Abstract: Optical parts are obtained from the thermoplastic resin compositions containing alicyclic polyester, e.g., polycyclohexanedimethanolcyclohexane dicarboxylate as the alicyclic resin. The thermoplastic resin compositions contain alicyclic polyester as well as polycarbonate with the polycarbonate: alicyclic polyester weight ratio is in the range of 0:100 to 95:5, for optical elements having excellent chemical resistance and transmittance characteristics.

Abstract: Disclosed is a novel aromatic ester compound represented by the general formula ##STR1## in which Pn is a 1,4-phenylene group, R.sup.1 is an alkyl group having 1 to 4 carbon atoms, R.sup.2 is a group selected from the group consisting of perfluoroalkyl groups having 1 to 4 carbon atoms, cyano group, nitro group, 2,2-dicyanoethenyl group and methylsulfonyl group and the subscript n is a number of 2, 3 or 4. These aromatic ester compounds are useful as a second-order non-linear optical material in the ultraviolet wavelength range so that a resin film containing the compound has a good second-order non-linear optical coefficient d.sub.33 of 2-4.times.10.sup.-9 esu.