Polyamide-imide film and preparation method thereof

Abstract

Embodiments relate to a polyamide-imide film that secures excellent tensile toughness and elastic restoring force, and a process for preparing the same. The polyamide-imide film comprises a polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound, wherein the area value up to the yield point derived by the 0.2% off-set method on a stress-strain curve of the polyamide-imide film as measured using a universal testing machine (UTM) is 80 to 150 J/m 2 .

1 . A polyamide-imide film, which comprises:
 a polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound,   wherein the area value up to the yield point derived by the 0.2% off-set method on a stress-strain curve of the polyamide-imide film as measured using a universal testing machine (UTM) is 80 to 150 J/m 2 .   
     
     
         2 . The polyamide-imide film of  claim 1 , wherein the area value is 100 to 140 J/m 2 . 
     
     
         3 . The polyamide-imide film of  claim 1 , which has a modulus of 5.0 GPa or more based on a thickness of 50 μm. 
     
     
         4 . The polyamide-imide film of  claim 1 , which has a surface hardness of HB or higher. 
     
     
         5 . The polyamide-imide film of  claim 1 , which has a yellow index (YI) of 5 or less based on a thickness of 50 μm. 
     
     
         6 . The polyamide-imide film of  claim 1 , which has a haze of 2% or less based on a thickness of 50 μm. 
     
     
         7 . The polyamide-imide film of  claim 1 , which has a light transmittance measured at 550 nm of 85% or more based on a thickness of 50 μm. 
     
     
         8 . The polyamide-imide film of  claim 1 , wherein the polyamide-imide film has a restoration angle of 60° or more at the time of evaluating the folding restoring force, and
 the restoration angle at the time of evaluating the folding restoring force refers to the angle at which the film bent and inserted between zigs of a 5 mm interval is restored after 24 hours under the conditions of 85° C. and 85% RH. 
 
     
     
         9 . The polyamide-imide film of  claim 1 , wherein the diamine compound is represented by the following Formula 1,
 the dianhydride compound is represented by the following Formula 2, and   the dicarbonyl compound is represented by the following Formula 3:   
       
         
           
           
               
               
           
         
         in the above Formulae 1 to 3, 
         E and J are each independently selected from a substituted or unsubstituted divalent C 6 -C 30  aliphatic cyclic group, a substituted or unsubstituted divalent C 4 -C 30  heteroaliphatic cyclic group, a substituted or unsubstituted divalent C 6 -C 30  aromatic cyclic group, a substituted or unsubstituted divalent C 4 -C 30  heteroaromatic cyclic group, a substituted or unsubstituted C 1 -C 30  alkylene group, a substituted or unsubstituted C 2 -C 30  alkenylene group, a substituted or unsubstituted C 2 -C 30  alkynylene group, —O—, —S—, —C(═O)—, —CH(OH)—, —S(═O) 2 —, —Si(CH 3 ) 2 —, —C(CH 3 ) 2 —, and —C(CF 3 ) 2 —, 
         e and j are each independently selected from integers of 1 to 5, 
         when e is 2 or more, then the 2 or more E are the same as, or different from, each other, 
         when j is 2 or more, then the 2 or more J are the same as, or different from, each other, 
         G is bonded by a bonding group selected from a substituted or unsubstituted tetravalent C 6 -C 30  aliphatic cyclic group, a substituted or unsubstituted tetravalent C 4 -C 30  heteroaliphatic cyclic group, a substituted or unsubstituted tetravalent C 6 -C 30  aromatic cyclic group, a substituted or unsubstituted tetravalent C 4 -C 30  heteroaromatic cyclic group, wherein the aliphatic cyclic group, the heteroaliphatic cyclic group, the aromatic cyclic group, or the heteroaromatic cyclic group may be present alone or may be bonded to each other to form a condensed ring, a substituted or unsubstituted C 1 -C 30  alkylene group, a substituted or unsubstituted C 2 -C 30  alkenylene group, a substituted or unsubstituted C 2 -C 30  alkynylene group, —O—, —S—, —C(═O)—, —CH(OH)—, —S(═O) 2 —, —Si(CH 3 ) 2 —, —C(CH 3 ) 2 —, and —C(CF 3 ) 2 —, and 
         X is a halogen atom. 
       
     
     
         10 . The polyamide-imide film of  claim 1 , wherein the dianhydride compound is composed of a compound having a fluorine-containing substituent. 
     
     
         11 . The polyamide-imide film of  claim 1 , wherein the dicarbonyl compound comprises at least two dicarbonyl compounds different from each other. 
     
