EP1376641A2 - Emetteur electronique, circuit de commande pour un emetteur electronique et procede pour commander un emetteur electronique - Google Patents

Emetteur electronique, circuit de commande pour un emetteur electronique et procede pour commander un emetteur electronique Download PDF

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Publication number
EP1376641A2
EP1376641A2 EP03253962A EP03253962A EP1376641A2 EP 1376641 A2 EP1376641 A2 EP 1376641A2 EP 03253962 A EP03253962 A EP 03253962A EP 03253962 A EP03253962 A EP 03253962A EP 1376641 A2 EP1376641 A2 EP 1376641A2
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EP
European Patent Office
Prior art keywords
electrode
emitter
voltage
electron
emitter section
Prior art date
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Application number
EP03253962A
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German (de)
English (en)
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EP1376641A3 (fr
Inventor
Yukihisa. c/o NGK Insulators Ltd Takeuchi
Tsutomu. c/o NGK Insulators Ltd Nanataki
Iwao. c/o Int.Prop.Dpt NGK Insulators Ltd Ohwada
Nobuyuki c/o NGK Insulators Ltd Kokune
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NGK Insulators Ltd
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NGK Insulators Ltd
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Publication of EP1376641A2 publication Critical patent/EP1376641A2/fr
Publication of EP1376641A3 publication Critical patent/EP1376641A3/fr
Withdrawn legal-status Critical Current

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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
    • H01J1/02—Main electrodes
    • H01J1/30—Cold cathodes, e.g. field-emissive cathode
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • 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
    • H01J1/316—Cold cathodes, e.g. field-emissive cathode having an electric field parallel to the surface, e.g. thin film cathodes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00—Aspects of the constitution of display devices
    • G09G2300/04—Structural and physical details of display devices
    • G09G2300/0439—Pixel structures
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/06—Details of flat display driving waveforms
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/043—Preventing or counteracting the effects of ageing
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/04—Display protection
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007—Display of intermediate tones
    • G09G3/2011—Display of intermediate tones by amplitude modulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/32—Secondary emission electrodes
    • 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 an electron emitter comprising a first electrode and a second electrode formed on an emitter section, and a slit between the first electrode and the second electrode. Further, the present invention relates to a circuit for driving the electron emitter, and a method of driving the electron emitter.
  • FEDs field emission displays
  • backlight units a plurality of electron emitters are arranged in a two-dimensional array, and a plurality of fluorescent bodies are positioned at predetermined intervals in association with the respective electron emitters.
  • Preferred objects of the present invention include: to provide an electron emitter having an emitter section made of a dielectric material, to provide a circuit for driving the electron emitter, and to provide a method of driving the electron emitter in which a first electrode and a second electrode of the electron emitter may be prevented from being damaged due to the emission of electrons, so that the electron emitter may have a longer service life and higher reliability.
  • An electron emitter has an emitter section made of a dielectric material, a first electrode disposed in contact with the emitter section, and a second electrode disposed in contact with the emitter section and cooperating with the first electrode in providing a slit, wherein electrons are emitted from the emitter section by reversing the polarization of at least a portion of the emitter section which is exposed through the slit under a drive voltage applied between the first electrode and the second electrode, the slit having a width ranging from 0.1 ⁇ m to 50 ⁇ m.
  • the drive voltage is applied between the first electrode and the second electrode, the polarization of at least the portion of the emitter section which is exposed through the slit is reversed, causing the emitter section to emit electrons from the first electrode which is lower in potential than the second electrode.
  • the reversed polarization produces a locally concentrated electric field on the first electrode and the positive poles of dipole moments in the vicinity thereof, emitting primary electrons from the first electrode.
  • the primary electrons emitted from the first electrode impinge upon the emitter section, causing the emitter section to emit secondary electrons.
  • the electron emitter has a triple point in which the first electrode, the portion of the emitter section which is exposed through the slit, and a vacuum atmosphere are present, then the primary electrons are emitted from a portion of the first electrode near the triple point, and the secondary electrons are emitted from the emitter section when the primary electrons emitted from the portion of the first electrode impinge upon the emitter section.
  • the secondary electrons referred to herein include in-solid electrons and Auger electrons expelled out of the emitter section and also all primary electrons scattered in the vicinity of the surface of the emitter (reflected electrons). If the thickness of the first electrode is very small (up to 10 nm), then electrons are emitted from the interface between the first electrode and the emitter section.
  • the electron emission is stable, and is carried out more than 2000,000,000 times, making the electron emitter highly practical.
  • the number of emitted electrons increases substantially in proportion to the level of the drive voltage applied between the first electrode and the second electrode, the number of emitted electrons can easily be controlled.
  • a third electrode is disposed over the emitter section at a position confronting at least the slit, the third electrode being coated with a fluorescent layer.
  • some are emitted to the third electrode to excite the fluorescent layer, which produces a fluorescent emission directed outwardly.
  • Other electrons are emitted to the second electrode.
  • the electrons emitted to the second electrode ionize a gas or atoms of the second electrode which are present mainly in the vicinity of the second electrode into positive ions and electrons. Atoms of the second electrode which are present in the vicinity of the second electrode occur as a result of evaporation of part of the second electrode and float in the vicinity of the second electrode. Since electrons produced by the ionization further ionize the gas and the atoms, the electrons are increased exponentially. As exponential increase of the electrons goes on until electrons and positive ions are present neutrally, a local plasma is generated.
  • the first electrode When the positive ions produced by the ionization impinge upon the first electrode, the first electrode is damaged.
  • the applied voltage V is increased, then (1) since the withstand voltage of a drive circuit for the electron emitter needs to be increased, the drive circuit cannot be reduced in size and tends to become highly expensive, and (2) because positive ions generated by the plasma gains energy under the voltage V and impinge upon the first electrode, the first electrode is more liable to be damaged.
  • the width d of the slit is reduced.
  • the conventional electron emitters for emitting electrons under an electric field require an electric field of about 5 ⁇ 10 9 V/m, and need a small slit width of 20 nm if the applied voltage is less than 100 V.
  • the width d of the slit is not required to be as small as 20 nm, but may be about 20 ⁇ m.
  • the width d of the slit should preferably be selected in the range from 0.1 ⁇ m to 50 ⁇ m, or more preferably in the range from 0.1 ⁇ m to 10 ⁇ m. If the applied voltage is about 10 V, then the width d of the slit should preferably be selected in the range from 0.1 ⁇ m to 1 ⁇ m.
  • the width d of the slit should be 0.1 ⁇ m or greater because it makes it easy to form the slit and also keeps the first electrode and the second electrode insulated from each other.
  • the width d of the slit should be 50 ⁇ m or less, 10 ⁇ m or less, or 1 ⁇ m or less because it is effective to lower the electron emission voltage depending on the selected value of the applied voltage. With the width d of the slit selected in the above range, the drive circuit can be reduced in size and cost, and the first electrode can be prevented from being damaged for a longer service life.
  • the first electrode and the second electrode may be formed on an upper surface of the emitter section, and the slit may comprise a gap.
  • the first electrode may be formed in contact with one side surface of the emitter section, and the second electrode may be formed in contact with another side surface of the emitter section.
  • the emitter section may be present in the slit.
  • the slit comprises a gap
  • the width of the slit increases when the first electrode is damaged, making it difficult to keep the applied voltage low.
  • the emitter section is present in the slit, then the width of the slit remains unchanged even when the first electrode is damaged. As a result, electrons can be emitted stably under a constant voltage, and the electrodes can have a longer service life.
  • the emitter section is interposed between the two electrodes, the emitter section can be polarized completely, emitting electrons stably and efficiently due to the reversed polarization.
  • the emitter section is formed in a tortuous pattern, then the area of contact between the first electrode and the emitter section and the area of contact between the second electrode and the emitter section are increased for efficiently emitting electrons.
  • the electron emitter may further comprise a third electrode disposed over the substrate, the third electrode having an upper surface coated with a fluorescent layer.
  • the electron emitter is constructed as a display pixel, then a plurality of electron emitters are arranged in a matrix, a display panel is disposed in confronting relation to the electron emitters. A spacer is disposed adjacent to the electron emitters.
  • a third electrode is formed on the reverse side of the display panel (the surface facing the electron emitters), and the fluorescent layer is formed on the third electrode, then some of the electrons emitted from the electron emitters may impinge upon the spacer, tending to negatively charge the spacer.
