EP1403897A2 - Elément génerateur de lumière - Google Patents

Elément génerateur de lumière Download PDF

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Publication number
EP1403897A2
EP1403897A2 EP20030256144 EP03256144A EP1403897A2 EP 1403897 A2 EP1403897 A2 EP 1403897A2 EP 20030256144 EP20030256144 EP 20030256144 EP 03256144 A EP03256144 A EP 03256144A EP 1403897 A2 EP1403897 A2 EP 1403897A2
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EP
European Patent Office
Prior art keywords
electrode
emitter
electrons
light emission
serving
Prior art date
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Application number
EP20030256144
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German (de)
English (en)
Inventor
Yukihisa NGK Insulators Ltd. Takeuchi
Tsutomu NGK INSULATORS LTD. NANATAKI
NGK Insulators Ltd. Ohwada Iwao
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NGK Insulators Ltd
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NGK Insulators Ltd
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Publication of EP1403897A2 publication Critical patent/EP1403897A2/fr
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    • 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
    • H01J1/53—Electrodes intimately associated with a screen on or from which an image or pattern is formed, picked-up, converted, or stored
    • 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
    • H01J2329/00—Electron emission display panels, e.g. field emission display panels

Definitions

  • the present invention relates to a light emission device having a first electrode, a second electrode, and a fluorescent body which are disposed on a substance that serves as an emitter.
  • the electron emitter has an anode electrode and a cathode electrode as a basic element.
  • a plurality of electron emitters are arranged in a two-dimensional array, and a plurality of fluorescent bodies are positioned in association with the respective electron emitters with a predetermined gap left therebetween.
  • a spacer is often provided between the electron emitter and the collector electrode for keeping the gap between the electron emitter and the collector electrode at a predetermined distance and also for achieving desired rigidity of the light emission device.
  • some of the accelerated electrons are liable to hit the spacer, negatively charging the spacer.
  • a field distribution between the electron emitter and the collector electrode i.e., a field distribution for directing electrons emitted from the electron emitter toward the collector electrode, is changed, so that the fluorescent body will not be excited accurately by the electron beam, tending to cause image quality failures and crosstalk.
  • Another problem is that positive ions generated by a plasma in the vacuum atmosphere impinge upon the cathode electrode, damaging the cathode electrode in a so-called ion bombardment phenomenon.
  • the conventional light emission device is disadvantageous in that it is not practical as its electron emission is not stable and it can emit electrons as many times as several ten thousands at most.
  • a light emission device has a substance disposed in a vacuum atmosphere and serving as an emitter made of a dielectric material, and a first electrode, a second electrode, and a fluorescent body which are disposed in contact with the substance serving as the emitter.
  • a drive voltage is applied between the first electrode and the second electrode, the polarization of at least a portion of the substance serving as the emitter is reversed or changed to emit electrons from at least a portion of the first electrode.
  • the substance serving as the emitter may be made of a piezoelectric material, an anti-ferroelectric material, or an electrostrictive material.
  • the first electrode and the fluorescent body are disposed on a first surface of the substance serving as the emitter, and the second electrode is disposed on a second surface of the substance serving as the emitter.
  • the first electrode and the second electrode are disposed in contact with a principal surface (the first surface) of the substance serving as the emitter, with a slit defined between the first electrode and the second electrode, the fluorescent body being disposed in at least the slit.
  • the substance serving as the emitter may have a portion exposed between the first electrode and the fluorescent body and/or between the second electrode and the fluorescent body.
  • a step may include a preparatory period in which a first voltage making the potential of the first electrode higher than the potential of the second electrode is applied between the first electrode and the second electrode to polarize the substance serving as the emitter, and an electron emission period in which a second voltage making the potential of the first electrode lower than the potential of the second electrode is applied between the first electrode and the second electrode to reverse or change the polarization of the substance serving as the emitter to emit electrons therefrom, and the step may be repeated.
  • Electrons are emitted from a portion of the first electrode in the vicinity of a triple point made up of the first electrode, the substance serving as the emitter, and a vacuum atmosphere during the electron emission period in the step, and the emitted electrons impinge upon the fluorescent body to emit light therefrom.
  • electrons are emitted from a portion of the first electrode in the vicinity of a triple point made up of the first electrode, the substance serving as the emitter, and a vacuum atmosphere during the electron emission period in the step, and the emitted electrons are reflected by a surface of the substance serving as the emitter and impinge upon the fluorescent body to emit light therefrom.
  • electrons are emitted from a portion of the first electrode in the vicinity of a triple point made up of the first electrode, the substance serving as the emitter, and a vacuum atmosphere during the electron emission period in the step, the emitted electrons impinge upon the substance serving as the emitter to emit secondary electrons therefrom, and the secondary electrons impinge upon the fluorescent body to emit light therefrom.
  • a step includes a preparatory period in which a first voltage making the potential of the first electrode higher than the potential of the second electrode is applied between the first electrode and the second electrode to polarize the substance serving as the emitter, and an electron emission period in which a second voltage making the potential of the first electrode lower than the potential of the second electrode is applied between the first electrode and the second electrode to reverse the polarization of the substance serving as the emitter to emit electrons from the first electrode, and a first cycle includes at least one the step, a step includes a preparatory period in which the second voltage is applied between the first electrode and the second electrode to polarize the substance serving as the emitter, and an electron emission period in which the first voltage applied between the first electrode and the second electrode to reverse the polarization of the substance serving as the emitter to emit electrons from the second electrode, and a second cycle includes at least one the step, and operation of the first cycle and operation of the second cycle are selectively performed.
