JPH0335516A - Solid electrolytic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a solid electrolytic capacitor having excellent adhesive properties with a dielectric film, small impedance in a high frequency range, and a large electrostatic capacity by forming a dielectric oxide film formed on a film forming metal, a thin film of conductive polymer made of polyaniline as solid electrolyte on the oxide film. CONSTITUTION:Film forming metal roughed on its surface is formed as a metal oxide by electrolytic oxidation or air oxidation as a dielectric film, organic solvent soluble polyaniline solution is cast or coated on the film, dried as a thin film, and doped with protonic acid to easily form a thin film of conductive organic polymer on the dielectric film, thereby obtaining a solid electrolytic capacitor. Particularly, since the steps of coating the polyaniline and doping on the film can be separately executed, the formation of the thin film on the dielectric can be facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid electrolytic capacitor using a conductive organic polymer as a solid electrolyte, and a method for manufacturing the same.

Conventionally, electrolytic capacitors, which are known as large-capacity capacitors, come in two types: electrolyte type and solid type. Among these, solid capacitors using solid electrolytes include manganese dioxide or ? , 7,8.8-tetracyanoquinodimethane (TCNQ) is known, but the former has various problems such as high impedance and the latter poor thermal stability. ing.

Therefore, in recent years, various solid electrolytic capacitors using conductive organic polymers as solid electrolytes have been proposed. For example, in Japanese Patent Application Laid-Open No. 63-158829, aluminum is vacuum-deposited on an aluminum foil with an aluminum oxide dielectric formed on the surface, this is used as an anode, and a supporting electrolyte is placed between the aluminum foil and a stainless steel cathode. It has been described that a solid electrolytic capacitor can be obtained by electrolytically oxidizing an aqueous solution containing a conductive polypyrrole to form a film of conductive polypyrrole on an anode.

However, according to this method, since the aluminum oxide dielectric film is insulating, in order to form a thin film of conductive polypyrrole thereon by electrolytic polymerization, aluminum is preliminarily coated on the surface of the dielectric film. The manufacturing process is complicated, and the manufacturing cost is inevitably high.

The amount you can swallow.

The present invention was made in order to solve the above-mentioned problems in conventional solid electrolytic capacitors using conductive polymer as a solid electrolyte, and uses a so-called coating method.
The purpose of the present invention is to provide a solid electrolytic capacitor with low impedance and high capacitance in a high frequency range obtained by forming a thin film of conductive polymer on a dielectric material, and a method for manufacturing such a solid electrolytic capacitor. .

That is, the present inventors have discovered that organic solvent-soluble polyaniline can be made into a thin film by casting, and by doping it, a conductive polymer thin film made of polyaniline can be formed. By forming a thin film of polyaniline on a dielectric film and doping it, the adhesion to the dielectric film can be improved by a method that is much simpler than the method that involves electrolytic oxidation of polymerizable monomers as described above. The present invention was achieved based on the discovery that it is possible to obtain a solid electrolytic capacitor with excellent performance, low impedance in the high frequency range, and large capacitance.

The solid electrolytic capacitor according to the present invention for the purpose of In particular, the solid electrolytic capacitor according to the present invention is characterized in that:
The conductive polymer made of polyaniline has the general formula (where m and n respectively represent the molar fraction of the quinone diamine structural unit and the phenylenediamine structural unit in the repeating unit, and O<m<1.0<n <1, m+n=1) as the main repeating unit, is soluble in organic solvents in a dedoped state, and
Intrinsic viscosity [η
] is 0.40 dl/g or more, and 457.9
Among the skeletal vibrations of para-substituted benzene in the laser Raman spectrum obtained by excitation with light with a wavelength of nm,
Intensity 1a of the Raman line of the skeleton stretching vibration occurring at a wave number higher than 1600 cm-' and Raman line intensity of the skeleton stretching vibration occurring at a wave number lower than 1600 cm-'! b ratio 1
It is preferable that an organic solvent-soluble polyaniline having a/I b of 1.0 or more is doped with a protonic acid having a pKa (I!! of 4.8 or less).

Furthermore, the solid electrolytic capacitor according to the present invention has a general formula (where ', m and n each represent the molar fraction of the quinonediimine structural unit and the phenylenediamine structural unit in the repeating unit, O<m<1, Q<n<l, m+n=1) as the main repeating unit, is soluble in organic solvents in a dedoped state, and has N-
Intrinsic viscosity [η
] is 0.40 dl/g or more, and 457.9
Among the skeletal vibrations of para-substituted benzene in the laser Raman spectrum obtained by excitation with light with a wavelength of nm,
Ratio I of the Raman line intensity 1a of the skeleton stretching vibration occurring at a wave number higher than 1600 cm-' and the Raman line intensity rb of the skeleton stretching vibration occurring at a wave number lower than 1600 cm-'
An organic polymer having a/Ib of 1.0 or more is dissolved in an organic solvent, the resulting solution is applied onto a dielectric film, and dried to form a film of organic solvent-soluble polyaniline. , can be obtained by doping this film with a protonic acid having a pKa value of 4.8 or less.

In the present invention, the conductive polymer made of polyaniline used as a solid electrolyte has the general formula , Q<
rn<1.0<n<1, m+n=1. ) as the main repeating unit, is soluble in organic solvents in a dedoped state, and has N-
Intrinsic viscosity [η
] is 0.40 dl/g or more, and 457.9
Among the skeletal vibrations of para-substituted benzene in the laser Raman spectrum obtained by excitation with light with a wavelength of nm,
The ratio of the Raman line intensity 1a of the skeleton stretching vibration occurring at a wave number higher than 1600 cm-' and the Raman line intensity 1b of the skeleton stretching vibration occurring at a wave number lower than 1600 cn+-' 1 a / I b is 1.0 or more It is made by doping organic solvent-soluble polyaniline with a protonic acid having a pKa value of 4.8 or less.

