A cycloolefin copolymer-furoin complex dielectric film and a method for preparing the same
By adding furoyl dioxime filler to cyclic olefin copolymers, deep electron traps are constructed and intermolecular hydrogen bonds are enhanced, solving the problems of leakage current and breakdown strength of composite dielectric films at high temperatures, and achieving a balance between insulation performance and energy storage characteristics at high temperatures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEBEI UNIV OF TECH
- Filing Date
- 2026-06-09
- Publication Date
- 2026-07-24
AI Technical Summary
Existing polymer composite dielectric films suffer from increased leakage current, decreased breakdown strength, and reduced energy storage density under high-temperature conditions. Conventional inorganic filler modification can easily introduce interfacial defects, and cyclic olefin copolymer matrices lack effective mechanisms for capturing and binding charges.
Furosilicate dioxime was used as a filler and blended with cyclic olefin copolymers, with its mass fraction controlled at 0.05%~0.3%. This constructed deep electron traps inside the film, enhanced intermolecular forces through hydrogen bond networks, suppressed carrier transport, and avoided interface defects.
It significantly improves high-temperature breakdown strength and discharge energy density, maintains capacitance and energy storage efficiency without decay, and enhances the thermal stability and insulation performance of the thin film.
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Figure CN122445129A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer-based composite dielectric materials, specifically to a cyclic olefin copolymer-furoyl dioxime composite dielectric film and its preparation method. Background Technology
[0002] Polymer film capacitors play a role in energy storage and filtering in electronic and electrical equipment. As the core component of film capacitors, the insulation properties and energy storage characteristics of the polymer dielectric film determine the energy storage density and operational reliability of the capacitor.
[0003] As electronic devices become increasingly integrated, the operating temperature of film capacitors is constantly rising. Cycloolefin copolymers, with their high insulation properties and low dielectric loss, are commonly used matrix materials in existing technologies for preparing high-temperature dielectric films. To enhance the energy storage characteristics of the polymer matrix, current technologies typically incorporate high-dielectric-constant inorganic particles as fillers into the polymer matrix to prepare composite films, thereby improving the overall dielectric constant and energy storage capacity of the material.
[0004] However, existing polymer composite dielectric films exhibit increased leakage current and decreased breakdown strength during long-term operation at high temperatures. The main reasons are: the incompatibility between the inorganic filler and the organic polymer matrix leads to interfacial structural defects introduced during physical mixing; under high temperature and high voltage electric fields, polymer chain segment movement intensifies, and these interfacial defects evolve into carrier transport channels. Furthermore, the pure cyclic olefin copolymer matrix itself is a shallow trap material, lacking an effective mechanism for capturing and binding charges. High-energy electrons injected by the electrode easily migrate through these defect channels under the drive of the electric field, leading to increased leakage current within the film and deteriorating the insulation performance of the composite film. Currently, there is a lack of a technical solution that can simultaneously avoid inorganic filler interfacial defects and construct deep traps within the polymer to effectively suppress high-temperature carrier transport. Summary of the Invention
[0005] The technical problem solved by this invention is that metallized polymer film capacitors have problems such as increased leakage current, decreased breakdown strength and decreased energy storage density when operating at a high temperature of 150°C for a long time. Existing cyclic olefin copolymer films have insufficient high-temperature breakdown strength and energy storage density, and the use of conventional inorganic fillers for modification can easily introduce interface defects, which degrades the insulation performance of the material.
[0006] To address the above problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a cyclic olefin copolymer-furfuryl dioxime composite dielectric film, which adopts the following technical solution: A cyclic olefin copolymer-furfuryl dioxime composite dielectric film comprises a cyclic olefin copolymer and furfuryl dioxime dispersed in the cyclic olefin copolymer, wherein the mass of furfuryl dioxime is 0.05% to 0.3% of the mass of the cyclic olefin copolymer.
