Solid electrolytic capacitor and method for manufacturing same

Abstract

A solid electrolytic capacitor including a porous body containing a valve metal, a dielectric layer formed on a surface of the porous body, and two or more conductive layers covering the dielectric layer, the two or more conductive layers including a first conductive layer formed on a surface of the dielectric layer and a second conductive layer laminated on the first conductive layer, the second conductive layer contains a polyaniline composite in which polyaniline is doped with a proton donor.

Description

Technical Field

[0001] This invention relates to solid electrolytic capacitors and methods for manufacturing the same. Background Technology

[0002] In solid electrolytic capacitors such as aluminum electrolytic capacitors and tantalum capacitors, conductive polymers are used as the material for the solid electrolyte layer. The outer layer of a solid electrolytic capacitor typically has a three-layer stacked structure consisting of a conductive polymer layer, a carbon layer, and a silver paste layer. The charge stored inside the capacitor element is extracted to the outside through these layers.

[0003] Patent Document 1 discloses a tantalum capacitor in which a conductive polymer layer, a carbon layer and a silver layer are sequentially formed on a tantalum sintered body having a dielectric oxide layer (Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2023-99299 Summary of the Invention

[0007] However, in the conventional configuration disclosed in Patent Document 1, there is a problem that tantalum capacitors have low resistance to damp heat and moisture, and the environment in which they can be used is limited.

[0008] Therefore, the inventors conducted in-depth research and found that by adopting a specific structure in each layer of the solid electrolytic capacitor, a solid electrolytic capacitor with excellent resistance to damp heat can be obtained, thus completing the present invention.

[0009] The purpose of this invention is to provide a solid electrolytic capacitor with excellent resistance to damp heat and moisture, and a method for manufacturing the same.

[0010] According to the present invention, the following solid electrolytic capacitors and the like are provided.

[0011] 1. A solid electrolytic capacitor comprising a porous body containing a valve metal, a dielectric layer formed on the surface of the porous body, and two or more conductive layers covering the dielectric layer.

[0012] The two or more conductive layers described above each have a first conductive layer formed on the surface of the dielectric layer and a second conductive layer stacked on the first conductive layer.

[0013] The second conductive layer described above comprises a polyaniline composite doped with polyaniline using a proton donor.

[0014] 2. The solid electrolytic capacitor according to 1 above, wherein the dielectric layer comprises an oxide of the valve metal.

[0015] 3. The solid electrolytic capacitor described in 1 or 2 above, wherein the polyaniline composite is doped with sulfosuccinic acid.

[0016] 4. The solid electrolytic capacitor according to any one of 1 to 3 above, wherein the second conductive layer further comprises a thixotropic agent.

[0017] 5. The solid electrolytic capacitor described in section 4 above, wherein the thixotropic agent comprises inorganic particles.

[0018] 6. The solid electrolytic capacitor described in 5 above, wherein the inorganic particles comprise one or more selected from silicon dioxide, titanium dioxide, aluminum oxide, and zirconium oxide.

[0019] 7. The solid electrolytic capacitor according to any one of 4 to 6 above, wherein the content of the thixotropic agent relative to the entire second conductive layer is 0.01 to 50% by mass.

[0020] 8. The solid electrolytic capacitor according to any one of 1 to 7 above, wherein the second conductive layer further comprises a thickener.

[0021] 9. The solid electrolytic capacitor described in section 8 above, wherein the thickener is a polyether compound or a cellulose compound.

[0022] 10. The solid electrolytic capacitor according to 8 or 9 above, wherein the content of the thickener relative to the entire second conductive layer is 0.001 to 5 by mass.

[0023] 11. The solid electrolytic capacitor according to any one of 1 to 10 above, wherein the second conductive layer is formed of a conductive polymer composition that satisfies the following conditions (P1) and (P2).

[0024] (P1) The viscosity at a shear rate of 10 (1 / s) is above 1 Pa·s.

[0025] (P2) After applying shear at a shear rate of 10 (1 / s) for 30 seconds, the viscosity at a shear rate of 0.0001 (1 / s) is 10 Pa·s or higher and satisfies the following formula (P2-1).

[0026]

Mathematical Formula 1

[0027]

[0028] 12. The solid electrolytic capacitor described in any one of 1 to 11 above, wherein the valve metal is selected from aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth and antimony.

[0029] 13. A method for manufacturing a solid electrolytic capacitor, comprising the following steps (A-1) or (A-2), step (B), and step (C).

[0030] Process (A-1): Impregnating part or all of the porous body containing the valve metal oxide in a first conductive polymer composition comprising a conductive polymer and a solvent;

[0031] Step (A-2): Impregnate part or all of the porous body containing the valve metal oxide in a first conductive polymer composition comprising a conductive polymer, a solvent and a phenolic compound;

[0032] Step (B): The porous body is removed from the first conductive polymer composition used in step (A-1) or (A-2) and held at a temperature below the boiling point of the solvent contained in the first conductive polymer composition.

[0033] Step (C): Immerse a portion or the entire porous body after step (B) in a second conductive polymer composition containing a conductive polymer, a thixotropic agent, and a solvent that are the same as or different from the first conductive polymer composition, and then dry it.

[0034] 14. The method for manufacturing a solid electrolytic capacitor as described in 13 above, wherein the content of the thixotropic agent relative to the total content of the second conductive polymer composition is 0.2 to 5% by mass.

[0035] 15. The method for manufacturing a solid electrolytic capacitor according to 13 or 14 above, wherein the second conductive polymer composition satisfies the following conditions (P1) and (P2).

[0036] (P1) The viscosity at a shear rate of 10 (1 / s) is above 1 Pa·s.

[0037] (P2) After applying shear at a shear rate of 10 (1 / s) for 30 seconds, the viscosity at a shear rate of 0.0001 (1 / s) is 10 Pa·s or higher and satisfies the following formula (P2-1).

[0038]

Mathematical Formula 2

[0039]

[0040] 16. A solid electrolytic capacitor obtained by the manufacturing method of a solid electrolytic capacitor described in any one of 13 to 15 above.

[0041] According to the present invention, a solid electrolytic capacitor with excellent resistance to damp heat and a method thereof can be provided. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of a solid electrolytic capacitor according to one aspect of the present invention.

[0043] Figure 2 This is an enlarged schematic diagram of the cross-section of a solid electrolytic capacitor according to one embodiment of the present invention. Detailed Implementation

[0044] The solid electrolytic capacitor and its manufacturing method of the present invention will be described in detail below.

[0045] It should be noted that in this specification, "x~y" refers to a numerical range "above x and below y". The upper and lower limits of the numerical range can be combined arbitrarily.

[0046] [Solid electrolytic capacitors]

[0047] One embodiment of the solid electrolytic capacitor of the present invention comprises a porous body containing a valve metal, a dielectric layer formed on the surface of the porous body, and two or more conductive layers covering the dielectric layer. Furthermore, the two or more conductive layers have a first conductive layer formed on the surface of the dielectric layer and a second conductive layer stacked on the first conductive layer, wherein the second conductive layer comprises a polyaniline composite doped with polyaniline using a proton donor.

[0048] One embodiment of the present invention provides a solid electrolytic capacitor with the above-described configuration, which exhibits excellent resistance to damp heat.

[0049] Figure 1 This is a schematic diagram of a solid electrolytic capacitor according to one aspect of the present invention. Figure 2 This is an enlarged schematic diagram of the cross-section of the solid electrolytic capacitor.

[0050] In one embodiment, a solid electrolytic capacitor 100 of the present invention includes an anode body 110, a first conductive layer 120 coated with a dielectric layer, a second conductive layer 130 stacked on the first conductive layer, a carbon layer 140 stacked on the second conductive layer, and a silver layer 150 stacked on the carbon layer. The anode body 110 includes a porous body 111 containing a valve metal and a dielectric layer 112 formed on the surface of the porous body.

[0051] One aspect of the solid electrolytic capacitor of the present invention may include leads 160 containing valve metal. The leads 160 penetrate at least a portion of the porous body 111.

[0052] The first conductive layer 120 is also known as the inner solid electrolyte layer, inner coating layer, inner layer, etc.

[0053] The second conductive layer 130 is also known as the external coating layer, outer layer, etc.

[0054] The components of a solid electrolytic capacitor constituting one aspect of the present invention will now be described.

[0055] [Porous body]

[0056] The porous body contains valve metal. The porous body is a material with fine pores, preferably having multiple fine pores with a diameter of about 1 nm to 10 μm.

[0057] By using porous materials, the surface area of ​​the valve metal can be increased. As a result, the capacitance of the capacitor can be increased, enabling the creation of small capacitors with large capacitance.

[0058] There are no particular restrictions on the shape of porous bodies; for example, they can be shaped bodies or films (foils) with a certain thickness.

[0059] The length, width, and thickness of the porous body as a shaped body are not particularly limited, for example, each can be 15 μm or more and 5 mm or less.

[0060] The thickness of the porous body used as a membrane (foil) is not particularly limited, for example, it is 15 μm or more and 300 μm or less.

[0061] Examples of porous structures include tunnel-like pits, sponge-like pits, or dense gaps between powder particles, but are not limited to these. A porous body may contain only one of these structures, or it may contain two or more.

[0062] There are no particular limitations on the manufacturing method of porous bodies. For example, porous bodies can be formed by sintering metal powder containing valve metal, or by etching a film (foil) containing valve metal to form multiple pores.

[0063] In one embodiment, the porous body is a sintered body containing valve metal, which is formed by sintering a shaped body containing valve metal powder and a binder.

[0064] Sintered bodies containing valve metal can be manufactured by mixing valve metal powder, binder and solvent in a certain ratio, compressing the mixed powder into a cuboid, and then sintering it under high temperature and high vibration.

[0065] Metals that can be used as valve metals include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth and antimony, with aluminum or tantalum being preferred.

[0066] These metals can be used alone or in combination of two or more.

[0067] Examples of adhesives include cellulose-based adhesives.

[0068] Examples of cellulose-based binders include one or more selected from nitrocellulose, methylcellulose, ethylcellulose, and hydroxypropylcellulose.

[0069] One type of adhesive can be used alone, or two or more types can be used together.

[0070] [Dielectric layer]

[0071] The dielectric layer is formed on the surface of the porous body.

[0072] In one embodiment, the dielectric layer comprises an oxide of the valve metal contained in the porous body.

[0073] There are no particular limitations on the manufacturing method of the dielectric layer. Examples include anodic oxidation, which involves passing an electric current through a porous body as an anode in an electrolyte solution to grow an oxide film on the surface.

[0074] Examples of electrolyte solutions include phosphates, borates, citrates, and adipates. One type of electrolyte solution can be used alone, or two or more can be used in combination.

[0075] The thickness of the dielectric layer is designed according to the required voltage resistance, electrostatic capacitance, etc., and is preferably 1 nm or more and 500 nm or less, more preferably 10 nm or more and 100 nm or less.

