# Patent

## Title
Method of manufacture of an ink jet printer having a thermal actuator comprising an external coil spring

## Abstract

A method of manufacturing an ink jet printer having a thermal actuator comprising an external coil spring is disclosed wherein an array of nozzles are formed on a substrate utilising planar monolithic deposition, lithographic and etching processes. Multiple ink jet heads are preferably formed simultaneously on a single planar substrate. The substrate can be a silicon wafer. The print heads are preferably formed utilising standard vlsi/ulsi processing. Integrated drive electronics are preferably formed on the same substrate. The integrated drive electronics can comprise a CMOS process. Ink can be ejected from the substrate substantially normal to the substrate.

## Background
CROSS REFERENCES TO RELATED APPLICATIONS
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 (U.S. Ser. No.) are listed alongside the Australian applications from which the U.S. patent applications claim the right of priority.












CROSS-REFERENCED




AUSTRALIAN
U.S. PAT./PAT. APPLICATION


PROVISIONAL PATENT
(CLAIMING RIGHT OF PRIORITY FROM


APPLICATION NO.
AUSTRALIAN PROVISIONAL APPLICATION)
DOCKET NO.







PO7991
09/113,060
ART01


PO8505
09/113,070
ART02


PO7988
09/113,073
ART03


PO9395
09/112,748
ART04


PO8017
09/112,747
ART06


PO8014
09/112,776
ART07


PO8025
09/112,750
ART08


PO8032
09/112,746
ART09


PO7999
09/112,743
ART10


PO7998
09/112,742
ART11


PO8031
09/112,741
ART12


PO8030
09/112,740
ART13


PO7997
09/112,739
ART15


PO7979
09/113,053
ART16


PO8015
09/112,738
ART17


PO7978
09/113,067
ART18


PO7982
09/113,063
ART19


PO7989
09/113,069
ART20


PO8019
09/112,744
ART21


PO7980
09/113,058
ART22


PO8018
09/112,777
ART24


PO7938
09/113,224
ART25


PO8016
09/112,804
ART26


PO8024
09/112,805
ART27


PO7940
09/113,072
ART28


PO7939
09/112,785
ART29


PO8501
 09/112,797;
ART30



6,137,500


PO8500
09/112,796
ART31


PO7987
09/113,071
ART32


PO8022
09/112,824
ART33


PO8497
09/113,090
ART34


PO8020
09/112,823
ART38


PO8023
09/113,222
ART39


PO8504
09/112,786
ART42


PO8000
09/113,051
ART43


PO7977
09/112,782
ART44


PO7934
09/113,056
ART45


PO7990
09/113,059
ART46


PO8499
09/113,091
ART47


PO8502
09/112,753
ART48


PO7981
09/113,055
ART50


PO7986
09/113,057
ART51


PO7983
09/113,054
ART52


PO8026
09/112,752
ART53


PO8027
09/112,759
ART54


PO8028
09/112,757
ART56


PO9394
09/112,758
ART57


PO9396
09/113,107
ART58


PO9397
09/112,829
ART59


PO9398
09/112,792
ART60


PO9399
6,106,147
ART61


PO9400
09/112,790
ART62


PO9401
09/112,789
ART63


PO9402
09/112,788
ART64


PO9403
09/112,795
ART65


PO9405
09/112,749
ART66


PP0959
09/112,784
ART68


PP1397
09/112,783
ART69


PP2370
09/112,781
DOT01


PP2371
09/113,052
DOT02


PO8003
09/112,834
Fluid01


PO8005
09/113,103
Fluid02


PO9404
09/113,101
FIuid03


PO8066
09/112,751
IJ01


PO8072
09/112,787
IJ02


PO8040
09/112,802
IJ03


PO8071
09/112,803
IJ04


PO8047
09/113,097
IJ05


PO8035
09/113,099
IJ06


PO8044
09/113,084
IJ07


PO8063
09/113,066
IJ08


PO8057
09/112,778
IJ09


PO8056
09/112,779
IJ10


PO8069
09/113,077
IJ11


PO8049
09/113,061
IJ12


PO8036
09/112,818
IJ13


PO8048
09/112,816
IJ14


PO8070
09/112,772
IJ15


PO8067
09/112,819
IJ16


PO8001
09/112,815
IJ17


PO8038
09/113,096
IJ18


PO8033
09/113,068
IJ19


PO8002
09/113,095
IJ20


PO8068
09/112,808
IJ21


PO8062
09/112,809
IJ22


PO8034
09/112,780
IJ23


PO8039
09/113,083
IJ24


PO8041
09/113,121
IJ25


PO8004
09/113,122
IJ26


PO8037
09/112,793
IJ27


PO8043
09/112,794
IJ28


PO8042
09/113,128
IJ29


PO8064
09/113,127
IJ30


PO9389
09/112,756
IJ31


PO9391
09/112,755
IJ32


PP0888
09/112,754
IJ33


PP0891
09/112,811
IJ34


PP0890
09/112,812
IJ35


PP0873
09/112,813
IJ36


PP0993
09/112,814
IJ37


PP0890
09/112,764
IJ38


PP1398
09/112,765
IJ39


PP2592
09/112,767
IJ40


PP2593
09/112,768
IJ41


PP3991
09/112,807
IJ42


PP3987
09/112,806
IJ43


PP3985
09/112,820
IJ44


PP3983
09/112,821
IJ45


PO7935
09/112,822
IJM01


PO7936
09/112,825
IJM02


PO7937
09/112,826
IJM03


PO8061
09/112,827
IJM04


PO8054
09/112,828
IJM05


PO8065
6,071,750
IJM06


PO8055
09/113,108
IJM07


PO8053
09/113,109
IJM08


PO8078
09/113,123
IJM09


PO7933
09/113,114
IJM10


PO7950
09/113,115
IJM11


PO7949
09/113,129
IJM12


PO8060
09/113,124
IJM13


PO8059
09/113,125
IJM14


PO8073
09/113,126
IJM15


PO8076
09/113,119
IJM16


PO8075
09/113,120
IJM17


PO8079
09/113,221
IJM18


PO8050
09/113,116
IJM19


PO8052
09/113,118
IJM20


PO7948
09/113,117
IJM21


PO7951
09/113,113
IJM22


PO8074
09/113,130
IJM23


PO7941
09/113,110
IJM24


PO8077
09/113,112
IJM25


PO8058
09/113,087
IJM26


PO8051
09/113,074
IJM27


PO8045
6,110,754
IJM28


PO7952
09/113,088
IJM29


PO8046
09/112,771
IJM30


PO9390
09/112,769
IJM31


PO9392
09/112,770
IJM32


PP0889
09/112,798
IJM35


PP0887
09/112,801
IJM36


PP0882
09/112,800
IJM37


PP0874
09/112,799
IJM38


PP1396
09/113,098
IJM39


PP3989
09/112,833
IJM40


PP2591
09/112,832
IJM41


PP3990
 09/112,831;
IJM42



6,171,875


PP3986
09/112,830
IJM43


PP3984
09/112,836
IJM44


PP3982
09/112,835
IJM45


PP0895
09/113,102
IR01


PP0870
09/113,106
IR02


PP0869
09/113,105
IR04


PP0887
09/113,104
IR05


PP0885
09/112,810
IR06


PP0884
09/112,766
IR10


PP0886
09/113,085
IR12


PP0871
09/113,086
IR13


PP0876
09/113,094
IR14


PP0877
09/112,760
IR16


PP0878
09/112,773
IR17


PP0879
09/112,774
IR18


PP0883
09/112,775
IR19


PP0880
6,152,619
IR20


PP0881
09/113,092
IR21


PO8006
6,087,638
MEMS02


PO8007
09/113,093
MEMS03


PO8008
09/113,062
MEMS04


PO8010
6,041,600
MEMS05


PO8011
09/113,082
MEMS06


PO7947
6,067,797
MEMS07


PO7944
09/113,080
MEMS09


PO7946
6,044,646
MEMS10


PO9393
09/113,065
MEMS11


PP0875
09/113,078
MEMS12


PP0894
09/113,075
MEMS13









STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
FIELD OF THE INVENTION
The present invention relates to the field of inkjet printing and, in particular, discloses a method of manufacture of an ink jet printer having a thermal actuator comprising an external coil spring.
BACKGROUND OF THE INVENTION
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 add a substantial expense in manufacturing.
Additionally, side shooting ink jet technologies (U.S. Pat. No. 4,899,181) are often used but again, this limits 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. Pat. 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 inkjet print heads could be developed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide for a method of manufacture of an ink jet printer having a thermal actuator comprising an external coil spring.
In accordance with a first aspect of the present invention, there is provided a method of manufacture of an ink jet printer having a thermal actuator comprising an external coil spring wherein an array of nozzles are formed on a substrate utilising planar monolithic deposition, lithographic and etching processes.
Multiple ink jet heads are preferably formed simultaneously on a single planar substrate which can comprise a silicon wafer.
The print beads are preferably formed utilising standard vlsi/ulsi processing with integrated drive electronics are preferably formed on the same substrate. The integrated drive electronics may be formed utilising a CMOS fabrication process.
Ink can be ejected from the substrate substantially normal to the substrate.
In accordance with a further aspect of the present invention, there is provided a method of manufacture of a thermally actuated ink jet printer comprising a series of nozzle chambers which ejects ink via the utilization of a thermal actuator device, comprising the steps of: (a) initially providing a silicon wafer having a circuitry wafer layer including the electrical circuitry necessary for the operation of the thermal actuators on demand; (b) etching an ink inlet aperture in the circuitry wafer layer; (c) depositing and etching a first sacrificial layer on top of the silicon and circuitry wafer layer and etching the first sacrificial layer in an area defining a first portion of a nozzle chamber wall, a thermal actuator anchor and a thermal actuator end point; (d) depositing and etching a first inert material layer in defining a first actuator path starting at the thermal actuator anchor; (e) depositing and etching a first conductive material layer adjacent the first actuator path and attached to the first inert material layer; (f) depositing and etching a non-conductive layer over the first conductive material layer, the etching including etching predetermined vias for interconnection of the first conductive material layer with a second conductive material layer; (g) depositing and etching a second inert material layer on top of the first inert material layer; (h) depositing and etching a second conductive material layer on top of the non-conductive layer having a conductive interconnect to the first conductive material layer; (i) depositing and etching a series of inert material layers and sacrificial layers to form a nozzle chamber including an ink ejection hole and a nozzle chamber paddle attached to one of the inert material layers or the conductive layers at the thermal actuator end point; (j) etching an ink supply channel through the wafer to the nozzle chamber; and (k) etching away the sacrificial layers.
The conductive material layers are preferably formed from a material having a high Young's modulus such as titanium nitride. The first and second inert material layers can comprise substantially glass. The first actuator path can comprise substantially a coil.
The steps are preferably also utilized to simultaneously separate the wafer into separate printheads.



