WO1999034390A1 - Dispositif d'emission par champ electrique muni d'un separateur de haute capacite - Google Patents

Dispositif d'emission par champ electrique muni d'un separateur de haute capacite Download PDF

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Publication number
WO1999034390A1
WO1999034390A1 PCT/US1998/020069 US9820069W WO9934390A1 WO 1999034390 A1 WO1999034390 A1 WO 1999034390A1 US 9820069 W US9820069 W US 9820069W WO 9934390 A1 WO9934390 A1 WO 9934390A1
Authority
WO
WIPO (PCT)
Prior art keywords
capacitance
spacer
field emission
capacitance spacer
emission device
Prior art date
Application number
PCT/US1998/020069
Other languages
English (en)
Inventor
Robert Adler
Joyce K. Yamamoto
Peter A. Smith
Original Assignee
Motorola Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Motorola Inc. filed Critical Motorola Inc.
Publication of WO1999034390A1 publication Critical patent/WO1999034390A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/028—Mounting or supporting arrangements for flat panel cathode ray tubes, e.g. spacers particularly relating to electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/86—Vessels; Containers; Vacuum locks
    • H01J29/864—Spacers between faceplate and backplate of flat panel cathode ray tubes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
    • H01J31/12—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen
    • H01J31/123—Flat display tubes
    • H01J31/125—Flat display tubes provided with control means permitting the electron beam to reach selected parts of the screen, e.g. digital selection
    • H01J31/127—Flat display tubes provided with control means permitting the electron beam to reach selected parts of the screen, e.g. digital selection using large area or array sources, i.e. essentially a source for each pixel group
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2329/00—Electron emission display panels, e.g. field emission display panels
    • H01J2329/86—Vessels
    • H01J2329/8625—Spacing members
    • H01J2329/864—Spacing members characterised by the material

