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(11) | EP 0 123 496 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method of making a display panel |
| (57) A method of making a display panel made up of a base plate carrying an array of anodes
and an array of cathodes disposed transverse to each other, insulating strips on the
face plate to space the cathodes from a first apertured plate electrode, a second
apertured electrode whose apertures are display cells seated on the first plate electrode,
and the face plate assembly carrying an A.C. electrode. According to the method, the
insulating strips, the first apertured plate electrode, and the second apertured plate
are made by coating the apertured plate electrode on both surfaces with insulating
material and photoetchable material, exposing and developing strip patterns in one
layer and aperture patterns in the other, and then etching to remove undesired material
to leave the desired strips on one surface of the plate electrode and the apertured
plate on the other. |
BACKGROUND OF THE INVENTION
[0001] A recently invented display panel which comprises a dot matrix display having memory is relatively complex and includes several support plates, insulating layers, and electrode arrays which must be prepared and assembled accurately. This panel is described and claimed in copending application Serial No. 051,313, filed June 22, 1979.
DESCRIPTION OF THE DRAWINGS
[0003]
Fig. 1 is a perspective, exploded view of a display panel embodying the invention;
Fig. 2 is a sectional view through the panel of Fig. 1 along lines 2-2, with the panel shown assembled;
Fig. 3 is a sectional view of the priming plate-glow isolator assembly of the display panel of the invention at one stage in its manufacture;
Fig. 4 is a view of the apparatus of Fig. 3 at a later stage in its prepdaration; and
Fig. 5 is a perspective view of a portion of the assembly of Fig. 4 at a later stage in its preparation.
DESCRIPTION OF THE INVENTION
[0004] The present invention is used to manufacture a display panel 10 of the type described and claimed in copending application of George E. Holz and James A. Ogle, Serial No. 051,313, filed June 22, 1979, and incorporated herein by reference, along with the patents and publications cited therein. This application describes a dot matrix memory display panel including a D.C. scanning portion and an A.C. display portion.
[0005] The display panel 10 includes a gas-filled envelope made up of an insulating base plate 20 and a glass face plate 30, which are hermetically sealed together, as illustrated in Fig. 2, along a closed periphery which surrounds the operating inner portion of the panel and the various gas cells provided therein. The base plate has a top surface 22, in which a plurality of relatively deep parallel longitudinal slots 40 are formed and in each of which a scan/address anode electrode, for example a wire 50, is seated and secured.
[0006] A plurality of scan cathode electrodes in the form of wires or strips 60 are seated on the top surface of the base plate or in shallow slots 70. The scan cathodes 60 are disposed transverse to the scan anodes 50, and each crossing of a scan cathode 60 and a scan anode 40 defines a scanning cell 72 (Fig. 2). It can be seen that the scanning cells are arrayed in rows and columns. More specifically, the cathode portions 61, the underlying portions of anodes 50, and the intermediate gaseous regions define the scanning cells.
[0007] The scan cathodes 60A, B, C, etc., form a series of cathodes which can be energized serially in a scanning cycle, with cathode 60A being the first cathode energized in the scanning cycle.
[0008] A reset cathode electrode 62 is disposed in a slot 64 in the top surface of the base plate adjacent to the first scan cathode 60A, so that, when it is energized, it provides excited particles for cathode 60A at the beginning of a scanning cycle to be described. Where the reset cathode crosses each scan anode, a reset cell is formed, and the crossing of all of the scan anodes by the reset cathode provides a column of reset cells. These reset cells are turned on or energized at the beginning of each scanning cycle, and they expedite the turn-on of the first column of scanning cells associated with the first cathode 60A.
[0009] In the panel 10, it is desirable that the cathodes 60, or at least the portions 61 thereof which are disposed in the scanning cells, be spaced uniformly from an electrode 80 positioned above the cathodes and described below. Thus, the cathode grooves or slots 70 must be of uniform depth. It is also desirable to provide means for preventing the spread of cathode glow from the operating portions 61 of the cathodes to the intermediate portions. These conditions are satisfied by providing insulating strips 74 between the top surface 22 of the base plate and the cathodes 60 and adjacent electrode plate 80, the priming plate. The strips are aligned with the anode slots 40 and are seated on the lands between these slots.
[0010] The portions of the panel described up to this point comprise the base plate assembly. This is the D.C. portion and the scanning and addressing portion of the panel.
[0011] Adjacent to the base plate assembly is the second portion of the panel which is a quasi A.C. assembly; that is, it includes A.C. and D.C. features. This portion of the panel includes an electrode in the form of a thin metal plate 80 having an array of rows and columns of relatively small apertures 92, each overlying one of the scanning cells. The plate 80 is positioned close to cathodes 60 and may be seated on insulating sheet 74. Electrode plate 80 includes a terminal 88 for making electrical connection thereto.
[0012] Adjacent to plate 80, and preferably in contact with the upper surface thereof, is an apertured plate or layer 86 having-rows and columns of apertures 94 which are considerably larger than apertures 92. The apertures 94 comprise the display cells of panel 10.
[0013] The sheet 86 may be of insulating material, as shown in Fig. 2, or it may be ot metal, and, if it is of metal, the plates 80 and 86 may be made in one piece, if desired and if feasible.
[0014] The quasi A.C. assembly also includes a face plate assembly which comprises face plate 30 and a large-area transparent conductive electrode 100 on the inner surface of the plate 30, together with a narrow conductor 110 of silver or the like which outlines and reinforces the- -electrode layer 100 to increase its conductivity. The conductor 110 includes a portion 114, to which external connection can be made. The large-area electrode 100 overlies the entire array of display cells 94 in plate 86. An insulating coating 120 of glass or the like covers electrode 100, and, if desired, a dielectric layer 132 of magnesium oxide, thorium oxide, or the like is coated on layer 120.
