JPH11214264A - Solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor which realizes simple formation of an electrolyte, has a high heat resistance property and excellent capacitance, internal resistance, dielectric loss and impedance from low frequencies to high frequencies, and has less specific drop due to stress in the process. SOLUTION: In a solid electrolytic capacitor in which an electrolyte 9 made of polyaniline is formed inside and outside a solid electrolytic capacitor element by repeating a process of impregnating the solid electrolytic capacitor element with a composition for forming the electrolyte of the solid electrolytic capacitor produced by mixing a first solution containing (A) aniline, (B) organic sulfonic acid, (C) water, and (D) organic solvent, and a second solution containing (E) oxidizing agent and (F) water, the weight average molecular weight of the electrolyte made of polyaniline is set at 5,000 to 250,000, and the weight average molecular weight of the electrolyte made of polyaniline inside of the solid electrolytic capacitor element is made greater than the weight average molecular weight of the electrolyte made of polyaniline outside of the solid electrolytic capacitor element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor, and more particularly to a solid electrolytic capacitor in which an electrolyte is formed using a composition for forming an electrolyte of a solid electrolytic capacitor in which an electrolyte is formed by oxidative polymerization of aniline.

[0002]

2. Description of the Related Art In a conventional solid electrolytic capacitor, a sintered body of tantalum called valve metal or a molded body obtained by expanding aluminum is used as an anode body, and an oxide film is formed on the surface of the anode body to form a dielectric. Manganese (MnO ₂ ), 7, 7 ',
8,8'-tetracyanoquinodimethane complex salt (TCNQ)
Etc. as an electrolyte layer. However,
Since manganese dioxide has an insufficient conductivity of 0.1 S / cm, a solid electrolytic capacitor using the manganese dioxide as an electrolyte layer has a large impedance in a high frequency range, and a manganese dioxide electrolyte which requires a high process temperature. Because of the necessity of recoating many times, there is a drawback that a leakage current defect is liable to occur essentially. To avoid this, M
Each time a layer of nO ₂ is formed, it is necessary to perform a re-chemical treatment for repairing the oxide film as a dielectric, so that the electrolyte forming step is complicated. Further, those using TCNQ as the electrolyte layer were inferior in heat resistance because TCNQ melted at a temperature lower than the solder temperature. Further, since the conductivity of TCNQ is limited to about 1 S / cm, it has not been possible to meet the demand for a capacitor having more excellent high frequency characteristics. Therefore, a solid electrolytic capacitor using a conductive polymer having higher conductivity than MnO ₂ or TCNQ and having higher heat resistance than TCNQ as an electrolyte layer has been proposed. For example, Japanese Patent Application Laid-Open No. 60-37114 discloses a capacitor in which a conductive polymer composed of a doped five-membered cyclic compound polymer is used as an electrolyte layer. Also, JP-A-63
JP-A-80517 discloses a capacitor in which a thin film layer is formed by applying a solution of a heteropentacyclic polymer compound in a volatile solvent, and the doped thin film layer is used as an electrolyte layer.

However, the method of forming an electrolyte comprising a conductive polymer described in Japanese Patent Application Laid-Open No. 60-37114 is an electrolytic oxidation polymerization method, so the steps are complicated, and particularly, such as a tantalum solid electrolytic capacitor. However, it has been difficult in terms of mass production to form a small capacitor element. Also,
Performing such electrode reactions on the dielectric surface of a capacitor that is insulative usually involves considerable difficulty. Also,
As shown in JP-A-63-80517,
In the method of applying a volatile solvent solution of the conductive polymer in an insulated state, it is not possible to form a conductive polymer layer with a sufficient thickness inside the capacitor element, so that the heat resistance of the capacitor is poor and the conductivity is high. Since the molecular film is too dense, the change due to the stress in the process is large, so that the characteristics after molding the exterior tend to decrease.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to use a composition for forming an electrolyte of a solid electrolytic capacitor capable of easily producing a solid electrolytic capacitor excellent in capacity from low frequency to high frequency and excellent in internal resistance. In order to provide a solid electrolytic capacitor that is easy to form an electrolyte, has high heat resistance, and has excellent capacity, internal resistance, dielectric loss, and impedance from low to high frequencies, and less specific reduction due to process stress. is there.

