JP2015010161A - Conductive polymer solution, conductive polymer material, and solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive polymer material with high water retainability for use in a solid electrolyte, and to provide a solid electrolytic capacitor with low LC.SOLUTION: A conductive polymer solution contains: conductive polymer particles which contain a polyanion having a structure crosslinked by a crosslinking agent and a conductive polymer; and at least one of water and a water-miscible organic solvent. A crosslinking proportion indicating the ratio of the number of moles of the crosslinking agent to the number of moles of anions on the main chain of the polyanion is higher at the surface of the conductive polymer particles than inside the conductive polymer particles.

Description

  The present invention relates to a conductive polymer solution, a conductive polymer material, and a solid electrolytic capacitor.

  Conductive polymer materials are used for capacitor electrodes, dye-sensitized solar cell electrodes, electroluminescent display electrodes, and the like. As such conductive polymer materials, polymer materials obtained by increasing the molecular weight of pyrrole, thiophene, 3,4-ethylenedioxythiophene, aniline, etc. are known, and related techniques are disclosed in Patent Documents 1 to 6. Has been.

  Patent Document 1 discloses a conductive polymer composition formed by drying a conductive polymer suspension containing a polyanion having a crosslinked structure and conductive polymer particles. Yes. Patent Document 2 discloses a water-absorbing polymer layer in which predetermined moisture is held on a dielectric oxide film of an anode body made of a valve metal and having a dielectric oxide film formed thereon, and a conductive polymer. There is disclosed a solid electrolytic capacitor including a capacitor element in which a solid electrolyte layer is sequentially formed, and water retained by a water-absorbing polymer at the time of aging is supplied for repairing a dielectric oxide film. Further, Patent Documents 3 to 6 disclose conductive polymer materials and / or solid electrolytic capacitors.

JP 2010-182426 A JP 2009-246288 A JP 2006-310365 A Special table 2011-511653 gazette JP 2011-26503 A Special table 2008-526502 gazette

  However, the conductive polymer materials described in Patent Documents 1 to 6 have low water retention, and the dielectric oxide film is not sufficiently repaired. A solid electrolytic capacitor using the conductive polymer material as a solid electrolyte leaks. Current (hereinafter referred to as LC) tends to increase. An object of the present invention is to provide a conductive polymer material having high water retention and a solid electrolytic capacitor having low LC.

  The conductive polymer solution according to the present invention comprises conductive polymer particles containing a polyanion having a structure crosslinked with a crosslinking agent and a conductive polymer, and at least one of water and a water-miscible organic solvent. A conductive polymer solution containing a cross-linking ratio indicating a ratio of the number of moles of the cross-linking agent to the number of moles of anions on the main chain of the poly anion is greater than that of the conductive polymer particles. The surface of the conductive polymer particles is higher.

  The conductive polymer material according to the present invention is obtained by drying the conductive polymer solution according to the present invention and removing at least one of water and a water-miscible organic solvent.

  The solid electrolytic capacitor according to the present invention includes a solid electrolyte containing the conductive polymer material according to the present invention.

  The method for producing a solid electrolytic capacitor according to the present invention comprises a step of forming a dielectric layer on the surface of an anode conductor containing a porous valve action metal, and a conductive polymer solution according to the present invention on the dielectric layer. It includes a step of applying and drying to form a conductive polymer layer, and a step of re-forming.

  The method for producing a conductive polymer solution according to the present invention includes a monomer that gives a conductive polymer, a polyanion having a structure crosslinked with a crosslinking agent, and at least one of water and a water-miscible organic solvent. It includes a step of polymerizing in a solution to obtain a solution containing conductive polymer particles, and a step of crosslinking the surface of the conductive polymer particles with a crosslinking agent.

  According to the present invention, a conductive polymer material with high water retention and a solid electrolytic capacitor with low LC can be obtained.

It is sectional drawing which shows an example of the solid electrolytic capacitor which concerns on this invention.

(Conductive polymer solution)
The conductive polymer solution according to the present invention comprises conductive polymer particles containing a polyanion having a structure crosslinked with a crosslinking agent and a conductive polymer, and at least one of water and a water-miscible organic solvent. A conductive polymer solution containing a cross-linking ratio indicating a ratio of the number of moles of the cross-linking agent to the number of moles of anions on the main chain of the poly anion is greater than that of the conductive polymer particles. The surface of the conductive polymer particles is higher.

  In a solid electrolytic capacitor having a conventional conductive polymer layer as a solid electrolyte, the conductive polymer layer cannot sufficiently hold water. For this reason, in re-forming, which is one of the manufacturing processes of a solid electrolytic capacitor, the conductive polymer on the dielectric layer becomes a barrier, and the chemical liquid is not sufficiently supplied to the dielectric layer. Defects are not fully repaired. Therefore, the LC of the solid electrolytic capacitor is high.

