JP2018206868A - Solid electrolytic capacitor and manufacturing method thereof - Google Patents

Abstract

To provide a solid electrolytic capacitor having a large electrostatic capacity and suppressing an LC rise during a high temperature and high humidity test, and a manufacturing method thereof.SOLUTION: There is provided a solid electrolytic capacitor that includes a valve metal, an oxide film layer formed on the surface of the valve metal, and a solid electrolyte layer formed on the oxide film layer, and the solid electrolyte layer includes a set of a first conductive polymer and a first solid electrolyte layer containing a moisture retaining substance and a set of a second conductive polymer and a second solid electrolyte layer containing a resin which is a polycondensate of at least one water-soluble polyhydric alcohol and at least one water-soluble polyvalent carboxylic acid. There is provided a manufacturing method of the solid electrolytic capacitor.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a solid electrolytic capacitor using a conductive polymer material for a solid electrolyte layer, and a method for manufacturing the same.

  A solid electrolytic capacitor usually includes a valve metal (valve action metal), an oxide film layer formed on the surface of the valve metal, and a solid electrolyte layer formed on the oxide film layer. . Various conductive polymer materials used for the solid electrolyte layer have been studied so far.

  Patent Document 1 discloses a solid electrolytic capacitor in which the capacitor element including the valve metal, the oxide film layer, and the solid electrolyte layer includes an organic compound having a boiling point of 150 ° C. or higher and a melting point of 150 ° C. or lower.

  Patent Document 2 discloses a conductive polymer, at least one water-soluble polyhydric alcohol, and at least one water-soluble organic substance having two or more functional groups capable of polycondensation with the water-soluble polyhydric alcohol. An electrolytic capacitor having an electrolyte layer containing a conductive polymer suspension aqueous solution containing bismuth is disclosed.

JP 2001-196271 A JP 2011-086393 A

  However, in the solid electrolytic capacitors described in Patent Documents 1 and 2, the following phenomenon may occur. One is an increase in leakage current (hereinafter sometimes referred to as LC) accompanying leakage of the organic compound used from the solid electrolyte layer. This rise in LC is due to the influence of moisture from the outside in a high temperature and high humidity test (for example, a test in which the rated voltage is 16 V applied for 1000 hours in an environment of 85 ° C. and relative humidity: 85% RH). There was a tendency to be more prominent. On the other hand, if the penetration of moisture into the capacitor element is hindered by a low hygroscopic resin, the capacitance may be lowered.

  Accordingly, an object of the present invention is to provide a solid electrolytic capacitor that has a large capacitance and suppresses an increase in LC during a high-temperature and high-humidity test, and a method for manufacturing the same.

The present invention is a solid electrolytic capacitor comprising a valve metal, an oxide film layer formed on the surface of the valve metal, and a solid electrolyte layer formed on the oxide film layer,
The solid electrolyte layer includes a first conductive polymer, a first solid electrolyte layer containing a moisturizing substance, a second conductive polymer, and at least one water-soluble polyhydric alcohol and at least A solid electrolytic capacitor comprising a second solid electrolyte layer containing a resin that is a condensation polymer of one kind of water-soluble polyvalent carboxylic acid.

The present invention also includes a valve metal, an oxide film layer formed on the surface of the valve metal, and a first solid electrolyte layer and a second solid electrolyte layer formed on the oxide film layer. A method for producing a solid electrolytic capacitor including a solid electrolyte layer,
Forming an oxide film layer on the surface of the valve metal;
Forming a first solid electrolyte layer containing a first conductive polymer and a moisturizing substance on the oxide film layer;
On the first solid electrolyte layer, a second conductive polymer and a resin that is a polycondensation product of at least one water-soluble polyhydric alcohol and at least one water-soluble polyvalent carboxylic acid are included. Forming a second solid electrolyte layer;
It is a manufacturing method of the solid electrolytic capacitor characterized by having.

  According to the present invention, it is possible to provide a solid electrolytic capacitor having a large capacitance and suppressing an increase in LC during a high-temperature and high-humidity test, and a method for manufacturing the same.

It is typical sectional drawing which shows the structure of an example of the solid electrolytic capacitor of this invention. It is a typical fragmentary sectional view showing the composition of an example of the solid electrolytic capacitor of the present invention.

  The solid electrolytic capacitor of the present invention has a valve metal, an oxide film layer formed on the surface of the valve metal, and a solid electrolyte layer formed on the oxide film layer. The solid electrolyte layer includes a first solid electrolyte layer including at least a first conductive polymer and a moisturizing substance, and a second solid including at least a second conductive polymer and a specific polyester resin (hydrophobic resin). It has a solid electrolyte layer and can have a two-layer configuration. The specific polyester resin is a condensation polymer of at least one water-soluble polyhydric alcohol and at least one water-soluble polyvalent carboxylic acid.

  Usually, when a moisture-containing substance containing moisture is covered with a highly hydrophobic substance (hydrophobic substance), specifically, a moisture-containing layer containing the moisture-containing substance (for example, the first solid electrolyte layer) is replaced with a hydrophobic substance. In the case of covering with a hydrophobic layer containing water, moisture contained in the moisturizing substance may be gasified and expanded by a heating operation when forming the hydrophobic layer or a heating operation when reflowing when mounting the substrate. Due to this expansion, delamination occurs between the moisturizing layer and the hydrophobic layer, and ESR may increase, so such a configuration is usually not taken.

However, in the solid electrolytic capacitor of the present invention, by adopting the above-described configuration, the increase in ESR can be suppressed, the capacitance can be increased, and the increase in LC during the high temperature and high humidity test can also be suppressed. . This is thought to be due to the following. The leakage current (LC) is the sum of the current that flows through the dielectric (oxide film layer) that should be an insulator and the current that flows when the cathode and anode conductors are short-circuited by another path. Means current.
That is, the second solid electrolyte layer corresponding to the hydrophobic layer includes, for example, a second conductive polymer, at least one water-soluble polyhydric alcohol, and at least one water-soluble polyvalent carboxylic acid. It can produce by apply | coating the liquid mixture containing on a 1st solid electrolyte layer, and drying (for example, heating) as needed. For this reason, since a polyester resin is gradually formed in the second solid electrolyte layer, the second solid electrolyte layer gradually becomes hydrophobic. Therefore, before the hydrophobicity of the second solid electrolyte layer becomes strong, moisture is appropriately removed from the moisturizing material contained in the first solid electrolyte layer by a drying operation or the like, so that delamination hardly occurs. It is considered that the increase in ESR is suppressed. In addition, the moisture retention substance is contained in the first solid electrolyte layer disposed inside the second hydrophobic solid electrolyte layer having high hydrophobicity, and is included, so that the electrostatic capacity is influenced by the moisture contained in the moisture retention substance. Can be increased (with a large capacity). Furthermore, by covering the first solid electrolyte layer containing the moisturizing substance with the second solid electrolyte layer having high hydrophobicity, the moisturizing substance existing in the solid electrolyte layer on the cathode side leaks out from the solid electrolyte layer, and the anode side It is possible to prevent a short circuit path from flowing out to the other terminal. As a result, an increase in LC during the high temperature and high humidity test can be suppressed.

  Hereinafter, the solid electrolytic capacitor of the present invention will be described in detail. 1 and 2 are schematic (partial) cross-sectional views showing the configuration of an example of the solid electrolytic capacitor of the present invention.

