US2958009A - Electroluminescent device - Google Patents

Description

'Filed oct. 1, 1959 R. BowERMAN, JR

ELEcTRoLuMINEscENr DEVICE 3 Sheets-Sheet 1 Anh" ATTORNEY E. R. BowERMAN. JR 2,958,009

ELECTROLUMINESCENT DEVICE 3 Sheets-Sheet 2 Oct. 25, 1960 Filed oct. 1, 1959 Byjw , OGL 25, 1960 E. R. BowERMAN, JR 2,958,009

ELECTROLUMINESCENT DEVICE '3 Sheets-Sheet 3 Filed Oct. 1, 1959 lNvENToR EDWIN R.0WERM/4NJR.

BY w

AT'ORN EY 2,958,009 ELECTROLUMINESCENT DEVICE Edwin 'Rz Bowerman, Jr., Whitestone, N.Y., assigner t0 Sylvania Electric Products Inc., a corporation of Delaware Filed oct. A1, 1959-, ser. No. 843,766 l'lrclaims. (Cl. 315-169) My invention relates to electroluminescent display de- Vices.

groups, each of which can be sequentially activated in turn. Each group, depending upon the informa-tion carried by the electrical signals supplied thereto, can display Iany digit or any letter. Consequently, when the information carried bythe signals is changing and each group is sequentially activated, the device can display a message V.containing both letters and numbers.

My device can be so constructed that any group, when activated, will display the information'supplied thereto at the instant of activation, for as long a time interval as desired. Under these conditions, the information supplied to each group in sequence can be displayed simultaneously as the complete message; when desired, the complete message can be erased.

Alternatively, the information displayed .by any group can be erased before the next successive group is activated, thus permitting each number or letter ofthe message to be individually and sequentially displayed.

In accordance with the principles of my invention, I

-provide anelectroluminescent layer, one surface of which carries `the following: an electrode; N different spaced apart conductive areas, these areas being electrically connected in common to the electrode; and N different spaced apart staircase conductors, each conductor beingvpositioned adjacent a corresponding area, each conductor containing M dierent interconnected conductive segments. (As will be explained in more detail hereinafter, thev term "staircase conductor defines an arrangement wherein the interconnected segments of any such conductor are so displaced relative to each other as to resemble the steps ofv a staircase.)

The other surface of the electroluminescent layer carries N ditlerent electrode groups, and M different spaced Aapart light transparent electrode strips. Each electrode group, which contains M different spaced apart electrode elements, is in registration with the corresponding conductive area. Each electrode strip extends over a corresponding conductive segment of each of the staircase conductors.

I further provide N different conductor arrays, each array being in registration with a corresponding staircase conductor. Each array contains M separate conductive members, the conductive members in each array being electrically connected to corresponding electrode segments of the corresponding electrode group. Photoconductor means are interposed between each conductive member and the corresponding electrode strip.

The structure thus far described can display a message containing a total of N characters which can be either numbers or letters or a combination of letters and numbers. In `one method, the structure is rst electrically connected in a circuit in the following manner. The common electrode is connected to av rst terminal. Each stairately'open-ing and closing the segment selector switches, the

` ICC caseconductor is coupled through a corresponding one of N different group selector switches'to the rst terminal. Each electrode strip is connected through a corresponding one of M different segment selector switches to a second terminal. A suitable operating voltage is applied across the two terminals.

Then, if one or more segment selector switches are closed, and a group selector switch is closed, acharacter will be displayed by the electrode group associated with the closed group selector switch. Therportions of the electroluminescent layer subtended between the conductive area in registration with this group and those conductive segments of this group which are connected to closed 4segment selector switches will be energized and emit light in a pattern defining the displayed character. By appropridisplayed character can be changed from one digit or letter to another digit or letter. The character itself can be displayed Vby any group by closing the associated group -selector switch.

In other words, the pattern of the character to be displayed is determined by the positions of the segment selector switches, While the positions of the group selector switches determine the position of the particular group which displays this character.

