Patent ID: 8389073

Claim:
A compound represented by formula (1): wherein R 1 and R 2 are independently hydrogen, alkyl having 1 to 10 carbons, alkoxy having 1 to 9 carbons or alkoxyalkyl having 2 to 9 carbons and in the alkyl, alkoxy and alkoxyalkyl arbitrary hydrogen may be replaced by fluorine; the ring A 1 , the ring A 2 and the ring A 3 are independently 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,4-phenylene, tetrahydropyran-2,5-diyl, tetrahydropyran-3,6-diyl, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or 2,3-difluoro-1,4-phenylene; the ring G is tetrahydropyran-2,5-diyl or tetrahydropyran-3,6-diyl; Z 1 , Z 2 , Z 3 and Z 4 are a single bond; and k, m and n are independently 0 or 1, and the sum of k, m and n is 1.