JP2001102263A - Electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic capacitor which has low impedance characteristic can be used in 100V specification, and high reliability at 125 deg.C. SOLUTION: An electrolyte where a quanternary cyclic amidium salt of benzoic acid is dissolved in a mixed solvent of γ-butyrolactone and ethylene glycol, and colloidal silica and alkyl phosphoric acid having a 3-8C alkyl group are added is used as electrolyte of an electrolytic capacitor. A ceramics coating layer is formed on a contact part with a sealing member of a cathode lead-out means, so that an electrolytic capacitor which has low impedance characteristic, stability of breakdown voltage characteristic or the like at 125 deg.C and satisfactory liquid leakage characteristic and can be used in 100V specification can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor, in particular, having a low impedance characteristic and capable of 100V specification.
Further, the present invention relates to an electrolytic capacitor having high reliability at 125 ° C.

[0002]

2. Description of the Related Art An electrolytic capacitor generally has a structure as shown in FIG. That is, the strip-like high-purity aluminum foil is chemically or electrochemically etched to enlarge the aluminum foil surface, and the aluminum foil is subjected to a chemical conversion treatment in a chemical conversion solution such as an ammonium borate aqueous solution. An anode electrode foil 2 having an oxide film layer formed on the surface thereof and a cathode electrode foil 3 made of a high-purity aluminum foil subjected to only an etching treatment are wound through a separator 11 made of manila paper or the like to form a capacitor. An element 1 is formed. And this capacitor element 1
Is impregnated with an electrolytic solution for driving an electrolytic capacitor, and then stored in a bottomed cylindrical outer case 10 made of aluminum or the like. A sealing body 9 made of elastic rubber is attached to the opening of the outer case 10, and the outer case 10 is sealed by drawing.

As shown in FIG. 2, a lead wire 4 serving as a cathode lead means and a lead wire 5 serving as an anode lead means are provided on an anode electrode foil 2 and a cathode electrode foil 3, respectively, for extracting both electrodes. Are connected by means such as stitching and ultrasonic welding. Each of the lead wires 4 and 5 has a round bar portion 6 made of aluminum, a flat portion 7 in contact with the bipolar electrode foils 2 and 3, and a solderable metal fixed to the tip of the round bar portion 6 by welding or the like. And an external connection unit 8 composed of

[0004]

In recent years, there has been an increasing demand for the use of electrolytic capacitors in the fields of vehicles and exchanges. In the on-vehicle field, it is a high-temperature specification, and in the exchange field, it is a long-life specification. In both cases, high reliability at 125 ° C. is required. In this field, low impedance characteristics and 100 V specification must be satisfied.

Conventionally, as an electrolytic solution of 100 V and 125 ° C. specification, an electrolytic solution using ethylene glycol as a solvent and ammonium benzoate as a solute has been used. I do not endure. In addition, as the conventional electrolytic solution for electrolytic capacitors having low impedance characteristics, γ-butyrolactone is used as a solvent, and an electrolytic solution using a phthalate or maleate of a quaternized cyclic amidinium as a solute is used. Withstand voltage is low and cannot meet 100V specification. Therefore, using γ-butyrolactone as a main solvent and using a quaternized cyclic amidinium salt of benzoic acid as a solute,
By adding silica particles or a phosphoric acid compound, which is known to have a withstand voltage improving effect, a withstand voltage characteristic of 100 V can be obtained. However, this electrolyte has problems such as a decrease in withstand voltage during a life test and the occurrence of leakage, and cannot satisfy high reliability at 125 ° C. In particular, in the electrolytic solution using a quaternized cyclic amidinium salt, there is a problem that leakage occurs, but with an electrolyte using γ-butyrolactone as a solvent and a quaternized cyclic amidinium salt of benzoic acid as a solute, This liquid leakage characteristic tends to deteriorate. As described above, in reality, it has not been possible to obtain an electrolytic capacitor that can satisfy the above-mentioned requirements.

