How electroluminescent circuits are made and applications for them
By John Jacobs
Electroluminescent (EL) circuitry is used today in the automotive industry, in specialty lighting, low-energy and flexible lighting, point-of-purchase displays, and for collectibles and specialty items. EL-circuit design and printing are as much art as science. Companies that have mastered or specialized in this kind of flexible-circuit printing have developed their own techniques and standards and keep them largely to themselves.
The basic elements of the EL circuit are no mystery. Conductive and dielectric materials sandwich a phosphor, similar to two slices of bread with condiments around a central core of deli meats, to produce a circuit that, when an alternating current (AC) is applied, excites the phosphor into emitting light (Figure 1).
The most obvious challenge in assembling this functional sandwich is that one side of the sandwich, both the conductor and dielectric, must be as translucent as possible to allow the light of the excited phosphor to emit from the circuit. There are direct current (DC) EL circuits, but those are presently less common than the traditional AC circuits and use distinctly different materials in the functional sandwich, so they are not discussed in this article.
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