JP4927604B2 - Method for producing conductive polymer solid electrolytic capacitor - Google Patents

Description

  The present invention relates to a method for producing a conductive polymer solid electrolytic capacitor having excellent withstand voltage characteristics and impedance characteristics.

  In recent years, conductive polymer solid 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 conductive polymer solid 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 conductive polymer solid electrolytic capacitor typically uses a solid conductive polymer such as polypyrrole or 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 (that is, anodic oxidation action) of the oxide film of the electrolytic capacitor, 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 in 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. A tantalum electrolytic capacitor usually 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, as 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, but there is a problem that the withstand voltage cannot be increased in either structure.

In order to solve such problems, the present inventors have already developed an electrolyte composed of an ionic liquid and a conductive polymer (Patent Document 1). This was made by discovering that the ionic liquid has an excellent anodic action of the valve metal and can repair defects in the oxide film of aluminum, for example, and by this invention, a high withstand voltage electrolytic capacitor could be realized. . However, many ionic liquids have 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 capacitor There is a problem that the impedance characteristic is deteriorated.
Further, 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 much 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 chemical polymerization or electrolytic polymerization (Patent Document 2). However, in this method, it is described that the electrostatic capacity and the capacity impregnation rate are improved, but it is not described that good withstand voltage characteristics can be obtained. It is considered that these characteristics can be achieved only by using a plurality of ionic liquids and a plurality of addition methods.
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 a method for manufacturing an electrolytic capacitor having high withstand voltage and excellent impedance characteristics.

  As a result of diligently investigating the addition of an ionic liquid to the electrolyte of the conductive polymer solid capacitor, the present inventors have found that the effect of increasing the withstand voltage differs depending on the type of ionic liquid, and a small amount of a specific ionic liquid is added. Thus, the present inventors have found that the impedance characteristics are improved, the improvement effect of the impedance characteristics is different depending on the kind of the ionic liquid, and that these effects are different depending on the method of adding the ionic liquid to the electrolyte.

  As a result, when one kind of ionic liquid is used, or when only one addition method is used, it is difficult to obtain a capacitor electrolyte having sufficient high withstand voltage performance and impedance characteristics. The present inventors have found that the above-mentioned problems can be solved by using a combination of ionic liquids having different effects on two or more kinds of characteristic parameters and utilizing a plurality of addition methods. In particular, the above problem can be solved most effectively by combining a plurality of ionic liquids and a plurality of addition methods. Here, a plurality of addition methods are a method of bringing a dielectric into contact with a liquid to which an ionic liquid has been added in advance before forming the conductive polymer, and a method of adding the ionic liquid in the step of forming the conductive polymer. Is shown.

  That is, the present invention is an electrolytic capacitor manufacturing method comprising 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 anode comprising an anode metal and a dielectric film. After the dielectric film is brought into contact with a liquid containing an ionic liquid, the electrolyte layer is formed in contact with the dielectric film, and at least a part of the electrolyte layer comprises an ionic liquid and a conductive polymer. The present invention relates to a method for producing an electrolytic capacitor.

  In the electrolytic capacitor manufacturing method of the present invention, it is preferable that the electrolyte layer is formed so as to cover the entire surface of the dielectric film. In the electrolytic capacitor that is the subject of the present invention, at least a part of the electrolyte is formed as a composite containing an ionic liquid and a conductive polymer.

  In the electrolytic capacitor of the present invention, the cation component of the ionic liquid is preferably composed of at least one selected from an imidazolium cation, a pyridinium cation, a pyrrolidinium cation, an ammonium cation, and a triazine derivative cation. It is not limited. The effect of the present invention is often mainly governed by the anion component of the ionic liquid and is not significantly affected by the type of cation. However, it is not preferable to select a cation in which an ionic liquid existing as a salt becomes a solid in a specific environment.

In the method for producing an electrolytic capacitor of the present invention, the anionic component of the ionic liquid is R _A OSO ₃ ⁻ , R _A SO ₃ ⁻ , R _A OOSO ₃ ⁻ , R _A COOOSO ₃ ⁻ , R _A OCOOSO ₃ ⁻ , R _A COO ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , F ₃ CSO ₂ ⁻ , N (SO ₂ CF ₃ ) ₂ ⁻ (wherein, R _A is an aliphatic hydrocarbon group which may have a substituent, R _A represents an aromatic hydrocarbon group, and R _A is preferably an aliphatic hydrocarbon group containing a fluorine atom or an aromatic hydrocarbon group.
In particular, the anion component of the ionic liquid used in the electrolyte layer forming step of forming the electrolyte ^{_{layer, R A OSO 3 -, R}} A SO 3 -, R A OOSO 3 -, R A COOSO 3 -, R A OCOOSO 3 ^- it is preferably made from at least one selected from.

