COMPACT INKJET NOZZLE DEVICE WITH HIGH DEGREE OF SYMMETRY

Abstract

An inkjet nozzle device includes a main chamber having a floor, a roof and a perimeter wall extending between the floor and the roof. The main chamber includes: a firing chamber having a nozzle aperture defined in the roof and a bar heater for ejection of ink through the nozzle aperture; an antechamber for supplying ink to the firing chamber, the antechamber having a chamber inlet defined in the floor; and a baffle plate extending parallel with the bar heater, which partitions the main chamber to define the firing chamber and the antechamber. The nozzle device has mirror symmetry about a symmetry plane extending perpendicular to the longitudinal axes of the bar heater and the baffle plate

Claims

1. An inkjet nozzle device comprising an elongate main chamber having a floor, a roof and a perimeter wall extending between the floor and the roof, the perimeter wall having a pair of longer sidewalls and a pair of shorter end walls, the main chamber comprising: a firing chamber disposed towards one of the sidewalls, the firing chamber having a nozzle aperture defined in the roof and an elongate bar heater for ejection of ink through the nozzle aperture, the bar heater having a longitudinal axis; an antechamber disposed towards an opposite sidewall for supplying ink to the firing chamber, the antechamber having at least one chamber inlet defined in the floor; and an elongate baffle plate having a longitudinal axis extending parallel with the longitudinal axis of the bar heater, the baffle plate partitioning the main chamber to define the firing chamber and the antechamber, wherein the inkjet nozzle device has mirror symmetry about a symmetry plane extending perpendicular to the longitudinal axes of the bar heater and the baffle plate.

2. The inkjet nozzle device of claim 1, wherein the floor and the roof are common to the firing chamber and the antechamber.

3. The inkjet nozzle device of claim 1, wherein the symmetry plane bisects the nozzle aperture, the actuator and the baffle plate.

4. The inkjet nozzle device of claim 3 comprising first and second chamber inlets positioned towards respective first and second opposite ends of the baffle plate, and wherein the first and second chamber inlets are equidistant from symmetry plane.

5. The inkjet nozzle device of claim 4, wherein each of the first and second chamber inlets has a higher capillary pressure than the nozzle aperture.

6. The inkjet nozzle of claim 5, wherein each of the first and second chamber inlets has a smaller area than the nozzle aperture.

7. The inkjet nozzle device of claim 3 comprising single chamber inlet, and wherein the symmetry plane bisects the single chamber inlet.

8. The inkjet nozzle device of claim 3, wherein the baffle plate has a pair of side edges such that a gap extends between each side edge and the end walls to define a pair of firing chamber entrances flanking the baffle plate, the firing chamber entrances being disposed symmetrically about symmetry plane.

9. The inkjet nozzle device of claim 1, wherein the baffle plate extends beyond the chamber inlet along a longitudinal axis of the inkjet nozzle device.

10. The inkjet nozzle device of claim 1, wherein the nozzle aperture is elongate having a longitudinal axis perpendicular to the plane of symmetry.

11. The inkjet nozzle device of claim 1, wherein the nozzle aperture is elliptical having a major axis parallel to the longitudinal axis of the bar heater and perpendicular symmetry plane.

12. The inkjet nozzle device of claim 11, wherein the baffle plate has a length dimension greater than a length dimension of the nozzle aperture along its major axis.

13. The inkjet nozzle device of claim 9, wherein at least part of the chamber inlet extends beyond each end of the nozzle aperture along its major axis.

14. The inkjet nozzle device of claim 1, wherein the baffle plate has a length of at least 80% of a length of the bar heater.

15. The inkjet nozzle device of claim 1, wherein a length of the bar heater is at least 70% of a total length of the inkjet nozzle device.

16. The inkjet nozzle device of claim 1, wherein the perimeter wall and the baffle plate are comprised of a same material.

17. The inkjet nozzle device of claim 1, wherein the firing chamber has a larger volume than the antechamber.

18. A print chip comprising at least one pair of nozzle rows, each nozzle row comprising a plurality of inkjet nozzle devices according to claim 1, and wherein the nozzle apertures, baffle plates and bar heaters of said inkjet nozzle devices are co-aligned along a direction of each nozzle row.

19. The print chip of claim 1, wherein the chamber inlets of the pair of nozzle rows meet with a common backside ink supply channel of the print chip, the backside ink supply channel supplying a same ink to each inkjet nozzle device in the pair of nozzle rows.