An illustrative embodiment of my invention will now `be described with reference to the accompanying drawings wherein:

Fig. 1 is an exploded view of a display device in accordance with my invention;

Fig. 2 is a partially cut away plan view of the device of Fig. 1;

Figure 3 is a crosssectonal view of the device of Fig. 1;

Fig. 4 shows one arrangement of electrode segments used in theelectrode groups of the device of Fig. 1;

Fig. 5 shows another arrangement of electrode segments used in the electrode groups of the device of Fig. l; and

Figs. 6, 7 and 8 showalternative arrangements for the photoconductive layers or strips and associated electrodes `as employed in the device of Figs. 1, 2 and 3.

Referring now to Figs. 1, 2, and 3, vthere is shown -a glass substrate 10. The substrate carries the following: a first opaque electrode 14; N different spaced apart opaque conductive areas l2electrically connected in common to electrode V14 (for ease of illustration only three such areas are shown in Fig. 1 and four of theseareas are shown in Fig. 2); a second opaque electrode 16 parallel to Ythe lirst electrode 14; and N different spaced apart lopaque staircase Vconductors 21.

Each staircase conductor 2l is positioned adjacent a corresponding conductive area 12.

lEach staircase conductor 21 contains M vdifferent opaque conductive segments in the form of conductive squares 18 which are horizontally and vertically spaced apart in such manner as to resemble the steps of a stairand MN spaced apart transparent electrically conductive rectangles 28.

The electrode lfilm 30 Vis provided with a plurality of rectangular shaped holes or openings 32, each hole 32 vbeing inregistration with a corresponding connection 20 of the staircase conductors 21.

Each electrode group 24 is'in registration with acorresponding conductive area 12. Further, each group contains M different spacedzapart electrode elements. (A detail view of the electrode element arrangement of the gnoups 26 shown in Figs. 1 and 2 is shown in Fig. 4.)

The conductive rectangles 28 are in registration with electrode 16. There are M rectangles 28 associated with each electrode group 24, each of these rectangles 28 being electrically connected to a corresponding electrode element of the corresponding group by means of conductive lines 26. Each conductive line 26 is actually in two parts, one part connecting one end of the rectangle 28 to the corresponding electrode element, the other part connecting the other end of the rectangle to a superimposed conductive member 42 (as will be explained in more detail hereinafter) A transparent enamel layer 34 is applied over electrode film 30. M different spaced apart transparent electrode strips 36 are applied over the enamel layer 34, each strip 36 being in registration with the corresponding conductive square 18 of each of the staircase conductors 21.

A photoconductive layer 38 is applied over electrode strips 36. N different conductor arrays 43 are applied over the photoconductor layer 38, each array containing M different transparent conductive members 42. Each array is in registration with a corresponding staircase conductor 21.

Each of the members 42 of each array is connected through a conductive line 26 and a conductive rectangle 28 to a corresponding element'of the electrode group 24 associated with the array. Further, each of members 42 extends over the photoconductor layer 34 in registration with the corresponding square 18 of the corresponding staircase conductor 21. (As shown in Figs. 1 and 2, each member 42 terminates in a position in registration with the corresponding square 18; however, if desired, all members 42 can extend across the entire width of the photoconductor layer.)

A photoconductor strip 40 is applied in registration with the second electrode 16 over all of the conductive rectangles 28. A third transparent conductive electrode 44 is applied over strip 40.

In operation, as shown in Fig. 1, the first and second electrodes 14 and 16 can be connected directly to terminal 100. Each staircase conductor 21 can be connected to terminal 100 through a corresponding one of N different group lSelector switches 104, 106, 108 to terminal 100. Each electrode strip 36 can be connected through a corresponding one of M different segment selector switches 112, 114, 116, 118, 120, 122, 124 to terminal 102 (which can be grounded). Electrode film and the third electrode 44 are grounded. A suitable operating voltage, as for example a 200 volt R.M.S. voltage, is applied between terminals 100 and 102.

