Liquid crystal device and a method for manufacturing thereof

Abstract

The invention relates to a liquid crystal device comprising a liquid crystal bulk layer and a surface-director alignment layer comprising side-chains arranged to interact with the bulk layer, wherein the orientation of the bulk layer molecules and the orientation of said side-chains each is directly controllable by an electric field via dielectric coupling, thus resulting in a decreased total time period (rise and decay times) needed to switch and relax the liquid crystal bulk molecules in response to an applied external field. The invention also relates to a method for manufacturing a liquid crystal device and a method of controlling a liquid crystal bulk layer.

1 . A liquid crystal device comprising a liquid crystal bulk layer presenting a surface-director at a bulk surface thereof, and a surface-director alignment layer comprising side-chains arranged to interact with the bulk layer at said bulk surface for facilitating the obtaining of a preferred orientation of the surface-director of the bulk layer, wherein the orientation of the molecules of the liquid crystal bulk layer and the orientation of said side-chains of the surface-director alignment layer each is directly controllable by an electric field via dielectric coupling.  
   
   
       2 . A liquid crystal device according to  claim 1 , wherein the liquid crystal bulk layer and the surface-director alignment layer exhibit dielectric anisotropies (Δε) of opposite signs.  
   
   
       3 . A liquid crystal device according to  claim 1 , wherein the liquid crystal bulk layer and the surface-director alignment layer exhibit dielectric anisotropies (Δε) of same sign.  
   
   
       4 . A liquid crystal device according to  claim 1  comprising a first and a second surface-director alignment layer, wherein the liquid crystal bulk layer and the first surface-director alignment layer exhibit dielectric anisotropies (Δε) of opposite signs, and the liquid crystal bulk layer and the second surface-director alignment layer exhibit dielectric anisotropies (Δε) of same sign.  
   
   
       5 . A liquid crystal device according to  claim 1 , wherein the surface-director alignment layer comprises structural parts exhibiting dielectric anisotropies (Δε) of opposite signs.  
   
   
       6 . A liquid crystal device according to  claim 2  further comprising at least one confining substrate, and wherein an orthogonal projection of said surface-director on said substrate, termed projected surface-director, presents said preferred orientation in a geometrical plane in parallel with said substrate, termed preferred field-off planar orientation, and the orientation of the molecules of said bulk layer is directly controllable by an applied electric field to perform an out-of-plane switching of said preferred planar orientation of the projected surface-director to a field-induced vertical orientation.  
   
   
       7 . A liquid crystal device according to  claim 2  further comprising at least one confining substrate, and wherein an orthogonal projection of said surface-director on a geometrical plane perpendicular to said substrate, termed projected surface-director, presents said preferred orientation, termed preferred field-off vertical orientation, and the orientation of the molecules of said bulk layer is directly controllable by an applied electric field to perform an out-of-plane switching of said preferred vertical orientation of the projected surface-director to a field-induced planar orientation.  
   
   
       8 . A liquid crystal device according to  claim 6 , wherein the electric field is applied normally to said at least one confining substrate.  
   
   
       9 . A liquid crystal device according to  claim 3  further comprising at least one confining substrate, and the orientation of the molecules of said bulk layer is directly controllable by an applied electric field to perform an in-plane switching of an initial first planar orientation to a field-induced second planar orientation, whereas an orthogonal projection of said surface-director, termed projected surface-director, presents said preferred orientation in a geometrical plane in parallel with said substrate, termed preferred field-induced planar orientation.  
   
   
       10 . A liquid crystal device according to  claim 9 , wherein the electric field is applied in parallel with said at least one confining substrate.  
   
   
       11 . A liquid crystal device according to  claim 1 , wherein the liquid crystal bulk layer comprises a nematic liquid crystal.  
   
   
       12 . A liquid crystal device according to  claim 1 , wherein the surface-director alignment layer comprises a polymer having a polymeric backbone and side-chains attached thereto, said polymeric backbone lacks directly coupled ring structures and each side-chain of at least some of the side-chains, 
 (i) comprises at least two unsubstituted and/or substituted phenyls coupled via a coupling selected from the group consisting of a carbon-carbon single bond (—), a carbon-carbon double bond containing unit (—CH═CH—), a carbon-carbon triple bond containing unit (—C≡C—), a methylene ether unit (—CH 2 O—), an ethylene ether unit (—CH 2 CH 2 O—), an ester unit (—COO—) and an azo unit (—N═N—),    (ii) exhibits a permanent and/or induced dipole moment that in ordered phase provides dielectric anisotropy, and    (iii) is attached to the polymeric backbone via at least two spacing atoms.    
   
   
       13 . A liquid crystal device according to  claim 12 , wherein the polymer is a polyvinyl acetal.  
   
   
       14 . A method for manufacturing a liquid crystal device comprising the steps of: 
 providing a surface-director alignment layer on an inner surface of at least one substrate, and    sandwiching a liquid crystal bulk layer between two substrates, said liquid crystal bulk layer presenting a surface-director at a bulk surface thereof, and said surface-director alignment layer comprising side-chains arranged to interact with the bulk layer at said bulk surface for facilitating the obtaining of a preferred orientation of the surface-director of the bulk layer, wherein the orientation of the molecules of the liquid crystal bulk layer and the orientation of said side-chains of the surface-director alignment layer each is directly controllable by an electric field via dielectric coupling.    
   
   
       15 . A method of controlling a liquid crystal bulk layer comprising the step of aligning a liquid crystal bulk layer presenting a surface-director at a bulk surface thereof by use of a surface-director alignment layer comprising side-chains arranged to interact with the bulk layer at said bulk surface for facilitating the obtaining of a preferred orientation of the surface-director of the bulk layer wherein the orientation of the molecules of the liquid crystal bulk layer and the orientation of said side-chains of the surface-director alignment layer each is directly controllable by an electric field via dielectric coupling.  
   
   
       16 . A liquid crystal device according to  claim 7 , wherein the electric field is applied normally to said at least one confining substrate.  
   
   
       17 . A liquid crystal device according to  claim 2 , wherein the liquid crystal bulk layer comprises a nematic liquid crystal.  
   
   
       18 . A liquid crystal device according to  claim 3 , wherein the liquid crystal bulk layer comprises a nematic liquid crystal.  
   
   
       19 . A liquid crystal device according to  claim 4 , wherein the liquid crystal bulk layer comprises a nematic liquid crystal.  
   
   
       20 . A liquid crystal device according to  claim 5 , wherein the liquid crystal bulk layer comprises a nematic liquid crystal.