Aluminium electrolytic capacitor

Abstract: The present invention aims to provide a highly reliable aluminum electrolytic capacitor which has no flash points and shows little change or degradation in external appearance and properties. The water content of electrolytic solution of the electrolytic capacitor of this invention is 20-90wt% and one or more following compounds are included as main electrolytes in the electrolytic solution ; ammonium formate, ammonium acetate, ammonium lactate, ammonium glycolate, ammonium oxalate, ammonium sccinate, ammonium malonate, ammonium adipate, ammonium benzoate, ammonium glutarate, and ammonium azelate. The electrolytic solution also contains not less than 1wt% of one or more compounds selected from organic carboxylic acids with a particular structure and ammonium salts of these organic acids. The melting point of the electrolytic solution is -10°C and under, the chlorine content of a sealing material of the capacitor is not more than 300ppm to the weight of the sealing material. The impedance ratio of 20°C, 100kHz to-10°C, 100kHz of the aluminum electrolytic capacitor is 4 or less. The present invention can provide a highly reliable aluminum electrolytic capacitor of rated voltage of under 100V, which achieves superior impedance and low temperature properties, and has little risk of ignition even when the electrolytic solution is released.

Description: FIELD OF INVENTION The present invention relates to a highly reliable aluminum electrolytic capacitor which uses an electrolytic solution with no flash points. The aluminum electrolytic capacitor enjoys such superior low temperature properties that it can be used at high temperatures for a long time without showing significant external changes or property deterioration. BACKGROUND OF THE INVENTION Fig. 1 is a cross-sectional view of a prior art aluminum electrolytic capacitor of this kind. As shown in Fig. 1, the anode foil 1 and cathode foil 2 are wound together with the separator 4 made of Manila hemp or Kraft paper to form a capacitor element. This capacitor element is placed together with a driving electrolytic solution (hereinafter, electrolytic solution) in a bottomed metal case 5 and an opening of the foregoing metal case is closed by sealing using a sealing material 6. The anode foil 2 is produced by anodizing and forming a dielectric layer on an aluminum foil after expanding (roughening) its surface area by etching. The electrolytic solution boosts the electrostatic capacity through absorption to the anode foil 2, the surface of which is roughened. The electrolytic solution plays a role in maintaining a low level of leakage current since it can repair the dielectric layer of the anodized aluminum film using its own anodizing ability. Among the properties of the electrolytic solution, electricity conductivity has a significant influence on the impedance of the electrolytic capacitor. Considering above mentioned points, highly conductive electrolytic solutions stable at high temperatures are used especially for a low impedance capacitor of guaranteed temperature of not less than 105 °C and rated voltage of not more than 100V in particular. Such electrolytic solutions typically use γ-butyrolactone which has good low temperature and anodizing properties as a solvent, and quaternary ammonium salts of phthalic acid and maleic acid as electrolytes (refer to Japanese Laid Open Patent Publication No. S62-145713 and Japanese Laid Open Patent Publication No. S62-145715). However, if the electrolytic capacitor which uses γ-butyrolactone as a solvent and quaternary ammonium salts of phthalic acid and maleic acid as an electrolyte, is continuously used in a high-humidity atmosphere, a strong alkali compound is generated at the cathode. The strong alkali compound corrodes especially the cathode lead and the sealing material 6 which contacts with the cathode lead. The corrosion causes leakage of the electrolytic solution to the outside of the capacitor. The effective alternative to avoid the foregoing problem is to use an electrolytic solution which does not generate many alkali compounds, namely the electrolytic solution using ethylene glycol and water as solvent and ammonia salts such as ammonium adipate as electrolyte. The electrolytic solution using γ-butyrolactone as a solvent has a flash point of around 