Bis-benzimidazole diamine and preparation method thereof, polyimide film and preparation method and application thereof

Abstract

The invention provides bis-benzimidazole diamine and a preparation method thereof, a polyimide film and a preparation method and application thereof. The bis-benzimidazole diamine has a structure as shown in a formula (I) and / or a formula (II). The polyimide film is prepared from the following raw materials: a diamine monomer and a dianhydride monomer, wherein the diamine monomer comprises the bis-benzimidazole diamine. The bis-benzimidazole diamine provided by the invention is a class of non-coplanar aromatic heterocyclic diamine containing a bis-benzimidazole unit; the polyimide film prepared by polymerizing the diamine and the dianhydride monomer has low thermal expansion coefficient, high Tg and excellent optical performance, and can be applied to a flexible substrate material for flexible display.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyimide, and relates to a bis(benzimidazole) diamine and its preparation method, a polyimide film and its preparation method and application, and particularly relates to a non-coplanar aromatic heterocyclic diamine containing a bis(benzimidazole) unit and its preparation method, a transparent polyimide film and its preparation method and application. Background Art

[0002] With the rapid development of electronic technology, flexible display has gradually become the mainstream direction in the display field. The development of flexible display has put forward more requirements for the required materials, including flexible circuits and flexible substrates, etc. The substrate of traditional rigid screen display uses glass, and display devices and circuits are processed on the glass. In order to produce flexible displays, glass substrates are no longer suitable. Only polyimide (PI), a flexible material that can withstand high-temperature processes, can meet the requirements. However, traditional polyimide has a high coefficient of thermal expansion, which is not conducive to device processing, and internal stress is generated at the interface between material layers during expansion and contraction, resulting in changes in the display accuracy of the device. At the same time, problems such as delamination between layers during bending cannot meet the usage requirements. In addition, due to insufficient transmittance, it is difficult to meet the light transmission requirements of the under-screen camera, which is not conducive to the use of flexible substrate displays.

[0003] To improve the heat resistance of polyimide while taking into account its low coefficient of thermal expansion, a currently effective method is to introduce an imidazole heterocyclic structure into the main chain structure. The literature "High performance polyimide films containing benzimidazole moieties for thin film solar cells. e-Polymers, 19, 1, 2019, 555-562." introduced trifluoromethyl-2-phenylbenzimidazole into the PI main chain structure, and the polyimide polymer showed significant improvements in thermal stability, thermal expansion, hygroscopicity and mechanical properties. The literature "Synthesis and properties of polyimides derived from diamine monomer containing bi-benzimidazole unit. J Polym Res 21, 2014, 424." introduced an aromatic heterocyclic diamine monomer containing a bibenzimidazole unit into the main chain structure, and the glass transition temperature was increased to above 415 °C, and the modulus could be as high as 15.5 GPa. However, this series of monomers only solved the problem of high temperature resistance, and the improvement of optics was not significant; in order to utilize the excellent heat resistance of the aromatic heterocycle of the benzimidazole unit, the literature "Synthesis of novel colorless polyimides from benzimidazole diamines isomeride which have improved transparency," introduced an aromatic heterocyclic diamine monomer with a non-coplanar benzimidazole unit into the main chain structure and polymerized it with an alicyclic ring to prepare a transparent polyimide with a certain transmittance. However, the introduction of this type of monomer did not have a significant effect on reducing the coefficient of thermal expansion.

[0004] Although high temperature resistance, low expansion and even excellent optical properties can be achieved individually through existing technologies, further improvement in monomer development and polyimide synthesis is still needed to integrate these three properties into a system and apply them to flexible substrate materials. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the object of the present invention is to provide a method for synthesizing diamine monomers of transparent polyimide applicable to flexible substrates, as well as the preparation and application of corresponding transparent polyimide. The diamine monomers are a class of non-coplanar aromatic heterocyclic diamines containing bisbenzimidazole units; after polymerizing the diamine with the corresponding dianhydride monomer to form polyamic acid, polyimide films with low coefficient of thermal expansion, high Tg and excellent optical properties can be obtained through imidization, and the films can be applied to flexible substrate materials for flexible displays.

[0006] To achieve the object of the present invention, the following technical solutions are adopted:

[0007] In the first aspect, the present invention provides a bisbenzimidazole diamine having the structure shown in the following formula (I) and / or formula (II):

[0008]

[0009]

[0010] Among them, each R1 is independently any one of -H, a linear or branched alkyl group of substituted or unsubstituted C1-C10 (such as C1, C2, C3, C4, C5, C6, C7, C8, C9 or C10), an aryl group of substituted or unsubstituted C6-C20 (such as C6, C8, C10, C12, C14, C16, C18, C20, etc.), and a heteroaryl group of substituted or unsubstituted C3-C20 (such as C3, C4, C5, C6, C8, C10, C12, C14, C16, C18, C20, etc.); R1 can be at the ortho or meta position of the nitro group;

[0011] Each R2 is independently any one of -H, an aryl group of substituted or unsubstituted C6-C20 (such as C6, C8, C10, C12, C14, C16, C18, C20, etc.), and a heteroaryl group of substituted or unsubstituted C3-C20 (such as C3, C4, C5, C6, C8, C10, C12, C14, C16, C18, C20, etc.);

[0012] The substituents of the substitution are any one of halogen (such as -F, -Cl, -Br, -I), a linear or branched alkyl group of C1-C10 (such as C1, C2, C3, C4, C5, C6, C7, C8, C9 or C10), and an aryl group of substituted or unsubstituted C6-C20 (such as C6, C8, C10, C12, C14, C16, C18, C20, etc.).

