Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J11/00—Gas-filled discharge tubes with alternating current induction of the discharge, e.g. alternating current plasma display panels [AC-PDP]; Gas-filled discharge tubes without any main electrode inside the vessel; Gas-filled discharge tubes with at least one main electrode outside the vessel
  • H01J11/10—AC-PDPs with at least one main electrode being out of contact with the plasma
  • H01J11/12—AC-PDPs with at least one main electrode being out of contact with the plasma with main electrodes provided on both sides of the discharge space
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J11/00—Gas-filled discharge tubes with alternating current induction of the discharge, e.g. alternating current plasma display panels [AC-PDP]; Gas-filled discharge tubes without any main electrode inside the vessel; Gas-filled discharge tubes with at least one main electrode outside the vessel
  • H01J11/20—Constructional details
  • H01J11/34—Vessels, containers or parts thereof, e.g. substrates
  • H01J11/38—Dielectric or insulating layers

Definitions

• the invention relates to display screens of the plasma panel type, and more particularly to the electrically insulating elements used in these devices.
• Plasma panels are flat display screens that operate on the principle of luminescent discharges in a gas. They include two insulating tiles, joined together so as to define a calibrated space between them. This space is tightly closed at the periphery of the slabs in order to form a gas space.
• the electrical discharges in the gas are obtained using electrodes to which electrical voltages are applied.
• the electrodes can be distributed on either side of the gas space: in this case most often an array of electrodes is carried by a slab and at least one other array of electrodes is carried by the other slab.
• the two networks are orthogonal to each other, and an elementary cell or pixel is defined at each intersection of electrodes.
• the electrodes can also be arranged on the same side with respect to the gas space, that is to say be carried by the same slab.
• the alternative panels have the advantage of presenting a memory effect which makes it possible to address the useful information only to the pixels whose state one wishes to change (on or off); on the other pixels, the state of the latter is simply maintained by repeating alternating electrical discharges, called maintenance discharges.
• This memory effect is obtained by electrically isolating the electrodes from the discharge gas, by covering with a dielectric layer on which accumulate the charged particles generated by the discharge in the gas.
• the structure described in this document relates more particularly to a structure of the coplanar maintenance type.
• this type of panel three electrodes are used to define a pixel: two parallel and coplanar electrodes carry out the maintenance discharges in each pixel; the coplanar electrodes are crossed with so-called addressing electrodes, the function of which is generally only to carry out the addressing in cooperation with one of the coplanar electrodes.
• addressing electrodes so-called addressing electrodes
• Such discharge barriers can also be used in "PAPs” whose cells or pixels are formed at the crossing of only two electrodes, and their presence is practically essential in “PAPs” of the “continuous” type.
• landfills barriers can be constituted by parts forming shims called spacers, which define the height of the gas space.
• the function of such spacers is illustrated by the figure which shows a plasma panel of the type with two crossed electrodes to define a cell or pixel.
• the figure is a sectional view parallel to one of these two electrodes.
• the panel 1 comprises two tiles 2, 3 each carrying an array of electrodes.
• the slabs 2, 3 constitute substrates, they commonly have a thickness El of the order of 1 to 6 mm.
• the first panel 2 carries a first network of electrodes Yl to Yn parallel.
• the second panel 3 carries a second array of parallel electrodes represented by an electrode X (shown parallel to the plane of the figure) orthogonal to the electrodes Y1 to Yn.
• the electrodes Yl to Yn are covered with a dielectric layer
• the dielectric layer 4 is covered by a protective layer 5 often made of MgO, the thickness of which is very small, of the order of 0.2 micrometers.
• the electrodes X of the second network are covered by a second dielectric layer 6 having substantially the same thickness E2 as the first.
• This second dielectric layer is itself covered with a second protective layer 7 similar to the first 5.
• ends 8 of the electrode X, not covered by the dielectric layer G, constitute sockets contact .
• the two tiles 2, 3 are intended to be assembled so as to provide between them a space 10 which must contain a _f az > of neon for example, at a pressure of for example
• the panel .1 has sealing joints 11 arranged at the periphery of one of the slabs. the second panel 3 for example.
• the height H1 of the gas space 10 is defined using spacers 12 called spacers, arranged at the periphery of a slab, of the first slab 2 for example.