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. 1 illustrates a single ink ejection mechanism as constructed in accordance with the principles of the preferred embodiment;
FIG. 2 is a section through the line II—II of the actuator arm of FIG. 1;
FIGS. 3-5 illustrate the basic operation of the ink ejection mechanism of the preferred embodiment;
FIG. 3 shows the paddle before it has started moving.
FIG. 4 shows actuation with a meniscus formed.
FIG. 5 shows formation of an ink drop.
FIG. 6 is an exploded perspective view of an ink ejection mechanism.
FIG. 7 provides a legend of the materials indicated in FIGS. 8 to 22; and
FIGS. 8 to 22 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle.
FIG. 8 shows a wafer with a CMOS layer.
FIG. 9 shows formation of an ink inlet.
FIG. 10 shows etching to define the nozzle chamber wall and actuator anchor point.
FIG. 11 shows formation of a heater.
FIG. 12 shows definition of an actuator loop and a further heater layer.
FIG. 13 shows etching of sacrificial material to define the actuator and nozzle chamber wall.
FIG. 14 shows etching sacrificial material to define the nozzle chamber wall.
FIG. 15 shows plagiarized sacrificial material.
FIG. 16 shows etching to define the nozzle chamber wall and paddle.
FIG. 17 shows etching sacrificial material to define the nozzle chamber wall.
FIG. 18 shows etching to define the nozzle rim.
FIG. 19 shows etching to define the roof of the nozzle chamber and nozzle.
FIG. 20 shows etched ink inlets.
FIG. 21 shows etching sacrificial material to free the actuators and to separate into chips.
FIG. 22 shows a filled nozzle.



DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS
In the preferred embodiment, there is provided an inkjet printer having a series of ink ejection mechanisms wherein each ink ejection mechanism includes a paddle actuated by a coil actuator, the coil spring actuator having a unique cross section so as to provide for efficient actuation as a coiled thermal actuator.
Turning initially to FIG. 1, there is illustrated a single ink ejection mechanism 1 constructed in accordance with the principles of the preferred embodiment. The ink ejection mechanism 1 includes a chamber 2 having a rim 3. The chamber 2 is normally filled with ink which bulges out around a surface having a border along the edge of rim 3, the ink being retained within the chamber 2 by means of surface tension around the rim 3. Outside of the chamber 2 is located a thermal actuator device 5. The thermal actuator device 5 is interconnected via a strut 6 through a hole 7 to a paddle device within the chamber 2. The strut 6 and hole 7 are treated so as to be hydrophobic. Further, the hole 7 is provided in a thin elongated form so that surface tension characteristics also assist in stopping any ink from flowing out of the hole 7.
The thermal actuator device 5 comprises a first arm portion 9 which can be constructed from glass or other suitable material. A second arm portion 10 can be constructed from material such as titanium dibromide which has a large Young's modulus or bending strength and hence, when a current is passed through the titanium dibromide layer 10, it expands with a predetermined coefficient of thermal expansion. The thin strip 10 has a high Young's modulus or bending strength and therefore the thin strip 10 is able to bend the much thicker strip 9 which has a substantially lower Young's modulus.
Turning to FIG. 2, there is illustrated a cross-section of the arm through the line II—II of FIG. 1 illustrating the structure of the actuator device 5. As described previously, the actuator device 5 includes two titanium diboride portions 10a, 10b forming a circuit around the coil in addition to the glass portion 9 which also provides for electrical isolation of the two arms, the arms being conductively joined at the strut end.
Turning now to FIGS. 3-5, there will now be explaining the operation of the ink ejection mechanism 1 for the ejection of ink. Initially, before the paddle 8 has started moving, the situation is as illustrated in FIG. 3 with the nozzle chamber 2 being filled with ink and having a slightly bulging meniscus 12. Upon actuation of the actuator mechanism, the paddle 8 begins to move towards the nozzle rim 3 resulting in a substantial increase in pressure in the area around the nozzle rim 3. This in turn results in the situation as illustrated in FIG. 4 wherein the meniscus begins to significantly bulge as a result of the increases in pressure. Subsequently, the actuator is deactivated resulting in a general urge for the paddle 8 to return to its rest position. This results in the ink being sucked back into the chamber 2 which in turn results in the meniscus necking and breaking off into a meniscus 12 and ink drop 14, the drop 14 proceeding to a paper or film medium (not shown) for marking. The meniscus 12 has generally a concave shape and surface tension characteristics result in chamber refilling by means of in flow 13 from an ink supply channel etched through the wafer. The refilling is as a consequence of surface tension forces on the meniscus 12. Eventually the meniscus returns to its quiescent state as illustrated in FIG. 3.
Turning now to FIG. 6, there is illustrated an exploded perspective view of a single ink ejection mechanism 1 illustrating the various material layers. The ink ejection mechanism 1 can be formed as part of a large array of mechanisms forming a print head with multiple print heads being simultaneously formed on a silicon wafer 17. The wafer 17 is initially processed so as to incorporate a standard CMOS circuitry layer 18 which provides for the electrical interconnect for the control of the conductive portions of the actuator. The CMOS layer 18 can be completed with a silicon nitride passivation layer so as to protect it from subsequent processing steps in addition to ink flows through channel 20. The subsequent layers eg. 9, 10 and 2 can be deposited utilising standard micro-electro mechanical systems (MEMS) construction techniques including the deposit of sacrificial aluminum layers in addition to the deposit of the layers 10 constructed from titanium diboride the layer 9 constructed from glass material and the nozzle chamber proper 2 again constructed from titanium diboride. Each of these layers can be built up in a sacrificial material such as aluminum which is subsequently etched away. Further, an ink supply channel eg. 21 can be etched through the wafer 17. The etching can be by means of an isotropic crystallographic silicon etch or an isotropic dry etch. A dry etch system capable of high aspect ratio silicon trench etching such as the Surface Technology Systems (STS) Advance Silicon Etch (ASE) system is recommended.
Subsequent to construction of the nozzle arangement 1, it can be attached to an ink supply apparatus for supplying ink to the reverse surface of the wafer 17 so that ink can flow into chamber 2.
The external surface of nozzle chamber 2 including rim 3, in addition to the area surrounding slot 7, can then be hydrophobically treated so as to reduce the possibility of any ink exiting slot 7.
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 17, Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process to form layer 18. This step is shown in FIG. 8. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 7 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.
        2. Etch oxide layer 18 down to silicon or aluminum using Mask 1. This mask defines the ink inlet, the heater contact vias, and the edges of the print heads chip. This step is shown in FIG. 9.
        3. Deposit 1 micron of sacrificial material 30 (e.g. aluminum).
        4. Etch the sacrificial layer 30 using Mask 2, defining the nozzle chamber wall and the actuator anchor point. This step is shown in FIG. 10.
        5. Deposit 1 micron of glass 31.
        6. Etch the glass 31 using Mask 3, which defines the lower layer of the actuator loop.
        7. Deposit 1 micron of heater material 32, for example titanium nitride (TiN) or titanium diboride (TiB2). Planarize using CMW. Steps 5 to 7 form a ‘damascene’ process. This step is shown in FIG. 11.
        8. Deposit 0.1 micron of silicon nitride (not shown).
        9. Deposit 1 micron of glass 33.
        10. Etch the glass 33 using Mask 4, which defines the upper layer of the actuator loop.
        11. Etch the silicon nitride using Mask 5, which defines the vias connecting the upper layer of the actuator loop to the lower layer of the actuator loop.
        12. Deposit 1 micron of the same heater material 34 as in step 7 heater material 32. Planarize using CMP. Steps 8 to 12 form a ‘dual damascene’ process. This step is shown in FIG. 12.
        13. Etch the glass down to the sacrificial layer 30 using Mask 6, which defines the actuator and the nozzle chamber wall, with the exception of the nozzle chamber actuator slot. This step is shown in FIG. 13.
        14. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.
        15. Deposit 3 microns of sacrificial material 35.
        16. Etch the sacrificial layer 35 down to glass using Mask 7, which defines the nozzle chamber wall, with the exception of the nozzle chamber actuator slot. This step is shown in FIG. 14.
        17. Deposit 1 micron of PECVD glass 36 and planarize down to the sacrificial layer 35 using CMP. This step is shown in FIG. 15.
        18. Deposit 5 microns of sacrificial material 37.
        19. Etch the sacrificial material 37 down to glass using Mask 8. This mask defines the nozzle chamber wall and the paddle. This step is shown in FIG. 16.
        20. Deposit 3 microns of PECVD glass 38 and planaize down to the sacrificial layer 37 using CMP.
        21. Deposit 1 micron of sacrificial material 39.
        22. Etch the sacrificial material 39 down to glass using Mask 9. This mask defines the nozzle chamber wall. This step is shown in FIG. 17.
        23. Deposit 3 microns of PECVD glass 40.
        24. Etch to a depth of (approx.) 1 micron using Mask 10. This mask defines the nozzle rim 3. This step is shown in FIG. 18.
        25. Etch down to the sacrificial layer 39 using Mask 11. This mask defines the roof of the nozzle chamber, and the nozzle itself. This step is shown in FIG. 19.
        26. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 12. This mask defines the ink inlets 21 which are etched through the wafer. The wafer is also diced by this etch. This step is shown in FIG. 20.
        27. Etch the sacrificial material 30, 35, 37, 39. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in FIG. 21.
        28. 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.
        29. 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.
        30. Hydrophobize the front surface of the print heads.
        31. Fill the completed print heads with ink 41 and test them. A filled nozzle is shown in FIG. 22.
    
