Title of Invention	PRINTED MEDIA PRODUCTION
Abstract	The present invention relates to a nozzle guard 80 for an ink jet printer printhead with an array 14 of nozzles 10 and respective colorant ejection means for ejecting colorant onto a substrate to be printed, wherein the nozzle guard 80 is adapted to be positioned on the printhead to inhibit damaging contact with the exterior of the array 14 of nozzles 10. [fig. 7)

Full Text

FIELD OF THE INVENTION The present inventioii relates to an apparatus for printing out or duplicating photogn^jhs from information recorded in infrared ink on the top of the photograph using an ink jet printing system. CO-PENDtNG APPLICATIONS Various me&ods, systems and apparatus relating to the present invention are disclosed in the following co-pending applications filed by the :^licant or assignee of the present invoition simultaneously with the present application: . Viiifci —« -.^——_—^ Ihterniitlonal Patent Applicadon Number Docket No. PCT/AUOl/01317 ART80 PCT/AUOl/01328 ART81 PCT/AUOl/01326 ART82 PCT/AUOl/01327 ART83 PCT/AUOl/01325 ART 84 The disclosures of these co-pmding applications are incorporated herein by reference. Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending application filed by the applicant or assignee of the present invention on 10 July 1998: USSN 09/112,781 USSN 09/112,785 USSN 09/112.824 The disclosures of these co-pending qiplications are incorporated herein by reference. Various methods, systems and ^paratus relatbg to the present invention are disclosed in the following co-pending applications filed by the applicant or assignee of the present invention on June 30,2000: Various methods, systems and apparatus relating to the present invention are disclosed in the folldwing co-pending applications filed by the applicant or assignee of the present invention on 30 June 2001. PCT/AU0G/0G764, PCT/AUOO/00765, PCT/AUOO/00766 and PCT/AUOO/00772 FIELD OF THE INVENTION The present invention relates to printed media production and in particular ink jet printers. BAf^GROUND TO THE INVENTION Ink jet printers are a well known and widely used form of printed media production. Colorants, usually ink, are fed to an array of micro-processor controlled nozzles on a printhead. As the print head passes over the media, colorant is ejected from the array of nozzles to produce the printing on the media substrate. Printer performance depends on factors such as operating cost, print quality, operating speed and ease of use. The mass, frequency and velocity of individual ink drops ejected fi-om the nozzles will affect these performance parameters. In general terms, smaller, faster droplets ejected at higher frequency provide cost, speed and print quality advantages. In light of this, it has been an overriding aim of printhead design to reduce the size of the ink nozzles and thereby the size of the droplets ejected. Recently, the array of nozzles has been formed using microelectromechanical systems (MEMS) technology, which have mechanical structures with sub-micron thicknesses. This allows the production of printheads that can rapidly eject ink droplets sized in the picolitre (x 10'^ litre) range. The ^Ucant has disclosed in co-pending applications PCT/AUOl/01317 (Docket No. ART80), PCT/AUOl/01328 (Docket No. ART81) and PCT/AUOl/01326 (Docket No. ART82) filed concuirently herewith, methods for tecordmg data relating to an image captured by ft camera system on top of or coincident with the printing of die image itself, that is, the image and the data are recorded on the same side and in the same area of the print media. Such a method requires a pagewidth ink jet prinfliead having at least four ink jet nozzles per printed "dot", three for printing the color image namely for printing with cyan, magenta and yellow inJcs and one for printing with an infrared ink for printing the data corresponding to the image afier it has been processed into an encoded fault tolerant digital form. SUMMARY OF THE INVENTION The present invention seeks to provide an apparatus for decoding the data printed on a photograph and printing out an image decoded fiom said data on a print media. The data printed on top of the image may be a digital representation of the image itself in an encoded fault tolerant digital form, or the image so encoded and an image processing program for producing a particular effect upon the image, or two images, one being the image per se and the other being the image as transformed by an image processing program. In the former case the image itself can be printed out notwithstanding substantial damage to tiie print media upon which the image and the encoded image data is recorded. In the second case the image can be printed out in its original taim or as modified by the image processing program recorded along with that image data. In the third case either the image per se or the image as transformed can be printed out. The data whldi is recorded on the photographic