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

  The conductive polymer is preferably made of poly- (2,3-dihydrothieno- [3,4-b] -1,4dioxin) (PEDOT) or polypyrrole.

  The present invention is also a manufacturing method for obtaining the above electrolytic capacitor, wherein an anode forming step of forming an anode composed of an anode metal and a dielectric film, an anode surface treatment step of bringing the formed anode surface into contact with a liquid, An electrolyte layer forming step of forming an electrolyte layer on the dielectric film and a cathode forming step of forming a cathode on the surface of the electrolyte layer. Further, the liquid to be contacted in the anode surface treatment step contains an ionic liquid, and the electrolyte layer forming step immerses the anode in a chemical polymerization composition containing at least the ionic liquid and the polymerizable material, and then the polymerizable material. And a chemical polymerization step of forming a complex containing an ionic liquid and a conductive polymer by polymerizing by a chemical polymerization method, and the chemical polymerization step is performed only once or repeated a plurality of times The present invention relates to a method for manufacturing an electrolytic capacitor. However, in the case of repeating a plurality of chemical polymerization steps, it is not always necessary that all chemical polymerization compositions used in all chemical polymerization steps contain an ionic liquid, and some chemistry that does not use an ionic liquid. A polymerization composition can be used, and can be cited as one of the embodiments of the present invention.

  The molar ratio of the ionic liquid contained in the composition for chemical polymerization used in the electrolyte layer forming step of the present invention and the monomer consumed to form the electrolyte should be 0.001: 1 or more and 10: 1 or less. Is more preferable, and 0.001: 1 or more and 0.6: 1 or less is more preferable.

  In the method for producing an electrolytic capacitor of the present invention, the conductive polymer obtained in the chemical polymerization step is poly- (2,3-dihydrothieno- [3,4-b] -1,4dioxin) or polypyrrole. It is preferable. In the former case, it is easy to obtain a good quality electrolyte with a stable process, and in the latter case, a good quality electrolyte can be obtained at low cost by stabilizing the process.

  In the method for producing an electrolytic capacitor of the present invention, for example, an ionic liquid may be interposed together with the monomers at the time of chemical polymerization of these monomers. It is also possible to manufacture an electrolytic capacitor with a small amount of oxidizing agent by performing washing for removing a polymerization accelerator such as an oxidizing agent after polymerization and then immersing it again in an ionic liquid.

  An electrolytic capacitor comprising at least an electrolyte containing an ionic liquid and a conductive polymer, an anode made of an anode metal and a dielectric, and an electrolytic capacitor sandwiched between the cathodes, the dielectric layer on the anode metal, By contacting the liquid containing the ionic liquid and then forming the electrolyte layer using the polymerizable solution containing the ionic liquid, it is possible to obtain an electrolytic capacitor having a high compatibility between the withstand voltage characteristic and the impedance characteristic. Become.

  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. The electrolyte layer contains at least an ionic liquid and a conductive polymer, and the electrolyte layer is formed in contact with the dielectric film. In the present invention, at least an anion of the ionic liquid is contained in the electrolyte layer.

  The ionic liquid contained in the electrolyte is introduced for the purpose of reducing the impedance of the capacitor. Furthermore, the anion of the ionic liquid can also improve the withstand voltage of the capacitor, and can effectively perform the role of repairing and protecting the dielectric film in the electrolytic capacitor of the present invention.

  As described above, according to the examination results of the present inventors, when a specific ionic liquid is interposed during the chemical polymerization of the conductive polymer, an effect of improving the conductivity is seen. Although the detailed cause is unknown, it is presumed that it affects the polymerization degree, morphology, and doping of the conductive polymer in relation to the polymerization mechanism. However, since the ionic liquid has essentially no electronic conductivity, if the content of the ionic liquid in the entire electrolyte layer is excessively increased, the electronic conductivity of the entire electrolyte layer is reduced and a good impedance as an electrolytic capacitor is obtained. It becomes difficult to obtain characteristics. For this reason, there is an appropriate value for the amount of ionic liquid added to the conductive polymer electrolyte exhibiting good impedance characteristics. This value depends on the type of ionic liquid, particularly the type of anion. Therefore, if the ionic liquid to be introduced is limited to only one type, it is desirable to select an ionic liquid having an impedance reduction effect with a small amount as much as possible.

