EP1640162B1

EP1640162B1 - Inkjet nozzle arrangement having paddle forming a portion of a wall

Info

Publication number: EP1640162B1
Application number: EP05109701A
Authority: EP
Inventors: Kia Silverbrook; Gregory Mcavoy
Original assignee: Silverbrook Research Pty Ltd
Current assignee: Silverbrook Research Pty Ltd
Priority date: 1997-07-15
Filing date: 1998-07-15
Publication date: 2007-03-28
Anticipated expiration: 2018-07-15
Also published as: ATE409119T1; EP0999934B1; EP1650030B1; EP1650030A1; JP4160250B2; EP0999934A4; EP1637330A1; ATE358019T1; EP1650031A1; EP1640162A1; ATE359915T1; WO1999003681A1; EP1650031B1; EP0999934A1; JP2003521389A; ATE386638T1; EP1637330B1; ES2302134T3

Abstract

An inkjet nozzle arrangement is provided. The nozzle arrangement comprises a nozzle chamber having a slotted sidewall in a first surface and an ink ejection port defined in a second surface thereof, an ink supply channel interconnected to the nozzle chamber, a moveable vane located within the nozzle chamber and being moveable so as to cause ejection of ink from the nozzle chamber, and an actuator located outside the nozzle chamber and interconnected to the moveable vane through the slotted sidewall.

Description

Field of Invention

The present invention relates to the field of ink jet printing systems.

Background of the Art

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 of 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 utilisation of a continuous stream ink in ink jet printing appears to date back to at least 1929 wherein US Patent No. 1941001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.
US Patent 3596275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilised by several manufacturers including Elmjet and Scitex (see also US Patent No. 3373437 by Sweet et al)
Piezo-electric ink jet printers are also one form of commonly utilised ink jet printing device. Piezo-electric systems are disclosed by Kyser et. al. in US Patent No. 3946398 (1970) which utilises a diaphragm mode of operation, by Zolten in US Patent 3683212 (1970) which discloses a squeeze mode of operation of a piezo electric crystal, Stemme in US Patent No. 3747120 (1972) discloses a bend mode of piezo-electric operation, Howkins in US Patent No. 4459601 discloses a Piezo electric push mode actuation of the ink jet stream and Fischbeck in US 4584590 which discloses a sheer mode type of piezo-electric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in US Patent 4490728. Both the aforementioned references disclosed ink jet printing techniques 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 utilising 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.
Many ink jet printing mechanisms are known. Unfortunately, in mass production techniques, the production of ink jet heads is quite difficult. For example, often, the orifice or nozzle plate is constructed separately from the ink supply and ink ejection mechanism and bonded to the mechanism at a later stage (Hewlett-Packard Journal, Vol. 36 no 5, pp33-37 (1985)). These separate material processing steps required in handling such precision devices often adds a substantially expense in manufacturing.
Additionally, side shooting ink jet technologies (U.S. Patent No. 4,899,181) are often used but again, this limit the amount of mass production throughput given any particular capital investment.
Additionally, more esoteric techniques are also often utilised. These can include electroforming of nickel stage (Hewlett-Packard Journal Vol. 36 no 5, pp33-37 (1985)), electro-discharge machining, laser ablation (U.S. Patent No. 5,208,604), micro-punching, etc.
The utilisation of the above techniques is likely to add substantial expense to the mass production of ink jet print heads and therefore add substantially to their final cost.
It would therefore be desirable if an efficient system for the mass production of ink jet print heads could be developed.
Further, during the construction of micro electromechanical systems, it is common to utilize a sacrificial material to build up a mechanical system, within the sacrificial material being subsequently etched away so as to release the required mechanical structure. For example, a suitable common sacrificial material includes silicon dioxide which can be etched away in hydrofluoric acid. MEMS devices are often constructed on silicon wafers having integral electronics such as, for example, using a multi-level metal CMOS layer. Unfortunately, the CMOS process includes the construction of multiple layers which may include the utilization of materials which can be attacked by the sacrificial etchant. This often necessitates the construction of passivation layers using extra processing steps so as to protect other layers from possible unwanted attack by a sacrificial etchant.
In micro-electro mechanical system, it is often necessary to provide for the movement of objects. In particular, it is often necessary to pivot objects in addition to providing for fulcrum arrangements where a first movement of one end of the fulcrum is translated into a corresponding measurement of a second end of the fulcrum. Obviously, such arrangements are often fundamental to mechanical apparatuses.
Further, When constructing large integrated circuits or micro-electro mechanical systems, it is often necessary to interconnect a large number of wire to the final integrated circuit device. To this end, normally, a large number of bond pads are provided on the surface of a chip for the attachment of wires thereto. With the utilization of bond pads normally certain minimal spacings are utilized in accordance with the design technologies utilised. Where are large number of interconnects are required, an excessive amount of on chip real estate is required for providing bond pads. It is therefore desirable to minimize the amount of real estate provided for bond pads whilst ensuring the highest degree of accuracy of registration for automated attachment of interconnects such as a tape automated bonding (TAB) to the surface of a device. WO9712689 is an example of a fluid drop ejector and
discloses one wall comprising a thin elastic membrane having an orifice
defining a nozzle and means responsive to electrical signals for deflecting the membrane to eject drops of fluid from said nozzle.

