Polyimide dielectric film and preparation method and application thereof

Abstract

The invention relates to the field of dielectric films, in particular to a polyimide dielectric film and a preparation method and application thereof. The preparation method of the polyimide dielectric film comprises the following steps: mixing 1, 3-m-phenylenediamine, a tC diamine monomer, an anhydride monomer and an organic solvent in an inert atmosphere to obtain a mixed solution; carrying out condensation polymerization on the mixed solution in an inert atmosphere to obtain a precursor solution; and coating a substrate with the precursor solution for imidization to obtain the polyimide dielectric film. Semi-aromatic PI constructed by common MPD is used as a matrix, tC type diamine monomers with high rigidity and configuration disturbance characteristics are copolymerized and introduced into a main chain in a controllable proportion, cooperative regulation and control of chain segment thermal motion and an aggregation state structure are achieved, and therefore better high-temperature energy storage stability and breakdown reliability are obtained.

Description

Technical Field

[0001] This invention relates to the field of dielectric thin films, and more particularly to a polyimide dielectric thin film, its preparation method, and its application. Background Technology

[0002] High-temperature dielectric thin-film capacitors are key components in aerospace electric propulsion, deep well exploration, and pulsed power systems. Their service environment requires long-term stable operation under high electric fields and high temperatures, placing comprehensive performance requirements on the core dielectric materials, demanding high energy density, high efficiency, high stability, and a wide temperature range. Currently, existing dielectric materials are insufficient to meet these extreme service demands, exhibiting significant performance shortcomings. While general-purpose polymer dielectrics, such as polypropylene, possess advantages like low loss and high breakdown strength, their low heat resistance upper limit and insufficient temperature stability create a natural bottleneck in high-temperature power capacitor applications, making them unsuitable for long-term stable operation under high-temperature conditions. Inorganic ceramic dielectrics, despite their high temperature resistance and high dielectric constant, are limited by high brittleness, difficulties in thin-film forming, and sensitivity to interface defects. Furthermore, they are prone to dielectric nonlinearity under alternating electric fields, compromising reliability. Therefore, developing polymer dielectric materials that balance flexible processing characteristics with high temperature resistance and strong electric field tolerance has become an important research direction in the field of high-temperature energy storage devices.

[0003] Among various high-temperature polymer dielectrics, polyimide (PI) films are considered one of the most promising materials due to their excellent thermal stability, mechanical strength, and chemical resistance. However, the energy storage applications of polyimide under high-temperature and strong electric fields still face several intractable performance constraints. Specifically: on the one hand, improving the dielectric constant of polyimide usually requires the introduction of strongly polar groups or the enhancement of segment charge polarization ability, but this approach often leads to increased dielectric loss and enhanced conductivity contribution, resulting in decreased charge and discharge efficiency and increased Joule heating, affecting the long-term stability of the device. On the other hand, improving the breakdown strength of the material requires reducing defect density, suppressing charge injection and transport, and reducing local electric field distortion. However, while high planar rigidity or highly conjugated structures improve the thermal stability and mechanical modulus of the material, they can induce stronger intermolecular interactions and ordered stacking, forming "fast channels" for charge migration, or even forming electron transfer complexes, which in turn reduces the breakdown strength of the material. Furthermore, high-temperature environments exacerbate the aforementioned performance degradation: high temperatures significantly enhance the mobility and free volume evolution of polyimide molecular chain segments, promote space charge accumulation and increase conductivity loss, ultimately leading to a rapid decline in the material's energy density and charge / discharge efficiency as temperature increases.

[0004] To address the performance contradictions arising from the coupling of chain segment structure, aggregate state, and charge excitation behavior, existing modification approaches mainly include composite reinforcement, intrinsic structure design, and copolymerization regulation. Among these, the filler / interface-dependent composite approach is extremely sensitive to dispersion effects and interface quality, easily introducing micro-defects and amplifying local electric field distortion, making it difficult to achieve stable improvements in overall performance. In contrast, while the copolymerization regulation approach promises to simultaneously adjust chain segment rigidity and inter-chain interactions at the molecular backbone level, thereby synergistically improving the material's thermal stability, aggregate state structure, and charge migration behavior, better meeting the performance requirements of high-temperature energy storage films, existing copolymerization regulation schemes still fail to effectively solve the challenge of balancing polyimide's ability to increase glass transition temperature (Tg) with maintaining film toughness and suppressing ordered inter-chain stacking, thus failing to meet the extreme service requirements of high-temperature dielectric film capacitors. Summary of the Invention

