US3740616A

US3740616A - Electrically luminescent device

Info

Publication number: US3740616A
Application number: US00482000A
Authority: US
Inventors: T Kohashi; N Suzuki; Y Takiguchi
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1966-10-27
Filing date: 1970-01-02
Publication date: 1973-06-19
Anticipated expiration: 1990-06-19
Also published as: FR1550278A; DE1589234A1; GB1208308A; DE1589234B2; NL6714421A; NL142310B

Abstract

An electrically luminescent device having an electroluminescent element and associated power supply electrodes, at least one of the electrodes being in the form of a gapped structure consisting of fine metal wires which are arranged in parallel with each other or in a reticulate fashion. In the device, mere coating or placement of a low-resistance substance such as water, an alcohol, a conductive paint or an evaporated metal film on the gap portion of the gapped electrode in such a manner as to conform with the shape of a character or pattern to be displayed can easily attain the luminous display of the character or pattern.

Description

United States Patent 1 Suzuki et al.

[451 June 19,1973

1 1 ELECTRICALLY LUMINESCENT DEVICE [73] Assignee: Matsushita Electric Industrial Co.,

Ltd., Osaka, Japan [22] Filed: Jan. 2, 1970 [21] Appl. No.: 482

Related U.S. Application Data [63] Continuation of Ser. No. 677,138, Oct. 23, 1967,

abandoned. I

[30] Foreign Application Priority Data om. 27, 1966 Japan 41 71302 Oct. 27, 1966 Japan 41171304 Oct. 27, 1966 Japan 41/71305 Oct. 27, 1966 Japan 41/71306 Oct. 27, 1966 Japan... 41/71307 Oct. 27, 1966 Japan 41/71308 [52] U.S. Cl 317/234 R, 313/108 A, 317/235 N [51] Int. Cl. H011 15/00 [58] Field of Search 317/235 N; 313/108,

[5 6] References Cited UNITED STATES PATENTS 3,211,663 10/1965 Bueleza 252/301.l 3,167,677 1/1965 Fremonth 313/108 3,048,732 8/1962 Lehmann 313/108 3,152,994 10/1964 Thornton..... 252/3016 3,252,845 5/1966 Schindler..... 156/67 3,290,537 12/1966 Logan 313/108 3,348,056 10/1967 Kobashi 250/213 Primary ExaminerMartin H. Edlow Att0rneyStevens, Davis, Miller & Mosher [57] ABSTRACT An electrically luminescent device having an electroluminescent element and associated power supply electrodes, at least one of the electrodes being in the form of a gapped structure consisting of fine metal wires which are arranged in parallel with each other or in a reticulate fashion. in the device, mere coating or placement of a low-resistance substance such as water, an alcohol, a conductive paint or an evaporated metal film on the gap portion of' the gapped electrode in such a manner as to conform with the shape of a character or pattern to be displayed can easily attain the luminous display of the character or pattern.

7 Claims, 8 Drawing Figures Patented June 19, 1973 3,740,616

3 Shoots-Shoot 1 Patented June 19, 1973 I 3,740,616

3 Shoots-Shoot 5 l ELECTRICALLY LUMINESCENT DEVICE This application is a continuation of Ser. No. 677,138 filed Oct. 23, 1967 (now abandoned).

This invention relates to an electrically luminescent device employing therein an electrically luminescent element such as an electroluminescent element which luminesces depending on the strength of an electric field applied thereto, and contemplates to provide an electrically luminescent device of the above kind whose luminously displaying section can easily be controlled for the display of the desired character or pattern.

Prior electrically luminescent devices employing therein electroluminescent elements which are adapted to give a luminous display of a character or pattern have such a structure that at least one of the electrodes is shaped to the form of the character or pattern to be displayed and power is supplied to this electrode by some suitable means to effect the display of the desired character or pattern. In view of such a structure, many electrodes must be provided and individually connected by way of feeder wires to a power supply in order to display acomplex character or pattern consisting of many elements which are isolated from one another, with the result that the structure of the electrically luminescent device becomes very complex and an extreme difficulty is involved in the manufacture of the electrodes representing the character or pattern to be displayed. 7

It is therefore the primary object of the present invention to provide a novel electrically luminescent device having a power supply electrode which is in the form of a plural-gapped electrode consisting of very fine metal wires arranged in a parallel or reticulate relation for thereby enabling to display a character or pattern of whatever shape.

