Patent Application
20060009111
The present invention relates in general to a method of fabricating a cathode structure of a field-emission display, and more particularly, to a method of fabricating a cathode structure using low-cost ink material. In addition, the planarity of the electrode layer and the electron emission source are enhanced by the method as provided, which is advantageous to the post stacking process.
The conventional method for forming the electrode layer and the electron emission layer of a cathode of a field-emission display typically uses thin-film or thick-film technique. The thin-film technique normally provides higher planarity and precision. However, it is more costly compared to the thick-film technique which uses low-cost process such as screen printing or thick-film photolithography for fabricating partial structure of the field-emission display as disclosed in the Taiwanese Patent No. 502395 and 511108, for example.
The thin-film photolithography process such as sputtering or evaporation used to fabricate electrode is not only costly, but is also restricted to a thickness up to tens or hundreds of nanometers only. Under a high voltage, the electrode often flares or open-circuited due to breakdown. In contrast, the electrode material formed by thick-film technique. Therefore, the electrode layer formed by thick-film technique has been widely applied in industry recently.
The screen printing or thick-film photolithography process used for various electrode layers is described as follows. In the example for forming the electrode layer of the cathode, a silver ink is printed and patterned to form the electrode layer, and an electron-emission source layer is formed by printing an ink containing carbon nanotube on the electrode layer. Alternatively, the electron-emission source layer is formed using spray coating or photolithography or electrophoresis or other electrochemical method.
Although screen printing can greatly reduce fabrication cost, such process is restricted to reticulation, knots and emulsion to result in non-uniform planarity. The accumulated error of the stack of the electrode layers can be more than 10 microns. In the example as shown in
The insufficient planarity uniformity of the first and second electrode layers causes an uneven surface of the dielectric layer formed subsequently, which further results in the following drawbacks.
1. Light scattering occurs during exposure step of photolithography process, such that the fabrication of photoresist is affected.
2. An uneven stack structure is obtained for tripolar or tetrapolar structure. The electric field within a unit area is non-uniform, such that the current density generated by electron beam is no uniform to affect the display quality.
3. As shown in
The present invention uses surface polishing technique following formation of cathode of a field-emission display fabricated by thick-film technique, such that the planarity of the cathode is enhanced, and the subsequent process is more easily to perform.
As provided, a thick-film technique is used to apply low-cost silver ink and carbon nanotube on a substrate to form a first electrode layer and a second electrode layer. The silver ink is sintered, and the first and second electrode layers are polished to control a thickness error under 0.1 microns.
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
To fabricate the cathode structure, a substrate 1 such as a glass is provided.
A first electrode layer 11 and a second electrode layer 12 are formed on the substrate 1 by thick-film technique 2. The second electrode layer 12 serving as an electron emission source is preferably fabricated from carbon nanotube, and the first electrode layer 12 is preferably fabricated from low-cost silver ink or silver paste. Preferably, the first 11 and/or the second electrode layer 12 are patterned as desired.
A sintering step 3 is performed with parameters according to specific need. For example, the temperature for the sintering step performed on the first electrode layer 11 is about 400° C. in this embodiment.
A polish technique 4 is performed on the first and second electrode layers 11 and 12, such that the surface planarity error is no more than 0.1 microns.
After the polishing step, the electrode is rinsed by water 5, baked 6, and subjected to a high-pressure air 7 to remove any unwanted residual medium or particles thereon. The cathode structure of the field-emission display is thus formed.
Referring to
The cathode structure fabricated by the above process has the following advantages.
1. The stack of the carbon nanotube for forming the electron emission source is intensified.
2. The surface planarity error of the second electrode layer (the electron emission source) 12 and the first electrode layer 11 is controlled under 0.1 microns.
3. The planarity of the stacked structure, particularly those of tripolar or tetrapolar structure is enhanced, such that the brightness uniformity of the image is improved.
4. The photoresist layer formed in the subsequent process will not be degraded due to light scatter during exposure step.
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.
