CA1191192A - Electroluminescent lighting panel circuit and process - Google Patents

Abstract

Inventor: (1) ALBERTO W. COLLIE, (a citizen of Venezuela and resident of 1112 Angela Drive, Cedar Hill, in the County of Dallas and State of Texas 75104). Title: "ELECTROLUMINESCENT LIGHTING PANEL CIRCUIT AND PROCESS" . Described is a process and an apparatus for the generation of high light intensity electroluminescence. The combination of electroluminescent cells triggered using solid state circuits. More specifically, described is the use of solid state blocking oscillator circuits in conjunction with electroluminescent lighting panels which, when in operation, have high diffuse light intensities when operated using standard line alternating current power sources, or high frequency alternating current power sources or direct current power sources.

Description

SOLII~ ST~TE CIRCUIT AND PROCESS FO~
USING EL.ECTROLIJMINESCE~NT E'ANEI.

Background of the Invention (Par-t A) There is a need for increasing the brightness of electroluminescent lamps (referred to herein also as "EL lamp"). Typically, when operated from standard line al-ternating current power "AC power") (110 volts, 60 Hz), elec-troluminescent lamps give from 1 up to 2 Eootlamberts of brightness. This is increased to from 3 up to 4 foot-lamberts when operated at 400 Hz as in military environments.
These sinusoida] sources do not efficien-tly drive the 1amps because the elec-troluminescent lamps act as "lossy capacitors".
In general, the brightness as well as the color of an elec-troluminescent light source is dependen-t on both the applied vol-tage and frequency. At a given voltage, -the brightness increases wi-th rising frequency up to severa1 thousand cycles per second before decreasing, due to elec-trical losses which occur in the plate of the electroluminescen-t device a-t higher frequencies. The efEects of both applied voltage and frequency on the light output from a "ceramic"
electroluminescent lamp such as that described in United States Letters Patent 2,824,994 issued on February 25, 1985 are shown in the curves of ~igure C and are discussed infra.
The light output from the electroluminescent lamps of the prior art usually increases during the early hours of operation and then slowly decreases in intensity over many thousands of hours. The initial surface brightness of a green ceramic lamp operating from a 120 volt, 400 cycles per second (or hertz, Hz) supply is about 4 foot-lamberts (lumens per square foot) and the panel takes about 0.75 milliamperes per square inch (mA/in ).

3~`

~;

. ~_ .
A similar lamp operating from a 300 volt, 400 Hz supply is about ~ foot-lamberts; 600 volts, ~00 Hz at 20 foot-lamber-ts; 700 volts; 400 Hz at 35 foot-lamberts; 600 volts, 1000 Hz at 50 foot-lamberts and 700 volts, 1000 Hz at l 70 foot-lam`oerts.
Variations as to surface brightness depends upon applied voltage and frequency. Different coloured phosphors, as discussed previously, give different readings.
~ The brightness of an electroluminescent panel using high lll voltage and high frequency is composition and process dependent.
With a well-characterized process using particular phosphors and having certain thickness a change can be made in the dielectric layer. Such specially designed panels using a power conditioner of the type set forth in instant invention run much bright.er.
Several factors in the manufac-ture of electro-luminescent devices in conjunction with the circuit of its invention have been considered. Use of computer-aided design and control procedures gave rise to the development 1 of more efficient and brighter panels useful in conjunction . with the circuit of my invention, as discussed infra.
An electroluminescent lamp can be easily and smoothly dimmed to extinction by varying the applied voltage with a small variable resistance and it operates

2~ instantly upon application of the required potential.
Surface brightness values of metal-ceramic lamps of several colours under typical initial phases of operation without the use of the power conditioner of my invention are shown in Table 1 below:

. , .

, ., :

I~ !

~3~

3--Table 1. Typical Initial Brightness Values of Unadjusted Power Metal-Ceramic h`lectroluminescent Lamps Colour _ _ l 120V,60Hz 120V,400Hz ~OOV,250Hz 600V,60Hz 600V,400Hz . , . _ . _ . . . _ . _ ;
Green 1.0 4.0 S.O 8.0 20.0 Yellow 0.4 1.0 2.0 4.0 n/a ' ~ Blue 0.4 0.7 1.5 4.0 n/a White 0.3 0.7 2.0 5.0 n/a _ __ . .. .. . . .. . .. ... _ _ n/a - not available The ~ minating Engineering Society Handbook states in the chapter on "Lighting Eor Advertising" that adequate sign brightness should be provided but it is important that it should not be "overdone". This depends primarily upon the desired sign brightnessl use and the environment. An l incandescent or fluorescent sign which is too bright can ~ suffer loss of readability from the halo effect. With an electroluminescent sign, there is no halo effect.
The equivalent circuit for an electroluminescent lamp operating at frequellcies less than 1000 Hz can be approximated as shown in Figure 35A discussed infra. In l, Figure 25A, Rl represents the i R loss of the translucent conductive electrode. R2 represents current leakage I through the dielectric phosphor layer plus any edge leakage between electrodes. R2 is a decreasing function of voltage.
The capacitance C is determined by the size and voltage ~ rating of the electroluminescent lamp. This is the most ; representative model using linear parameters. An electro-luminescent lamp is actually a nonlinear device. A more precise electrical analog is shown in E`igure 25B. A cross Il section of an electroluminescent lamp is accurately ~I described by this circuit. The translucent conductive , coat being less than a perfect conductor is similar to, I
in characteristic, a transmission line of relatively high 3~

frequenci.es. ~5 can be seen, each increment of distance removed from a perfec-t cooductor serves -to sligh-tly reduce the voltage. Therefore, it is necessary to locate copper or silver conductive strips approxima-tel~ every 4-6 inches across the lighted surface o~ the electroluminescent lamp in order to maintain perfect uniformity at high frequencies.
Sixty hertz operation remains uniform with high conductive mediums as far apart as 30 inches.
A typical alternating current-drive waveform, such as might be applied to an electroluminescent element, consists of a series of narrow pulses (2-50Js), with alternating polarity that repeats at 100-10000 Hz (sine wave).
Electrically and physically, an electroluminescent lamp resembles an electrical capacitor but cannot be precisely equated from a mathematical or physical standpoint to a mere capacitor. Electrically it appears as a capacitor and resistor in parallel resulting in a leading power Eactor from 0.40 to 0.80. Sample electrical characteristics are presented in Table 2, infra.
Table 2 Electrical Characteristics -. . _ . _ . .
Operating Frequency Maximum Impedance 2 Breakdown Phase Voltage(~z) Curren~ (k.ohms/in ) Voltage Angle ( RMS) (ma~in ) ( RMS) ( ) .
120 60 0.25350 min 18050-70 120 400 0.75240-480 18050-70 200 250 0.50400 1000 30055-75 300 60 0.50833-2670 45050-70 600 60 1.251200-2400 90050-70 600 400 4.50262 545 90040-60 .~

~ 3~ J`~
. ., ~. f~

Circuits provlded by the prior art have not been practical for use in conjunction with electroluminescent lamps because of an inability to create a steady appropriate bright ligh~ source.
United States Letters Patent 3,611,177 issued on October 5, 1971 discloses an electroluminescent circuit for DC operation comprising a discrete electroluminescen-t element the capacitive reactance characteristic of which is utilized in a circuit containing bidirectional threshold switching device having inheren-t turn-on time delay and inherent recovery time delay characteristics and, toyether with suitable circuit resistance form a bistable electroluminescent relaxation oscillator circuit which has stable ON and stable OFF conditions with a DC operating potential continuously applied thereto. In accordance with U.S. Letters Patent 3,611,177, when a start signal, which may be a pulse of predetermined time duration and amplitude, is applied to the electroluminescent circuit the circuit will begin to oscillate a-t a frequency determined by, among other things, the electrical values of the circuit components and -the amplitude of the applied voltage and will continue to oscillate as a relaxation oscillator after termination of the start signal to energize the electroluminescent element of the circuit so that light will be emitted therefrom. When a stop signal of the proper time duration is applied to the electroluminescent relaxation oscillator circuit the circuit will stop oscillating and -the electroluminescent element will no longer emit light.
United States Let-ters Patent 3,026,440 issued March 20, 19~2 discloses a close circuit which will supply a low frequency alternating voltage to an electroluminescent cell to efEect illumination of the electroluminescent cell.

~ ,t~

Also provldecl in U.S. Letters Patent 3,026,440 i5 a control circuit for an electrolumlnescent lamp which will illuminate the electroluminescent lamp and can be easily actuated or deactivated to thereby turn "ON" or "OF'F" -the electroluminescent cell. Also provided in V.S. Letters Patent 3,026,440 is an electroluminescent cell which can be actuated to hold the cell illuminated in response to relatively short pulse and retain the cell illuminated until other discrete pulse is supplied to the device. Also described in U.S. Letters Patent 3,026,440 is a control circuit for the electroluminescent cell utili~ing a negative resistance semiconductor such as a unijunction transistor or double base diode. The control circuit of U.S. Letters Patent 3,026,440 supplies a low frequency alternating current voltage to the electroluminescent cell in response to a pulse and continues to supply this a]ternating curren-t to the capacitor until a subsequen-t pulse is applied to the device.
Thus, U.S. Letters Patent 3,026,440, as described infra, discloses a circui-t having a double base diode having an emitter and a base electrode, a pair of base terminals connected on opposite sides of said base, a direct-current voltage supply connected betweer. said pair of terminals for establishing a voltage gradient along said base, an emitter circuit including a first winding means, an emitter bias supply, one of said pair of base terminals and said emitter, said emitter being normally back biased, a second winding means inductively coupled to said first winding means, an electroluminescent cell connected across said second winding means, and a pulse generator connected across said first winding means for applying a forward pulse thereto to forward bias said emitter and render said emi-t-ter circuit conductive.

Although Elyback voltaqe control circuits are known .in -the prior art, the prior art neither specifically nor inferentially discloses the applica-tion thereof to the powering of electroluminescent cells. Thus, Uni-ted S-tates Let-ters Patent ~,377,8~2 issued on March 22, 1983 discloses a flyback power supply with secondary circuit damping during primary charging which is stated to reduce the induced or reflected oscillations into the primary circuit and super-imposition onto the primary current so that the latter becomes a monotonically increasing function, permitting and facilitating feedback control. U.S. Letters Patent 4,377,842 specifically claims a combination comprising:
(i) resonant circuit means, in the secondary circuit of a flyback power supply, including stray capacitance, for storing energy;
(ii) means for supplying current periodically -to said resonant circuit means; and (iii) means operable during the supplying current for reducing fluctuations in said current;
whereby the energy stores in said resonant circuit can be closely controlled.
Although solid state blocking oscillator circuits are known in the prior art, the prior art neither specifically nor inferentially discloses the application thereof to the powering of electroluminescent cells or electroluminescent panels. Furthermore, the prior art does not teach either expressly or implicitly the creation of the unexpected, unobvious and advantageous brightness effec-ts created in practice by the use of certain solid state blocking oscillator circuits in conjunction with electroluminescent cells, more specifically, electroluminescent lighting panels. Thus l~nited States Letters Patent 3,334,619 issued Auyust 8, 1967 discloses a capac-tive discharge sys-tem, specifically an ignition system for internal combustion engines and a blocking oscilla-tor power supply therefor. The blocking oscillator power supply circuit is illustrated herein in Figures A
and B.
United States Letters Patent 3,334,619 thus discloses an ignition system wherein a capacitor is charged by a blocking oscillator power supply comprising a transistor the base circuit of which is connected to charge the capacitor through a diode and which is reseneratively coupled to the emitter-collector circuit of the transistor by a voltage s-tep-up transformer having the primary winding and the emitter-collector circuit and the secondary winding in the base circuit. In IJ.S. Letters Patent 3,334,619, the increased voltage induced in the base circuit both charges the capacitor to several hundred volts from a 12 volt source and also rapidly sa-turates the transis-tor until further current increase is prohibited by saturation of the base circuit.
The capacitor is then discharged through the primary winding of the ignition coil or other transformer to fire the spark plug selected by the distributor.
Furthermore, in ~.S. Letters Patent 3,334,619, the blocking OSCillator power supply circuit is made to free-run by a second capacitor interconnecting the base currentbetween the diode and the base and the emitter~collector circuit. The combined voltage stored on the second capacitor and induced in the secondary winding during the flyback is stated to reverse-bias the base of the transistor at a very high voltage to make the transistor thermally stable and also cause the blocking oscillator to free-run.

_cc~round_of the_ n nt:ion (Par~ B) Brief Description of the ~rawings of Certain Prior Ar-t __ _ _ .
Figure A is a circuit diagram oE the blo~king oscillator power supply of the invention described in U.S.
Letters Patent 3,334,619.
Figure_ is a circuit diagram of yet ano-ther embodiment of the blocking oscillator power supply of the lnvention of U.S. Letters Patent 3,334,619 which also operated in the flyback mode.
_gure C is a graph showing the effects of both applied voltage and light output from a standard "metal-ceramie" electrolumineseent ligh-t panel uslng prior art circuitry.
Figure D is a schematic diagram of a flyback power supply with a damping circuit according to the disclosure of U.S. Letters Paten-t 4,377,842.
~'iqure 27 is a circuit diagram of four-transistor push-pull circuit of the prior art used in conjunction with columns and rows of a multiplicity of electroluminescent lamps as described in the publication "Miniature Flat Panel Display Feasibility Model", a Rockwell International publication discussed and referenced in V.S. Letters Patent 4,361,384 at pages 23 and 24.
Background of the Invention (Part C) Detailed Description of Certain Drawings of Prior Art Referring to Figure A herein (which is Figure 1 of U.S. Letters Patent 3,334,619) a blocking oscillator power supply is comprised of a transistor Q and a voltage step-up transformer T in which .he secondary winding T2 has a greater number of turns than the primary winding Tl.

