Abstract:
An improved multi-fluid jetting device. The jetting device includes a nozzle plate having a substantially planar surface for ejecting a fluid therefrom. The nozzle plate has at least 10 or more nozzles wherein groups of three adjacent nozzles are arranged in a triad orientation and wherein at least two adjacent nozzles in said triad orientation are coupled to two different fluid sources for fluid ejection from said adjacent nozzles substantially perpendicular to said nozzle plate surface.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to improved multi-fluid jetting devices for dispensing a variety of fluids, preferably for dispensing two or more different fluids for a variety of applications.  
         BACKGROUND OF THE INVENTION  
         [0002]    Micro-miniature fluid jetting devices are suitable for a wide variety of applications including hand-held ink jet printers, ink jet highlighters, ink jet air brushes, miniature evaporative coolers, and delivery of controlled quantities of medicinal fluids and purified water to precise locations. One of the challenges facing the manufacture and use of such miniature jetting devices is providing a device that is capable of dispensing two or more fluids at a time to provide a desired result. Such a process is particularly useful for providing color images, however, the process is not limited to ink jet printing applications.  
           [0003]    Another challenge facing the manufacture and use of such devices is the provision of a device capable of dispensing multiple fluids without significant separation distance or white space between the different fluids being dispensed. In a color printing application, the white space between the different color dots inhibits a visual perception that the different colors have been mixed to provide a desired or substantially uniform hue. Accordingly, there remains a need for improved fluid jetting devices for dispensing multiple fluids to provide reduced amount of white space between deposited dots of fluid.  
         SUMMARY OF THE INVENTION  
         [0004]    With regard to the foregoing and other objects and advantages the invention provides an improved multi-fluid jetting device. The multi-fluid jetting device includes a nozzle plate having a substantially planar surface for ejecting a fluid therefrom. The nozzle plate has at least 10 or more nozzles wherein groups of three adjacent nozzles are arranged in a triad orientation and wherein at least two adjacent nozzles in said triad orientation are coupled to two different fluid sources for fluid ejection from said adjacent nozzles substantially perpendicular to said nozzle plate surface.  
           [0005]    In another embodiment, the invention provides a nozzle for a miniature multi-fluid jetting device. The nozzle plate has a substantially planar surface and includes a plurality of  10  or more nozzles having groups of three adjacent nozzles arranged in a triad orientation wherein at least two adjacent nozzles in said group are coupled to two different fluid sources for fluid ejection substantially perpendicular to said nozzle plate surface.  
           [0006]    Providing a multi-fluid jetting device with a nozzle plate having nozzles for jetting different fluids such as different color inks arranged in a triad or triangular orientation according to the invention provides several important advantages. For one, apparent mixing of different fluids to provide a desired result such as a desired color on a print media is simpler and requires less motion of the jetting device. Another advantage of the invention is that ink jet printers containing nozzle plates with such nozzle arrangements for jetting different color inks are less prone to dot placement variations which can produce print quality defects. Scanning type color ink jet printheads containing nozzle groups as described herein are effective to reduce shifts in the color table for left-to-right versus right-to-left motion of the printhead. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    Further advantages of the invention will become apparent by reference to the detailed description of preferred embodiments when considered in conjunction with the drawings, wherein like reference characters designate like or similar elements throughout the several drawings as follows:  
         [0008]    [0008]FIG. 1 is a plan view, not to scale, of a prior art nozzle plate containing three spaced-apart columns of nozzles for jetting different fluids;  
         [0009]    [0009]FIG. 2 is a plan view, not to scale, of dot placement of different fluids on a media using a prior art nozzle plate;  
         [0010]    [0010]FIG. 3 is plan view, not to scale, of dot placement of different fluids on a media using a nozzle plate according to the invention;  
         [0011]    [0011]FIG. 4 is a top plan view, not to scale, of a nozzle plate according to a first aspect of the invention;  
         [0012]    [0012]FIG. 5 is a top plan view, not to scale, of a nozzle plate according to the first aspect of the invention containing a barrier layer for separating different fluids from each other;  
         [0013]    [0013]FIG. 6 is a side elevational view, not to scale, taken along lines  6 - 6  of FIG. 5;  
         [0014]    [0014]FIG. 7 is a cross-sectional end view, not to scale, through a barrier layer nozzle plate, and substrate according to one aspect of the invention;  
         [0015]    [0015]FIG. 8 is plan view, not to scale, of dot placement of different fluids on a media using a nozzle plate according to another embodiment of the invention;  
         [0016]    [0016]FIG. 9 is a top plan view, not to scale, of a nozzle plate according to a second aspect of the invention;  
         [0017]    [0017]FIG. 10 is a top plan view, not to scale, of a nozzle plate according to the second aspect of the invention containing a barrier layer for separating different fluids from each other;  
         [0018]    [0018]FIG. 11 is a side elevational view, not to scale, taken along lines  11 - 11  of FIG. 10;  
         [0019]    [0019]FIG. 12 is a side elevational view, not to scale, taken along lines  12 - 12  of FIG. 10.  