  • the electric field distribution between the electron emitters and the third electrode i.e., the electric field distribution for directing the electrons emitted from the electron emitters toward the third electrode, is changed to fail to accurately excite the fluorescent layer with an electron beam, resulting in a displayed image quality failure.
  • the distribution of emitted electrons may be progressively wider toward the third electrode. Such an electron distribution may possibly be disadvantageous in reducing the pitch of pixels (increasing the image resolution).
  • the distribution of emitted electrons may be prevented from being spread by positioning at least one control electrode between the electron emitters and the third electrode.
  • the overall assembly would be complex in structure and would be highly costly to manufacture.
  • the third electrode may be disposed on the upper surface of the substrate, and the upper surface of the third electrode is coated with the fluorescent layer. Therefore, even when the spacer is negatively charged, the electric field distribution for directing the electrons emitted from the electron emitters toward the third electrode is essentially not changed. Therefore, the fluorescent layer can accurately be excited with the electron beam, preventing a displayed image quality failure.
  • some of the electrons emitted from the electron emitters may not be directed toward the third electrode on the substrate, but toward the display panel. Therefore, if a fourth electrode is positioned over the emitter section in confronting relation to the emitter section and a negative voltage is applied to the fourth electrode, then the electrons emitted from the electron emitters can be directed efficiently toward the third electrode for thereby increasing the contribution of the emitted electrons to the excitation of the fluorescent layer.
  • a drive circuit for energizing an electron emitter comprising an emitter section made of a dielectric material, a first electrode disposed in contact with the emitter section, and a second electrode disposed in contact with the emitter section and cooperating with the first electrode in providing a slit, wherein electrons are emitted from the emitter section by reversing the polarization of at least a portion of the emitter section which is exposed through the slit under a drive voltage applied between the first electrode and the second electrode, the drive circuit comprising a capacitor connected in series to the electron emitter.
  • the waveform of the voltage applied between the first electrode and the second electrode is of a gradual nature as a whole due to the CR time constant based on the electrostatic capacitance and other resistive component between the first electrode and the second electrode.
  • the voltage level that rises or falls steeply is low, and the voltage waveform until the voltage level reaches 95 %, for example, of a prescribed voltage (the rising or falling voltage of the source for generating the drive voltage) is gradual.
  • the electron emitter is regarded as a type of capacitor, then since the voltage (the applied voltage) applied between the first electrode and the second electrode is increased, electrons are emitted by a high-speed charging with a large current. However, a subsequent application of a high voltage causes an excessive current to flow, tending to damage the first electrode owing to the Joule heat generated thereby and positive ions impinging upon the first electrode.
  • the electrostatic capacitance of the capacitor is connected in series to the electrostatic capacitance formed by the first electrode and the second electrode, the overall capacitance becomes smaller than the electrostatic capacitance formed by the first electrode and the second electrode, and the CR time constant becomes smaller accordingly.
  • a voltage change going quickly up or down to a voltage level (e.g., 95 % of the prescribed voltage) which is required for emitting electrons as the waveform of the applied voltage, so that the electron emission voltage can be lowered.
  • a voltage level e.g., 95 % of the prescribed voltage
  • a drive circuit for energizing an electron emitter comprising an emitter section made of a dielectric material, a first electrode disposed in contact with the emitter section, and a second electrode disposed in contact with the emitter section and cooperating with the first electrode in providing a slit, wherein electrons are emitted from the emitter section by reversing the polarization of at least a portion of the emitter section which is exposed through the slit under a drive voltage applied between the first electrode and the second electrode, the drive circuit comprising a current-suppressing resistive element connected in series to the electron emitter.
  • the above arrangement suppresses an excessive current flowing through the electron emitter for thereby reducing damage to the first electrode, etc.
  • current-suppressing resistive element has nonlinear resistance characteristics.
  • the current-suppressing resistive element should preferably comprises a MOSFET device for preventing the voltage applied between the first electrode and the second electrode from changing gradually, but causing the voltage applied between the first electrode and the second electrode to change sharply.
  • An inductor may be connected in series to the electron emitter.
  • the inductor thus connected is effective to reduce the time required until the voltage between the first electrode and the second electrode becomes a predetermined voltage (coercive voltage if the emitter section is made of a piezoelectric material) from the time when the second voltage starts to be applied. Furthermore, a quick rise or fall time can be achieved without lowering the resistance of the resistive element.
  • a step comprising a preparatory period in which a first voltage of such a level that the first electrode is higher in potential than the second electrode is applied between the first electrode and the second electrode to polarize the emitter section, and an electron emission period in which a second voltage of such a level that the first electrode is lower in potential than the second electrode is applied between the first electrode and the second electrode to polarize the emitter section to emit electrons therefrom, may be repeated.
  • the emitter section which is made of a dielectric material is polarized.
  • the polarization of the emitter section is reversed.
  • the reversed polarization produces a locally concentrated electric field on the first electrode and the positive poles of dipole moments in the vicinity thereof, emitting primary electrons from the first electrode.
  • the primary electrons emitted from the first electrode impinge upon the emitter section, causing the emitter section to emit secondary electrons. According to the present invention, therefore, electrons can efficiently be emitted from the electron emitter.
  • the second voltage is greater in absolute value than the first voltage, then electric power consumption due to the application of the first voltage is reduced, and electrode damage is prevented.
  • the drive circuit may further comprise a switching circuit for switching between a first cycle and a second cycle, the first cycle including at least one step which comprises a preparatory period in which a first voltage of such a level that the first electrode is higher in potential than the second electrode is applied between the first electrode and the second electrode to polarize the emitter section, and an electron emission period in which a second voltage of such a level that the first electrode is lower in potential than the second electrode is applied between the first electrode and the second electrode to polarize the emitter section to emit electrons from the first electrode, the second cycle including at least one step which comprises a preparatory period in which the second voltage is applied between the first electrode and the second electrode to polarize the emitter section, and an electron emission period in which the first voltage is applied between the first electrode and the second electrode to polarize the emitter section to emit electrons from the second electrode.
  • the first cycle including at least one step which comprises a preparatory period in which a first voltage of such a level that the first electrode is higher in potential than the second electrode
  • the drive circuit may further comprise a pulse generation circuit for applying a voltage which turns the polarity of the potential of the second electrode into a polarity different from the polarity of the potential of the first electrode, to the second electrode in at least the electron emission period.
  • the drive voltage has its dynamic range determined by the withstand voltage of a source of the drive voltage.
  • the pulse generation circuit is effective to increase the dynamic range of the drive voltage applied between the first electrode and the second electrode to a withstand voltage which is the sum of the withstand voltage of the source of the drive voltage and the withstand voltage of the pulse generation circuit. Therefore, the source of the drive voltage may comprise a circuit having a withstand voltage which is one half of the usual withstand voltage, so that the drive circuit may be reduced in size and cost.
  • the preparatory period is longer than the electron emission period.
  • ⁇ and the electron emission period T satisfy the following relationship: 0 ⁇ T ⁇ 3 ⁇ . Since the electron emission period is the period of a sharp voltage change which contributes to electron emission, a wasteful current supply is eliminated, resulting in a reduction of electric power consumption, and an emission of excessive electrons is suppressed.
  • the circuit for driving the electron emitter may further comprise a switching element connected in series to the electron emitter, wherein if a time constant determined by an electrostatic capacitance and other resistive component between the first electrode and the second electrode is represented by ⁇ , the electron emission period by T, and an on-time of the switching element by t, then the time constant ⁇ , the electron emission period T, and the on-time t satisfy the following relationship: 0 ⁇ t ⁇ 3 ⁇ ⁇ T.
  • the circuit for driving the electron emitter may further comprise at least one parallel circuit connected in series to the electron emitter, the parallel circuit comprising a resistor and a capacitor which are connected parallel to each other, wherein the electron emission period includes an effective electron emission period from the start of application of the second voltage to the time when the voltage between the first electrode and the second electrode reaches a divided level on the capacitor of the amplitude of the drive voltage.
  • the capacitor of the parallel circuit is connected in series to the electrostatic capacitance formed by the first electrode and the second electrode of the electron emitter, the overall capacitance becomes smaller than the electrostatic capacitance formed by the first electrode and the second electrode, and the CR time constant becomes smaller accordingly. As a result, there is obtained a voltage change going quickly up or down to a voltage level which is required for emitting electrons as the applied voltage, so that the electron emission voltage can be lowered.
