A high-fluorine-containing biphenyl diamine, a colorless polyimide optical film, and preparation methods and applications thereof

Abstract

The present invention discloses a high-fluorine-containing biphenyl diamine, a colorless polyimide optical film, and a preparation method and application thereof. Specifically, based on Ullmann coupling, nitration, and reduction reactions, a series of high-fluorine-containing biphenyl diamines can be efficiently synthesized; then, the high-fluorine-containing biphenyl diamine is homopolymerized (or copolymerized) with commercial dianhydrides and diamines to prepare high-performance polyimide materials. The synthesis of the high-fluorine-containing biphenyl diamine of the present invention has the advantages of simple route, low cost, mild conditions, and efficient reaction; the high-performance polyimide prepared therefrom exhibits excellent optical transparency, high colorlessness, high heat resistance (high glass transition temperature, high decomposition temperature), high mechanical properties, excellent low dielectric properties, etc., and can be actually applied to flexible displays, wearable devices, flexible batteries, and 5G high-frequency communications.

Description

Technical Field

[0001] The present invention belongs to the field of optical films, and in particular relates to a high-fluorine-containing biphenyl diamine, a colorless polyimide optical film, and a preparation method and application thereof. Background Art

[0002] For future flexible devices, lightweight, wearable, high-frequency signal capability, and safety are key functional requirements, particularly in flexible displays, flexible batteries, and 5G+ communications. Key to the realization and next-generation upgrades of these functional devices lies in the development of flexible materials, including cover plates and substrates for flexible organic light-emitting diodes (OLEDs), substrates for thin-film solar cells (TFSCs), and substrates for high-frequency flexible copper-clad laminates (FCCLs). Currently, commercially available transparent cover plates and substrates for OLEDs and TFSCs are made of ultra-thin glass (UTG). Its brittleness, high density, and complex processing significantly limit its development for larger, more flexible designs. For the next generation of flexible display upgrades, including fully transparent displays, under-display cameras, and facial recognition, colorless, transparent polyimide (CPI) film is the optimal solution. Its performance requirements include: 1) high transparency; 2) high colorlessness and low yellowness; 3) high heat resistance, including a high glass transition temperature and high thermal decomposition temperature; 4) high dimensional thermal stability; 5) high mechanical properties; and 6) ease of processing. Based on the fluorine-containing structure design, due to its extremely low molar electronic polarization rate, the CPI film can be further endowed with excellent high transparency and low dielectric properties, greatly improving the dilemma of the yellow PI film used in traditional FCCL substrates, especially effectively reducing its dielectric loss (D f Based on this, the difficulty in designing and realizing this type of CPI film material lies in simultaneously meeting multiple properties such as high transparency, high heat resistance, low expansion, high mechanical properties, and low dielectric properties. Once realized, it will have great application potential in the above-mentioned flexible electronics field.

[0003] At present, the vast majority of published or public CPI films can only meet one, two, or even three of the following requirements: high transparency, high heat resistance, low expansion, high mechanical properties, and low dielectric constant. However, none of them can achieve a comprehensive performance balance, which greatly limits their long-term service applications in high-performance, high-end flexible electronic products. For example, the PI films disclosed in CN 112500568B, Polymer 2020,209,122963, etc. effectively meet the requirements of high heat resistance (Tg>400℃, T d5％>560℃) and low expansion (CTE <10ppm / K) performance requirements, but are limited by their intrinsic deep yellow color (not meeting the high transparency requirements), and cannot effectively meet the requirements of the above-mentioned new flexible devices. The films disclosed in CN 115557848A, CN 110606949A, Polymer, 2023, 273, 125883, etc. effectively meet the high transparency (T 550 >86%, YI<5) and high heat resistance (Tg>350℃, T d5％ >520℃) performance requirements, but there is an obvious intrinsic high expansion (CTE>35ppm / K), which greatly reduces the service life and reliability of the device. Polym.Chem., 2021, 12, 5364, Polymer, 2020, 206, 122889, etc. have excellently proposed the high transparency (T 550 >86%, YI<10), high heat resistance (Tg>330℃, T d5％ >450℃), low expansion (CTE<15ppm / K) meet the three requirements at the same time. Even though its transparency and colorlessness are not as good as the former method, its mechanical properties are still poor (σ m <200MPa, E t <4 GPa). In general, the structure and preparation of CPI optical films that meet the above-mentioned multiple performance requirements remain a huge and important challenge, and the effective implementation of its solution is of great significance. Summary of the Invention

[0004] Aiming at the key optical films in the background technology, especially the inability to simultaneously meet multiple requirements such as high transparency, high heat resistance, low expansion, high mechanical properties, and low dielectric constant, the present invention provides a high-fluorine-containing biphenyl diamine, a colorless polyimide optical film, and a preparation method and application thereof.

[0005] Specifically, a series of highly fluorinated biphenyl diamines (IV-1 to IV-6) can be efficiently synthesized through Ullmann coupling, nitration, and reduction reactions. These highly fluorinated biphenyl diamines are then homopolymerized (or copolymerized) with commercially available dianhydrides (V-1 to V-10) and diamines (VI-1 to VI-10). Through processes such as casting and heat treatment, high-performance CPI optical film materials are prepared. These optical film materials simultaneously meet multiple performance requirements, including high transparency, high heat resistance, low expansion, high mechanical properties, and low dielectric constant, and are suitable for key applications in flexible displays, wearable devices, thin-film batteries, and high-frequency signal substrates.