[0076] [Anode]

[0077] In this specification, the porous body containing valve metal and the dielectric layer formed on the surface of the porous body are collectively referred to as the anode body.

[0078] The liquid capacitance of the anode is preferably 100 μF or more and 2000 μF or less, and more preferably 500 μF or more and 1500 μF or less.

[0079] The liquid capacitance of the anode can be measured using the method described in the examples.

[0080] [First conductive layer]

[0081] The first conductive layer (hereinafter also referred to as the "internal solid electrolyte layer") is covered with a dielectric layer.

[0082] The material constituting the first conductive layer is not particularly limited as long as it is a material capable of forming a conductive layer. For example, the first conductive layer preferably contains a conductive polymer.

[0083] In one embodiment, the first conductive layer comprises one or more selected from polyaniline, polyaniline derivatives, polythiophene, polythiophene derivatives, polypyrrole, and polypyrrole derivatives. Here, as polythiophene, polyanion-doped polythiophene such as polystyrene sulfonic acid, or self-doped polythiophene, etc., can be used.

[0084] These conductive polymers can be polymerized after the monomers have been impregnated inside the anode body, or the polymers can be impregnated inside the anode body.

[0085] These conductive polymers can be used alone or in combination of two or more.

[0086] In one embodiment, the first conductive layer comprises polyaniline or a polyaniline derivative.

[0087] The weight-average molecular weight of polyaniline is preferably 10,000 or more, more preferably 20,000 or more, even more preferably 30,000 or more and 1,000,000 or less, even more preferably 40,000 or more and 1,000,000 or less, and particularly preferably 52,000 or more and 1,000,000 or less.

[0088] For example, in the case of a solid electrolyte layer used in a solid electrolytic capacitor, from the viewpoint of improving the strength of the resulting electrolyte layer, a higher molecular weight of the conductive polymer is generally preferred. On the other hand, if the molecular weight is large, the viscosity becomes high, and therefore, it may be difficult to penetrate into the fine pores of the porous body.

[0089] The weight-average molecular weight of polyaniline was determined using the method described in the examples.

[0090] From the perspective of versatility and economy, polyaniline is preferably unsubstituted polyaniline.

[0091] Examples of substituents that have substituents include straight-chain or branched hydrocarbon groups such as methyl, ethyl, hexyl, and octyl; alkoxy groups such as methoxy and ethoxy; aryloxy groups such as phenoxy; and halogenated hydrocarbons such as trifluoromethyl (-CF3 group).

[0092] In one embodiment, the first conductive layer comprises a polyaniline composite doped with polyaniline using a proton donor. The use of the polyaniline composite facilitates improved solubility in solvents.

[0093] The fact that proton donors are doped with polyaniline can be confirmed by ultraviolet-visible-near-infrared spectroscopy and X-ray photoelectron spectroscopy. Proton donors can be used without particular restrictions as long as they have sufficient acidity to generate charge carriers in polyaniline.

[0094] Examples of proton donors include Brønsted acids or their salts. Organic acids or their salts are preferred, and proton donors represented by the formula (I) below are even more preferred.

[0095] M(XARn)m (I)

[0096] In formula (I), M is a hydrogen atom, an organic free radical, or an inorganic free radical.

[0097] Examples of organic free radicals include pyridinium, imidazolium, and phenylamine. Examples of inorganic free radicals include lithium, sodium, potassium, cesium, ammonium, calcium, magnesium, and iron.

[0098] In formula (I), X is an anionic group, such as -SO3. - -PO3 2- radical, -PO4(OH) - base, -OPO3 2- radical, -OPO2(OH) - base, -COO - The base is preferably -SO3. - base.

[0099] In formula (I), A is a substituted or unsubstituted hydrocarbon group (with the number of carbon atoms ranging from 1 to 20, for example).

[0100] The hydrocarbon group can be a chain or cyclic saturated aliphatic hydrocarbon group, a chain or cyclic unsaturated aliphatic hydrocarbon group, or an aromatic hydrocarbon group.

[0101] Examples of chain-like saturated aliphatic hydrocarbon groups include straight-chain or branched alkyl groups (with, for example, 1 to 20 carbon atoms).

[0102] Examples of cyclic saturated aliphatic hydrocarbon groups include cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl (with, for example, 3 to 20 carbon atoms).

[0103] Cyclic saturated aliphatic hydrocarbon groups can be fused together with multiple cyclic saturated aliphatic hydrocarbon groups. Examples include norbornyl, adamantyl, and fused adamantyl.

[0104] Examples of chain-like unsaturated aliphatic hydrocarbons (with, for example, 2 to 20 carbon atoms) include straight-chain or branched alkenyl groups.

[0105] Examples of cyclic unsaturated aliphatic hydrocarbon groups (with, for example, 3 to 20 carbon atoms) include cyclic alkenyl groups.

[0106] Examples of aromatic hydrocarbon groups (with 6 to 20 carbon atoms) include phenyl, naphthyl, and anthracene.

[0107] When A is a substituted hydrocarbon group, the substituent can be alkyl (e.g., 1 to 20 carbon atoms), cycloalkyl (e.g., 3 to 20 carbon atoms), vinyl, allyl, aryl (e.g., 6 to 20 carbon atoms), alkoxy (e.g., 1 to 20 carbon atoms), halogen atom, hydroxyl, amino, imino, nitro, silyl or a group containing an ester bond.

[0108] In equation (I), R is bonded to A and is -H, -R. 1 -OR 1 -COR 1 -COOR 1 -(C=O)-(COR) 1 ), or -(C=O)-(COOR) 1 The substituents shown are shown in the diagram.

[0109] R 1 It can contain substituents such as hydrocarbon groups, silyl groups, alkylsilyl groups, and -(R) groups. 2 O)xR 3 base, or - (OSiR) 3 2) x-OR 3 base.

[0110] R 2 It is an alkylene group, R 3 It is a hydrocarbon group, and x is an integer greater than or equal to 1.

[0111] When x is greater than 2, multiple R 2 They can be the same or different, multiple Rs 3 They can be the same or different.

[0112] As R 1 Examples of hydrocarbon groups (with 1 to 20 carbon atoms) include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, pentadecyl, and eicosyl. Hydrocarbon groups can be linear or branched.

[0113] The substituents of the hydrocarbon group are alkyl (e.g., 1 to 20 carbon atoms), cycloalkyl (e.g., 3 to 20 carbon atoms), vinyl, allyl, aryl (e.g., 6 to 20 carbon atoms), alkoxy (e.g., 1 to 20 carbon atoms), halogen atom, hydroxyl, amino, imino, nitro or a group containing an ester bond. R 3 The hydrocarbon group also has the same properties as R. 1 same.

[0114] As R 2 Alkylenes (with 1 to 20 carbon atoms, for example), such as methylene, ethylene, propylene, etc.

[0115] In equation (I), n is an integer greater than or equal to 1. When n is greater than or equal to 2, multiple Rs can be the same or different from each other.

[0116] In equation (I), m represents the valence of M / the valence of X.

[0117] As the compound represented by formula (I), dialkylbenzene sulfonic acid, dialkylnaphthalene sulfonic acid, or a compound containing two or more ester bonds are preferred.

[0118] The compounds containing two or more ester bonds are more preferably sulfophthalic acid esters or compounds represented by formula (II).

[0119]

Chemical Formula 1

[0120]

[0121] In equation (II), M and X are the same as in equation (I). X is preferably -SO3. - base.

[0122] R 4 R 5 and R 6 Each is independently a hydrogen atom, a hydrocarbon group, or an R group. 9 3Si-based. 3 R 9 Each is an independent hydrocarbon group.

[0123] As R 4 R 5 and R 6 Examples of hydrocarbon groups that are hydrocarbon groups include straight-chain or branched alkyl groups with 1 to 24 carbon atoms, aryl groups containing an aromatic ring (with 6 to 20 carbon atoms for example), and alkylaryl groups (with 7 to 20 carbon atoms for example).

[0124] As R 9 hydrocarbon group, with R 4 R 5 and R 6 The situation is the same.

[0125] R in equation (II) 7 and R 8 Each is independently a hydrocarbon group or -(R) 10 O) q -R 11 base.

[0126] R 10 It is a hydrocarbon group or a methylene silyl group.

[0127] R 11 It is a hydrogen atom, a hydrocarbon group, or R 12 3Si-.

[0128] q is an integer greater than or equal to 1.

[0129] 3 Rs 12 Each is an independent hydrocarbon group.

[0130] As R 7 and R 8 Examples of hydrocarbon groups that are hydrocarbon groups include straight-chain or branched alkyl groups with 1 to 24 carbon atoms, preferably with 4 or more carbon atoms, aryl groups containing an aromatic ring (with 6 to 20 carbon atoms, for example), and alkylaryl groups (with 7 to 20 carbon atoms, for example).

[0131] Specific examples include butyl, pentyl, hexyl, octyl, decyl, etc., which are all straight-chain or branched.

[0132] As R 7 and R 8 R in 10 When the hydrocarbon group is a hydrocarbon group, it can be a straight-chain or branched alkylene group having 1 to 24 carbon atoms, an arylene group containing an aromatic ring (having, for example, 6 to 20 carbon atoms), an alkylarylene group (having, for example, 7 to 20 carbon atoms), or an arylalkylene group (having, for example, 7 to 20 carbon atoms).

[0133] Additionally, as R 7 and R 8 R in 11 and R 12 When the hydrocarbon group is a hydrocarbon group, it is related to R. 4 R 5 and R 6 The situation is the same, and q is preferably 1 to 10.

[0134] As R 7 and R 8 For - (R 10 O) q -R 11 Specific examples of compounds represented by formula (II) at the base time can be given by two compounds represented by the following formulas.

[0135]

Chemical Formula 2

[0136]

[0137] (In the formula, X is the same as in formula (I).)

[0138] The compound represented by formula (II) above is further preferably a sulfosuccinic acid derivative represented by formula (III) below.

[0139]

Chemical Formula 3

[0140]

[0141] In equation (III), M is the same as in equation (I).

[0142] m' is the valence of M.

[0143] R 13 and R 14 Each is independently a hydrocarbon group or -(R) 15 O) r -R 16 base.

[0144] R 15 R is a hydrocarbon group or a methylene silyl group. 16 It is a hydrogen atom, a hydrocarbon group, or R 17 3Si-based, where r is an integer greater than or equal to 1.

[0145] 3 Rs 17 Each is an independent hydrocarbon group.

[0146] When r is 2 or higher, multiple R 15 They can be the same or different.

[0147] As R 13 and R 14 When the hydrocarbon group is a hydrocarbon group, it is related to R. 7 and R 8 same.

[0148] R 13 and R 14 In, as R 15 When the hydrocarbon group is a hydrocarbon group, it is related to the above R. 10 same.

[0149] Additionally, R 13 and R 14 In, as R 16 and R 17 When the hydrocarbon group is a hydrocarbon group, it is related to the above R. 4 R 5 and R 6 same.

[0150] r is preferably 1 to 10.

