Abstract
The drying process plays an important part in manufacturing optical thin film by application of chromonic liquid crystals. The influence of the thickness of the applied wet film in the degree of orientation and homogeneity of the dry film is experimentally examined. An aqueous solution of Sunset Yellow FCF in 36wt% is used as a test sample. We introduced a new evaluation method of the dichroism and the film thickness simultaneously from the extinction and the transmitted light intensity. The extinction distribution of the whole application film is evaluated by the polarimetry technique with two-dimensional scanning and the distribution of the drying time from at each local point is measured by visualized images taken by the polarized light. The correlation of dying time and the evaluated dichroism and thickness is examined. In the case of the wet film applied by gap=2μm, the dichroism becomes higher and uniform compared with the case of gap=10μm. The film thickness of gap=2μm increases with increasing the dry time monotonically. The thick liquid film reduces the homogeneity and the result shows the widely scattered pattern. It is thought that the thicker liquid film is strongly affected by the phenomena of advection and transport in the drying process.
