FR2655459A1 - POLYCHROME VISUALIZATION SCREEN. - Google Patents

Abstract

The invention relates to a display screen, in particular of the plasma panel type. The object of the invention is to improve the purity of the primary colors. The display screen (21) comprises a plurality of elementary image points (PX'1 to PX'12) each comprising three cells (C1, C2, C3) of different colors. According to one characteristic of the invention, the elementary image points or pixels (PX'1 to PX'12) comprise several types of pixels which differ from one another by the relative positions of the cells of different colors which they comprise. A pixel of a given type is adjacent to at least one pixel of another type, so that at least two adjacent cells of different pixels are of the same color. This arrangement prevents the excitation of a cell of a given color from leading to an emission of light of a different color by a diaphotia effect between two neighboring cells.

Description

The invention relates to polychrome visualization screens, and it has

  The invention has a particularly interesting application in display screens which are affected by a fairly pronounced defect as to the crosstalk or optical intermodulation between neighboring pixels, as shown in FIG. This is particularly the case in plasma panels. Taking as an example the plasma panels, these panels are now well-known flat-screen display devices They operate on the principle of the light discharge in the gases They are used for the visualization of alphanumeric, graphic or other image, monochrome or polychrome Plasma panels generally comprise two insulating slabs delimiting a space filled with gas (generally a neon-based mixture). These slabs support two or more networks of crossed electrodes, the electrodes of a network being for example arranged according to columns and crossed with the electrodes of the other network which are arranged in lines, so as to define a matrix of elementary cells each formed substantially to

  the intersection of row and column electrodes.

  The operating principle is the selective generation (that is to say at the level of selected cells) of electric discharges in the gas. Each discharge in the gas is accompanied by a light emission localized at the level of each cell o occurs. this discharge called elemental discharge Each cell can thus constitute an elementary source of light whose state can be changed (on or off).

off).

  Given the matrix layout of the cells, their addressing is matrix, that is to say that for each cell this addressing is achieved by controlling two crossed electrodes at the selected cell. For example, in the plasma panels operating continuously, in which each cell is generally defined at the intersection between only one column electrode and only one line electrode, for a given cell, it is necessary to select the column electrode and the row electrode which define this cell and apply between these two electrodes a so-called "ignition" voltage as long as it is desired to obtain a light emission by this cell; the ignition voltage is a voltage whose value is equal to or greater than the starting voltage of the cell, the starting voltage being the minimum voltage to be applied between the two electrodes of a

  cell to obtain ionization of the gas.

  There are also alternating plasma panels In these panels, the addressing of a given cell is also carried out by the control of two electrodes which are crossed at this cell and which serve to define it. so-called "alternative" have certain advantages, one of which is a memory effect that makes it possible to address the useful information only to the cell whose state one wishes to change, whereas the state of the other cells is simply maintained or maintained (in the case of the lit state) by repetition of alternating electric discharges called maintenance discharges In the plasma panels of alternative type, the electrodes are covered with a layer of dielectric material, and they are thus no longer in contact

with the gas or with the discharge.

  Among the alternative type plasma panels, some use only two crossed electrodes to define a cell, as described for example in a French patent in the name of THOMSON-CSF published under No. 2,417,848 Other alternative plasma panels are said In this last type of plasma panels, three or more electrodes are used to form a cell In this case, most often each cell of the matrix is constituted substantially at the intersection between a column electrode (whose function is then only addressing) with two parallel and coplanar maintenance electrodes which form a pair of maintenance electrodes, the discharge maintenance of each cell, i.e. the repetition of the alternating electrical discharges previously mentioned, is ensured between the two maintenance electrodes of the same pair, and the addressing of a given cell is done by generating discharges between e two electrodes crossed at this cell. Such a coplanar maintenance alternative plasma panel is shown in FIGS. 1 and 2, in accordance with the teaching of the European patent application EP-A-0135382. This plasma panel comprises a glass slab 1 covered with a first and second families of maintenance electrodes 2 and 3 disposed in line, parallel and coplanar and arranged in alternation of an electrode 2 of the first family and an electrode 3 of the second family A succession of An electrode 2 with an electrode 3 constitutes a pair of maintenance electrodes for forming the same cell line. These electrodes are provided with recess or protruding part 2a and 3a which, in a single pair of electrodes, maintenance, are oriented towards each other so as to concentrate between them

  The set is covered with an insulating layer 4.

