JP4776338B2 - Conductive polymer dopant solution, conductive polymer oxidant / dopant, conductive composition, solid electrolytic capacitor and method for producing the same - Google Patents

Description

  The present invention relates to a dopant solution and an oxidant / dopant used for forming a conductive composition, the conductive composition, a solid electrolytic capacitor having the conductive composition, and a method for manufacturing the same.

  Solid electrolytic capacitors using a conductive polymer as a solid electrolyte have various characteristics such as less ignition and lower ESR (equivalent series resistance) than conventional solid electrolytic capacitors using manganese dioxide as a solid electrolyte. The market is expanding at a rapid pace.

  The conductive polymer is generally produced by a chemical oxidative polymerization method. For example, a transition metal salt of an organic sulfonic acid such as iron paratoluenesulfonate is used as an oxidizing agent and a dopant, and 3,4-ethylene is used. This is performed by polymerizing monomers such as dioxythiophene (Patent Documents 1 and 2).

  However, although this method is suitable for mass production, there is a problem that the transition metal used as the oxidizing agent remains in the conductive polymer. Therefore, even if a washing process is performed to remove the transition metal, the transition metal has a property that it is difficult to remove completely. If the transition metal remains in the conductive polymer, the conductivity is changed by the change in the valence of the transition metal. The deterioration of the polymer is remarkably accelerated, and the solid electrolytic capacitor using the polymer as a solid electrolyte has a problem of impairing long-term reliability. For this reason, it has been proposed to use a peroxide other than a transition metal salt as an oxidizing agent, for example, a peroxide as an oxidizing agent, but when 3,4-ethylenedioxythiophene is used as a monomer, In comparison, the reaction efficiency is very bad, and the conductivity of the obtained conductive polymer is very bad.

Japanese Patent Laid-Open No. 10-50558 JP 2000-106331 A

  The present invention has been made in view of the above circumstances, and an oxidant / dopant for forming a conductive composition having high conductivity with good reaction efficiency, and a dopant solution for constituting the oxidant / dopant. It is an object of the present invention to provide a conductive electrolytic composition, a solid electrolytic capacitor using the conductive composition, and a method for producing the same.

  The conductive polymer dopant solution of the present invention that has achieved the above object is characterized in that it contains at least one alkylamine salt or imidazole salt of naphthalenesulfonic acid at a concentration of 20% by mass or more. To do.

  The “imidazole salt of naphthalene sulfonic acid” as used in the present invention is not only a salt composed of naphthalene sulfonic acid and imidazole, but also naphthalene sulfonic acid and an imidazole derivative (for example, 2-position or 4 of the imidazole ring described later) It is a concept including a salt composed of an imidazole derivative whose position is substituted with an alkyl group or a phenyl group.

  In addition, the oxidizing agent / dopant of the present invention is characterized by having the following aspect (1) or (2).

  (1) The conductive polymer dopant solution of the present invention and an aqueous solution containing persulfate at a concentration of 20% by mass or more, and the alkyl of naphthalene sulfonic acid contained in the conductive polymer dopant solution The persulfate contained in the aqueous persulfate solution is 0.3 to 2.5 mol per 1 mol of the amine salt or imidazole salt.

  (2) Naphthalene sulfone, which is a precipitate formed by bringing the dopant solution for a conductive polymer of the present invention into contact with an aqueous solution containing a persulfate at a concentration of 20% by mass or more, and is measured by the following method The ratio of acid to persulfuric acid is 0.3 to 2.5 moles of persulfuric acid per mole of naphthalenesulfonic acid.

  Here, the ratio of naphthalenesulfonic acid and persulfuric acid in the precipitate is determined by putting the precipitate in distilled water, sealing it, and allowing it to stand at 50 ° C. for 1 week to decompose persulfuric acid into sulfuric acid. Obtained as the ratio of naphthalene sulfonic acid and sulfuric acid obtained by analysis by ion chromatography.

  The conductive composition of the present invention is characterized by being formed by a reaction between the oxidizing agent / dopant of the aspect (2) and thiophene or a derivative thereof.

  Furthermore, the solid electrolytic capacitor of the present invention is characterized by having, as a solid electrolyte, a conductive composition formed by a reaction between the oxidizing agent / dopant of the aspect (2) and thiophene or a derivative thereof. is there.

  Further, the method for producing a solid electrolytic capacitor of the present invention comprises a solution containing the above-described conductive polymer dopant solution of the present invention in a capacitor element, and then an aqueous solution containing a persulfate at a concentration of 20% by mass or more. After the capacitor element is immersed or an aqueous solution containing a persulfate at a concentration of 20% by mass or more is immersed in the capacitor element, the capacitor element is added to the conductive polymer dopant solution of the present invention. By immersing, the step (A) of precipitating the oxidant / dopant for conductive polymer and the oxidant / dopant for conductive polymer and thiophene or a derivative thereof are reacted to form a conductive composition. It has a process (B) and the process (C) which assembles a solid electrolytic capacitor using the capacitor | condenser element which has the said electroconductive composition.

  The conductive composition of the present invention is composed of a thiophene polymer or a derivative thereof polymerized by incorporating the oxidant / dopant of the present invention as a main component. In the present invention, the conductive composition is a conductive polymer. Since the oxidizer / dopant does not contain a metal salt, the conductive composition is composed of thiophene polymerized by incorporating the above dopant or polymer thereof, even if some unreacted components or reaction residues are contained. Without accelerating the deterioration of the polymer of the derivative, it has almost the same characteristics as the conductive polymer and can be used for almost the same application as the conductive polymer. It means that it may be configured to include them without removing them. In other words, the conductive composition of the present invention is not only composed of a conductive polymer (thiophene polymerized by incorporating the above specific dopant or a derivative thereof) as a main component, In addition to the conductive polymer, it is a concept that includes an unreacted component or a reaction residue.

  According to the oxidant / dopant for conductive polymer of the present invention, a conductive composition having high conductivity can be formed with good reaction efficiency. The conductive polymer dopant solution of the present invention can constitute the conductive polymer oxidizing agent and dopant of the present invention having the above-described effects.

  And according to the solid electrolytic capacitor of this invention and its manufacturing method, a solid electrolytic capacitor with high long-term reliability can be provided.

  That is, in the present invention, as an oxidizing agent / dopant used to obtain a conductive composition, a precipitate produced from a dopant solution containing an alkylamine salt or imidazole salt of naphthalenesulfonic acid and a persulfate aqueous solution is used. In addition, the oxidant / dopant does not contain a metal salt that causes the deterioration of the conductive polymer. In addition, since the oxidant / dopant can polymerize thiophene or a derivative thereof in a state where it exists as a precipitate rather than in a low concentration solution state, the thiophene or the derivative thereof can be polymerized efficiently. For this reason, a conductive composition having high reaction efficiency and high conductivity can be formed.

