JPH0668926B2 - Conductive polymer, method for producing the same, and electrolytic capacitor using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel conductive polymer, a method for producing the same, and an electrolytic capacitor using the same, which is excellent in frequency characteristics and stability over time.

2. Description of the Related Art A conductive polymer is a polymer having a greatly expanded conjugated π-electron system, such as polyacetylene, polypyrrole, polythiophene, polyaniline, and polyacene, and is an electron donor or electron acceptor (anion such as Lewis acid or protonic acid). It is widely known to contain as a dopant to exhibit high conductivity. However, these dopants have a major drawback in that they diffuse in the polymer matrix due to an electric field and reduce the conductivity.

In view of its drawbacks, phthalocyanine tetrasulfonic acid,
High molecular weight dopants such as polystyrene sulphonic acid can be used, for example, in Journal of Chemical Society 1
983 edition, page 684 (K. Okabayashi, J. Chem. Sci., Che
m.Commun., p684 (1983)) and Ibid 1985 edition 8th
71 (N. Bates et al., Ibid., P871 (1985)). However, these dopants have the drawback that their conductivity is not as high as that of low molecular weight dopants due to their bulky molecular structure.

As described above, when only a low molecular weight dopant is used as the dopant, the conductivity can be increased, but the dopant is moved by the DC component electric field, and the conductivity of the conductive polymer layer is extremely large. The disadvantage is that it produces a non-uniform distribution. On the other hand, when a bulky dopant is used, there is a drawback that the conductivity does not increase. In addition, when such a conductive polymer is applied to an electrolytic capacitor, this becomes a major drawback and the impedance inside the pores of the surface of the dielectric layer cannot be lowered for a long period of time. There was a drawback that the major features of the S were damaged.

In view of these phenomena, it is an object of the present invention to provide a conductive polymer that gives high conductivity without significantly impairing the conductivity even under a DC component electric field.

It is another object of the present invention to provide an electrolytic capacitor in which a conductive polymer is applied to an electrolytic capacitor, the porous surface of the anode is stably made into a low impedance, and the frequency characteristic and the stability over time are excellent.

Means for Solving the Problems To form a conductive polymer in which both an immobilizing dopant and a mobile dopant are doped in an electron-conjugated polymer as dopants.

Action The immobilizing dopant used in the present invention is composed of an ionic polymer having a molecular weight of 800 or more or at least 0.01 to 1 μm ionic group-bonded particles having an ionic group covalently bonded to the surface thereof. It consists of low molecular weight ions of 200 or less. Since the fixed dopant is a bulky dopant, it cannot give high conductivity by itself, but it also works to generate micropores in the vicinity of the fixed dopant in the electron-conjugated polymer assembly, so that it is a low molecular weight dopant. Penetration into the microstructure is easier. Therefore, the combination of both can give a high conductivity which has never been obtained. As the fixing dopant, among others, 0.
Ionic group-bonded particles with a diameter of 0 to 1 μm are preferred.

Further, the conductive polymer of the present invention is extremely effective in densely forming a high-conductivity layer on the surface of a dielectric layer having a large surface area, such as an electrolytic conductor in an electrolytic capacitor. Regarding the conductivity σ of the conductive polymer layer which is the electrolytic conductor, it is preferable that both the conductivity in the vicinity of the surface of the porous alumina and the conductivity in the electrolytic conductor layer are high, and the frequency characteristic is greatly improved. However, the capacitance of the capacitor is C = εS ^* /
Since d (S ^* : effective surface area (large), ε: permittivity, d: thickness), the conductivity σ of the conductive polymer layer may be σ (dielectric surface)> σ (bulk). It's important. In such an electrolytic capacitor using the conductive polymer of the present invention, a high conductivity layer rich in mobile dopant is formed on the surface of the dielectric layer having a large surface area by the electric field of the direct current component. on the other hand,
Even if the dopant moves to the surface of the dielectric layer due to the DC component electric field, the fixed dopant (bulky dopant) remains in the conductive polymer, so that the conductivity of the conductive polymer layer does not significantly decrease. Therefore, since the conductive polymer as a whole does not have a dedoped portion having extremely high resistance, it becomes an excellent electrolytic conductor.