         [0020]    [0020]FIG. 13 is a perspective view, not to scale, of a handheld jetting device containing a nozzle plate according to the invention;  
         [0021]    [0021]FIG. 14 is a perspective view, not to scale, of a fluid reservoir and jet head containing a nozzle plate according to the invention; and  
         [0022]    [0022]FIG. 15 is a cross-sectional view, not to scale, of components of a jetting device illustrating typical construction thereof. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    With reference to FIG. 1, a prior art multi-fluid nozzle plate  10  for a jetting device is shown. The nozzle plate  10  includes three columns  12 ,  14 , and  16  containing a plurality of nozzles  18  in each column. Nozzle column  14  is displaced from nozzle columns  12  and  16  by distance D. Each column  12 ,  14 , and  16  is dedicated to depositing a different color ink or different fluid on a print media. It will be appreciated that deposition of two or more dots of fluids other than inks is possible with such fluid jetting devices. However, for ease of describing the invention, the discussion will be focused on the deposition of ink.  
         [0024]    In FIG. 2, ink dots  20  represent blue color dots, ink dots  22  represent yellow color dots, and ink dots  24  represent magenta color dots. Dots  20 ,  22 , and  24  deposited from the nozzle plate  10  attached to a jetting device at substantially the same time will also have a significant amount of white space  26  between adjacent dots as deposited, for example, on the print media. Moving the jetting device during the deposition process may increase color mixing provided there is little or no variation in the speed or direction of motion of the jetting device during the deposition process.  
         [0025]    Ideally, for good color mixing, different color ink dots  28 ,  30 , and  32  should be closely adjacent one another on the print media as shown in FIG. 3 to reduce the amount of white space between the dots. If the dots  28 ,  30 , and  32  are small enough, individual ink colors will appear as a single color on the print media. Multi-color dots as small as about  120  microns appear to a human eye to be a single color. Minimizing the white space  26  between the dots will thus sharpen the image and improve color saturation and hue properties of the deposited dots. While the dots  28 ,  30  and  32  are shown in FIG. 3 as touching one another, there may be a small amount of separation between the dots  28 ,  30 , and  32 , however this separation is substantially less than the separation between dots  20 ,  22 , and  24  (FIG. 2). It is preferred that the white space  26  or separation between adjacent dots  28 ,  30 , and  32  be less than about 1.1 times the dot diameter on the print media.  
         [0026]    It is evident that a nozzle plate, such as nozzle plate  10 , having individual columns of nozzles is ineffective to produce closely adjacent dots  18 ,  30 , and  32  as shown in FIG. 3. Accordingly, preferred multi-fluid nozzle plates are illustrated in FIGS. 4-6. FIG. 4 is a top plan view of a multi-fluid nozzle plate  34  according to a first embodiment of the invention. The nozzle plate  34  contains a triad or triangular arrangement of nozzles  36 ,  38 , and  40  wherein adjacent nozzles are dedicated to different fluids, in this case, different color inks. For example, nozzle  36  is dedicated to depositing blue ink (C), nozzle  38  is dedicated to depositing yellow ink (Y), and nozzle  40  is dedicated to depositing magenta ink (M). The nozzles  36 ,  38 , and  40  are preferably substantially equidistant from one another. The center to center separation distance SD between adjacent nozzles preferably ranges from about 0.8 times the dot size on the print media to about 1.7 times the dot size on the print media.  
         [0027]    Ink is provided to the nozzles  36 ,  38 , and  40  from separate ink supplies through separate fill slots  42 ,  44 , and  46 . The ink fill slots  42 ,  44 , and  46  are preferably formed in a semiconductor substrate  48  (FIG. 6) attached to the nozzle plate  34 . Ink flows through a supply channel  50  from ink fill slot  44  to an ink chamber  52  for flow through a nozzle, such as nozzle  38 . The semiconductor substrate  48  preferably contains a fluid ejection device such as a heater resistor or piezoelectric device for causing ink or other fluids to flow out the ink chamber  52  through nozzle  38 .  
         [0028]    With most drop on demand ink jetting devices, ink occasionally drools out of the nozzle holes and forms a puddle on the nozzle plate when the ejection device is not in use. These puddles of ink should be occasionally wiped off of the nozzle plate so that formation of dried ink sufficient to affect nozzle performance will not occur. However, with the nozzle plate  34  having closely adjacent nozzles  36 ,  38  and  40  for depositing different colors of ink or different fluids, there is a possibility of ink colors mixing on the surface of the nozzle plate  34  when the nozzles  36 ,  38 , and  40  drool. If a puddle on the nozzle plate  34  connects different color nozzles, a difference in back pressure for a color ink adjacent the puddle may occur. A difference in back pressure may cause ink to flow from one ink feed slot to another thereby cross-contaminating the ink supplies and ruining the jetting device.  
         [0029]    In order to reduce mixing of different colors of inks on a surface  54  of a nozzle plate, a barrier system is provided by barrier layer  56  on the surface  54  of the nozzle plate  34  as shown in FIGS. 5 and 6. The barrier layer  56  is preferably provided by an ink resistant material such as a polyimide film available from DuPont High Performance Materials of Circleville, Ohio under the trade name KAPTON. The barrier layer  56  may be adhered to the surface  54  by a variety of means including adhesives, spin-coating and the like. Channels, such as channels  58 ,  60 ,  62 , and  64  may be cut into the barrier layer  56  to form individual barrier fingers  66 ,  68 , and  70  between adjacent nozzles to prevent color mixing and to direct puddles away from the nozzle holes.  
         [0030]    Because the barrier layer  56  may make it difficult to clean the nozzle plate  34  adequately, it is preferred that the surface  54  of the nozzle plate be coated with a hydrophobic material to reduce wetting of the nozzle plate surface  54 . Examples of hydrophobic coatings for nozzle plates include, but are not limited to, polytetrafluoroethylene, polyperfluoroalkoxybutadiene, polyfluorovinylidene, poly-fluorovinyl, polydiperfluoroalkyl fumarate, as described in U.S. Pat. No. 5,387,440to Takemoto et al., and a cross-linked silicone resin, such as the methyltrimethoxysilane manufactured by Dow Coming of Midland, Mich. under the trade name Z 6070 silane as described in U.S. Pat. No. 5,434,606 to Hindagolla et al.  
         [0031]    Hydrophilic material may be used as a nozzle plate coating to induce ink to flow away from the nozzle holes. Such wetting materials include, but are not limited to, polyethylene terphthalate (PET), and polycarbonate as described in U.S. Pat. No. 5,434,606 to Hindagolla et al., and titanium dioxide as described in U.S. Pat. No. 6,312,103 to Haluzak.  
