Solid electrolytic capacitor element, solid electrolytic capacitor, and method for manufacturing solid electrolytic capacitor element

Abstract

This solid electrolytic capacitor element comprises: a positive electrode foil having a porous portion on a surface layer thereof, and also including a first portion including a first end and a second portion including a second end opposite to the first end; a dielectric layer formed on the surface of the porous portion; and a solid electrolyte layer covering at least a portion of the dielectric layer. The solid electrolytic capacitor element has an insulating region containing a cured product of a resin composition between the first end and the second end of the positive electrode foil. In the insulating region, pores of the porous portion are filled with the cured product. The resin composition includes an insulating resin material and an additive that modifies the insulating resin material. The content of the additive in the resin composition is at least 3 mass%. The glass transition point of the cured product is at least 230 °C.

Description

[Technical Field]

[0001] The present disclosure relates to a solid electrolytic capacitor element, a solid electrolytic capacitor, and a method for manufacturing a solid electrolytic capacitor element. [Background technology]

[0002] The solid electrolytic capacitor includes, for example, a solid electrolytic capacitor element and an exterior casing that seals the solid electrolytic capacitor element. The solid electrolytic capacitor element includes, for example, an anode foil, a dielectric layer formed on the surface of the anode foil, and a cathode portion including a solid electrolyte layer that covers at least a portion of the dielectric layer. To ensure high capacity, a porous portion having numerous pores is formed on the surface of the anode foil. The anode foil is divided into a first portion including a first end and a second portion including a second end opposite the first end, and an insulating region may be provided at a predetermined position between the first end and the second end. The insulating region ensures insulation between the first portion and the cathode portion when the cathode portion is formed on the second portion of the anode foil via a dielectric layer. The insulating region may be formed, for example, by attaching an insulating sheet to the surface of the dielectric layer or by filling the pores of the porous portion with an insulating material.

[0003] Patent Document 1 proposes a solid electrolytic capacitor having a shielding layer in a region separating an anode region and a cathode region of a substrate for a solid electrolytic capacitor having a porous layer on the surface, characterized in that the shielding layer is formed from a solution or dispersion of a heat-resistant resin or its precursor, with a content of a shielding layer modifying additive (excluding silane coupling agents) of 0 to 0.1 mass % (based on the mass of the heat-resistant resin or its precursor).

[0004] Patent Document 2 proposes a solid electrolytic capacitor having a shielding layer formed by laminating multiple layers in a region separating an anode region and a cathode region of a substrate for a solid electrolytic capacitor having a porous layer on the surface, wherein the first shielding layer formed by laminating the multiple layers directly on the substrate for a solid electrolytic capacitor does not contain a shielding layer modifying additive (excluding silane coupling agents), or is formed from a solution or dispersion of a heat-resistant resin or its precursor, in which the content of the shielding layer modifying additive is 0.1 mass % or less (based on the mass of the heat-resistant resin or its precursor). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2007 / 061005 [Patent Document 2] International Publication No. 2008 / 038584 Summary of the Invention [Problem to be solved by the invention]

[0006] When forming an insulating region by filling the pores of a porous portion with an insulating resin material (such as a resin composition) and curing it, it is difficult to fill the pores with a high amount of resin material because the pores are small. If the filling rate of the resin material in the pores of the porous portion is low, when forming a solid electrolyte layer in the second portion, for example, the conductive material, such as a conductive polymer, that constitutes the solid electrolyte layer will penetrate into the pores of the insulating region or through these pores into the first portion. This makes it difficult to ensure insulation between the cathode portion including the solid electrolyte layer and the first portion, resulting in increased leakage current. [Means for solving the problem]

[0007] A first aspect of the present disclosure provides an anode foil having a porous portion in a surface layer, and having a first portion including a first end and a second portion including a second end opposite to the first end; a dielectric layer formed on the surface of the porous portion; and A solid electrolytic capacitor element including a solid electrolyte layer covering at least a portion of the dielectric layer, the solid electrolytic capacitor element has an insulating region containing a cured product of a resin composition between the first end and the second end of the anode foil, In the insulating region, the cured material fills the pores of the porous portion, the resin composition includes an insulating resin material and an additive that modifies the insulating resin material; the content of the additive in the resin composition is 3% by mass or more, The solid electrolytic capacitor element has a glass transition temperature of 230°C or higher after curing.

[0008] A second aspect of the present disclosure relates to a solid electrolytic capacitor including at least one of the above-described solid electrolytic capacitor elements.

[0009] A third aspect of the present disclosure is a first step of preparing an anode foil having a porous portion on a surface layer thereof, the anode foil having a first portion including a first end portion and a second portion including a second end portion opposite to the first end portion; a second step of forming a dielectric layer on the surface of the porous portion; a third step of forming an insulating region containing a cured product of a resin composition between the first end and the second end of the anode foil; a fourth step of forming a solid electrolyte layer covering at least a portion of the dielectric layer; the resin composition includes an insulating resin material and an additive that modifies the insulating resin material, the content of the additive in the resin composition is 3 mass% or more, and the glass transition point of the cured product is 230°C or more; The third step relates to a method for manufacturing a solid electrolytic capacitor element, which includes a sub-step of filling the pores of the porous portion with a treatment liquid containing the resin composition and a solvent, and curing the resin composition. [Effects of the Invention]

[0010] In a solid electrolytic capacitor having an insulating region containing a cured product of an insulating resin material, leakage current can be kept low. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view schematically showing a solid electrolytic capacitor according to a first embodiment of the present disclosure. [Figure 2] 2 is a cross-sectional view schematically showing a solid electrolytic capacitor element included in the solid electrolytic capacitor of FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0013] When forming an insulating region, if the pores of the porous portion formed on the surface of the anode foil are not densely filled with the resin composition that constitutes the insulating region, leaving many voids, a conductive material such as a conductive polymer may penetrate into the voids in the insulating region during the formation of the solid electrolyte layer. Furthermore, the conductive material may penetrate into the first portion (anode portion) through the voids in the insulating region. In such cases, electrical conduction occurs between the anode portion and the cathode portion including the solid electrolyte layer through the conductive material that has penetrated into the voids in the insulating region or the voids in the anode portion, resulting in increased leakage current. The solid electrolyte layer can be formed, for example, by in situ polymerization, such as chemical polymerization or electrolytic polymerization, or by using a liquid composition containing a conductive polymer (e.g., a conjugated polymer and a dopant). In particular, when forming a solid electrolyte layer by in situ polymerization, the polymerization liquid contains relatively low-molecular-weight components (e.g., a conjugated polymer precursor, a dopant, and an oxidizing agent), which tend to penetrate into the pores and the voids. Furthermore, when forming a solid electrolyte layer by electrolytic polymerization, a conductive material may be precoated prior to electrolytic polymerization. The liquid dispersion (liquid composition) containing the conductive material used for precoating has a relatively low concentration and low viscosity, and therefore easily penetrates into the insulating region and voids in the anode region. Therefore, to reduce the penetration of these conductive materials, it is important to highly fill the pores of the porous region with a resin composition (or its cured product) when forming the insulating region.

