Polyimide-based polymer film, substrate for display device, and optical device using the same

A polyimide-based resin film comprising a polyimide-based resin containing repeating units, wherein the repeating units consist of a polyimide repeating unit represented by the following Chemical Formula 1 and a polyimide repeating unit represented by the following Chemical Formula 5, wherein an absolute value of a change in yellow index (ΔYI) obtained by the following Equation 1 is 3.2 or less:

• in the Chemical Formula 1,
• X1 is a tetravalent functional group represented by the following Chemical Formula 2,
• in the Chemical Formula 2, Ar is a polycyclic aromatic divalent functional group,
• Y1 is an aromatic divalent functional group having at least 15 carbon atoms in which at least one hydrogen atom is substituted with an electron-withdrawing group,
• wherein the aromatic divalent functional group having at least 15 carbon atoms in which at least one hydrogen atom is substituted with an electron-withdrawing includes a functional group represented by the following Chemical Formula 3:
• in the Chemical Formula 3,
• T1 to T3 are the same as or different from each other, and each independently, an electron-withdrawing group,
• m1 to m3 are the same as or different from each other, at least one of m1 to m3 is an integer of 1 to 4, the rest are an integer of 0 to 4, and
• n is an integer of 1 to 10,
• in the Chemical Formula 5,
• X2 is one of tetravalent functional groups represented by the following Chemical Formula 6, and
• Y2 is an aromatic divalent functional group having at least 15 carbon atoms in which at least one hydrogen atom is substituted with an electron-withdrawing group,
• in the Chemical Formula 6,
• R1 to R6 are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms, L is any one selected from the group consisting of a single bond, —O—, —CO—, —COO—, —S—, —SO—, —SO2—, —CR7R8—, —(CH2)t—, —O(CH2)O—, —COO(CH2)tOCO—, —CONH—, phenylene or a combination thereof, where R7 and R8 are each independently one of hydrogen, an alkyl group having 1 to 10 carbon atoms, or a haloalkyl group having 1 to 10 carbon atoms, and t is an integer from 1 to 10,
• Change in Yellow Index (ΔYI)=YIf−YI0 [Equation 1]
• in the Equation 1,
• YIf is a final yellow index of the film measured after heat treatment of the polyimide-based resin film at a temperature of 400° C. to 450° C. for 130 minutes to 200 minutes, and
• YI0 is a yellow index of the polyimide-based resin film before the heat treatment.