EP0971386B1 - Affichage à écran plat à structure triode utilisant des cathodes plates à émission de champ - Google Patents

Affichage à écran plat à structure triode utilisant des cathodes plates à émission de champ Download PDF

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Publication number
EP0971386B1
EP0971386B1 EP99202988A EP99202988A EP0971386B1 EP 0971386 B1 EP0971386 B1 EP 0971386B1 EP 99202988 A EP99202988 A EP 99202988A EP 99202988 A EP99202988 A EP 99202988A EP 0971386 B1 EP0971386 B1 EP 0971386B1
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EP
European Patent Office
Prior art keywords
cathodes
grid
cathode
layer
emission
Prior art date
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EP99202988A
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German (de)
English (en)
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EP0971386A2 (fr
EP0971386A3 (fr
Inventor
Nalin Kumar
Chenggang Xie
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Applied Nanotech Holdings Inc
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Applied Nanotech Holdings Inc
Nano Propietary Inc
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Publication of EP0971386A3 publication Critical patent/EP0971386A3/fr
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J63/00—Cathode-ray or electron-stream lamps
    • H01J63/06—Lamps with luminescent screen excited by the ray or stream
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J19/00—Details of vacuum tubes of the types covered by group H01J21/00
    • H01J19/02—Electron-emitting electrodes; Cathodes
    • H01J19/24—Cold cathodes, e.g. field-emissive cathode
    • 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
    • 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
    • H01J1/3042—Field-emissive cathodes microengineered, e.g. Spindt-type
    • 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
    • H01J9/027—Manufacture of electrodes or electrode systems of cold cathodes of thin film 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
    • H01J2201/30457—Diamond
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/30—Cold cathodes
    • H01J2201/319—Circuit elements associated with the emitters by direct integration
    • 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

