Display system and method of operating same

Description

[0001] This invention relates to monochromatic and polychromatic display systems and a method of operating same. In particular, this invention relates to the construction and operation of display systems which provide matrix displays resulting from the conversion of long wave ultraviolet photons into visible light energy through the fluorescent excitation of fluorescent material compositions, such as synthetic Phosphors.

[0002] Gas discharge display systems are known in the art and although the present display systems cannot truly be classified as gas discharge displays, such gas discharge systems are believed to be the closest prior art. In prior art gas discharge systems, a plurality of plasma displays may be attained either as alpha-numeric displays having generally linearly or arcuately segmented cathodes, or dot matrix displays. Such prior art systems are generally based on the ionization of a noble gas or gas mixtures. In such prior art systems, the ionization occurs between two flat and parallel electrodes with generally the anode electrode being transparent to light generated in the neighbourhood of the cathode electrode.

[0003] As one example of a prior art system there may be mentioned the electro-optical device disclosed in US-E-27273. This device comprises a gas filled display tube having a viewing window with an insulating plate parallel therewith and spaced a small distance therefrom. The front surface of the insulating plate facing the window is formed with a plurality of channels in each of which is seated an elongated cold cathode electrode located in the space separating the window from the insulating space. Associated with each cathode is a plurality of anodes spaced along the length of the cathode, the anodes being selectively energisable to cause the respective cathode electrode to exhibit cathode glow which is visible through the window of the device. The cathodes are arranged according to a segmented numerical or alpha-numerical display pattern, whereby, depending upon the anodes selectively energised a numerical or alpha-numerical display is achieved.

[0004] Numerous disadvantages are apparent when such prior art gas discharge display systems are utilized. In such prior art gas discharge systems, the visible glow from the cathode surface is visibly stable only if the whole of the surface area of the cathode is uniformly covered by the glow and the cathode surface has uniform properties. In the event that either of these two conditions is not present, the visible light will provide a flickering effect which is deleterious to the eye of an observer.

[0005] Another major disadvantage of such prior art gas discharge systems is that the operating life is dependent on the sputtering rate from the cathode electrode. This is due to the fact that the sputtering of the material from the cathode electrode generally deposits itself on the anode, thus obviously reducing the anode's transparency. The sputtering also reduces the gas pressure by physical adsorption of the filling gas. In order to provide an acceptable operating light in such prior art systems, they are generally operated at lower than maximum current density thereby resulting in less than optimum light output.

[0006] Some prior art work has investigated the generation of polychromatic systems based on the conversion of ultraviolet photons into visible light with Phosphor compositions. One such prior work is reported by V. Van Gelder, Proc. IEEE, Vol. 61, No. 7, July 1973, and is directed to the utilization of ultraviolet photons emitted by re- combinations in a positive column. In such prior work, the positive column is obtained through the well-known Principle of Similarity. In that system, the gaseous discharge occurs in a tubular structure for the ion/electron recombination on the walls of the tubular structure. Additionally, such prior work based on the Principle of Similarity dictates a particular relationship between the length, diameter and pressure of the tubular structure which is extremely difficult to produce. In normal tubes, the length/diameter ratio approximates 30.0 and such prior work dictates that such ratio should be preserved. Where the length in the tube in such prior work is two orders of magnitude smaller than an available fluorescent tube, in order to maintain the prescribed ratio, the diameter correspondingly must be two orders of magnitude less and the pressure two orders of magnitude larger than that found in an available fluorescent tubular structure. Such conditions would be extremely difficult to produce with the known technology, and at the present time are not capable of being manufactured. Another disadvantage of such theoretical prior art is the directionality of the system. In such prior art, the eye of the observer must be aligned with the axis of the tube in order to observe an optimized light intensity. A still further disadvantage is that as the resolution is increased, resulting in the tube diameter decreasing, it is extremely difficult to coat the inner wall of the tube uniformly with the Phosphor composition.

[0007] Other attempts to generate polychromatic displays based on the conversion of ultraviolet photons into visible light relies on the negative glow of the cathode. Such prior art work in this field has been published by M. Fukushiwa, Digest SID, P.120, 1975. However, just as in the case of the positive column type prior work, the Phosphor composition in this prior art using the negative glow is also immersed in the gas plasma and this results in similar disadvantages to those previously described for the positive column approach. Additionally, there is a lower efficiency in generating ultraviolet light in the plasma with flat parallel cathode-anode electrodes since the spectrum of the light released by the gas ionization does not consist solely of ultraviolet light, but includes spectral lines in the visible spectrum which prevent colour saturation due to colour mixing with the Phosphorspectrum.

[0008] Other prior art gas discharge type displays using hollow cathodes are represented in U.S. Patents Nos. 3,882,342 and 4,021,695. As in the case of other types of work, such references use the back filling gas to produce ultraviolet radiation in the positive column. This type of approach suffers the same disadvantages as hereinbefore described.

[0009] Of somewhat more immediate relevance to the present invention is the flat plate display panel disclosed in US-A-3,886,395. This panel comprises an insulating substrate provided with a plurality of parallel slots in which are seated a plurality of subsidiary anodes which establish a subsidiary discharge in said slots with an overlying cathode. Disposed on the surface of the insulating substrate and covered by a further insulating layer is a second series of anodes which establish a main discharge with the overlying cathode through holes in the further insulating layer which expose portions of the underlying main anodes and serve to define the main discharge space. The series of strip-like cathodes which overlie the further insulation layer are provided with through holes axially aligned with the through holes in the underlying insulating layer which expose the main anodes. A plurality of cells are thus formed comprising an anode located substantially centrally of the cathode. The whole unit is hermetically sealed with a translucent cover overlying the cathode strips and with an inert gas sealed into the cathode cells. In operation of the device ultraviolet radiation generated in the negative cathode glow in the main discharge is caused to impinge on a suitably placed phosphors, one of the specific objects of that invention being to shorten as much as possible the path of travel of the ultraviolet radiation and minimise absorption by the gaseous medium. In that type of device the subsidiary discharge facilitates the initiation of the main discharge.

[0010] The present invention seeks to improve on that type of device by providing a system capable of generating more intensive ultraviolet radiation, and hence greater brilliance and power in the visual display.

[0011] In my copending European Application No. 81305328.7 (Publication No. 0057315 A2) there is disclosed (Art. 54(3) EPC) a segmented display device and a method of operating same which relies on the sputtering of atoms of metal from a cathode into a gaseous medium and the subsequent ionization of the metal atoms in said medium under an applied electric field to produce an intense ultraviolet glow which in turn impinges on a fluorescent coating aligned with the cathode thereby to provide a fluorescent visual display substantially devoid of any flicker within the visible bandwidth of the electromagnetic spectrum. Such a display system allows for a wide dynamic range of light intensity with an optimization of the reproducability of physical characteristics and the present invention takes advantage of this in applying this technique to an alternative form of the display device.