  On the other hand, in the conductive polymer solution according to the present invention, the water retention of the obtained conductive polymer material is improved by using a polyanion having a structure crosslinked by a crosslinking agent as a dopant for the conductive polymer. be able to. In addition, since the cross-linking ratio of the surface of the conductive polymer particles is higher than the internal cross-linking ratio of the conductive polymer particles, when the resulting conductive polymer material absorbs water, the outflow of moisture to the outside is suppressed. And water retention can be further improved. Therefore, since the conductive polymer material obtained from the conductive polymer solution has high water retention, the solid electrolyte layer containing the conductive polymer material can sufficiently hold the chemical conversion solution during re-forming. Thereby, since the chemical liquid is sufficiently supplied onto the dielectric layer at the time of re-forming, defects in the dielectric layer are sufficiently repaired, and a solid electrolytic capacitor having a low LC can be obtained.

[Conductive polymer]
The conductive polymer according to the present invention is dissolved or dispersed in at least one of water and a water-miscible organic solvent. As the conductive polymer according to the present invention, a π-conjugated conductive polymer can be used, and examples thereof include polymers containing repeating units such as pyrrole, thiophene, and aniline. Specifically, examples of the conductive polymer include polypyrrole, polythiophene, polyaniline, and derivatives thereof. In particular, the conductive polymer is preferably a polymer containing repeating units of 3,4-ethylenedioxythiophene or a derivative thereof. Specifically, as the conductive polymer, poly (3,4-ethylenedioxythiophene) containing a repeating unit represented by the following formula (1) or a derivative thereof is preferable.

  Examples of 3,4-ethylenedioxythiophene derivatives include 3,4- (1-alkyl) ethylenedioxythiophene such as 3,4- (1-hexyl) ethylenedioxythiophene. The conductive polymer may be a homopolymer or a copolymer. Moreover, these conductive polymers may use 1 type, and may use 2 or more types together.

  The content of the conductive polymer in the conductive polymer solution is 0.1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of at least one of water as a solvent and a water-miscible organic solvent. Preferably, it is 0.5 parts by mass or more and 20 parts by mass or less.

  The method for synthesizing the conductive polymer according to the present invention is not particularly limited. For example, a monomer that gives the conductive polymer in a solvent containing a polyanion as a dopant is chemically oxidatively polymerized using an oxidizing agent. Can be synthesized.

[Poly anion]
The poly anion according to the present invention functions as a dopant that imparts conductivity to the conductive polymer by extracting electrons from the conductive polymer or by giving electrons to the conductive polymer. It has a crosslinked structure crosslinked by a crosslinking agent. Specifically, the polyanion refers to a compound having a crosslinked structure and having a plurality of anions, for example, a polymer having a crosslinked structure and having a plurality of anions in the main chain. Can do. Examples of the anion of the polyanion include a carboxyl group anion and a sulfo group anion. The poly anion may have one kind or two or more kinds.

  Examples of the polyanion crosslinked by the crosslinking agent include polycarboxylic acids such as polyacrylic acid, polymethacrylic acid, and polymaleic acid; polysulfonic acids such as polyvinyl sulfonic acid and polystyrene sulfonic acid; and co-polymers having these structural units. Examples include coalescence. Among these, as the polyanion, polystyrene sulfonic acid containing a repeating unit represented by the following formula (2) is preferable.

  One kind of poly anions crosslinked by these crosslinking agents may be used, or two or more kinds may be used in combination.

  The mass average molecular weight of the polyanion is preferably 2,000 or more and 500,000 or less, more preferably 10,000 or more and 200,000 or less, and further preferably 30,000 or more and 100,000 or less. The mass average molecular weight is a value calculated by GPC (Gel Permeation Chromatography) measurement.

  The cross-linked portion of the polyanion preferably has an anion. When the cross-linked portion of the polyanion has an anion, hydrophilicity in the cross-linked portion is improved and water retention is improved. As the anion possessed by the crosslinked portion of the polyanion, an anion having a sulfo group and an anion having a carboxyl group are preferable. In addition, a crosslinked part shows the part bridge | crosslinked by the crosslinking agent of poly anion, and in order for the crosslinked part of poly anion to have an anion, a crosslinking agent should just have an anion on the principal chain. .

  The number of carbon atoms on the main chain of the cross-linking agent is preferably 7 to 12, more preferably 8 to 11, and particularly preferably 10. When the carbon number is 7 or more, the amount of water absorption increases because the expansion during water absorption increases. On the other hand, when the carbon number is greater than 12, the water retention amount may be increased, but the water retention may be lowered. Therefore, the carbon number is preferably 12 or less.

  The main chain of the polyanion has a crosslinking point for bonding with the crosslinking agent. Examples of the crosslinking point include an anion and an unsaturated bond. The crosslinking agent may be a compound having two or more functional groups that react with an anion of the polyanion main chain, or a compound having two or more functional groups that react with an unsaturated bond of the poly anion main chain. If it does not specifically limit. However, since the water absorption decreases when the anion is crosslinked with the crosslinking agent, the crosslinking agent is preferably a compound having two or more functional groups that react with the unsaturated bond of the polyanion main chain. The unsaturated bond may be a double bond or a triple bond.

