FTIR reflection-absorption spectra of monolayers containing liquid crystals on LB film of a polyion complex with azobenzene-containing fatty acid and polycation were measured for various combinations of light irradiation and temperature, and the results provided clarification of molecular orientation in the liquid crystal layers and trans-cis photoisomerization of the polyion complex for each set of conditions. The driving force of change in orientation due to photoisomerization of the azobenzene-containing fatty acid was found to be mechanical force generated by steric interactions between liquid crystals in the upper layer and azobenzene-containing fatty acid in the bottom layer, while surface characteristics of the bottom layer had no effect. Further, greater inclination of the long axis of the liquid crystal was observed in the Liquid crystalline state at 50 degrees C, compared to the solid state at 25 degrees C.