JP2734652B2 - Solid electrolytic capacitor and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor using a conductive polymer as an electrolyte and having excellent capacitor characteristics, especially excellent frequency characteristics and temperature characteristics, and a method for producing the same.

2. Description of the Related Art In recent years, with the digitization of electric devices, capacitors having a small size, a large capacity, and a low impedance in a high frequency region have been required. Conventionally, capacitors used in a high-frequency region include plastic capacitors, mica capacitors, and multilayer ceramic capacitors. However, these capacitors have a problem that when the capacitance is increased, the shape becomes large or it is difficult to increase the capacitance. On the other hand, as a small and large capacity capacitor, there is an electrolytic capacitor such as an aluminum dry electrolytic capacitor or an aluminum or tantalum solid electrolytic capacitor. In these capacitors, since the electrolyte (liquid electrolyte or solid manganese dioxide) used has a high resistance, a sufficiently low impedance cannot be obtained in a high-frequency region.

On the other hand, recently, instead of manganese dioxide as a solid electrolyte, 7,7,8,8, -tetracyanoquinodimethane complex salt (hereinafter referred to as “TCNQ salt”), an organic semiconductor having high conductivity and excellent anodic oxidation properties )) Has been proposed. Invention by the same applicant (Japanese Patent Publication No. 56-1077)
No. 7) and an invention by Shinichi Niwa (JP-A-58-176).
As disclosed in Japanese Patent Application Laid-Open No. 09-2009, in an aluminum solid electrolytic capacitor using such a TCNQ salt, frequency characteristics and temperature characteristics are significantly improved, and low leakage current characteristics are achieved. In addition, since the TCNQ salt has excellent thermal stability as an organic conductive material, the TCNQ salt is said to far outperform that of a conventional dry-type electrolytic capacitor in which the obtained capacitor has a high-temperature life. In recent years, by electropolymerizing a heterocyclic monomer such as pyrrolethiophene using a supporting electrolyte, a highly conductive polymer containing the anion of the supporting electrolyte as a dopant is formed on the anode body, and this is used as an electrolyte. Solid electrolytic capacitors to be used have been proposed (JP-A-60-37114, JP-A-60-233).
No. 017).

Problems to be Solved by the Invention According to electrolytic polymerization, pyrrole which is a heterocyclic compound,
It is known that a dense and highly conductive polymer film can be easily formed on a normal anode (for example, platinum, carbon, etc.) from a solution of thiophene or a derivative thereof and a suitable supporting electrolyte. ing.

However, in electropolymerization, it is theoretically difficult to form a conductive polymer film on an anode valve metal having an oxide film because no current flows. On the other hand, it is possible to form a conductive polymer film on the valve metal surface without an oxide film by electrolytic polymerization, but in this case, anodization must be performed via the conductive polymer film. ,
As a result, deterioration or deterioration of the conductive polymer film formed in advance, and peeling off from the anode surface occur. All of these are undesirable because they degrade the characteristics of the capacitor.

It is also possible to form a conductive polymer by oxidative polymerization.However, in this case, the obtained polymer is in the form of a powder, and as it is, adhesion to the anode valve metal having an oxide film, coating Because of its poor properties, it has been difficult to use it as an electrolyte for capacitors.

Furthermore, it is generally difficult to dissolve the above-mentioned conductive polymer having a heterocyclic compound as a repeating unit in a solvent, and it is difficult to form a film by a solution coating method.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and provides a solid electrolytic capacitor having excellent frequency characteristics and temperature characteristics, and a method for manufacturing the same.

Means for Solving the Problems The technical means of the present invention is to previously form a thin conductive layer made of a substance which is soluble in dissolution and expresses conductivity by heating on an anode valve metal on which an oxide film is formed. Then, by conducting electrolytic polymerization through the conductive layer, a highly conductive heterocyclic electrolytic polymerized polymer film layer is formed on the anode valve metal having an oxide film, which has been difficult in the past, to form an electrolyte layer. The solid electrolytic capacitor has high conductivity as a whole, and can easily obtain a solid electrolytic capacitor having excellent capacitor characteristics, especially excellent frequency characteristics and temperature characteristics.

