JP2010045180A - Electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem in an electrolytic capacitor comprising an electrolyte including ion liquid: even though improvement of breakdown voltage characteristics due to anode oxidation capability of the ion liquid can be recognized, the anode oxidation capability is not sufficient in conventional ion liquid, and it is hard to manufacture a capacitor of high breakdown voltage at favorable yield. <P>SOLUTION: The electrolytic capacitor having compatibility between low impedance characteristics and high breakdown voltage characteristics can be provided by using an electrolyte including a particular ion liquid with superior anode oxidation capability. It is preferable that valve metal of the electrolytic capacitor is selected from a group comprising aluminum, tantalum, and niobium. Also, it is preferable that a negative electrode includes metal that comes into contact with the electrolyte. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrolytic capacitor including an anode made of a valve metal, an oxide film formed on the valve metal, and a cathode made of an electrolytic solution containing an ionic liquid having a specific anion.

  In general, an electrolytic capacitor has a structure in which a valve metal such as aluminum or tantalum is used as an anode, an oxide film formed on the surface thereof is used as a dielectric, and a cathode is formed by sandwiching the dielectric and an electrolytic solution. The electrolytic solution for driving in this electrolytic capacitor has two important roles. One is an action as a practical cathode, which plays a role of extracting a capacitance from a dielectric on the anode, and requires high electrical conductivity, that is, high electronic conductivity. The other is the action of protecting and repairing an extremely thin oxide film, and a chemical action that forms a new oxide on the defective part of the oxide film of the valve metal based on the ionic conductivity of the electrolyte. Is used for the purpose of forming a dielectric oxide film in an electrolytic capacitor and repairing defects in the oxide film. Therefore, the electrolytic solution of the electrolytic capacitor needs to have an anodic oxidation ability.

Generally, as an electrolytic solution for an electrolytic capacitor, an organic solvent such as ethylene glycol or γ-butyrolactone to which an organic acid, an inorganic acid or a salt thereof is added is used. The reason why such a composite electrolyte system is used is to make the electrolyte excellent in ion conductivity (Patent Document 1).
In recent years, with the miniaturization and high performance of electronic devices, electrolytic capacitors are required to satisfy low impedance characteristics and high withstand voltage characteristics. In order to satisfy these characteristics, the electrolytic solution of the electrolytic capacitor is required to have a high withstand voltage and high conductivity, and various additives and the like have been studied. Among them, the ionic liquid has good ionic conductivity and is considered to be effective as one of the additives. For example, electrolysis using an electrolytic solution to which an ionic liquid in which the anion portion is a dicyanoamide ion is added. A capacitor is disclosed (Patent Document 2). However, there are anxiety factors related to reliability, such as the fact that dicyanoamide salts are unstable with respect to water and the possibility of hydrogen cyanide being generated by electrolysis. In addition, the addition of a nitro compound is indispensable for obtaining high withstand voltage characteristics.
On the other hand, although it is a conductive polymer electrolytic capacitor, the conductive polymer electrolytic capacitor which has a high withstand voltage characteristic is implement | achieved by adding an ionic liquid (patent documents 3-5). This utilizes the fact that a specific ionic liquid has an anodizing ability (Patent Document 3). By using such an ionic liquid having an anodic oxidation ability as an additive, it is possible to realize an electrolytic solution having a high withstand voltage and high conductivity, and as a result, an electrolytic capacitor having excellent impedance characteristics and high withstand voltage characteristics can be realized. It is done.
However, in electrolytic capacitors, the ionic liquids disclosed so far have an insufficient anodic oxidation capability as described above, which may lead to a decrease in yield, such as short-circuiting during aging. This is a major obstacle to realizing an electrolytic capacitor having higher withstand voltage characteristics. That is, it is necessary to set the working voltage with respect to the formation voltage lower, and it is impossible to obtain a capacitor that can be used at a substantially high voltage. For these reasons, the development of an electrolytic capacitor using an electrolytic solution that is further excellent in anodizing ability, that is, has high withstand voltage characteristics, is awaited.
Japanese Patent No. 3182793 JP2006-165001 International Publication WO2005 / 012599 Pamphlet International publication WO2005 / 051897 pamphlet International Publication WO2006 / 088033 Pamphlet

  The present invention has been made to solve the above-described problems, and the object of the present invention is to achieve both high withstand voltage characteristics and low impedance characteristics by using an electrolytic solution containing a specific ionic liquid. It is to provide an electrolytic capacitor.

  As a result of intensive studies in view of the above, the present inventors have used an electrolytic solution containing at least one ionic liquid selected from a group of ionic liquids having a specific anion component. The inventors have found that an electrolytic capacitor excellent in voltage characteristics and low impedance characteristics can be obtained, and have completed the present invention. This is considered to be due to the fact that the ionic liquid having the specific anion has a high anodic oxidation ability that has not been conventionally available.

  That is, the present invention provides an anode made of a valve metal, an oxide film formed on the valve metal, and a formate anion or the general formula (1);

(Wherein R ¹ and R ² are each independently a hydrogen atom, a protected or unprotected hydroxyl group, a protected or unprotected amino group, an alkoxy group, a nitro group, a cyano group, a carboxyl group, a halogen atom, a straight chain or branched or alkyl group optionally C ₁ -C ₂₀ optionally may have a substituent to form a ring, may have a straight-chain or branched or may substituents may form a ring C ₂ -C ₂₀ alkenyl group, straight chain, branched or ring may be formed and optionally substituted C ₂ -C ₂₀ alkynyl group, optionally substituted C _{6 to} C ₂₀ aryl group, optionally having C _{4 to} C ₂₀ heteroaryl group, optionally having C _{7 to} C ₂₀ aralkyl group and having substituent Represents a C _{4 to} C ₂₀ heteroaralkyl group which may be Or they may be different, and together may form a ring)
It is related with the electrolytic capacitor comprised from the cathode which consists of an electrolyte solution which contains at least 1 or more types of ionic liquid which has an anion represented by these.

