Patent ID: 7397651

Claim:
An electrolytic solution for electrolytic capacitor, comprising a quaternary cyclic amidinium tetrafluoroaluminate represented by the following formula (1) and a solvent, and the electrolytic solution containing compounds represented by the following formulae (2) to (4) in a total amount of 0.6% by weight or less: wherein: each of R 1 to R 3 independently represents an alkyl group which may be substituted, a cycloalkyl group which may be substituted, an aryl group which may be substituted or an aralkyl group which may be substituted; X represents an alkylene group which may be substituted or an arylene group which may be substituted; or any of two selected from R 1 to R 3 and X may be connected together to form a ring, wherein the ring may have a nitrogen atom(s) in addition to the nitrogen atoms in the formula (1), wherein: each of R 11 to R 13 independently represents a hydrogen atom, an alkyl group which may be substituted, a cycloalkyl group which may be substituted, an aryl group which may be substituted or an aralkyl group which may be substituted; X 1 represents an alkylene group which may be substituted or an arylene group which may be substituted; or any of two selected from R 11 to R 13 and X 1 may be connected together to form a ring, wherein the ring may have a nitrogen atom(s) in addition to the nitrogen atoms in the formula (2), wherein the amino group may be protonated to form a salt, wherein: each of R 22 and R 23 independently represents a hydrogen atom, an alkyl group which may be substituted, a cycloalkyl group which may be substituted, an aryl group which may be substituted or an aralkyl group which may be substituted; X 2 represents an alkylene group which may be substituted or an arylene group which may be substituted; or any of two selected from R 22 , R 23 and X 2 may be connected together to form a ring, wherein the ring may have a nitrogen atom(s) in addition to the nitrogen atoms in the formula (3), wherein the amidine group may be protonated to form a salt, wherein: each of R 31 , R 33 and R 34 independently represents an alkyl group which may be substituted, a cycloalkyl group which may be substituted, an aryl group which may be substituted or an aralkyl group which may be substituted; X 3 represents an alkylene group which may be substituted or an arylene group which may be substituted; or any of two selected from R 31 , R 33 and X 3 may be connected together to form a ring, wherein the ring may have a nitrogen atom(s) in addition to the nitrogen atoms in the formula (4).