[0151] As R 13 and R 14 For - (R 15 O) r -R 16 Specific examples of base time, and R 7 and R 8 - (R) 10 O) q -R 11 same.

[0152] As R 13 and R14 hydrocarbon group, with R 7 and R 8 The same, preferably butyl, hexyl, 2-ethylhexyl, or decyl.

[0153] As the compound represented by formula (I), di(2-ethylhexyl)sulfosuccinic acid and sodium di(2-ethylhexyl)sulfosuccinate are preferred.

[0154] It is known that the conductivity and solubility of polyaniline composites in solvents can be controlled by modifying the structure of the aforementioned proton donors (Japanese Patent No. 3384566). In this embodiment, the optimal proton donor can be selected according to the required characteristics for each application.

[0155] The doping ratio of the proton donor relative to polyaniline is preferably 0.30 or higher and 0.65 or lower, more preferably 0.32 or higher and 0.60 or lower, even more preferably 0.33 or higher and 0.57 or lower, and particularly preferably 0.34 or higher and 0.55 or lower. Generally, if the doping ratio is 0.30 or higher, the solubility of the polyaniline composite in organic solvents becomes sufficient.

[0156] The doping rate is defined as (the number of moles of proton donors doped in polyaniline) / (the number of moles of monomer units in polyaniline). For example, a doping rate of 0.5 for a polyaniline complex containing unsubstituted polyaniline and proton donors means that one proton donor is doped for every two monomer units of polyaniline.

[0157] It should be noted that the doping rate can be calculated simply by measuring the molar number of proton donors and monomer units of the polyaniline composite. For example, when the proton donor is an organic sulfonic acid, the doping rate can be calculated by quantifying the molar number of sulfur atoms derived from the proton donor and the molar number of nitrogen atoms derived from the monomer units of polyaniline using organic elemental analysis and taking the ratio of these values.

[0158] The polyaniline complex preferably comprises unsubstituted polyaniline and sulfonic acid as a proton donor, and satisfies the following formula (1).

[0159] 0.32≤S5 / N5≤0.60 (1)

[0160] (In the formula, S5 is the total number of moles of sulfur atoms contained in the polyaniline composite, and N5 is the total number of moles of nitrogen atoms contained in the polyaniline composite.)

[0161] It should be noted that the molar numbers of nitrogen and sulfur atoms mentioned above are, for example, values ​​determined by organic elemental analysis.

[0162] There are no particular limitations on the method for manufacturing polyaniline composites; for example, they can be manufactured using the methods described below.

[0163] For example, the proton donor, the aniline corresponding to the polyaniline, and the desired surfactant (e.g., a nonionic emulsifier) ​​are dissolved in a water-immiscible organic solvent (e.g., a hydrocarbon solvent (preferably toluene or xylene)), an acidic aqueous solution (e.g., an aqueous solution of phosphoric acid) is added, the reaction mixture having two liquid phases of water-immiscible organic solvent and water is stirred, a polymerization initiator (e.g., ammonium persulfate) is added, and polymerization is carried out.

[0164] After polymerization, the water-immiscible organic solvent phase is separated by allowing it to stand, thereby obtaining a water-immiscible organic solvent solution of the polyaniline composite. This solution is then transferred to an evaporator to evaporate and distill off the volatile components, yielding the polyaniline composite (protonated polyaniline).

[0165] [Second conductive layer]

[0166] like Figure 1 As shown, a second conductive layer (hereinafter also referred to as the "outer coating layer") is stacked on top of a first conductive layer. The first conductive layer penetrates into the pores of the anode body. In contrast, the second conductive layer further coats the anode body and the first conductive layer from the outside.

[0167] The second conductive layer comprises a polyaniline composite doped with polyaniline using a proton donor. The polyaniline composite doped with proton donor can be used alone or in combination with two or more types.

[0168] As a polyaniline, proton donor, and polyaniline complex, it can be applied to the matters described in the first conductive layer.

[0169] In one embodiment, the proton donor used in the second conductive layer is preferably a compound shown in formulas (I) to (III) above, and particularly preferably di(2-ethylhexyl)sulfosuccinic acid or sodium di(2-ethylhexyl)sulfosuccinate. Since the polyaniline composite doped with these proton donors has high solubility in organic solvents, it is easy to prepare a conductive polymer composition used in forming the second conductive layer. Specifically, the selection of solvents used in the conductive polymer composition can be expanded. Furthermore, since the viscosity (concentration) of the conductive polymer composition is easily adjustable, the thickness of the second conductive layer is easily adjusted. In addition, high solubility in organic solvents implies high hydrophobicity, which can be expected to improve the capacitor's resistance to damp heat.

[0170] In one embodiment, the second conductive layer further comprises a thixotropic agent.

[0171] The thixotropic agent can be incorporated, for example, into the conductive polymer composition used to form the second conductive layer. The second conductive layer is formed by impregnating a porous body having the first conductive layer in the conductive polymer composition, and the second conductive layer can contain the thixotropic agent.

[0172] If a thixotropic agent is contained, the conductive polymer composition exhibits the property that its viscosity increases at low shear forces and decreases at high shear forces. That is, the conductive polymer composition containing the thixotropic agent flows well when impregnated with an anode having formed a first conductive layer, and its viscosity increases when the anode is removed from the composition, readily forming a second conductive layer of a certain thickness.

[0173] As a thixotropic agent, any material capable of imparting thixotropy can be used without particular restrictions. Examples include inorganic particles, carbon nanotubes, carbon powder, and fluoropolymer powder. Inorganic particles are preferred as thixotropic agents.

[0174] Examples of inorganic particles include silicon dioxide, titanium dioxide, aluminum oxide, and zirconium oxide.

[0175] The surface of inorganic particles can be modified as needed using silane coupling agents, etc.

[0176] Thixotropic agents can be used alone or in combination of two or more.

[0177] The average particle size of inorganic particles is not particularly limited as long as it is within the range that can impart thixotropy, for example, 1 to 100 nm, preferably 1 to 50 nm, and more preferably 2 to 40 nm.

[0178] The average particle size of inorganic particles can be calculated by using the BET method to determine the specific surface area, which is then converted to the desired value. The specific surface area calculation based on the BET method is performed under the conditions described in JIS Z8830 (2013).

[0179] In one embodiment, the thixotropic agent contains 0.01 to 50% by mass relative to the total content of the second conductive layer, preferably 0.1 to 40% by mass, and more preferably 1 to 20% by mass.

[0180] In one embodiment, the second conductive layer further comprises a thickener.

[0181] Thickeners and thixotropic agents can similarly be incorporated, for example, into a conductive polymer composition used to form the second conductive layer. The second conductive layer is formed by impregnating a porous body having the first conductive layer in this conductive polymer composition, and the second conductive layer can contain a thickener.

[0182] If the conductive polymer composition used to form the second conductive layer contains a thickener, a second conductive layer with a desired thickness can be easily formed. In particular, in the case of manufacturing a square capacitor, a second conductive layer with a desired thickness can be easily formed at the side edges and the flat side portions.

[0183] The side edge refers to the corner of the side surface (the part where adjacent side surfaces intersect each other) when the bottom surface is used as the bottom surface during the formation of the second conductive layer of the square capacitor.

[0184] The side flat portion refers to the portion of the side surface in the formation of the second conductive layer of a square capacitor, where the bottom surface is used as the base during dip coating.

[0185] The thickness of the second conductive layer at the side edge (side edge thickness) and the thickness of the second conductive layer at the side flat portion (side flat portion thickness) can be measured by the method described in the embodiments.

[0186] In addition, if the conductive polymer composition used to form the second conductive layer contains a thickener, it is easy to reduce the number of dip coatings required to obtain the second conductive layer with the desired thickness.

[0187] Examples of thickeners include polyether compounds and cellulose compounds.

[0188] Examples of polyether compounds include polyethylene oxide (EO)-polypropylene oxide (PO) copolymers (e.g., EP1550H (manufactured by Meisei Chemical Industry Co., Ltd.)).

[0189] Examples of cellulose-based compounds include cellulose ethers (e.g., ethyl cellulose, methyl cellulose), hydroxyethyl cellulose, or hydroxypropyl methyl cellulose. Cellulose ethers are particularly suitable from the viewpoint of high thickening effect and ease of acquisition. Among cellulose ethers, ethyl cellulose is particularly suitable.

[0190] In addition, commercially available cellulose compounds include EC-N300 (manufactured by Ashland), N200 (manufactured by Ashland), and Klucel G (manufactured by Ashland).

[0191] Thickeners can be used alone or in combination of two or more.

[0192] In one embodiment, the content of the thickener relative to the entire second conductive layer is, for example, 0.001% by mass or more, 0.002% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.02% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more.

[0193] In one embodiment, the content of the thickener relative to the entire second conductive layer is, for example, 10% by mass or less, 5% by mass or less, 3% by mass or less, 2% by mass or less, or 1% by mass or less.

[0194] In one embodiment, the thickener contains 0.001 to 10% by mass, 0.001 to 5% by mass, 0.01 to 5% by mass, 0.1 to 5% by mass, or 0.3 to 1% by mass relative to the total content of the second conductive layer.

[0195] In one embodiment, the second conductive layer comprises a thixotropic agent and a thickener.

[0196] In one embodiment, the second conductive layer is formed from a conductive polymer composition that satisfies the following conditions (P1) and (P2).

[0197] (P1) The viscosity at a shear rate of 10 (1 / s) is above 1 Pa·s.

[0198] (P2) After applying shear at a shear rate of 10 (1 / s) for 30 seconds, the viscosity at a shear rate of 0.0001 (1 / s) is 10 Pa·s or higher and satisfies the following formula (P2-1).

[0199]

Mathematical Expression 3

[0200]

[0201] If the second conductive layer satisfies conditions (P1) and (P2), then when the second conductive layer is formed by impregnating a porous body with the first conductive layer, a thick second conductive layer can be easily formed even with fewer impregnation cycles.

[0202] In one embodiment, the conductive polymer composition used in the formation of the second conductive layer has a viscosity of 1 Pa·s or more at a shear rate of 10 (1 / s), or it may be 2 Pa·s or more or 5 Pa·s or more.

[0203] In one embodiment, the conductive polymer composition used in the formation of the second conductive layer has a viscosity of 10 Pa·s or more when a shear rate of 0.0001 (1 / s) is applied after 30 seconds of shearing at a shear rate of 10 (1 / s), or it may be 50 Pa·s or more, 100 Pa·s or more, or 500 Pa·s or more.

[0204] In one embodiment, the conductive polymer composition used in the formation of the second conductive layer satisfies formula (P2-1), or it may satisfy the following formula (P2-2), or it may satisfy the following formula (P2-3).

[0205]

Mathematical Expression 4

[0206]

[0207]

Mathematical Expression 5

[0208]

[0209] Hereinafter, the components that can be used in a solid electrolytic capacitor according to one aspect of the present invention and the materials that can form each layer will be described.

