EP0376829A1 - Low resolution plasma panel display - Google Patents

Abstract

The invention relates to a display device having a plasma panel (12) forming the display area (SA). It relates in particular to the case where the display area (SA) is divided up into elementary image points (PI1 to PI4) each having a relatively large area, so as to permit reading, with good legibility, at relatively large distances. The plasma panel (12) comprises column electrodes (X1 to X6) crossed with row electrodes (Y1 to Y6) so as to constitute a network of cells (C1 to C36). According to a characteristic of the invention, at least two contiguous cells (C1 to C36) are grouped together to constitute an elementary image point (PI1 to PI4). <IMAGE>

Description

The invention relates to a display device using a so-called "low resolution" plasma panel (of the order of a few millimeters for example), which in particular can be read, with good readability, at medium distances (between 1 and 10 meters for example). Such a display device is called in the following description "display device of the sign type".

Plasma panels are flat screen display devices, now well known, which allow the display of alphanumeric, graphic or other images. Generally plasma panels include two insulating tiles limiting a volume occupied by a gas. These slabs support conductive electrodes, arranged in columns called column electrodes, and electrodes arranged in lines called row electrodes. These column and line electrodes are crossed so as to define a matrix of cells each formed substantially at the intersection of line and column electrodes.

The operating principle is the selective generation (that is to say at the level of the selected cells) of electric discharges in the gas. The visualization of the information is ensured by an emission of light which accompanies these discharges and which is located at the level of each cell where an electrical discharge occurs. Each cell can thus constitute an elementary light source whose state can be changed (on or off).

There are different types of plasma panels, in particular panels of the continuous operating type, and so-called "alternative" panels in which the electrodes are covered with a layer of dielectric material. One of the advantages of plasma panels of the alternative type, is to present a memory effect which makes it possible to address the useful information only to the cell whose state it is desired to change, while the state of the other cells is simply maintained, or maintained (in the case of the lit state) by repetition of alternating electrical discharges called maintenance discharges.

It should be noted that among plasma panels of the alternative type, some use only two electrodes to define a cell: a column electrode crossed with a row electrode. The operation of such a panel is known in particular from a French patent No. 78 04893 in the name of THOMSON-CSF, published under No. 2,417,848; this patent also describes a method of controlling such a panel.

Also known are alternative plasma panels called "coplanar maintenance", in which three or more electrodes are used to form a cell. In this case, most often, each cell of the matrix is formed substantially at the intersection between a column electrode with two parallel maintenance electrodes forming a pair of maintenance electrodes. With this type of screen, it is known that the maintenance of the discharges, that is to say the repetition of the alternating electrical discharges previously mentioned, is ensured between the two maintenance electrodes of the same pair, and that addressing is done by generation of discharges between two crossed electrodes.

Such a plasma panel of the alternative type with coplanar maintenance is shown in FIGS. 1 and 2, in accordance with the teaching of the European patent document EP-A-0135 382. It comprises a glass slab 1, covered with a first and a second family of maintenance electrodes 2 and 3 arranged in lines, parallel and coplanar, and arranged according to an alternation of an electrode 2 of the first family and an electrode 3 of the second family. Thus, a succession of an electrode 2 of the first family with an electrode 3 of the second family constitutes a pair of maintenance electrodes used to form the same row of cells. These electrodes are provided with a recess or protruding part 2a and 3a which, in the same pair of maintenance electrodes are oriented towards one another so as to concentrate maintenance discharges between them. The assembly is covered with an insulating layer 4. Addressing electrodes 5 or column electrodes are crossed with the maintenance electrodes 2 and 3; the latter generally being arranged in lines and the addressing electrodes 5 generally being arranged in columns. The assembly is covered with an insulating layer 6 and a protective layer 7 made of MgO. A second slab 8 completes the set. A gas 9 is retained between the slabs 1 and 8 held apart by watertight shims (not shown).

The operating principle of a plasma panel of this type is as follows: an address discharge is selectively generated at the intersection of a column electrode 5 with a line electrode 2 of a given pair of electrodes maintenance (in a pair of maintenance electrodes, the line 2 electrode performs an addressing function and a maintenance function). This addressing discharge results in the storage of electrical charges on the insulator covering these electrodes. These charges are then used to facilitate the initiation of maintenance charges between the two electrodes of each pair. Maintenance discharges are those which provide most of the useful light; they are maintained using voltage slots, which are applied between the two electrodes of each pair of maintenance electrodes, and which succeed each other with opposite polarities.