To form a conductive polymer made of polyaniline as described above on a dielectric film, first, a conductive oxidized polymer of aniline doped with protonic acid is prepared, and this is dedoped to form an organic Solvent-soluble polyaniline is prepared, then this organic solvent-soluble polyaniline is made into a solution, cast or coated on a dielectric film, dried to form a thin film, and finally, this thin film is doped with protonic acid.

First, the conductive oxidized polymer of aniline doped with the protic acid is treated with aniline in a solvent at a temperature of 5°C or less in the presence of a protic acid with an acid dissociation constant pKa value of 3.0 or less. The mark i4! is defined as the electromotive force in a reduction half-cell reaction using a standard hydrogen electrode as a base while maintaining the temperature preferably below O'C. Electrode potential is 0.6 V
The equivalent of the above aqueous solution of the oxidizing agent per mole of aniline is defined as the amount obtained by dividing 1 mole of the oxidizing agent by the number of electrons required to reduce one molecule of the oxidizing agent, and 2 equivalents or more,
It can be obtained by oxidative polymerization of aniline, preferably by gradually adding 2 to 2.5 equivalents.

Next, by dedoping the oxidized aniline polymer doped with a protonic acid with a basic substance, an organic solvent-soluble polyaniline can be obtained.

In the above oxidative polymerization of aniline, the oxidizing agent is
Manganese dioxide, ammonium peroxonisulfate, hydrogen peroxide, ferric salts, iodates, and the like are particularly preferably used. Among these, for example, ammonium peroxonisulfate and hydrogen peroxide both have 1
Since two electrons are involved per molecule, amounts in the range from 1 to 1.25 mol per mol of aniline are usually used.

In particular, the protonic acid used in the oxidative polymerization of aniline has an acid dissociation constant pKa value of 3.0 or less.
Examples include, but are not limited to, hydrochloric acid, sulfuric acid, nitric acid,
Inorganic acids such as perchloric acid, hydrofluoroboric acid, hydrofluoric phosphoric acid, hydrofluoric acid, and hydroiodic acid, aromatic sulfonic acids such as benzenesulfonic acid and p-toluenesulfonic acid, methanesulfonic acid, ethanesulfone Examples include alkanesulfonic acids such as acids, phenols such as picric acid, aromatic carboxylic acids such as m-nitrobenzoic acid, and aliphatic carboxylic acids such as dichloroacetic acid and malonic acid.

Polymeric acids can also be used. Examples of such polymer acids include polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallylsulfonic acid, polyvinyl sulfuric acid, and the like.

The amount of protic acid used depends on the reaction mode of the oxidizing agent used. For example, in the case of manganese dioxide, the oxidation reaction is Mn0z-1-411"-1-2e--+ Mn"+2
Since it is represented by H,0, it is necessary to use a protic acid that can supply at least four times the molar amount of protons as the manganese dioxide used. Also, in the case of hydrogen peroxide, the oxidation reaction is expressed as )1202 + 2H" +28- →2LO, so it is necessary to use a protonic acid that can supply at least twice the molar amount of protons as the hydrogen peroxide used. On the other hand, in the case of ammonium beroxon disulfate, the oxidation reaction is represented by S, 0."+2e--+2SO4"-, so there is no need to use a protonic acid.However, ammonium beroxon disulfate is used as the oxidizing agent. Even in this case, it is preferable to use a protic acid in an equimolar amount to the oxidizing agent.

As a solvent for oxidative polymerization of aniline, aniline,
A substance that dissolves the protonic acid and the oxidizing agent and is not oxidized by the oxidizing agent is used.

Water is most preferably used, but if necessary, alcohols such as methanol and ethanol, nitriles such as acetonitrile, N-methyl-2-pyrrolidone,
Polar solvents such as dimethyl sulfoxide, ethers such as tetrahydrofuran, and organic acids such as acetic acid can also be used. Moreover, a mixed solvent of these organic solvents and water can also be used.

In the preparation of the organic solvent-soluble polyaniline, it is important to always maintain the temperature of the reaction mixture below 5° C. during the reaction, especially during the addition of the oxidizing agent solution to the aniline solution. Therefore, the oxidizing agent solution must be added gradually to the aniline so that the temperature of the reaction mixture does not exceed 5°C. When adding an oxidizing agent rapidly, external cooling may raise the temperature of the reaction mixture and produce a low molecular weight polymer, or even after dedoping as described below, a solvent-insoluble oxidized polymer may be produced. do.

In particular, in the above reaction, it is preferable to maintain the reaction temperature below 0°C, so that after dedoping, the measurement was carried out at 30°C in N-methyl-2-pyrrolidone (the same applies hereinafter). A high molecular weight organic solvent-soluble polyaniline having an intrinsic viscosity [η] of 1.0 dl/g or more can be obtained.

In this way, a polyaniline doped with the protic acid used can be obtained. In a doped state,
Since this polyaniline forms a salt with a protonic acid, it does not dissolve in an organic solvent as described below. It is well known that salts of high molecular weight amines are generally poorly soluble in organic solvents.

However, by dedoping this organic solvent-insoluble polyaniline, organic solvent-soluble polyaniline can be obtained.

This dedoping of polyaniline doped with protonic acid is a kind of neutralization reaction, so if it is a basic substance that can neutralize the protonic acid as a dopant,
Although not particularly limited, metal hydroxides such as aqueous ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, and calcium hydroxide are preferably used. For dedoping, a basic substance may be added directly to the reaction mixture after the above-mentioned oxidative polymerization of aniline, or the polymer may be isolated and then treated with a basic substance.

Doped polyaniline obtained by oxidative polymerization of aniline usually has a conductivity of 10-'S/c+s or more and has a black edge color, but after dedoping, it has a purple or purplish copper color. be. This discoloration is due to the amine nitrogen in the salt structure in the polymer being converted to free acorn.