The above and other objects, advantages and features of the present invention will become apparent from the following description with reference to the accompanying drawings.

In'the drawings:

FIG. 1 is a schematic sectional view of an electrically luminescent device embodying the present invention;

FIGS. 2, 3, 4, 5 and 6 are schematic sectional views of other embodiments according to the present invention;

FIG. 7 is a diagrammatic view showing the manner of operation of the device shown in FIG. 6; and

FIG. 8 is a'schematic sectional view of another embodiment according to the present invention.

FIG. 1 shows the structure of an embodiment of the electrically luminescent device according to the present invention and a power supply system therefor. The electrically luminescent device shown in FIG. 1 comprises a support base 1, a planar electrode 2, an electrically luminescent layer 3 which luminesces depending on the strength of an electric field applied thereto, a dielectric layer 4 of a material such as plastics having a high resistivity, and a plural-'gapped electrode 5 consisting of plural fine wire electrodes which are arranged in parallel with each other. In the device, a voltage is applied across the

electrodes

5 and 2 from a power supply8 by way of

lead wires

6 and 7.

The support base I may be made of a transparent material such as glass or of an opaque material such as bakelite. The term transparent" used herein is intended to denote the fact that a transparent" material or layer permits transmission therethrough of the luminescence emitted from the electrically luminescent layer 3.

The conductive electrode 2 is bonded or otherwise fixed to the support base 1, but where the support base 1 is made of, for example, transparent glass, the conductive electrode 2 must also be transparent and may be made from a conductive transparent metal oxide such as tin oxide. In case the support base 1 of opaque nature is employed, the electrode 2 need not be transparent and may be an opaque metal film such as an evaporated aluminum film.

When the device is intended to operate with an alternating current, the electrically luminescent layer 3 may be made by preparing a composition consisting of, for example, zinc sulfide powder activated with copper and aluminum and a plastic binder such as urea resin and laminating the composition to a thickness of, for example, 50 microns. The electrically luminescent layer 3 having the above composition has such a property that it emits a green luminescence when an ac electric field is applied thereto, and its luminous output varies nonlinearly in proportion to any increase or decrease in the strength of the ac. electric field.

The dielectric layer 4 having a high resistivity may, for example, be a layer of an epoxy resin. At least either the layer 4 or the support base 1 should be transparent with respect to the luminescence emitted from the electrically luminescent layer 3. Accordingly, the highly resistive dielectric layer 4 may be either opaque or transparent when the support base 1 is transparent. When both the support base 1 and the highly resistive dielectric layer 4 are transparent, the luminescence emitted from the electrically luminescent layer 3 can be observed through the base 1 and the dielectric layer 4. When the support base 1 is opaque, the highly resistive dielectric layer 4 must be transparent with respect to the luminescence emitted from the electrically luminescent layer 3. The highly resistive dielectric layer 4 may preferably be such that its specific resistance and- /or its surface insulation resistivity is greatly varied by moisture or water. For example, the dielectric layer 4 may be molded to a laminar form having a thickness of about 10 microns from a composition consisting of an epoxy resin made by Union Carbide Co. under the trade name ERL-2774 and a suitable amount of a plasticizer made by the same company under the trade name ZZL-O845.

The electrode 5 may consist of tungsten wires having a diameter of, for example, 10 microns which are arranged in an equally spaced parallel relation with a spacing in the order to microns therebetween. The spacing between the adjacent wires need be narrowed as much as possible in order to display a very fine and complex character or pattern, but the spacing may desirably be larger than the total thickness of the layers lying between the

electrodes

5 and 2 in order that the luminescence emitted without giving any display, that is, the dark luminescence may not become so intense. Further, the diameter of the metal wire may preferably be as small as possible in order to avoid the undesirable high intensity of the luminescence emitted in the absence of any display, that is, the dark luminescence.