[0006] The first aspect of the present invention is to provide a method for preparing highly fluorinated biphenyl diamines, including a synthetic route for highly fluorinated biphenyl diamines: first, halogenated fluorinated monobenzenes (structural formulas I-1 to I-6) are subjected to an Ullmann coupling reaction under certain solvent, catalytic, temperature, and atmospheric conditions to synthesize fluorinated aromatic biphenyls (structural formulas II-1 to II-6). Furthermore, the aforementioned fluorinated aromatic biphenyls are subjected to a nitration reaction under certain acidic solvent and nitrating agent conditions to synthesize fluorinated biphenyl dinitro groups (structural formulas III-1 to III-6). Subsequently, the fluorinated biphenyl dinitro groups (structural formulas III-1 to III-6) are converted into target monomers, i.e., fluorinated biphenyl diamines (structural formulas IV-1 to IV-6), under a classical reduction system.

[0007] A method for preparing high-fluorine-containing biphenyl diamine specifically comprises the following steps:

[0008] (1) Under the protection of an inert atmosphere, halogenated fluorinated monobenzenes undergo Ullmann coupling reaction in a non-protonic polar solvent with the help of a metal catalyst to obtain fluorinated aromatic biphenyls.

[0009] The halogenated fluorine-containing monobenzene is limited to one or more of the following structural formulas 1-1 to 1-6:

[0010]

[0011] Wherein, X is a halogen, limited to bromine or iodine;

[0012] The fluorinated aromatic biphenyl is limited to one of the following structural formulas Ⅱ-1 to Ⅱ-6:

[0013]

[0014] (2) The fluorinated aromatic biphenyl in step (1) undergoes a nitration reaction under the conditions of a nitrating agent to obtain a fluorinated dinitro biphenyl.

[0015] The fluorinated biphenyl dinitro group is limited to one of the following structural formulas Ⅲ-1 to Ⅲ-6:

[0016]

[0017] (3) Under the protection of an inert atmosphere, the fluorinated biphenyl dinitro in step (2) is subjected to a reduction reaction to obtain the target high-fluorinated biphenyl diamine.

[0018] The high fluorine-containing biphenyl diamine is limited to one of the following structural formulas IV-1 to IV-6,

[0019]

[0020] Preferably, the inert atmosphere in step (1) is one of nitrogen and argon.

[0021] Preferably, the aprotic polar solvent in step (1) includes one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), and 1,3-dimethyl-2-imidazolidinone (DMI).

[0022] More preferably, the aprotic polar solvent in step (1) is one or more of DMF and NMP.

[0023] Preferably, the metal catalyst in step (1) includes one or more of Cu, CuI, CuCl, CuBr, Cu2O, and Cu(OTf)2; more preferably, the metal catalyst in step (1) is one or more of Cu, CuI, and CuCl.

[0024] Preferably, the temperature of the Ullmann coupling reaction in step (1) is 50-250°C; more preferably, the temperature of the Ullmann coupling reaction in step (1) is 120-180°C.

[0025] Preferably, the nitrating agent in step (2) is one or more of fuming nitric acid, concentrated nitric acid, nitrogen pentoxide, and sodium nitrate.

[0026] Preferably, the solvent for the nitration reaction in step (2) is one or more of concentrated sulfuric acid, glacial acetic acid, oxalic acid, acetic anhydride, P2O5, methanol, ethanol, dichloromethane, chloroform, and deionized water.

[0027] Preferably, the temperature of the nitration reaction in step (2) is -80 to 150°C; more preferably, the temperature of the nitration reaction in step (2) is -10 to 80°C.

[0028] Preferably, the inert atmosphere in step (3) is one of nitrogen and argon.

[0029] Preferably, the solvent for the reduction reaction in step (3) is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), ethanol, isopropanol, tetrahydrofuran, ethyl acetate, dioxane, toluene, benzene and water.

[0030] Preferably, the temperature of the reduction reaction in step (3) is 50-150°C.

[0031] Preferably, the reduction reaction in step (3) is carried out using a Pd / C and N2H4·H2O system or a SnCl2 and HCl system.

[0032] More preferably, in the Pd / C and N2H4·H2O system, the Pd / C feed amount is 1-15 wt% of the fluorinated biphenyl dinitro group, and the N2H4·H2O feed amount is 2-8 times the amount of the fluorinated biphenyl dinitro group.

[0033] More preferably, the amount of HCl solution in the SnCl2 and HCl system is 1 to 100 wt% of the amount of SnCl2 used, and the amount of SnCl2 added is 2 to 16 times the amount of the fluorinated biphenyl dinitro substance.

[0034] The second aspect of the present invention is to provide a colorless polyimide optical film, wherein the colorless polyimide optical film is composed of polyimide, and the general structural formula of the polyimide is as follows:

[0035]

[0036] Wherein, X Part is the residue of highly fluorinated biphenyl diamine; Ar1 ​​is independently the residue of commercial dianhydride; Ar2 is the residue of commercial diamine, n and m are the repetition numbers of the corresponding structural units, and the ratio of n:m ranges from 1:0 to 5:95.

[0037] The high fluorine-containing biphenyl diamine is limited to one or more of the following structural formulas IV-1 to IV-6:

[0038]

[0039] The commercial dianhydride is defined as one or more of the following structural formulas V-1 to V-10:

[0040]

[0041] Wherein, R1 and R2 are independently selected from one or two of F and CF3; p and q are the number of R1 and R2 groups, p is 1 to 2, q is 1 to 4; R3 is independently selected from

[0042] The commercial diamine is one or more of the following structural formulas VI-1 to VI-10:

[0043]

[0044] Wherein R1 and R2 are independently selected from one or two of F and CF3; p and q are the number of R1 and R2 groups, p is 1 to 2, q is 1 to 4; R3 is independently selected from

[0045] Preferably, the glass transition temperature Tg of the colorless polyimide optical film is 371-453°C, and the thermal weight loss temperature T corresponding to 5 wt% isd5％ The value is 568~592℃, and the coefficient of thermal expansion CTE is 1.3~8.8ppm / K.

