FR2797991A1 - Color plasma display unit, comprises panel formed by two slabs with black matrix covering peaks of barriers separating rows of cells - Google Patents

Abstract

Color plasma display unit comprises a panel formed by two slabs with a black matrix covering the peaks of barriers separating rows of cells. A black matrix (40) covers at least part of the exposed area of the peaks (16a) of the barriers (16). An Independent claim is included for method of manufacture, in which the black matrix is deposited to obscure the peaks from view.

Description

The present invention relates to plasma display panels (PAP), and in particular color display PAPs implementing a black network to improve the contrast and saturation of the images. BACKGROUND OF THE INVENTION colors.

PAPs belong to the family of so-called flat panel display devices which are characterized by their small thickness (a few centimeters) compared to several tens of centimeters for a cathode-shaped display tube of similar format.

At the current level of technology, large-format PAPs - exceeding 100 cm diagonal - are produced on an industrial scale as monitor screens or television receivers. The quality of the image obtained is generally satisfactory, especially at the luminance level. It is known to use the use of a black network (better known by the term "black matrix") to guarantee the achievement of optimal color saturation and contrast due to the effects parasitic scattering and reflection of light respectively emitted and received by the internal structure elements of the PAP.

Indeed, in PAP, the color emission is obtained by the excitation of phosphors by UV rays. Each pixel is made up of three cells of elementary colors: red, green and blue. In order to obtain maximum color purity, for example for green, it is essential that a discharge on a green cell does not illuminate neighboring red and blue cells. It is therefore necessary to block the diffusion of ultraviolet rays produced in one cell to its neighbors of different colors and to prohibit the luminescence of the phosphors on the inter-cell zones. In fact, in these inter-cell zones, the phosphor-type deposit (which conditions the emission color) is poorly defined and depends on the technological constraints. It is also necessary to look for as low a diffuse reflection coefficient as possible for the panel, which amounts to reducing the backscattered radiation. This is one of the conditions to obtain a contrast. For this, surfaces must be made as dark as possible in non-emissive areas.

To better understand these phenomena, it will now be described with reference to Figures 1 and 2 the structure of a PAP 1 having a black network 30 on the front panel, according to the state of the art. The 1 in question is of the alternative type with surface discharge separation of the primary colors by barriers.

 PAP 1 comprises first and second glass slabs 2 and 4 a few millimeters thick arranged face to face with separation of the order of 100 microns between the inner faces when they are assembled (Figure 1).

The first slab 2 has on its inner face an array of parallel electrodes grouped into pairs of closely spaced electrodes Y, a- Y, b, Y2a-Y2b, ..., Y5 ,, - Y5b, ... Each pair of electrodes constitutes a display line of the panel. The electrodes are embedded in a thick layer of dielectric material 6, for example glass, which covers the entire useful surface of the slab 2. This layer 6 is itself optionally covered with a thin layer 8 (less than 1 micron) another dielectric material, in this case magnesium oxide (MgO), the surface of which is exposed to the discharge gas.

In the example, the inner surface of the first slab 2 is provided with a black network allowing in particular to separate the colors.

The second slab 4 has on its inner face an array of parallel electrodes uniformly spaced X 1, X 2,..., X 6, perpendicular to the row electrodes Y 1a-Y 1b, Y 2a-Y 2b, _, Y5-Y 5b,. .., which constitute the addressing electrodes of the plasma panel.

As for the first slab 2, these electrodes X1, X2, ...., X6, are embedded in a thick layer of dielectric 12, itself optionally covered with a thin layer of magnesium oxide 14. that this thin layer of magnesium oxide on the back slab is not absolutely necessary.

A discharge cell of the PAP is thus formed by the intersection of an address electrode Xi, X2, ...., X6, with a pair of electrodes Yla Y2a-Y2b, ..., Y5a-Ysb, ..., from a display line.

In operation, an alternating voltage, called maintenance voltage, is applied between the electrodes forming the pair of electrodes of each display line. Discharges occur at the surface between these electrodes as a function of a voltage signal applied to the addressing electrode, according to well-established multiplexing techniques.

In particular, it is possible to modify the light discharge state of each cell according to line-by-line scanning to produce a video mode display.

