EP0404645B1 - Plasma display having delimited discharge areas - Google Patents

Description

The invention relates to plasma panels of the coplanar maintenance type, and it particularly relates to means for confining in predetermined zones the discharges in the gas.

Plasma panels are flat screen display devices, now well known, which allow the display of alphanumeric, graphic or other images, in color or not. Generally plasma panels include two insulating tiles limiting a volume occupied by a gas (generally a mixture based on neon). These slabs support conductive electrodes arranged in columns and in lines, so as to be crossed and to define a matrix of cells, each cell forming an elementary image or pixel surface (a cell being the gas space substantially comprised between two electrodes crossed). The operating principle is the selective generation (at the intersection of line electrodes and column electrodes, that is to say at the level of selected pixels) of electric discharges in the gas. The visualization of the information is ensured by a light emission which accompanies these discharges.

Some plasma panels operate continuously, but it is more often preferred to use panels of the so-called "alternative" type, the operation of which is based on excitation in alternating conditions of the electrodes. In this case, the electrodes are covered with a layer of dielectric material, and they are no longer in direct contact with the gas or with the discharge. One of the advantages of this type of so-called "alternative" plasma panels is that it has a memory effect which allows useful information to be addressed only pixels whose state you want to change (on or off). For the other pixels, their state is simply maintained by repeating alternating electrical discharges, called maintenance discharges, discharges which are obtained only at the level of the pixels which are in the on state.

Among the plasma panels of alternative type, some use only two electrodes to define a pixel: an electrode arranged in columns called column electrode which is crossed with an electrode arranged in line called line electrode. These two electrodes perform both the addressing and maintenance functions.

In particular in order to improve the luminance of the plasma panels, and also to allow the display of several colors, it is preferred to use plasma panels of the excited type in alternating mode as described above, and which are also maintenance coplanar. In this latter type of plasma panels called "coplanar maintenance", each pixel of the matrix is constituted by at least three electrodes, more precisely at the intersection between an addressing electrode with two parallel maintenance electrodes forming a pair of maintenance electrodes. In this type of plasma panel, the maintenance of the discharges, that is to say the repetition of the alternating discharges previously mentioned, is ensured between the two maintenance electrodes of the same pair, and the addressing of a given pixel is produced by generation of discharge between two crossed electrodes, one of which is the addressing electrode, and the other of which is one of the two electrodes of the pair of maintenance electrodes. The addressing electrode only fulfills an addressing function and is most often arranged in the direction of the columns. The maintenance electrodes are parallel and most often arranged in the direction of the lines, and among the two electrodes of the same pair of maintenance electrodes: one is called address-maintenance electrode and it fills a addressing function in cooperation with the addressing electrode, and it fulfills on the other hand a maintenance function in cooperation with the second maintenance electrode of the same pair; the second maintenance electrode is called "maintenance electrode only" and it fulfills only a discharge maintenance function.

The operation of a plasma panel of the coplanar maintenance type, with three electrodes per pixel, is known for example from the European patent document EP-A-0135382.

Plasma panels with coplanar maintenance have many advantages, but also raise some difficulties, in particular with regard to individualization or limitation of discharges throughout the electrodes.

To better define the maintenance discharge zone at the pixel level, it is known for example in patent document EP-A-135-382 to give the maintenance electrodes a shape such that they each have a protrusion or protruding surface capable of promoting discharge: in the same pair of maintenance electrodes, the protruding surfaces of one electrode are oriented towards those of the other electrode so that, at a pixel level, the protruding surfaces of the two electrodes are opposite one another, aligned on the same axis identical or parallel to the axis of the addressing electrode which intersects them, so that the distance between the protruding parts of the two electrodes are smaller than the distance between the electrodes themselves (of the same pair), which tends to delimit between the two projecting surfaces the area of the start of maintenance discharges. However, it can be seen that it can be difficult to obtain correct confinement of the discharges in the allocated area, which has the consequence in particular of limiting the range of operating voltages applied between the two electrodes of the same pair of electrodes d 'interview.

In document JP-A-59-79937, the pixels have only a single projecting surface.

