JP2904453B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a solid electrolytic capacitor in which a conductive polymer film is formed on a conductive polyaniline film by electrolytic polymerization to form a solid electrolyte.

[0002]

2. Description of the Related Art There has been proposed a solid electrolytic capacitor having a structure in which a dielectric oxide film is formed on the surface of a valve metal and a conductive polymer film is formed on the dielectric oxide film to form a solid electrolyte. In forming a conductive polymer film by electrolytic polymerization on a dielectric oxide film, since the dielectric oxide film is an insulator, it is difficult to form a conductive polymer film by direct electrolytic polymerization. A capacitor having a structure in which a conductive polymer film is formed as a conductive precoat layer by chemical oxidation polymerization, and then a conductive polymer film is formed on the conductive polymer film by electrolytic polymerization to form a solid electrolyte 63-1
73313) is disclosed. Also, after forming a conductive metal oxide thin film such as manganese dioxide as a conductive pre-coat layer on the dielectric oxide film, a conductive polymer film is formed on the thin film by electrolytic polymerization to form a solid electrolyte. A capacitor having a structure (Japanese Patent Laid-Open No. 63-158829) has been proposed. These capacitors have better frequency characteristics, electrical characteristics, and heat resistance than conventional capacitors.
However, in the method of forming a conductive pre-coat layer by chemical oxidative polymerization, there has been a need for an improvement since a conductive polymer that does not adhere to the dielectric oxide film during chemical oxidative polymerization is by-produced and wasted. On the other hand, in the method of forming a precoat layer of a conductive metal oxide thin film, a step of thermally decomposing manganese nitrate or the like at a high temperature is required, which makes the process complicated, and the dielectric oxide film is easily damaged. I was

[0003] Polyaniline, which is one of the conductive polymers, is very economically advantageous because it uses inexpensive aniline as a raw material. However, in general, a high concentration of protons such as sulfuric acid is required for synthesizing conductive polyaniline. It is necessary to react in the coexistence of acid.On the other hand, aluminum, which is widely used for capacitors, is extremely weak to acid, and dielectric oxide film and aluminum are damaged when directly forming conductive polyaniline film on aluminum foil. Therefore, it was hardly used for a solid electrolyte of a capacitor.

[0004] A solvent-soluble undoped polyaniline solution is coated on a dielectric oxide film and dried to obtain a pKa value of 4.8.
The following solid electrolytic capacitors have been proposed in which a conductive polyaniline film is formed by doping with a protonic acid to form a solid electrolyte and a method for manufacturing the same (Japanese Patent Laid-Open No. 3-35516). This method has a simple manufacturing process, but the conductivity of the formed conductive polyaniline film is insufficient, and the filling into the etching pits formed on the valve metal surface is also insufficient. After forming a conductive precoat layer on the body oxide film, a conductive polymer film is formed on the precoat layer by electrolytic polymerization to form a solid electrolyte. The loss is large and the capacity impregnation rate (the value of the capacitance when the solid electrolyte is formed to the capacitance when the electrolyte is impregnated on the dielectric oxide film expressed in percentage) is small.

[0005] The valve metal surface is subjected to an etching treatment to enlarge the surface area in order to increase the capacitance per unit area. In order to increase the enlargement ratio, a method of reducing the diameter of the etching pits to increase the number of pits or increasing the etching pit length is used. However, when the enlargement ratio of the valve metal is increased by such a method, it is generally difficult to sufficiently form the solid electrolyte to the deepest portion in the etching pit, so that the capacity impregnation ratio tends to decrease.

When the manufacturing method disclosed in JP-A-3-35516 is applied to an etching foil, the capacity impregnation rate is small. The reason for this is that the high molecular weight (intrinsic viscosity is 0.40 g / l) used to form a tough polyaniline thin film.
It is presumed that the solvent-soluble polyaniline (00 ml or more) cannot be sufficiently impregnated to the deepest part in the etching pit. In order to solve this problem, it is easy to reduce the molecular weight of the solvent-soluble polyaniline. However, when such a low molecular weight polyaniline is used, the packing density is reduced, resulting in a large dielectric loss and a high heat resistance. If the capacitor is left in a high-temperature atmosphere for a long time, the change over time in the capacitor characteristics becomes large, and a solution has been required.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solid electrolytic capacitor having a conductive polymer film formed on the surface of a dielectric oxide film on a valve metal with a simple manufacturing method and a large area magnification. Manufacture of solid electrolytic capacitors that have a large capacity impregnation rate even for valve-acting metals with large values, low equivalent series resistance and low initial value of dielectric loss of the obtained capacitors, and capacitor characteristics that do not deteriorate even if left in a high-temperature atmosphere for a long time. Is to provide a way.