We also know from the publication of GW Dick in PROCEEDINGS OF THE SID, vol. 3/7, 1986, p. 183-187, a plasma panel with three electrodes per pixel with coplanar maintenance as well as a method for controlling this panel.

One of the constant concerns of the manufacturers of plasma panels has been to improve the resolution or definition of the displayed image, that is to say to increase the number of elementary points of images contained in a given surface of l 'display screen ; which corresponds to increasing the number cells contained in a given surface. Efforts in this direction have led to the development of techniques which currently make it possible to produce high-resolution plasma panels, the cells of which are formed using electrodes having a width which is sufficiently small to be able to be brought together to the point that the rows and columns of cells thus obtained are arranged in steps of low value, of the order of 0.2 mm for example. Of course, such an improvement in image resolution is accompanied by certain drawbacks, such as in particular:
- greater complexity in manufacturing, due to the increase in the density of the conductors;
- an increase in the addressing output control elements, in line and in column;
- it is further observed that one of the direct and particularly unfortunate consequences of the increase in the number of conductors is to increase the number of cuts in the conductors which form the electrodes,
- we also observe that it is necessary to increase the quantity of tracks or conductors to leave the panel itself, if we want to keep an essential option which lies in the possibility of repairing cuts in the conductors forming electrodes, such as taught for example in French patent application No. 84 168 72 filed on November 6, 1984 in the name of THOMSON-CSF (that is to say without using technology with crossing conductors inside the panel).

In the case of plasma panels for display devices of the "sign" type, correct readability at medium distance requires above all that the display screen be divided into a number of elementary image points each having a sufficient area, and emitting light of sufficient intensity. As a result, image resolution is no longer a problem, and the manufacturers have followed a path opposite to the previous path for these “sign” type plasma panels, that is to say that they have adopted a solution which consists in increasing the width of the electrodes and their spacing, so that each cell can comprise a larger surface, that is to say that each cell can constitute the source of a discharge much greater in intensity and in dimensions.

Such a solution for plasma panels of the "sign" type is relatively satisfactory because it facilitates manufacturing and reduces costs, in particular because, compared to high resolution panels, the electrodes can be further apart from one another. , and that the width of these electrodes can be increased; it can also be noted that this last point can also have a favorable consequence insofar as it tends to reduce the number of electrodes or conductors cut.

Among the drawbacks of this solution, one can cite an implementation different from that of conventional plasma panels, that is to say high resolution plasma panels: in particular as regards the operating voltages, the duration landfills, etc; it is known in fact that these characteristics depend on the geometry of the discharge cells. Consequently, the implementation of "sign" type panels based on this solution requires modifying the electronic equipment and materials which are necessary for the operation of the plasma panels, and which exist in a standard manner.

Despite the undeniable advantages attached to the solution represented by large area cells, the authors of the invention thought, contrary to general opinion, that plasma panels of the "sign" type or low resolution plasma panels could advantageously be made from conventional plasma panels or more precisely plasma panels of the high resolution type. The latter solution has the advantage of being able to be implemented under the same conditions as the usual plasma panels at higher resolution, and it has also been found that this last solution made it possible to obtain better luminance, better homogeneity, and finally to provide better reliability.

According to the invention, a display device comprising, a display surface formed by a plasma panel, means for controlling and addressing the plasma panel, the display surface being shared at a plurality of elementary points of images, the plasma panel comprising cells arranged in lines and in columns, the cells being formed by conductors in crossed lines with conductors in columns, is characterized in that at least one elementary point of image is formed from a group of cells comprising at least two contiguous cells

There is thus produced a grouping of two or more cells, that is to say a grouping of discharges, and each group of cells corresponds to an elementary image point of a lower resolution display device.

It results from this arrangement in particular: better luminance of the elementary image point, because in the case of "small discharges", the efficiency is improved; there is also a better homogeneity by an average effect within the elementary image point, owing to the fact that the latter is formed from a greater number of cells, that is to say with a greater number landfills; on the other hand, reliability is improved, in particular in the case of a defective discharge.

