Low-dielectric high-modulus polyimide film material, preparation method thereof and application of low-dielectric high-modulus polyimide film material in flexible display substrate

Abstract

The invention discloses a low-dielectric high-modulus polyimide film material, a preparation method thereof and an application of the low-dielectric high-modulus polyimide film material in a flexible display substrate. The preparation method comprises the following steps: reacting aromatic dianhydride with an aromatic amine compound to generate polyimide; the aromatic dianhydride has a naphthalene structure or an anthracene structure, and the aromatic amine compound at least comprises a mixture of aromatic triamine and aromatic diamine. The aromatic dianhydride with a naphthalene structure or an anthracene structure is adopted, the macromolecular rigid structure of the aromatic dianhydride can effectively improve the orientation and stacking state of internal molecules, so that the prepared polyimide film has high modulus and high heat resistance, and the crosslinking degree can be further improved by adding the aromatic triamine, so that the modulus is improved; the obtained polyimide film material has the advantages of low dielectric constant, high modulus and high temperature resistance, and has a wide application prospect in the field of novel flexible display.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a low dielectric high modulus polyimide thin film material, its preparation method, and its application in flexible display substrates. Background Technology

[0002] Polyimide, as a special organic polymer material, is widely used in aerospace, rail transportation, electronics, optoelectronics, display and high-end equipment fields due to its high and low temperature resistance, excellent mechanical properties and flame retardancy. Especially in the field of optoelectronics, in the flexible functional devices, polyimide film can be used as a flexible substrate material that integrates structure and function to replace the traditional rigid glass substrate in OLED display devices, thereby realizing that the screen can be rolled up and folded.

[0003] As OLED display devices continue to be updated, narrow bezels, rollable screens, and foldable screens are gradually becoming the mainstream development direction in the market. The requirements for substrate materials are also constantly increasing. Although replacing rigid glass with polymer flexible substrate films can achieve screen bending and folding functions, the dielectric properties, mechanical strength, and temperature resistance of the thin film substrate still need to be further improved to meet the latest application requirements of new OLED screens, such as rollable, foldable, and narrow bezel packaging.

[0004] However, existing flexible polyimide substrates for OLED screens typically suffer from low modulus and temperature resistance, as well as high dielectric constants. For example, Japanese patent application JP2006131706A discloses a low-dielectric material containing a hyperbranched polyimide obtained by reacting an aromatic tetracarboxylic dianhydride (4,4'-(hexafluoroisopropylidene)phthalic dianhydride) with an aromatic triamine (1,3,5-tris(4-aminophenoxy)benzene and 1,3,5-tris(4-aminophenoxy)triazine). Although this polyimide material has a low dielectric constant (2.8), its modulus is only about 5 GPa.

[0005] Therefore, there is an urgent need to develop a polyimide material that combines low dielectric constant and high modulus. Summary of the Invention

[0006] The purpose of this invention is to provide a low-dielectric-high-modulus polyimide thin film material, its preparation method, and its application in flexible display substrates, so as to solve the defect that polyimide thin films in the prior art cannot have both low dielectric properties and high modulus.

[0007] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows: This invention first provides a method for preparing a low-dielectric-high-modulus polyimide thin film material, the method comprising the step of reacting an aromatic dianhydride with an aromatic amine compound to generate polyimide; The aromatic dianhydride has a naphthalene or anthracene structure, and the aromatic amine compound comprises at least a mixture of aromatic triamines and aromatic diamines.

[0008] The present invention uses aromatic dianhydrides with naphthalene or anthracene structures. Their macromolecular rigid structure can effectively improve the internal molecular orientation and stacking state, so that the polyimide film produced has high modulus and high heat resistance. The addition of aromatic triamine can further improve the degree of crosslinking and thus improve the modulus. The resulting polyimide film material has low dielectric constant, high modulus and high temperature resistance, and has broad application prospects in the field of novel flexible displays.

[0009] Preferably, in the above preparation method, the aromatic dianhydride is selected from at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,3,6,7-anthracitetetracarboxylic dianhydride, and 3,4,9,10-perylenetetracarboxylic dianhydride.

[0010] Preferably, in the above preparation method, the aromatic triamine is selected from at least one of the following formulas (I), (II), (III) and (IV): (I); wherein R1 is independently selected from -H, -CH3, -C2H5; (II); (III); (Ⅳ); More preferably, at least one of formulas (I), (II), and (IV).