[0012] Broadly speaking the display system of the present invention comprises

a) a cathode assembly comprising a cathode plate having a plurality of apertures therethrough lined with a metallic lining and forming a plurality of cathode cells, said lining comprising a metal the atoms of which are capable of ionisation in the vapour phase with concomitant emission of ultraviolet radiation;

b) a dielectric film applied to one surface of said cathode plate and having a plurality of apertures therein aligned with the apertures in the cathode plate;

c) an anode assembly disposed on the side of said dielectric film remote from the cathode plate and comprising a plurality of anode elements with apertures therein aligned with the apertures in the cathode plate and dielectric film;

d) a display panel transparent to ultraviolet radiation overlying the face of the cathode plate opposite the dielectric film and supporting on its surface opposite the cathode plate a plurality of patches of fluorescent material aligned with the apertures in the cathode plate so asto be impinged by ultraviolet radiation emitted from said apertures upon energization of the device; and

e) a backing panel spaced from said dielectric film in the direction away from the cathode plate and defining with the dielectric film a chamber containing a gaseous medium ionizable by an electrical field applied to the cathode and anode assemblies, thereby providing gaseous ionswhich impinge on the metallic lining of the cathode cells to cause sputtering of metal atoms from said lining and the subsequent ionization thereof in the gaseous medium with the consequential generation of said ultraviolet radiation;

said cathode and anode assemblies, said dielectric film and said display and backing panels together forming a hermetically sealed display unit.

[0013] Also in accordance with this invention there is provided a method of operating such a display system which comprises applying a first potential between said cathode plate and said anode elements, said first potential corresponding to or exceeding the breakdown potential of the gaseous medium contained within the cathode cells and thereby to obtain ionization of said gaseous medium, and subsequently applying a second potential between said cathode plate and said anode elements, whereby the ions generated in the gaseous medium by the first potential are accelerated towards said metallic lining on the walls of the apertures in said cathode plate with sufficient energy that upon collision with that coating metal atoms are sputtered therefrom into the gaseous phase and ionized therein with the consequential emission of ultraviolet radiation which impinges on said phosphors, thereby to activate the display.

[0014] In its overall concept, display system of the present invention converts energy within the ultraviolet bandwidth of the electromagnetic spectrum into energy within the visible bandwidth of the electromagnetic spectrum through excitation of fluorescent materials, the ultraviolet radiation being generated by a gaseous plasma which originates in the negative glow captured in a cylindrically shaped cathode. More particularly, the energy produced comes from ionized atoms of metal which is sputtered from the cathode surface and generally consists of the ionized metals largest spectral lines which are generally found in the ultraviolet bandwidth of the electromagnetic radiation spectrum.

[0015] In the concept of this invention a noble gas is ionized by application of a voltage potential between an anode and a generally cylindrical cathode. Application of the potential ionizes the gas producing electrons and gaseous ions. The electrons are displaced toward the anode and the ions are displaced toward the cathode for impingement thereon. The cathode is formed of a metallic coating layer which when impinged by the ion, displaces an electron and subsequently an atom of the metal which is ionized. The atom of metal may be termed to be in a gaseous state and emits ultraviolet energy along its strongest spectral line.

[0016] The negative glow on the cathode thus provides the origination of the gaseous plasma which is confined within the cylindrical envelope of the cathode structure. The gaseous plasma includes the atoms of metal which are ionized and the particulates of metal sputtered from the cathode surface provides for the ultraviolet spectral radiation lines. When impinged by ionized or metastable atoms of a noble gas such as argon, neon, krypton, or some like gas, a nickel coated cathode would provide an intense radiation at approximately 2300 A (0.23 pm). The element mercury would emit at a level of approximately 2500 A (0.25 pm) however, such would have approximately twice the intensity of the nickel spectral line. A copper coated cathode would emit energy approximately four times as intense as the nickel coated cathode; but at a spectral line of approximately 3200 Å (0.32 pm). Additionally, other metals such as aluminum would emit at approximately 3900 A (0.39 pm) and lead at 2200 A (0.22 pm) however, having different intensity levels.

[0017] Referring to the basic theory of operation of the display system of this invention in a preferred form this comprises a hollow cavity cathode having a metallic coating layer formed on the side walls thereof. An annular extension of the metallic coating lies in a plane substantially parallel to an anode element displaced from the cathode. Upon application of a potential between the anode and the cathode, there is applied a predetermined voltage corresponding to the breakdown which is described in Paschen's Law, which essentially states that the breakdown potential between two terminals in a gas is proportional to the pressure times the gap length. Thus, the gap length is inversely proportional to the pressure of the gas. The current that flows is limited by the resistance provided in the circuit and if the current is limited to a low value, the flow that occurs is provided on the annular extension of the cathode mechanism.

[0018] In this phase, the gas is being ionized and generates electrons, metastables, and ions. Metastables as well as photons are neutral particles and the field has substantially no effect on them and their path direction is generally random. Thus, in flat parallel electrode systems, only a small number of metastables and photons are able to intercept the cathode and contribute to secondary emissions of electrons.

[0019] In contrast, in the present invention, the ions attracted to the cathode and the electrons produced in the gaseous medium are attracted to the anode. Ions intercept the surface of the cathode metallic coating, and if the ions have a sufficient energy they extract an electron from the cathode surface which initially must neutralize the ion. In the event that more than one electron is released during this operation phase, the extra electron is accelerated by the field in a displacement path toward the anode.

[0020] As the electron is displaced, it collides with gas atoms and additional ions are produced whichprogressively increases the current. The positive ions satisfying this process, therefore, have an energy at least twice the work function of the metal coating of the cathode. Photons of energy equal to or greater than the work function of the metal coating also extract electronsfrom the metal by photoelectric effect.

[0021] The work function for most clean surface metals is between 4.0 and 5.0 electron volts. This energy corresponds to ultraviolet radiation in the approximate bandwidth of 2500 to 3100 A (0.25 to 0.31 pm). However, noble gases have low intensity of ultraviolet radiation compared to their radiation intensity in the visible portion of the electromagnetic spectrum. Such photons contribute minutely in producing secondary electrons from the radiative emission of the gases.

[0022] Subsequent to this phase of the operation, the series resistance placed between one of the electrodes, either the anode or the cathode and the supply energy is decreased. This secondary phase of the operation may be attained through well-known scanning mechanisms or in general, by modulation well-known in the art. When the resistance is decreased, the current that flows is greater than the current attained in the initial phase of the operation between the annular cathode section and the anode.

[0023] The glow now penetrates internal to the cavity of the cathode mechanism and the efficiency of producing secondary electrons is increased due to the fact that the fraction of metastable atoms and photons reaching the cathodic surface is in the neighbourhood of unity as compared to a fraction much less than 0.5 for flat parallel electrodes. Additionally, each electron will effect more collisions both ionizing and exciting prior to reaching the anode. Thus, the efficiency of the gas discharge is further increased and more electrons are produced. In this manner, there is provided more current as well as light energy.

[0024] It must be remembered that when system is initially fired, there is a low current flowing between the annular section of the cathode and the anode elements. Thus, there is a small potential drop across the load resistance which is subtracted from the total voltage that is supplied from the source of energy. This represents the voltage that appears between the anode and cathode elements and corresponds to the striking voltage which is dependent on the pressure and the anode to cathode gap distance.