Definitions

  • This invention relates, in general, to flat panel displays for computers and the like, and, more specifically, to flat panel displays that are of a field emission type using a triode (three terminal) pixel structure with flat cathode emitters in which the pixels are individually addressable.
  • Field emission computer displays in the general sense, are not new. For years there have been displays which comprise a plurality of field emission cathodes and corresponding anodes, the anodes emitting light in response to electron bombardment from corresponding the cathodes. Before entering a discussion on such displays, however, it is helpful to gain an understanding of the nature of field emission.
  • Field emission is a phenomenon which occurs when an electric field proximate the surface of an emission material narrows the width of a potential barrier existing at the surface of the emission material. This allows a quantum tunnelling effect to occur, whereby electrons cross through the potential barrier and are emitted from the material.
  • the field strength required to initiate emission of electrons from the surface of a particular material depends upon that material's "work function.” Many materials have a positive work function and thus require a relatively intense electric field to bring about field emission. Some materials do, in fact, have a low, or even negative, work function and thus do not require intense fields for emission to occur. Such materials may be deposited as a thin film onto a conductor, resulting in a cathode with a relatively low threshold voltage required to produce electron emissions.
  • micro-tip cathode In prior art devices, it was desirable to enhance field emission of electrons by providing for a cathode geometry which focussed electron emission at a single, relatively sharp point at a tip of a conical cathode (called a micro-tip cathode). These micro-tip cathodes, in conjunction with extraction grids proximate the cathodes, have been in use for years in triode field emission displays.
  • U.S. Patent No. 4,857,799 which issued on August 15, 1989, to Spindt et al., is directed to a matrix-addressed flat panel display using field emission cathodes.
  • the cathodes are incorporated into the display backing structure, and energize corresponding cathodoluminescent areas on a face plate.
  • the face plate is spaced 40 microns from the cathode arrangement in the preferred embodiment, and a vacuum is provided in the space between the plate and cathodes. Spacers in the form of legs interspersed among the pixels maintain the spacing, and electrical connections for the bases of the cathodes are diffused sections through the backing structure.
  • the display described in Spindt et al. is a triode display.
  • micro-tips employ a structure which is difficult to manufacture, since the micro-tips have fine geometries. Unless the micro-tips have a consistent geometry throughout the display, variations in emission from tip to tip will occur, resulting in unevenness in illumination of the display. Furthermore, since manufacturing tolerances are relatively tight, such micro-tip displays are expensive to make.
  • micro-tip cathodes are found in U.S. Patent No. 5,038,070, which issued on August 6, 1991 to Bardai et al., directed to a triode display and discloses a plurality of field emitters in the form of hollow, upstanding pointed cones or pyramids formed by a molding process.
  • the plurality of field emitters extend from a surface of an electrically conductive layer.
  • An electrically conductive mesh is adhered to an opposite surface of the conductive layer by a high temperature brazing process in electrical connection with the conductive layer.
  • the mesh provides a strong metal base with good thermal conductivity for mounting. Additional elements such as a gate and anode structure may be formed on the conductive layer in alignment with the field emitters to form a field emitting triode array or the like.
  • a disadvantage of the field emitter structure taught in Bardai et al. is that emitter cones must be photolithographically grown, which is a very complex and expensive procedure.
  • An attribute of the invention disclosed in Spindt et al. is that it provides its matrix-addressing scheme entirely within the cathode assembly.
  • Each cathode includes a multitude of spaced-apart electron emitting tips which project upwardly therefrom toward a face structure.
  • An electrically conductive gate or extraction electrode arrangement is positioned adjacent the tips to generate and control electron emission from the latter. Such arrangement is perpendicular to the base stripes and includes apertures through which electrons emitted by the tips may pass.
  • the extraction electrode is addressed in conjunction with selected individual cathodes to produce emission from the selected individual cathodes.
  • the grid-cathode arrangement is necessary in micro-tip cathodes constructed of tungsten, molybdenum or silicon, because the extraction field necessary to cause emission of electrons exceeds 50 MV/m.
  • the grid must be placed close (within approximately 1 micrometer) to the micro-tip cathodes.
  • These tight tolerances require that the gate electrodes be produced by optical lithographic techniques on an electrical insulating layer which electrically separates the gates of each pixel from the common base. Such photolithography is expensive and difficult to accomplish with the accuracy required to produce such a display, thereby raising rejection rates for completed displays.
  • the extraction grid taught in Spindt et al. was specifically designed to operate in conjunction with micro-tip cathodes, and not with other geometries.
  • the two major problems with the device disclosed in Spindt et al. are 1) formation of the micro-tip cathodes and 2) formation and alignment of the extraction electrodes with respect to the cathodes.
  • the structure disclosed in Spindt et al. is extremely intricate and difficult to fabricate in the case of large area displays.
  • the grid In a triode (three terminal) pixel structure, an electron extraction grid structure is interspersed between corresponding cathode and anode pairs.
  • the grid gives an extra control parameter which produces several advantages.
  • the grid can be controlled independent of the cathodes and anodes to thereby produce independently controllable cathode-anode and cathode-grid electric fields. This allows use of a very low control voltage to be applied to the cathode-grid field to effect electron emission, while the grid-anode voltage can be very high (several hundred to several thousand volts) to thereby result in higher power efficiency of the display.
  • anode phosphor material can be excited by electrons falling through a greater potential and, hence, be struck by electrons having a greater kinetic energy.
  • voltages selectively applied to address and excite individual grid-anode pairs can be lower (on the order of 40 volts), thereby allowing use of more conventional electronics in drive circuitry.
  • the lower electric field between the grid and the anode (on the order of 1-5 volts per micrometer) reduces dielectric requirements for spacer material used to separate cathode and anode assemblies.