    


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 in-built 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 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.
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. 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 print head, but is a major impediment to the fabrication of pagewidth print heads 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 above 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 print head is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the print head is 100 mm long, with a width which depends upon the ink jet type. The smallest print head designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The print heads each contain 19,200 nozzles plus data and control circuity.
Ink is supplied to the back of the print head 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 print head 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 which matches the docket numbers in the 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 print heads 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, a printer 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 Bubblejet


bubble
heater heats the ink to
generated
Ink carrier limited to
1979 Endo et al GB



above boiling point,
Simple construction
water
patent 2,007,162



transferring significant
No moving parts
Low efficiency
Xerox heater-in-pit



heat to the aqueous
Fast operation
High temperatures
1990 Hawkins et al



ink. A bubble
Small chip area
required
U.S. Pat No. 4,899,181



nucleates and quickly
required for actuator
High mechanical
Hewlett-Packard TIJ



forms, expelling the

stress
1982 Vaught et al



ink.

Unusual materials
U.S. Pat. No. 4,490,728



The efficiency of the

required



process is low, with

Large drive



typically less than

transistors



0.05% of the electrical

Cavitation causes



energy being

actuator failure



transformed into

Kogation reduces



kinetic energy of the

bubble formation



drop.

Large print heads





are difficult to





fabricate


Piez-
A piezoelectric crystal
Low power
Very large area
Kyser et al U.S. Pat. No.


electric
such as lead
consumption
required for actuator
3,946,398



lanthanum zirconate
Many ink types can
Difficult to integrate
Zoltan U.S. Pat. No.



(PZT) is electrically
be used
with electronics
3,683,212



activated, and either
Fast operation
High voltage drive
1973 Stemme U.S. Pat. No.



expands, shears, or
High efficiency
transistors required
3,747,120



bends to apply

Full pagewidth print
Epson Stylus



pressure to the ink,

heads impractical
Tektronix



ejecting drops.

due to actuator size
IJ04





Requires electrical





poling in high field





strengths during





manufacture


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


strictive
used to activate
consumption
strain (approx.
et all JP 253401/96



electrostriction in
Many ink types can
0.01%)
IJ04



relaxor materials such
be used
Large area required



as lead lanthanum
Low thermal
for actuator due to



zirconate titanate
expansion
low strain



(PLZT) or lead
Electric field
Response speed is



magnesium niobate
strength required
marginal ( ̃10 μs)



(PMN).
(approx. 3.5 V/μm)
High voltage drive




can be generated
transistors required




without difficulty
Full pagewidth print




Does not require
heads impractical




electrical poling
due to actuator size


Ferro-
An electric field is
Low power
Difficult to integrate
IJ04


electric
used to induce a phase
consumption
with electronics



transition between the
Many ink types can
Unusual materials



antiferroelectric (AFE)
be used
such as PLZSnT are



and ferroelectric (FE)
Fast operation
required



phase. Perovskite
(<1 μs)
Actuators require a



materials such as tin
Relatively high
large area



modified lead
longitudinal strain



lanthanum zirconate
High efficiency



titanate (PLZSnT)
Electric field



exhibit large strains of
strength of around 3



up to 1% associated
V/μm can be readily



with the AFE to FE
provided



phase transition.


Electro-
Conductive plates are
Low power
Difficult to operate
IJ02, IJ04


static
separated by a
consumption
electrostatic devices


plates
compressible or fluid
Many ink types can
in an aqueous



dielectric (usually air).
be used
environment



Upon application of a
Fast operation
The electrostatic



voltage, the plates

actuator will



attract each other and

normally need to be



displace ink, causing

separated from the



drop ejection. The

ink



conductive plates may

Very large area



be in a comb or

required to achieve



honeycomb structure,

high forces



or stacked to increase

High voltage drive



the surface area and

transistors may be



therefore the force.

required





Full pagewidth print





heads are not





competitive due to





actuator size


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


static pull
is applied to the ink,
consumption
required
U.S. Pat. No. 4,799,068


on ink
whereupon
Low temperature
May be damaged by
1989 Miura et al,



electrostatic attraction

sparks due to air
U.S. Pat. No. 4,810,954



accelerates the ink

breakdown
Tone-jet



towards the print

Required field



medium.

strength increases as





the drop size





decreases





High voltage drive





transistors required





Electrostatic field





attracts dust


Permanent
An electromagnet
Low power
Complex fabrication
IJ07, IJ10


magnet
directly attracts a
consumption
Permanent magnetic


electro-
permanent magnet,
Many ink types can
material such as


magnetic
displacing ink and
be used
Neodymium Iron



causing drop ejection.
Fast operation
Boron (NdFeB)



Rare earth magnets
High efficiency
required.



with a field strength
Easy extension from
High local currents



around 1 Tesla can be
single nozzles to
required



used. Examples are:
pagewidth
Copper metalization



Samarium Cobalt
heads
should be used for



(SaCo) and magnetic

long



materials in the

electromigration



neodytnium iron boron

lifetime and low



family (NdFeB,

resistivity



NdDyFeBNb,

Pigmented inks are



NdDyFeB, etc)

usually infeasible





Operating





temperature limited





to the Curie





temperature (around





540 K.)


Soft
A solenoid induced a
Low power
Complex fabrication
IJ01, IJ05, IJ08,


magnetic
magnetic field in a soft
consumption
Materials not
IJ10, IJ12, IJ14,


core
magnetic core or yoke
Many ink types can
usually present in a
IJ15, IJ17


electro-
fabricated from a
be used
CMOS fab such as


magnetic
ferrous material such
Fast operation
NiFe, CoNiFe, or



as electroplated iron
High efficiency
CoFe are required



alloys such as CoNiFe
Easy extension from
High local currents



[1], CoFe, or NiFe
single nozzles to
required



alloys. Typically, the
pagewidth print
Copper metalization



soft magnetic material
heads
should be used for



is in two parts, which

long



are normally held

electromigration



apart by a spring.

lifetime and low



When the solenoid is

resistivity



actuated, the two parts

Electroplating is



attract, displacing the

required



ink.

High 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, IJ13,


force
acting on a current
consumption
twisting motion
IJ16



carrying wire in a
Many ink types can
Typically, only a



magnetic field is
be used
quarter of the



utilized.
Fast operation
solenoid length



This allows the
High efficiency
provides force in a



magnetic field to be
Easy extension from
useful direction



supplied externally to
single nozzles to
High local currents



the print head, for
pagewidth print
required



example with rare
heads
Copper metalization



earth permanent

should be used for



magnets.

long



Only the current

electromigration



carrying wire need be

lifetime and low



fabricated on the print-

resistivity



head, simplifying

Pigmented inks are



materials

usually infeasible



requirements.


Magneto-
The actuator uses the
Many ink types can
Force acts as a
Fischenbeck, U.S. Pat. No.


striction
giant magnetostrictive
be used
twisting motion
4,032,929



effect of materials
Fast operation
Unusual materials
IJ25



such as Terfenol-D (an
Easy extension from
such as Terfenol-D



alloy of terbium,
single nozzles to
are required



dysprosium and iron
pagewidth print
High local currents



developed at the Naval
heads
required



Ordnance Laboratory,
High force is
Copper metalization



hence Ter-Fe-NOL).
available
should be used for



For best efficiency, the

long



actuator should be pre-

electromigration



stressed to approx. 8

lifetime and low



MPa.

resistivity





Pre-stressing may





be required


Surface
Ink under positive
Low power
Requires
Silverbrook, EP


tension
pressure is held in a
consumption
supplementary force
0771 658 A2 and


reduction
nozzle by surface
Simple construction
to effect drop
related patent



tension. The surface
No unusual
separation
applications



tension of the ink is
materials required in
Requires special ink



reduced below the
fabrication
surfactants



bubble threshold,
High efficiency
Speed may be



causing the ink to
Easy extension from
limited by surfactant



egress from the
single nozzles to
properties



nozzle.
pagewidth print




heads


Viscosity
The ink viscosity is
Simple construction
Requires
Silverbrook, EP


reduction
locally reduced to
No unusual
supplementary force
0771 658 A2 and



select which drops are
materials required in
to effect drop
related patent



to be ejected. A
fabrication
separation
applications



viscosity reduction can
Easy extension from
Requires special ink



be achieved
single nozzles to
viscosity properties



electrothermally with
pagewidth print
High speed is



most inks, but special
heads
difficult to achieve



inks can be engineered

Requires oscillating



for a 100:1 viscosity

ink pressure



reduction.

