Thermal ink jet printhead with bubble nucleation offset from ink supply passage
View Patent ↗There is disclosed an ink jet printhead that has a plurality of nozzles 3 each defining a nozzle aperture 5 with a nozzle axis extending through the center of the nozzle aperture 5 and normal to the nozzle aperture. An ejectable liquid inlet 31 for establishing fluid communication between the nozzle aperture 5 and an ejectable liquid supply, the inlet having a central axis substantially parallel to the nozzle axis. 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 paint 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 is configured to nucleate the gas bubble at a point that is laterally offset from the inlet. Laterally offsetting the heater element 10 from the ink inlet 31 increases the fluidic drag retarding flow back through the inlet and ink supply passage. The fluidic drag through the nozzle aperture 5 is comparatively much smaller so little energy is lost to a reverse flow of ink through the inlet when a gas bubble forms on the element.
1. An ink jet printhead comprising:
a plurality of nozzles, each defining a nozzle aperture with a nozzle axis extending through the center of the nozzle aperture and normal to the nozzle aperture;
an ejectable liquid inlet for establishing fluid communication between the nozzle aperture and an ejectable liquid supply, the inlet having a central axis substantially parallel to, and laterally offset from, the nozzle axis;
a bubble forming chamber corresponding to each of the nozzles respectively;
at least one heater element disposed in each of the bubble forming chambers respectively, the heater element configured as a suspended beam extending between opposing sides of the bubble forming chamber for thermal contact with a bubble forming liquid; such that,
heating the heater element to a temperature above the boiling point of the bubble forming liquid forms a gas bubble that causes the ejection of a drop of the ejectable liquid through the nozzle corresponding to that heater element; wherein,
the heater element is configured to nucleate the gas bubble at a point that is laterally offset from the inlet.
2. The printhead of claim 1 wherein the heater element has an enclosed geometric shape formed between the ends of the suspended beam.
3. The printhead of claim 2 wherein the enclosed geometric shape has a higher resistance than the remainder of the element.
4. The printhead of claim 1 wherein the bubble forming liquid and the ejectable liquid are of a common body of liquid.
5. The printhead of claim 1 being configured to print on a page and to be a page-width printhead.
6. The printhead of claim 1 wherein each heater element is predominantly formed from titanium nitride.
7. The printhead of claim 1 wherein each heater element is configured such that an actuation energy of less than 500 nanojoules (nJ) is required to be applied to that heater element to heat that heater element sufficiently to form a said bubble in the bubble forming liquid thereby to cause the ejection of a said drop.
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 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.
9. The printhead of 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. The printhead of claim 1 wherein each heater element has two opposite sides and is configured such that a said gas bubble formed by that heater element is formed at both of said sides of that heater element.
11. 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.
12. The printhead of claim 1 comprising a structure that is formed by chemical vapor deposition (CVD), the nozzles being incorporated on the structure.
13. The printhead of claim 1 comprising a structure which is less than 10 microns thick, the nozzles being incorporated on the structure.
14. The printhead of claim 1 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. The printhead of 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. The printhead of 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. The printhead of claim 1 wherein each 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.
18. A printer system which incorporates a printhead, the printhead comprising:
a plurality of nozzles, each defining a nozzle aperture with a nozzle axis extending through the center of the nozzle aperture and normal to the nozzle aperture;
an ejectable liquid inlet for establishing fluid communication between the nozzle aperture and an ejectable liquid supply, the inlet having a central axis substantially parallel to, and laterally offset from, the nozzle axis;
a bubble forming chamber corresponding to each of the nozzles respectively;
at least one heater element disposed in each of the bubble forming chambers respectively, the heater element configured as a suspended beam extending between opposing sides of the bubble forming chamber for thermal contact with a bubble forming liquid; such that,
heating the heater element to a temperature above the boiling point of the bubble forming liquid forms a gas bubble that causes the ejection of a drop of the ejectable liquid through the nozzle corresponding to that heater element; wherein,
the heater element is configured to nucleate the gas bubble at a point that is laterally offset from the inlet.
19. The system of claim 18 wherein the heater element has an enclosed geometric shape formed between the ends of the suspended beam.
20. The system of claim 19 wherein the enclosed geometric shape has a higher resistance than the remainder of the element.
21. The system of claim 18 being configured to support the bubble forming liquid in thermal contact with each said heater element, and to support the ejectable liquid adjacent each nozzle.