  • Prior art extraction grid structures were designed to cooperate with micro-tip cathodes to enhance control of electron extraction and emission.
  • US Patent No 5,543,684 published after the priority date of the present application discloses a cathode having a relatively flat emission surface.
  • the cathode in its preferred embodiment, employs an emission material having a relatively low effective work function.
  • the material is deposited over a conductive layer and forms a plurality of emission sites, each of which can field-emit electrons in the presence of a relatively low intensity electric field.
  • amorphic diamond comprises a plurality of micro-crystallites, each of which has a particular structure dependent upon the method of preparation of the film. The manner in which these micro-crystallites are formed and their particular properties are not entirely understood.
  • Diamond has a negative electron affinity in the (lll) direction.
  • n-type diamond has a negative work function. That is, only a relatively low electric field is required to distort the potential barrier present at the surface of diamond.
  • diamond is a very desirable material for use in conjunction with field emission cathodes.
  • the prior art has employed diamond films to advantage as an emission surface on micro-tip cathodes.
  • amorphic diamond which has physical qualities which differ substantially from other forms of diamond, makes a particularly good emission material.
  • US Patent No 5,543,684 discloses use of amorphic diamond film as an emission material.
  • amorphic diamond film was used in conjunction with a flat cathode structure to result in a radically different field emission cathode design.
  • the micro-crystallites present in the amorphic diamond film are more or less disposed to function as electron emission sites, depending upon their individual structure. Therefore, over the surface of a relatively flat cathode emission surface, amorphic diamond micro-crystallites will be distributed about the surface, a percentage of which will act as localized electron emission sites.
  • triode flat panel displays based on micro-tip cathodes constructed of molybdenum, tungsten, silicon or similar materials.
  • the prior art has failed to provide a matrix-addressable flat panel display that is 1) relatively simple in design, 2) relatively inexpensive to manufacture and 3) uses a triode (three terminal) pixel structure employing a cathode which has a relatively flat emission surface comprising a plurality of distributed localized electron emission sites.
  • the purpose of the present invention is to build on the idea of depositing amorphic diamond film on the surface of relatively flat field emission cathodes, by providing a triode display structure employing a novel extraction grid proximate the flat cathodes to cause emission therefrom.
  • a flat panel display having the features of the preamble of claim 1 is disclosed in International patent specification number WO 91/05361.
  • the emitter objects may either be conductors or may be insulators coated with a thin layer of conductive material. In either case, the emitting "objects" are analogous to the micro-tips described above.
  • a flat panel display comprising:
  • the present invention relates to a flat panel display arrangement which employs the advantages of a luminescent phosphor of the type used in CRTs, while maintaining a physically thin profile.
  • the present invention provides for a flat panel display comprising (1) a plurality of corresponding light-emitting anodes and field-emission cathodes, each of the anodes emitting light in response to emission from each of the corresponding cathodes, each of the cathodes including a layer of low work function material having a relatively flat emission surface comprising a plurality of distributed localized electron emission sites and (2) a grid assembly interspersed between the corresponding anodes and cathodes to thereby control emission levels to the anodes from the corresponding cathodes, the grid assembly having apertures therein, the apertures having diameters equal to that of corresponding cathodes, such that the cathodes do not lie under the grid assembly.
  • the flat panel display is of a field emission type using a triode (three terminal) pixel structure.
  • the display is matrix-addressable by using grid and cathode assemblies arranged in strips in a perpendicular relationship whereby each grid strip and each cathode strip are individually addressable by grid and cathode voltage drivers, respectively. Effectively, a "pixel" is formed at each intersection of a grid strip and a cathode strip. The result is that each pixel within the display may be individually illuminated.
  • the grid strips themselves have a novel construction which allows them to operate with flat cathodes. More specifically, the grid strips comprise a substrate, preferably of SiO 2 , upon which is deposited a conductive layer, preferably of a metal. The conductive layer is etched to produce apertures therein, the apertures corresponding to particular cathode-anode pairs, edges of the apertures being located substantially above edges of corresponding cathodes.
  • the cathode assembly comprises a plurality of flat cathodes are, in the preferred embodiment of the present invention, photolithographically patterned either (1) through the apertures in the grid or (2) in alignment with the apertures in the grid.
  • Each cathode comprises a conductive material deposited over a substrate and a resistive material deposited over the conductive material. A thin film of low effective work function is then deposited over the resistive layer. The resistive layer provides a degree of electrical isolation between various subdivisions of the cathode strips.
  • the anode assembly consists of a conductive material (such as indium-tin oxide in the preferred embodiment) deposited over a substrate with a low energy phosphor (such as zinc oxide in the preferred embodiment), deposited over the conductive layer.
  • a conductive material such as indium-tin oxide in the preferred embodiment
  • a low energy phosphor such as zinc oxide in the preferred embodiment
  • a plurality of red, green and blue phosphors can be deposited over the conductive layer to provide a color display.
  • the resulting anode assembly and cathode assemblies are joined together with a peripheral glass frit seal onto a printed circuit board. Proper spacing between the assemblies is maintained by spacers consisting of either glass fibers or glass balls or a fixed spacer produced by typical deposition technology.
  • the assemblies are hermetically sealed and a vacuum drawn within the space between the anode and cathode assemblies via an exhaust tube. Systems for maintaining vacuums within such structures are well known in the art. Residual gases within the vacuum are collected together by a device called a getter.
  • the individual rows and columns of grid strips and cathode strips are externally accessible by flexible connectors provided by typical semiconductor mounting technology. These connectors are attached to grid and cathode drivers so as to provide the addressability of each pixel within the display.