The conductivity is usually on the order of 10'S/cm.

The dedoped polyaniline thus obtained has a high molecular weight and is soluble in various organic solvents. Examples of such organic solvents include N-methyl-2-pyrrolidone, N,N-dimethylacedodando, N,N-dimethylformamide, dimethylsulfoxide, 1,3-dimethyl-2-imidazolidinone, and sulfolane. I can do it. Solubility depends on the average molecular weight of the polymer and the solvent, but 0.5 to 100% of the polymer is dissolved, and 1 to 30% by weight.
A solution of can be obtained. In particular, formamide in this undoped state exhibits high solubility in N-methyl-2-pyrrolidone, typically 20-100% of that of polyaniline.
can be dissolved to obtain a 3-30% by weight solution. However, tetrahydrofuran, 80% acetic acid aqueous solution, 60%
It does not dissolve in formic acid aqueous solution, acetonitrile, etc.

Therefore, if such organic solvent-soluble polyaniline is dissolved in an organic solvent and cast, a self-supporting, flexible and strong film can be obtained, and if it is cast or coated on a dielectric film, A strong and flexible thin film can be formed on the dielectric film.

In order to obtain a strong film or thin film, organic solvent-soluble polyaniline must have an intrinsic viscosity [η] of 0.40 di/g or more when measured at 30°C in N-methylpyrrolidone. It is desirable to use one.

The soluble polyaniline was determined from elemental analysis, infrared absorption spectrum, ESR spectrum, laser/Raman spectrum, thermogravimetric analysis, solubility in solvents, and visible to near infrared absorption spectrum (where m and n are each a repeating unit). It shows the molar fraction of the quinonediimine structural unit and the phenylenediamine structural unit in the quinone diimine structural unit, O<m<1, O<n<l, m+n=1) as the main repeating unit.

Here, the characteristics of organic solvent-soluble polyaniline obtained from laser Raman spectra will be explained while comparing it with conventionally known so-called polyaniline.

Generally, there is vibrational spectroscopy as a means of obtaining information regarding vibrations between atoms constituting a substance, and this includes infrared spectroscopy and Raman spectroscopy. Infrared spectroscopy is active on vibrational modes that result in a change in dipole moment, and Raman spectroscopy is active on vibrational modes that result in a change in polarizability. Therefore,
The two have a complementary relationship, and in terms of −i, the vibrational mode that is strong in infrared spectroscopy is weak in Raman spectroscopy.
On the other hand, the vibrational modes that appear strongly in Raman spectroscopy are
It is weak in infrared spectroscopy.

Infrared absorption spectra are obtained by detecting energy absorption between vibrational levels, and Raman spectra are
Scattered light (Raman scattering) that occurs when molecules fall to a higher vibrational level of the ground state after being excited by light irradiation.
obtained by detecting. At this time, the vibrational energy level can be determined from the energy difference between the scattered light and the irradiated light.

Usually, a Raman spectrum is obtained by visible light excitation from an argon laser or the like. It is known that when a sample has an absorption band in the visible region, a very strong Raman line can be obtained when the wavelength of the irradiated laser beam and the absorption band are matched.

This phenomenon is called the resonance Raman effect, and according to this, a Raman line that is 104 to 105 times stronger than a normal Raman line can be obtained. According to such a resonance Raman effect, information about the chemical structure portion excited by the wavelength of the irradiated laser light can be obtained in a more emphasized manner. Therefore, by measuring the Raman spectrum while changing the wavelength of the irradiated laser light, the chemical structure of the sample can be analyzed more accurately. Such features are features of Raman spectroscopy that are not found in infrared spectroscopy.

Figure 1 shows organic solvent soluble N-methyl-2-
Intrinsic viscosity [η] measured at 30°C in pyrrolidone is 1
．． For a sample formed into a disk shape from dedoped polyaniline powder with a concentration of 2 dl/g, the excitation wavelength was 457.
．． This is a laser Raman spectrum obtained by irradiation at 9 nm. The hum of the Raman line is as follows. 162
2 and 1591ca+-' are the skeletal stretching vibrations of para-substituted benzene, 1489 and 1479cm-' are the stretching vibrations of C=C and C=N in the quinone diimine structure, 1220c
m-' is a mixture of C-N stretching vibration and C-C stretching vibration, 11
85 and 1165 cm-' are in-plane bending vibrations of C-H.

Figure 2 shows Y, Fujiwara et al.
5ynth, Net, +16, 189 (1986)
This is a laser Raman spectrum obtained by irradiating the dedoped polyaniline shown in Figure 1 with an excitation wavelength of 457.9 nm. This polyaniline was obtained by electrolytic oxidative polymerization of aniline on a platinum electrode.

As shown in FIG. 1, in the solvent-soluble dedoped polyaniline used in the present invention, among the skeletal vibrations of para-substituted benzene, the Raman line intensity of the skeletal stretching vibration that occurs at a wave number higher than 1600 cm-' 1a and 1600c
The ratio 1a/Ib of Raman ray intensity 1b occurring at a lower wave number than m-' is 1.0 or more. In contrast, conventionally known polyanilines, including those shown in Figure 2, including those produced by chemical oxidative polymerization, all have the above ratio! a/f b is less than 1.0.

The Raman lines at 1622 and 1591 cm-' are both based on skeletal stretching vibrations of para-substituted benzene. Polyaniline in a reduced state does not have a quinone diimine structure and therefore produces a Raman line only at 1621 cm-', but undoped polyaniline, which has a quinone diimine structure, produces Raman lines at 1622 and 159 cm-', as described above.
A Raman line is detected at 1 cm-'. These Raman lines exhibit excitation wavelength dependence as shown in FIG.