The plural-gapped electrode 5 may consist of a plurality of strip-like evaporated films of a metal such as aluminum which are evaporated onto the highly resistive dielectric layer 4. In another form of the electrode 5, the plural-gapped electrode may have a reticulate structure. The reticulate electrode may be obtained by arranging a plurality of fine metal wires in a perpendicular relation with one another, or by employing a metal network, or by evaporating a plurality of metal films in a reticulate fashion.

The electrode 5 may desirably be disposed in such a way that it is partly projected above the surface of the highly resistive dielectric layer 4 in order that it can satisfactorily serve as a power supply electrode, but the electrode 5 may not necessarily be projected above the surface of the dielectric layer 4 in case the specific resistance of the highly resistive dielectric layer 4 itself is greatly varied by the presence of moisture or the like. In the latter case too, the electrode 5 can properly act as a power supply electrode.

The operating principle of the present embodiment will be described in detail with reference to FIG. 1. A voltage is applied across the

electrodes

2 and 5 from the power supply'8 by way of the

lead wires

6 and 7. In this case, those portions of the electrically luminescent layer 3 underlying the wires of the pIural-gapped electrode 5 may emit some luminescence due to the fact that an electric field is applied thereto. However, in view of the fact that the electrode wires have the diameter in the order of 10 microns and are spaced from each other by the distance in the order of 100 microns and the total thickness of the electrically luminescent layer 3 and the highly resistive dielectric layer 4 is in the order of 60 microns as described previously, the luminescence emitted from the electricallyluminescent layer 3 as a whole is such that it is very weak or substantially negligible, and as a matter of fact, so weak that it can be hardly detected. Thus, the electrode 5 is only operative to merely supply the power to the electrically luminescent layer 3 and does not energize directly the electrically luminescent layer 3.

Under the state in which the applied voltage is suitably adjusted so that the electrically luminescent layer 3 can hardly emit the luminescence in the manner as described above, a liquid such as water which has a low resistance may be dropped onto the surface of the highly resistive dielectric layer 4. When at least a portion of the liquid contacts a wire of the electrode 5, the surface potential of the dielectric layer 4 about the particular wire of the electrode 5 makes an increase due to the fact that the surface conductivity along the surface of the highly resistive dielectric layer 4 between ..the wires of the electrode 5 makes an increase by the presence of the liquid. As -a result, the internal portion of the electrically luminescent layer -3 which corresponds to the position of existence of the liquid is subjected to the action of an increased electric field and thus emits a stronger luminescence. Thus, the portion wetted with the liquid, such as water, which has a low resistance, that is, the portion of a character or pattern depicted by the liquid is made to intensely luminesce.

Moisture acts in the same manner as in application of a substance such as water which has a low insulation resistance. The presence of local moisture also acts to cause a remarkable reduction in the insulation resistance at the surface of the highly resistive dielectric layer 4 so that, when at least a portion of the surface having its insulation resistance lowered by the presence 7 of moisture is in contact with a wire of the electrode 5,

that portion of the electrically luminescent layer 3 corresponding to the portion of local existence of the moisture luminesces as in the case of wetting the layer 4 with water which has a low insulation resistance. When it is desired to cease the luminescence emitted from the portion wetted with the liquid such as water, theliquid may merely be wiped away by a piece of cloth or the like to restore the surface of the highly resistive dielectric layer 4 to its non-wetted state, which ceases the luminescence of the electrically luminescent layer 3.

In FIG. 2, there is shown the structure of another embodiment of the electrically luminescent device according to the present invention and a power supply system therefor. I

The embodiment shown in FIG. 2 is generally similar to that shown in FIG. 1, but is featured by the provision of a electrically insulating layer 9 such as a polyester film on an electrically luminescent layer 3 in order to give an increased insulation thereto. The provision of such layer 9 is effective because those portions of the electrically luminescent layer 3 contacted by electrode wires of an electrode 5 are generally liable to cause a dielectric breakdown. The insulation layer 9 may be prepared by laminating a composition consisting of powdery barium titanate and a plastic binder. In this case, the dielectric layer 9' is white in color and therefore reflects the luminescence emitted from the electri cally luminescent layer 3, thus intensifying the light output and giving an increased effectiveness.

