Liquid ejection head and image forming apparatus

A liquid ejection head, comprising:

• a nozzle through which liquid is ejected;
• a pressure chamber which is connected to the nozzle;
• a diaphragm which pressurizes the pressure chamber;
• and
• a laminated piezoelectric element which causes the diaphragm to deform and is bonded to a section of the diaphragm by means of a thin film forming technique, wherein:
• an effective surface area of the diaphragm forming one inner surface of the pressure chamber is greater than a surface area of the bonding section between the diaphragm and the laminated piezoelectric element;
• a surface area of an active section of the laminated piezoelectric element is greater than the effective surface area of the diaphragm;
• a width of the bonding section between the diaphragm and the laminated piezoelectric element through which the laminated piezoelectric element directly presses is ⅓an effective width of the diaphragm;
• and
• the laminated piezoelectric element has a projection on a lower section which corresponds with the bonded section between the diaphragm and the laminated piezoelectric element, the projection being in contact with the diaphragm, and cross-sectional areas extending on planes parallel to the diaphragm, and the larger a distance from the diaphragm to the plane is, the smaller the cross-sectional area of the laminated piezoelectric element extending on the plane becomes.