  On the other hand, paying attention to the withstand voltage of the capacitor, the introduction of ionic liquid into the electrolyte has the effect of repairing and protecting the dielectric film in the electrolytic capacitor. As stated. The effect of improving the withstand voltage also depends on the type of ionic liquid, particularly the type of anion. Furthermore, the withstand voltage tends to improve as the amount of ionic liquid introduced increases, but there is a problem with strength such as self-supporting ability, and an extreme amount cannot be introduced. Further, it is obvious that the introduction of an amount in which the above-described decrease in impedance is observed is not preferable in terms of device characteristics. Therefore, if the ionic liquid to be introduced is limited to only one type, it is desirable to select an ionic liquid that has the effect of improving the withstand voltage with a small amount and introduce an amount that does not adversely affect the impedance.

  As a result of investigations by the present inventors, it has been found that the effect of improving the withstand voltage of the capacitor tends to depend on the anion species of the ionic liquid. This is thought to be due to the large influence of anions on defect repair of the dielectric layer and anodic oxidation. However, even if the anion species is the same, a phenomenon in which these effects are different is observed. Specifically, when a solid salt is introduced instead of an ionic liquid, the withstand voltage improvement effect decreases even if the anion species is the same. In order to expect the same effect as the ionic liquid, more anions are required.

  For example, iron salt is often used as a polymerization accelerator responsible for the polymerization reaction of conductive polymers, but the effect of improving the withstand voltage by adding a polymerization accelerator is much higher than that of an ionic liquid even if the anion species is the same. small. This is presumed to be due to the presence of anions as solid salts in the electrolyte. This indicates that the ionic liquid is preferably present in a liquid state at the operating temperature of the capacitor. Further, when the phase transition from liquid to solid and from liquid to solid is repeated, the leakage current of the capacitor may gradually increase, and an ionic liquid that causes a phase transition in the use state or in the transportation / storage process is not preferable. The conductive polymer solid electrolytic capacitor of the present invention is obtained when the ionic liquid, which is an anion supply raw material contained in the electrolyte, is a liquid salt at 25 ° C or higher, preferably 0 ° C or higher, more preferably -40 ° C or higher. Is desired for.

  The present inventors have made use of the effect of application of such a conductive polymer solid capacitor to an electrolyte by introducing an ionic liquid containing at least two types of anions into the conductive polymer electrolyte layer. It was discovered that both withstand voltage and impedance are possible to some extent. As a more effective means, the present inventors have devised a method for introducing an ionic liquid, discovered that the characteristics of these capacitors can be remarkably improved by the combination thereof, and have completed the present invention. The method of introducing the ionic liquid includes a method of immersing the dielectric material in the ionic liquid before forming the conductive polymer, a method of mixing in a polymerization accelerator such as a monomer or oxidant of the conductive polymer, and a method of immersing after polymerization. Or combinations thereof and repetitions are possible. In the present invention, the former, that is, a method of immersing a dielectric in an ionic liquid before forming a conductive polymer, and a polymerization accelerator such as a conductive polymer monomer or an oxidant during chemical polymerization are mixed. It can implement by combining the method to make.

  The basic form of the present invention includes an anode forming step for forming an anode composed of an anode metal and a dielectric film, an anode surface treatment step for bringing the formed anode surface into contact with a liquid, and an electrolyte layer for forming an electrolyte layer on the dielectric film And forming a cathode and forming a cathode on the surface of the electrolyte layer. The liquid to be brought into contact with the anode surface only needs to contain an ionic liquid. Further, it is necessary that at least a part of the chemical polymerization composition used in the electrolyte forming step contains an ionic liquid.

  It is particularly effective to use an ionic liquid having a high withstand voltage improvement effect for the ionic liquid used in the anode surface treatment process and an ionic liquid having a high impedance reduction effect in the electrolyte layer forming process. The ionic liquid may be the same.

  When the composition for chemical polymerization used in the electrolyte layer forming step is repeated a plurality of times, it is not always necessary to use the same composition, and it is also possible to use a composition for chemical polymerization that does not contain an ionic liquid in part. is there. It is also possible to wash with water or the like during or after the electrolyte layer forming process in order to remove unnecessary components such as polymerization accelerators. It is also possible to introduce.