image is encoded in such a way that even if substantial damage occurs to the surface of the photograph, the data will allow recovery of the image. Ibis is possible by suitable duplication and redundancy in the data compression and scrambling of the data and encoding the data in a fault tolerant, for example a Reed-Solomon, code form. The size of the photograph is approximately 4" x 6" (102mm X lS2mm). The data can be recorded on substantially the whole area of the photograph in a variety of formats, one of which is to record it as a series of data blocks (the so-called "alternative Artcard" fbmiat) eod another of which is to record the data continuously over the data area as a series of columns (the so-called "Artcard" format) both of which are described in detail in USSN 09/112,781 or USSN 09/112,785. The former method of encoding, described in applicant's co-pending jqjplications PCT/AUOl/01317 (Docket No. ART80), PCT/AUOl/01328 (Docket No. ART81), PCT/AUOl/01326 (Docket No. ART82), would allow recovery of the image even if one third of the data blocks were damaged. Other sizes of print media are also disclosed for example a panoramic print which is approximately the same height but twice the width of the standard print 4" x 6" desraibed above. By having the image data recorded on the image itsdf the need to have a separate photogTJ^hic negative and to store it along with the photograph is avoided. Presently, the storage of image data in a digital form is on a computer system and is subject to the limited capacity of the hard drive, the ability to find the data and the risk of damage to the hard drive storing the data, the obsolescence of the hard drive, or the obsolescence of the image data foimat. These defects are avoided in the current arrangement whereby the data is recoverable if the photograph itself is available, if it has not suffered more than one third damage, that is approximately two thirds is available for processing. It is an object of the present invention to provide for an apparatus of reading digital data printed on a photogr^h in infrared ink wherdn the data is encoded image data from a camera system, the apparatus including a scanner means for scanning data in infrared printed on the photograph; means for advancing the print media through the scanning means; means for illuminating the print media with infrared radiation; means for processing data output from said scanner means including means for decoding said data; ink jet printer means for printing out the image derived from said decoded data on a print media attached to said ink jet printer means. The encoded fault tolerant digital data may also be reprinted on top of the recovered or replicated image if the Inkjet piinthead has provisions for printing in the necessary number of colors, namely cyan, magenta, yellow and infrared. If the photograph is undamaged then a direct copying or rq)lication of the infrared data and/or color image can be produced in the manner of the applicant's mediod and apparatus disclosed in the application USSN 09/112,824. If the photograph is damaged then the fiill data would have to be recovered before being printed and, if required encoded again into its ftult tolerant digital form for print out simultaneously with the image on the print media. Other versions of the image can also be printed if the apparatus is provided with means for reading an "Artcard" and for processing the data received tiierefrom in the manner as described in USSN 09/112,781 and USSN 09/112,785 by the applicant. In this instance, the Artcard reader may be the same device as &e photogrq}h scanning means or may be a sq)ar&te integer. An Artcard as disclosed in said applicatioiis is of a credit card size approximately S:>mm x 8Smm and the scanning means for scanning a photograph as required for the present invention would be wider to accommodate the 102mm x 152mm (4" x 6") size of the photograph. In that case, the scanner means may be provided with means for accommodating various width cards for example, for altering the size of the slot tihrough which the Artcard or the photograph is to be inserted. The print media used to print out the recovered or duplicated photograph is the same as the photogr^h itself namely approximately 102mm x 152mm (4" x 6"), although it is contemplated that the print media may be of a larger size sudi as to provide a panoramic print of the same height but approximately twice the width of the standard photograph. A panoramic print may require an image processing program to be employed using the appropriate Artcaid for that purpose or the original photograph may have been a panoramic print with the encoded, data including the necessary image processing program encoded therewith, for example as described in the applicant's application PCT/AUOl/01328 (Docket No. ART81). BRIEF DESCRIPTION OF THE DRAWINGS Notwithstanding any other forms which may fidl 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 