Another object of the present invention is to provide a solid electrolytic capacitor using a composition for forming an electrolyte of a solid electrolytic capacitor having excellent storage stability of a solution containing aniline.

[0006]

The present invention comprises a first solution containing (A) aniline, (B) an organic sulfonic acid, (C) water and (D) an organic solvent, (E) an oxidizing agent, And (F) repeating the step of impregnating the solid electrolytic capacitor element with the solid electrolytic capacitor electrolyte-forming composition prepared by mixing the second solution containing water to form the inside and outside of the solid electrolytic capacitor element. Wherein the weight average molecular weight of the polyaniline electrolyte is from 5,000 to 25.
000, wherein the weight average molecular weight of the polyaniline electrolyte inside the solid electrolytic capacitor element is larger than the weight average molecular weight of the polyaniline electrolyte outside the solid electrolytic capacitor element. .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The aniline which is the component (A) in the first solution of the present invention is oxidatively polymerized by the action of the oxidizing agent which is the component (E) in the second solution of the present invention, and is polyaniline. To form The acid generated by decomposition of the organic sulfonic acid as the component (B) in the first solution of the present invention or the oxidizing agent as the component (E) in the second solution of the present invention is added to the polyaniline. Thus, the polyaniline becomes conductive and functions as an electrolyte of the solid electrolytic capacitor.

The organic sulfonic acid as the component (B) in the first solution of the present invention forms a salt with the aniline as the component (A) in the first solution of the present invention. Such salt formation is necessary for aniline to undergo oxidative polymerization under the action of an oxidizing agent to form polyaniline. Further, the organic sulfonic acid, which is the component (B) in the first solution in the present invention, forms a salt with polyaniline produced by oxidative polymerization under the action of an oxidizing agent, and makes the polyaniline conductive. It is a necessary component to obtain. As the organic sulfonic acid which is the component (B) in the first solution in the present invention, known organic sulfonic acids can be used without any particular limitation. It is preferred in that respect.

For example, benzenesulfonic acid, toluenesulfonic acid, n-hexanesulfonic acid, n-octylsulfonic acid, dodecylsulfonic acid, cetylsulfonic acid,
Dodecylbenzenesulfonic acid, camphorsulfonic acid,
Poly (vinyl) sulfonic acid, dinonylnaphthalenesulfonic acid, naphthalenesulfonic acid, p-chlorobenzenesulfonic acid, phenolsulfonic acid, phenoldisulfonic acid, trichlorobenzenesulfonic acid, 4-nitrotoluene-2-sulfonic acid, 1-octanesulfonic acid , Sulfonated polystyrene, sulfonated polyethylene, nitrobenzenesulfonic acid, 2-sulfobenzoic acid, 4-octylbenzenesulfonic acid, 2-methyl-5-isopropylbenzenesulfonic acid, and sulfosuccinic acid. Phenolsulfonic acid, phenoldisulfonic acid, sulfosuccinic acid, and nitrobenzenesulfonic acid are preferred in terms of heat resistance and conductivity of polyaniline.
Nitrobenzenesulfonic acid includes o-, m- and p-
There is nitrobenzene sulfonic acid, more preferably o
-Or p-nitrobenzenesulfonic acid, most preferably o-nitrobenzenesulfonic acid, is used.

The water as the component (C) in the first solution of the present invention dissolves the salt formed by the organic sulfonic acid as the component (B) of the present invention with the aniline as the component (A) of the present invention. Needed to do so. Water as the component (F) in the second solution of the present invention is necessary for dissolving the oxidizing agent in the second solution of the present invention. In the present invention, water as the component (C) in the first solution and the water as the component (F) in the second solution preferably do not contain ionic impurities, organic substances, and the like. Is preferably performed.

The second solution in the present invention preferably contains (G) an organic solvent. (G) By blending the organic solvent, the stability of the second solution is increased, and the thickness of the polyaniline formed by the oxidative polymerization becomes uniform.

