Solid electrolytic capacitor

Abstract

This solid electrolytic capacitor includes at least one capacitor element including: an anode body including a porous section in at least a surface layer thereof; a dielectric layer covering at least a portion of the surface of the anode body; and a solid electrolyte layer covering at least a portion of the dielectric layer. The solid electrolyte layer has: a first section which fills voids of the porous section; and a second section which protrudes from a main surface of the anode body having the dielectric layer. The first section includes at least one first component selected from the group consisting of 1,2,4-trihydroxybenzene compounds and 1,3,5-trihydroxybenzene compounds.

Description

Solid electrolytic capacitors Cross-reference of related applications

[0001] This disclosure claims priority rights to Japanese Patent Application No. 2025-040277, filed with the Japan Patent Office on 13 March 2025, and the entirety of the said patent application is incorporated herein by reference.

[0002] This disclosure relates to solid electrolytic capacitors.

[0003] A solid electrolytic capacitor comprises, for example, a capacitor element and an outer casing that encloses the capacitor element. The capacitor element comprises, for example, a conductor (more specifically, an anode), a dielectric layer formed on the surface of the conductor, and a solid electrolyte layer covering at least a portion of the dielectric layer. The solid electrolyte layer is formed, for example, by chemical polymerization or electrolytic polymerization, or by using a processing solution (such as a liquid dispersion) containing a conductive polymer. As the conductive polymer, for example, a self-doped conductive polymer or a non-self-doped conductive polymer (such as a conjugated polymer and a dopant) is used.

[0004] Patent Document 1 proposes a process for manufacturing a capacitor, comprising: a) a step of preparing an electrode body (1) of an electrode material (2), wherein a dielectric (3) at least partially covers one surface (4) of the electrode material (2) under the formation of an anode body (5); b) a step of introducing a dispersion containing a dispersant, a heterogeneously doped conductive polymer, and counterions that do not covalently bond with the heterogeneously doped conductive polymer into at least a portion of the anode body (5); and c) a step of at least partially removing the dispersant while obtaining a solid electrolyte (6) in the capacitor body, wherein a self-doped conductive polymer is further introduced into at least a portion of the anode body (5).

[0005] Patent Document 2 proposes a solid electrolytic capacitor comprising: an anode body made of valve metal; a dielectric layer formed on the anode body; and a solid electrolyte layer formed on the dielectric layer, wherein the solid electrolyte layer comprises: a first conductive polymer layer formed on the dielectric layer and heterogeneously doped with a single-molecule dopant; a block layer formed on the first conductive polymer layer; and a second conductive polymer layer formed on the block layer and made of a self-doped conductive polymer having a plurality of side chains having dopeable functional groups, wherein the block layer blocks the movement of the self-doped conductive polymer from the second conductive polymer layer to the first conductive polymer layer, and / or the movement of the self-doped conductive polymer from the second conductive polymer layer into the pores of the porous anode body.

[0006] Japanese Patent Publication No. 2015-532525, Japanese Patent Publication No. 2023-13918

[0007] One aspect of the present disclosure relates to a solid electrolytic capacitor comprising at least one capacitor element including an anode body having a porous portion on at least its surface, a dielectric layer covering at least a portion of the surface of the anode body, and a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer has a first portion filled in the voids of the porous portion and a second portion extending beyond the main surface of the anode body having the dielectric layer, and the first portion comprises at least one first component selected from the group consisting of 1,2,4-trihydroxybenzene compounds and 1,3,5-trihydroxybenzene compounds.

[0008] According to the above aspect of this disclosure, high adhesion of the solid electrolyte layer can be obtained in a solid electrolytic capacitor.

[0009] This is a schematic cross-sectional view of a solid electrolytic capacitor according to one embodiment of the present disclosure.

[0010] While novel features of the present invention are described in the appended claims, the present invention, both in terms of its structure and content, will be better understood by the following detailed description in conjunction with the drawings, in conjunction with other objects and features of the present invention.

[0011] In solid electrolytic capacitors, the adhesion of the solid electrolyte is often poor, which can lead to delamination between the dielectric layer and the solid electrolyte layer, or within the solid electrolyte layer itself. When such delamination occurs, the electronic contacts are lost, and the capacitance decreases. Therefore, high adhesion of the solid electrolyte layer is required.

[0012] If the adhesion of the solid electrolyte layer is poor, delamination of the solid electrolyte layer may occur as described above, which can lead to a decrease in capacitance. In addition, in solid electrolytic capacitors, repeated charging and discharging or exposure to high temperatures can easily cause defects in the dielectric layer. When current flows through the defective areas of the dielectric layer, the surrounding solid electrolyte deteriorates or the solid electrolyte undergoes oxidative degradation, reducing the conductivity of the solid electrolyte and thus decreasing capacitance.

[0013] Technical (1) A solid electrolytic capacitor according to one aspect of the present disclosure includes at least one capacitor element comprising an anode body having a porous portion on at least its surface, a dielectric layer covering at least a portion of the surface of the anode body, and a solid electrolyte layer covering at least a portion of the dielectric layer. The solid electrolyte layer has a first portion filled in the voids of the porous portion and a second portion extending beyond the main surface of the anode body having the dielectric layer. The first portion comprises at least one first component selected from the group consisting of 1,2,4-trihydroxybenzene compounds and 1,3,5-trihydroxybenzene compounds.

[0014] In this disclosure, since the first portion of the solid electrolyte layer contains the first component, high adhesion to the solid electrolyte layer is obtained, and delamination between the dielectric layer and the solid electrolyte layer, as well as within the solid electrolyte layer, can be suppressed. This is thought to be because the film quality of the solid electrolyte is improved by the action of the first component. In addition, the oxidation-preventive effect of the first component suppresses oxidative degradation of the solid electrolyte. As a result, even when the solid electrolytic capacitor is subjected to repeated charging and discharging or exposure to high temperatures, the high conductivity between the dielectric layer and the solid electrolyte layer, and the high conductivity of the solid electrolyte layer, is maintained. Even when the solid electrolytic capacitor is subjected to repeated charging and discharging or exposure to high temperatures, high heat resistance and high reliability are obtained.

[0015] Technology (2) In the above technology (1), it is preferable that the first component is water-soluble. In this case, it is believed that the film quality of the solid electrolyte layer and the adhesion between the solid electrolyte layer and the dielectric layer are greatly improved. The water-soluble first component dissolves in the water contained in the liquid component which contains the conductive polymer that is the raw material for the solid electrolyte layer. The antioxidant dissolved in water can be widely and uniformly dispersed in the first part (or a predetermined part in the first part), and oxidative degradation of the conductive polymer can be suppressed in almost the entire first part, thereby improving the film quality.

