EP1407443B1 - Method for monitoring a plasma display panel with discharge between triad-mounted electrodes - Google Patents

Description

• une dalle avant et une dalle arrière parallèles ménageant entre elles un espace rempli de gaz de décharge,
• l'une des dalles 12 comprenant au moins un premier réseau d'électrodes 5 et l'autre dalle 11 comprenant au moins un deuxième réseau de triades d'électrodes 13, 20, 14 dont la direction générale est approximativement orthogonale à celle des électrodes 5 du premier réseau,
• les espaces situés aux croisements des électrodes 5 du premier réseau et des triades d'électrodes 13, 20, 14 du second réseau d'électrodes constituant une matrice de zones 9 de décharges lumineuses et de points de l'image à visualiser,
• les électrodes des triades 13, 20, 14 étant revêtues d'une couche diélectrique 17 pour obtenir l'effet mémoire classique selon lequel une décharge peut être générée entre ces électrodes par application d'une tension inférieure à la tension d'amorçage.

With reference to the document FR 2790583 (SAMSUNG), in particular figure 4 of this document reproduced schematically hereafter at figure 1 the invention relates to a method for controlling a plasma display panel for displaying alternating current images, co-planar maintenance discharges, and memory effect, of the type comprising:

• a front slab and a rear slab parallel between them a space filled with discharge gas,
• one of the slabs 12 comprising at least one first electrode array 5 and the other slab 11 comprising at least one second array of electrode triads 13, 20, 14 whose general direction is approximately orthogonal to that of the electrodes 5 of the first network,
• the spaces at the intersections of the electrodes 5 of the first array and the electrode triads 13, 20, 14 of the second array of electrodes constituting a matrix of zones 9 of light discharges and points of the image to be displayed,
• the electrodes of the triads 13, 20, 14 being coated with a dielectric layer 17 to obtain the conventional memory effect according to which a discharge can be generated between these electrodes by applying a voltage lower than the starting voltage.

Generally, the adjacent discharge zone walls are partially coated with phosphors emitting different colors when excited by ultraviolet radiation from the discharges; thus, the adjacent points corresponding to these zones of different colors are associated in pixels or elements of the image to be displayed.

Generally, the discharge zones, at least those of different colors, are separated by barriers.

The memory effect mentioned above is obtained in a discharge zone 9 when charges are deposited on the surface of the dielectric 17 in this zone, in particular by application of a so-called pulse. addressing between the electrode 5 and at least one of the opposite electrodes of the triad 14, 20, 13 which intersect in this area; the dielectric layer is generally coated with a protective layer and secondary electron emission, for example based on MgO.

• classiquement, l'application d'au moins une série d'impulsions de tension de maintien entre les électrodes opposées 13, 14 de chaque triade de manière à générer des décharges de maintien dans chacune des zones de croisement 9 « adressées », c'est à dire celle dans lesquelles on souhaite maintenir une décharge ;
• en outre, à un instant antérieur (revendication 3) ou égal (revendication 6) à celui de l'application d'une impulsion de maintien de cette série, application d'une impulsion sur l'électrode centrale 20 de ladite triade de manière à obtenir :
  • o soit (revendication 4) l'élévation du potentiel de l'électrode centrale 20 au niveau du potentiel le plus élevé [ central = anode ] des deux électrodes opposées 13, 14 au moment de ladite impulsion de maintien générant une décharge lumineuse de maintien, puis, lorsque ladite décharge décroît, abaissement du potentiel de cette électrode centrale 20 au niveau du potentiel le plus bas des deux électrodes opposées 13, 14 [ central = cathode ] .
  • o soit (revendication 5) l'abaissement du potentiel de l'électrode centrale 20 au niveau du potentiel le plus bas [ central = cathode ] des deux électrodes opposées 13, 14 au moment de ladite impulsion de maintien générant une décharge lumineuse de maintien, puis, lorsque ladite décharge décroît, élévation du potentiel de cette électrode centrale 20 au niveau du potentiel le plus élevé des deux électrodes opposées 13, 14 [ central = anode ].

To obtain a succession of holding discharges in the zones thus "addressed", the control method described in this document comprises:

• conventionally, the application of at least one set of holding voltage pulses between the opposite electrodes 13, 14 of each triad so as to generate holding discharges in each of the "addressed" crossing zones 9 is to say the one in which one wishes to maintain a discharge;
• in addition, at a previous time (claim 3) or equal (claim 6) to that of the application of a holding pulse of this series, application of a pulse on the central electrode 20 of said triad so as to get :
  • or (claim 4) raising the potential of the central electrode 20 to the level of the highest potential [central = anode] of the two opposite electrodes 13, 14 at the time of said holding pulse generating a holding light discharge, then, when said discharge decreases, lowering the potential of this central electrode 20 at the lowest potential of the two opposite electrodes 13, 14 [central = cathode].
  • o either (claim 5) the lowering of the potential of the central electrode 20 at the lowest potential [central = cathode] of the two opposite electrodes 13, 14 at the time of said holding pulse generating a holding light discharge, then, when said discharge decreases, raising the potential of this central electrode 20 at the highest potential of the two opposite electrodes 13, 14 [central = anode].

The chronograms corresponding to the staggering of pulses and discharges are represented on the one hand by figures 5 and 6 of this document, on the other hand to figures 8 and 9 .

Still according to this document FR 2790583 , the central electrode 20 must be thin so as not to increase the electrostatic capacity of the holding electrodes of each triad.