  • An individual pixel is illuminated when the electrical potential difference between portions of a cathode and grid strip corresponding to that pixel is sufficient to extract electrons from the emission material coating the cathode, thereby causing emission of electrons from the cathode, through the control grid and toward the anode. As the electrons travel to the anode, they strike the low energy phosphor material, thereby producing light.
  • the gap between the cathode and grid is on the order of 1 micrometer. Because the spacing is so close, only 40 volts or so is required to cause emission. Commercially available devices are available in the prior art to switch 40 volts. These voltage drivers are also referred to as grid drivers and cathode drivers. A pixel is addressed and illuminated when the required driver voltage is applied to a corresponding grid strip and cathode strip resulting in emission of electrons from that portion of the cathode strip adjacent to the grid strip. Electrons are not emitted in a particular pixel area if only the corresponding cathode strip or corresponding grid strip is driven by the required driver voltage since the required threshold potential between the cathode and grid is not achieved.
  • the present invention has the ability to implement the display in grey scale mode by controlling the voltage supplied to the control grid which, in turn, modulates emissions of electrons from the cathode to the anode, thus varying photon emission of the phosphor material deposited on the anode.
  • the grid is supported by a layer of dielectric material.
  • the dielectric material is anisotropically etched to eliminate dielectric material between the cathode and its corresponding aperture. This results in the existence of a plurality of mushroom-shaped structures of dielectric material supporting the grid layer.
  • the dielectric layer can be isotropically etched until the mushroom-shaped structures are etched away, leaving the grid locally suspended. This results in an air-bridge structure.
  • Some of the advantages of the present invention include low power consumption, high brightness and low cost. Additionally, the cathode assembly of the present invention is less complicated and less expensive to manufacture since sophisticated photolithography is not required to produce the preferred flat cathode arrangement and grid assembly.
  • FIGURE 1 shown is a top view of joined cathode and extraction grid assemblies of the present invention. Their structure and function will be more completely described in a description pertaining to FIGURE 2.
  • the grid structure 102 is divided into electrically isolated and individually addressable strips which are arranged in a perpendicular manner with cathode strips, which, together, form a cathode structure 101.
  • the cathode strips are parallel to anode strips (not shown).
  • the strips in the structures 101, 102 provide a vertically and horizontally addressable structure which forms the basis for a flat panel display.
  • External connectors 220 provide electrical access to the cathode structure 101 and the grid structure 102.
  • the cathode strips and grid strips are separated by a dielectric layer.
  • FIGURE 2 shown is a side view of a "pixel" 100 of a triode flat panel display of the present invention.
  • Each cathode strip 103 of the cathode structure 101 of FIGURE 1 comprises a substrate 101, a conductive layer 150, a resistive layer 160 and flat cathodes 170.
  • the individual flat cathodes 170 are spaced apart from each other resulting in their isolation maintained by the resistive layer 160.
  • the anode assembly 104 consists of a substrate 120, typically glass, a conductive layer 130, typically indium-tin oxide (ITO) and a low energy phosphor 140, such as zinc oxide (ZnO).
  • ITO indium-tin oxide
  • ZnO zinc oxide
  • the anode assembly 104 is separated from a grid structure 102 by a plurality of dielectric spacers 190, which maintain a desired distance of separation between the anode assembly 104 and the grid structure 102.
  • the grid structure 102 Interspersed between the cathode strips 103 and anode assembly 104 is the grid structure 102. Electrons passing through openings in the grid structure 102 are accelerated toward the conductive layer 130, striking the low energy phosphor 140 and causing the low energy phosphor to emit light in response thereto.
  • the grid structure 102 is separated from a substrate under the cathode strips 103 by a spacer 180 which, in the preferred embodiment of the present invention, is a layer of dielectric material, preferably silicon dioxide (SiO 2 ).
  • SiO 2 silicon dioxide
  • apertures will be etched through the grid structure and the SiO 2 to form a channel from the cathodes, through corresponding apertures in the grid structure and to the corresponding anodes.
  • the pixel 100 is illuminated when a sufficient driver voltage is applied between the conductive layer 150 associated with the pixel 100 and the grid structure 102 corresponding to that particular pixel 100.
  • the two driver voltages combine with the constant DC supply voltage to provide a sufficient threshold potential between the sections of the grid and cathode structures 102, 101 (both of FIGURE 1) associated with the pixel 100.
  • the threshold potential results in electron emission from the flat cathodes 170.
  • FIGURE 3 shown is a partial side view of the joined cathode and extraction grid assemblies of FIGURE 2, taken along Section 3-3 of FIGURE 2.
  • spacers 180 are provided to maintain the proper distance between the grid structure 102 and the substrate under the cathode strips 103.
  • the spacers 300 are preferably a layer of dielectric material.
  • the grid structure 102 is provided with a plurality of apertures 310 therein, the apertures aligned or to be aligned with corresponding cathodes (not shown).
  • FIGURE 4 shown is a partial side view of an emitter array without supporting pillars before cathode deposition.
  • the emitter array comprises the substrate, cathode conductive layer and resistive layer, all illustrated and described in detail with respect to FIGURE 1.
  • An SiO 2 dielectric layer 400 is deposited over the substrate and provides a base for an extraction gate conductive layer 102.
  • layer 102 has already been deposited on layer 400 and apertures photolithographically etched therein. Since FIGURE 4 is a cross-section, the apertures are shown as spaces in the layer 102. Once the apertures have been etched, the SiO 2 layer is isotropically etched until it is removed from under that part of the layer 102 which is between the dielectric layer 400.
  • isotropic etching of the SiO 2 layer results in an air-bridge structure wherein the layer 102 is locally suspended over the pixel, without support from pillars therein. Even though a particular pixel comprises a plurality of cathodes and gate apertures in the preferred embodiment of the present invention, the layer 102 is still supported on all sides around the pixel by the layer 400, as shown in FIGURE 4. Note in particular, however, that the isotropic etch of the SiO 2 results in the layer 102 being etched back somewhat from the edges of the various apertures. This is an important feature of the present invention and will be explained in detail with respect to FIGURE 5.
