Patent ID: 7789498
Filing Date: 2010-09-07
Classification: B41J

Abstract:
1. An inkjet head, comprising: a passage unit having a pressure chamber which is in communication with a nozzle and which is defined by a recessed portion provided in one surface of the passage unit; and an actuator unit including: (a) an oscillating plate fixed to the one surface of the passage unit so as to close the recessed portion defining the pressure chamber; (b) a piezoelectric layer disposed on the oscillating plate so that the piezoelectric layer and the oscillating plate cooperate with each other to constitute a piezoelectric unimorph; (c) a first electrode provided on a side of one surface of the piezoelectric layer so as to correspond to the pressure chamber; and (d) a second electrode provided on a side of an other surface of the piezoelectric layer and opposed to the first electrode in a direction of thickness of the piezoelectric layer, wherein the pressure chamber has an elongate shape, wherein the piezoelectric layer includes an active portion that is interposed between the first electrode and the second electrode and, as seen in the direction of thickness of the piezoelectric layer, is not located in a central portion of an opposed area thereof opposed to the pressure chamber and is located on either side of said central portion of the opposed area in a widthwise direction perpendicular to a lengthwise direction of the pressure chamber, the opposed area of the piezoelectric layer being deformed to increase a volume of the pressure chamber when an electric field is applied to the active portion, wherein the first electrode includes a pair of electrode portions which extend along respective two sides of an opening of the elongate pressure chamber that extend in the lengthwise direction and are opposed to each other, a substantial entirety of the pair of electrode portions being located within an area defined by the two sides of the opening of the pressure chamber, as seen in the direction of thickness of the piezoelectric layer, and wherein a clearance is provided, on at least a middle portion of the pressure chamber in the lengthwise direction thereof, between a periphery of the opening of the pressure chamber and an outer periphery of each electrode portion, as seen in the direction of thickness of the piezoelectric layer.