EP0964423B1 - Gitterelektroden fur eine Anzeigevorrichtung - Google Patents

Gitterelektroden fur eine Anzeigevorrichtung Download PDF

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Publication number
EP0964423B1
EP0964423B1 EP19980304629 EP98304629A EP0964423B1 EP 0964423 B1 EP0964423 B1 EP 0964423B1 EP 19980304629 EP19980304629 EP 19980304629 EP 98304629 A EP98304629 A EP 98304629A EP 0964423 B1 EP0964423 B1 EP 0964423B1
Authority
EP
European Patent Office
Prior art keywords
grid
conductors
row
column
magnet
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
Application number
EP19980304629
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English (en)
French (fr)
Other versions
EP0964423A1 (de
Inventor
John Stuart Beeteson
Andrew Ramsay Knox
Christopher Carlo Pietrzak
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Lenovo Singapore Pte Ltd
Original Assignee
International Business Machines Corp
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 International Business Machines Corp filed Critical International Business Machines Corp
Priority to EP19980304629 priority Critical patent/EP0964423B1/de
Priority to DE1998620599 priority patent/DE69820599T2/de
Publication of EP0964423A1 publication Critical patent/EP0964423A1/de
Application granted granted Critical
Publication of EP0964423B1 publication Critical patent/EP0964423B1/de
Anticipated expiration legal-status Critical
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    • 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
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/467—Control electrodes for flat display tubes, e.g. of the type covered by group H01J31/123
    • 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
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/58—Arrangements for focusing or reflecting ray or beam
    • H01J29/64—Magnetic lenses
    • H01J29/68—Magnetic lenses using permanent magnets only
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2329/00—Electron emission display panels, e.g. field emission display panels