In FIG. 3, there is shown the structure of a further embodiment of the electrically luminescent device according to the present invention and a power supply system therefor.

The embodiment shown in FIG. 3 is generally similar to that shown in FIG. 1, but is featured by the provision of a direct current power supply 8. The direct current power supply 8 may be employed to cooperate with an electrically luminescent layer 3 when such layer is formed from a luminescent material such as cadmium sulfide or silicon carbide which luminesces when energized by a direct current, or such layer is made by evaporating zinc sulfide powder activated with copper or manganese. in a thin film form. In this case, the resistivity of a highly resistive dielectric layer 4 must be slightly reduced in order to allow for passage there through of the direct current.

In FIG. 4, there is shown the structure of another embodiment of the electrically luminescent device according to the present invention and a power supply system therefor.

The embodiment shown in FIG. 4 is featured by the provision of a pair of plural-

gapped electrodes

2 and 5 each consisting of plural electrode wires, a support base 1 which supports a pair of dielectric layers 4' on opposite faces thereof, and a pair of electrically

luminescent layers

3 and 10 interposed between the base 1 and the layers 4, so that a character or pattern can be displayed on the opposite faces of the layers 4 contacted by the

electrodes

2 and 5. In this embodiment, the electrically luminescent layer 3 is principally operative to display a character or pattern on the surface including the-electrode 2, while the electrically luminescent layer 10 is principally operative to display a character or pattern on the surface including the electrode 5. A character or pattern displayed on the surface including the electrode 2 can be made quite independent of a character or pattern displayed on the surface including the electrode 5 when an opaque dielectric material is employed to form the support base 1.

Further, characters or patterns having different colors may be displayed when the electrically luminescent layers 3 and are so selected as to emit the luminescence of different colors. Although the

electrodes

2 and 5 are shown herein as disposed in a registered relation, it will easily be understoodthat the electrode 2 may be disposed to overlie the gap portions of the electrode 5, or the

electrodes

2 and 5 may be disposed to intersect in a perpendicular relation or in an angular relation with each other.

In FIG. 5, there is shown a further embodiment of the electrically luminescent device according to the present invention and a power supply system therefor.

The embodiment shown in FIG. 5 is similar to that shown in FIG. 4 in the provision of a pair of

pluralgapped electrodes

2 and 5, but is different in that a single electrically luminescent layer 3 is provided in lieu of the two layers in the embodiment shown in FIG. 4. In this embodiment, when the voltage at a power supply 8 may be suitably adjusted, characters or patterns depicted on the surfaces including the

electrodes

2 and 5 may luminesce solely at their intersections to thereby give a display of points in the two-dimensional display device. In FIG. 6, there is shown the structure of another embodiment of the electrically luminescent device according to the present invention and a power supply system therefor.

The embodiment shown in FIG. 6 is featured by the fact that three electrodes, two of which are pluralgapped electrodes, are connected with two power supplies, and two electrically luminescent elements emitting the luminescence of different colors are employed so that a portion having thereon a conductive substance depicted in the shape to conform with a character or pattern to be displayed luminesces with a color different from a color with which the remaining portion luminesces.

Referring to FIG. 6, the electrically luminescent device comprises a transparent support base 11 of glass or like material, a transparent electrode 12 of a metal oxide such as tin oxide, a transparent impedance layer 13 of a material such as plastics, electrically

luminescent layers

14 and 16, a plural-gapped electrode 15 interposed between the electrically

luminescent layers

14 and 16, a electrically insulating layer 17 in the form of, for example, a polyester film, a dielectric layer 18 having a high resistivity made from a material such as an epoxy resin, a plural-gapped electrode 19, and a.c. power supplies 23 and 24 for applying voltages at the same frequency across the

electrodes

15 and 19 by way of

lead wires

20 and 21 and across the

electrodes

15 and 12 by way of

lead wires

20 and 22, respectively.