  • FIGURE 5 shown is a partial side view of an emitter array without supporting pillars after cathode deposition.
  • Cathodes 500 are shown as having been deposited through the apertures and on the resistive layer. It is important to note that the cathodes are as wide as the apertures in the grid structure. It is a key feature of the present invention that the cathodes lie entirely under the apertures. This is so that the electric field existing about a cathode by virtue of the grid is relatively uniform over the surface of the cathode. This results in even electron emission over the surface. Furthermore, since no part of the cathodes lie directly under the grid, electrons, once emitted, do not have a tendency to strike the grid instead of the anode. This results in greater display efficiency, because power is not wasted on electrons which will fail to strike the anode.
  • FIGURE 6 shown is a partial side view of an emitter array with supporting pillars before cathode deposition.
  • FIGURE 7 shown is a partial side view of an emitter array with supporting pillars before cathode deposition. It is important to note that the cathodes are as wide as the apertures in the grid layer. It is also important to note that the pillars 600 are etched somewhat back from the edges of the apertures in the grid layer. Recall, as in the case of FIGURE 5, that the cathodes to be deposited are of the same diameter as the apertures.
  • the method of depositing the cathodes through the apertures in the grid conductive layer, using the grid conductive layer as a mask, is the preferred manner of producing the present invention.
  • the cathodes can be formed over the cathode conductive layer prior to deposition of the dielectric layer and the grid conductive layer, instead of depositing the cathodes through apertures in the grid conductive layer.
  • One disadvantage of this alternative method is that careful attention must be paid to alignment of the cathodes with respect to the apertures in the grid conductive layer. Should misalignment occur, display inefficiency or inoperability might result.
  • the structure generally designated 801, comprises a cathode substrate 802, upon which is deposited a cathode conductive layer 803 and strips of a cathode emission material layer 804.
  • a dielectric layer 805 is deposited on the material layer 804 to form strips which are oriented so as to be perpendicular to the strips of cathode emission material and etched to form apertures which define individual cathode-anode pairs.
  • a grid layer 806 of conductive material is next deposited on the dielectric layer 805, the grid layer 806 formed in strips corresponding to those of the dielectric layer 805 and having corresponding apertures therein.
  • An anode assembly 807 comprising a phosphor layer is placed above the grid layer 806 and held a controlled distance from the grid layer by a plurality of fibrous dielectric spacers 808.
  • the structure 801 is compatible with flat cathodes, it has several disadvantages.
  • the electric field under the grid layer 806 is much higher than the field existing between the grid layer 806 strips. As previously mentioned, this results in many of the emitter electrons being directed, not to the anode 807, but to the grid layer 806. Since these electrons never strike a phosphor, the energy in them is wasted.
  • the ratio of the electric field at and in the apertures in the grid layer 806 strips depends upon the diameter of the grid layer 806 apertures and the thickness of the dielectric layer 805.
  • the diameter of the apertures and the thickness of the dielectric layer 805 should have, at most, a one-to-one correspondence.
  • the size of the apertures is approximately 1 to 20 micrometers in diameter.
  • the fact that the emission layer 804 extends fully across the aperture gives rise to excess emission from the parts of the emission layer proximate the dielectric material (at the "triple junction").
  • emission from the emission layer 804 is not uniform from one side to another. It is much stronger on the edges of the cathode. This gives rise to leakage currents along the surface of the dielectric layer 805, causing the emission layer 804 and the grid layer 806 to short across the dielectric layer 805, thereby hampering or totally disabling operation of the pixel.
  • the structure 801 is deficient.
  • FIGURE 8 The key difference between the structure of FIGURE 8 and those preferred structures shown in FIGURES 5 and 7 is that the emission layer 804 is a uniform layer having triple junctions, whereas individual cathodes are shown in FIGURES 5 and 7, the cathodes having been deposited through the gate apertures or previously deposited in alignment with the apertures. In either case, the cathodes reside directly underneath the apertures and do not extend to under the gate conductors, which has been previously described as disadvantageous and is evident in FIGURE 8.
  • the dielectric supports are separated from the cathodes so as to eliminate triple junctions and thereby reduce the occurrence of surface current leakage.
  • These emitters do not extend from one side to another of the aperture formed into the grid layer and thus do not come into contact with the dielectric layer, thereby minimizing the occurrence of leakage currents.
  • the cathodes are discrete units, deposited separately upon the conductive layer.
  • FIGURE 9 shown is a perspective view of the joined cathode and extraction grid assemblies with an intervening dielectric layer. Shown is a substrate 901 upon which is deposited a conductive layer 902, as described before. The conductive layer 902 is deposited in strips, as shown. A dielectric layer 903 is deposited in a blanket layer over the conductive layer 902 and portions of the substrate 901. Next, a control grid layer 904 is deposited on the dielectric layer 903 in the form of strips oriented perpendicularly with respect to the conductive layer 902 strips and provided with a plurality of apertures corresponding to those in the dielectric layer 903.
  • a plurality of apertures 906 are formed in the dielectric layer 903 which correspond to cathodes created or to be created in the conductive layer 902.
  • the grid layer 904 terminates in a plurality of end conductors 905 which can be coupled to drive circuitry allowing the grid layer 904 to be selectively potentially separated from the conductive layer 902.
  • the anode layer and fibrous spacing material have not been shown although, if shown, would reside over the grid layer 904.
  • the present invention is the first to provide a flat panel display comprising (1) a plurality of corresponding light-emitting anodes and field-emission cathodes, each of the anodes emitting light in response to emission from each of the corresponding cathodes, each of the cathodes including a layer of low work function material having a relatively flat emission surface comprising a plurality of distributed localized electron emission sites and (2) a grid assembly interspersed between the corresponding anodes and cathodes to thereby control emission levels to the anodes from the corresponding cathodes.

