A composition solution, polyimide film, and preparation method and application

Abstract

The present application relates to the field of polyimide film, in particular to a composition solution, a polyimide film and a preparation method and application. The composition solution comprises a functional compound solution and a polyamide acid solution, and the functional compound solution comprises a functional compound and a first solvent. The present application can increase the peeling strength of the polyimide film and copper foil, aluminum foil and other materials, thereby enhancing the reliability of the polyimide film material application, by mixing the specific functional compound solution with the polyamide acid solution to prepare the polyimide film or the modified polyimide film, while ensuring that the main performance of the polyimide film remains unchanged.

Description

Technical Field

[0001] This invention relates to the field of polyimide films, specifically to a composition solution, a polyimide film, a preparation method thereon, and its applications. Background Technology

[0002] Polyimide (PI) films possess excellent comprehensive properties such as high temperature resistance, high strength and toughness, high electrical insulation, low thermal expansion, and low dielectric constant. They are widely used in high-tech fields such as aerospace, ultra-large-scale microelectronics manufacturing and packaging, and electrical insulation, and have important and extensive application value, playing a role that cannot be replaced by other materials.

[0003] In recent years, with the rapid development of miniaturization, thinning, and intelligence of electronic devices, flexible IC packaging substrates are being driven towards ultra-thinness, finer wiring, and multi-layering. The narrow line width and narrow line spacing of flexible circuit boards require that the copper foil and PI film have sufficiently strong bonding strength to ensure the reliability of electronic devices during long-term use. However, most PI films currently used in industrial applications are processed from polyamic acid solutions obtained by polycondensation of aromatic dianhydrides such as pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride with semi-rigid or rigid aromatic diamines. The molecular structure of these PI films has high rigidity and is highly oriented along the film plane, resulting in low surface free energy. This leads to poor bonding performance between the PI film and other dielectric materials such as copper foil and aluminum foil, which seriously affects the in-depth application of PI films in high-tech fields.

[0004] Zheng Chaoluan et al. reported that treating PI films with oxygen plasma can effectively improve the peel strength between PI films and copper foils, reaching a maximum of 0.25 N / mm ("Influence of Plasma Treatment Conditions on the Surface Treatment Effect of Polyimide Films", Surface Technology, Vol. 41, No. 3, 2012). Que Zhengbo et al. reported that immersing PI films sequentially in 10% sodium hydroxide solution and 10% hydrochloric acid solution can significantly improve the hydrophilicity of the PI film surface ("Surface Modification of Polyimide Films by Acid and Alkali Treatment", Polymer Materials Science and Engineering, Vol. 25, No. 5, 2010). Zhang Fan et al. reported that corona treatment of PI film surfaces can significantly improve their surface roughness. However, all three methods will damage the surface structure of the PI film, change its surface morphology and roughness, and have a significant destructive impact on the mechanical properties of thinner PI films. JP1988225629A reports a PI resin containing siloxane segments. When prepared into PI films, it can effectively improve the surface adhesion of PI films. However, the PI resin is synthesized from a monomer containing siloxane diamine. The preparation of this monomer is complex and expensive, which is not conducive to industrialization. At the same time, an excessive proportion of siloxane segments will also affect other properties of the PI film.

[0005] The aforementioned existing technologies have the following problems: Traditional PI films (such as the pyromellitic dianhydride / aromatic diamine system) suffer from poor adhesion and insufficient peel strength to copper / aluminum foils due to their rigid molecular structure and low surface free energy. Existing modification methods (plasma, acid-base treatment, corona treatment) can damage the film surface structure, affecting mechanical properties and exhibiting significant side effects. While PI resins containing siloxane segments can improve adhesion, the monomers are expensive and may sacrifice other properties, presenting a cost-performance contradiction. Summary of the Invention

[0006] This application provides a composition solution, a polyimide film, a preparation method, and an application. By mixing a specific functional compound solution with a polyamic acid solution, a polyimide film or a coated modified polyimide film can be prepared. This can increase the peel strength of the polyimide film to materials such as copper foil and aluminum foil while ensuring that the main properties of the polyimide film remain unchanged, thereby enhancing the reliability of the polyimide film material application.

[0007] In a first aspect, this application provides a composition solution comprising a functional compound solution and a polyamic acid solution, wherein the functional compound solution comprises a functional compound and a first solvent, wherein the functional compound has the structural formula shown in Formula I:

[0008]

[0009] Formula I

[0010] Wherein, R1 is methyl or ethyl; R2 is the following functional group:

[0011] .

[0012] The composition solution described above, wherein the functional compound comprises at least one of 2-((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid, 4-((3-carboxyphenyl)sulfonyl)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid, and 4-(3-acetoxyphenoxy)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid;

[0013] And / or, the first solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, acetone, butanone, toluene, ethyl acetate, tetrahydrofuran, chloroform, m-cresol, γ-butyrolactone, and water.

[0014] In the composition solution described above, the functional compound accounts for 5-20% by mass in the functional compound solution;

[0015] And / or, the mass ratio of the functional compound solution to the polyamic acid solution is 10:1 to 1:10.

[0016] The composition solution described above, wherein the polyamic acid solution is formed by the condensation polymerization of aromatic dianhydride and aromatic diamine in a dipolar aprotic solvent;

[0017] And / or, the solid content of the polyamic acid solution is 15-30%;

[0018] And / or, the viscosity of the polyamic acid solution is 100~3000P.

[0019] Secondly, this application provides a method for preparing a composition solution, comprising the following steps:

[0020] A1. Under a nitrogen atmosphere, γ-aminopropyltriethoxysilane or γ-aminopropyltrimethoxysilane is dissolved in a first solvent and stirred until homogeneous. Then, an acid anhydride compound is added, and the mixture is reacted at 0-80℃ for 1-72 hours to obtain a solution containing the functional compound.

[0021] A2. The crude functional compound is separated from the solution containing the functional compound, and then washed and dried to obtain the functional compound.

[0022] A3. Dissolve the functional compound in a first solvent to obtain a functional compound solution, and mix the functional compound solution with a polyamic acid solution to obtain a composition solution.

[0023] In the above-mentioned method for preparing the composition solution, in step A1, the molar ratio of γ-aminopropyltriethoxysilane or γ-aminopropyltrimethoxysilane to the acid anhydride compound is 1.01:1 to 1.1:1.

[0024] And / or, in step A1, the anhydride compound includes at least one of 1,2,4-benzenetricarboxylic anhydride, 3-chlorophthalic anhydride, 2-ethylhexyl-1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid ester, 3-acetamidophthalic anhydride, 1,3-dioxo-1,3-dihydroisobenzofuran-4-sulfonic acid, 3-((1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)sulfonyl)benzoic acid, 1,3-dioxo-1H,3H-benzo[de]isocoumarin-6-carboxylic acid, 1,2,4-cyclohexanetricarboxylic anhydride, and 3-((1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)oxy)benzoic acid ester.

[0025] In the above-mentioned method for preparing the composition solution, in step A2, when separating the crude functional compound from the solution containing the functional compound, the crude functional compound is obtained by vacuum distillation and recrystallization.

[0026] And / or, when separating crude functional compounds from a solution containing functional compounds, the solution containing functional compounds is added dropwise to a precipitating agent, precipitate, separate, and obtain crude functional compounds.

[0027] Thirdly, this application provides a polyimide film prepared using a solution comprising the composition described above, or prepared using a solution comprising a composition prepared according to the method described above.

[0028] The polyimide film described above is a single-layer structure and is formed by reacting and converting a composition solution.

[0029] The method for preparing the polyimide film with the single-layer structure described above includes the following steps:

[0030] B1. The composition solution is extruded through a die onto an annular steel strip to form a first adhesive film;

[0031] B2. Heat and dry the first adhesive film to form the second adhesive film;

[0032] B3. Peel the second adhesive film off the steel strip, and after imidization and biaxial stretching, obtain a polyimide film.

[0033] In the above-described method for preparing a single-layer polyimide film, in step B3, the polyimide film contains compound α, the structural formula of which is shown in Formula II:

[0034]

[0035] Formula II

[0036] Wherein, R3 is at least one of the following groups:

[0037] .

[0038] In the method for preparing a single-layer polyimide film as described above, in step B1, a chemical imidizing agent is also added to the composition solution;

[0039] The chemical imidizing agent includes one or more components selected from dehydrating agents, catalysts, second solvents, and auxiliaries.

[0040] In the method for preparing a single-layer polyimide film as described above, in step B1, the mass ratio of the functional compound solution to the polyamic acid solution in the composition solution is 10:1 to 1:10.

[0041] The mass ratio of the composition solution to the chemical imidizing reagent is 20:1 to 1:1;

[0042] And / or, in step B2, the heating temperature of the first adhesive film is 45-180℃, and the drying time is 90-360s.

