The present invention relates to an optical article comprising a birefringent liquid crystal composition, said composition comprising more than 30% by weight based on the total weight of the composition of tolane compounds of formula R—S—Z1-A-Z2—NCS, in which R is a substituted or unsubstituted, linear or branched alkyl group, Z1 and Z2 are aryl groups, and A is an ethynyl group, an arylethynyl group or an ethynylarylethynyl group.