WO2006099652A1 - Inkjet printhead having isolated nozzles - Google Patents

Inkjet printhead having isolated nozzles Download PDF

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Publication number
WO2006099652A1
WO2006099652A1 PCT/AU2005/000392 AU2005000392W WO2006099652A1 WO 2006099652 A1 WO2006099652 A1 WO 2006099652A1 AU 2005000392 W AU2005000392 W AU 2005000392W WO 2006099652 A1 WO2006099652 A1 WO 2006099652A1
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WO
WIPO (PCT)
Prior art keywords
nozzle
printhead
ink ejection
ejection surface
roof
Prior art date
Application number
PCT/AU2005/000392
Other languages
French (fr)
Inventor
Kia Silverbrook
Gregory John Mcavoy
Original Assignee
Silverbrook Research Pty Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Silverbrook Research Pty Ltd filed Critical Silverbrook Research Pty Ltd
Priority to CA2592267A priority Critical patent/CA2592267C/en
Priority to AU2005329726A priority patent/AU2005329726B2/en
Priority to EP05714264A priority patent/EP1861256A4/en
Priority to JP2007555422A priority patent/JP4473314B2/en
Priority to PCT/AU2005/000392 priority patent/WO2006099652A1/en
Priority to KR1020077024048A priority patent/KR100973614B1/en
Publication of WO2006099652A1 publication Critical patent/WO2006099652A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads
    • B41J2/14016—Structure of bubble jet print heads
    • B41J2/14088—Structure of heating means
    • B41J2/14112—Resistive element
    • B41J2/1412—Shape
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads
    • B41J2/1433—Structure of nozzle plates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads
    • B41J2/14427—Structure of ink jet print heads with thermal bend detached actuators
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/16—Production of nozzles
    • B41J2/1601—Production of bubble jet print heads
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/16—Production of nozzles
    • B41J2/1606—Coating the nozzle area or the ink chamber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/16—Production of nozzles
    • B41J2/1621—Manufacturing processes
    • B41J2/1626—Manufacturing processes etching
    • B41J2/1628—Manufacturing processes etching dry etching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/16—Production of nozzles
    • B41J2/1621—Manufacturing processes
    • B41J2/1631—Manufacturing processes photolithography
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/16—Production of nozzles
    • B41J2/1621—Manufacturing processes
    • B41J2/1637—Manufacturing processes molding
    • B41J2/1639—Manufacturing processes molding sacrificial molding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/16—Production of nozzles
    • B41J2/1621—Manufacturing processes
    • B41J2/164—Manufacturing processes thin film formation
    • B41J2/1642—Manufacturing processes thin film formation thin film formation by CVD [chemical vapor deposition]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/16—Production of nozzles
    • B41J2/1621—Manufacturing processes
    • B41J2/164—Manufacturing processes thin film formation
    • B41J2/1645—Manufacturing processes thin film formation thin film formation by spincoating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads
    • B41J2/14427—Structure of ink jet print heads with thermal bend detached actuators
    • B41J2002/14443—Nozzle guard
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads
    • B41J2002/14475—Structure thereof only for on-demand ink jet heads characterised by nozzle shapes or number of orifices per chamber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads
    • B41J2002/14491—Electrical connection

Definitions

  • the present invention relates to the field of inkjet printers and, discloses an inkjet printing system using printheads manufactured with microelectro-mechanical systems (MEMS) techniques.
  • MEMS microelectro-mechanical systems
  • Ink Jet printers themselves come in many different types.
  • the utilization of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein US Patent No. 1941001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.
  • US Patent 3596275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also US Patent No. 3373437 by Sweet et al)
  • Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in US Patent No. 3946398 (1970) which utilizes a diaphragm mode of operation, by Zolten in US Patent 3683212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in US Patent No. 3747120 (1972) discloses a bend mode of piezoelectric operation, Howkins in US Patent No. 4459601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in US 4584590 which discloses a shear mode type of piezoelectric transducer element.
  • the ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in US Patent 4490728. Both the aforementioned references disclosed ink jet printing techniques that rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media.
  • Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.
  • a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.
  • a problem with inkjet printheads, and especially inkjet printheads having a high nozzle density, is that ink can flood across the printhead surface contaminating adjacent nozzles. This is undesirable because it results in reduced print quality.
  • cross- contamination of ink across the printhead surface can potentially result in electrolysis and accelerated corrosion of nozzle actuators. Previous attempts to minimize ink flooding across the printhead surface typically involve coating the printhead with a hydrophobic material. However, hydrophobic coatings have only had limited success in minimizing the extent of flooding.
  • printheads are wiped regularly to remove particles of paper dust or paper fibers, which build up on the ink ejection surface.
  • a wiping mechanism comes into contact with nozzle structures on the printhead surface, there is an obvious risk of damaging the nozzles.
  • a printhead comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle.
  • a method of operating a printhead whilst minimizing cross-contamination of ink between adjacent nozzles, the method comprising the steps of: (a) providing a printhead comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzles having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle; and
  • a method of fabricating a printhead having isolated nozzles comprising the steps of: (a) providing a substrate, the substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate;
  • each nozzle enclosure having an opening defined in a roof and sidewalls extending from the roof to the ink ejection surface; and (f) removing the photoresist.
  • the formations have a hydrophobic surface.
  • InkJet inks are typically aqueous-based inks and hydrophobic formations will repel any flooded ink.
  • hydrophobic formations minimize as far as possible any cross-contamination of ink by acting as a physical barrier and by intermolecular repulsive forces.
  • hydrophobic formations promote ingestion of any flooded ink back into respective nozzle chambers and ink supply channels. Since nozzle chambers are typically hydrophilic, ink will tend to be drawn back into the nozzle and away from a surrounding hydrophobic formation.
  • each nozzle enclosure comprising sidewalls surrounding a respective nozzle, the sidewalls forming a seal with the ink ejection surface.
  • each nozzle is isolated from its adjacent nozzles by a nozzle enclosure.
  • each nozzle enclosure further comprises a roof spaced apart from the respective nozzle, the roof having a roof opening aligned with a respective nozzle opening for allowing ejected ink droplets to pass therethrough onto the print medium.
  • each nozzle enclosure may typically take the form of a cap, which covers or encapsulates an individual nozzle on the ink ejection surface.
  • the roof not only provides additional containment of any flooded ink, it also provides further protection of each nozzle from, for example, the potentially damaging effects of paper dust, paper fibers or wiping.
  • the sidewalls extend from a perimeter region of each roof to the ink ejection surface. Sidewalls of adjacent nozzle enclosures are usually spaced apart across the ink ejection surface.
  • the printhead is an inkjet printhead, such as a pagewidth inkjet printhead.
  • the printhead has a nozzle density, which is sufficient to print at up to 1600 dpi. The present invention is particularly beneficial for printheads having a high nozzle density, because high density printheads are especially prone to flooding between adjacent nozzles.