The excitation wavelength was changed from 488.0 nm to 476.5 nm to 4
As the wavelength changes to 57.9 nm, the I
a/Ib changes. That is, at 488.0 nm, I a / I b is smaller than 1.0, but 457
At ゜9 nm, it is 1.0 or more, 488.0
Compared to the case of nm, the I a / I b intensity is reversed. This reversal phenomenon may be explained as follows.

Figure 4 shows the electronic spectrum of solvent-soluble polyaniline. The peak at 647 nm disappears when polyaniline is reduced, so it appears to be derived from the quinone diimine structure. Conversely, the peak at 334 nm disappears when polyaniline is reduced. Since the intensity increases, it seems to originate from the ππ9 transition of para-substituted benzene. FIG. 4 shows the Raman excitation wavelengths described above. Here, for the para-substituted benzene skeleton stretching vibration band, the excitation wavelength is set to 48
When changing to the short wavelength side from 8°Onm to 457.9nrn, compared to the band of 1591cm-', the band becomes 162cm-'.
It is thought that the resonance conditions of the resonance Raman effect of the 2 cm-' band become more favorable, and the above-mentioned change in relative intensity occurs.

Next, in the spectra shown in Figures 1 and 2, 15
The reason why the relative intensities of the Raman lines at 91 cm-' and 1622 cm-' are different despite having the same excitation wavelength (457,9 m) may be explained as follows. That is, N as a model compound of phenylenediamine structure,
N'-diphenyl-p-phenylenecyamine is 1617
N,N''-diphenyl-ρ-benzoquinone diimine, which has a Raman line only at cm-' and is a model compound with a quinone diimine structure, has a Raman line at 1568 cm-' and 1621 cm.
-' has a Raman line, as shown in (a) below, the rose-substituted benzene ring that is nonconjugated with the quinone diimine structure has a 1622 cm
-' Raman line and as shown in (b) below, the para-substituted benzene ring conjugated with the quinone diimine structure is
It is estimated to have Raman lines of 1591 CO+-' and 1622 cm-'.

■ N,N'-diphenyl- one phenylene diagonal quinone diimine structure ■ (a) (b) 1622cwaku1591co+ 622 From the results of elemental analysis, in the undoped solvent-soluble polyaniline, the number of quinone diimines and the number of phenylene diamines ξ are Since they appear to be almost the same, the structural chain of such undoped solvent-soluble polyaniline is an alternating copolymer of quinone diimine structures and phenylene diamine structures, as shown in (C), from the connection mode of the quinone diimine structure and the phenylene diamine structure. It is classified into two types: a physical chain, and a block copolymer chain of a quinone diimine structure and a phenylene diamine structure, as shown in (d). In the figure, the individually substituted benzene rings indicated by arrows indicate benzene rings that are non-conjugated with the quinone diimine. In a coalescing chain, for example, 8
There are three per mer chain unit. When the chain unit is long, the difference in the number of quinone diimine and non-conjugated benzene rings in both becomes even larger. This difference is 1591
It can be said that this is caused by the difference in relative intensity between the Raman lines at cm-' and 1622 cm-'.

In solvent-soluble polyaniline, since the I a / I b ratio in the laser Raman spectrum is 1.0 or more, it contains many quinone diimine structures and non-conjugated Hensen rings, and thus the block copolymer-like It seems that there is a chain.

The solubility of polyaniline in organic solvents is rationally explained by the presence of such block copolymer-like chains.

Generally, the imine nitrogen (-N
=) is known to form a hydrogen bond with the nearby secondary amino group nitrogen (-NH-) (Macromo
lecules, 2L 1297 (1988y'),
Hydrogen bonds between secondary amino group nitrogens are not strong.

Therefore, when polyaniline has the above-mentioned alternating copolymer chains, it forms a strong network of hydrogen bonds as shown in (g). The fact that conventionally known polyaniline is insoluble in many Ja-containing solvents even in an undoped state is thought to be due to the formation of such a strong network of hydrogen bonds. On the other hand, when the polymer chain is a block copolymer-like chain, such as dedoped solvent-soluble polyaniline, the block chains usually have different lengths, so (e) As can be seen, even if the phenylenediamine structural part and the quinonediimine structural part are adjacent, many hydrogen bonds cannot be formed, and the solvent may enter between the polymer chains and form hydrogen bonds with the solvent. , it will be dissolved in organic solvent. If all parts of the block chain had exactly the same length, it would form a network of hydrogen bonds as described above, but the probability of having such a structure is extremely small.
Normally it can be ignored.

\ / Furthermore, such interchain interactions can also be explained from the C-H in-plane bending vibration in the laser Raman spectrum.

The C- of polyaniline in the dedoped state shown in FIG.
The Raman line at 1 162 cm-', which is attributed to H in-plane bending vibration, becomes 1181 cm-' when polyaniline is reduced and all imine nitrogens are converted to secondary amino nitrogens.
Shift to a higher wave number.

As described above, in a dedoped state, solvent-soluble polyaniline has two Raman lines, 1165 and 1185 cm-', which are attributed to C-H in-plane bending vibration. This Raman line at 1185 cm-' is not seen in conventionally known undoped polyaniline, and is close to 1181 cm-', which is attributed to the C-H in-plane bending vibration in the reduced state. It shows the value.

From these points, it is considered that the solvent-soluble polyaniline has a block copolymer-like chain in a dedoped state and has an atmosphere of a reduced structure.

This suggests that the solvent-soluble polyaniline used in the present invention is different from conventionally known polyanilines because it has high solubility in organic solvents despite its high molecular weight. It is a novel polymer with structural chains.

In this way, the oxidized polymer of aniline has a quinone diimine structural unit and a phenylene diamine structural unit as repeating units in a block copolymer chain as described above, so when it is doped with protonic acid, It is explained as having electrical conductivity only through acid-base reactions without any redox reactions. This conductive mechanism is based on Ha, G, MacDiara+id et al. (A, G.