[0043] In the method for preparing a single-layer polyimide film as described above, step B3 includes one of thermal imidization, chemical imidization, or a combination of chemical imidization and thermal imidization during imidization.

[0044] During thermal imidization, the temperature is 180-450℃ and the thermal imidization time is 180-300s;

[0045] During chemical imidization, the second film is placed in a tank containing a chemical imidizing reagent and heated; the heating temperature is 30~100℃ and the heating time is 30-60s.

[0046] In the process of combining chemical imidization with thermal imidization, the second film, which has undergone at least one chemical imidization treatment, is then subjected to at least one thermal imidization treatment.

[0047] And / or, in step B3, during bidirectional stretching, the stretching ratio of the longitudinal stretching is 1:1-1.1, and the stretching ratio of the transverse stretching is 1:1-1.2;

[0048] During longitudinal stretching, the stretching temperature is 80-150℃ and the stretching time is 10-30s;

[0049] When stretching laterally, the stretching temperature is 180-450℃ and the stretching time is 180-300s.

[0050] The polyimide film described above has a double-layer structure, comprising a first layer and a second layer, wherein the second layer is disposed on the first layer; the first layer is formed by imidization of a polyamic acid solution, and the second layer is formed by reaction of a composition solution.

[0051] The method for preparing the bilayer polyimide film as described above includes the following steps:

[0052] C1. The polyamic acid solution is extruded through a die onto an annular steel strip to form a third adhesive film;

[0053] C2. Heat and dry the third adhesive film to obtain the fourth adhesive film;

[0054] C3. The composition solution is extruded through a die and cast onto the surface of the fourth film to form the fifth film;

[0055] C4. Heat and dry the fifth adhesive film to obtain the sixth adhesive film;

[0056] C5. The sixth adhesive film is peeled off from the steel strip, and then imidized and biaxially stretched to obtain a polyimide composite film.

[0057] In the above-described method for preparing a double-layer polyimide film, the heating temperature of the third adhesive film is 45-100℃, and the drying time is 15-60s.

[0058] And / or, the heating temperature of the fifth adhesive film is 80-180℃, and the drying time is 75-300s.

[0059] In the preparation method of the double-layer polyimide film described above, in step C1, a chemical imidizing agent is added to the polyamic acid solution, mixed evenly, degassed, and then extruded through a die.

[0060] Fourthly, this application provides an application of a composition solution for the surface modification of polyimide films.

[0061] As described above, the surface modification of the polyimide film includes the following steps:

[0062] D1. Perform surface corona treatment on the polyimide film;

[0063] D2. Coat the surface of the polyimide film treated in step D1 with a functional compound solution;

[0064] D3. The polyimide film treated by D2 is heated, dried, and subjected to high-temperature treatment to obtain a surface-modified polyimide film.

[0065] As described above, in step D1, the power of the corona treatment is 15-30 kW, and the treatment time is 1-10 seconds.

[0066] And / or, in step D3, the heating temperature is 80-240℃ and the drying time is 60-180s;

[0067] And / or, in step D3, the high-temperature treatment is carried out at a temperature of 180-450℃ for a time of 30-90 seconds.

[0068] Fifthly, this application provides a flexible copper-clad laminate, which is prepared by combining the above-mentioned polyimide film or a polyimide film with a copper plate.

[0069] Sixthly, this application provides a polyimide aluminum foil composite film, which is prepared by combining the above-mentioned polyimide film or a polyimide film with a composition solution surface modified with aluminum foil.

[0070] The present invention, employing the above-described solution, has at least the following beneficial effects:

[0071] In this application, a polyimide film or a coated and modified polyimide film is prepared by mixing a specific functional compound solution with a polyamic acid solution. This can increase the peel strength between the polyimide film and materials such as copper foil and aluminum foil while ensuring that the main properties of the polyimide film remain unchanged, thereby enhancing the reliability of the polyimide film material application. Attached Figure Description

[0072] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application.

[0073] Figure 1 This is a schematic diagram of a double-layer polyimide film in an embodiment of this application. Detailed Implementation

[0074] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0075] To increase the peel strength of polyimide films to materials such as copper and aluminum foil while maintaining the overall properties of the polyimide film, the inventors researched the raw materials and preparation methods of polyimide films. They discovered that existing modification methods (plasma, acid-base treatment, corona treatment) damage the film surface structure, negatively impacting mechanical properties and exhibiting significant side effects. While PI resins containing siloxane segments can improve adhesion, the monomers are expensive and may sacrifice other properties, presenting a trade-off between cost and performance.

[0076] In view of this, embodiments of this application provide a composition solution comprising a functional compound solution and a polyamic acid solution, wherein the functional compound solution comprises a functional compound and a first solvent, wherein the structural formula of the functional compound is shown in Formula I:

[0077]

[0078] Formula I

[0079] Wherein, R1 is methyl or ethyl; R2 is the following functional group:

[0080] .

[0081] In this embodiment, the polyimide film or coating-modified polyimide film prepared by mixing a specific functional compound solution with a polyamic acid solution can increase the peel strength between the polyimide film and materials such as copper foil and aluminum foil while ensuring that the main properties of the polyimide film remain unchanged, thereby enhancing the reliability of polyimide film material applications.

[0082] In one specific embodiment, the functional compound includes at least one of 2-((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid, 4-((3-carboxyphenyl)sulfonyl)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid, and 4-(3-acetoxyphenoxy)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid.

[0083] In one specific embodiment, the first solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, acetone, butanone, toluene, ethyl acetate, tetrahydrofuran, chloroform, m-cresol, γ-butyrolactone, and water.

[0084] In this embodiment, the first solvent includes water and one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, acetone, butanone, toluene, ethyl acetate, tetrahydrofuran, chloroform, m-cresol, and γ-butyrolactone; wherein the water may be deionized water. Exemplarily, the first solvent includes water and N,N-dimethylformamide or water and N,N-dimethylacetamide.

[0085] In one specific embodiment, the functional compound accounts for 5-20% of the mass of the functional compound solution. By controlling the mass percentage of the functional compound in the functional compound solution, the quality of the film prepared by the subsequent imidization reaction can be improved.

[0086] In one specific embodiment, water accounts for 0.1-1% of the mass of the functional compound solution. By controlling the amount of water, the imidization reaction can occur prematurely, thereby improving the stability of the solution.

[0087] In one specific embodiment, the mass ratio of the functional compound solution to the polyamic acid solution is 10:1 to 1:10. By controlling the mass ratio, on the one hand, the film-forming properties and mechanical strength of the film can be improved, and the process controllability of film preparation can be enhanced; on the other hand, the application scenarios of the prepared film can be expanded.

[0088] In this embodiment, those skilled in the art can adjust the mass ratio of the functional compound and water in the functional compound solution, and can also adjust the mass ratio of the functional compound solution to the polyamic acid solution; this application does not impose any particular limitation.

[0089] In one specific embodiment, the polyamic acid solution is formed by the condensation polymerization of aromatic dianhydride and aromatic diamine in a dipolar aprotic solvent.

[0090] In one specific embodiment, the solid content of the polyamic acid solution is 15-30%; wherein, the solid content refers to the mass percentage of polyamic acid solids in the polyamic acid solution. By controlling the solid content in the polyamic acid solution, on the one hand, the viscosity, rheological properties, and storage stability of the polyamic acid solution can be adjusted; on the other hand, the film-forming properties and imidization reaction during subsequent film preparation can be affected. Those skilled in the art can adjust the solid content of the polyamic acid solution.

[0091] In one specific embodiment, the viscosity of the polyamic acid solution is 100~3000P. By controlling the viscosity of the polyamic acid solution, its rheological properties can be adjusted, and its processing performance, film quality, mechanical properties, and process stability can be optimized. Those skilled in the art can adjust the viscosity of the polyamic acid solution.

[0092] This application also provides a method for preparing the above-mentioned composition solution, including the following steps:

[0093] A1. Under a nitrogen atmosphere, γ-aminopropyltriethoxysilane or γ-aminopropyltrimethoxysilane is dissolved in a first solvent and stirred until homogeneous. Then, an acid anhydride compound is added, and the mixture is reacted at 0-80℃ for 1-72 hours to obtain a solution containing the functional compound.

[0094] A2. The crude functional compound is separated from the solution containing the functional compound, and then washed and dried to obtain the functional compound.

[0095] A3. Dissolve the functional compound in a first solvent to obtain a functional compound solution, and mix the functional compound solution with a polyamic acid solution to obtain a composition solution.

[0096] Using the above-mentioned technical means, under nitrogen protection, a solution containing functional compounds is first generated by reaction, and then crude functional compounds are separated from the solution containing functional compounds. Finally, pure functional compounds are obtained by washing and drying. The pure functional compounds are dissolved in water and organic solvents to obtain a functional compound solution, which is then mixed with a polyamic acid solution to obtain a composition solution. The preparation method is simple and easy to produce.

