FLAT PANEL DISPLAY USING FIELD EMISSION DEVICES

Abstract: A flat screen display constructed through use of cold cathode field emission devices (112), wherein the devices (112) serve to support the structural integrity of the resultant assembly, and wherein edge emission is utilized to energized luminescent material in support of the display function

Description: FLAT PANEL DISPLAY USING FIELD EMISSION DEVICES Technical Field This invention relates generally to flat panel displays and to cold cathode field emission devices. Background of the Invention Flat panel displays are known in the art. Such displays, often comprised of LCD, LED, or electroluminescent elements, provide a multiple pixel platform to allow the display of graphic and alphanumeric information. Flat panel displays are preferable in many applications where the display screen apparatus volume is a prime consideration. Such displays are quite costly, however, when compared to non-flat screen display technologies, particularly as the size of the screen increases. The use of cold cathode field emission devices has been proposed for use in implementing a flat screen display. To date, however, the manufacturability of cold cathode field emission devices in a form suitable for use with a flat screen display has not supported this desired application. In particular, prior art cold cathode devices are either unsuitable for use in a flat screen display, or require the provision of difficult-to-manufacture cathode structures. A need therefore exists for a cold cathode field emission device that is both readily manufacturable and suitable for use in a flat screen display. Brief Description of the Drawings Fig. 1 comprises a side elevational detail view of a first step in manufacturing a device in accordance with the invention; Fig. 2 comprises a side elevational detail view of a second step in manufacturing a device in accordance with the invention; Fig. 3 comprises a side elevational detail view of a third step in manufacturing a device in accordance with the invention; Fig. 4 comprises a side elevational detail view of a fourth step in manufacturing a device in accordance with the invention; Fig. 5 comprises a side elevational detail view of a fifth step in manufacturing a device in accordance with the invention; Fig. 6 comprises a side elevational detail view of a sixth step in manufacturing a device in accordance with the invention; Fig. 7 comprises a side elevational detail view of a seventh step in manufacturing a device in accordance with the invention; Fig. 8 comprises a side elevational detail view of an eighth step in manufacturing a device in accordance with the invention;. Fig. 9 comprises a top plan partially section view of a plurality of devices constructed in accordance with the invention; and Fig. 10 comprises a side elevational detail view of an alternative embodiment constructed in accordance with the invention. Best Mode For Carrying Out The Invention A transparent (or translucent, depending upon the application) glass plate (100) (Fig. 1 ) provides a device support substrate on one surface (101) thereof, and also serves as the screen for the display itself. Preferably, the support surface (101) will have disposed thereon an appropriate luminescent material, such as phosphor. An appropriate insulating material, such as polyimide (102) (Fig. 2) is deposited on the glass (100). A suitable masked etching process forms a plurality of cavities (103) (Fig. 3) in the insulating material (102). Preferably, these cavities (103) extend sufficiently deep within the insulating material (102) to cause exposure of the glass (100) or phosphor coated thereon. In an appropriate embodiment, however, this may not necessarily be required. A metallized layer (104) (Fig. 4) is then deposited, resulting in a conductive layer on both the upper surface of the insulating material (102) and within the cavity (103). Using an appropriate strip resist process, the metallization layer on the upper surface of the insulator (102) can then be removed (as depicted generally in Fig. 5). A first oxide layer (106) can then be grown over the assembly, followed by a metal deposition layer (107) and a second oxide growth layer (108). A strip resist process can then again be utilized to remove the latter layers from the upper surface of the insulating material (102). This will result in leaving the various layers 5 described as disposed within the oval-shaped cavities (103) only (see Fig. 9). Next, a third metallization layer (109) (Fig. 6) is deposited over the assembly, followed by additional oxide growths (1 11 ). Following this, a strip resist step 10 removes the latter layers from the surface of the insulating layer (102). This will leave a plurality of oval shaped conductors (109) (as viewed from above; see Fig. 9) that may be coupled together in groups by a conductive strip. This will allow an appropriate 15 electrical potential to be applied thereto during use of the finished device. Next, an appropriate etching process that selectively etches the insulating material (102) (Fig. 7) removes the initial insulating material (102) from the 20 assembly, leaving only the metallization layers and oxide growth structure (which serves as a cold cathode field emission device (112) as described below) and a plurality of spaces (113) as shown in Figs. 7 and 9. Lastly, a low angle vapor phase deposition process 25 provides an insulating encapsulating layer (114) over the entire assembly, as depicted in Fig. 8. Preferably, this step will occur in a vacuum, such that the resulting cavity (113) will contain a vacuum. It is appropriate to note that the field emitter structure provides a support 30 function in favor of the structural integrity of the combined apparatus, and in opposition to the tendency of the vacuum to cause the glass layer (100) and the final deposition layer (114) to be urged towards one another by atmospheric pressure. So configured, the first metallization layer (104) will serve as an anode for the resulting field emission device. The second metallization layer (107) will serve as the gate for the field emission device. Finally, the third metallization layer (109) functions as a cold cathode for the resulting field emission device. In particular, when the resultant devices (112) are formed having a length, the third metallization layer (109) will present an edge that will support edge mode field emission activity. Electrons emitted from this edge will make their way to the anode (104). Some of these electrons, however, will strike the glass surface (101), and hence will energize the luminescent material deposited thereon, causing the luminescent material to illuminate. This illumination can be discerned from the opposite side of the glass. In the alternative, when forming the third conductive layer (109) and its supporting oxide growths, a facet can be formed in the oxide growth using well known techniques, to allow subsequent formation of a third conductive layer (109) having a more pronounced geometric discontinuity (1001). Depending upon the application, this geometric discontinuity (1001) may provide enhanced field emission activity in comparison to the first embodiment described, though again emission will occur in an edge mode fashion. By appropriate disposition of the above described structure, these areas of controllable illumination can function as pixels, or groups of these illumination spots can be collected together to represent a single display pixel. Which pixels are illuminated, and to some extent the degree of illumination, can be influenced through appropriate control of the potential of the gate (107) with respect to the potential between the cathode (109) and the anode (104). In this way, selected portions of the luminescent material disposed on the glass (100) can be selectively energized through appropriate control of the electrons as emitted from the edge emitters of the cathodes (109) provided. These devices (112) can be readily manufactured using known manufacturing techniques, and do not require the provision of non-planar cathodes that are difficult to manufacture. What is claimed is:

Claims: Claims 1. A display screen, comprising: A) a luminescent material; B) an edge emitter to selectively emit electrons to thereby energize at least a part of the luminescent material. 8 2. The display screen of claim 1 , further including a plurality of the edge emitters, wherein each of the edge emitters selectively energizes a selected portion of the luminescent material. 5 3. The display screen of claim 1 , and further including a screen and an encapsulating layer, wherein the edge emitter is disposed therebetween. 10 4. The display screen of claim 3 wherein the edge emitter is a part of a support structure that is positioned between the screen and the encapsulating layer. 15 5. The display screen of claim 4, wherein the support structure contacts both the screen and the encapsulating layer. 6. The display screen of claim 5, wherein at least one 20 area between the screen and the encapsulating layer has a vacuum formed therein. 7. The display screen of claim 6, wherein the support structure contributes, at least in part, to maintaining a 25 distance between the screen and the encapsulating layer. 8. The display screen of claim 1 , further including a plurality of the edge emitters, wherein each of the edge emitters includes a pronounced geometric discontinuity. 9. A method of forming a display screen, comprising the steps of: A) providing a screen; B) disposing a first material support surface on at least a part of the screen; C) forming at least one cavity in the first material support surface; D) forming a cold cathode field emission device within the cavity; E) removing at least a substantial portion of the first material support surface. 10. The method of claim 9, and further including the step of: F) encapsulating the cold cathode field emission device with respect to the screen. 11. The method of claim 10, wherein the step of encapsulating includes the step of encapsulating the cold cathode field emission device in combination with a substantially evacuated area. 12. The method of claim 9, wherein the step of forming the cold cathode field emission device includes the steps of: D1) disposing a first conductive layer in the cavity; D2) disposing a first insulating layer in the cavity; D3) disposing at least a second conductive layer in the cavity; D4) disposing a second insulating layer in the cavity; D5) disposing a third conductive layer in the cavity. 13. The method of claim 12, wherein the first conductive layer comprises an anode, the second conductive layer comprises at least a first gate, and the third conductive layer comprises a cathode.

Inventors: KANE ROBERT C, KANE, ROBERT, C.
Applicants: MOTOROLA INC, MOTOROLA, INC.
Application year: 1990
Main classification: H01J19
IPC codes: H01J1, H01J9, H01J29, H01J31