  By using an electrolytic solution containing at least one ionic liquid having a specific anion component, or an electrolytic solution comprising an ionic liquid having a specific anion component and a specific salt, it has excellent high withstand voltage characteristics and low impedance characteristics. An electrolytic capacitor can be obtained.

Hereinafter, embodiments of the present invention will be described in detail.
First, the ionic liquid used in the present invention will be described. An ionic liquid, also called a room temperature molten salt, refers to a liquid that is liquid at room temperature despite being composed only of ions, and is composed of a combination of a cation such as imidazolium and an appropriate anion. The ionic liquid is not partially ionized and dissociated like a normal organic solvent, but is considered to be formed from only ions and 100% ionized. As described above, the ionic liquid is usually a liquid at room temperature, but the ionic liquid used in the present invention does not necessarily have to be a liquid at room temperature, and becomes a liquid during the aging process or heat treatment of the capacitor. Any material that spreads and becomes a liquid by Joule heat generated during the repair of the dielectric oxide film may be used.

  In the present invention, an ionic liquid having a formate anion and / or general formula (1);

An ionic liquid having an anion represented by can be used. The ionic liquid having an anion represented by the formula (1) will be described. The anion represented by the formula (1) is paired with a cation described later to form a liquid salt at room temperature, that is, an ionic liquid. In the formula (1), R ¹ and R ² are each independently a hydrogen atom, a protected or unprotected hydroxyl group, a protected or unprotected amino group, an alkoxy group, a nitro group, a cyano group, a carboxyl group, a halogen atom, A C ₁ -C ₂₀ alkyl group which may form a chain, a branch or a ring and may have a substituent, a straight chain or a branch or a ring which may have a substituent alkenyl group which may C ₂ -C _20, linear or form a branched or ring which may have a even better substituents C ₂ -C ₂₀ alkynyl group, which may have a substituent C ₆ -C ₂₀ aryl group, C ₄ -C ₂₀ heteroaryl group optionally having substituent, C ₇ -C ₂₀ aralkyl group optionally having substituent, substituent A C ₄ -C ₂₀ heteroaralkyl group which may have And they may be the same or different from each other, and may form a ring together.

  In the present invention, “may have a substituent” means that it may be substituted with another atom or substituent. The “substituent” is not particularly limited as long as it does not adversely affect the reaction. Specifically, the hydroxyl group, alkyl group, alkoxy group, alkylthio group, nitro group, amino group, cyano group, carboxyl group, A halogen atom etc. are mentioned.

The above R ¹ and R ² will be further described. The C ₁ -C ₂₀ alkyl group which may form a straight chain, a branched chain or a ring and may have a substituent is not particularly limited, and examples thereof include a methyl group, a hydroxymethyl group, Ethyl group, n-propyl group, isopropyl group, cyclopropyl group, n-butyl group, sec-butyl group, tert-butyl group, cyclobutyl group, n-pentyl group, cyclopentyl group, n-hexyl group, cyclohexyl group, n -Heptyl group, n-octyl group, n-decyl group, etc. can be mentioned, and those in which an arbitrary number of hydrogen atoms of these alkyl groups are substituted with fluorine atoms can be mentioned. Examples of the C ₂ -C ₂₀ alkenyl group which may form a straight chain, branched chain or ring and may have a substituent include, for example, vinyl group, propenyl group, styryl group, isopropenyl group, cyclopropenyl Group, butenyl group, cyclobutenyl group, cyclopentenyl group, hexenyl group, cyclohexenyl group and the like. Examples of the C _{2 to} C ₆ alkynyl group which may form a straight chain, a branched chain or a ring and may have a substituent include, for example, an ethynyl group, a propynyl group, a phenylethynyl group, a cyclopropylethynyl group, Examples include butynyl group, pentynyl group, cyclobutylethynyl group, and hexynyl group. Examples of the aryl group that may have a substituent include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a terphenyl group, and a 3,4,5-trifluorophenyl group. Examples of the heteroaryl group which may have a substituent include, for example, pyrrolinyl group, pyridyl group, quinolyl group, imidazolyl group, furyl group, indolyl group, thienyl group, oxazolyl group, thiazolyl group, 2-phenylthiazolyl group. , 2-anisyl thiazolyl group and the like. Examples of the aralkyl group which may have a substituent include benzyl, chlorobenzyl, bromobenzyl, salicyl, α-hydroxybenzyl, phenethyl, α-hydroxyphenethyl, naphthylmethyl, and anthracyl. Examples include senylmethyl group, 3,5-difluorobenzyl group, and trityl group. Examples of the heteroaralkyl group which may have a substituent include a pyridylmethyl group, a difluoropyridylmethyl group, a quinolylmethyl group, an indolylmethyl group, a furfuryl group, and a thienylmethyl group. Alternatively, R ¹ and R ² may be combined to form a ring, and examples thereof include a cyclohexyl group and a phenyl group. Further, when R ¹ and / or R ² is a hydroxyl group or has a hydroxyl group as a substituent, the hydroxyl group may be protected or unprotected, and when protected, the protecting group is particularly limited. For example, a general protecting group may be used, and examples thereof include those described in “PROTECTIVE GROUPS in ORGANIC SYNTHESIS THIRD EDITION” (page 17 WILEY-INTERSCIENCE). Specific examples of hydroxyl protecting groups include ether protecting groups such as methyl, methoxymethyl, methylthiomethyl, trimethylsilyl, and triethylsilyl groups, and ester protecting groups such as acetyl and chloroacetyl groups. Can be mentioned.
Further, when R ¹ and / or R ² is an amino group or has an amino group as a substituent, the amino group may be protected or unprotected. Although not limited, for example, a general protecting group may be used, and examples thereof include those described in “PROTECTIVE GROUPS in ORGANIC SYNTHESIS THIRD EDITION” (page 494, WILEY-INTERSCIENCE). Specific examples of protecting groups for amino groups include benzyl, trityl, formyl, acetyl, chloroacetyl, tetrachloroacetyl, tetrafluoroacetyl, benzoyl, phenylacetoxy, methoxycarbonyl, ethoxy A carbonyl group, 9-fluorenylmethoxycarbonyl group, t-butoxycarbonyl group, etc. are mentioned. From the viewpoint of ease of introduction and deprotection, among the above groups, benzyl, trityl, formyl, acetyl, chloroacetyl, tetrachloroacetyl, tetrafluoroacetyl, benzoyl, phenyl An acetoxy group, a 9-fluorenylmethoxycarbonyl group, and a t-butoxycarbonyl group;