Substances that exhibit conductivity by heating are widely known as pyropolymers, but those used in the present invention may exhibit conductivity at the lowest possible temperature in consideration of damage to oxide films. Desirable, and particularly considering the use of aluminum having a melting point of about 659 ° C. as the anode valve metal, it is still more desirable that the conductivity be exhibited at a lower temperature.

Any substance can be used as long as it exhibits conductivity at a low temperature as described above. As such a substance, for example, the following substance having 3-aminophenylacetylene at the terminal is known.

These are super heat resistant conductive polymer precursors
1000 "and" Thermcon EXP. 1b "are commercially available from Kanebo NS Co., Ltd. and are readily available. These are dissolved in dichloromethane, tetrahydrofuran, 2-butanone, ethylene glycol dimethyl ether, N, N-dimethylformamide, N-methylpyrrolidone, etc., and after evaporation of the solvent, heated at a relatively low temperature of about 500 to 600 ° C. Conductivity is 10 ^-6 to 10
It is known to increase to ^-2 S / cm (magazine "Electronic Materials" December 1986 issue). By using such a substance, a thin-film conductive layer can be easily formed on the anode valve metal surface having an oxide film by a coating method, and further, such a conductive surface can be formed of pyrrole, thiophene, or the like. An electropolymerized polymer film can be easily formed using a solution in which a heterocyclic compound such as a derivative thereof and an appropriate supporting electrolyte are dissolved.

The electrolytic polymerization may be carried out through minute defects of the oxide film using the anode valve metal itself as an anode, or by contacting an externally provided auxiliary electrode with the surface of the anode valve metal on which the conductive layer is formed as described above. You can also. The supporting electrolyte may be any as long as it can be subjected to electrolytic polymerization to give a polymer having a conductivity of about 10 ^-1 S / cm or more, and the present invention is not specified by the type of supporting electrolyte.

In addition, the substance which expresses conductivity by the above-mentioned heating may be used alone, or may be used as a mixture.

As described above, by forming a conductive layer using a substance that is soluble in a solvent and exhibits polymerization conductivity by heating at a relatively low temperature on the anode valve metal having an oxide film, It becomes possible to form an electropolymerized conductive polymer composed of a heterocyclic compound via the conductive layer. And the conductivity of the polymer obtained by electrolytic polymerization is 10 ² S / cm
High conductivity of the order of is easily obtained,
By forming the conductive layer formed of the above-mentioned substance soluble in a solvent and exhibiting conductivity by heating sufficiently thin compared to the electropolymerized conductive polymer layer, an electrolyte layer having high conductivity as a whole laminated conductive layer Can be formed. The thickness of the former conductive layer can be easily adjusted by adjusting the concentration of the solution to be applied. Therefore, the capacitor obtained by the present invention has a higher conductivity than a material formed solely by a substance in which the electrolyte is soluble and soluble and exhibits conductivity by heating, so that a capacitor having a small loss and excellent frequency characteristics can be obtained. . Since the electrolyte is solid, the temperature characteristics are much better than those of an electrolytic capacitor using an electrolytic solution. Aluminum, tantalum, titanium, niobium and the like can be used as the anode valve metal, but the former two are preferably used.

Examples Hereinafter, examples of the present invention will be described.

Example 1 An 8 × 10 mm aluminum-etched foil was applied with a 3% aqueous ammonium adipate solution at about 70 ° C. at 35 V to form a dielectric film by anodic oxidation. , A substance obtained by dehydration condensation from one molecule of 4-diformylbenzene, di (3-ethynylphenylamino) -1,4-diformylbenzene (trade name: THERMCON
1000) dipped in a 1% solution of ethylene glycol dimethyl ether
The composition was heated and cured at 100 ° C. for 100 hours to form a conductive layer. A stainless steel auxiliary electrode is brought into contact with this foil, and pyrrole (0.3
M), sodium 2-naphthalene sulfonate (0.1
M), and immersed in an electrolytic solution composed of water, and a voltage of 2 V was applied to form an electrolytic polymer film in which polypyrrole was doped with 2-naphthalene sulfonate anion. After washing with water and drying, a carbon lead and a silver paste were applied on the electropolymerized film, the cathode lead was taken out, and the package was completed using epoxy resin to complete five capacitors.
After aging at 13 V, the average values of the initial capacitance, loss, and 1 MHz impedance at 120 Hz were 13.1 μF, 2.1%, and 15 mΩ, respectively. The rate of change of capacity based on 20 ° C is -4% at -55 ° C, 7% at 125 ° C,
Furthermore, the loss change is 1.4 at -55 ° C, 20 ° C, and 125 ° C respectively.
%, 1.3% and 1.7%. From these, it has been proved that the solid electrolytic capacitor according to the present invention has extremely excellent capacitor characteristics, especially frequency characteristics and temperature characteristics.

