Patent ID: 8710716

Claim:
An actuator comprising: a diaphragm having a thickness equal to or greater than 0.5 μm and equal to or less than 20 μm; a piezoelectric body layer which is provided on a first surface side of the diaphragm, and receives stress from the diaphragm; a pair of electrodes which is provided on the first surface side of the diaphragm together with the piezoelectric body layer, and is mutually opposing in a thickness direction of the piezoelectric body layer via the piezoelectric body layer; and a stress adjusting layer which is provided on a second surface side of the diaphragm on an opposite side to the first surface of the diaphragm in order to suppress warping of the diaphragm caused by a first stress acting on the first surface side, the first stress due to a difference in coefficients of thermal expansion of the diaphragm and the piezoelectric body layer, and receives stress from the diaphragm in a same direction as the stress that the piezoelectric body layer receives from the diaphragm, wherein warping of the diaphragm is suppressed by applying a second stress, balancing with the first stress on the first surface side, on the second surface side of the diaphragm by the stress adjusting layer, and wherein a coefficient of thermal expansion of the stress adjusting layer is greater than a coefficient of thermal expansion of the diaphragm, and is equal to or greater than 5 ppm/° C.