| CPC C08L 79/08 (2013.01) [C08G 73/1039 (2013.01); C08G 73/1078 (2013.01); C08J 7/046 (2020.01); C08L 2203/16 (2013.01)] | 10 Claims |
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1. A polyimide-based film satisfying the following Expressions 1 and 2,
Max[R(θ,ψ0 to 360°)]<R0×[sin(θ)cos(0)+5 sin(θ)+1]3 [Expression 1]
wherein R0 represents an in-plane phase difference (Rin) when light is incident perpendicularly to the polyimide-based film (θ═0°), θ represents an inclination angle of the incident light, ψ represents an azimuth angle, R(θ, ψ) represents a phase difference according to an incident angle, and Max[R(θ, ψ0 to 306°)] represents a maximum phase difference value among phase difference values measured with the fixed inclination angle θ and the azimuth angle ψ of 0° to 360° at an interval of 5°,
1−Min[R(θ50°,ψ0 to 360°)]/Avg[R(θ50°,ψ0 to 360°)]≤50% or Max[R(θ50°,ψ0 to 360°)]/Avg[R(θ50°,ψ0 to 360°)]−1≤50% [Expression 2]
wherein Min[R(θ50°, ψ0 to 360°)], Avg[R(θ50°, ψ0 to 360°)], and Max[R(θ50°, ψ0 to 360°)] represent a minimum phase difference, an average phase difference, and a maximum phase difference, respectively, among phase difference values measured with the fixed inclination angle of 50° and the azimuth angle ψ of 0° to 360° at an interval of 5°, and
wherein the polyimide-based film is prepared from a polyamide-imide based resin comprising a polyamide-imide polymer derived from an amine-terminated polyamide oligomer derived from a first fluorine-based aromatic diamine and aromatic diacid dichloride; a second fluorine-based aromatic diamine; and an aliphatic cyclic dianhydride.
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