Patent ID: 11873371
Assignee: LG CHEM, LTD.
Field: Measurement (Instruments)
Classification: CPC C  G  H | IPC C  G  H

Claim 0:
1. A method of selecting a polyimide film having a life time limit of 0.05 hours or more at a temperature of 500° C. or higher, wherein a lntf value is calculated according to Equation 1 when the polyimide film exhibits a weight loss of 5% measured by a thermogravimetric analysis:, Ea
            RT
          
          +
          
            ln
            ⁢
            
              {
              
                
                  Ea
                  
                    β
                    ⁢
                    
                      
                    
                    ⁢
                    R
                  
                
                ⁢
                
                  P
                  ⁡
                  
                    (
                    
                      X
                      f
                    
                    )
                  
                
              
              }
            
          
        
        =
        
          ln
          ⁢
          
            
          
          ⁢
          
            t
            f
          
        
      
    
    
      
        [
        
          Equation
          ⁢
          
            
          
          ⁢
          1
        
        ]
      
    
  

wherein,
Ea is a thermal decomposition activation energy (KJ/mol) according to the weight loss (%),
R is a gas constant of 8.314 J/mol·K,
T is a temperature of 773.15K,
β is a heating rate of 600° C./hr,
P(Xf) is a function (Xf=Ea/RTd) related to the thermal decomposition activation energy at a thermal decomposition temperature (Td) at which the weight loss of 5(%) occurs, and
tf is a lifetime limit (hr);
wherein the thermal decomposition activation energy (Ea) is calculated by Equation 2:, Ea
        =
        
          -
          
            {
            
              
                R
                b
              
              ⁢
              
                
                  d
                  ⁢
                  
                    
                  
                  ⁢
                  log
                  ⁢
                  
                    
                  
                  ⁢
                  
                    β
                    1
                  
                
                
                  d
                  ⁡
                  
                    (
                    
                      1
                      
                        T
                        1
                      
                    
                    )
                  
                
              
            
            }
          
        
      
    
    
      
        [
        
          Equation
          ⁢
          
            
          
          ⁢
          2
        
        ]
      
    
  

wherein,
b is a constant of 0.457,
R is a gas constant of 8.314 J/mol·K,
T1 is a temperature at which a weight loss of 5% occurs, and
β1 is a heating rate,
wherein the polyimide has a repeat unit of Formula 1:, wherein X is a tetravalent organic group selected from the group consisting of Formulae 2b to 2k:, , and
wherein Y is a divalent organic group selected from the group consisting of Formulae 3a to 3k:,