Polyimide film

摘要

The present invention provides a polyimide film which is both outstandingly transparent and highly heat resistance, and which can be usefully employed as a transparent electrically conductive film, a TFT substrate, a flexible printed circuit substrate, and the like.

主权项

1. A polyimide powder that is imides of polyamic acid obtained by polymerizing diamines and acid dianhydrides, wherein a degree of imidization of the polyimide powder is at least 80%; an absolute molecular weight (Mw) is 40,000 to 150,000, determined by the following Formula 1:RθK*⁢c=MP⁡(θ)-2⁢A2⁢cM2⁢P2⁡(θ)Formula⁢⁢1 wherein, the above Formula 1 is induced from a principle determining molar mass and size of polymer from angular variation and amount of scattered light measured by an irradiation of laser light to a solution containing any polymer and solvent, using a principle that the amount of charge transfer and the amount of light emission are depended on a polarizability of material for the phenomenon, of which a polarizing is occurred according to an interaction between the material and light, and hence light is scattered in all directions by oscillating charges; Rθ is the excess Rayleigh ratio; K*=4π2n02(dn/dc)2λ0−4NA−1, here n0 is a refractive index of solvent, NA is Avogadro's number, and dn/dc is a specific refractive index increment, that is differentiated from a change rate of refractive index changed according to a change rate of concentration of dilute solution and is determined within the range of 0.001 to 0.1 g/ml as a concentration change section, when a refractive index is detected by injecting a polyimide powder in a state of dilute solution in an organic solvent into a flow cell of differential refractometer; c is a polymer concentration (g/ml) in a solution; M is molar mass, and weight average molecular weight (Mw) in the case of polydisperse sample; A2 is the second virial coefficient; and P(θ)=Rθ/R0, wherein a polydispersity index of the absolute molecular weight is 1.1 to 1.5, and wherein the diamines include a 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl; the acid dianhydrides include a 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride with one or more selected from the group consisting of pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, and oxyphthalic dianhydride; and the imides of polyamic acid is obtained by finally injecting the 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride out of the acid dianhydride on polymerizing.