100°C. Therefore, it is impossible to avoid the possibility of ignition occurring when the electrolytic solution is released due to malfunction of the electric device or similar reasons. With regard to low rating voltage electrolytic capacitors of 100V or less at the guaranteed temperature of 85°C, an electrolytic solution in which the solvent is a mixed solvent of ethylene glycol and water and electrolyte, ammonium salts such as ammonium adipate and so on, can be used. Water is used to enhance electric conductivity. However, this kind of capacitor has the problem of not being able to be used for a long time at and above the boiling point of one of the solvents or water (100°C). For example, a large amount of hydrogen gas was generated in a rated voltage test at 110°C due to the reaction between aluminum and water. Generated hydrogen raised internal pressure. As a result, in some cases, the safety valve at the bottom of the aluminum case breaks. In a no-load shelf test at 110°C, the rate of change of post-test leakage current within 1000 hours was found to exceed +5000%. In order to solve these problems a variety of methods have been proposed. Among them is a method in which various phosphor compounds are added to the electrolytic solution to suppress the reaction between electrode foils and the water. Japanese Laid Open Patent Publication H01-114020 discloses a driving electrolytic solution for an electrolytic capacitor, wherein p-nitro benzoic acid and/or alkyl phosphoric acid ester is (are) added to a solvent mixture comprising ethylene glycol as a main solvent and pure water, while the mixture solvent including glutaric acid or its salts as a solute. Another method suggests that various nitro-compounds be added to absorb generated hydrogen gas. Japanese Laid Open Patent Publication S54-93443 discloses a driving electrolytic solution for an electrolytic capacitor, wherein 0.05 - 3 weight % of p-nitro phenol is added to a buffer solution having a pH value of 4 - 6.5, that is containing carboxylic acid and its ammonium salts dissolved in a solution comprising 0 - 20 weight % of water and ethylene glycol. However, even with these methods, when it comes to electrolytic capacitors of rated voltage being 100V or less, it is difficult to maintain electric performance for a long time at 100°C and higher if an electrolytic solution with the water content of over 20% by weight is used. Moreover, when highly conductive electrolytic solution with water content being over 20% by weight is used, chlorine contained in the sealing rubber causes a problem, which would not be a problem with an electrolytic solution of low water content of less than 20%. Namely, in a long-term load test at high temperatures, the anode aluminum lead was corroded, sometimes leading to an increase in current leakage or breaking of anode aluminum lead due to corrosion. The present invention aims to provide highly reliable electrolytic capacitors by solving these problems associating with conventional electrolytic capacitors. SUMMARY OF THE INVENTION The water content of electrolytic solution of the electrolytic capacitor of the present invention is 20~90wt% and more than one of the following compounds are included as a main electrolyte in the electrolytic solution ; ammonium formate, ammonium acetate, ammonium lactate, ammonium glycolate, ammonium oxalate, ammonium succinate, ammonium malonate, ammonium adipate, ammonium benzoate, ammonium glutarate, and ammonium azelate. The electrolytic solution also contains not less than 1 wt% of one or more compounds selected from ; trimethyl adipate, 1,6-decan dicarboxylic acid, sebacic acid, 1,7-octane dicarboxylic acid, butyl octane dicarboxylic acid, 3-tert-butyladipic acid, 3-tert-octyl-hexanedioic acid, 3-n-dodecyl-hexanedioic acid; organic carboxylic acids shown in the following formula (compounds 1), organic carboxylic acids shown in the following formula (compounds 2), or ammonium salts of these organic acids. (compounds 1) R 2 : a lower alkyl radical, R 1 : a hydrogen atom or following radical; (compounds 2) R 3 R 4 : lower alkyl radicals and R 5 : a phenyl radical. Further, according to electrolytic capacitor of the present invention, one or more compound(s) selected from alkyl phosphoric acid ester, hypophosphorous acid, pyrophosphoric acid and salts of these acids, silicone compounds shown