[0097] In one specific embodiment, in step A1, the molar ratio of γ-aminopropyltriethoxysilane or γ-aminopropyltrimethoxysilane to the acid anhydride compound is 1.01:1 to 1.1:1. By controlling the molar ratio, the reaction rate can be regulated, process efficiency can be improved, and the utilization rate of raw materials can be increased.

[0098] In one specific embodiment, in step A1, the anhydride compound includes at least one selected from 1,2,4-benzenetricarboxylic anhydride, 3-chlorophthalic anhydride, 2-ethylhexyl-1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid ester, 3-acetamidophthalic anhydride, 1,3-dioxo-1,3-dihydroisobenzofuran-4-sulfonic acid, 3-((1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)sulfonyl)benzoic acid, 1,3-dioxo-1H,3H-benzo[de]isocoumarin-6-carboxylic acid, 1,2,4-cyclohexanetricarboxylic anhydride, and 3-((1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)oxy)benzoate. In this embodiment, the specific selection of the anhydride compound is not limited.

[0099] In one specific embodiment, in step A2, when separating the crude functional compound from the solution containing the functional compound, the crude functional compound is obtained by vacuum distillation followed by recrystallization.

[0100] In one specific embodiment, in step A2, when separating the crude functional compound from the solution containing the functional compound, the solution containing the functional compound is added dropwise to a precipitant, precipitate, and separate to obtain the crude functional compound. In this embodiment, the method for preparing the crude functional compound is simple and convenient. Those skilled in the art can choose from the two methods provided above for obtaining the crude functional compound; there is no limitation on how the crude functional compound is obtained from the solution containing the functional compound.

[0101] Specifically, when a solution containing a functional compound is added dropwise to a precipitant, and the mixture is precipitated and separated to obtain a crude functional compound, the precipitant includes one or a mixture of two of methanol, ethanol, propanol, water, toluene, and isopropanol. In this embodiment, the specific choice of precipitant is not limited.

[0102] This application also provides a polyimide film prepared using a solution comprising the above-described composition, or prepared using a solution comprising a composition prepared according to the method described above.

[0103] This application also provides a polyimide film, which is a single-layer structure. The single-layer polyimide film is formed by the transformation of a composition solution through reactions such as imidization, hydrolysis, and crosslinking.

[0104] In one specific embodiment, the thickness of the polyimide film is 5~200μm, and those skilled in the art can adjust the thickness of the polyimide film according to the actual situation.

[0105] This application also provides a method for preparing the above-mentioned monolayer polyimide film, including the following steps:

[0106] B1. The composition solution is extruded through a die onto an annular steel strip to form a first adhesive film;

[0107] B2. Heat and dry the first adhesive film to form the second adhesive film;

[0108] B3. Peel the second adhesive film off the steel strip, and after imidization and biaxial stretching, obtain a polyimide film.

[0109] Using the above-mentioned technical means, after the composition solution undergoes reactions such as imidization, hydrolysis, and crosslinking (this reaction process is a complex physical and chemical reaction process, and the imidization, hydrolysis, and crosslinking reactions described are the main reactions), the functional compound is transformed into compound α. Compound α is uniformly distributed inside and on the surface of the film, which can enhance the peel strength with materials such as copper foil and aluminum foil.

[0110] In step B3, the polyimide film contains compound α, the structural formula of which is shown in Formula II:

[0111]

[0112] Formula II

[0113] The wavy line represents cross-linking, which allows the molecules to form chemical bonds with other molecules. R3 is at least one of the following groups:

[0114] .

[0115] In one specific embodiment, in step B1, a chemical imidizing agent is also added to the composition solution. By adding the chemical imidizing agent, the formation or transformation of the imine structure is promoted, which can optimize the performance of the prepared film and improve the process efficiency.

[0116] In one specific embodiment, the chemical imidizing agent includes one or more components selected from dehydrating agents, catalysts, second solvents, and auxiliaries.

[0117] Specifically, the dehydrating agent includes one or a combination of two of acetic anhydride, trifluoroacetic anhydride, benzoic anhydride, acetyl chloride, and thionyl chloride. In this embodiment, the specific choice of dehydrating agent is not limited.

[0118] Specifically, the catalyst includes one or more combinations of quinoline, isoquinoline, pyridine, 3-methylpyridine, triethylamine, and N-methylimidazole. In this embodiment, the specific choice of catalyst is not limited.

[0119] Specifically, the second solvent includes one or more combinations of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. In this embodiment, the specific choice of the second solvent is not limited.

[0120] Specifically, the additives include one or a combination of two of tricresyl phosphate, triphenyl phosphate, diphenyltoluene phosphate, and trioctyl trimellitate. In this embodiment, the specific selection of the additives is not limited.

[0121] In one specific embodiment, in step B1, the mass ratio of the functional compound solution to the polyamic acid solution in the composition solution is 10:1 to 1:10. By controlling the mass ratio of the two, on the one hand, the film-forming properties and mechanical strength of the film can be improved, and the process controllability of film preparation can be enhanced; on the other hand, the application scenarios of the prepared film can be expanded.

[0122] In one specific embodiment, during step B1, when the chemical imidizing agent is added, the mass ratio of the composition solution to the chemical imidizing agent is 20:1 to 1:1. By controlling the amount of chemical imidizing agent added, the degree of completion of the imidization reaction can be controlled, thereby optimizing the physicochemical properties of the film. In this embodiment, those skilled in the art can adjust the mass ratio of the functional compound solution and the polyamic acid solution in the composition solution, as well as the mass ratio of the composition solution to the chemical imidizing agent.

[0123] In one specific embodiment, in step B2, the heating temperature of the first adhesive film is 45-180℃, and the drying time is 90-360s. By heating and drying the first adhesive film under the above conditions, on the one hand, the adhesive film can be cured, facilitating subsequent processing; on the other hand, the first adhesive film can be pre-imidized, which is beneficial for subsequent processing. In this embodiment, those skilled in the art can adjust and select the heating temperature and drying time of the first adhesive film.

[0124] In one specific embodiment, during step B3, the imidization process includes one of thermal imidization, chemical imidization, or a combination of chemical imidization and thermal imidization. By employing different imidization methods, on the one hand, it is beneficial to improve the performance of the polyimide film; on the other hand, it facilitates the selection of different imidization methods according to different situations.

[0125] Furthermore, during thermal imidization, the temperature is 180-450℃, and the thermal imidization time is 180-300s. By controlling the temperature and time, the reaction kinetics of thermal imidization are controlled to optimize the molecular chain structure, balance process efficiency and film performance, and achieve a comprehensive improvement in the film's high-temperature resistance, mechanical strength, surface quality, and process stability. In this embodiment, those skilled in the art can adjust and select the temperature and time for thermal imidization.

[0126] Furthermore, during chemical imidization, the second film is placed in a tank containing a chemical imidizing agent and heated; the heating temperature is 30-100°C, and the heating time is 30-60 seconds. Through treatment with the chemical imidizing agent and heating, the imidization of the polyimide film can react rapidly at a relatively low temperature, avoiding thermal damage and side reactions. Simultaneously, it can regulate the molecular chain structure, optimizing and improving the performance of the polyimide film. In this embodiment, those skilled in the art can adjust and select the temperature and time for chemical imidization.

[0127] Furthermore, in the combination of chemical imidization and thermal imidization, the second film, which has undergone at least one chemical imidization treatment, is then subjected to at least one thermal imidization treatment. By combining chemical imidization with thermal imidization, the overall performance of the polyimide film can be improved, meeting the application requirements of polyimide films in different scenarios. In this embodiment, the number of chemical imidization and thermal imidization treatments is not limited; those skilled in the art can select the number of treatments for each imidization process according to actual conditions.

[0128] In one specific embodiment, during step B3, the longitudinal stretching ratio is 1:1-1.1, and the transverse stretching ratio is 1:1-1.2. By controlling the ratio of transverse to longitudinal stretching, the molecular chain orientation and crystal structure of the film can be optimized to adapt the film to different application scenarios. In this embodiment, those skilled in the art can adjust the stretching ratio of longitudinal and transverse stretching.

[0129] In one specific embodiment, during longitudinal stretching, the stretching temperature is 80-150℃ and the stretching time is 10-30s. By controlling the temperature and time of longitudinal stretching, the molecular chain mobility can be activated, improving the mechanical properties and dimensional stability of the film, which is beneficial to improving the overall performance of the polyimide film. In this embodiment, those skilled in the art can adjust the temperature and time of longitudinal stretching.

[0130] In one specific embodiment, during transverse stretching, the stretching temperature is 180-450℃, and the stretching time is 180-300s. By controlling the temperature and time of transverse stretching, the molecular chain mobility can be activated, improving the mechanical properties and dimensional stability of the film, which is beneficial to improving the overall performance of the polyimide film. In this embodiment, those skilled in the art can adjust the temperature and time of transverse stretching.