The device can then be operated in the following manner. When any group selector switch, for example 104, is closed, a voltage will be applied between the electrode film 30 and the staircase conductor 21. M different squares of light will then appear on film 30 (due to the selective action of the applied voltage on the electroluminescent layer 22). The light emitted from these squares will pass through the transparent enamel layer 34, the transparent electrode strips 36, into the photoconductor 38.

Thus far, no electrode group has been activated. However, the emitted light upon striking the photoconductor layer has selectively lowered its impedance (in regions corresponding to the lighted squares) from the relatively high dark value to its relatively low illuminated value; as a result, all of the electrode segments of group 24 are connected through a low impedance path (conductive lines 26, conductive rectangles 28, electrode array 43', the low impedance portions of photoconductive layer 38, and electrode strips 36) to one contact of the segment selector switches.

When the segment switches 112, 114, 118, 120 and 124 are closed, the portions of the electroluminescent layer subtended between conductive area 12 and the appropriate electrode elements of electrode group 24 will be energized and the numeral 2 will be displayed (see Fig. 4).

Further, when this numeral is displayed, a voltage appears between the appropriate rectangles 28 and the second electrode 16, and the portions of the electroluminescent layer 22 subtended therebetween emit light. This light strikes the photoconductor strip 40. As a result, the photoconductor strip impedance is lowered, and all of the appropriate electrode elements of electrode group 24' are grounded directly through the photoconductor strip and electrode 44. Thereafter, the group selector switch 104 and the segment selector switches 112, 114, 118, 120 and 124 can be opened, and the numeral 2 will continue to be displayed. (This action can be regarded as analogous to the operation of a holding circuit for a relay.) Since the previously energized electroluminescent portions are now connected (in series with the low impedance photoconductor strip) directly across the terminals and 102, numeral 2 can be extinguished by removing the applied voltage between terminals 100 and 102, or by opening the circuit to 16.

When each electrode group contains seven electrode elements, appropriate combinations of energized elements can display any digit from 0 to 9. When each electrode group contains seventeen electrode elements, as shown in Fig. 5, appropriate combinations of energized elements can display any letter from A to Z.

In the device thus far described, the photoconductor circuit connections shown are of the layer type wherein electrodes are placed on opposite sides of a photoconductor layer. Alternatively, the photoconductor circuit connections can be of a known gap type, wherein spaced apart electrodes are secured to one surface of a photoconductor layer. These two types of photoconductor circuit connections are interchangeable.

For example, electrode 40 and photoconductor film 44 in the device of Fig. 2 can be rearranged as shown in Fig. 8. More particularly, a transparent non-conductive enamel strip 341 can be applied over conductive rectangles 28. Thereafter, a plurality of thin electrode fingers 45 can be applied over the transparent layer 341 in such manner that each finger 45 is in registration with the left hand edge of each conductive rectangle 28 and further is in electrical contact therewith. A second elongated electrically conductive member 401 is also applied over the transparent layer 341 and is also provided with fingers 500. Each finger 500 is in registration with the right hand edge of a corresponding rectangle 28. Each finger 500 is separated from each corresponding finger 45 by a small gap and further each finger 500 is insulated from the corresponding conductive square 28 by strip 341. A photoconductor layer 40 is applied over these fingers and extends therebetween. When fingers 500 are grounded, this gap type of photoconductive circuit connection will function in the same manner as the layer type shown in Figs. 1 and 2.

As a further modification, a gap type photoconductor can be used in place of the layer type photoconductor cells formed between strips 36 and members 42 with the photoconductor layer 38 inserted therebetween.

More particularly, as shown in Figs. 6 and 7, a second transparent enamel layer S2' can be applied over conductive strips 36. Electrically conductive arrays are applied over the enamel layer 52 in such manner that each member 56 of the array terminates in registration with a corresponding strip 36. Adjacent each array member 56 an opening is cut through the transparent layer 52 to expose the underlying electrode strip 36. Thereafter, a photoconductive layer 38 is applied over these electrode arrays. The photoconductor fills each opening 54, thus forming a gap photoconductor cell between each array member 42 and the corresponding electrode strip 36.

operated inthe same manner The electrode strips 36 can be very .closely spaced.

