Liquid crystal alignment film, method for preparing the same and liquid crystal display device using the same

Abstract

The present invention provides a liquid crystal alignment film not only having an excellent alignment property and stability, but also having high film strength, and thus exhibiting excellent durability and a high residual image property, a method for preparing the same, and a liquid crystal display device using the same.

1 - 8 . (canceled) 
     
     
         9 . A method for preparing a liquid crystal alignment film including the steps of:
 1) coating a liquid crystal aligning agent composition onto a substrate to form a coating film;   2) drying the coating film;   3) irradiating the coating film with light immediately after the drying step to perform alignment treatment;   4) subjecting the alignment-treated coating film to a low-temperature heat treatment at 200° C. or lower; and   5) subjecting the heat-treated coating film to heat treatment at a higher temperature than that of the low-temperature heat treatment to cure it,   wherein the liquid crystal aligning agent composition includes: i) a first polymer for a liquid crystal aligning agent including at least two repeating units selected from the group consisting of a repeating unit represented by Chemical Formula 21 below, a repeating unit represented by Chemical Formula 22 below, and a repeating unit represented by Chemical Formula 23 below, wherein the repeating unit represented by Chemical Formula 21 below is contained in an amount of 5 mol % to 74 mol % relative to the entire repeating units represented by Chemical Formulae 21 to 23 below; ii) a second polymer for a liquid crystal aligning agent including a repeating unit represented by Chemical Formula 24 below; and iii) a reactive mesogenic epoxy:   
       
         
           
           
               
               
           
         
         wherein, in Chemical Formulae 21 to 24, 
         R 22  and R 23  are each independently hydrogen or a C 1-10  alkyl, with the proviso that R 22  and R 23  are not all hydrogen, 
         R 24  and R 25  are each independently hydrogen or a C 1-10  alkyl, and 
         X 11  is a tetravalent organic group represented by Chemical Formula 25 below: 
       
       
         
           
           
               
               
           
         
         wherein, in Chemical Formula 25, 
         R 26  to R 29  are each independently hydrogen or a C 1-6  alkyl, 
         X 12 , X 13 , and X 14  are each independently a tetravalent organic group derived from a hydrocarbon having 4 to 20 carbon atoms, or a tetravalent organic group in which at least one hydrogen in the tetravalent organic groups is substituted with a halogen or in which at least one —CH 2 — is substituted with —O—, —CO—, —S—, —SO—, —SO 2 —, or —CONH—, so that it is not directly bonded to oxygen or sulfur atoms, and
 Y 11 , Y 12 , Y 13 , and Y 14  are each independently a divalent organic group represented by Chemical Formula 26 below: 
 
       
       
         
           
           
               
               
           
         
         wherein, in Chemical Formula 26, 
         R 30  and R 31  are each independently a halogen, a cyano, a C 1-10  alkyl, a C 2-10  alkenyl, a C 1-10  alkoxy, a C 1-10  fluoroalkyl, or a C 1-10  fluoroalkoxy, 
         h and i are each independently an integer of 0 to 4, 
         L 3  is a single bond, —O—, —CO—, —S—, —SO 2 —, —C(CH 3 ) 2   − , —C(CF 3 ) 2 —, —CONH—, —COO—, —(CH 2 ) z —, —O(CH 2 ) z O—, —O(CH 2 ) z —, —OCH 2 —C(CH 3 ) 2 —CH 2 O—, —COO—(CH 2 ) z —OCO—, or —OCO—(CH 2 ) z —COO—, 
         z is an integer of 1 to 10, and 
         j is an integer of 0 to 3. 
       
     
     
         10 . The method for preparing a liquid crystal alignment film of  claim 9 , wherein the X 12 , X 13 , and X 14  are each independently a tetravalent organic group represented by Chemical Formula 27 below: 
       
         
           
           
               
               
           
         
         wherein, in Chemical Formula 27, 
         R 32  to R 35  are each independently hydrogen or a C 1-6  alkyl, 
         L 4  is a single bond, —O—, —CO—, —S—, —C(CH 3 ) 2 —, —C(CF 3 ) 2 —, —CONH—, —COO—, —(CH 2 ) z —, —O(CH 2 ) z O—, or —COO—(CH 2 ) z —OCO—, and 
         z is an integer of 1 to 10. 
       
     
     
         11 . The method for preparing a liquid crystal alignment film of  claim 9 , wherein the reactive mesogenic epoxy is represented by Chemical Formula 28 below:
   R 36 -MG-R 36   [Chemical Formula 28]
   wherein, in Chemical Formula 28,   R 36  is glycidyloxy or N(glycidyloxy) 2 , and   MG is a divalent mesogenic group.   
     
     
         12 . The method for preparing a liquid crystal alignment film of  claim 11 , wherein the MG is represented by Chemical Formula 29 below: 
       
         
           
           
               
               
           
         
         wherein, in Chemical Formula 29, 
         Ar 3  and Ar 4  are each independently phenylene or naphthylene, 
         each L 5  is independently a single bond, an alkylene having 1 to 3 carbon atoms, —COO—, —C(CH 3 )═CH—, or —C(CH 3 )═N═N═C(CH 3 )—, 
         n is 0, 1, or 2, and 
         m is an integer of 1. 
       
     
     
         13 . The method for preparing a liquid crystal alignment film of  claim 11 , wherein the MG is any one selected from the groups listed below: 
       
         
           
           
               
               
           
         
       
     
     
         14 . The method for preparing a liquid crystal alignment film of  claim 9 , wherein the mesogenic epoxy is included in an amount of 0.1% by weight to 30% by weight relative to the weight of the polymers for the liquid crystal aligning agent. 
     
     
         15 . The method for preparing a liquid crystal alignment film of  claim 9 , wherein the first polymer for the liquid crystal aligning agent and the second polymer for the liquid crystal aligning agent may be mixed in a weight ratio of 15:85 to 85:15. 
     
     
         16 . The method for preparing a liquid crystal alignment film of  claim 9 , wherein the drying of Step 2 is performed at 50° C. to 130° C. 
     
     
         17 . The method for preparing a liquid crystal alignment film of  claim 9 , wherein the alignment treatment of Step 3 is performed by irradiating polarized ultraviolet light having a wavelength of 150 nm to 450 nm. 
     
     
         18 . The method for preparing a liquid crystal alignment film of  claim 9 , wherein the low-temperature heat treatment of Step 4 is performed at 110° C. to 200° C. 
     
     
         19 . The method for preparing a liquid crystal alignment film of  claim 9 , wherein the heat treatment of Step 5 is performed at 200° C. to 250° C. 
     
     
         20 . (canceled)