EP0923106A1

EP0923106A1 - Electrodes for electronic displays

Info

Publication number: EP0923106A1
Application number: EP97403002A
Authority: EP
Inventors: Jerome Davidovits; Laurent Guiziou; Bernard Eid
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 1997-12-11
Filing date: 1997-12-11
Publication date: 1999-06-16

Abstract

An electrode design for use in electronic displays, in particular AC plasma display panels, in which a plurality of conductive metallic strips are employed as electrode bus members which make up each of the pair of electrodes which make up a display electrode in an AC plasma electronic display panel.

Description

Field of the Invention

The present invention relates to a new electrode design for use in electronic displays, in particular to electrode designs which are useful as display electrodes for the front plate of a plasma display panel.

Background of the Invention

A conventional three electrode type surface gas discharge alternating current (ac) plasma display panel is illustrated in Figs. 1 and 2. Such displays are disclosed, for example, in U.S. Patent No. 5,674,553, the specification of which is hereby incorporated by reference. Fig. 1 is a plane view of an arrangement of display electrodes X and Y in an image element EG and Fig. 2 is a schematic perspective view of a structure of an image element. This display device comprises pairs of lines of display electrodes X and Y; lines of address electrodes 22 insulated from the display electrodes X and Y and running in a direction intersecting the lines of display electrodes X and Y; areas of three phosphor layers 28R, 28G and 28B different from each other in luminescent color, facing the display electrodes. A discharge gas is retained in a space 30 between the display electrodes X and Y and the phosphors, such that the adjacent three phosphor layers of the three different luminescent colors 28R, 28G and 28B in a pair of lines of display electrodes X and Y define one pixel or image element EG of a full color display, as shown in Fig. 1. In this construction, only one display electrode pair, i.e., two display electrodes, is arranged in one image element.
Referring to Fig. 2, a three electrode type surface gas discharge AC plasma display panel is shown that comprises a front plate glass substrate 11 on the side of the display surface H, a pair of display electrodes X and Y extending transversely parallel to each other; a dielectric layer 17 for an ac drive; a protecting layer 18 of MgO; a glass substrate 21 on the background side; a plurality of barriers 29 extending vertically and defining the pitch of discharge spaces 30 by contacting the top thereof with the protecting layer 18; address electrodes 22 disposed between the barriers 29; and phosphor layers 28R, 28G and 28B of three primary colors of red R, green G and blue B.
The discharge spaces 30 are defined as unit luminescent areas EU by the barriers 29 and are filled with a penning gas, for example a mixture of neon with xenon (about 1-15 mole %) at a pressure of about 500 Torr as an electric discharge gas emitting ultra-violet rays for exciting the phosphor layers 28R, 28G and 28B.
Each of the display electrodes X and Y comprises a transparent conductor strip 41, and a metal layer 42 for supplementing the conductivity of the transparent conductor strip 41. The transparent conductor strip 41 can be, for example, a tin oxide layer (indium tin oxide-ITO or fluorine tin oxide-FTO) and the metal layers 42 can be, for example, a Cr/Cu/Cr three sublayer structure, or other conductive metal such as silver or aluminum. Depending on the design of the display, the transparent conductor strip 41 could have a width which varies from, for example, 40-300 microns wide, and the metal layer 42 can have a width L₂ which varies from, for example, 30-100 microns wide.
The distance between a pair of the display electrodes X and Y, i.e., the discharge gap, is selected to be about 40-150 µm and an MgO layer 18 about a few hundred nano meters thick is formed on the dielectric layer 17. The interruption of a discharge between adjacent display electrode pairs, or lines, L can be prevented by providing a predetermined distance between the adjacent display electrode pairs, or lines, L.
The phosphors 28R, 28G and 28B are disposed in the order of R, G and B from the left to the right to cover the surfaces of the substrate 21 and the barriers 29 defining the respective discharge spaces there-between. The phosphor 28R emitting red luminescence can be, for example, (Y, Gd)BO₃:Eu²⁺. The compositions of the phosphors 28R, 28G and 28B are selected such that the color of the mixture of luminescence of the phosphors 28R, 28G and 28B when simultaneously excited under the same conditions is white.
At an intersection of one of a pair of display electrodes X and Y with an address electrode 22, a selected discharge cell for selecting display or nondisplay of the unit luminescent area EU is defined. A primary discharge cell is defined near the selected discharge cell by a space corresponding to the phosphor. By this construction, a portion, corresponding to each unit luminescent area EU, of each of the vertically extending phosphor layers 28R, 28G and 28B can be selectively illuminated and a full color display by a combination of R, G and B can be realized.
Referring to Fig. 1, respective image elements EG are comprised of three unit luminescent areas EU arranged transversely and having the same areas. The image elements advantageously have the shape of a square for high image quality and, accordingly, the unit luminescent areas EU have a rectangular shape elongated in the vertical direction, for example, about 660 µmX220 µm.
A pair of display electrodes are made corresponding to each image element EG, namely, one image element EG corresponds to one line L.
The displayed picture is produced by plasma discharges which are induced locally in the penning gas by applying a suitable voltage between address electrodes 22 and the electrode pairs X and Y which make up each sustain or display electrode. This causes a gas discharge to occur in the area immediately surrounding the display electrodes X and Y. The gas discharge induces luminescence of the phosphors which produces a colored light to be emitted.
Thus, for alternating current plasma display panels, the front plate electrode geometry consists of a plurality of display electrodes, each consisting of an electrode pair X and Y. Because light is emitted out of the front plate and to the eyes of the viewer, it is desirable to block as little of the light emitted by the phosphor luminescence as possible. Consequently, it would be desirable to make the electrodes X and Y entirely out of a highly transparent conductive material, such as ITO or FTO. However, the conductivity of such transparent conductive materials is not high enough to operate as an electrode material over the relatively long panel lengths desired (i.e., lengths of 30 inches or more). Consequently, a metallic bus electrode 42 has typically been employed to help distribute the current over the entire length of the transparent conductive strip 41, thereby effectively minimizing the distance current has to travel across the transparent conductive strip film to the width of the transparent conductive strip (typically about 160 microns). Such metallic bus electrodes (which are typically made of aluminum or some other conductive metal) are obviously not transparent. However, if the metal buses are made thin enough, enough emitted light will be transmitted through the front plate for the display to operate effectively.
The manufacturing of this type of sustain electrode configuration involves printing photoresist masks on the substrate and selectively etching the desired pattern for both the transparent conductive strip and the conductive metal bus. The process for making the front plate electrodes is thus technologically difficult due to the need to register the second mask with respect to the location of the first mask, as well as the need to employ etching processes.

