US3069596A

US3069596A - Electroluminescent screen and device

Info

Publication number: US3069596A
Application number: US857897A
Authority: US
Inventors: David W Morgan
Original assignee: Westinghouse Electric Corp
Current assignee: Westinghouse Electric Corp
Priority date: 1959-12-07
Filing date: 1959-12-07
Publication date: 1962-12-18
Anticipated expiration: 1979-12-18

Description

Dec 18, 1962 0. w. MORGAN ELECTROLUMINESCENT SCREEN AND DEVICE 2 Sheets-Sheet 1 Filed Dec. 7, 1959 H LN BE W R L R T N E T a P FIG.I.

FlG.2.

INVENTOR DAVID W. MORGAN.

BY WQ 1 W ATTORNEY Dec. 18, 1962 n. w. MORGAN 3,069,596

ELECTROLUMINESCENT SCREEN AND DEVICE Filed Dec. 7, 1959 2 Sheets-Sheet 2 AMPLIFIER OSCILLATOR.

MANUAL 6 A SPEED 4 INVENTOR CONTROL DAVID w. MORGAN.

' MODULATOR N U SIGNALTOBE PRESENTED WQ/ W.

ATTORNEY United States Patent ()fifice 3,969,596 Patented Dec. 18, 1952 3,069,5'i 6 ELECTROLUMlNEStlENT SCREEN AND DEVEQE David W. Morgan, East Orange, N.J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 7, 1959, Ser. No. 357,897 7 Claims. (Cl. 315-469) This invention relates to electroluminescent display screens and devices and, more particularly, to an electroluminescent display screen for visually presenting signal information and an electroluminescent device which incorporates such a display screen.

The phenomenon of electroluminescence was first disclosed by G. Destriau, one of his earlier publications appearing in London, Edinburg and Dublin Philosophical Magazine, Series 7, volume 38, No. 285, pages 700-737 (October 1947). Since this time, electroluminescent dev1ces have been marketed commercially and considerable developments have been made with respect to application devices which utilize electroluminescence. A fairlly recent summary of electroluminescene and related subjects can be found in Destriau and Ivey article in Proceedings of the I.R.E., volume 43, No. 12, pages 1911-1940 (December 1955).

Present oscillographs rely on a cathode-ray tube for visual presentation of signal information. The tube is cumbersome and the oscillograph must be made correspondingly large. In addition, the signal information is necessarily presented as a trace on the screen of the cathode-ray tube. For some applications, it is desirable to have signal information presented in an integrated fashion so that all of the area below the trace is illuminated. Such a presentation is not practical with present cathode-ray tubes.

It is the general object of this invention to provide an electroluminescent display screen for presenting signal information in an integrated fashion so that all of the area below the top portion of the presented signal is illuminated.

It is a further object to provide an electroluminescent oscillograph wherein the cathode-ray tube is replaced by a compact electroluminescent display screen.

It is an additional object to provide an electroluminescent oscillograph wherein the electroluminescent display screen presents information in such fashion that all area below the top portion of the presented signal is illuminated.

The aforesaid objects of the invention, and other objects which will become apparent as the description proceeds, are achieved by providing an electroluminescent display screen which comprises a plurality of closely-spaced and side-by-side electroluminescent cells. Each of the cells has a varying physical spacing between the electrodes so that a cell cross section has a generally wedge-shaped configuration. Each of the cells which comprise the screen are a part of a different tuned circuit, each having a different resonant frequency. Such a display screen can be used as a part of an electroluminescent oscillograph wherein an alternating potential periodically varying over a range of frequencies is applied to the tuned circuits and cell electrodes of the display screen. The

period of frequency variation is synchronized with the A period of the signal to be presented and the varying frequency potential is amplitude modulated with this signal. When the resulting varying frequency, modulated potential is applied across the tuned circuits and electroluminescent cells comprising the screen, the individual tuned circuits will resonate in sequence. As each tuned circuit resonates, the cell which forms a part of such tuned circuit electroluminesces in amount Varying with the voltage which is applied across the cell electrodes.

The persistance of the observers eye blends together the resulting individual light signals so that all area below the top or upper portion of the presented signal is illuminated.