Therefore, the present invention is intended to improve this drawback, has a low impedance characteristic, is capable of 100 V specification, and has a stability such as a withstand voltage characteristic at 125 ° C. and a good liquid leakage characteristic. An object of the present invention is to provide an electrolytic capacitor having high reliability characteristics.

[0007]

A capacitor element formed by winding an anode electrode foil provided with anode extraction means and a cathode electrode foil provided with cathode extraction means through a separator is impregnated with an electrolytic solution. In an electrolytic capacitor in which the capacitor element is housed in a bottomed cylindrical outer case and the open end of the outer case is sealed with a sealing body, the electrolytic solution is a mixed solvent of γ-butyrolactone and ethylene glycol. An electrolytic solution obtained by dissolving a quaternized cyclic amidinium salt of benzoic acid and adding colloidal silica and an alkyl phosphoric acid represented by the following formula (2) is used. It is characterized by forming a ceramic coating layer.

Embedded image

Further, the cathode extraction means includes an aluminum conductor having a round bar portion and a flat portion, and the ceramic coating layer is formed on the round bar portion in advance of a capacitor manufacturing process.

Further, the ceramic coating layer comprises:
It is characterized by being formed using a coating agent composed of a metal alkoxide-based ceramic using one or two or more selected from Al ₂ O ₃ , SiO ₂ and ZrO ₂ .

The anode extracting means includes a round bar portion made of aluminum and a flat connection portion, and an insulating layer made of aluminum oxide covers at least substantially the entire surface of the round bar portion. I have.

Further, the electrolyte solution contains an oxidizing agent.

The oxidizing agent is a nitro compound.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of an aluminum electrolytic capacitor has the same structure as that of the prior art, as shown in FIGS. The capacitor element 1 is formed by winding an anode electrode foil 2 and a cathode electrode foil 3 with a separator 8 interposed therebetween. FIG. 2
As shown in (1), lead wires 4 and 5 are connected to the anode electrode foil 2 and the cathode electrode foil 3, respectively. These lead wires 4 and 5 are made of aluminum and include a flat portion 7 connected to each foil, a round bar portion 6 continuous with the flat portion 7, and an external connection portion 8 connected to the round bar portion 6. I have. The electrode foils 2 and 3 and the flat portion 7 are mechanically connected by a stitch method, ultrasonic welding, or the like.

The anode electrode foil 2 is formed by chemically or electrochemically etching an aluminum foil having a purity of 99% or more in an acidic solution to expand the surface, and then forming the foil in an aqueous solution of ammonium borate or ammonium adipate. After the treatment, an anodic oxide film layer is formed on the surface.

The cathode electrode foil 3 is obtained by etching an aluminum foil having a purity of 99% or more in the same manner as the anode electrode foil 2. Here, as in the case of the anode electrode foil 2, 1
A chemical conversion treatment of up to 2 V may be performed.

According to the present invention, when producing the electrode lead-out means, first, an aluminum wire rod formed by cutting an aluminum wire rod intermittently pressed to a predetermined size and having a round bar portion 6 and a flat portion 7 is formed. A conductor is formed, and then a chemical conversion treatment is performed to form an anodic oxide film on the surface. Then, on the end face of this aluminum conductor,
The external connection portion 8 made of a CP wire is welded to form a lead wire 4,
5 is constituted.

Here, the aluminum conductor serving as the cathode extraction means is coated with ceramics.
That is, a coating agent composed of a metal alkoxide ceramic is discharged and coated on the round bar portion 6 of the aluminum conductor having the anodic oxide film formed on the surface as described above,
Thereafter, a heat treatment is performed, and then the coating agent is discharged and coated again. Then, a heat treatment is performed again to form a coating layer on the aluminum conductor.

