PURPOSE: To obtain the title particles having high-speed response in low electric fields and saved electric power consumption by coating neutralized salt particles of ion-exchange resin which are impregnated with a solution of an inorganic salt electrolyte in an aprotic polar solvent, with a polymeric membrane.

CONSTITUTION: An inorganic salt electrolyte, preferably lithium perchlorate, benzylpyridinium chloride, sodium thiocyanate or the like is dissolved in an aprotic polar solvent such as ethylene carbonate, dimethylformamide or N- methylpyrrolidone, preferably in a super-saturated concentration. Dried particles of neutralized salt of ion-exchange resin is impregnated with the solution, then added to a solution of polyisoprene, polyethylene, polypropylene or the like in cyclohexane, toluene, chloroform or the like, treated with ultrasonic waves at about 70 to 80°C into coated microcapsules whereby the subject particles are obtained.