Preparation method of low-dielectric fluorinated graphene composite film

Abstract

The invention provides a preparation method of a low-dielectric fluorinated graphene composite film, and aims to develop a low-dielectric interlayer dielectric material suitable for a flexible printed circuit board (FPCB). Compared with a traditional SiO2 film, the composite film has the advantages that the dielectric constant is extremely low, interconnection resistance / capacitance (RC) delay and power dissipation of the polymer substrate are reduced, meanwhile, the dielectric stability and environmental weather resistance are good, and the service life of the composite film in a high-temperature environment is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of dielectric materials, and particularly to a method for preparing a low-dielectric fluorinated graphene composite film. Background Art

[0002] With the development of 5G communication and ultra-large scale integrated circuits (ULSIs), the size of optoelectronic devices in ULSI circuits is continuously shrinking. Due to their large rigidity and high dielectric constant, traditional inorganic materials are no longer applicable in some optoelectronic fields. Therefore, low-dielectric flexible materials have gradually attracted people's attention. Low-dielectric materials have important application prospects in fields such as interlayer dielectrics (transistor devices, etc.), semiconductor packaging (chip modules, etc.), and high-frequency low-loss polymer substrates. Low-dielectric interlayer dielectrics can reduce interconnect resistance / capacitance (RC) delay, signal crosstalk, and power loss, etc., and play an irreplaceable role in military radars, aerospace vehicles, and high-frequency communication fields.

[0003] Traditional silica-based low-dielectric materials cannot meet the demands of higher frequencies, seriously affecting the frequency stability of 5G communication and the signal transmission quality. Chen et al. prepared porous composite films by the bubble stretching method, introducing polyethylene glycol as a foaming agent into the system. The dielectric constant was reduced to as low as 2.29. However, the introduction of pores increases the water absorption rate, affects the frequency stability, and reduces the service life.

Chen, Z.G., et al., Overall improvement in dielectric and mechanical properties of porous graphene fluoroxide / polyimide nanocomposite films via bubble-stretching approach. Materials & Design, 2017.117: p.150-156.

Kumar, R.S. and M. Alagar, Dielectric and thermal behaviors of POSS reinforced polyurethane based polybenzoxazine nanocomposites. Rsc Advances, 2015.5(42): p.33008-33015.

[0004] In view of the above problems, the object of the present invention is to provide a method for preparing a low-dielectric graphene fluoride composite film. To achieve the above object, the technical solution adopted by the present invention is: using graphene as a raw material, F 2 / N 2 mixed gas as a fluorinating agent, and preparing graphene fluoride by the direct gas fluorination method; using graphene fluoride as a filler to prepare a series of graphene fluoride / fluorinated polyimide composite films.

[0005] In the first aspect, the object of the present invention is to provide a method for preparing a low-dielectric graphene fluoride composite film, which is specifically prepared according to the following steps:

[0006] Step 1: Place a certain amount of graphene in a fluorination reactor, evacuate the air, heat to a set temperature, and then introduce a certain volume fraction of F 2 / N 2 mixed gas to react for a period of time to obtain a fluorinated graphene product.

[0007] Step 2: Take a certain amount of the fluorinated graphene product obtained in Step 1, add a solvent and ultrasonicate for a period of time, then add a diamine monomer, and add a dianhydride monomer in batches while mechanically stirring, and carry out in-situ polymerization for a period of time to obtain a polyamic acid solution.

[0008] Step 3: Coating the polyamic acid solution described in Step 2 on glass by a film-forming process, then transferring it to an oven, heating at a set temperature for a period of time to remove the excess solvent, and then putting the glass plate into a muffle furnace for temperature-raising treatment to obtain a fluorinated graphene / fluorinated polyimide composite film.

[0009] The present invention prepares a composite film with fluorinated graphene having different fluorocarbon ratios as an inorganic filler, with simple operation and convenient for industrial preparation. In addition, the fluorinated graphene filler prepared by the present invention does not require additional chemical modification treatment, has a high yield, and significant economic benefits. In particular, excellent dielectric properties can be obtained with a small addition amount of fluorinated graphene, and the excellent stability and weather resistance meet the requirements of high-frequency and high-speed communication.

[0010] Preferably, the graphene raw material described in Step 1 can be monolayer graphene, graphene oxide, reduced graphene oxide, sponge graphite or other modified graphite, preferably monolayer graphene.