in the formula provided below, silane coupling agent, or alkoxysilane are absorbed to at least one of anode aluminum foil and cathode aluminum foil. X 1 , X 5 , X 6 : alkyl radicals, alkenyl radicals, aryl radicals and aralkyl radicals X 2 , X 3 , X 4 : hydroxyl radical, alkyloxy radicals. The electrolytic solution of the present invention does not have a flash point, and the melting point is not higher than -10°C. The chlorine content of the sealing material of the electrolytic capacitor to its weight is not more than 300ppm. Moreover, the rated voltage of the electrolytic capacitor is 100V or less, and the impedance ratio of 20°C, 100kHz to -10°C, 100kHz is not more than 4. The present invention can achieve highly reliable aluminum electrolytic capacitor which is superior in the impedance property and the low temperature property, and would hardly suffer ignition when electrolytic solution is released. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows partially broken perspective view illustrating construction of an electrolytic capacitor including a preferred embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention are described below. A capacitor element of an electrolytic capacitor of the present invention is produced by rolling up a laminate of an anode aluminum foil where a dielectric layer made of aluminum oxide is formed on the surface and a cathode aluminum foil, with a separator inbetween. The capacitor element is soaked with an electrolytic solution and placed in an bottomed aluminum case and sealed at the opening to provide the electrolytic capacitor. A water content of the electrolytic solution is between 20 and 90 wt%. The electrolytic solution contains more than one of following compounds as main electrolytes in the electrolytic solution; ammonium formate, ammonium acetate, ammonium lactate, ammonium glycolate, ammonium oxalate, ammonium succinate, ammonium malonate, ammonium adipate, ammonium benzoate, ammonium glutarate and ammonium azelate. The electrolytic solution also contains not less than 1 wt% of one or more compounds (hereinafter, reaction inhibitor) selected from; trimethyl adipate, 1,6-decan dicarboxylic acid, sebacic acid, 1,7-octane dicarboxylic acid, butyl octane dicarboxylic acid, 3-tert-butyladipic acid, 3-tert-octyl-hexanedioic acid, 3-n-dodecyl-hexanedioic acid, organic carboxylic acids shown in compounds 1, organic carboxylic acids shown in compounds 2, or ammonium salts of these organic acids. The electrolytic solution does not have flash point, and the melting point of a electrolytic solution is not more than -10°C. The rated voltage of the electrolytic capacitor is 100V or less, and the impedance ratio of 20°C, 100kHz to -10°C, 100kHz is not more than 4. When the water content of the electrolytic solution is less than 20%, electric conductivity at low temperatures is not sufficient. Therefore, it is not desirable because the impedance ratio of 20°C, 100kHz to -10°C, 100kHz exceed 4. When the water content is over 90%, the melting point of the electrolytic solution possibly becomes over -10°C. Although the impedance property at 20°C is secured, it is not desirable since guaranteed temperature range is narrowed to over -10°C at the lower temperature. The reaction inhibitors are absorbed to the surface of the electrode foils, inhibiting a reaction with the water. They are especially effective when a electrolytic capacitor is used at high temperatures. When the content of the reaction inhibitors is 1wt% or less, the protective effect of the anode foil deteriorates significantly. The chlorine content of the sealing material of the electrolytic capacitor is not more than 300ppm to the weight of the sealing material. When a sealing material whose chlorine content to its own weight is over 300ppm was used to construct the capacitor, chlorine compounds extracted from the sealing rubber was dissociated into ions in a rated voltage test conducted at 100°C and over. The dissociated chlorine ions cause the anode aluminum lead corrosion under high temperatures. Thus, such sealing material is not desirable. The amount of the swell of the valve at the bottom of the aluminum case was found to be +1 mm or less within 1000 hours in a rated voltage test and a no-load shelf test conducted at 100°C and over. The rate of change of leakage current within 100 hours in a