Definitions

  • the present invention pertains to the area of cathodoluminescent devices and, more particularly, to field emission displays. Background of the Invention
  • spacer structures between the cathode and anode of a field emission display.
  • the spacer structures maintain the separation between the cathode and the anode. They must also withstand the potential difference between the cathode and the anode.
  • spacers can adversely affect the flow of electrons toward the anode in the vicinity of the spacer.
  • Some of the electrons emitted from the cathode can cause electrostatic charging of the surface of the spacer, changing the voltage distribution near the spacer from the desired voltage distribution.
  • the change in voltage distribution near the spacer can result in distortion of the electron flow.
  • this distortion of the electron flow proximate to the spacers can result in distortions in the image produced by the display.
  • the distortions render the spacers "visible" by producing a dark region in the image at the location of each spacer .
  • Several prior art spacers attempt to solve the problems associated with spacer charging. For example, it is known in the art to provide a spacer having a surface which has a sheet resistance that is low enough to remove the impinging electrons by conduction, yet high enough to keep power loss due to electrical current from the anode to the cathode at a tolerable level.
  • the resistive surface can be realized by coating the spacer with a film having the desired resistance.
  • these films are susceptible to mechanical damage and/or alteration, such as may occur during the handling of the spacers . They are also susceptible to chemical alteration, which may change their resistivity.
  • FIGURE is a cross-sectional view of an embodiment of a field emission device in accordance with the invention.
  • the invention concerns a field emission device having high-capacitance spacers.
  • the invention takes advantage of the fact that matrix-based display devices, including field emission display devices, are generally addressed one line at a time.
  • a field emission display device contains a plurality of gate electrodes and a plurality of cathode conductors, which define an array of individually addressable pixels .
  • Each gate electrode defines one horizontal row
  • each cathode conductor defines one vertical column.
  • the operation of the field emission display device includes activating one row at a time (i.e., all gates in that row are driven positive) , while electrical signals appropriate to the desired light distribution in that particular row are applied to the cathode conductors.
  • each row is active during only 1/240 of the total time; the rest of the time it remains inactive.
  • the active period ranges from about 30 to about 100 microseconds, depending upon the number of rows and upon the frame rate.
  • the inactive period lasts between 13,000 and 20,000 microseconds.
  • the electrostatic charging process previously described produces adverse potential distributions on the spacer surface within the first few microseconds of the active period of each row. During the remainder of the active period, the electron flow remains distorted, and a dark region appears at the location of the spacer .
  • the large capacitance results in a controlled low rate of increase of the voltage on the surface of the high-capacitance spacer.
  • the controlled rate of increase of the voltage limits the cumulative change in voltage at the high-capacitance spacer during the emission time of the electron emitters proximate to the high- capacitance spacer.
  • the controlled voltage increase results in reduced distortion of the electron flow.
  • the field emission device is a field emission display having high-capacitance spacers, which are invisible to a viewer of the field emission display. By controlling the distortion of the electron flow, a field emission display in accordance with the invention maintains the desired activation of phosphors proximate to the spacers.
  • FIG. 1 is a cross-sectional view of a field emission display (FED) 100 in accordance with the invention.
  • FED 100 has a cathode assembly 102, which opposes an anode 104.
  • An evacuated region 106 exists between cathode assembly 102 and anode 104.
  • the pressure within evacuated region 106 is about 10 "6 Torr.
  • a high-capacitance spacer 108 extends between cathode assembly 102 and anode 104.
  • High-capacitance spacer 108 provides mechanical support to maintain the separation between cathode assembly 102 and anode 104.
  • High- capacitance spacer 108 has features that ameliorate distortion of the flow of an electron current 132 proximate to high- capacitance spacer 108.
  • high-capacitance spacer 108 further has features that render it invisible to a viewer of FED 100 during its operation.
  • Cathode assembly 102 includes a substrate 116, which can be made from glass, silicon, and the like. Upon substr?te 116 is disposed a cathode conductor 118, which can include a thin layer of molybdenum. A dielectric layer 120 is formed on cathode conductor 118. Dielectric layer 120 can be made from, for example, silicon dioxide. Dielectric layer 120 defines a plurality of emitter wells 122, in which are disposed one each of a plurality of electron emitters 124. In the embodiment of the FIGURE, electron emitters 124 include Spindt tips.
  • Electron emitters for use in a device in accordance with the invention include thermionic electron emitters, photocathode electron emitters, field emission electron emitters, and the like. These types of electron emitters are known to one skilled in the art. For example, another useful type of field emission electron emitter is an electron-emissive carbon film. It is desired to be understood that the invention can be embodied by a cathodoluminescent display device having electron emitters other than Spindt tip field emission electron emitters. In general , the cathodoluminescent display device is operated one line at a time so as to define a charging period for each spacer.
  • Cathode assembly 102 further includes a plurality of gate electrodes.
  • a first gate electrode 126 and a second gate electrode 128 are illustrated in the FIGURE.
  • the gate electrodes are used to selectively address the electron emitters .
  • Anode 104 includes a transparent substrate 110, upon which is disposed a transparent anode conductor 112, which can include a thin layer of indium tin oxide.
  • a plurality of phosphors 114 is disposed upon anode conductor 112. Phosphors 114 oppose electron emitters 124.
  • a first voltage source 136 is connected between anode conductor 112 and ground.
  • a second voltage source 138 is connected between second gate electrode 128 and ground.
  • a third voltage source 140 is connected between first gate electrode 126 and ground, and a fourth voltage source 142 is connected between cathode conductor 118 and ground.
  • High-capacitance spacer 108 extends between cathode assembly 102 and anode 104. One end of high-capacitance spacer 108 contacts anode 104, at a surface that is not covered by phosphors 114; the opposing end of high-capacitance spacer 108 contacts cathode assembly 102, at a portion that does not define emitter wells 122.
  • high-capacitance spacer 108 has a capacitance that is selected to reduce the distortion of the trajectory of electron current 132 proximate to high-capacitance spacer 108.
  • the capacitance is provided so that the distortion of the trajectory of electron current 132 is controlled to an extent sufficient to render high-capacitance spacer 108 invisible to a viewer of FED 100 during its operation.
  • the capacitance of high-capacitance spacer 108 is determined by several variables. These variables include the dielectric or permittivity constant of the material of high-capacitance spacer 108 and the geometry of high-capacitance spacer 108. Any combination of these variables can be manipulated to realize the desired capacitance .
