Additive for organic conductor

Abstract

The additive for an organic conductor includes a naphthalene ring, a sulfo group bonded to the naphthalene ring, and a carboxyl group bonded to the naphthalene ring. When a carbon atom of a naphthalene ring to which a sulfo group is bonded and a carbon atom of a naphthalene ring to which a carboxyl group is bonded are respectively a first carbon atom and a second carbon atom, the number n of carbon atoms sandwiched between the first carbon atom and the second carbon atom is 3 or less. As a result, it is possible to provide an additive capable of significantly improving the moisture resistance of an organic conductor.

Description

Technical Field

[0001] The present disclosure relates to an additive for an organic conductor, and an organic conductor and an electrolytic capacitor using the additive. Background Art

[0002] Conjugated polymers such as polythiophene or polypyrrole show conductivity by adding dopants. Conjugated polymers added with dopants are called conductive polymers or organic conductors. In addition, self-doped organic conductors have also been developed in recent years. Organic conductors can control performance by selecting the type of conjugated polymers or the type of additives (dopants, etc.), and are cheap and lightweight, so they are used in various electronic components. As dopants of additives, proton addition type compounds and electron oxidation type compounds are used.

[0003] For example, it has been proposed to add an organic sulfonic acid to a solid electrolyte layer of a solid electrolytic capacitor (Patent Documents 1 and 2).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2006-108650

[0007] Patent Document 2: International Publication No. 2019 / 131476 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] Electrolytic capacitors using organic conductors have the following problems: when operating in a high humidity environment, the capacitance deteriorates and the equivalent series resistance (ESR) increases.

[0010] Solutions for solving problems

[0011] The first aspect of the present disclosure relates to an additive for an organic conductor, which contains a naphthalene compound, wherein the naphthalene compound includes a naphthalene ring, a sulfonic group bonded to the naphthalene ring, and a carboxyl group bonded to the naphthalene ring, and when the carbon atom of the naphthalene ring to which the sulfonic group is bonded and the carbon atom of the naphthalene ring to which the carboxyl group is bonded are set as the first carbon atom and the second carbon atom, respectively, the number n of carbon atoms adjacent to the first carbon atom and the second carbon atom, or sandwiched between the first carbon atom and the second carbon atom is 3 or less, and the purity of the naphthalene compound is 41% by mass or more.

[0012] A second aspect of the present disclosure relates to an organic conductor comprising a conjugated polymer and the above-mentioned additive.

[0013] A third aspect of the present disclosure relates to an electrolytic capacitor including: an anode body having a dielectric layer on its surface; and a solid electrolyte covering a portion of the dielectric layer, wherein the solid electrolyte includes the organic conductor described above.

[0014] A fourth aspect of the present disclosure relates to an electrolytic capacitor, comprising: an anode body having a dielectric layer on a surface thereof, and a solid electrolyte covering a portion of the dielectric layer, wherein the solid electrolyte comprises an organic conductor, the organic conductor comprises a conjugated polymer and a dopant, 80% by mass or more of the dopant is a naphthalene compound, the naphthalene compound comprises a naphthalene ring, a sulfonic group bonded to the naphthalene ring, and a carboxyl group bonded to the naphthalene ring, and when the carbon atom of the naphthalene ring to which the sulfonic group is bonded and the carbon atom of the naphthalene ring to which the carboxyl group is bonded are respectively set as a first carbon atom and a second carbon atom, the number n of carbon atoms adjacent to the second carbon atom or interposed between the first carbon atom and the second carbon atom is 3 or less.

[0015] A fifth aspect of the present disclosure relates to an additive for an organic conductor, wherein a content of at least one selected from the group consisting of 7-sulfo-2-naphthoic acid compounds, 7-sulfo-1-naphthoic acid compounds, and 6-sulfo-1-naphthoic acid compounds is 80% by mass or more.

[0016] A sixth aspect of the present disclosure relates to an additive for an organic conductor, wherein a content of at least one selected from the group consisting of 7-sulfo-2-naphthoic acid and 7-sulfo-1-naphthoic acid compounds is 80% by mass or more.

[0017] The seventh aspect of the present disclosure relates to an organic conductor comprising a conjugated polymer and a dopant, wherein 80% by mass or more of the dopant is at least one selected from the group consisting of a 7-sulfo-2-naphthoic acid compound, a 7-sulfo-1-naphthoic acid compound and a 6-sulfo-1-naphthoic acid compound.

[0018] An eighth aspect of the present disclosure relates to an organic conductor comprising a conjugated polymer and a dopant, wherein 80% by mass or more of the dopant is at least one selected from the group consisting of 7-sulfo-2-naphthoic acid and 7-sulfo-1-naphthoic acid compounds.

[0019] Effects of the Invention

[0020] Provided are an additive capable of significantly improving the moisture resistance of an organic conductor, an organic conductor having excellent moisture resistance, and an electrolytic capacitor using the same.

[0021] The novel features of the present invention are described in the appended claims, but the present invention, both in terms of configuration and content, together with other objects and features of the present application, will be further well understood from the following detailed description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a cross-sectional view of an electrolytic capacitor according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] Hereinafter, the embodiments of the present disclosure are described by giving examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials are sometimes exemplified, but other numerical values ​​and other materials may also be applied as long as the invention of the present disclosure can be implemented. In this specification, the description of "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read interchangeably as "above numerical value A and below numerical value B". In the following description, when the lower limit and upper limit of numerical values ​​related to specific physical properties, conditions, etc. are exemplified, any of the exemplified lower limits and any of the exemplified upper limits may be arbitrarily combined as long as the lower limit is not above the upper limit.

[0024] In addition, the present disclosure includes a combination of matters recorded in two or more claims arbitrarily selected from the plurality of claims recorded in the attached claims. That is, matters recorded in two or more claims arbitrarily selected from the plurality of claims recorded in the attached claims may be combined as long as no technical contradiction occurs.

