Printhead integrated circuit with low voltage thermal actuators
View Patent ↗There is disclosed a printhead integrated circuit (IC) which comprises a plurality of nozzles and one or more heater elements 10 corresponding to each nozzle. Each heater element 10 is configured to heat a bubble forming liquid 11 in the printhead to a temperature above its boiling point to form a gas bubble 12 therein. The generation of the bubble 12 causes the ejection of a drop of an ejectable liquid (such as ink) through an ejection aperture 5 in each nozzle, to effect printing. In each nozzle, the heater element 10 requires an electrical pulse with a voltage less than 8 volts and a duration less than 1.5 microseconds, to form the vapor bubble that causes the ejection of the drop. With the realization that drive pulse voltages above, say, 12 volts are not a fixed parameter of printhead design, the benefits of low voltage printhead operation can be incorporated into a design that yields efficiencies that negate the circumstances that created the initial demand for high voltage operation.
1. A printhead integrated circuit (IC) comprising:
a silicon substrate defining a supporting substrate surface;
an array of nozzles formed on the substrate surface;
at least one heater element corresponding to each of the nozzles respectively, the heater element being in the form of a beam and positioned in thermal contact with a liquid, wherein
the heater element is heated to a temperature above the liquid's boiling point to form a vapor bubble for ejecting a drop of the liquid through the nozzle corresponding to that heater element, and
the heater element requires an electrical pulse with a voltage less than 8 volts and a duration less than 1.5 microseconds to form the vapor bubble that causes the ejection of the drop.
2. A printhead IC according to claim 1 wherein the electrical pulse has a voltage less than 5 volts and duration less than 1.5 microseconds.
3. A printhead IC according to claim 1 wherein the electrical pulse has a voltage less than 3 volts and duration less than 1.5 microseconds.
4. A printhead IC according to claim 1 wherein each of the nozzles defines an ejection aperture positioned less than 50 microns from the heater element.
5. A printhead IC according to claim 1 configured to receive a supply of the 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 liquid equal to the volume of the said drop, from a temperature equal to said ambient temperature to said boiling point.
6. A printhead IC according to claim 1 wherein the areal density of the nozzles relative to the substrate surface exceeds 10,000 nozzles per square cm of substrate surface.
7. A printhead IC according to claim 1 wherein each heater element is a generally planar beam extending between two ends which are supported such that during use the beam is immersed in the liquid.
8. A printhead IC according to claim 1 wherein the array of nozzles are formed in a nozzle layer, the nozzle layer being parallel to and spaced less than 10 microns from the silicon substrate.
9. A printhead IC 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.
10. A printhead IC 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.
11. A printhead IC 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.
12. A printhead IC according to claim 1 wherein the electrical pulse has less than 200 nano-Joules of energy.
13. A printhead IC according to claim 1 wherein the electrical pulse has less than 150 nano-Joules of energy.
14. A printhead IC according to claim 1 wherein the electrical pulse has less than 100 nano-Joules of energy.
15. A printhead IC according to claim 1 wherein the electrical pulse has less than 80 nano-Joules of energy.