Abstract:
An electroluminescent display with integrated touch screen, including: a transparent substrate having two faces; a flat panel display matrix forming an electroluminescent display located on one face of the substrate for emitting light through the substrate; touch sensitive elements of a touch screen located on the other face of the substrate; and a single flex-cable containing a plurality of conductors electrically connected to both the flat panel display matrix and the touch sensitive elements for providing external electrical connection to the display.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to color flat panel displays and, more particularly, to an electroluminescent flat panel display with integral touch sensitive elements.  
         BACKGROUND OF THE INVENTION  
         [0002]    Modem electronic devices provide an increasing amount of functionality with a decreasing size. By continually integrating more and more capabilities within electronic devices, costs are reduced and reliability increased. Touch screens are frequently used in combination with conventional soft displays such as cathode ray tubes (CRTs), liquid crystal displays (LCDs), plasma displays and electroluminescent displays. The touch screens are manufactured as separate devices and mechanically mated to the viewing surfaces of the displays.  
           [0003]    [0003]FIG. 1 shows a prior art touch screen  10 . A touch screen  10  includes a transparent substrate  12 . This substrate  12  is typically glass, but other materials, such as plastic, may be used. Various additional layers of materials comprising touch sensitive elements  14  of the touch screen  10  are formed on top of the substrate  12 . The touch sensitive elements  14  include transducers and circuitry that is necessary to detect a touch by an object, in a manner that can be used to compute the location of such a touch. A cable  16  is attached to the circuitry so that various signals may be brought onto or off of the touch screen  10 . The other end of the cable  16  is connected to an external controller  18 .  
           [0004]    [0004]FIG. 2 shows a cross section view of a typical prior art electroluminescent display such as an organic light emitting diode (OLED) flat panel display  20  of the type shown in U.S. Pat. No. 5,937,232, issued Aug. 10, 1999 to Tang. The OLED display includes a substrate  22  that provides mechanical support for the display device, a transistor switching matrix layer  24  comprised of a two dimensional array of thin film transistors  26 , a light emission layer  28  containing materials forming organic light emitting diodes, and a cable  30  for connecting circuitry within the flat panel display to external controller  32 . The substrate  22  is typically glass, but other materials, such as plastic, may be used. The transistor switching matrix layer  24  is formed and patterned using typical semiconductor manufacturing processes. Together, transistor switching matrix layer  24  and the light emission layer  28  comprise a flat panel display matrix  29 .  
           [0005]    Conventionally, when a touch screen is used with a flat panel display, the touch screen is simply placed over the flat panel display, and the two are held together by a mechanical mounting means such as a frame. FIG. 3 shows such a prior art arrangement with a touch screen mounted on an OLED flat panel display. After the touch screen and the OLED display are assembled, the two substrates  12  and  22  are placed together in a frame  34 , often separated by a mechanical separator  36 . The resulting assembly contains two cables  16  and  30  that connect the touch screen and the flat panel display to external controllers.  
           [0006]    U.S. Ser. No. 09/826,194, filed Apr. 4, 2001 by Siwinski et al. proposes a device in which an organic electroluminescent flat panel display is integrated with a touch screen, sharing a common substrate. FIG. 4 shows this structure. A display with touch screen  38  contains a single substrate  40  with two faces. An image display containing a flat panel display matrix  29  and a cable  30  is manufactured on one face. Touch sensitive elements  14  and cable  16  are manufactured on the opposite face. This invention has advantages over existing touch screen and flat panel display combinations with decreased cost, no integration steps, decreased weight and thickness, and improved optical quality.  
           [0007]    However, the invention of Kilmer et al. still contains two cables  16  and  30 . This duplication adds to system cost, since two cables are needed to interface one display module to external circuitry, and therefore two connectors to receive these cables are needed as well. Additionally, the presence of two cables, rather than one, requires an additional assembly step during system integration, since the two cables must be connected to two different connectors. This makes system integration unnecessarily complex, since room must be made for two separate cables and therefore connectors in which these cables must plug.  
