Abstract: Between adjacent matrix type electrodes in a thin-film EL display panel, one of which is transparent, there is disposed an EL layer sandwiched by a pair of dielectric layers, which manifests a hysteresis curve when plotted with respect to the applied voltage vs light intensity characteristics. The thin-film EL display panel is further provided with at least one reference electrode. In reading out the memory state of the display panel, current is derived which has an amplitude equal to the difference between the current drawn through the reference electrode and the readout current.

Abstract: For a thin-film EL display panel which exhibits the hysteresis loop phenomenon in the applied voltage versus brightness relationship, a string of alternating sustain pulses are applied, the amplitude of which is chosen at the voltage level appearing at the point in the hysteresis loop characteristics where the difference between the minimum light brightness on the voltage increasing curve and the maximum light brightness on the voltage decreasing curve is substantially a maximum. A flash lamp, for example, a xenon lamp which releases light beams toward the thin-film EL display panel, is energized in synchronism with the application period and pause period of the alternating sustain pulses. There are provided means for controlling the application period of the alternating sustain pulses and the illumination period of the flash lamp in accordance with the light activated write mode or erase mode.