<Example 2> A substance obtained by dehydration condensation from two molecules of 3-ethynylphenylamine and one molecule of 1,4-diformylbenzene, di (3-ethynylphenylamino) -1,4-diformylbenzene (trade name: Thermocon) 1000), a substance obtained by dehydration condensation from two molecules of 3-ethynylphenylamine and one molecule of 1,3-diformylbenzene, di (3-ethynylphenylamino) -1,3-diformylbenzene (trade name) Five capacitors were produced in the same manner as in Example 1 except that a 2% solution of thermcon EXP. 1b) in ethylene glycol dimethyl ether was used and cured by heating at 500 ° C. for 100 hours. After aging at 13 V, the average value of the initial capacitance, loss, and 1 MHz impedance at 120 Hz is 13.3 μF, 1.9%, and 14 mΩ, respectively. Has been demonstrated.

Example 3 A prototype of a capacitor was produced in the same manner as in Example 1, except that the heat curing temperature was changed between 450 and 600 ° C. and the heat curing time was changed between 50 and 300 hours. Only when heated at 500 ° C for 200 hours or more, it was possible to form an electrolytic polymerized film, and a capacitor could be produced.However, when the heat treatment was performed at a temperature lower than 500 ° C and at 500 ° C for less than 200 hours, No electropolymerized film was formed. Note that the capacitor characteristics when the electrolytic polymerized film could be formed were almost the same as those in Example 1.

Example 4 A prototype of a capacitor was produced in the same manner as in Example 2, except that the heat curing temperature was changed between 450 and 600 ° C. and the heat curing time was changed between 50 and 300 hours. Only when heated at 500 ° C for 100 hours or more, it was possible to form an electrolytic polymerized film, and a capacitor could be manufactured.However, when the heat treatment was lower than 500 ° C and shorter than 100 hours at 500 ° C, No electropolymerized film was formed. Note that the capacitor characteristics obtained when the electrolytic polymerized film was formed were almost the same as those in Example 2.

Example 5 Di (3-ethynylphenylamino) -1,4-diformylbenzene (trade name: Thermocon) obtained by dehydration condensation of two molecules of 3-ethynylphenylamine and one molecule of 1,4-diformylbenzene 1000), a substance obtained by dehydration condensation from two molecules of 3-ethynylphenylamine and one molecule of 1,3-diformylbenzene, di (3-ethynylphenylamino) -1,3-diformylbenzene (trade name: THERMCON EXP .1b) in a weight ratio of 75:25, 50:50 and 25:75, except that a mixture was prepared in the same manner as in Example 1 except that a capacitor was prepared. Was obtained.

<Example 6> Example 1 was repeated except that a mixture of pyrrole and N-methylpyrrole was used instead of pyrrole, and thiophene and an organic solvent acetonitrile were used instead of pyrrole and water as a solvent.
When a capacitor was produced in the same manner as in Example 1, the same result as in Example 1 was obtained.

<Example 7> After embossing, using a 10% phosphoric acid aqueous solution at about 90 ° C
Five capacitors were produced in the same manner as in Example 1 except that 8 × 10 mm tantalum foil anodized by applying 35 V was used. After aging at 13 V, the average values of the initial capacitance, loss, and 1 MHz impedance at 120 Hz are 1.03 μF, 0.8%, and 95 mΩ, respectively, and the temperature characteristics of the capacitance and loss are almost the same as those in the first embodiment. It has been demonstrated that they are equivalent and have extremely excellent capacitor characteristics.

In the examples, the case where ethylene glycol dimethyl ether is used as a solvent of a substance that expresses conductivity by heating, and the case where the concentration is 2% are described. It can be used in the same manner, the concentration can be applied, and after heating, the electropolymerized film may be substantially enough to secure a conductive layer having a thickness capable of forming a laminate. It is not limited to type and concentration. When pyrrole is used as the monomer, only the case where water is used as the solvent has been described. However, other solvents may be used as long as they dissolve the supporting electrolyte and the monomer, and the present invention is not limited by the type of the solvent.

