Abstract:
A flexible electronic color display includes a light-emitting diode (LED) matrix formed from an interweaved weft of conductive strands and warp of light-emitting diode (LED) fiber of a conductive core coated with a p-doped semiconductor and then an n-doped semiconductor of light-emitting polymer. Each conductive strand physically and electrically couples to each LED fiber at one location to form an LED that may activated as a pixel. Alternating LED fibers of different hues may provide a color display, especially for a relatively fine weave or for displays viewed from a distance. Alternatively, conductive strands and LED fibers may be selected having sufficient transparency that layers of multiple LED matrices, each having a selected hue, may form a color flexible display. In addition, methods for fabricating the LED matrix and for detecting and eliminating flaws from the LED matrix allow for economical manufacture.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to electronic, light-emitting displays. 
     BACKGROUND OF THE INVENTION 
     Electronic displays present various forms of display information, such as text, graphics, and video, as a pixelized image to a user. The presentation of pixelized display information may be an essential function of an electronic device, such as personal computer. In other applications, pixelized display information enhances the features of an electronic device, such as enabling a cellular telephone to be readily programmable and to provide functions such as digital paging. 
     A number of electronic display technologies are available, each having specific attributes that limit their application. Cathode Ray Tubes (CRTs), for instance, are widely used for computer monitors and televisions. CRTs have good color, contrast, and brightness, as well as being a mature, economical technology. CRTs are not particularly compact, being limited by the geometries imposed by its electron gun and pixel elements formed at substantially perpendicular relation to the electron gun. Moreover, the vacuum requirements of a CRT dictate a heavy glass construction. Thus, the size, weight, rigid fragile construction, and power consumption of CRTs limits their use in portable applications. 
     As an alternative to CRTs, plasma screen technology allows for a display flatter and wider than CRTs and rear projection televisions. However, plasma screen technology is difficult to manufacture, and thus expensive. Moreover, although flatter than CRTs, plasma screens have similar limitations as do CRTs for weight and rigidity. Consequently, plasma screen displays are used in certain notebook computers and relatively expensive portable devices. 
     Various other technologies allow for flat, lighter weight, and lower power consumption than CRTs, appropriate to more portable applications. Liquid Crystal Displays (LCD) and active matrix LCDs are widely used in notebook computers and personal digital assistant (PDA) products, for example. To provide a degree of flexibility and resistance to impact, plastic LCDs are known. Also, LCDs are generally less expensive than other displays of comparable size; however, LCDs are generally too expensive to incorporate into limited life, disposable products. 
     Consequently, a significant need exists for a light weight, inexpensive display, especially a color display that is suitable for use in portable electronic devices and a variety of applications. 
     SUMMARY OF THE INVENTION 
     The present invention generally provides a light-emitting fabric that provides for a flexible display suitable for use as a substitute for known portable electronic displays, as well as enabling new applications unsuited to known display technology. 
     In one aspect consistent with the invention, a light-emitting diode (LED) matrix is formed from interlaced weft of conductive strands and warp of LED fibers. The LED fibers have a conducting core, a first doped layer surrounding the core, and a second doped layer surrounding the first doped layer. The first and second doped layers form a light-emitting semiconductor junction. Each conductive strand electrically couples to each LED fiber at a respective lateral location, forming a light-emitting diode (LED) at each lateral location. 
     In another aspect consistent with the invention, a method of fabricating a light-emitting diode (LED) matrix includes making an LED fiber. The LED fiber is formed from a conducting core that is clad with a p-doped semiconductor to form an inner strand. Then, the inner strand is clad with an n-doped semiconductor. At least one of the p-doped semiconductor and n-doped semiconductor includes a light-emitting polymer so that the conducting a current at a lateral location on the LED fiber creates an LED. 