[0008]

As a result of intensive studies, the present inventors have completed a method for manufacturing a solid electrolytic capacitor which can solve the above-mentioned problems.

That is, the intrinsic viscosity at 30 ° C. in N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) is 0.30 g / 100 ml or more, 0.40 g / 1
Forming a conductive polyaniline film by contacting a solvent-soluble undoped polyaniline solution and a naphthalene sulfonic acid solution of less than 00 ml, and then forming a conductive polymer film by electrolytic polymerization; This is a method for manufacturing a capacitor. Hereinafter, the method for manufacturing the solid electrolytic capacitor will be described in detail.

As the valve metal, aluminum, tantalum, titanium or the like is used.
It is used in the form of a wound or sintered body. Next, the case where aluminum is used as a valve metal in the present invention will be described.

After etching the surface of the aluminum foil, an anode lead is connected through a lead tab, and electrolytic oxidation is performed in an aqueous solution of ammonium adipate or the like to form a dielectric oxide film on the surface to obtain an element.

An aluminum foil 1 which is an index representing a magnification ratio when the aluminum foil is enlarged by etching.
The CV product value per cm square means that a 1 cm square aluminum foil is formed with "V" V, and the capacitance when impregnated with the electrolytic solution is "C".
This is the product of “C” and “V” at μF, and the larger this is, the larger the magnification.

Next, the intrinsic viscosity at 30 ° C. in the NMP is 0.30 g / 100 ml or more and 0.40 g / 100 ml on the element on which the dielectric oxide film is formed.
An operation of impregnating a solvent-soluble undoped polyaniline solution having a concentration of less than 100 g / 100 ml and then drying the same is repeated several times to form a undoped polyaniline film, and then performing a doping operation by contacting with a naphthalenesulfonic acid solution. A conductive polyaniline film is formed by repeating the operation several times, or repeating the operation of impregnating the solution containing the undoped polyaniline and naphthalenesulfonic acid and then drying the solution. The latter significantly simplifies the process.

The solvent-soluble undoped polyaniline used in the present invention has an intrinsic viscosity at 30 ° C. of 0.30 g in NMP.
/ 100ml or more and less than 0.40g / 100ml. 0.3 intrinsic viscosity
If it is less than 0 g / 100 ml, since the packing density of polyaniline is low and the molecular weight is low, the initial value of the dielectric loss and equivalent series resistance of the obtained capacitor is large, and the change over time of the characteristics when left in a high-temperature atmosphere is large. . Also, 0.40g / 100
If it is more than ml, the capacity impregnation rate will decrease and the surface area of the dielectric oxide film will not only be wasted, but also there will be many voids in which no solid electrolyte is formed in the etching pits. Deteriorates.

The undoped polyaniline solution is obtained by chemically oxidizing and polymerizing an aniline monomer and then undoping the obtained polyaniline and dissolving it in an organic solvent.
The chemical oxidative polymerization of an aniline monomer is carried out using an oxidizing agent in a solution of an aniline salt in the presence of a protonic acid. Examples of the aniline salt to be used include salts of aniline such as hydrochloric acid, sulfuric acid, perchloric acid and borofluoric acid. In addition, as the protonic acid, hydrochloric acid, sulfuric acid, perchloric acid, borofluoric acid, hexafluorophosphoric acid, or the like is used. Examples of the oxidizing agent include persulfates such as ammonium persulfate and potassium persulfate; peroxides such as hydrogen peroxide, sodium percarbonate and sodium perborate; potassium permanganate, potassium dichromate; Any oxidizing agent that can oxidize aniline such as a high-valent metal compound such as iron can be used,
An oxidant having a standard electrode potential of 0.7 V or more and less than 1.8 V is preferable. Such oxidizing agents include ferric salts, perchlorates, chlorates, chlorites, periodates, iodates, permanganates, manganese dioxide, dichromates,
Examples include sodium percarbonate and sodium perborate. When the standard electrode potential is less than 0.7 V, the chemical oxidation polymerization is insufficient. When the standard electrode potential is 1.8 V or more, there are many by-products, and the obtained capacitor has a large change with time in characteristics when left in a high-temperature atmosphere. When the polyaniline chemically oxidized and polymerized by this method is brought into contact with an alkaline solution such as ammonia, sodium hydroxide, an amine compound, etc., it becomes undoped polyaniline, and dimethylformamide (hereinafter abbreviated as DMF), dimethylsulfoxide (hereinafter abbreviated as DMSO)
), And becomes soluble in NMP and the like. By dissolving in these solvents or a mixed solvent of these and other solvents, a undoped polyaniline solution is obtained.