[0015] In panel 10, the apertures 94 in plate 86 comprise display cells, and, as can be seen in Fig. 2, each display cell has one end wall 134 formed by a portion of insulating layer 132, and an opposite end wall 136 formed by a portion of the top surface of plate 80. To provide cell uniformity and to minimize cathode sputtering, a coating of the material of layer 132 should also be provided on the base or lower wall 136 of each display cell 94, such as the layer 1.33 shown in Fig. 2.
[0016] Panel 10 has a keep-alive arrangement which includes an A.C. electrode 140 in the form of a linear conductive film or layer of opaque metal, such as silver, provided on the inner surface of the face plate 30 adjacent to one edge of the transparent conductive electrode 100. The A.C. keep-alive electrode 140 is positioned so that it is in optimum operative relation with the column of reset cells and reset cathode 62, to which it supplies excited particles. The.A.C. keep-alive electrode 140 is covered by the insulating layers 120 and 132. The plate 86 is provided with a slot 142, and plate 80 is provided with a column of holes 150, the slot 142 overlying and being aligned with the column of holes 150, and both lie beneath and are aligned with the A.C. electrode 140. The slot 142 in the plate 86 is narrower than the opaque A.C. electrode 140 so that a viewer, looking through face plate 30, cannot see any glow which is present in slot 142 and holes 150. Electrode 140 operates with plate 80 to produce glow discharge between them and produce excited particles in slot 142 and holes 150. These excited particles are available to the reset cathode 62 and assist the firing of the column of reset cells.
[0017] The gas filling in panel 10 is preferably a Penning gas mixture of, for example, neon and a small percentage of xenon, at a pressure of about 400 Torr. When the panel has been constructed and evacuated, the gas filling is introduced through a tubulation 24 secured to base plate 20 (Fig. 2), or a non-tubulated construction can be employed.
[0018] In making the panel 10, the base plate assembly, including plate 20 and the anodes 50 and cathodes 60, is prepared in any suitable manner, for example, as described in the herein-incorporated U. S. Patent No. 4,352,050 of Nicholas C. Andreadakis. According to the invention, the assembly of priming plate 80, glow isolator plate 86, and insulating strips 74 is prepared as a subassembly as follows. The metal plate 80 having holes 92 and 150 formed therein is coated on its top surface with a thin layer of glass or other etchable dielectric material such as Corning 7575 glass. A similar layer 170 is provided on its bottom surface. Both dielectric layers 160 and 170 are coated with layers 180 and 190 of a suitable photoresist.
[0019] The bottom photoresist layer 190 is then exposed and developed to provide non-removable strip- like regions 200 which extend along the photoresist layer between the rows of holes 92 and will ultimately form strips 74. The top photoresist layer 180 is exposed and developed to provide a pattern of regions which, when the layer is later etched, will form the apertures or cells 94. The assembly thus described is then treated with a suitable acid to etch layers 170 and 180 at the same time to provide the strips 74 and the layer of cells 94, as shown in Fig. 4. This subassembly is then joined with the base plate assembly and the face plate assembly described above, as illustrated in dash lines in Fig. 4, and the parts are sealed together and processed to form the completed panel.
[0020] The operation of the panel 10 is not set forth in detail herein since it is described in detail in the above-mentioned applications. However, a brief description of the panel operation is as follows: With the keep-alive electrodes generating excited particles, and with operating potential applied to the scan anodes 50, the reset cathode 62 is energized to fire the column of reset cells, and then the scan cathodes 60 are energized sequentially to carry out a scanning operation in the lower portion of the panel. At the same time, with sustaining pulses applied between the electrodes 80 and 100, as each column of scan cells is energized, information or display signals are applied to the proper scan anodes 50 to cause glow to develop in the associated display cells 94 where it is sustained by the sustaining pulses. When all of the columns of scan cells have been energized and the appropriate associated display cells have been energized, a sustained and visible message is present in the upper display portion of the panel.
forming a plurality of relatively deep parallel longitudinal first slots in a glass base plate having a top surface, upper and lower edges, and left and right ends,
securing an anode electrode in each of said first slots,forming a plurality of relatively shallow parallel second slots in the top surface of said base plate, said second slots being oriented generally transverse to said first slots,
securing a cathode wire in each of said second slots, said cathodes being all substantially uniformly positioned depth-wise in said base plate and all spaced uniformly beneath the top surface of the base plate,
said cathode wires crossing said anode wires and forming a first glow cell at each crossing, said first glow cells being disposed in rows and columns in a first layer,
forming an electrode assembly including an electrode plate having arrays of rows and columns of small holes and having a top surface and a bottom surface, the bottom surface carrying spaced-apart, parallel strips of insulating material disposed between said rows of holes, the top surface carrying a layer of insulating material having an array of relatively large apertures comprising display cells, one aligned with each of said small holes,
placing said assembly on said base plate with said strips of insulating material disposed across the cathode electrodes, and
seating a face plate assembly on said electrode assembly, said face plate assembly including a glass face plate having a bottom surface carrying a large-area transparent electrode coated with a layer of glass which is in contact with said layer of display cells.
providing a first coating of insulating material on the top surface of said electrode plate and a second coating of insulating material on the bottom surface of said electrode plate,
providing a first layer of photoetchable material on said first coating and a second layer of photoetchable material on said second layer of said insulating material,
exposing and developing said first photoetchable layer on said top surface to form parallel strips of exposed and developed regions,
exposing and developing the second photoetchable layer on said bottom surface to form regions which define said display cells, and
treating both of said first layers and both of said second layers to remove the undesired material of said layers to leave spaced-apart, parallel strips of insulating material on said top surface and an insulating layer having an array of apertures on the other surface.