[0014] To achieve high filling of the pores of the porous portion, it is important that the treatment liquid containing the resin composition for forming the insulating region has a high dry solids concentration. However, as the dry solids concentration of the treatment liquid increases, the viscosity tends to increase. This tendency is particularly pronounced when the glass transition temperature (Tg) of the cured product is high. A high viscosity treatment liquid reduces the ability to fill the pores of the porous portion. Using a solvent to lower the viscosity of the treatment liquid reduces the dry solids concentration of the treatment liquid. Because the pores of the porous portion are very fine, even if a treatment liquid with a low dry solids concentration is repeatedly applied to the porous portion, the openings of the pores tend to become clogged in the early stages, making it difficult to fill the pores to the depths. Therefore, even in this case, it is difficult to increase the ability of the resin composition to fill the pores.

[0015] In view of the above, (1) the present disclosure provides a solid electrolytic capacitor element including an anode foil having a porous portion on its surface and a first portion including a first end and a second portion including a second end opposite the first end, a dielectric layer formed on the surface of the porous portion, and a solid electrolyte layer covering at least a portion of the dielectric layer. The solid electrolytic capacitor element has an insulating region between the first end and the second end of the anode foil, the insulating region including a cured product of a resin composition. In the insulating region, the cured product fills the pores of the porous portion. The resin composition includes an insulating resin material and an additive that modifies the insulating resin material. The content of the additive in the resin composition is 3% by mass or more. The glass transition temperature of the cured product is 230°C or higher.

[0016] As described above, in the solid electrolytic capacitor element of the present disclosure, the insulating region is formed using a resin composition containing an insulating resin material and an additive that modifies the insulating resin material. The insulating region includes a cured product of the resin composition. Here, the content of the additive in the resin composition is 3% by mass or more, and the Tg of the cured product is 230°C or higher. In the insulating region of the solid electrolytic capacitor element, the cured product of the resin composition fills the pores of the porous portion. When the Tg of the cured product is high, such as 230°C or higher, the viscosity of the treatment liquid containing the resin composition for forming the insulating region tends to increase. However, by using 3% by mass or more of an additive that modifies the insulating resin material, the viscosity can be reduced while maintaining a high dry solids concentration of the treatment liquid, thereby improving the filling of the resin composition into the pores of the porous portion. In the insulating region, the insulating cured product is densely packed into the pores of the porous portion, thereby suppressing the intrusion of conductive materials into the voids of the insulating region during the formation of the solid electrolyte layer. This more reliably ensures insulation between the first portion (anode portion) and the cathode portion including the solid electrolyte layer. As a result, leakage current can be reduced. Furthermore, the present disclosure can ensure high initial capacitance, and can also keep initial tan δ and equivalent series resistance (ESR) low, ensuring excellent capacitor performance.

[0017] (2) In the above (1), the resin composition may have a viscosity at 25°C of 1,000 mPa·s or more and 10,000 mPa·s or less in a gamma-butyrolactone solution containing the resin composition at a concentration of 30% by mass.

[0018] (3) In the above (1) or (2), the content of the additive in the resin composition may be 60% by mass or less.

[0019] (4) In any one of the above (1) to (3), the additive may interact or react with the insulating resin material.

[0020] (5) In any one of the above (1) to (4), the additive may include a polymer of an epoxy compound.

[0021] (6) In any one of the above (1) to (5), the insulating resin material may include a polyimide resin.

[0022] (7) With regard to any one of (1) to (6) above, in the cross section of the solid electrolytic capacitor element in the insulating region, the ratio of the area of ​​the cured material filled in the pores to the total area of ​​the pores may be 80% or more.

[0023] (8) In any one of the above (1) to (7), in the insulating region, the cured product may be further formed on a main surface of the anode foil via the dielectric layer. In the main surface of the anode foil, the maximum thickness of the cured product formed on the dielectric layer on one main surface side of the anode foil is t c and the thickness of the anode foil is t f At this time, the maximum thickness t c The thickness t of the anode foil f Ratio to (=t c / t f ) may be 0.12 or less.

[0024] The present disclosure also includes (9) a solid electrolytic capacitor including at least one of the above solid electrolytic capacitor elements.

[0025] (10) In the above (9), the solid electrolytic capacitor may include an exterior body that seals the solid electrolytic capacitor element.

[0026] The present disclosure also includes a method for manufacturing a solid electrolytic capacitor element. a first step of preparing an anode foil having a porous portion on a surface layer thereof, the anode foil having a first portion including a first end portion and a second portion including a second end portion opposite to the first end portion; a second step of forming a dielectric layer on the surface of the porous portion; a third step of forming an insulating region containing a cured product of the resin composition between the first end and the second end of the anode foil; A fourth step of forming a solid electrolyte layer covering at least a portion of the dielectric layer.

[0027] More specifically, (11) the method for producing a solid electrolytic capacitor element of the present disclosure includes: a first step of preparing an anode foil having a porous portion on a surface layer thereof, the anode foil having a first portion including a first end portion and a second portion including a second end portion opposite to the first end portion; a second step of forming a dielectric layer on the surface of the porous portion; a third step of forming an insulating region containing a cured product of a resin composition between the first end and the second end of the anode foil; and a fourth step of forming a solid electrolyte layer covering at least a portion of the dielectric layer. The resin composition contains an insulating resin material and an additive that modifies the insulating resin material. The content of the additive in the resin composition is 3% by mass or more. The cured product has a glass transition temperature of 230°C or higher. The third step includes a sub-step of filling the pores of the porous portion with a treatment liquid containing the resin composition and a solvent, and curing the resin composition.

[0028] (12) In the above (11), the treatment liquid may have a dry solid content of 30% by mass or more, and a viscosity at 25° C. of 1,000 mPa·s or more and 50,000 mPa·s or less.

[0029] (13) In the above (11) or (12), the fourth step may include a second substep of forming at least a part of the solid electrolyte layer by in situ polymerization of a precursor of a conjugated polymer in the presence of a dopant.

[0030] (14) In the above (13), the fourth step may include a first substep of precoating the surface of the dielectric layer with a liquid composition containing a conductive material prior to the second substep.

