| 摘要 |
To improve switching times, especially at low temperatures, one or more reactive liquid crystalline compounds is added to a liquid crystal mixture used in an electroptical system. The electroptical system comprises a PDLC film comprising a liquid crystal mixture forming micro- droplets in an optically isotropic, transparent polymer matrix between 2 electrode layers, one of the refractive indices of the liquid crystal mixture is matched to the refractive index of the polymer matrix, the PDLC film exhibits an electrically switching transparency essentially independent of the polarization of the incident light, the precursor of the PDLC film comprises one or more monomers, oligomers and/or prepolymers and a photoinitiator, and is cured photoradically, the liquid crystal mixture comprises one or more compounds of the formula I wherein R, A1, A2, Z1, Z2, X1, X2, Q, Y and n are as defined herein. independently of one another, are trans-1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene or 3,5-difluoro-1,4-phenylene and one of may also be pyrimidine-2,5-diyl, pyridine-2,5-diyl or trans-1,3-dioxane-2,5-diyl, X1 and X2, independently from one another, are H or F, Q is -CF2, -OCF2, -C2F4, -OC2F4 or a single bond, Y is -H, -F, -Cl or -CN, n is 0, 1 or 2 and R is alkyl having up to 13 C atoms, in which one or two non-adjacent CH2 groups can also be replaced by -O- and/or -CH=CH- characterized in that the liquid crystal mixture additionally contains one or more reactive liquid crystalline compounds in order to obtain improved switching times especially at low temperatures.
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