An ionic compound has the formula (I): in which, R1 is selected from the group consisting of hydrogen, a C1-C20 alkyl, and an aromatic group; R2 is selected from the group consisting of a carbonyl and a C1-C10 alkyl; and R3 is selected from the group consisting of an imidazole ring, a C1-C20 alkyl, an acrylic group, and an aromatic group; X− is selected from the group consisting of Cl−, Br−, I−, NO3−, AlCl4−, BF4−, CF3SO3−, (CF3SO3)−, CF3COO−, CH3COO−, and PF6−; and k is an integer 1 or 2. The ionic compound can be added in a pressure-sensitive adhesive of a polarizer of a liquid crystal display panel to avoid the phenomenon of the static electricity residual when the release film is removed from the pressure-sensitive adhesive.