A cell used for metal alkoxy ceramics
As Lamix, Al_TwoO_Three, SiO_Two, Zr
O_Two, TiO_Two, MgO, H_TwoBO_Three, Cr_TwoO_Three, B
aTiO _Three, PbTiO_Three, KTaO_ThreeEtc.
You. The ceramics used here are core
In consideration of the_TwoO_Three, SiO_Two,
ZrO_TwoOne or more selected from
Is preferable, and considering the strength, Al_TwoO_Three,
SiO_TwoIt is preferable to use a mixture consisting of

As a coating method, a round bar 6
Is also immersed in a coating agent for coating. That is, the aluminum conductor is immersed in the coating agent, then heat-treated, then immersed again in the coating agent, and then heat-treated again to form a coating layer on the aluminum conductor. Thereafter, the flat portion 7 is immersed in a methanol solution, the coating layer is removed by ultrasonic waves or the like, and the ceramic coating layer is left only on the round bar portion 6. However,
In this method, the adjustment at the time of removing the coating layer is not easy, and in order to form the coating layer on the round bar portion with high accuracy, the above-described method using discharge and coating is more preferable.

The flat portions 7 of the lead wires 4 and 5 formed as described above are mechanically connected to the electrode foils 2 and 3 by a stitch method, ultrasonic welding, or the like. Here, there is a method of performing ceramic coating after connecting the lead wire 5 to the cathode electrode foil 3, but in consideration of coating accuracy, it is preferable that the ceramic coating layer is formed in advance before the capacitor manufacturing process. Further, in order to obtain a sufficient liquid leakage prevention effect, the lead wire 5 must be formed at least on the round bar portion 6.

The capacitor element 1 configured as described above
Is impregnated with an electrolytic solution for driving an electrolytic capacitor. As an electrolytic solution, a mixed solvent of γ-butyrolactone and ethylene glycol is used, an electrolytic solution obtained by dissolving a quaternized cyclic amidinium salt of benzoic acid and adding colloidal silica and an alkyl phosphoric acid represented by the following chemical formula (2) is used.

As a low-impedance electrolytic solution using γ-butyrolactone as a solvent, ethylene glycol is used as a secondary solvent in order to obtain a high-voltage specification of 100 V, and the chemical conversion of the electrolytic solution is improved. The content of ethylene glycol in the mixed solvent is 5 to 30 wt%, preferably 10 to 20 wt%. If the content is less than this range, the leakage current characteristics of the electrolytic capacitor will be reduced, and if it exceeds this range, the impedance characteristics will be reduced.

In this mixed solvent, a quaternized cyclic amidinium salt of benzoic acid is dissolved as a solute. The content of the quaternized cyclic amidinium salt of benzoic acid in the electrolyte is 5 to 30 watts.
When the amount is less than t%, preferably 10 to 20% by weight, the impedance characteristic is deteriorated. When the amount exceeds this range, the withstand voltage characteristic is deteriorated.

The quaternized cyclic amidinium ion serving as the cation component is a cation obtained by quaternizing a cyclic compound having an N, N, N'-substituted amidine group.
Examples of the cyclic compound having an N′-substituted amidine group include the following compounds. Imidazole monocyclic compound (1-
Methylimidazole, 1-phenylimidazole, 1,
2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1,2-dimethylimidazole, 1,2,2
Imidazole homologs such as 4-trimethylimidazole, 1-ethyl-2,3-dimethylimidazole, 1,2,3,4-tetramethylimidazole, 1-methyl-2
Oxyalkyl derivatives such as -oxymethylimidazole and 1-methyl-2-oxyethylimidazole, nitro derivatives such as 1-methyl-4 (5) -nitroimidazole, 1,2-dimethyl-5 (4) -aminoimidazole and the like Aminoderivatives), benzimidazole compounds (1
-Methylbenzimidazole, 1-methyl-2-benzimidazole, 1-methyl-5 (6) -nitrobenzimidazole, etc., compounds having a 2-imidazoline ring (1-methylimidazoline, 1,2-dimethylimidazoline, 1 , 2,4-trimethylimidazoline, 1-methyl-2-phenylimidazoline, 1-ethyl-2-methyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-ethoxymethylimidazoline, etc.), Compound having a tetrahydropyrimidine ring (1
-Methyl-1,4,5,6-tetrahydropyrimidine,
1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1,5-diazabicyclo [4,3,0] nonene-5, and the like. Among them, quaternized amidinium such as 1-ethyl-2,3-dimethylimidazole and 1,2,3,4-tetramethylimidazole is preferred.

