JP2008016835A - Electrolytic capacitor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-voltage electrolytic capacitor that excels in impedance properties, and its manufacturing method. <P>SOLUTION: This invention is related to the electrolytic capacitor which is equipped with at least an electrolytic layer, an anode and a cathode that are arranged so that they may counter on both sides of the electrolytic layer. The anode consists of anode metal and a dielectric film. The electrolytic layer contains at least ionic liquid and conductive high polymer. The electrolytic layer is formed in contact with the dielectric film. In a region that includes the surface on the anode side of the electrolytic layer, a high ion-conducting region is formed, which contains ionic liquid with a higher content rate than that of the ionic liquid of the electrolytic layer as a whole. In this invention, it is desirable that the high ion-content region is formed to cover the whole surface of the dielectric film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrolytic capacitor and an electrolyte excellent in withstand voltage characteristics and impedance characteristics, and a manufacturing method thereof.

  In recent years, electrolytic capacitors using a conductive polymer as an electrolyte are expanding the market due to their excellent impedance characteristics.

  Electrolytic capacitors generally have a valve metal such as aluminum, tantalum, or niobium as an anode metal, an oxide film formed on the surface thereof as a dielectric film, and a cathode formed by sandwiching an electrolyte layer formed on the dielectric film. It has a configuration. The electrolyte in this electrolytic capacitor has two important functions. One is an action of protecting and repairing an extremely thin oxide film, and the other is an action as a de facto cathode which serves to extract a capacitance from a dielectric on the anode.

  The electrolytic capacitor typically uses a solid conductive polymer such as polypyrrole or a polythiophene derivative as an electrolyte. Since these conductive polymers have a much higher electrical conductivity (ie, electronic conductivity) than electrolytic capacitors using ordinary liquids as electrolytes, capacitors with these conductive polymers as electrolytes have internal impedance. In particular, it exhibits excellent characteristics as a capacitor for high-frequency circuits.

  However, since the conductive polymer has essentially no ionic conductivity, in terms of the restorability of the oxide film of the electrolytic capacitor (that is, the anodic oxidation action), compared to a capacitor using a conventional electrolytic solution. It was inferior. As a result, the electrolytic capacitor has a drawback that a capacitor having a high withstand voltage cannot be produced. Specifically, in an electrolytic capacitor using aluminum as an anode, for example, when 40V conversion is performed, the actual use voltage is about 16V, and for an electrolytic capacitor using tantalum, for example, 24V conversion is performed. In actual use, the voltage is about 12V. Here, 40V conversion means that the DC voltage applied when the dielectric oxide film is formed on the valve metal surface is 40V, and ideally, a capacitor having a withstand voltage of 40V should be obtained. It is. In principle, it is possible to increase the withstand voltage in actual use by increasing the formation voltage, but in that case, the capacitor capacity decreases as the formation voltage increases, and even if the formation voltage is further increased, There is a problem that the withstand voltage in use does not increase proportionally.

  Typical electrolytic capacitors include an aluminum electrolytic capacitor using aluminum as an anode metal and a tantalum electrolytic capacitor using tantalum as an anode metal. Usually, a tantalum electrolytic capacitor often uses a porous electrode obtained by sintering tantalum powder. On the other hand, there are two types of aluminum electrolytic capacitors: chip capacitors and wound capacitors.

  In the manufacture of chip-type electrolytic capacitors, a conductive polymer electrolyte is formed on an anode foil by electrolytic polymerization or chemical polymerization, and then a carbon paste / silver paste is applied, and then laminated and dried to form a capacitor element. Make it. A chip-type electrolytic capacitor has a very excellent frequency characteristic because it is manufactured with the above-described configuration, but on the other hand, the drawback is that the element manufacturing technique is extremely difficult and the defect rate is high.

  On the other hand, a wound electrolytic capacitor is provided with an anode foil formed of a valve metal such as aluminum having a dielectric oxide film formed on the surface, a cathode foil, and further between the cathode foil and the anode foil. And a separator. Capacitors are produced by winding them and then impregnating and polymerizing a monomer of a conductive polymer to form an electrolyte.

  The separator is composed of a continuous porous substrate, and includes a continuous porous substrate made of a synthetic polymer or cellulose fiber, a continuous porous substrate made of glass fiber, or a nonwoven fabric. Examples of the synthetic polymer include polyolefin, polyester, nylon, polyamide, polyimide, and fluorinated polyolefin. In addition, as the above cellulose fiber, regenerated cellulose fiber, viscose rayon, cupra rayon, etc., as non-wood pulp fiber, Manila hemp, red hemp, sisal hemp, esparto grass, etc., and as wood pulp fiber, conifer pulp fiber , Hardwood pulp fiber and the like. Among the above, polyolefin and cellulose fiber are particularly preferably used.

  The separator is indispensable for preventing a short-circuit of the wound capacitor, but has a problem of deteriorating the impedance characteristic of the capacitor. That is, the wound electrolytic capacitor is advantageous for increasing the capacity, but is inferior to the high frequency characteristics.

  As described above, there are two typical types of electrolytic capacitors. However, with any structure, the problem of withstand voltage has been a major issue.

  In order to solve such problems, the present inventors have already developed an electrolyte comprising an ionic liquid (referred to as an ionic liquid but referred to as an ionic liquid in the present invention) and a conductive polymer ( Patent Document 1). This was made by discovering that an ionic liquid has excellent anodizing action of valve metal, for example, that it can repair defects in aluminum oxide film, and this invention realizes a high withstand voltage electrolytic capacitor did it. However, the ionic liquid has excellent ionic conductivity but not electronic conductivity. Therefore, when a large amount of ionic liquid is added to realize a capacitor with a high withstand voltage, the capacitance of the capacitor There is a problem that the impedance characteristic is deteriorated. In addition, when the amount of the ionic liquid is small, good impedance characteristics can be obtained, but the essential withstand voltage characteristics are not improved as expected. That is, in an electrolyte composed of an ionic liquid and a conductive polymer, how to achieve both good withstand voltage characteristics and good electrical characteristics has been a major issue.

A method is also disclosed in which an electrode foil is impregnated in advance with an ionic liquid, and then an electrolyte is formed by a chemical polymerization method or an electrolytic polymerization method (Patent Document 2). However, even with this method, there is a problem that it is difficult to achieve relatively good withstand voltage characteristics.
International Publication No. 2005/012599 pamphlet JP 2006-24708 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electrolytic capacitor having a high withstand voltage and excellent impedance characteristics, and a method for manufacturing the same.

  As a result of intensive studies, the present inventors have found that the above problem can be solved by making the presence state of the ionic liquid in the electrolyte layer containing the conductive polymer non-uniform in the thickness direction of the electrolyte layer. It came to make.

  That is, the present invention is an electrolytic capacitor comprising at least an electrolyte layer and an anode and a cathode disposed with the electrolyte layer interposed therebetween, the anode comprising an anode metal and a dielectric film, and the electrolyte layer comprising an ionic liquid The present invention relates to an electrolytic capacitor containing at least a conductive polymer and a non-uniform content of an ionic liquid in the electrolyte layer.

  Further, the present invention is an electrolytic capacitor comprising at least an electrolyte layer and an anode and a cathode disposed with the electrolyte layer interposed therebetween, the anode comprising an anode metal and a dielectric film, and the electrolyte layer comprising an ionic liquid And the conductive polymer, the electrolyte layer is formed in contact with the dielectric layer, and the content ratio of the ionic liquid in the entire electrolyte layer in a region near the dielectric interface in the electrolyte layer The present invention relates to an electrolytic capacitor in which a region containing the ionic liquid is formed at a higher content.

  In the electrolytic capacitor of the present invention, it is preferable that the high ion conductivity region is formed so as to cover the entire surface of the dielectric film.

  In the electrolytic capacitor of the present invention, the dielectric film and the electrolyte are arranged on a virtual axis that connects an arbitrary point of the interface between the dielectric film and the electrolyte layer to the interface between the cathode and the electrolyte layer with the shortest distance. It is preferable that the content of the ionic station or the like is reduced as the distance from the interface with the layer increases.

  Further, the present invention is an electrolyte including at least an ionic liquid and a conductive polymer, and the concentration of the ionic liquid is not uniform in the electrolyte, and the electrolyte layer is in the vicinity of the dielectric interface in the electrolyte layer. It is related with the electrolyte for conductive polymer capacitors in which the area | region containing the said ionic liquid is formed with the content rate higher than the content rate of the said ionic liquid in the whole.

In the electrolytic capacitor or electrolyte of the present invention, the cation component of the ionic liquid is ammonium and derivatives thereof, imidazolinium 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 derivative cations, 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 its derivatives, Morpholinium and its derivatives, Piperazine and its derivatives Conductor preferably contains at least one member selected from the group consisting of.
In the electrolytic capacitor or electrolyte of the present invention, the anionic component of the ionic liquid is a carboxylate anion derivative, a sulfonylimide anion derivative, a fluorobromine anion derivative, a fluoroboron anion derivative, a nitrate anion derivative, a boron fluoride anion derivative, cyano. It preferably contains an atomic group of an imide anion derivative, a sulfonate anion derivative, or a sulfuric monoester anion derivative.

  In the electrolytic capacitor or the electrolyte of the present invention, the conductive polymer is preferably composed of at least one of polypyrrole or a derivative thereof, polythiophene or a derivative thereof, polyaniline or a derivative thereof, polyquinone or a derivative thereof.

  In the electrolytic capacitor or the electrolyte of the present invention, the conductive polymer is preferably made of poly- (2,3-dihydroxythieno- [3,4-b] -1,4-dioxin) or polypyrrole. .

  The present invention is also a method for producing an electrolyte for a conductive polymer capacitor by a chemical polymerization method for obtaining an electrolytic capacitor, comprising at least a step of previously immersing an electrode foil in a liquid containing an ionic liquid, The present invention relates to a method for producing an electrolyte for obtaining the above-mentioned conductive polymer capacitor, characterized by comprising a step of performing chemical polymerization using a polymerization solution in which a liquid coexists. The chemical polymerization step is preferably performed only once or repeated a plurality of times.

  The present invention is also a method for producing an electrolyte for a conductive polymer capacitor by a chemical polymerization method, wherein the electrolyte for a conductive polymer capacitor is formed by at least a plurality of chemical polymerization steps, and an ionic liquid is formed by each polymerization step. The present invention relates to a method for producing an electrolyte for obtaining the conductive polymer capacitor, wherein the ratio of the polymerizable monomer is changed. That is, the electrolyte layer forming step includes immersing the anode in a chemical polymerization composition containing at least the ionic liquid and a polymerizable monomer, and then polymerizing the polymerizable substance by a chemical polymerization method to thereby form an ionic liquid. And a chemical polymerization step of forming an electrolyte containing the conductive polymer, and the chemical polymerization step is repeated a plurality of times while changing the weight ratio of the ionic liquid and the polymerizable monomer. The present invention relates to an electrolyte manufacturing method.