<Solid electrolytic capacitor>
As shown in FIGS. 1 and 2, the solid electrolytic capacitor of the present invention includes a valve metal (anode conductor) 1, a dielectric oxide film layer (oxide film layer) 2 formed on the surface of the valve metal 1, an oxidation A solid electrolyte layer 3 formed on the coating layer 2 is included at least as a constituent element. Further, as shown in FIG. 2, the solid electrolyte layer 3 includes a first solid electrolyte layer 3A and a second solid electrolyte layer 3B.
The solid electrolytic capacitor shown in these drawings includes an oxide film layer 2, a solid electrolyte layer 3 composed of a first solid electrolyte layer 3A and a second solid electrolyte layer 3B, and a graphite layer on the valve metal 1. 5 has a structure in which a cathode conductor 4 composed of 5 and a silver layer 6 is formed in this order.
The valve metal 1 has a valve metal lead 9, and the valve metal lead 9 is connected to the electrode 8 by welding. The silver layer 6 is connected to the other electrode 8 through the conductive adhesive layer 7. Furthermore, the solid electrolytic capacitor shown in these drawings is covered with the exterior resin 10 with a part of the two electrodes 8 exposed to the outside.
In the solid electrolytic capacitor of the present invention, a capacitor element (reference numeral 11 in FIG. 2) in which a structure from the valve metal 1 to the silver layer 6 is formed on a substrate on which wiring is arranged instead of the electrode 8 is provided with a conductive adhesive. Alternatively, the substrate structure may be covered with exterior resin after being connected by welding or welding.

  Below, these structural members are demonstrated. The solid electrolytic capacitor of the present invention is basically the same as the conventional solid electrolytic capacitor except that the solid electrolyte layer is composed of the above-described specific plural (two or more) solid electrolyte layers. It can be set as this structure. That is, any member other than the solid electrolyte layer can be used in the field of solid electrolytic capacitors, including the shape and material, and is not particularly limited.

(Valve metal)
The valve metal 1 can be formed by, for example, a valve metal plate, foil, or wire; a sintered body containing fine particles of the valve metal; a porous metal that has been subjected to surface expansion treatment by etching.
The valve metal forming the valve metal 1 is preferably at least one valve metal selected from aluminum, tantalum, niobium, tungsten, titanium, and zirconium, or an alloy of these valve metals.

(Oxide film layer)
The oxide film layer 2 is a layer that can be formed by electrolytic oxidation of the surface of the valve metal 1. When the valve metal 1 is a sintered body or a porous metal, the oxide film layer 2 can be formed also in the pores inside the sintered body or the porous metal. The thickness of the oxide film layer 2 can be appropriately adjusted by the voltage of electrolytic oxidation.

(Solid electrolyte layer)
The solid electrolyte layer 3 includes at least a first solid electrolyte layer 3A containing a first conductive polymer and a moisturizing substance, at least one water-soluble polyhydric alcohol, and at least one water-soluble polyvalent carboxylic acid. And a second solid electrolyte layer 3B containing a second resin polymer and a polyester resin. In addition, the solid electrolyte layer 3 can also have another solid electrolyte layer in the range with which the effect of this invention is acquired. That is, the solid electrolyte layer 3 can have a multilayer structure of two or more layers including at least the first solid electrolyte layer 3A and the second solid electrolyte layer 3B.

(I) First Solid Electrolyte Layer The first solid electrolyte layer 3A includes a first conductive polymer (first conductive polymer compound) and a moisturizing substance.

  The first solid electrolyte layer 3A may contain other components in addition to the first conductive polymer and the moisturizing substance. Examples of other components include a strong binding force with the oxide film layer. An organic polymer resin can be used.

-1st conductive polymer As a 1st conductive polymer, a well-known conductive polymer in the field of a solid electrolytic capacitor can be used suitably. As the first conductive polymer, for example, polymerized (for example, chemical oxidative polymerization and electrolytic polymerization) of at least one compound (monomer) selected from the group consisting of pyrrole, thiophene, aniline and derivatives thereof (Polymer) or those obtained by compounding a dopant such as polyacid (composite) with these polymers can be used. In addition, the 1st conductive polymer may be used individually by 1 type, and may use 2 or more types together.

  These first conductive polymers will be described in detail later, but can be used in the form of a solution or suspension by dissolving or dispersing in a solvent or the like. At that time, for example, a soluble first conductive polymer can be used for the solution, and a dispersible first conductive polymer can be used for the suspension. The dopant such as the polyacid can serve as a dispersant for dispersing the polymer in the suspension.

Examples of the soluble first conductive polymer include polymers of thiophene derivatives and pyrrole derivatives having a sulfo group in the side chain, and polyaniline.
In addition, as the dispersible first conductive polymer, for example, at least one polymer selected from the group consisting of pyrrole, thiophene, aniline and derivatives thereof, polystyrene sulfonic acid, polyester sulfonic acid, Examples thereof include conductive polymers in which polyacids such as polyvinyl sulfonic acid are combined.

  Among the conductive polymers described above, a polythiophene-based conductive polymer (PEDOT-PSS), which is a composite of polyethylene dioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS), is used as the first conductive polymer. It is preferable to use from the viewpoint of conductivity and heat resistance.

  The content ratio of the first conductive polymer in the first solid electrolyte layer is preferably 60% by mass or more from the viewpoint of conductivity of the solid electrolyte layer and 99% by mass or less from the viewpoint of capacitance. Further, from the same viewpoint, it is more preferably 80% by mass or more and 95% by mass or less.

  If the content ratio of the first conductive polymer in the first solid electrolyte layer is 60% by mass or more, the electrical conductivity of the solid electrolyte layer can be easily prevented from greatly decreasing, and the ESR can be easily increased. Can be prevented. Moreover, if the content rate of a 1st conductive polymer is 99 mass% or less, the improvement effect of an electrostatic capacitance can fully be exhibited.

-Moisturizing substance In the present invention, by containing the moisturizing substance in the first solid electrolyte layer, it is possible to retain an appropriate amount of moisture inside the capacitor element, and as a result, the capacitance is reduced when the capacitor element is dried. It can be prevented from becoming low.

  The moisturizing substance can be appropriately used as long as it exhibits water absorbency and hygroscopicity, and is not particularly limited. The moisturizing substance used in the present invention may be in a liquid state, a solid state or a gel state at room temperature (25 ° C.), for example, and its form is not limited.

Examples of the moisturizing substance include the following. In addition, a moisturizing substance may be used individually by 1 type, and may use 2 or more types together.
That is, alcohols such as ethylene glycol, propylene glycol, glycerin and polyvinyl alcohol;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, polyethylene glycol , Ethers such as diglycerin and polyglycerin;
Amides such as N-methylformamide, N, N-dimethylformamide, N-methylacetamide, N-ethylacetamide, N, N-dimethylacetamide, N, N-dimethylpropionamide, N-methylpyrrolidone;
Lactones such as γ-butyrolactone, β-butyrolactone, γ-valerolactone, δ-valerolactone, α-acetyl-γ-butyrolactone;
Carbonates such as ethylene carbonate and propylene carbonate;
Nitriles such as acetonitrile, propionitrile, butyronitrile, acrylonitrile;
Urea derivatives such as N, N′-dimethylimidazolidinone:
Examples include sulfolane, sulfone such as 3-methylsulfolane, dimethylsulfone, and the like.

  The moisturizing substance is a substance (compound) having a hydrophilic group (for example, a hydroxyl group, an ether group, a carboxyl group, etc.) and increasing the mass by 10% or more of the mass of the moisturizing substance itself when absorbed. Is preferred. Examples of moisturizing substances that satisfy this condition include ethylene glycol, propylene glycol, glycerin, polyethylene glycol, diglycerin, polyglycerin, γ-butyrolactone, polyvinyl alcohol, N-methylacetamide, N-ethylacetamide, N-methylpyrrolidone, Examples thereof include β-butyrolactone, γ-valerolactone, δ-valerolactone, ethylene carbonate, propylene carbonate, N, N′-dimethylimidazolidinone, sulfolane, 3-methylsulfolane, and dimethyl sulfone.

  The moisturizing substance is preferably an organic compound having a boiling point of 200 ° C. or higher at 1 atm (101325 Pa). A moisturizing substance having a boiling point of 200 ° C. or higher at 1 atm has low volatility, and further suppresses gasification of the moisturizing substance itself even in a high-temperature environment when forming a solid electrolytic capacitor (for example, during drying). Therefore, ESR increase due to delamination of capacitor elements formed in layers (particularly, delamination between the first and second solid electrolyte layers) can be easily prevented.