Then, colloidal silica and an alkyl phosphoric acid represented by the formula (2) are added. The electrolytic solution having the above configuration has a high conductivity and a withstand voltage characteristic of 100 V. Here, the colloidal silica is dispersed in a dispersion solvent and added as a colloid solution. The alkyl group of the alkyl phosphoric acid represented by Chemical Formula ₂ , R ₁ and R ₂ have 3 to 8 carbon atoms. If it is less than 3, the alkylphosphoric acid is hydrolyzed at high temperatures, and the withstand voltage characteristic is reduced. If it exceeds 8, the impedance characteristic is reduced. Therefore, high reliability at 125 ° C. cannot be obtained with an alkyl phosphoric acid having an alkyl group having less than 3 carbon atoms, such as diethyl phosphate.

The content of colloidal silica in the electrolyte is as follows:
2 to 12 wt%, preferably 4 to 8 wt%, if less than this range, the withstand voltage decreases, and if it exceeds this range, the impedance characteristics deteriorate. The content of the alkyl phosphoric acid in the electrolyte is 1 to 10 wt%, preferably 2 to 6 wt%,
Below this range, the withstand voltage decreases, and beyond this range, both the impedance characteristics and the withstand voltage characteristics decrease.

Further, an oxidizing agent can be contained in the electrolytic solution. As the oxidizing agent, nitro compounds such as nitrobenzoic acids, nitroanisole, nitrophenol and nitronaphthol are used. The content of the oxidizing agent in the electrolyte is 0.2 to 5 wt%, preferably 0.5 to 4 wt%.
%, If it is less than this range, the liquid leakage characteristics deteriorate, and if it exceeds this range, the impedance characteristics deteriorate.

The above-described electrolytic capacitor of the present invention has low impedance characteristics, is capable of 100 V specification,
Good stability of withstand voltage characteristics at ℃ and good liquid leakage characteristics.

Here, it is considered that the reason why the liquid leakage property is good in the present invention is as follows. In general, the mechanism by which the electrolyte in which the quaternized cyclic amidinium salt is dissolved leaks from the cathode lead portion is considered as follows. That is, in the conventional electrolytic capacitor,
Since the spontaneous immersion potential of the cathode lead 5 shows a more noble potential than the spontaneous immersion potential of the cathode electrode foil 3, when left unloaded, a local battery is constituted by the cathode lead and the cathode electrode foil, The cathode current will flow through the lead wire,
In a DC load state, more cathode current flows through the cathode lead wire than the cathode electrode foil. In this way, in both cases of load and no load, a cathode current flows through the cathode lead wire, and as a result,
A reduction reaction of dissolved oxygen or hydrogen ions occurs on the cathode lead wire side, and hydroxyl ions are generated at the electrolyte interface between the round bar portion 6 and the connection portion 7 of the cathode lead wire.

When the hydroxyl ions are generated in this way, the quaternized cyclic amidinium is hydrolyzed by the hydrolysis reaction.
Combines with hydroxyl ions, resulting in secondary amines. Further, when hydroxyl ions are generated and become basic at pH = 7 or more, γ-butyrolactone as a solvent is combined with hydroxyl ions by a hydrolysis reaction to form γ-hydroxybutyric acid. This reduces the hydroxyl ions and the basicity. Thus, when the basicity decreases, the secondary amine generated by the hydrolysis reaction of the quaternized cyclic amidinium becomes the quaternized cyclic amidinium again,
This quaternized cyclic amidinium has no volatility and is highly hygroscopic, so the quaternized cyclic amidinium regenerated between the round bar portion of the cathode lead wire and the sealing member absorbs moisture and becomes a liquid leakage state. Become. The above is inferred from the results of analysis that the liquid leakage is composed of most of water and quaternized cyclic amidinium.

