Ultrathin polyimide film and preparation method thereof

Abstract

The invention discloses an ultrathin polyimide film and a preparation method thereof, and belongs to the technical field of polyimide films. The preparation method comprises the following steps: adding aromatic diamine into a polar organic solvent, and uniformly stirring; in a nitrogen atmosphere, aromatic dianhydride is added into the diamine solution in batches for condensation polymerization, and a polyamide acid resin solution is obtained; carrying out low-temperature plasma modification treatment on polyether block amide, then adding the polyether block amide into a polyamide acid resin solution to be dissolved, and uniformly stirring to obtain a resin solution; adding a metal salt accelerant into the resin solution, and uniformly mixing to obtain a solution A; coating a substrate with the solution A, and performing heat treatment to form a gel film; and carrying out imidization treatment on the gel film on a needle plate to obtain the ultrathin polyimide film. The ultrathin polyimide film has excellent mechanical strength while keeping the ultrathin characteristic, can be widely applied to the field of flexible printed circuit boards, and meets the requirements of miniaturization, light weight and high-density integrated circuits of electronic products.

Description

Technical Field

[0001] The invention belongs to the technical field of polyimide films, and in particular relates to an ultra-thin polyimide film and a preparation method thereof. Background Art

[0002] Polyimide (PI) film has good high and low temperature resistance, environmental stability, mechanical properties and excellent dielectric properties. It is currently the best performing thin film insulating material in the world and is widely used in microelectronics, 5G communications, aerospace and other fields. Since polyimide film not only meets the basic physical requirements of various products, but also has special properties such as high strength and toughness, wear resistance, high temperature resistance, and corrosion resistance, especially it can be designed to be both light and thin, it has been widely used in the field of microelectronics, promoting the vigorous development of the microelectronics industry.

[0003] With the rapid development of aviation, aerospace and microelectronics technology, electronic products are becoming smaller and lighter, and integrated circuits are developing towards high density. Therefore, higher requirements are also put forward for polyimide films used in this field, such as lightweight, high specific strength, high specific modulus, high heat resistance, etc. Therefore, ultra-thinness is an important trend in the development of PI films, and its driving force mainly comes from the application needs of aerospace, electronics and other industries for device weight reduction, thinning and functionalization.

[0004] At present, the preparation of ultra-thin polyimide films (thickness ≤ 5μm) is limited in monomer types, complex processes, high costs, long time, and low commercialization. As a result, domestic ultra-thin polyimide films are rarely mass-produced and are expensive. Therefore, how to prepare thinner polyimide films in a short time, low cost, simple process, and wide application range is of great significance. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide an ultra-thin polyimide film and a preparation method thereof, which solves the problems in the prior art.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing an ultra-thin polyimide film comprises the following steps:

[0008] Add aromatic diamine to polar organic solvent and stir evenly;

[0009] Under nitrogen protection, aromatic dianhydride is added to the diamine solution in batches to carry out polycondensation reaction to obtain a polyamic acid resin solution;

[0010] Low temperature plasma modification treatment of polyether block amide;

[0011] Adding the modified polyether block amide into the polyamic acid resin solution to dissolve, stirring evenly, to obtain a resin solution;

[0012] Adding a metal salt accelerator to the resin solution and mixing evenly to obtain a solution A;

[0013] The solution A is coated on the substrate and heat-treated to form a gel film;

[0014] The needle plate on the gel membrane is imidized to obtain the product.

[0015] Furthermore, the aromatic diamine is one or a combination of p-phenylenediamine and 4,4'-diaminodiphenyl ether; the aromatic dianhydride is one or a combination of pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0016] Furthermore, the molar ratio of the aromatic diamine to the aromatic dianhydride is 1:1.

[0017] Furthermore, the polar organic solvent is one or a combination of N,N'-dimethylacetamide and N,N'-dimethylformamide.

[0018] Further, the polyether block amide is MX, 72R53, 7033 and One or more combinations of E62.