     These and other objects, advantages and features of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a block diagram of a light emitting diode fiber matrix activated by a display driver to form a flexible display consistent with aspects of the invention; 
     FIG. 2 is a perspective view of the flexible display along line  2 — 2  of FIG. 1; 
     FIG. 3A is a cross-sectional view of a light-emitting diode fiber and a conductor along line  3 A— 3 A of FIG. 2; 
     FIG. 3B is a schematic of the light-emitting diode formed by a junction of the light-emitting diode fiber and the conductor of FIG. 3A; 
     FIG. 4 is a schematic of the light-emitting diode matrix of FIG. 1; 
     FIG. 5 is a simplified depiction of fabricating the light-emitting diode fiber of FIG  1 ; 
     FIG. 6 is a simplified depiction of a continuous plasma processing system for fabricating LED fibers; 
     FIG. 7 is an illustrative depiction of weaving the light-emitting diode fibers into the light emitting diode fiber matrix of FIG. 1; 
     FIG. 8 is an illustrative depiction of extracting one or more light emitting diode fiber matrices from a flawed light emitting diode fiber matrix formed by the method of FIG. 7; 
     FIG. 9 is a backing surface enhanced light emitting diode fiber matrix; 
     FIG. 10 is a color light emitting diode fiber matrix composed of a stack of monochrome light emitting diode fiber matrices; 
     FIG. 11 is a multi-woven, pacified LED matrix; and 
     FIGS. 12A-12J are illustrative applications of a flexible display of FIG. 1 consistent with aspects of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning to the Drawings, wherein like numbers denote like parts throughout the several views, FIG. 1 depicts a light emitting diode fiber matrix  10  activated by a display driver  12  to form a flexible display  14  consistent with aspects of the invention. 
     The LED fiber matrix  10  includes a plurality of LED fibers  1   6  forming a warp  18  interlaced with a plurality of conductive strands  20  forming a weft  22 . The interlacing physically and electrically isolates each LED fiber  16  from other LED fibers  16  as well as physically and electrically isolating each conductive strand  20  from the other conductive strands  20 . Each LED fiber  16  contacts each conductive strand  20  at a lateral location  24 . A light-emitting diode (LED)  26  is formed at each lateral location  24 , as will be discussed in more detail below with regard to FIGS. 3A and 3B. 
     Each lateral location  24  is electrically addressable by the display driver  12  by a control circuit  28  and a multiplexer (MUX)  30  completing an electrical circuit that includes one LED fiber  16  and one conductive strand  20 . An image is generated upon the LED fiber matrix  10  by coordinating, such as with a central processing unit (CPU)  32 , the activation of the LED  26  at each lateral location  24 . For example, the CPU  32  may sequentially couple each conductive strand  20  to ground with MUX  30 . Each lateral location  24  on the grounded conductive strand  20  is then activated, either sequentially or simultaneously, by the control circuit  28  coupling a voltage to the corresponding LED fibers  16 , to illuminate a row of pixels that occur at the intersection of a currently grounded conductive strand  20  and LED fibers  16 . 
     The CPU  32  maps each pixel contained in a transmitted, stored or generated signal to the one or more lateral locations  24  to form a display pixel such as shown at  34 . It should be appreciated that the display pixel  34  may be formed from a single lateral location  24 , especially for a high resolution, monochromatic flexible display  14 . Alternatively, a plurality of adjacent lateral locations  24  may be simultaneously, or nearly simultaneously, activated to form a display pixel  34 . For example, a color display pixel  34  may be formed from adjacent LED fibers sequentially provided with hues of red, green and blue. 
     Referring to FIG. 2, a perspective depiction of the LED fiber matrix  10 , viewed along the line  2 — 2  of FIG. 1, shows the interlaced, or woven, relationship of the LED fibers  16  and conductive strands  20 . Cylindrical cross sections for the LED fibers  16  and conductive strands  20  are for illustrative purposes only. For example, the LED fibers  16  and/or the conductive strands  20  may be ribbon shaped. Ribbon-shaped LED fibers  16  may further be single sided in that the P-N junction described below may be formed on one side. 
     Turning to FIG. 3A, a cross-sectional depiction of a lateral location  24  illustrates how an LED  26  is formed from a core forming an electrical base B. About the base B is a semiconductor, light-emitting polymer p-doped layer P. About the p-doped layer P is a semiconductor, light-emitting polymer n-doped layer N. The n-doped layer N contacts the conductor at terminal A. 
     An insulating layer  36  is advantageously depicted as coating the external portions of the lateral location  24 . It should also be appreciated that the insulating layer  36  may advantageously insulate the LED fiber matrix  10  from external contact, and/or assist electrically isolating individual LED fiber  16  or conductive strands  20  from internal shorting. Alternatively, the insulating layer  36  may comprise an oxidation layer. In addition, the insulating layer  36  may enhance the physical coupling of the LED fibers  16  to the conductive strands  20 . The insulating layer may contain a pigment so that coated portions of the LED fiber matrix  10  are provided a hue, as an alternative to tinting the LED fibers  16  and/or the conductive strands  20 . 
