New liquid crystal mixtures keep touchscreens from freezing

Researchers from the University of Central Florida have been working to develop new liquid crystal mixtures for use in LCDs inside cars and other devices that are able to operate at both high and low temperatures. The goal of the team of researchers is to create a display screen that performs just as well in temperature extremes as it does in moderate climates. According to the team, current LCDs have images that blur and displays are slow to respond in extreme temperatures.

The research is being led by Shin-Tson Wu, Pegasus Professor of Optics and Photonics and colleagues from Xi'an Modern Chemistry Research Institute in Xi'an China and DIC Corporation in Japan. "When we turn on the car, we want to be certain our GPS is functioning properly and not affected by extreme winter or summer temperatures," said Wu. Wu and his team have come up with three new liquid crystal mixtures that are able to overcome the limitations of current mixtures in extreme high and low temperatures.

Wu says that the mixtures he and his team have devised have a clearing point higher than 100C or 212F and a melting point below -40C. Outside that temperature range, the LCD wouldn't function. The new mixtures contain a combination of a dozen three-ring and four-ring compounds with low molecular weights; the mixture is a eutectic system. The mixture is able to maintain a low viscosity in low temperatures.

In Europe, automotive standards dictate that LCDs need a response time for pixel change from one brightness to another of 200ms at -20C and 300ms at -30C to avoid image blurring. The mixture that Wu and his colleagues have invented is able to deliver response times of 10ms in both conditions making it about 20 times faster than the standards dictate.

Another benefit of these new liquid crystal mixtures is the enabling of field-sequential color displays at elevated temperatures offering triple the resolution density and brightness. The increase in brightness and resolution will improve ambient contrast ratio for heads-up displays during daylight hours.

The researchers plan to use the mixtures to develop very thin LCDs in the future that can be integrated into rearview mirrors to eliminate blind spots for drivers and to improve the readability of automotive screens in direct sunlight. I hope that the new materials can also keep GPS screens from dying prematurely when left in a car during the Texas summer.