[0025] In the second phase of the operation, when a greater current flows through the system, then the voltage drop across the series resistance increases since there is a current that may be orders of magnitude greater than previously achieved in the first phase. Obviously, the drop of potential corresponds to the increase of the current. The voltage that now appears between the anode and the cathode would be smaller than the normal sustaining voltage that would be used between a parallel anode and cathode of the prior art. The glow between the annulus and the anode thus goes off, since it cannot be sustained, however, such is sustained within the cathode cavity. It is to be remembered that when a low current produces a glow between the annulus of the cathode and the anode, it is only the spectrum of the gas that is produced, there is little sputtering since the current is too low for that condition to occur. As soon as the glow penetrates the cathode and the density of sputtering increases, atoms of metal are ionized which emit the ultraviolet radiation. It is thus the spectrum of the metal that is radiated and not the spectrum of the gas, as is generally provided in prior art systems.

[0026] The invention will now be further described with reference to the accompanying drawings, in which:-

Fig. 1 is an exploded perspective view of a cut-away section of the display system;

Fig. 2 is a cross-sectional view of a cut-away portion of the display system taken along the section lines 2-2 of Fig. 1;

Fig. 3 is a cross-sectional view of the display system cut-away portion taken along the section lines 3-3 of Fig. 2;

Fig. 4 is a plane view of the display system showing the vertical layers of the system; and

Fig. 5 is a structural schematic plane view of the display system showing alignment of fluorescent material with the anode and cathode elements of the display system.

[0027] Referring now to Figs. 1-4, there is shown the overall structure of a display system 10 in accordance with this invention which may be a monochromatic or a polychromatic system. In Fig. 1 the parts are shown in exploded relationship for clarity and ease of understanding although it will be understood that in actuality the display system 10 is formed into a hermetically sealed housing structure as is shown in Figs. 2 and 3 in order to maintain the internal gases at a predetermined pressure, the concept of which is well known in the art. Thus, display system 10 is generally formed into a monolithic type structure which greatly aids in optimizing display system 10, due tothe high path accuracies of the energy, as well as the close tolerances needed in the overall construction as will be discussed in following paragraphs. Display system 10 includes a cathode assembly 12 which is used for producing energy in the ultraviolet bandwidth of the electromagnetic spectrum from ionization of metallic atoms. Cathode assembly 12 comprises a cathode plate 14 having opposing first and second surfaces 16 and 18 shown in Figs. 2-4. The first and second surfaces 16 and 18 generally are planar in contour and form a plane substantially normal to a vertical direction defined by arrow 20 shown in Figs. 2 and 3. Cathode plate 14 is formed of a generally electrically insulating material such as glass, ceramic, or some like material not important to the inventive concept as is herein described. The thickness of cathode plate 14 may be .060-.170 inches (1.52 to 4.32 mm) with a typical thickness of .080 inches (2.03 mm). Various dimensional characteristics of display system 10 will be elucidated in following paragraphs to generally show scaling and relative dimensions between elements of the display system 10 due to the fact that Figures 1-4 are greatly enlarged.

[0028] Each cathode plate 14 includes a plurality of cathode openings 22 formed therethrough extending in vertical direction 20, as is clearly seen in Figs. 1-3. Each of cathode openings 22 includes cathode opening axis lines 24, each of which extend in vertical direction 20. In general, cathode openings 22 define asubstantially circular contour in a plane normal to axis line 24 of each of cathode plate member openings 22.

[0029] As is clearly seen in Figs. 2 and 3, cathode openings 22 generally provide a cross-sectional area at the first surface 16 of the cathode plate which is larger than the cross-sectional area at the second surface 18. In this manner, cathode openings 22 are seen to be frustoconical in contour. Each of cathode openings 22 is defined by side walls 26 which are inclined. The inclination in upward vertical direction 20 provides an angle with respect to axis lines 24 within the approximate range of 1.0°-5.0° with a preferred angle of inclination approximating 3.0°. Although cathode openings 22 may be formed in a non-inclined cylindrical contour it has been found that inclination of cathode opening sidewalls 26, as herein described, optimizes the directional displacement of the ultraviolet energy formed from the ionization of metallic atoms in an upward vertical direction 20 to impinge on fluorescent material to be described in following paragraphs.

[0030] The side walls 26 of each cathode opening 22 includes a metallic coating 28 formed thereon. Metallic coating 28 may be formed of aluminum, nickel, or some like metallic coating which would allow ionization of metallic atoms displaced from the surface during the operation of system 10. Metallic coating 28 forms a metallic film on side walls 26 having a thickness of about .001-.005 inches (0.025 to 0.127 mm) with a preferred thickness of about .002 inches (0.05 mm).

[0031] Cathode assembly 12 includes a further metallic coating 30 formed in an annular contour, as is seen in Figs. 1-3 around the cathode opening and bonded to cathode plate member 14 on the second surface 18. Metallic coating annular portions 30 may be and generally are in the preferred embodiment, formed of the same composition as metallic coating 28. Annular portions 30 are generally planar in contour and extend to a predetermined external diameter. Annular portions 30 and side wall metallic coatings 28 may be formed in one-piece formation, or bonded each to the other separately, such not being important to the inventive concept as herein described with the exception that metallic coatings 28 and metallic coating annular portions 30 be electrically conductive and electrically coupled to each other. Thus, metallic coating annular portions 30 include an internal diameter substantially equal to the diameter of the cathode opening 22 adjacent the second surface 18 of the cathode plate 14. Metallic coating annular portion 30 has a predetermined external diameter larger than plate member opening 22, with the external diameter to be discussed in following paragraphs in relation to other elements of system 10.

[0032] Metallic coatings 28 and metallic coating annular portion 30 may be defined as the cathode elements of the overall cathode assembly 12. Additionally, the plurality of openings 22 are seen to be formed in a matrix pattern within cathode plate 14 defining rows and columns of openings 22 which are common in the display system art. For purposes of ease of description, column direction 32 is shown in Fig. 4. Additionally, row direction 34 passes normal to column direction 32 and is also provided in Fig. 4.

[0033] In order to couple the cathode elements in column direction 32, metallic coatings 28 and 30 of each cathode opening 22 are electrically coupled to the adjacent coatings 28 and 30 in a particular column. To couple consecutive cathode elements, recess 36 shown in Fig. 3 and 4, is formed within second surface 18 of cathode plate 14 and extends in column direction 32. Recess 36 extends between successive plate member openings 22 formed in a predetermined column. Recesses 36 are filled with a continuous metallic film which is electrically conductive and may be formed of aluminum, or some like electrically conductive composition. In this manner, metallic coatings 28 and 30 of particular openings 22 in a predetermined column are electrically coupled each to the other.

[0034] Referring to the dimensions of cavities or openings 22 shown in Figs. 1-4, such may typically range from 0.10-0.005 inches (2.54 to 0.127 mm) in diameter, with a separation distance of about 0.004 inches (0.1 mm) between peripheral side walls 26. Typically, an opening 22 having a 0.010 inch (0.25 mm) diameter would be separated from a next consecutive or adjacent opening 22 by approximately 0.014 inches (0.356 mm) to provide a resolution of 70.0 display areas or dots per inch (2.75 dots per mm).

