US3109959A

US3109959A - Electroluminescent device with a fusible element

Info

Publication number: US3109959A
Application number: US126416A
Authority: US
Inventors: Richard P Delachapelle; Henry T Hidler
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1961-06-21
Filing date: 1961-06-21
Publication date: 1963-11-05
Anticipated expiration: 1980-11-05

Description

N0v- 5, 1963 R. P. DELACHAPELLE ETAL 3,109,959

ELECTROLUMINESCENT DEVICE WITH A Fusr'BLE ELEMENT Filed June 2l, 1961 /Wlll 7 www rmxmammw \'f////////////////////////////// RICHARD P. DELACHAPELLE HENRY T. HIDLER INVENTORS need safes Patent on@ 3,109,959 Patented Nov. 5, 1963 3,109,959 ELECTROLUMINESCENT DEVICE `WllI-l A FUSIBLE ELEMENT Richard P. Delachapelle, Gloucester, and Henry T. Hidler, Peabody, Mass., assignors to Sylvania Eiectrie Products Inc., a corporation of Delaware Filed June 2l, 1961, Ser. No. 126,416 2 Claims. (Cl. S15-,74)

This invention relates toelectroluminescent devices. Most electroluminescent devices have two superposcd electrodes, at least one of which is light transmitting, with a layer of an electroluminescent photophor, usually dis- `al, posi- When a voltage, generally varying or alternating, is applied, light is emitted from the phosphor and passes through the light-transmitting electrode. In most devices having commercial application,

electrical contact with the light-transmitting electrode is rather difficult to establish since the material is usually prepared of a very thin, fragile coating of electrically conducting material, such as tin oxide. Conventional means for establishing electrical contact, such as soldering or welding, are unsatisfactory, since the attaching material will not readily adhere to the coating.

Because of such diiculties, prior means of establishing electrical contact with the electrodes have been rather planar shape, electrical contact elements which protrude from the lat surface are often undesirable.

Accordingly, an object of our invention is the attainment of a compact electroluminescent device having an easily assembled, generally ilat electrical contact.l

Another object of our invention is the inclusion of a fuse in the electrical contact, thereby increasing the com pactness of the device and minimizing parts.

An advantage of our invention is the reliable and positive nature of the electrical connection with the lighttransmitting electrode of the d'evice and a further advantage is that such contact is obtained with a minimum of parte FIGURE 2 is a rear view of an electroluminescent device showing a cross-over connector including a fuse at-` tached to and insulated from the device. v

FIGURE 3 is a view of the light-emitting face of an electroluminescent device showing the cross-over connector in electrical Contact with a metallized surface on the light-transmitting electrode.

In each of the figures of the drawing, similar numerical designations are indicative of similar elements.

shaped cross-over connector for conducting electricity from lead-in prongs to the light-transmitting electrode. Base electrode l of the device is preferably prepared of a steel plate, since this material is relatively economical and structurally is quite stable. However, it is apparent that many other materials also have applicability, for example, base electrode l may be prepared of metal foil or ol materials, such 'as plastic or glass, which have been rendered electrically conductive. When using these latter examples, the device has the added features that it may have two light-emitting faces or may be flexible or both.

When desired, a ground coat 3, generally prepared of a layer of low melting, ceramic dielectric material of known and suitable composition, is coated over the base electrode 1, to provide a bonding surface for light-producing layer 5. It has been found that when using a metal plate for the base electrode l, permanent adherence ot a glass dielectric, light-producing layer 5 is rather difticult to establish, unless a ground coat is used. However, the ground coat 3 may be omitted if the light-producing layer 5 readily adheres to the base electrode l, such as would be the case if the base electrode l is prepared of electrically conductive glass or if the phosphor suspending dielectric is plastic.

Super-imposed on the ground coat 3 or on the base electrode 1, as desired, is alight-producing layer 5, which is generally prepared of an electroluminescent phosphor suspended in a light-transmitting dielectric material. The electroluminescent phosphor may be for example, a copper-activated zine sulfide such as described in the copending application of Goldberg et al. entitled Electroluminescent Device, Serial No. 714,481, led February 11, 1958, now Patent No. 3,050,655,l issued August 2l, 1962. The light-transmitting dielectric material may be for example, a glass frit such as' described in the application of Richard M. Rulon, Serial No. 365,617, led July 2, 1953, now abandone although a suitable plastic dielectric may also be used, such as described in the copending application of Sentementes et al. entitled Electroluminescent Devices and an Improved Dielectric Material for Such Electroluminescent Devices, Serial No. 94,536, led March 9, 1961.

superimposed on the light-emitting layer 5 is a coating which-forms a light-transmitting electrode 7. The coating may be applied by spraying the light-emitting layer 5 with av solution of metal compounds, for example chlorides, oxides, sulfates or organic complexes of tin, antimony or indium; however other available methods of applying such compounds or the metals to form an electrically conductive coating are for example, dipping and vapor deposition. If the light-emitting layer 5 is hot when the solution of metal compounds is applied, the metal oxide of the metal compound will be formed; however such metal oxides may also be formed by subsequently heating a light-emitting layer which was coated while cold.

