EP0867908A1 - Uniformisation de l'émission électronique potentielle d'une cathode d'écran plat à micropointes - Google Patents
Uniformisation de l'émission électronique potentielle d'une cathode d'écran plat à micropointes Download PDFInfo
- Publication number
- EP0867908A1 EP0867908A1 EP98410033A EP98410033A EP0867908A1 EP 0867908 A1 EP0867908 A1 EP 0867908A1 EP 98410033 A EP98410033 A EP 98410033A EP 98410033 A EP98410033 A EP 98410033A EP 0867908 A1 EP0867908 A1 EP 0867908A1
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- EP
- European Patent Office
- Prior art keywords
- cathode
- layer
- conductors
- inter
- columns
- 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.)
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Classifications
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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
- H01J1/304—Field-emissive cathodes
- H01J1/3042—Field-emissive cathodes microengineered, e.g. Spindt-type
Definitions
- the present invention relates to the production of a cathode with microtips of a flat display screen.
- Figure 1 shows an example of a classic structure a color microtip flat screen.
- Such a microtip screen essentially consists a cathode 1 with microtips 2 and a grid 3 provided of holes 4 corresponding to the locations of the microtips 2.
- the cathode 1 is placed opposite a cathodoluminescent anode 5 of which a glass substrate constitutes the screen surface.
- Cathode 1 is organized in columns and is made up, on a glass substrate 10, cathode conductors organized in mesh from a conductive layer.
- the microtips 2 are made on a resistive layer 11 deposited on the cathode conductors and are arranged inside meshes defined by the cathode conductors.
- Figure 1 partially represents the interior of a mesh and the conductors cathode do not appear in this figure.
- Cathode 1 is associated with grid 3 organized in lines. The intersection a row of grid 3 and a column of cathode 1 defines a pixel.
- This device uses the electric field that is created between cathode 1 and grid 3 so that electrons are extracted from microtips 2. These electrons are then attracted by phosphor elements 7 from anode 5 if these are suitably polarized.
- the anode 5 is provided with alternating bands phosphor elements 7r, 7g, 7b each corresponding to one color (Red, Green, Blue). The bands are parallel to the cathode columns and are separated from each other by an insulator 8.
- the phosphors 7 are deposited on electrodes 9, consisting of corresponding strips of a conductive layer transparent such as indium tin oxide (ITO).
- the sets of red, green, blue bands are alternately polarized with respect to cathode 1 so that electrons extracts of microtips 2 from a pixel of the cathode / grid are alternately directed towards the phosphors 7 opposite of each of the colors.
- the anode In the case of a monochrome screen (not shown), the anode consists of a plane of phosphor elements similarly color or two sets of alternating bands of phosphor elements of the same color.
- FIG. 2A schematically illustrate the mesh of cathode conductors of such a microtip screen.
- FIG. 2A partially represents and seen from above, a microtip cathode and
- Figure 2B is a sectional view along line B-B 'of Figure 2A.
- the grid (3, Figure 1) and the insulation layer between this grid and the resistive layer (11, figure 1) have not been shown in Figures 2A and 2B.
- microtips 2 are arranged in each mesh 12 defined by the cathode conductors 13. Although a reduced number of meshes has been shown for each pixel 14 defined by the intersection of a column 15 of the cathode 1 and a grid line (not shown), we note that the microtips are generally several in number thousands per screen pixel.
- the cathode 1 generally consists of layers deposited successively on the glass substrate 10.
- a conductive layer 13, for example made of niobium, is deposited on the substrate 10. This layer 13 is etched according to the pattern of columns 15, each column comprising meshes 12 surrounded by cathode conductors 13.
- a resistive layer 11 is then deposited on these cathode conductors 13.
- This resistive layer 11, consisting for example of amorphous silicon doped with phosphorus, has the purpose of protecting each microtip 2 against excess current at the start of a microtip 2.
