Multicolor gaseous discharge display device

Abstract

An improved gaseous discharge display device is disclosed for providing a multicolor capability with nominal modification of existing gaseous display technology. A dielectric glass over the conductor array on the viewing side of the device is doped with discrete transition elements arranged in a predetermined configuration, such elements being adapted to generate a specific color dot when the associated site is energized by appropriate selection signals. The panel is fabricated essentially as a conventional gaseous discharge panel, and requires no substantial modification of existing addressing and control circuitry.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

Application Ser. No. 410,009 filed Oct. 25, 1973, for "Gas Discharge Device for Multicolor Information Display" by Frank Tsui et al.

Application Ser. No. 372,384 filed June 21, 1973, for "Method and Apparatus for Gas Display Panel" by Tony N. Criscimagna et al.

Application Ser. No. 405,205 filed Oct. 10, 1973, for "Gas Panel Fabrication" by Peter H. Haberland et al now U.S. Pat. No. 3,837,724.

BACKGROUND OF THE INVENTION

This invention relates to display devices and more particularly to an improved gaseous discharge display device for generating images in selected colors by the selective energization of individual display sites.

Gaseous discharge display and storage devices have been developed as possible replacement for cathode ray tubes since they afford economy of manufacture, consume relatively low power and their flat panel configuration is more readily adaptable for packaging. One example of such gaseous discharge display and storage panels is disclosed in U.S. Pat. No. 3,559,190 "Gaseous Discharge and Memory Apparatus" patented Jan. 26, 1971, by Donald L. Bitzer et al. Such devices may comprise three layer glass cell construction including a center layer of physically isolated cells, or alternatively may comprise an open panel configuration of electrically isolated but not physically isolated cells or sites. Individual sites are selected by energizing associated pairs of orthogonal drive lines disposed on opposite sides of the panel to produce a breakdown potential of the gas resulting in light emitting plasma. The resulting wall charge produced at potential permits the display to be maintained at a lower potential designated sustain. While the intensity of the display may be varied by variation of the amplitude, frequency or duration of the write signals, practical design considerations dictate uniformity of signals such that a single intensity level display is provided.

Alphanumeric display terminals, particularly when associated with a processor, utilize different techniques for visual cueing or highlighting of certain aspects of the display. Such visual cueing features include dual intensity, blinking, underscore and color. From a human factors standpoint, a preferred highlighting technique is color which can draw the attention of the operator to areas of the display without undue visual fatique or strain.

The enhancement of the efficiency of gas discharge devices through the use of phosphors is, of course, well known. One example of this technique is disclosed in U.S. Pat. No. 3,589,789, "Method of Producing an Open Cell Color Plasma Display Device" by Carl C. Hubert et al and assigned to the assignee of the instant invention. In the Hubert et al apparatus color plasma diaplay panels are produced by selectively applying, by cataphoretic deposition, predetermined phosphors to certain conductors carried on the inner faces of panel walls whereby the cells exhibit either multiple or single color effects during operation.

An interesting extension of this technique is the deposition of different color phosphors over adjacent cells in the manner of the shadow mask television tubes. An example of this technique utilizing three different phosphors in a triad color group and coincident selection of individual colors is shown in the aforereferenced copending application Ser. No. 410,009. Each of the phosphors is located at a corresponding intersection point so that it may be addressed. By suitably addressing the cells within a color group, a variety of colors can be produced. Phosphors, however, age rapidly when exposed to gas discharges. Other techniques for producing color in gaseous discharge displays comprise complex structures utilizing different gases, one example being shown in U.S. Pat. No. 3,588,596 to Donald D. Tech.