[0019] Furthermore, the amount of the modified polyether block amide is 5% to 20% of the total mass of the aromatic dianhydride and the aromatic diamine.

[0020] Furthermore, the metal salt promoter is one or more combinations of zinc salts, aluminum salts, iron salts, magnesium salts and rare earth metal salts.

[0021] Furthermore, the amount of the metal salt accelerator is 0.1% to 1% of the total mass of the aromatic dianhydride and the aromatic diamine.

[0022] Furthermore, the low-temperature plasma modification treatment is carried out in an O2 atmosphere, with a treatment power of 100W to 500W and a treatment time of 1 to 10 minutes.

[0023] An ultra-thin polyimide film is prepared using the above-mentioned method for preparing an ultra-thin polyimide film.

[0024] Beneficial effects of the present invention:

[0025] 1. In the process of preparing ultra-thin polyimide film, due to the extremely thin film thickness, the coating thickness needs to be appropriately increased during coating, which usually requires reducing the solid content of the polyamic acid resin; however, the reduction in the solid content of the resin will cause its viscosity to decrease, thereby affecting the coating effect. In view of this problem, the present invention introduces polyether block amide into the polyamic acid resin. The polyether block amide has good organic solvent solubility and can increase the viscosity of the resin system, which not only solves the problem of insufficient viscosity caused by low solid content, but also provides strong support for the high-quality preparation of ultra-thin polyimide film.

[0026] 2. The polyether soft segment of the polyether block amide in the present invention can interact with the polyimide molecular chain through van der Waals force, hydrogen bond, etc., to achieve mutual interpenetration and entanglement of the molecular chains to a certain extent, giving the ultra-thin polyimide film a certain flexibility. At the same time, the polyether block amide modified by low-temperature plasma treatment introduces polar groups (hydroxyl, carboxyl), and the polar groups (hydroxyl, carboxyl) on the polyether block amide and the reactive groups (such as epoxy and amino) on the polyimide molecular chain react chemically to form covalent bonds, form a cross-linked network, improve the compatibility between the two, and form a more stable composite material, so that the ultra-thin polyimide film has better mechanical properties, which is more conducive to the production and subsequent application of ultra-thin polyimide films.

[0027] 3. The thermal decomposition temperature of polyether block amide is 300-350°C. In order to ensure that the polyether block amide molecular chain is not affected when the polyimide is cured, a metal salt accelerator is added in the present invention. The metal ions coordinate with the polyamic acid chain segments to promote the intramolecular cyclization reaction, accelerate the rate of the imidization reaction, reduce the curing temperature, and prevent the polyether block amide from being decomposed by heat.

[0028] 4. The ultra-thin polyimide film prepared by the present invention has a thickness in the range of 2-5 μm, which can be adjusted according to actual needs. The film has uniform thickness and excellent mechanical properties. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] A method for preparing an ultra-thin polyimide film comprises the following steps:

[0031] S1, adding aromatic diamine into polar organic solvent and stirring evenly;

[0032] S2, under nitrogen protection, after the aromatic diamine is dissolved, adding the aromatic dianhydride into the diamine solution in batches to carry out polycondensation reaction to obtain a polyamic acid resin solution;

[0033] S3, performing low-temperature plasma modification treatment on the polyether block amide;

[0034] S4, adding the modified polyether block amide to the polyamic acid resin solution to dissolve, stirring evenly, to obtain a resin solution;

[0035] S5, adding a metal salt accelerator to the resin solution and mixing evenly to obtain a solution A;

[0036] S6, coating the solution A on the substrate by using a coating machine, and heat treating the solution A to form a gel film;

[0037] S7, performing imidization treatment on the needle plate on the gel film to obtain an ultra-thin polyimide film.

[0038] In S1, the aromatic diamine is one or a combination of p-phenylenediamine and 4,4'-diaminodiphenyl ether, and the polar organic solvent is one or a combination of N,N'-dimethylacetamide and N,N'-dimethylformamide.

[0039] In S2, the aromatic dianhydride is one or a combination of pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0040] The molar ratio of the aromatic diamine to the aromatic dianhydride is 1:1.

[0041] In S2, the reaction temperature of the polycondensation reaction is 10 to 30°C, the reaction time is 6 to 24 hours, the solid content of the polyamic acid resin solution is 8 to 20%, and the rotational viscosity is 10,000 to 50,000 mPa·s.

[0042] In S3, the polyether block amide is a high temperature resistant, high molecular weight MX, 72R53, 7033 and One or more combinations of E62;

[0043] In S3, the low-temperature plasma modification treatment is carried out in an O2 atmosphere, with a treatment power of 100W to 500W and a treatment time of 1 to 10 minutes.

[0044] In S4, the amount of the modified polyether block amide is 5% to 20% of the total mass of the aromatic dianhydride and the aromatic diamine. The modified polyether block amide is added to the polyamic acid resin solution and dissolved, and then stirred for 2 to 4 hours. The rotational viscosity of the resin solution is 100,000 to 150,000 mPa·s.

[0045] S5, the salt accelerator is one or more combinations of zinc salt, aluminum salt, iron salt, magnesium salt and rare earth metal salt; the amount of the metal salt accelerator is 0.1% to 1% of the total mass of the aromatic dianhydride and the aromatic diamine.

[0046] In S5, the metal salt accelerator is added to the resin solution and stirred for 1 to 2 hours to mix evenly.

[0047] In S6, solution A is coated on the substrate with a coating thickness of 4 to 10 μm, and heat-treated by heating the temperature to 70 to 90° C. at 2 to 10° C. / min and keeping the temperature for 10 to 20 minutes to form a gel film.

[0048] In S7, the specific steps of imidization treatment are: peeling the gel film from the substrate, fixing it on a pin plate, putting it into a blast drying oven, heating it to 150-200°C at 2-10°C / min and keeping it warm for 30 minutes, heating it to 200-250°C at 2-10°C / min and keeping it warm for 30 minutes, and then heating it to 250-300°C at 2-10°C / min and keeping it warm for 30 minutes for imidization treatment; finally, heating it to 300-340°C at 2-10°C / min and keeping it warm for 30 minutes for annealing treatment; after cooling to room temperature, an ultra-thin polyimide film is obtained.

[0049] The low-temperature plasma-treated modified polyether block amide introduces polar groups (hydroxyl, carboxyl), and the polar groups (hydroxyl, carboxyl) on the polyether block amide react with the reactive groups (such as epoxy and amino) on the polyimide molecular chain to form a covalent bond connection and a cross-linked network. The addition of metal salt accelerators can reduce the curing temperature of polyimide and ensure that the polyether block amide will not decompose due to heat.

[0050] The scheme of the present invention is described below by the following examples and comparative examples; wherein the sources of the raw materials in the examples and comparative examples are as follows:

[0051] p-phenylenediamine: Tianjin Zotye, CAS: 106-50-3;

[0052] 4,4'-Diaminodiphenyl ether: Tianjin Zotye, CAS: 101-80-4;

[0053] N,N'-Dimethylacetamide: Aladdin, CAS: 127-19-5;

[0054] Pyromellitic dianhydride: Tianjin Zotye, CAS: 89-32-7;

[0055] 7033: Arkema, 7033SP 01;

[0056] Zinc acetate: Aladdin, CAS: 557-34-6.

[0057] Example 1

[0058] A method for preparing an ultra-thin polyimide film comprises the following steps:

[0059] S1: 3.888 g of p-phenylenediamine (36 mmol) and 16.8 g of 4,4'-diaminodiphenyl ether (84 mmol) were placed in 450 mL of N,N'-dimethylacetamide (DMAc), and mechanically stirred at room temperature for 1 h to completely dissolve the diamine.

[0060] S2: Under nitrogen protection, 26.16 g of pyromellitic dianhydride (120 mmol) was added to the diamine solution in batches and reacted at room temperature for 8 h to obtain a polyamic acid solution with a solid content of 10% and a viscosity of 40000 mPa·s.

[0061] S3: weigh 2.3424g 7033 was placed in a low-temperature plasma machine, in an O2 atmosphere, with a processing power of 300 W and a processing time of 5 minutes.

[0062] S4: Under nitrogen protection, 2.3424 g of modified 7033 was added into the polyamic acid solution and dissolved, and mechanically stirred at room temperature for 2 h to obtain a polyether block / polyamic acid solution (resin solution) with a viscosity of 120,000 mPa·s.

[0063] S5: Weigh 0.094 g of zinc acetate and add it to the above resin solution, stir mechanically for 1 hour, mix well, and obtain solution A;

[0064] S6: Use a coating machine to coat solution A on a glass substrate with a coating thickness of 8 μm; place the glass substrate in an oven, raise the temperature to 80° C. at a rate of 4° C. / min, and keep the temperature for 12 minutes to form a gel film.

[0065] S7: Fix the gel film on a pin plate, place it in an oven, heat it to 180°C at 4°C / min and keep it for 25 min, heat it to 250°C at 4°C / min and keep it for 30 min, then heat it to 300°C at 4°C / min and keep it for 30 min for imidization treatment; finally, heat it to 340°C at 4°C / min and keep it for 30 min for annealing treatment, so as to prepare an ultra-thin polyimide film.

[0066] Example 2

[0067] A method for preparing an ultra-thin polyimide film comprises the following steps:

[0068] S1: 3.888 g of p-phenylenediamine (36 mmol) and 16.8 g of 4,4'-diaminodiphenyl ether (84 mmol) were placed in 450 mL of N,N'-dimethylacetamide (DMAc), and mechanically stirred at room temperature for 1 h to completely dissolve the diamine.

[0069] S2: Under nitrogen protection, 26.16 g of pyromellitic dianhydride (120 mmol) was added to the diamine solution in batches and reacted at room temperature for 8 h to obtain a polyamic acid solution with a solid content of 10% and a viscosity of 40000 mPa·s.

[0070] S3: weigh 4.6848g 7033 was placed in a low-temperature plasma machine, in an O2 atmosphere, with a processing power of 300 W and a processing time of 5 minutes.

[0071] S4: Under nitrogen protection, 4.6848 g of modified 7033 was added into the polyamic acid solution and dissolved, and mechanically stirred at room temperature for 2 h to obtain a polyether block / polyamic acid solution (resin solution) with a viscosity of 120,000 mPa·s.

[0072] S5: Weigh 0.094 g of zinc acetate and add it to the above resin solution. Mechanically stir for 1 hour and mix well to obtain solution A.

[0073] S6: Use a coating machine to coat solution A on a glass substrate to a coating thickness of 8 μm. Place the glass substrate in an oven, raise the temperature to 80° C. at a rate of 4° C. / min, and keep the temperature for 12 minutes to form a gel film.

[0074] S7: Fix the gel film on a pin plate, place it in an oven, heat it to 180°C at 4°C / min and keep it for 25 min, heat it to 250°C at 4°C / min and keep it for 30 min, then heat it to 300°C at 4°C / min and keep it for 30 min for imidization treatment; finally, heat it to 340°C at 4°C / min and keep it for 30 min for annealing treatment, so as to prepare an ultra-thin polyimide film.

[0075] Example 3

[0076] A method for preparing an ultra-thin polyimide film comprises the following steps:

[0077] S1: 3.888 g of p-phenylenediamine (36 mmol) and 16.8 g of 4,4'-diaminodiphenyl ether (84 mmol) were placed in 450 mL of N,N'-dimethylacetamide (DMAc), and mechanically stirred at room temperature for 1 h to completely dissolve the diamine.

[0078] S2: Under nitrogen protection, 26.16 g of pyromellitic dianhydride (120 mmol) was added to the diamine solution in batches and reacted at room temperature for 8 h to obtain a polyamic acid solution with a solid content of 10% and a viscosity of 40000 mPa·s.

[0079] S3: weigh 7.0272g 7033 was placed in a low-temperature plasma machine, in an O2 atmosphere, with a processing power of 300 W and a processing time of 5 minutes.