~r 3~

The em:itter of transistor Q :is connected through the primary winding T1 to a posi-tive voltage supply terrninal 6 and the collectox is connected to ground such that the primary winding Tl is connec-tion in a series D.C. power circuit includiny the emitter-collector circuit of the transistor Q. The base circuit of the translstor Q is regeneratively coupled to the emitter-collector circuit through the secondary winding T2 and also drives the load which in the case illustrated in F'igure A is a capacitor C which is charged through a diode Dl. The other side of the capacitor C is connected to ground so as to forrn a second series circuit interconnecting the base of the transistor and the D.C.
power circuit. Although the second series circuit interconnects the base and the emit-ter of the transis-tor Q by way oE -the battery, the circui-t may be connected from the base direct].y back to the emitter or back to -the positi.ve terminal 6 (in Figure A) because of the voltage induced in the secondary winding T2. It is disclosed in ~.S. Letters Patent 3,334,619 that an ou-tput terminal 7 (in F'igure A) may be connected to drive any number of loads by discharge of the capacitor, such as ignition systems, photoflash units, stroboscopes, electric fences and sweep circuits for oscilloscopes and television sets.
In order to unders-tand the operation of the blocking oscillator power supply (as set forth in the prior art, e.g., U.S. Let-ters Patent 3,334,619) assume that the capacitor C1 is d1scharged and that no emitter power voltage is applied to the positive terminal 6 (in Figure A). When a positive voltage is applied to the terminal 6 (in F'igure A), the emitter-base diode within -the transistor Q will conduct through the primary winding T1, thesecondary winding T2, diode D1 and capacitor Cl. The base current flow produces collector current through T1 as well and induces a voltage ,;,, - :Lo -in the secondclry wincling T2 of a polarity which wi:ll make the base become more negative. 1'his increases the collector current and therefore increases the current throu~h the primary winding of T1 to further increase the voltage induced in the secondaxy winding T2. Thus, the transistor Q very rapidly goes to saturation and substantially the full posi-tive voltage is applied across the primary winding T1. This induces a high voltage on T2 which charges capacitor C1 by the base current of transistor Q. When the losses of the charging clrcuit for the capacitor C1 approach the gain, i.e., when the feedback loop gain approaches unity, the regenerative process ceases and the transistor Q is very rapidly turned off. The diode D1 has a very high resistance and prevents the d:ischarge of capacitor C1 and incidentaL:Ly protects transistor Q from the reverse polarity voltage or flyback voltage genera-ted in the secondar~ winding T2 is preferably substan-tially greater than the number of turns in the primary winding T1 so that the voltage lnduced in the base circuit materially exceeds the voltage in the emitter-collector circuit. For example, 12 volts applied at theterminal 6 (in Figure A) may easily produce a charge of several hundred volts (400 V in one embodiment of U.S. Letters Patent 3,334,619) across the capacitor C1. When the capacitor C1 is discharged through a load attached to the output terminal 7 (in Figure A)/ the transistor Q will again conduct and recharge the capacitor.
Referring now to Figure B (Figure 4 of U.S. Letters Patent 3,334,619) another blocking oscillator power suppLy is similar to the circuit of Figure A described supra and correspond~ng components are therefore designated by corresponding reference characters. However, the circuit - 10 . 1. -of ~igure B cliffers from the circuit of Figure A in thatthe capacitor C1 :is charyed d~ring the f:Lyback of the transformer T rather than during -the forward conduction of the transistor Q. Further, a resistor R1 :inter-connecting the base circuit be-tween the secondary wind.ing T2 and the diode D1 provides a conduction path for forward base current and also makes the blocking oscillator circuit free-run.

diode D3 connected from base to emitter of transistor Q
provides a path for the flyback current and prevents da~nage to transistor Q. The base of the transistor Q is connected through the secondary winding T2 and the resistor R1 -to I ground. The diode D1a ls reversed to the diode Dl in the circuit ~f Figure A and connects the capacitor C1 to , the junction between the resistor Rl and the secondary winding T2. The other side of the capacitor Cl is Il connected to ground.
~ When the positive vol-taye i5 applied to the terminal 8 in Figure B, the base current through the primary winding Tl produces collector current which induces a yreater voltage in the secondary winding T2 so as to make the base of -the transistcr more negative and thereby very rapidly sa-turates ~ the transistor Q. During the conduction of the transistor Q, the voltage induced in the secondary winding T2 reverse-biases the diode Dla and the current passes through the ,' resistor Rl to ground. When the regenerative process ceases 1 and the flux in the transformer collapses, the flyback l' voltage induced in the secondary winding T2 has a reversed polarity and the diode Dl is then forward-biased and the capacitor Cl is charged through -the circuit from the ground through the capacitor Cl, diode Dla, secondary winding T2, 1 diode D3, a primary winding Tl and the battery connected between terminal 8 and ground. ~s mentioned, diode D3 ! prevents transistor Q from being damaged during the charging of capacitor Cl. The diode Dla then prevents discharge of the capacitor Cl. ~owever, the resistor Rl permits the Il flux in the transformer T to collapse such as that base I current in the transistor Q will start the regenerative process to again fire the transistor. The blocking oscillator circuit will thus free-run and the diode Dla will conduct to the extent that the flyback voltage induced ¦l, in the secondary winding by the collapsing flux exeeds the ~I voltage stored on the capacitor Cl. The rate a-t which the blocking oscillator will fire is determined by the value of the resis~or Rl. The capacitor Cl may be discharged through outp~t terminal 9 by any suitable circuit.

1 ~
. . , ,1 , I .

"Push-Pull" circui-ts are disclosed in the p-rior art -to be useful in conjunction with supplying power for the operation or elec-troluminescent cells. A circuit of high complexity is disclosed in the publication "Miniature Flat Panel Disp],ay ~easibility Model", a Rockwell Interna-tional publication discussed and referenced in United S-ta-tes Le-tters Patent 4,361,384 at pages 23 and 24. More specifically, the high voltage driver breadboard circuit of the Rockwell publication is shown in Figure 27 and discussed infra. The circuit consists of a PNP-NPN pair connecte~ in a complimentary configuration. A complimentary pair appears on the column and another pair on the row. The circuit operates as follows: during the negative transis-tion oE the input signal transistor 974A (PNP) turns on transistor 974B (NPN) off putting the column side high at the sarne time the input signal to the row side is going positive which turns transistor 977B (NPN) on and -transistor 977A (PNP) off, pulling the row side to ground. This places video information on this par-ticular cell. The non-addressed row is in a high impendance state and never exceeds threshold voltage.
In the next half cycle, the signal on the column side goes high and transistor 974A turns off and transistor 974B
turns on. On the row side, transistor 977A turns on and transistor 977~ turns off; this reverses the polarity on the cell. The advantage of this circuit is that it consumes less power than other conventionalcircuits since the PNP transistor 977A acts as a dynamic load.
~ owever, nothiny in the prior art discloses the utilization of the specific push-pull blocking oscillator circuit or the use of othe:r b~ockiny osci:Llatox circuit~
in conjunction wi-th electrolurnir)escent cells whereby unexpected, unobvious and advantayeous effec-ts are produced in -the operation of such circui.t with such electxoluminescent cell, particularly electroluminescent ceramic panels.

;' I I ~

i : , Summary_of he_Inven_ion I have discovered that a certain class of solid state circuits, specifically a type of blocking oscillator, is ideally suited to supplying power to cause electroluminescent l, lamps to function efficiently and with a high degree of brightness. The circuits are self-starting, free running and are capable of driving electroluminescent lamps at high brightness, high efficiency and low cost. A number of the lll circuits of my invention will perform satisfactorily using ¦~ a reverse polarity voltage and change the transistors thereof to NPN types along with the reversal of the diode.
The advantages of using the circuits of my invention in conjunction with electroluminescent lamps are as follows:
(a) the circuits have few parts and are more reliable;
(b) the circuits are selE-starting and free running;
(c) the circuits have high voltage output but require low input;
(d) the circuits and their operation are inexpensive; and (e) ~he circuits represent a practical technique for mass production of electroluminescent , lamp-containing devices since they can easily be incorporated into miniature ~Ichips~.
Hence, a need has been fulfilled for increasing the brightness of electroluminescent lamps. Electric power sources including AC power sources or sinusiodal sources I have now been found to have the ability to efficiently drive 1 electrQluminescent lamps with high brightness in a steady manner.

,1 ;

Brief Descri_tion of the Drawlngs Figure A is a circuit diagram of the bloc~ing oscillator power supply of the invention descrlbed in U.S.
Letters Patent 3,334,619.
; Figure s is a circuit diagram of yet ano~her i - ~
embodiment of the blocking oscilla-tor power supply of the invention of U.S. Letters Patent 3,334,619 which also operates in the flyback mode.
Il Figure C is a graph showing the eEfects of both il applied voltage and light outpu~ from a standard "metal ceramic"
; electroluminescent light panel using prior art circuitry.
Figure D is a schematic diagram of a flyback power supply with a damping circuit according to the disclosure of U.S. Letters Patent 4,377,842.
Fig_re 1 is a circuit diagram of a blocklng oscillator power supply o:E this invention, interconnected with an electroluminescent ]amp, the circuit operating in the flyback mode.
~ ure 2 is an embodiment of the blocking oscillator ~ of Figure 1 specifically shown adapted to an outside alterna-ting current source operating using a transformer and rectifier.
Fig re 3 is another embodiment of ~he circuit of Figure 1 using an outside direct current source, a battery Figure 4 is a circuit diagram of another embodiment of the blocking oscillator power supply of this invention interconnected with an electroluminescent lamp with the positive voltage feed poin~ being at the center tap of the ~ transformer primary, the circuit producing a more symmetrical wave form to the electroluminescent lamp due to the "push-pull" nature of opposing transistors.
Figure 5 is a specific em~odiment of the circuit of Figure 4 showing the use of an outside alternating current source operating using a transformer and rectifier.

Il :

~15-Fi~ure 6 is a specific embodiment of the circuit of Figure 4 ~perating through a direct curren-t power source.
Figure 7 is a circui~ diagram of still another ~ embodiment of the circuit of Figure 1. having irnproved thermal l~ stability.
Figure 8 is a circuit diagram of the blocking , osci.llator power supply of the present lnvention directly " interconnected with an electroluminescent lamp.
Fiqure 9 is a circuit diagram of yet another ~I modification of the circuit of Figure 8 which is free-running and thermally stable. '.
Figure 10 is a schematic circuit diagram of one embodiment of the invention of U.S. Letters Patent 3,026,440 (shown as Figure 1 in said U.S. Letters Patent 3,026,440).
Flgure 11 is a schematic circuit diagram including the semiconductor employed i.n the embodirnent in Figure 10 ; (Figure 1 oE U.S. Letters Patent 3,026,440).
ure 12 is a characteristic curve of the semi-'~ conductor employed in the embodiment of U.S. I,etters Patent 1 3,026,440 shown herein in E`igure 10 (Figure 1 of U.S. Letters !~ Patent 3,026,440).
Figure 13 is another schematic circuit diagram of an embodiment of the invention of V.S. Letters Patent 3,026,440.
: Figure 14 is a schematic view of an electroluminescent i , lamp useful in the practice of my invention, disclosed in U.S. Letters Patent 2,824,992 (as Figure 1 in said U.S. Letters Patent 2,824,992).
Figure 15 is a schematic view of a two superposed phosphor-dielectric layers useful in forming an electro-. luminescent lamp useful in my invention, which layers are disclosed in V.S. Letters Patent 2,824,992 (Figure 15 is ` Figure 2 in U.S. Letters Patent 2,824,992).
¦I Figure 16 is a side elevation cross-sectional view Il of an electroluminescent lamp useful in the practice of my l, invention incorporating a phosphor layer sandwiched between two semi-insu].ator layers, as described in U.S. Letters Patent 4,326,007 (Figure 1 in said U.S. Letters Patent

4,326,007)~

1~ 1 - l6 -Fig~l:re 17 is a side elevat:ion cross-sectional _.__ _ view o.E an elec-trolurni.nescent lamp i.ncorporating -two isolated phosphor layers separated one from the other by a central semi-insulator layer, the composite being then sandwiched between top and bottom semi-insulator layers as disclosed in U.S. Letters Patent 4,326,007 (Figure 2 of said U.S.
Le-t-ters Patent 4,326,007).
_ ure 18 is a plot of phosphor layer thickness on the abcissa versus brightness on the ordinate for the structure of Fiaure 16 (Figure 18 is the same as Figure 3 of U.S. Letters Patent 4,326,007).
Figure 19 is a plot of wavelength on the abcissa versus intensity on the ordinate for the electroluminescent lamp structure of Figure 16 (Figure 19 is the same as Figure 4 of U.S. Letters Patent 4,326,007).
Figure 20 is a schematic cliagram of a thin film _ __ electroluminescent device useful in carrying out -the operation of my invention, speciEically described in U.S. Letters Patent 4,373,135.
Figure 21 is a schematice diagram of the AC thin-. . .
film electroluminescent device useful in the opera-tion of my invention and further described in the paper Theis, et al, "Electrooptical Properties of AC Thin-Film Electro-luminescent De~ices'l, Siement Forsch.-Entwicklungsber. 1982, 11(5), 265-70.
Figure 22 is an equiva.lent circuit of AC thin-film electroluminescent device of the Theis, et al paper which electroluminescent device is useful in the operation of my invent ion .
Figure 23 is a cross-sectional view of an AC zinc sulfide:manganese electroluminescent cell useful in the practice of my invention, and described ln the paper by Tornquist and Ylilammi, "The Decay and Saturation of the Emlssion in AC Electroluminescent ZnS:Mn Thin Films", - 1.7 -Journal of Luminescence 27 (1982), 285-29l, North-~lolland Publishing Company.
Fi ~re 24 is a fragmentary perspective view of a thin-film electrolumine~cent display panel useful in the practice of my invention and specifically described in U.S.
Letters Patent 4,366,504 issued on December 28, 1982 (E~igure 24 is the same as Figure 1 in said U.S. Letters Paten-t 4,366,504).
_gure 25A is a simplified eguivalent circuit for an electroluminescent lamp.
Figure 25B is a more accurate representation of an equivalent circuit for an electrolumlnescent lamp which is of the ceramic metal type useful in the prac-tice of my invention.
Figure 26 is a cross-secti.onal view oE A th.in film electroluminescent lamp structure useful in the practice of my invention.
F _ re 27 is a circuit diagram of a four-transistor push-pull circuit of -the prior ar-t used in conjunction wi-th columns and rows of a multip].icity of electroluminescent lamps.
~ure 28 is a voltage wave form for a half wave rectifier with smoothing capacitance of the type which would exist in practicing the process of my invention.
Figure 29 is a plan view of an electroluminescent display which can be used in the operation of my invention and which is more specifically described in U.S. Letters Patent 4,376,145 issued Ol- March 8, 1983.
Figure_30 is an enlarged cross-sectional view of the electroluminescent display of Figure 29 taken at 30-30 of Figure 29. Figure 30 is the same as Figure 2 of U.S. Letters Patent 4,376,145.