A high temperature





difference (typically





80 degrees) is





required


Acoustic
An acoustic wave is
Can operate without
Complex drive
1993 Hadimioglu et



generated and
a nozzle plate
circuitry
al, EUP 550,192



focussed upon the

Complex fabrication
1993 Elrod et al,



drop ejection region.

Low efficiency
EUP 572,220





Poor control of drop





position





Poor control of drop





volume


Thermo-
An actuator which
Low power
Efficient aqueous
IJ03, IJ09, IJ17,


elastic
relies upon differential
consumption
operation requires a
IJ18, IJ19, IJ20,


bend
thermal expansion
Many ink types can
thermal insulator on
IJ21, IJ22, IJ23,


actuator
upon Joule heating is
be used
the hot side
IJ24, IJ27, IJ28,



used.
Simple planar
Corrosion
IJ29, IJ30, IJ31,




fabrication
prevention can be
IJ32, IJ33, IJ34,




Small chip area
difficult
IJ35, IJ36, IJ37,




required for each
Pigmented inks may
IJ38 ,IJ39, IJ40,




actuator
be infeasible, as
IJ41




Fast operation
pigment particles




High efficiency
may jam the bend




CMOS compatible
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 very
High force can be
Requires special
IJ09, IJ17, IJ18,


thermo-
high coefficient of
generated
material (e.g. PTFE)
IJ20, IJ21, IJ22,


elastic
thermal expansion
Three methods of
Requires a PTFE
IJ23, IJ24, IJ27,


actuator
(CTE) such as
PTFE deposition are
deposition process,
IJ28, IJ29, IJ30,



polytetrafluoroethylene
under development:
which is not yet
IJ31, IJ42, IJ43,



(PTFE) is used. As
chemical vapor
standard in ULSI
IJ44



high CTE materials
deposition (CVD),
fabs



are usually non-
spin coating, and
PTFE deposition



conductive, a heater
evaporation
cannot be followed



fabricated from a
PTFE is a candidate
with high



conductive material is
for low dielectric
temperature (above



incorporated. A 50 μm
constant insulation
350° C.) processing



long PTFE bend
in ULSI
Pigmented inks may



actuator with
Very low power
be infeasible, as



polysilicon heater and
consumption
pigment particles



15 mW power input
Many ink types can
may jam the bend



can provide 180 μN
be used
actuator



force and 10 μm
Simple planar



deflection. Actuator
fabrication



motions include:
Small chip area



Bend
required for each



Push
actuator



Buckle
Fast operation



Rotate
High efficiency




CMOS compatible




voltages and




currents




Easy extension from




single nozzles to




pagewidth print




heads


Conduct-
A polymer with a high
High force can he
Requires special
IJ24


ive
coefficient of thermal
generated
materials


polymer
expansion (such as
Very low power
development (High


thermo-
PTFE) is doped with
consumption
CTE conductive


elastic
conducting substances
Many ink types can
polymer)


actuator
to increase its
be used
Requires a PTFE



conductivity to about 3
Simple planar
deposition process,



orders of magnitude
fabrication
which is not yet



below that of copper.
Small chip area
standard in ULSI



The conducting
required for each
fabs



polymer expands
actuator
PTFE deposition



when resistively
Fast operation
cannot be followed



heated.
High efficiency
with high



Examples of
CMOS compatible
temperature (above



conducting dopants
voltages and
350° C.) processing



include:
currents
Evaporation and



Carbon nanotubes
Easy extension from
CVD deposition



Metal fibers
single nozzles to
techniques cannot



Conductive polymers
pagewidth print
be used



such as doped
heads
Pigmented inks may



polythiophene

be infeasible, as



Carbon granules

pigment particles





may jam the bend





actuator


Shape
A shape memory alloy
High force is
Fatigue limits
IJ26


memory
such as TiNi (also
available (stresses
maximum number


alloy
known as Nitinol -
of hundreds of MPa)
of cycles



Nickel Titanium alloy
Large strain is
Low strain (1%) is



developed at the Naval
available (more than
required to extend



Ordnance Laboratory)
3%)
fatigue resistance



is thermally switched
High corrosion
Cycle rate limited



between its weak
resistance
by heat removal



martensitic state and
Simple construction
Requires unusual



its high stiffness
Easy extension from
materials (TiNi)



austenic state. The
single nozzles to
The latent heat of



shape of the actuator
pagewidth print
transformation must



in its martensitic state
heads
be provided



is deformed relative to
Low voltage
High current



the austenic shape.
operation
operation



The shape change

Requires pre-



causes ejection of a

stressing to distort



drop.

the martensitic state


Linear
Linear magnetic
Linear Magnetic
Requires unusual
IJ12


Magnetic
actuators include the
actuators can be
semiconductor


Actuator
Linear Induction
constructed with
materials such as



Actuator (LIA), Linear
high thrust, long
soft magnetic alloys



Permanent Magnet
travel, and high
(e.g. CoNiFe)



Synchronous Actuator
efficiency using
Some varieties also



(LPMSA), Linear
planar
require permanent



Reluctance
semiconductor
magnetic materials



Synchronous Actuator
fabrication
such as Neodymium



(LRSA), Linear
techniques
iron boron (NdFeB)



Switched Reluctance
Long actuator travel
Requires complex



Actuator (LSRA), and
is available
multi-phase drive



the Linear Stepper
Medium force is
circuitry



Actuator (LSA).
available
High current




Low voltage
operation




operation



















BASIC OPERATION MODE












Description
Advantages
Disadvantages
Examples















Actuator
This is the simplest
Simple operation
Drop repetition rate
Thermal ink jet


directly
mode of operation: the
No external fields
is usually limited to
Piezoelectric inkjet


pushes ink
actuator directly
required
around 10 kHz.
IJ01, IJ02, IJ03,



supplies sufficient
Satellite drops can
However, this is not
IJ04, IJ05, IJ06,



kinetic energy to expel
be avoided if drop
fundamental to the
IJ07, IJ09, IJ11,



the drop. The drop
velocity is less than
method, but is
IJ12, IJ14, IJ16,



must have a sufficient
4 m/s
related to the refill
IJ20, IJ22, IJ23,



velocity to overcome
Can be efficient,
method normally
IJ24, IJ25, IJ26,



the surface tension.
depending upon the
used
IJ27, IJ28, IJ29,




actuator used
All of the drop
IJ30, IJ31, IJ32,





kinetic energy must
IJ33, IJ34, IJ35,





be provided by the
IJ36, IJ37, IJ38,





actuator
IJ39, IJ40, IJ41,





Satellite drops
IJ42, IJ43, IJ44





usually form if drop





velocity is greater





than 4.5 m/s


Proximity
The drops to be
Very simple print
Requires close
Silverbrook, EP



printed are selected by
head fabrication can
proximity between
0771 658 A2 and



some manner (e.g.
be used
the print head and
related patent



thermally induced
The drop selection
the print media or
applications



surface tension
means does not need
transfer roller



reduction of
to provide the
May require two



pressurized ink).
energy required to
print heads printing



Selected drops are
separate the drop
alternate rows of the



separated from the ink
from the nozzle
image



in the nozzle by

Monolithic color



contact with the print

print heads are



medium or a transfer

difficult



roller.



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


static pull
printed are selected by
head fabrication can
electrostatic field
0771 658 A2 and


on ink
some manner (e.g.
be used
Electrostatic field
related patent



thermally induced
The drop selection
for small nozzle
applications



surface tension
means does not need
sizes is above air
Tone-Jet



reduction of
to provide the
breakdown



pressurized ink).
energy required to
Electrostatic field



Selected drops are
separate the drop
may attract dust



separated from the ink
from the nozzle



in the nozzle by a




strong electric field.



Magnetic
The drops to be
Very simple print
Requires magnetic
Silverbrook, EP


pull on ink
printed are selected by
head fabrication can
ink
0771 658 A2 and



some manner (e.g.
be used
Ink colors other than
related patent



thermally induced
The drop selection
black are difficult
applications



surface tension
means does not need
Requires very high



reduction of
to provide the
magnetic fields



pressurized ink).
energy required to



Selected drops are
separate the drop



separated from the ink
from the nozzle



in the nozzle by a



strong magnetic field



acting on the magnetic



ink.