[0013] The bis(benzimidazole) diamine provided by the present invention is a non-coplanar aromatic heterocyclic diamine containing a bis(benzimidazole) unit. Formula (I) and Formula (II) are isomers; the polyimide film prepared by using it has excellent thermodynamic properties. This non-coplanar diamine monomer contains a bis(benzimidazole) unit structure, which is symmetric and linear. When it is used in the preparation of polyimide films, on the one hand, the distance between molecular chains is relatively large, loosening the chain packing, reducing or even eliminating the formation of charge transfer complex (CTC) complexes, and improving the optical transparency of the polyimide film; on the other hand, the symmetry and linearity of the bis(benzimidazole) unit make the polyimide film molecules more regular, which can effectively reduce the thermal expansion coefficient of the film; in addition, the introduction of the bis(benzimidazole) unit greatly improves the heat resistance of the entire polymerization unit, effectively improving the heat resistance of the polyimide film, and the Tg temperature is above 430 °C, which can meet the subsequent high-temperature processing requirements; thus, the problems of poor optical properties, relatively high thermal expansion coefficient, and difficult-to-meet relationship performance of polyimide films are solved.

[0014] Preferably, each of the R1 is independently any one of -H, methyl, ethyl, trifluoromethyl, and phenyl.

[0015] Preferably, the R2 is -H or phenyl.

[0016] Preferably, the bis(benzimidazole) diamine is selected from any one or a combination of at least two of the following compounds;

[0017]

[0018]

[0019] In the second aspect, the present invention provides a preparation method of the bis(benzimidazole) diamine as described in the first aspect. The preparation method includes the following steps:

[0020] Couple phenyltetramine with R2-X, and then react the obtained product with to carry out a condensation reaction, and then through a hydrogenation catalytic reduction reaction, the bis(benzimidazole) diamine is obtained;

[0021] Among them, the values of R1 and R2 are the same as those in the first aspect, and X is a halogen (such as -F, -Cl, -Br, -I).

[0022] The coupling reaction is a typical Buchwald–Hartwig reaction. Preferably, the coupling reaction is carried out in the presence of a palladium catalyst and an inorganic base.

[0023] Preferably, the inorganic base includes cesium carbonate.

[0024] Preferably, the solvent used in the coupling reaction includes benzene derivatives, preferably any one or a combination of at least two of toluene, xylene, and mesitylene.

[0025] Preferably, the temperature of the coupling reaction is 80 - 140 °C, such as 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125 °C, 130 °C, 135 °C, 140 °C, etc., and the time of the coupling reaction is 5 - 24 h, such as 5 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, etc. There is a certain relationship between the reaction temperature and time and the electronegativity of R2.

[0026] Isomers will be produced during the coupling reaction, and the isomers can be further reacted without separation.

[0027] Preferably, the solvent used in the condensation reaction includes polar organic solvents.

[0028] Preferably, the solvent used in the condensation reaction includes any one or a combination of at least two of N,N - dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N - methylpyrrolidone (NMP), or N,N - dimethylacetamide (DMAc).

[0029] Preferably, the temperature of the condensation reaction is 120 - 200 °C, such as 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, etc., and preferably 140 - 180 °C.

[0030] Preferably, the time of the condensation reaction is 3 - 24 h, such as 3 h, 4 h, 5 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, etc., which has a certain relationship with the position and charge property of R1.

[0031] Preferably, the catalyst used in the hydrogenation catalytic reduction reaction includes palladium - carbon (more economical).

[0032] Preferably, the solvent used in the hydrogenation catalytic reduction reaction includes alcohol solvents.

[0033] Preferably, the alcohol solvents include any one or a combination of at least two of methanol, ethanol, or isopropanol.

[0034] Preferably, the temperature of the hydrogenation catalytic reduction reaction is 20 - 70 °C, such as 20 °C, 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, etc., and the time of the hydrogenation catalytic reduction reaction is 5 - 24 h, such as 5 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, etc.

[0035] The synthetic route of the bis(benzimidazole)diamine provided by the present invention is as follows:

[0036]

[0037] The preparation method of the aromatic heterocyclic diamine monomer of the non - coplanar bis(benzimidazole) unit provided by the present invention starts from the coupling reaction as a mixture of isomers. Even for isomers, each ring in the two monomers is non - coplanar and has a large repulsive effect, so the effects are equivalent. The separation process is reduced during the preparation process, simplifying the purification time and cost.

[0038] In the third aspect, the present invention provides a polyimide film. The raw materials for preparing the polyimide film include a diamine monomer and a dianhydride monomer; the diamine monomer includes the bis(benzimidazole)diamine as described in the first aspect or the bis(benzimidazole)diamine prepared according to the preparation method as described in the second aspect.

