EP0279746A1 - Plasma panel having four electrodes per elementary image point, and method of controlling such a plasma panel - Google Patents

Abstract

The present invention relates to plasma panels of the alternative type. Each elementary image point is defined by three parallel and coplanar electrodes (G1, D1, X1, G2, D2, X2 ...) and by an electrode (Y1, Y2 ...) perpendicular to the other three and separated from the three others at least by a dielectric layer. Two of the three parallel electrodes (G1, D1, G2, D2) are connected to circuits supplying in operation the maintenance signals to each elementary image point. The electrode (Y1, Y2) perpendicular to the other three and that (X1, X2) of the three electrodes parallel to each other which is not connected to a maintenance circuit, are connected to circuits supplying in operation the signals of addressing to each elementary image point (A1 to A8). The electrodes (G1, D1, G2, D2 ...) which are connected to the maintenance circuits constitute two networks of electrodes (D, G) connected to two maintenance circuits (E1, E2).

Description

The present invention relates to plasma panels of the alternative type. It also relates to methods of controlling these panels.

Plasma panels of the alternative type, as they are currently marketed, consist, as shown diagrammatically in FIG. 1, of two glass slabs 1 and 2 each carrying a network of electrodes parallel to each other x₁, x₂ , x₃ ..., y₁, y₂, y₃ ..., which are covered with a dielectric layer 3. The two plates are mounted and sealed so that the two arrays of electrodes are perpendicular to each other and that there are a very small distance between the two dielectric layers facing each other 3. This space between the two dielectric layers is filled with a gas, generally based on neon. Each elementary image point is defined by the intersection of two perpendicular electrodes. The information is displayed by repeated ignition of a luminescent discharge within the gas by means of addressing and maintenance signals conveyed by the electrodes. The addressing signals make it possible to create discharges or to eliminate the possibility of subsequent discharges for the elementary points of selected images. The maintenance signals allow the creation of periodic discharges for the elementary points of images which are lit.

This plasma panel structure with two electrodes per elementary image point has the advantages of being of simple technological realization, of being robust and of using well-known electrical control circuits. However, this structure has the following two drawbacks:
- the number of electrodes to be connected is large. Thus, in the case of high definition screens where one wants to control 1000 elementary image points, it is necessary to connect at least 2000 electrodes. Consequently, the connections to be made and the control circuits of these screens generally represent a higher cost than the panel itself;
- It has proved difficult in practice to obtain with plasma panels with two electrodes per elementary image point a color other than the traditional red-orange neon.

Indeed, obtaining light of another color with good light output and a fortiori, the restitution of several colors simultaneously, requires depositing on the dielectric layers 3 one or more layers of phosphors converting the visible radiation ultraviolet generated by landfills. In conventional structures with two electrodes per elementary image point, the deposition of these phosphors, their positioning with respect to the electrodes and their degradation by the ions present in the discharges pose problems.

Other plasma panel structures than the conventional structure illustrated in Figure 1 have been proposed. None were entirely satisfactory.

By way of example, there will be mentioned a panel structure with three electrodes per elementary image point which is described in European patent 0.135.382. This structure is illustrated in Figure 2.

Each elementary image point is defined by two parallel and coplanar electrodes X and Y and by a Z electrode perpendicular to the other two. In FIG. 2, the three electrodes X, Y and Z are carried by the same glass slab 1. The dielectric layer 3 isolates the electrodes X and Y from the electrode Z and also covers the electrode Z. Consequently, the glass slab 2 does not carry any electrode and can therefore receive phosphors, emitting by photoluminescence, the or the desired colors. The addressing signals are applied to the crossed electrodes Z and X or Z and Y and the maintenance signals are applied to the parallel electrodes X and Y. Maintenance is therefore carried out by creating lateral discharges between the two electrodes X and Y , parallel and coplanar.

European patents 0.0135.382 and 0.157.248 describe methods for controlling the plasma panels shown in FIG. 2. These methods make it possible to reduce the number of control circuits, but in return the number of connections can be increased.

Thus in the case of a panel comprising 1024 elementary points, depending on the control method used, the number of control circuits varies between 64 and 1025 and the number of connections varies between 1056 and 1025.