  • a method of driving an electron emitter comprising an emitter section made of a dielectric material, a first electrode disposed in contact with the emitter section, and a second electrode disposed in contact with the emitter section and cooperating with the first electrode in providing a slit, the method comprising repeating a step which comprises a preparatory period in which a first voltage of such a level that the first electrode is higher in potential than the second electrode is applied between the first electrode and the second electrode to polarize the emitter section, and an electron emission period in which a second voltage of such a level that the first electrode is lower in potential than the second electrode is applied between the first electrode and the second electrode to polarize the emitter section to emit electrons therefrom.
  • the above method can efficiently emit electrons from the electron emitter.
  • electrons are emitted from the emitter section near a triple point in which the first electrode, the portion of the emitter section which is exposed through the slit, and a vacuum atmosphere.
  • the absolute value of the second voltage is greater than the absolute value of the first voltage.
  • switching may be made between a first cycle and a second cycle, the first cycle including at least one step which comprises a preparatory period in which a first voltage of such a level that the first electrode is higher in potential than the second electrode is applied between the first electrode and the second electrode to polarize the emitter section, and an electron emission period in which a second voltage of such a level that the first electrode is lower in potential than the second electrode is applied between the first electrode and the second electrode to polarize the emitter section to emit electrons from the first electrode, the second cycle including at least one step which comprises a preparatory period in which the second voltage is applied between the first electrode and the second electrode to polarize the emitter section, and an electron emission period in which the first voltage is applied between the first electrode and the second electrode to polarize the emitter section to emit electrons from the second electrode.
  • damage can be distributed to both the first electrode and the second electrode, so that the electrodes will have a longer service life.
  • a voltage which turns the polarity of the potential of the second electrode into a polarity different from the polarity of the potential of the first electrode may be applied to the second electrode in at least the electron emission period.
  • the dynamic range of the applied voltage can be increased, and hence the withstand voltages of the source for generating the drive signal and the source for generating a common potential can be reduced, so that the drive circuit can be made smaller in size and lower in cost.
  • the preparatory period should preferably be longer than the electron emission period.
  • the time constant ⁇ and the electron emission period T may satisfy the following relationship: 0 ⁇ T ⁇ 3 ⁇ . Since the electron emission period is the period of a sharp voltage change which contributes to electron emission, a wasteful current supply is eliminated, resulting in a reduction of electric power consumption, and an emission of excessive electrons is suppressed.
  • a switching element may be connected in series to the electron emitter, and if a time constant determined by an electrostatic capacitance and other resistive component between the first electrode and the second electrode is represented by ⁇ , the electron emission period by T, and an on-time of the switching element by t, then the time constant ⁇ , the electron emission period T, and the on-time t may satisfy the following relationship: 0 ⁇ t ⁇ 3 ⁇ ⁇ T.
  • an on-time of the switching element for emitting electrons is represented by t1
  • a subsequent off-time of the switching element for keeping electrons emitted and suppressing a current flowing into the first electrode by t2
  • the time constant ⁇ , the electron emission period T, the on-time t1, and the off-time t2 may satisfy the following relationship: 0 ⁇ t1 ⁇ 3 ⁇ ⁇ t2 ⁇ T.
  • At least one parallel circuit may be connected in series to the electron emitter, the parallel circuit comprising a resistor and a capacitor which are connected parallel to each other, wherein the electron emission period includes an effective electron emission period from the start of application of the second voltage to the time when the voltage between the first electrode and the second electrode reaches a divided level on the capacitor of the amplitude of the drive voltage.
  • Embodiments of an electron emitter, of a circuit for driving the electron emitter, and of a method of driving the electron emitter according to the present invention will be described below by way of example, with reference to FIGS. 1 through 37.
  • electron emitters can be used in displays, electron beam irradiation apparatus, light sources, alternatives to LEDs, and electronic parts manufacturing apparatus.
  • Electron beams in an electron beam irradiation apparatus have a high energy and a good absorption capability in comparison with ultraviolet rays in ultraviolet ray irradiation apparatus that are presently in widespread use. Electron emitters 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.
  • the electron emitters are also used as high-luminance, high-efficiency light sources such as a projector having a high pressure mercury lamp.
  • the electron emitter according to the present embodiment is suitably used as a light source.
  • the light source using the electron emitter according to the present embodiment is compact, has a long service life, has a fast response speed for light emission.
  • the electron emitter does not use any mercury, and the electron emitter is environmentally friendly.
  • the electron emitters are also used as alternatives to LEDs in indoor lights, automobile lamps, surface light sources for traffic signal devices, chip light sources, and backlight units for traffic signal devices, small-size liquid-crystal display devices for cellular phones.
  • the electron emitters are also used in apparatus for manufacturing electronic parts, 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.
  • the electron emitters are also used as vacuum micro devices such as high speed switching devices operated at a frequency on the order of Tera-Hz, and large current outputting devices.
  • the electron emitter are used suitably as parts of printers, such as light emitting devices for emitting light to a photosensitive drum, and electron sources for charging a dielectric material.
  • the electron emitters are also used as electronic circuit devices including digital devices such as switches, relays, and diodes, and analog devices such as operational amplifiers.
  • the electron emitters are used for realizing a large current output, and a high amplification ratio.
  • an electron emitter 10 comprises an emitter section 14 formed on a substrate 12, a first electrode (cathode electrode) 16 formed on one surface of the emitter section 14, and a second electrode (anode electrode) 20 formed on the same one surface of the emitter section 14 and cooperating with the cathode electrode 16 in providing a slit 18.
  • a pulse generation source 22 applies a drive voltage Va between the cathode electrode 16 and the anode electrode 20.
  • the anode electrode 20 is connected to GND (ground) and hence set to a zero potential. However, the anode electrode 20 may be set to a potential other than the zero potential.
  • a third electrode (collector electrode) 24 is disposed above the emitter section 14 at a position confronting the slit 18.
  • the collector electrode 24 is coated with a fluorescent layer 28.
  • a bias voltage source 102 (having a bias voltage V3) is connected to the collector electrode 24 through a resistor 104 (having a resistance R3).
  • the electron emitter 10 is placed in a vacuum space. As shown in FIG. 1, the electron emitter 10 has electric field concentration points A, B.
  • the point A can also be defined as a triple point where the cathode electrode 16, the emitter section 14, and a vacuum are present at one point.
  • the point B can also be defined as a triple point where the anode electrode 20, the emitter section 14, and a vacuum are present at one point.
  • the vacuum level in the atmosphere should preferably in the range from 10 2 to 10 -6 Pa and more preferably in the range from 10 -3 to 10 -5 Pa.
  • the emitter section 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 stannate, lead titanate, barium titanate, lead magnesium tungstenate, lead cobalt niobate, etc.
  • nPMN-mPT nPMN-mPT
  • PT lead titanate
  • MPB morphotropic phase boundary
  • a dielectric material may be mixed with 20 weight % of platinum.
  • the emitter section 14 may be in the form of a piezoelectric/electrostrictive layer or an anti-ferroelectric layer. If the emitter section 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 antimony stannate, 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 antimony stannate, lead titanate, barium titanate, lead magnesium tungstenate, lead cobalt niobate
  • the emitter section 14 may be made of chief components including 50 weight % or more of any of the above compounds. Of the above ceramics, the ceramics including lead zirconate is most frequently used as a constituent of the piezoelectric/electrostrictive layer of the emitter section 14.
  • the piezoelectric/electrostrictive layer is made of ceramics, then 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 stannate as chief components, lead zirconate with lanthanum oxide added thereto, or lead zirconate and lead stannate 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.
  • Strontium bismuthate tantalate is used suitably for the emitter section 14.
  • the emitter section 14 made of strontium bismuthate tantalate is not damaged by the polarization reversal easily.
  • lamellar ferroelectric compounds represented by a general formula (BiO 2 ) 2+ (A m - 1 B m O 3m+1 ) 2- are used.
  • the ionized metal A includes Ca 2+ , Sr 2+ , Ba 2+ , Pb 2+ , Bi 2+ , La 2+
  • the ionized metal B includes Ti 4+ , Ta 5+ , Nb 5+ .
  • Piezoelectric/electrostrictive/anti-ferroelectric ceramics is mixed with glass components such as lead borosilicate glass or other compounds having a low melting point such as bismuth oxide to lower the firing temperature.
  • glass components such as lead borosilicate glass or other compounds having a low melting point such as bismuth oxide to lower the firing temperature.