[0035] Display system 10 further includes dielectric film member 38 having first and second opposing surfaces 40 and 42 formed in a planar contour. As can be seen in Figs. 2 and 3, dielectric film member first surface 40 is bonded or otherwise securely fastened to second surface 18 of cathode plate 14. Further, dielectric film member 38 includes a plurality of openings 44 formed therethrough with each opening 44 having an axis line substantially aligned with axis lines 24 of each opening 22 in the cathode plate. Dielectric film member openings 44 are substantially aligned with metallic coating annular portions 30 and include a diameter substantially equal to the external diameter of annular portions 30. In this manner, openings 44 are insertable around each of annular portions 30, as is clearly evident in Figs. 2 and 3. In general, dielectric film member first surface 40 is fused to cathode plate member second surface 18 or otherwise bonded in fixed securement thereto. Dielectric film member 38 is used as an electrical insulator and may be formed of a glass film or some like composition.

[0036] Display system 10 further includes a plurality of anode elements 46 bonded to second surface 42 of dielectric film member 38. As can clearly be seen in Fig. 1, anode elements 46 are generally annular in contour and are coupled each to the other in row direction 34. Anode elements 46 include openings 48 defining a vertically directed axis line coincident with the axis lines 24 of the cathode openings. Additionally, anode elements 46 have an internal diameter substantially equal to the external diameter of metallic coating annular portions 30 of cathode elements 12. Thus, the diameter of anode openings 48 are substantially equal to the diameter of the dielectric film member openings 44 as is clearly seen in Fig. 2. In this manner, a shoulder section is formed between metallic coating annular portion 30 and the internal surfaces of dielectric film member openings 44 and anode openings 48.

[0037] Anode elements 46 further include anode coupling elements 50 for electrically coupling a plurality of anode elements 46 in row direction 34 to each other. The purpose of anode coupling elements 50 is to electrically couple consecutively positioned rows of anode elements 46 each with respect to the other, as is shown.

[0038] Anode elements 46 and corresponding anode coupling elements 50 are formed of an electrically conducting material such as aluminum, or some like metal which may be applied to dielectric film member second surface 42. In one form, anodes 46 and coupling elements 50 may be silk- screened to second surface 42 of dielectric film member 38. However, the basic mechanism of securing anode elements 46 and coupling elements 50 to dielectric film member 38 is not important to the inventive concept, with the exception that the method utilized provides for the fixed positional location of the elements, as has hereinbefore been described.

[0039] Display panel member 52 is secured to first surface 16 of cathode plate member 14. Display panel member 52, as will be described in following paragraphs, is substantially transparent to a bandwidth of the electromagnetic spectrum substantially comprising the ultraviolet bandwidth. Additionally, display panel member 52 has formed thereon a plurality of fluorescent material patches or coatings 54 for intercepting ultraviolet energy from the ionization of metal atoms from metallic coating 28 within the cathode cavity.

[0040] Display panel member 52 includes opposing first and second surfaces 56 and 58, as is shown in Figs. 2 and 3. Display panel member 52 is bonded or secured to cathode plate member 14 through sealing black glass frit film 60, shown in Figs. 2 and 3. Film 60 provides a vacuum seal between display panel member 52 and cathode plate member 14 and further provides for substantial optical isolation of each cathode cavity when taken with respect to other cathode cavities formed adjacent thereto. Glass frit film 60 may have a thickness within the range of about 0.0005-0.001 inches (0.013 to 0.025 mm). In order to apply frit film 60 to cathode plate member first surface 16, a printing screen may be used having openings corresponding to all but cathode openings 22. In this manner, panel member first surface 56 is bonded to cathode plate member first surface 16 in secured fashion.

[0041] Display panel member 52 is formed of an ultraviolet transparent glass having a thickness of about 0.004 inches (0.1 mm). Fluorescent material 54 is secured to panel member second surface 58 in registration above cathode openings 22. Thus, fluorescent material 54 includes a diameter substantially equal to cathode openings 22 and having axis lines coincident with cathode opening axis line 24. Fluorescent material 54 may be one of a number of compositions such as various Phosphor compositions which radiate responsive to ultraviolet energy impinging thereon. A wide range of Phosphor compositions well-known in the art may be used as fluorescent material 54. Fluorescent material Phosphor elements 54 may be protected against abrasion by protective layer element 62. Layer element 62 may be a microsheet of glass, or such may be a metallo organic solution to form a coating of low refractive index and high abrasion resistance. Thus, protective layer element 62, as is seen in Figs. 2 and 3, contacts both fluorescent material elements 54 and display panel member second surface 58.

[0042] Display system 10 further includes back panel member 64 displaced from the anode element 46 and the dielectric film member 38. Back panel member 64 is in fixed displacement with respect to element 30 and 46 forming internal chamber 66, as is shown in Fig. 3. In order to maintain structural integrity of back panel member 64, frame rod members 68 extend in column direction 32, as is shown in Figs. 2-4. Frame rod members 68 maintain a fixed spaced relation of back panel member 64 with respect to the structure of cathode plate member 14. Frame rod members 68 may be formed of glass having an approximate diameter of 0.010 inches (0.25 mm). Frame rod members 68 are secured to back panel member 64 by adhesive means such as a frame paste, or some like material.

[0043] Back panel member 64 may be formed of a glass composition having a thickness within the range of about 0.060-.120 inches (1.5 to 3 mm). Back panel member 64 includes internal surface 70 which is coated with a film of aluminum or like metallic coating which is reflective for ultraviolet radiation. The metallic coating over back panel member internal surface 70 is continuous in nature and is used for providing an equipotential electrode as well as providing an ion collection element for ions escaping from cathode mechanism 12.

[0044] In order to ensure a hermetic seal of the generally monolithic display system 10, as has herein been described, a frame of sealing glass frit may be screen printed around a common peripheral boundary in order to form a gas tight enclosure. One of frame rod member 68 may be formed in the overall peripheral contour of display system 10 and inserted between back panel member 64 and cathode mechanism 12.

[0045] Internal chamber 66 has a gaseous medium inserted therein to essentially fill the volume provided by the internal chamber 66, as well as cathode cavities. The gaseous medium is ionized by an electrical field applied to anode elements 46 and cathode mechanism 12. Gaseous ions impinging on metallic coating 28 sputter the metal atoms to produce ultraviolet energy, as has hereinbefore been described. The gaseous medium inserted internal to display system 10 is formed of a substantially inert gaseous composition and may be formed from the group consisting of neon, argon, krypton, xenon or combinations thereof.

[0046] Back panel member 64 serves as a common or equipotential electrode. Due to the cylindrical contour of cathode mechanism 12, a minimum of sputtering exits from cathode openings 22. As is well-known, prior art plasma display sputtering forms deposits on the anode surfaces. However, with the electrode configuration as provided by metallic coating 28 and annular portion 30 of the subject display system, an electric field is established between common electrode or back panel member 64 and cathode annular portion 30. An electric field is also established between anode 46 and cathode annular portion 30. The field gradient which exists between back panel internal surface 70 and annular portion 30 is sufficient to attract metal atoms passing from cathode metallic coating 30 and such are deposited on internal surface 70 of back panel member 64 rather than on anode elements 46. However, the electrical field between back panel member internal surface 70 and annular portion 30 is not sufficient to initiate any discharge between the displaced but parallel electrodes defined by metallic coating annular portion 30 and internal surface 70 of back panel member 64. Due to the fact that internal surface 70 is reflecting and opaque in composition, surface 70 continues to reflect light which may escape from cathode cavities defined by the cathode openings 22.

[0047] Referring to the method of manufacturing discharge display system 10, as has hereinbefore been described, the initial step is in providing cathode mechanism 12 for producing energy in the ultraviolet bandwidth of the electromagnetic spectrum from ionization of metal atoms. A matrix of through or cathode openings 22 are formed in cathode plate member 14 which has opposing first and second surfaces 16 and 18, respectively. Through cathode openings 22 define cathode opening side walls 28 within plate member 14, as is clearly shown in Figs. 2 and 3. As has been described, cathode plate member 14 is formed of an insulating material such as a glass or ceramic composition. A number of fabrication techniques may be used in forming cathode plate member 14 having appropriate cathode openings 22. In one method of fabrication, a moulded plate of ceramic or glass having the appropriate matrix cathode openings 22 corresponding to a predetermined resolution may be formed. In such a moulding type method, cathode plate member 14 may be produced by using a ceramic coating such as No. 528 ceramic from Aremco Products, Inc., or a fritted glass commonly referred to as No. EE 10 from Owens-Illinois Company, have been successfully utilized. Another method of fabrication can easily be seen in providing cathode plate member 14 in continuous form and establishing a plurality of drill heads positionally located in the appropriate matrix alignment necessary to produce a predetermined resolution. In this type of fabrication, the drill heads would be tapered within the approximating range of 1 °-5° with a preferred taper of 3°. Actuation of the drill heads in unison and contact as well as passage through cathode plate member 14 may be accomplished in one step, and provide the necessary through or cathode openings 22.

[0048] Subsequent to either the moulding operation, the drilling operation, photoetching, or some like step to form cathode openings 22, the step of providing cathode mechanism 22 further will include the step of coating through opening side walls 26 with a metallic coating such as aluminum, or some like metal. The step of coating side walls 26 with metallic coating 28 may be provided in a plurality of method steps. One step is by applying a metallic fluid paste on cathode plate member first surface 16 and compressively forcing the metallic paste through the through openings 22. This may be done by application of a squeegee, a roller mechanism, or some like device which would provide displacement characteristics to the metallic paste being used. The metallic paste would then be forcibly actuated or displaced within openings 22.

[0049] Another way in which coating of side walls 26 may be accomplished is by positioning a screen member over plate member first surface 16 wherein the screen member has a multiplicity of openings formed therethrough in axial alignment with cathode opening axis lines 24. As in the previous case, a metallic fluid paste is then inserted on an upper surface of the screen member and compressively displaced through the openings formed in the screen member. Whether the metallic paste is placed in direct contact with cathode plate member first surface 16 or applied to an upper surface of a screen member having the appropriate aligned openings, the metallic paste is then forced or displaced through the plate member openings 22.

[0050] The step of displacing the metallic paste through the openings 22 includes the step of applying a pressure differential between first and second surfaces 16 and 18 respectively of cathode plate member 14. A lower pressure is established at plate member second surface 18 when taken with respect to plate member first surface 16. In this manner, the metallic fluid paste is drawn through plate member openings 22 to form a metallic coating of predetermined thickness on side walls 26. The step of drawing the metallic paste through openings 22 may be accomplished in a variety of ways, one of which being to apply a low pressure vacuum pump suction surface at plate member second surface 18.

[0051] The printing screen previously described is commercially well-known in the art and would include a plurality of matrix openings aligned with cathode openings 22 in plate member 14. The openings within the printing screen would be positionally located in alignment with openings 22 and opaque throughout the remainder of the surface of the printing screen. A number of metallic fluid pastes may be utilized, one of which being a metallic fluid paste formed of an aluminum composition, such as No. 6110 manufactured by Electro-Oxide Corporation, or another paste formed of nickel such as No. 9531 Nycil, produced by Dupont Corporation may be used. Although the metallic paste or ink passing through openings 22 may be produced by gravity assist, as has been stated, a moderate suction may be applied on second surface 18 of plate member 14, which would leave a film of metallic paste approximating 0.002 inches (0.05 mm) in thickness on side walls 26. It is to be understood that the film thickness may be controlled by adjusting the viscosity of the metallic ink in well-known manners.

[0052] The basic step of providing cathode mechanism 12further includes the step of establishing metallic coating annular portions 30 on cathode plate member second surface 18. As may be seen, the formation of metallic coating 28 on side walls 26 may include the formation of annular portions 30, however, a number of fabrication techniques may be utilized in providing annular portion 30. The important concept being that annular portion 30 is coupled to coating 28 on side walls 26. Additionally, annular portions 30 are electrically coupled each to the other in row direction 34 by the inclusion of linearly directed recesses 36 formed within second surface 18 of cathode plate member 14. Recesses 36 may be formed by moulding, milling, or some like technique not important to the inventive concept as herein described. Recesses 36 may then be filled with a metallic ink or paste to provide appropriate coupling between row directed annular portions 30.

[0053] The step of establishing annularly contoured metallic extension layers or annular portions 30 may include the step of masking plate member second surface 18 with a screen having screen openings formed therethrough. The screen openings are axially aligned with plate member openings 22 and the screen openings having a predetermined diameter greater than plate member through opening diameters at plate member second surface 18. A metallic coating layer may be applied to the masking screen and compressively interfaced in order to force the metallic coating paste through the openings formed in the masking screen.

[0054] Dielectric film member 38 is bonded to second surface 18 of cathode plate member 14. Dielectric film member 38 has a plurality of openings of predetermined diameter substantially equal to the external diameter of annular portions 30. Dielectric film member openings have an axis line which is aligned with axis lines 24 of each of the matrix of two openings 22 of plate member 14. Bonding of dielectric film member 38 may be provided by fusing, adhesive coupling, or some like technique not important to the inventive concept as is herein described. A masking screen having a negative type pattern in relation to openings 22 may be used for forming dielectric film member 38 on second surface 18 in a manner similar to that previously provided for application of metallic paste for metallic coatings 28.

[0055] Anode elements 46 are secured to dielectric film member second surface 42. Anode elements 46 include a plurality of annularly contoured configurations having an internal diameter which is substantially equal to the predetermined diameter of the openings formed in dielectric film member 38. Anode elements 46 are electrically coupled each to the other through anode coupling elements 50, as is clearly seen in the Figures. Once again, application of anode elements 46 and their associated coupling elements 50 may be applied through a masking screen type technique, well-known in the art.

[0056] The method of manufacturing or fabricating discharge display system 10 further includes the step of establishing display panel member 52 in bonded relation to first surface 16 of cathode plate member 14. Display panel member 52 includes a plurality of fluorescent material coatings 54 secured thereto. Coatings 54 are positionally located in registration with plate member through openings 22. A printing screen having formed thereon a negative pattern of the screen used to fill through openings 22 is used to deposit a film of sealing black glass frit 60 to a thickness in the range 0.0005-0.001 inches (0.013 to 0.025 mm). Black glass frit film 60 provides a vacuum tight seal between cathode plate member 14 and display panel member 52.

