Temperature-Dependent Electro-Optic Performance Of Polymer-Dispersed Liquid Crystal Films

G. Paul Montgomery Jr.; Nuno A. Vaz; George W. Smith

doi:10.1117/12.947723

24 October 1988 Temperature-Dependent Electro-Optic Performance Of Polymer-Dispersed Liquid Crystal Films

G. Paul Montgomery Jr., Nuno A. Vaz, George W. Smith

Proceedings Volume 0958, Automotive Displays and Industrial Illumination; (1988) https://doi.org/10.1117/12.947723
Event: SPIE International Symposium on Optical Engineering and Industrial Sensing for Advance Manufacturing Technologies, 1988, Dearborn, MI, United States

Abstract

Polymer-dispersed liquid crystal (PDLC) films, consisting of micrometer-sized liquid crystal (LC) droplets dispersed in a polymer matrix, have considerable promise for a variety of electro-optic applications. VVe report the first measurements of the electro-optic performance of PDLC films over an extended temperature range. These properties are strongly sensitive to the liquid crystal microdroplet size. Calorimetric studies have shown that the droplet size is controlled by the rate at which the film is cured while the operating temperature range is determined, not by cure rate, but by the choice of liquid crystal and polymer matrix material. We have measured transmittance vs voltage and response time characteristics of PDLC films for temperatures from -10°C to 60°C. For thin (≈ 17.5 μm) films, transmittance of 70% or greater is achieved over this entire temperature range for driving voltages below 60 Vrms. Off-state transmittance of collimated light) is typically about 17o. The threshold voltage, at which transmittance begins to increase from its off-state value, and the voltage needed to achieve maximum transmittance both decrease with increasing temperature. Response times are rapid compared to those of conventional nematic liquid crystal devices. At a 60 Vrms driving voltage, rise time decreases from about 250 μs to 500 μs as temperature increases from -10°C to 60°C; even shorter rise times are measured at higher driving voltages. Decay times are nearly independent of voltage at temperatures above 0°C; at subzero temperatures, decay time increases with increasing voltage. This behavior can be explained in terms of molecular reorientation within the PDLC film. Decay times at -10°C range from 300 ms to 600 ms for voltages between 60 and 120 Vrms ; at temperatures above 15°C, decay times are below 50 ms for all voltages in this range. These results suggest that PDLC films of 12-25µm thickness are promising systems for future automotive displays.

Citation Download Citation

G. Paul Montgomery Jr., Nuno A. Vaz, and George W. Smith "Temperature-Dependent Electro-Optic Performance Of Polymer-Dispersed Liquid Crystal Films", Proc. SPIE 0958, Automotive Displays and Industrial Illumination, (24 October 1988); https://doi.org/10.1117/12.947723

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