MacDiarmid et al., J. Che
lIl, Soc,, Chem.

By doping with a protic acid, the quinone diimine structure is protonated, as shown below, and this forms a 75-quinone cation radical structure, which has electrical conductivity.

Such a state is called a polaron state.

1 1HX (Proton 61I) ↓ Intramolecular redox reaction (Se[quinone cation radical (Polaron)) As mentioned above, polyaniline, which is solvent-soluble in an undoped state, is dissolved in an organic solvent and applied to the dielectric film. By casting or coating, thin films can be formed, which can easily be made conductive by doping with protic acids, and thus, according to the present invention, can easily be made dielectric. A thin film of conductive polymer can be formed on the body membrane. Here, as the protonic acid, those mentioned above can be used.

The conductivity of the conductive thin film obtained by doping depends on the pKa value of the protonic acid used. In this method, protonic acids with a pKa value of 4.8 or less are effective,
When a protonic acid having a pKa value of 1 to 4.8 is used, the smaller the pKa value, that is, the stronger the acidity, the higher the electrical conductivity of the obtained thin film.

However, when the pKa value is less than 1, the conductivity of the thin film no longer changes much and is almost constant.

However, of course, a protonic acid having a pKa value of 1 or less may be used if necessary.

The conductivity of the thin film thus obtained by doping with protonic acid is usually greater than or equal to 10-'S/Cm, often greater than or equal to 10-'S/c+n.

This conductive thin film is strong and does not break easily even when bent. However, this iR membrane, similar to the conductive aniline oxidized polymer prepared in the presence of protic acids,
Since it is doped with protonic acid, it does not dissolve in the organic solvent mentioned above for the reason mentioned above.

In the present invention, by using polyvinylsulfonic acid as the protonic acid, it is possible to obtain a conductive thin film in which dedoping is particularly difficult to occur.

Generally, polyaniline obtained by oxidative polymerization is doped with a protonic acid used during polymerization and has electrical conductivity. However, it is known that such conductive polyaniline releases protonic acid, which is a dopant, in a weakly acidic, neutral, or alkaline aqueous solution or a basic organic solvent, and its conductivity decreases significantly. ing.

Furthermore, the protic acids commonly used as dopants are low-molecular acids such as hydrochloric acid, sulfuric acid, and perchloric acid. It spreads easily and can corrode surrounding metal parts in which it is used.

However, according to the present invention, the conductive polyaniline thin film with polyvinylsulfonic acid as a dopant is
Not only polyaniline doped with the above-mentioned low molecular acids, but also polystyrene sulfonic acid, polyallylsulfonic acid,
Even compared to polyaniline doped with a polymeric acid such as polyvinyl sulfuric acid, the decrease in electrical conductivity is significantly smaller in an aqueous solution of pt+2.5 or higher, especially around neutrality.

The reason why the electrical conductivity of polyaniline doped with polyvinyl sulfonic acid is so small is not necessarily clear, but it is due to the polymer effect due to polyvinyl sulfonic acid being a polymeric acid with polyvalent charges. This is thought to be due to the molecular structure effect in which polyvinylsulfonic acid strongly interacts with polyaniline at the molecular level.

To dope a dedoped polyaniline thin film with polyvinylsulfonic acid, the polyaniline thin film is usually immersed in an aqueous polyvinylsulfonic acid solution having a pH of 2 or less. The time required for doping depends on the thickness of the polyaniline thin film used and the pH of the polyvinylsulfonic acid aqueous solution, but usually ranges from several tens of seconds to several days. In order to shorten the doping time, it is preferable to use an aqueous solution with a pH of 1 or less. Furthermore, in general, if polyvinyl sulfonic acid with a low degree of polymerization is used, doping can be carried out quickly, whereas if polyvinyl sulfonic acid with a high degree of polymerization is used, conductive polyaniline, which is difficult to dedope, can be doped. A thin film can be obtained.

In this way, a polyaniline thin film containing polyvinylsulfonic acid as a dopant is difficult to release the dopant in a weakly acidic, neutral, or alkaline aqueous solution or in a basic organic solvent, so it is difficult to form a thin film on a current reading body. In various processes, the conductivity does not change even when washed with water or organic solvents, and it is possible to advantageously form a conductive thin film. It is possible to maintain its excellent charging properties without causing any damage.

Further, for example, by doping a polyaniline thin film with polyvinylsulfonic acid and washing it thoroughly with water, it is possible to obtain a conductive thin film that does not contain other protonic acids, such as the above-mentioned low molecular acids, as a dopant. Therefore, in such a conductive thin film, there is no risk of corrosion of surrounding metal parts by low molecular acids that may be partially mixed into conductive polyaniline as a dopant.

According to the present invention, a film-forming metal with a roughened surface is subjected to electrolytic oxidation or air oxidation to form an oxide of the metal to form a dielectric film, and then a solution of the organic solvent-soluble polyaniline described above is formed. By casting or coating on this dielectric film, drying it to form a film, and doping it with protonic acid,
A thin film of a conductive organic polymer can be easily formed on a dielectric film, and thus a solid electrolytic capacitor can be obtained.

In particular, according to the present invention, since the process of applying solvent-soluble polyaniline onto the dielectric and the doping process can be performed separately, it is possible to easily form a conductive thin film on the dielectric.

Generally, aluminum or tantalum is preferably used as the film-forming metal, and therefore, an aluminum oxide or tantalum oxide film is preferably used as the dielectric film.

In general, dielectrics, as mentioned above, usually consist of a film of aluminum oxide or tantalum oxide, and this film is
It is usually roughened and porous to increase surface area. The solid electrolyte needs to be in close contact with the porous rough surface of the oxide film. According to the present invention, since the solvent-soluble polyaniline can be made into a thin film by casting or coating, the thickness of the thin film on the dielectric material can be adjusted as desired. Further, the type of dopant and the amount of doping can also be adjusted.

Therefore, by selecting the film thickness and doping conditions of the thin film, the conductivity of the conductive polymer thin film can be freely adjusted. For example, according to the present invention, a thin film with a thickness of 0.01 to 200 μm can be formed on a dielectric material, and as described above, such a thin film has a pKa value of 4.
．． If doped with a protonic acid of 8 or less, the conductivity is 1.
O-6~30S/cm, preferably 10-''~105
7cm can be given.

Moreover, according to the solid electrolytic capacitor according to the present invention,
Since the conductivity of the conductive polymer is based on electron conduction, the impedance is lower and the capacitance is higher in the high frequency range than an ion conductive electrolyte capacitor.

As described above, according to the solid electrolytic capacitor of the present invention, a conductive polymer thin film made of polyaniline having conductivity due to electron conduction is formed on the dielectric film, and the impedance is reduced in the high frequency region. Small and large capacity.

Furthermore, unlike many conventionally known conductive polymers, the conductive polymer made of polyaniline used in the present invention is obtained by forming a thin film of organic solvent-soluble polyaniline and doping it. According to the method, a conductive thin film with excellent adhesion can be easily formed on a dielectric film.

EXAMPLES The present invention will be explained below using examples together with reference examples for illustrating the production of organic solvent-soluble polyaniline used in the present invention, but the present invention is not limited in any way by these examples.

Reference Example 1 (Production of doped conductive organic polymer by oxidative polymerization of aniline) 10ff equipped with a stirring device, thermometer and straight pipe adapter
i 6000 g of distilled water in a volume separable flask, 36
% hydrochloric acid and 400 g (4,295 mol) of aniline were charged in this order to dissolve the aniline. Separately, distilled water in a beaker while cooling with ice water.
434 g (4,295 mol) of 97% concentrated sulfuric acid was added to 3 g and mixed to prepare an aqueous sulfuric acid solution. This sulfuric acid aqueous solution was added to the separable flask, and the entire flask was cooled to -4°C in a low temperature constant temperature bath.

Next, 980 g (4,295 mol) of ammonium beloxonisulfate was added to 2293 g of distilled water in a beaker.
An oxidizing agent aqueous solution was prepared by dissolving it.

The entire flask was cooled in a low-temperature thermostatic bath, and while the temperature of the reaction mixture was maintained at -3°C or less, the above aqueous solution of ammonium beroxon disulfate was added to the acidic aqueous solution of aniline salt from a straight tube adapter using a tubing pump while stirring. was gradually added dropwise at a rate of 1 ml/min or less. Initially, the colorless and transparent solution turned from greenish-blue to a black-rimmed color as the polymerization progressed, and then a black-rimmed powder was precipitated.

Although an increase in temperature is observed in the reaction mixture during this powder precipitation, in this case as well, in order to obtain a high molecular weight polymer according to the present invention, the temperature in the reaction system must be kept below O'C, preferably at 13°C. It is important to keep it below C. After the powder is precipitated, the dropping rate of the aqueous solution of beroxonisulfate may be slightly faster, for example, about 8 ml/min. However, even in this case, it is necessary to monitor the temperature of the reaction mixture and adjust the rate of addition so as to maintain the temperature below -3°C. (It took 7 hours,
After the dropwise addition of the aqueous solution of ammonium belloxonisulfate was completed, stirring was continued for an additional hour at a temperature of -3°C or lower.

The obtained polymer powder was filtered, washed with water and acetone,
It was vacuum dried at room temperature to obtain 430 g of a black-rimmed polymer powder. This was pressure-molded into a disk with a diameter of 13 mm and a thickness of 700 μm, and its electrical conductivity was measured by the van der Pauw method and found to be 14 S/cm.

(Dedoping of conductive organic polymer with ammonia) 350 g of the above doped conductive organic polymer powder was mixed with 41 g of 2N ammonia water! , and stirred for 5 hours at 5000 rpm using an autohomogen mixer. The mixture changed from a black border color to a blue-purple color.

The powder was filtered out using a Buchner funnel, washed repeatedly with distilled water while stirring in a beaker until the filtrate became colorless, and then washed with acetone until the filtrate became neutral. Thereafter, the powder was vacuum dried at room temperature for 10 hours to obtain 280 g of a dark brown undoped polymer powder.

This polymer is soluble in N-methyl-2-pyrrolidone, and the solubility is 8 g (7.4%) per 100 g of the same solvent.
)Met. Further, the intrinsic viscosity [η] measured using this as a solvent at 30°C was 1.23.

This polymer had a solubility of less than 1% in dimethyl sulfoxide and dimethyl formamide.

Tetrahydrofuran, pyridine, 80% acetic acid aqueous solution, 6
It was not substantially dissolved in 0% formic acid aqueous solution and acetonitrile.

FIG. 1 shows a laser Raman spectrum obtained by irradiating a disk-shaped sample of this undoped polyaniline powder with an excitation wavelength of 457.degree. 9 nm.

For comparison, Y. Fujiwara et al.
5ynth, Met,, 16.189 (198
Regarding the undoped polyaniline shown in 6),
FIG. 2 shows a laser Raman spectrum obtained by irradiation with an excitation wavelength of 457.9 nm. This polyaniline was obtained by electrolytic oxidative polymerization of aniline on a platinum electrode.

In addition, by changing the wavelength of the laser excitation light,
Figure 3 shows the results of Raman spectra measured in a range of 1700 cm-'. The excitation wavelength was set to 488.0n.
As the wavelength changes from m to 476.5 nm to 457°9 nm, la/Ib changes, and 457°
．． At 9 nm, it is 1.0 or more, which is 488. On
It is shown that the Ia/Ib intensity is reversed compared to when m.

