Liquid crystal mixture

摘要

1. Liquid crystal mixture possessing a net positive dielectric anisotropy consisting essentially of an at most weakly polar (DKA = 3) anisotropic and non-cyano component (A) and a strongly polar (DKA = 4) anisotropic cyano component (B), whereby, a) the non-cyano component (A) consists of one to five compounds of formula (1) see diagramm : EP0056501,P33,F1 wherein R**1 and R**2 are the same or different and are groups of the formulae CH3 (CH2 )n -, CH3 (CH2 )n-1 NH-, CH3 (CH2 )n-2 see diagramm : EP0056501,P33,F2 CH3 (CH2 )n-2 see diagramm : EP0056501,P33,F3 or CH3 (CH2 )n-1 -O- wherein n is an integer between 0 and 11, A**1 , A**2 and A**3 each represent a ring of formula (1a) to (1g), see diagramm : EP0056501,P33,F4 see diagramm : EP0056501,P33,F5 see diagramm : EP0056501,P33,F6 see diagramm : EP0056501,P33,F7 see diagramm : EP0056501,P33,F8 see diagramm : EP0056501,P33,F9 see diagramm : EP0056501,P33,F10 m is zero, one or two, and Z**1 and Z**2 are the same or different and represent covalent bonds, methyleneoxy (-CH2 O-), ethylene (-CH2 -CH2 -) or carboxyl groups see diagramm : EP0056501,P33,F11 with the provision that Z**1 and Z**2 cannot both be carboxyl groups at the same time, b) the cyano component (B) consists of one to five compounds of formula (2) see diagramm : EP0056501,P34,F1 in which R**3 is a group of formulae CH3 (CH2 )r -, CH3 (CH2 )r-1 NH-, CH3 (CH2 )r-2 see diagramm : EP0056501,P34,F2 CH3 (CH2 )r-2 see diagramm : EP0056501,P34,F3 or CH3 (CH2 )r-1 -O-, wherein r is an integer from 0 to 11, p is zero or one, Z**3 and Z**4 have the meaning given above for Z**1 and Z**2 and A**4 , A**5 and A**6 are rings of formulae (1a), (1b), (1c), (1d), (1e), (1f) or (1g) with the proviso that Z**3 and Z**4 are not both carboxyl groups and that Z**3 is not the carboxyl group when p is zero and A**4 is a ring of formula (1b), c) the non-cyano component (A) forms 50 to 95 mole of the mixture of (A) and (B) and d) either the non-cyano component (A) consists solely of compounds of formula (1) wherein in one of the groups R**1 , R**2 n = 2, or the cyano component (B) consists solely of compounds of formula (2) wherein in the group R**3 r = 2.