• après une impulsion d'adressage classique appliquée à un croisement d'une électrode 5 du premier réseau et d'une triade d'électrodes 13, 20, 14 du second réseau d'électrodes, entre cette électrode 5 d'adressage et au moins une électrode de cette triade, on obtient la répartition de charges illustrée à la figure 2A, l'électrode 14 étant portée à + 300 V par rapport aux autres électrodes 20 (0 V) et 13 (0 V) ; des électrons sont donc accumulés sur une électrode latérale de la triade, et des ions sont accumulés principalement sur l'électrode centrale de la triade.
• comme dans une séquence d'entretien classique, les potentiels des deux électrodes latérales sont inversés et l'électrode 13 est portée à + 200 V par rapport à l'électrode latérale opposée 14 (0 V) ; au moment de l'application de cette première impulsion de maintien, le potentiel de l'électrode centrale 20 est alors élevé au niveau du potentiel le plus élevé des deux électrodes opposées 13, 14, soit ici 200 V, et l'électrode centrale joue alors le rôle d'anode ; on aboutit à la configuration décrite à la figure 2B1 et une première décharge lumineuse principale de maintien surgit (voir flèche) qui entraîne l'inversion des charges représentée à la figure 2C1 ; lors de cette inversion de charges, les électrons s'étalent sur la largeur de l'électrode centrale 20 et sur celle de l'électrode latérale 13, ce qui donne lieu à un allongement important de la pseudo-colonne positive du plasma et donc à une décharge de bon rendement lumineux ;
• puis, lorsque cette décharge décroît, le potentiel de l'électrode centrale 20 est abaissé au niveau du potentiel le plus bas des deux électrodes opposées 13, 14, ici 0 V, et l'électrode centrale joue alors le rôle de cathode, comme représenté à la figure 2B2 ; le mouvement des charges qui s'amorce alors (flèches) génère une première décharge lumineuse secondaire de maintien et aboutit à la distribution des charges représentée à la figure 2C2 ; cette décharge présente un mauvais rendement lumineux, car elle ne donne pas lieu à un étalement significatif et important d'électrons ;
• on applique maintenant la deuxième impulsion de maintien en inversant à nouveau les potentiels des deux électrodes latérales ; l'électrode 14 est maintenant portée à + 200V par rapport à l'électrode latérale opposée 13 (0 V) ; au moment de l'application de cette deuxième impulsion de maintien, le potentiel de l'électrode centrale 20 est alors à nouveau élevé au niveau du potentiel le plus élevé des deux électrodes opposées 13, 14, soit ici 200 V, et l'électrode centrale joue alors le rôle d'anode ; on aboutit à la configuration décrite à la figure 2D1 ; la deuxième décharge lumineuse principale de maintien (voir flèche) qu'on attend n'a quasiment pas lieu, car la zone centrale de la surface du diélectrique est fortement déchargée et l'effet mémoire est en partie perdu ; la séquence précédente a donc conduit à un auto-effacement ; la configuration des charges à laquelle on aboutit est très peu modifiée (figure 2F1).
• ensuite, le potentiel de l'électrode centrale 20 est à nouveau abaissé au niveau du potentiel le plus bas des deux électrodes opposées 13, 14, ici 0 V, et l'électrode centrale joue alors le rôle de cathode, comme représenté à la figure 2D2 ; le mouvement des charges qui s'amorce alors (flèches) génère une deuxième décharge lumineuse secondaire de maintien et aboutit à la distribution des charges représentée à la figure 2F2 ; cette décharge présente un mauvais rendement lumineux, car l'étalement auquel elle donne lieu concerne ici les ions ;
• après ce premier cycle complet de maintien comprenant deux impulsions principales de maintien, on aborde alors un deuxième cycle ; on applique ainsi la première impulsion de maintien du deuxième cycle en inversant à nouveau les potentiels des deux électrodes latérales ; l'électrode 13 est maintenant portée à + 200V par rapport à l'électrode latérale opposée 14 (0V) ; au moment de l'application de cette impulsion de maintien, le potentiel de l'électrode centrale 20 est alors élevé au niveau du potentiel le plus élevé des deux électrodes opposées 13, 14, soit ici 200 V, et l'électrode centrale joue le rôle d'anode ; on aboutit à la configuration décrite à la figure 2G1 ; et une nouvelle décharge lumineuse principale de maintien surgit (voir flèche) qui entraîne l'inversion des charges représentée à la figure 2H1, identique à la figure 2C1 représentant la fin de la première décharge de maintien ; lors de cette inversion de charges, les électrons s'étalent sur la largeur de l'électrode centrale et sur celle de l'électrode latérale 13, ce qui donne lieu à un allongement important de la pseudo-colonne positive du plasma et donc à une décharge de bon rendement lumineux ;

In the coplanar maintenance discharge plasma panels, discharges occur by charge transfer through zone 9 onto the inner surface of the dielectric layer 17 of slab 11 carrying the coplanar electrodes, here the triads 13 , 2014 ; we will now describe the various steps of charge transfer which give rise, possibly, to maintenance light discharges in the case of controlling the panel as described in the document FR 2790583 ; 2A to 2H1, where the zones filled with signs - _- - represent negative charges or electrons on the surface of the dielectric 17, where the gridded zones correspond to positive charges or ions on the surface of the dielectric 17:

• after a conventional addressing pulse applied to a crossing of an electrode 5 of the first array and an electrode triad 13, 20, 14 of the second array of electrodes, between this addressing electrode 5 and at least one electrode of this triad, we obtain the load distribution illustrated in FIG. Figure 2A the electrode 14 being raised to +300 V relative to the other electrodes (0 V) and 13 (0 V); electrons are thus accumulated on a lateral electrode of the triad, and ions are accumulated mainly on the central electrode of the triad.
• as in a conventional maintenance sequence, the potentials of the two side electrodes are reversed and the electrode 13 is raised to + 200 V relative to the opposite lateral electrode 14 (0 V); at the moment of application of this first holding pulse, the potential of the central electrode 20 is then raised at the highest potential of the two opposite electrodes 13, 14, here 200 V, and the central electrode plays then the role of anode; we arrive at the configuration described in Figure 2B1 and a first main luminous discharge of maintenance arises (see arrow) which causes the reversal of the charges represented in FIG. figure 2C1 ; during this inversion of charges, the electrons are spread over the width of the central electrode 20 and that of the lateral electrode 13, which gives rise to an elongation important of the positive pseudo-column of the plasma and thus to a discharge of good luminous yield;
• then, when this discharge decreases, the potential of the central electrode 20 is lowered at the lowest potential of the two opposite electrodes 13, 14, here 0 V, and the central electrode then plays the role of cathode, as shown to the figure 2B2 ; the movement of the charges which then starts (arrows) generates a first secondary luminous discharge of maintenance and leads to the distribution of the charges represented in FIG. Figure 2C2 ; this discharge has a poor light output, because it does not give rise to a significant and significant spread of electrons;
• the second holding pulse is now applied by reversing again the potentials of the two lateral electrodes; the electrode 14 is now raised to + 200V relative to the opposite lateral electrode 13 (0 V); at the moment of application of this second holding pulse, the potential of the central electrode 20 is then raised again at the highest potential of the two opposite electrodes 13, 14, here 200 V, and the electrode central then plays the role of anode; we arrive at the configuration described in figure 2D1 ; the second main maintenance light discharge (see arrow) that is expected is almost non-existent because the central area of the surface of the dielectric is heavily discharged and the memory effect is partly lost; the preceding sequence has therefore led to an auto-erasure; the resulting configuration of the loads is very little modified ( Figure 2F1 ).
• then, the potential of the central electrode 20 is again lowered at the lowest potential of the two opposite electrodes 13, 14, here 0 V, and the central electrode then plays the role of cathode, as shown in FIG. figure 2D2 ; the movement of the charges which then begins (arrows) generates a second secondary luminous discharge of maintenance and leads to the distribution of the charges represented in FIG. Figure 2F2 ; this discharge has a poor light output, because the spreading to which it gives rise concerns here the ions;
• after this first complete maintenance cycle comprising two main sustaining pulses, then a second cycle is approached; we apply thus the first pulse maintaining the second cycle by reversing again the potentials of the two lateral electrodes; the electrode 13 is now raised to + 200V relative to the opposite lateral electrode 14 (0V); at the moment of application of this holding pulse, the potential of the central electrode 20 is then raised at the highest potential of the two opposite electrodes 13, 14, here 200 V, and the central electrode plays the anode role; we arrive at the configuration described in Figure 2G1 ; and a new main luminous discharge of maintenance arises (see arrow) which causes the reversal of the loads represented in the figure 2H1 , identical to the figure 2C1 representing the end of the first sustainment discharge; during this inversion of charges, the electrons spread over the width of the central electrode and that of the lateral electrode 13, which gives rise to a significant elongation of the positive pseudo-column of the plasma and therefore to a discharge of good light output;

