Electrolytic capacitor and its manufacturing method

Abstract

This electrolytic capacitor is provided with at least one capacitor element equipped with: a sheet-shaped anode body that has an anode lead-out section including a first end and a cathode-forming section including a second end; a dielectric layer formed at least on the surface of the cathode-forming section of the anode body; and a cathode section covering at least part of the dielectric layer. The cathode section is provided with a solid electrolyte layer containing a conductive polymer that covers at least part of the dielectric layer. The ratio T1 / T2 of the thickness T1 of the solid electrolyte layer formed in a corner section of the anode body to the thickness T2 of the solid electrolyte layer formed in the central section of the main surface of the anode body is 0.8-1.7 in a cross section perpendicular to a direction leading from the first end of the capacitor element toward the second end in a discretionary position in a part on the first end side of the cathode section, thus resulting in an electrolytic capacitor in which the solid electrolyte formed in the corner of an anode section is inhibited from becoming less thick.

Description

[Technical Field]

[0001] The present disclosure relates to an electrolytic capacitor having a solid electrolyte layer containing a conductive polymer, and a method for manufacturing the same. [Background technology]

[0002] The electrolytic capacitor includes a capacitor element, an exterior body that seals the capacitor element, and an external electrode electrically connected to the capacitor element. The capacitor element includes an anode body having an anode lead portion that includes a first end and a cathode forming portion that includes a second end, a dielectric layer formed on at least the surface of the cathode forming portion of the anode body, and a cathode portion that covers at least a portion of the dielectric layer. The cathode portion includes a solid electrolyte layer that includes a conductive polymer and covers at least a portion of the dielectric layer, and a cathode lead layer that covers at least a portion of the solid electrolyte layer. An electrolytic capacitor that includes a solid electrolyte layer that includes a conductive polymer is also called a solid electrolytic capacitor.

[0003] Patent Document 1 proposes providing an intermediate layer between a first conductive polymer layer and a second conductive polymer layer, the intermediate layer containing a cationic agent containing a cationic group and an anionic agent containing a first anionic group and a second anionic group.

[0004] Patent Document 2 proposes a solid electrolytic capacitor including a first solid electrolyte layer, a second solid electrolyte layer, and at least one continuous or discontinuous layer of an amine compound present between the first and second solid electrolyte layers and within the second solid electrolyte layer.

[0005] Patent Document 3 describes an anode body of We have proposed a method for manufacturing a solid electrolytic capacitor in which an oxide film is formed on a valve metal, and a conductive polymer layer, a graphite layer, and a silver layer are formed in that order on the oxide film to form a cathode.The method for forming the conductive polymer layer containing a sulfonate ester compound is characterized by dissolving a nonionic surfactant having a hydroxyl group in a conductive polymer solution or dispersion containing a sulfonated polymer compound as a dopant, applying the solution to the oxide film, and then heating and drying to cause dehydration condensation.

[0006] Patent Document 4 discloses a multilayer capacitor element in which the end of an anode substrate made of a flat valve metal having a dielectric oxide film layer on its surface is used as an anode portion, and a solid electrolyte layer and a conductor layer are sequentially formed on the dielectric oxide film layer in the portion excluding the anode portion to form a cathode portion. A plurality of single-plate capacitor elements are stacked and fixed on an anode-side lead frame with the anode portions aligned in the same direction, and a conductive adhesive layer is formed on the cathode-side lead frame so that the cathode portions of the single-plate capacitor elements are stacked and fixed in a shape that diverges from the anode portion side toward the cathode portion tip, and Anode substrate The present inventors have proposed a stacked solid electrolytic capacitor characterized in that the cathode lead frame is stacked approximately parallel to the cathode lead frame. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2016 / 006236 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-43958 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-245313 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-230156 Summary of the Invention

[0008] In conventional techniques, the thickness of the solid electrolyte layer formed at the corners of the main surface of the anode body tends to be smaller than that near the center, and there are also cases where the corners of the anode body are not covered with the solid electrolyte layer.

[0009] One aspect of the present disclosure Electrolytic capacitors related to teeth , yang Pole pull-out section and Shadowa sheet-like anode body having an electrode forming portion; a dielectric layer formed on the surface of at least the cathode forming portion of the anode body; and a cathode portion covering at least a part of the dielectric layer. The anode body includes a first end and a second end, the anode lead-out portion includes the first end, and the cathode formation portion includes the second end. The cathode section includes a solid electrolyte layer containing a conductive polymer that covers at least a portion of the dielectric layer. do. In a cross section perpendicular to a direction from the first end to the second end of the capacitor element at an arbitrary position in a portion of the cathode portion on the first end side, a ratio T1 / T2 of a thickness T1 of the solid electrolyte layer formed at a corner of the anode body to a thickness T2 of the solid electrolyte layer formed at a center of a main surface of the anode body is 0.8 or more and 1.7 or less. do.

[0010] Other aspects of the disclosure Manufacturing method of electrolytic capacitor The method includes a first step of preparing an anode body, a second step of forming a dielectric layer on the surface of the anode body, a third step of treating the anode body on which the dielectric layer has been formed with a first treatment liquid containing a first conductive polymer or a precursor thereof, a fourth step of treating the anode body treated with the first treatment liquid with a second treatment liquid containing a surface conditioner, and a fifth step of treating the anode body treated with the second treatment liquid with a third treatment liquid containing a second conductive polymer. nothing.

[0011] This can prevent the thickness of the solid electrolyte layer formed at the corners of the anode body from becoming thin. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is an enlarged view of the area surrounded by the solid line α in FIG. [Figure 3] FIG. 3 is a schematic front view of the capacitor element as viewed from one main surface side. [Figure 4] FIG. 4 is a schematic cross-sectional view of the capacitor element taken along line IV-IV in FIG. 3, viewed in the direction of the arrows. DETAILED DESCRIPTION OF THE INVENTION

[0013] A treatment solution containing a conductive polymer has a relatively high surface tension. Therefore, it is difficult to uniformly wet the entire surface of the cathode-forming portion of an anode body with the treatment solution. As a result, it is difficult to form a solid electrolyte layer of uniform thickness on the surface of the cathode-forming portion. Anode bodies are generally made of sheet-like anodes, such as metal foils or sintered bodies. When a sheet-like anode body is treated with a treatment solution containing a conductive polymer, a solid electrolyte layer of relatively uniform thickness is formed near the center of the main surface of the sheet. However, it is more difficult to apply the treatment solution to the corners of the sheet than near the center of the main surface of the sheet. As a result, the thickness of the solid electrolyte layer at the corners of the sheet may be smaller, or portions without the conductive polymer may be formed. The formation of portions without the conductive polymer is likely to cause short circuits, resulting in product defects and reduced yield.

[0014] According to the present disclosure, an electrolytic capacitor is manufactured using a manufacturing method including the steps of treating an anode body having a dielectric layer formed thereon with a first treatment liquid containing a first conductive polymer or its precursor, treating the anode body treated with the first treatment liquid with a second treatment liquid containing a surface conditioner, and treating the anode body treated with the second treatment liquid with a third treatment liquid containing the second conductive polymer. In this manner, by treating the anode body with the second treatment liquid containing the surface conditioner and then with the third treatment liquid containing the second conductive polymer, the second conductive polymer can be attached not only near the center of the main surface of the anode body but also to the corners. This prevents the thickness of the solid electrolyte layer formed at the corners of the anode body from becoming thin.

[0015] The following reasons are believed to be why the thickness of the solid electrolyte layer formed at the corners of the anode body is prevented from becoming thin. First, by using a second treatment liquid containing a surface conditioner, the second treatment liquid can be spread over the entire surface of the anode body in the cathode-forming portion. As a result, components of the second treatment liquid, such as the surface conditioner, adhere to the entire surface of the cathode-forming portion. When the anode body is treated in this state with a third treatment liquid containing a second conductive polymer, the third treatment liquid can be spread over the entire surface of the cathode-forming portion. This prevents the second conductive polymer from agglomerating near the center of the main surface of the anode body on the surface of the cathode-forming portion. As a result, a solid electrolyte layer of appropriate thickness can be formed not only near the center of the main surface of the anode body but also at the corners, reducing thickness variation.

[0016] Thus, according to the present disclosure, the relative ratio of the thickness of the solid electrolyte layer formed at the corners of the anode body to the thickness of the solid electrolyte layer formed near the center of the main surface can be made larger than conventionally.

[0017] More specifically, in the electrolytic capacitor of the present disclosure, the ratio T1 / T2 of the thickness T1 of the solid electrolyte layer formed at the corners of the anode body to the thickness T2 of the solid electrolyte layer formed at the center of the main surface of the anode body is 0.8 or more and 1.7 or less. In this way, in the electrolytic capacitor, the thickness of the solid electrolyte layer formed at the corners of the anode body is prevented from becoming smaller. Furthermore, a solid electrolyte layer with a more uniform thickness is formed over the entire surface of the cathode-forming portion of the anode body. As a result, product defects due to short circuits are reduced. Furthermore, excessive leakage current is prevented, while a decrease in capacitance and an increase in ESR and dielectric loss tangent tanδ are also suppressed, further stabilizing the quality of the electrolytic capacitor.

[0018] In order to suppress the variation in the thickness of the solid electrolyte layer, it is considered important to spread the third treatment liquid containing the second conductive polymer over the entire surface of the cathode-forming portion of the anode body. Therefore, it is conceivable to add a surface conditioner to the third treatment liquid in order to reduce the surface tension of the third treatment liquid. However, even if a surface conditioner is actually added to the third treatment liquid, the effect of suppressing the thickness of the solid electrolyte layer from becoming smaller at the corners is small. Furthermore, since the third treatment liquid usually contains various additives in addition to the second conductive polymer, adding a surface conditioner may shorten the pot life of the third treatment liquid. According to the present disclosure, since a second treatment liquid containing a surface conditioner is used, it is possible to suppress the thickness of the solid electrolyte layer from becoming smaller at the corners. Third Unlike adding a surface conditioner to the treatment solution, Third From this viewpoint, it is preferable that the second treatment liquid does not contain a conductive polymer.