  • the emitter section 14 is formed easily on the substrate 12.
  • the emitter section 14 may be made of a material which does not contain any lead, i.e., made of a material having a high melting temperature, or a high evaporation temperature. Thus, the emitter section 14 is not damaged easily when electrons or ions impinge upon the emitter section 14.
  • the emitter section 14 may be formed on the substrate 12 by any of various thick-film forming processes including screen printing, dipping, coating, electrophoresis, etc., or any of various thin-film forming processes including an ion beam process, sputtering, vacuum evaporation, ion plating, chemical vapor deposition (CVD), plating, etc.
  • various thick-film forming processes including screen printing, dipping, coating, electrophoresis, etc.
  • various thin-film forming processes including an ion beam process, sputtering, vacuum evaporation, ion plating, chemical vapor deposition (CVD), plating, etc.
  • the emitter section 14 is formed on the substrate 12 by any of various thick-film forming processes including screen printing, dipping, coating, electrophoresis, etc.
  • These thick-film forming processes are capable of providing good piezoelectric operating characteristics as the emitter section 14 can be formed using a paste, a slurry, a suspension, an emulsion, a sol, or the like which is chiefly made of piezoelectric ceramic particles having an average particle diameter ranging from 0.01 to 5 ⁇ m, preferably from 0.05 to 3 ⁇ m.
  • electrophoresis is capable of forming a film at a high density with high shape accuracy, and has features described in technical documents such as "Electrochemical and industrial physical chemistry, Vol. 53. No. 1 (1985), p. 63 - 68, written by Kazuo Anzai", and "1st electrophoresis high-degree ceramic forming process research/discussion meeting, collected preprints (1998), p. 5 - 6, p. 23 - 24".
  • the piezoelectric/electrostrictive/anti-ferroelectric material may be formed into a sheet, or laminated sheets.
  • the laminated sheets of the piezoelectric/electrostrictive/anti-ferroelectric material may be laminated on, or attached to another supporting substrate. Any of the above processes may be chosen in view of the required accuracy and reliability.
  • the cathode electrode 16 is made of materials as 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 pressure of 1.3 ⁇ 10 -3 Pa at a temperature of 1800 K or higher are preferable.
  • Such materials include platinum, molybdenum, tungsten, etc.
  • the cathode electrode 16 is 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 electrode should preferably be made of carbon or a graphite-base material, e.g., diamond thin film, diamond-like carbon, or carbon nanotube. Ceramics to be added to the electrode material should preferably have a proportion ranging from 5 to 30 volume %.
  • oxide electrode is used.
  • the oxide electrode is made by mixing any of these materials with platinum resinate paste, for example.
  • the cathode electrode 16 may be made of any of the above materials by an ordinary film forming process which may be any of various thick-film forming processes including screen printing, spray coating, dipping, coating, electrophoresis, etc., or any of various thin-film forming processes including sputtering, an ion beam process, vacuum evaporation, ion plating, CVD, plating, etc. As shown FIG. 2, the cathode electrode 16 has a width W1 of 2 mm and a length L1 of 5 mm. The cathode electrode 16 has a thickness of 20 ⁇ m or less, or preferably 5 ⁇ m or less.
  • 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 width W2 of 2 mm and a length L2 of 5 mm.
  • the substrate 12 should preferably be made of an electrically insulative material in order to electrically isolate the wire electrically connected to the cathode electrode 16 and the wire electrically connected to the anode electrode 20 from each other.
  • the substrate 12 may be made of a highly heat-resistant metal or a metal material such as an enameled metal whose surface is coated with a ceramic material such as glass or the like. However, the substrate 12 should preferably be made of ceramics.
  • Ceramics which the substrate 12 is made of include stabilized zirconium oxide, aluminum oxide, magnesium oxide, titanium oxide, spinel, mullite, aluminum nitride, silicon nitride, glass, or a mixture thereof.
  • aluminum oxide or stabilized zirconium oxide is preferable from the standpoint of strength and rigidity.
  • Particularly preferable is stabilized zirconium oxide because its mechanical strength is relatively high, its tenacity is relatively high, and its chemical reaction with the cathode electrode 16 and the anode electrode 20 is relatively small.
  • Stabilized zirconium oxide includes stabilized zirconium oxide and partially stabilized zirconium oxide. Stabilized zirconium oxide does not develop a phase transition as it has a crystalline structure such as a cubic system.
  • Zirconium oxide develops a phase transition between a monoclinic system and a tetragonal system at about 1000°C and is liable to suffer cracking upon such a phase transition.
  • Stabilized zirconium oxide contains 1 to 30 mol % of a stabilizer such as calcium oxide, magnesium oxide, yttrium oxide, scandium oxide, ytterbium oxide, cerium oxide, or an oxide of a rare earth metal.
  • the stabilizer should preferably contain yttrium oxide.
  • the stabilizer should preferably contain 1.5 to 6 mol % of yttrium oxide, or more preferably 2 to 4 mol % of yttrium oxide, and furthermore should preferably contain 0.1 to 5 mol % of aluminum oxide.
  • the crystalline phase may be a mixed phase of a cubic system and a monoclinic system, a mixed phase of a tetragonal system and a monoclinic system, a mixed phase of a cubic system, a tetragonal system, and a monoclinic system, or the like.
  • the main crystalline phase which is a tetragonal system or a mixed phase of a tetragonal system and a cubic system is optimum from the standpoints of strength, tenacity, and durability.
  • the substrate 12 is made of ceramics, then the substrate 12 is made up of a relatively large number of crystalline particles.
  • the crystalline particles should preferably have an average particle diameter ranging from 0.05 to 2 ⁇ m, or more preferably from 0.1 to 1 ⁇ m.
  • the assembly is heated (sintered) into a structure integral with the substrate 12.
  • the cathode electrode 16, and the anode electrode 20 are formed, they may simultaneously be sintered so that they may simultaneously be integrally coupled to the substrate 12.
  • they may not be heated (sintered) so as to be integrally combined with the substrate 12.
  • the sintering process for integrally combining the substrate 12, the emitter section 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 section 14 For heating the emitter section 14 which is in the form of a film, the emitter section 14 should be sintered together with its evaporation source while their atmosphere is being controlled.
  • the emitter section 14 may be covered with an appropriate member for preventing the surface thereof from being directly exposed to the sintering atmosphere when the emitter section 14 is sintered.
  • the covering member should preferably be made of the same material as the substrate 12.
  • the drive voltage Va outputted from the pulse generation source 22 has 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 Val is such a voltage that the potential of the cathode electrode 16 is higher than the potential of the anode electrode 20
  • the second voltage Va1 is such a voltage that the potential of the cathode electrode 16 is lower than the potential of the anode electrode 20.
  • the preparatory period T1 is a period in which the first voltage Val is applied between the cathode electrode 16 and the anode electrode 20 to polarize the emitter section 14, as shown in FIG. 4.
  • the first voltage Va1 may be a DC voltage, as shown in FIG. 3, 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 sufficient polarization.
  • the preparatory period T1 should preferably be 100 ⁇ sec. or longer. This is because the absolute value of the first voltage Va1 for polarizing the emitter section 14 is smaller than the absolute value of the second voltage Va2.
  • 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, as shown in FIG. 5A
  • the polarization of at least the portion of the emitter section 14 which is exposed through the slit 18 is reversed. Because of the reversed polarization, a locally concentrated electric field is generated on the cathode electrode 16 and the positive poles of dipole moments in the vicinity thereof, emitting primary electrons from the cathode electrode 16.
  • FIG. 5B the primary electrons emitted from the cathode electrode 16 impinge upon the emitter section 14, causing the emitter section 14 to emit secondary electrons.
  • the electron emitter 10 having the triple point A where the cathode electrode 16, the emitter section 14, and the vacuum are present at one point, primary electrons are emitted from the cathode electrode 16 near the triple point A, and the primary electrons thus emitted from the triple point A impinge upon the emitter section 14, causing the emitter section 14 to emit secondary electrons. If the thickness of the cathode electrode 16 is very small (up to 10 nm), then electrons are emitted from the interface between the cathode electrode 16 and the emitter section 14.
  • the electron emission is stable, and is carried out more than 2 billion times, making the electron emitter 10 highly practical.
  • the number of emitted electrons increases substantially in proportion to the amplitude Vin of the drive voltage Va applied between the cathode electrode 16 and the anode electrode 20, the number of emitted electrons can easily be controlled.
