Flat Panel Light-Emitting Sounder Using Thin-Film EL Devices with a Ceramic Insulating Layer

Sound emission has been achieved from an EL device consisting of a ZnS:Mn thin-film phosphor and a thick piezoelectric BaTiO3 ceramic insulator. The BaTiO3 ceramic, serving not only as the insulating layer of the EL device but also as the substrate, functioned as the sounder. A high sound pressure level as well as a high luminance was obtained in the device driven with audio-frequency voltages: above 90 dB in a flat panel speaker composed of four sound-emitting EL devices with a maximum luminance of 8000 cd/m2. Test results have shown that the sound emission is related to the electroluminescence.