  Examples of moisturizing substances having a boiling point of 200 ° C. or higher at 1 atmosphere include the following. That is, glycerin, polyethylene glycol, diglycerin, polyglycerin, polyvinyl alcohol, N-methylacetamide, N-ethylacetamide, N-methylpyrrolidone, γ-butyrolactone, β-butyrolactone, γ-valerolactone, δ-valerolactone, ethylene Examples include carbonate, propylene carbonate, N, N′-dimethylimidazolidinone, sulfolane, 3-methylsulfolane, and dimethyl sulfone.

Further, as the moisturizing substance, it is more preferable to use an organic compound having a total of two or more of one or both of a hydroxyl group (—OH) and an ether group (—O—) in addition to the above boiling point condition. That is, the moisturizing material used in the present invention has an organic compound having a total of two or more of hydroxyl groups and ether groups in the molecular structure and a boiling point of 200 ° C. or higher (at 1 atm). More preferably, it is a compound.
When the moisturizing substance has one or both of hydroxyl group and ether group in total in the molecular structure, it becomes easy to sufficiently hold the moisturizing substance inside the capacitor element, and the capacitance is reduced. Decline can be easily prevented.

  Examples of moisturizing substances that satisfy all of the above conditions include glycerin, polyethylene glycol, diglycerin, polyglycerin, and polyvinyl alcohol.

  The moisturizing substance particularly preferably has a boiling point of 260 ° C. or higher at 1 atmosphere. During reflow soldering when mounting a solid electrolytic capacitor, the capacitor element is usually temporarily exposed to a high temperature of about 260 ° C. For this reason, by using a moisturizing substance having a boiling point of 260 ° C. or higher, sufficient volatilization can be suppressed, and delamination in the capacitor element can be easily prevented even during reflow soldering, Occurrence of product defects can be easily prevented. In recent years, the use of lead-free solder has been demanded, and during reflow soldering, capacitor elements are exposed to higher temperatures than before, so that the moisturizing substance has a higher boiling point. Is desirable.

  In addition, as the moisturizing substance having a total of two or more of hydroxyl groups and ether groups in the molecular structure and having a boiling point of 260 ° C. or higher (at 1 atm), for example, glycerin, Examples include diglycerin and polyglycerin.

The content ratio of the moisturizing substance in the first solid electrolyte layer is 1 part by mass or more with respect to 100 parts by mass of the first conductive polymer from the viewpoint of capacitance, and is first from the viewpoint of conductivity of the solid electrolyte layer. 40 parts by mass or less is preferable with respect to 100 parts by mass of the conductive polymer.
As shown in FIG. 2, the solid electrolyte layer can have a space between the first solid electrolyte layer and the second solid electrolyte layer, and the moisturizing substance exists alone in this space. You can also. The presence of the humectant alone in this space can complement the function of the humectant in the first solid electrolyte layer.
In the first solid electrolyte layer, the first conductive polymer and the moisturizing substance may be contained in a chemically bonded state.

-Organic polymer resin Although it does not specifically limit as an organic polymer resin, For example, the following can be mentioned. The organic polymer resin does not include the first conductive polymer and the moisturizing substance. An organic polymer resin may be used individually by 1 type, and may use 2 or more types together.
That is, polystyrene, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polymethyl methacrylate, polyamide, polyimide, polyamideimide, polyester, polyphthalate, polyethylene terephthalate, polyethylene glycol phthalate, polycarbonate, polyphenylene oxide, Polyurethane, polyacetal, diallyl phthalate, polyacrylate, polymethacrylate, polyacrylonitrile, polytetrafluoroethylene, polybutadiene, polyisoprene, polysiloxane, cellulose, methylcellulose, ethylcellulose, fluororesin, urea resin, silicon resin, phenolic resin, melamine resin , Epoxy resin, acrylic resin, alkyd resin, butyral resin, Recone resins, polylactic acid, and the like.
The content ratio of other components such as the organic polymer resin in the first solid electrolyte layer can be appropriately set and is not particularly limited.

(II) Second Solid Electrolyte Layer The second solid electrolyte layer 3B is composed of a second conductive polymer (second conductive polymer compound), at least one water-soluble polyhydric alcohol and at least one. A resin (hereinafter, sometimes referred to as a hydrophobic resin or a polyester resin) that is a polycondensation product with a water-soluble polyvalent carboxylic acid of a kind is included.

Second conductive polymer As the second conductive polymer, a conductive polymer known in the field of solid electrolytic capacitors can be appropriately used. As the second conductive polymer, for example, the conductive polymer described above in the first conductive polymer can be used similarly. In addition, as a 2nd conductive polymer, it is preferable to use a polythiophene type conductive polymer (PEDOT-PSS) from a viewpoint of electrical conductivity or heat resistance.

  Here, the first conductive polymer and the second conductive polymer may be different types of conductive polymers or the same type of conductive polymers. However, from the viewpoint of ESR, it is preferable to use the same type (including those having different dopants) of the first and second conductive polymers. In addition, a 2nd conductive polymer may be used individually by 1 type, and may use 2 or more types together.

  The content ratio of the second conductive polymer in the second solid electrolyte layer is 30% by mass or more from the viewpoint of the conductivity of the solid electrolyte layer, and 80% from the viewpoint of holding the moisturizing substance in the first solid electrolyte layer. The mass% or less is preferable.

  The content ratio of the second conductive polymer in the second solid electrolyte layer forming material to be described later is preferably 0.5% by mass or more and 10% by mass or less. If the content ratio of the second conductive polymer is 0.5% by mass or more, the formation of the second solid electrolyte layer can be easily performed as few times as possible. Moreover, if the content rate of a 2nd conductive polymer is 10 mass% or less, it will be easy to maintain the dispersibility or solubility of a 2nd conductive polymer.

-Hydrophobic resin As described above, the hydrophobic resin contained in the second solid electrolyte layer is a polycondensation of at least one water-soluble polyhydric alcohol and at least one water-soluble polyvalent carboxylic acid. It is resin obtained by this. This hydrophobic resin may be used individually by 1 type, and may use 2 or more types together.

  The content ratio of the hydrophobic resin in the second solid electrolyte layer is 20% by mass or more from the viewpoint of retaining the moisturizing substance in the first solid electrolyte layer, and 70% by mass or less from the viewpoint of conductivity of the solid electrolyte layer. Is preferred.

(A) Water-soluble polyhydric alcohol The water-soluble polyhydric alcohol is an alcohol having two or more hydroxyl groups.
Here, “water-soluble” means completely dissolved in a solution containing water as a main solvent. Here, the “main solvent” means the most contained component (solvent) among the solvents (solvents) used in the solution. A water-soluble polyhydric alcohol may be used individually by 1 type, and may use 2 or more types together.

  Preferred examples of the water-soluble polyhydric alcohol include ethylene glycol, butylene glycol, propylene glycol, 3-methyl-1,3-butanediol, hexylene glycol, diethylene glycol, dipropylene glycol, glycerin, diglycerin, inositol, and xylose. Glucose, mannitol, trehalose, erythritol, xylitol, sorbitol, maltitol, pentaerythritol, polyethylene glycol, polypropylene glycol, polyvinyl alcohol and the like.

  Among these, it is more preferable to use either or both of erythritol and pentaerythritol as the water-soluble polyhydric alcohol. Erythritol and pentaerythritol are used when forming the second solid electrolyte layer, the second solid electrolyte layer containing a second conductive polymer, a water-soluble polyhydric alcohol, and a water-soluble polyvalent carboxylic acid. The forming material is more preferable because it has the following effects. That is, in the above material, an undoped anion (for example, polyacid anion) (resistance component) existing in the vicinity of the second conductive polymer particle interacts with these water-soluble polyhydric alcohols. Thus, since the resistance between the second conductive polymer particles can be lowered and the density of the second conductive polymer can be increased, it is possible to further increase the conductivity.

