▎ 摘　　要

NOVELTY - A colorless and transparent polyimide film is prepared by using polyimide resin and thermally conductive filler. The polyimide resin is obtained by performing polycondensation of dianhydride (A) and diamine under the action of dehydrating agent and catalyst. The dianhydride comprises dianhydride (A). The dianhydride (A) is chosen from one or more of 4,4'-hexafluoroisopropyl phthalic anhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,3,4-cyclopentatetracarboxylic dianhydride. The diamine comprises diamine (d1). The diamine (d1) is chosen from one or more of 2,2'-bis(trifluoromethyl)diaminobiphenyl, 1,3-cyclohexanediamine, 1,3-cyclohexanedimethylamine, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 2,2-bis(3-aminophenyl)hexafluoropropane, 2,2-bis(3-amino-4-tolyl)hexafluoropropane and 3,5-diaminobenzotrifluoride. The colorless and transparent polyimide film has transmittance of 60-87%. USE - Colorless and transparent polyimide film for LED film screen (claimed). ADVANTAGE - The colorless and transparent polyimide film has high transmittance and excellent thermal conductivity. The LED film screen will not affect the appearance of the building wall. The heat generated when the LED emits light can be quickly conducted, and the heat will not accumulate and cause the temperature to increase, thereby affecting the luminous efficiency of the LED film screen. The colorless and transparent polyimide film has high elastic modulus, excellent heat resistance and excellent dimensional stability at high temperature, and is not easy to deform at high temperature. DETAILED DESCRIPTION - A colorless and transparent polyimide film is prepared by using polyimide resin and thermally conductive filler. The polyimide resin is obtained by performing polycondensation of dianhydride (A) and diamine under the action of a dehydrating agent and a catalyst. The dianhydride comprises dianhydride (A). The dianhydride (A) is chosen from one or more of 4,4'-hexafluoroisopropyl phthalic anhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,3,4-cyclopentatetracarboxylic dianhydride. The diamine comprises diamine (d1). The diamine (d1) is chosen from one or more of 2,2'-bis(trifluoromethyl)diaminobiphenyl, 1,3-cyclohexanediamine, 1,3-cyclohexanedimethylamine, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 2,2-bis(3-aminophenyl)hexafluoropropane, 2,2-bis(3-amino-4-tolyl)hexafluoropropane and 3,5-diaminobenzotrifluoride. The thermally conductive filler is unmodified inorganic thermally conductive filler and/or modified inorganic thermally conductive filler. The thermally conductive filler is added in an amount of 5-60% with respect to the total mass of the colorless and transparent polyimide film, The colorless and transparent polyimide film has transmittance of 60-87% and thermal conductivity of 0.4-4.5 W/m.K. An INDEPENDENT CLAIM is included for preparation of the colorless and transparent polyimide film, which involves providing a thermally conductive paste formed by a thermally conductive filler and an organic polar solvent, providing polyimide slurry formed by polyimide resin and organic polar solvent, and mixing the thermally conductive slurry and the polyimide slurry.