Patent Application
20060049736
The present invention relates in general to a structure and a method for forming a converging-type electron-emission source of a field-emission display, and more particularly, to a method of forming an electron-emission source recessed from a peripheral electrode layer is formed, such that potential distribution established by the electric field of the electrode layer provides converging effect of an electron beam generated by the electron-emission source.
In the conventional bipolar or tri-polar field-emission display having a carbon nanotube as an electron-emission source (as shown in
To resolve the electron-beam diffusion problem of the conventional bipolar or tri-polar field-emission display, tetra-polar (as shown in
The converging electrode layer formed between the cathode structure and the anode structure of a tetra-polar field-emission display provides a voltage to converge the electron beam. The fabrication process of this type of tetra-polar field-emission display includes forming a converging electrode layer on a gate electrode layer by photolithography, or forming a shadow mask between the cathode and anode structures to serve as the converging electrode layer. Either type of converging electrode layer does not only increase the complexity of fabrication, but also increase the material cost.
It is therefore a substantial need for redesigning the cathode structure of a field-emission display without causing extra fabrication process and cost. The redesign of the cathode structure provides a converging electrode layer that does not require extra circuit control, while the fabrication process is simplified, and material cost is greatly reduced. By the redesign of the cathode structure as provided, the electron beam generated by the electron-emission source is converged and concentrated to precisely impinge the phosphor of the corresponding anode unit.
The method of forming a converging-type electron-emission source of a field-emission display as provided has the following steps. A glass substrate is provided. A first electrode layer is formed on the substrate. At least one pit is formed in the first electrode layer. A protection layer to cover the first electrode layer around the pit and expose the pit. A second electrode layer is formed in the exposed pit, wherein the second electrode layer is lower than the first electrode layer. Preferably, the first electrode layer is fabricated from silver ink and the second electrode layer is fabricated from carbon nanotube.
A cathode structure of a field-emission display is also provided to comprise a substrate, a first electrode layer and a second electrode layer. The first electrode layer is formed on the substrate and includes a plurality of pits therein. In each of the pits, a second electrode layer is formed with a height lower than that of the first electrode layer.
The above objects and advantages of the present invention will be become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
Referring to
While fabricating the cathode structure 10 of the field-emission display, a glass substrate 1 provided. A first electrode layer 2 is formed on the substrate 1 from photoresist-type silver ink. The method for forming the first electrode layer 2 includes thick-film photolithography, and the thickness of the first electron layer 2 is about 40 microns to 50 microns, for example.
A photolithography and etching step is the performed on the first electrode layer 2 to form at least a pit 3 therein. The depth of the pit 3 is preferably 20 microns to 40 microns, for example.
When the pit 3 is formed in the first electrode layer 2, a photoresist protection layer 4 is formed to cover the first electrode layer 2 around the pit 3 and expose the pit 3. The photoresist protection layer 4 prevent the material for forming a electron-emission layer from being attached to the first electrode layer 3.
Carbon nanotube is used as the source material for forming a second electrode layer 5 in the pit 3 by coating and photolithography or electrophoresis. The thickness of the second electrode layer 5 is about 1 micron to 5 microns. The second electrode layer 5 serves as the electron source of the cathode structure 10. As the pit 3 recessed from the peripheral first electrode layer 2 by a depth of about 20 microns to 40 microns, while the second electrode layer 5 has a thickness of about 1 micron to 5 microns only, the second electrode layer 5 is lower than the peripheral first electrode layer 2. The geometry and potential of the first electrode layer 2 around the second electrode layer 5 thus forms a converging opening 6 for the electrons generated from the second electrode layer 5. The converging effect can be optimized by adjusting the interior diameter of the converging opening 6.
When the second electrode layer 5 is formed, an etching or polishing process is performed to remove the photoresist protection layer 4. A sintering process is then performed.
When a voltage is applied to the field-emission display 10 to excite an electron beam 7 from the second electrode layer 5, the converging opening 5 formed by the first electrode layer 2 causes the electron beam 7 to be concentrated, such that the electron beam 7 can precisely impinge the phosphor layer of the corresponding anode unit without causing gamut.
Therefore, the electron-emission source of the field-emission display has at least the following advantages:
While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those of ordinary skill in the art the various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.
