Electro-optical characteristics of polymer dispersed liquid crystal films based on electrohydrodynamic effect with applying high-frequency voltage

• Main Authors: Chih-Kuo Huang, 黃智國
• Other Authors: Ting-Shan Mo
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/tsf4jf

碩士 === 崑山科技大學 === 電子工程研究所 === 97 === In traditional polymer dispersed liquid crystal (PDLC) films, the transmittance-voltage curve (T-V curve) is a monotonously rising curve. In this thesis, we successfully fabricated the PDLC films with very large (20μm-30μm) and uniformly distributed liquid crystal droplets through controlling the film-grew temperature and cured UV light intensity. We applied high-frequency electric field (50 KHz-700 KHz) on the films and observed the variation of T-V curves. In the range of 0V-10V, the direction of liquid crystal molecules within the droplets reoriented parallel electric field direction and transmittance gradually increased to 40%. Increasing the voltage to 20V, the transmittance of the films decreased as a result of electro-hydrodynamic is produced and scattered the incident light. As the voltage increasing to 30V, influenced by electro-hydrodynamic and thermal effect, the LC molecules near the boundary between LC droplets and polymer walls could be reoriented easily. The scattering was reduced dramatically resulted from the boundary disappeared and the transmittance could reach to the value of 100%. Utilizing this film, we successfully fabricated a frequency switchable electro-optical device and its contrast ratio could be 250.