[0131] This application also provides a bilayer polyimide film, which includes a first layer and a second layer, with the second layer disposed on the first layer. The first layer is formed by imidization of a polyamic acid solution, and the second layer is formed by imidization, hydrolysis, and crosslinking of a composition solution.

[0132] In one specific embodiment, the polyimide film with a bilayer structure has a first layer with a thickness of 5-200 μm and a second layer with a thickness of 1-20 μm. Those skilled in the art can adjust and select the thickness of the first and second layers.

[0133] This application also provides a method for preparing the above-mentioned bilayer polyimide film, including the following steps:

[0134] C1. The polyamic acid solution is extruded through a die onto an annular steel strip to form a third adhesive film;

[0135] C2. Heat and dry the third adhesive film to obtain the fourth adhesive film;

[0136] C3. The composition solution is extruded through a die and cast onto the surface of the fourth film to form the fifth film;

[0137] C4. Heat and dry the fifth adhesive film to obtain the sixth adhesive film;

[0138] C5. The sixth adhesive film is peeled off from the steel strip, and then imidized and biaxially stretched to obtain a polyimide composite film.

[0139] Using the above-mentioned technical means, after the polyamic acid solution is first converted to an imidization to form a film, the composition solution is then formed into a film, and then imidization, hydrolysis, crosslinking and other reactions are carried out (this reaction process is a complex physical and chemical reaction process, and the imidization, hydrolysis and crosslinking reactions described are the main reactions), a polyimide composite film with a double-layer structure is obtained. The functional compound in the composition solution is transformed into compound α, which is uniformly distributed in the interior and surface of the second layer. This not only enhances the peel strength between the first layer and the second layer, but also enhances the peel strength with materials such as copper foil and aluminum foil.

[0140] In this embodiment, the compound α in the bilayer polyimide film has the same structural formula as the compound α in the monolayer polyimide film, and achieves the same effect. Therefore, it will not be described in detail here.

[0141] In the above method for preparing the double-layer polyimide film, the heating temperature of the third adhesive film is 45-100℃, and the drying time is 15-60s. Pre-curing the third adhesive film by heating and drying facilitates subsequent processing.

[0142] In the above-described method for preparing a double-layer polyimide film, the heating temperature of the fifth film is 80-180℃, and the drying time is 75-300s. Heating and drying the fifth film not only cures and pre-imides it, but also facilitates subsequent imidization and stretching. In this embodiment, those skilled in the art can adjust the heating temperature and drying time of the third and fifth films.

[0143] In one specific embodiment, in step C1, a chemical imidizing agent is added to the polyamic acid solution, mixed thoroughly, degassed, and then extruded through a die. By adding the chemical imidizing agent first, the polyamic acid solution is partially pre-imidized, which optimizes the solution rheological properties, suppresses volume shrinkage during heat treatment, improves the overall performance of the film, and reduces the difficulty and defect rate of the subsequent thermal imidization process.

[0144] In this embodiment, the chemical imidizing agent used in the preparation method of the bilayer polyimide film has the same composition as that used in the preparation method of the monolayer polyimide film, so it will not be described in detail here.

[0145] In the above-mentioned method for preparing a bilayer polyimide film, the mass ratio of the functional compound solution to the polyamic acid solution in the composition solution is 10:1 to 1:10. By controlling the mass ratio of the two, on the one hand, the film-forming properties and mechanical strength of the film can be improved, and the process controllability of film preparation can be enhanced; on the other hand, the application scenarios of the prepared film can be expanded.

[0146] In the above-described method for preparing a bilayer polyimide film, the mass ratio of the composition solution to the chemical imidizing agent is 20:1 to 1:1. By controlling the amount of chemical imidizing agent added, the degree of completion of the imidization reaction can be controlled, thereby optimizing the physicochemical properties of the film. In this embodiment, those skilled in the art can adjust the mass ratio of the functional compound solution and the polyamic acid solution in the composition solution, as well as the mixing mass ratio of the composition solution to the chemical imidizing agent.

[0147] In one specific embodiment, during step C5, the imidization process includes one of thermal imidization, chemical imidization, or a combination of chemical imidization and thermal imidization. In this embodiment, the imidization method is not limited; those skilled in the art can select a specific imidization method based on the actual situation.

[0148] In this embodiment, the specific implementation conditions for thermal imidization, chemical imidization, or a combination of chemical imidization and thermal imidization are the same as those for imidization in the preparation method of monolayer polyimide films, and therefore will not be described in detail here.

[0149] In one specific embodiment, during step C5, the longitudinal stretching ratio is 1:1-1.1, and the transverse stretching ratio is 1:1-1.2. By controlling the ratio of transverse to longitudinal stretching, the molecular chain orientation and crystal structure of the film can be optimized to adapt the film to different application scenarios. In this embodiment, those skilled in the art can adjust the stretching ratio of longitudinal and transverse stretching.

[0150] In one specific embodiment, during longitudinal stretching, the stretching temperature is 80-150℃ and the stretching time is 10-30s. By controlling the temperature and time of longitudinal stretching, the molecular chain mobility can be activated, improving the mechanical properties and dimensional stability of the film, which is beneficial to improving the overall performance of the polyimide film. In this embodiment, those skilled in the art can adjust the temperature and time of longitudinal stretching.

[0151] In one specific embodiment, during transverse stretching, the stretching temperature is 180-450℃, and the stretching time is 180-300s. By controlling the temperature and time of transverse stretching, the molecular chain mobility can be activated, improving the mechanical properties and dimensional stability of the film, which is beneficial to improving the overall performance of the polyimide film. In this embodiment, those skilled in the art can adjust the temperature and time of transverse stretching.

[0152] Through the above-mentioned technical means, this application can prepare single-layer polyimide films and double-layer polyimide films, enabling polyimide films with different structures to be used in different fields, thus increasing their applicability.

[0153] This application also provides an application of a composition solution for the surface modification of polyimide films.

[0154] In the above applications, the surface modification of polyimide films includes the following steps:

[0155] D1. Perform surface corona treatment on the polyimide film;

[0156] D2. Coat the surface of the polyimide film treated in step D1 with a functional compound solution;

[0157] D3. The polyimide film treated by D2 is heated, dried, and subjected to high-temperature treatment to obtain a surface-modified polyimide film.

[0158] By employing the aforementioned technical methods, the surface adhesion properties of the polyimide film modified with a functional compound solution can be enhanced. This allows for the upgrading and modification of existing polyimide films, thereby expanding their application range.

[0159] In one specific embodiment, in step D1, the polyimide film is a film prepared from the polyamic acid solution in this application or a commercially available polyimide film.

[0160] For example, the commercially available polyimide film is one of the following: Kanekachi Chemical's Apcial series (Japan), DuPont's Kapton series (USA), or Ube Industries' Upliex series (Japan). It can also be a domestically produced polyimide film; in this embodiment, the specific selection of the commercially available polyimide film is not limited.

[0161] In one specific embodiment, in step D1, the power of the corona treatment is 15-30 kW, and the treatment time is 1-10 seconds. By adopting the above conditions, the surface energy of the polyimide film can be controlled and the interfacial bonding force optimized, thereby improving processing efficiency. In this embodiment, those skilled in the art can adjust the power and time of the corona treatment.

[0162] In this embodiment, after corona treatment, the finished polyimide film has a dyn value ≥60 dyn on its surface, which enables the functional compound solution to have a stronger surface bonding ability with the finished polyimide film.

[0163] In one specific embodiment, in step D2, the functional compound solution is coated by at least one of the following methods: blade coating, gravure coating, extrusion, spraying, spin coating, and dip coating. This embodiment does not limit the specific coating method; those skilled in the art can choose according to the actual situation.

[0164] In one specific embodiment, in step D3, the heating temperature is 80-240°C, and the drying time is 60-180 seconds; through heating and drying, the functional compound solution can be cured onto the surface of the polyimide film. In this embodiment, those skilled in the art can adjust the heating temperature and drying time.

[0165] In one specific embodiment, during step D3, the high-temperature treatment is performed at a temperature of 180-450°C for 30-90 seconds. This high-temperature treatment enables thermal imidization, converting the functional compound into compound α, thereby enhancing the surface adhesion of the treated polyimide film and improving the peel strength between the finished polyimide film and copper plates, aluminum foils, etc. In this embodiment, those skilled in the art can adjust the temperature and time of the high-temperature treatment.

[0166] This application also provides a flexible copper-clad laminate, which is prepared by combining a single-layer polyimide film, a double-layer polyimide film, or a polyimide film with a composition solution surface modified obtained in this application with a copper plate.

[0167] This application also provides an application of flexible copper-clad laminates in the fields of consumer electronics and automotive electronics.

[0168] This application also provides a polyimide aluminum foil composite film, which is prepared by combining a single-layer polyimide film, a double-layer polyimide film, or a polyimide film with a composition solution surface modified obtained in this application with aluminum foil.