  • Electrons are emitted from a portion of the first electrode in the vicinity of a triple point made up of the first electrode, the substance serving as the emitter, and a vacuum atmosphere during the electron emission period in the step of the first cycle, and the emitted electrons impinge upon the fluorescent body to emit light therefrom, and electrons are emitted from a portion of the second electrode in the vicinity of a triple point made up of the second electrode, the substance serving as the emitter, and a vacuum atmosphere during the electron emission period in the step of the second cycle, and the emitted electrons impinge upon the fluorescent body to emit light therefrom.
  • electrons are emitted from a portion of the first electrode in the vicinity of a triple point made up of the first electrode, the substance serving as the emitter, and a vacuum atmosphere during the electron emission period in the step of the first cycle, and the emitted electrons are reflected by a surface of the substance serving as the emitter and impinge upon the fluorescent body to emit light therefrom, and electrons are emitted from a portion of the second electrode in the vicinity of a triple point made up of the second electrode, the substance serving as the emitter, and a vacuum atmosphere during the electron emission period in the step of the second cycle, and the emitted electrons are reflected by a surface of the substance serving as the emitter and impinge upon the fluorescent body to emit light therefrom.
  • electrons are emitted from a portion of the first electrode in the vicinity of a triple point made up of the first electrode, the substance serving as the emitter, and a vacuum atmosphere during the electron emission period in the step of the first cycle, the emitted electrons impinge upon a surface of the substance serving as the emitter to emit secondary electrons therefrom, and the secondary electrons impinge upon the fluorescent body to emit light therefrom, and electrons are emitted from a portion of the second electrode in the vicinity of a triple point made up of the second electrode, the substance serving as the emitter, and a vacuum atmosphere during the electron emission period in the step of the second cycle, the emitted electrons impinge upon the substance serving as the emitter to emit secondary electrons therefrom, and the secondary electrons impinge upon the fluorescent body to emit light therefrom.
  • the light emission device With the light emission device according to the present invention, electrons emitted from the surface of the first electrode, the second electrode, or the substance serving as the emitter impinge upon the fluorescent body disposed in the vicinity of the first electrode, exciting the fluorescent body to emit light therefrom.
  • the light emission device does not need to have a collector electrode.
  • the light emission device may be low in profile, lightweight, and low in cost.
  • atoms produced when a portion of the substance serving as the emitter is evaporated are floating in the vicinity of the emitter.
  • atoms produced when a portion of the second electrode and the substance serving as the emitter is evaporated are floating in the vicinity of the electrode (e.g., the second electrode) to which a positive voltage is applied.
  • the electrons would ionize the gas and the atoms into positive ions and electrons. Since the electrons thus generated by the ionization would further ionize the gas and the atoms, electrons are exponentially multiplied to generate a local plasma in which the electrons and the positive ions are neutrally present.
  • the generated positive ions would impinge upon the substance serving as the emitter and the electrode (e.g., the first electrode) to which a negative voltage is applied, tending to damage the substance serving as the emitter and the first electrode (ion bombardment phenomenon).
  • the discharged electrons do not substantially ionize the gas present in the vicinity of the substance serving as the emitter or atoms of the second electrode into positive ions and electrons.
  • the number of areas where positive ions are generated in the vacuum atmosphere is reduced, and the problem of damage caused to the substance serving as the emitter and the first electrode by the ion bombardment phenomenon is avoided.
  • one or more spacers may be interposed between the light emission devices and the display panel in order to keep rigid the display including the display panel and to maintain the gap between the light emission devices and the display panel at a predetermined distance.
  • the spacer or spacers are not charged because electrons emitted from the light emission devices do not fly to the spacer. Even if the spacer is charged for some reasons, producing an unwanted field distribution between the light emission devices and the spacer, the electrons are not affected by the unwanted field distribution because the distance that the discharged electrons are accelerated and fly is small.
  • the light emission device in which the substance serving as the emitter made of the dielectric material according to the present invention, therefore, electrons discharged from the emitter are caused to impinge upon the fluorescent body without using a collector electrode, exciting the fluorescent body to emit light.
  • the light emission device can effectively be rendered low in profile, lightweight, and low in cost.
  • the first electrode and the fluorescent body may have an outer peripheral edge and an inner peripheral edge, respectively, which face each other, i.e., the outer peripheral edge of the first electrode may be surrounded by the fluorescent body.
  • the outer peripheral portion of the first electrode contributes to the emission of electrons, thus increasing the amount of emitted light.
  • the fluorescent body and the first electrode may have an outer peripheral edge and an inner peripheral edge, respectively, which face each other. If this structure is combined with the above structure in which the outer peripheral edge of the first electrode and the inner peripheral edge of the fluorescent body face each other, then the light emission device can emit a maximum amount of light with a minimum level of power consumption.
  • the first electrode and the second electrode may have respective projected shapes as viewed in plan, and the projected shape of the second electrode may have a protruding portion which protrudes from a peripheral edge of the projected shape of the first electrode.
  • the projected shape of the first electrode and the projected shape of the second electrode may be similar to each other.
  • the portion of the substance serving as the emitter which corresponds to the protruding portion of the second electrode can have its polarization reversed or changed easily. Since the electric field is concentrated from the protruding portion toward the peripheral edge of the first electrode, electrons can easily be emitted from around the triple point.