[0005] This invention provides a polyimide dielectric film, its preparation method, and its application, to solve the problem that existing high-temperature polyimide dielectric materials struggle to balance increasing Tg with maintaining film toughness and inhibiting ordered chain stacking.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a method for preparing a polyimide dielectric thin film, comprising the following steps: Under an inert atmosphere, 1,3-m-phenylenediamine, tC-type diamine monomer, acid anhydride monomer and organic solvent are mixed to obtain a mixed solution; Under an inert atmosphere, the mixed solution undergoes a polycondensation reaction to obtain a precursor solution; The precursor solution is coated onto the substrate and imidized to obtain a polyimide dielectric film.

[0007] In some specific embodiments, the molar ratio of the 1,3-m-phenylenediamine to the tC-type diamine monomer is (90~99):(1~10).

[0008] In some specific embodiments, the molar ratio of the anhydride monomer to the total molar ratio of the 1,3-m-phenylenediamine and tC-type diamine monomers is 1:1 to 1:1.05.

[0009] In some specific embodiments, the solute content in the mixed solution is 10wt%~20wt%.

[0010] In some specific embodiments, the tC-type diamine monomer includes at least one selected from 4,4'-(propane-2,2-diyl)diphenylamine, 1,1-bis(4-aminophenyl)cyclohexane, 2,2-bis(4-aminophenyl)hexafluoropropane, and 4,4'-diamino-3,3'-dimethyldiphenylmethane.

[0011] In some specific embodiments, the anhydride monomer includes dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, or 4,4'-(hexafluoroisopropene)phthalic anhydride.

[0012] In some specific embodiments, the temperature of the polycondensation reaction is 15~25°C, and the time of the polycondensation reaction is 12~24h.

[0013] In some specific embodiments, the ambient temperature for coating is 50~80°C.

[0014] In some specific embodiments, after the coating is completed, the process further includes: drying. In some specific embodiments, the imidization process is as follows: First, react in an oxygen atmosphere at 160~210℃ for 2~3 hours, then react in a vacuum at 260~300℃ for 2~3 hours.

[0015] A second aspect of the present invention also provides a polyimide dielectric film prepared by the above-described method for preparing polyimide dielectric films.

[0016] In some specific embodiments, the thickness of the polyimide dielectric film is 9~11 μm.

[0017] A third aspect of the present invention also provides the application of the above-described polyimide dielectric film in a dielectric capacitor.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing polyimide dielectric films by introducing tC-type diamine monomers to prepare semi-aromatic polyimide copolymer (CoPI-tC) dielectric materials. Using semi-aromatic PI constructed with commonly used MPD as the matrix, tC-type diamine monomers with high rigidity and configurational perturbation characteristics are copolymerized into the main chain in a controllable proportion, achieving synergistic regulation of chain segment thermal motion and aggregated structure. On the one hand, this significantly increases the material's Tg, suppressing chain segment relaxation and free volume evolution at high temperatures; on the other hand, it weakens the tendency of MPD-PI to achieve ordered interchain stacking, reducing the possibility of continuous charge migration channels and electron transfer complexes (CTCs), thereby obtaining superior high-temperature energy storage stability and breakdown reliability. Furthermore, this invention employs a conventional polyimide solution polymerization, film formation, and imidization route, requiring no additional crosslinking agents or inorganic fillers. The process path is simple, highly manufacturable, and the solvent system is recyclable, facilitating green preparation and large-scale application. Based on the above structural design, the copolyimide dielectric film material maintains efficient and stable energy storage and rapid charge-discharge capabilities under high temperature and high electric field conditions of 200~250℃, and has a high level of energy storage density, meeting the extreme service requirements of high temperature dielectric film capacitors. Attached Figure Description

[0019] The above and other objects, features, and advantages of the invention will be apparent from the following description of preferred embodiments illustrating the gist of the invention and its use, and the accompanying drawings, in which: Figure 1 The images show actual pictures of the precursor solutions for Comparative Examples 1-2 and Example 1.

[0020] Figure 2 This is the reaction flow chart for Comparative Example 1.

