FLEXIBLE FLAT COLOR DISPLAY

FLEXIBLE FLAT COLOR DISPLAY

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

FIGURE 1 is 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;

FIGURE 2 is a perspective view of the flexible display along

line 2-2 of FIG. 1 ;

FIGURE 3A is a cross-sectional view of a light-emitting diode

fiber and a conductor along line 3A-3A of FIG. 2;

FIGURE 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;

FIGURE 4 is a schematic of the light-emitting diode matrix of

FIG. 1 ;

FIGURE 5 is a simplified depiction of fabricating the light-

emitting diode fiber of FIG. 1 ;

FIGURE 6 is a simplified depiction of a continuous plasma

processing system for fabricating LED fibers;

FIGURE 7 is an illustrative depiction of weaving the light-

emitting diode fibers into the light emitting diode fiber matrix of FIG. 1 ; FIGURE 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;

FIGURE 9 is a backing surface enhanced light emitting diode

fiber matrix;

FIGURE 1 0 is a color light emitting diode fiber matrix

composed of a stack of monochrome light emitting diode fiber matrices;

FIGURE 1 1 is a multi-woven, pacified LED matrix; and

FIGURES 1 2A-1 2J 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 1 2 to form a flexible display 14

consistent with aspects of the invention.

The LED fiber matrix 1 0 includes a plurality of LED fibers 1 6

forming a warp 1 8 interlaced with a plurality of conductive strands 20

forming a weft 22. The interlacing physically and electrically isolates each

LED fiber 1 6 from other LED fibers 1 6 as well as physically and electrically

isolating each conductive strand 20 from the other conductive strands 20.

Each LED fiber 1 6 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 1 2 by a control circuit 28 and a multiplexer (MUX) 30

completing an electrical circuit that includes one LED fiber 1 6 and one

conductive strand 20. An image is generated upon the LED fiber matrix 1 0

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 1 6, to illuminate a row

of pixels that occur at the intersection of a currently grounded conductive

strand 20 and LED fibers 1 6.

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 1 0, viewed along the line 2-2 of FIG. 1 , shows the interlaced, or

woven, relationship of the LED fibers 1 6 and conductive strands 20. Cylindrical cross sections for the LED fibers 1 6 and conductive strands 20

are for illustrative purposes only. For example, the LED fibers 1 6 and/or the

conductive strands 20 may be ribbon shaped. Ribbon-shaped LED fibers 1 6

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 1 0 from external contact, and/or assist electrically isolating

individual LED fiber 1 6 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 1 6 to the conductive strands 20. The insulating layer may

contain a pigment so that coated portions of the LED fiber matrix 1 0 are

provided a hue, as an alternative to tinting the LED fibers 1 6 and/or the

conductive strands 20.

It should further be appreciated that an LED fiber matrix 1 0

consistent with aspects of the invention may be formed as a nonwoven fabric in which the conductive strands 20 merely overlay the LED fibers 1 6,

with the physical contact created by adhesion rather than interlacing.

Adhesion may be achieved by dispensing the conductive strands 20 onto

the LED fibers 1 6, whereupon the LED fibers 1 6 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 1 6

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.

3B. 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

(AIGalnP) and indium gallium nitride (InGaN) are used for various colors.

Turning to FIG. 4, the LED fiber matrix 1 0 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 1 6 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 1 6.

Turning to FIG. 6, a simplified depiction of a plasma processing

system 56 provides for continuous fabrication of an LED fiber 1 6'.

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 S}(Ga₁._yAl_y)_{0 5}P, n doping = 1 E1 8, 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 G2 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 ln₅(Ga.,._yAl_y)₅P, n doping = 1 E1 7, 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 G3 is introduced through gas inlet port

1 00. Discharge electrodes 1 02, 1 03 are electrified by RF source 104 to

deposit an upper cladding of such as an ln_α5(Gaι__yAl_y)_α5P, p doping = 1 E1 7,

of 1 μm thickness to form the LED fiber 1 6' .

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 ln_{0 5}(Ga_{0 3}AI_{0 7})_{0 5}P. The resulting LED fiber 1 6' 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, 1 02, 1 03, the concentration

of precursor gas G 1 , G2, G3, 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, 1 02, 1 03 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 1 8 of LED fibers 1 6 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 1 1 0 of FIG. 7 is a

large LED fiber matrix 1 0, that contains flaws 1 1 6a-1 1 6c. From this, one

or more LED fiber matrices 10a-1 0c are extracted that do not contain the

flaws 1 1 6a-1 1 6c. 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

1 6 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 1 6 may be broken or be improperly doped to be conductive. As

another type of flaw, the LED fiber 1 6 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 1 6 may

be evident as inadequate luminescence in response to activation of the p-n

junction of the diode D.