Summary of the Invention

One aspect of the present invention relates to a new configuration of display electrodes suitable for use in the front plate of an AC plasma display panel by employing a plurality of metallic electrodes (rather than a single metallic bus electrode) for each one of the pair of display electrodes employed in an alternating current plasma display.
In one embodiment of the present invention, the transparent conductive layer is entirely omitted. We have found that by employing a plurality of metallic buses to form both of the electrodes which make up the pair of electrodes comprising the sustain electrode, the transparent conductive layer can be omitted without effecting the performance of the display electrode. For example, in one embodiment, each display electrode is comprised of three metallic buses approximately 20 microns wide rather than a single metallic electrode 60 microns wide. Each of the three metallic bus members (each of which are 20 microns wide) are spread over an area equal to that of the previously employed transparent conductive layer, that is, for example, about 160 microns. Two such electrodes are employed as each display electrode pair. The total width of each display electrode (X and Y) thus remains the same (i.e. about 60 microns), as well as the gap between each display electrode (about 75 microns).
The metallic bus electrode designs of the present invention are capable of obtaining relatively the same luminescence as prior art configurations which utilized both a metallic bus and a transparent conductive coating. The designs of the present invention are also capable of exhibiting the same line resistance as the prior art configurations.
By eliminating the transparent conductive layer, manufacture of the display electrodes is facilitated by elimination of process steps needed to both deposit the conductive transparent layer and etch it to have its desired configuration.

Brief Description of the Drawings

Fig. 1 schematically shows the basic construction of a prior art full color surface discharge type plasma display device.
Fig. 2 is a perspective view of a prior art full color flat panel AC plasma display device.
Fig. 3 is a schematic diagram of the basic construction of a full color surface discharge type plasma display device of the present invention.
Fig. 4 is a perspective view of a full color flat panel AC plasma display device of the present invention.
Fig. 5 is a side view of a display electrode configuration in accordance with the invention.
Fig. 6 is a side view of an alternative display electrode configuration in accordance with the present invention.
Fig. 7 is a perspective view of the electrode configuration illustrated in Fig. 6.
Fig. 8 illustrates an alternative display electrode configuration in accordance with the prior art.
Fig. 9 illustrates an alternative display electrode configuration in accordance with the prior art.