The second maintenance cycle then continues as the first cycle and the movements of the charges are identical to that of the first cycle: from the end of this first main sustaining discharge of the second cycle ( figure 2C1 similar to 2H1 ), a secondary discharge of poor efficiency leads to self-erasure ( Figures 2B2 and 2C2 ), a very low main sustaining discharge ( Figures 2D1 and 2F1 ), finally another secondary discharge of poor performance ( Figures 2D2 and 2F2 ).

If necessary, other identical cycles of maintenance succeed each other until the desired holding time is exhausted, and the voltage pulses applied to the electrodes form a series of holding pulses.

It can therefore be seen that over a complete cycle comprising two main pulses and two secondary sustaining pulses, a single discharge has a good luminous efficiency; overall, the luminous efficiency of the plasma panel is therefore not satisfactory when using, for coplanar maintenance, triad arrays of electrodes and the control method described in the document. FR 2790583 .

It can thus be seen that, in a series of holding pulses, the central electrode alternately plays the role of anode and cathode.

Moreover, the small width of the central electrode of these triads, as described and recommended in the document FR 2790583 limits the possibilities of electron spreading and elongation of the positive pseudo-column of the plasma, which brings about no improvement in light efficiency compared to conventional coplanar configurations, the improvement of the light output not being elsewhere not the purpose of this document.

The object of the invention is to propose a coplanar plasma panel structure and a method for controlling the pulses for maintaining this panel, bringing about a significant improvement in the luminous efficiency; the invention is particularly intended to avoid the aforementioned drawbacks.

To this end, the subject of the invention is a method for controlling a plasma display panel for viewing alternating-current images, co-planar maintenance discharges, and memory effects, according to claim 1.

With this arrangement, the luminous efficiency of the panel is substantially improved; according to the invention, and contrary to the control methods described in the document FR 2790583 already mentioned, during the entire duration of the holding operations (or "maintenance phases"), the potential of the central electrode is always strictly greater than that of one or the other lateral electrode, so that this central electrode always plays the role of anode.

An advantageous way to make the central electrode play the role of anode during the entire holding operation (or all the maintenance phases) is to make this electrode floating; indeed, in principle, the capacitive divider bridge, in such a configuration, the central electrode then has a potential between the potential of the two adjacent side electrodes so that the potential of the central electrode is always strictly greater than that of the central electrode. one or the other side electrode; the economic advantage of such a configuration is that it does not require a specific power supply for the central electrodes of the panel or switches or "drivers" for their power supply.

To obtain an even greater improvement in light output, it is preferable, contrary to the teachings of the document FR 2790583 already cited, that the central electrode has a width sufficiently high to promote the spreading of electrons and elongation of the pseudo-positive column of the plasma during sustaining discharges; ; preferably, the width of this central electrode is greater than 80 microns.

The width of this central electrode may especially be between 100 and 200 μm.

• les gaps séparant et isolant les électrodes adjacentes d'une même triade sont inférieurs à 80 µm, et
• l'espacement entre les dalles ménageant l'espace rempli de gaz de décharge est supérieur à 130 µm.

Advantageously, the central electrode may even be wider than 200 microns; especially in this case, there is a risk then of a matrix ignition of the discharges, ie a priming of these discharges, not between the electrodes of the triad (coplanar ignition case), but between an electrode of the first network belonging to a slab and an electrode of a triad belonging to the other slab; we try to avoid matrix ignitions because, unlike coplanar ignitions, they fluctuate widely from one cell to another panel depending on the electrical characteristics of the wall materials of these cells, including phosphors, which differ from one another. cell to another; these electrical characteristics include the permittivity, the static charge, the dielectric thickness, the electronic secondary emission; in order to avoid or limit this matrix ignition, preferably:

• the gaps separating and isolating the adjacent electrodes of the same triad are less than 80 μm, and
• the spacing between the slabs leaving the space filled with discharge gas is greater than 130 microns.

Advantageously, the width of the central electrode is then greater than the width of each of the lateral electrodes.

Between each series of holding pulses, selective addressing or selective erasure operations are generally carried out; prior to selective addressing, an English preparation operation (or "priming") and an erasure operation, both semi-selective and non-selective, are generally carried out. For this purpose, the invention also relates to the above method according to the invention also comprising, before or after each holding operation, a selective addressing or erasing operation applied only in each of said zones where the it is desired to maintain a light discharge during said series, by applying at least one voltage pulse between the electrode of said first network crossing said zone and at least one of the electrodes of the triad crossing said zone.

In the case of an addressing operation, this is done before each holding operation and the corresponding addressing pulse is adapted in a manner known per se to generate electric charges on the dielectric layer in said zone and thus obtain the well-known memory effect of the plasma panels.

This method corresponds to a conventional control mode by selective addressing, which can be used in the processes where it is addressed successively lines or groups of lines of discharge zones before a maintenance phase (so-called "ADS" or "ADM" cases) or in processes where lines or groups of lines are addressed during maintenance other lines or groups of lines (so-called "AWD").

In the case of an erase operation, this occurs after each holding operation and the corresponding erasure pulse is adapted in a manner known per se to suppress the electrical charges on the dielectric layer in said area and terminate the memory effect.

This method corresponds to a conventional control mode by selective erasure.

Preferably, the voltage selective pulse is applied between the electrode of said first network crossing said zone and the central electrode of the triad crossing said zone.

By transferring all the selective addressing or erasing operations to the central electrodes, the lateral electrodes of series of adjacent discharge zones can be grouped together, to the point of even using common electrodes, for example as a lateral electrode. lower of a triad corresponding to a line n and as upper lateral electrode of the triad corresponding to the next adjacent line (n + 1); thus, the subject of the invention is also a method according to the invention in which all the areas served by the same triad forming a line of said panel, on any two adjacent lines traversed respectively by a first triad on the one hand and by a second triad on the other hand, the lateral electrode of the first triad is electrically connected to the same potential as the lateral electrode closest to the second triad.