The grouping of discharges or grouping of cells forming an elementary image point can be achieved by adapting the control and addressing method so as to control simultaneously for all the cells of the same group, namely the extinction, either ignition or maintenance discharges. The method to be used to carry out these commands can easily be deduced for the specialist in the control methods described in the documents cited above.

According to another characteristic of the invention, the grouping of cells to form an elementary image point is obtained by a "hardware link", that is to say by electrically connecting at least two contiguous column electrodes and / or to the at least two contiguous line electrodes or by connecting the conductors which lead to these electrodes; this can be done both inside the plasma panel itself and outside of it, that is to say at any level between the areas which constitute the cells and the outputs of the addressing and control means.

• - les figures 1 et 2 déjà décrites montrent la structure d'un panneau à plasma classique ;
• - la figure 3 illustre la version de l'invention dans sa forme à "liaison matérielle", appliquée au cas d'un panneau à plasma du type continu ou alternatif dans lequel chaque cellule est formée à l'aide de seulement deux électrodes croisées ;
• - la figure 4 illustre l'invention également dans sa version "à liaison matérielle", mais appliquée au cas d'un panneau à plasma de type alternatif à entretien coplanaire ;
• - la figure 5 montre une forme de réalisation dans laquelle des cellules d'un même groupe sont constituées à l'aide d'électrodes de largeur différente ;

The invention will be better understood and other advantages which it provides will appear on reading the description which follows, given by way of nonlimiting example with reference to the appended figures, among which:

• - Figures 1 and 2 already described show the structure of a conventional plasma panel;
• - Figure 3 illustrates the version of the invention in its "hardware link" form, applied to the case of a plasma panel of the continuous or alternating type in which each cell is formed using only two crossed electrodes;
• - Figure 4 illustrates the invention also in its "hardware link" version, but applied to the case of an alternative type plasma panel with coplanar maintenance;
• - Figure 5 shows an embodiment in which cells of the same group are formed using electrodes of different width;

Figure 3 schematically shows a display device 10 by plasma panel, according to the invention. In the nonlimiting example described, the plasma panel 12 is of the type with two crossed electrodes to form a cell, and of the alternative type for example.

In its classic part, the display device 10 comprises:
addressing and control means constituted by a column addressing and control device 13, and by a line 14 addressing and control device;
the plasma panel 12 comprises electrodes arranged in columns X1, X2, ..., X6 called column electrodes, and row electrodes Y1, Y2, ..., Y6 called row electrodes and which are perpendicular to the column electrodes X1 to X6.

In the nonlimiting example described, and for clarity of the figure, only 6 column electrodes X1 to X6 and only 6 row electrodes Y1 to Y6 are shown but, of course, these electrodes can be in different numbers, in particular larger . Consequently, there are only 36 points of intersections or crossings which each form a cell C1 to C36; these cells are shown in the figure at each of these crossings by a hatched surface Sc which represents the crossing surface itself corresponding to the facing surfaces between a row electrode Y1 to Y6 and a column electrode X1 to X6.

The plasma panel 12 is mainly represented by the electrodes X1 to X6 and Y1 to Y6, but of course these two types of electrodes are mounted on two slabs (not shown in the figure) as was previously explained in the preamble in reference to FIGS. 1 and 2. These two tiles are sealed to each other by a joint (not shown) so as to define an active part 16 containing the ionizable gas of the plasma panel 12; this active part 16 represents a display surface SA which is divided into elementary image surfaces or points PI1, PI2, PI3, PI4. The row electrodes Y1 to Y6 can for example be located in a deeper plane than that which contains the column electrodes X1 to X6, the latter being carried by the slab located on the side by which one looks at the plasma panel 12, the row electrodes Y1 to Y6 being carried by the other slab.

Conventionally, the slabs have an overhanging part 17, that is to say beyond the active part 16. Also, the column and row electrodes X1 to X6 and Y1 to Y6 are extended on the overhanging part 17 , and therefore the outside of the active part 16, by conductors 18, 19, 23, 31, 32, 33 which connect these electrodes to the addressing and control devices 13, 14 by means of connection element 15, 24 , 27 and connecting wires F1, F2 of a first cable 11X and connecting wires F3, F4 of a second cable 11Y.

According to a characteristic of the invention, at least two column electrodes X1 to X6 consecutive or adjacent and / or at least two row electrodes Y1 to Y6 consecutive or adjacent are electrically connected to each other in a physical manner, that is to say physically connected to each other.