  Further, it is possible to stack electrolyte layers having different ionic liquid concentrations. For example, a method of mixing an ionic liquid with a monomer of a conductive polymer or a polymerization accelerator such as an oxidizer, and performing polymerization a plurality of times while changing the concentration of the ionic liquid, gives a desired concentration distribution of the ionic liquid. An electrolyte layer can be formed. In the electrolyte layer of the electrolytic capacitor that is the subject of the present invention, the entire conductive polymer may be formed as a composite containing an ionic liquid and a conductive polymer, or a part of the conductive polymer. Only the composite may be formed, and the remaining portion may be formed of the conductive polymer alone.

<Ionic liquid>
The ionic liquid used in the present invention refers to a liquid that is in the vicinity of room temperature despite being composed only of ions, and is composed of a combination of a cation such as imidazolium and an appropriate anion. In the present invention, at the time of forming the electrolyte layer, the ionic liquid can be used in the presence of a polymerization accelerator, water, a solvent such as an organic solvent, etc. And it is preferable to use a lipophilic ionic liquid properly.

  Examples of the cation component constituting the ionic liquid preferably used in the present invention include an imidazolium cation, a pyridinium cation, a pyrrolidinium cation, an ammonium cation, and a triazine derivative cation. Of these, imidazolium cations are preferably used from the viewpoint of ease of handling.

Examples of the anion component constituting the ionic liquid include R _A OSO ₃ ⁻ , R _A SO ₃ ⁻ , R _A OSO ₃ ⁻ , R _A COOSO ₃ ⁻ , R _A OCOOSO ₃ ⁻ , R _A COO ⁻ , BF ₄ ⁻ , PF ^{_{6 -, F 3 CSO 2 -}} , N (SO 2 CF 3) 2 - but like can be exemplified, but not limited thereto. Here, _RA represents a substituent, particularly an aliphatic hydrocarbon group or an aromatic hydrocarbon group. R _A may be a substituent containing a fluorine atom. Furthermore, R _A itself may have a substituent. Among them, an ionic liquid having an anion containing a sulfonate anion (—SO ₃ ⁻ ), a sulfate anion (—SO ₄ ²⁻ ), and BF ₄ ^— is particularly preferable for the purpose of the present invention because of its high repair ability with respect to the dielectric film. .

Specific examples of ionic liquids preferably used in the present invention include methyl ethyl imidazolium p-toluenesulfonic acid, butyl methyl imidazolium p-toluenesulfonic acid, ethyl methyl imidazolium-BF ₄ , and butyl methyl imidazole. potassium -BF _4, butyl ethylimidazolium _{-F 3 CSO 2 NSO 2 CF 3} -, ethyl methyl imidazolium _{-F 3 CSO 2 NSO 2 CF 3} - , and the like. However, preferred ionic liquids for the present invention are not limited to these.

<Conductive polymer>
As the conductive polymer contained in the electrolyte layer in the present invention, for example, polythiophene or a derivative thereof, polypyrrole or a derivative thereof, polyaniline or a derivative thereof, polyquinone or At least one selected from the derivatives is particularly preferably used.

  For example, polythiophene derivatives include polyethylene dioxythiophene (PEDOT) synthesized from 1,4-dioxythiophene monomer, polyalkylthiophene synthesized from 3-methylthiophene monomer, and the like. PEDOT is particularly preferable for the purpose of the present invention from the viewpoint of electron conductivity, but is not limited thereto.

  Examples of the derivative of polypyrrole include, but are not limited to, those having a pyrrole skeleton and having a substituent such as a hydroxyl group, a carboxyl group, and an alkyl group.

  Examples of the polyaniline derivative include, but are not limited to, those having an alkyl group, a cyano group, a sulfone group, or a carboxyl group in the polyaniline skeleton.

  Polyquinone derivatives include polybenzoquinone derivatives synthesized from benzoquinone monomers having substituents, polynaphthoquinone derivatives synthesized from naphthoquinone monomers having substituents, polyanthraquinone derivatives synthesized from anthraquinone monomers having substituents, etc. However, it is not limited to these.

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

In the present invention, examples of the combination of the ionic liquid and the conductive polymer described above preferably include a combination of an ionic liquid composed of an imidazolium cation and a sulfonate anion (—SO ₃ ⁻ ) and polypyrrole. This combination is preferable in that an electrolytic capacitor having excellent withstand voltage characteristics and impedance characteristics can be realized because of the high repair capability of the ionic liquid with respect to the dielectric film, while the electrical conductivity of the conductive polymer is high.

