Matthew Francis

Improved Liquid Crystal Mixtures for STN Displays

Supertwisted nematic (STN) liquid crystal displays remain a leading technology for mobile communications applications, personal digital assistants (PDA) and personal convergence devices. Higher demands on display information content place ever increasing demands on the physical parameters of the liquid crystal mixture. To satisfy current and future display requirements, it is necessary to develop mixtures showing: ? Fast response times achieved by rotational viscosity reduction and birefringence increase. ? Small temperature dependence of the operating voltage (dV/dT), especially at low temperatures. ? Small frequency dependence of the operating voltage (dV/df), necessary for multi-level greyscale operation. ? Improved steepness (V90/V10) of the electro-optical curve to enable higher duty multiplexing of the display. In order to fulfil these requirements, liquid crystal mixtures with improved physical properties were developed. Examples of these mixtures are presented.