The component (D) in the first solution and the component (G) in the second solution according to the present invention function to improve the solubility of aniline, and the first solution according to the present invention and the component (G) according to the present invention are used. The aniline in the mixed solution prepared by mixing the oxidizing agent solution, which is the second solution, can be oxidized and polymerized to delay the start of the reaction that generates polyaniline, and the subsequent step of impregnating the capacitor element can be easily performed. Become.
The component (G) in the second solution of the present invention has a function of suppressing the decomposition reaction of the oxidizing agent and a function of improving the storage stability of the second solution of the present invention. Examples of the organic solvent of the components (D) and (G) in the first solution in the present invention include methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and the like. Tripropylene glycol, methyl cellosolve, ethyl cellosolve, methyl carbitol, ethyl carbitol, butyl carbitol, triethylene glycol monomethyl ether,
Triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diglyme, triglyme, tetraethylene glycol dimethyl ether, Tetrahydrofuran, dimethyl ether, trioxane, dioxane, acetone, methyl ethyl ketone, methyl acetate, ethylene carbonate, ethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether acetate, diethylene glycol diacetate,
There are N, N-dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, acetonitrile, picoline, sulfolane, and the like, and two or three of these can be used in combination. Of these solvents, glycol monoethers or diethers are preferred in view of the solubility of the component (A). Ethylene carbonate, tetrahydrofuran, acetonitrile, and the like are preferably used because they are not easily oxidized by an oxidizing agent. Of course, the organic solvent in the present invention is not limited to the above.

The oxidizing agent which is the component (E) in the second solution in the present invention acts on aniline to oxidize and polymerize it to form polyaniline. The oxidizing agent as the component (E) in the second solution according to the present invention has a standard electrode potential close to or higher than the aniline oxidation potential of 0.79 V when a standard hydrogen electrode is used as a reference electrode. Are preferred, for example, ammonium peroxodisulfate, dichromate,
Potassium permanganate, trivalent iron, tetravalent cerium, hydrogen peroxide, perchlorate, perbromate, trivalent cobalt and the like are preferred. Of these, ammonium peroxodisulfate is most preferable in that the weight average molecular weight of polyaniline is increased and the conductivity of polyaniline is increased.

It is preferable that (A) aniline, (C) water and (D) the organic solvent in the first solution of the present invention are all degassed. In the present invention, degassing refers to an operation of discharging a gas contained in a liquid by exhausting in a vacuum, or bubbling with an inert gas such as nitrogen or argon to remove a reactive gas such as oxygen from the system. Operation, etc. By degassing, the reaction of the electrolyte forming composition of the solid electrolyte of the present invention starts before contact with the oxidizing agent, or the conductivity of the polyaniline obtained by oxidative polymerization by the action of the oxidizing agent decreases. Since the tendency of the solid electrolyte can be prevented, the storage stability of the electrolyte forming composition of the solid electrolyte of the present invention can be improved. In addition, by degassing, a polyaniline film having excellent uniformity of the film thickness can be obtained.

The solid electrolytic capacitor in the present invention is:
A metal (valve metal) that becomes a dielectric when oxidized, such as aluminum, tantalum, niobium, vanadium, titanium, and zirconium, is used as an anode. After forming a thin oxide film as a dielectric on the surface of the anode metal, the dielectric Capacitors formed by forming a conductive substance for obtaining electrical contact with the cathode, connecting to the cathode, and thereafter performing sealing, canning, and the like are collectively referred to.

The electrolyte in the present invention is used for obtaining an electrical contact between the dielectric and the cathode after forming a thin oxide film as a derivative on the surface of a metal (valve metal) used for the anode of the solid electrolytic capacitor. Refers to a conductive substance.

The capacitor element according to the present invention refers to a capacitor element in which an oxide film serving as a dielectric is formed on a valve metal surface.
The method of forming an oxide film on the surface of these valve metals is usually
Any method can be used as long as it is used at the time of manufacturing an electrolytic capacitor. For example, a method of forming an oxide film by applying a voltage to an aluminum foil expanded by etching in an aqueous solution of ammonium adipate, or tantalum A known method such as a method of forming an oxide film by applying a voltage to a sintered body in a nitric acid aqueous solution is used. As the valve metal, a tantalum sintered body is most preferable in terms of the dielectric constant of the oxide film, which is a dielectric substance, the ease of forming the oxide film, and acid resistance, etc. It is called a tantalum element.

