Thermal ink jet printhead with heater element that forms symmetrical bubbles

摘要

There is disclosed an ink jet printhead which comprises a plurality of nozzles 3 and 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 has a serpentine form configured to generate the gas bubble substantially symmetrically about an axis extending normal to the plane of the aperture. The gap between the electrodes in the side of the bubble forming chamber 7 create a discontinuity in the serpentine path of the heater element 10. This causes the bubble formation to be asymmetrical and skewed toward one side of the heater element. This in turn can influence the trajectory of the ejected drop. By configuring the heater element to compensate for the gap, the symmetry and position of the bubble within the chamber can be controlled. Greater control of bubble formation provides a more predictable trajectory of the ejected drop.