[0046] Preferably, the optical transmittance T of the colorless polyimide optical film at 550 nm is 550 The value is 88.1%~89.7%, and the yellow index YI value is 2.2~4.9.

[0047] Preferably, the colorless polyimide optical film has a tensile strength σm value of 268 to 367 MPa and a tensile modulus Et value of 5.7 to 7.2 GPa.

[0048] Preferably, the dielectric constant D of the colorless polyimide optical film at a high frequency of 10 GHz is k Value 2.70~2.98, dielectric loss D f Values: 0.0013~0.0042.

[0049] The third aspect of the present invention is to provide a method for preparing a colorless polyimide optical film according to any one of the second aspects of the present invention. First, a halogenated fluorine-containing monobenzene (structural formulas I-1 to I-6) is subjected to a key Ullmann coupling reaction to produce a fluorine-containing aromatic biphenyl (structural formulas II-1 to II-6), which is then nitrated to produce a fluorine-containing biphenyl dinitro (structural formulas III-1 to III-6), which is then reduced to a high-fluorine-containing biphenyl diamine (structural formulas IV-1 to IV-6). Next, the fluorine-containing diamine is homopolymerized or copolymerized with commercial (or known) dianhydrides (structural formulas V-1 to V-10) or diamines (structural formulas VI-1 to VI-10), and then subjected to processes such as casting and heat treatment to prepare a high-performance CPI optical film material.

[0050] A method for preparing a colorless polyimide optical film comprises the following steps:

[0051] (a) homopolymerizing / copolymerizing the high-fluorinated biphenyl diamine (structural formulas IV-1 to IV-6) prepared by the method for preparing a high-fluorinated biphenyl diamine according to any one of the first aspects of the present invention with commercial dianhydrides (structural formulas V-1 to V-10) and commercial diamines (structural formulas VI-1 to VI-10) to obtain a polyimide (or polyamic acid precursor) solution;

[0052] (b) The polyimide (or polyamic acid precursor) described in step (a) is subjected to a film-forming process to obtain a colorless polyimide optical film.

[0053] Preferably, the high-fluorine-containing biphenyl diamine in step (a) is one or more of the structural formulas IV-1 to IV-6.

[0054] Preferably, the commercial dianhydride in step (a) is one or more of the structural formulas V-1 to V-10.

[0055] Preferably, the commercial diamine in step (a) is one or more of the structural formulas VI-1 to VI-10.

[0056] Preferably, in step (a), the ratio of the sum of the amounts of the high-fluorine-containing biphenyl diamine and the commercial diamine to the amount of the commercial dianhydride is 1:(0.9-1.1).

[0057] Preferably, the homopolymerization / copolymerization reaction in step (a) is carried out in a one-step process or a two-step process.

[0058] More preferably, the one-step method is to carry out high-fluorine-containing biphenyl diamine, commercial dianhydride, and commercial diamine condensation at high temperature in a high-boiling point solvent under inert atmosphere protection, with or without adding a catalyst, to obtain a uniform and viscous polyimide solution, wherein the catalyst is one or two of benzoic acid and isoquinoline, the high-boiling point solvent is one or more of m-cresol, p-chlorophenol, and m-chlorophenol, the reaction temperature is 150-200° C., the reaction time is 5-36 h, and the inert atmosphere is one of nitrogen atmosphere and argon.

[0059] More preferably, the two-step method is to polycondense high fluorine-containing benzyl diamine with commercial dianhydride and commercial diamine at low temperature in an aprotic polar solvent under the protection of an inert atmosphere to obtain a uniform and viscous polyamic acid solution, wherein the aprotic polar solvent is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and N-methylpyrrolidone (NMP). The reaction temperature is -10 to 50°C, the reaction time is preferably 10 to 120 hours, and the inert atmosphere is one of nitrogen and argon.

[0060] Preferably, the film-making process in step (b) includes casting and heat treatment.

[0061] More preferably, the casting process includes one or more of direct casting film forming, precision slit coating film forming, casting and stretching continuous film forming.

[0062] More preferably, the heat treatment process includes a desolvation process and an imidization process, the heating method is continuous heating or gradient heating, the temperature range is 20 to 450° C., and the high temperature atmosphere is one of nitrogen, argon, and vacuum.

[0063] More preferably, the imidization comprises a thermal imidization or a chemical imidization method.

[0064] A fourth aspect of the present invention is to provide a flexible display, wherein the flexible display comprises the colorless polyimide optical film according to the second aspect of the present invention.

[0065] A fifth aspect of the present invention is to provide a wearable device, wherein the wearable device includes the colorless polyimide optical film described in the second aspect of the present invention.

[0066] A sixth aspect of the present invention is to provide a flexible battery, wherein the flexible battery comprises the colorless polyimide optical film according to the second aspect of the present invention.

[0067] The seventh aspect of the present invention is to provide a 5G high-frequency communication device, which includes a colorless polyimide optical film described in the second aspect of the present invention.

[0068] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0069] The CPI film prepared by the method for preparing a colorless polyimide optical film provided by the present invention satisfies the requirements of high transparency (T 550 ≥88.1%, the highest is 89.7%, YI≤4.9), high heat resistance (Tg≥371℃, T d5％ ≥568℃), low expansion (CTE≤8.8ppm / K, minimum 1.3ppm / K), high mechanical properties (σ m ≥268MPa, E t ≥5.7GPa), low dielectric (D k As low as 2.70, D f The overall solution surpasses existing patent and literature performance requirements, demonstrating that this type of CPI film has great application potential in key areas such as flexible displays, wearable devices, thin-film batteries, and high-frequency signal substrates.