- the affixing of such a resistive layer 11 aims to homogenize the electronic emission of the microtips 2 from a pixel of the cathode 1 and thereby increase its lifetime.
- the resistive layer is, if necessary, etched according to the pattern of the columns and / or open, at least partially, directly above the cathode conductors.
- An insulating layer (not shown), for example made of silicon oxide (SiO 2 ), is deposited on the resistive layer 11 to isolate the cathode conductors 13 from the grid 3 (FIG. 1).
- a microtip cathode of this type is described, for example, in European patent application No. 0696045.
- the cathode conductors 13 can be deposited on the resistive layer 11 which can, as in the previous case, be full plate or not.
- a microtip cathode of this type is described, for example, in the application for French Patent No. 2,722,913.
- a disadvantage of conventional screens is that one finds, during operation of the screen, differences of brightness from one column to another of the resulting screen, in particular, of a drift in the quantity of electrons emitted by the cathode microtip columns for a luminance setpoint given. This phenomenon which occurs both for color screens and for monochrome screens results in the appearance of highlight columns regardless of the pattern image to be displayed.
- the present invention aims to overcome this drawback by making the screen brightness of a screen substantially uniform column to another.
- the present invention provides a flat display cathode of the type comprising, on a substrate, columns of polarizable cathode conductors individually and associated with a resistive layer on which electronic emission microtips are deposited, and comprising means for canceling a lateral electric field between two neighboring columns brought to potentials different.
- the cathode has, between two adjacent columns, a track inter-column conductor capable of being polarized at a potential at most equal to the minimum potential of polarization of the conductors cathode.
- the inter-column conductive tracks are interconnected by one of their ends.
- the cathode has an insulating layer attached to the conductors cathode associated with the resistive layer, a layer grid conductor organized in lines being deposited on the insulating layer open directly above each inter-column track.
- the insulating layer is also open, at least partially, directly above the cathode conductors.
- said inter-column tracks are deposited directly on the substrate and are made of the same material as the conductors of cathode.
- the inter-column tracks are deposited directly on the substrate and are made of the same material as the layer resistive.
- the cathode has a counter electrode deposited on the rear face of the substrate.
- said counter-electrode consists of a conducting plane, extending over the entire surface of the cathode and suitable for being polarized at a strongly positive potential.
- said counter electrode is coated with a protective layer.
- the present invention originates from an interpretation phenomena that cause the above problems in classic screens.
- This electric field modifies the resistivity of the layer resistive column at zero potential, which results in a modification of the quantity of electrons emitted by the microtips of this column under a given gloss setpoint.
- the resistive layer can no longer play its protective role microtips and we see short circuits appear between the grid and the cathode.
- the present invention proposes to cancel the inter-column lateral electric field.
- Figures 3 and 4 illustrate a first embodiment of a microtip cathode of a flat screen according to the present invention.
- the cathode 1 ' is organized in columns 15 and is constituted, on a glass substrate 10 ( Figure 3) of cathode conductors organized in mesh with from a conductive layer. 2 microtips are produced on a resistive layer deposited, for example, on the cathode conductors and are arranged inside the meshes defined by the cathode conductors.
- the detail of the structure of columns 15 has not been shown and the cathode conductors associated with the resistive layer have been generally designated by the reference 20.
- the cathode 1 ' is associated to a grid 3 organized in lines (not shown in the Figure 4) deposited on an insulating layer 21.
- the grid layer 3 and the insulating layer 21 are open at the locations of the microtips 2. For clarity, only four microtips by column have been represented in FIG. 3. We will note however that each pixel (14, Figure 4), defined by the intersection of a column 15 of the cathode with a line of the grid 3, includes several thousand microtips.
- conductive tracks are deposited on the substrate 10 while being inserted between the columns 15 of the cathode 1 '.
- These tracks 22 are interconnected at one of their ends by means of a track 23 and are polarized at a potential at most equal to the potential minimum polarization of the columns 15 of the cathode 1 '.