  • Fig. 1 is a schematic cross-sectional view through an ink chamber of a unit cell of a printhead according to an embodiment using a bubble forming heater element
  • Fig. 2 is a schematic cross-sectional view through the ink chamber Fig. 1, at another stage of operation;
  • Fig. 3 is a schematic cross-sectional view through the ink chamber Fig. 1, at yet another stage of operation;
  • Fig. 4 is a schematic cross-sectional view through the ink chamber Fig. 1, at yet a further stage of operation;
  • Fig. 5 is a diagrammatic cross-sectional view through a unit cell of a printhead in accordance with an embodiment of the invention showing the collapse of a vapor bubble.
  • Fig. 6 is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead.
  • Figs. 7 to 20 are schematic perspective views of the unit cell shown in Fig. 6, at various successive stages in the fabrication process of the printhead.
  • the unit cell 1 of one of the Applicant's printheads comprises a nozzle plate 2 with nozzles 3 therein, the nozzles having nozzle rims 4, and apertures 5 extending through the nozzle plate.
  • the nozzle plate 2 is plasma etched from a silicon nitride structure which is deposited, by way of chemical vapor deposition (CVD), over a sacrificial material which is subsequently etched.
  • CVD chemical vapor deposition
  • the printhead also includes, with respect to each nozzle 3, side walls 6 on which the nozzle plate is supported, a chamber 7 defined by the walls and the nozzle plate 2, a multi- layer substrate 8 and an inlet passage 9 extending through the multi-layer substrate to the far side (not shown) of the substrate.
  • a looped, elongate heater element 10 is suspended within the chamber 7, so that the element is in the form of a suspended beam.
  • the printhead as shown is a microelectromechanical system (MEMS) structure, which is formed by a lithographic process which is described in more detail below.
  • MEMS microelectromechanical system
  • ink 11 from a reservoir enters the chamber 7 via the inlet passage 9, so that the chamber fills to the level as shown in Figure 1.
  • the heater element 10 is heated for somewhat less than 1 microsecond, so that the heating is in the form of a thermal pulse.
  • the heater element 10 is in thermal contact with the ink 11 in the chamber 7 so that when the element is heated, this causes the generation of vapor bubbles 12 in the ink.
  • the ink 11 constitutes a bubble forming liquid.
  • Figure 1 shows the formation of a bubble 12 approximately 1 microsecond after generation of the thermal pulse, that is, when the bubble has just nucleated on the heater elements 10. It will be appreciated that, as the heat is applied in the form of a pulse, all the energy necessary to generate the bubble 12 is to be supplied within that short time.
  • the bubble 12 forms along the length of the element, this bubble appearing, in the cross-sectional view of Figure 1, as four bubble portions, one for each of the element portions shown in cross section.
  • the bubble 12, once generated, causes an increase in pressure within the chamber 7, which in turn causes the ejection of a drop 16 of the ink 11 through the nozzle 3.
  • the rim 4 assists in directing the drop 16 as it is ejected, so as to minimize the chance of drop misdirection.
  • the bubble 12 generates further, and hence grows, with the resultant advancement of ink 11 through the nozzle 3.
  • the shape of the bubble 12 as it grows, as shown in Figure 3, is determined by a combination of the inertial dynamics and the surface tension of the ink 11. The surface tension tends to minimize the surface area of the bubble 12 so that, by the time a certain amount of liquid has evaporated, the bubble is essentially disk-shaped.
  • the increase in pressure within the chamber 7 not only pushes ink 11 out through the nozzle 3, but also pushes some ink back through the inlet passage 9.
  • the inlet passage 9 is approximately 200 to 300 microns in length, and is only approximately 16 microns in diameter. Hence there is a substantial viscous drag. As a result, the predominant effect of the pressure rise in the chamber 7 is to force ink out through the nozzle 3 as an ejected drop 16, rather than back through the inlet passage 9.
  • the printhead is shown at a still further successive stage of operation, in which the ink drop 16 that is being ejected is shown during its "necking phase" before the drop breaks off.
  • the bubble 12 has already reached its maximum size and has then begun to collapse towards the point of collapse 17, as reflected in more detail in Figure 21.
  • the collapsing of the bubble 12 towards the point of collapse 17 causes some ink 11 to be drawn from within the nozzle 3 (from the sides 18 of the drop), and some to be drawn from the inlet passage 9, towards the point of collapse. Most of the ink 11 drawn in this manner is drawn from the nozzle 3, forming an annular neck 19 at the base of the drop 16 prior to its breaking off.
  • the drop 16 requires a certain amount of momentum to overcome surface tension forces, in order to break off.
  • the diameter of the neck 19 reduces thereby reducing the amount of total surface tension holding the drop, so that the momentum of the drop as it is ejected out of the nozzle is sufficient to allow the drop to break off.
  • cavitation forces are caused as reflected by the arrows 20, as the bubble 12 collapses to the point of collapse 17. It will be noted that there are no solid surfaces in the vicinity of the point of collapse 17 on which the cavitation can have an effect.
  • the aperture 5 is surrounded by a nozzle enclosure 60, which isolates adjacent apertures on the printhead.
  • the nozzle enclosure 60 has a roof 61 and sidewalls 62, which extend from the roof to the nozzle plate 2 and form a seal therewith.
  • An opening 63 is defined in the roof 61, which allows ink droplets (not shown) to pass through the nozzle enclosure and onto a print medium (not shown).
  • the nozzle enclosure 60 minimize cross-contamination between adjacent apertures 5 by containing any flooded ink in the immediate vicinity of each nozzle. Flooding of ink from each nozzle may be caused by a variety of reasons, such as nozzle misfires or pressure fluctuations in ink supply channels.
  • the nozzle enclosure may be formed from or coated with a hydrophobic material during the fabrication process, which further minimizes the risk of cross-contamination.
  • a further advantage of the printhead according to the invention is that it allows the nozzle plate 2 of the printhead to be wiped without risk of damaging the sensitive nozzle structures.
  • inkjet printheads are cleaned by a wiping mechanism as part of a warm-up cycle.
  • the nozzle enclosures 60 provide a protective barrier between the nozzles and the wiping mechanism (not shown).
  • CMOS processing of a silicon wafer provides a silicon substrate 21 having drive circuitry 22, and an interlayer dielectric ("interconnect") 23.
  • the interconnect 23 comprises four metal layers, which together form a seal ring for the inlet passage 9 to be etched through the interconnect.
  • the top metal layer 26, which forms an upper portion of the seal ring, can be seen in Figure 7.
  • the metal seal ring prevents ink moisture from seeping into the interconnect 23 when the inlet passage 9 is filled with ink.
  • a passivation layer 24 is deposited onto the top metal layer 26 by plasma-enhanced chemical vapour deposition (PECVD). After deposition of the passivation layer 24, it is etched to define a circular recess, which forms parts of the inlet passage 9. At the same as etching the recess, a plurality of vias 50 are also etched, which allow electrical connection through the passivation layer 24 to the top metal layer 26.
  • the etch pattern is defined by a layer of patterned photoresist (not shown), which is removed by O 2 ashing after the etch.