Preferably, said two electrically connected electrodes form an electrode common to two adjacent lines.

The invention also relates to a plasma panel that can be used for carrying out the method according to the invention according to claim 8.

In the case cited above where the central electrodes are floating and without external connections, the panel does not include a specific power supply for these electrodes or switches or "drivers" for their power supply.

Preferably, the width of the central electrode is greater than 80 microns; other preferences concerning the geometry of the electrodes and / or cells of the panel have been mentioned above, especially the advantageous case where the width of the central electrode is greater than the width of each of the lateral electrodes.

Preferably, all the areas served by the same triad forming a line of the panel, on any two adjacent lines traversed respectively by a first triad on the one hand and by a second triad on the other hand, the lateral electrode of the first triad is electrically connected to the same potential as the nearest lateral electrode of the second triad; preferably, said two electrically connected electrodes form an electrode common to two adjacent lines.

• la figure 1, déjà décrite, est une vue schématique en coupe d'une cellule à trois électrodes coplanaires d'un panneau à plasma de l'art antérieur, avec les mêmes références que la figure 4 du document FR 2790583 ;
• les figures 2A à 2H1 (pas de figure 2E), déjà décrites, illustrent l'évolution des charges électriques et le surgissement des décharges lumineuses dans une cellule de la figure 1, lorsqu'elle est pilotée selon l'art antérieur comme décrit dans le document FR 2790583 ;
• les figures 3A à 3F illustrent l'évolution des charges électriques et le surgissement des décharges lumineuses dans une cellule analogue à celle de la figure 1 mais avec une électrode centrale plus large selon l'invention, lorsqu'elle est pilotée selon un mode de réalisation de l'invention ;
• la figure 4 illustre schématiquement, par quatre chronogrammes référencés 20, 13, 14 et 5, l'évolution, au cours du temps, du potentiel appliqué aux électrodes d'une triade coplanaire (électrodes latérales 13, 14 et électrode centrale 20) et aux électrodes d'adressage 5 selon un mode de réalisation de l'invention ;
• les figures 5A à 5C illustrent l'étalement des décharges dans une cellule à deux électrodes coplanaires d'un panneau à plasma de l'art antérieur, en fonction de la largeur des électrodes coplanaire et du gap séparant ces électrodes ;
• la figure 6 représente une vue de dessus et deux vues en coupe latérale d'un groupe de trois cellules adjacentes de différentes couleurs d'un panneau à plasma selon un mode particulier de réalisation de l'invention, où chaque électrode latérale d'une triade est commune à deux lignes adjacentes du panneau et est réalisée en matériau conducteur transparent ;
• la figure 7 représente une vue de dessus analogue à celle de la figure 6, à la différence près que les électrodes latérales sont formées de grilles de conducteurs opaques ;
• la figure 8 représente une variante de la figure 6 avec une électrode centrale de grande largeur dotée de bus disposés au niveau des bords d'amorçage de décharge de cette électrode ;
• la figure 9 représente une variante de la figure 7 avec une électrode centrale de grande largeur ;

The invention will be better understood on reading the description which follows, given by way of nonlimiting example, and with reference to the appended figures in which:

• the figure 1 , already described, is a schematic sectional view of a cell with three coplanar electrodes of a plasma panel of the prior art, with the same references as the figure 4 of the document FR 2790583 ;
• the Figures 2A to 2H1 (no figure 2E), already described, illustrate the evolution of electric charges and the emergence of light discharges in a cell of the figure 1 when it is driven according to the prior art as described in the document FR 2790583 ;
• the Figures 3A to 3F illustrate the evolution of electric charges and the emergence of light discharges in a cell similar to that of the figure 1 but with a wider central electrode according to the invention, when it is controlled according to an embodiment of the invention;
• the figure 4 illustrates diagrammatically, by four chronograms referenced 20, 13, 14 and 5, the evolution, over time, of the potential applied to the electrodes of a coplanar triad (lateral electrodes 13, 14 and central electrode 20) and to the electrodes of addressing 5 according to one embodiment of the invention;
• the FIGS. 5A to 5C illustrate the spreading of the discharges in a coplanar two-electrode cell of a plasma panel of the prior art, as a function of the width of the coplanar electrodes and the gap separating these electrodes;
• the figure 6 represents a top view and two side sectional views of a group of three adjacent cells of different colors of a plasma panel according to a particular embodiment of the invention, wherein each lateral electrode of a triad is common to two adjacent lines of the panel and is made of transparent conductive material;
• the figure 7 represents a view from above similar to that of the figure 6 with the difference that the side electrodes are formed of opaque conductor grids;
• the figure 8 represents a variant of the figure 6 with a wide-width central electrode provided with buses arranged at the discharge initiation edges of this electrode;
• the figure 9 represents a variant of the figure 7 with a central electrode of great width;

In order to simplify the description and to show the differences and advantages that the invention presents with respect to the prior art, identical references are used for the elements that provide the same functions.

The plasma panel according to the invention is identical to that previously described ( figure 1 ) and the one described in the document FR 2790583 ( figure 4 ), with the difference, essential for optimizing the light output, that the central electrode 20 of each triad is sufficiently wide to promote the elongation of the positive pseudo-column of the plasma and the spreading of the electrons during a light discharge; in practice, the width of this central electrode is greater than the gap between the electrodes; thus, the width of this central electrode is greater than 50 microns, preferably greater than 80 microns; the width of the central electrode of each triad is generally between 100 and 200 microns approximately.

