Polyimide film and flexible display panel including the same

1. A polyimide-based film of which a modulus measured according to ASTM D882 is 5 GPa or more and a rate of change of the modulus, after the polyimide-based film is maintained under a high-temperature and high-humidity condition of 60° C. and 90% RH for 500 hours, is 10% or less,

wherein the polyimide-based film has an elongation at break of 8% or more when measured according to ASTM D882, a light transmittance of 5% or more when measured at 388 nm according to ASTM D1746, a total light transmittance of 87% or more when measured at 400 to 700 nm according to ASTM D1746, a haze of 2.0% or less, a yellow index of 5.0 or less, and a b* value of 2.0 or less, and

wherein the polyimide-based film is formed from a polyamide-imide-based resin prepared by polymerizing an amine-terminated polyamide oligomer derived from a first fluorine-based aromatic diamine and an aromatic diacid dichloride, with a second fluorine-based aromatic diamine, an aromatic dianhydride, and an alicyclic dianhydride.

2. The polyimide-based film of claim 1 , wherein a rate of change of an in-plane phase difference of the polyimide-based film, after the polyimide-based film is maintained under the high-temperature and high-humidity condition of 60° C. and 90% RH for 500 hours, is 5% or less.

3. The polyimide-based film of claim 1 , wherein an in-plane phase difference and a phase difference in a thickness direction of the polyimide-based film measured at a wavelength of 550 nm are 200 nm or less and 6,000 nm or less, respectively.

4. The polyimide-based film of claim 1 , wherein a thickness of the polyimide-based film is 30 to 100 μm.

5. A window cover film comprising the polyimide-based film of claim 1 .

6. The window cover film of claim 5 , further comprising one or more coating layers selected from a hard coating layer, an antistatic layer, an anti-fingerprint layer, an anti-fouling layer, an anti-scratch layer, a low-refractive layer, an anti-reflective layer, and an impact absorption layer, the coating layer being formed on one surface of the polyimide-based film.

7. A flexible display panel comprising the polyimide-based film of claim 1 .

8. The polyimide-based film of claim 1 , wherein the polyimide-based film is formed of a polyimide-based resin having a block polyamide-imide structure.

9. The polyimide-based film of claim 3 , wherein an in-plane phase difference and a phase difference in a thickness direction of the polyimide-based film measured at a wavelength of 550 nm are 173 to 200 nm and 5,797 to 6,000 nm, respectively.

10. The polyimide-based film of claim 1 , wherein the polyimide-based film has a yellow index of 1.9.

11. The polyimide-based film of claim 1 , wherein the polyimide-based film has a total light transmittance of 89% or more when measured at 400 to 700 nm according to ASTM D1746.

12. A polyimide-based film of which a modulus measured according to ASTM D882 is 5 GPa or more and a rate of change of the modulus, after the polyimide-based film is maintained under a high-temperature and high-humidity condition of 60° C. and 90% RH for 500 hours, is 10% or less,

wherein an in-plane phase difference and a phase difference in a thickness direction of the polyimide-based film measured at a wavelength of 550 nm are 173 nm to 200 nm and 5,797 nm to 6,000 nm, respectively, and

wherein the polyimide-based film is formed from a polyamide-imide-based resin prepared by polymerizing an amine-terminated polyamide oligomer derived from a first fluorine-based aromatic diamine and an aromatic diacid dichloride, with a second fluorine-based aromatic diamine, an aromatic dianhydride, and an alicyclic dianhydride.