Straight barriers 16 are arranged on the thin layer 14 of the second slab 4, at each location between adjacent addressing electrodes X1, X2,..., X6, and parallel thereto. The barriers 16 comprise walls perpendicular to the surface of the slab 4 and a flat top that can possibly serve as a support for the inner face of the first slab 2. They thus partition the discharge cells in the direction perpendicular to the addressing electrodes Xi, X2, ..., X6, Typically, the barriers 16 have a height of the order of 100 microns and a pitch of 220 microns for a width of 50 microns.

Phosphors 18R, 18V, 18B are arranged in strips on the exposed surface of the second slab 4. (In the following, these luminophores are designated by "18" when referring generically.) A strip of The phosphor covers a surface portion of the thin layer of magnesium oxide 14 bordered by two adjacent barriers 16. It also covers the perpendicular walls of the two barriers 16 which are turned towards this surface portion. Each phosphor strip 18R, 18V, 18B has its own elemental emission color in red, green or blue in response to a D light discharge (typically in the ultraviolet) within a cell. Together, the phosphors constitute a repeating pattern of three successive bands each having a different emission color, so that a succession of elemental color triads is created in the direction of the line electrodes Yla-Ylb, Y2a. Y2b ..._, Y5a-, ...

The two slabs 2 and 4 are sealed together and the space they contain is filled with a discharge gas at a low pressure after vacuum pumping through a tube.

note that the presence of the layers of dielectric material 6, 8, 12 and above the electrodes Y1a-Y1b, Y2a-Y2b, ..., Y5a-Ysb, ... and X1, X2, ...., is characteristic of alternative PAPs. The dielectric material forms with its electrode a capacitor through which the voltages necessary to generate and maintain the light discharges are applied in the gas.

The specificity of the alternative PAPs is that the alternating maintenance voltage automatically freezes the state of a point of light discharge since last received command: either the maintained discharge, or it remains absent, according to the command previously transmitted. This results in an effect of inherent memory of the image, hence the possibility of addressing the points only when their luminous state must change.

Barriers 16 play an important role in conditioning

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<tb> in <SEP> this <SEP> concerns <SEP><SEP> PAP <SEP> to <SEP> discharges <SEP> into <SEP> surface. <SEP> effect, <SEP> they <SEP> have several distinct functions that directly affect the image quality they serve as a support for a relatively large portion of the deposited phosphor 18; as such, their walls at right angles to the base of the substrate 2 - that is to say their flanks - also covered with phosphor then allows to obtain a very open angle of vision; and being intrinsically opaque or by phosphor deposition, they make it possible to separate the primary colors.

We note that the barriers perform all the better these functions that their height is important. Thus, according to certain designs implement barriers 16 said full height ", that is to say that the top of the barriers joined the inner face of the opposite slab 2. In this case it is possible to confer the barriers also a spacer role, serving to establish and maintain the correct spacing between slabs against crushing forces due to external atmospheric pressure.

This solution also used today to reduce the visible emission of light emitted by a phosphor of an unaddressed cell. Indeed, the opacity of the barriers over the entire separation distance between the two facing slabs 2 and 4 maintains the phosphor strips in optically tight compartments vis-à-vis neighboring bands.

However, such a design provides a limitation, namely a poor distribution on the slab ionized gas, and a difficulty for pumping the panel by reducing the space available for the diffusion of gas to the exhaust.

To counter this limitation, a so-called "non-carrier barrier" technology has developed, the top of barriers not quite reaching the internal face of the facing slab. The opening thus created between the adjacent cells transversely with respect to the barriers allows ionized circulation over the entire useful surface between the slabs, thus ensuring homogeneous operation of the PAP at the responses to the ignition control and extinguishing signals. cells.

However, when the tops of the barriers are thus exposed, the latter receive phosphor deposits, as shown in FIG. 2. Indeed, to have maximum coverage, the phosphors 18 are deposited up to the top of the flanks of the barriers 16. As a result, phosphor is also deposited on the top of the barriers. There then occurs on each vertex mixtures of two colors on poorly separated surface portions. Thus, in the example illustrated in FIG. 2, the presence of 18R red phosphor and 18V green phosphor is observed on one of the vertices of the barriers 16. However, these zones at the top of the barriers are illuminated by the ultraviolet rays of the neighboring discharges on both sides and then emit with a mixture of colors which impairs the purity of color of the visualized image.