           [0008]    There remains a need for an improved touch screen electroluminescent display system that removes redundant materials, decreases cost, and simplifies system integration tasks.  
         SUMMARY OF THE INVENTION  
         [0009]    The need is met according to the present invention by providing an electroluminescent display with integrated touch screen, including: a transparent substrate having two faces; a flat panel display matrix forming an electroluminescent display located on one face of the substrate for emitting light through the substrate; touch sensitive elements of a touch screen located on the other face of the substrate; and a single flex-cable containing a plurality of conductors electrically connected to both the light emitting elements and the touch sensitive elements for providing external electrical connection to the display.  
         ADVANTAGES  
         [0010]    The present invention has the advantage that it reduces complexity of the display, thereby reducing manufacturing costs and improving reliability of the display. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a schematic diagram showing the basic structure of a prior art touch screen;  
         [0012]    [0012]FIG. 2 is a schematic diagram showing the structure of a prior art organic electroluminescent display;  
         [0013]    [0013]FIG. 3 is a schematic diagram showing the combination of a touch screen with a flat panel electroluminescent display mounted using a bracket, as would be accomplished in the prior art;  
         [0014]    [0014]FIG. 4 is a schematic diagram showing the combination of a touch screen with a flat panel electroluminescent display manufactured on a single substrate, and provided with separate external connections for the display and the touch screen;  
         [0015]    [0015]FIG. 5 is a schematic diagram showing the basic structure of an electroluminescent display with a touch screen and a single flex-cable according to the present invention;  
         [0016]    [0016]FIGS. 6 a  and  6   b  are schematic diagrams showing an embodiment of the present invention with a split flex-cable;  
         [0017]    [0017]FIGS. 7 a  and  7   b  are schematic diagrams showing an embodiment of the present invention with an unsplit flex-cable and metal contacts connecting the two sides of the substrate; and  
         [0018]    [0018]FIGS. 8 a  and  8   b  are schematic diagrams showing an embodiment of the present invention with a single metallized cable connecting to contacts on two sides of the substrate. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    Referring to FIG. 5, an electroluminescent display generally designated  38  according to the present invention includes a single substrate  40  having a flat panel display matrix  29  of an electroluminescent display formed on one face of the substrate for emitting light through the substrate, touch sensitive elements  14  of a touch screen formed on the other face of the substrate  40 , and a single flex-cable  50  used for connecting the electroluminescent display  38  with external electronics  52 . As used herein, the term flex-cable refers to a flat, flexible laminated cable, for example of the type sold by the Parlex Corporation, Methuen, Mass.. The substrate  40  is made of a transparent material, such as glass or hard plastic, and is thick enough to provide mechanical support for the flat panel display matrix  29  and the touch sensitive elements  14 .  
         [0020]    The flex-cable  50  contains conductors that allow image data, display control signals, bias voltages, and touch screen signals to pass between external electronics  52  and the electroluminescent display  38 . External electronics  52  contain circuitry to control the touch sensitive elements  14  and the flat panel display matrix  29 , and is typically some combination of external controllers  18  and  32 . The circuitry can physically be either in one integrated circuit, or in a multiplicity of packages. The signals carried by conductors in flex-cable  50  are routed on a circuit board to the appropriate circuitry. The number of conductors in the flex-cable  50  of this embodiment is equal to the number of conductors needed in the cable  16  plus the number of conductors needed in the cable  30 .  
         [0021]    This improved display eliminates the need for a second cable, a second connector for mating with this second cable, and therefore eliminates one assembly step during system integration, as well as the cost of a second cable and connector. This reduces system cost, manufacturing cost, and system integration complexity.  