[0169] This application also provides an application of polyimide aluminum foil composite film, which is used in electromagnetic shielding materials, solar cell backsheet materials, and reflective materials.

[0170] The preparation and application of polyimide films are described in detail below:

[0171] Example 1

[0172] Preparation of functional compound solutions:

[0173] A1. Under nitrogen protection, at room temperature, 100g of N,N-dimethylformamide and 20g of γ-aminopropyltriethoxysilane were added to a 250mL three-necked flask, stirred and dissolved for 5min, and then 17.1g of 1,2,4-tricarboxylic anhydride was added. The mixture was stirred and reacted at 30℃ for 24h to obtain a solution containing 2-((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid.

[0174] A2. The solution containing 2-((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid in A1 was distilled at room temperature under a vacuum of -0.1 MPa to remove N,N-dimethylformamide, and recrystallized with ethanol to obtain 2-((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid, i.e., functional compound A. The structural formula of 2-((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid is:

[0175]

[0176] A3. Weigh 5g of 2-((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid and place it in a 100ml single-necked flask. Add 50g of N,N-dimethylacetamide and 0.2g of deionized water, and stir for 1h to obtain a functional compound solution.

[0177] Preparation of polyamic acid solution:

[0178] Under nitrogen protection, 410g of N,N-dimethylacetamide was added to a 1000ml three-necked flask and stirring was started; 27.28g of 4,4-diaminodiphenyl ether and 3.68g of 1,4-phenylenediamine were weighed and added to the reaction vessel and stirred at room temperature for 30min.

[0179] Weigh 26g of pyromellitic dianhydride and 15.03g of 3,3',4,4'-biphenyltetracarboxylic dianhydride and slowly add them to the reaction vessel in sequence. Stir for 300 minutes to obtain a polyamic acid solution with a viscosity of 1028P. Store frozen at -10℃ for later use.

[0180] Preparation of the composition solution:

[0181] The polyamic acid solution and the functional compound solution were mixed at a mass ratio of 1:1 and stirred until homogeneous to obtain the composition solution.

[0182] Preparation of chemical imidizing reagent solution:

[0183] Under nitrogen protection, 156g DMAc, 435g acetic anhydride, 173g pyridine, and 16g triphenyl phosphate were added sequentially to a 1000ml two-necked flask. The mixture was stirred for 120min to obtain a chemical imidizing reagent solution, which was then frozen and stored at -10℃ for later use.

[0184] Preparation of bilayer polyimide films:

[0185] C1. After mixing the polyamic acid solution and the chemical imidizing reagent solution at a mass ratio of 2:1 and completely degassing, the mixture is extruded through a die onto a ring-shaped steel strip to form a third adhesive film.

[0186] C2. The third adhesive film is heated and dried at 60°C for 30 seconds to obtain the fourth adhesive film, forming the first layer B;

[0187] C3. The composition solution is extruded through a die and cast onto the surface of the fourth film to form the fifth film;

[0188] C4. The fifth adhesive film is heated and dried at 80°C for 90 seconds, then heated and dried at 100°C for 45 seconds, and then heated and dried at 175°C for 15 seconds to obtain the sixth adhesive film, forming the second layer A.

[0189] C5. After peeling the sixth adhesive film off the steel strip, it is first stretched for 15 seconds at a longitudinal stretch ratio of 1:1.05 and a temperature of 120℃.

[0190] The polyimide composite film was then stretched for 120 seconds at a transverse stretch ratio of 1:1.03 and a temperature of 300℃; for 60 seconds at a transverse stretch ratio of 1:1.05 and a temperature of 350℃; and for 30 seconds at a transverse stretch ratio of 1:1.08 and a temperature of 400℃, respectively, to obtain a bilayer polyimide composite film. Figure 1 As shown.

[0191] Preparation of flexible copper clad laminate

[0192] A flexible copper-clad laminate with a 25μm adhesive layer was prepared by laminating a two-layer polyimide composite film (layer B, 2μm thick) to a 35μm copper foil using epoxy adhesive. The peel strength test, conducted according to IPC-TM-650 standard, showed a peel strength of 2.0 N / mm. This flexible copper-clad laminate is applicable to consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0193] Example 2

[0194] In this embodiment, the preparation of the polyamic acid solution, the composition solution, the chemical imidizing reagent solution, and the bilayer polyimide film is the same as in Example 1, with the following differences:

[0195] Preparation of functional compound solutions:

[0196] A1. Under nitrogen protection, at room temperature, 100g of N,N-dimethylformamide and 20g of γ-aminopropyltriethoxysilane were added to a 250ml three-necked flask and stirred to dissolve for 5min. Then, 29.1g of 3-((1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)sulfonyl)benzoic acid was added and the mixture was stirred at 30℃ for 24h to obtain a solution containing 4-((3-carboxyphenyl)sulfonyl)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid.

[0197] A2. A solution containing 4-((3-carboxyphenyl)sulfonyl)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid was distilled at room temperature under a vacuum of -0.1 MPa to remove N,N-dimethylformamide, and recrystallized with ethanol to obtain 4-((3-carboxyphenyl)sulfonyl)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid, i.e., functional compound B. The structural formula of 4-((3-carboxyphenyl)sulfonyl)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid is:

[0198]

[0199] A3. Weigh 5g of 4-((3-carboxyphenyl)sulfonyl)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid and place it in a 100ml single-necked flask. Add 50g of N,N-dimethylacetamide and 0.2g of deionized water, and stir for 1h to obtain a functional compound solution.

[0200] Preparation of flexible copper clad laminates:

[0201] A flexible copper-clad laminate with a 25μm adhesive layer was prepared by laminating a two-layer polyimide composite film (layer B, 2μm thick) to a 35μm copper foil using epoxy adhesive. The peel strength test, conducted according to IPC-TM-650 standard, showed a peel strength of 2.4 N / mm. This flexible copper-clad laminate is applicable to consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0202] Example 3

[0203] In this embodiment, the preparation of the polyamic acid solution, the composition solution, the chemical imidizing reagent solution, and the bilayer polyimide film is the same as in Example 1, with the following differences:

[0204] Preparation of functional compound solutions:

[0205] A1. Under nitrogen protection, at room temperature, 100g of N,N-dimethylformamide and 20g of γ-aminopropyltriethoxysilane were added to a 250ml three-necked flask and stirred to dissolve for 5min. Then, 26.2g of 3-((1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)oxy)benzoate was added and the mixture was stirred at 30℃ for 24h to obtain a solution containing 4-(3-acetoxyphenoxy)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid.

[0206] A2. A solution containing 4-(3-acetoxyphenoxy)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid was distilled at room temperature under a vacuum of -0.1 MPa to remove N,N-dimethylformamide, and recrystallized with ethanol to obtain 4-(3-acetoxyphenoxy)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid, i.e., functional compound C. The structural formula of 4-(3-acetoxyphenoxy)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid is:

[0207]

[0208] A3. Weigh 5g of 4-(3-acetoxyphenoxy)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid and place it in a 100ml single-necked flask. Add 50g of N,N-dimethylacetamide and 0.2g of deionized water, and stir for 1h to obtain a functional compound solution.

[0209] Preparation of flexible copper clad laminates:

[0210] A flexible copper-clad laminate with a 25μm adhesive layer was prepared by laminating a two-layer polyimide composite film (layer B, 2μm thick) to a 35μm copper foil using epoxy adhesive. The peel strength test, conducted according to IPC-TM-650 standard, yielded a peel strength of 1.8 N / mm. This flexible copper-clad laminate is applicable to consumer electronics and automotive electronics, including electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0211] Example 4

[0212] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, chemical imidizing reagent solution, and bilayer polyimide film is the same as in Example 1, with the following differences:

[0213] In the functional compound solution, the mass ratio of 2-((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid, N,N-dimethylacetamide and water is 15:84.5:0.5.

[0214] Preparation of flexible copper clad laminates:

[0215] A flexible copper-clad laminate with a 25μm adhesive layer was prepared by laminating a 2μm thick polyimide film (layer B) and a 25μm thick polyimide film (layer A) to a 35μm thick copper foil using epoxy adhesive. The peel strength was tested and found to be 2.2 N / mm. This flexible copper-clad laminate is applicable to consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0216] Example 5

[0217] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, chemical imidizing reagent solution, and bilayer polyimide film is the same as in Example 1, with the following differences:

[0218] In the functional compound solution, the mass ratio of 2-((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid, N,N-dimethylacetamide and water is 20:79.5:0.5.

[0219] Preparation of flexible copper clad laminates:

[0220] A flexible copper-clad laminate with a 25μm adhesive layer was prepared by laminating a 2μm thick polyimide film (layer B) and a 25μm thick polyimide film (layer A) to a 35μm thick copper foil using epoxy adhesive. Peel strength testing, conducted according to the IPC-TM-650 standard, yielded a peel strength of 2.5 N / mm. This flexible copper-clad laminate is applicable to consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0221] Example 6

[0222] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, chemical imidizing reagent solution, and bilayer polyimide film is the same as in Example 1, with the following differences:

[0223] Preparation of flexible copper clad laminates:

[0224] A flexible copper-clad laminate with a 25μm adhesive layer was prepared by laminating a double-layer polyimide film (layer B, 1μm thick) with a 35μm copper foil using epoxy adhesive. The film was tested for peel strength according to the IPC-TM-650 standard, and the peel strength was 1.6 N / mm. This flexible copper-clad laminate is applicable to consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0225] Example 7

[0226] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, chemical imidizing reagent solution, and bilayer polyimide film is the same as in Example 1, with the following differences:

[0227] Preparation of flexible copper clad laminates:

[0228] A flexible copper-clad laminate with a 25μm adhesive layer was prepared by laminating a 3μm thick polyimide film (layer B) and a 25μm thick polyimide film (layer A) to a 35μm thick copper foil using epoxy adhesive. Peel strength testing, conducted according to the IPC-TM-650 standard, yielded a peel strength of 2.3 N / mm. This flexible copper-clad laminate is applicable to consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0229] Example 8

[0230] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, chemical imidizing reagent solution, and bilayer polyimide film is the same as in Example 1, with the following differences:

[0231] Preparation of flexible copper clad laminates:

[0232] A flexible copper-clad laminate with a 25μm adhesive layer was prepared by laminating a double-layer polyimide film (layer B, 5μm thick) with a 35μm copper foil using epoxy adhesive. The peel strength was tested according to the IPC-TM-650 standard and found to be 2.3 N / mm. This flexible copper-clad laminate is applicable to consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0233] Example 9

[0234] In this embodiment, the preparation of the functional compound solution, the composition solution, the chemical imidizing reagent solution, and the bilayer polyimide film is the same as in Example 1, with the following differences:

[0235] Preparation of polyamic acid solution:

[0236] Under nitrogen protection, 635g of N,N-dimethylacetamide was added to a 1000ml three-necked flask and stirring was started; 56.2g of 4,4'-diaminodiphenyl ether was weighed and added to the reaction vessel and stirred at room temperature for 30min.

[0237] Weigh 45.2g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 43.6g of 3,3',4,4'-diphenyl ether dianhydride and slowly add them to the reaction vessel in sequence. Stir for 360 minutes to obtain a polyamic acid solution with a viscosity of 1566P. Store frozen at -10℃ for later use.

[0238] Preparation of flexible copper clad laminates:

[0239] A flexible copper-clad laminate with a 25μm adhesive layer was prepared by laminating a 2μm thick polyimide film (layer B) and a 25μm thick polyimide film (layer A) to a 35μm thick copper foil using epoxy adhesive. Peel strength testing, conducted according to the IPC-TM-650 standard, yielded a peel strength of 2.6 N / mm. This flexible copper-clad laminate is applicable to consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0240] Example 10

[0241] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, chemical imidizing reagent solution, and bilayer polyimide film is the same as in Example 1, with the following differences:

[0242] Preparation of polyimide aluminum foil composite film:

[0243] A polyimide-aluminum foil composite film with a 25μm adhesive layer was prepared by laminating a 2μm thick first layer (B) and a 25μm thick second layer (A) of polyimide film to a 35μm thick aluminum foil using a polyurethane adhesive. The peel strength was tested according to the IPC-TM-650 standard and found to be 1.8 N / mm. This polyimide-aluminum foil composite film has applications in electromagnetic shielding materials (shielding layers in high-speed / high-frequency circuits), solar cell backsheet materials, and reflective materials.

[0244] Example 11

[0245] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, and chemical imidizing reagent solution is the same as in Example 1, with the following differences:

[0246] Preparation of monolayer polyimide films:

[0247] B1. The composition solution and the chemical imidizing reagent solution are mixed evenly at a mass ratio of 4:1 and completely degassed. The mixture is then extruded through a die onto a ring-shaped steel strip to form the first adhesive film.

[0248] B2. The first adhesive film is heated and dried at 80°C for 45 seconds, then heated and dried at 100°C for 90 seconds, and then heated and dried at 135°C for 45 seconds to form the second adhesive film.

[0249] B3. Peel the second adhesive film off the steel strip and stretch it for 15 seconds at a longitudinal stretch ratio of 1:1.05 and a temperature of 120°C.

[0250] Then, under the conditions of a transverse stretch ratio of 1:1.03 and a temperature of 300℃, the materials were stretched for 120 seconds.

[0251] Under the conditions of a transverse stretch ratio of 1:1.05 and a temperature of 350℃, the stretching treatment lasted for 60 seconds.

[0252] A single-layer polyimide film was obtained by stretching at a transverse stretch ratio of 1:1.08 and a temperature of 400℃ for 30 seconds.

[0253] Preparation of flexible copper clad laminates:

[0254] A flexible copper-clad laminate with a 25μm thick adhesive layer was prepared by laminating a 25μm thick monolayer polyimide film with a 35μm thick copper foil using epoxy adhesive. The peel strength was tested according to the IPC-TM-650 standard, and the peel strength was 1.6 N / mm. This flexible copper-clad laminate has applications in consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0255] Example 12

[0256] In this embodiment, the functional compound solution, composition solution, and chemical imidizing reagent solution are the same as in Example 1, and the preparation of the monolayer polyimide film is the same as in Example 11. The differences are as follows:

[0257] In the functional compound solution, the mass ratio of 2-((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid, N,N-dimethylacetamide and water is 15:84.5:0.5.

[0258] Preparation of polyamic acid solution:

[0259] Under nitrogen protection, 635g of N,N-dimethylacetamide was added to a 1000ml three-necked flask and stirring was started; 56.2g of 4,4'-diaminodiphenyl ether was weighed and added to the reaction vessel and stirred at room temperature for 30min.

[0260] Weigh 45.2g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 43.6g of 3,3',4,4'-diphenyl ether dianhydride and slowly add them to the reaction vessel in sequence. Stir for 360 minutes to obtain a polyamic acid solution with a viscosity of 1566P. Store frozen at -10℃ for later use.

[0261] Preparation of flexible copper clad laminates:

[0262] A flexible copper-clad laminate with a 25μm thick monolayer polyimide film was prepared by laminating a 35μm thick copper foil with an epoxy adhesive. The peel strength was tested according to the IPC-TM-650 standard, and the peel strength was 1.9 N / mm. This flexible copper-clad laminate has applications in consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0263] Example 13

[0264] In this embodiment, the preparation of the functional compound solution, the composition solution, and the chemical imidizing reagent solution is the same as in Example 1, and the preparation of the monolayer polyimide film is the same as in Example 11. The differences are as follows:

[0265] In the functional compound solution, the mass ratio of 2-((3-(triethoxysilyl)propyl)carbamoyl)terephthalic acid, N,N-dimethylacetamide and water is 20:79.5:0.5.

[0266] Preparation of polyamic acid solution:

[0267] Under nitrogen protection, 635g of N,N-dimethylacetamide was added to a 1000ml three-necked flask and stirring was started; 56.2g of 4,4'-diaminodiphenyl ether was weighed and added to the reaction vessel and stirred at room temperature for 30min.

[0268] Weigh 45.2g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 43.6g of 3,3',4,4'-diphenyl ether dianhydride and slowly add them to the reaction vessel in sequence. Stir for 360 minutes to obtain a polyamic acid solution with a viscosity of 1566P. Store frozen at -10℃ for later use.

[0269] Preparation of flexible copper clad laminates:

[0270] A flexible copper-clad laminate with a 25μm thick monolayer polyimide film was prepared by laminating a 35μm thick copper foil with an epoxy adhesive. The peel strength was tested according to the IPC-TM-650 standard, and the peel strength was 1.9 N / mm. This flexible copper-clad laminate has applications in consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0271] Example 14

[0272] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, and chemical imidizing reagent solution is the same as in Example 1, with the following differences:

[0273] Preparation of monolayer polyimide films:

[0274] B1. After the composition solution is completely degassed, it is extruded through a die onto an annular steel strip to form the first adhesive film;

[0275] B2. The first adhesive film is heated and dried at 80°C for 45 seconds, then heated and dried at 100°C for 90 seconds, and then heated and dried at 135°C for 45 seconds to form the second adhesive film.

[0276] B3. Peel the second adhesive film off the steel strip and stretch it for 15 seconds at a longitudinal stretch ratio of 1:1.05 and a temperature of 120°C.

[0277] Then, under the conditions of a transverse stretch ratio of 1:1.03 and a temperature of 300℃, the materials were stretched for 120 seconds.

[0278] Under the conditions of a transverse stretch ratio of 1:1.05 and a temperature of 350℃, the stretching treatment lasted for 60 seconds.

[0279] A single-layer polyimide film was obtained by stretching at a transverse stretch ratio of 1:1.08 and a temperature of 400℃ for 30 seconds.

[0280] Preparation of flexible copper clad laminates:

[0281] A flexible copper-clad laminate with a 25μm thick adhesive layer was prepared by laminating a 25μm thick monolayer polyimide film with a 35μm thick copper foil using epoxy adhesive. Peel strength testing, conducted according to the IPC-TM-650 standard, yielded a peel strength of 1.5 N / mm. This flexible copper-clad laminate has applications in consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0282] Example 15

[0283] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, and chemical imidizing reagent solution is the same as in Example 1, with the following differences:

[0284] Preparation of monolayer polyimide films:

[0285] B1. After the composition solution is completely degassed, it is mixed with the chemical imidizing reagent solution at a mass ratio of 2:1. After complete degasing, it is extruded through a die onto an annular steel belt to form the first adhesive film.

[0286] B2. The first adhesive film is heated and dried at 80°C for 45 seconds, then heated and dried at 100°C for 90 seconds, and then heated and dried at 135°C for 45 seconds to form the second adhesive film.

[0287] B3. Peel the second adhesive film off the steel strip and stretch it for 15 seconds at a longitudinal stretch ratio of 1:1.05 and a temperature of 120°C.

[0288] Then, under the conditions of a transverse stretch ratio of 1:1.03 and a temperature of 300℃, the materials were stretched for 120 seconds.

[0289] Under the conditions of a transverse stretch ratio of 1:1.05 and a temperature of 350℃, the stretching treatment lasted for 60 seconds.

[0290] A single-layer polyimide film was obtained by stretching at a transverse stretch ratio of 1:1.08 and a temperature of 400℃ for 30 seconds.

[0291] The composition solution is applied to the surface modification of polyimide films, as detailed below:

[0292] D1. A single-layer polyimide film is subjected to surface corona treatment with a corona power of 25 kW and a corona time of 5 s, so that the dyn value of the single-layer polyimide film after corona treatment is 60 dyn.

[0293] D2. Apply the functional compound solution by spraying onto a single-layer polyimide film treated in step D1;

[0294] D3. The monolayer polyimide film treated in step D2 is heated at 150°C for 120s, 180°C for 120s, and 350°C for 90s to obtain a surface-modified monolayer polyimide film.

[0295] Preparation of flexible copper clad laminates:

[0296] A flexible copper-clad laminate with a 25μm thick adhesive layer was prepared by laminating a 25μm thick surface-modified monolayer polyimide film with a 35μm thick copper foil using epoxy adhesive. Peel strength testing, conducted according to the IPC-TM-650 standard, yielded a peel strength of 1.3 N / mm. This flexible copper-clad laminate has applications in consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0297] Example 16

[0298] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, and chemical imidizing reagent solution is the same as in Example 1. The application of the composition solution to the surface modification of the polyimide film is the same as in Example 15. The differences are as follows:

[0299] For surface modification, the polyimide film used is a 25μm Apical-NPI type polyimide film from Kaneka Chemicals, Japan.

[0300] Preparation of flexible copper clad laminates:

[0301] A flexible copper-clad laminate with a 25μm thick adhesive layer was prepared by laminating a 25μm thick surface-modified monolayer polyimide film with a 35μm thick copper foil using epoxy adhesive. Peel strength testing, conducted according to the IPC-TM-650 standard, yielded a peel strength of 1.3 N / mm. This flexible copper-clad laminate has applications in consumer electronics and automotive electronics, such as electronic display devices in mobile phones, laptops, iPads, and new energy vehicles.

[0302] Example 17

[0303] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, chemical imidizing reagent solution, and bilayer polyimide film is the same as in Example 1, with the following differences:

[0304] Preparation of flexible copper clad laminates:

[0305] A 25μm thick reinforcing plate was prepared by laminating a double-layer polyimide film (layer B, 2μm thick) with a 25μm thick polyimide film (layer A, 25μm thick) to a 25μm thick Apical-NPI polyimide film from Kaneka Corporation of Japan using epoxy adhesive. Peel strength testing, conducted according to IPC-TM-650 standard, yielded a peel strength of 2.1 N / mm.

[0306] Comparative Example 1

[0307] In this embodiment, the preparation of the polyamic acid solution, the composition solution, the chemical imidizing reagent solution, and the bilayer polyimide film is the same as in Example 1, with the following differences:

[0308] The functional compound solution is a mixture of γ-aminopropyltriethoxysilane (KH550), N,N-dimethylacetamide and water, with a mass ratio of γ-aminopropyltriethoxysilane, N,N-dimethylacetamide and water of 10:89.5:0.5.

[0309] Preparation of flexible copper clad laminates:

[0310] A flexible copper-clad laminate with an adhesive layer thickness of 25 μm was prepared by laminating a double-layer polyimide film (layer B, 2 μm thick) with a 35 μm copper foil using epoxy adhesive. Peel strength testing, conducted according to the IPC-TM-650 standard, yielded a peel strength of 1.1 N / mm.

[0311] Comparative Example 2

[0312] In this embodiment, the preparation of the polyamic acid solution, the composition solution, the chemical imidizing reagent solution, and the bilayer polyimide film is the same as in Example 1, with the following differences:

[0313] The functional compound solution is a mixture of γ-glycidoxypropyltrimethoxysilane (KH560), N,N-dimethylacetamide and water, with a mass ratio of γ-glycidoxypropyltrimethoxysilane (KH560), N,N-dimethylacetamide and water of 10:89.5:0.5.

[0314] Preparation of flexible copper clad laminates:

[0315] A flexible copper-clad laminate with an adhesive layer thickness of 25 μm was prepared by laminating a double-layer polyimide film (layer B, 2 μm thick) with a 35 μm copper foil using epoxy adhesive. Peel strength testing, conducted according to the IPC-TM-650 standard, yielded a peel strength of 1.1 N / mm.

[0316] Comparative Example 3

[0317] In this embodiment, the preparation of the functional compound solution, polyamic acid solution, composition solution, and chemical imidizing reagent solution is the same as in Example 1. The preparation of the monolayer polyimide film is the same as in Example 14. The differences are as follows:

[0318] The composition solution is applied to the surface modification of polyimide films, as detailed below:

[0319] D1. A single-layer polyimide film is subjected to surface corona treatment with a corona power of 25 kW and a corona time of 5 s, so that the dyn value of the single-layer polyimide film after corona treatment is 60 dyn.

[0320] Preparation of flexible copper clad laminates:

[0321] A 25 μm thick monolayer polyimide film, after surface corona treatment, was laminated with a 35 μm thick copper foil using epoxy adhesive to prepare a flexible copper-clad laminate with an adhesive layer thickness of 25 μm. Peel strength testing, conducted according to the IPC-TM-650 standard, yielded a peel strength of 0.9 N / mm.

[0322] Comparative Example 4

[0323] In this embodiment, the preparation of the polyamic acid solution, the composition solution, and the chemical imidizing reagent solution is the same as in Example 1; the functional compound solution is the same as in Comparative Example 1; and the preparation of the monolayer polyimide film is the same as in Example 14. The differences are as follows:

[0324] Preparation of flexible copper clad laminates:

[0325] A flexible copper-clad laminate with a 25μm thick adhesive layer was prepared by laminating a 25μm thick monolayer polyimide film with a 35μm thick copper foil using epoxy adhesive. Peel strength testing was conducted according to the IPC-TM-650 standard, and the peel strength was 1.0 N / mm.

[0326] Comparative Example 5

[0327] In this embodiment, the preparation of the polyamic acid solution, the composition solution, and the chemical imidizing reagent solution is the same as in Example 1; the functional compound solution is the same as in Comparative Example 1; and the preparation of the monolayer polyimide film is the same as in Example 15. The differences are as follows:

[0328] The composition solution is applied to the surface modification of polyimide films, as detailed below:

[0329] D1. A single-layer polyimide film is subjected to surface corona treatment with a corona power of 25 kW and a corona time of 5 s, so that the dyn value of the single-layer polyimide film after corona treatment is 60 dyn.

[0330] Preparation of flexible copper clad laminates:

[0331] A 25 μm thick monolayer polyimide film, after surface corona treatment, was laminated with a 35 μm thick copper foil using epoxy adhesive to prepare a flexible copper-clad laminate with an adhesive layer thickness of 25 μm. Peel strength testing, conducted according to the IPC-TM-650 standard, yielded a peel strength of 0.8 N / mm.

[0332] Statistical analysis was performed on the data from Examples 1-17 and Comparative Examples 1-5, as shown in Tables 1 and 2. The statistical items in Tables 1 and 2 are the same.

