A polyimide film contains fluorinated substituents and cardo structures. The polyimide film exhibits excellent heat-resistance, transparency and mechanical properties. The polyimide film has a glass-transition temperature (Tg) of at least 360° C., a coefficient of thermal expansion (CTE) of 50 ppm/° C. or lower, a modulus of at least 4.0 Gpa, a b* value of 5 or lower and yellowness index of 8 or less. The polyimide film can be used as a display substrate or an optical film in a liquid crystal display (LCD), an organic light-emitting diode (OLED) and in other fields where the characteristic features are required.

The present disclosure relates to a method for manufacturing a polyimide film and a polyimide film manufactured thereby. In one embodiment, the method for preparing a polyimide film includes: preparing a polyamic acid by polymerizing a mixture containing an aromatic diamine and an aromatic acid dianhydride; preparing a first composition containing the polyamic acid, an amine-based catalyst, an acid anhydride-based dehydrating agent, and a solvent; and forming a polyimide film at 150° C. or less using the first composition, wherein the first composition contains the amine-based catalyst and the acid anhydride-based dehydrating agent in a molar ratio of 1:2 to 1:5.

Disclosed herein are a highly thick polyimide film that contains a reduced number of bubbles therein and exhibits high elasticity and high heat resistance, and a manufacturing method therefor. The polyimide film is obtained by imidizing a poly(amic acid) solution containing an acid dianhydride component including 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA), and a diamine component including 4,4′-oxydianiline (ODA), para-phenylenediamine (p-phenylenediamine, PPD), and 3,5-diaminobenzoic acid (DABA), and contains a phosphorus (P)-based compound.

Provided herein is a method for manufacturing a polyimide film, the method including the steps of: preparing a polyamic acid solution; preparing a polyamic acid composition by adding a dehydrating agent and an imidizing catalyst to the polyamic acid solution; and applying the polyamic acid to a support to form a film, followed by thermosetting the film in a heater, wherein the thermosetting step comprises a first heating step, a second heating step, and a third heating step, each of the first, the second, and the third step being carried out in a processing temperature range of 100° C. to 550° C.

Disclosed herein are a polyimide film for graphite sheets, a method of fabricating the same, and a graphite sheet fabricated using the same. The polyimide film is fabricated by imidizing a polyamic acid formed by reaction between a dianhydride monomer and a diamine monomer, wherein the reaction is carried out in the presence of a metal compound and the polyamic acid forms a chelate with metal ions.

Disclosed herein are a polyimide film for graphite sheets, a method of fabricating the same, and a graphite sheet fabricated using the same. The polyimide film is fabricated by imidizing a polyamic acid formed by reaction between a dianhydride monomer and a diamine monomer, wherein the reaction is carried out in the presence of particles of a metal compound having an average particle diameter (D.sub.50) of about 1 μm to about 6 μm.

Disclosed herein is provided a method for manufacturing a polyimide film, the method comprising the steps of: preparing a polyamic acid solution; preparing a polyamic add composition by adding 2-3 mole equivalents of a dehydrating agent to the polyamic acid solution; and applying the polyamic acid to a support to form a film, followed by thermosetting the film in a heater.

A polyimide is provided, which contains at least one repeating unit selected from a group consisting of the following general formulas, M, N, and O:

##STR00001##

X is a residue derived from TCA represented by formula I. Y.sub.1 is a residue derived from a diamine with a cardo structure. Y.sub.2 is a residue derived from a diamine with the structure of a benzene ring, biphenyl, phenylbenzimidazole or phenylbenzoxazole. Y.sub.3 is a residue derived from a diamine with an ether or an ester group.

##STR00002##

The present disclosure provides a multilayer polyimide film in which the core layer is made of a non-thermoplastic polyimide resin comprising one or more imidization catalysts and one or more dehydrating agents, and the skin layer laminated on one or both surfaces of the core layer contains one or more imidization catalysts, but does not contain a dehydrating agent, and a method for manufacturing the same.

The present invention relates to a method for manufacturing a polyimide-powder composite separator using water and a polyimide-powder composite separator manufactured by the method, and is environmentally friendly since an organic solvent is not used in the overall process of manufacturing the composite separator and has advantageous effects in terms of time, cost, and manufacturing process since a high temperature/high pressure environment is not required.