JPH0455322B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a solid electrolytic capacitor using an organic semiconductor as an electrolyte. 2. Description of the Related Art A solid electrolytic capacitor has a structure in which a solid electrolyte is attached to a dielectric-forming valve metal such as aluminum having an anodized film. Up until now, most capacitors of this type have used manganese dioxide as the solid electrolyte. Problems to be Solved by the Invention However, when forming the above-mentioned manganese dioxide on an electrode, it is generally immersed in a manganese nitrate solution and then thermally decomposed, which damages the anodic oxide film. The drawback was that the repairability of the anodic oxide film was poor. Means for solving the problems In order to improve the above-mentioned drawbacks, organic semiconductors, mainly TCNQ (hereinafter 7, 7,
It has been proposed to use a complex called 8,8 tetracyanoquinodimethane. TCNQ is used as an acceptor material, and donor materials include quinoline, tetrathiafulvalene, N-methylphanadium, and tetraselenafulvalene, and research on new donor materials is currently underway. Its characteristics as a donor material include a moderately small ionization potential, a large π-electron system that stabilizes the ions, and a high polarizability. Satisfying all of these conditions is an important factor in molecular design, but it is extremely difficult to satisfy all of them.
In addition, in order to apply TCNQ complexes with donor materials to electrolytic capacitors, there is a problem with electrical connection with electrodes, and TCNQ complexes with extremely fine crystal grains and good compatibility with metal oxides are needed. desirable. In addition, a TCNQ complex is required that does not change much in terms of electromotive properties from low to high temperatures and does not easily decompose even at high temperatures. The present inventors repeated various experiments and found mixing conditions for TCNQ complexes that satisfied the above requirements as much as possible. That is, the present invention uses alkylated orthophenanthroline as an electrolyte interposed between an anode electrode made of a valve metal having an anodic oxide film on its surface and a cathode electrode configured to face the electrode.
It has been found that the product properties are significantly improved by using a mixture of TCNQ complex and alkylated isoquinoline TCNQ complex. Effect Generally, when a capacitor element is impregnated with a TCNQ complex, an isoquinoline TCNQ complex, such as a butylisoquinoline (TCNQ) ₂ complex, has good adhesion to the electrode foil, improves the impregnation rate, and shows a low tanδ value, but it is easy to It is easily oxidized by carbon dioxide, which poses a problem in terms of long-term reliability. On the other hand, phenanthroline (TCNQ) ₂ complex has the disadvantage that it has poor impregnating properties and increases tan δ during impregnation compared to isoquinoline complex, but it is extremely stable and excellent in reliability. The inventor has developed this phenanthroline (TCNQ) ₂
In order to improve the impregnability and tan δ of the complex, we have investigated impregnation methods to improve its properties, but isoquinoline complexes were better in all impregnation methods. Therefore, in order to take into account the advantages of both phenanthroline TCNQ complex and isoquinoline complex,
As a result of repeating various experiments using a mixture of both, it was possible to obtain a solid electrolytic capacitor with significantly increased capacitance and low loss. For example, if you use heptylphenanthroline (TCNQ) ₂ complex (hereinafter referred to as HPT ₂ ) and N-butyl isoquinoline (TCNQ) ₂ complex (hereinafter referred to as NBT ₂ ) and set the mixing ratio of both as follows, the following results. It becomes like this. The mixing ratio is a molar ratio.

[Table] Specific resistance values are measured using pellets pressurized to 400 kg/cm ³ . As shown in Table 1, the specific resistance when mixed is between the two TCNQ complexes. however,
When this mixed complex is used to impregnate an electrolytic capacitor element, the product exhibits the following characteristics. The rating of the element used in the sample is 6.3WV-3.3μF.

[Table] From the changes in capacitance and tanδ, the effect of mixing was observed for HPT ₂ :NBT ₂ =8:2-5:
The molar ratio was in the range of 5. The hydrocarbon group quaternizing the N-position of phenanthroline and isoquinoline preferably has 1 to 18 carbon atoms. If the number of carbon atoms is 19 or more, it becomes thermally unstable and the reliability as a capacitor decreases significantly, making it unsuitable. Furthermore, the synthesis method is difficult and the cost of chemicals is extremely high. Examples Next, specific examples of the present invention will be described. As the anode electrode foil, an etched aluminum foil used in ordinary electrolytic capacitors was subjected to 35V conversion using an aluminum phosphate solution and thoroughly dried, and the cathode electrode foil was wound facing each other with a separator in between. A capacitor element was formed. Next, a mixture of HPT ₂ and NBT ₂ in a molar ratio of 6:4 is prepared, and this is melted and liquefied, impregnated into the capacitor element by a known impregnation method, and cooled. A) was produced. In addition, a capacitor sample using only HPT ₂ as the solid electrolyte (sample group B) and a capacitor sample using only NBT ₂ (sample group C) were similarly produced for comparison. In addition, the rating of both capacitors is 25WV-33μF. Table 3 shows the initial characteristics of the capacitor samples described above and the results of a high temperature load test in which the rated voltage was applied for 2000 hours in an atmosphere of 105°C. The capacitance and tanδ in the table are the values at room temperature and 120kHz,
The leakage current is the value after 1 minute of applying the rated voltage at room temperature, and all values are the average value of 10 samples.

[Table] In addition to the above-mentioned examples, the above-mentioned mixed TCNQ complex is also applied to a sintered solid electrolytic capacitor in which valve metal powder is molded, sintered, and chemically treated in place of the electrode foil. However, similar test results were obtained. Effects of the Invention As described above, when the mixed complex according to the present invention is used, the product properties, particularly the impregnation rate, tanδ, and reliability are better than those used with each individual complex, and it has great industrial and practical value. There is something.

Claims (1)

[Claims] 1. A mixture of an orthophenanthroline TCNQ complex and an isoquinoline TCNQ complex, using a valve metal with a dielectric oxide film formed on its surface as an electrode body.
A solid electrolytic capacitor characterized by using a TCNQ complex as a solid electrolyte. 2. The solid electrolytic capacitor according to claim 1 _, wherein the orthophenanthroline and _isoquinoline are N-quaternized salts consisting of _C1H3- to _C18H37- groups. 3. The solid electrolytic capacitor according to claim 1, wherein the mixing ratio of the orthophenanthroline TCNQ complex and the isoquinoline TCNQ complex is in the range of 8:2 to 5:5 in molar ratio.