Thermal ink jet printhead with bubble nucleation laterally offset from nozzle

摘要

There is disclosed an ink jet printhead which comprises a plurality of nozzles 3 each defining a nozzle aperture 5 with a nozzle axis extending through the center of the nozzle aperture 5 and normal to the nozzle aperture. An ejectable liquid inlet 31 for establishing fluid communication between the nozzle aperture 5 and an ejectable liquid supply, the inlet having a central axis substantially parallel to the nozzle axis. A bubble forming chamber 7 corresponding to each nozzle respectively. At least one heater element 10 disposed in each bubble forming chamber 7 to heat a bubble forming liquid 11 to a temperature above its boiling point to form a gas bubble 12 therein. The generation of the bubble 12 causes the ejection of a drop 16 of an ejectable liquid (such as ink) through an ejection aperture 5 in each nozzle 3, to effect printing. The heater element 10 is configured to nucleate the gas bubble at two or more regions such that each nucleation region is laterally offset from the nozzle aperture 5. Gas bubbles nucleate from opposing sides of the nozzle aperture and converge to form a single bubble. The bubble formed is symmetrical about at least one plane extending along the nozzle axis. This enhances the control of the symmetry and position of the bubble within the chamber so the ejected drop trajectory is more reliable.