[0019] The electrolytic capacitor includes at least one capacitor element. , yang Pole pull-out section and Shadow The battery includes an anode body having an electrode forming portion, a dielectric layer formed on the surface of at least the cathode forming portion of the anode body, and a cathode portion covering at least a portion of the dielectric layer. The anode lead-out portion includes a first end of the anode body, and the cathode formation portion includes a second end of the anode body.The anode body is typically sheet-shaped. The cathode section includes a solid electrolyte layer containing a conductive polymer covering at least a portion of the dielectric layer. The thicknesses T1 and T2 are determined in a cross section perpendicular to the direction from the first end to the second end of the capacitor element at an arbitrary position on the first end side of the cathode section. This cross section may be simply referred to as cross section G. More specifically, thickness T1 is determined by measuring and averaging the thicknesses of the solid electrolyte layer formed at the four corners of the anode body in cross section G. First, a line is drawn through the vertices of the corners of the anode body at a 45° angle relative to a line extending outward from a line segment corresponding to the main surface of the anode body in cross section G. The distance between the point where this line intersects with the outer edge of the solid electrolyte layer and the corresponding vertex of the corner is defined as the thickness of the solid electrolyte layer formed at each corner. Thickness T2 is determined by measuring and averaging the thicknesses of the solid electrolyte layer formed at the center of each of the pair of main surfaces of the anode body in cross section G. First, a center line passing through each midpoint of the line segments corresponding to the main surfaces of the anode body is drawn on cross section G. Then, the distance between the intersection of this center line with the outer edge of the solid electrolyte layer and the corresponding midpoint is defined as the thickness of the solid electrolyte layer formed at the center of each main surface.

[0020] The direction from the first end toward the second end is a direction parallel to the line connecting the center of the end face of the first end and the center of the end face of the second end. This direction may be referred to as the longitudinal direction of the anode body or capacitor element. Cross section G is a cross section perpendicular to the longitudinal direction of the capacitor element at any position between the halfway point of the cathode portion in the direction parallel to the longitudinal direction of the capacitor element and the end of the cathode portion on the first end side in the portion where the cathode portion of the capacitor element is formed. The cross section of the capacitor element can be observed, for example, using an optical microscope.

[0021] The solid electrolyte layer may include a first layer containing a first conductive polymer that covers at least a portion of the dielectric layer, a second layer containing a second conductive polymer that covers at least a portion of the first layer, and at least one continuous or discontinuous layer interposed between the first and second layers. Here, the continuous or discontinuous layer contains a surface modifier. In such a solid electrolyte layer, the surface modifier can be said to be unevenly distributed between the first and second layers. The presence of the surface modifier between the first and second layers makes it easier for the second layer to cover the entire surface of the cathode-forming portion of the anode body. This prevents the thickness of the solid electrolyte layer formed at the corners from becoming thin. As a result, the variation in thickness of the solid electrolyte layer is reduced.

[0022] The surface conditioner may be present at least between the first layer and the second layer. In the portion of the dielectric layer not covered by the first layer, the surface conditioner may be present between the dielectric layer and the second layer. The surface conditioner may be distributed so as to cover the entire surface of the cathode-forming portion of the anode body. Therefore, the layer containing the surface conditioner does not necessarily have to be continuous and may be a discontinuous layer. A portion of the layer containing the surface conditioner may be embedded in the first layer. At least one layer containing the surface conditioner may be present between the first layer and the second layer, and two or more layers may be present.

[0023] The electrolytic capacitor and the manufacturing method thereof according to the present disclosure will be described in more detail below, with reference to the drawings as necessary.

[0024] [Electrolytic capacitor] (anode body) The anode body can contain a valve metal, an alloy containing a valve metal, or a compound containing a valve metal. These materials can be used alone or in combination. Preferred examples of the valve metal include aluminum, tantalum, niobium, and titanium.

[0025] The anode body is usually in a sheet shape. The sheet shape also includes a foil shape and a plate shape. The sheet-shaped anode body has a pair of main surfaces. Corners are present between each main surface and each end surface of the anode body.

[0026] The anode body , yang Pole pull-out section and ,shadow and a pole forming portion. The anode lead-out portion includes a first end of the anode body, and the cathode formation portion includes a second end of the anode body opposite 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.

[0027] The anode body typically has a porous portion in the surface layer of at least the cathode-forming portion. The porous portion is formed in the surface layer by roughening the surface of at least the portion of a substrate (e.g., a sheet-like substrate) containing a valve metal, which corresponds to the cathode-forming portion. The porous portion may be formed in the surface layer of the anode lead-out portion. The anode body may also be a compact of particles containing a valve metal or a sintered body thereof. Since the sintered body has a porous structure, the entire anode body can be a porous portion.

[0028] (dielectric layer) The dielectric layer is an insulating layer that functions as a dielectric and is formed so as to cover at least a portion of the surface of the anode body.

[0029] The dielectric layer may be formed so as to cover at least a portion of the anode body. For example, the dielectric layer may be formed on the surface of at least the cathode-forming portion of the anode body. The dielectric layer may be formed on the surface of the anode lead-out portion.

[0030] The dielectric layer is usually formed on the surface of the anode body. The surface layer of the anode body usually has a porous portion formed therein. Therefore, the dielectric layer is formed along the inner wall surfaces of the holes and depressions (pits) on the surface of the anode body, including the inner wall surfaces of the holes in the porous portion.

[0031] The dielectric layer contains an oxide of a valve metal. For example, when tantalum is used as the valve metal, the dielectric layer contains Ta2O5, and when aluminum is used as the valve metal, the dielectric layer contains Al2O3. However, the dielectric layer is not limited to these and may be any material that functions as a dielectric.

[0032] (cathode) The cathode portion includes at least a solid electrolyte layer that covers at least a portion of the dielectric layer. The cathode portion is typically formed on the surface of the cathode-forming portion of the anode body via a dielectric layer. The cathode portion typically includes a solid electrolyte layer and a cathode extraction layer that covers at least a portion of the solid electrolyte layer. The solid electrolyte layer and the cathode extraction layer are described below.

[0033] (Solid electrolyte layer) The solid electrolyte layer is formed to cover the dielectric layer. The solid electrolyte layer does not necessarily need to cover the entire dielectric layer (entire surface), but may be formed to cover at least a portion of the dielectric layer. The solid electrolyte layer includes, for example, a first layer containing a first conductive polymer, a second layer containing a second conductive polymer formed on the first layer, and a continuous or discontinuous layer containing a surface conditioner interposed between the first and second layers. If there is a region on the dielectric layer where the first layer is not formed, the second layer may be formed on the dielectric layer in this region, or the second layer may be formed on the dielectric layer via a layer containing a surface conditioner.

[0034] (1st layer) The first conductive polymer may be a known polymer used in electrolytic capacitors, such as a π-conjugated conductive polymer. Examples of the first conductive polymer include polymers having a basic skeleton of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, and polythiophene vinylene. Of these, polymers having a basic skeleton of polypyrrole, polythiophene, or polyaniline are preferred.

[0035] The above polymers include homopolymers, copolymers of two or more monomers, and derivatives thereof (e.g., substituted products having substituent groups). For example, polythiophenes include poly(3,4-ethylenedioxythiophene).

[0036] The first conductive polymer may be used alone or in combination of two or more.

[0037] The weight average molecular weight (Mw) of the first conductive polymer is not particularly limited, but is, for example, 1,000 or more and 1,000,000 or less.

[0038] In this specification, the weight-average molecular weight (Mw) is a value calculated as polystyrene measured by gel permeation chromatography (GPC), which is usually performed using a polystyrene gel column and water / methanol (volume ratio 8 / 2) as the mobile phase.

[0039] The first layer may be a single layer or may be composed of multiple layers. When the first layer is composed of multiple layers, the first conductive polymer contained in each layer may be the same or different.

[0040] The first layer may further contain a dopant, for example, at least one selected from the group consisting of anions and polyanions.

[0041] Examples of anions include, but are not limited to, sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, carboxylate ions, etc. Examples of dopants that generate sulfonate ions include paratoluenesulfonic acid and naphthalenesulfonic acid.

[0042] Examples of polyanions include polymeric polysulfonic acids and polymeric polycarboxylic acids. Polymeric polysulfonic acids include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, and polymethacrylic sulfonic acid. Polymeric polycarboxylic acids include polyacrylic acid and polymethacrylic acid. Polyanions also include polyester sulfonic acid and phenol sulfonic acid novolac resin. However, polyanions are not limited to these.

[0043] When using an anionic agent described below, it is advantageous to use a dopant with a relatively high electron-withdrawing property (e.g., sulfonate ions or polymer-type polysulfonic acid) from the viewpoint of easily suppressing undoping. Also from the viewpoint of easily ensuring high conductivity of the solid electrolyte layer, it is preferable to use sulfonate ions or polymer-type polysulfonic acid as the dopant.

[0044] The anion and the polyanion may each be contained in the first layer in the form of a salt. In the first layer, the anion and the polyanion may each form a conductive polymer complex together with the first conductive polymer. For example, the sulfonic acid group may exist in the first layer in the form of a free sulfonic acid group (-SO3H) or an anion (-SO3 - ), or a salt form, or may be contained in a form bound to or interacting with the conductive polymer. In this specification, all of these forms of sulfonic acid groups may be simply referred to as "sulfonic acid groups." Similarly, in the first layer, the carboxyl group may be contained in a free form (-COOH), an anionic form (-COO - ), or a salt thereof, or may be contained in a form bonded to or interacting with the conductive polymer. In this specification, all of these forms of carboxy groups may be simply referred to as a "carboxy group."

[0045] The amount of dopant contained in the first layer is, for example, 10 to 1000 parts by mass, or may be 50 to 200 parts by mass, relative to 100 parts by mass of the first conductive polymer.

[0046] The first layer may further contain a water-soluble polymer. Polymer-type dopants are also included in the term "water-soluble polymer." It is preferable to use a water-soluble polymer with a lower electron-withdrawing property than the dopant. When the solid electrolyte layer contains a water-soluble polymer, the thickness of the solid electrolyte layer at the center of the main surface of the anode body can be increased, further reducing the variation in the thickness of the solid electrolyte layer. This further stabilizes the quality of the electrolytic capacitor. Furthermore, by increasing the thickness of the solid electrolyte layer at the main surface of the anode body, it is possible to reduce leakage current and improve voltage resistance while suppressing increases in the ESR and tanδ of the electrolytic capacitor.

