Classifications

• • 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
  • H01J9/24—Manufacture or joining of vessels, leading-in conductors or bases
  • H01J9/241—Manufacture or joining of vessels, leading-in conductors or bases the vessel being for a flat panel display
  • H01J9/242—Spacers between faceplate and backplate
• • 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
  • H01J1/54—Screens on or from which an image or pattern is formed, picked-up, converted, or stored; Luminescent coatings on vessels
  • H01J1/62—Luminescent screens; Selection of materials for luminescent coatings on vessels
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
  • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
  • H01J29/028—Mounting or supporting arrangements for flat panel cathode ray tubes, e.g. spacers particularly relating to electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
  • H01J29/86—Vessels; Containers; Vacuum locks
  • H01J29/864—Spacers between faceplate and backplate of flat panel cathode ray tubes
• • 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
  • H01J9/18—Assembling together the component parts of electrode systems
  • H01J9/185—Assembling together the component parts of electrode systems of flat panel display devices, e.g. by using spacers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2201/00—Electrodes common to discharge tubes
  • H01J2201/02—Arrangements for eliminating deleterious effects
  • H01J2201/025—Arrangements for eliminating deleterious effects charging
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2329/00—Electron emission display panels, e.g. field emission display panels
  • H01J2329/86—Vessels
  • H01J2329/8625—Spacing members
  • H01J2329/863—Spacing members characterised by the form or structure
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2329/00—Electron emission display panels, e.g. field emission display panels
  • H01J2329/86—Vessels
  • H01J2329/8625—Spacing members
  • H01J2329/864—Spacing members characterised by the material