Detecting each flaw 1 1 6a-1 1 6c may be achieved by

connecting a test circuit 1 20 that sequentially biases the LED fibers 1 6, 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 1 1 6a-1 1 6c in the larger LED fiber matrix 1 0,

smaller LED fiber matrixes 1 0a-1 0c may be extracted by cutting from large

matrix 1 0, such that flaws 1 1 6a-1 1 6c are outside of the periphery of each

matrix 10a- 1 0c.

Turning to FIG. 9, a flexible display 1 4 that includes an LED

fiber matrix 1 0 is placed in front of a backing surface 1 26. The backing

surface 1 26 may provide physical support to provide a desired contour to

the LED fiber matrix 1 0. In addition, the backing surface 1 26 may

advantageously illuminate to increase the overall brightness of the flexible

display 14. Alternatively, the backing surface 1 26 may be reflective to

increase the illumination from the LED fiber matrix 1 0 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 1 26 may

include a phosphor to enhance the illumination from the LED fiber matrix

1 0.

Turning to FIG. 10, a color flexible display 1 0 is depicted

where a color LED fiber matrix 1 30 is formed from a stack of a first LED

fiber matrix 1 32, a second LED fiber matrix 1 33, and a third LED fiber

matrix 1 34. Each of the first, second and third LED fiber matrices 1 32-1 34

is given a different hue, such as red, green and blue. Alternatively, the

sequentially positioned fibers in each matrix 1 32-1 34 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

1 32-1 34.

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. 1 1 , a flexible LED matrix 1 0' illustrates a

warp 1 8' formed from a plurality of woven LED fibers 1 6' . Each woven

LED fiber 1 6' may allow greater illumination or selection of hues at a given

lateral location 24' than available from each individual strand 1 36 woven to

form a woven LED fiber 1 6'. Thus, each strand 136 of the woven LED

fiber 1 6' may be individually tinted to achieve a desired hue. Also, one of

the strands 1 36 of a woven LED fiber 1 6' 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 1 6'. 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

1 0' at each lateral location 24'.

Laminating sheets 1 38, 1 39 advantageously sandwich the

matrix 10' to pacify and protect the matrix 1 0'.

It should be appreciated that LED fiber matrices 1 0' consistent

with aspects of the invention may be achieved with various weave designs.

In addition, an LED fiber matrix 1 0' may include additional fibers such as for

reflectance, strength, thermal insulation, and/or heat conduction.

Turning to FIGS. 1 2A-1 2J, examples are illustrated of the

many uses of a flexible display 1 0 consistent with aspects of the invention.

FIG. 1 2A depicts a curved surface 1 40, such as a sign post,

upon which an advertisement or announcement is displayed on a flexible

display 14.

FIG. 1 2B 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. 1 2C depicts a sheet-like article 1 44 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 1 46

so that the sheet-like article may function as a portable computer, a data

browser, a calculator, a programmable calendar, etc. FIG. 1 2D depicts a garment 147 onto which is affixed, or the

fabric of the garment 1 47 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 1 may

enhance safety, such as for wearing the garment 147 while running at

night.

FIG. 1 2E depicts a window 1 48 having a window blind 1 50

that incorporates a flexible display 14, thus allowing a window blind that

may be used for presenting still or video images.

FIG. 1 2F depicts a vehicle 1 52 that has a heads-up display

(HUD) 1 54 affixed to, or embedded in, a windshield 1 56. The HUD 1 54

includes a flexible display 14 positioned to be conveniently viewed by a

driver. The HUD 1 54 may have a translucence and/or looseness of weave

allows for viewing through the flexible display 14.

FIG. 1 2G depicts a self-illuminating flag 1 60 that may include,

or be entirely composed of, a flexible display 14. In addition to providing

self-illumination, the flag 1 60 may be selectable to provide various color

images.

FIG. 1 2H depicts a curved banner display 1 62, such as a

scrolling alphanumeric message board or stock ticker. The banner display 1 62 incorporates a flexible display 14, and thus can readily adapt to the

contour of various underlying structures.

FIG. 1 21 depicts a flexible vehicle entertainment system 1 64

that incorporates a flexible display 14. Unlike generally known rigid

displays, the entertainment system 1 64 does not pose a safety hazard due

to a passenger inadvertently bumping the display 14.

FIG. 1 2J depicts a dynamic book 1 66 that incorporates a

plurality of sheet-like flexible displays 14. The dynamic book 1 66 is

programmed to display graphics or text so that a user may use the dynamic

book 1 66 like a traditional book or magazine. In addition, the dynamic book

1 66 may store additional display information so that the sheet-like flexible

displays 1 4 only show a portion at a time of the available display

information. Furthermore, unlike traditional books and magazines, the

dynamic book 1 66 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 I claim: