Patent ID: 7195342

Claim:
An ink jet printhead comprising: a plurality of nozzles; a bubble forming chamber corresponding to each of the nozzles respectively, the bubble forming chambers adapted to contain a bubble forming liquid; and, a generally planar heater element disposed in each of the bubble forming chambers respectively, the heater element configured for thermal contact with the bubble forming liquid; such that, heating the heater element to a temperature above the boiling point forms a gas bubble in the bubble forming liquid in order to cause the ejection of a droplet of ejectable liquid from the nozzle; wherein, the heater element extends in a plane parallel to the plane of the nozzle, and the heater element is laterally enclosed by the bubble forming chamber such that the plane of the heater element extends through the interior surface of the bubble forming chamber; and, the printhead receives a supply of the ejectable liquid at an ambient temperature, and each heater element is configured such that the energy required to be applied thereto to heat said part to cause the ejection of a said drop is less than the energy required to heat a volume of said ejectable liquid equal to the volume of the said drop, from a temperature equal to said ambient temperature to said boiling point.