  Examples of the functional group that reacts with the anion of the main chain of the polyanion include an epoxy group, an isocyanate group, a carboxyl group, an amino group, a hydroxyl group, a mercapto group, and an aldehyde group. Examples of the compound having two or more of these functional groups include epoxy compounds such as diepoxyalkane, diepoxyalkanesulfonic acid, diepoxyol; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, etc. Examples thereof include polyglycidyl ethers; haloepoxidized products such as epichlorohydrin and α-methylepichlorohydrin; polyaldehydes such as glutaraldehyde and glyoxal; polyols such as glycerin, pentaerythritol and ethylene glycol. Among these, as the crosslinking agent, a compound having two or more epoxy groups is preferable from the viewpoint of high reactivity with the anion of the polyanion main chain, particularly the anion of the sulfo group.

  The functional group that reacts with the unsaturated bond of the polyanion main chain is preferably a vinyl group. Examples of the compound having two or more vinyl groups include alkadienes such as pentadiene, hexadiene, octadiene, nonadiene, decadiene, undecadiene, and dodecadiene, and diene compounds such as alkadienesulfonic acid and alkadienol. These cross-linking agents may be used alone or in combination of two or more.

[Conductive polymer particles]
The conductive polymer particle according to the present invention includes a polyanion having a structure crosslinked by a crosslinking agent and a conductive polymer. In the conductive polymer solution, the conductive polymer and the polyanion gather and exist as particles having an average particle diameter of 1 to 5000 nm. In the present invention, the surface of the conductive polymer particles has a higher crosslinking ratio indicating the ratio of the number of moles of the crosslinking agent to the number of moles of anions on the main chain of the polyanion than the inside of the conductive polymer particles. . The surface of the conductive polymer particles refers to a region of 4 nm from the outermost surface of the conductive polymer particles to the inside. Further, the inside of the conductive polymer particles refers to a region other than the surface of the conductive polymer particles. The crosslinking ratio can be measured by FT-IR.

  The cross-linking ratio inside the conductive polymer particles is preferably 0.001 to 7 mol, and preferably 0.1 to 4 mol of the cross-linking agent with respect to 100 mol of the anion on the polyanion main chain. More preferably, the amount is more preferably 0.5 to 2.5 mol, and particularly preferably 1 to 1.5 mol. In particular, the crosslinking ratio inside the conductive polymer particles is preferably 1.3 mol of the crosslinking agent with respect to 100 mol of the anion on the polyanion main chain. When the crosslinking ratio is 0.001 mol or more with respect to 100 mol of the anion on the main chain of the polyanion, it is possible to prevent the dissolution due to the small number of crosslinking portions at the time of re-forming. . In addition, when the crosslinking ratio is 7 mol or less with respect to 100 mol of the anion on the polyanion main chain, inhibition of water absorption due to a large number of cross-linking parts during re-forming is suppressed. Can do. Further, from the viewpoint of water retention of the obtained conductive polymer material, the crosslinking ratio of the surface of the conductive polymer particles is such that the crosslinking agent is 1 to 10 moles per 100 moles of anions on the main chain of the polyanion. It is preferable that it is 2-9 mol, it is more preferable that it is 3-8 mol. As described above, the cross-linking ratio on the surface of the conductive polymer particles is higher than the cross-linking ratio inside the conductive polymer particles. By further cross-linking the conductive polymer particles with a crosslinking agent, the cross-linking ratio on the surface of the conductive polymer particles can be made higher than the cross-linking ratio inside the conductive polymer particles.

  The poly anion is a poly anion having an unsaturated bond, and the cross-linking inside the conductive polymer particle is a cross-link formed by combining the poly anionic unsaturated bond and the cross-linking agent. The cross-linking of the molecular particle surface is preferably a cross-linking formed by combining an anion of a polyanion and a cross-linking agent because the water retention of the conductive polymer particles can be further improved. As the crosslinking agent used for crosslinking inside the conductive polymer particles, a compound having two or more vinyl groups is preferable. Moreover, as a crosslinking agent used for bridge | crosslinking of the conductive polymer particle surface, the compound which has 2 or more of functional groups which react with the anion of the principal chain of the said poly anion is preferable.

  As a method of further crosslinking the conductive polymer particles with a crosslinking agent, for example, the conductive polymer particles can be reacted with the crosslinking agent in a solution containing the conductive polymer particles. In addition, after a solution containing conductive polymer particles is applied and dried to form a conductive polymer layer, a solution in which a crosslinking agent is dissolved or dispersed is dipped and dried, so that the surface of the conductive polymer particles is dried. It can also be crosslinked. Furthermore, the surface of the conductive polymer particles can be crosslinked by adding a crosslinking agent to the solution containing the conductive polymer particles, applying the solution, and drying to form a conductive polymer layer. The drying temperature is preferably 80 ° C. or more and 300 ° C. or less. The cross-linking agent used for cross-linking the surface of the conductive polymer particles may be the same as or different from the cross-linking agent used when the poly anion is cross-linked.

