For backlighting displays in handheld devices or watches, design engineers look for a high level of performance, efficiency and economy. Backlights illuminate LCDs from the back and are used in small displays to increase readability in low light conditions, such as on wristwatches. These backlights are also used in smart phones and other handheld devices to produce light in a manner similar to a CRT display.
Designers use Electroluminescent (EL) backlighting where a relatively simple passive-matrix monochrome display is required with geometrical flexibility and brightness of around 30 ft-L. In EL technology, a material emits light in response to the passage of an electric current or to a strong electric field. Advantages of EL backlights in handheld devices and timepieces include their uniform illumination of complex shapes, thinness, flexibility and minimal addition of weight to the design. EL lights are not directional like LCDs so they provide good visibility at all angles, another bonus for handheld device designs. In addition, they are relatively low in wattage and offer longer life than typical lighting solutions.