SUMMARY OF THE INVENTION

By utilizing a gas display panel with a gas which is panchromatic in light emission such as xenon and a dielectric doped with various transition elements in a discrete manner on the viewing side of the panel, a multicolor capability is provided by selective energization of the site having the desired color producing transition element. A transition element is one of several groups of elements in the periodic table having an incomplete inner shell. Such elements, as more fully described hereinafter, are all metals and most possess color ions and have a tendency to form complexes. When formed over conductor arrays on a glass substrate and overcoated with a glass frit which is reflowed, the transition elements diffuse into the glass. When the area beneath the desired transition element is ionized by appropriate drive signals applied to the associated conductors, the resulting panchromatic light emission causes the color ions in the transition element to emit light of the selected color. The device can be fabricated by gaseous discharge panel technology such as described in the aforenoted copending application Ser. No. 405,205, and is driven by logic and drive circuitry such as shown in aforenoted copending application Ser. No. 372,384.

Accordingly, a primary object of the present invention is to provide an improved multicolor gaseous discharge display device.

Another object of the present invention is to provide an improved multicolor gaseous discharge display device comprising an array of discrete transition elements in a predetermined configuration, each of said elements being adapted when ionized to produce a color light output.

Still another object of the present invention is to provide an improved multicolor gaseous discharge display device having an array of color dots on the display surface of said panel, said dots being composed of transition elements adapted to emit a specified color when the associated site is discharged by appropriate drive signals.

The foregoing and other objects, features and advantages of the present invention will be apparent from the following description of a preferred embodiment of the invention as illustrated in the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front edge view of a multicolor gaseous discharge display assembly constructed in accordance with the teaching of the instant invention.

FIG. 2 is a top view of the display surface of one of the panel components shown in FIG. 1 illustrating the array of transition elements.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to the drawings and more particularly to FIG. 1 thereof, there is illustrated a gaseous discharge display assembly 10 comprising glass substrates 11 and 13, substrate 10 having a plurality of conductors 15 formed thereon, with a layer of dielectric glass 17 formed over the conductor array. The gas chamber 21 is filled in the preferred embodiment with xenon gas which is panchromatic in light emission. The panel is sealed about its edges to form a gas containing envelope. An additional layer of a refractory material 19 is disposed over the dielectric to protect the conductors against sputtering or ion bombardment during ionization of selected cells or sites. Refractory materials having a high coefficient of secondary emission such as magnesium oxide, for example, are well known in the art and permit operation at lower signal levels. On the opposite or viewing side of gas chamber 21 is a second layer of refractory material 23 identical to layer 19, and a dielectric layer 25. In addition to conductors 31 which are orthogonal to conductors 15, the preferred embodiment of the present invention utilizes a series of discrete transition elements 35, 39 in a predetermined array, the particular transition elements in the preferred embodiment being selected for a specific color definition. As is well known in the art, transition elements include a series of group of elements comprising elements 21 through 30 (scandium -- zinc) in the periodic table as well as three other groups of elements, elements 39 through 48 (yttrieum -- cadmium), 56 through 80 (lanthanum -- mercury), and 80 through 103 (actinium -- lawrencium). However, for the three colors utilized in the preferred embodiment of the instant invention, only elements in group 1 are used. Copper, cobalt and copper mixed with a small percentage of tin are the transition elements utilized to provide the three colors. Transition elements of copper provide an aqua-greenish color, transition elements of cobalt a blue color and transition elements of copper with a small percentage of tin provide a red color. An alternative method of providing a three color display would be to utilize two transition elements for two of the colors, while the discharge of the gas without a transition element would produce a third color. The transition elements may be applied in individual sites through conventional masking techniques, the method employed in the preferred embodiment, although photo etching techniques might also be utilized. For a tricolor display such as contemplated in the preferred embodiment of the instant invention utilizing three transition elements, three separate evaporations through different masks would be required, one for each of the transition element colors. The size and shape of the pads of transition elements would vary as the function of the desired resolution and size of the panels, but the pads utilized in the preferred embodiment for a resolution of 50 lines per inch would be approximately 180 mils on each side. A 50 line per inch resolution would provide a display resolution of 25 lines per inch, since two lines are required for selection of one of the three basic colors. Each transition element is located at the intersection of an associated pair of orthogonal conductors. The transition elements as more clearly shown in FIG. 2 are driven from one side by drive conductor 31A-31N while they are driven from the opposite side by drive conductor 33A-33N, the preferred embodiment of the instant invention utilizing a driving arrangement from both sides of the panel. However, this driving arrangement is merely as a matter of design choice, and driving from either or both sets of conductors from either or both sides of the panel is contemplated within the present invention.