[solvent]
The conductive polymer solution according to the present invention contains at least one of water and a water-miscible organic solvent as a solvent. The water-miscible organic solvent is not particularly limited as long as it is an organic solvent miscible with water, but is a protic polar solvent such as methanol, ethanol, propanol, acetic acid; N, N-dimethylformamide, dimethyl sulfoxide, acetonitrile, acetone, etc. Are preferred aprotic polar solvents. As the water-miscible organic solvent, dimethyl sulfoxide is more preferable. These may use 1 type and may use 2 or more types together.

(Conductive polymer material)
The conductive polymer material according to the present invention can be obtained by drying the conductive polymer solution according to the present invention and removing at least one of water and a water-miscible organic solvent. As described above, the conductive polymer material according to the present invention exhibits high water retention. The drying temperature for removing at least one of the solvent water and the water-miscible organic solvent is not particularly limited as long as it is not higher than the decomposition temperature of the conductive polymer, but is preferably 300 ° C. or lower.

(Solid electrolytic capacitor)
The solid electrolytic capacitor according to the present invention includes a solid electrolyte containing the conductive polymer material according to the present invention. Since the solid electrolyte includes the conductive polymer material according to the present invention, water retention is improved, and defects in the dielectric layer are sufficiently repaired at the time of re-forming, so that low LC can be realized.

  A cross-sectional view of an example of a solid electrolytic capacitor according to the present invention is shown in FIG. In the solid electrolytic capacitor shown in FIG. 1, a dielectric layer 2, a solid electrolyte layer 3, and a cathode conductor 4 are formed in this order on an anode conductor 1.

  The anode conductor 1 is formed of a metal plate having a valve action metal, a foil or a wire, a sintered body containing metal fine particles having a valve action, a porous metal subjected to surface expansion treatment by etching, or the like. Examples of the valve action metal include tantalum, aluminum, titanium, niobium, zirconium, and alloys thereof. Among these, the valve metal is preferably at least one metal selected from the group consisting of tantalum, aluminum, and niobium. These may use 1 type and may use 2 or more types together.

  The dielectric layer 2 is an oxide film obtained by electrolytic oxidation of the surface of the anode conductor 1, and is also formed in the pores of the anode conductor 1. The thickness of the dielectric layer 2 can be adjusted as appropriate by the voltage of electrolytic oxidation.

  The solid electrolyte layer 3 includes the conductive polymer material according to the present invention. In addition to the conductive polymer material according to the present invention, the solid electrolyte layer 3 includes oxide derivatives such as manganese dioxide and ruthenium oxide, TCNQ (7,7,8,8-tetracyanoquinodimethane complex salt) and the like. Organic semiconductors or the like may be included. The solid electrolyte layer 3 may contain a solution such as water, an electrolytic solution, or an ionic solution. Although it does not specifically limit as a formation method of the solid electrolyte layer 3, For example, the method shown below is mentioned. The conductive polymer solution according to the present invention is applied or impregnated on the dielectric layer 2 formed on the surface of the anode conductor 1 and dried to form the solid electrolyte layer 3. Thereafter, this is impregnated in an aqueous solution of adipic acid, citric acid, phosphoric acid, or an ammonium salt thereof, and re-chemical conversion is performed by applying a voltage, thereby repairing defects in the dielectric layer 2.

  Further, the solid electrolyte layer 3 may be two or more layers. In this case, at least one of the solid electrolyte layers 3 including a plurality of layers may include the conductive polymer material according to the present invention. Examples of a method for forming the solid electrolyte layer 3 including the first conductive polymer layer 3A and the second conductive polymer layer 3B shown in FIG. 1 include the following methods. On the dielectric layer 2 formed on the surface of the anode conductor 1, the first conductive polymer layer 3A is formed by applying or impregnating the conductive polymer solution according to the present invention and drying. After that, re-forming is performed. Next, by conducting chemical oxidative polymerization or electrolytic polymerization using a solution containing a monomer that gives a conductive polymer, the first conductive polymer layer 3A containing no conductive polymer material according to the present invention is added. The second conductive polymer layer 3B is formed. The first conductive polymer layer 3A does not include the conductive polymer material according to the present invention, and the second conductive polymer layer 3B includes the conductive polymer material according to the present invention. Alternatively, the first conductive polymer layer 3A and the second conductive polymer layer 3B may include different conductive polymer materials according to the present invention.

  The cathode conductor 4 is not particularly limited as long as it is a conductor. For example, as shown in FIG. 1, the cathode conductor 4 may have a two-layer structure including a carbon layer 5 made of graphite or the like and a silver conductive resin layer 6.

(Method for manufacturing solid electrolytic capacitor)
The method for producing a solid electrolytic capacitor according to the present invention includes a step of forming a dielectric layer on the surface of an anode conductor containing a porous valve-acting metal, and a conductive polymer solution according to the present invention on the dielectric layer. And a step of forming a conductive polymer layer by drying, and a step of re-forming. As described above, since the conductive polymer material obtained from the conductive polymer solution according to the present invention has high water retention, by forming a conductive polymer layer using the conductive polymer material, At the time of re-forming, a chemical conversion solution is sufficiently supplied onto the dielectric layer, and defects in the dielectric layer are sufficiently repaired. Thereby, a solid electrolytic capacitor having a low LC can be obtained.

