EP0806788A1 - Anode d'écran plat de visualisation à anneau de protection - Google Patents

Anode d'écran plat de visualisation à anneau de protection Download PDF

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Publication number
EP0806788A1
EP0806788A1 EP97410050A EP97410050A EP0806788A1 EP 0806788 A1 EP0806788 A1 EP 0806788A1 EP 97410050 A EP97410050 A EP 97410050A EP 97410050 A EP97410050 A EP 97410050A EP 0806788 A1 EP0806788 A1 EP 0806788A1
Authority
EP
European Patent Office
Prior art keywords
track
active area
anode
potential
anode according
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.)
Withdrawn
Application number
EP97410050A
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German (de)
English (en)
French (fr)
Inventor
Stéphane Mougin
Francis Courreges
Bernard Bancal
Lionel Riviere-Cazaux
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.)
Pixtech SA
Original Assignee
Pixtech SA
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 Pixtech SA filed Critical Pixtech SA
Publication of EP0806788A1 publication Critical patent/EP0806788A1/fr
Withdrawn legal-status Critical Current

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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 flat display screens, and more particularly to so-called cathodoluminescence screens, the anode of which carries luminescent elements separated from each other by insulating zones and capable of being excited by electronic bombardment.
  • This electronic bombardment requires that the luminescent elements are polarized and can come from microtips, from layers with low extraction potential or from a thermionic source.
  • microtip screens To simplify the present description, below only the microtip screens will be considered, but it will be noted that the present invention relates, in general, to the various types of screens mentioned above and the like.
  • Figure 1 shows the structure of a color microtip flat screen.
  • Such a microtip screen essentially consists of a cathode 1 with microtips 2 and a grid 3 provided with holes 4 corresponding to the locations of the microtips 2.
  • the cathode 1 is placed opposite a cathodoluminescent anode 5 including a substrate of glass 6 constitutes the screen surface.
  • the cathode 1 is organized in columns and consists, on a glass substrate 10, of cathode conductors organized in meshes from a conductive layer.
  • the microtips 2 are produced on a resistive layer 11 deposited on the cathode conductors and are arranged inside the meshes defined by the cathode conductors.
  • Figure 1 partially shows the interior of a mesh and the cathode conductors do not appear in this figure.
  • the cathode 1 is associated with the grid 3 organized in lines. The intersection of a line of the grid 3 and a column of the cathode 1 defines a pixel.
  • This device uses the electric field which is created between the cathode 1 and the grid 3 so that electrons are extracted from the microtips 2. These electrons are then attracted by phosphor elements 7 from the anode 5 if these are suitably polarized.
  • the anode 5 is provided with alternating bands of phosphor elements 7r, 7g, 7b each corresponding to a color (Red, Green, Blue). The strips are parallel to the columns of the cathode and are separated from each other by an insulator 8, generally silicon oxide (SiO 2 ).
  • the phosphor elements 7 are deposited on electrodes 9, made up of corresponding strips of a transparent conductive layer such as indium tin oxide (ITO).
  • ITO indium tin oxide
  • the sets of red, green and blue bands are alternately polarized with respect to the cathode 1, so that electrons extracted from the microtips 2 of a pixel of the cathode / grid are alternately directed towards the phosphor elements 7 opposite of each of the colors.
  • the command to select the phosphor 7 (the phosphor 7g, in FIG. 1) which must be bombarded by the electrons coming from the microtips of the cathode 1 means that it is necessary to command, selectively, the polarization of the phosphor elements 7 of the anode 5, color by color.
  • the rows of the grid 3 are sequentially polarized at a potential of the order of 80 volts while the strips of phosphor elements (for example 7g, in Figure 1) to be excited are polarized under a voltage of the order 400 volts via the ITO strip on which these phosphors are deposited.
  • the ITO bands, carrying the other bands of phosphor elements (for example 7r and 7b in FIG. 1), are at low or zero potential.
  • the columns of cathode 1 are brought to respective potentials between a maximum emission potential and a non-emission potential (for example, 0 and 30 volts respectively). The brightness of a color component of each of the pixels of a line is thus fixed.
  • the choice of the values of the polarization potentials is linked to the characteristics of the phosphor elements and of the microtips 2. Conventionally, below a potential difference of 50 volts between the cathode and the grid, there is no electronic emission. , and the maximum emission used corresponds to a potential difference of 80 volts.
  • a space 12 between the substrates 6 and 10 is generally defined by means of spacers (not shown) regularly distributed over the entire surface of the screen between the grid 3 and the anode 5.
  • the substrates 6 and 10 are assembled one to the other by means of a peripheral seal, for example by means of a bead of fusible glass constituting, once hardened, a rigid peripheral seal.