  The present invention is also a method for producing an electrolyte for a conductive polymer capacitor comprising a chemical polymerization method and an electrolytic polymerization method, wherein the chemical polymerization is performed using at least a solution in which an ionic liquid and a polymerizable monomer coexist in advance. And a second step of performing electropolymerization in a polymerization solution containing at least a polymerizable monomer, and a method for producing an electrolyte for obtaining a conductive polymer capacitor. That is, in the electrolyte layer forming step of the present invention, the anode is immersed in a composition for chemical polymerization containing at least an ionic liquid and a polymerizable monomer, and then the polymerizable substance is polymerized by a chemical polymerization method to obtain ions. A chemical polymerization step of forming an electrolyte layer containing an ionic liquid and a conductive polymer, and immersing the anode in a polymerization composition containing at least an ionic liquid and a polymerizable monomer, And an electrolytic polymerization step of forming an electrolyte containing an ionic liquid and a conductive polymer by polymerization by an electrolytic polymerization method. The polymerization process may be performed once or may be repeated a plurality of times.

The present invention relates to a method for producing an electrolyte for a conductive polymer capacitor using a solution containing an ionic liquid in which at least a part of the conductive polymer is dissolved, and the electrolyte layer is formed by impregnating at least the solution into an electrode. It is the manufacturing method of the electrolyte for obtaining the conductive polymer capacitor of this invention characterized by having a process to form. That is, the electrolyte layer forming step includes immersing and drying the anode in a conductive polymer solution containing at least an ionic liquid and a conductive polymer, thereby forming an electrolyte layer containing the ionic liquid and the conductive polymer. Form. The conductive polymer solution immersion step is preferably repeated a plurality of times while changing the concentrations of the ionic liquid and the conductive polymer. The weight ratio (M / A) of the weight (M) of the ionic liquid and the mass (A) of the conductive polymer in the conductive polymer solution is in the range of 1/100 to 10/1. It is preferred that
The present invention further relates to a method for producing an electrolyte for a conductive polymer capacitor using a solution containing an ionic liquid in which at least a part of the conductive polymer is dissolved, wherein the electrode is impregnated with at least the solution. It is the manufacturing method of the electrolyte for obtaining the conductive polymer capacitor of this invention characterized by including the process of forming the electrolyte by chemical polymerization, and the 1st process of forming this.

  The present invention is also a method for producing an electrolyte for a conductive polymer capacitor using a solution containing an ionic liquid in which at least a part of the conductive polymer is dissolved, wherein the electrolyte layer is obtained by impregnating at least the solution with an electrode. It is the manufacturing method of the electrolyte for obtaining the electroconductive polymer capacitor of this invention characterized by including the process of forming the electrolyte by electrolytic polymerization and the 1st process of forming this.

  According to the present invention, a region having a relatively high ionic liquid concentration is formed in the vicinity of the surface on the anode side of the electrolyte layer, thereby obtaining an electrolytic capacitor having both a high withstand voltage characteristic and an impedance characteristic. Is possible.

  The electrolytic capacitor according to the present invention includes at least an electrolyte layer, and an anode and a cathode disposed so as to face each other with the electrolyte layer interposed therebetween, and the anode includes an anode metal and a dielectric film. As described above, typical conductive polymer electrolytic capacitors include aluminum electrolytic capacitors using aluminum as an anode metal and tantalum electrolytic capacitors using tantalum as an anode metal. Chip electrolytic capacitors are used as aluminum electrolytic capacitors. There are two types: winding type and winding type capacitor. In the chip type electrolytic capacitor, after forming a conductive polymer electrolyte on the anode foil, a carbon paste / silver paste is applied, and these are laminated and dried to produce a capacitor element. On the other hand, a wound electrolytic capacitor is provided with an anode foil formed of a valve metal such as aluminum having a dielectric oxide film formed on the surface, a cathode foil, and further between the cathode foil and the anode foil. The separator is wound, and then impregnated and polymerized with a conductive polymer monomer to form an electrolyte. The electrolytic capacitor and the method of forming the electrolyte of the present invention are applied to both a chip type and a wound type, and do not depend on the type of capacitor.

  The electrolyte layer contains at least an ionic liquid and a conductive polymer so that the concentration of the ionic liquid in the electrolyte is nonuniform. The electrolyte layer is formed in contact with the dielectric film, and in the present invention, the ionic liquid having a higher content than the content of the ionic liquid in the entire electrolyte layer is formed in the region including the surface on the anode side in the electrolyte layer. An electrolyte is prepared so that a region containing s is formed. The electrolyte may contain, as other components of the ionic liquid and the conductive polymer, an oxidant component added in the electrolyte layer forming step.

  A region containing an ionic liquid at a relatively high concentration (hereinafter simply referred to as a high concentration region) exhibits a satisfactory role of repairing and protecting the dielectric film in the electrolytic capacitor of the present invention. However, since the ionic liquid has essentially no electronic conductivity, when the content of the ionic liquid in the entire electrolyte layer is increased, the electronic conductivity of the entire electrolyte layer is low, so that the impedance characteristic of the electrolytic capacitor is desired. It becomes difficult to obtain a degree. In the present invention, the ionic liquid is unevenly distributed in the vicinity of the anode side surface of the electrolyte layer, thereby achieving both the repair / protective action of the dielectric film in the electrolytic capacitor and the electron conductivity as the electrolyte layer, It becomes possible to make the impedance characteristic and the withstand voltage characteristic of the electrolytic capacitor in which the layer is formed highly compatible.

  A typical embodiment of the high concentration region will be described below. For example, an electrode foil is formed as an anode metal, such as an aluminum electrolytic capacitor, an etching hole is provided in the electrode foil, and a dielectric film made of an oxide film is formed on the surface of the electrode foil by, for example, anodic oxidation. In the case of the structure to be formed, (1) the case where the ionic liquid concentration inside the etching hole is different from the concentration of the ionic liquid outside the etching hole, and (2) the ionic liquid near the dielectric film surface in the etching hole. A wide aspect including a case where the concentration and the ionic liquid concentration in other portions are different is included.

  The shape of the high concentration region may be any one of the cases described above, or may satisfy both. The above is the description of the etched aluminum foil electrode, but the same applies to the case of using a sintered tantalum powder electrode. In this case, the space formed between the tantalum powders corresponds to the etching hole.

  Since the main role of the ionic liquid contained in the electrolyte layer used in the electrolytic capacitor of the present invention is to repair and protect the dielectric film, the ionic liquid is in principle near the surface of the dielectric film in the electrolytic capacitor. If it exists only in

  A typical mode for increasing the concentration of the ionic liquid near the surface of the dielectric film will be described below. That is, in the case of (1) above, it means that the average concentration of the ionic liquid inside the etching hole is higher than the average concentration of the ionic liquid outside the etching hole. For example, a mode in which the concentration of the ionic liquid in the vicinity of the surface of the dielectric film is made higher than the concentration of the surrounding ionic liquid in the etching hole can be exemplified.

  In the case of (2) above, when the depth of the etching hole varies, the ratio of the diameter to the depth of the etching hole, that is, the aspect ratio becomes small at the portion where the etching hole is relatively deep. Therefore, even when a high concentration region is formed, the ionic liquid is unlikely to flow out of the etching hole. Therefore, the concentration of the ionic liquid inside the etching hole is the concentration of the ionic liquid at the shallower etching hole. Higher than.

  In the present invention, the high concentration region is preferably formed so as to cover the entire surface of the dielectric film. Here, covering the entire surface of the dielectric film means that the electrolyte layer is used in all cases including, for example, an anode in which etching holes are formed and an anode made of a powder electrode having a space between powders. This means that the portion other than the high concentration region and the dielectric film cover the entire surface of the dielectric film so as to be in contact with each other through the high concentration region. In this case, since the high concentration ionic liquid is in contact with the entire surface of the dielectric film, the function of repairing and protecting the dielectric film is satisfactorily exhibited, and the reduction in withstand voltage is effectively suppressed. This is advantageous.

  In the electrolyte layer of the present invention, it is formed simply as an electrolyte composed of a conductive polymer and an ionic liquid, or as an electrolyte having some interaction between the conductive polymer and the ionic liquid (hereinafter also simply referred to as a composite). It is preferred that As a typical complex having some kind of interaction, a case where a conductive polymer is dissolved in an ionic liquid can be exemplified. In this case, it is relatively easy to form the high concentration region in the vicinity of the anode side surface of the electrolyte layer with relative ease, and it is advantageous in that an excellent improvement in withstand voltage can be imparted to the electrolytic capacitor.

  In the present invention, the high concentration region formed in the electrolyte layer is formed by allowing the ionic liquid to be present at a higher content than the content of the entire electrolyte layer. For example, in a method of forming a conductive polymer layer that does not contain an ionic liquid after immersing the electrode foil in the ionic liquid, the ionic liquid is washed away when the conductive polymer layer is formed. Therefore, it is difficult to reliably form a high ion conductive region on the anode side surface of the electrolyte layer.

  When at least a part of the electrolyte layer is formed as the above composite, for example, even when an ionic liquid is present alone on the anode side surface of the above electrolyte layer, the above composite is also used. As a result, even if a part of the ionic liquid is washed away in the production process, the composite film covers the surface of the dielectric film where the ionic liquid is washed away. be able to. Further, when the high concentration region is composed of the composite, the ionic liquid is not easily lost in the manufacturing process, so that the surface of the electrolyte layer on the anode side can be covered with the uniform high ion conductivity region.

  In the electrolyte layer of the electrolytic capacitor of the present invention, the entire conductive polymer may be formed as a composite containing an ionic liquid and a conductive polymer, or only a part of the conductive polymer. The composite may be formed, and the remaining portion may be formed of a conductive polymer alone.

  When all of the conductive polymer of the electrolyte layer is formed as a composite, the ionic liquid is present throughout the electrolyte layer. In this case, since the high ion conductive region is more reliably formed in the vicinity of the interface between the dielectric film and the electrolyte layer, the direct contact between the dielectric film and the conductive polymer is effectively prevented, Good withstand voltage characteristics are imparted to the electrolytic capacitor on which the electrolyte layer is formed.

  On the other hand, when only a part of the conductive polymer is formed as the composite and the remaining part is formed of the conductive polymer alone, the electrolyte layer is formed while reliably forming the high ion conductive region. Since the content of the entire ionic liquid can be kept low and the electron conductivity can be maintained well, good impedance characteristics can be imparted to the electrolytic capacitor in which the electrolyte layer is formed. In this case, the dielectric film can be sufficiently protected and repaired to impart good withstand voltage characteristics to the electrolytic capacitor.

  In the electrolytic capacitor of the present invention, the imaginary axis connecting the shortest distance from the arbitrary point of the interface between the dielectric film and the electrolyte layer to the interface between the cathode and the electrolyte layer is from the interface between the dielectric film and the electrolyte layer. It is preferable that the content of the ionic liquid is reduced as the distance increases. Such a content rate gradient can be easily formed when the electrolyte layer is formed on the anode foil by many times of application as in the case of the chip type electrolytic capacitor. This is because in the initial application, the ratio with the polymerizable monomer should be set so that the content of the ionic liquid is increased, and the ratio should be decreased as the number of applications increases. In this case, the high concentration region can be reliably formed in the region including the surface on the anode side of the electrolyte layer, and the content of the ionic liquid in the entire electrolyte layer can be kept low. Good impedance characteristics and withstand voltage characteristics can be imparted.

