Thermally actuated ink jet printing mechanism including a tapered heater element

[0002] The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, U.S. patent applications identified by their U.S. patent application serial numbers (USSN) are listed alongside the Australian applications from which the US patent applications claim the right of priority.

[0003] TATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Not applicable.

[0004] The present invention relates to the field of inkjet printers and discloses an inkjet printing system which includes a bend actuator connected to a paddle for the ejection of ink through an ink ejection nozzle. In particular, the present invention includes a thermally actuated ink jet including a tapered heater element.

[0005] Many different types of printing have been invented, a large number of which are presently in use. The known forms of printers 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.

[0006] 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.

[0007] 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).

[0008] Ink Jet printers themselves come in many different types. The utilisation 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.

[0009] U.S. Pat. No. 3,596,275 by Sweet also discloses a process of continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electrostatic 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).

[0010] 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, by Stemme in U.S. Pat. No. 3,747,120 (1972) which discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 which discloses a piezoelectric push mode actuation of the ink jet stream and by Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.

[0011] 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 by Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned reference 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 in communication with the confined space onto a relevant print media. Printing devices utilizing the electrothermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.

[0012] 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.

[0013] 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.

[0014] Firstly, inkjet printheads are normally constructed utilizing micro-electromechanical systems (MEMS) techniques. As such, they tend to rely upon the 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 more well 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, gallium arsenide etc. Hence, it is desirable, in any MEMS construction, to utilize well proven semi-conductor fabrication techniques which do not require the utilization of any “exotic” processes or materials. Of course, a certain degree of trade off will be undertaken in that if the use of the exotic material far outweighs its disadvantages then it may become desirable to utilize the material anyway.

[0015] 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.

[0016] 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 mechanisms with each ejection mechanism, in the worst case, being fired in a rapid sequence.

[0017] It is an object of the present invention to provide for 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 manner.

[0018] In accordance with a first aspect of the present invention, there is provided an inkjet nozzle arrangement comprising a nozzle chamber having a fluid ejection nozzle in one surface of the chamber; a paddle vane located within the chamber, the paddle vane being adapted to be actuated by an actuator device for the ejection of fluid out of the chamber via the fluid ejection nozzle; and a thermal actuator device located externally of the nozzle chamber and attached to the paddle vane.

[0019] Preferably, the thermal actuator device includes a lever arm having one end attached to the paddle vane and a second end attached to a substrate. The thermal actuator preferably operates upon conductive heating along a conductive trace and the conductive heating includes the generation of a substantial portion of the heat in the area adjacent the second end. The conductive heating preferably occurs along a region of reduced cross-section adjacent the second end.

[0020] Preferably, the thermal actuator includes first and second layers of a material having similar thermal properties such that, upon cooling after deposition of the layers, the two layers act against one another so as to maintain the actuator substantially in a predetermined position. The layers can comprise substantially either a copper nickel alloy or titanium nitride.

[0021] The paddle vane can be constructed from a similar conductive material to portions of the thermal actuator. However, the paddle vane is conductive insulated from the thermal actuator.

[0022] The thermal actuator can be constructed from multiple layers utilizing a single mask to etch the multiple layers.

[0023] The nozzle chamber preferably includes an actuator access port in a second surface of the chamber which comprises a slot in a periphery of the chamber and the actuator is able to move in an arc through the slot. The actuator can include an end portion which mates substantially with a wall of the chamber at substantially right angles to the paddle vane.

[0024] The paddle vane can include a dished portion substantially opposite the fluid ejection port.

[0025] In accordance with a further aspect of the present invention, there is provided a thermal actuator device including two layers of material having similar thermal properties such that upon cooling after deposition of the layers, the two layers act against one another so as to maintain the actuator substantially in a predetermined position.

[0026] In accordance with a further aspect of the present invention, there is provided a thermal actuator including a lever arm 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.