  • the connecting tracks of the strips 9 by set of strips carrying phosphor elements of the same color require the formation, on the substrate 6, of a stack of insulating and conductive layers because one must connect three sets of alternating strips.
  • a disadvantage of conventional screens is that they suffer from a short lifespan, that is to say that after a relatively short operating time (of the order of a hundred hours) , we see destructive phenomena appearing due to the formation of arcs at the periphery of the screen.
  • the object of the present invention is to propose a new solution to the abovementioned problems of appearance of arcs at the periphery of the screen.
  • the present invention provides a flat screen display anode of the type comprising an active area provided with phosphor elements, said active area being surrounded by at least one secondary electron collection track capable of being re-emitted by the active area following an electronic bombardment of the latter, and said track being separated from the periphery of the active area, at least in large part, by a space made of an insulating material.
  • the width of said track is greater than the distance capable of being traveled by secondary electrons re-emitted by said insulating material.
  • the width of said track is greater than 50 ⁇ m.
  • the width of said insulating space is less than the distance capable to be traversed by secondary electrons re-emitted by the material of which it is made.
  • said track is brought to a potential much lower than the polarization potential of said active area.
  • the anode comprises at least two concentric tracks surrounding said active area, a first track proximal to the active area being brought to a potential intermediate between the potential of this active area and a potential at which is carried a second distal track from the active area.
  • the track or tracks are open to allow the passage of a bias track of the active area.
  • said track has a shape of a spiral between the active area and a connection terminal at a potential lower than that of the active area.
  • resistors are inserted in each section of said spiral.
  • the track or tracks are made of a weakly resistive material.
  • the track or tracks are made of a material having a secondary emission coefficient less than or equal to unity.
  • the present invention originates from an interpretation of the phenomenon which gives rise to the aforementioned problem in conventional screens.
  • the inventors consider that this problem is due, in particular, to a phenomenon of secondary emission occurring at the periphery of the anode.
  • Figure 2 shows, schematically and in cross section, the edge of a flat display screen. For reasons of clarity, the details constituting the cathode 1 and the grid 3 have not been shown.
  • the internal space 12 is surrounded by a glass gasket 14 ensuring the sealing of the substrates 6 and 10 carrying the anode and the cathode of the screen respectively.
  • the gasket 14 must be placed at a distance from the edge of the active area of the anode carrying the phosphor elements to allow the interconnection of the strips in sets of the same color.
  • the stack of conductive and insulating layers has not been shown in FIG. 2. Only a peripheral insulating strip 8 'has been shown. This strip 8 ′ can either extend to the joint 14 or leave the substrate 6 accessible in certain parts of the periphery of the screen as shown in FIG. 2.
  • Any material has a secondary emission coefficient, called ⁇ , which represents the average number of secondary electrons re-emitted for an incident electron arriving on this material.
  • ⁇ secondary emission coefficient
  • the predominant energy of the statistical distribution of secondary electrons is of the order of 30 to 50 eV, whatever the energy of the incident electrons.
  • the secondary emission factor of a material varies depending on the energy of the electrons touching its surface. In general, this coefficient begins by increasing until it reaches a maximum level ⁇ max then decreases towards an asymptote value. In the case of microtip screens, the energy of the primary electrons is linked to the polarization potential of the anode and is, for example, of the order of 400 eV.
  • the secondary emission coefficient ⁇ is greater than 1, this means that the surface of the material re-emits more electrons than it receives and tends to charge positively. Conversely, when the secondary emission coefficient ⁇ is less than 1, there is an accumulation of electrons.
  • microtip screens are produced using technologies derived from those used in the manufacture of integrated circuits, has led to the use of silicon oxide to produce the insulating strips 8 ′.
  • silicon oxide constitutes a usual material and which one masters use well.
  • silicon oxide has a particularly high secondary emission coefficient ( ⁇ max is of the order of 3 for an energy of the order of 400 eV).
  • the glass constituting the substrate 6 and the seal 14 also has a very high secondary emission coefficient ( ⁇ max is of the order of 4 for an energy of the order of 400 eV).
  • the track 8 ', the substrate 6 and the joint 14 are at zero potential.
  • the primary electrons which arrive on the edge of track 8 '(or on the substrate 6) at the edge of track 9g when it is polarized cause, by emission of secondary electrons, a positive charge on the surface of the oxide. layer 8 'silicon (or on the surface of substrate 6).