[0210] [Carbon layer]

[0211] A carbon layer is laminated onto the second conductive layer. The carbon layer contains carbon material as its main component. The carbon material content in the carbon layer is, for example, 60% by mass or more, preferably 70% by mass or more. When the carbon material content is within this range, it is easy to ensure high adhesion between the second conductive layer and the silver layer.

[0212] Examples of carbon materials include activated carbon, carbon black, carbon nanotubes, graphene, amorphous carbon, natural graphite, artificial graphite, graphitized Kojen black, mesoporous carbon, carbon nanotubes, and carbon nanofibers.

[0213] These carbon materials can be used alone or in combination of two or more.

[0214] The carbon layer may contain known binders, additives, and other components.

[0215] The upper limit of the carbon particle content in the carbon layer can be determined based on the content of other components, without any particular restriction, such as below 99% by mass.

[0216] The carbon layer is formed, for example, by coating a carbon paste onto the surface of the second conductive layer and then drying it.

[0217] Carbon paste coating can be performed by methods such as dip coating, sponge transfer, screen printing, spray coating, dispenser, and inkjet printing.

[0218] Carbon paste comprises carbon material and a dispersion medium. Examples of dispersion media include water, organic media, or mixtures thereof. Carbon paste may also contain other components such as known binders and additives.

[0219] In one embodiment, a carbon layer is laminated by immersing an anode having the first and second conductive layers described above in a dispersion medium in which the carbon material described above is dispersed, and then drying it at a specified temperature to allow the organic solvent to evaporate.

[0220] [Silver layer]

[0221] Silver (Ag) layers are stacked on top of carbon layers.

[0222] The silver layer contains silver as its main component. The silver content in the silver layer is, for example, 60% by mass or more, preferably 70% by mass or more. With a silver content within this range, sufficient electrical conductivity is easily obtained.

[0223] The silver layer may contain other components such as known binders and additives.

[0224] The upper limit of the silver content in the silver layer can be determined based on the content of other components, without any particular restriction, such as below 99% by mass.

[0225] The silver layer can be laminated, for example, by applying silver paste to the surface of a carbon layer and then drying it. As the silver paste, a form in which silver is dispersed in a solvent can be used.

[0226] The shape of silver is not limited as long as it can be dispersed in a solvent; examples include plate-shaped silver and granular silver.

[0227] As a solvent, there are no particular limitations as long as silver can be dispersed, and any known solvent can be used. For example, aromatic hydrocarbons, aliphatic hydrocarbons, alcohols, ketones, ethers, esters, etc. can be used. In addition, specific examples listed in solvent (b) below can be used.

[0228] Silver paste can be applied by methods such as dip coating, sponge transfer, screen printing, spray coating, dispenser, and inkjet printing.

[0229] In one embodiment, a silver layer is laminated by immersing an anode having the first conductive layer, the second conductive layer, and the carbon layer described above in an organic solvent in which silver is dispersed, and then drying it at a specified temperature to allow the organic solvent to evaporate.

[0230] The solid electrolytic capacitor of this embodiment can be manufactured, for example, by the manufacturing method of the present invention described below.

[0231] [Manufacturing method of solid electrolytic capacitors]

[0232] One method of manufacturing a solid electrolytic capacitor according to the present invention includes the following steps (A-1) or (A-2), step (B) and step (C).

[0233] Process (A-1): Impregnating part or all of the porous body containing the valve metal oxide in a first conductive polymer composition comprising a conductive polymer and a solvent;

[0234] Step (A-2): Impregnate part or all of the porous body containing the valve metal oxide in a first conductive polymer composition comprising a conductive polymer, a solvent and a phenolic compound;

[0235] Step (B): The porous body is removed from the first conductive polymer composition used in step (A-1) or (A-2) and held at a temperature below the boiling point of the solvent contained in the first conductive polymer composition.

[0236] Step (C): Immerse a portion or the entire porous body after step (B) in a second conductive polymer composition containing a conductive polymer, a thixotropic agent, and a solvent that are the same as or different from the first conductive polymer composition, and then dry it.

[0237] The above-mentioned process (A-1) or (A-2) and process (B) are processes for forming a first conductive layer on the surface of the above-mentioned anode body. The above-mentioned process (C) is a process for forming a second conductive layer.

[0238] In one embodiment, a method for manufacturing a solid electrolytic capacitor according to one aspect of the present invention includes steps (A-1), (B), and (C).

[0239] In one embodiment, a method for manufacturing a solid electrolytic capacitor according to one aspect of the present invention includes steps (A-2), (B), and (C).

[0240] [The formation process of the first layer]

[0241] <Processes (A-1) and (A-2)>

[0242] The formation process of layer 1 includes either process (A-1) or (A-2).

[0243] In step (A-1), a portion or the entire porous body containing the oxide of the valve metal is impregnated in a first conductive polymer composition comprising a conductive polymer and a solvent.

[0244] In step (A-2), a portion or all of the porous body containing the oxide of the valve metal is impregnated in a first conductive polymer composition comprising a conductive polymer, a solvent, and a phenolic compound.

[0245] The following points are described: as porous bodies and valve metals, which can be applied in a solid electrolytic capacitor according to one aspect of the present invention.

[0246] The first conductive polymer composition in process (A-1) comprises a conductive polymer and a solvent.

[0247] The first conductive polymer composition in step (A-2) comprises a conductive polymer, a solvent, and a phenolic compound.

[0248] [(a) Conductive polymers]

[0249] Examples of conductive polymers (hereinafter also referred to as "component (a)") include polyaniline, polyaniline derivatives, polythiophene and polythiophene derivatives.

[0250] They can be used individually or in combination with two or more.

[0251] The following are matters described that can be applied to a solid electrolytic capacitor of one aspect of the present invention, as polyaniline, polyaniline derivatives, polythiophene, and polythiophene derivatives.

[0252] In one embodiment, the first conductive polymer composition comprises polyaniline or a polyaniline derivative. To allow the first conductive polymer composition to penetrate the pores of the anode body and coat the surface of the dielectric layer with the first conductive layer, the weight-average molecular weight of the polyaniline and polyaniline derivative used in the first conductive polymer composition is preferably lower than that of the polyaniline and polyaniline derivative used in the second conductive polymer composition (described later). For example, the weight-average molecular weight of the polyaniline and polyaniline derivative used in the first conductive polymer composition is preferably 100,000 or less.

[0253] In one embodiment, the first conductive polymer composition comprises a polyaniline composite doped with polyaniline using a proton donor.

[0254] In one embodiment, the first conductive polymer composition comprises a polyaniline composite doped with polyaniline using sulfosuccinic acid.

[0255] [(b) Solvent]

[0256] The solvent (hereinafter also referred to as "component (b)") is not particularly limited as long as it is a solvent that dissolves or disperses the conductive polymer. The solvent (component (b)) is particularly preferred as a solvent that dissolves the conductive polymer. However, component (c) described later is not included.

[0257] Organic solvents are preferred. Examples include aromatic hydrocarbons, aliphatic hydrocarbons, alcohols, ketones, ethers, and esters.

[0258] They can be used individually or in combination of two or more.

[0259] The organic solvent can be a water-soluble organic solvent, or it can be an organic solvent that is substantially immiscible with water (a water-immiscible organic solvent).

[0260] As a water-soluble organic solvent, it can be a highly polar organic solvent, a protic polar solvent, or an aprotic polar solvent.

[0261] Examples of water-soluble organic solvents include methanol, ethanol, isopropanol, 1-propanol, 1-ethoxy-2-propanol, 2-ethoxy-1-propanol, 1-butanol, 2-butanol, 2-pentanol, benzyl alcohol, alkoxy alcohols (e.g., 1-methoxy-2-propanol, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol), ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ethers such as tetrahydrofuran, 4-methyltetrahydropyran, dioxane, diethyl ether, and ethylene glycol monotert-butyl ether, and nonprotic polar solvents such as N-methylpyrrolidone.

[0262] As a water-immiscible organic solvent, low-polarity organic solvents can be used, such as hydrocarbon solvents like hexane, benzene, toluene, xylene, ethylbenzene, and tetrahydronaphthalene; halogen-containing solvents like dichloromethane, chloroform, carbon tetrachloride, dichloroethane, and tetrachloroethane; ester solvents like ethyl acetate, isobutyl acetate, n-butyl acetate, ethyl lactate, and methyl lactate; ketone solvents like methyl isobutyl ketone (MIBK), methyl ethyl ketone, cyclopentanone, and cyclohexanone; and ether solvents like cyclopentyl methyl ether.

[0263] In addition, as a hydrocarbon solvent, an isoparaffin solvent containing one or more isoparaffins can be used.

[0264] Alternatively, commercially available solvents such as "KYOWASOL C900" (manufactured by KH Neochem Co., Ltd.) can also be used.

[0265] Among them, toluene, xylene, methyl isobutyl ketone, chloroform, trichloroethane and ethyl acetate are preferred, based on the excellent solubility of conductive polymers.

[0266] It should be noted that in the case of polyaniline composites, even solvents such as isopropanol, 1-butanol, 2-butanol, 2-pentanol, benzyl alcohol, and alkoxy alcohols can dissolve the polyaniline. From the perspective of reducing environmental impact, alcohols are preferred over aromatic solvents such as toluene.

[0267] When using organic solvents as solvents, it is preferable to use a mixed organic solvent prepared by mixing a water-immiscible organic solvent and a water-soluble organic solvent in a mass ratio of 99 to 1:1 to 99. This can prevent the formation of gels or the like during storage and allows for long-term storage.

[0268] Mixed organic solvents may contain one or more water-immiscible organic solvents, or one or more water-soluble organic solvents.

[0269] The concentration of component (a) relative to the total amount of solvent (component (b)) [component (a) × 100 / (component (a) + component (b))] can be 0.01% by mass or more, 0.03% by mass or more, 0.05% by mass or more, or 2.0% by mass or more. Alternatively, it is typically 15.0% by mass or less, but can be 13.0% by mass or less, 12.0% by mass or less, 10.0% by mass or less, 9.0% by mass or less, or 8.0% by mass or less.

[0270] When the conductive polymer composition further includes the component (c) described later, the concentration of component (a) is typically 0.3 to 20% by mass, preferably 0.5 to 20% by mass, more preferably 1 to 15% by mass, even more preferably 1 to 10% by mass, and even more preferably 1 to 7% by mass, relative to the conductive polymer composition.

[0271] The content of component (b) can be adjusted appropriately according to the amount of other components, without limitation. For example, relative to 100 parts by mass of component (a), it can be 200 to 20,000 parts by mass, 300 to 17,000 parts by mass, 500 to 12,000 parts by mass, 500 to 5,000 parts by mass, or 500 to 1,500 parts by mass.

[0272] [(c) Phenolic compounds]

[0273] The phenolic compound (component (c)) is not particularly limited, and is a compound represented by ArOH (where Ar is aryl or substituted aryl). It should be noted that component (c) is a different component from component (b).

