New Liquid Crystals Prevent Freezing of Car Touchscreens

Apart from appearing in almost every consumer electronic device, liquid crystal displays have recently found their way in car interiors such as in entertainment displays, navigation systems, instrument cluster displays and heads-up displays. However, due to restrictions in current display technology, the images blur and the displays sluggishly respond in harsh temperatures.

According to Shin-Tson Wu, Pegasus Professor of Optics and Photonics, University of Central Florida – College of Optics and Photonics, USA, when they turn on the car, they wanted to be sure that their GPS functions properly and not affected by extreme summer or winter temperatures.

Wu, along with his colleagues from the University of Central Florida, DIC Corporation, Japan, and Xi’an Modern Chemistry Research Institute in Xi’an, China, have recently developed three, new liquid crystal mixtures that have overcome previous physical restrictions on upper and lower operation temperatures.

Wu said in a statement that the liquid crystals must have a clearing point higher than 100° C, and a melting point below -40° C. Beyond this range, the liquid crystal would not function as it would be either isotropic or frozen.

In order to keep their liquid crystals operating at such a broad temperature range, the research team combined a dozen three-ring and four-ring compounds together with low molecular weight compounds. This mixture type is regarded a eutectic system. Apart from boosting the clearing point, the mixtures demonstrate activation energies and low viscoelastic coefficients. These properties play a huge role in maintaining low viscosity of the liquid crystals at low temperatures, as a liquid crystal display device’s response time is largely governed by the liquid crystal layer thickness and the viscoelastic coefficient.

Current European automotive standards need a response time for pixels to change from one brightness to another of 200 milliseconds at -20° C and 300 milliseconds at -30° C), which are inadequately quick to prevent an image blur. Wu and his colleagues reported a response time of nearly 10 milliseconds, around 20 times faster than the European requirements. Moreover, these mixtures enable field-sequential color display at a higher temperature, which leads to a tripling in display brightness and resolution density. Through this approach, the ambient contrast ratio of heads-up displays improve in the daytime.

Wu and his colleagues plan to develop extremely thin liquid crystal displays for integration with rearview mirrors to eliminate blind spots for drivers as well as enhance the readability of all types of automotive displays in harsh sunlight.