FIG. 1 schematically and partially shows a plasma panel with coplanar maintenance as described in patent document EP-A-135 382, a panel which is mainly represented by addressing electrodes and maintenance electrodes, and which allows a better understanding of the problem posed. The plasma panel 1 in FIG. 1 comprises addressing electrodes X1, X2 arranged in columns, and pairs of maintenance electrodes p1, p2 arranged in lines. To simplify the figure, only two addressing electrodes X1, X2 and only two pairs of maintenance electrodes p1, p2 are shown, and consequently only four pixels PX1 to PX4 are shown.

The pairs p1, p2 of maintenance electrodes each comprise a addressing-maintenance electrode Y1, Y2 and a maintenance-only electrode E1, E2.

The addressing electrodes X1, X2 are perpendicular to the pairs p1, p2 of maintenance electrodes and in the example shown in FIG. 1, the addressing electrodes X1, X2 are represented in a plane less deep than the plane in which are arranged the pairs p1, p2 of maintenance electrodes; also, the pairs p1, p2 of maintenance electrodes appear seen through the address electrodes X1, X2 in the part where they are crossed with the latter, and for greater clarity of the figure the address electrodes X1 , X2 are shown in dotted lines. It should be noted that such an arrangement corresponds to the most common conventional structure, in which the discharges in the gas are partially masked by the addressing electrodes or seen through the latter when these are transparent.

At the level of each pixel, each of the electrodes of each pair p1, p2 of maintenance electrodes is provided with a recess or protuberance or projecting surface. These surfaces are marked SA1, SA2 for the addressing-maintenance electrodes Y1, Y2, and marked SE1, SE2 for the maintenance-only electrodes E1, E2. These projecting surfaces SA1, SA2, SE1, SE2 are all formed in the same way for each pixel, and taking for example the first pixel PX1, formed at the intersection of the first addressing electrode X1 and the first pair p1, the first addressing-maintenance electrode Y1 and the first maintenance only electrode E1 respectively have a projecting surface SA1 and a projecting surface SE1 which are oriented towards one another, opposite and aligned on the same axis X1 which constitutes the axis of the first addressing electrode X1. There is a similar arrangement at the level of the other pixels PX2, PX3, PX4.

By taking again for example the first pixel PX1, the opposite ends of the projecting surfaces SA1, SE1 are at a distance D less than the distance which is necessary to initiate a discharge between these two projecting parts SA1, SE1, taking into account the difference potential V which is applied to these two projecting surfaces, that is to say which is applied between the two electrodes of each pair p1, p2 of maintenance electrodes.

In operation, after the addressing has been carried out using a discharge between for example the first addressing electrode X1 and the first addressing-maintenance electrode Y1, assuming that the first pixel PX1 has been selected , alternating maintenance discharges produce the light emitted by the pixel PX1.

The electrodes and the projecting parts are isolated by dielectric layers, and during a maintenance discharge, electric charges are deposited on the dielectric layers and create an internal electric field which opposes the electric field induced between the two. electrodes of the same pair, by the voltage pulses of opposite polarity which are applied to the two electrodes of the same pair p1, p2 of maintenance electrodes. The internal field created by these charges increases until causing the end of the discharge, that is to say the extinction of the pixel. But the cell or pixel keeps in memory the internal field previously acquired, and for the next maintenance discharge, this internal field promotes the initiation of the discharge, by adding to the internal electric field which results from application to the electrodes. maintenance voltage maintenance pulse whose polarities are reversed compared to the previous time. Thus when maintenance pulses are applied to the address-maintenance electrodes and only maintenance electrodes which constitute these pairs p1, p2, all the address-maintenance electrodes Y1, Y2 are brought to a first polarity while the electrodes only for maintenance E1, E2 are brought to the opposite polarity. Assuming that at a given time when a maintenance discharge is carried out at the level of the first pixel PX1 for example, the address-maintenance electrodes Y1, Y2 are at a polarity + V, the maintenance only electrodes E1, E2 are brought to the opposite polarity -V, and the ionization of the gas creates positive and negative charges identified by + signs and - signs. Positive charges + are mainly deposited on the protruding surface SE1, but also on a part of the maintenance only E1 electrode near this protruding surface, and negative charges - are mainly fixed on the edges of the protruding surface SA1 , but also on a part of the addressing-maintenance electrode Y1 near this projecting surface SA1; these positive and negative charges being generated until the end of the discharge.