[0039] Preferably, the dianhydride monomer includes any one or a combination of at least two of 4,4'-oxybis(phthalic anhydride) (alias 4,4'-oxydiphthalic anhydride), 9,9 - bis(3,4 - dicarboxyphenyl)fluorene dianhydride, 2,2'-bis(3,4 - dicarboxylic acid)hexafluoropropane dianhydride (alias hexafluorodiacid anhydride), hydrogenated pyromellitic dianhydride (HPMDA), bicyclo[2.2.2]octane - 2,3,5,6 - tetracarboxylic 2,3:5,6 - dianhydride, bicyclo[2.2.2]oct - 7 - ene - 2,3,5,6 - tetracarboxylic dianhydride, cyclobutane tetracarboxylic anhydride, 1,2,3,4 - butanetetracarboxylic dianhydride, 9,9 - bis(trifluoromethyl)-2,3,6,7 - xanthene tetracarboxylic dianhydride. Preferably, it includes any one or a combination of at least two of hydrogenated pyromellitic dianhydride, bicyclo[2.2.2]octane - 2,3,5,6 - tetracarboxylic 2,3:5,6 - dianhydride, bicyclo[2.2.2]oct - 7 - ene - 2,3,5,6 - tetracarboxylic dianhydride, cyclobutane tetracarboxylic anhydride, 1,2,3,4 - butanetetracarboxylic dianhydride.

[0040] The polyimide film provided by the present invention uses the diamine compound represented by formula (I) and / or formula (II) of the present invention as the diamine monomer, and undergoes self - polymerization or copolymerization with the above - mentioned aromatic tetracarboxylic dianhydride to prepare a polyimide film, which is more conducive to achieving excellent optical properties of the polyimide film, with TT > 80% in the full wavelength range, YI < 10 for yellowness, and high thermodynamic performance T g> 430 °C. This transparent polyimide can be applied to flexible display substrates; more importantly, this transparent polyimide can achieve high heat resistance while being fluorine-free.

[0041] Preferably, the molar ratio of the diamine monomer to the dianhydride monomer is 1:(0.9 - 1.2), such as 1:0.9, 1:1, 1:1.1, 1:1.2, etc., preferably 1:(0.92 - 1.1), more preferably 1:(0.95 - 1.05), and most preferably 1:1.

[0042] Fourthly, the present invention provides a method for preparing a polyimide film as described in the third aspect, and the preparation method includes the following steps:

[0043] Mix the diamine monomer, dianhydride monomer, and organic solvent, and carry out a polymerization reaction to obtain a polyamic acid slurry. The polyamic acid slurry is coated into a wet film and then subjected to thermal imidization to obtain the polyimide film.

[0044] Preferably, the organic solvent is an aprotic organic solvent, including any one or a combination of at least two of N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, propylene glycol monomethyl ether, cyclopentanone, cyclohexanone, ethyl acetate, toluene, and methyl ethyl ketone, preferably N,N-dimethylformamide and / or N,N-dimethylacetamide.

[0045] Preferably, the temperature of the polymerization reaction is -10 °C to 50 °C, such as -10 °C, -5 °C, 0 °C, 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, 50 °C, etc., preferably -5 °C to 30 °C, more preferably -5 °C to 10 °C.

[0046] Preferably, the time of the polymerization reaction is 3 - 48 h, such as 3 h, 4 h, 5 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, 42 h, 44 h, 46 h, 48 h, etc., preferably 5 - 36 h, more preferably 10 - 24 h.

[0047] Preferably, the polymerization reaction is carried out in an inert gas (such as nitrogen, etc.) atmosphere.

[0048] Preferably, the thermal imidization is carried out by gradient heating, and there is a heat preservation section between the gradient heating sections.

[0049] Preferably, the temperature for thermal imidization is 60°C - 450°C, such as 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C, 450°C, etc. The total heat preservation time is 2 - 10 hours, such as 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc. The heating rate is 1 - 10°C / minute, such as 1°C / minute, 2°C / minute, 3°C / minute, 4°C / minute, 5°C / minute, 6°C / minute, 7°C / minute, 8°C / minute, 9°C / minute, 10°C / minute, etc.

[0050] Preferably, the process of thermal imidization sequentially includes at least five of the following steps: heating at a rate of 1 - 10°C / minute (such as 1°C / minute, 2°C / minute, 3°C / minute, 4°C / minute, 5°C / minute, 6°C / minute, 7°C / minute, 8°C / minute, 9°C / minute, 10°C / minute, etc., the same enumeration for the same range involved hereinafter will not be repeated) to 60 - 80°C (such as 60°C, 70°C, 80°C, etc.) and keeping warm for 10 min - 1 h (such as 10 min, 20 min, 30 min, 40 min, 50 min, 1 h, etc., the same enumeration for the same range involved hereinafter will not be repeated); heating at a rate of 1 - 10°C / minute to 90 - 120°C (such as 90°C, 100°C, 110°C, 120°C, etc.) and keeping warm for 10 min - 1 h; heating at a rate of 1 - 10°C / minute to 140 - 160°C (such as 140°C, 150°C, 160°C, etc.) and keeping warm for 10 min - 1 h; heating at a rate of 1 - 10°C / minute to 170 - 190°C (such as 170°C, 180°C, 190°C, etc.) and keeping warm for 10 min - 1 h; heating at a rate of 1 - 10°C / minute to 190 - 210°C (such as 190°C, 200°C, 210°C, etc.) and keeping warm for 10 min - 1 h; heating at a rate of 1 - 10°C / minute to 240 - 260°C (such as 240°C, 250°C, 260°C, etc.) and keeping warm for 10 min - 1 h; heating at a rate of 1 - 10°C / minute to 300°C and keeping warm for 10 min - 1 h, heating at a rate of 1 - 10°C / minute to 450°C and keeping warm for 30 min - 1 h (such as 30 min, 40 min, 50 min, 1 h, etc.).