The mixed solution according to the present invention is a solution obtained by mixing the first solution according to the present invention and the second solution according to the present invention.

The step of impregnating in the present invention means a step of impregnating the capacitor element of the present invention with the mixed solution of the present invention, and then drying. Simultaneously with drying, aniline is oxidatively polymerized to form polyaniline, and an electrolyte made of polyaniline is formed on the surface of the oxide film, which is the dielectric of the capacitor element of the present invention. Since the mixed solution in the present invention contains aniline and an oxidizing agent at the same time, polyaniline is gradually produced over time.
For this reason, the impregnating step in the present invention needs to be performed before polyaniline precipitates in the mixed solution in the present invention.

The amount of aniline as the component (A) in the first solution in the present invention is preferably 5 mol / L or less, more preferably 4 mol / L or less. When the amount of the aniline as the component (A) in the first solution of the present invention exceeds 5 mol / L, the amount of the component (B) in the present invention increases.
The salt formed between the organic sulfonic acid and aniline as components tends to precipitate as a solid.

The concentration of aniline as the component (A) in the mixed solution prepared by mixing the first solution of the present invention and the second solution of the present invention is from 0.1 mol / L to 1 mol / L. Is more preferably 0.15 mol / L to 1 mol / L, particularly preferably 0.2 mol / L to 0.9 mol / L. When the concentration of the component (A) in the mixed solution in the present invention is less than 0.1 mol / L, the thickness of the polyaniline formed on the oxide film surface of the capacitor element tends to be thin, and the characteristics of the obtained capacitor tend to deteriorate. In addition, if it exceeds 1 mol / L, the conductivity of the polyaniline film formed on the oxide film surface of the electrolytic capacitor tends to decrease, and the characteristics of the capacitor also tend to deteriorate.

The compounding amount of the organic sulfonic acid as the component (B) in the first solution of the present invention is a molar ratio with respect to the concentration of the aniline as the component (A) in the first solution of the present invention. 0.1 to 2.0, preferably 0.1 to 2.0.
It is more preferably from 5 to 1.5, most preferably from 0.2 to 1.0. When the blending amount of the component (B) in the first solution of the present invention is less than 0.1 in a molar ratio to aniline as the component (A) of the first solution of the present invention,
When the polyaniline obtained by oxidative polymerization of aniline is held at a high temperature, the electrical conductivity tends to decrease. When it exceeds 2.0, the electrical conductivity of the polyaniline obtained by oxidative polymerization of aniline tends to decrease. .

In the present invention, the ratio of water as the component (C) to the organic solvent as the component (D) in the first solution is as follows: It is preferable that the volume of the organic solvent as a component is between 0.2 and 4, more preferably between 0.3 and 3. When the volume of the organic solvent as the component (D) is larger than 4 when the volume of the water as the component (C) in the first solution in the present invention is 1, the salt of the salt formed with aniline and sulfonic acid is obtained. Insufficient dissolution tends to cause precipitation,
If it is less than 0.2, aniline tends to be difficult to dissolve.

The amount of water as the component (F) in the second solution according to the present invention is such that the concentration of the oxidizing agent as the component (E) in the second solution according to the present invention is the same as that of the component (F). The amount is preferably at least 3 mol / L or less in terms of the concentration with respect to a certain water, and more preferably the amount of the oxidizing agent (E) is at least 2.5 mol / L or less. . The concentration of the oxidizing agent as the component (E) in the second solution according to the present invention with respect to the water as the component (F) is 3 mol / L.
When it exceeds, the storage stability of the second solution in the present invention tends to decrease.

The amount of the organic solvent as the component (G) in the second solution of the present invention is such that the volume of water as the component (F) in the second solution of the present invention is 1 Is preferably 3 or less, and more preferably 2 or less by volume. When the volume of water as the component (F) in the second solution of the present invention is set to 1, if the volume of the organic solvent as the component (G) in the second solution of the present invention is larger than 3 by volume. The oxidizing agent tends to precipitate due to insufficient dissolution.