[0333] Table 1

[0334]

[0335] Table 2

[0336]

[0337] Based on the above data, it can be seen that by combining functional compound A, functional compound B, or functional compound C with polyamic acid solution to prepare polyimide film or coating modified polyimide film, the peel strength between polyimide film and materials such as copper foil and aluminum foil can be increased while ensuring that the main properties of polyimide film remain unchanged, thereby enhancing the reliability of polyimide film material applications.

[0338] Furthermore, functional compound A, B, or C can be transformed into compound α. Compound α is uniformly distributed inside and on the surface of the second layer, which can change the surface structure and composition of the polyimide film, increase the proportion of polar functional groups on the surface of the polyimide film, and improve the peel strength of the polyimide film to materials such as copper foil and aluminum foil without reducing the main performance of the polyimide film. This effectively solves the problem of insufficient peel strength of polyimide film composites and enhances the reliability of polyimide film material applications.

[0339] Compound α in this application can also be used as an additive for adhesives (PI adhesives, polyurethane adhesives, epoxy adhesives, etc.) to improve the adhesion and temperature resistance of the adhesives.

[0340] The polyimide film prepared in this application increases the reliability of flexible electronic substrate materials. This method can also be used to composite polyimide films with other organic, inorganic, and metallic materials, and can also expand the application range of polyimide films and increase their added value.

[0341] It should be noted that: for experimental steps or conditions not specified in the examples, the procedures and conditions described in conventional experimental procedures in the literature of this art can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0342] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composition solution, characterized in that, The solution comprises a functional compound solution and a polyamic acid solution; the functional compound solution comprises a functional compound and a first solvent, wherein the structural formula of the functional compound is shown in Formula I: Formula I Wherein, R1 is methyl or ethyl; R2 is the following functional group: 。 2. The composition solution according to claim 1, characterized in that, The functional compounds include 4-((3-carboxyphenyl)sulfonyl)-2-((3-(triethoxysilyl)propyl)carbamoyl)benzoic acid; And / or, the first solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, acetone, butanone, toluene, ethyl acetate, tetrahydrofuran, chloroform, m-cresol, γ-butyrolactone, and water.

3. The composition solution according to claim 1, characterized in that, The functional compound accounts for 5-20% of the mass of the functional compound solution; And / or, the mass ratio of the functional compound solution to the polyamic acid solution is 10:1 to 1:

10.

4. The composition solution according to any one of claims 1-3, characterized in that, The polyamic acid solution is formed by the condensation polymerization of aromatic dianhydride and aromatic diamine in a dipolar aprotic solvent; And / or, the solid content of the polyamic acid solution is 15-30%; And / or, the viscosity of the polyamic acid solution is 100~3000P.

5. A method for preparing a composition solution according to any one of claims 1-4, characterized in that, Includes the following steps: A1. Under a nitrogen atmosphere, γ-aminopropyltriethoxysilane or γ-aminopropyltrimethoxysilane is dissolved in a first solvent and stirred until homogeneous. Then, an acid anhydride compound is added, and the mixture is reacted at 0-80℃ for 1-72 hours to obtain a solution containing the functional compound. A2. The crude functional compound is separated from the solution containing the functional compound, and then washed and dried to obtain the functional compound. A3. Dissolve the functional compound in a first solvent to obtain a functional compound solution, and mix the functional compound solution with a polyamic acid solution to obtain a composition solution.

6. The method for preparing the composition solution according to claim 5, characterized in that, In step A1, the molar ratio of γ-aminopropyltriethoxysilane or γ-aminopropyltrimethoxysilane to the acid anhydride compound is 1.01:1 to 1.1:1; And / or, in step A1, the anhydride compound includes 3-((1,3-dioxo-1,3-dihydroisobenzofuran-5-yl)sulfonyl)benzoic acid.

7. The method for preparing the composition solution according to claim 5 or 6, characterized in that, In step A2, when separating the crude functional compound from the solution containing the functional compound, the crude functional compound is obtained by vacuum distillation and recrystallization. And / or, when separating crude functional compounds from a solution containing functional compounds, the solution containing functional compounds is added dropwise to a precipitating agent, precipitate, separate, and obtain crude functional compounds.

8. A polyimide film, characterized in that, The composition is prepared by means of a solution comprising the composition of any one of claims 1-4, or by means of a method comprising a solution comprising the composition of any one of claims 5-7.

9. The polyimide film according to claim 8, characterized in that, The polyimide film has a single-layer structure, which is formed by reacting and converting the composition solution.

10. The polyimide film according to claim 9, characterized in that, The method for preparing the monolayer polyimide film includes the following steps: B1. The composition solution is extruded through a die onto an annular steel strip to form a first adhesive film; B2. Heat and dry the first adhesive film to form the second adhesive film; B3. Peel the second adhesive film off the steel strip, and after imidization and biaxial stretching, obtain a polyimide film.

11. The polyimide film according to claim 10, characterized in that, In step B1, a chemical imidizing agent is also added to the composition solution; The chemical imidizing agent includes one or more components selected from dehydrating agents, catalysts, second solvents, and auxiliaries.

12. The polyimide film according to claim 11, characterized in that, In step B1, the mass ratio of the functional compound solution to the polyamic acid solution in the composition solution is 10:1 to 1:

10. The mass ratio of the composition solution to the chemical imidizing reagent is 20:1 to 1:1; And / or, in step B2, the heating temperature of the first adhesive film is 45-180℃, and the drying time is 90-360s.

13. The polyimide film according to claim 10, characterized in that, In step B3, the imidization process includes one of thermal imidization, chemical imidization, or a combination of chemical imidization and thermal imidization. During thermal imidization, the temperature is 180-450℃ and the thermal imidization time is 180-300s; During chemical imidization, the second film is placed in a tank containing a chemical imidizing reagent and heated; the heating temperature is 30~100℃ and the heating time is 30-60s. In the process of combining chemical imidization with thermal imidization, the second film, which has undergone at least one chemical imidization treatment, is then subjected to at least one thermal imidization treatment. And / or, in step B3, during bidirectional stretching, the stretching ratio of the longitudinal stretching is 1:1-1.1, and the stretching ratio of the transverse stretching is 1:1-1.2; During longitudinal stretching, the stretching temperature is 80-150℃ and the stretching time is 10-30s; When stretching laterally, the stretching temperature is 180-450℃ and the stretching time is 180-300s.

14. The polyimide film according to claim 8, characterized in that, The polyimide film has a double-layer structure, comprising a first layer and a second layer, with the second layer disposed on the first layer; the first layer is formed by imidization of a polyamic acid solution, and the second layer is formed by reaction of a composition solution.

15. The polyimide film according to claim 14, characterized in that, The method for preparing the bilayer polyimide film includes the following steps: C1. The polyamic acid solution is extruded through a die onto an annular steel strip to form a third adhesive film; C2. Heat and dry the third adhesive film to obtain the fourth adhesive film; C3. The composition solution is extruded through a die and cast onto the surface of the fourth film to form the fifth film; C4. Heat and dry the fifth adhesive film to obtain the sixth adhesive film; C5. The sixth adhesive film is peeled off from the steel strip, and then imidized and biaxially stretched to obtain a polyimide composite film.

16. The polyimide film according to claim 15, characterized in that, The heating temperature of the third adhesive film is 45-100℃, and the drying time is 15-60s; And / or, the heating temperature of the fifth adhesive film is 80-180℃, and the drying time is 75-300s.

17. The polyimide film according to claim 15 or 16, characterized in that, In step C1, a chemical imidizing agent is added to the polyamic acid solution, mixed evenly, degassed, and then extruded through a die.

18. The use of a composition solution according to any one of claims 1-4, characterized in that, Application in surface modification of polyimide films.

19. The application according to claim 18, characterized in that, The surface modification of the polyimide film includes the following steps: D1. Perform surface corona treatment on the polyimide film; D2. Coat the surface of the polyimide film treated in step D1 with a functional compound solution; D3. The polyimide film treated by D2 is heated, dried, and subjected to high-temperature treatment to obtain a surface-modified polyimide film.

20. The application according to claim 19, characterized in that, In step D1, the power of the corona treatment is 15-30 kW, and the treatment time is 1-10 seconds. And / or, in step D3, the heating temperature is 80-240℃ and the drying time is 60-180s; And / or, in step D3, the high-temperature treatment is carried out at a temperature of 180-450℃ for a time of 30-90 seconds.

21. A flexible copper-clad laminate, characterized in that, A modified polyimide film obtained by surface modification of a polyimide film using the polyimide film of claim 8 or the composition solution of claim 18, is then laminated with a copper plate to obtain a flexible copper-clad laminate.

22. A polyimide aluminum foil composite film, characterized in that, A polyimide film obtained by surface modification of a polyimide film using the polyimide film of claim 8 or the composition solution of claim 18, and then laminated with aluminum foil, yields a polyimide-aluminum foil composite film.

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