Inkjet printhead heater with high surface area
View Patent ↗There is disclosed an ink jet printhead which comprises a plurality of nozzles and one or more heater elements corresponding to each nozzle. Each heater element is configured to heat a bubble forming liquid in the printhead to a temperature above its boiling point to form a gas bubble therein. The generation of the bubble causes the ejection of a drop of an ejectable liquid (such as ink) through respective corresponding nozzle, to effect printing. Each heater element has a surface area to volume ratio greater than 4:1. This configuration ensures that heat is quickly transferred from the elements to the ink for efficient operation and minimal heating of the printhead substrate.
1. An inkjet nozzle comprising:
a nozzle chamber for containing ink, said chamber comprising a roof and sidewalls, said
roof having a nozzle opening defined therein;
a heater element positioned in said nozzle chamber, said heater element being configured to
heat at least part of said ink to a temperature above its boiling point, thereby forming a gas bubble and causing ejection of an ink droplet through said nozzle opening;
wherein
said heater element has a surface area to volume ratio of at least 4:1 and comprises a heating loop adapted to be in thermal contact with said ink.
2. The inkjet nozzle of claim 1 wherein said heater element has a surface area to volume ratio of at least 6:1.
3. The inkjet nozzle of claim 1 wherein said heater element has a surface area to volume ratio of approximately 8.7:1.
4. The inkjet nozzle of claim 1 being configured for assembly into a page-width printhead.
5. The inkjet nozzle of claim 1 wherein said heater element is in the form of a cantilever beam.
6. The inkjet nozzle of claim 1 wherein said heater element is configured such that an actuation energy of less than 500 nanojoules (nJ) is required to be applied to heat said heater element sufficiently to form said bubble.
7. The inkjet nozzle of claim 1 configured to receive a supply of ink at an ambient temperature, wherein said each heater element is configured such that the energy required to be applied thereto to cause the ejection of said droplet is less than the energy required to heat a volume of said ink, equal to the volume of the said droplet, from a temperature equal to said ambient temperature to said boiling point.
8. The inkjet nozzle of claim 1 wherein said heater element has two opposite sides and is configured such that said gas bubble formed by that heater element is formed at both of said sides of that heater element.
9. The inkjet nozzle of claim 1 wherein the bubble which each element is configured to form is collapsible and has a point of collapse, and wherein said heater element is configured such that the point of collapse of said bubble formed thereby is spaced from that heater element.
10. The inkjet nozzle of claim 1 wherein at least part of said nozzle chamber is formed by chemical vapor deposition (CVD).
11. The inkjet nozzle of claim 1 , wherein at least one wall of said nozzle chamber is less than 10 microns thick.
12. The inkjet nozzle of claim 1 wherein said 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.
13. The inkjet nozzle of claim 1 wherein said heater element is covered by a conformal protective coating, said coating having been applied to all sides of the heater element simultaneously such that said coating is seamless.