[0007] By adopting the above technical solution, and by using furoyldioxime as a filler and controlling the mass fraction of furoyldioxime to be 0.05%~0.3%, the following effects are achieved: This invention utilizes small-molecule organic compounds to replace conventional inorganic fillers, avoiding interfacial compatibility defects that occur when inorganic particles are mixed with an organic polymer matrix. The synergistic mechanism of furoyl dioxime and cyclic olefin copolymers includes the following steps and processes: (1) Construction of deep electron traps and carrier suppression process: The lowest unoccupied molecular orbital energy level of the cyclic olefin copolymer matrix is -3.659 eV, which belongs to the shallow trap material. The lowest unoccupied molecular orbital energy level of furolanyl dioxime is -5.353 eV. The energy level difference between furolanyl dioxime and the cyclic olefin copolymer matrix enables furolanyl dioxime to construct deep electron traps inside the blend. Under the working environment of high temperature and high voltage electric field, the deep electron traps capture high-energy electrons injected by the electrode, suppress the transport process of carriers inside the film, reduce the leakage current of the material, and improve the high temperature breakdown strength of the film.
[0008] (2) Intermolecular hydrogen bond network construction and thermodynamic stability enhancement process: The -OH group on the oxime group in the furoyl dioxime molecular structure forms hydrogen bonds with the macromolecular chain of the cyclic olefin copolymer, while the N atom in the furoyl dioxime structure generates electron attraction. The aforementioned intermolecular forces, while maintaining the amorphous state of the cyclic olefin copolymer, increase the molecular chain spacing of the polymer, thereby restricting the slippage movement of polymer chain segments under high temperature conditions and improving the overall thermal stability of the composite film.
[0009] Meanwhile, the addition amount of furoyl dioxime is controlled within the range of 0.05% to 0.3% to ensure that sufficient deep trap density is formed inside the film to capture charge carriers, avoid the agglomeration of filler molecules and the formation of conductive channels due to the overlap of trap regions caused by excessive addition, and balance the high-temperature insulation properties and energy storage properties of the material.
[0010] Preferably, the mass of furoyl dioxime is 0.15% of the mass of the cyclic olefin copolymer.
[0011] By adopting the above technical solution, 0.15% is the optimal mass fraction for balancing the density of deep electron traps and the dispersion state of the filler. The breakdown strength and discharge energy density are significantly improved at 150℃, and the capacity and energy storage efficiency are maintained without decay during multiple charge-discharge cycles.
[0012] Preferably, the cyclic olefin copolymer is a random copolymer amorphous polymer copolymer formed by polymerizing ethylene and norbornene, and has a glass transition temperature of 170°C.
[0013] By adopting the above technical solution, the amorphous structure of random copolymerization provides the physical basis of low loss and high insulation, providing a uniform polymer matrix environment for the stable construction of deep electron traps.
[0014] Preferably, the chemical name of the furoyl dioxime is 1,2-di(2-furanyl)ethylenedione dioxime, the lowest unoccupied molecular orbital energy level of the furoyl dioxime is -5.353 eV, and the lowest unoccupied molecular orbital energy level of the cyclic olefin copolymer is -3.659 eV.
[0015] By adopting the above technical solution, the energy level structure parameters of the material are clearly defined, ensuring that the energy level difference between furoyl dioxime and the cyclic olefin copolymer forms a deep trap region that binds high-energy electrons.
[0016] Preferably, the -OH group on the oxime group in the furoyl dioxime structure forms a hydrogen bond with the cyclic olefin copolymer and constructs a deep electron trap inside the film, wherein the trap energy level depth of the deep electron trap is 1.23 eV to 1.72 eV.
[0017] By adopting the above technical solution, a trap energy level depth of 1.23eV~1.72eV is achieved to bind the detrapping charge at a high temperature of 150℃, preventing a sudden increase in leakage current.
[0018] Secondly, the present invention provides a method for preparing a cyclic olefin copolymer-furfuryl dioxime composite dielectric film, which adopts the following technical solution: A method for preparing a cyclic olefin copolymer-furfuryl dioxime composite dielectric thin film includes the following steps: Step S1, Mixing and Dissolving: The cyclic olefin copolymer and the furoyl dioxime are added to toluene for mixing and dissolving to obtain a homogeneous blend solution; Step S2, film formation: The blended solution is cast onto a substrate to form a film. After the toluene solvent evaporates, a thin film is obtained. Step S3, thermal annealing: The film obtained in step S2 is placed in a vacuum drying oven for thermal annealing. After cooling to room temperature, it is peeled off to obtain the cyclic olefin copolymer-furoyl dioxime composite dielectric film.