[0274] Examples of phenolic compounds include, specifically, phenol, o-cresol, m-cresol or p-cresol, o-ethylphenol, m-ethylphenol or p-ethylphenol, o-propylphenol, m-propylphenol or p-propylphenol, o-butylphenol, m-butylphenol or p-butylphenol, o-chlorophenol, m-chlorophenol or p-chlorophenol, salicylic acid, hydroxybenzoic acid, hydroxynaphthalene and other substituted phenols; catechol, resorcinol and other polyphenolic compounds; as well as phenolic resins, polyphenols, poly(hydroxystyrene) and other polymers.

[0275] Alternatively, phenolic compounds represented by the following formula (C1) can be used.

[0276] [Chemical Formula 4]

[0277]

[0278] (In the formula, n is an integer from 1 to 5. When n is 2 or more, multiple R...) 21 They can be the same, or they can be different.

[0279] R 21 It can be an alkyl group with 2 to 10 carbon atoms, an alkenyl group with 2 to 20 carbon atoms, an alkylthio group with 1 to 20 carbon atoms, a cycloalkyl group with 3 to 10 carbon atoms, an aryl group with 6 to 20 carbon atoms, an alkylaryl group with 7 to 20 carbon atoms, or an arylalkyl group with 7 to 20 carbon atoms.

[0280] As mentioned above, R 21 Alkyl groups, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and tert-pentyl, can be examples.

[0281] Examples of alkenyl groups include substituents that have unsaturated bonds within the molecules of the aforementioned alkyl groups.

[0282] Examples of cycloalkyl groups include cyclopentane and cyclohexane.

[0283] Examples of alkylthio groups include methylthio and ethylthio.

[0284] Examples of aryl groups include phenyl and naphthyl groups.

[0285] Examples of substituents include alkylaryl groups and arylalkyl groups, which are obtained by combining the above-mentioned alkyl groups with aryl groups.

[0286] Among these groups, R 21 Methyl or ethyl is preferred.

[0287] Examples of phenolic compounds represented by formula (C1) include, specifically, 4-tert-amylphenol, 2-isopropylphenol, 4-isopropyl-3-methylphenol, 2-isopropyl-5-methylphenol (thymol), 5-isopropyl-2-methylphenol (carvacrol), and 4-(1,1,3,3-tetramethylbutyl)phenol.

[0288] The content of component (c) is preferably 10 to 5000 parts by mass relative to 100 parts by mass of component (a), more preferably 10 to 2000 parts by mass, and even more preferably 10 to 1000 parts by mass.

[0289] In addition, the content of component (c) can be 100 to 10,000 parts by mass relative to 100 parts by mass of component (a).

[0290] The use of phenolic compounds improves electrical conductivity or solubility in alcohols, and is therefore preferred.

[0291] The content of component (c) in the conductive polymer composition is 1 to 80% by mass, more preferably 5 to 60% by mass, and even more preferably 10 to 40% by mass. The conductivity or solubility in alcohol is improved by using this phenolic compound, therefore it is preferred.

[0292] Alternatively, component (c) can be mixed with component (b) and used as a mixed solvent. In this case, the concentration of component (a) relative to the solvent is calculated relative to the total mass of components (b) and (c).

[0293] [(d) Heat stabilizer]

[0294] The conductive polymer composition may further include (d) a heat stabilizer (hereinafter also referred to as "component (d)").

[0295] As a heat-resistant stabilizer (component (d)), examples include acidic substances or salts of acidic substances. Component (d) does not include component (c).

[0296] The acidic substance can be any of the following: an organic acid that is an acid of an organic compound or an inorganic acid that is an acid of an inorganic compound, preferably an organic acid.

[0297] As an acidic substance, an organic acid containing one or more sulfonic acid groups is preferred.

[0298] The organic acids having sulfonic acid groups mentioned above are preferably cyclic, chain, or branched alkyl sulfonic acids, substituted or unsubstituted aromatic sulfonic acids, or polysulfonic acids having one or more sulfonic acid groups.

[0299] Examples of alkyl sulfonic acids include methanesulfonic acid, ethanesulfonic acid, and di(2-ethylhexyl)sulfosuccinic acid. Here, the alkyl group is preferably a straight-chain or branched alkyl group having 1 to 18 carbon atoms.

[0300] Examples of aromatic sulfonic acids include those with 6 to 20 carbon atoms, such as sulfonic acids having a benzene ring, sulfonic acids having a naphthalene skeleton, and sulfonic acids having an anthracene skeleton. Additionally, examples of aromatic sulfonic acids include substituted or unsubstituted benzenesulfonic acids, substituted or unsubstituted naphthalenesulfonic acids, and substituted or unsubstituted anthracenesulfonic acids.

[0301] As a substituent, it may be a substituent selected from alkyl (e.g., alkyl with 1 to 20 carbon atoms), alkoxy (e.g., alkoxy with 1 to 20 carbon atoms), hydroxyl, nitro, carboxyl, acyl, and may replace one or more substituents.

[0302] Specifically, as aromatic sulfonic acids, compounds represented by the following formulas (D1) or (D2) can be cited.

[0303] [Chemical Formula 5]

[0304]

[0305] (In equation (D1), l is 1 or higher, m is an integer greater than or equal to 0 and less than 5, and n is an integer greater than or equal to 0 and less than 5. If either m or n is 0, the other is 1 or higher.)

[0306]

Chemical Formula 6

[0307]

[0308] (In formula (D2), q is 1 or more, p is an integer between 0 and 7, and R is an alkyl, carboxyl, hydroxyl, nitro, cyano, or amino group with 1 to 20 carbon atoms.)

[0309] l is preferably 1 to 3. m is preferably 1 to 3. n is preferably 0 to 3.

[0310] q is preferably 1 to 3. p is preferably 0 to 3. R is preferably an alkyl, carboxyl, or hydroxyl group with 1 to 20 carbon atoms.

[0311] Examples of aromatic sulfonic acids include 4-sulfophthalic acid, 5-sulfoisophthalic acid, 5-sulfosalicylic acid, 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, 2-hydroxy-6-naphthalenesulfonic acid, 1,5-naphthalenedisulfonic acid, 2,6-naphthalenedisulfonic acid, p-phenolsulfonic acid, toluenesulfonic acid, p-xylene-2-sulfonic acid, 4,4'-biphenyldisulfonic acid, dibenzofuran-2-sulfonic acid, flavianic acid, (+)-10-camphorsulfonic acid, monoisopropylnaphthalenesulfonic acid, and 1-pyrenesulfonic acid. From the perspective of improving heat resistance, 4-sulfophthalic acid, 5-sulfosalicylic acid, 5-sulfoisophthalic acid, 2-naphthalenesulfonic acid, dibenzofuran-2-sulfonic acid, flavianic acid, 2-hydroxy-6-naphthalenesulfonic acid, and 1-pyrenesulfonic acid are preferred.

[0312] Salts that are acidic substances include the salts of the compounds listed above. Counterions that are ions of salts include sodium, lithium, potassium, cesium, ammonium, calcium, and barium.

[0313] Component (d) can be a hydrate.

[0314] The content of component (d) is preferably 0.1 to 1000 parts by mass relative to 100 parts by mass of component (a), more preferably 1 to 100 parts by mass, even more preferably 1 to 30 parts by mass, and even more preferably 2 to 8 parts by mass.

[0315] [(e) Additives]

[0316] In addition to the above-mentioned components, the conductive polymer composition may also contain additives (hereinafter also referred to as "component (e)") as needed. Component (e) does not include components equivalent to components (a) to (d) above.

[0317] Examples of additives include adhesion promoters, fillers, rheology control agents, and adhesive resins.

[0318] Examples of binding agents include isocyanate silanes, glycidyl silanes, and other silane coupling agents, as well as acidic polyesters and other polymer coupling agents.

[0319] As a commercially available adhesive, for example, "BYK-4510" (made by BYK Additives & Instruments) can be used.

[0320] Examples of fillers include alumina, silicon dioxide, titanium dioxide, and zirconium oxide.

[0321] The conductive polymer composition may consist essentially of components (a) and (b), and optionally components (c), (d), and (e). In this case, unavoidable impurities may be present. For example, 70% or more by mass, 80% or more by mass, 90% or more by mass, 98% or more by mass, 99% or more by mass, or 99.5% or more by mass of the conductive polymer composition may be components (a) and (b), and optionally components (c), (d), and (e). Alternatively, the conductive polymer composition may consist only of components (a) and (b), and optionally components (c), (d), and (e).

[0322] There is no particular limitation on the method of impregnating the porous body with the valve metal oxide into the first conductive polymer composition. The porous body can be impregnated into the conductive polymer composition in a single impregnation action, or the porous body can be impregnated into the conductive polymer composition in sections or continuously.

[0323] "Segmented impregnation" refers to moving the porous body multiple times, impregnating it in segments with the conductive polymer composition. In other words, "segmented impregnation" means performing the impregnation action in stages, followed by removal from the conductive polymer composition in step (B) after a series of staged impregnation actions.

[0324] "Continuous impregnation" refers to moving the porous material continuously at a specified speed and gradually impregnating it in a conductive polymer composition.

[0325] By impregnating the porous body in segments or continuously with a conductive polymer composition, the conductive polymer can be smoothly penetrated into the pores of the porous body.

[0326] When the porous body is completely immersed in the conductive polymer composition in a single immersion action, the time the porous body is held in the conductive polymer composition (hereinafter referred to as immersion time) is typically 1 to 30 minutes, preferably 1 to 10 minutes.

[0327] When the porous body is moved multiple times and impregnated in sections in a conductive polymer composition, the portion from the lower end of the porous body to a specified height is first impregnated in the conductive polymer composition and kept in an impregnated state for, for example, 1 to 30 minutes, preferably 1 to 10 minutes.

[0328] Next, the porous body is moved so that a portion of the unimpregnated portion is further impregnated in the conductive polymer composition, and the impregnation is maintained for, for example, 1 to 20 minutes, preferably 1 to 10 minutes.

[0329] There is no particular limitation on the temperature for impregnating porous conductive polymer compositions, which is usually room temperature (e.g., 15–30°C or 25°C).

[0330] <Process (B)>

[0331] Step (B) involves removing the porous body from the first conductive polymer composition used in step (A-1) or (A-2) and maintaining it at a temperature below the boiling point of the solvent contained in the first conductive polymer composition. This eliminates the liquid film formed at the openings of the pores in the porous body, thus removing the liquid seal. Therefore, it is possible to increase the amount of conductive polymer composition filling the pores.

[0332] In step (B), the temperature is maintained below the boiling point of the solvent contained in the first conductive polymer composition. The temperature can be appropriately selected depending on the type of solvent, for example, room temperature. The holding time is typically 30 seconds to 5 minutes, preferably 1 minute to 2 minutes.

[0333] In one implementation, the cycle of steps (A) and (B) can be repeated multiple times before step (C).

[0334] If multiple cycles of processes (A) and (B) are repeatedly performed before process (C), the multiple layers formed through a series of cycles are collectively referred to as the inner solid electrolyte layer (first conductive layer).