     
         12 . The polyamide-imide film of  claim 1 , wherein the polyamide-imide polymer comprises a repeat unit represented by the following Formula A and a repeat unit represented by the following Formula B: 
       
         
           
           
               
               
           
         
         in the above Formulae A and B, 
         E and J are each independently selected from a substituted or unsubstituted divalent C 6 -C 30  aliphatic cyclic group, a substituted or unsubstituted divalent C 4 -C 30  heteroaliphatic cyclic group, a substituted or unsubstituted divalent C 6 -C 30  aromatic cyclic group, a substituted or unsubstituted divalent C 4 -C 30  heteroaromatic cyclic group, a substituted or unsubstituted C 1 -C 30  alkylene group, a substituted or unsubstituted C 2 -C 30  alkenylene group, a substituted or unsubstituted C 2 -C 30  alkynylene group, —O—, —S—, —C(═O)—, —CH(OH)—, —S(═O) 2 —, —Si(CH 3 ) 2 —, —C(CH 3 ) 2 —, and —C(CF 3 ) 2 —, 
         e and j are each independently selected from integers of 1 to 5, 
         when e is 2 or more, then the 2 or more E are the same as, or different from, each other, 
         when j is 2 or more, then the 2 or more J are the same as, or different from, each other, and 
         G is bonded by a bonding group selected from a substituted or unsubstituted tetravalent C 6 -C 30  aliphatic cyclic group, a substituted or unsubstituted tetravalent C 4 -C 30  heteroaliphatic cyclic group, a substituted or unsubstituted tetravalent C 6 -C 30  aromatic cyclic group, a substituted or unsubstituted tetravalent C 4 -C 30  heteroaromatic cyclic group, wherein the aliphatic cyclic group, the heteroaliphatic cyclic group, the aromatic cyclic group, or the heteroaromatic cyclic group may be present alone or may be bonded to each other to form a condensed ring, a substituted or unsubstituted C 1 -C 30  alkylene group, a substituted or unsubstituted C 2 -C 30  alkenylene group, a substituted or unsubstituted C 2 -C 30  alkynylene group, —O—, —S—, —C(═O)—, —CH(OH)—, —S(═O) 2 —, —Si(CH 3 ) 2 —, —C(CH 3 ) 2 —, and —C(CF 3 ) 2 —. 
       
     
     
         13 . A process for preparing a polyamide-imide film, which comprises:
 simultaneously or sequentially mixing and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent in a polymerization apparatus to prepare a polymer solution;   transferring the polymer solution to a tank;   casting the polymer solution in the tank and then drying it to prepare a gel-sheet;   thermally treating the gel-sheet, while it is moved on a belt, to prepare a cured film; and   winding the cured film using a winder,   wherein the ratio of the moving speed of the gel-sheet on the belt at the time of thermal treatment to the moving speed of the cured film at the time of winding is 1:0.95 to 1:1.40.   
     
     
         14 . The process for preparing a polyamide-imide film of  claim 13 , wherein the step of preparing the polymer solution may comprise:
 (a) simultaneously or sequentially mixing and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent in a polymerization apparatus to prepare a first polymer solution;   (b) measuring the viscosity of the first polymer solution and evaluating whether the target viscosity is reached; and   (c) if the viscosity of the first polymer solution does not reach the target viscosity, further adding the dicarbonyl compound to prepare a second polymer solution having the target viscosity.   
     
     
         15 . The process for preparing a polyamide-imide film of  claim 14 , wherein the target viscosity at room temperature is 100,000 cps to 300,000 cps. 
     
     
         16 . The process for preparing a polyamide-imide film of  claim 13 , wherein, once the polymer solution is prepared, the step of transferring the polymer solution to the tank is carried out without any additional steps. 
     
     
         17 . The process for preparing a polyamide-imide film of  claim 13 , wherein the temperature inside the tank is −20° C. to 0° C. 
     
     
         18 . The process for preparing a polyamide-imide film of  claim 13 , which, after the polymer solution is transferred to the tank, further comprises carrying out vacuum degassing; and
 purging the tank with an inert gas.   
     
     
         19 . The process for preparing a polyamide-imide film of  claim 13 , which, after the polymer solution is transferred to the tank, further comprise storing the polymer solution in the tank for 12 hours to 60 hours. 
     
     
         20 . The process for preparing a polyamide-imide film of  claim 13 , wherein the polymer solution is cast and then dried at a temperature of 60° C. to 150° C. for 5 minutes to 60 minutes to prepare a gel-sheet. 
     
     
         21 . The process for preparing a polyamide-imide film of  claim 13 , wherein the thermal treatment is carried out in a temperature range of 80° C. to 500° C. at a temperature elevation rate of 2° C./min to 80° C./min for 5 to 40 minutes. 
     
     
         22 . The process for preparing a polyamide-imide film of  claim 13 , which, after the cured film is prepared by thermal treatment, further comprises cooling the cured film while it is moved on a belt. 
     
     
         23 . The process for preparing a polyamide-imide film of  claim 13 , wherein the ratio of the moving speed of the gel-sheet on the belt at the time of thermal treatment to the moving speed of the cured film at the time of winding is 1:0.99 to 1:1.10. 
     
     
         24 . The process for preparing a polyamide-imide film of  claim 13 , wherein the area value up to the yield point derived by the 0.2% off-set method on a stress-strain curve of the polyamide-imide film as measured using a universal testing machine (UTM) is 80 to 150 J/m 2 . 
     
     
         25 . The process for preparing a polyamide-imide film of  claim 13 , wherein the polyamide-imide film has a modulus of 5.0 GPa or more based on a thickness of 50 μm. 
     
     
         26 . The process for preparing a polyamide-imide film of  claim 13 , wherein the polyamide-imide film has a restoration angle of 60° or more at the time of evaluating the folding restoring force, and
 the restoration angle at the time of evaluating the folding restoring force refers to the angle at which the film bent and inserted between zigs of a 5 mm interval is restored after 24 hours under the conditions of 85° C. and 85% RH.