[0070] The glass transition temperature Tg of the colorless polyimide optical film prepared by the present invention is 371-453°C, and the thermal weight loss temperature Tg corresponding to 5 wt% is 371-453°C. d5％ The value is 568~592℃, the thermal expansion coefficient CTE is 1.3~8.8ppm / K; at the same time, the optical transmittance T 550 The value is 88.1% to 89.7%, and the yellow index YI value is 2.2 to 4.9; and in the mechanical properties, the tensile strength σm value is 268 to 367 MPa, and the tensile modulus Et value is 5.7 to 7.2 GPa; In addition, the dielectric properties D at a high frequency of 10 GHz k Value 2.70~2.98, D f Values: 0.0013~0.0042.

[0071] The preparation method of high-fluorine-containing biphenyl diamine provided by the present invention has a clear and concise synthesis route, simple post-processing operation, high yield (reaction yield is maintained at 80%-90%), and key steps (such as Ullmann coupling reaction) do not use expensive catalysts containing elements such as platinum, palladium, and rhodium. The reaction conditions are mild and the reaction can be completed without high temperature and high pressure conditions, making it suitable for large-scale synthesis.

[0072] The CPI film prepared by the present invention is prepared using a high-fluorine-containing diamine monomer. The introduction of a large number of fluorine-containing groups has the following advantages: on the one hand, it can inhibit the intra-chain or inter-chain CTC charge transfer effect, effectively improve the transparency of the optical film, and significantly reduce the yellowness of the film; on the other hand, a large number of low-polarity fluorine atoms can significantly reduce the molecular polarity and the response ability of the molecular chain segments to the electric field, thereby reducing the dielectric constant and dielectric loss of the polymer, so that the film has excellent dielectric properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 The present invention is a flow chart of a method for preparing a high-fluorine-containing biphenyl diamine and a colorless polyimide optical film.

[0074] Figure 2 The UV-Vis (optical transparency) curves of the CPI films prepared in Example 1 and Example 4 are shown.

[0075] Figure 3 DMA (glass transition temperature) curves of the CPI films prepared in Examples 2 and 3.

[0076] Figure 4 The TMA (thermal expansion) curves of the CPI films prepared in Examples 1 and 3 are shown.

[0077] Figure 5 Graph showing the high-frequency dielectric properties of the CPI films prepared in Examples 1-6. DETAILED DESCRIPTION

[0078] The specific implementation of the present invention is further described below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are any processes not specifically described below, they can be implemented or understood by those skilled in the art with reference to the prior art. If the manufacturer of the reagents or instruments used is not indicated, they are deemed to be conventional products that can be purchased commercially.

[0079] A method for preparing a high-fluorine-containing biphenyl diamine and a colorless polyimide optical film Figure 1 shown.

[0080] Example 1

[0081] 1. Synthesis of high fluorinated biphenyl diamine

[0082] Under nitrogen, 2-bromo-4-fluorobenzotrifluoride (19.44 g, 80 mmol, Formula I-1), Cu powder (0.50 g, 7.87 mmol), and N,N-dimethylformamide (DMF) (80 mL) were placed in a 200 mL Schlenk flask, heated to 150°C, and stirred until the reaction was complete. Subsequently, extraction with ethyl acetate (EA) and column separation afforded the corresponding fluorinated biphenyl, 3,5'-difluoro-6,2'-bis(trifluoromethyl)biphenyl (Structural Formula II-1), as a colorless, transparent liquid. Yield: 83%. NMR results: 1 H NMR (500MHz, DMSO-d6) δ7.97-7.94(m,2H),7.58-7.54(m,2H),7.42-7.40(m,2H).

[0083] The above-mentioned 3,5'-difluoro-6,2'-bis(trifluoromethyl)biphenyl (10.00 g, 30.66 mmol, Formula II-1), concentrated HNO3 (7.72 g, 122.63 mmol), and concentrated sulfuric acid (40 mL) were added to a 100 ml beaker and heated to 70°C with stirring until the reaction was complete. The reaction mixture was then poured into ice water, extracted with dichloromethane (DCM), and recrystallized to obtain the target 3,5'-difluoro-6,2'-bis(trifluoromethyl)-4,4'-dinitrobiphenyl (pale yellow crystals, Structure III-1). Yield: 95%. 1 H NMR (500MHz, DMSO-d6) δ8.66-8.65(m,2H),8.04-8.02(m,2H).

[0084] Under argon protection, 3,5'-difluoro-6,2'-bis(trifluoromethyl)-4,4'-dinitrobiphenyl (10.00 g, 24.03 mmol, Formula III-1), SnCl2·2H2O (54.20 g, 240.35 mmol), and concentrated HCl solution (40 mL) were dissolved in 100 ml of ethyl acetate and then heated to 78°C with stirring until the reaction was complete. Subsequently, the mixture was neutralized with NaOH solution to a weak base (pH = 8), extracted with dichloromethane (DCM), and recrystallized to obtain the target fluorinated diamine, 3,5'-difluoro-6,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (white crystals, Structural Formula IV-1). Yield: 83%. NMR results: 1 H NMR (500 MHz, DMSO-d6) δ 7.16-7.14 (m, 2H), 6.95-6.92 (m, 2H), 5.71 (s, 4H). The structure of the fluorinated diamine is shown below.

[0085]

[0086] 2. Synthesis of CPI and film preparation

[0087] Under nitrogen protection, the above-mentioned 3,5'-difluoro-6,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2.49g, 7mmol, Formula IV-1), 2,2'-bis(trifluoromethyl)diaminobiphenyl (0.96g, 3.0mmol, Formula VI-4), biphenyl dianhydride (2.94g, 10mmol, Formula V-3), and N,N-dimethylacetamide (DMAc) (25mL) were added to a 100mL three-necked flask. After being fully dissolved, the mixture was stirred at room temperature for 24 hours to obtain a viscous polyamic acid solution (intrinsic viscosity of 1.751dL / g). The solution was precision slit coated and imidized at a gradient temperature of 20-150-300℃ under vacuum conditions. The CPI film material was then peeled off to obtain the CPI film material.

