Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/15—Nano-sized carbon materials
  • C01B32/158—Carbon nanotubes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/04—Carbon
  • C08K3/041—Carbon nanotubes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/40—Glass
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/20—Conductive material dispersed in non-conductive organic material
  • H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising carbon-silicon compounds, carbon or silicon
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
  • H01J1/02—Main electrodes
  • H01J1/30—Cold cathodes, e.g. field-emissive cathode
  • H01J1/304—Field-emissive cathodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J31/00—Cathode ray tubes; Electron beam tubes
  • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
  • H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
  • H01J31/12—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen
  • H01J31/123—Flat display tubes
  • H01J31/125—Flat display tubes provided with control means permitting the electron beam to reach selected parts of the screen, e.g. digital selection
  • H01J31/127—Flat display tubes provided with control means permitting the electron beam to reach selected parts of the screen, e.g. digital selection using large area or array sources, i.e. essentially a source for each pixel group
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
  • H01J9/02—Manufacture of electrodes or electrode systems
  • H01J9/022—Manufacture of electrodes or electrode systems of cold cathodes
  • H01J9/025—Manufacture of electrodes or electrode systems of cold cathodes of field emission cathodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2201/00—Electrodes common to discharge tubes
  • H01J2201/30—Cold cathodes
  • H01J2201/304—Field emission cathodes
  • H01J2201/30446—Field emission cathodes characterised by the emitter material
  • H01J2201/30453—Carbon types
  • H01J2201/30469—Carbon nanotubes (CNTs)

Definitions

• CNTs Uniformly and selectively depositing CNTs over a large substrate is one of the main issues for an FED fabrication process.
• a typical means of growing carbon nanotubes on a substrate is to use chemical vapor deposition (CVD) techniques with catalyst activation. This technique requires a relatively high growth temperature, thereby increasing the production cost. It is also difficult to achieve a film with uniform properties over a large area.
• CVD chemical vapor deposition
• Other methods, such as screen-printing or dispensing have been developed to deposit CNTs in paste or ink composites.
• the composites consist of CNT powder mixed with conductive or non- conductive particles, carriers or vehicles and binders in some cases.
• CNT deposition is the last step in the cathode fabrication procedure, especially for triode structures.
• FIGURE 1(a) illustrates a side view of one embodiment of a well structure
• FIGURE 1(b) illustrates the well structure with integrated gate electrodes
• FIGURE 1(c) illustrates a metal grid electrode mounted after CNT deposition in the wells
• FIGURE 2(a) illustrates cathode electrodes printed using a screen-printing process
• FIGURE 2(b) illustrates an insulator layer printed using a screen-printing process
• FIGURE 3(a) illustrates filling the wells with a CNT ink
• FIGURE 3(b) illustrates spreading of the CNT ink within the wells
• FIGURE 3(c) illustrates
• An embodiment of the present invention provides a process for uniformly depositing CNTs into well structures as shown in FIGURE 1(a).
• Well structures may have four or more walls to form a hole (or one wall if a round hole).
• the well structure may also be employed as gated, triode structures in which the grid electrodes are deposited on the top of an insulator in advance of CNT deposition (as shown in FIGURE 1(b)), or a metal grid is mounted on after CNT deposition in the wells (as shown in FIGURE 1(c)).
• the metal grid can be used to modulate the current from the CNT material placed inside the well structure, as shown in the FIGURE 1(c). Both embodiments (FIGURES 1(b) and 1(c)) require CNT material inside the well structure.
• Each well may correspond to an individual pixel or sub-pixel. In some cases, several well structures may together be part of a pixel or sub-pixel.
• the well structures can be prepared using thick film process for low-resolution applications, such as screen printing (as shown in FIGURES 2(a) and 2(b)), or using thin film process for high-resolution well structures.
• Cathode electrodes are printed using screen- printing.
• a conducting cathode electrode can also be patterned onto a substrate.
• the electrode lines can be defined by etching the pattern from a thin film of conducting metal deposited onto the substrate using many techniques available in the art (e.g., evaporation, sputter, CVD, etc.)
• the etch pattern is defined using one of several lithography techniques (e.g., optical lithography, e-beam lithography, embossing, etc).