For a better understanding of the invention, reference should be had to the accompanying drawings wherein:

FIG. 1 is a perspective view, partly broken away, showing an electroluminescent display screen fabricated in accordance with the present invention;

REG. 2 is a cross-sectional side elevation of an alternative construction for a screen generally as shown in PEG. 1;

FIG. 3 is a cross-sectional side elevation of another alternative construction for a screen generally as shown in PEG. 1;

FIG. 4 is a diagrammatic sketch showing an electroluminescent signal display device which functions as an oscillograph.

With specific reference to the form of the invention illustrated in the drawings, the electroluminescent screen It) as shown in FIG. 1 generally comprises a glass foundation 12 having coated thereover a light-transmitting, tin oxide electrode layer 14. Coated over the tin oxide layer 14 is a phosphor-dielectric layer 16. Carried over the phosphor-dielectric layer 16 is a wedge-shaped layer 18 of polyethylene teraphthalate. Over the wedgeshaped dielectric layer is are carrieda series of closely-spaced aluminum electrode strips 26 positioned in side-by-side relationship, with each of the electrodes 2t] having a length dimension of considerable magnitude and a width dimension of small magnitude. Each of these electrode segments 2ft is insulated from the adjacent electrode segment and this in effect forms a plurality of side-by-side electroluminescent cels 22, even though the light-transmitting electrode 14 is common to all cells.

There is also provided a plurality of different tuned circuits, one of each of which incorporates as a circuit element a different one of the cells 22. comprising the screen 10. in the example as shown, each tuned circuit is formed as a series-connected inductor 24, 24a, etc. and capacitor 2d, 26a, etc. connecting across the screen input terminals. Each tuned circuit thus essentially comprises an inductor having two parallelconnected capacitors connecting in series therewith, one of which capacitors is a cell 22. The individual values of inductance and capacitance are so chosen that each tuned circuit displays a different resonant frequency and the resonant frequencies vary from a minimum for the tuned circuit including the cell 22 positioned at one edge of the screen 10 to a maximum for the tuned circuit including the cell 22 positioned at the opposite edge of the screen it).

As a specific example, the screen It? as illustrated in PEG. 1 is formed of twenty-five individual electroluminescent cells. The electrode strip Ztl, which define the dimensions of each of the cells 22 which comprise the screen it), each have a length of 5 centimeters and a Width of 2 millimeters with a spacing of 2 mils therebetween. The phosphor-dielectric layer 16 has a thickness of 2 mils and the wedge-shaped plastic layer 18 has a thickness of 1 mil at the thinnest end and 4 mils at the thickest end. The display screen It} thus has overall dimensions of approximately 5 cms. by 5 ems. As a specific example, the average capacitance for each of the cells 22 is approximately 109 micromicrofarads and the individual tuned circuits which include the individual cells 22 as a component are designed to resonate at frequencies varying from 940 c.p.s. to 1,060 c.p.s., with a resonant frequency differential of 5 c.p.s. between each adjacent cell 22. The circuit components required to cause resonance under such conditions of operation are readily calculated. As an example, the tuned circuit incorporating the individual cell 22 which is positioned at the left-hand edge of the screen 10, as viewed in FIG. 1, is intended to resonate at a frequency of 940 cps. F or this condition of resonance, the inductance of this tuned circuit can have a value of l 10 henry and the added capacitance of this tuned circuit can have a Value of 6.25 microfarads. T e tuned circuit incorporating the individual cell 22 which is positioned at the right-hand edge of the screen ill as viewed in FIG. 1, resonates at a frequency of 1060 cps. in order to produce this desired resonant frequency, t is inductance 24 of this tuned circuit can have a value of 1X10 henry and the added capacitance 26 of this tuned circuit can have a value of 2.5 microfarads. The other inductances and added capacitances required to cause each tuned circuit to resonate as indicated are readily calculated.

Any suitable electroluminescent phosphor can be used in forming the layer in. As a specific example, a greenemitting electroluminescent phosphor is prepared by mixing 1,000 grams Zinc sulfide with 30 grams sulphur, 12.8 grams copper acetate and 4.5 grams ammonium chloride. This mixture is fired in a partially-closed container in a nitrogen atmosphere at a temperature of about 950 C. for about 100 minutes. Thereafter the phosphor is slightly crushed, 3 grams of sulphur are added to the phosphor and it is refired in a similar manner. After final firing, the phosphor is lightly crushed and is washed with a solution which is a solvent for cuprous sulfide, but which is not a solvent for zinc sulfide. An example of such a washing solution is sodium cyanide. Any other electroluminescent phosphor can be substituted for the foregoing ex ample and reference is made to the aforementioned Destriau and Ivey publication for a listing of other electroluminescent phosphors. For best delineadon of the presented signal, it is preferred to use a so-czzlled steep-slope electroluminescent phosphor and such phosphors are well known.