The distance D which separates the two projecting surfaces SA1, SE1 in a pixel PX1 being less than a distance D1 which separates the maintenance addressing electrode Y1 from the maintenance only electrode E1, the potential difference between these two electrodes determines equipotential lines marked a, b, c, which correspond respectively for example to + V / 2, to zero Volt, to -V / 2, and which are much more tightened between the parts opposite the projecting surfaces SA1, SE1 than along the electrodes outside these opposite parts, that is to say for example in the direction of the second projecting surfaces SA2, SE2, of the second pixel PX2. Consequently, the forces exerted on these positive and negative charges +, - may be insufficient to prevent these charges from spreading towards the second pixel PX2 during the ionization of the gas.

It follows that for the next maintenance discharge, the polarity of the voltage pulses applied to the addressing-maintenance electrodes Y1, Y2 and only maintenance electrodes E1, E2 being reversed, the charges thus accumulated favor the initiation of the discharge between the projecting surfaces SA1, SE1 opposite, belonging to the first pixel PX1, but these charges can also promote the creation of discharges along the two electrodes Y1 and E1 until they overflow in the zone reserved for the neighboring pixel PX2.

One solution to this problem of charge migration consists in using barriers made of insulating material, to physically isolate the pixels from each other. Such a structure is described in an article by G. W. DICK published in PROCEEDINGS OF THE SIDE, Vol. 3/7, 1986, p. 183-187. It should be noted that in the structure described in this document, the maintenance electrodes have a constant width, that is to say that they do not have a projecting surface facing one another in a pair of maintenance electrodes.

One of the disadvantages of this solution based on barriers serving to confine the maintenance discharges in predetermined zones, is that it considerably complicates the manufacturing.

It should be noted that another drawback of the structures of the type shown in FIG. 1, resides in the fact that the light emitted by a pixel has a greater intensity at the level of the protruding parts opposite than for the rest of the pixel, and that it is precisely in front of this part forming a source of light of higher intensity that the addressing electrode is arranged, from which it results in a loss of the light output.

The present invention relates to a plasma panel having maintenance electrodes provided with projecting surfaces, the arrangement of which allows both better confinement of the discharges, and an increase in the luminance of each pixel. The solution of the invention is of simple implementation and inexpensive, which can be applied in the case of all plasma panels with coplanar maintenance.

The invention relates to a plasma panel as claimed in claim 1.

• la figure 1 déjà décrite représente les électrodes d'un panneau à plasma de l'art antérieur à trois électrodes par pixel;
• la figure 2 montre des électrodes d'un panneau à plasma conforme à l'invention ;
• la figure 3 montre une variante de la forme de réalisation de l'invention montrée à la figure 2 ;
• la figure 4 montre une autre forme de réalisation d'un panneau à plasma à trois électrodes par pixel mais celle-ci n'est pas revendiquée.

The invention will be better understood on reading the following description, given by way of nonlimiting example with reference to the figures, among which:

• FIG. 1 already described represents the electrodes of a plasma panel of the prior art with three electrodes per pixel;
• Figure 2 shows electrodes of a plasma panel according to the invention;
• Figure 3 shows a variant of the embodiment of the invention shown in Figure 2;
• FIG. 4 shows another embodiment of a plasma panel with three electrodes per pixel, but this is not claimed.

FIG. 2 schematically shows electrodes which symbolize a plasma panel 10 according to the invention. The panel 10 is formed of addressing electrodes X1, X2, X3 which fulfill only an addressing function. The panel 10 further comprises maintenance electrodes which are formed on the one hand, by electrodes addressing-maintenance Y1, Y2, and on the other hand, by electrodes called maintenance only E1, E2. Each addressing-maintenance electrode Y1, Y2 is associated with a maintenance-only electrode E1, E2 so as to constitute a pair p1, p2 of maintenance electrodes. The pairs p1, p2 are mutually parallel and perpendicular to the addressing electrodes X1 to X3, and crossed with the latter. At each crossing of an addressing electrode X1 to X3 with a pair p1, p2 is formed a pixel PX1, PX2 ..., PX6. For clarity of the figure only three addressing electrodes X1, X2, X3 and only two pairs p1, p2 of maintenance electrodes are represented so that only 6 pixels PX1 to PX6 (delimited by dashes) are formed in figure 2.