[0088]

[0089] Example 2

[0090] Under argon protection, 3,5'-difluoro-6,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (35.6 g, 100 mmol, formula IV-1) and Pyromellitic dianhydride (12.0g, 55mmol, formula V-1), hexafluorodianhydride (20.0g, 45mmol, formula V-5), and N,N-dimethylformamide (DMF) (250mL) were placed in a 500mL three-necked flask. After being fully dissolved, they were mechanically stirred at room temperature for 24 hours to obtain a viscous polyamic acid solution (intrinsic viscosity of 2.287dL / g). The solution was cast into a film, and the temperature was continuously increased from 20°C to 290°C at a heating rate of 20°C / min under argon to complete the imidization. The CPI film material was then peeled off to obtain the CPI film material.

[0091]

[0092] Example 3

[0093] Under argon protection, 3,5'-difluoro-6,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (1.42 g, 4 mmol, formula IV-1), 2,2',2",5'-tetrakis(trifluoromethyl)diamine (3.19 g, 6 mmol, formula VI-10), Pyromellitic dianhydride(0.87g, 4mmol, formula V-1), 1,4-bis(trifluoromethyl)benzene tetracarboxylic dianhydride (2.12g, 6mmol, formula V-2), and dimethyl sulfoxide (DMSO) (25mL) were put into a 100mL three-necked flask. After being fully dissolved, the reaction was stirred at room temperature for 24 hours to obtain a viscous polyamide acid solution. Triethylamine (0.01mol, 1.01g) and acetic anhydride (0.02mol, 2.04g) were slowly added to the solution and stirred for 36 hours to complete the chemical imidization process. Then, a CPI solution of the corresponding structure (solid content 15wt%, intrinsic viscosity 2.434dL / g, structure as follows) was obtained by methanol precipitation, drying, and NMP dissolution. Subsequently, the CPI solution was cast into a film, and the temperature was increased gradually from 50-100-150-250°C under vacuum conditions, and then the CPI film material was obtained by peeling.

[0094]

[0095] Example 4

[0096] 1. Synthesis of high fluorinated biphenyl diamine

[0097] Under argon, 3-bromo-4-fluorobenzotrifluoride (19.44 g, 80 mmol, Formula I-3), CuI (1.52 g, 8.00 mmol), and N,N-dimethylacetamide (DMAc) (80 mL) were placed in a 200 mL Schlenk flask, heated to 130°C, and stirred until the reaction was complete. Subsequently, extraction with dichloromethane (DCM) and column separation afforded the corresponding fluorinated biphenyl, 2,6'-difluoro-5,3'-bis(trifluoromethyl)biphenyl (Structural Formula II-3), as a colorless, transparent liquid. Yield: 81%. Mass spectrometry results: HRMS (ESI) m / z calculated for C 14 H6F8 + [M+H] + :327.0419,found 327.0421.

[0098] 2,6'-difluoro-5,3'-bis(trifluoromethyl)biphenyl (10.00 g, 30.66 mmol, Formula II-3), fuming HNO3 (7.72 g, 122.63 mmol), and glacial acetic acid (40 mL) were added to a 100 ml beaker and then heated to 30°C with stirring until the reaction was complete. The reaction mixture was then poured into ice water and extracted with ethyl acetate (EA), followed by recrystallization, to obtain the target 2,6'-difluoro-5,3'-bis(trifluoromethyl)-3,5'-dinitrobiphenyl (pale yellow crystals, structural formula III-3). Yield: 94%. Mass spectrometry results: HRMS (ESI) m / z calcd for C 14 H4F8N2O4+ [M+H] + :417.0118,found 417.0115.

[0099] Under nitrogen, dinitrofluorobiphenyl (10.00 g, 24.03 mmol, Formula III-3) and Pd / C (1 g) were dispersed and dissolved in 100 ml of tetrahydrofuran (THF). N₂H₄·H₂O (8.01 g, 160 mmol) was then added dropwise. The entire system was stirred and refluxed at 60°C for 8 h. After the reaction was completed, the Pd / C was filtered through diatomaceous earth. The product was extracted with DCM, separated by column chromatography, and recrystallized to obtain the target compound, 2,6'-difluoro-5,3'-bis(trifluoromethyl)-3,5'-diaminobiphenyl (white crystals, Structure IV-3). Yield: 82%. NMR results: 1 H NMR (500 MHz, DMSO-d6) δ 8.18-8.15 (m, 2H), 7.03-7.00 (m, 2H), 4.34 (s, 4H). The structure of the fluorinated diamine is shown below.

[0100]

[0101] 2. Synthesis of CPI and film preparation

[0102] Under nitrogen protection, the above-mentioned 2,6'-difluoro-5,3'-bis(trifluoromethyl)-3,5'-diaminobiphenyl (1.78g, 5mmol, formula IV-3), hexafluorotriphenylenediamine (1.84g, 5mmol, formula VI-10), difluorobiphenyl dianhydride (2.64g, 8mmol, formula V-4), hexafluorobiphenyl dianhydride (0.86g, 2mmol, formula V-4), and N-methylpyrrolidone (NMP) (25mL) were added to a 100mL three-necked flask. After being fully dissolved, the mixture was stirred at room temperature for 24 hours to obtain a viscous polyamic acid solution (intrinsic viscosity of 1.978dL / g). The solution was poured onto a clean glass plate and directly cast into a film. The imidization was completed by heating to 310℃ in a nitrogen environment, and then peeled off to obtain a CPI film material.