3,~

I"Detailed Description of the Invention and _ eferred Embodiments My invention is directed to apparatus and a process ,~ for effecting the emission of diffuse intense light at a 1 substantially constant brightness and substantially constant ' intensity from an electxoluminescent cell using means for applying AC or DC power from an AC or DC power source to the positive terminal of a circuit wherein the circuit comprises:
~ (i) an electroluminescent cell which has an l' anode and a cathode;
i (ii) a discharge circuit means connected to : the electroluminescent cell for discharging :~ the electroluminescent cell; and (iii) a blocking oscillator power supply comprising a transistor, the base circui-t of which is connected to charge the electroluminescent cell at the anode of the electroluminescent i cell and is regeneratively coupled -to the , emi.tter collector circuit of the transistor by voltage step-up transformer, the primary wi.nding oE which is connected to the emitter- I
collector circuit and the secondary winding 1~ of which is connected to the base circuit.
I~ Preferably, the blocking oscillator power supply 1l circuit contains a diode which is connected rom the transistor base to the transistor emitter and is connected from the primary windiny to the secondary winding of the step-up transformer whereby a path is provided for flyback current.
' Furthermore, the blocking oscilla~or power supply . circuit may be a two transistor push-pull circuit wherein ; the power input location is at the center tab of the primary winding of the step-up transformer.
More preferably if an AC power source is used, the b~oc~ing oscillator power supply will comprise:

, 1 ~ ' 9.. ~'~ :

¦l (i) a first voltage step-up -transformer having a first primary winding and a firs-t secondary winding;
(ii) a trans.istor having a base, an emi-tter and ll a collector;
(iii) first circuit means for connecting the first primary winding, the emitter and the base to the first secondary winding; a first diode 1 being connected from said trans.istor base to 1I said transistor emitter and being connected I from said primary winding to said first ~ secondary winding whereby a path is provided I for flyback surrent;
~ (iv) second circuit means including the first secondary winding of the first step-up transformer, the electroluminescent cell and ,. a capacitor, the capacitor connecting the first ! primary winding with the electroluminescent ; cell and the electroluminescent cell being connected to the first secondary winding, the purpose of the second circuit means being for , charging the electroluminescent cell;
1~ (v) third circuit means including the capacitor I of the second circuit means connected in . series to a second diode and an AC power source through the second secondary windings of a second step-up transformer.
When using a direct current source, the blocking ' oscillator power supply comprises:
1 (i) a first voltage step~up transformer having a primary winding and a secondary winding;
(ii) a transistor having a base, an emitter and j a collector;
(iii) first circuit means for connecting one end ,' of first primary windings, the emi~ter and , the base to one end of the first secondary windings, a first diode being connected from 1 '.

,. ~
" :

ll l ,, , , said transistor base to sald transistor emitter and being connected from said one end of said primary winding to said ; one end of said first secondary winding I whereby a path is provided for flyback current;
(iv) second circuit means including the ; secondaxy winding of the step-up transformer lll and the electroluminescent with the electro-ll luminescent cell being connected at its anode to a second end of said secondary winding, the purpose of sAid secondary circult means being for charging the electroluminescent cell; and (v) a DC power means, e.g., A battery having a positive end and a negative end (e.g., an anode and a cathode, respectively), said positive end connected to the second end oE said primary winding and said negative end being connected to the cathode of the electroluminescent cell.
When a substantially symmetrical wave form is desired to be induced in the electroluminescent cell when a relatively large amount of power is desired to be applied, 1 a ~ush-pull two transistor blocking oscillator circuit is preferred where power is supplied (AC or DC power) at a location proximate the mid point of the primary windinys of a first transformer which is part of the circuit and wherein the blocking oscillator circuit comprises:
33 1 (i) an electroluminescent cell;
(ii) a first voltage step-up transformer having a first primary winding and a first secondary winding;
1 (iii) a first transistor having a first base, a ¦I first emitter and a first collector;

. . , 1, . ~ ~

I ! -21-li I (iv) a second transistor in an opposing juxtaposition I to said first transistor having a second base, a second emitter and a second collec-tor;
!l (v) the first primary winding of the first voltage 1l step-up transformer belng connected to a power source at a location proximate the mid point of said first primary winding;
I (vi) a first circuit means for connecting a first I end of said first primary winding, said first I emitter and said first base to a first end ¦l of said first secondary winding; with a first diode being connected from said first base , to said first emitter, whereby a first path is provided for a first flybaek current; and (vii) a second circuit means for connec-ting a second end of said Eirst primary winding, the 1. electroluminescent cell, said second emitter : I and said seeond base to a seeond end of said ll, secondary winding, with a second diode being 1I connected from said second base to said second 1 emitter, wherehy a second path is provided for I l a second flyback current~
When the power source to the aforementioned push pull .~ circuit is an ~C power source, the AC power souree is used ~5 I to apply power in a third eireuit means to seeond primary l windings of a second voltage step-up transformer and the blocking oseillator additionally comprises a fourth cireuit means which in turn comprises: I
I (viii) a capaeitor means having a positive side and ~, ' a negative side;
(ix) a third diode means conneeted to the negative '.
side of said capacitor; and (x) secondary windings of the second voltage I step-up transformer one end of which is I connected to said third diode means and the other end of which is connected to the positive end of said capacitor means and to the first ~, 1~ , I, :

primary winding of the first voltage step-up transformer at a location proximate the mid point of said first primary windings of said first transformer, the capacitor means and ¦~ the third diode means also being connected to said second collector of said second transistor.
ll In the event that rather than an AC power source ¦l a DC power source is used to power the aforementioned push-pull 1 blocking oscillator circuit, the blocking oscillator circuit l, additionally comprises a third circuit means comprising a DC
i power means (e.g., a battery) having a positive side (anode) ; and a negative side ~cathode), the positive side of the DC
power means being connected to the first primary winding of the first voltage step-up transformer at a location proximate the mid point of the first primary windings of the first voltaye step-up transformer; the negative side oE the DC
power means being connected to said second collector of said second transistor.
l~ The blocking oscillator circuit can be thermally ' protected using resistors or combinations of resistors and diodes. Thus, for example, the blocking oscillator circuit may comprise:
(i) a voltage step-up transformer having primary ' windings and secondary windings;
,l (ii) a transistor having a base, an emitter and a collector;
(iii) a diode connected to said emitter and a first end of said primary winding;
(iv) a resistor connected to said diode, a first l end of said primary windings, a first end of said secondary windings and said base; the second end of said primary windings being connected to the power supply; and (v) the second end of the secondary windings being '~ connected to the electroluminescent cell which 1 is connected to groundO
.. ;
!

. ' .
. ' 3~

I` On the other hand, the blocking oscillator circuit can comprise:
(i~ a voltage step-up transformer having primary windings and secondary windingsi 1 (ii) a transistor having a base, an emitter and a collector;
I~ (iii) a first resistor connected to said emitter, a first end of said primary windings, a first ¦l end of said secondary wind.ings and said base;
l¦ (iv) a second resistor connected to said collector, !` said base and said first end of said primary I winding;
il (v) the second end of said primary windings being , connected to said power supply; and ~ (vi) the second end of the secondary windings be connected to the electroluminescent cell which is ccnnected to ground.
A number of dielectric electroluminescent cells 1' may be utilized in my invention. These are exemplified , as follows:
I (i) the electrolumineseent lamps o U.S. Letters I! Patent 2,824,992 issued on February 25, 1958 comprising an electrode, a coating of phosphor ~l and dielectric material over said electrode, I a second coating of phosphor and dielectric I material over said first coating, and a transparent l~ electrode over said second coating, each of said coatings varying in composition from a nearly clear glass on one side of the coating ~ to a nearly pure layer of phosphor on the other;
(ii) the electroluminescent structures of U.S~ Letters Patent 4,326,007 issued on ~pril 20, 1982 comprising a laminar, composite made up of Il pairs of semi-insulator films fabricated from 3~ ~I substances developing hîgh energy electrons when subjected to an electrical voltage each in association with phosphor films luminescing under electron impact from the semi-insulators;

I (iii) the thin-film electrol~minescent devices of U.S. Letters Patent 4,373,145 issued on February 8, 1983 which are construc-ted on 1 a smooth surface substrate on which a base ~ conductive layer is formed followed in sequence by an impurity built barrier layer, an l~ electrically resistive layer and a counter- 1, il electxode layer with the impurity built barrier ¦ layer being built with a material which i exhibits electroluminescence;
(iv) the thin-film electroluminescent image display panels disclosed in V.S. Letters Patent 4,366,504 issued on December 28, 1982 having a three-~ layered structure including a number of ~ transparent electrode strips disposed on a glass support with a layer of dielectric material such as Y~O3, SiN4, TiO2 and A12O3, a layer , of electrolum.inescent material, for example, ZnS doped with Mn and a second layer of dielectric material, such as Y2O3, SiN~, TiO2, and jl Al~O3;
' (v) electroluminescent display devices as disclosed j in U.S. Letters Patent 4,376,1~5 issued on March 8, 1983 including, for example, a layer ' of electroluminescent host material, such as zinc sulfide, selected portions of the host j, materi.al being activated with an electroluminescent activator, such as manganese, said selected portions being transversely separated from I one another by unactivated portions of said host material and said selected portions defining a desired display pattern, and an electrode extending transversely over a plurality 1, of said selected portions in order that said ~ plurality may be illuminated by activatlon of said electrode;

, , ~

~ 9 .~

(vi) electrolumineSCent display strips with light pipe valves as disclosed in U.S. Letters ~atent 4,373,956 issued on April 5, 1983;
(vii) thin-film electroluminescent devices as j disclosed in the Rockwell International Report .~ on Contract No. DAAK70-78-C-0123 dated Il December, 1979 and referenced at lines 36, 37, j 38 and 39 of column 2 of U.S Letters Patent Il 4,361,384 issued on November 30, 1982 and ll exemplified by a glass substrate supporting a transparent InO electrode on which is suppor-ted an insulating dielectric, such as Y2O3 or SrTi.03, on which is supported an . electroluminescent layer, for example, ZnS:Mn, on which is supported anothe:r inslllating surface, for example, Y2O3 or SrTiO3,on which is supported another aluminum electrode;
. (viii) elec-troluminescent ZnS:Mn thin-film as disclosed in the article by Tornquist and Ylilammi. in I the Journal of Luminescence 27 (1982), pages 285-291 puhlished by the North Holland Publishing Company;
(ix) AC th.in-film electroluminescent devices as disclosed in the article by Theis, Venghaus 1 and Ebbinghaus in Siemens Forsch.-EntwicklungsberO
1982, 11(5), pages 265-70 and abstracted in Chem. Abstracts 97:225929n.
l~ Now referring to Figure 1, an electroluminescent ~ lamp of the type exemplified supra, indicated by reference 1 numeral 10, is charged during the flyback of the transformer . ~11, 12) rather than during the forward conduction of the transistor 16. Moreover, the resistance loss in the electro-¦' luminescent l~mp 10 provides a conduction path for forward I base current and causes the circuit to free-run. The diode ii _ connected from base to emitter of transistor 16 provides a path for flyback current and prevents damage to the 'I transistor 16. The base of transistor 16 is connected through __ the secondary winding of the transformer 11-12 and the resistance of the electroluminescent lamp 10 to ground 13. When the ~ positive voltage is applied to the terminal 14, the base current through the primaxy winding of transformer 11-12 produces Il collector current which induces a greater voltage in the secondary winding of transformer 11-12 so as to make the Il base of the transistor 16 more negative and thereby rapidly l~ saturates the transistor 16. At this time, the flyback ,' cycle begins again. Specifically referring to ~igure 1, a circuit which can be used to effect the process of my j invention for producing intense diffuse light irradiated from electroluminescent cell 10 consists of applying AC or DC power from an ~C or DC power source 14 to the positive terminal of the circuit 14 where the circuit consists of:
: (i) the electroluminescent cell .lO having an anode and a cathode;
(ii) a discharge circuit means 13 connected to ~ said electroluminescent cell 10 for discharging the electroluminescent cell 10;
(iii) a blocking oscillator power supply consisting of a transistor 16, the base circuit of which . is connected to charge the electroluminescent cell 10 at the anode of the electroluminescent cell 10 and is regeneratively coupled to the ; emitter-collector circuit of the transistor 16 by a voltage step-up transformer 11-12, the ' primary winding 12 of which is connected to the emitter-collector circuit and the secondary winding 11 of which is connected in the base circui-t with a diode 15 being connected from the transistor 16 base to the transistor 16 ~ emitter and being connected from the primary winding 12 t~ the seeendary winding 11 o~ the I . , 3 ~

step-up transformer l.:L-12 whereby a path is provided for Elyback currentO Tlle collector of transistor 16 is connected to ground at 17. The electro-luminescent cell ].0 is connected to ground at 13.
In all blocking oscillator power supplies of my invention, the secondary winding of the transformer has a greater number of turns than the primary winding. Thus, in Figure 1, a number of turns in the primary winding 11 is greater than the number of turns in the secondary winding 12. In Figure 1, the diode 15 serves to provide a path for the flyback current and also prevents damage to transistor 16.
Figure 2 is a circuit of my invention which includes another embodiment of the blocking oscillator power supply of my invention consisting of:
(i) a first voltage step-up transformer lg-20 having firs-t primary winding 20 and first secondary winding 19 with the number of turns in the secondary winding being greater than the number of turns in the primary winding 20;
(ii) a transistor 22 having a base, an emitter and a collector with the collector beiny connected to ground at 23;
(iii) fixst circuit means for connecting -the first primary winding 20, the emitter of transistor 22 and the base of transis-tor 22 to the first secondary winding 19; a first diode 21 being connected from the transistor 22 base to the transistor 22 emitter and being connected Erom the primary winding 20 to the first secondary winding 19 whereby a path is provided for flyback current and whereby the transistor 22 is protected by the diode;

.r~ D

~ 27.:L --(iv) second circult means .inc].uding the first secondary winding 11 of the first step-up -transformer 11-12, the elec-troluminescent cell 18 and a capacitor 28 with the capacitor ~' :

connecting the first pr:imary winding 20 with the electroluminescent ce].1 18 and the electro-luminescent cell 18 being connected to the li first seconclary winding 19, the purpose of said l' second circuit means being for charging the electroluminescent cell 18; and ~v) third circuit means including the capacitor 28 of the second circult means connected in series 1 to a second diode 24 and an AC power source 27 1. through seoond seconda~y winding 25 of a second step-up transformer 25, 26 whereby intense light will be emitted rom electroluminescent cell 18 at substantially cvnstant br.ightness on discharge 1 thereof. The secor~ diode 24, the electroluminescent 18 and the negative end of capacitor 28 are all connected to ground at 29.
Another embodiment of the blocking oscillator of .` Figure 1 using a DC pGwer source is set forth in ~igure 3.
i Thus, in Figure 3, the blocking oscillator power supply ' consists of:
(i) a first voltage step-up transformer 31-32 ~ having a primary winding 32 and a secondary : winding 31 with the number of turns in the , secondary winding 31 being greater than the ,. number of turns in the prlmary winding 32;
(ii) a transistor 34 having a base, an emitter and a collector which collector is connected to ~ ground at 35;
t (iii) flrst circuit means for connecting one end 11 of the first primary winding 32, the emitter and the base to one end of the fiLst secondary winding 31; a first diode 33 being connected , from the transistor 34 base to the transistor 1 34 emitter and being connected to one end of ¦i the primary winding 32 to one end of the -¦ first secondary winding 31 whereby a path is ! I provided for flyback current and whereby the diode 33 also protects the transistor 34;