According to a characteristic of the invention, the addressing-maintenance electrodes Y1, Y2 and the solely maintenance electrodes E1, E2 have protruding surfaces which, in the same pair p1, p2 and in the same pixel PX1 to PX6, are arranged along different axes, transverse to the pairs p1, p2.

Consequently, in the same pixel, an addressing electrode X1 to X3 can cross only a projecting surface. Thus, for the first pixel PX1 formed at the intersection of the first addressing electrode X1 and the first pair p1, the first addressing-maintenance electrode Y1 is provided with a projecting surface SB1 which is oriented towards the electrode only of maintenance E1 of this pair of electrodes p1; on the other hand, the first electrode E1 is also provided with a projecting surface SC1 which is oriented towards the first addressing-maintenance electrode Y1.

In the nonlimiting example of the description, the first addressing electrode X1 crosses the first projecting surface SB1 of the electrode Y1, the latter being situated along the same axis x1 as the first addressing electrode X1. The protruding surface SC1 that the first electrode has only maintenance E1 is located on an x′1 axis parallel to the x1 axis.

These two projecting surfaces SB1, SC1 belonging to the first pixel PX1, have a length L1 parallel to the addressing electrode X1, which preferably (but not necessarily) is greater than half the distance D1 which separates the inner edges respectively 11, 12 of the addressing-maintenance electrodes and only maintenance Y1, E1 belonging to the first pair P1.

The second pixel PX2 formed at the intersection of the second addressing electrode X2 and the first pair p1 is constituted in the same way as the first pixel PX1: the first addressing-maintenance electrode Y1 is provided with a second surface projection SB2 aligned on an axis x2 of the second addressing electrode X2; the maintenance-only electrode E1 also has a second projecting surface SC2 arranged along an axis x′2 parallel to the axis x2 of the addressing electrode X2. The third pixel PX3 at the intersection of the third addressing electrode X3 and the first pair p1, is formed in a manner similar to that of the first and second pixels PX1, PX2: the first addressing-maintenance electrode Y1 comprises a third projecting surface SB3 aligned on an axis x3 of the third addressing electrode X3; and the first maintenance only electrode E1 also has a third projecting surface SC3 aligned on an axis x′3 parallel to the third addressing electrode X3.

In the nonlimiting example described, all of these projecting surfaces have the same length L1, and the same width L2 parallel to the maintenance electrodes. On the other hand, the two projecting surfaces SB1 to SB3, SC1 to SC3 of the same pixel are at a distance d1 from one another significantly less than the distance d2 which separates two consecutive projecting surfaces but belonging to pixels different. So for example as shown in Figure 2, the distance d1 which in the first pixel PX1 separates the two projecting surfaces SB1, SC1 parallel to a pair of electrodes p1, p2, this distance d1 is much less than the distance d2 which separates the first projecting surface SC1 (belonging to the first electrode only for maintenance E1 in the first pixel PX1) of the second projecting surface SB2 which in the second pixel PX2 belongs to the first maintenance addressing electrode Y1; and the same is true for the protruding surfaces of the pixels PX2, PX3.

An identical arrangement is made at the fourth, fifth and sixth plxels PX4, PX5, PX6 formed at the intersections of the second pair p2 with the first, second and third addressing electrodes X1, X2, X3; these pixels PX4, PX5, PX6 comprising in the same way projecting surfaces marked SB1 to SB3 and SC1 to SC3 which, as in the examples above, are aligned on the axes x1, x′1, x2, x′2, x3, x′3.

