] (High purity process) The purification step may include, for example, a step of adding and dispersing the first compound in ion-exchanged water, then adding an ion-exchange resin to the ion-exchanged water, stirring, and filtering the resulting mixture, or a step of adding and dispersing the first compound in ion-exchanged water, then ultrafiltering the resulting mixture.

[0046] In the high-purification step, for example, known separation methods, purification methods, etc. can be used. The high-purification step must be carried out by appropriately selecting the separation and / or purification method and conditions. Examples of separation and / or purification include filtration, washing, extraction, distillation, crystallization, recrystallization, chromatography, etc.

[0047] In the purification step, it is preferable to carry out the following ion exchange treatment, evaporation to dryness treatment, and reprecipitation treatment.

[0048] (ion exchange treatment) A commercially available first compound (a first compound in which the sulfo group is SO3M and M is an alkali metal such as Na) is prepared. This first compound is subjected to an ion exchange treatment. Specifically, the first compound is added to an aqueous dispersion of cation exchange resin to prepare a treatment solution, which is then stirred for a predetermined period of time. The treatment solution after stirring is passed through a glass tube filled with cation exchange resin. This converts the poorly water-soluble first compound (the sulfo group is SO3M) into a water-soluble first compound (the sulfo group is SO3H). In this way, the first compound is dissolved in water by ion exchange, and an aqueous solution of the first compound is obtained.

[0049] (evaporation to dryness) The aqueous solution of the first compound obtained above is subjected to an evaporation-to-dryness treatment. Specifically, the aqueous solution of the first compound is heated and dried at a predetermined temperature (e.g., 30 to 80°C) for a predetermined time (e.g., 1 to 30 hours) to remove water by evaporation. The sulfate ion content of the first compound obtained here is, for example, 10,000 ppm by mass or more. The heating temperature and heating time may be appropriately adjusted depending on the water adsorption property of the first compound, from the viewpoint of obtaining a high-quality precipitate in the reprecipitation treatment described below.

[0050] (Reprecipitation treatment) The first compound obtained by the evaporation-to-dryness treatment is subjected to a reprecipitation treatment. Specifically, the first compound is dissolved in a good solvent, a poor solvent is added to cause precipitation, and the precipitate is then filtered, washed, and dried. This reduces the content of sulfate ions remaining in the first compound to 100 mass ppm or less. The amount of sulfate ions in the first compound is more easily reduced to a high level than in other additives (e.g., the second compound) other than the first compound. The anthraquinone skeleton is relatively larger than other aromatic ring skeletons (benzene skeleton, naphthalene skeleton) and has high solubility in organic solvents, so the amount of sulfate ions in the first compound can be reduced to a high level by the reprecipitation treatment.

[0051] The good solvent is preferably a polar organic solvent. Examples of the good solvent include ethyl acetate, tetrahydrofuran, acetone, acetonitrile, etc. Among these, ethyl acetate is preferred. In the case of ethyl acetate, the organic solvent has high stability against acids, and the anthraquinone sulfonic acid produced by reprecipitation has good crystallinity (easy reprecipitation), and is easy to remove by vacuum drying.

[0052] The poor solvent is preferably a non-polar organic solvent. Examples of the poor solvent include hexane, pentane, heptane, cyclohexane, etc. Among these, hexane is preferred. In the case of hexane, the anthraquinone sulfonic acid produced by reprecipitation has good crystallinity (easy reprecipitation) and can be easily removed by vacuum drying.

[0053] (Monomer compound preparation process) The monomer compound is a raw material for a conjugated polymer, and includes, for example, a monomer and / or an oligomer capable of forming a conjugated polymer. Examples of the monomer compound include pyrrole, aniline, thiophene, and derivatives thereof. From the viewpoint of easily obtaining a high bonding strength between the additive and the conjugated polymer, it is preferable that the monomer compound includes a pyrrole compound (pyrrole and its derivatives).