The impedance layer 13 may not necessarily be transparent when it is possible to observe the luminescence of the electrically

luminescent layers

14 and 16 from the side of the electrode 19. The electrically

luminescent layers

14 and 16 give luminescences of different colors and may, for example, be a green-emitting electroluminescent element in the form of ZnS: Cu,Al and an orange-emitting electroluminescent element in the form of ZnCdS: Ag, respectively. In this case, it is desirable that the electrically luminescent element layer emitting the. luminescence of a shorter wavelength is disposed nearer to the surface through which the luminescence is to be observed. The plural-gapped electrode 15 in this embodiment consists of a plurality of fine wires of a metal such as tungsten having a diameter in the order of 20 microns which are parallelly disposed with a spacing in the order of 200 to 300 microns. The electrode 15 may be a reticulate electrode which is made by knitting a plurality of metal wires in a reticulate fashion. The plural-gapped electrode 19 in this embodiment consists of plural fine wires of a metal such as tungsten having a diameter in the order of 20 microns which are parallelly disposed with a spacing in the order of microns.

The operating principle of the device shown in FIG. 6 will be described with reference to FIG. 7. In FIG. 7, voltages V, and V at the

respective power supplies

23 and 24, and currents I and I associated with these voltages respectively are shown in their ideal situation in which they have an antiphase relation with each other. As will be apparent from FIG. 7, the currents l,

and I operate in a differential fashion. In a dark state in which any character or pattern is not displayed due to mere application of the voltages, the current flowing in the vicinity of the electrode 15 is given by /l, l When the voltage V is so selected as to be slightly higher than V, in order to have a relation /I /l,/, the luminescence is primarily governed by the current I flowing between the

electrodes

15 and 12, and the electrically luminescent layer 14 luminesces due to the high density of the current flowing through the electrically luminescent layer 14 which is nearer to the electrode 12. On the other hand, due to the small density of the current flowing through the electrically luminescent layer 16 which is nearer to the electrode 19, the electrically luminescent layer 16 hardly luminesces, and therefore the color of luminescence of the device as a whole is represented by the color of luminescence of the electrically luminescent layer 14.

Suppose now that a droplet 25 ofa liquid, such as water, having a low insulation resistance is placed on the surface of the highly resistive dielectric layer 18, and at least a portion of the droplet 25 contacts the electrode wire of the electrode 19. Then, due to the fact that the surface conductivity along the surface portion of the highly resistive dielectric layer 18 between the electrode wires 19 is increased, the surface potential about the particular wire of the electrode 19 increases so that the density of the current flowing in the vicinity of the portion underlying the conductive liquid droplet 25 working as an electrode makes a corresponding increase as shown by I,'. Since the conductive liquid droplet 25 is placed in a shape to conform with the shape of a character or pattern to be displayed, the resultant increase in the density of the current flowing through the portion of the electrically luminescent layer 16 which underlies the liquid droplet 25 causes the electrically luminescent layer 16 to strongly luminesce at that portion. On the other hand, the current I, flowing into the electrically luminescent layer 14 disposed nearer to the electrode 12 is operative to cancel the current to thereby weaken the luminescence of the electrically luminescent layer 14 having luminesced in its dark state by being energized by the current I Therefore, the portion representing the character or pattern is intensely illuminated by the luminescence of the electrically luminescent layer 16, while the remaining or non-depicted portion is illuminated by the weak luminescence of the electrically luminescent layer 14.

In case the voltage V, is solely applied, the luminescence occurs substantially solely in the electrically luminescent layer 16 due to less flow of the current I, through the electrically luminescent layer 14. In such a case, therefore, the portion representing a character or pattern is illuminated by the luminescence of the electrically luminescent layer 16, while the remaining or non-depicted portion is substantially free from any luminescence.

Further, by suitably selecting the magnitude of the voltage V relative to the voltage V, in such a manner that the current I exactly cancels the dark luminescence caused by the current I, produced by the voltage V the image of a character or pattern produced by the current I can be displayed with a very high black-towhite contrast. Moreover, by suitably selecting the magnitude of the voltages V and V it is possible to freely obtain an image in which the color of luminescence of the electrically luminescent layer 14 is intensified or an image in which the color of luminescence of the electrically luminescent layer l6 is intensified.

The above description has referred to a case in which the currents I and 1 are in a differential relation and have the phases opposite to each other, that is, a case in which the voltages V, and V are arranged to have the phases substantially opposite to each other in consideration of the nature of the impedance of the layers including the impedance layer 13, the highly resistive dielectric layer 18 and the high insulation layer 17.