  The water-soluble polyhydric alcohol preferably has a valence of 3 or more. Hydrophobic resins obtained by polycondensation of water-soluble polyhydric alcohols having a valence of 3 or more and water-soluble polyvalent carboxylic acids have a crosslinked structure, and therefore have a low water absorption and water resistance compared to linear resins. Also excellent. Also from this viewpoint, it is more preferable to use one or both of erythritol and pentaerythritol as the water-soluble polyhydric alcohol.

  In addition, since erythritol has high crystallinity compared with sorbitol, maltitol, etc., for example, its hygroscopic property is small and handling is easy. In addition, erythritol is known as a food additive used as a sweetener, is excellent in safety and stability, and has a solubility in water several times higher than that of, for example, ethylene glycol or glycerin. There is an advantage that the degree of freedom in designing the addition amount is high.

  Pentaerythritol has a characteristic that it gradually sublimates when heated, and dehydrates and polymerizes when heated above its melting point. This has the advantage that the physical properties of the organic material using pentaerythritol change, and the density and strength are improved. Such a reaction is caused by the chemical structure, and is unlikely to occur in a chemical structure such as erythritol or sorbitol.

  The content ratio of the water-soluble polyhydric alcohol in the second solid electrolyte layer forming material is based on 100 parts by mass of the second conductive polymer in order to obtain the effect of the water-soluble polyhydric alcohol described above. The amount is preferably 100 parts by mass or more, and more preferably 200 parts by mass or more. Moreover, the upper limit of the content ratio of the water-soluble polyhydric alcohol in the second solid electrolyte layer forming material is not particularly limited as long as it is an amount that can be dissolved in a solvent (for example, water) used in this material, but the solid electrolyte layer From the viewpoint of electrical conductivity, it is preferably 500 parts by mass or less with respect to 100 parts by mass of the second conductive polymer.

(B) Water-soluble polyvalent carboxylic acid The water-soluble polyvalent carboxylic acid is a carboxylic acid having two or more carboxyl groups (—COOH groups) capable of polycondensation with the above-described water-soluble polyhydric alcohol. One type of water-soluble polyvalent carboxylic acid may be used alone, or two or more types may be used in combination.

  Examples of the water-soluble polycarboxylic acid include oxalic acid, acetylenedicarboxylic acid, malonic acid, succinic acid, fumaric acid, malic acid, oxaloacetic acid, glutaric acid, oxoglutaric acid, adipic acid, citric acid, oxalosuccinic acid, Ortho-phthalic acid, hemimellitic acid, trimesic acid, merophanic acid, benzenepentacarboxylic acid, mellitic acid, 4-sulfophthalic acid, 5-sulfoisophthalic acid, 2-sulfoterephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,3 -Naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 3-hydroxy-2,7-naphthalenedicarboxylic acid, 4-chloro-1,8-naphthalenedicarboxylic acid, 4-sulfo-1 , 8-Naphthalenedicarboxylic acid, naphthalene-1,4,5,8-tetracar Phosphate, 1,1'-bis (2-hydroxy-3,6-naphthalene dicarboxylic acid, and 2,3-anthracene dicarboxylic acid.

  Among these, the water-soluble polyvalent carboxylic acid is a resin produced by stability in the second solid electrolyte layer forming material, reactivity with the water-soluble polyhydric alcohol, and condensation polymerization with the water-soluble polyhydric alcohol. From the viewpoint of heat resistance and water resistance, ortho-phthalic acid is preferred.

  A polyester resin having high hydrophobicity can be obtained by polycondensation of a water-soluble polyhydric alcohol and a water-soluble polyvalent carboxylic acid.

  The content ratio of the water-soluble polyvalent carboxylic acid in the second solid electrolyte forming material is preferably in the following range with respect to 100 parts by mass of the second conductive polymer. That is, the content of the water-soluble polyvalent carboxylic acid is 1 part by mass or more from the viewpoint of making the second solid electrolyte layer hydrophobic by containing a hydrophobic resin in the second solid electrolyte layer. It is preferable that it is 200 mass parts or less from an electroconductive viewpoint. Further, the content ratio of the water-soluble polyvalent carboxylic acid is more preferably 50 parts by mass or more from the viewpoint of increasing the hydrophobicity of the solid electrolyte layer, and 100 parts by mass or less from the viewpoint of conductivity of the solid electrolyte layer.

  From the viewpoint of preventing a decrease in the hydrophobicity of the second solid electrolyte layer due to the unreacted product of the water-soluble polyhydric alcohol and water-soluble polyvalent carboxylic acid being contained in the second solid electrolyte layer, The blending ratio of the alcohol and the water-soluble polyvalent carboxylic acid is preferably as follows. That is, the blending ratio of the hydroxyl group contained in the water-soluble polyhydric alcohol and the carboxyl group contained in the water-soluble polyvalent carboxylic acid is preferably 8: 1 to 1: 1 (hydroxyl group: carboxyl group). . More preferably, it is 4: 1 to 1: 1.

  In the second solid electrolyte layer, the second conductive polymer and the hydrophobic resin may be contained in a chemically bonded state.

(Cathode conductor)
The cathode conductor 4 is not particularly limited as long as it is a conductor. The cathode conductor 4 is composed of a graphite layer 5, a silver layer 6, and the like, and is formed to collect a capacity drawn by the solid electrolyte layer 3. The cathode conductor may not be formed, and the solid electrolyte layer 3 and the cathode-side electrode 8 may be directly joined.

  As described above, in the solid electrolytic capacitor of the present invention, since members other than the solid electrolyte layer 3 can be appropriately used, detailed descriptions other than the constituent members described above are omitted.

<Method for manufacturing solid electrolytic capacitor>
The manufacturing method of the solid electrolytic capacitor of this invention has the following processes.
A step of forming an oxide film layer on the surface of the valve metal (oxide film layer forming step).
A step of forming a first solid electrolyte layer containing a first conductive polymer and a moisturizing substance on the oxide film layer (first solid electrolyte layer forming step).
Forming a second solid electrolyte layer containing the second conductive polymer and the above-described hydrophobic resin on the first solid electrolyte layer (second solid electrolyte layer forming step);

  The production method of the present invention further includes a step of forming a valve metal (anode conductor) (valve metal formation step), other components (cathode conductors (graphite layer, silver layer, etc.), and conductive adhesive layer. , Electrodes, exterior resin, etc.).

(Valve metal (anode conductor) formation process)
As a method of forming the valve metal 1, a method conventionally performed in the field of solid electrolytic capacitors can be appropriately used. For example, the anode conductor can be produced by etching a valve metal foil or forming a sintered body of valve metal powder.

(Oxide film layer forming process)
As a method of forming the oxide film layer 2 on the surface of the valve metal film, a method conventionally performed in the field of solid electrolytic capacitors can be appropriately used. For example, an oxide film layer can be formed by electrolytically oxidizing the surface of the obtained valve metal.

(First solid electrolyte layer forming step)
In this step, any method can be used without particular limitation as long as it can form the first solid electrolyte layer 3A containing the first conductive polymer and the moisturizing substance on the oxide film layer. These two methods can be used. In addition, you may form a 1st solid electrolyte layer combining these methods.

By forming a first conductive polymer layer containing the first conductive polymer on the oxide film layer and adding a moisturizing substance to the obtained first conductive polymer layer A method of forming the first solid electrolyte layer (first method).
On the oxide film layer, a mixed liquid (first solid electrolyte layer forming material) containing the first conductive polymer and a moisturizing substance is applied or impregnated to form the first solid electrolyte layer. Method of forming (second method).

  Each method will be described below.