[0054] (Organic conductor manufacturing process) The process for preparing an organic conductor preferably includes the steps of preparing a polymerization solution containing a monomer compound and an additive, and electropolymerizing the monomer compound using the polymerization solution. The electropolymerization can be carried out, for example, by immersing an anode body having a dielectric layer in the polymerization solution containing the monomer compound and the additive, and passing a current through the anode body as an electrode, or by scanning the potential of the electrode. The concentration of the monomer compound in the polymerization solution is, for example, 0.1 mol / L or more and 2 mol / L or less. The concentration of the additive in the polymerization solution is, for example, 0.01 mol / L or more and 1 mol / L or less.

[0055] A solid electrolyte layer covering at least a portion of the dielectric layer can be formed, for example, by carrying out the above-described electrolytic polymerization on an anode body having a dielectric layer. The dielectric layer is formed on the surface of the anode body (the surface including the inner wall surfaces of the holes and pits of the anode body). Polymerizing the monomer compound in the presence of the dielectric layer facilitates the formation of a solid electrolyte layer deep inside the holes and pits. Alternatively, the solid electrolyte layer covering at least a portion of the dielectric layer may be formed by adding a solvent (or dispersion medium) to the organic conductor obtained above to prepare a treatment liquid containing the organic conductor, impregnating the anode body having the dielectric layer with the treatment liquid, and drying the treatment liquid. Examples of the solvent (or dispersion medium) include water, organic solvents, etc.

[0056] The polymerization solution may contain an acid component different from the first compound as the second compound. To smoothly carry out electropolymerization, it is conceivable to add sulfuric acid to the polymerization solution as an acid component different from the first compound, but from the viewpoint of reducing ESR by increasing the purity of the first compound, it is desirable not to add sulfuric acid to the polymerization solution.

[0057] [Electrolytic capacitor] The electrolytic capacitor includes an anode body, a dielectric layer covering at least a portion of the anode body, and a solid electrolyte covering at least a portion of the dielectric layer. The solid electrolyte includes the organic conductor described above. This allows the ESR of the electrolytic capacitor to be significantly reduced. The solid electrolyte constitutes a cathode portion of the electrolytic capacitor. A capacitor element of the electrolytic capacitor includes the anode body having a dielectric layer and the cathode portion.

[0058] (anode body) The anode body can contain a valve metal, an alloy containing a valve metal, a compound containing a valve metal, or the like. These materials can be used alone or in combination of two or more. Examples of preferred valve metals include aluminum, tantalum, niobium, and titanium. Anode bodies with porous surfaces can be obtained by roughening the surface of a substrate (such as a foil- or plate-shaped substrate) containing a valve metal by etching or the like. The anode body can also be a compact of particles containing a valve metal, or a sintered body thereof. The sintered body has a porous structure.

[0059] (dielectric layer) The dielectric layer is formed by anodizing the valve metal on the surface of the anode body by chemical conversion treatment or the like. The dielectric layer may be formed so as to cover at least a portion of the anode body. The dielectric layer is usually formed on the surface of the anode body. Since the dielectric layer is formed on the surface of a porous anode body, it is formed along the inner wall surfaces of holes and depressions (pits) on the surface of the anode body (including the inner wall surfaces of the holes).

[0060] The dielectric layer contains an oxide of a valve metal. For example, when tantalum is used as the valve metal, the dielectric layer contains Ta2O5, and when aluminum is used as the valve metal, the dielectric layer contains Al2O3. However, the dielectric layer is not limited to these and may be any material that functions as a dielectric.

[0061] (cathode) The cathode section includes at least a solid electrolyte covering at least a portion of the dielectric layer, and includes, for example, a solid electrolyte and a cathode extraction layer covering at least a portion of the solid electrolyte.

[0062] (solid electrolyte) The solid electrolyte contains the organic conductor and is formed to cover the dielectric layer. The solid electrolyte does not necessarily have to cover the entire dielectric layer (the entire surface), but may be formed to cover at least a part of the dielectric layer. In the electrolytic capacitor, the solid electrolyte may form a solid electrolyte layer.

[0063] The solid electrolyte contains the additives described above, and may also contain other dopants as necessary. The other dopants include at least one selected from the group consisting of anions and polyanions. Examples of anions include sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions. Examples of polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacrylic sulfonic acid, polyacrylic acid, and polymethacrylic acid. Examples of polyanions include polyester sulfonic acid and phenol sulfonic acid novolac resin.