  On the other hand, in a wound-type electrolytic capacitor, a high concentration region can be formed near the dielectric interface by the same method although the situation is different. The principle is as described below. The wound aluminum foil and the cathode aluminum foil have different etching magnifications, and the anode aluminum foil has a much higher etching magnification. An electrolytic solution composed of at least an ionic liquid and a polymerizable monomer is formed by impregnating a wound foil in the electrolytic solution, followed by heat treatment. At this time, more electrolytic solution is impregnated inside the etching hole of the anode aluminum foil. As the number of impregnations increases, the probability that the electrolytic solution is consumed between the anode and the cathode or for filling the separator increases. As a result, a concentration gradient occurs if the content of the ionic liquid in the impregnating liquid in the latter half of the process is lowered.

In the present invention, the existence of the high ion conductive region in the region including the surface on the anode side of the electrolyte layer is, for example, when the ionic liquid is ethyl methylimidazolium-BF ₄ , This can be confirmed by elemental analysis using X-ray photoelectron spectroscopy.

  In the present invention, the mass ratio (P / D) of the mass (P) of the ionic liquid in the entire electrolyte layer and the mass (D) of the conductive polymer is preferably 0.001-1. It is more preferable that it is 0.01-0.5, and the range which is in the range of 0.05-0.3 is most preferable. When the mass ratio (P / D) is 0.001 or more, the ionic liquid can be present at a high concentration in the vicinity of the interface between the dielectric film and the electrolyte layer by the high ion conductivity region, so that the withstand voltage is improved. When the effect is obtained satisfactorily and the mass ratio (P / D) is 1 or less, the electron conductivity of the electrolyte layer is good, and good impedance characteristics can be imparted to the electrolytic capacitor.

  The mass ratio can be estimated by, for example, a method in which, after forming the electrolyte layer, an ionic liquid is extracted with an alcohol solution such as methanol or butanol, and the mass change of the extract and the electrolyte layer is measured. However, in some cases, additive components such as a polymerization oxidizing agent blended in the electrolyte layer forming step may be dissolved in a solvent such as methanol or butanol. In such a case, the content of each component in the extract can be calculated by ion chromatography or the like, and the mass ratio can be calculated from the result.

<Ionic liquid>
The ionic liquid (abbreviated as “ILs” as necessary) contained in the electrolyte of the present invention is also referred to as a room temperature molten salt, and refers to a liquid that is liquid at room temperature despite being composed of only ions. It is composed of a combination of a cation such as lithium 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 body 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 can be used as long as it spreads throughout the electrolyte and becomes liquid by the Joule heat generated when the oxide film is repaired. Among these, imidazolinium or a derivative thereof, ammonium or a derivative thereof, pyridinium or a derivative thereof can be preferably used for this purpose.

The ionic liquid used in the present invention is not limited in any way since the anionic component can utilize its ability to form and repair any ionic liquid. Preferably, the anionic component of the ionic liquid is a carboxylic acid anion derivative, sulfonyl. It is an ionic liquid containing an atomic group of an imide anion derivative, a fluorobromine anion derivative, a fluoroboron anion derivative, a nitrate anion derivative, a boron fluoride anion derivative, a cyanoimide anion derivative, a sulfonate anion derivative, or a sulfate anion derivative. A conductive polymer capacitor is preferable. More preferably, the sulfonate anion derivative or sulfate anion derivative of the anion component is represented by R ₁ —SO ₃ ⁻ , R ₁ —OSO ₃ ⁻ , or the like (where R ₁ represents carbon It is a monovalent aliphatic hydrocarbon group having a number of 5 to 50, may be branched, and is substituted by a group capable of bonding between alkyl groups such as O, S, NHCO, CO, and OCO. It is preferable that the conductive polymer capacitor is characterized in that it may contain one or more fluorine atoms. However, preferred ionic liquids for the present invention are not limited to these as long as they can be inferred from general knowledge of those skilled in the art.

<Conductive polymer>
The conductive polymer contained in the electrolyte layer in the present invention is not particularly limited as long as it has high conductivity and excellent stability such as heat resistance, but pyrrole or its derivative, thiophene or its It is preferably selected from a derivative, aniline or a derivative thereof, quinone or a derivative thereof, quinoline or a derivative thereof, furan or a derivative thereof. At least one of them is particularly preferably used.

  For example, as derivatives of thiophene, 1,4-dioxythiophene, 3,4-dioxythiophene, 3,4-ethylenedioxythiophene, 3-alkylthiophene (alkyl groups include butyl, hexyl, octyl Group, dodecyl group, etc.), fluorophenylthiophene, allylthiophene and the like, but are not limited thereto.

Examples of aniline derivatives include, but are not limited to, those having an aniline skeleton having an alkyl group, a cyano group, a sulfone group, or a carboxyl group.
Examples of quinone derivatives include, but are not limited to, benzoquinone having a substituent, naphthoquinone having a substituent, and anthraquinone having a substituent.

  Examples of pyrrole derivatives include, but are not limited to, those having a pyrrole skeleton and having substituents such as a hydroxyl group, a carboxyl group, and an alkyl group.

  In particular, a conductive polymer composed of pyrrole or a derivative thereof, poly- (2,3-dihydrothieno- [3,4-b] -1,4-dioxin) is preferably used in terms of conductivity and heat resistance.

<Electrolytic capacitor>
The electrolytic capacitor of the present invention is formed using an electrolyte layer provided with a high ion conductivity region, and includes at least an electrolyte layer, and an anode and a cathode disposed so as to face each other with the electrolyte layer interposed therebetween. The electrolytic capacitor of the present invention can be formed in either a chip type or a wound type. A chip-type electrolytic capacitor typically has a capacitor element in which an electrolyte layer and a cathode are laminated in this order on the dielectric film of an anode made of an anode metal having a dielectric film formed on the surface thereof. A connection terminal electrically connected to the capacitor element is provided. On the other hand, a wound-type electrolytic capacitor typically has an electrolyte layer, a separator, a cathode, and a separator on the dielectric film of an anode made of an anode metal having a dielectric film formed on the surface thereof from the radially inner side. Are arranged so as to be arranged in this order, and the capacitor element is laminated and wound, and a connection terminal electrically connected to the capacitor element. In the separator, usually, a separator material made of, for example, polyolefin or cellulose fiber and a conductive polymer are combined.

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

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

  Hereinafter, an example of a typical manufacturing method of the electrolytic capacitor of the present invention will be described. The components of the capacitor not specifically mentioned in the electrolytic capacitor of the present invention are not particularly limited, and conventionally known components can be appropriately applied. In the following description, a case where a chip-type electrolytic capacitor is formed using an anode provided with an etching hole will be described as an example. However, the present invention is not limited to this.

<Embodiment 1>
In the present embodiment, a case where an electrolyte layer is formed by an ionic liquid immersion process and a chemical polymerization process will be described. An electrolytic capacitor manufacturing method according to the present embodiment includes an anode forming step of forming an anode composed of an anode metal and a dielectric film, an electrolyte layer forming step of forming an electrolyte layer in contact with the dielectric film, and an electrolyte layer A cathode forming step of forming a cathode on the surface. The electrolyte layer forming step includes an ionic liquid dipping step in which the anode is immersed in an ionic liquid, a chemical polymerization composition after the anode is immersed in a chemical polymerization composition including at least the ionic liquid and the polymerizable material. And a chemical polymerization step of forming a complex including an ionic liquid and a conductive polymer by polymerization by a polymerization method. The chemical polymerization process can be performed only once or can be repeated multiple times.

  Further, the chemical polymerization step can be repeated a plurality of times while changing the mass ratio of the ionic liquid and the polymerizable substance in the chemical polymerization composition.

  In the method of the present embodiment, the anode is first immersed in the ionic liquid, and the ionic liquid is present at a high concentration near the surface of the dielectric film. Subsequently, in the chemical polymerization step, a complex including the ionic liquid and the conductive polymer is formed. That is, in the composite, the content of the ionic liquid is lower than the vicinity of the interface with the dielectric film.

  For example, a dielectric film is formed on the surface of an etched anode metal to produce an anode, the anode is immersed in an ionic liquid, and then the surface of the anode is chemically polymerized containing a raw material monomer for a conductive polymer. In the method of forming a conductive polymer layer using a composition for an ionic liquid, the ionic liquid at the back of the etching hole can exist without completely dissolving, but the ionic liquid is chemically present near the surface of the anode. There is a high possibility that the dielectric film dissolves in the polymerization composition and the dielectric film and the conductive polymer layer are in direct contact with each other, and a predetermined withstand voltage improvement effect may not be obtained.

  On the other hand, when a chemical polymerization step is performed in a state where an ionic liquid is contained in a composition for chemical polymerization containing a polymerizable substance to form a composite containing an ionic liquid and a conductive polymer, In a region including the surface on the anode side of the electrolyte layer, a high ion conductive region in which the ionic liquid exists at a high concentration can be surely formed.

  In this embodiment, since the chemical polymerization process is performed after the ionic liquid immersion process, a high ion conductive region can be formed on the anode side surface of the electrolyte layer even if the chemical polymerization process is performed only once. However, the chemical polymerization step may be repeated a plurality of times while keeping the mass ratio of the ionic liquid and the polymerizable substance in the chemical polymerization composition constant or changing the mass ratio. In this case, it is preferable to repeat the chemical polymerization step a plurality of times while lowering the content of the ionic liquid in the chemical polymerization composition for each step.

(Anode formation process)
The anode of the electrolytic capacitor is produced by etching the surface of an anode metal such as an aluminum foil to form an etching hole, and then forming a dielectric film made of an oxide film by anodization. Anodization can be performed by a conventionally known method such as a method in which an anode metal is immersed in an oxidizing agent such as an aqueous solution of sodium adipate and a predetermined formation voltage is applied.

  Next, an electrolyte layer is formed on the surface of the dielectric film of the anode formed by the method as described above.

(Electrolyte layer forming process)
1. Ionic liquid dipping step The anode obtained in the above-described anode forming step is dipped in the ionic liquid suitably used in the present invention as described above, thereby attaching the ionic liquid to the surface of the anode (ionic liquid) Dipping process).

  In the ionic liquid dipping step, it is desirable to allow the ionic liquid to penetrate deep into the etching holes of the anode. Therefore, after immersing the anode in the ionic liquid, it is preferable to perform treatments such as vacuum impregnation, liquid heating, and ultrasonic waves as necessary. At this time, whether or not the ionic liquid has entered the inside of the etching hole can be estimated by measuring the liquid volume of the anode.

  That is, the in-liquid capacity of the specimen foil obtained by impregnation with the ionic liquid is measured in the ionic liquid, and this value is compared with the foil capacity obtained in advance in the anode forming step. At this time, when the capacity of the ionic liquid-impregnated foil is 95% or more of the foil capacity obtained in the anode forming step, it can be determined that the ionic liquid has penetrated into the etching hole of the anode. The submerged capacity of the foil can be measured using a charge / discharge measuring device (for example, Solartron, model number 1480 manufactured by Toyo Technica Co., Ltd.).

  After the anode is lifted from the ionic liquid, excess ionic liquid may be dropped and removed as necessary for the purpose of causing an optimum amount of ionic liquid to be present in the etching hole of the anode. In this case, dropping may be promoted by lowering the viscosity of the ionic liquid by heating. Further, excess ionic liquid may be removed by absorbing it with filter paper or the like.

  A binder such as a polymer or a binder may be added to the ionic liquid used in the ionic liquid dipping step, if necessary. As the binder, those which are excellent in film forming properties and are soluble in an ionic liquid or a mixed solvent of an ionic liquid and an organic solvent are preferable. Specific examples include polyvinyl pyrrolidone, polyvinyl alcohol, water-soluble polyester, water-soluble acrylic resin, carboxymethyl cellulose, polyvinyl sulfonate, polystyrene sulfonate, polyvinyl butyral, vinyl acetate, ethylene / vinyl acetate copolymer. , Cellulose acetate, polyethylene oxide, and the like.

