Electroluminescent device having connections on the base

Oct. 13, 1964

W. A. THORNTON, JR., ETAL

3,153,166

ELECTROLUMINESCENT DEVICE HAVING CONNECTIONS ON THE BASE

Sheets-Sheet 1

Filed Aug. 5, 1960

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a. c. SUPPLY

FIG.2.

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FIG. 4.

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FIG. 3.

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FIG. 5.

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FIG. 6.

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BY

INVENTORS WILLIAM A. THORN7ZW, Robert l. fttzmaur/ce:.

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ATTORNEY.

Oct. 13, 1964 W. _A. THORNTON, JR., ETAL 3,153,166

ELECTROLUMINESCENT DEVICE HAVING CONNECTIONS ON THE BASE

Filed Aug. 5, 1960 ₂ Sheets-Sheet 2

FIG. 7.

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® ® A.C.SUPPLY

FIG. 8.

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INVENTORS

WfiLHW A. THORNTON, fr.

ROBERT-1. F/TZWWR/CE·. BY

ATTORNEY

United States Patent Office _Palented

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

FIG. 1 is a plan view of an electroluminescent device constructed in accordance with the present invention, to5 gether with the energizing source therefor;

FIG. 2 is a sectional elevational view of the device as shown in FIG. 1, taken on the line Π—II in FIG. 1 in the direction of the arrows;

FIG. 3 is a -side elevational view of the device as shown 10 in FIG. 1, taken on the line III—III in FIG. 1 in the direction of the arrows;

FIG. 4 is a plan, view of the foundation portion of the device as shown in FIG. 1, illustrating the arrangement of the contact areas carried thereon;

FIG. 5 is a fragmentary sectional view of a device generally as shown in FIGS. 1-3, but illustrating an alternative construction;

FIG. 6 is a fragmentary elevational view of a device generally similar to that shown in FIG. 5, but illustrating 20 still another alternative construction;

FIG. 7 is a sectional view of yet another alternative construction, taken on the line VII—VI! in FIG. 8 in the direction of the arrows;

FIG. 8 is a sectional view of the device as shown in 25 FIG. 7, taken on the line VIII—VIII in FIG. 7 in the direction of the arrows.

With specific reference to the form of the invention illustrated in the drawing, the electroluminescent device 10 as shown in FIGS. 1, 2 and 3 is adapted to be ener30 gized to emit different preselected colors or color blends and comprises an electrically insulating foundation 12 with the operative portions of the device carried thereon. Considering FIGS. 1 and 3, a first conducting layer 14 is carried on a substantial portion of the insulating founda35 tion 12 and a portion of the conducting layer 14 which is proximate one edge of -the foundation 12 serves as a first contact area 16. Also carried on the foundation 12 is a second contact area 18, a third contact area 20 and a fourth contact area 22. The contact areas are each 40 positioned proximate edge portions of the foundation 12 and all contact areas .16-22 are electrically insulated from one another, both by a spacing therebetween and the phosphor-dielectric insulating material which is carried thereon. The arrangement of the contact areas 16-22 4.5 on the foundation 12 is shown in detail in FIG. 4. Over a substantial portion of the first conducting layer 14, and extending onto portions of the contact area 16-22, is carried a first electrically insulating, light-transmitting layer 24 comprising phosphor, which electroluminesces when. 50 energized, with a first preselected color, such as red. Over a substantial portion of the first phosphor layer 24 is carried a light-transmitting electrically conducting layer 26 which also electrically connects to the electrically conducting contact area 18, as shown in FIGS. 1 and 2. Coated 55 over the second conducting layer 26 is a second insulating layer 28 comprising phosphor material which electroluminesces when energized to emit a second predetermined color, such as blue. The second phosphor layer 28 also overlaps all contact areas 16-22 in -order to insure that in60 dividual conducting coatings which are interposed between the phosphor layers are insulated from one another, Over a substantial portion of the second phosphor layer 28 is a third light-transmitting, conducting layer 30 which also electrically connects to the third contact area 65 20, as shown in FIGS. 1 and 2, Coated over the third conducting layer 30 is a third insulating layer 32. comprising phosphor material which electroluminesces when energized to emit a third predetermined color, such as green. The third phosphor layer 32 also overlaps all contact areas 16-22. Over a substantial portion of the third phosphor layer 32 is a fourth conducting layer 34,

3,153,166 ELECTROLUMINESCENT DEVICE HAVING CONNECTIONS ON THE BASE

William A. Thornton, Jr., Cranford, and Robert L. Fitzmaurice, Bloomfield, NJ,, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania

Filed Aug. 5, 1960, Ser. No. 47,793

Ciaims. (CI. 313—108)

This invention relates to electroluminescent devices and, more particularly, to electroluminescent devices which are adapted to be energized to produce radiations of different colors and color blends.