[0051] Preferably, the thermal imidization is carried out in an inert gas (such as nitrogen, etc.) atmosphere.

[0052] Preferably, the polyamic acid slurry is defoamed under vacuum and then coated into a wet film.

[0053] Preferably, the thickness of the polyimide film is 4 μm - 15 μm, such as 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., and preferably 5 - 10 μm.

[0054] In a fifth aspect, the present invention provides an application of the polyimide film as described in the third aspect in a flexible substrate.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] (1) The bisbenzimidazole diamine provided by the present invention is a non-coplanar aromatic heterocyclic diamine containing a bisbenzimidazole unit, and Formula (I) and Formula (II) are isomers; the polyimide film prepared by using it has excellent thermodynamic properties. This non-coplanar diamine monomer contains a bisbenzimidazole unit structure, which is symmetric and linear. When it is used in the preparation of polyimide films, on the one hand, the distance between molecular chains is relatively large, loosening the chain packing, reducing or even eliminating the formation of CTC complexes, and improving the optical transparency of the polyimide film; on the other hand, the symmetry and linearity of the bisbenzimidazole unit make the polyimide film molecules more regular, which can effectively reduce the thermal expansion coefficient of the film; in addition, the introduction of the bisbenzimidazole unit greatly improves the heat resistance of the entire polymerization unit, effectively improving the heat resistance of the polyimide film, and the Tg temperature is above 430 °C, which can meet the subsequent high-temperature processing requirements; thus, the problems of poor optical properties, high thermal expansion coefficient, and difficult-to-meet relationship performance of polyimide films are solved.

[0057] (2) The preparation method of the bisbenzimidazole diamine provided by the present invention is a mixture of isomers from the coupling reaction. Even for isomers, each ring in the two monomers is non-coplanar and has a relatively large repulsive effect, so the effects are equivalent. The separation process is reduced during the preparation process, simplifying the purification time and cost.

[0058] (3) The polyimide film provided by the present invention uses the diamine compound represented by Formula (I) and / or Formula (II) of the present invention as a diamine monomer, and undergoes self-polymerization or copolymerization with the above-mentioned aromatic tetracarboxylic dianhydride to prepare a polyimide film, which is more conducive to realizing the excellent optical properties of the polyimide film, with TT > 80% in the full wavelength range, YI < 10 for yellowness, and high thermodynamic properties T g > 430 °C. This transparent polyimide can be applied to flexible display substrates; more importantly, this transparent polyimide can achieve high heat resistance without containing fluorine elements. Description of the Drawings

[0059] Figure 11H NMR spectrum of compound M1 prepared in Preparation Example 1. Detailed implementation manners

[0060] The technical solutions of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0061] Preparation Example 1

[0062] In this preparation example, a bis(benzimidazole)diamine (M1) is provided, and the synthesis route is as follows:

[0063]

[0064] The preparation method includes the following steps:

[0065] Reactants 4-nitro-2-(trifluoromethyl)benzoic acid (31.04 g, 132 mmol) and 3,3'-diaminobenzidine (12.86 g, 60 mmol) were successively added to 300 ml of DMF. After adding KI, the mixture was slowly heated to 110 °C and reacted for 12 hours. After the reaction was completed, the reaction solution was washed with 10% sodium carbonate solution under ice bath conditions, and the filter cake was washed with ethyl acetate / petroleum ether (1:5) as the solvent to obtain (26.18 g, yield 78.97%) yellow powder.

[0066] 26.18 g of the powder was added to a mixed solvent of 100 ml of ethanol and ethyl acetate, 3 g of palladium-carbon (10%) was added, the mixture was purged with nitrogen three times and then hydrogen was introduced, and the mixture was refluxed for 5 hours. After hot filtration, the filtrate was rotary evaporated to obtain 24.82 g of yellow powder (M1 and M1-iso); 12 g of the mixture was subjected to column chromatography separation to obtain 7.6 g of M1. 1 1H NMR (500 MHz, DMSO-d6, ppm): δ 12.49 (s, 2H), δ 7.87 (s, 1H), δ 7.69 (s, 2H), δ 7.55 (s, 2H), δ 7.51 (s, 1H), δ 7.46 (d, J = 10 Hz, 2H), δ 7.06 (s, 2H), δ 6.90 (d, J = 10 Hz, 2H), δ 6.01 (s, 4H); iso-M2 1 1H NMR (500 MHz, DMSO-d6, ppm): δ 12.37 (s, 2H), δ 7.66 (s, 1H), δ 7.59 (s, 2H), δ 7.52 (s, 2H), δ 7.51 (s, 1H), δ 7.47 (d, J = 10 Hz, 2H), δ 7.08 (s, 2H), δ 6.91 (d, J = 10 Hz, 2H), δ 6.04 (s, 4H).