  Therefore, the solid electrolytic capacitor according to the present invention having the conductive composition of the present invention as a solid electrolyte becomes more reliable than the conventional one.

  In addition, according to the oxidizing agent / dopant of the present invention, a conductive composition having high conductivity and not containing a metal salt can be polymerized. No degradation occurs. Therefore, the conductive composition of the present invention is mainly used for a solid electrolyte of a solid electrolytic capacitor. In addition to this, for example, a positive electrode active material of a battery, an antistatic sheet, and an antistatic paint are utilized by utilizing these characteristics. It can be suitably used as an antistatic agent such as an antistatic resin, and a corrosion-resistant agent for anti-corrosion paints.

  The dopant solution for a conductive polymer of the present invention is for constituting an oxidizing agent and a dopant for a conductive polymer together with a persulfate aqueous solution. The alkylamine salt or imidazole salt of naphthalenesulfonic acid (hereinafter referred to as both) At least one of which may be referred to collectively as “naphthalene sulfonate” in a concentration of 20% by mass or more.

  The dopant solution for a conductive polymer of the present invention contains naphthalene sulfonate at a high concentration, and immediately comes into contact with a high-concentration persulfate aqueous solution. Dopant) can be produced.

  For example, in the production of a solid electrolytic capacitor, in order to attach a conductive polymer that is a solid electrolyte to a capacitor element, the capacitor element is immersed in a solution containing a monomer for forming the conductive polymer. There is a case where a method of polymerizing and forming a conductive polymer directly on the surface of the capacitor element is employed. Conventionally, an oxidizing agent / dopant that functions as an oxidant for polymerizing monomers and is incorporated into the formed conductive polymer and serves as a dopant is contained in the monomer-containing solution to increase the conductivity. It was difficult to increase the concentration of the oxidizer and dopant in the monomer solution, and it was difficult to improve the reaction efficiency and the conductivity of the conductive polymer after polymerization. there were.

  On the other hand, the dopant solution of the present invention has a high concentration and can easily generate an oxidant / dopant as a precipitate by contacting with the high concentration persulfate aqueous solution. Therefore, for example, since an oxidizing agent and a dopant can be directly deposited on the surface of the capacitor element, a conductive composition having excellent conductivity can be obtained with high reaction efficiency on the surface of the capacitor element.

  The naphthalene sulfonate used in the dopant solution of the present invention is an alkylamine salt or imidazole salt of naphthalene sulfonic acid. With these naphthalene sulfonates, it is possible to form a high-concentration solution using water as a solvent, and it is possible to constitute an oxidizing agent and dopant for a conductive polymer having a good function.

  The alkylamine constituting the alkylamine salt of naphthalenesulfonic acid preferably has 1 to 12 carbon atoms. Preferable specific examples include methylamine, ethylamine, propylamine, butylamine, octylamine, dodecylamine, 3-ethoxypropylamine, 3- (2-ethylhexyloxy) propylamine and the like.

  As the imidazole constituting the imidazole salt of naphthalenesulfonic acid, imidazole itself, or an imidazole substituted with an alkyl group having 1 to 20 carbon atoms or a phenyl group is preferable. In addition, when the imidazole constituting the imidazole salt of naphthalenesulfonic acid is an imidazole substituted with an alkyl group having 1 to 20 carbon atoms or a phenyl group, it can be produced at low cost and has good productivity. The substitution position is preferably the 2-position or 4-position of imidazole.

  Preferable specific examples of imidazole constituting the imidazole salt of naphthalenesulfonic acid include, for example, imidazole, 1-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-butylimidazole, 2-undecylimidazole, 2- Phenyl imidazole, 4-methyl imidazole, 4-undecyl imidazole, 4-phenyl imidazole, 2-ethyl-4-methyl imidazole, 1,2-dimethyl imidazole, etc. are mentioned, especially imidazole, 2-methyl imidazole, 4-methyl Imidazole is preferred.

  The naphthalene sulfonic acid constituting the naphthalene sulfonate has α and β isomers. Among the naphthalene sulfonates contained in the dopant solution of the present invention, the content of β naphthalene sulfonate is included. The amount is preferably 95 mol% or more, for example. The reason is not clear, but among the contained naphthalene sulfonate, the conductive composition obtained using a dopant solution having a content of β-naphthalene sulfonate of 95 mol% or more has better conductivity. Therefore, the characteristics of the solid electrolytic capacitor using this can be further improved.

  Examples of the method for increasing the ratio of β-naphthalene sulfonic acid in naphthalene sulfonate include, for example, a method of synthesizing naphthalene sulfonic acid for constituting naphthalene sulfonate at a lower temperature, α-naphthalene sulfonate and β-naphthalene. A method for adjusting the purification conditions by utilizing the difference in crystallinity of the sulfonate is exemplified.

  Examples of the solvent for the dopant solution of the present invention include water-compatible organic solvents such as water and alcohol. These may be used alone or in combination of two or more.

  In particular, when the alcohol content in the solvent is 5% by mass or more, for example, when the dopant solution is attached to the capacitor element in order to form a conductive composition on the surface of the capacitor element, the dopant solution This is preferable because it penetrates better into the pores of the capacitor element which is a porous body. Moreover, the higher the alcohol content in the solvent, the easier the dopant solution dries during the formation of the precipitate. Furthermore, even if the persulfate aqueous solution is attached after the dopant solution is attached to the capacitor element or the like, Since the salt is difficult to dissolve in the dopant solution solvent, the persulfate can be prevented from flowing without adhering, and the precipitate generation efficiency is improved. It becomes. In addition, the higher the alcohol content in the solvent, the more difficult the naphthalene sulfonate has water of crystallization, so the surface of the precipitate becomes smoother. Therefore, when the deposit is deposited on the surface of the capacitor element and used for forming a conductive composition, the adhesion of the resulting conductive composition to the surface of the capacitor element is also improved.

  As an alcohol used for the solvent of the dopant solution, for example, an alcohol having 1 to 4 carbon atoms (methanol, ethanol, propanol, butanol) is preferable, and ethanol is particularly preferable.

  The concentration of naphthalene sulfonate in the dopant solution of the present invention is 20% by mass or more, and preferably 40% by mass or more. By containing naphthalene sulfonate at a high concentration in this way, a precipitate (oxidant and dopant) can be generated favorably and quickly by contact with a high concentration persulfate aqueous solution. Therefore, it is possible to facilitate the production of a solid electrolytic capacitor using a conductive composition formed using this precipitate. That is, when forming the precipitate (oxidizing agent for conductive polymer and dopant) using the dopant solution of the present invention and a persulfate aqueous solution, for example, a capacitor element or other substrate is used as the dopant solution. Is then immersed in a persulfate aqueous solution, or in a persulfate aqueous solution followed by a dopant solution. If the concentration of naphthalene sulfonate in the dopant solution is too low, naphthalene sulfone is used. Since the acid salt does not sufficiently adhere to the capacitor element and other base materials, the precipitate cannot be formed satisfactorily, and as a result, the conductive composition cannot be satisfactorily formed. In addition, it is preferable that the upper limit of the density | concentration of the naphthalenesulfonate of a dopant solution is 80 mass%, for example.