Further, FIG. 4 shows the electronic spectrum.

Next, regarding the organic solvent soluble polyaniline, N-
Using a GPC column for methyl-2-pyrrolidone, G
PC measurement was performed. Three types of columns for N-methyl-2-pyrrolidone were used in combination. Further, as an eluent, a solution of lithium bromide in N-methyl-2-pyrrolidone with a concentration of 0.01 mol/l was used. FIG. 5 shows the results of GPC measurement.

From this result, the organic solvent-soluble polyaniline has a number average molecular weight of 23,000 and a weight average molecular weight of 160,000.
(All values are based on polystyrene standards).

Similarly, by varying the reaction conditions, organic solvent-soluble polyanilines with different intrinsic viscosities [η] measured in N-methyl 2-pyrrolidone at 30°C were obtained. Regarding these,
Table 1 shows the intrinsic viscosity [η] and the number average molecular weight and weight average molecular weight determined by GPC.

Table Reference Example 2 (Preparation of self-supporting film using soluble aniline oxide polymer) Add 5 g of the dedoped aniline oxide polymer powder obtained in Reference Example 1 little by little to 95 g of N-methyl-2-pyrrolidone. Dissolution at room temperature yielded a black-blue solution. When this solution was vacuum filtered using a 03 glass filter, extremely small amounts of insoluble matter remained on the filter. This filter was washed with acetone, and after drying the remaining insoluble matter, the weight was measured and found to be 15 mg. Therefore, 98.5% of the polymer is dissolved and 1.5% of the insoluble matter is dissolved.
It was 5%.

The polymer solution thus obtained was cast onto a glass plate and squeezed with a glass rod, followed by continuous evaporation of N-methyl-2-pyrrolidone in a hot air circulating drying layer.

After this, by immersing the glass plate in cold water, the polymer film will peel off naturally from the glass plate, thus
A polymer film with a thickness of 40 μm was obtained.

After washing this film with acetone, it was air-dried at room temperature to obtain a film with copper-colored metallic luster.

Films differ in strength and solubility depending on their drying temperature. When the drying temperature is below 100° C., the resulting film dissolves in a small amount in N-methyl-2-pyrrolidone and has relatively low strength. However, the film obtained by heating at a temperature of 130° C. or higher is very tough and does not dissolve in N-methyl-2-pyrrolidone or other organic solvents. It also does not dissolve in concentrated sulfuric acid.

Thus, it appears that when heated at high temperatures, the polymer molecules crosslink with each other in the process and become insoluble.

The dedoped films thus obtained all had electrical conductivities on the order of 10-''37 cm.

Further, the film did not crack even after being bent 100 times, and its tensile strength was 850 kg/cffl.

Reference Example 3 (Doping of self-supporting film with protonic acid) In Reference Example 2, the self-supporting film obtained by heating and drying at 160°C for 2 hours was placed in IN aqueous solutions of sulfuric acid, perchloric acid, and hydrochloric acid at room temperature. After being immersed for 66 hours, it was washed with acetone and air-dried to obtain conductive films.

Both films exhibit a deep blue color and have electrical conductivities of 9 S/cab, 13 S/cm, and 6, respectively.
It was S/cm. Further, the tensile strength of the film doped with perchloric acid was 520 kg/cffl.

Reference Example 4 (Spectrum and structure of soluble polymer and insoluble film-formed polymer both in dedoped state) Spectrum and structure of soluble polymer powder obtained in Reference Example 1 and insoluble polymer film obtained in Reference Example 2 FT-IR spectra obtained by the KBri two-agent method are shown in FIGS. 6 and 7, respectively. The spectrum of the insoluble polymer film obtained in Reference Example 2 contains 1 due to benzoquinone, an impurity thought to have been generated by heating.
Although some absorption at 660 cm-' is observed, the two spectra are almost the same, so although the polymer becomes solvent-insolubilized by crosslinking when the solvent is heated and dried after casting the solvent-soluble polymer, it has a large chemical structure. It is recognized that no change has occurred.

Next, the results of elemental analysis of the soluble polymer and insoluble polymer are shown below.

Danpo Sumitomo Kanatome C, 77, 19, 11, 4, 7 (i; N, 14.8
6 (total 96.81) Tamasumi and heavy standing C, 7B, 34; H, 4,99; N, 15.16
(Total 98.49) Based on this elemental analysis, C
The compositional formula of the soluble polymer standardized to 12,OO is C82
,. . H8,8□N1.911, and the m strength of the insoluble polymer is C62. . 11,1N+, 99.

On the other hand, similarly, CI 2. The quinonediimine structural unit and phenylenediamine structural unit normalized to OO are as follows.

Kinonshi Dann “Confession* Ct□H,N.

Phenylenecyan CC12111ON Therefore, as described above, both the soluble polymer and the solvent-insoluble polymer are polymers having quinonediimine structural units and phenylenediamine structural units as main repeating units.

Reference Example 5 The polymer film obtained in Reference Example 2 was immersed in aqueous or alcoholic solutions of protonic acids having various pKa values, and the possibility of doping was investigated. The electrical conductivity of polymer films obtained by doping with protic acids having various pKa values is shown in Table 2. It is shown that protic acids with pKa values of 4.8 or less are effective for doping polymers.

Example 1 5 g of dedoped organic solvent-soluble polyaniline powder obtained in Reference Example 1 was mixed with 9 g of N-methyl 2-pyrrolidone.
It was added little by little to 5 g and dissolved to obtain a black-blue solution.

This solution was applied onto an alumina dielectric film heated to 95°C to form a polyaniline thin film.

After repeating this operation three times, the thin film was doped with sulfuric acid. Further, silver was deposited thereon over an area of 1010 mm x 13 mm to produce a solid electrolytic capacitor.

