Scientists from Philips have replaced a laminated optical foil used in a transflective liquid-crystal display (LCD) by a patterned coating. The result is a thinner and brighter LCD that is also less power hungry.
Transflective LCDs are widely used mobile applications because their use of both backlighting and reflection of ambient light makes them highly visibile in virtually all lighting conditions.
A major disadvantage of conventional systems, however, is that the retarder (a laminated foil that modifies the polarisation state) cannot be oriented for both transmission and reflection modes independently. This results in a trade-off between contrast and brightness, or between contrast and viewing angle.
The new technology, invented by Philips Research, replaces the external foil retarder with an ‘in-cell retarder’ integrated as a coating into the liquid-crystal cell itself. A major advantage of the in-cell technology is that the optical properties can be varied (‘patterned’) across each pixel, allowing the retarder to be optimised for both transmissive and reflective modes.
Replacement of the external retarder with an in-cell solution which is no more than 1um thick also significantly reduces the overall thickness of the LCD cell.
Displays using the new technology will be shown for the first time at the International Symposium of the Society for Information Display 2003, which starts today in Baltimore, MD.