  • a charge conductor 130 is provided between high-capacitance spacer 108 and cathode assembly 102.
  • Charge conductor 130 is provided to avoid the occurrence of large electric fields at the base of high- capacitance spacer 108, due to microscopic roughness of the surface of high-capacitance spacer 108 in that region.
  • Charge conductor 130 is made from a convenient conductive material, such as molybdenum, aluminum, and the like.
  • Charge conductor 130 can be connected to electrical ground or to one of first and second gate electrodes 126, 128.
  • FIG. 1 An embodiment of a field emission device in accordance with the invention will now be described with reference to the FIGURE. It is desired to be understood that a device embodying the invention is not limited to this configuration.
  • This exemplary configuration is useful for operation of FED 100 at a potential difference between cathode assembly 102 and anode 104, which is greater than about 300 volts, and preferably within a range of about 3000 - 5000 volts. It also includes a VGA configuration.
  • high-capacitance spacer 108 is a rectangular platelet, which has a length (into the page) of about 5 millimeters, a height (extending between cathode assembly 102 and anode 104) of about 1 millimeter, and a thickness, t, of about 0.07 millimeters.
  • the center-to- center distance between first and second gate electrodes 126, 128 is about 0.3 millimeters.
  • the aspect ratio (ratio of height to thickness) of high-capacitance spacer 108 is determined by variables such as the potential difference between cathode assembly 102 and anode 104 and by the separation distance between adjacent gate electrodes.
  • the height of high- capacitance spacer 108 is selected to be sufficient to prevent electrical arcing between cathode assembly 102 and anode 104.
  • the separation distance between adjacent gate electrodes is determined by the desired resolution of the display. While the geometry of high-capacitance spacer 108 is affected by the above factors, the dielectric or permittivity constant of high-capacitance spacer 108 can be manipulated to provide the desired capacitance.
  • the dielectric constant of high-capacitance spacer 108 is selected to control the potential rise at high- capacitance spacer 108, so that any resulting distortion of the trajectory of electron current 132 due to the electrical charging of high-capacitance spacer 108 is not visibly discernable to a viewer of FED 100.
  • high-capacitance spacer 108 has a dielectric constant, which is greater than 80, preferably greater than 500.
  • high-capacitance spacer 108 is made from a high permittivity material.
  • Exemplary high permittivity materials for use in the embodiment of the FIGURE include niobate materials, tantalate materials, titanate materials, titania
  • titanate materials include barium titanate, strontium titanate, strontium calcium titanate
  • rare earth barium titanates are samarium barium titanate (BaSm-Ti0 6 ) ; neodymium barium titanate; and rare earth barium titanates having the general formula BaRE 2 Ti 4 0 12 , wherein RE is a rare earth trivalent cation (eg. La, Sm) ; and the like.
  • the neodymium barium titanate material can be a mixture of three phases: a first phase of Nd 2 BaTi 5 0 (175 _ x) , wherein 0 ⁇ x ⁇ 3.5, a second phase of NdTi0 3 , and a third phase of Nd 2 Ti 2 0 7 .
  • Another useful material is a mixture of barium titanate and the titanate of one or more other Group IIA elements of the Periodic Table.
  • Exemplary niobate materials are bismuth-based niobates, such as zinc bismuth niobate (Bi 2 (ZnNb 2 ) 0 9 ) , nickel bismuth niobate (Bi 3 (Ni 2 Nb) 0 9 ) , and the like.
  • FED 100 potentials are applied to gate electrodes 126, 128, cathode conductor 118, and anode conductor 112 to cause selected electron emission at electron emitters 124 and to direct the electrons through evacuated region 106 toward phosphors 114. Phosphors 114 are caused to emit light by the impinging electrons.
  • the gate electrodes of FED 100 are sequentially addressed. As each gate electrode is addressed, a voltage is applied to each of the cathode conductors . Each gate electrode is addressed for a period of time referred to as the active period or "line time.” The entirety of gate electrodes within FED 100 is addressed during a frame. The time required to address once each of the gate electrodes within FED 100 is referred to as the "frame time.”
  • the charging period during which the surfaces of high- capacitance spacer 108 are becoming electrostatically charged
  • the quiescent period which is equal to the remainder of the frame time, not including the charging period
  • the capacitance of high-capacitance spacer 108 is provided to control the rate of change of the potentials at the surface of high-capacitance spacer 108.
  • the controlled rate of change of the surface potentials results in reduced distortion of the trajectory of electron current 132, so that the desired activation of phosphors 114 is maintained.
  • the controlled rate of change of the surface potentials also results in reduced incremental charge accumulation at high- capacitance spacer 108, which reduces the charge dissipation requirements.
  • the capacitance is selected so that the potential changes at the surfaces of high-capacitance spacer 108 during the charging period are low enough to prevent undesirable distortion of the flow of electron current 132 proximate to high-capacitance spacer 108.
  • the selected value of the dielectric constant depends upon the value of the electron current impinging upon high-capacitance spacer 108. In general, the dielectric constant increases with increasing impinging electron current.
  • the capacitance of high-capacitance spacer 108 from its center to either anode conductor 112 or charge conductor 130, each of which is connected to ground potential for the purpose of this measurement is about 14 picoFarad.
  • the maximum rate of potential rise at the surface of high-capacitance spacer 108 is about 0.36 V/ ⁇ s for operation of FED 100 at an anode-to-cathode potential difference of about 5 kilovolts.
  • the end-to-end resistance of high- capacitance spacer 108 can be selected to provide a slight electrical current, which is sufficient to dissipate during the quiescent time the accumulated charge.
  • the end-to-end resistance is also high enough to control power loss due to current between anode 104 and cathode assembly 102.
  • a useful end-to-end resistance for high-capacitance spacer 108 is of the order of 10 gigaohms .
  • the discharge current flows out of FED 100 through charge conductor 130.
  • High-capacitance spacer 108 can be rendered slightly conductive by, for example, adding a useful concentration of a dopant to the dielectric material of high- capacitance spacer 108.
  • the accumulated charge at high-capacitance spacer 108 can be neutralized by activating, at the termination of each frame time, some or all of electron emitters 124. In this manner, electrons are emitted into evacuated region 106 and are made available to neutralize the positive charge at high-capacitance spacer 108.
  • the potential at anode 104 is dropped to a value substantially below the potential at high-capacitance spacer 108, so that the electrons are attracted toward high- capacitance spacer 108 and not toward anode 104.
  • the number and configuration of electron emitters 124, which are caused to emit electrons during the neutralization step, are selected to effect the desired neutralization. In an exemplary neutralization step, only electron emitters 124 that are proximate to high-capacitance spacer 108 are activated.
  • the invention concerns a field emission device having high-capacitance spacers.
  • the field emission device of the invention ameliorates electron flow distortion due to the presence of spacers.
  • a field emission display includes high-capacitance spacers, which are invisible to a viewer of the field emission display.