2. Chemical Polymerization Step Next, the anode to which the ionic liquid is attached is immersed in a composition for chemical polymerization containing at least the ionic liquid and the polymerizable substance, and then pulled up, and then the polymerizable substance is subjected to a chemical polymerization method. To form a complex containing an ionic liquid and a conductive polymer (chemical polymerization step).

  As the ionic liquid to be blended in the chemical polymerization composition, various ionic liquids suitably used in the present invention as described above can be used. As the ionic liquid, the same type of ionic liquid as that used in the above-mentioned ionic liquid immersion step may be used, or a different type of ionic liquid may be used. When a solvent is blended in the chemical polymerization composition, it is preferable to use an ionic liquid that is compatible with the solvent. In this case, an electrolyte layer having a more uniform structure can be formed.

  Examples of the polymerizable substance include a raw material monomer and a raw material oligomer that give a target conductive polymer in the electrolyte layer. For example, as a monomer that gives polythiophene as a conductive polymer contained in the electrolyte layer, 1,4-dioxythiophene monomer, thiophene monomer, 3-hexylthiophene monomer, 3-octylthiophene monomer, 3-butylthiophene monomer, Examples include 3-cyclohexylthiophene monomer. Examples of the raw material monomer that gives a conductive polymer that is preferably formed by a chemical polymerization method include a pyrrole monomer, an aniline monomer, and a 1,4-phenylene vinylene monomer.

  As a preferable combination of the ionic liquid and the raw material monomer in the chemical polymerization method, for example, a combination of an ionic liquid composed of an imidazolium cation and a sulfonate anion and a 1,4-dioxythiophene monomer can be exemplified. This combination is preferable in that an electrolytic capacitor having excellent withstand voltage characteristics and impedance characteristics can be realized because the repair ability of the ionic liquid to the dielectric film is high, while the polythiophene obtained by polymerization has high electrical conductivity. .

  The chemical polymerization composition preferably contains a solvent, and in this case, the chemical polymerization can proceed more uniformly. Although it does not restrict | limit especially as a solvent, For example, water, butanol, ethanol, methanol, acetone etc. can be mentioned.

  A preferable mass ratio (N / B) of the mass (N) of the ionic liquid and the mass (B) of the polymerizable substance in the composition for chemical polymerization is in the range of 1/100 to 10/1, and more preferable. The mass ratio is in the range of 1/20 to 5/1, and the most preferred mass ratio is in the range of 1/10 to 2/1. When the ionic liquid is less than 1/100 in the mass ratio (N / B), the withstand voltage improvement effect tends to be small. On the other hand, when there is more ionic liquid than 10/1 by said mass ratio (N / B), the electric conductivity of the electrolyte layer in an electrolytic capacitor falls by presence of excess ionic liquid, and the electrolytic capacitor of the obtained There is a tendency for impedance characteristics to deteriorate.

  In addition, the preferable range shown here shows the composition in the composition for chemical polymerization, and does not show the preferable range of the ionic liquid in an actual electrolyte layer. The optimal range of the ionic liquid contained in the chemical polymerization composition is as described above, but the amount of the ionic liquid present in the actually formed electrolyte layer is the ratio in the chemical polymerization composition. Expected to be less than This is because the chemically polymerized conductive polymer does not dissolve in the solvent used in the chemical polymerization process, whereas the ionic liquid normally dissolves in the solvent, so that the ionic liquid escapes during the chemical polymerization process or washing process. This is because a phenomenon occurs.

  Since the solvent contained in the chemical polymerization composition sequentially evaporates in the heating process of the chemical polymerization step, a complex containing an ionic liquid and a conductive polymer is formed at the end of the chemical polymerization step.

  In addition to the ionic liquid and the polymerizable substance, the chemical polymerization composition may contain an oxidizing agent, a surfactant, and the like. An oxidizing agent is used as a polymerization catalyst. Examples thereof include ferric paratoluenesulfonate, ferric naphthalenesulfonate, ferric n-butylnaphthalenesulfonate, ferric triisopropylnaphthalenesulfonate. It is done. Among them, it is preferable to use ferric paratoluenesulfonate as a dopant as an oxidizing agent.

  The mixing ratio of the polymerizable substance and the oxidizing agent in the chemical polymerization composition is not particularly limited, but the mixing ratio of raw material monomer: oxidizing agent is 1: 0.1 to 1: 5 in molar ratio. It is preferably within the range, more preferably within the range of 1: 0.2 to 1: 3. By preparing the composition for chemical polymerization at such a mixing ratio, an electrolyte layer having particularly high electron conductivity can be obtained.

  When the chemical polymerization composition containing the ionic liquid, the polymerizable substance, and the oxidizing agent is used, for example, when the conductive polymer is PEDOT, the heat treatment is performed at a temperature of 20 to 140 ° C., particularly 20 to 120 ° C. For 0.5 to 10 hours. When the temperature is 20 ° C. or higher, the polymerization reaction proceeds satisfactorily, and when the temperature is 140 ° C. or lower, a dense chemical polymerization layer can be formed without the reaction proceeding too quickly.

  The chemical polymerization step may be performed only once, or may be repeated a plurality of times while keeping the mass ratio of the ionic liquid and the polymerizable substance in the composition for chemical polymerization constant or changing the mass ratio. good. In particular, by reducing the concentration of the ionic liquid in the chemical polymerization composition step by step for each process, a high ion conductivity region where the ionic liquid is present at a high concentration on the anode side surface of the electrolyte layer. Can be reliably formed, and the content of the ionic liquid in the entire electrolyte layer can be kept low. Thereby, an electrolytic capacitor having excellent impedance characteristics and withstand voltage characteristics can be obtained.

  As a mass ratio (N / B) of the mass (N) of the ionic liquid of the composition for chemical polymerization and the mass (B) of the polymerizable substance when the chemical polymerization step is repeated a plurality of times, for example, the chemical polymerization step is 2 For example, the condition may be about 2/1 for the first time and about 1/2 for the second time. In this case, after the second chemical polymerization step, the same treatment as the chemical polymerization step is performed using a polymerization solution containing a polymerizable substance and not containing an ionic liquid, and a conductive polymer containing no ionic liquid. A post-process for forming the layer may be provided. In this case, the electronic conductivity of the electrolyte layer is improved, and the impedance characteristics of the electrolytic capacitor are improved.

(Cathode formation process)
After forming the electrolyte layer by the above method, a cathode is formed by applying a carbon paste, a silver paste, or the like by a conventionally known method (cathode forming step). In order to increase the capacity of the electrolytic capacitor, a capacitor element may be formed by laminating a plurality of elements including an anode, an electrolyte layer, and a cathode before the carbon paste or the silver paste is dried as necessary.

  After the above-described cathode formation step, the electrolytic capacitor of the present invention can be obtained by connecting terminals to the anode and the cathode, respectively.

  In an electrolytic capacitor in which the anode metal is aluminum, for example, when 40V conversion is performed, when an electrolyte layer is formed by a normal chemical polymerization method that does not use an ionic liquid, the breakdown voltage of the capacitor is between 20V and 35V, for example. For example, the actual use voltage in consideration of safety is about 16V. On the other hand, in the electrolytic capacitor in which the electrolyte layer is formed by the method of the present embodiment, the withstand voltage of the capacitor can be stably obtained in a narrow range of, for example, 38V to 45V. It is possible to obtain a withstand voltage approximately twice that of an electrolytic capacitor, that is, an actual use withstand voltage of 32V. In addition, the impedance characteristics can be made almost the same as those of an electrolytic capacitor produced without an ionic liquid. Such a tendency is also observed in an electrolytic capacitor using tantalum as an anode metal.

<Embodiment 2>
In the present embodiment, after the anode is immersed in the composition for chemical polymerization containing at least the ionic liquid and the polymerizable substance without passing through the ionic liquid immersion step as described in the first embodiment, the polymerizable substance An example in which a complex containing an ionic liquid and a conductive polymer is formed by a chemical polymerization process in which is polymerized by a chemical polymerization method will be described. The chemical polymerization step in the present embodiment is repeated a plurality of times while changing the mass ratio between the ionic liquid and the polymerizable substance in the chemical polymerization composition. Note that materials and methods similar to those in the first embodiment are preferably employed for steps not particularly mentioned.

  The method implemented in the present embodiment can be considered as a method in which only the chemical polymerization step of the first embodiment is repeated a plurality of times in the electrolyte layer forming step. In the present embodiment, the mass ratio (N / B) between the mass (N) of the ionic liquid of the composition for chemical polymerization and the mass (B) of the polymerizable substance when the chemical polymerization step is repeated a plurality of times, for example, For example, the case of repeating twice may be exemplified by the condition that the first time is about 2/1 and the second time is about 1/2. In this case, after the second chemical polymerization step, the same treatment as the chemical polymerization step is performed using a polymerization solution containing a polymerizable substance and not containing an ionic liquid, and a conductive polymer containing no ionic liquid. A post-process for forming the layer may be provided. In this case, the electronic conductivity of the electrolyte layer is improved, and the impedance characteristics of the electrolytic capacitor are improved.

<Embodiment 3>
In the present embodiment, an example in which the electrolyte forming step includes a chemical polymerization step and an electrolytic polymerization step will be described. FIG. 4 is a conceptual diagram illustrating an electropolymerization apparatus used for electropolymerization. In the present invention, the electrolytic polymerization is typically performed as follows. That is, a conductive layer 4 made of, for example, a chemical polymerization layer is formed on the surface of the anode made of the anode metal 2 and the dielectric film 3, and the anode formed with the conductive layer is immersed in the electrolytic solution 6. The cathode 7 is immersed in the electrolytic solution 6 in close proximity to the polymerization initiation electrode 1. In the electrolytic solution, an ionic liquid to be contained in an electrolytic polymerization layer formed by electrolytic polymerization and a polymerizable substance that gives a conductive polymer to be contained in the electrolytic polymerization layer are dissolved. As the polymerizable substance, a raw material monomer, a raw material oligomer, or the like that gives the conductive polymer is used. A predetermined voltage is applied between the polymerization start electrode 1 and the cathode 7 to polymerize the polymerizable substance on the surface of the conductive layer 4, and the electrolytic polymerization layer 5 is formed on the surface of the conductive layer 4.

  That is, in the present invention, when the electrolyte layer forming step includes an electrolytic polymerization step, it is first necessary to form a conductive layer that acts as a base electrode on the surface of the dielectric film by some method. In the present invention, as the conductive layer, as shown in FIG. 4, a chemical polymerization layer made of a complex containing an ionic liquid formed in the chemical polymerization step may be used, and the ionic liquid is included. A polymer layer made of a composite containing an ionic liquid formed using a conductive polymer solution may be used. In this embodiment, the case where a chemical polymerization layer is used as the conductive layer will be described.

  The chemical polymerization for forming the conductive layer can be performed, for example, by the method described in the chemical polymerization step of Embodiment 1, and may be repeated once or multiple times. For example, as the composition for chemical polymerization, the mass ratio (N / B) of the mass (N) of the ionic liquid and the mass (B) of the polymerizable substance is in the range of 1/20 to 5/1, more preferably A composition for chemical polymerization in a range of 1/5 to 2/1 can be used.