'Under these conditions, the rectangular shaped holes 32 optically separate adjacent squares of light to prevent one lit square from energizing more than one adjacent element. When these holes are illuminated, undesired light triggering of sneak paths can ensue. However, these sneak paths can be substantially eliminated by increasing the electrode spacings suiciently.

Further, the use of the transparent enamel layer 34 electrically isolates the electrode 30 over the electroluminescent layer from the strips 36. Where such isolation is not required, layer 34 and electrode film V30 can'be eliminated, the electrode strips, 36 then vbeing applied` directly over the electroluminescent layer 22 in registration with the conductive squares 18'.

Themernory or storage action of the photoconductor strip 40 may not be required (i.e. where each displayed character should be erased prior to the display of the next character). Under these conditions, electrodes 16 and 44, rectangles 28 and the photoconductor strip 40 can all be eliminated, the two parts of conductive lines 26 then being directly connected together.

The transparent conductive materials used can example, stannic oxide. rials used can be, for example, gold or aluminum. Indeed, transparent conductive materials can be substituted for the opaque materials. Further, the reverse-substitution can be made. For example, when the transparent electrode elements 24 are quite narrow, opaque conductive materials can be used instead because of the light produced by fringe electric elds around the edges of the elements, as described in the copending patent applibe, for

cation of Bowerman and Marko, Serial No. 808,745,4

led April 24, 1959.

The electroluminescent layer can be of any known type, as for example, electroluminescent phosphor grains embedded in a ceramic dielectric. Similarly, the photoconductor layer can be of any known type or can consist of photoconductor grain embedded in a glass enamel as disclosed in U.S. Patent 2,937,353 granted May `17, 1960.

What is claimed is:

l. An electroluminescent `device comprising an electroluminescent layer; an electrode secured to one surface of said electroluminescent layer; N different spaced apart conductive areas secured to said one layer surface, said areas being electrically connected in common to said electrode; N different spaced apart staircase conductors secured to said one layer surface, each conductor being positioned adjacent a corresponding area, each conductor containing M different interconnected conductive segments; N different electrode groups-secured to the opposite surface of said electroluminescent layer, each group being in registration with-the corresponding conductive area, each group containing -M different spaced apart electrode elements; M different light transparent electrode strips secured to said opposite surface of said electroluminescent layer, each strip being in registration with a corresponding conductive segment in each of said staircase conductors; a photoconductive layer applied over said electrode strips; and N different conductor arrays, each array being in registration with a corresponding staircase conductor, each array con-n taining M separate conductive members, the'conductive members in each array being electrically connected to corresponding electrode elements of the corresponding electrode group and further extending over said photoconductive layer. p

2. An electrolumescent device comprising angelectroluminescent layer; rst, and second electrodes secured to one surface of said electroluminescent layer at spaced apart positions; N dierent spaced apart conductive areassecured to said one layer surface, said areas `being The opaque conductive mate- .electrically connected ,in common to said rst electrode;

N different spaced apart staircase conductorsA secured ,tosaid one layer surface, each conductor `being positioned adjacent a corresponding area, eachconductor containing M different interconnected conductive tsegments; N dierent electrode groups secured to the opposite `surface of said electroluminescent layer, each group being in registration with the corresponding conductive area, each group containing M different spaced apart electrode elements; MN different transparent conductive sections secured to said opposite surface at spaced apartpositions in registration with said second electrode, each section being connected to a corresponding element in a corresponding group; M `different light transparent electrode strips secured to said opposite surface of said electroluminescent layer, each strip being in registration with a corresponding conductive segment in each of said staircase conductors; a photoconductive Ylayer applied over said electrode strips; a photoconductive strip applied over said conductive sections in registration with said second electrode; a third electrode applied over said photoconductive strip; and N different conductor arrays, each array being in registration with -a vcorresponding staircase conductor, each array containing M `separate conductive members, the conductive members vconductor containing M different interconnected conductive segments; N different electrode groups secured -to the opposite surface of said electroluminescent layer,

each group being in registration with the corresponding conductive area, each group containing M different .staircase conductor, each array containing M separate conductive members, the conductive members in each array being electrically connected to corresponding electrode elements of the corresponding electrode group and further extending over said photoconductive layer.