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  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)

Abstract

La présente invention concerne un dispositif d'émission par champ électrique (100) comprenant un ensemble cathode (102), un ensemble anode (104), et un séparateur de haute capacité (108) qui s'étend entre l'ensemble cathode (102) et l'ensemble anode (104). Le séparateur de haute capacité (108) possède une capacité choisie de façon qu'elle réduit la distorsion du flux d'un courant électronique (132) causée par la charge du séparateur de haute capacité (108).
PCT/US1998/020069 1997-12-29 1998-09-25 Dispositif d'emission par champ electrique muni d'un separateur de haute capacite WO1999034390A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US99904597A 1997-12-29 1997-12-29
US08/999,045 1997-12-29
US7211698A 1998-05-04 1998-05-04
US09/072,116 1998-05-04

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WO1999034390A1 true WO1999034390A1 (fr) 1999-07-08

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001009919A1 (fr) * 1999-08-02 2001-02-08 Motorola Inc. Dispositif d'espacement dote d'une couche de passivation pour afficheur a emission de champ et procede de fabrication d'un tel afficheur
WO2001084587A2 (fr) * 2000-04-28 2001-11-08 Motorola, Inc. Ecran d'affichage a emission par effet de champ a dispositif d'ecartement invisible
WO2001084582A2 (fr) * 2000-04-28 2001-11-08 Motorola, Inc. Decharge partielle d'un ecran d'affichage a emission par effet de champ
WO2002005307A1 (fr) * 2000-07-12 2002-01-17 Motorola, Inc. Afficheur a emission de champ pourvu d'un emetteur d'electrons de decharge