one form of card reader according to the invention; Fig. 2 illustrates an exploded view of Fig. 1; Fig. 3 illustrates a side pwspective view, partly in section, of one form of construction of CCD reader unit; Fig. 4 illustrates a chedcerboard pattern wift which tiie data surface may be modulated; Fig. 5 illustrates the reading process; and Fig. 6 illustrates the steps necessary to decode data read in fiom a photograph. DESCRIPTION OF THE PREFERRED EMBODIMENT Dm The dots printed on &e photograph are in infrared ink over a color image. Consequently a "data dof' is physically different from a "non-data dof', When the photograph is illuminated by an infrared source having complementary spectral properties to the absorption or response characteristics of the infrared (JR.) ink the data appears as a DETAILED DESCRIPTION OF THE DRAWINGS Referring initially to Figure 1 of the drawings, a nozzle assembly, in accordance with the invention is designated generally by the reference numeral 10. An ink jet printhead has a plurality of nozzle assemblies 10 arranged in an array 14 (Figures 5 and 6) on a silicon substrate 16. The array 14 will be described in greater detail below. The assembly 10 includes a silicon substrate or wafer 16 on which a dielectric layer 18 is deposited. A CMOS passivation layer 20 is deposited on the dielectric layer 18. Each nozzle assembly 10 includes a nozzle 22 defining a nozzle opening 24, a connecting member in the form of a lever arm 26 and an actuator 28. The lever arm 26 connects the actuator 28 to the nozzle 22. As shown in greater detail in Figures 2 to 4, the nozzle 22 comprises a crown portion 30 with a skirt portion 32 depending from the crown portion 30. The skirt portion 32 forms part of a peripheral wall of a nozzle chamber 34. The nozzle opening 24 is in fluid communication with the nozzle chamber 34. It is to be noted that the nozzle opening 24 is surrounded by a raised rim 36 which "pins" a meniscus 38 (Figure 2) of a body of ink 40 in the nozzle chamber 34. An ink inlet aperture 42 (shown most clearly in Figure 6 of the drawing) is defined in a floor 46 of the nozzle chamber 34. The aperture 42 is in fluid communication with an ink inlet channel 48 defined through the substrate 16. A wall portion 50 bounds the aperture 42 and extends upwardly from the floor portion 46. The skirt portion 32. as indicated above, of the nozzle 22 defines a first part of a peripheral wall of the nozzle chamber 34 and the wall portion 50 defines a second part of the peripheral wall of the nozzle chamber 34. Hie wall 50 has an inwardly directed lip 52 at its free end which serves as a fluidic seal which inhibits the escape of ink when the nozzle 22 is displaced, as will be described in greater detail below. It will be appreciated that, due to the viscosity of the ink 40 and the small dimensions of the spacing between the lip 52 and the skirt portion 32, the inwardly directed Up 52 and surface tension function as an effective seal for inhibiting the escape of ink from the nozzle chamber 34. The actuator 28 is a thermal bend actuator and is connected to an anchor 54 extending upwardly from the substrate 16 or, more particularly from the CMOS passivation layer 20. The anchor 54 is mounted on conductive pads 56 which form an electrical connection with the actuator 28. The actuator 28 comprises a first, active beam 58 arranged above a second, passive beam 60. In a preferred embodiment, both beams 58 and 60 are of, or include, a conductive ceramic material such as titanium nitride (TiN), Both beams 58 and 60 have their first ends anchored to the anchor 54 and their opposed ends connected to the arm 26. When a current is caused to flow through the active beam 58 thermal expansion of the beam 58 results. As the passive beam 60, through which there is no cun-ent flow, does not expand at the same rate, a bending moment is created causing the arm 26 and, hence, the nozzle 22 to be displaced downwardly towards the substrate 16 as shown in Figure 3. This causes an ejection of ink through the nozzle opening 24 as shown at 62. When the source of heat is removed from the active beam 58, i.e. by stopping current flow, the nozzle 22 returns to its quiescent position as shown in Figure 4. ■ When the nozzle 22 returns to its quiescent position, an ink droplet 64 is formed as a result of the breaking of an ink droplet neck as illustrated at 66 in Figure 4. The ink droplet 64 then travels on to the print media such as a sheet of paper. As a result of the formation of Reading Data from the CCD - General Considerations In what follows, it is assumed that the data is encoded on a photograph using the so-called "Artcard" fomat as disclosed in applicant's USSN 09/112,781 or USSN 09/112,785 in a data area of 97nun x 147inm for a 102nim x 152mm photograph (4" x 6") with 2.5mm borders (0.1"). In this format the data area is continuous and bordered by targets at the leading and trailing edges of the data area and by o&er