Printhead nozzle having heater of higher resistance than contacts

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

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.

In 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 jet 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 U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.

U.S. Pat. No. 3,596,275 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 U.S. Pat. No. 3,373,437 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 U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 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 U.S. Pat. No. 4,490,728. 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.

In the construction of any inkjet printing system, there are a considerable number of important factors which must be traded off against one another especially as large scale printheads are constructed, especially those of a pagewidth type. A number of these factors are outlined in the following paragraphs.

Firstly, inkjet printheads are normally constructed utilizing micro-electromechanical systems (MEMS) techniques. As such, they tend to rely upon standard integrated circuit construction/fabrication techniques of depositing planar layers on a silicon wafer and etching certain portions of the planar layers. Within silicon circuit fabrication technology, certain techniques are better known than others. For example, the techniques associated with the creation of CMOS circuits are likely to be more readily used than those associated with the creation of exotic circuits including ferroelectrics, galium arsenide etc. Hence, it is desirable, in any MEMS constructions, to utilize well proven semi-conductor fabrication techniques which do not require any “exotic” processes or materials. Of course, a certain degree of trade off will be undertaken in that if the advantages of using the exotic material far out weighs its disadvantages then it may become desirable to utilize the material anyway. However, if it is possible to achieve the same, or similar, properties using more common materials, the problems of exotic materials can be avoided.

With a large array of ink ejection nozzles, it is desirable to provide for a highly automated form of manufacturing which results in an inexpensive production of multiple printhead devices.

Preferably, the device constructed utilizes a low amount of energy in the ejection of ink. The utilization of a low amount of energy is particularly important when a large pagewidth full color printhead is constructed having a large array of individual print ejection mechanism with each ejection mechanisms, in the worst case, being fired in a rapid sequence.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an ink ejection nozzle arrangement suitable for incorporation into an inkjet printhead arrangement for the ejection of ink on demand from a nozzle chamber in an efficient and reliable manner.

According to a first aspect, the present invention provides an ink jet printhead comprising:

a plurality of nozzles;

a bubble forming chamber corresponding to each of the nozzles respectively, the bubble forming chambers adapted to contain a bubble forming liquid; and,

at least one heater element disposed in each of the bubble forming chambers respectively, the heater elements configured for thermal contact with the bubble forming liquid; such that, heating the heater element to a temperature above the boiling point of the bubble forming liquid forms a gas bubble that causes the ejection of a drop of an ejectable liquid through the nozzle corresponding to that heater element; wherein, the bubble forming chamber is at least partially formed by an amorphous ceramic material.

Amorphous ceramic material provides the bubble forming chamber with high strength. The non-crystalline structure avoids any points of weakness due to crystalline defects. These defects can act as stress concentration areas and are prone to failure.

According to a second aspect, the present invention provides a printer system which incorporates a printhead, the printhead comprising:

a plurality of nozzles;

a bubble forming chamber corresponding to each of the nozzles respectively, the bubble forming chambers adapted to contain a bubble forming liquid; and,

at least one heater element disposed in each of the bubble forming chambers respectively, the heater elements configured for thermal contact with the bubble forming liquid; such that,

heating the heater element to a temperature above the boiling point of the bubble forming liquid forms a gas bubble that causes the ejection of a drop of an ejectable liquid through the nozzle corresponding to that heater element; wherein,

the bubble forming chamber is at least partially formed by an amorphous ceramic material.

According to a third aspect, the present invention provides a method of ejecting drops of an ejectable liquid from a printhead, the printhead comprising a plurality of nozzles;

a chamber corresponding to each of the nozzles respectively, the chambers adapted to contain an ejectable liquid; and,

at least one droplet ejection actuator associated with each of the chambers respectively; wherein, the chamber is at least partially formed by an amorphous ceramic material;

the method comprising the steps of:

placing the ejectable liquid into contact with the drop ejection actuator; and actuating the droplet ejection actuator such that a droplet of an ejectable liquid is ejected through the corresponding nozzle.

Preferably, the amorphous ceramic material is silicon nitride. In another form, the amorphous ceramic material is silicon dioxide. In yet another embodiment, the amorphous ceramic material is silicon oxynitride.

Preferably, the thermal actuator units are interconnected at a first end to a substrate and at a second end to a rigid strut member. The rigid strut member can, in turn, be interconnected to the arm having one end attached to the paddle vane. The thermal actuator units can operate upon conductive heating along a conductive trace and the conductive heating can include the generation of a substantial portion of the heat in the area adjacent the first end. The conductive heating trace can include a thinned cross-section adjacent the first end. The heating layers of the thermal actuator units can comprise substantially either a copper nickel alloy or titanium nitride. The paddle can be constructed from a similar conductive material to portions of the thermal actuator units however it is conductively insulated therefrom.

Preferably, the thermal actuator units are constructed from multiple layers utilizing a single mask to etch the multiple layers.

The nozzle chamber can include an actuator access port in a second surface of the chamber. The access port can comprise a slot in a corner of the chamber and the actuator is able to move in an arc through the slot. The actuator can include an end portion that mates substantially with a wall of the chamber at substantially right angles to the paddle vane. The paddle vane can include a depressed portion substantially opposite the fluid ejection port.

In accordance with a further aspect of the present invention, there is provided a thermal actuator including a series of lever arms attached at one end to a substrate, the thermal actuator being operational as a result of conductive heating of a conductive trace, the conductive trace including a thinned cross-section substantially adjacent the attachment to the substrate.

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.

FIG. 7 is a schematic, partially cut away, exploded perspective view of the unit cell of FIG. 6.

FIG. 8 is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead.

FIG. 9 is a schematic, partially cut away, exploded perspective view of the unit cell of FIG. 8.

FIG. 10 is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead.

FIG. 11 is a schematic, partially cut away, exploded perspective view of the unit cell of FIG. 10.

FIG. 12 is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead.

FIG. 13 is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead.

FIG. 14 is a schematic, partially cut away, exploded perspective view of the unit cell of FIG. 13.

FIGS. 15 to 25 are schematic perspective views of the unit cell shown in FIGS. 29 and 30, at various successive stages in the production process of the printhead.

FIGS. 26 and 27 show schematic, partially cut away, schematic perspective views of two variations of the unit cell of FIGS. 13 to 25.

FIG. 28 is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead.

FIG. 29 is a schematic, partially cut away, perspective view of a further embodiment of a unit cell of a printhead.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

Bubble Forming Heater Element Actuator

With reference to FIGS. 1 to 4, the unit cell 1 of a printhead according to an embodiment of the invention 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 FIG. 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. FIG. 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 FIG. 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.

FIGS. 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 FIG. 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 FIG. 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 FIG. 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.

Features and Advantages of Further Embodiments

FIGS. 6 to 29 show further embodiments of unit cells 1 for thermal inkjet printheads, each embodiment having its own particular functional advantages. These advantages will be discussed in detail below, with reference to each individual embodiment. For consistency, the same reference numerals are used in FIGS. 6 to 29 to indicate corresponding components.

Referring to FIGS. 6 and 7, the unit cell 1 shown has the chamber 7, ink supply passage 32 and the nozzle rim 4 positioned mid way along the length of the unit cell 1. As best seen in FIG. 7, the drive circuitry 22 is partially on one side of the chamber 7 with the remainder on the opposing side of the chamber. The drive circuitry 22 controls the operation of the heater 14 through vias in the integrated circuit metallisation layers of the interconnect 23. The interconnect 23 has a raised metal layer on its top surface. Passivation layer 24 is formed in top of the interconnect 23 but leaves areas of the raised metal layer exposed. Electrodes 15 of the heater 14 contact the exposed metal areas to supply power to the element 10.

Alternatively, the drive circuitry 22 for one unit cell is not on opposing sides of the heater element that it controls. All the drive circuitry 22 for the heater 14 of one unit cell is in a single, undivided area that is offset from the heater. That is, the drive circuitry 22 is partially overlaid by one of the electrodes 15 of the heater 14 that it is controlling, and partially overlaid by one or more of the heater electrodes 15 from adjacent unit cells. In this situation, the center of the drive circuitry 22 is less than 200 microns from the center of the associate nozzle aperture 5. In most Memjet printheads of this type, the offset is less than 100 microns and in many cases less than 50 microns, preferably less than 30 microns.

Configuring the nozzle components so that there is significant overlap between the electrodes and the drive circuitry provides a compact design with high nozzle density (nozzles per unit area of the nozzle plate 2). This also improves the efficiency of the printhead by shortening the length of the conductors from the circuitry to the electrodes. The shorter conductors have less resistance and therefore dissipate less energy.

The high degree of overlap between the electrodes 15 and the drive circuitry 22 also allows more vias between the heater material and the CMOS metalization layers of the interconnect 23. As best shown in FIGS. 14 and 15, the passivation layer 24 has an array of vias to establish an electrical connection with the heater 14. More vias lowers the resistance between the heater electrodes 15 and the interconnect layer 23 which reduces power losses. However, the passivation layer 24 and electrodes 15 may also be provided without vias in order to simplify the fabrication process.

In FIGS. 8 and 9, the unit cell 1 is the same as that of FIGS. 6 and 7 apart from the heater element 10. The heater element 10 has a bubble nucleation section 158 with a smaller cross section than the remainder of the element. The bubble nucleation section 158 has a greater resistance and heats to a temperature above the boiling point of the ink before the remainder of the element 10. The gas bubble nucleates at this region and subsequently grows to surround the rest of the element 10. By controlling the bubble nucleation and growth, the trajectory of the ejected drop is more predictable.