In the case of an electrolytic solution using quaternized amidinium salt of γ-butyrolactone and benzoic acid, the electrolyte is leaked due to the above-described reaction. Further, in this electrolyte, the pH must be increased in order to increase the electric conductivity, and therefore, the concentration of hydroxide ions in the electrolyte is increased, and the amount of the quaternized cyclic amidinium regenerated as a whole is increased. It seems that the leaked state became worse and the liquid leakage state became worse.

However, in the present invention, since the ceramic coating layer is formed on the contact portion of the lead wire with the sealing member, that is, on the round bar portion, no current flows through the round bar portion. In the case of no load, a local battery is not formed between the cathode extraction means and the cathode electrode foil.

As described above, according to the configuration of the present invention, it is possible to prevent the cathode current from flowing to the cathode extraction means, and prevent the generation of hydroxyl ions near the cathode extraction means. Accordingly, regeneration of the quaternized cyclic amidinium in the vicinity of the cathode extracting means due to the above-described reaction is prevented, and a liquid leakage state is prevented.

Further, when the cathode lead wire and the anode lead wire come into contact with each other when no load is left, if the anode lead wire is more noble than the cathode electrode foil, a local battery is formed using the anode lead wire and the cathode electrode foil. Thus, a reduction reaction of dissolved oxygen or hydrogen ions occurs on the anode lead side. As a result, hydroxide ions are generated, and the sealing accuracy is deteriorated. Therefore, the anode lead wire includes a round bar portion made of aluminum and a flat connection portion so that the anode lead wire is more base than the cathode electrode foil, and the insulating layer made of aluminum oxide has at least substantially the surface of the round bar portion. Preferably, it covers all. Similar effects can be obtained by forming a ceramic coating layer on the round bar portion of the anode lead wire, as in the round bar portion of the cathode lead wire.

When the electrolyte contains an oxidizing agent,
This oxidizing agent acts as a depolarizer for the natural immersion potential of the cathode electrode foil, and the natural immersion potential shifts to the noble side. As a result, the current flowing through the cathode extraction means is reduced, and the generation of hydroxide ions can be suppressed, so that the adverse effect on the sealing body can be further suppressed. That is, in the invention of the present application, even when the ceramic coating layer formed on the round bar portion is damaged during the production of the capacitor or the like, and a slight current flows to the cathode extraction means,
Liquid leakage can be prevented by the action of the oxidizing agent to suppress the generation of hydroxide ions. In addition, due to the effect of the oxidizing agent, the same effect can be obtained even when the cathode lead wire and the anode lead wire come into contact with each other when no load is left.

For the above reasons, in the present invention, even when γ-butyrolactone is used as a solvent and a quaternized cyclic amidinium salt of benzoic acid is used as a solute,
It is considered that liquid leakage was prevented under both load and no load.

As described above, the quaternized cyclic amidinium salt of benzoic acid is dissolved in the mixed solvent of γ-butyrolactone and ethylene glycol of the present invention, and the colloidal silica and the alkyl phosphorus having an alkyl group having 3 to 8 carbon atoms are dissolved. It has low impedance characteristics due to the synergistic action of the electrolytic solution to which the acid is added, the cathode electrode foil of the present invention and the cathode extraction means,
It is possible to provide an electrolytic capacitor that can be specified, and has good stability such as withstand voltage characteristics at 125 ° C. and good liquid leakage characteristics.

[0038]

Next, the present invention will be described with reference to embodiments. Since the structure of the electrolytic capacitor is the same as that of the related art, it will be described with reference to FIGS. The capacitor element 1 is formed by winding an anode electrode foil 2 and a cathode electrode foil 3 with a separator 11 interposed therebetween. As shown in FIG. 2, the anode electrode foil 2 and the cathode electrode foil 3 have a lead wire 4 for leading the anode,
Lead wires 5 for drawing out the cathode are connected to each other.