The foregoing specific screen is subject to considerable variation. In the preferred example, the light-transmitting electrode .M- is formed as one continuous elect: de, common to all cells 22. If desired, the light-transmitting electrode can be scribed so as to form a plurality of small electrodes, each having a configuration which conforms with that of the opposing electrode strip 2%. While tin oxide is preferred for the light-transmitting electrode 1 2-, this electrode can be formed as a series of parallel wires or alternatively, other light-transmitting electrically-conducting materials such as indium oxide be substituted for the tin oxide. The phosphor-dielectric layer is subject to variation with respect to thickness and with respect to composition. As an example, equal parts by weight of the foregoing specific electroluminescent phosphor and a light-transmitting dielectric material such as polyvinyl-chloride acetate can be mixed and used as the layer 16. Other suitable plastic or ceramic dielectric ma terials can be substituted for this specific exan ole. The thickness of the phosphor-dielect ic layer ie can be varied considerably and the relative proportions of phosphor and dielectric are also subject to variation. Different plastic and ceramic dielectric materials can also be used in forming the wedge-shaped layer 13. The electrode strips While desirably fabricated of vacuum-metalized aluminum, can also be fabricated of any suitable conducting m aterial conformed as indicated and light-transmitting electrode material such as copper iodide can be substituted for the vacuurn-metallized aluminum. The actual configuration of the electro e strips is subject to considerable variation and more or fewer strips can be used as desired. Variation of the foregoing example with respect to dimensions, etc. will require that the elements of the tuned circuits be modified in order to cause the tuned circuits incorporating the individual cells to resonate at the desired frequencies and the required values for these elements can be readily calculated. Likewise, the freouency differential between adjacent cells and the overall frequency range used can be varied or shifted if desired.

in FIG. 2 is shown an alternative screen embodiment which P A liy co: s al t-trans ing foung a l ducting layer 14;; therec-ver. The phosphor-dielectric 5 layer lea has a varying thickness, gradually increasing from a minimum thickness at the bottom of the screen to a maximum at the top. The surface of the phosphorctric l -oved from the li' transmng found on ..z has a stepped configuration with dimensions of the risers of the steps 23 determining The outer- ,ctrodes 2% are vacuum metallized over the steps Sucn a construction results in more contrast in the delineation of the top portion of any signal which is to be presented and resolution for the top portion of any signal is determined by the width of each of vidual steps 3 is sh wn anotler alte tive screen cone found llOil 12b and lighttransmitting ccann l t b are t s previously illustrated. The

phosphor-dielectric layer has a thickness which gradually increases as a greater-than-linear rate. The uneven rate at which the thickness increases will produce a cut-off the top portion of any signal which t csented. Other than this, the screen embodi- 53/2 generally corresponds to the other screen ts shown. ti 4 is shown in diagrammatic form an electrolu iescent signal display device which functions "ly to an os ograp'n, but wherein the usual cathode-ray tub: is r- "laced by a compact electroluminescent di play some Briefly, the device comprises a conventional Hartley oscillator which is variable with respect to frequency. The oscillator capacitor 34 1 n by a rector as adapted to be man- VASE a 35 is variable and is cri e sally controlled with respect to speed. The capacitor 34 is preferably formed of two individual sections which J2 tuned circuits of which the cells 22 comprising the n 18 form a part.

1.3 varying freque fed into the cy output potential of the oscillator of a conventional modulating and the sigr l to be presented is impressed the primary of transformer to modulate the vo ta e of the An additional tuned isolates the r from the output Such circuit arrangement is convenrnod lated varying frequemy potentu output of the tube is fed into a standard arriplifier shown in block diagram. The output of the amplifier 5-4 is connected across the input terminals of the As the frequency is varied over the predetermined range, each of the tuned circuits which include the individual electrolmi escent cells 22 will resenate in turn, resu 'ng in applying a large potential across the cell componc s of the tuned circuits during resonance. The maximum applied potential varies with the amplitude moduation of tie output of the amplifier and because of the varying thickness between electrodes of the cells 22, the individual cell which forms a part of a resonating circuit electroluminesces in brightness and area in an amount which corresponds to the applied voltage. in other words, a larger voltage will cause a greater portion of the cell to emit visible light during resonance. This produces in visual fashion on the electroluminescent screen a signal presentation which corresponds to the signal input to the modulating tube 38.

