Patent Application
20080024060
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.
As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the invention. The terms a or an, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language). The term coupled, as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically.
An electroluminescent display contains an array of dynamically addressable pixels. The pixels are arranged on one side of a carrier substrate. Conductive vias in the substrate are electrically connected to each of the pixels. Each pixel consists of a bottom electrode that is coupled to a via, an electroluminescent material, and a dielectric material. A common top electrode is disposed on the dielectric material. Driver circuit conductors are situated on the other side of the substrate, electrically coupled to each of the conductive vias and to the common top electrode, so that each pixel can be individually addressed to illuminate the electroluminescent material on individual pixels. Referring now to
Each pixel element 120 contains a bottom electrode 140 that is disposed on the top surface of the substrate 110. The bottom electrode is typically an electrically conductive material such as copper, carbon, silver, platinum, titanium, indium-tin oxide, conductive alloys, etc. that is mechanically affixed to the surface of the substrate. These electrodes may be formed in conventional fashion, such as electroless plating, electroplating, screen printing, vacuum deposition, etc. Overlying each electrode is an EL material 150 containing a phosphor. In one embodiment shown in
Overlying the dielectric material 160 is a common top, or second, electrode 170. The second electrode is transparent or translucent so as to enable the EL material 150 to transmit the emitted visible light when energized. The top and bottom electrodes are electrically separated by EL material 150 and dielectric material 160. The top electrode 170 acts in concert with the bottom electrode 140 to form a capacitor-like structure that causes the phosphors in the EL material 150 that is sandwiched between the electrodes to fluoresce when the two electrodes are electrically energized. Since each bottom electrode in the array is individually addressable, the top electrode does not need to be individually addressable, but can instead be electrically common to all the bottom electrodes. Optionally, a second dielectric material 180 can be placed between the individual pixel elements 120 to fill in the space between the elements. This facilitates the formation of the top electrode 170, allowing it to be a single continuous layer over the pixels 120 and the second dielectric 180.
A driver circuit 190 is electrically coupled to each of the pixel elements 120 and to the top electrode 170. Driver circuits are commonly known and used in devices such as liquid crystal displays (LCD) to selectively address the various segments of the LCD. In simplistic form, driver circuits contain a plurality of switches (typically transistors) that can be turned on and off to address the various pixels as desired. Each of the switches 192 is coupled to a single conductive via, and in turn, to a single pixel, so as to make each pixel individually addressable. Another portion 194 of the driver circuit 190 is coupled to the common top electrode 170. When any one or more of the individual switches 192 is enabled, an electrical circuit is completed from the bottom electrode through the EL material to the top electrode, causing that individual segment of EL material to fluoresce and emit visible light. By selectively energizing the various pixels, the array of pixels can be caused to form a dynamic display that can be rapidly changed, much in the manner of an LCD.
Driver circuit conductors are situated on the bottom of the substrate 110, opposite the side that contains the pixels 120. The driver circuit can be located anywhere, on a separate module or even on the top surface, as long as the conductors leading to the driver circuits are electrically coupled to the vias. This facilitates the routing of the various electrical connections required to couple the individual pixels in the array to the driver circuit. In one embodiment, the circuitry on the back side of the substrate is routed in multiple layers. In another embodiment, the driver circuit 190 is laminated to the back side of the substrate to form a monolithic package.
Having now described our invention, we now present additional embodiments. Referring now to
In summary, without intending to limit the scope of the invention, operation of a pixelated electroluminescent display according to certain embodiments of the invention can be carried out by coupling an array of dynamically addressable pixels on one side of a carrier substrate to a driver circuit situated on the other side of the substrate. Conductive vias in the substrate electrically connect each of the pixels to the driver. Each pixel consists of a bottom electrode that is coupled to a via, an electroluminescent material, a dielectric material, and a common top electrode. The driver circuit makes each pixel individually addressable to illuminate the electroluminescent material in individual pixels.
While the invention has been described in conjunction with specific embodiments, it is evident that many alternatives, modifications, permutations and variations will become apparent to those of ordinary skill in the art in light of the foregoing description. Accordingly, it is intended that the present invention embrace all such alternatives, modifications and variations as fall within the scope of the appended claims.