In the present invention, the doping of the undoped polyaniline uses naphthalenesulfonic acid.
Acids other than naphthalene sulfonic acid have poor initial properties,
Alternatively, even if the initial characteristics are excellent, the characteristics are significantly deteriorated when left in a high-temperature atmosphere. The naphthalenesulfonic acid used in the present invention includes 2-naphthalenesulfonic acid,
1,7-naphthalenedisulfonic acid, 2,6-naphthalenedisulfonic acid, 2,7-naphthalenedisulfonic acid, 1,3,
It is an alkyl-substituted or unsubstituted form of naphthalenesulfonic acid in which 1 to 4 sulfonic acid groups such as 6-naphthalenetrisulfonic acid and 1,3,5,7-naphthalenetetrasulfonic acid are substituted, and the number of substituted alkyl groups is 0 to 0. 4. The alkyl length of the alkyl group is 1 to 24 carbon atoms, preferably a 14 to 24 linear alkyl group. These doping agents are aqueous solutions or ketones, esters, alcohols, aromatic hydrocarbons, nitriles, cellosolves,
It is used by dissolving it in a single solvent such as a nitrogen-containing compound or a mixed solvent, and its concentration may be 1 mol / l or less.

After repeating the operation of impregnating and drying the undoped polyaniline solution on the dielectric oxide film several times, the operation of impregnating and drying the naphthalenesulfonic acid solution is repeated several times to form a conductive polyaniline film. I do.
The impregnation time may be several minutes to several tens of minutes, and the drying temperature is from room temperature to 200 ° C. Alternatively, polyaniline and naphthalene sulfonic acid dedoped in a dielectric oxide film are added to DMF,
An operation of impregnating and drying a solution dissolved in DMSO, NMP or a mixed solvent of these and another solvent is repeated several times to form a conductive polyaniline film. The contact time may be several minutes to several tens of minutes, and the drying temperature is from room temperature to 200 ° C.

Thereafter, electrolytic polymerization is carried out between the formed conductive polyaniline film as an anode and an external cathode to form a conductive polymer film by electrolytic polymerization on the polyaniline film.
The electrolytic polymerization is performed in an electrolytic solution containing 0.01 to 2 mol / l of a supporting electrolyte and 0.01 to 5 mol / l of a conductive polymer monomer. As the conductive polymer monomer, pyrrole, thiophene, furan, thienylenevinylene, an alkyl-substituted product thereof, or the like is used. From the viewpoint of the stability of the conductive polymer, pyrrole is particularly preferably used. Capacitors made of only a conductive polyaniline film doped with naphthalenesulfonic acid without forming a conductive polymer film by electrolytic polymerization have excellent characteristics regardless of how the intrinsic viscosity and the standard electrode potential of the oxidizing agent used are controlled. Can not be obtained.

The supporting electrolyte used in the electropolymerization of the present invention includes, as anions, halide ions such as hexafluoroline, hexafluoroarsenic, tetrafluoroboron, perchloric acid, halogen ions such as iodine, bromine and chlorine, and methane. Alkyl sulfonic acid ions such as sulfonic acid and dodecyl sulfonic acid, alkyl-substituted or unsubstituted benzene mono- or disulfonic acid ions such as benzene sulfonic acid, paratoluene sulfonic acid, dodecyl benzene sulfonic acid and benzene disulfonic acid, or 2-naphthalene Alkyl-substituted or unsubstituted naphthalenesulfonic acid ions of naphthalenesulfonic acid having 1 to 4 substituted sulfonic acid groups, such as sulfonic acid and 1,7-naphthalenedisulfonic acid, or alky such as alkylbiphenylsulfonic acid and biphenyldisulfonic acid. Killed or unsubstituted biphenylsulfonic acid ions, high molecular sulfonic acid ions such as polystyrenesulfonic acid and naphthalenesulfonic acid formalin condensate, boron compound ions such as bissulfylate boron and biscatecholate boron, PMo ₁₂ O _{40 and the} like And preferably a naphthalenesulfonic acid ion. Further, as the cation, lithium,
These are alkali metal ions such as potassium and sodium, and quaternary ammonium ions such as ammonium and tetraalkylammonium. Compounds include LiPF ₆ and LiAsF.
₆ , LiBF ₄ , KI, NaPF ₆ , NaClO ₄ , sodium toluenesulfonate, tetrabutylammonium toluenesulfonate, sodium 1,7-naphthalenedisulfonic acid, tetraethylammonium N-octadecylnaphthalenesulfonate, tetramethylammonium bissulfylate Ammonium and the like.

Thereafter, a capacitor is obtained by forming a conductive coating on the element surface with a carbon paste and a conductive paste, taking out a cathode lead from a part of the coating, and sealing the resultant in a resin mold or an outer case.

According to the present invention, a conductive polyaniline film as a precoat layer can be formed on the valve metal surface on which a dielectric oxide film is formed by a simple method such as impregnation, so that the production process is simplified, and the aniline monomer is simplified. Is not wasted. In addition, N of the undoped polyaniline
Inherent viscosity at 30 ° C in MP is 0.30g / 100ml or more, 0.40g / 1
By controlling the volume to less than 00 ml, even a valve metal having a large enlargement ratio can be sufficiently impregnated to the deepest portion of the etching hole, and the capacity impregnation rate increases. Furthermore, capacitors obtained by using naphthalenesulfonic acid as a dopant for polyaniline and forming a conductive polymer film by electrolytic polymerization on a conductive polyaniline film have low initial values of equivalent series resistance and dielectric loss. In addition, even if left in a high-temperature atmosphere for a long time, the characteristics do not deteriorate.

[0022]

The present invention will be described in detail below with reference to examples and comparative examples.

Example 1 4.7 g of aniline and concentrated sulfuric acid were placed in a 200 ml glass reaction vessel.
Take 30 ml of an aqueous solution containing 5 g, drop 30 ml of an aqueous solution containing 3.2 g of potassium permanganate (standard electrode potential 1.5 V) over 2 hours while maintaining the temperature at 10 ° C., and react for 3 hours to remove polyaniline by chemical oxidation polymerization. Obtained. After adding 50 ml of 25 wt% ammonia water and stirring for 3 hours, the mixture was centrifuged and washed with water to obtain undoped polyaniline powder. The undoped polyaniline has an intrinsic viscosity of 0.3 in NMP at 30 ° C.
It was 37 g / 100 ml. The undoped polyaniline 0.
A 3 wt% NMP / DMF (50 wt% / 50 wt%) solution was obtained. A roughened aluminum etched foil having a thickness of 90 μm and a width of 5 mm was obtained. After the foil was cut to 10 mm, the lead was attached by caulking, and 25% aqueous ammonium adipate was added.
A chemical conversion treatment was performed with V to form a dielectric oxide film. 5 wt% of boric acid, 5 wt% of citric acid, 1.4 wt% of ammonia
% Was 23.5 μF and the CV product value was 1175. The operation of impregnating the device with a undoped polyaniline solution for 5 minutes and drying at 70 ° C. was repeated three times, and then 0.2 mol of 2-naphthalenesulfonic acid was added.
/ L butanol solution was impregnated for 20 minutes and dried at 100 ° C to form a conductive polyaniline film. This element was reformed at 25 V in an aqueous solution of ammonium adipate, immersed in an aqueous solution of 0.2 mol / l of a pyrrole monomer and 0.2 mol / l of sodium 1,7-naphthalenedisulfonic acid as a supporting electrolyte, and applied to a conductive polyaniline film. A stainless steel wire was contacted from the outside to form an anode, and a constant current electrolytic polymerization (0.3 mA / unit, 120 minutes) was performed between the anode and the external electrode to form a polypyrrole film by electrolytic polymerization. This element is immersed in colloidal carbon, a silver paste is applied to form a conductive coating, a counter electrode is taken out from a part of the element, and then molded with an epoxy resin to form a capacitor having a rated voltage of 10 V and a rated capacitance of 22 μF. Was completed. Table 1 shows the conditions for preparing the capacitors, and the initial characteristics, capacity impregnation rate and
Table 3 shows the results of the high-temperature storage life test at 000 hours.

Example 2 The procedure of Example 1 was repeated, except that the reaction temperature of the chemical oxidative polymerization was changed to 20 ° C., and undoped with an intrinsic viscosity at 30 ° C. of 0.32 g / 100 ml in NMP. Polyaniline was prepared, and a capacitor was completed in the same manner as in Example 1. Table 1 shows the conditions for forming the capacitors, and Table 3 shows the characteristic values of the obtained capacitors.

EXAMPLE 3 4.7 g of aniline and concentrated sulfuric acid in a 200 ml glass reaction vessel.
30 ml of an aqueous solution containing 5 g was taken, 40 ml of an aqueous solution containing 11.4 g of ammonium persulfate (standard electrode potential 2.06 V) was added dropwise over 3 hours while maintaining at 5 ° C., and then reacted for 3 hours to obtain polyaniline by chemical oxidation polymerization. . After adding 50 ml of 25 wt% ammonia water and stirring for 3 hours, the mixture was centrifuged and washed with water to obtain undoped polyaniline powder. The undoped polyaniline has an intrinsic viscosity of 0.3 in NMP at 30 ° C.
It was 38 g / 100 ml. The undoped polyaniline 0.
A 3 wt% NMP / DMF (50 wt% / 50 wt%) solution was obtained. Using this undoped polyaniline, a capacitor was completed in the same manner as in Example 1. Table 1 shows the conditions for forming the capacitors, and Table 3 shows the characteristic values of the obtained capacitors.

The capacitor obtained in Example 3 has a large capacity impregnation rate and good initial characteristics. However, since ammonium persulfate is used as an oxidizing agent, dielectric loss and equivalent series resistance in a high-temperature standing life test are high. The change over time is slightly large.

Example 4 4.7 g of aniline and concentrated sulfuric acid were placed in a 200 ml glass reaction vessel.
Take 30 ml of an aqueous solution containing 5 g, add 50 ml of an aqueous solution containing 16.6 g of sodium peroxocarbonate (standard electrode potential 0.88 V) over 4 hours while maintaining the temperature at 15 ° C., and react for 5 hours to obtain polyaniline by chemical oxidation polymerization. Was. After adding 50ml of 25wt% ammonia water and stirring for 3 hours, centrifugation
After washing with water, undoped polyaniline powder was obtained. The intrinsic viscosity of the undoped polyaniline in NMP at 30 ° C. was 0.35 g / 100 ml. 0.2% by weight of the undoped polyaniline in NMP / ethanol (90% by weight / 10% by weight)
A solution was obtained. A roughened aluminum etched foil having a thickness of 90 μm and a width of 5 mm was obtained. After cutting the foil to 10 mm, a lead was attached by crimping, and a chemical conversion treatment was performed at 50 V in an aqueous solution of ammonium adipate to form a dielectric oxide film. The capacitance of this element immersed in an electrolytic solution for measuring capacity of 5 wt% of boric acid, 5 wt% of citric acid, and 1.4 wt% of ammonia is as follows:
It was 5.2 μF and the CV product value was 520. The operation of impregnating the device with the undoped polyaniline solution for 5 minutes and drying at 70 ° C. was repeated three times, and then impregnated with a 0.2 mol / l n-octadecylnaphthalenesulfonic acid butanol solution for 20 minutes and dried at 100 ° C. Then, a conductive polyaniline film was formed. This element was re-formed at 50 V in an aqueous solution of ammonium adipate, and then 0.2 mol / l of a pyrrole monomer and 0.2 mol of sodium 2-naphthalenesulfonate as a supporting electrolyte.
/ L containing water / ethanol (60wt% / 40wt%) solution, contact stainless steel wire from outside with conductive polyaniline film to make anode, and constant current electrolytic polymerization between external electrode (0.3mA) / Piece, 120 minutes) to form a polypyrrole film by electrolytic polymerization. This element is immersed in colloidal carbon, a silver paste is applied to form a conductive coating film, a counter electrode is taken out from a part of the element, and then molded with epoxy resin to form a capacitor with a rated voltage of 16 V and a rated capacitance of 4.7 μF. Was completed. Table 1 shows the conditions for making capacitors.
Table 3 shows the characteristic values of the obtained capacitors.

EXAMPLE 5 4.7 g of aniline and concentrated sulfuric acid were placed in a 200 ml glass reaction vessel.
Take 30 ml of an aqueous solution containing 5 g, and keep at 50
Then, 50 ml of an aqueous solution containing 4.0 g of periodic acid (standard electrode potential 1.59 V) was added dropwise over 4 hours, and the mixture was reacted for 5 hours to obtain polyaniline by chemical oxidation polymerization. After adding 50 ml of 25 wt% ammonia water and stirring for 3 hours, the mixture was centrifuged and washed with water to obtain undoped polyaniline powder. The undoped polyaniline has an intrinsic viscosity of 0.3 in NMP at 30 ° C.
It was 31 g / 100 ml. The undoped polyaniline 0.
A 2 wt% NMP / ethanol (90 wt% / 10 wt%) solution was obtained. A roughened aluminum etch foil having a thickness of 90 μm and a width of 10 mm was obtained. After the foil was cut to 10 mm, a lead was attached by crimping, and 100% aqueous ammonium adipate was added.
A chemical conversion treatment was performed with V to form a dielectric oxide film. This element was mixed with 5 wt% of boric acid, 5 wt% of citric acid, and 1.4 w of ammonia.
The capacitance was measured by immersion in a t% electrolytic solution for capacitance measurement. The capacitance was 0.1 μF, and the CV product value was 10. This device was immersed in a undoped polyaniline solution for 5 minutes and then heated to 70 ° C.
Was repeated three times, then immersed in a butanol solution of 0.2 mol / l of disecondary-butylnaphthalenesulfonic acid for 20 minutes and dried at 100 ° C. to form a conductive polyaniline film. This element was reformed at 70 V in an aqueous ammonium adipate solution, and then water / ethanol (60 wt% / 40 wt%) containing 0.2 mol / l of a pyrrole monomer and 0.2 mol / l of sodium 2-naphthalenesulfonate as a supporting electrolyte was used.
Immerse in a solution, contact stainless steel wire from outside with conductive polyaniline film to form an anode, conduct constant current electrolytic polymerization (0.6 mA / piece, 120 minutes) with external electrode, and polypyrrole film by electrolytic polymerization Was formed. This element is immersed in colloidal carbon, a silver paste is applied to form a conductive coating film, a counter electrode is taken out from a part of the element, and then molded with epoxy resin to obtain a rated voltage of 25 V and a rated capacitance of 0.
A 1 μF capacitor was completed. Table 1 shows the conditions for forming the capacitors, and Table 3 shows the characteristic values of the obtained capacitors.

Example 6 In Example 1, a 0.2 mol / l butanol solution of 2,6-naphthalenedisulfonic acid was used instead of a 0.2 mol / l solution of 2-naphthalenesulfonic acid as a doping agent for the undoped polyaniline. A capacitor was completed in the same manner as in Example 1 except that the capacitor was used. Table 1 shows the conditions for forming the capacitors, and Table 3 shows the characteristic values of the obtained capacitors.

Example 7 A capacitor was completed in the same manner as in Example 1, except that tetraethylammonium n-octadecylnaphthalenesulfonate was used instead of sodium 1,7-naphthalenedisulfonic acid as the supporting electrolyte. Table 1 shows the conditions for forming the capacitors, and Table 3 shows the characteristic values of the obtained capacitors.

Comparative Example 1 The procedure of Example 1 was repeated, except that the reaction temperature of the chemical oxidative polymerization was changed to 4 ° C., and undoped with an intrinsic viscosity at 30 ° C. of 0.45 g / 100 ml in NMP. Polyaniline was prepared, and a capacitor was completed in the same manner as in Example 1. Table 2 shows the conditions for forming the capacitors, and Table 4 shows the characteristic values of the obtained capacitors.

The capacitor obtained in Comparative Example 1 has a large intrinsic viscosity, a small capacity impregnation rate, a large initial value of dielectric loss, and a large change with time in dielectric loss and equivalent series resistance in a high-temperature storage life test. Furthermore, when left in a high humidity atmosphere, the dielectric loss increased significantly.

Comparative Example 2 The procedure of Example 1 was repeated, except that the reaction temperature of the chemical oxidative polymerization was 25 ° C. and the time of dropping the aqueous solution of potassium permanganate was 1 hour. Dedoped polyaniline having an intrinsic viscosity of 0.28 g / 100 ml was prepared, and a capacitor was completed in the same manner as in Example 1. Table 2 shows the conditions for forming the capacitors, and Table 4 shows the characteristic values of the obtained capacitors.

The capacitor obtained in Comparative Example 2 has a large capacity impregnation rate due to a small intrinsic viscosity, but has a large initial value of dielectric loss and equivalent series resistance. Further, since the molecular weight of polyaniline is small, the dielectric loss and the equivalent series resistance change over time in a high-temperature storage life test.