Table 3 shows the results of measuring the frequency characteristics of the capacitance and impedance of this capacitor.

Example 2 2 g of the same organic solvent-soluble polyaniline powder as in Example 1 was added little by little to 98 g of N-methyl-2-pyrrolidone and dissolved to obtain a black-blue solution.

This solution was applied onto an alumina dielectric film heated to 95°C to form a polyaniline thin film.

After repeating this operation five times, the thin film was doped with perchloric acid. Further, silver was deposited thereon over an area of 10 mm x 10 mm x 13 to produce a solid electrolytic capacitor.

Table 3 shows the results of measuring the frequency characteristics of the capacitance and impedance of this capacitor.

Example 2 2 g of the same organic solvent-soluble polyaniline powder as in Example 1 was added little by little to 98 g of N-methyl-2-pyrrolidone and dissolved to obtain a black-blue solution.

This solution was applied onto an alumina dielectric film heated to 95°C to form a polyaniline thin film.

After repeating this operation five times, the thin film was doped with perchloric acid. Further, silver was deposited thereon over an area of 10 mm x 10 mm x 13 to produce a solid electrolytic capacitor.

Table 3 shows the results of measuring the frequency characteristics of the capacitance and impedance of this capacitor.

Example 3 2 g of the same organic solvent-soluble polyaniline powder as in Example 1 was added little by little to 98 g of N-methyl-2-pyrrolidone and dissolved to obtain a black-blue solution.

This solution was applied onto an alumina dielectric film heated to 95°C to form a polyaniline thin film.

After repeating this operation 10 times, the thin film was doped with perchloric acid. Further, silver was deposited thereon over an area of 10 mm x 13 squares to produce a solid electrolytic capacitor.

Table 3 shows the results of measuring the frequency characteristics of the capacitance and impedance of this capacitor.

Table 3 Comparative Example 1 A commercially available electrolyte type electrolytic capacitor was disassembled, an aluminum foil with a diameter of 2511II11 was placed on the isolation paper containing the electrolyte, and the same characteristics as above were measured under a load of 2 kg. did. The results are shown in Table 3.

[Brief explanation of drawings]

Figure 1 shows the laser Raman spectrum of an organic solvent-soluble aniline oxidized polymer in a dedoped state used for manufacturing a solid electrolytic capacitor according to the present invention when excited with light at a wavelength of 457.9 nm, and Figure 2 shows the following: Figure 3 shows the laser Raman spectrum of conventionally known polyaniline when excited with light at a wavelength of 457.9 nm.
Figure 1 shows the laser Raman spectra of the same solvent-soluble polyaniline excited with light of various excitation wavelengths. Figure 4 shows the N of the organic solvent-soluble aniline oxidation polymer.
-Electronic spectrum of methyl-2-pyrrolidone solution, 5th
The figure is a graph showing the molecular weight distribution of solvent-soluble polyaniline by GPC, Figure 6 is the FT-IR spectrum of solvent-soluble polyaniline oxidized polymer by KBrBr method, and Figure 7 is the graph showing the molecular weight distribution of solvent-soluble polyaniline oxidized polymer by KBrBr method. FT- of the obtained solvent-insoluble film by KBrBr method
This is an IR spectrum. Figure 4 Ichiromasu) Figure 5 1i (molecular weight)

Claims (3)

[Claims] (1) A dielectric oxide film formed on the film-forming metal;
A solid electrolytic capacitor characterized in that a thin film of a conductive polymer made of polyaniline is formed as a solid electrolyte on the dielectric oxide film. (2) A conductive polymer made of polyaniline has a general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. 0<m<1, 0<n<1, m+n=1) as the main repeating unit, which is soluble in organic solvents in a dedoped state, and N-
Intrinsic viscosity [η] measured at 30°C in methylpyrrolidone
is 0.40 dl/g or more and 457.9 nm
Among the skeletal vibrations of para-substituted benzene in the laser Raman spectrum obtained by excitation with light of wavelength, 16
The ratio Ia/Ib of the Raman line intensity Ia of the skeleton stretching vibration that appears at a wave number higher than 00 cm^-^1 and the Raman line intensity Ib of the skeleton stretching vibration that appears at a wave number lower than 1600 cm^-^1 is 1.0 or more 2. The solid electrolytic capacitor according to claim 1, wherein the organic solvent-soluble polyaniline is doped with a protic acid having a pKa value of 4.8 or less. (3) a dielectric oxide film formed on the film-forming metal;
In the manufacturing method of solid electrolytic capacitors, in which a thin film of conductive polymer made of polyaniline is formed as a solid electrolyte on this dielectric oxide film, there are general formulas ▲mathematical formulas, chemical formulas, tables, etc.▼ (in the formulas, m and n indicates the mole fraction of the quinonediimine structural unit and phenylenediamine structural unit in the repeating unit, respectively, and 0<m<1, 0<n<1, m+n=1.) as the main repeating unit. is soluble in organic solvents in a dedoped state, and N-
Intrinsic viscosity [η] measured at 30°C in methylpyrrolidone
is 0.40 dl/g or more and 457.9 nm
Among the skeletal vibrations of para-substituted benzene in the laser Raman spectrum obtained by excitation with light of wavelength, 16
The ratio Ia/Ib of the Raman line intensity Ia of the skeleton stretching vibration that appears at a wave number higher than 00 cm^-^1 and the Raman line intensity Ib of the skeleton stretching vibration that appears at a wave number lower than 1600 cm^-^1 is 1.0 or more An organic polymer having a pKa value of 4.8 is dissolved in an organic solvent, and the resulting solution is applied onto a dielectric film and dried to form a thin film of organic solvent-soluble polyaniline. A method for manufacturing a solid electrolytic capacitor, characterized by doping with the following protonic acid.