In a preferred version of the invention, this hardware connection is made in the active part 16 of the plasma panel 12.

Thus for example for the column electrodes X1 to X6, in the nonlimiting example described: the first three column electrodes X1, X2, X3 are electrically connected to each other in the active part 16, using a connecting conductor 26 located on the side of their first end 21 (this first end being that which is oriented towards the extension conductors 18, 19); the fourth, fifth and sixth column electrodes X4, X5, X6 are connected in the same way by a connecting conductor 26. Consequently the first three column electrodes X1, X2, X3 are extended by a single conductor 18 which connects these electrodes to a column control output SC1 of the column addressing device 13, via the connection element 15 and a wire F1 of the cable 11X; whereas in the prior art three column electrodes, even contiguous, are connected to three different control outputs. It is the same for the fourth, fifth and sixth column electrodes X4, X5, X6 which are extended by a single conductor 19 itself connected to a control output SC2, via a second wire F2 of the cable 11X.

In the nonlimiting example shown in FIG. 3, the first three line electrodes Y1, Y2, Y3 are also connected to each other by a connecting conductor 20 in the active part 16, on the side of their first end 29 oriented towards the connection elements 24, 27. As a result, the three line electrodes Y1 to Y3 are extended by a single conductor 23, and are connected by this single conductor 23 to an output SL1 of the line addressing device 14, via the connection elements 24, 27 and a wire F3 of the second 11Y cable. Groups GX1, GX2 of column electrodes and groups GL1, GL2 of row electrodes are thus produced, in which the electrodes of the same group are connected together; from which it follows that groups of cells GC1, GC2, GC3, GC4 are each produced corresponding to an elementary point of image PI1 to PI4.

Under these conditions, if at the same time, on the one hand, for example, the first three column electrodes X1, X2, X3 are addressed by an address and control signal VX (the address and control signals d column electrodes are generally constituted by sets of cyclic voltage pulses, not shown, in themselves well known), and which are addressed on the other hand the first three electrodes Y1, Y2, Y3, by a VL line addressing and command signal (VL line command and addressing signals also generally consist of sets of cyclic voltage pulses, in themselves well known, whose phase is correlated to the phase of VX signals applied to the column electrodes), the cells C1, C2, C3, C7, C8, C9, C13, C14, C15, that is to say, generate discharges in the area of these cells; these discharges 25 are symbolized in the figure by point clouds. The grouping of these discharges 25 tends to constitute a single light spot contained in the surface of the first elementary point PI1; this light spot is relatively homogeneous insofar as the distance d1 between two row electrodes connected together and the distance d2 between two connected column electrodes together is sufficiently weak so that the edges of these discharges merge; each discharge 25 being of course substantially centered around the crossing surface Sc which represents the cell. In the nonlimiting example described, a group GC1 of cells formed from contiguous cells and controlled simultaneously in the same way is thus put in the "on" state, and it is possible to control the others in a similar manner. groups GC2, GC3, GC4 in such a way that they each define an elementary image point whose surface contains all the discharges which are generated in such a group of cells GC1 to GC4.

Recall that the desired effect is to group at least two cells C1 to C36 to increase the area of an elementary image point PI1 to PI4 starting from a plasma panel 12 whose cells C1 to C36 have a surface Sc crossing much less than the desired area of the elementary image point. Of course, to obtain such an effect, it is sufficient to connect only two adjacent column electrodes X1 to X6, and not to connect any of the row electrodes Y1 to Y6 to each other; or on the contrary to connect together two adjacent row electrodes Y1 to Y6, and not to connect any of the column electrodes X1 to X6 together; or else to connect adjacent column electrodes X1 to X6 and adjacent row electrodes Y1 to Y6 according to different numbers for the row electrodes and the column electrodes.

