PURPOSE: To provide a new trifluorolactic acid derivative exhibiting smectic C phase over a wide temperature range, having large spontaneous polarization and effective in increasing the response speed when applied to an optical switching element.

CONSTITUTION: The compound of formula I [R1 and R2 are (substituted) alkyl; A, D and E are (substituted) 1,4-phenylene, 1,4-cyclohexylene, 2,5-pyrimidylene or 2,5-pyridylene; X is single bond, O, COO, OCO, OCOO or CO; Y and Z are COO, OCO, OCH2, CH2O or single bond; (n) is 0 or 1], e.g. 4-(4'- octyloxybiphenyl-4-carbonyloxy)benzoic acid 2,2,2-trifluoro-1-hexyloxycarbonylethyl ester. The compound can be produced by reacting a carboxylic acid having the core part of formula II with a trifluorolactic acid ester of formula III.