The heater element 10 is configured to accommodate thermal expansion in a specific manner. As heater elements expand, they will deform to relieve the strain. Elements such as that shown in FIGS. 6 and 7 will bow out of the plane of lamination because its thickness is the thinnest cross sectional dimension and therefore has the least bending resistance. Repeated bending of the element can lead to the formation of cracks, especially at sharp corners, which can ultimately lead to failure. The heater element 10 shown in FIGS. 8 and 9 is configured so that the thermal expansion is relieved by rotation of the bubble nucleation section 158, and slightly splaying the sections leading to the electrodes 15, in preference to bowing out of the plane of lamination. The geometry of the element is such that miniscule bending within the plane of lamination is sufficient to relieve the strain of thermal expansion, and such bending occurs in preference to bowing. This gives the heater element greater longevity and reliability by minimizing bend regions, which are prone to oxidation and cracking.

Referring to FIGS. 10 and 11, the heater element 10 used in this unit cell 1 has a serpentine or ‘double omega’ shape. This configuration keeps the gas bubble centered on the axis of the nozzle. A single omega is a simple geometric shape which is beneficial from a fabrication perspective. However the gap 159 between the ends of the heater element means that the heating of the ink in the chamber is slightly asymmetrical. As a result, the gas bubble is slightly skewed to the side opposite the gap 159. This can in turn affect the trajectory of the ejected drop. The double omega shape provides the heater element with the gap 160 to compensate for the gap 159 so that the symmetry and position of the bubble within the chamber is better controlled and the ejected drop trajectory is more reliable.

FIG. 12 shows a heater element 10 with a single omega shape. As discussed above, the simplicity of this shape has significant advantages during lithographic fabrication. It can be a single current path that is relatively wide and therefore less affected by any inherent inaccuracies in the deposition of the heater material. The inherent inaccuracies of the equipment used to deposit the heater material result in variations in the dimensions of the element. However, these tolerances are fixed values so the resulting variations in the dimensions of a relatively wide component are proportionally less than the variations for a thinner component. It will be appreciated that proportionally large changes of components dimensions will have a greater effect on their intended function. Therefore the performance characteristics of a relatively wide heater element are more reliable than a thinner one.

The omega shape directs current flow around the axis of the nozzle aperture 5. This gives good bubble alignment with the aperture for better ejection of drops while ensuring that the bubble collapse point is not on the heater element 10. As discussed above, this avoids problems caused by cavitation.

Referring to FIGS. 13 to 26, another embodiment of the unit cell 1 is shown together with several stages of the etching and deposition fabrication process. In this embodiment, the heater element 10 is suspended from opposing sides of the chamber. This allows it to be symmetrical about two planes that intersect along the axis of the nozzle aperture 5. This configuration provides a drop trajectory along the axis of the nozzle aperture 5 while avoiding the cavitation problems discussed above. FIGS. 27 and 28 show other variations of this type of heater element 10.

FIG. 28 shows a unit cell 1 that has the nozzle aperture 5 and the heater element 10 offset from the center of the nozzle chamber 7. Consequently, the nozzle chamber 7 is larger than the previous embodiments. The heater 14 has two different electrodes 15 with the right hand electrode 15 extending well into the nozzle chamber 7 to support one side of the heater element 10. This reduces the area of the vias contacting the electrodes which can increase the electrode resistance and therefore the power losses. However, laterally offsetting the heater element from the ink inlet 31 increases the fluidic drag retarding flow back through the inlet 31 and ink supply passage 32. The fluidic drag through the nozzle aperture 5 comparatively much smaller so little energy is lost to a reverse flow of ink through the inlet when a gas bubble form on the element 10.

The unit cell 1 shown in FIG. 29 also has a relatively large chamber 7 which again reduces the surface area of the electrodes in contact with the vias leading to the interconnect layer 23. However, the larger chamber 7 allows several heater elements 10 offset from the nozzle aperture 5. The arrangement shown uses two heater elements 10; one on either side of the chamber 7. Other designs use three or more elements in the chamber. Gas bubbles nucleate from opposing sides of the nozzle aperture and converge to form a single bubble. The bubble formed is symmetrical about at least one plane extending along the nozzle axis. This enhances the control of the symmetry and position of the bubble within the chamber 7 and therefore the ejected drop trajectory is more reliable.

Fabrication Process

In the interests of brevity, the fabrication stages have been shown for the unit cell of FIG. 13 only (see FIGS. 15 to 25). It will be appreciated that the other unit cells will use the same fabrication stages with different masking.

Referring to FIG. 15, there is shown the starting point for fabrication of the thermal inkjet nozzle shown in FIG. 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 FIG. 15. 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 O₂ashing after the etch.

Referring to FIG. 16, 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. O₂/C₄F₈). 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. FIG. 17 shows the unit cell after etching the front ink hole 52 and removal of the photoresist 51.

Referring to FIG. 18, 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 FIG. 13). 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 side faces 55. These sloped 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 FIG. 19, 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 comprised of TiAlN. The heater element 10 may be formed from a monolayer of the heater material 38. However, the heater element 10 may alternatively comprise the heater material sandwiched between upper and lower passivation films, such as tantalum, tantalum nitride or silicon nitride films. Passivation films covering the heater element 10 minimize corrosion and improve heater longevity.

Referring to FIG. 20, 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 FIG. 21, 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 reflow of the photoresist during subsequent high-temperature deposition of the silicon nitride roof material.

Referring to FIG. 22, 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 FIG. 23, 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 FIG. 24, 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.

With the nozzle structure 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 FIG. 25, after formation of the ink supply channel 32, the first and second sacrificial scaffolds of photoresist, together with the front plug 53 are ashed off using an O₂plasma. Accordingly, fluid connection is made from the ink supply channel 32 through to the nozzle aperture 5.

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 O₂ashing 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 thermal bend actuators and 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 ink jet 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 IJ01 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 IJ01 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 IJ01 to IJ45 series are also listed in the examples column. In 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.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS)

Description
Advantages
Disadvantages
Examples

Thermal
An electrothermal
Large force
High power
Canon

bubble
heater heats the
generated
Ink carrier
Bubblejet 1979

ink to above
Simple
limited to water
Endo et al GB

boiling point,
construction
Low
patent 2,007,162

transferring
No moving
efficiency
Xerox heater-

significant heat to
parts
High
in-pit 1990

the aqueous ink. A
Fast operation
temperatures
Hawkins et al

bubble nucleates
Small chip
required
U.S. Pat. No. 4,899,181

and quickly forms,
area required for
High
Hewlett-

expelling the ink.
actuator
mechanical
Packard TIJ

The efficiency of

stress
1982 Vaught et

the process is low,

Unusual
al U.S. Pat. No.

with typically less

materials
4,490,728

than 0.05% of the

required

electrical energy

Large drive

being transformed

transistors

into kinetic energy

Cavitation

of the drop.

causes actuator

failure

Kogation

reduces bubble

formation

Large print

heads are

difficult to

fabricate

Piezo-
A piezoelectric
Low power
Very large
Kyser et al

electric
crystal such as
consumption
area required for
U.S. Pat. No. 3,946,398

lead lanthanum
Many ink
actuator
Zoltan U.S. Pat. No.

zirconate (PZT) is
types can be
Difficult to
3,683,212

electrically
used
integrate with
1973 Stemme

activated, and
Fast operation
electronics
U.S. Pat. No. 3,747,120

either expands,
High
High voltage
Epson Stylus

shears, or bends to
efficiency
drive transistors
Tektronix

apply pressure to

required
IJ04

the ink, ejecting

Full

drops.

pagewidth print

heads

impractical due

to actuator size

Requires

electrical poling

in high field

strengths during

manufacture

Electro-
An electric field is
Low power
Low
Seiko Epson,

strictive
used to activate
consumption
maximum strain
Usui et all JP

electrostriction in
Many ink
(approx. 0.01%)
253401/96

relaxor materials
types can be
Large area
IJ04

such as lead
used
required for

lanthanum
Low thermal
actuator due to

zirconate titanate
expansion
low strain

(PLZT) or lead
Electric field
Response

magnesium
strength required
speed is

niobate (PMN).
(approx. 3.5 V/μm)
marginal (~10 μs)

can be
High voltage

generated
drive transistors

without
required

difficulty
Full

Does not
pagewidth print

require electrical
heads

poling
impractical due

to actuator size

Ferro-
An electric field is
Low power
Difficult to
IJ04

electric
used to induce a
consumption
integrate with

phase transition
Many ink
electronics

between the
types can be
Unusual

antiferroelectric
used
materials such as

(AFE) and
Fast operation
PLZSnT are

ferroelectric (FE)
(<1 μs)
required

phase. Perovskite
Relatively
Actuators

materials such as
high longitudinal
require a large

tin modified lead
strain
area

lanthanum
High

zirconate titanate
efficiency

(PLZSnT) exhibit
Electric field

large strains of up
strength of

to 1% associated
around 3 V/μm

with the AFE to
can be readily

FE phase
provided

transition.

