Inkjet head

An inkjet head comprising:

• a pressure-chamber substrate in which pressure chambers to contain ink are formed, the pressure chambers communicating with respective nozzles from which the ink is ejected in a predetermined direction;
• a spacer substrate disposed on an opposite side of a diaphragm from the predetermined direction, wherein the diaphragm forms one surface of each of the pressure chambers, and the one surface is on an opposite side of the each of the pressure chambers from the predetermined direction;
• a wiring substrate disposed on an opposite side of the spacer substrate from the predetermined direction;
• and
• actuators in contact with the diaphragm in a space formed by the spacer substrate between the wiring substrate and the diaphragm, the actuators being electrically connected to respective wires of the wiring substrate,
• wherein
• differences in coefficients of thermal expansion between the pressure-chamber substrate, the diaphragm, the spacer substrate, and the wiring substrate are equal to or less than a predetermined value,
• the spacer substrate includes ink connection paths communicating with the respective pressure chambers, and
• at least the ink connection paths are subjected to a surface treatment.