The temperature dependence of the infrared absorbance of the two discotic liquid crystals: hexapentyloxytriphenylene and hexaheptyloxytriphenylene was investigated in the columnar and isotropic phases. The orientational transition from the edge-on to the side-on alignment is observed for both materials in the columnar phases on the material heating. Temperature dependence of the orientational order parameter, S, for two transition dipole moments located in the molecular core have been evaluated; first for C-C stretching band and the second for C-H out of plane band of the triphenylene. At low temperature, the parameters are in excellent coincidence. On heating, however, the S parameter for the stretching band seems to be strongly affected by the tails disorder, while the other S parameter, for the C-H out-of-plane band, remains constant.