  By the way, naphthalene sulfonates such as sodium naphthalene sulfonate, calcium naphthalene sulfonate, ammonium naphthalene sulfonate, etc., when dissolved in an aqueous solution, can only be dissolved at a concentration of about 10% by mass. Since only a solution having a lower concentration can be obtained, a high-concentration naphthalene sulfonate solution such as the dopant solution of the present invention cannot be obtained.

  Moreover, it is preferable to add an emulsifier to the dopant solution of the present invention. This is because the polymerization reaction of thiophene or a derivative thereof can proceed more uniformly by adding an emulsifier. Various emulsifiers can be used, and alkylamine oxide is particularly preferable. Even if the alkylamine oxide remains in the conductive composition, the electrical conductivity of the conductive composition is greatly reduced, or when the conductive composition is used as a solid electrolyte of a solid electrolytic capacitor, the capacitor There will be no significant degradation of the function. The alkyl group in the alkylamine oxide preferably has 1 to 20 carbon atoms. Further, when the polymerization reaction of thiophene or a derivative thereof proceeds, the pH of the reaction system decreases accordingly, and the alkylamine oxide also has an action of suppressing such a decrease in pH.

  The emulsifier concentration in the dopant solution of the present invention is preferably 0.01 to 2% by mass, for example.

  The dopant solution of the present invention preferably has a pH of 1 or more, more preferably 4 or more. As will be described in detail later, when producing a solid electrolytic capacitor having a conductive composition obtained using the dopant solution of the present invention, there is a step of immersing the capacitor element in the dopant solution. For example, in the case of an aluminum capacitor If the pH of the dopant solution is too low, the dielectric layer of the capacitor element may be destroyed during the immersion, and an aluminum capacitor having excellent characteristics may not be obtained. However, a tantalum capacitor, a niobium capacitor, or the like may have a pH of less than 1 because the acid resistance of the dielectric layer related to the capacitor element is strong. Incidentally, in the case of an organic sulfonic acid iron salt that has been used in the production of a conventional solid electrolytic capacitor, the pH is about 0.5, and is not necessarily suitable for the production of an aluminum capacitor.

  In the dopant solution of the present invention, for example, by using the above alkylamine oxide as an emulsifier, a decrease in pH of the reaction system accompanying the polymerization reaction of thiophene or a derivative thereof is suppressed. Therefore, a dopant solution having such an emulsifier can be preferably used particularly for the production of an aluminum capacitor.

  Of the oxidant / dopant for conductive polymer of the present invention, the above aspect (1) comprises the above-described dopant solution for conductive polymer of the present invention and an aqueous solution having a persulfate concentration of 20% by mass or more. Has been.

  The oxidant / dopant for conductive polymer of the aspect (1) is for forming the oxidant / dopant (precipitate) of the aspect (2). That is, when the dopant solution for a conductive polymer of the present invention comes into contact with a persulfate aqueous solution that is an oxidant used for conductive polymer polymerization, the precipitate [oxidant and dopant in the form of (2) as described above] ] Cannot be mixed with the persulfate aqueous solution before the stage of actually polymerizing the conductive polymer. Therefore, the conductive polymer oxidizing agent / dopant of aspect (1) is composed of a combination of the above-described specific persulfate aqueous solution and the above-described specific persulfate aqueous solution of the present invention, which are packaged separately. Is done.

  Examples of the persulfate according to the aqueous persulfate solution for constituting the conductive polymer oxidizing agent / dopant of the aspect (1) include sodium persulfate, potassium persulfate, barium persulfate, persulfate, and the like. Examples include persulfates excluding transition metal salts of persulfates, such as ammonium sulfate. Since sodium, potassium, barium, and the like are not transition metals, there is almost no effect of deteriorating the conductivity of the conductive polymer. However, ammonium persulfate is particularly preferable from the viewpoint that the influence of the metal salt remaining in the capacitor on the electrical characteristics of the capacitor remains.

  The persulfate concentration in the persulfate aqueous solution is 20% by mass or more, and preferably 40% by mass or more. By containing the persulfate at a high concentration in this way, a precipitate (oxidant / dopant) can be generated satisfactorily and quickly by contact with the dopant solution of the present invention. Therefore, it is possible to facilitate the production of a solid electrolytic capacitor using a conductive composition formed using this precipitate. That is, when forming the precipitate [oxidant and dopant of aspect (2)] using the oxidant and dopant of aspect (1), as described above, for example, a capacitor element or other group. The material is immersed in a dopant solution and then immersed in a persulfate aqueous solution, or immersed in a persulfate aqueous solution and then immersed in a dopant solution, but the persulfate concentration of the persulfate aqueous solution is If it is too low, the persulfate does not sufficiently adhere to the capacitor element and other base materials, so that the precipitate cannot be formed satisfactorily, and as a result, the conductive composition cannot be satisfactorily formed. In addition, it is preferable that the upper limit of the persulfate density | concentration of persulfate aqueous solution is 50 mass%, for example.

  In the oxidizing agent / dopant of aspect (1), the persulfate contained in the persulfate aqueous solution is 0.3 mol or more with respect to 1 mol of naphthalenesulfonate contained in the dopant solution of the present invention. More preferably, it is 0.5 mol or more, 2.5 mol or less, more preferably 2.0 mol or less. If the naphthalene sulfonate in the dopant solution and the persulfate in the aqueous persulfate solution are an oxidizing agent and a dopant configured in the above ratio, the dopant solution and the aqueous persulfate solution are brought into contact with each other. By this, it is possible to generate a precipitate (oxidant / dopant) capable of forming a conductive composition having excellent conductivity with good reaction efficiency.

  The dopant solution relating to the oxidizing agent / dopant of the aspect (1) is relatively expensive while it can be stored for a long time. On the other hand, the persulfate aqueous solution is inexpensive, but it is a persulfate even at room temperature. Because of the decomposition of, the long-term storage is not possible. In the oxidizing agent / dopant of aspect (1) of the present invention, the dopant solution and the persulfate aqueous solution are packaged separately, so that an expensive dopant solution can be stored for a long period of time, while being inexpensive as necessary. Since only a new persulfate aqueous solution can be changed to a new one, it is possible to produce a precipitate having always good characteristics while suppressing an increase in cost.

  The oxidizer and dopant for the conductive polymer of the aspect of (2) is a precipitate produced by bringing the dopant solution of the present invention into contact with an aqueous solution of persulfate having a concentration of 20% by mass. It is obtained by using the oxidant and dopant for conductive polymer of the aspect.

