外加高頻電壓下高分子分散液晶薄膜在電流體動力效應的光電特性

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

黃智國(Chih-Kuo Huang)

指導教授 ： 莫定山

崑山科技大學/工程學院/電子工程研究所/碩士(2009年)

https://doi.org/10.6828/KSU.2009.00077

摘要

在一般的高分子分散液晶薄膜，其電壓–穿透率曲線是一個單調上升的曲線，本論文利用強度極低的 UV 光照射固化，並且控制成膜時的溫度，可以成功的製作出大尺寸（20μm~30μm）液晶顆粒球、且分布均勻的高分子分散液晶薄膜。當此薄膜外加高頻率（50kHz~700KHz）電壓時，其液晶顆粒球內的液晶分子隨著電壓增加（0V~10V）而逐漸平行電場方向排列，進而使得穿透度逐漸上升至約40％；而當電壓繼續增加（11V~20V）時，則由於電流體渦流的產生，使得液晶顆粒球產生散射而造成穿透度下降的情形；持續增加電壓（21V~30V），則由於顆粒球內的液晶分子受到電流體渦流及熱效應的影響，使得在 polymer wall 附近的液晶分子也開始受到電場影響而能轉動，造成液晶顆粒球與聚合物間的光學邊界逐漸消失，進而形成顆粒球邊界散射減少，而使穿透度增加，其最高穿透度可達到接近100％。最後利用此薄膜對於不同頻率下所產生不同的光電曲線，而能夠製作出以頻率控制光穿透開關的元件，其對比度可達250左右。

關鍵字

高分子分散液晶薄膜 ； 電流體 ； 高頻電壓

並列摘要

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.

並列關鍵字

PDLC ； electrohydrodynamic ； high-frequency voltage

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