[0027] 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:

[0028] FIGS. 1-3 illustrate the operational principles of the preferred embodiment;

[0029] FIG. 4 is a side perspective view of a single nozzle arrangement of the preferred embodiment;

[0030] FIG. 5 illustrates a sectional side view of a single nozzle arrangement;

[0031] FIGS. 6 and 7 illustrate operational principles of the preferred embodiment;

[0032] FIGS. 8-15 illustrate the manufacturing steps in the construction of the preferred embodiment;

[0033] FIG. 16 illustrates a top plan view of a single nozzle;

[0034] FIG. 17 illustrates a portion of a single color printhead device;

[0035] FIG. 18 illustrates a portion of a three color printhead device;

[0036] FIG. 19 provides a legend of the materials indicated in FIGS. 20 to 29; and

[0037] FIGS. 20 to FIG. 29 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle.

[0038] In the preferred embodiment, there is provided a nozzle chamber having ink within it and a thermal actuator device interconnected to a paddle, the thermal actuator device being actuated so as to eject ink from the nozzle chamber. The preferred embodiment includes a particular thermal actuator structure which includes a tapered heater structure arm for providing positional heating of a conductive heater layer row. The actuator arm is connected to the paddle through a slotted wall in the nozzle chamber. The actuator arm has a mating shape so as to mate substantially with the surfaces of the slot in the nozzle chamber wall.

[0039] Turning initially to FIGS. 1-3, there is provided schematic illustrations of the basic operation of the device. A nozzle chamber 1 is provided filled with ink 2 by means of an ink inlet channel 3 which can be etched through a wafer substrate on which the nozzle chamber 1 rests. The nozzle chamber 1 includes an ink ejection nozzle or aperture 4 around which an ink meniscus forms.

[0040] Inside the nozzle chamber 1 is a paddle type device 7 which is connected to an actuator arm 8 through a slot in the wall of the nozzle chamber 1. The actuator arm 8 includes a heater means 9 located adjacent to a post end portion 10 of the actuator arm. The post 10 is fixed to a substrate.

[0041] When it is desired to eject a drop from the nozzle chamber, as illustrated in FIG. 2, the heater means 9 is heated so as to undergo thermal expansion. Preferably, the heater means itself or the other portions of the actuator arm 8 are built from materials having a high bend efficiency where the bend effeciency is defined as $\mathrm{bend}\mathrm{efficiency}=\frac{\mathrm{Young}’s\mathrm{Modulus}\times \left(\mathrm{Coefficient}\mathrm{of}\mathrm{thermal}\mathrm{Expansion}\right)}{\mathrm{Density}\times \mathrm{Specific}\mathrm{Heat}\mathrm{Capacity}}$

[0042] A suitable material for the heater elements is a copper nickel alloy which can be formed so as to bend a glass material.

[0043] The heater means is ideally located adjacent the post end portion 10 such that the effects of activation are magnified at the paddle end 7 such that small thermal expansions near post 10 result in large movements of the paddle end. The heating 9 causes a general increase in pressure around the ink meniscus 5 which expands, as illustrated in FIG. 2, in a rapid manner. The heater current is pulsed and ink is ejected out of the nozzle 4 in addition to flowing in from the ink channel 3. Subsequently, the paddle 7 is deactivated to again return to its quiescent position. The deactivation causes a general reflow of the ink into the nozzle chamber. The forward momentum of the ink outside the nozzle rim and the corresponding backflow results in a general necking and breaking off of a drop 12 which proceeds to the print media. The collapsed meniscus 5 results in a general sucking of ink into the nozzle chamber 1 via the in flow channel 3. In time, the nozzle chamber is refilled such that the position in FIG. 1 is again reached and the nozzle chamber is subsequently ready for the ejection of another drop of ink.

