Abstract
We report three liquid crystal (LC) mixtures with a wide nematic range (−40°C to ~100°C), small visco-elastic coefficient and low activation energy for vehicular displays. Physical properties at different temperatures were characterized. These LCs greatly improve the performance of different display devices in a car: 1) for head-up projection using liquid-crystal-on-silicon with an average gray-to-gray (GTG) response time less than 1 ms at an elevated temperature. 2) The average GTG response time is maintained at ~10 ms for fringing field switching LCD at T = 0°C and also ~10 ms for twisted nematic LCD at T = −20°C.
Highlights
Several liquid crystal display (LCD) devices have been widely used in a vehicle [1], such as head-up display (HUD) [2], wearable display, instrument cluster display, center information display, and entertainment display [3]
1) MTN is commonly used for liquid-crystal-on-silicon (LCOS) reflective projection displays (e.g. HUD and wearable displays) [9], since it exhibits high transmittance, low operation voltage and small fringing field effect [10]
With a similar Tc, |Δε| and Δn, −Δε LC shows a much higher rotational viscosity than that of + Δε LC. This is because more dipole groups are needed for a −Δε LC to achieve the same |Δε| as a + Δε LC
Summary
Several liquid crystal display (LCD) devices have been widely used in a vehicle [1], such as head-up display (HUD) [2], wearable display, instrument cluster display, center information display, and entertainment display [3]. 1) MTN is commonly used for liquid-crystal-on-silicon (LCOS) reflective projection displays (e.g. HUD and wearable displays) [9], since it exhibits high transmittance, low operation voltage and small fringing field effect [10]. 2) Transmissive TN LCD is employed in instrument cluster displays since the device requires fast response time and high brightness. 2) The displays should remain operational at cold temperature, at least the LC should not freeze at −40°C, while keeping a reasonably fast response time below 0°C [14]. With overdrive voltage [17], the average GTG response time is further reduced by ~2X (< 10ms) at these low temperatures
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