- the material of the tracks inter-columns 22 can be a conductive material, for example, the same material as that constituting the conductors of cathode.
- the inter-column tracks 22 can be made of the same material as the resistive layer.
- Figures 5 and 6 illustrate a variant of the first embodiment of the present invention.
- the insulating layer 21, separating the conductors of cathode 20 of grid 3 has openings 24, at least, directly above the inter-column tracks 22.
- An advantage of this variant is that the openings 24 in the insulating layer 21 allow only positive ions, which conventionally fall back on silicon oxide (insulating layer 21) between the pixels and cause an accumulation of charge on the insulation, are collected by the inter-column tracks 22. We thus avoids the appearance of breakdowns linked to this accumulation between the columns of the cathode.
- this resistive layer may or may not be open together with the insulating layer 21.
- the insulating layer 21 is not only open directly above the inter-column tracks 22, but also at plumb with the cathode conductors 20 (associated or not with a resistive layer), at least between the pixels 14, to increase the surface covered by metallic and non-insulating layers, in order to increase the collection of positive charges.
- the potential for polarization of the inter-column tracks 22 may be negative, note that it is sufficient to avoid the accumulation of charges by the insulating surface and that a polarization 22 to 0 volt inter-column tracks is sufficient, in the since these tracks are conductive.
- Figure 7 illustrates a second embodiment of a microtip cathode of a flat screen according to the present invention.
- an electric field is created vertical (dotted lines 26) by means of a counter electrode 27 deposited full plate on the rear face of the substrate lens 10 and polarized to a suitable potential.
- the counter electrode 27 is covered with a protective layer 28 insulating.
- the potential (for example, on the order of a kilovolt) of polarization of the counter-electrode 27 is chosen to cancel the lateral electric field due to the polarization of the columns 15 of the cathode 1 "and depends, in particular, on the thickness of the substrate of glass.
- counter electrode 27 can be used to adjust resistivity cathode columns after the manufacture of the cathode, in order to compensate for any manufacturing drifts. For example, applying a negative potential during a certain duration increases the resistivity of the supporting layer microtips and, consequently, will generate a decrease in overall screen luminance. Note that the screen does not need to be in operation for this adjustment resistivity. In particular, the screen anode can be disconnected during this phase.
- the polarization of the counter-electrode 27 may be periodic during the operation of the screen.
- the present invention is capable of various variants and modifications which will appear to the man of art.
- the different embodiments of the invention described above may be combined within a same screen.
- the counter electrode 27 which influences the resistivity of layer 11 will preferably be used for calibrate the screen brightness at the end of production or during maintenance operations. Then, in normal operation, we will use tracks 22 which have the advantage of give the cathode a potential electronic emission more stable than the counter electrode 27.
Landscapes
- Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
- Electrodes For Cathode-Ray Tubes (AREA)
- Devices For Indicating Variable Information By Combining Individual Elements (AREA)
Abstract
Description
Claims (10)
- Cathode (1', 1") d'écran plat de visualisation du type comportant, sur un substrat, des colonnes (15) de conducteurs de cathode polarisables individuellement et associés à une couche résistive (11) sur laquelle sont déposées des micropointes (2) d'émission électronique, caractérisée en ce qu'elle comporte des moyens pour annuler un champ électrique latéral éventuel entre deux colonnes voisines portées à des potentiels différents.
- Cathode selon la revendication 1, caractérisée en ce qu'elle comporte, entre deux colonnes voisines, une piste conductrice inter-colonnes (22) propre à être polarisée à un potentiel au plus égal au potentiel minimal de polarisation des conducteurs de cathode.
- Cathode selon la revendication 1, caractérisée en ce que les pistes conductrices inter-colonnes (22) sont interconnectées par une de leurs extrémités.