[0011] The aromatic amine compounds further include aromatic diamines, wherein the aromatic diamines are selected from at least one of 3,3'-biphenyldiamine, 3,4'-biphenyldiamine, 4,4'-biphenyldiamine, 2,6'-naphthyldiamine, 2,7'-naphthyldiamine, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diaminobenzoylaniline, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 3,3',5,5'-tetramethylbiphenylamine, 4,4'-diaminoterphenyl, 2,6-diaminopyridine, 2,6-diaminoanthracene, 2,6-diaminoanthraquinone, 1,6-pyrenediamine, and 2,7-pyrenediamine. In a more preferred embodiment, a mixture of aromatic triamine and aromatic diamine is used as an aromatic amine compound to react with an aromatic dianhydride. In this case, the molar ratio of the aromatic amine compound to the aromatic dianhydride is preferably 1:(0.9-1.1). The preferred molar ratio of aromatic triamine to aromatic dianhydride is (0-0.2):1, with the balance being aromatic diamine.

[0012] Preferably, the above preparation method includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds and auxiliaries are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; S2. Add aromatic dianhydride to the mixed solution described in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is then peeled off from the substrate to obtain a low dielectric high modulus polyimide film material.

[0013] Preferably, in step S1 of the above preparation method, the auxiliary agent is an aminopropyl-terminated polydimethylsiloxane with a number average molecular weight Mn of 500 Da. The molar ratio of the auxiliary agent to the aromatic dianhydride is (0-0.02):1; With the aid of this additive, the dielectric constant of the polyimide film material can be further reduced to below 3.0.

[0014] Preferably, in step S1 of the above preparation method, the polar solvent is selected from at least one of N-methylpyrrolidone, γ-butyrolactone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, m-cresol, cyclopentanone, and γ-valerol.

[0015] Preferably, in step S2 of the above preparation method, the reaction temperature of the copolymerization reaction is -15 to 100°C, the reaction time is 6 to 72 h, and the solid content of the obtained polyamic acid resin is 5 to 35%. In step S3, the imidization reaction process is as follows: first, vacuum drying at 60-120℃ for 5-60 min, and then heating treatment in an inert atmosphere in the following stages: holding at 80-100℃ for 10-150 min, holding at 140-200℃ for 10-150 min, holding at 220-300℃ for 10-150 min, and reacting at 350-500℃ for 10-150 min.

[0016] Under these imidization reaction conditions, polyamic acid resin can rapidly form a film.

[0017] The present invention also provides a low dielectric high modulus polyimide film material, which is prepared by the above-described preparation method; the material has the characteristics of low dielectric constant, high modulus and high temperature resistance.

[0018] This invention also provides the application of the aforementioned low-dielectric-high-modulus polyimide thin film material in flexible display substrates. The polyimide substrate material prepared using this invention exhibits high toughness, resistance to bending and folding, and a long service life.

[0019] Compared with the prior art, the beneficial effects of the present invention are reflected in: 1. The present invention uses aromatic dianhydrides with naphthalene or anthracene structures. Their macromolecular rigid structure can effectively improve the internal molecular orientation and stacking state, so that the polyimide film produced has high modulus and high heat resistance. The addition of aromatic triamine can further improve the degree of crosslinking and thus improve the modulus. The obtained polyimide film material has low dielectric constant, high modulus and high temperature resistance, and has broad application prospects in the field of novel flexible displays.

[0020] 2. In the preparation method of the present invention, the presence of the additives can further reduce the dielectric constant of the material to below 3.0, which is beneficial to further improve the overall performance of the polyimide film material. Detailed Implementation

[0021] The following examples illustrate the technical solution of the present invention in a more detailed manner.