It can be observed that in the configuration of the invention, in the same pixel, the projecting parts SB1 to SB3, SC1 to SC3 belonging to the addressing and maintenance electrode Y1, Y2 and the only maintenance electrode E1, E2 are not face to face as in the prior art, but offset, in such a way that in the pixels, these projecting surfaces make it possible to form a channel C (delimited in FIG. 2 in thicker lines) having a relatively small width , formed for at least part by the distance d1, which can correspond for example to the distance which in the prior art separates the opposite ends from the projecting surfaces. However, in the prior art, the length of these opposite projecting surfaces is relatively short, and it is much greater in the configuration of the invention where the average length of the channel C corresponds substantially to the addition of two widths L2 and of a length L1 of projecting surfaces, plus a distance d1 between two projecting surfaces in the same pixel. This has the effect of increasing the length of the surfaces by look, and therefore to improve the operation, in particular because the potential difference required between the two electrodes of a pair p1, p2 of maintenance electrodes is reduced.

Furthermore, in the configuration of the invention, with the same pitch P as in the prior art between the addressing electrodes X1, X2, X3 or column electrodes, because the two projecting surfaces of the same pixel are offset, we obtain between two neighboring pixels that the two closest projecting parts belong one to an addressing and maintenance electrode Y1, Y2, and the other to a solely maintenance electrode E1, E2, in such a way that these two nearest projecting parts between two consecutive pixels are at opposite polarities; further taking into account that these two protruding parts brought to opposite polarities are located at a distance d2 from each other less than the distance which in the prior art separates the protruding parts from two neighboring pixels, these two parts protrusions each have a tendency to strongly repel the charges which would tend to deposit near these protruding surfaces.

This is illustrated in FIG. 2 at the level of the fifth pixel PX5, and between the latter and the sixth pixel PX6. It is observed that for a potential difference, applied between the addressing-maintenance electrodes Y1, Y2 and only maintenance electrodes E1, E2, equal to that which is applied in the prior art shown in FIG. 1, the equipotential lines a , b, c which are generated between these electrodes in the configuration of the invention, exist in the channel C with as high a concentration as between the surfaces opposite the case of the prior art (shown in FIG. 1); and exist with a much greater concentration than in the case of the prior art in the part situated between two projecting parts of two neighboring pixels, from which it follows that a much greater force than in the prior art is applied to the charges to prevent them from migrating from one pixel to a neighboring pixel. This of course provided that this force remains less than that which is sufficient to generate a parasitic discharge between these two neighboring pixels.

Thus, assuming that the fifth pixel PX5 is in state 1, the potential V applied between the addressing-maintenance electrodes Y1, Y2 and the solely maintenance electrodes E1, E2 causes a discharge in the fifth pixel PX5, between the facing surfaces which border the channel C; these surfaces being delimited in FIG. 2 by thicker lines marked 30, 31, lines which constitute the edges of channel C. During this discharge, the negative charges - are fixed at the first edge 30 of channel C which is of positive polarity the fact that it belongs to a addressing-maintenance electrode Y1, Y2, and positive charges + are accumulated on the second edge 31 which is of negative polarity because it belongs to a maintenance-only electrode E1 , E2. On the side of the sixth pixel PX6, the third projecting surface SB3 which belongs to the second addressing-maintenance electrode Y2, due to its proximity and its position, tends to repel positive charges + which would tend to migrate towards the sixth pixel PX6 ; in the same way, the first projecting surface SC1 which in the fourth pixel PX4 belongs to the second solely maintenance electrode E2 repels negative charges - which would tend to migrate towards the fourth pixel PX4.

This illustrates the advantageous effect provided by the invention on the confinement of landfills.

It should be noted another particularly important effect which results from the application of the invention, and which is that the addressing electrodes or column electrodes X1, X2, X3 are no longer interposed between an observer and the most intense part. of the light source of a pixel, as in the prior art, but only before a relatively small fraction of this most intense part, part the more intense which in the invention is represented by the entire channel C.

It should also be noted that the offset of the projecting parts in the panel of the invention makes it possible to bring the two electrodes of the same pair p1, p2 closer to each other, which optionally allows, for the same panel dimensions, placing more pairs of service electrodes, and thereby increasing the resolution.