[0021] Figure 3 This is the reaction flow chart for Comparative Example 2.

[0022] Figure 4 This is a reaction flow diagram of Example 1.

[0023] Figure 5 The DSC curves are for the polyimide dielectric films obtained in Comparative Examples 1-2 and Example 1.

[0024] Figure 6 The dielectric constant and dielectric loss of the polyimide dielectric films obtained in Comparative Examples 1-2 and Example 1 vary with temperature.

[0025] Figure 7 The leakage current density of the polyimide dielectric films obtained in Comparative Examples 1-2 and Example 1 is shown at 200°C and 250°C, where (a) is at 200°C and (b) is at 250°C.

[0026] Figure 8 The energy storage density and energy efficiency of the polyimide dielectric films obtained in Comparative Examples 1-2 and Example 1 are shown at 200°C and 250°C, respectively, where (a) is at 200°C and (b) is at 250°C.

[0027] Figure 9 The service life of the polyimide dielectric films obtained in Comparative Example 1 and Example 1 at 250°C. Detailed Implementation

[0028] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments described below are for illustrative purposes only and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the following embodiments, conditions and methods known in the art can be used for processing.

[0029] This invention provides a method for preparing a polyimide dielectric thin film, comprising the following steps: Under an inert atmosphere, 1,3-m-phenylenediamine, tC-type diamine monomer, acid anhydride monomer and organic solvent are mixed to obtain a mixed solution; Under an inert atmosphere, the mixed solution undergoes a polycondensation reaction to obtain a precursor solution; The precursor solution is coated onto the substrate and imidized to obtain a polyimide dielectric film.

[0030] The preparation of polyimide dielectric films of the present invention is based on the polycondensation reaction of 1,3-m-phenylenediamine and acid anhydride monomers, and further introduces tC-type diamine monomers with high rigidity and configuration disturbance characteristics as copolymerization modifiers. By adjusting the copolymerization molar ratio of tC and MPD diamines, CoPI-tC film materials with different copolymerization compositions are obtained.

[0031] This invention focuses on the synthesis and preparation of three types of polyimides: the first is a semi-aromatic polyimide (MPD-PI) based on 1,3-m-phenylenediamine (MPD); the second is a pure tC-type polyimide (Pure-tC) constructed by introducing high-rigidity tC-type diamine monomers, such as 4,4'-(propane-2,2-diyl)diphenylamine, which is characterized by significantly improving polymer segment rigidity and Tg, and generating structural perturbations in the inter-chain stacking mode; the third is a CoPI-tC film system obtained by copolymerizing MPD with tC-type diamines. Among them, MPD-PI films have good film-forming properties and certain toughness, but a low glass transition temperature (Tg). At high temperatures, segment relaxation intensifies, easily leading to conductive loss and space charge accumulation. Although the Pure-tC system has a higher Tg and stronger segment thermal stability, its inter-chain stacking efficiency and film toughness are insufficient, and the material is generally brittle. To this end, the present invention introduces tC-type diamine monomers into the main chain of MPD-PI via copolymerization: on the one hand, it utilizes the rigid structure to increase the Tg of the system and suppress the thermal motion of chain segments at high temperatures; on the other hand, it uses the configuration characteristics to disturb the original inter-chain stacking and orderly aggregation of MPD-PI, reducing the formation of charge continuous migration channels and electron transfer complexes (CTC), thereby synergistically improving the low-loss characteristics and breakdown reliability of the film under high-temperature conditions.

[0032] In this invention, an inert atmosphere includes, but is not limited to, nitrogen, argon, etc.

[0033] In some embodiments, the molar ratio of the 1,3-m-phenylenediamine to the tC-type diamine monomer is (90~99):(1~10). As an example, the molar ratio of the 1,3-m-phenylenediamine to the tC-type diamine monomer can be 99:1, 98:2, 97:3, 96:4, 95:5, 96:4, 97:3, 98:2, and 99:1, etc.

[0034] In this invention, by controlling the molar ratio of 1,3-m-phenylenediamine to tC-type diamine monomers within the aforementioned range, it is beneficial to the complete formation of the film and to prevent the introduction of excessive internal stress that could lead to thermal cracking. If the content of 1,3-m-phenylenediamine is too high, it will result in severe charge transfer between imide rings, severe intermolecular stacking, and a decrease in Tg; if the content of tC-type diamine monomers is too high, it will result in excessive steric hindrance of the film, leading to film cracking.

