JPH0228886B2 - KOTAIDENKAIKONDENSA - Google Patents

Description

[Detailed description of the invention]

The present invention involves coating a porous dielectric with a catalyst solution, then introducing acetylene gas to form an acetylene polymer on the dielectric, and then doping the acetylene polymer with a dopant to obtain conductive acetylene. This invention relates to a solid electrolytic capacitor with good performance using a high polymer as a solid electrolyte. Conventional solid electrolytic capacitors, such as aluminum electrolytic capacitors, have an aluminum oxide dielectric layer on an etched porous aluminum foil with a large specific surface area, and a liquid electrolyte is applied to the electrolytic paper between the cathode foil and the etched porous aluminum foil. However, the liquid state of the electrolyte is not desirable as it causes problems such as leakage, and attempts have been made to replace this 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. Manganese dioxide, which is formed by However, due to the high heat required during this thermal decomposition and the oxidizing effect of the NOx gas generated,
There is damage to the metal oxide film of the dielectric material, such as aluminum or tantalum, resulting in extremely large drawbacks such as a decrease in withstand voltage, an increase in leakage current, and a 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 electrically conductive organic semiconductor material as the solid electrolyte. An example of this is described in Japanese Patent Application Laid-Open No. 79255/1983. A solid electrolytic capacitor containing a conductive polymer composition containing a 7,7,8,8-tetracyanoquinodimethane (TSNQ) complex salt as a solid electrolyte, the N- n-propylisoquinoline and 7,7,
A solid electrolytic capacitor using a complex salt of 8,8-tetracyanoquinodimethane is known. these
Since the TCNQ complex salt compound has poor adhesion to the anodic oxide film and insufficient conductivity of 10 ^-3 to 10 ^-2 S·cm ^-1 , 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. SUMMARY OF THE INVENTION An object of the present invention is to provide a solid electrolytic capacitor using an organic semiconductor having high conductivity and good adhesion to a dielectric film as a solid electrolyte, in order to solve the above-mentioned drawbacks of the conventional capacitor. The present invention involves coating a porous dielectric with a catalyst solution, then introducing acetylene gas to form an acetylene polymer on the dielectric, and then doping the acetylene polymer with a dopant to obtain conductive acetylene. This invention relates to a solid electrolytic capacitor using a high polymer as a solid electrolyte. The solid electrolytic capacitor obtained by the present invention 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. The porous dielectric material used in the present invention is not particularly limited, but for example, known aluminum, tantalum,
Metal oxides such as niobium can be used. The catalyst used for acetylene polymerization in the present invention may be any of the conventionally known homogeneous and heterogeneous acetylene polymerization catalysts, but homogeneous catalysts are preferred. Specific examples of these catalysts are disclosed in Japanese Patent Application Laid-Open No. 32-10597, USP-
No. 4200716, JP-A-57-53509, JP-A No. 57-5707
No. 57-70114, Angew, Chem, Int, Ed.
Engl, 20 , 361 (1981); Polymer, 23 , 243
(1982); Makromol, Chem., Rapid Commun., 1 , 621 (1980), etc., but are not necessarily limited thereto. Conventionally known methods can be used to uniformly coat the catalyst on the porous dielectric, but in order to improve the wetting of the catalyst solution with the porous dielectric, methods such as charging the catalyst solution under reduced pressure can be used. You may also use
Further, as the coating method, either a batch method or a continuous method can be used. One specific example of a method of continuously applying a catalyst solution to a porous dielectric is a method of applying a catalyst solution to a continuously moving porous dielectric. There are no particular restrictions on the polymerization conditions for acetylene, but the polymerization temperature is usually -80°C to 100°C, preferably 0°C to
The temperature is in the range of 80°C and the acetylene pressure is usually below 10 atmospheres, preferably below 5 atmospheres. There is no particular restriction on the polymerization time. After the polymerization is completed, the residual catalyst in the acetylene high polymer may be removed, but there is no problem even if it is not removed. It is preferable to remove the residual solvent by a conventional drying method such as vacuum degassing. In this way, a dielectric film coated with an acetylene polymer is obtained. This acetylene polymer is a semiconductor with an electrical conductivity of 10 ^-10 to ^{10 -5} S/cm, and it is necessary to dope it with a dopant to keep its electrical conductivity in the range of 10 ^-2 to 10 ³ S/cm. is necessary. 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, ammothine pentafluoride, silicon tetrafluoride, Metal halides such as phosphorus chloride, phosphorus pentafluoride, aluminum chloride, aluminum bromide and aluminum fluoride; () protonic 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,
Examples include 2,3-dichloro-5,6-dicyanoparabenzoquinone, 2,3-dibromo-5,6-dicyanoparabenzoquinone, and alkali metals such as ()Li, Na, and K. On the other hand, dopants to be electrochemically doped into the acetylene polymer include (i) PF ^- ₆ , SbF ^- ₆ ,
Halide anions of group Va elements such as AsF ^- ₆ , SbCl ^- ₆ , halide anions of group A elements such as BF ^- ₄ , halogen anions such as I ^- (I ^- ₃ ), Br ^- 3Cl ^- , ClO ^- Anions such as perchlorate anions such as ₄ .
Dopants and (ii) cations/dopants such as alkali metal ions such as Li ⁺ , Na ⁺ , K ^{+ ,} quaternary ammonium ions such as R ₄ N ⁺ (R: carbon hydrogen group having 1 to 20 carbon atoms), etc. I can give you, but
It is 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 ,
Examples include NO.BF ₄ , NO _{2.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
An anion, and a cation dopant other than the above is a 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 0 to 5. ) Also, carbonium cations 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), carbon number is 1
-15 alkyl group, allyl group, aryl group having 6 to 15 carbon atoms or -OR ⁵ group, provided that R ⁵ is an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 15 carbon atoms (aryl) group, R ₄ is a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, and 6 carbon atoms.
~15 aryl groups. ] It is. The HF ₂ anion used typically has the following general formula (), () or (): [However, in the above formula, R', R'' is a hydrogen atom or an alkyl group having 1 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, R is an alkyl group having 1 to 10 carbon atoms,
An aryl group having 6 to 15 carbon atoms, X is an oxygen atom or a nitrogen atom, and n is 0 or a positive integer of 5 or less. M is an alkali metal] It can be obtained by dissolving a compound represented by (hydrogen fluoride salt) in a suitable organic solvent. Specific examples of 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 ⁺ , (CH ₃ ) ₃ C ⁺ ,

【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.
Specific examples of carbonium salts include (C ₆ H ₅ ) ₃ C・BF ₄ , (CH ₃ )C・BF ₄ , HCO・AlCl ₄ , HCO・
Examples include BF ₄ , C ₆ H ₅ CO・SnCl ₅ . The solid electrolytic capacitor of the present invention has the following advantages over conventionally known solid electrolytic capacitors. Since the electrolyte layer can be formed without high-temperature heating, there is no damage to the oxide film of the anode, and there is no need to perform anodization (reformation) 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. Example: 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 determine the average pore diameter.
2 μm and a specific surface area of 12 m ² /g. A thin dielectric layer was then electrochemically applied to the etched aluminum foil in an ammonium borate solution. A separately prepared toluene solution of tetrabutoxytitanium and triethyaluminum (Al/Ti = 2, [Ti] = 0.005 mol/l) was applied to the above dielectric layer, and then polymerized for 15 minutes at an acetylene pressure of 0.5 atm. . After the polymerization was completed, it was washed twice with a large excess of toluene, and then degassed under vacuum. Next, this device was immersed in a nitromethane solution of NO ⁺ BF ^- ₄ to dope it with acetylene polymer BF ^- ₄ , and the electrical conductivity of the acetylene polymer was adjusted to 2.5 S/cm. Characteristics were measured using an aluminum foil for the cathode and sealing it with rubber. The results are shown in the table. As a comparative example, the characteristics of a conventional solid electrolytic capacitor using dimanganese as a solid electrolyte are shown in the table.

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Claims (1)

[Claims] 1 A conductive acetylene polymer obtained by applying a catalyst solution to a porous dielectric, then introducing acetylene gas to form an acetylene polymer on the dielectric, and then doping the acetylene polymer with a dopant. A solid electrolytic capacitor that uses a combination as a solid electrolyte.