     It should further be appreciated that an LED fiber matrix  10  consistent with aspects of the invention may be formed as a nonwoven fabric in which the conductive strands  20  merely overlay the LED fibers  16 , with the physical contact created by adhesion rather than interlacing. Adhesion may be achieved by dispensing the conductive strands  20  onto the LED fibers  16 , whereupon the LED fibers  16  or conductive strands  20  are initially adhesive before setting, or rendered adhesive through heating. Alternatively, the insulating layer  36  may act as the adhesive. 
     It should be further appreciated that, although an LED fiber  16  is depicted having an outer n-doped layer N, it is consistent with aspects of the invention for the p-doped layer P to be outside the n-doped layer N in FIG. 3A, and thus inverting the p-n junction of the diode  26  depicted in FIG.  3 B. Thus, diode  26  would be active with a positive voltage across terminal A and base B. 
     It will be appreciated that various known LED structures may be fabricated in a fiber consistent with aspects of the invention. Variation in materials, thickness, and combinations of layers may be selected to achieve a desired color, efficiency, manufacturing cost, and brightness. Examples of materials used include gallium, arsenic, and phosphorus (GaAsP) to obtain a red, orange or yellow light source; gallium phosphorus (GaP) for green and red; and gallium nitride (GaN) and silicon carbide (SiC) for a blue light source. In addition, aluminum gallium indium phosphide (AlGaInP) and indium gallium nitride (InGaN) are used for various colors. 
     Turning to FIG. 4, the LED fiber matrix  10  is depicted as a schematic of an LED matrix  38 , generally known for discrete LEDs (e.g., 8 by 8 alphanumeric indicator) and semiconductor LED matrices formed on a wafer substrate. 
     Turning to FIG. 5, a method of fabricating an LED fiber  16  is shown in simplified form. A first reservoir  40  contains a conductive liquid  42  that is drawn out, or extruded, as a core strand  44 . The core strand  44  solidifies and is then passed through a second reservoir  46  containing a semiconductor light-emitting polymer p-doped liquid  48  that is allowed to solidify as the p-doped layer P on the core strand  42 , forming an inner strand  50 . The inner strand  50  is passed through a third reservoir  52  containing a semiconductor light-emitting polymer n-doped liquid  54  that is allowed to solidify as the n-doped layer N, forming the LED fiber  16 . 
     Turning to FIG. 6, a simplified depiction of a plasma processing system  56  provides for continuous fabrication of an LED fiber  16 ′. Depending on the materials selected, various types of plasma processing may be used, such as Metallo Organic Chemical Vapor Deposition (MOCVD). Liquid Phase Epitaxy (LPE) is also used. 
     Three reaction chambers  60 ,  62 ,  64  within a vacuum chamber  66  illustrate an application of three layers onto a core strand  44 ′ taken from a supply roll  68  in a supply chamber  70  and stored on a take-up roll  72  in a take-up chamber  74 . Each chamber  60 ,  62 ,  64 ,  70 ,  74  is gas isolated from each other by buffer chambers  76 ,  78 ,  80 ,  82 . 
     Within the first reaction chamber  60 , a precursor gas G 1  is introduced through gas inlet port  84 . Discharge electrodes  85 ,  86  are electrified by a Radio Frequency (RF) source  88  to create a plasma discharge atmosphere to deposit a lower cladding, such as an In 0.5 (Ga 1−y Al y ) 0.5 P, n doping=1E18, of 1 μm thickness, forming an inner strand  90 . 
     Then, the inner strand  90  passes into the second reaction chamber  62  where a second precursor gas G 2  is introduced through gas inlet port  92 . Discharge electrodes  94 ,  95  are electrified by RF source  96  to deposit an active layer, such as an In 0.5 (Ga 1−y Al y ) 0.5 P, n doping=1E17, of 0.5 μm thickness to form an intermediate strand  98 . 
     Then, the intermediate strand  98  passes into the third reaction chamber  64  where a gas precursor G 3  is introduced through gas inlet port  100 . Discharge electrodes  102 ,  103  are electrified by RF source  104  to deposit an upper cladding of such as an In 0.5 (Ga 1−y Al y ) 0.5 P, p doping=1E17, of 1 μm thickness to form the LED fiber  16 ′. 