  • the protruding portion should preferably have a maximum length of at least 1 ⁇ m. Since the increase in the concentration of the electric field becomes saturated at a certain level, the maximum length of the protruding portion should preferably be of a value which does not adversely affect efforts to reduce the size of the light emission device, i.e., at most 500 pm.
  • the first electrode and the fluorescent body may have an outer peripheral edge and an inner peripheral edge, respectively, which face each other, i.e., the outer peripheral edge of the first electrode may be surrounded by the fluorescent body.
  • the fluorescent body and the second electrode may have an outer peripheral edge and an inner peripheral edge, respectively, which face each other, i.e., the outer peripheral edge of the fluorescent body may be surrounded by the second electrode.
  • the second electrode and the fluorescent body may have an outer peripheral edge and an inner peripheral edge, respectively, which face each other, i.e., the outer peripheral edge of the second electrode may be surrounded by the fluorescent body.
  • the fluorescent body and the first electrode may have an outer peripheral edge and an inner peripheral edge, respectively, which face each other, i.e., the outer peripheral edge of the fluorescent body may be surrounded by the first electrode.
  • the fluorescent body may be is disposed in covering relation to the second electrode.
  • the fluorescent body thus performs the function of a charged film. Specifically, when some of the discharged electrons are drawn to the second electrode, they negatively charge the surface of the fluorescent body.
  • the positive polarity of the anode electrode is now weakened, reducing the intensity of the electric field between the first electrode and the second electrode, thereby instantaneously stopping the ionization.
  • almost no positive ions are produced, thus preventing the first electrode from being damaged by positive ions.
  • the light emission device can thus have an increased service life.
  • the fluorescent body covering the second electrode also performs the function of a protective film.
  • the light emission device in which the substance serving as the emitter made of the dielectric material according to the present invention, as described above, electrons discharged from the emitter are caused to impinge upon the fluorescent body without using a collector electrode, exciting the fluorescent body to emit light.
  • the light emission device can effectively be rendered low in profile, lightweight, and low in cost.
  • Light emission devices can be used in displays, electron beam irradiation apparatus, light sources, LED alternatives, and electronic parts manufacturing apparatus.
  • An electron beam in an electron beam irradiation apparatus has a higher energy and a better absorption capability than ultraviolet rays in ultraviolet ray irradiation apparatus that are presently in widespread use.
  • Light emission devices are used to solidify insulating films in superposing wafers for semiconductor devices, harden printing inks without irregularities for drying prints, and sterilize medical devices while being kept in packages.
  • Light emission devices are also used as high-luminance, high-efficiency light sources for use in projectors, for example, which employ an ultrahigh-pressure mercury lamp or the like. If an electron pulse emission device according to the present invention is applied to a light source, then it can be reduced in size, has a longer service life, can be turned on at a higher speed, and is capable of reducing environmental burdens because it is free of mercury.
  • Light emission devices are also used as LED alternatives in planar light source applications including indoor illumination devices, automobile lamps, and traffic signal devices, and also in chip light sources, traffic signal devices, and backlight units for small-size liquid-crystal display devices for cellular phones.
  • Light emission devices are also used in electronic parts manufacturing apparatus including electron beam sources for film growing apparatus such as electron beam evaporation apparatus, electron sources for generating a plasma (to activate a gas or the like) in plasma CVD apparatus, and electron sources for decomposing gases.
  • Light emission devices are also used in vacuum micro devices including ultrahigh-speed devices operable in a tera-Hz range and large-current output devices.
  • Light emission devices are also used in printer parts, i.e., light emission devices for exposing photosensitive drums to light, and electron sources for charging dielectric bodies.
  • Light emission devices are also used in electronic circuit parts including digital devices such as switches, relays, diodes, etc. and analog devices such as operational amplifiers, etc. as they can be designed for outputting large currents and high amplification factors.
  • a light emission device 10A As shown in FIG. 1, a light emission device 10A according to a first embodiment of the present invention has a plate-like emitter (a substance serving as an emitter) 14, a first electrode (cathode electrode) 16 formed on one surface of the emitter 14, a second electrode (anode electrode) 20 formed on the reverse surface of the emitter 14, and a pulse generation source 22 for applying a drive voltage Va between the cathode electrode 16 and the anode electrode 20 through a resistor R1.
  • the anode electrode 20 is connected to GND (ground) through a resistor R2, and hence is maintained at the zero potential.
  • the anode electrode 20 may be maintained at a potential other than the zero potential.
  • the drive voltage Va is applied between the cathode electrode 16 and the anode electrode 20 through, as shown in FIG. 2, a lead electrode 17 extending to the cathode electrode 16 and a lead electrode 21 extending to the anode electrode 20.
  • the light emission device 10A also has a fluorescent body 28 disposed on the surface of the emitter 14 out of contact with, but as closely as possible, to the cathode electrode 16.
  • the electron emitter 10A according to the first embodiment is placed in a vacuum space. As shown in FIG. 1, the electron emitter 10A has an electric field concentration point A.
  • the point A can also be defined as a point including a triple point where the cathode electrode 16, the emitter 14, and the vacuum are present at one point.
  • the vacuum level in the atmosphere should preferably in the range from 2000 to 10 -6 Pa and more preferably in the range from 10 -3 to 10 -5 Pa.
  • the emitter 14 is made of a dielectric material.
  • the dielectric material should preferably have a relatively high dielectric constant, e.g., a dielectric constant of 1000 or higher.