In order to block this parasitic emission originating from the tops of the barriers, a black grating is deposited on the slab 2 at the vertices ie the front slab, as indicated in FIG. 2. In other words, strips of opaque material are formed -normally on the internal face of the above-mentioned slab - directly in front of the vertices 16a so that an observer in front of the front slab 2 can not directly perceive the light emitted by the vertices 16a.

However, the opacity of the material constituting the black network is not perfect, and lets part of the light emitted by the phosphors on the vertices 16a.

Regarding the contrast, it is important to reduce the fraction of the retro-diffused light Rr by the panel relative to the light Ri incident on the panel. The black grating 30 deposited on the front plate 2 makes it possible to reduce this fraction by attenuating the coefficient of diffuse reflection. However, the partial opacity of the black network, associated with a very diffusing structure of the rear panel 4 due to the presence of phosphors 18, does not achieve a diffuse reflection coefficient of less than 18 - 20%.

On the other hand, the alignment constraints between the front face 2 and the rear face 4 make it necessary to maintain a margin between the black network 30 on the front face and the emission zones of the rear face 4, which reduces the same area covered by the black network 30 to avoid reducing the brightness.

In view of these problems, an object of the present invention is to propose a plasma panel comprising a first slab and a second facing slab, enclosing a discharge space, and an array of cells, at least one of the slabs comprising barriers. separating rows of adjacent cells, wherein a black array that overlaps at least a portion of the exposed surfaces of the apices of the barriers.

Preferably, the black network comprises strips of substantially opaque material with a width substantially equal to the width of the tops of the barriers.

Advantageously, the black network conceals any other coating, such as phosphor material, located at the vertices of the barriers.

For optimum efficiency, the black network can cover substantially all the exposed surfaces of the tops of the barriers.

The PAP according to the present invention may comprise phosphor material on the tops of the barriers, the black network then drowning the phosphor material on the vertices.

In a preferred embodiment, the tops of the barriers are exposed to the discharge space, a gap existing between the black network and the structure of the slab facing the latter.

black network is advantageously present on a slab for constituting the back panel of the panel, this slab comprising phosphor layers covering at least part of the sidewalls of the barriers.

Advantageously, the black network is in the form of a layer having a thickness of between 2 and 12 microns, a typical value being 4 microns.

It can be made of a black material or a very dark color. can use for this purpose a dark blue pigment for photolithography needs, black only being sometimes too opaque.

The composition of the black pigment may be a mixture of metal oxides among iron, nickel, cobalt, aluminum. A typical mixture of iron, chromium, cobalt and aluminum.

The composition of the blue pigment that can be used for producing the black (i.e. dark) network can be a mixture of metal oxides of iron, cobalt, and aluminum. Whatever the composition, the particle size is of the order of 0.5 to 6 microns, a typical value being 1.5 microns.

Black network according to the present invention may be present with a second black network located opposite the apices of the barriers so that it consists of a first and a second black networks facing respective slabs.

second black network may have narrower black bands black bands forming the first black network, in particular to account for the alignment accuracy of the respective two slabs.

The subject of the invention is also a method for manufacturing a plasma panel comprising a first slab and a second slab facing each other, enclosing a discharge space, and a network of cells, at least one slab comprising barriers separating rows of adjacent cells, the method comprising a step of producing a black network covering at least a portion of the exposed surfaces of the apices of the barriers.

The method can be adapted to achieve various optional features described above relatively plasma panel, these features are not repeated here concision concern.

Preferably, prior to the production of the black grating, phosphor material is deposited on at least portions of the slab comprising the barriers, and in that the constituent material of the black grating is then deposited by at least partially embedding any portions of phosphor located on the tops of the barriers.

Advantageously, the phosphor material is deposited at least on a portion of the flanks of the barriers.

In this case, it is possible to deposit, on either side of the apices, barrier means or luminophores having emission colors different from each other in the preferred embodiments. for the barriers a height lower than the planned separation between the first and second slabs, so that the tops of the barriers are exposed to the discharge space, a gap being provided between the black network and the structure of the slab in look at it.

Advantageously, the black photolithography network is produced. Similarly, one can also realize barriers by photolithography. In this case, the photolithography mask used to define the pattern of the barriers can also be used as a mask for defining the pattern of the black network.