Definitions

  • the present invention relates to a magnetic matrix display device and more particularly to grid electrodes for use in such a display. Yet more particularly, the present invention relates to the use of differing first grid (G1) and second grid (G2) apertures in such a display and to a combined sensor element and second grid electrode.
  • G1 first grid
  • G2 second grid
  • a magnetic matrix display of the present invention is particularly although not exclusively useful in flat panel display applications such as television receivers and visual display units for computers, especially although not exclusively portable computers, personal organisers, communications equipment, and the like.
  • GB Patent Application 2304981 discloses a magnetic matrix display having a cathode for emitting electrons, a permanent magnet with a two dimensional array of channels extending between opposite poles of the magnet, the direction of magnetisation being from the surface facing the cathode to the opposing surface.
  • the magnet generates, in each channel, a magnetic field for forming electrons from the cathode means into an electron beam.
  • the display also has a screen for receiving an electron beam from each channel.
  • the screen has a phosphor coating facing the side of the magnet remote from the cathode, the phosphor coating comprising a plurality of pixels each corresponding to a different channel.
  • each of the corresponding phosphor pixels may be a group of phosphor elements, each group corresponding to a different channel and each group typically comprising a Red, a Green and a Blue phosphor element.
  • the first and second deflection anodes are arranged as a pair of combs.
  • control grids disposed between the cathode and the magnet for controlling the flow of electrons from the cathode into each channel.
  • These control grids comprise a first group of parallel control grid conductors (first grid) extending across the magnet surface in a column direction and a second group of parallel control grid conductors (second grid) extending across the magnet surface in a row direction so that each of the channels is situated at the intersection of a different combination of a row grid conductor and a column grid conductor.
  • first grid parallel control grid conductors
  • second grid parallel control grid conductors
  • the grid drive voltages for certain applications such as a display using a very low beam current or using a high beam current may be outside the range desirable in order to minimise the cost of the grid drivers.
  • the second grid conductors which are driven by digital to analog converters (DACs), should ideally be capable of being driven at CMOS compatible voltages. Too high a voltage leads to expensive drivers, such as those which are used in Plasma panels. Too low a voltage leads to excessive difficulty in controlling beam current due to sensitivity to electrical noise, DAC linearity and the like.
  • a display device comprising: cathode means for emitting electrons; a permanent magnet; a two dimensional array of channels extending between opposite poles of the magnet; the magnet generating, in each channel, a magnetic field for forming electrons from the cathode means into an electron beam; a screen for receiving an electron beam from each channel, the screen having a phosphor coating comprising a plurality of groups of adjacent pixels facing the side of the magnet remote from the cathode, each corresponding to a different channel; grid electrode means disposed between the cathode means and the magnet for controlling flow of electrons from the cathode means into each channel, the grid electrode means comprising a plurality of parallel row conductors and a plurality of parallel column conductors arranged orthogonally to the row conductors, each channel being located at a different intersection of a row conductor and a column conductor, each intersection having a corresponding aperture in each of the row conductor and the column conductor, the apertures
  • the differing sizes of apertures allows the DACs driving the second grid or row conductors to be within a range of voltages which is compatible with the use of CMOS technology for the drivers and also to improve the control of the beam current and reduce sensitivity to electrical noise, DAC linearity and the like.
  • the apertures in the row conductors are smaller than the corresponding apertures in the column conductors. This increases the voltage sensitivity of the second grid (the row conductors) and allows the use of lower voltage drivers for a given beam current. Additionally, the edges of the first grid and second grid do not precisely coincide meaning that an insulating layer used between the first grid and the second grid may be extended.
  • the grid electrode means further comprises a first insulating layer disposed between the row conductors and the column conductors, the first insulating layer having apertures intermediate in size between those of the row conductors and those of the column conductors.
  • the positioning of such an insulating layer can be done with a low accuracy whilst still ensuring that the first and second grid tracks do not short together.
  • an example of a magnetic matrix display device 10 comprises a plane cathode 20 facing a plane anode 30.
  • a phosphor coating 150 is disposed on the side of the anode 30 remote from the cathode.
  • a permanent magnet 140 is disposed between the anode 30 and the cathode 20.
  • the magnet 140 is perforated by a two dimensional matrix of channels 160.
  • a grid assembly is disposed between the magnet 140 and the cathode 20.
  • the grid assembly comprises first and second electrically isolated arrays of parallel conductors hereinafter referred to as first grids 71 and second grids 72 respectively.
  • the first grids 71 are arranged orthogonally to the second grids 72 to form a lattice pattern.
  • Apertures are formed in the first grids 71 and the second grids 72.