  • Dielectric materials of such a nature may be ceramics including barium titanate, lead zirconate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead magnesium tantalate, lead nickel tantalate, lead antimony tinate, lead titanate, lead magnesium tungstenate, lead cobalt niobate, etc., ceramics containing a desired combination of these compounds, materials whose chief constituent contains 50 weight % or more of these compounds, or materials containing the above ceramics and oxides of lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium, zinc, nickel, manganese, etc., any combinations thereof, or other compounds added thereto.
  • n-PMN-mPT compound (n, m represent molar ratios) of lead magnesium niobate (PMN) and lead titanate (PT) has its Curie point lowered and its specific dielectric constant increased at room temperature when the molar ratio of PMN is increased.
  • a three-component compound of lead magnesium niobate (PMN), lead titanate (PT), and lead zirconate (PZ) may have its specific dielectric constant increased by making the compound have a composition in the vicinity of a morphotropic phase boundary (MPB) between a tetragonal system and a pseudo-cubic system or a tetragonal system and a rhombohedral system.
  • MPB morphotropic phase boundary
  • It is also preferable to increase the dielectric constant by mixing the above dielectric materials with a metal such as platinum insofar as electric insulation is maintained.
  • the dielectric materials are mixed with 20 weight % of platinum.
  • the emitter 14 may be in the form of a piezoelectric/electrostrictive layer or an anti-ferroelectric layer. If the emitter 14 comprises a piezoelectric/electrostrictive layer, then it may be made of ceramics such as lead zirconate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead magnesium tantalate, lead nickel tantalate, lead antimony tinate, lead titanate, barium titanate, lead magnesium tungstenate, lead cobalt niobate, or the like. or a combination of any of these materials.
  • ceramics such as lead zirconate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead magnesium tantalate, lead nickel tantalate, lead antimony tinate, lead titanate, barium titanate, lead magnesium tungstenate, lead co
  • the emitter 14 may be made of chief components including 50 weight % or more of any of the above compounds.
  • the ceramics including lead zirconate is mostly frequently used as a constituent of the piezoelectric/electrostrictive layer of the emitter 14.
  • the piezoelectric/electrostrictive layer is made of ceramics, then oxides of lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium, zinc, nickel, manganese, or the like, or a combination of these materials, or any of other compounds may be added to the ceramics.
  • the piezoelectric/electrostrictive layer should preferably be made of ceramics including as chief components lead magnesium niobate, lead zirconate, and lead titanate, and also including lanthanum and strontium.
  • the piezoelectric/electrostrictive layer may be dense or porous. If the piezoelectric/electrostrictive layer is porous, then it should preferably have a porosity of 40 % or less.
  • the anti-ferroelectric layer may be made of lead zirconate as a chief component, lead zirconate and lead tin as chief components, lead zirconate with lanthanum oxide added thereto, or lead zirconate and lead tin as components with lead zirconate and lead niobate added thereto.
  • the anti-ferroelectric layer may be porous. If the anti-ferroelectric layer is porous, then it should preferably have a porosity of 30 % or less.
  • the emitter 14 is made of strontium tantalate bismuthate, then its polarization reversal fatigue is small.
  • Materials whose polarization reversal fatigue is small are laminar ferroelectric compounds and expressed by the general formula of (BiO 2 ) 2+ (A m-1 B m O 3m+1 ) 2- .
  • Ions of the metal A are Ca 2+ , Sr 2+ , Ba 2+ , Pb 2+ , Bi 3+ , La 3+ , etc.
  • ions of the metal B are Ti 4+ , Ta 5+ , Nb 5+ , etc.
  • the baking temperature can be lowered by adding glass such as lead borosilicate glass or the like or other compounds of low melting point (e.g., bismuth oxide or the like) to the piezoelectric/electrostrictive/ceramics.
  • glass such as lead borosilicate glass or the like or other compounds of low melting point (e.g., bismuth oxide or the like) to the piezoelectric/electrostrictive/ceramics.
  • the emitter 14 is made of a material having a high melting point or a high evaporation temperature, such as a non-lead material, then it is less liable to be damaged by the impingement of electrons or ions.
  • the cathode electrode 16 is made of materials to be described below.
  • the cathode electrode 16 should preferably be made of a conductor having a small sputtering yield and a high evaporation temperature in vacuum.
  • materials having a sputtering yield of 2.0 or less at 600 V in Ar + and an evaporation temperature of 1800 K or higher at an evaporation pressure of 1.3 ⁇ 10 -3 Pa are preferable.
  • Such materials include platinum, molybdenum, tungsten, etc.
  • the cathode electrode 16 may be made of a conductor which is resistant to a high-temperature oxidizing atmosphere, e.g., a metal, an alloy, a mixture of insulative ceramics and a metal, or a mixture of insulative ceramics and an alloy.
  • the cathode electrode 16 should be chiefly composed of a precious metal having a high melting point, e.g., platinum, iridium, palladium, rhodium, molybdenum, or the like, or an alloy of silver and palladium, silver and platinum, platinum and palladium, or the like, or a cermet of platinum and ceramics.
  • the cathode electrode 16 should be made of platinum only or a material chiefly composed of a platinum-base alloy.
  • the cathode electrode 16 should also preferably be made of carbon or a graphite-base material, e.g., diamond thin film, diamondlike carbon, or carbon nanotube. Ceramics to be added to the electrode material should preferably have a proportion ranging from 5 to 30 volume %.