     The value of y for the lower cladding, active layer, and upper cladding is selected for the desired color. For example, for red the cladding or confinement layers are In 0.5 (Ga 0.3 Al 0.7 ) 0.5 P. The resulting LED fiber  16 ′ is high brightness LED having a heterostructure. The thickness of each layer or cladding may be controlled with the frequency and power of the RF field from the discharge electrodes  85 ,  86 ,  94 ,  95 ,  102 ,  103 , the concentration of precursor gas G 1 , G 2 , G 3 , and speed of the strand  44 . Furthermore, for arrangements in which the plasma discharge atmosphere is asymmetric with respect to the strand  44 , a rotation may be imparted to the strand  44  or the discharge electrodes  85 ,  86 ,  94 ,  95 ,  102 ,  103  to more evenly coat the strand  44 . 
     Alternatively, the plasma processing system  56  may use one reaction chamber  60  with the precursor gas G 1  changed during each pass of the strand  44  to sequentially build up the desired layers. 
     Turning to FIG. 7, a simplified loom  90  is depicted for interlacing the warp  18  of LED fibers  16  with a weft  22  of conducting material, each pass of the weft  22  disconnected from the preceding and subsequent passes forming the conductive strands  20  of the woven LED fiber matrix  10 . 
     Turning to FIG. 8, the output of the loom  110  of FIG. 7 is a large LED fiber matrix  10 , that contains flaws  116   a - 116   c.  From this, one or more LED fiber matrices  10   a - 10   c  are extracted that do not contain the flaws  116   a - 116   c.  Various types of flaws may occur due to process variations. One type of flaw may be an open circuit at the lateral location. For example, the conductive strand  20  may fail to contact the LED strand  16  at the lateral location, or be separated by an insulating material such as a contaminant. As another example, the conductive strand  20  or the LED fiber  16  may be broken or be improperly doped to be conductive. As another type of flaw, the LED fiber  16  may be improperly fabricated such that a p-n junction is not formed, detectable as an out-of-range resistance. As another type of flaw, the light-emitting polymer in the LED fiber  16  may be evident as inadequate luminescence in response to activation of the p-n junction of the diode D. 
     Detecting each flaw  116   a - 116   c  may be achieved by connecting a test circuit  120  that sequentially biases the LED fibers  16 , grounds the conductive strands  20 , and senses the activation of each diode D, such as by the current, resistance or luminescence of the diode D. In response to detecting flaws  116   a - 116   c  in the larger LED fiber matrix  10 , smaller LED fiber matrixes  10   a - 10   c  may be extracted by cutting from large matrix  10 , such that flaws  116   a - 116   c  are outside of the periphery of each matrix  10   a - 10   c.    
     Turning to FIG. 9, a flexible display  14  that includes an LED fiber matrix  10  is placed in front of a backing surface  126 . The backing surface  126  may provide physical support to provide a desired contour to the LED fiber matrix  10 . In addition, the backing surface  126  may advantageously illuminate to increase the overall brightness of the flexible display  14 . Alternatively, the backing surface  126  may be reflective to increase the illumination from the LED fiber matrix  10  to one side. A reflective backing surface  126  may advantageously balance the luminescence from downward oriented lateral locations  24  and upward oriented lateral locations  24 . Furthermore, the backing surface  126  may include a phosphor to enhance the illumination from the LED fiber matrix  10 . 
     Turning to FIG. 10, a color flexible display  10  is depicted where a color LED fiber matrix  130  is formed from a stack of a first LED fiber matrix  132 , a second LED fiber matrix  133 , and a third LED fiber matrix  134 . Each of the first, second and third LED fiber matrices  132 - 134  is given a different hue, such as red, green and blue. Alternatively, the sequentially positioned fibers in each matrix  132 - 134  may be arranged such that red, green and blue fibers overlap in the stacked matrix  1   30 . Consequently, a full range of colors may be generated at a display pixel that encompasses a corresponding lateral location from each of the matrices  132 - 134 . 
     It should be appreciated that the use of three colors (red, green, blue) in either lateral arrangement or in vertical arrangement is for illustration only. In some applications, different hues may be combined to produce colors of interest. Also, rather than varying the intensity of light generated by certain lateral locations  24  to produce a color, multiples of one hue may be used such that a full range of colors may be produced. For example, since the visual spectrum is dominated by green for human perception, two strands or layers of green for each strand or layer of red and blue may be used to produce colors. 
