A high dielectric polyimide film and its preparation method

Abstract

The present invention provides a high-dielectric polyimide film and a method for preparing the same. The method comprises: conducting a polycondensation reaction between a diamine monomer and a dianhydride monomer in a polar solvent to obtain a polyamic acid solution; mixing the polyamic acid solution with graphene surface-grafted with polyvinylidene fluoride; and then subjecting the polyimide film to a thermal imidization reaction and film formation to obtain the high-dielectric polyimide film. By introducing graphene surface-grafted with polyvinylidene fluoride into the polyimide, the high-dielectric polyimide film and its preparation method provide a polyimide film with a high dielectric constant, high breakdown strength, and low dielectric loss.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric film materials, and in particular to a high-dielectric polyimide film and a preparation method thereof. Background Art

[0002] In recent years, metallized organic dielectric film capacitors have attracted extensive attention and research in the electrical and electronic industries and electronic energy systems due to their extremely high charge and discharge rates, excellent flexibility, processability, outstanding insulation properties, and good self-healing properties. Currently, to further extend the operational limits of film capacitors, there is an urgent need for advanced dielectric film materials with high dielectric constants, low dielectric losses, high breakdown strength, good processability, and excellent thermal stability.

[0003] Polyimide (PI) refers to a class of polymers containing imide rings in their backbone. Due to its excellent electrical insulation, mechanical properties, chemical stability, and low dielectric loss, polyimide is widely used in aerospace, microelectronics, nanomaterials, liquid crystals, and separation membranes. Furthermore, polyimide exhibits excellent heat resistance, reaching temperatures exceeding 400°C, making it the most practical polymer film material with the highest heat resistance currently available.

[0004] However, polyimide, as an energy storage dielectric film, needs to have a high dielectric constant, low dielectric loss, and excellent heat resistance. Conventional polyimide, due to its low relative dielectric constant (3.2-3.4), is generally difficult to meet the requirements of high-temperature capacitor energy storage applications. Although there has been a surge in research on polyimide modification in recent years, researchers generally use methods such as adding inorganic fillers with high dielectric constants to polyimide or surface modifying the fillers to prepare dielectric composite dielectric films. However, the introduction of high volume fractions of ceramic particles and poor compatibility lead to the generation of carrier traps within the film, thereby increasing energy loss, reducing breakdown strength, and reducing service life. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a high dielectric polyimide film and a preparation method thereof. By introducing graphene with surface grafted polyvinylidene fluoride into polyimide, the obtained polyimide film has a high dielectric constant while also having high breakdown strength and low dielectric loss.

[0006] The present invention provides a method for preparing a high dielectric polyimide film, comprising the following steps:

[0007] S1, performing a polycondensation reaction on a diamine monomer and a dianhydride monomer in a polar solvent to obtain a polyamic acid solution;

[0008] S2. Mixing the polyamic acid solution obtained in step S1 with the graphene with polyvinylidene fluoride grafted on its surface, and then performing a thermal imidization reaction and forming a film to obtain the high dielectric polyimide film.

[0009] Preferably, in step S1, the diamine monomer is at least one of p-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone or 4,4'-diaminodiphenyl sulfone;

[0010] The dianhydride monomer is at least one of pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride or 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride;

[0011] Preferably, the molar ratio of the diamine monomer to the dianhydride monomer is 0.95-1.05:1.

[0012] Preferably, in step S1, the polar solvent is at least one of N,N-dimethylacetamide, N,N-dimethylformamide or N-methylpyrrolidone.

[0013] Preferably, in step S1, the temperature of the polycondensation reaction is 0-30° C., and the time is 4-10 h.

[0014] Preferably, in step S2, the amount of graphene surface-grafted with polyvinylidene fluoride copolymer is 1-10 wt% of the total mass of the diamine monomer and the dianhydride monomer.

[0015] In the present invention, if the amount of graphene surface-grafted polyvinylidene fluoride copolymer added is too much, structural defects such as micropores will be generated inside the obtained polyimide film, but if the amount of graphene surface-grafted polyvinylidene fluoride copolymer added is too little, the dielectric constant of the obtained polyimide film cannot be effectively improved.