[0064] In order to more effectively exert the effects of the additives, the ratio of the additives to the entire dopant may be, for example, 90% by mass or more and 100% by mass or less, or 95% by mass or more and 100% by mass or less.

[0065] The solid electrolyte may contain other additives, such as known additives other than dopants and known conductive materials other than organic conductors (e.g., conductive inorganic materials such as manganese dioxide).

[0066] The solid electrolyte can be formed, for example, by performing at least one of chemical polymerization and electrolytic polymerization of constituent monomers of a conjugated polymer on a dielectric layer in the presence of the additive. Alternatively, a solution in which the conjugated polymer and the additive are dissolved, or a dispersion in which the conjugated polymer and the additive are dispersed, can be brought into contact with the dielectric layer to form a solid electrolyte covering the dielectric layer. After the solution or dispersion is brought into contact with the dielectric layer, drying or heat treatment may be performed as necessary.

[0067] The solid electrolyte layer may be a single layer or may be composed of multiple layers. When the solid electrolyte layer is composed of multiple layers, the compositions of the layers (e.g., the type of conjugated polymer, the type of dopant or additive, the ratio of each component, etc.) may be the same or different. If necessary, a layer for improving adhesion may be interposed between the dielectric layer and the solid electrolyte.

[0068] (Cathode extraction layer) The cathode extraction layer includes, for example, a carbon layer formed on the surface of the solid electrolyte and a metal paste layer formed on the surface of the carbon layer, which are sequentially laminated to form the cathode extraction layer.

[0069] The carbon layer can be formed by immersing an anode element having a dielectric layer at least partially covered with a solid electrolyte in a dispersion containing conductive carbon, or by applying a paste containing conductive carbon to the surface of the solid electrolyte. Examples of the conductive carbon include graphites such as artificial graphite and natural graphite. Examples of the dispersion and paste include conductive carbon dispersed in an aqueous liquid medium.

[0070] The metal paste layer can be formed, for example, by laminating a composition containing metal particles on the surface of a carbon layer. For example, a silver paste layer formed using a composition containing silver particles and a resin (binder resin) can be used as the metal paste layer. While a thermoplastic resin can be used as the resin, it is preferable to use a thermosetting resin such as an imide resin or an epoxy resin.

[0071] The configuration of the cathode extraction layer is not limited to this, and any configuration may be used as long as it has a current collecting function.

[0072] (others) For example, an electrolytic capacitor is obtained by housing a capacitor element including an anode body and a cathode portion in a container or sealing it with an exterior body or the like. The electrolytic capacitor may be either a chip type or a laminate type, or may be a wound type. The configuration of the capacitor element may be selected depending on the type of electrolytic capacitor. The capacitor element may, if necessary, include a cathode body using a metal foil, similar to the anode body. When a metal foil is used as the cathode body, a separator may be disposed between the metal foil and the anode body.

[0073] The electrolytic capacitor may include a plurality of capacitor elements. The plurality of capacitor elements are stacked. The number of stacked capacitor elements is not particularly limited, and may be, for example, 2 to 20. At least one of the plurality of capacitor elements may be the capacitor element according to this embodiment. The others may be conventionally known capacitor elements. Preferably, all of the plurality of capacitor elements arranged in the electrolytic capacitor are the capacitor elements according to this embodiment.

[0074] The anode portions of the stacked capacitor elements are joined together by welding for electrical connection. The anode portions may be welded together after being crimped with a bent anode lead terminal, for example. The anode lead terminal is joined to the anode portion of at least one capacitor element.

[0075] The cathode lead layers of the stacked capacitor elements are also electrically connected to each other. A cathode lead terminal is bonded to the cathode lead layer of at least one capacitor element. The cathode lead terminal is bonded via a conductive adhesive or solder, or by resistance welding or laser welding. The conductive adhesive is, for example, a mixture of a curable resin and carbon particles or metal particles.

[0076] (Lead terminal) The material of the lead terminals is not particularly limited as long as it is electrochemically and chemically stable and conductive, and may be metallic or non-metallic. The shape is also not particularly limited. From the viewpoint of reducing the height, the thickness of the lead terminals (the distance between the main surfaces of the lead terminals) is preferably 25 μm or more and 200 μm or less, and more preferably 25 μm or more and 100 μm or less.

[0077] (exterior body) The capacitor element may be sealed in an exterior package such that at least a portion of the anode lead terminal and the cathode lead terminal are exposed.

[0078] Examples of materials for the exterior body include cured products of curable resins and engineering plastics. Examples of thermosetting resins include epoxy resins, phenolic resins, silicone resins, melamine resins, urea resins, alkyd resins, polyurethanes, and unsaturated polyesters. Examples of engineering plastics include general-purpose engineering plastics and super engineering plastics. Examples of engineering plastics include polyimides and polyamideimides.

[0079] Fig. 1 is a cross-sectional view schematically showing an example of an electrolytic capacitor, and Fig. 2 is a cross-sectional view schematically showing an example of a capacitor element.

[0080] Electrolytic capacitor 100 includes a plurality of stacked capacitor elements 10. Capacitor element 10 includes anode body 11, dielectric layer 12 covering at least a portion of anode body 11, solid electrolyte layer 13 covering at least a portion of dielectric layer 12, and cathode extraction layer 14. Cathode extraction layer 14 includes carbon layer 141 and metal paste layer 142. The electrolytic capacitor in FIG. 1 includes a plurality of capacitor elements, but may also include a single capacitor element.

[0081] Electrolytic capacitor 100 includes an anode lead terminal 30, a cathode lead terminal 40, and an exterior body 20 that seals capacitor element 10. Anode lead terminal 30 is joined to anode body 11 of capacitor element 10. Cathode lead terminal 40 is joined to metal paste layer 142 of capacitor element 10.

[0082] [Note] The above description of the embodiments discloses the following techniques. (Technology 1) a first compound; the first compound has an anthraquinone skeleton and at least one sulfo group bonded to the anthraquinone skeleton, An additive for organic conductors, having a sulfate ion content of 100 ppm by mass or less. (Technology 2) The additive for an organic conductor according to Technical 1, wherein the content of the sulfate ions is 50 ppm by mass or less. (Technology 3) the first compound further has at least one substituent selected from the group consisting of a nitro group, a hydroxy group, a hydrocarbon group, a methoxy group, and a carboxy group; 3. The additive for organic conductor according to claim 1 or 2, wherein the at least one substituent is bonded to the anthraquinone skeleton. (Technology 4) The additive for an organic conductor according to Technology 1 or 2, wherein the first compound includes at least one selected from the group consisting of anthraquinone-2-sulfonic acid, anthraquinone-1-sulfonic acid, anthraquinone-1,5-disulfonic acid, anthraquinone-1,4-disulfonic acid, anthraquinone-1,6-disulfonic acid, anthraquinone-2,6-disulfonic acid, and anthraquinone-2,7-disulfonic acid. (Technology 5) An organic conductor comprising a conjugated polymer and the additive according to any one of techniques 1 to 4. (Technology 6) 6. The organic conductor according to claim 5, wherein the conjugated polymer contains a monomer unit corresponding to a pyrrole compound. (Technology 7) 7. The organic conductor according to claim 5 or 6, having a conductivity of 190 S / cm or more. (Technology 8) an anode body; a dielectric layer covering at least a portion of the anode body; a solid electrolyte covering at least a portion of the dielectric layer, The solid electrolyte of the electrolytic capacitor comprises the organic conductor according to any one of the fifth to seventh aspects. (Technology 9) A step of preparing an additive according to any one of techniques 1 to 4; providing a monomer compound; and polymerizing the monomer compound in the presence of the additive to obtain an organic conductor containing a conjugated polymer and the additive. (Technology 10) 10. The method for producing an organic conductor according to claim 9, wherein the monomer compound contains a pyrrole compound. (Technology 11) 10. The method for producing an organic conductor according to claim 8 or 9, wherein the organic conductor has a conductivity of 190 S / cm or more.

[0083] [Example] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0084] 《Organic conductors A1~A2, B1~B4》 (Preparation of additive a1) High-purity anthraquinone-2-sulfonic acid (sulfate ion content: 15 mass ppm) was prepared as the additive (dopant) a1. Hereinafter, anthraquinone-2-sulfonic acid will also be referred to as "AQ2S."