[0031] The dry solids concentration of the treatment liquid or the dry solids content of the treatment liquid is the total content of components other than the solvent in the mass of the treatment liquid.

[0032] The solid electrolytic capacitor element, solid electrolytic capacitor, and method for manufacturing the solid electrolytic capacitor element according to the present disclosure will be described in more detail below, including the above (1) to (14). At least one of the above (1) to (14) may be combined with at least one of the elements described below, provided that this is not technically inconsistent.

[0033] [Solid electrolytic capacitor] The solid electrolytic capacitor element included in the solid electrolytic capacitor includes an anode body, a dielectric layer formed on the surface of the anode body, and a cathode portion covering at least a portion of the dielectric layer. The cathode portion includes a solid electrolyte layer covering at least a portion of the dielectric layer. Hereinafter, the solid electrolytic capacitor element may be simply referred to as a capacitor element.

[0034] (Capacitor element) (anode foil) The anode foil may contain a valve metal, an alloy containing a valve metal, or a compound containing a valve metal. The anode foil may contain one of these materials or a combination of two or more of them. Preferred examples of the valve metal include aluminum, tantalum, niobium, and titanium.

[0035] The anode foil has a porous portion at least on the surface layer. The anode foil has a large number of fine pores in the porous portion. Due to such porous portion, the anode body has a fine uneven shape at least on the surface. An anode foil having a porous portion on the surface layer can be obtained, for example, by roughening the surface of a base material (such as a metal foil) containing a valve metal. The roughening may be performed, for example, by etching (electrolytic etching, chemical etching, etc.). Such an anode foil has, for example, porous portions formed integrally with the core on the surfaces of both the base material (core) and the core.

[0036] The anode foil is divided into a second portion where the cathode portion is formed, with a dielectric layer interposed between them, and a first portion that is the remaining portion. The second portion is sometimes referred to as the cathode forming portion, and the first portion is sometimes referred to as the anode lead portion (or anode portion). The anode foil has a first end and a second end opposite the first end. The first end and second end correspond to both ends of the anode foil in the longitudinal direction. The first portion includes the first end, and the second portion includes the second end. An insulating region is formed between the first end and the second end. The longitudinal direction of the anode foil is the direction connecting the center of the end face of the first end and the center of the end face of the second end when the anode foil is stretched (unbent).

[0037] The porous portion may be formed in the portion that forms the second portion and the insulating region, or may be formed on the entire surface of both the anode foils (specifically, the second portion and the first portion). The first portion is used for electrical connection with an external electrode on the anode side. For example, one end of an anode lead is electrically connected to the first portion, and the other end of the anode lead is pulled out from the exterior body and electrically connected to the external electrode.

[0038] Anode foil thickness (t fThe thickness t of the anode foil may be 50 μm or more and 200 μm or less, or 70 μm or more and 150 μm or less. f is determined by measuring the thickness of the anode foil at multiple points (for example, five points) using a sample for determining the filling rate of the cured product described below, and averaging the measured values.

[0039] (dielectric layer) The dielectric layer is formed, for example, so as to cover at least a portion of the surface of the anode foil. The dielectric layer is an insulating layer that functions as a dielectric. The dielectric layer is formed by anodizing the valve metal on the surface of the anode foil using a chemical conversion treatment or the like. Because the dielectric layer is formed on the porous surface of the anode foil, the surface of the dielectric layer has a fine uneven shape corresponding to the shape of the porous portion of the anode foil.

[0040] 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 examples, as long as it functions as a dielectric.

[0041] (insulation area) The insulating region is provided with a predetermined width in a portion where the porous portion is formed between the first end and the second end of the anode foil. The insulating region may be formed, for example, at the end of the first portion on the second portion side. However, there are cases where a cathode portion is formed at the end of the surface of the insulating region on the second portion side. In other words, there are cases where the insulating region is provided from the end of the first portion on the second portion side to the end of the second portion on the first portion side. From the viewpoint of more reliably ensuring insulation between the first portion and the cathode portion, it is preferable that the insulating region is not provided in the second portion.

[0042] The insulating region includes a cured product of the resin composition. In the insulating region, the cured product fills the pores of the porous region. The Tg of the cured product is 230°C or higher, and may be 250°C or higher. When the Tg of the cured product is as high as this, the viscosity of the treatment liquid containing the resin composition for forming the insulating region tends to increase, and the ability of the resin composition to fill the pores of the porous region tends to decrease. Furthermore, even if the treatment liquid is diluted with a solvent, the dry solid content of the treatment liquid decreases, and the ability of the resin composition to fill the pores tends to decrease. In the present disclosure, the resin composition includes an insulating resin material and an additive (hereinafter sometimes referred to as a first additive) that modifies the insulating resin material, and the content of the additive in the resin composition is 3% by mass or higher. Therefore, despite the Tg of the cured product of the resin composition being high as described above and the tendency for the viscosity of the treatment liquid containing the resin composition to increase, the pores can be highly filled with the resin composition (or its cured product). Therefore, the insulating region makes it easier to ensure insulation between the cathode part and the first part (anode part), thereby reducing leakage current.

[0043] The content of the first additive in the resin composition is 3% by mass or more, and may be 5% by mass or more, 10% by mass or more, or 13% by mass or more. When the resin composition contains the first additive at such a content, the viscosity of the treatment liquid for forming an insulating region can be kept low while maintaining a high dry solids content, and the pore filling ability of the resin composition (or its cured product) can be improved. The content of the first additive in the resin composition is, for example, 60% by mass or less, and may be 55% by mass or less, or 50% by mass or less. When the content of the first additive is within such a range, it is easy to ensure a high Tg of the cured product. These lower and upper limits can be arbitrarily combined. The content of the first additive in the resin composition may be, for example, 3% by mass or more (or 5% by mass or more) and 60% by mass or less, or 10% by mass or more (or 13% by mass or more) and 60% by mass or less. Within these ranges, the upper limit may be changed to the above value.

[0044] The viscosity at 25°C of a γ-butyrolactone solution containing a resin composition at a concentration of 30% by mass may be 10,000 mPa·s or less, 8,000 mPa·s or less, or even 6,000 mPa·s or less. The concentration of the resin composition in the solution is the dry solids content (mass%) in the solution. Because the Tg of the cured product is high as described above, solutions containing resin compositions with such high dry solids content tend to have high viscosities. However, in the present disclosure, the first additive is used at the above-described content, thereby enabling the viscosity of the solution to be kept low. From the viewpoint of easily retaining the treatment liquid for forming an insulating region in a predetermined position and forming an insulating region, the viscosity of the solution at 25°C may be, for example, 1,000 mPa·s or more, or even 2,000 mPa·s or more. These upper and lower limits may be combined arbitrarily.