The method may also provide for the realization of a second black network located opposite the vertices of the barriers so as to constitute first and second black networks facing respective slabs.

The invention will be better understood and the advantages which emerge from it will appear more clearly on reading the preferred embodiments, given purely by way of non-limiting examples with reference to the appended drawings in which - FIG. 1, already analyzed, is a three-quarter view of a known surface-discharge color plasma panel structure; - Figure 2, already analyzed, is a sectional view along the axis II-II 'of Figure 1; - Figure 3 is a sectional view similar to that of Figure 2 showing the structure of a plasma panel according to a first embodiment of the invention; - Figure 4 is a sectional view similar to that of Figure 3 showing the structure of a plasma panel according to a second embodiment of the invention; FIGS. 5a to 5d are cross-sectional views of a rear slab of the PAP of FIG. 3 or 4 during the successive steps of producing barriers; FIGS. 6a to 6f are cross-sectional views of a PAP rear slab of FIG. 3 or 4 during the successive steps of making phosphor layers; FIGS. 7a to 7d are cross-sectional views of a PAP back-plate of FIG. 3 or 4 during the successive steps of black network embodiment; and - Figure 8 shows a plasma display panel made according to the invention.

Figures 3 and 4 are sectional views of a plasma panel (PAP) similar to that described with reference to Figures 1 and 2. Also, the common aspects between Figures 1 to 4 will not be described again for the sake of clarity. conciseness. It will be understood that the parts of Figures 3 and 4 bearing the same references are already described in the context of Figures 1 and 2.

It will be noted in particular that, as in the case of FIG. 2, the barriers 16 of the embodiments represented in FIGS. 3 and 4 are disposed on the face 4a of the slab 4, designated after the rear slab, and do not reach the inner face 2a of the slab 2, designated front slab thereafter.

Fig. 3 shows a PAP according to a first embodiment of the present invention. It differs from that described with reference to the figure essentially in that it comprises a black network 40 located at the vertices16a of the barriers 16 of the rear panel 4. More particularly, the black network 40 covers the phosphor 18 located on the top 16a barriers. It is recalled in fact that in the presence of barriers covered with phosphors on their flanks, especially when these barriers do not reach the inner face 4a of the opposite slab, vertices are at least partially covered with phosphor 18.

black network 40 is dimensioned so that it occupies substantially the entire width L1 of the barrier, the latter being defined as the distance separating two opposite sides of the latter. In this way, all the vertex portions 16a are coated by the black network 40 without masking the phosphor portions on the flanks 16c of the barriers.

This feature is made possible by the fact that it is relatively easy to index the barriers 16 with precision the mask used for producing the black network 40, as will be described later.

Thus, to give a numerical example, mention may be made of a width L1 barrier for example of 50 microns - and therefore a black network elementary width 40 also of the order of 50 microns - for the case of a P1 between two adjacent barriers 16 of the order 220 microns.

Such correspondence between the elementary width of the black grating and the width of the barriers can not be practically envisaged in the case of a black grating 30 made in the front slab, in accordance with the state of the art (see FIG. ). Indeed, there is in case the problem of alignment between the slabs before 2 and back 4 which always leads to a margin of error. However, it is made such that such an error can not have the effect of placing an edge portion of the black network 30 of the front slab 2 outside the vertices of the vertices 16a of the barriers on the rear slab. (Such an overflow in the alignment would have the effect of inadmissibly permitting the light emission from flanks 16b of the barriers, or even of the phosphor layer 18 on the slab 2 in the vicinity of the latter.) In the context of the example above, the accuracy of the alignment of the front panel 2 with the back panel 4 is of the order of 20 microns, or 40% of the width L1 of the barriers. In this way, the maximum elementary width Lma (see FIG. 2) possible of the black grating 30 to take into account criterion is 10 microns, ie 50 microns for the width L1 of the barrier 16 minus two times 20 microns (once for each of the two edges).

Thus, still in the numerical example, the black network 30 placed on useful surface 'corresponds to only 4.5% of the usable area of the screen, the network being composed of strips occupying only 10 microns every 220 microns the elementary step P1 between the barriers 16. This figure is to be compared to the case of a black grating 40 deposited on the rear slab 2 according to the present invention, thus having an elementary width of 50 microns, which thus covers 23% of the useful surface.

