ELECTROOPTICAL LIQUID CRYSTAL SYSTEM

摘要

The invention relates to an electrooptical liquid crystal system - which contains a dielectrically positive liquid crystal mixture and a further optically transparent medium between 2 electrodes which are optionally applied to substrate sheets, - whose liquid crystal molecules in the switched-off state have an irregular orientation, - in which one of the refractive indices of the liquid crystal mixture essentially agrees with the refractive index of the matrix nM and/or in which the quotient of the mass of the liquid crystal mixture and of the mass of the optically transparent medium is 1.5 or more and, - which, independently of the polarization of the incident light, has a reduced transmission in one of the two switch states compared to the other state and - whose liquid crystal mixture contains one or more compounds of the formula I I in which Q1 is and are independently of one another trans-1,4-cyclohexylene, 1,4phenylene, 2-fluoro-1,4-phenylene, 3fluoro-1,4-phenylene and one of A1 and, if present, A2, is also pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,3dioxane-2,5-diyl, tetrahydropyran-2,5-diyl or naphthalene-2,6-diyl, Z1 and Z2 are independently of one another a single bond, -CH2CH2-, -COO-, -OCO-, -C=C-, -CH2O- or any desired combinations of these bridge groups, Y and X are independently of one another H or F, and one of X and Y is also Cl, W is -CN, -Cl, -F, -CF3, -OCF3, -OCHF2, -NCS or R2 R1 and R2 independently of one another are alkyl having 1-12 C atoms, in which one or 2 non-adjacent CH2 groups can also be replaced by -O- or -HC=CH-, and m is 0, 1 or 2.