Method of achieving high pretilt angles in a lilquid crystal cell

Abstract

A new method of obtaining high pretilt angles of predetermined values in a liquid crystal cell is disclosed. Appropriate amounts of compatible homogeneous and homeotropic alignment materials are mixed with special treatment methods to achieve the desired results.

1 . A method of producing an alignment layer in a liquid crystal cell, comprising the steps of: 
 a) forming a solution of a homogeneous (horizontal) alignment material;    b) forming a solution of a homeotropic (vertical) alignment material;    c) mixing the alignment materials in steps (a) and (b) to form a clear and slightly colored solution without precipitates;    d) applying the mixture in step (c) on a substrate to form a solid film;    e) curing the film in step (e), in one or multiple steps to form a hardened solid film; and    f) treating the solid film in step (f) mechanically to obtain a uniform alignment direction.    
   
   
       2 . The method of  claim 1 , wherein said homogeneous alignment material is a polymer such as polyimide (PI), polystyrene (PS), poly-methyl methacrylate (PMMA), polycarbonates (PC), polyamic acid (PAA) or polyvinyl alcohol (PVA).  
   
   
       3 . The method of  claim 1 , wherein said homeotropic alignment material is a polymer such as polyimide (PI), polystyrene (PS), poly-methyl methacrylate (PMMA), polycarbonates (PC), polyamic acid (PAA) or polyvinyl alcohol (PVA).  
   
   
       4 . The method of  claim 1 , wherein step (c) includes the step of mixing the alignment materials in steps (a) and (b) in an appropriate ratio such that the weight ratio of the homeotropic material is from 0.1 to 99 percent of the total weight of the final mixture excluding the weight of the solvent(s).  
   
   
       5 . The method of  claim 1 , wherein step (c) includes the step of ensuring that the solubility of said homogeneous alignment material and the solubility of said homeotropic alignment material are different in the solvent mixture formed in step (c).  
   
   
       6 . The method of  claim 1 , wherein the hardened solid film of step (e) is of thickness between 10 nm and 300 nm.  
   
   
       7 . The method of  claim 1 , wherein the application of the mixture of said homogeneous and homeotropic alignment materials to said substrate is by the method of spin coating.  
   
   
       8 . The method of  claim 1 , wherein the application of the mixture of said homogeneous and homeotropic alignment materials to said substrate is by the method of screen printing.  
   
   
       9 . The method of  claim 1 , wherein the curing of the solid film in step (e) is thermal curing.  
   
   
       10 . The method of  claim 1 , wherein the curing of the solid film in step (e) is photo-curing.  
   
   
       11 . The method of  claim 1 , wherein the mechanical treatment in step (f) is mechanical rubbing by a piece of fabric in a fixed direction.  
   
   
       12 . The method of  claim 1 , wherein the mechanical treatment in step (f) is irradiation by an ion beam in a vacuum in a fixed direction at a fixed incident angle.  
   
   
       13 . The method of  claim 1 , wherein the substrate is indium tin oxide coated glass.  
   
   
       14 . The method of  claim 13 , wherein the indium tin oxide is patterned into rows and columns in a passive matrix display.  
   
   
       15 . The method of  claim 1 , wherein the substrate has an active matrix thin film transistor array.