  • a material such as an organic metal paste which can produce a thin film after being baked e.g., a platinum resinate paste or the like, should preferably be used.
  • the cathode electrode 16 may be made of any of the above materials by any of thick-film forming processes including screen printing, spray coating, coating, dipping, electrophoresis, etc., or any of various thin-film forming processes including sputtering, an ion beam process, vacuum evaporation, ion plating, chemical vapor deposition (CVD), plating, etc.
  • the cathode electrode 16 is made by any of the above thick-film forming processes.
  • the cathode electrode 16 has a thickness tc (see FIG. 1) of 20 ⁇ m or less and preferably 5 ⁇ m or less. Therefore, the thickness tc of the cathode electrode 16 may be 100 nm or less. If the thickness tc of the cathode electrode 16 is very thin (10 nm or less), then electrons are emitted from the interface between the cathode electrode 16 and the emitter 14, so that the electron emission efficiency can be increased furthermore.
  • the anode electrode 20 is made of the same material by the same process as the cathode electrode 16.
  • the anode electrode 20 is made by any of the above thick-film forming processes.
  • the anode electrode 20 has a thickness of 20 ⁇ m or less and preferably 5 ⁇ m or less.
  • the assembly may be heated (sintered) into an integral structure.
  • the cathode electrode 16 and the anode electrode 20 may not be heated (sintered) so as to be integrally combined.
  • the sintering process for integrally combining the emitter 14, the cathode electrode 16, and the anode electrode 20 may be carried out at a temperature ranging from 500 to 1400°C, preferably from 1000 to 1400°C.
  • the emitter 14 should be sintered together with its evaporation source while their atmosphere is being controlled, so that the composition of the emitter 14 will not become unstable at the high temperature.
  • the emitter 14 may be covered with an appropriate member for concealing the surface thereof against direct exposure to the sintering atmosphere when the emitter 14 is sintered.
  • the cathode electrode 16 as viewed in plan has a projected shape which is a slender rectangular shape as shown in FIG. 2.
  • the cathode electrode 16 is shaped such that its outer peripheral edge confronts the inner peripheral edge of the fluorescent body 28, i.e., the outer peripheral edge of the cathode electrode 16 is surrounded by the fluorescent body 28.
  • the anode electrode 20 as viewed in plan has a projected shape which is an elongate rectangular shape whose area is greater than the cathode electrode 16, such that the projected shape of the cathode electrode 16 is fully contained in the projected shape of the anode electrode 20.
  • the projected shape of the anode electrode 20 has a protruding portion 20a which protrudes out of the projected shape of the cathode electrode 16.
  • the protruding portions 20a has a maximum length that should preferably range from 1 ⁇ m to 500 ⁇ m.
  • the portion of the emitter 14 which corresponds to the protruding portion 20a of the anode electrode 20 can have its polarization reversed or changed easily. Since the electric field is concentrated from the protruding portion 20a toward the peripheral edge of the cathode electrode 16, electrons can easily be emitted from around the triple point on the cathode electrode 16.
  • the outer peripheral portion of the cathode electrode 16 contributes to the emission of electrons, thus increasing the amount of emitted light.
  • the amount of emitted light and the electrostatic capacitance between the cathode electrode 16 and the anode electrode 20 can be optimized for reducing the power consumption and increasing the amount of emitted light.
  • the projected shapes as viewed in plan of the cathode electrode 16 and the anode electrode 20 may be an elliptical shape as with a light emission device 10Aa according to a first modification as shown in FIG. 3.
  • the projected shapes of the cathode electrode 16 and the anode electrode 20 are similar to each other.
  • a light emission device 10Ab according to a second modification as shown in FIG. 4 has a cathode electrode 16 having a ring-like projected shape and an anode electrode 20 having an elongate rectangular projected shape.
  • the cathode electrode 16 surrounds the outer peripheral edge of a central fluorescent body 28a, and an outer fluorescent body 28b surrounds the outer peripheral edge of the cathode electrode 16. Therefore, the triple point where the cathode electrode 16, the emitter 14, and the vacuum are present, i.e., the electric field concentration point A, is present on not only the outer periphery, but also the inner periphery, of the cathode electrode 16 for an increased electron emission efficiency.
  • a light emission device 10Ac according to a third modification as shown in FIG. 5 has a cathode electrode 16 having a comb-toothed projected shape and an anode electrode 20 having an elongate rectangular projected shape.
  • the length of the outer periphery of the cathode electrode 16 where the triple point of the cathode electrode 16, the emitter 14, and the vacuum is present is greatly increased without changing the overall size of the cathode electrode 16, for increasing the electron emission efficiency and easily optimizing the electrostatic capacitance and power consumption.
  • the drive voltage Va outputted from the pulse generation source 22 has the waveform of alternating-current pulses in the form of repeated steps each including a period in which a first voltage Va1 is outputted (preparatory period T1) and a period in which a second voltage Va2 is outputted (electron emission period T2).
  • the first voltage Va1 is a voltage that makes the potential of the cathode electrode 16 higher than the potential of the anode electrode
  • the second voltage Va2 is a voltage that makes the potential of the cathode electrode 16 lower than the potential of the anode electrode 20.
  • the preparatory period T1 is a period in which the first voltage Va1 is applied between the cathode electrode 16 and the anode electrode 20 to polarize the emitter 14.
  • the first voltage Val may be a DC voltage, as shown in FIG. 6, but may be a single pulse voltage or a succession of pulse voltages.