  In the precipitate which is the oxidizing agent and dopant of the aspect (2), the ratio of naphthalenesulfonic acid and persulfuric acid measured by the following method is 0.3 mol or more per mole of naphthalenesulfonic acid. More preferably, it is 0.6 mol or more and 2.5 mol or less, more preferably 1.8 mol or less.

  Here, the ratio of naphthalenesulfonic acid and persulfuric acid in the precipitate is determined by putting the precipitate in distilled water, sealing it, and allowing it to stand at 50 ° C. for 1 week to decompose persulfuric acid into sulfuric acid. The ratio of naphthalene sulfonic acid and sulfuric acid is determined by analysis by ion chromatography. That is, since the sulfuric acid is derived from persulfuric acid, the ratio of naphthalenesulfonic acid and sulfuric acid is directly the ratio of naphthalenesulfonic acid and persulfuric acid in the precipitate. In order to determine the ratio of naphthalenesulfonic acid and sulfuric acid in the supernatant, a calibration curve prepared in advance using an aqueous solution in which the ratio of naphthalenesulfonic acid and sulfuric acid is varied may be used.

  The ratio of naphthalene sulfonic acid and persulfuric acid by the above measurement is based on the ratio of naphthalene sulfonate in the dopant solution used in the formation of the precipitate and the persulfate in the aqueous persulfate solution. If it is a precipitate obtained from the dopant solution of the present invention and a high-concentration persulfate aqueous solution and the ratio of naphthalene sulfonic acid and persulfuric acid determined by the above measurement method is the above predetermined value, the conductivity is excellent. Can be formed with good reaction efficiency.

  In the conductive composition of the present invention, thiophene or a derivative thereof is used as a monomer. Examples of thiophene derivatives include 3,4-ethylenedioxythiophene, 3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene, 3,4-alkylthiophene, and 3,4-alkoxythiophene. And the alkyl group or alkoxy group preferably has 1 to 16 carbon atoms.

  In the polymerization of thiophene or a derivative thereof, since thiophene or a derivative thereof is in a liquid state, it can be used as it is. However, in order to make the polymerization reaction proceed more smoothly, thiophene or a derivative thereof can be used, for example, methanol, ethanol, propanol. It is preferable to dilute with an organic solvent such as butanol, acetone or acetonitrile to form a solution (organic solvent liquid).

  As an aspect at the time of polymerization of this thiophene or a derivative thereof, it is preferable to adopt a different aspect depending on the usage form of the conductive composition. For example, when the conductive composition is formed into a film or the like and incorporated in an application device of the conductive composition, any mode may be adopted, but the conductive composition is solid of a solid electrolytic capacitor. When used as an electrolyte, in the production process of a solid electrolytic capacitor, the precipitate as an oxidizing agent and a dopant is formed on the surface of the capacitor element, and thiophene or a derivative thereof is immersed in the monomer solution in the capacitor. Polymerization is preferably performed on the element surface.

  Hereinafter, a polymerization mode of thiophene or a derivative thereof will be described by taking as an example a case where a conductive composition is directly formed on a capacitor element of a solid electrolytic capacitor. By continuously performing the following steps (A) and (B), thiophene or a derivative thereof can be polymerized to form a conductive composition.

  Step (A) (Oxidizing agent / dopant precipitation step): The capacitor element is immersed in the dopant solution so that the dopant solution is immersed into the fine holes of the capacitor element, and then the above-described excess is added. After immersing in the aqueous solution of sulfate or immersing the capacitor element in the aqueous solution of persulfate so that the aqueous solution of persulfate is immersed into the fine pores of the capacitor element, this is added to the dopant solution. By immersing, the oxidant and dopant for the conductive polymer is deposited. The immersion time of the capacitor element in the dopant solution is preferably 5 seconds to 2 minutes, for example, and is preferably left for 1 to 10 minutes after taking out the capacitor element from the solution. Further, the immersion time of the capacitor element in the persulfate aqueous solution is preferably, for example, 5 seconds to 2 minutes, and after the capacitor element is taken out from the aqueous solution, it is preferably left, for example, for 1 to 10 minutes.

  Step (B) (polymerization step of thiophene or a derivative thereof); a solution obtained by diluting thiophene or a derivative thereof with an organic solvent so as to have a concentration of 5 to 100% by mass, more preferably 10 to 40% by mass (organic solvent solution) ), The capacitor element to which the precipitate is attached is immersed, and after 10 to 300 seconds, more preferably 20 to 120 seconds, the capacitor element is taken out from the monomer solution (organic solvent liquid of thiophene or a derivative), and 0 to 120 Polymerization of thiophene or a derivative thereof is carried out by allowing to stand at a temperature of ° C, more preferably 30 to 70 ° C for 1 minute to 1 day, more preferably 10 minutes to 2 hours.

  The step (A) and the step (B) may be carried out once each, but a series of operations for carrying out the step (A) and the step (B) continuously is performed twice or more (twice, three times). It is preferable to repeat such operations four times, and by performing such an operation, the entire surface including the inner surface of the hole of the capacitor element can be satisfactorily covered with the conductive composition.

  In the case where a film-like conductive composition is required depending on the use of the conductive composition, for example, in the above step (A), a substrate such as a ceramic plate is used instead of the capacitor element. And depositing the precipitate on the surface of the base material, then subjecting it to the step (B) to form the conductive composition on the surface of the base material, and then peeling the conductive composition from the base material. Methods can be adopted. In this case, for each condition in the step (A) and the step (B), the same conditions as those described above in the case where the conductive composition is formed on the surface of the capacitor element can be adopted.

  The conductive composition of the present invention obtained as described above includes, for example, a tantalum capacitor having an element composed of tantalum, a niobium capacitor having an element composed of niobium, and an aluminum capacitor having an element composed of aluminum. It is suitably used as a solid electrolyte of a solid electrolytic capacitor such as (aluminum multilayer capacitor, aluminum wound capacitor, etc.). That is, the solid electrolytic capacitor of the present invention has the conductive composition of the present invention as a solid electrolyte.

  In addition, when using the electrically conductive composition of this invention as a solid electrolyte of a solid electrolytic capacitor, it is preferable to superpose | polymerize a thiophene or its derivative (s) in the manufacturing process of the said solid electrolytic capacitor as mentioned above.

  The solid electrolytic capacitor of the present invention is manufactured through the step (C) of assembling a solid electrolytic capacitor using the capacitor element having the conductive composition obtained through the step (A) and the step (B). . The solid electrolytic capacitor of the present invention only needs to have the conductive composition of the present invention as a solid electrolyte (cathode layer), and other configurations are employed in conventionally known solid electrolytic capacitors. Configuration can be adopted.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention. The “pH” of the dopant solution (eg, naphthalene sulfonate solution) in the examples and comparative examples described later is the pH in the case of an aqueous solution and a mixed solvent solution of water and ethanol, and in the case of an ethanol solution. It means the pH when diluted twice with water.