[0022] Example 1 This embodiment discloses a low-dielectric-high-modulus polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds and auxiliaries are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, N-methylpyrrolidone (892.4695 g), p-phenylenediamine (54.0700 g, 0.5 mol), N1,N3,N5 tris(4-aminophenyl)benzene-1,3,5-tricarboxamide (12.2533 g, 0.0255 mol), and aminopropyl-terminated polydimethylsiloxane (1.3 g, 0.0026 mol, Mn=500 Da) were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at room temperature to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, at 15°C, 3,3',4,4'-biphenyltetracarboxylic dianhydride (150.0522 g, 0.51 mol) was slowly added in batches to the mixed solution, and the reactant powder adhering to the wall was washed with 99.1633 g of N-methylpyrrolidone to completely dissolve it into the reaction solution. Then, the temperature was raised to 25°C and the reaction was stirred for 12 h to obtain polyamic acid resin PAA-1 with a solid content of 18%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-1 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 85°C for 15 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: holding at 85°C for 30 min, holding at 180°C for 30 min, holding at 270°C for 30 min, and holding at 470°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-1 of this embodiment.

[0023] Example 2 This embodiment discloses a low-dielectric-high-modulus polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, N-methylpyrrolidone (756.6106 g), p-phenylenediamine (48.6630 g, 0.45 mol), N1,N3,N5 tris(4-aminophenyl)benzene-1,3,5-tricarboxamide (29.4078 g, 0.0612 mol), and 2,6'-naphthylenediamine (1.4554 g, 0.0092 mol) were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at room temperature to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, at 10°C, pyromellitic dianhydride (34.8992 g, 0.16 mol) was slowly added to the mixed solution and reacted for 2 h. Then, 3,3',4,4'-biphenyltetracarboxylic dianhydride (102.9770 g, 0.35 mol) was slowly added in batches, and the reactant powder adhering to the wall was washed with 104.4015 g of N-methylpyrrolidone to completely dissolve it into the reaction solution. Then, the temperature was raised to 20°C and the reaction was stirred for 12 h to obtain polyamic acid resin PAA-2 with a solid content of 20%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-2 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 85°C for 15 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: holding at 85°C for 30 min, holding at 180°C for 30 min, holding at 270°C for 30 min, and holding at 480°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-2 of this embodiment.

[0024] Example 3 This embodiment discloses a low-dielectric-high-modulus polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, N-methylpyrrolidone (646.1061 g), p-phenylenediamine (54.0700 g, 0.5 mol), and N1,N3,N5 tris(4-aminophenyl)benzene-1,3,5-tricarboxamide (21.6899 g, 0.0612 mol) were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at 20 °C to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, at 5°C, 42.9088 g of 2,3,6,7-naphthalenetetracarboxylic dianhydride (0.16 mol) was slowly added to the mixed solution and reacted for 2 h. Then, 120.6302 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (0.41 mol) was slowly added in batches. The reactant powder adhering to the wall was washed with 71.7895 g of N-methylpyrrolidone to completely dissolve it into the reaction solution. The temperature was then raised to 25°C and the reaction was stirred for 20 h to obtain polyamic acid resin PAA-3 with a solid content of 25%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-3 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 85°C for 15 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: holding at 85°C for 30 min, holding at 180°C for 30 min, holding at 270°C for 30 min, and holding at 480°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-3 of this embodiment.

[0025] Example 4 This embodiment discloses a low-dielectric-high-modulus polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds and auxiliaries are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, N-methylpyrrolidone (856.3644 g), p-phenylenediamine (54.0700 g, 0.5 mol), N1,N3,N5 tris(4-aminophenyl)benzene-1,3,5-tricarboxamide (21.6899 g, 0.0612 mol), and aminopropyl-terminated polydimethylsiloxane (1.6 g, 0.0032 mol, Mn=500 Da) were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at room temperature to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, at 0°C, 13.4091 g of 2,3,6,7-naphthalenetetracarboxylic dianhydride (0.05 mol) was slowly added to the mixed solution and reacted for 2 h. Then, 147.1100 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (0.50 mol) was slowly added in batches. The reactant powder adhering to the wall was washed with 95.1516 g of N-methylpyrrolidone to completely dissolve it into the reaction solution. The temperature was then raised to 25°C and the mixture was stirred for 16 h to obtain polyamic acid resin PAA-4 with a solid content of 20%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-4 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 85°C for 15 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: holding at 85°C for 30 min, holding at 180°C for 30 min, holding at 270°C for 30 min, and holding at 470°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-4 of this embodiment.