• the spacers 12 are produced on the first dielectric layer 4, and in the bringing together of the two slabs 2, 3, these spacers must come into abutment on the second protective layer 7; these conditions are taken into account to define the height H2 of these spacers 12 in order to give the gas space the desired height Hl, height Hl (of the gas space) which is commonly of the order of 100 micrometers .
• the sealing joints 11 generally consist of a glass with a low melting point (between 380 ° C. and 450 ° C.). They have a height H3 such that, taking into account the surface on which they are arranged (surface of the second dielectric layer in the example), it is necessary to crush them to bring the spacers 12 into abutment on the second slab 3 , so as to thus seal the gas space 10.
• the quality of operation of the "PAP" can be degraded if the height Hl of the gas space shows too great variations.
• central spacers 15 it is also possible to use such central spacers 15 to further perform a separation barrier function between the discharges of contiguous pixels.
• Each pixel being defined in the area of intersection of electrodes X and Y, it is known to produce such central spacers 15, with a parallelepiped shape for example and to arrange them so as to surround each pixel.
• the separators or barriers 12, 15 are generally made of mineral glass: walls of mineral glass are formed in several intermediate layers by successive screen printing. These successive serigraphs are followed by a final baking to densify and harden the material.
• the layers produced by successive screen prints are difficult to superimpose with precision: thus for a layer whose width is for example 50 micrometers, it it is not uncommon for it to overflow 10 micrometers from the previous layer, so that finally these partitions or barriers have variable widths, the dimensions of which are difficult to control. This further results in a degradation of the operation of the plasma panel.
• Another drawback of this technique is that during the final baking of the layers forming these spacers or barriers, the temperature can reach, for example, 530 ° C. to 600 ° C. This may result in degradation of the glass which forms the slabs 2, 3 and / or degradation of the conductive deposits which form the electrodes. For example, the glass softens and loses its flatness if it does not rest on a perfectly flat support.
• Another method for making spacers (which in this case does not additionally fulfill the discharge barrier function) consists in depositing a dense network of calibrated glass beads, regularly arranged between the electrodes.
• the precision on the diameter of the balls is insufficient to obtain that the greatest number of balls are in contact at the same time with the two slabs or substrates.
• the general structure shown in the figure is the same, the difference being that in this case the dielectric layers 4, 6 and the protective layers 5, 7 do not exist, so that the electrodes X, Yl to Yn are in contact with the gas contained in the gas space 10.
• a finely ground glass powder is mixed with a solvent or an oil which decomposes at temperatures above 400 ° C;
• the mixture is then deposited by screen printing, or by dipping or by "spray” (projection), then dried on the substrate or glass slab and the electrodes;
• the glass slab is then heated to temperatures above 530 ° C, and the mixture reacts to form a vitreous layer whose thickness is generally between 20 micrometers and 30 micrometers.
• the glass begins to react with the conductive or dielectric layers deposited on its surface, and in particular with the materials constituting the electrodes.
• this vitreous dielectric offers the advantage of very good mechanical and chemical stability, during the subsequent step of sealing the plasma panel, which step requires temperatures of at least 400 ° C.
• the invention proposes to produce these elements from materials whose implementation work does not require exposing the entire plasma panel to a temperature much higher than that required in the sealing step.
• the invention proposes to produce at least one of the electrically insulating elements mentioned above in an organic polymerizable compound, and thermostable for temperatures equal to or lower than the sealing temperature of the plasma panel in which it is mounted.
• the resulting advantage is that the highest temperature imposed on the plasma panel is that necessary to effect the sealing.
• the organic compound used can be photosensitive, which makes it possible to engrave it in a simple manner by conventional photolithography methods, and to obtain any type of pattern with excellent resolution and uniform thickness.
• the invention therefore relates to a plasma panel in which at least one of the electrically insulating elements is made from an organic polymerizable compound, thermostable at a temperature equal to or lower than the sealing temperature of the panel.
• the invention further relates to a method for producing such electrically insulating elements.
• the plasma panel 1 comprises two plates 2, 3 each carrying an array of electrodes X, Yl to Yn, so that these electrodes are arranged on either side of the gas space 10 formed between the slabs 2, 3.
• at least one dielectric layer 4, f is required. interposed between each network of electrodes and the gas space 10, or at least two dielectric layers.
• the invention proposes to make them with a thermostable polymerizable organic compound.