  The electrodes only addressing 5 or column electrodes are crossed with the maintenance electrodes 2 and 3; these are generally arranged in lines and the addressing electrodes 5 are generally arranged in columns The assembly is covered with an insulating layer 6 and

  a protective layer 7 magnesium oxide (Mg O).

  A second slab 8 completes the assembly A gas is contained in a tight space 9 formed between the slabs 1 and 8 held

  spaced apart by shims (not shown).

  FIG. 3 shows another embodiment of a 3-electrode coplanar maintenance plasma panel for forming a cell. In the example shown in FIG. 3, the column electrodes are carried by a slab while the electrodes maintenance are carried by the other slab, as described in a French patent application published under the

  No. 2,629,265 To simplify Figure 3 and the description,

  represented only a cell formed substantially at the intersection of a single addressing electrode or X-column electrode with two coplanar maintenance electrodes Yae and Ye

  which constitute a PE pair of maintenance electrodes.

  The column electrode X is carried by a first slab 50, for example made of glass. The assembly is covered with a layer 51 of dielectric material, for example low-temperature glass.

fusion (enamel).

  The PE pair of maintenance electrodes is supported by a second slab 60, and is covered by a layer of dielectric material 62. Conventionally, among the two electrodes that constitute the pair of PE maintenance electrodes: first electrode YAE provides an addressing function in cooperation with the column electrode X, and a maintenance function in cooperation with the other maintenance electrode of the same PE pair; the second maintenance electrode YE only provides a maintenance function with the first electrode YAE of the same pair Each of the electrodes of the pair of maintenance electrodes PE has a projection 66,68 formed at the cross (or in proximity) between the column electrode X and the electrodes of the pair of PE electrodes These projecting surfaces 66, 68 define a zone of electric discharges in the gas or maintenance discharges, zone

  whose contour is substantially defined by line 70.

  In the case of a color display, the first slab 50 may furthermore conventionally carry pellets of luminophores such as, for example, the tablet 56 shown in FIG. 3. In such a case, the elementary cell formed at the intersection of the electrode X and the pair of electrodes PE, constitutes one of the cells (colored to the color of the phosphor which the cell is provided with) with different colors that each elementary point of images or pixels comprises. During the electric discharges in the gas between the electrodes of a cell, both in the case where the cell consists only of two crossed electrodes and in the case of the coplanar maintenance, ultraviolet rays generated during these discharges excite the phosphor pellets The phosphors then emit by photoluminescence a visible light whose color is

  determined by the nature of the phosphor.

  Thus, each elementary image point of the plasma panel is constituted by the juxtaposition of small areas covered with phosphors of different colors, in a way that in itself is also found in other types of flat screen visualization or in the ray tubes

cathodic color.

  In plasma panels as in other types of display screen, two or three or even four cells of different colors are provided for each elementary point of image or pixel most often there are three colors per pixel, red, green and blue, and often a fourth color, white or one of three colors

above.

  In the plasma panels (as in other color display screens) the different colors are restored by composition of the basic colors whose balancing makes it possible to obtain the different desired shades This color balancing can be achieved for example according to the method described in the French patent application No. 87 03456 published under No. 2,612,326, and in which is described the operation of a color plasma panel, the text of this patent application to be

  considered as part of this description.

  FIG. 4 schematically shows one of the conventional arrangements (in a plasma panel), cells of different colors constitute an elementary point of image

  or pixel To simplify Figure 4 and the description,

  only six pixels P1 to P6 are represented, each comprising four cells C4 to C4 of which, in the traditional way, two cells are green in color. C 1 to C 4 cells consist of luminophores arranged substantially each in front of each other. a crossing of electrodes o is constituted the cell of discharges, as it was previously explained; and in the interest of simplification, these discharge cells are formed at the intersection of only two electrodes, a column electrode and a line electrode, but they could equally well be formed for example using a column electrode and a pair of electrodes lines (coplanar interview). Taking as an example the cells of the first pixel P1, the first cell C1 (top left of the pixel) is formed using a green phosphor V arranged at the intersection of a first column electrode Xi with a first electrode line Y1 ; a second red cell c 2 R is formed at the intersection of a second column electrode X 2 with the first line electrode Y 1; a third cell C 3 of blue color B is formed at the intersection of the first column electrode Xi and a second line electrode Y 2; the fourth cell c 4 is green in color V, and it is formed at the intersection of the second column electrode X 2 and the second electrode Y 2. In the same way, each of the other pixels P 2 to P 6 comprises four key cells at c 4 formed at the intersection of a column electrode Xi to X 6, and in all these other pixels the relative position of the cells of red, green and blue colors R, V, B is the same as that described

in the first pixel Pl.

