JP2902685B2 - Electrolyte for electrolytic capacitors - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in an electrolytic solution for an electrolytic capacitor, and more particularly to an electrolytic solution for an electrolytic capacitor having improved withstand voltage.

[Conventional technology]

Normal electrolytic capacitors consist of electrolytic paper consisting of an anode electrode foil with an insulating oxide layer formed on the surface of a valve metal foil made of roughened aluminum, tantalum, etc., and a cathode electrode foil for current collection. A capacitor element is formed by being wound around the substrate, and is impregnated with an electrolytic solution and housed in an outer case.

The oxide film layer formed on the anode electrode foil of the capacitor element becomes a dielectric, and the electrolytic solution becomes an electrolyte layer. Then, the electrolyte serving as the electrolyte layer functions as a true cathode. That is, the electrolytic solution is interposed between the dielectric layer formed on the anode foil and the cathode foil for current collection, and the resistance component is inserted in series with the electrolytic capacitor.

Therefore, when the conductivity of the electrolytic solution is low, the equivalent series resistance inside the electrolytic capacitor increases, which adversely affects high-frequency characteristics and loss characteristics. However, generally, when the conductivity of the electrolytic solution is improved, the spark voltage tends to decrease, and the withstand voltage characteristics of the electrolytic capacitor may be impaired. Conversely, when various additives are added to improve the withstand voltage characteristics, the electrical conductivity is reduced,
As a result, the loss increases.

Therefore, means for adding various additives to the electrolyte has been proposed as a means for improving the withstand voltage characteristics without lowering the conductivity of the electrolytic capacitor. For example, sulfamic acid (JP-A-49-82963), suberic acid (JP-A-49-82963)
-133860) dodecyl phosphate (JP-A-49-73659),
Alkyl phosphoric acid (JP-A-52-153154), diphosphorous acid (JP-A-57-141913), boric acid-mannite system (JP-A-57-60829), boric acid-mannitol-polyvinyl Alcohols (JP-A-59-177915), modified silicone oils (JP-A-1-175722) and the like.

[Problems to be solved by the invention]

However, demands for improvement and improvement of the performance of electrolytic capacitors have increased due to an increase in the range of use of electronic devices, and the conductivity of a conventional electrolytic solution is no longer sufficient. Therefore, it is necessary to further improve the conductivity of the electrolytic solution, and as a result, it is difficult to maintain the withstand voltage characteristics.

An object of the present invention is to provide an electrolytic solution having improved withstand voltage characteristics while maintaining high conductivity.

[Means for solving the problem]

An electrolytic solution for an electrolytic capacitor using an organic polar solvent as a main solvent and an organic acid, an inorganic acid or a salt thereof as a solute has a general formula: (Wherein X ₁ to X ₄ are the same or different hydrogen atoms,
R _n Y, a higher acyl group and a higher alcohol residue, at least one of which represents a higher acyl group;
_{In n} Y, n is an integer of 1 or more, R is ethylene oxide and / or propylene oxide, and Y represents the same or different hydrogen atom and higher acyl group, respectively.

In the above general formula, n is not particularly limited as long as it is 1 or more. However, when the degree of polymerization is extremely high, inconveniences such as difficulty in synthesis and decrease in solubility are caused. About 100 or less is appropriate.

Examples of the fatty acid include saturated fatty acids represented by the general formula: CH ₃ (CH ₂ ) _n COOH (n is an integer of 9 or more). For example, undecylic acid (n = 9), lauric acid (n = 10 ), Tridecylic acid (n = 11), myristic acid (n = 12), pentadecylic acid (n = 13), palmitic acid (n = 14), heptadecylic acid (n = 15), stearic acid (n = 16), Nonadecanoic acid (n = 17), arachiic acid (n = 18), behenic acid (n = 20), lignoceric acid (n = 22), cellotic acid (n = 24), heptacosanoic acid (n = 25), montanic acid (N = 27), melisic acid (n = 28), lacceric acid (n = 30) and the like.

As unsaturated fatty acids, undecylenic acid <10>
(11), oleic acid (cis) <9> (18), elaidic acid (trans) <9> (18), setreic acid <11> (2
2), erucic acid (sis) <13> (22), brassic acid (tr
ans) <13> (22), linoleic acid <9,12> (18), linolenic acid <9,12,15> (18), arachidonic acid <5,8,11,14>
(20), stearolic acid <triple bond, 9> (18 [<] indicates the position of the unsaturated bond, and () indicates the total number of carbon atoms).

 Further, specific examples of higher alcohols include hexyl alcohol, heptyl alcohol, octyl alcohol, caprylic alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, hepta alcohol. Decyl alcohol, stearyl alcohol, nonadecyl alcohol, eicosyl alcohol, seryl alcohol, melisyl alcohol, oleyl alcohol, phytol and the like.