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  • Manufacturing & Machinery (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
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Claims (7)

  1. Affichage à panneau ou écran plat comprenant:
    une pluralité de cathodes à émission de champ discrètes (170);
    une couche conductrice (102) qui est déposée sur ladite pluralité de cathodes discrètes (170), ladite couche conductrice comportant des ouvertures (310) en son sein, chacune desdites ouvertures (310) correspondant à chacune desdites cathodes discrètes (170), des bords desdites ouvertures (310) étant localisés sensiblement au dessus de bords desdites cathodes discrètes (170),
       caractérisé en ce que chacune desdites cathodes discrètes (170) inclut une couche en un film en diamant amorphe qui est déposée de manière à former une surface d'émission relativement plane.
  2. Affichage selon la revendication 1, dans lequel lesdites cathodes discrètes (170) sont jointes ensemble selon un assemblage de cathodes (101).
  3. Affichage selon la revendication 2, dans lequel ledit assemblage de cathodes (101) comprend une pluralité de bandes de cathode (103).
  4. Affichage selon la revendication 3, dans lequel ladite couche conductrice (102) est structurée en tant qu'assemblage de grilles qui comprend une pluralité de bandes de grille.
  5. Affichage selon la revendication 4, dans lequel lesdites bandes de grille (102) sont agencées selon une relation perpendiculaire par rapport auxdites bandes de cathode (103).
  6. Affichage selon la revendication 4 ou 5, dans lequel une couche diélectrique (180) est prévue entre ledit assemblage de grilles (102) et ledit assemblage de cathodes (101) de manière à maintenir une distance souhaitée entre ledit assemblage de grilles (102) et ledit assemblage de cathodes (101).
  7. Affichage selon l'une quelconque des revendications précédentes, dans lequel chacune desdites cathodes discrètes (170) comprend:
    un substrat (101);
    une couche résistive électroniquement (160) qui est déposée sur ledit substrat (101); et
    ladite couche constituant ladite surface d'émission qui est déposée sur ladite couche résistive (160).
EP99202988A 1992-12-23 1993-12-06 Affichage à écran plat à structure triode utilisant des cathodes plates à émission de champ Expired - Lifetime EP0971386B1 (fr)