It should also be noted that the row or column electrodes can be connected together outside of the active part 16 of the panel 2. Thus for example, as shown for the fourth, fifth and sixth row electrodes Y4, Y5 , Y6, in the nonlimiting example described, each of these electrodes is extended outside of the active part 16, by a conductor 31, 32, 33, these conductors respectively leading to contact pads 31a, 32a, 33a of the connection element 24 which is integral with the panel 12; so that in this conflguration, it is possible to make no modification to the plasma panel 12 itself whatever its use, either that it is used in cases where a high image resolution is required, or that 'it is used to form a display device of the "sign" type. The line electrodes Y4, Y5, Y6 can be connected to each other between the connection element 24 and a line control output SL2 (of the line addressing and control device 14) to which these line electrodes must be connected. Thus for example, the hardware connection between these three electrodes Y4, Y5, Y6 can take place at the level of the line addressing and control device 14, or, as in the nonlimiting example represented in FIG. 3, by a connecting wire 40 which joins the contact pads 31a, 32a, 33a via pads 31b, 32b, 33b, contained in a connection element 27 attached to the second connecting cable 11Y; it is thus possible to use a single wire F4 to connect these three pads to the output SL2.

It is observed that with this type of "hardware link", the number of outputs which are necessary for controlling the column electrodes X1 to X6 and / or for controlling the row electrodes Y1 to Y6 can be considerably reduced, compared to a grouping of cells which would only be obtained by acting on the control process.

It should be noted that by connecting column electrodes X1 to X6 and / or row electrodes Y1 to Y6 inside the active part 16, the manufacturing complexity is significantly increased. However, it can be observed that this drawback is largely offset by the fact that, in this case, it is necessary to remove from the active part 16 a single conductor 18, 19, 23 per set of column electrodes and / or row electrodes interconnected, which is an important advantage if we take into account the difficulties encountered in achieving this type of external conductor, particularly when the plasma panels are made to operate in a aggressive environment.

In addition, if consecutive or adjacent electrodes are connected together, for example on the side of their first end 20, 21, either inside the active part 16, or outside the latter, it becomes particularly advantageous to also join them on the side of their second end. This is illustrated in FIG. 3 where, on the one hand, the first, second and third line electrodes Y1, Y2, Y3 are connected on the side of their second end 34 inside the active part 16, by a conductor of link 35; and where, on the other hand, the fourth, fifth, sixth row electrodes Y4, Y5, Y6 are also interconnected on the side of their second end 34 by a connecting conductor 35; as regards the column electrodes, on the one hand the first, second and third column electrodes X1 to X3 are connected on the side of their second end 38 by a connecting conductor 39 located inside the active part 16, and on the other hand, the fourth, fifth and sixth column electrodes X4, X5, X6 are also connected on the side of their second end 38 by a connecting conductor 39.

As a result, the electrodes of the same group are interconnected at their two ends, and there is a self-healing effect of the cuts. Indeed, if we take for example the group GL1 formed by the first, second and third row electrodes Y1, Y2, Y3, there can be both a cut 42 towards the middle of the first electrode Y1, and a cut 43 towards the middle of the second electrode Y2, without compromising the operation of any of the cells produced using these electrodes, owing to the fact that the two line electrodes Y1, Y2 remain supplied by their two ends 20, 34 thanks to the presence of the third line electrode Y3.

This version of the invention is also applicable in the case of alternative plasma panels with coplanar maintenance.

FIG. 4 illustrates the application of the invention to a display device 10 using a plasma panel 12a of the alternative type with coplanar maintenance. The plasma panel 12a is mainly represented by column electrodes X1 to X4 and by electrodes arranged in line. The electrodes arranged in line are constituted, in a manner which is in itself conventional, in pairs of maintenance electrodes P1 to P6; the column electrodes X1 to X4 and the pairs of electrodes P1 to P6 being limited respectively to the number of 4 and to the number of 6 to simplify the description and for greater clarity in FIG. 4.

The pairs of electrodes P1 to P6 are crossed with the column electrodes X1 to X4, and the intersections of these crossed electrodes form cells C′1 to C′24 materialized in the figure by hatched surfaces in solid lines. It is known that generally, in plasma panels of the alternative type with coplanar maintenance with three electrodes to define a cell, one or more cells are addressed for recording (switching on) or erasing (switching off) by discharges carried out. between the column electrode X1 to X4, which has only an addressing function, and only one of the two electrodes which constitute a pair P1 to P6 of maintenance electrodes; and, between the two electrodes of the same pair, the maintenance discharges which constitute the main part of the light emitted by the cells are produced. It should be noted that for each pair P1 to P6 of maintenance electrodes, the two electrodes each have, at each cell C′1 to C′24, a projecting surface 50, 51, that is to say say a surface or part in excess with respect to the longitudinal edges of these electrodes. Each pair of electrodes P1 to P6 comprises a first electrode YA1 to YA6 called the addressing-maintenance electrode which provides an addressing function and a maintenance function, and comprises a second electrode E1 to E6 which only performs the function d 'interview ; so that these maintenance-only electrodes E1 to E6 do not have to be individualized, and in Consequently, they can be connected as shown in FIG. 4, to the same output 47 of a maintenance pulse generator 45 delivering in the conventional manner cyclic maintenance voltage pulses VE (not shown).