<Electrolytic capacitor>
An electrolytic capacitor that is an object of the present invention is an anode that is formed using an electrolyte layer in which an ionic liquid and a conductive polymer coexist at least in part, and is disposed so as to face the electrolyte layer with the electrolyte layer interposed therebetween And a cathode. 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.

<Manufacture of electrolytic capacitors>
In this embodiment, a case where an electrolyte layer is formed by 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 anode surface treatment step of bringing the formed anode surface into contact with a liquid containing an ionic liquid, a dielectric An electrolyte layer forming step of forming an electrolyte layer in contact with the body membrane; and a cathode forming step of forming a cathode on the surface of the electrolyte layer. The electrolyte layer forming step includes immersing the anode in a chemical polymerization composition containing at least an ionic liquid and a polymerizable substance, and then polymerizing the polymerizable substance by a chemical polymerization method to thereby form an ionic liquid and a conductive polymer. A chemical polymerization step of forming a composite containing The chemical polymerization process can be performed only once or can be repeated multiple times. Moreover, this chemical polymerization process can also be repeated in multiple times, changing the mass ratio of the ionic liquid and polymeric substance in the composition for chemical polymerization.

(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. The anodization can be performed by a conventionally known method such as a method in which an anode metal is immersed in a polymerization accelerator such as an aqueous solution of sodium adipate and a predetermined formation voltage is applied.

(Anode surface treatment step) Ionic liquid immersion step Next, a liquid containing an ionic liquid is brought into contact with the dielectric surface formed in the anode formation step to form a thin film of ionic liquid on the surface. Specific examples include soaking in a liquid containing an ionic liquid and spraying a mist liquid. The liquid may be an ionic liquid itself or a liquid obtained by dissolving an ionic liquid in a volatile solvent such as alcohol. The ionic liquid may be a plurality of mixtures or a simple substance. Further, by reducing the atmosphere at the time of contact with the liquid or after the contact, contact inhibition due to bubbles or the like can be avoided, and the fine portion can be filled with the ionic liquid.

  After immersion in the liquid, the volatile components can be removed by heating. Since the ionic liquid is non-volatile, it remains on the dielectric surface even after heating. The type of ionic liquid varies depending on the purpose. The same thing as the ionic liquid used at the electrolyte layer formation process mentioned later may be included, and the same thing may be included. It is effective to use an ionic liquid having a high effect of improving the withstand voltage.

  As a special embodiment of this process, it is conceivable to perform anodic oxidation and / or repair conversion in an electrolytic solution containing an ionic liquid. After such a step of bringing the ionic liquid into contact with the dielectric, the present invention can be carried out by forming an electrolyte containing the ionic liquid and the conductive polymer.

(Electrolyte Layer Forming Step) 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 the polymerizable substance is pulled up. Is polymerized by 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 aforementioned 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.

  Preferred combinations of the ionic liquid and the raw material monomer in the chemical polymerization method include, for example, an ionic liquid composed of an imidazolium cation and a sulfonate anion, an ionic liquid composed of an imidazolium cation and a tetrafluoroborate anion, and 1,4-dioxy. Examples include combinations with thiophene monomers. The combination has a higher ability to repair a dielectric film than an electrolyte composed of one kind of ionic liquid and a conductive polymer, while the polythiophene obtained by polymerization has a higher electric conductivity, so that it has excellent withstand voltage characteristics and impedance. This is preferable in that an electrolytic capacitor having characteristics can be realized.

  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.

The preferred molar ratio (N _A / B) and (N _B / B) of the number of moles of ionic liquid (N _A ), (N _B ) and the number of moles of polymerizable substance (B) in the chemical polymerization composition are: It is in the range of 1/100 to 10/1, and a more preferable molar ratio is in the range of 1/100 to 0.6 / 1. The molar ratio of the _(N A / B) and _(N B / B) when the ionic liquid is less than 1/100, there is a tendency that the withstand voltage improvement effect is reduced. On the other hand, when the molar ratio (N _A / B) and (N _B / B) contains more ionic liquid than 10/1, the electric conductivity of the electrolyte layer in the electrolytic capacitor decreases due to the presence of excess ionic liquid. The impedance characteristics of the obtained electrolytic capacitor tend 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 optimum range of the ionic liquid contained in the chemical polymerization composition is as described above. However, the amount of the ionic liquid present in the actually formed electrolyte layer is larger than the ratio in the chemical polymerization composition. Is expected to decrease. 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. Is caused by

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

  The chemical polymerization composition may contain a polymerization accelerator, a surfactant and the like in addition to the ionic liquid and the polymerizable substance. An oxidizing agent is used as a polymerization catalyst. Examples thereof include ferric paratoluenesulfonate, ferric naphthalenesulfonate, ferric n-butylnaphthalenesulfonate, ferric triisopropylnaphthalenesulfonate. It is done. Of these, ferric paratoluenesulfonate as a dopant is preferably used as a polymerization accelerator.

