Patent ID: 7125107

Claim:
A method for driving a piezoelectric ink jet head that comprises a plate-shaped substrate having a plurality of recesses that would become pressure chambers to be filled with an ink being formed on one side of the substrate in the direction of substrate surface, with a nozzle that discharges the ink filling the pressure chamber as ink droplet to communicate with each recess, and a piezoelectric actuator having a first piezoelectric ceramic layer of transverse vibration mode, a first common electrode, a second piezoelectric ceramic layer of transverse vibration mode and a second common electrode, all having such a size that covers the plurality of pressure chambers, are stacked in this order from a position far from the substrate on the surface of the substrate where the recesses are formed, and having a plurality of individual electrodes formed thereon in correspondence to the pressure chambers is disposed on the first piezoelectric ceramic layer, characterized that the piezoelectric actuator is put in the initial state by removing the electric fields applied to both of the piezoelectric ceramic layers in the period of standby, while an electric field of opposite sense to the polarizing direction is applied to the second piezoelectric ceramic layer by using the first and second common electrodes when forming a dot, and in synchronization thereof, (1) for the pressure chambers from which ink droplet should be discharged through the nozzle, an electric field of the same sense to the polarizing direction of the layer is applied to a region of the first piezoelectric ceramic layer disposed between the individual electrode corresponding to the pressure chamber and the first common electrode by using the electrodes, thereby causing the corresponding region of the piezoelectric actuator to deflect and protrude toward the pressure chamber, while (2) for the pressure chambers from which ink droplet should not be discharged through the nozzle, an electric field of the opposite sense to the polarizing direction of the layer is applied to a region of the first piezoelectric ceramic layer disposed between the individual electrode corresponding to the pressure chamber and the first common electrode by using the electrodes, thereby maintaining the corresponding region of the piezoelectric actuator in the initial state, so as to discharge an ink droplet selectively through the nozzle that communicates with the pressure chamber described in (1) and form a dot.