  • a layer of photoresist is spun onto the passivation later 24.
  • the photoresist is exposed and developed to define a circular opening.
  • the dielectric interconnect 23 is etched as far as the silicon substrate 21 using a suitable oxide-etching gas chemistry (e.g. (VC 4 F 8 ).
  • Etching through the silicon substrate is continued down to about 20 microns to define a front ink hole 52, using a suitable silicon-etching gas chemistry (e.g. 'Bosch etch').
  • a suitable silicon-etching gas chemistry e.g. 'Bosch etch'.
  • the same photoresist mask 51 can be used for both etching steps.
  • Figure 9 shows the unit cell after etching the front ink hole 52 and removal of the photoresist 51.
  • the front ink hole 52 is plugged with photoresist to provide a front plug 53.
  • a layer of photoresist is deposited over the passivation layer 24.
  • This layer of photoresist is exposed and developed to define a first sacrificial scaffold 54 over the front plug 53, and scaffolding tracks 35 around the perimeter of the unit cell.
  • the first sacrificial scaffold 54 is used for subsequent deposition of heater material 38 thereon and is therefore formed with a planar upper surface to avoid any buckling in the heater element (see heater element 10 in Figure 10).
  • the first sacrificial scaffold 54 is UV cured and hardbaked to prevent reflow of the photoresist during subsequent high-temperature deposition onto its upper surface.
  • the first sacrificial scaffold 54 has sloped or angled side faces 55. These angled side faces 55 are formed by adjusting the focusing in the exposure tool (e.g. stepper) when exposing the photoresist.
  • the sloped side faces 55 advantageously allow heater material 38 to be deposited substantially evenly over the first sacrificial scaffold 54.
  • the next stage of fabrication deposits the heater material 38 over the first sacrificial scaffold 54, the passivation layer 24 and the perimeter scaffolding tracks 35.
  • the heater material 38 is typically a monolayer of TiAlN.
  • the heater material 38 may alternatively comprise TiAlN sandwiched between upper and lower passivating materials, such as tantalum or tantalum nitride. Passivating layers on the heater element 10 minimize corrosion of the and improve heater longevity.
  • the heater material 38 is subsequently etched down to the first sacrificial scaffold 54 to define the heater element 10.
  • contact electrodes 15 are defined on either side of the heater element 10.
  • the electrodes 15 are in contact with the top metal layer 26 and so provide electrical connection between the CMOS and the heater element 10.
  • the sloped side faces of the first sacrificial scaffold 54 ensure good electrical connection between the heater element 10 and the electrodes 15, since the heater material is deposited with sufficient thickness around the scaffold 54. Any thin areas of heater material (due to insufficient side face deposition) would increase resistivity and affect heater performance.
  • Adjacent unit cells are electrically insulated from each other by virtue of grooves etched around the perimeter of each unit cell.
  • the grooves are etched at the same time as defining the heater element 10.
  • a second sacrificial scaffold 39 of photoresist is deposited over the heater material.
  • the second sacrificial scaffold 39 is exposed and developed to define sidewalls for the cylindrical nozzle chamber and perimeter sidewalls for each unit cell.
  • the second sacrificial scaffold 39 is also UV cured and hardbaked to prevent any refiow of the photoresist during subsequent high-temperature deposition of the silicon nitride roof material.
  • silicon nitride is deposited onto the second sacrificial scaffold 39 by plasma enhanced chemical vapour deposition.
  • the silicon nitride forms a roof 44 over each unit cell, which is the nozzle plate 2 for a row of nozzles.
  • Chamber sidewalls 6 and unit cell sidewalls 56 are also formed by deposition of silicon nitride.
  • the nozzle rim 4 is etched partially through the roof 44, by placing a suitably patterned photoresist mask over the roof, etching for a controlled period of time and removing the photoresist by ashing.
  • the nozzle aperture 5 is etched through the roof 24 down to the second sacrificial scaffold 39. Again, the etch is performed by placing a suitably patterned photoresist mask over the roof, etching down to the scaffold 39 and removing the photoresist mask.
  • a third sacrificial scaffold 64 is deposited over the roof 44.
  • the third sacrificial scaffold 64 is exposed and developed to define sidewalls for the cylindrical nozzle enclosure over each aperture 5.
  • the third sacrificial scaffold 64 is also UV cured and hardbaked to prevent any refiow of the photoresist during subsequent high-temperature deposition of the nozzle enclosure material.
  • silicon nitride is deposited onto the third sacrificial scaffold 64 by plasma enhanced chemical vapour deposition.
  • the silicon nitride forms an enclosure roof 61 over each aperture 5.
  • Enclosure sidewalls 62 are also formed by deposition of silicon nitride.
  • the enclosure roof 61 may equally be formed from silicon oxide, silicon oxynitride etc.
  • a layer of hydrophobic material ⁇ e.g. fluoropolymer
  • This extra deposition step may be performed at any stage after deposition (e.g. after etching or after ashing).
  • the nozzle enclosure 60 is formed by etching through the enclosure roof layer 61.
  • the enclosure opening 63 is defined by this etch.
  • the enclosure roof material which is located outside the enclosure sidewalls 62 is removed.
  • the etch pattern is defined by standard photoresist masking.
  • the first, second and sacrificial scaffolds of photoresist, together with the front plug 53 are ashed off using an O 2 plasma. Accordingly, fluid connection is made from the ink supply channel 32 through to the nozzle aperture 5 and the nozzle enclosure opening 63.
  • a portion of photoresist, on either side of the nozzle chamber sidewalls 6, remains encapsulated by the roof 44, the unit cell sidewalls 56 and the chamber sidewalls 6.
  • This portion of photoresist is sealed from the O 2 ashing plasma and, therefore, remains intact after fabrication of the printhead.
  • This encapsulated photoresist advantageously provides additional robustness for the printhead by supporting the nozzle plate 2.
  • the printhead has a robust nozzle plate spanning continuously over rows of nozzles, and being supported by solid blocks of hardened photoresist, in addition to support walls.
  • Embodiments The invention has been described above with reference to printheads using bubble forming heater elements. However, it is potentially suited to a wide range of printing system including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with inbuilt pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic "minilabs", video printers, PHOTO CD (PHOTO CD is a registered trade mark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.
  • PHOTO CD PHOTO CD is a registered trade mark of the Eastman Kodak Company
  • the embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.
  • thermal ink jet The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. In conventional thermal inkjet printheads, this leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.
  • piezoelectric inkjet The most significant problem with piezoelectric inkjet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per printhead, but is a major impediment to the fabrication of pagewidth printheads with 19,200 nozzles.
  • the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications.
  • new ink jet technologies have been created.
  • the target features include: low power (less than 10 Watts) high resolution capability (1,600 dpi or more) photographic quality output low manufacturing cost small size (pagewidth times minimum cross section) high speed ( ⁇ 2 seconds per page).
  • ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems.
  • the printhead is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing.
  • the printhead is 100 mm long, with a width which depends upon the ink jet type.
  • the smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm.
