US3189786A - Lighting device and electrical connection therefor - Google Patents

Description

June 15, 1965 w. J. KNOCHEL 3,189,786

LIGHTING DEVICE AND ELECTRICAL CONNECTION THEREFOR Filed Aug. 10. 1960 I i a 5 v a 4 2 1 United States Patent 3,189,786 LKGHTING DEVICE AND ELECTRICAL CUNNEIITEQN THEREFOR William Ii. Knochel, West Grange, Nl, assigncr to Westinghouse Electric Corporation, East Pittsburgh, Pa, a

corporation of Fennsylvania Filed Aug. 10, 1966, Ser. No. 43,661 Claims. (Cl. 315-71) This invention relates to electric lighting devices and, more particularly, to an electroluminescent lamp and an improved electrical connection therefor.

In order to protect the phosphor employed in electroluminescent devices from the deteriorating effects of Water vapor and contaminating atmospheric gases it is necessary to seal these portions of the devices through which such gases could penetrate. In glass-plastic type lamps this is accomplished by coating the back and sides of the lamp with a suitable thermosetting plastic such as epoxy or the like, or by encapsulating the entire lamp in such material. In ceramic type lamps the desired vapor barrier is provided by firing a protective glass layer over the glass-phosphor layer or front of the lamp.

While such protective layers prevent the ingress of contaminating gases they present a problem in that the power leads or lead-in conductors must frequently be hermetically sealed therethrough. This is difiicult to accomplish, particularly when the lamps are exposed to a wide ambient temperature range insofar as the conductor tends to tear away from the seal because of the diiferen tial in the coeflicient of expansion of the conductor and the vitreous or plastic layer. In addition, due to the low current rating of such electroluminescent devices the leadin conductors must be maintained in positive contact with the lamp at all times to keep the contact resistance as low as possible. Thus, a hermetic seal around the leadin conductors and a low-resistance juncture between such conductors and the lamp contacts are essential if the lamp is to have good life performance, particularly under varying ambient temperature and high humidity conditions.

This problem of effecting a durable low-resistance connection between the device contacts and the lead-in conductors is even more complicated when a prong type leadin conductor is employed and an arc-suppressing series resistor is interposed between the end of the conductor and the lamp contacts insofar as only l-ine contact is effected between the resistor and lead-in conductor. A combination arc-suppressing and electrical connection of this type is disclosed and claimed in copending U.S. application, Serial No. 42,931, of G. Saviers, filed July 14, 1960, now Patent No. 3,121,817, assigned to the assignee of the present invention.

With the foregoing in mind it is the general object of this invention to provide an improved electroluminescent lighting device which will have a long useful life even when operated under high humidity and varying ambient temperature conditions.

Another and more specific object is the provision of an electrical power connection for an electroluminescent lamp or similar device which can be very conveniently and inexpensively fabricated and will not deteriorate under adverse operating conditions.

Still another object is the provision of an electrical ice power connection that is hermetically sealed and will withstand a wide range of ambient temperature.

The aforesaid objects, and others which will become apparent as the description proceeds, are achieved by using a layer of highly conductive material such as silver or the like to connect the lead-in conductors and lamp contacts, which layer is firmly bonded to and sealed within the protective layer of glass or plastic applied to the lamp and over the contacts. The conductive material is placed in contact with the protective material while it is still in a fluid state and thus forms a plating thereon when the material hardens which plating effects a sealed-in lowresistance juncture between the lead-in conductor and lamp contacts that is very durable and inexpensive to fabricate.

A thin strip of highly conductive material may also be used as the lead-in conductor itself to provide a ribbon or foil type conductor that is hermetically sealed through the protective non-conductive layer and extends to any desired point on the exposed surface thereof.

A better understanding of the invention will be obtained by referring to the accompanying drawing wherein:

FIG. 1 is a perspective view of a plugin electroluminescent lighting unit which incorporates the present invention;

FIG. 2 is an enlarged cross-sectional view along the line II-II of FIG. 1, in the direction of the arrows;

FIG. 3 is a perspective view of the electroluminescent lamp component employed in the lighting unit shown in the preceding figures, the central portion of the lamp being removed for convenience of illustration;

FIG. 4 is an enlarged side elevational view of one end of the lighting unit shown in FIGS. 1 and 2;

FIG. 5 is a perspective view of one of the resilient leadin prong conductors;

FIG. 6 is a perspective view of one of the resistor elements; and

FIG. 7 is a view corresponding to FIG. 4 but shows another form of electrical connection according to the present invention.