  The method for applying the conductive polymer solution onto the dielectric layer is not particularly limited. For example, the conductive polymer solution can be applied by immersing the anode conductor in the conductive polymer solution. The re-chemical conversion is a step of performing chemical conversion treatment with a chemical conversion solution, and defects in the dielectric layer are repaired by performing chemical conversion. As the chemical conversion solution, for example, adipic acid, citric acid, phosphoric acid, or an ammonium salt aqueous solution thereof can be used. These may use 1 type and may use 2 or more types together. The re-chemical conversion method can be performed, for example, by impregnating a conductive polymer layer into the chemical conversion solution and applying a voltage.

(Method for producing conductive polymer solution)
The method for producing a conductive polymer solution according to the present invention includes a monomer that gives a conductive polymer, a polyanion having a structure crosslinked with a crosslinking agent, and at least one of water and a water-miscible organic solvent. It includes a step of polymerizing in a solution to obtain a solution containing conductive polymer particles, and a step of crosslinking the surface of the conductive polymer particles with a crosslinking agent. By further crosslinking the surface of the conductive polymer particles with a crosslinking agent, a conductive polymer solution having a higher crosslinking ratio on the surface of the conductive polymer particles than in the interior of the conductive polymer particles can be obtained.

Example 1
[Preparation of conductive polymer solution]
20 g of polystyrene sulfonic acid and 0.2 g of 1,2,5,6-diepoxyhexane as a crosslinking agent were dissolved in 100 ml of water as a solvent. The solution was kept at 80 ° C. and stirred for 24 hours to react, thereby synthesizing polystyrene sulfonic acid having a crosslinked structure as a polyanion. 5 g of polystyrene sulfonic acid having the crosslinked structure, 1.25 g of 3,4-ethylenedioxythiophene and 0.125 g of iron (III) sulfate were dissolved in 50 ml of water. Air was introduced into this solution for 24 hours to produce a solution containing conductive polymer particles. 0.05 g of 1,2,5,6-diepoxyhexane as a crosslinking agent was added to 50 ml of a solution containing conductive polymer particles prepared. This solution was kept at 80 ° C. and stirred for 24 hours to react to further crosslink the surface of the conductive polymer particles. Thereby, a conductive polymer solution was prepared.

[Measurement of water absorption of conductive polymer materials]
15 μl of the conductive polymer solution was dropped on an aluminum substrate. This was placed in a thermostat at 125 ° C. and the water was volatilized to produce a conductive polymer material film having a thickness of about 5 μm. Thereafter, the film of the conductive polymer material was immersed in water for 10 minutes and left in the air for 1 hour. Using a Karl Fischer method moisture content meter (product name: CP-200 type tabletop coulometric method moisture meter, VA-200 type moisture vaporizer, manufactured by Mitsubishi Chemical Analytech Co., Ltd.), the film of the conductive polymer material In order to evaluate the water retention, the water absorption was measured. The results are shown in Table 1. The water absorption is a value indicating the ratio of the mass of moisture to the mass excluding moisture of the film of the conductive polymer material.

(Example 2)
1,2: 6,7-diepoxyheptane was used in place of 1,2,5,6-diepoxyhexane as a crosslinking agent used for crosslinking polystyrene sulfonate and the surface of the conductive polymer particles. Except for the above, a conductive polymer solution was prepared in the same manner as in Example 1, and the water absorption rate of the conductive polymer material was measured. The results are shown in Table 1.

Example 3
1,2: 7,8-diepoxyoctane was used in place of 1,2,5,6-diepoxyhexane as a crosslinking agent used for crosslinking of polystyrene sulfonic acid and the surface of the conductive polymer particles. Except for the above, a conductive polymer solution was prepared in the same manner as in Example 1, and the water absorption rate of the conductive polymer material was measured. The results are shown in Table 1.

Example 4
Instead of 1,2,5,6-diepoxyhexane, 1,2,11,12-diepoxydodecane was used as a crosslinking agent for crosslinking of polystyrene sulfonic acid and the surface of the conductive polymer particles. Except for the above, a conductive polymer solution was prepared in the same manner as in Example 1, and the water absorption rate of the conductive polymer material was measured. The results are shown in Table 1.

(Example 5)
Instead of 1,2,5,6-diepoxyhexane, 1,2,11,12-diepoxytridecane is used as a crosslinking agent for crosslinking of polystyrene sulfonic acid and the surface of conductive polymer particles. A conductive polymer solution was prepared in the same manner as in Example 1 except that the water absorption rate of the conductive polymer material was measured. The results are shown in Table 1.

