Patent Application
20060103288
1. Field of the Invention
The present invention relates to field emission technology and, more particularly, to a field emission cathode and a field emission device employing the same.
2. Discussion of the Related Art
Field emission devices operate based on emission of electrons in a vacuum and the subsequent impingement of those electrons on a fluorescent layer, thereby producing illumination. Electrons are emitted from micron-sized tips (i.e. field emitters) in a strong electric field. The electrons are accelerated and then collide with the fluorescent material, thereby producing the light. Field emission devices are thin and light and capable of providing high brightness.
As shown in
A triode field emission device is another common type of the field emission device. Compared to the diode field emission device, the triode field emission device further includes a grid electrode located between the cathode 60 and the anode 64.
However, the above-described field emission devices 6 and 7 both employ flat panel bases for carrying the field emitters. The field emitters are generally densely arranged. Most of the neighboring emitters can become tangled with each other. Therefore, a shielding effect between the adjacent emitters is undesirably enhanced. The performance of the field emission device is impaired, accordingly.
A field emission cathode provided herein generally includes a network base and a plurality of field emitters. The network base is formed of a plurality of electrically conductive elongate carriers, with at least one portion of each of the carriers having a curved surface. Each field emitter is provided on and extends substantially radially from a given curved surface of a given carrier. The plurality of elongate carriers may be woven to form the network base. Alternatively, the network base may formed of a non-woven batt of the elongate carriers or may be made of a series of aligned carriers metallurgically or adhesively bonded together.
The field emitters each comprise a material selected from metals, non-metals, composites, and essentially one-dimensional nanomaterials, the material advantageously being selected for its emissive properties.
The plurality of electrically conductive carriers used for the network base may be made of any various electrically conductive fibers, for example, metal fibers, carbon fibers, organic fibers or another suitable fibrous material. The plurality of electrically conductive carriers may be cylindrical or oval or otherwise have at least one arcuate or curved surface upon which the emitters may be formed. Alternatively, the carriers could be prism-shaped or polyhedral, especially if enough sides are present so as, together, to substantially approximate a curved surface.
Additionally, a field emission device further provided herein generally includes a field emission cathode and an electron extracting electrode. The field emission cathode incorporates a network base and a plurality of field emitters. The network base is formed of a plurality of electrically conductive elongate carriers, each carrier having at least one portion that forms a curved surface. The plurality of field emitters is provided on the respective carriers. Each field emitter extends substantially radially from a respective curved surface of a particular carrier. The electron extracting electrode disposed spatially corresponding to the field emission cathode.
In one exemplary embodiment, the electronic-extracting electrode is an anode facing toward the field emission cathode. In another exemplary embodiment, the electronic-extracting electrode is a grid electrode. The field emission device may further include an anode facing toward the field emission cathode, and the grid electrode may be disposed between the anode and the field emission cathode. Furthermore, the field emission device may include a gate electrode facing toward the field emission cathode, and the field emission cathode may be disposed between the electron-extracting electrode and the gate electrode.
These and other features, aspects and advantages will become more apparent from the following detailed description and claims, as well as the accompanying drawings.
Many aspects of the present field emission device can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the present device. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Referring to
Referring to
Preferably, the field emitters 82 are configured to be substantially perpendicular to the surfaces of the corresponding carrier. In other words, each of the field emitters 82 extends radially outwardly from outer circumferential surface of. Preferably, the field emitters 82 are only formed on the outer circumferential surface portions of the respective conductive carriers 812 that are located at a base side facing the anode 84. Understandably, due to the surfaces of the carriers 812 being curved, a first distance between distal ends of neighboring field emitters 82 (i.e., the distance between adjacent emitter tips) is longer/greater than a second distance between proximal ends of the neighboring field emitters 82. Accordingly, tip portions of the field emitters 82 are advantageously configured to be spaced apart the first distance. As such, the shielding effect occurring between neighboring field emitters 82 is effectively minimized or even eliminated. Accordingly, an electron-emitting efficiency of the cathode 80 is increased. As such, the performance of the light source apparatus is improved.
In addition, the field emitters 82 may be formed of a material selected from the group consisting of metals, non-metals/semidcondutors, compositions (e.g., ceramic oxides, carbides, or nitrides), and other essentially one-dimensional nanomaterials, in addition to carbon. The compositions advantageously include zinc oxide and any other suitable substances known to those skilled in the art. The one-dimensional nanomaterials may include nanotubes or nanowires, such as silicon nanowires and/or molybdenum nanowires. Any material chosen for field emitters 82 advantageously has favorable emissive qualities.
The base 81 may advantageously be obtained by weaving the elongate carriers 812 into a flat network body. The field emitters 82 are formed on the elongate carriers 812 of the base 81. Alternatively, the field emitters 82 could be initially formed on the surfaces of the elongate carriers 812. The carriers 812 with the field emitters 82 formed thereon could then be woven into the base 81.
A variety of conventional methods for manufacturing the carbon nanotubes (for example, a chemical vapor deposition (CVD) method and/or an electric arc discharge method) may be suitably employed to form the carbon nanotubes. For instance, a method of manufacturing carbon nanotubes is described in an article of Shoushan Fan et al., entitled “Self-oriented regular arrays of carbon nanotubes and their field emission properties”, published in Science (Vol. 283) 512-514 on Jan. 22, 1999, which is incorporated herein by reference.
Generally, the anode 84 is a transparent conductive layer formed on a surface of the front plate that faces the cathode. The anode 84 may advantageously be formed by depositing indium-tin oxide on the surface of the front plate. A fluorescent layer 85 is formed on the anode 84 and faces the carriers 812. The fluorescent layer 85 is patterned to include a plurality of pixels. In operation, a high voltage is applied between the anode 84 and the cathode 80 such that electrons are extracted from the field emitters 82 and are accelerated to bombard the fluorescent layer 85.
Similarly, the cathode 90 includes a base 91 and a plurality of field emitters 92 formed thereon. The base 91 is a flat network body, formed of a plurality of electrically conductive elongate carriers 812 (not labeled in
The grid electrode 94 and the second isolating layer 93 define a plurality of apertures (not labeled), spatially corresponding to the field emitters 92, such apertures being configured for allowing electrons to pass therethrough. Alternatively, the first and second insulating layers 95, 93 could be made of an insulating material such as SiO2, polyimide, a nitride, and/or a composite made of such materials.
In operation, working voltages applied to the grid electrode 94, the cathode 90, and the gate electrode 96 are markedly reduced. Due to the existence of the gate electrode 96, the working voltage applied to the grid electrode 94 is decreased.
The field emission cathode device 9 can be employed to be assembled to an anode (not shown in
It should be noted that the carriers 812 may be configured to have other suitable shapes to practice the present field emission device. For example, the carriers 812 may alternatively be oval or otherwise have at least one arcuate/curved surface upon which the emitters may be formed. Alternatively, the carriers could be prism-shaped or polyhedral, especially if enough sides are present so as, together, to substantially approximate a curved surface (e.g., six longitudinal faces minimum; preferably 10 or more such faces).
Finally, while the present invention has been described with reference to particular embodiments, the description is intended to be illustrative of the invention and is not to be construed as limiting the invention. Therefore, various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200410052265.2 | Nov 2004 | CN | national |