no-load shelf test conducted at 100°C and over was found to be within +5000 % to the initial leakage current. When the swell of the valve at the bottom of the aluminum case exceeded 1mm and the rate of change of the current leakage within 1000 hours in a no-load shelf test became over +5000 %, external appearance and properties of the product were deteriorated remarkably. Thus, it is not desirable. In the following specific components and their composition of the present invention will be described. The electrolytic solution of the present invention contains organic solvent comprising one or more compounds selected from polyhydric alcohols, polyethylene glycol, and copolymer of ethylene oxide and propylene oxide. It also contains main electrolytes, reaction inhibitors and one or more phosphor compounds (of not less than 0.01 wt %) selected from alkyl phosphoric acid ester, hypophosphorous acid, pyrophosphoric acid and salts of these acids. It further contains not less than 0.01 wt% of one or more nitro compounds selected from p-nitro phenol, m-nitro phenol, o-nitro phenol and p-nitro benzoic acid, m-nitro benzoic acid, o-nitro benzoic acid, p-nitro anisole, m-nitro anisole and o-nitro anisole. Examples of solvents include alcohols such as mono-hydric alcohols (butyl alcohol, di-acetone alcohol, benzyl alcohol, amino alcohol etc.); di-hydric alcohols (ethylene glycol, poly ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butandiol, 1,3-butandiol, 1,4-butandiol, 2,3-butandiol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, diethyleneglycol, hexyleneglycol, phenyl glycol etc.); tri-hydric alcohols (glycerol, polyglycerol, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 1,2,6-hexanetriol, 3-methy-pentane-1,3,5-triol etc.); hexytol etc., ether compounds such as monoethers (ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monophenyl ether etc; diether compounds (ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether and so on. Further, copolymer of ethylene oxide and propylene oxide or the mixture of more than two compounds of the above alcohols, ether compounds and copolymers can be used as a solvent. Particularly preferable solvent among them is ethylene glycol, which has high solubility for any solutes and superior temperature properties. The mixing ratio of the foregoing reaction inhibitors, when ethylene glycol is used as solvent, requires that the total content of the reaction inhibitors be from 0.05 to less than 5.0 of the main electrolytes. Furthermore, it is desirable that the total content of the main electrolytes and reaction inhibitors to be 10wt% or more of the weight of the electrolytic solution. With the above described mixing ratio, those compounds can be absorbed to electrode foils, performing their own function, and inhibit the hydrating reaction between the electrode foils and the water to avoid damaging the properties of the capacitor. If the electrolytic solution contains not less than 0.01 wt% of one or more phosphor compounds selected from alkyl phosphoric acid ester , hypophosphorous acid, pyrophosphoric acid and salts of these acids, these compounds are absorbed by the electrode films and inhibit the reaction between the electrodes and the water to avoid damaging the properties of the capacitor. Furthermore, one or more nitro-compounds selected from p-nitro phenol, m-nitro phenol, o-nitro phenol and p-nitro benzoic acid, m-nitro benzoic acid, o-nitro benzoic acid, p-nitro anisole, m-nitro anisole and o-nitro anisole, perform the function of absorbing hydrogen gas due to the reducing property of nitro groups. The foregoing phosphor compounds are especially absorbed by the cathode foil. In addition, the foregoing nitro-compounds further enhance the absorption of the reaction inhibitors to the cathode foil. Thus the nitro-compounds can effectively enhance the protective effect of the cathode foil against water. The concentration of the nitro-compounds is desirably 0.01wt% or more against the electrolytic solution, otherwise the combined effect is lost. One or more phosphor compounds selected from alkyl phosphoric acid ester , hypophosphorous acid, pyrophosphoric acid, and salts of these acids, or silicone compounds, silane coupling agent and alkoxy silane which can be described by the following general formula (compound 6) are absorbed to the electrode foils