Definitions

• the present invention pertains to the area of field emission devices and, more particularly, to field emission displays .
• spacer structures between the cathode and anode plates of a field emission display.
• the spacer structures maintain the separation between the cathode and the anode. They must also withstand the potential difference between the cathode and the anode.
• spacers can adversely affect the flow of electrons toward the anode in the vicinity of the spacer.
• Some of the electrons emitted from the cathode can electrostatically charge the surface of the spacer, changing the voltage distribution near the spacer from the desired voltage distribution.
• the change in voltage distribution near the spacer can result in distortion of the electron flow. It can also result in electrical arcing, as between the spacer and the cathode.
• this distortion of the electron flow proximate to the spacers can result in distortions in the image produced by the display.
• the distortions render the spacers "visible" by producing a dark region in the image at the location of each spacer.
• prior art spacers attempt to solve the problems associated with spacer charging. For example, it is known in the art to provide a spacer having a surface, which has a sheet resistance that is low enough to remove the impinging electrons by conduction, yet high enough to ameliorate power loss due to electrical current from the anode to the cathode.
• the resistive surface can be realized by coating the spacer with a film having the desired resistance.
• these films are susceptible to mechanical damage and/or alteration, such as may occur during the handling of the spacers. These films may also introduce chemical incompatibilities with, for example, the cathode. Chemical incompatibilities can adversely affect the emission characteristics of the electron emitters on the cathode. Also, coated spacers can be difficult to manufacture.
• FIGURE is a cross-sectional view of an embodiment of a field emission device in accordance with the invention.
• the invention is for a field emission device having composite spacers.
• Each composite spacer has a first layer, which can be made from a dielectric material or a bulk resistive material, and a conductive layer, which is attached to the first layer.
• the conductive layer is proximate to the cathode, and the first layer is proximate to the anode.
• the conductive layer causes electrons to be directed away from the composite spacer, so that charging of the spacer surfaces is controlled.
• the controlled charging provides the benefit of reduced distortion of the trajectory of electrons due to the presence of spacers.
• the composite spacer also has a height that is greater than 500 micrometers, which renders the composite spacer of the invention useful in high-voltage field emission devices, which are operated at cathode-to-anode potential differences exceeding about 2500 volts.
• the field emission device is a field emission display having composite spacers, which are invisible to a viewer of the field emission display.
• FIGURE is a cross-sectional view of a field emission display (FED) 100 in accordance with the invention.
• FED 100 has a cathode 102, which opposes an anode 104.
• An evacuated region 106 exists between cathode 102 and anode 104.
• the pressure within evacuated region 106 is less than about 10 " e r p orr _
• a composite spacer 108 extends between cathode 102 and anode 104.
• Composite spacer 108 provides mechanical support to maintain the separation between cathode 102 and anode 104.
• Composite spacer 108 also has features that ameliorate electrostatic charging of composite spacer 108.
• Cathode 102 includes a substrate 116, which can be made from glass, silicon, and the like. Upon substrate 116 is disposed a cathode conductor 118, which can include a thin layer of molybdenum. A dielectric layer 120 is formed on cathode conductor 118. Dielectric layer 120 can be made from, for example, silicon dioxide. Dielectric layer 120 defines a plurality of emitter wells 122, in which are disposed one each a plurality of electron emitters 124.
• electron emitters 124 include Spindt tips.
• a field emission device in accordance with the invention is not limited to Spindt tip electron sources.
• an emissive carbon film can alternatively be employed for the electron source of the cathode.
• Cathode 102 further includes a plurality of gate extraction electrodes.
• a first gate extraction electrode 126 and a second gate extraction electrode 128 are illustrated in the FIGURE.
• the gate extraction electrodes are used to selectively address the electron emitters.
• Anode 104 includes a transparent substrate 110, upon which is disposed an anode conductor 112, which is transparent and can include a thin layer of indium tin oxide.
• a plurality of phosphors 114 is disposed upon anode conductor 112. Phosphors 114 oppose electron emitters 124.
• a first voltage source 136 is connected to anode conductor 112.
• a second voltage source 138 is connected to second gate extraction electrode 128.
• a third voltage source 140 is connected to first gate extraction electrode 126, and a fourth voltage source 142 is connected to cathode conductor 118.
• Composite spacer 108 extends between cathode 102 and anode 104 to provide mechanical support. The height of composite spacer 108 is sufficient to aid in the prevention of electrical arcing between anode 104 and cathode 102. For example, for a potential difference between anode 104 and cathode 102 of greater than about 2500, the height of composite spacer 108 is greater than about 500 micrometers, preferably within a range of 700 - 1200 micrometers.
• composite spacer 108 contacts anode 104, at a surface that is not covered by phosphors 114; the opposing end of composite spacer 108 contacts cathode 102, at a portion that does not define emitter wells 122.
• composite spacer 108 includes a first layer 107, which extends from a point intermediate the ends of composite spacer 108 toward anode 104.
• First layer 107 has a height, H.
• Composite spacer 108 also includes a conductive layer 109, which is connected to first layer 107 and extends toward cathode 102.
• Conductive layer 109 has a conductive surface 111, which is disposed within evacuated region 106.
• Conductive layer 109 has a height, h.
• First layer 107 includes a dielectric material or a bulk resistive material.
• the material of first layer 107 is selected to withstand the applied potential.
• the material of first layer 107 preferably has a high work function in order to ameliorate spurious electron emission from first layer 107.
• First layer 107 also preferably has very smooth surfaces in order to reduce charge accumulation and spurious emission.
• Dielectric materials useful for first layer 107 include ceramic, glass, sapphire, quartz, and the like.
• Bulk resistive materials useful for first layer 107 include iron- containing glass ceramics, tin oxide, nickel oxide, silicon nitride, neodymium titanate, zirconium oxide, and the like. In general, the bulk resistive material has a resistivity within a range of 10 5 - 10 13 ⁇ cm.
• Conductive layer 109 includes a conductive material.
• conductive layer 109 is made from a metal, such as aluminum, gold, copper, and the like. It can also be made from a metal alloy.
• conductive layer 109 includes a ceramic-metal composite material.
• the conductive nature of conductive layer 109 is necessary for causing the electron deflection or focusing, as described above .
• the material comprising conductive layer 109 can be selected to provide additional advantages. For example, a ductile metal reduces the risk of damage to cathode 102 during assembly of FED 100.
• the material of conductive layer 109 can have a high work function in order to control spurious electron emission from conductive layer 109.
• the material chosen for conductive layer 109 must also be very inert with respect to the materials of cathode 102, to prevent the formation of intermetallics and other undesirable chemical reactions .