  • the printheads each contain 19,200 nozzles plus data and control circuitry.
  • Ink is supplied to the back of the printhead by injection molded plastic ink channels.
  • the molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The printhead is connected to the camera circuitry by tape automated bonding.
  • ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes.
  • Most of the IJOl to IJ45 examples can be made into ink jet printheads with characteristics superior to any currently available ink jet technology.
  • Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.

Abstract

A printhead suitable for minimizing cross-contamination between nozzles (3) is provided. The printhead comprises a substrate (8), which includes a plurality of nozzles (3) for ejecting ink droplets onto a print medium. Each nozzle (3) has a nozzle aperture (5), which is defined in an ink ejection surface of the substrate (8). The printhead also comprises a plurality of formations on the ink ejection surface. The surface formations are configured to isolate each nozzle (3) from at least one adjacent nozzle (3), and typically take the form of enclosure (60) surrounding each nozzle (3).

Description

INKJET PREVTHEAD HAVING ISOLATED NOZZLES
CROSS REFERENCES TO RELATED APPLICATIONS
The following patents or patent applications filed by the applicant or assignee of the present invention are hereby incorporated by cross-reference.
6795215 10/884881 PECOlNP 09/575109 10/296535 09/575110 6805419
09/607985 6398332 6394573 6622923 6747760 10/189459 10/943941
10/949294 10/727181 10/727162 10/727163 10/727245 10/727204 10/727233
10/727280 10/727157 10/727178 10/727210 10/727257 10/727238 10/727251
10/727159 10/727180 10/727179 10/727192 10/727274 10/727164 10/727161
10/727198 10/727158 10/754536 10/754938 10/727227 10/727160 10/934720
10/854521 10/854522 10/854488 10/854487 10/854503 10/854504 10/854509
10/854510 10/854496 10/854497 10/854495 10/854498 10/854511 10/854512
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10/854528 10/854523 10/854527 10/854524 10/854520 10/854514 10/854519
PLT036US 10/854499 10/854501 10/854500 10/854502 10/854518 10/854517
PLT043US 10/728804 10/728952 10/728806 10/728834 10/729790 10/728884
10/728970 10/728784 10/728783 10/728925 10/728842 10/728803 10/728780
10/728779 10/773189 10/773204 10/773198 10/773199 10/773190 10/773201
10/773191 10/773183 10/773195 10/773196 10/773186 10/773200 10/773185
10/773192 10/773197 10/773203 10/773187 10/773202 10/773188 10/773194
10/773193 10/773184 10/760272 10/760273 10/760187 10/760182 10/760188
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10/760201 10/760185 10/760253 10/760255 10/760209 10/760208 10/760194
10/760238 10/760234 10/760235 10/760183 10/760189 10/760262 10/760232
10/760231 10/760200 10/760190 10/760191 10/760227 10/760207 10/760181
6746105 6623101 6406129 6505916 6457809 6550895 6457812
6428133 IJ52NP 10/407212 10/407207 10/683064 10/683041 10/882774
10/884889 10/922890 JUM008US 10/922885 10/922889 10/922884 10/922879
10/922887 10/922888 10/922874 10/922873 10/922871 10/922880 10/922881
10/922882 10/922883 10/922878 JUM023US 10/922876 10/922886 10/922877
10/815625 10/815624 10/815628 10/913375 10/913373 10/913374 10/913372
10/913377 10/913378 10/913380 10/913379 10/913376 10/913381 10/986402
09/575187 6727996 6591884 6439706 6760119 09/575198 09/722148
09/722146 09/721861 6290349 6428155 6785016 09/608920 09/721892
09/722171 09/721858 09/722142 10/171987 10/202021 10/291724 10/291512
10/291554 10/659027 10/659026 10/831242 10/884885 10/884883 10/901154 10/932044 10/962412 10/962510 10/962552 10/965733 10/965933 10/974742
10/986375 10/659027 09/693301 09/575197 09/575195 09/575159 09/575132
09/575123 09/575148 09/575130 09/575165 6813039 09/575118 09/575131
09/575116 6816274 09/575139 09/575186 6681045 6728000 09/575145
09/575192 09/575181 09/575193 09/575183 6789194 09/575150 6789191
6549935 09/575174 09/575163 6737591 09/575154 09/575129 09/575124
09/575188 09/575189 09/575170 09/575171 09/575161 6644642 6502614
6622999 6669385 11/003786 11/003354 CAA003US 11/003418 11/003334
CAA006US 11/003404 11/003419 11/003700 CAAOlOUS CAAOI lUS CAA012US
11/003337 CAAO 14US 11/003420 CAAO 16US CAA017US 11/003463 CACOOlUS
11/003683 CAEOOlUS 11/003702 11/003684 CAF003US CAF004US 10/760254
10/760210 10/760202 10/760197 10/760198 10/760249 10/760263 10/760196
10/760247 10/760223 10/760264 10/760244 10/760245 10/760222 10/760248
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10/760270 10/760259 10/760271 10/760275 10/760274 10/760268 10/760184
10/760195 10/760186 10/760261 10/760258 RRBOOlUS RRB002US RRB003US
RRB004US RRB005US RRB006US RRB007US RRB008US RRB009US RRBOlOUS
RRBOI lUS RRB012US RRB013US RRB014US RRBO 15US RRBO 16US RRBO 17US
RRBO 18US RRBO 19US RRB020US RRB021US RRB022US RRB023US RRB024US
RRB025US RRB026US RRB027US RRB030US RRB031US RRB032US RRB033US
RRCOOlUS RRC002US RRC003US RRC004US RRC005US RRC006US RRC007US
RRC008US RRC009US RRCOlOUS RRCOI lUS RRCO 12US RRCO 13US RRC014US
RRCO 15US RRCO 16US RRC017US RRCOl 8US RRCO 19US RRC020US RRC021US
6750901 6476863 6788336 6322181
Some applications have been listed by docket numbers. These will be replaced when application numbers are known.
FIELD OF THE INVENTION
The present invention relates to the field of inkjet printers and, discloses an inkjet printing system using printheads manufactured with microelectro-mechanical systems (MEMS) techniques.
BACKGROUND OF THE INVENTION
Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc. hi recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature. Many different techniques on ink j et printing have been invented. For a survey of the field, reference is made to an article by J Moore, "Non-Impact Printing: Introduction and Historical Perspective", Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207 - 220 (1988).
Ink Jet printers themselves come in many different types. The utilization of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein US Patent No. 1941001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.
US Patent 3596275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also US Patent No. 3373437 by Sweet et al)
Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in US Patent No. 3946398 (1970) which utilizes a diaphragm mode of operation, by Zolten in US Patent 3683212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in US Patent No. 3747120 (1972) discloses a bend mode of piezoelectric operation, Howkins in US Patent No. 4459601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in US 4584590 which discloses a shear mode type of piezoelectric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in US Patent 4490728. Both the aforementioned references disclosed ink jet printing techniques that rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables. A problem with inkjet printheads, and especially inkjet printheads having a high nozzle density, is that ink can flood across the printhead surface contaminating adjacent nozzles. This is undesirable because it results in reduced print quality. Moreover, cross- contamination of ink across the printhead surface can potentially result in electrolysis and accelerated corrosion of nozzle actuators. Previous attempts to minimize ink flooding across the printhead surface typically involve coating the printhead with a hydrophobic material. However, hydrophobic coatings have only had limited success in minimizing the extent of flooding.