(Example 6)
In place of 1,2,5,6-diepoxyhexane, 1,2: 7,8-diepoxyoctane-4-4 instead of 1,2,5,6-diepoxyhexane is used as a crosslinking agent for crosslinking of polystyrenesulfonic acid and the surface of the conductive polymer particles. A conductive polymer solution was prepared in the same manner as in Example 1 except that sulfonic acid was used, and the water absorption rate of the conductive polymer material was measured. The results are shown in Table 1.

(Example 7)
20 g of sodium styrenesulfonate and 0.2 g of acetylene were dissolved in 60 g of water. Moreover, 0.05 g of ammonium persulfate was dissolved in 5 g of water. 20 g of water was charged in a polymerization vessel previously purged with nitrogen, and the temperature was raised to 90 ° C. while stirring, and then the sodium styrenesulfonate solution and the ammonium persulfate solution were added over 4 hours to perform polymerization. Thereafter, aging was performed for 2 hours to obtain a polymer aqueous solution. The polymer aqueous solution was ion-exchanged using an electrodialyzer to remove impurity ions. Thereby, the aqueous solution containing the poly anion before crosslinking which has an unsaturated bond was prepared.

  Next, hexadiene (0.2 g) as a crosslinking agent was dissolved in 100 g of an aqueous solution containing a polyanion before crosslinking having an unsaturated bond. Moreover, 0.05 g of ammonium persulfate was dissolved in 5 g of water. An aqueous solution containing a polyanion before crosslinking having an unsaturated bond in which hexadiene was dissolved was heated to 90 ° C., and then the ammonium persulfate solution was added over 4 hours to carry out polymerization. Thereafter, polyanions having an unsaturated bond were synthesized by aging for 2 hours.

  5 g of the polyanion having an unsaturated bond, 1.25 g of 3,4-ethylenedioxythiophene and 0.125 g of iron (III) sulfate were dissolved in 50 ml of water. Air was introduced into this solution for 24 hours to prepare a solution containing conductive polymer particles. 0.05 g of 1,7-octadiene-4-sulfonic acid as a cross-linking agent was added to 50 ml of the solution containing the conductive polymer particles. Moreover, 0.05 g of ammonium persulfate was dissolved in 5 g of water. The temperature of the solution containing conductive polymer particles added with 1,7-octadiene-4-sulfonic acid was raised to 90 ° C., and then the ammonium persulfate solution was added over 4 hours to carry out polymerization. Thereafter, aging was performed for 2 hours, and the surface of the conductive polymer particles was further crosslinked to prepare a conductive polymer solution. Thereafter, the water absorption rate of the conductive polymer material was measured in the same manner as in Example 1. The results are shown in Table 1.

(Example 8)
A solution containing conductive polymer particles was produced in the same manner as in Example 7. 0.05 g of 1,2: 7,8-diepoxyoctane-4-sulfonic acid as a cross-linking agent was added to 50 ml of the solution containing the conductive polymer particles. The solution was kept at 80 ° C., stirred for 24 hours to react, and the surface of the conductive polymer particles was further crosslinked to prepare a conductive polymer solution. Thereafter, the water absorption rate of the conductive polymer material was measured in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
5 g of polystyrene sulfonic acid having a mass average molecular weight of 50,000, 1.25 g of 3,4-ethylenedioxythiophene and 0.125 g of iron (III) sulfate were dissolved in water (50 ml). Air was introduced into this solution for 24 hours to produce a polythiophene solution. Thereafter, a film of a conductive polymer material was produced using the polythiophene solution in the same manner as in Example 1, and the water absorption rate was measured. The results are shown in Table 1.

(Comparative Example 2)
20 g of polystyrene sulfonic acid and 0.2 g of 1,2,5,6-diepoxyhexane as a crosslinking agent were dissolved in 100 ml of water as a solvent. The solution was kept at 80 ° C. and stirred for 24 hours to react, thereby synthesizing polystyrene sulfonic acid having a crosslinked structure as a polyanion. 5 g of polystyrene sulfonic acid having the crosslinked structure, 1.25 g of 3,4-ethylenedioxythiophene and 0.125 g of iron (III) sulfate were dissolved in 50 ml of water. Air was introduced into this solution for 24 hours to produce a solution containing conductive polymer particles. Thereafter, a film of a conductive polymer material was produced using the solution in the same manner as in Example 1, and the water absorption rate was measured. The results are shown in Table 1.

Example 9
[Production of solid electrolytic capacitors]
A solid electrolytic capacitor was produced using the conductive polymer solution prepared in Example 1. As the anode conductor, a 3 × 4 mm porous aluminum foil that had been subjected to surface expansion by etching was used. The anode conductor includes a dielectric layer that is an oxide film on the surface. The anode conductor was immersed in the conductive polymer solution prepared in Example 1. This was dried in a constant temperature bath at 125 ° C. and solidified to form a solid electrolyte layer. Thereafter, re-chemical conversion was performed by applying a voltage in 0.3% by mass of phosphoric acid to repair defects in the dielectric layer. Thereafter, a graphite layer and a silver conductive resin layer were sequentially formed on the solid electrolyte layer to produce a solid electrolytic capacitor.