Detailed Description of the Invention

Figs. 3 and 4 illustrate a full color flat panel AC plasma display device in accordance with the invention. The display device illustrated in Figs. 3 and 4 is identical to the display device illustrated in Figs. 1 and 2, with the exception that the pairs of lines of display electrodes X and Y are comprised of pluralities of bus electrodes 42, and these display electrodes X and Y do not utilize a transparent conductor strip 41 (as was the case in Figs. 1 and 2). In the embodiment illustrated in Figs. 3 and 4, the bus electrodes 42 are comprised of conductive metallic strips 42 arranged generally parallel to one another and running the width or length of the display. These strips could be made, for example, from one or more of the metals selected from the group consisting of aluminum, silver, chrome, copper, nickel, gold, zinc, and alloys or multilayers thereof. In the embodiment illustrated in Figs. 3 and 4, three bus electrodes 42 are employed to make up each bus structure. Two such bus structure make up an AC electrode pair X and Y.
Thus, the display device illustrated in Figs. 3 and 4 comprises pairs of lines of display electrodes X and Y; lines of address electrodes 22 insulated from the display electrodes X and Y and running in a direction intersecting the lines of display electrodes X and Y; areas of three phosphor layers 28R, 28G and 28B different from each other in luminescent color, facing the display electrodes. A discharge gas is retained in a space 30 between the display electrodes X and Y and the phosphors, such that the adjacent three phosphor layers of the three different luminescent colors 28R, 28G and 28B in a pair of lines of display electrodes X and Y define one image element EG of a full color display, as shown in Fig. 3.
Referring to Fig. 4, the surface gas discharge AC plasma display panel illustrated comprises a front plate glass substrate 11 on the side of the display surface H, a pair of display electrodes X and Y in accordance with the invention extending parallel to each other; a dielectric layer 17 for an ac drive; a protective layer 18 of MgO; a glass substrate 21 on the background side; a plurality of barriers 29 extending vertically and defining the pitch of discharge spaces 30 by contacting the top thereof with the protecting layer 18; address electrodes 22 disposed between the barriers 29; and phosphor layers 28R, 28G and 28B of three primary colors of red R, green G and blue B.
The discharge spaces 30 are defined as unit luminescent areas EU by the barriers 29 and are filled with a penning gas, for example a mixture of neon with xenon (about 1-15 mole %) at a pressure of about 500 Torr as an electric discharge gas emitting ultra-violet rays for exciting the phosphor layers 28R, 28G and 28B.
Each of the display electrodes X and Y comprises a plurality of metal bus members 42 capable of being operated at the same voltage. This can be achieved, for example, by connecting the bus members at one end, as will be discussed further below with respect to Figure 8 and 9, to form a metallic electrode bus structure. The metal bus members 42 can be, for example, a Cr/Cu/Cr three sublayer structure, or other conductive metal such as, for example silver or aluminum. In the display illustrated in Figs. 3 and 4, no transparent conductive layer is employed, i.e., the metallic electrode bus structures are deposited directly onto the glass substrate surface. In order to have a similar optical effect as in prior art configurations, in one embodiment, the total width of the metallic buses which make up each display electrode X and Y preferably remains about the same as in prior art designs, i.e. between about 30 to 100 µm. These electrode bus members 42 can be distributed over an area ranging from 30 to 100 microns.
In the embodiment illustrated, for example, each of the three metal buses 42 which make up each display electrode X and Y may be designed to be about 20 microns wide, for a total display electrode width of about 60 microns for each of the display electrodes X and Y.
The electrode bus structures of the present invention could be formed using various depositions techniques, including, for example, screen printing and other conventional deposition techniques for making thin conductive lines of conductive (e.g. metal) material. In one embodiment, such bus structures can be deposited from a recessed pattern which corresponds to the desired electrode bus structure pattern.
As mentioned above, one embodiment of the present invention thus consists in removing the transparent conductive layer and instead employing two or more narrow metallic bus members, as shown in Figs. 5 and 6. For example, it is believed that, using the electrode configuration illustrated in Fig. 5, the total width L₂ of the metallic buses which make up each display electrodes X and Y can remain about the same as a prior art design it is meant to replace. Likewise, the global width L₁ of one sustain electrode can remain about the same as the particular prior art design it is meant to replace. The same holds true for the three metallic bus design illustrated in Fig. 6. For example, in one embodiment, such a design (which corresponds to the design illustrated in Figs. 3 and 4) is comprised of three metallic bus members 42, each 20 microns wide, thereby achieving a total width L₂ for each display electrode X and Y of 60 microns. The global width L₁ of each of these sustaining X and Y can be, for example, about 175 microns.
In a preferred embodiment, the distance between a pair of display electrodes X and Y, i.e., the discharge gap, is selected to be about 40 to 150 microns. Dielectric layer 17 is preferably about 20 microns thick. MgO layer 18 about a few hundred nanometers thick is formed on the dielectric layer 17. The interruption of a discharge between adjacent display electrode pairs, or lines, L can be prevented by providing a predetermined distance between the adjacent display electrode pairs, or lines, L.
Fig. 7 illustrates a perspective view of the front plate for a display electrode employing three metallic buses. The three buses 42 that make up each electrode in the pair of display electrodes X and Y are connected at electrode connector 43 at the extremities of the display and thus are operated at the same voltage. The materials employed to form the metallic buses 42 can be adjusted to achieve a line resistance of the electrode similar to that in prior art configurations.
In an alternative embodiment of the invention, the multi-bus-member sustain electrode designs of the present invention can be deposited over or in addition to a transparent conductive material. By doing so, it is believed that the plasma discharge achieved will be enhanced (i.e. it will be brighter).
In another alternative embodiment, the metallic buses 42 employed to form electrode grids are interconnected as illustrated in Figures 8 and 9. By interconnecting the metallic buses together, line breakages in metallic bus members are less likely to result in dead display lines (i.e. areas where no current is traveling). In addition, it is believed that by appropriately interconnecting the metallic buses together, the luminance of the resultant plasma can be increased. In Fig. 8, the lines connecting metallic bus members 42 are in line with one another, whereas in Fig. 9, the lines connecting individual metallic bus members 42 are staggered (combinations of both could also be employed). In one embodiment, the bus members are interconnected along lines which are parallel with the barrier ribs 29. In this manner, the interconnecting lines are not visible to the viewer of the display, nor do they contribute to interference with the light which is emitted from the display. It should be noted, of course, that the metal bus designs illustrated in Figs. 8 and 9 are not to the scale that would be desired for an electronic display. In an actual display, a great many more interconnecting members would likely be employed. If desired, such interconnecting bus lines could be employed between each and every pixel, if desired. Alternatively, fewer interconnecting lines could also be successfully employed.
Although the invention has been described in detail for the purpose of illustration, it is understood that such detail with solely for that purpose and variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention which is defined by the following claims