After the application of the light-transmitting electrode 7 on the face of the light-emitting layer 5, it is good practice to protect the various layers of the electroluminescent device from the effects of humidity and the possibility of scratching. Such protection is conveniently atorded by forming a glass or plastic protective layer 9 over the light-transmitting electrode 7. In some cases, however, the protective layer may be eliminated and the light-transmitting electrode 7 will then serve as the face of the device. Since protective layer 9 is an insulator and since electricity must be conducted to the lightemitting electrode 7 to illuminate the device, a cavity ll is provided in the protective layer 9 to expose the conductive material for an electrical connection. Conveniently, the cavity l1 may be prepared by masking the light-transmitting electrode 7 before the protective layer 9 is applied, and afterward removing the mask so that the light-transmitting electrode 7 is exposed.

Because of the fragilityv of the light-transmitting electrode 7 and to inhibit the effect of the humidity upon the phosphor, a small dab of finely divided metal dispersed in a resin, such as silver dispersed in epoxy, is placed in the cavity 11. The preferred method of preparing the cavity l1, however is to spray-paint a small silver area on the light-transmitting electrode 7, before the protective layer 9 is applied and afterwards remove the protective layer over the silver to expose a silver area. After hardening, the metal will ll the bottom of cavity 11 and form a solid, electrically conducting, metallized surface 18 on light-transmitting electrode 7, thus providing a durable foundation for resilient, U-shaped cross-over connector 15. We have found that metals which are not readily oxidized, such as the noble metals, are most appropriate for the metallized surface 18 although other metals, such as aluminum or copper may also beused.

For many-applications of electroluminescence, such as room illumination, it is desirable to plug the device directly into convention wall sockets. Therefore, lead-in

prongs

17 and 19, having outer ends of well known and suitable design for use with such sockets are placed in a supporting holder (not shown) and the inner ends are placed in electrical contact with the electroluminescent device. Lead-in prong 19 biases against lead-in contact portion 26 of cross-over connector 15 and lead-in prong 17 biases against back electrode 1. Current will be conducted from a power source (not shown) through lead-in prong 19 and lead-in contact 26, through fuse 27 and thence to light-transmitting electrode 7 through metallized surface 18.

Insulator 28 is disposed beneath the device and between cross-over connector 15 and base electrode 1, thereby insulating the'cross-over connector 15 from base electrode 1. A side insulator 6 is wrapped about the side of the electroluminescent device to insulate crossover connector 15 from the sides of the various layers of the device. To insure adequate insulation, save materials and eliminate inordinate bulk, the side insulator 6, which wraps about the side of the electroluminescent device, is formed of a unitary prolongation of the insulator 26. The side insulator 6 is at least suciently long to wrap over the side of the electroluminescent device and preferably long enough to cover a small area of the protective layer 9. It is at least as Wide as the cross-over connector 15 and preferably a little wider to insure electrieal insulation. Insulator 28 and side insulator 6 may be prepared of any suitable and we1l-known pliant insulating material, for example a plastic such as Mylar or vinyl, although other flexible insulators, such as rubber, may also be used. In addition to insulation, when using the preferred dimensions for side insulator 6, the possibility that'a cross-over connector 15 might scratch the protective layer 9 is reduced.

The cross-over connector 15 not. only is the electrical connection between the light-transmitting electrode 7 and the lead-in prong 19, but it also secures and retains the insulator 28 on the electroluminescent device. Greater retention and permanence of electrical contact is pre1 duced by increasing the resiliency of the cross-over connector and such increased resiliency can be obtained by doubling the light-transmitting electrode contact end of the connector 15 back over itself, so that there are two layers of resilient material biasing against the upper surface of the device. We have found that tempered steel is quite eicient for conducting electricity and retaining the insulator 26, however many other materials such as aluminum, bronze, copper and nickel may also be used.