In addition, as in the case of panels with two electrodes per elementary image point, the control circuits are complex because the same X or Y electrodes are used both for addressing and for maintenance, and while the address signals are weak, service signals are strong.

The present invention relates to a new plasma panel structure of the alternative type.

The present invention relates to an alternating type plasma panel, comprising a plurality of elementary image points, each point being defined by electrodes perpendicular to each other, connected to circuits supplying in operation address signals and signals. maintenance at each elementary image point, characterized in that each elementary image point is defined by three parallel and coplanar electrodes and by an electrode perpendicular to the other three, separated from the other three at least by a dielectric layer, two of the three parallel electrodes being connected to circuits supplying, in operation the maintenance signals, to each elementary image point, while the electrode perpendicular to the other three and that of the three electrodes parallel to each other which is not connected to a circuit supplying the maintenance signals in operation, are connected to circuits supplying in operation the addressing signals to each elementary image point .

The invention also relates to methods for controlling such a plasma panel.

Among the main advantages of the panel according to the invention, there may be mentioned:
- the simplification of the control circuits. In the panel according to the invention, the addressing and maintenance functions are fulfilled by separate electrodes. In addition, in a first preferred embodiment of the invention, the electrodes of the panel which receive the maintenance signals are connected in two networks D and G. Consequently, it is sufficient to apply the maintenance signals of two circuits high power control. In addition, in a second preferred embodiment of the invention where, with respect to the first preferred embodiment of the invention, one of the three electrodes parallel to each other, the one which carries the addressing signals is common to two neighboring rows of elementary image points, the number of control circuits for addressing the elementary points which are connected to these electrodes can be halved. Consequently, the invention makes it possible to reduce the cost and the reliability of the control circuits;
the reduction in the number of connections, in particular in the two preferred embodiments of the invention mentioned in the preceding paragraph. This reduction does not require any crossing of electrodes and results in a reduction in cost;
- the possibility of addressing each elementary image point separately. This is particularly interesting when only part of the information displayed on the panel needs to be modified. With the panels according to the invention, it is quite possible to address the panel line by line or point by point;
- an improvement in luminance, with equal consumption compared to standard panels with two electrodes per elementary image point.

• - les figures 1 et 2, des schémas illustrant la structure de deux modes de réalisation de panneaux à plasma selon l'Art Antérieur ;
• - la figure 3, un schéma représentant les quatre électrodes définissant chaque point élémentaire d'image dans les panneaux à plasmas selon l'invention ;
• - les figures 4 et 6, deux modes de réalisation représentés de façon schématique de panneaux à plasma selon l'invention ;
• - les figures 5a à d et 7a à d, des signaux de commande des panneaux des figures 4 et 6 ;
• - la figure 8, une variante de la figure 3.

Other objects, characteristics and results of the invention will emerge from the following description, given by way of nonlimiting example and illustrated by the appended figures which represent:

• - Figures 1 and 2, diagrams illustrating the structure of two embodiments of plasma panels according to the Prior Art;
• - Figure 3, a diagram showing the four electrodes defining each elementary image point in the plasma panels according to the invention;
• - Figures 4 and 6, two embodiments shown schematically of plasma panels according to the invention;
• - Figures 5a to d and 7a to d, control signals of the panels of Figures 4 and 6;
• - Figure 8, a variant of Figure 3.

In the different figures, the same references designate the same elements, but, for reasons of clarity, the dimensions and proportions of the various elements are not observed.

In the plasma panel according to the invention, each elementary image point is defined by four electrodes, as shown diagrammatically in FIG. 3.

In FIG. 3, it is shown that an elementary image point is defined on the one hand by three parallel electrodes G, D, X and on the other hand by an electrode Y perpendicular to the other three.

The three electrodes G, D, X are located in the same plane, on the same support, which can be one of the two glass slabs 1 or 2 that the panel contains - see for example in FIG. 1 relating to the Prior Art, the two glass slabs which bear the references 1 and 2.

The electrode Y is separated from the other three electrodes G, D, X at least by a dielectric layer.