  • the preparatory period T1 should preferably be longer than the electron emission period T2 for sufficiently polarizing the emitter 14. For example, the preparatory period T1 should preferably be 100 ⁇ sec.
  • the absolute value of the first voltage Va1 for polarizing the emitter 14 is set to a smaller value than the absolute value of the second voltage Va2 for the purpose of reducing the power consumption when the first voltage Va1 is applied and preventing damage to the cathode electrode 16.
  • the first voltage Va1 and the second voltage Va2 should preferably be of voltage levels for reliably polarizing the emitter 14 into positive and negative poles. For example, if the dielectric material of the emitter 14 has a coercive voltage, then the absolute values of the first voltage Va1 and the second voltage Va2 should preferably be higher than the coercive voltage.
  • the electron emission period T2 is a period in which the second voltage Va2 is applied between the cathode electrode 16 and the anode electrode 20.
  • the second voltage Va2 is applied between the cathode electrode 16 and the anode electrode 20
  • the polarization of at least a portion of the emitter 14 is reversed or changed, as shown in FIG. 8.
  • the portion of the emitter 14 where the polarization is reversed or changed includes not only a portion directly below the cathode electrode 16, but also a portion having an exposed surface with no cathode electrode 16 thereon, in the vicinity of the cathode electrode 16.
  • the portion of the emitter 14 which as an exposed surface in the vicinity of the cathode electrode 16 has its polarization seeping out. Because of the reversed or changed polarization, a locally concentrated electric field is produced in the cathode electrode 16 and the positive poles of dipole moments in the vicinity of the cathode electrode 16, causing the cathode electrode 16 to emit primary electrons.
  • the distance L between the outer peripheral edge of the cathode electrode 16 and the inner peripheral edge of the fluorescent body 28, which confront each other, is small, then primary electrons discharged from the cathode electrode 16 directly impinge upon the fluorescent body 28, exciting the fluorescent body 28 to emit fluorescent light. If the thickness of the cathode electrode 16 is very small (up to 10 nm), then electrons are discharged from the interface between the cathode electrode 16 and the emitter 14, and the discharged electrons directly impinge upon the fluorescent body 28, exciting the fluorescent body 28.
  • primary electrons may impinge upon the emitter 14, causing the emitter 14 to discharge secondary electrons.
  • the discharged secondary electrons may be accelerated by an electric field generated in the vicinity of the surface of the cathode electrode 16 and impinge upon the fluorescent body 28, exciting the fluorescent body 28.
  • the emitter 14 When electrons discharged from the emitter 14 impinge again upon the emitter 14, or when ionization occurs in the vicinity of the surface of the emitter 14, the emitter 14 may be damaged or crystalline defects may be induced, tending to make the emitter 14 weak structurally.
  • the emitter 14 of a dielectric material having a high evaporation temperature in vacuum, e.g., BaTiO 3 or the like which does not contain Pb.
  • the emitter 14 thus constructed has its constituent atoms less liable to evaporate due to the Joule heat, obstructing the promotion of ionization by electrons. This is effective in protecting the surface of the emitter 14.
  • the light emission device 10A does not need to have a collector electrode. As a result, the light emission device 10A may be low in profile, lightweight, and low in cost.
  • the gas and atoms that are produced when part of the emitter 14 is evaporated are floating in the vicinity of the emitter 14. If a collector electrode were present, then when the discharged electrodes travel toward the collector electrode, the electrons would ionize the gas and the atoms into positive ions and electrons. Since the electrons thus generated by the ionization would further ionize the gas and the atoms, electrons are exponentially multiplied to generate a local plasma in which the electrons and the positive ions are neutrally present. The generated positive ions would impinge upon the emitter 14 and the cathode electrode 16, tending to damage the emitter 14 and the cathode electrode 16 (ion bombardment phenomenon).
  • the discharged electrons do not substantially ionize the gas present in the vicinity of the emitter 14 or atoms of the emitter 14 into positive ions and electrons.
  • the number of areas where positive ions are generated in the vacuum atmosphere is reduced, and the problem of damage caused to the emitter 14 and the cathode electrode 16 by the ion bombardment phenomenon is avoided.
  • one or more spacers may be interposed between the light emission devices 10A and a display panel in order to keep rigid the display including the display panel and to maintain the gap between the light emission devices 10A and the display panel at a predetermined distance.
  • the spacer or spacers are not charged because electrons emitted from the light emission devices 10A do not fly to the spacer. Even if the spacer is charged for some reasons, producing an unwanted field distribution between the light emission devices 10A and the spacer, the electrons are not affected by the unwanted field distribution because the distance that the discharged electrons are accelerated and fly is small.
  • the light emission device 10A therefore, electrons discharged from the cathode electrode 16 are caused to impinge upon the fluorescent body 28 without using a collector electrode, exciting the fluorescent body 28 to emit light.
  • the light emission device 10A can effectively be rendered small in size, lightweight, and low in cost.
  • a light emission device 10B according to a second embodiment of the present invention will be described below with reference to FIGS. 10 through 15D.
  • the light emission device 10B according to the second embodiment is substantially similar in structure to the light emission device 10A according to the first embodiment, but differs therefrom in that the cathode electrode 16 and the anode electrode 20 are disposed in contact with a principal surface of the emitter 14, with a slit 30 defined between the cathode electrode 16 and the anode electrode 20, and the fluorescent body 28 is disposed in at least the slit 30.
