| Method of manufacturing carbon nanotube electron field emitters by dot-matrix sequential electrophoretic deposition -> Monitor Keywords |
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  Method of manufacturing carbon nanotube electron field emitters by dot-matrix sequential electrophoretic depositionUSPTO Application #: 20070187246Title: Method of manufacturing carbon nanotube electron field emitters by dot-matrix sequential electrophoretic deposition Abstract: A method of manufacturing carbon nanotube electron field emitters by do-matrix sequential electrophoretic deposition forms an electric field for only one pixel in the electrophoretic deposition, so that only the electrophoretic area has the electrophoretic effect. Longitudinally aligned cathode electrodes of a cathode plate include a plurality of electron field transmitters at the depositing positions, and anode electrodes of an anode plate perpendicular to the cathode electrodes are preinstalled, and a switch unit provides a potential difference for each cathode or anode electrode by a sequential change, and only one alternating pixel having an electric field between the cathode and anode plates per unit time of the electrophoresis produces a deposition effect in the area for manufacturing a carbon nanotube electron field transmitter, and the sequential voltage change of each cathode or anode electrode is used to achieve the electrophoretic deposition effect for all pixels of the cathode plate. (end of abstract) Agent: Hdsl - Fairfax, VA, US Inventors: Kuei-Wen Cheng, Jin-Lung Tsai, Shie-Heng Lee, Yu-An Li, Chun-Yen Hsiao USPTO Applicaton #: 20070187246 - Class: 204471000 (USPTO) Related Patent Categories: Chemistry: Electrical And Wave Energy, Non-distilling Bottoms Treatment, Electrophoresis Or Electro-osmosis Processes And Electrolyte Compositions Therefor When Not Provided For Elsewhere, Coating Or Forming Of Object The Patent Description & Claims data below is from USPTO Patent Application 20070187246. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a field emission display, and more particular to an electrophoretic deposition technology for manufacturing electron field emitters for pixels by dot-matrix sequential electrophoretic carbon nanotubes. [0003] 2. Description of Prior Art [0004] In a field emission display referred by this invention, an electric field is used for driving a cathode electron emitter to produce electrons, and the electrons excite phosphors of an anode plate, such that the phosphors produce photons to emit light. The field emission display has lightweight and thin features, and the size of an effective display area can be made according to the manufacturing process and product requirements. Furthermore, the field emission displays do not have the viewing angle issue occurred in the flat panel displays. [0005] The structure of a prior art triode field emission display includes an anode plate, a cathode plate, and a spacer installed between the anode plate and the cathode plate for providing an interval with a vacuum area between the anode plate and the cathode plate as a support between the anode plate and the cathode plate. The anode plate includes an anode substrate, an anode conducting layer, and a phosphors layer, and the cathode plate includes a cathode substrate, a cathode conducting layer, an electron field transmitter layer, a dielectric layer, and a gate layer, wherein the gate layer provides a potential difference to draw electron emissions of the electron field transmitter layer, and the high voltage provided by the anode conducting layer accelerates the electron beams, so that the electrons have sufficient kinetic energy to impinge the phosphors layer on the anode plate to excite the phosphors to emit light. Thus, when the electrons are moving in the field emission display, it requires a vacuum equipment to maintain the display at a vacuum level lower than 10 to 5 torrs, such that the electrons can obtain a good mean free path, while avoiding contaminations and infections to the electron field transmitter and phosphors area To provide sufficient energy for electrons to impinge the phosphors, an appropriate gap is maintained between the two plates, so that the electrons can have enough space for their acceleration to impinge the phosphors and maximize the effect of producing lights. [0006] The so-called electron field transmitter layer uses carbon nanotubes as its major components. Since carbon nanotube was introduced by Sumio Iijima in 1991 (Nature, Vol. 354, p 56 (1991)), the carbon nanotube has very high electronic characteristics and thus it is used extensively in various different electronic components, and the carbon nanotube comes with a high aspect ratio greater than 500 and a high rigidity with a Young's Modulus greater than 1000 GPn, and the tip or recession of the carbon nanotube is exposed at an atomic level. The aforementioned characteristics are considered ideal for being used as a material for making electron field transmitters, such as an electron field transmitter used for a cathode plate of a field emission display. Since carbon nanotubes have the aforementioned physical properties, therefore they can be designed for different manufacturing processes such as screen printing or thin film process and used for patterning electronic components. [0007] In the so-called cathode plate manufacturing technology, the carbon nanotube is used as the material for making electron field transmitters and is manufactured on the cathode conducting layer, and the manufacturing method includes a chemical vapor deposition (CVD) to directly grow carbon nanotubes onto the cathode electrode layer of each cathode pixel, or uses a photosensitive carbon nanotube solution to be patterned onto the cathode conducting layer of each pixel, or coats a carbon nanotube solution accompanied with a masking process. However, the electron field transmitter structure of the foregoing triode field emission display adopts carbon nanotubes which are applied to the cathode electrode structure of each pixel, and such manufacturing process still has issues on its manufacturing costs and limitations on its three-dimensional structure, and more specifically it is difficult to achieve the evenness for large-size electron field transmitters. [0008] Recently, a so-called electrophoretic deposition (EPD) technology disclosed in U.S. Pat. Publication No. 2003/0102222 prepares an alcohol suspension by employing carbon nanotubes and uses magnesium, lanthanum, yttrium, or aluminum ion salts as secondary salts (chargers) to produce the electrophoresis solution, and connects the cathode electrode with the electrophoresis solution for the electrophoretic deposition, such that an AD or DC voltage is supplied to form an electric field in the solution, and the ions in the secondary salt solution are attached on the carbon nanotube phosphors. The electrophoretic mobility