Summary of the invention

Accordingly the invention provides an ink jet nozzle arrangement according to claim 1. Advantageous embodiments are provided in the dependent claims. The invention also provides a printhead according to claim 16.

Brief Description of the Drawings

Notwithstanding any other forms which 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. 638 to Fig. 640 are schematic sectional views illustrating the operational principles of an embodiment;
Fig. 641(a) and Fig. 641(b) are again schematic sections illustrating the operational principles of the thermal actuator device;
Fig. 642 is a side perspective view, partly in section of a single nozzle arrangement constructed in accordance with an embodiments;
Fig. 643 to Fig. 650 side perspective views partly in section illustrating the manufacturing steps of an embodiments; and
Fig. 651 illustrates an array of ink jet nozzles formed in accordance with the manufacturing procedures of an embodiment.
Fig. 652 provides a legend of the materials indicated in Fig. 653 to Fig. 660;
Fig. 653 to Fig. 660 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle arrangement;
Fig. 661 to Fig. 663 are schematic sectional views illustrating the operational principles of an embodiment;
Fig. 664(a) and Fig. 664(b) illustrate the operational principles of the thermal actuator of an embodiment;
Fig. 665 is a side perspective view of a single nozzle arrangement of an embodiment;
Fig. 666 illustrates an array view of a portion of a print head constructed in accordance with the principles of an embodiment.
Fig. 667 provides a legend of the materials indicated in Fig. 668 to Fig. 676; and
Fig. 668 to Fig. 677 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle.
Fig. 678 is a perspective view of an arrangement of four single thermal actuators constructed in accordance with a further embodiment.
Fig. 679 is a close-up perspective view, partly in section, of a single thermal actuator constructed in accordance with a further embodiment.
Fig. 680 is a perspective view of a single thermal actuator constructed in accordance with a further embodiment, illustrating the thermal actuator being moved up and to a side.
Fig. 681 is an exploded perspective view illustrating the construction of a single thermal actuator in

