Colour technology for transflective displays

Philips has just introduced a technology that enhances luminance and colour saturation in transflective liquid-crystal displays without significantly increasing power consumption.

With the colour-adjusting technology, users of mobile devices with these enhanced displays will be able to enjoy brighter colours and better viewing capability, regardless of lighting conditions.

With reflective and transmissive colour technologies, there has traditionally been a trade-off between colour saturation and reflectance (ie, colour performance and brightness). In current LCD technology, a single-colour film, or filter, always covers each pixel. Generally, thick filters are used for transmissive displays, while reflective displays utilise thin filters because the light passes the filter twice. If a filter is thin, it enables good reflectance but colour saturation is worse, creating a washed-out look. On the other hand, if the filter is thick enough to allow for better colour saturation, its poor reflectance results in too-dark a picture.

Philips' technology couples the advantages afforded by reflective displays with the strengths inherent in transmissive displays. Transflective displays operate in transmissive and reflective mode simultaneously. With a conventional filter, one can optimise the colour saturation and brightness of one mode only. One can favour good colour saturation in transmissive mode with a thick filter resulting in a poor reflectance and a washed-out look in reflective mode. On the other hand, a thin filter yields good colour saturation in reflective mode, but a washed-out look in transmissive mode.

The colour-adjusting technology optimises these tradeoffs, however, to ensure that neither brightness nor colour performance is sacrificed. With this technology, a corner of the pixel filter is made thinner than the rest of it, allowing light to pass through the filter unimpeded and without adding colour. As a result, colour saturation is improved through the thicker colour filter, while reflectance is equally improved as a result of the filter's partial reflectance window.