[0057] Display panel member 52 is composed of substantially an ultraviolet transparent glass having a thickness approximating 0.004 inches (0.1 mm). Display panel member 52 is commercially available and may be No. 75183A manufactured by Owens-Illinois Corp., or Microsheet No. 9741 manufactured by Corning Glass Work, Inc. The combination of display panel member 52, frit film 60, and cathode plate member 14 is fired with a uniform pressure maintained in a compressive state on panel member 52 in order to provide uniformity of sealing.

[0058] Prior to the registration of fluorescent material 54 in alignment with cathode openings 22, a frame of sealing glass frit may be screen printed on dielectric film member second surface 42 around the periphery of display system 10. The sealing glass frit which is printed may have a thickness within the range 0.0015-0.002 inches (0.038-0.051 mm) with a width of about 0.1-0.2 inches (2.5 to 5 mm). A glass rod member similar to the cylindrical contour of frame rod members 68 is deformed to assume the periphery of the sealing glass frit and is positionally located over the printed peripherally directed frit. The deformed glass rod may be maintained in place by frame paste being applied between surface 42 and the rod itself. A plurality of frame rod members 68 having a diameter within the approximate range of 0.005-0.010 inches (0.13-0.26 mm) and then positionally located and fixedly secured by the aforementioned frame paste. The entire panel system is then fired in a nitrogen environment with a compressive pressure applied to the frame rod, as well as frame rod members 68 until the glass forms a glaze.

[0059] Back panel member 64 formed of a standard glass composition and having a substantially equal cross-sectional area to that of cathode plate member 14 is coated on internal surface 70 with a film of aluminum, or some like metallic coating which is reflective to ultraviolet light. The overall thickness of back panel member 64 may be within the range 0.060-0.120 inches (1.5 to 3 mm). A peripheral frame of glass frit substantially identical to the frame glass frit secured to second surface 42 is deposited or otherwise coated on the metallic coating of internal surface 70. Cathode plate member 14 and back panel member 64 are placed in contiguous relation each to the other between a pair of flat carbon susceptors with the aforementioned panels being aligned each with respect to the other. The entire system is then placed in a vacuum environment to achieve a residual pressure approximating 10-⁷ mm Hg where the system is then heated to a temperature approximating 450°C for a predetermined time to eliminate various residual gases from the glass compositions.

[0060] At the time that pressure/temperature equilibrium is achieved, the vacuum environment is isolated from a pumping station and an inert gas or mixture of gas which may comprise approximately 98.0% argon and 2.0% krypton is inserted into internal chamber 66 to establish a pressure approximating 24.0-25.0 mm Hg. At the time that equilibrium in temperature is achieved with the particular gas being introduced, the temperature of the susceptors is raised to the softening point of the glass frit which makes up the sealing frame. Referring to the glass frit produced by Owens-Illinois Corp., the temperature is in the neighbourhood of 530°C. When this limiting temperature is achieved by display system 10, the temperature is then lowered at a rate compatible with residual stress constraints.

[0061] The panel system now has applied to panel member second surface 58, a photographic emulsion composition layer which may be one or a number of photographic emulsion compositions, one of such being commercially available is referred to as Kodak Photo Resist. Anode elements 46 and predetermined cathode elements of cathode mechanism 12 are energised by voltage pulses in order to sensitize corresponding areas of the photographic emulsion composition above predetermined cathode openings 22. The energization is provided for positionally locating rows of the same colour. In this manner, the photographic emulsion composition is formed into a tacking composition in an area intercepted by ultraviolet energy emitted from cathode openings 22. Of important consequence is that the area being energized is substantially axially in alignment with plate member openings 22 being energized defining the sensitized region.

[0062] The photographic emulsion composition is then removed from the unsensitized region of display panel member 52 by washing away the unsensitized photographic emulsion composition. Thus, there remains on surface 58 the predetermined areas which are aligned with openings 22. A fluorescent material composition is then applied to display panel 52 and the fluorescent material composition is adhesively captured by the sensitized photographic emulsion composition. The entire structure is then heated to permanently fix or secure the fluorescent material composition to the sensitized emulsion composition. The method steps are then repeated for each colour in order to finally form a polychromatic display panel 52.

[0063] The step of heating is then followed by the step of applying a protective layer over the now fixed fluorescent material composition. The protective layer 62 may be a microsheet of glass or a metallo organic composition such as No. GR650 produced by Owens-Illinois Corp., which forms a coating of low refractive index and high abrasion resistance.

[0064] Fig. 5 is presented to provide clarification of the alignment and coupling of cathode mechanism 12 and anode elements 46. It is to be understood, that this figure is not structurally drawn, but is used as a pictorial schematic to show alignment of the various elements when used in a polychromatic display system 10. As can be seen, there appears a pair of anode lines 72 and 74 directed orthogonal to cathode couplings 36 with appropriate fluorescent material compositions 54 applied at the intersection positional location. The various fluorescent material dots 54 are provided to produce the visible colours of red, blue, and green to achieve appropriate polychromatic visual displays.

Claims

1. A flat plate fluorescent display system comprising a plurality of individual cells each comprising an anode and a cathode and an inert gas and in which ultraviolet radiation generated as the result of a discharge occurring between said anodes and said cathodes and caused to impinge on phosphors aligned with said cells, thereby to activate the display, characterised in that the display system comprises:

a) a cathode assembly (12) comprising a cathode plate (14) having a plurality of apertures (22) therethrough lined with a metallic lining (28) and forming a plurality of cathode cells, said lining comprising a metal the atoms of which are capable of ionisation in the vapour phase with concomitant emission of ultraviolet radiation;

b) a dielectric film (38) applied to one surface of said cathode plate and having a plurality of apertures (44) therein aligned with the apertures (22) in the cathode plate (14);

c) an anode assembly disposed on the side of said dielectric film remote from the cathode plate and comprising a plurality of anode elements (46) with apertures (48) therein aligned with the apertures (22 and 44) in the cathode plate and dielectric film;

d) a display panel (52) transparent to ultraviolet radiation overlying the face of the cathode plate (14) opposite the dielectric film and supporting on its surface opposite the cathode plate a plurality of patches (54) of fluorescent material aligned with the apertures in the cathode plate so as to be impinged by ultraviolet radiation emitted from said apertures upon energization of the device; and

e) a backing panel (64) spaced from said dielectric film (38) in the direction away from the cathode plate (14) and defining with the dielectric film a chamber (66) in communication with the cathode apertures (22), said chamber containing a gaseous medium ionizable by an electrical field applied to the cathode and anode assemblies, thereby providing gaseous ions which impinge on the metallic lining (28) of the cathode cells to cause sputtering of metal atoms from said lining and the ionisation thereof in the gaseous phase with consequential generation of said ultraviolet radiation;

said cathode and anode assemblies, said dielectric film and said display and backing panels together forming a hermetically sealed display unit.

2. A display system according to claim 1, characterised in that the apertures (22) in the cathode plate (14) are of circular cross-section.

3. A display system according to claim 2, characterised in that the apertures (22) in the cathode plate (14) are frustoconical in contour and inverted with relation to the display panel (52).

4. A display system according to claim 3, characterised in that the side walls of said apertures (22) in the cathode plate (14) are inclined at an angle of from 1-5⁰ to the axis of the aperture.