and further may be absorbed to the separator or the inside of an aluminum case of the electrolytic capacitor of the present invention. (compound 6) The silicone compounds include reactive silicone compounds such as hydroxy modified silicone, amino modified silicone, carboxy modified silicone, alcohol modified silicone, epoxy modified silicone etc. Examples of X 1 through X 6 of silicone compounds are alkyl radicals such as methylradical , ethylradical, propyl radical, and butyl radical, alkenyl radicals such as vinyl radical, and allyl radical, aryl radicals such as phenyl radical, and naphthyl radical, aralkyl radicals such as benzyl radical, and phenethyl radical, hydroxide radicals or oxy-hydrocarbon radicals such as methoxy radical, ethoxy radical, propoxy radical, butoxy radical, vinyloxy radical, phenoxy radical, and benzyloxy radical. The examples of X1~X6 further include fatty acid carboxy radicals such as methyl carboxy radical, ethyl carboxy radical, and propyl carboxy radical, amino-hydrocarbon radicals such as methyl amin radical, ethyl amin radical, propyl amin radical, phenyl amin etc. The silicone compounds for the electrolytic capacitor are not limited to the foregoing examples. Reactive silicone compounds in general can be used as well. As silane coupling agents, the following examples can be used; N-β (aminoethyl) γ -aminopropyl trimethoxy silane, N-β (aminoethyl) γ -aminopropyl methyl dimethoxy silane, N-β (aminoethyl) γ - aminopropyl triethoxy silane, γ-glycidoxy propyl trimethoxy silane, vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tris (β methoxy ethoxysilane), β-(3,4 epoxy cyclohexyl)ethyl trimethoxy silane, γ-glycidoxy propyl methyl diethoxy silane, γ -metacryloxy propyl methyl dimethoxy silane, γ-metacryloxy propyl methyl diethoxy silane, γ-aminopropyl triethoxy silane, N-phenyl- γ -aminopropyl trimethoxy silane, γ mercaptopropyl trimethoxy silane and so on. Examples of alkoxy silane include tetra-methoxy silane, and tetra-ethoxy silane. The phosphor compounds (alkyl phosphoric acid ester) for the present invention are selected from one or more of the following examples; mono methyl phosphate ester, mono ethyl phosphate ester, mono propyl phosphate ester, mono butyl phosphate ester, mono hexyl phosphate ester, mono octyl phosphate ester, mono decyl phosphate ester, dimethyl phosphate ester, diethyl phosphate ester, dipropyl phosphate ester, dihexyl phosphate ester, dioctyl phosphate ester, didecyl phosphate ester, trimethyl phosphate ester, triethyl phosphate ester, tripropyl phosphate ester, trihexyl phosphate ester, trioctyl phosphate ester, and tridecyl phosphate ester. Comparing to the method of simply immersing a capacitor element into an electrolytic solution which is mixed with phosphor compounds and silicone compounds similar to the foregoing examples in advance, the construction of the present invention allows those compounds easily to be close to the core of the capacitor element. Therefore, decline in electrostatic capacity and increase in hydrogen gas generation caused by the hydration reaction of the electrode foil can be further mitigated. Thus, a highly reliable capacitor can be provided. On the other hand, a conventional production method of immersing a rolled-up type capacitor element into an electrolytic solution containing phosphoric compounds fails to allow phosphor compounds additives and silicone compounds to reach the center of the capacitor element, resulting in uneven absorption of the compounds. With such problems, an electrolytic capacitor of the conventional production method is susceptible to degradation of electrode foils caused by hydration reaction. Inhibiting effect against degradation caused by hydration reaction is not sufficient when the amount of the foregoing phosphor compounds and silicon compounds absorbed by the electrode foils is less than 0.5 mg/g of unit weight of the electrode foil. This is not desirable. On the contrary when the amount of the absorbing compounds to the electrode foils exceeds 5.0 mg/g of unit weight of the electrode foil, resistor components on the contacting surface between electrolytic solution and electrode foils increase, thereby raising the impedance of the capacitor. Regarding the cathode foil, both anodized and non-anodized foils have the same effect. However, in order to enhance reliability, it