Optical properties of the difluoro substituted 4-(2-(or 3- ) fluoro phenylazo (-2'-(or 3'-) fluoro phenyl-4" -dodecyloxybenzoates thermotropic liquid crystal (III) were affected by the special new position and orientation of the two fluorine atoms. The compound III was dissolved in methylene chloride of different concentrations in order to determine its absorbance and transmittance in UV-visible region at room temperature. The maximum absorbance for the compound was in the blue region (447nm) and the molar absorption coefficient was found to be 0.93 (L. mMol^-1 .cm ^-1). The phase transition temperature was determined for the thermotropic LC compound III by using DSC, POM and modified spectrophotometer techniques as a new method. Nematic and smectic A phases during cooling process were observed. Refractive indices, birefringence, order parameter were measured. The molecular polarizability was determined also with different temperatures for the LC phases of compound III.