Patent ID: 7351452

Claim:
A liquid crystal compound of formula (I) or a dimer thereof; where R 1 and R 2 are independently selected from optionally substituted alkyl, and a functional group selected from halo, cyano, nitro, oxo, C(O)R a , OR a , S(O) t R a , NR b R c , OC(O)NR b R c , C(O)NR b R c , OC(O)NR b R c , —NR c C(O) n′ R b , —NR a CONR b R c , —NR a CSNR b R c , —C═NOR a , —N═CR b R c , S(O) t NR b R c , or —NR b S(O) t R a where R a , R b and R c are independently selected from hydrogen or optionally substituted hydrocarbyl, or R b and R c together form an optionally substituted ring which optionally contains further heteroatoms such as S(O) s , oxygen and nitrogen, s is 0, 1 or 2, t is 0 or an integer of 1-3, or a group of sub-formula (i) provided that at least one of R 1 or R 2 is a group of sub-formula (i); —(O) m —(CH 2 ) p —R 7 (i) where m is 0 or 1; p is an integer of from 3 to 12; R 7 is a group of formula —C q X 2q+1 where q is an integer of from 2 to 12 and X is halogen, or R 7 is a group of sub-formula (ii) where k is an integer of from 1 to 10, R 8 , R 10 , and R 12 and each R 9 and R 11 are independently selected from alkyl, alkenyl or aryl; R 3 , R 4 , R 5 and R 6 are independently selected from hydrogen or halogen, n is 0 or 1, and A is a group of sub-formula (iii), (iv), (v), (vi) or (vii) where R 13 , R 14 , R 15 , R 16 , R 17 , R 18 and R 19 are independently selected from hydrogen or halo, and the group A may be orientated in either direction, so that the group R 2 is attached at either of the available bonds in sub-formula (iii)-(vii); and further provided that where R 2 is a group of sub-formula (i), m=1, n=0, p=3 and R 3 , R 4 , R 5 and R 6 are each hydrogen and R 7 is a group of sub-formula (ii) in which k=1, R 8 , R 9 , R 10 and R 11 are each methyl and R 12 is a phenyl group, then R 1 shall not be either OMe or OBu; and further provided that at least one of the rings carries one or more halo atoms.