• pendant une impulsion d'adressage classique appliquée à un croisement d'une électrode 5 du premier réseau et d'une triade d'électrodes 13, 20, 14 du second réseau d'électrodes, entre cette électrode 5 d'adressage et au moins une électrode de cette triade, on obtient, après la décharge d'adressage, la répartition de charges illustrée à la figure 3A, l'électrode latérale 14 étant portée à + 300 V par rapport aux autres électrodes latérale 13 (0 V) ou centrale 20 (0 V) ; des électrons sont donc accumulés sur une électrode latérale de la triade, et des ions sont accumulés principalement sur l'électrode centrale de la triade, qui est plus large que dans l'art antérieur.
• comme dans une séquence d'entretien classique, les potentiels des deux électrodes latérales sont inversés et l'électrode 13 est portée à + 200V par rapport à l'électrode latérale opposée 14 (0 V) ; au moment de l'application de cette première impulsion de maintien, le potentiel de l'électrode centrale 20 est alors élevé au niveau du potentiel le plus élevé des deux électrodes opposées 13, 14, soit ici 200 V et est maintenu à cette valeur jusqu'à la fin de la première impulsion de maintien contrairement à l'art antérieur ; l'électrode centrale joue alors le rôle d'anode ; on aboutit à la configuration décrite à la figure 3B et, comme dans l'art antérieur, une première décharge lumineuse principale de maintien surgit (voir flèche) qui entraîne l'inversion des charges représentée à la figure 3C ; lors de cette inversion de charges, les électrons s'étalent sur l'électrode centrale 20 qui est beaucoup plus large que dans l'art antérieur et sur l'électrode latérale 13, ce qui donne lieu à un allongement plus important que dans l'art antérieur de la pseudo-colonne positive du plasma et donc à une décharge de meilleur rendement lumineux ;
• on applique ensuite directement la deuxième impulsion de maintien en inversant à nouveau les potentiels des deux électrodes latérales ; l'électrode 14 est maintenant portée à + 200 V par rapport à l'électrode latérale opposée 13 (0 V) ; au moment de l'application de cette deuxième impulsion de maintien, le potentiel de l'électrode centrale 20 est toujours maintenu au niveau du potentiel le plus élevé des deux électrodes opposées 13, 14, soit ici 200 V ; l'électrode centrale joue toujours le rôle d'anode ; on aboutit à la configuration décrite à la figure 3D et une deuxième décharge lumineuse principale de maintien (voir flèche) se déclenche qui entraîne l'inversion des charges représentée à la figure 3F avec un état transitoire représenté à la figure 3E ; lors de cette inversion de charges, les électrons s'étalent à nouveau sur l'électrode centrale 20 qui est beaucoup plus large que dans l'art antérieur et sur l'électrode latérale 14, ce qui donne lieu à un allongement plus important de la pseudo-colonne positive du plasma et donc à une décharge de rendement lumineux plus élevé ;
• après ce premier cycle complet de maintien comprenant uniquement deux impulsions principales de maintien, on aborde alors un deuxième cycle ; on applique alors une première impulsion principale de maintien du deuxième cycle en inversant à nouveau les potentiels des deux électrodes latérales mais toujours sans changer le potentiel de l'électrode centrale 20 ; l'électrode 13 est maintenant portée à + 200V par rapport à l'électrode latérale opposée 14 (0 V) et l'électrode centrale 20 joue toujours le rôle d'anode ; cette configuration entraîne l'inversion des charges déjà représentée à la figure 3C, représentant la fin de la première décharge de maintien du deuxième cycle, et la décharge obtenue présente un très bon rendement lumineux comme pour le premier cycle.

The control method of the plasma panel according to the invention will now be described, in particular in a holding phase according to the invention, with reference to the Figures 3A to 3F which represent the evolution of the charges on the surface of the dielectric layer 17, with the same conventions of representation as for the Figures 2A to 2H1 :

• during a conventional addressing pulse applied to a crossing of an electrode 5 of the first array and an electrode triad 13, 20, 14 of the second array of electrodes, between this addressing electrode 5 and at least one electrode of this triad, we obtain, after the discharge of addressing, the distribution of charges illustrated in FIG. figure 3A , the lateral electrode 14 being brought to +300 V relative to the other lateral electrodes 13 (0 V) or central 20 (0 V); electrons are thus accumulated on a lateral electrode of the triad, and ions are accumulated mainly on the central electrode of the triad, which is wider than in the prior art.
• as in a conventional maintenance sequence, the potentials of the two side electrodes are reversed and the electrode 13 is brought to + 200V relative to the opposite lateral electrode 14 (0 V); at the time of application of this first holding pulse, the potential of the central electrode 20 is then raised at the highest potential of the two opposite electrodes 13, 14, here 200 V and is maintained at this value until at the end of the first sustain pulse contrary to the prior art; the central electrode then plays the role of anode; we arrive at the configuration described in figure 3B and, as in the prior art, a first main sustaining light discharge arises (see arrow) which causes the charge reversal shown in FIG. figure 3C ; during this inversion of charges, the electrons are spread over the central electrode 20 which is much wider than in the prior art and on the lateral electrode 13, which gives rise to a longer elongation than in the prior art of the pseudo-positive column of the plasma and therefore to a discharge of better light output;
• the second holding pulse is then applied directly by reversing the potentials of the two lateral electrodes again; the electrode 14 is now raised to + 200 V with respect to the opposite lateral electrode 13 (0 V); at the time of application of this second holding pulse, the potential of the central electrode 20 is always maintained at the highest potential of the two opposite electrodes 13, 14, here 200 V; the central electrode always plays the role of anode; we arrive at the configuration described in 3D figure and a second main luminous discharge of maintenance (see arrow) is triggered which causes the reversal of the charges represented in FIG. figure 3F with a transitional state represented at figure 3E ; during this inversion of charges, the electrons are spread again on the central electrode 20 which is much wider than in the prior art and on the lateral electrode 14, which gives rise to a longer elongation of the pseudo-positive column of the plasma and therefore to a discharge of higher light output;
• after this first complete maintenance cycle comprising only two main sustaining pulses, then a second cycle is approached; we then apply a first main impulse to maintain the second cycle by reversing the potentials of the two side electrodes again but still without changing the potential of the central electrode 20; the electrode 13 is now raised to + 200V relative to the opposite lateral electrode 14 (0 V) and the central electrode 20 still acts as anode; this configuration leads to the reversal of the charges already represented in the figure 3C , representing the end of the first sustaining discharge of the second cycle, and the discharge obtained has a very good light output as for the first cycle.

The second maintenance cycle then continues as the first cycle and the movements of the charges are identical to those of the first cycle: from the end of this first sustaining discharge of the second cycle ( figure 3C ), there is a second sustaining discharge of the second cycle ( 3D figures at 3F ) also having a very good light output.

If necessary, other identical cycles of maintenance succeed each other until the desired holding time is exhausted, and the voltage pulses applied to the electrodes form a series of holding pulses.

It can thus be seen that the series of holding pulses only cause discharges of very good luminous efficiency; overall, the luminous efficiency of the plasma panel is therefore substantially improved and optimized, thanks to a control system where the central electrode always plays the role of anode and thanks to the width of the central electrode, greater than in the prior art.

According to the invention, the elongation of the discharge that is obtained allows, in each zone, to increase, within the plasma, the volume of the pseudo-positive column where there is a weak electric field and where the emission of Ultraviolet photons are generated with very good performance.

• par augmentation de la largeur des électrodes de chaque paire, de manière à obtenir un allongement de la décharge comme représenté à la figure 5B ; mais les risques d'interférences entre différentes zones de décharge (« crosstalk » en langue anglaise) imposent une limite supérieure à cette largeur, et donc à l'amélioration du rendement lumineux ;
• par augmentation du gap qui sépare les électrodes coplanaires d'une paire, afin de limiter le champ électrique dans les zones de décharge ; on obtient alors un allongement du chemin de décharge dans la profondeur de chaque zone comme représenté à la figure 5C, parce que les lignes de champ prennent alors approximativement la forme de demi-cercles (contrairement à la figure 5B où le gap est trop petit) ; mais cette augmentation du gap modifie défavorablement les conditions d'allumage des décharges (loi de Paschen), nécessite des tensions d'allumage élevées, et entraîne des surcoûts prohibitifs au niveau des composants électroniques ; la nécessité de pouvoir piloter le panneau avec des impulsions de tension suffisamment faible limite donc considérablement l'augmentation du gap.