  • the apertures are located at each intersection of a first grid 71 and a second grid 72.
  • Each aperture is aligned with a different channel 160.
  • the phosphor coating comprises a plurality of pixels each corresponding to a different channel.
  • each of the corresponding phosphor pixels may be a group of phosphor elements, each group corresponding to a different channel and each group typically comprising a Red, a Green and a Blue phosphor element.
  • Deflection anodes 302,304 are arranged as a pair of combs between the magnet 140 and the anode 30 to sequentially address electron beams emerging from the channels to different ones of the phosphor elements.
  • column drive circuitry 170 is connected to the first grids 71.
  • Row drive circuitry 180 is connected to the second grids 72.
  • This has the advantage that for a conventional display having a four to three aspect ratio, with more columns than rows, the number of more complex expensive analog drivers is reduced at the cost of having more simple, cheap digital switches.
  • the anode 30 is held at a higher potential than the cathode 20. Electrons emitted from the cathode 20 are thus accelerated towards the anode 30. As electrons enter each of the channels 160 in the magnet 140 they are collimated into a dense beam by the magnetic field therein. In operation, admittance of electrons to the channels is selectively controlled via the grid assembly.
  • Each channel 160 is addressable by appropriate voltage signals applied by the row drive circuitry 180 and the column drive circuitry 170 to the corresponding first grid 71 and second grid 72. Electrons are thus selectively admitted or blocked from entering each channel 160, passing through the magnet 140 and reaching the corresponding region of the phosphor coating 150 to generate a pixel of a displayed image on the screen. The pixels of the displayed image are scanned in a refresh pattern. To produce the refresh pattern, a column of pixels is energised by applying an appropriate voltage, via the row drive circuitry 180 to the corresponding second grid 72 with the voltage on the first grids 71 set via the column drive circuitry 170 so that no beam current flows.
  • the voltages on the remaining first grids 72 are set by the column drive circuitry 170 so that no beam current flows for any operating voltage on the second grids 71.
  • the voltages on the second grids 72 are then modulated by row drive circuitry 180 as a function of input video data corresponding to the energised column of pixels. The process is then repeated for the next successive column.
  • the row and column functions are transposed relative to that conventionally used in LCDs, that is the rows are driven by an analog voltage and the columns are switched between two analog levels, however such transposition is not an essential feature of a magnetic matrix display.
  • the design of a magnetic matrix display may require the grid electrode drive voltages to be kept within a certain range of voltages in order to minimise the cost of the grid electrode drivers.
  • a typical desired range is that of CMOS technology, in which the desired range of output voltages is between zero volts and approximately ten volts.
  • "Conventional" grid apertures are sometimes not sufficient to achieve the desired beam current with these drive voltages. Two specific examples where these "conventional" grid apertures are not sufficient are:
  • Figure 3 shows a conventional magnetic matrix display grid structure in which the apertures in the second grid 72 structure and the first grid 71 structures are equal in diameter.
  • Figure 4 shows a magnetic matrix display grid structure in which the apertures in the first grid are larger than the apertures in the second grid. This has the effect of "unmasking" the second grid and increasing the voltage sensitivity of the second grid, thus allowing lower second grid drive voltages to be used for a given beam current.
  • Figure 5 shows a magnetic matrix display grid structure in which the apertures in the second grid are larger than the apertures in the first grid. This has the effect of "masking" the second grid and decreasing the voltage sensitivity of the second grid, thus reducing the sensitivity of the second grid and improving the voltage quantisation and hence beam current quantisation.
  • Table 2 shows the beam currents obtained with the second grid set at voltages between 0 volts and 5 volts. One volt steps were used in the simulation, except for the case where the first grid aperture was 100 ⁇ m, where 0.5 volt steps were used from 0 volts to 1 volt. Above this voltage the beam current increased rapidly. Second grid (G2) voltage (from cutoff) vs.
  • Figure 6 shows the results of Table 2 in graphical form. It should be noted that the nature of the computer simulation is such that the true space charge behaviour in front of the physical cathode is not necessarily modelled. If this were modelled, then an increase in beam current for a given second grid (G2) voltage would be seen, that is the gamma would increase. Thus with increasing beam current, the quantised current drawn from the emitter does not increase (as would be the real case), but instead remains constant, that is, the cathode is operating in a thermally saturation limited mode. Increases in beam current are due to increases in the cathode electron collection area. However, despite this being the case, the effect of changing relative grid hole diameters is clearly demonstrated.
  • G2 second grid
  • a further advantage of using a second grid aperture smaller than a first grid aperture is that the edges of the first grid and second grid apertures do not precisely coincide.
  • the insulating layer used between the first grid and the second grid can be extended.
  • the aperture in the insulating layer could be, for example, 200 ⁇ m diameter, thus permitting low accuracy of placement of the insulating layer whilst still ensuring that the first grid and second grid tracks do not short together.