Shutter
The actuator moves a
High speed (>50
Moving parts are
IJ13, IJ17, IJ21



shutter to block ink
kHz) operation can
required



flow to the nozzle. The
be achieved due to
Requires ink



ink pressure is pulsed
reduced refill time
pressure modulator



at a multiple of the
Drop timing can be
Friction and wear



drop ejection
very accurate
must be considered



frequency.
The actuator energy
Stiction is possible




can be very low


Shuttered
The actuator moves a
Actuators with
Moving parts are
IJ08, IJ15, IJ18,


grill
shutter to block ink
small travel can be
required
IJ19



flow through a grill to
used
Requires ink



the nozzle. The shutter
Actuators with
pressure modulator



movement need only
small force can be
Friction and wear



be equal to the width
used
must be considered



of the grill holes.
High speed (>50
Stiction is possible




kHz) operation can




be achieved


Pulsed
A pulsed magnetic
Extremely low
Requires an external
IJ10


magnetic
field attracts an ‘ink
energy operation is
pulsed magnetic


pull on ink
pusher’ at the drop
possible
field


pusher
ejection frequency. An
No heat dissipation
Requires special



actuator controls a
problems
materials for both



catch, which prevents

the actuator and the



the ink pusher from

ink pusher



moving when a drop is

Complex



not to be ejected.

construction



















AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES)












Description
Advantages
Disadvantages
Examples















None
The actuator directly
Simplicity of
Drop ejection
Most ink jets,



fires the ink drop, and
construction
energy must be
including



there is no external
Simplicity of
supplied by
piezoelectric and



field or other
operation
individual nozzle
thermal bubble.



mechanism required.
Small physical size
actuator
IJ01, IJ02, IJ03,






IJ04, IJ05, 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 external
Silverbrook, EP


ink
oscillates, providing
pressure can provide
ink pressure
0771 658 A2 and


pressure
much of the drop
a refill pulse,
oscillator
related patent


(including
ejection energy. The
allowing higher
Ink pressure phase
applications


acoustic
actuator selects which
operating speed
and amplitude must
IJ08, IJ13, IJ15,


stimu-
drops are to be fired
The actuators may
be carefully
IJ17, IJ18, IJ19,


lation)
by selectively
operate with much
controlled
IJ21



blocking or enabling
lower energy
Acoustic reflections



nozzles. The ink
Acoustic lenses can
in the ink chamber



pressure oscillation
be used to focus the
must be designed



may be achieved by
sound on the
for



vibrating the print
nozzles



head, or preferably by



an actuator in the ink



supply.


Media
The print head is
Low power
Precision assembly
Silverbrook, EP


proximity
placed in close
High accuracy
required
0771 658 A2 and



proximity to the print
Simple print head
Paper fibers may
related patent



medium. Selected
construction
cause problems
applications



drops protrude from

Cannot print on



the print head further

rough substrates



than unselected drops,



and contact the print



medium. The drop



soaks into the medium



fast enough to cause



drop separation.


Transfer
Drops are printed to a
High accuracy
Bulky
Silverbrook, EP


roller
transfer roller instead
Wide range of print
Expensive
0771 658 A2 and



of straight to the print
substrates can be
Complex
related patent



medium. A transfer
used
construction
applications



roller can also be used
Ink can be dried on

Tektronix hot melt



for proximity drop
the transfer roller

piezoelectric ink jet



separation.


Any of the IJ series


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


static
used to accelerate
Simple print head
required for
0771 658 A2 and



selected drops towards
construction
separation of small
related patent



the print medium.

drops is near or
applications





above air
Tone-Jet





breakdown


Direct
A magnetic field is
Low power
Requires magnetic
Silverbrook, EP


magnetic
used to accelerate
Simple print head
ink
0771 658 A2 and


field
selected drops of
construction
Requires strong
related patent



magnetic ink towards

magnetic field
applications



the print medium.



Cross
The print head is
Does not require
Requires external
IJ06, IJ16


magnetic
placed in a constant
magnetic materials
magnet


field
magnetic field. The
to be integrated in
Current densities



Lorenz force in a
the print head
may be high,



current carrying wire
manufacturing
resulting in



is used to move the
process
electromigration



actuator.

problems


Pulsed
A pulsed magnetic
Very low power
Complex print head
IJ10


magnetic
field is used to
operation is possible
construction


field
cyclically attract a
Small print head
Magnetic materials



paddle, which pushes
size
required in print



on the ink. A small

head



actuator moves a



catch, which



selectively prevents



the paddle from



moving.



















ACTUATOR AMPLIFICATION OR MODIFICATION METHOD












Description
Advantages
Disadvantages
Examples















None
No actuator
Operational
Many actuator
Thermal Bubble Ink



mechanical
simplicity
mechanisms have
jet



amplification is used.

insufficient travel,
IJ01, IJ02, IJ06,



The actuator directly

or insufficient force,
IJ07, IJ16, IJ25,



drives the drop

to efficiently drive
IJ26



ejection process.

the drop ejection





process


Differ-
An actuator material
Provides greater
High stresses are
Piezoelectric


ential
expands more on one
travel in a reduced
involved
IJ03, IJ09, IJ17,


expansion
side than on the other.
print head area
Care must be taken
IJ18, IJ19, IJ20,


bend
The expansion may be

that the materials do
IJ21, IJ22, IJ23,


actuator
thermal, piezoelectric,

not delaminate
IJ24, IJ27, IJ29,



magnetostrictive, or

Residual bend
IJ30, IJ31, IJ32,



other mechanism. The

resulting from high
IJ33, IJ34, IJ35,



bend actuator converts

temperature or high
IJ36, IJ37, IJ38,



a high force low travel

stress during
IJ39, IJ42, IJ43,



actuator mechanism to

formation
IJ44



high travel, lower




force mechanism.



Transient
A trilayer bend
Very good
High stresses are
IJ40, IJ41


bend
actuator where the two
temperature stability
involved


actuator
outside layers are
High speed, as a
Care must be taken



identical. This cancels
new drop can be
that the materials do



bend due to ambient
fired before heat
not delaminate



temperature and
dissipates



residual stress. The
Cancels residual



actuator only responds
stress of formation



to transient heating of



one side or the other.


Reverse
The actuator loads a
Better coupling to
Fabrication
IJ05, IJ11


spring
spring. When the
the ink
complexity



actuator is turned off,

High stress in the



the spring releases.

spring



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 travel
Increased
Some piezoelectric


stack
actuators are stacked.
Reduced drive
fabrication
ink jets



This can be
voltage
complexity
IJ04



appropriate where

Increased possibility



actuators require high

of short circuits due



electric field strength,

to pinholes



such as electrostatic



and piezoelectric



actuators.


Multiple
Multiple smaller
Increases the force
Actuator forces may
IJ12, IJ13, IJ18,


actuators
actuators are used
available from an
not add linearly,
IJ20, IJ22, IJ28,



simultaneously to
actuator
reducing efficiency
IJ42, IJ43



move the ink. Each
Multiple actuators



actuator need provide
can be positioned to



only a portion of the
control ink flow



force required.
accurately


Linear
A linear spring is used
Matches low travel
Requires print head
IJ15


Spring
to transform a motion
actuator with higher
area for the spring



with small travel and
travel requirements



high force into a
Non-contact method



longer travel, lower
of motion



force motion.
transformation


Coiled
A bend actuator is
Increases travel
Generally restricted
IJ17, IJ21, IJ34,


actuator
coiled to provide
Reduces chip area
to planar
IJ35



greater travel in a
Planar
implementations



reduced chip area.
implementations are
due to extreme




relatively easy to
fabrication difficulty




fabricate.
in other orientations.


Flexure
A bend actuator has a
Simple means of
Care must be taken
IJ10, IJ19, IJ33


bend
small region near the
increasing travel of
not to exceed the


actuator
fixture point, which
a bend actuator
elastic limit in the



flexes much more

flexure area



readily than the

Stress distribution is



remainder of the

very uneven



actuator. The actuator

Difficult to



flexing is effectively

accurately model



converted from an

with finite element



even coiling to an

analysis



angular bend, resulting



in greater travel of the



actuator tip.


Catch
The actuator controls a
Very low actuator
Complex
IJ10



small catch. The catch
energy
construction



either enables or
Very small actuator
Requires external



disables movement of
size
force



an ink pusher that is

Unsuitable for



controlled in a bulk

pigmented inks



manner.


Gears
Gears can be used to
Low force, low
Moving parts are
IJ13



increase travel at the
travel actuators can
required



expense of duration.
be used
Several actuator



Circular gears, rack
Can be fabricated
cycles are required



and pinion, ratchets,
using standard
More complex drive



and other gearing
surface MEMS
electronics



methods can be used.
processes
Complex





construction





Friction, friction,





and wear are





possible


Buckle
A buckle plate can be
Very fast movement
Must stay within
S. Hirata et al, “An


plate
used to change a slow
achievable
elastic limits of the
Ink-jet Head Using



actuator into a fast

materials for long
Diaphragm



motion. It can also

device life
Microactuator”,



convert a high force,

High stresses
Proc. IEEE MEMS,



low travel actuator

involved
Feb. 1996, pp 418-



into a high travel,

Generally high
423.



medium force motion.

power requirement
IJ18, IJ27


Tapered
A tapered magnetic
Linearizes the
Complex
IJ14


magnetic
pole can increase
magnetic
construction


pole
travel at the expense
force/distance curve



of force.



Lever
A lever and fulcrum is
Matches low travel
High stress around
IJ32, IJ36, IJ37



used to transform a
actuator with higher
the fulcrum



motion with small
travel requirements



travel and high force
Fulcrum area has no



into a motion with
linear movement,



longer travel and
and can be used for



lower force. The lever
a fluid seal



can also reverse the




direction of travel.



Rotary
The actuator is
High mechanical
Complex
IJ28


impeller
connected to a rotary
advantage
construction



impeller. A small
The ratio of force to
Unsuitable for



angular deflection of
travel of the actuator
pigmented inks



the actuator results in
can be matched to



a rotation of the
the nozzle



impeller vanes, which
requirements by



push the ink against
varying the number



stationary vanes and
of impeller vanes



out of the nozzle.


Acoustic
A refractive or
No moving parts
Large area required
1993 Hadimioglu et


lens
diffractive (e.g. zone

Only relevant for
al, EUP 550,192



plate) acoustic lens is

acoustic ink jets
1993 Elrod et al,



used to concentrate


EUP 572,220



sound waves.