[0080] S4: Under nitrogen protection, 7.0272 g of modified 7033 was added into the polyamic acid solution and dissolved, and mechanically stirred at room temperature for 2 h to obtain a polyether block / polyamic acid solution (resin solution) with a viscosity of 120,000 mPa·s.

[0081] S5: Weigh 0.094 g of zinc acetate and add it to the above resin solution. Mechanically stir for 1 hour and mix well to obtain solution A.

[0082] S6: Use a coating machine to coat solution A on a glass substrate to a coating thickness of 8 μm. Place the glass substrate in an oven, raise the temperature to 80° C. at a rate of 4° C. / min, and keep the temperature for 12 min to form a gel film.

[0083] S7: Fix the gel film on a pin plate, place it in an oven, heat it to 180°C at 4°C / min and keep it for 25 min, heat it to 250°C at 4°C / min and keep it for 30 min, then heat it to 300°C at 4°C / min and keep it for 30 min for imidization treatment; finally, heat it to 340°C at 4°C / min and keep it for 30 min for annealing treatment, so as to prepare an ultra-thin polyimide film.

[0084] Example 4

[0085] A method for preparing an ultra-thin polyimide film comprises the following steps:

[0086] S1: 3.888 g of p-phenylenediamine (36 mmol) and 16.8 g of 4,4'-diaminodiphenyl ether (84 mmol) were placed in 450 mL of N,N'-dimethylacetamide (DMAc), and mechanically stirred at room temperature for 1 h to completely dissolve the diamine.

[0087] S2: Under nitrogen protection, 26.16 g of pyromellitic dianhydride (120 mmol) was added to the diamine solution in batches and reacted at room temperature for 8 h to obtain a polyamic acid solution with a solid content of 10% and a viscosity of 40000 mPa·s.

[0088] S3: weigh 9.3696g 7033 was placed in a low-temperature plasma machine, in an O2 atmosphere, with a processing power of 300 W and a processing time of 5 minutes.

[0089] S4: Under nitrogen protection, 9.3696 g of modified 7033 was added to the polyamic acid solution to dissolve, and mechanically stirred at room temperature for 2 h to obtain a polyether block / polyamic acid solution (resin solution) with a viscosity of 120000 mPa·s;

[0090] S5: Weigh 0.094 g of zinc acetate and add it to the above resin solution. Mechanically stir for 1 hour and mix well to obtain solution A.

[0091] S6: Use a coating machine to coat solution A on a glass substrate to a coating thickness of 8 μm. Place the glass substrate in an oven, raise the temperature to 80° C. at a rate of 4° C. / min, and keep the temperature for 12 min to form a gel film.

[0092] S7: Fix the gel film on a pin plate, place it in an oven, heat it to 180°C at 4°C / min and keep it for 25 min, heat it to 250°C at 4°C / min and keep it for 30 min, then heat it to 300°C at 4°C / min and keep it for 30 min for imidization treatment; finally, heat it to 340°C at 4°C / min and keep it for 30 min for annealing treatment, so as to prepare an ultra-thin polyimide film.

[0093] Comparative Example 1

[0094] A method for preparing an ultra-thin polyimide film comprises the following steps:

[0095] S1: 3.888 g of p-phenylenediamine (36 mmol) and 16.8 g of 4,4'-diaminodiphenyl ether (84 mmol) were placed in 450 mL of N,N'-dimethylacetamide (DMAc), and mechanically stirred at room temperature for 1 h to completely dissolve the diamine.

[0096] S2: Under nitrogen protection, 26.16 g of pyromellitic dianhydride (120 mmol) was added to the diamine solution in batches and reacted at room temperature for 8 h to obtain a polyamic acid solution with a solid content of 10% and a viscosity of 40000 mPa·s.

[0097] S3: Use a coating machine to coat the polyamic acid solution on the glass substrate to a coating thickness of 8 μm. Place the glass substrate in an oven, raise the temperature to 80° C. at 4° C. / min, and keep the temperature for 12 minutes to form a gel film.