A Description of IJ43 T

In an embodiment, ink is ejected out of a nozzle chamber via an ink ejection hole as the result of the utilisation of a series of radially placed thermal actuator devices that are arranged around the ink ejection nozzle and are activated so as to compress the ink within the nozzle chamber thereby causing ink ejection.
Turning now to Fig. 638 to Fig. 640, there will first be illustrated the basic operational principles of an embodiment. Fig. 638 illustrates a single nozzle chamber arrangement 4401 when it is in its quiescent state. The arrangement 4401 includes a nozzle chamber 4402 which is normally filled with ink so as to form a meniscus 4403 around an ink ejection nozzle 4404. The nozzle chamber 4402 is formed within a wafer 4405. The nozzle chamber 4402 supplied from an ink supply channel 4406 which can be etched through the wafer 4405 through the utilisation of a highly isotropic plasma etching system. A suitable etcher can be the Advance Silicon Etch (ASE) system available from Surface Technology Systems of the United Kingdom.
The top of the nozzle chamber arrangement 4401 includes a series of radially placed thermoactuator devices e.g. 4408, 4409. These devices comprise polytetrafluoroethylene (PTFE) layer actuators having an internal serpentine copper core. Upon heating of the copper core, the surrounding PTFE expands rapidly resulting in a generally downward movement of the actuator 4408, 4409. Hence, when it is desired to eject ink from the ink ejection nozzle 4404, a current is passed through the actuators 4408, 4409 which results in them generally rapidly bending downwards as illustrated in Fig. 639. The downward bending movement of actuators 4408, 4409 results in a substantial increase in pressure within the nozzle chamber 4402. The rapid increase in pressure in nozzle chamber 4402, in turn results in a rapid expansion of the meniscus 4403 as illustrated in Fig. 639.
The actuators are turned on for a limited time only and subsequently deactivated. A short time later the situation is as illustrated in Fig. 640 with the actuators 4408, 4409 rapidly returning to their original positions. This results in a general inflow of ink back into the nozzle chamber and a necking and breaking of the meniscus 4403 resulting in the ejection of a drop 4412. The necking and breaking of the meniscus is a consequence of the forward momentum of the ink associated with drop 4412 and the backward pressure experienced as a result of the return of the actuators 4408, 4409 to their original positions. The return of the actuator also results in a general inflow of ink 4406 from the supply channel as a result of surface tension effects and, eventually, the state returns to the quiescent position as illustrated in Fig. 638.
Fig. 641(a) and Fig. 641(b) illustrate the principle of operation of the thermal actuator. The thermal actuator is preferably constructed from a material 4414 having a high coefficient of thermal expansion. Embedded within the material 4414 is a series of heater elements e.g. 4415 which can be a series of conductive elements designed to carry a current. The conductive elements 4415 are heated by means of passing a current through the elements with the heating resulting in a general increase in temperature in the area around the heating elements. The increase in temperature causes a corresponding expansion of the PTFE which has a high coefficient of thermal expansion. Hence, as illustrated in Fig. 641(b), the PTFE is bent generally in a down direction.
Turning now to Fig. 642, there is illustrated a side perspective view of one nozzle arrangement constructed in accordance with the principles previously outlined. The nozzle chamber 4402 can be constructed by means of an isotropic surface etch of the wafer surface 4405. The wafer surface 4405 can include a CMOS layer including all the required power and drive circuits. Further, a series of leaf or petal type actuators e.g. 4408, 4409 are provided each having an internal copper core e.g. 4417 which winds in a serpentine nature so as to provide for substantially unhindered expansion of the actuator device. The operation of the actuator is similar to that as illustrated in Fig. 641 (a) and Fig. 641(b) such that, upon activation, the petals e.g. 4408 bend down as previously described. The ink supply channel 4406 can be created via a deep silicon back edge of the wafer utilising a plasma etcher or the like. The copper or aluminium coil e.g. 4417 can provide a complete circuit around each petal. A central arm 4418 which can include both metal and PTFE portions provides the main structural support for the petal arrangement in addition to providing a current trace for the conductive heaters.
Turning now to Fig. 643 to Fig. 650, there will now be explained one form of manufacturing of a printhead device operational in accordance with the principles of an embodiment. The device is preferably constructed utilising microelectromechanical (MEMS) techniques and can include the following construction techniques:
As shown initially in Fig. 643, the initial processing starting material is a standard semi-conductor wafer 4420 have a complete CMOS level 4421 to the first level metal step. The first level metal includes portions eg. 4422 which are utilized for providing power to the thermal actuator.
The first step, as illustrated in Fig. 644, is to etch a nozzle region down to the silicon wafer 4420 utilizing an appropriate mast
Next, as illustrated in Fig. 645, a 2 micron layer of polytetrafluoroethylene (PTFE) is deposited and etched so as to include vias eg. 4424 for interconnecting multiple levels.
Next, as illustrated in Fig. 646, the second level metal layer is deposited, masked and etched so as to form heater structure 4425. The heater structure 4425 including via interconnect 4426 with the lower aluminium layer.
Next, as illustrated in Fig. 647, a further 2µm layer of PTFE is deposited and etched to the depth of 1µm utilizing a nozzle rim mask so as to form nozzle rim eg. 4428 in addition to ink flow guide rails eg. 4429 which generally restrain any wicking along the surface of the PTFE layer. The guide rails eg. 4429 surround small thin slots and, as such, surface tension effects are a lot higher around these slots which in turn results in minimal outflow of ink during operation.
Next, as illustrated in Fig. 648, the PTFE is etched utilizing a nozzle and paddle mask so as to define nozzle portion 4430 and slots eg. 4431 and 4432.
Next, as illustrated in Fig. 649, the wafer is crystal calligraphically etched on the < 111 > plane utilizing a standard crystallographic etchant such as KOH. The etching forms chamber 4432, directly below the ink ejection nozzle.
Next, turning to Fig. 650, the ink supply channel 4434 can be etched from the back of the wafer utilizing a highly anisotropic etcher such as the STS etcher from Silicon Technology Systems of United Kingdom.
Obviously, an array of ink jet nozzles can be formed simultaneously with a portion of an array 4436 being illustrated in Fig. 651 with a portion of the printhead being formed simultaneously and diced by the ST etch etching process. The array 4436 shown provides for four column printing with each separate column attached to a different colour ink supply channel being supplied from the back of the wafer. The bond pads 4437 provide for electrical control of the ejection mechanism.
In this manner, large pagewidth printheads can be formulated so as to provide for a drop on demand ink ejection mechanism.
One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