  The mixing ratio of the polymerizable substance and the polymerization accelerator in the composition for chemical polymerization is not particularly limited, but the mixing ratio of raw material monomer: polymerization accelerator is a molar ratio of 1: 0.1 to 1: It is preferably in the range of 5, more preferably in the range of 1: 0.3 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 a small amount is added to the composition for chemical polymerization, there exists an ionic liquid that can reduce impedance compared with the case where it is not added. However, when the added amount is excessive, the impedance is increased. Therefore, when attention is paid only to the impedance characteristics, there is an appropriate addition amount, and the amount varies depending on the type of the ionic liquid.

  On the other hand, the withstand voltage of the capacitor is also improved by adding the ionic liquid. In general, the withstand voltage increases as the amount added increases. However, since it is a liquid, the shape of the electrolyte itself cannot be maintained if it is added excessively. The effect of improving withstand voltage also varies depending on the type of ionic liquid. It should be noted that the effect of improving the impedance characteristics and the effect of improving the withstand voltage are manifested by different mechanisms, so that an ionic liquid having a high effect of improving the impedance characteristics does not necessarily have a high effect of improving the withstand voltage. It is.

  Further, it is considered that the ionic liquid that improves the withstand voltage acts effectively when it exists in the electrolyte near the dielectric surface. On the other hand, it is desirable that the ionic liquid that improves the impedance characteristics exists in the entire electrolyte because it acts during the formation of the electrolyte. Moreover, as described above, if it is excessively present, the impedance is increased, so that it is desirable to be present in a small amount.

  When an electrolytic capacitor is manufactured by the manufacturing method of the present invention, the ionic liquid concentration in the electrolyte near the dielectric surface can be increased by the effect of the anode surface treatment step, and good withstand voltage characteristics can be obtained. At that time, if the ionic liquid concentration of the composition for chemical polymerization used in the electrolyte layer forming step is kept low, both withstand voltage characteristics and good impedance characteristics can be achieved. Further, as an effective means, use of a plurality of ionic liquids can be mentioned. That is, the effect can be enhanced by using different types of ionic liquids used in the anode surface treatment step and the electrolyte layer forming step. In this case, it is desirable to use an ionic liquid having a high withstand voltage improvement effect in the anode surface treatment step and to use an ionic liquid having a high impedance characteristic improvement effect in the electrolyte layer forming step.

  When the chemical polymerization composition containing the ionic liquid, the polymerizable substance, and the polymerization accelerator described above 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 molar ratio of the ionic liquid and the polymerizable substance in the chemical polymerization composition constant or changing the molar ratio. . 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 in which the ionic liquid is present at a high concentration is ensured on the surface of the electrolyte layer on the anode side. And the ionic liquid content in the entire electrolyte layer can be kept low. Thereby, an electrolytic capacitor excellent in impedance characteristics and withstand voltage characteristics can be obtained.

(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 silver paste is dried, if 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 the 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. The voltage in actual use in consideration of variation and safety is, for example, 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 35 V to 45 V, for example. It is possible to obtain a withstand voltage approximately twice that of an electrolytic capacitor, that is, an actual use withstand voltage of 30V. In addition, the impedance characteristic can be made to be almost equal to or higher than that of an electrolytic capacitor manufactured without an ionic liquid. Such a tendency is also observed in an electrolytic capacitor using tantalum as an anode metal.

(Comparative Example 1)
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.

Conductive polymer raw material monomer, that is, PEDOT monomer (EDOT) as a polymerization substance, paratoluenesulfonic acid ferric acid as a polymerization accelerator, 1-butanol as a solvent, and blended in the following blending ratio, A composition for chemical polymerization used for forming the electrolyte layer was prepared.
-Conductive polymer raw material monomer 1g
・ Polymerization accelerator 2g
・ Solvent 3g
This chemical polymerization composition was mixed in a well-dried 30 cm ³ beaker, and then the anode was dipped in the chemical polymerization composition and pulled up, then at 100 ° C. for 1 hour, and further at 140 ° C. for 1 hour. Heat treatment for hours was performed. 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 impedance and withstand voltage (V) at 10 KHz and 100 KHz were measured.