A further problem with inkjet printheads, especially inkjet printheads having senstitive MEMS nozzles formed on an ink ejection surface of the printhead, is that the nozzle structures can become damaged by cleaning the printhead surface. Typically, printheads are wiped regularly to remove particles of paper dust or paper fibers, which build up on the ink ejection surface. When a wiping mechanism comes into contact with nozzle structures on the printhead surface, there is an obvious risk of damaging the nozzles. It would be desirable to provide a printhead, which minimizes cross-contamination by ink flooding between adjacent nozzles. It would be further desirable to provide a printhead, which allows regular cleaning of the printhead surface by a wiping mechanism without risk of damaging nozzle structures on the printhead.
SUMMARY OF THE INVENTION
In a first aspect, there is provided a printhead comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle.
In a second aspect, there is provided a method of operating a printhead, whilst minimizing cross-contamination of ink between adjacent nozzles, the method comprising the steps of: (a) providing a printhead comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzles having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle; and
(b) printing onto a print medium using said printhead.
In a third aspect, there is provided a method of fabricating a printhead having isolated nozzles, the method comprising the steps of: (a) providing a substrate, the substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate;
(b) depositing a layer of photoresist over the ink ejection surface;
(c) defining recesses in the photoresist, each recess revealing a portion of the ink ejection surface surrounding a respective nozzle aperture;
(d) depositing a roof material over the photoresist and into the recesses;
(e) etching the roof material to define a nozzle enclosure around each nozzle aperture, each nozzle enclosure having an opening defined in a roof and sidewalls extending from the roof to the ink ejection surface; and (f) removing the photoresist.
Optionally, the formations have a hydrophobic surface. InkJet inks are typically aqueous-based inks and hydrophobic formations will repel any flooded ink. Hence, hydrophobic formations minimize as far as possible any cross-contamination of ink by acting as a physical barrier and by intermolecular repulsive forces. Moreover, hydrophobic formations promote ingestion of any flooded ink back into respective nozzle chambers and ink supply channels. Since nozzle chambers are typically hydrophilic, ink will tend to be drawn back into the nozzle and away from a surrounding hydrophobic formation.
Optionally, the formations are arranged in a plurality of nozzle enclosures, each nozzle enclosure comprising sidewalls surrounding a respective nozzle, the sidewalls forming a seal with the ink ejection surface. Hence, each nozzle is isolated from its adjacent nozzles by a nozzle enclosure. Optionally, each nozzle enclosure further comprises a roof spaced apart from the respective nozzle, the roof having a roof opening aligned with a respective nozzle opening for allowing ejected ink droplets to pass therethrough onto the print medium. Hence, each nozzle enclosure may typically take the form of a cap, which covers or encapsulates an individual nozzle on the ink ejection surface. The roof not only provides additional containment of any flooded ink, it also provides further protection of each nozzle from, for example, the potentially damaging effects of paper dust, paper fibers or wiping.
Typically, the sidewalls extend from a perimeter region of each roof to the ink ejection surface. Sidewalls of adjacent nozzle enclosures are usually spaced apart across the ink ejection surface. Optionally, the printhead is an inkjet printhead, such as a pagewidth inkjet printhead. Optionally, the printhead has a nozzle density, which is sufficient to print at up to 1600 dpi. The present invention is particularly beneficial for printheads having a high nozzle density, because high density printheads are especially prone to flooding between adjacent nozzles.
BRIEF DESCRIPTION OF THE DRAWINGS
Notwithstanding any other forms that may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Fig. 1 is a schematic cross-sectional view through an ink chamber of a unit cell of a printhead according to an embodiment using a bubble forming heater element; Fig. 2 is a schematic cross-sectional view through the ink chamber Fig. 1, at another stage of operation;
Fig. 3 is a schematic cross-sectional view through the ink chamber Fig. 1, at yet another stage of operation;
Fig. 4 is a schematic cross-sectional view through the ink chamber Fig. 1, at yet a further stage of operation; and
Fig. 5 is a diagrammatic cross-sectional view through a unit cell of a printhead in accordance with an embodiment of the invention showing the collapse of a vapor bubble.
Fig. 6 is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead.
Figs. 7 to 20 are schematic perspective views of the unit cell shown in Fig. 6, at various successive stages in the fabrication process of the printhead.
DESCRIPTION OF OPTIONAL EMBODIMENTS
Bubble Forming Heater Element Actuator
With reference to Figures 1 to 4, the unit cell 1 of one of the Applicant's printheads is shown. The unit cell 1 comprises a nozzle plate 2 with nozzles 3 therein, the nozzles having nozzle rims 4, and apertures 5 extending through the nozzle plate. The nozzle plate 2 is plasma etched from a silicon nitride structure which is deposited, by way of chemical vapor deposition (CVD), over a sacrificial material which is subsequently etched.
The printhead also includes, with respect to each nozzle 3, side walls 6 on which the nozzle plate is supported, a chamber 7 defined by the walls and the nozzle plate 2, a multi- layer substrate 8 and an inlet passage 9 extending through the multi-layer substrate to the far side (not shown) of the substrate. A looped, elongate heater element 10 is suspended within the chamber 7, so that the element is in the form of a suspended beam. The printhead as shown is a microelectromechanical system (MEMS) structure, which is formed by a lithographic process which is described in more detail below.
When the printhead is in use, ink 11 from a reservoir (not shown) enters the chamber 7 via the inlet passage 9, so that the chamber fills to the level as shown in Figure 1. Thereafter, the heater element 10 is heated for somewhat less than 1 microsecond, so that the heating is in the form of a thermal pulse. It will be appreciated that the heater element 10 is in thermal contact with the ink 11 in the chamber 7 so that when the element is heated, this causes the generation of vapor bubbles 12 in the ink. Accordingly, the ink 11 constitutes a bubble forming liquid. Figure 1 shows the formation of a bubble 12 approximately 1 microsecond after generation of the thermal pulse, that is, when the bubble has just nucleated on the heater elements 10. It will be appreciated that, as the heat is applied in the form of a pulse, all the energy necessary to generate the bubble 12 is to be supplied within that short time.
When the element 10 is heated as described above, the bubble 12 forms along the length of the element, this bubble appearing, in the cross-sectional view of Figure 1, as four bubble portions, one for each of the element portions shown in cross section.
The bubble 12, once generated, causes an increase in pressure within the chamber 7, which in turn causes the ejection of a drop 16 of the ink 11 through the nozzle 3. The rim 4 assists in directing the drop 16 as it is ejected, so as to minimize the chance of drop misdirection.