Production example of naphthalene sulfonate (1)
To the reactor equipped with a stirrer, 150 mol of 98% concentrated sulfuric acid was added and heated to 80 ° C. with stirring. Thereto was added 100 moles of naphthalene over 10 minutes. After the addition, the temperature was raised to 140 ° C. and reacted for 3 hours. After completion of the reaction, the temperature was gradually lowered and water was added at about 80 ° C. to complete the reaction. Thereafter, naphthalenesulfonic acid was precipitated by lowering the temperature to 20 ° C., and this was recovered by a centrifuge. This naphthalenesulfonic acid was dissolved in pure water at 80 ° C. so that the concentration became 65% by mass. Thereafter, the temperature was gradually lowered while stirring the solution, and the precipitate deposited at room temperature (20 ° C.) was taken out by a centrifuge. After repeating this operation twice, 2-methylimidazole was slowly added to this until it was dissolved in pure water so that it might finally become 50 mass%, and pH was set to 5.0. This solution was filtered through a 0.3 μm glass filter, and then the concentration was calculated by measuring the dry weight of the solution. Pure water was added to a concentration of 40% by mass. An aqueous solution of 2-methylimidazole naphthalene sulfonate to be used was obtained. Analysis by ion chromatography to determine the isomer ratio (molar ratio) of 2-methylimidazole naphthalene sulfonate in this solution was β: α = 99: 1.

  For the naphthalene sulfonate [β: α = 99: 1 (molar ratio)] used in Examples 2 to 7, 13 and Comparative Examples 1 to 5 described later, the raw materials used may be changed as necessary. Other than that, it was manufactured by the same method as in the above manufacturing example (1).

Production example of naphthalene sulfonate (2)
The same operation as in the above production example (1) is performed until the step of filtering with a 0.3 μm glass filter, followed by concentration by distillation, and subsequently adding ethanol four times, and then measuring the dry weight. The concentration was calculated by adding ethanol so that the concentration was 50% by mass, and 2-methylimidazole naphthalenesulfonate [β: α = 99: 1 (molar ratio)] used in Example 8 described later. An ethanol solution was obtained.

  For the naphthalene sulfonate [β: α = 99: 1 (molar ratio)] used in Examples 9 to 11 and 14 and Comparative Examples 12 to 15 described later, the raw materials used may be changed as necessary. Other than that, it was produced by the same method as in Production Example (2) above.

Production example of naphthalene sulfonate (3)
To the reactor equipped with a stirrer, 150 mol of 98% concentrated sulfuric acid was added and heated to 80 ° C. with stirring. Thereto was added 100 moles of naphthalene over 10 minutes. After the addition, the temperature was raised to 120 ° C. and reacted for 3 hours. After completion of the reaction, the temperature was gradually lowered and water was added at about 80 ° C. to complete the reaction. Thereafter, naphthalenesulfonic acid was precipitated by lowering the temperature to 20 ° C., and this was recovered by a centrifuge. This naphthalenesulfonic acid was dissolved in pure water so as to have a concentration of 50% by mass, and 2-methylimidazole was slowly added until the pH reached 5.0. Then, after concentrating by distillation, ethanol was added so that it might become a 50 mass% concentration, and the ethanol solution of 2-methylimidazole naphthalenesulfonate used in Example 12 mentioned later was obtained. When analyzed by ion chromatography to determine the isomer ratio (molar ratio) of 2-methylimidazole naphthalenesulfonate in this solution, β: α = 90: 10.

<Formation and evaluation of conductive composition>
Example 1
10 ml of an aqueous solution of 2-methylimidazole naphthalenesulfonate having a concentration of 40% by mass (pH 5) obtained in Production Example (1) was placed in a 10 ml vial. This was impregnated with a ceramic plate of 5 × 30 mm (thickness 1 mm), and slowly pulled up after being left for 30 seconds. The ceramic plate taken out was allowed to stand at room temperature for 5 minutes, then impregnated with 10 ml of a 40% by weight ammonium persulfate aqueous solution contained in a 10 ml vial prepared in advance, slowly pulled up after standing for 30 seconds, and left at room temperature for 5 minutes. Thereafter, the ceramic plate was impregnated with 100% by mass of 3,4 ethylenedioxythiophene (liquid, the same applies hereinafter), slowly pulled up after 10 seconds, and left at 50 ° C. for 20 minutes. Thereafter, the ceramic plate was placed in 10 ml of pure water contained in a 10 ml vial for washing, allowed to stand for 5 minutes, pulled out, and dried at 50 ° C. for 5 minutes. This operation was repeated three times and then dried at 150 ° C. for 1 hour to form a conductive composition. Then, the sample was allowed to stand for 5 minutes with a load of 1.5 tons to make the film thickness uniform, and then the conductivity was measured at room temperature (about 25 ° C.) according to JIS K 7194. It was measured with a needle type conductivity measuring device [MCP-T600 (trade name) manufactured by Mitsubishi Chemical Corporation]. The results are shown in Table 1. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 1, ammonium persulfate was 1.27 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Example 2
Conductivity was the same as in Example 1 except that a 40% by mass naphthalene sulfonic acid 4-methylimidazole aqueous solution (pH 5) was used instead of the 40% by mass naphthalene sulfonic acid 2-methyl imidazole aqueous solution (pH 5). An electrically conductive composition was formed and its conductivity was measured. The results are shown in Table 1. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 2, ammonium persulfate was 1.27 mol with respect to 1 mol of naphthalene sulfonate in the dopant solution.

Example 3
A conductive composition was obtained in the same manner as in Example 1, except that a 40% by weight naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5) was used instead of a 40% by weight naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5). And the conductivity was measured. The results are shown in Table 1. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 3, ammonium persulfate was 1.23 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Example 4
Conductivity was the same as in Example 1 except that a 50% by weight naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5) was used instead of the 40% by weight naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5). An electrically conductive composition was formed and its conductivity was measured. The results are shown in Table 1. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 4, ammonium persulfate was 1.02 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Example 5
A conductive composition was formed in the same manner as in Example 1 except that a 30% by mass ammonium persulfate aqueous solution was used instead of the 40% by mass ammonium persulfate aqueous solution, and the conductivity was measured. The results are shown in Table 1. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 5, ammonium persulfate was 0.95 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Example 6
The same procedure as in Example 1 was performed except that an ethanol solution (pH 5) of naphthalenesulfonic acid 2-methylimidazole having a concentration of 40% by mass was used instead of the aqueous solution of 2-methylimidazole naphthalenesulfonic acid having a concentration of 40% by mass (pH 5). Then, a conductive composition was formed, and its conductivity was measured. The results are shown in Table 1. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 6, ammonium persulfate was 1.27 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Example 7
The same procedure as in Example 1 was performed except that an ethanol solution (pH 5) of 2-methylimidazole naphthalenesulfonate having a concentration of 60% by mass was used instead of the aqueous solution of 2-methylimidazole naphthalenesulfonate having a concentration of 40% by mass (pH 5). Then, a conductive composition was formed, and its conductivity was measured. The results are shown in Table 1. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 7, ammonium persulfate was 0.85 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Comparative Example 1
A conductive composition was formed in the same manner as in Example 1 except that a 10% by mass ammonium persulfate aqueous solution was used instead of the 40% by mass ammonium persulfate aqueous solution, and the conductivity was measured. The results are shown in Table 1.

