JPH0546692B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a solid electrolytic capacitor with good performance using a conductive polymer compound obtained by doping a specific polymer compound with a dopant as a solid electrolyte. Conventional electrolytic capacitors, such as aluminum electrolytic capacitors, have an aluminum oxide dielectric layer placed on an etched porous aluminum foil with a large specific surface area, and the electrolytic paper between the cathode foil and the electrolytic paper is impregnated with a liquid electrolyte. However, it is not preferable that the electrolyte is in a liquid state because it causes problems such as leakage, and therefore attempts have been made to replace the conductive layer with a solid electrolyte. These solid electrolytic capacitors have a structure in which a solid electrolyte is attached to a film-forming metal such as aluminum or tantalum that has an anodized film. Formed by thermal decomposition. Manganese dioxide is used. but,
Due to the high heat required during this thermal decomposition and the oxidizing effect of _NO However, it has extremely large drawbacks such as deterioration of dielectric properties. In addition, a process called reconstitution is also necessary. In order to compensate for these drawbacks, attempts have been made to form a solid electrolyte layer without applying high heat, that is, to use a highly conductive organic semiconductor material as the solid electrolyte. An example of this is a solid electrolyte containing a conductive polymer composition containing a 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex salt as described in JP-A-52-79255. Electrolytic capacitor, N-n-propylisoquinoline and 7,7, described in JP-A-58-17609
Solid electrolytic capacitors containing a complex salt of 8,8-tetracyanoquinodimethane as a solid electrolyte are known. These TCNQ complex salt compounds have poor adhesion to the anodic oxide film and have a conductivity of 10 ^-3 to 10 ^-2.
Since the value of S cm ^-1 is insufficient, the capacitance value of the capacitor is small and the dielectric loss is large. Furthermore, thermal stability over time is poor and reliability is low. An object of the present invention is to solve the above-mentioned conventional drawbacks and to provide a solid electrolytic capacitor in which an organic semiconductor having high conductivity and good adhesion to a dielectric film is used as a solid electrolyte. It has been found that this objective can be achieved by using a specific conductive polymer compound as a solid electrolyte. That is, the present invention is based on the following formula and/or [In the formula, R ₁ and R ₂ are hydrogen or a saturated hydrocarbon group having 6 or less carbon atoms, and Y ₁ and Y ₂ are anions. The combination of R ₁ Y ₁ and R ₂ Y ₂ may be present at the same time, or either combination may be absent. The number of carbon atoms is limited to 6 or less in order to obtain high conductivity. The present invention relates to a solid electrolytic capacitor characterized in that a conductive polymer compound obtained by doping a polymer compound having a repeating unit represented by the following formula with a dopant is used as a solid electrolyte. The solid electrolytic capacitor obtained by the present invention is
It has significantly superior performance in terms of capacity, dielectric loss, and stability over time compared to conventional solid electrolytic capacitors using inorganic oxide semiconductors or organic semiconductors. Furthermore, the solid electrolytic capacitor of the present invention has the following advantages compared to conventionally known solid electrolytic capacitors. Since the electrolyte layer can be formed without high-temperature heating, there is no damage to the oxide film on the anode, and there is no need to perform anodization (re-formation) for repair.
Therefore, the rated voltage can be increased several times compared to conventional capacitors, and the shape can be made smaller to obtain a capacitor with the same capacity and rated voltage. Leakage current is small. Capacitors with high withstand voltage can be manufactured. Since the electrolyte has a sufficiently high conductivity of 10 ⁻² to ^{10 3} S·cm ⁻¹ , there is no need to provide a conductive layer such as graphite. This simplifies the process and is advantageous in terms of cost. The electrolyte used in the solid electrolytic capacitor of the present invention is a polymer compound having repeating units represented by the above formula (1) and/or formula (2). Y ₁ and Y ₂ in formula (2) are anions, and specific examples thereof include halogen ions, BF ₄ ions, BR ₄ ions (R is a saturated hydrocarbon group having 6 or less carbon atoms or a phenyl group), PF ₆ ion, CH ₃ COO ion,
