EP0649162A1 - Flaches Kaltkathodeanzeigegerät mit geschalteter Anode - Google Patents

Flaches Kaltkathodeanzeigegerät mit geschalteter Anode Download PDF

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Publication number
EP0649162A1
EP0649162A1 EP94410089A EP94410089A EP0649162A1 EP 0649162 A1 EP0649162 A1 EP 0649162A1 EP 94410089 A EP94410089 A EP 94410089A EP 94410089 A EP94410089 A EP 94410089A EP 0649162 A1 EP0649162 A1 EP 0649162A1
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EP
European Patent Office
Prior art keywords
groups
bands
phosphor elements
cathode
anode
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Granted
Application number
EP94410089A
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English (en)
French (fr)
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EP0649162B1 (de
Inventor
Michel Garcia
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Pixel International SA
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Pixel International SA
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Publication date
Application filed by Pixel International SA filed Critical Pixel International SA
Publication of EP0649162A1 publication Critical patent/EP0649162A1/de
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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
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/08—Electrodes intimately associated with a screen on or from which an image or pattern is formed, picked-up, converted or stored, e.g. backing-plates for storage tubes or collecting secondary electrons
    • H01J29/085—Anode plates, e.g. for screens of flat panel displays

Definitions

  • the present invention relates to a flat display screen with microtips. It applies more particularly to the production of a cathodoluminescent anode of such a screen and, in particular, connections of luminescent elements of the anode for operation as a switched anode.
  • Figures 1 and 2 show, respectively in section and in perspective, the structure of a flat screen with microtips of the type to which the invention relates.
  • Such a microtip screen essentially consists of a cathode 11 with microtips 10 and a grid 5 provided with holes at the locations of the microtips.
  • the cathode 11 is placed opposite a cathodoluminescent anode 12 including a glass substrate 2 constitutes the screen surface.
  • the cathode 11 consists, on a glass substrate 1, of cathode conductors 3 organized in columns. These cathode conductors 3 are generally coated with a resistive layer (not shown) for homogenizing the electronic emission.
  • the cathode 11 is associated with the grid 5 with interposition of an insulating layer 4 to isolate the cathode conductors 3 from the grid 5. Holes are respectively made in the grid 5 and insulation 4 layers to receive the microtips 10 which are formed on the resistive layer.
  • the grid 5 is organized in rows L1, L2, L3, the intersection of a row L of the grid 5 and a column 3 of the cathode 11, defining a pixel. For reasons of clarity, only a few microtips 10 have been shown in FIG. 2 at the intersection of a row L and a column 3. In practice, these microtips 10 are several thousand per screen pixel .
  • This device uses the electric field created between the cathode 11 and the grid 5 so that electrons are extracted from the microtips 10 towards phosphor elements 8 of the anode 12 by crossing an empty space 6.
  • the anode 12 is provided with alternating bands of phosphor elements 8 each corresponding to a color (Blue, Red, Green). Each strip is electrically isolated from the two neighboring strips.
  • the phosphor elements 8 are deposited on electrodes 7, made up of corresponding strips of a transparent conductive layer such as indium tin oxide (ITO).
  • ITO indium tin oxide
  • the strips are arranged parallel to the cathode columns 3, a group of three strips (one per color) being opposite a cathode column.
  • the width of a group of bands of the anode 12 corresponds to the width of a pixel.
  • the sets of blue, red and green bands are selectively polarized with respect to the cathode 11, so that the electrons extracted from the microtips 10 of a pixel of the cathode / grid are selectively directed towards the phosphor elements 8 opposite each colours.
  • the display of an image takes place during a frame time (for example 20 ms) by suitably polarizing the anode 12, the cathode 11 and the grid 5 by means of the control electronics.
  • the bands of phosphor elements 8 of the anode 12 are sequentially polarized by sets of bands of the same color, that is to say for a duration of sub-frame corresponding to one third of the frame time (for example 6.6 ms).
  • the display is carried out line by line, sequentially polarizing the grid rows during a "line time" during which each cathode column is brought to a potential which is a function of the brightness of the pixel to be displayed along the row current in the considered color.
  • the polarization of the columns 3 of the cathode 11 changes with each new row of the line scan.
  • a "line time” (for example 13.7 ⁇ s) corresponds to the duration of a subframe divided by the number of grid rows.
  • the sets of bands of phosphor elements 8 are therefore sequentially brought to a potential making it possible to attract the electrons emitted by the microtips 10.
  • This potential is a function of the distance (empty space 6) which separates the cathode / grid from the anode and is for example greater than 250 V.