4. A device as set forth in claim 2 wherein said conductive lm is provided with a plurality of spaced apart holes, each hole being in registration with a corresponding electrical connection between adjacent segments of said staircase conductors.

5. A device asset forth in claim 1 wherein the seg- ,ments of said staircase conductors have a rectangular shape.

V6. An electroluminescent device comprising an electroluminescent layer; a staircase conductor having M different interconnected conductive segments secured to one surface of said layer; and a light transparent electrode secured to the other surface of said layer.

7. An electroluminescent device comprising an electroluminescent layer; a rst area electrode secured to one surface of said electroluminescent layer; a second strip ,electrode secured to said one surface, an electrode group secured to the opposite surface of said electroluminescent layer in registration with said rst electrode, said group containing M different spaced apart electrode elements; M different transparent conductive sections secured to the opposite surface of said electroluminescent layer in registration with said second electrode, each section being connected to a corresponding element; a photoconductor strip applied over said sections in registration with said second electrode; and a third electrode applied over said strip.

8. An electroluminescent device comprising an electroluminescent layer; N different spaced apart staircase conductors secured to one surface of said layer, each conductor containing M different interconnected segments; and M different spaced apart electrode strips secured to the other surface of said layer, each strip being in registration with a corresponding segment in each of said conductors.

9. An electroluminescent device comprising an electroluminescent layer; an electrode secured to one surface of said electroluminescent layer; N dilerent spaced apart conductive areas secured to said one layer surface, said areas being electrically connected in common to said electrode; N different spaced apart staircase conductors secured to said one layer surface, each conductor being positioned adjacent a corresponding area, each conductor containing M different interconnected conductive segments; N different electrode groups secured to the opposite surface of said electroluminescent layer, each group being in registration with the corresponding conductive area, each group containing M different spaced apart elec-trode elements; M different light transparent electrode strips secured to said opposite surface of said electroluminescent layer, each strip being in registration with a corresponding conductive segment in each of said staircase conductors; N different conductor arrays, each array being in registration with a corresponding staircase conductor, each array containing M separate conductive members, the conductive members in each array being electrically connected to corresponding electrode elements of the corresponding electrode group; and photoconductor means interposed between each conductive member and the corresponding electrode strip.

10. An electroluminescent device comprising an electroluminescent layer; rst and second electrodes secured to one surface of said electroluminescent layer at spaced apart positions; N different spaced apart conductive areas secured to said one layer surface, said areas being electrically connected in common to said rst electrode; N different spaced apart staircase conductors secured to said one layer surface, each conductor being positioned `adjacent a corresponding area, each conductor containing M different interconnected conductive segments; N different electrode groups secured to the opposite surface of said electroluminescent layer, each group being in registration with the corresponding conductive area, each group containing M different spaced apart electrode elements; MN derent transparent conductive sections secured to said opposite surface at spaced apart positions in registration with said second electrode, each section being connected to a corresponding element in a corresponding group; M diierent light transparent electrode strips secured to said opposite surface of said electroluminescent layer, each strip being in registration with a corresponding conductive segment in each of said staircase conductors; N different conductor arrays, each array being in registration with a corresponding staircase conductor, each array containing M separate conductive members, the conductive members in each array being electrically connected to corresponding electrode elements of the corresponding electrode group; photoconductor means interposed between each conductive member and the corresponding electrode strip; a first set of MN spaced apart conductive fingers, each nger in said rst set being in contact with a corresponding section; a third electrode having MN conductive fingers, each of which is in registration with a corresponding section but which is insulated from said corresponding section 'and is spaced apart from the corresponding first set finger; and second photoconductor means interposed between said first set ngers and the fingers of said third electrode.