  • this positive charge zone develops, insofar as the primary electrons are more and more attracted to the surface of the strip 8 ′ or of the substrate 6 as and when that its positive charge increases.
  • the emission of a secondary electron generally results in turn in a re-emission of secondary electrons.
  • the zone of positive charge propagates towards the seal 14, then on the surface of the glass seal 14 and thus gradually approaches the cathode. When the positive charge area becomes close enough to the cathode, an arcing phenomenon occurs due to the potential difference with the cathode.
  • the invention proposes to trap the secondary electrons to prevent the propagation of the phenomenon of secondary emission up to the sealing joint.
  • a feature of the present invention is to interpose, between the active area carrying the phosphor elements of the anode and the sealing joint, a secondary electron collection track.
  • This collection track is according to the invention, either in a conductive material polarized at a determined potential, or in a material having a secondary emission coefficient less than or equal to unity, preferably polarizable.
  • the collection track is separated from the periphery of the active area, at least in part, by a space made of an insulating material.
  • the track is polarized, its polarization potential is chosen so as not to attract electrons emitted by the cathode.
  • ⁇ secondary emission coefficient
  • ⁇ secondary emission coefficient
  • FIGS. 3 to 5 refer to monochrome screen anodes made up of a plane 20 of phosphor elements of a same color carried by a corresponding ITO map (not visible in the figures). It will however be noted that the various embodiments which will be explained below also apply to the case of a color screen whose anode consists of several sets of alternating parallel strips of phosphor elements of different colors as well as a monochrome screen whose anode is made up of two sets of alternating parallel strips of phosphor elements of the same color.
  • the position of the internal limit of the sealing joint (14, FIG. 2) has been symbolized by a dotted frame 14 '.
  • FIG. 3 represents a first embodiment of a flat screen anode according to the present invention.
  • the active area 20 is surrounded by a single track 21 for collecting the secondary electrons.
  • the track 21 constitutes a ring around the active area 20 and is biased at a potential much lower than the bias potential of the active area so as not to interfere with the operation of the screen by attracting electrons from the cathode (not shown).
  • the ring 21 must not be in contact with the active area 20.
  • the ring 21 and the active area 20 are separated by an insulating material 22, for example, the glass of the substrate 6 on which the anode is formed. or a band of silicon oxide added to the substrate 6.
  • the ring 21 If it is not polarized, the ring 21, because its secondary emission coefficient is less than 1, charges negatively when it receives secondary electrons re-emitted by the surface of the material 22 and, once charged , focuses the electrons towards the active area 20.
  • this negative charge is difficult to control.
  • it is difficult to determine the width of the insulating space 22 which makes it possible to avoid the appearance of electric arcs between the active area 20 and the track 21.
  • the potential of the ring 21 is, for example, zero or close to zero (preferably, slightly negative).
  • the width of the ring 21 is chosen to be greater than the average distance that the secondary electrons re-emitted by the insulating material 22 are likely to travel and which, as before, is capable of receiving primary electrons from the microtips. Typically, with an energy of the order of 30 eV, a secondary electron travels a distance of about 50 ⁇ m. Thus, the width of the ring 21 is preferably substantially greater than 50 ⁇ m.
  • the insulating space 22 must be sufficient to prevent an electric arc from developing between the active area 20 and the collection ring 21. However, it will be sought to be as small as possible to avoid development of a positive charge area in this space. Ideally and if the polarization potentials allow it, the width of the space 22 is less than the average distance that the secondary electrons emitted by the surface of this space are likely to travel, ie, preferably, less than 50 ⁇ m. This guarantees that all the secondary electrons re-emitted by the insulating material 22 are collected by the material 21.
  • the material of the track 21 preferably has a secondary emission coefficient ⁇ max less than 1. This guarantees the absence of secondary emission independently of the energy of the primary electrons, that is to say independently of the polarization values of the anode and the cathode. It will be noted that, in the first embodiment, the material of the track 21 may, if necessary, be insulating if it is not desired to polarize it.
  • An advantage of the present invention is that it avoids any phenomenon of propagation of secondary emissions up to the sealing joint 14 'between the anode and cathode plates.
  • the polarization of the ring 21 makes it possible to evacuate the corresponding charges.
  • the ring 21 is continuous and therefore covers, with the interposition of an insulator (not shown) a track 24 for polarizing the active area 20.
  • This track 24 extends beyond the joint 14 'and is intended to be connected, via a connector 25, to a screen control electronics (not shown).