  • the grid rows are sequentially polarized during a subframe. A given row L is brought to a potential (for example 80 V) while the other rows are at zero potential during the "line time" of the current row.
  • the cathode columns, the potential of which represents on each line the brightness of the pixel defined by the intersection of column 3 and row L in the color considered, are brought to respective potentials between a maximum emission potential and a potential for no emission (for example 0 and 30 V respectively).
  • the choice of the values of the polarization potentials is linked to the characteristics of the phosphor elements 8 and of the microtips 10. Conventionally, below a potential difference of 50 V between the cathode and the grid, there is no electronic emission and, the maximum emission used corresponds to a potential difference of 80 V.
  • a drawback of conventional screens lies in the fact that the electrons emitted by microtips 10 of a given column 3 of the cathode 11 tend to excite the strips of phosphors 8 of the same color which are opposite the two neighboring columns 3. Indeed, although two bands of the same color are separated by two bands of another color, the distance (of the order of 0.2 mm) between the phosphor elements 8 and the microtips 10 leads to the fact that the electrons have tendency to deviate to the nearest bands of the same color. This phenomenon of illumination of neighboring pixels is increased in the event of misalignment of the groups of bands of phosphor elements 8 with respect to the cathode columns, which can occur during assembly of the screen.
  • anode 12 In the case of a monochrome screen, the simplest way to produce an anode 12 is to deposit, over the entire substrate 2 of the anode 12, a conductor 7 coated with phosphors 8 without discontinuity. The anode 12 is permanently polarized. The selection of the areas of the screen excited by the electrons emitted by the microtips 10 is controlled by the respective polarizations of the cathode columns and of the grid rows. The drawbacks of color screens are found even more significantly in such monochrome screens.
  • the present invention aims to overcome these drawbacks by proposing a flat display screen which has good definition and good proximity contrast.
  • the present invention provides a flat display screen of the type comprising a cathode with electronic emission microtips organized in columns, a grid organized in rows and an anode provided with phosphor elements organized in groups of juxtaposed bands. and electrically isolated from each other.
  • the intersection of a row of the grid and a column of the cathode defines a pixel of the screen.
  • the groups of anode bands are electrically connected in two networks, a first network comprising the groups of bands of odd rank, while a second network comprises the groups of bands of even rank.
  • the screen includes control electronics suitable for sequentially addressing groups of odd, respectively even rank.
  • the groups of bands of phosphor elements are parallel to the columns of the cathode and have a width substantially identical to the width of these columns.
  • the cathode columns are addressed individually by the control electronics into two networks corresponding to the connection networks of the groups of bands of the anode.
  • control electronics include an inverter for addressing the connection networks of the groups of bands of phosphor elements.
  • the groups of bands of phosphor elements are parallel to the rows of the grid and have a width substantially identical to the width of these rows.
  • control electronics comprises means for sequentially addressing the rows of grid of even rank, respectively odd, at the same time as it addresses the groups of bands of phosphor elements of even rank , respectively odd.
  • each of said groups consists of a strip of phosphor elements, the phosphor elements of all the groups being of the same type.
  • each of said groups consists of three bands of phosphor elements of different colors, each network comprising three sets of bands of phosphor elements electrically connected together, and the control electronics comprising means for individually addressing each set of the same network.
  • the essential characteristic of the present invention resides in the electrical interconnection of the strips of phosphor elements of the anode. These bands are no longer interconnected by color, but in two networks (R1, V1, B1; R2, V2, B2) of bands by color.
  • a given band (for example B1) is not only electrically isolated from all the bands of the other two colors (for example R1, V1, R2, V2) but also from two bands of the same color which are closest to it (for example B2).
  • the bands of two neighboring groups 13, 14 are each connected to a different network.
  • This interconnection structure of the bands of phosphor elements 8 of the anode 12 is accompanied by a sequential addressing of the two arrays of bands to each image frame, in addition to the sequential addressing of the bands of the same color belonging to the same network.
  • the display of an image is always carried out for a frame time (for example 20 ms) by means of control electronics (not shown).
  • a frame time for example 20 ms
  • the bands of phosphor elements 8 of the anode 12 are sequentially polarized by sets of bands of the same color, but network by network.
