Patent ID: 7700531

Claim:
A cleaning agent which may contain water as an impurity, said cleaning agent consisting of: (i) a lactone represented by the following formula (1): wherein R 1 is an alkylene group having 3 to 6 carbon atoms, and (ii) at least one other solvent selected from the group consisting of a cyclic carbonate represented by the following formula (2): wherein R 2 is an alkylene group having 3 to 6 carbon atoms, a glycol ether represented by the following formula (3): R 3 O R 4 O n R 5 (3) wherein R 3 and R 5 are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, an acetyl group or a propionyl group, R 4 is an alkylene group having 2 to 4 carbon atoms, and n is 1 to 3, with the proviso that R 3 and R 5 are not a hydrogen atom at the same time, and a dimethyl sulfoxide, wherein said at least one other solvent is present in an amount of not more than 80% by mass based on the cleaning agent, and said cleaning agent contains not more than 1% by mass of water, said cleaning agent optionally containing a stabilizer, and optionally containing metal ions in an amount not higher than 100 ppb based on the mass of the cleaning agent, and optionally containing anions in an amount not higher than 100 ppb based on the mass of the cleaning agent.