  In this configuration, assuming that it is desired to display only a blue color at the second pixel P 2 for example, the blue color corresponding to the third cell c 3 Just turn on this cell, that is, say to apply the appropriate tensions between the

  third column electrode X 3 and the second row electrode Y 2.

  This results in an elementary electric discharge at this third cell c 3, and this electric discharge produces ultraviolet rays that bombard the closest phosphor which in this case is the blue phosphor B This blue phosphor emits a colored light blue that appears all the more sustained, saturated, that there are fewer cells to

  the "lit" state of different colors nearby.

  Unfortunately, ultraviolet rays propagate easily and can create a crosstalk phenomenon by the fact that they can bombard phosphors belonging to pixels neighboring the one in which they were emitted. As a result, the neighboring elementary cells if they are for example normally extinct, can emit under the effect of these ultraviolet rays a parasitic light, the color of the phosphor it contains, where it results in a deterioration of the color that one seeks to emit Indeed if instead of having only a blue color, there is a mixture of blue plus red plus green, this mixture generally results in a desaturation, that is to say by a drift towards the white

of the color considered.

  In the example of FIG. 4, the arrangement of the cells of different colors in a pixel corresponds to a structure called "Quad structure", in which each pixel P1 to P9 has a square shape and each side is formed by two cells of different colors (the square shape of a pixel of "Quad structure" or rectangular of a pixel of structure called "triad" supposes that cells repeat with a same pitch in both axes) The advantage of this structure is that it allows to distribute the loss of resolution equally between the two horizontal and vertical axes that is to say along the column electrodes and along the line electrodes: in each direction the size of the pixels is double of that of the elementary cells, the

  phosphors being divided into small blocks.

  Another conventional arrangement is that of the so-called "triad" structure t which is schematically represented in FIG. 5. In this "triad" structure, the blue, red and green phosphors are constituted by strips which in this example are vertical, respectively b B, b R, b V, which succeed each other with different colors In this configuration, each elementary pixel pixel P'1 to P'6 comprises three elementary cells C'l, C'2, C ' 3 of different colors, which succeed in a direction perpendicular to that of the strips, that is to say in the horizontal direction in the example described Thus the pixels have the shape of a rectangle whose length is parallel to the electrodes lines, and whose width parallel to the column electrodes

  (not shown) is that of a single elementary cell.

  It should be noted that in this arrangement, the above-mentioned phenomenon of cross-talk or intermodulation also exists: for example, an elementary discharge produced in the third cell C'3 of blue color of the first pixel P'l produces ultra-violet radiation. violet which not only can excite the luminophore of this cell, but can also excite the luminophores of green and red colors of adjacent cells C'2 and C'1 which belong to the pixels

neighbors P'2, P'3 and P'4.

  In plasma panels, a known solution to the problem of color degradation by crotch effect, consists in partitioning the different elementary cells by barriers, in order to prevent the propagation of ultraviolet rays from one cell to another. neighboring cell This solution can be very effective, but it is unsatisfactory by the fact that it complicates significantly

  technology and industrialization.

  The invention provides a relatively simple and easy solution to this problem of color deterioration due to the effects of crosstalk or optical intermodulation. It applies to display screens in which different colors are obtained by composition of at least two primary colors, and they are particularly applicable to plasma panels in which it reduces visible light emission other than that desired, without affecting the ultraviolet radiation itself. According to the invention, a polychromatic display screen, comprising a plurality of elementary image points or pixels, each pixel comprising at least two cells of different colors, is characterized in that the pixels consist of at least two types of pixels. pixels which differ from each other by the relative positions of the cells in these pixels, a pixel of a given type being adjacent to at least one pixel of a different type so that at least two adjacent cells belonging to pixels of different types

be of the same color.

