Method for manufacturing solid electrolytic capacitor

1. A method of manufacturing a solid electrolytic capacitor, including:

a step (A) of providing a conjugated conductive polymer-containing dispersion by polymerizing, in a dispersion medium containing seed particles turned into protective colloid by a polyanion or in a dispersion medium containing the polyanion, a monomer for obtaining a conjugated conductive polymer;

a step (B) of preparing a dispersion containing a morpholine compound represented by the following formula (1) and the conjugated conductive polymer by adding the morpholine compound to the conjugated conductive polymer-containing dispersion:

where R 1 represents (1) a hydrogen atom, (2) an alkyl group having 1 to 8 carbon atoms that may be substituted with a hydroxy group, a cyano group, or an amino group, (3) a cycloalkenyl group having 5 or 6 carbon atoms, (4) a phenyl group that may be substituted with an amino group, a cyano group, or a formyl group, (5) an acetyl group, (6) an acetoacetyl group, (7) an allyl group, (8) an acryloyl group, (9) a pyridyl group, (10) an alkylsulfo group that may be substituted with a hydroxy group, or (11) a formyl group, and “n” represents 0, 1, or 2;

a step (C) of causing the dispersion to adhere to a porous anode body formed of a valve metal having a dielectric film on a surface thereof; and

a step (D) of forming a solid electrolyte layer by removing the dispersion medium from the dispersion containing the morpholine compound and the conjugated conductive polymer, the dispersion adhering to the porous anode body.

2. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein the morpholine compound represented by the formula (1) is morpholine, 4-ethylmorpholine, 4-n-butylmorpholine, 4-isobutylmorpholine, 4-phenylmorpholine, 4-(2-hydroxypropyl)morpholine, 4-(2-hydroxyethyl)morpholine, or 4-(3-hydroxypropyl)morpholine.

3. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein the seed particles are particles of a polymer of an ethylenically unsaturated monomer.

4. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein the seed particles turned into the protective colloid by the polyanion have a d50 particle diameter of from 0.01 μm to 10 μm.

5. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein the step (A) of providing the conjugated conductive polymer-containing dispersion includes further adding a polyanion or a dispersion of seed particles turned into a protective colloid by a polyanion during the polymerization of the monomer for obtaining the conjugated conductive polymer.

6. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein the step (A) of providing the conjugated conductive polymer-containing dispersion includes subjecting the conjugated conductive polymer to be produced to a dispersion treatment.

7. The method of manufacturing a solid electrolytic capacitor according to claim 6 , wherein the dispersion treatment is ultrasonic irradiation.

8. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein the monomer for obtaining the conjugated conductive polymer includes at least one selected from a pyrrole compound, an aniline compound, and a thiophene compound each of which may have a substituent.

9. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein the monomer for obtaining the conjugated conductive polymer is a compound represented by the following formula (2):

where R 2 and R 3 each independently represent a hydrogen atom, a hydroxy group, an alkyl group having 1 to 18 carbon atoms that may have a substituent, an alkoxy group having 1 to 18 carbon atoms that may have a substituent, or an alkylthio group having 1 to 18 carbon atoms that may have a substituent, or R 2 and R 3 are bonded to each other to represent an alicycle having 3 to 10 carbon atoms that may have a substituent, an aromatic ring having 6 to 10 carbon atoms that may have a substituent, an oxygen atom-containing heterocycle having 2 to 10 carbon atoms that may have a substituent, a sulfur atom-containing heterocycle having 2 to 10 carbon atoms that may have a substituent, or a sulfur atom and oxygen atom-containing heterocycle having 2 to 10 carbon atoms that may have a substituent.

10. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein the polyanion is a polymer having a sulfo group.

11. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein a ratio of anion groups in the polyanion is from 0.25 mol to 30 mol with respect to 1 mol of the monomer for obtaining the conjugated conductive polymer.

12. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein in the step (A) of providing the conjugated conductive polymer-containing dispersion, the dispersion medium contains water, and the polymerization is performed by using at least one oxidant selected from peroxodisulfuric acid and a salt thereof.

13. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein the step (B) includes adding at least one selected from ethylene glycol, propylene glycol, and glycerin as an electrical conductivity improver.

14. The method of manufacturing a solid electrolytic capacitor according to claim 1 , wherein the step (A) is a step of providing the conjugated conductive polymer-containing dispersion by polymerizing a monomer for obtaining the conjugated conductive polymer in a dispersion medium containing seed particles turned into a protective colloid by a polyanion.