Electro-
Conductive plates
Low power
Difficult to
IJ02, IJ04

static
are separated by a
consumption
operate

plates
compressible or
Many ink
electrostatic

fluid dielectric
types can be
devices in an

(usually air). Upon
used
aqueous

application of a
Fast operation
environment

voltage, the plates

The

attract each other

electrostatic

and displace ink,

actuator will

causing drop

normally need to

ejection. The

be separated

conductive plates

from the ink

may be in a comb

Very large

or honeycomb

area required to

structure, or

achieve high

stacked to increase

forces

the surface area

High voltage

and therefore the

drive transistors

force.

may be required

Full

pagewidth print

heads are not

competitive due

to actuator size

Electro-
A strong electric
Low current
High voltage
1989 Saito et

static pull
field is applied to
consumption
required
al, U.S. Pat. No.

on ink
the ink, whereupon
Low
May be
4,799,068

electrostatic
temperature
damaged by
1989 Miura et

attraction

sparks due to air
al, U.S. Pat. No.

accelerates the ink

breakdown
4,810,954

towards the print

Required field
Tone-jet

medium.

strength

increases as the

drop size

decreases

High voltage

drive transistors

required

Electrostatic

field attracts dust

Permanent
An electromagnet
Low power
Complex
IJ07, IJ10

magnet
directly attracts a
consumption
fabrication

electro-
permanent magnet,
Many ink
Permanent

magnetic
displacing ink and
types can be
magnetic

causing drop
used
material such as

ejection. Rare
Fast operation
Neodymium Iron

earth magnets with
High
Boron (NdFeB)

a field strength
efficiency
required.

around 1 Tesla can
Easy
High local

be used. Examples
extension from
currents required

are: Samarium
single nozzles to
Copper

Cobalt (SaCo) and
pagewidth print
metalization

magnetic materials
heads
should be used

in the neodymium

for long

iron boron family

electromigration

(NdFeB,

lifetime and low

NdDyFeBNb,

resistivity

NdDyFeB, etc)

Pigmented

inks are usually

infeasible

Operating

temperature

limited to the

Curie

temperature

(around 540 K)

Soft
A solenoid
Low power
Complex
IJ01, IJ05,

magnetic
induced a
consumption
fabrication
IJ08, IJ10, IJ12,

core
magnetic field in a
Many ink
Materials not
IJ14, IJ15, IJ17

electro-
soft magnetic core
types can be
usually present

magnetic
or yoke fabricated
used
in a CMOS fab

from a ferrous
Fast operation
such as NiFe,

material such as
High
CoNiFe, or CoFe

electroplated iron
efficiency
are required

alloys such as
Easy
High local

CoNiFe [1], CoFe,
extension from
currents required

or NiFe alloys.
single nozzles to
Copper

Typically, the soft
pagewidth print
metalization

magnetic material
heads
should be used

is in two parts,

for long

which are

electromigration

normally held

lifetime and low

apart by a spring.

resistivity

When the solenoid

Electroplating

is actuated, the two

is required

parts attract,

High

displacing the ink.

saturation flux

density is

required (2.0-2.1

T is achievable

with CoNiFe

[1])

Lorenz
The Lorenz force
Low power
Force acts as a
IJ06, IJ11,

force
acting on a current
consumption
twisting motion
IJ13, IJ16

carrying wire in a
Many ink
Typically,

magnetic field is
types can be
only a quarter of

utilized.
used
the solenoid

This allows the
Fast operation
length provides

magnetic field to
High
force in a useful

be supplied
efficiency
direction

externally to the
Easy
High local

print head, for
extension from
currents required

example with rare
single nozzles to
Copper

earth permanent
pagewidth print
metalization

magnets.
heads
should be used

Only the current

for long

carrying wire need

electromigration

be fabricated on

lifetime and low

the print-head,

resistivity

simplifying

Pigmented

materials

inks are usually

requirements.

infeasible

Magneto-
The actuator uses
Many ink
Force acts as a
Fischenbeck,

striction
the giant
types can be
twisting motion
U.S. Pat. No. 4,032,929

magnetostrictive
used
Unusual
IJ25

effect of materials
Fast operation
materials such as

such as Terfenol-D
Easy
Terfenol-D are

(an alloy of
extension from
required

terbium,
single nozzles to
High local

dysprosium and
pagewidth print
currents required

iron developed at
heads
Copper

the Naval
High force is
metalization

Ordnance
available
should be used

Laboratory, hence

for long

Ter-Fe-NOL). For

electromigration

best efficiency, the

lifetime and low

actuator should be

resistivity

pre-stressed to

Pre-stressing

approx. 8 MPa.

may be required

Surface
Ink under positive
Low power
Requires
Silverbrook,

tension
pressure is held in
consumption
supplementary
EP 0771 658 A2

reduction
a nozzle by surface
Simple
force to effect
and related

tension. The
construction
drop separation
patent

surface tension of
No unusual
Requires
applications

the ink is reduced
materials
special ink

below the bubble
required in
surfactants

threshold, causing
fabrication
Speed may be

the ink to egress
High
limited by

from the nozzle.
efficiency
surfactant

Easy
properties

extension from

single nozzles to

pagewidth print

heads

Viscosity
The ink viscosity
Simple
Requires
Silverbrook,

reduction
is locally reduced
construction
supplementary
EP 0771 658 A2

to select which
No unusual
force to effect
and related

drops are to be
materials
drop separation
patent

ejected. A
required in
Requires
applications

viscosity reduction
fabrication
special ink

can be achieved
Easy
viscosity

electrothermally
extension from
properties

with most inks, but
single nozzles to
High speed is

special inks can be
pagewidth print
difficult to

engineered for a
heads
achieve

100:1 viscosity

Requires

reduction.

oscillating ink

pressure

A high

temperature

difference

(typically 80

degrees) is

required

Acoustic
An acoustic wave
Can operate
Complex
1993

is generated and
without a nozzle
drive circuitry
Hadimioglu et

focussed upon the
plate
Complex
al, EUP 550,192

drop ejection

fabrication
1993 Elrod et

region.

Low
al, EUP 572,220

efficiency

Poor control

of drop position

Poor control

of drop volume

Thermo-
An actuator which
Low power
Efficient
IJ03, IJ09,

elastic
relies upon
consumption
aqueous
IJ17, IJ18, IJ19,

bend
differential
Many ink
operation
IJ20, IJ21, IJ22,

actuator
thermal expansion
types can be
requires a
IJ23, IJ24, IJ27,

upon Joule heating
used
thermal insulator
IJ28, IJ29, IJ30,

is used.
Simple planar
on the hot side
IJ31, IJ32, IJ33,

fabrication
Corrosion
IJ34, IJ35, IJ36,

Small chip
prevention can
IJ37, IJ38, IJ39,

area required for
be difficult
IJ40, IJ41

each actuator
Pigmented

Fast operation
inks may be

High
infeasible, as

efficiency
pigment particles

CMOS
may jam the

compatible
bend actuator

voltages and

currents

Standard

MEMS

processes can be

used

Easy

extension from

single nozzles to

pagewidth print

heads

High CTE
A material with a
High force
Requires
IJ09, IJ17,

thermo-
very high
can be generated
special material
IJ18, IJ20, IJ21,

elastic
coefficient of
Three
(e.g. PTFE)
IJ22, IJ23, IJ24,

actuator
thermal expansion
methods of
Requires a
IJ27, IJ28, IJ29,

(CTE) such as
PTFE deposition
PTFE deposition
IJ30, IJ31, IJ42,

polytetrafluoroethylene
are under
process, which is
IJ43, IJ44

(PTFE) is
development:
not yet standard

used. As high CTE
chemical vapor
in ULSI fabs

materials are
deposition
PTFE

usually non-
(CVD), spin
deposition

conductive, a
coating, and
cannot be

heater fabricated
evaporation
followed with

from a conductive
PTFE is a
high temperature

material is
candidate for
(above 350° C.)

incorporated. A 50 μm
low dielectric
processing

long PTFE
constant
Pigmented

bend actuator with
insulation in
inks may be

polysilicon heater
ULSI
infeasible, as

and 15 mW power
Very low
pigment particles

input can provide
power
may jam the

180 μN force and
consumption
bend actuator

10 μm deflection.
Many ink

Actuator motions
types can be

include:
used

Bend
Simple planar

Push
fabrication

Buckle
Small chip

Rotate
area required for

each actuator

Fast operation

High

efficiency

CMOS

compatible

voltages and

currents

Easy

extension from

single nozzles to

pagewidth print

heads

Conductive
A polymer with a
High force
Requires
IJ24

polymer
high coefficient of
can be generated
special materials

thermo-
thermal expansion
Very low
development

elastic
(such as PTFE) is
power
(High CTE

actuator
doped with
consumption
conductive

conducting
Many ink
polymer)

substances to
types can be
Requires a

increase its
used
PTFE deposition

conductivity to
Simple planar
process, which is

about 3 orders of
fabrication
not yet standard

magnitude below
Small chip
in ULSI fabs

that of copper. The
area required for
PTFE

conducting
each actuator
deposition

polymer expands
Fast operation
cannot be

when resistively
High
followed with

heated.
efficiency
high temperature

Examples of
CMOS
(above 350° C.)

conducting
compatible
processing

dopants include:
voltages and
Evaporation

Carbon nanotubes
currents
and CVD

Metal fibers
Easy
deposition

Conductive
extension from
techniques

polymers such as
single nozzles to
cannot be used

doped
pagewidth print
Pigmented

polythiophene
heads
inks may be

Carbon granules

infeasible, as

pigment particles

may jam the

bend actuator

Shape
A shape memory
High force is
Fatigue limits
IJ26

memory
alloy such as TiNi
available
maximum

alloy
(also known as
(stresses of
number of cycles

Nitinol - Nickel
hundreds of
Low strain

Titanium alloy
MPa)
(1%) is required

developed at the
Large strain is
to extend fatigue

Naval Ordnance
available (more
resistance

Laboratory) is
than 3%)
Cycle rate

thermally switched
High
limited by heat

between its weak
corrosion
removal

martensitic state
resistance
Requires

and its high
Simple
unusual

stiffness austenic
construction
materials (TiNi)

state. The shape of
Easy
The latent

the actuator in its
extension from
heat of

martensitic state is
single nozzles to
transformation

deformed relative
pagewidth print
must be

to the austenic
heads
provided

shape. The shape
Low voltage
High current

change causes
operation
operation

ejection of a drop.

Requires pre-

stressing to

distort the

martensitic state

Linear
Linear magnetic
Linear
Requires
IJ12

Magnetic
actuators include
Magnetic
unusual

Actuator
the Linear
actuators can be
semiconductor

Induction Actuator
constructed with
materials such as

(LIA), Linear
high thrust, long
soft magnetic

Permanent Magnet
travel, and high
alloys (e.g.