I

, 3~

(iv) second circuit means including the secondary winding 31 of the step~up t:ransformer 31-32 and an electroluminescent cell 30 with the electroluminescent cell 30 being connected at its anode to a second end of the secondary winding 31 and to ground at 37 from its cathode, the purpose of the second circuit rneans being for charging the electroluminescent cell Il 30; and i (v) a DC power means such as battery 36 having a positive end and a negative end, the positive end being connected to the second end of the primary winding 32 and the negative end beiny connected to the cathode of -the electroluminescent cell 30 and to ground at 37 whereby intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.
In the circuits of Figures 4, 5 and 6, the same type of flyback action occurs as in the blocking oscillator circuits of Figures 1, 2 and 3; except in the blocking oscillator circuits of Figures 4, 5 and 6, the positive voltage feed point is the center tap of a first transformer primary. In addition, the circuits as shown in Figures 4, 5 and 6 produce ~ a more symmetrical wave form to the electroluminescent lamp due to the push-pull nature of opposing transistors in this embodiment of the blocking oscillator circuit containing electroluminescent cells of my invention.
Whereas the circuits of Figures 1, 2 ana 3 can be used for electroluminescent lamps up to 20 watts, the circuits as illustrated in Figures 4, 5 and 6 are useful for higher power delivery to electroluminescent lamps.
i' More specifically, Figure 4 sets forth a circuit for effecting a pxocess for producing high intensity diffuse ~l light irradiated from electroluminescent cell 40 consisting of the st~p of applying AC or DC power from an AC or DC
` power source 43 to a push-pull two~transistor blocking - oscillator circuit at a location proximate the mid point of primary winding 42 of a first transformer 41-42 which i5 part of said circuit, which bl~cking oscillator conslsts of:

' I
, ' ' (i) the electroluminescent cell 40;
(ii) a first voltage step--up transformer 41-42 having Eirst primary windings 42 and first secondary windings 41 with the number of turns 1 inthe secondary windings 41 being greater than the number of turns in the primary ~indinys 42;
Il (iii) a first ~ransistor A5 having a first base, a ¦I first emitter and a first collector with the l,l first collector of the transistor 45 being ~, connected to ground at 46;
(iv) a second transistor 47 in an opposing juxta-position to said first transistor 45 having a ~ second base, a second emitter and a second : collector with the second collector of transistor 47 being connected to ground at 48;
(v~ the first primary winding 42 of the first voltage step-up transformer 41-42 being . connected to a power source 43 at a loca-tion " proximate the mid point of the first primary winding 42;
~vi) a first circuit means fvr connecting a first : end of the first primary winding 42, the first emitter and the first base of trans.istor 45 ~5 , to a first end of the first secondary winding 41; with a first diode 44 being connected from , khe first transistor 45 base to the first transistor 45 emitter whereby a Eirst path ~ is provided for a first flyback current and ; whereby the transistor 45 is protected by the first diode 44;
~vii) a second circuit means for connecting a second ¦ end of the first primary winding 42, the Il electroluminescent cell 40, the second transistor 1l 47 emitter and the second transistor 47 base to ~ a second end of the secondary winding 41, with .

, . , a second diode ~9 being collnected frorn the second -transistor 47 base to the second transistor 47 emitter whereby a second path is provided Eor a second flyback current and whereby the second transistor 47 is protected by the second diode 49;
whereby a substantially symmetrical wave form is induced in the electroluminescent cell 40 due to the push-pull nature of the opposing transistors 45 and 47 when sufficient power is applied from the power source 43; and whereby intense light will be emitted from the electroluminescent cell 40 at substantially constant brightness on discharge thereof.
Figure 5 sets forth a more specific circuitry for effecting a process for producing high in-tensity diffuse light irradiated from an electroluminescent cell 50 consisting of the step of applying rectified AC power originating from an AC power source 62 to a push~pulltwo-transistor blocking oscillator circuit at a location proximate the mid polnt 53 of the primary windings 52 of a first transformer 51-52 which is part of said circuit, which blocking oscillator consists of:
~i) an electroluminescent cell 50, (ii) a first voltage step-up transformer 51-52 having first primary windings 52 and first secondary windings 51, with the number of turns in the first primary windings 52;
(iii) a flrst transistor 55 having a first base, a first emitter and a firs-t collec-tor, with a first collector of the first -transistor 55 being connected to ground at 56;

~.Y, "

- 31.1 -~iv) a second transistor 58 .situated in an opposing jux-taposition to said Eirst transistor 55, said second transistor 58 having a second base, a second emitter and a second collector, with the second collector of the second transistor 58 being connected to ground at 63;

r3~ 3~

~1 (v) the first primary winding 52 of the first , voltage step-up transformer 51-52 beinq connected to the AC power source 62 at a location . 53 proximate the mid point of the first , primary windiny 52;
' (vi) a first circuit means for connecting a first end of said first primary winding 52, said first transistor 55 emitter and said first Il transistor 55 base to a first end of said l' secondary winding 51; with a fixst diode 54 being connected from said first transistor 55 : base to said first transistor 55 emitter, whereby .
l, a first path is provided for a first flyback ,. current and whereby the first transistor 55 is protected by the first diode 54;
(vii) a second circuit means for connecting a second end of the first primary winding 52, the electroluminescent cell 50, the second transis-tor 58 emitter, and the second trans.i.stor 58 base to l~ a second end of the secondary winding 51 with , a second diode 57 being connected from the second transistor 58 base to the second transis-tor 58 emitter whereby a second path is provided Eor a second flyback current and whereby the ~ transistor 58 is protected by the second I diode 57;
with AC power source 62 used to apply power in a third circuit means to the second primary windings 60 of a second voltage step-up transEormer 60-61; the blocking oscillator circuit thus additionally comprising a fourth circuit means consisting of:
(viii) a capacitor 64 having a positive and a negative ~I side;
¦, (ix~ a third diode S9 connected to the negative l' side of said capacitor 64;
, (x) secondary windings 61 of second voltage step-up transformer 60-61, one end of which is connected to the third diode 59 and the other end oE which is connected to the positive end of the capacitor I;

1, ~

3~

I

64 and to the first primary windiny .52 of the first vv~.tage step-up transformer 51-52 at location S3 proxi.mate the mid point of the first primary w1ndings 52 of the first transformer ~, 51-52; said capacitor 61 and said third diode 59 also being connected to the second collector Il of the second transistor 58; the cathode of capacitor 64, the third diode 59 and the I collector of transistor 58 being connected toli ground at 63;
whereby a substantially s~mmetrical wave form is induced in the electroluminescent cell 50 due to the push-pull nature I of the opposing transistors 55 and 58 when power is applied ! from the AC power source 62; and whereby intense light will ' be emitted from the electroluminescent cell 50 at substantially constant brightness on discharge thereof.
Specifically, .referring to Figure 6, Figure 6 sets forth more specific circuitry for effecting a process for producing a high intensity diffuse light irradiated from an ~l electrolunlnescent cell 70 consisting of the step of ap~lying DC power from a DC power source, e.g., a battery 77, to a push-pull two transistor (75 and 78) blocking oscil1.ator circuit at a location 73 proximate the mid point 73 of the primary windings 72 oE a first transformer 71-72 which is part of ` said circuit, which blocking oscillator circuit consists of:
l (i) an electroluminescent cell 70;
I (ii) a first voltage step-up transformer 71-72 having ,: first primary windings 72 and first secondary . windings 71 with the number of turns of the ~I secondary windings 71 being greater than the number of turns of the primary windings 72;
(iii) a first transistor 75 having a first base, a ¦¦ first emitter and a first collector with the ~.
Il first collector being connected to ground at 1l 76;
¦ (iv) a second transistor 78 situated in an opposing juxtaposition to said first transistor 75 . having a second base, a second emitter and a second collector which second collector of said 1. :

1~
,~

I

~3~-second transistor 78 is connected to ground at 79;
(v) the -first primary windi.ng 72 of the first voltaye step-up -transforrner 71-72 being connected to the DC power source (the ba-ttery) 77 at a location 73 proximate the mid point of . said first primary winding 72;
(vi) a first circuit means for connecting a first end 1, of said first primary windings 72, said first ! transistor 75 emitter and said first transistor 75 base to a first end of said first secondary windings 71; with a first diode 7a being .. connected from said first transistor 75 base ~ to said first transistor 75 emitter, whereby a first path is provided for a first flyback current and whereby the transistor 75 is protected by the first diode 74;
(vii) a second circuit means for connecting a second end of said first primary windings 72; the elec~rolumi.nescent cell 70, said second transistor 78 emitter, and said second transistor 78 base __ _ _ to a second end of said secondary winding 71 with a second diode being connected from said second transistor 78 base to said second transistor 78 emitter whereby a second path is provided for a second flyback current and whereby the transistor 78 is protected by diode 79;
with the DC power source (the battery) 77 bei.ng used to apply ~ power in a third circuit means, and with said blocking 30~ oscillator circuit additionally comprising a third circuit means consisting of: :
~viii) a battery or other DC power source 77 having a positive side and a negative side; the ~ positive side of said battery 77 ~eing connected I to the first primary winding 72 of the first voltage step-up transformer 71-72 at a location 73 proximate the mid point of the first primary wind:ing 72 of the first transformer 71=72;

.. I

the nega-tive side of said battery 77 beinc3 connected to the second collector of the second -transistor 78 and also belng connected to ground at location 79;
whereby a substantially symmetrical wave form is induced in the electroluminescent cell 70 due to the push-pull nature jl of the opposing transistors 75 and 78 when sufficient power j is supplied from the DC power source, e.g., the battery 77;
; and whereby intense light will be emitted from the electro-~ luminescent cell 70 at substantially constant brightness on discharge thereof.
In Figure 7, the blocking o~cillator circuit consists of:
(i) a voltage step-up transformer 123-125 having primary windings 125 and secondary windings 123;
(ii) a transistor 129 having a base, an emitter and a collector which collector is connected to ground at 130;
(iii) a diode 128 connected to said emitter and a first end of said primary windings 125; a resistor (a key purpose of which is to thermally protect transistor 129) 127 connected to said diode 128, a first end of said primary windings 125, a first end of said secondary windings 123 and said transistor 129 base;
(iv) tl~e second end of said primary windings 125 being connected to the power supply at 126; and (v) the second end of the secondary wlndings 123 being connected to the electroluminescent cell which is connected to ground at 122 whereby when sufficient power is applied at 126 to the blocking oscillator circuit, lntense light will be emited from the I electroluminescent cell 120 at substantially constant brightness on discharge thereof. Resistor 127 improves the thermal -Il stability of tra~sis~or 129 by reducing impedance in the circuit.

~31~L~3~:

As the resistance of resistor ~27 clecreases, the current gain required in transistor 129 increases. Diode 12~ assures a small voltage drop from base to emitter of transistor 129 under what would otherwise be an open base condition, whereby thermal stability is insured.
Figure 8 sets forth a simplified circuit for carryiny out the process of my invention for producing intense diffused light irradiated from an electroluminescent cell 140 by means 'I~ of the step of applying AC or DC power from an AC or DC power ! source to the positive terminal 145 of the circuit of Figure 8 which circuit comprises:
(i) an electroluminescent cell 140 having an anode and a cathode;
(ii) a discharge circuit means 142 connected to said electroluminescent cell 140 for discharging said electroluminescent cell ~40;
(iii) a blocking oscillator power supply comprising a transis-tor 149, the base circuit of which is connected to charge the electroluminescent cell 140 at the anode of the electroluminescent cell and is regeneratively coupled to the emitter-collector circuit of the transistor 149 by a voltage step-up transformer l -147-148, the_ _ primary winding 146 of which is connected to the emitter-collector circuit and the secondary winding 147 of which is connected to the base circuit. The collector of transistor 149 is connected to ground at location 150. The cathode of the electroluminescent cell 140 is connected to ground at 142. The number of windings in the primary windlng 146 is less than the number of windings in the secondary winding 147 of the voltage step-up transformer 146-147-148.
'll In another embodiment of my in~ention as illustrated l in Figure 9, the blocking oscillat-or circuit consists of:

~3 ~

I (i) a voltage step-up transformer 165-166-167 having .__ _ __ pximary windings 166 and secondary windings 165 with the number of turns of the secondary windings 165 being yreater than the number of turns of the primary windings 166;
(ii) a transistor 169 having a base, an emitter and .l a collector with the collector being connected ,~ to ground at 171;
! (iii) a first resistor 168 connected to said If $ransistor 169 emitter, a first end of the : primary windings 166, a first end of the secondary windings 165 and the transistor 169 base;
(iv) a second resistor ].70 connected to transistor ~69 collector, the transistor 169 base and the f:irs-t end of the secondary windings 165l the seeond resistor l?o beiny connected to ground at locat.ion 171;
(v) the second end of the primary windings 166 ~ being connected to the power supply at 163; and (vi) the second end of the secondary windings 165 being eonnected to the electrolumineseent cell : 160 which is connected to ground at 162 whereby when sufficient power is supplied at 163 to the blocking ~ oscillator circuit, intense light will be emitted from the electrolumineseent cell 160 at substantially eonstant brightness on discharge thereof. The resistor 168 which is connected from base to emitter of transistor 169 has as its purpose the insurance of thermal stability of the transistor 169.
The resistor 170 interconnects the base and colleetor of transistor 169 to in.sure that a base c~rrent will flow when . the transistor 169 is cold and initiate operation of the bloeking oscillator system. The regenerative feed baek I to the base load circuit rapidly turns transistor 169 full .~. "ON". The resistox 170 insures that a suEficient base current will flow through the transistor 169 in cold weather to star~
operation of the bloeking oscil1ator as stated supra. Onee the 0 'f.3 ~L ~ `s3~Z

-3~-' transistor 169 conducts, the transistor 169 will be heated sufficiently to produce the necessary current to start the regenerative process through the secondary winding 165.
The number of turns in the secondary winding 165 is greater than the number of turns in the primary winding 166 in the transformer 165-166-167.