Electroluminescent devices which produce radiations of different colors are well known and such devices usually comprise a pluarlity of stacked or superimposed individual electroluminescent cells. Each of the individual cells of the stack can be energized to produce a different color. By selectively energizing different cells of the stack, any preselected color or blend of such colors can be obtained. In the fabrication of such stacked cells, difficulties have been encountered in making electrical connections to the intermediate electrodes and in properly insulating the several superimposed electrodes which are required.

It is the general object of this invention to avoid and overcome the foregoing and other difficulties of and objections to prior-art practices by the provision of an electroluminescent device which can be energized to produce different preselected colors and color blends and which device is very positive in operation.

It is another object to provide an electroluminescent device which can be energized to produce different colors or color blends and which device is very simple to fabricate.

It is a further object to provide a stacked electroluminescent device to which electrical connections can be readily, made.

It .is an additional object to. provide alternative constructions for an electroluminescent device which can be energized to produce different colors and color blends.

The aforesaid objects of the invention, and other objects which will become apparent as the description proceeds, are achieved by providing an electroluminescent device which is formed as a plurality of stacked or superimposed individual cells. In the construction of this device, an insulating foundation, has provided thereon a first conducting layer, an edge portion of which provides a first contact area for purposes of energization. At least three other contact, areas are provided on the foundation and all of the contact areas are electrically insulated from one another. The first phosphor layer of the combination is coated or carried over the first conducting coating in such manner -that the phosphor layer overlaps the first conducting coating and also overlaps onto a portion of all contact areas. Over this first phosphor coating is applied a second conducting coating which is light transmitting and electrically connects to one of the contact areas. Second and third phosphor coatings and the respective successive conducting coatings are similarly applied, with the latter electrically connecting to predetermined individual contact areas which are provided on the foundation.. In this manner, all electrical contacts as required to energize the device are made to the foundation-supported contact areas. Because of the foundation support, these contact areas are readily adapted to be connected to an energizing source. By properly preselecting the contact areas across which an energizing potential is applied, any individual cell of the stacked combination, or any combination of cells, can be cause to electroluminesce to produce any preselected color of light..

3,153,168

As a possible alternative embodiment, the device 10α as shown in FIG. 5 can be provided with a plastic foundation 12α which can be either opaque or light transmitting in nature. Urea formaldehyde is a suitable opaque 5 plastic and polystyrene is a suitable light-transmitting plastic. With such a construction, the first electrode layer 14α and the contact segments adjacent thereto are formed of copper iodide or similar light-transmitting material which does not require high temperatures of 10 formation which could melt or damage the plastic foundation 12α. The embodiment 10α is also modified from the embodiment 10 as shown in FIGS. 1-3 in that an additional layer 42 of insulating material is provided over the fourth electrode layer 34 in order to prevent shock 15 hazard. The additional insulating layer 42 can be made light transmitting or opaque, depending on which side of the device 10α is to serve as the viewing face. A further additional separate layer 44 of dielectric material has also been included adjacent the third phosphor layer 20 32, in order to improve the electrical breakdown characteristics of this phosphor layer. Any of the device embodiments as illustrated and described hereinbefore can incorporate additional separate dielectric layers between the individual electrodes or conducting layers which de25 fine each electroluminescent cell or layer of the combination devices.

In FIG. 6 is shown a further alternative embodiment 1®έ which is modified from the embodiment as shown in FIGS. 1-3 in that metal mesh electrodes 46 are uti30 lized, wherein the interstices between the individual meshes serve to transmit the light which is generated. Such mesh-type electrodes are well known. Conducting glass fiber mesh electrodes can be substituted for the metal mesh electrodes and are generally described in 35 U.S. Patent No. 2,774,004, dated December 11, 1956. The plastic foundation 12έ can also be made flexible to enable the device 10έ to be conformed into desired shapes and better withstand shock hazards. In the embodiment 10έ as shown, the metal mesh electrodes are 40 embedded in light-transmitting plastic material.

In FIGS. 7 and 8 are shown yet another alternative embodiment 10c, which generally corresponds to the device embodiment 10 as shown in FIGS. 1-3, except that an additional layer 47 comprising electroluminescent phosphor has been provided over the fourth conducting layer 34c, which is formed of light-transmitting copper iodide. Over the fourth phosphor layer 47 is provided a fifth conducting layer 48 which is formed of vacuummetallized silver or aluminum or copper iodide. The contact areas on the foundation 12 are also slightly modi^ύ fled in that the contact area 18, as shown in FIG. 1, has been broken into two insulated segments 18c and 50, in order to provide the additional contact area 50 which electrically connects to the fifth conducting layer 48. -₅ As in the previous embodiments, the phosphor comprising the layer 47 is selected to electroluminesce with a preselected color, such as yellow. Zinc sulfide phosphor which is activated by copper and manganese electroluminesces with a yellow color and such a phosphor is well known. Additional phosphor layers can be provided ^J if it is desired to add other preselected colors to the Output of the device 10c. If additional phosphor layers are desired, an additional electrically conducting electrode layer is provided over each such additional phosphor layer, with the electrically conducting electrode layers positioned between such additional phosphor layers being formed of light-transmitting material such as copper iodide, for example, in order to transmit the generated light An additional contact area on the device foundaγθ tion, proximate the edge portions thereof, is also required for each additional conducting layer which is utilized and each of these additional contact areas are necessarily insulated from all of the other contact areas. Such a modified construction is readily obtained by further di75 viding any of the contact areas 18-22 in the device emwhich also electrically connects to the fourth contact area 22, as shown in FIGS. 1 and 3.