[0085] High-purity AQ2S was obtained by preparing commercially available sodium anthraquinone-2-sulfonate and performing the following ion exchange, evaporation to dryness, and reprecipitation processes. Hereinafter, sodium anthraquinone-2-sulfonate will also be referred to as "AQ2SNa."

[0086] (ion exchange treatment) AQ2SNa (commercially available) was subjected to ion exchange treatment. Specifically, AQ2SNa was added to an aqueous dispersion of cation exchange resin to prepare a treatment solution, which was then stirred for 1 hour. The stirred treatment solution was passed through a glass tube filled with cation exchange resin. This converted the poorly water-soluble AQ2SNa into water-soluble AQ2S. In this way, AQ2S was dissolved in water by ion exchange, and an aqueous solution of AQ2S was obtained.

[0087] (evaporation to dryness) The aqueous solution of AQ2S obtained by the ion exchange treatment was subjected to evaporation to dryness. Specifically, the aqueous solution of AQ2S was heated and dried at 60°C for 12 hours to remove water by evaporation. The sulfate ion content of the AQ2S obtained by the evaporation to dryness treatment was 30,000 ppm by mass. The sulfate ion content was determined by the method described above.

[0088] (Reprecipitation treatment) The AQ2S obtained by evaporation to dryness was re-precipitated. Specifically, AQ2S was dissolved in a good solvent, ethyl acetate, and then precipitated by adding a poor solvent, hexane. The precipitate was then filtered, washed, and dried. The reprecipitation treatment reduced the sulfate ion content, and high-purity AQ2S (sulfate ion content: 15 mass ppm) was obtained.

[0089] (Preparation of additives a2 and b4) AQ2S (sulfate ion content: 80 ppm by mass) was prepared as additive a2. AQ2S (sulfate ion content: 150 ppm by mass) was prepared as additive b4. Specifically, dilute sulfuric acid was added to AQ2S (sulfate ion content: 15 ppm by mass) of additive a1 to adjust the sulfate ion content of AQ2S to 80 ppm by mass or 150 ppm by mass.

[0090] (Preparation of additive b1) As additive b1, AQ2S (sulfate ion content: 30,000 mass ppm) was prepared. Specifically, additive b1 was obtained in the same manner as additive a1, except that the above AQ2SNa was not subjected to reprecipitation treatment.

[0091] (Preparation of additive b2) High-purity 2-naphthalenesulfonic acid (sulfate ion content: 380 mass ppm) was prepared as additive b2. Hereinafter, 2-naphthalenesulfonic acid will also be referred to as "N2S."

[0092] High-purity N2S was obtained by preparing commercially available sodium 2-naphthalenesulfonate and performing the following ion exchange treatment, evaporation to dryness treatment, and ultrasonic cleaning treatment. Hereinafter, sodium 2-naphthalenesulfonate will also be referred to as "N2SNa."

[0093] N2SNa (commercially available product) was subjected to ion exchange and evaporation to dryness in the same manner as additive a1. The N2S obtained by evaporation to dryness was subjected to ultrasonic cleaning. Specifically, 15 ml of cleaning solution was added to 1 g of N2S, followed by ultrasonic cleaning and filtration. This process was repeated six times. A mixed solvent containing ethyl acetate and hexane in a volume ratio of 2:1 was used as the cleaning solution.

[0094] If reprecipitation treatment is used for N2S, layer separation occurs, making it difficult to reduce sulfuric acid. For this reason, ultrasonic cleaning treatment was used for N2S, which involves irradiating the N2S particles in a mixed solvent with ultrasound to finely crush them, thereby dissolving and removing the sulfuric acid in the mixed solvent.

[0095] (Preparation of additive b3) As additive b3, N2S (sulfate ion content: 37000 mass ppm) was prepared. Specifically, additive b3 was obtained in the same manner as additive b2, except that the above N2SNa was not subjected to ultrasonic cleaning treatment.

[0096] Organic conductor B3 was prepared in the same manner as organic conductor A1, except that additive b3 was used instead of additive a1.