  The invention will be better understood in the light of

  following description, given by way of non-limiting example in

  reference to the 7 appended figures, among which: Figures 1 and 2 already described show the conventional architecture of a plasma panel of the known type; FIG. 3 already described schematically illustrates the relative positions of an elementary discharge cell and a phosphor pellet in a known type plasma panel; FIG. 4 already described illustrates a conventional arrangement of the different cells of different colors in a pixel, in the case of a structure with four cells per pixel; FIG. 5 already described shows a standard arrangement of cells of different colors in a pixel in the case of a structure with three cells per pixel; FIG. 6 schematically illustrates, by way of nonlimiting example, an application of the invention to a polychrome display screen in the case of a four-cell structure per pixel; FIG. 7 illustrates the application of the invention to

  a polychrome screen of the type with three cells per pixel.

  FIG. 6 partially shows a display screen 20 which, in the nonlimiting example described, is a plasma panel. Screen 20 is of the basic three-color type: red R, green V, blue B It is represented in FIG. using only 12 pixels PX 1 to PX 12, but of course it can include many more pixels PX 1 to PX 12 comprise cells C1 to C4 of different colors, according to a structure (Quad) with four elementary cells per pixel, also the pixels PX 1 to PX 12 have the general shape of a quadrilateral and more precisely that of a square. In the context of the invention, the plasma panel may be of the continuous as well as the alternative type, Whether or not coplanar maintenance Each cell C1 to C4 is formed at an intersection of electrodes in a manner in itself conventional, at the intersection of a column electrode and a line electrode as in the example of FIG. 4 for example, such column electrodes and Electrodes lines not shown in Figure 6 to simplify

  the latter and the description; as a result the cells

  C1 to C4 are represented by luminophore pellets of the color they comprise, namely: green V for Cl cells, red R for C 2 cells, blue B for cells

  C 3 and green V cells for C 4 cells.

  According to a characteristic of the invention, the arrangement of the different cells C1 to C4 in a pixel is not the same from one pixel to a neighboring pixel, so that each cell of a given color is surrounded by a maximum of

  neighboring cells having the same color.

  In the nonlimiting example shown in FIG. 6, this leads to form four types of pixels which differ from one another by the relative positions of the elementary cells, that is to say the cells of different colors that they comprise: two adjacent pixels, for example the first and second pixels PX 1, PX 2, are of different types. If the relative positions of the cells C 1 to C 4 are observed in the second pixel PX 2, for example, at the top left a cell Cl (green color) and at the top right a cell C 2 (red color); under cell C1 is arranged cell C 3 (blue color), cell C 4 (green color) being placed next to cell C 3 and below cell C 2; this arrangement is also valid for the pixels PX 4, PX 10, PX 12 which are of the same type as the pixel PX 2 The pixels PX 1, PX 3, PX 9, PX 11 are of the same type and are a different type of the second pixel PX 2: it is observed that on the one hand, the position of the first and second cells C1, C2 with respect to each other is reversed with respect to the position they occupy in the second pixel PX 2, and that on the other hand, the positions of the cells C 3 and C 4 are also inverted with respect to the second pixel PX 2; in fact it observes, for two such neighboring pixels of a different type, for example the pixels PX 1 and PX 2, that the cells C1 to C4 in these two pixels occupy positions that are symmetrical with respect to the axis of

separation of these two pixels.

  The sixth pixel PX 6 is located under the second pixel PX 2 and, with the eighth pixel PX 8, it constitutes a third type of pixel: in the eighth pixel PX 8, the third and fourth cells C 3 and C 4 respectively blue and green are on the same horizontal line at the top of the pixel (they respectively occupy the same position as the first and second cells C1, C 2 in the second pixel PX 2); the first cell C1 (green color) is located in the bottom of the pixel PX 8 under the third cell C 3 (blue color), and the second cell C 2 is positioned in the bottom of the pixel under the fourth cell

C 4 (green color).

  A fourth type of pixel is represented by the fifth and seventh pixels PX 5, PX 7 respectively located under the first and third pixels PX 1, PX 3 In the fifth pixel PX 5, the first cell C1 (of green color) is at the top on the left, and at the top right is a third cell C 3 (blue color); the second cell C 2 (red color) of this fifth pixel is arranged under the first cell C1 (green color), and the fourth cell (green color) is

  located under the third cell (blue color).

  It follows from such an arrangement that each cell C1 to C4 is surrounded by a maximum of neighboring cells of

same colour.

