| Summary: | 碩士 === 國立成功大學 === 物理學系 === 102 === The photo-alignment of liquid crystals by laser-induced adsorption in an azo-dye doped liquid crystal (ADDLC) is studied in this work. The adsorption efficiency of azo-dye (methyl red) in a DDLC cell fabricated using different substrates, such as as-clean glass, ITO coated glass, ITO coated PET and barrier coated PET, differs from one another. The surface energies of different substrates are investigated with sessile drop method. The result shows that surface polarity controls the nucleation and initial growth of methyl red adsorption on different surfaces while the laser intensity is responsible for the time required for complete adsorption. It is found that adsorption rate is proportional to the pumping intensity. Yet, the order of the adsorbed dye decreases with increasing laser intensity. Also, the adsorption rate on various cell substrates in order is glass, ITO PET, ITO glass and finally barrier PET. Furthermore, oxygen plasma is applied for modifying the surface condition of different substrates. The morphology of as-formed methyl red layer on different surfaces is highly influenced by oxygen plasma via the change of surface energy, the polar term especially. Therefore, the performance and efficiency of photo-alignment can be enhanced by oxygen plasma treatment.
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