Actuator unit and manufacturing method thereof, and liquid ejection head

A manufacturing method of an actuator unit to be fixed to a surface of a passage unit in which liquid passages including a plurality of pressure chambers are formed, the actuator unit serving to apply pressure to liquid in each pressure chamber,

• the method comprising:
• a common electrode forming step of forming a common electrode on one surface of a piezoelectric layer, the common electrode having its size capable of covering the plurality of pressure chambers;
• an electric field blocking layer forming step of forming a plurality of electric field blocking layers respectively in a plurality of first regions on an opposite surface of the piezoelectric layer from the one surface, the first regions being opposed to the common electrode, the first regions being arranged on the opposite surface of the piezoelectric layer so as to be distant from each other in the plane of the opposite surface, each electric field blocking layer having one or more holes, each electric field blocking layer being lower in dielectric constant than the piezoelectric layer;
• an individual electrode forming step of forming a plurality of individual electrodes respectively in a plurality of second regions on the opposite surface of the piezoelectric layer, the second regions being opposed to the common electrode and neighboring the respective electric field blocking layers, each individual electrode being further formed on a surface of the electric field blocking layer neighboring the corresponding second region;
• and
• a land forming step of forming a plurality of lands in regions of the respective individual electrodes opposed to the respective electric field blocking layers.

A liquid ejection head comprising a passage unit in which a plurality of pressure chambers each connected to an ejection port are arranged adjacent to each other in a matrix along a surface of the passage unit;

• and an actuator unit fixed to the surface of the passage unit for changing the volume of each pressure chamber,
• the actuator unit having a layered structure in which a common electrode positioned over the plurality of pressure chambers, a piezoelectric layer capable of expanding and contracting by an externally applied electric field, and a plurality of individual electrodes positioned so as to be opposed to the respective pressure chambers are put in layers in this order on a vibrating plate that covers the plurality of pressure chambers,
• the piezoelectric layer having been polarized along its thickness and being able to expand or contract perpendicularly to its thickness to change the volumes of pressure chambers when an external electric field is applied along its thickness,
• each individual electrode having on an upper surface of the piezoelectric layer a main electrode portion opposed to the corresponding pressure chamber, and an outside electrode portion opposed to an outside region of the pressure chamber, both of the main and outside electrode portions being opposed to the common electrode,
• a plurality of electric field blocking layers lower in dielectric constant than the piezoelectric layer being positioned on the upper surface of the piezoelectric layer so as to be opposed the outside regions of the respective pressure chambers and the common electrode, the electric field blocking layers being sandwiched between the piezoelectric layer and a plurality of lands that are electrically connected to the outside electrode portions of the respective individual electrodes so that drive signals can be supplied to the respective individual electrodes through the lands,
• each electric field blocking layer being a porous layer having therein at least one hole.