  • a distribution of emitted secondary electrons will be described below.
  • most of the secondary electrons have an energy level near zero.
  • the secondary electrons are emitted from the surface of the emitter section 14 into the vacuum, they move according to only an ambient electric field distribution. Specifically, the secondary electrons are accelerated from an initial speed of about 0 (m/sec) according to the ambient electric field distribution. Therefore, as shown in FIG. 5B, if an electric field E is generated between the emitter section 14 and the collector electrode 24, the secondary electrons has their emission path determined along the electric field E. Therefore, the electron emitter 10 can serve as a highly straight electron source.
  • the secondary electrons which have a low initial speed are in-solid electrons which are expelled out of the emitter section 14 under an energy that has been obtained by a coulomb collision with primary electrons.
  • the emission path of the secondary electrons can easily be controlled and the diameter of the electron beam can easily be converged, increased, or modified by establishing an electric field distribution between the emitter section 14 and the collector electrode 24 as desired by changing the pattern shape and potential of the collector electrode 24 or positioning a non-illustrated control electrode between the emitter section 14 and the collector electrode 24.
  • the highly straight electron source and the easy control of the emission path of the secondary electrons provide advantages in reducing the pitch of pixels if the electron emitter 10 according to the present embodiment is constructed as a display pixel.
  • secondary electrons having an energy level which corresponds to the energy E 0 of primary electrons are emitted. These secondary electrons are primary electrons that are emitted from the cathode electrode 16 and scattered in the vicinity of the surface of the emitter section 14 (reflected electrons).
  • the thickness of the cathode electrode 16 is greater than 10 nm, then almost all of the reflected electrons are directed toward the anode electrode 20.
  • the secondary electrons referred to in the present description are defined as including both the reflected electrons and Auger electrons.
  • the thickness of the cathode electrode 16 is very small (up to 10 nm), then primary electrons emitted from the cathode electrode 16 are reflected by the interface between the cathode electrode 16 and the emitter section 14, and directed toward the cathode electrode 24.
  • the electrons emitted to the anode electrode 20 ionize a gas or atoms of the anode electrode 20 which are present mainly in the vicinity of the anode electrode 20 into positive ions and electrons.
  • Atoms of the anode electrode 20 which are present in the vicinity of the anode electrode 20 occur as a result of evaporation of part of the anode electrode 20 and float in the vicinity of the anode electrode 20. Since electrons produced by the ionization further ionize the gas and the atoms, the electrons are increased exponentially. As exponential increase of the electrons goes on until electrons and positive ions are present neutrally, a local plasma is generated.
  • the cathode electrode is of a conventional conical shape, then the tip of the electrode would be deformed into a round shape due to damage, requiring an increased electron emission voltage.
  • One solution would be to make the electrode of a material having a high melting point such as molybdenum or the like, but the electrode itself would become highly expensive, resulting in an increase in the cost required to manufacture the electron emitter.
  • a separate gate electrode or the like would be provided to prevent positive ions from concentrating and impinging upon the cathode electrode 16. This approach would be problematic in that the electrode structure would be complicated and the cost required to manufacture the electron emitter would tend to become high.
  • various specific examples described below are employed to reduce the size and cost of the electron emitter, lower the electron emission voltage, and minimize damage to the cathode electrode 16 (and the anode electrode 20) for a longer service life thereof.
  • the width d of the slit 18 between the cathode electrode 16 and the anode electrode 20 is reduced to lower the electron emission voltage.
  • the intensity of the electric field at the electric field concentration point A is represented by E
  • the voltage applied between the cathode electrode 16 and the anode electrode 20 the voltage appearing between the cathode electrode 16 and the anode electrode 20 when the drive voltage Va outputted from the pulse generation source 22 is applied between the cathode electrode 16 and the anode electrode 20
  • Vak the intensity of the electric field at the electric field concentration point A
  • the width of the slit 18 by d
  • the width d of the slit 18 is reduced.
  • the conventional electron emitters for emitting electrons under an electric field require an electric field of about 5 ⁇ 10 9 V/m, and need a small slit width of 20 nm if the voltage Vak is less than 100 V.
  • the width d of the slit 18 is not required to be as small as 20 nm, but may be about 20 ⁇ m.
  • the width d of the slit 18 should preferably be selected in the range from 0.1 ⁇ m to 50 ⁇ m, or more preferably in the range from 0.1 ⁇ m to 10 ⁇ m. If the voltage Vak is about 10 V, then the width d of the slit 18 should preferably be selected in the range from 0.1 ⁇ m to 1 ⁇ m.
  • the width d of the slit 18 should be 0.1 ⁇ m or greater because it makes it easy to form the slit 18 and also keeps the cathode electrode 16 and the anode electrode 20 insulated from each other.
  • the width d of the slit 18 should be 50 ⁇ m or less, 10 ⁇ m or less, or 1 ⁇ m or less because it is effective to lower the electron emission voltage depending on the selected value of the voltage Vak. With the width d of the slit 18 selected in the above range, the drive circuit can be reduced in size and cost, and the cathode electrode 16 can be prevented from being damaged for a longer service life.
  • An electron emitter 10B according to a second specific example will be described below with reference to FIGS. 7 through 9.
  • the cathode electrode 16 and the anode electrode 20 are formed on one surface of the emitter section 14, with the slit 18 being defined as a gap.
  • the electron emitter 10B has an emitter section 14 formed on the substrate 12, the emitter section 14 having a width d in the range from 0.1 to 50 ⁇ m, a cathode electrode 16 formed on one side surface of the emitter section 14, and an anode electrode 20 formed on the other side surface of the emitter section 14.
  • the emitter section 14 is present in the slit 18 between the cathode electrode 16 and the anode electrode 20, and is sandwiched between the cathode electrode 16 and the anode electrode 20.
  • the electron emitter 10B is capable of emitting electrons stably under a constant voltage even if the cathode electrode 16 is damaged because the distance between the cathode electrode 16 and the anode electrode 20, i.e., the width d of the slit 18, remains unchanged. As a result, the applied voltage Va may be lowered, and the cathode electrode 16 may have a longer service life.
  • the emitter section 14 made of dielectric material is sandwiched between the cathode electrode 16 and the anode electrode 20, as shown in FIG. 9, the emitter section 14 can be polarized completely, emitting electrons stably and efficiently due to the reversed polarization.
  • An electron emitter 10B according to a second specific example, which is constructed as a display pixel, will be described below with reference to FIGS. 10 and 11.
  • a plurality of electron emitters 10B are arranged in a matrix on a substrate 12, and a display panel 190 is disposed in confronting relation to the electron emitters 10B.
  • a spacer 192 is disposed adjacent to the electron emitters 10B.
  • a collector electrode 24 is formed on the reverse side of the display panel 190 (the surface facing the electron emitters 10B), and the fluorescent layer 28 is formed on the collector electrode 24.
  • the electron emitters 10B can now function as display pixels when electrons are emitted from the electron emitters 10B.
  • some of the electrons emitted from the electron emitters 10B may impinge upon the spacer 192, tending to negatively charge the spacer 192.
  • the electric field distribution between the electron emitters 10B and the collector electrode 24, i.e., the electric field distribution for directing the electrons emitted from the electron emitters 10B toward the collector electrode 24, is changed to fail to accurately excite the fluorescent layer 28 with the electron beam, resulting in a displayed image quality failure.
  • the distribution of emitted electrons may be progressively wider toward the collector electrode 24. Such an electron distribution may possibly be disadvantageous in reducing the pitch of pixels (increasing the image resolution).
  • the distribution of emitted electrons may be prevented from being spread by positioning at least one control electrode between the electron emitters 10B and the collector electrode 24.
  • the overall assembly would be complex in structure and would be highly costly to manufacture.
  • the collector electrode 24 As shown in FIG. 11, it is preferable to form the collector electrode 24 on the upper surface of the substrate 12, and to form the fluorescent layer 28 on the upper surface of the collector electrode 24.
  • the spacer 192 is negatively charged, the electric field distribution for directing the electrons emitted from the electron emitters 10B toward the collector electrode 24 is essentially not changed. Therefore, the fluorescent layer 28 can accurately be excited with the electron beam, preventing a displayed image quality failure.
  • some of the electrons emitted from the electron emitters 10B may not be directed toward the collector electrode 24, but toward the display panel 190. Therefore, it is preferable to position a control electrode 194 on the reverse side of the display panel 190, and to apply a negative voltage Ve to the control electrode 194.