In FIG. 3, the electrode Y is carried by the same glass slab 1 or 2 as the electrodes G, D, X; in this case a dielectric layer not shown in Figure 3, separates the electrodes G, D, X and Y and also covers the electrode or electrodes located towards the inside of the panel. The electrode Y can also be carried by the other glass slab than that which carries the electrodes G, D, X. In this case a layer of dielectric covers the electrode Y and another layer of dielectric covers the electrodes G, D, X. In FIG. 1, these dielectric layers which cover the electrodes have been designated by the reference 3.

Two of the three parallel electrodes, for example the electrodes G and D are used to convey the maintenance signals. It is therefore a coplanar type interview. The two perpendicular electrodes X and Y are used to convey the addressing signals.

It is therefore clear that in the plasma panels according to the invention the addressing and maintenance functions are fulfilled by separate electrodes, which makes it possible to use electronic circuits well suited to the high power required by the signal signals. maintenance and at the low power required by the addressing signals allowing the use of high impedance circuits. It is also clear that the plasma panels according to the invention make it possible to address each elementary image point separately, since the addressing of each point is carried out by two given perpendicular electrodes. Addressing can of course also be done line by line.

In Figure 4, there is shown schematically, that is to say only by its electrodes, a plasma panel according to the invention.

The panel in FIG. 4 has four rows and four columns of elementary image points.

As in FIG. 3, each elementary image point is defined by four electrodes Y and G, D, X.

In FIG. 4, the electrodes used have been designated by Y₁ to Y₄, G₁ to G₄, D₁ to D₄ and X₁ to X₄.

The electrodes G₁ to G₄ and D₁ to D₄ are connected together and create two networks called D and G.

The creation of the two networks D and G makes it possible to limit the number of circuits E₁ and E₂ to two, providing in operation the maintenance signals at each elementary image point, and necessary for the operation of the panel. In addition, the number of panel connections is reduced.

The electrodes Y₁ to Y₄ and X₁ to X₄ are connected to circuits called A₁ to A₈ which supply in operation the addressing signals at each elementary image point.

FIGS. 5a, b, c and d show the signals conveyed by the electrodes Y _j , X _i , with i = 1 to 4 and j = 1 to 4, D and G so as to carry out the addressing and the maintenance of the elementary points of images of a panel according to the invention. What is shown in FIGS. 5a to d constitutes only one of the control methods among others for a panel according to the invention.

Above FIG. 5a, it has been indicated how the different phases 1, 2, 3, 4, 5 which the control of the panel comprises are distributed as a function of time t, plotted on the abscissa.

Phase 1 is an initialization phase during which a discharge is created between all the electrodes X _i and Y _j of the panel so as to conduct charges of a given sign towards each electrode X _i . These charges are located in the space corresponding to the intersection of the electrodes X _i and Y _j . for this, we see in Figures 5a and b that during phase 1, we apply to the electrode Y _j a positive voltage pulse of value + V _Y and we apply to the electrode X _i a negative voltage pulse of value -V _X , V _Y and V _X being positive values. Between the electrodes X _i and Y _j considered, a sufficient potential difference is created to create a discharge.

During phase 2, the charges created on the electrode X _i are transferred during phase 1 to the electrode D. This is done while maintaining the reference potential taken equal to OV for example, the electrodes Y _j and G and by applying to the electrodes X _i and D slots of voltage of amplitude successively equal to + V₁ and -VH1Y and in phase opposition on the electrodes X _i and D. Thus one creates between the electrode X _i and electrode D, a discharge or an odd number of discharges. Each discharge has the effect of reversing the sign of the charges thus transferred to the electrode D. An odd number of discharges leads to an identical and very stable result.

Phase 3 is an addressing phase during which it is possible to create a discharge between the electrodes X _i and Y _j , if it is desired to light a given elementary image point. We therefore carry out a selective addressing of each elementary image point which is also called random addressing. In the embodiment of the control signals shown in FIGS. 5a to d, the electrodes D and G are at 0 Volt during phase 3. The electrode Y _j receives a pulse of voltage equal to + V _Y. As regards the electrode X _i , it changes to -V _X if it is desired to set the elementary image point in question to the on state. If it is desired to extinguish an elementary image point or keep it in the extinguished state, it is sufficient that the two voltages indicated above are not present simultaneously on the two electrodes Y _j and X _i .