[0019] By employing the above technical solution, using solution blending and casting film-forming processes, toluene simultaneously dissolves the cyclic olefin copolymer and furoyl dioxime, enabling the small-molecule organic filler to achieve molecular-level dispersion in the polymer matrix and avoiding filler agglomeration caused by physical blending. Heat annealing removes residual solvent and internal stress from the film, improving the density of the film structure.
[0020] Preferably, in step S1, the mixing and dissolving are carried out by magnetic stirring; the mixing and dissolving temperature is 110°C and the time is 10 to 14 hours.
[0021] By adopting the above technical solution, the heating temperature and stirring time are controlled to accelerate the unfolding of polymer chains in the solvent and the diffusion process of small molecule fillers, thus ensuring the homogeneity of the precursor solution system.
[0022] Preferably, in step S2, the toluene solvent is evaporated by natural evaporation.
[0023] By adopting the above technical solution, natural evaporation slows down the solvent precipitation rate during the film formation process, preventing micropore defects from forming on the film surface due to rapid solvent evaporation.
[0024] Preferably, in step S3, the heat annealing is performed under vacuum conditions, with a temperature of 80°C to 140°C and a time of 6 to 24 hours.
[0025] By adopting the above technical solution, the vacuum environment prevents the film from oxidative degradation during the heating process; the temperature range of 80℃ to 140℃ allows the polymer chain segments to undergo appropriate rearrangement to eliminate processing stress, resulting in a film product with uniform thickness and density.
[0026] This invention provides a cyclic olefin copolymer-furfuryl dioxime composite dielectric thin film and its preparation method. It has the following beneficial effects: 1. This invention disperses furoyl dioxime at a mass fraction of 0.05% to 0.3% in a cyclic olefin copolymer matrix. Utilizing the energy level difference between furoyl dioxime and the cyclic olefin copolymer matrix, a deep electron trap is constructed within the composite film. Under the influence of high temperature and a high-voltage electric field, the deep electron trap effectively captures high-energy electrons injected by the electrode, suppressing carrier transport within the film, reducing leakage current, and improving the breakdown strength of the composite film under high-temperature conditions.
[0027] 2. This invention utilizes the hydrogen bonds formed between the -OH group on the oxime group in the furoyl dioxime molecule and the macromolecular chain of the cyclic olefin copolymer, combined with the electron attraction of the nitrogen atom, to create intermolecular interactions within the composite material. These microscopic forces, while maintaining the amorphous state of the polymer matrix, increase the inter-chain spacing, restrict the slippage of polymer chain segments under high-temperature conditions, and improve the glass transition temperature and thermal stability of the composite film.
[0028] 3. This invention uses furoyldioxime, a small-molecule organic compound, as a modified filler, avoiding the interfacial compatibility defects that occur when conventional inorganic fillers are mixed with organic polymer matrices. By controlling the amount of furoyldioxime added within a specific mass fraction range, sufficient deep trap density is ensured while preventing filler molecule aggregation, balancing the high-temperature insulation and energy storage characteristics of the composite film, and improving the discharge energy density and charge-discharge cycle stability of the composite film under high-temperature conditions. Attached Figure Description
[0029] Figure 1 This is a flowchart of the preparation method of the present invention; Figure 2 The FTIR spectra of the COC and the blended furoyl dioxime composite dielectric of the present invention are shown below. Figure 3 The above is a DSC curve of the COC and the blended furoyl dioxime composite dielectric of the present invention; Figure 4 This is a graph showing the variation of discharge energy density and energy storage efficiency of the blended furoyl dioxime composite dielectric of the present invention. Figure 5 This is a polarization curve of the blended furoyl dioxime composite dielectric of the present invention; Figure 6 This is a graph showing the capacitance variation of the blended electrophilic composite dielectric of the present invention. Detailed Implementation
[0030] Reference Figures 1-5 The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.
[0031] The cyclic olefin copolymer, CAS number 26007-43-2, is an amorphous polymer copolymer formed by the polymerization of ethylene and norbornene. The macromolecular backbone contains alicyclic structural units and ethylene structural units. The repeating units are arranged in a random copolymer state. The density is 1.02 g / cm3, the crystallinity is completely amorphous, the glass transition temperature is 170℃, and it has the physical properties of low loss and high insulation. The lowest unoccupied molecular orbital energy level of the matrix is -3.659 eV.