[0047] Examples of water-soluble polymers include water-soluble polymer compounds having hydrophilic groups in the main chain or side chain. Examples of hydrophilic groups include polyoxyalkylene chains, hydroxy groups, and acid groups (carboxy groups, sulfonic acid groups, etc.). Examples of water-soluble polymers include polyalkylene glycol compounds, water-soluble polyurethanes, water-soluble polyamides, water-soluble polyimides, water-soluble acrylic resins, and polyvinyl alcohols.

[0048] Examples of polyalkylene glycol compounds include compounds having a polyoxyalkylene chain. Examples of polyoxyalkylene chains include polyoxy C 2-4An alkylene chain is preferred. It is more preferred that the polyalkylene glycol compound contains at least a polyoxyethylene chain. Examples of polyalkylene glycol compounds include polyalkylene glycols (diethylene glycol, triethylene glycol, oligoethylene glycol, polyethylene glycol, oxyethylene-oxypropylene block copolymers, etc.), and polyalkylene glycols having substituents (halogen atoms, hydroxy groups, etc.) (e.g., polyalkylene glycol chlorohydrin or bromohydrin (diethylene glycol monochlorohydrin, triethylene glycol monochlorohydrin, oligoethylene glycol monochlorohydrin, polyethylene glycol monochlorohydrin, diethylene glycol monobromohydrin, triethylene glycol monobromohydrin, oligoethylene glycol monobromohydrin, etc.)) and other hydroxy compounds. Polyalkylene glycol compounds also include derivatives of these hydroxy compounds (e.g., ether compounds, ester compounds, amide compounds).

[0049] Examples of water-soluble polyurethanes, water-soluble polyamides, and water-soluble polyimides include polymers having acid groups (e.g., at least one selected from the group consisting of carboxyl groups and sulfonic acid groups) in their side chains. These water-soluble polymers have high water solubility due to the introduction of multiple acid groups into the skeleton (main chain) of each polymer.

[0050] The water-soluble acrylic resin preferably has a carboxyl group in the side chain. Examples of such water-soluble acrylic resins include polyacrylic acid, polymethacrylic acid, acrylic acid-methacrylic acid copolymers, and copolymers of at least one selected from the group consisting of acrylic acid and methacrylic acid with other copolymerizable monomers. Examples of other copolymerizable monomers include acrylic acid esters (e.g., alkyl esters, hydroxyalkyl esters), methacrylic acid esters (e.g., alkyl esters, hydroxyalkyl esters), vinyl compounds (e.g., vinyl cyanide, olefins, aromatic vinyl compounds), and polycarboxylic acids having polymerizable unsaturated bonds (e.g., maleic acid, fumaric acid) or their acid anhydrides. The copolymer may contain one or more monomer units derived from the other copolymerizable monomers.

[0051] The first layer may contain one type of water-soluble polymer, or may contain two or more types of water-soluble polymer.

[0052] Water-soluble polymers also include those that function as dopants. When a dopant with relatively high electron-withdrawing properties, such as a dopant containing sulfonic acid groups (e.g., sulfonate ions or polymeric polysulfonic acids), is used as a dopant, the dopant function of the water-soluble polymer often does not function properly, even when a water-soluble polymer with relatively low electron-withdrawing properties, such as a carboxyl group, is coexistent. When the solid electrolyte layer contains such a water-soluble polymer, the insulating properties of the polymer are adequately exhibited and the thickness of the solid electrolyte layer can be increased, thereby reducing the leakage current of the electrolytic capacitor and improving its voltage resistance. Therefore, it is preferable to use a water-soluble polymer with lower electron-withdrawing properties than the dopant. Examples of such water-soluble polymers include water-soluble polymers having at least one selected from the group consisting of a carboxyl group, a hydroxyl group, and a polyoxyalkylene chain.

[0053] The carboxyl and sulfonic acid groups of the water-soluble polymer exist in the free form (-COOH) and the anionic form (-COO - ), or a salt form, may be contained in the first layer. Furthermore, some of the carboxy groups and sulfonic acid groups may be contained in the first layer in a form in which they are bonded to or interact with the conductive polymer. In this specification, all of these forms of carboxy groups may be simply referred to as "carboxy groups," and all of these forms of sulfonic acid groups may be simply referred to as "sulfonic acid groups."

[0054] Water-soluble polymers Weight average molecular weight ( Mw ) is, for example, 100 or more, and preferably 400 or more. For higher withstand voltage characteristics, the Mw of the water-soluble polymer is, for example, 5 million or less, and may be 1 million or less. These lower and upper limits can be combined in any desired manner.

[0055] The content of the water-soluble polymer in the first layer is preferably adjusted so that the content of the water-soluble polymer in the solid electrolyte layer is, for example, in the range of 25% by mass to 70% by mass. layer The content of the water-soluble polymer in the solid electrolyte may be 30% by mass or more and 70% by mass or less (or 68% by mass or less), 40% by mass or more and 70% by mass or less (or 68% by mass or less), or 43% by mass or more and 70% by mass or less (or 68% by mass or less). layer When the content of the water-soluble polymer in the electrolytic capacitor is within this range, the increase in ESR and tan δ of the electrolytic capacitor can be suppressed, while the leakage current can be reduced and higher voltage resistance can be ensured.

[0056] The content of the water-soluble polymer in the first layer is preferably 30% by mass or less, more preferably 20% by mass or less or 10% by mass or less. The first layer does not need to contain a water-soluble polymer. In this case, higher conductivity of the solid electrolyte layer can be ensured, which is preferable.

[0057] The content of the water-soluble polymer in the solid electrolyte layer can be determined using a sample taken from the capacitor element. More specifically, the electrolytic capacitor is first embedded in a curable resin, and the curable resin is cured. The cured product is subjected to a polishing process or cross-section polisher process to expose a cross section parallel to the thickness direction of the solid electrolyte layer. The solid electrolyte layer is scraped off, and a predetermined amount of sample is taken and its mass is measured. The water-soluble polymer is extracted from the sample with water at 20°C to 40°C. The extract is concentrated, and Liquid chromatography mass spectrometry ( LC-MS ) or Gas chromatography mass spectrometry ( GC-MS ) The water-soluble polymer is identified by the above method. The concentration of the water-soluble polymer in the extract is determined using the calibration curve method. The content (mass) of the water-soluble polymer in the solid electrolyte layer is determined from this concentration and the mass of the sample. The content of the water-soluble polymer in the first layer is determined using the same procedure as above, except that a sample is used that is collected by scraping off the solid electrolyte layer formed in the pits of the anode body.

[0058] (Layer containing surface conditioner) (surface conditioner) Examples of the surface conditioner include a leveling agent and an antifoaming agent. From the viewpoint of spreading the second treatment liquid containing the surface conditioner over the entire surface of the cathode-forming portion of the anode body, the surface conditioner is preferably one having a leveling effect. A surfactant is preferably used as the surface conditioner.

[0059] The surfactant may be either a nonionic surfactant or an ionic surfactant. The surfactant has a hydrophilic group and a hydrophobic group. Ionic surfactants include cationic surfactants, anionic surfactants, and amphoteric surfactants. One type of surfactant may be used alone, or two or more types may be used in combination.

[0060] Examples of nonionic surfactants include ether-type (polyether-type, etc.), ester-ether-type (fatty acid polyethylene glycol, fatty acid polyoxyethylene sorbitan, etc.), ester-type (glycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester, etc.), and alkanolamide-type (fatty acid alkanolamide, etc.) nonionic surfactants. Examples of polyether-type nonionic surfactants include those having a polyoxyalkylene chain such as a polyoxyethylene chain (polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene polyoxypropylene glycol, etc.). The nonionic surfactant may have a halogen atom. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms. Among these, fluorine atoms are preferred.

[0061] Examples of cationic surfactants include alkylamine salt type (monoalkylamine salt, dialkylamine salt, trialkylamine salt, etc.) and quaternary ammonium salt type (alkyltrimethylammonium halide, dialkyldimethylammonium halide, alkylbenzalkonium chloride, etc.).

[0062] Examples of anionic surfactants include carboxylic acid type, sulfonic acid type, sulfate ester type, and phosphate ester type anionic surfactants. Examples of carboxylic acid type anionic surfactants include aliphatic monocarboxylates, polyoxyethylene alkyl ether carboxylates, N-acylsarcosinates, and N-acyl glutamates. Examples of sulfonic acid type anionic surfactants include dialkyl sulfosuccinates, alkanesulfonates, α-olefin sulfonates, alkylbenzene sulfonates, naphthalenesulfonic acid-formaldehyde condensates, alkylnaphthalenesulfonates, and N-methyl-N-acyltaurates. Examples of sulfate ester type anionic surfactants include alkyl sulfates, polyoxyethylene alkyl ether sulfates, and fat sulfate esters. Examples of phosphate ester type anionic surfactants include alkyl phosphates, polyoxyethylene alkyl ether phosphates, and polyoxyethylene alkyl phenyl ether phosphates.

[0063] Examples of amphoteric surfactants include carboxybetaine type (alkylbetaine, fatty acid amidopropyl betaine, etc.), 2-alkylimidazoline derivative type (2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolium betaine, etc.), glycine type (alkyldiethylenetriaminoacetic acid, dialkyldiethylenetriaminoacetic acid, etc.), and amine oxide type (alkylamine oxide, etc.).

[0064] The use of a nonionic surfactant can prevent the pot life of the second treatment liquid from being shortened and can also prevent dedoping of the conductive polymer in the first and second layers. A cationic surfactant or an amphoteric surfactant may be used to more easily promote adhesion of the second conductive polymer to the anode body surface. An anionic surfactant may be used to more easily prevent volatilization of the cationic agent described below.

[0065] The continuous or discontinuous layer containing the surface conditioner may contain components other than the surface conditioner. The amount of the surface conditioner contained in the continuous or discontinuous layer is, for example, 0.01 to 30 mass %, or may be 0.1 to 15 mass %. When the amount of the surface conditioner is within this range, the surface conditioner can be more uniformly distributed over the entire surface of the cathode-forming portion of the anode body, making it easier to reduce variations in the thickness of the solid electrolyte layer. In addition, the resistance of the solid electrolyte layer can be kept low, thereby suppressing increases in ESR.