In the mixed solution prepared by mixing the first solution of the present invention and the second solution of the present invention, water as the component (C), an organic solvent as the component (D), and a component (F). It is necessary to adjust the total amount of certain water and the organic solvent that is the component (G) so that the concentration of the aniline that is the component (A) in the mixed solution of the present invention is the above-described predetermined concentration. . Further, (C) in the mixed solution in the present invention
The ratio of the total amount of water as the component and the component (F) to the ratio of the organic solvent as the component (D) and the organic solvent as the component (G) in the mixed solution of the present invention is as follows. It is necessary that the mixing ratio is such that both the organic sulfonic acid as the component) and the oxidizing agent as the component (E) can be dissolved, and further, the sulfonic acid as the component (B) must be easily dissociated. . Therefore, when the total volume of the components (C) and (F) in the mixed solution in the present invention is set to 1, the total volume of the components (D) and (G) is 0.1 to 9
, More preferably 0.15 to 8.5, and most preferably 0.2 to 8. When the total volume of the components (D) and (G) is smaller than 0.1 when the total volume of the components (C) and (F) is 1, the first solution and the present invention The reaction of the aniline in the mixed solution prepared by mixing the oxidizing agent solution, which is the second solution in the invention, is oxidized and polymerized to generate polyaniline, so that the reaction starts too early, making the subsequent impregnation step for the capacitor element difficult. Tend to be. On the other hand, when this ratio is greater than 9, the salt formed by aniline and sulfonic acid is difficult to dissolve, and the precipitation tends to occur.

The compounding amount of the oxidizing agent as the component (E) in the second solution in the present invention needs to be a concentration at which the oxidizing agent can be dissolved, and is the component (F) in the second solution. The concentration is preferably 3 mol / L or less, more preferably 2.5 mol / L or less, in terms of the concentration with respect to water. When the concentration of the oxidizing agent as the component (E) in the second solution of the present invention with respect to the water as the component (F) exceeds 3 mol / L, the storage stability of the second solution according to the present invention decreases. There is a tendency.

The concentration of the oxidizing agent as the component (E) in the mixed solution prepared by mixing the first solution of the present invention and the second solution of the present invention is (A) in the mixed solution of the present invention.
The molar ratio with respect to the component aniline is preferably from 0.5 to 2, more preferably from 0.6 to 1.6, and most preferably from 0.75 to 1.4. When this ratio is smaller than 0.5, polyaniline produced by oxidative polymerization of aniline tends to be underoxidized, and the conductivity tends to decrease. When this ratio is larger than 2, the weight average molecular weight of polyaniline produced by oxidative polymerization of aniline tends to decrease, and the conductivity tends to decrease.

As a preferred method of manufacturing the solid electrolytic capacitor of the present invention, the capacitor element of the present invention is impregnated with a mixed solution prepared by mixing the first solution of the present invention and the second solution of the present invention. After that, the drying step is repeated once to several tens of times, and then further dried to evaporate the remaining moisture and the like, and polyaniline is applied to the oxide film surface which is a dielectric formed on the valve metal surface of the capacitor element. After forming an electrolyte layer, a carbon paste layer and a silver paste layer are formed in this order on an electrolyte made of polyaniline, and the element is adhered to a lead frame or the like with a conductive adhesive, and further sealed if necessary. There is a method in which the package is sealed with a stopper and packaged.

The weight average molecular weight of the electrolyte outside the polyaniline electrolyte outside the solid electrolytic capacitor element of the present invention is determined by the appearance of an oxide film of the capacitor element on the electrolyte layer on the surface of the capacitor element on which the electrolyte layer is formed. The resulting powder was stirred for 2 hours in aqueous ammonia adjusted to a concentration of 3% by weight, filtered, washed with distilled water, and dried at 100 ° C. with a vacuum drier.
For 10 hours, and further dissolved in an N-methylpyrrolidone solution of lithium chloride adjusted to a concentration of 0.1% by weight.
The measurement was performed at a flow rate of 0.3 ml / min.