Claims

An electrode structure for an electronic plasma display, comprised of a plurality of parallel display electrode pairs, each electrode pair comprised of two conductive metal electrode bus structures, each electrode bus structure comprising a plurality of conductive bus members.
The electrode structure of claim 1, wherein said conductive bus members are comprised of strips of conductive material.
The electrode structure of claim 2, wherein said conductive bus members are comprised of generally linear strips of conductive material, said conductive strips at least substantially parallel with one another.
The electrode structure of claim 1, wherein said conductive bus structures are comprised of at least one metal selected from the group consisting of aluminum, silver, chrome, copper, nickel, gold, zinc, and alloys or multilayers thereof.
The electrode structure of claim 1, wherein said conductive bus members are deposited directly onto a glass substrate.
The electrode structure of claim 2, wherein said conductive bus members comprise a total conductive material width between about 20 and 100 microns, and each bus structure has a global width L₁ of about 40-200 microns.
The electrode structure of claim 2, wherein each of said electrode bus structures comprise at least three metallic bus members having a total width between about 20 and 100 microns, and each bus structure has a global width L₁ of about 40-200 microns.
The electrode structure of claim 4, wherein the metallic bus members are deposited over a transparent conductive material.
The electrode structure of claim 2, wherein said conductive strips are connected with one another at a plurality of locations along the length of said strips by connecting strips of conductive material.
An electronic plasma emissive display having a front plate electrode structure in accordance with claim 9, wherein said connecting strips of conductive material are aligned with barrier ribs disposed on a backplate of said plasma display.
A method of making a front plate structure for an electronic display, comprising: forming a plurality of parallel display electrode pairs on a substrate, each electrode pair comprised of two conductive metal electrode bus structures, each electrode bus structure comprising at least two conductive metallic bus members.
The method of claim 11. wherein said forming step comprises forming said metallic bus structures from at least one metal selected from the group consisting of aluminum, silver, chrome, copper, nickel, gold, zinc, and alloys or multilayers thereof.
The method of claim 11, wherein said forming step comprises forming said metallic bus members directly on a glass substrate.
The method of claim 11, wherein each of said electrode bus structures which make up each of said electrode pair comprises at least two parallel metallic bus members, said metallic bus members having a total width between about 20 and 100 microns, and each bus structure has a global width L₁ of about 40-200 microns.
The method of claim 11, wherein the metallic bus members are deposited over a transparent conductive material.
An alternating current electronic plasma emissive display comprising a front plate electrode structure, said electrode structure comprised of a plurality of parallel display electrode pairs, each electrode pair comprised of two conductive metal electrode bus structures, each electrode bus structure comprising a plurality of conductive bus members.
The plasma display of claim 16, wherein said conductive bus members are comprised of generally parallel and linear strips of conductive material spread over an electrode bus width distance of about 40-200 microns, said strips of conductive material comprised of at least one metal selected from the group consisting of aluminum, silver, chrome, copper, nickel, gold, zinc, and alloys or multilayers thereof.
The plasma display of claim 16, wherein said conductive bus members are deposited directly onto a glass substrate.
The plasma display of claim 16, wherein said conductive bus members comprise a total conductive material width between about 20 and 100 microns, and said bus structures comprise a global width L₁ of about 40-200 microns.
The plasma display of claim 16, wherein each of said electrode bus structures comprise at least three metallic bus members having a total width between about 20 and 100 microns, and each bus structure has a global width L₁ of about 40-200 microns.