[0066] (Other ingredients) The component other than the surface conditioner contained in the continuous or discontinuous layer may be, for example, at least one selected from the group consisting of a cationic agent and an anionic agent. However, the cationic agent and the anionic agent are different from the surface conditioner. For example, the cationic agent and the anionic agent are not surfactants.

[0067] The first and second layers each typically contain an anionic dopant along with a conductive polymer, and this dopant is likely to be present on the surface of the first and second layers. In other words, the surfaces of both the first and second layers tend to be negatively charged, making it difficult to form the second layer on the surface of the first layer. If a continuous or discontinuous layer interposed between the first and second layers contains a cationic agent, the film-forming or coating properties of the second layer can be improved.

[0068] When a continuous or discontinuous layer contains an anionic agent, the film repairability of the dielectric layer can be enhanced.

[0069] To fully obtain the effect of the cationic agent, it is preferable to dissociate the cationic agent sufficiently in the second treatment liquid. However, since cationic agents have low solubility and high volatility, it is difficult to increase the content of the cationic agent in a continuous or discontinuous layer. From the viewpoint of promoting dissociation of the cationic agent, it is preferable to use a second treatment liquid containing both a cationic agent and an anionic agent. A continuous or discontinuous layer obtained using such a second treatment liquid contains both a cationic agent and an anionic agent.

[0070] (cationic agent) The cationic agent having a cationic group is not particularly limited as long as it can generate cations in a dissociated state. The cationic agent may be, for example, a metal compound (e.g., an inorganic base such as a metal hydroxide), but an organic compound (e.g., an organic base) is preferred. Preferred cationic groups of organic compounds are amino groups (e.g., primary amino groups, secondary amino groups, and tertiary amino groups) and quaternary ammonium groups. Such cationic groups also include salts of amino groups and salts of quaternary ammonium groups. A continuous or discontinuous layer containing a surface conditioner may contain one type of cationic agent, or two or more types of cationic agents.

[0071] Among cationic agents, cationic agents having an amino group as the cationic group (such as amine compounds) are preferred. Examples of amine compounds include amines (primary to tertiary amines) having one to three substituents on the nitrogen atom, and diamines that may have one or two alkyl groups on the nitrogen atom. The substituents are selected from the group consisting of, for example, alkyl groups, cycloalkyl groups, and aryl groups. Each of the alkyl groups, cycloalkyl groups, and aryl groups may further have a substituent (for example, at least one selected from the group consisting of hydroxy groups and alkoxy groups).

[0072] The above diamines include diamino C such as diaminoalkanes and diaminocycloalkanes (diaminocyclohexane). 5-8 Cycloalkanes, etc.), diaminoarenes (diaminobenzyl Diamino C such as benzene and diaminonaphthalene 6-14 Examples of diaminoalkanes include diamino C 2-14 Alkane or diamino C 4-12 Specific examples of diaminoalkanes include 1,4-diaminobutane, 1,6-diaminohexane, 1,8-diaminooctane, and 1,10-diaminodecane.

[0073] The amine may be at least one selected from the group consisting of primary amines and tertiary amines. The tertiary amine may be N,N-diC 1-10 Alkyl-NC 4-16 Alkylamine, N,N-diC 4-16 Alkyl-NC 1-10 Alkylamine, Tri C 4-16 Examples include alkylamines.

[0074] The continuous or discontinuous layer (or the second treatment liquid) containing the surface conditioner may contain the cationic agent in any form of an amine compound, a cation corresponding to the amine compound, a quaternary ammonium compound, or a salt of the cation. For example, in the continuous or discontinuous layer (or the second treatment liquid), the cationic agent may form a salt with an anionic agent.

[0075] (anionic agent) The anionic agent may be, for example, at least one selected from the group consisting of the anions and polyanions exemplified as the dopants for the first layer. However, from the viewpoint of suppressing dedoping from the first layer and the second layer, it is preferable to use an anionic agent that is different from the dopants for the first layer and the second layer. From the same viewpoint, the anionic agent may be one that has lower electron-withdrawing properties than the dopants for the first layer and the second layer.

[0076] From the viewpoint of suppressing corrosion of the valve metal constituting the anode body, an anionic agent containing a first anionic group having high electron-withdrawing ability and a second anionic group having lower electron-withdrawing ability than the first anionic group may be used. Examples of such an anionic agent include a polymer (first anionic agent) containing the first anionic group and the second anionic group. The first anionic agent can be used alone or in combination of two or more.

[0077] Examples of the first anionic group and the second anionic group include sulfonic acid groups, phosphoric acid groups, phosphonic acid groups, boric acid groups, carboxy groups, and hydroxy groups. The first anionic group and the second anionic group, which have different electron-withdrawing properties, can be selected from these anionic groups. The anionic group is not particularly limited as long as it can generate an anion in a dissociated state, and may be a salt of these groups.

[0078] Examples of the first anionic agent that is a polymer (polymer compound) include a copolymer (p1) containing at least a monomer unit having a first anionic group and a monomer unit having a second anionic group, and a polymer (p2) containing at least a monomer unit having a first anionic group and a second anionic group. These polymerizable compounds may further contain other copolymerizable monomer units. The first anionic agent may be used alone or in combination of two or more.

[0079] Examples of the monomer unit that serves as the base for the above-mentioned monomer units include aliphatic vinyl monomer units such as ethylene and propylene, aromatic vinyl monomer units such as styrene, and diene monomer units such as butadiene and isoprene.

[0080] polymer Weight average molecular weight ( Mw ) is, for example, 5,000 to 500,000, and may be 10,000 to 200,000.

[0081] The first anionic agent may be used in combination with a second anionic agent, which is a low molecular weight compound (monomer compound) having an anionic group, as needed.

[0082] The second anionic agent may be, for example, a monomer compound selected from the anions and polyanions described as the dopants of the first layer. The second anionic agent may be any of an aliphatic compound, an alicyclic compound, and an aromatic compound. The second anionic agent may be used alone or in combination of two or more.

[0083] Examples of the second anion agent include aliphatic sulfonic acids (C such as methanesulfonic acid) 1-6 Alkanesulfonic acids, etc.), alicyclic sulfonic acids (C such as cyclohexanesulfonic acid) 5-8 cycloalkanesulfonic acids, aromatic sulfonic acids (benzenesulfonic acid, styrenesulfonic acid, etc.) 6-14 Acid phosphooxy polyoxyalkylene glycol monoacrylates (acid phosphooxy polyoxyethylene glycol mono(meth)acrylates (P(=O)(OH)2-(O-CH2CH2) of carboxylic acids such as arenesulfonic acid, acid phosphooxy ethyl acrylate, acid phosphooxy ethyl methacrylate) n -OC(=O)-CR=CH2) (n is an integer of 2 to 10, and R is a hydrogen atom or or methyl group), aliphatic phosphonic acids (vinylphosphonic acid, etc.), aromatic phosphonic acids (phenylphosphonic acid, etc.), carboxylic acids [aliphatic carboxylic acids (C such as propanoic acid, butanoic acid, hexanoic acid, etc.] 2-10 C such as alkanecarboxylic acids, hexanedioic acid 4-12 alkanedicarboxylic acids, etc.), alicyclic carboxylic acids (carboxy C such as carboxycyclohexane) 5-8 Dicarboxylates such as cycloalkanes and cyclohexanedicarboxylic acids 5-8 cycloalkanes, etc.), aromatic carboxylic acids (carboxy C such as benzoic acid) 6-14Carboxyhydroxy C such as arenes and salicylic acid 6-14 Arenes, dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid 6-14 arenes, etc.), phenolic compounds (phenol, hydroxytoluene, vinylphenol, hydroxyvinyltoluene, etc.), hydroxyalkyl esters of the above carboxylic acids (e.g., hydroxy C such as hydroxyethyl acrylate, hydroxyethyl methacrylate, etc.), 1-4 alkyl esters) Examples include:

[0084] The second anionic agent may have two or more types of anionic groups. Examples of such second anionic agents include those having a sulfonic acid group and a carboxy group (e.g., aliphatic compounds (e.g., sulfosuccinic acid), aromatic compounds (e.g., sulfobenzoic acid, sulfosalicylic acid, disulfosalicylic acid, sulfophthalic acid, sulfoisophthalic acid, sulfoterephthalic acid, naphtholsulfonic acid), those having a phosphoric acid group and a carboxy group (e.g., 2-(dihydroxyphosphinyloxy)acrylic acid), and those having a phosphonic acid group and a carboxy group (e.g., phosphonoacrylic acid, 2-methyl-3-phosphonoacrylic acid).

[0085] In a continuous or discontinuous layer (or a second treatment liquid) containing a surface conditioner, the anionic group of the anionic agent may be contained in any form selected from the above-mentioned anionic groups, anions corresponding to the above-mentioned anionic groups, and salts of the anions.

[0086] (2nd layer) The second layer may be formed so as to cover at least a portion of the first layer, or may be formed so as to cover the entire surface of the first layer. The second layer is formed so as to cover the first layer in at least a portion of the surface of the first layer via a continuous or discontinuous layer containing a surface conditioner, but there may also be regions where the second layer is formed directly on the surface of the first layer without an intervening continuous or discontinuous layer. Furthermore, in regions where the first layer and a continuous or discontinuous layer are not formed, the second layer may be in contact with the dielectric layer (i.e., the second layer may be formed so as to cover the dielectric layer).

[0087] (Second conductive polymer) The second conductive polymer contained in the second layer can be a known polymer used in electrolytic capacitors, and specifically, can be appropriately selected from the conductive polymers exemplified for the first conductive polymer. Weight average molecular weight ( Mw ) The first conductive polymer and the second conductive polymer may be the same or different.

[0088] The second layer may be a single layer or may be composed of multiple layers. When the second layer is composed of multiple layers, the second conductive polymer contained in each layer may be the same or different.