[0025] In the following description, the term "comprising" or "including" includes "comprising (or including)", "consisting essentially of", and "consisting of".

[0026] The additive for an organic conductor disclosed in the present invention contains a naphthalene compound (hereinafter also referred to as "naphthalene compound D"), wherein the naphthalene compound includes a naphthalene ring, a sulfonic group bonded to the naphthalene ring, and a carboxyl group bonded to the naphthalene ring. The carbon atom of the naphthalene ring to which the sulfonic group is bonded and the carbon atom of the naphthalene ring to which the carboxyl group is bonded are respectively set as the first carbon atom and the second carbon atom. In this case, the number n of carbon atoms adjacent to the first carbon atom and the second carbon atom or sandwiched between the first carbon atom and the second carbon atom is 3 or less.

[0027] The naphthalene compound D has the function of taking away electrons from the conjugated polymer, converting the insulator or semiconductor into a good conductor. Therefore, additives having such a function are generally called dopants. In this specification, the additive or the naphthalene compound D can be replaced by "dopant".

[0028] It is shown that if an organic conductor containing a naphthalene compound D having a purity of 41% by mass or more and a conjugated polymer is used in a solid electrolyte layer of an electrolytic capacitor, the rate of change of the ESR when the electrolytic capacitor is operated in a high humidity environment can be significantly reduced. The purity of the naphthalene compound D can be 45% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more.

[0029] It should be noted that the purity of naphthalene compound D being 41% by mass or more means that the content of one type of naphthalene compound contained in the category of naphthalene compound D is 41% by mass or more, and at least any of other types of naphthalene compounds D contained in the category of naphthalene compound D, naphthalene compounds not included in the category of naphthalene compound D, and impurities that are not naphthalene compounds can be contained in an amount lower than 59% by mass.

[0030] Generally, when an electrolytic capacitor using an organic conductor is operated in a high humidity environment, the capacitance deteriorates and the ESR tends to increase. This is because water molecules are adsorbed in the organic conductor and additives can be stripped from the conjugated polymer.

[0031] In the following, the rate of change of ESR when operating in a high humidity environment is sometimes referred to as ΔESR. ΔESR tends to increase when the electrolytic capacitor is operated, especially at high temperatures (e.g., above 80°C). Therefore, even if the increase of ΔESR does not become a problem at relatively low temperatures (e.g., below 60°C), the increase of ΔESR at high temperatures becomes significant.

[0032] Naphthalene compound D has at least one sulfonic group and one carboxyl group in the naphthalene ring at a relatively close position. Therefore, at least one sulfonic group and one carboxyl group are easy to become close to the conjugated polymer. It can be considered that the binding force between naphthalene compound D and the conjugated polymer becomes larger. That is, even if the organic conductor adsorbs water molecules in a high humidity environment, the molecules of naphthalene compound D are greatly suppressed from being peeled off from the conjugated polymer, the increase in the resistance of the organic conductor is suppressed, and high conductivity is maintained. Therefore, when an organic conductor containing a high-purity naphthalene compound D as a dopant is used as a solid electrolyte for an electrolytic capacitor, ΔESR can be significantly reduced. Such an effect can also be ensured under high temperature (for example, above 80°C) and high humidity environments.

[0033] The position numbers of carbon atoms constituting the naphthalene ring are as shown in the following formula (I).

[0034] [Chemistry 1]

[0035]

[0036] In this specification, the number n is the number of carbon atoms located between the first carbon atom and the second carbon atom when the shortest carbon chain in the carbon chain connecting the first carbon atom and the second carbon atom in the naphthalene ring is focused. In this way, the number n is determined in a manner that the number n of carbon atoms located between the first carbon atom and the second carbon atom becomes the smallest. The number n does not include the number of the first carbon atom and the second carbon atom. When the first carbon atom and the second carbon atom are adjacent, the number n is 0.

[0037] It should be noted that the carbon chain connecting the first carbon atom and the second carbon atom is a carbon chain constituting a naphthalene ring, and does not contain a substituent possessed by the naphthalene ring. For example, in the case of 7-sulfo-2-naphthoic acid shown in the following formula (ia), the shortest carbon chain in the carbon chain connecting the first carbon atom at position 7 and the second carbon atom at position 2 is a carbon chain connecting the carbon atoms at positions 1, 8a, and 8 in sequence. There are three carbon atoms sandwiched between the first carbon atom at position 7 and the second carbon atom at position 2, so the number n is 3. In the case of 7-sulfo-1-naphthoic acid shown in the following formula (ib), the shortest carbon chain in the carbon chain connecting the first carbon atom at position 7 and the second carbon atom at position 1 is a carbon chain connecting the carbon atoms at positions 8a and 8 in sequence. There are two carbon atoms at positions 8a and 8 between the first carbon atom at position 7 and the second carbon atom at position 1, so the number n is 2.

[0038] [Chemistry 2]

[0039]

[0040] For example, when the number of sulfonic groups and carboxyl groups is 1 each, n is 3 or less, and therefore, the naphthalene compound D does not include a compound having a sulfonic group and a carboxyl group bonded to the 2-position and 6-position of the naphthalene ring, a compound having a sulfonic group and a carboxyl group bonded to the 3-position and 7-position, a compound having a sulfonic group and a carboxyl group bonded to the 1-position and 5-position, and a compound having a sulfonic group and a carboxyl group bonded to the 4-position and 8-position. This is because n is 4 in these compounds.

[0041] It should be noted that, in the naphthalene compound D and the organic conductor, the sulfonic group may be contained in the form of free (-SO3H) or anion (-SO3-), or in the form of a salt. In the organic conductor, the sulfonic group is bonded to the conjugated polymer, or is contained in the form of interacting with the conjugated polymer. In this specification, the sulfonic group including all these forms is sometimes referred to as a "sulfonic group". Similarly, in the naphthalene compound D and the organic conductor, the carboxyl group may be contained in the form of free (-COOH) or anion (-COO-), or in the form of a salt. In this specification, the carboxyl group including all these forms is sometimes referred to as a "carboxyl group". It should be noted that the salt may be a salt formed by a sulfonic acid anion or a carboxylic acid anion and any of an organic base (organic amine, organic ammonium, etc.), an inorganic base (metal hydroxide, ammonia, etc.), and a metal cation (Na, Li, etc.).