         [0032]    The barrier layer  56  may also include additional flow channels for ink flow to the nozzles. Such flow channels  72  may be formed through a portion of the barrier layer  56  adjacent surface  54  of the nozzle plate  34  as shown by an end cross-sectional view of the nozzle plate  34 , barrier layer  56 , and substrate  48  in FIG. 7. Each of the flow channels  72  preferably connect to a fluid source such as provided by fill slot  42 .  
         [0033]    Another method for preventing the formation of puddles on the surface  54  of the nozzle plate  34 , instead of or in addition to the use of the barrier layer  56 , is to provide a solid flexible plug that can be pressed against the nozzle holes when the ejection device is capped. The plug would be sufficiently flexible to seal the nozzle holes thus preventing ink puddles from forming when the ejection device was not in use. It is preferred to apply the plug to the nozzle plate  34  after cleaning or wiping the surface  54  of the nozzle plate  34  to remove excess ink therefrom.  
         [0034]    In another embodiment, the nozzles in a nozzle plate for a jetting device may be arranged in a staggered array of triad nozzles to produce a staggered array of colored ink dots  74 ,  76 , and  78  as shown in FIG. 8. In this case, the nozzle triad dots  80  are offset from adjacent nozzle triad dots  82  rather than being aligned in a single column as shown by ink dots  28 ,  30 , and  32  in FIG. 3. In this embodiment, the nozzle contains nozzle holes in locations sufficient to produce the staggered array of colored ink dots  74 ,  76 , and  78 . In all other respects, the nozzle plate, nozzle holes, ink chambers, ink channels, and ink fill slots are similar to those described with respect to FIGS. 4-6. An advantage of such an arrangement of triad nozzles is that more space is provided on the substrate and in the nozzle plate for wiring and flow paths while maintaining a reduction in white space between the triad dots  80  and  82  as compared to colored dots in FIG. 2.  
         [0035]    Another arrangement of triad nozzles is provided in FIGS. 9-12. In this arrangement, instead of repeating CMY CMY CMY triad nozzles, the repeating sequence of nozzles is CMY YMC CMY YMC so that adjacent nozzles can share ink fills slots and flow channels as shown in FIGS. 9-12. With reference to FIG. 9, a nozzle plate  84  is provided containing a triad arrangement of nozzles  86 ,  88 , and  90 . As before, each of the nozzles  86 ,  88 , and  90  is preferably dedicated to a different color ink or different fluid. However, unlike the embodiment illustrated in FIGS. 4-6, adjacent nozzles such as nozzles  90  and  92  are dedicated to the same fluid or same color ink. In this case, nozzles  90  and  92  share a common ink flow channel  94  and a common ink fill slot  96 . Likewise, nozzles  86  and  98  share a common ink flow channel  100  and ink fill slot  102 , and nozzles  88  and  104  share a common ink flow channel  106  and ink fill slot  108 .  
         [0036]    An advantage of the repeating sequence of nozzles CMY YMC CMY YMC is that a simpler barrier layer  110  may be provided on a surface  112  of the nozzle plate as shown in FIGS. 10-12. As before, the barrier layer  110  provides channels  114 ,  116 , and  118  and fingers  120 ,  122 ,  124 ,  126 , and  127  (FIG. 11). Channels  128  and  130  and fingers  132 ,  134 , and  136  are shown in FIG. 12 for an opposite side of the nozzle plate  84 .  
         [0037]    An ink jetting device  138  incorporating nozzle plate  34  or nozzle plate  84  according to the invention is illustrated for example in FIG. 13. The nozzle plate  34  is attached to a jet head portion  140  of the jetting device  138 . An elongate body portion  142  to which the jet head portion  140  is attached preferably contains a power source such as a battery, logic devices for activating jetting devices on the jet head substrate, and a fluid reservoir. An activation switch  144  is preferably provided to activate the jetting devices. A cap or cover  146  is provided to seal the jet head portion  140  and nozzle plate  34  when the jetting device  138  is not being used.  