[0016] Technology (3) In Technology (1) or Technology (2) described above, the first portion preferably contains the 1,2,4-trihydroxybenzene compound. In this case, a higher capacity can be obtained even after repeated charging and discharging, and the reliability of the solid electrolytic capacitor can be improved. This is thought to be because the inclusion of the 1,2,4-trihydroxybenzene compound in the first portion provides an even higher film quality improvement effect for the solid electrolyte layer, as well as a higher antioxidant effect.

[0017] Technology (4) In any one of the above technologies (1) to (3), the first part may include a first conductive polymer covering at least a portion of the dielectric layer and a second conductive polymer layer covering at least a portion of the first conductive polymer. Preferably, the second conductive polymer layer includes a non-self-doped second conductive polymer and the first component. The first component acts on the non-self-doped second conductive polymer, further suppressing oxidative degradation and dedoping of the second conductive polymer. Therefore, when the solid electrolytic capacitor is repeatedly charged and discharged, or when the solid electrolytic capacitor is exposed to a high-temperature environment, the decrease in capacitance and conductivity is suppressed, and higher heat resistance and higher reliability are obtained.

[0018] Technology (5) In the above technology (4), the first conductive polymer is preferably self-doped. Self-doped conductive polymers have small particle size and are easily impregnated into porous parts. Therefore, the conductive polymer particles can penetrate deep into the pores of the dielectric layer and cover a wider surface of the dielectric layer. Thus, high conductivity and high capacitance are easily obtained.

[0019] Technology (6) In Technology (4) or Technology (5) described above, the second conductive polymer preferably comprises a conjugated polymer and a polymer anion. In this case, higher heat resistance is more likely to be obtained.

[0020] Technology (7) In any one of the above technologies (1) to (6), it is preferable that the mass content of the first component in the first part is higher than the mass content of the first component in the second part. In the solid electrolyte layer, the mass ratio of the second part is greater than the mass ratio of the first part. Since the first component is an insulator, if a large amount of the first component is contained in the second part, the conductivity of the solid electrolyte tends to decrease and the capacity decreases. On the other hand, in the first part, the adhesion of the solid electrolyte greatly affects the conductivity in the first part. Therefore, by having a higher mass content of the first component in the first part compared to the second part, relatively high conductivity can be obtained in the first part due to high adhesion and oxidation prevention effect, and deterioration of the solid electrolyte after charging and discharging or exposure to a high-temperature environment is suppressed. In addition, high conductivity can be obtained in the second part. Thus, high conductivity can be obtained for the solid electrolyte layer as a whole, and higher heat resistance and reliability can be obtained.

[0021] Technology (8) In any one of the above technologies (1) to (7), it is more preferable that the second portion does not contain the first component. The first portion, which is closer to the dielectric layer, has a greater impact on the heat resistance and reliability of the solid electrolytic capacitor than the second portion, which is further away from the dielectric layer. Therefore, by having the first portion contain the first component and the second portion not contain the first component, high conductivity of the solid electrolyte layer can be obtained, a higher capacitance can be obtained, and heat resistance and reliability can be improved.

[0022] The presence of the first component in the first part (or solid electrolyte layer) can be confirmed, for example, by TOF-SIMS (time-of-flight secondary ion mass spectrometry) of the cross-section of the solid electrolyte layer. TOF-SIMS allows for the confirmation of the presence of the first component in any part of the cross-section of the solid electrolyte layer. Furthermore, by performing TOF-SIMS analysis of the cross-section of the solid electrolyte layer at equal intervals along the thickness direction (depth direction) of the solid electrolyte layer, the distribution state of the first component in the thickness direction of the solid electrolyte layer can be estimated. TOF-SIMS analysis may also be performed at multiple locations (e.g., five locations) in the cross-section of the solid electrolyte layer along the circumferential direction of the cross-section of the anode. In that case, the estimated concentrations of the first component at multiple locations at the same depth in the solid electrolyte layer may be averaged.

[0023] The solid electrolyte layer sample used for analysis is prepared by embedding a solid electrolytic capacitor or capacitor element in acrylic resin, cutting it in the center of the capacitor element's width direction in a direction parallel to its length direction to expose the cross-section (for example, a cross-section like that shown in Figure 1), and then polishing it.

[0024] The solid electrolytic capacitor of this disclosure will be described in more detail below, including the above techniques (1) to (8), with reference to the drawings as necessary. To the extent that it is not technically inconsistent, at least one of the above techniques (1) to (8) may be combined with at least one of the elements described below. Note that each figure is for illustrative purposes only, and the proportions of the dimensions (e.g., thickness) of each component may differ from those of the actual components.

[0025] The following descriptions may include examples of embodiments of the Disclosure, but the Disclosure is not limited to these examples. The following descriptions may include specific numerical values ​​and materials, but other numerical values ​​and materials may be used as long as the effects of the Disclosure are achieved. In the following descriptions, when lower and upper limits of numerical values ​​relating to specific physical properties or conditions are given as examples, any combination of either of the given lower limits and either of the given upper limits may be used, as long as the lower limit does not exceed the upper limit. When multiple materials are given as examples, one may be selected and used alone, or two or more may be used in combination.

[0026] [Solid Electrolytic Capacitor] The solid electrolytic capacitor of this disclosure comprises at least one capacitor element. The capacitor element includes a solid electrolyte layer. Since the solid electrolytic capacitor of this disclosure is mainly characterized by the solid electrolyte layer, there are no particular limitations on other components. Components used in known solid electrolytic capacitors may be applied to each component.

[0027] (Capacitor element) The capacitor element includes an anode, a dielectric layer, and a cathode. The cathode includes a solid electrolyte layer that covers at least a portion of the dielectric layer.

[0028] (Anode) The anode is made of a conductive material. The anode may be a sheet-like anode foil, or it may be a molded or sintered body of metal particles.

[0029] The conductive material constituting the anode may include valve metals, alloys containing valve metals, compounds containing valve metals, etc. The anode may contain one of these materials, or a combination of two or more. As valve metals, aluminum, tantalum, niobium, and titanium are preferred, for example.

[0030] The anode body has a porous region at least on its surface. The anode body has numerous fine voids in the porous region. Due to this porous region, the anode body has a fine, uneven surface.

