膽固醇液晶盒指紋結構形成之研究

Abstract

在本論文中，我們研究由改變邊界條件來觀察對膽固醇液晶分子相轉變所造成的影響，並由此討論及推測指紋結構形成的機制，同時也觀察當電壓與液晶盒厚度螺距比改變時，對指紋結構的影響，並找出形成的區間。其次，我們也對指紋結構的相位光柵，討論邊界與液晶盒厚度螺距比對繞射光的相位與偏極性的影響，同時觀察繞射點角度上的變化，也就是膽固醇液晶螺距對電場的變化。最後，我們實際量測了光柵對偏光片光效率提昇的效果。

The electric field induced cholesteric liquid crystal phase grating was formed by adjusting the thickness-natural pitch ratio d/p0 and applying voltage. The electric field was a quasi-static field and there was no backflow effect in the film. In this experiment we use two different surface rubbing directions to form fingerprint patterns. Substrates of the film were horizontally aligned by hard rubbing. Angle between the alignment directions of the upper and lower substrates was changed for investigating the stripes direction of fingerprint texture. We found that the rubbing directions on upper and lower substrates can change the direction of phase grating. In addition, the phase grating’s stripe can be changed by external field and LC elastic energy and surface anchoring energy. We also study the polarization characteristic of the light for some diffraction orders in various electric fields.