1. Using a double sided polished wafer, complete a 0.5 micron, one poly, 2 metal CMOS process. This step is shown in Fig. 653. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. Fig. 652 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.
2. Etch the CMOS oxide layers down to silicon or second level metal using Mask 1. This mask defines the nozzle cavity and the edge of the chips. This step is shown in Fig. 653.
3. Deposit a thin layer (not shown) of a hydrophilic polymer, and treat the surface of this polymer for PTFE adherence.
4. Deposit 1.5 microns of polytetrafluoroethylene (PTFE).
5. Etch the PTFE and CMOS oxide layers to second level metal using Mask 2. This mask defines the contact vias for the heater electrodes. This step is shown in Fig. 654.
6. Deposit and pattern 0.5 microns of gold using a lift-off process using Mask 3. This mask defines the heater pattern. This step is shown in Fig. 655.
7. Deposit 1.5 microns of PTFE.
8. Etch 1 micron of PTFE using Mask 4. This mask defines the nozzle rim and the rim at the edge of the nozzle chamber. This step is shown in Fig. 656.
9. Etch both layers of PTFE and the thin hydrophilic layer down to silicon using Mask 5. This mask defines the gap at the edges of the actuator petals, and the edge of the chips. It also forms the mask for the subsequent crystallographic etch. This step is shown in Fig. 657.
10. Crystallographically etch the exposed silicon using KOH. This etch stops on <111> crystallographic planes, forming an inverted square pyramid with sidewall angles of 54.74 degrees. This step is shown in Fig. 658.
11. Back-etch through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 6. This mask defines the ink inlets which are etched through the wafer. The wafer is also diced by this etch. This step is shown in Fig. 659.
12. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer.
13. Connect the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.
14. Fill the completed print heads with ink and test them. A filled nozzle is shown in Fig. 660.