The weight average molecular weight of the electrolyte inside the polyaniline electrolyte inside the element of the solid electrolytic capacitor of the present invention can be determined by removing the capacitor from which the external electrolyte has been cut off in ammonia water adjusted to a concentration of 3% by weight. After stirring for an hour, washing with distilled water, drying in a vacuum dryer at 100 ° C. for 10 hours, and remaining in the capacitor element with an N-methylpyrrolidone solution of lithium chloride adjusted to a concentration of 0.1% by weight. The electrolyte was dissolved, and the solution was subjected to column temperature 60 ° C. and flow rate 0.3 ml / g using GPC.
It was measured under the condition of min.

The weight average molecular weight of the electrolyte formed on the capacitor element in the present invention is from 5,000 to 250,000.
It is preferably in the range of 0, more preferably 1
000-200,000, most preferably 2
It is between 0000 and 150,000. When the weight average molecular weight is smaller than 5,000, the conductivity of polyaniline produced by oxidative polymerization of aniline decreases. When the weight average molecular weight is larger than 250,000, the second and subsequent impregnation steps for the capacitor element become difficult.

In the present invention, the weight-average molecular weight of the electrolyte differs between the inside and the outside of the capacitor element. The weight-average molecular weight of the internal electrolyte is larger than that of the external electrolyte, and the internal electrolyte is larger than the external electrolyte. It is preferable that the weight average molecular weight is larger by 10% or more. When the weight average molecular weight of the electrolyte inside is large, an electrolyte having a sufficient thickness can be formed inside, and a decrease in characteristics due to stress in subsequent steps is reduced.

[0034]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Aniline (Wako Pure Chemical Industries, Ltd., reagent), phenolsulfonic acid (Wako Pure Chemical Industries, Ltd., reagent), ion-exchanged water, and acetonitrile (Wako Pure Chemical Industries, Ltd., reagent) )
Was used to obtain a first solution of the present invention having the composition shown in Table 1. Further, ammonium peroxodisulfate (reagent, Wako Pure Chemical Industries, Ltd.) was dissolved in ion-exchanged water to obtain a second solution of the present invention having the composition shown in Table 1. From these solutions, the solid electrolytic capacitor of Example 1 was obtained by the following method.

FIG. 1 is a sectional view of a solid electrolytic capacitor of the present invention using tantalum as a valve metal. 20V in nitric acid aqueous solution
Using a prismatic tantalum fine powder sintered body pellet (porosity 60%, design capacity 100 μF) on which an oxide film has been formed, the tantalum oxide film 5
Is impregnated with a mixed solution obtained by mixing the first solution according to the present invention shown in Table 1 with the second solution according to the present invention shown in Table 1 so that the volume ratio thereof becomes 1 to 1 at room temperature. , And dried at 80 ° C for 20 minutes with a hot air drier. This impregnation process is repeated 13 times,
An electrolyte layer 9 made of polyaniline was formed. Table 3 shows the weight average molecular weight of the obtained electrolyte.

Further, a carbon paste layer 7 and a silver paste layer 8 are sequentially formed on the tantalum element 2 on which the electrolyte is formed, and a cathode lead 10 is connected to the silver paste layer 8 using a silver paste. Was connected to an anode 3 and molded with a sealing material 1 to obtain a solid electrolytic capacitor of the present invention using a tantalum sintered body as a valve metal. Table 3 shows the electrical characteristics of the obtained solid electrolytic capacitor.

Example 2 In the composition of the first solution of Example 1, phenol disulfonic acid (reagent, Wako Pure Chemical Industries, Ltd.) was used instead of phenol sulfonic acid, and the mixing ratio was changed. Except for the above, the first solution and the second solution of the example 2 were obtained in the same manner as the example 1. Further, a solid electrolytic capacitor of Example 2 was obtained in the same manner as in Example 1 except that the first solution and the second solution of Example 2 were used and the number of times of impregnation was changed. Table 1 shows the compositions of the first solution and the second solution of Example 2, and Table 3 shows the weight average molecular weight of the obtained electrolyte and the electrical characteristics of the obtained solid electrolytic capacitor.

