A crosslinked polyimide dielectric film material and its preparation method

Abstract

The present invention relates to the technical field of dielectric material preparation, and discloses a crosslinked polyimide-based dielectric film material. A diamine monomer with a carboxyl group is introduced into the polyimide-based material for co-condensation, and then through imidization and decarboxylation crosslinking, the crosslinked polyimide-based electrolyte film material is obtained. The preparation method of the crosslinked polyimide-based dielectric film provided by the present invention does not add additional process technologies on the basis of synthesizing commercial polyimide-based dielectrics, and the surface and cross-section of the prepared dielectric film are flat, smooth and have no obvious defects.

Description

Technical Field

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

[0002] At present, with the growing demand for social production and development, more and more electrostatic capacitors are used in extreme environments under high temperature and high pressure, such as hybrid vehicles, oil and gas exploration and aerospace equipment. Compared with inorganic ceramic dielectrics, polymer dielectrics have become the preferred material in the field of electrostatic capacitors due to their high voltage resistance, low dielectric loss (tanδ), light weight and good flexibility. However, commercial polymer capacitors on the market are difficult to operate stably in high temperature environments. For example, the operating temperature of a typical commercial polymer dielectric biaxially oriented polypropylene (BOPP) does not exceed 105°C. Especially when the actual application temperature exceeds 85°C, the breakdown strength (E b ) and energy storage efficiency (η) are seriously reduced, thereby reducing the capacitance performance of the capacitor. In addition, BOPP has another well-known disadvantage, that is, the energy storage density (U) caused by the low dielectric constant e ) is low, which will inevitably increase the volume of energy storage devices in practical applications. Ferroelectric polyvinylidene fluoride (PVDF) has high dipole polarization and high U e It is another popular typical polymer dielectric, but its high dipole density causes high ferroelectric loss, especially when the molecular chain moves violently and thermally degrades under high temperature environment, the energy storage density caused by ferroelectric loss is seriously reduced. Therefore, the development of polymer dielectric materials that can be used in extreme environments for a long time and have excellent energy storage performance is a key challenge facing current research.

[0003] In order to meet the new requirements of advanced electronic devices and power systems for thinness, low cost, high throughput, scalability and stable operation under harsh conditions, the market continues to develop polymer dielectric materials with high temperature resistance, high Ue and high η, such as high glass transition temperature (T g ) and their composites. However, these dielectric materials have increased leakage current, increased conduction loss, and reduced discharge efficiency under high temperature (>150°C) and high field, which is not conducive to energy storage and conversion in extreme environments.

[0004] Generally, for the energy storage density of a dielectric (U e ) is calculated as follows: e =∫EdD, where E is the applied electric field and D is the electric displacement. For a linear dielectric, U e It can also be expressed as a formula: where ε 0is the vacuum permittivity, ε r is the intrinsic permittivity of the material, E b is the breakdown electric field. It can be seen from the above formula that by E b and ε r are the key factors to improve the dielectric energy storage density. It is worth noting that E b has a more significant impact on dielectric energy storage.

[0005] In recent years, many studies have used cross-linking methods to suppress the movement of molecular chains at high temperatures to obtain polymer dielectrics with high Tg. At the same time, the cross-linking network can be used to capture the transported carriers and suppress the leakage current, thereby effectively increasing the breakdown field strength. Therefore, constructing a cross-linking network in polymer dielectric materials to improve their high-temperature resistance and dielectric energy storage performance is a simple and effective strategy. However, traditional thermal cross-linking usually requires the additional introduction of toxic and expensive cross-linking agents. In particular, it is inevitable to produce cross-linking by-products that are difficult to remove completely during the cross-linking process. This not only relates to environmental protection and cost issues in actual production, but may also lead to a decrease in Eb and a significant reduction in energy storage performance. In addition, the cross-linking agent introduced in polyimide-based polymers may act as a capping agent for polymer molecular chains, resulting in a low polymer molecular weight and a decrease in heat resistance. Therefore, how to simply and effectively construct a cross-linking structure in polymer dielectrics and enable them to have excellent capacitance performance in extreme environments is the main technical challenge currently faced. Summary of the Invention

[0006] In view of this, the present invention provides a cross-linked polyimide-based dielectric thin film material and a preparation method thereof. The preparation method is simple and easy to operate, the reaction is controllable, and the prepared cross-linked polyimide-based dielectric thin film material has excellent high-temperature energy storage performance.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] On the one hand, the present invention provides a cross-linked polyimide-based dielectric thin film material. A diamine monomer with a carboxyl group is introduced into the polyimide-based material for co-condensation, and then imidization and decarboxylation cross-linking are carried out to obtain the cross-linked polyimide-based electrolyte thin film material.

