Invented by Jin-Shou Fang, Teco Nanotech Co Ltd
The Teco Nanotech Co Ltd invention works as followsAn electron emission type field-emission display is disclosed and a method for fabricating it are described. The beeline distance of electron emission is identical. The field-emission display structure has a cathode electro so that the beeline distances between the surface points of the cathode and the gate conductive layers are identical. The cathode electrode is made from a silver paste, and a carbon-nanotube. A gray-scale mask with a gradient in light transmission from the center to the periphery of the silver paste is used to configure the silver paste.
Background for Electron emission type field-emission display, and method for fabricating it
The invention is generally directed to an electron-emission type of field-emission display, and a method for fabricating it, and more specifically to a cathode electro having a configuration where the beeline distance between each surface point of the cathode layer and the gate conductive layer above the cathode layer is identical.
The discovery of the carbon nanotube (CNT), has sparked a new competition in the field of nanotechnology development worldwide. The current application of the carbon-nanotube in optoelectronic displays includes the carbon-nanotube-field-emission display, or CNT FED. This panel is considered to be the most versatile flat display panel in the industry. A conventional field-emission display consists of a front panel and substrate. This creates an electron beam by emitting a spike at the cathode spike. To create an image, the electron beam hits the phosphor coating on the screen. This type of display offers a larger display area, a shorter response time and a wider viewing angle. It can be used to replace conventional cathode-ray tube (CRT), screens by electronic products.
The vacuum package houses the front panel and substrate. To prevent glass plate cracking by atmospheric pressure, a spacer is placed between the front panel & substrate. The high cost of fabrication was a major problem in the development of field-emission displays. The development of carbon nanotube solves this problem while maintaining the image quality of the cathode-ray tube. The field emission display of carbon nanotube also features power-saving and small-volume features.
However, the current carbon nanotube field emission display is still problematic in its application. FIG. FIG. 1 shows a conventional field-emission display. It includes an anode layer 1a and a cathode layer 2a. Anode electrode layer 1a comprises a substrate 11a, a first layer of conductive 12a on the substrate 11a, and a second layer 13a covering the second layer 12a. Anode 14a is formed by the first and second conductive layers 12a and 13a. The electron beam from an anode 26a will be impinged on it by an electron beam. The cathode electrode 2a comprises a substrate 21a, a first layer of conductive material (silver paste), 24a (silver paste), formed on substrate 21a, and 25a second layer (carbon nanotube), 25a formed on the 24a first conductive layers. The cathode 26a is constructed by the first and second conductive layers 24a and 25a. The substrate 2 a surrounds the cathode 26a. A dielectric layer 26a is formed. The field-emission display also includes a gate conductive 3a layer that was formed on top of the dielectric 22a. The gate conductive layer 3, a has a throughhole 31 a that is aligned above the cathode 26, a. The beeline distance between periphery of second conductive layers 25 a, and gate conductive layers 3 a is less than the distance between central area of second conductive layers 25 a, and gate conductive Layer 3 a. The electric field at 25 a’s periphery is greater than the one at 25 a’s central area. The electrons that are drained from the periphery of the second conductive layer 25 a have a density greater than those that are drained from the central area. This results in an electron beam that is donut-shaped due to the distribution of electrons. Leakage of electron beams through gate conductive layer 3a is also possible due to the non-uniform distribution of electrons.
The present invention creates a cathode that is so constructed that there is no beeline between the cathode’s point and the gate conductive layer. The cathode produces an uniform electric field at all points. The electron emission from cathode is uniform and produces an electron beam with uniform distribution. The image quality is therefore enhanced.
The cathode structure of the present invention has both a higher and lower center. This means that the center of the cathode slowly descends towards its periphery, so that the beeline distance between each cathode point and the gate conductor layer is the same to produce an uniform electron beam.
Referring to FIG. 2. A pixel structure for a carbon nanotube-emission display is shown. The carbon nanotube field emission display has an anode electrode and cathode layers 1, 2 and 3. A gate conductive layer 3, which is positioned between the cathode and anode electrode layers 1 & 2. Anode electrode layer 1 contains a number of anode layers 14 that are formed on the same substrate 11. Each anode electrode 14 has a first conductive coating 12 on the substrate 11, and a second layer 13 that wraps the first layer 12. The substrate 11 should be made from glass material and the second layer from phosphor material.
The cathode layer 2 contains a number of cathode 26 that are formed on a common substrate 21. A dielectric layer 22 is patterned and formed on the substrate 21 around at least one cathode 26. The photolithography and etching processes are used to pattern the dielectric layer 22, forming a recessed area 23 that contains the cathode 26, as shown. On the dielectric layer 22, the gate conductive layer is formed. As seen, an aperture 31 (gatehole) is located in the gate conductive layers 3. As shown in FIG. 26, each cathode 26 has a first layer 24 that is semi-spherical and shaped like a lump. 2. The center protruding from the first conductive layer 24 slowly descends towards its periphery. A second conductive layer 25, which is either photolithography or spray, is created on top of the first conductive layers 24. The cathode 26 is then formed, with all surface points equal to the gate conductive layers 3.
FIGS. FIG. 3 through 5 shows the fabrication process for the field-emission display. 2. FIGS. FIGS. 3 through 5. 3 to 5. The thickness of the paste may vary depending on specific requirements. The gray-scale photomask 5 is used for photolithography of the silver paste 4. A yellow light is radiated from the gray-scale mask 5, which is placed over substrate 4. The gray-scale mask 5, which is placed over the substrate 4, allows approximately 20% of the yellow radiation to pass through a center 52 of the structure and about 100% from the periphery 51. The transmission rate of gray-scale mask 5 should increase gradually from 20% at its center 52 to 100% at its periphery 51. The next step is to produce a pattern silver paste 4, as shown in FIG. 4. FIG. 4. The patterned silver paste gradually drops from the middle to the edges. The patterned silver paste 4 is the first conductive layer 24.
As shown at FIG. 5. Carbon nanotube powders 7 can be sprayed onto the first conductive layer 24, as shown in FIG. The second conductive layer 25, which is the carbon nanotube powders 7, can then be attached to the first layer 24 by vacuum sintering.
Referring FIG. “Referring to FIG. The beeline distance between each surface point and the gate conductor layer 3 is identical because the center of cathode electrode 26 extends over its periphery. The electric field used to generate the electron beam by the 26-cathode electrode 26 is therefore uniform across the entire cathode. The electron beam 8’s current density is uniform and each pixel displays an image without any donut impurities.
While the preferred embodiment of the invention is illustrative, it should be understood that inventive concepts can be used in other ways. The appended claims are meant to cover such variations except as restricted by the prior art.