Synchronous
efficiency using
CoNiFe)

Actuator
planar
Some varieties

(LPMSA), Linear
semiconductor
also require

Reluctance
fabrication
permanent

Synchronous
techniques
magnetic

Actuator (LRSA),
Long actuator
materials such as

Linear Switched
travel is
Neodymium iron

Reluctance
available
boron (NdFeB)

Actuator (LSRA),
Medium force
Requires

and the Linear
is available
complex multi-

Stepper Actuator
Low voltage
phase drive

(LSA).
operation
circuitry

High current

operation

BASIC OPERATION MODE

Description
Advantages
Disadvantages
Examples

Actuator
This is the
Simple
Drop
Thermal ink

directly
simplest mode of
operation
repetition rate is
jet

pushes
operation: the
No external
usually limited
Piezoelectric

ink
actuator directly
fields required
to around 10 kHz.
ink jet

supplies sufficient
Satellite drops
However,
IJ01, IJ02,

kinetic energy to
can be avoided if
this is not
IJ03, IJ04, IJ05,

expel the drop.
drop velocity is
fundamental to
IJ06, IJ07, IJ09,

The drop must
less than 4 m/s
the method, but
IJ11, IJ12, IJ14,

have a sufficient
Can be
is related to the
IJ16, IJ20, IJ22,

velocity to
efficient,
refill method
IJ23, IJ24, IJ25,

overcome the
depending upon
normally used
IJ26, IJ27, IJ28,

surface tension.
the actuator used
All of the drop
IJ29, IJ30, IJ31,

kinetic energy
IJ32, IJ33, IJ34,

must be
IJ35, IJ36, IJ37,

provided by the
IJ38, IJ39, IJ40,

actuator
IJ41, IJ42, IJ43,

Satellite drops
IJ44

usually form if

drop velocity is

greater than 4.5 m/s

Proximity
The drops to be
Very simple
Requires close
Silverbrook,

printed are
print head
proximity
EP 0771 658 A2

selected by some
fabrication can
between the
and related

manner (e.g.
be used
print head and
patent

thermally induced
The drop
the print media
applications

surface tension
selection means
or transfer roller

reduction of
does not need to
May require

pressurized ink).
provide the
two print heads

Selected drops are
energy required
printing alternate

separated from the
to separate the
rows of the

ink in the nozzle
drop from the
image

by contact with the
nozzle
Monolithic

print medium or a

color print heads

transfer roller.

are difficult

Electro-
The drops to be
Very simple
Requires very
Silverbrook,

static pull
printed are
print head
high electrostatic
EP 0771 658 A2

on ink
selected by some
fabrication can
field
and related

manner (e.g.
be used
Electrostatic
patent

thermally induced
The drop
field for small
applications

surface tension
selection means
nozzle sizes is
Tone-Jet

reduction of
does not need to
above air

pressurized ink).
provide the
breakdown

Selected drops are
energy required
Electrostatic

separated from the
to separate the
field may attract

ink in the nozzle
drop from the
dust

by a strong electric
nozzle

field.

Magnetic
The drops to be
Very simple
Requires
Silverbrook,

pull on
printed are
print head
magnetic ink
EP 0771 658 A2

ink
selected by some
fabrication can
Ink colors
and related

manner (e.g.
be used
other than black
patent

thermally induced
The drop
are difficult
applications

surface tension
selection means
Requires very

reduction of
does not need to
high magnetic

pressurized ink).
provide the
fields

Selected drops are
energy required

separated from the
to separate the

ink in the nozzle
drop from the

by a strong
nozzle

magnetic field

acting on the

magnetic ink.

Shutter
The actuator
High speed
Moving parts
IJ13, IJ17,

moves a shutter to
(>50 kHz)
are required
IJ21

block ink flow to
operation can be
Requires ink

the nozzle. The ink
achieved due to
pressure

pressure is pulsed
reduced refill
modulator

at a multiple of the
time
Friction and

drop ejection
Drop timing
wear must be

frequency.
can be very
considered

accurate
Stiction is

The actuator
possible

energy can be

very low

Shuttered
The actuator
Actuators with
Moving parts
IJ08, IJ15,

grill
moves a shutter to
small travel can
are required
IJ18, IJ19

block ink flow
be used
Requires ink

through a grill to
Actuators with
pressure

the nozzle. The
small force can
modulator

shutter movement
be used
Friction and

need only be equal
High speed
wear must be

to the width of the
(>50 kHz)
considered

grill holes.
operation can be
Stiction is

achieved
possible

Pulsed
A pulsed magnetic
Extremely low
Requires an
IJ10

magnetic
field attracts an
energy operation
external pulsed

pull on
‘ink pusher’ at the
is possible
magnetic field

ink
drop ejection
No heat
Requires

pusher
frequency. An
dissipation
special materials

actuator controls a
problems
for both the

catch, which

actuator and the

prevents the ink

ink pusher

pusher from

Complex

moving when a

construction

drop is not to be

ejected.

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES)

Description
Advantages
Disadvantages
Examples

None
The actuator
Simplicity of
Drop ejection
Most ink jets,

directly fires the
construction
energy must be
including

ink drop, and there
Simplicity of
supplied by
piezoelectric and

is no external field
operation
individual nozzle
thermal bubble.

or other
Small physical
actuator
IJ01, IJ02,

mechanism
size

IJ03, IJ04, IJ05,

required.

IJ07, IJ09, IJ11,

IJ12, IJ14, IJ20,

IJ22, IJ23, IJ24,

IJ25, IJ26, IJ27,

IJ28, IJ29, IJ30,

IJ31, IJ32, IJ33,

IJ34, IJ35, IJ36,

IJ37, IJ38, IJ39,

IJ40, IJ41, IJ42,

IJ43, IJ44

Oscillating
The ink pressure
Oscillating ink
Requires
Silverbrook,

ink
oscillates,
pressure can
external ink
EP 0771 658 A2

pressure
providing much of
provide a refill
pressure
and related

(including
the drop ejection
pulse, allowing
oscillator
patent

acoustic
energy. The
higher operating
Ink pressure
applications

stimulation)
actuator selects
speed
phase and
IJ08, IJ13,

which drops are to
The actuators
amplitude must
IJ15, IJ17, IJ18,

be fired by
may operate
be carefully
IJ19, IJ21

selectively
with much lower
controlled

blocking or
energy
Acoustic

enabling nozzles.
Acoustic
reflections in the

The ink pressure
lenses can be
ink chamber

oscillation may be
used to focus the
must be

achieved by
sound on the
designed for

vibrating the print
nozzles

head, or preferably

by an actuator in

the ink supply.

Media
The print head is
Low power
Precision
Silverbrook,

proximity
placed in close
High accuracy
assembly
EP 0771 658 A2

proximity to the
Simple print
required
and related

print medium.
head
Paper fibers
patent

Selected drops
construction
may cause
applications

protrude from the

problems

print head further

Cannot print

than unselected

on rough

drops, and contact

substrates

the print medium.

The drop soaks

into the medium

fast enough to

cause drop

separation.

Transfer
Drops are printed
High accuracy
Bulky
Silverbrook,

roller
to a transfer roller
Wide range of
Expensive
EP 0771 658 A2

instead of straight
print substrates
Complex
and related

to the print
can be used
construction
patent

medium. A
Ink can be

applications

transfer roller can
dried on the

Tektronix hot

also be used for
transfer roller

melt

proximity drop

piezoelectric ink

separation.

jet

Any of the IJ

series

Electro-
An electric field is
Low power
Field strength
Silverbrook,

static
used to accelerate
Simple print
required for
EP 0771 658 A2

selected drops
head
separation of
and related

towards the print
construction
small drops is
patent

medium.

near or above air
applications

breakdown
Tone-Jet

Direct
A magnetic field is
Low power
Requires
Silverbrook,

magnetic
used to accelerate
Simple print
magnetic ink
EP 0771 658 A2

field
selected drops of
head
Requires
and related

magnetic ink
construction
strong magnetic
patent

towards the print

field
applications

medium.

Cross
The print head is
Does not
Requires
IJ06, IJ16

magnetic
placed in a
require magnetic
external magnet

field
constant magnetic
materials to be
Current

field. The Lorenz
integrated in the
densities may be

force in a current
print head
high, resulting in

carrying wire is
manufacturing
electromigration

used to move the
process
problems

actuator.

Pulsed
A pulsed magnetic
Very low
Complex print
IJ10

magnetic
field is used to
power operation
head

field
cyclically attract a
is possible
construction

paddle, which
Small print
Magnetic

pushes on the ink.
head size
materials

A small actuator

required in print

moves a catch,

head

which selectively

prevents the

paddle from

moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD

Description
Advantages
Disadvantages
Examples

None
No actuator
Operational
Many actuator
Thermal

mechanical
simplicity
mechanisms
Bubble Ink jet

amplification is

have insufficient
IJ01, IJ02,

used. The actuator

travel, or
IJ06, IJ07, IJ16,

directly drives the

insufficient
IJ25, IJ26

drop ejection

force, to

process.

efficiently drive

the drop ejection

process

Differential
An actuator
Provides
High stresses
Piezoelectric

expansion
material expands
greater travel in
are involved
IJ03, IJ09,

bend
more on one side
a reduced print
Care must be
IJ17, IJ18, IJ19,

actuator
than on the other.
head area
taken that the
IJ20, IJ21, IJ22,

The expansion

materials do not
IJ23, IJ24, IJ27,

may be thermal,

delaminate
IJ29, IJ30, IJ31,

piezoelectric,

Residual bend
IJ32, IJ33, IJ34,

magnetostrictive,

resulting from
IJ35, IJ36, IJ37,

or other

high temperature
IJ38, IJ39, IJ42,

mechanism. The

or high stress
IJ43, IJ44

bend actuator

during formation

converts a high

force low travel

actuator

mechanism to high

travel, lower force

mechanism.

Transient
A trilayer bend
Very good
High stresses
IJ40, IJ41

bend
actuator where the
temperature
are involved

actuator
two outside layers
stability
Care must be

are identical. This
High speed, as
taken that the

cancels bend due
a new drop can
materials do not

to ambient
be fired before
delaminate

temperature and
heat dissipates

residual stress. The
Cancels

actuator only
residual stress of

responds to
formation

transient heating of

one side or the

other.