[0045] The viscosity of the solution can be measured using a cone-plate viscometer at a rotation speed of 60 rpm.

[0046] Examples of insulating resin materials include resin materials whose cured product has a Tg in the above range. Examples of insulating resin materials include curable resins, but thermoplastic resins can also be used. When a thermoplastic resin is used as the insulating resin material, a cured product of the resin composition is formed, for example, by a reaction between the first additive and the thermoplastic resin. When the insulating resin material is a curable resin, it is preferable that the Tg of the cured product of the curable resin itself is also high. The Tg of the cured product of the curable resin may be 230°C or higher, or 250°C or higher.

[0047] Examples of insulating resin materials include curable resins (such as polyimide resins, silicone resins, phenolic resins, urea resins, melamine resins, unsaturated polyesters, furan resins, polyurethanes, silicone resins (silicones), curable acrylic resins, and epoxy resins), photoresists, and thermoplastic resins (such as polyamides, polyamideimides, thermoplastic polyimides, polyphenylene sulfone resins, polyethersulfone resins, cyanate ester resins, and fluororesins). Polyimide resins (especially curable polyimide resins) are preferred because they provide a high Tg for the cured product and ensure high heat resistance. Examples of curable polyimide resins include curable polyamideimides and curable polyimides. The insulating resin material may contain one of these resins or a combination of two or more of them. Depending on the type of resin, the insulating resin material may include polymerized resins as well as resin precursors (such as monomers, oligomers, or prepolymers). The curable resin may be a one-component curing type or a two-component curing type. The resin composition may contain, in addition to the insulating resin material and the first additive, at least one selected from the group consisting of a curing agent, a curing accelerator, a polymerization initiator, a catalyst, and the like.

[0048] The Tg of the cured product of the resin composition can be determined, for example, by dynamic mechanical analysis (DMA) under conditions of a temperature rise rate of 2°C / min and a frequency of 1 Hz.

[0049] The first additive is a component that modifies the insulating resin material. The first additive preferably contains a component that interacts or reacts with the insulating resin material. Examples of the first additive include a silane coupling agent, a surface tension modifier, an epoxy compound or a polymer thereof. However, a component different from the insulating resin material is used as the first additive. The resin composition may contain one type of first additive or a combination of two or more types. It is believed that when the resin composition contains the first additive at a relatively high content, such as 3 mass% or more, the first additive penetrates between the molecular chains of the insulating resin material, improving the fluidity and the permeability of the resin composition into the pores of the porous portion.

[0050] Examples of silane coupling agents include tetraalkoxysilanes (such as tetramethoxysilane), alkoxysilanes having a hydrocarbon group (such as methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, and phenyltrimethoxysilane), and alkoxysilanes having a functional group (such as 3-(trimethoxysilyl)propylamine, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-(trimethoxysilyl)propyl methacrylate, and 3-glycidoxypropyltrimethoxysilane). The content of the silane coupling agent in the resin composition may be low, or the resin composition may not contain a silane coupling agent.

[0051] Surface tension modifiers include antifoaming agents, silicone-based and non-silicone-based surface tension modifiers, etc. Silicon-based surface tension modifiers include silicone oil, silicone-based surfactants, and silicone-based synthetic lubricating oils, etc. Non-silicone surface tension modifiers include lower alcohols, mineral oils, oleic acid, polypropylene glycol, glycerin higher fatty acid esters, higher alcohol borate esters, and fluorine-containing surfactants, etc.

[0052] Examples of epoxy compounds include glycidyl ethers, glycidyl esters, and alicyclic epoxy compounds. Examples of epoxy compounds include bisphenol-type epoxy compounds (such as bisphenol A-type epoxy compounds and bisphenol F-type epoxy compounds), polycyclic aromatic epoxy compounds (such as naphthalene-type epoxy compounds), and novolac-type epoxy compounds. Examples of epoxy compound polymers include reaction products of epoxy compounds with active hydrogen-containing compounds (such as amines, hydroxy compounds, phenolic compounds, and acid anhydrides). Epoxy compounds and their polymers are preferably liquid (fluid) at 25°C. These epoxy compounds and their polymers not only reduce the viscosity of the treatment solution but also react with insulating resin materials such as polyimide resins to be incorporated into the cured product, making them particularly effective in enhancing the filling of the pores of porous portions with the cured product.

[0053] The resin composition may optionally contain, in addition to the first additive, a known additive (second additive) used to form the insulating region of the capacitor element, such as a flame retardant, a filler, a colorant, a release agent, or an inorganic ion scavenger.

[0054] In the present disclosure, the pores of the porous portion in the insulating region can be highly filled with a resin composition (or a cured product thereof) containing an insulating resin material. In a cross section of the solid electrolytic capacitor element in the insulating region (more specifically, a cross section of the portion including the insulating region and the anode foil), the ratio of the area of ​​the cured material filled in the pores to the total area of ​​the pores (filling rate of the cured material) is, for example, 80% or more.

[0055] The filling rate of the cured product can be determined using an anode foil with an insulating region formed before the solid electrolyte layer is formed (before precoating). More specifically, the anode foil with an insulating region formed thereon is embedded in a curable resin, and the curable resin is cured. The cured product is polished or cross-section polished to expose a cross section parallel to the thickness direction of the insulating region and the length direction of the anode foil. This cross section is taken as a cross section passing through the center of the width of the insulating region (in other words, the length in the direction parallel to the width direction of the anode foil). In this way, a sample for measurement is obtained. The cross section of the sample is then image-processed to separate the metal portion (including the dielectric layer portion) constituting the anode foil, the void portion, and the portion occupied by the cured product. The percentage (%) of the area occupied by the cured product relative to the total area of ​​the void portion and the portion occupied by the cured product is determined and used as the filling rate of the cured product. Each area is measured in an image that allows observation of the cross section of the anode foil in the thickness direction, including the entire portion where the insulating region is formed, for a portion 0.5L long centered at the center of the length L of the insulating region in the length direction, and for the entire porous portion in the thickness direction (both porous portions if porous portions are formed on both surface layers).

[0056] In the insulating region, the cured product may be formed not only in the pores but also on the main surface of the anode foil via a dielectric layer. If necessary, a sheet-like insulating material such as insulating tape may be attached to the main surface of the anode foil.

