Tetralin compound, liquid crystal material and liquid crystal composition

The invention to provide novel tetralin compounds, liquid crystal materials and liquid crystal compositions, which can constitute a liquid crystal element affording a wide operating temperature range, a high switching speed and a small consumption of electric power as well as a stable contrast. The tetralin compound of the invention is represented by the following formula [I]wherein R1 is an alkyl group or a polyfluoroalkyl group of 3-20 carbon atoms (wherein one -CH2- or 2 or more -CH2- or -CF2- not adjacent to each other in these groups may be substituted with -O-), X is -COO-, -O- or a single bond, A is each independently selected from (Z1 and Z2 are hydrogen or fluorine), Y is a group selected from -COO-, -CH2O-, -OCH2-, and -CH2CH2-, R1* is an optically active group represented by the formula -C*H-(CF3)-(CH2)m-O-CnH2n+1 [II]. (m is an integer of 2-5, and n is an integer of 1-3.).