[0042] Hereinafter, the additive for an organic conductor (naphthalene compound D), the method for producing the additive, the organic conductor, and the electrolytic capacitor of the present disclosure will be described in more detail.

[0043] [Additives for organic conductors]

[0044] When the naphthalene compound D has one sulfonic group and one carboxyl group, the number n of carbon atoms interposed between the first carbon atom and the second carbon atom to which the substituent is bonded is 0 to 3. In the naphthalene compound D, one sulfonic group and one carboxyl group are located at relatively close positions in the naphthalene ring. As a result, it is considered that a high binding force to the conjugated polymer is obtained as described above, and an increase in the resistance of the organic conductor can be suppressed even in a high humidity environment.

[0045] The number of the sulfo group is at least 1, may be 1 to 5, and may be 1 or 2. The number of the sulfo group is preferably 1 from the viewpoint of easily exerting the electron-withdrawing property of the carboxyl group.

[0046] The number of carboxyl groups is at least 1, and may be 1 to 6 or 1 to 4, or may be 1 or 2. If the number of carboxyl groups in the naphthalene ring is 3 or more, steric repulsion with the conjugated polymer may increase, and therefore, it is preferably 2 or less, and 1 is more preferable than 2.

[0047] The naphthalene compound D may have a first substituent other than a sulfonic group and a carboxyl group on the naphthalene ring. The additive disclosed herein also includes a compound having a first substituent. The first substituent may be an electron-donating group, an electron-withdrawing group other than a sulfonic group and a carboxyl group, etc., but a hydrocarbon group is preferred from the viewpoint of easily exerting a higher electron acceptor function due to the balance between the sulfonic group and the carboxyl group.

[0048] The hydrocarbon group may be any of aliphatic, alicyclic and aromatic. From the viewpoint of easy coordination to the conjugated polymer, the hydrocarbon group is preferably an aliphatic hydrocarbon group. The carbon number of the aliphatic hydrocarbon group is, for example, 1 to 10, 1 to 6 or 1 to 4. The aliphatic hydrocarbon group may be any of saturated or unsaturated.

[0049] Examples of the aliphatic hydrocarbon group include alkyl, alkenyl, alkynyl, and diene groups. Among these, alkyl groups are preferred. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl, and 2-ethylhexyl groups.

[0050] The naphthalene compound D may have one first substituent or two or more first substituents. When the naphthalene compound D has two or more first substituents, at least two first substituents may be the same, or all first substituents may be different.

[0051] From the viewpoint of easily exhibiting a higher electron acceptor function due to the balance between the sulfonic group and the carboxyl group, it is also preferred that the naphthalene compound D has no first substituent.

[0052] The non-aromatic ring Z may be condensed on the naphthalene ring of the naphthalene compound D. In the naphthalene compound D having such a structure, for example, a plurality of (e.g., two) carbon atoms at positions 1 to 8 of the naphthalene ring are connected by an aliphatic chain. The aliphatic chain may be saturated or unsaturated. As such a structure, for example, an acenaphthene ring may be mentioned.

[0053] The naphthalene compound D may have one or more second substituents on the aliphatic chain. Examples of the second substituent include a sulfo group, a carboxyl group, and the groups described for the first substituent. When the naphthalene compound D has two or more second substituents, at least two second substituents may be the same, or all second substituents may be different.

[0054] From the viewpoint of facilitating access to a conjugated polymer, it is preferred that the naphthalene ring of the naphthalene compound D is not condensed with the non-aromatic ring Z described above.

[0055] From the viewpoint of improving the effect of suppressing the increase in resistance of the organic conductor in a high humidity environment, it is preferred to have one sulfonic group and one carboxyl group. Among them, it is preferred that one group selected from these two groups is bonded to one benzene ring constituting the naphthalene ring, and the remaining one group is bonded to the other benzene ring.

[0056] From the viewpoint of further suppressing the increase in resistance of the organic conductor in a high humidity environment, the number of carbon atoms between the sulfonic group and the carboxyl group is preferably 2 or less. It is believed that when the number of carbon atoms between the sulfonic group and the carboxyl group is 2 or less, both the sulfonic group and the carboxyl group are more likely to come closer to the conjugated polymer, and the conductivity of the organic conductor is likely to be improved.

[0057] The naphthalene compound D has the above structure, thereby ensuring a high binding force to the conjugated polymer. The interaction energy of the additive to the conjugated polymer is preferably -13 kcal / mol or less, more preferably -14 kcal / mol or less, more preferably -15 kcal / mol or less, and can also be as low as -17 kcal / mol or -19 kcal / mol or less. It should be noted that the interaction energy between naphthalenesulfonic acid, which is commonly used as a dopant, and polypyrrole is about -10 kcal / mol.

[0058] The interaction energy of the naphthalene compound D with the conjugated polymer is obtained by subtracting the potential energy of the complex of the naphthalene compound D and the conjugated polymer when the naphthalene compound D and the conjugated polymer exist independently. Each potential energy is obtained from the Schrödinger equation using quantum chemical calculation software (Gaussian, Gaussian09).

[0059] The naphthalene compound D can also be represented by the following formula (1).

[0060] [Chemistry 3]

[0061]

[0062] (In formula (1), R 1 ~R 8 are hydrogen atom, sulfo group, carboxyl group or the first substituent, R 1 ~R 8 At least one of them is a sulfo group, R 1 ~R 8 At least one of them is a carboxyl group, selected from R 1 ~R 8 Two of them may be linked to each other to form a non-aromatic ring Z condensed to the naphthalene ring. Ring Z may have a second substituent. 1 ~R 8 When two of them are sulfo groups, exclude R 2 and R 6 When both are sulfonic groups and R 3 and R 7 In the case of a sulfonic group.)