Example 3 Example 1 was the same as Example 1 except that in the composition of the first solution, sulfosuccinic acid (Aldrich, reagent) was used instead of phenolsulfonic acid, and the mixing ratio was changed. Thus, a first solution and a second solution of Example 3 were obtained. Further, a solid electrolytic capacitor of Example 3 was obtained in the same manner as in Example 1 except that the first solution and the second solution of Example 3 were used and the number of times of impregnation was changed. Example 3
Table 1 shows the composition of the first solution and the second solution, and Table 3 shows the weight average molecular weight of the obtained electrolyte and the electrical characteristics of the obtained solid electrolytic capacitor.

Example 4 The composition of the first solution of Example 1 was changed in that o-nitrobenzenesulfonic acid (Tokyo Kasei Kogyo Co., Ltd., reagent) was used instead of phenolsulfonic acid, and the mixing ratio was changed. Except for the above point, the same procedure as in Example 1 was repeated except that the first solution of Example 4
And a second solution was obtained. Also, the first solution of Example 4,
A solid electrolytic capacitor of Example 4 was obtained in the same manner as in Example 1, except that the second solution was used and the number of times of impregnation was changed. Table 1 shows the compositions of the first solution and the second solution of Example 4, and Table 3 shows the weight average molecular weight of the obtained electrolyte and the electrical characteristics of the obtained solid electrolytic capacitor.

Example 5 The procedure of Example 1 was repeated, except that ethanol (reagent, Wako Pure Chemical Industries, Ltd.) was used instead of acetonitrile in the composition of the first solution of Example 1. A first solution and a second solution were obtained. Further, a solid electrolytic capacitor of Example 5 was obtained in the same manner as in Example 1 except that the first solution and the second solution of Example 5 were used. Table 1 shows the compositions of the first solution and the second solution of Example 5, and Table 3 shows the weight average molecular weight of the obtained electrolyte and the electrical characteristics of the obtained solid electrolytic capacitor.

Comparative Example 1 After mixing the first solution and the second solution of Example 1,
After impregnating the tantalum element with the mixed solution, the hot air dryer dries to 40 ° C.
For 30 minutes, and dried in a hot air drier at 100 ° C. for 60 minutes to obtain a solid electrolytic capacitor of Comparative Example 1 in the same manner as in Example 1. Table 4 shows the weight average molecular weight of the polyaniline electrolyte of the solid electrolytic capacitor of Comparative Example 1 and the electrical characteristics of the obtained solid electrolytic capacitor. The weight average molecular weight of the polyaniline electrolyte in the tantalum element of the solid electrolytic capacitor of Comparative Example 1 was out of the range of the present invention.

Comparative Example 2 After mixing the first solution and the second solution of Example 1,
A comparative example was prepared in the same manner as in Example 1 except that the tantalum element was impregnated with the mixed solution, reacted at 0 ° C. for 30 minutes, and dried at 40 ° C. for 20 minutes with a hot air drier, and the number of times of impregnation was changed. 2 was obtained. Table 4 shows the weight average molecular weight of the polyaniline electrolyte of the solid electrolytic capacitor of Comparative Example 2 and the electrical characteristics of the obtained solid electrolytic capacitor. The weight average molecular weight of the electrolyte made of polyaniline inside the tantalum element of the solid electrolytic capacitor of Comparative Example 2 was:
The weight average molecular weight of the electrolyte made of polyaniline outside the tantalum element was smaller than the range of the present invention.

Comparative Example 3 The tantalum of Comparative Example 3 was replaced with a valve metal in the same manner as in Example 1 except that the amount of the oxidizing agent (E) in the present invention was outside the preferred range of the present invention. A solid electrolytic capacitor was manufactured. Table 2 shows the compositions of the first solution and the second solution of Comparative Example 3, and Table 4 shows the weight average molecular weight of the obtained electrolyte and the electrical characteristics of the obtained solid electrolytic capacitor. The weight average molecular weight of the electrolyte made of polyaniline outside the tantalum element of Comparative Example 3 was out of the range of the present invention.

Comparative Example 4 Comparative Example 4 was carried out in the same manner as in Example 1 except that phenolsulfonic acid as the component (B) in the present invention was not used.
A solid electrolytic capacitor using tantalum as a valve metal was manufactured. Table 2 shows the compositions of the first solution and the second solution of Comparative Example 4, and Table 4 shows the weight average molecular weight of the obtained electrolyte and the electrical characteristics of the obtained solid electrolytic capacitor.