[0089] The second layer may further contain a dopant. Known dopants used in electrolytic capacitors can be used as the dopant, and specifically, they can be appropriately selected from those exemplified for the first layer. The dopants used in the first layer and the second layer may be the same or different.

[0090] The dopant may be contained in the second layer in the form of a salt. In the second layer, the dopant may form a conductive polymer complex together with the second conductive polymer. As in the first layer, the anionic group of the dopant may be contained in the second layer in the form of an organic group, an anion, or a salt, or may be contained in a form bonded to or interacting with the conductive polymer.

[0091] The amount of dopant contained in the second layer is, for example, 10 to 1000 parts by mass, or may be 50 to 200 parts by mass, relative to 100 parts by mass of the second conductive polymer.

[0092] The second layer may further contain a water-soluble polymer. For details about the water-soluble polymer, please refer to the description of the water-soluble polymer in the first layer. The content (mass%) of the water-soluble polymer in the second layer is preferably adjusted so that the content (mass%) of the water-soluble polymer in the solid electrolyte layer falls within the above-mentioned range. When the second layer contains a water-soluble polymer, the effect of increasing the thickness of the solid electrolyte layer at the center of the anode body is easily achieved, further improving the effects of reducing leakage current and increasing voltage resistance. Therefore, it is preferable that at least the second layer contains a water-soluble polymer. The content (mass%) of the water-soluble polymer in the second layer may be within the range described for the content (mass%) of the water-soluble polymer in the solid electrolyte layer. The content of the water-soluble polymer in the second layer can be determined using the same procedure as for determining the content of the water-soluble polymer in the solid electrolyte layer, except that a sample collected by scraping near the surface of the solid electrolyte layer is used.

[0093] (others) In a cross section G perpendicular to the longitudinal direction of the capacitor element at an arbitrary position on the first end side of the cathode section, the ratio T1 / T2 is, for example, 0.8 or more, or may be 0.9 or more, or 1 or more or greater than 1. When the ratio T1 / T2 is in this range, the thickness of the solid electrolyte layer at the corners is prevented from decreasing, thereby preventing product defects due to short circuits. In particular, when the ratio T1 / T2 is 1 or more or greater than 1, the effect of reducing leakage current is enhanced, thereby preventing product defects due to leakage current. The ratio T1 / T2 is, for example, 1.7 or less, or may be 1.5 or less, or 1.4 or less. When the ratio T1 / T2 is in this range, a decrease in capacitance and an increase in ESR and dielectric tangent tanδ are prevented, thereby further stabilizing the quality of the electrolytic capacitor. These upper and lower limit values ​​can be combined arbitrarily.

[0094] According to the present disclosure, the thickness of the solid electrolyte layer formed at the corners of the anode body can be made greater than the thickness of the solid electrolyte layer formed near the center of the main surface. While the details are unclear, the following mechanism is presumed to be involved. First, by using a second treatment liquid containing a surface treatment agent, the second treatment liquid can be spread over the entire surface of the cathode-forming portion of the anode body. Generally, the liquid medium in a droplet evaporates faster from the edges than from the center, so components other than the liquid medium tend to remain at the edges. This phenomenon is also known as the coffee ring effect or ring stain effect. Due to this phenomenon, in a coating of the second treatment liquid formed over the entire surface of the cathode-forming portion, the liquid medium evaporates faster from the corners than from the center of the main surface of the anode body, leaving more components of the second treatment liquid other than the liquid medium on the surface of the corners. As a result, components of the third treatment liquid adhere more to the corners of the cathode-forming portion of the anode body, which is thought to facilitate aggregation of the second conductive polymer at the corners. For example, the ratio T1 / T2 can be made greater than 1 by adjusting the type and concentration of the surface conditioner, the type of liquid medium used in the second treatment liquid, the drying conditions for the coating of the second treatment liquid, and the like.

[0095] The average thickness of the solid electrolyte layer is, for example, 5 μm or more and 20 μm or less, and may be 10 μm or more and 15 μm or less. The average thickness of the solid electrolyte layer is determined by measuring the thickness at any number of points (for example, 10 points) on a cross section perpendicular to the longitudinal direction of the capacitor element and passing through the center of the cathode part in a direction parallel to the longitudinal direction of the capacitor element, and averaging the measured values.

[0096] Each of the first layer and the second layer may further contain, as necessary, known additives and known conductive materials other than conductive polymers (e.g., conductive inorganic materials such as manganese dioxide; and / or TCNQ complex salts, etc.). A layer for enhancing adhesion may be interposed between the dielectric layer and the first layer.

[0097] Fig. 1 is a cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure, and Fig. 2 is an enlarged view conceptually illustrating the region surrounded by a solid line α in Fig. 1.

[0098] Electrolytic capacitor 1 includes capacitor element 11, resin outer casing 12 that seals capacitor element 11, and anode terminal 13 and cathode terminal 14 that are exposed to the outside of resin outer casing 12. Capacitor element 11 includes a sheet-like anode body 2, a dielectric layer 3 that covers the second end side of anode body 2, and a cathode portion 15 that covers dielectric layer 3. The portion of anode body 2 where cathode portion 15 is formed is a cathode-forming portion, and the portion where cathode portion 15 is not formed is an anode lead portion. Anode terminal 13 is electrically connected to a first end of the anode lead portion of anode body 2. Cathode terminal 14 is electrically connected to cathode portion 15. Resin outer casing 12 has a substantially rectangular parallelepiped outer shape, and therefore electrolytic capacitor 1 also has a substantially rectangular parallelepiped outer shape.

[0099] The anode body 2 and the cathode section 15 face each other via the dielectric layer 3. The cathode section 15 has a solid electrolyte layer 4 covering the dielectric layer 3, and a cathode layer 5 covering the solid electrolyte layer 4. The cathode layer 5 in the illustrated example has a two-layer structure and has a carbon layer 5a in contact with the solid electrolyte layer 4 and a metal paste layer 5b covering the surface of the carbon layer 5a.

[0100] The anode lead portion of the anode body 2 protruding from the cathode portion 15 has an insulating separator 16 formed in a strip-like shape covering the surface of the anode body 2 in a region on the cathode portion 15 side, thereby restricting contact between the cathode portion 15 and the anode body 2. The first end of the anode body 2 protruding from the cathode portion 15 is electrically connected to one end 13a of the anode terminal 13 by welding or the like. Meanwhile, the cathode layer 5 formed on the outermost layer of the cathode portion 15 is electrically connected to one end 14a of the cathode terminal 14 via a conductive adhesive 17 (e.g., a mixture of thermosetting resin and metal particles). The other end 13b of the anode terminal 13 and the other end 14b of the cathode terminal 14 are each drawn out from different side surfaces of the resin outer casing 12 and extend in an exposed state to one of the main flat surfaces (the bottom surface in FIG. 1 ). The exposed portions of each terminal on this flat surface are used for soldering or the like to a substrate (not shown) on which the electrolytic capacitor 1 is to be mounted.

[0101] The dielectric layer 3 is formed on part of the surface of the conductive material that constitutes the anode body 2. Specifically, the dielectric layer 3 can be formed by anodizing the surface of the conductive material that constitutes the anode body 2. Therefore, as shown in FIG. 2, the dielectric layer 3 is formed along the surface of the anode body 2 (including the inner wall surfaces of holes and depressions on the inner surface).

[0102] A first layer 4a containing a first conductive polymer is formed to cover the dielectric layer 3, and a second layer 4b containing a second conductive polymer is formed to cover the first layer 4a. A layer 4c containing a surface conditioner is interposed between the first layer 4a and the second layer 4b. In the illustrated example, the layer 4c containing the surface conditioner is formed to cover the first layer 4a, and the second layer 4b is formed to cover the layer 4c containing the surface conditioner. In FIG. 2, the layer 4c of the surface conditioner is a continuous layer. However, this is not limited to this case, and the layer 4c of the surface conditioner may be a discontinuous layer. In this capacitor element 11, the thickness of the solid electrolyte layer 4 formed at the corners of the anode body 2 is prevented from becoming thin, and the variation in the thickness of the solid electrolyte layer 4 is reduced.

[0103] The first layer 4a does not necessarily have to cover the entire dielectric layer 3 (entire surface), but it is sufficient that it is formed so as to cover at least a portion of the dielectric layer 3, although it is desirable that it be formed so as to cover as much of an area as possible. Similarly, each of the second layer 4b and the layer 4c containing a surface conditioner does not necessarily have to cover the entire first layer 4a (entire surface), but it is sufficient that it is formed so as to cover at least a portion of the first layer 4a, although it is desirable that it be formed so as to cover as much of an area as possible.

[0104] Dielectric layer 3 is formed along the surface of anode body 2, and therefore has projections and depressions on the surface of dielectric layer 3 according to the shape of the surface of anode body 2. First layer 4a is preferably formed so as to bury these projections and depressions of dielectric layer 3.

[0105] In the above configuration, anode body 2 is an anode member of capacitor element 11, and first layer 4a, second layer 4b, and cathode layer 5 are cathode members of capacitor element 11. Dielectric layer 3 is a dielectric member of capacitor element 11.

[0106] In the above embodiment, the capacitor element 11 has been described as having two layers containing a conductive polymer, the first layer 4a and the second layer 4b. However, the capacitor element 11 may have three or more layers containing a conductive polymer. In this case, one or more layers containing a conductive polymer may be formed between the first layer 4a and the second layer 4b. For example, one or more layers containing a conductive polymer may be formed at least either between the first layer 4a and the layer containing a surface conditioner 4c, or between the layer containing a surface conditioner 4c and the second layer 4b.

[0107] In the electrolytic capacitor of the present disclosure, as described above, the ratio T1 / T2 of the thickness T1 of the solid electrolyte layer formed at the corners of the anode body to the thickness T2 of the solid electrolyte layer formed at the center of the main surface can be made larger than before.

[0108] Fig. 3 is a schematic front view of the capacitor element as viewed from one main surface side. Fig. 4 is a schematic cross-sectional view of the capacitor element taken along line IV-IV (cross-section G) as viewed in the direction of the arrows in Fig. 3. The thicknesses T1 and T2 of the solid electrolyte layer can be determined, for example, by the following procedure.