[0067] The 1H NMR spectrum of compound M1 is as follows Figure 1 shown

[0068] Preparation Example 2

[0069] In this preparation example, a bis(benzimidazole)diamine (M2 and M2-iso) is provided, and the synthesis route is as follows

[0070]

[0071] The feeding and polymerization method refers to Preparation Example 1, and a yellow powder (19.6 g, yield 65%) is obtained. M2( 1 1H NMR (500 Hz, DMSO-D6, ppm): δ7.97 (d, J = 7.8 Hz, 1H), 7.89 (d, J = 2.0 Hz, 1H), 7.77 (dd, J = 7.6, 2.1 Hz, 1H), 7.72 (d, J = 7.9 Hz, 1H), 7.50–7.44 (m, 2H), 7.44–7.37 (m, 1H), 7.33–7.24 (m, 3H), 6.67 (dd, J = 7.9, 2.0 Hz, 1H).); iso-M( 1 1H NMR (500 MHz, DMSO-D6, ppm) δ8.05 (d, J = 7.7 Hz, 1H), 7.98–7.93 (m, 2H), 7.77 (ddd, J = 18.5, 7.7, 2.2 Hz, 2H), 7.72 (d, J = 7.9 Hz, 2H), 7.51–7.45 (m, 5H), 7.44–7.39 (m, 2H), 7.32–7.24 (m, 7H), 6.67 (dd, J = 7.9, 2.0 Hz, 2H).

[0072] In the following examples and comparative examples of the present invention, the viscosity test method of the polyamic acid slurry is as follows

[0073] Use a Cannon-Fenske viscometer to measure the logarithmic viscosity of the polyamic acid slurry at 25 °C. The logarithmic viscosity (μ) is obtained by the following formula: μ = ln(t s / t0) / C;

[0074] where, t0: the flow-through time of the solvent for the reaction; t s : the flow-through time of the slurry; C: 0.5 g / dL

[0075] Example 1

[0076] In this example, a polyimide film is provided, and the preparation method includes the following steps

[0077] (1) Preparation of polyamic acid slurry: Under nitrogen protection, 5.52 g (10 mmol) of diamine monomer M1 was added to a three-necked flask equipped with mechanical stirring, and then 53.48 g of anhydrous dimethylacetamide (DMAc) was added. After stirring until diamine monomer M1 was completely dissolved, 4.44 g (10 mmol) of 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA) was added in three portions at 0 °C. Stirring was carried out at 0 °C for 24 h to carry out a polymerization reaction. After filtration and defoaming, a viscous and homogeneous polyamic acid slurry was obtained, with a viscosity of 11786 cp and a solid content of 15.7%.

[0078] The synthesis route is as follows:

[0079]

[0080] (2) Preparation of polyimide film: The polyamic acid slurry was blade-coated onto a glass plate. Under a nitrogen atmosphere, it was heated to 60 °C at a heating rate of 5 °C / min and held for 10 min. Then, it was successively heated to 100 °C at the same heating rate and held for 10 min, heated to 150 °C and held for 10 min, heated to 180 °C and held for 10 min, heated to 200 °C and held for 10 min, heated to 250 °C and held for 10 min, heated to 450 °C and held for 1 h. After cooling to room temperature, a polyimide film with a thickness of 10 μm was formed.

[0081] Example 2

[0082] In this example, a polyimide film is provided, and the preparation method includes the following steps:

[0083] (1) Preparation of polyamic acid slurry: Under nitrogen protection, 5.52 g (10 mmol) of diamine monomer M1 was added to a three-necked flask equipped with mechanical stirring, and then 40.75 g of anhydrous dimethylacetamide (DMAc) was added. After stirring until diamine monomer M1 was completely dissolved, HPMDA (2.242 g, 10 mmol) was added. Stirring was carried out at 0 °C for 24 h to carry out a polymerization reaction. After filtration and defoaming, a viscous and homogeneous polyamic acid slurry was obtained, with a viscosity of 8753 cp and a solid content of 16%.

[0084] The synthesis route is as follows:

[0085]

[0086] (2) Preparation of polyimide film: The polyamic acid slurry was blade-coated onto a glass plate. Under a nitrogen atmosphere, it was heated to 60 °C at a heating rate of 5 °C per minute, held for 10 min, then successively heated to 100 °C at the same heating rate, held for 10 min, heated to 150 °C, held for 10 min, heated to 180 °C, held for 10 min, heated to 200 °C, held for 10 min, heated to 250 °C, held for 10 min, heated to 450 °C, held for 1 h, and after cooling to room temperature, a polyimide film with a thickness of 10 μm was formed.

[0087] Example 3

[0088] In this example, a polyimide film is provided, and the preparation method includes the following steps:

[0089] (1) Preparation of polyamic acid slurry: Under nitrogen protection, 5.52 g (10 mmol) of diamine monomer M1 was added to a three-necked flask equipped with mechanical stirring, and then 41.39 g of anhydrous dimethylacetamide (DMAc) was added; after stirring until diamine monomer M1 was completely dissolved, BTA (2.482 g, 10 mmol) was added, and stirring was carried out at 0 °C for 24 h to carry out a polymerization reaction. After filtration and defoaming, a viscous and uniform polyamic acid slurry with a viscosity of 5233 cp and a solid content of 16.1% was obtained;

[0090] The synthesis route is as follows:

[0091]

[0092] (2) Preparation of polyimide film: The polyamic acid slurry was blade-coated onto a glass plate. Under a nitrogen atmosphere, it was heated to 60 °C at a heating rate of 5 °C / minute, held for 10 min, then successively heated to 100 °C at the same heating rate, held for 10 min, heated to 150 °C, held for 10 min, heated to 180 °C, held for 10 min, heated to 200 °C, held for 10 min, heated to 250 °C, held for 10 min, heated to 450 °C, held for 1 h, and after cooling to room temperature, a polyimide film with a thickness of 10 μm was formed.