These ionic liquids may be used alone or in admixture of two or more at any ratio. Moreover, when it has an asymmetric point in a molecule | numerator, an optically active body may be sufficient and a racemic body may be sufficient. From the viewpoint of anodic oxidation capability and availability, at least one of R ¹ and R ² is a hydrogen atom, a hydroxyl group, or an amino group, and the other is a methyl group, an ethyl group, an n-butyl group, or an n-hexyl group. N-heptyl group, trifluoromethyl group, phenyl group, benzyl group, naphthyl group and the like are preferable. When at least one of R ¹ and R ² is a hydroxyl group, it may be protected or unprotected, but generally unprotected is preferable because it exhibits a higher anodic oxidation ability. Also preferred are those in which R ¹ and R ² together form a cyclohexyl group or a phenyl group.

  The type and amount of the ionic liquid used are not particularly limited, but the total amount of ionic liquid added is preferably 1 to 100% by weight based on the total amount of the electrolytic solution, and if the concentration is too low Since it is difficult to obtain high electrical conductivity, 5 to 100% by weight is particularly preferable.

  The electrolytic solution used in the present invention includes a nitro compound, a phosphoric acid compound, a boric acid compound, and a polyhydric alcohol as necessary in order to improve thermal stability, suppress electrode deterioration due to hydration and the like, and realize further high withstand voltage characteristics. , Silicon compounds, ammonium salts, amine salts, quaternary ammonium salts, tertiary amines and organic acids, imidazolium salts and other additives can be added. Examples of nitro compounds include nitrophenol, nitroacetophenone, nitrobenzoic acid, nitrobenzyl alcohol, nitrocresol, nitrotoluene, nitroanisole and the like. Examples of phosphoric acid compounds include orthophosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, polyphosphoric acid, methyl phosphate, ethyl phosphate, butyl phosphate, isopropyl phosphate, dibutyl phosphate, dioctyl phosphate, etc. Is mentioned. Examples of boric acid compounds include boric acid and its complex compounds. Examples of the polyhydric alcohols include erythritol, glycerin, threitol, ribitol, arabinitol, allitol, glucitol, mannitol, sorbitol, xylitol, iditol, galactitol, taritol, polyvinyl alcohol and the like. Examples of the silicon compound include colloidal silica, aluminosilicate, silicone compound, silane coupling agent and the like. Examples of ammonium salts include ammonium adipate, ammonium borate, ammonium phosphate, ammonium adipate, and ammonium maleate. Examples of the amine salt include triethylamine maleate, and examples of the quaternary ammonium salt include quaternary ammonium maleate and quaternary ammonium phthalate. Examples of tertiary amines and organic acids include combinations of tertiary amines such as triethylamine and diisopropylethylamine and adipic acid, phosphoric acid, boric acid, salicylic acid, malic acid, succinic acid, and the like. Examples of the imidazolium salt include 1,3-ethylmethylimidazolium-p-toluenesulfonate, 1,3-butylmethylimidazolium-p-toluenesulfonate, 1,3-ethylmethylimidazolium-p-tri Examples thereof include fluoromethylphenyl sulfonate and 1,3-butylmethylimidazolium-p-trifluoromethylphenyl sulfonate.

  The addition amount of these additives can be arbitrarily selected as long as the properties of the ionic liquid as a liquid are not lost. For example, when ammonium adipate is added to the ionic liquid, although it depends on the type of the ionic liquid, generally it is preferably in the range of 1% by weight to 50% by weight for improving the anodizing ability. Moreover, these additives may be used independently and may mix and use 2 or more types by arbitrary ratios.

  The term “anodic oxidation ability” as used herein refers to the ability to form an oxide film on the valve metal and the ability to repair defects in the previously formed oxide film. It has already been reported that an ionic liquid has an anodic oxidation capability. For example, a high-voltage conductive polymer capacitor is produced by utilizing the ability to repair defects in an aluminum oxide film (Patent Documents 3 to 5). ). However, conventional ionic liquids have insufficient anodizing ability, and development of ionic liquids having higher anodizing ability has been desired. The ionic liquid described in the present invention has been found to meet such a demand, and exhibits a higher anodic oxidation ability than conventional ionic liquids (an anodic oxidation evaluation method and results will be described later). . As a result, it is possible to realize a capacitor that can be used in an unprecedented high voltage region.