indicia along the top and bottom margins to ensure correct reading of the data notwithstanding up to 1** rotation of the photograph with respect to the linear CCD JR sensor's orientation. The data is scrambled and encoded using a Reed-Solomon algorithm or process. In addition, the data may be compressed before encoding and scrambling. The data may be image data from a camera system, image data and an image processing program, or two images, one the image as photographed and another an image as transformed by an image processing program such as described in applicant's co-pending appUcations PCT/AUOl/01317 (Docket No. ART80), PCT/AUOl/01328 (Docket No. ART81), PCT/AUOl/01326 (Docket No. ART82). As illustrated in Fig. 5, the reading process has 4 phases operated while the pixel data is read from the card. The phases are as follows: Phase 1. Detect data area on photograph Phase 2. Detect bit pattern from photograph based on CCD pixels, and write as bytes. Phases. Desa:ambIeandXORthebyt»-pattem Phase 4, Decode data (Reed-Solomon decode) The photograph 9 must be sampled at at least double the printed resolution to satisfy Nyquist's Theorem. In practi(?e it is better to sample at a higher rate flian this. Preferably, the pixels are sampled at 3 times the resolution of a printed dot m each dimension, requiring 9 pixels to define a single dot. Thus if the resolution of the photograph 9 is 1600 dpi, and the resolution of the sensor 34 is 4800 dpi, flien using a 100mm width CCD image sensor (98.7mm. is required to cover the width of the data area of 97mm x 147mm with margins of 2.5mm printed at 1600 dpi print resolution and allowing for up to a 1" rotation of a photograph of 4" X 6" or 102mm x 152mm) results in 18900 pixels per column (100*1600*3/25.4). Therefore if a photograph stores 8MB of dot data (at 9 pixels per dot) then this entails 8MB*8*9/18900 = 30,476 columns or approximately 30,500 columns. Of course if a dot is not exactly aligned with die sampling CCD the worst and most likely case is that a dot will be I to one side of the rows 72 and 74. Hence, the ink ejected from the nozzles 22 in the row 72 and the ink ejected from the nozzles 22 in the row 74 are offset with respect to'each other . by the same angle resulting in an improved print quality. Also, as shown in Figure 5 of the drawings, the substrate 16 has bond pads 76 arranged thereon which provide the electrical connections, via the pads 56, to the actuators 28 of the nozzle assemblies 10. These electrical connections are formed via the CMOS layer (not shown). Referring to Figure 7, a nozzle guard according to the present invention is shown. With reference to the previous drawings, like reference numerals refer to like parts, unless otherwise specified. A nozzle guard 80 is mounted on the silicon substrate 16 of the array 14. The nozzle guard 80 includes a shield 82 having a plurality of passages 84 defined therethrough. The passages 84 are in register with the nozzle openings 24 of the nozzle assemblies 10 of the array 14 such that, when ink is ejected from any one of the nozzle openings 24, the ink passes through the associated passage before striking the print media. The guard 80 is silicon so that it has the necessary strength and rigidity to protect the nozzle array 14 from damaging contact with paper, dust or the users' fingers. By forming the guard from silicon, its coefficient of thermal expansion substantially matches that of the nozzle array. This aims to prevent the passages 84 in the shield 82 from falling out of register with the nozzle array 14 as the printhead heats up to its normal operating temperature. Silicon is also well suited to accurate micro-machining using MEMS techniques discussed in greater detail below in relation to the manufacture of the nozzle issemblieslO. space (l-2Mbyte). Decoding fl^ejata A simple look at the data sizes shows the impossibility of fitting the process into, for ■ example, 8MB of memoiy for example, as used in the jq)plicant's Artcaid reader of USSN 09/112,781 if the entire pixel data (560 MB if each bit is read as a 3x3 array) as read by the linear CCD 34 is kept For this reason, the reading of the linear CCD, decoding of the bitmap, and the un-bitmap process should take place in real- time (while the photograph 9 is traveling past the linear CCD 34), and these processes must effectively work without having entire data stores available. The unscrambling process requires two sets of 8JMB areas of memory since unscrambling cannot occur in place. It is assumed here that the data was encoded using the Artcard format as described in USSN 09/112,781 or USSN 09/112,785 with a checkerboard modulation. In the Artcard format, the data is printed in a continuous data area the start and end of which is marked by targets, for ^cample 16 targets for a card of S5mm x 85mm, each target having a white dot in the centre of an array of 31 x 31 black dots wi& the data beginning 24 dots from that cwitral dot