The reason that there is only one nozzle 3 and chamber 7 per inlet passage 9 is so that the pressure wave generated within the chamber, on heating of the element 10 and forming of a bubble 12, does not affect adjacent chambers and their corresponding nozzles. The pressure wave generated within the chamber creates significant stresses in the chamber wall. Forming the chamber from an amorphous ceramic such as silicon nitride, silicon dioxide (glass) or silicon oxynitride, gives the chamber walls high strength while avoiding the use of material with a crystal structure. Crystalline defects can act as stress concentration points and therefore potential areas of weakness and ultimately failure. Figures 2 and 3 show the unit cell 1 at two successive later stages of operation of the printhead. It can be seen that the bubble 12 generates further, and hence grows, with the resultant advancement of ink 11 through the nozzle 3. The shape of the bubble 12 as it grows, as shown in Figure 3, is determined by a combination of the inertial dynamics and the surface tension of the ink 11. The surface tension tends to minimize the surface area of the bubble 12 so that, by the time a certain amount of liquid has evaporated, the bubble is essentially disk-shaped.
The increase in pressure within the chamber 7 not only pushes ink 11 out through the nozzle 3, but also pushes some ink back through the inlet passage 9. However, the inlet passage 9 is approximately 200 to 300 microns in length, and is only approximately 16 microns in diameter. Hence there is a substantial viscous drag. As a result, the predominant effect of the pressure rise in the chamber 7 is to force ink out through the nozzle 3 as an ejected drop 16, rather than back through the inlet passage 9.
Turning now to Figure 4, the printhead is shown at a still further successive stage of operation, in which the ink drop 16 that is being ejected is shown during its "necking phase" before the drop breaks off. At this stage, the bubble 12 has already reached its maximum size and has then begun to collapse towards the point of collapse 17, as reflected in more detail in Figure 21.
The collapsing of the bubble 12 towards the point of collapse 17 causes some ink 11 to be drawn from within the nozzle 3 (from the sides 18 of the drop), and some to be drawn from the inlet passage 9, towards the point of collapse. Most of the ink 11 drawn in this manner is drawn from the nozzle 3, forming an annular neck 19 at the base of the drop 16 prior to its breaking off.
The drop 16 requires a certain amount of momentum to overcome surface tension forces, in order to break off. As ink 11 is drawn from the nozzle 3 by the collapse of the bubble 12, the diameter of the neck 19 reduces thereby reducing the amount of total surface tension holding the drop, so that the momentum of the drop as it is ejected out of the nozzle is sufficient to allow the drop to break off. When the drop 16 breaks off, cavitation forces are caused as reflected by the arrows 20, as the bubble 12 collapses to the point of collapse 17. It will be noted that there are no solid surfaces in the vicinity of the point of collapse 17 on which the cavitation can have an effect.
Advantages of Nozzle Enclosures
Referring to Figure 6, an embodiment of the unit cell 1 according to the invention is shown. The aperture 5 is surrounded by a nozzle enclosure 60, which isolates adjacent apertures on the printhead. The nozzle enclosure 60 has a roof 61 and sidewalls 62, which extend from the roof to the nozzle plate 2 and form a seal therewith. An opening 63 is defined in the roof 61, which allows ink droplets (not shown) to pass through the nozzle enclosure and onto a print medium (not shown).
The nozzle enclosure 60 minimize cross-contamination between adjacent apertures 5 by containing any flooded ink in the immediate vicinity of each nozzle. Flooding of ink from each nozzle may be caused by a variety of reasons, such as nozzle misfires or pressure fluctuations in ink supply channels. The nozzle enclosure may be formed from or coated with a hydrophobic material during the fabrication process, which further minimizes the risk of cross-contamination.
A further advantage of the printhead according to the invention is that it allows the nozzle plate 2 of the printhead to be wiped without risk of damaging the sensitive nozzle structures. Typically, inkjet printheads are cleaned by a wiping mechanism as part of a warm-up cycle. The nozzle enclosures 60 provide a protective barrier between the nozzles and the wiping mechanism (not shown).
Fabrication Process
In the interests of brevity, the fabrication stages have been shown for the unit cell of Figure 6 only (see Figures 7 to 20). It will be appreciated that the other unit cells will use the same fabrication stages with different masking.
Referring to Figure 7, there is shown the starting point for fabrication of the thermal inkjet nozzle shown in Figure 13. CMOS processing of a silicon wafer provides a silicon substrate 21 having drive circuitry 22, and an interlayer dielectric ("interconnect") 23. The interconnect 23 comprises four metal layers, which together form a seal ring for the inlet passage 9 to be etched through the interconnect. The top metal layer 26, which forms an upper portion of the seal ring, can be seen in Figure 7. The metal seal ring prevents ink moisture from seeping into the interconnect 23 when the inlet passage 9 is filled with ink.
A passivation layer 24 is deposited onto the top metal layer 26 by plasma-enhanced chemical vapour deposition (PECVD). After deposition of the passivation layer 24, it is etched to define a circular recess, which forms parts of the inlet passage 9. At the same as etching the recess, a plurality of vias 50 are also etched, which allow electrical connection through the passivation layer 24 to the top metal layer 26. The etch pattern is defined by a layer of patterned photoresist (not shown), which is removed by O2 ashing after the etch.
Referring to Figure 8, in the next fabrication sequence, a layer of photoresist is spun onto the passivation later 24. The photoresist is exposed and developed to define a circular opening. With the patterned photoresist 51 in place, the dielectric interconnect 23 is etched as far as the silicon substrate 21 using a suitable oxide-etching gas chemistry (e.g. (VC4F8). Etching through the silicon substrate is continued down to about 20 microns to define a front ink hole 52, using a suitable silicon-etching gas chemistry (e.g. 'Bosch etch'). The same photoresist mask 51 can be used for both etching steps. Figure 9 shows the unit cell after etching the front ink hole 52 and removal of the photoresist 51.
Referring to Figure 10, in the next stage of fabrication, the front ink hole 52 is plugged with photoresist to provide a front plug 53. At the same time, a layer of photoresist is deposited over the passivation layer 24. This layer of photoresist is exposed and developed to define a first sacrificial scaffold 54 over the front plug 53, and scaffolding tracks 35 around the perimeter of the unit cell. The first sacrificial scaffold 54 is used for subsequent deposition of heater material 38 thereon and is therefore formed with a planar upper surface to avoid any buckling in the heater element (see heater element 10 in Figure 10). The first sacrificial scaffold 54 is UV cured and hardbaked to prevent reflow of the photoresist during subsequent high-temperature deposition onto its upper surface.
Importantly, the first sacrificial scaffold 54 has sloped or angled side faces 55. These angled side faces 55 are formed by adjusting the focusing in the exposure tool (e.g. stepper) when exposing the photoresist. The sloped side faces 55 advantageously allow heater material 38 to be deposited substantially evenly over the first sacrificial scaffold 54.