[0035] In some embodiments, the molar ratio of the anhydride monomer to the total molar ratio of the 1,3-m-phenylenediamine and tC-type diamine monomers is 1:1 to 1:1.05. As examples, the molar ratio of the anhydride monomer to the total molar ratio of the 1,3-m-phenylenediamine and tC-type diamine monomers can be 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.04, and 1:1.05, etc.

[0036] In some embodiments, the solute content in the mixed solution is 10 wt% to 20 wt%. As examples, the solute content in the mixed solution can be 10 wt%, 12 wt%, 15 wt%, 18 wt%, and 20 wt%, etc.

[0037] In this invention, the solute content in the mixed solution has a certain influence on the film thickness and film-forming properties.

[0038] In some embodiments, the tC-type diamine monomer includes, but is not limited to, at least one of 4,4'-(propane-2,2-diyl)diphenylamine, 1,1-bis(4-aminophenyl)cyclohexane, 2,2-bis(4-aminophenyl)hexafluoropropane, and 4,4'-diamino-3,3'-dimethyldiphenylmethane.

[0039] In some embodiments, the anhydride monomer includes, but is not limited to, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, or 4,4'-(hexafluoroisopropene)diphthalic anhydride.

[0040] In some embodiments, the temperature of the polycondensation reaction is 15~25°C, and the time of the polycondensation reaction is 12~24h. As an example, the temperature of the polycondensation reaction can be 15°C, 18°C, 20°C, 22°C, and 25°C, etc., and the time of the polycondensation reaction can be 12h, 15h, 16h, 18h, 22h, 22h, and 24h, etc.

[0041] In some embodiments, the polycondensation reaction is carried out in a sealed environment to avoid the adsorption of water molecules during the reaction process, which could affect the reaction progress.

[0042] In some embodiments, before coating the precursor solution onto the substrate, the process further includes: performing a vacuum process to remove bubbles from the precursor solution.

[0043] In some embodiments, the ambient temperature for coating is 50~80°C. As an example, the ambient temperature for coating can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, and 80°C, etc.

[0044] In this invention, the material of the substrate is not specifically limited, and a glass substrate can be selected.

[0045] In some embodiments, after the coating process is completed, the process further includes drying.

[0046] In this invention, the drying conditions are not specifically limited; the solvent can be removed. In some embodiments, the drying temperature can be 60-80°C, and the drying time can be 30-60 minutes.

[0047] In some embodiments, the imidization process: First, react in an oxygen atmosphere at 160-210°C for 2-3 hours, then react in a vacuum at 260-300°C for 2-3 hours. For example, in an oxygen atmosphere, the reaction temperature can be 160°C, 170°C, 180°C, 190°C, 200°C, and 210°C, and the reaction time can be 2 hours, 2.5 hours, and 3 hours, respectively; in a vacuum, the reaction temperature can be 260°C, 270°C, 280°C, 290°C, and 300°C, and the reaction time can be 2 hours, 2.5 hours, and 3 hours, respectively.

[0048] A second aspect of the present invention also provides a polyimide dielectric film prepared by the above-described method for preparing polyimide dielectric films.

[0049] In some specific embodiments, the thickness of the polyimide dielectric film is 10 μm.

[0050] A third aspect of the present invention also provides the application of the above-described polyimide dielectric film in a dielectric capacitor.

[0051] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Comparative Example 1 The preparation process of polyimide dielectric thin films MPD-PI is as follows: Figure 2 As shown, it includes the following steps: Under a nitrogen atmosphere, 1,3-m-phenylenediamine (MPD) and N-methylpyrrolidone (NMP) were mixed and dissolved by stirring at room temperature (25°C). Then, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride was added, with a molar ratio of dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride to 1,3-m-phenylenediamine of 1:1, to obtain a mixed solution with a solute concentration of 15 wt%. The solution was then subjected to a polycondensation reaction at room temperature (25°C) for 24 h under sealed conditions to obtain a precursor solution. The precursor solution was vacuum-treated to remove air bubbles, and then uniformly coated onto a glass substrate at an ambient temperature of 50°C. After drying in a 70°C forced-air drying oven for 45 min, imidization was performed. The imidization process involved reacting at 190°C for 2 h in an oxygen atmosphere, followed by reacting at 260°C for 2 h under vacuum conditions to obtain a polyimide dielectric film MPD-PI with a thickness of 10 μm.