A Description of IJ44 T

An embodiment of the present invention discloses an inkjet printing device made up of a series of nozzle arrangements. Each nozzle arrangement includes a thermal surface actuator device which includes an L-shaped cross sectional profile and an air breathing edge such that actuation of the paddle actuator results in a drop being ejected from a nozzle utilizing a very low energy level.
Turning initially to Fig. 661 to Fig. 663, there will now be described the operational principles of an embodiment. In Fig. 661, there is illustrated schematically a sectional view of a single nozzle arrangement 4501 which includes an ink nozzle chamber 4502 containing an ink supply which is resupplied by means of an ink supply channel 4503. A nozzle rim 4504 is provided, across which a meniscus 4505 forms, with a slight bulge when in the quiescent state. A bend actuator device 4507 is formed on the top surface of the nozzle chamber and includes a side arm 4508 which runs generally parallel to the surface 4509 of the nozzle chamber wall so as to form an "air breathing slot" 4510 which assists in the low energy actuation of the bend actuator 4507. Ideally, the front surface of the bend actuator 4507 is hydrophobic such that a meniscus 4512 forms between the bend actuator 4507 and the surface 4509 leaving an air pocket in slot 4510.
When it is desired to eject a drop via the nozzle rim 4504, the bend actuator 4507 is actuated so as to rapidly bend down as illustrated in Fig. 662. The rapid downward movement of the actuator 4507 results in a general increase in pressure of the ink within the nozzle chamber 4502. This results in a outflow of ink around the nozzle rim 4504 and a general bulging of the meniscus 4505. The meniscus 4512 undergoes a low amount of movement.
The actuator device 4507 is then turned off so as to slowly return to its original position as illustrated in Fig. 663. The return of the actuator 4507 to its original position results in a reduction in the pressure within the nozzle chamber 4502 which results in a general back flow of ink into the nozzle chamber 4502. The forward momentum of the ink outside the nozzle chamber in addition to the back flow of ink 4515 results in a general necking and breaking off of the drop 4514. Surface tension effects then draw further ink into the nozzle chamber via ink supply channel 4503. Ink is drawn in the nozzle chamber 4503 until the quiescent position of Fig. 661 is again achieved.
The actuator device 4507 can be a thermal actuator which is heated by means of passing a current through a conductive core. Preferably, the thermal actuator is provided with a conductive core encased in a material such as polytetrafluoroethylene which has a high level coefficient of expansion. As illustrated in Fig. 664, the conductive core 4523 is preferably of a serpentine form and encased within a material 4524 having a high coefficient of thermal expansion. Hence, as illustrated in Fig. 664(b), on heating of the conductive core 4523, the material 4524 expands to a greater extent and is therefore caused to bend down in accordance with requirements.
Turning now to Fig. 665, there is illustrated a side perspective view, partly in section, of a single nozzle arrangement when in the state as described with reference to Fig. 662. The nozzle arrangement 4501 can be formed in practice on a semiconductor wafer 4520 utilizing standard MEMS techniques.
The silicon wafer 4520 preferably is processed so as to include a CMOS layer 4521 which can include the relevant electrical circuitry required for the full control of a series of nozzle arrangements 4501 formed so as to form a print head unit On top of the CMOS layer 4521 is formed a glass layer 4522 and an actuator 4507 which is driven by means of passing a current through a serpentine copper coil 4523 which is encased in the upper portions of a polytetrafluoroethylene (PTFE) layer 4524. Upon passing a current through the coil 4523, the coil 4523 is heated as is the PTFE layer 4524. PTFE has a very high coefficient of thermal expansion and hence expands rapidly. The coil 4523 constructed in a serpentine nature is able to expand substantially with the expansion of the PTFE layer 4524. The PTFE layer 4524 includes a lip portion 4508 which upon expansion, bends in a scooping motion as previously described. As a result of the scooping motion, the meniscus 4505 generally bulges and results in a consequential ejection of a drop of ink. The nozzle chamber 4504 is later replenished by means of surface tension effects in drawing ink through an ink supply channel 4503 which is etched through the wafer through the utilization of a highly an isotropic silicon trench etcher. Hence, ink can be supplied to the back surface of the wafer and ejected by means of actuation of the actuator 4507. The gap between the side arm 4508 and chamber wall 4509 allows for a substantial breathing effect which results in a low level of energy being required for drop ejection.
Obviously, a large number of arrangements 4501 of Fig. 665 can be formed together on a wafer with the arrangements being collected into print heads which can be of various sizes in accordance with requirements. Turning now to Fig. 666, there is illustrated one form of an array 4530 which is designed so as to provide three colour printing with each colour providing two spaced apart rows of nozzle arrangements 4534. The three groupings can comprise groupings 4531, 4532 and 4533 with each grouping supplied with a separate ink colour so as to provide for full colour printing capability. Additionally, a series of bond pads e.g. 4536 are provided for TAB bonding control signals to the print head 4530. Obviously, the arrangement 4530 of Fig. 666 illustrates only a portion of a print head which can be of a length as determined by requirements.
One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