[0335] In one embodiment, a drying step (B1) may be performed after step (B) and before step (C). The temperature in the drying step need not be below the boiling point of the solvent contained in the first conductive polymer composition. The drying temperature is typically 30–200°C, preferably 100–180°C. The drying time is typically 10–120 minutes, preferably 30–90 minutes.

[0336] The cycle of steps (A) and (B) can be repeated multiple times before the drying step (B1).

[0337] [The process of forming the second conductive layer]

[0338] <Process (C)>

[0339] Step (C) is the process of immersing part or all of the porous body after step (B) in a second conductive polymer composition and drying it to form a second conductive layer, wherein the second conductive polymer composition contains the same or different conductive polymer, thixotropic agent and solvent as described in the first conductive polymer composition.

[0340] For conductive polymers, solvents, and impregnation, the matters described in step (A) above can be applied.

[0341] The following points are described regarding the application of thixotropic agents in a solid electrolytic capacitor according to one aspect of the present invention.

[0342] The content of the thixotropic agent relative to the overall second conductive polymer composition is not particularly limited, as long as it imparts thixotropy to the second conductive polymer composition. Those skilled in the art can appropriately select the content of the thixotropic agent based on the composition of the second conductive polymer composition.

[0343] In one embodiment, the thixotropic agent is present in an amount of 0.2 to 5% by mass relative to the total amount of the second conductive polymer composition (preferably 0.3 to 4% by mass, more preferably 0.4 to 3% by mass).

[0344] In one embodiment, the second conductive polymer composition comprises polyaniline or a polyaniline derivative. Since the second conductive polymer composition does not need to penetrate the pores of the anode body, the weight-average molecular weight of the polyaniline and polyaniline derivative used in the second conductive polymer composition can be greater than that of the polyaniline and polyaniline derivative used in the first conductive polymer composition. This allows the coating to acquire the strength, heat resistance, and other properties required for its function. For example, the weight-average molecular weight of the polyaniline and polyaniline derivative used in the second conductive polymer composition is preferably 100,000 or more.

[0345] In one embodiment, the second conductive polymer composition comprises a polyaniline composite doped with polyaniline using a proton donor.

[0346] In one embodiment, the second conductive polymer composition comprises a polyaniline composite doped with polyaniline using sulfosuccinic acid.

[0347] In one embodiment, the second conductive polymer composition further comprises a thickener.

[0348] Regarding the thickener, the following points are described in relation to the solid electrolytic capacitor of one aspect of the present invention.

[0349] In one embodiment, the second conductive polymer composition satisfies the following conditions (P1) and (P2).

[0350] (P1) The viscosity at a shear rate of 10 (1 / s) is above 1 Pa·s.

[0351] (P2) After applying shear at a shear rate of 10 (1 / s) for 30 seconds, the viscosity at a shear rate of 0.0001 (1 / s) is 10 Pa·s or higher and satisfies the following formula (P2-1).

[0352]

Mathematical Expression 6

[0353]

[0354] It should be noted that whether the second conductive polymer composition meets conditions (P1) and (P2) can be confirmed separately with process (C).

[0355] In step (C), the drying temperature is not particularly limited and can be selected appropriately according to the type of solvent. The drying temperature is usually 30–200°C, preferably 100–180°C. The drying time is usually 10–120 minutes, preferably 30–90 minutes.

[0356] One method of manufacturing a solid electrolytic capacitor according to the present invention may include a carbon layer formation step (D) and a silver layer formation step (E) after step (C).

[0357] [Carbon layer formation process]

[0358] Process (D) is the process of immersing part or all of the porous body after process (C) in a liquid containing carbon slurry and then drying it.

[0359] As a carbon paste, it can be applied in a solid electrolytic capacitor according to one aspect of the present invention.

[0360] In the carbon layer formation process, the immersion time is usually 5 seconds to 1 minute, preferably 10 to 30 seconds.

[0361] The drying temperature is typically 30–200°C, preferably 100–180°C. The drying time is typically 10–120 minutes, preferably 30–90 minutes.

[0362] [Silver layer formation process]

[0363] Process (E) is the process of immersing part or all of the porous body after process (D) in a liquid containing silver paste and then drying it.

[0364] As a silver paste, it can be applied to the solid electrolytic capacitor described in one aspect of the present invention.

[0365] In the silver layer formation process, the immersion time is usually 5 seconds to 1 minute, preferably 10 to 30 seconds.

[0366] The drying temperature is typically 30–200°C, preferably 100–180°C. The drying time is typically 10–120 minutes, preferably 30–90 minutes.

[0367] One embodiment of the present invention provides a solid electrolytic capacitor that can be used as a circuit element mounted on an electrical and electronic circuit board, particularly as a circuit element mounted in automobiles, etc.

[0368] In one implementation, the process (C) can be repeated multiple times. In this case, the multiple layers formed through a series of cycles are collectively referred to as the outer coating layer (second conductive layer).

[0369] One embodiment of the present invention provides a solid electrolytic capacitor that can be used as a circuit element mounted on an electrical and electronic circuit board, particularly as a circuit element mounted in automobiles, etc.

[0370] Example

[0371] Manufacturing Example 1 (Manufacturing of Polyaniline Composite 1)

[0372] Add 32.4 g of "NEOCOL SWC" (sodium di-2-ethylhexyl sulfosuccinate, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), 13.3 g of aniline, and 0.9 g of "SORBON T-20" (a nonionic emulsifier with a polyoxyethylene dehydrated sorbitol fatty acid ester structure, manufactured by Toho Chemical Co., Ltd.) to a 1,000 mL separable flask, and dissolve it in 320.4 g of toluene. Add 450 g of 8.5% (w / w) aqueous phosphoric acid solution, stir the reaction mixture containing the two liquid phases of toluene and water, and cool the internal temperature of the reaction mixture to 5°C.

[0373] When the internal temperature of the reaction solution reaches 5°C, while stirring the reaction solution, add a solution made by dissolving 39.3g of APS (ammonium persulfate) in 90.2g of 8.5% (w / w) phosphoric acid aqueous solution using a dropping funnel, and stir for 4 hours while maintaining the internal temperature of the solution at 5°C.

[0374] After stirring was stopped, the contents were transferred to a separatory funnel, and the aqueous phase and the toluene phase (organic phase) were allowed to stand and separate. After separation, the toluene phase (organic phase) was washed once with 180.3 g of 8.5% (w / w) phosphoric acid aqueous solution and then washed five times with 328.0 g of deionized water, thus obtaining a polyaniline composite toluene solution.

[0375] The solution was transferred to an evaporator and heated in a hot water bath at 60°C under reduced pressure to evaporate and distill off the volatile components, yielding polyaniline complex 1 (protonated polyaniline). The weight-average molecular weight (Mw) of the polyaniline in polyaniline complex 1 was 73,000.

[0376] The weight-average molecular weights of polyaniline in polyaniline composite 1 and polyaniline composite 2 (described later) were determined as follows.

[0377] A 0.01 M lithium bromide NMP solution was prepared by dissolving 1.65–1.85 g of lithium bromide in 2000 mL of NMP (N-methyl-2-pyrrolidone). 14 μL of triethylamine was added to 10 mL of this 0.01 M lithium bromide NMP solution, and the mixture was stirred to dissolve, forming a homogeneous solution. Subsequently, 50 μL of a polyaniline composite toluene solution was added dropwise, and after mixing, the solution was passed through a 0.45 μM filter to prepare a sample for gel permeation chromatography (GPC) determination.

[0378] Using samples for GPC testing, the GPC test was performed using a GPC column (Shodex KF-806M manufactured by Showa Denko Corporation, with two columns connected) under the following test conditions.

[0379] Solvent: NMP containing 0.01M LiBr

[0380] Flow rate: 0.70 ml / minute

[0381] Column temperature: 60℃

[0382] Injection volume: 100μL

[0383] UV detection wavelength: 270 nm

[0384] The weight-average molecular weight obtained by the above method is the converted value of polystyrene (PS).

[0385] The proton donor (sodium di-2-ethylhexyl sulfosuccinate) has a doping rate of 0.36 relative to polyaniline.

[0386] Manufacturing Example 2 (Manufacturing of Polyaniline Composite 2)

[0387] Add 10.13 g of "NEOCOL SWC" (sodium di-2-ethylhexyl sulfosuccinate, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), 4.17 g of aniline, and 0.32 g of "SORBON T-20" (a nonionic emulsifier with a polyoxyethylene dehydrated sorbitol fatty acid ester structure, manufactured by Toho Chemical Co., Ltd.) to a 1,000 mL separable flask, and dissolve it in 238.37 g of toluene. Add 353.70 g of 17% (w / w) phosphoric acid aqueous solution, stir the reaction mixture containing the two liquid phases of toluene and water, and cool the internal temperature of the reaction mixture to -2°C.

[0388] When the internal temperature of the reaction solution reaches -2℃, while stirring the reaction solution, add a solution made by dissolving 12.3g of APS (ammonium persulfate) in 48g of 17% phosphoric acid aqueous solution using a dropping funnel, and stir for 18 hours while maintaining the internal temperature of the solution at -2℃.

[0389] After stirring was stopped, the contents were transferred to a separatory funnel, and the aqueous phase and the toluene phase (organic phase) were allowed to stand and separate. After separation, the toluene phase (organic phase) was washed once with 59.4 g of 8.5% (w / w) phosphoric acid aqueous solution and three times with 108.14 g of deionized water, thus obtaining a polyaniline composite toluene solution.

[0390] The solution was transferred to an evaporator and heated in a hot water bath at 60°C under reduced pressure to evaporate and distill off the volatile components, yielding polyaniline complex 2 (protonated polyaniline). The weight-average molecular weight (Mw) of the polyaniline in polyaniline complex 2 was 112,000.

[0391] The proton donor (sodium di-2-ethylhexyl sulfosuccinate) has a doping rate of 0.36 relative to polyaniline.

[0392] Manufacturing Example 3 (Anode)

[0393] For 20 granular tantalum powder sintered bodies (1.71 mm × 3.01 mm × 2.89 mm porous bodies) made of tantalum powder with a specific capacitance of 250,000 μFV / g, anodizing was performed by applying a voltage of 8.8 V in 0.5% phosphoric acid electrolyte to form a dielectric (tantalum oxide) on the surface of the tantalum powder sintered bodies (porous bodies), thus obtaining the anode body of the tantalum capacitor.

[0394] The electrolyte was 10% phosphoric acid, and the liquid capacitance of the anode was measured using a platinum black electrode. The liquid capacitance of the anode was 961 μF.

[0395] Example 1

[0396] (1) Preparation of conductive polymer composition D (first conductive polymer composition) for forming the first conductive layer

[0397] Mixed solvent α was prepared by stirring 49g of 1-propanol (component (b), boiling point 97°C, manufactured by Tokyo Chemical Industry Co., Ltd.), 49g of p-tert-amylphenol (component (c), manufactured by Fujifilm and Koh Genuine Chemical Co., Ltd.), and 42g of KYOWASOL C900 (component (b), manufactured by KH Neochem Co., Ltd.) until homogeneous.

[0398] 7 g of polyaniline composite 1 (component (a)) obtained in Manufacturing Example 1 was dissolved in 133 g of mixed solvent α to obtain polyaniline composite solution A (polyaniline composite concentration: 5% by mass).

[0399] 10 g of 2-naphthalenesulfonic acid hydrate (component (d), manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 90 g of isopropanol (component (b), boiling point 82.5°C, manufactured by Fujifilm and Kohden Chemical Co., Ltd.) to prepare heat-resistant stabilizer solution B.

[0400] 20g of BYK-4510 (component (e), manufactured by BYK Additives & Instruments) was dissolved in 100g of mixed solvent α to prepare a sealing-enhancing solution C.

[0401] 0.237 g of heat-resistant stabilizer solution B and 0.105 g of adhesion-improving solution C were added to 21 g of polyaniline composite solution A (polyaniline composite concentration: 5% by mass), and mixed while stirring, thereby obtaining conductive polymer composition D (first conductive polymer composition) for forming the first conductive layer.

[0402] (2) Formation of the internal solid electrolyte layer (first conductive layer)

[0403] [First immersion]

[0404] The anode body obtained in Manufacturing Example 3 is fixed to a metal rod and suspended. It is then immersed in the conductive polymer composition D from the lower end to one-third of its height, and held for 2 minutes. Next, it is immersed in the conductive polymer composition D from the lower end to two-thirds of its height, and held for 2 minutes. Finally, the entire anode body is immersed in the conductive polymer composition D and held for 1 minute. This constitutes the first immersion of the anode body.

[0405] Next, the anode body is pulled out from the conductive polymer composition D and kept at room temperature for 1 minute with the entire anode body exposed to air.

[0406] [Second immersion]

[0407] Next, the anode body is immersed in the conductive polymer composition D from the lower end to one-third of its height, and held for 2 minutes. Next, the anode body is immersed in the conductive polymer composition D from the lower end to two-thirds of its height, and held for 2 minutes. Next, the entire anode body is immersed in the conductive polymer composition D, and held for 1 minute. This constitutes the second immersion of the anode body.

[0408] Next, the anode body was pulled out from the conductive polymer composition D and dried at 40°C for 7 minutes, and then further dried at 140°C for 5 minutes to form an inner solid electrolyte layer (first conductive layer).

[0409] (3) Preparation of conductive polymer composition G (second conductive polymer composition) for forming the second conductive layer

[0410] 30g of 1-ethoxy-2-propanol (component (b), manufactured by Tokyo Chemical Industry Co., Ltd.), 30g of 1-propanol, and 40g of p-tert-amylphenol were stirred until homogeneous to prepare a mixed solvent ε.

[0411] 10 g of polyaniline composite 2 (component (a)) obtained in manufacturing example 2 was dissolved in 90 g of mixed solvent ε to obtain polyaniline composite solution E (polyaniline composite concentration: 10% by mass).

[0412] Two parts by weight (0.2 g) of microparticle silica AEROSIL 380 (manufactured by AEROSIL Corporation of Japan) were added to 10 g of polyaniline composite solution E. The mixture was stirred at 1000 rpm for 5 minutes using a HOMODISPER (PRIMIX HOMODISPER 2.5 type) to prepare polyaniline composite / microparticle silica mixed solution H.

[0413] 20g of BYK-4510 (component (e), manufactured by BYK Additives & Instruments) was dissolved in 100g of mixed solvent ε to prepare a sealing-enhancing solution F.

[0414] 0.564 g of heat-resistant stabilizer solution B and 0.075 g of adhesion-improving solution F were added to 7.5 g of polyaniline composite / micro-silica mixed solution H (polyaniline composite concentration: 10% by mass) and mixed while stirring to obtain conductive polymer composition G (second conductive polymer composition) for forming the second conductive layer.

[0415] (4) Formation of the outer coating layer (second conductive layer)

[0416] First, the entire anode body obtained in (2) above is immersed in a 4-sulfophthalic acid solution (4-sulfophthalic acid concentration: 1% by mass) prepared by dissolving 4-sulfophthalic acid (component (d), manufactured by Tokyo Chemical Industry Co., Ltd.) in isopropanol and kept for 10 minutes.

[0417] Next, the anode body was pulled out from the 4-sulfophthalic acid solution and removed, and dried at 150°C for 60 minutes.

[0418] Next, the entire anode body is immersed in the conductive polymer composition G used to form the second conductive layer and held for 5 minutes.

[0419] Next, the anode body is pulled out from the conductive polymer composition G and dried at 100°C for a specified time of 30 to 60 minutes, and then further dried at 150°C for a specified time of 30 to 60 minutes to perform external coating of the anode body. The process of impregnating the conductive polymer composition used to form the second conductive layer with the anode body and drying it is called dip coating, and the dip coating is performed three times.

[0420] Next, the entire anode body is immersed in a 4-sulfophthalic acid solution (4-sulfophthalic acid concentration: 1% by mass) prepared by dissolving 4-sulfophthalic acid (component (d), manufactured by Tokyo Chemical Industry Co., Ltd.) in isopropanol and kept for 10 minutes.

[0421] Next, the anode body was pulled out from the 4-sulfophthalic acid solution and dried at 150°C for 60 minutes to obtain an anode body with an inner solid electrolyte layer (first conductive layer) and an outer coating layer (second conductive layer).

[0422] (5) Formation of carbon layers

[0423] Carbon paste: Using FUAE in its original state (solvent: ketone-based, manufactured by Nippon Graphite Industries Co., Ltd.), the anode body (having a first conductive layer and a second conductive layer) obtained in (4) above was immersed for 10 seconds and then dried at 150°C for 30 minutes.

[0424] (6) Formation of the silver layer

[0425] Next, the silver paste H9113-6 (granular, manufactured by NAMICS Corporation) was diluted to 1.2 times with diethylene glycol monobutyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.), and stirred and mixed. The anode obtained in (5) above was immersed in the obtained silver paste solution for 10 seconds, dried at 100°C for 30 minutes, and then further dried at 150°C for 30 minutes to obtain the capacitor.

[0426] <Evaluation of Electrical Characteristics>

[0427] For the capacitors obtained above, before and after heat treatment, the electrostatic capacitance (Cap) and dielectric loss (tanδ) at a frequency of 120Hz and the equivalent series resistance (ESR) at a frequency of 100kHz were measured using an LCR meter “Precision LCR Meter E4980A” (manufactured by Agilent Technologies Japan, Ltd.). The evaluation results are shown in Table 1.

[0428] <Evaluation of resistance to damp heat>

[0429] The capacitors obtained above were exposed to an environment of 85% temperature and 95% RH (Relative Humidity) for 3 days, and then dried at 100°C for 30 minutes. The Cap and ESR were then measured using a Precision LCRMeter E4980A to evaluate their resistance to damp heat. The evaluation results are shown in Table 1.

[0430] In Table 1, cases where the changes in Cap and ESR values ​​compared to the pre-exposure baseline are within 30% are marked as 0. Cases where the changes in Cap and ESR values ​​compared to the pre-exposure baseline exceed 30%, or cases where the Cap and ESR values ​​cannot be determined, are marked as ×.

[0431] Example 2

[0432] In Example 1, the number of dip-coating cycles was set to 1 during the formation of the outer coating layer (second conductive layer). Otherwise, the capacitor was manufactured in the same manner as in Example 1, and the evaluation was conducted. The evaluation results are shown in Table 1.

[0433] Example 3

[0434] In Example 1, in the formation of the outer coating layer (second conductive layer), instead of the conductive polymer composition G, a conductive polymer composition G' was used, obtained by adding 0.564 g of heat-resistant stabilizer solution B and 0.075 g of adhesion-improving solution F to 7.5 g of polyaniline composite solution E (polyaniline composite concentration: 10% by mass) while stirring. Otherwise, a capacitor was manufactured in the same manner as in Example 1, and its performance was evaluated. The evaluation results are shown in Table 1.

[0435] Comparative Example 1

[0436] In Example 2, in the formation of the outer coating layer (second conductive layer), PEDOT / PSS (an article containing ethylene glycol, manufactured by Sigma-Aldrich) was used undiluted instead of the conductive polymer composition G. Otherwise, the capacitor was manufactured in the same manner as in Example 2, and its performance was evaluated. The evaluation results are shown in Table 1.

[0437] Table 1

[0438]

[0439] Manufacturing Example 4 (Anode)

[0440] A sintered tantalum powder body (porous body) with a CV volume of 120kCV and EIA marking 1206 (JIS marking 3216) was anodized in 0.5% phosphoric acid electrolyte by applying a voltage of 30V to form a dielectric (tantalum oxide) on the surface of the sintered tantalum powder body (porous body), thus obtaining the anode of a tantalum capacitor.

[0441] The electrolyte was 10% phosphoric acid (w / w), and the liquid capacitance of the anode was measured using a platinum black electrode. The liquid capacitance of the anode was 50 μF.

[0442] Example 4

[0443] (1) Formation of the internal solid electrolyte layer (first conductive layer)

[0444] Instead of the anode body obtained in Manufacturing Example 3, the anode body obtained in Manufacturing Example 4 is used. Otherwise, the same procedure is followed as in Example 1 to form an internal solid electrolyte layer (first conductive layer).

[0445] (2) Preparation of conductive polymer composition K (second conductive polymer composition) for forming the second conductive layer

[0446] Mixed solvent ε was prepared by mixing 30g of 1-ethoxy-2-propanol (component (b), manufactured by Tokyo Chemical Industry Co., Ltd.), 30g of 1-propanol, and 40g of p-tert-amylphenol while stirring until homogeneous.

[0447] In 90g of mixed solvent ε, 10g of polyaniline complex 2 (component (a)) obtained in manufacturing example 2 and 0.4g of ethyl cellulose Aqualon EC-N300 (manufactured by Ashland Inc.) were dissolved at room temperature to obtain polyaniline complex solution I (polyaniline complex concentration: 10% by mass).

[0448] Four parts by weight (0.4 g) of microparticle silica AEROSIL 380 (manufactured by AEROSIL Corporation of Japan) were added to 10 g of polyaniline composite solution I. The mixture was stirred at 3000 rpm for 5 minutes using a HOMODISPER (PRIMIX HOMODISPER 2.5 type) to prepare polyaniline composite / microparticle silica mixed solution J.

[0449] For the polyaniline composite / micro-silica mixture J, using an Anton Paar MCR302 rheometer and a P-PTD200 / H-PTD200 for temperature control, the viscosity was 9 Pa·s at a shear rate of 10 (1 / s) under the conditions of parallel plates with a diameter of 25 mm and a gap of 1 mm. After applying a shear rate of 10 (1 / s) for 30 seconds, the viscosity was 1500 Pa·s at a shear rate of 0.0001 (1 / s). The viscosity changed by 11 times after 5 minutes.