[0103]

[0104] Example 5

[0105] 1. Synthesis of fluorinated biphenyl diamine

[0106] Under argon, 1-fluoro-2-iodobenzotrifluoride (19.44 g, 80 mmol, Formula I-2), CuI (0.76 g, 4.00 mmol), Cu (0.25 g, 4.00 mmol), and 1,3-dimethyl-2-imidazolidinone (DMI) (80 mL) were placed in a 200 mL Schlenk flask, heated to 180°C, and stirred until the reaction was complete. Subsequently, extraction with dichloromethane (DCM) and column separation afforded the corresponding fluorinated biphenyl, 2,2'-difluoro-6,6'-bis(trifluoromethyl)biphenyl (Structural Formula II-2), as a colorless, transparent liquid. Yield: 80%. Mass spectrometry results: HRMS (ESI) m / z calculated for C 14 H6F8 + [M+H] + :327.0419,found327.0421.。

[0107] 2,2'-difluoro-6,6'-bis(trifluoromethyl)biphenyl (10.00 g, 30.66 mmol, Formula II-2), fuming HNO3 (7.72 g, 122.63 mmol), and glacial acetic acid (40 mL) were added to a 100 ml beaker and then heated to 55°C with stirring until the reaction was complete. The reaction mixture was then poured into ice water and extracted with ethyl acetate (EA), recrystallized, and the corresponding target 2,2'-difluoro-6,6'-bis(trifluoromethyl)-4,4'-dinitrobiphenyl (light yellow crystals, structural formula III-2) was obtained. Yield: 90%. Mass spectrometry results: HRMS (ESI) m / z calcd for C 14 H4F8N2O4 + [M+H] + :417.0118,found 417.0115.。

[0108] Under nitrogen, the above-mentioned fluorinated dinitrobiphenyl (10.00 g, 24.03 mmol, Formula III-2) and Pd / C (1 g) were dispersed and dissolved in 100 ml of ethanol (EtOH). N2H4·H2O (8.01 g, 160 mmol) was then added dropwise. The entire system was stirred and refluxed at 90°C for 12 hours. After the reaction was completed, the Pd / C was filtered through diatomaceous earth, and the product was extracted with DCM, separated by column chromatography, and recrystallized to obtain the target 2,2'-difluoro-6,6'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (white crystals, structural formula IV-3). Yield: 81%. NMR results: 1 H NMR (500 MHz, DMSO-d6) δ 6.9-6.7 (m, 2H), 6.5-6.3 (m, 2H), 4.80 (s, 4H). The structure of the fluorinated diamine is shown below.

[0109]

[0110] 2. Synthesis of CPI and film preparation

[0111] Under argon, 2,6'-difluoro-5,3'-bis(trifluoromethyl)-3,5'-diaminobiphenyl (2.14 g, 6 mmol, Formula IV-3), 2,2'-difluoro-6,6'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (1.28 g, 4 mmol, Formula VI-4), hexafluorobiphenyl dianhydride (1.29 g, 7 mmol, Formula V-4), difluoroterphenyl dianhydride (1.22 g, 3 mmol, Formula V-8), and m-cresol (25 mL) were placed in a 100 mL three-necked flask. After complete dissolution, the mixture was heated to 180°C and maintained for 15 hours. Toluene was used to remove small molecular weight byproducts to promote polymerization and complete imidization. Subsequently, a CPI solution of the corresponding structure was obtained by methanol precipitation, drying, and dissolution in DMAc (solids content 18 wt%, intrinsic viscosity 3.068 dL / g, PI structure shown below). The solution was poured onto a clean glass plate and directly cast into a film, and the temperature was raised to 250°C in a nitrogen environment to complete the desolvation process, and then the CPI film material was obtained by peeling.

[0112]

[0113] Example 6

[0114] 1. Synthesis of fluorinated biphenyl diamine

[0115] Under nitrogen, 2-bromo-4-fluorotrifluoromethoxybenzene (20.72 g, 80 mmol, Formula I-4), CuCl (0.79 g, 8.00 mmol), and dimethyl sulfoxide (DMSO) (80 mL) were placed in a 200 mL Schlenk flask, heated to 170°C, and stirred until the reaction was complete. Subsequently, extraction with ethyl acetate (EA) and column separation afforded the corresponding fluorinated biphenyl, 3,5'-difluoro-6,2'-bis(trifluoromethoxy)biphenyl (Structural Formula II-4), as dark brown crystals. Yield: 83%. Mass spectrometry results: HRMS (ESI) m / z calculated for C 14 H6F8 O2 + [M+H] + :359.0319,found 359.0327.。

[0116] Fluorinated biphenyl (10.00 g, 27.92 mmol, Formula II-4), HNO3 (7.72 g, 122.63 mmol), and concentrated sulfuric acid (40 mL) were added to a 100 ml beaker and then heated to 50 ° C with stirring until the reaction was completed. Then, the reaction was poured into ice water and extracted with ethyl acetate (EA) and recrystallized to obtain the corresponding target 3,5'-difluoro-6,2'-bis(trifluoromethoxy)-4,4'-dinitrobiphenyl (light yellow crystals, structural formula III-4). Yield: 88%. Mass spectrometry results: HRMS (ESI) m / z calcd for C 14 H4F8N2O6 + [M+H] + :449.0018,found 449.0016.。

[0117] Under argon protection, 3,5'-difluoro-6,2'-bis(trifluoromethoxy)-4,4'-dinitrobiphenyl (10.00 g, 22.31 mmol, Formula III-4), SnCl2·2H2O (54.20 g, 240.35 mmol), and concentrated HCl solution (40 mL) were dissolved in 100 ml of dichloromethane, then stirred and heated to 40°C until the reaction was complete. Subsequently, the mixture was neutralized with NaOH solution to a weak alkaline solution (pH = 7-8), extracted with ethyl acetate (EA), and recrystallized to obtain the target 3,5'-difluoro-6,2'-bis(trifluoromethoxy)-4,4'-diaminobiphenyl (white crystals, structural formula IV-4). Yield: 85%. NMR results: 1 H NMR (500 MHz, DMSO-d6) δ 7.22-7.19 (m, 2H), 7.00-6.98 (m, 2H), 3.76 (s, 4H). The structure of the fluorinated diamine is as follows.