[0031] An anode body having a porous portion on its surface can be obtained, for example, by roughening the surface of a substrate containing a valve-acting metal (such as a sheet-like substrate (e.g., foil-like or plate-like substrate)). Surface roughening may be performed, for example, by etching (electrolytic etching, chemical etching, etc.). Such an anode body (anode foil) has, for example, a core portion and porous portions formed integrally with the core portion on the surfaces of both the core and the core.

[0032] The anode body may be a sintered or molded body of particles containing a valve metal. The molded and sintered bodies are porous and may have a rectangular parallelepiped, cubic, or similar shape. As a sintered body, for example, it may be a sintered body of particles containing tantalum.

[0033] The anode body may have an electrode lead portion (also referred to as the anode lead portion) including a first end, and a cathode forming portion including a second end opposite to the first end. A cathode portion including a solid electrolyte layer is formed on the surface of the cathode forming portion of the anode body. The anode lead portion is used, for example, for electrical connection with an external electrode on the anode side. An anode lead terminal may be connected to the anode lead portion.

[0034] (Anode Wire) If the anode body is a porous sintered or molded body, the anode portion may include an anode wire. The anode wire may be a metal wire. Examples of materials for the anode wire include the valve metals, copper, or copper alloys mentioned above. A portion of the anode wire is embedded in the anode body, and the remaining portion protrudes outward from the end face of the anode body. The end of the anode wire protruding outward corresponds to the first end, and the end of the anode body opposite the first end corresponds to the second end.

[0035] (Dielectric layer) The dielectric layer is formed to cover at least a portion of the surface of the anode body (including the surface of the porous portion). The dielectric layer can be formed by known methods. The dielectric layer may be formed by oxidizing the valve metal on the surface of the anode body or the porous portion by chemical conversion treatment, or by a vapor phase method. The dielectric layer has a fine uneven surface shape that follows the surface shape of the porous portion.

[0036] The dielectric layer contains an oxide of the valve metal. For example, when tantalum is used as the valve metal, the dielectric layer contains Ta ２ O ５ The dielectric layer contains tantalum oxide, and when aluminum is used as the valve metal, the dielectric layer is Al ２ O ３ This includes aluminum oxides such as those mentioned above. Note that the dielectric layer is not limited to these examples; any dielectric material that functions as a dielectric is acceptable.

[0037] (Cathode portion) The cathode portion includes at least a solid electrolyte layer covering at least a portion of the dielectric layer. The solid electrolyte layer is formed via the dielectric layer in the portion on the second end side of the anode body (in other words, the cathode forming portion). The cathode portion usually includes a solid electrolyte layer covering at least a portion of the dielectric layer and a cathode extraction layer covering at least a portion of the solid electrolyte layer.

[0038] (Solid Electrolyte Layer) In a capacitor element, the solid electrolyte layer is formed so as to cover at least a part of the dielectric layer. The solid electrolyte layer has a first part filled in voids of a porous part in an anode body having at least a part of a surface thereof covered with the dielectric layer, and a second part protruding from a main surface of the anode body provided with the dielectric layer. Hereinafter, the "anode body having at least a part of the surface thereof covered with the dielectric layer" may be simply referred to as "the anode body covered with the dielectric layer".

[0039] In the present disclosure, the first part of the solid electrolyte layer contains a first component. The first component has a function as an antioxidant. The first part may contain an antioxidant (second component) other than the first component.

[0040] In the present specification, an antioxidant refers to a component having an effect of inactivating radicals generated by involvement of oxygen. In addition to components generally referred to as antioxidants, antioxidants also include components called deterioration inhibitors, anti-aging agents, radical chain inhibitors, peroxide decomposers, chain initiation inhibitors, light stabilizers, heat stabilizers (or heat-resistant stabilizers), metal deactivators, ultraviolet absorbers, weathering stabilizers, and the like.

[0041] (First Component) The first component is at least one selected from the group consisting of 1,2,4-trihydroxybenzene compounds and 1,3,5-trihydroxybenzene compounds. In addition to 1,2,4-trihydroxybenzene and 1,3,5-trihydroxybenzene (also known as phloroglucinol), each of these trihydroxybenzene compounds also includes compounds having a substituent (second substituent) other than the three hydroxy groups (first substituent).

[0042] Examples of the second substituent include a halogen atom, an alkyl group, a hydroxyalkyl group, an alkoxy group, a carboxy group, and an alkoxycarbonyl group. Halogen atoms include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like. The alkyl moiety of an alkyl group or a hydroxyalkyl group, and the alkoxy moiety of an alkoxy group or an alkoxycarbonyl group may be linear or branched. The number of carbon atoms in the alkyl moiety of an alkyl group, a hydroxyalkyl group, an alkoxy group, and the alkoxy moiety of an alkoxycarbonyl group is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the hydroxyalkyl group include hydroxyalkyl groups corresponding to the examples of the above alkyl groups. Examples of the alkoxy moiety of an alkoxy group and an alkoxycarbonyl group include alkoxy groups corresponding to the examples of the above alkyl groups. The number of the second substituents in the first component is 0 or more and 3 or less, preferably 0 or more and 2 or less, more preferably 0 or 1.

[0043] The first portion may contain one type of the first component, or may contain two or more types thereof.

[0044] From the viewpoint that higher dispersibility of the first component is easily obtained, the first component is preferably water-soluble. Here, that the first component is water-soluble means that the first component is water-soluble at the temperature at which the first component is applied to the first portion (for example, room temperature). In the present specification, room temperature refers to a temperature in the range of 20°C or more and 35°C or less.

[0045] From the viewpoint that higher heat resistance and higher reliability of a solid electrolytic capacitor are easily obtained, the first portion preferably contains at least a 1,2,4-trihydroxybenzene compound among the first components. The first portion may contain a 1,2,4-trihydroxybenzene compound and a 1,3,5-trihydroxybenzene compound.

[0046] (Second component) The second component may include antioxidants not included in the first component. The second component may include, for example, at least one selected from the group consisting of a hydroxyl group, a nitrogen atom, an oxygen atom, a sulfur atom, and a phosphorus atom. Examples of such antioxidants include phenolic antioxidants (excluding the first component), amine antioxidants, phosphorus antioxidants, sulfur antioxidants, benzimidazole antioxidants, and carotenoid compounds. The first part may contain one or more second components.

[0047] From the viewpoint of easily obtaining higher heat resistance and moisture resistance, it is preferable that the mass ratio of the first component in the first part (or solid electrolyte layer) is greater than the mass ratio of the second component. For the same reason, it is also preferable that the second component is not included in the first part, the second part, or the solid electrolyte layer. The presence of the second component in the first part (or solid electrolyte layer) can be confirmed by TOF-SIMS, in the same manner as in the case of the first component.