During phase 3, in the event of the ignition of the elementary image point, there is inversion of the charges stored on the electrode X _i .

During phase 4, there is a succession of discharges between the electrodes X _i and D. This is obtained by applying to these electrodes of the voltage slots, in phase opposition, of amplitude successively equal to + V₁ and -V₂.

Phase 5 is a maintenance phase during which the electrodes Y _j and X _i are at the reference potential, equal to 0 Volt for example and the electrodes D and G receive voltage slots in phase opposition, amplitude successively equal to + V₁ and -V₂. There is therefore creation of a succession of discharges between the electrodes D and G.

Random addressing is used to switch on or off an elementary image point without this modifying the state of the other elementary image points because during phases 1 and 3, signals must be applied to the electrodes X _i and Y _j . Other non-random addressing is possible with the same structure, for example line-by-line addressing.

FIG. 6 represents another embodiment of a panel according to the invention. This panel differs from that of FIG. 4 by the fact that the electrodes X₂ and X₄ are removed and that the electrodes X₁ and X₃ connected to the circuits A₅ and A₇ are common to two columns of elementary points of neighboring images. This embodiment therefore makes it possible to reduce the number of connections and the number of selection circuits, while retaining the possibility of performing random addressing.

In the embodiment of FIG. 6, for a panel comprising 1024 rows of elementary image points, it will be necessary to use only two high power maintenance circuits and sixteen low power addressing circuits, each having 32 bits. Whereas the panels known so far required at least 64 maintenance circuits.

For n rows of elementary image points, the panels according to the invention require only n / 2 + 2 connections on one side of the panel and n connections on the other side.

FIGS. 7a, b, c, d show an example of the addressing signals Y _j , X _i , D and G of the panel in FIG. 6.

Such a panel requires the succession of two types of phases which have been called phases 10, 20, 30, 40, 50 and phases 100, 200, 300, 400, 500. Phases 10 to 50 make it possible to address the elementary image points situated to the left of the electrodes X₁ and X₃. Phases 100 to 500 make it possible to address the elementary points of images situated to the right of the electrodes X₁ and X₃, and for which the role of the electrodes G and D is reversed with respect to the elementary points of images situated to the left of the electrodes X₁ and X₃.

The control signals shown in Figures 7a to d during phases 10, 20, 30, 40, 50 are identical to the control signals shown in Figures 5a to d. The control signals shown in FIGS. 7a to g during phases 100 to 500 differ from those of phases 10 to 50, only as regards the signals applied to the electrodes D and G which have been inverted.

This modification corresponds to the position of the electrodes in FIG. 6, where the electrodes X₁ and X₃ are framed on the left by the electrodes D₁ and D₃ and on the right by the electrodes G₂ and G₄.

During the addressing phase 20, the charge transfer described with regard to phase 2 only occurs between the electrodes X₁, X₃ and their neighboring electrodes D₁ and D₃. By cons, this transfer does not occur between the electrodes X₁, X₃ and the electrodes D₂ and D₄, because the electrodes G₂ and G₄ are interposed between the electrodes X₁, D₂ and X₃, D₄. Consequently, during phase 30, only the elementary image points situated to the left of the electrodes X₁ and X₃ can be addressed since the maintenance pulses which took place during phase 20 could only occur between the electrodes D₁, X₁ and D₃, X₃.

During phase 200, on the contrary, there can be maintenance pulses only between the electrodes G₂ and X₁ and G₄ and X₃. Consequently, during phase 300 only the elementary image points located to the right of the electrodes X₁ and X₃ can be addressed.

As in the case of FIG. 5, the addressing signals of FIG. 7 are given only by way of example.

It is understood that the invention also relates to plasma panels in which, as in FIG. 6, an electrode such as X₁, X₃ ..., used for addressing, is common to two rows of elementary points of neighboring images, but for which, contrary to what is shown in FIG. 6, the electrodes D₁ to D₄ and G₁ to G₄ are not connected according to two networks D and G.