[0009] Preferably, the diamine monomer with a carboxyl group is 3,5-diaminobenzoic acid, hereinafter referred to as the DBA monomer.

[0010] Preferably, the thickness of the cross-linked polyimide-based dielectric thin film material is 9-25 μm.

[0011] On the other hand, the present invention also provides a preparation method of the cross-linked polyimide-based dielectric thin film material according to any one of the above, including the following steps:

[0012] (1) Dissolve the anhydride monomer in an organic reagent to obtain an anhydride solution for later use;

[0013] (2) Dissolve the diamine monomer and the DBA monomer in an organic reagent to obtain a diamine mixed solution for later use;

[0014] (3) Mix and stir the anhydride solution and the diamine mixed solution to obtain a prepolymer solution;

[0015] (4) Uniformly coat the prepolymer solution on a glass plate, and perform imidization and decarboxylation crosslinking in a vacuum oven to obtain a crosslinked polyimide dielectric film material.

[0016] Preferably, the anhydride monomer in step (1) includes any one or more of 4,4'-(4,4'-isopropyl diphenoxy) diphthalic anhydride (i.e., BPADA), 4,4'-(hexafluoroisopropyl) diphthalic anhydride (6FDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), and 3,3,4,4-diphenylsulfone tetracarboxylic dianhydride (DSDA);

[0017] The organic reagent includes any one of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), and m-phenol;

[0018] The temperature for dissolving the anhydride monomer in the organic reagent is 15 - 25 °C.

[0019] Preferably, the ratio of the diamine monomer to the DBA monomer in step (2) is (1 - 100):(1 - 100);

[0020] The diamine monomer includes any one or more of 1,3-phenylenediamine, 4,4'-diaminodiphenyl ether, 1,4-phenylenediamine, and 4,4'-diaminodiphenyl sulfone.

[0021] Preferably, the ratio of the sum of the amounts of the diamine monomer and the DBA monomer to the amount of the anhydride monomer in step (3) is (1 - 1.02):(1 - 1.02).

[0022] Preferably, the conditions for the mixing and stirring in step (3) are: stirring and reacting under ice bath conditions for 12 - 36 h.

[0023] Preferably, in step (4), an imidization and decarboxylation crosslinking are carried out in the vacuum oven using a heating program, and the heating program is:

[0024] Keep the temperature at 75 - 85 °C for 2 - 3 h;

[0025] Raise the temperature from 75 - 85 °C to 95 - 110 °C and keep the temperature for 1 - 2 h;

[0026] Heat up from 95 - 110 °C to 140 - 160 °C and keep warm for 0.8 - 1 h;

[0027] Heat up from 140 - 160 °C to 190 - 210 °C and keep warm for 0.8 - 1 h;

[0028] Heat up from 190 - 210 °C to 240 - 280 °C and keep warm for 0.8 - 1 h;

[0029] Heat up from 240 - 280 °C to 330 - 370 °C and keep warm for 1 - 2 h.

[0030] Preferably, before step (4), it further includes: evacuating the prepolymer solution to remove gas.

[0031] The present invention provides a crosslinked polyimide - based dielectric film material and its preparation method. Compared with the prior art, its beneficial effects are as follows:

[0032] The preparation method of the crosslinked polyimide - based dielectric film provided by the present invention does not add additional process technologies on the basis of synthesizing commercial polyimide - based dielectrics. The surface and cross - section of the prepared dielectric film are flat, smooth and have no obvious defects.