Example The present invention comprises a conductive polymer in which both a fixed dopant and a mobile dopant are doped as dopants in an electron-conjugated polymer.

FIG. 1 is a conceptual cross-sectional view showing the constitution of an electrically conductive polymer doped with an anionic group-bonding particle as an example of the present invention and a mobile dopant, and FIG. 2 is an ionic group bond used in the present invention. The conceptual diagram which shows an example of a particle is shown.

The fixed dopant 6 used in the present invention has a molecular weight of 8
There is an ionic polymer of 00 or more or an ionic group-bonded particle of 0.01 to 1 μm in which an ionic group is covalently bonded to at least the surface. In order for the ionic polymer to be the fixed dopant 6 that does not move by an electric field, a molecular weight of 800 or more is required.

As the ionic polymer, toluene sulfonic acid-aldehyde condensation polymer, benzene sulfonic acid-aldehyde condensation polymer, polystyrene sulfonic acid, terminal sulfonation (polyphenylene sulfide, polysulfone or polyphenylene oxide), p-oxybenzoic acid-aldehyde At least one selected from a condensation polymer and a salicylic acid-aldehyde condensation polymer is used.

As the ionic group-bonded particles, toluene sulfonic acid-
Aldehyde polycondensate, benzenesulfonic acid-aldehyde polycondensate, polystyrene sulfonic acid, p-oxybenzoic acid-aldehyde polycondensate, salicylic acid-aldehyde polycondensate, polyvinyl benzyl ammonium salt, at least one selected from, Spherical particles having ionic groups on the surface are preferred. As the ionic group 1, an anionic group is preferable. As the anion group, a sulfonic acid group,
Either an oxybenzoic acid group or a quaternary ammonium group is used. These ionic group-bonded particles 2 can be easily produced by crushing a resin or emulsion polymerization.

On the other hand, in the present invention, the mobile dopant 5 has a molecular weight of 2
Ions of 00 or less are used. Specifically, an acceptor composed of halogen, a Lewis acid, a protonic acid or the like, or a donor such as an alkali metal, an alkaline earth metal, an ammonium ion or a phosphonium ion is used. Above all, B
Anions such as F ₄ ⁻ , AlCl ₄ ⁻ , ClO ₄ ⁻ , Li ⁺ ,
Alkali metals such as Na ⁺ are practical. Molecular weight 20
When it exceeds 0, the ion becomes bulky and mobility decreases. Iodine is doped with I ₃ ⁻ and has a molecular weight of 381 and 200 or more, but since it also behaves as I ⁻ when moving, it belongs to the scope of the present invention.

The electron-conjugated polymer used in the present invention is synthesized by chemical polymerization or electrolytic polymerization (anodic oxidation polymerization, cathodic reduction polymerization), and specifically, polyphenylene, polynaphthalene, polypyrrole, polyphenylene sulfide, polythiophene, polyaniline. Alternatively, one selected from these derivatives and copolymers may be used. Anodizing polymerization is a method in which anionic group-bonded particles are dispersed colloidally in a solution of an electron-conjugating monomer, and the electron-conjugating monomer is electrolytically polymerized on the anode by an electric field generated by at least a pair of electrodes. As described above, the conductive polymer 4 obtained by doping the anionic group-bonded particles 2 and the low molecular weight ions 5 as the fixed dopant 6 and the mobile dopant 5 is obtained.

The electroconductive polymer of the present invention is a solution containing an electron-conjugated monomer and a salt having a molecular weight of 200 or less, which serves as a mobile dopant 5, and has an ionic group covalently bonded to at least the surface serving as the immobilizing dopant 6 at least on its surface. When the anionic group-bonded particles 2 having a size of 0 to 1 μm are dispersed in a colloidal form, and the electron-conjugated monomer is electrolytically polymerized on the anode by an electric field generated by at least one pair of electrodes, a good quality conductive polymer is obtained. Can be obtained. When the electron-conjugated monomer solution is water-insoluble, the anionic group-bonded particles are colloidally dispersed with a cationic surfactant and electrolytically polymerized.

By the way, the particle size of the ionic binding particles 2 used in the present invention is preferably 0.01 to 1 μm. If it is less than 0.01 μm, it is difficult to form particles and the characteristics as a molecule are approached. On the other hand, if it is 1 μm or more, it is too large to obtain the number of conductive carriers, and it does not become a colloid in the polymerization solution and precipitates.