[0044] Turning now to FIG. 4, there is illustrated a single nozzle arrangement 20 of the preferred embodiment. The arrangement includes an actuator arm 21 which includes a bottom layer 22 which is constructed from a conductive material such as a copper nickel alloy (hereinafter called cupronickel) or titanium nitride (TiN). The layer 22, as will become more apparent hereinafter includes a tapered end portion near the end post 24. The tapering of the layer 22 near this end means that any conductive resistive heating occurs near the post portion 24.

[0045] The layer 22 is connected to the lower CMOS layers 26 which are formed in the standard manner on a silicon substrate surface 27. The actuator arm 21 is connected to an ejection paddle which is located within a nozzle chamber 28. The nozzle chamber includes an ink ejection nozzle 29 from which ink is ejected and includes a convoluted slot arrangement 30 which is constructed such that the actuator arm 21 is able to move up and down while causing minimal pressure fluctuations in the area of the nozzle chamber 28 around the slot 30.

[0046] FIG. 5 illustrates a sectional view through a single nozzle. FIG. 5 illustrates more clearly the internal structure of the nozzle chamber which includes the paddle 32 attached to the actuator arm 21 having face 33. Importantly, the actuator arm 21 includes, as noted previously, a bottom conductive layer 22. Additionally, a top layer 25 is also provided.

[0047] The utilization of a second layer 25 of the same material as the first layer 22 allows for more accurate control of the actuator position as will be described with reference to FIGS. 6 and 7. In FIG. 6, there is illustrated the example where a high Young's Moduli material 40 is deposited utilizing standard semiconductor deposition techniques and on top of which is further deposited a second layer 41 having a much lower Young's Moduli. Unfortunately, the deposition is likely to occur at a high temperature. Upon cooling, the two layers are likely to have different coefficients of thermal expansion and different Young's Moduli. Hence, in ambient room temperature, the thermal stresses are likely to cause bending of the two layers of material as shown at 42.

[0048] By utilizing a second deposition of the material having a high Young's Modulus, the situation in FIG. 7 is likely to result wherein the material 41 is sandwiched between the two layers 40. Upon cooling, the two layers 40 are kept in tension with one another so as to result in a more planar structure 45 regardless of the operating temperature. This principle is utilized in the deposition of the two layers 22, 25 of FIGS. 4-5.

[0049] Turning again to FIGS. 4 and 5, one important attribute of the preferred embodiments includes the slotted arrangement 30. The slotted arrangement results in the actuator arm 21 moving up and down thereby causing the paddle 32 to also move up and down resulting in the ejection of ink. The slotted arrangement 30 results in minimum ink outflow through the actuator arm connection and also results in minimal pressure increases in this area. The face 33 of the actuator arm is extended out so as to form an extended interconnect with the paddle surface thereby providing for better attachment. The face 33 is connected to a block portion 36 which is provided to provide a high degree of rigidity. The actuator arm 21 and the wall of the nozzle chamber 28 have a general corrugated nature so as to reduce any flow of ink through the slot 30. The exterior surface of the nozzle chamber adjacent the block portion 36 has a rim eg. 38 so to minimize wicking of ink outside of the nozzle chamber. A pit 37 is also provided for this purpose. The pit 37 is formed in the lower CMOS layers 26. An ink supply channel 39 is provided by means of back etching through the wafer to the back surface of the nozzle.

[0050] Turning to FIGS. 8-15 there will now be described the manufacturing steps utilized on the construction of a single nozzle in accordance with the preferred embodiment.

[0051] The manufacturing uses standard micro-electro mechanical techniques. For a general introduction to a micro-electro mechanical system (MEMS) reference is made to standard proceedings in this field including the proceeding of the SPIE (International Society for Optical Engineering) including volumes 2642 and 2882 which contain the proceedings of recent advances and conferences in this field.

[0052] 1. The preferred embodiment starts with a double sided polished wafer complete with, say, a 0.2 μm 1 poly 2 metal CMOS process providing for all the electrical interconnects necessary to drive the inkjet nozzle.