In the prior art, plasma panels with pairs of coplanar electrodes 3, 4 for holding as shown schematically in FIG. Figure 5A at least two means of improving the light output are known:

• by increasing the width of the electrodes of each pair, so as to obtain an elongation of the discharge as shown in FIG. figure 5B ; but the risk of interference between different discharge zones ("crosstalk" in English) imposes an upper limit to this width, and therefore to the improvement of the light output;
• by increasing the gap separating the coplanar electrodes of a pair, in order to limit the electric field in the discharge zones; we then obtain an extension of the discharge path in the depth of each zone as represented in FIG. Figure 5C because the field lines then take approximately the form of semicircles (unlike the Figure 5B where the gap is too small); but this increase in the gap adversely modifies the ignition conditions of the discharges (Paschen's law), requires high ignition voltages, and leads to prohibitive additional costs for the electronic components; the need to be able to drive the panel with sufficiently low voltage pulses therefore considerably limits the increase in the gap.

The invention makes it possible to use these two means while avoiding these limitations; the central electrode makes it possible to space the two opposite coplanar electrodes without modifying the ignition conditions of the discharges.

• comme l'électrode centrale est maintenue au même potentiel pendant toute la phase de maintien, le système de pilotage du panneau est donc très simple à mettre en oeuvre, donc très économique ;
• comme l'électrode centrale est plus large que dans l'art antérieur, cette électrode est facile à réaliser à moindre coût.

The invention furthermore has the following advantages:

• since the central electrode is maintained at the same potential throughout the holding phase, the control system of the panel is therefore very simple to implement, therefore very economical;
• since the central electrode is wider than in the prior art, this electrode is easy to produce at a lower cost.

• dans une première phase I non sélective dite de préparation ou de « priming » en langue anglaise, on applique à l'électrode centrale 20 du deuxième réseau coplanaire une tension uniformément croissante, supérieure à celle de l'électrode d'adressage 5 du premier réseau, de manière à générer une décharge dite « à résistance positive » entre l'électrode centrale 20 et une électrode latérale et à produire ainsi les charges électriques dites « primaires » nécessaires à la phase d'adressage, tout en générant un minimum d'émission lumineuse pour conserver un bon contraste d'image ;
• dans une deuxième phase II toujours non sélective dite d'effacement, sans modifier la tension de l'électrode d'adressage 5, on applique à l'électrode centrale 20 une tension uniformément décroissante et à l'une 14 seulement des électrodes latérales une tension constante adaptée pour être en permanence supérieure à celle de l'électrode centrale 20, de manière à produire une décharge de faible émission lumineuse pour effacer les charges électriques stockées à la surface de la couche diélectrique 17 lors de l'opération précédente de préparation ;
• dans une troisième phase III cette fois sélective dite d'adressage, tout en maintenant la tension de l'électrode latérale 14 au même potentiel que dans la phase précédente et en appliquant à l'autre électrode latérale 13 une tension identique à celle la plus basse de l'électrode d'adressage 5, tout en maintenant, en dehors des impulsions d'adressage, la tension de l'électrode centrale 20 entre celle des deux électrodes latérales 13, 14, on applique des impulsions d'adressage d'une part simultanément aux différentes électrodes 5 du premier réseau et d'autre part successivement aux différentes électrodes centrales 20 du deuxième réseau, de manière à obtenir un dépôt de charges électriques à la surface du diélectrique 17 dans les zones où l'on souhaite maintenir des décharges électriques dans la phase suivante de maintien ;
• dans une dernière phase IV non sélective de maintien, après avoir appliqué approximativement la même tension positive Ve aux trois électrodes coplanaires 13, 20, 14 tout en maintenant les électrodes d'adressage 5 du premier réseau à une tension nulle, on applique alternativement une tension nulle à chaque électrode latérale 13, 14 sans modifier la tension de l'électrode centrale 20 ; ainsi, cette électrode centrale 20 joue le rôle d'anode pendant toute la phase de maintien ; la tension Ve est adaptée d'une manière connue en elle-même pour obtenir des décharges dans les zones précédemment adressées sans en obtenir dans les zones non adressées.

Referring to the figure 4 , a complete example of the "ADS" type of diagram of a complete cycle of addressing and maintaining the discharge zones of a plasma panel according to the invention will now be described:

• in a first non-selective phase I called preparation or "priming" in English, is applied to the central electrode 20 of the second coplanar network a uniformly increasing voltage, greater than that of the addressing electrode 5 of the first network , so as to generate a so-called "positive resistance" discharge between the central electrode 20 and a lateral electrode and thus to produce the so-called "primary" electrical charges necessary for the addressing phase, while generating a minimum of light emission to maintain a good image contrast;
• in a second phase II still non-selective said erasing, without changing the voltage of the addressing electrode 5, is applied to the central electrode 20 a uniformly decreasing voltage and only one 14 of the lateral electrodes a voltage constant adapted to be permanently higher than that of the central electrode 20, so as to produce a discharge of low light emission to erase the electric charges stored on the surface of the dielectric layer 17 during the previous preparation operation;
• in a third phase III this time selective so-called addressing, while maintaining the voltage of the lateral electrode 14 at the same potential as in the previous phase and applying to the other lateral electrode 13 a voltage identical to the lowest one of the addressing electrode 5, while maintaining, apart from the addressing pulses, the voltage of the central electrode 20 between that of the two lateral electrodes 13, 14, addressing pulses are applied on the one hand simultaneously to the different electrodes 5 of the first network and secondly successively to the different central electrodes 20 of the second network, so as to obtain a deposit of electrical charges on the surface of the dielectric 17 in the areas where it is desired to maintain electrical discharges in the next phase of maintenance;
• in a last non-selective holding phase IV, after having applied approximately the same positive voltage Ve to the three coplanar electrodes 13, 20, 14 while maintaining the addressing electrodes 5 of the first network at a zero voltage, alternately applying a voltage zero at each lateral electrode 13, 14 without changing the voltage of the central electrode 20; thus, this central electrode 20 acts as anode during the entire holding phase; the voltage Ve is adapted in a manner known per se to obtain discharges in the previously addressed areas without obtaining them in the unaddressed areas.

After this last maintenance phase, a new addressing and holding cycle can resume in a manner known per se for viewing images on an alternating plasma memory effect panel.