  Valve metal, also called valve metal, shows excellent corrosion resistance because the metal surface is uniformly covered with the surface of the metal oxide film by anodic oxidation, and the oxide film flows current only in one direction and reverse direction. Means a so-called rectifying action (valve action) that is very difficult to flow. Aluminum, tantalum, niobium, titanium, hafnium, zinc, tungsten, bismuth, antimony, and the like are known as metals that are covered with an oxide film by anodic oxidation and exhibit a rectifying action. Among these, aluminum, tantalum, and the like are known. Niobium and the like are used for electrolytic capacitors.

  Next, the cation component of the ionic liquid or salt will be described. As the cationic component, ammonium and derivatives thereof, imidazolium and derivatives thereof, pyridinium and derivatives thereof, pyrrolidinium and derivatives thereof, pyrrolinium and derivatives thereof, pyrazinium and derivatives thereof, pyrimidinium and derivatives thereof, triazonium and derivatives thereof, triazinium and derivatives thereof , Triazine and derivatives thereof, quinolinium and derivatives thereof, isoquinolinium and derivatives thereof, indolinium and derivatives thereof, quinoxalinium and derivatives thereof, piperazinium and derivatives thereof, oxazolinium and derivatives thereof, thiazolinium and derivatives thereof, morpholinium and derivatives thereof, piperazine And its derivatives, but the resulting ionic liquid has a relatively low viscosity. From exhibit, imidazolium derivatives are preferred, diethyl imidazolium as imidazolium derivatives, ethyl butyl imidazolium, dimethyl imidazolium are preferred, particularly preferably ethyl methyl imidazolium, methyl butyl imidazolium.

  The solvent of the electrolytic solution used in the present invention is not particularly limited, and examples thereof include alcohols, ethers, amides, oxazolidinones, lactones, nitriles, carbonates, and sulfones. Examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, benzyl alcohol, amyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, hexylene glycol, and glycerin. Examples of ethers include diisopropyl ether, t-butyl methyl ether, tetrahydrofuran, dimethoxyethane, 1,4-dioxane and the like. Examples of the high molecular weight material include polyalkylene glycols such as polyethylene glycol and polypropylene glycol, and copolymers thereof. Examples of amides include N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-methylacetamide, N-ethylacetamide, N, N- Examples include ethylacetamide, N-methyl-2-pyrrolidone, N, N, N, N, N, N-hexamethylphosphoric triamide. Examples of oxazolidinones include N-methyl-2-oxazolidinone and 3,5-dimethyl-2-oxazolidinone. Examples of lactones include γ-butyrolactone, β-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of nitriles include acetonitrile, propionitrile, t-butyl nitrile, benzonitrile, adiponitrile, 3-methoxypropionitrile and the like. Examples of carbonates include ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate. Examples of the sulfones include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methyl sulfolane, and 2,4-dimethyl sulfolane. Examples of other solvents include dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, toluene, xylene, and paraffins. Among the above solvents, lactones are preferable, and γ-butyrolactone is particularly preferable.

  Next, an electrolytic capacitor using the electrolytic capacitor electrolytic solution of the present invention will be described. The electrolytic capacitor including the electrolytic solution and the electrode of the present invention is not particularly limited. For example, an anode foil made of a valve metal having a dielectric oxide film formed on the surface thereof in a wound aluminum electrolytic capacitor, and a cathode foil therebetween. The capacitor element may be configured by winding with a separator interposed between the anode foil and the cathode foil, and an electrolyte including an ionic liquid is provided between the anode foil and the cathode foil. After being housed in the aluminum case, the aluminum electrolytic capacitor can be configured by sealing the opening of the aluminum case with a sealing agent.

  As the anode of the electrolytic capacitor of the present invention, a conventionally known capacitor can be preferably used. For example, as an anode metal, etching is performed on the surface of an electrode foil such as aluminum to form an etching hole, and anodic oxidation or the like is performed on the surface. By combining a dielectric composed of an oxide film formed by the above method, an anode composed of an anode metal and a dielectric oxide film can be formed. The above anodic oxidation can be performed by immersing the anode metal in, for example, an aqueous solution of ammonium adipate and applying a conversion voltage.

  As the cathode, for example, a carbon paste and a silver paste can be formed by a conventionally known method. The anode and cathode are each connected to a terminal. In this manner, an electrolytic capacitor including at least an anode, an electrolyte, and a cathode can be formed.

In the electrolytic capacitor of the present invention using the electrolyte formed by the above method, constituent elements of the capacitor not particularly mentioned are not particularly limited, and conventionally known ones can be appropriately applied.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples, In the range which does not change the summary, it can change suitably.

<Ionic liquid and salt>
First, a method for synthesizing or obtaining ionic liquids and salts used as examples will be described.

1-butyl-3-methylimidazolium bis (perfluoromethylsulfonyl) imide (hereinafter abbreviated as [BMIm] [TFSI])

Purchased from Kanto Chemical.

1-butyl-3-methylimidazolium trifluoromethanesulfonate (hereinafter abbreviated as [BMIm] [TfO])

Purchased from Wako Pure Chemical.

1-butyl-3-methylimidazolium tetrafluoroborate (hereinafter abbreviated as [BMIm] [BF ₄ ])

Purchased from Merck.

1-butyl-3-methylimidazolium acetate (hereinafter abbreviated as [BMIm] [AcO])

Purchased from Aldrich.

1-butyl-3-methylimidazolium trifluoroacetate (hereinafter abbreviated as [BMIm] [TFA])

Purchased from Merck.