[0093] Example 4

[0094] In this example, a polyimide film is provided, and the preparation method includes the following steps:

[0095] (1) Preparation of polyamic acid slurry: Under nitrogen protection, 7.046 g (10 mmol) of diamine monomer M2 was added to a three-necked flask equipped with mechanical stirring, and then 48.762 g of anhydrous dimethylacetamide (DMAc) was added. After stirring until the diamine monomer M2 was completely dissolved, 2.242 g (10 mmol) of HPMDA was added, and the mixture was stirred at 0 °C for 24 h to undergo a polymerization reaction. After filtration and defoaming, a viscous and homogeneous polyamic acid slurry was obtained, with a viscosity of 5561 cp and a solid content of 16.1%.

[0096] The synthesis route is as follows:

[0097]

[0098] (2) Preparation of polyimide film: The polyamic acid slurry was scrape-coated onto a glass plate. Under a nitrogen atmosphere, it was heated to 60 °C at a heating rate of 5 °C / min and held for 10 min. Then, it was successively heated to 100 °C at the same heating rate and held for 10 min, heated to 150 °C and held for 10 min, heated to 180 °C and held for 10 min, heated to 200 °C and held for 10 min, heated to 250 °C and held for 10 min, heated to 400 °C and held for 1 h. After cooling to room temperature, a polyimide film with a thickness of 10 μm was formed.

[0099] Example 5

[0100] In this example, a polyimide film is provided, and the preparation method includes the following steps:

[0101] (1) Preparation of polyamic acid slurry: Under nitrogen protection, 7.046 g (10 mmol) of diamine monomer M2 was added to a three-necked flask equipped with mechanical stirring, and then 49.286 g of anhydrous dimethylacetamide (DMAc) was added. After stirring until the diamine monomer M2 was completely dissolved, 2.482 g (10 mmol) of BTA was added, and the mixture was stirred at 0 °C for 24 h to undergo a polymerization reaction. After filtration and defoaming, a viscous and homogeneous polyamic acid slurry was obtained, with a viscosity of 4956 cp and a solid content of 16.2%.

[0102] The synthesis route is as follows:

[0103]

[0104] (2) Preparation of polyimide film: The polyamic acid slurry was blade-coated onto a glass plate. Under a nitrogen atmosphere, it was heated to 60 °C at a heating rate of 5 °C per minute, held for 10 min, then successively heated to 100 °C at the same heating rate, held for 10 min, heated to 150 °C, held for 10 min, heated to 180 °C, held for 10 min, heated to 200 °C, held for 10 min, heated to 450 °C, held for 1 h, and after cooling to room temperature, a polyimide film with a thickness of 10 μm was formed.

[0105] Example 6

[0106] In this example, a polyimide film is provided, and the preparation method includes the following steps:

[0107] (1) Preparation of polyamic acid slurry: Under nitrogen protection, 7.046 g (10 mmol) of diamine monomer M2-iso was added to a three-necked flask equipped with mechanical stirring, and then 49.286 g of anhydrous dimethylacetamide (DMAc) was added. After stirring until the diamine monomer M2-iso was completely dissolved, BTA (2.482 g, 10 mmol) was added, and stirring was carried out at 0 °C for 24 h to carry out a polymerization reaction. After filtration and defoaming, a viscous and homogeneous polyamic acid slurry was obtained, with a viscosity of 5231 cp and a solid content of 16.2%.

[0108] The synthesis route is as follows:

[0109]

[0110] (2) Preparation of polyimide film: The polyamic acid slurry was blade-coated onto a glass plate. Under a nitrogen atmosphere, it was heated to 60 °C at a heating rate of 5 °C per minute, held for 10 min, then successively heated to 100 °C at the same heating rate, held for 10 min, heated to 150 °C, held for 10 min, heated to 180 °C, held for 10 min, heated to 200 °C, held for 10 min, heated to 450 °C, held for 1 h, and after cooling to room temperature, a polyimide film with a thickness of 10 μm was formed.

[0111] Example 7

[0112] In this example, a polyimide film is provided, and the preparation method includes the following steps:

[0113] (1) Preparation of polyamic acid slurry: Under nitrogen protection, 49.268 g of anhydrous dimethylacetamide (DMAc) was added to a three-necked flask equipped with mechanical stirring after adding diamine monomer M2-mix (7.046 g, 10 mmol); after stirring until the diamine monomer M2-mix was completely dissolved, BTA (2.482 g, 10 mmol) was added, and the mixture was stirred at 0 °C for 24 h to undergo a polymerization reaction. After filtration and defoaming, a viscous and homogeneous polyamic acid slurry was obtained, with a viscosity of 4899 cp and a solid content of 16.2%;

[0114] The synthesis route is as follows:

[0115]

[0116] (2) Preparation of polyimide film: The polyamic acid slurry was blade-coated onto a glass plate. Under a nitrogen atmosphere, it was heated to 60 °C at a heating rate of 5 °C / min and held for 10 min, then successively heated to 100 °C at the same heating rate, held for 10 min, heated to 150 °C, held for 10 min, heated to 180 °C, held for 10 min, heated to 200 °C, held for 10 min, heated to 450 °C, held for 1 h, and cooled to room temperature to form a polyimide film with a thickness of 10 μm.