is desirable to anodize the cathode at 1~2V As a sealing material for the present invention, isobutylene isoprene rubber, ethylene-propylene terpolymer and their mixture are used. The hardness of the sealing material(rubber) is desirably from 65 to 100 IRHD (International Rubber Hardness Unit). If the hardness of the sealing material is less than 65 IRHD, external appearance of the capacitor may change and the sealing rubber protrudes from the case undesirably when it is over 100°C, even with a capacitor which does not generate a large amount of gas. This is caused by vaporization of the water contained in the electrolytic solution. On the other hand, when the hardness exceeds 100 IRHD, the rubber becomes brittle and cracks during tests. Thus it is not desirable either. If the sealing material contains or covered with silicone compounds, corrosion of anode lead is especially suppressed. An evaporation of the solvents in the electrolytic solution is also inhibited, thereby curbing the decline of the electrostatic capacity. The present invention is described below with reference to specific examples. Table 1 shows amount of phosphor or silicone compounds absorbed by the separator and electrode films, chlorine content of the sealing material, hardness of the sealing material, silicone compounds for which the surface treatment is provided, thickness of the bottom board of the aluminum case, and compounds used to treat the inside of the aluminum case. With regard to composition of the electrolytic solution (parts by weight of the electrolytic solution), preferred embodiments 1,3-22,25 can be described as follows; ethylene glycol (65 parts by weight, hereinafter, the unit is omitted), pure water (35), ammonium adipate (12), ammonium 1,7-octane dicarboxylate (7), p-nitro benzoate(1), and ammonium hypophosphite (1). In the preferred embodiment 2, ammonium 1,7-octane dicarboxylate (7) is replaced with ammonium 1,5- decan dicarboxylate (7). In a preferred embodiments 23 and 24, chemical compounds 7 (7) and 8 (7) described in an attached table are used respectively instead of ammonium 1,7-octane dicarboxylate (7). Hardness of the sealing rubber is 70 IRHD and its chlorine content is 100 ppm. In comparison, a test was conducted using a separator having 100mg/g of ammonium hypophosphite absorbed thereto as a comparative example 8. In a Cleaveland open-cup flash point test conducted on the electrolytic solution of the preferred embodiments 1~25, no flash points were observed between 128°C~134°C. When the electrolytic solution of the preferred embodiments were kept in a cryostat at constant temperature of -30°C, no change in the properties of the electrolytic solution was found. According to the test, melting point of the electrolytic solution is confirmed to be -10°C or less. The chemical formula of the chemical compounds 7~14 shown in Table 1 and 2 are described in an attached paper. Tables 4-7 show the impedance ratio of 20°C/100kHz to - 10°C/100kHz of an electrolytic capacitor using the electrolytic solutions of the preferred embodiments 1~25 and the comparative examples 1~8 , and the amount of swell of the bottom of the case, current leakage, the rate of change according to a 1000-hour rated voltage application test and a non-load shelf test conducted at 110°C, volume of the solvents permeated through the sealing rubber, the corrosive properties and the condition of the sealing rubber. In the research, two different rating aluminum electrolytic capacitors were used; capacitors with rated voltage of 6.3V, the electrostatic capacity of 560 µF (8 mm in diameter ×11 mm L), and 50V,1500 µF (16 mm in diameter×35.5 mm L). To deal with absorption of phosphor compounds and silicone compounds to the separator (using Manila hemp fiber), the electrode foils and the sealing rubber [isobutylene isopropylene rubber (butyl rubber) vulcanized with resin], the separator, the electrode films and sealing rubber are dipped in aqueous solution of phosphor compounds or silicone compounds of any specific concentration, then dried at 100°C for one hour. The chlorine content of the sealing rubber was measured with a total chlorine analyzer(Mitsubishi Chemical Co., Ltd. TSX-10) and the results were converted to the chlorine content per unit weight. Tables 4-7 show that the aluminum electrolytic capacitor of the present invention is