[0063] In formula (1), the above description may be referred to for the sulfo group and the carboxyl group, their number, and their positions. The above description may also be referred to for the first substituent, ring Z, and the second substituent.

[0064] Among the naphthalene compounds D, at least one selected from the group consisting of 7-sulfo-2-naphthoic acid compounds, 7-sulfo-1-naphthoic acid compounds, 6-sulfo-1-naphthoic acid compounds, 1-sulfo-2-naphthoic acid compounds and 4-sulfo-1-naphthoic acid compounds is preferred, and at least one selected from the group consisting of 7-sulfo-2-naphthoic acid compounds, 7-sulfo-1-naphthoic acid compounds and 6-sulfo-1-naphthoic acid compounds is more preferred. In addition to each sulfonaphthoic acid, each compound also includes a sulfonaphthoic acid having a first substituent. Among them, 7-sulfo-2-naphthoic acid and 7-sulfo-1-naphthoic acid compounds are preferred.

[0065] The content of at least one selected from the group consisting of 7-sulfo-2-naphthoic acid compounds, 7-sulfo-1-naphthoic acid compounds and 6-sulfo-1-naphthoic acid compounds in the additive for organic conductor may be, for example, 80% by mass or more. The content of at least one selected from the group consisting of 7-sulfo-2-naphthoic acid and 7-sulfo-1-naphthoic acid compounds in the additive for organic conductor may be, for example, 80% by mass or more.

[0066] The naphthalene compound D may be used alone or in combination of two or more.

[0067] The additive preferably contains 80% to 100% by mass of the naphthalene compound D, more preferably 90% to 100% by mass, and further preferably 95% to 100% by mass.

[0068] [Organic conductors]

[0069] The organic conductor contains: a dopant containing 41% or more of a high-purity naphthalene compound D, and a conjugated polymer. Preferably, more than 80% of the dopant contained in the organic conductor is a naphthalene compound D. More than 80% of the dopant can be selected from at least one of the group consisting of 7-sulfo-2-naphthoic acid compounds, 7-sulfo-1-naphthoic acid compounds and 6-sulfo-1-naphthoic acid compounds. More than 80% of the dopant can be selected from at least one of the group consisting of 7-sulfo-2-naphthoic acid and 7-sulfo-1-naphthoic acid compounds. Naphthalene compound D has excellent electron acceptor performance and can function effectively as a dopant for conjugated polymers. By using naphthalene compound D, a high binding force with a conjugated polymer is obtained. Therefore, even if the organic conductor adsorbs water molecules in a high humidity environment, dedoping is suppressed, and the increase of ΔESR can be suppressed. Thus, even if used in a high humidity environment, the high reliability of the electrolytic capacitor can be ensured.

[0070] The conjugated polymer can be a good conductor as long as it is subjected to the action of a dopant, and examples thereof include π-conjugated polymers and σ-conjugated polymers. The organic conductor may contain one naphthalene compound D as a dopant, or two or more. The organic conductor may contain one conjugated polymer, or two or more.

[0071] As conjugated polymers, polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, or polymers with polythienylene vinylene as basic skeletons can be cited. These polymers also include homopolymers, copolymers of two or more monomers, and their derivatives (substituted products with substituents, etc.). For example, polythiophene includes poly (3,4-ethylenedioxythiophene) and the like.

[0072] Among the conjugated polymers, preferably a conjugated polymer containing a monomer unit corresponding to a pyrrole compound. If such a conjugated polymer is combined with a naphthalene compound D, a higher binding force is easily obtained. As a pyrrole compound, as long as it has a pyrrole skeleton, compounds in which pyrrole, aliphatic rings or heterocycles are condensed in pyrrole or their substitution bodies (compounds with substituents) etc. can be cited. As substituents, alkyl (also including aminoalkyl, hydroxyalkyl), amino, substituted amino, alkoxy, hydroxyl, mercapto, halogen atoms etc. can be cited. Pyrrole or condensation compounds can contain one of these substituents, or can contain two or more. The conjugated polymer preferably has a repeating structure of a monomer unit corresponding to a pyrrole compound.

[0073] The weight average molecular weight (Mw) of the conjugated polymer is not particularly limited, and is, for example, 1,000 or more and 1,000,000 or less.

[0074] In this specification, the weight average molecular weight (Mw) is a value in terms of polystyrene measured by gel permeation chromatography (GPC). GPC is usually measured using a polystyrene gel column and water / methanol (volume ratio 8 / 2) as a mobile phase.

[0075] The amount of the naphthalene compound D is, for example, 0.1 to 400 parts by mass, 1 to 350 parts by mass, or 10 to 300 parts by mass, based on 100 parts by mass of the conjugated polymer.

[0076] Such an organic conductor suppresses an increase in resistance even in a high humidity environment, and therefore has excellent reliability and can be used in various electronic devices. It is particularly suitable for use as a solid electrolyte for electrolytic capacitors.

[0077] [Electrolytic capacitors]

[0078] The electrolytic capacitor includes an anode body having a dielectric layer on its surface and a solid electrolyte covering at least a portion of the dielectric layer. The solid electrolyte includes the organic conductor described above. The solid electrolyte constitutes a cathode portion of the electrolytic capacitor.

[0079] (Anode)

[0080] The anode body may contain: a valve metal, an alloy containing a valve metal, a compound containing a valve metal, and the like. These materials may be used alone or in combination of two or more. As valve metals, for example, aluminum, tantalum, niobium, and titanium are preferably used. An anode body having a porous surface may be obtained, for example, by roughening the surface of a substrate (a foil-like or plate-like substrate, etc.) containing a valve metal by etching or the like. In addition, the anode body may be a molded body of particles containing a valve metal or a sintered body thereof. It should be noted that the sintered body has a porous structure.

