Influence of Drying Process on Distribution of Aggregates Orientation for Optical Anisotropic Film by Application of Chromonic Liquid Crystal

A process to produce the dichroic thin film by applying the chromonic liquid crystal, which is in the nematic phase, on the glass substrate is investigated. The influence of the drying process in the degree of orientation and homogeneity of the dry film is experimentally evaluated. During the drying process, the extinction suddenly increases at when the drying-front that is boundary of the wet and dry regions passes through the measurement point. The local drying time is defined by the time from the application of the thin film till the time when the drying-front passes at each local measurement point. We introduce a new evaluation method of the dichroism and the film thickness and evaluate their two-dimensional distribution on the dry film. In the case of the high concentration and high viscosity liquid, the dichroism is independent of the drying time. The thicker liquid film reduces the homogeneity and the dichroic property during the drying process. It means that the advection and the transport are caused and they disturb the aggregates orientation in the drying process. In order to produce the higher quality dichroic film, the higher viscous and thinner liquid film should be applicated to reduce the disturbance of the orientation in the drying process.