• the basic organic compound may be a solution in a suitable solvent (xylene or metacresol for example) of a dianhydride and a diamine (the formulas of which are given below) for obtaining a
• polyimide 4- - AR 2 4-;
• AR j . and AR are aromatic chains.
• the organic compound can be deposited by usual methods of depositing so-called "thick" layers, for example the following methods: spinning, spray (spraying), soaking, roller or screen printing; conventionally in itself, the viscosity of the product can be adapted to the method used by varying the fraction of polymer in the solvent. Then heated gradually to slowly evaporate the solvents and polymerize.
• the final polymerization temperature should preferably be greater than or equal to the temperature of the panel sealing step. For example, a layer of final thickness of approximately 5 micrometers of polyphenylquinoxaline polymerized at 410 ° C. for 10 minutes, will no longer evolve chemically and mechanically during a sealing step at 400 ° C.
• the step of sealing a PAP is the step in which the two slabs 2, 3 are brought together, to obtain the desired height Hl of the gas space 10, and in which we deform the sealing joints
• organic compound can be loaded with mineral and / or metallic compounds, for example in order to modify the dielectric constant and / or to modify the color thereof.
• the relative dielectric constant Er of the organic compounds used can be between 2 and 4 for the pure compound (for example a polyimide) and it can be increased to reach values greater than 10.
• the thicknesses can vary from less than 1 micrometer to several tens of micrometers, depending on the dielectric capacity desired by the layer.
• the uncharged organic compound for example,
• the possible color of the final deposit can also be adjusted by adding an organic dye or a mineral compound. Black or white deposits can also be obtained in this way.
• thermostable organic compound as defined above, can be polymerized at relatively low temperatures, so as not to cause deformation of the substrate. glass or slab 2, 3, or degrade the other layers deposited on this substrate. In particular, the organic compound does not react with the electrode material (ITO, metal, etc.).
• the organic compound allows a homogeneous covering of the electrodes and therefore supports high electric fields without showing any phenomenon of electrical breakdown.
• a polymerizable organic compound similar to that indicated above for the dielectric layers, can constitute the basic material for the production of the spacers and barriers 12, 15.
• the organic compound can be loaded with mineral and / or metallic compounds, in order to vary the viscosity and / or the color and / or the resistance to crushing after polymerization.
• the organic compound can be spread on the substrate or slab 2, 3 by usual methods similar to those mentioned above for the dielectric layers (spin, spray, serigraphy, etc.).
• the exposure and photogravure phase occurs after the last deposit has dried, and before polymerization or following partial polymerization of the organic compound.
• the polymerization of the organic compound is obtained by exposing it to a heat treatment and / or by exposure to ultra-violet rays, in a manner which is in itself conventional.
• the photo-imageable nature of the organic compound makes it possible to confer, in a simple and sure manner, on the spacers and barriers 12, 15, the desired dimensions as well as the desired positions in particular with respect to the electrodes X, Yl to Yn. This characteristic is particularly advantageous in the case of barriers 15 whose width L, relative to the pitch P of the cells, must remain relatively small, and whose position between the cells is also important.
• spacers or barriers 12, 15 thus produced are thermostable and do not tend to creep: it is therefore possible to obtain height H2 to width L (Hl / L) ratios greater than 1, for heights H2 greater than 200 micrometers .
• the invention can be applied to the production of any electrically insulating element carried by a PAP slab, whether the latter is of the continuous or alternative type, monochrome or polychrome, whatever the distribution of the electrodes relative to the gas space. , and regardless of the number of electrodes used to define a cell.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Gas-Filled Discharge Tubes (AREA)
• Devices For Indicating Variable Information By Combining Individual Elements (AREA)

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• 1991
  • 1991-06-27 FR FR9108004A patent/FR2678424A1/fr active Pending
• 1992
  • 1992-06-19 EP EP92912967A patent/EP0546137B1/de not_active Expired - Lifetime
  • 1992-06-19 DE DE69204632T patent/DE69204632T2/de not_active Expired - Fee Related
  • 1992-06-19 US US07/969,222 patent/US5336121A/en not_active Expired - Fee Related
  • 1992-06-19 JP JP50135393A patent/JP3270045B2/ja not_active Expired - Fee Related
  • 1992-06-19 WO PCT/FR1992/000561 patent/WO1993000698A1/fr active IP Right Grant

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