20. A printhead comprising a plurality of print chips according to claim 18.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0037] FIG. 1 is a plan view of an inkjet nozzle device according to a first embodiment;

[0038] FIG. 2 is a sectional view through line A-A of the inkjet nozzle device shown in FIG. 1;

[0039] FIG. 3 is a plan view of a pair of nozzle rows in a print chip;

[0040] FIG. 4 is a plan view of an inkjet nozzle device according to a second embodiment; and

[0041] FIG. 5 is sectional perspective through line B-B of the inkjet nozzle device shown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment (Single Chamber Inlet)

[0042] Referring to FIGS. 1 and 2, there is shown an inkjet nozzle device 10 according to a first embodiment. The inkjet nozzle device 10 comprises a main chamber 12 having a floor 14, a roof 16 and a continuous perimeter wall 18 extending between the floor and the roof. The perimeter wall 18 encircling the main chamber 12, defines a generally elongate main chamber, which takes the form, in plan view, of an oblong having rounded corners. The perimeter wall 18 comprises a pair of opposite sidewalls 18a and 18b extending longitudinally parallel with a nominal y-axis and a pair of opposite end walls 18c and 18d curvedly interconnecting the sidewalls.

[0043] The floor 14 is defined by a passivation layer 19 covering a CMOS layer 20 containing drive circuitry for the nozzle device 10. The CMOS layer 20 may comprise a plurality of metal layers interspersed with interlayer dielectric (ILD) layers, as known to those skilled in the art. Typically, the roof 16 and perimeter wall 18 are comprised of ceramic materials, which may be the same or different from each other (e.g., silicon dioxide, silicon nitride, etc.).

[0044] The main chamber 12 of the nozzle device 10 comprises a firing chamber 22 and an antechamber 24. The firing chamber 22 comprises an elliptical nozzle aperture 26 defined in the roof 16 and an actuator in the form of a resistive bar heater 28 bonded to the floor 14. The antechamber 24 comprises a chamber inlet 30 defined in the floor 14.

[0045] An elongate baffle plate 32 (or baffle wall), having a height dimension extending between the floor 14 and the roof 16, partitions the main chamber 12 to define the firing chamber 22 and the antechamber 24. The baffle plate 32 is positioned laterally adjacent the bar heater 28 and extends lengthwise parallel to the bar heaterthat is, along the nominal y-axis. The baffle plate 32 and bar heater 28 are substantially coextensive with each other along the y-axis. Rounded ends of the baffle plate 32 advantageously minimize mechanical stresses and reduce the risk of roof cracking during fabrication and operation of the device.

[0046] The nozzle device 10 has a plane of symmetry extending along a nominal x-axis of the main chamber 12 to provide mirror symmetry about the x-axis. The plane of symmetry is indicated by the broken line A-A in FIG. 1, which is coincident with a minor axis and bisects a major axis of the elliptical nozzle aperture 26, as well as bisecting the longitudinal axes of the heater element 28, the baffle plate 32 and the chamber inlet 30.

[0047] The antechamber 24 fluidically communicates with the firing chamber 22 via a pair of firing chamber entrances 34 which flank the baffle plate 32 at opposite ends thereof. Each firing chamber entrance 34 is defined by a gap defined between respective ends of the baffle plate 32 and the end walls 18c and 18d of the main chamber 12. Typically, the baffle plate 32 occupies about most of the length (e.g., at least 60% of the length) of the main chamber 12 along the y-axis. In plan view, the baffle plate 32 fully shields the chamber inlet 30 from the bar heater 28.

[0048] The nozzle aperture 26 is elongate and takes the form of an ellipse having a major axis extending along the y-axis and a minor axis coincident with the plane of symmetry A-A and extending along the x-axis. A longitudinal axis of the heater element 28 is coincident with a major axis of the elliptical nozzle aperture 26, while the plane of symmetry A-A bisects the bar heater 28 across its longitudinal axis. Typically, the centroid of the nozzle aperture 26 is aligned with the centroid of the bar heater 28.

[0049] The bar heater 28 is connected at each end thereof to respective electrodes in the CMOS layer 20 by one or more vias 37 defined through the floor 14. The bar heater 28 may be comprised of any suitable resistive material, for example, a titanium-aluminum alloy, titanium aluminum nitride etc. In one embodiment, the bar heater 28 is coated with one or more protective layers, as described in U.S. Pat. No. 9,573,368, the contents of which are incorporated herein by reference.

[0050] The vias 37 may be filled with any suitable conductive material (e.g., copper, aluminum, tungsten etc.) to provide electrical connection between the heater element 28 and an upper metal layer of the CMOS layer 20. A suitable process for forming electrode connections from the heater element 28 to the CMOS layer 20 is described in U.S. Pat. No. 8,453,329, the contents of which are incorporated herein by reference.

[0051] As shown most clearly in FIG. 2, the main chamber 12 is defined in a blanket layer of wall material 40 deposited onto the passivation layer 19 by a suitable etching process (e.g., plasma etching, wet etching, photo etching etc.). The baffle plate 32 and the perimeter wall 18 are defined simultaneously by this etching process, which simplifies the overall MEMS fabrication process. Hence, the baffle plate 32 and perimeter wall 18 are comprised of the same wall material, which may be any suitable etchable ceramic or polymer material suitable for use in printheads.

[0052] A print chip may be comprised of a silicon substrate 102 having the CMOS layer 20 and a plurality of the inkjet nozzle devices 10 arranged in rows, such as the pair of nozzle rows shown in FIG. 3. The chamber inlet 30 of each nozzle device 10 meets with a relatively wider ink supply channel 104 defined in a backside of the print chip. As shown in FIG. 3, the pair of nozzle rows are arranged for printing odd and even dots and a common backside ink supply channel 104 for supplying ink to each nozzle row is shown in dotted outline. The ink supply channel 104 supplies ink to the odd and even nozzle rows via respective chamber inlets 30 of the nozzle devices 10, as described in U.S. Pat. No. 7,441,865 (the contents of which are incorporated herein by reference).

[0053] The advantages of the nozzle device 10 are like those of the nozzle devices described in U.S. Pat. No. 8,998,383. However, those advantages are achieved with a nozzle device having a minimal MEMS footprint and a minimal dimension along the y-axis. The minimal dimension of each nozzle device 10 along the y-axis enable closer inter-row separation of nozzle apertures 26 in a pair of adjacent nozzle rows, as indicated by double-headed arrow d in FIG. 3.

[0054] During droplet ejection, the baffle plate 32 and its opposed sidewall 18a of the firing chamber 24 symmetrically constrain the expanding bubble such that ink droplets are ejected with minimal skew along both the x- and y-axes. Furthermore, any backflow and/or fluidic crosstalk during droplet ejection is minimized by virtue of the MEMS design having the baffle plates 32, chamber inlets 30 and backside ink supply channel 104 providing a tortuous fluidic path between neighboring devices.

Second Embodiment (Dual Chamber Inlets)

[0055] Referring to FIGS. 4 and 5, there is shown an inkjet nozzle device 50 according to a second embodiment. The inkjet nozzle device 50 is identical in every respect to the inkjet nozzle device 10 described above in connection with FIGS. 1 and 2, with the exception that the single chamber inlet 30 is replaced with first and second chamber inlets 30a and 30b.

[0056] The first and second chamber inlets 30a and 30b are identically sized and are disposed at either side of a plane of symmetry (indicated by broken line B-B in FIG. 4) extending along the x-axis of the nozzle device 50. Like the first embodiment, the plane of symmetry B-B bisects the longitudinal axes of the nozzle aperture 26, the bar heater 28 and the baffle plate 32, while the first and second chamber inlets 30a and 30b are spaced equidistant therefrom in order to maintain overall mirror symmetry in the nozzle device 50.

[0057] In contrast with the single chamber inlet 30 described above, each of the first and second chamber inlets 30a and 30b has a higher capillary pressure than the nozzle aperture 26 by virtue of having a relatively smaller area (and consequently greater curvature) than the nozzle aperture. The relatively higher capillary pressures of the first and second chamber inlets 30a and 30b advantageously minimizes the risk of de-priming during printhead operation, while still allowing sufficient flow rates into the firing chamber 22 for high frequency operation.

[0058] In the inkjet nozzle device 10 shown in FIG. 1, the nozzle aperture 26 has a higher capillary pressure than the chamber inlet 30, potentially allowing nozzle suction to suck air bubbles from backside ink supply channels 104 into the firing chamber 22. This configuration risks connecting a relatively large air bubble in the ink supply channel 104 with atmosphere, consequently risking de-priming of the printhead. Although such risks are minimized when using degassed ink, it is desirable for printheads to be compatible with non-degassed inks, especially in printers employing gravity control of backpressures (such as Memjet? printers described in U.S. Pat. No. 8,740,360).

[0059] Accordingly, in the inkjet nozzle device 50, the higher capillary pressure of the first and second chamber inlets 30A and 30B, relative to the nozzle aperture 26, minimizes the risk of nozzle suction drawing air bubbles into the firing chamber 22, with potential de-priming of the printhead. At the same time, flow rates into the antechamber 24 are still sufficient for rapid refilling after each droplet ejection by virtue of the two chamber inlets 30A and 30B, albeit with smaller cross-sectional areas than the single chamber inlet 30. In addition, positioning of the first and second chamber inlets 30A and 30B towards respective firing chamber entrances 34 in the nozzle device 50 minimizes flow resistance between the chamber inlets and the firing chamber 22, thereby maximizing flow rates into the firing chamber and enabling high frequency operation of the device.

[0060] It will, of course, be appreciated that the present invention has been described by way of example only and that modifications of detail may be made within the scope of the invention, which is defined in the accompanying claims.