[0016] Preferably, the graphene with surface grafted polyvinylidene fluoride is prepared by the following method:

[0017] Graphene oxide is subjected to an esterification condensation reaction with hydroxylated benzophenone, and then reduced to obtain graphene bonded with benzophenone; the obtained graphene bonded with benzophenone is added to a polyvinylidene fluoride solution containing double bonds, and free radical polymerization is carried out under ultraviolet light conditions to obtain the graphene with surface grafted polyvinylidene fluoride.

[0018] In the present invention, after the carboxyl groups contained in the surface of graphene oxide and the hydroxyl groups contained in hydroxylated benzophenone are subjected to an esterification condensation reaction, a benzophenone photopolymerization initiator is bonded to the surface of the graphene oxide, and then reduced with a reducing agent to obtain graphene bonded with benzophenone; thereafter, the sites on the graphene bonded with benzophenone are used as the starting points of photopolymerization, which can initiate the self-radical polymerization of polyvinylidene fluoride containing double bonds, thereby obtaining the graphene with the surface grafted with polyvinylidene fluoride.

[0019] Preferably, the double bond-containing polyvinylidene fluoride is obtained by heating polyvinylidene fluoride and an organic base;

[0020] Preferably, the organic base is at least one of tetrabutylammonium hydroxide, tetraethylammonium hydroxide or tetramethylammonium hydroxide.

[0021] In the present invention, the phase transfer catalysis of an organic base is utilized to generate carbon-carbon double bonds in the polyvinylidene fluoride molecular chain, thereby obtaining polyvinylidene fluoride containing double bonds.

[0022] Preferably, the temperature of the thermal imidization reaction is 80-300° C., and the time is 3-8 hours.

[0023] The present invention also provides a high dielectric polyimide film, which is prepared by the above preparation method.

[0024] Preferably, the polyimide film has a thickness of 10-50 μm.

[0025] The method for preparing a high-dielectric polyimide film of the present invention comprises introducing graphene with surface-grafted polyvinylidene fluoride into polyimide, wherein the graphene with surface-grafted polyvinylidene fluoride is obtained by grafting polyvinylidene fluoride onto the surface of graphene. On the one hand, the presence of polyvinylidene fluoride results in a strong repulsive force between graphene sheets, a large specific surface area, and the ability to be fully dispersed in a polyimide matrix, thereby forming a good network and obtaining excellent electrical properties. On the other hand, the presence of polyvinylidene fluoride enhances the affinity between graphene and the polyimide matrix, so that the graphene can not only work together with the polyimide matrix to form a large number of micro-capacitors, but also more conducive to leveraging the electrical performance advantages of graphene to improve the dielectric properties of the film, while also achieving both low dielectric loss and high dielectric breakdown strength.

[0026] The high dielectric polyimide film prepared by the present invention can achieve the advantages of high dielectric constant, low dielectric loss and high dielectric breakdown strength under high temperature and high field environment. As a dielectric material, it can achieve good dielectric properties and energy storage properties. DETAILED DESCRIPTION

[0027] Hereinafter, the technical solutions of the present invention will be described in detail through specific embodiments. However, it should be clearly stated that these embodiments are provided for illustration only and are not to be construed as limiting the scope of the present invention.

[0028] Example 1

[0029] A method for preparing a high dielectric polyimide film comprises the following steps:

[0030] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene was added into 20 mL of N-methylpyrrolidone (NMP) and ultrasonically dispersed uniformly, and then 0.2 g of 4-hydroxybenzophenone, heated to 60 ° C and stirred for reaction for 4 hours, then 1g of hydrated hydrazine was added, heated to 40 ° C and stirred for reaction for 6 hours, filtered, washed, and dried to obtain graphene bonded with benzophenone; 1g of polyvinylidene fluoride (PVDF) was added to 10mL of N, N-dimethylacetamide (DMAc), stirred and dissolved completely at 50 ° C, and then 3mL of tetraethylammonium hydroxide (TEAH) methanol solution (1wt%) was added under a nitrogen (N2) atmosphere, stirred and reacted at 40 ° C for 0.5h, and then continued to heat to 120 ° C and kept warm for 5min to obtain a polyvinylidene fluoride solution containing double bonds; the graphene bonded with benzophenone was added to the polyvinylidene fluoride solution containing double bonds, irradiated under ultraviolet light with a wavelength of 365nm for 1h, filtered, washed, and dried to obtain graphene with surface grafted polyvinylidene fluoride;