Sharp
A sharp point is used
Simple construction
Difficult to fabricate
Tone-jet


conductive
to concentrate an

using standard VLSI


point
electrostatic 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 construction
High energy is
Hewlett-Packard


expansion
actuator changes,
in the case of
typically required to
Thermal Ink jet



pushing the ink in all
thermal ink jet
achieve volume
Canon Bubblejet



directions.

expansion. This





leads to thermal





stress, cavitation,





and kogation in





thermal ink jet





implementations


Linear,
The actuator moves in
Efficient coupling to
High fabrication
IJ01, IJ02, IJ04,


normal to
a direction normal to
ink drops ejected
complexity may be
IJ07, IJ11, IJ14


chip
the print head surface.
normal to the
required to achieve


surface
The nozzle is typically
surface
perpendicular



in the line of

motion



movement.


Parallel to
The actuator moves
Suitable for planar
Fabrication
IJ12, IJ13, IJ15,


chip
parallel to the print
fabrication
complexity
IJ33, IJ34, IJ35,


surface
head surface. Drop

Friction
IJ36



ejection may still be

Stiction



normal to the surface.


Membrane
An actuator with a
The effective area of
Fabrication
1982 HowkinS U.S. Pat.


push
high force but small
the actuator
complexity
No. 4,459,601



area is used to push a
becomes the
Actuator size



stiff membrane that is
membrane area
Difficulty of



in contact with the ink.

integration in a





VLSI process


Rotary
The actuator causes
Rotary levers may
Device complexity
IJ05, IJ08, IJ13,



the rotation of some
be used to increase
May have friction at
IJ28



element, such a grill or
travel
a pivot point



impeller
Small chip area




requirements


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



when energized. This
in dimensions can
actuator to be made
U.S. Pat. No. 3,946,398



may be due to
be converted to a
from at least two
1973 Stemme U.S. Pat. No.



differential thermal
large motion.
distinct layers, or to
3,747,120



expansion,

have a thermal
IJ03, IJ09, IJ10,



piezoelectric

difference across the
IJ19, IJ23, IJ24,



expansion,

actuator
IJ25, IJ29, IJ30,



magnetostriction, or


IJ31, IJ33, IJ34,



other form of relative


IJ35



dimensional change.


Swivel
The actuator swivels
Allows operation
Inefficient coupling
IJ06



around a central pivot.
where the net linear
to the ink motion



This motion is suitable
force on the paddle



where there are
is zero



opposite forces
Small chip area



applied to opposite
requirements



sides of the paddle,



e.g. Lorenz force.


Straighten
The actuator is
Can be used with
Requires careful
IJ26, IJ32



normally bent, and
shape memory
balance of stresses



straightens when
alloys where the
to ensure that the



energized.
austenic phase is
quiescent bend is




planar
accurate


Double
The actuator bends in
One actuator can be
Difficult to make
IJ36, IJ37, IJ38


bend
one direction when
used to power two
the drops ejected by



one element is
nozzles.
both bend directions



energized, and bends
Reduced chip size.
identical.



the other way when
Not sensitive to
A small efficiency



another element is
ambient temperature
loss compared to



energized.

equivalent single





bend actuators.


Shear
Energizing the
Can increase the
Not readily
1985 Fishbeck U.S. Pat.



actuator causes a shear
effective travel of
applicable to other
No. 4,584,590



motion in the actuator
piezoelectric
actuator



material.
actuators
mechanisms


Radial
The actuator squeezes
Relatively easy to
High force required
1970 Zoltan U.S. Pat. No.


con-
an ink reservoir,
fabricate single
Inefficient
3,683,212


striction
forcing ink from a
nozzles from glass
Difficult to integrate



constricted nozzle.
tubing as
with VLSI




macroscopic
processes




structures


Coil/
A coiled actuator
Easy to fabricate as
Difficult to fabricate
IJ17, IJ21, IJ34,


uncoil
uncoils or coils more
a planar VLSI
for non-planar
IJ35



tightly. The motion of
process
devices



the free end of the
Small area required,
Poor out-of-plane



actuator ejects the ink.
therefore low cost
stiffness


Bow
The actuator bows (or
Can increase the
Maximum travel is
IJ16, IJ18, IJ27



buckles) in the middle
speed of travel
constrained



when energized.
Mechanically rigid
High force required


Push-Pull
Two actuators control
The structure is
Not readily suitable
IJ18



a shutter. One actuator
pinned at both ends,
for ink jets which



pulls the shutter, and
so has a high out-
directly push the ink



the other pushes it.
of-plane rigidity


Curl
A set of actuators curl
Good fluid flow to
Design complexity
IJ20, IJ42


inwards
inwards to reduce the
the region behind



volume of ink that
the actuator



they enclose.
increases efficiency


Curl
A set of actuators curl
Relatively simple
Relatively large
IJ43


outwards
outwards, pressurizing
construction
chip area



ink in a chamber



surrounding the



actuators, and



expelling ink from a



nozzle in the chamber.


Iris
Multiple vanes enclose
High efficiency
High fabrication
IJ22



a volume of ink. These
Small chip area
complexity



simultaneously rotate,

Not suitable for



reducing the volume

pigmented inks



between the vanes.


Acoustic
The actuator vibrates
The actuator can be
Large area required
1993 Hadimiogiu et


vibration
at a high frequency.
physically distant
for efficient
al, EUP 550,192




from the ink
operation at useful
1993 Elrod et al,





frequencies
EUP 572,220





Acoustic coupling





and crosstalk





Complex drive





circuitry





Poor control of drop





volume and position


None
In various inkjet
No moving parts
Various other
Silverbrook, EP



designs the actuator

tradeoffs are
0771 658 A2 and



does not move.

required to
related patent





eliminate moving
applications





parts
Tone-jet



















NOZZLE REFILL METHOD












Description
Advantages
Disadvantages
Examples















Surface
This is the normal way
Fabrication
Low speed
Thermal ink jet


tension
that ink jets are
simplicity
Surface tension
Piezoelectric ink jet



refilled. After the
Operational
force relatively
IJ01-IJ07, IJ10-IJ14,



actuator is energized,
simplicity
small compared to
IJ16, IJ20, IJ22-IJ45



it typically returns

actuator force



rapidly to its normal

Long refill time



position. This rapid

usually dominates



return sucks in air

the 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 common
IJ08, IJ13, IJ15,


oscillating
chamber is provided at
Low actuator
ink pressure
IJ17, IJ18, IJ19,


ink
a pressure that
energy, as the
oscillator
IJ21


pressure
oscillates at twice the
actuator need only
May not be suitable



drop ejection
open or close the
for pigmented inks



frequency. When a
shutter, instead of



drop is to be ejected,
ejecting the ink drop



the shutter 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 the
Requires two
IJ09


actuator
actuator has ejected a
nozzle is actively
independent



drop a second (refill)
refilled
actuators per 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 slight
High refill rate,
Surface spill must
Silverbrook, EP


ink
positive pressure.
therefore a high
be prevented
0771 658 A2 and


pressure
After the ink drop is
drop repetition rate
Highly hydrophobic
related patent



ejected, the nozzle
is possible
print head surfaces
applications



chamber fills quickly

are required
Alternative for:,



as surface tension and


IJ01-IJ07, IJ10-IJ14,



ink pressure both


IJ16, IJ20, IJ22-IJ45



operate to refill the



nozzle.



















METHOD OF RESTRICTING BACK-FLOW THROUGH INLET












Description
Advantages
Disadvantages
Examples















Long inlet
The ink inlet channel
Design simplicity
Restricts refill rate
Thermal ink jet


channel
to the nozzle chamber
Operational
May result in a
Piezoelectric ink jet



is made long and
simplicity
relatively large chip
IJ42, IJ43



relatively narrow,
Reduces crosstalk
area



relying on viscous

Only partially



drag to reduce inlet

effective



back-flow.


Positive
The ink is under a
Drop selection and
Requires a method
Silverbrook, EP


ink
positive pressure, so
separation forces
(such as a nozzle
0771 658 A2 and


pressure
that in the quiescent
can be reduced
rim or effective
related patent



state some of the ink
Fast refill time
hydrophobizing, or
applications



drop already protrudes

both) to prevent
Possible operation



from the nozzle.

flooding of the
of the following:



This reduces the

ejection surface of
IJ01-IJ07, IJ09-



pressure in the nozzle

the print head.
IJ12, IJ14, IJ16,



chamber which is


IJ20, IJ22, IJ23-



required to eject a


IJ34, IJ36-IJ41,



certain volume of ink.


IJ44



The reduction in



chamber pressure



results in a reduction



in ink pushed out



through the inlet.


Baffle
One or more baffles
The refill rate is not
Design complexity
HP Thermal Ink Jet



are placed in the inlet
as restricted as the
May increase
Tektronix



ink flow. When the
long inlet method.
fabrication
piezoelectric ink jet



actuator is energized,
Reduces crosstalk
complexity (e.g.



the rapid ink

Tektronix hot melt



movement creates

Piezoelectric print



eddies which restrict

heads).



the flow through the



inlet. The slower refill



process is unrestricted,



and does not result in



eddies.


Flexible
In this method recently
Significantly
Not applicable to
Canon


flap
disclosed by Canon,
reduces back-flow
most ink jet


restricts
the expanding actuator
for edge-shooter
configurations


inlet
(bubble) pushes on a
thermal ink jet
Increased



flexible flap that
devices
fabrication



restricts the inlet.

complexity





Inelastic





deformation of





polymer flap results





in creep over





extended use


Inlet filter
A filter is located
Additional
Restricts refill rate
IJ04, IJ12, IJ24,



between the ink inlet
advantage of ink
May result in
IJ27, IJ29, IJ30



and the nozzle
filtration
complex



chamber. The filter
Ink filter may be
construction



has a multitude of
fabricated with no



small holes or slots,
additional process



restricting ink flow.
steps



The filter also removes



particles which may



block the nozzle.


