Abstract:
A printer for digital printing in which ink is deposited in metered amounts on a substrate. The printer includes a wheel rotatable by a shaft of a motor, an idler disposed in a paint reservoir, and a segment of wire disposed around the wheel and the idler. A computer controls movement of the wire by controlling the rotation of the wheel. As the motor rotates the wheel, electroluminescent material contained within the paint reservoir coats the wire and is drawn by the wire in front of an air stream, which pulls the electroluminescent material from the wire and carries it toward the substrate to make an electroluminescent sign.

Description:
BACKGROUND 
       [0001]    Two conventional printing techniques include ink jet printing and screen printing. Ink jet printers work by depositing small droplets of ink in various colors, typically cyan, magenta, yellow and black, on a print medium or substrate to form a color image. Conventional thermal ink jet printing heads include several nozzles and thermal elements. Ink is expelled from the nozzles in a jet by bubble pressure created by heating the ink using the thermal elements while the nozzles and thermal elements are in close proximity. Ink jet print heads use relatively small orifices, valves, and nozzles for depositing the desired quantity and color of ink on the print medium. Therefore, very fine grade inks are required in which particle sizes of the pigments within the inks are kept to a minimum to help keep the orifices, valves, and nozzles of the ink system from becoming clogged. 
         [0002]    In screen printing, ink is forced through a design-bearing screen onto the substrate being printed. The screen is made of a piece of porous, finely woven fabric stretched over a wood or aluminum frame. Areas of the screen are blocked off with a non-permeable material, a stencil, which is a negative of the image to be printed. The screen is placed on top of a piece of print substrate, often paper or fabric. Ink is placed on top of the screen, and scraper blade is used to push the ink evenly into the screen openings and onto the substrate. The ink passes through the open spaces in the screen onto the print substrate; then the screen is lifted away. The screen can be re-used for multiple copies of the image, and cleaned for later use. If more than one color is being printed on the same surface, the ink is allowed to dry and then the process is repeated with another screen and different color of ink. Screen printing requires use of inks having a relatively high viscosity to prevent all the ink from simply passing through the screen onto the print substrate. 
         [0003]    Accordingly, a need exists for an improved apparatus and method for printing inks. 
       SUMMARY 
       [0004]    A method, consistent with the present invention, can be used to form a pattern on a substrate to make an electroluminescent sign. The method includes coating at least a portion of an exterior surface of a cable with an electroluminescent material, directing an air stream at the portion of the cable coated with the electroluminescent material, and electronically controlling advancement and position of the cable through the air stream such that a metered amount of the electroluminescent material is removed from the exterior surface of the cable and is deposited onto the substrate to form a pattern on the substrate. 
         [0005]    An apparatus, consistent with the present invention, can deposit an ink on a substrate. The apparatus includes an electronically controllable drive mechanism and a structure associated with the drive mechanism and movable thereby. An electroluminescent material supply is in communication with the structure for depositing electroluminescent material on at least a portion of the structure. At least one fluid nozzle having at least one nozzle orifice is positioned and oriented for directing at least one jet of fluid toward at least a portion of the structure to remove an amount of the electroluminescent material from the structure and direct the amount toward a substrate. The movement of the structure relative to the at least one fluid nozzle substantially controls the amount of the electroluminescent material removed from the structure, and the amount of the electroluminescent material directed to the substrate to form a pattern on the substrate to make an electroluminescent sign. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, explain the advantages and principles of the invention. In the drawings, 
           [0007]      FIG. 1  is a perspective view of one embodiment of a fluid delivery system or printer; 
           [0008]      FIG. 2  is a side view of the fluid delivery system of  FIG. 1 ; and 
           [0009]      FIG. 3  is a diagram of a system to use the printer to print materials onto a substrate. 
       
    
    
     DETAILED DESCRIPTION 
     Printing System 
       [0010]      FIG. 1  is a perspective view of one embodiment of the fluid delivery system or printer, generally indicated at  10 .  FIG. 2  is a side view of the fluid delivery system or printer of  FIG. 1 . A pulley  13  having a circumscribing groove  38  defined therein is secured to a shaft  15  of a motor  14 . An elongate frame member  32  is secured to frame or plate  12  and extends into a reservoir of ink  24 . A rotatable or stationary guide  34  is attached to a distal end  37  of elongate frame member  32 . Guide  34  is illustrated as a cylindrical, non-rotatable member having a groove  40  circumscribing guide  34  in which a wire cable  36  can slide during rotation of wheel  13 . Alternatively, guide  34  can be implemented with a rotatable member. As used herein, the term “cable” or “wire” or “wire cable” or “elongate segment” is meant to include the use of a wire, a cable formed of multiple wires, a rod, a saw tooth wheel, or variations thereof. Wire cable  36  is disposed in groove  38  circumscribing the wheel  13  and in groove  40  circumscribing guide  34 . 