  • the ring 21 is polarized by means of a conductive track 26, extending beyond the seal 14 'and intended to receive a connector 27 for connection to the control electronics.
  • FIG. 4 represents a second embodiment of a flat screen anode according to the invention.
  • the active area 20 of the anode is surrounded by two concentric rings for collecting secondary electrons.
  • a first ring 21 ' is separated from the zone 20 by a space made of an insulating material 22.
  • a second ring 21 "surrounds the ring 21' being separated from the latter by a second space made of an insulating material 22 '(for example the glass of the substrate 6 or of the silicon oxide deposited on the latter).
  • the material constituting the rings 21 ′ and 21 ′′ is chosen to be polarizable (with a coefficient of less than 1 if it is not weakly resistive).
  • the width of the rings 21 'and 21 is chosen to be greater than the average distance that the secondary electrons re-emitted by the insulating materials are likely to travel 22 and 22', respectively.
  • the active area 20 is polarized by means of a track 24 and a connector 25.
  • the rings 21 'and 21 are polarized by means of tracks, respectively 26' and 26", and of connectors, respectively 27 'and 27 ".
  • the rings 21 'and 21 " are polarized at different potentials, the ring 21' being preferably at a potential intermediate between the potential of the active area 20 and the potential of the external ring 21 ".
  • the ring 21 ' is at a potential of 200 volts and the ring 21 "is at a potential zero.
  • An advantage of this second embodiment is that by making the decrease in potential from the active area to the edge of the screen more progressive, it avoids edge effects by spreading the electric field lines.
  • Another advantage of this second embodiment is that it makes it possible to reduce the width of the spaces 22 and 22 'between the active zone 20 and the ring 21' and between the rings 21 'and 21 ". Indeed, the distance electric arc creation limit is lower insofar as the potential difference between the zone 20 and the ring 21 'and between the rings 21' and 21 "is reduced. This minimizes the development of the positive charge zone in space 22 by facilitating compliance with the width compromise of space 22, linked to the need to prevent the formation of an electric arc between zone 20 and ring 21 'and the desire to have a width less than the distance traveled by the secondary electrons.
  • FIG. 5 represents a third embodiment of a flat screen anode according to the present invention.
  • the collection of secondary electrons is carried out by means of a spiral-shaped track 31 which connects an edge of the active area 20 to a connection terminal 36, by means of a connector 27, to a zero or near zero potential.
  • track 31 is chosen to have a secondary emission coefficient less than 1.
  • Spaces made of an insulating material 22, 22 ′ and 22 are provided between the active zone 20 and the first turn of the turn and between each turn of the turn of the track 31.
  • the width of the turns of track 31 is sufficient to prevent secondary electrons from jumping the turns by propagating from insulating space 22 into insulating space 22 'or 22 "to reach the edge of the screen.
  • the width of the turns is also conditioned by the desired resistivity to obtain a progressive decrease in potential from the active area (at 400 volts) to terminal 36 (for example at 0 volts).
  • the width of the track 31 is chosen so that this track 31 has sufficient resistivity to minimize the flow of current therein.
  • resistors 33 for example obtained by screen printing, in each turn of the coil defined by the track 31.
  • the polarization of the active area 20 is, as previously, obtained by means of a track 24 intended to receive a connector 25 connected to the control electronics of the screen.
  • An advantage of the third embodiment shown in FIG. 5 is that it creates a progressive and controlled decrease in the potential between the active area 20 and the seal 14 '.
  • Another advantage of this third embodiment is that it does not require an intermediate potential source while minimizing the edge effects.
  • the constituent material of the secondary electron collection rings 21, 21 ′, 21 "or 31 according to one of the preceding embodiments is, for example, ITO (weakly resistive material).
  • the possible polarization of the collection track (s) is obtained by means of a conductive layer of the same pattern (for example made of ITO), on which is deposited a layer of chromium oxide.
  • chromium oxide is chosen to produce track 31 of the third embodiment shown in FIG. 5
  • resistors 33 will generally be superfluous insofar as chromium oxide is a material having a higher resistivity than ITO.
  • the use of chromium oxide makes it possible, according to this third mode of realization, wider turns which improves the absence of propagation of secondary electrons.
  • the present invention is susceptible to various variants and modifications which will appear to those skilled in the art.
  • the choice of the polarization potential (s) of the secondary electron collection rings depends on the respective potentials of the anode and the cathode of the screen.
  • the invention also applies to a color screen.
  • the ring or rings of secondary electron collection are deposited above the stack allowing the interconnection of the strips of phosphor elements.