[0031] (2) Under nitrogen (N2) atmosphere, 3.0 g (15 mmol) of 4,4'-diaminodiphenyl ether was added to 40 mL of N,N-dimethylacetamide (DMAc) and stirred until completely dissolved. Then, 4.4 g (15 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added and stirred until completely dissolved. The mixture was stirred at room temperature for 6 h to obtain a polyamic acid solution.

[0032] (3) 0.5 g of graphene with surface grafted polyvinylidene fluoride was added to 5 mL of N, N-dimethylacetamide (DMAc), and after ultrasonic dispersion, the resulting solution was added to the polyamide acid solution, stirred and mixed evenly, and then vacuum degassed, and then evenly coated on a glass substrate. The resulting coating was treated at 80°C, 150°C, 200°C, and 300°C for 1 hour each, cooled naturally to room temperature, taken out, and then placed in water for demolding. After taking out, vacuum drying was obtained to obtain the high dielectric polyimide film with a film thickness of 20 μm.

[0033] Example 2

[0034] A method for preparing a high dielectric polyimide film comprises the following steps:

[0035] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene was added into 20 mL of N-methylpyrrolidone (NMP) and ultrasonically dispersed uniformly, and then 0.2 g of 4-hydroxybenzophenone, heated to 60 ° C and stirred for reaction for 4 hours, then 1g of hydrated hydrazine was added, heated to 40 ° C and stirred for reaction for 6 hours, filtered, washed, and dried to obtain graphene bonded with benzophenone; 1g of polyvinylidene fluoride (PVDF) was added to 10mL of N, N-dimethylacetamide (DMAc), stirred and dissolved completely at 50 ° C, and then 3mL of tetraethylammonium hydroxide (TEAH) methanol solution (1wt%) was added under a nitrogen (N2) atmosphere, stirred and reacted at 40 ° C for 0.5h, and then continued to heat to 120 ° C and kept warm for 5min to obtain a polyvinylidene fluoride solution containing double bonds; the graphene bonded with benzophenone was added to the polyvinylidene fluoride solution containing double bonds, irradiated under ultraviolet light with a wavelength of 365nm for 1h, filtered, washed, and dried to obtain graphene with surface grafted polyvinylidene fluoride;

[0036] (2) Under nitrogen (N2) atmosphere, 1.6 g (15 mmol) of p-phenylenediamine was added to 40 mL of N,N-dimethylacetamide (DMAc) and stirred until completely dissolved. Then, 4.7 g (15 mmol) of 3,3',4,4'-diphenylether tetracarboxylic dianhydride was added and stirred until completely dissolved. The mixture was stirred at room temperature for 6 h to obtain a polyamic acid solution.

[0037] (3) 0.5 g of graphene with surface grafted polyvinylidene fluoride was added to 5 mL of N, N-dimethylacetamide (DMAc), and after ultrasonic dispersion, the resulting solution was added to the polyamide acid solution, stirred and mixed evenly, and then vacuum degassed, and then evenly coated on a glass substrate. The resulting coating was treated at 80°C, 150°C, 200°C, and 300°C for 1 hour each, cooled naturally to room temperature, taken out, and then placed in water for demolding. After taking out, vacuum drying was obtained to obtain the high dielectric polyimide film with a film thickness of 20 μm.

[0038] Example 3

[0039] A method for preparing a high dielectric polyimide film comprises the following steps:

[0040] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene was added into 20 mL of N-methylpyrrolidone (NMP) and ultrasonically dispersed uniformly, and then 0.2 g of 4-hydroxybenzophenone, heated to 60 ° C and stirred for reaction for 4 hours, then 1g of hydrated hydrazine was added, heated to 40 ° C and stirred for reaction for 6 hours, filtered, washed, and dried to obtain graphene bonded with benzophenone; 1g of polyvinylidene fluoride (PVDF) was added to 10mL of N, N-dimethylacetamide (DMAc), stirred and dissolved completely at 50 ° C, and then 3mL of tetraethylammonium hydroxide (TEAH) methanol solution (1wt%) was added under a nitrogen (N2) atmosphere, stirred and reacted at 40 ° C for 0.5h, and then continued to heat to 120 ° C and kept warm for 5min to obtain a polyvinylidene fluoride solution containing double bonds; the graphene bonded with benzophenone was added to the polyvinylidene fluoride solution containing double bonds, irradiated under ultraviolet light with a wavelength of 365nm for 1h, filtered, washed, and dried to obtain graphene with surface grafted polyvinylidene fluoride;

[0041] (2) Under nitrogen (N2) atmosphere, 3.2 g (15 mmol) of 4,4'-diaminodiphenyl sulfide was added to 40 mL of N,N-dimethylacetamide (DMAc) and stirred until completely dissolved. Then, 3.3 g (15 mmol) of pyromellitic anhydride was added and stirred until completely dissolved. After stirring at room temperature for 6 h, a polyamic acid solution was obtained.

[0042] (3) 0.5 g of graphene with surface grafted polyvinylidene fluoride was added to 5 mL of N, N-dimethylacetamide (DMAc), and after ultrasonic dispersion, the resulting solution was added to the polyamide acid solution, stirred and mixed evenly, and then vacuum degassed, and then evenly coated on a glass substrate. The resulting coating was treated at 80°C, 150°C, 200°C, and 300°C for 1 hour each, cooled naturally to room temperature, taken out, and then placed in water for demolding. After taking out, vacuum drying was obtained to obtain the high dielectric polyimide film with a film thickness of 20 μm.

[0043] Example 4

[0044] A method for preparing a high dielectric polyimide film comprises the following steps:

[0045] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene was added into 20 mL of N-methylpyrrolidone (NMP) and ultrasonically dispersed uniformly, and then 0.2 g of 4-hydroxybenzophenone, heated to 60 ° C and stirred for reaction for 4 hours, then 1g of hydrated hydrazine was added, heated to 40 ° C and stirred for reaction for 6 hours, filtered, washed, and dried to obtain graphene bonded with benzophenone; 1g of polyvinylidene fluoride (PVDF) was added to 10mL of N, N-dimethylacetamide (DMAc), stirred and dissolved completely at 50 ° C, and then 3mL of tetraethylammonium hydroxide (TEAH) methanol solution (1wt%) was added under a nitrogen (N2) atmosphere, stirred and reacted at 40 ° C for 0.5h, and then continued to heat to 120 ° C and kept warm for 5min to obtain a polyvinylidene fluoride solution containing double bonds; the graphene bonded with benzophenone was added to the polyvinylidene fluoride solution containing double bonds, irradiated under ultraviolet light with a wavelength of 365nm for 1h, filtered, washed, and dried to obtain graphene with surface grafted polyvinylidene fluoride;

[0046] (2) Under nitrogen (N2) atmosphere, 1.6 g (15 mmol) of p-phenylenediamine was added to 40 mL of N,N-dimethylacetamide (DMAc) and stirred until completely dissolved. Then, 4.8 g (15 mmol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride was added and stirred until completely dissolved. After stirring at room temperature for 6 h, a polyamic acid solution was obtained.

[0047] (3) 0.5 g of graphene with surface grafted polyvinylidene fluoride was added to 5 mL of N, N-dimethylacetamide (DMAc), and after ultrasonic dispersion, the resulting solution was added to the polyamide acid solution, stirred and mixed evenly, and then vacuum degassed, and then evenly coated on a glass substrate. The resulting coating was treated at 80°C, 150°C, 200°C, and 300°C for 1 hour each, cooled naturally to room temperature, taken out, and then placed in water for demolding. After taking out, vacuum drying was obtained to obtain the high dielectric polyimide film with a film thickness of 20 μm.