         [0011]    An elongate reservoir retaining member  16  is attached to plate  12  and includes a flange  18  defining a notch  20  between the flange  18  and elongate reservoir retaining member  16 . Notch  20  is configured to receive a top lip  22  of ink reservoir  24 . A bottom plate  26  is secured to a distal end  28  of elongate reservoir retaining member  16  with a threaded nut  31  that is threaded onto a threaded shaft  33 . Threaded shaft  33  is secured to distal end  28  of elongate reservoir retaining member  16 . Bottom plate  26  abuts against the bottom  30  of ink reservoir  24  and holds it between flange  18  and bottom plate  26 . 
         [0012]    An air supply hose  42  is secured to a nozzle body  44  and supplies air through a nozzle orifice  46  that is aimed at a portion of cable  36 . A cable guide  48  defining a longitudinal slot  50  is positioned proximate nozzle orifice  46 . Cable  36  rides within slot  50  and is thus held in relative position to nozzle orifice  46  so that air passing therethrough does not substantially move cable  36  from in front of nozzle orifice  46  or cause cable  36  to substantially vibrate. Slot  50  can alternatively include a small rotatable guide. 
         [0013]    Rotation of shaft  15  may be controlled by a controller, generally indicated at  57 . Any type of controller may be used. In one embodiment, the controller includes circuitry  54  in a module  56  that receives signals from a signal generating device  52 , such as a microprocessor or other devices that can supply discrete signals to instruct selective rotation of the shaft  15  of the motor. Circuitry  54  receives a signal(s) from generating device  52  and rotates shaft  15  of the motor according to the signal(s). 
         [0014]    In operation, ink contained in reservoir  24  is picked up by wire cable  36  and advanced by rotation of wheel  13 , indicated by the arrow, in front of nozzle orifice  46 . Fluid that is blown through nozzle orifice  46  disperses or pulls the ink from cable  36  toward the print medium. Depending on the viscosity of the ink in the reservoir, the cross-sectional diameter of cable  36 , and the diameter of wheel  13 , a relatively precise amount of ink can be dispensed. The ink is dispersed onto a substrate  58 , as illustrated in  FIG. 2 . 
         [0015]    The print head in system  10  can include alternative implementations, as shown in FIG. 1A in U.S. Pat. No. 5,944,893 and described in the corresponding text. For example, the print head can include a discontinuous wire, guide  34  can be rotatable, a spring tensioning mechanism can be used, and an air solenoid can be used to turn the air supply on and off. 
         [0016]    The fluid delivery system or printer of the present invention is based on printer technology that is described in U.S. Pat. Nos. 5,944,893; 5,972,111; 6,089,160; 6,090,445; 6,190,454; 6,319,555; 6,398,869; and 6,786,971, all of which are incorporated herein by reference as if fully set forth. 
         [0017]    As used herein, the term “ink” is meant to include any pigmented material, including, but not limited to, inks, dyes, paints, particle loaded suspensions, or other similarly pigmented liquids. 
         [0018]    As used herein, the term “print medium” or “substrate” are meant to include any print medium known in the art, including but not limited to paper, plastic, polymer, synthetic paper, non-woven materials, cloth, metal foil, vinyl, films, glass, wood, cement, and combinations or variations thereof. The print medium or substrate can be a rigid material or a flexible material. 
         [0019]      FIG. 3  is a diagram of a system  130  to use the printer to print ink onto a substrate. System  130  includes a print head  148  mounted on a track  142  supported by vertical posts  144  and  146 , a wall, or other support. Print head  148  corresponds with printing system  10 . A drive unit  134 , using a motor, controls movement of print head  148  along track  142  in an x-direction as indicated by arrows  140 . A substrate support  150  is located on a track  136 , which would be supported by a vertical post, wall, or other support. A drive unit  132 , using a motor, controls movement of substrate support  150  along track  136  in a y-direction as indicated by arrows  138 . A substrate can be mounted or otherwise affixed to substrate support  150 , and a line or pattern can be printed upon the substrate by print head  148 . The configuration of the line or pattern is determined by the coordinated movement of print head  148  along track  142  and the substrate on substrate support  150  along track  136 . 
         [0020]    A computer  100 , corresponding with controller  57  and used to implement controller  57 , electronically controls print head  148  and drive units  132  and  134  for moving substrate support  150  and print head  148 , respectively. Computer  100  can include, for example, the following components: a memory  112  storing one or more applications  114 ; a secondary storage  120  for providing non-volatile storage of information; an input device  116  for entering information or commands into computer  100 ; a processor  122  for executing applications stored in memory  112  or secondary storage  120 , or as received from another source; an output device  118  for outputting information, such as information provided in hard copy or audio form; and a display device  124  for displaying information in visual or audiovisual form. Computer  100  can optionally include a connection to a network such as the Internet, an intranet, or other type of network. 