First Method (a) First Conductive Polymer Layer Formation Step In the first method, first, the first conductive polymer layer (first before the moisturizing substance is contained on the oxide film layer) A solid electrolyte layer).
This first conductive polymer layer can be formed, for example, by the following method. That is, by applying or impregnating the first conductive polymer layer forming material (first conductive polymer solution or suspension) on the oxide film layer, and performing a drying operation as necessary, It can be formed by removing the solvent from this material. In addition, without performing this drying operation, the drying operation can be performed after the obtained first conductive polymer layer contains a moisturizing substance.

  In addition, for example, when the first conductive polymer layer forming material contains the first conductive polymer in the form of a polymer or composite polymerized in advance, this polymer or composite is The first conductive polymer layer can be formed by applying the above-described material to the oxide film layer and solidifying it by performing a drying operation as necessary.

  The first conductive polymer solution is a liquid in which the first conductive polymer is completely dissolved in a solvent (solvent). The first conductive polymer suspension is a liquid in which first conductive polymer particles are dispersed in a solvent (dispersion medium). This solution and suspension can be used in combination.

The first conductive polymer contained in the first conductive polymer layer forming material is composed of a compound of a compound (monomer) used for forming the first conductive polymer and a dopant. It is preferably in the form of a composite (conductive polymer).
The first conductive polymer (polymer) can be prepared, for example, by the following method. As a specific preparation method, first, a conductive polymer is prepared by performing chemical oxidation polymerization or electrolytic polymerization on a compound (monomer) that gives a conductive polymer in a solvent containing a dopant. Then, if necessary, high-purity conductive polymer is obtained by removing impurities (dopants, unreacted monomers, impurities derived from oxidizing agent, etc.) by filtration, centrifugation, washing with a solvent, and the like. Can do.

  Here, for example, when the obtained conductive polymer is the above-described soluble conductive polymer, this conductive polymer is used as the first conductive polymer and dissolved in the solvent as described above. By doing so, a first conductive polymer layer forming material (first conductive polymer solution) containing the first conductive polymer (polymer) can be prepared.

  When preparing the above-described dispersive conductive polymer as the first conductive polymer, for example, an oxidizing agent is allowed to act on the obtained conductive polymer in a solvent containing a polyacid. In this way, the first conductive polymer layer-forming material (first conductive polymer) having good dispersibility of the conductive polymer can be obtained by allowing the polyacid and oxidant acting as a dispersant to act on the conductive polymer. Polymer suspension).

  Examples of the solvent used for the first conductive polymer layer forming material include water, a mixed solvent containing water and a water-soluble (water-soluble) organic solvent, and a water-soluble organic solvent. Can do. The content ratio (concentration) of the first conductive polymer in the first conductive polymer layer forming material can be appropriately set.

As a method of applying or impregnating the first conductive polymer layer forming material on the oxide film layer, a conventionally performed method can be appropriately used and is not particularly limited. However, when the valve metal is formed of a sintered body or a porous body, the first conductive polymer layer forming material is sufficiently filled also on the oxide film layer inside these pores. In order to achieve this, it is preferable to leave it for several minutes to several tens of minutes after applying or impregnating this material. Moreover, it is preferable to repeat application | coating operation (for example, immersion operation) of the 1st conductive polymer layer forming material, or to employ | adopt a pressure reduction system or a pressurization system.
In addition, when forming a 1st conductive polymer layer, it is also possible to use application | coating of a 1st conductive polymer layer forming material, and an impregnation together.

  The removal of the solvent from the first conductive polymer layer forming material can be performed, for example, by a drying operation. The drying temperature is not particularly limited as long as the temperature can be removed by the solvent, but is preferably less than 260 ° C. so as not to impair the conductivity of the first conductive polymer contained in the material. . The drying time can be appropriately selected depending on the drying temperature, but is not particularly limited as long as the conductivity of the first conductive polymer is not impaired.

  The first conductive polymer layer polymerizes (for example, chemical oxidative polymerization) a monomer of the first conductive polymer contained in the first conductive polymer layer forming material on the oxide film layer. Thus, the first conductive polymer layer can be formed. Note that the monomer can be polymerized a plurality of times on the oxide film layer. When the first conductive polymer layer forming material contains the first conductive polymer in the form of a monomer, the material includes the first conductive polymer (monomer), a solvent, and a dopant. , An oxidizing agent and other components.

  The first conductive polymer layer forming material includes one type (first material) containing the first conductive polymer (monomer) and one type (second type) containing the dopant and the oxidizing agent. It is also possible to make up of two materials. And, for example, these materials are alternately applied or impregnated on the oxide film layer, and the first conductive polymer monomer is polymerized on the oxide film layer to thereby form the first conductive polymer layer. It can also be formed. Note that the first material containing the first conductive polymer (monomer) and the second material containing the dopant and the oxidizing agent may each contain a solvent. In addition, the content ratio (concentration) of each component in each of these materials (first material and second material) can be set as appropriate.

  In addition, as a dopant which can be used when polymerizing the above monomer to obtain the first conductive polymer, for example, benzenesulfonic acid, naphthalenesulfonic acid, phenolsulfonic acid and styrenesulfonic acid, and derivatives thereof And the like, and any of them can be preferably used. In addition, the molecular weight of a dopant is not specifically limited, It can select suitably. In addition, a dopant may be used individually by 1 type and may use 2 or more types together.

  As an oxidizing agent used at the time of superposition | polymerization or composite_body | complex formation, a well-known thing can be used suitably without a restriction | limiting, for example, iron salts of organic acids, such as ferric p-toluenesulfonic acid, can be used.

  In addition, what was mentioned above can be used for the compound (monomer) and polyacid used for preparation of a 1st conductive polymer.

(B) Moisturizing substance-containing step The method of incorporating the moisturizing substance in the first conductive polymer layer is not particularly limited, and can be performed, for example, by the following two kinds of methods.
That is, a method of impregnating a liquid moisturizing substance in the first conductive polymer layer, or a solution containing a moisturizing substance and a solvent (moisturizing solution) is impregnated in the first conductive polymer layer, Thereafter, this solvent is removed.
Examples of the liquid moisturizing substance include ethylene glycol, propylene glycol, glycerin, polyethylene glycol, diglycerin, polyglycerin, and γ-butyrolactone.
As the solvent used in the moisturizing solution, for example, water, a mixed solvent containing water and an organic solvent soluble in water, an organic solvent soluble in water, or the like can be used. The content (concentration) of the moisturizing substance in the moisturizing solution is preferably 60% by mass or less from the viewpoint of permeability to the first conductive polymer layer.

  As a method of impregnating the first moisturizing substance or moisturizing solution on the first conductive polymer layer, a conventionally performed method can be appropriately used, and is not particularly limited. However, in order to sufficiently fill the moisturizing substance in the first conductive polymer layer, it is preferable to leave it for several minutes to several tens of minutes after impregnating the moisturizing substance.

The removal of the solvent after the impregnation can be performed by, for example, a drying operation. The drying temperature is not particularly limited as long as the solvent can be removed, but it is 260 ° C. so as not to impair the conductivity of the first conductive polymer contained in the first conductive polymer layer. It is preferable to make it less than. It is more preferable to perform the drying operation at a temperature at which the used moisturizing substance does not volatilize (below its boiling point).
The drying time can be appropriately selected depending on the drying temperature, but is not particularly limited as long as the conductivity of the first conductive polymer is not impaired and the moisture retaining substance is not volatilized.

Method II In the method II, a mixed liquid (first solid electrolyte) containing a first conductive polymer (complexed with a polymer and, if necessary, a polyacid or the like) and a moisturizing substance. Layer forming material), and applying or impregnating the mixed solution on the oxide film layer (by performing a drying operation if necessary (by removing the solvent etc.)) An electrolyte layer is formed.