With specific reference to the drawing, in FIGS. 1 and 2 there is shown a lighting unit 10 comprising an electroluminescent lamp 12 that is mounted in a frame 1 10f plastic or the like. As shown more particularly in FIG. 2, a pair of prongs 17 and 19 project from the back of the lighting unit to provide plug-in terminals which prongs constitute the outer ends of generally L-shaped resilient lead-in conductors 26 and 27 that are rigidly anchored to and project through a back panel 16' secured to the back of the frame 14. The inner ends of the aforesaid lead-in conductors are compressed against flat composite type limiting resistors 30 and 32 which, in turn, overlie and connect with bus-bars or contacts 28 and 29, respectively, on the back of the lamp. A layer of cured plastic 25 (FIGS. 2 and 4) such as epoxy or the like is cast over the back of the lamp 12 and around its edges to provide the necessary vapor barrier and permanently seal the lamp within the frame. The inner ends of the lead-in conductors 26 and 27 are embedded in and rigidly held in operative relation with the lamp and the aforesaid resistors by the protective layer 25.

As shown in FIGS. 2 and 3, the electroluminescent lamp 12 is of the glass-plastic type and comprises, in the following order, a glass base plate 18, an overlying light-transmitting electrode 20 such as tin oxide or the like, an electroluminescent phosphor-dielectric layer 22 and a second electrode 24 of vaporized aluminum or the like. A pair of bus-bars or contacts 28 and 29 are provided along opposite side edges of the back of the lamp by applying strips of silver paint or the like. The contact 28 is connected to the light-transmitting electrode 20 whereas the contact 29 connects with the metallic elec trode 24 through an overlapping extension thereof, as shown. The exposed surface of the contact 29 accordingly comprises the overlying part of the metallic electrode 42. The limiting resistors 30 and 32 are of the composite type and of generally rectangular configuration the flat surfaces whereof are provided with a coating 34 of suitable highly conductive material such as copper or the like, as shown in FIGS. 2 to 4 and FIG. 6. A more detailed description of the lighting unit and limiting resistorsand mode of assembly thereof is given in the previously referred to copending application of George Saviers and in copending US. application Serial No. 825,961, of W. J. Knochel et al., filed July 9, 1959, which application now Patient No. 3,056,898, which. is also assigned to the assignee of the present invention.

In accordance with the present invention the desired positive juncture between the lead-in conductors 26 and 27 and the resistors 30 and 32 is achieved by providing a coating 36 of highly conductive material such as silver or the like on the end of the conductors. Only the end segment of the. lead-in conductors that is subsequently embedded in the protective layer 25 is coated, as shown in FIG. 5. Thus, when the lamp 12 is placed into the frame 14 and the back panel 16 is snapped in place, after the plastic 25 is cast over the back and sides of the lamp, the coated ends of the lead-in conductors are pressed into and through the plastic material and against the copper-coated surfaces of the limiting resistors 30 and 32, as shown in FIGS. 2 and 4. It has been found that during curing of the plastic layer 25 the silver'coating 36 becomes firmly bonded to the contiguous surfaces thereof forming a continuous plating thereon that electrically connects the leadin conductors and copper-coated surfaces of the resistors. In this manner a positive low-resistance juncture is provided which is embedded within and thus hermetically sealed from the atmosphere by the protective plastic layer 25.

Experience has shown that the plating formed on the surrounding surfaces of the protective layer 25 by the adhesion thereto of the coating 36 is such that it forms a highly conductive ribbon-like conductor which is very durable and is bonded to the copper-coated resistors. This was discovered when lighting units fabricated in accordance with the foregoing were taken apart and the prong lead-in conductors 26 and 27 very carefully removed from the protective layer 25. The lamps were then placed in a humidity cabinet for over six weeks and upon being removed operated at their rated voltage simply by making contact with the silver coating 36 that had becomebonded with and adhered to the plastic layer. This shows that the plating forms a continuous low-resistance path that extends along the embedded end of the prong conductor and, in effect, serves as a second lead-in conductor which is extremely durable and not affected by temperature variations orhigh humidity conditions.

It should be noted that even-if the prong conductors 26 and 27 should tear away from the protective layer and become separated from their respective resistors because of extreme temperature variations to which the lamp is subjected in use or shipment, apositive connection will still be maintained insofar as the ends of the prongs will elfect sliding contact wth the aforesaid plating.

While the protective layer 25 as here shown comprises a layer of plastic, the same type of sealed in low-resistance connection obviously would be obtained if the protective layer comprised a layer of glass, as would be the case in ceramic type electroluminescent lamps. In addition, it will also be obvious that the limiting resistors 30 and 32 could be omitted if desired and connection made directly with the lamp contacts 28and 29.

In FIG. 7 there is shown an alternative embodiment of the present invention wherein a thin layer of highly conductive material such as silver paint or the like is sealed through the protective layer 25 of insulating material to provide a ribbon lead-in conductor'38 that connects the lamp contact (or resistor 34' as here shown) to a point on the exposed surface of the aforesaid layer. This type connection can be very readily fabricated by embedding a suitable member in the protective layer 25 during the assembly of the lamp 12 and the frame 14 and, after the plastic or glass has hardened, removing the aforesaid member to provide a cavity that extends through the protective layer to the conductive coating 34 on the resistor 32. The walls of the cavity are then painted with silver paste or the like to provide a thin continuous conductive strip 38 that may be extended to any point on the exposed surface of the protective layer and the back of the lamp. The cavity is then filled with epoxy or other hardenable insulating material to provide a plug that hermetically seals the cavity and the inner segment of the conductive strip38 therein.