     Referring to FIG. 11, a flexible LED matrix  10 ′ illustrates a warp  18 ′ formed from a plurality of woven LED fibers  16 ′. Each woven LED fiber  16 ′ may allow greater illumination or selection of hues at a given lateral location  24 ′ than available from each individual strand  136  woven to form a woven LED fiber  16 ′. Thus, each strand  136  of the woven LED fiber  16 ′ may be individually tinted to achieve a desired hue. Also, one of the strands  136  of a woven LED fiber  16 ′ may be a phosphor to advantageously increase the visible illumination from strands  1   36  that emit non-visible energy, such as ultraviolet. 
     The weft  22 ′ is illustrated as being formed of double-woven conductive strand pairs  20 ′. The conductive strand pairs  20 ′ may increase physical positioning and isolation of each LED fiber  16 ′. In addition, the conductive strand pairs  20 ′ increase the illumination from each lateral location  24 ′ since LEDs  26  are formed on both faces of the LED fiber matrix  10 ′ at each lateral location  24 ′. 
     Laminating sheets  138 ,  139  advantageously sandwich the matrix  10 ′to pacify and protect the matrix  10 ′. 
     It should be appreciated that LED fiber matrices  10 ′ consistent with aspects of the invention may be achieved with various weave designs. In addition, an LED fiber matrix  10 ′ may include additional fibers such as for reflectance, strength, thermal insulation, and/or heat conduction. 
     Turning to FIGS. 12A-12J, examples are illustrated of the many uses of a flexible display  10  consistent with aspects of the invention. 
     FIG. 12A depicts a curved surface  140 , such as a sign post, upon which an advertisement or announcement is displayed on a flexible display  14 . 
     FIG. 12B depicts a notebook computer  142  incorporating a flexible display  14  stored as roll or other convenient shape within the case of the notebook computer  142 . 
     FIG. 12C depicts a sheet-like article  144  that contains a flexible display  14 . The sheet-like article  144  allows for convenient storage such as by the depicted rolling. Furthermore, the sheet-like article  144  may advantageously include interactive features such as a thin-film keypad  146  so that the sheet-like article may function as a portable computer, a data browser, a calculator, a programmable calendar, etc. 
     FIG. 12D depicts a garment  147  onto which is affixed, or the fabric of the garment  147  is itself, a flexible display  14 , enabling dynamically illuminated displays while retaining the comfort of a fabric garment. A garment  147  may advantageously be selectively colored or patterned to coordinate with other garment items. For example, a garment  147  such as a scarf or tie may be selectively changed in color to match a shirt or blouse. In addition, the illumination of the flexible display  14  may enhance safety, such as for wearing the garment  147  while running at night. 
     FIG. 12E depicts a window  148  having a window blind  150  that incorporates a flexible display  14 , thus allowing a window blind that may be used for presenting still or video images. 
     FIG. 12F depicts a vehicle  152  that has a heads-up display (HUD)  154  affixed to, or embedded in, a windshield  156 . The HUD  154  includes a flexible display  14  positioned to be conveniently viewed by a driver. The HUD  154  may have a translucence and/or looseness of weave allows for viewing through the flexible display  14 . 
     FIG. 12G depicts a self-illuminating flag  160  that may include, or be entirely composed of, a flexible display  14 . In addition to providing self-illumination, the flag  160  may be selectable to provide various color images. 
     FIG. 12H depicts a curved banner display  162 , such as a scrolling alphanumeric message board or stock ticker. The banner display  162  incorporates a flexible display  14 , and thus can readily adapt to the contour of various underlying structures. 
     FIG. 12I depicts a flexible vehicle entertainment system  164  that incorporates a flexible display  14 . Unlike generally known rigid displays, the entertainment system  164  does not pose a safety hazard due to a passenger inadvertently bumping the display  14 . 
     FIG. 12J depicts a dynamic book  166  that incorporates a plurality of sheet-like flexible displays  14 . The dynamic book  166  is programmed to display graphics or text so that a user may use the dynamic book  166  like a traditional book or magazine. In addition, the dynamic book  166  may store additional display information so that the sheet-like flexible displays  14  only show a portion at a time of the available display information. Furthermore, unlike traditional books and magazines, the dynamic book  166  may include animated graphics, or interactive controls. 
     While the present invention has been illustrated by a description of the preferred embodiments and while these embodiments have been described in some detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. This has been a description of the present invention, along with the preferred methods of practicing the present invention as currently known. Various aspects of this invention may be used alone or in different combinations. The scope of the invention itself should only be defined by the appended claims, wherein