low in the impedance ratio, small in the amount of swell of the bottom of the aluminum case (changes in the length) and small in changes in leakage current, and its anode aluminum lead is not corroded, and the sealing rubber is not protruded. As thus far described, the impedance ratio of 20°C, 100kHz to -10°C, 100kHz of the electrolytic capacitor of the present invention is not more than 4. The amount of swell of the valve at the bottom of the aluminum case was found to be +1mm or less within 1000 hours in a rated voltage load test and a no-load shelf test conducted at 100°C and over. The rate of change in leakage current within 100 hours in a no-load shelf test conducted at 100°C and over was found to be within +5000 % to the initial leakage current. Thus, external appearance and the properties of the product are little affected when used at high temperatures for a long time. The electrolytic solutions have superior low temperature properties and high water content. Therefore, the risk of ignition is small even when the safety valve works and the electrolytic solution is released due to abnormal voltage or inverse voltage applied to the electrolytic capacitor by malfunction of electric components. Thus, the present invention can provide a highly reliable aluminum electrolytic capacitor of rated voltage of under 100V, which achieves superior impedance and low temperature properties. Compound 7 Compound 8 Compound 9 Compound 10 Compound 11 Compound 12 Compound 13 Compound 14

Claims: An aluminum electrolytic capacitor containing a driving electrolytic solution comprising a water content of 20 - 90 % by weight, main electrolyte(s) and not less than 1 wt % of organic carboxylic acid(s) and/or ammonium salt(s) of organic carboxylic acid(s), wherein; said main electrolyte(s) is(are) selected from more than one of the following compounds; ammonium formate, ammonium acetate, ammonium lactate, ammonium glycolate, ammonium oxalate, ammonium succinate, ammonium malonate, ammonium adipate, ammonium benzoate, ammonium glutarate and ammonium azelate, and said organic carboxylic acid(s) and/or ammonium salt(s) of organic carboxylic acid is(are) one or more compounds selected from : trimethyl adipate, 1,6-decan dicarboxylic acid, sebacic acid, 1,7-octane dicarboxylic acid, butyl octane dicarboxylic acid, 3-tert-butyladipic acid, 3-tert-octyl-hexanedioic acid, 3-n-dodecyl-hexanedioic acid, organic carboxylic acids shown in chemical formula 1, organic carboxylic acids shown in chemical formula 2, and/or ammonium salt(s) of above organic acid(s). (chemical formula 1) R 1 ,R 2 : lower alkyl radicals, R 1 : hydrogen atom or following radicals; (chemical formula 2) R 3 , R 4 : lower alkyl radicals R 5 : a phenyl radical, and wherein one or more compound(s) selected from alkyl phosphoric acid ester, hypophosphorous acid, pyrophosphoric acid and salts of these acids, silicone compounds shown in the formula provided below, silane coupling agent, or alkoxysilane are absorbed to at least one of anode aluminum foil and cathode aluminum foil, said formula being: X 1 , X 5 , X 6 : alkyl radicals, alkenyl radicals, aryl radicals and aralkyl radicals X 2 , X 3 , X 4 : hydroxyl radical, alkyloxy radicals. The aluminum electrolytic capacitor as set forth in claim 1, wherein the absorbing amount of said compounds is 5.0 to 50.0 mg/g per unit weight of the electrode foils. The aluminum electrolytic capacitor as set forth in claim 1, wherein the ratio of said organic carboxylic acid(s) and/or ammonium salt(s) of organic carboxylic acid to said main electrolyte(s) is 0.05 - 5.0, and the total content of said main electrolyte(s) and said organic carboxylic acid(s) and/or ammonium salt(s) of organic carboxylic acid(s) is not less than 10 wt % of the weight of the electrolytic solution. The aluminum electrolytic capacitor as set forth in claim 1, wherein said driving electrolytic solution further comprises: organic solvent comprising one or more compounds selected from poly hydric alcohols, poly ethylene glycol, copolymer of ethylene oxide and propylene oxide, not less than 0.01 % by weight of one or more phosphor compounds selected from alkyl phosphoric acid ester, hypophosphorous acid, pyrophosphoric acid and salts of these acids, and not less than 0.01 % by weight of one or more nitro compounds selected from p-nitro phenol, m-nitro