1-ethyl-3-methylimidazolium lactate (hereinafter abbreviated as [EMIm] [LA])

Purchased from Aldrich.

1-ethyl-3-methylimidazolium dicyanoamide (hereinafter abbreviated as [EMIm] [DCA])

Purchased from Kanto Chemical.

1-butyl-3-methylimidazolium benzoate (hereinafter abbreviated as [BMIm] [BA])

1-butyl-3-methylimidazolium hydrogen carbonate 50% aqueous solution (4.0 g, 9.98 mmol) was added and cooled to 0 ° C. Thereafter, an aqueous solution of benzoic acid (1.2 g, 9.98 mmol) was slowly added dropwise and stirred at room temperature for 1 hour. The reaction solution was concentrated as it was, the solvent was distilled off under reduced pressure, dichloromethane was added to the resulting residue, and the organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain 1.8 g of the objective compound as a light brown oil. (Yield 70%)
¹ H NMR (CDCl ₃ , 300 MHz) δ 0.90 (t, 3H), 1.28-1.35 (m, 2H), 1.76-1.87 (m, 2H), 4.06 (s, 3H), 4.27 (t, 2H), 7.14 (d, 2H), 7.27-7.34 (m, 3H), 8.07-8.10 (m, 2H), 11.39 (S, 1H)

1-butyl-3-methylimidazolium mandelate (hereinafter abbreviated as [BMIm] [MA])

1-butyl-3-methylimidazolium hydrogen carbonate 50% aqueous solution (5.0 g, 12.48 mmol) was added, and the mixture was cooled to 0 ° C. Thereafter, an aqueous solution of mandelic acid (1.9 g, 12.48 mmol) was slowly added dropwise and stirred at room temperature for 1 hour. The reaction solution was concentrated as it was, the solvent was distilled off under reduced pressure, dichloromethane was added to the resulting residue, and the organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain 3.6 g of the objective compound as a light brown oil. (Yield 100%)
¹ H NMR (CDCl ₃ , 300 MHz) δ 0.93 (t, 3H), 1.29-1.34 (m, 2H), 1.74-1.79 (m, 2H), 3.84 (s, 3H), 4.10 (t, 2H), 4.92 (s, 1H), 7.04 (s, 1H), 7.14-7.26 (m, 1H), 7.23-7.26 (M, 3H), 7.54 (d, 2H), 10.74 (s, 1H)

1-butyl-3-methylimidazolium caprylate (hereinafter abbreviated as [BMIm] [CA])

1-butyl-3-methylimidazolium hydrogen carbonate 50% aqueous solution (5.0 g, 12.48 mmol) was added, and the mixture was cooled to 0 ° C. Thereafter, an aqueous solution of caprylic acid (1.8 g, 12.48 mmol) was slowly added dropwise and stirred at room temperature for 1 hour. The reaction solution was concentrated as it was, the solvent was distilled off under reduced pressure, dichloromethane was added to the resulting residue, and the organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain 2.2 g of the objective compound as a yellow oil. (Yield 62%)
¹ H NMR (CDCl ₃ , 300 MHz) δ 0.83-0.92 (m, 7H), 1.21-1.29 (m, 11H), 1.38 (m, 2H), 1.73-1. 78 (m, 2H), 3.85 (s, 3H), 4.17 (t, 2H), 7.72 (s, 1H), 7.79 (s, 1H), 9.39 (s, 1H) )

1-ethyl-3-methylimidazolium tosylate (hereinafter abbreviated as [EMIm] [TsO])

Purchased from Aldrich.

1-ethyl-3-methylimidazolium 4- (trifluoromethyl) benzenesulfonate (hereinafter abbreviated as [EMIm] [TFBSA])

Ethyl 4- (trifluoromethyl) benzenesulfonate (2.0 g, 7.86 mmol), 1-methylimidazole (0.6 mg, 7.86 mmol), 1,1,1-trichloroethane (8.0 mL) were added to the reaction vessel. Sequentially added and heated to reflux for 8 hours. The reaction solution was concentrated as it was, and the obtained solid was washed with 1,1,1-trichloroethane. Then, dichloromethane (6.0 mL) was added, this was washed 3 times with water (3.0 mL), and the organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain 2.3 g of the target compound as a white solid. (Yield 88%)
¹ H NMR (CDCl ₃ , 300 MHz) δ 1.53 (t, 3H), 4.02 (s, 3H), 4.29 (q, 2H), 7.30 (brs, 2H), 7.63 (d 2H), 8.02 (d, 2H), 9.80 (s, 1H)
Ethyl 4- (trifluoromethyl) benzenesulfonate was synthesized by the following method.

An ethanol / dichloromethane solution (0.7 g, 15.27 mmol / 5.0 mL) was placed in a reaction vessel, brought to 0 ° C., and triethylamine (2.3 g, 22.90 mmol), 4- (trifluoromethyl) benzenesulfonyl chloride / dichloromethane. The solution (3.7 g, 15.27 mmol / 10 mL) was added dropwise sequentially. After stirring at room temperature for 1 hour, the reaction was stopped by adding ice water. After extraction with dichloromethane, the mixture was washed with water and saturated brine, and the obtained organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the obtained residue was purified by silica gel column chromatography (hexane / ethyl acetate = 5/1, silica gel 30 g) to obtain 3.3 g of the objective compound as a colorless transparent oil. (Yield 85%)
¹ H NMR (CDCl ₃ , 300 MHz) δ 1.34 (t, 3H), 4.19 (q, 2H), 7.83 (d, 2H), 8.05 (d, 2H)