 Since the contrast enhancement by a black grating depends on the surface it occupies, the arrangement of a single black network 40 on a back slab as described with reference to FIG. 3 brings a gain contrast very much greater than that brought by the classic black network structure 30, illustrated in Figure 2, and without loss of overall brightness the screen.

the presence of the black network 40 on the vertices 16a of the barriers above the luminophores also makes it possible to improve the purity of the colors. It is recalled that a significant source of loss of color purity is the presence of phosphor 8 on the tops of the barriers, these phosphor portions emit the stray light with a mixture of colors being excited by rays emitted by the discharge zone D to the front slab 2 at grazing angles (The little inclined relative to the general plane of the slabs). By way of example, if the black network 30 placed on the front slab according to the state of the art has a transmission coefficient of 20% and if it is assumed that the entire rear slab reflects 100% of the incident light. , then the portion of light that passes through the black grating 30 is reflected back through the latter as reflected light is 4%, or 20% x 20%.

On the other hand, because the black array 40 in accordance with the present invention substantially covers all the phosphor portions on the vertices 16a of the barriers, the latter can not be excited by the radii of the discharge zone. Even if some rays coming from this zone managed to reach the luminophore under the black grating 40 - for example because of an imperfect opacity of the material forming the lattice or of a local defect of material deposition, a significant proportion of. the parasitic light thus emitted would be diffused and reabsorbed by the entire black network. In this way, the diffuse reflection coefficient of the PAP at the vertices 16a of the barriers is substantially zero.

FIG. 4 shows a second embodiment of the invention which differs from that of FIG. 3 in that it comprises at the same time a black network 40 on the rear panel 4 as described with reference to the latter figure and a black network 30 such which is described by reference in FIG.

It will be noted that these two black networks 30 and 40 are perfectly compatible both in terms of manufacturing and improving the electro-optical characteristics of the PARs When two black networks 30 and 40 are thus implemented, their qualities are reinforce each other. Indeed, the presence of the black network 30 on the front slab 2 absorbs at least a portion of the incident rays and reflected rays, which reduces all possible light leakage from the black network 40 on the rear slab 4.

It will now be described with reference to Figures 5 and 6 the main steps of manufacturing one and more precisely the rear panel 4 of the latter, comprising a black network 40 according to the present invention.

The operations of producing the barriers 16 on the back panel 4 are begun. In the example, the slab is previously provided with the addressing network Xi, X 2,..., Xs, of the thick dielectric layer 12 and the thin layer of magnesium oxide 14 (see Figure 1), these elements being made according to conventional techniques.

In general, for the realization of the barriers and layers of phosphor and black network can be chosen between 1. make the barriers of dense and hard material, bake (at 550 C approximately), then deposit the phosphors and the black network and make a second firing (at 420 C approximately) after the deposition and development of the black network. This arrangement allows phosphors, fragile after cooking, not to be degraded by the process of producing the black network; or 2. make the porous material barriers, remove phosphors and the black network and make only one final cure at about C.

Barriers 16 are produced by lithography of a pasty layer deposited by screen printing on the thin layer of MgO (FIG. The paste forming the layer is composed for example of a mineral filler in the form of particles of alumina mixed with vitreous filler and of a photosensitive resin.

Using a squeegee 22, the paste 16 is uniformly spread over the MgO layer 14 through a screen-printing mask 24 having an opening in the format of the effective surface of the slab. The dough layer has a thickness of the order of 20 microns.

Next, a photolithography mask 26 is applied to the dough layer 16 '. The mask has a pattern of fungiform openings modeled on the pattern of barriers to be printed on the MgO layer 14. The parts of the layer revealed by the mask are exposed to ultraviolet radiation so as to render them resistant to development (FIG. 5b). ). It will be understood by those skilled in the art that other pastes using equivalent methods which result in the same result can be used in an equivalent manner.

The layer thus exposed is developed using, for example, water with sodium carbonate, and the surface is then dried with a knife of air.

A first layer of barrier material 16 'of elementary height of approximately 20 microns is then obtained (FIG. 5c).