[0053] Comparative Example 2 The preparation process of the polyimide dielectric thin film Pure-tC is as follows: Figure 3 As shown, the steps include: Under a nitrogen atmosphere, 4,4'-(propane-2,2-diyl)diphenylamine and N-methylpyrrolidone (NMP) were mixed and dissolved by stirring at room temperature (25°C). Then, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride was added, with a molar ratio of 1:1 to 4,4'-(propane-2,2-diyl)diphenylamine, to obtain a mixed solution with a solute concentration of 15 wt%. The solution was then subjected to a polycondensation reaction at 25°C for 24 h under sealed conditions to obtain a precursor solution. The precursor solution was vacuum-treated to remove air bubbles, and then uniformly coated onto a glass substrate at an ambient temperature of 50°C. After drying in a 60°C forced-air drying oven for 1 hour, imidization was performed. The imidization process involved reacting at 200°C in an oxygen atmosphere for 2 hours, followed by reacting at 260°C under vacuum for 2 hours to obtain a polyimide dielectric film Pure-tC with a thickness of 10 μm.

[0054] Example 1 The preparation process of polyimide dielectric films CoPI-tC is as follows: Figure 4 As shown, it includes the following steps: Under a nitrogen atmosphere, 1,3-m-phenylenediamine (MPD) and N-methylpyrrolidone were mixed and dissolved by stirring at room temperature (25°C). Then, 4,4'-(propane-2,2-diyl)diphenylamine and dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride were added sequentially to obtain a mixed solution with a solute content of 15 wt%. The molar ratio of 1,3-m-phenylenediamine to 4,4'-(propane-2,2-diyl)diphenylamine was 95:5, and the molar ratio of dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride to the total molar ratio of 1,3-m-phenylenediamine and 4,4'-(propane-2,2-diyl)diphenylamine was 1:1. The mixture was then subjected to a polycondensation reaction at room temperature (25°C) for 24 h under sealed conditions to obtain a precursor solution. The precursor solution was vacuum-treated to remove air bubbles, and then uniformly coated onto a glass substrate at an ambient temperature of 50°C. After drying in a 70°C forced-air drying oven for 45 min, imidization was performed. The imidization process involved reacting at 190°C for 2 h in an oxygen atmosphere, followed by reacting at 260°C for 2 h under vacuum conditions, to obtain a polyimide dielectric film CoPI-tC with a thickness of 10 μm.

[0055] Figure 1 The images show the precursor solutions in Comparative Examples 1-2 and Example 1, from left to right: Comparative Example 1, Example 1, and Comparative Example 2.

[0056] according to Figures 2-4 It is understood that the present invention introduces the tC-type diamine monomer 4,4'-(propane-2,2-diyl)diphenylamine as a comonomer into the MPD-based semi-aromatic PI backbone, thereby achieving synergistic regulation of chain segment rigidity and aggregated structure without introducing inorganic fillers and additional crosslinking agents.

[0057] Performance testing The polyimide dielectric films prepared in Comparative Examples 1-2 and Example 1 were sandwiched between two metal masks with circular holes of 3 mm in diameter, and gold electrodes were symmetrically sputtered onto the upper and lower surfaces. Performance tests were conducted using a ferroelectric workstation, a differential scanning calorimeter, and a mechanical property testing machine.

[0058] Figure 5 The DSC curves are for the polyimide dielectric films obtained in Comparative Examples 1-2 and Example 1. (From...) Figure 5 It can be seen that the Tg of the polyimide dielectric film CoPI-tC obtained in Example 1 is increased from 262.18℃ to 269.52℃ compared with the single MPD-based film. The polyimide dielectric film in Example 1 has enhanced resistance to deformation and thermal stability at high temperatures, while maintaining good film-forming properties and structural integrity.

[0059] Figure 6 The dielectric constant and dielectric loss of the polyimide dielectric films obtained in Comparative Examples 1-2 and Example 1 vary with temperature.

[0060] Figure 7 The leakage current density of the polyimide dielectric films obtained in Comparative Examples 1-2 and Example 1 at 200°C and 250°C.

