Electroluminescent (EL) panels are found in many electronics applications, particularly as backlighting for LCD displays, keypads, watches, and other areas requiring uniform, low-power illumination. While relatively flexible, when EL panels made from plastic are bent too sharply, fractures and a severely diminished output usually result. As a result, EL panels have generally been restricted to flat or slightly curved surfaces. However, researchers from Karlsruhe Institute of Technology (KIT) and Franz Binder GmbH & Co have now developed a new manufacturing process to print EL panels directly onto the surface of almost any convex and concave shape. Even, apparently, onto spheres.
Inessence, the new technique involves printing electroluminescent layers directlyonto an object without any intermediate carrier layer (the plastic material mentioned earlier). In this way, convex and concavesurfaces of various materials can be made to glow when an electric current isapplied.
"By meansof the innovative production process we developed together with our industrypartner, any type of three-dimensional object can be provided with electroluminescentcoatings at low costs," said Doctor Ing. Rainer Kling, associate professor at the Light TechnologyInstitute of KIT.
Electroluminescentpanels are a very popular way to backlight a screen, particularly as theyprovide an even glow across their entire face, use very little power, andgenerate almost no heat. And they have been around for longer than you mightthink. Believe it or not, General Electric has had patents on them since 1938,and EL panels have been in use in automobiles since at least 1960 when Chryslerused them in their prestige models.
Essentiallythe equivalent of a capacitor when used in an AC (Alternating Current) circuit,EL panels encase theirlight-emitting material between two electrodes. In standardpanels, one electrode is generally clear glass or plastic coated with a transparent conductive coating, while theopaque rear electrode is generally made from a reflective metal foil.
In theKIT/Binder EL panel, however, the production process sees different componentsof the coating (specifically the electroluminescent and electrically conductiveingredients) applied using a new and unique pad printing process. The printingmachine is furnished with an elastic rubber pad that deforms when applying thecoatings, thereby being able to conform to uneven or complex 3D shapes.
"In thisway, it is possible to provide surfaces and even spheres with homogeneouscoatings at low costs," said Elodie Chardin, an engineer working on theproject. "Homogeneity of the coating of about one tenth of a millimeter inthickness was one of the challenges of this project."
Though Saarland University announced a prototype EL printing method earlier this year using ink-jet printers, the KIT/Binder version seems to be the first to produce such coatings on a commercial scale. The process also only requiresvery few production steps, which saves money and resources, and a large range colors may beapplied to the same surface, thereby providing more versatility to the 3D EL panels.
The short video below shows the process in action on ordinary paper.
Source: Karlsruhe Institute of Technology