• the height, h, of conductive layer 109 is selected to provide sufficient deflection of electron current 132 to ameliorate electrostatic charging of composite spacer 108 and to direct electron current 132 toward the appropriate phosphor. That is, the height, h, is selected to cause the electrons to strike the phosphor that opposes the originating electron emitter. By deflecting the electrons, conductive layer 109 prevents excessive electrostatic charging of composite spacer 108, which would otherwise produce undesirable results, such as excessive distortion of the trajectory of electron current 132, visibly discernable spacers, electrical arcing, and the like. In the preferred embodiment of the invention, conductive layer 109 is connected to a potential, which is useful for removing the electrostatic charge developed on composite spacer 108 during operation of FED 100.
• the discharging potential is provided at a second conductive layer 130.
• Second conductive layer 130 is disposed on dielectric layer 120 and includes a thin layer of a conductive material, such as molybdenum, aluminum, and the like.
• the potential at second conductive layer 130 can be independently controlled. Most preferably second conductive layer 130 is connected to electrical ground. The connection to electrical ground provides enhanced electron deflection, while not requiring additional power. However, it can also be connected to a fifth potential source (not shown) for applying a potential selected to provide the desired extent of electron deflection and/or charge dissipation characteristics of composite spacer 108. Alternatively, second conductive layer 130 can be, connected to or be a portion of one of the gate extraction electrodes of FED 100, which does not require an additional potential source.
• electron current 132 is controlled to an extent sufficient to render composite spacer 108 invisible to a viewer of FED 100 during its operation.
• conductive layer 109 is required for shaping the electric field in the vicinity of composite spacer 108. To provide this field shaping function, it is critical that the conductive material of conductive layer 109 be exposed to evacuated region 106.
• a field emission device embodying the invention is not limited to the geometric configuration described with reference to the FIGURE. This configuration is useful for operation of FED 100 at potential differences between cathode 102 and anode 104, which are greater than about 300 volts, and preferably within a range of about 2500 - 10,000 volts. It also includes a VGA configuration. It is desired to be understood, however, that a field emission display embodying the invention is not limited to a VGA configuration.
• transparent substrate 110 and substrate 116 each have a thickness of about one millimeter.
• Composite spacer 108 includes a rectangular platelet, which has a length (into the page) of about 5 millimeters, a height (extending between cathode 102 and anode 104) of about 1 millimeter, and a thickness, t, of about 0.07 millimeters.
• the center-to-center distance between first and second gate extraction electrodes 126, 128 is about 0.3 millimeters.
• FED 100 can be operated at a potential difference between anode conductor 112 and first and second gate extraction electrodes 126, 128 within a range of about 2500 - 10,000 volts.
• first and second gate extraction electrodes 126, 128, cathode conductor 118, and anode conductor 112 are applied to first and second gate extraction electrodes 126, 128, cathode conductor 118, and anode conductor 112 to cause selected electron emission at electron emitters 124 and to direct the electrons through evacuated region 106 toward phosphors 114. Phosphors 114 are caused to emit light by the impinging electrons .
• Conductive layer 109 shapes the electric field in the vicinity of composite spacer 108, so that electrons emitted proximate to composite spacer 108 are directed toward phosphors 114 and do not impinge upon composite spacer 108.
• the height, h, of conductive layer 109 is preferably within a range of about 75 - 150 micrometers.
• a composite spacer in accordance with the invention can be made using very economical and simple methods .
• the composite spacer of the invention does not require photolithographic steps, expensive x-ray lithography, or highly directional etching and deposition techniques . It also does not require steps that coat the electron emitters, which can risk the integrity of the electron emitters.
• Composite spacer 108 can be made by first providing a sheet of dielectric or bulk resistive material. Such sheets are commercially available.
• a metal layer is formed on the dielectric or bulk resistive sheet by one of a number of convenient methods, such as silk screening, brazing of a metal foil, electroplating, electroless plating, acoustophoresis, and the like.
• the composite sheet which has the metal layer attached to the dielectric or bulk resistive layer, is then cut into individual spacers, as by cutting with a wire saw or dicing saw.
• the cutting operation is initiated at the surface of the dielectric or bulk resistive material, in order to avoid coating the surfaces of first layer 107 with the conductive material .
• conductive layer 109 is made from a ceramic-metal composite material
• the ceramic-metal composite material is made by dispersing an insulating ceramic phase in a metallic powder.
• the mixture is formed into thin sheets via a standard ceramic forming method, such as tape casting, dry pressing, slip casting, and the like. From the forming operation, a monolith is cut out.
• the monolith is laminated to a layer of the selected dielectric or bulk resistive material.
• the lamination step is performed by applying pressure at the bonding interface at a temperature less than about 200°C.
• a bond can be achieved by heat treatment at temperatures above 200°C in a reducing atmosphere to prevent oxidation of the metal component .
• the mechanical and thermal properties can be tailored to achieve the desired characteristics, such as the desired thermal expansion coefficient of conductive layer 109. This embodiment is useful, for example, if greater mechanical strength, rather than compliance, is desired at conductive layer 109.
• anode 104 and cathode 102 Methods for forming anode 104 and cathode 102 are known to one skilled in the art.
• composite spacers 108 can be bonded to second conductive layer 130 by, for example, thermal compression bonding to maintain a perpendicular configuration with respect to cathode 102.
• Anode 104 is then placed upon composite spacers 108 and the package is hermetically sealed in a vacuum environment .
• the invention is for a field emission device having composite spacers.
• the field emission device of the invention can be operated at anode-to-cathode potential differences greater than 300 volts, preferably within a range of about 2500 - 10,000 volts.
• a field emission display in accordance with the invention has "invisible spacers", which are not visibly discernable to a viewer of the display.
• the composite spacer of the invention can be fabricated using simple, economical methods. While we have shown and described specific embodiments of the present invention, further modifications and improvements will occur to those skilled in the art. We desire it to be understood, therefore, that this invention is not limited to the particular forms shown, and we intend in the appended claims to cover all modifications that do not depart from the spirit and scope of this invention.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
• Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)

Applications Claiming Priority (3)

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• 1998
  • 1998-09-04 WO PCT/US1998/018612 patent/WO1999031699A1/en not_active Application Discontinuation
  • 1998-09-04 KR KR1020007004846A patent/KR20010031780A/ko not_active Application Discontinuation
  • 1998-09-04 EP EP98944785A patent/EP1048045A1/de not_active Withdrawn
  • 1998-09-04 CN CN98812198A patent/CN1282448A/zh active Pending
  • 1998-09-04 JP JP2000539505A patent/JP2002509337A/ja active Pending
  • 1998-09-30 TW TW087116290A patent/TW463204B/zh active

Non-Patent Citations (1)

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