[0033] The carboxyl group in the present invention serves as a cross - linking functional group. The cross - linking degree between molecular chains can be controlled by adjusting the content of DBA. Through cross - linking, the thermal expansion coefficient and free volume of the polyimide - based dielectric film are reduced, which helps to achieve the thermal dimensional stability of the dielectric material in extreme environments and inhibit the injection and transportation of carriers under high temperature and high field, reducing the leakage current. In addition, the uncrosslinked carboxyl groups can act as dipoles and functional groups with high electron affinity, used to enhance dipole polarization and adsorb injected electrons, inhibiting conductance loss, thereby comprehensively improving the breakdown electric field and energy storage density of commercial polyimide - based dielectric materials in extreme environments. Brief Description of the Drawings

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0035] Figure 1 It is a schematic diagram of the synthesis principle of the crosslinked polyimide - based dielectric film material;

[0036] Figure 2 It is the FT - IR diagram of the crosslinked polyetherimide in Example 1;

[0037] Figure 3It is the TGA graph of the crosslinked polyetherimide in Example 1;

[0038] Figure 4 It is the SEM graph of the crosslinked polyetherimide in Example 1;

[0039] Figure 5 It is the TMA graph of the crosslinked polyetherimide in Example 1;

[0040] Figure 6 It is the positron annihilation lifetime spectrum graph of the crosslinked polyetherimide in Example 1;

[0041] Figure 7 It is the dielectric spectrum graph of the crosslinked polyetherimide in Example 1;

[0042] Figure 8 It is the energy storage performance graph of the crosslinked polyetherimide in Example 1 at 250 °C;

[0043] Figure 9 It is the performance comparison graph of the dielectric materials of uncrosslinked PEI and crosslinked system 80PEI. Detailed implementation manners

[0044] The embodiments of the present invention will be described in detail below. The examples are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention. For those technical or conditions not specified in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0045] On the one hand, the embodiments of the present invention propose a crosslinked polyimide-based dielectric thin film material. A diamine monomer with a carboxyl group is introduced into the polyimide-based material for co-condensation, and then through imidization and decarboxylation crosslinking, the crosslinked polyimide-based electrolyte thin film material is obtained.

[0046] Specifically, the preparation method of the crosslinked polyimide-based dielectric thin film material includes the following steps:

[0047] S100. Under a nitrogen atmosphere, dissolve the anhydride monomer in an organic reagent, and stir and dissolve it in a low-temperature environment to obtain an anhydride solution for standby.

[0048] In this step, the anhydride monomer includes any one or more of 4,4'-(4,4'-isopropyl diphenoxy) diphthalic anhydride (i.e., BPADA), 4,4'-(hexafluoroisopropyl) diphthalic anhydride (6FDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), and 3,3,4,4-diphenyl sulfone tetracarboxylic dianhydride (DSDA);

[0049] The organic reagent includes any one of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), and m-phenol;

[0050] The temperature for dissolving the anhydride monomer in the organic reagent is 15-25 °C, for example, it can be 15 °C, 20 °C, 25 °C, etc.

[0051] S200. Dissolve the diamine monomer and the DBA monomer in the organic reagent to obtain a diamine mixed solution for standby.

[0052] In this step, the diamine monomer includes any one or more of 1,3-phenylenediamine (PDA), 4,4'-diaminodiphenyl ether (ODA), 1,4-phenylenediamine (p-PDA), and 4,4'-diaminodiphenyl sulfone (BOS).

[0053] The ratio of the diamine monomer to DBA is (1-100):(100-1), for example, it can be 10:90, 20:80, 40:60, 50:50, 60:40, 80:20, 90:10, etc. As the ratio increases, the crosslinking degree of the polymer increases, and the mechanical properties of the resulting polymer such as Young's modulus are improved and the heat resistance is greatly enhanced, thereby improving the application of the polymer dielectric material in extreme environments. However, if the ratio is too large and the crosslinking degree is too high, the biphenyl structure will cause the traps to become shallower, which is not conducive to energy storage in extreme environments. Therefore, this crosslinking degree needs to be appropriately controlled.

[0054] S300. Mix and stir the anhydride solution and the diamine mixed solution, and stir and react fully for 12-36 h under ice bath conditions to obtain a viscous prepolymer solution.