Thus, according to an advantageous variant of the invention, all the selective addressing or erasing operations are transferred to the central electrode; thanks to this improvement, one can group and electrically connect each lateral electrode of a triad to the side electrode closest to the adjacent triad on the slab.

These two connected electrodes may even only form a single electrode 21, so that the total number of electrodes of the triad network is reduced by one third; thus, the total number of electrodes of the second electrode array, or network of coplanar discharges, is identical, to an electrode, to the total number of electrodes of the coplanar networks of the prior art, which are networks of pairs electrodes; the manufacture of plasma panel slabs and that of the control means according to this variant are therefore not more expensive than that of plasma panels with only two coplanar electrodes of the prior art.

An embodiment of a plasma panel according to this advantageous variant will now be described, with reference to FIGS. figures 5 and 6 which represent plasma panel discharge areas, where each pixel P comprises three adjacent discharge areas 9R, 9G, 9B, separated by barriers 16 extending from the dielectric layer 15 of the back panel carrying the first network of electrodes 5 to the dielectric layer 17 of the front plate carrying the electrode triads 13, 20, 14; the adjacent triads 13, 20, 14 on the one hand and 13 ', 20', 14 '(not shown) on the other hand are separated from each other by barriers 6 orthogonal to the barriers 16; the electrodes 5 of the first network are here shifted and positioned under the barriers 16, and are provided with branches 51 positioned at each discharge zone 9R, 9G, 9B, and extending towards the middle of this zone; preferably, the electrodes 5 of the first network are provided with means for promoting the formation of the maintenance discharges between each lateral electrode 13, 14 of a triad and the central electrode 20 of this same triad: thus, it is preferable to find two branches 51 per discharge zone, positioned on either side of the central electrode 20; the barriers 6, 16 delimit with the dielectric layers 15, 17 of the discharge cells; the walls of the discharge cells 9R, 9G, 9B, except that of the front slab, are coated with phosphors of different colors, respectively red, green and blue, adapted to emit radiation of these colors when they are excited by the ultraviolet radiation from the discharges; in areas overlying the electrodes, the dielectric layers are generally coated with a thin layer of protection and secondary electron emission, generally based on MgO.

According to the advantageous variant of the invention which has just been described, the lower lateral electrode 14 of the first triad, corresponding to a line n of the panel, is connected to the same bus 22 'as the upper lateral electrode 13' of the second triad, adjacent to the first, corresponding here to the next line (n + 1) of the panel; as each triad lateral electrode is shared between two adjacent lines, if N is the total number of lines of the panel, there is only a total of only 2N + 1 electrodes in the coplanar network or second network, which simplifies the manufacture of the panel, each electrode being served by a central bus 20, 20 ', or by a lateral bus 22, 22'; the side buses 22, 22 'are opaque and positioned here at the top of the barriers 6, so as not to obscure the emission of visible light from the discharge areas 9R, 9G, 9B.

A lateral bus 22 'then forms, with the two lateral electrodes 14 and 13' to which it is connected, one and the same electrode 21; the whole of the second network of electrodes or network of lines, is formed of alternations of central electrodes 20, 20 'which serve for the selective operations of addressing or erasure, and electrodes 21, common to two lines adjacent discharge areas, which are not used for selective addressing or erasure operations.

According to the embodiment described in figure 6 the electrodes 13, 14, 13 'are made of transparent conductive material, for example tin oxide (SnO) or mixed indium tin oxide ("ITO"), so as not to absorb visible light from the discharge areas 9R, 9G, 9B.

• l'électrode centrale 20, 20' comprend deux conducteurs parallèles opaques 201, 203 présentant chacun un front délimitant l'un des gaps et reliés électriquement entre eux par des dérivations transversales opaques 202 disposées au centre de chaque cellule 9R, 9G, 9B ;
• l'électrode 14 alimentant les cellules 9R, 9G, 9B et l'électrode 13' alimentant les cellules 9'R, 9'G, 9'B de la ligne voisine, toutes deux reliées au même bus 22' pour former l'électrode 21 commune à deux lignes successives, comprennent chacune un conducteur latéral opaque 140 présentant un front délimitant un gap et, disposé parallèlement aux conducteurs 201, 203 de l'électrode centrale 20 ; chaque conducteur latéral 140 est relié électriquement au bus 22' par l'intermédiaire de dérivations opaques en forme de Y, disposées au centre de chaque cellule 9R, 9G, 9B, 9'R, 9'G, 9'B ; chaque dérivation en forme de Y comprend un conducteur principal 141 pour le « pied » du Y, et deux conducteurs secondaires 142, 143 formant les « branches » du Y ; ces dérivations sont reliées au bus 22' par l'intermédiaire des « branches » 142, 143, alors qu'elles sont reliées à l'autre extrémité au conducteur latéral 140 par l'intermédiaire des « pieds » 141 ; une telle disposition en forme de Y des dérivations est avantageuse pour l'évolution de la longueur de décharge en cours de décharge, et, en conséquence, pour le rendement lumineux du panneau.

According to an alternative embodiment of the same type of plasma panel shown in FIG. figure 7 the central electrodes 20, 20 'or lateral electrodes 21 are formed of a sub-network of opaque conductors arranged in a grid; for example :

• the central electrode 20, 20 'comprises two opaque parallel conductors 201, 203 each having an edge delimiting one of the gaps and electrically connected to each other by opaque transverse branches 202 arranged in the center of each cell 9R, 9G, 9B;
• the electrode 14 supplying the cells 9R, 9G, 9B and the electrode 13 'feeding the 9'R, 9'G, 9'B cells of the neighboring line, both connected to the same bus 22' to form the electrode 21 common to two successive lines, each comprise an opaque lateral conductor 140 having a front defining a gap and disposed parallel to the conductors 201, 203 of the central electrode 20; each lateral conductor 140 is electrically connected to the bus 22 'via Y-shaped opaque shunts, arranged at the center of each cell 9R, 9G, 9B, 9'R, 9'G, 9'B; each Y-shaped branch comprises a main conductor 141 for the "foot" of the Y, and two secondary conductors 142, 143 forming the "branches" of the Y; these branches are connected to the bus 22 'via the "branches" 142, 143, while they are connected at the other end to the lateral conductor 140 via the "feet"141; such an Y-shaped arrangement of the taps is advantageous for the evolution of the discharge length during discharge, and, consequently, for the luminous efficiency of the panel.

The grid arrangement of opaque conductors of the central electrodes 20, 20 'and / or side 21 is more economical, because it avoids the expensive implementation of transparent conductive materials, as in the previous embodiment of the invention. figure 6 ; the conductors and branches forming the grids are of a sufficiently small width to limit the occultation of the cells or discharge zones but sufficiently large to obtain the electrical conductivity necessary for obtaining the discharges.