[0048] (Conductive Polymer) Each of the first part, the second part, and the solid electrolyte layer contains a conductive polymer (solid electrolyte). For example, the first part may include a first conductive polymer covering at least a portion of the dielectric layer and a second conductive polymer layer covering at least a portion of the first conductive polymer.

[0049] From the viewpoint of easily obtaining higher heat resistance and reliability, it is preferable that the second conductive polymer layer comprises the first component and a non-self-doped second conductive polymer.

[0050] The first conductive polymer is preferably self-doped.

[0051] (Self-doped conductive polymers) A self-doped first conductive polymer has, for example, a conjugated polymer skeleton and functional groups (such as anionic groups) that function as dopants directly or indirectly bonded to this skeleton by covalent bonds.

[0052] Examples of anionic groups include sulfo groups, carboxyl groups, phosphate groups, and phosphonic acid groups. The self-doped conductive polymer may contain one type of anionic group, or two or more types. From the viewpoint of easily ensuring higher conductivity of the first self-doped conductive polymer, the first conductive polymer may contain at least a sulfo group.

[0053] The anionic groups of the self-doped first conductive polymer may be present in any form, such as anions, acids, esters, and salts, and may be present in a form that interacts with or is complexed with components contained in the solid electrolyte layer. In this specification, all of these forms are simply referred to as anionic groups.

[0054] Examples of conjugated polymers that constitute the skeleton of the self-doped first conductive polymer include polymers with a π-conjugated polymer (such as polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene) as the basic skeleton. The above polymers only need to contain at least one monomer unit that constitutes the basic skeleton. The above polymers also include homopolymers, copolymers of two or more monomers, and derivatives thereof (such as substituted products having substituents). For example, polythiophene includes poly(3,4-ethylenedioxythiophene). The self-doped first conductive polymer has anionic groups in the skeleton of these conjugated polymers. The anionic groups may be directly introduced into the skeleton of the conjugated polymer or introduced via linking groups. Preferred linking groups include polyvalent groups (divalent groups) containing alkylene groups. Examples of linking groups include aliphatic polyvalent groups (divalent groups, etc.) such as alkylene groups, -R １ -X-R ２ - group (X is an oxygen element or a sulfur element, R １ and R ２are the same or different alkylene groups.). Examples are given below. The number of carbon atoms in each alkylene group contained in the linking group is, for example, 1 or more and 10 or less, and may be 1 or more and 6 or less. The alkylene group may be linear or branched. For example, the linking group may contain at least an alkylene group having 2 or more carbon atoms. The number of carbon atoms of such an alkylene group may be 2 or more (or 3 or more) and 10 or less, or 2 or more (or 3 or more) and 6 or less. For example, R １ is an alkylene group having 1 to 6 carbon atoms, and R ２ may be an alkylene group having 2 or more (or 3 or more) to 10 carbon atoms. However, the linking group is not limited only thereto.

[0055] The conjugated polymer constituting the skeleton of the self-doped first conductive polymer may be polypyrrole, polythiophene or polyaniline. From the viewpoint of easily obtaining high conductivity and the like, as the self-doped first conductive polymer, a polymer having a conjugated polymer skeleton containing a repeating structure of monomer units corresponding to a thiophene compound and an anionic group introduced into the skeleton is preferred.

[0056] Examples of the thiophene compound include compounds having a thiophene ring and capable of forming a repeating structure of corresponding monomer units. The thiophene compound can form a repeating structure of monomer units by linking at the 2-position and 5-position of the thiophene ring.

[0057] The thiophene compound may, for example, have a substituent (third substituent) on at least one of the 3-position and 4-position of the thiophene ring. The third substituent at the 3-position and the third substituent at the 4-position may be linked to each other to form a ring fused to the thiophene ring. Examples of the thiophene compound include thiophene which may have a third substituent on at least one of the 3-position and 4-position, and alkylenedioxythiophene compounds (C such as ethylenedioxythiophene compounds ２－４ alkylenedioxythiophene compounds, etc.). Alkylenedioxythiophene compounds also include compounds having a third substituent in the alkylene group moiety.

[0058] Preferred third substituents include alkyl groups, alkoxy groups, hydroxyl groups, and hydroxyalkyl groups, but are not limited to these. For alkyl groups, alkoxy groups, and hydroxyalkyl groups as third substituents, refer to the description of the second substituent. If a thiophene compound has two or more third substituents, each third substituent may be the same or different. The thiophene ring (or, in the case of an alkylenedioxythiophene ring, at least one of the thiophene ring and the alkylene group) may have the above-mentioned anionic group or a group containing an anionic group (e.g., a sulfoalkyl group) as the third substituent.

[0059] The self-doped first conductive polymer may have a conjugated polymer backbone (such as PEDOT) containing a repeating structure of monomer units corresponding to at least a 3,4-ethylenedioxythiophene compound (such as 3,4-ethylenedioxythiophene (EDOT)). The conjugated polymer backbone containing a repeating structure of monomer units corresponding to at least EDOT may contain only monomer units corresponding to EDOT, or it may contain monomer units corresponding to thiophene compounds other than EDOT in addition to said monomer units.

[0060] An example of monomer units for self-doped conductive polymers is shown below.

[0061]

[0062] The weight-average molecular weight (Mw) of the self-doped conductive polymer may be 1,000 or more and 1,000,000 or less, or 1,000 or more and 50,000 or less.

[0063] In this specification, the weight-average molecular weight (Mw) is the polystyrene-converted value measured by gel permeation chromatography (GPC). GPC is typically measured using a polystyrene gel column and water / methanol (volume ratio 8 / 2) as the mobile phase.

[0064] (Non-self-doped conductive polymer) The second type of non-self-doped conductive polymer includes, for example, a conjugated polymer and a dopant. Here, the conjugated polymer is a non-self-doped conjugated polymer (for example, a conjugated polymer without anionic groups).

