Patent ID: 7618688

Claim:
A nematic liquid crystal compound represented by any one of formulas (a-1) to (a-6): wherein in formulas (a-1) to (a-6), (i) Ra and Rb are each independently alkyl having 1 to 10 carbons, provided that in the alkyl, —CH 2 — may be replaced by —O—, —(CH 2 ) 2 — may be replaced by —CH═CH—, and hydrogen may be replaced by a halogen; (ii) ring A 1 and ring A 2 are each independently trans-1,4-cyclohexylene or 1,4-phenylene, provided that in these rings hydrogen may be replaced by a halogen, and in the case where the ring is trans-1,4-cyclohexylene, —CH 2 — may be replaced by —O—, and —CH 2 CH— may be replaced by —CH═C—; and (iii) Z 1 and Z 2 are each independently a single bond, —COO—, —OCO—, —OCH 2 —, —CH 2 O— or —CH 2 CH 2 —; and wherein in formula (a-3) Z 2 is a single bond, —COO—, —OCO—, —OCH 2 — or —CH 2 O— when ring A 2 is trans-1,4-cyclohexylene; and Z 2 is a single bond and ring A 2 is trans-1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2-fluoro-3-chloro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene or 2,3-dichloro-1,4-phenylene when Ra is —C 3 H 7 , Rb is —OC 2 H 5 ; and wherein in formula (a-4) Z 1 is a single bond, —COO—, —OCO—, —OCH 2 — or —CH 2 O— when ring A 1 is trans-1,4-cyclohexylene.