Small inlet
The ink inlet channel
Design simplicity
Restricts refill rate
IJ02, IJ37, IJ44


compared
to the nozzle chamber

May result in a


to nozzle
has a substantially

relatively large chip



smaller cross section

area



than that of the nozzle

Only partially



resulting in easier ink

effective



egress out of the



nozzle than out of the



inlet.


Inlet
A secondary actuator
Increases speed of
Requires separate
IJ09


shutter
controls the position of
the ink-jet print
refill actuator and



a shutter, closing off
head operation
drive circuit



the ink inlet when the



main actuator is



energized.


The inlet
The method avoids the
Back-flow problem
Requires careful
IJ01, IJ03, IJ05,


is located
problem of inlet back-
is eliminated
design to minimize
IJ06, IJ07, IJ10,


behind the
flow by arranging the

the negative
IJ11, IJ14, IJ16,


ink-
ink-pushing surface of

pressure behind the
IJ22, IJ23, IJ25,


pushing
the actuator between

paddle
IJ28, IJ31, IJ32,


surface
the inlet and the


IJ33, IJ34, IJ35,



nozzle.


IJ36, IJ39, IJ40,






IJ41


Part of the
The actuator and a
Significant
Small increase in
IJ07, IJ20, IJ26,


actuator
wall of the ink
reductions in back-
fabrication
IJ38


moves to
chamber are arranged
flow can be
complexity


shut off
so that the motion of
achieved


the inlet
the actuator closes off
Compact designs



the inlet.
possible


Nozzle
In some configurations
Ink back-flow
None related to ink
Silverbrook, EP


actuator
of ink jet, there is no
problem is
back-flow on
0771 658 A2 and


does not
expansion or
eliminated
actuation
related patent


result in
movement of an


applications


ink back-
actuator which may


Valve-jet


flow
cause ink back-flow


Tone-jet



through the inlet.



















NOZZLE CLEARING METHOD












Description
Advantages
Disadvantages
Examples















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


nozzle
fired periodically,
complexity on the
sufficient to
IJ01, IJ02, IJ03,


firing
before the ink has a
print head
displace dried ink
IJ04, IJ05, IJ06,



chance to dry. When


IJ07, IJ09, IJ10,



not in use the nozzles


IJ11, IJ12, IJ14,



are sealed (capped)


IJ16, IJ20, IJ22,



against air.


IJ23, IJ24, IJ25,



The nozzle firing is


IJ26, IJ27, IJ28,



usually performed


IJ29, IJ30, IJ31,



during a special


IJ32, IJ33, IJ34,



clearing cycle, after


IJ36, IJ37, IJ38,



first moving the print


IJ39, IJ40,, IJ41,



head to a cleaning


IJ42, IJ43, IJ44,,



station.


IJ45


Extra
In systems which heat
Can be highly
Requires higher
Silverbrook, EP


power to
the ink, but do not boil
effective if the
drive voltage for
0771 658 A2 and


ink heater
it under normal
heater is adjacent to
clearing
related patent



situations, nozzle
the nozzle
May require larger
applications



clearing can be

drive transistors



achieved by over-



powering the heater



and boiling ink at the



nozzle.


Rapid
The actuator is fired in
Does not require
Effectiveness
May be used with:


success-
rapid succession. In
extra drive circuits
depends
IJ01, IJ02, IJ03,


ion of
some configurations,
on the print head
substantially upon
IJ04, IJ05, IJ06,


actuator
this may cause heat
Can be readily
the configuration of
IJ07, IJ09, IJ10,


pulses
build-up at the nozzle
controlled and
the ink jet nozzle
IJ11, IJ14, IJ16,



which boils the ink,
initiated by digital

IJ20, IJ22, IJ23,



clearing the nozzle. In
logic

IJ24, IJ25, IJ27,



other situations, it may


IJ28, IJ29, IJ30,



cause sufficient


IJ31, IJ32, IJ33,



vibrations to dislodge


IJ34, IJ36, IJ37,



clogged nozzles.


IJ38, IJ39, IJ40,






IJ41, IJ42, IJ43,






IJ44, IJ45


Extra
Where an actuator is
A simple solution
Not suitable where
May be used with:


power to
not normally driven to
where applicable
there is a hard limit
IJ03, IJ09, IJ16,


ink
the limit of its motion,

to actuator
IJ20, IJ23, IJ24,


pushing
nozzle clearing may be

movement
IJ25, IJ27, IJ29,


actuator
assisted by providing


IJ30, IJ31, IJ32,



an enhanced drive


IJ39, IJ40, IJ41,



signal to the actuator.


IJ42, IJ43, IJ44,






IJ45


Acoustic
An ultrasonic wave is
A high nozzle
High
IJ08, IJ13, IJ15,


resonance
applied to the ink
clearing capability
implementation cost
IJ17, IJ18, IJ19,



chamber. This wave is
can be achieved
if system does not
IJ21



of an appropriate
May be
already include an



amplitude and
implemented at very
acoustic actuator



frequency to cause
low cost in systems



sufficient force at the
which already



nozzle to clear
include acoustic



blockages. This is
actuators



easiest to achieve if



the ultrasonic wave is



at a resonant



frequency of the ink



cavity.


Nozzle
A microfabricated
Can clear severely
Accurate
Silverbrook, EP


clearing
plate is pushed against
clogged nozzles
mechanical
0771 658 A2 and


plate
the nozzles. The plate

alignment is
related patent



has a post for every

required
applications



nozzle. A post moves

Moving parts are



through each nozzle,

required



displacing dried ink.

There is risk of





damage to the





nozzles





Accurate fabrication





is required.


Ink
The pressure of the ink
May be effective
Requires pressure
May be used with


pressure
is temporarily
where other
pump or other
all IJ series ink jets


pulse
increased so that ink
methods cannot be
pressure actuator



streams from all of the
used
Expensive



nozzles. This may be

Wasteful of ink



used in conjunction



with actuator



energizing.


Print head
A flexible ‘blade’ is
Effective for planar
Difficult to use if
Many ink jet


wiper
wiped across the print
print head surfaces
print head surface is
systems



head surface. The
Low cost
non-planar or very



blade is usually

fragile



fabricated from a

Requires



flexible polymer, e.g.

mechanical parts



rubber or synthetic

Blade can wear out



elastomer.

in high volume print





systems


Separate
A separate heater is
Can be effective
Fabrication
Can be used with


ink boiling
provided at the nozzle
where other nozzle
complexity
many IJ series ink


heater
although the normal
clearing methods

jets



drop e-ection
cannot be used



mechanism does not
Can be implemented



require it. The heaters
at no additional cost



do not require
in some ink jet



individual drive
configurations



circuits, as many



nozzles can be cleared



simultaneously, and no



imaging is required.



















NOZZLE PLATE CONSTRUCTION












Description
Advantages
Disadvantages
Examples















Electro-
A nozzle plate is
Fabrication
High temperatures
Hewlett Packard


formed
separately fabricated
simplicity
and pressures are
Thermal Ink jet


nickel
from electroformed

required to bond



nickel, and bonded to

nozzle plate



the print head chip.

Minimum thickness





constraints





Differential thermal





expansion


Laser
Individual nozzle
No masks required
Each hole must be
Canon Bubblejet


ablated or
holes are ablated by an
Can be quite fast
individually formed
1988 Sercel et al.,


drilled
intense UV laser in a
Some control over
Special equipment
SPIE, Vol. 998


polymer
nozzle plate, which is
nozzle profile is
required
Excimer Beam



typically a polymer
possible
Slow where there
Applications, pp.



such as polyimide or
Equipment required
are many thousands
76-83



polysulphone
is relatively low cost
of nozzles per print
1993 Watanabe et





head
al., U.S. Pat. No.





May produce thin
5,208,604





burrs at exit holes


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


micro-
plate is
attainable
construction
Transactions on


machined
micromachined from

High cost
Electron Devices,



single crystal silicon,

Requires precision
Vol. ED-25, No. 10,



and bonded to the

alignment
1978, pp 1185-1195



print head wafer.

Nozzles may be
Xerox 1990





clogged by adhesive
Hawkins et al.,






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


Glass
Fine glass capillaries
No expensive
Very small nozzle
1970 Zoltan U.S. Pat. No.


capillaries
are drawn from glass
equipment required
sizes are difficult to
3,683,212



tubing. This method
Simple to make
form



has been used for
single nozzles
Not suited for mass



making individual

production



nozzles, but is difficult



to use for bulk



manufacturing of print



heads with thousands



of nozzles.


Mono-
The nozzle plate is
High accuracy
Requires sacrificial
Silverbrook, EP


lithic,
deposited as a layer
(<1 μm)
layer under the
077 1 658 A2 and


surface
using standard VLSI
Monolithic
nozzle plate to form
related patent


micro-
deposition techniques.
Low cost
the nozzle chamber
applications


machined
Nozzles are etched in
Existing processes
Surface may be
IJ01, IJ02, IJ04,


using
the nozzle plate using
can be used
fragile to the touch
IJ11, IJ12, IJ17,


VLSI
VLSI lithography and


IJ18, IJ20, IJ22,


litho-
etching.


