Abstract: Embodiments relate to a polyimide-based composite film, which comprises a base film comprising a polyimide-based resin; and a functional layer disposed on the base film, wherein when the side of the functional layer located opposite to the side in contact with the base film is referred to as a first side and when the side of the base film in contact with the functional layer is referred to as a second side, the leveling index represented by Equation 1 is less than 0.75.

Abstract: The embodiments relate to a polyamide-based film excellent in optical properties, mechanical properties, and processing suitability and to a cover window and a display device comprising the same. The polyamide-based film comprises a polyamide-base polymer, wherein a dipolar solvent compatibility represented by the following equation is 18.5 to 24: Dipolar solvent compatibility=?{square root over ((?d??1d)2+(?p??1p)2)}. In the equation, ?d is a value of a dispersible component in surface energy of the polyamide-based film, ?p is a value of a polar component in surface energy of the polyamide-based film, ?1d is a value of a dispersible component in Hansen solubility parameter of the dipolar solvent, and ?1p a value of a dipolar component in Hansen solubility parameter of the dipolar solvent.

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/m2.

Abstract: The polyester film according to the embodiment can maintain its original characteristics even after a plurality of repeated folding by adjusting the deformed dimension as compared with the initial dimension of the film, in particular, by adjusting the ratio between the deformed dimensions in two in-plane directions perpendicular to each other to a specific range, in the cycle of straining and relaxing the film. Accordingly, the polyester film can be applied to a cover of a flexible display device, in particular, a foldable display device to exhibit excellent characteristics.

Abstract: The embodiments relate to a polyamide-based composite film that has excellent curl characteristics, mechanical properties, and optical properties, as well as, in particular, is effective in preventing reflection in the visible light region, remarkably reduces the rainbow phenomenon, and achieves a texture similar to that of glass, and a display device comprising the same. There are provided a polyamide-based composite film, which comprises a base film comprising a polyamide-based polymer; and a functional layer disposed on the base film, wherein the in-plane retardation (Re) measured with light having a wavelength of 550 nm is 100 nm to 220 nm, and a display device comprising the same.

Abstract: The polymer film according to an embodiment comprises at least one polymer resin selected from the group consisting of a polyamide-based resin, a polyimide-based resin, and a polyamide-imide-based resin, and has a haze of 0.6% or less and an in-plane retardation within a specific range for each wavelength band in the visible light region. The polymer film, which has an in-plane retardation within a specific range for each wavelength band in the visible light region, is excellent in transparency and optical properties, and it can remarkably reduce the rainbow phenomenon and improve the reflection appearance.

Abstract: An embodiment relates to an optical polyester film. The optical polyester film according to one embodiment can minimize the difference between the orientation angle at the center and the orientation angle at the end of the film while producing a difference between the tensile strengths in the lengthwise/widthwise directions of the film, thereby increasing mechanical strength and brightness and suppressing the occurrence of polarization Mura defects. Further, the optical polyester film employs a single layer film, and thus is more easily processed and has a slimmer thickness. Therefore, the optical polyester film can be usefully applied to small-sized thin film display devices and, specifically, can be favorably used as a substrate material of a prism sheet or a polarized reflection sheet.

Abstract: A heat shrinkable film shows a heat shrinkage rate in the direction perpendicular to the main shrinkage direction that is not high even at high temperature and is printable thereon. The heat shrinkable film includes a polyester resin, wherein the heat shrinkage characteristics in the direction perpendicular to the main shrinkage direction satisfy the following Relationships 1 and 2: ?15??T70-65?0??Relationship 1 0??T100-95?5??Relationship 2 wherein ?TX-Y is a value obtained by subtracting heat shrinkage rate of the heat shrinkable film in the direction perpendicular to the main shrinkage direction after the heat shrinkable film is immersed in water bath for 10 seconds at Y° C. from heat shrinkage rate of the heat shrinkable film in the direction perpendicular to the main shrinkage direction after the heat shrinkable film is immersed in water bath for 10 seconds at X° C.