[0065] Examples of conjugated polymers include those exemplified as conjugated polymers constituting the backbone of self-doped conductive polymers (such as π-conjugated polymers). Conjugated polymers may be used individually or in combination of two or more types. From the viewpoint of easily ensuring high initial capacity, higher heat resistance, and reliability, unself-doped conjugated polymers containing repeating structures of monomer units of thiophene compounds may be used. Examples of thiophene compounds corresponding to the monomer units of unself-doped conjugated polymers include the thiophene compounds described for self-doped conductive polymers. Unself-doped conjugated polymers may include conjugated polymers (such as PEDOT) containing repeating structures of monomer units corresponding to at least 3,4-ethylenedioxythiophene compounds (such as EDOT). Conjugated polymers containing at least repeating structures of monomer units corresponding to EDOT may contain only the monomer units corresponding to EDOT, or they may contain monomer units corresponding to thiophene compounds other than EDOT in addition to the monomer units.

[0066] The dopant can be at least one selected from the group consisting of anions and polyanions (such as polymer anions). Examples of anions include sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions. Examples of dopants that generate sulfonate ions include p-toluenesulfonic acid and naphthalenesulfonic acid. From the viewpoint of easily obtaining higher heat resistance and reliability, as well as higher dielectric strength, it is preferable to use polymer anions.

[0067] Examples of polymer anions having a sulfo group include high-molecular-weight polysulfonic acids. Specific examples of polymer anions include polyvinyl sulfonic acid, polystyrene sulfonic acid (PSS (including copolymers and substituted products having substituents)), polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacrylate sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyester sulfonic acid (such as aromatic polyester sulfonic acid), and phenolsulfonic acid novolac resin. However, dopants are not limited to these specific examples.

[0068] The second conductive polymer may contain one dopant (such as a polymer anion), or a combination of two or more dopants.

[0069] In a non-self-doped second conductive polymer, the amount of dopant (such as polymer anions) may be 10 to 1000 parts by mass, or 20 to 500 parts by mass, per 100 parts by mass of the conjugated polymer.

[0070] (Method for forming a solid electrolyte layer) The step of forming a solid electrolyte layer so as to cover at least a portion of the dielectric layer includes, for example, a first step of forming a first portion and a second step of forming a second portion. The step of performing an optional processing may be further included between the first and second steps.

[0071] (First step for forming the first part) The first step includes, for example, the step of applying a first conductive polymer to the surface of a dielectric layer and the step of forming a second conductive polymer layer containing a non-self-doped second conductive polymer.

[0072] (Step of applying the first conductive polymer) In the step of forming the first layer, for example, a processing solution (first processing solution) containing a self-doped first conductive polymer may be applied to the surface of the dielectric layer. More specifically, by applying the first processing solution to the surface of the dielectric layer, the first conductive polymer is applied so as to cover at least a part of the dielectric layer. The dielectric layer may be dried after the first processing solution has been applied. If necessary, the application of the first processing solution to the dielectric layer and drying may be repeated two or more times.

[0073] The first processing solution includes, for example, a first conductive polymer and a liquid medium. The first processing solution may contain one type of first conductive polymer, or two or more types. The liquid medium is, for example, a medium that is liquid at room temperature (for example, 20°C to 35°C). Examples of liquid media include water, organic solvents, or mixtures thereof. Water is preferred among these.

[0074] The first treatment solution may be a dispersion in which particles of the first conductive polymer are dispersed in a liquid medium, or it may be a solution in which the first conductive polymer is dissolved in a liquid medium. The self-doped first conductive polymer has relatively flexible polymer chains and the positions of functional groups such as anionic groups are random. Furthermore, the self-doped first conductive polymer has low orientation of polymer chains and low crystallinity. Therefore, compared to the non-self-doped conductive polymer, it is easier to dissolve in a liquid medium or disperse into fine particles. As a result, the viscosity of the first treatment solution is relatively low, and it is easy to impregnate the voids in the porous part with high permeability.

[0075] The concentration of the first conductive polymer in the first processing solution may be 0.5% by mass or more and 5% by mass or less, or 1% by mass or more and 3% by mass or less.

[0076] The first treatment solution may contain the first and second components, but may not contain the first and second components from the viewpoint of ensuring higher reliability and heat resistance. If the first treatment solution contains the first component, it is preferable that the concentration of the first component in the first treatment solution is lower than the concentration of the first component in the second treatment solution described later. The concentration of the first component in the first treatment solution may be 5% by mass or less, less than 3% by mass, 1% by mass or less, or 0.1% by mass or less. The concentration of the second component in the first treatment solution is also selected from these ranges.

[0077] (Step to form the second conductive polymer layer) In the step to form the second conductive polymer layer, for example, the second conductive polymer layer may be formed using a processing solution (second processing solution) that contains a non-self-doped second conductive polymer, preferably further containing the first component. More specifically, the second conductive polymer layer is formed by applying the second processing solution containing the non-self-doped second conductive polymer and the first component to the dielectric layer. The dielectric layer may be dried after the application of the second processing solution. If necessary, the application of the second processing solution to the dielectric layer and drying may be repeated two or more times.

[0078] The second treatment solution comprises, for example, a non-self-doped second conductive polymer, a first component, and a liquid medium. The second treatment solution may be a dispersion in which particles of the second conductive polymer are dispersed in the liquid medium. The first component is preferably dissolved in the dispersion. The second treatment solution may contain one type of second conductive polymer, or two or more types. The second treatment solution may contain one type of first component, or two or more types. Examples of the liquid medium include water, an organic solvent, or a mixture thereof. Water is preferred among these.

[0079] The concentration of the second conductive polymer in the second processing solution may be 0.5% by mass or more and 5% by mass or less, or 1% by mass or more and 3% by mass or less.

[0080] The second treatment solution may contain the first component. If the liquid medium of the second treatment solution contains water, it is preferable to use a water-soluble first component. The concentration of the first component in the second treatment solution may be appropriately controlled in accordance with the concentration of the second conductive polymer in the second treatment solution. The concentration of the first component in the second treatment solution may be 0.1% by mass or more and 10% by mass or less, 1% by mass or more and 5% by mass or less, or 3% by mass or more and 5% by mass or less. The second treatment solution may contain the first component in an amount equal to or greater than the mass of the second conductive polymer.

[0081] It is presumed that a portion of the first component volatilizes during the drying process of the treatment solution. As a result, a second conductive polymer layer containing the first component can be formed, for example, with a content of 3% to 40% by mass, 5% to 35% by mass, or 10% to 30% by mass. Preferably, the mass content of the first component in the second conductive polymer layer is higher than the mass content of the first component in the first conductive polymer attached to the surface of the dielectric layer.

[0082] If the second treatment solution contains the second component, the mass-based concentration of the second component in the second treatment solution is adjusted so that the mass ratio of the first component to the total amount of the first and second components falls within the range described above.

