Abstract: An electrolytic solution for use in an electrolytic capacitor including a capacitor element and a casing containing the capacitor element, the capacitor element including a pair of electrodes, and a conductive separator (E) which is formed with a conductive polymer layer (F) containing a dopant agent (H) on its surface and is interposed between the pair of electrodes, the conductive separator (E) and the pair of electrodes being rolled up in an overlapped state with each other, and spaces between the pair of electrodes being impregnated with the electrolytic solution, wherein an acid component (D) and a base component (C) as electrolytic components to be contained in the electrolytic solution are at such a molar ratio that the acid component (D) is excessive. By use of the electrolytic solution, increase in the ESR with the elapse of time in an electrolytic capacitor is suppressed.

Abstract: The present invention has its object to provide an electrolyte anion which is high in decomposition temperature, in order to inhibit the electrolyte anion in the electrolyte solution for electrolytic capacitors from undergoing decarboxylation in the lead-free solder reflowing step to thereby prevent valve opening. The present invention uses an electrolyte solution comprising, as an electrolyte, the salt (A) composed of ammonium cation (a) and a polybasic carboxylic acid (b) anion, wherein the proton part charge of each carboxyl group in the polybasic carboxylic acid (b) as calculated by the quantum mechanics calculation software CAChe-based AM1 method is not higher than 0.243.

Abstract: It is provided the electrolytic solution for use in the electrolytic capacitor including a capacitor element and a casing containing said capacitor element, said capacitor element including a pair of electrodes, and a conductive separator (E) which is formed with a conductive polymer layer (F) containing a dopant agent (H) on its surface and is interposed between said pair of electrodes, said conductive separator (E) and said pair of electrodes being rolled up in an overlapped state with each other, and spaces between said pair of electrodes being impregnated with the electrolytic solution for electrolytic capacitor, wherein an acid component (D) and a base component (C) as electrolytic components to be contained in said electrolytic solution are at such a molar ratio that the acid component (D) is excessive. By use of said electrolytic solution for electrolytic capacitor, the increase in the ESR with the elapse of time in an electrolytic capacitor is suppressed.