  • the applied negative voltage Ve is effective to direct the electrons emitted from the electron emitters 10B efficiently toward the collector electrode 24 over the substrate 12 for thereby increasing the contribution of the emitted electrons to the excitation of the fluorescent layer.
  • An electron emitter 10Ba according to a first modification is based on the concept of the electron emitter 10B according to the second specific example. As shown in FIGS. 12 and 13, the electron emitter 10Ba has an emitter section 14 which has a tortuous shape as viewed in plan.
  • the width d of the slit 18 between the cathode electrode 16 and the anode electrode 20 should preferably be in the range from 0.1 to 50 ⁇ m.
  • the electron emitter 10B is capable of emitting electrons efficiently because the area of contact between the cathode electrode 16 and the emitter section 14 and the area of contact between the emitter section 14 and the anode electrode 20 are increased.
  • an electron emitter 10Bb has an emitter section 14 of dielectric material formed on the substrate 12, and a cathode electrode 16 and an anode electrode 20 which are embedded in windows defined in the emitter section 14.
  • the cross-sectional areas of the cathode electrode 16 and the anode electrode 20 are thus increased to reduce the resistance of the cathode electrode 16 and the anode electrode 20 for suppressing the generation of the Joule heat. That is, the cathode electrode 16 and the anode electrode 20 can be protected.
  • the width of portion of the emitter section 14 between the cathode electrode 16 and the anode electrode 20, i.e., the width d of the slit 18, should preferably be in the range from 0.1 to 50 ⁇ m.
  • the thickness of the cathode electrode 16 and the anode electrode 20 is essentially the same as the thickness of the emitter section 14.
  • the thickness of the cathode electrode 16 and the anode electrode 20 may be smaller than the thickness of the emitter section 14 as with an electron emitter 10Bc according to a third modification shown in FIGS. 15 and 16.
  • the cathode electrode 16 and the anode electrode 20 are formed in contact with side walls of a portion of the emitter section 14 which is present at least in the slit 18.
  • the cathode electrode 16 and the anode electrode 20 may be made of a reduced amount of metal, the cathode electrode 16 and the anode electrode 20 may be made of an expensive metal (e.g., platinum or gold) for improved characteristics.
  • an expensive metal e.g., platinum or gold
  • the sample 10Bd has the same structure as the electron emitter 10Bc (see FIG. 15) according to the third modification.
  • the sample 10Bb is dimensioned as follows:
  • the substrate 12 has a thickness ta of 140 ⁇ m.
  • the emitter section 14 has a thickness tb of 40 ⁇ m.
  • the cathode electrode 16 has a width W1 of 40 ⁇ m.
  • the anode electrode 20 has a width W2 of 40 ⁇ m.
  • the slit 18 has a width d of 30 ⁇ m.
  • the end of the cathode electrode 16 (which is opposite to the end thereof in the slit 18) is spaced from a near side end of the emitter section 14 by a distance D1 of 40 ⁇ m.
  • the end of the anode electrode 20 (which is opposite to the end thereof in the slit 18) is spaced from a near side end of the emitter section 14 by a distance D2 of 40 ⁇ m.
  • Both the cathode electrode 16 and the anode electrode 20 are made of gold (Au), and the emitter section 14 is made of PZT (lead zirconate titanate) .
  • the drive voltage Va has a first voltage Va1 of 50 V in the preparatory period T1.
  • the drive voltage Va changes from the preparatory period T1 to the electron emission period T2 at a time t0.
  • the drive voltage Va has a second voltage Va2 of - 120 V in the electron emission period T2.
  • the drive voltage Va changes to the preparatory period T1 at a time t1.
  • FIG. 18B shows the measured waveform of the current Ia flowing from the anode electrode 20 to GND.
  • the current Ia has a peak Pa at a time t2 which is about 1 ⁇ sec. later than the time t0 of the negative-going edge of the drive voltage Va.
  • the peak Pa has a value of about - 80 mA.
  • FIG. 18C shows the measured waveform of the current Ik flowing from the pulse generation source 22 into the cathode electrode 16.
  • the current Ik has a peak Pk at the time t2 which is about 1 ⁇ sec. later than the time t0 as with the current Ia.
  • the peak Pk has a value of about- 110 mA.
  • FIG. 18D shows the measured waveform of the current Ic flowing from the collector electrode 24 to GND.
  • the current Ic has a peak Pc at the time t2 which is about 1 ⁇ sec. later than the time t0 as with the currents Ia, Ik.
  • the peak Pc has a value of about - 30 mA.
  • FIG. 18E shows the measured waveform of the voltage Vak between the cathode electrode 16 and the anode electrode 20.
  • the voltage Vak has a peak Vap at a time t3 which is about 2 ⁇ sec. later than the time t0 of the negative-going edge of the drive voltage Va.
  • the peak Vap has a value of about - 120 V.
  • the amplitude Vin of the drive voltage Va has a value of about 170 V at the maximum for the purpose of reliably emitting electrons.
  • electrons are emitted at the time t2 which is about 1 ⁇ sec. prior to the time t3 when the peak Vap of the applied voltage Va occurs, and the voltage Vak has a value Vs of about - 77 V at the time t2.
  • the electron emission efficiency (Ic/Ik) at this time is 27 %.
  • the level of the amplitude Vin of the applied voltage Va which is actually required to emit electrons is not as high as 170V.
  • electrons are emitted at the time when the voltage Vak between the cathode electrode 16 and the anode electrode 20 is about -77V.
  • the applied voltage Va can be lowered to emit electrons.
  • the drive voltage Va may be lowered by optimizing the electron emitter 10 itself and also optimizing drive circuits therefor.
  • the following description is aimed at optimization of drive circuits based on the present experimental example.
  • the voltage Vak between the cathode electrode 16 and the anode electrode 20 is of a gradual nature as a whole, as shown in FIG. 19B, due to the CR time constant based on the electrostatic capacitance C and other resistive component between the cathode electrode 16 and the anode electrode 20.
  • the voltage waveform immediately after the positive-going edge or negative-going edge of the drive voltage Va is relatively steep.
  • the voltage level that rises or falls steeply is low, and the subsequent voltage waveform until the voltage level reaches 95 %, for example, of a prescribed voltage (the amplitude Vin of the drive voltage Va) is gradual.
  • the electron emitter 10 is regarded as a type of capacitor, then since the voltage Vak between the cathode electrode 16 and the anode electrode 20 is increased, electrons are emitted by a high-speed charging with a large current. However, a subsequent application of a high voltage causes an excessive current to flow, tending to damage the cathode electrode 16 owing to the Joule heat generated thereby and positive ions impinging upon the cathode electrode 16.
  • drive circuits according to various specific examples shown below are employed to reduce the size and cost of the electron emitter, lower the electron emission voltage, and minimize damage to the cathode electrode 16 (and the anode electrode 20) for a longer service life thereof.
  • the electron emitter 10 (including various specific examples and modifications thereof) is applicable to drive circuits according to various specific examples described below.
  • the electron emitter 10 is represented by a parallel circuit of a capacitor C and a resistor R in FIG. 20 and the subsequent figures.
  • a drive circuit 100A has a resistor 106 (resistance R1) connected between the cathode electrode 16 and the pulse generation source 22, and a resistor 108 (resistance R2) connected between the anode electrode 20 and a common potential generation source (GND in this example).
  • resistor 106 and the resistor 108 are serially connected to the electron emitter 10.
  • the electron emission period T2 of the drive voltage Va is in a range 0 ⁇ T2 ⁇ 3 ⁇ where ⁇ represents a time constant determined by the electrostatic capacitance C provided by the cathode electrode 16 and the anode electrode 20 and the resistors 106, 108.
  • the resistors 106, 108 are effective to suppress an excessive current flowing in the electron emitter 10. Since the electron emission period T2 is the period of a sharp voltage change which contributes to electron emission, a wasteful current supply is eliminated, resulting in a reduction of electric power consumption, and an emission of excessive electrons is suppressed, reducing damage to the cathode electrode 16, etc.
  • both the resistors 106, 108 are connected. However, only the resistor 106 or only the resistor 108 may be connected.
  • a drive circuit 100B according to a second specific example has essentially the same structure as the drive circuit 100A according to the first specific example, but differs therefrom in that the resistor 106 is replaced with a circuit 110 having nonlinear resistance characteristics, as shown in FIG. 22.