[0055] In this step, the molar ratio of the sum of the diamine monomer and the DBA monomer to the anhydride monomer is (1-1.02):(1-1.02), and the resulting prepolymer solution is a terpolymer. Reacting under ice bath conditions can promote the prepolymerization reaction to proceed in the direction of forming polymer chains.

[0056] In the present invention, the carboxyl group serves as a crosslinking functional group. The crosslinking degree between molecular chains can be controlled by adjusting the content of DBA. Crosslinking is used to reduce the thermal expansion coefficient and free volume of the polyimide-based dielectric film, which helps to achieve the thermal dimensional stability of the dielectric material in extreme environments and suppress the injection and transportation of carriers under high temperature and high electric field, thereby reducing the leakage current. In addition, the uncrosslinked carboxyl groups can act as dipoles and functional groups with high electron affinity, which are used to enhance dipole polarization and adsorb the injected electrons, suppressing the conduction loss, and thus comprehensively improving the breakdown electric field and energy storage density of commercial polyimide-based dielectric materials in extreme environments.

[0057] S400. The prepolymer solution is evacuated to remove the gas in the solution, and then the prepolymer solution is uniformly coated on a clean glass plate and subjected to imidization and decarboxylation crosslinking in a vacuum oven to obtain a crosslinked polyimide-based dielectric film material.

[0058] In this step, an imidization and decarboxylation crosslinking process is carried out in the vacuum oven using a temperature-rising program, and the temperature-rising program is as follows:

[0059] Keep the temperature at 75 - 85 °C for 2 - 3 h;

[0060] Raise the temperature from 75 - 85 °C to 95 - 110 °C and keep it for 1 - 2 h;

[0061] Raise the temperature from 95 - 110 °C to 140 - 160 °C and keep it for 0.8 - 1 h;

[0062] Raise the temperature from 140 - 160 °C to 190 - 210 °C and keep it for 0.8 - 1 h;

[0063] Raise the temperature from 190 - 210 °C to 240 - 280 °C and keep it for 0.8 - 1 h;

[0064] Raise the temperature from 240 - 280 °C to 330 - 370 °C and keep it for 1 - 2 h.

[0065] It should be noted that the present invention uses a temperature-rising process under vacuum conditions, which can effectively avoid the influence of impurities such as air. The slow gradient temperature-rising process is beneficial to the imide ring formation of the polymer.

[0066] In another aspect of the present invention, a crosslinked polyimide-based dielectric film material is proposed. This crosslinked polyimide-based dielectric film material is prepared by using the method described above, and its thickness is 9 - 25 μm. Thus, the above-mentioned crosslinked polyimide-based dielectric film material has all the characteristics and advantages of the method described above, which will not be elaborated here. Generally speaking, this crosslinked polyimide-based dielectric film material has outstanding high-temperature energy storage performance, stable and reliable performance, and is suitable for large-scale industrial production.

[0067] The present invention will be described below through specific embodiments. Those skilled in the art can understand that the following specific embodiments are only for the purpose of illustration and do not limit the scope of the present invention in any way. In addition, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If the specific processing conditions and methods are not clearly described in the following embodiments, the conditions and methods known in the art can be used for processing.

[0068] Example 1

[0069] (1) Under a nitrogen atmosphere, 0.6 mmol of BPADA was added, and then 1 - 1.5 mL of NMP was added. It was stirred and dissolved at 15 - 25 °C to obtain an acid anhydride solution. PDA and DBA (a total of 0.6 mmol) were formulated in proportion and dissolved in 1 - 1.5 mL of NMP. After the above two monomers were completely dissolved, the diamine mixed solution was dropped into the acid anhydride solution, and after addition, it was stirred and reacted under ice bath conditions for 24 h to obtain a PAA solution;

[0070] (2) The PAA solution was placed under vacuum conditions to remove excess gas, and then it was poured onto a clean glass plate for coating. Then it was placed at 80 °C for 2.5 h, 100 °C for 1.5 h, 150 °C for 1 h, 200 °C for 1 h, 250 °C for 1 h, 350 °C for 1.5 h, cooled down, and the polymer was peeled off with warm water. Then it was placed at 80 °C for drying to obtain a crosslinked polyetherimide film.