Comparative Example 3 The procedure of Example 1 was repeated, except that a 0.2 mol / l butanol solution of sulfuric acid was used instead of a 0.2 mol / l solution of 2-naphthalenesulfonic acid as a doping agent for the undoped polyaniline. A capacitor was completed in the same manner as in Example 1. Table 2 shows the conditions for forming the capacitors, and Table 4 shows the characteristic values of the obtained capacitors.

The capacitor obtained in Comparative Example 3 has a large capacity impregnation ratio and relatively good initial characteristics. However, since sulfuric acid is used, the dielectric loss and the equivalent series resistance change over time in a high-temperature storage life test. large.

Comparative Example 4 In Example 1, except that a 0.2 mol / l butanol solution of perchloric acid was used instead of a 0.2 mol / l solution of 2-naphthalenesulfonic acid as a doping agent for the undoped polyaniline. A capacitor was completed in the same manner as in Example 1. Table 2 shows the conditions for forming the capacitors, and Table 4 shows the characteristic values of the obtained capacitors.

The capacitor obtained in Comparative Example 4 has a large capacity impregnation ratio and relatively good initial characteristics. However, since perchloric acid is used, the loss of dielectric loss and equivalent series resistance in a high-temperature storage life test was evaluated. The change is large.

COMPARATIVE EXAMPLE 5 In Example 1, 0.2 mol of polyvinyl sulfonic acid was used as a doping agent for undoped polyaniline instead of 0.2 mol / l of 2-naphthalene sulfonic acid in butanol.
A capacitor was completed in the same manner as in Example 1 except that a butanol solution of / l was used. Table 2 shows the conditions for forming the capacitors, and Table 4 shows the characteristic values of the obtained capacitors.

The capacitor obtained in Comparative Example 5 has a large capacitance impregnation rate but a large initial dielectric loss and an equivalent series resistance. In addition, since polyvinyl sulfonic acid is used, a change with time in dielectric loss and equivalent series resistance is large in a high-temperature storage life test.

Comparative Example 6 4.7 g of aniline and 5.25 g of concentrated sulfuric acid were placed in a 200 ml glass reaction vessel.
Take 30 ml of an aqueous solution containing 0 g, and add 30 ml of an aqueous solution containing 11.4 g of ammonium persulfate (standard electrode potential 2.06 V) over 3 hours while maintaining the temperature at -4 ° C, and then react for 3 hours to synthesize polyaniline by chemical oxidation polymerization. The mixture was filtered, washed with water and dried. Add 2N ammonia water 50g to 4g of this polyaniline.
The mixture was stirred for 5 hours, filtered and washed with water to obtain a undoped polyaniline powder. The intrinsic viscosity of the undoped polyaniline in NMP at 30 ° C. is 0.76 g / 100 ml
Met. The undoped polyaniline 0.3 wt% N
An MP solution was obtained. Using this undoped polyaniline, a capacitor was completed in the same manner as in Example 4. Table 2 shows the conditions for forming the capacitors, and Table 4 shows the characteristic values of the obtained capacitors.

Although the aluminum foil used in Comparative Example 6 had a relatively small CV product value, the resulting capacitor had a low capacitance impregnation rate, so that the initial values of dielectric loss and equivalent series resistance were large, and the capacitor was left at high temperature. In the life test, the time-dependent changes in the dielectric loss and the equivalent series resistance are slightly large. Further, when left in a high humidity atmosphere, the dielectric loss increased remarkably.

Comparative Example 7 4.7 g of aniline and 5.
A 30 ml aqueous solution containing 1 g of ammonium persulfate (standard electrode potential 2.06 V) was added dropwise over 3 hours while maintaining the solution at −4 ° C. over 30 ml of an aqueous solution containing 0 g, and then reacted for 3 hours to obtain polyaniline by chemical oxidation polymerization. Was synthesized, filtered, washed with water and dried. To 4 g of this polyaniline was added 50 ml of 2N ammonia water, and the mixture was stirred for 5 hours.
An undoped polyaniline powder was obtained. The intrinsic viscosity of the undoped polyaniline in NMP at 30 ° C. is 0.76 g.
/ 100 ml. The undoped polyaniline 3wt
% NMP solvent solution was obtained. A roughened aluminum etched foil having a thickness of 90 μm and a width of 10 mm was obtained. After cutting the foil to 10 mm, a lead was attached by crimping, and a chemical conversion treatment was performed at 100 V in an aqueous solution of ammonium adipate to form a dielectric oxide film. This element was immersed in an electrolytic solution for measuring capacity of 5 wt% of boric acid, 5 wt% of citric acid, and 1.4 wt% of ammonia, and had a capacitance of 0.1 μF and a CV product value of 10. This device was added to the undoped polyaniline solution for 5 minutes.
After repeating the operation of immersion for 10 minutes and drying at 70 ° C 10 times, sulfuric acid
After being immersed in a 0.2 mol / l butanol solution for 20 minutes, it was dried at 100 ° C. to form a conductive polyaniline film. This element is immersed in colloidal carbon, a silver paste is applied to form a conductive coating film, a counter electrode is taken out from a part of the element, and then molded with epoxy resin to obtain a rated voltage of 25 V and a rated capacitance of 0.
A 1 μF capacitor was completed. Table 2 shows the conditions for forming the capacitors, and Table 4 shows the characteristic values of the obtained capacitors.