phenol, o-nitro phenol and p-nitro benzoic acid, m-nitro benzoic acid, o-nitro benzoic acid, p-nitro anisole, m-nitro anisole and o-nitro anisole. The aluminum electrolytic capacitor as set forth in claim 4, wherein said alkyl phosphoric acid ester comprises one or more compound(s) selected from monoalkyl phosphoric acid ester, dialkyl phosphoric acid ester and trialkyl phosphoric acid ester, and the total number of carbon atoms of said alkyl chain in one molecule is 3-36. The aluminum electrolytic capacitor as set forth in claim 5, wherein said alkyl phosphoric acid ester comprises one or more compound(s) selected from; mono methyl phosphate ester, mono ethyl phosphate ester, mono propyl phosphate ester, mono butyl phosphate ester, mono hexyl phosphate ester, mono octyl phosphate ester, mono decyl phosphate ester, dimethyl phosphate ester, diethyl phosphate ester, dipropyl phosphate ester, dihexyl phosphate ester, dioctyl phosphate ester, didecyl phosphate ester, trimethyl phosphate ester, triethyl phosphate ester, tripropyl phosphate ester, trihexyl phosphate ester, trioctyl phosphate ester, and tridecyl phosphate ester. The aluminum electrolytic capacitor as set forth in claim 1, wherein one or more compounds selected from alkyl phosphoric acid ester, hypophosphorous acid, pyrophosphoric acid and salts of these acids, silicone compounds shown in the formula provided below, silane coupling agent, or alkoxysilane are absorbed by a separator, said formula being : X 1 , X 5 , X 6 : alkyl radicals, alkenyl radicals, aryl radicals and aralkyl radicals X 2 , X 3 , X 4 : hydroxyl radical, alkyloxy radicals. The aluminum electrolytic capacitor as set forth in claim 7, wherein the amount of the absorbed compound(s) is 5.0 to 50.0 mg/g per unit weight of the separator. The aluminum electrolytic capacitor as set forth in claim 1, wherein a sealing rubber comprises one of isobutylene isoprene rubber, ethylene-propylene terpolymer and their mixed compounds, and hardness of said rubber is 65-100 IRHD (International Rubber Hardness Unit). The aluminum electrolytic capacitor as set forth in claim 9, wherein chlorine content of the sealing material is 300 ppm and less to the weight of the sealing material. The aluminum electrolytic capacitor as set forth in claim 9, wherein silicone compounds shown in the formula provided below, silane coupling agent, or alkoxysilane are included in the sealing material or adhered to it, said formula being : X 1 , X 5 , X 6 : alkyl radicals, alkenyl radicals, aryl radicals and aralkyl radicals X 2 , X 3 , X 4 : hydroxyl radical, alkyloxy radicals. The aluminum electrolytic capacitor as set forth in claim 1, wherein one or more compounds selected from alkyl phosphoric acid ester, hypophosphorous acid, pyrophosphoric acid and salts of these acids, silicone compounds shown in the formula provided below, silane coupling agent, or alkoxysilane are absorbed to the inside of an aluminum case, said formula being: X 1 , X 5 , X 6 : alkyl radicals, alkenyl radicals, aryl radicals and aralkyl radicals X 2 , X 3 X 4 : hydroxyl radical, alkyloxy radicals. The aluminum electrolytic capacitor as set forth in claim 1, wherein the melting point of said driving electrolytic solution is -10°C or less. The aluminum electrolytic capacitor as set forth in claim 1 of which the rated voltage is 100V or less, and the impedance ratio of 20°C, 100 kHz to -10°C, 100 kHz is 4 or less. The aluminum electrolytic capacitor as set forth in claim 1, wherein the amount of swell of a valve at the bottom of the aluminum case is +1 mm or less within 1000 hours according to a rated voltage load test and a no-load shelf test conducted at 100°C and over, and the rate of change in current leakage within 100 hours according to a no-load shell test conducted at 100°C and over is within +5000 % to the initial current leakage. The aluminum electrolytic capacitor as set forth in any one of claim 1, 5, and 11, wherein the thickness of the bottom board of the aluminum case which is made of either aluminum or aluminum alloy, is over 0.30 mm.

Inventors: MATSUURA HIROYUKI, MINATO KOICHIRO, MOROKUMA MUNEHIRO, NITTA YUKIHIRO, TSUBAKI YUICHIRO, MATSUURA, HIROYUKI, MINATO, KOICHIRO, MOROKUMA, MUNEHIRO, NITTA, YUKIHIRO, TSUBAKI, YUICHIRO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1999
Main classification: H01G9
IPC codes: H01G9