  After forming the conductive layer, a polymerization start electrode is provided, and electrolytic polymerization is performed using this electrode. Examples of the conductive polymer obtained by electropolymerization and the raw material monomer that gives the conductive polymer include pyrrole as a raw material monomer for polypyrrole, thiophene as a raw material monomer for polythiophene, and furan as a raw material monomer for polyfuran.

  For example, when electrolytic polymerization is performed using a pyrrole monomer, a polypyrrole layer as an electrolytic polymerization layer is formed using an electrolytic solution composed of pyrrole (0.5 M), a 30 mass% alcohol solution of sodium triisopropylnaphthalenesulfonate and water. be able to.

  The ionic liquid is preferably added to the electrolytic solution. The mass ratio (O / C) of the mass (O) of the ionic liquid in the electrolytic solution and the mass (C) of the polymerizable monomer is, for example, in the range of 1/20 to 100/1, more preferably 1/5. It is preferable to be within the range of ˜20 / 1. When the ionic liquid is less than 1/20 at the above mass ratio (O / C), the withstand voltage improvement effect tends to be small, and the ionic liquid is more than 100/1 at the above mass ratio. Tends to deteriorate the impedance characteristics of the electrolytic capacitor.

  Since the ionic liquid has an extremely low vapor pressure, it remains in the electrolytic polymerization layer as an ionic liquid even after the solvent is removed by the polymerization heat treatment or the drying treatment. That is, an electrolytic polymerization layer made of a composite containing a conductive polymer made of polypyrrole and an ionic liquid is formed. Thereby, in this Embodiment, the electrolyte layer which consists of a chemical polymerization layer and an electrolytic polymerization layer can be formed.

  In the present embodiment, the entire electrolyte layer composed of the chemical polymerization layer and the electrolytic polymerization layer is an imaginary axis that connects an arbitrary point on the interface between the dielectric film and the electrolyte layer to the interface between the cathode and the electrolyte layer with the shortest distance. In this case, it is preferable that the content of the ionic liquid is reduced as the distance from the interface between the dielectric film and the electrolyte layer increases. In this case, it is advantageous in that the withstand voltage characteristic and the impedance characteristic are good.

  For example, in the conventional electrolytic polymerization method, a manganese dioxide layer by thermal decomposition or a conductive polymer layer by chemical polymerization is used as the conductive layer. When this conductive layer is formed, the dielectric film is damaged and the leakage current of the capacitor In some cases, the problem of an increase in voltage and a decrease in withstand voltage may occur. In the present embodiment, the dielectric film can be protected / restored by allowing an ionic liquid to be present in the chemical polymerization layer which is a conductive layer. Thereby, the improvement effect of withstand voltage is given to the electrolytic capacitor.

  In both cases of chemical polymerization and electrolytic polymerization, a method of first forming a conductive polymer layer not containing an ionic liquid on the anode surface and then impregnating the ionic liquid can provide an effect of improving the withstand voltage. hard. This is because it is difficult to allow the ionic liquid to exist throughout the interface between the dielectric film and the electrolyte layer in the method of impregnating / adding the ionic liquid later. This is because the conductive polymer layer that does not have is in direct contact with the dielectric film.

  In addition, for example, a method in which the anode is immersed in an ionic liquid in advance and then a conductive polymer layer not containing the ionic liquid is formed by a chemical polymerization method, an electrolytic polymerization method, or a combination thereof is also used. Significant improvements are difficult to achieve. The reason for this is that even if immersion treatment is performed using an ionic liquid, the ionic liquid on the anode surface will flow out during the subsequent polymerization step, so that it is highly proximate to the interface between the electrolyte layer and the dielectric film. This is because the ion conductive region cannot be formed reliably, and a portion where the conductive polymer and the dielectric film are in direct contact is formed.

  In the present embodiment, an example of forming an electrolyte layer composed of a chemical polymerization layer and an electrolytic polymerization layer has been described. However, in the present invention, before the chemical polymerization step of the present embodiment, an ionic liquid is subjected to an anode. It is also preferable to further provide an ionic liquid immersion step for immersing the electrolyte layer. In this case, an electrolyte layer composed of the ionic liquid, the chemical polymerization layer, and the electrolytic polymerization layer is formed.

<Embodiment 4>
In the present embodiment, an example will be described in which the electrolyte layer forming step includes a conductive polymer solution immersing step of immersing the anode in a conductive polymer solution containing an ionic liquid and a conductive polymer. Note that materials and methods similar to those in the first embodiment are preferably employed for steps not particularly mentioned.

  In the present embodiment, the electrolyte layer forming step immerses the anode in an ionic liquid immersion step of immersing the anode in the ionic liquid, and a conductive polymer solution containing at least the ionic liquid and the conductive polymer. And a conductive polymer solution dipping step for forming a composite containing the ionic liquid and the conductive polymer. The conductive polymer solution dipping step is performed only once, or is repeated a plurality of times while maintaining a constant mass ratio between the ionic liquid and the conductive polymer in the conductive polymer solution or changing the mass ratio. be able to.

  In the present embodiment, since the conductive polymer solution immersion step is performed after the ionic liquid immersion step, high ions are formed on the anode side surface of the electrolyte layer even if the conductive polymer solution immersion step is performed only once. A conductive region can be formed.

  In the present invention, when the electrolyte layer is formed by the conductive polymer solution dipping step, it is advantageous in that it is not necessary to remove the metal oxidation catalyst, which is a problem in the case of chemical polymerization.

  In the present embodiment, after the anode forming step, the anode is immersed in a conductive polymer solution containing at least the ionic liquid and the conductive polymer through the same ionic liquid immersion step as in the first embodiment. To form a complex containing the ionic liquid and the conductive polymer (conductive polymer solution dipping step). When the conductive polymer solution immersion step is repeated a plurality of times, it is preferable that the concentration of the ionic liquid in the conductive polymer solution is lowered for each step.

  The preferable mass ratio (M / A) of the mass (M) of the ionic liquid and the mass (A) of the conductive polymer in the conductive polymer solution is in the range of 1/100 to 10/1, and more A preferred mass ratio is in the range of 1/20 to 5/1, and a most preferred mass ratio is in the range of 1/10 to 2/1. When the ionic liquid is less than 1/100 in the mass ratio (M / A), the withstand voltage improvement effect tends to be small. On the other hand, when there is more ionic liquid than 10/1 by said mass ratio (M / A), the electrical conductivity of the electrolyte layer in an electrolytic capacitor falls by presence of excess ionic liquid, and the electrolytic capacitor obtained is There is a tendency for impedance characteristics to deteriorate.

  As the ionic liquid blended in the conductive polymer solution, various ionic liquids suitably used in the present invention as described above can be used. As the ionic liquid, the same type of ionic liquid as that used in the above-mentioned ionic liquid immersion step may be used, or a different type of ionic liquid may be used. When a solvent is blended in the conductive polymer solution, it is preferable to use an ionic liquid that is compatible with the solvent. In this case, an electrolyte layer having a more uniform structure can be formed.

The preferred conductive polymer used in the conductive polymer solution is not particularly limited as a co-component of the conductive polymer monomer, but it has high conductivity during polymer formation and is stable in the air. Therefore, it is preferably selected from pyrrole or a derivative thereof, thiophene or a derivative thereof, aniline or a derivative thereof, quinone or a derivative thereof, quinoline or a derivative thereof, furan or a derivative thereof.
More specifically, polypyrrole, polythiophene, polyaniline, poly1,4-dioxythiophene, poly-3-hexylthiophene, poly-3-octylthiophene, poly-3-butylthiophene, poly-3-cyclohexylthiophene, poly-3-nitrothiophene Etc. can be illustrated.

  The conductive polymer solution is preferably prepared by dissolving the conductive polymer in an ionic liquid. Examples of the conductive polymer solution include DMF, THF, acetone, fluorinated alcohol, methanol. In addition, a solvent such as acetonitrile may be included.

  In the present invention, the conductive polymer solution immersion step and the chemical polymerization step may be combined. In this case, typically, first, a conductive polymer solution dipping process using a conductive polymer solution containing an ionic liquid is performed, followed by a chemical polymerization process. The chemical polymerization step may be repeated once or multiple times while changing the content of the ionic liquid in the chemical polymerization composition. It is preferable that a chemical polymerization step using a chemical polymerization composition containing an ionic liquid is performed after the conductive polymer solution immersion step, but a chemical polymerization composition that does not contain an ionic liquid is used. A conductive polymer layer may be formed by chemical polymerization.

  In the present invention, the conductive polymer solution dipping step and the electrolytic polymerization step may be combined. In this case, typically, first, a conductive polymer solution dipping process using a conductive polymer solution containing an ionic liquid is performed, followed by an electrolytic polymerization process. Although it is preferable that an electrolytic polymerization process using an electrolytic solution containing an ionic liquid is performed after the conductive polymer solution dipping process, a high conductivity by electrolytic polymerization using an electrolytic solution containing no ionic liquid is used. A molecular layer may be formed.

  In the present invention, the conductive polymer solution immersion step may be combined with the electrolytic polymerization step and the chemical polymerization step. In this case, a conductive polymer layer not containing an ionic liquid may be further formed in a region between the high ion conductive region and the cathode.

<Embodiment 5>
In the fourth embodiment, the case where the conductive polymer solution immersion step is performed after the ionic liquid immersion step has been described. However, in the present embodiment, the conductive polymer solution immersion is performed without the ionic liquid immersion step. A case where the process is directly performed will be described. Note that materials and methods similar to those in the first embodiment are preferably employed for steps not particularly mentioned.

  In the present embodiment, after the anode formation step, the conductive polymer solution dipping step is performed using the same conductive polymer solution as in Embodiment 4, so that the ionic liquid and the conductive high solution are formed on the anode surface. Form a complex directly with the molecule.

  In the case where the anode is directly immersed in the conductive polymer solution, the elution of the ionic liquid can be prevented to some extent by the presence of the conductive polymer, compared to the case where the anode is impregnated with only the ionic liquid, and This is advantageous in that it is not necessary to remove the metal oxidation catalyst, which is a problem in the case of chemical polymerization.

  In this embodiment, since the ionic liquid immersion process is not performed, the conductive polymer solution immersion process is repeated a plurality of times or the conductive polymer solution immersion process is performed in order to reliably form the high ion conductive region. It is preferable to combine the electrolytic polymerization step and / or the chemical polymerization step. In this case, a conductive polymer layer not containing an ionic liquid may be further formed in a region between the high ion conductive region and the cathode.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Synthesis of ionic liquid>
First, a method for synthesizing and obtaining an ionic liquid will be described.

(1) (ILs-1) (1-C 2 H 5 -3-CH 3 -Im) + (BF 4) -
Purchased from Kanto Chemical Co., Ltd. (Im stands for imidazolium).

(2) (ILs-2) :( 1-C 2 H 5 -3-CH 3 -Im) + (p-TsO) -
2. A well-dried 200 ml round bottom flask was charged with 2.30 g (28.0 mmol) N-methylimidazole and 20 ml DMF and stirred well. 5.61 g (28.0 mmol) of ethyl p-toluenesulfonate was quickly added into the flask under ice cooling. After completion of the addition, the mixture was further stirred for 23 hours. The reaction solution was dropped into 200 ml of ice-cooled ether, the ether was removed by decantation, and 5.90 g of a yellow liquid was recovered. The yield was 74.4%. ^{From the 1} H-NMR spectrum, the recovered liquid could be identified as an imidazolium salt. The resulting imidazolium salt had a glass transition temperature (Tg) of -85.7 ° C.