i~

3~

Deta.iled Descr~on of Drawinqs of Circuits and Electroluminescertt Device S_ructures of the Prlor P.rt F'i ure D is a circuit diagram of a f lyback power supply wi th secondary circuit damping during primary charging ~ as disclosed in U.S. Letters Patent A,377,842 issued on March 22, 1983. A damper resistance Rd is added to the ' secondary circuit to reduce its quality factor. The damper ,, secondary circuit during the charge cycle only, a diode I I Sd is added to cause the damper Rd to be effec-tively switched I, out of the circuit during the discharge cycle. The optimal value for the damping resistor Rd can be determined from the following considerations. The key to the analysis is to use transformer T-model with a parallel resis-tor and capacitor combination across -the secondary -terminals . The capaci tor value is determined from the secondary resonan-t frequency so that -the value of the resistor de-termines the inpu-t admittance, Yln=(ll/Vm) =(I/~IL~ '2)))N(s)/L>(s) where N(s)-s'2-~s/~C~ I~L~C, and 2 0 , D(s) =5'2 =s~R C+ l /(L2C( I--k'2)).
Applying a step input voltage produces the following response , in the primary circuit:
Il=(Vn/l.l)(jl~'2)L2/LIR+~ '2/(~ . cos (WI+Q) ~p (--IM/O
2 5 where w ;s approximateIy l/(L2C(l--k~2)) The effect on the gain is determ}ned hy an anaIysis of the energy input to the primary, dU/dt(~)= v(t)i(t) ~vhere t(c) is the charge time.
V(t) is t~te instantaneous input voltag~, and i~t) is the instantaneous input current. The output 3 0 voItage is express~bIe as a function of the energy, vO-nu, gO .hat dYo/dU-r(U), the gain runction being I '' tVo/dt(c)=(dVo/dU)(dU/dt(c))=~t)i(l2t(U).
Wi~h a resistive load (Rl) and parashic secondary ca-pachance, ¦ I U= Yo'2 T/RI ~ C Vo'2/2 with Yo'2= U/~tl+~
and ~1 O dYo/d1(c~ev(t)i(t)/(2(U(J~tl+C/2~'(3~

,, ~, , ! i .9~ 2 - ~o-Usinq commercially availahle CAD (computer-aided clesign) programs, the primary cllrrent waveform and gain functions functions with respect to time can be calculated. ~rom these values the proper damping resis-tance can be calculated for acceptable closed loop response. In Figure D, transistor 9b is connected through its base to a drive circuit 9a which alterna-tely turns the transistor 9b "ON" and "OFF". At T=O, and transistor 9b is turned on but current cannot flow instantaneously through the primary winding of the transformer.
At time tl, the transistor 9b is turned off by the drive circuit 9a and a magnetic field having no primary current to sustain it, collapses rapidly because of the sharp cut-off by the transistor 9b. The full operation of this circuit is set for-th in detail in U.S. Let-ters Patent 4, 377~842 issued on March 22~ 1983.
Figures 10, 11, 12 and 13 are identical to Figures 1~ 2~ 3 and 4 of U~S~ Letters Patent 3~026~440~
In Figure 10 there is set forth a circuit which comprises a silicon unijunction transistor, sometimes called a double base diode 220 having an emitter and a base having two connections thereon. The quiescent state, the emitter 221 is back biased so as to have no emitter current. The base circuit of the semiconductor 220 is actuated to produce emitter current by applying either a pulse to the emitter circuit or to the base circuit. After application of one of these two pulses or of both, oscillations are set up in a load line 230 including an electroluminescent lamp. Being a nega-tive resistance semiconductor, the oscillations in the load line 230 are sustained by the emitter current of the semiconductor 220 so that illumination of the electro-luminescen~ lamp is sustained by the emitter circuit even after the actuating pulse has been removed. A second pulse being applied to the semiconductor 220 ~ again back biases the emitter and the oscillations in the load line 230 are 3~r; discontinued so as to switch oEf the electroluminescent lamp.

I The clevice illustrated in Figure 10 comprises, more specifically, a rectangular pulse generator 210 which produces positive goin~ pulses 211 selectively or negative going pulses 212.
A single positive going pulse from the generator 210 will I; actuate the device to illuminate the electroluminescent cell whereas the negative going ~ulse 212 will turn off the cell~
The pulse generator 210 is connected across an inductor member 225 which is a primary winding of the transformer 226.
Il A unijunction transistor 220 includes an emitter 221 and a l' base _22 having two terminals 223 and 224 and the opposite ends thereo~. The emitter circuit of the semiconductor 220 is connected between the base terminal 224 and the emitter 221 and includes a back bias supply 227 and the primary inductor 225. The base circuit includes a load resistor 229 and a base voltage suppl~ 228~ connec-ted between base terminals 223 and 224.
The inductor 225 is inductively coupled to an inductor 231 of the transformer 226. The load line oE the emitter circuit 230 includes the secondary winding 231 and an electro-luminescent cell 232.
A rectangular pulse generator 240 is connected across or between the base connections 223 and 224, to produce either a negative going pulse 241 or a positive going pulse 242. ~s will be explained~ the negative going pulse 2~1 will actuate the semiconductor 220 to effect forward bias of the emitter and thereby initiate an emitter current in the device.
Similarly, the positive going pulse 211 from the generator 210 will result in ~orward biasing of the emitter to produce ~ emitter current which will be sustained due to the negative resistance characteristic of the device.
When either an "ON" pulse is produced from the generator 210 or from the generator 240 oscillations will be ,I set up in the load line 230 to provide a low frequency 1 alternating ~oltage to the electroluminescent device 232 due I to the negative resistance characteristic of the double diode 220, mese oscillations will be sustained by the emitter circuit of the double diode 220 until such time as an "OFF"
pulse is applied to the device by either the generator 210 or ~he generator 240.

:; :

,~
., i 3~

~2 : Fic3~1re 11 illustrates generally the operation of the semiconductor 220 in U.S. Letters Patent 3,026,440 as applied to the embodiment illustrated in Figure 10. The double base diode 220 includes an end type silicon base with a p-type emitter 221. At either end of the base 222 are base : connections 223 and 224 between which is applied a base voltage j to establish voltage gradients between the base. The figures shown in Figure 11 are for purposes of illustration and Il disregard any base resistance such as the base resistor 229 ~I shown in Figure 10. If the base voltage 228 is ten volts the voltage gradient will vary between the base connection 224 : to the base connection 223 in voltage increments as shown in Figure ll. The emltter 221 is connected at a predetermined point relative to the voltage gradient on the base 222. The emitter voltage 221 is chosen so that its voltage is less than the voltage gradient opposite the p-type material 221. P,y this connection and the voltage supply 227, the emitter is back biased thereby preventing an emitter current. As illustrated in Figure 11, the emitter voltage 227 is four volts whereas the p-type emitter 221 is connected approximately opposite the five volt gradient of the base 222. Hence, the emitter 2_ is back biased so that emitter current will not flow.
; If the voltage between the base connections 223 and ! 224 is decreased sufficiently or if the voltage of the p~type junction is increased sufficiently, the emitter can become forward biased so as to provide emitter current in the emitter circuit. This can be accomplished by applying a positive I pulse to the windings 225 to thereby increase the emitter potential or by applying a negative going pulse between the base terminals 223 and 224 thereby decreasing the voltage gradient of the base 222. This is done in the embodiment i' !
shown in Figure 10 by the pulse generator 210 or by the pulse ! ¦ generator 240. When the potential of the emitter 221 exceeds 1! the ~oltage gradient opposite the p-type material, the emitter 'i will be forward biased and bias current will flow, and the !` emitter circuit will pass from the point Q shown in Figure 12 ;

li :

-to the point PE, on the characteristlc curve and through and into the negative resistance reg.iorl on the characteris-tic curve shown at Fi.gure 12. Figure 12 is a graph plotting emitter voltage against emitter current for the unijunction transistor 220 shown in solid lines. In dotted lines is the characteristic of the astable load line 230 plotted against the emitter voltage in current to produce a as~able state in the load line 230. Hence, the intersecti.on of the characteristic curve of the unijunction 220 and the character-istic curve of astable load line 230 represents the pointat which oscil.lations will be sustained in the device.
Following the turn on pulse 211 or 241, emitter 221 of device 220 is biased "ON". Current flows in the emitter circuit which i.ncludes transformer primary 225. The voltage induced in transformer secondary 231 then inaugurates oscilla-tions in the LC circuit composed of an electroluminescent device 232 and winding 231. This is fed back to 225 and varies the current in the emitter circuit such that variations in the current are effectively amplified by the negative resistance found in the emitter characteristic. These variations in current reinforce the oscillations found in LC circuit 232 and 231.
In the case of a direct current, (e.g. battery), electroluminescent excitation, the uni~unction transistor is utilized as a bistable trigger in U.S. Letters Patent 3,026,440 shown in Figure 13 (corresponding to Figure 4 of .S. Letters Patent 3,026,440). The emitter load line is now composed of electroluminescent device 232 and resistor 233 shown in Figure 13 and forms a load line for bistable - ~3,1 _ operation. The emitter is biased rearwardly by source 227 until turned "ON" by a pulse at which time the point of operation i9 shifted -to point in a hyperconductive region of -the semiconductor where it will remain until device 220 is triggered "OFF". The voltage drop across the resistor 233 is used to excite the direct current electxoluminescent cell 232.

g~
;

-4~--' This circui~ in Figure 13 can be turned "ON" b~
pulses 211 or 242, shown in F'igure 13, and turned "OFF"
by pulses 211 or 241. The first stable state of the device is when the emitter is rearwardly biased with no emitter I current and the electroluminescent device therefore is not excited. When a pulse 211 or 241 is applied to the device, the double base diode 220 is swung into the hyperconductive region so that there will be emitter current and the electro-ll luminescent device 232 will be excited.
1 As is evident, the complexities of the circuits of U.S. Letters Patent 3,026,440 are of a combo using the circuits ~ of my invention.
i Figures 14 and 15 show the structure of an electro-luminescent lamp whi.ch i5 useful in the practice of my invention. rrhis electroluminescent lamp is described in dek~il in U.S. Letters Patent 2,824,992 issued on February 25, 1958.
Thus, the electroluminescent lamp of Figure 14 may be used as the following devices in the following figures:
F'igure 1 - Device indicated by reference numeral 10.
Figure 2 - Device i.ndicated by reference numeral lB.
Figure 3 - Device indicated by reference numeral 30.
Figure 4 - Device indicated by ~eference numeral 40.
Figure 5 - Device indicated by reference numeral 50.
Figure 6 - Device indicated by reference numeral 70.
Figure 7 - Device indicated by reference numeral 120.
Figure 8 - Device indicated by reference numeral 140.
Figure 9 - Device indicated by reference numeral 160.
In F'igure 14, the metal backing plate 301 carries a porcelain enamel coating 302 such as is known in the a~t, . the ena~el indicated in U.S. Letters Patent 2,824,992 to be preferably white, and which can have any convenient thickness, ,~ for example, 10 mils. A transparent conductive coating 203 of stannous chloride or the like is preferably applied Il over the enamel. The first and second coatings 304 and 305 ll are phosphor and ceramic and are over the conductive coating 303 and another transparent conductive coating 306 is applied over the coating 305. Provisions for connections to an electric power line can be made. In Figure 15, the phosphor-dielectric 3.~ 7~

- ~5 ~
layers 304, 305 are shown schernatically. The layers 304, 305 contain a ceramic materia~ 307, 309 with -the phosphor particles 308, 310 mos-tly at the bottom of each layer. The Eigure is schematic and while mos-t of the phosphor particles are near the bot-tom of the layer, not all of them are in that position. The holes 311, 311 in the top layers 305 are seen to be out of register with the holes 312, 312,312 of the bottom layer 304 so that there is no direct breakdown path -through both layers 304, 305 in series. Moreover, the portion of nearly clear glass, almost free from phosphor at the top of each layer also improves the dielectric strength as stated in U.S. Letters Pa-tent 2,824,992 issued on February 25, 1958. The technique of producing this electroluminescent lamp is set forth in V.S. Letters Patent 2,824,992 a-t columns 2 and 3.
Figures 16 and 17 set forth elec-troluminescent structures of the type produced according to the teachings of U.S. Letters Patent 4,326,007 issued on April 20, 1982.
These structures may also be utiliæed i.n the circuits of my invention of Figures 1-9 inclusive which contained elec-tro-luminescent devices 10, 18, 30, 40, 50, 70, 120, 140 and 170 respectively.
Figures 16, 17, 18 and 19 are substantially the same as Figures 1, 2, 3 and 4 of U~S. Letters Patent 4,326,007 issued April 20, 1982.
Referring now to the electroluminescent devices of Figure 16, (Figure 1 in U.S. Letters Patent 4,326,007), there is shown a laminar electroluminescent structure useful in operation of the circuits of Figures 1-9, supra, in which the phosphor layer 410 is a ZnF2:Mn, w}lerein said Mn is ''3~

- 46 ~-present in relatively sma:l:L proportion, e.g., 1~, and functions as a dopant for the ZnF2 layer 410 which ls typically 150 to about 5000 ~ -thick. ZnF2 has a rutile structure and is a weakly N-type semlconductor with low electron ~obility (as indicated by J.H. Crawford and F.E. Williams, J. Chern.
Phys. 18, p. 775 (1950)).
As taught in F.E. Williams in J. Opt. Soc. ~m., 37, p. 302 (1947) ZnF2:Mn is unique among luminescent materials in being capable of rather efficient catho-doluminescence in the form of transparent thin films formedby vacuum evaporation. No postdeposition anneal is needed.
Moreover, its lower refractive index minimizes the internal trapping of the emission, which reduces substantially the efficiency of the ZnS thin films. In the design of Flgure 16, phosphor layer 410 is sandwiched between two semi-insulator SiO layers 411 also laid down by vapor deposition, which also seal the ends of the phosphor layer against atmospheric exposure. Layers 411 are typically 500 to about 7000A -thick.
The substrate of the laminar structure can be a layer of electrically conducting glass 412, bonded to the lower semi-insulator 411. This can conveniently comprise the Corning Company product consisting of an integral composite of a #7059glass coated on the side adjacent the lower layer 411 of semiconductor with a layer of electrically conductive Sn204 denoted 415 of a thickness displaying a resistance of approximately 100 ohms per square inch. As shown in Figures 16 and 17, a portion of layer 415 denoted area 415a extends outside the semi-insulator-phosphor sandwich, thereby affording a seat for attachment of the second exterior electrode of the structure. All of the layers of the structure of Figure 16 are quite transparent to visible radiation, e.g., about 50 percent.

7~

- ~7 The structllre of ~.S. I,etters Patent 4,325,007 is useful in my inven-tion is comple~ed by the addition of vapor deposi-ted aluminum metal electrodes 416 typically greater than 2000 A thick.
In operation when a voltage (either DC or AC) of sufficien-t magnitude, typically 4 X 10 v/cm thickness is applied across the structure of Figure 16, relatively highly energetic electrons are generated which impact the atoms of phosphor layer 410, thereby causing the phosphor to luminesce lr~ whereupon visible radiation is emitted from conductive glass layer 412 as denoted by the arrows 418.
As shown in F'igure 18, the brightness (in arbi-trary units) of luminescent radiation as a function of phosphor layer 412 thickness in the structure of Figure 16 (for both D.C. and A.C. operation) is a maximum at a thickness of approximately 1200 A; however, substantial ligh-t output is achieved over a rela-tively wide range of thicknesses to either side of the maximum particularly when using the circuits of Figures 1-9 of my invention.
As shown in Figure 19, the intensity (arbitrary units) of luminescent radiation as a function of wavelength is in the range of about 560-570 nanometers (nm) for a thickness of phosphor layer 412 of about 12G0 A. The visibly perceptive radiation 418 is variously sensed as yellow~green to reddish orange, which is highly effective for information display (reference is made at this point to the display of Figure 29, infra)~ By appropriately preseI;ectin~ the thickness of phosphor layer 410, -the maximum of emission plotted in Figure 19 can be shifted over the range of about 56 nm to 615 nm for ZnF2:Mn phosphor specifically.

