Liquid-crystalline medium, and liquid-crystal display containing same

Abstract

Liquid-crystalline media comprising one or more compounds of each of the formulae I and II in which R 1 , R 21 , R 22 , L, Y 21 , Y 22 , n and m are as defined herein, and liquid-crystal displays containing same, have low frequency dependence of the dielectric properties in particular at low temperatures.

1 . A liquid-crystalline medium of positive dielectric anisotrophy, comprising: one or more compounds of formula I  
       
         
           
           
               
               
           
         
       
       wherein 
 R 1  is alkyl or alkoxy having in each case 1 to 12 carbon atoms, or alkenyl, alkoxyalkyl or alkenyloxy having in each case 2 to 12 carbon atoms, and  
 L is H or F; and 
 one or more compounds of formula II  
                     
 wherein  
 
 R 21  is alkyl or alkoxy having in each case 1 to 7 carbon atoms, alkenyl, alkoxyalkyl or alkenyloxy having in each case 2 to 7 carbon atoms, F, Cl, OCF 3  or OCF 2 H,  
 R 22  is H or alkyl having 1 to 10 carbon atoms,  
 Y 21  and Y 22  are each, independently of one another, H or F,  
 n is from 0 to 5, and  
 m is 0 or 1.  
 
     
     
         2 . A liquid-crystalline medium according to    claim 1   , wherein said medium contains one or more compounds of formula Ia  
       
         
           
           
               
               
           
         
       
       wherein 
 R 1  is alkyl having 1 to 12 carbon atoms or alkenyl having 2 to 12 carbon atoms.  
 
     
     
         3 . A liquid-crystalline medium according to    claim 1   , wherein said medium contains one or more compounds of formula IIa  
       
         
           
           
               
               
           
         
       
     
     
         4 . A liquid-crystalline medium according to    claim 2   , wherein said medium contains one or more compounds of formula IIa  
       
         
           
           
               
               
           
         
       
     
     
         5 . A liquid-crystalline medium according to    claim 1   , wherein said medium contains one or more compounds of formula II, in which 
 R 21  is alkyl having 1 to 7 carbon atoms or alkenyl having 2 to 7 carbon atoms,    R 22  is H or alkyl having 1 to 3 carbon atoms, and    n is 0.    
     
     
         6 . A liquid-crystalline medium according to    claim 1   , wherein said medium contains two or more compounds of the formula I.  
     
     
         7 . A liquid-crystalline medium according to    claim 2   , characterized wherein said medium contains one or more compounds of formula Ia in which R′ is alkenyl having 3 to 5 carbon atoms.  
     
     
         8 . A liquid-crystalline medium according to    claim 1   , wherein said medium contains one or more compounds of formula Ia  
       
         
           
           
               
               
           
         
       
       and one or more compounds of formula IIb  
       
         
           
           
               
               
           
         
       
     
     
         9 . A liquid-crystalline medium according to    claim 1   , further comprising one or more compounds selected from the formulae III to VII:  
       
         
           
           
               
               
           
         
       
       wherein 
 R 31 , R 32 , R 41 , R 42 , R 51  and R 52  are each, independently of one another, H, alkyl or alkenyl having 1 to 15 carbon atoms, alkyl or alkenyl having 1 to 15 carbon atoms and which is monosubstituted by CN, CF 3  or halogen, wherein in each case one or more CH 2  groups in the alkyl or alkenyl radicals is optionally replaced by, in each case independently of one another, —O—, —S—,  
                     
 —CO—, —CO—O—, —O—CO or —O—CO—O—, in such a way that O atoms are not linked directly to one another;  
 A 31 , A 32 , A 41 , A 42 , A 43 , A 51 , A 52 , A 53 , A 54 , A 71  and A 72  are each, independently of one another, 
 (a) trans-1,4-cyclohexylene, in which, optionally, one or more nonadjacent CH 2  groups is replaced by, in each case independently, —O— or —S—,  
 (b) 1,4-phenylene, in which, optionally, one or two CH groups is replaced by N,  
 (c) 1,4-cyclohexenylene, 1,4-bycyclo[2.2.2]octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl,  
 
 where the radicals of group (a) and (b) are unsubstituted or substituted by one or two fluorine atoms;  
 Z 3 , Z 41 , Z 42 , Z 51 , Z 52 , Z 53 , Z 71  and Z 72  are each, independently of one another, —CO—O—, —O—CO—, —CH 2 O—, —OCH 2 —, —CH 2 CH 2 —, —CH═CH—, —C≡C— or a single bond, or alternatively —(CH 2 ) 4 — or —CH═CH—CH 2 CH 2 —;  
 R 6  is alkyl having 1 to 7 carbon atoms;  
 X is F, Cl or OCF 3 ;  
 Y 61  Y 62 , Y 71  and Y 72  are each independently of one another, H or F;  
 R 7  is alkyl or alkoxy group having 1 to 12 carbon atoms, or alkenyl or alkenyloxy group having 2 to 12 carbon atoms;  
 X 7  is CN, F, Cl, —CF 3 , —CF 2 Cl, —CFHCl, —CF 2 H, —OCF 3 , —OCF 2 Cl, —OCFHCl or —OCHF 2 ; and  
 l is 0 or 1.  
 
     
     
         10 . A liquid crystal medium according to    claim 9   , wherein said medium contains one or more compounds of formulae IIIa-IIIc.  
       
         
           
           
               
               
           
         
       
       wherein 
 R 31  and R 32 , independently of one another, are each alkyl or alkoxy having 1 to 7 carbon atoms, or alkenyl, alkenyloxy or alkoxyalkyl having 2 to 7 carbon atoms.  
 
     
     
         11 . A liquid crystal medium according to    claim 9   , wherein said medium contains one or more compounds of formulae IVa-IVb  
       
         
           
           
               
               
           
         
       
       wherein 
 R 41  and R 42 , independently of one another, are each alkyl or alkoxy having 1 to 7 carbon atoms, or alkenyl, alkenyloxy or alkoxyalkyl having 2 to 7 carbon atoms, and  
 L 41  is H or F.  
 
     
     
         12 . A liquid crystal medium according to    claim 9   , wherein said medium contains one or more compounds of formulae Va-Vb  
       
         
           
           
               
               
           
         
         R 51  and R 52 , independently of one another, are each alkyl or alkoxy having 1 to 7 carbon atoms, or alkenyl, alkenyloxy or or alkoxyalkyl having 2 to 7 carbon atoms, and  
         L 51  is H or F.  
       
     
     
         13 . A liquid crystal medium according to    claim 9   , wherein said medium contains one or more compounds of formulae VIIa-VIIb  
       
         
           
           
               
               
           
         
       
       wherein 
 R 7  is n-alkyl having 2 to 7 carbon atoms or alkenyl having 2 to 7 carbon atoms,  
 X 7  is F or CN, and  
 Y 71  is H or F.  
 
     
     
         14 . In an electro-optical display element containing a liquid-crystalline medium, the improvement wherein said medium is a medium according to    claim 1   .  
     
     
         15 . In an electro-optical display containing one or more electro-optical display elements, the improvement wherein said display contains at least one display elements according to    claim 14   .  
     
     
         16 . In a method of generating an electro-optical display using one or more electro-optical display elements, the improvement wherein at least one display element according to    claim 14    is used to generate said display.