Novel borate compound

A compound represented by the following formula (1):

• wherein R1, R2, R3 and R4 are each independently a C6-14 aryl group substituted by one or more fluorine atoms or fluoro C1-4 alkyl groups, and
• [A+-H] is a cation in which the ring nitrogen atom of a 5- or 6-membered monocyclic nitrogen-containing aromatic heterocyclic compound having a total carbon number of not less than 25 and substituted by the same or different, two or more C1-30 alkyl groups or C1-30 alkoxy groups is protonated.