1-butyl-3-methylimidazolium 4- (trifluoromethyl) benzenesulfonate (hereinafter abbreviated as [EMIm] [TFBSA])

Into a reaction vessel were added butyl 4- (trifluoromethyl) benzenesulfonate (0.5 g, 1.77 mmol), 1-methylimidazole (0.14 g, 1.77 mmol), 1,1,1-trichloroethane (1.8 mL). Sequentially added and heated to reflux for 6 hours. The reaction solution was concentrated as it was, and the obtained solid was washed with 1,1,1-trichloroethane. Thereafter, dichloromethane (3.0 mL) was added, this was washed 3 times with water (2.0 mL), and the organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain 0.66 g of the target compound as a light brown solid. (Yield 100%)
¹ H NMR (CDCl ₃ , 300 MHz) δ 0.92 (t, 3H), 1.29-1.36 (m, 2H), 1.78-1.88 (m, 2H), 4.04 (s, 3H), 4.23 (t, 2H), 7.23 (s, 1H), 7.30 (s, 1H), 7.63 (d, 2H), 8.03 (d, 2H), 9. 85 (s, 1H)
Butyl 4- (trifluoromethyl) benzenesulfonate was synthesized by the following method.

A butanol / dichloromethane solution (0.3 g, 4.08 mmol / 1.0 mL) was placed in a reaction vessel, brought to 0 ° C., and triethylamine (0.6 g, 6.13 mmol), 4- (trifluoromethyl) benzenesulfonyl chloride / dichloromethane. The solution (1.0 g, 4.08 mmol / 3.0 mL) was added dropwise sequentially. After stirring at room temperature for 1 hour, the reaction was stopped by adding ice water. After extraction with dichloromethane, the mixture was washed with water and saturated brine, and the obtained organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the resulting residue was purified by silica gel column chromatography (hexane / ethyl acetate = 5/1, silica gel 10 g) to obtain 0.99 g of the objective compound as a colorless transparent oil. (Yield 84%)
¹ H NMR (CDCl ₃ , 300 MHz) δ 0.88 (t, 3H), 1.32-1.39 (m, 2H), 1.61-1.71 (m, 2H), 4.11 (t, 2H), 7.83 (d, 2H), 8.05 (d, 2H)

1-ethyl-3-methylimidazolium 2-aminopropionate (hereinafter abbreviated as [EMIm] [Ala])

Amberlite IRA400 (OH) (140 mL) was added to the chromatographic column tube, 1N NaOH aqueous solution (2.5 L) was poured to activate the Amberlite IRA400 (OH), and then purified water (1.5 L) until the filtrate became neutral. ). After adding pure water (50 mL) to 1-ethyl-3-methylimidazolium bromide (5.0 g, 26.16 mmol) and dissolving it, this was passed through the previously activated Amberlite IRA400 (OH) to give 1-ethyl. An aqueous solution of -3-methylimidazolium hydroxide was obtained. After adding pure water (200 mL) to alanine (3.0 g, 33.67 mmol) to make a homogeneous solution, 1-ethyl-3-methylimidazolium hydroxide aqueous solution is slowly added dropwise thereto and stirred at 0 ° C. for 12 hours. did. The reaction solution was concentrated as it was, acetonitrile (90 mL) and methanol (10 mL) were added to the obtained residue, and the mixture was stirred at 0 ° C. for 30 min. The filtrate was concentrated and dried under reduced pressure to obtain 4.4 g of the target compound as a pale yellow oil. (Yield 73%)

1-butyl-3-methylimidazolium phenylacetate (hereinafter abbreviated as [BMIm] [PA])

Amberlite IRA400 (OH) (140 mL) was added to the chromatographic column tube, 1N NaOH aqueous solution (2.5 L) was poured to activate the Amberlite IRA400 (OH), and then purified water (1.5 L) until the filtrate became neutral. ). After adding pure water (50 mL) to 1-butyl-3-methylimidazolium chloride (5.0 g, 28.63 mmol) and dissolving it, this was passed through the previously activated Amberlite IRA400 (OH) to give 1-butyl An aqueous solution of -3-methylimidazolium hydroxide was obtained. After adding pure water (200 mL) and THF (100 mL) to phenylacetic acid (3.9 g, 28.63 mmol) to make a homogeneous solution, 1-butyl-3-methylimidazolium hydroxide aqueous solution was slowly added dropwise thereto. Stir at 0 ° C. for 12 hours. The reaction solution was concentrated as it was, acetonitrile (90 mL) and methanol (10 mL) were added to the obtained residue, and the mixture was stirred at 0 ° C. for 30 min. The filtrate was concentrated and heated under reduced pressure to obtain 8.0 g of the target compound as a pale yellow oil. (Yield 100%)
¹ H NMR (DMSO-d ⁶ , 300 MHz) δ 0.89 (t, 3H), 1.21-1.28 (m, 2H), 1.70-1.77 (m, 2H), 3.23 ( s, 2H), 3.83 (s, 3H), 4.15 (t, 2H), 7.09-7.19 (m, 5H), 7.70 (s, 1H), 7.77 (s) 1H), 9.29 (s, 1H)

1-butyl-3-methylimidazolium 2-phenylbutyrate (hereinafter abbreviated as [BMIm] [2-PB])