3~

While ZnF2:Mn i.s preferrecl as a phosphor layer ~10 (because oE i.ts high light out:put) other substances such as CaF2:Mn, ZnSoAg and ZnS;Mn are possi.ble s~bstitutes for application of the electroluminescent device of U.S, Letters Patent 4,326,007 to the circuits of Figures 1 to 9. In addition, certain compounds formed from elements in Groups 2b and 6a of the Periodic Table, such as ZnTe, ZnSe, ZnS, CdTe, CdSe and Cds are considered to be appropriate for -the phosphor layer 410 of the structures of Figure 16.
It is practicable to employ multiple layers to both phosphor and semi-insulator in a single unitary structure with the advantage of enhanced ligh-t output, and such a design is shown in Figure 17 wherein the same reference numerals with primes appended correspond yenerally to -the same components in Figure 16.
In Figure 16, a second layer 410a is incorpora-ted in vertical allgnment with phosphor layer 410' separated therefrom by a layer of SiO semi-insulator 411a which latter can have a thickness in the same region as the layers 411 and 411'. If desired, the interleaved structures of Figure 17 can be expanded to accommodate three or even more phosphor layers, each separated from its neighbors by layers of semi-insulatorO Structures incorporating from one to ten pairs of semi--insulator and phosphor layers are functional in the operation of my invention with respect to the use of the structures of Figures 16 and 17, one additional semi-insulator being utilized to complete the composite in all cases.
The terms "semi-insulator" as used herein refers to substances having lower conductivities than those of semi-conductors. For example, ZnF2:Mn is a semiconductor and it has a conductivity about two ti.mes greater than that of SiO. Moreover, semi-insulators are no-t doped as distinguished from semiconductors. In brief, the semi-insulator associated with a given phosphor in the structures of Figures 16 and 35 ~ 17 should develop maxirnum voltage drop across the semi-,, _ ~9 _ insula-tor as compared wi-th the phosphor l~yer.
While SiO is preferred as a semi-insula-tor with respect to structures of Figures 16 and 17, other substances can be substituted, MnO being a specific example. In addition, reduced TiO2 is a suitable material. (Reduced TiO2 is produced by heating TiO2 in a H2 atmosphere until the resistance attains 105 ohms/cm2).
The advantage obtained through use of aluminum electrodes 416 is that their undersurfaces are bright enough to function as mirrors thereby reflecting radiation back toward glass plate 412, thus enhancing the device light output even further particularly when using the circuits of Figures 1-9 of my invention. Of course, some light escapes from the sides of the structure, but this is minimal.
In use as an information display device, electrodes 416 can be Eormed into a multiplicity of discrete contacts to which vol-tage is applied in selective pattern, whereupon a corresponding electrical circuit is completed through the semi-insulator, phosphor composite via Sn2O~ conductive layer 415 and area 415a to which latter an electrical lead is attached.
This produces an electroluminescent output in a pattern imparting the information desired. Electroluminescent structures are prepared as set forth on lines 29 et seq at column 4 of U.S. Letters Patent 4,326,007.
Figure 20 is in cross-section another electro-luminescent device (a thin-film electroluminescent device) useful in conjunction with the practice of my invention.
This device is described in detail in U.S. Letters Patent 4,373,145 issued on February 8, 1983.

.~ i ' 3~

- 50 ~
rrhus, :i.n ~'igure 2.0, a substrate 5lO havi.ng a srnooth surface i9 coated with a base electrode 512 which is alurninum layer alloyed to a minor extent with an impurity such as manganese. A barrier layer 514 is formed on the base ' elect,~-ode 512`by an anodization techni.que which results in an aluminum oxide layer doped with impurity ions of the alloyed materi.al. The oxide barrier layer 514 contains the impurity ion of manganese. As a result of the particular anodi~ation process, the impurity doped barrier 514 is a nonporous structure which is also uniform in thickness. A film of electrically resistive materials, e.g., manganese oxide, is deposited over the insulative barrier layer 514 to a thickness of several thousand angstroms and serves as a ballast resistor 516 to limit transient currents and thereby extend the :Life of the device. It is impor-tant that the electrically resistive material be substantially transparent to allow emi-tted light to pass through from the underlying insulative layer 514.
A counterelec-trode 518 is a thin semi-transparent metal film of gold or aluminum evaporated -to a thickness oE
approximately 100 angstroms and is electrically connected to one side of a power source 508.
The other side of the power source 50~ is connected to the base electrode 512 to provide an alternating field across the insulative layer 514 and the resistive layer 516 to activate the device. Such a field is useful in my invention as shown particularly in Figures 2 and 5 which have alternating current power sources.

Durirlg room temperature operation, the A.C. voltage source 508 operates at approximately 1 KHz and ha~ a voltage output oE approximately 60 volts rms. The transport current a-t this voltage is approximately I mn when using circuits 2 and 5. The device of U.S. Letters Patent 4,373,145 employs manganese as the impurity dopes material for the insulative layer 514. The example of the device exhibits electro-luminescence when activated by the electric field generated between electrodes 512 and 518 and emits a yellow-orange light having an intensity of approximately 30 ft. lamberts when using the circuits of Figures 2 and 5. The technique for producing the device of U.S. Letters Patent 4,373,145 is set forth at columns 2, 3 and 4 thereof.
Figures 21 and 22 illustrate -the ~.C. thin-film electroluminescent devices of Theis, Venghaus and Ebbinghaus (Siemens Forsch. U. Entwickl.-Ber. Bd. 11 (1982) Nr. 5) published by Springer-Verlac3 1982. The A.C. thin-filrn electro-luminescent device of Theis, et al is shown in cross section in Figure 21 (corresponding to Figure 1 of the Theis, et al paper). In Figure 21, a Zns:Mn film 603 is deposited on a BaTiO3-coated substrate by electron--beam evaporation.
The substrate temperature is held between 100 and 250 during ZnS deposition. The aluminum electrode at the anode is indicated by reference numeral 601. The barriurn titanate current blocking insulating layer is indicated by reference numberal 602. The light emitting ZnS:Mn film is indicated by reference numeral 603. Additional current blocking insulating layers:BaTiO3 and A12O3 are indicated by reference numeral 604. The transparent conductor is indicated by reference numeral 605. This transparent conductor is In2O3:SnO2 (ITO). The transparent conduc-tor is connected to the power supplying circuit 607 at the cathode thereof.

- 51.1 --The transparent conductor is co~-t.ed on a gl.~ss substrate.
I'he glass substra-te has a sheet resistivity of abou-t 200 ohms and may be, for example, a soda lime glass.
The equivalen-t circu.it of the A.C. thin-film electroluminescent device oE Theis, et al is set forth in Figure 22. In Figure 22, the capacitor 603' is the electrical analog for the capacitance of the AnS:Mn light emitting film.
The capacitor 602' in Figure 22 is an additional capacitor being the electrical analog of an additional voltage drop ~d across the dielectric. Obviously, to obtaln a desired voltage drop across the ZnS:Mn layer, a correspondingly higher external voltage (Vrms) rnust be applied from power source 607'. Capacitor 603' is in parallel with an additional electrical analog:a resistor. Thus, the sandwich structure of the A.C. thin-film electroluminescent device is composed in the Theis, et al structure of dielectric layers on both si.des of the ZnS:Mn layer which is designed to limit current flow across the AnS:Mn layer. The use of BaTiO3 has the advantage of a much larger safety margin between the operating voltage and the device breakdown voltage. Surprisingly, a much greater brightness and practical useability of the device of Theis, et al is effected by use of the circuits of Figures 2 and 5 of my invention. Thus, for example, electroluminescent device of Theis, et al could be the electroluminescent device 18 in Figure 2 or the electrolumin-escent device 50 in Figure 5, supra.
Another thin-film electroluminescent device haviny a structure similar to the structure of the Theis, et al device but disclosed by Tornquist and Ylilammi in Journal of Luminescence 27, (1982), pages 285-291, North-Holland - 5l.2 -Publishi.ng Company entitled "The Decay and Satu:ration of the Emission in A.C. EL, ZnS:Mn Thin Films" is set forth in Figure 23. In Figure 23, the power supply 708 (which would be the blocking oscillator power supply and circuit in Figures 2 and 5 of my invention)is connected to the aluminurn electrode at the anode, 702 and to the ITO electrode at the cathode (IT0 again standing for In203:SnO2). The ~.g~ 3~

aluminum electrode 702 is fused to aluminum ox.ide d:ielectric 703 which in turn is fu.sed to a ligh-t emitting film, %nS:Mn (shown by reference numeral 704) which in turn is fused to another Al2O3 dielectric layer 705 which in turn is fused to ITO electrode 706. The ITO electrode 706 is coated onto a glass base 707.
The Tornquist electroluminescent device can be used equally as well as the Theis, et al electroluminescent ,, dev.i.ce in conjunction with the circuits of Figures 2 and 5 of my invention.
Another electroluminescent device useable in conjunction with all of the circuits of my invention, e.g., the circuits shown in Figures l-9, inclusive, supra is described in U.S. Letters Patent 4,366,504 issued on December 28, 1982. Thus, Figure 24 (which is the same as Figure l in U.S. Letters Patent 4,366,504) may be used as device 10, 18, 30, 40, 50, 70, 120, 1~0 or 160 in the circuits depicted in ~'igures l, 2, 3, 4, 5, 6, 7, 8, and 9, supra, respectivel.y.
Thus, in Figure 2~, a thin-Eilm electroluminescent display panel is shown which has a three-layered structure.
A num~er of transparent electrode strips 802 are disposed on a glass support 801. Further, a layer 803 of dielectric ; material, such as Y2O3, SiN~, TiO2 and A12O3, a layer 804 of electroluminescent material, for example, ZnS doped with ~n (yellowish-orange light) and a second layer 805 of dielectric material such as Y2O3, SiN4, TiO2 or Al2O3 are disposed by a well known thin-film technique such as vacuum deposition and sputtering, each having a thickness ranging from 500 to 1000 A. This results in a double isolation three-layered structure of the electroluminescent display panel. A different family of strip electrodes 806 ,,l is disposed in a direction normal to the direction of the Il transparent electrodes 802 to form an electrode matrix array together with the transparent electrodes. With such three-i layered thin-film electroluminescent display panel, if one of the first family 802 of the electrodes and one of the second family 806 of the electrodes are selected, the minute area j 53-I

where the selec-ted ones of the electrodes cross or intersect will emit light. This corresponds to a picture element of an image-like a character, a symbol and a pat-tern being ~ displayed. The electroluminescent panel with such structure , is advantageously attractive and useable from a practical standpoint in conjunction with the process and means and circuits of my invention as shown in Figures 1-9.
Equivalent circuits for electroluminescent lamps Il are shown in Figures 25A and 25B.
l Thus, in Figure 25A a simplified electrical analog for an electroluminescent lamp is shown wherein a resistor 901a is connected to xesistor 902a and capacitor gO2. The capacitor is connected to resistor 902a and resigtor 902a.
The positive part of the circuit supplying power to the electroluminescent device is at one end of resistor and the negative part of the circuit is connected to the capacitor 902 and to the resistor 902a.
In Figure 25B another more accurate electrical analog for an electroluminescent lamp is shown wherein ; inductor 905a is in series with inductor 905b which in turn is in series with resistor 906a which in turn is in series with inductor 905c which in turn is in series with a resistor which in turn is in series with inductor 905d. In parallel ~ are capacitor 903a resistor 904a, capacitor 9Q3b, another resistor, a capacitor 903c and another resistor. Power is supplied at one end of inductor 905a from a blockiny oscillating circuit of the nature of circuits shown in Figures 1-9, supra. ~he negative end of the circuit as ,I shown in the circuits of Figures 1-9 is connected to capacitor 903a resistor 904a, capacitor 903b, a resistor, capacitor 903c another resistor and the like. The electroluminescent lamp is thus shown as an analog to a power transmission line.
! I Figure 26 shows a schematic cross section of I another electroluminescent device useful in conjunction with ,l the circuits of Figures 1-9 of my invention. Etched ¦ transparent electrodes of indium oxide 952 contained on the glass substrate 959 form the electrode pattern in one direction.

1~ ~
,, 3~

- 5~ -Vapor deposited layers of yttrium oxid~ (953a and g53b;
dielectrics) are located on either side oE the vapor deposited zinc sulfide:manganese activated phosphor 951. The rear aluminum electrode 950 is applied orthogonal to the original indium oxide el.ectrodes 952 to provide the XY addressing of the emitter elements in a matri~ of the process of U.S.
Letters Patent 4,361,384 issued on November 30, 1982;
referencing Rockwell International Report on Contract No.
DA~K70-78-C-0123 dated December, 1979 (at column 2, lines 36-39 of said ~.S. Letters Patent ~,361,384). In Figure 26, the electroluminescent emission is in the direction of the arrow at 960. The power is applied to aluminum electrode 950 at contact 954 from power source 955 (connected -to ground at 957). The circui-t ls completed from contact 956 at transparent indium oxicle electrode 952 to ground at 958.
The power source 955 can be any of the circuits illustrated in Figures 1-9 of my i.nvention.
Figure 27 is discussed in detail in the "Background of the Invention", supra.
Figure 28 is a wave form for the electroluminescent devlce blocking oscillator circuits of Figures 1-9 of my invention. This wave form shows voltage on the Y axis and time on the X axis. Without the use of the electroluminescent device, the graphs is that of a "half sine wave" as shown by reference numerals g90a and 990b. This sine wave is "smoothed" using the electroluminescent devices as shown in the plots indicated by reference numerals 991a and 991b in Figure 28 Figures 29 and 30 show other electroluminescent devices which can be used in conjunction with the circuits - 5~ 1 , ,. ~_ . ...
as set forth in Flgures l-9, supra. Figure,s 29 and 30 show devices of U.S. Letters Paterlt 4,376,145 issued on March 8, 19~3. ReEerring to F.igures 29 ancl 30, there is shown an electroluminescent display panel indicated generally at 1010.