Claims (3)

  1. Anzeigevorrichtung, welche Folgendes umfasst: ein Katodenmittel (20) zum Emittieren von Elektronen; einen Dauermagneten (140); eine zweidimensionale Matrix von Kanälen (160), die sich zwischen entgegengesetzten Polen des Magneten erstrecken; wobei der Magnet in jedem Kanal ein Magnetfeld zum Bilden eines Elektronenstrahls aus den vom Katodenmittel kommenden Elektronen erzeugt; einen Bildschirm zum Empfangen eines Elektronenstrahls von jedem Kanal, wobei der Bildschirm eine Leuchtstoffschicht (150) aufweist, die eine Vielzahl von Gruppen benachbarter Pixel umfasst, welche der der Katode abgewandten Seite des Magneten gegenüber liegen und jeweils einem bestimmten Kanal entsprechen; ein zwischen dem Katodenmittel und dem Magneten zur Steuerung des Elektronenstroms vom Katodenmittel in jeden Kanal angebrachtes Gitterelektrodenmittel (71, 72), wobei das Gitterelektrodenmittel eine Vielzahl paralleler Zeilenleitungen (72) und eine Vielzahl senkrecht zu den Zeilenleitungen angeordneter paralleler Spaltenleitungen (71) umfasst, jeder Kanal an einem anderen Schnittpunkt zwischen einer Zeilenleitung und einer Spaltenleitung angeordnet ist und jeder Schnittpunkt in jeder Zeilenleitung und in jeder Spaltenleitung eine entsprechende Öffnung aufweist, dadurch gekennzeichnet, dass die Öffnungen in den Zeilenleitungen und den Spaltenleitungen unterschiedlich groß sind.
  2. Anzeigevorrichtung nach Anspruch 1, bei der die Öffnungen in den Zeilenleitungen (72) kleiner als die entsprechenden Öffnungen in den Spaltenleitungen (71) sind.
  3. Anzeigevorrichtung nach Anspruch 2, bei der das Gitterelektrodenmittel (71, 72) ferner eine zwischen den Zeilenleitungen (72) und den Spaltenleitungen (71) angeordnete Isolationsschicht umfasst, wobei die Isolationsschicht Öffnungen aufweist, deren Größe zwischen der Größe der Zeilenleitungen und der Größe der Spaltenleitungen liegt.
EP19980304629 1998-06-11 1998-06-11 Gitterelektroden fur eine Anzeigevorrichtung Expired - Lifetime EP0964423B1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP19980304629 EP0964423B1 (de) 1998-06-11 1998-06-11 Gitterelektroden fur eine Anzeigevorrichtung
DE1998620599 DE69820599T2 (de) 1998-06-11 1998-06-11 Gitterelektroden fur eine Anzeigevorrichtung

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19980304629 EP0964423B1 (de) 1998-06-11 1998-06-11 Gitterelektroden fur eine Anzeigevorrichtung

Publications (2)

Publication Number Publication Date
EP0964423A1 EP0964423A1 (de) 1999-12-15
EP0964423B1 true EP0964423B1 (de) 2003-12-17

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EP19980304629 Expired - Lifetime EP0964423B1 (de) 1998-06-11 1998-06-11 Gitterelektroden fur eine Anzeigevorrichtung

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DE (1) DE69820599T2 (de)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6710525B1 (en) 1999-10-19 2004-03-23 Candescent Technologies Corporation Electrode structure and method for forming electrode structure for a flat panel display

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2179784B (en) * 1985-08-30 1989-12-06 Philips Electronic Associated Cathode ray tubes
GB2193372A (en) * 1986-07-23 1988-02-03 Philips Electronic Associated Cathode ray tube
DE69430568T3 (de) * 1993-02-01 2007-04-26 Candescent Intellectual Property Services, Inc., San Jose Flacher bildschirm mit innerer tragstruktur
WO1997008730A1 (en) * 1995-08-25 1997-03-06 International Business Machines Corporation Display system
GB2304984B (en) * 1995-08-25 1999-08-25 Ibm Electron source
GB2304981A (en) * 1995-08-25 1997-03-26 Ibm Electron source eg for a display
GB2317987A (en) * 1996-10-04 1998-04-08 Ibm Display devices

Also Published As

Publication number Publication date
DE69820599D1 (de) 2004-01-29
DE69820599T2 (de) 2004-10-07
EP0964423A1 (de) 1999-12-15

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