[0097] Hereinafter, organic conductors A1 to A2 and B1 to B4 were prepared using additives a1 to a2 and b1 to b4, respectively.

[0098] (Preparation of organic conductors) A polymerization solution (additive concentration: 23 mmol / L, pyrrole concentration: 210 mmol / L) containing additive, pyrrole (monomer compound), and water was prepared. A voltage of 1 V was applied between the working electrode and counter electrode in the polymerization solution (electropolymerization). Stainless steel (SUS) plates were used for the working electrode and counter electrode. In this way, polypyrrole (conjugated polymer) was synthesized by polymerization of pyrrole, and a film-like organic conductor (conductive polymer) containing polypyrrole and additive was formed on the working electrode. The working electrode on which the organic conductor was formed was washed with water, peeled off from the working electrode, and dried. In this way, a film-like organic conductor (thickness: 20 to 50 μm) was obtained. Specifically, organic conductor A1 containing additive a1 and polypyrrole was obtained. Organic conductor A2 containing additive a2 and polypyrrole was obtained. Organic conductor B1 containing additive b1 and polypyrrole was obtained. Organic conductor B2 containing additive b2 and polypyrrole was obtained. Organic conductor B3 containing additive b3 and polypyrrole was obtained. Organic conductor B4 containing additive b4 and polypyrrole was obtained.

[0099] [Evaluation of organic conductors] The conductivity (S / cm) of the obtained organic conductor was measured by the method already described.

[0100] The evaluation results are shown in Table 1. In Table 1, additives a1 to a2 and organic conductors A1 to A2 are examples, and additives b1 to b4 and organic conductors B1 to B4 are comparative examples.

[0101] [Table 1]

[0102] The additives a1 and a2 contained AQ2S and had a sulfate ion content of 100 mass ppm or less, and therefore the electrical conductivity of the organic conductors A1 and A2 was improved. Additives b1 and b4 contained AQ2S, but the content of sulfate ions was greater than 100 ppm by mass, so the electrical conductivity of organic conductors B1 and B4 decreased.

[0103] Additives b2 and b3 contained N2S and had a sulfate ion content of more than 100 ppm by mass, which reduced the electrical conductivity of organic conductors B2 and B3. Additive b2 was subjected to ultrasonic cleaning to remove N2S, but the sulfate ion content was more than 100 ppm by mass.

[0104] Next, an electrolytic capacitor having a laminate in which seven capacitor elements were stacked was fabricated in the following manner.

[0105] Electrolytic capacitors E1-E2, R1-R4 (Fabrication of capacitor elements) An aluminum foil (thickness 100 μm) was prepared as a substrate, and the surface of the aluminum foil was etched to obtain an anode body. The anode body was immersed in a chemical conversion solution and a DC voltage of 70 V was applied for 20 minutes to form a dielectric layer containing aluminum oxide (Al2O3) on the surface of the anode body. The anode foil with the dielectric layer formed thereon was immersed in a liquid composition containing a conductive material to form a precoat layer.

[0106] A dopant (additive) was prepared. The additive used was additive a1, b1, b2, or b3 prepared above. The dopant was dispersed in water to obtain a dopant solution (dopant concentration 30% by mass). 1 part by mass of pyrrole was added to 100 parts by mass of the dopant solution to prepare a polymerization solution. The anode foil on which the dielectric layer and precoat layer had been formed was immersed in the obtained polymerization solution, and electrolytic polymerization was performed at an applied voltage of 3 V to form a solid electrolyte layer containing an organic conductor.

[0107] A dispersion of graphite particles in water was applied to the solid electrolyte layer and then dried to form a carbon layer on the surface of the solid electrolyte layer. Next, a silver paste containing silver particles and a binder resin (epoxy resin) was applied to the surface of the carbon layer, and then heated to harden the binder resin, forming a metal paste layer. In this way, a cathode extraction layer composed of the carbon layer and the metal paste layer was formed, and a capacitor element was obtained.

[0108] The seven obtained capacitor elements were stacked, and the anode portions were joined together by laser welding to obtain a laminate.