Referring to Figure 11 , the next stage of fabrication deposits the heater material 38 over the first sacrificial scaffold 54, the passivation layer 24 and the perimeter scaffolding tracks 35. The heater material 38 is typically a monolayer of TiAlN. However, the heater material 38 may alternatively comprise TiAlN sandwiched between upper and lower passivating materials, such as tantalum or tantalum nitride. Passivating layers on the heater element 10 minimize corrosion of the and improve heater longevity.
Referring to Figure 12, the heater material 38 is subsequently etched down to the first sacrificial scaffold 54 to define the heater element 10. At the same time, contact electrodes 15 are defined on either side of the heater element 10. The electrodes 15 are in contact with the top metal layer 26 and so provide electrical connection between the CMOS and the heater element 10. The sloped side faces of the first sacrificial scaffold 54 ensure good electrical connection between the heater element 10 and the electrodes 15, since the heater material is deposited with sufficient thickness around the scaffold 54. Any thin areas of heater material (due to insufficient side face deposition) would increase resistivity and affect heater performance.
Adjacent unit cells are electrically insulated from each other by virtue of grooves etched around the perimeter of each unit cell. The grooves are etched at the same time as defining the heater element 10.
Referring to Figure 13, in the subsequent step a second sacrificial scaffold 39 of photoresist is deposited over the heater material. The second sacrificial scaffold 39 is exposed and developed to define sidewalls for the cylindrical nozzle chamber and perimeter sidewalls for each unit cell. The second sacrificial scaffold 39 is also UV cured and hardbaked to prevent any refiow of the photoresist during subsequent high-temperature deposition of the silicon nitride roof material.
Referring to Figure 14, silicon nitride is deposited onto the second sacrificial scaffold 39 by plasma enhanced chemical vapour deposition. The silicon nitride forms a roof 44 over each unit cell, which is the nozzle plate 2 for a row of nozzles. Chamber sidewalls 6 and unit cell sidewalls 56 are also formed by deposition of silicon nitride.
Referring to Figure 15, the nozzle rim 4 is etched partially through the roof 44, by placing a suitably patterned photoresist mask over the roof, etching for a controlled period of time and removing the photoresist by ashing.
Referring to Figure 16, the nozzle aperture 5 is etched through the roof 24 down to the second sacrificial scaffold 39. Again, the etch is performed by placing a suitably patterned photoresist mask over the roof, etching down to the scaffold 39 and removing the photoresist mask.
Referring to Figure 17, in the next stage a third sacrificial scaffold 64 is deposited over the roof 44. The third sacrificial scaffold 64 is exposed and developed to define sidewalls for the cylindrical nozzle enclosure over each aperture 5. The third sacrificial scaffold 64 is also UV cured and hardbaked to prevent any refiow of the photoresist during subsequent high-temperature deposition of the nozzle enclosure material.
Referring to Figure 18, silicon nitride is deposited onto the third sacrificial scaffold 64 by plasma enhanced chemical vapour deposition. The silicon nitride forms an enclosure roof 61 over each aperture 5. Enclosure sidewalls 62 are also formed by deposition of silicon nitride. Whilst silicon nitride is deposited in the embodiment shown, the enclosure roof 61 may equally be formed from silicon oxide, silicon oxynitride etc. Optionally, a layer of hydrophobic material {e.g. fluoropolymer) is deposited onto the enclosure roof 61 after deposition. This extra deposition step may be performed at any stage after deposition (e.g. after etching or after ashing).
Referring to Figure 19, the nozzle enclosure 60 is formed by etching through the enclosure roof layer 61. The enclosure opening 63 is defined by this etch. In addition, the enclosure roof material which is located outside the enclosure sidewalls 62 is removed. The etch pattern is defined by standard photoresist masking. With the nozzle structure, including nozzle enclosure 60, now fully formed on a frontside of the silicon substrate 21, an ink supply channel 32 is etched from the backside of the substrate 21, which meets with the front plug 53.
Referring to Figure 20, after formation of the ink supply channel 32, the first, second and sacrificial scaffolds of photoresist, together with the front plug 53 are ashed off using an O2 plasma. Accordingly, fluid connection is made from the ink supply channel 32 through to the nozzle aperture 5 and the nozzle enclosure opening 63.
It should be noted that a portion of photoresist, on either side of the nozzle chamber sidewalls 6, remains encapsulated by the roof 44, the unit cell sidewalls 56 and the chamber sidewalls 6. This portion of photoresist is sealed from the O2 ashing plasma and, therefore, remains intact after fabrication of the printhead. This encapsulated photoresist advantageously provides additional robustness for the printhead by supporting the nozzle plate 2. Hence, the printhead has a robust nozzle plate spanning continuously over rows of nozzles, and being supported by solid blocks of hardened photoresist, in addition to support walls.
Other Embodiments The invention has been described above with reference to printheads using bubble forming heater elements. However, it is potentially suited to a wide range of printing system including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with inbuilt pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic "minilabs", video printers, PHOTO CD (PHOTO CD is a registered trade mark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays. It will be appreciated by ordinary workers in this field that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.
Ink Jet Technologies
The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.
The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. In conventional thermal inkjet printheads, this leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.
The most significant problem with piezoelectric inkjet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per printhead, but is a major impediment to the fabrication of pagewidth printheads with 19,200 nozzles.
Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new ink jet technologies have been created. The target features include: low power (less than 10 Watts) high resolution capability (1,600 dpi or more) photographic quality output low manufacturing cost small size (pagewidth times minimum cross section) high speed (< 2 seconds per page).
All of these features can be met or exceeded by the ink jet systems described below with differing levels of difficulty. Forty-five different ink jet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture.
These technologies form part of separate applications assigned to the present Assignee as set out in the table under the heading Cross References to Related Applications.
The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems.
For ease of manufacture using standard process equipment, the printhead is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the printhead is 100 mm long, with a width which depends upon the ink jet type.
The smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The printheads each contain 19,200 nozzles plus data and control circuitry.
Ink is supplied to the back of the printhead by injection molded plastic ink channels.
The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The printhead is connected to the camera circuitry by tape automated bonding.
Tables of Drop-on-Demand Ink Jets
Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee. The following tables form the axes of an eleven dimensional table of ink jet types. Actuator mechanism (18 types) Basic operation mode (7 types) Auxiliary mechanism (8 types) Actuator amplification or modification method (17 types)
Actuator motion (19 types) Nozzle refill method (4 types)
Method of restricting back-flow through inlet (10 types) Nozzle clearing method (9 types) Nozzle plate construction (9 types)
Drop ejection direction (5 types) Ink type (7 types)
The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. These are designated IJOl to IJ45 above which matches the docket numbers in the table under the heading Cross References to Related Applications.
Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJOl to IJ45 examples can be made into ink jet printheads with characteristics superior to any currently available ink jet technology.
Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJOl to IJ45 series are also listed in the examples column, hi some cases, print technology may be listed more than once in a table, where it shares characteristics with more than one entry.
Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.
The information associated with the aforementioned 11 dimensional matrix are set out in the following tables.