22. The system of claim 18 wherein the bubble forming liquid and the ejectable liquid are of a common body of liquid.
23. The system of claim 18 being configured to print on a page and to be a page-width printhead.
24. The system of claim 18 wherein each heater element is predominantly formed from titanium nitride.
25. The system of claim 18 wherein each heater element is configured such that an actuation energy of less than 500 nanojoules (nJ) is required to be applied to that heater element to heat that heater element sufficiently to form a said bubble in the bubble forming liquid thereby to cause the ejection of a said drop.
26. The system of claim 18 , wherein the printhead is configured to receive a supply of the ejectable liquid at an ambient temperature, and wherein 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.
27. The system of claim 18 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.
28. The system of claim 18 wherein each heater element has two opposite sides and is configured such that a said gas bubble formed by that heater element is formed at both of said sides of that heater element.
29. The system of claim 18 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.
30. The system of claim 18 comprising a structure that is formed by chemical vapor deposition (CVD), the nozzles being incorporated on the structure.
31. The system of claim 18 comprising a structure which is less than 10 microns thick, the nozzles being incorporated on the structure.
32. The system of claim 18 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.
33. The system of claim 18 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.
34. The system of claim 18 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.
35. The system of claim 18 wherein each 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.
36. A method of ejecting drops of an ejectable liquid from a plurality of nozzles, each defining a nozzle aperture with a nozzle axis extending through the center of the nozzle aperture and normal to the nozzle aperture;
an ejectable liquid inlet for establishing fluid communication between the nozzle aperture and an ejectable liquid supply, the inlet having a central axis substantially parallel to, and laterally offset from, the nozzle axis;
a bubble forming chamber corresponding to each of the nozzles respectively;
at least one heater element disposed in each of the bubble forming chambers respectively, the heater element configured as a suspended beam extending between opposing sides of the bubble forming chamber for thermal contact with a bubble forming liquid; the method comprising the steps of:
heating the heater element to a temperature above the boiling point of the bubble forming liquid to form a gas bubble that causes the ejection of a drop of the ejectable liquid from the nozzle; and
supplying the nozzle with a replacement volume of the ejectable liquid equivalent to the ejected drop; wherein,
the heater element is configured to nucleate the gas bubble at a point that is laterally offset from the inlet.
37. The method of claim 36 wherein the heater element has an enclosed geometric shape formed between the ends of the suspended beam.
38. The method of claim 37 wherein the enclosed geometric shape has a higher resistance than the remainder of the element.
39. The method of claim 36 wherein the bubble forming liquid and the ejectable liquid are of a common body of liquid.
40. The method of claim 36 wherein the printhead is configured to print on a page and to be a page-width printhead.
41. The method of claim 36 wherein said step of heating the at least one heater element is effected by applying an actuation energy of less than 500 nJ to each such heater element.
42. The method of claim 36 wherein prior to the step of heating the at least one heater element, a supply of the ejectable liquid, at an ambient temperature, is fed to the printhead, wherein the step of heating is effected by applying heat energy to the at least one heater element, wherein said applied heat energy is less than the energy required to heat a volume of said ejectable liquid equal to the volume of said drop, from a temperature equal to said ambient temperature to said boiling point.
43. The method of claim 36 wherein the printhead includes a substrate on which said nozzles are disposed, the substrate having a substrate surface and the areal density of the nozzles relative to the substrate surface exceeding 10,000 nozzles per square cm of substrate surface.
44. The method of claim 36 wherein the at least one heater element has two opposing sides and the bubble is generated at both of said sides of each heated heater element.
45. The method of claim 36 wherein the generated bubble is collapsible and has a point of collapse, and is generated such that the point of collapse is spaced from the at least one heater element.
46. The method of claim 36 wherein the printhead has a structure that is less than 10 microns thick and which incorporates said nozzles thereon.
47. The method of claim 36 wherein the nozzles of the printhead are formed by chemical vapor deposition (CVD).
48. The method of claim 36 wherein the printhead has a plurality of nozzle chambers each chamber corresponding to a respective nozzle and a plurality of said heater elements are formed in each of the chambers, such that the heater elements in each chamber are formed on different respective layers to one another.
49. The method of claim 36 wherein the heater elements are 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.
50. The method of claim 36 wherein the heater elements include solid material and wherein the step of heating at least one heater element comprises heating a mass of less than 10 nanograms of the solid material of each such heater element to a temperature above said boiling point.
51. The method of claim 36 wherein a conformal protective coating is applied to substantially to all sides of each of the heater elements simultaneously, such that the coating is seamless.