An aluminum conductor comprising a flat portion 7 made of 99% aluminum and in contact with the electrode foil and a round bar portion 6 integrally formed with the flat portion 7 is formed. Next, an aluminum oxide film is formed on the surface of the aluminum conductor by a chemical conversion treatment. CP is attached to the end face of this round bar part 6.
The lead wires 8 are welded to form the lead wires 4 and 5.

Then, a ceramic coating layer is formed on the surface of the round bar portion 6 of the aluminum conductor used for the cathode extracting means. This ceramic coating layer
A coating agent composed of a metal alkoxide-based ceramic using one or two or more selected from Al ₂ O ₃ , SiO ₂ and ZrO ₂ as components is discharged to the round bar portion 6, and 1
After heat treatment at 80 ° C. for 10 seconds, and then discharging the coating agent again, heat treatment again at 180 ° C. for 10 seconds,
Further, a heat treatment is performed at 180 ° C. for 20 minutes.

The lead wires 4 and 5 are electrically connected to the bipolar electrode foils 2 and 3 at the flat portion 7 by means such as stitching and ultrasonic welding.

The anode electrode foil 2 is obtained by chemically or electrochemically etching an aluminum foil having a purity of 99.9% in an acidic solution and expanding the surface thereof, and then performing a chemical conversion treatment in an aqueous solution of ammonium adipate. An anodic oxide film layer is formed on the surface.

The cathode electrode foil 3 is formed by etching an aluminum foil having a purity of 99.9% similarly to the anode electrode foil 2.
A material subjected to a chemical conversion treatment of 1 V is used.

The capacitor element 1 configured as described above
Is impregnated with an electrolytic solution for driving an electrolytic capacitor. As an electrolyte, benzoic acid (1-ethyl-2,3-dimethylimidazolium) salt (20 wt%) is dissolved as a solute in a mixed solvent of γ-butyrolactone (62 wt%) and ethylene glycol (11 wt%), and colloidal. Silica (5
wt.) and dioctyl phosphate (2 wt.%) were used.

The capacitor element 1 impregnated with the electrolytic solution as described above is housed in an outer case 10 made of aluminum having a bottomed cylindrical shape, and a sealing body 9 is attached to an opening of the outer case 10. Is subjected to a drawing process to seal the outer case 10. The sealing body 9 is made of an elastic rubber such as butyl rubber, for example, and has through holes for leading the lead wires 4 and 5, respectively.

The initial characteristics and the load and no-load characteristics at 125 ° C. for 2,000 hours were examined for the electrolytic capacitors according to the examples of the present invention configured as described above, and the electrolytic capacitors according to Conventional Examples 1, 2 and Comparative Examples. . Here, Conventional Example 1
Ethylene glycol (80 wt%) as an electrolyte of
Ammonium benzoate (10 wt%) and γ-butyrolactone (83 wt%), maleic acid (10 wt%), and triethylamine (7 wt%) were used as the electrolytic solution of Conventional Example 2. And the rating of the electrolytic capacitor is 100WV
−56 μF. The specifications and initial characteristics of these electrolytic capacitors are shown in (Table 1), and the results of 125 ° C. load and no-load tests are shown in (Table 2). In addition, in order to evaluate the liquid leakage characteristics,
Using an electrolytic capacitor of 100 WV-4.7 μF (6.3φ-11 L), the state of liquid leakage was determined under conditions of 85 ° C./85%, which is a strict condition for 3000 hours, as a liquid leakage evaluation test. The results are shown in (Table 3).

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

As is clear from Table 1, in the embodiment, a capacitor having a low tan δ is obtained. In addition, as is clear from (Table 2) and (Table 3), 125 ° C.
It can be seen that the characteristics after the load and no-load tests were stable, high reliability was obtained at 125 ° C., and no liquid leakage occurred.
In comparison, in the conventional example 1, the initial tan δ is high, and in the conventional example 2, the tan δ is remarkably increased in both the 125 ° C. load test and the no-load test. Further, in the comparative example not using the cathode extraction means formed with the ceramic coating layer of the present invention, liquid leakage has occurred,
High reliability cannot be obtained.