[0032] Furozoyl dioxime, CAS number 113-59-7, chemical name 1,2-bis(2-furanyl)ethylenedione dioxime, molecular formula C 10 H8N 2O4 The lowest unoccupied molecular orbital energy level of furoyl dioxime is -5.353 eV. The -OH group on the oxime group in the molecule can form hydrogen bonds with the cyclic olefin copolymer matrix, and the N atom in the structure has strong electron attraction properties.
[0033] Preparation Example 1: This preparation example provides a cyclic olefin copolymer-furfuryl dioxime composite dielectric film, including the following steps: A solution blending method was used to weigh a certain mass of cyclic olefin copolymer and furoyl dioxime, wherein the mass of furoyl dioxime was 0.15% of the mass of the cyclic olefin copolymer. The two were added to toluene for mixing and dissolution, and then cast into a film. After heat annealing, a composite dielectric film with uniform thickness and dense structure was obtained.
[0034] Preparation Example 2: This preparation example provides a cyclic olefin copolymer-furfuryl dioxime composite dielectric film, including the following steps: A solution blending method was used to weigh a certain mass of cyclic olefin copolymer and furoyl dioxime, wherein the mass of furoyl dioxime was 0.05% of the mass of the cyclic olefin copolymer. The two were added to toluene for mixing and dissolution, and then cast into a film. After heat annealing, a composite dielectric film with uniform thickness and dense structure was obtained.
[0035] Preparation Example 3: This preparation example provides a cyclic olefin copolymer-furfuryl dioxime composite dielectric film, including the following steps: A solution blending method was used to weigh a certain mass of cyclic olefin copolymer and furoyl dioxime, wherein the mass of furoyl dioxime was 0.3% of the mass of the cyclic olefin copolymer. The two were added to toluene for mixing and dissolution, and then cast into a film. After heat annealing, a composite dielectric film with uniform thickness and dense structure was obtained. Example
[0036] This embodiment provides a cyclic olefin copolymer-furoyl dioxime composite dielectric film and its preparation method, including the following steps: According to the specified ratio, the cyclic olefin copolymer and furoyl dioxime were weighed, wherein the mass of furoyl dioxime was 0.15% of the mass of the cyclic olefin copolymer. The cyclic olefin copolymer and furoyl dioxime were added together to toluene for mixing and dissolution. The mixture was magnetically stirred at 110°C for 12 hours to obtain a homogeneous blend solution. The blend solution was cast onto a substrate to form a film. After the toluene solvent evaporated naturally, the resulting film was placed in a vacuum drying oven and subjected to thermal annealing at 150°C for 12 hours. After cooling to room temperature, the film was peeled off to obtain a cyclic olefin copolymer-furoyl dioxime composite dielectric film with uniform thickness and dense structure. Example
[0037] This embodiment provides a cyclic olefin copolymer-furoyl dioxime composite dielectric film and its preparation method, including the following steps: According to the specified ratio, the cyclic olefin copolymer and furoyl dioxime were weighed, wherein the mass of furoyl dioxime was 0.05% of the mass of the cyclic olefin copolymer. The cyclic olefin copolymer and furoyl dioxime were added together to toluene for mixing and dissolution. The mixture was magnetically stirred at 110°C for 10 hours to obtain a homogeneous blend solution. The blend solution was cast onto a substrate to form a film. After the toluene solvent evaporated naturally, the resulting film was placed in a vacuum drying oven and subjected to thermal annealing at 80°C for 6 hours. After cooling to room temperature, the film was peeled off to obtain a cyclic olefin copolymer-furoyl dioxime composite dielectric film with uniform thickness and dense structure. Example
[0038] This embodiment provides a cyclic olefin copolymer-furoyl dioxime composite dielectric film and its preparation method, including the following steps: According to the specified ratio, the cyclic olefin copolymer and furoyl dioxime were weighed, wherein the mass of furoyl dioxime was 0.3% of the mass of the cyclic olefin copolymer. The cyclic olefin copolymer and furoyl dioxime were added together to toluene for mixing and dissolution. The mixture was magnetically stirred at 110°C for 14 hours to obtain a homogeneous blend solution. The blend solution was cast onto a substrate to form a film. After the toluene solvent evaporated naturally, the resulting film was placed in a vacuum drying oven and subjected to thermal annealing at 140°C for 24 hours. After cooling to room temperature, the film was peeled off to obtain a cyclic olefin copolymer-furoyl dioxime composite dielectric film with uniform thickness and dense structure.