[0061] Depend on Figure 6 and Figure 7 It is evident that the configuration characteristics of the tC structural unit can weaken the tendency of ordered interchain stacking in MPD-PI, reduce the possibility of continuous charge migration channels and electron transfer complexes (CTCs), suppress space charge accumulation, and maintain dielectric loss at a lower level. This is manifested in the reduction of thin film leakage current density to 3.3 × 10⁻⁶ under high temperature conditions of 200℃ and 250℃ and an electric field of 300 MV / m. -8 A·cm -2 and 1.92×10 -7 A·cm -2 .

[0062] Figure 8 The energy storage density and energy efficiency of the polyimide dielectric films obtained in Comparative Examples 1-2 and Example 1 at 200°C and 250°C are shown.

[0063] Figure 9The service life of the polyimide dielectric films obtained in Comparative Example 1 and Example 1 at 250°C.

[0064] Depend on Figure 8 and Figure 9 It is evident that the CoPI-tC semi-aromatic polyimide dielectric film prepared by this invention exhibits excellent energy storage performance and cycle stability under high temperature and high electric field conditions: with an energy storage efficiency ≥90%, the energy storage density can reach 6.0-8.5 J·cm at 200℃. -3 At 250℃, the energy storage density can reach 3.5-5.0 J·cm³. -3 At 250℃ and 400MV·m -1 The electric field circulation exceeds 5×10 4 Second-rate.

[0065] The technical solution of this invention does not require the introduction of inorganic fillers or additional crosslinking systems. The process route can follow the conventional polyimide solution polymerization, film formation, and imidization process. The raw materials are readily available, the process is controllable, and it is easy to scale up. It is suitable for industrial-scale preparation and provides a new technical path for developing high-temperature stable and high-efficiency polymer dielectric energy storage film materials.

[0066] Although preferred embodiments of the invention have been shown and described, it is conceivable that those skilled in the art can devise various modifications to the invention within the spirit and scope of the appended claims.

Claims

1. A method for preparing a polyimide dielectric thin film, characterized in that, Includes the following steps: Under an inert atmosphere, 1,3-m-phenylenediamine, tC-type diamine monomer, acid anhydride monomer and organic solvent are mixed to obtain a mixed solution; Under an inert atmosphere, the mixed solution undergoes a polycondensation reaction to obtain a precursor solution; The precursor solution is coated onto the substrate and imidized to obtain a polyimide dielectric film.

2. The method for preparing polyimide dielectric films according to claim 1, characterized in that, The molar ratio of the 1,3-m-phenylenediamine to the tC-type diamine monomer is (90~99):(1~10).

3. The method for preparing polyimide dielectric films according to claim 1, characterized in that, The molar ratio of the anhydride monomer to the total molar ratio of the 1,3-m-phenylenediamine and tC-type diamine monomers is 1:1 to 1:1.

05.

4. The method for preparing polyimide dielectric films according to claim 1, characterized in that, The solute content in the mixed solution is 10wt%~20wt%.

5. The method for preparing polyimide dielectric films according to claim 1, characterized in that, The tC-type diamine monomers include at least one of 4,4'-(propane-2,2-diyl)diphenylamine, 1,1-bis(4-aminophenyl)cyclohexane, 2,2-bis(4-aminophenyl)hexafluoropropane, and 4,4'-diamino-3,3'-dimethyldiphenylmethane.

6. The method for preparing polyimide dielectric films according to claim 1, characterized in that, The anhydride monomers include dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, or 4,4'-(hexafluoroisopropene)diphthalic anhydride.

7. The method for preparing polyimide dielectric films according to claim 1, characterized in that, The polycondensation reaction is carried out at a temperature of 15~25℃ for 12~24h. The ambient temperature for coating is 50~80℃; After the coating process is completed, the next step is drying.

8. The method for preparing polyimide dielectric films according to claim 1, characterized in that, The iminolation process: First, react in an oxygen atmosphere at 160~210℃ for 2~3 hours, then react in a vacuum at 260~300℃ for 2~3 hours.

9. A polyimide dielectric film prepared by the method of any one of claims 1 to 8; The thickness of the polyimide dielectric film is 9-11 μm.

10. The application of the polyimide dielectric film of claim 9 in a dielectric capacitor.

Images