[0026] Example 5 This embodiment discloses a low-dielectric-high-modulus polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, N-methylpyrrolidone (880.6792 g), p-phenylenediamine (54.0700 g, 0.5 mol), and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (21.6898 g, 0.0612 mol) were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at room temperature to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, at 5°C, pyromellitic dianhydride (23.5569 g, 0.108 mol) was slowly added to the mixed solution and reacted for 2 h. Then, 3,3',4,4'-biphenyltetracarboxylic dianhydride (127.1031 g, 0.432 mol) was slowly added in batches, and the reactant powder adhering to the wall was washed with 150.7885 g of N-methylpyrrolidone to completely dissolve it into the reaction solution. Then, the temperature was raised to 15°C and the reaction was stirred for 8 h to obtain polyamic acid resin PAA-5 with a solid content of 18%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-5 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 85°C for 15 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: holding at 85°C for 30 min, holding at 180°C for 30 min, holding at 270°C for 30 min, and holding at 480°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-5 of this embodiment.

[0027] Example 6 This embodiment discloses a low-dielectric-high-modulus polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, 880.6792 g of N-methylpyrrolidone, 43.2560 g (0.4 mol) of p-phenylenediamine, 21.2290 g (0.1 mol) of 4,4'-diamino-2,2'-dimethylbiphenyl, and 9.0374 g (0.0255 mol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at room temperature to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, at 10°C, pyromellitic dianhydride (23.5569 g, 0.108 mol) was slowly added to the mixed solution and reacted for 2 h. Then, 3,3',4,4'-biphenyltetracarboxylic dianhydride (127.1031 g, 0.432 mol) was slowly added in batches, and the reactant powder adhering to the wall was washed with 150.7885 g of N-methylpyrrolidone to completely dissolve it into the reaction solution. Then, the temperature was raised to 20°C and the reaction was stirred for 12 h to obtain polyamic acid resin PAA-6 with a solid content of 18%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-6 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 85°C for 15 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: holding at 85°C for 30 min, holding at 180°C for 30 min, holding at 270°C for 30 min, and holding at 470°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-6 of this embodiment.

[0028] Example 7 This embodiment discloses a low-dielectric-high-modulus polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds and auxiliaries are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, γ-valerol (855.3235 g), p-phenylenediamine (54.0700 g, 0.5 mol), 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (18.0749 g, 0.0510 mol), and aminopropyl-terminated polydimethylsiloxane (1.6 g, 0.0032 mol, Mn=500 Da) were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at 30 °C to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, at 15°C, 2,3,6,7-naphthalenetetracarboxylic dianhydride (21.4544 g, 0.08 mol) was slowly added to the mixed solution and reacted for 2 h. Then, 3,3',4,4'-biphenyltetracarboxylic dianhydride (135.3412 g, 0.46 mol) was slowly added in batches, and the reactant powder adhering to the wall was washed with 64.3791 g of γ-valerol to completely dissolve it into the reaction solution. Then, the temperature was raised to 30°C and the reaction was stirred for 16 h to obtain polyamic acid resin PAA-7 with a solid content of 20%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-7 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 85°C for 20 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: holding at 85°C for 30 min, holding at 180°C for 30 min, holding at 270°C for 30 min, and holding at 470°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-7 of this embodiment.

[0029] Example 8 This embodiment discloses a low-dielectric-high-modulus polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds and auxiliaries are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, γ-valerol (923.1956 g), p-phenylenediamine (54.0700 g, 0.5 mol), N1,N3,N5 tris(4-aminophenyl)benzene-1,3,5-tricarboxamide (24.5065 g, 0.0510 mol), and aminopropyl-terminated polydimethylsiloxane (1.6 g, 0.0032 mol, Mn=500 Da) were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at 30 °C to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, at 35°C, 2,3,6,7-anthracite dianhydride (27.3686 g, 0.086 mol) was slowly added to the mixed solution and reacted for 2 h. Then, 3,3',4,4'-biphenyltetracarboxylic dianhydride (141.2256 g, 0.48 mol) was slowly added in batches, and the reactant powder adhering to the wall was washed with 69.4878 g of γ-valerol to completely dissolve it into the reaction solution. Then, the temperature was lowered to 30°C and the reaction was stirred for 12 h to obtain polyamic acid resin PAA-8 with a solid content of 20%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-7 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 80°C for 20 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: 85°C for 30 min, 180°C for 30 min, 270°C for 30 min, and 480°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-8 of this embodiment.

[0030] Example 9 This embodiment discloses a low-dielectric-high-modulus polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds and auxiliaries are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, N-methylpyrrolidone (878.9752 g), p-phenylenediamine (54.0700 g, 0.5 mol), 1,3,5-tris(4-aminophenyl)benzene (8.9620 g, 0.0255 mol), and aminopropyl-terminated polydimethylsiloxane (1.3 g, 0.0026 mol, Mn = 500 Da) were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at room temperature to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, at 15°C, 3,3',4,4'-biphenyltetracarboxylic dianhydride (150.0522 g, 0.51 mol) was slowly added in batches to the mixed solution, and the reactant powder adhering to the wall was washed with 97.6639 g of N-methylpyrrolidone to completely dissolve it into the reaction solution. Then, the temperature was raised to 25°C and the reaction was stirred for 12 h to obtain polyamic acid resin PAA-9 with a solid content of 18%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-9 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 85°C for 15 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: holding at 85°C for 30 min, holding at 180°C for 30 min, holding at 270°C for 30 min, and holding at 470°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-9 of this embodiment.

[0031] Example 10 This embodiment discloses a low-dielectric-high-modulus polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds and auxiliaries are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, N-methylpyrrolidone (879.2844 g), p-phenylenediamine (54.0700 g, 0.5 mol), 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (9.0374 g, 0.0255 mol), and aminopropyl-terminated polydimethylsiloxane (1.3 g, 0.0026 mol, Mn = 500 Da) were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at room temperature to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, at 15°C, 3,3',4,4'-biphenyltetracarboxylic dianhydride (150.0522 g, 0.51 mol) was slowly added in batches to the mixed solution, and the reactant powder adhering to the wall was washed with 97.6983 g of N-methylpyrrolidone to completely dissolve it into the reaction solution. Then, the temperature was raised to 25°C and the reaction was stirred for 12 h to obtain polyamic acid resin PAA-10 with a solid content of 18%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-10 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 85°C for 15 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: holding at 85°C for 30 min, holding at 180°C for 30 min, holding at 270°C for 30 min, and holding at 470°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-10 of this embodiment.

[0032] Comparative Example 1 This comparative example describes a polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, N-methylpyrrolidone (683.3278 g) and p-phenylenediamine (54.0700 g, 0.5 mol) were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at room temperature to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, pyromellitic dianhydride (34.8992 g, 0.16 mol) was slowly added to the mixed solution and reacted for 2 h. Then, 3,3',4,4'-biphenyltetracarboxylic dianhydride (102.9770 g, 0.35 mol) was slowly added in batches, and the reactant powder adhering to the wall was washed with 84.4562 g of N-methylpyrrolidone to completely dissolve it into the reaction solution. The reaction was then stirred at 25 °C for 32 h to obtain polyamic acid resin PAA-12 with a solid content of 20%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-9 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 100°C for 20 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: 80°C for 30 min, 180°C for 30 min, 260°C for 30 min, and 460°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-12.

[0033] Comparative Example 2 This comparative example describes a polyimide film material, the preparation method of which includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; Specifically, under a nitrogen atmosphere, N-methylpyrrolidone (719.3078 g), p-phenylenediamine (32.4420 g, 0.3 mol), and 4,4'-benzylenediamine (36.8474 g, 0.2 mol) were added to a reaction flask equipped with a mechanical stirrer, and the mixture was stirred thoroughly at room temperature to dissolve and obtain a mixed solution. S2. Add aromatic dianhydride to the mixed solution in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; Specifically, pyromellitic dianhydride (32.7180 g, 0.15 mol) was slowly added to the mixed solution and reacted for 2 h. Then, 3,3',4,4'-biphenyltetracarboxylic dianhydride (100.0348 g, 0.34 mol) was slowly added in batches, and the reactant powder adhering to the wall was washed with 88.9032 g of N-methylpyrrolidone to completely dissolve it into the reaction solution. The reaction was then stirred at 25 °C for 24 h to obtain polyamic acid resin PAA-13 with a solid content of 20%. S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is peeled off from the substrate to obtain the low dielectric high modulus polyimide film material of this embodiment. Specifically, the above-mentioned polyamic acid resin PAA-10 was uniformly coated on the surface of a glass substrate, with a wet film thickness of 150 μm. The wet film was then vacuum dried at 100°C for 20 min, and then subjected to segmented heating under a nitrogen atmosphere. The heating program was as follows: 80°C for 30 min, 180°C for 30 min, 260°C for 30 min, and 460°C for 30 min. After cooling to room temperature, the film was peeled off from the glass substrate to obtain the polyimide film material PI-13.