  • a frame is therefore divided into six sub-frames of duration (for example 3.3 ms) corresponding to one sixth of the frame time.
  • the display is always done line by line by sequentially polarizing the rows L of the grid 5. But here, each row L is polarized six times for a given frame, the sequential polarization of all the rows L being repeated for each sub- frame.
  • the addressing of the cathode columns is also modified to reproduce, on the cathode side, a sequential addressing of two arrays of columns 3 similar to the arrays formed on the anode side 12.
  • an inverter or a simple jumper to reverse the order of the networks of the anode 12 in their sequential operation controlled by the control electronics.
  • Such an inverter or jumper will, for example, be positioned once and for all during the test of the screen after it has been assembled.
  • the invention allows the electrons emitted by the microtips 10 of the cathode 11 to be attracted to a polarized strip of phosphor elements 8 of the anode 12 (for example R2), without the possibility for the electrons to be picked up by the strips of the same color (for example R1) of the two neighboring groups 13.
  • the first embodiment according to the invention makes it possible to considerably improve the proximity contrast of the screen .
  • the invention also makes it possible to increase the anode-cathode distance 6.
  • the short distance 6, necessary for the collection of electrons on a single anode strip in conventional screens limits the anode voltage -cathode to avoid the formation of electric arcs which would destroy the screen.
  • the invention therefore makes it possible, by authorizing the increase in the inter-electrode distance without harming the collection of electrons, to apply to the anode 12 a higher potential for increasing the brightness of the screen.
  • the invention also allows the reduction of the size of the pixels to improve the resolution of the screen.
  • FIG. 4 illustrates the application of the first embodiment according to the invention to a monochrome screen.
  • the technique of color screens is applied, namely, the deposition of the phosphors 8 on parallel conductive strips electrically isolated from each other, but the phosphors are here all of the same type insofar as it is a monochrome screen .
  • the bands are interconnected in two networks (I, P), two neighboring bands each being connected to one of the two networks.
  • the width of a strip corresponds to the width of a pixel defined, as above, by the intersection of a cathode column with a row of grids. Columns 3 and rows L have been symbolized by dotted lines in FIG. 4.
  • FIG. 5 represents a second embodiment of the invention which makes it possible to reduce the number of switches of the columns 3 of the cathode 11 to the same value as that of conventional screens and thus limit the consumption of the control electronics.
  • the strips of phosphor elements 8 carried by the conductors 7 of the anode 12 are now parallel to the rows of the grid 5.
  • a pixel is always defined by the intersection of a row L of the grid 5 and of a column 3 of the cathode 11, and the width of a group of bands (R, G, B) of the anode 12 corresponds to the width of a row of the grid 5.
  • the respective polarizations of the cathode 11, the anode 12 and the grid 5 are here provided by the control electronics in the following manner.
  • the display of an image is always carried out during a frame time (for example 20 ms).
  • the bands of phosphor elements 8 of the anode 12 are sequentially polarized by color and, inside each set of color bands, by network.
  • the bands of even (or odd) rank of a first color are polarized, then the bands of odd (or even) rank of this first color. Then it is the turn of the odd (or even) rows of the second color, and so on.
  • the display is always done line by line, sequentially polarizing the grid rows, but every other line.
  • a first sequence of a sub-frame which corresponds to the polarization of the bands of the first network of a color (ie a half-frame)
  • the rows of odd rank or even
  • the polarization of the cathode 11 again becomes similar to that of conventional screens. That is to say that during each "line time" which corresponds to the polarization of a grid row during the line scanning, all the cathode columns are brought to a potential which is a function of the brightness of the pixel at display along the current line in the color considered.
  • the number of line scans is divided by two with respect to the first embodiment.
  • the number of switches of the cathode 11 which are the most current consuming within the control electronics is therefore divided by two, compared with the first embodiment. Indeed, while in the first embodiment, all the grid rows are sequentially polarized six times per frame (once for each of the six sub-frames), they are now only polarized three times per frame.
  • anode voltage can now be higher, to increase the anode / cathode space 6 and have recourse to a thin aluminum film affixed to the phosphor elements 8.
  • the increase in energy of the electrons allows them to pass through this thin film of aluminum.
EP94410089A 1993-10-14 1994-10-13 Flaches Kaltkathodeanzeigegerät mit geschalteter Anode Expired - Lifetime EP0649162B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9312530 1993-10-14
FR9312530A FR2711273B1 (fr) 1993-10-14 1993-10-14 Ecran plat à anode doublement commutée, utilisant des bandes de couleur dans le sens des lignes .