The organic polar solvent, which is the main solvent of the electrolytic solution according to the present invention,
Monohydric alcohols such as ethanol, propanol, butanol, and pentanol as protic polar solvents;
Further, there are polyhydric alcohols such as ethylene glycol, propylene glycol, glycerin, and methoxyethanol, and alcohol ethers. Examples of aprotic polar solvents include N-methylformamide, N, N-dimethylformamide, N-ethylformamide, and N-ethylformamide. , N-diethylformamide and other amine-based polar solvents, γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate and other lactones, cyclic amide-based solvents, and nitriles such as acetonitrile, And the like. Examples of the aprotic polar solvent include oxides such as these, and these main solvents can be used alone or in combination.

The electrolyte used in the present invention is not particularly limited, and may be a commonly used electrolyte. For example, organic acids as anion source, for example, formic acid, aliphatic monocarboxylic acids such as acetic acid and malonic acid, aliphatic dicarboxylic acids such as succinic acid, or benzoic acid, aromatic carboxylic acids such as phthalic acid, and inorganic acids include , Boric acid, phosphoric acid, silicic acid and the like. Examples of the cation source include monoalkylammonium cations such as ammonium and methylammonium, dialkylammonium cations such as dimethylammonium and diethylammonium, trialkylammonium cations such as trimethylammonium and triethylammonium, tetramethylammonium, triethylmethylammonium And quaternary ammonium cations, and the like, and phosphonium and arsonium cations.

The electrolytic solution for an electrolytic capacitor according to the present invention is prepared by preparing 100 parts by weight of the organic polar solvent singly or plurally described above, and if necessary, a solute comprising an electrolyte substance in a solvent mixed with 0 to 30 parts by weight of water. What is necessary is just to melt | dissolve 1-50 weight part alone or in combination of two or more. Then, the above-mentioned pentaerythritol fatty acid ester is preferably added to the electrolytic solution in an amount of 0.1 to 20 parts by weight, more preferably 0.5 to 6 parts by weight.
Desired characteristics can be obtained by adding parts by weight.

(Operation)

The action of improving the withstand voltage characteristic of the pentaerythritol fatty acid ester used in the present invention is as follows. The pentaerythritol fatty acid ester micelle layer as a nonionic surfactant is formed at the interface of the aluminum oxide film which is a dielectric of the electrolytic capacitor. It is thought that formation is involved.

〔Example〕

Hereinafter, examples of the electrolytic solution for an electrolytic capacitor according to the present invention will be described.

In each example, an electrolytic solution was prepared using the same solvent and solute as the conventional example, and pentaerythritol fatty acid ester was added thereto. The following pentaerythritol fatty acid esters were used.

A) Polyoxyethylene (POE = 60) pentaerythritol stearic acid ester [Sum of 1 to n = 60] B) Polyoxyethylene (POE = 30) Polyoxypropylene (POP = 10) Pentaerythrit dioleate [Sum of m to n = 30 / p to q = 10] C) Polyoxypropylene monopalmitate (POP = 4
0) Pentaerythrit behenate [Sum of 1 to n = 40] D) Polyoxyethylene (POE = 20) pentaerythritol dibehenate [Sum of m to n = 20] E) Pentaerythritol monooleate As can be seen from the above results, the electric conductivity of the electrolytic solution of the present invention is equal to or slightly lower than that of the conventional example, but the withstand voltage can be improved by about 10% to 50%.

〔The invention's effect〕

As described above, the present invention provides an electrolytic solution for an electrolytic capacitor in which an organic polar solvent is used as a main solvent and an organic acid, an inorganic acid or a salt thereof is used as a solute. (Wherein X ₁ to X ₄ are the same or different hydrogen atoms,
R _n Y, a higher acyl group and a higher alcohol residue, at least one of which represents a higher acyl group;
_{In n} Y, n is an integer of 1 or more, R is ethylene oxide and / or propylene oxide, and Y represents the same or different hydrogen atoms and higher acyl groups, respectively. By adding a small amount of these additives to a normal electrolytic solution, the withstand voltage characteristics can be improved while maintaining the electric conductivity. Therefore, the electrical characteristics at a high voltage are satisfactorily stabilized, and the reliability of the electrolytic capacitor using this electrolytic solution is improved.

Claims (1)

(57) [Claims] 1. An electrolyte for an electrolytic capacitor comprising an organic polar solvent as a main solvent and an organic acid, an inorganic acid or a salt thereof as a solute, having the general formula: (Wherein X ₁ to X ₄ are the same or different hydrogen atoms,
R _n Y, a higher acyl group and a higher alcohol residue, at least one of which represents a higher acyl group;
In _n Y, n is characterized by an integer of 1 or more, R represents added ethylene oxide and / or propylene oxide, Y are each the same or different hydrogen atom, a pentaerythritol fatty acid esters of higher acyl represents a group) electrolytic Electrolyte for capacitors.