The steps are repeated successively until the height required for the barriers, for example of the order of 100 microns (Figure 5d). Each new deposit of pulp 16 'by screen printing completely covers the useful surface of the slab, including the tops of the barriers in formation. Depending on the number of iterations of the steps, the vertical positioning of the screen-printing mask 26 or the depth thereof is modified to take account of the evolution of the deposits remaining on the slab. At the end of the photolithography cycles, the pattern is cooked at a temperature of about 550 ° C. for one hour in order to burn the organic part and bind the glass filler.

The phosphor layers 18R, 18V, 18B are then deposited using screen printing techniques similar to those used to create barriers 16. The three luminophores 18R, 18V, 18B of different emission colors are used separately.

For each phosphor, for example, a paste composed of a phosphor charge and a photoresist in a volume ratio of 1: 1 is prepared. This paste is deposited uniformly by serigraphy using a squeegee 22 on the useful surface of the rear slab 4 in order to form a sufficiently thick layer to embed the barriers. The configuration following this step represented in FIG. 6a, for the case of a first deposit intended to form the red phosphor 18R.

As shown in Figure 6b, the passage of the squeegee 22 above the barriers 16 inevitably leaves traces T18 phosphor on the vertices 16a of the barriers.

This gives a uniform filling of phosphor paste, overflowing slightly on the vertices 16 of the barriers, as shown in Figure 6c.

Next, a photolithography mask 50 is applied over the paste by applying it to the surfaces at the apices 16a of the barriers. The photolithography mask has a pattern of cutouts modeled on the areas to be formed the pattern for the phosphor in question, the red phosphor 18R for the example considered. For this purpose, the mask 50 comprises fungiform cutouts 50a whose width L2 corresponds to the separation between two flanks 16b facing adjacent barriers. These cuts 52 are spaced at a pitch such that every third space between two flanks 16b facing adjacent barriers is exposed, in accordance with the desired pattern for this phosphor 18R. The mask 50 is placed so that the cuts are located entirely outside the vertices 16a of the barriers, as shown in Figure 6d.

then exposes the mask 50 to an ultraviolet source so as to irradiate the portions above the cutouts 52. The irradiated parts are thus fixed and remain after the development that follows.

The same operations are repeated for the green and blue luminophores so as to obtain the repetitive pattern of three successive colors (red, blue) between the barriers 16.

Note that the residues formed on the vertices 16a of the barriers remain even after application of the photolithography mask 50 and development. After the deposition of the three phosphors of different colors and the cooking is thus mixed 18M phosphor residues on the vertices 16a of the barriers, as shown in Figure 6f.

Then, the black network 40 is deposited on the vertices 16 of the barriers, above the 18M phosphor mixed residues. This phase is also performed by a silkscreen deposit of a black network precursor material 40, followed by photolithography, development and firing steps.

In the first step, the precursor material of the black network is prepared in the form of a photosensitive paste.

Preferably, the black network is made of a black material or a very dark color. For this purpose, a dark blue pigment may be used for photolithography purposes, black being sometimes too opaque.

The composition of the black pigment may be a mixture of metal oxides among iron, nickel, cobalt, aluminum. A typical mixture of iron, chromium, cobalt and aluminum.

The composition of the blue pigment which can be used for producing the black (i.e. dark) network may be a mixture of metal oxides of iron, cobalt, and aluminum. Whatever the composition, the particle size is of the order of 0.5 6 microns, a typical value being 1.5 microns.

This precursor material 40 'is prepared in the form of a paste having a viscosity of the order of 1000 cps, ie 1 Pa.s. It is deposited by screen printing through a mask 14 and using a squeegee 22 as described for the constituent material deposition steps of the barriers 16 and the phosphors 18. The layer thus deposited has an extra thickness of about 2 to 12 microns at the above general plane of the vertices 16a of the barriers, a typical value being 4 microns.

Then, as shown in Figure 7b, is affixed to the layer of precursor material 40 'a mask 26 having cutting pattern 26a width L1 substantially the same width of the barriers 16, these cuts being repeated on a pitch equal to that of the barriers. It will be noted that the mask has a cutout configuration 26a identical to that of the photolithography mask (FIG. 5b) used to make the barriers 16. Also, it is conceivable to use the same mask 26 for the photolithography steps related to the production of the barriers 16 and the black network 40. This provision also has the advantage of ensuring that the positioning and shape of the black network will be modeled exactly on those of the barriers. Indeed, any inequality or distortion in the configuration of the mask 26 (for example due to manufacturing tolerances, mechanical thermal stresses, etc.) will change the uniformity of the barriers 16 and the network 40 above exactly in the same way . In other words, the errors and inaccuracies will be canceled between the barrier pattern and the black network 40.

