Liquid-crystalline medium

Abstract

The invention relates to a liquid-crystalline medium based on a mixture of polar compounds of positive dielectric anisotropy, characterised in that it comprises one or more ester compounds of the formula I and one or more compounds of the formula IA in which R 1 , R 2 , ring A, ring B. L 1-6 , Z 1 , Z 2 , X 1 and X 2 are as defined in claim 1.

1 . A liquid-crystalline medium based on a mixture of polar compounds of positive dielectric anisotropy, comprising at least one ester compound of formula I  
       
         
           
           
               
               
           
         
       
       and at least one compound of formula Ia  
       
         
           
           
               
               
           
         
       
       wherein: 
 R 1  and R 2  are each, independently H, a halogenated unsubstituted alkyl radical having from 1 to 15 carbon atoms, where one or more CH 2  groups in these radicals is optionally independently replaced by —C≡C—, —CH═CH—, —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another,  
 X 1  and X 2  are each, independently F, Cl, CN, SF 5 , SCN, NCS, a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, each having up to 6 carbon atoms,  
 Z 1  and Z 2  are each, independently —CF 2 O—, —OCF 2 — or a single bond, where Z 1 ≠Z 2 ,  
                     
 are each, independently  
                     
 L 1-6  are each, independently H or F.  
 
     
     
         2 . The liquid-crystalline medium according to  claim 1 , comprising at least one compound of formulae IA1-IA25:  
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
         3 . The liquid-crystalline medium according to  claim 1 , comprising at least one compound of formulae I-1 to I-5 
       
         
           
           
               
               
           
         
       
     
     
         4 . The liquid-crystalline medium according to  claim 1 , additionally comprising at least one compound of the formulae II, III, IV, V or VI:  
       
         
           
           
               
               
           
         
       
       wherein: 
 R 0  is H, n-alkyl, oxaalkyl, fluoroalkyl or alkenyl, each having up to 9 carbon atoms,  
 X 0  is F, Cl, halogenated alkyl, alkenyl or alkoxy having up to 6 carbon atoms,  
 Z 0  is —C 2 F 4 —, —CF═CF—, —C 2 H 4 —, —(CH 2 ) 4 —, —CF 2 O—, —OCF 2 —, —OCH 2 — or —CH 2 O—,  
 Y 1  and Y 2  are each, independently H or F, and  
 r is 0 or 1.  
 
     
     
         5 . The medium according to  claim 4 , having a proportion of compounds of formulae IA and I to VI together in the mixture as a whole of at least 50% by weight.  
     
     
         6 . The medium according to  claim 1 , additionally comprising at least one compound of formulae Ea to Ed  
       
         
           
           
               
               
           
         
       
       in which R 0  is H, n-alkyl, oxaalkyl, fluoroalkyl or alkenyl, each having up to 9 carbon atoms.  
     
     
         7 . The medium according to  claim 1 , comprising at least one compound of formulae IIa to IIg  
       
         
           
           
               
               
           
         
       
       in which R 0  is H, n-alkyl, oxaalkyl, fluoroalkyl or alkenyl, each having up to 9 carbon atoms.  
     
     
         8 . The liquid-crystalline medium according to  claim 1 , comprising at least one compound of following formulae:  
       
         
           
           
               
               
           
         
       
       in which 
 R 0  is n-alkyl, oxaalkyl, fluoroalkyl, alkenyloxy or alkenyl, each having up to 9 carbon atoms,  
 Y 1  is H or F,  
 alkyl and alkyl* are each, independently a straight-chain or branched alkyl radical having 1-9 carbon atoms,  
 alkenyl and alkenyl* are each, independently a straight-chain or branched alkenyl radical having up to 9 carbon atoms.  
 
     
     
         9 . The liquid-crystalline medium according to  claim 1 , characterised in that the proportion of compounds of the formula IA in the mixture as a whole is 5 to 40% by weight.  
     
     
         10 . An electro-optical liquid-crystal display containing a liquid-crystalline medium according to  claim 1.