[0118]

[0119] 2. Synthesis of CPI and film preparation

[0120] Under nitrogen protection, 3,5'-difluoro-6,2'-bis(trifluoromethoxy)-4,4'-diaminobiphenyl (1.36g, 3.5mmol, Formula IV-4), 2,2'-bis(trifluoromethyl)diaminobiphenyl (2.08g, 6.5mmol, Formula VI-4), biphenyl dianhydride (1.03g, 3.5mmol, Formula V-3), hexafluorodianhydride (2.89g, 6.5mmol, Formula V-5), and N,N-dimethylformamide (DMF) (25mL) were placed in a 100mL three-necked flask. After being fully dissolved, the mixture was stirred at room temperature for 24 hours to obtain a viscous polyamic acid solution (intrinsic viscosity of 2.399dL / g). The solution was cast onto a glass plate to form a film. The temperature was gradually increased from 20-100-150-300℃ under vacuum, and then peeled off to obtain a CPI film material.

[0121]

[0122] The performance of the CPI films obtained in Examples 1 to 6 was tested, and the results are shown in Table 1. The intrinsic viscosity was measured using an Ubbelohde viscometer at 30°C, with a polymer (PAA or PI) concentration of 0.5 g / dL. The average value of three measurements was taken to reflect the molecular weight level of the polymer. The glass transition temperature (T g ) was measured by DMA, the characterization instrument was TA Q800, the heating rate was 3℃ / min, nitrogen atmosphere; 5wt% thermal decomposition temperature (T d5％ ) was measured by TGA using a TA Q50 instrument at a heating rate of 10°C / min in a nitrogen atmosphere. The optical transparency of the CPI film was measured by UV-Vis using a Shimadzu 3600Plus instrument in the range of 200-800nm. The yellowness (YI) and haze (Haze) were measured using a HunterLab film colorimeter using a D65 light source. The dielectric properties of the CPI film (dielectric constant D k , dielectric loss D f ) was measured by a vector network analyzer, the characterization instrument was Agilent N5244A, the frequency was 10 GHz, and the resonant cavity mode.

[0123] Table 1

[0124]

[0125] The above data show that the T g The value is 371~453℃, T d5％ The value is 568~592℃, CTE is 1.3~8.8ppm / K; at the same time, the optical transmittance T 550The value is 88.1% to 89.7%, and the yellow index YI value is 2.2 to 4.9; and in the mechanical properties, the σm value is 268 to 367 MPa, and the Et value is 5.7 to 7.2 GPa; In addition, the dielectric properties D k Value 2.70~2.98, D f Values: 0.0013~0.0042.

[0126] Figure 2 The UV-Vis curves of the CPI films prepared in Example 1 and Example 4 reflect their high optical transparency at a wavelength of 400-800 nm. Figure 3 DMA curves of the CPI films prepared in Examples 2 and 3. The peak value of tanδ reflects the high glass transition temperature Tg value. Figure 4 The TMA curves of the CPI films prepared in Examples 1 and 3 are shown. The slope of the curves reflects their ultra-low coefficient of thermal expansion (CTE) values. Figure 5 The high-frequency dielectric properties of the CPI films prepared in Examples 1-6 show that the low high-frequency dielectric constant D k and dielectric loss D f .

[0127] It can be seen from the above examples that the CPI film obtained based on the synthesis of high fluorine-containing aromatic diamine and the preparation method of high-performance polyimide provided by the present invention meets the requirements of high transparency (T 550 ≥88.1%, the highest is 89.7%, YI≤4.9), high heat resistance (Tg≥371℃, the highest is 453℃, T d5％ ≥568℃), low expansion (CTE≤8.8ppm / K, minimum 1.3ppm / K), high mechanical properties (σ m ≥268MPa, E t ≥5.7GPa), low dielectric (D k As low as 2.70, D f It has great application potential in key areas such as flexible display, wearable devices, thin-film batteries, and high-frequency signal substrates.

[0128] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing high-fluorine-containing biphenyl diamine, characterized in that: The steps include: (1) Under inert atmosphere, a halogenated fluorinated monobenzene undergoes an Ullmann coupling reaction in an aprotic polar solvent with a metal catalyst to obtain a fluorinated aromatic biphenyl, wherein the Ullmann coupling reaction is carried out before the nitration reaction, the reaction temperature is 120-180° C., and the metal catalyst is Cu or CuI; The halogenated fluorine-containing monobenzene is limited to one or more of the following structural formulas 1-1 to 1-6: Wherein, X is a halogen, limited to bromine or iodine; The fluorinated aromatic biphenyl is limited to one of the following structural formulas Ⅱ-1 to Ⅱ-6: (2) The fluorinated aromatic biphenyl in step (1) undergoes a nitration reaction in the presence of a nitrating agent to obtain a fluorinated biphenyl dinitro group, wherein the nitration system is a mixed system of nitric acid / sulfuric acid or nitric acid / acetic acid, and the nitration temperature is -10-80°C; The fluorinated biphenyl dinitro group is limited to one of the following structural formulas Ⅲ-1 to Ⅲ-6: (3) Under inert atmosphere, the fluorinated biphenyl dinitro group in step (2) is subjected to a reduction reaction to obtain the target high-fluorinated biphenyl diamine, wherein the reduction reaction adopts a Pd / C and hydrazine hydrate or SnCl2 and HCl system, and the reaction temperature is 50-150°C; The high fluorine-containing biphenyl diamine is limited to one of the following structural formulas IV-1 to IV-6, 2. The method for preparing high-fluorine-containing biphenyl diamine according to claim 1, wherein: The inert atmosphere in step (1) is one of nitrogen and argon; The aprotic polar solvent in step (1) includes one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), and 1,3-dimethyl-2-imidazolidinone (DMI); The temperature of the nitration reaction in step (2) is -80 to 150° C. The reduction reaction in step (3) is carried out in a Pd / C and N2H4·H2O system or a SnCl2 and HCl system, wherein the amount of Pd / C in the Pd / C and N2H4·H2O system is 1 to 15 wt% of the fluorinated biphenyl dinitro group, and the amount of N2H4·H2O is 2 to 8 times the amount of the fluorinated biphenyl dinitro group; In the SnCl2 and HCl system, the HCl content is 1 to 100 wt% of the fluorinated side biphenyl dinitro group, and the SnCl2 feed amount is 2 to 16 times the amount of the fluorinated side biphenyl dinitro group. The solvent for the reduction reaction in step (3) is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, ethanol, isopropanol, tetrahydrofuran, ethyl acetate, dioxane, toluene, benzene and water; The temperature of the reduction reaction in step (3) is 50-150° C.; The inert atmosphere in step (3) is one of nitrogen and argon.

3. A colorless polyimide optical film, characterized in that: The polyimide comprises a copolymer of highly fluorinated biphenyl diamine and commercial dianhydrides V-1 to V-10; the general structural formula of the polyimide is: Wherein, X Part is the residue of highly fluorinated biphenyl diamine; Ar1 ​​is independently the residue of a commercial dianhydride; Ar2 is the residue of a commercial diamine, n and m are the repeating numbers of the corresponding structural units, and the ratio of n:m ranges from 1:0 to 5:95; The high fluorine-containing biphenyl diamine is limited to one or more of the following structural formulas IV-1 to IV-6: The commercial dianhydride is defined as one or more of the following structural formulas V-1 to V-10: Wherein, R1 and R2 are independently selected from one or two of F and CF3; p and q are the number of R1 and R2 groups, p is 1 to 2, q is 1 to 4; R3 is independently selected from The commercial diamine is one or more of the following structural formulas VI-1 to VI-10: Wherein R1 and R2 are independently selected from one or two of F and CF3; p and q are the number of R1 and R2 groups, p is 1 to 2, q is 1 to 4; R3 is independently selected from The glass transition temperature Tg of the colorless polyimide optical film is 371-453°C, and the thermal weight loss temperature Tg corresponding to 5 wt% is 371-453°C. d5％ The value is 568-592°C, the thermal expansion coefficient CTE is 1.3-8.8 ppm / K; the optical transmittance T of the colorless polyimide optical film at 550nm is 550 The value is 88.1% to 89.7%, and the yellow index YI value is 2.2 to 4.9; the tensile strength σm value of the colorless polyimide optical film is 268 to 367 MPa, and the tensile modulus Et value is 5.7 to 7.2 GPa; the dielectric constant D of the colorless polyimide optical film at a high frequency of 10 GHz is k Value 2.70~2.98, dielectric loss D f Values: 0.0013~0.0042.

4. The method for preparing a colorless polyimide optical film according to claim 3, characterized in that: The steps include: (a) homopolymerizing / copolymerizing the high-fluorine-containing biphenyl diamine prepared by the method for preparing the high-fluorine-containing biphenyl diamine according to any one of claims 1 to 2 with commercial dianhydride and commercial diamine to obtain a polyimide (or polyamic acid precursor) solution; (b) The polyimide (or polyamic acid precursor) solution in step (a) is subjected to a film-forming process to obtain a colorless polyimide optical film.

5. The method for preparing a colorless polyimide optical film according to claim 4, characterized in that: The ratio of the sum of the amounts of the high-fluorine-containing biphenyl diamine and the commercial diamine to the amount of the commercial dianhydride in step (a) is 1:(0.9-1.1); The homopolymerization / copolymerization reaction in step (a) is carried out in a one-step or two-step process. The one-step method comprises the following steps: under the protection of an inert atmosphere, polycondensing high-fluorinated biphenyl diamine with commercial dianhydride and commercial diamine at high temperature in a high-boiling-point solvent with or without a catalyst, to obtain a uniform and viscous polyimide solution; the catalyst is one or both of benzoic acid and isoquinoline; the high-boiling-point solvent is one or more of m-cresol, p-chlorophenol, and m-chlorophenol; the reaction temperature is 150-200° C.; the reaction time is 5-36 hours; and the inert atmosphere is one of nitrogen and argon. The two-step method involves low-temperature polycondensation of high-fluorine-containing benzyl diamine with commercial dianhydride and commercial diamine in an aprotic polar solvent to produce a uniform and viscous polyamic acid solution. The aprotic polar solvent is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and N-methylpyrrolidone (NMP). The reaction temperature is -10 to 50° C., the reaction time is 10 to 120 hours, and the inert atmosphere is one of nitrogen and argon. The film-making process in step (b) includes casting and heat treatment, The casting process includes one or more of direct casting film forming, precision slit coating film forming, casting and stretching continuous film forming; The heat treatment process includes a desolvation process and an imidization process. The heating method is continuous heating and gradient heating. The temperature range is 20 to 450° C. The high-temperature atmosphere is one of nitrogen, argon and vacuum.

6. A flexible display, characterized in that: The invention comprises a colorless polyimide optical film as described in any one of claims 3-4.

7. A wearable device, characterized in that: The invention comprises a colorless polyimide optical film as described in any one of claims 3-4.

8. A flexible battery, characterized in that: The invention comprises a colorless polyimide optical film as described in any one of claims 3-4.

9. A 5G high-frequency communication device, characterized in that: The invention comprises a colorless polyimide optical film as described in any one of claims 3-4.

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