Reverse
The actuator loads
Better
Fabrication
IJ05, IJ11

spring
a spring. When the
coupling to the
complexity

actuator is turned
ink
High stress in

off, the spring

the spring

releases. This can

reverse the

force/distance

curve of the

actuator to make it

compatible with

the force/time

requirements of

the drop ejection.

Actuator
A series of thin
Increased
Increased
Some

stack
actuators are
travel
fabrication
piezoelectric ink

stacked. This can
Reduced drive
complexity
jets

be appropriate
voltage
Increased
IJ04

where actuators

possibility of

require high

short circuits due

electric field

to pinholes

strength, such as

electrostatic and

piezoelectric

actuators.

Multiple
Multiple smaller
Increases the
Actuator
IJ12, IJ13,

actuators
actuators are used
force available
forces may not
IJ18, IJ20, IJ22,

simultaneously to
from an actuator
add linearly,
IJ28, IJ42, IJ43

move the ink. Each
Multiple
reducing

actuator need
actuators can be
efficiency

provide only a
positioned to

portion of the
control ink flow

force required.
accurately

Linear
A linear spring is
Matches low
Requires print
IJ15

Spring
used to transform a
travel actuator
head area for the

motion with small
with higher
spring

travel and high
travel

force into a longer
requirements

travel, lower force
Non-contact

motion.
method of

motion

transformation

Coiled
A bend actuator is
Increases
Generally
IJ17, IJ21,

actuator
coiled to provide
travel
restricted to
IJ34, IJ35

greater travel in a
Reduces chip
planar

reduced chip area.
area
implementations

Planar
due to extreme

implementations
fabrication

are relatively
difficulty in

easy to fabricate.
other

orientations.

Flexure
A bend actuator
Simple means
Care must be
IJ10, IJ19,

bend
has a small region
of increasing
taken not to
IJ33

actuator
near the fixture
travel of a bend
exceed the

point, which flexes
actuator
elastic limit in

much more readily

the flexure area

than the remainder

Stress

of the actuator.

distribution is

The actuator

very uneven

flexing is

Difficult to

effectively

accurately model

converted from an

with finite

even coiling to an

element analysis

angular bend,

resulting in greater

travel of the

actuator tip.

Catch
The actuator
Very low
Complex
IJ10

controls a small
actuator energy
construction

catch. The catch
Very small
Requires

either enables or
actuator size
external force

disables movement

Unsuitable for

of an ink pusher

pigmented inks

that is controlled

in a bulk manner.

Gears
Gears can be used
Low force,
Moving parts
IJ13

to increase travel
low travel
are required

at the expense of
actuators can be
Several

duration. Circular
used
actuator cycles

gears, rack and
Can be
are required

pinion, ratchets,
fabricated using
More complex

and other gearing
standard surface
drive electronics

methods can be
MEMS
Complex

used.
processes
construction

Friction,

friction, and

wear are

possible

Buckle
A buckle plate can
Very fast
Must stay
S. Hirata et al,

plate
be used to change
movement
within elastic
“An Ink-jet

a slow actuator
achievable
limits of the
Head Using

into a fast motion.

materials for
Diaphragm

It can also convert

long device life
Microactuator”,

a high force, low

High stresses
Proc. IEEE

travel actuator into

involved
MEMS, February

a high travel,

Generally
1996, pp 418-423.

medium force

high power
IJ18, IJ27

motion.

requirement

Tapered
A tapered
Linearizes the
Complex
IJ14

magnetic
magnetic pole can
magnetic
construction

pole
increase travel at
force/distance

the expense of
curve

force.

Lever
A lever and
Matches low
High stress
IJ32, IJ36,

fulcrum is used to
travel actuator
around the
IJ37

transform a motion
with higher
fulcrum

with small travel
travel

and high force into
requirements

a motion with
Fulcrum area

longer travel and
has no linear

lower force. The
movement, and

lever can also
can be used for a

reverse the
fluid seal

direction of travel.

Rotary
The actuator is
High
Complex
IJ28

impeller
connected to a
mechanical
construction

rotary impeller. A
advantage
Unsuitable for

small angular
The ratio of
pigmented inks

deflection of the
force to travel of

actuator results in
the actuator can

a rotation of the
be matched to

impeller vanes,
the nozzle

which push the ink
requirements by

against stationary
varying the

vanes and out of
number of

the nozzle.
impeller vanes

Acoustic
A refractive or
No moving
Large area
1993

lens
diffractive (e.g.
parts
required
Hadimioglu et

zone plate)

Only relevant
al, EUP 550,192

acoustic lens is

for acoustic ink
1993 Elrod et

used to concentrate

jets
al, EUP 572,220

sound waves.

Sharp
A sharp point is
Simple
Difficult to
Tone-jet

conductive
used to concentrate
construction
fabricate using

point
an electrostatic

standard VLSI

field.

processes for a

surface ejecting

ink-jet

Only relevant

for electrostatic

ink jets

ACTUATOR MOTION

Description
Advantages
Disadvantages
Examples

Volume
The volume of the
Simple
High energy is
Hewlett-

expansion
actuator changes,
construction in
typically
Packard Thermal

pushing the ink in
the case of
required to
Ink jet

all directions.
thermal ink jet
achieve volume
Canon

expansion. This
Bubblejet

leads to thermal

stress, cavitation,

and kogation in

thermal ink jet

implementations

Linear,
The actuator
Efficient
High
IJ01, IJ02,

normal to
moves in a
coupling to ink
fabrication
IJ04, IJ07, IJ11,

chip
direction normal to
drops ejected
complexity may
IJ14

surface
the print head
normal to the
be required to

surface. The
surface
achieve

nozzle is typically

perpendicular

in the line of

motion

movement.

Parallel to
The actuator
Suitable for
Fabrication
IJ12, IJ13,

chip
moves parallel to
planar
complexity
IJ15, IJ33,, IJ34,

surface
the print head
fabrication
Friction
IJ35, IJ36

surface. Drop

Stiction

ejection may still

be normal to the

surface.

Membrane
An actuator with a
The effective
Fabrication
1982 Howkins

push
high force but
area of the
complexity
U.S. Pat. No. 4,459,601

small area is used
actuator
Actuator size

to push a stiff
becomes the
Difficulty of

membrane that is
membrane area
integration in a

in contact with the

VLSI process

ink.

Rotary
The actuator
Rotary levers
Device
IJ05, IJ08,

causes the rotation
may be used to
complexity
IJ13, IJ28

of some element,
increase travel
May have

such a grill or
Small chip
friction at a pivot

impeller
area
point

requirements

Bend
The actuator bends
A very small
Requires the
1970 Kyser et

when energized.
change in
actuator to be
al U.S. Pat. No.

This may be due to
dimensions can
made from at
3,946,398

differential
be converted to a
least two distinct
1973 Stemme

thermal expansion,
large motion.
layers, or to have
U.S. Pat. No. 3,747,120

piezoelectric

a thermal
IJ03, IJ09,

expansion,

difference across
IJ10, IJ19, IJ23,

magnetostriction,

the actuator
IJ24, IJ25, IJ29,

or other form of

IJ30, IJ31, IJ33,

relative

IJ34, IJ35

dimensional

change.

Swivel
The actuator
Allows
Inefficient
IJ06

swivels around a
operation where
coupling to the

central pivot. This
the net linear
ink motion

motion is suitable
force on the

where there are
paddle is zero

opposite forces
Small chip

applied to opposite
area

sides of the paddle,
requirements

e.g. Lorenz force.

Straighten
The actuator is
Can be used
Requires
IJ26, IJ32

normally bent, and
with shape
careful balance

straightens when
memory alloys
of stresses to

energized.
where the
ensure that the

austenic phase is
quiescent bend is

planar
accurate

Double
The actuator bends
One actuator
Difficult to
IJ36, IJ37,

bend
in one direction
can be used to
make the drops
IJ38

when one element
power two
ejected by both

is energized, and
nozzles.
bend directions

bends the other
Reduced chip
identical.

way when another
size.
A small

element is
Not sensitive
efficiency loss

energized.
to ambient
compared to

temperature
equivalent single

bend actuators.

Shear
Energizing the
Can increase
Not readily
1985 Fishbeck

actuator causes a
the effective
applicable to
U.S. Pat. No. 4,584,590

shear motion in the
travel of
other actuator

actuator material.
piezoelectric
mechanisms

actuators

Radial
The actuator
Relatively
High force
1970 Zoltan

constriction
squeezes an ink
easy to fabricate
required
U.S. Pat. No. 3,683,212

reservoir, forcing
single nozzles
Inefficient

ink from a
from glass
Difficult to

constricted nozzle.
tubing as
integrate with

macroscopic
VLSI processes

structures

Coil/
A coiled actuator
Easy to
Difficult to
IJ17, IJ21,

uncoil
uncoils or coils
fabricate as a
fabricate for
IJ34, IJ35

more tightly. The
planar VLSI
non-planar

motion of the free
process
devices

end of the actuator
Small area
Poor out-of-

ejects the ink.
required,
plane stiffness

therefore low

cost

Bow
The actuator bows
Can increase
Maximum
IJ16, IJ18,

(or buckles) in the
the speed of
travel is
IJ27

middle when
travel
constrained

energized.
Mechanically
High force

rigid
required

Push-Pull
Two actuators
The structure
Not readily
IJ18

control a shutter.
is pinned at both
suitable for ink

One actuator pulls
ends, so has a
jets which

the shutter, and the
high out-of-
directly push the

other pushes it.
plane rigidity
ink

Curl
A set of actuators
Good fluid
Design
IJ20, IJ42

inwards
curl inwards to
flow to the
complexity

reduce the volume
region behind

of ink that they
the actuator

enclose.
increases

efficiency

Curl
A set of actuators
Relatively
Relatively
IJ43

outwards
curl outwards,
simple
large chip area

pressurizing ink in
construction

a chamber

surrounding the

actuators, and

expelling ink from

a nozzle in the

chamber.

Iris
Multiple vanes
High
High
IJ22

enclose a volume
efficiency
fabrication

of ink. These
Small chip
complexity

simultaneously
area
Not suitable

rotate, reducing

for pigmented

the volume

inks

between the vanes.

Acoustic
The actuator
The actuator
Large area
1993

vibration
vibrates at a high
can be
required for
Hadimioglu et

frequency.
physically
efficient
al, EUP 550,192

distant from the
operation at
1993 Elrod et

ink
useful
al, EUP 572,220

frequencies

Acoustic

coupling and

crosstalk

Complex

drive circuitry

Poor control

of drop volume

and position

None
In various ink jet
No moving
Various other
Silverbrook,

designs the
parts
tradeoffs are
EP 0771 658 A2

actuator does not

required to
and related

move.

eliminate
patent

moving parts
applications

Tone-jet

NOZZLE REFILL METHOD

Description
Advantages
Disadvantages
Examples

Surface
This is the normal
Fabrication
Low speed
Thermal ink

tension
way that ink jets
simplicity
Surface
jet

are refilled. After
Operational
tension force
Piezoelectric

the actuator is
simplicity
relatively small
ink jet

energized, it

compared to
IJ01-IJ07,

typically returns

actuator force
IJ10-IJ14, IJ16,

rapidly to its

Long refill
IJ20, IJ22-IJ45

normal position.

time usually

This rapid return

dominates the

sucks in air

total repetition

through the nozzle

rate

opening. The ink

surface tension at

the nozzle then

exerts a small

force restoring the

meniscus to a

minimum area.

This force refills

the nozzle.

Shuttered
Ink to the nozzle
High speed
Requires
IJ08, IJ13,

oscillating
chamber is
Low actuator
common ink
IJ15, IJ17, IJ18,

ink
provided at a
energy, as the
pressure
IJ19, IJ21

pressure
pressure that
actuator need
oscillator

oscillates at twice
only open or
May not be

the drop ejection
close the shutter,
suitable for

frequency. When a
instead of
pigmented inks

drop is to be
ejecting the ink

ejected, the shutter
drop

is opened for 3

half cycles: drop

ejection, actuator

return, and refill.

The shutter is then

closed to prevent

the nozzle

chamber emptying

during the next

negative pressure

cycle.

Refill
After the main
High speed, as
Requires two
IJ09

actuator
actuator has
the nozzle is
independent

ejected a drop a
actively refilled
actuators per

second (refill)

nozzle

actuator is

energized. The

refill actuator

pushes ink into the

nozzle chamber.

The refill actuator

returns slowly, to

prevent its return

from emptying the

chamber again.

Positive
The ink is held a
High refill
Surface spill
Silverbrook,

ink
slight positive
rate, therefore a
must be
EP 0771 658 A2

pressure
pressure. After the
high drop
prevented
and related

ink drop is ejected,
repetition rate is
Highly
patent

the nozzle
possible
hydrophobic
applications

chamber fills

print head
Alternative

quickly as surface

surfaces are
for:, IJ01-IJ07,

tension and ink

required
IJ10-IJ14, IJ16,

pressure both

IJ20, IJ22-IJ45

operate to refill the

nozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET

Description
Advantages
Disadvantages
Examples

Long inlet
The ink inlet
Design
Restricts refill
Thermal ink

channel
channel to the
simplicity
rate
jet

nozzle chamber is
Operational
May result in
Piezoelectric

made long and
simplicity
a relatively large
ink jet

relatively narrow,
Reduces
chip area
IJ42, IJ43

relying on viscous
crosstalk
Only partially

drag to reduce

effective

inlet back-flow.

Positive
The ink is under a
Drop selection
Requires a
Silverbrook,

ink
positive pressure,
and separation
method (such as
EP 0771 658 A2

pressure
so that in the
forces can be
a nozzle rim or
and related

quiescent state
reduced
effective
patent

some of the ink
Fast refill time
hydrophobizing,
applications

drop already

or both) to
Possible

protrudes from the

prevent flooding
operation of the

nozzle.

of the ejection
following: IJ01-IJ07,

This reduces the

surface of the
IJ09-IJ12,

pressure in the

print head.
IJ14, IJ16, IJ20,

nozzle chamber

IJ22,, IJ23-IJ34,

which is required

IJ36-IJ41, IJ44

to eject a certain

volume of ink. The

reduction in

chamber pressure

results in a

reduction in ink

pushed out through

the inlet.

Baffle
One or more
The refill rate
Design
HP Thermal

baffles are placed
is not as
complexity
Ink Jet

in the inlet ink
restricted as the
May increase
Tektronix

flow. When the
long inlet
fabrication
piezoelectric ink

actuator is
method.
complexity (e.g.
jet

energized, the
Reduces
Tektronix hot

rapid ink
crosstalk
melt

movement creates

Piezoelectric

eddies which

print heads).

restrict the flow

through the inlet.

The slower refill

process is

unrestricted, and

does not result in

eddies.

Flexible
In this method
Significantly
Not applicable
Canon

flap
recently disclosed
reduces back-
to most ink jet

restricts
by Canon, the
flow for edge-
configurations

inlet
expanding actuator
shooter thermal
Increased

(bubble) pushes on
ink jet devices
fabrication

a flexible flap that

complexity

restricts the inlet.

Inelastic

deformation of

polymer flap

results in creep

over extended

use

Inlet filter
A filter is located
Additional
Restricts refill
IJ04, IJ12,

between the ink
advantage of ink
rate
IJ24, IJ27, IJ29,

inlet and the
filtration
May result in
IJ30

nozzle chamber.
Ink filter may
complex

The filter has a
be fabricated
construction

multitude of small
with no

holes or slots,
additional

restricting ink
process steps

flow. The filter

also removes

particles which

may block the

nozzle.

Small
The ink inlet
Design
Restricts refill
IJ02, IJ37,

inlet
channel to the
simplicity
rate
IJ44

compared
nozzle chamber

May result in

to nozzle
has a substantially

a relatively large

smaller cross

chip area

section than that of

Only partially

the nozzle,

effective

resulting in easier

ink egress out of

the nozzle than out

of the inlet.

Inlet
A secondary
Increases
Requires
IJ09

shutter
actuator controls
speed of the ink-
separate refill

the position of a
jet print head
actuator and

shutter, closing off
operation
drive circuit

the ink inlet when

the main actuator

is energized.

The inlet
The method avoids
Back-flow
Requires
IJ01, IJ03,

is located
the problem of
problem is
careful design to
IJ05, IJ06, IJ07,

behind
inlet back-flow by
eliminated
minimize the
IJ10, IJ11, IJ14,

the ink-
arranging the ink-

negative
IJ16, IJ22, IJ23,

pushing
pushing surface of

pressure behind
IJ25, IJ28, IJ31,

surface
the actuator

the paddle
IJ32, IJ33, IJ34,

between the inlet

IJ35, IJ36, IJ39,

and the nozzle.

IJ40, IJ41

Part of
The actuator and a
Significant
Small increase
IJ07, IJ20,

the
wall of the ink
reductions in
in fabrication
IJ26, IJ38

actuator
chamber are
back-flow can be
complexity

moves to
arranged so that
achieved

shut off
the motion of the
Compact

the inlet
actuator closes off
designs possible

the inlet.

Nozzle
In some
Ink back-flow
None related
Silverbrook,

actuator
configurations of
problem is
to ink back-flow
EP 0771 658 A2

does not
ink jet, there is no
eliminated
on actuation
and related

result in
expansion or

patent

ink back-
movement of an

applications

flow
actuator which

Valve-jet

may cause ink

Tone-jet

back-flow through

the inlet.

NOZZLE CLEARING METHOD

Description
Advantages
Disadvantages
Examples

Normal
All of the nozzles
No added
May not be
Most ink jet

nozzle
are fired
complexity on
sufficient to
systems

firing
periodically,
the print head
displace dried
IJ01, IJ02,

before the ink has

ink
IJ03, IJ04, IJ05,

a chance to dry.

IJ06, IJ07, IJ09,

When not in use

IJ10, IJ11, IJ12,

the nozzles are

IJ14, IJ16, IJ20,

sealed (capped)

IJ22, IJ23, IJ24,

against air.

IJ25, IJ26, IJ27,

The nozzle firing

IJ28, IJ29, IJ30,

is usually

IJ31, IJ32, IJ33,

performed during a

IJ34, IJ36, IJ37,

special clearing

IJ38, IJ39, IJ40,,

cycle, after first

IJ41, IJ42, IJ43,

moving the print

IJ44,, IJ45

head to a cleaning

station.

Extra
In systems which
Can be highly
Requires
Silverbrook,

power to
heat the ink, but do
effective if the
higher drive
EP 0771 658 A2

ink heater
not boil it under
heater is
voltage for
and related

normal situations,
adjacent to the
clearing
patent

nozzle clearing can
nozzle
May require
applications

be achieved by

larger drive

over-powering the

transistors

heater and boiling

ink at the nozzle.

Rapid
The actuator is
Does not
Effectiveness
May be used

succession
fired in rapid
require extra
depends
with: IJ01, IJ02,

of
succession. In
drive circuits on
substantially
IJ03, IJ04, IJ05,

actuator
some
the print head
upon the
IJ06, IJ07, IJ09,

pulses
configurations, this
Can be readily
configuration of
IJ10, IJ11, IJ14,

may cause heat
controlled and
the ink jet nozzle
IJ16, IJ20, IJ22,

build-up at the
initiated by

IJ23, IJ24, IJ25,

nozzle which boils
digital logic

IJ27, IJ28, IJ29,

the ink, clearing

IJ30, IJ31, IJ32,

the nozzle. In other

IJ33, IJ34, IJ36,

situations, it may

IJ37, IJ38, IJ39,

cause sufficient

IJ40, IJ41, IJ42,

vibrations to

IJ43, IJ44, IJ45

dislodge clogged

nozzles.

Extra
Where an actuator
A simple
Not suitable
May be used

power to
is not normally
solution where
where there is a
with: IJ03, IJ09,

ink
driven to the limit
applicable
hard limit to
IJ16, IJ20, IJ23,

pushing
of its motion,

actuator
IJ24, IJ25, IJ27,

actuator
nozzle clearing

movement
IJ29, IJ30, IJ31,

may be assisted by

IJ32, IJ39, IJ40,

providing an

IJ41, IJ42, IJ43,

enhanced drive

IJ44, IJ45

signal to the

actuator.

Acoustic
An ultrasonic
A high nozzle
High
IJ08, IJ13,

resonance
wave is applied to
clearing
implementation
IJ15, IJ17, IJ18,

the ink chamber.
capability can be
cost if system
IJ19, IJ21

This wave is of an
achieved
does not already

appropriate
May be
include an

amplitude and
implemented at
acoustic actuator

frequency to cause
very low cost in

sufficient force at
systems which

the nozzle to clear
already include

blockages. This is
acoustic

easiest to achieve
actuators

if the ultrasonic

wave is at a

resonant frequency

of the ink cavity.

Nozzle
A microfabricated
Can clear
Accurate
Silverbrook,

clearing
plate is pushed
severely clogged
mechanical
EP 0771 658 A2

plate
against the
nozzles
alignment is
and related

nozzles. The plate

required
patent

has a post for

Moving parts
applications

every nozzle. A

are required

post moves

There is risk

through each

of damage to the

nozzle, displacing

nozzles

dried ink.

Accurate

fabrication is

required

Ink
The pressure of the
May be
Requires
May be used

pressure
ink is temporarily
effective where
pressure pump
with all IJ series

pulse
increased so that
other methods
or other pressure
ink jets

ink streams from
cannot be used
actuator

all of the nozzles.

Expensive

This may be used

Wasteful of

in conjunction

ink

with actuator

energizing.

Print
A flexible ‘blade’
Effective for
Difficult to
Many ink jet

head
is wiped across the
planar print head
use if print head
systems

wiper
print head surface.
surfaces
surface is non-

The blade is
Low cost
planar or very

usually fabricated

fragile

from a flexible

Requires

polymer, e.g.

mechanical parts

rubber or synthetic

Blade can

elastomer.

wear out in high

volume print

systems

Separate
A separate heater
Can be
Fabrication
Can be used

ink
is provided at the
effective where
complexity
with many IJ

boiling
nozzle although
other nozzle

series ink jets

heater
the normal drop e-
clearing methods

ection mechanism
cannot be used

does not require it.
Can be

The heaters do not
implemented at

require individual
no additional

drive circuits, as
cost in some ink

many nozzles can
jet

be cleared
configurations

simultaneously,

and no imaging is

required.

NOZZLE PLATE CONSTRUCTION

Description
Advantages
Disadvantages
Examples

Electro-
A nozzle plate is
Fabrication
High
Hewlett

formed
separately
simplicity
temperatures and
Packard Thermal

nickel
fabricated from

pressures are
Ink jet

electroformed

required to bond

nickel, and bonded

nozzle plate

to the print head

Minimum

chip.

thickness

constraints

Differential

thermal

expansion

Laser
Individual nozzle
No masks
Each hole
Canon

ablated or
holes are ablated
required
must be
Bubblejet

drilled
by an intense UV
Can be quite
individually
1988 Sercel et

polymer
laser in a nozzle
fast
formed
al., SPIE, Vol.

plate, which is
Some control
Special
998 Excimer

typically a
over nozzle
equipment
Beam

polymer such as
profile is
required
Applications, pp.

polyimide or
possible
Slow where
76-83

polysulphone
Equipment
there are many
1993

required is
thousands of
Watanabe et al.,

relatively low
nozzles per print
U.S. Pat. No. 5,208,604

cost
head

May produce

thin burrs at exit

holes

Silicon
A separate nozzle
High accuracy
Two part
K. Bean,

micro-
plate is
is attainable
construction
IEEE

machined
micromachined

High cost
Transactions on

from single crystal

Requires
Electron

silicon, and

precision
Devices, Vol.

bonded to the print

alignment
ED-25, No. 10,

head wafer.

Nozzles may
1978, pp 1185-1195

be clogged by
Xerox 1990

adhesive
Hawkins et al.,

U.S. Pat. No. 4,899,181

Glass
Fine glass
No expensive
Very small
1970 Zoltan

capillaries
capillaries are
equipment
nozzle sizes are
U.S. Pat. No. 3,683,212

drawn from glass
required
difficult to form

tubing. This
Simple to
Not suited for

method has been
make single
mass production

used for making
nozzles

individual nozzles,

but is difficult to

use for bulk

manufacturing of

print heads with

thousands of

nozzles.

Monolithic,
The nozzle plate is
High accuracy
Requires
Silverbrook,

surface
deposited as a
(<1 μm)
sacrificial layer
EP 0771 658 A2

micro-
layer using
Monolithic
under the nozzle
and related

machined
standard VLSI
Low cost
plate to form the
patent

using
deposition
Existing
nozzle chamber
applications

VLSI
techniques.
processes can be
Surface may
IJ01, IJ02,

litho-
Nozzles are etched
used
be fragile to the
IJ04, IJ11, IJ12,

graphic
in the nozzle plate

touch
IJ17, IJ18, IJ20,

processes
using VLSI

IJ22, IJ24, IJ27,

lithography and

IJ28, IJ29, IJ30,

etching.

IJ31, IJ32, IJ33,

IJ34, IJ36, IJ37,

IJ38, IJ39, IJ40,

IJ41, IJ42, IJ43,

IJ44

Monolithic,
The nozzle plate is
High accuracy
Requires long
IJ03, IJ05,

etched
a buried etch stop
(<1 μm)
etch times
IJ06, IJ07, IJ08,

through
in the wafer.
Monolithic
Requires a
IJ09, IJ10, IJ13,

substrate
Nozzle chambers
Low cost
support wafer
IJ14, IJ15, IJ16,

are etched in the
No differential

IJ19, IJ21, IJ23,

front of the wafer,
expansion

IJ25, IJ26

and the wafer is

thinned from the

back side. Nozzles

are then etched in

the etch stop layer.

No nozzle
Various methods
No nozzles to
Difficult to
Ricoh 1995

plate
have been tried to
become clogged
control drop
Sekiya et al U.S. Pat. No.

eliminate the

position
5,412,413

nozzles entirely, to

accurately
1993

prevent nozzle

Crosstalk
Hadimioglu et al

clogging. These

problems
EUP 550,192

include thermal

1993 Elrod et

bubble

al EUP 572,220

mechanisms and

acoustic lens

mechanisms

Trough
Each drop ejector
Reduced
Drop firing
IJ35

has a trough
manufacturing
direction is

through which a
complexity
sensitive to

paddle moves.
Monolithic
wicking.

There is no nozzle

plate.

Nozzle slit
The elimination of
No nozzles to
Difficult to
1989 Saito et

instead of
nozzle holes and
become clogged
control drop
al U.S. Pat. No.

individual
replacement by a

position
4,799,068

nozzles
slit encompassing

accurately

many actuator

Crosstalk

positions reduces

problems

nozzle clogging,

but increases

crosstalk due to

ink surface waves

DROP EJECTION DIRECTION

Description
Advantages
Disadvantages
Examples

Edge
Ink flow is along
Simple
Nozzles
Canon

(‘edge
the surface of the
construction
limited to edge
Bubblejet 1979

shooter’)
chip, and ink drops
No silicon
High
Endo et al GB

are ejected from
etching required
resolution is
patent 2,007,162

the chip edge.
Good heat
difficult
Xerox heater-

sinking via
Fast color
in-pit 1990

substrate
printing requires
Hawkins et al

Mechanically
one print head
U.S. Pat. No. 4,899,181

strong
per color
Tone-jet

Ease of chip

handing

Surface
Ink flow is along
No bulk
Maximum ink
Hewlett-

(‘roof
the surface of the
silicon etching
flow is severely
Packard TIJ

shooter’)
chip, and ink drops
required
restricted
1982 Vaught et

are ejected from
Silicon can

al U.S. Pat. No.

the chip surface,
make an

4,490,728

normal to the
effective heat

IJ02, IJ11,

plane of the chip.
sink

IJ12, IJ20, IJ22

Mechanical

strength

Through
Ink flow is through
High ink flow
Requires bulk
Silverbrook,

chip,
the chip, and ink
Suitable for
silicon etching
EP 0771 658 A2

forward
drops are ejected
pagewidth print

and related

(‘up
from the front
heads

patent

shooter’)
surface of the chip.
High nozzle

applications

packing density

IJ04, IJ17,

therefore low

IJ18, IJ24, IJ27-IJ45

manufacturing

cost

Through
Ink flow is through
High ink flow
Requires
IJ01, IJ03,

chip,
the chip, and ink
Suitable for
wafer thinning
IJ05, IJ06, IJ07,

reverse
drops are ejected
pagewidth print
Requires
IJ08, IJ09, IJ10,

(‘down
from the rear
heads
special handling
IJ13, IJ14, IJ15,

shooter’)
surface of the chip.
High nozzle
during
IJ16, IJ19, IJ21,

packing density
manufacture
IJ23, IJ25, IJ26

therefore low

manufacturing

cost

Through
Ink flow is through
Suitable for
Pagewidth
Epson Stylus

actuator
the actuator, which
piezoelectric
print heads
Tektronix hot

is not fabricated as
print heads
require several
melt

part of the same

thousand
piezoelectric ink

substrate as the

connections to
jets

drive transistors.

drive circuits

Cannot be

manufactured in

standard CMOS

fabs

Complex

assembly

required

INK TYPE

Description
Advantages
Disadvantages
Examples

Aqueous,
Water based ink
Environmentally
Slow drying
Most existing

dye
which typically
friendly
Corrosive
ink jets

contains: water,
No odor
Bleeds on
All IJ series

dye, surfactant,

paper
ink jets

humectant, and

May
Silverbrook,

biocide.

strikethrough
EP 0771 658 A2

Modern ink dyes

Cockles paper
and related

have high water-

patent

fastness, light

applications

fastness

Aqueous,
Water based ink
Environmentally
Slow drying
IJ02, IJ04,

pigment
which typically
friendly
Corrosive
IJ21, IJ26, IJ27,

contains: water,
No odor
Pigment may
IJ30

pigment,
Reduced bleed
clog nozzles
Silverbrook,

surfactant,
Reduced
Pigment may
EP 0771 658 A2

humectant, and
wicking
clog actuator
and related

biocide.
Reduced
mechanisms
patent

Pigments have an
strikethrough
Cockles paper
applications

advantage in

Piezoelectric

reduced bleed,

ink-jets

wicking and

Thermal ink

strikethrough.

jets (with

significant

restrictions)

Methyl
MEK is a highly
Very fast
Odorous
All IJ series

Ethyl
volatile solvent
drying
Flammable
ink jets

Ketone
used for industrial
Prints on

(MEK)
printing on
various

difficult surfaces
substrates such

such as aluminum
as metals and

cans.
plastics

Alcohol
Alcohol based inks
Fast drying
Slight odor
All IJ series

(ethanol,
can be used where
Operates at
Flammable
ink jets

2-butanol,
the printer must
sub-freezing

and
operate at
temperatures

others)
temperatures
Reduced

below the freezing
paper cockle

point of water. An
Low cost

example of this is

in-camera

consumer

photographic

printing.