Therefore, since the ionic group-bonded particle 2 of this size is much larger than the molecular chain, it does not significantly affect the crystallinity or orientation of the electron-conjugated polymer in the part away from the particle,
It is characterized by providing a good quality conductive polymer 4.

On the surface of the ionic group-bonded particle 2, a sulfonic acid group and an oxybenzoic acid group and an ammonium group are covalently bonded as shown in FIG. 2 (a), and these groups on the particle surface are electron-conjugated. It acts as a dopant for organic polymers and greatly contributes to the improvement of conductivity (increase in the number of carriers). 0.01
A major feature is that the ionic group-bonded particles 2 having a size of ˜1 μm are colloidally dispersed in the polymerization solution to give a uniform reaction solution composition and also dispersed in the generated conductive polymer 4. have.

It is also possible to make the ionic group-bonded particles porous particles and supply mobile dopant ions from the bulk of the particles to have this function.

The conductive polymer containing the ionic dopant thus obtained has a hydrophilic ionic dopant,
Conductivity may depend on humidity. In this case, for example, a metal ion that produces an insoluble salt (for example, Ba ²⁺ , P
b ²⁺ ) to make it water resistant.

The present invention exerts its greatest characteristics when it is used as the above-mentioned electrolytic conductor of an electrolytic capacitor comprising a metal anode, an oxide dielectric layer, an electrolytic conductor and a cathode as described above.

Next, the present invention will be described using examples.

Example 1 In a 200 ml separable flask, 4 g of pyrrole, 1 g of tetrabutylammonium perchlorate, and 2 g of toluenesulfonic acid-formaldehyde condensation polymer particles (average particle size of 0. 03
μm) and 100 ml of acetonitrile were added to obtain a colloidal solution.

Indium-tin oxide (ITO) was used as an anode and a Pt plate was used as a cathode in this solution, and electricity was applied in a nitrogen stream to obtain a polypyrrole film of about 35 μm on the anode.

The film was peeled from the electrode, silver paint was applied, and the conductivity was measured and found to be 300 S / cm (25 ° C.).
An electrode is taken from this film in the direction of the film, and the DC voltage is 0.3 V at room temperature
Was applied and the change with time of the current value was measured, and the change as shown in FIG. 3 was shown. The characteristic 7 of the film of this example is that the conductivity is higher than that of the film formed of a single dopant, that is, the film 8 of toluene sulfonic acid-formaldehyde condensation polymer particles, and the change over time is smaller than that of the film 9 formed of perchloric acid. Also had high conductivity.

Further, this film was set in a furnace at 80 ° C., a DC electric field was applied, and the change in current with time was measured. As a result, the change after 300 hours was 15%. This stability was remarkably more stable than the conventional low molecular weight dopant.

Example 2 In a 200 ml separable flask, 5 g of 3-methylthiophene, 1 g of tetrabutylammonium perchlorate and 3 g of polystyrene sulfonic acid polymer particles (average particle size of 0. 04μ
m) and 150 ml of nitrobenzene were added to obtain a colloidal solution.

Indium-tin oxide (ITO) was used as an anode, and a Pt plate was used as a cathode in this solution, and electricity was applied in a nitrogen stream to obtain a poly (3-methylthiophene) film of about 35 μm on the anode.
The film was peeled from the electrode, silver paint was applied, and the conductivity was measured and found to be 200 S / cm (25 ° C.).

Further, this film was set in a furnace at 80 ° C., a DC electric field was applied, and the change in current with time was measured. As a result, the change after 300 hours was 8%. This stability was remarkably more stable than the conventional low molecular weight dopant.

Example 3 First, an oxide dielectric layer was formed on a roughened aluminum film having a thickness of 0.03 mm, conductive nuclei were formed on the aluminum film, and then the conductive polymer forming bath was used to form the same reaction solution composition as in Example 1. A conductive polymer film was formed.

Then, after folding it, the cathode was formed with silver paint, the lead wire was taken out, and the exterior resin was coated on it.

The solid electrolytic capacitor thus obtained showed almost the same electric capacitance as the multilayer capacitor of the same type using a low molecular dopant.