Comparative Example 2
Except having changed each operation as follows, the electrically conductive composition was formed like Example 1 and the electrical conductivity was measured. A 10% by mass ammonium persulfate aqueous solution was used in place of the 40% by mass ammonium persulfate aqueous solution, and a ceramic plate impregnated in a 40% by mass naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5) was dried. And then slowly pulled up and left at room temperature for 5 minutes. Subsequently, after the operation of impregnating with an aqueous ammonium persulfate solution and allowing to stand at room temperature in the above procedure was repeated 4 times, 100% by mass of 3,4 ethylenedioxythiophene was impregnated with a ceramic plate, and then the same as in Example 1 Was performed. Table 1 shows the results of the conductivity measurement of the conductive composition.

Comparative Example 3
Conductivity was the same as in Example 1 except that a 10% by weight naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5) was used instead of the 40% by weight naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5). An electrically conductive composition was formed and its conductivity was measured. The results are shown in Table 1.

Comparative Example 4
Instead of a 40% by weight aqueous solution of naphthalenesulfonic acid 2-methylimidazole (pH 5), 10 ml of a 10% by weight aqueous solution of 2-methylimidazole naphthalenesulfonic acid (pH 5) was placed in a 10 ml vial. Here, a series of operations of impregnating a 5 × 30 mm (thickness 1 mm) ceramic plate, leaving it for 30 seconds, slowly raising it, and then leaving it at room temperature for 5 minutes was repeated four times. Thereafter, a conductive composition was formed in the same manner as in Example 1, and its conductivity was measured. The results are shown in Table 1.

Comparative Example 5
Conductivity was the same as in Example 1 except that a 40% by mass concentration of 2-methylimidazole aqueous solution of phenol sulfonic acid (pH 5) was used instead of the 40% concentration of β-naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5). An electrically conductive composition was formed and its conductivity was measured. The results are shown in Table 1.

Comparative Example 6
Conductivity was the same as in Example 1 except that a 40% by mass aqueous 2-methylimidazole sulfone isophthalate solution (pH 5) was used instead of the 40% by mass aqueous naphthalenesulfonic acid 2-methylimidazole solution (pH 5). An electrically conductive composition was formed and its conductivity was measured. The results are shown in Table 1.

Comparative Example 7
It replaced with 40 mass% concentration naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5), and it was carried out similarly to Example 1 except having used 40 mass% concentration butyl naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5). A conductive composition was formed and its conductivity was measured. The results are shown in Table 1.

Comparative Example 8
It replaced with 40 mass% concentration naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5), and carried out similarly to Example 1 except having used 40 mass% concentration para-toluenesulfonic acid 2-methylimidazole aqueous solution (pH 5). A conductive composition was formed and its conductivity was measured. The results are shown in Table 1.

Comparative Example 9
Implementation was carried out except that 40% by mass concentration of 1,3,6-naphthalene trisulfonic acid 2-methylimidazole aqueous solution (pH 5) was used instead of 40% by mass naphthalene sulfonic acid 2-methylimidazole aqueous solution (pH 5). A conductive composition was formed in the same manner as in Example 1, and its conductivity was measured. The results are shown in Table 1.

Comparative Example 10
A 40% by weight solution of ferric paratoluenesulfonate and butanol and 3,4 ethylenedioxythiophene were mixed at a mass ratio of 4: 1, shaken vigorously for 10 seconds, and then impregnated with a ceramic plate. After slowly pulling up later, it was left at 50 ° C. for 20 minutes. Thereafter, for washing, the ceramic plate was placed in 10 ml of pure water contained in a 10 ml vial, left for 5 minutes, pulled out, and dried at 50 ° C. for 5 minutes. After repeating this operation three times, a conductive composition was formed in the same manner as in Example 1 except that it was dried at 150 ° C. for 1 hour, and its conductivity was measured. The results are shown in Table 1.

  In Table 1, “(* 1)” means that the conductive composition was sparsely formed and the measurement of conductivity was impossible.

  As is clear from Table 1, in Examples 1 to 7, conductive compositions having excellent conductivity were obtained favorably, but Comparative Examples 1 to 1 using a low concentration dopant solution or persulfate solution. 4. In Comparative Examples 5 to 9 in which a solution of naphthalene sulfonate was not used as the dopant solution, precipitates that were both an oxidant and a dopant were not generated well on the ceramic plate surface, and the conductive composition was formed on the ceramic plate surface. It could not be formed uniformly. In particular, in Comparative Examples 2 and 4, although the number of impregnations with a low concentration dopant solution or persulfate aqueous solution was increased, the formation of precipitates and the conductive composition could not be formed well, It can be seen that it is important to use a high concentration dopant solution and a persulfate solution. Moreover, in the comparative example 10 which used the solution of the transition metal salt of organic sulfonic acid for the dopant solution, the electrical conductivity of the obtained electroconductive composition was inferior.

<Ratio of naphthalene sulfonic acid and persulfuric acid in precipitate (oxidizer and dopant)>
About the ceramic plate used in Examples 1-7 and Comparative Examples 2-4, the deposit formed with the dopant solution and the persulfate aqueous solution before impregnating 100 mass% 3,4 ethylenedioxythiophene adheres. Ten ceramic plates in the above state were put into a 10 ml vial, and 10 ml of distilled water was put therein. Then, with the vial sealed, the persulfuric acid was decomposed into sulfuric acid by leaving it at 50 ° C. for 1 week, and the supernatant was analyzed by ion chromatography. The ratio of naphthalenesulfonic acid as a dopant to persulfuric acid ( Molar ratio) was analyzed. The results are shown in Table 2.