1-butyl-3-methylimidazolium hydrogen carbonate 50% aqueous solution (6.0 g, 14.98 mmol) was added and cooled to 0 ° C. Thereafter, an aqueous solution of 2-phenylbutyric acid (2.4 g, 14.98 mmol) was slowly added dropwise and stirred at room temperature for 1 hour. The reaction solution was concentrated as it was, the solvent was distilled off under reduced pressure, dichloromethane was added to the resulting residue, and the organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain 4.5 g of the target compound as a yellow oil. (Yield 100%)
¹ H NMR (DMSO-d ⁶ , 300 MHz) δ 0.66 (t, 3H), 0.80 (t, 3H), 1.12-1.19 (m, 1H), 1.31-1.35 ( m, 1H), 1.61-1.80 (m, 3H), 2.82 (t, 1H), 3.74 (s, 3H), 4.06 (t, 2H), 6.95-7 .15 (m, 5H), 7.62 (d, 1H), 7.68 (d, 1H), 9.28 (s, 1H)

1-butyl-3-methylimidazolium 4-phenylbutyrate (hereinafter abbreviated as [BMIm] [4-PB])

1-butyl-3-methylimidazolium hydrogen carbonate 50% aqueous solution (6.0 g, 14.98 mmol) was added and cooled to 0 ° C. Thereafter, an aqueous solution of 4-phenylbutyric acid (2.4 g, 14.98 mmol) was slowly added dropwise and stirred at room temperature for 1 hour. The reaction solution was concentrated as it was, the solvent was distilled off under reduced pressure, dichloromethane was added to the resulting residue, and the organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain 4.4 g of the target compound as a yellow oil. (Yield 98%)
¹ H NMR (CDCl ₃ , 300 MHz) δ 0.94 (t, 3H), 1.32-1.39 (m, 2H), 1.82-1.87 (m, 2H), 1.95-2. 01 (m, 2H), 2.30 (t, 2H), 2.68 (t, 2H), 4.06 (s, 3H), 4.29 (t, 2H), 7.07-7.27 (M, 7H), 11.68 (s, 1H)

1-butyl-3-methylimidazolium naphthyl acetate (hereinafter abbreviated as [BMIm] [NA])

1-butyl-3-methylimidazolium hydrogen carbonate 50% aqueous solution (6.0 g, 14.98 mmol) was added and cooled to 0 ° C. Thereafter, an aqueous solution of 1-naphthaleneacetic acid (2.7 g, 14.98 mmol) was slowly added dropwise and stirred at room temperature for 1 hour. The reaction solution was concentrated as it was, the solvent was distilled off under reduced pressure, dichloromethane was added to the resulting residue, and the organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain 5.0 g of the target compound as a yellow oil. (Yield 100%)
¹ H NMR (DMSO-d ⁶ , 300 MHz) δ 0.88 (t, 3H), 1.19-1.26 (m, 2H), 1.70-1.75 (m, 2H), 3.59 ( s, 2H), 3.81 (s, 3H), 4.12 (t, 2H), 7.22-7.44 (m, 4H), 7.64-7.76 (m, 3H), 7 .80-7.83 (m, 1H), 8.15-8.18 (m, 1H), 9.36 (s, 1H)

Example 1
Next, anodic oxidation was performed in an ionic liquid, and the anodizing ability was evaluated by measuring a change in flowing current by applying a voltage.

An aluminum wire (1.5 mm diameter) with a purity of 99.99% was immersed in a mixed solution of 70% HNO ₃ (15 parts) and 85% H ₃ PO ₄ (85 parts) for 2 minutes, and then washed with pure water. Next, it was etched with 1N NaOH aqueous solution for 10 minutes, washed with pure water, immersed in acetone and dried. Next, the aluminum wire was subjected to chemical conversion treatment in an adipic acid aqueous solution (1 g / L). Chemical conversion was performed at a constant current of 10 mA / cm ² , and held at a constant voltage of 200 V for 10 minutes after the voltage reached 200 V. Subsequently, the chemical conversion film was treated with boiling water while applying a direct current of 100 V so that the aluminum side became a positive electrode. A part of the chemical conversion film is destroyed by this treatment.

  Next, the chemical conversion film subjected to such a treatment was immersed in an ionic liquid, and a change in current value was measured when the voltage was increased at a rate of 1 V / second in room temperature. FIG. 1 shows a change in current when [EMIm] [LA] is used.

Initially, the current value flows through the broken part of the oxide film (region 1). However, when the electrolyte has an anodic oxidation property, a new oxide film is formed at the broken part due to its ability to repair the film. The value decreases after reaching the maximum value (point A: around 10 V) (region 2). The minimum value of the current value (point B: around 30 to 40 V) is the time when the repair is completed, and thereafter, a certain current rising region based on ionic conduction proportional to the voltage rise appears (region 3). However, when the voltage is further increased, the linear relationship deviates from a certain voltage (C point: around 120V) and current starts to flow (region 4). This shows the actual withstand voltage of the electrolyte. Of course, when there is no anodic oxidation capability, current flows only in the region 1 and the oxide film is destroyed. From this, it was confirmed that [EMIm] [LA] has an excellent anodic oxide film.
(Examples 2 to 11)
The experiment was performed in the same manner as in Example 1 except that the ionic liquid was changed to the type shown in Table 1. The obtained results are shown in Table 1.
(Comparative Examples 1-4)
The experiment was performed in the same manner as in Example 1 except that the ionic liquid was changed to the type shown in Table 1. The obtained results are shown in Table 1.