[0053] 2. As shown in FIG. 8, the CMOS wafer 26 is etched at 50 down to the silicon layer 27. The etching includes etching down to an aluminum CMOS layer 51, 52.

[0054] 3. Next, as illustrated in FIG. 9, a 1 μm layer of sacrificial material 55 is deposited. The sacrificial material can be aluminum or photosensitive polyimide.

[0055] 4. The sacrificial material is etched in the case of aluminum or exposed and developed in the case of polyimide in the area of the nozzle rim 56 and including a dished paddle area 57.

[0056] 5. Next, a 1 μm layer of heater material 60 (cupronickel or TiN) is deposited.

[0057] 6. A 3.4 μm layer of PECVD glass 61 is then deposited.

[0058] 7. A second layer 62 equivalent to the first layer 60 is then deposited .

[0059] 8. All three layers 60-62 are then etched utilizing the same mask. The utilization of a single mask substantially reduces the complexity in the processing steps involved in creation of the actuator paddle structure and the resulting structure is as illustrated in FIG. 10. Importantly, a break 63 is provided so as to ensure electrical isolation of the heater portion from the paddle portion.

[0060] 9. Next, as illustrated in FIG. 11, a 10 μm layer of sacrificial material 70 is deposited.

[0061] 10. The deposited layer is etched (or just developed if polyimide) utilizing a fourth mask which includes nozzle rim etchant holes 71, block portion holes 72 and post portion 73.

[0062] 11. Next a 10 μm layer of PECVD glass is deposited so as to form the nozzle rim 71, arm portions 72 and post portions 73.

[0063] 12. The glass layer is then planarized utilizing chemical mechanical planarization (CMP) with the resulting structure as illustrated in FIG. 11.

[0064] 13. Next, a 3 μm layer of PECVD glass is deposited.

[0065] 14. The deposited glass is then etched as shown in FIG. 12, to a depth of approximately 1 μm so as to form nozzle rim portion 81 and actuator interconnect portion 82.

[0066] 15. Next, as illustrated in FIG. 13, the glass layer is etched utilizing a 6th mask so as to form final nozzle rim portion 81 and actuator guide portion 82.

[0067] 16. Next, as illustrated in FIG. 14, the ink supply channel is back etched 85 from the back of the wafer utilizing a 7th mask. The etch can be performed utilizing a high precision deep silicon trench etcher such as the STS Advanced Silicon Etcher (ASE). This step can also be utilized to nearly completely dice the wafer.

[0068] 17. Next, as illustrated in FIG. 15 the sacrificial material can be stripped or dissolved to also complete dicing of the wafer in accordance with requirements.

[0069] 18. Next, the printheads can be individually mounted on attached molded plastic ink channels to supply ink to the ink supply channels.

[0070] 19. The electrical control circuitry and power supply can then be bonded to an etch of the printhead with a TAB film.

[0071] 20. Generally, if necessary, the surface of the printhead is then hydrophobized so as to ensure minimal wicking of the ink along external surfaces. Subsequent testing can determine operational characteristics.

[0072] Importantly, as shown in the plan view of FIG. 16, the heater element has a tapered portion adjacent the post 73 so as to ensure maximum heating occurs near the post.

[0073] Of course, different forms of inkjet printhead structures can be formed. For example, there is illustrated in FIG. 17, a portion of a single color printhead having two spaced apart rows 90, 91, with the two rows being interleaved so as to provide for a complete line of ink to be ejected in two stages. Preferably, a guide rail 92 is provided for proper alignment of a TAB film with bond pads 93. A second protective barrier 94 can also preferably be provided. Preferably, as will become more apparent with reference to the description of FIG. 18 adjacent actuator arms are interleaved and reversed.

[0074] Turning now to FIG. 18, there is illustrated a full color printhead arrangement which includes three series of inkjet nozzles 95, 96, 97 one each devoted to a separate color. Again, guide rails 98, 99 are provided in addition to bond pads, eg. 100. In FIG. 18, there is illustrated a general plan of the layout of a portion of a full color printhead which clearly illustrates the interleaved nature of the actuator arms.