[LC measurement]
About the produced solid electrolytic capacitor, LC was measured using LC meter. The results are shown in Table 2.

(Example 10)
An anode conductor having a dielectric layer similar to that in Example 9 was prepared by using a monomer solution containing 3,4-ethylenedioxythiophene, 1,3,6-naphthalenetrisulfonic acid as a dopant, and peroxodioxide as an oxidizing agent. And an oxidizer solution containing ammonium sulfate. Immersion was repeated several times, and a first conductive polymer layer containing poly 3,4-ethylenedioxythiophene was formed by chemical oxidative polymerization. Then, this was immersed in the conductive polymer solution prepared in Example 1. This was dried in a constant temperature bath at 125 ° C. and solidified to form a second conductive polymer layer. Thereafter, re-chemical conversion was performed by applying a voltage in 0.3% by mass of phosphoric acid to repair defects in the dielectric layer. Thereafter, a graphite layer and a silver conductive resin layer were sequentially formed on the second conductive polymer layer to produce a solid electrolytic capacitor. The solid electrolytic capacitor was subjected to LC measurement in the same manner as in Example 9. The results are shown in Table 2.

(Example 11)
An anode conductor having a dielectric layer similar to that in Example 9 was immersed in the conductive polymer solution prepared in Example 1. This was dried in a constant temperature bath at 125 ° C. and solidified to form a first conductive polymer layer. Thereafter, re-chemical conversion was performed by applying a voltage in 0.3% by mass of phosphoric acid to repair defects in the dielectric layer. Next, this was immersed in the conductive polymer solution prepared in Comparative Example 1. This was dried in a constant temperature bath at 125 ° C. and solidified to form a second conductive polymer layer. Thereafter, a graphite layer and a silver conductive resin layer were sequentially formed on the second conductive polymer layer to produce a solid electrolytic capacitor. The solid electrolytic capacitor was subjected to LC measurement in the same manner as in Example 9. The results are shown in Table 2.

(Example 12)
In the formation of the conductive polymer layer, a solid electrolytic capacitor was produced in the same manner as in Example 9 except that the conductive polymer solution prepared in Example 2 was used, and LC measurement was performed. The results are shown in Table 2.

(Example 13)
In the formation of the conductive polymer layer, a solid electrolytic capacitor was produced in the same manner as in Example 9 except that the conductive polymer solution prepared in Example 3 was used, and LC measurement was performed. The results are shown in Table 2.

(Example 14)
In the formation of the conductive polymer layer, a solid electrolytic capacitor was produced in the same manner as in Example 9 except that the conductive polymer solution prepared in Example 4 was used, and LC measurement was performed. The results are shown in Table 2.

(Example 15)
In the formation of the conductive polymer layer, a solid electrolytic capacitor was produced in the same manner as in Example 9 except that the conductive polymer solution prepared in Example 5 was used, and LC measurement was performed. The results are shown in Table 2.

(Example 16)
In the formation of the conductive polymer layer, a solid electrolytic capacitor was produced in the same manner as in Example 9 except that the conductive polymer solution prepared in Example 6 was used, and LC measurement was performed. The results are shown in Table 2.

(Example 17)
In the formation of the conductive polymer layer, a solid electrolytic capacitor was produced in the same manner as in Example 9 except that the conductive polymer solution prepared in Example 7 was used, and LC measurement was performed. The results are shown in Table 2.

(Example 18)
In the formation of the conductive polymer layer, a solid electrolytic capacitor was produced in the same manner as in Example 9 except that the conductive polymer solution prepared in Example 8 was used, and LC measurement was performed. The results are shown in Table 2.

(Comparative Example 3)
In the formation of the conductive polymer layer, a solid electrolytic capacitor was produced in the same manner as in Example 9 except that the conductive polymer solution prepared in Comparative Example 1 was used, and LC measurement was performed. The results are shown in Table 2.

(Comparative Example 4)
In the formation of the conductive polymer layer, a solid electrolytic capacitor was produced in the same manner as in Example 9 except that the conductive polymer solution prepared in Comparative Example 2 was used, and LC measurement was performed. The results are shown in Table 2.

  From Table 1, Examples 1-8 had a higher water absorption than Comparative Examples 1 and 2. From this, it was confirmed that a water absorption rate can be improved by using as a dopant the poly anion which has the structure bridge | crosslinked by the crosslinking agent which concerns on this invention. This is because the water is retained in the crosslinked structure of the polyanion according to the present invention, so that the water does not easily evaporate even if it is left in the air for 1 hour after being immersed in water. Moreover, the outflow of moisture to the outside could be further suppressed by further crosslinking the surface of the conductive polymer particles. On the other hand, in Comparative Example 1, polyanions having no cross-linked structure are used, and the surface of the conductive polymer particles is not cross-linked, so that the water evaporates when left in the air after being immersed in water. The water absorption decreased. Further, although Comparative Example 2 has a cross-linked structure, the surface of the conductive polymer particles is not cross-linked, so that sufficient suppression of water evaporation when left in the air after being immersed in water is sufficient. Rather, the water absorption decreased.