[0057] When the cured product is formed on the main surface of the anode foil via a dielectric layer, the maximum thickness t of the cured product formed on the dielectric layer on the main surface of the anode foil is c The maximum thickness t may be 20 μm or less, or may be 15 μm or less. c When the thickness t is in this range, the leakage current is further reduced, and the incidence of short circuits can be kept low. In addition, when stacking capacitor elements, the stress on the bent lead frame can be kept low. c The maximum thickness t may be 0 μm or more. cis the maximum thickness of the cured product on one main surface of the anode foil. The thickness of the cured product is measured using the cross-sectional sample used to measure the filling rate.

[0058] The maximum thickness of the cured product t c of the anode foil thickness t f Ratio to (=t c / t f ) may be 0.12 or less, 0.11 or less, or 0.10 or less. c / t f When the ratio is in this range, the leakage current is further reduced, and the incidence of short circuits can be kept low. c / t f The ratio may be 0.01 or greater.

[0059] The insulating region can be formed, for example, by a process (third process) including a sub-step of filling the pores of the porous portion with a treatment liquid containing a resin composition and a solvent, and curing the resin composition.

[0060] The dry solids content of the treatment liquid (concentration of the resin composition) may be, for example, 30% by mass or more, or 30% by mass to 50% by mass. The viscosity of the treatment liquid at 25°C may be 1,000 mPa·s to 50,000 mPa·s, 2,000 mPa·s to 35,000 mPa·s, or 2,500 mPa·s to 30,000 mPa·s. In the present disclosure, by combining a resin composition having a high Tg of cured product as described above with a specific content of a first additive, the viscosity of the treatment liquid for forming the insulating region can be kept low, even if the dry solids content of the treatment liquid is high as described above. This allows the resin composition (or its cured product) to be densely filled into the pores of the porous portion, reducing the penetration of conductive material into voids remaining in the insulating region and thus reducing leakage current. The viscosity of the treatment liquid can be measured using a cone-plate viscometer at a rotation speed of 60 rpm.

[0061] In the method for manufacturing a capacitor element, prior to the third step of forming an insulating region, a first step of preparing an anode foil having a porous portion on its surface and a first portion including a first end and a second portion including a second end opposite the first end, and a second step of forming a dielectric layer on the surface of the porous portion are performed. For each step, please refer to the descriptions of the anode foil and the dielectric layer.

[0062] (cathode) The cathode section is formed so as to cover at least a portion of the dielectric layer formed on the surface of the anode body. The cathode section includes at least a solid electrolyte layer. The cathode section may include, for example, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte layer. Each layer constituting the cathode section can be formed by a known method depending on the layer configuration of the cathode section.

[0063] The components of the cathode section will be described below.

[0064] (Solid electrolyte layer) The solid electrolyte layer contains, for example, a conductive polymer (such as a conjugated polymer or a dopant), and may contain a manganese compound, an additive, or the like.

[0065] Examples of conjugated polymers include known conjugated polymers used in solid electrolytic capacitors, such as π-conjugated polymers. Examples of conjugated polymers include polymers with a basic skeleton of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, and polythiophene vinylene. The polymer may contain at least one monomer unit constituting the basic skeleton. The monomer unit may also contain a monomer unit having a substituent. Examples of the polymers include homopolymers and copolymers of two or more monomers. For example, polythiophenes include poly(3,4-ethylenedioxythiophene). The solid electrolyte layer may contain one type of conjugated polymer or a combination of two or more types.

[0066] As the dopant, a polymer anion such as polystyrene sulfonic acid (PSS) may be used. Alternatively, as the dopant, a compound capable of generating an anion (e.g., aromatic sulfonic acid such as naphthalene sulfonic acid or toluene sulfonic acid) may be used. However, the dopant is not limited to these.

[0067] The solid electrolyte layer is formed so as to cover at least a portion of the dielectric layer (fourth step). From the viewpoint of ensuring insulation from the first portion, the solid electrolyte layer is formed after the insulating region is formed (after the third step).

[0068] The solid electrolyte layer may be formed, for example, by in situ polymerization (more specifically, polymerization on a dielectric layer) of a conjugated polymer precursor (e.g., a monomer or oligomer) in the presence of a dopant. Examples of the dopant include aromatic sulfonic acid. In situ polymerization may involve at least one of chemical polymerization and electrolytic polymerization. Alternatively, the solid electrolyte layer may be formed by depositing a treatment liquid (solution or dispersion) containing a conductive polymer (e.g., a conjugated polymer and a dopant) on the dielectric layer and drying it. Examples of the dispersion medium (solvent) include water, an organic solvent, or a mixture thereof. The solid electrolyte layer may be formed by combining a method using in situ polymerization and a method using a treatment liquid containing a conductive polymer. For example, a portion of the solid electrolyte layer may be formed using in situ polymerization, and then the remaining portion of the solid electrolyte layer may be formed using a treatment liquid containing a conductive polymer.

[0069] In electropolymerization, the surface of the dielectric layer may be precoated prior to polymerization. The precoating may be performed, for example, using a liquid composition (such as a liquid dispersion) containing a conductive material. More specifically, the precoating may be performed using a liquid dispersion containing a conductive polymer (such as a conjugated polymer and a dopant). The liquid dispersion used for precoating has a small particle size and a low concentration of the conductive polymer. For example, the average primary particle size of the conductive polymer particles contained in the liquid dispersion for precoating is, for example, 100 nm or less.

[0070] Because the polymerization liquid used in in-situ polymerization easily penetrates into the fine recesses of the dielectric layer, methods using in-situ polymerization are suitable for forming a solid electrolyte at least in the fine recesses of the dielectric layer. Therefore, the step of forming a solid electrolyte layer (step 4) may include a substep (substep 2) of forming at least a portion of the solid electrolyte layer by in-situ polymerization of a conjugated polymer precursor in the presence of a dopant. Furthermore, prior to the second substep, a substep (substep 1) of precoating the surface of the dielectric layer with a liquid composition containing a conductive material may be performed. The precoating liquid composition also easily penetrates into the fine recesses of the dielectric layer. In the present disclosure, the filling ability of the cured resin composition in the porous portion of the insulating region can be improved. Therefore, even when forming at least a portion of the solid electrolyte layer by in-situ polymerization or when precoating is performed, the penetration of the polymerization liquid or the precoating liquid composition into voids in the insulating region or the first portion can be effectively prevented. Therefore, even in such cases, leakage current can be reduced.

[0071] (Cathode extraction layer) The cathode extraction layer may include at least a first layer that is in contact with the solid electrolyte layer and covers at least a portion of the solid electrolyte layer, and may also include a first layer and a second layer that covers the first layer. Examples of the first layer include a layer containing conductive particles and metal foil. Examples of the conductive particles include at least one selected from conductive carbon and metal powder. For example, the cathode extraction layer may be formed of a first layer containing conductive carbon (also referred to as a carbon layer) and a second layer containing metal powder or metal foil. When metal foil is used as the first layer, the cathode extraction layer may be formed of this metal foil.

