- 學位論文
高分子分散型液晶之液晶滴特性
Characteristics of Liquid Crystal Droplet of Polymer Dispersed Liquid Crystal
摘要
高分子分散型液晶為具有光學異方性的液晶滴均勻分散在固化的高分子網絡中。在無外加電壓的情況下，因液晶與高分子折射率的不匹配造成入射光散射而呈現霧狀。當外加電壓使液晶分子轉動至與電場平行的方向後，此時入射光因液晶滴與高分子的折射率相近而穿透。故可藉由調控外加電場，改變液晶滴與高分子間折射率的關係， 造成光散射與光穿透狀態。 在本研究中，我們探討高分子分散型液晶中液晶滴的光學、電性及表面特性等三部分：當照光強度越強或照光時樣品溫度越高時，液晶滴的尺寸會越小，光散射也越強，閾值電壓也越高。閾值電壓隨液晶盒厚度增加而增大。 在控制以上變因後，量測高分子分散型液晶的介電異方性(Δε)會隨摻雜鈦酸鋇濃度增加而增上升，閾值電壓下降。此外，高分子和液晶之接觸角隨液晶摻雜鈦酸鋇濃度增加而增大，推得液晶滴表面能隨之下降。
並列摘要
Polymer dispersed liquid crystal (PDLC) consists of the liquid crystal droplets which are uniformly dispersed in the polymer matrixes. When there is no external electric field, the light is scattered from the droplets because of the mismatched refractive index between the polymer and LC droplets, so that the appearance of PDLC is white. When an electric field is applied across the PDLC, the LC molecules rotate to the direction of the electric field, and the PDLC is transparent because the refractive index of polymer and LC droplet are matched. Therefore, we can manipulate the opaque and transparent states by the external electric field through the changes of the refractive index of the LC droplet. In this study, we explore the optical, electrical and surface characteristics of the liquid crystal droplets. When we increase the intensity of the curing light or temperature of the curing environments, the liquid crystal droplet size becomes smaller, the threshold voltage of PDLC is higher and scattered light is stronger. The threshold voltage is also higher in larger cell thickness. By controlling all the parameters, the dielectric anisotropy (Δε) of PDLC increases and hence the threshold voltage decreases as the concentration of BaTiO3 increases. In addition, that the contact angel between the polymer and LC increases as the concentration of BaTiO3 increases is due to the decrease of the surface energy.