  Next, Examples 2-4 had a higher water absorption rate than Examples 1 and 5. In Example 1, the number of carbons on the main chain of the crosslinking agent is 6, whereas in Examples 2 to 4, the number of carbons on the main chain of the crosslinking agent is 7 or more. Therefore, in Examples 2 to 4, it is considered that the film swelled greatly during water absorption, and a high water absorption rate could be obtained. On the other hand, in Example 5, the carbon number on the main chain of the cross-linking agent is 13, so water retention is lowered, and it is considered that water was evaporated when left for 1 hour.

  In Example 6, the water absorption rate was higher than that in Example 3. In Example 6, since it has an anion also in the bridge | crosslinking part of a poly anion, it is thought that the higher water absorption was obtained. In Example 7, the water absorption rate was higher than that in Example 6. Example 6 is crosslinked with an anion in the polyanion main chain, whereas Example 7 is crosslinked with an unsaturated bond in the poly anion main chain, and the anion is not used for crosslinking. Conceivable. In Example 8, the water absorption rate was higher than that in Example 7. In Example 8, since the anions in the main chain of the polyanion are cross-linked at the time of surface cross-linking, it is considered that the water inside the conductive polymer particles is less likely to go outside through the surface of the conductive polymer particles. .

  From Table 2, Examples 9-18 had low LC compared with Comparative Examples 3 and 4. From this, it was confirmed that a solid electrolytic capacitor having a low LC can be obtained by using the conductive polymer solution according to the present invention. This is presumably because the conductive polymer material produced using the conductive polymer solution according to the present invention has high water retention and sufficient re-forming.

  As described above, the conductive polymer material produced using the conductive polymer solution according to the present invention exhibits high water absorption. In addition, since the conductive polymer material exhibits a high water absorption rate, a solid electrolytic capacitor using the conductive polymer material as a solid electrolyte exhibits a low LC.

  The conductive polymer solution according to the present invention can be used for manufacturing a cathode of a lithium ion secondary battery.

1 Anode conductor 2 Dielectric layer 3 Solid electrolyte layer 3A First conductive polymer layer 3B Second conductive polymer layer 4 Cathode conductor 5 Carbon layer (graphite layer)
6 Silver conductive resin layer

Claims (12)

A conductive polymer solution comprising conductive polymer particles containing a polyanion having a structure crosslinked by a crosslinking agent and a conductive polymer, and at least one of water and a water-miscible organic solvent,
The cross-linking ratio indicating the ratio of the number of moles of the crosslinking agent to the number of moles of anions on the polyanion main chain is higher on the surface of the conductive polymer particles than in the interior of the conductive polymer particles. Conductive polymer solution.   2. The conductivity according to claim 1, wherein the crosslinking ratio in the conductive polymer particle is 0.001 to 7 mol with respect to 100 mol of the anion on the main chain of the poly anion. Polymer solution.   The conductive polymer solution according to claim 1, wherein the crosslinking agent has 7 to 12 carbon atoms on the main chain.   The conductive polymer solution according to any one of claims 1 to 3, wherein the cross-linked portion of the poly anion has an anion.   The conductive polymer solution according to any one of claims 1 to 4, wherein the polyanion is a compound in which a main chain of the polyanion is crosslinked by a compound having two or more epoxy groups.   The poly anion is a poly anion having an unsaturated bond, and the main chain of the poly anion is crosslinked by a compound having two or more vinyl groups. The conductive polymer solution described in 1. The polyanion is a polyanion having an unsaturated bond;
The cross-linking inside the conductive polymer particles is a cross-linking formed by bonding the unsaturated bond of the poly anion and the cross-linking agent,
5. The conductive polymer according to claim 1, wherein the cross-linking of the surface of the conductive polymer particles is a cross-link formed by combining an anion of the poly anion and the cross-linking agent. 6. solution.   A conductive polymer material obtained by drying the conductive polymer solution according to claim 1 and removing at least one of the water and the water-miscible organic solvent.   A solid electrolytic capacitor comprising a solid electrolyte containing the conductive polymer material according to claim 8. Forming a dielectric layer on the surface of the anode conductor containing a porous valve metal, and
Applying the conductive polymer solution according to any one of claims 1 to 7 on the dielectric layer and drying to form a conductive polymer layer;
A step of re-forming, and a method for producing a solid electrolytic capacitor. A monomer that gives a conductive polymer is polymerized in a solution containing a polyanion having a structure cross-linked by a cross-linking agent and at least one of water and a water-miscible organic solvent to contain conductive polymer particles Obtaining a solution;
Cross-linking the surface of the conductive polymer particles with a cross-linking agent;
The manufacturing method of the conductive polymer solution containing this.   The cross-linking ratio indicating the ratio of the number of moles of the cross-linking agent to the number of moles of anions on the main chain of the poly anions inside the conductive polymer particles contained in the conductive polymer solution, The method for producing a conductive polymer solution according to claim 11, wherein the crosslinking agent is 0.001 to 7 mol per 100 mol of anions on the main chain of anions.

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