it is necessary to synchronize the speed of the motor 36 with the period of the signal which is to be presented so that the speed of the motor as is either a whole 7 multiple or a whole fraction of the period of the signal which is to be presented. This is readily accomplished by means of the manual speed control 46, which can be adjusted accordingly. As an example, if the period of the signal to be presented is 4 sec., the capacitor .34 is rotated at 40 r.p.s. The varying frequency output potential of the oscillator 32, the input signal to be presented, the amplitude-modulated varying-frequency output of the amplifier -40 and the resulting signal presentation on the screen are all shown as diagrammatic signal representation in FIG. 4.

Some of the circuit components comprising the foregoing electroluminescent oscillograph 30 can be replaced by other conventional components which function in a similar manner. As an example, the potential generating means, which is preferably a Hartley oscillator, can be replaced by other conventional oscillators. The manually controlled motor 36, which essentially functions as a synchronizing means to synchronize the periodic variations in frequency of potential generated by the oscillator 32 with the period of the signal to be presented, can be replaced by conventional electronic synchronizing means. The modulating tube 38 can be replaced by other conventional modulating means, in order to modulate the synchronized varying-frequency potential with amplitude modulation corresponding to the signal to be displayed.

The present screen can also be used in applications other than an oscilloscope. As an example, the individual electroluminescent cells 22 which comprise the screen It as shown in FIG. 1 can be calibrated with respect to voltage and with respect to the resonant frequency of the tuned circuits of which the cells 22 form a part. In this manner, a direct simultaneous reading of frequency and potential can be obtained when a potential of unknown voltage and unknown frequency is applied across the screen input terminals.

It will be recognized that the objects of the invention have been achieved by providing an electroluminescent display screen for presenting signal information in an integrated fashion so that all of the area below the top portion of the presented signal is illuminated. There has also been provided an electro-luminescent oscillograph wherein the cathode-ray tube is replaced by a compact electroluminescent display screen and wherein all the area below the top portion of any signal presented is illuminated.

While best specific examples of the invention have been illustrated and described hereinbefore, it is to be particularly understood that the invention is not limited thereto or hereby.

I claim:

1. A display screen comprising: a plurality of closelyspaced and side-by-side electroluminescent cells; each closely-spaced cell of said screen comprising, two spaced electrodes at least one of which is light transmitting and each having a length dimension of considerable magnitude and a width dimension of small magnitude, the physical spacing between said electrodes gradually varying from a minimum proximate one end of said cell to a maximum proximate the other end of said cell, and material comprising electroluinescent phosphor included between said spaced electrodes; like ends of each of the closely-spaced cells comprising said screen positioned in sideby-side relationship; a plurality of tuned circuits each incorporating as a component thereof a difierent one of the cells comprising said screen; and each said tuned circuit displaying a different resonant frequency varying from a minimum for the circuit incorporating the cell positioned at one edge of said screen to a maximum for the circuit incorporating the cell positioned at the opposite edge of said screen.

2. A display screen comprising: a plurality of closelyspaced and side-by-side electroluminescent cells; each closely-spaced cell of said screen comprising, two spaced electrodes at least one of which is light transmitting and each having a length dimension of considerable magnitude and a width dimension of small magnitude, the physical spacing between said electrodes stepped in gradual fashion from a minimum proximate one end of said cell to a maximum proximate the other end of said cell, and material comprising electroluminescent phosphor included between said spaced electrodes; like ends of each of the closely-spaced cells comprising said screen positioned in side-by-side relationship; a plurality of tuned circuits each incorporating as a component thereof a different one of the cells comprising said screen; and each said tuned circuit displaying a different resonant frequency varying from a minimum for the circuit incorporating the cell positioned at one edge of said screen to a maximum for the circuit incorporating the cell positioned at the opposite edge of said screen.

