Polyamic acid, polyimide film and fabrication method of the polyimide film

Abstract

A polyamic acid according to an embodiment is formed by a polymerization reaction of a dianhydride compound, a first diamine compound represented by the following Formula 1, and a second diamine compound, which is different from the first diamine compound. A polyimide film derived from the polyamic acid may exhibit excellent heat resistance and improved optical properties:

What is claimed is: 
     
         1 . A polyamic acid being a polymerization product of:
 a dianhydride compound;   a first diamine compound represented by the following Formula 1; and   a second diamine compound different from the first diamine compound:   
       
         
           
           
               
               
           
         
         wherein in Formula 1, R 1  and R 2  are each independently selected from a hydrogen atom, a deuterium atom, a halogen atom, and a substituted or unsubstituted alkyl group of 1 to 20 carbon atoms, and 
         n 1  and n 2  are each independently an integer of 0 to 4. 
       
     
     
         2 . The polyamic acid of  claim 1 , wherein the second diamine compound is represented by the following Formula 2: 
       
         
           
           
               
               
           
         
         wherein in Formula 2, Ar is a substituted or unsubstituted phenyl group, and m is an integer of 1 to 4. 
       
     
     
         3 . The polyamic acid of  claim 1 , wherein the second diamine compound is represented by the following Formula 2-1: 
       
         
           
           
               
               
           
         
       
     
     
         4 . The polyamic acid of  claim 1 , wherein in Formula 1,
 n 1  and n 2  are each independently an integer of 1 or more, and   R 1  and R 2  are each independently an alkyl group of 1 to 20 carbon atoms substituted with at least one fluorine atom.   
     
     
         5 . The polyamic acid of  claim 1 , wherein the first diamine compound Formula 1 is represented by the following Formula 1-1: 
       
         
           
           
               
               
           
         
         wherein in Formula 1-1, definitions of R 1 , R 2 , n 1  and n 2  are the same as those in Formula 1. 
       
     
     
         6 . The polyamic acid of  claim 1 , wherein the first diamine compound of Formula 1 is represented by the following Formula 1-2: 
       
         
           
           
               
               
           
         
       
     
     
         7 . The polyamic acid of  claim 1 , wherein a molar ratio of a sum of the first diamine compound and the second diamine compound with respect to the dianhydride compound is from 1:0.9 to 1:1.1. 
     
     
         8 . The polyamic acid of  claim 7 , wherein a molar ratio of the first diamine compound to the second diamine compound is from 0.01:0.99 to 0.99:0.01. 
     
     
         9 . The polyamic acid of  claim 1 , wherein the dianhydride compound comprises at least one selected from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, cyclobutane-1,2,3,4-tetracarboxyl dianhydride and pyromellitic dianhydride. 
     
     
         10 . The polyamic acid of  claim 1 , wherein
 the dianhydride compound is 3,3′,4,4′-biphenyltetracarboxylic dianhydride,   the first diamine compound is 2,2′-bis(trifluoromethyl)benzidine, and   the second diamine compound is 3,5-diaminobenzoic acid.   
     
     
         11 . The polyamic acid of  claim 1 , wherein the polyamic acid comprises a repeating unit represented by the following Formula 3: 
       
         
           
           
               
               
           
         
         wherein in Formula 3, X and Y are each independently an integer of 1 or more. 
       
     
     
         12 . A polyimide film comprising a repeating unit derived from the polyamic acid according to  claim 1 . 
     
     
         13 . The polyimide film of  claim 12 , wherein a thermal expansion coefficient of the polyimide film is from 10 ppm/° C. to 20 ppm/° C. 
     
     
         14 . The polyimide film of  claim 12 , wherein a glass transition temperature of the polyimide film is from 300° C. to 420° C. 
     
     
         15 . The polyimide film of  claim 12 , wherein a thermal decomposition temperature of the polyimide film is from 400° C. to 500° C.,
 wherein the thermal decomposition temperature is a temperature at which a weight reduction ratio of the polyimide film reaches 1%. 
 
     
     
         16 . The polyimide film of  claim 12 , wherein a light transmittance of the polyimide film is 95% or more. 
     
     
         17 . The polyimide film of  claim 12 , wherein a yellow index of the polyimide film is from 1 to 10. 
     
     
         18 . The polyimide film of  claim 12 , wherein the polyimide film has a light transmittance of 95% or more, a thermal expansion coefficient of 10 ppm/° C. to 20 ppm/° C., and a glass transition temperature of 300° C. to 420° C. 
     
     
         19 . The polyimide film of  claim 12 , wherein the polyimide film comprises a repeating unit represented by the following Formula 4: 
       
         
           
           
               
               
           
         
         wherein in Formula 4, A and B are each independently an integer of 1 or more. 
       
     
     
         20 . A fabrication method of a polyimide film, the method comprising:
 preparing a polyamic acid according to  claim 1  by a polymerization reaction of a dianhydride compound and at least two kinds of diamine compounds;   providing the polyamic acid on a substrate to form a polyamic acid layer; and   heat treating the polyamic acid layer.   
     
     
         21 . The fabrication method of a polyimide film of  claim 20 , wherein the preparing of the polyamic acid is performed at a temperature range of −10° C. to 80° C. 
     
     
         22 . The fabrication method of a polyimide film of  claim 20 , wherein the heat treating of the polyamic acid layer comprises heat treating at a temperature range of 250° C. to 550° C. 
     
     
         23 . The fabrication method of a polyimide film of  claim 22 , further comprising cooling after the heat treating of the polyamic acid layer. 
     
     
         24 . The fabrication method of a polyimide film of  claim 20 , wherein the heat treating of the polyamic acid layer comprises:
 first heat treating at a first temperature; and   second heat treating at a second temperature higher than the first temperature.   
     
     
         25 . The fabrication method of a polyimide film of  claim 24 , wherein the first temperature is from 250° C. to less than 300° C., and the second temperature is from 300° C. to 550° C. 
     
     
         26 . The fabrication method of a polyimide film of  claim 20 , wherein the heat treating of the polyamic acid layer is conducted in a vacuum state.