For a card of 4" x &* (102mm x 152mm) size, 32 similar targets may be used. Alternatively, the data may have been recorded in the "alternative Artcard" format which is equally disclosed in USSN 09/112,785, or in PCT/AUOl/01317 (Docket No. ART80), PCT/AUOl/01328 (Docket No. ART81), PCT/AUOl/01326 (Docket No. ART82). In this format, data is arranged in data blocks having spectfic characteristics wherein the data blocks are locatable by a distinctive set of targets. Turning now to Fig. 6, there is shown A flowchart 220 of the steps necessary to decode the data. These steps include reading in flie photographic data 221, decoding the read data to produce corresponding encoded XORed soambled bitmap data 223. Next a checkerboard XOR is applied to the data to produce encoded scrambled data 224. This data is then unscrambled 227 to produce data 225 before this data is subjected to Reed-Solomon decoding to produce the original raw data 226. Alternatively, unscrambling and XOR process can take place together, not requiring a separate pass of the data. Each of the above steps is discussed in detail in the applicant's appUcations USSN 09/112,781 or USSN 09/112,785. As noted previously with reference to Fig. S, the process of scanning data therefore, has 4 phases, the jEirst 2 of which are time-critical, and must take place while pixel data is being read &om the CCD. is stripped and the device is cleaned. This step provides the bond pads and interconnects to the Inkjet actuator 28. This interconnect is to an NMOS drive transistor and a power plane with connections made in the CMOS layer (not shown). Approximately 0.5 microns of PECVD nitride is deposited as the CMOS passivation layer 20. Resist is spun on and the layer 20 is exposed to mask 106 whereafter it is developed. After development, the nitride is plasma etched down to the aluminum layer 102 and the silicon layer 16 in the region of the inlet aperture 42. The resist is stripped and the device cleaned. A layer 108 of a sacrificial material is spun on to the layer 20. The layer 108 is 6 microns of photo-sensitive polyimide or approximately 4 p.m of high temperature resist. The layer 108 is softbaked and is then exposed to mask 110 whereafter it is developed. The layer 108 is then hardbaked at 400°C for one hour where the layer 108 is comprised of polyimide or at greater than SOO'C where the layer 108 is high temperature resist. It is to be noted in the drawings that the pattern-dependent distortion of the polyimide layer 108 caused by shrinkage is taken into account in the design of the mask 110. In the next step, shown in Figure 8e of the drawings, a second sacrificial layer 112 is applied. The layer 112 is either 2 ^m of photo-sensitive polyimide which is spun on or approximately 1.3 jam of high temperature resist. The layer 112 is softbaked and exposed to mask 114. After exposure to the mask 114, the layer 112 is developed. In the case of the layer 112 being polyimide, the layer 112 is hardbaked at 400°C for approximately one hour. Where the layer 112 is resist, it is hardbaked at greater than 300°C for approximately one hour. A 0.2 micron multi-layer metal layer 116 is then deposited. Part of this layer 116 forms the passive beam 60 of the actuator 28. ofdata. If the data was encoded and printed on the photograph, using the "alternative Artcard" format, such as described in PCT/AUOl/01317 CDocket Nos. ART80), PCT/AUOl/01328 (Docket No. ART81) or USSN 09/01326 (Docket No. ART82), then the procedure for reading and recovering the data is substantially as described in applicant's applications USSN 09/112,781 or USSN 09/112,785.-Print Out Decoded Data Once the data has been recovered, the image, the image as transformed by the encoded image processing program or either of these, depending on whether the data recorded on the photogrc^h is, for example, as disckised in applicant's co-pending applications PCT/AUOl/01317 (Docket No. ART80), PCT/AUOl/01328 (Docket No. ART81) or PCT/AUOl/01326 (Docket No. ART82), can be printed out using an ink jet printhead of the required characteristics. If only the image is to be printed a 3-ink ink jet printhead will suffice. If the image and the encoded data is to be printed then an at least 4-ink Inkjet printhead would be necessary. If the data can be stored either in the printer or in a RAM area of the processor which decodes the encoded data tiien the printer can be provided with means for enabling copies of the image to be printed as desired, for example dedicated switches or at least a numeric keypad. Alternatively, if a number of copies is required, the photograph may be passed repeatedly Ibrough thfe scanner. The foregoing description has been limited to specific embodiments of this invention. It will be apparent, however, that variations and modifications may be made to the invention, with the attainment of some or all of the advantages of the invention. For exaniple, it will be appreciated that the invention may be embodied in either hardware or software it a suitably programmed digital data processing system, both of which are readily accomplished by those of ordinary skill in the respective arts. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the invention. 13 Figure 9k of the drawings. The remaining portions of the layer 128 are hardbaked at 400'C for approximately one hour in the case of polyimide or at greater than 300'C for resist. As shown in Figure 81 of the drawing a high Young's modulus dielectric layer 132 is deposited. The layer 132 is constituted by approximately l^im of silicon nitride or aluminum oxide. The layer 132 is deposited at a temperature below the hardbaked temperature of the sacrificial layers 108,112,120,128, The primary characteristics required for this dielectric layer 132 are a high elastic modulus, chemical inertness and good adhesion to TiN. A fifth sacrificial layer 134 is applied by spinning on 2nm of photo-sensitive polyimide or approximately 1.3|am of high temperature resist. The layer 134 is softbaked, exposed to mask 136 and developed, The remaining portion of the layer 134 is then hardbaked at 400°C for one hour in the case of the polyimide or at greater than 300°C for the resist. The dielectric layer 132 is plasma etched down to the sacrificial layer 128 taking care not to remove any of the sacrificial layer 134, This step defines the nozzle opening 24, the lever arm 26 and the anchor 54 of the nozzle assembly 10. A high Young's modulus dielectric layer 138 is deposited. This layer 138 is formed, by depositing 0.2|im of silicon nitride or aluminum nitride at a temperature below the hardbaked temperature of the sacrificial layers 108,112,120 and 128. Then, as shown in Figure 8p of the drawings, the layer 138 is anisotropically plasma etched to a depth of 0.35 microns. This etch is intended to clear the dielectric from all of the surface except the side walls of the dielectric layer 132 and the sacrificial layer 134. 14 This step creates the nozzle rim 36 around the nozzle opening 24 which "pins" the meniscus of ink, as described above. An ultraviolet (UV) release tape 140 is applied. 4^m of resist is spun on to a rear of the silicon wafer 16. The wafer 16 is exposed to mask 142 to back etch the wafer 16 to define the ink inlet channel 48. The resist is then stripped from the wafer 16. ' A further UV release tape (not shown) is applied to a rear of the wafer 16 and the tape 140 is removed. The sacrificial layers 108,112,120,128 and 134 are stripped in oxygen plasma to provide the final nozzle assembly 10 as shovm in Figures 8r and 9r of the drawings. For ease of reference, the reference numerals illustrated in these two drawings are the same as those in Figure I of the drawings to indicate the relevant parts of the nozzle assembly 10. Figures 11 and 12 show the operation of the nozzle assembly 10, manufactured in accordance with the process described above with reference to Figures 8 and 9 and these figures correspond to Figures 2 to 4 of the drawings. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the 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 as illustrative and not restrictive. 15 WE CLAIM : 1. A printhead for an ink jet printer, the printhead comprising: an array of nozzles and respective colorant ejection means for ejecting colorant onto a media substrate to be printed; and, a nozzle guard positioned to inhibit damaging contact with the exterior of the array of nozzles; characterized in that said nozzle guard comprises a shield covering the exterior of the nozzles, said shield having an array of passages in registration with the array of nozzles so as not to impede the normal trajectory of the colorant ejected from each nozzle; said nozzle guard comprising fluid inlet openings for directing fluid through said passages, to inhibit the build up of foreign particles on the nozzle array, wherein: said fluid is passed through said passages at a velocity that is less than the velocity of the^ ejected colorant. 2. The printhead as claimed in claim 1 wherein the shield is formed from silicon. 3. The printhead as claimed in claim 1 wherein the nozzle guard has a support means for supporting the nozzle shield on the printhead. 4. The printhead as claimed in claim 3 wherein the support means is integrally formed with the shield, the support means comprising a pair of spaced support elements one being arranged at each end of the nozzle shield. 5. The printhead as claimed in claim 4 wherein the fluid inlet openings are arranged in one of the support elements. 6. The printhead as claimed in claim 1 wherein the fluid inlet openings are arranged in the support element remote from a bond pad of the nozzle array. 16 7. The printhead as claimed in claim 1 wherein colorant droplets are ejected at a velocity of 3m/s. 8. The printhead as claimed in claim 1 wherein the fluid is passed through the passages at Im/s.

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