Next, the Al ₂ O ₃ and Si
In an electrolytic capacitor using a coating agent composed of a metal alkoxide ceramic using O ₂ as a component, a microcrack was formed on the ceramic coating layer by pressing with a pointed instrument to prepare a capacitor. Then, using the electrolytic solution and an electrolytic solution obtained by adding paranitrobenzoic acid (1 part) to the electrolytic solution, together with the capacitor of the comparative example, under the same conditions as in the above-described example, 5000
The liquid leakage characteristics over time were determined. The results are shown in (Table 4).

[0052]

[Table 4]

As is clear from Table 4, the electrolytic capacitor to which paranitrobenzoic acid was not added leaked, but the electrolytic capacitor to which paranitrobenzoic acid was added did not leak, and leaked to paranitrobenzoic acid. It turns out that there is a prevention effect.

As described above, the synergistic action of the electrolytic solution and the cathode extracting means in the present invention realizes low impedance characteristics, 100 V specifications, stability such as withstand voltage characteristics at 125 ° C., and good liquid leakage characteristics. Further, by adding an oxidizing agent to the electrolytic solution, the liquid leakage characteristics are improved.

[0055]

According to the present invention, a quaternized cyclic amidinium salt of benzoic acid is dissolved in a mixed solvent of γ-butyrolactone and ethylene glycol as an electrolytic solution, and colloidal silica and an alkyl phosphoric acid represented by the formula (2) are dissolved. A ceramic coating layer is formed on the contact portion of the cathode extraction means with the sealing body using the electrolyte solution added. As described above, the synergistic action of the electrolytic solution of the present invention and the cathode extracting means can realize low impedance characteristics, 100 V specifications, stability such as withstand voltage characteristics at 125 ° C., and good liquid leakage characteristics. .

[Brief description of the drawings]

FIG. 1 is an internal sectional view showing a structure of an electrolytic capacitor.

FIG. 2 is an exploded perspective view showing the structure of the capacitor element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode electrode foil 3 Cathode electrode foil 4 Lead wire for lead out of anode 5 Lead wire for lead out of cathode 6 Round bar part 7 Flat part 8 External connection part 9 Sealing body 10 Exterior case 11 Separator 12 Insertion part

Claims (6)

[Claims] 1. An anode electrode foil provided with anode extraction means,
A cathode electrode foil provided with a cathode extraction means is impregnated with an electrolytic solution in a capacitor element formed by winding the same through a separator, and the capacitor element is housed in a bottomed cylindrical outer case. In an electrolytic capacitor having an open end sealed with a sealing body, γ-
A quaternized cyclic amidinium salt of benzoic acid is dissolved in a mixed solvent of butyrolactone and ethylene glycol, and an electrolyte obtained by adding colloidal silica and an alkyl phosphoric acid represented by the formula (1) is used. An electrolytic capacitor, wherein a ceramic coating layer is formed in a contact portion with the sealing body. Embedded image 2. The method according to claim 1, wherein the cathode extraction means includes an aluminum conductor including a round bar portion and a flat portion, and the ceramic coating layer is formed on the round bar portion in advance of a capacitor manufacturing process. Electrolytic capacitor. 3. The ceramic coating layer is made of Al _2
2. The electrolytic capacitor according to claim 1, wherein the electrolytic capacitor is formed using a coating agent composed of a metal alkoxide ceramic using one or two or more selected from O ₃ , SiO ₂ and ZrO ₂ . 4. The anode extraction means includes a round bar portion made of aluminum and a flat connection portion, and an insulating layer made of aluminum oxide covers at least substantially the entire surface of the round bar portion. Electrolytic capacitors. 5. The electrolytic capacitor according to claim 1, wherein the electrolytic solution contains an oxidizing agent. 6. The electrolytic capacitor according to claim 5, wherein the oxidizing agent is a nitro compound.