[0081] (Dielectric layer)

[0082] 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. The dielectric layer is formed on the porous surface of the anode body and is formed along the inner wall surface of the pores and pits on the surface of the anode body.

[0083] The dielectric layer includes an oxide of a valve metal. For example, when tantalum is used as the valve metal, the dielectric layer includes Ta2O5, and when aluminum is used as the valve metal, the dielectric layer includes Al2O3. It should be noted that the dielectric layer is not limited thereto, as long as it functions as a dielectric. When the surface of the anode body is porous, the dielectric layer is formed along the surface of the anode body (including the inner wall surface of the pores).

[0084] (Cathode)

[0085] The cathode portion includes at least a solid electrolyte covering at least a portion of the dielectric layer. The cathode portion generally includes a solid electrolyte and a cathode extraction layer covering at least a portion of the solid electrolyte.

[0086] (Solid Electrolyte)

[0087] The solid electrolyte includes the above-mentioned organic conductor and is formed in a manner covering the dielectric layer. The solid electrolyte does not necessarily need to cover the entire dielectric layer (the entire surface), as long as it is formed in a manner covering at least a portion of the dielectric layer. In an electrolytic capacitor, the solid electrolyte can form a solid electrolyte layer.

[0088] The solid electrolyte includes a naphthalene compound D and may include other dopants as needed. As other dopants, at least one selected from the group consisting of anions and polyanions is used. As anions, for example, sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, carboxylic acid ions, etc. can be cited. As polyanions, polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylamide sulfonic acid, polymethacrylamide sulfonic acid, polyacrylic acid, polymethacrylic acid, etc. can be cited. Polyanions also include polyester sulfonic acid and phenolsulfonic acid novolac resin.

[0089] From the viewpoint of more efficiently exerting the effect of the naphthalene compound D, the ratio of the naphthalene compound D in the entire dopant is, for example, preferably 80 mass % or more, may be 90 mass % or more, or may be 95 mass % or more. The ratio of the naphthalene compound D in the entire dopant is 100 mass % or less. It is also possible to use only the naphthalene compound D as a dopant.

[0090] That is, the electrolytic capacitor may be an electrolytic capacitor comprising an anode body having a dielectric layer on its surface and a solid electrolyte covering a portion of the dielectric layer, wherein the solid electrolyte comprises an organic conductor, the organic conductor comprises a conjugated polymer and a dopant, and 80% by mass or more of the dopant is the naphthalene compound D.

[0091] The solid electrolyte may contain other additives. Examples of other additives include known additives other than dopants, and known conductive materials other than organic conductors (for example, conductive inorganic materials such as manganese dioxide).

[0092] The solid electrolyte can be formed, for example, by chemically polymerizing and / or electrolytically polymerizing the constituent monomers of the conjugated polymer on the dielectric layer in the presence of a high-purity naphthalene compound D. Alternatively, a solid electrolyte covering the dielectric layer can be formed by bringing a solution in which the conjugated polymer and the naphthalene compound D are dissolved, or a dispersion in which the conjugated polymer and the naphthalene compound D are dispersed, into contact with the dielectric layer. After the solution or the dispersion is brought into contact with the dielectric layer, it can be dried or heated as needed.

[0093] 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 composition of each layer (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.

[0094] If necessary, a layer for improving adhesion or the like may be interposed between the dielectric layer and the solid electrolyte.

[0095] (Cathode extraction layer)

[0096] The cathode lead layer includes, for example, a carbon layer formed on the surface of a solid electrolyte and a metal paste layer formed on the surface of the carbon layer. The cathode layer is formed by sequentially laminating these layers.

[0097] The carbon layer can be formed by immersing the anode body having the dielectric layer at least partially covered by the solid electrolyte in a dispersion containing conductive carbon, or applying a paste containing conductive carbon to the surface of the solid electrolyte. As conductive carbon, for example, graphite such as artificial graphite and natural graphite is used. As the dispersion and paste, for example, conductive carbon is dispersed in an aqueous liquid medium.

[0098] The metal paste layer can be formed, for example, by laminating a composition containing metal particles on the surface of the carbon layer. As the metal paste layer, for example, a silver paste layer formed using a composition containing silver particles and a resin (binder resin) can be used. As the resin, a thermoplastic resin can also be used, but a thermosetting resin such as an imide resin or an epoxy resin is preferably used.

[0099] It should be noted that the structure of the cathode layer is not limited to this, and any structure may be used as long as it has a current collecting function.

[0100] (other)

[0101] For example, a capacitor element having an anode body and a cathode portion is housed in a container or sealed by an outer shell, thereby obtaining an electrolytic capacitor. The electrolytic capacitor can be any of a chip type or a stacked type, or a winding type. The composition of the capacitor element can be selected according to the type of electrolytic capacitor. The capacitor element can also be provided with a cathode body using a metal foil as required, similarly to the anode body. When a metal foil is used for the cathode body, a separator can be configured between the metal foil and the anode body.

[0102] Figure 1 1 is a cross-sectional view schematically showing the structure of an electrolytic capacitor according to one embodiment of the present invention. Figure 1 As shown, the electrolytic capacitor 1 includes: a capacitor element 2; a resin sealing material 3 for sealing the capacitor element 2; an anode terminal 4, at least a portion of which is exposed outside the resin sealing material 3; and a cathode terminal 5. The anode terminal 4 and the cathode terminal 5 can be made of metal such as copper or a copper alloy. The resin sealing material 3 has a substantially rectangular parallelepiped shape, and the electrolytic capacitor 1 also has a substantially rectangular parallelepiped shape. As a raw material for the resin sealing material 3, for example, epoxy resin can be used.

[0103] Capacitor element 2 includes an anode body 6, a dielectric layer 7 covering anode body 6, and a cathode portion 8 covering dielectric layer 7. Cathode portion 8 includes a solid electrolyte layer 9 covering dielectric layer 7 and a cathode lead layer 10 covering solid electrolyte layer 9. Cathode lead layer 10 includes a carbon layer 11 and a metal paste layer 12.