~5 The power supply source is indicate~ by reference numeral 1028 and, if an alternati~g curren-t power supply source is required, the circuits of Figures 2 and 5 are used with the electroluminescent device of Figures 29 or 30 shown j in Figure 2 by reference numeral 18 and in Figure 5 by reference numeral 70.
Soda lime glass support 1012, 0.125 inches in j thickness supports transparent conductor layer 1014 of Il electrically conductive SnO2, 3000 A units in thickness 1' (deposited by RF sputtering tin in the presence of oxygen.
Supported thereon is insulating layer 1016 of tantalum pentoxide, 4,000 A units in thickness (deposited by RF
sputterlng of tantalum in the presence of oxygen). On layer ~ 1016 is more complex layer 1018 which includes electro-luminescent portion 1020 and non-electroluminescent portion 1022. Layer _018 is formed by first evaporating ~inc sulfide to a thickness of 6,500 A units over the entire area of support 1012. Following this, rnanganese is deposited through a mask -to a thickness of 75 A units over the round areas 1020 as shown in E'igure 29. Thereafter a vacuum is drawn, helium is backfilled to a pressure of 1,000 microns, and temperature is raised to 500C for one hour to diffuse the manganese into zinc sulfide. On layer 1018 is deposited, over the area indicated at 1024 in Figuxe 29, a convertible semiconductor layer 1026 of manganese dioxide 3000 A units in thickness (deposited by RF sputtering of manganese, in the presence of oxygen through a mask). Supported by layers 1018 and 1026 over the entire area of the device is insulating layer 1028 of tantalum pentoxide 4000 A units in thickness (deposited by RF sputtering tantalum in the presence of oxygen).
; Next is electrode layer 1030 of aluminum, de~osited over the area 1024 but with tail 1031 extending therefrom to Il the exterior for electrical connection through power source ll 1029 with layer 1014.
I The device is finished off with a black silastic potting layer 1032, for protection and added contrast enhancement.

The operation, the manganesedlo~:ide :layer 1026 counteracts the effect oE deEects such as pinholes in tantalurn pentoxide layer 1028 as well as defects in layers 1016 and 1018. 'I'he manganese layer 1026 additionally advantageously provides the advantage of contrast enhancement.
The technique of defining of electroluminescent zones using -this device of Figures 29 and 30 and the circuits of Figures 1-9 permits the achie~ement of complex and interestingdisplay patterns, all activatable by -the single 10 electrode 1030 so that the zones 1020 becomes luminescent when the electrical source 1029 is activated.
In place of the inorganic electroluminescent devices illustrated herein, organic electroluminescent devices may be used as electroluminescent device 10 in Figure 1; 18 in 15 Figure 2; 30 in Figure 3, 40 in Figure 4; 50 in F'igure 5;
70 in Figure 6; 120 in Figure 7; 140 in Figure 8 and 160 in Figure 9. Such organic electroluminescen-t cells that may be used are descxibed in Canadian Letters Patent 1,141,498.
Such electroluminescent cells include an anode electrode, a cathode electrode and an luminescent ~one between the electrodes comprising an organic lumin-es-cent agen-t and a binder having a breakdown field strength of at least about 105 volts/c.m..
In Canadian Letters Patent 1,141,498, between the luminescent zone and the anode electrode is a hole-injecting zone which comprises a layer of porphyrinic compound, such as phthalo-cyanine, such as that defined according to the structure:

~ --Z'-- 2 T~ ~T~

X~--T' / N~ T--~j Z 1I N--N--N 1I Z' --2 -T2 ~ ~N~ ~ T~ ~
\ _/
/--\
.,` X'~_ z,_IX~

wherein:
Q is -N- or ~CH-;
M is a metal ~ Tl and T2 aré both S or both C, or one of T and T is N and S ' the other is C;
l xl and X are the same or different, and are each hydrogen .1 or halogen, such as chlorine, fluorine and bromine; and Z
represents the atoms necessary to form a six-membered ;l unsaturated ring.
Ij A further option is to modify the compouds of structure (I), to provide a non-metallic complex wherein two of the four nitrogens are hydrogenated.
!

'i ~58-Exanple A preferred embodiment of my invention, the circuit of Figure 2 i5 utilized wherein the electrolurninescent device 18 is the device of Figures 29 and 30. The components of the circuit of Figure 2 have the following values:
(i) The transistor 22 TI-3027, 40V-7A;
(ii) The transformer 19-296.3V, CT 2.5A (min.);
, (iii) The diode 21... 800 PIV, 750 MA, IN-2071;
I~(iv) The capacitor 280.. 0.01 microfaravds, 1 KV, ',! disc ceramic;
(v) The diode 24...50~100 PIV;
(vi) The transformer 25-26...120V, CT, 200~ (min.) When operated with the circuit of Figure 2 (as opposed to other circuits of the prior art, for example, -the circuit of Figure 10) unexpected, unobvious and advanta~eous results from the standpoint of steady brightness and intensity of the sine are observed over a period of four months.

Claims (45)

The embodiments of the invention in which the exclusive property or a privilege is claimed are defined as follows:

1. A process for producing intense diffuse light ir-radiated from an electroluminescent cell comprising the steps of:
(a) providing an electroluminescent cell having an anode and a cathode;
(b) providing a transistor having a base, an emitter and a collector;
(c) providing a step-up transformer having a primary winding and a secondary winding;
(d) connecting discharge circuit means to the cathode of said electroluminescent cell for discharging said electroluminescent cell;
(e) building a blocking oscillator power supply circuit by connecting the base of the transistor to one end of the secondary winding of the step-up transformer and connecting the anode of the electroluminescent cell to the other end of the secondary winding of the step-up transformer;
and connecting the emitter to one end of the primary winding of the step-up transformer; and connecting the collector of the transistor to the negative output of a power source and connecting the other end of the primary winding to the positive terminal of the power source whereby the base circuit of the transistor is connected to charge the electroluminescent cell at the anode of the electroluminescent cell and whereby the base circuit is regeneratively coupled to the emitter collector circuit of the transistor by means of the voltage step-up transformer and then (f) applying rectified power to the blocking oscillator power supply circuit at the positive and negative terminals thereof thereby causing the circuit to operate as a power conditioner discharging into the electroluminescent cell whereby intense diffuse light is irradiated from said electroluminescent cell.

2. The process of claim 1 wherein in the blocking oscillator power supply circuit, a diode is connected from the transistor base to the transistor emitter and is connected from the primary winding to the secondary winding of the step-up transformer whereby a path is provided for flyback current.

3. The process of claim 1 wherein the blocking oscillator power supply circuit is a two-transistor push-pull circuit wherein the power input location is at the center tap of the primary winding of said step-up transformer.

4. A process defined according to claim 1 wherein the blocking oscillator power supply comprises:
(i) said first voltage step-up transformer;
(ii) said transistor;
(iii) first circuit means for connecting said first primary winding, said emitter and said base to said first secondary winding including a first diode being connected from said transistor base to said transistor emitter and being connected from said first primary winding to said first secondary winding whereby a path is provided for flyback current;

(iv) second circle means including the first secondary winding of the first step-up transformer, the electroluminescent cell and a capacitor; with the capacitor connecting the first primary winding with the electroluminescent cell and the electroluminescent cell being connected to the first secondary winding, the purpose of said second circuit means being for charging the electroluminescent cell; and (v) third circuit means including the capacitor of the second circuit means connected in series to a second diode and an A.C. power source to second the secondary winding of a second step-up transformer whereby intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.

5. A process for providing high intensity diffuse light irradiated from an electroluminescent cell comprising the step of applying rectified A.C. or D.C. power from an A.C. or D.C.
power source to a push-pull two-transistor blocking oscillator circuit at a location proximate the mid point of the primary windings of a first transformer which is part of said circuit, which blocking oscillator circuit comprises:
(i) an electroluminescent cell;
(ii) a first voltage step-up transformer having a first primary winding and a first secondary winding;
(iii) a first transistor having a first base, a first emitter and a first collector;

(iv) a second transistor situated in an opposing juxtaposition to said first transistor having a second base, a second emitter and a second collector;
(v) the first primary winding of the first voltage step-up transformer being connected to a power source at a location proximate the mid point of said first primary winding;
(vi) a first circuit means for connecting a first end of said first primary winding, said first emitter and said first base to a first end of said first secondary winding; with a first diode being connected from said first base to said first emitter, with said first collector being connected to ground whereby a first path is provided for a first flyback current;
(vii) a second circuit means for connecting a second end of said primary winding, the electroluminescent cell, the second emitter and said second base to a second end of said secondary winding, with a second diode being connected from said second base to said second emitter with said second collector being connected to ground whereby a second path is provided for a second flyback current whereby a substantially symmetrical wave form is induced in the electroluminescent cell due to the push-pull nature of the opposing transistors when sufficient power is applied from said power source, and whereby intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.

6. The process of claim 5 wherein the power source used is a rectified A.C. power source and the rectified A.C. power source is used to apply power in a third circuit means to a second primary winding of a second voltage step-up transformer, said blocking oscillator circuit additionally comprising a fourth circuit means comprising:
(viii) a capacitor having a positive side and a negative side;
(xi) a third diode connected to the negative side of said capacitor and to said second collector with the negative capacitor also being connected to said second collector; and (x) a secondary winding of said second voltage step-up transformer, one end of which is connected to said third diode and the other end of which is connected to the positive end of said capacitor and to the first primary winding of the first voltage step-up transformer at a location proximate the mid point of said first primary winding of said first transformer; said capacitor and said third diode also being connected to said second collector of said second transistor.

7. The process of claim 5 wherein the power source used is a D.C. power source and the D.C. power source is used to apply power in a third circuit means, said blocking oscillator circuit additionally comprising a third circuit means comprising:

(viii) a D.C. power means having a positive side and a negative side;
the positive side of said D.C. power means being connected to the first primary winding of the first voltage step-up transformer at a location proximate the mid point of said first primary windings of said first transformer, the negative side of said D.C. power means being connected to said second collector of said second transistor.

8. A process defined according to claim 1 wherein the blocking oscillator circuit comprises:
(i) said voltage step-up transformer;
(ii) said transistor;
(iii) a diode connected to said emitter and a first end of said primary winding;
(iv) a resistor connected to said diode, a first end of said primary windings, a first end of said secondary winding and said base;
(v) the second end of said primary winding being connected to the power supply; and (vi) the second end of the secondary widing being connected to the electroluminescent cell which, in turn, is connected to ground whereby when power is applied to the blocking oscillator circuit, intense light will be emitted from the electoluminescent cell at substantially constant brightness on discharge thereof.

9. A process defined according to claim 1 wherein the blocking oscillator circuit comprises:

(i) said voltage step-up transformer, (ii) said transistor;
(iii) a first resistor connected to said emitter, a first end of said primary winding, a first end of said secondary winding, and said base;
(iv) a second resistor connected to said collector, said base and said first end of said secondary winding;
(v) the second end of said primary winding being connected to said power supply; and (vi) the second end of the secondary winding being connected to the electroluminescent cell which, in turn, is connected to ground whereby when sufficient power is applied to the blocking oscillator, intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.

10. A process defined according to claim 1 wherein the blocking oscillator power supply comprises:
(i) said first voltage step-up transformer;
(ii) said transistor;
(iii) a first circuit means for connecting one end of the first primary winding, the emitter and the base to one end of the first secondary winding including a first diode being connected from said transistor base to said transistor emitter and being connected from said one end of said primary winding to said one end of said first secondary winding whereby a path is provided for flyback current;

(iv) a second circuit means including the secondary winding of the step-up transformer and the electroluminescent cell with the electroluminescent cell being connected at its anode to a second end of said secondary winding;
the purpose of said second circuit means being for charging the electroluminescent cell;
(v) a D.C. power means having a positive end and a negative end, said positive end connected to the second end of said primary winding and said negative end being connected to the cathode of the electroluminescent cell whereby intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.

11. Apparatus for effecting production of intense diffuse light irradiated from an electroluminescent cell comprising a direct current power means for application of direct current power to the positive terminal of a circuit which circuit comprises:
(i) an electroluminescent cell having an anode and a cathode;
(ii) a discharge circuit means connected to said electroluminescent cell for discharging said electroluminescent cell;
(iii) a blocking oscillator power supply comprising a transistor having a base, an emitter and a collector, the base circuit of said transistor being connected to charge the electroluminescent cell at the anode of the electroluminescent cell, the base circuit being regeneratively coupled to the emitter-collector circuit of the transistor by a voltage step-up transformer, the one end of the primary winding of said voltage step-up transformer being connected to the emitter-collector circuit and the other end being connected to the positive portion of the direct current power supply and the secondary winding of said voltage step-up transformer being connected to the base circuit; the collector when operating at steady state being connected to the negative portion of the direct current power supply;
whereby the current in the circuit discharges into the anode of the electroluminescent cell and leaves from the cathode of the electroluminescent cell so that the electroluminescent cell is excited sufficiently to emit energy in the form of visible light.

12. The apparatus of claim 11 wherein in the blocking oscillator power supply, a diode is connected from the transistor base to the transistor emitter and is connected from the primary winding to the secondary winding of the step-up transformer whereby a path is provided for flyback current.

13. The apparatus of claim 11 wherein the blocking oscillator power supply circuit is a two-transistor push-pull circuit wherein the power input location is at the center tap of the primary winding of the step-up transformer.

14. Apparatus for effecting production of intense diffuse light irradiated from an electroluminescent cell comprising rectified A.C. power means for application of power to the positive terminal of a circuit which circuit comprises:

(i) an electroluminescent cell having an anode and a cathode;
(ii) a discharge circuit means connected to said electroluminescent cell for discharging said electroluminescent cell;
(iii) a blocking oscillator power supply circuit which comprises:
(a) a first voltage step-up transformer having a first primary winding and a first secondary winding;
(b) a transistor having a base, an emitter and a collector;
(c) a first circuit means for connecting the first primary winding, the emitter and the base to the first secondary winding; a first diode being connected from said transistor base to said transistor emitter and being connected from said first primary winding to said first secondary winding with said collector being connected to ground whereby a path is provided for flyback current;
(d) second circuit means including the first secondary winding of the first step-up transformer; the electroluminescent cell and a capacitor, with the capacitor connecting the first primary winding with the electroluminescent cell and the electroluminescent cell being connected to the first secondary winding; the purpose of said second circuit means being for charging electroluminescent cell; and (e) third circuit means including the capacitor of the second circuit means connected in series to a second diode and an A.C. power source through a second secondary winding of a second step up transformer whereby intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.

15. Apparatus for effecting production of high intensity diffuse light irradiated from an electroluminescent cell comprising D.C. power means for application of D.C. power for a push-pull two transistor blocking oscillator circuit at a location proximate the mid point of the primary winding of a first transformer which is part of said circuit, which blocking oscillator circuit comprises:
(i) an electroluminescent cell;
(ii) a first voltage step-up transformer having a first primary winding and a first secondary winding;
(iii) a first transistor having a first base, a first emitter and a first collector connected to a negative terminal of the power source;
(iv) a second transistor situated in an opposing juxtaposition to said first transistor having a second base, a second emitter and a second collector connected to a negative terminal of the power source;
(v) the first primary winding of the first voltage step-up transformer being connected to a power source at a location proximate the mid point of said first primary winding;

(vi) a first circuit means for connecting a first end of said first primary winding, said first emitter and said first base to a first end of said first secondary winding, with a first diode being connected from said first base to said first emitter whereby a first path is provided for a first flyback current;
(vii) a second circuit means for connecting a second end of said first primary winding, the electroluminescent cell, said second emitter, and said second base to a second end of said secondary winding, with a second diode being connected from said second base to said second emitter whereby a second path is provided for a second flyback current;
whereby a substantially symmetrical wave form is induced in the electroluminescent cell due to the push-pull nature of the opposing transistors when sufficient power is applied from the power source; and whereby intense light will be emitted from the electroluminescent cell at substantially constant brightness of discharge thereof.