[0109] The ratio T1 / T2 is determined at a cross section G of cathode portion 15 perpendicular to a direction from first end E1 to second end E2 of capacitor element 11 (sometimes referred to as the length direction of anode body 2 or capacitor element 11). Cathode part 15 The first end E1 side portion of cathode portion 15 is formed at an arbitrary position on the first end E1 side of cathode portion 15. When the length of cathode portion 15 in the longitudinal direction of capacitor element 11 is L, the first end E1 side portion of cathode portion 15 is a portion from the end of cathode portion 15 on the first end E1 side to a position at a distance of length L / 2. In FIG. 3 , the first end E1 side portion of cathode portion 15 corresponds to the upper half of cathode portion 15.

[0110] 4 shows the capacitor element 11 taken along line IV-IV of the portion of the cathode portion 15 on the first end E1 side. Chief4 shows a cross section G perpendicular to the thickness direction. Line IV-IV corresponds to an arbitrarily selected position on the first end E1 side of cathode section 15. Note that hatching indicating a cross section is omitted in FIG.

[0111] In the cross section G, a pair of main surfaces Ms of the sheet-like anode body 2 and a pair of end surfaces Es located at the ends of the pair of main surfaces Ms can be seen. Because there are corners between each main surface Ms and each end surface Es, four corners can be seen in the cross section G of the anode body 2. Lines corresponding to each main surface Ms are extended outward to draw imaginary straight lines L1 and L2, and a straight line passing through the vertex of the corner is drawn at a 45° angle with line L1 or L2. The points where these straight lines intersect with the outer edge of the solid electrolyte layer 4, and the distances D11, D12, D13, and D14 between these points and the vertices of the corners, are defined as the thickness of the solid electrolyte layer 4 at each corner. These four distances (D11, D12, D13, D14) T1 is found by averaging the values ​​of

[0112] In the cross section G, when the width of the anode body 2, which corresponds to the length of the line segment corresponding to the main surface Ms, is W, a center line CL is drawn at a position W / 2 from each end face Es. The center line CL passes through the midpoint of the line segment corresponding to each main surface Ms of the anode body 2. The distances D21 and D22 between the intersection of the center line CL with the outer edge of the solid electrolyte layer 4 and the midpoint of the line segment are respectively defined as the thickness of the solid electrolyte layer at the center of the main surface Ms. These two distances (D21, D22) T2 is found by averaging the values ​​of

[0113] [Manufacturing method of electrolytic capacitors] A method for manufacturing an electrolytic capacitor according to one embodiment of the present disclosure includes a first step of preparing an anode body, a second step of forming a dielectric layer on the surface of the anode body, a third step of treating the anode body on which the dielectric layer has been formed with a first treatment liquid containing a first conductive polymer or a precursor thereof, a fourth step of treating the anode body treated with the first treatment liquid with a second treatment liquid containing a surface conditioner, and a fifth step of treating the anode body treated with the second treatment liquid with a third treatment liquid containing a second conductive polymer. Each step will be described in more detail below.

[0114] (1st step) In the first step, the anode body is formed by a known method depending on the type of anode body. The anode body is prepared by, for example, forming a porous portion in at least the surface layer of at least a portion corresponding to the cathode formation portion. The porous portion may be formed over the entire surface layer of the anode body, or the porous portion may be formed over the entire anode body.

[0115] The porous portion can be formed, for example, by roughening the surface of a sheet-like substrate made of a conductive material containing a valve metal. Surface roughening may be performed in any manner that allows for the formation of irregularities on the substrate surface. Surface roughening may be performed, for example, by etching the substrate surface, or by depositing particles of a conductive material containing a valve metal on the substrate surface using a gas phase method such as vapor deposition. Known etching techniques, such as electrolytic etching, may be used. For example, by roughening the surface of the anode lead portion after placing a predetermined masking member on the surface, a porous portion can be formed in the surface layer of the cathode formation portion. The masking member is not particularly limited and may be an insulator such as a resin, or a conductor containing a conductive material.

[0116] Alternatively, a sintered body obtained by sintering particles containing a valve metal may be used as the anode body.

[0117] (2nd process) In the second step, a dielectric layer is formed on the anode body by anodizing the surface of the anode body. The anodization oxidizes the valve metal present at least on the surface of the anode body, generating an oxide.

[0118] Anodization can be carried out by a known method, such as chemical conversion treatment, etc. However, the anodization is not limited to chemical conversion treatment as long as it can form an oxide of the valve metal.

[0119] The chemical conversion treatment can be performed, for example, by immersing the anode body in a chemical conversion solution so that the chemical conversion solution penetrates all the way to the surface of the anode body (the inner wall surfaces of holes and depressions on the inner surface), and applying a voltage between the anode body as the anode and a cathode immersed in the chemical conversion solution. As the chemical conversion solution, for example, an aqueous solution of phosphoric acid, an aqueous solution of ammonium phosphate, or an aqueous solution of ammonium adipate is preferably used.

[0120] (3rd step) In the third step, it is sufficient that the first treatment liquid be brought into contact with at least the dielectric layer. For example, the first treatment liquid can be brought into contact with at least the dielectric layer by immersing the anode body on which the dielectric layer has been formed in the first treatment liquid or by pouring the first treatment liquid into the anode body on which the dielectric layer has been formed. The first treatment liquid may be impregnated into the surface of the anode body on which the dielectric layer has been formed (the inner wall surfaces of holes or depressions on the inner surface on which the dielectric layer has been formed) by immersion or pouring. Furthermore, the method is not limited to impregnation or pouring, and known coating methods (e.g., spray coating) or printing methods may also be used. These methods may be combined as necessary.

[0121] When using a first treatment liquid containing a precursor of the first conductive polymer, it is preferable to immerse the anode body in the first treatment liquid and polymerize the precursor by chemical polymerization or electrolytic polymerization to produce the first conductive polymer. After being removed from the first treatment liquid, the anode body is usually dried. During drying, the anode body may be heated as needed. The anode body removed from the first treatment liquid may be washed as needed prior to drying. In this manner, a first layer containing the first conductive polymer is formed.

[0122] When using a first treatment liquid containing a first conductive polymer, for example, the first treatment liquid is brought into contact with at least the dielectric layer of the anode body and then dried. In this manner, a first layer containing the first conductive polymer is formed. During drying, the anode body may be heated as necessary.

[0123] The first treatment liquid is prepared by dissolving or dispersing the components of the first treatment liquid in a liquid medium. Examples of the components include a first conductive polymer or its precursor, a dopant, a water-soluble polymer, and an additive. For details about the first conductive polymer, the dopant, and the water-soluble polymer, see the description of the first layer.

[0124] Examples of the precursor of the first conductive polymer include a monomer, oligomer, and prepolymer of the first conductive polymer. The first treatment liquid may contain one type of precursor or two or more types of precursors.

[0125] The first treatment liquid may contain one type of first conductive polymer or two or more types of first conductive polymers. The first treatment liquid may contain one type of dopant or two or more types of dopants. The first treatment liquid may contain one type of water-soluble polymer or two or more types of water-soluble polymers.

[0126] Examples of the liquid medium contained in the first treatment liquid include water, an organic medium, and a mixture thereof. Examples of the organic medium include aliphatic alcohols, aliphatic ketones (e.g., acetone), nitriles (e.g., acetonitrile, benzonitrile), amides (e.g., N,N-dimethylformamide), and sulfoxides (e.g., dimethyl sulfoxide). The aliphatic alcohol is preferably an aliphatic alcohol having 1 to 5 carbon atoms. The aliphatic alcohol may be either a monool or a polyol. Examples of the aliphatic monool include methanol, ethanol, propanol, and butanol. Examples of the aliphatic polyol include ethylene glycol and glycerin.

[0127] The first treatment liquid may contain a known additive used in forming a solid electrolyte layer, such as a silane compound.

[0128] When a first treatment liquid containing a precursor of the first conductive polymer is used, an oxidizing agent is used to polymerize the precursor. The oxidizing agent may be contained in the first treatment liquid as an additive. Alternatively, the oxidizing agent may be applied to the anode body on which the dielectric layer has been formed before or after the first treatment liquid is brought into contact with the anode body. Examples of such oxidizing agents include sulfates, sulfonic acids, and salts thereof. The oxidizing agents may be used alone or in combination of two or more.

[0129] Examples of sulfates include salts of metals with sulfates such as ferric sulfate and sodium persulfate, and persulfates. Examples of metals constituting the salts include alkali metals such as sodium and potassium; iron, copper, chromium, and zinc. Sulfonic acids or their salts function not only as oxidizing agents but also as dopants. Examples of sulfonic acids or their salts include low-molecular-weight sulfonic acids or their salts exemplified for dopants.

[0130] The process of forming the first layer by immersion in the first treatment liquid and polymerization (or drying) may be carried out once or may be repeated multiple times, with the conditions, such as the composition and viscosity of the first treatment liquid, remaining the same each time, or at least one of the conditions being changed.

[0131] (4th step) The fourth step can be carried out, for example, by contacting the anode body treated with the first treatment liquid with a second treatment liquid containing a surface conditioner. After contact with the second treatment liquid, the anode body may be dried as needed. During drying, the anode body may be heated as needed.

[0132] In the fourth step, the second treatment liquid may be applied so as to cover the first conductive polymer adhered to the surface of the dielectric layer. From the viewpoint of forming the second layer more uniformly over the entire surface of at least the cathode-forming portion of the anode body, it is preferable to apply the second treatment liquid so that the surface conditioner is distributed over at least the entire surface of the cathode-forming portion.

[0133] The second treatment liquid is applied to the surface of the anode body by, for example, at least one method selected from immersion, pouring, coating, and printing, in the same manner as in the case of the first treatment liquid.

[0134] The second treatment liquid may contain a liquid medium, such as the liquid media exemplified for the first treatment liquid.

[0135] The second treatment liquid may contain at least one selected from the group consisting of a cationic agent and an anionic agent.

[0136] For the components contained in the second treatment liquid, the description of the continuous or discontinuous layer containing the surface conditioner can be referred to.

[0137] The amount of the surface conditioner in the second treatment liquid is, for example, 0.01% by mass or more and 5% by mass or less, and may be 0.05% by mass or more and 2.5% by mass or less. When the amount of the surface conditioner is within this range, the surface conditioner can be more uniformly distributed over the entire surface of the cathode-forming portion of the anode body, making it easier to reduce variations in the thickness of the solid electrolyte layer. In addition, the resistance of the solid electrolyte layer can be kept low, thereby suppressing an increase in ESR. The amount of the surface conditioner in the second treatment liquid refers to the concentration of the surface conditioner in the second treatment liquid.

[0138] The amount of the surface conditioner relative to the dry solid content in the second treatment liquid is selected from the ranges described for the amount of the surface conditioner contained in the continuous or discontinuous layer containing the surface conditioner. In this specification, the amount of surface conditioner in the dry solid content of the second treatment liquid is used synonymously with the amount of surface conditioner in the components other than the liquid medium in the second treatment liquid.

[0139] As described above, the second treatment liquid preferably does not contain a conductive polymer.

[0140] (5th step) The fifth step can be carried out in the same manner as the third step, except that the anode body treated with the second treatment liquid is used, and a third treatment liquid containing a second conductive polymer (and a dopant and a water-soluble polymer, if necessary) is used instead of the first treatment liquid. As the third treatment liquid, the same treatment liquid as described for the first treatment liquid can be used, except that the second conductive polymer is contained instead of the first conductive polymer. By the fifth step, a second layer containing the second conductive polymer is formed. 4 This process distributes components contained in the second treatment liquid, such as a surface conditioner, over the entire surface of at least the cathode-forming portion of the anode body. In this state, treating the surface of the cathode-forming portion with a third treatment liquid allows the second conductive polymer to adhere to the entire surface of the cathode-forming portion, including the corners. Furthermore, when the third treatment liquid contains a water-soluble polymer, it is more effective in reducing variations in the thickness of the solid electrolyte layer, thereby reducing the leakage current of the electrolytic capacitor and achieving high voltage resistance.

[0141] (Step of forming a cathode layer) The method for manufacturing an electrolytic capacitor may further include a step (sixth step) of forming a cathode layer. In the sixth step, for example, a carbon layer and a metal paste layer are sequentially laminated on the surface of the anode body obtained in the fifth step to form a cathode layer.

[0142] The carbon layer can be formed by immersing an anode element having a dielectric layer on which a second layer has been formed in a dispersion containing conductive carbon, or by applying a paste containing conductive carbon to the surface of the second layer. Examples of conductive carbon include graphites such as artificial graphite and natural graphite. Examples of dispersions and pastes that can be used include those in which conductive carbon is dispersed in an aqueous liquid medium.

[0143] The metal paste layer can be formed, for example, by laminating a composition containing metal particles on the surface of a carbon layer. For example, a silver paste layer formed using a composition containing silver particles and a resin (binder resin) can be used as the metal paste layer. While a thermoplastic resin can also be used as the resin, it is preferable to use a thermosetting resin such as an imide resin or an epoxy resin.

[0144] The configuration of the cathode layer is not limited to this, and any configuration may be used as long as it has a current collecting function.

[0145] A cathode terminal is connected to the cathode layer, and the cathode terminal is bonded to the cathode layer via a conductive adhesive, for example, which is applied to the cathode layer.

[0146] (Process for sealing the capacitor element) The capacitor element thus formed is sealed with an outer casing. Specifically, the capacitor element and the resin material of the outer casing (e.g., uncured thermosetting resin and filler) are placed in a mold, and the capacitor element is sealed with the outer casing by transfer molding, compression molding, or the like. At this time, portions of the anode terminal and cathode terminal connected to the anode lead drawn from the capacitor element are exposed from the mold. The molding conditions are not particularly limited, and time and temperature conditions may be set appropriately taking into account the curing temperature of the thermosetting resin used, etc.

[0147] [Example] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0148] 《Electrolytic Capacitor A1》 An electrolytic capacitor 1 shown in FIG. 1 was fabricated in the following manner, and its characteristics were evaluated. (1) Step of preparing anode body 2 (first step) Anode body 2 was produced by roughening both surfaces of an aluminum foil (thickness: 100 μm) used as a substrate by etching.

[0149] (2) Step of forming dielectric layer 3 (second step) The portion of the anode body 2 on the second end side was immersed in a chemical conversion solution, and a DC voltage of 70 V was applied for 20 minutes to form a dielectric layer 3 containing aluminum oxide.

[0150] (3) Step of forming the first layer 4a (third step) Under stirring, 3,4-ethylenedioxythiophene monomer was added to an aqueous solution of polystyrene sulfonic acid (Mw: 75,000), followed by the addition of oxidizing agents (iron(III) sulfate and persulfuric acid). A solution containing poly(3,4-ethylenedioxythiophene) (PEDOT) as the first conductive polymer and poly(styrene sulfonate) (PSS) as the dopant was obtained by filtering the resulting polymerization solution using an ion exchanger to remove impurities.

[0151] Pure water was added to the obtained solution, which was then homogenized using a high-pressure homogenizer and filtered through a filter to prepare a first treatment liquid in the form of a dispersion.

[0152] The anode element 2 having the dielectric layer 3 formed thereon obtained in (2) above was immersed in the first treatment liquid, then removed from the first treatment liquid, and further dried for 10 to 30 minutes at 120° C. The immersion in the first treatment liquid and drying were repeated once more, thereby forming a first layer 4a containing a first conductive polymer so as to cover the surface of the dielectric layer 3.

[0153] (4) Step of forming a layer 4c containing a surface conditioner (fourth step) A second treatment liquid was prepared by dissolving an ester-type nonionic surfactant (surface conditioner), N,N-dimethyloctylamine (cationic agent), and a copolymer of styrene sulfonic acid and acid phosphooxyethyl acrylate (P(=O)(OH)2-O-CH2CH2-OC(=O)-CH=CH2) (anionic agent) in pure water. The amount of surface conditioner in the second treatment liquid was 0.5% by mass. The concentration of the cationic agent in the second treatment liquid was 0.05 mol / L, and the concentration of the anionic agent was 0.03 mol / L. The amount of surface conditioner relative to the total components of the second treatment liquid, excluding water as the liquid medium, was 12.5% ​​by mass.

[0154] The anode body 2 treated in (3) above was immersed in the second treatment liquid, then removed and further dried at 100°C for 3 minutes, thereby forming a layer 4c containing a surface conditioner so as to cover the surface of the first layer 4a.

[0155] The anionic agent used in the second treatment liquid was prepared as follows. A monomer solution was prepared by adding and mixing sodium styrenesulfonate and acid phosphooxyethyl acrylate to a predetermined amount of pure water. The sodium styrenesulfonate and acid phosphooxyethyl acrylate were used in a ratio such that the copolymerization ratio (molar ratio) of styrenesulfonic acid to acid phosphooxyethyl acrylate in the copolymer was 75:25. A predetermined amount of ammonium persulfate (oxidizing agent) was added to the monomer solution under stirring, and the polymerization reaction was carried out over 8 hours. The resulting polymer solution was purified by adding pure water and ion exchange resin, stirring, and filtering. This purification process was repeated multiple times to finally obtain the above copolymer. The molecular weight of the copolymer was measured by GPC, and Mw was 83,000.

[0156] (5) Step of forming the second layer 4b (fifth step) A third treatment liquid having the same composition as the first treatment liquid used in (3) above was used. The anode element 2 treated in (4) above was immersed in the third treatment liquid, then removed and further dried at 120°C for 10 to 30 minutes. The immersion in the third treatment liquid and drying were alternately repeated two more times, thereby forming a second layer 4b containing a second conductive polymer so as to cover the surface of the layer 4c containing the surface conditioner. In this manner, the solid electrolyte layer 4 including the first layer 4a, the layer 4c containing the surface conditioner, and the second layer 4b was formed so as to cover the surface of the dielectric layer 3.

[0157] (6) Step of forming cathode layer 5 (sixth step) Anode body 2 obtained in (5) above was immersed in a dispersion liquid in which graphite particles were dispersed in water, removed from the dispersion liquid, and then dried to form carbon layer 5a at least on the surface of second layer 4b. Drying was performed at 130 to 180°C for 10 to 30 minutes.

[0158] Next, a silver paste containing silver particles and a binder resin (epoxy resin) was applied to the surface of the carbon layer 5a, and the binder resin was cured by heating at 150 to 200°C for 10 to 60 minutes to form a metal paste layer 5b. In this way, a cathode layer 5 composed of the carbon layer 5a and the metal paste layer 5b was formed. In this manner, the capacitor element 11 was produced.

[0159] (7) Assembly of electrolytic capacitors Cathode layer 5 of capacitor element 11 obtained in (6) above and one end 14a of cathode terminal 14 were joined with conductive adhesive 17. A first end of anode body 2 protruding from capacitor element 11 and one end 13a of anode terminal 13 were joined by laser welding. Next, a resin outer package 12 made of insulating resin was formed by transfer molding around the periphery of capacitor element 11. At this time, the other end 13b of anode terminal 13 and the other end 14b of cathode terminal 14 were left pulled out from resin outer package 12. In this way, electrolytic capacitor 1 (A1) was completed. In the same manner as above, a total of 20 electrolytic capacitors 1 were produced.

[0160] (8) Evaluation The electrolytic capacitors were evaluated as follows.

[0161] (a) Thickness ratio T1 / T2 of solid electrolyte layer 4 The thickness ratio T1 / T2 of the solid electrolyte layer 4 of each electrolytic capacitor was determined using the procedure described above. Then, the ratios T1 / T2 of the 20 electrolytic capacitors were averaged to determine an average value.

[0162] (b) Initial capacitance, tanδ, and ESR Using a four-terminal LCR meter at 20°C, the initial capacitance (μF) and initial tanδ of each electrolytic capacitor at a frequency of 120 kHz were measured, as well as the initial ESR (mΩ) at a frequency of 100 kHz. The average values ​​for the 20 electrolytic capacitors were then calculated.

[0163] (c) Leakage current (LC) A 1 kΩ resistor was connected in series to the electrolytic capacitor, and the leakage current (μA) was measured after applying a rated voltage of 25 V from a DC power supply for 1 minute, and the average value for 20 electrolytic capacitors was calculated.