  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. The obtained characteristics are shown in Table 1. The impedance (10 KHz and 100 KHz) was 2.5Ω and 0.4Ω, respectively, and the withstand voltage (V) was 39.2V.

(Comparative Example 2)
Except that the composition of the chemical polymerization composition was as follows, an anode foil and an electrolyte were formed in the same manner as in Comparative Example 1, an electrolytic capacitor was produced in the same manner, and the same measurement was performed. In addition, the ionic liquid A contained in the blend is ethylmethylimidazolium paratoluenesulfonic acid (EMImPTSO).
-Conductive polymer raw material monomer 1g
・ Polymerization accelerator 2g
・ Solvent 3g
-0.141 g of ionic liquid A (molar ratio to monomer 0.1)
The obtained characteristics are shown in Table 1. The impedances (10 KHz and 100 KHz) were 0.5Ω and 0.2Ω, and the withstand voltage (V) was 43.8 V. Compared with Comparative Example 1, the impedance (10 KHz and 100 KHz) was reduced and the withstand voltage was improved. .

(Comparative Example 3)
An anode foil was formed in the same manner as in Comparative Example 1. Thereafter, the anode foil was immersed in EMImPTSO at room temperature (anode surface treatment step). Thereafter, an electrolyte was formed by the same method as in Comparative Example 1, an electrolytic capacitor was produced by the same method, and the same measurement was performed. In addition, the ionic liquid is not included in the chemical polymerization composition as in Comparative Example 1.

  The obtained characteristics are shown in Table 1. The impedances (10 KHz and 100 KHz) were 2.5Ω and 0.4Ω, and the withstand voltage (V) was 50.4 V. The withstand voltage was improved with respect to Comparative Example 1 over Comparative Example 2, but the impedance was large. There was no improvement.

Example 1
An anode foil was formed in the same manner as in Comparative Example 1. Thereafter, the anode foil was immersed in EMImPTSO at room temperature (anode surface treatment step). Thereafter, an anode foil and an electrolyte were formed in the same manner as in Comparative Example 1 except that the composition of the chemical polymerization composition was as follows, and an electrolytic capacitor was produced in the same manner, and the same measurement was performed. It was. The ionic liquid A included in the formulation is EMImPTSO. That is, an electrolytic capacitor was produced and measured in the same anode surface treatment process as in Comparative Example 3 and the electrolyte formation process as in Comparative Example 2.
-Conductive polymer raw material monomer 1g
・ Polymerization accelerator 2g
・ Solvent 3g
-0.141 g of ionic liquid A (molar ratio to monomer 0.1)
The obtained characteristics are shown in Table 1. The impedance (10 KHz and 100 KHz) is 0.5Ω and 0.2Ω, respectively, and the withstand voltage (V) is 49.6 V. Like the comparative example 2, the impedance (10 KHz and 100 KHz) is reduced with respect to the comparative example 1. In addition, the withstand voltage was improved over that of Comparative Example 2.

(Comparative Example 4)
Except for using BMImTFSI instead of the ionic liquid EMImPTSO in the anode surface treatment step, an anode foil and an electrolyte were formed in the same manner as in Comparative Example 3 , an electrolytic capacitor was produced in the same manner, and the same measurement was performed. It was. In addition, the ionic liquid is not included in the chemical polymerization composition as in Comparative Example 1.
The obtained characteristics are shown in Table 1. The impedance (10 KHz and 100 KHz) is 2.6Ω and 0.6Ω, and the withstand voltage (V) is 57.1 V. Although the impedance (10 KHz and 100 KHz) does not change compared to Comparative Example 1, the withstand voltage is large. Improved. In addition, even when compared with Comparative Example 3, it can be seen that the effect of improving the withstand voltage is large, and the effect of improving the withstand voltage is higher in BMImTFSI than in EMImPTSO.

(Example 2)
An anode foil was formed in the same manner as in Comparative Example 1. Thereafter, the anode foil was immersed in BMImTFSI at room temperature (anode surface treatment step). Thereafter, except that the composition of the chemical polymerization composition was changed as follows, an anode foil and an electrolyte were formed in the same manner as in Comparative Example 1, an electrolytic capacitor was produced in the same manner, and the same measurement was performed. It was. In addition, the ionic liquid A contained in a mixing | blending is BMImTFSI used for the anode surface treatment process. That is, an electrolytic capacitor was prepared and measured in the same anode surface treatment process as in Comparative Example 4 and the electrolyte formation process as in Comparative Example 2 . This is equivalent to performing Example 1 using BMImTFSI instead of the ionic liquid EMImPTSO.
-Conductive polymer raw material monomer 1g
・ Polymerization accelerator 2g
・ Solvent 3g
・ Ionic liquid A 0.210 g (molar ratio to monomer 0.1)
The obtained characteristics are shown in Table 1. The impedance (10 KHz and 100 KHz) is 1.5Ω and 0.2Ω, and the withstand voltage (V) is 58.5 V, respectively. Compared with Comparative Example 1, the impedance (10 KHz and 100 KHz) is reduced, and the withstand voltage is a comparative example. Improved to be equivalent to 4.

(Example 3)
An anode foil was formed in the same manner as in Comparative Example 1. Thereafter, the anode foil was immersed in BMImTFSI at room temperature (anode surface treatment step). Thereafter, except that the composition of the chemical polymerization composition was changed as follows, an anode foil and an electrolyte were formed in the same manner as in Comparative Example 1, an electrolytic capacitor was produced in the same manner, and the same measurement was performed. It was. The ionic liquid A contained in the blend is EMImPTSO used in the anode surface treatment process. That is, after performing the same anode surface treatment process as in Comparative Example 2, an electrolyte using EMImPTSO was formed, and an electrolytic capacitor was produced and measured. This corresponds to the implementation of Example 1 or Example 2 using the ionic liquid BMImTFSI for the anode surface treatment step and the ionic liquid EMImPTSO for the electrolyte formation step.
-Conductive polymer raw material monomer 1g
・ Polymerization accelerator 2g
・ Solvent 3g
-0.141 g of ionic liquid A (molar ratio to monomer 0.1)
The obtained characteristics are shown in Table 1. The impedances (10 KHz and 100 KHz) are 0.6Ω and 0.2Ω, respectively, and the withstand voltage (V) is 55.5 V. The same impedance as in Comparative Example 2 and Example 1, and Comparative Example 4 and Example 2 It means that the withstand voltage was realized at the same time.

Table 1 shows the measurement results of the impedance (10 KHz and 100 KHz) and withstand voltage (V) of the electrolytic capacitors obtained in Examples 1 to 3 and Comparative Examples 1 to 4 .

  In the electrolytic capacitor of the present invention, the withstand voltage characteristic and the impedance characteristic are highly compatible, and the electrolytic capacitor can be suitably applied to, for example, a power supply rectifier circuit, a high frequency circuit, a coupling circuit, various communication devices, and the like.

3 is a diagram showing a cross-sectional form of an electrolyte layer of the electrolytic capacitor produced in Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode metal 2 Dielectric film 3 Conductive layer 4 Cathode.

Claims (6)

An electrolytic capacitor manufacturing method in which an electrolyte containing an ionic liquid and a conductive polymer is sandwiched between an anode made of an anode metal and a dielectric, and a cathode,
The contacting with the dielectric layer a liquid containing the ionic liquid (excluding the case where the repair chemical conversion in a liquid containing an ionic liquid) process and, of the conductive polymer containing an ionic liquid monomer over or O Forming an electrolyte for polymerizing ligomer. A first step of bringing the dielectric layer on the anode metal into contact with a first liquid containing an ionic liquid; and a second liquid for forming the electrolyte, which is performed after the first step. and a second step of contacting the second liquid, wherein the conductive polymer monomer over or O oligomer, and contains a polymerization accelerator of the monomer over or O oligomer, and, an ionic liquid The electrolytic capacitor manufacturing method according to claim 1, wherein the electrolytic capacitor is contained. The first type of ionic liquid contained in the liquid, method of manufacturing an electrolytic capacitor according to differ from the type of ionic liquid contained in 請 Motomeko 2 you wherein said second liquid. The anion component of the ionic liquid contained in the second liquid is at least one selected from the group of the ionic liquid represented by the general formula (1) and the general formula (2). to method of electrolytic capacitors according to claim 2 or 3.
R _A OSO ₃ ^- (1)
R _A SO ₃ ^- (2)
(In the above general formulas (1) and (2), R _A represents an aliphatic hydrocarbon group or an aromatic hydrocarbon group which may have a substituent.) Characterized in that R _A is an aliphatic hydrocarbon group, an aromatic hydrocarbon group containing a fluorine atom, according to claim 4 manufacturing method of electrolytic capacitors according. Anionic component of the at least one ionic liquid contained in the first liquid, the electrolytic capacitor according to any one of claims 3-5, characterized in that it is not contained in said second liquid Production method.

Images