In Figure 8, there is shown a particular embodiment of a panel according to the invention in which the electrodes G, D, X parallel to each other are no longer in the form of a strip but are crenellated. This shape of the electrodes makes it possible to better locate the discharges corresponding to each elementary image point. It is clear that the discharges remain localized between the portions of electrodes which are closest.

FIG. 8 also shows an electrode Z, parallel and coplanar with the electrodes Y, which also serves to locate the discharges at each elementary image point.

These Z electrodes, referred to in the European patent 0.125.382 already cited, are called separation electrodes. They can either be electrically floating or connected to a voltage source.

Claims (7)

1. Plasma panel of alternative type, comprising a plurality of elementary image points, each point being defined by electrodes perpendicular to each other, connected to circuits supplying in operation addressing signals and maintenance signals to each elementary image point, characterized in that each elementary image point is defined by three parallel and coplanar electrodes (G, D, X) and by an electrode (Y) perpendicular to the other three, separated from the other three at least by a dielectric layer, two of the three parallel electrodes (G, D) being connected to circuits providing, in operation of the maintenance signals, to each elementary image point, while the electrode perpendicular to the other three (Y) and that (X) of the three electrodes parallel to each other which is not connected to a circuit supplying the maintenance signals in operation, are connected to circuits supplying in operation the addressing signals at each elementary image point. 2. Panel according to claim 1, characterized in that the two electrodes parallel to each other connected to circuits supplying in operation the maintenance signals to each elementary image point are connected to the other similar electrodes of the panel so as to constitute two networks of electrodes (D, G) connected to two circuits (E₁, E₂) supplying in operation the maintenance signals to each elementary image point. 3. Panel according to one of claims 1 or 2, characterized in that that (X₁, X₃) of the three electrodes parallel to each other which is connected to a circuit (A₅, A₇) supplying in operation the addressing signals to each elementary image point is common to two rows adjacent to elementary image points and in that the plasma panel has the following repetition of groups of five electrodes parallel to each other:
- first and second electrodes (G₁, D₁) connected to circuits (E₂, E₁) supplying in operation the maintenance signals to each elementary image point;
- a third electrode (X₁) connected to a circuit (A₅) supplying in operation the addressing signals to each elementary image point;
- a fourth and a fifth electrodes (G₂, D₂) connected to circuits (E₂, E₁) supplying in operation the maintenance signals to each elementary image point, the fourth electrode receiving the same signals as the first, and the fifth electrode receiving the same signals as the second. 4. Panel according to one of claims 1 to 3, characterized in that the three parallel and coplanar electrodes (G, D, X) have a crenellated shape so as to allow a better location of the discharges between parallel electrodes. 5. Panel according to one of claims 1 to 4, characterized in that each elementary image point comprises a separation electrode (Z), substantially parallel to the electrode (Y) perpendicular to the other three. 6. A method of controlling a panel according to one of claims 1 to 5, characterized in that it includes the repetition of the following five phases:
- a first phase during which a discharge is created between the two electrodes (X, Y) receiving the addressing signals;
a second phase during which at least one discharge is created between that (X) of the three parallel and coplanar electrodes receiving the addressing signals and one of the other two parallel and coplanar electrodes (L or R);
- a third phase during which, when it is desired to register an elementary image point, a discharge is created between the two electrodes receiving the addressing signals (X, Y);
a fourth phase during which a succession of discharges is created between the electrodes solicited during the second phase;
- A fifth phase during which a succession of discharges is created between the electrodes (D, G) receiving the maintenance signals. 7. A method of controlling a panel according to claim 3, characterized in that it comprises the repetition of the five phases defined in claim 6, with during the second and the fourth phases discharges between that (X) of the three parallel and coplanar electrodes receiving the addressing signals and one of the other two parallel and coplanar electrodes (L or R), then the repetition of the five phases defined in claim 6, with during the second and the fourth phase of the discharges between that (X) of the three parallel and coplanar electrodes receiving the addressing signals and that of the other two parallel and coplanar electrodes which was not used in the five preceding phases.

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