[0164] 《Electrolytic capacitor B1》 In the fourth step, no surface conditioner was used when preparing the second treatment liquid. Except for this, electrolytic capacitor B1 was produced in the same manner as electrolytic capacitor A1, and was then evaluated.

[0165] 《Electrolytic capacitor B2》 In the fifth step, the same ester-type nonionic surfactant (surface conditioner) used in the second treatment liquid for electrolytic capacitor A1 was added to the third treatment liquid. The amount of the surface conditioner in the third treatment liquid was 0.5 mass %. In addition, in the fourth step, no surface conditioner was used when preparing the second treatment liquid. Except for these points, electrolytic capacitor B2 was produced in the same manner as electrolytic capacitor A1 and evaluated.

[0166] Electrolytic capacitors A2 and A3 In the fourth step, commercially available nonionic surfactants different from those used in electrolytic capacitor A1 were used as surface conditioners. Other than these, electrolytic capacitors A2 and A3 were fabricated and evaluated in the same manner as electrolytic capacitor A1. Note that different nonionic surfactants were used in electrolytic capacitors A2 and A3. The nonionic surfactant used in electrolytic capacitor A2 was an ester type, while the nonionic surfactant used in electrolytic capacitor A3 was a linear alkyl polyether type.

[0167] The results for electrolytic capacitors A1 to A3 and B1 to B2 are shown in Table 1. Each evaluation was expressed as a percentage, with the measured value for electrolytic capacitor A1 being 100%. Electrolytic capacitors A1 to A3 are examples, and electrolytic capacitors B1 and B2 are comparative examples.

[0168] [Table 1]

[0169] As shown in Table 1, the ratios T1 / T2 of electrolytic capacitor B1, which did not use a surface conditioner, and electrolytic capacitor B2, which used a third treatment solution containing a surface conditioner, were low, ranging from 0.552 to 0.769. In contrast, the ratios T1 / T2 of electrolytic capacitors A1 to A3, which used a second treatment solution containing a surface conditioner, were significantly improved, ranging from 0.932 to 1.280, compared to electrolytic capacitors B1 and B2. The T2 values ​​of electrolytic capacitors A1 to A3 were not significantly different from those of electrolytic capacitors B1 and B2. Therefore, it can be said that the thickness of the solid electrolyte layer formed at the corners of the anode body is less likely to decrease in electrolytic capacitors A1 to A3 than in electrolytic capacitors B1 to B2, and that the variation in the thickness of the solid electrolyte layer is reduced.

[0170] In particular, in electrolytic capacitor A1, the thickness of the solid electrolyte layer is increased at the corners, and the capacitance, tan δ, and ESR are maintained at good levels while the leakage current is significantly reduced.

[0171] Electrolytic capacitors A2 and A3 provide excellent results in terms of capacitance, tan δ, and ESR while preventing excessive leakage current.

[0172] The larger the T1 / T2 ratio, the lower the risk of product defects due to short circuits. Therefore, electrolytic capacitors A1 to A3 can reduce the occurrence of product defects due to short circuits compared to electrolytic capacitors B1 and B2.

[0173] Electrolytic capacitors A4 to A8 A treatment liquid prepared by adding a water-soluble polymer to a dispersion liquid having the same composition as the first treatment liquid was used as the third treatment liquid. Except for this, electrolytic capacitors A4 to A8 were fabricated and evaluated in the same manner as electrolytic capacitor A1. Furthermore, the amount of water-soluble polymer added to the third treatment liquid was adjusted so that the content (mass%) of the water-soluble polymer in the solid electrolyte layer was the value shown in Table 2. A copolymer of acrylic acid and methacrylic acid (Mw: approximately 100,000) was used as the water-soluble polymer.

[0174] The electrolytic capacitors A4 to A8, A1 and B1 were evaluated for voltage resistance according to the following procedure. (pressure resistance) A voltage was applied to the electrolytic capacitor while increasing it at a rate of 1.0 V / second, and the breakdown voltage at which an overcurrent of 0.5 A flowed was measured. The breakdown voltage was expressed as an index (voltage resistance index V), with the breakdown voltage of electrolytic capacitor A1 taken as 100 (%). The voltage resistance was evaluated based on this voltage resistance index. A higher voltage resistance index indicates higher voltage resistance. The results are shown in Table 2. Electrolytic capacitors A4 to A8 are examples.

[0175] [Table 2]

[0176] As shown in Table 2, the inclusion of a water-soluble polymer in the solid electrolyte layer results in high voltage resistance (electrolytic capacitors A4 to A8). In electrolytic capacitors A4 to A8, LC can be significantly reduced while suppressing increases in tanδ and ESR. The ratio T1 / T2 is improved in electrolytic capacitors A4 to A8 compared to electrolytic capacitor B1 (and B2 in Table 1). The T1 values ​​of electrolytic capacitors A4 to A8 were not significantly different from the T1 value of electrolytic capacitor A1. Therefore, in electrolytic capacitors A4 to A8, the thickness T2 of the solid electrolyte layer formed in the center of the main surface of the anode body is larger than in electrolytic capacitor A1, and it can be said that the variation in the thickness of the solid electrolyte layer is further reduced. This is thought to have resulted in a significant reduction in LC and high voltage resistance in electrolytic capacitors A4 to A8. [Industrial Applicability]

[0177] According to the present disclosure, it is possible to reduce the variation in thickness of the solid electrolyte layer, thereby reducing short-circuit defects and providing a high-quality electrolytic capacitor, which can be used in a variety of applications. [Explanation of symbols]

[0178] 1: electrolytic capacitor, 2: anode body, 3: dielectric layer, 4: solid electrolyte layer, 4a: first layer, 4b: second layer, 4c: layer containing surface conditioner, 5: cathode layer, 5a: carbon layer, 5b: metal paste layer, 11: capacitor element, 12: resin outer casing, 13: anode terminal, 13a: one end of anode terminal, 13b: other end of anode terminal, 14: cathode terminal, 14a: one end of cathode terminal, 14b: other end of cathode terminal, 15: cathode part, 16: separation part, 17: conductive adhesive, E1: first end of anode body, E2: second end of anode body, Ms: main surface of anode body, Es: end surface of anode body, L1, L2: straight lines extending line segments corresponding to a pair of main surfaces of the anode body, CL: center line of each main surface of the anode body

Claims

1. a sheet-like anode body having an anode lead portion and a cathode forming portion; a dielectric layer formed on at least the surface of the cathode-forming portion of the anode body; a cathode portion covering at least a portion of the dielectric layer; the anode body includes a first end and a second end; the anode lead-out portion includes the first end, and the cathode formation portion includes the second end, the cathode section includes a solid electrolyte layer containing a conductive polymer that covers at least a portion of the dielectric layer, in a cross section perpendicular to a direction from the first end to the second end of the capacitor element at an arbitrary position in a portion of the cathode portion on the first end side, a ratio T1 / T2 of a thickness T1 of the solid electrolyte layer formed at a corner of the anode body to a thickness T2 of the solid electrolyte layer formed in a central portion of a main surface of the anode body is 0.835 or greater and 1.280 or less, The solid electrolyte layer is a first layer including a first conductive polymer covering at least a portion of the dielectric layer; a second layer including a second conductive polymer covering at least a portion of the first layer; at least one continuous or discontinuous layer interposed between the first layer and the second layer; The electrolytic capacitor, wherein the continuous or discontinuous layer comprises a surface conditioner and a cationic agent (excluding surfactants) containing cationic groups.

2. 2. The electrolytic capacitor according to claim 1, wherein the ratio T1 / T2 is 0.9 or greater.

3. 3. The electrolytic capacitor according to claim 1, wherein the ratio T1 / T2 is greater than 1.

4. 4. The electrolytic capacitor according to claim 1, wherein the solid electrolyte layer further contains a water-soluble polymer.

5. The solid electrolyte layer is a first layer including a first conductive polymer covering at least a portion of the dielectric layer; a second layer including a second conductive polymer covering at least a portion of the first layer; at least one continuous or discontinuous layer interposed between the first layer and the second layer; the continuous or discontinuous layer comprises a surface conditioner; The electrolytic capacitor according to claim 4 , wherein at least the second layer contains the water-soluble polymer.

6. 6. The electrolytic capacitor according to claim 4, wherein the content of the water-soluble polymer in the solid electrolyte layer is 25% by mass or more and 70% by mass or less.

7. 7. The electrolytic capacitor according to claim 1, wherein the surface conditioner comprises at least one surfactant selected from the group consisting of a nonionic surfactant, a cationic surfactant, an anionic surfactant, and an amphoteric surfactant.

8. the continuous or discontinuous layer further comprises an anionic agent comprising an anionic group; The electrolytic capacitor according to any one of claims 1 to 7, wherein the anionic agent is different from the surface conditioner.

9. 9. The electrolytic capacitor according to claim 1, wherein the amount of the surface conditioner contained in the continuous or discontinuous layer is 0.01% by mass or more and 30% by mass or less.

10. a first step of preparing an anode body; a second step of forming a dielectric layer on the surface of the anode body; a third step of treating the anode body on which the dielectric layer has been formed with a first treatment solution containing a first conductive polymer or a precursor thereof; a fourth step of treating the anode element treated with the first treatment liquid with a second treatment liquid containing a surface conditioner and a cationic agent having a cationic group (excluding a surfactant); a fifth step of treating the anode element treated with the second treatment liquid with a third treatment liquid containing a second conductive polymer.

11. 11. The method for producing an electrolytic capacitor according to claim 10, wherein the surface conditioner comprises at least one surfactant selected from the group consisting of a nonionic surfactant, a cationic surfactant, an anionic surfactant, and an amphoteric surfactant.

12. the second treatment liquid further contains an anionic agent containing an anionic group, The method for manufacturing an electrolytic capacitor according to claim 10 or 11, wherein the anionic agent is different from the surface conditioner.

13. 13. The method for manufacturing an electrolytic capacitor according to claim 10, wherein the amount of the surface conditioner in the second treatment liquid is 0.01% by mass or more and 5% by mass or less.

14. The method for manufacturing an electrolytic capacitor according to claim 10, wherein the third treatment liquid further contains a water-soluble polymer.

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