produced by the electric field assists depositing the carbon nanotubes onto a specific electrode, so that the carbon nanotubes can be deposited and patterned onto the electrode. The aforementioned technology is called electrophoretic deposition technology, which can deposit carbon nanotubes onto an electrode layer easily, and also can avoid the limitation of the cathode structure on the triode field emission display, and thus this technology can be used extensively for manufacturing the cathode plate structure. [0009] Since the prior art electrophoretic deposition can only deposit carbon nanotubes onto a cathode electrode without depositing the carbon nanotubes on the gates that will electrically connect the gates with the cathode electrode, therefore a sacrificial layer or a protective layer is usually installed between the gate and the dielectric layer to expose the patterned cathode electrode area before performing the electrophoretic deposition, and then the protective layer as well as any unnecessary carbon nanotubes remained in regions that do not require carbon nanotubes are removed to avoid improper electrical connections. Another prior art disclosed in Japan Pat. Publication No. 2001020093 forms a protrusion at the anode electrode corresponding to a specific region of the cathode in an electrophoresis. Since the protrusions form a specific electric field to the corresponding cathode electrode, the carbon nanotubes in the solution can be deposited in the specific region and the deposited carbon nanotubes can be centralized at the specific electrode layer region. A further prior art disclosed by the present inventor's previous patent application teaches a simple and easy way of making patterned electrophoresis anode structure to effectively centralize the electrophoretic deposition regions of an anode plate device. [0010] Although the present electrophoretic deposition method limits and reduces the electrophoretic deposition area, yet the prior art also provides a voltage to the cathode plate and the anode plate to form an electric field, and thus a meticulous computation or design is required for producing the electric field to maximize the effective regions, or else a poor applicability for the high-resolution panels may result. The unit area of the electrophoresis region so produced will become smaller, and the point-to-point electric field so produced will be affected by the electric field in the neighborhood and thus making it difficult to achieve the expected effect. Although the point-to-point electrophoretic deposition technology is employed, an electric field is produced at the same time, so that the electric fields of adjacent pixels will interfere with each other easily, and the dot-matrix point-to-point electrophoretic deposition effect can no longer be maintained. SUMMARY OF THE INVENTION [0011] In view of the foregoing shortcomings of the prior art, the inventor of the present invention based on years of experience in the related industry to conduct experiments and modifications, and finally invented a method of manufacturing carbon nanotube electron field emitters by do-matrix sequential electrophoretic deposition [0012] Therefore, the present invention is to provide an alternating electrophoretic deposition technology to improve the electrophoretic deposition effect on the regions of a dot-matrix structure, so that the electrophoresis time can be focused on the electrophoretic deposition of a pixel only to centralize the electrophoretic deposition region and simplify the design of the anode plate and the electric field produced by the electrophoresis. The invention enhances the current density used for the electrophoresis and greatly lowers the equipment cost and reduces the power consumption for manufacturing large panels, and the present invention also improves the operating safety. [0013] Accordingly, a method of manufacturing carbon nanotube electron field emitters by do-matrix sequential electrophoretic deposition according to the invention comprises the following steps: [0014] An anode of a power supply is connected to a plurality of anode electrodes of an anode plate and a cathode of a power supply is connected to a switch unit, and the switch unit is connected to a plurality of cathode electrodes of a cathode plate, and the plurality of cathode electrodes and the plurality of anode electrodes are perpendicular to each other, and a signal generator is connected to an input end of the plurality of switch units, and the cathode plate and the anode plate are parallel with each other and placed in an electrophoresis tank. [0015] The anode of the power supply outputs a voltage to the plurality of anode electrodes of the anode plate, and the signal generator produces a pulse signal outputted to the plurality of switch units. During the electrophoretic deposition process, only one switch unit is electrically connected, and the rest of the switch units is electrically disconnected, and the electrically connected switch unit applies a pulse signal produced by the signal generator to a cathode electrode of the cathode plate, such that the cathode electrode is electrically connected, and only one pixel forms a potential different with an electric field between the electrically connected cathode electrode and anode electrode, and the cathode electrode forms carbon nanotubes disposed at positions for depositing an electron field transmitter. [0016] When one of the electrically connected cathode electrodes of the cathode plate goes through the electrophoresis process, the electrically connected switch unit counts the time, so that if the time counted by the switch unit is up, the electric power supplied to the cathode electrode will be disconnected to allow the next switch unit to be connected electrically and the rest of the switch unit will remain disconnected, and such sequence will apply to the next cathode electrode for continuing the electrophoretic deposition process. BRIEF DESCRIPTION OF DRAWINGS [0017] The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself however may be best understood by reference to the following detailed description of the invention, which describes certain exemplary embodiments of the invention, taken in conjunction with the accompanying drawings in which: [0018] FIG. 1 is a schematic view of a cathode plate and an anode plate of the present invention; [0019] FIG. 2 is a schematic view of connecting a cathode plate and an anode plate to an electrophoresis equipment according to the present invention; [0020] FIG. 3 is a schematic view of a cathode plate and an anode plate in an electrophoresis process according to the present invention; [0021] FIG. 4 is a schematic view of connecting a cathode plate and an anode plate to an electrophoresis equipment in a simple and easy way according to the present invention; and Continue reading... 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