[0083] (Second step for forming the second part) The second step involves forming a second part that covers at least a portion of the first part, extending beyond the main surface of the anode body covered with the dielectric layer, using, for example, a processing solution (third processing solution) containing a third conductive polymer. More specifically, the third processing solution containing the third conductive polymer is applied to the dielectric layer to form the second part. The third processing solution may be applied to the first part and then dried. If necessary, the application of the third processing solution to the first part and drying may be repeated two or more times. From the viewpoint of easily forming a second part having a certain thickness in a small number of steps, the third conductive polymer is preferably of the non-self-doped type. For the third conductive polymer, refer to the description of the non-self-doped type second conductive polymer.

[0084] The third treatment solution includes, for example, a third conductive polymer and a liquid medium. The third treatment solution may be a dispersion in which particles larger in size than the non-self-doped conductive polymer used to form the second conductive polymer layer are dispersed in the liquid medium. The third treatment solution may contain one type of third conductive polymer, or two or more types. Examples of the liquid medium include water, an organic solvent, or a mixture thereof. Water is preferred among these.

[0085] The concentration of the third conductive polymer in the third treatment solution may be 0.5% by mass or more and 5% by mass or 1% by mass or more and 3% by mass. The non-self-doped third conductive polymer contained in the third treatment solution tends to have a large particle size and high viscosity. Therefore, it is preferable that the concentration of the non-self-doped third conductive polymer in the third treatment solution is lower than the concentration of the non-self-doped second conductive polymer in the second treatment solution. The large particle size of the non-self-doped third conductive polymer makes it difficult to fill the pores of the porous portion of the anode body, and it tends to form a skin-like film of the third conductive polymer on the outside of the porous portion.

[0086] The third treatment solution may contain the first and second components, but may not contain the first and second components from the viewpoint of ensuring higher reliability and heat resistance. If the third treatment solution contains the first component, it is preferable that the concentration of the first component in the third treatment solution is lower than the concentration of the first component in the second treatment solution. The concentration of the first component in the third treatment solution may be 5% by mass or less, less than 3% by mass, 1% by mass or less, or 0.1% by mass or less. The concentration of the second component in the third treatment solution is also selected from these ranges.

[0087] (Cathode Extraction Layer) The cathode extraction layer may include, for example, a first extraction layer that is in contact with the solid electrolyte layer and covers at least a portion of the solid electrolyte layer. The cathode extraction layer may also include a first extraction layer and a second extraction layer that covers at least a portion of the first extraction layer.

[0088] Examples of the first extraction layer include a layer containing conductive particles and a metal foil. Examples of conductive particles include at least one selected from conductive carbon and metal powder. The cathode extraction layer may include a layer containing metal powder (such as a metal particle-containing layer). The cathode extraction layer may consist, for example, a layer containing conductive carbon as the first extraction layer (carbon layer) and a layer containing metal powder (such as a metal particle-containing layer) or a metal foil as the second extraction layer.

[0089] If the cathode extraction layer includes a metal foil or a metal particle-containing layer, the entire cathode extraction layer may be composed of the metal foil or metal particle-containing layer. Alternatively, at least one of the first extraction layer and the second extraction layer may be composed of the metal particle-containing layer.

[0090] Examples of conductive carbon include graphite (artificial graphite, natural graphite, etc.).

[0091] A layer containing metal powder, which serves as a second extraction layer, can be formed, for example, by laminating a composition containing metal powder onto the surface of the first extraction layer. An example of such a second extraction layer is a metal particle-containing layer formed using a paste containing metal powder and a resin binder. While thermoplastic resins can be used as the resin binder, thermosetting resins such as imide resins and epoxy resins are preferred. From the viewpoint of easily obtaining high conductivity in the second extraction layer, silver-containing particles may be used as the metal powder. Examples of silver-containing particles include silver particles and silver alloy particles. The second extraction layer may contain one type of silver-containing particle, or a combination of two or more types. The silver particles may contain small amounts of impurities.

[0092] When a metal foil is used as the first lead layer, the type of metal is not particularly limited. Preferably, the metal foil is a valve metal (such as aluminum, tantalum, or niobium) or an alloy containing a valve metal. The surface of the metal foil may be roughened as needed. The surface of the metal foil may be coated with a chemical conversion film, or a coating of a metal different from the metal constituting the metal foil (a dissimilar metal) or a nonmetal. Examples of dissimilar metals or nonmetals include metals such as titanium or nonmetals such as carbon (such as conductive carbon).

[0093] The above-mentioned dissimilar metal or nonmetal (for example, conductive carbon) coating may be used as the first draw-out layer, and the above-mentioned metal foil may be used as the second draw-out layer.

[0094] The cathode extraction layer is formed by known methods depending on its layer configuration. For example, if the cathode extraction layer includes a metal foil as a first or second extraction layer, the first or second extraction layer is formed by laminating the metal foil so as to cover at least a portion of the solid electrolyte layer or the first extraction layer. The first extraction layer containing conductive particles is formed, for example, by applying a conductive paste or liquid dispersion containing conductive particles and optionally a resin binder (water-soluble resin, curable resin, etc.) to the surface of the solid electrolyte layer. The second extraction layer containing metal powder is formed, for example, by applying a paste containing metal powder and a resin binder to the surface of the first extraction layer. During the process of forming the cathode extraction layer, drying treatment, heat treatment, etc., may be performed as needed.

[0095] (Other) A solid electrolytic capacitor includes at least one capacitor element. The solid electrolytic capacitor may be wound type, chip type, or multilayer type. For example, a solid electrolytic capacitor may include multiple stacked capacitor elements. Alternatively, a solid electrolytic capacitor may include two or more wound type capacitor elements. The configuration of the capacitor elements should be selected according to the type of solid electrolytic capacitor.

[0096] When a metal foil is used as the cathode lead layer, a separator may be placed between the metal foil and the anode foil, which serves as the anode body. The separator is not particularly limited, and may be a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (e.g., aliphatic polyamide, aromatic polyamide such as aramid).

[0097] In a capacitor element, one end of the cathode lead terminal may be electrically connected to the cathode lead layer. The cathode lead terminal is joined to the cathode lead layer, for example, by applying a conductive adhesive to the cathode lead layer and bonding it to the cathode lead layer via this conductive adhesive. One end of the anode lead terminal may be electrically connected to the anode lead portion of the anode body. The other end of the anode lead terminal and the other end of the cathode lead terminal are led out from the resin casing or case, respectively. The other ends of each terminal exposed from the resin casing or case are used for soldering to a substrate on which a solid electrolytic capacitor is to be mounted. Furthermore, not limited to cases where lead terminals are led out, at least one end face of the anode portion and the cathode portion may be exposed from the outer surface of the encapsulant and electrically connected to an external electrode.

[0098] The capacitor element is sealed using a resin casing or case. For example, the capacitor element and the resin material for the casing (e.g., uncured thermosetting resin and filler) may be placed in a mold, and the capacitor element may be sealed with the resin casing by a transfer molding method, compression molding method, or the like. In this case, the other ends of the anode lead terminal and cathode lead terminal connected to the anode lead drawn out from the capacitor element are exposed from the mold. Alternatively, the capacitor element may be housed in a bottomed case such that the other ends of the anode lead terminal and cathode lead terminal are located on the opening side of the bottomed case, and a solid electrolytic capacitor may be formed by sealing the opening of the bottomed case with a sealing body. The leads may be wire-shaped or frame-shaped (e.g., lead frame).

[0099] The solid electrolytic capacitors disclosed herein offer high adhesion of the solid electrolyte layer and thus high capacitance. Furthermore, high capacitance can be maintained even after repeated charging and discharging or exposure to high-temperature environments, thereby improving the heat resistance and reliability of the solid electrolytic capacitors. For this reason, the solid electrolytic capacitors disclosed herein are particularly suitable for applications requiring high heat resistance and high reliability. However, the applications of solid electrolytic capacitors are not limited to these.

[0100] Figure 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to one embodiment of the present disclosure. The solid electrolytic capacitor 20 includes a capacitor element including an anode portion 6 and a cathode portion 7, an outer casing 11 that encloses the capacitor element, an anode lead frame 13 electrically connected to the anode portion 6, and a cathode lead frame 14 electrically connected to the cathode portion 7.

[0101] The anode section 6 comprises an anode body 1 and an anode wire 2. A portion of the anode wire 2 is embedded within the anode body 1, while the remaining portion protrudes outward from the outer surface of the anode body 1. A portion of the anode lead frame 13 is joined to this protruding portion of the anode wire 2 by welding or other means, and is electrically connected to it.

[0102] A dielectric layer 3 is formed on the surface of the anode 1. The cathode 7 has a solid electrolyte layer 4 that covers at least a portion of the dielectric layer 3, and a cathode extraction layer 5 that covers at least a portion of the surface of the solid electrolyte layer 4. The cathode extraction layer 5 has a carbon layer formed to cover at least a portion of the surface of the solid electrolyte layer 4, and a metal particle-containing layer formed to cover at least a portion of the carbon layer. A portion of the cathode lead frame 14 is bonded to the cathode extraction layer 5 via a conductive adhesive layer 8 and electrically connected.

[0103] [Examples] The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0104] Example 1: A capacitor element was fabricated according to the following procedure.

[0105] (1) Preparation of the anode covered with a dielectric layer A tantalum sintered body (porous body) in which a portion of the anode wire is embedded was prepared as the anode. By anodic oxidation of the surface of this tantalum sintered body, a dielectric layer containing tantalum oxide was formed on the surface of the anode.

[0106] (2) Formation of a solid electrolyte layer (2-1) First step (Step of imparting the first conductive polymer) An aqueous dispersion (first treatment solution) containing a self-doped polythiophene polymer (first conductive polymer) was prepared. The concentration of the polythiophene polymer in the first treatment solution was set to 1% by mass or more and 3% by mass or less. As the self-doped polythiophene polymer, PEDOT (Mw: approximately 10,000) having a sulfo group bonded to the PEDOT skeleton via a linking group containing a butylene group was used.

[0107] The tantalum sintered body prepared in (1) above was immersed in the first processing solution for approximately 30 to 60 seconds, and then removed from the first processing solution. Next, the tantalum sintered body removed from the first processing solution was heated (dried) at a temperature of 140°C to 180°C for 10 to 20 minutes, thereby imparting a self-doped first conductive polymer to the surface of the dielectric layer.

[0108] (Step to form the second conductive polymer layer) An aqueous dispersion (second treatment solution) containing a non-self-doped second conductive polymer (PSS-doped PEDOT) was prepared. The second treatment solution was prepared by dissolving 30% by mass of 1,2,4-trihydroxybenzene (first component) relative to the mass of the second conductive polymer in this aqueous dispersion. The concentration of the second conductive polymer in the second treatment solution was set to 1% by mass or more and 3% by mass or less. The tantalum sintered body on which the first layer was formed was immersed in the second treatment solution for approximately 30 seconds or more and 60 seconds or less, and then removed from the second treatment solution. Next, the tantalum sintered body removed from the second treatment solution was heated (dried) at a temperature of 140°C or more and 180°C or less for 10 minutes or more and 20 minutes or less. In this way, a second conductive polymer layer was formed so as to cover the first conductive polymer.

[0109] Following this procedure, a first portion, comprising a first conductive polymer layer and a second conductive polymer layer, was formed within the voids of the tantalum sintered body via a dielectric layer.

[0110] (2-2) In the second step, an aqueous dispersion (third treatment solution) containing a non-self-doped third conductive polymer (PSS-doped PEDOT) was prepared. The concentration of PSS-doped PEDOT in the third treatment solution was set to 1% by mass or more and 3% by mass or less. The tantalum sintered body with the first part formed was immersed in the third treatment solution for approximately 30 seconds or more and 60 seconds or less, and then removed from the third treatment solution. Next, the tantalum sintered body removed from the third treatment solution was heated (dried) at a temperature of 140°C or more and 180°C or less for 10 minutes or more and 20 minutes or less. The second part of the solid electrolyte layer was formed by repeating the immersion of the tantalum sintered body in the third treatment solution and the above heating (drying) multiple times.

[0111] (3) Formation of the cathode extraction layer The tantalum sintered body on which the solid electrolyte layer obtained in (2) was formed was immersed in a dispersion of graphite particles dispersed in water, and after being removed from the dispersion, it was dried to form a carbon layer (first extraction layer) on the surface of the solid electrolyte layer. Drying was carried out at 180°C for a time of 10 to 30 minutes.

[0112] Next, a silver paste containing silver particles and a binder resin (epoxy resin) was applied to the surface of the carbon layer and dried at a temperature of 60°C to 80°C for 20 to 40 minutes. After that, the binder resin was cured by further heating at 180°C for 30 to 60 minutes, forming a metal particle-containing layer (second extraction layer). In this way, a cathode extraction layer composed of the carbon layer and the metal particle-containing layer was formed.