It is noted that in the prior art, the main axis along which the discharges take place is substantially parallel to the addressing electrodes or column electrodes, while in the plasma panel of the invention, this main axis marked XP s '' performs substantially at an angle of 45 ° to the addressing electrodes or column electrodes X1, X2, X3, which tends to modify the shape of the pixels in the panel of the invention compared to a pixel in the art anterior, and consequently to slightly degrade the alignment of the pixels in the direction of the columns; but this defect remains entirely minor in view of the importance of the improvements obtained in the panel of the invention.

FIG. 3 illustrates an application of the invention in the case where the plasma panel 10 comprises pairs of maintenance electrodes p1, p2, p3, p4 formed by an arrangement in which two electrodes solely for maintenance are followed by two addressing-maintenance electrodes, themselves followed by two maintenance-only electrodes, etc. To simplify FIG. 3, only two addressing electrodes X1, X2 or column electrodes are shown, crossed with four pairs of electrodes p1, p2, p3, p4.

• la première électrode d'adressage-entretien Y1, suivie de la première électrode uniquement d'entretien E1 ; ces deux électrodes formant la première paire p1 d'électrodes ;
• après la première électrode uniquement d'entretien E1, on trouve une seconde électrode uniquement d'entretien E2 qui est suivie par une seconde électrode d'adressage-entretien Y2, ces deux dernières électrodes formant la deuxième paire p2 d'électrodes d'entretien ;
• on trouve après, une troisième électrode d'adressage-entretien Y3 qui est suivie d'une troisième électrode uniquement d'entretien E3 avec laquelle elle constitue une troisième paire p3 ;
• puis une quatrième électrode uniquement d'entretien E4 est suivie d'une quatrième électrode d'adressage-entretien Y4, ces deux dernières électrodes formant une quatrième paire p4.

By examining the electrodes from the top of the figure to the bottom, we find:

• the first addressing-maintenance electrode Y1, followed by the first maintenance-only electrode E1; these two electrodes forming the first pair p1 of electrodes;
• after the first maintenance-only electrode E1, there is a second maintenance-only electrode E2 which is followed by a second addressing-maintenance electrode Y2, these latter two electrodes forming the second pair p2 of maintenance electrodes;
• next, there is a third addressing-maintenance electrode Y3 which is followed by a third maintenance-only electrode E3 with which it constitutes a third pair p3;
• then a fourth maintenance-only electrode E4 is followed by a fourth addressing-maintenance electrode Y4, these last two electrodes forming a fourth pair p4.

As mentioned above, there is in this arrangement a succession of two electrodes of the addressing-maintenance type followed by two electrodes of the maintenance-only type and so on, the two electrodes of the same type serving to form two pairs of different but consecutive electrodes. Among the advantages of such an arrangement of maintenance electrodes, there may be mentioned in particular a reduction or elimination of the capacities between electrodes, and also the possibility of obtaining protection against cuts which could occur in the continuity of the electrodes only d interview E1 to E4. Indeed, the only maintenance electrodes E1 to E4 are all brought at the same times to the same potentials, and consequently they can be electrically connected to each other on the side not only of their first end 30 by a link 31 (shown in lines dashed), but also on the side of their second end 32, as shown in FIG. 3 where they are connected by a connecting conductor 33. Because two electrodes which are only consecutive maintenance are connected to each other on the side of their two ends 30, 32, part of one of these two electrodes, located after a cut (not shown), would remain supplied on the side of the second end 32. It should also be noted that these two electrodes could be combined into a single electrode E′1, E′3 by filling the space between these two electrodes with conductive material.

In this configuration with two successive maintenance electrodes of the same type, there may occur a migration of the charges in the direction of the addressing electrodes or column electrodes X1, X2, that is to say that the discharge at level d a pixel PX1 to PX8 can extend beyond the region of a neighboring pixel considered in the direction of the addressing electrodes X1, X2. The pixels PX1 to PX8 are each formed substantially at the intersection of an addressing electrode X1, X2 with a pair p1 to p4 of maintenance electrodes. These pairs p1 to p4 are arranged according to a pitch P ′ which plays on the image resolution, and the fact of arranging the projecting parts SB1, SB2 and SC1, SC2 of the same pixel in an offset manner, in accordance with the principle of the invention, increases the distance between two consecutive pixels in the direction of the addressing electrodes X1, X2, without losing image resolution.