<Evaluation with solid electrolytic capacitors (tantalum capacitors)>
Example 8
After immersing the tantalum sintered body in an aqueous phosphoric acid solution, electrolytic oxidation was performed by applying a voltage, and a dielectric film was formed on the surface of the tantalum sintered body to obtain a capacitor element. Next, the capacitor element was impregnated with the ethanol solution (pH 5 to 6) of 50% by mass of 2-methylimidazole naphthalenesulfonate produced in Production Example (2), taken out after 1 minute, and left for 5 minutes. Thereafter, this capacitor element was impregnated with a 45% by mass ammonium persulfate aqueous solution prepared in advance, taken out after 30 seconds, and left at room temperature for 10 minutes. Thereafter, the capacitor element was impregnated with 100% by mass of 3,4 ethylenedioxythiophene, pulled up after 5 seconds, and left at room temperature for 60 minutes. Thereafter, the device was impregnated with pure water, left for 30 minutes, taken out, and dried at 105 ° C. for 30 minutes. After repeating this operation 6 times, the layer of the conductive composition formed on the capacitor element was covered with a carbon paste and a silver paste to obtain a tantalum capacitor. In addition, in the dopant solution and ammonium persulfate aqueous solution which were used in Example 8, ammonium persulfate was 1.14 mol with respect to 1 mol of naphthalenesulfonate in a dopant solution.

Example 9
Tantalum was obtained in the same manner as in Example 8, except that an ethanol solution (pH 5) of 60% by mass of 2-methylimidazole naphthalene sulfonate was used instead of an ethanol solution (pH 5) of 50% by mass of 2-methylimidazole naphthalene sulfonate. A capacitor was produced. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 9, ammonium persulfate was 0.95 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Example 10
Instead of an ethanol solution (pH 5) of 50% by mass of naphthalenesulfonic acid 2-methylimidazole, a solution of 50% by mass of naphthalenesulfonic acid 2-methylimidazole [solvent is water: ethanol = 5: 5 (mass ratio), pH 5]. A tantalum capacitor was fabricated in the same manner as in Example 8 except that was used. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 10, ammonium persulfate was 1.14 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Example 11
Tantalum was obtained in the same manner as in Example 8 except that an ethanol solution (pH 5) of 50 mass% naphthalenesulfonic acid 4-methylimidazole was used instead of an ethanol solution (pH 5) of 2-methylimidazole 50 mass% naphthalenesulfonic acid. A capacitor was produced. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 11, ammonium persulfate was 1.14 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Example 12
50% by mass of 2-methylimidazole naphthalene sulfonate having a β: α = 90: 10 (molar ratio) produced in the above production example (3) instead of an ethanol solution (pH 5) of 50% by mass of 2-methylimidazole naphthalene sulfonate A tantalum capacitor was produced in the same manner as in Example 8 except that a mass% ethanol solution (pH 5) was used. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 12, ammonium persulfate was 1.14 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Example 13
A tantalum capacitor was prepared in the same manner as in Example 8 except that a 50% by mass naphthalenesulfonic acid 2-methylimidazole aqueous solution (pH 5) was used instead of the 50% by mass naphthalenesulfonic acid 2-methylimidazole ethanol solution (pH 5). Produced. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 13, ammonium persulfate was 1.14 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Example 14
The order in which the capacitor elements were impregnated was changed, and the impregnation was carried out with the exception that 45 mass% ammonium persulfate aqueous solution was impregnated first and then 50 mass% naphthalenesulfonic acid 2-methylimidazole ethanol solution (pH 5). A tantalum capacitor was produced in the same manner as in Example 8. In addition, in the dopant solution and ammonium persulfate aqueous solution used in Example 14, ammonium persulfate was 1.14 mol with respect to 1 mol of naphthalenesulfonate in the dopant solution.

Comparative Example 11
Tantalum was obtained in the same manner as in Example 8 except that an ethanol solution (pH 5) of 10% by mass of 2-methylimidazole naphthalenesulfonate was used instead of an ethanol solution (pH 5) of 2-methylimidazole of 50% by mass naphthalene sulfonate. A capacitor was produced.

Comparative Example 12
Instead of an ethanol solution (pH 5) of 50% by mass of 2-methylimidazole naphthalenesulfonate, an ethanol solution (pH 5) of 10% by mass of 2-methylimidazole naphthalenesulfonate was used, and a capacitor element (tantalum sintered body) was used as the solution. The tantalum capacitor was manufactured in the same manner as in Example 8, except that the operation of taking out the sample and then taking it out for 5 minutes was repeated 5 times.

Comparative Example 13
A tantalum capacitor was fabricated in the same manner as in Example 8 except that a 15% by mass ammonium persulfate aqueous solution was used instead of the 45% by mass ammonium persulfate aqueous solution.

Comparative Example 14
In place of the 45 mass% ammonium persulfate aqueous solution, a 15 mass% ammonium persulfate aqueous solution was used. The capacitor element was impregnated with the solution, taken out after 30 seconds and allowed to stand at room temperature for 10 minutes. A tantalum capacitor was produced in the same manner as in Example 8.

Comparative Example 15
A tantalum capacitor was prepared in the same manner as in Example 8 except that a 50% by mass aqueous solution of 2-methylimidazole of phenolsulfonic acid (pH 5) was used instead of the ethanol solution (pH 5) of 50% by mass of naphthalenesulfonic acid 2-methylimidazole. Produced.

Comparative Example 16
A tantalum capacitor in the same manner as in Example 8 except that a 50% by mass para-toluenesulfonic acid 2-methylimidazole aqueous solution (pH 5) was used instead of the 50% by mass naphthalenesulfonic acid 2-methylimidazole ethanol solution (pH 5). Was made.

Comparative Example 17
A tantalum capacitor was prepared in the same manner as in Example 8 except that a 50% by mass aqueous solution of 2-methylimidazole of 2-methylimidazole (pH 5) was used instead of the ethanol solution (pH 5) of 2-methylimidazole of 50% by mass naphthalene sulfonate. Produced.

Comparative Example 18
A tantalum capacitor was prepared in the same manner as in Example 8 except that a 50% by weight aqueous solution of 2-methylimidazole sulfoisophthalate (pH 5) was used instead of an ethanol solution (pH 5) of 50% by weight 2-methylimidazole naphthalenesulfonic acid. Produced.

Comparative Example 19
A tantalum capacitor was fabricated in the same manner as in Example 8 except that a 40 mass% ethanol solution of ferric paratoluenesulfonate was used instead of the dopant solution and the persulfate aqueous solution.

  In Examples 8 to 14, the ratio of naphthalene sulfonic acid and persulfuric acid was determined in the same manner as in Example 1 for the precipitate formed by impregnating the capacitor element with the dopant solution and the persulfate aqueous solution. The results are shown in Table 3.

  Moreover, about the tantalum capacitor of Examples 8-14 and Comparative Examples 11-19, the electrostatic capacitance and ESR were measured with the following method. The results are shown in Table 4.

Capacitance:
The capacitance was measured at 25 ° C. and 120 Hz using an LCR meter (4284A) manufactured by HEWLETT PACKARD.

ESR:
ESR was measured at 25 ° C. and 100 kHz using an LCR meter (4284A) manufactured by HEWLETT PACKARD.

  Note that “(* 2)” in Table 4 means that the capacitance and ESR were not measured because the entire capacitor element could not be covered with the conductive composition.