Before continuing with the description of the present invention, a brief description of the theory of gaseous discharge displays will facilitate an understanding of the subject invention. Gaseous discharge panels or plasma display panels operate under the "wall charge" theory wherein writing is accomplished by applying a discharge potential across the conductors associated with selected sites to generate a discharge, the resulting light output being then maintained or sustained by a lower level signal. An alternating potential from associated pairs of conductors is capacitatively coupled to the gas through the dielectric material, producing an alternating voltage across the gas in the region or site defined by the conductor intersection. When this potential exceeds the breakdown voltage of the gas, the gas becomes conductive through the voltage induced production of electrons and gas ions, and selected gas cells or sites are said to have broken down. In this conductive state, electrons in the gas migrate to the wall which is temporarily positive while the ions migrate to the wall which is temporarily negative. The charge particles collected on the dielectric walls or wall charges produce a potential between the dielectric surface and the conductors which opposes the externally applied potential and thus reduces the voltage across the cell. As current continues to flow through the gas, the opposing wall charge increases until the gas voltage drops below that necessary to maintain the gas in a conductive state, i.e., the sustain level, and the current discharge is extinguished. On the following phase reversed half cycle of the a.c. signal, the voltage produced by the wall charge initially adds to the externally produced signal so that the gas voltage is augmented and the cell reignited. Thus, due to wall charge effect and after an initial discharge, the breakdown voltage of the gas is obtained at a lower value of external potential, a current discharge of opposite sense to the initial discharge is initiated and a wall charge of opposite polarity to the initial wall charge is established with sufficient magnitude to cause the discharge to be extinguished. Thus, after initial breakdown, the wall charge condition is maintained in selected cells by application of a lower potential sustain signal which, combined with the wall charge, causes the selected cells to be reignited and extinguish continuosly at the frequency of the sustained signals to maintain a continuous display. Since the drive signals of a plasma display are in the kilocycle range, a flicker-free display is provided. The light upward for display purposes is produced during the passage of the discharge of current. For additional details regarding the operation of such panels and light sustain and erase mode, reference is made to the aforenoted Criscimagna et al application Ser. No. 372,384.

In the preferred embodiment of the instant invention, the conductors 31 and 33 are shown as comprising multiple conductors to increase the light output since the light might otherwise be obstructed by opaque conductors. However, depending on the desired intensity of light output, either single opaque conductors or single transparent conductors could be substituted. The vertical conductors, since they are not on the viewing side of the invention, may be single opaque conductors, conductors of chrome-copper-chrome being utilized in the preferred embodiment of the instant invention. The lower chrome layer provides adherence to glass while the upper chrome layer protects the copper conductors from chemical attack by the dielectric glass during reflow of the dielectric layer over the conductors.

Referring now to FIG. 2, there is illustrated a top view of panel 13 which is inverted 180.degree. to illustrate the details of the configuration of transition elements employed in the instant invention. As heretofore noted, the particular configuration selected for the preferred embodiment of the instant invention utilizes three transition elements, 35 and 37 on alternate vertical lines, 39 on alternate horizontal lines and this particular triad combination is repeated in both directions. Transition elements 35 are copper mixed with a small percentage of tin to produce a reddish color; transition elements 37 are copper which produce an aqua greenish color, and transistion elements 39 are cobalt which produce a blue color.