Phase
The ink is solid at
No drying
High viscosity
Tektronix hot

change
room temperature,
time-ink
Printed ink
melt

(hot melt)
and is melted in
instantly freezes
typically has a
piezoelectric ink

the print head
on the print
‘waxy’ feel
jets

before jetting. Hot
medium
Printed pages
1989 Nowak

melt inks are
Almost any
may ‘block’
U.S. Pat. No. 4,820,346

usually wax based,
print medium
Ink
All IJ series

with a melting
can be used
temperature may
ink jets

point around 80° C.
No paper
be above the

After jetting
cockle occurs
curie point of

the ink freezes
No wicking
permanent

almost instantly
occurs
magnets

upon contacting
No bleed
Ink heaters

the print medium
occurs
consume power

or a transfer roller.
No
Long warm-

strikethrough
up time

occurs

Oil
Oil based inks are
High
High
All IJ series

extensively used in
solubility
viscosity: this is
ink jets

offset printing.
medium for
a significant

They have
some dyes
limitation for use

advantages in
Does not
in ink jets, which

improved
cockle paper
usually require a

characteristics on
Does not wick
low viscosity.

paper (especially
through paper
Some short

no wicking or

chain and multi-

cockle). Oil

branched oils

soluble dies and

have a

pigments are

sufficiently low

required.

viscosity.

Slow drying

Micro-
A microemulsion
Stops ink
Viscosity
All IJ series

emulsion
is a stable, self
bleed
higher than
ink jets

forming emulsion
High dye
water

of oil, water, and
solubility
Cost is

surfactant. The
Water, oil,
slightly higher

characteristic drop
and amphiphilic
than water based

size is less than
soluble dies can
ink

100 nm, and is
be used
High

determined by the
Can stabilize
surfactant

preferred curvature
pigment
concentration

of the surfactant.
suspensions
required (around

5%)

Claims

1. A printhead nozzle comprising: a plurality of electrodes;a heater having contacts abutting the electrodes, a heater element for heating a quantity of fluid and sloped side portions extending between the heater element and the contacts; anda nozzle spaced from the heater such that the heated fluid is ejected through the nozzle,wherein the heater element has higher electrical resistance than the contacts and the sloped side portions.
2. A printhead nozzle according to claim 1 wherein the heater comprises TiAlN.
3. A printhead nozzle according to claim 1 wherein the heater element is ring shaped.
4. A printhead nozzle according to claim 1 wherein the heater element is coated with a passivating material.
5. A printhead nozzle according to claim 1 wherein the heater element is configured such that an actuation energy of less than 500 nanojoules is required to be applied to that heater element to heat that heater element sufficiently to cause the ejection of said drop.
6. A printhead nozzle according to claim 1 incorporated in a structure that is formed by chemical vapor deposition.
7. A printhead nozzle according to claim 6 wherein the structure is less than 10 microns thick.
8. A printhead nozzle according to claim 1 wherein the heater element is formed of solid material more than 90% of which, by atomic proportion, is constituted by at least one periodic element having an atomic number below 50.
9. A printhead nozzle according to claim 1 wherein the heater element is substantially covered by a conformal protective coating, the coating of having been applied substantially to all sides of the heater element simultaneously such that the coating is seamless.

Priority Claims (2)

Number	Date	Country	Kind
PP7991	Jul 1997	AU	national
PP2592	Mar 1998	AU	national

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a Continuation of U.S. application Ser. No. 12/618,750, filed Nov. 15, 2009, now issued U.S. Pat. No. 7,950,779, which is a Continuation of U.S. application Ser. No. 12/272,753 filed Nov. 17, 2008, now issued U.S. Pat. No. 7,628,471, which is a Continuation of U.S. application Ser. No. 11/060,805, filed Feb. 18, 2005, now issued U.S. Pat. No. 7,468,139, which is a Continuation-In-Part of U.S. application Ser. No. 10/728,970 filed Dec. 8, 2003, now abandoned, which is a Continuation-In-Part of U.S. application Ser. No. 10/160,273 filed Jun. 4, 2002, now issued U.S. Pat. No. 6,746,105, which is a Continuation of U.S. application Ser. No. 09/112,767 filed Jul. 10, 1998, now issued U.S. Pat. No. 6,416,167, the entire contents of which are herein incorporated by reference. The following Australian provisional patent applications/granted patents are hereby incorporated by cross-reference. For the purposes of location and identification, US patent applications identified by their US patent application serial numbers (USSN)/granted numbers are listed alongside the Australian applications from which the US patent applications claim the right of priority. U.S. PAT./PATENTCROSS-REFERENCEDAPPLICATIONAUSTRALIAN(CLAIMING RIGHT OFPROVISIONALPRIORITY FROMPATENTAUSTRALIAN PROVISIONALAPPLICATION NO.APPLICATION)PO79916,750,901PO85056,476,863PO79886,788,336PO93956,322,181PO80176,597,817PO80146,227,648PO80256,727,948PO80326,690,419PO79996,727,951PO80306,196,541PO79976,195,150PO79796,362,868PO79786,831,681PO79826,431,669PO79896,362,869PO80196,472,052PO79806,356,715PO80186,894,694PO79386,636,216PO80166,366,693PO80246,329,990PO79396,459,495PO85016,137,500PO85006,690,416PO79877,050,143PO80226,398,328PO84977,110,024PO80206,431,704PO85046,879,341PO80006,415,054PO79346,665,454PO79906,542,645PO84996,486,886PO85026,381,361PO79816,317,192PO79866,850,274PO80266,646,757PO80286,624,848PO93946,357,135PO93976,271,931PO93986,353,772PO93996,106,147PO94006,665,008PO94016,304,291PO94036,305,770PO94056,289,262PP09596,315,200PP13976,217,165PP23706,786,420PO80036,350,023PO80056,318,849PO80666,227,652PO80726,213,588PO80406,213,589PO80716,231,163PO80476,247,795PO80356,394,581PO80446,244,691PO80636,257,704PO80576,416,168PO80566,220,694PO80696,257,705PO80496,247,794PO80366,234,610PO80486,247,793PO80706,264,306PO80676,241,342PO80016,247,792PO80386,264,307PO80336,254,220PO80026,234,611PO80686,302,528PO80626,283,582PO80346,239,821PO80396,338,547PO80416,247,796PO80046,557,977PO80376,390,603PO80436,362,843PO80426,293,653PO80646,312,107PO93896,227,653PO93916,234,609PP08886,238,040PP08916,188,415PP08906,227,654PP08736,209,989PP09936,247,791PP08906,336,710PP13986,217,153PP25926,416,167PP25936,243,113PP39916,283,581PP39876,247,790PP39856,260,953PP39836,267,469PO79356,224,780PO79366,235,212PO79376,280,643PO80616,284,147PO80546,214,244PO80656,071,750PO80556,267,905PO80536,251,298PO80786,258,285PO79336,225,138PO79506,241,904PO79496,299,786PO80606,866,789PO80596,231,773PO80736,190,931PO80766,248,249PO80756,290,862PO80796,241,906PO80506,565,762PO80526,241,905PO79486,451,216PO79516,231,772PO80746,274,056PO79416,290,861PO80776,248,248PO80586,306,671PO80516,331,258PO80456,110,754PO79526,294,101PO80466,416,679PO93906,264,849PO93926,254,793PP08896,235,211PP08876,491,833PP08826,264,850PP08746,258,284PP13966,312,615PP39896,228,668PP25916,180,427PP39906,171,875PP39866,267,904PP39846,245,247PP39826,315,914PP08956,231,148PP08696,293,658PP08876,614,560PP08856,238,033PP08846,312,070PP08866,238,111PP08776,378,970PP08786,196,739PP08836,270,182PP08806,152,619PO80066,087,638PO80076,340,222PO80106,041,600PO80116,299,300PO79476,067,797PO79446,286,935PO79466,044,646PP08946,382,769

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Related Publications (1)

	Number	Date	Country
	20110211025 A1	Sep 2011	US

Continuations (4)

	Number	Date	Country
Parent	12618750	Nov 2009	US
Child	13101142		US
Parent	12272753	Nov 2008	US
Child	12618750		US
Parent	11060805	Feb 2005	US
Child	12272753		US
Parent	09112767	Jul 1998	US
Child	10160273		US

Continuation in Parts (2)

	Number	Date	Country
Parent	10728970	Dec 2003	US
Child	11060805		US
Parent	10160273	Jun 2002	US
Child	10728970		US

Printhead nozzle having heater of higher resistance than contacts

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Date Issued

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CPC

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US

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Abstract