• Photo-active pastes such as DuPont FodelTM can be used to form the cathode electrode.
• the insulator layer may be printed using screen- printing.
• the walls of the well structure may also be printed using dispensing (including ink- jet printing) techniques, or they may be formed by sand or bead blasting techniques typically used in the plasma display industry.
• Photo-active pastes such as DuPont FodelTM can be used to form the insulator wall structure.
• FIGURES 2(a) and 2(b) show fabrication of a well structure.
• insulating material such as glass and ceramics
• semiconducting materials such as Si
• conducting materials such as metal sheets or foils, either pure metals or metal alloys
• CNT ink or paste composites such as dispensing, ink-jet printing, screen-printing, dipping, painting, brushing, spraying and spin-coating.
• the dispensing head moves relative to the substrate and is placed in position to dispense one or more drops of the ink or paste using a computer program before moving to the next spot to deposit more material (see FIGURE 3(a)).
• a Musashi SHOT miniTM was used, although other dispensers or ink-jet dispensers may be used.
• the formulations may need adjusting, depending on the model and type of dispenser used.
• This process may require heat or UV (ultraviolet) curing steps, depending on the CNT ink material used.
• CNTs are contained inside the well structure. It is possible to make the well structures very accurate using printing or dispensing techniques or using sand or bead blasting processes. If the well structures are made accurately, then using the process just described will result in uniform CNT deposition for each pixel. The well structures also effectively avoid edge emission issues that may also lead to non-uniform performance.
• the shape of the wells can define the shape and effective emitting area of a CNT cathode for an individual pixel or sub-pixel.
• FIGURE 5 illustrates a vacuum-sealed CNT field emission display configurated with well- formation processes as described herein.
• the sidewall spacer (wall spacer) and the internal spacers hold the gap between the anode plate (phosphor screen) and the cathode plate after the vacuum sealed display is evacuated.
• CNT-based inks with good field emission properties have been developed according to a process(es) of the present invention.
• a dispenser, an inkjet printer, a screen-printer and the like and combinations thereof can be used to fill the wells with a relatively accurate volume of CNT-ink.
• no further post-deposition processes are performed, such as the removal of sacrificial layers, which could damage the CNT ink.
• Such sacrificial layers are central to the processes disclosed in U.S. Patent No. 6,705,910. Such damage to the CNT ink will adversely affect its field emission capabilities.
• Examples of suitable means for filling the CNT-ink into the wells of the pixels include, but are not limited to, dispensing, inkjet printing, screen-printing, spin-on coating, brushing, dipping, and the like and combinations thereof.
• dispensing inkjet printing, screen-printing, spin-on coating, brushing, dipping, and the like and combinations thereof.
• the following examples are presented to further illustrate the present invention and are not to be construed as unduly limiting the scope of the present invention.
• the following illustrate sample formulations of CNT-ink that can be utilized according to a process of the present invention, and the field emission properties obtained with the various formulations.
• SWNTs Single wall carbon nanotubes
• the SWNTs were in a range of from 1 nm (nanometer) to 2 nm in diameter and in a range of from 5 ⁇ m (micrometers) to 20 ⁇ m in length.
• MWNTs multiwall carbon nanotubes
• the other components of the composite that were prepared were contained in an inorganic adhesive material. This inorganic adhesive material was obtained from Cotronics Corp., Brooklyn, New York, under the name/identifier of Resbond 989, that is a mixture of Al 2 O 3 particles, water, and inorganic adhesives.
• Composites that contain other particles may also be used, such as SiO 2 . These particles may be insulating, conducting or semiconducting. The particle sizes may be less than 50 ⁇ m.
• the carrier in the Resbond 989 is believed to be water, but other carrier materials may be used and they may also be organic or inorganic. Other materials that promote other properties of this material, such as binders (e.g., alkali silicates or phosphates) may also be present in the composite in small quantities.
• a Musashi-made dispenser (model: SHOT miniTM) was employed to deposit the CNT ink mixture into the well structures
• Other dispenser machines can be used, including ink-jet approaches.