[0450] 20g of BYK-4510 (component (e), manufactured by BYK Additives & Instruments) was dissolved in 100g of mixed solvent ε to prepare a sealing-enhancing solution F.

[0451] 0.564 g of heat-resistant stabilizer solution B and 0.075 g of adhesion-improving solution F were added to 7.5 g of polyaniline composite / micro-silica mixed solution J (polyaniline composite concentration: 10% by mass) while stirring to obtain conductive polymer composition K (second conductive polymer composition) for forming the second conductive layer.

[0452] (3) Formation of the outer coating layer (second conductive layer)

[0453] First, the entire anode body obtained in (1) above is immersed in a 4-sulfophthalic acid solution (4-sulfophthalic acid concentration: 1% by mass) prepared by dissolving 4-sulfophthalic acid (component (d), manufactured by Tokyo Chemical Industry Co., Ltd.) in isopropanol and kept for 180 minutes.

[0454] Next, the anode body was pulled out from the 4-sulfophthalic acid solution and dried at 100°C for 18 hours.

[0455] Next, the entire anode body is immersed in the conductive polymer composition K used to form the second conductive layer and held for 5 minutes.

[0456] Next, the anode body is pulled out of the conductive polymer composition K at a pulling speed of 1 second (the speed from the start of pulling until the entire anode body is exposed outside the conductive polymer composition K takes 1 second), and then dried at 100°C for a specified time of 30 to 60 minutes, followed by further drying at 150°C for a specified time of 30 to 60 minutes to perform external coating of the anode body. The process of impregnating and drying the conductive polymer composition used to form the second conductive layer is called dip coating, and the dip coating is performed once.

[0457] Next, the entire anode body is immersed in a 4-sulfophthalic acid solution (4-sulfophthalic acid concentration: 1% by mass) prepared by dissolving 4-sulfophthalic acid (component (d), manufactured by Tokyo Chemical Industry Co., Ltd.) in isopropanol, and kept for 180 minutes.

[0458] Next, the anode body was pulled out from the 4-sulfophthalic acid solution and dried at 75°C for 18 hours to obtain an anode body with an inner solid electrolyte layer (first conductive layer) and an outer coating layer (second conductive layer).

[0459] (4) Formation of carbon layers

[0460] Carbon paste: Using FUAE in its original state (solvent: ketone-based, manufactured by Nippon Graphite Industries Co., Ltd.), the anode body (having a first conductive layer and a second conductive layer) obtained in (3) above was immersed for 10 seconds and then dried at 150°C for 30 minutes.

[0461] (5) Formation of the silver layer

[0462] Next, the silver paste EC209A (plate form + granules, manufactured by Mitsuboshi Belting Co., Ltd.) was diluted to 1.1 times with the diluent N-methylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.), and stirred and mixed. The anode obtained in (4) above was immersed in the obtained silver paste solution for 10 seconds, dried at 100°C for 30 minutes, and then further dried at 150°C for 180 minutes to obtain the capacitor.

[0463] Example 5

[0464] In Example 4, the number of dip-coating cycles was set to 2 during the formation of the outer coating layer (second conductive layer). Otherwise, the capacitor was manufactured in the same manner as in Example 4, and the evaluation was conducted. The evaluation results are shown in Table 2.

[0465] Example 6

[0466] In Example 5, in the preparation of the conductive polymer composition K (second conductive polymer composition) for forming the second conductive layer, the amount of particulate silica added to the polyaniline composite solution I was set to 2 parts by mass (0.2 g). Otherwise, a capacitor was manufactured in the same manner as in Example 5, and its performance was evaluated. The evaluation results are shown in Table 2. Polyaniline composite / particulate silica mixed solution J

[0467] Example 7

[0468] In Example 4, during the formation of the outer coating layer (second conductive layer), the pulling speed when the anode body was pulled from the conductive polymer composition K was set to 30 seconds. Otherwise, the capacitor was manufactured in the same manner as in Example 4, and the evaluation was conducted. The evaluation results are shown in Table 2.

[0469] Example 8

[0470] In Example 4, ethyl cellulose was not added in the preparation of the conductive polymer composition K (second conductive polymer composition) for forming the second conductive layer. The number of dip-coating cycles was set to 3 in the formation of the outer coating layer (second conductive layer). Otherwise, the capacitor was manufactured in the same manner as in Example 4, and its performance was evaluated. The evaluation results are shown in Table 2.

[0471] Example 9

[0472] In Example 4, in the preparation of the conductive polymer composition K (second conductive polymer composition) for forming the second conductive layer, the amount of ethyl cellulose dissolved in the mixed solvent ε was set to 0.2 g, and in the formation of the outer coating layer (second conductive layer), the number of dip coatings was set to 3. Otherwise, the capacitor was manufactured in the same manner as in Example 4, and the evaluation was carried out. The evaluation results are shown in Table 2.

[0473] Example 10

[0474] In Example 4, no particulate silica was added in the preparation of the conductive polymer composition K (second conductive polymer composition) for forming the second conductive layer. The number of dip-coating cycles was set to 3 in the formation of the outer coating layer (second conductive layer). Otherwise, the capacitor was manufactured in the same manner as in Example 4, and its performance was evaluated. The evaluation results are shown in Table 2.

[0475] <Evaluation of side edge thickness>

[0476] For the capacitor obtained above, the side that was the bottom during dip coating was used as the base surface. In the direction between the base surface and the top surface, at a position 1 / 3 from the base surface, the capacitor was cut with a surface parallel to the base surface. The cross-section was observed using an optical microscope, and the thickness of the side edge portion and the thickness of the side flat portion were measured. The evaluation results are shown in Table 2.

[0477] <Evaluation of resistance to damp heat>

[0478] The capacitors obtained above were evaluated for their resistance to damp heat in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0479] Table 2

[0480]

[0481] The capacitors in Examples 4 to 10 all have resistance to damp heat.

[0482] It can be seen that the capacitors of Examples 4 to 6 with a lifting speed of 1 second are thicker in the side edge and side flat portion than the capacitor of Example 7 with a lifting speed of 30 seconds.

[0483] Furthermore, it is known that the capacitors of Examples 4 to 6, which contain both thixotropic agent (silica) and thickener (ethyl cellulose), are thicker at the side edges and side flat areas than the capacitors of Examples 8 and 10, which contain only one of the thixotropic agent (silica) and thickener (ethyl cellulose), even if the number of dip coatings is 1 or 2.

[0484] Furthermore, compared with Example 6, where the amount of thickener (ethyl cellulose) added is 0.36% by mass, and Example 9, where the amount of thickener (ethyl cellulose) added is 0.18% by mass, the amount of thixotropic agent (silica) added is 1.8% by mass. However, it can be seen that the capacitor of Example 6 is thick at the side edge and side flat portion even with fewer dip coatings.

[0485] Several embodiments and / or examples of the present invention have been described in detail above. However, those skilled in the art can readily make various modifications to these exemplary embodiments and / or examples without substantially departing from the new teachings and effects of the present invention. Therefore, these various modifications are included within the scope of the present invention.

[0486] The contents of the documents described in this specification and the application that forms the basis of this application based on the priority of the Paris Convention are incorporated herein by reference.

Claims

1. A solid electrolytic capacitor comprising a porous body containing a valve metal, a dielectric layer formed on the surface of the porous body, and two or more conductive layers covering the dielectric layer. The two or more conductive layers have a first conductive layer formed on the surface of the dielectric layer and a second conductive layer stacked on the first conductive layer. The second conductive layer comprises a polyaniline composite doped with polyaniline using a proton donor.

2. The solid electrolytic capacitor according to claim 1, wherein, The dielectric layer contains an oxide of the valve metal.

3. The solid electrolytic capacitor according to claim 1 or 2, wherein, The polyaniline complex was doped with sulfosuccinic acid.

4. The solid electrolytic capacitor according to any one of claims 1 to 3, wherein, The second conductive layer also contains a thixotropic agent.

5. The solid electrolytic capacitor according to claim 4, wherein, The thixotropic agent comprises inorganic particles.

6. The solid electrolytic capacitor according to claim 5, wherein, The inorganic particles comprise one or more selected from silicon dioxide, titanium dioxide, aluminum oxide, and zirconium oxide.

7. The solid electrolytic capacitor according to any one of claims 4 to 6, wherein, The thixotropic agent is present in an amount of 0.01% to 50% by mass relative to the entire second conductive layer.

8. The solid electrolytic capacitor according to any one of claims 1 to 7, wherein, The second conductive layer also contains a thickener.

9. The solid electrolytic capacitor according to claim 8, wherein, The thickener is a polyether-based compound or a cellulose-based compound.

10. The solid electrolytic capacitor according to claim 8 or 9, wherein, The thickener contains 0.001% to 5% by mass relative to the entire second conductive layer.

11. The solid electrolytic capacitor according to any one of claims 1 to 10, wherein, The second conductive layer is formed of a conductive polymer composition that satisfies the following conditions (P1) and (P2). (P1) The viscosity at a shear rate of 10 (1 / s) is greater than 1 Pa·s; (P2) After applying shear at a shear rate of 10 (1 / s) for 30 seconds, the viscosity at a shear rate of 0.0001 (1 / s) is greater than or equal to 10 Pa·s and satisfies the following formula (P2-1). 。 12. The solid electrolytic capacitor according to any one of claims 1 to 11, wherein, The valve metal is selected from aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth and antimony.

13. A method for manufacturing a solid electrolytic capacitor, comprising the following steps (A-1) or (A-2), step (B), and step (C). Process (A-1): Impregnating part or all of the porous body containing the valve metal oxide in a first conductive polymer composition comprising a conductive polymer and a solvent; Step (A-2): Impregnate part or all of the porous body containing the valve metal oxide in a first conductive polymer composition comprising a conductive polymer, a solvent and a phenolic compound; Step (B): The porous body is removed from the first conductive polymer composition used in step (A-1) or (A-2) and held at a temperature below the boiling point of the solvent contained in the first conductive polymer composition; Step (C): Impregnate a portion or the entire porous body after step (B) in a second conductive polymer composition containing the same or different conductive polymer, thixotropic agent and solvent as the first conductive polymer composition, and then dry it.

14. The method for manufacturing a solid electrolytic capacitor according to claim 13, wherein, The thixotropic agent is present in an amount of 0.2% to 5% by mass relative to the total amount of the second conductive polymer composition.

15. The method for manufacturing a solid electrolytic capacitor according to claim 13 or 14, wherein, The second conductive polymer composition satisfies the following conditions (P1) and (P2): (P1) The viscosity at a shear rate of 10 (1 / s) is greater than 1 Pa·s; (P2) After applying shear at a shear rate of 10 (1 / s) for 30 seconds, the viscosity at a shear rate of 0.0001 (1 / s) is greater than or equal to 10 Pa·s and satisfies the following formula (P2-1). 。 16. A solid electrolytic capacitor obtained by the manufacturing method of the solid electrolytic capacitor according to any one of claims 13 to 15.

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