In the prior art, the address-maintenance electrodes YA1 to YA6 are each connected to a different output of a line addressing and control device, and the same is true for the column electrodes which are each connected to a different output from a column addressing and control device. On the contrary, in the plasma panel 12a according to the invention, at least two adjacent or consecutive addressing-maintenance electrodes YA1 to YA6 and / or two adjacent column electrodes X1 to X4 are connected to the same output of the addressing and command line and column 14, 13, so as to produce at least one group of cells, the grouping of at least two adjacent cells C′1 to C′24 serving to define an elementary image point, as it has already been explained with reference to FIG. 3.

In the nonlimiting example of the description, and taking into account the nonlimiting example represented in FIG. 4, where the column electrodes X1 to X4 overlap the projecting surfaces 50, 51 in a substantially central zone of the latter (then that the electrodes X1 to X4 could also cross the pairs P1 to P6 of electrodes on the side of the projecting parts 50, 51) and taking into account the length L1 of the projecting surfaces 50, 51, the 24 cells C′1 to C ′24 form four groups G′C1 to G′C4, each group G′C1 to G′C4 defining an elementary image point PI1, PI4.

To this end, with regard to the column electrodes, the first two adjacent electrodes X1, X2 are connected together and then connected to a first output S′C1 of the column addressing and control device 13; and on the other hand, the third and fourth column electrodes X3, X4 which are adjacent are also connected together, then connected to a second output S′C2 of the column addressing device 13. With regard to the line electrodes, and with a view to forming elementary, roughly square image points, on the one hand, the address-maintenance electrodes YA1 to YA3 of the first three pairs P1 to P3 are linked together and forming a group of electrodes G′L1, then connected to an output S′L1 of the line addressing device 14; and on the other hand, the three other addressing-maintenance electrodes YA4, YA5, YA6 are connected together and form a group of electrodes G′L2, then they are connected by a single conductor to the second output S′L2 of the line addressing device 14.

Taking for example the first group of cells G′C1, it is observed that the discharges 25 ′ (represented by point clouds) obtained at the level of each cell extend a little beyond the length L1 of the projecting surfaces 50, 51, so that these discharges 25 ′ have a longer elongated shape parallel to the pairs P1 to P6 of electrodes; on the other hand, for two discharges 25 ′ produced by neighboring cells belonging to the same pair of electrodes, for example cells C′1, C′2 formed with the first pair of electrodes P1, it is observed that these discharges 25 ′ Tend to merge at their ends so as to form substantially only a single light spot, which tends to increase homogeneity, despite the fact that the column electrodes X1, X2, whose width L2 is relatively weak, are interposed between an observer and its light zones.

It should be noted that the maintenance electrodes forming the pairs P1 to P6 could be arranged in a succession of a addressing-maintenance electrode YA1 to YA6 followed by a solely maintenance electrode E1 to E6 then again a addressing-maintenance electrode and a maintenance-only electrode etc ... But FIG. 4 shows another arrangement which illustrates an important advantage brought by the realization of "material connections" inside the plasma panel itself, c that is to say in the active part 16 shown in FIG. 3. In indeed, if the electrodes YA1 to YA6 and E1 to E6 arranged in line, are connected together in the active part 16 (not shown in FIG. 4), they can be arranged in a different succession as shown in FIG. 4, where, starting from the top, there is a first maintenance only electrode E1, followed by a first addressing-maintenance electrode YA1 forming the first pair P1, then a second addressing-maintenance electrode YA2 followed by a second only maintenance electrode E2 to form the second pair P2. It is observed that between the first and the second pair P1, P2, the facing electrodes are both electrodes of the addressing-maintenance type, so that not only can these electrodes be connected on the side of their first end 60, but that they can also be connected together on the side of their second end 61; from which there results a self-repair of possible cuts, as has been explained with reference to FIG. 3. It is even possible in such a case, to make these two address-maintenance electrodes YA1 to YA2 in a single conductor, this that is to say, fill the space 63 between these two electrodes with electrically conductive material.