To this end, the projecting parts SB1, SB2 which belong to the addressing-maintenance electrodes Y1 to Y4 are aligned on the axes x1, x2 of the addressing electrodes X1, X2. For the projecting parts SC1, SC2 which belong to two successive maintenance only electrodes E1 to E4: these projecting parts belonging to the first of these two electrodes are arranged so as to be offset on a first side of the addressing electrodes X1, X2, and the projections belonging to the next electrode are arranged on the opposite side. Thus, in the nonlimiting example shown in FIG. 3, the projecting surfaces SB1, SB2 of the addressing-maintenance electrodes Y1 to Y4 are aligned on the axes x1, x2, of the addressing electrodes X1, X2. The first and second solely maintenance electrodes E1, E2 constitute a group E′1 of two successive maintenance electrodes or constitute a single electrode as has been said above, and the projecting surfaces SC1, SC2, which belong to the first maintenance only electrode E1, are arranged aligned respectively on axes xa1, xa2, situated on one side of the addressing electrodes X1, X2, while the projecting surfaces SC1, SC2, which belong to the second maintenance only electrode E2 are arranged on an opposite side, namely aligned on axes x′1, x′2, as in the example in FIG. 2. The third and fourth electrodes maintenance only E3, E4 form another group E′3 of two consecutive maintenance-only electrodes, and the projecting surfaces SC1, SC2 of the third maintenance-only electrode E3 are arranged in the same way as in the case of the first maintenance-only electrode E1, while the protruding surfaces SC1, SC2 of the fourth maintenance-only electrode E4 are arranged in the same way as the protruding surfaces of the second e maintenance only electrode E2.

The result of this arrangement is a staggered arrangement of the pixels PX1 to PX8 which tends to increase the distance between the pixels in the direction of the addressing electrodes, which makes it possible to obtain better confinement of the discharges without increasing the pitch P ′ between the pairs p1 to p4.

FIG. 4 schematically shows another embodiment of a plasma panel 10, with three electrodes per pixel.

In this embodiment, each pixel has a single projecting surface which, for a given pixel belongs to one of the electrodes of the pair of maintenance electrodes, and which, for a next pixel along the same pair of 'maintenance electrodes, belongs to the other maintenance electrode.

To simplify the figure and for greater clarity thereof, only three addressing electrodes X1, X2, X3 have been shown crossed with only two pairs p1, p2 of maintenance electrodes, resulting in the formation of only six pixels PX1 to PX6. The first pair p1 is formed by the first addressing-maintenance electrode Y1 and by the first maintenance electrode E1, and the second pair p2 is formed by the second addressing-maintenance electrode Y2 and by the second electrode only d interview E2.

The first pixel PX1, formed at the intersection of the first addressing electrode X1 and the first pair p1, comprises a single protruding part SB1 which belongs to the addressing-maintenance electrode Y1. Consequently, the maintenance discharge in the first pixel PX1 occurs between this projecting surface SB1 and directly the only maintenance electrode E1, more precisely by a part Se of the latter symbolized by hatching in FIG. 4, part which is located opposite the projecting surface SB1.

For the second pixel PX2, there is also a single protruding part SC1, but which this time belongs to the maintenance only electrode E1, and the third pixel PX3 is constituted as the first pixel PX1, With this arrangement, and although qu '' a single projecting surface exists per pixel, we find the principle according to which the two projecting parts closest to two consecutive pixels, along the same pair of maintenance electrodes, belong one to an electrode of addressing-maintenance and the other to a maintenance-only electrode, which makes it possible to obtain the technical effects already described with reference to FIG. 2.

The absence of a projecting surface belonging to the first addressing-maintenance electrode Y1 in the second pixel PX2, means that the maintenance discharge occurs between the first addressing-maintenance electrode Y1 itself and the projecting part SC1 which belongs to the first maintenance only E1 electrode.