Publications (2)

Publication Number Publication Date
EP0649162A1 true EP0649162A1 (de) 1995-04-19
EP0649162B1 EP0649162B1 (de) 1997-07-30

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EP94410089A Expired - Lifetime EP0649162B1 (de) 1993-10-14 1994-10-13 Flaches Kaltkathodeanzeigegerät mit geschalteter Anode

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US (1) US5654729A (de)
EP (1) EP0649162B1 (de)
JP (1) JPH07191628A (de)
DE (1) DE69404599T2 (de)
FR (1) FR2711273B1 (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2730843B1 (fr) * 1995-02-17 1997-05-09 Pixtech Sa Dispositif d'adressage d'une electrode d'ecran plat de visualisation a micropointes
FR2736465B1 (fr) * 1995-07-03 1997-08-08 Commissariat Energie Atomique Dispositif d'amorcage et/ou de maintien d'une decharge et jauge a vide a cathode froide comportant un tel dispositif
US5940052A (en) * 1997-01-15 1999-08-17 Micron Technology, Inc. Current monitor for field emission displays
US6072272A (en) * 1998-05-04 2000-06-06 Motorola, Inc. Color flat panel display device
US6798131B2 (en) 2000-11-20 2004-09-28 Si Diamond Technology, Inc. Display having a grid electrode with individually controllable grid portions

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6054146A (ja) * 1983-09-02 1985-03-28 Matsushita Electric Ind Co Ltd 平板形陰極線管
EP0349425A1 (de) * 1988-06-29 1990-01-03 Commissariat A L'energie Atomique Dreifarben-Leuchtschirm mit Mikrospitzen-Kathoden

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0727337B2 (ja) * 1986-12-26 1995-03-29 双葉電子工業株式会社 蛍光表示装置
FR2623013A1 (fr) * 1987-11-06 1989-05-12 Commissariat Energie Atomique Source d'electrons a cathodes emissives a micropointes et dispositif de visualisation par cathodoluminescence excitee par emission de champ,utilisant cette source
US5225820A (en) * 1988-06-29 1993-07-06 Commissariat A L'energie Atomique Microtip trichromatic fluorescent screen
US5402143A (en) * 1991-12-23 1995-03-28 Panocorp Display Systems Color fluorescent liquid crystal display

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6054146A (ja) * 1983-09-02 1985-03-28 Matsushita Electric Ind Co Ltd 平板形陰極線管
EP0349425A1 (de) * 1988-06-29 1990-01-03 Commissariat A L'energie Atomique Dreifarben-Leuchtschirm mit Mikrospitzen-Kathoden

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 9, no. 185 (E - 332)<1908> 31 July 1985 (1985-07-31) *

Also Published As

Publication number Publication date
US5654729A (en) 1997-08-05
JPH07191628A (ja) 1995-07-28
FR2711273B1 (fr) 1996-01-19
EP0649162B1 (de) 1997-07-30
FR2711273A1 (fr) 1995-04-21
DE69404599T2 (de) 1997-12-04
DE69404599D1 (de) 1997-09-04

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