Electroluminescent Lamps (EL)
An EL lamp is a LEC (Light Emitting Capacitor). As with any capacitor the LEC is made of a dielectric material sandwiched between two parallel conductors. It differs from a normal capacitor because the dielectric is a phosphor that will emit light when energised with an alternating electric field and the top conductor is transparent which allows the illuminating phosphor to be visible.
EL lamps are thin, flat, with flexible cold illumination sources that can be cut into complex shapes and be easily inserted into products where space and/or power are limited. They are commonly used where back lighting is required, for example in LCD displays, aircraft instrument panels, mobile phones, advertising signage etc.
The flexibility of an EL lamp allows curved surfaces to be illuminated and they can withstand stress when used over a membrane touch switch. The transparent conductor in an EL lamp is usually a polyester film with a conductive coating, this coating is either Indium Tin Oxide (ITO) which is sputtered evenly across the surface of the film or created with conductive inks screen printed on to the surface. The polyester films used in the construction of EL lamps can either be heat stabilised or hard coated films, the choice is determined by the actual application.
MacDermid Autotype offer a range of heat stabilised and hard coated polyester films that have excellent receptivity to both ITO sputtering and screen printing with conductive inks. For further details on these products see the product information section on Autostat for heat stabilised films and Autoflex and Autotex for hard coated films.