[0072] Examples of conductive carbon include graphite (artificial graphite, natural graphite, etc.).

[0073] The second layer containing metal powder can be formed, for example, by laminating a composition containing metal powder on the surface of the first layer. Examples of such second layers include metal paste layers (such as silver paste layers) formed using a composition containing metal powder such as silver particles and a resin (binder resin). While thermoplastic resins can be used as the resin, it is preferable to use thermosetting resins such as imide resins and epoxy resins.

[0074] When a metal foil is used as the first layer, the type of metal is not particularly limited, but it is preferable to use a valve metal such as aluminum, tantalum, or niobium, or an alloy containing a valve metal. If necessary, the surface of the metal foil may be roughened. The surface of the metal foil may be provided with a chemical conversion coating, or may be provided with a coating of a metal (dissimilar metal) or a nonmetal different from the metal constituting the metal foil. Examples of dissimilar metals and nonmetals include metals such as titanium and nonmetals such as carbon (e.g., conductive carbon).

[0075] The coating of the dissimilar metal or non-metal (for example, conductive carbon) may be the first layer, and the metal foil may be the second layer.

[0076] The method for producing a capacitor element may further include a step (fifth step) of forming a cathode extraction layer.

[0077] (separator) When a metal foil is used for the cathode extraction layer, a separator may be disposed between the metal foil and the anode foil. The separator is not particularly limited, and may be, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (e.g., aliphatic polyamide, aromatic polyamide such as aramid).

[0078] (others) A solid electrolytic capacitor includes, for example, at least one capacitor element and an exterior body that seals the capacitor element. A solid electrolytic capacitor may include two or more capacitor elements. A solid electrolytic capacitor may be a wound type, or may be either a chip type or a stacked type. For example, a solid electrolytic capacitor may include two or more wound capacitor elements, or may include two or more stacked capacitor elements. The configuration of the capacitor elements may be selected depending on the type of solid electrolytic capacitor.

[0079] In the capacitor element, one end of the cathode lead is electrically connected to the cathode extraction layer. One end of the anode lead is electrically connected to the anode body. The other end of the anode lead and the other end of the cathode lead are each drawn out from the resin exterior body or the case. The other end of each lead exposed from the resin exterior body or the case is used for soldering to a substrate on which the solid electrolytic capacitor is to be mounted. Each lead may be a lead wire or a lead frame.

[0080] A solid electrolytic capacitor can be obtained, for example, by a manufacturing method including a step of forming a capacitor element and a step of sealing at least one solid electrolytic capacitor element with an exterior body. The capacitor element is formed, for example, by the above-mentioned manufacturing method (for example, a manufacturing method including steps 1 to 5, etc.). For example, when manufacturing a solid electrolytic capacitor including two or more stacked capacitor elements, the manufacturing method further includes a step of stacking the two or more capacitor elements prior to the sealing step. Then, in the sealing step, the two or more stacked capacitor elements are sealed with an exterior body.

[0081] The exterior body also includes a case. The exterior body may contain a resin. For example, the capacitor element and the resin material of the exterior body (e.g., uncured thermosetting resin and filler) may be placed in a mold, and the capacitor element may be sealed in the resin exterior body by transfer molding, compression molding, or the like. At this time, the other end of the anode lead and the other end of the cathode lead drawn out from the capacitor element are exposed from the mold. Alternatively, the capacitor element may be housed in a bottomed case such that the other end of the anode lead and the other end of the cathode lead are positioned on the opening side of the bottomed case, and the opening of the bottomed case may be sealed with a sealant to form a solid electrolytic capacitor.

[0082] The solid electrolytic capacitor may further include a case disposed on the outside of the resin outer casing, as needed. Examples of resin materials constituting the case include thermoplastic resins and compositions containing thermoplastic resins. Examples of metal materials constituting the case include metals such as aluminum, copper, and iron, and alloys thereof (including stainless steel and brass).

[0083] Fig. 1 is a cross-sectional view schematically illustrating the structure of a solid electrolytic capacitor according to a first embodiment of the present disclosure, and Fig. 2 is an enlarged cross-sectional view schematically illustrating a capacitor element 2 included in the solid electrolytic capacitor of Fig. 1.

[0084] The solid electrolytic capacitor 1 includes a capacitor element 2, an exterior housing 3 that seals the capacitor element 2, and an anode lead terminal 4 and a cathode lead terminal 5, at least a portion of which is exposed to the outside of the exterior housing 3. The exterior housing 3 has a substantially rectangular parallelepiped outer shape, and the solid electrolytic capacitor 1 also has a substantially rectangular parallelepiped outer shape.

[0085] Capacitor element 2 includes anode foil 6, a dielectric layer (not shown) covering the surface of anode foil 6, and cathode portion 8 covering the dielectric layer. The dielectric layer may be formed on at least a portion of the surface of anode foil 6.

[0086] Cathode section 8 includes solid electrolyte layer 9 and cathode extraction layer 10. Solid electrolyte layer 9 is formed so as to cover at least a portion of the dielectric layer. Cathode extraction layer 10 is formed so as to cover at least a portion of solid electrolyte layer 9. Cathode extraction layer 10 has a first layer 11 which is a carbon layer and a second layer 12 which is a metal paste layer. Cathode lead terminal 5 is electrically connected to cathode section 8 via adhesive layer 14 formed of a conductive adhesive.

[0087] The anode foil 6 includes a substrate portion (core portion) 6a and a porous portion 6b formed on the surface of the substrate portion 6a. The anode foil 6 includes a second portion II, which is a cathode-forming portion where a solid electrolyte layer 9 (or cathode portion 8) is formed, and a first portion I other than the second portion II. The first portion I includes at least an anode portion ia. The anode portion ia of the anode foil 6 is electrically connected to the anode lead terminal 4 by welding. The anode foil 6 has a first end portion Ie on the side connected to the anode lead terminal 4 and a second end portion IIe on the opposite side to the first end portion Ie.

[0088] An insulating region 13 is provided between the first end Ie and the second end IIe of the anode foil 6. The insulating region 13 may be provided on the end side of the first portion I on the second portion II side. The insulating region 13 contains at least a cured product of the resin composition that has filled the pores of the porous portion 6b.

