Printhead having hydrophobic polymer coated on ink ejection face
View Patent ↗A printhead having a hydrophobic ink ejection face is provided. At least part of the ink ejection face is coated with a hydrophobic polymeric material selected from the group comprising: polymerized siloxanes and fluorinated polyolefins.
1. A printhead having an ink ejection face, wherein at least part of the ink ejection face is coated with a hydrophobic polymeric material selected from the group consisting of: polymerized siloxanes.
2. The printhead of claim 1 , wherein said polymeric material is resistant to removal by ashing.
3. The printhead of claim 1 , wherein said polymeric material forms a passivating surface oxide in an oxygen plasma.
4. The printhead of claim 3 , wherein said polymeric material recovers its hydrophobicity after being subjected to an oxygen plasma.
5. The printhead of claim 1 , wherein the polymeric material is polydimethylsiloxane (PDMS).
6. The printhead of claim 1 comprising a plurality of nozzle assemblies formed on a substrate, each nozzle assembly comprising: a nozzle chamber, a nozzle opening defined in a roof of the nozzle chamber and an actuator for ejecting ink through the nozzle opening.
7. The printhead of claim 6 , wherein a nozzle surface, having the hydrophobic polymer coated thereon, at least partially defines the ink ejection face.
8. The printhead of claim 7 , wherein each roof defines at least part of the nozzle surface of the printhead, each roof having a hydrophobic outside surface relative to the inside surfaces of each nozzle chamber by virtue of said hydrophobic coating.
9. The printhead of claim 6 , wherein at least part of the ink ejection face has a contact angle of more than 90° and the inside surfaces of the nozzle chambers have a contact angle of less than 90°.
10. The printhead of claim 6 , wherein each nozzle chamber comprises a roof and sidewalls comprised of a ceramic material.
11. The printhead of claim 10 , wherein the ceramic material is selected from the group comprising: silicon nitride, silicon oxide and silicon oxynitride.
12. The method of claim 6 , wherein said roof is spaced apart from a substrate, such that sidewalls of each nozzle chamber extend between said nozzle surface and said substrate.
13. The printhead of claim 6 , wherein said actuator is a heater element configured for heating ink in said chamber so as to form a gas bubble, thereby forcing a droplet of ink through said nozzle opening.
14. The printhead of claim 13 , wherein said heater element is suspended in said nozzle chamber.
15. The printhead of claim 6 , wherein said actuator is a thermal bend actuator comprising:
a first active element for connection to drive circuitry; and
a second passive element mechanically cooperating with the first element, such that when a current is passed through the first element, the first element expands relative to the second element, resulting in bending of the actuator.
16. The printhead of claim 15 , wherein said thermal bend actuator defines at least part of a roof of each nozzle chamber, whereby actuation of said actuator moves said actuator towards a floor of said nozzle chamber.
17. The printhead of claim 15 , wherein said nozzle opening is defined in said actuator or in a static portion of said roof.
18. The printhead of claim 15 , wherein said hydrophobic polymeric material defines a mechanical seal between said actuator and a static portion of said roof, thereby minimizing ink leakage during actuation.
19. The printhead of claim 18 , wherein said hydrophobic polymeric material has a Young's modulus of less than 1000 MPa.
20. The printhead of claim 1 , wherein the ink ejection face is hydrophobic relative to ink supply channels in the printhead.