[0098] S4: Fix the gel film on a pin plate, place it in an oven, heat it to 180°C at 4°C / min and keep it warm for 25 min, heat it to 250°C at 4°C / min and keep it warm for 30 min, then heat it to 300°C at 4°C / min and keep it warm for 30 min for imidization treatment; finally, heat it to 340°C at 4°C / min and keep it warm for 30 min for annealing treatment, so as to prepare an ultra-thin polyimide film.

[0099] Comparative Example 2

[0100] A method for preparing an ultra-thin polyimide film comprises the following steps:

[0101] S1: 3.888 g of p-phenylenediamine (36 mmol) and 16.8 g of 4,4'-diaminodiphenyl ether (84 mmol) were placed in 450 mL of N,N'-dimethylacetamide (DMAc), and mechanically stirred at room temperature for 1 h to completely dissolve the diamine.

[0102] S2: Under nitrogen protection, 26.16 g of pyromellitic dianhydride (120 mmol) was added to the diamine solution in batches and reacted at room temperature for 8 h to obtain a polyamic acid solution with a solid content of 10% and a viscosity of 40000 mPa·s.

[0103] S3: weigh 11.712g 7033 was placed in a low-temperature plasma machine for modification under an O2 atmosphere, with a processing power of 300 W and a processing time of 5 min.

[0104] S4: Under nitrogen protection, 11.712 g of modified 7033 was added into the polyamic acid solution and dissolved, and mechanically stirred at room temperature for 2 h to obtain a polyether block / polyamic acid solution (resin solution) with a viscosity of 120,000 mPa·s.

[0105] S5: Weigh 0.094 g of zinc acetate and add it to the above resin solution. Mechanically stir for 1 hour and mix well to obtain solution A.

[0106] S6: Use a coating machine to coat the solution A on the glass substrate to a coating thickness of 8 μm. Place the glass substrate in an oven, raise the temperature to 80° C. at 4° C. / min, and keep the temperature for 12 minutes to form a gel film.

[0107] S7: Fix the gel film on a pin plate, place it in an oven, heat it to 180°C at 4°C / min and keep it for 25 min, heat it to 250°C at 4°C / min and keep it for 30 min, then heat it to 300°C at 4°C / min and keep it for 30 min for imidization treatment; finally, heat it to 340°C at 4°C / min and keep it for 30 min for annealing treatment, so as to prepare an ultra-thin polyimide film.

[0108] Comparative Example 3

[0109] A method for preparing an ultra-thin polyimide film comprises the following steps:

[0110] S1: 3.888 g of p-phenylenediamine (36 mmol) and 16.8 g of 4,4'-diaminodiphenyl ether (84 mmol) were placed in 450 mL of N,N'-dimethylacetamide (DMAc), and mechanically stirred at room temperature for 1 h to completely dissolve the diamine.

[0111] S2: Under nitrogen protection, 26.16 g of pyromellitic dianhydride (120 mmol) was added to the diamine solution in batches and reacted at room temperature for 8 h to obtain a polyamic acid solution with a solid content of 10% and a viscosity of 40000 mPa·s.

[0112] S3: weigh 7.0272g 7033 was placed in a low-temperature plasma machine for modification under an O2 atmosphere, with a processing power of 300 W and a processing time of 5 min.

[0113] S4: Under nitrogen protection, 7.0272 g of modified 7033 was added to the polyamic acid solution to dissolve, and mechanically stirred at room temperature for 2 h to obtain a polyether block / polyamic acid solution (resin solution) with a viscosity of 120000 mPa·s;

[0114] S5: Weigh 0.94 g of zinc acetate and add it to the above resin solution. Mechanically stir for 1 hour and mix well to obtain solution A.

[0115] S6: Use a coating machine to coat solution A on a glass substrate to a coating thickness of 8 μm. Place the glass substrate in an oven, raise the temperature to 80° C. at a rate of 4° C. / min, and keep the temperature for 12 min to form a gel film.

