Patent ID: 8511162

Claim:
A method of forming an image with use of an ink jet head, comprising steps of: a step (a) of preparing the ink jet head, wherein: the ink jet head comprises: a piezoelectric film having a piezoelectric layer sandwiched between a first electrode and a second electrode; a vibration layer bonded to the piezoelectric film; and a pressure chamber member having a pressure chamber for storing ink and bonded to a surface of the vibration layer opposite to a surface to which the piezoelectric film is bonded, the vibration layer is bonded to the piezoelectric film so that the vibration layer is displaceable in its film thickness direction according to a deformation of the piezoelectric film produced by a piezoelectric effect, the vibration layer and the pressure chamber member are bonded to each other so that a volumetric capacity of the pressure chamber changes according to a displacement of the vibration layer and so that the ink in the pressure chamber is ejected according to a change in the volumetric capacity of the pressure chamber, the first electrode includes an electrode layer with a (001) orientation, the piezoelectric layer comprises a (Bi,Na,Ba)TiO 3 layer composed of (Na x Bi y )TiO 0.5x+1.5y+2 —BaTiO 3 with a (001) orientation only, x is not less than 0.30 and not more than 0.46, y is not less than 0.51 and not more than 0.62, the (Na x Bi y )TiO 0.5x+1.5y+2 —BaTiO 3 layer has composition around a Morphotropic Phase Boundary; and a step (b) of applying a voltage to the piezoelectric layer through the first electrode and the second electrode to displace, based on the piezoelectric effect, the vibration layer in its film thickness direction so that the volumetric capacity of the pressure chamber changes and the ink is ejected from the pressure chamber by the displacement, wherein an amount B of the deformation of the piezoelectric film and an electric field A between the first electrode and the second electrode satisfy the following equation: B=cA ( c is a constant).