  Indeed, at the sixth pixel PX 6 for example, the second cell C 2 of red color has for direct neighboring cells three other C 2 cells of red color, one of which belongs to the seventh pixel PX 7, another to the tenth pixel PX 1 O, and finally the last to the eleventh pixel PX 11 A similar result is obtained for the other cells C1, C3, C4 which are each adjacent to three elementary cells likewise

  type, that is to say, of the same color.

  In operation, an elementary discharge which is accomplished at a cell C1 to C4 of a given color of a given pixel PX 1 to PX 12, conventionally produces ultraviolet radiation to excite the photoluminescence of the With the invention, if this ultraviolet radiation extends towards the cells of the neighboring pixels, the light mainly emitted by these neighboring pixels will be of the same color as that in which the elementary discharge was carried out. As a result without reducing the rate of crosstalk,

we reduce the harmful effects.

  Tests carried out according to an arrangement such as

  above have given particularly interesting results.

  These results have been reported conventionally in a color chart (not shown) established in accordance with the standards defined by the International Commission on Illumination for the case where the three colors red, green and blue are used in the same elementary point d image, and these results have made it possible to draw, in a manner known in itself, a triangle of colors called "Maxwel's triangle" (not shown) whose surface is almost double that of a triangle established with a panel to plasma o the phosphors of different colors are arranged according to the prior art This means that with the arrangement according to the invention, the number of possible colors is increased in the same ratio as the increase in the area of the triangle, which leads in practice to divide in the same report the rate of crosstalk. It should be noted that in view of the fact that the pixels PX 1 to PX 12 are of different types (4 types in the example of FIG. 6), as a function of the relative positions of the cells C1 to C4 in these pixels, the control electronics of a plasma panel must take into account this additional complexity in the logical processing of information In practice, however, this most often poses few problems, especially in the (most numerous) cases where There is an image memory in which all the information is stored: it is then enough to modify the protocol of

reading this image memory.

  Another disadvantage brought about by the arrangement of the invention lies in the fact that it destroys the regularity of the color arrangement with respect to the prior art. It can be seen that cells C1 to C4 of the same color, of four adjacent pixels PX 1 to PX 12, constitute the same group. Taking for example the case of the second C 2 cells of red color R (this example being valid also for the cells of another color), it is observed that the four second adjacent C 2 cells belonging to the pixels PX 6, PX 7, PX 10, PX 11 may have luminophores formed from the same phosphor pellet 30 (symbolized in FIG. 6 by a dotted square); this example is also valid for the cells of another color Also considering the distance between cells of the same color in the vertical direction for example, (assuming that a whole column of pixels is lit in red), we see that the cells C 2 (red) of the fifth and the ninth pixels PX 5, PX 9 are at an average distance from each other lower than the average distance d 2 which separates the C 2 (red) cells from the first and the fifth pixel PX 1, PX 5 This irregular distribution of the cells of the same color may however not be troublesome if the resolution of the screen is fine enough or,

  which amounts to the same, if the observer is far enough away.

  This shows that the disadvantages attached to the invention, even if they can initially dissuade the specialist from using such a solution, are not prohibitive, and are largely offset by an improvement.

  calorimetric characteristics.

  FIGS. 7 and 8 illustrate the application of the invention to a polychrome screen 21 of plasma panels, in which three-color pixels PX'1 to PX'12 have a so-called "triad" structure. In fact, apart from the arrangement of the colors within each pixel PX'1 to PX'12, the screen 21

  is similar to that shown in Figure 5.

  Each pixel PX'1 to PX'12 comprises three cells C1, C2, C3 of different colors. FIG. 8 shows luminophores in the form of bands b1, b2, b3 which serve to constitute cells C1 to C3 of the screen 21, these bands bl to b 3 being respectively red R, green V and blue B In the non-limiting example described, the bands b1 to b3 are arranged vertically side by side so as to

  constitute a succession of bands of different colors.

  With reference again to FIG. 7, it can be seen that the pixels PX'1 to PX'12 are of two different types which differ from one another by the relative positions of the cells C1 to C3 that they comprise. A first type of pixel is represented by the pixels PX'1, PX'5, PX'9 on the one hand, and PX'3, PX'7, PX'11 on the other hand, which are superimposed in the vertical direction; a second type of pixel is represented on the one hand by the pixels PX'2, PX'6, PX'10, and by the pixels PX'4, PX'8, PX'12 on the other hand. Taking as an example the second pixel PX'2 (example valid for all the pixels of the same type): it comprises in central position, a cell C1 (green color), with on its left a cell C 2 (red color) and with on his right a

cell C 3 (blue color).

