Patent ID: 7042138

Claim:
A piezoelectric type electroacoustic transducer comprising: a piezoelectric vibrating plate including a plurality of piezoelectric ceramic layers laminated to each other with an internal electrode interposed between each of the plurality of piezoelectric ceramic layers, and main surface electrodes provided on front and back side main surfaces of the piezoelectric vibrating plate, whereby the piezoelectric vibrating plate is surface-flexural-vibrated in a thickness direction thereof with an AC signal applied between the main surface electrodes and the internal electrode; and a box including supporting portions on which the outer peripheral portions of the back side of the piezoelectric vibrating plate is supported, the piezoelectric vibrating plate having a protecting film provided on both of the front and back side surfaces of the piezoelectric vibrating plate, the protecting film being formed by applying a paste resin in a film-shape and hardening the resin, or by bonding an adhesive sheet and hardening the sheet, and the piezoelectric vibrating plate is warped on the front-side thereof by the hardening shrink stresses of the protecting films; wherein the protecting film on the back side surface has a thickness that is greater than that of the protecting film on the front side surface.