_SO4 ions, _CF3COO ions, _ClO4 ions and
Examples include AsF ₆ ion. Representative examples of polymer compounds having repeating units represented by formula (1) and/or formula (2) above include polybenzopyrroline, polybenzopyrroline hydrochloride, polybenzopyrroline fluoroacetate, and polybenzopyrroline iodide. Examples include methyl salt, polybenzopyrroline hydrogen tetrafluoroborate salt, and the like. The method for producing these polymer compounds is not particularly limited; for example, in the case of polybenzopyrroline, it can be produced by treating dicyanobenzene with an appropriate base. The above-mentioned polymer compounds are manufactured using a compound that can be used as a dopant, except when the product has an electrical conductivity of 10 ^-2 to ^{10 3} S cm ^-1. It is necessary to dope the dopant so that its electrical conductivity is in the range of 10 ⁻² to 10 ³ S·cm ⁻¹ . In the present invention, a conductive polymer compound includes a polymer compound manufactured using a compound that can serve as a dopant during the manufacture of the polymer compound. In addition, when a polymer compound is manufactured using a compound that can serve as a dopant, the dopant may be removed by an appropriate method and then a new dopant may be doped. For doping, either chemical doping or electrochemical doping may be used. As dopants for chemical doping,
Various electron-accepting and electron-donating compounds known in the art include () halogens such as iodine, bromine and bromine iodide, () arsenic pentafluoride, antimony pentafluoride, silicon tetrafluoride, Metal halides such as phosphorus chloride, phosphorus pentafluoride, aluminum chloride, aluminum bromide and aluminum fluoride; () protic acids such as sulfuric acid, nitric acid, fluorosulfuric acid, trifluoromethanesulfuric acid and chlorosulfuric acid; () sulfur trioxide; Oxidizing agents such as nitrogen dioxide, difluorosulfonyl peroxide, ()AgClO ₄ , ()tetracyanoethylene, tetracyanoquinodimethane, chloranil, 2,3-dichloro-5,6-dicyanoparabenzoquinone, 2,3-dibrome Examples include -5,6-dicyanoparabenzoquinone, alkali metals such as ()Li, Na, and K. On the other hand, dopants to be electrochemically doped include () halide anions of Va group elements such as PF ^- ₆ , SbF ^- ₆ , AsF ^- ₆ and SbCl ^- ₆ , and a halide anion of group A elements such as BF ^- ₄ . halide anion, ^-
( ^-3 ), halogen anions such _as ^Br- , ^Cl- , ClO ^- ₄
anionic dopants such as perchlorate anions, and alkali metal ions such as Li ⁺ , Na ⁺ , K ^{+ ,} quaternary dopants such as R ₄ N ⁺ (R: hydrocarbon group having 1 to 20 carbon atoms); Examples include cations and dopants such as ammonium ions, but are not necessarily limited to these. The above-mentioned anion dopant and cation dopant
Specific examples of compounds that provide dopants include:
LiPF ₆ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , NaI,
_NaPF6 , _NaSbF6 , _NaAsF6 , _NaClO4 , KI,
KPF ₆ , KSbF ₆ , KAsF ₆ , KClO ₄ , [(n-Bu) ₄
N] ⁺・(AsF ₆ ) ^- , [(n-Bu) ₄ N] ⁺・(PF ₆ ) ^- ,
[(n-Bu) ₄ N] ⁺・ClO ^- ₄ , LiAlCl ₄ , LiBF ₄ ,
NO・AsF ₆ , NO ₂・AsF ₆ , NO・BF ₄ , NO ₂・
Examples include BF ₄ and NO/PF ₆ , but are not necessarily limited to these. These dopants may be used alone or in combination of two or more. Anion dopants other than those mentioned above include HF ₂
It is an anion, and as a cation dopant other than the above, pyrylium or pyridium cation represented by the following formula (): [In the formula, ~10 alkyl group, aryl group having 6 to 15 carbon atoms, m is 0 when X is an oxygen atom, and 1 when X is a nitrogen atom. n is 0 or 1 to 5. ] Or a carbonium cation represented by the following formula () or (): and [In the above formula, R ¹ , R ² , R ³ are hydrogen atoms (R ¹ , R ² ,
R ³ is not a hydrogen atom at the same time) an alkyl group having 1 to 15 carbon atoms, an allyl group, an aryl group having 6 to 15 carbon atoms, or an -OR ⁵ group,
However, R ⁵ represents an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 15 carbon atoms, and R ₄ represents a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or an aryl group having 6 to 15 carbon atoms. It is an aryl group. ] It is. The HF ₂ anion used typically has the following general formula (), () or (): R′ ₄ N·HF ₂ () M·HF ₂ () (However, in the above formula, R', R'' is a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, and R is an alkyl group having 1 to 10 carbon atoms, a carbon An aryl group of numbers 6 to 15, X is an oxygen atom or a nitrogen atom, n is O or a positive integer of 5 or less, and M is an alkali metal. It can be obtained by dissolving it in a suitable organic solvent. Specific examples of the compounds represented by the above formulas (), () and () include H ₄ N.HF ₂ , n-Bu ₄ N.HF ₂ ,
Na・HF ₂ , K・HF ₂ , Li・HF ₂ and

[Formula] can be given. The pyrylium or pyridinium cation represented by the above formula () is a combination of the cation represented by the formula () and ClO ^- ₄ , BF ^- ₂ , AlCl ^- ₄ , FeCl ^- ₄ , SnCl ^- ₅ ,
It can be obtained by dissolving a salt with an anion such as PF ^- ₆ , PCl ^- ₆ , SbF ^- ₆ , AsF ^- ₆ , CF ₃ SO ^- ₃ or HF ^- ₂ in a suitable organic solvent. Examples of such salts include

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[Formula] etc. can be given. Specific examples of carbonium cations represented by the above formula () or () are (C ₆ H ₅ ) ₃ C ⁺ ,
( _CH3 ) _3C ⁺ ,

【formula】

[Formula] can be given. These carbonium cations can be obtained by dissolving salts of them and anions (carbonium salts) in a suitable organic solvent. Representative examples of anions used here include BF ^- ₄ , AlCl ^- ₄ ,
AlBr ₃ Cl ^- , FeCl ^- ₄ , SnCl ^- ₃ , PF ^- ₆ , PCl ^- ₆ , SbCl ^- ₆ ,
Examples include SbF ^- ₆ , ClO ^- ₄ , CF ₃ SO ^- ₃ , etc.
Further, specific examples of carbonium salts include (C ₆ H ₅ ) ₃ C・BF ₄ , (SH ₃ ) ₃ C・BF ₄ , HCO・
Examples include AlCl ₄ , HCO・BF ₄ , C ₆ H ₅ CO・SnCl ₅ and the like. For the anode of the solid capacitor in the present invention, a metal foil of aluminum, tantalum, niobium, or the like, or a sintered body of metal powder thereof is used. In the case of metal foil, the surface is etched to create pores. The metal foil or sintered body is electrolytically oxidized, for example in a solution of ammonium borate, to form a thin layer of dielectric material on top of the metal foil or sintered body. The conductive polymer compound in the present invention comes into contact with this dielectric thin layer, and a portion of the conductive polymer compound enters into the pores. The figure schematically shows a case where metal foil is used in a solid electrolytic capacitor that is a specific example of the present invention. EXAMPLES The present invention will be explained in more detail with reference to Examples and Comparative Examples below. Note that the characteristic values of each solid electrolytic capacitor produced in Examples and Comparative Examples are collectively shown in a table. Example 1 100μm thick aluminum foil (99.99% purity)
is used as an anode, and the surface of the foil is electrochemically etched using alternating direct current and alternating current to reduce the average pore size.
The porous aluminum foil was 2 μm in diameter and had a specific surface area of 12 m ² /g. The etched aluminum foil was then immersed in an ammonium borate solution, and a thin dielectric layer was electrochemically formed on the aluminum foil in the solution. Meanwhile, add 0.2 mol of dicyanobenzene to methanol
Dissolved in 100ml. 0.1 mol of sodium methylate was added dropwise to this solution, and the mixture was reacted at 65°C for 10 hours.
After the reaction was completed, the product was separated, thoroughly washed with acetone, and then dried under reduced pressure to obtain polybenzopyrroline. This polybenzopyrroline was dissolved in benzene and applied to the dielectric layer. After repeating vacuum degassing and coating to sufficiently fill the pores with the solution, benzene was dry-upped. Next, iodine vapor was applied to the polybenzopyrroline layer for 10 hours to form a solid electrolyte layer using a conductive polymer compound consisting of polybenzopyrroline and iodine. A solid electrolytic capacitor was created by using aluminum foil for the cathode and sealing it with resin. The conductivity of the conductive polymer compound at this time was 0.7S·cm ^-1 . Example 2 Benzopyrroline 2 obtained in the same manner as Example 1
g was dissolved in a large amount of methyl alcohol. 3 moles of methyl iodide was added to this solution and reacted. After drying up the solution, it was thoroughly washed with acetone and dried under reduced pressure. It was confirmed by elemental analysis and infrared analysis that the product was a methyl iodide salt having a repeating unit partially represented by the above-mentioned formula (2). Polybenzopyrroline, part of which was in the form of a salt, was dissolved in methyl alcohol, applied to the same dielectric layer as in Example 1, and degassed under reduced pressure. After repeating this application and vacuum degassing to sufficiently fill the pores with the solution, meryl alcohol was dry-applied. Next, the polybenzopyrroline layer, which is partially in the form of a salt, is doped with sulfur trioxide vapor for 1 hour, and the polybenzopyrroline, which is partially in the form of a salt, is doped with sulfur trioxide. A solid electrolyte made of a conductive polymer compound was formed. A solid electrolytic capacitor was created by using SUS304 metal foil as the cathode and sealing it with resin. The conductivity of the conductive polymer compound at this time was 1.2S·cm ^-1 . Comparative Example 1 A solid electrolytic capacitor was produced using an aluminum foil having the same dielectric layer as in Example 1, using conventional manganese dioxide as a solid electrolyte, and using aluminum foil as a cathode. Example 3 A sintered body of tantalum powder was anodized in an aqueous phosphoric acid solution to form a dielectric film on the sintered body, and a tantalum element was obtained using polybenzopyrroline in the same manner as in Example 1. It was dipped in a benzene solution and dried. This dipping and drying operation was repeated. Next, this device was immersed in a nitromethane solution of NO ⁺ BF ^- ₄ to dope it with BF ^- ₄ to form a solid electrolyte layer made of a conductive polymer compound. Next, the cathode was surrounded by a silver case, and the joint with the anode was sealed with resin to create a solid electrolytic capacitor. The conductivity of the conductive polymer compound at this time was 1.0 S·cm ^-1 . Comparative Example 2 A solid electrolytic capacitor was produced using a tantalum powder sintered body made of a conventional manganese dioxide solid electrolyte.

[Table] As is clear from the table, the solid electrolytic capacitor using a dopant-doped conductive polymer compound as an electrolyte according to the present invention has a higher dielectric loss leakage than the conventional solid electrolytic capacitor using manganese dioxide as an electrolyte. It is possible to create solid electrolytic capacitors with low current, high rated voltage, and high withstand voltage. Further, the value of capacity x rated voltage of the solid electrolytic capacitor according to the present invention is larger than that of a solid electrolytic capacitor using manganese dioxide, and a large capacity can be obtained with the same shape.

[Brief explanation of drawings]

The figure is a sectional view showing a specific example of a solid electrolytic capacitor according to the present invention. 1... Anode lead wire, 2... Anode, 3... Oxide film, 4... Cathode, 5... Cathode lead wire, 6...
Conductive polymer compound, 7...Resin.

Claims (1)

[Claims] 1. The following formula and/or [In the formula, R ₁ and R ₂ are hydrogen or a saturated hydrocarbon group having 6 or less carbon atoms, and Y ₁ and Y ₂ are anions. The combination of R ₁ Y ₁ and R ₂ Y ₂ may be present at the same time, or either combination may be absent. ] A solid electrolytic capacitor characterized in that a conductive polymer compound obtained by doping a dopant into a polymer compound having a repeating unit represented by the following formula is used as a solid electrolyte.