1. Using a double sided polished wafer, complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process. Relevant features of the wafer at this step are shown in Fig. 668. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. Fig. 667 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.
2. Etch the CMOS oxide layers down to silicon or second level metal using Mask 1. This mask defines the nozzle cavity and the edge of the chips. Relevant features of the wafer at this step are shown in Fig. 668.
3. Plasma etch the silicon to a depth of 20 microns using the oxide as a mask. This step is shown in Fig. 669.
4. Deposit 23 microns of sacrificial material and planarize down to oxide using CMP. This step is shown in Fig. 670.
5. Etch the sacrificial material to a depth of 15 microns using Mask 2. This mask defines the vertical paddle at the end of the actuator. This step is shown in Fig. 671.
6. Deposit a thin layer (not shown) of a hydrophilic polymer, and treat the surface of this polymer for PTFE adherence.
7. Deposit 1.5 microns of polytetrafluoroethylene (PTFE).
8. Etch the PTFE and CMOS oxide layers to second level metal using Mask 3. This mask defines the contact vias for the heater electrodes. This step is shown in Fig. 672.
9. Deposit and pattern 0.5 microns of gold using a lift-off process using Mask 4. This mask defines the heater pattern. This step is shown in Fig. 673.
10. Deposit 1.5 microns of PTFE.
11. Etch 1 micron of PTFE using Mask 5. This mask defines the nozzle rim and the rim at the edge of the nozzle chamber. This step is shown in Fig. 674.
12. Etch both layers of PTFE and the thin hydrophilic layer down to the sacrificial layer using Mask 6. This mask defines the gap at the edges of the actuator and paddle. This step is shown in Fig. 675.
13. Back-etch through the silicon wafer to the sacrificial layer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 7. This mask defines the ink inlets which are etched through the wafer. This step is shown in Fig. 676.
14. Etch the sacrificial layers. The wafer is also diced by this etch.
15. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer.
16. Connect the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.
17. Fill the completed print heads with ink and test them. A filled nozzle is shown in Fig. 677.