3. A display screen comprising: a plurality of closelyspaced and side-by-side electroluminescent cells; each closely-spaced cell of said screen comprising, two spaced electrodes at least one of which is light transmitting and each having a length dimension of considerable magnitude and a width dimension of small magnitude, the physical spacing between said electrodes gradually varying from a minimum proximate one end of said cell to a maximum proximate the other end of said cell, and a mixture of electroluminescent phosphor and light-transmitting dielectric material sandwiched between said spaced electrodes; like ends of each of the closely-spaced cells comprising said screen positioned in side'by-side relationship; a plurality of tuned circuits each incorporating as a component thereof a different one of the cells comprising said screen; and each said tuned circuit displaying a different resonant frequency varying from a minimum for the circuit incorporating the cell positioned at one edge of said screen to a maximum for the circuit incorporating the cell positioned at the opposite edge of said screen.

4. A display screen comprising: a plurality of closelyspaced and side-by-side electroluminescent cells; each closely-spaced cell of said screen comprising, two spaced electrodes at least one of which is light transmitting and each having a length dimension of considerable magnitude and a Width dimension of small magnitude, the physical spacing between said electrodes gradually varying from a minimum proximate one end of said cell to a maximum proximate the other end of said cell, a layer of even thickness comprising electroluminescent phosphor included between said spaced electrodes, and an additional layer of dielectric material of gradually increasing thickness also included between said electrodes; like ends of each of the closely-spaced cells comprising said screen positioned in side-by-side relationship; a plurality of tuned circuits each incorporating as a component thereof a different one of the cells comprising said screen; and each said tuned circuit displaying a different resonant frequency varying from a minimum for the circuit incorporating the cell positioned at one edge of said screen to a maximum for the circuit incorporating the cell positioned at the opposite edge of said screen.

5. A display screen comprising: a plurality of closelyspaced and side-by-side electroluminescent cells; each of the closely-spaced cells of said screen comprising, two spaced electrodes at least one of which is light transmitting and each having a length dimension of considerable magnitude and a width dimension of small magnitude, a cross section taken between said electrodes having a generally wedge-shaped configuration, and material compris ing electroluminescent phosphor included between said spaced electrodes; like ends of each of said closely-spaced cells positioned in side-by-side relationship in said screen; a different tuned circuit connecting to each of the cells comprising said screen; and each said tuned circuit and connecting cell displaying a diiferent resonant frequency varying from a minimum for the circuit and connecting cell positioned at one edge of said screen to a maximum 7 for the circuit and connecting cell positioned at the opposite edge of said screen.

6. A display screen comprising: a plurality of closelyspaced and side-by-side electroluminescent cells; each closely-spaced cell of said screen comprising, two spaced electrodes at least one or which is light transmitting and each having a length dimension of considerable magnitude and a width dimension or" small in 'tude, the physical spacing between said electrodes g idually increasing at a greater-thanear rate from a maximum proximate one end of said cell to a maximum proximate the o her end of said cell, and material comprising electrolurninescent phosphor included hetweei said spaced electrodes; like ends of each of the closely-spaced cells comnrising said screen pos. oned in side-by-side relatio ga plurality of tuned circuits each incorporating as a component thereof a difierent one of the cells comprising said screen; and each said t ed circuit displaying a different res-o1 t fre uency vary i ii a minimum for the circuit incorporati' the cell p0 ned at one edge of said screen to a mamrnum for the circuit incorporating the cell positioned at the opposite edge of said screen.

7. A signal display device comprising: a signal-presentation screen comprising a plurality of closely spaced and side-t-y-side electroluminescent cells; each closely-spaced cell of said screen comprising, two spaced electrodes at least one of which is light transmitting and each having a length dimension of considerable magnitude and a width dimension or" small magnitude, the physical spacing between said electrodes gradually varying from a minimum proximate one end of said cell to a maximum proximate the other end of said cell, and material comprising electroluminescent phosphor included between said spaced electrodes; like ends of each or" the closely-spaced cells coinr ing said screen positioned in side-by-side relationship; a plurality of tuned circuits each incorpors 'ing as a conponent thereof a different one of the cells comprising said screen; each said tuned circuit displaying a different resonant frequency varying fro a minimum for the circuit incorporating the cell posi oned at one edge of said screen to a maximum for the circuit incorporating the cell positioned at the opposite edge of said screen; potential-genera ing means for c: aerating alternating potential periodically varying in uency throughout the go established by the resort requencies of said tuned c s; synchronizing means for synchronizing the variations in f equency c ential genercwed by tn the period of the icy potential generated uns with amplitude modu- ;l to be displayed; and

lation c rresponoing to the means for apol ing across 5 tuned circuits the synchronized modulated varying irequency output of said modulating means; whereby the signal to be displayed is me of this patent