To provide a method for driving a polymer network liquid crystal glass plate, which avoids an optical interference phenomenon such as a flicker and stripes and is economically constructed with simplified circuitry.

The circuitry consists of a power switching element, an inductance in series therewith and a switching control circuit. Timing of turning on the switching element is determined by a period of time elapsed after the instant at which the absolute value of AC voltage was zero or by the instant it reaches the maximum value. For example, if the switching element is turned on at the instant the voltage reaches the positive maximum value, a capacitance of the liquid crystal glass is charged to the positive maximum value of the voltage in a time period of a half of a resonance frequency, t=π√LC, caused by the capacitance of the liquid crystal glass. If the switching element is turned off at the instant the positive charge of the liquid crystal glass is retained. If the switching element is turned on at the instant the AC voltage reaches the negative maximum value, and turned off after a lapse of π√LC time period the negative charge of the liquid crystal glass is retained. Driving similar to driving with a square wave is attained.