5. A display system according to any one of claims 1-4, characterised in that metallic lining (28) of the apertures (22) in the cathode plate (14) extend into a flange (30) surrounding those apertures on the face of the cathode plate directed towards said dielectric film.

6. A display system according to any one of claims 1-5, characterised in that the face of the backing panel (64) directed toward the dielectric film (36) is coated with a continuous metal layer capable of reflecting radiation in the ultraviolet bandwidth.

7. A display system according to any one of claims 1-6, characterised by spacer elements (68) located in said chamber (66) between the dielectric film (38) and the backing panel (64).

8. A display system according to any one of claims 1-7, characterised by an optically transparent abrasion resistant film or layer (62) covering said fluorescent patches (54).

9. A display system according to any one of the preceding claims, characterised in that the said gaseous medium is argon, neon, krypton, xenon, hydrogen or helium.

10. A display system according to any one of claims 1-9, characterised in that the cathode plate (12), the dielectric film (38), the anode elements (46) and the display panel (52) are bonded one to the other in face-to-face relation.

11. A method of operating a fluorescent display according to any one of claims 1-10, characterised by applying a first potential between the cathode plate (14) and the anode elements (46), said first potential corresponding to or exceeding the breakdown voltage of the gaseous medium contained within the cathode cells, and subsequently applying a second potential between said cathode plate (14) and said anode elements (46), whereby gaseous ions generated in said medium by the application of said first potential are accelerated towards said metallic lining (28) on the walls of the apertures (22) in said cathode plate (14) with sufficient energy that upon collision with that coating metal atoms are sputtered therefrom into the gaseous phase and ionised therein with consequential generation of ultraviolet radiation which impinges on said phosphors, thereby to activate the display.

12. A method according to claim 11, characterised in that second potential is effective to extinguish the negative cathode glow that is established by the application of said first potential between the anode elements (46) and the cathode plate (14).

Ansprüche

1. Fluoreszenzanzeigesystem mit flachem Schirm, umfassend eine Mehrzahl an individuellen Zellen, von denen jede eine Anode, eine Kathode und ein Inertgas enthält und in denen ultraviolette Strahlung als Folge einer zwischen den genannten Anoden und den genannten Kathoden auftretenden Entladung erzeugt wird und dazu veranlaßt wird, auf Leuchtstoffe aufzutreffen, die mit den genannten Zellen ausgerichtet sind, und dabei die Anzeige zu aktivieren, dadurch gekennzeichnet, daß das Anzeigesystem umfaßt:

a) eine Kathodenanordnung (12) umfassend eine Kathodenplatte (14) mit einer Mehrzahl an dort durchgehenden Öffnungen (22), die mit einem metallischen Belag (28) ausgekleidet sind und eine Mehrzahl an Kathodenzellen bilden, wobei der genannte Belag ein Metall enthält, dessen Atome zur Ionisierung in der Dampfphase mit gleichzeitiger Emission ultravioletter Strahlung fähig sind;

b) einen dielektrischen Film (38), der auf eine Oberfläche der genannten Kathodenplatte aufgebracht ist und in sich eine Mehrzahl an Öffnungen (44) aufweist, die mit den Öffnungen (22) in der Kathodenplatte (14) ausgerichtet sind;

c) eine Anodenanordnung, die an der von der Kathodenplatte abgewandten Seite des genannten dielektrischen Films angeordnet ist und eine Mehrzahl an Anodenelementen (46) mit Öffnungen (48) darin umfaßt, die mit den Öffnungen (22 und 44) in der Kathodenplatte und im dielektrischen Film ausgerichtet sind;

d) eine für ultraviolette Strahlung transparente Anzeigetafel (52), die die Seite der Kathodenplatte (14) bedeckt, die dem dielektrischen Film gegenüberliegt, und die auf ihrer der Kathodenplatte gegenüberliegenden Oberfläche eine Mehrzahl an Flecken (54) aus fluoreszierendem Material trägt, die mit den Öffnungen in der Kathodenplatte ausgerichtet sind, um von ultravioletter Strahlung getroffen zu werden, die von den genannten Öffnungen bei Anschalten der Einrichtung emittiert wird; und

e) eine Trägertafel, die vom genannten dielektrischen Film (38) in Richtung weg von der Kathodenplatte (14) beabstandet ist und mit dem dielektrischen Film eine mit den Kathodenöffnungen (22) in Verbindung stehende Kammer (66) definiert, wobei die genannte Kammer ein gasförmiges Medium enthält, das durch ein zwischen den Kathoden- und Anodenanordnungen angelegtes elektrisches Feld ionisierbar ist, wobei dadurch Gasionen bereitgestellt werden, die auf den metallischen Belag (28) der Kathodenzellen auftreffen, um Sputtern von Metallatomen aus dem genannten Belag und deren Ionisation in der gasförmigen Phase mit folgender Erzeugung ultravioletter Strahlung zu bewirken; wobei die genannten Kathoden- und Anodenanordnungen, der genannte dielektrische Film und die genannten Anzeige- und Trägertafeln zusammen eine hermetisch dicht verschlossene Anzeigeinheit bilden.

2. Anzeigesystem nach Anspruch 1, dadurch gekennzeichnet, daß die Öffnungen (22) in der Kathodenplatte (12) von kreisförmigem Querschnitt sind.

3. Anzeigesystem nach Anspruch 2, dadurch gekennzeichnet, daß die Öffnungen (22) in der Kathodenplatte (14) kegelstumpfförmig in der Kontur sind und von der Anzeigetafel (52) weg konvergieren.

4. Anzeigesystem nach Anspruch 3, dadurch gekennzeichnet, daß die Seitenwände der genannten Öffnungen (22) in der Kathodenplatte (14) unter einem Winkel von 1-5° zur Achse der Öffnung geneigt sind.

5. Anzeigesystem nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß sich der metallische Belag (28) der Öffnungen (22) in der Kathodenplatte (15) in einen Flansch (30) erstreckt, der diese Öffnungen auf der Seite der Kathodenplatte umgibt, die dem genannten dielektrischen Film zugewandt ist.

6. Anzeigesystem nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die dem dielektrischen Film (36) zugewandte Seite der Trägertafel (64) mit einer durchgehenden Metallschicht beschichtet ist, die fähig ist, Strahlung im ultravioletten Bandbereich zu reflektieren.

7. Anzeigesystem nach einem der Ansprüche 1 bis 6, gekennzeichnet durch Abstandhalteelemente (68), die in der genannten Kammer (66) zwischen dem dielektrischen Film (38) und der Trägertafel (64) angeordnet sind.

8. Anzeigesystem nach einem der Ansprüche 1 bis 7, gekennzeichnet durch einen optisch transparenten, abriebfesten Film oder Schicht (62), die die genannten fluoreszierenden Flecken (54) bedeckt.

9. Anzeigesystem nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß das genannte gasförmige Medium Argon, Neon, Krypton, Xenon, Wasserstoff oder Helium ist.

10. Anzeigesystem nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, daß die Kathodenplatte (12), der dielektrische Film (38), die Anodenelemente (46) und die Anzeigetafel (52) aneinander deckungsgleich gebunden sind.