Alternatively, it is possible to produce the layers forming the black network by direct screen printing. In other words, the constituent material of the black network is prepared in non-photosensitive paste form. This paste is applied directly to the tops of barriers 16 through a screen-printing mask having the same configuration as the photolithography mask 26 described above. It should be noted that this technique of direct silk screen deposition can also be applied for the production of barriers and / or phosphor layers.

ultraviolet irradiation apertures 26a through the mask to fix the precursor portions located above vertices 6a of the barriers. As shown in FIG. 7c, the black grating layer entirely covers the residual traces formed of the phosphor mixture on the tops of barriers.

Then, we go through a development step to remove all portions of the precursor material 40 ', not irradiated through the mask 26, proceeding as for the development phase previously described in the context of the realization of barriers 5c and 5d ).

Normally, a single photolithography photolithography selective deposition and removal cycle is necessary to obtain the desired thickness for the black grating 40. However, it is of course possible to repeat cycles as many times as necessary to obtain the desired thickness for the photolithography. black network, like iterations to obtain the required barrier height.

Finally, the layer - or possibly the successive layers - thus formed is subjected to firing in an oven at 420 ° C. for approximately 30 minutes in order to burn the organic elements (resins) and to solidify the various layers.

At the end of this step, the black grating 40 formed above the vertices 16a of the barriers is obtained and entirely covering the 18M phosphor mixture traces therein, as shown diagrammatically in FIG.

Note that the black network 40 is positioned on the normally non-emissive areas. It does not degrade the luminance of the panel.

The black network 30 on the front panel 2 according to the second embodiment of the invention can be realized according to techniques known in themselves and which will not be detailed here. For example, it is possible to use the same method of depositing precursor material by screen printing, followed by the steps of photolithography, development and cooking.

However, being a black network on the front slab 2, it is necessary to take into account the tolerances in the positioning of the latter relative to the rear panel 4, as explained above. Also, for the photolithography steps, it will be possible to use a mask having openings whose width will be smaller than the mask 26 used to make the black network 40 of the rear face. 4. Positioning of the photolithography mask for the black slab network before 2 will be such that openings - which will give rise to deposition areas forming the black network - will be located vertically above the vertices 16a of the barriers when the two slabs are assembled.

The black network 30 of the front panel 2 is formed on the inner face, either directly on the exposed side of the thin dielectric layer of MgO 8, between the latter and the thick dielectric layer 6. The black network 30 can also be deposited directly on internal face of the front slab 2, before the deposition of the dielectric layers and 8.

It will be appreciated that because of the absence of phosphor or other high temperature sensitive material, it is possible to use a precursor material for the black network having high firing temperature. This material may be for example glass filler mixed with a dark pigment.

The present invention has been described based on an example of an alternative surface discharge PAP. However, it is clear that the invention can also be implemented with any type PAP using barriers, such PAPs can be of technology - alternating current discharge of the surface discharge or matrix discharge type, in which the light discharges are produced from one slab to the next between crossed electrodes on the respective inner faces, direct current, in which the discharge occurs between electrodes having the same polarity in time <B>; </ B > - full color, that is to say based on at least three elementary colors, either restricted color range or monochrome.

Furthermore, it is also conceivable to implement the invention in which the vertices are not exposed to the discharge space, ie when the barriers meet the opposite slab. In this case, the opposite slab may rest on the black network, with a possible settlement of the latter under atmospheric pressure.

The invention can also be implemented in PAPs whose two slabs have barriers, those of one slab being in a cross direction relative to those of the other, or the barrier patterns are aligned so that the vertices meet between the internal faces two slabs. In these cases, it is possible to provide a black network on vertices of one of the barrier patterns or possibly two.

