A heater of a bubble-jet type ink jet printhead enabling gray scale and manufacturing method thereof are provided. The heater includes two or more heating elements arranged concentrically around a nozzle. Each of the heating elements is formed in polygonal or annular shape and spaced apart by a different...http://www.google.de/patents/US6460961?utm_source=gb-gplus-sharePatent US6460961 - Heater of bubble-jet type ink-jet printhead for gray scale printing and manufacturing method thereof
