Solid electrolytic capacitor element, solid electrolytic capacitor and production method thereof

1. A process for producing a solid electrolytic capacitor element, comprising forming a semiconductor layer containing a conductive polymer on a conductor having a dielectric layer on its surface, next impregnating the conductor with a dopant and, after the conductor is impregnated with the dopant, forming a semiconductor layer on the doped conductor having a dielectric layer on its surface by an electrification method.

2. The process for producing a solid electrolytic capacitor element as claimed in claim 1 , wherein the dopant is an electron donating compound providing, upon doping through electrolytic polymerization, a conductive polymer having a conductivity of from 10 −1 to 10 3 S·cm −1 .

3. The process for producing a solid electrolytic capacitor element as claimed in claim 1 , wherein the dopant is at least one selected from a compound having a sulfuric acid group and a boron compound having a carboxylic acid coordinated to a boron atom.

4. The process for producing a solid electrolytic capacitor element as claimed in claim 1 , wherein the conductor is a metal containing as a major component at least one selected from tantalum, niobium, titanium and aluminum, niobium oxide, or a mixture of two or more thereof.

5. The process for producing a solid electrolytic capacitor element as claimed in claim 1 , wherein the semiconductor layer is a layer comprising at least one selected from a semiconductor containing as a major component a conductive polymer obtained by doping a polymer containing a repeating unit represented by formula (1) or (2) with a dopant:

wherein R 1 to R 4 each independently represent a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms or an alkoxy group having from 1 to 6 carbon atoms; X represents an oxygen atom, a sulfur atom or a nitrogen atom; and R 5 , which exists only when X is a nitrogen atom, represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms, provided that R 1 and R 2 , and R 3 and R 4 each may be bonded to form a ring.

6. The process for producing a solid electrolytic capacitor element as claimed in claim 5 , wherein the polymer containing a repeating unit represented by formula (1) is a polymer containing a structural unit represented by formula (3) as a repeating unit:

wherein R 6 and R 7 each independently represent a hydrogen atom, a linear or branched and saturated or unsaturated alkyl group having from 1 to 6 carbon atoms, or a substituent having at least one 5- to 7-membered saturated hydrocarbon ring structure containing two oxygen atoms formed by bonding the alkyl groups at an arbitrary position, provided that the ring structure encompasses a structure having a vinylene bond, which may be substituted, and a phenylene structure, which may be substituted.

7. The process for producing a solid electrolytic capacitor element as claimed in claim 5 , wherein the conductive polymer is selected from polyaniline, polyoxyphenylene, polyphenylene sulfide, polythiophene, polyfuran, polypyrrole, polymethylpyrrole and substituted derivatives and copolymers thereof.

8. The process for producing a solid electrolytic capacitor element as claimed in claim 7 , wherein the conductive polymer is poly(3,4-ethylenedioxythiophene).

9. The process for producing a solid electrolytic capacitor element as claimed in claim 5 , wherein the semiconductor has a conductivity in a range of from 10 −2 to 10 3 S·cm −1 .

10. A solid electrolytic capacitor element produced by the production process described in claim 1 .

11. A solid electrolytic capacitor obtained by sealing the solid electrolytic capacitor element described in claim 10 .

12. An electronic circuit comprising the solid electrolytic capacitor described in claim 11 used therein.

13. An electronic equipment comprising the solid electrolytic capacitor described in claim 11 mounted therein.