Claims (17)

<B> CLAIMS </ B> 1. Plasma panel (1) comprising a first slab (2) and a second slab (4) opposite, enclosing a discharge space, and a network of cells, at least one (4) slabs having barriers 6) separating rows of adjacent cells, characterized in that it comprises a black network (40) which covers at least a portion of exposed surfaces of the vertices (16a) of the barriers (16). 2. Plasma panel according to claim 1, characterized in that the black network (40) comprises strips of substantially opaque material with a width substantially equal to the width (L1) of the vertices (16a) of the barriers (16). 3. Plasma panel according to claim 1 or 2, characterized in that the black network (40) conceals any other coating, such as phosphor material (18M), on the tops (1 of the barriers (16). 4. Plasma panel according to one of claims 1 to 3, characterized in that the black network (40) substantially covers all of the exposed surfaces of the vertices (16a) of the barriers (1). 5. Plasma panel according to one of claims 1 to 4, characterized in that it comprises phosphor material (18M) on the vertices (16a) of the barriers (40), and that the black network (40) drowns said phosphor material (18M) on the vertices. 6. Plasma panel according to one of claims 1 to 5, characterized in that the vertices (16a) of the barriers (16) are exposed to the discharge space, a gap (e1) existing between the black network (40). ) and the slab (2) next to the latter. 7. Plasma panel according to one of claims 1 to characterized in that the black network (40) is present on a slab for constituting the rear panel of the panel, the slab comprising phosphor layers (18R, 18V, 18B ) covering at least part of the flanks (16b) of the barriers (16). 8. Plasma panel according to one of claims 1 to 7, characterized in that the black network (40) is in the form of a layer having a thickness of between 2 and 12 microns. 9. Plasma panel according to one of claims 1 to 8, characterized in that the black network is made of a material comprising at least one metal oxide among iron, nickel, cobalt or aluminum. 10. Plasma panel according to one of claims 1 to characterized in that it further comprises a second black array (30) located opposite the vertices (16a) of the barriers (16) so that it is consisting of a first and a second black network facing (40, 30) respective slabs (2, 4). 11. Plasma panel according to claim 10, characterized in that the second black network (30) has black bands narrower than the black bands forming the first black network (40). 12. A method of manufacturing a plasma panel (1) comprising a first slab (2) and a second slab (4) facing, containing a discharge space, and an array of cells, at least one (4) ) slabs having barriers (16) separating rows of adjacent cells, characterized in that it comprises a black grating step (40) covering at least a portion of the exposed surfaces of the vertices (16a) of the barriers (16) . 13. The method of claim 12, characterized in that the black array (40) is formed in the form of substantially opaque material strips of a width substantially equal to width (L1) of the vertices (16a) of the barriers (16). 14. The method of claim 12 or 13, characterized in that black network (40) substantially covers the entire exposed surfaces of the vertices (16a) of the barriers (16). 15. Method according to one of claims 12 to 14, characterized in that, prior to the realization of the black network (40), phosphor material is deposited on at least portions of the slab (4) comprising the barriers (16). ), and in that the material (40 ') constituting the black network is then deposited by at least partially embedding any portions of phosphor (18M) located on the vertices (16a) of the barriers. 16. Method according to one of claims 12 to 15, characterized in that is provided for the barriers (16) a height less than the separation provided between the first and second slabs (2 and 4), so that the vertices (16a) of the barriers (16) are exposed to the discharge space, a gap (e1) being provided between the black network (40) and the slab (2) facing the latter. 17. Method according to one of claims 12 to 16, characterized in that one carries out the black network (40) on a slab (4) intended to form the back panel of the panel, this slab having phosphor layers (18R , 18V, 18B) covering at least part of the flanks (16b) of the barriers (16). Method according to one of claims 12 to characterized in that the black network (40) in the form of a layer with a thickness between 2 and 12 microns is produced. 9. Method according to one of claims 12 to characterized in that carries the black network (40) of a material comprising at least metal oxide among iron, nickel, cobalt aluminum. 20. Method according to one of claims 12 to 19, characterized in that one carries out the black network (40) by photolithography. 21. A method according to claim 20, characterized in that the barriers (16) are made by photolithography, the photolithography mask for defining the pattern of the barriers being used also as a mask for defining the pattern of the black network (40). ). 22. Method according to one of claims 12 to 21, characterized in that it also carries a second black network (30) located opposite the vertices 6a) of the barriers (16) so as to constitute a first and a second black networks facing each other (40, 30) on respective slabs (2, 4). 23. The method of claim 22, characterized in that the second black network has (30) black bands narrower than the black bands forming the first black network (40).