16. Apparatus for effecting production of high intensity diffuse light irradiated from an electroluminescent cell comprising rectified A.C. power means for application of A.C.
power for a push-pull two-transistor blocking oscillator circuit at a location proximate the mid point of the primary winding of the first transformer which is part of said circuit which blocking oscillator circuit comprises:

(i) an electroluminescent cell;
(ii) a first voltage step-up transformer having a first primary winding and a first secondary winding;
(iii) a first transistor having a first base, a first emitter and a first collector connected to a negative terminal of said rectified A.C. power means;
(iv) a second transistor situated in an opposing juxtaposition to said first transistor having a second base, a second emitter and a second collector connected to a negative terminal of said rectified A.C. power means;
(v) the first primary winding of the first voltage step-up transformer being connected to a power source at a location proximate the mid point of said first primary winding;
(vi) a first circuit means for connecting a first end of said first primary winding, said first emitter ; and said first base to a first end of said first secondary winding; with a first diode being connected from said first base to said first emitter whereby a first path is provided for a first flyback current;
(vii) a second circuit means for connecting a second end of said first primary winding, the electroluminescent cell, said second emitter, and said second base to a second end of said secondary winding, with a second diode being connected from said second base to said second emitter whereby a second path is provided for a second flyback current;

(viii) A.C. power being applied in a third circuit means to second primary windings of a second voltage step-up transformer for effecting rectified A.C.
power;
(ix) a fourth circuit means comprising;
(a) a capacitor having a positive side and a negative side;
(b) a third diode connected to the negative side of said capacitor; and (c) secondary winding of said second voltage step-up transformer, one end of which is connected to said third diode and the other end of which is connected to the positive end of said capacitor and to the first primary winding of the first voltage step-up transformer at a location proximate the mid point of said first primary windings first transformer; said capacitor and said diode also being connected to said second collector of said second transistor;
whereby a substantially symmetrical wave form is induced in the electroluminescent cell due to the push-pull nature of the opposing transistor when sufficient power is applied from said power source; and whereby intense light will be emitted from the electroluminescent at substantially constant brightness on discharge thereof.

17. The apparatus of claim 15 wherein a D.C. power source is used to apply D.C. power in a third circuit means, said blocking oscillator circuit additionally comprising a third circuit means comprising:

. , .

(viii) D.C. power means, having a positive side and a negative side;
the positive side of said D.C. power means being connected to the first primary winding of the first voltage step-up transformer at a location proximate the mid point of said first primary winding of said first transformer; the negative side of said D.C. power means being connected to said second collector of said second transistor.

18. Apparatus defined according to claim 11 wherein the blocking oscillator circuit comprises:
(i) said voltage step-up transformer;
(ii) said transistor;
(iii) a diode connected to said emitter and a first end of said primary winding;
(iv) a resistor connected to said diode, a first end of said primary winding, a first end of said secondary winding and said base;
(v) the second end of said primary winding being connected to the power supply; and (vi) the second end of the secondary winding being connected to the electroluminescent cell which, in turn, is connected to ground whereby when sufficient power is applied to the blocking oscillator circuit, intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.

19. Apparatus defined according to claim 11 wherein the blocking oscillator circuit comprises:

(i) said voltage step-up transformer;
(ii) said transistor;
(iii) a first resistor connected to said emitter, a first end of said primary winding, a first end of said secondary winding, and said base;
(iv) a second resistor connected to said collector, said base and said first end of said secondary winding;
(v) the second end of said primary winding being connected to said power supply; and (vi) the second end of the secondary winding being connected to the electroluminescent cell which, in turn, is connected to ground whereby when sufficient power is applied to the blocking oscillator circuit, intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.

20. Apparatus defined according to claim 11 wherein the blocking oscillator power supply circuit comprises:
(i) said first voltage step-up transformer;
(ii) said transistor;
(iii) a first circuit means for connecting one end of the first primary winding, the emitter and the base to one end of the first secondary winding, a first diode being connected from said transistor base to said transistor emitter and being connected from said one end of said primary winding to one end of said first secondary winding whereby a path is provided for a flyback current;

(iv) second circuit means including the secondary winding of the step-up transformer and the electroluminescent cell with the electroluminescent cell being connected at its anode to a second end of said secondary winding, the purpose of said second circuit means being for charging the electroluminescent cell; and (v) a D.C. power means having a positive end and a negative end, said positive end being connected to the second end of said primary winding and said negative end being connected to the cathode of the electroluminescent cell whereby intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.

21. The apparatus of claim 11 wherein the electroluminescent cell comprises a layer of electroluminescent host material, selected portions of said host material being activated with an electroluminescent activator; said selected portions being transversely separated from one another by unactivated portions of said host material; and said selected portions defining a desired display pattern; and an electrode extending transversely over a plurality of said selected portions in order that said plurality may be illuminated by activation by said electrode.

22. The apparatus of claim 15 wherein the electroluminescent cell comprises a layer of electroluminescent host material which is zinc sulfide; selected portions of said host material being activated with electroluminescent activator which is manganese; said selected portions being transversely eparated from one another by unactivated portions of said host material; and said selected portions defining a desired display pattern; and an electrode extending traversely over a plurality of said selected portions in order that said plurality may be illuminated by activation of said electrode.

23. The apparatus of claim 11 wherein the electroluminescent cell comprises:
(i) a support substrate having a first surface;
(ii) a base conductor film overlaying said substrate surface;
(iii) an electroluminescent barrier layer of impurity;
(iv) a semi-transparent electrically resistive layer overlaying said barrier layer;
(v) a relatively transparent counterelectrode overlaying said resistive layer; wherein said device emits visible radiation when voltage is applied between said base conductor and said counterelectrode.

24. The apparatus of claim 23 wherein the electroluminescent device comprises:
(i) a support substrate having a first surface;
(ii) a base conductor film of doped aluminum overlaying said substrate surface;
(iii) an electroluminescent barrier layer of impurity doped aluminum oxide overlaying said base conductor film;
(iv) a semi-transparent electrically resistive layer overlaying said barrier layer;

(v) a relatively transparent counterlectrode overlaying said resistive layer wherein said device emits visible radiation when voltage is applied between said base conductor and said counterelectrode and further wherein said barrier layer of aluminum oxide contains ions of said impurity.

25. The apparatus of claim 11 wherein the electroluminescent cell includes an anode electrode, a cathode electrode and a luminescent zone between its electrodes comprising the organic luminescent agent and a binder, and further comprising, between said luminescent zone and said anode electrode, a hole-injecting zone comprising a layer of a porphyrinic compound.

26. The apparatus of claim 25 wherein the porphyrinic compound is a phthalocyanine.

27. The apparatus of claim 15 wherein the electroluminescent cell includes an anode electrode, a cathode electrode and a luminescent zone between said electrodes comprising an organic luminescent agent and a binder, wherein between said luminescent zone and said a node electrode there is a hole-injecting zone comprising a layer of a porphyrinic compound.

28. The apparatus of claim 27 wherein the porphyrinic compound is a phthalocyanine.

29. The apparatus of claim 11 wherein the electroluminescent cell comprises a glass substrate and bonded to said glass substrate a polycrystalline counterelectrode; and coated on said polycrystalline counterelectrode, a current blocking insulated layer; and coated on said current blocking nsulating layer a light emitting film and coated on said light emitting film a current blocking insulated layer and bonded to said current blocking insulating layer an electrode.

30. The apparatus of claim 15 wherein the electroluminescent cell comprises: (i) a glass substrate and bonded to said glass substrate (ii) a transparent conductor;
and bonded to said transparent conductor (iii) a current blocking insulating layer; and bonded to said current blocking insulating layer (iv) a light emitting film; and bonded to said light emitting film,(v) a current blocking insulating layer;
and bonded to said current blocking insulating layer (vi) an electrode.

31. The apparatus of claim 29 wherein in the electroluminescent cell the said polycrystalline counterelectrode is a transparent polycrystalline In2O3:SnO2composition and said current blocking insulating layers consist essentially of BaTiO3 and said light emitting film is a mixture of zinc sulfide and manganese.

32. The apparatus of claim 30 wherein in the electroluminescent cell, the counterelectrode is a transparent polycrystalline In2O3:SnO2 composition and said current blocking insulating layers consist essentially of BaTiO3 and said light emitting film is a mixture of zinc sulfide and manganese.

33. Apparatus for effecting production of intense diffuse light irradiated from an electroluminescent cell comprising rectified A.C. power means for application of rectified A.C.
power to the positive terminal of the circuit which circuit comprises:

(i) an electroluminescent cell having an anode and a cathode;
(ii) a discharge circuit means connected to said electroluminescent cell for discharging said electroluminescent cell;
(iii) a blocking oscillator power supply comprising a transistor, the base circuit of which is connected to charge the electroluminescent cell at the anode of the electroluminescent cell and regeneratively coupled to the emitter-collector circuit of the transistor by a voltage step-up transformer, the primary winding of which is connected to the emitter-collector circuit and the secondary winding of which is connected in the base circuit;
(iv) the transistor collector being connected to a negative terminal of the rectified A.C. power source;
(v) the emitter of said transistor being connected to a positive terminal of said rectifed A.C. power source;
(vi) the base of said transistor being connected to a negative terminal of said rectified A.C. power source; and (vii) the cathode of said electroluminescent device being connected to a negative terminal of said rectified A.C. power source whereby the current in the circuit discharges into the anode of the electroluminescent device and leaves from the cathode of said electroluminescent device so that the electroluminescent device is excited sufficiently to emit energy in the form of intense and diffuse visible light.

.

34. The apparatus of claim 33 wherein in the blocking oscillator power supply, a diode is connected from the transistor winding to the secondary winding of the step-up transformer whereby a path is provided for flyback current.

35. The apparatus of claim 33 wherein the blocking oscillator power supply circuit is a two-transistor push-pull circuit wherein the power input location is at the center tap of the primary winding of the step-up transformer.

36. Apparatus defined according to claim 33 wherein the blocking oscillator circuit comprises:
(i) said voltage step-up transformer;
(ii) said transistor;
(iii) a diode connected to said emitter and a first end of said primary winding;
(iv) a resistor connected to said diode, a first end of said primary winding, a first end of said secondary winding and said base;
(v) the second end of said primary winding being connected to the power supply; and (vi) the second end of the secondary winding being connected to the electroluminescent cell which, in turn, is connected to ground whereby when sufficient power is applied to the blocking oscillator circuit, intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.

37. Apparatus defined according to claim 33 wherein the blocking oscillator circuit comprises:

(i) said voltage step-up transformer;
(ii) said transistor;
(iii) a first resistor connected to said emitter, a first end of said primary winding, a first end of said secondary winding; and said base;
(iv) a second resistor connected to said collector, said base and said first end of said secondary winding;
(v) the second end of said primary winding being connected to said power supply; and (vi) the second end of the secondary winding being connected to the electroluminescent cell which, in turn, is connected to ground whereby when sufficient power is applied to the blocking oscillator circuit, intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.

38. Apparatus defined according to claim 33 wherein the blocking oscillator power supply circuit comprises:
(i) said first voltage step-up transformer;
(ii) said transistor;
(iii) a first circuit means for connecting one end of the first primary winding, the emitter and the base to one end of the first secondary winding, a first diode being connected from said transistor base to said transistor emitter and being connected to one end of said first secondary winding whereby a path is provided for a flyback current;

(iv) second circuit means including the secondary winding of the step-up transformer and the electroluminescent cell with the electroluminescent cell being connected at its anode to a second end of said secondary winding, the purpose of said second circuit means being for charging the electroluminescent cell; and (v) a D.C. power means having a positive end and a negative end of said primary winding and said negative end being connected to the cathode of the electroluminescent cell whereby intense light will be emitted from the electroluminescent cell at substantially constant brightness on discharge thereof.

39. The apparatus of claim 33 wherein the electroluminescent cell comprises a layer of electroluminescent host material, selected portions of said host material being activated with an electroluminescent activator; said selected portions being transversely separated from one another by unactivated portions of said host material; and said selected portions defining a desired display pattern; and an electrode extending transversely over a plurality of said selected portions in order that said plurality may be illuminated by activation by said electrode.

40. The apparatus of claim 33 wherein the electroluminescent cell comprises:
(i) a support substrate having a first surface;
(ii) a base conductor film overlaying said substrate surface;
(iii) an electroluminescent barrier layer of impurity;

(iv) a semi-transparent electrically resistive layer overlaying said barrier layer;
(v) a relatively transparent counterelectrode overlaying said resistive layer; wherein said device emits visible radiation when voltage is applied between said base conductor and said counterlectrode.

41. The apparatus of claim 40 wherein the electroluminescent device comprises:
(i) a support substrate having a first surface;
(ii) a base conductor film of doped aluminum overlaying said substrate surface;
(iii) an electroluminescent barrier layer of impurity doped aluminum oxide overlaying said base conductor film;
(iv) a semi-transparent electrically resistive layer overlaying said barrier layer;
(v) a relatively transparent counterelectrode overlaying said resistive layer wherein said device emits visible radiation when voltage is applied between said base conductor and said counterelectrode and further wherein said barrier layer of aluminum oxide contains ions of said impurity.

42. The apparatus of claim 33 wherein the electroluminescent cell includes an anode electrode, a cathode electrode and a luminescent zone between its electrodes comprising the organic luminescent agent and a binder, and further comprising, between said luminescent zone and said anode electrode, a hole-injecting zone comprising a layer of a porphyrinic compound.

83 13. The apparatus of claim 42 wherein the porphyrinic compound is a phthalocyanine.

44. The apparatus of claim 33 wherein the electroluminescent cell comprises a glass substrate and bonded to said glass substrate a polycrystalline counterelectrode; and coated on said polycrystalline counterelectrode, a current blocking insulated layer; and coated on said current blocking insulating layer a light emitting film and coated on said light emitting film a current blocking insulated layer and bonded to said current blocking insulating layer an electrode.

45. The apparatus of claim 44 wherein in the electroluminescent cell, bonded to said glass substrate, the transparent counterelectrode is a polycrystalline In203:Sn02 composition and said current blocking insulating layers consist essentially of BaTiO3 and said light emitting film is a mixture of zinc sulfide and manganese.