The first solid electrolyte layer forming material may contain a solvent in addition to the first conductive polymer, the moisturizing substance and other components (organic polymer resin, etc.). It can be a mixed solution (solution or suspension) in which molecules, moisturizing substances and other components are dissolved or dispersed in a solvent.
The first conductive polymer (combined with polymer and polyacid if necessary), moisturizing substance, other components and solvent used for the first solid electrolyte layer forming material are as described above. Can be used as well.
The method for applying or impregnating the first solid electrolyte layer forming material is not particularly limited, but this material is applied or impregnated in order to sufficiently fill the oxide film layer inside the pores. It is preferable to leave it for several minutes to several tens of minutes later. Moreover, it is preferable to repeat the application | coating operation (for example, immersion operation) of the 1st solid electrolyte layer forming material, or to employ | adopt a pressure reduction system or a pressurization system. In addition, when forming a 1st solid electrolyte layer, it is also possible to use application | coating of a 1st solid electrolyte layer formation material, and an impregnation together.

  In addition, when a solvent is used for the first solid electrolyte layer forming material, the removal of the solvent can be performed by, for example, a drying operation. The drying temperature is not particularly limited as long as the temperature can be removed by the solvent, but is preferably less than 260 ° C. so as not to impair the conductivity of the first conductive polymer contained in the material. . It is more preferable to perform the drying operation at a temperature at which the used moisturizing substance does not volatilize (below its boiling point). The drying time can be appropriately selected depending on the drying temperature, but is not particularly limited as long as the conductivity of the first conductive polymer is not impaired and the moisture retaining substance is not volatilized.

  The content ratio of the first conductive polymer (polymer or composite) in the first solid electrolyte layer forming material is preferably 0.5% by mass or more and 10% by mass or less. When the content ratio of the first conductive polymer is 0.5% by mass or more, the first solid electrolyte layer can be easily formed as few times as possible. Moreover, if the content rate of a 1st conductive polymer is 10 mass% or less, it will be easy to maintain the dispersibility or solubility of a 1st conductive polymer.

  In addition, the content of the moisturizing substance in the first solid electrolyte layer forming material is 1 part by mass or more with respect to 100 parts by mass of the first conductive polymer from the viewpoint of capacitance, and the conductivity of the solid electrolyte layer. In view of the above, 40 parts by mass or less is preferable with respect to 100 parts by mass of the first conductive polymer.

(Second solid electrolyte layer forming step)
In this step, there is no particular limitation as long as the second solid electrolyte layer 3B including the second conductive polymer and the above-described hydrophobic resin can be formed on the first solid electrolyte layer 3A. For example, the following method can be used.
That is, a mixed liquid (second liquid) containing the second conductive polymer (polymer or complex), at least one water-soluble polyhydric alcohol, and at least one water-soluble polyvalent carboxylic acid. The solid electrolyte layer forming material) is applied onto the first solid electrolyte layer and heated as necessary, so that at least one water-soluble polyhydric alcohol and at least one water-soluble polyhydric alcohol are prepared. A method of forming a condensate of a polyvalent carboxylic acid and forming a second solid electrolyte layer.
The second conductive polymer, water-soluble polyhydric alcohol and water-soluble polyvalent carboxylic acid used in this material, and the amount of these compounds used can be applied as they are.

  The second solid electrolyte layer forming material can contain a solvent, and can be a mixed solution (solution or suspension) in which these compounds are dissolved or dispersed in this solvent. The water-soluble polyhydric alcohol and the water-soluble polyvalent carboxylic acid are preferably dissolved in this solvent. By dissolving the water-soluble polyhydric alcohol and the water-soluble polyvalent carboxylic acid in the solvent, the hydrophobic resin obtained by condensation polymerization can be uniformly contained in the second solid electrolyte layer without segregation. As this solvent, for example, water, a mixed solvent containing water and an organic solvent soluble in water, an organic solvent soluble in water, or the like can be used.

  In addition, after apply | coating the 2nd solid electrolyte layer forming material on a 1st solid electrolyte layer, drying operation can also be performed as needed and the said solvent can also be removed. The heating operation for causing the condensation reaction can be performed either during or after the removal of the solvent, or both. Then, by this heating operation, the water-soluble polyhydric alcohol and the water-soluble polycarboxylic acid used are subjected to condensation polymerization, and at least water-soluble is contained in the second conductive polymer layer containing the second conductive polymer. A resin (hydrophobic resin) composed of a polyhydric alcohol and a water-soluble polycarboxylic acid can be uniformly contained. Thereby, the second solid electrolyte layer containing the second conductive polymer and the hydrophobic resin can be formed. The drying operation accompanying the removal of the solvent and the heating operation for the condensation polymerization of the water-soluble polyhydric alcohol and the water-soluble polyvalent carboxylic acid can be performed simultaneously, that is, by the same operation (step).

  The drying (or heating) temperature in these operations is not particularly limited as long as it is a temperature range in which solvent removal and polycondensation of a water-soluble polyhydric alcohol and a water-soluble polycarboxylic acid can be performed. However, from the viewpoint of not impairing the conductivity of the conductive polymer, it is preferably less than 260 ° C. In addition, the drying (or heating) temperature is preferably 140 ° C. or higher in order to perform solvent removal and polycondensation of a water-soluble polyhydric alcohol and a water-soluble polycarboxylic acid together (simultaneously). .

  The drying (or heating) time is appropriately selected depending on the drying temperature, but the range in which the conductivity of the conductive polymer is not impaired, and the condensation polymerization of the water-soluble polyhydric alcohol and the water-soluble polycarboxylic acid is sufficient. There is no particular limitation as long as it occurs.

  In the present invention, the solvent removal and the above condensation polymerization can also be performed separately. Specifically, using a means such as heating or leaving in dry air, a solvent (for example, at a temperature of 80 ° C. or less at which polycondensation reaction between a water-soluble polyhydric alcohol and a water-soluble polycarboxylic acid does not easily occur. Water) is removed, and at the same time the amount of water in the moisturizing substance is reduced. And it can heat at the temperature of 140 degreeC or more, and can raise | generate a polycondensation reaction of water-soluble polyhydric alcohol and water-soluble polyhydric carboxylic acid. By using this method, when the hydrophobic second solid electrolyte layer is formed by the above condensation polymerization, it is easy to cause a large amount of moisture gasification from the moisturizing substance in the first solid electrolyte layer. It is possible to prevent the delamination between the first solid electrolyte layer and the second solid electrolyte layer.

(Cathode conductor formation process)
The step of forming the cathode conductor can include, for example, the following graphite layer forming step and silver layer forming step.

(Graphite layer forming process)
For the formation of the graphite layer 5, a method conventionally performed in the field of solid electrolytic capacitors can be appropriately used. For example, a method of applying or impregnating a graphite paste on the solid electrolyte layer 3 (specifically, the second solid electrolyte layer 3B), drying as necessary, and removing the solvent used in the graphite paste is used. Can do. At that time, the drying temperature is not particularly limited as long as the solvent can be removed, but it is preferably less than 260 ° C. so as not to impair the conductivity of the conductive polymer contained in the solid electrolyte layer. . The drying time is appropriately selected depending on the drying temperature, but is not particularly limited as long as it does not impair the conductivity of the conductive polymer.

(Silver layer forming process)
For the formation of the silver layer 6, a method conventionally performed in the field of solid electrolytic capacitors can be appropriately used. For example, a method can be used in which a silver paste is applied or impregnated on the graphite layer 5 and, if necessary, dried to remove the solvent used in the silver paste. At that time, the drying temperature is not particularly limited as long as the solvent can be removed, but it is preferably less than 260 ° C. so as not to impair the conductivity of the conductive polymer contained in the solid electrolyte layer. . The drying time is appropriately selected depending on the drying temperature, but is not particularly limited as long as it does not impair the conductivity of the conductive polymer.

(Conductive adhesive layer formation process and electrode installation process)
For the formation of the conductive adhesive layer 7, a method conventionally performed in the field of solid electrolytic capacitors can be appropriately used. For example, a conductive adhesive paste is applied on the silver layer 6, In the state where the electrodes 8 are stacked, drying may be performed as necessary to remove the solvent used in the conductive adhesive paste. The drying temperature is not particularly limited as long as the solvent can be removed, but is preferably less than 260 ° C. so as not to impair the conductivity of the conductive polymer contained in the solid electrolyte layer. The drying time is appropriately selected depending on the drying temperature, but is not particularly limited as long as it does not impair the conductivity of the conductive polymer.