Other forms of grids may be used, such as that of the electrode 13 of the figure 7 , comprising three parallel conductors 131, 132, 133 interconnected by transverse branches 134 disposed above the barriers 16 to limit the occultation of the cells.

The figure 8 represents a variant of the figure 6 (identical references of the components) with a central transparent electrode 20 whose width is greater than that of each of the side electrodes 13 or 14, and which is further provided with two opaque conductive buses 201, 203 which are disposed at the discharge initiation edges of this electrode; as the thickness of such conductive bus is generally greater than the thickness of the transparent portion of the electrode, generally based on ITO, the dielectric layer thickness covering these buses is less than the thickness of the dielectric layer covering the transparent part of the electrode; thus, the dielectric layer thickness being lower than the level of the initiation edges of the central electrode with respect to the thickness between outside of the priming edges, it is advantageous to lower the discharge initiation voltage, to to avoid a matrix start of the discharges, to favor the coplanar initiation in accordance with one of the aims pursued by the invention.

The figure 9 represents a variant of the figure 7 (identical references of the components) with a central electrode 20 whose width is advantageously greater than that of each of the lateral electrodes 13 or 14; the opaque transverse branches 202 of the central electrode 20 and those 134 of the lateral electrodes 13, 14 are here disposed on the barriers 16 delimiting the cells; they may overflow slightly along these barriers.

The present invention has been described with reference to a conventional reciprocating plasma panel and a driving mode where the sustaining discharges involve a charge reversal on the surface of the dielectric; it is obvious to those skilled in the art that it can be applied to other types of billboards and other modes of driving without departing from the scope of the claims below; the invention thus applies in particular to plasma panels with high frequency or radio frequency control, where the holding discharges are at least partially stabilized between the electrodes.

Claims (15)

1. Method for driving an AC image-display plasma panel with coplanar sustain discharges, and with memory effect, the said panel comprising:

   - a front tile and a rear tile, which are parallel and provide between them a space filled with a discharge gas;

   - one (12) of the tiles comprising at least a first array of electrodes (5) and the other tile (11) comprising at least a second array of triads of electrodes (13, 20, 14), the general direction of which is approximately orthogonal to that of the electrodes (5) of the first array;

   - each triad comprising two opposed lateral electrodes (13, 14) and one central electrode (20);

   - the spaces located at the intersections of the electrodes (5) of the first array with the triads of electrodes (13, 20, 14) of the second electrode array forming a matrix of light-discharge regions (9) and of dots of the image to be displayed;

   - the electrodes (13, 20, 14) of the triads being coated with a dielectric layer (17);

   the said method comprising at least one sustain operation by applying a series of sustain voltage pulses between the electrodes of each triad so as to generate sustain discharges in each of the intersection regions (9) in which it is desired to sustain a light discharge;
   characterized in that,
   during the said sustain operation, the voltage of the central electrode (20) of each triad is always superior or equal to the one of one or the other lateral electrode (13, 14);.
   the width of the said central electrode (20) of each triad of said panel is greater than the gaps separating and isolating the adjacent electrodes of the same triad.
2. Method according to Claim 1, characterized in that the width of the said central electrode (20) is greater than 80 µm.
3. Method according to Claim 2, characterized in that the width of the said central electrode (20) is between 100 and 200 µm.
4. Method according to claim 2, characterized in that the width of said central electrode (20) is superior to the width of each of said lateral electrodes (13, 14).
5. Method according to any one of the preceding claims, characterized in that it also comprises, before or after each sustain operation, a selective addressing or erasing operation applied only in each of the said regions in which it is desired to sustain a light discharge during the said series, by applying at least one voltage pulse between the electrode of the said first array crossing the said region and at least one of the electrodes of the triad crossing the said region.
6. Method according to Claim 5, characterized in that the said selective voltage pulse is applied between the electrode of the said first array crossing the said region and the central electrode of the triad crossing the said region.
7. Method according to Claim 6, characterized in that, all of the regions (9R, 9G, 9B, etc) supplied via the same triad (13, 20, 14; 13', 20', 14') forming one row of the said panel, on any two adjacent rows through which a first triad (13, 20, 14) on the one hand and a second triad (13', 20', 14') on the other hand pass respectively, the lateral electrode (14) of the first triad is electrically connected to the same potential as the closest lateral electrode (13') of the second triad.
8. Plasma panel capable of being used for implementing the method according to any one of the preceding claims, comprising:

   - a front tile and a rear tile, which are parallel and provide between them a space filled with a discharge gas;

   - one (12) of the tiles comprising at least a first array of electrodes (5) and the other tile (11) comprising at least a second array of triads of electrodes (13, 20, 14), the general direction of which is approximately orthogonal to that of the electrodes (5) of the first array;

   - each triad comprising two opposed lateral electrodes (13, 14) and one central electrode (20);

   - the spaces located at the intersections of the electrodes (5) of the first array with the triads of electrodes (13, 20, 14) of the second electrode array forming a matrix of light-discharge regions (9) and of dots of the image to be displayed;

   - the electrodes (13, 20, 14) of the triads being coated with a dielectric layer (17);

   - means for controlling the discharges in each of the said intersection regions (9), especially by means of sustain operations;

   characterized in that
   the said control means are designed so that, during the sustain operations, the voltage of the central electrode (20) of each triad is always superior or equal to the one of one or the other lateral electrodes (13, 14).
   the width of the said central electrode (20) is greater than the gaps separating and isolating the adjacent electrodes of the same triad.
9. Plasma panel according to Claim 8, characterized in that the width of the said central electrode (20) is greater than 80 µm.
10. Plasma panel according to Claim 9, characterized in that the width of the said central electrode (20) is between 100 and 200 µm.
11. Plasma panel according to Claim 10, characterized in that the gaps separating and isolating the adjacent electrodes of the same triad are less than 80 µm and in that the spacing between the tiles providing the said discharge-gas-filled space is greater than 130 µm.
12. Plasma panel according to Claim 11, characterized in that the width of the said central electrode (20) is greater than 200 µm.
13. Plasma panel according to anyone of claims 9 to 12, charaterized in that the width of said central electrode (20) is superior to the width of each lateral electrodes (13, 14).
14. Plasma panel according to any one of Claims 9 to 13, characterized in that all of the regions (9R, 9G, 9B, etc) supplied via the same triad (13, 20, 14; 13', 20', 14') forming one row of the said panel, on any two adjacent rows through which a first triad (13, 20, 14) on the one hand and a second triad (13', 20', 14') on the other hand pass respectively, the lateral electrode (14) of the first triad is electrically connected to the same potential as the closest lateral electrode (13') of the second triad.
15. Plasma panel according to Claim 14, characterized in that the said two electrically connected electrodes (14, 13') form an electrode (21) common to two adjacent rows.

Images