Patent ID: 8450912

Claim:
An actuator element comprising: a piezoelectric body; a pair of electrodes mutually opposing to each other via the piezoelectric body; a diaphragm to which the piezoelectric body sandwiched between the pair of electrodes is bonded; and a base substrate arranged to oppose a movable part including the piezoelectric body and the diaphragm, the movable part being displaced in a direction toward the base substrate by application of a drive voltage to the pair of electrodes, wherein: polarization (Pr)-electric field (E) hysteresis characteristics of the piezoelectric body are biased with respect to an electric field; by application of a voltage in an opposite direction to the drive voltage, to the pair of electrodes, the movable part is displaced in a direction away from the base substrate; and wherein, of a coercive electric field on a positive electric field side and a coercive electric field on a negative field side in the Pr-E hysteresis characteristics, when a coercive electric field in an electric field direction at a time of driving by application of the drive voltage is represented by Ec_a and a coercive electric field in an electric field direction at a time of the movable part being displaced in the direction away from the base substrate by application of the voltage in the opposite direction is represented by Ec_b, then |Ec_b|>|Ec_a| is established; the drive voltage, applied when driving to displace the movable part in the direction toward the base substrate is performed, produces an electric field not less than the coercive electric field |Ec_a| of the piezoelectric body; and the voltage applied when the movable part is displaced in the direction away from the base substrate produces an electric field that is not greater than 80% of the coercive electric field |Ec_b| of the piezoelectric body and not less than 30% of the coercive electric field |Ec_b| the piezoelectric body.