  In addition, the method of installing the electrode 8 is not particularly limited. For example, the electrode 8 can be connected to the valve metal lead 9 or the conductive adhesive layer 7 by welding or a conductive adhesive.

(Exterior resin forming process)
The method for forming the exterior resin 10 is not particularly limited, and a method conventionally performed in the field of solid electrolytic capacitors can be appropriately used. The resin used for the exterior resin is not particularly limited, but a thermosetting epoxy resin is usually used. Note that when the exterior resin is formed by transfer molding, the capacitor element is temporarily exposed to heat of about 180 ° C.

  Hereinafter, the present invention will be described in detail using examples. However, the present invention is not limited to the embodiments shown in these examples.

[Example 1]
In Example 1, the solid electrolytic capacitor shown in FIGS. 1 and 2 was manufactured by the following method.
Specifically, a sintered body (pellet) of fine tantalum powder as a valve metal was electrolytically oxidized at 40 V in a phosphoric acid aqueous solution, and the entire surface of the sintered body of fine tantalum powder was coated with an oxide film layer ( Oxide film layer forming step).

  Next, the pellet coated with this oxide film layer was immersed in 30% by mass of a ferric methanol solution of p-toluenesulfonic acid, which is an oxidizing agent and a dopant, for 10 minutes, and then at room temperature (25 ° C.) for 30 minutes. Dried for minutes. Thereafter, the pellets to which the ferric p-toluenesulfonate is adhered are immersed in 3,4-ethylenedioxythiophene, a thiophene derivative, which is a monomer for forming the first conductive polymer, for 10 minutes. The polymerization was carried out at room temperature for 30 minutes to polymerize 3,4-ethylenedioxythiophene. Then, the pellet in which the 1st conductive polymer layer was formed was immersed in ethanol, and the unreacted substance and the oxidizing agent residue were wash | cleaned. A series of polymerizations of these operations, that is, immersion (filling) of oxidant / dopant into pellets having an oxide film layer, immersion (filling) of 3,4-ethylenedioxythiophene, and washing with ethanol. The operation was repeated 5 times in total to form a thin first conductive polymer layer made of polyethylenedioxythiophene (PEDOT) -p-toluenesulfonic acid (TS) on the oxide film layer (first conductive Functional polymer layer forming step).

  Subsequently, the obtained pellets having the first conductive polymer layer were immersed in a 5% by mass aqueous solution of propylene glycol (boiling point: 188.2 ° C.) that is a moisturizing substance for 1 minute and held at room temperature for 30 minutes. . Thereafter, in a constant temperature bath at 120 ° C., the pellets in which the moisturizing substance was immersed were dried for 15 minutes, and water as a solvent was removed (moisturizing substance-containing step).

  As described above, the first solid electrolyte layer containing propylene glycol as the moisturizing substance and PEDOT-TS as the first conductive polymer was formed on the oxide film layer (first solid electrolyte layer forming step). .

  Subsequently, pentaerythritol, which is a water-soluble polyhydric alcohol, ortho-phthalic acid, which is a water-soluble polyvalent carboxylic acid, and PEDOT-PSS, which is a second conductive polymer, are mixed with a water-dimethylsulfoxide mixed solution ( Water: dimethyl sulfoxide = 85: 15 (mass ratio)) was dissolved and dispersed to prepare a second solid electrolyte layer forming material. In this material, the content of pentaerythritol was 2% by mass, the content of ortho-phthalic acid was 1% by mass, and the content of PEDOT-PSS was 2% by mass.

  Next, the pellet on which the first solid electrolyte layer is formed is dipped in the second solid electrolyte layer forming material for 10 minutes, and then held for 60 minutes in an environment of temperature: 25 ° C. and relative humidity: 50% RH. And drying for 30 minutes in a thermostatic bath at 150 ° C. As a result, removal of the solvent in the deposited second solid electrolyte layer forming material and formation of a polyester resin containing pentaerythritol and ortho-phthalic acid as constituents by condensation polymerization of pentaerythritol and ortho-phthalic acid And went.

  As described above, the second solid electrolyte layer containing the second conductive polymer and the polyester resin was formed on the first solid electrolyte layer (second solid electrolyte layer forming step).

  Next, the pellet on which the second solid electrolyte layer was formed was dipped in a graphite paste, pulled up, and then dried at 120 ° C. for 1 hour to form a graphite layer on the second solid electrolyte layer (graphite Layer forming step).

  Subsequently, the pellet on which the graphite layer was formed was immersed in a silver paste, pulled up, and then dried at 120 ° C. for 1 hour to form a silver layer on the graphite layer (silver layer forming step). Thereby, a capacitor element having a valve metal, an oxide film layer, a first solid electrolyte layer, a second solid electrolyte layer, a graphite layer, and a silver layer was obtained.

  Next, for the obtained capacitor element, connection by welding the valve metal lead and the electrode, connection of the silver layer and the electrode with a conductive adhesive, and formation of the exterior resin were performed in order to obtain a solid electrolytic capacitor. .

After the obtained solid electrolytic capacitor is reflow soldered to the evaluation board and mounted, evaluation of capacitor characteristics, specifically, evaluation of capacitance, evaluation of equivalent series resistance (ESR), and leakage current ( LC) was evaluated. Here, LC is evaluated twice after mounting and after mounting and after a high-temperature and high-humidity test (temperature: 85 ° C., relative humidity: 85% RH, rated voltage: used for 1000 hours with 16 V applied). went. The evaluation results are shown in Table 1.
The evaluations of the capacitance, ESR, and LC are all performed on 1000 solid electrolytic capacitors obtained by the manufacturing method, and each evaluation result is expressed as an average value of these 1000 capacitors. did. Moreover, about the evaluation result of LC, the number in which LC defect occurred among all the numbers (1000) was described as incidence (%). The LC defect was defined as a value of not less than 132 μA 5 minutes after application of the rated voltage at 25 ° C. ((capacitor rated voltage 20 V) × (capacitance 33 μF) × 0.2 = 132 μA).

[Example 2]
A solid electrolytic capacitor was produced and evaluated in the same manner as in Example 1 except that γ-butyrolactone (boiling point: 204 ° C.) was used instead of propylene glycol as the moisturizing substance. The results are shown in Table 1.

[Example 3]
A solid electrolytic capacitor was produced and evaluated in the same manner as in Example 1 except that glycerin (boiling point: 290 ° C.) was used instead of propylene glycol as the moisturizing substance. The results are shown in Table 1.

[Example 4]
A solid electrolytic capacitor was produced and evaluated in the same manner as in Example 1 except that the first solid electrolyte layer was formed by the following method. The results are shown in Table 1.

Specifically, first, glycerin as a moisturizing substance and PEDOT-PSS as a first conductive polymer were dissolved and dispersed in an aqueous solvent to prepare a first solid electrolyte layer forming material. In addition, the content rate of glycerol in this material was 0.8 mass%, and the content rate of PEDOT-PSS was 2 mass%.
Subsequently, the pellets coated with the above-described oxide film layer are immersed in the first solid electrolyte layer forming material for 10 minutes, and the temperature is 25 ° C. and the relative humidity is 50% RH for 60 minutes. After holding, drying was performed in a thermostatic bath at 150 ° C. for 30 minutes to remove the solvent. As a result, a first solid electrolyte layer containing glycerin as a moisturizing substance and PEDOT-PSS as a first conductive polymer was formed on the oxide film layer (first solid electrolyte layer forming step). .

[Example 5]
A solid electrolytic capacitor was manufactured and evaluated in the same manner as in Example 3 except that the second solid electrolyte layer was formed by the following method. The results are shown in Table 1.