On the other hand, it is observed that by making the second maintenance-only electrode E2 succeed, a third maintenance-only electrode E3, itself followed by a third addressing-maintenance electrode YA3 to form the third pair P3 , it is also possible to connect the second and the third solely maintenance electrodes E2, E3 not only at their first end 70, but also at their second end 71, and also to produce them in the form of a single conductor by filling, for example, with an electrically conductive material, the space 74 located between these two electrodes E2, E3; this can be achieved for all electrodes of the same type which are consecutive and not separated by an electrode of another type, and which of course are intended to be connected together.

FIG. 5 illustrates a version of the invention which allows in particular to obtain an adjustment of the general level of luminance of the panel.

The structure of the plasma panels being generally well known, and the structure of a plasma panel according to the invention having already been described with reference to Figures 3 and 4, Figure 5 shows only line electrodes and column electrodes intended to form a single elementary image point.

In the nonlimiting example described, a first and a second line electrode Y1, Y2, are shown, connected together and intended to be connected, as has been explained above, to an output of an addressing device and of line command (not shown).

These row electrodes Y1, Y2 are crossed with a first and a second column electrodes X1, X2 which are connected together and which are intended to be connected to the same output of a column addressing and control device (not shown) .

In the configuration shown in FIG. 1, four crossing surfaces SC1, SC2, SC3, SC4 are formed, each capable of constituting a cell Ca1, Ca2, Ca3, Ca4. In the nonlimiting example of the description, the first row electrode Y1 and the first column electrode X1 have the same width L3; the second column electrode X2 and the second row electrode Y2 have the same width L4 greater than the width L3 of the first row and column electrodes Y1, X1.

It follows from this arrangement that: the fourth cell Ca4 has a crossing surface SC4 larger than the first, second and third crossing surfaces SC1, SC2, SC3; the second and third cells Ca2, Ca3 have crossing surfaces SC2, SC3 equal to and greater than the crossing surface SC1 of the first cell Ca1.

Under such conditions, it is possible, when the electrodes Y1, Y2 and X1, X2 are simultaneously addressed, interest by this addressing: either only the fourth cell Ca4, or the fourth cell Ca4 plus the second and third cells Ca2, Ca3, or the fourth cell Ca4 plus the second, third cells Ca2, Ca3 and the first cell Ca1 , that is to say simultaneously these four cells. This can be obtained by adjusting in particular the potential differences VX-VL (not shown) which are developed in a conventional manner between column electrodes X1, X2 and row electrodes Y1 and Y2, and this as well for the phases in themselves conventional of semi-selective addressing, or selective addressing and maintenance. The potential differences which are generated by the voltage pulses applied to these electrodes Y1, Y2 and X1, X2 may have an amplitude just sufficient to generate a discharge between the second electrode X2 and the second line electrode Y2, at the level of the fourth Ca4 cell which has the largest crossing surface SC4, and which therefore requires the smallest potential difference; the amplitude of this potential difference being at the same time insufficient to generate a discharge at the level of the first, second and third cells whose surfaces SC1, SC2, SC3 are smaller. This difference in potential can also be increased so that its amplitude is sufficient to generate discharges at the level of the fourth, third and second cells Ca4, Ca3, Ca2, and is insufficient to generate discharges at the level of the first cell Ca1. The amplitude of the highest potential difference makes it possible to obtain discharges at the level of the four cells simultaneously.

The values of the potential differences necessary to obtain such effects depend on different parameters specific to the plasma panel itself, the nature of the ionizable gas for example, the distance between the plane of the column electrodes and the plane of the line electrodes and depends well heard of the width L3, L4 of these electrodes. So for example it was found that in the case of a plasma panel of a type current, in which the first column electrode X1 and the first row electrode Y1 have a width L3 of the order of 0.1 mm, it suffices to increase the width L4 of the second electrode X2 by approximately 0.1 mm to that the increase in surface area which results at the level of the second crossing surface SC2, that is to say of the second cell Ca2, makes it possible to lower by approximately 10 volts the voltage necessary to ensure discharges at this level cell with respect to the first Ca1 cell.

