New type fluorine-containing copolyimide and preparation method thereof

The invention relates to new type fluorine-containing copolyimide and a preparation method thereof. The fluorine-containing copolyimide is obtained by condensation copolymerization of three monomers, i.e. the fluorine-containing copolyimide is prepared by the steps of carrying out condensation copolymerization reaction on one type of alicyclic dianhydride monomer and two types of fluorine-containing aromatic diamine monomers, or two types of the alicyclic dianhydride monomers and one type of the fluorine-containing aromatic diamine monomer in an aprotic polar solvent at low temperature, and then carrying out a thermal imidization reaction, and the new type fluorine-containing copolyimide has the advantages of high transparency, good heat resistance and the like. A fluorine-containing copolyimide film has a glass transition temperature of 200 DEG C to 350 DEG C, and is colorless and transparent; the ultraviolet absorption cutoff wavelength is between 270nm and 340 nm; the light transmittance at 450 nm is between 88% and 98%; and the fluorine-containing copolyimide film has good processing performance, and can be used as a bottom plate of a solar cell, a liquid crystal display material, a flexible transparent conductive film substrate material, an electromagnetic shielding material and the like.