[0075] The presently disclosed ink jet printing technology 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 trademark 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.

[0076] One alternative form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

[0077] 1. Using a double sided polished wafer 27, complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process to form layer 26. Relevant features of the wafer at this step are shown in FIG. 20. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 19 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.

[0078] 2. Etch oxide down to silicon or aluminum using Mask 1. This mask defines the nozzle chamber, the surface anti-wicking notch 37, and the heater contacts 110. This step is shown in FIG. 21.

[0079] 3. Deposit 1 micron of sacrificial material 55 (e.g. aluminum or photosensitive polyimide)

[0080] 4. Etch (if aluminum) or develop (if photosensitive polyimide) the sacrificial layer using Mask 2. This mask defines the nozzle chamber walls 112 and the actuator anchor point. This step is shown in FIG. 22.

[0081] 5. Deposit 1 micron of heater material 60 (e.g. cupronickel or TiN). If cupronickel, then deposition can consist of three steps—a thin anti-corrosion layer of, for example, TiN, followed by a seed layer, followed by electroplating of the 1 micron of cupronickel.

[0082] 6. Deposit 3.4 microns of PECVD glass 61.

[0083] 7. Deposit a layer 62 identical to step 5.

[0084] 8. Etch both layers of heater material, and glass layer, using Mask 3. This mask defines the actuator, paddle, and nozzle chamber walls. This step is shown in FIG. 23.

[0085] 9. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.

[0086] 10. Deposit 10 microns of sacrificial material 70.

[0087] 11. Etch or develop sacrificial material using Mask 4. This mask defines the nozzle chamber wall 112. This step is shown in FIG. 24.

[0088] 12. Deposit 3 microns of PECVD glass 113.

[0089] 13. Etch to a depth of (approx.) 1 micron using Mask 5. This mask defines the nozzle rim 81. This step is shown in FIG. 25.

[0090] 14. Etch down to the sacrificial layer using Mask 6. This mask defines the roof 114 of the nozzle chamber, and the nozzle itself. This step is shown in FIG. 26.

[0091] 15. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 7. This mask defines the ink inlets 30 which are etched through the wafer. The wafer is also diced by this etch. This step is shown in FIG. 27.

[0092] 16. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in FIG. 28.

[0093] 17. Mount the printheads 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.

[0094] 18. Connect the printheads 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.

[0095] 19. Hydrophobize the front surface of the printheads.

[0096] 20. Fill the completed printheads with ink 115 and test them. A filled nozzle is shown in FIG. 29.

[0097] It would be appreciated by a person skilled in the art 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.

[0098] Ink Jet Technologies

[0099] 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.

[0100] 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. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

[0101] 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.

[0102] 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:

[0103] low power (less than 10 Watts)

[0104] high resolution capability (1,600 dpi or more)

[0105] photographic quality output

[0106] low manufacturing cost

[0107] small size (pagewidth times minimum cross section)

[0108] high speed (<2 seconds per page).

[0109] 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 Reference to Related Applications.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] Tables of Drop-on-Demand Ink Jets

[0114] 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.

[0115] The following tables form the axes of an eleven dimensional table of ink jet types.

[0116] Actuator mechanism (18 types)

[0117] Basic operation mode (7 types)

[0118] Auxiliary mechanism (8 types)

[0119] Actuator amplification or modification method (17 types)

[0120] Actuator motion (19 types)

[0121] Nozzle refill method (4 types)

[0122] Method of restricting back-flow through inlet (10 types)

[0123] Nozzle clearing method (9 types)

[0124] Nozzle plate construction (9 types)

[0125] Drop ejection direction (5 types)

[0126] Ink type (7 types)

[0127] 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 Reference to Related Applications.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] The information associated with the aforementioned 11 dimensional matrix are set out in the following tables.