[0034] The properties of the polyimide film materials prepared in Examples 1-11 and Comparative Examples 1-2 were tested, and the test results are shown in Table 1.

[0035] Table 1 As can be seen from Table 1, compared with Comparative Examples 1 and 2, the embodiments of the present invention use aromatic dianhydrides with naphthalene or anthracene structures, and also introduce aromatic triamines, which enables the embodiments to obtain excellent elastic modulus while maintaining a low dielectric constant.

Claims

1. A method for preparing a low-dielectric-high-modulus polyimide thin film material, characterized in that, This includes the step of reacting aromatic dianhydrides with aromatic amine compounds to generate polyimide; The aromatic dianhydride has a naphthalene or anthracene structure, and the aromatic amine compound comprises at least a mixture of aromatic triamines and aromatic diamines.

2. The preparation method according to claim 1, characterized in that, The aromatic dianhydride is selected from at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3',3,4'-biphenyltetracarboxylic acid dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-anthracitetetracarboxylic acid dianhydride, and 3,4,9,10-perylenetetracarboxylic acid dianhydride.

3. The preparation method according to claim 1, characterized in that, The aromatic triamine is selected from at least one of the following formulas (I), (II), (III) and (IV): （Ⅰ）； R1 is independently selected from -H, -CH3, -C2H5; （Ⅱ）； （Ⅲ）； （Ⅳ）。 4. The preparation method according to claim 3, characterized in that, The aromatic amine compounds further include aromatic diamines selected from at least one of 3,3'-biphenyldiamine, 3,4'-biphenyldiamine, 4,4'-biphenyldiamine, 2,6'-naphthyldiamine, 2,7'-naphthyldiamine, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diaminobenzoylaniline, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 3,3',5,5'-tetramethylbiphenylamine, 4,4'-diaminoterphenyl, 2,6-diaminopyridine, 2,6-diaminoanthracene, 2,6-diaminoanthraquinone, 1,6-pyrenediamine, and 2,7-pyrenediamine.

5. The preparation method according to claim 1, characterized in that, The molar ratio of aromatic amines to aromatic dianhydrides is 1:(0.9-1.1). The molar ratio of aromatic triamine to aromatic dianhydride is (0-0.2):

1.

6. The preparation method according to claim 1, characterized in that, Includes the following steps: S1. Under an inert atmosphere, aromatic amine compounds and auxiliaries are added to a polar solvent and dissolved thoroughly to obtain a mixed solution; S2. Add aromatic dianhydride to the mixed solution described in step S1 in batches, and form a cross-linked polyamic acid resin through copolymerization reaction; S3. The polyamic acid resin obtained in step S2 is uniformly coated on the substrate, and an imidization reaction is carried out under the protection of an inert atmosphere to form a thin film. The thin film is then peeled off from the substrate to obtain a low dielectric high modulus polyimide film material.

7. The preparation method according to claim 6, characterized in that, In step S1, the auxiliary agent is an aminopropyl-terminated polydimethylsiloxane with a number average molecular weight of 500 Da. The molar ratio of the auxiliary agent to the aromatic dianhydride is (0-0.02):1; The polar solvent is selected from at least one of N-methylpyrrolidone, γ-butyrolactone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, m-cresol, cyclopentanone, and γ-valerol.

8. The preparation method according to claim 6, characterized in that, In step S2, the copolymerization reaction temperature is -15 to 100°C, the reaction time is 6 to 72 hours, and the solid content of the resulting polyamic acid resin is 5% to 35%. In step S3, the imidization reaction process is as follows: first, vacuum drying at 60-120℃ for 5-60 min, and then heating treatment in an inert atmosphere in the following stages: holding at 80-100℃ for 10-150 min, holding at 140-200℃ for 10-150 min, holding at 220-300℃ for 10-150 min, and reacting at 350-500℃ for 10-150 min.

9. A low-dielectric-high-modulus polyimide film material, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8.

10. The application of the low dielectric high modulus polyimide thin film material as described in claim 9 in flexible display substrates.

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