INKJET PRINTHEAD WITH NOZZLE ARRANGEMENTS HAVING COATED HEATER ELEMENTS
Provided is an inkjet printhead having an array of micro-electromechanical nozzle arrangements. Each nozzle arrangement includes side walls located on a wafer substrate with a roof layer deposited on said walls to define an ink chamber. The roof layer defines a nozzle aperture and an inlet is defined in the substrate to supply the ink chamber with printing fluid. The nozzle arrangement also includes at least one heater element suspended between the side walls in the chamber, so that when electrical actuation energy of less than 500 nanojoules is applied to the heater element, a vapour bubble is formed in the fluid leading to a pressure increase in the chamber thereby ejecting the fluid via the nozzle aperture. The heater element is substantially covered by a conformal protective coating applied to all sides of the heater element simultaneously such that the coating is seamless.
1 . An inkjet printhead having an array of micro-electromechanical nozzle arrangements each comprising:
side walls located on a wafer substrate with a roof layer deposited on said walls to define an ink chamber, the roof layer defining a nozzle aperture and an inlet defined in the substrate to supply the ink chamber with printing fluid; and
at least one heater element suspended between the side walls in the chamber, so that when electrical actuation energy of less than 500 nanojoules is applied to the heater element, a vapour bubble is formed in the fluid leading to a pressure increase in the chamber thereby ejecting the fluid via the nozzle aperture, wherein the heater element is substantially covered by a conformal protective coating applied to all sides of the heater element such that the coating is seamless.
2 . The printhead of claim 1 , wherein each nozzle arrangement includes a CMOS driving layer in the wafer substrate for electrically driving the heater element, said element having two separate portions with separate contacts whereby each portion is individually actuatable.
3 . The printhead of claim 1 , wherein the heater element has a mass of less than 10 nanograms.
4 . The printhead of claim 1 , wherein the heater element has an annular shape with a point of collapse of the vapour bubble near a centre thereof.
5 . The printhead of claim 1 , wherein the ink inlet is 200 to 300 microns in length and 8 to 24 microns in diameter.
6 . The printhead of claim 1 , having a nozzle density of more than 10,000 nozzles per square cm of substrate surface.
7 . The printhead of claim 1 , wherein the nozzle arrangements are formed at least partially by chemical vapor deposition (CVD).