  Taking for example the first PX'1 to represent the pixels of the other type: it has in the central position a cell C1 (green color), with a cell C 3 on the left (blue color) and on the right a C 2 cell

(Red color).

  In the nonlimiting example of the description, the

  The difference between the two types of pixels lies in the positions of the second and third cells which are inverted from one type of pixel to another. As a result of this arrangement, as in the case of the preceding example, the cells of a given red or blue color belonging to a given pixel have, for directly adjacent cells belonging to other pixels, cells of the same color; this can be verified in Figure 7 both in the horizontal direction that

in the vertical direction.

  Of course, there is also an irregularity of the distance between cells of the same color, as illustrated in FIG. 7 in the horizontal direction by an average distance of 1 between two adjacent C 2 cells and a distance of 2 which separates two non-neighboring C 2 cells but

belonging to contiguous pixels.

  It should be noted that the positioning according to the invention of the cells of different colors, that is to say the phosphors of different colors with respect to the intersections (not shown) of electrodes, tends towards a simplification with respect to the prior art in the production of phosphors at the required positions In fact, in the case of the arrangement shown in FIG. 7 o the pixels P Xt 1 to PX'12 extend in the horizontal direction, and are constituted in the vertical direction only by a phosphor of a given color, the embodiment of the luminophores in the form of bands remains valid The grouping of cells of one and the same color simply leads to placing side by side phosphor strips of the same color or, as shown in FIG. FIG. 8, successively giving them a single width L1 and a width L 2 double. The width L 2 doubles makes it possible to form the end cells (ie the C 2 and C 3 cells. in the nonlimiting example described) two adjacent pixels located on the same axis (that is to say a horizontal line in the non-limiting example described); the central cells (C1) having the same color for all the pixels As regards the previous example, shown in FIG. 6 and which refers to a structure called "QUAD", the provision of the invention can even lead to a simplification, since in this case the phosphors can be in the form of pellets or blocks whose surface is sufficient to be divided into four parts

  each assigned to a cell C1 to C4 of the same color.

  The positions of cells stained in a pixel, shown in FIGS. 6 and 7, are given by way of nonlimiting example, and other arrangements come within the scope of the invention as soon as they lead to surrounding a cell. a color given by a maximum of cells of the same color.

Claims (6)

  1 full-color display screen, comprising a plurality of elementary image points or pixels (PX 1 to PX 12), each pixel comprising at least two cells (C1, C 2, C 3) of different colors, characterized in that the pixels (PX 1 to PX 12) comprise at least two types of pixels which differ from each other by the relative positions of the cells (C1, C 2, C 3) in these pixels, a pixel (PX 2) of a given type being adjacent to at least one pixel (PX 6) of a different type, such that at least two adjacent cells (C1, C2, C3) belonging to   pixels of different types are of the same color.   2 viewing screen according to claim 1,   characterized in that it is of the plasma panel type.   3 Display screen according to one of the   preceding claims, characterized in that the pixels   (PX 1 to PX 12) have three cells (C1, C 2, C 3) of different colors. 4 viewing screen according to claim 3, characterized in that the three cells (C1, C 2, C 3) of different colors of the same pixel are arranged on the same axis, the central cell (C1) having the same color for everyone the pixels.   Display screen according to one of   claims 3 or 4, characterized in that the cells (C1 to   C 3) of different colors are formed using three strips of phosphors (bl, b 2, b 3), the bands (bl, b 3) which serve to form end cells (C 2, C 3 ) having a width (L 2) twice the width of the strips (b 2) used to   constitute the central (Cl) cells.   6 Display screen according to one of the   claims 1 or 2, characterized in that each pixel   comprises four cells (C 1 to C 4) arranged substantially for to form a quadrilateral.   7 viewing screen according to claim 6, characterized in that two cells (C 1, C 4) of the same pixel   (PX 1 to PX 12) are the same color.   8 Display screen according to one of the   claims 6 or 7, characterized in that four cells   (C 2) adjacent pixels (PX 1 to PX 12) different have the same color. 9 Display screen according to one of the   claims 6 or 7 or 8, comprising pellets of   phosphors of given colors, characterized in that one luminophore pellet is common to four cells (C 2) adjacent to different pixels.