         [0021]    Computer  100  can be programmed to control movement of print head  148  along track  142  and substrate support  150  along track  136 . In particular, computer  100  can be programmed to electronically control movement of print head  148 , via drive unit  134 , in x-direction  140  laterally across a substrate on substrate support  150 , and computer  100  can be programmed to electronically control movement of the substrate on substrate support  150 , via drive unit  132 , in y-direction  138  vertically with respect to print head  148 . Computer  100  also controls print head  148 , as described above, for movement of the wire and delivery of the ink from the wire to the substrate. Computer  100  can also be programmed to control an air solenoid in system  10 . The use of tracks  136  and  142  for coordinated movement of substrate support  150  and print head  148 , respectively, thus effectively functions as an X-Y stage for using the printer to print a wide variety of shapes and configurations of patterns, lines, or other elements. As an alternative, lines or patterns can be printed using one of the following techniques: coordinated movement of print head  148  in the y-direction and substrate support  150  in the x-direction; movement of print head  148  in both the x-direction and y-direction; or movement of substrate support  150  in both the x-direction and y-direction. 
         [0022]    Computer  100  can also be programmed to control the printer for radial printing. In particular, a first orifice can direct an air jet at the wheel or wire to remove paint in a purely radial direction, while other orifices supplying air can be angled above the air jet created by the first orifice to help eliminate conical divergence of the paint as it is pulled from the surfaces of the wheel or wire. 
       Printing Electroluminescent Lamps 
       [0023]    As described above, the printer uses a wire to carry ink from the ink reservoir to the air jet, which blows the ink off the wire and onto the surface being coated. The quantity and quality of ink applied to the surface depends on the wire feed rate, rheologic properties of the ink, air flow, orifice geometry, and distance from the print head to the surface, among other things. The mechanism for this ink transport is shown in  FIGS. 1 and 2 .  FIG. 3  illustrates an exemplary system for printing a line or pattern on a substrate using the printer. 
         [0024]    Embodiments of the present invention include methods to digitally print electroluminescent signs using the printer described above. The printer is especially suited to digitally printing electroluminescent materials that cannot be digitally printed using standard techniques. The term “electroluminescent material” can refer to an electroluminescent material, an encapsulated electroluminescent material, or particles of electroluminescent materials. These materials can be suspended in a fluid possibly containing a binder or other materials. 
         [0025]    The Luxprint electroluminescent system from DuPont Microcircuit Materials is a set of materials that, when screen printed in layers, creates electroluminescent lamps. That system includes compatible electroluminescent phosphors, dielectric compositions, carbon conductors, translucent conductors, and silver conductors. All of these materials are designed to be applied using standard screen printing techniques. 
         [0026]    The printer described above provides for a technique to allow the user to digitally print multiple color electroluminescent signs and to control color blending and gradients currently not possible with screen printing. Digital printing also improves the versatility of the process, allowing for easy customization and quick changeover of printing patterns. In addition, the rear electrode for an electroluminescent sign can be printed using conductive ink provided into sections of the sign that can then be lit at different times, producing motion. 
       EXAMPLE 
       [0027]    The following three different color phosphors were obtained from DuPont 
         [0028]    Microcircuit Materials Luxprint 8150B White High Brightness Electroluminescent Phosphor; Luxprint 8152B Blue-Green High Brightness Electroluminescent Phosphor; and Luxprint 8154B yellow-Green High Brightness Electroluminescent Phosphor. The Microencapsulated electroluminescent phosphors were diluted with diethylene glycol monoethyl ether acetate (Alfa Aesar, 99% purity) as a solvent. The diluted inks were loaded into the magenta, cyan, and yellow cans of the 3-color printer. 
         [0029]    Images stored in JPG files were imported into the Photoshop program and modified to optimize the look of the image with the three available colors, and resulting JPG images were loaded into the driver software for the printer. The images were printed with the phosphors onto poly(ethylene terephthalate) (PET) coated with indium tin oxide. 
         [0030]    The samples were then screen printed using a 157 mesh nylon screen with two layers of dielectric (Luxprint 8153 High K Dielectric Insulator), then a layer of carbon conductor (Luxprint 8144 Carbon Conductor). The resulting multi-layer prints were connected to an electroluminescent lamp driver (electroluminescent backlighting HV809 Demo Board, Mouser electronics part number 689-HV809 DB1).