Comparative Example 5 Comparative Example 5 was carried out in the same manner as in Example 1 except that hydrochloric acid which was outside the scope of the present invention was used as the component (B) in the present invention.
A solid electrolytic capacitor using tantalum as a valve metal was manufactured. Table 2 shows the compositions of the first solution and the second solution of Comparative Example 5, and Table 4 shows the weight average molecular weight of the obtained electrolyte and the electrical characteristics of the obtained solid electrolytic capacitor.

As is clear from comparison of Tables 3 and 4, a solid electrolytic capacitor according to a comparative example in which an electrolyte having a weight average molecular weight outside the range of the present invention was formed or a composition for forming an electrolyte outside the range of the present invention was used. The solid electrolytic capacitor according to the example was superior in both the low-frequency characteristics and the high-frequency characteristics to the solid electrolytic capacitor according to the comparative example manufactured as described above.

In addition, when the first solution in the present invention is prepared without degassing the components (A), (C) and (D) and stored at room temperature (25 ° C.), it takes about 2 weeks. Although precipitation occurred, when the first solution in the present invention was prepared by degassing the components (A), (C) and (D), no precipitation occurred even after storage at room temperature for one month. The storage stability of the first solution was improved.

Further, the second solution of the present invention in which ammonium peroxodisulfate was dissolved at 10% by weight in water was 25%.
After storage at 50 ° C. for 50 days, polyaniline did not precipitate at all even when mixed with the first solution of the present invention. On the other hand, the second solution of the present invention prepared by dissolving ammonium peroxodisulfate in a solvent having a volume ratio of acetonitrile and water of 1: 1 is mixed with the first solution even after storage at 25 ° C. for 50 days. Then, precipitation of polyaniline occurred, and the storage stability of the second solution was improved.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

The solid electrolytic capacitor of the present invention has a simple electrolyte formation, high heat resistance, and excellent capacity, internal resistance, dielectric loss, and impedance from low to high frequencies. Less decrease.

Further, the solid electrolytic capacitor of the present invention is excellent in uniformity of the electrolyte film thickness by using an electrolyte-forming composition excellent in storage stability of a solution containing aniline.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of the solid electrolytic capacitor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sealant 2 Tantalum element 3 Anode 4 Tantalum wire 5 Tantalum oxide film 6 Tantalum 7 Carbon paste layer 8 Silver paste layer 9 Electrolyte layer 10 Cathode lead

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ikutora 4-3-1-1, Higashicho, Hitachi, Ibaraki Prefecture Inside the Ibaraki Research Laboratory, Hitachi Chemical Co., Ltd. (72) Inventor Toru Yoshikawa 4-3-1-1, Higashicho, Hitachi City, Ibaraki Prefecture Within Ibaraki Research Laboratory, Hitachi Chemical Co., Ltd.

Claims (3)

[Claims] 1. A first solution containing (A) aniline, (B) an organic sulfonic acid, (C) water and (D) an organic solvent, and a first solution containing (E) an oxidizing agent and (F) water. The step of impregnating the solid electrolytic capacitor element with the electrolyte forming composition of the solid electrolytic capacitor prepared by mixing the two solutions was repeated to form an electrolyte made of polyaniline inside and outside the solid electrolytic capacitor element. In a solid electrolytic capacitor, the weight average molecular weight of the polyaniline electrolyte is 5,000 to 250,000, and the weight average molecular weight of the polyaniline electrolyte inside the solid electrolytic capacitor element is outside the solid electrolytic capacitor element. A solid electrolytic capacitor having a weight average molecular weight larger than that of an electrolyte composed of polyaniline. 2. The solid electrolytic capacitor according to claim 1, wherein (B) the organic sulfonic acid is phenolsulfonic acid, phenoldisulfonic acid, sulfosuccinic acid or nitrobenzenesulfonic acid. 3. An aniline, (C) in a first solution.
2. The solid electrolytic capacitor according to claim 1, wherein both the water and the organic solvent (D) are degassed.