  • the emitter 14 has portions exposed between the cathode electrode 16 and the fluorescent body 28 and between the anode electrode 20 and the fluorescent body 28.
  • the light emission device 10A has an electric field concentration point B made up of the anode electrode 20, the emitter 14, and the vacuum, in addition to the electric field concentration point A.
  • the outer peripheral edge of the cathode electrode 16 and the inner peripheral edge of the fluorescent body 28 face each other, i.e., the outer peripheral edge of the cathode electrode 16 is surrounded by the fluorescent body 28, and the outer peripheral edge of the fluorescent body 28 and the inner peripheral edge of the anode electrode 20 face each other, i.e., the outer peripheral edge of the fluorescent body 28 is surrounded by the anode electrode 20.
  • the outer peripheral edge of the anode electrode 20 and the inner peripheral edge of the fluorescent body 28 may face each other, i.e., the outer peripheral edge of the anode electrode 20 may be surrounded by the fluorescent body 28, and the outer peripheral edge of the fluorescent body 28 and the inner peripheral edge of the cathode electrode 16 may face each other, i.e., the outer peripheral edge of the fluorescent body 28 may be surrounded by the cathode electrode 16.
  • a first process of driving the light emission device 10B will be described below with reference to FIGS. 6, 7, 10, 12, and 13.
  • a step including a period in which the first voltage Va1 is outputted (preparatory period T1) and a period in which the second voltage Va2 is outputted (electron emission period T2) is repeated.
  • the first voltage Va1 is applied between the cathode electrode 16 and the anode electrode 20 to polarize the emitter 14 in one direction.
  • the second voltage Va2 is applied between the cathode electrode 16 and the anode electrode 20 to reverse the polarization of at least a portion (corresponding to the slit 30) of the emitter 14, as shown in FIG. 12. Because of the reversed polarization, a locally concentrated electric field is produced in the cathode electrode 16 and the positive poles of dipole moments in the vicinity of the cathode electrode 16, causing the cathode electrode 16 to emit primary electrons.
  • the distance L between the outer peripheral edge of the cathode electrode 16 and the inner peripheral edge of the fluorescent body 28, which confront each other, is small, then primary electrons discharged from the cathode electrode 16 directly impinge upon the fluorescent body 28, exciting the fluorescent body 28 to emit fluorescent light. If the thickness of the cathode electrode 16 is very small (up to 10 nm), then electrons are discharged from the interface between the cathode electrode 16 and the emitter 14, and the discharged electrons directly impinge upon the fluorescent body 28, exciting the fluorescent body 28.
  • primary electrons may impinge upon the emitter 14, causing the emitter 14 to discharge secondary electrons.
  • the discharged secondary electrons may be accelerated by an electric field generated in the vicinity of the surface of the cathode electrode 16 and impinge upon the fluorescent body 28, exciting the fluorescent body 28.
  • a second process of driving the light emission device 10B will be described below with reference to FIGS. 14 through 15D.
  • the second driving process is different from the first driving process as follows:
  • a drive voltage VA1 outputted from the first pulse generation source 22a has a voltage waveform such that the first voltage Va1 (e.g., 30 V) is applied between the cathode electrode 16 and GND in the preparatory period T1 and the second voltage Va2 (e.g., -100 V) applied between the cathode electrode 16 and GND in the electron emission period T2.
  • the first voltage Va1 e.g., 30 V
  • the second voltage Va2 e.g., -100 V
  • a drive voltage VA2 outputted from the second pulse generation source 22b has a voltage waveform such that the second voltage Va2 (e.g., - 100 V) is applied between the cathode electrode 16 and GND in the preparatory period T1 and the first voltage Va1 (e.g., 30 V) applied between the cathode electrode 16 and GND in the electron emission period T2.
  • the second voltage Va2 e.g., - 100 V
  • the first voltage Va1 e.g., 30 V
  • a drive voltage VB1 outputted from the first pulse generation source 44a has a voltage waveform such that the second voltage Va2 (e.g., - 100 V) is applied between the anode electrode 20 and GND in the preparatory period T1 and the first voltage Va1 (e.g., 30 V) applied between the anode electrode 20 and GND in the electron emission period T2.
  • the second voltage Va2 e.g., - 100 V
  • the first voltage Va1 e.g., 30 V
  • a drive voltage VB2 outputted from the second pulse generation source 22b has a voltage waveform such that the first voltage Va1 (e.g., 30 V) is applied between the anode electrode 16 and GND in the preparatory period T1 and the second voltage Va2 (e.g.,-100 V) applied between the anode electrode 20 and GND in the electron emission period T2.
  • the first voltage Va1 e.g., 30 V
  • the second voltage Va2 e.g.,-100 V
  • the first and second switching circuits 40, 42 are ganged switching circuits having respective switches operable by the single switch control signal Sc.
  • the switch control signal Sc may be a command signal from a computer or a timer (not shown).
  • the first and second switching circuits 40, 42 are operated based on the voltage levels (high and low levels) of the switch control signal Sc.
  • the first and second switching circuits 40, 42 are supplied with the switch control signal Sc (e.g., the high voltage level) to select the first pulse generation sources 22a, 44a, respectively, the first voltage Va1 is applied between the cathode electrode 16 and GND in the preparatory period T1, polarizing the emitter 14, and the second voltage Va2 is applied between the cathode electrode 16 and GND in the electron emission period T2, reversing or changing the polarization of the emitter 14 for causing the cathode electrode 16 to discharge primary electrons, which excite the fluorescent body 28 to emit light.