In this manner, a ribbon type lead-in conductor is provided which enables the lamp contacts, in effect, to be extended to any point on the back of the lamp without exposing the phosphor layer to the atmosphere. This type connection would be especially advantageous in the manufacture of digital electroluminescent devices, for example, where connections to a plurality of discrete segments are required. To prevent leaky seals the conductive strip 38 should be kept as thin as possible consistent with the required current-carrying capacity. Satisfactory results have been obtained by maintaining the thickness between about 0.0002" and 0.01".

As in the case of the first embodiment shown in FIGS. 2 to 4, the ribbon type lead-in conductor construction shown in FIG. 7 can also be employed in ceramic type electroluminescent lamps in which case the protective layer 25 would comprise a vitreous rather than a plastic layer.

It will be apparent from the foregoing that the objects of the invention have been achieved by providing a very inexpensive and reliable electric power connection for an electroluminescent device which is not aifected by the deteriorating eifects of high humidity conditions and extreme temperature variations.

While several embodiments have been illustrated and described in detail, it will be understood that various modifications in the configuration and arrangement of parts can be made without departing from the spirit and scope of this invention.

I claim:

1. In a lighting device, the combination comprising: an electrical contact on an exposed part of said device, a body of insulating material completely covering said contact and sealing it off from the atmosphere, and a thin layer of electrically conductive material connected to said contact and hermetically bonded to and'sealed through said insulating body and extending therealong to a point on the exposed surface thereof.

2. In an electroluminescent lighting device having a pair of electrodes, the combination comprising a contact integral with said lighting device and connected to one of said electrodes, a layer of electrically non-conductive material protectively covering said contact and a substantial adjoining portion of said light source, a lead-in conductor having one end embedded in said non-conductive protective layer and anchored thereby in close proximity to said contact, and a layer of electrically conductive material between and connecting the embedded end of said lead-in conductor and said contact, said layer of conductive material being firmly bonded to the contiguous surface of said non-conductive layer and thereby providing a sealed-in low-resistance juncture between said lead-in conductor and said contact.

3. The combination as set forth in claim 2 wherein said layer of electrically conductive material extends beyond the end of said lead-in conductor and forms a continuous plating on the surrounding surface of said protective layer.

4. The combination as set forth in claim 2 wherein said contact comprises one face of a composite type resistor connected in series between one of the device electrodes and said lead-in conductor.

5. The combination as set forth in claim 2 wherein, said contact is located on the back of said lighting device, said lead-in conductor comprises a resilient member that is pressured against said lighting device, and said protective layer covers the back of said lighting device.

References Cited by the Examiner UNITED STATES PATENTS 625,395 5/99 Houston 3l768 2,168,769 8/39 Fisher 317-66 2,650,310 8/53 White.

2,774,004 12/56 Jafiee. 2,901,652 8/59 Fridrich. 2,922,912 1/ 60 Miller. 2,983,837 5/61 Mash.

FOREIGN PATENTS 764,867 1/57 Great Britain.

GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, Examiner.

Claims (1)

1. 2. IN AN ELECTROLUMINESCENT LIGHTING DEVICE HAVING A PAIR OF ELECTRODES, THE COMBINATION COMPRISING A CONTACT INTEGRAL WITH SAID LIGHTING DEVICE AND CONNECTED TO ONE OF SAID ELECTRODES, A LAYER OF ELECTRICALLY NON-CONDUCTIVE MATERIAL PROTECTIVELY COVERING SAID CONTACT AND A SUBSTANTIAL ADJOINING PORTION OF SAID LIGHT SOURCE, A LEAD-IN CONDUCTOR HAVING ONE END EMBEDDED IN SAID NON-CONDUCTIVE PROTECTIVE LAYER AND ANCHORED THEREBY IN CLOSE PROXIMITY TO SAID CONTACT, AND A LAYER OF ELECTRICALLY CONDUCTIVE MATERIAL BETWEEN AND CONNECTING THE EMBEDDED END OF SAID LEAD-IN CONDUCTOR AND SAID CONTACT, SAID LAYER OF CONDUCTIVE MATERIAL BEING FIRMLY BONDED TO THE CONTIGUOUS SURFACE OF SAID NON-CONDUCTIVE LAYER AND THEREBY PROVIDING A SEALED-IN LOW-RESISTANCE JUNCTURE BETWEEN SAID LEADIN CONDUCTOR AND SAID CONTACT.

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