When the frequency characteristics and stability over time of this were measured,
The frequency characteristics were improved to a higher frequency than those of low molecular weight dopants, and the stability with time also showed a life of 125 ° C. for 2000 hours or more.

Advantageous Effects of Invention The conductive polymer according to the present invention has high conductivity and high reliability, and a high conductivity layer is densely formed on a surface of a dielectric layer having a large surface area, such as an electrolytic conductor in an electrolytic capacitor. It is extremely effective when forming into. In addition, the ionic group-bonded particles are also characterized in that they are dispersed colloidally in the polymerization solution to give a uniform reaction solution composition and are evenly dispersed in the conductive polymer that is produced. Form a permeable polymer film.

[Brief description of drawings]

FIG. 1 is a conceptual cross-sectional view showing the structure of an ionic group-bonded particle and a conductive polymer doped with a mobile dopant in the conductive polymer of the present invention, and FIG. 2 (a) is an ion of the present invention. FIG. 2B is a conceptual diagram showing an example of a functional group-bonded particle.
Is a conceptual diagram showing an anion group-bonded particle treated with a cation activator, and FIG. 3 is a graph showing a change over time in current when a DC electric field is applied to a conductive polymer in one example of the present invention. 2 ... Ionic group-bonded particles, 4 ... Conductive polymer, 5 ...
… Mobile dopant, 6… Fixed dopant.

Claims (10)

[Claims] 1. A conductive polymer, wherein both the fixed dopant and the mobile dopant are doped in the electron-conjugated polymer as dopants. 2. The immobilizing dopant comprises an ionic polymer having a molecular weight of 800 or more, or at least 0.01 to 1 μm ionic group-bonded particles having an ionic group covalently bonded to the surface thereof. 1. The conductive polymer described in 1. 3. The ionic polymer is a toluene sulfonic acid-aldehyde condensed polymer, a benzene sulfonic acid-aldehyde condensed polymer, a polystyrene sulfonic acid, a terminal sulfonation (polyphenylene sulfide, polysulfone or polyphenylene oxide), p-oxy. The conductive polymer according to claim 2, which is at least one selected from a benzoic acid-aldehyde condensation polymer and a salicylic acid-aldehyde condensation polymer. 4. An ionic group-bonded particle is a toluene sulfonic acid-aldehyde condensation polymer, a benzene sulfonic acid-aldehyde condensation polymer, a polystyrene sulfonic acid, a p-oxybenzoic acid-aldehyde condensation polymer, a salicylic acid-aldehyde condensation polymer. The electrically conductive polymer according to claim 2, which is a spherical particle composed of at least one kind selected from a coalesced material and a polyvinylbenzyl ammonium salt. 5. The conductive polymer according to claim 1, wherein the mobile dopant comprises ions having a molecular weight of 200 or less. 6. The electron-conjugated polymer is one selected from polyphenylene, polynaphthalene, polypyrrole, polyphenylene sulfide, polythiophene, polyaniline, or derivatives or copolymers thereof. The conductive polymer described in 1. 7. An anion group of 0.01 to 1 .mu.m in which an ionic group is covalently bonded to at least the surface which is a fixed dopant in a solution containing an electron-conjugated monomer and a salt having a molecular weight of 200 or less which is a mobile dopant. The binding particles are dispersed in a colloidal form, and an electric field generated by at least a pair of electrodes
A method for producing a conductive polymer, comprising electrolytically polymerizing the electron-conjugated monomer on an anode. 8. The method for producing a conductive polymer according to claim 7, wherein the electron-conjugated monomer solution is a non-aqueous solution, and the anionic group-bonded particles are colloidally dispersed with a cationic surfactant. 9. The method for producing a conductive polymer according to claim 7, wherein the electron-conjugated monomer is at least one selected from benzene, naphthalene, anthracene, pyrrole, thiophene and diphenylamine. 10. An electrolytic capacitor comprising a metal anode, an oxide dielectric layer and an electrolytic conductor cathode, wherein both the fixed dopant and the mobile dopant are used as dopants in the electron-conjugated polymer as the electrolytic conductor. An electrolytic capacitor characterized by using a conductive polymer which is doped in.