[0109] (assembly of electrolytic capacitors) An anode lead terminal and a cathode lead terminal were joined to the laminate, and then the laminate and a portion of each lead terminal were sealed with epoxy resin to form an exterior body, completing the electrolytic capacitor.

[0110] In the production of the above electrolytic capacitors, additives a1 and a2 were used to form solid electrolyte layers containing organic conductors A1 and A2, resulting in electrolytic capacitors E1 and E2.Additives b1 and b4 were used to form solid electrolyte layers containing organic conductors B1 and B4, resulting in electrolytic capacitors R1 and R4.

[0111] [Electrolytic capacitor evaluation] (initial capacitance) The initial capacitance of the obtained electrolytic capacitors was measured at a frequency of 100 kHz / Ω using an LCR meter in an environment of 20° C., and the average value was calculated. The evaluation results are shown in Table 2.

[0112] (initial ESR) The initial ESR of the obtained electrolytic capacitor was measured at a frequency of 100 kHz / Ω using an LCR meter in an environment of 20° C., and the average value was calculated.

[0113] The evaluation results are shown in Table 2. In Table 2, electrolytic capacitors E1 and E2 are examples, and electrolytic capacitors R1 to R4 are comparative examples. In Table 2, the capacitance and ESR are expressed as relative values, with the capacitance and ESR of electrolytic capacitor E1 set to 100.

[0114] [Table 2]

[0115] In the electrolytic capacitors E1 to E2, the conductivity of the solid electrolyte (organic conductors A1 to A2) was high, and high capacitance and low ESR were obtained. In electrolytic capacitors R1 to R4, the electrical conductivity of the solid electrolyte (organic conductors B1 to B4) was low, and the ESR increased. [Industrial Applicability]

[0116] According to the present disclosure, an additive capable of significantly increasing the conductivity of an organic conductor can be provided. When such an additive is used in an organic conductor and utilized in various electronic devices such as electrolytic capacitors, the quality of the product can be stabilized even in a high-humidity environment. [Explanation of symbols]

[0117] 100: electrolytic capacitor, 10: capacitor element, 11: anode body, 12: dielectric layer, 13: solid electrolyte layer, 14: cathode lead layer, 141: carbon layer, 142: metal paste layer, 20: exterior body, 30: anode lead terminal, 40: cathode lead terminal

Claims

1. a first compound, the first compound has an anthraquinone skeleton and at least one sulfo group bonded to the anthraquinone skeleton, An additive for an organic conductor, having a sulfate ion content of 100 ppm by mass or less.

2. The additive for an organic conductor according to claim 1 , wherein the content of the sulfate ions is 50 ppm by mass or less.

3. the first compound further has at least one substituent selected from the group consisting of a nitro group, a hydroxy group, a hydrocarbon group, a methoxy group, and a carboxy group; The additive for organic conductors according to claim 1 , wherein the at least one substituent is bonded to the anthraquinone skeleton.

4. The additive for an organic conductor according to claim 1, wherein the first compound comprises at least one selected from the group consisting of anthraquinone-2-sulfonic acid, anthraquinone-1-sulfonic acid, anthraquinone-1,5-disulfonic acid, anthraquinone-1,4-disulfonic acid, anthraquinone-1,6-disulfonic acid, anthraquinone-2,6-disulfonic acid, and anthraquinone-2,7-disulfonic acid.

5. An organic conductor comprising the additive according to claim 1 and a conjugated polymer.

6. The organic conductor according to claim 5 , wherein the conjugated polymer contains a monomer unit corresponding to a pyrrole compound.

7. 6. The organic conductor according to claim 5, having a conductivity of 190 S / cm or more.

8. an anode body; a dielectric layer covering at least a portion of the anode body; a solid electrolyte covering at least a portion of the dielectric layer, An electrolytic capacitor, wherein the solid electrolyte comprises the organic conductor according to claim 5 .

9. providing the additive of claim 1; providing a monomer compound; and polymerizing the monomer compound in the presence of the additive to obtain an organic conductor containing the additive and a conjugated polymer.

10. The method for producing an organic conductor according to claim 9 , wherein the monomer compound includes a pyrrole compound.

11. The method for producing an organic conductor according to claim 9 , wherein the organic conductor has a conductivity of 190 S / cm or more.

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