For the third pixel PX3, we find the same structure as for the first pixel PX1, namely that the first addressing-maintenance electrode Y1 is provided with a protruding surface SB3 aligned on the axis x3 of the third addressing electrode X3, the first maintenance-only electrode E1 having no protruding surface at this third pixel PX3. The pixels PX4, PX5, PX6 can be formed respectively in the same way as the first, second and third pixels PX1, PX2, and PX3.

With regard to the addressing of the pixels, this addressing can be done in the same way as in the case of the previous examples for pixels whose sole projecting surface belongs to an addressing-maintenance electrode Y1, Y2, as this is the case for pixels PX1, PX3, PX4, PX6. On the other hand, for the pixels such as the pixels PX2, PX5 of which the only projecting surface belongs to the electrodes solely for maintenance E1, E2, the addressing may require a higher addressing voltage for these pixels than for the others, of the the fact that for these pixels the addressing electrode Y1, Y2 has, opposite the addressing electrode X2, a surface Sa1, Sa2 reduced by the fact that it does not include the surface provided by the projecting surfaces. However, this difference in addressing voltage can be made up, for example as it is conventional to do in the case where it is desired to compensate for a disparity between two cells, disparity due for example to a difference in the nature of phosphors in the case of a color type plasma panel.

Claims (4)

1. Plasma panel with coplanar hold, including addressing electrodes (X1, X2, X3), intersected by hold electrodes arranged in pairs (p1, p2), each pair of hold electrodes being formed by an addressing/hold electrode (Y1, Y2) and by a hold-only electrode (E1, E2), a pixel (PX1 to PX6) being constituted substantially at each intersection of an addressing electrode (X1, X2, X3) with a pair (p1, p2) of hold electrodes, each of the two electrodes (Y1, E1) of the same pair (p1) including, in the region of each pixel (PX1 to PX6) a projecting surface (SB1 to SB3, SC1, SC3) turned towards the other electrode, characterized in that the two projecting surfaces (SB1 to SB3, SC1 to SC3) of the same pair (p1, p2) are offset with respect to one another and are arranged along different axes (x1, x′1) in such a way that, between two consecutive pixels (PX1 to PX6) of the same pair (p1, p2), the two projecting surfaces which are closest together belong, in one case, to an addressing/hold electrode (Y1, Y2) and, in the other case, to a hold-only electrode (E1, E2).
2. Plasma panel according to Claim 1, characterized in that the projecting surfaces (SB1, SC1) have a length (L1), parallel to the addressing electrodes (X1, X2, X3), which is larger than half of a distance (D1) which separates the two electrodes (Y1, E1) of the same pair (p1, p2) of hold electrodes.
3. Plasma panel according to one of the preceding claims, characterized in that the addressing electrodes (X1, X2, X3) intersect the pairs (p1, p2) of hold electrodes above a projecting surface (SB1, SB2, SB3), belonging to an addressing/hold electrode (Y1, Y2).
4. Plasma panel according to one of the preceding claims, the hold electrodes (Y1 to Y4, E1 to E4), being arranged into a succession of two addressing/hold electrodes (Y1 to Y4) followed by two hold-only electrodes (E1 to E4), in such a way that two consecutive hold-only electrodes (E1 to E4) serve to form two consecutive pairs (p1, p2) and in such a way that these two electrodes possibly constitute a single electrode (E′1) common to these two consecutive pairs (p1, p2), characterized in that the projecting surfaces (SB1, SB2, SB3) belonging to the addressing/hold electrodes (Y1 to Y4) are arranged aligned substantially on the same axis (x1, x2, x3) as the addressing electrodes (X1, X2, X3), whereas for the projecting surfaces (SC1, SC2, SC3) of the hold-only electrodes (E1 to E4) which form a group (E′1, E′3) of two consecutive electrodes, the projecting surfaces (SC1 to SC3) of the first of these two electrodes are arranged on a first side of the axes (x1, x2, x3) of the addressing electrodes (X1 to X3) and the projecting surfaces (SC1 to SC3) of the second electrode are arranged on the side opposite the first one.

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