Patent ID: 7510749

Claim:
A liquid crystal compound comprising a compound selected from a group of compounds represented by formula (a): wherein Ra and Rb are each independently hydrogen, alkyl having 1 to 10 carbons or alkenyl having 2 to 10 carbons, provided that in the alkyl, â€”CH 2 â€” may be replaced by â€”Oâ€”, but plural â€”Oâ€” are not adjacent to each other, and hydrogen may be replaced by fluorine; ring A 1 and ring A 2 are each independently trans-1,4-cyclohexylene or 1,4-phenylene, provided that one or two hydrogens of the 1,4-phenylene may be replaced by halogen, and in a 6-membered ring of these groups, one â€”CH 2 â€” or two â€”CH 2 â€” that are not adjacent to each other may be replaced by â€”Oâ€”, and one or two â€”CHâ• may be replaced by â€”Nâ•; Z 1 and Z 2 are each independently a single bond, â€”(CH 2 ) 2 â€”, â€”(CH 2 ) 4 â€”, â€”CHâ•CHâ€”, â€”Câ‰¡Câ€”, â€”CH 2 Oâ€”, â€”OCH 2 â€”, â€”COOâ€”, â€”OCOâ€” or â€”OCF 2 â€”; l and m are each independently 0, 1 or 2, provided that l+m is 0, 1, 2 or 3; and n is an integer of from 0 to 6, provided that in â€”(CH 2 ) n â€”, â€”CH 2 â€” may be replaced by â€”Oâ€”, but plural â€”Oâ€” are not adjacent to each other, and hydrogen may be replaced by fluorine.