As a specific preferred example, the electroluminescent device as shown in FIGS. 1-3 is formed on a lighttransmitting foundation which preferably is fabricated of glass. In this embodiment, the foundation 12 and conducting layer 14 comprise the viewing face for the device 10. The first conducting layer 14 and the contact areas 16-22 are all fabricated of electrically conducting, lighttransmitting tin oxide which is applied to the glass foundation 12 in accordance with well-known techniques. Other known conducting material such as indium oxide can be substituted for the tin oxide. The second, third and fourth contact areas 18-22 are all insulated from the first contact area 16, such as by scribing or abrading the tin oxide, as initially applied, from the surface of the foundation 12. As a specific example, the first phosphor layer 24 comprises zinc-cadmium-mercuric sulfide activated by copper. Such phosphor has a red electroluminescent emission and is described in detail in copending application S.N. 807,730, filed April 20, 1959, by A. Wachtel and owned by the present assignee. The phosphor desirably is in finely divided form and for best performance is mixed with a light-transmitting dielectric material. As an example, the phosphor is mixed with equal parts by weight of polyvinyl-chloride acetate and the layer 24 is applied by spraying to a thickness of approximately two mils. The second conducting coating is formed of light-transmitting, electrically conducting copper iodide. Such copper iodide coatings are well known in the art and are formed by vacuum metallizing a thin layer of copper onto the surface which is to be coated and thereafter passing the copper surface through iodine vapor until the copper is converted to copper iodide and becomes light transmitting in nature. The second phosphor layer 28 is preferably formed of zinc sulfide which is activated by copper and coactivated by chlorine and has a blue emission. Such phosphors are known. As in the case of the first phosphor layer 24, the phosphor material comprising the layer 28 desirably is mixed with a light-transmitting dielectric material, as previously desscribed. The third conducting layer 3® is also formed of copper iodide, as previously described. The third phosphor layer 32 preferably comprises zinc sulfide phosphor which is activated by copper and coactivated with chlorine and has a green emission. Such green-emitting phosphors are well known and the emission color is readily obtained by controlling the amounts of copper and chlorine with respect to one another, in accordance with well-known procedures. The uppermost fourth conducting layer 34 is preferably formed of vacuum-metallized, reflecting aluminum or silver, although it can be formed of copper iodide if both sides of the device 10 are desired to serve as viewing faces.

Energization for the device as shown in FIGS. 1-3 is preferably accomplished with a conventional potentiometer-transformer arrangement, wherein three potentiometers 36 are each connected across the supply line with the slide contacts for the potentiometers each connecting to the primary windings of conventional transformers 38, the secondary windings of which connect to the contact areas 16-22. By adjusting the individual potentiometers 36 to energize predetermined electroluminescent layers of the device 10, any color from red through blue or any preselected desired color blend can be readily obtained.

In contrast to previous multi-layer electroluminescent devices, electrical connections to all of the individual electrically conducting layers are very simple to make and are very positive, as well as rugged in performance. As an example, electrical connections can be made by means of conventional bus bars 40 to a portion of each individual contact area 16-22 which is uncoated with phosphor material. Alternatively, a clamp or pressure contact can be readily made by clamping across the sides of the foundation 12,

3,153,163 bodiment 1® as shown in FIGS. 1-3. An energizing potential is adapted to· be electrically connected to each such additional contact area or areas which are provided, either by means of a bus bar connection or by clamping across the foundation of the device.

The devices as illustrated and described hereinbefore are subject to further .considerable modification. As an example, the device 10 as shown in FIG. 1 can be fabri. cated entirely of ceramic material and the plastic dielectric which has been described hereinbefore replaced by suitable ceramic dielectric mixed with the phosphor. In addition, while the phosphors as described emit respectively in red, blue and green, phosphors which emit in colors different from those indicated can be substituted therefor and such phosphors are well known. It is preferred, however, that the phosphors emit in the primary red, blue and green colors in order that by selectively energizing the device, any predetermined color can be achieved merely by controlling the energization of the individual cells which comprise the combination device.

It will be recognized that the objects of the invention have been achieved by providing an electroluminescent device which can be energized to produce different preselected colors and color blends and which device is very positive in operation. The device is simple to fabricate ⁴ and electrical connections thereto can be readily made.

: In addition, alternative constructions for such a device &lt; have been provided.

While best embodiments of the invention have been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby.