Patent ID: 7087292

Claim:
A solid electrolytic capacitor comprising an oxide dielectric film having provided thereon an electrically conducting polymer composition layer, which is produced by covering a valve-acting metal anode foil having formed on the surface thereof an oxide dielectric film with repeating sequence of a solution containing a monomer of an electrically conducting polymer and a solution containing an oxidizing agent and then polymerizing to form an electrically conducting polymer composition film on the dielectric film, wherein the solution containing a monomer of an electrically conducting polymer and/or the solution containing an oxidizing agent has a viscosity of less than 100 cp at 23° C., wherein the electrically conducting polymer in said composition contains as a repeating chemical structure a structureal unit represented by the following formula (1a): wherein the substituents R 1 and R 2 each independently represents a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated hydrocarbon group having from 1 to 6 carbon atoms, a linear or branched, saturated or unsaturated alkoxy group having from 1 to 6 carbon atoms, a hydroxyl group, a halogen atom, a nitro group, a cyano group, a trifluoromethyl group, a phenyl group and a substituted phenyl group; R 1 and R 2 may combine with each other at an arbitrary position to form at least one divalent chain for forming at least one 5-, 6- or 7- membered saturated or unsaturated ring structure; X a represents a hetero atom selected from the group consisting of S, O, Se and Te; the alkyl group and the alkoxy group represented by R 1 or R 2 each may optionally contain in the chain thereof a carbonyl bond, an ether bond, an ester bond, an amide bond or an imino bond; and δ represents a number of from 0 to 1; and wherein the electroconducting polymer is formed by setting the humidity in the atmosphere of the polymerization process to from 10% to less than 60%.