Optically isotropic liquid crystal medium and optical device

A liquid crystal composition, comprising a compound of formula (1) and a chiral dopant, and exhibiting an optically isotropic liquid crystal phase:

• wherein in formula (1), R1 is a hydrogen atom, or C1-20 alkyl in which arbitrary —CH2— may be replaced by —O—, —S—, —COO—, —OCO—, —CH═CH—, —CF═CF— or —C≡C— and arbitrary hydrogen atom may be replaced by a halogen atom or C1-3 alkyl;
• the rings A1, A2, A3, A4 and A5 are each independently a benzene ring, a naphthalene ring, a thiophene ring, a piperidine ring, a cyclohexene ring, a bicyclooctane ring, a tetrahydronaphthalene ring or a cyclohexane ring, and in these rings arbitrary hydrogen atom may be replaced by a halogen atom, C1-3 alkyl, C1-3 alkoxy or C1-3 haloalkyl, —CH2— may be replaced by —O— or —S— and —CH═ may be replaced by —N═;
• Z1, Z2, Z3, Z4, Z5 and Z6 are each independently a single bond, or C1-4 alkylene in which arbitrary —CH2— may be replaced by —O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —CH═CH—, —CF═CF— or —C≡C— and arbitrary hydrogen atom may be replaced by a halogen atom;
• L1, L2 and L3 are each independently a hydrogen atom or a halogen atom;
• X1 is a hydrogen atom, a halogen atom, —C≡N, —N═C═S, —C≡C—C≡N, —SF5, or C1-10 alkyl in which —CH2— may be replaced by —O—, —S—, —CH═CH— or —C≡C—, and arbitrary hydrogen atom may be replaced by a halogen atom;
• l, m, n, o, and p are each independently 0 or 1, and 1+m+n+o+p≦4.