(3) (ILs-3) (1-nC 4 H 9 -3-CH 3 -Im) + (BF 4) -
Purchased from Kanto Chemical Co., Inc.

(4) (ILs-4) (1-C 4 H 9 -3-C 2 H 5 -Im) + (p-TsO) -
0.60 g (4.83 mmol) of N-butylimidazole was dissolved in 20 ml of DMF, and 0.97 g (4.83 mmol) of ethyl p-toluenesulfonate was quickly added under ice cooling. After completion of the addition, the mixture was further stirred for 23 hours. The reaction solution was dropped into 200 ml of ether cooled with ice, and ether was removed by decantation to recover 0.36 g of a yellow liquid. The yield was 0.26%. ^{From the 1} H-NMR spectrum, the recovered liquid could be identified as an imidazolium salt. The resulting imidazolium salt had a glass transition temperature (Tg) of −73.8 ° C.

(5) (ILs-5) (1-C 2 H 5 -3-CH 3 -Im) + ((CF 3 SO 2) 2 N) -
Purchased from Kanto Chemical Co., Inc.

(6) (ILs-6) (1-C 4 H 9 -3-C 2 H 5 -Im) + (CH 3 OSO 3) -
Purchased from MERCK.

(7) (ILs-7) (1-C 2 H 5 -3-CH 3 -Im) + (H (CH 2) 6 OSO 3) -
Purchased from SOLVENT INOVATION.

(8) (ILs-8) (1-C 2 H 5 -3-CH 3 -Im) + (H (CH 2) 4 OSO 3) -
Purchased from SOLVENT INOVATION.

(Example 1)
(Anode formation process)
An aluminum etched foil (size: 4 × 3.3 mm) as an anode metal is immersed in a 3% by mass aqueous solution of ammonium adipate and raised from 0 to 40 V at a rate of 10 mV / sec. A dielectric film made of an oxide film was formed on the surface of the aluminum etched foil by chemical conversion by applying for a minute. This was washed with running deionized water for 10 minutes and then dried at 105 ° C. for 5 minutes to produce an anode composed of an anode metal and a dielectric film. The capacity of the obtained anode in liquid was 4.2 μF.

(Electrolyte layer forming process)
First, the anode was immersed in (ILs-1) as an ionic liquid (ionic liquid immersion step), and vacuum impregnated and dried. Next, a raw material monomer of a conductive polymer, that is, 3,4-ethylenedioxythiophene monomer (manufactured by HC Starck-V TECH) as a polymerization substance, ferric paratoluenesulfonate as an oxidizing agent, Using 1-butanol as the solvent and ILs-1 as the ionic liquid, the chemical polymerization composition used for forming the electrolyte layer was prepared by blending at the following blending ratio.
-Conductive polymer raw material monomer 1g
・ Oxidizing agent 2g
・ Solvent 3g
・ Ionic liquid 1g
This chemical polymerization composition was mixed in a well-dried 30 cm ³ beaker, and then the anode impregnated with the ionic liquid was immersed in the chemical polymerization composition and pulled up, and then heated to 100 ° C. For 1 hour and further at 140 ° C. for 1 hour. Immersion and heat treatment were repeated three times so that the surface of the anode was uniformly covered with the electrolyte (chemical polymerization step). Thus, an electrolyte layer was formed.

  On the electrolyte layer obtained above, carbon paste (“Bunny Height FU” manufactured by Nippon Graphite Co., Ltd.) is applied, dried, and then silver paste (“Everyome ME” manufactured by Nippon Graphite Co., Ltd.) is applied. Dried to form a cathode. Lead wires were drawn from the silver paste and connected to the terminals. The electrolytic capacitor of the present invention thus obtained was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance at 100 KHz, and withstand voltage (V) were measured. The initial capacitance, tan δ, and impedance measurement devices are all solartron, model number “1480” manufactured by Toyo Technica, and the withstand voltage measurement device is model number “TR6143” manufactured by Advantest Corporation.

  The withstand voltage value was defined as a withstand voltage when the voltage was increased at a rate of 20 mV / sec and a current of 10 mA flowed. Table 1 shows the characteristics of the obtained electrolytic capacitor. The results in Table 1 are average values for 10 elements. The initial capacitance was 4.0 μF, tan δ was 1.0%, the impedance (100 KHz) was 1.8Ω, and the withstand voltage (V) was 38 V, all showing excellent capacitor characteristics. In particular, with respect to the withstand voltage characteristic, the formation voltage was 38 V compared to 40 V, which was extremely superior to Comparative Example 1 described later.

  In order to investigate the distribution of the ionic liquid in the electrolyte layer, the distribution of the C element and the F element in the depth direction was evaluated by XPS (X-ray photoelectron spectroscopy) analysis on the sample of the electrolyte layer formed in Example 1. . Moreover, cross-sectional observation of the electrolyte layer was performed with SEM (scanning electron microscope). The SEM observation was carried out with Hitachi “S4800” under the condition of an acceleration voltage of 10 kV. The XPS measurement was carried out with “Quantum 2000” manufactured by Phi Corp. at an X-ray intensity of Alkα / 15 kV · 12.5 W, an X-ray beam diameter of 50 μmφ, and a path energy of 93.9 eV.

  1 is a diagram showing a cross-sectional form of an electrolyte layer of the electrolytic capacitor produced in Example 1. FIG. In FIG. 1, (A) is a core portion of an etched aluminum layer (hereinafter, also simply referred to as (A) layer), and (B) is a portion (hereinafter, referred to as an etching hole and an electrolyte layer filled in the etching hole). And (C) are portions of the electrolyte layer outside the etching holes (hereinafter also simply referred to as the (C) layer).

  FIG. 2 is a diagram showing the results of XPS analysis of the electrolytic capacitor produced in Example 1. In the electrolyte layer formed in Example 1, it is considered that the C element is derived from the conductive polymer and the ionic liquid, and the F element is derived from the anion component of the ionic liquid. FIG. 2 shows the relative concentration distribution of the ionic liquid in the electrolyte layer. In FIG. 2, the peak intensity is converted so that the sum of the C element and the F element is 100%, but this does not necessarily indicate the mole fraction of both elements.

  As is clear from the results of FIG. 2, when the concentration of the F element in the (B) layer and the (C) layer is compared, the relative concentration of the F element in the (C) layer is about 4 atm%. There is a tendency that the relative concentration of the F element is higher in the etching hole of the layer (B). The relative concentration of the F element in the deep part of the etching hole in the (B) layer (that is, the part closer to the (A) layer) is about 18%, and the shallow part of the etching hole in the (B) layer (ie, (C) It is higher than about 8% of the density of the portion closer to the layer. That is, in the layer (B), the relative concentration of the F element decreases as it approaches the shallow portion of the etching hole. From these results, in the electrolytic capacitor fabricated in Example 1, the ionic liquid is non-uniformly present in the electrolyte layer, and the content of the ionic liquid in the vicinity of the interface with the dielectric film is the entire electrolyte layer. It was proved that it was higher than the average content of. The reason why the electrolytic capacitor obtained by the method of the present invention has excellent electrical characteristics and withstand voltage characteristics is that the ionicity having a concentration gradient is due to the high ion conductivity region in the region including the anode side surface of the electrolyte layer. This is thought to be due to the formation of a liquid distribution state.

(Examples 2 to 8)
An electrolytic capacitor of the present invention was produced in the same manner as in Example 1 except that the type of ionic liquid was changed from ILs-1 to ILs-2 to ILs-8, respectively, and the obtained electrolytic capacitor of the present invention was obtained. After aging at 20 V for 1 hour, the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured in the same manner as in Example 1. Table 1 shows the characteristics of the obtained electrolytic capacitor. It can be seen that excellent electrical characteristics and withstand voltage characteristics are compatible when any ionic liquid is used. In particular, in Examples 2, 4, 6, 7, and 8 containing (TsO) ⁻ and (OSO ₃ ) ⁻ in the anion component, the withstand voltage characteristic was 40 V or more, and a withstand voltage that was the same as the formation voltage could be realized.

(Comparative Example 1)
An electrolytic capacitor was produced in the same manner as in Example 1 except that the impregnation treatment of the anode with the ionic liquid (ILs-1) was not performed and the chemical polymerization composition used in the chemical polymerization step was not allowed to contain the ionic liquid. . After the obtained electrolytic capacitor was aged at 20 V for 1 hour, the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured in the same manner as in Example 1. Table 1 shows the characteristics of the obtained electrolytic capacitor. The obtained electrolytic capacitor had excellent electrical characteristics (tan δ, impedance), but the withstand voltage was 19 V and did not have the desired withstand voltage characteristics.

(Comparative Example 2)
Using an element that had been subjected to anode formation and chemical polymerization in the same manner as in Comparative Example 1, the element was immersed in a methanol solution of (ILs-1), which is an ionic liquid, and then dried to obtain methanol. By removing the ionic liquid, the ionic liquid was attached to the surface of the conductive polymer to form an electrolyte layer. The addition amount of the ionic liquid was estimated to be 5% by mass of the conductive polymer from the mass change of the element. Thereafter, a carbon paste / silver paste was applied in the same manner as in Example 1 to form a cathode, thereby obtaining an electrolytic capacitor. After aging at 20 V for 1 hour, the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 1 shows the characteristics of the obtained electrolytic capacitor. The withstand voltage was 23 V, and the addition of the ionic liquid showed a slight improvement with respect to the withstand voltage as compared with Comparative Example 1, but the tan δ characteristics and the impedance characteristics were worse than those of Comparative Example 1.

  With respect to the electrolyte layer in the electrolytic capacitor of Comparative Example 2, in order to investigate the distribution of the ionic liquid in the electrolyte layer, the distribution of the C element and the F element in the depth direction was evaluated by XPS ray analysis. FIG. 3 is a diagram showing the results of XPS analysis of the electrolytic capacitor produced in Comparative Example 2. The measuring apparatus was the same as that used in Example 1.

As shown in FIG. 3, in the (C) layer of the electrolytic capacitor fabricated in Comparative Example 2, the relative concentration of the F element is higher as it is closer to the surface, that is, the distance from the (B) layer is higher. The closer to the inside of the layer, that is, the closer to the (B) layer, the lower. In the layer (B), it was found that although the F element is present in the shallow portion of the etching hole, the F element is hardly present in the deep portion of the etching hole. From these results, the reason why the withstand voltage improvement could not be realized with the electrolytic capacitor of Comparative Example 2 is that there is a portion where the dielectric film and the conductive polymer are in direct contact in the deep portion of the etching hole. Conceivable.
(Comparative Example 3)
An electrolytic capacitor was prepared without immersing and vacuum impregnating the anode foil in an ionic liquid (ILs-1) in advance. In addition, the polymerization liquid used for electrolytic capacitor preparation is the same as Example 1. Table 1 shows the characteristics of the obtained electrolytic capacitor. The withstand voltage was 34 V due to the addition of the ionic liquid, and the withstand voltage was improved as compared with Comparative Example 1, but was worse than the characteristic of Example 1 (38 V). Further, the tan δ characteristic was 1.6%, and the impedance (100 KHz) characteristic was 4.6Ω, which was also worse than that in Example 1. In the electrolytic capacitor produced in Comparative Example 3, the polymerization was repeated three times as in Example 1, but the composition of the polymerization solution used was the same, so the distribution state of the ionic liquid in the electrolyte layer was: It is considered that both the (B) layer and the (C) layer are uniform.