Thus in a group of cells GC1 intended to form an elementary image point, one or more of these cells can be given surfaces or geometries or shapes different from the other cells of this same group, so that one can in particular selectively creating certain discharges within the same group of cells, with a view in particular to adjusting the general level of luminance of the display screen, that is to say of the plasma panel.

It should be noted that the desired effect would also be obtained with a single column electrode and several line electrodes, or on the contrary with several column electrodes and a single line electrode. Of course, this version of the invention can also be applied in the case of plasma panels of the alternative type with coplanar maintenance. In the case for example illustrated in FIG. 4, it suffices for example to give the second electrode X2 a width different from the width 12 that the first column electrode X1 has. It is also possible to intervene on the shape and dimensions of the protruding surfaces of the addressing electrodes YA1 to YA6, for example by conferring different surfaces on some of the protruding surfaces 50, 51 of the addressing-maintenance electrodes (pairs P1 to P6), interconnected and which are crossed by the same column conductor X1 to X4 or by different column conductors but connected to each other.

Claims (8)

1 - Display device using plasma panels, comprising addressing and control means (13, 14, 45), the plasma panel (12) comprising a network of cells (C1 to C36, C′1 to C ′24), at least one array of row electrodes (Y1 to Y6, YA1 to YA6), one array of column electrodes (X1 to X6), the row electrodes being crossed with the column electrodes, each cell (C1 to C3₆ ) being made up substantially at the intersection of a line electrode (Y1 to Y6, YA1 to YA6) and a column electrode (X1 to X6), all of the cells (C1 to C36, C′1 to C′24) forming a display surface (SA) divided into a plurality of elementary image points (PI1, PI2, PI3, PI4), characterized in that at least one elementary image point (PI1 to PI4) is formed at from a group of cells (GC1 to GC4) consisting of at least two cells (C1 to C36, C′1 to C′24, Ca1 to Ca4)) contiguous. 2 - Display device according to claim 1, characterized in that the line electrodes (Y1 to Y6, YA1 to YA6) and / or the column electrodes (X1 to X6) are shared in group of electrodes (Gl1, GL2, G′L1, G′L2, GX1, GX2), each group being formed of at least two consecutive electrodes of the same type (Y1 to Y6, YA1 to YA6, X1 to X6, the electrodes of the same group (GL1, GL2 , G′L1, G′L2, GX1, GX2) being connected to the same control output (SL1, SL2, SX1, SX2) of the addressing and control means (3, 4). 3 - Display device according to one of the preceding claims, characterized in that the electrodes of the same group (GL1, GL2, G′L1, G′L2, GX1, GX2) are connected together before being connected to a control output (SL1, SL2, SX1, SX2). 4 - Display device according to one of the preceding claims, the plasma panel (2) comprising an active part (16) in which the cells are contained (C1 to C36), characterized in that the electrodes (Y1 to Y6, YA1 to YA6, X1 to X6) belonging to the same group of electrodes (GL1, GL2, G′L1, G′L2, GX1, GX2) are connected between they inside the active part (16). 5 - Display device according to one of the preceding claims, characterized in that at least two electrodes of the same group (GL1, GL2, GX1, GX2) are interconnected on the side of at least one of their two ends (34, 29, 21, 38). 6 - Display device according to one of the preceding claims, characterized in that at least two contiguous cells (Ca1 to Ca4) belonging to the same elementary image point (PI1 to PI4) have a surface (SC) and / or a different shape, so as to adjust the number of cells capable of being lit in the same group (GC1) of cells, by adjusting the potential differences (VX - VL) applied to the electrodes (Y1 to Y6, YA1 to YA6, X1 to X6) using the addressing and control means (3, 4, 45). 7 - Display device according to one of the preceding claims, characterized in that the line electrodes (Y1 to Y6, Ya1 to Ya6) provide at least one addressing function. 8 - Display device according to one of the preceding claims, characterized in that the plasma panel (12) is of the coplanar maintenance type, and in that the line electrodes (YA1 to YA6, E1 to E6) form pairs (P1 to P6) of maintenance electrodes, each pair (P1 to P6) comprising an address-maintenance type electrode (YA1 to YA6) and a maintenance-only type electrode (E1 to E6), the groups line electrodes (G′L1, G′L2) being constituted by address-maintenance type electrodes (YA1 to YA6).

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