Comparing the results of the ionic liquids shown in Examples 1 to 11 and the ionic liquids shown in Comparative Examples 1 to 4, the ionic liquids shown in Examples 1 to 11 have a lower voltage at point A, and conversely C The voltage at the point has a higher result. From this, it can be seen that the ionic liquids discovered by the present inventors show a high anodizing ability that has not been achieved in both the low pressure region and the high pressure region.
Example 12
An oxide film analysis was performed as an evaluation of the anodizing ability. First, an aluminum plate processed to 10 mm × 10 mm × 0.5 mm is immersed in [EMIm] [LA] using the cell shown in FIG. 2, and the voltage is increased to 40 V at a rate of 100 mV / second to form a film. Then, the sample for analysis was prepared by washing with methanol and drying. In this test, the voltage was set to 40 V in order to confirm the anodic oxidation ability in the high-pressure region, which is more important. For the oxide film analysis by XPS of the obtained sample, Quantum 2000 manufactured by ULVAC-PHI was used, X-ray intensity: AlKα / 15 kV · 12.5 W, X-ray beam diameter: 50 μmΦ, sputtering rate: 0.9 nm / min (SiO 2 ₂ ), a depth profile measurement was performed by an argon ion etching method. In the obtained depth profile, a sputtering time in which both Al _2P data and O _1S data values fluctuate by 5% or more compared with the immediately preceding data after passing through a steady state for a certain time is “corresponding to the oxide film thickness. It was defined as “sputtering time”. In addition, in the data using ammonium phosphate, the film thickness using the ionic liquid was obtained by calculation using the result of 0.4 nm / min recognized in the film thickness and sputtering time. The results are shown in Table 2.
(Examples 13 to 25)
The experiment was performed in the same manner as in Example 12 except that the ionic liquid and / or salt were changed to the types shown in Table 2. The obtained results are shown in Table 2.
(Comparative Examples 5-7)
An experiment was performed in the same manner as in Example 12 except that the ionic liquid was changed to the type shown in Table 2. The obtained results are shown in Table 2. In the depth profile, it is determined that a clear oxide film is not formed for a sample in which a steady state does not exist for a certain time in the Al _2P data and O _1S data values, and the film thickness is not calculated.

In all of the ionic liquids shown in Examples 12 to 25, a clear oxide film was confirmed, but in any of the ionic liquids shown in Comparative Examples 5 to 7, no oxide film could be confirmed. From these results, it was confirmed that the ionic liquid found by the present inventors has an excellent anodizing ability.

Diagram of IV characteristics in anodizing ability evaluation Cell used for anodic oxidation of aluminum with ionic liquid

Claims (10)

An anode made of a valve metal, an oxide film formed on the valve metal, and a formate anion or general formula (1);
(Wherein R ¹ and R ² are each independently a hydrogen atom, a protected or unprotected hydroxyl group, a protected or unprotected amino group, an alkoxy group, a nitro group, a cyano group, a carboxyl group, a halogen atom, a straight chain or branched or alkyl group optionally C ₁ -C ₂₀ optionally may have a substituent to form a ring, may have a straight-chain or branched or may substituents may form a ring C ₂ -C ₂₀ alkenyl group, straight chain, branched or ring may be formed and optionally substituted C ₂ -C ₂₀ alkynyl group, optionally substituted C _{6 to} C ₂₀ aryl group, optionally having C _{4 to} C ₂₀ heteroaryl group, optionally having C _{7 to} C ₂₀ aralkyl group and having substituent Represents a C _{4 to} C ₂₀ heteroaralkyl group which may be Or they may be different, and together may form a ring)
The electrolytic capacitor comprised from the cathode which consists of electrolyte solution which contains at least 1 or more types of ionic liquid which has an anion represented by these.   The electrolytic capacitor according to claim 1, wherein the valve metal contains one or more metals selected from the group consisting of aluminum, tantalum, and niobium.   3. The electrolytic capacitor according to claim 1, wherein the cathode contains a metal in contact with the electrolytic solution. 4. The electrolytic capacitor according to claim 1, wherein in the formula (1), at least one of R ^{1 and} R ² is a protected or unprotected hydroxyl group or a protected or unprotected amino group. . In the formula (1), at least one of R ^{1 and} R ² may form a straight chain, a branched chain or a ring, and may have a substituent, a C _{1 to} C ₂₀ alkyl group or substituent. The electrolytic capacitor according to claim 1, wherein the electrolytic capacitor is a C _{6 to} C ₂₀ aryl group which may contain In the formula (1), one of R ^{1 and} R ² may be a protected or unprotected hydroxyl group, or a protected or unprotected amino group, and the other may form a straight chain, a branched chain or a ring. any one of the preceding claims, characterized in that substituted have an alkyl group or substituent of the C ₁ -C ₂₀ be an aryl group which may C ₆ -C ₂₀ The electrolytic capacitor described in 1.   The electrolytic capacitor according to claim 1, wherein the ionic liquid has an ability to form an oxide film on the surface of the valve metal by an anodic oxidation method.   The cation component of the ionic liquid is ammonium ion, imidazolium ion, pyridinium ion, pyrrolidinium ion, pyrrolium ion, pyrazinium ion, pyrimidinium ion, triazonium ion, triazinium ion, triazine ion, quinolinium ion , Isoquinolinium ion, indolinium ion, quinoxalinium ion, piperazinium ion, oxazolinium ion, thiazolinium ion, morpholinium ion, piperazine ion, and derivatives thereof The electrolytic capacitor according to claim 1, wherein:   The electrolyte solution is further selected from the group consisting of nitro compounds, phosphate compounds, boric acid compounds, polyhydric alcohols, silicon compounds, ammonium salts, amine salts, quaternary ammonium salts, tertiary amines and organic acids, imidazolium salts. The electrolytic capacitor according to claim 1, comprising one or more selected.   The solvent of the electrolytic solution is selected from the group consisting of alcohols, ethers, amides, oxazolidinones, lactones, nitriles, carbonates, and sulfones. The electrolytic capacitor described in 1.