[0048] Example 5

[0049] A method for preparing a high dielectric polyimide film comprises the following steps:

[0050] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene was added into 20 mL of N-methylpyrrolidone (NMP) and ultrasonically dispersed uniformly, and then 0.2 g of 4-hydroxybenzophenone, heated to 60 ° C and stirred for reaction for 4 hours, then 1g of hydrated hydrazine was added, heated to 40 ° C and stirred for reaction for 6 hours, filtered, washed, and dried to obtain graphene bonded with benzophenone; 1g of polyvinylidene fluoride (PVDF) was added to 10mL of N, N-dimethylacetamide (DMAc), stirred and dissolved completely at 50 ° C, and then 3mL of tetraethylammonium hydroxide (TEAH) methanol solution (1wt%) was added under a nitrogen (N2) atmosphere, stirred and reacted at 40 ° C for 0.5h, and then continued to heat to 120 ° C and kept warm for 5min to obtain a polyvinylidene fluoride solution containing double bonds; the graphene bonded with benzophenone was added to the polyvinylidene fluoride solution containing double bonds, irradiated under ultraviolet light with a wavelength of 365nm for 1h, filtered, washed, and dried to obtain graphene with surface grafted polyvinylidene fluoride;

[0051] (2) Under nitrogen (N2) atmosphere, 3.0 g (15 mmol) of 4,4'-diaminodiphenyl ether was added to 40 mL of N,N-dimethylacetamide (DMAc) and stirred until completely dissolved. Then, 3.3 g (15 mmol) of pyromellitic anhydride was added and stirred until completely dissolved. The mixture was stirred at room temperature for 6 h to obtain a polyamic acid solution.

[0052] (3) 0.5 g of graphene with surface grafted polyvinylidene fluoride was added to 5 mL of N, N-dimethylacetamide (DMAc), and after ultrasonic dispersion, the resulting solution was added to the polyamide acid solution, stirred and mixed evenly, and then vacuum degassed, and then evenly coated on a glass substrate. The resulting coating was treated at 80°C, 150°C, 200°C, and 300°C for 1 hour each, cooled naturally to room temperature, taken out, and then placed in water for demolding. After taking out, vacuum drying was obtained to obtain the high dielectric polyimide film with a film thickness of 20 μm.

[0053] Comparative Example 1

[0054] A method for preparing a polyimide film comprises the following steps:

[0055] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene was added into 20 mL of N-methylpyrrolidone (NMP) and ultrasonically dispersed uniformly. 1 g of hydrazine hydrate was added, and the mixture was heated to 40 ° C and stirred for 6 h. After filtering, washing, and drying, graphene was obtained;

[0056] (2) Under nitrogen (N2) atmosphere, 3.0 g (15 mmol) of 4,4'-diaminodiphenyl ether was added to 40 mL of N,N-dimethylacetamide (DMAc) and stirred until completely dissolved. Then, 4.4 g (15 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added and stirred until completely dissolved. The mixture was stirred at room temperature for 6 h to obtain a polyamic acid solution.

[0057] (3) 0.5 g of graphene was added to 5 mL of N, N-dimethylacetamide (DMAc), and after ultrasonic dispersion, the resulting solution was added to the polyamic acid solution, stirred and mixed evenly, and then vacuum degassed, and then evenly coated on a glass substrate. The resulting coating was treated at 80°C, 150°C, 200°C, and 300°C for 1 hour each, cooled naturally to room temperature, taken out, and then placed in water for demolding. After taking out, vacuum drying was obtained to obtain the polyimide film with a film thickness of 20 μm.

[0058] Comparative Example 2

[0059] A method for preparing a high dielectric polyimide film comprises the following steps:

[0060] (1) Under nitrogen (N2) atmosphere, 3.0 g (15 mmol) of 4,4'-diaminodiphenyl ether was added to 40 mL of N,N-dimethylacetamide (DMAc) and stirred until completely dissolved. Then, 4.4 g (15 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added and stirred until completely dissolved. The mixture was stirred at room temperature for 6 h to obtain a polyamic acid solution.