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5614221A (en) * 1979-07-17 1981-02-12 Showa Denko Kk Spacer material for display panel
EP0580244A1 (fr) * 1992-07-23 1994-01-26 Koninklijke Philips Electronics N.V. Dispositif de reproduction d'images du type à panneau mince muni de canaux de propagation d'electrons
JPH06222369A (ja) * 1993-01-26 1994-08-12 Hayakawa Rubber Co Ltd 液晶表示パネル用スペーサー
WO1994018694A1 (fr) * 1993-02-01 1994-08-18 Silicon Video Corporation Dispositif a panneau plat pourvu d'une structure interne de support et/ou d'une matrice noire en relief
EP0725417A1 (fr) * 1995-01-31 1996-08-07 AT&T Corp. Structure de pilier multicouches pour dispositifs à émission de champ
WO1996030926A1 (fr) * 1995-03-31 1996-10-03 Candescent Technologies Corporation Structures d'espacement destinees a des panneaux d'affichage plats et procedes pour les former
US5619097A (en) * 1993-03-11 1997-04-08 Fed Corporation Panel display with dielectric spacer structure
WO1998003986A1 (fr) * 1996-07-18 1998-01-29 Candescent Technologies Corporation Structures d'espacement pour ecran plat et leurs procedes d'utilisation

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5614221A (en) * 1979-07-17 1981-02-12 Showa Denko Kk Spacer material for display panel
EP0580244A1 (fr) * 1992-07-23 1994-01-26 Koninklijke Philips Electronics N.V. Dispositif de reproduction d'images du type à panneau mince muni de canaux de propagation d'electrons
JPH06222369A (ja) * 1993-01-26 1994-08-12 Hayakawa Rubber Co Ltd 液晶表示パネル用スペーサー
WO1994018694A1 (fr) * 1993-02-01 1994-08-18 Silicon Video Corporation Dispositif a panneau plat pourvu d'une structure interne de support et/ou d'une matrice noire en relief
US5619097A (en) * 1993-03-11 1997-04-08 Fed Corporation Panel display with dielectric spacer structure
EP0725417A1 (fr) * 1995-01-31 1996-08-07 AT&T Corp. Structure de pilier multicouches pour dispositifs à émission de champ
WO1996030926A1 (fr) * 1995-03-31 1996-10-03 Candescent Technologies Corporation Structures d'espacement destinees a des panneaux d'affichage plats et procedes pour les former
WO1998003986A1 (fr) * 1996-07-18 1998-01-29 Candescent Technologies Corporation Structures d'espacement pour ecran plat et leurs procedes d'utilisation

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 005, no. 060 (P - 058) 23 April 1981 (1981-04-23) *
PATENT ABSTRACTS OF JAPAN vol. 018, no. 596 (P - 1825) 14 November 1994 (1994-11-14) *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001009919A1 (fr) * 1999-08-02 2001-02-08 Motorola Inc. Dispositif d'espacement dote d'une couche de passivation pour afficheur a emission de champ et procede de fabrication d'un tel afficheur
US6366009B1 (en) 1999-08-02 2002-04-02 Motorola, Inc. Method for fabricating a field emission display having a spacer with a passivation layer
WO2001084587A2 (fr) * 2000-04-28 2001-11-08 Motorola, Inc. Ecran d'affichage a emission par effet de champ a dispositif d'ecartement invisible
WO2001084582A2 (fr) * 2000-04-28 2001-11-08 Motorola, Inc. Decharge partielle d'un ecran d'affichage a emission par effet de champ
WO2001084582A3 (fr) * 2000-04-28 2002-02-14 Motorola Inc Decharge partielle d'un ecran d'affichage a emission par effet de champ
WO2001084587A3 (fr) * 2000-04-28 2002-02-14 Motorola Inc Ecran d'affichage a emission par effet de champ a dispositif d'ecartement invisible
US6441559B1 (en) 2000-04-28 2002-08-27 Motorola, Inc. Field emission display having an invisible spacer and method
KR100812111B1 (ko) * 2000-04-28 2008-03-12 모토로라 인코포레이티드 전계 방출 디스플레이, 스페이서를 전계 방출 디스플레이의 뷰어에게 보이지 않게 하는 방법 및 전계 방출 디스플레이에서 스페이서상의 전압 변화를 제어하는 방법
KR100840881B1 (ko) * 2000-04-28 2008-06-24 모토로라 인코포레이티드 전계 방출 디스플레이의 부분 방전
WO2002005307A1 (fr) * 2000-07-12 2002-01-17 Motorola, Inc. Afficheur a emission de champ pourvu d'un emetteur d'electrons de decharge

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