[0089] The exterior housing 3 covers the capacitor element 2 and portions of the lead terminals 4 and 5. From the viewpoint of preventing air from entering the exterior housing 3, it is desirable that the capacitor element 2 and portions of the lead terminals 4 and 5 are sealed within the exterior housing 3. While FIG. 1 shows a case in which the exterior housing 3 is a resin exterior housing, this is not limiting and the exterior housing 3 may be a case that can house the capacitor element 2. The resin exterior housing is formed by sealing the capacitor element 2 and portions of the lead terminals 4 and 5 with a resin material.

[0090] One end of each of the lead terminals 4 and 5 is electrically connected to the capacitor element 2, and the other end is drawn out of the exterior of the package 3. In the solid electrolytic capacitor 1, the one end side of each of the lead terminals 4 and 5 is covered by the package 3 together with the capacitor element 2.

[0091] [Example] The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0092] Examples 1 and 2 and Comparative Example 1 (1) Preparation of anode foil with a dielectric layer An aluminum foil (thickness: 100 μm) was prepared as a substrate, and both surfaces of the aluminum foil were etched to obtain an anode foil having a porous surface layer (thickness: 35 μm on one main surface of the aluminum foil and 35 μm on the other main surface).

[0093] The anode foil was immersed in the chemical conversion solution, and a direct current voltage was applied to form a dielectric layer containing aluminum oxide on the surface of the anode foil.

[0094] (2) Formation of insulating regions At a predetermined position between the first and second ends of the anode foil on which the dielectric layer was formed, both surfaces of the anode foil were impregnated with a treatment liquid containing a resin composition in a band-like pattern along the entire width of the anode foil. The resin composition was then cured by heating at 200°C for 30 minutes. The resin composition cured while filling the pores of the porous portion. In this way, an insulating region containing a cured product was formed. The treatment liquid used was a liquid composition containing a curable polyamide-imide resin (precursor), γ-butyrolactone as a solvent, and a bisphenol A-type liquid epoxy resin (polymer) as a first additive. The dry solids content (mass%) of the liquid composition, the content (mass%) of the first additive in the resin composition (dry solids content of the liquid composition), the viscosity (mPa·s) of the liquid composition at 25°C, and the Tg (°C) of the cured resin composition are shown in Table 1.

[0095] (3) Formation of solid electrolyte layer The second portion of the anode foil having the insulating region obtained in (2) above on the second end side was immersed in a liquid composition containing a conductive material, removed, and dried to perform precoating. A power supply tape was attached to the surface of the insulating region.

[0096] A polymerization solution (liquid composition) containing pyrrole (monomer of conjugated polymer), naphthalenesulfonic acid (dopant), and water was prepared. A precoated anode foil and a counter electrode were immersed in the resulting polymerization solution. A voltage was applied to the power supply tape so that the potential of the power supply tape was 2.0 V (=polymerization voltage), and electrolytic polymerization was performed at 25°C to form a solid electrolyte layer. The polymerization voltage was the potential of the power supply relative to the reference electrode (silver / silver chloride reference electrode).

[0097] (4) Formation of cathode extraction layer The anode foil with the solid electrolyte layer formed thereon obtained in (3) above was immersed in a dispersion liquid in which graphite particles were dispersed in water, and then removed from the dispersion liquid and dried to form a carbon layer (first layer) at least on the surface of the solid electrolyte layer. The drying was carried out at 150°C for 30 minutes.

[0098] A silver paste containing silver particles and a binder resin (epoxy resin) was applied to the surface of the carbon layer, and the binder resin was cured by heating at 150°C for 30 minutes to form a silver paste layer (second layer). In this way, a cathode extraction layer consisting of the carbon layer and the silver paste layer was formed, and a cathode part consisting of the solid electrolyte layer and the cathode extraction layer was completed.

[0099] (5) Assembly of solid electrolytic capacitors The cathode part of the capacitor element obtained in (4) above was joined to one end of a cathode lead terminal via an adhesive layer of a conductive adhesive. One end of the anode lead terminal was joined by laser welding to the surface of the first end side of the first part of the anode foil protruding from the capacitor element.

[0100] Next, a resin outer package made of insulating resin was formed around the capacitor element by molding. At this time, the other end of the anode lead terminal and the other end of the cathode lead terminal were extended from the resin outer package. In this way, a total of 20 solid electrolytic capacitors were completed.

[0101] (6) Evaluation The following evaluations were carried out using a liquid composition containing a resin composition or a solid electrolytic capacitor.

[0102] (a) Viscosity of treatment liquid (liquid composition) and solution with a concentration of 30% by mass The viscosity of the treatment liquid at 25°C was measured using the procedure described above. The treatment liquid was diluted with γ-butyrolactone so that the concentration of the resin composition in the treatment liquid was 30% by mass. The viscosity of the resulting solution at 25°C was measured.

[0103] (b) Tg of the cured product of the resin composition A cured product of the resin composition was prepared using the treatment liquid, and the Tg of the cured product was measured according to the procedure described above.

[0104] (c) Initial capacitance, tanδ, and ESR (equivalent series resistance) Using a four-terminal LCR meter at 20°C, the initial capacitance (μF) and initial tanδ at a frequency of 120 Hz of each solid electrolytic capacitor were measured, as well as the initial ESR (mΩ) at a frequency of 100 kHz. The average values ​​for 20 solid electrolytic capacitors were calculated. The results for each example are shown as relative values, with the result for Comparative Example 1 set at 100.

[0105] (d) Leakage current (LC) A 1 kΩ resistor was connected in series to the solid electrolytic capacitor, and a rated voltage of 25 V was applied from a DC power supply for 1 minute, after which the leakage current (μA) was measured and the average value for 20 solid electrolytic capacitors was calculated. The results for each example are shown as relative values, with the result of Comparative Example 1 being set at 100.

[0106] The evaluation results are shown in Table 1. In Table 1, E1 and E2 are Examples 1 and 2, and C1 is Comparative Example 1.

[0107] [Table 1]

[0108] As shown in Table 1, the leakage current in the Examples was significantly reduced compared to Comparative Example 1, in which the content of the first additive in the resin composition was 0.1% by mass. Polyimide-based resins, such as polyamide-imide resins, tend to have high Tg values ​​and thus high viscosity treatment solutions. Diluting such resins with a solvent reduces the dry solid content of the treatment solution, making it difficult to fill the pores of the porous portion at a high filling rate. Even when the first additive is added, if the content of the first additive is low, maintaining a certain dry solid content makes it difficult to highly fill the pores of the porous portion with the resin composition. In contrast, the resin compositions in the Examples contain a higher amount of the first additive than in Comparative Example 1. This allows the viscosity of the treatment solution containing the resin composition to be reduced while maintaining a relatively high dry solid content, despite the use of an insulating resin material that provides a high Tg, such as a polyimide-based resin. Therefore, the resin composition can be highly filled into the pores of the porous portion, and the precoat liquid composition or the polymerizable liquid for forming the solid electrolyte layer is prevented from penetrating into the pores of the porous portion in the insulating region or through the pores to the first portion. Therefore, in the examples, the insulating properties of the insulating region were improved, ensuring insulation between the cathode portion and the first portion, which is thought to have significantly reduced leakage current. In the examples, the filling rate of the cured material in the insulating region determined by the above-described procedure was 80% or more.