  Specifically, first, erythritol as a water-soluble polyhydric alcohol, adipic acid as a water-soluble polyvalent carboxylic acid, PEDOT-PSS as a second conductive polymer, and a water-dimethylsulfoxide mixed solution (water: A second solid electrolyte layer forming material was prepared by dissolving and dispersing in dimethyl sulfoxide = 85: 15 (mass ratio). In addition, the content rate of erythritol in this material was 2 mass%, the content rate of adipic acid was 1 mass%, and the content rate of PEDOT-PSS was 2 mass%. Subsequently, the pellet on which the first solid electrolyte layer described above is formed is immersed in the second solid electrolyte layer forming material for 10 minutes, and the temperature is 25 ° C. and the relative humidity is 50% RH for 60 minutes. After holding, drying was performed in a thermostatic bath at 150 ° C. for 30 minutes. As a result, removal of the solvent in the adhered second solid electrolyte layer forming material and formation of a polyester resin containing erythritol and adipic acid as constituents by condensation polymerization of erythritol and adipic acid were performed.

  As described above, the second solid electrolyte layer containing the second conductive polymer and the polyester resin was formed on the first solid electrolyte layer (second solid electrolyte layer forming step).

[Comparative Example 1]
A solid electrolytic capacitor was manufactured and evaluated in the same manner as in Example 3 except that the second solid electrolyte layer was formed by the following method. The results are shown in Table 1.

  Specifically, first, PEDOT-PSS as a second conductive polymer is dispersed in a water-dimethylsulfoxide mixture (water: dimethylsulfoxide = 85: 15 (mass ratio)) to form a second solid electrolyte layer. Preparation materials were prepared. In addition, the content rate of PEDOT-PSS in this material was 2 mass%. Subsequently, the pellet on which the first solid electrolyte layer described above is formed is immersed in the second solid electrolyte layer forming material for 10 minutes, and the temperature is 25 ° C. and the relative humidity is 50% RH for 60 minutes. After holding, drying was performed in a thermostatic bath at 150 ° C. for 30 minutes to remove the solvent. Thus, a second solid electrolyte layer containing only the second conductive polymer was formed on the first solid electrolyte layer (second solid electrolyte layer forming step).

[Comparative Example 2]
In Example 1, a solid electrolytic capacitor was produced and evaluated in the same manner as in Example 1 except that the moisturizing substance was not included in the first solid electrolyte layer. The results are shown in Table 1.

  From the above results, it can be seen that the LC failure rate of Examples 1 to 5 is lower than the LC failure rate after the high-temperature and high-humidity test of Comparative Example 1. This is because the second solid electrolyte layer contains a resin (polyester resin) formed by condensation polymerization of a water-soluble polyhydric alcohol and a water-soluble polyvalent carboxylic acid. The second solid electrolyte layer contains the polyester resin to prevent leakage of the moisturizing substance contained in the first solid electrolyte layer, and the occurrence of a short circuit path due to leakage of the moisturizing substance to the terminal on the anode side. Can be prevented. Here, in the high-temperature and high-humidity test, the moisture-retaining substance is likely to flow out due to moisture entering from the outside, but the second solid electrolyte layer containing the polyester resin has high hydrophobicity. Can prevent intrusion.

  In addition, the LC defect rate of Examples 1 to 4 was lower than that of Example 5. This shows that the resin to be contained in the second solid electrolyte layer is preferably a resin made from pentaerythritol and ortho-phthalic acid rather than a resin made from erythritol and adipic acid.

  Moreover, the electrostatic capacitance in Examples 1-5 was 10% or more higher than the electrostatic capacitance in Comparative Example 2. This is because the first solid electrolyte layer contains a moisturizing substance. This is because when the first solid electrolyte layer contains the moisture retaining substance, it is possible to retain appropriate moisture in the capacitor element, and as a result, it is possible to retain a high capacitance.

  Furthermore, it turns out that the electrostatic capacitance in Example 1, 3-5 is larger than the electrostatic capacitance in Example 2. FIG. This is probably because the moisture retention effect of propylene glycol and glycerin, which are the moisturizing substances used in Examples 1 and 3 to 5, is higher than the moisture retention effect of γ-butyrolactone used in Example 2. .

  Further, by comparing the ESR of Examples 3 to 5 with the ESR of Examples 1 and 2, the boiling point as a moisturizing substance is reduced from the viewpoint of ESR suppression by preventing delamination due to gasification inside the capacitor element. It can be seen that it is preferable to use a high one and a high moisture retention effect.

1: Valve metal (anode conductor)
2: Dielectric oxide film layer (oxide film layer)
3: Solid electrolyte layer 3A: First solid electrolyte layer 3B: Second solid electrolyte layer 4: Cathode conductor 5: Graphite layer 6: Silver layer 7: Conductive adhesive layer 8: Electrode 9: Valve metal lead 10: Exterior resin 11: capacitor element

Claims (8)

A solid electrolytic capacitor comprising a valve metal, an oxide film layer formed on the surface of the valve metal, and a solid electrolyte layer formed on the oxide film layer,
The solid electrolyte layer is
A first solid electrolyte layer comprising a first conductive polymer and a moisturizing substance;
And
A second solid electrolyte layer comprising a second conductive polymer and a resin that is a polycondensation product of at least one water-soluble polyhydric alcohol and at least one water-soluble polyvalent carboxylic acid;
A solid electrolytic capacitor comprising:   2. The moisturizing substance according to claim 1, wherein the moisturizing substance is an organic compound having a total of two or more of one or both of a hydroxyl group and an ether group and a boiling point of 200 ° C. or higher in the molecular structure. Solid electrolytic capacitor. A valve metal; an oxide film layer formed on the surface of the valve metal; and a solid electrolyte layer having a first solid electrolyte layer and a second solid electrolyte layer formed on the oxide film layer. A method for producing a solid electrolytic capacitor, comprising:
Forming an oxide film layer on the surface of the valve metal;
Forming a first solid electrolyte layer containing a first conductive polymer and a moisturizing substance on the oxide film layer;
On the first solid electrolyte layer, a second conductive polymer and a resin that is a polycondensation product of at least one water-soluble polyhydric alcohol and at least one water-soluble polyvalent carboxylic acid are included. Forming a second solid electrolyte layer;
A method for producing a solid electrolytic capacitor, comprising: Forming the first solid electrolyte layer comprises:
A first conductive polymer layer containing the first conductive polymer is formed on the oxide film layer, and a moisturizing substance is contained in the obtained first conductive polymer layer. The manufacturing method of the solid electrolytic capacitor of Claim 3 which is a process of forming this 1st solid electrolyte layer by.   In the step of forming the first solid electrolyte layer, the method of including the moisturizing substance in the first conductive polymer layer includes the liquid moisturizing substance in the first conductive polymer layer. 5. The solid electrolytic capacitor according to claim 4, which is a method of impregnation or a method of impregnating the first conductive polymer layer with a solution containing the moisturizing substance and a solvent and then removing the solvent. Manufacturing method. Forming the first solid electrolyte layer comprises:
4. The step of forming the first solid electrolyte layer by applying or impregnating a mixed solution containing the first conductive polymer and the moisturizing substance on the oxide film layer. The manufacturing method of the solid electrolytic capacitor of description. Forming the second solid electrolyte layer comprises:
A mixed liquid containing the second conductive polymer, the at least one water-soluble polyhydric alcohol, and the at least one water-soluble polyvalent carboxylic acid is applied onto the first solid electrolyte layer. The manufacturing method of the solid electrolytic capacitor of any one of Claims 3-6 which is a process of forming this condensate and forming this 2nd solid electrolyte layer by doing.   The moisturizing substance is an organic compound having a total of two or more of one or both of a hydroxyl group and an ether group in a molecular structure and a boiling point of 200 ° C or higher. The manufacturing method of the solid electrolytic capacitor of any one of Claims 1.

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