[0117] Comparative Example 1

[0118] In this comparative example, a polyimide film was provided, and the preparation method included the following steps:

[0119] (1) Preparation of polyamic acid slurry: Under nitrogen protection, 40.04 g of anhydrous dimethylacetamide (DMAc) was added to a three-necked flask equipped with mechanical stirring after adding diamine monomer TFDB (3.202 g, 10 mmol); after stirring until the diamine monomer TFDB was completely dissolved, 6FDA (4.424 g, 10 mmol) was added, and the mixture was stirred at 0 °C for 24 h to undergo a polymerization reaction. After filtration and defoaming, a viscous and homogeneous polyamic acid slurry was obtained, with a viscosity of 8869 cp and a solid content of 16%;

[0120] (2) Preparation of polyimide film: The polyamic acid slurry was blade-coated onto a glass plate. Under a nitrogen atmosphere, it was heated to 60 °C at a heating rate of 5 °C / min and held for 10 min, then successively heated to 100 °C at the same heating rate, held for 10 min, heated to 150 °C, held for 10 min, heated to 180 °C, held for 10 min, heated to 200 °C, held for 10 min, heated to 450 °C, held for 1 h, and cooled to room temperature to form a polyimide film with a thickness of 10 μm.

[0121] Comparative Example 2

[0122] In this comparative example, a polyimide film is provided, and the preparation method includes the following steps:

[0123] (1) Preparation of polyamic acid slurry: Under nitrogen protection, 3.202 g (10 mmol) of diamine monomer TFDB was added to a three-necked flask equipped with mechanical stirring, and then 28.25 g of anhydrous dimethylacetamide (DMAc) was added; after stirring until the diamine monomer TFDB was completely dissolved, PMDA (2.18 g, 10 mmol) was added, and the mixture was stirred at 0 °C for 24 h to carry out a polymerization reaction. After filtration and defoaming, a viscous and homogeneous polyamic acid slurry was obtained, with a viscosity of 8869 cp and a solid content of 16%.

[0124] (2) Preparation of polyimide film: The polyamic acid slurry was blade-coated onto a glass plate. Under a nitrogen atmosphere, the temperature was raised to 60 °C at a heating rate of 5 °C / min and held for 10 min, then successively raised to 100 °C at the same heating rate and held for 10 min, raised to 150 °C and held for 10 min, raised to 180 °C and held for 10 min, raised to 200 °C and held for 10 min, raised to 450 °C and held for 1 h. After cooling to room temperature, a polyimide film with a thickness of 10 μm was formed.

[0125] The polyimide films provided in the examples and comparative examples were subjected to performance tests, and the test methods were as follows:

[0126] (1) Tensile strength and elongation at break: Tested using a universal tensile machine;

[0127] (2) Glass transition temperature (T g ): Tested using a dynamic thermomechanical analyzer (DMA);

[0128] (3) Transmittance, yellowness, and haze: Tested using a spectrophotometer; haze was tested using a haze meter;

[0129] (4) Coefficient of thermal expansion (CTE): Tested using a static thermomechanical analyzer (TMA), and the expansion coefficient at 100 - 200 °C was taken.

[0130] The performance test results are shown in Table 1.

[0131] Table 1

[0132]

[0133] As can be seen from Table 1, the polyimide films prepared using the bisbenzimidazole diamine provided by the present invention all have excellent optical properties (TT in the full wavelength range: 83.5% - 88.3%, yellowness index YI: 3.1 - 5.8), and relatively high thermodynamic properties (T g: 441 - 468 °C), and a relatively low coefficient of thermal expansion (19 - 25 ppm / k).

[0134] Compared with the examples, the thermodynamic properties of the polyimide film provided in Comparative Example 1 decreased significantly, and the optical properties of the polyimide film provided in Comparative Example 2 decreased significantly.

[0135] The applicant declares that the present invention uses the above examples to illustrate the bisbenzimidazole diamine of the present invention and its preparation method, the polyimide film and its preparation method and application, but the present invention is not limited to the above examples, that is, it does not mean that the present invention must rely on the above examples to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A bisbenzimidazole diamine, characterized in that, The dibenzimidazole diamine has the structure as described in the following formula (I) and / or formula (II): Wherein, each R1 is independently any one of -H, substituted or unsubstituted C1-C10 linear or branched alkyl, substituted or unsubstituted C6-C20 aryl, and substituted or unsubstituted C3-C20 heteroaryl; Each R2 is independently any one of substituted or unsubstituted -H, C6-C20 aryl, and substituted or unsubstituted C3-C20 heteroaryl; The substituents of the substitution are any one of halogen, C1-C10 linear or branched alkyl, and substituted or unsubstituted C6-C20 aryl.

2. The bisbenzimidazole diamine according to claim 1, wherein Each of the said R1 is independently any one of -H, methyl, ethyl, trifluoromethyl, and phenyl; Preferably, the said R2 is -H or phenyl.