  As is apparent from Table 4, the tantalum capacitors of Examples 8 to 14 show good capacitance and ESR. In particular, the tantalum capacitors of Examples 8 to 12 and 14 using ethanol as an alcohol as the solvent of the dopant solution are better in both capacitance and ESR than the tantalum capacitor of Example 13 in which the dopant solution is an aqueous solution. .

  In contrast, the tantalum capacitors of Comparative Examples 11 to 14 using a low-concentration dopant solution or a persulfate aqueous solution, and the tantalum capacitors of Comparative Examples 15 to 18 using no naphthalene sulfonate solution as the dopant solution In addition, precipitates as an oxidizer and a dopant were not generated well on the surface of the capacitor element, and the entire capacitor element could not be covered with the conductive composition, so that it could not function effectively as a solid electrolytic capacitor. In particular, in Comparative Examples 12 and 14, although the number of impregnations with a low-concentration dopant solution or persulfate aqueous solution was increased, the capacitor element could not be satisfactorily covered with the conductive composition. It can be seen that it is important to use a high concentration dopant solution and a persulfate solution. In the tantalum capacitor of Comparative Example 19 in which the organic sulfonic acid transition metal salt solution was used as the dopant solution, both the capacitance and ESR were at the same level as the tantalum capacitors of Examples 8-14.

  40 tantalum capacitors of Examples 8 to 14 and Comparative Example 19 described above were prepared, and 20 capacitors randomly selected from the tantalum capacitors were measured for capacitance and ESR after being left at 125 ° C. for 300 hours. The average value was determined for each of the examples and comparative examples. The results are shown in Table 5.

  As is apparent from Table 5, the tantalum capacitors of Examples 8 to 14 are substantially maintained in capacitance and ESR even after being left at 125 ° C. for 300 hours, and have excellent long-term reliability. On the other hand, in the tantalum capacitor of Comparative Example 19, the electrostatic capacity and ESR after being left standing are deteriorated.

Claims (18)

Conductive polymer dopant solution containing at least one alkylamine salt or imidazole salt of naphthalenesulfonic acid at a concentration of 20% by mass or more, and an aqueous solution containing persulfate at a concentration of 20% by mass or more. The persulfate contained in the persulfate aqueous solution is 0.3 to 2.5 per 1 mol of the alkylamine salt or imidazole salt of naphthalenesulfonic acid contained in the dopant solution for conductive polymer. An oxidizing agent / dopant solution for a conductive polymer, characterized in that it is a mole. The oxidizing agent / dopant solution for a conductive polymer according to claim 1, wherein the concentration of at least one of an alkylamine salt or an imidazole salt of naphthalenesulfonic acid in the conductive polymer dopant solution is 40% by mass or more . The oxidant for conductive polymer according to claim 1 or 2, wherein the content of the alkylamine salt or imidazole salt of β-naphthalenesulfonic acid among the alkylamine salt or imidazole salt of naphthalenesulfonic acid is 95 mol% or more. Cum dopant solution . The oxidant and dopant solution for a conductive polymer according to any one of claims 1 to 3, wherein the conductive polymer dopant solution further contains an emulsifier . The oxidant / dopant solution for a conductive polymer according to claim 4, wherein the emulsifier is an alkylamine oxide having an alkyl group having 1 to 20 carbon atoms . The oxidant and dopant solution for a conductive polymer according to any one of claims 1 to 5, wherein the alkyl group of the alkylamine constituting the alkylamine salt of naphthalenesulfonic acid has 1 to 12 carbon atoms . The imidazole constituting the imidazole salt of naphthalene sulfonic acid is substituted at the 2- or 4-position with an alkyl group or phenyl group having 1 to 20 carbon atoms. Molecular oxidant and dopant solution . The pH of the dopant solution for conductive polymers is 1 or more, The oxidizing agent and dopant solution for conductive polymers according to any one of claims 1 to 7 . The oxidant and dopant solution for a conductive polymer according to claim 8, wherein the pH of the dopant solution for the conductive polymer is 4 or more . Alcohol is 5 mass% or more among all the solvents of the dopant solution for conductive polymers, The oxidizing agent and dopant solution for conductive polymers in any one of Claims 1-9 . Conductive polymer dopant solution containing at least one alkylamine salt or imidazole salt of naphthalenesulfonic acid at a concentration of 20% by mass or more, and an aqueous solution containing persulfate at a concentration of 20% by mass or more. The ratio of naphthalene sulfonic acid and persulfuric acid measured by the following method is 0.3 to 2.5 mol persulfuric acid per 1 mol of naphthalene sulfonic acid. An oxidizing agent and dopant for conductive polymers, characterized by
Here, the ratio of naphthalenesulfonic acid and persulfuric acid in the precipitate is determined by putting the precipitate in distilled water, sealing it, and allowing it to stand at 50 ° C. for 1 week to decompose persulfuric acid into sulfuric acid. Obtained as the ratio of naphthalene sulfonic acid and sulfuric acid obtained by analysis by ion chromatography. A conductive composition formed by a reaction of the oxidant and dopant for a conductive polymer according to claim 11 with thiophene or a derivative thereof. A solid electrolytic capacitor comprising, as a solid electrolyte, a conductive composition formed by a reaction between the oxidant and dopant for a conductive polymer according to claim 11 and thiophene or a derivative thereof. The solid electrolytic capacitor according to claim 13 , comprising a capacitor element made of aluminum, tantalum, or niobium. After impregnating the capacitor element with a conductive polymer dopant solution containing at least one of an alkylamine salt or an imidazole salt of naphthalenesulfonic acid at a concentration of 20% by mass or more, 20 persulfate is added. After immersing the capacitor element in an aqueous solution containing a concentration of not less than mass%, or soaking an aqueous solution containing a persulfate concentration of not less than 20 mass% into the capacitor element, an alkylamine of naphthalene sulfonic acid By immersing the capacitor element in a conductive polymer dopant solution containing at least one salt or imidazole salt at a concentration of 20% by mass or more , the conductive polymer oxidizing agent / dopant is deposited. Step (A);
A step (B) of reacting the oxidant and dopant for a conductive polymer with thiophene or a derivative thereof to form a conductive composition;
Step of assembling a solid electrolytic capacitor using the capacitor element having the conductive composition (C)
A method for producing a solid electrolytic capacitor, comprising: The manufacturing method of the solid electrolytic capacitor of Claim 15 which implements the said process (C), after repeating the series of operation which implements the said process (B) following the said process (A) twice or more. The method for producing a solid electrolytic capacitor according to claim 15 or 16 , wherein an aqueous solution containing persulfate at a concentration of 40% by mass or more is used in the step (A). Aluminum, the manufacturing method of solid electrolytic capacitor according to any one of claims 15-17 for use a capacitor element composed of a tantalum or niobium.