[0109] Furthermore, in the example, while maintaining a high initial capacitance equivalent to that of the comparative example, tan δ and ESR can be significantly reduced compared to the comparative example. Thus, in the example, while maintaining excellent initial capacitor performance, the leakage current can be reduced as described above.

[0110] Examples 3 to 6 In Example 1 (2), the dry solid content (mass%) of the liquid composition and the viscosity of the liquid composition at 25°C were adjusted to obtain a ratio of t c / t f was adjusted to the values ​​shown in Table 2. A solid electrolytic capacitor was fabricated in the same manner as in Example 1 except for these. The leakage current (LC) was evaluated using the procedure (d) above, and the percentage (%) of the number of solid electrolytic capacitors for which a leakage current exceeding 0.068 mA was measured was calculated as the LC defect rate. At this time, the percentage (%) of the number of solid electrolytic capacitors for which a leakage current exceeding 1 mA was measured was calculated as the short-circuit defect rate. The results are shown in Table 2. In Table 2, E3 to E6 are Examples 3 to 6.

[0111] [Table 2]

[0112] As shown in Table 2, in order to ensure a lower LC defect rate, the ratio t c / t f is preferably 0.12 or less, more preferably 0.11 or less or 0.10 or less. c / t f When is in such a range, the short-circuit defect rate can also be kept low.

[0113] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention. [Industrial Applicability]

[0114] The solid electrolytic capacitor of the present disclosure has reduced leakage current and excellent capacitor performance, and therefore can be used in a variety of applications that require high reliability, for example. [Explanation of symbols]

[0115] 1: Solid electrolytic capacitor 2: Capacitor element 3: Exterior body 4: Anode lead terminal 5: Cathode lead terminal 6: Anode foil 6a: Base material part (core part) 6b: Porous part 8: Cathode 9: Solid electrolyte layer 10: Cathode extraction layer 11: Carbon layer (first layer) 12: Silver paste layer (second layer) 13: Insulation area 14: Adhesive layer I: Part 1 II:Second part Ie: 1st end IIe: Second end ia: Anode part

Claims

1. an anode foil having a porous portion on a surface layer thereof, and having a first portion including a first end portion and a second portion including a second end portion opposite to the first end portion; a dielectric layer formed on the surface of the porous portion; and A solid electrolytic capacitor element including a solid electrolyte layer covering at least a portion of the dielectric layer, the solid electrolytic capacitor element has an insulating region containing a cured product of a resin composition between the first end and the second end of the anode foil, In the insulating region, the cured material fills the pores of the porous portion, the resin composition includes an insulating resin material and an additive that modifies the insulating resin material; The content of the additive in the resin composition is 3% by mass or more, The glass transition point of the cured product is 230°C or higher, In the insulating region, the cured product is further formed on a main surface of the anode foil via the dielectric layer, On a main surface of the anode foil, the maximum thickness of the cured material formed on the dielectric layer on one main surface side of the anode foil is tc, and the thickness of the anode foil is tf, A solid electrolytic capacitor element, wherein the ratio of the maximum thickness tc of the cured product to the thickness tf of the anode foil (=tc / tf) is 0.12 or less.

2. 2. The solid electrolytic capacitor element according to claim 1, wherein the viscosity of a gamma-butyrolactone solution containing the resin composition at a concentration of 30% by mass at 25°C is 1,000 mPa·s or more and 10,000 mPa·s or less.

3. 3. The solid electrolytic capacitor element according to claim 1, wherein the content of the additive in the resin composition is 60% by mass or less.

4. The solid electrolytic capacitor element according to claim 1 , wherein the additive interacts or reacts with the insulating resin material.

5. 3. The solid electrolytic capacitor element according to claim 1, wherein the additive comprises a polymer of an epoxy compound.

6. 3. The solid electrolytic capacitor element according to claim 1, wherein the insulating resin material includes a polyimide resin.

7. 3. The solid electrolytic capacitor element according to claim 1, wherein in the cross section of the solid electrolytic capacitor element in the insulating region, the ratio of the area of ​​the cured material filled in the pores to the total area of ​​the pores is 80% or more.

8. A solid electrolytic capacitor comprising at least one solid electrolytic capacitor element according to claim 1 or 2.

9. The solid electrolytic capacitor according to claim 8 , further comprising an exterior body that seals the solid electrolytic capacitor element.

10. a first step of preparing an anode foil having a porous portion on a surface layer thereof and having a first portion including a first end and a second portion including a second end opposite to the first end; a second step of forming a dielectric layer on the surface of the porous portion; a third step of forming an insulating region containing a cured product of a resin composition between the first end and the second end of the anode foil; a fourth step of forming a solid electrolyte layer covering at least a portion of the dielectric layer; the resin composition includes an insulating resin material and an additive that modifies the insulating resin material, the content of the additive in the resin composition is 3 mass% or more, and the glass transition point of the cured product is 230°C or more; In the third step, a treatment liquid containing the resin composition and a solvent is applied to a main surface of the anode foil on which the dielectric layer is formed, and the treatment liquid is filled into pores of the porous portion, and the resin composition is cured to form the insulating region containing the cured product; On a main surface of the anode foil, the maximum thickness of the cured material formed on the dielectric layer on one main surface side of the anode foil is tc, and the thickness of the anode foil is tf, a ratio of a maximum thickness tc of the cured product to a thickness tf of the anode foil (=tc / tf) of 0.12 or less.

11. 11. The method for producing a solid electrolytic capacitor element according to claim 10, wherein the treatment liquid has a dry solid content of 30% by mass or more and a viscosity at 25°C of 1,000 mPa·s or more and 50,000 mPa·s or less.

12. 12. The method for manufacturing a solid electrolytic capacitor element according to claim 10, wherein the fourth step includes a second substep of forming at least a part of the solid electrolyte layer by in situ polymerization of a precursor of a conjugated polymer in the presence of a dopant.

13. The method for manufacturing a solid electrolytic capacitor element according to claim 12, wherein the fourth step includes a first substep of precoating the surface of the dielectric layer with a liquid composition containing a conductive material prior to the second substep.

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