Even when a metallized surface 18 is applied to the light-transmitting electrode 7, care must be taken to avoid the possibility of scratching. Therefore, as an additional safeguard, a depression 25 is placed in the end of crossover connector 15 which contacts the light-transmitting electrode and because of this construction, only smooth, rounded Surfaces will touch the more easily scratched portions of the device. Since the rounded surfaces yield more freely, the legs of the U of the cross-over connector 15 will spread more readily and thus, the connector 15 is easily slipped over the side of the electroluminescent device.

Referring jointly to FIGURES 2 and 3, the cross-over connector 15 is a unitary strip of metal in electrical contact with lead-in prong 19 and insulated from the back electrode 1 by insulator 28. Lead-in contact portion 26 of the cross-over connector may be of any appropriate size and may be shaped as desired, however for elicient electrical contact we prefer a contact portion -at least as large as the lead-in prong. Spring biased prongs are generally preferred for conducting current to the leadt-in contact portion 26, although many other suitable means for conducting current to the device may also be used, for example it is possible to weld or solder lead-in wires to the lead-in contact portion 26. Although the peripheral shape and size of the lead-in contact portion 26 is not critical, we prefer a generally rectangular shape, since the entire cross-over connector 15, including the fuse, is formed from a single strip of metal.

Insulator 28 must be of sucient area to separate crossover connector 15 and fuse 27 from the electroluminescent device. Any desired shape insulator may be used, but for convenience of manufacture we prefer one having a generally rectangular shape. Extending from the central portion of one edge of the insulator 2S is a side insulator 6 which wraps around the side of the device and insulates the cross-over connector 15 from the sides of the various layers. Because heat is generated if the fuse 27 burns out, the insulator 28 must be sutiiciently thick to absorb such generated heat without burning through and we have found that for a 10 amp. circuit a Mylar insulator should be at least 0.005 inch thick. The thickness of the insulator, of course, will vary depending upon the characteristics of the circuit and may be determined by routine experimentation.

With regard to the construction of the fuse, we prefer to grind a recession on opposing sides ofone end of the cross-over clip 15, however other procedures may also be used, for example, it may be possible to stamp out or acid etch these recessions on one or both sides of the metal strip. The peripheral shape of the recession forming the fuse is of no particular significance, so long as the fuse breaks at the desired current value and although we have shown rounded neck, it is possible to use rectangular or other angular shapes with equal success. The width and thickness of the neck of the fuse is quite important however, and may be determined empirically to satisfy the characteristics of the circuit. For example, a 10 amp. steel fuse, which will be operated with a 1 10 volt circuit should have a neck which is 1,56 inch wide at its narrowest point and should be 0.003 inch thick.

It is apparent that changes and modifications may be vmade within the spirit and scope of the instant invention,

but it is our intention however, to be limited only by the scope of the appended claims.

As our invention we claim:

l. In combination, an electroluminescent device hava ing a light-transmitting electrode superposed on a base electrode and a layer of light-emitting material including an electroluminescent phosphor positioned between said electrodes; a fuse disposed under said base electrode, said fuse being defined by a pair of opposed recesses disposed on either side of a resilient metal Strip;.means to conduct current from said fuse to said light-transmitting electrode, said means comprising a resilient, U-shaped crossover connector positioned about the side of said device Aand disposed at one end in electrical contact with said light transmitting electrode and extending at the other end as a unitary prolongation of said fuse; an insulator positioned between said base electrode and said fuse adapted to insulate said fuse from said base electrode;

a side insulator extending as a prolongation of said insulator and positioned between said cross-over connector and the side of said device.

' 2. The device according to claim 1 wherein said U- shaped crossover connector is doubled on itself and clamped on the top and bottom of said device.

References Cited in the le of this patent UNITED STATES PATENTS Stacy et al Mar. 15, 1955 Cohen Oct. 13, 1959 Miller Jan. 26, 1960 Bristol et al. Apr. 26, 1960

Claims

1. IN COMBINATION, AN ELECTROLUMINESCENT DEVICE HAVING A LIGHT-TRANSMITTING ELECTRODE SUPERPOSED ON A BASE ELECTRODE AND A LAYER OF LIGHT-EMITTING MATERIAL INCLUDING AN ELECTROLUMINESCENT PHOSPHOR POSITIONED BETWEEN SAID ELECTRODES; A FUSE DISPOSED UNDER SAID BASE ELECTRODE, SAID FUSE BEING DEFINED BY A PAIR OF OPPOSED RECESSES DISPOSED ON EITHER SIDE OF A RESILIENT METAL STRIP; MEANS TO CONDUCT CURRENT FROM SAID FUSE TO SAID LIGHT-TRANSMITTING ELEC-