[0071] In this embodiment, the ratio of PDA and DBA was used as a variable for research. The specific ratios of PDA and DBA were 1:0 (PEI), 8:2 (20PEI), 6:4 (40PEI), 4:6 (60PEI), 2:8 (80PEI), 0:1 (100PEI), respectively. And the performance tests were carried out on each obtained crosslinked polyetherimide film. The results are shown in Figure 2-8 .

[0072] Among them, the electrical properties of the crosslinked polyetherimide film were tested by the following method: A metal mask plate with a circular hole diameter of 2 mm was designed. The prepared dielectric material was sandwiched between two metal mask plates, and gold electrodes were sputtered symmetrically on the upper and lower surfaces. The upper and lower surfaces were sputtered at a power of 120 W for 140 s, and then the performance tests were carried out using a ferroelectric workstation and an impedance analyzer.

[0073] As Figure 2 shown are the FT-IR diagrams of the crosslinked polyetherimide under various PDA and DBA ratio conditions, which can illustrate the existence of the crosslinked structure;

[0074] As Figure 3The TGA graph of crosslinked polyetherimide under the condition that the ratio of PDA to DBA is 2:8 is shown, indicating the presence of a decarboxylation crosslinking structure;

[0075] As Figure 4 The SEM graphs of crosslinked polyetherimide under various ratios of PDA to DBA are shown, proving that the crosslinked film has no obvious defects;

[0076] As Figure 5 The TMA graph of crosslinked polyetherimide under the condition that the ratio of PDA to DBA is 2:8 is shown, indicating the thermal dimensional stability of the crosslinked film;

[0077] As Figure 6 The positron annihilation lifetime spectrum graph of crosslinked polyetherimide under the condition that the ratio of PDA to DBA is 2:8 is shown, proving that crosslinking reduces its free volume;

[0078] As Figure 7 The dielectric spectroscopy graphs of crosslinked polyetherimide under various ratios of PDA to DBA are shown, proving that the uncrosslinked carboxyl groups and the crosslinked structure are beneficial to increasing the dipole density, thereby enhancing polarization;

[0079] As Figure 8 The energy storage performance graph of crosslinked polyetherimide under the condition that the ratio of PDA to DBA is 2:8 at 250 °C is shown. The structure shows that the polymer dielectric material with the optimal composition obtains 3.65 J / cm 3 , and the efficiency (η) is 92.69%. This indicates that the presence of the crosslinked structure is beneficial to extending the operating temperature limit of commercial polymers for energy storage applications and suppressing losses, improving the energy storage performance in extreme environments.

[0080] Comparative Example 1

[0081] (1) Under a nitrogen atmosphere, 0.6 mmol of BPADA was added, and then 1 - 3 mL of NMP was added. The mixture was stirred and dissolved at 15 - 25 °C to obtain an anhydride solution. PDA and DBA (a total of 0.6 mmol) were prepared in a ratio of 2:8 and dissolved in 1 - 3 mL of NMP. After the above two monomers were completely dissolved, the diamine mixed solution was dropped into the anhydride solution, and after addition, the mixture was stirred and reacted in an ice bath for 24 h to obtain a PAA solution;

[0082] (2) The PAA solution was placed under vacuum conditions to remove excess gas, and then it was poured onto a clean glass plate for coating. Then it was subjected to stepwise heating and insulation at 70 - 350 °C for a total of 8.5 h, cooled, and the polymer was peeled off with warm water. Then it was placed in an oven at 80 °C to dry, and a crosslinked polyetherimide film could be obtained.

[0083] Comparative Example 2

[0084] This comparative example is a conventional method for preparing crosslinked polyetherimide films in the current industry. When the diamine monomer is only PDA, the preparation process is as follows:

[0085] (1) Under a nitrogen atmosphere, add 0.6 mmol of BPADA, then add 1 - 3 mL of NMP, stir and dissolve at 15 - 25 °C to obtain an anhydride solution. Dissolve PDA (0.6 mmol) in 1 - 3 mL of NMP. After the above two monomers are completely dissolved, drop the diamine solution into the anhydride solution, and stir and react for 24 h under ice bath conditions to obtain a prepolymer solution;

[0086] (2) Place the prepolymer solution under vacuum conditions to remove excess gas, then pour it onto a clean glass plate for coating. Then place it under stepwise heating and insulation at 70 - 350 °C for a total of 8.5 h, cool down, peel the polymer with warm water, and then dry it at 80 °C to obtain a commercial polyetherimide film, that is, PEI. The structural characterization and thermal characterization are as shown in Example 1.

[0087] The polyetherimide film prepared from Comparative Example 2 can only be used at temperatures not exceeding 200 °C, and the polymer capacitance performance is poor, as Figure 9 shown. The results show that PEI obtains an energy storage density of 2.25 J / cm 3 at 200 °C, while the energy storage density of the crosslinked dielectric 80PEI is 5.67 J / cm 3 .

[0088] In the description of this specification, the descriptions referring to terms such as "one embodiment", "another embodiment", "yet another embodiment", "some embodiments", "some specific embodiments", "some other specific embodiments", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment are included in at least one embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Additionally, it should be noted that in this specification, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features.

[0089] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. An application of a cross-linked polyimide film material, characterized in that: Using the cross-linked polyimide film material as a dielectric film material; A cross-linked polyimide film material is obtained by introducing a carboxyl-containing diamine monomer into a polyimide material for co-condensation, and then cross-linking by imidization and decarboxylation; the carboxyl-containing diamine monomer is 3,5-diaminobenzoic acid; The cross-linked polyimide film material is prepared by the following method: (1) dissolving anhydride monomer in an organic reagent to obtain anhydride solution for later use; (2) dissolving the diamine monomer and 3,5-diaminobenzoic acid in an organic reagent at a molar ratio of (1-100):(1-100) to obtain a diamine mixed solution for later use; (3) mixing and stirring the acid anhydride solution and the diamine mixed solution to obtain a prepolymer solution; (4) uniformly coating the precursor solution on a glass plate, and performing imidization and decarboxylation cross-linking in a vacuum oven to obtain a cross-linked polyimide dielectric film material; The acid anhydride monomer is 4,4'-(4,4'-isopropyldiphenoxy) diphthalic anhydride.

2. The use of the cross-linked polyimide film material according to claim 1, characterized in that: The thickness of the cross-linked polyimide dielectric film material is 9-25 μm.

3. The use of the cross-linked polyimide film material according to claim 1, characterized in that: The organic reagent in step (1) includes any one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and m-phenol; The temperature at which the anhydride monomer is dissolved in the organic reagent is 15-25°C.

4. The use of the cross-linked polyimide film material according to claim 1, characterized in that: The diamine monomer in step (2) includes any one or more of 1,3-phenylenediamine, 4,4'-diaminodiphenyl ether, 1,4-phenylenediamine, and 4,4'-diaminodiphenyl sulfone.

5. The use of the cross-linked polyimide film material according to claim 1, characterized in that: In step (3), the ratio of the sum of the amounts of the diamine monomer and the DBA monomer to the amount of the anhydride monomer is (1-1.02):(1-1.02).

6. The use of the cross-linked polyimide film material according to claim 1, characterized in that: The mixing and stirring conditions in step (3) are: stirring the reaction in an ice bath for 12-36 hours.

7. The use of the cross-linked polyimide film material according to claim 1, characterized in that: In step (4), the vacuum oven adopts a temperature rising program to carry out imidization and decarboxylation cross-linking, and the temperature rising program is: Keep warm at 75-85℃ for 2-3h; Raise the temperature from 75-85℃ to 95-110℃ and keep warm for 1-2h; Raise the temperature from 95-110℃ to 140-160℃, keep warm for 0.8-1h; Raise the temperature from 140-160℃ to 190-210℃, keep warm for 0.8-1h; Raise the temperature from 190-210℃ to 240-280℃, keep warm for 0.8-1h; Raise the temperature from 240-280℃ to 330-370℃ and keep warm for 1-2h.

8. The use of the cross-linked polyimide film material according to claim 1, characterized in that: Before performing step (4), the method further includes: evacuating the precursor solution to remove gas.

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