[0104] The anode body 6 includes a region facing the cathode portion 8 and a region not facing the cathode portion 8. In the region of the anode body 6 not facing the cathode portion 8 and in the portion adjacent to the cathode portion 8, an insulating separation layer 13 is formed in a band-like manner to cover the surface of the anode body 6, and the contact between the cathode portion 8 and the anode body 6 is restricted. In the region of the anode body 6 not facing the cathode portion 8, another portion is electrically connected to the anode terminal 4 by welding. The cathode terminal 5 is electrically connected to the cathode portion 8 via an adhesive layer 14 formed of a conductive adhesive.

[0105] The main surfaces 4S and 5S of the anode terminal 4 and the cathode terminal 5 are exposed from the same surface of the resin sealing material 3. The exposed surfaces are used for solder connection with a substrate (not shown) on which the electrolytic capacitor 1 is to be mounted.

[0106] [Example]

[0107] Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0108] The following (A1) to (A5) were used as additives. The naphthalene compound (A1) was 7-sulfo-2-naphthoic acid, the naphthalene compound (A2) was 7-sulfo-1-naphthoic acid, and the naphthalene compound (A3) was 6-sulfo-1-naphthoic acid. (A4) was 1-sulfo-2-naphthoic acid, and (A5) was 4-sulfo-1-naphthoic acid.

[0109] [Chemistry 4]

[0110]

[0111] 《Examples 1 to 5》

[0112] (Manufacturing of electrolytic capacitors)

[0113] Follow the steps below to make Figure 1 The electrolytic capacitor 1 shown was used and its characteristics were evaluated.

[0114] (1) Step of Preparing Anode Body 6

[0115] Anode body 6 was produced by roughening the surface of an aluminum foil (thickness: 100 μm) as a base material by etching.

[0116] (2) Step of forming dielectric layer 3

[0117] Anode body 6 was immersed in a 0.3 mass % phosphoric acid solution at a temperature of 70° C., and a DC voltage of 70 V was applied for 20 minutes, thereby forming dielectric layer 7 containing aluminum oxide.

[0118] (3) Step of forming solid electrolyte layer 9

[0119] Solid electrolyte layer 9 containing polypyrrole and each of naphthalene compounds D (with a purity of 99% or more) (A1) to (A5) as a dopant was formed on dielectric layer 7 by electrolytic polymerization according to the following procedure.

[0120] First, aqueous solutions containing pyrrole monomer and additives (A1) to (A5) were prepared. The concentration of pyrrole monomer in the aqueous solution was 0.5 mol / L, and the concentration of naphthalene compound D was 0.3 mol / L. Sulfuric acid was added to the aqueous solution to adjust the pH to 3.0.

[0121] Anode body 2 and counter electrode having the dielectric layer formed in (2) above were immersed in the obtained aqueous solution, and electrolytic polymerization was performed at 25° C. and a polymerization voltage of 3 V, thereby forming solid electrolyte layer 9 .

[0122] (4) Step of forming cathode lead layer 10

[0123] A dispersion in which graphite particles are dispersed in water is applied to the surface of the solid electrolyte layer 9 obtained in (3) above, and dried in the air, thereby forming a carbon layer 11. Next, a silver paste containing silver particles and an epoxy resin is applied to the surface of the carbon layer 11, and heated, thereby forming a metal paste layer 12. In this way, a cathode extraction layer 10 composed of the carbon layer 11 and the metal paste layer 12 is formed.

[0124] Capacitor element 2 is manufactured in this manner.

[0125] (5) Assembly of electrolytic capacitors

[0126] Cathode lead layer 10 of capacitor element 2 obtained in (4) above is bonded to one end of cathode terminal 5 by conductive adhesive 14. One end of anode body 6 protruding from capacitor element 2 is bonded to one end of anode terminal 4 by laser welding.

[0127] Next, resin sealing material 3 made of insulating resin is formed around capacitor element 2 . At this time, the other end of anode terminal 4 and the other end of cathode terminal 5 are drawn out from resin sealing material 3 .

[0128] In this way, the electrolytic capacitor 1 having a rated voltage of 2 V and an electrostatic capacity of 30 μF was completed.

[0129] (6) Evaluation

[0130] The electrolytic capacitor or the additive was evaluated as follows.

[0131] (a) ΔESR

[0132] In an environment of 20° C., the initial ESR (=Z0) (mΩ) of each electrolytic capacitor at a frequency of 100 kHz was measured using a four-terminal LCR meter.

[0133] After the rated voltage is applied to the electrolytic capacitor for 125 hours at 85°C and 85% RH, the ESR (=Z) (mΩ) is measured at 20°C in the same procedure as the initial ESR. The rate of change in the high humidity environment, ΔESR, is calculated based on ΔESR = (Z-Z0) / Z0.

[0134] (b) Interaction energy

[0135] According to the above steps, the interaction energy between the additive and polypyrrole was calculated.

[0136] Comparative Example 1

[0137] An electrolytic capacitor was produced and evaluated in the same manner as in Example 1 except that naphthalenesulfonic acid was used instead of the naphthalene compound (A1).

[0138] Comparative Example 2

[0139] An electrolytic capacitor was produced and evaluated in the same manner as in Example 1 except that 6-sulfo-2-naphthoic acid was used instead of the naphthalene compound (A1).

[0140] Comparative Example 3

[0141] An electrolytic capacitor was prepared and evaluated in the same manner as in Example 1 except that 5-sulfo-1-naphthoic acid was used instead of the naphthalene compound (A1).

[0142] 《Comparative Example 4》

[0143] The 2Na sulfo-1-naphthoic acid in Example 1 of Patent Document 2 is a mixture containing the following dopant compounds in the ratio of 5:10:40:10:35 in order from the left.

[0144] [Chemistry 5]

[0145]

[0146] An electrolytic capacitor was prepared and evaluated in the same manner as in Example 1 except that the above mixture of 2Na sulfo-1-naphthoic acid was used in place of the naphthalene compound (A1).

[0147] 《Comparative Example 5》

[0148] The 2-Na sulfo-2-naphthoic acid of Example 2 of Patent Document 2 is a mixture containing the following dopant compounds in a ratio of 20:35:5:35:5 in order from the left.

[0149] [Chemistry 6]

[0150]

[0151] An electrolytic capacitor was prepared and evaluated in the same manner as in Example 1 except that the above mixture of 2-naphthoic acid sulfo- was used instead of the naphthalene compound (A1).

[0152] 《Comparative Example 6》

[0153] The sulfo-1-naphthoic acid of Example 4 of Patent Document 2 is a mixture containing the following dopant compounds in the ratio of 5:10:40:10:35 in order from the left.

[0154] [Chemistry 7]

[0155]

[0156] An electrolytic capacitor was prepared and evaluated in the same manner as in Example 1 except that the above mixture of sulfo-1-naphthoic acid was used instead of the naphthalene compound (A1).

[0157] 《Comparative Example 7》

[0158] The sulfo-2-naphthoic acid of Example 5 of Patent Document 2 is a mixture containing the following dopant compounds in a ratio of 20:35:5:35:5 in order from the left.

[0159] [Chemistry 8]

[0160]

[0161] An electrolytic capacitor was prepared and evaluated in the same manner as in Example 1 except that the above mixture of sulfo-2-naphthoic acid was used instead of the naphthalene compound (A1).

[0162] The evaluation results of Examples and Comparative Examples are shown in Table 1. In Table 1, E1 to E5 are Examples 1 to 5, and C1 to C7 are Comparative Examples 1 to 7.

[0163] [Table 1]

[0164]

[0165]

[0166] As shown in Table 1, in E1 to E5 using additives A1 to A5, the increase in the ESR change rate under a high humidity environment is significantly reduced compared to C1 to C3 using naphthalenesulfonic acid. The smaller the interaction energy between the additive and the conjugated polymer, the smaller the ΔESR. It is believed that in E1 to E5, a high binding force between the naphthalene compound D and the conjugated polymer is obtained, thereby suppressing the increase in the resistance of the solid electrolyte layer even in a high humidity environment, and suppressing the increase in ESR.

[0167] Postscript

[0168] The following techniques are disclosed based on the description of the above embodiments.

[0169] (Technology 1)

[0170] An additive for an organic conductor, comprising a naphthalene compound, wherein the naphthalene compound comprises a naphthalene ring, a sulfone group bonded to the naphthalene ring, and a carboxyl group bonded to the naphthalene ring.

[0171] When the carbon atom of the naphthalene ring to which the sulfonic group is bonded and the carbon atom of the naphthalene ring to which the carboxyl group is bonded are respectively the first carbon atom and the second carbon atom, the number n of carbon atoms adjacent to the first carbon atom and the second carbon atom or interposed between the first carbon atom and the second carbon atom is 3 or less,

[0172] The purity of the naphthalene compound is 41% by mass or more.

[0173] (Technique 2)

[0174] According to the additive for organic conductor described in technology 1, the aforementioned naphthalene compound is at least one selected from the group consisting of 7-sulfo-2-naphthoic acid compounds, 7-sulfo-1-naphthoic acid compounds, 6-sulfo-1-naphthoic acid compounds, 1-sulfo-2-naphthoic acid compounds and 4-sulfo-1-naphthoic acid compounds.

[0175] (Technique 3)

[0176] The additive for an organic conductor according to the technique 1 or 2 has an interaction energy with the conjugated polymer of -13 kcal / mol or less.

[0177] (Technique 4)

[0178] The additive for an organic conductor according to any one of techniques 1 to 3, wherein the content of the naphthalene compound is 80% by mass or more.

[0179] (Technique 5)

[0180] An organic conductor comprising: a conjugated polymer and an additive as described in any one of Techniques 1 to 4.

[0181] (Technique 6)

[0182] The organic conductor according to technology 5, wherein the conjugated polymer includes a monomer unit corresponding to a pyrrole compound.

[0183] (Technique 7)

[0184] An electrolytic capacitor comprising: an anode body having a dielectric layer on its surface, and a solid electrolyte covering a portion of the dielectric layer.

[0185] The solid electrolyte includes the organic conductor described in Technology 5 or 6.

[0186] (Technology 8)

[0187] An electrolytic capacitor comprising: an anode body having a dielectric layer on its surface, and a solid electrolyte covering a portion of the dielectric layer.

[0188] The solid electrolyte comprises an organic conductor.

[0189] The organic conductor comprises a conjugated polymer and a dopant.

[0190] More than 80% of the aforementioned dopant is a naphthalene compound,

[0191] The naphthalene compound comprises a naphthalene ring, a sulfone group bonded to the naphthalene ring, and a carboxyl group bonded to the naphthalene ring.

[0192] When the carbon atom of the naphthalene ring to which the sulfonic group is bonded and the carbon atom of the naphthalene ring to which the carboxyl group is bonded are set as the first carbon atom and the second carbon atom, respectively, the number n of carbon atoms adjacent to the first carbon atom and the second carbon atom, or interposed between the first carbon atom and the second carbon atom, is 3 or less.

[0193] (Technique 9)

[0194] In the electrolytic capacitor including the organic conductor according to the eighth aspect, the purity of the naphthalene compound is 41% by mass or more.

[0195] (Technology 10)

[0196] An organic conductor comprising a conjugated polymer and a dopant,

[0197] The aforementioned dopant comprises a naphthalene compound,

[0198] The naphthalene compound comprises a naphthalene ring, a sulfone group bonded to the naphthalene ring, and a carboxyl group bonded to the naphthalene ring.