11. Verfahren zum Betrieb einer Fluoreszenzanzeige nach einem der Ansprüche 1 bis 10, gekennzeichnet durch Anlegen eines ersten Potentials zwischen der Kathodenplatte (14) und den Anodenelementen (46), wobei dieses erste Potential der Zündspannung des in den Kathodenzellen enthaltenen gasförmigen Mediums entspricht oder diese überschreitet, und durch das darauffolgende Anlegen eines zweiten Potentials zwischen der genannten Kathodenplatte (14) und den genannten Anodenelementen (46), wodurch Gasionen, die im genannten Medium durch das Anlegen des genannten ersten Potentials erzeugt sind, gegen den genannten Belag (28) auf den Wänden Öffnungen (22) in der genannten Kathodenplatte (14) mit ausreichender Energie beschleunigt werden, sodaß beim Zusammenstoß mit dieser Beschichtung Metallatome von dort in die gasförmige Phase gesputtert werden und darin mit folgender Erzeugung von ultravioletter Strahlung ionisiert werden, welche auf die genannten Leuchtstoffe auftrifft, um damit die Anzeige zu aktivieren.

12. Verfahren nach Anspruch 11, dadurch gekennzeichnet, daß das zweite Potential das negative Kathodenglimmlicht auslöscht, das durch das Anlegen des genannten ersten Potentials zwischen den Anodenelementen (46) und der Kathodenplatte (14) aufgebaut ist.

Revendications

1. Système d'affichage fluorescent à plaque plate comprenant une pluralité de cellules individuelles comprenant chacune une anode et une cathode et un gaz inerte et dans lequel le rayonnement ultraviolet engendré par suite d'une décharge se produisant entre lesdites anodes et lesdites cathodes et amené à frapper des luminophores alignés avec lesdites cellules, ce qui a pour effet d'activer l'affichage, caractérisé en ce que le système d'affichage comprend:

a) un ensemble cathodique (12) comprenant une plaque cathodique (14) pourvue d'une pluralité d'ouvertures (22) qui la traversent, alignées avec un revêtement métallique (28) et formant une pluralité de cellules cathodiques, ledit revêtement étant constitué par un métal dont les atomes sont capables de ionisation en phase vapeur avec émission concomittante de rayonnement ultraviolet.

b) une pellicule diélectrique (38) appliquée à une face de ladite plaque cathodique et pourvue d'une pluralité d'ouvertures (44) alignées avec les ouvertures (22) de la plaque cathodique (14).

c) un ensemble anodique disposé sur Je côté de ladite pellicule diélectrique à distance de la plaque cathodique et comprenant une pluralité d'éléments anodiques (46) comportant des ouvertures (48) alignées avec les ouvertures (22 et 44) de la plaque cathodique et de la pellicule diélectrique.

d) un panneau d'affichage (52) transparent au rayonnement ultraviolet recouvrant la face de la plaque cathodique (14) à l'opposé de la pellicule diélectrique et portant à sa surface opposée à la plaque cathodique une pluralité de pastilles (54) de matière fluorescente alignées avec les ouvertures de la plaque cathodique de façon à être frappées par le rayonnement ultraviolet émis à partir desdites ouvertures lors de l'excitation du dispositif;

e) un contre-panneau (64) séparé de ladite pellicule diélectrique (38) dans le sens opposé à la plaque cathodique (14) et délimitant avec la pellicule diélectrique une chambre (6) communiquant avec les ouvertures cathodiques (22), ladite ladite chambre contenant un milieu gazeux ionisable par un champ électrique appliqué aux ensembles cathodique et anodique, produisant ainsi des ions gazeux qui frappent le revêtement métallique (28) des cellules cathodiques afin de provoquer la pulvérisation d'atomes de métal à partir dudit revêtement et la ionisation de ces derniers en phase gazeuse en entraînant la génération dudit rayonnement ultraviolet;

lesdits ensembles cathodique et anodique, ladite pellicule diélectrique, ledit panneau d'affichage et ledit contre-panneau formant ensemble une unité d'affichage hermétiquement close.

2. Système d'affichage selon la revendication 1, caractérisé en ce que les ouvertures (22) et la plaque cathodique (14) ont une section transversale circulaire.

3. Système d'affichage selon la revendication 2, caractérisé en ce que les ouvertures (22) de la plaque cathodique (14) ont le profil d'un cône tronqué et inversé par rapport au panneau d'affichage (52).

4. Système d'affichage selon la revendication 3, caractérisé en ce que les parois latérales desdites ouvertures (22) de la plaque cathodique (14) sont inclinées selon un angle de 1 à 5° par rapport à l'axe de l'ouverture.

5. Système d'affichage selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le revêtement métallique (28) des ouvertures (22) de la plaque cathodique (14) s'étend en une collerette (30) entourant les ouvertures situées sur la face de la plaque cathodique dirigée vers ladite pellicule diélectrique.

6. Système d'affichage selon l'une quelconque des revendications 1 à 5, caractérisé en ce que la face du contre-panneau (64) dirigée vers la pellicule diélectrique (36) est recouverte par une couche métallique continue capable de réfléchir un rayonnement dans la bande passante ultraviolette.

7. Système d'affichage selon l'une quelconque des revendications 1 à 6, caractérisé par des éléments d'écartement (68) situés dans ladite chambre (66) entre la pellicule diélectrique (38) et le contre-panneau (64).

8. Système d'affichage selon l'une quelconque des revendications 1 à 7, caractérisé par une pellicule ou une couche (62) résistante au frottement et transparente optiquement recouvrant lesdites pastilles fluorescentes (54).

9. Système d'affichage selon l'une quelconque des revendications précédentes, caractérisé en ce que ledit milieu gazeux est de l'argon, du néon, du krypton, du xénon, de l'hydrogène ou de l'hélium.

10. Système d'affichage selon l'une quelconque des revendications 1 à 9, caractérisé en ce que la plaque cathodique (12), la pellicule diélectrique (38) les éléments anodiques (46) et le panneau d'affichage (52) sont soudés l'un à l'autre en vis à vis.

11. Méthode de fonctionnement d'un affichage fluorescent selon l'une quelconque des revendications 1 à 10, caractérisée par l'application d'un premier potentiel entre la plaque cathodique (14) et les éléments anodiques (46), ledit premier potentiel étant égal ou supérieur à la tension de rupture du milieu gazeux contenu à l'intérieur des cellules cathodiques, et par l'application ultérieure d'un second potentiel entre ladite plaque cathodique (14) et lesdits éléments anodiques (46), ce qui entraîne que des ions gazeux engendrés dans ledit milieu par l'application dudit premier potentiel sont accélérés vers ledit revêtement métallique (28) sur les parois des ouvertures

(22) de ladite plaque cathodique (14) avec un énergie suffisante pour que lorsqu'ils entrent en collision avec ce revêtement, des atomes de métal soient pulvérisés à partir de ce dernier en phase gazeuse et ionisés dans celle-ci en entraînant la génération d'un rayonnement ultraviolet qui frappe lesdits luminophores, ce qui entraîne l'activation de l'affichage.

12. Méthode selon la revendication 11, caractérisée en ce que le second potentiel a pour effet d'éteindre la lueur cathodique négative qui est créée par l'application dudit premier potentiel entre les éléments anodiques (46) et la plaque cathodique (14).

Drawing