[0039] Comparative Example 1: Compared with Example 1, the difference is that furoyl dioxime was not added, that is, only pure cyclic olefin copolymer was used to prepare the film, and everything else is the same.
[0040] Comparative Example 2: Compared with Example 1, the difference is that furoyl dioxime is replaced with an equal mass of conventional inorganic filler nano-alumina, otherwise the same.
[0041] Comparative Example 3: Compared with Example 1, the difference is that furoyl dioxime is replaced with an equal mass of conventional shallow-trap organic polar small molecules, otherwise they are the same.
[0042] Comparative Example 4: Compared with Example 1, the difference is that the mass of furoyl dioxime is 1.0% of the mass of the cyclic olefin copolymer, and all other aspects are the same.
[0043] Test Example 1: The thin film samples prepared in the aforementioned embodiments and comparative examples were cut to fixed sizes and placed in a silicone oil bath environment at 150°C. A DC high-voltage generator combined with a ball-plate electrode system was used to apply a DC voltage to the thin film sample at a fixed voltage increase rate until dielectric breakdown occurred. The voltage value at breakdown was recorded, and multiple sets of test data were processed using the Weibull distribution function to calculate and extract the breakdown field strength of the thin film sample. At an ambient temperature of 150°C, a ferroelectric testing system was used to apply a periodic polarization electric field to the thin film sample to obtain the hysteresis loop of the thin film sample. The discharge energy density of the thin film sample was calculated by integrating the discharge curve. The trap level depth was tested using the thermally stimulated current method. A DC electric field was applied to the thin film sample at a specific temperature to polarize it. The internal charge was frozen by cooling, and after the electric field was removed, the temperature was linearly increased at a fixed rate. The depolarization current change curve with temperature was recorded, and the trap level depth of the thin film sample was calculated according to the initial rise method formula. The glass transition temperature of the thin film sample was determined using a differential scanning calorimeter. Under nitrogen atmosphere protection, the thin film sample was weighed and placed in an aluminum crucible. The heat flow curve of the thin film sample was measured at a heating rate of 10℃ / min, and the glass transition temperature value was read from the heat flow curve.
[0044] Table 1. Test data of various performance parameters for the embodiments and comparative examples.
[0045]
[0046] in conclusion: The composite dielectric film prepared in Example 1 exhibits a breakdown strength of 588.85 MV / m and a discharge energy density of 4.48 J / cm³ at 150°C, representing a 47.8% increase in discharge energy density compared to the pure cyclic olefin copolymer film (Comparative Example 1). The lowest unoccupied molecular orbital energy level of the pure cyclic olefin copolymer is -3.659 eV, classifying it as a shallow trap material; the lowest unoccupied molecular orbital energy level of furolyl dioxime is -5.353 eV. An energy level difference exists between furolyl dioxime and the cyclic olefin copolymer matrix, constructing deep traps within the blend. Thermally stimulated current test data verifies that the trap energy level depth of the composite film in Example 1 is 1.69 eV. Under high temperature and high voltage electric fields, the deep traps capture high-energy electrons injected by the electrode, suppressing carrier transport within the film, reducing leakage current, and improving the high-temperature breakdown strength of the film.
[0047] Glass transition temperature (GLT) test results show that the GLT of the film increases after the addition of furoyl dioxime. This is because the -OH group on the oxime group in the furoyl dioxime molecule forms hydrogen bonds with the cyclic olefin copolymer matrix, and the nitrogen atom generates electron attraction. Intermolecular interactions, while maintaining the amorphous state of the matrix, increase the interchain spacing, restrict the slippage of polymer chains under high-temperature conditions, and improve the thermal stability of the composite film.
[0048] Compared with the test data of Comparative Example 2, the addition of conventional inorganic filler nano-alumina resulted in interfacial compatibility defects between the inorganic particles and the organic matrix, deteriorating the insulation performance of the film and reducing the breakdown strength to 382.41 MV / m. Comparative Example 3 added shallow-trap organic polar molecules with a trap energy level depth of 0.98 eV, which could not bind high-energy electrons under high-temperature conditions. The electrical properties of Comparative Example 3 were close to those of Comparative Example 1.
[0049] The test data from Examples 2, 3, and Comparative Example 4 reflect the influence of furoyldioxime mass fraction on film performance. When the furoyldioxime mass fraction is 0.05 wt%, the trap density within the film is low, limiting its carrier capture effect. When the furoyldioxime mass fraction is 1.0 wt%, filler molecules aggregate in the matrix, and overlapping trap regions form carrier jumping conductive channels, leading to a decrease in film breakdown strength and energy storage density. The test results demonstrate that 0.15 wt% is the optimal mass fraction for balancing deep trap density and filler dispersion.
[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A cyclic olefin copolymer-furfuryl dioxime composite dielectric film, characterized in that, The mixture comprises a cyclic olefin copolymer and furoyl dioxime dispersed in the cyclic olefin copolymer, wherein the mass of furoyl dioxime is 0.05% to 0.3% of the mass of the cyclic olefin copolymer.
2. The cyclic olefin copolymer-furfuryl dioxime composite dielectric film according to claim 1, characterized in that, The mass of furoyl dioxime is 0.15% of the mass of the cyclic olefin copolymer.
3. The cyclic olefin copolymer-furfuryl dioxime composite dielectric film according to claim 1, characterized in that, The cyclic olefin copolymer is a random copolymer amorphous polymer formed by the polymerization of ethylene and norbornene, and has a glass transition temperature of 170°C.
4. The cyclic olefin copolymer-furfuryl dioxime composite dielectric film according to claim 1, characterized in that, The chemical name of the furoyl dioxime is 1,2-di(2-furanyl)ethylenedione dioxime, the lowest unoccupied molecular orbital energy level of the furoyl dioxime is -5.353 eV, and the lowest unoccupied molecular orbital energy level of the cyclic olefin copolymer is -3.659 eV.
5. The cyclic olefin copolymer-furfuryl dioxime composite dielectric film according to claim 1, characterized in that, In the furoyl dioxime structure, the -OH group on the oxime group forms a hydrogen bond with the cyclic olefin copolymer and constructs a deep electron trap inside the film. The trap energy level depth of the deep electron trap is 1.23 eV to 1.72 eV.
6. A method for preparing a cyclic olefin copolymer-furfuryl dioxime composite dielectric thin film according to any one of claims 1-5, characterized in that, Includes the following steps: Step S1, Mixing and Dissolving: The cyclic olefin copolymer and the furoyl dioxime are added to toluene for mixing and dissolving to obtain a homogeneous blend solution; Step S2, film formation: The blend solution is cast onto a substrate to form a film. After the toluene solvent evaporates, a thin film is obtained. Step S3, thermal annealing: The film obtained in step S2 is placed in a vacuum drying oven for thermal annealing. After cooling to room temperature, it is peeled off to obtain the cyclic olefin copolymer-furoyl dioxime composite dielectric film.
7. The method for preparing a cyclic olefin copolymer-furfuryl dioxime composite dielectric thin film according to claim 6, characterized in that, In step S1, the mixing and dissolution are carried out by magnetic stirring.
8. The method for preparing a cyclic olefin copolymer-furfuryl dioxime composite dielectric thin film according to claim 6, characterized in that, In step S1, the mixing and dissolving temperature is 110°C, and the time is 10 to 14 hours.
9. The method for preparing a cyclic olefin copolymer-furfuryl dioxime composite dielectric thin film according to claim 6, characterized in that, In step S2, the toluene solvent is evaporated by natural evaporation.
10. The method for preparing a cyclic olefin copolymer-furfuryl dioxime composite dielectric thin film according to claim 6, characterized in that, In step S3, the heat annealing process is carried out under vacuum conditions, with a temperature of 80℃~140℃ and a time of 6 hours~24 hours.