IJ24, IJ27, IJ28,


graphic



IJ29, IJ30, IJ31,


processes



IJ32, IJ33, IJ34,






IJ36, IJ37, IJ38,






IJ39, IJ40, IJ41,






IJ42, IJ43, IJ44


Mono-
The nozzle plate is a
High accuracy
Requires long etch
IJ03, IJ05, IJ06,


lithic,
buried etch stop in the
(<1 μm)
times
IJ07, IJ08, IJ09,


etched
wafer. Nozzle
Monolithic
Requires a support
IJ10, IJ13, IJ14,


through
chambers are etched in
Low cost
wafer
IJ15, IJ16, IJ19,


substrate
the front of the wafer,
No differential

IJ21, IJ23, IJ25,



and the wafer is
expansion

IJ26



thinned from the back



side. Nozzles are then



etched in the etch stop



layer.


No nozzle
Various methods have
No nozzles to
Difficult to control
Ricoh 1995 Sekiya


plate
been tried to eliminate
become clogged
drop position
et al U.S. Pat. No.



the nozzles entirely, to

accurately
5,412,413



prevent nozzle

Crosstalk problems
1993 Hadimioglu



clogging. These


et al EUP 550,192



include thermal bubble


1993 Elrod et al



mechanisms and


EUP 572,220



acoustic lens



mechanisms


Trough
Each drop ejector has
Reduced
Drop firing
IJ35



a trough through
manufacturing
direction is sensitive



which a paddle moves.
complexity
to wicking.



There is no nozzle
Monolithic



plate.


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


instead of
nozzle holes and
become clogged
drop position
U.S. Pat. No. 4,799,068


individual
replacement by a slit

accurately


nozzles
encompassing many

Crosstalk problems



actuator positions



reduces nozzle



clogging, but



increases cross-



talk due to ink



surface waves



















DROP EJECTION DIRECTION












Description
Advantages
Disadvantages
Examples















Edge
Ink flow is along the
Simple construction
Nozzles limited to
Canon Bubblejet


(‘edge
surface of the chip,
No silicon etching
edge
1979 Endo et al GB


shooter’)
and ink drops are
required
High resolution is
patent 2,007,162



ejected from the chip
Good heat sinking
difficult
Xerox heater-in-pit



edge.
via substrate
Fast color printing
1990 Hawkins et al




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




Ease of chip
head per color
Tone-jet




handing


Surface
Ink flow is along the
No bulk silicon
Maximum ink flow
Hewlett-Packard TIJ


(‘roof
surface of the chip,
etching required
is severely restricted
1982 Vaught et al


shooter’)
and ink drops are
Silicon can make an

U.S. Pat. No. 4,490,728



ejected from the chip
effective heat sink

IJ02, IJ11, IJ12,



surface, normal to the
Mechanical strength

IJ20, IJ22



plane of the chip.


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


chip,
chip, and ink drops are
Suitable for
silicon etching
0771 658 A2 and


forward
ejected from the front
pagewidth print

related patent


(‘up
surface of the chip.
heads

applications


shooter’)

High nozzle packing

IJ04, IJ17, IJ18,




density therefore

IJ24, IJ27-IJ45




low manufacturing




cost


Through
Ink flow is through the
High ink flow
Requires wafer
IJ01, IJ03, IJ05,


chip,
chip, and ink drops are
Suitable for
thinning
IJ06, IJ07, IJ08,


reverse
ejected from the rear
pagewidth print
Requires special
IJ09, IJ10, IJ13,


(‘down
surface of the chip.
heads
handling during
IJ14, IJ15, IJ16,


shooter’)

High nozzle packing
manufacture
IJ19, IJ21, IJ23,




density therefore

IJ25, IJ26




low manufacturing




cost


Through
Ink flow is through the
Suitable for
Pagewidth print
Epson Stylus


actuator
actuator, which is not
piezoelectric print
heads require
Tektronix hot melt



fabricated as part of
heads
several thousand
piezoelectric ink jets



the same substrate as

connections to drive



the drive transistors.

circuits





Cannot be





manufactured in





standard CMOS





fabs





Complex assembly





required



















INK TYPE












Description
Advantages
Disadvantages
Examples















Aqueous,
Water based ink which
Environmentally
Slow drying
Most existing ink


dye
typically contains:
friendly
Corrosive
jets



water, dye, surfactant,
No odor
Bleeds on paper
All IJ series ink jets



humectant, and

May strikethrough
Silverbrook, EP



biocide.

Cockles paper
0771 658 A2 and



Modern ink dyes have


related patent



high water-fastness,


applications



light fastness


Aqueous,
Water based ink which
Environmentally
Slow drying
IJ02, IJ04, IJ21,


pigment
typically contains:
friendly
Corrosive
IJ26, IJ27, IJ30



water, pigment,
No odor
Pigment may clog
Silverbrook, EP



surfactant, humectant,
Reduced bleed
nozzles
0771 658 A2 and



and biocide.
Reduced wicking
Pigment may clog
related patent



Pigments have an
Reduced
actuator
applications



advantage in reduced
strikethrough
mechanisms
Piezoelectric ink-



bleed, wicking and

Cockles paper
jets



strikethrough.


Thermal ink jets






(with significant






restrictions)


Methyl
MEK is a highly
Very fast drying
Odorous
All IJ series ink jets


Ethyl
volatile solvent used
Prints on various
Flammable


Ketone
for industrial printing
substrates such as


(MEK)
on difficult surfaces
metals and plastics



such as aluminum



cans.


Alcohol
Alcohol based inks
Fast drying
Slight odor
All IJ series inkjets


(ethanol,
can be used where the
Operates at sub-
Flammable


2-butanol,
printer must operate at
freezing


and
temperatures below
temperatures


others)
the freezing point of
Reduced paper



water. An example of
cockle



this is in-camera
Low cost



consumer



photographic printing.


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


change
room temperature, and
instantly freezes on
Printed ink typically
piezoelectric ink jets


(hot melt)
is melted in the print
the print medium
has a ‘waxy’ feel
1989 Nowak U.S. Pat. No.



head before jetting.
Almost any print
Printed pages may
4,820,346



Hot melt inks are
medium can be used
‘block’
All IJ series ink jets



usually wax based,
No paper cockle
Ink temperature



with a melting point
occurs
may be above the



around 80° C. After
No wicking occurs
curie point of



jetting the ink freezes
No bleed occurs
permanent magnets



almost instantly upon
No strikethrough
Ink heaters consume



contacting the print
occurs
power



medium or a transfer

Long warm-up time



roller.


Oil
Oil based inks are
High solubility
High viscosity: this
All IJ series inkjets



extensively used in
medium for some
is a significant



offset printing. They
dyes
limitation for use in



have advantages in
Does not cockle
ink jets, which



improved
paper
usually require a



characteristics on
Does not wick
low viscosity. Some



paper (especially no
through paper
short chain and



wicking or cockle).

multi-branched oils



Oil soluble dies and

have a sufficiently



pigments are required.

low viscosity.





Slow drying


Micro-
A microemulsion is a
Stops ink bleed
Viscosity higher
All IJ series ink jets


emulsion
stable, self forming
High dye solubility
than water



emulsion of oil, water,
Water, oil, and
Cost is slightly



and surfactant. The
amphiphilic soluble
higher than water



characteristic drop size
dies can be used
based ink



is less than 100 nm,
Can stabilize
High surfactant



and is determined by
pigment
concentration



the preferred curvature
suspensions
required (around



of the surfactant.

5%)

## Claims

1. A method of manufacture of a thermally actuated ink jet printer comprising a series of nozzle chambers from each of which ink is ejected via the utilization of a thermal actuator device, the method comprising the steps of:
(a) initially providing a silicon wafer having a circuitry wafer layer including electrical circuitry necessary for the operation of the thermal actuators on demand; 
(b) etching an ink inlet aperture in said circuitry wafer layer; 
(c) depositing and etching a first sacrificial layer on top of the silicon and circuitry wafer layer and etching said first sacrificial layer in an area defining a first portion of a nozzle chamber wall, a thermal actuator anchor and a thermal actuator end point; 
(d) depositing and etching a first inert material layer defining an actuator path starting at said thermal actuator anchor; 
(e) depositing and etching a first conductive material layer adjacent said actuator path and attached to said first inert material layer; 
(f) depositing and etching a non-conductive layer over said first conductive material layer, said etching including etching predetermined vias for interconnection of said first conductive material layer with a second conductive material layer; 
(g) depositing and etching a second inert material layer on top of said first inert material layer; 
(h) depositing and etching said second conductive material layer on top of said non-conductive layer, the second conductive material layer having a conductive interconnect to said first conductive material layer; 
(i) depositing and etching a series of inert material layers and sacrificial layers to form a nozzle chamber including an ink ejection hole and a nozzle chamber paddle attached at said thermal actuator end point; 
(j) etching an ink supply channel through said wafer to said nozzle chamber; and 
(k) etching away said sacrificial layers.

2. A method as claimed in claim 1 wherein said conductive material layers are formed from a material having a Youngs modulus which is higher than that of the inert material layers.

3. A method as claimed in claim 1 wherein said conductive material layers comprise substantially titanium nitride.

4. A method as claimed in claim 1 wherein said first and second inert material layers comprise substantially glass.

5. A method as claimed in claim 1 wherein said actuator path comprises substantially a coil.

6. A method as claimed in claim 1 further comprising the step of etching an ink supply channel through said wafer from a back surface thereof.

7. A method as claimed in claim 1 wherein said wafer comprises a double side polished CMOS wafer.

8. A method as claimed in claim 1 wherein at least step (k) is also utilized to simultaneously separate said wafer into separate printheads.