Polyamide-imide-based film, preparation method thereof, and cover window and display device comprising the same

A cover window for a display device, which comprises a polyamide-imide-based film and a functional layer, wherein the polyamide-imide-based film comprises a polyamide-imide-based polymer that is free of fluorine atoms, and the polyamide-imide-based polymer comprises an imide-based repeat unit, a first amide-based repeat unit, and a second amide-based repeat unit, and

• wherein, when the sum of the imide-based repeat unit, the first amide-based repeat unit, and the second amide-based repeat unit is 100% by mole,
• the molar ratio of the imide-based repeat unit is 40% by mole or less,
• the molar ratio of the first amide-based repeat unit is 70% by mole or less, and
• the sum of the molar ratios of the first amide-based repeat unit and the second amide-based repeat unit is 60 to 97% by mole.

A display device, which comprises a display unit;

• and a cover window disposed on the display unit, wherein the cover window comprises a polyamide-imide-based film and a functional layer, the polyamide-imide-based film comprises a polyamide-imide-based polymer that is free of fluorine atoms, and the polyamide-imide-based polymer comprises an imide-based repeat unit, a first amide-based repeat unit, and a second amide-based repeat unit, and
• wherein, when the sum of the imide-based repeat unit, the first amide-based repeat unit, and the second amide-based repeat unit is 100% by mole,
• the molar ratio of the imide-based repeat unit is 40% by mole or less,
• the molar ratio of the first amide-based repeat unit is 70% by mole or less, and
• the sum of the molar ratios of the first amide-based repeat unit and the second amide-based repeat unit is 60 to 97% by mole.