  • the switch control signal Sc e.g., the high voltage level
  • the step is performed one time or a plurality of times as long as the switch control signal Sc is of the high voltage level, thereby carrying out one cycle (first cycle) of operation.
  • the first and second switching circuits 40, 42 are supplied with the switch control signal Sc (e.g., the low voltage level) to select the second pulse generation sources 22b, 44b, respectively, the first voltage Va1 is applied between the anode electrode 20 and GND in the preparatory period T1, polarizing the emitter 14, and the second voltage Va2 is applied between the anode electrode 20 and GND in the electron emission period T2, reversing the polarization of the emitter 14 for causing the anode electrode 20 to discharge primary electrons, which excite the fluorescent body 28 to emit light.
  • the switch control signal Sc e.g., the low voltage level
  • the step is performed one time or a plurality of times as long as the switch control signal Sc is of the low voltage level, thereby carrying out one cycle (second cycle) of operation.
  • the first and second switching circuits 40, 42 switch between the first cycle and the second cycle per step or per number of steps.
  • primary electrons can be discharged from the cathode electrode in the first cycle and primary can be discharged from the anode electrode in the second cycle for further increasing the electron emission efficiency.
  • the outer peripheral edge of the cathode electrode 16 is surrounded by the fluorescent body 28, and the outer peripheral edge of the fluorescent body 28 is surrounded by the anode electrode 20, or the outer peripheral edge of the anode electrode 20 is surrounded by the fluorescent body 28, and the outer peripheral edge of the fluorescent body 28 is surrounded by the cathode electrode 16. Consequently, the outer peripheral portion of the cathode electrode 16 and the outer peripheral portion of the anode electrode 20 contribute to the emission of electrons, thus increasing the amount of emitted light.
  • the amount of emitted light and the electrostatic capacitance between the cathode electrode 16 and the anode electrode 20 can be optimized for reducing the power consumption and increasing the amount of emitted light.
  • a light emission device 10C according to a third embodiment of the present invention will be described below with reference to FIGS. 16 through 18.
  • the light emission device 10C according to the third embodiment is substantially similar in structure to the light emission device 10B according to the second embodiment, but differs therefrom in that the fluorescent body 28 covers the surface of the anode electrode 20.
  • the fluorescent body 28 thus performs the function of a charged film and the function of a protective film.
  • a process of driving the light emission device 10C will be described below with reference to FIGS. 6, 16 through 18.
  • a step including a period in which the first voltage Va1 is outputted (preparatory period T1) and a period in which the second voltage Va2 is outputted (electron emission period T2) is repeated.
  • the first voltage Va1 is applied between the cathode electrode 16 and the anode electrode 20 to polarize the emitter 14 in one direction.
  • the second voltage Va2 is applied between the cathode electrode 16 and the anode electrode 20 to reverse the polarization of at least a portion (corresponding to the slit 30) of the emitter 14, as shown in FIG. 18. Because of the reversed polarization, a locally concentrated electric field is produced in the cathode electrode 16 and the positive poles of dipole moments in the vicinity of the cathode electrode 16, causing the cathode electrode 16 to emit primary electrons.

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  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Discharge Lamps And Accessories Thereof (AREA)
  • Cold Cathode And The Manufacture (AREA)
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Applications Claiming Priority (4)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7276462B2 (en) 2004-08-25 2007-10-02 Ngk Insulators, Ltd. Dielectric composition and dielectric film element
EP1630842A3 (fr) * 2004-08-25 2008-05-28 Ngk Insulators, Ltd. Emetteur d'électrons
US7511409B2 (en) 2004-08-25 2009-03-31 Ngk Insulators, Ltd. Dielectric film element and composition

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006054161A (ja) 2004-07-15 2006-02-23 Ngk Insulators Ltd 誘電体デバイス
US7482739B2 (en) 2004-07-15 2009-01-27 Ngk Insulators, Ltd. Electron emitter comprised of dielectric material mixed with metal
JP4662140B2 (ja) 2004-07-15 2011-03-30 日本碍子株式会社 電子放出素子
US7495378B2 (en) 2004-07-15 2009-02-24 Ngk Insulators, Ltd. Dielectric device
US7816847B2 (en) 2004-07-15 2010-10-19 Ngk Insulators, Ltd. Dielectric electron emitter comprising a polycrystalline substance
JP4678832B2 (ja) * 2004-07-27 2011-04-27 日本碍子株式会社 光源
CN100400465C (zh) * 2004-08-25 2008-07-09 日本碍子株式会社 电介质组成物及电介质膜元件
JP4749065B2 (ja) * 2004-08-25 2011-08-17 日本碍子株式会社 電子放出素子
JP5053524B2 (ja) 2005-06-23 2012-10-17 日本碍子株式会社 電子放出素子
JP2007095409A (ja) 2005-09-28 2007-04-12 Ngk Insulators Ltd 電子放出素子、及び電子放出素子の製造方法

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7276462B2 (en) 2004-08-25 2007-10-02 Ngk Insulators, Ltd. Dielectric composition and dielectric film element
EP1630842A3 (fr) * 2004-08-25 2008-05-28 Ngk Insulators, Ltd. Emetteur d'électrons
US7511409B2 (en) 2004-08-25 2009-03-31 Ngk Insulators, Ltd. Dielectric film element and composition

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