         [0022]    [0022]FIG. 6 a  shows a side view of an embodiment of the present invention where the flex-cable  50  is bifurcated near the end that is attached to metallic pads within the flat panel display matrix  29  and within the touch sensitive elements  14 . FIG. 6 b  shows a front view of this embodiment. Here, all conductors within the flex-cable  50  that connect to the touch sensitive elements  14  are within the portion of the flex-cable that is attached to the touch sensitive elements  14 . All conductors within the flex-cable  50  that connect the flat panel display matrix  29  are within the portion that is attached to the flat panel display matrix  29 .  
         [0023]    Metallic pads are formed on each side of the substrate  40  via a photolithography process in conjunction with chemical vapor deposition (CVD), electroplating, ebeam, ion-beam, or x-ray processing. The metallic pad formation occurs simultaneous to the manufacturing of the touch sensitive elements  14  and the flat panel display matrix  29 ; the metallic pads are a part of these layers. The flex-cable  50  is attached to these metallic pads via a conventional bonding process, such as wire bonding or crimp bonding. Contacts of the cable adhere to both semiconducting and insulating layers, are highly conductive, and are capable of handling high current densities while still maintaining their electrical integrity. The contacts are typically made of gold, silver, or aluminum, but any other highly conductive materials could be used. This embodiment has the advantage of simplicity of manufacturing of the image display.  
         [0024]    [0024]FIG. 7 a  shows an edge view of an embodiment of the present invention where flex-cable  50  is not bifurcated, and is attached to only one face of the substrate  40 . FIG. 7 b  shows a front view of this embodiment. The flex-cable  50  is attached to the flat panel display matrix  29 , rather than to the touch sensitive elements, since more conductors are typically needed for the display. The touch sensitive elements are connected to the appropriate conductors in the flex-cable  50  via conductors  54  such as metal connectors that are attached to the sides of the substrate  40 . The metal connectors  54  are vacuum deposited, electrochemically attached, screen printed, or glued along the edges of the substrate  40  and bonded to the two faces of the substrate  40 . Metallic pads are formed within the flat panel display matrix  29  for attaching the flex-cable to the electroluminescent display  38 .  
         [0025]    This arrangement increases the robustness of the resulting electroluminescent display by allowing the attachment of the flex-cable  50  to the electroluminescent display  38  on just one face of the substrate  40 , thereby reducing the strain on flex-cable  50 , which may be subjected to various forces during system integration. This embodiment has the advantage of simplicity in cable bonding, since no bifurcation of the flex-cable is required, and all conductors are attached to the same side of the substrate  40 .  
         [0026]    [0026]FIG. 8 a  shows an edge view of an embodiment of the present invention where flex-cable  50  is not bifurcated, or connected to one face of the substrate  40  but is connected directly to a metallization layer  56  deposited on a side of the substrate  40 . FIG. 8 b  shows a front view of this embodiment. The metallization layer  56  is vacuum deposited, electrochemically attached, screen printed, or glued along the edges of the substrate  40  and bonded to the two faces of the substrate  40 . Connections to both the flat panel display matrix  29  and the touch sensitive elements  14  are made via metal connectors formed within the metallization layer  56 . The flex-cable  50  is attached to the metallization layer  56  via a cable bonding method such as wire bonding or crimp bonding, and held in place by cable clip  58 . This embodiment has the advantage of increased robustness of the resulting electroluminescent display by allowing the attachment of the flex-cable  50  to both the flat panel display matrix  29  and the touch sensitive elements  14  in only one location, reducing the strain on flex-cable  50 , which may be subjected to various forces during system integration.  
         [0027]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.  
                       PARTS LIST                                       10  touch screen           12  substrate           14  touch sensitive elements           16  cable           18  external controller           20  flat panel display           22  substrate           24  transistor switching matrix layer           26  thin film transistor           28  light emission layer           29  flat panel display matrix           30  cable           32  external controller           34  frame           36  mechanical separator           38  display with touch screen           40  substrate           50  flex-cable           52  external electronics           54  metal connector           56  metallization layer           58  cable clip