In the examples, only the case where sodium 2-naphthalene sulfonate is used as the supporting electrolyte has been described. However, other materials may be used, or they may be used as a mixture. Not limited. For the mixture of monomers, pyrrole and N-
Although the case where methylpyrrole is used has been described, thiophene or a derivative thereof can be similarly mixed and used.

Effect of the Invention In summary, the present invention is composed of a substance which is soluble in a solvent and is polymerized by heating to exhibit conductivity on an anode valve metal having a dielectric film formed on the surface by anodization or anodization. A solid electrolytic capacitor provided with an electrolyte layer formed by sequentially laminating a polymer conductive layer and a polymer conductive layer containing a heterocyclic compound as a repeating unit, and a method for manufacturing the same are provided. This has the advantage that a solid electrolytic capacitor having excellent characteristics can be easily obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masao Fukuyama 3-10-1, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa Prefecture Inside Matsushita Giken Co., Ltd. (72) Susumu Yoshimura 3-chome, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa No. 10-1 Inside Matsushita Giken Co., Ltd. (56) References JP-A-61-174712 (JP, A)

Claims (9)

(57) [Claims] 1. A polymer conductive layer made of a substance which is soluble in a solvent and which is polymerized by heating to exhibit conductivity on an anode valve metal having a dielectric film formed on its surface by anodization or anodization. A solid electrolytic capacitor provided with an electrolyte layer formed by sequentially laminating polymer conductive layers each containing a heterocyclic compound as a repeating unit. 2. The solid electrolytic capacitor according to claim 1, wherein the substance which is soluble in a solvent and which is polymerized by heating to exhibit conductivity is a substance having aminophenylacetylene at a terminal. 3. A substance which is soluble in a solvent and polymerized by heating to exhibit electrical conductivity is at least di (3-ethynylphenylamino) 1,4-diformylbenzene and di (3-ethynylphenylamino). 3. The solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor contains one selected from 1,3-diformylbenzene. 4. The solid electrolytic capacitor according to claim 1, wherein the heterocyclic compound is pyrrole, thiophene or a dielectric thereof. 5. The solid electrolytic capacitor according to claim 1, wherein the anode valve metal is one selected from aluminum and tantalum. 6. A material which is soluble in a solvent and is polymerized by heating to exhibit conductivity and is dissolved in a solvent and coated on the anode valve metal having a dielectric film formed on the surface by anodization or anodization. After that, a solid electrolyte using at least a means for forming a conductive layer by heating at a temperature equal to or lower than the melting point of the anode valve metal and a means for forming a polymer conductive layer containing a heterocyclic compound as a repeating unit by electrolytic polymerization at least. Manufacturing method of capacitor. 7. A conductive material is formed by dissolving in a solvent a substance which is soluble in a solvent and which is polymerized by heating to exhibit conductivity and is coated with the solvent, and then heated at a temperature lower than the melting point of the anode valve metal to form a conductive layer. 7. The method for producing a solid electrolytic capacitor according to claim 6, wherein said means uses a substance containing aminophenylacetylene at the terminal as said substance and heats it at 500 to 600 ° C. 8. A conductive layer is formed by dissolving a substance which is soluble in a solvent and which is polymerized by heating to exhibit electrical conductivity, dissolves in the solvent and coats it, and heats it at a temperature lower than the melting point of the anode valve metal. The means uses a substance containing at least one selected from di (3-ethynylphenylamino) 1,4-diformylbenzene and di (3-ethynylphenylamino) 1,3-diformylbenzene as the substance, ~ 600 ℃
The method for manufacturing a solid electrolytic capacitor according to claim 6, wherein the heating is performed by: 9. The means for forming a polymer conductive layer containing a heterocyclic compound as a repeating unit by electrolytic polymerization is a means for conducting in a solution containing at least one of pyrrole, thiophene or a derivative thereof and a supporting electrolyte. Claim 6
9. The method for manufacturing a solid electrolytic capacitor according to any one of claims 1 to 8.