[0199] When the carbon atom of the naphthalene ring to which the sulfonic group is bonded and the carbon atom of the naphthalene ring to which the carboxyl group is bonded are respectively the first carbon atom and the second carbon atom, the number n of carbon atoms adjacent to the first carbon atom and the second carbon atom or interposed between the first carbon atom and the second carbon atom is 3 or less,

[0200] The purity of the naphthalene compound is 41% by mass or more.

[0201] (Technology 11)

[0202] An additive for an organic conductor, wherein the content of at least one selected from the group consisting of a 7-sulfo-2-naphthoic acid compound, a 7-sulfo-1-naphthoic acid compound and a 6-sulfo-1-naphthoic acid compound is 80% by mass or more.

[0203] (Technology 12)

[0204] The additive for an organic conductor according to technology 11, wherein the content of at least one selected from the group consisting of 7-sulfo-2-naphthoic acid and 7-sulfo-1-naphthoic acid compounds is 80% by mass or more.

[0205] (Technology 13)

[0206] An organic conductor comprising a conjugated polymer and a dopant,

[0207] 80 mass % or more of the dopant is at least one selected from the group consisting of 7-sulfo-2-naphthoic acid compounds, 7-sulfo-1-naphthoic acid compounds, and 6-sulfo-1-naphthoic acid compounds.

[0208] (Technology 14)

[0209] The organic conductor according to technology 13, wherein 80 mass % or more of the dopant is at least one selected from the group consisting of 7-sulfo-2-naphthoic acid and 7-sulfo-1-naphthoic acid compounds.

[0210] The present invention has been described with respect to the presently preferred embodiments, but such disclosure is not to be construed in a limiting sense. Various modifications and variations will be apparent to those skilled in the art upon reading the above disclosure. Therefore, the appended claims should be construed as including all modifications and variations without departing from the spirit and scope of the present invention.

[0211] Industrial Applicability

[0212] According to the present disclosure, an additive capable of significantly improving the moisture resistance of an organic conductor can be provided. Such an additive is used in an organic conductor and in various electronic devices such as an electrolytic capacitor, thereby stabilizing the quality of the product even in a high humidity environment.

[0213] Description of Reference Numerals

[0214] 1: electrolytic capacitor, 2: capacitor element, 3: resin sealing material, 4: anode terminal, 4S: main surface of anode terminal, 5: cathode terminal, 5S: main surface of cathode terminal, 6: anode body, 7: dielectric layer, 8: cathode part, 9: solid electrolyte layer, 10: cathode lead layer, 11: carbon layer, 12: metal paste layer, 13: separation layer, 14: adhesive layer.

Claims

1. An additive for an organic conductor, comprising a naphthalene compound, wherein the naphthalene compound comprises a naphthalene ring, a sulfonic group bonded to the naphthalene ring, and a carboxyl group bonded to the naphthalene ring, When the carbon atom of the naphthalene ring to which the sulfonic group is bonded and the carbon atom of the naphthalene ring to which the carboxyl group is bonded are respectively the first carbon atom and the second carbon atom, the number n of carbon atoms adjacent to the first carbon atom and the second carbon atom or interposed between the first carbon atom and the second carbon atom is 3 or less, The purity of the naphthalene compound is 41% by mass or more.

2. The additive for an organic conductor according to claim 1, wherein The naphthalene compound is at least one selected from the group consisting of 7-sulfo-2-naphthoic acid compounds, 7-sulfo-1-naphthoic acid compounds, 6-sulfo-1-naphthoic acid compounds, 1-sulfo-2-naphthoic acid compounds and 4-sulfo-1-naphthoic acid compounds.

3. The additive for an organic conductor according to claim 1 or 2, wherein the interaction energy with the conjugated polymer is -13 kcal / mol or less.

4. The additive for an organic conductor according to claim 1 or 2, wherein The content of the naphthalene compound is 80% by mass or more.

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

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

7. An electrolytic capacitor comprising: an anode body having a dielectric layer on its surface, and a solid electrolyte covering a portion of the dielectric layer; The solid electrolyte comprises the organic conductor according to claim 5 or 6.

8. An electrolytic capacitor comprising: an anode body having a dielectric layer on its surface, and a solid electrolyte covering a portion of the dielectric layer; The solid electrolyte comprises an organic conductor, The organic conductor comprises a conjugated polymer and a dopant. 80% by mass or more of the dopant is a naphthalene compound, The naphthalene compound comprises a naphthalene ring, a sulfone group bonded to the naphthalene ring, and a carboxyl group bonded to the naphthalene ring. When the carbon atom of the naphthalene ring to which the sulfonic group is bonded and the carbon atom of the naphthalene ring to which the carboxyl group is bonded are set as the first carbon atom and the second carbon atom, respectively, the number n of carbon atoms adjacent to the first carbon atom and the second carbon atom, or sandwiched between the first carbon atom and the second carbon atom, is 3 or less.

9. The electrolytic capacitor comprising an organic conductor according to claim 8, wherein: The purity of the naphthalene compound is 41% by mass or more.

10. An additive for an organic conductor, wherein: The content of at least one selected from the group consisting of 7-sulfo-2-naphthoic acid compounds, 7-sulfo-1-naphthoic acid compounds and 6-sulfo-1-naphthoic acid compounds is 80% by mass or more.

11. The additive for an organic conductor according to claim 10, wherein The content of at least one selected from the group consisting of 7-sulfo-2-naphthoic acid and 7-sulfo-1-naphthoic acid compounds is 80% by mass or more.

12. An organic conductor comprising a conjugated polymer and a dopant, 80 mass % or more of the dopant is at least one selected from the group consisting of 7-sulfo-2-naphthoic acid compounds, 7-sulfo-1-naphthoic acid compounds, and 6-sulfo-1-naphthoic acid compounds.

13. The organic conductor according to claim 12, wherein 80 mass % or more of the dopant is at least one selected from the group consisting of 7-sulfo-2-naphthoic acid and 7-sulfo-1-naphthoic acid compounds.

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