THERMAL INK JET PRINTHEAD WITH HEATER ELEMENT POSITIONED FOR MINIMIZED INK DROP MOMENTUM
An ink jet printhead comprises a plurality of nozzles each having a nozzle aperture; a bubble forming chamber corresponding to each of the nozzles respectively; an ejectable liquid inlet for establishing fluid communication between the nozzle aperture and an ejectable liquid supply, the ejectable liquid inlet and the nozzle aperture being aligned such that they have a common central axis; and a heater element disposed in each of the bubble forming chambers. Each heater element has two bubble nucleation regions suspended within the bubble forming chamber in a plane parallel to that of the nozzle aperture. The two bubble nucleation regions are laterally offset from the central axis, such that the lateral offset of one of the bubble nucleation regions is equal and opposite to the lateral offset of the other bubble nucleation region. The bubble nucleation regions are spaced from each other such that bubbles nucleated at each will grow until they unite to form the gas bubble that causes the ejection of a drop of ejectable liquid. The heater element is positioned such that a distance between a point of collapse of the gas bubble and the nozzle aperture is less than 50 microns.
1 . An ink jet printhead comprising:
a plurality of nozzles each having a nozzle aperture;
a bubble forming chamber corresponding to each of the nozzles respectively;
an ejectable liquid inlet for establishing fluid communication between the nozzle aperture and an ejectable liquid supply, the ejectable liquid inlet and the nozzle aperture being aligned such that they have a common central axis; and
a heater element disposed in each of the bubble forming chambers, wherein
each heater element has two bubble nucleation regions suspended within the bubble forming chamber in a plane parallel to that of the nozzle aperture,
the two bubble nucleation regions are laterally offset from the central axis, such that the lateral offset of one of the bubble nucleation regions is equal and opposite to the lateral offset of the other bubble nucleation region;
the bubble nucleation regions are spaced from each other such that bubbles nucleated at each will grow until they unite to form the gas bubble that causes the ejection of a drop of ejectable liquid, and
the heater element is positioned such that a distance between a point of collapse of the gas bubble and the nozzle aperture is less than 50 microns.
2 . The printhead of claim 1 , wherein the heater element is positioned such that the distance between a point of collapse of the gas bubble and the nozzle aperture is less than 25 microns.
3 . The printhead of claim 1 , wherein the heater element is positioned such that the distance between a point of collapse of the gas bubble and the nozzle aperture is less than 10 microns.
4 . The printhead of claim 1 , wherein the heater element is positioned such that the distance between a point of collapse of the gas bubble and the nozzle aperture is less than 5 microns.
5 . The printhead of claim 1 wherein the bubble forming liquid and the ejectable liquid are of a common body of liquid.
6 . The printhead of claim 1 being configured to print on a page and to be a page-width printhead.
7 . The printhead of claim 1 wherein each heater element is predominantly formed from titanium nitride.
8 . The printhead of claim 1 configured to receive a supply of the ejectable liquid at an ambient temperature, wherein each heater element is configured such that the energy required to cause the ejection of 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.
9 . The printhead of claim 1 , wherein the bubble which each element is configured to form is collapsible and has a point of collapse, and wherein each heater element is configured such that the point of collapse of a bubble formed thereby is spaced from that heater element.
10 . The printhead of claim 1 wherein each heater element has a conformal protective coating on any parts exposed to the bubble forming liquid, the coating of each heater element having been applied substantially to all sides of the heater element simultaneously such that the coating is seamless.