Applications Claiming Priority (3)

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US99386392A 1992-12-23 1992-12-23
US993863 1992-12-23
EP94905334A EP0676084B1 (fr) 1992-12-23 1993-12-06 Affichage a ecran plat a structures triode utilisant des cathodes plates a emission de champ

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EP0971386A2 EP0971386A2 (fr) 2000-01-12
EP0971386A3 EP0971386A3 (fr) 2000-05-17
EP0971386B1 true EP0971386B1 (fr) 2004-06-16

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EP99202988A Expired - Lifetime EP0971386B1 (fr) 1992-12-23 1993-12-06 Affichage à écran plat à structure triode utilisant des cathodes plates à émission de champ
EP94905334A Expired - Lifetime EP0676084B1 (fr) 1992-12-23 1993-12-06 Affichage a ecran plat a structures triode utilisant des cathodes plates a emission de champ

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EP (2) EP0971386B1 (fr)
JP (1) JPH08505259A (fr)
KR (1) KR100284830B1 (fr)
AU (1) AU5897494A (fr)
CA (1) CA2152472A1 (fr)
DE (2) DE69333555T2 (fr)
WO (1) WO1994015352A1 (fr)

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Also Published As

Publication number Publication date
JPH08505259A (ja) 1996-06-04
EP0676084B1 (fr) 2000-07-05
KR950704802A (ko) 1995-11-20
DE69328977D1 (de) 2000-08-10
EP0676084A4 (fr) 1997-02-19
DE69328977T2 (de) 2000-12-28
WO1994015352A1 (fr) 1994-07-07
EP0971386A2 (fr) 2000-01-12
KR100284830B1 (ko) 2001-04-02
CA2152472A1 (fr) 1994-07-07
EP0971386A3 (fr) 2000-05-17
DE69333555T2 (de) 2005-08-18
DE69333555D1 (de) 2004-07-22
EP0676084A1 (fr) 1995-10-11
AU5897494A (en) 1994-07-19

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