• the CNT material is placed in each of the well structures by moving the dispensing head and/or the substrate relative to each other and dispensing dots of material at pre-defined locations.
• the substrate was then dried at room temperature in air for 10 minutes, but it can also be dried (cured) in an oven at increased temperature (approximately 100°C or higher) in order to eliminate the water faster. If the solvent contains organic materials, then an even higher temperature may be set to remove the materials. For example, up to 300°C will be set to remove epoxy.
• the oven or curing vessel may contain a vacuum pump to exhaust the air out of the oven and form a vacuum inside the oven during the drying/curing process.
• the oven or curing vessel may also provide a gas environment or flow around the sample that further promotes curing or drying. This gas environment or flow may or may not be partially or completely from inert gases such as the noble gases or nitrogen. Ultraviolet or infrared light may also be used to aid the curing process.
• a surface activation process (as discussed in U.S. Patent Application Serial No. 10/269,577) was applied to the CNT cathodes to improve the field emission properties. 3) The samples were then ready for field emission tests.
• a reference substrate was utilized that had the same thickness of a substrate that was desired to be subjected to a depositing of a CNT-ink of the present invention to determine if the CNT-ink, and dots comprising CNT-ink, could be dispensed consistently.
• the size of the spot of dispensed material comprising CNT-ink depended on the viscosity, nozzle size of the dispenser, and the distance (gap) between the nozzle and substrate. The smaller the nozzle opening, the more sensitive the variable of the gap between the nozzle and substrate.
• the dispenser was programmed to adjust the substrate position to the proper location(s) and to provide for a good alignment.
• the dispensing volume of CNT-ink can be adjusted by, for example, air pressure, distance, suck-back vacuum, viscosity of the dispensing material, and the size of the nozzle opening.
• the distance and the viscosity of dispensing materials are the most important parameters for dispensing consistently because the other parameters are more easy to control.
• the distance control is dependent on how flat the substrate is and the leveling of the X-Y table and also can be accurately controlled by a height sensor.
• Firing Process The following discloses a firing process of the present invention to provide for a removal of organic materials from a CNT cathode of the present invention. After the wells are filled, a firing process is needed to remove the organic materials in the CNT cathode.
• a substrate, comprising a CNT-ink of the present invention was subjected to baking in an oven at 100°C for 10 minutes in air.
• the substrate was placed into another nitrogen-flowing oven for firing.
• the temperature was slowly increased (at a rate of 180°C/hour) to 315°C and maintained at 315°C for 10 minutes.
• the temperature was increased (at the same ramp rate of 180°C/hour) to 450°C and fired at 450°C for 10 minutes. 4) The temperature was slowly decreased to room temperature (at the same ramp rate of 180°C/hour), i.e., the substrate was cooled to room temperature.
• the thinner can be evaporated at 230°C without any remains or residues.
• a 5 mL quantity of thinner (Terpineol) was then added to the jar.
• Other organic materials can also be used to adjust the viscosity of the CNT ink.
• a 1 mL quantity of Kasil® 2135 was then added to the jar. The Kasil was used to improve ink adhesion to the substrate.
• Other inorganic materials such as potassium silicate can also be used.
• FIGURE 6(a) The cathodes prepared with different CNT-inks of the present invention were tested using a diode configuration as illustrated in FIGURE 6(a).
• the spacer thickness between the cathode and anode is about 0.5 mm.
• the anode is ITO glass coated with phosphor.
• a field emission image from a cathode (CNT-ink 2) made by filling the well structure using the process described herein for CNT-ink 2 is shown in FIGURE 6(b). Twenty-two pixels were in the sample.
• FIGURE 7 shows the I-V curves from various cathodes made by the different CNT-inks prepared as previously described.
• a CNT-ink is used to fill the wells of pixels using methods such as, but not limited to, dispensing or screen-printing methods.
• a uniform cathode can be obtained over individual pixels or sub-pixels.
• the edge-emission can also be reduced or eliminated.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Nanotechnology (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
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• Polymers & Plastics (AREA)
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• Medicinal Chemistry (AREA)
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• 2004
  • 2004-09-10 KR KR1020067006861A patent/KR20060121910A/ko not_active Application Discontinuation
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