Of course other forms of thermal actuator construction could be used and there will now be described one form of more complex thermal actuator construction of general use in MEMS devices such as ink jet printers.
Turning to Fig. 678, there are illustrated 4 MEMS actuators 4520, 4521, 4522, 4523 as constructed in accordance with a further embodiment. In Fig. 679, there is illustrated a close-up perspective view, partly in section, of a single thermal actuator constructed in accordance with the further embodiment. Each actuator, e.g. 4520, is based around three corrugated heat elements 4511, 4512 and 4513 which are interconnected 4514 to a cooler common current carrying line 4516. The two heater elements 4511, 4512 are formed on a bottom layer of the actuator 4520 with the heater element 4513 and common line 4516 being formed on a top layer of the actuator 4520. Each of the elements 4511, 4512, 4513, 4514 and 4516 can be formed from copper via means of deposition utilising semi-conductor fabrication techniques. The lines 4511, 4512, 4513, 4514 and 4516 are "encased" inside a polytetrafluoroethylene (PTFE) layer, e.g. 4518 which has a high coefficient of thermal expansion. The PTFE layer has a coefficient of thermal expansion which is much greater than that of the corresponding copper layers 4512, 4513, 4514 and 4516. The heater elements 4511-4513 are therefore constructed in a serpentine manner so as to allow the concertinaing of the heater elements upon heating and cooling so as to allow for their expansion substantially with the expansion of the PTFE layer 4518. The common line 4516, also constructed from copper is provided with a series of slots, e.g. 4519 which provide minimal concertinaing but allow the common layer 16 bend upwards and sideways when required.
Returning now to Fig. 678, the actuator, e.g. 4520, can be operated in a number of different modes. In a first mode, the bottom two heater elements 4511 and 4512 (Fig. 679) are activated. This causes the bottom portion of the polytetrafluoroethylene layer 4518 (Fig. 679) to expand rapidly while the top portion of the polytetrafluoroethylene layer 4518 (Fig. 679) remains cool. The resultant forces are resolved by an upwards bending of the actuator 4520 as illustrated in Fig. 678.
In a second operating mode, as illustrated in Fig. 678, the two heaters 4512, 4513 (Fig. 679) are activated causing an expansion of the PTFE layer 4518 (Fig. 679) on one side while the other side remains cool. The resulting expansion provides for a movement of the actuator 4520 to one side as illustrated in Fig. 678.
Finally, in Fig. 680, there is provided a further form of movement this time being up and to a side. This form of movement is activated by heating each of the resistive elements 4511-4513 (Fig. 679) which is resolved a movement of the actuator 4520 up and to the side.
Hence, through the controlled use of the heater elements 4511-4513 (Fig. 679), the position of the end point 4530 of the actuator 4520 (Fig. 678) can be fully controlled. To this end the PTFE portion 4518 is extended beyond the copper interconnect 4514 so as to provide a generally useful end portion 4530 for movement of objects to the like.
Turning to Fig. 681, there is illustrated an explosive perspective view of the construction of a single actuator. The actuator can be constructed utilising semi-conductor fabrication techniques and can be constructed on a wafer 4542 or other form of substrate. On top of the wafer 4542 is initially fabricated a sacrificial etch layer to form an underside portion utilising a mask shape of a actuator device. Next, a first layer of PTFE layer 4564 is deposited followed by the bottom level copper heater level 4545 forming the bottom two heaters. On top of this layer is formed a PTFE layer having vias for the interconnect 4514. Next, a second copper layer 4548 is provided for the top heater and common line with interconnection 4514 to the bottom copper layer. On top of the copper layer 4528 is provided a further polytetrafluoroethylene layer of layer 4544 with the depositing of polytetrafluoroethylene layer 4544 including the filling of the gaps, e.g. 4549 in the return common line of the copper layer. The filling of the gaps allows for a significant reduction in the possibilities of laminar separation of the polytetrafluoroethylene layers from the copper layer.
The two copper layers also allow the routing of current drive lines to each actuator.
Hence, an array of actuators could be formed on a single wafer and activated together so as to move an object placed near the array. Each actuator in the array can then be utilised to provide a circular motion of its end tip. Initially, the actuator can be in a rest position and then moved to a side position as illustrated for actuator 4520 in Fig. 678 then moved to an elevated side position as illustrated in Fig. 680 thereby engaging the object to be moved. The actuator can then be moved to nearly an elevated position as shown for actuator 4520 in Fig. 678. This resulting in a corresponding force being applied to the object to be moved. Subsequently, the actuator is returned to its rest position and the cycle begins again. Utilising continuous cycles, an object can be made to move in accordance with requirements. Additionally, the reverse cycle can be utilised to move an object in the opposite direction.
Preferably, an array of actuators are utilised thereby forming the equivalent of a cilia array of actuators. Multiple cilia arrays can then be formed on a single semi-conductor wafer which is later diced into separate cilia arrays. Preferably, the actuators on each cilia array are divided into groups with adjacent actuators being in different groups. The cilia array can then be driven in four phases with one in four actuators pushing the object to be moved in each portion of the phase cycle.
Ideally, the cilia arrays can then be utilised to move an object, for example to move a card past an information sensing device in a controlled manner for reading information stored on the card. In another example, the cilia arrays can be utilised to move printing media past a printing head in an ink jet printing device. Further, the cilia arrays can be utilised for manipulating means in the field of nano technology, for example in atomic force microscopy (AFM).
Preferably, so as to increase the normally low coefficient of friction of PTFE, the PTFE end 4520 is preferably treated by means of an ammonia plasma etch so as to increase the coefficient of friction of the end portion.
It would be evident to those skilled in the art that other arrangements maybe possible whilst still following in the scope of the present invention. For example, other materials and arrangements could be utilised. For example, a helical arrangement could be provided in place of the serpentine arrangement where a helical system is more suitable.
The presently disclosed ink jet printing technology is potentially suited to a wide range of printing system including: colour 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 colour and monochrome printers, colour and monochrome copiers, colour and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic "minilabs", video printers, PhotoCD printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.