  • the circuit 110 has an n-channel MOSFET (hereinafter referred to as n-MOSFET 114) including a drain-to-source protection diode 112 and a p-channel MOSFET (hereinafter referred to as p-MOSFET 118) including a drain-to-source protection diode 116, the n-MOSFET 114 and the p-MOSFET 118 being connected in series to each other.
  • the drain of the n-MOSFET 114 and the source of the p-MOSFET 118 are connected to each other at a junction 119.
  • the n-MOSFET 114 has its gate connected to the junction 119, and the p-MOSFET 118 has its gate connected to the drain thereof.
  • the voltage Vak between the cathode electrode 16 and the anode electrode 20 changes quickly from the first voltage Va1 to the second voltage Va2, as shown in FIG. 23B, thus providing a sharp voltage change.
  • the current from the pulse generation source 22 flows quickly due to the nonlinear resistance characteristics of the diode 112 and the p-MOSFET 118 at the end of the electron emission period T2, the voltage Vak between the cathode electrode 16 and the anode electrode 20 changes quickly from the second voltage Va2 to the first voltage Va1, as shown in FIG. 23B.
  • the circuit 110 is effective to quickly change the voltage Vak between the cathode electrode 16 and the anode electrode 20, and also to suppress an excessive current.
  • the electron emission period T2 can be set to a shorter period than a case in which the resistor 106 is used, and hence the preparatory period T1 (see FIG. 3) can also be set to a shorter period.
  • the frequency of a horizontal synchronizing signal can be increased, or a high resolution can be achieved.
  • a drive circuit 100Ba according to a first modification has essentially the same structure as the drive circuit 100B according to the second specific example, but differs therefrom in that, as shown in FIG. 24, the circuit 110 has two n-MOSFETs (first and second n-MOSFETs 124, 126) including respective drain-to-source protection diodes 120, 122 and connected in series to each other, with respective drains connected in common.
  • the first and second n-MOSFETs 124, 126 have respective gates connected to the respective common drains.
  • the source of the second n-MOSFET 126 when the source of the second n-MOSFET 126 goes low at the start of the electron emission period T2, a current flows from the electron emitter 10 through the diode 120 of the first n-MOSFET 124 and the drain and source of the second n-MOSFET 126.
  • the source of the second n-MOSFET 126 goes high at the end of the electron emission period T2, a current flows from the pulse generation source 22 through the diode 122 of the second n-MOSFET 126 and the drain and source of the first n-MOSFET 124.
  • the circuit 110 shown in FIG. 21 is effective to quickly change the voltage Vak between the cathode electrode 16 and the anode electrode 20, and also to suppress an excessive current.
  • a drive circuit 100Bb according to a second modification has essentially the same structure as the drive circuit 100B according to the second specific example, but differs therefrom in that, as shown in FIG. 25, the circuit 110 has two zener diodes (first and second zener diodes 130, 132) connected in series to each other, with respective anodes connected in common.
  • the first zener diode 130 has a cathode connected to the electron emitter 10
  • the second zener diode 132 has a cathode connected to the pulse generator source 22.
  • the first and second zener diodes 130, 132 have respective zener voltages set to 50 V, for example.
  • the first zener diode 130 is rendered conductive, allowing a current to flow from the electron emitter 10 through the first and second zener diodes 130, 132.
  • the current flows quickly due to the nonlinear resistance characteristics of the second zener diode 1 32, so that the voltage Vak between the cathode electrode 16 and the anode electrode 20 changes sharply.
  • the second zener diode 132 When the cathode of the second zener diode 132 goes high at the end of the electron emission period T2, the second zener diode 132 is rendered conductive, allowing a current to flow from the pulse generation source 22 through the first and second zener diodes 130, 132.
  • a drive circuit 100C according to a third specific example will be described below with reference to FIG. 26.
  • the drive circuit 100C according to the third specific example has essentially the same structure as the drive circuit 100A according to the first specific example, but differs therefrom in that it has a switching element 140 connected in series to the electron emitter 10.
  • the resistor 106 may be replaced with the circuit 110 shown in FIG. 22, 24, or 25.
  • ⁇ represents a time constant determined by the electrostatic capacitance C provided by the cathode electrode 16 and the anode electrode 20 and the resistors 106, 108, T2 the electron emission period, and t the on-time of the switching element 140
  • the time constant ⁇ , the electron emission period T2, and the on-time t satisfy the relationship: 0 ⁇ t ⁇ 3 ⁇ ⁇ T2.
  • the on-time t and the electron emission period T2 can be made shorter.
  • a drive circuit 100D according to a fourth specific example has essentially the same structure as the drive circuit 100C according to the third specific example, but differs therefrom in that, as shown in FIGS. 28A and 28B, if an on-time of the switching element 140 for emitting electrons is represented by t1, and a subsequent off-time of the switching element 140 for keeping electrons emitted and suppressing a current flowing into the cathode electrode is represented by t2, then these times are set in the range: 0 ⁇ t1 ⁇ 3 ⁇ ⁇ t2 ⁇ T2. In the preparatory period T1, the switching element 140 is in an arbitrary state (on or off).
  • a drive circuit 100E has a single parallel circuit 150 connected in series to the electron emitter 10.
  • the parallel circuit 150 comprises a resistor 152 and a capacitor 154 which are connected parallel to each other.
  • an effective electron emission period T2a in which electrons are actually emitted is a period from the start of the electron emission period T2 to the time when the voltage Vak between the cathode electrode 16 and the anode electrode 20 reaches a divided level on the capacitor 154 of the amplitude Vin of the drive voltage Va.
  • the applied voltage Va changes quickly and then gradually toward the high level Vb, and finally reaches the high level Vb when the electron emission period T2 elapses.
  • the capacitor 154 of the parallel circuit 150 is connected in series to the electrostatic capacitance C formed by the cathode electrode 16 and the anode electrode 20 of the electron emitter 10, the overall capacitance becomes smaller than the electrostatic capacitance C formed by the cathode electrode 16 and the anode electrode 20, and the CR time constant becomes smaller accordingly.
  • a voltage change going quickly up to a voltage level (Vin ⁇ ⁇ C1/(C + C1) ⁇ which is required for emitting electrons as the voltage Vak between the cathode electrode 16 and the anode electrode 20, so that the electron emission voltage can be lowered.
  • the drive circuit 100E since the applied voltage Va reaches the level Vin ⁇ ⁇ R/(R + R3) ⁇ after elapse of the effective electron emission period T2a, it is preferable to bring the level Vin ⁇ ⁇ R/(R + R3) ⁇ closely to 0 if the dynamic range of the applied voltage Va is to be increased.
  • the resistance R3 of the resistor 152 of the parallel circuit 150 may be set to infinity, but doing so tends to reduce the freedom with which to select the resistor 152.
  • a drive circuit 100Ea according to a modification shown in FIG. 31 has a resistor 156 of a low resistance R4 connected parallel to the resistance (resistance R) of the electron emitter 10. Since the resistor 156 thus connected lowers the combined resistance of the electron emitter 10, the freedom with which to select the resistor 152 of the parallel circuit 150 can be increased.
  • a drive circuit 100F according to a sixth specific example is of substantially the same structure as the drive circuit 100A according to the first specific example, but differs therefrom in that, as shown in FIG. 32, an inductor 196 is connected in series between the pulse generation source 22 and the resistor 106.
  • the inductor 196 thus connected is effective to reduce the time required until the voltage Vak between the cathode electrode 16 and the anode electrode 20 becomes a predetermined voltage (coercive voltage if the emitter section 14 is made of a piezoelectric material) from the time when the second voltage Va2 of the drive voltage Va starts to be applied. Furthermore, a quick rise or fall time can be achieved without lowering the resistances of the resistors 106, 108.
  • the inductor 196 may be formed by partially making tortuous the pattern shape of a lead connected to the cathode electrode 16.
  • a drive circuit 100G according to a seventh specific example has essentially the same structure as the drive circuit 100A according to the first specific example, but differs therefrom in that, as shown in FIG. 33, a pulse generation circuit 160 is connected to the drive circuit 100G.
  • the pulse generation circuit 160 apply a voltage Vb for changing the polarity of the anode electrode 20 into the polarity which is different from the polarity of the potential of the cathode electrode 16 at least in the electron emission period T2.
  • the pulse generation source 22 outputs a voltage Va1 of 30 V, and the pulse generation circuit 160 outputs a voltage Va2 of - 100V.