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  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
EP97410050A 1996-05-06 1997-05-02 Anode d'écran plat de visualisation à anneau de protection Withdrawn EP0806788A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9605931 1996-05-06
FR9605931A FR2748347B1 (fr) 1996-05-06 1996-05-06 Anode d'ecran plat de visualisation a anneau de protection

Publications (1)

Publication Number Publication Date
EP0806788A1 true EP0806788A1 (fr) 1997-11-12

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EP97410050A Withdrawn EP0806788A1 (fr) 1996-05-06 1997-05-02 Anode d'écran plat de visualisation à anneau de protection

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US (1) US5903108A (ja)
EP (1) EP0806788A1 (ja)
JP (1) JPH1097835A (ja)
FR (1) FR2748347B1 (ja)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000021112A1 (fr) * 1998-10-02 2000-04-13 Commissariat A L'energie Atomique Source d'electrons comportant au moins une electrode de protection contre des emissions parasites
US7554256B2 (en) 2004-08-19 2009-06-30 Canon Kabushiki Kaisha Light-emitting substrate, image display apparatus, and information display and reproduction apparatus using image display apparatus

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2765392B1 (fr) * 1997-06-27 2005-08-26 Pixtech Sa Pompage ionique d'un ecran plat a micropointes
JP3747154B2 (ja) * 1999-12-28 2006-02-22 キヤノン株式会社 画像形成装置
FR2807205A1 (fr) * 2000-03-28 2001-10-05 Pixtech Sa Plaque de cathode d'ecran plat de visualisation
JP3689651B2 (ja) * 2000-07-24 2005-08-31 キヤノン株式会社 電子線装置
FR2881270B1 (fr) * 2005-01-27 2007-04-20 Commissariat Energie Atomique Dispositif microelectronique emetteur d'electrons a plusieurs faisceaux
US7795615B2 (en) * 2005-11-08 2010-09-14 Infineon Technologies Ag Capacitor integrated in a structure surrounding a die

Citations (4)

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Publication number Priority date Publication date Assignee Title
US2858466A (en) * 1955-11-25 1958-10-28 Westinghouse Electric Corp Method of reducing secondary emission from bombarded surfaces
US3614504A (en) * 1970-04-09 1971-10-19 Zenith Radio Corp Color picture tube screen with phosphors dots overlapping portions of a partial-digit-transmissive black-surround material
DE2436622A1 (de) * 1974-07-30 1976-02-19 Licentia Gmbh Optoelektronische roehre, insbesondere bildverstaerkerroehre
EP0635865A1 (en) * 1993-07-21 1995-01-25 Sony Corporation Field-emission display

Family Cites Families (5)

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US5614781A (en) * 1992-04-10 1997-03-25 Candescent Technologies Corporation Structure and operation of high voltage supports
DE69407015T2 (de) * 1993-09-20 1998-03-19 Hewlett Packard Co Fokussier- und Ablenkelektroden für Elektronenquellen
US5508584A (en) * 1994-12-27 1996-04-16 Industrial Technology Research Institute Flat panel display with focus mesh
US5543691A (en) * 1995-05-11 1996-08-06 Raytheon Company Field emission display with focus grid and method of operating same
US5670296A (en) * 1995-07-03 1997-09-23 Industrial Technology Research Institute Method of manufacturing a high efficiency field emission display

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2858466A (en) * 1955-11-25 1958-10-28 Westinghouse Electric Corp Method of reducing secondary emission from bombarded surfaces
US3614504A (en) * 1970-04-09 1971-10-19 Zenith Radio Corp Color picture tube screen with phosphors dots overlapping portions of a partial-digit-transmissive black-surround material
DE2436622A1 (de) * 1974-07-30 1976-02-19 Licentia Gmbh Optoelektronische roehre, insbesondere bildverstaerkerroehre
EP0635865A1 (en) * 1993-07-21 1995-01-25 Sony Corporation Field-emission display

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000021112A1 (fr) * 1998-10-02 2000-04-13 Commissariat A L'energie Atomique Source d'electrons comportant au moins une electrode de protection contre des emissions parasites
US7554256B2 (en) 2004-08-19 2009-06-30 Canon Kabushiki Kaisha Light-emitting substrate, image display apparatus, and information display and reproduction apparatus using image display apparatus
US7965027B2 (en) 2004-08-19 2011-06-21 Canon Kabushiki Kaisha Light-emitting substrate, image display apparatus, and information display and reproduction apparatus using image display apparatus

Also Published As

Publication number Publication date
FR2748347B1 (fr) 1998-07-24
FR2748347A1 (fr) 1997-11-07
JPH1097835A (ja) 1998-04-14
US5903108A (en) 1999-05-11

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