However, it will be understood that the anti-phase relation between the currents I and I hence V, and V is not an essential requirement, and their phase difference or their amplitude may be suitably varied as required to thereby control the colors of luminescence or the black-to-white contrast or the gamma. In case there is a phase difference of between the voltages V, and V the control of the colors of luminescence can be most preferably attained by selecting the value of 6 in such a way as to lie in a range (11/2) s 0 s (31r/2).

A further embodiment of the present invention with an associated power supply system therefor is shown in FIG. 8.

The embodiment shown in FIG. 8 is generally similar to that shown in FIG. 6, but is different from the latter in that three spaced electrically luminescent layers 14,

16 and 26 emitting the luminescence of three different colors, or more preferably having the luminescence spectrum bands which may not appreciably overlap with each other, are disposed to lie in the gap portions of a plural-gapped electrode 15, and a dielectric layer 27 of transparent and non-luminous nature is employed to fill the space between the electrically

luminescent layers

14, 16, 26 and to fill the remaining space in the gap portions of the plural-gapped electrode 15. Currents flowing from a planar electrode 12 and a pluralgapped electrode 19 are concentrated to the pluralgapped electrode to establish a local high electric field around the plural-gapped electrode 15 so that the luminescence of the electrically

luminescent layers

14,16 and 26 takes place in a limited region substantially in the vicinity of the plural-gapped electrode 15.

It is also in the vicinity of the plural-gapped electrode 15 that the current compensation described previously can be completely performed. Accordingly, the best characteristics can be obtained when the'electrically luminescent layers are confined to the neighborhood of the plural-gapped electrode 15. The disposition of the non-luminous layer 27 between the electrically luminescent layers is effective for the desired color separation or for the separation of the luminescence spectrum bands since the electrically luminescent layers emitting the luminescence of different colors are isolated from each other. Although, in FIG. 8, the electrically luminescent elements are shown as disposed in a limited area in the vicinity of each electrode element of the electrode 15, these elements may be so disposed as to continuously extend between the adjacent electrode elements of the electrode 15.

The present invention disclosed herein provides an electrically luminescent device which can very easily display a character or pattern compared with prior art devices of this kind, and can operate in a more useful manner than heretofore.

In the embodiments disclosed hereinabove, the case of applying a water droplet in such a manner as to conform with the shape of a character or pattern to be displayed has been described by way of example. It will however be understood that a substance having an impedance which is lower than the electrical impedance of the layer portion lying in the gap portion of the plural-gapped electrode may be equally effectively used in place of water. Such substance is quite sufficient to serve as an electrode for the luminous display of a character or pattern depicted thereby. Therefore, when the material filling the gap portions between the adjacent electrode elements of the plural-gapped electrode has a high resistivity, a substance having a resistivity sufficiently lower than the resistivity of the material may be used so that it can serve as an electrode for the luminous display of a character or pattern depicted thereby. Such substance may be a conductive paint prepared by suspending powders of metals such as silver in a ther-' mosetting resin such as an epoxy resin, a solution of an electrolyte, a water-soluble solution such as an alcohol, or a liquid such as water having a low resistivity. Such conductive paint or liquid, when used to depict a character or pattern to be displayed on the layer including therein the plural-gapped electrode, can sufficiently serve as an electrode for the luminous display of the character or pattern. According to this method, any complex character or pattern can easily be depicted by a writing utensil such as a pen or brush. The character or pattern so depicted may easily be erased by merely wiping away the conductive paint or liquid.

Further,,the conductive paint may be hardened and bonded to the surface, or the conductive powder mixed with an enamel frit may be coated on and baked to the surface for the stable preservation of a character or pattern for a long period of time. Needless to say, an evaporated metal film may be deposited on the surface in lieu of the above baking procedure.

