Alignment film, composition for forming alignment film and liquid crystal display device

Abstract

Disclosed is a liquid crystal display device including: a first substrate and a second substrate, one of which is transparent; a liquid crystal layer disposed between the first substrate and the second substrate; a group of electrodes for applying an electric field to the liquid crystal layer, which is formed on one of the first substrate and the second substrate; a plurality of active elements connected to the group of electrodes; and an alignment film disposed on one of the first substrate and the second substrate, wherein the alignment film contains a polyimide and a precursor of the polyimide, each of which is formed from a diamine and an acid anhydride, and the diamine contains a first diamine having an acidic group and a second diamine having a nitrogen atom-containing functional group other than two amino groups.

What is claimed is: 
     
         1 . A composition for forming an alignment film, which is used for forming an alignment film imparted a liquid crystal alignment ability by irradiation with polarized ultraviolet light, comprising:
 a first diamine having at least one acidic group;   a second diamine having at least one nitrogen atom-containing functional group other than two amino groups; and   an acid anhydride.   
     
     
         2 . The composition for forming an alignment film according to  claim 1 , wherein the second diamine has at least one functional group selected from an amino group having a secondary amine structure, an amino group having a tertiary amine structure, a primary amide group, and a secondary amide group as the nitrogen atom-containing basic functional group. 
     
     
         3 . The composition for forming an alignment film according to  claim 1 , wherein the second diamine has at least one functional group selected from an amino group having a secondary amine structure, a primary amide group, and a secondary amide group as the nitrogen atom-containing basic functional group. 
     
     
         4 . The composition for forming an alignment film according to  claim 2 , wherein the second diamine comprises at least one of the compounds represented by the following chemical formulae (B-6), (B-7), (B-8), (B-9), (B-13), (B-15), (B-16), (B-17), (B-18), (B-19), (B-20), (B-21), (B-22), (B-23), (B-24), (B-25), (B-26), (B-27), (B-28), (B-30), (B-34) and (B-36): 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
       in which each n independently represents an integer of 1 to 8, and each R independently represents an alkyl group having 1 to 3 carbon atoms. 
     
     
         5 . The composition for forming an alignment film according to  claim 3 , wherein the second diamine comprises at least one of the compounds represented by the following chemical formulae (B-6), (B-7), (B-8), (B-9), (B-13), (B-15), (B-16), (B-17), (B-18), (B-19), (B-20), (B-21), (B-22), (B-23), (B-24), (B-28), (B-30) and (B-36): 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
       in which each n independently represents an integer of 1 to 8, and each R independently represents an alkyl group having 1 to 3 carbon atoms. 
     
     
         6 . The composition for forming an alignment film according to  claim 1 , wherein the first diamine contains at least one functional group selected from a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group as the acidic group. 
     
     
         7 . The composition for forming an alignment film according to  claim 1 , wherein the first diamine contains at least one functional group selected from a sulfonic acid group and a phosphoric acid group as the acidic group, or comprises at least one of the compounds represented by the following chemical formulae (A-5), (A-16), (A-17) and (A-18): 
       
         
           
           
               
               
           
         
       
     
     
         8 . The composition for forming an alignment film according to  claim 1 , wherein the ratio of the content of the first diamine to the content of the second diamine is from 20:80 to 80:20 in the diamine which is a starting material. 
     
     
         9 . A liquid crystal display device comprising:
 a first substrate and a second substrate, at least one of which is transparent;   a liquid crystal layer disposed between the first substrate and the second substrate;   a group of electrodes for applying an electric field to the liquid crystal layer, which is formed on at least one of the first substrate and the second substrate;   a plurality of active elements connected to the group of electrodes; and   an alignment film disposed on at least one of the first substrate and the second substrate, wherein   the alignment film contains a polyimide and a precursor of the polyimide, each of which is formed from a diamine and an acid anhydride, and is imparted a liquid crystal alignment ability by irradiation with polarized ultraviolet light, wherein the diamine contains a first diamine having at least one acidic group and a second diamine having at least one nitrogen atom-containing functional group other than two amino groups.   
     
     
         10 . The liquid crystal display device according to  claim 9 , wherein the second diamine has at least one functional group selected from an amino group having a secondary amine structure, an amino group having a tertiary amine structure, a primary amide group, and a secondary amide group as the nitrogen atom-containing basic functional group. 
     
     
         11 . The liquid crystal display device according to  claim 9 , wherein the second diamine has at least one functional group selected from an amino group having a secondary amine structure, a primary amide group, and a secondary amide group as the nitrogen atom-containing basic functional group. 
     
     
         12 . The liquid crystal display device according to  claim 10 , wherein the second diamine comprises at least one of the compounds represented by the following chemical formulae (B-6), (B-7), (B-8), (B-9), (B-13), (B-15), (B-16), (B-17), (B-18), (B-19), (B-20), (B-21), (B-22), (B-23), (B-24), (B-25), (B-26), (B-27), (B-28), (B-30), (B-34) and (B-36): 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
       in which each n independently represents an integer of 1 to 8, and each R independently represents an alkyl group having 1 to 3 carbon atoms. 
     
     
         13 . The liquid crystal display device according to  claim 11 , wherein the second diamine comprises at least one of the compounds represented by the following chemical formulae (B-6), (B-7), (B-8), (B-9), (B-13), (B-15), (B-16), (B-17), (B-18), (B-19), (B-20), (B-21), (B-22), (B-23), (B-24), (B-28), (B-30) and (B-36): 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
       in which each n independently represents an integer of 1 to 8, and each R independently represents an alkyl group having 1 to 3 carbon atoms. 
     
     
         14 . The liquid crystal display device according to  claim 9 , wherein the first diamine contains at least one functional group selected from a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group as the acidic group. 
     
     
         15 . The liquid crystal display device according to  claim 9 , wherein the first diamine contains at least one functional group selected from a sulfonic acid group and a phosphoric acid group as the acidic group, or comprises at least one of the compounds represented by the following chemical formulae (A-5), (A-16), (A-17) and (A-18): 
       
         
           
           
               
               
           
         
       
     
     
         16 . The liquid crystal display device according to  claim 9 , wherein the ratio of the content of the first diamine to the content of the second diamine is from 20:80 to 80:20 in the diamine which is a starting material. 
     
     
         17 . The liquid crystal display device according to  claim 9 , wherein liquid crystal molecules constituting the liquid crystal layer are homogeneously aligned.