Electricity: electrical systems and devices – Electrolytic systems or devices – Solid electrolytic capacitor
Reexamination Certificate
2003-07-15
2004-09-14
Reichard, Dean A. (Department: 2831)
Electricity: electrical systems and devices
Electrolytic systems or devices
Solid electrolytic capacitor
C361S523000, C361S528000, C361S508000, C361S509000, C361S516000
Reexamination Certificate
active
06791823
ABSTRACT:
FIELD OF INVENTION
The present invention relates to an electrolytic solution for electrolytic capacitors, that is, an electrolytic solution for driving electrolytic capacitors. Specifically, the invention relates to an electrolytic solution composition which is favorably employable as an electrolytic solution for driving medium-to-high pressure aluminum electrolytic capacitors.
BACKGROUND OF INVENTION
As the electrolytic solution for driving medium-to-high pressure aluminum electrolytic capacitors, heretofore has been widely employed an electrolytic solution comprising an aqueous organic solvent comprising ethylene glycol and a small amount of water and boric acid or ammonium borate (solute) dissolved therein, because this electrolytic solution shows a high spark voltage (namely, good resistance to a high voltage). However, since the electrolytic solution having such composition produces an excessive amount of water by the esterification reaction of ethylene glycol with boric acid, thus produced water is undesirabley apt to react with an aluminum oxide film of the electrode resulting in deterioration of the film or causes undesired increase of the inner pressure due to evaporation of water at a high temperature of higher than 100° C. Therefore, the electrolytic solution of this type is not suitably employed at an elevated temperature.
In order to solve the above-mentioned problems, an electrolytic solution employing an organic dicarboxylic acid such as adipic acid, sebacic acid, or azelaic acid or a salt thereof in place of boric acid or ammonium borate has been proposed and employed in practice. It is problem, however, that the solubility of the organic dicarboxylic acid in an aqueous organic solvent is low and therefore the resulting solution sometimes gives precipitation of crystals at a low temperature. Accordingly, the low temperature performances of the capacitor lowers, and it is not suitably employed at a low temperature.
JP-A-60-13293 describes an electrolytic solution for electrolytic capacitors which contains, as the solute, butyloctane diacid (i.e., 1,6-decanedicarboxylic acid) or a salt thereof. This patent publication describes that the electrolytic solution containing 1,6-decanedicarboxylic acid or a salt thereof shows a high spark voltage as well as a high electroconductivity and further a high solubility, and that the problem of the precipitation of crystals at a low temperature is solved.
JP-A-61-116815 describes an electrolytic solution for electrolytic capacitors which contains as the solute a tertiary monocarboxylic acid (such as pivalic acid) or a salt thereof. This patent publication further states that the use of the tertiary monocarboxylic acid or a salt thereof is effective to reduce an internal resistance of an electrolytic capacitor, increase resistance to a high voltage, and enlarge the range in which the capacitor can be employed.
JP-A-62-241322 describes an electrolytic solution for electrolytic capacitors having improved temperature characteristics which comprises a solution comprising ethylene glycol and a solute of a monocarboxylic acid having a total carbon atoms of 4 to 8 and an alkyl side chain (such as isobutyric acid or pivalic acid) or a salt thereof.
JP-A-6-275472 describes that an electrolytic solution comprising a solution which comprises ethylene glycol and a solute combination of a tertiary monocarboxylic acid such as pivalic acid and a secondary dicarboxylic acid such as 2,9-dimethylsebacic acid shows a high spark voltage and a high electroconductivity and further is chemically converted readily.
JP-A-6-302475 describes that an electrolytic solution comprising a solution which comprises ethylene glycol and a solute combination of a tertiary monocarboxylic acid such as pivalic acid and a secondary polycarboxylic acid such as 2,9-dimethylsebacic acid shows a high spark voltage and a high electroconductivity and further is chemically converted readily.
Recently, various electronic apparatuses employing a switching power supply are generally utilized as home appliances. Therefore, an electrolytic capacitor to be employed for the electronic apparatuses is desired to show increased safety. In order to increase safety of electrolytic capacitors, it is necessary to further enhance a spark voltage (resistance to a high voltage) of the electrolytic solution. The conventionally employed electrolytic capacitors cannot satisfy the requirement for enhancement of a spark voltage.
Accordingly, a principle object of the invention is to provide an electrolytic solution for electrolytic capacitors which shows performances at a practically satisfactory level in the electroconductivity and easiness of chemical conversion (in the procedure for producing an insulating oxide film on a metal element such as aluminum foil which is used as a positive electrode of electrolytic capacitors) and further shows a high voltage endurance at a voltage higher than that at which the conventional electrolytic solution endures.
DISCLOSURE OF INVENTION
The present invention resides in an electrolytic solution comprising water and a water-miscible organic solvent, which further contains 1,6-decanedicarboxylic acid or a salt thereof and at least one additive selected from the group consisting of a dinitrile compound, pivalic acid or a salt thereof, a diester compound, a lactone compound having an alkyl group, a cyanoalkanoic acid ester, a monocarboxylic acid having an alkyl chain of 3-7 carbon atoms and two alkyl groups of 1-4 carbon atoms at the &bgr;-position of the carboxyl group, a salt thereof, a monocarboxylic acid having an alkyl chain of 3-7 carbon atoms and one ethyl group at the &agr;-position of the carboxyl group, a salt thereof, a monocarboxylic acid of a cyclic saturated compound having 5 or 6 ring-forming carbon atoms, and a salt thereof.
The invention further resides in an electrolytic solution comprising water and a water-miscible organic solvent, which further contains a carboxylic acid or a salt thereof and at least one additive selected from the group consisting of a dinitrile compound, a diester compound, a lactone compound having an alkyl group, and a cyanoalkanoic acid ester.
The invention furthermore resides in an electrolytic capacitor comprising a metallic element having an oxide film on a surface thereof and an electrolytic solution in a sealed case, wherein the electrolytic solution is one of the above-mentioned electrolytic solution of the invention. A preferred metallic element is an aluminum foil.
The electrolytic capacitors employing the electrolytic solution of the invention show easy chemical conversion and electroconductivity similar to those shown by the conventionally used electrolytic capacitors of the same type, while show a high spark voltage (endurable voltage) such as 470 V or higher, further 480 V or higher or 490 V or higher by choosing a preferred combination of the additives to be incorporated into the electrolytic solution. Moreover, a high spark voltage of 500 V or higher can be attained.
DETAILED DESCRIPTION OF INVENTION
The electrolytic solution of the invention is characterized in that 1,6-decanedicarboxylic acid or a salt thereof as a first additive and one or more second additives are dissolved in an aqueous organic solvent comprising water and a water-miscible organic solvent.
First, the water-miscible organic solvent which is employed as an organic solvent of the electrolytic solution of the invention is described.
The conventional electrolytic solution for electrolytic capacitors uses a combination of water and an aqueous organic solvent (i.e., water-containing organic solvent). In the present invention, various known water-miscible organic solvents can be utilized. Examples of the water-miscible organic solvents include alcohols such as polyhydric alcohols and monoalcohols, diesters, cyanoalkanoic acid esters, lactones, and sulfoxides such as dimethylsulfoxide. The organic solvent can be a mixture of two or more organic solvents. A water-immiscible organic solvent can be used in mixture of the water-miscible organic
Abe Koji
Hamamoto Toshikazu
Ito Akikazu
Matsumori Yasuo
Ushigoe Yoshihiro
Costellia Jeffrey L.
Ha Nguyen T.
Nixon & Peabody LLP
Reichard Dean A.
UBE Industries, Ltd
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