A solution prepared by dissolving a deliquescent substance such as magnesium chloride into a volatile solution such as an alcohol or a mixture thereof may 'be used to easily obtain an electrode of the desired shape.

element which luminesces depending on the strength of an electric field applied thereto, one of the electrodes being formed as a plural-gapped electrode which serves as a power feeder for a conductive substance disposed on the gap portion between the electrode elements so that such substance can act as an electrode. It will be appreciated that the luminous display of a character or pattern can easily be effected by merely depicting the character or pattern with the conductive substance in such a manner that the conductive substance electrically contacts at least one of the electrode elements. It will further be appreciated that a plurality of portions isolated from each other can easily be made luminant by merely applying the conductive substance to those portions, thus obviating the need for the provision of separate feeder wires.

We claim:

1. An electrically luminescent display device comprising two electrically luminescent films having different luminescent colors and disposed adjacent to each other, first and second dielectric layers respectively disposed on the opposite outer surfaces of the combination of said electrically luminescent films, said second dielectric layer being light-permeable, a first electrode disposed on the outer surface of said first dielectric layer, a second electrode disposed on the outer surface of said second dielectric layer, a third electrode disposed between said two electrically luminescent films, said first-and third electrodes being formed by a plurality of fine wires in a grid-like configuration, means for applying a first voltage between said first and third electrodes, means for applying a second voltage between said second and third electrodes, and means for producing a pattern of visual color light emissions from said electrically luminescent films comprising a lowresistance material applied to preselected portions on said outer surface of said first dielectric layer, said lowresistance material being in electrical contact with adjacent portions of said electrode.

2. An electrically luminescent display device according to claim 1, further comprising a third dielectric layer, separate from said first dielectric layer, disposed between said first dielectric layer and said combination of electrically luminescent films.

3. An electrically luminescent display device, comprising: a first dielectric layer; an electrically luminescent film comprising first, second and third layers disposed within said first dielectric layer and spaced apart from each other by said first dielectric layer; a first electrode having a grid-like configuration, wherein said first, second and third electrically luminescent layers are disposed within the gaps in said first grid-like electrode; second and third dielectric layers disposed on opposite sides of said electrically luminescent film; second and third electrodes disposed on the outer surfaces of said second and third dielectric layers, respectively, and spaced from said electrically luminescent film by said respective second and third dielectric layers; and means applying a first voltage between said first and second electrodes and means applying a second voltage between said first and third electrodes.

4. An electrically luminescent display device according to claim 3, further comprising a fourth dielectric layer, distinct from said third dielectric layer, disposed between said third dielectric layer and said electrically luminescent film.

5. An electrically luminescent display device according to claim 3, wherein said first, second and third electrically luminescent layers have different luminescent spectrum bands.

6. An electrically luminescent display device, comprising: an electrically luminescent film; first and second second planer electrodes disposed on opposite sides of said electrically luminescent film, at least one of said electrodes being formed of a plurality of wires in a grid-like configuration; a dielectric layer disposed between said grid-like electrode and said electrically luminescent film; and a conductive substance having a resistivity lower than that of said phosphor layer and placed on said dielectric layer in the shape of characteristics or patterns to be displayed, the gridlike electrode serving as a feeder wire for said conductive substance.

7. An electrically luminescent display device according to claim 6, further comprising: a second dielectric layer, separate from the first-mentioned dielectric layer, disposed between and adjacent said firstmentioned dielectric layer and said electrically luminescent film.

Claims

1. An electrically luminescent display device comprising two electrically luminescent films having different luminescent colors and disposed adjacent to each other, first and second dielectric layers respectively disposed on the opposite outer surfaces of the combination of said electrically luminescent films, said second dielectric layer being light-permeable, a first electrode disposed on the outer surface of said first dielectric layer, a second electrode disposed on the outer surface of said second dielectric layer, a third electrode disposed between said two electrically luminescent films, said first and third electrodes being formed by a plurality of fine wires in a grid-like configuration, means for applying a first voltage between said first and third electrodes, means for applying a second voltage between said second and third electrodes, and means for producing a pattern of visual color light emissions from said electrically luminescent films comprising a low-resistance material applied to preselected portions on said outer surface of said first dielectric layer, said low-resistance material beIng in electrical contact with adjacent portions of said electrode.

7. An electrically luminescent display device according to claim 6, further comprising: a second dielectric layer, separate from the first-mentioned dielectric layer, disposed between and adjacent said first-mentioned dielectric layer and said electrically luminescent film.