Figure imgf000020_0001
Figure imgf000021_0001
Figure imgf000022_0001
Figure imgf000023_0001
Figure imgf000024_0001
Figure imgf000025_0001
Figure imgf000026_0001
BASIC OPERATION MODE
Description Advantages Disadvantages Examples
Figure imgf000027_0001
Figure imgf000028_0001
Figure imgf000029_0001
Figure imgf000030_0001
Figure imgf000031_0001
Figure imgf000032_0001
Figure imgf000033_0001
Figure imgf000034_0001
Figure imgf000035_0001
Figure imgf000036_0001
Figure imgf000037_0001
Figure imgf000039_0001
Figure imgf000040_0001
Figure imgf000041_0001
Figure imgf000042_0001
Figure imgf000043_0001
Figure imgf000043_0002
Figure imgf000044_0001
Figure imgf000045_0001
Figure imgf000046_0001

Claims

1. A printhead comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle.
2. The printhead of claim 1, wherein the surface formations each have a hydrophobic surface.
3. The printhead of claim 1 , wherein the surface formations are configured in a plurality of nozzle enclosures, each nozzle enclosure comprising sidewalls surrounding a respective nozzle, the sidewalls forming a seal with the ink ejection surface, thereby isolating each nozzle from at least one adjacent nozzle.
4. The printhead of claim 3, wherein each nozzle enclosure further comprises a roof spaced apart from the respective nozzle aperture, the roof having a roof opening aligned with its respective nozzle aperture, thereby allowing ejected ink droplets to pass therethrough onto the print medium.
5. The printhead of claim 4, wherein the sidewalls extend from each roof to the ink ejection surface.
6. The printhead of claim 5, wherein the sidewalls extend from a perimeter region of each roof.
7. The printhead of claim 1 , which is a pagewidth inkjet printhead.
8. The printhead of claim 1 , wherein the printhead has a nozzle density sufficient to print at up to 1600 dpi.
9. A printer comprising the printhead according to claim 1.
10. A method of printing from the printhead of claim 1 , whilst minimizing cross- contamination of ink between adjacent nozzles, the method comprising the steps of: (a) providing a printhead comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle; and (b) printing onto a print medium using said printhead.
11. A method of fabricating the printhead of claim 1 having isolated nozzles, the method comprising the steps of:
(a) providing a substrate, the substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate;
(b) depositing a layer of photoresist over the ink ejection surface;
(c) defining recesses in the photoresist, each recess revealing a portion of the ink ejection surface surrounding a respective nozzle aperture; (d) depositing a roof material over the photoresist and into the recesses;
(e) etching the roof material to define a nozzle enclosure around each nozzle aperture, each nozzle enclosure having an opening defined in a roof and sidewalls extending from the roof to the ink ejection surface; and
(f) removing the photoresist.
12. A method of printing from a printhead, whilst minimizing cross-contamination of ink between adjacent nozzles, the method comprising the steps of:
(a) providing a printhead comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle; and (b) printing onto a print medium using said printhead.
13. The method of claim 12, wherein the surface formations each have a hydrophobic surface.
14. The method of claim 13, wherein the surface formations are configured in a plurality of nozzle enclosures, each nozzle enclosure comprising sidewalls surrounding a respective nozzle, the sidewalls forming a seal with the ink ejection surface, thereby isolating each nozzle from at least one adjacent nozzle.
15. The method of claim 14, wherein each nozzle enclosure further comprises a roof spaced apart from the respective nozzle aperture, the roof having a roof opening aligned with its respective nozzle aperture, thereby allowing ejected ink droplets to pass therethrough onto the print medium.
16. The method of claim 15, wherein the sidewalls extend from each roof to the ink ejection surface.
17. The method of claim 16, wherein the sidewalls extend from a perimeter region of each roof.
18. The method of claim 12, wherein the printhead is a pagewidth inkjet printhead.
19. The method of claim 12, wherein the printhead has a nozzle density sufficient to print at up to 1600 dpi.
20. A printhead, for printing using the method of claim 12, comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle.
21. A method of fabricating a printhead, for printing using the method of claim 12, having isolated nozzles, the method comprising the steps of:
(a) providing a substrate, the substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate;
(b) depositing a layer of photoresist over the ink ejection surface;
(c) defining recesses in the photoresist, each recess revealing a portion of the ink ejection surface surrounding a respective nozzle aperture;
(d) depositing a roof material over the photoresist and into the recesses; (e) etching the roof material to define a nozzle enclosure around each nozzle aperture, each nozzle enclosure having an opening defined in a roof and sidewalls extending from the roof to the ink ejection surface; and (f) removing the photoresist.
22. A method of fabricating a printhead having isolated nozzles, the method comprising the steps of:
(a) providing a substrate, the substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; (b) depositing a layer of photoresist over the ink ejection surface;
(c) defining recesses in the photoresist, each recess revealing a portion of the ink ejection surface surrounding a respective nozzle aperture;
(d) depositing a roof material over the photoresist and into the recesses;
(e) etching the roof material to define a nozzle enclosure around each nozzle aperture, each nozzle enclosure having an opening defined in a roof and sidewalls extending from the roof to the ink ejection surface; and
(f) removing the photoresist.
23. The method of claim 22, wherein the photoresist is UV cured and/or hardbaked prior to deposition of the roof material.
24. The method of claim 22, wherein the recessed features are defined by exposure and development techniques.
25. The method of claim 22, wherein the roof material is deposited by plasma enhanced chemical vapour deposition (PECVD).
26. The method of claim 22, wherein the roof material is coated with a hydrophobic material after deposition.
27. The method of claim 22, wherein the printhead is a pagewidth inkjet printhead.
28. The method of claim 22, wherein the printhead has a nozzle density sufficient to print at up to 1600 dpi.
29. A printhead, fabricated using the method of claim 22, comprising: a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; and a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle.
30. A method of printing from a printhead, fabricated using the method of claim 22, whilst minimizing cross-contamination of ink between adjacent nozzles, the method comprising the steps of:
(a) providing a printhead comprising:
a substrate including a plurality of nozzles for ejecting ink droplets onto a print medium, each nozzle having a nozzle aperture defined in an ink ejection surface of the substrate; and
a plurality of formations on the ink ejection surface, the surface formations being configured to isolate each nozzle from at least one adjacent nozzle; and
(b) printing onto a print medium using said printhead.
PCT/AU2005/000392 2005-03-21 2005-03-21 Inkjet printhead having isolated nozzles WO2006099652A1 (en)

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AU2005329726A AU2005329726B2 (en) 2005-03-21 2005-03-21 Inkjet printhead having isolated nozzles
EP05714264A EP1861256A4 (en) 2005-03-21 2005-03-21 Inkjet printhead having isolated nozzles
JP2007555422A JP4473314B2 (en) 2005-03-21 2005-03-21 Print head, printer, and method for printing
PCT/AU2005/000392 WO2006099652A1 (en) 2005-03-21 2005-03-21 Inkjet printhead having isolated nozzles
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KR100973614B1 (en) 2010-08-02
AU2005329726A1 (en) 2006-09-28
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