[0061] (2) 0.5 g of polyvinylidene fluoride was added to 5 mL of N, N-dimethylacetamide (DMAc), and after ultrasonic dispersion, the resulting solution was added to the polyamic acid solution, stirred and mixed evenly, and then vacuum degassed, and then evenly coated on a glass substrate. The resulting coating was treated at 80°C, 150°C, 200°C, and 300°C for 1 hour each, cooled naturally to room temperature, taken out, and then placed in water for demolding. After taking out, vacuum drying was obtained to obtain the high dielectric polyimide film with a film thickness of 20 μm.

[0062] The polyimide films obtained in Examples 1-5 and Comparative Examples 1-2 were subjected to the performance tests shown in the following methods. The results are shown in Table 1.

[0063] The dielectric properties of the polyimide film were tested using an Agilent 4294A precision impedance analyzer at 150° C., and the dielectric constant (ε) and dielectric loss (tan δ) were calculated at a frequency of 1 MHz.

[0064] The breakdown field strength of the polyimide film was tested using a voltage tester (TH9201B HIPOT TESTER) and the breakdown field strength (E b );

[0065] Prior to the above tests, the polyimide films were all sputter coated with aluminum.

[0066] Table 1 Performance test results of polyimide films obtained in Examples and Comparative Examples

[0067]

[0068]

[0069] As can be seen from the above table, the high dielectric polyimide film prepared by the present invention can achieve the advantages of high dielectric constant, low dielectric loss and high dielectric breakdown strength under high temperature and high field environment. As a dielectric material, it can achieve good dielectric properties and energy storage properties.

[0070] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a high dielectric polyimide film, characterized in that: The steps include: S1, performing a polycondensation reaction on a diamine monomer and a dianhydride monomer in a polar solvent to obtain a polyamic acid solution; S2, mixing the polyamic acid solution obtained in step S1 with the graphene with polyvinylidene fluoride grafted on the surface, and then performing a thermal imidization reaction and forming a film to obtain the high dielectric polyimide film; In step S2, the amount of graphene with the surface grafted polyvinylidene fluoride copolymer is 1-10wt% of the total mass of the diamine monomer and the dianhydride monomer; The graphene with surface grafted polyvinylidene fluoride is prepared by the following method: esterifying and condensing graphene oxide with hydroxylated benzophenone, followed by reduction, to obtain graphene bonded with benzophenone; adding the obtained graphene bonded with benzophenone to a solution of polyvinylidene fluoride containing double bonds, and subjecting it to free radical polymerization under ultraviolet light to obtain the graphene with surface grafted polyvinylidene fluoride; The double-bond-containing polyvinylidene fluoride is obtained by heating polyvinylidene fluoride and an organic base; the organic base is at least one of tetrabutylammonium hydroxide, tetraethylammonium hydroxide or tetramethylammonium hydroxide.

2. The method for preparing a high dielectric polyimide film according to claim 1, wherein: In step S1, the diamine monomer is at least one of p-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone or 4,4'-diaminodiphenyl sulfone; The dianhydride monomer is at least one of pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, 3,3',4,4'-diphenyl ether tetracarboxylic anhydride, 3,3',4,4'-benzophenone tetracarboxylic anhydride or 3,3',4,4'-diphenyl sulfone tetracarboxylic anhydride.

3. The method for preparing a high dielectric polyimide film according to claim 1, wherein: The molar ratio of the diamine monomer to the dianhydride monomer is 0.95-1.05:

1.

4. The method for preparing a high dielectric polyimide film according to any one of claims 1 to 3, characterized in that: In step S1, the polar solvent is at least one of N,N-dimethylacetamide, N,N-dimethylformamide or N-methylpyrrolidone.

5. The method for preparing a high dielectric polyimide film according to any one of claims 1 to 3, characterized in that: In step S1, the temperature of the polycondensation reaction is 0-30° C., and the time is 4-10 hours.

6. The method for preparing a high dielectric polyimide film according to any one of claims 1 to 3, characterized in that: The temperature of the thermal imidization reaction is 80-300° C., and the time is 3-8 hours.

7. A high dielectric polyimide film, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 6.

8. The high dielectric polyimide film according to claim 7, characterized in that: The thickness of the polyimide film is 10-50 μm.

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