[0113] In this way, a total of 30 capacitor elements were fabricated, each including a cathode portion composed of a solid electrolyte layer and a cathode extraction layer.

[0114] Example 2: In the process of forming the second conductive polymer layer, 1,3,5-trihydroxybenzene was used as the first component instead of 1,2,4-trihydroxybenzene. Aside from this, 30 capacitor elements were fabricated in the same manner as in Example 1.

[0115] <Comparative Example 1> In the process of forming the second conductive polymer layer, the first component was not used. Aside from this, 30 capacitor elements were fabricated in the same manner as in Example 1.

[0116] <Comparative Example 2> In the step of forming the second conductive polymer layer, pyrogallol (second component) was used instead of 1,2,4-trihydroxybenzene. Aside from this, 30 capacitor elements were fabricated in the same manner as in Example 1.

[0117] <Comparative Example 3> In the step of forming the second conductive polymer layer, 2-methylresorcinol was used instead of 1,2,4-trihydroxybenzene. Aside from this, 30 capacitor elements were fabricated in the same manner as in Example 1.

[0118] Comparative Example 4: In the step of forming the second conductive polymer layer, 2,3-dimethylphenol was used instead of 1,2,4-trihydroxybenzene. Aside from this, 30 capacitor elements were fabricated in the same manner as in Example 1.

[0119] [Evaluation] The second treatment solution from the examples and comparative examples was applied to the surface of an alumina substrate and heated (dried) at a temperature of 140°C to 180°C for a time of 10 to 20 minutes. In this way, an evaluation sample having a thin film (thickness 5 μm) corresponding to the second conductive polymer layer was prepared on the alumina substrate. Using this evaluation sample, the following (1) tape peel test and the following (2) single-film heat resistance test were performed. In addition, the following (3) charge-discharge test was performed using the capacitor elements obtained in the examples and comparative examples.

[0120] (1) Tape peel test Adhesion evaluation was performed by a tape peel test in accordance with the cross-cut method (JIS K5600) specified in the JIS standard. A cutter knife was used to make grid-like cuts (1 mm intervals) on the thin film of the evaluation sample. Adhesive tape (Sellotape® manufactured by Nichiban Co., Ltd.) was attached to the thin film, and then peeled off by hand to perform a peel test, and the adhesion of the solid electrolyte layer was evaluated according to the following criteria. A: No peeling was observed in all areas (100%) where the adhesive tape was attached. B: Peeling was observed in more than 0% and up to 20% of the area where the adhesive tape was attached. C: Peeling was observed in more than 20% and up to 40% of the area where the adhesive tape was attached. D: Peeling was observed in more than 40% and up to 80% of the area where the adhesive tape was attached. E: Peeling was observed in more than 80% of the area where the adhesive tape was attached.

[0121] (2) Single-film heat resistance test The evaluation samples described above were heated at 125°C for 500 hours, and the conductivity (S / cm) of the thin film was measured before and after heating using a Lorestar-GP (MCP-T610 series 4 probe) manufactured by Nitto Seiko Analytech Co., Ltd. The change in conductivity due to the heat resistance test was calculated using the following formula, with the conductivity c0 before heating and the conductivity c1 after heating: Conductivity change Δc = 100 * (c1 - c0) / c0 (%)

[0122] (3) Charge / Discharge Test Under conditions of 20°C, the initial capacitance (μF) of the capacitor elements at a frequency of 120 Hz was measured using a four-terminal LCR meter. The average value C0 for 30 capacitor elements was then calculated.

[0123] Next, at 25°C, the capacitor elements were subjected to an ON-OFF test, repeatedly charging them to their rated voltage and discharging them to 0V for 10,000 cycles. Afterward, the capacitance was measured in the same manner as above, and the average value C1 of the 30 capacitor elements was determined. The capacitance change rate due to the charge-discharge test was calculated using the following formula: ΔCap = 100 * (C1 - C0) / C0 (%)

[0124] Evaluations (2) and (3) above were performed on Example 1 and Comparative Example. The results of evaluation (1) are shown in Table 1, and the results of evaluations (2) and (3) are shown in Table 2. In Table 1 or Table 2, E1 and E2 are Examples 1 and 2. C1 to C4 are Comparative Examples 1 to 4.

[0125]

[0126] As shown in Table 1, when the first component is included in the first portion of the solid electrolyte layer, no peeling of the solid electrolyte layer was observed, confirming that it has high adhesion.

[0127]

[0128] As shown in Table 2, in the examples, the change in conductivity (Δc) of the solid electrolyte layer due to the heat resistance test is kept relatively small compared to the comparative example, and the decrease in capacitance after the charge-discharge test is also suppressed. Thus, in the examples, high heat resistance and high reliability are obtained by including the first component in the first portion of the solid electrolyte layer.

[0129] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0130] 20: Solid electrolytic capacitor 1: Anode body 2: Anode wire 3: Dielectric layer 4: Solid electrolyte layer 5: Cathode lead layer 6: Anode part 7: Cathode part 8: Conductive adhesive layer 11: Outer casing 13: Anode lead frame 14: Cathode lead frame

Claims

1. A solid electrolytic capacitor comprising at least one capacitor element including an anode body having a porous portion on at least its surface, a dielectric layer covering at least a portion of the surface of the anode body, and a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer has a first portion filled in the voids of the porous portion and a second portion extending beyond the main surface of the anode body having the dielectric layer, and the first portion comprises at least one first component selected from the group consisting of 1,2,4-trihydroxybenzene compounds and 1,3,5-trihydroxybenzene compounds.

2. The solid electrolytic capacitor according to claim 1, wherein the first component is water-soluble.

3. The first part comprises the 1,2,4-trihydroxybenzene compound, as described in claim 1.

4. The solid electrolytic capacitor according to claim 1, wherein the first portion comprises a first conductive polymer covering at least a portion of the dielectric layer and a second conductive polymer layer covering at least a portion of the first conductive polymer, and the second conductive polymer layer comprises a non-self-doped second conductive polymer and the first component.

5. The solid electrolytic capacitor according to claim 4, wherein the first conductive polymer is self-doped.

6. The solid electrolytic capacitor according to claim 4 or 5, wherein the second conductive polymer comprises a conjugated polymer and a polymer anion.

7. The solid electrolytic capacitor according to any one of claims 1 to 5, wherein the mass content of the first component in the first portion is higher than the mass content of the first component in the second portion.

8. The solid electrolytic capacitor according to any one of claims 1 to 5, wherein the second part does not include the first component.

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