  • the pulse generation source 22 outputs a voltage Vb2 of - 100 V, and the pulse generation circuit 160 outputs a voltage Vb1 of 30 V.
  • the dynamic range of the voltage Va applied between the cathode electrode 16 and the anode electrode 20 is determined by the withstand voltage of the pulse generation source 22.
  • the pulse generation circuit 160 is effective to increase the dynamic range of the voltage Va applied between the cathode electrode 16 and the anode electrode 20 to a withstand voltage which is the sum of the withstand voltage of the pulse generation source 22 and the withstand voltage of the pulse generation circuit 160.
  • the amplitude Vin of the drive voltage Va in the electron emission period T2 is 260 V.
  • the drive circuit 100G can be made smaller in size and lower in cost.
  • a drive circuit 100H according to an eighth specific example will be described below with reference to FIG. 35.
  • the drive circuit 100H according to the eighth specific example has essentially the same structure as the drive circuit 100G according to the seventh specific example, but differs therefrom in that it has two pulse generation sources (first and second pulse generation sources 22a, 22b) for applying a drive voltage to the cathode electrode 16 and GND, a first switching circuit 170 for switching the pulse generation sources 22a, 22b based on a switching control signal Sc, two pulse generation circuits (first and second pulse generation circuits 160a, 160b) for applying a drive voltage to the anode electrode 20 and GND, and a second switching circuit 172 for switching the pulse generation circuits 160a, 160b based on the switching control signal Sc.
  • the first pulse generation source 22a outputs a drive voltage VA1 having such a voltage waveform that, as shown in FIG. 36A, a first voltage Va1 (e.g., 30 V) is applied to the cathode electrode 16 and GND in the preparatory period T1, and a second voltage Va2 (e.g., - 100 V) is applied to the cathode electrode 16 and GND in the electron emission period T2.
  • a first voltage Va1 e.g., 30 V
  • Va2 e.g., - 100 V
  • the second pulse generation source 22b outputs a drive voltage VA2 having such a voltage waveform that, as shown in FIG. 36B, a second voltage Va2 (e.g., - 100 V) is applied to the cathode electrode 16 and GND in the preparatory period T1, and a first voltage Va1 (e.g., 30 V) is applied to the cathode electrode 16 and GND in the electron emission period T2.
  • a second voltage Va2 e.g., - 100 V
  • a first voltage Va1 e.g., 30 V
  • the first pulse generation circuit 160a outputs a drive voltage VB1 having such a voltage waveform that, as shown in FIG. 36C, a second voltage Va2 (e.g., - 100 V) is applied to the anode electrode 20 and GND in the preparatory period T1, and a first voltage Va1 (e.g., 30 V) is applied to the anode electrode 20 and GND in the electron emission period T2.
  • a second voltage Va2 e.g., - 100 V
  • a first voltage Va1 e.g., 30 V
  • the second pulse generation circuit 160b outputs a drive voltage VB2 having such a voltage waveform that, as shown in FIG. 36D, a first voltage Va1 (e.g., 30 V) is applied to the anode electrode 20 and GND in the preparatory period T1, and a second voltage Va2 (e.g.,- 100 V) is applied to the anode electrode 20 and GND in the electron emission period T2.
  • a first voltage Va1 e.g., 30 V
  • a second voltage Va2 e.g.,- 100 V
  • the first and second switching circuits 170, 172 are ganged switching circuits for performing their switching operation based on one switching control signal Sc.
  • the switching control signal Sc may comprise a command signal from a computer or a timer, for example.
  • the switching circuits 170, 172 are operated by voltage levels (a high level and a low level) of the switching control signal Sc.
  • the first and second switching circuits 170, 172 select the first pulse generation source 22a and the first pulse generation circuits 160, respectively, with the switching control signal Sc (e.g., a high voltage level), the first voltage Va1 is applied between the cathode electrode 16 and the GND in the preparatory period T1, polarizing the emitter section 14, and the second voltage Va2 is applied to the cathode electrode 16 and the GND in the electron emission period T2, reversing the polarization of the emitter section 14 thereby to enable the cathode electrode 16 to emit secondary electrons.
  • the switching control signal Sc e.g., a high voltage level
  • the step is carried out once or a plurality of times while the switching control signal Sc is a high level, thus performing one cycle (first cycle) of operation.
  • the first and second switching circuits 170, 172 select the second pulse generation source 22b and the second pulse generation circuits 160b, respectively, with the switching control signal Sc (e.g., a low voltage level)
  • the switching control signal Sc e.g., a low voltage level
  • the first voltage Va1 is applied between the anode electrode 20 and the GND in the preparatory period T1
  • polarizing the emitter section 14
  • the second voltage Va2 is applied to the anode electrode 20 in the electron emission period T2 reversing the polarization of the emitter section 14 thereby to enable the anode electrode 20 to emit secondary electrons.
  • the step is carried out once or a plurality of times while the switching control signal Sc is a low level, thus performing one cycle (second cycle) of operation.
  • the first and second switching circuits 170, 172 can switch between the first cycle and the second cycle in every step or every several steps as desired.
  • the electron emitter 10 were energized in the first cycle only and plasma is generated, then positive ions generated by the plasma would impinge upon the cathode electrode 16, damaging the cathode electrode 16 only. Therefore, the durability of the electron emitter 10 would hinge only upon damage to the cathode electrode 16. If the electron emitter 10 were energized in the second cycle only, then the durability of the electron emitter 10 would hinge only upon damage to the anode electrode 20.
  • the first cycle and the second cycle are switched or selected as desired to distribute damage, which would otherwise be caused to one of the electrodes, to both the electrodes, with the result that the electrodes will have a longer service life.
  • the drive circuits 100A through 100H according to the first through eighth specific examples are arranged mainly for the purpose of suppressing excessive currents. If the electron emitter 10 is used as a pixel of a display, therefore, there may be a limitation posed on efforts to increase the luminance of the pixel.
  • the collector electrode 24 associated with the electron emitter 10 whose luminance may possibly be limited is moved toward the slit 18 of the electron emitter 10, or the voltage V3 of the bias voltage source 102, which is applied to the collector electrode 24, is increased.
  • the electron emitter, the circuit for driving the electron emitter, and the method of driving the electron emitter according to the present invention are not limited to the above embodiments, but may be embodied in various arrangements without departing from the scope of the present invention.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Cold Cathode And The Manufacture (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
EP03253962A 2002-06-24 2003-06-24 Emetteur electronique, circuit de commande pour un emetteur electronique et procede pour commander un emetteur electronique Withdrawn EP1376641A3 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP2002183481 2002-06-24
JP2002183481 2002-06-24
JP2002289127 2002-10-01
JP2002289127 2002-10-01
JP2003154412 2003-05-30
JP2003154412A JP3829127B2 (ja) 2002-06-24 2003-05-30 電子放出素子

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Cited By (1)

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CN102428650A (zh) * 2009-04-23 2012-04-25 三菱电机研发中心欧洲有限公司 用于控制缓冲电路的操作的方法和设备

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JP4504655B2 (ja) * 2003-10-15 2010-07-14 日本放送協会 電子放射装置、駆動装置およびディスプレイ
JP4746287B2 (ja) * 2004-07-06 2011-08-10 日本放送協会 電界放出型表示装置の駆動装置及びその駆動方法
JP6061288B2 (ja) * 2012-08-01 2017-01-18 国立大学法人金沢大学 プラズマ生成装置用の電源及びプラズマ生成装置
WO2021157337A1 (fr) * 2020-02-06 2021-08-12 シャープ株式会社 Dispositif d'analyse

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JP2622842B2 (ja) * 1987-10-12 1997-06-25 キヤノン株式会社 電子線画像表示装置および電子線画像表示装置の偏向方法
JP2608295B2 (ja) * 1987-10-21 1997-05-07 キヤノン株式会社 電子放出素子
US5453661A (en) * 1994-04-15 1995-09-26 Mcnc Thin film ferroelectric flat panel display devices, and methods for operating and fabricating same
JPH11185600A (ja) * 1997-12-22 1999-07-09 Minolta Co Ltd 電子放出デバイス及び画像表示装置
FR2789223B1 (fr) * 1999-01-29 2001-03-23 Univ Nantes Corps de cathode ferroelectrique pour la production d'electrons
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CN102428650A (zh) * 2009-04-23 2012-04-25 三菱电机研发中心欧洲有限公司 用于控制缓冲电路的操作的方法和设备

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