- Cathode selon la revendication 2 ou 3, du type comportant une couche isolante (21) rapportée sur les conducteurs de cathode associés à la couche résistive, une couche conductrice de grille (3) organisée en lignes étant déposée sur la couche isolante (21), caractérisée en ce que la couche isolante (21) est ouverte à l'aplomb de chaque piste inter-colonnes (22).
- Cathode selon la revendication 4, caractérisée en ce que la couche isolante (21) est également ouverte, au moins partiellement, à l'aplomb des conducteurs de cathode.
- Cathode selon l'une quelconque des revendications 2 à 5, caractérisée en ce que lesdites pistes inter-colonnes (22) sont déposées directement sur le substrat (10) et sont formées du même matériau que les conducteurs de cathode (13).
- Cathode selon l'une quelconque des revendications 2 à 5, caractérisée en ce que les pistes inter-colonnes (22) sont déposées directement sur le substrat (10) et sont constituées du même matériau que celui de la couche résistive (11).
- Cathode selon la revendication 1, caractérisée en ce qu'elle comporte une contre-électrode (27) déposée en face arrière du substrat (10).
- Cathode selon la revendication 8, caractérisée en ce que ladite contre-électrode (27) est constituée d'un plan conducteur, s'étendant sur toute la surface de la cathode et propre à être polarisé à un potentiel fortement positif.
- Cathode selon la revendication 8 ou 9, caractérisée en ce que ladite contre-électrode (27) est revêtue d'une couche de protection (28).
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9704097 | 1997-03-28 | ||
FR9704097A FR2761522B1 (fr) | 1997-03-28 | 1997-03-28 | Uniformisation de l'emission electronique potentielle d'une cathode d'ecran plat a micropointes |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0867908A1 true EP0867908A1 (fr) | 1998-09-30 |
Family
ID=9505501
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP98410033A Withdrawn EP0867908A1 (fr) | 1997-03-28 | 1998-03-26 | Uniformisation de l'émission électronique potentielle d'une cathode d'écran plat à micropointes |
Country Status (4)
Country | Link |
---|---|
US (1) | US6147445A (fr) |
EP (1) | EP0867908A1 (fr) |
JP (1) | JPH10326584A (fr) |
FR (1) | FR2761522B1 (fr) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6566804B1 (en) * | 1999-09-07 | 2003-05-20 | Motorola, Inc. | Field emission device and method of operation |
JP3919676B2 (ja) * | 2002-03-05 | 2007-05-30 | キヤノン株式会社 | 高電圧型画像表示装置 |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2708380A1 (fr) * | 1993-05-28 | 1995-02-03 | Futaba Denshi Kogyo Kk | Dispositif d'affichage d'images et circuit de commande associé. |
EP0713236A1 (fr) * | 1994-11-18 | 1996-05-22 | Texas Instruments Incorporated | Dispositif émitteur d'électrons |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5557159A (en) * | 1994-11-18 | 1996-09-17 | Texas Instruments Incorporated | Field emission microtip clusters adjacent stripe conductors |
-
1997
- 1997-03-28 FR FR9704097A patent/FR2761522B1/fr not_active Expired - Fee Related
-
1998
- 1998-03-26 EP EP98410033A patent/EP0867908A1/fr not_active Withdrawn
- 1998-03-27 JP JP10121580A patent/JPH10326584A/ja not_active Withdrawn
- 1998-03-27 US US09/049,364 patent/US6147445A/en not_active Expired - Fee Related
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2708380A1 (fr) * | 1993-05-28 | 1995-02-03 | Futaba Denshi Kogyo Kk | Dispositif d'affichage d'images et circuit de commande associé. |
EP0713236A1 (fr) * | 1994-11-18 | 1996-05-22 | Texas Instruments Incorporated | Dispositif émitteur d'électrons |
Also Published As
Publication number | Publication date |
---|---|
US6147445A (en) | 2000-11-14 |
FR2761522A1 (fr) | 1998-10-02 |
FR2761522B1 (fr) | 1999-06-04 |
JPH10326584A (ja) | 1998-12-08 |
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