Claims

An ink jet nozzle arrangement comprising:
a nozzle chamber for storing ink to be ejected;

and characterized by:
at least one moveable actuator paddle forming at least a portion of a first wall of said nozzle chamber; and

an ink ejection nozzle defined in said first wall,

wherein actuation of said at least one actuator paddle causes ejection of ink from said nozzle.
An ink jet nozzle arrangement as claimed in claim 1 wherein said actuation causes movement of said at least one actuator paddle inwards towards the centre of said nozzle chamber.
An ink jet nozzle arrangement as claimed in claim 1 or 2, wherein said at least one actuator paddle is actuated by means of a thermal actuator device.
An ink jet nozzle arrangement as claimed in any one of the preceding claims, wherein said thermal actuator device comprises a conductive resistive heating element encased within a second material having a high coefficient of thermal expansion.
An ink jet nozzle arrangement as claimed in any one of the preceding claims, wherein said element is serpentine shaped to allow for substantially unhindered expansion of said second material.
An ink ejection nozzle arrangement as claimed in any one of the preceding claims, wherein said first wall comprises a nozzle rim and a plurality of actuator paddles attached to the nozzle rim.
An ink ejection nozzle arrangement as claimed claim 6, wherein said actuator paddles are actuated in unison so as to eject ink from said nozzle chamber via said ink ejection nozzle.
An ink jet nozzle arrangement as claimed in claim 6, wherein said actuator paddles are arranged radially around said nozzle rim.
An ink jet nozzle arrangement as claimed in any one of claims 6 to 8, wherein said actuator paddles form a membrane between said nozzle chamber and an external atmosphere, wherein said paddles bend away from said external atmosphere so as to cause an increase in pressure within said nozzle chamber, thereby causing ejection of ink from said nozzle chamber.
An ink jet nozzle arrangement as claimed in any one of the preceding claims, wherein said arrangement is formed on a wafer utilizing micro-electro mechanical techniques, said wafer further comprises an ink supply channel in fluid communication with said nozzle chamber, said ink supply channel being etched through said wafer.
An inkjet nozzle arrangement as claimed in any one of claims 1 to 5, wherein one end of said paddle actuator traverses along a second wall of said nozzle chamber during ink ejection, said second wall being substantially perpendicular to said first wall.
An inkjet nozzle arrangement as claimed in claim 11, wherein said one end further comprises a flange sealingly engaged with said second wall.
An ink jet nozzle arrangement as claimed in claim 12 further comprising an ink supply channel interconnected to said nozzle chamber for the resupply of ink to said nozzle chamber, said interconnection comprising a slot in a wall of said chamber, said slot being substantially opposite an end of said flange.
An ink jet nozzle arrangement as claimed in claim 13 wherein said slot is arranged in a corner of a third wall of said chamber and wherein said second wall of said chamber further forms a wall of said ink supply channel.
An ink jet nozzle arrangement as claimed in claim 12 wherein said flange is configured to constrict the flow of ink into said nozzle chamber during movement of said paddle actuator.
An inkjet printhead comprising an inkjet nozzle arrangement as claimed in any one of the preceding claims.