[0116] S7: Fix the gel film on a pin plate, place it in an oven, heat it to 180°C at 4°C / min and keep it for 25 min, heat it to 250°C at 4°C / min and keep it for 30 min, then heat it to 300°C at 4°C / min and keep it for 30 min for imidization treatment; finally, heat it to 340°C at 4°C / min and keep it for 30 min for annealing treatment, so as to prepare an ultra-thin polyimide film.

[0117] Experimental testing

[0118] The performance of the ultra-thin polyimide film obtained in the embodiment of the present invention and the comparative example was tested, and the test results are shown in Table 1;

[0119] Table 1 Ultra-thin polyimide film performance test results

[0120]

[0121]

[0122] It can be seen from Table 1 that:

[0123] 1) Compared with Comparative Example 1, the addition of polyether block amide significantly improves the elongation at break of the ultra-thin polyimide film, and the tensile strength and modulus only fluctuate slightly, indicating that polyether block amide can effectively improve the toughness of the material while still maintaining the rigidity characteristics of the matrix.

[0124] 2) In terms of optimization of the amount of polyether block amide, when the amount of polyether block amide added in Examples 1-4 is 5-20% of the total mass of diamine dianhydride, the film exhibits excellent comprehensive mechanical properties, with both toughness and strength. However, when the amount of polyether block amide in Comparative Example 2 is increased to 25%, the film shows obvious performance degradation, and wrinkles appear on the film surface, which is attributed to the relaxation of molecular chain entanglement and intensified phase separation caused by excessive flexible segments.

[0125] 3) Comparing Examples 1 to 4 with Comparative Example 3, the amount of zinc acetate used as the metal promoter in Comparative Example 3 is increased. Too much promoter may cause excessive cross-linking reaction, resulting in excessive cross-linking of the molecular chains. The dense distribution of rigid cross-linking points restricts the movement of the molecular chains, making the material hard and brittle, and significantly reducing its flexibility.

[0126] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0127] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing an ultra-thin polyimide film, characterized in that: The following steps are involved: Add aromatic diamine to polar organic solvent and stir evenly; Under nitrogen protection, aromatic dianhydride is added to the diamine solution in batches to carry out polycondensation reaction to obtain a polyamic acid resin solution; Low temperature plasma modification treatment of polyether block amide; Adding the modified polyether block amide into the polyamic acid resin solution to dissolve, stirring evenly, to obtain a resin solution; Adding a metal salt accelerator to the resin solution and mixing evenly to obtain a solution A; The solution A is coated on the substrate and heat-treated to form a gel film; The needle plate on the gel membrane is imidized to obtain the product.

2. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The aromatic diamine is one or a combination of p-phenylenediamine and 4,4'-diaminodiphenyl ether; the aromatic dianhydride is one or a combination of pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

3. The method for preparing an ultra-thin polyimide film according to claim 1 or 2, characterized in that: The molar ratio of the aromatic diamine to the aromatic dianhydride is 1:

1.

4. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The polar organic solvent is one or a combination of N,N'-dimethylacetamide and N,N'-dimethylformamide.

5. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The polyether block amide is MX, 72R53, 7033 and One or more combinations of E62.

6. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The amount of the modified polyether block amide is 5% to 20% of the total mass of the aromatic dianhydride and the aromatic diamine.

7. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The metal salt promoter is one or more combinations of zinc salt, aluminum salt, iron salt, magnesium salt and rare earth metal salt.

8. The method for preparing an ultra-thin polyimide film according to claim 1 or 7, characterized in that: The amount of the metal salt accelerator is 0.1% to 1% of the total mass of the aromatic dianhydride and the aromatic diamine.

9. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The low-temperature plasma modification treatment is carried out in an O2 atmosphere, with a treatment power of 100W to 500W and a treatment time of 1 to 10 minutes.

10. An ultra-thin polyimide film, characterized in that: The ultra-thin polyimide film is prepared using the method for preparing the ultra-thin polyimide film according to any one of claims 1 to 9.

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