11. An electroluminescent device comprising an electroluminescent layer; an electrode secured to one surface of said electroluminescent layer; N different spaced apart conductive areas secured to said one layer surface, said areas being electrically connected in common to said electrode; N different spaced apart staircase conductors secured to said one layer surface, each conductor being positioned adjacent a corresponding area, each conductor containing M different interconnected conductive segments; N different electrode groups secured to the opposite surface of said electroluminescent layer, each group being in registration with the corresponding conductive area, each group containing M different spaced apart electrode elements; M different light transparent electrode strips secured to said opposite surface of said electroluminescent layer, each strip being in registration with a corresponding conductive segment in each of said staircase conductors; N different conductor arrays, each array being in registration with a corresponding staircase conductor, each array containing M separate conductive members, the conductive members in each array being electrically connected to corresponding electrode elements of the corresponding electrode group; photoconductor means interposed between each conductive member and the corresponding electrode strip; said electrode being connected to a first terminal; N different group selector switches, each group selector switch being coupled between said first terminal and a corresponding staircase conductor; and M different segment selector switches, each segment selector switch being coupled between a second terminal and a corresponding electrode strip.

12. An electroluminescent device comprising an electroluminescent layer; an electrode secured to one surface of said electroluminescent layer; N different spaced apart conductive areas secured to said one layer surface, said areas being electrically connected in common to said electrode; N different spaced apart staircase conductors secured to said one layer surface, each conductor being positioned adjacent a corresponding area, each conductor containing M different interconnected conductive segments; N different electrode groups secured to the opposite surface of said electroluminescent layer, each group being in registration with the corresponding conductive area, each group containing M different spaced apart electrode elements; M different light transparent electrode strips `secured to said opposite surface of said electroluminescent layer, each strip being in registration with a corresponding conductive segment in each of said staircase conductors; N different conductor arrays, each array being in registration with a corresponding staircase conductor, each array containing M separate conductive members, the conductive members in each array being electrically connected to corresponding electrode elements o-f the corresponding electrode group; photoconductor means interposed between each conductive member and the corresponding electrode strip; said electrode being connected to a first terminal; N different group selector switches, each group selector switch being coupled between said first terminal and a corresponding staircase conductor; M different segment selector switches, each segment selector switch being coupled between a second terminal and a corresponding electrode strip; and means to apply a voltage between said rst and second terminals.

13. An electroluminescent device comprising an electroluminescent layer; an electrode secured to one surface of said electroluminescent layer; N different spaced apart conductive areas secured to said one layer surface,

said areas being electrically connected in common to said electrode; N diierent spaced apart staircase conductors secured to said one layer surface, each conductor being positioned adjacent a corresponding area, each conductor containing M different interconnected conductive segments; N different electrode groups secured to the opposite surface of said electroluminescent layer, each group being in registration with the corresponding conductive area, each group containing M different spaced apart electrode elements; a transparent conductive lm secured to the opposite surface of said electroluminescent layer in registration with said staircase conductors; a transparent layer applied over said conductive tilm; M different light transparent electrode strips applied over said transparent layer in registration with said staircase conductors, each strip extending over a corresponding conductive segment in each of said staircase conductors; a photoconductive layer applied over said electrode strips; N different conductor arrays, each array being in regisrtration with a corresponding staircase conductor, each array containing M separate conductive members, the conductive members in each array bein-g electrically connected to corresponding electrode element-s of the corresponding electrode group and further extending over said photoconductive layer, said electrode being connected to a rst terminal, said conductive lm being connected to a second terminal; N different group selector switches, each group selector switch being coupled between said iirst terminal and a corresponding staircase conductor; and M different segment selector switches, each segment selector switch being coupled between a second terminal and a corresponding electrode strip.