The capacitor obtained in Comparative Example 7 has a relatively high initial capacity impregnation ratio because the CV product value of the aluminum foil is small, but has a large initial value of dielectric loss and equivalent series resistance, and particularly has a remarkable dielectric loss. large. In a high-temperature storage life test, the equivalent series resistance and the dielectric loss are remarkably increased.

Table 1 shows the conditions for forming the capacitor of the embodiment.
Table 2 shows the preparation conditions of the comparative example. The chemical names of the polyaniline doping agents indicated by the abbreviations in the table are shown below. 2-NS: 2-naphthalene sulfonic acid n-ODNS: n-octadecyl naphthalene sulfonic acid DsBNS: disecondary butyl naphthalene sulfonic acid 2,6-DNS: 2,6-naphthalene sulfonic acid 2-NS: 2-naphthalene sulfonic acid PVS : Polyvinyl sulfonic acid

[0046]

[Table 1]

[0047]

[Table 2]

Table 3 shows the results of the capacitor characteristics of the example, and Table 4 shows the results of the comparative example. The capacitance (C) and the dielectric loss (tan δ) were measured at 120 Hz, and the equivalent series resistance (ES
R) represents the measured value at 100 kHz.

[0049]

[Table 3]

Dedoped polyaniline in NMP 30
When the intrinsic viscosity at ° C is 0.3 g / 100 ml or more and less than 0.4 g / 100 ml (Examples 1 and 7), the volume impregnation rate is large,
The initial properties are also excellent. However, when the standard electrode potential of the oxidizing agent is 1.8 V or more (Example 3), the time-dependent change in characteristics in the high-temperature storage life test is slightly large.

[0051]

[Table 4]

[0052]

According to the method for manufacturing a solid electrolytic capacitor of the present invention, a conductive polyaniline film as a precoat layer can be formed on a valve metal surface having a dielectric oxide film formed thereon by a simple method such as impregnation. The production process is simplified, and the production cost can be reduced because the aniline monomer is not wasted. The intrinsic viscosity of the undoped soluble polyaniline at 30 ° C. in NMP is 0.30 g / 100 ml
As described above, by controlling to less than 0.40 g / 100 ml, even a valve action metal having a large surface enlargement ratio can be sufficiently impregnated to the deepest portion of the etching hole, the capacity impregnation ratio becomes large, and the dielectric oxide film surface area can be effectively used. The characteristics do not deteriorate even when left in a high-temperature atmosphere for a long time. Furthermore, by using naphthalenesulfonic acid as a doping agent for polyaniline and forming a conductive polymer film by electrolytic polymerization on a conductive polyaniline film, the obtained capacitor has an initial value of equivalent series resistance and dielectric loss. It is small and its characteristics do not deteriorate even if it is left in a high temperature atmosphere for a long time.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01G 9/02

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein the surface of the dielectric oxide film on the valve metal is
Intrinsic viscosity at 30 ° C. of 0.30 in N-methyl-2-pyrrolidone
A conductive polyaniline film is formed by contacting a solvent-soluble undoped polyaniline solution and a naphthalene sulfonic acid solution having a g / 100 ml or more and less than 0.40 g / 100 ml to form a conductive polymer film by electrolytic polymerization. A method for manufacturing a solid electrolytic capacitor. 2. The undoped polyaniline obtained by chemically oxidizing and polymerizing an aniline monomer using an oxidizing agent having a standard electrode potential of 0.7 V or more and less than 1.8 V is undoped. Method for manufacturing solid electrolytic capacitor.