(Comparative Example 4)
A capacitor element was produced in the same manner as in Example 1 except that no ionic liquid was added to the chemical polymerization composition. That is, the anode formed by the chemical conversion treatment is immersed in an ionic liquid (ILs-1), vacuum impregnated and dried, and then 3,4-ethylenedioxythiophene monomer (1 g) as a raw material monomer for the conductive polymer An electrolyte layer was formed using a chemical polymerization composition consisting of ferric paratoluenesulfonate (2 g) and 1-butanol (3 g). Thereafter, a carbon paste / silver paste was applied in the same manner as in Example 1 to form a cathode, and the obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and resistance The voltage (V) was measured. Table 1 shows the characteristics of the obtained electrolytic capacitor. The withstand voltage was 26 V, and a slight improvement was seen compared to Comparative Example 1 by the addition of the ionic liquid, but the tan δ characteristics and impedance characteristics were further inferior to Comparative Example 1.

Example 9
An aluminum foil subjected to the same chemical conversion treatment as in Example 1 was prepared as an anode, and the anode was immersed in an ionic liquid (ILs-1) and vacuum impregnated in the same manner as in Example 1. Next, a chemical polymerization composition was prepared in the same manner as in Example 1 except that the amount of the ionic liquid added was 0.5 g (that is, half the amount of Example 1). Mix in a well-dried 30 cm ³ beaker, then immerse the anode impregnated with the ionic liquid in the chemical polymerization composition, pull it up, pull it up at 120 ° C. for 1 hour, and further at 160 ° C. Heat treatment for 1 hour was performed. The above immersion and heat treatment were repeated 3 times so that the surface of the anode was uniformly covered with the electrolyte (chemical polymerization step).

  On the electrolyte layer thus obtained, a carbon paste was applied in the same manner as in Example 1. After drying, a silver paste was further applied and dried to form a cathode, and a lead wire was drawn from the silver paste and connected to a terminal. did. The electrolytic capacitor of the present invention thus obtained was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured in the same manner as in Example 1. . Table 1 shows the characteristics of the obtained electrolytic capacitor. The amount of the ionic liquid added when forming the electrolyte layer is half that of Example 1. However, although the withstand voltage characteristics slightly decreased as compared with Example 1, the impedance characteristics and tan δ characteristics were improved, and balanced capacitor characteristics could be realized.

(Example 10)
An electrolytic capacitor of the present invention was prepared in the same manner as in Example 1 except that the amount of the ionic liquid in the chemical polymerization composition was changed to 2 g (that is, twice the amount of Example 1), and the initial capacity, tan δ, Impedance (100 KHz) and withstand voltage (V) were measured. Table 2 shows the characteristics of the obtained electrolytic capacitor. In this embodiment, the withstand voltage is higher than the formation voltage of 40V, but when the voltage is increased at 20 mV / second, it gradually increases around 40 V and is 43 V when a current of 10 mA flows. It is due to that.

(Example 11)
The electrolytic capacitor of the present invention was prepared and evaluated in the same manner as in Example 2, except that the amount of the ionic liquid added to the chemical polymerization composition was half that in Example 2. Table 2 shows the characteristics (initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V)) of the obtained electrolytic capacitor. The addition amount of the ionic liquid at the time of forming the electrolyte layer is half that of Example 2, but the withstand voltage is 40 V, an excellent withstand voltage characteristic is realized, and an excellent impedance characteristic (2.2Ω), Coexistence with the tan δ characteristic (1.2%) was realized.

Example 12
An anode was prepared in the same manner as in Example 1, and then a chemistry composed of 3,4-ethylenedioxythiophene monomer (1 g), ferric paratoluenesulfonate (2 g), and 1-butanol solvent (3 g). A composition for polymerization was prepared. This composition for chemical polymerization was designated as 9A solution. In addition, a polymerization solution in which 0.5 g of ILs-1 was added as an ionic liquid to 6 g of 9A solution (referred to as 9B solution), and a polymerization solution in which 2 g of ILs-1 was added to 6 g of 9A solution (referred to as 9C solution) ) Was prepared.

  First, the anode was immersed in the 9C solution and pulled up, and then heat treatment was performed at 120 ° C. for 1 hour and further at 160 ° C. for 1 hour. Next, the 9B solution is used for immersion and heat treatment under the same conditions. Finally, the 9A solution is used for immersion and heat treatment under the same conditions so that the anode surface is uniformly covered with the electrolyte. A layer was formed (chemical polymerization step).

  On the electrolyte layer thus obtained, a carbon paste was applied in the same manner as in Example 1, and after drying, a silver paste was further applied and dried to form a cathode, and lead wires were drawn from the silver paste. The electrolytic capacitor thus obtained was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 3 shows the characteristics of the obtained electrolytic capacitor. The results in Table 3 are average values of 10 electrolytic capacitors.

(Examples 13 and 14)
An electrolytic capacitor was produced in the same manner as in Example 12 except that the type of ionic liquid added to the composition for chemical polymerization was ILs-2 or ILs-6. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 3 shows the characteristics of the obtained electrolytic capacitor.

(Example 15)
In this example, the electrolyte layer was formed by electrolytic polymerization. An aluminum foil measuring 7 mm in length and 10 mm in width with an anode lead was immersed in a 3% by weight aqueous solution of ammonium adipate and anodized at 70 ° C. under an applied voltage of 70 V to form the surface of the aluminum foil. A dielectric film made of an oxide film was formed to produce an anode.

  Next, for chemical polymerization comprising 3,4-ethylenedioxythiophene monomer (1 g), ferric paratoluenesulfonate (2 g), 1-butanol (3 g) and ILs-2 (1 g) which is an ionic liquid A composition was prepared, and the anode was immersed in the composition for chemical polymerization and pulled up, followed by heat treatment at 100 ° C. for 1 hour and 120 ° C. for 1 hour to form a thin chemical polymerization layer on the anode surface ( Chemical polymerization process).

  This chemical polymerization layer was used as a conductive layer, and a polypyrrole layer as an electrolytic polymerization layer 5 was formed by an electrolytic polymerization method using an apparatus configured as shown in FIG. The electrolytic solution 6 used for the electropolymerization is from pyrrole (0.5M), a 30% by mass aqueous alcohol solution of sodium triisopropylnaphthalenesulfonate (0.1M), and ILs-1 (0.3M) which is an ionic liquid. It is an electrolyte solution. In the electrolytic solution 6, the anode in which the chemical polymerization layer as the conductive layer 4 is formed is disposed, the polymerization start electrode 1 is brought close to the conductive layer 4, and 1. between the polymerization start electrode 1 and the cathode 7. An electropolymerization reaction was performed by applying a constant voltage of 5 V for 50 minutes, and a polypyrrole layer was formed as the electropolymerization layer 5.

  By the above method, an electrolyte layer composed of a chemical polymerization layer and an electrolytic polymerization layer was formed. On this electrolyte layer, carbon paste and silver paste were applied and dried in the same manner as in Example 1 to form a cathode, and an electrolytic capacitor was fabricated in the same manner as in Example 1. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 4 shows the characteristics of the obtained electrolytic capacitor. The results in Table 4 are average values for 10 elements.

(Examples 16 to 22)
The types of ionic liquids are ILs-2 in Example 16, ILs-3 in Example 17, ILs-4 in Example 18, ILs-5 in Example 19, ILs-6 in Example 20, and Examples. An electrolytic capacitor was produced in the same manner as in Example 15 except that ILs-7 was used for 21 and ILs-8 was used for Example 22. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 4 shows the characteristics of the obtained electrolytic capacitor.

(Comparative Example 5)
An electrolytic capacitor was produced in the same manner as in Example 15 except that the ionic liquid (ILs-1) was not blended in the chemical polymerization composition and the electrolytic solution at the time of electrolytic polymerization. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 4 shows the characteristics of the obtained electrolytic capacitor.

(Comparative Example 6)
The electrolytic capacitor produced in Comparative Example 5 was washed with water and dried, then immersed in a methanol solution of the ionic liquid, and then dried to remove the methanol, so that the ionic liquid was applied to the surface of the polypyrrole layer as the electrolytic polymerization layer. An electrolytic capacitor was produced by adhering. From the mass measurement, the adhesion amount of the ionic liquid was estimated to be 4.6% by mass of the conductive polymer. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 4 shows the characteristics of the obtained electrolytic capacitor.

(Comparative Example 7)
An electrolytic capacitor was produced in the same manner as in Example 15 except that the ionic liquid was not blended in the chemical polymerization composition. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 4 shows the characteristics of the obtained electrolytic capacitor.

(Example 23)
An etched aluminum foil (size: 100 × 3.3 mm) is immersed in a 3% by mass ammonium adipate aqueous solution, and is first increased from 0 to 40 V at a rate of 10 mV / sec, and then a constant voltage of 40 V is set to 40 V. A dielectric film made of an oxide film was formed on the surface of the aluminum foil. This was washed with running deionized water for 10 minutes and then dried at 105 ° C. for 5 minutes to produce an anode. The capacity of the anode obtained at this time was 102 μF.

  The anode is impregnated with an ionic liquid (ILs-2), and then a cellulose-based continuous porous film (trade name “EBAV3540” manufactured by Nippon Kogyo Paper Industries Co., Ltd.) and an aluminum foil not subjected to anodizing treatment, A wound type element was fabricated by winding the elements one after another.

  Next, an electrolyte layer was formed by chemical polymerization. That is, a composition for chemical polymerization comprising 3,4-ethylenedioxythiophene monomer (1 g), iron paratoluenesulfonate (2 g), 1-butanol (3 g), and ILs-2 (1 g) which is an ionic liquid Was prepared, and the wound-type element was immersed in the chemical polymerization composition and pulled up, followed by heat treatment at 100 ° C. for 1 hour and further at 120 ° C. for 1 hour. The above immersion and heat treatment were repeated twice to produce a wound type electrolytic capacitor.

  The obtained electrolytic capacitor of the present invention was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. The characteristics of the obtained electrolytic capacitor were an initial capacity of 98 μF, a tan δ of 2.9, an impedance of 20Ω, and a withstand voltage of 38 V, and exhibited excellent withstand voltage characteristics and impedance characteristics. Table 5 shows the characteristics of the obtained electrolytic capacitor. From this result, even in a wound type electrolytic capacitor, the anode is impregnated with an ionic liquid, and the ionic liquid is added to the chemical polymerization composition to form a composite of the ionic liquid and the conductive polymer. It was found that an electrolytic capacitor having excellent withstand voltage characteristics can be produced by forming the above.

(Example 24)
Instead of ILs-2, the same treatment as in Example 23 was performed except that the element was immersed in a conductive polymer solution in which 15% by mass of polypyrrole was dissolved in ILs-2, and an electrolytic capacitor was produced. The characteristics of the obtained electrolytic capacitor were an initial capacity of 102 μF, a tan δ of 2.8, an impedance (100 KHz) of 16Ω, a withstand voltage of 40 V, and exhibited excellent withstand voltage characteristics and impedance characteristics. Table 5 shows the characteristics of the obtained electrolytic capacitor. From this result, the conductive polymer solution immersion process is performed using the ionic liquid in which the conductive polymer is dissolved, and further, the composite containing the ionic liquid and the conductive polymer is formed by the chemical polymerization process. It was found that an electrolytic capacitor having excellent withstand voltage characteristics can be produced.