The fabrication of a gaseous display element is described in detail in the aforereferenced copending Application Ser. No. 405,205 to Haberland et al and one of the steps in the process is the spraying and reflow of glass frit over the conductor array to form the dielectric. In the instant invention, the transition elements are deposited through a mark on the glass frit after spraying, as shown in FIG. 1, but before reflow, and then reflowed in the conventional manner. However, during the reflow, the transition elements are diffused into the dielectric but extend only over the specific area afforded by the masking operation. Conductors 31A-31N and 33A-33N extend through an entire line of transition elements and are then joined so that conductor 31A, for example, terminates at point 45 and conductor 33A terminates at point 47. When a discharge is produced at a selected site, as described heretofore, the resulting panchromatic light emission at the discharge site causes the doped dielectric to emit a display of discrete color, each of the discrete elements being sufficiently closely spaced that reasonable resolution for a particular color display is available. The conductors 31 and 33 terminate in termination pads 43 and 41 respectively, conductors 31 being designed to select the red or aqua color embodied in alternate transition elements 35, 37, while conductors 33 will be used for selection of the blue transition elements 39 when selection is provided simultaneously by the associated vertical conductor. The associated vertical conductor array is provided with single vertical conductors associated with each of the columns such that alternate rows and columns will emcompass identical transition elements. The transition elements are spaced relative to each other so that they are in an abutting relationship to prevent the emission of light between elements.

As previously noted and described in FIG. 1, when connected in a panel arrangement, the conductor and transition element array will be on the lower surface of the substrate but on the viewing surface of the display since the light will be shining through the transition elements. In view of the large number of potential transition elements which may be employed, a variety of colors to suit the particular application would be available. As described, the normal fabrication techniques utilized to fabricate a gas panel such as described in the aforenoted Haberland et al application, Ser. No. 405,205 with the minor modifications as described may be employed, while conventional addressing techniques such as those described in the aforenoted Criscimagna et al application, Ser. No. 372,384 may be utilized to drive the panel, eliminating the necessity of additional development. The aging problems associated with phosphors are eliminated, and only 2 lines are utilized to select one of three colors.

While a 20 .times. 20 matrix of transition elements are shown in the interest of clarity, it will be appreciated that in practice the technique is extended to practical size panels using resolutions of 50 lines per inch or more depending on the application.

While the invention has been particularly shown and described as referenced to a preferred embodiment thereof, it will be understood by those skilled in the art that certain other changes and form of details may be made therein without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. A gaseous discharge display device adapted for multicolor display comprising in combination

a pair of support plates sealed to form a chamber filled with an ionizable gas,

said support plates having conductor arrays formed thereon, each of said conductor arrays comprising parallel conductors, said arrays being substantially orthogonally related to define gas discharge sites at respective intersections thereof,

a dielectric layer formed over each of said conductor arrays,

said dielectric on the support plate comprising the viewing side of said display device having an associated plurality of discrete transition elements positioned over said gas discharge sites whereby ionization of said gas by application of control signals applied to selected sites thereof produces a localized color display through said associated transition elements.

2. A display device of the type claimed in claim 1 wherein said plurality of discrete transition elements are arranged in a uniform configuration over the display portion of said display device.

3. A display device of the type claimed in claim 2 wherein said ionizable gas has panchromatic light emission characteristics.

4. A device of the type claimed in claim 3 wherein said gas having panchromatic light emission characteristics is Xenon.

5. A device of the character claimed in claim 1 wherein the conductors in said array positioned adjacent said viewing side of said device have multiple drive lines to increase the light intensity.

6. A device of the character claimed in claim 4 wherein said discrete transition elements are in elements 21-30 of the periodic table.

7. A device of the character claimed in claim 6 wherein said elements are copper, cobalt and copper with a small percentage of tin.

8. A device of the character claimed in claim 6 wherein said copper, cobalt and copper tin transition elements produce displays of aqua green, blue and red respectively.