Thermal ink jet printhead with suspended heater element parallel to the nozzle
An ink jet printhead with a plurality of nozzles that each nozzle defining a planar nozzle aperture. A bubble forming chamber corresponds to each of the nozzles and a heater is positioned in each of the chambers respectively. The heater has a planar structure with a heater element extending between two electrodes, so that it is suspended by the electrodes in the bubble forming chamber for thermal contact with a printing fluid. The heater element is suspended so that the plane of the heater is parallel to the planar nozzle aperture. The bubble forming chamber receives printing fluid at an ambient temperature, and energy is applied to the heater element through the electrodes to form a gas bubble that encircles at least some of the heater element, and cause a drop of the printing fluid to eject through the nozzle, the energy applied to the heater element being less than the energy required to heat a volume of the printing fluid equal to the volume of the drop, from ambient temperature to the boiling point of the printing fluid. The flat bubble formed by a planar suspended heater is energy efficient and generates a relatively broad flat impulse in the ink for better drop directionality.
1 . An ink jet printhead comprising:
a plurality of nozzles, each nozzle defining a planar nozzle aperture;
a bubble forming chamber corresponding to each of the nozzles; and
a heater positioned in each of the chambers respectively, the heater having a planar structure with a heater element extending between two electrodes, the heater element being suspended by the electrodes in the bubble forming chamber for thermal contact with a printing fluid, such that the plane of the heater is parallel to the planar nozzle aperture; wherein during use,
the bubble forming chamber receives printing fluid at an ambient temperature, and energy is applied to the heater element through the electrodes to form a gas bubble that encircles at least some of the heater element, and cause a drop of the printing fluid to eject through the nozzle, the energy applied to the heater element being less than the energy required to heat a volume of the printing fluid equal to the volume of the drop, from ambient temperature to the boiling point of the printing fluid.
2 . An inkjet printhead according to claim 1 wherein the heater element is predominantly titanium nitride.
3 . An inkjet printhead according to claim 1 wherein the heater element is a flat elongated strip.
4 . An inkjet printhead according to claim 1 wherein the bubble forming chamber has a circular cross section and the heater element has at least one arcuate section that is concentric with the longitudinal axis of the bubble forming chamber.
5 . An inkjet printhead according to claim 1 wherein the printing fluid is water based ink.
6 . An inkjet printhead according to claim 1 being configured to print on a page and to be a page-width printhead.
7 . An inkjet printhead according to claim 1 wherein the heater element is suspended in the form of a cantilever beam.
8 . An inkjet printhead according to claim 1 wherein the heater element is configured such that an actuation energy of less than 500 nanojoules (nJ) is required to form the gas bubble that ejects the drop.
9 . An inkjet printhead according to claim 1 comprising a substrate having a substrate surface, wherein the areal density of the nozzles relative to the substrate surface exceeds 10,000 nozzles per square cm of substrate surface.
10 . An inkjet printhead according to claim 1 wherein the gas bubble nucleates on both sides of the heater element before growing to encircle the heater element.
11 . An inkjet printhead according to claim 1 wherein the bubble collapses to 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.
12 . An inkjet printhead according to claim 1 further comprising a structure that is formed by chemical vapor deposition (CVD), the nozzles being incorporated on the structure.
13 . An inkjet printhead according to claim 1 further comprising a structure which is less than 10 microns thick, the nozzles being incorporated on the structure.
14 . An inkjet printhead according to claim 1 further comprising a plurality of nozzle chambers each corresponding to a respective nozzle, and a plurality of said heater elements being disposed within each chamber, the heater elements within each chamber being formed on different respective layers to one another.
15 . An inkjet printhead according to claim 1 wherein each heater element is formed of solid material more than 90 % of which, by atomic proportion, is constituted by at least one periodic element having an atomic number below 50.
16 . An inkjet printhead according to claim 1 wherein each heater element includes solid material and is configured for a mass of less than 10 nanograms of the solid material of that heater element to be heated to a temperature above said boiling point thereby to heat said part of the bubble forming liquid to a temperature above said boiling point to cause the ejection of a said drop.
17 . An inkjet printhead according to claim 1 wherein the heater element is substantially covered by a conformal protective coating, the coating of each heater element having been applied substantially to all sides of the heater element simultaneously such that the coating is seamless.