3. The bisbenzimidazole diamine according to claim 1 or 2, characterized in that, The dibenzimidazole diamine is selected from any one or a combination of at least two of the following compounds; 4. A method for preparing a bisbenzimidazole diamine as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: Perform a coupling reaction between phenyltetramine and R2-X, and then subject the resulting product to a condensation reaction with and then carry out a hydrogenation catalytic reduction reaction to obtain the said bisbenzimidazole diamine; Wherein, the values of R1 and R2 are the same as those in claim 1, and X is halogen.

5. The preparation method according to claim 4, wherein The coupling reaction is carried out in the presence of a palladium catalyst and an inorganic base; Preferably, the inorganic base includes cesium carbonate; Preferably, the solvent used in the coupling reaction includes benzene derivatives, preferably any one or a combination of at least two of toluene, xylene, and mesitylene; Preferably, the temperature of the coupling reaction is 80-140 °C, and the time of the coupling reaction is 5-24 h.

6. The preparation method according to claim 4 or 5, characterized in that The solvent used in the condensation reaction includes polar organic solvents; Preferably, the solvent used in the condensation reaction includes any one or a combination of at least two of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and N,N-dimethylacetamide; Preferably, the temperature of the condensation reaction is 120-200 °C, preferably 140-180 °C; Preferably, the time of the condensation reaction is 3-24 h.

7. The preparation method according to any one of claims 4-6, characterized in that, The catalyst used in the hydrogenation catalytic reduction reaction includes palladium on carbon; Preferably, the solvent used in the hydrogenation catalytic reduction reaction includes alcohol solvents; Preferably, the alcohol solvents include any one or a combination of at least two of methanol, ethanol, and isopropanol; Preferably, the temperature of the hydrogenation catalytic reduction reaction is 20-70 °C, and the time of the hydrogenation catalytic reduction reaction is 5-24 h.

8. A polyimide film, characterized in that, The raw materials for preparing the polyimide film include a diamine monomer and a dianhydride monomer; the diamine monomer includes the dibenzimidazole diamine as described in any one of claims 1-3 or the dibenzimidazole diamine prepared by the preparation method according to any one of claims 4-7; Preferably, the dianhydride monomer includes any one or a combination of at least two of 4,4'-oxybisphthalic anhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, hydrogenated pyromellitic dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic 2,3:5,6-dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, cyclobutane tetracarboxylic anhydride, 1,2,3,4-butane tetracarboxylic dianhydride, 9,9-bis(trifluoromethyl)-2,3,6,7-xanthene tetracarboxylic dianhydride. Preferably, it is any one or a combination of at least two of hydrogenated pyromellitic dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic 2,3:5,6-dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, cyclobutane tetracarboxylic anhydride, 1,2,3,4-butane tetracarboxylic dianhydride; Preferably, the molar ratio of the diamine monomer to the dianhydride monomer is 1:(0.9 - 1.2), preferably 1:(0.92 - 1.1), more preferably 1:(0.95 - 1.05), and most preferably 1:

1.

9. A method for preparing a polyimide film as described in claim 8, characterized in that, The preparation method includes the following steps: Mix the diamine monomer, dianhydride monomer, and organic solvent, and carry out a polymerization reaction to obtain a polyamic acid slurry. The polyamic acid slurry is coated into a wet film, and then undergoes thermal imidization to obtain the polyimide film; Preferably, the organic solvent is an aprotic organic solvent, including any one or a combination of at least two of N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, propylene glycol monomethyl ether, cyclopentanone, cyclohexanone, ethyl acetate, toluene, methyl ethyl ketone. Preferably, it is N,N-dimethylformamide and / or N,N-dimethylacetamide; Preferably, the temperature of the polymerization reaction is -10°C to 50°C, preferably -5°C to 30°C, more preferably -5°C to 10°C; Preferably, the time of the polymerization reaction is 3 - 48 h, preferably 5 - 36 h, more preferably 10 - 24 h; Preferably, the polymerization reaction is carried out in an inert gas atmosphere; Preferably, the thermal imidization is carried out by gradient heating, and there is a heat preservation section between the gradient heating sections; Preferably, the temperature of the thermal imidization is 60°C - 450°C, the total heat preservation time is 2 - 10 hours, and the heating rate is 1 - 10°C / minute; Preferably, the process of thermal imidization sequentially includes at least five of the following steps: heating at a rate of 1-10 °C / min to 60-80 °C and holding for 10 min-1 h; heating at a rate of 1-10 °C / min to 90-120 °C and holding for 10 min-1 h; heating at a rate of 1-10 °C / min to 140-160 °C and holding for 10 min-1 h; heating at a rate of 1-10 °C / min to 170-190 °C and holding for 10 min-1 h; heating at a rate of 1-10 °C / min to 190-210 °C and holding for 10 min-1 h; heating at a rate of 1-10 °C / min to 240-260 °C and holding for 10 min-1 h; heating at a rate of 1-10 °C / min to 300 °C and holding for 10 min-1 h; heating at a rate of 1-10 °C / min to 450 °C and holding for 30 min-1 h; Preferably, the thermal imidization is carried out in an inert gas atmosphere; Preferably, the polyamic acid slurry is defoamed under vacuum and then coated into a wet film; Preferably, the thickness of the polyimide film is 4 μm-15 μm, preferably 5-10 μm.

10. An application of the polyimide film according to claim 8 in a flexible substrate.

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