Flow-Induced Molecular Orientation in Coating Flow of Concentrated Solution of Rod-Like Polymers and Its Application to Alignment Layer for Liquid Crystals

Abstract

The numerical simulations for the model coating flow of concentrated solutions of hydroxypropylcellulose (HPC) are carried out using the Doi model for rod-like polymers. The high degree of molecular orientation is induced by an elongational flow at the die lip and the molecules align parallel to the free surface. This molecular orientation near the free surface in coating flow is discussed in connection with the surface alignment of liquid crystals (LCs) on the HPC films. In the experiment on surface alignment of 5CB on the HPC film formed by coating, parallel surface alignment of 5CB is obtained in the conditions of large coating speed, thin coating thickness and high concentration of HPC. This tendency is well explained from the simulation results. From both the results of the numerical simulation and the experiment, it is confirmed that the surface alignment of LCs on the HPC films formed by coating results from the interaction of LC molecules with HPC molecules oriented parallel to the free surface.