(Example 25)
The same anode as in Example 15 was prepared. First, an impregnation treatment of the anode was performed using a conductive polymer solution in which 15% by mass of polypyrrole was dissolved in ILs-2, which is an ionic liquid, and the anode surface was subjected to heavy coating. A coalesced layer was formed. Next, using the polymer layer as a conductive layer, a polypyrrole layer was formed as an electrolytic polymerization layer by the same electrolytic polymerization method as in Example 15, and an electrolyte layer composed of the polymer layer and the electrolytic polymerization layer was formed.

  Next, a carbon paste and a silver paste were applied and dried on the electrolyte layer in the same manner as in Example 15 to form a cathode, and an electrolytic capacitor was fabricated in the same manner as in Example 15. The characteristics measured after aging the electrolytic capacitor of the present invention thus obtained for 1 hour at 20 V are as follows: initial capacitance is 4.6 μF, tan δ is 1.0, impedance (100 KHz) is 1.5Ω, and withstand voltage is It was 70V, and showed an excellent withstand voltage characteristic. Table 5 shows the characteristics of the obtained electrolytic capacitor. From this result, the conductive polymer solution immersion process is performed using the ionic liquid in which the conductive polymer is dissolved, and further, the composite containing the ionic liquid and the conductive polymer is formed by the electrolytic polymerization process. It was found that an electrolytic capacitor having excellent withstand voltage characteristics can be produced.

(Example 26)
An electrolytic capacitor was produced in the same manner as in Example 15 except that no ionic liquid was added to the electrolytic polymerization composition. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 5 shows the characteristics of the obtained electrolytic capacitor.

(Example 27)
Each ion is used so that a concentration gradient is generated in the chemical polymerization composition as in Example 12, and so that a concentration gradient is generated in the electrolytic polymerization composition as in the chemical polymerization composition. An electrolytic capacitor was produced in the same manner as in Example 15 except that the ionic liquid was blended. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 5 shows the characteristics of the obtained electrolytic capacitor.

(Example 28)
An electrolytic capacitor was fabricated in the same manner as in Example 24 except that the electrolytic polymerization was not performed. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. The characteristics of the obtained electrolytic capacitor were an initial capacitance of 96 μF, a tan δ of 2.6, an impedance (100 KHz) of 18Ω, a withstand voltage of 41 V, and exhibited excellent withstand voltage characteristics and impedance characteristics.

(Example 29)
An electrolytic capacitor was fabricated in the same manner as in Example 24 except that an ILs immersion step was added using ILs-2 as in Example 1. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 5 shows the characteristics of the obtained electrolytic capacitor. The characteristics of the obtained electrolytic capacitor were an initial capacity of 106 μF, a tan δ of 1.8, an impedance (100 KHz) of 12Ω, a withstand voltage of 46 V, and exhibited excellent withstand voltage characteristics and impedance characteristics.

(Example 30)
An electrolytic capacitor was fabricated in the same manner as in Example 23 except that an ILs immersion step was added using ILs-2 as in Example 1. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured. Table 5 shows the characteristics of the obtained electrolytic capacitor. As for the characteristics of the obtained electrolytic capacitor, the initial capacitance was 104 μF, tan δ was 2.6, the impedance (100 KHz) was 14Ω, and the withstand voltage was 42 V, which showed excellent withstand voltage characteristics and impedance characteristics.

(Comparative Example 8)
An electrolytic capacitor was fabricated in the same manner as in Example 23, except that the ionic liquid (ILs-2) was changed to butanol and immersed in a suspension of polypyrrole and electrolytic polymerization was not performed. After the obtained electrolytic capacitor was aged at 20 V for 1 hour, the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured in the same manner as in Example 1. Table 5 shows the characteristics of the obtained electrolytic capacitor. The characteristics of the obtained electrolytic capacitor were an initial capacity of 84 μF, a tan δ of 5.6, an impedance (100 KHz) of 64Ω, and a withstand voltage of 22V.

(Comparative Example 9)
An electrolytic capacitor was fabricated in the same manner as in Example 23, except that the ionic liquid (ILs-2) was changed to butanol and immersed in a polypyrrole suspension. After the obtained electrolytic capacitor was aged at 20 V for 1 hour, the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured in the same manner as in Example 1. Table 5 shows the characteristics of the obtained electrolytic capacitor. The characteristics of the obtained electrolytic capacitor were an initial capacity of 100 μF, a tan δ of 2.5, an impedance (100 KHz) of 16Ω, and a withstand voltage of 32V.

(Comparative Example 10)
An electrolytic capacitor was produced in the same manner as in Example 24 except that the ionic liquid (ILs-2) was changed to butanol and immersed in a polypyrrole suspension. The obtained electrolytic capacitor was aged at 20 V for 1 hour, and then the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured in the same manner as in Example 1. Table 5 shows the characteristics of the obtained electrolytic capacitor. The characteristics of the obtained electrolytic capacitor were initial capacitance of 95 μF, tan δ of 2.7, impedance (100 KHz) of 21Ω, and withstand voltage of 30V.

(Comparative Example 11)
An electrolytic capacitor was fabricated in the same manner as in Example 27, except that the ionic liquid (ILs-2) was changed to butanol and immersed in a polypyrrole suspension. After the obtained electrolytic capacitor was aged at 20 V for 1 hour, the initial capacity, tan δ, impedance (100 KHz), and withstand voltage (V) were measured in the same manner as in Example 1. Table 5 shows the characteristics of the obtained electrolytic capacitor.

It should be understood that the embodiments and examples disclosed this time are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

3 is a diagram showing a cross-sectional form of an electrolyte layer of the electrolytic capacitor produced in Example 1. FIG. FIG. 4 is a diagram showing the results of XPS analysis of the electrolytic capacitor produced in Example 1. 6 is a diagram showing the results of XPS analysis of the electrolytic capacitor produced in Comparative Example 2. FIG. It is a conceptual diagram explaining the electrolytic polymerization apparatus used for electrolytic polymerization.

Explanation of symbols

1 polymerization start electrode,
2 Anode metal 3 Dielectric film 4 Conductive layer 5 Electropolymerization layer 6 Electrolytic solution 7 Cathode

Claims (15)

An electrolytic capacitor comprising at least an electrolyte layer and an anode and a cathode disposed with the electrolyte layer interposed therebetween, the anode comprising an anode metal and a dielectric film,
The electrolyte layer contains at least an ionic liquid and a conductive polymer,
An electrolytic capacitor in which the content of the ionic liquid in the electrolyte layer is not uniform. The electrolyte layer is formed in contact with the dielectric layer;
The electrolytic capacitor according to claim 1, wherein a region containing the ionic liquid is formed in a region near the dielectric interface in the electrolyte layer at a content rate higher than the content rate of the ionic liquid in the entire electrolyte layer. .   The electrolytic capacitor according to claim 2, wherein the region containing the ionic liquid at the high content is formed so as to cover the entire surface of the dielectric film.   The distance from the interface between the dielectric film and the electrolyte layer is an imaginary axis that connects an arbitrary point of the interface between the dielectric film and the electrolyte layer to the interface between the cathode and the electrolyte layer with the shortest distance. The electrolytic capacitor according to claim 1, wherein the content of the ionic liquid is reduced as the size increases.   An electrolyte containing at least an ionic liquid and a conductive polymer as essential components, wherein the concentration of the ionic liquid is non-uniform in the electrolyte, and the entire electrolyte layer is in the vicinity of the dielectric interface in the electrolyte layer. An electrolyte for a conductive polymer capacitor, wherein a region containing the ionic liquid is formed at a content rate higher than the content rate of the ionic liquid.   The cation component of the ionic liquid is ammonium and derivatives thereof, imidazolinium 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, Triazinium and its derivatives, triazine derivative cations, quinolinium and its derivatives, isoquinolinium and its derivatives, indolinium and its derivatives, quinoxalinium and its derivatives, piperazinium and its derivatives, oxazolinium and its derivatives, thiazolinium and its derivatives, morpholinium and its derivatives At least one selected from the group consisting of derivatives, piperazine and derivatives thereof No, electrolytic capacitor or electrolyte according to any one of claims 1 to 5.   The anionic component of the ionic liquid is a carboxylate anion derivative, a sulfonylimide anion derivative, a fluorobromine anion derivative, a fluoroboron anion derivative, a nitrate anion derivative, a boron fluoride anion derivative, a cyanoimide anion derivative, a sulfonate anion derivative, or The electrolytic capacitor or electrolyte in any one of Claims 1-6 containing the atomic group of a sulfuric-acid monoester anion derivative.   The electrolytic capacitor according to any one of claims 1 to 7, wherein the conductive polymer comprises at least one of polypyrrole or a derivative thereof, polythiophene or a derivative thereof, polyaniline or a derivative thereof, polyquinone or a derivative thereof, or Electrolytes. The conductive polymer is made of poly- (2,3-dihydroxythieno- [3,4-b] -1,4-dioxin) or polypyrrole according to any one of claims 1 to 8. Electrolytic capacitor, or electrolyte.   A method for producing an electrolyte for a conductive polymer capacitor by a chemical polymerization method, wherein at least a step of immersing an electrode foil in a liquid containing an ionic liquid in advance and a chemical polymerization using a polymerization solution in which the ionic liquid coexists The method for producing an electrolyte according to any one of claims 5 to 9, further comprising the step of:   A method for producing an electrolyte for a conductive polymer capacitor by a chemical polymerization method, wherein the electrolyte for a conductive polymer capacitor is formed by at least a plurality of chemical polymerization steps, and the ratio of the ionic liquid to the polymerizable monomer by each polymerization step. The method for producing an electrolyte according to claim 5, wherein the electrolyte is changed.   A method for producing an electrolyte for a conductive polymer capacitor comprising a chemical polymerization method and an electrolytic polymerization method, wherein at least a first step of performing chemical polymerization at least in advance using a solution in which an ionic liquid and a polymerizable monomer coexist, The method for producing an electrolyte according to any one of claims 5 to 9, further comprising a second step of performing electropolymerization in a polymerization liquid containing a polymerizable monomer.   A method for producing an electrolyte for a conductive polymer capacitor using a solution containing an ionic liquid in which at least a part of a conductive polymer is dissolved, wherein the electrolyte layer is formed by impregnating at least the solution with an electrode. The method for producing an electrolyte according to any one of claims 5 to 9, comprising the steps of: A method for producing an electrolyte for a conductive polymer capacitor using a solution containing an ionic liquid in which at least a part of a conductive polymer is dissolved, wherein the electrolyte layer is formed by impregnating at least the solution with an electrode. The method for producing an electrolyte according to any one of claims 5 to 9, characterized by comprising the step of forming an electrolyte by chemical polymerization.   A method for producing an electrolyte for a conductive polymer capacitor using a solution containing an ionic liquid in which at least a part of a conductive polymer is dissolved, wherein the electrolyte layer is formed by impregnating at least the solution with an electrode. The method for producing an electrolyte according to any one of claims 5 to 9, characterized by comprising the step of forming an electrolyte by electrolytic polymerization.