Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
1998-11-12
2001-06-12
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S509000, C313S511000, C200S314000
Reexamination Certificate
active
06246169
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to the art of electroluminescent lamps and, particularly, to an electroluminescent lamp particularly adapted for use in a key pad.
BACKGROUND OF THE INVENTION
Electroluminescent lamp panels are known in the art. In general, an electroluminescent lamp typically includes a base electrode spaced from a transparent electrode for sandwiching an electroluminescent or phosphorescent layer therebetween. Often a dielectric layer also is sandwiched between the two electrodes. The base electrode may be a foil layer, such as a thin aluminum foil layer, or the base electrode may be a printed layer of conductive ink. Conductive leads extend from the base and transparent electrodes of the lamp. When an AC voltage is applied across the leads, the current induced between the base and transparent electrodes causes the phosphorescent layer to emit light, a phenomenon known as luminescence. An electroluminescent lamp essentially is a light emitting capacitor having a dielectric layer between two conductive electrodes, one of which is transparent, and the dielectric layer may be a phosphorescent layer, or there may be a separate dielectric layer. The transparent electrode layer typically is made of indium tin oxide (“ITO”) or indium oxide. Light is visible through the transparent electrode, and various electroluminescent chemicals are known to provide lights of various colors. Lamp panels can include one or a plurality of individual electroluminescent lamps.
In a typical electroluminescent lamp panel used as a keyboard, individual electroluminescent switch keys are used to actuate individual circuits, and individual electroluminescent lamps are associated with each key. The respective lamp may or may not be energized by the associated key. In any event, each key includes a dome-shaped actuator key mounted on top of a spacer on top of a printed circuit board which, in turn, is mounted on top of the layered or laminated electroluminescent lamp. The actuator key moves a conductive switch member through a hole in the spacer to close a gap between two circuit traces on the board. The circuit board typically is separated from the laminated electroluminescent lamp by still a further insulator. In order for the lower electroluminescent lamp to light-up the actuator key, the components of the electrical circuit, including the printed circuit board substrate, the insulator and the switch member must be light-transmissive to allow light from the subjacent electroluminescent lamp to pass therethrough. Problems with such prior art structures center around the higher costs involved in their fabrication as well as the loss of light by diffusion through the many light-transmissive components between the electroluminescent lamp and the actuator as well as blockage by opaque components.
The present invention is directed to solving these various problems by providing a unique arrangement wherein the components of the electroluminescent lamp are located immediately below a substrate, such as a dome-shaped substrate which can function directly as a switch key.
SUMMARY OF THE INVENTION
An object, therefore, of the invention is to provide a new and improved electroluminescent lamp, particularly such a lamp which is especially applicable for use in an electroluminescent lamp panel or keyboard, as well as a method of fabricating an electroluminescent key.
In the exemplary embodiment of the invention, the electroluminescent lamp includes a flexible dome-shaped, light transmissive substrate defining a top side and a bottom side thereof. An upper light transmissive electrode layer is applied on at least a portion of the bottom side of the dome-shaped substrate. An electroluminescent layer is applied below the upper light transmissive electrode layer. A lower electrode layer is applied below the electroluminescent layer. Therefore, running electrical current through the upper and lower electrode layers causes the electroluminescent layer to emit light through the upper electrode layer and directly through the flexible dome-shaped substrate. There are no extraneous circuits or circuit boards disposed between the electroluminescent lamp and the dome-shaped substrate or key.
As disclosed herein, the flexible dome-shaped substrate is preferably fabricated of polycarbonate, but other soft plastic materials may be suitable. A dielectric layer may be disposed between the electroluminescent layer and the lower electrode layer. A layer of graphic ink may be applied on the bottom side of the dome-shaped substrate. A layer of easily stretchable conductive material may be applied about at least a portion of the upper electrode layer for connecting the upper electrode layer to an electrical circuit. A silicone material may be provided under the concave side of the dome-shaped substrate.
The flexible dome-shaped substrate includes a peripheral side wall and a top wall. The peripheral side wall is preferably at an obtuse angle with respect to the top wall. The upper electrode layer and the electroluminescent layer are located beneath the top wall of the dome-shaped substrate. Still further, the flexible dome-shaped substrate is shown to be substantially surrounded by a generally flat substrate separated from the dome-shaped substrate by a peripheral cutout.
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Guharay Karabi
Molex Incorporated
Patel Nimeshkumar D.
Yesukevich Robert A.
LandOfFree
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