         [0038]    A typical fluid reservoir  148  for the jetting device  138  is illustrated for example in FIG. 14. The fluid reservoir  148  may be removably or permanently attached to the jet head portion  140  containing the nozzle plate  38 . A tape automated bonding (TAB) circuit or flexible circuit  150  may be connected to the substrate  48  for activating ejection devices on the substrate  48 . Electrical contact pads  152  are provided on the TAB circuit or flexible circuit  150  for providing power to the ejection devices.  
         [0039]    A typical thermal type fluid jetting device  154  on a substrate  48  is illustrated for example in FIG. 15. The substrate  48  preferably provided by a silicon material containing a thermal barrier layer  156  and a resistive material layer  158 . The resistive layer may be made from a variety of materials including but not limited to tantalum/aluminum alloys. A first metal conductive layer  160  such as aluminum, copper, or gold provides anode  162  and cathode  164  connections to the resistive layer  158 . In order to protect the ejection device  154  from corrosion and erosion, a dual layer including a passivation layer  166  made of silicon nitride, silicon carbide, or a combination of silicon nitride and silicon carbide, and a cavitation layer  168  made of tantalum is preferably provided. A dielectric layer  170  is preferably provided over the first metal conductive layer  162  to insulate layer  162  from a second metal conductive layer  172 . Like the first metal conductive layer  160 , the second metal conductive layer  172  may be made of aluminum, copper, gold and the like. A nozzle plate, such as nozzle plate  34  described above is attached substrate  48  to provide ink chamber  52  for fluid to be ejected by ejection device  154 .  
         [0040]    With regard to operation of the jetting device  154 , ejection device wiring may be simplified by connecting multiple ejection devices in parallel to a single drive transistor. Typically all of the ejection devices connected in parallel would be for jetting the same fluid or same color ink. The ejection devices may be activated in bursts so that a time between dot deposits is less than a time required to completely refill an ink chamber  52 . Accordingly, the first dot deposit will be a full volume fluid and subsequent dot deposits will contain less than a full volume of fluid. The different volume fluid droplets will have different velocities and directions, thus encouraging mixing between different fluids or different color inks on the print media.  
         [0041]    Another advantage of the invention is that a conventional ink jet printer rather than a hand held jetting device may be designed to use triad nozzle hole configurations as set forth above. There are several advantages resulting from the use of a triad nozzle arrangement for an ink jet printer. For example, as the printhead is swept across a print media by a printhead carrier, the carrier motion often introduces unwanted vibrations into the printhead. Traditional spacing between different color ink jet nozzles may cause the nozzles to fire at different phases of the carrier vibrations. The resulting errors in relative CMY dot placement can cause print quality defects. With the triad nozzle arrangement described above, all three colors can fire at the same phase of carrier vibration thus improving print quality.  
         [0042]    Yet another advantage of the invention is that a printhead containing the triad nozzle arrangement is substantially unaffected by the direction of travel of the printhead across the print media because the CYM dots are fired at the same time and arrive on the print media at the same time. With traditional print heads, there is a shift in the color table for left-to-right versus right-to-left motion of the printhead across the print media due to the order in which the dots arrive on the print media.  
         [0043]    Still another advantage of the invention is that motion of the printhead is not required to mix the colors or to provide dots that appear to be a different color. Accordingly, applications that do not require a mechanism to move the printhead across the print media may be used.  
         [0044]    It is contemplated, and will be apparent to those skilled in the art from the preceding description and the accompanying drawings, that modifications and changes may be made in the embodiments of the invention. Accordingly, it is expressly intended that the foregoing description and the accompanying drawings are illustrative of preferred embodiments only, not limiting thereto, and that the true spirit and scope of the present invention be determined by reference to the appended claims.