14. An electroluminescent device comprising an electroluminescent layer; an electrode secured to one surface of said electroluminescent layer; N different spaced apart conductive areas secured to said one layer surface, said areas being electrically connected in common to said electrode; N different spaced apart staircase conductors secured to said one layer surface, each conductor being positioned adjacent a corresponding area, each conductor containing M different interconnected conductive segments; N diierent electrode groups secured to the opposite surface of said electroluminescent layer, each group being in registration with the corresponding conductive area, each group containing M different spaced apart electrode elements; a transparent conductive ilm secured to the opposite surface of said electroluminescent layer in registration with said staircase conductors; a transparent layer applied over said conductive film; M different light transparent electrode strips applied over said transparent layer in registration with said staircase conductors, each strip extending over a corresponding conductive segment in each of said staircase conductors; a photoconductive layer -applied over said electrode strips; N different conductor arrays, each array being in registration with a corresponding staircase conductor, each array containing M separate conductive members, the conductive members in each array being electrically connected to corresponding electrode elements of the corresponding electrode group and further extending over said photoconductive layer; said electrode being connected to a rst terminal, said conductive ilm being connected to a second terminal; N diiferent group selector switches, each group selector switch being coupled between said first terminal and a corresponding staircase conductor; M different segment selector switches, each segment selector switch being coupled between a second terminal and a corresponding electrode strip; and means to apply a voltage between said first and second terminals.

15. An electroluminescent device comprising an electroluminescent layer; first and second electrodes secured to one surface of said electroluminescent layer at spaced apart positions; N diierent spaced apart conductive areas secured to said one layer surface, said areas being electrically connected in common to said electrode; N dierent spaced apart staircase conductors secured to said one layer surface, each conductor being positioned adjacent a corresponding area, each conductor containing M different interconnected conductive segments; N different electrode groups secured to the opposite surface of said electroluminescent layer, each group being in registration with the corresponding conductive area, each group containing M different spaced apart electrode elements; MN different transparent conductive sections secured to said opposite surface at spaced apart positions in registration with said second electrode, each section being connected to a corresponding element in a corresponding group; a transparent conductive film secured to the opposite surface of said electroluminescent layer in registration with said staircase conductors; a transparent layer applied over said conductive lm; M different light transparent electrode strips applied over said transparent layer in registration with said stair case conductors, each strip eX- tending over a corresponding conductive segment in each of said staircase conductors; a photoconductive layer applied over said electrode strips; N different conductor arrays, each array being in registration with a corresponding staircase conductor, each array containing M separate conductive members, the conductive members in each array being electrically connected to corresponding electrode elements of the corresponding electrode group and further extending over said photoconductive layer; a photoconductive strip applied over said conductive sections in registration with said second electrode; and a third electrode applied over said photoconductive strip.

16. An electroluminescent device comprising an electroluminescent layer; a first area electrode secured to one surface of said electroluminescent layer; a second strip electrode secured to said one surface, an electrode group secured to the opposite surface of said electroluminescent layer in registration with said iirst electrode, said group containing M different spaced apart electrode elements; M different transparent conductive sections secured to the opposite surface of said electroluminescent layer in registration with said second electrode, each section being connected to a corresponding element; a first set of M different spaced apart conductive fingers, each iinger in said first set being in electrical contact with a corresponding section; a third electrode having M conductive fingers, each of which is in registration with a corresponding section but which is insulated from said corresponding section and is spaced apart from the corresponding inger; and photoconductor means interposed between said iirst set fingers and the fingers of said third electrode. I

17. An electroluminescent device comprising an electroluminescent layer; a conductive area secured to said one lay-er surface, a staircase conductor secured to said one layer surface and positioned adjacent said area, said conductor containing M different interconnected conductive segments; an electrode group secured to the opposite surface of said electroluminescent layer in registration with said conductive area, said group containing M different spaced apart electrode elements; M different light transparent electrode strips secured to said opposite surface of said electroluminescent layer, each strip being in registration with a corresponding conductive segment of said staircase conductor; a conductor array in registration with said staircase conductor, said array containing M separate conductive members, each conductive member being electrically connected to a corresponding electrode element of said electrode group; and photoconductor means interposed between each conductive member and the corresponding electrode strip.

References Cited in the tile of this patent UNITED STATES PATENTS

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