[0011] Preferably, the amount of graphene described in Step 1 is 100-500 mg, for example, it can be 100 mg, 300 mg, 450 mg or 500 mg, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0012] Preferably, the fluorinating agent described in Step 1 is F 2 F with a volume fraction of 10%-50% 2 / N 2 mixed gas, which can be 10%, 20%, 30%, 40% or 50%, preferably 30% F 2 / N 2 mixed gas.

[0013] Preferably, the flow rate of the mixed gas described in Step 1 is 1-5 m 3 / min, for example, it can be 1 m 3 / min, 2 m 3 / min, 3 m 3 / min or 5 m 3 / min, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0014] Preferably, the set temperature in Step 1 is 100°C to 400°C. For example, it can be 100°C, 200°C, 300°C, 400°C, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0015] Preferably, the reaction time in Step 1 is 2 to 6 h. For example, it can be 2 h, 4 h or 6 h, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0016] Preferably, the fluorine-carbon ratio of the graphene fluoride product in Step 1 is 0.8 to 1.4. For example, it can be 0.9, 1.0, 1.2 or 1.4, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0017] Preferably, the addition amount of the graphene fluoride product in Step 2 is 0.5 wt% to 3 wt%. For example, it can be 0.5 wt%, 0.75 wt%, 1.0 wt%, 2.0 wt% or 3.0 wt%, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] Preferably, the solvent in Step 2 can be N-methylpyrrolidone, dimethylacetamide, N,N-dimethylformamide, propionitrile, acetamide, and preferably N-methylpyrrolidone.

[0019] Preferably, the ultrasonic time in Step 2 is 30 to 60 min. For example, it can be 30 min, 40 min or 60 min, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0020] Preferably, the diamine monomers in Step 2 include 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, and preferably 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane.

[0021] Preferably, the dianhydride monomers in Step 2 include benzophenone-3,3,4,4-tetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, hexafluorodiacid dianhydride, and preferably hexafluorodiacid dianhydride.

[0022] Preferably, the in-situ polymerization time in Step 2 is 4 to 12 h. For example, it can be 4 h, 8 h or 12 h, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0023] Preferably, the film-forming process described in Step 3 can be a spin coating film-forming process, a casting film-forming process, a blade coating process or a hot pressing film-forming process, preferably a spin coating film-forming process.

[0024] Preferably, the set temperature described in Step 3 is 60-100 °C. For example, it can be 60 °C, 70 °C, 80 °C or 100 °C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0025] Preferably, the heating time described in Step 3 is 2-5 h. For example, it can be 2 h, 3 h or 5 h, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0026] Preferably, the temperature-raising treatment described in Step 3 can be heating at 100 °C, 150 °C, 200 °C, 250 °C, 300 °C for 1 h or 2 h respectively, or heating at 100 °C, 200 °C, 300 °C for 1.5 h or 2 h respectively, preferably heating at 100 °C, 150 °C, 200 °C, 250 °C, 300 °C for 1 h respectively.

[0027] As a preferred technical solution of the preparation method described in the first aspect of the present invention, the preparation method includes:

[0028] Step 1: Using graphene as the raw material, take 100-500 mg and place it in a fluorination reactor. Evacuate the air in the cavity, heat to 100-400 °C, and introduce F 2 F with a volume fraction of 10-50% 2 / N 2 mixed gas for reaction for 2-6 h to obtain a fluorinated product with a fluorine-carbon ratio of 0.8-1.4.

[0029] Step 2: Take 0.5 wt%-3 wt% of the fluorinated product described in Step 1, add a solvent and ultrasonicate for 30-60 min, and then add diamine monomers such as 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether or 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene. While mechanically stirring, add dianhydride monomers such as 3,3,4,4-benzophenonetetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, pyromellitic dianhydride or hexafluorodiacid dianhydride in batches, and carry out a polymerization reaction for 4-12 h to obtain a polyamic acid solution.

[0030] Step 3: Spin coat, cast or blade coat the polyamic acid solution described in Step 2 on glass, then place it in an oven at 60-100 °C and dry for 2-5 h, and then transfer it to a muffle furnace and heat at 100 °C, 150 °C, 200 °C, 250 °C, 300 °C for 1 h or 2 h respectively to obtain a series of fluorinated graphene composite films.

[0031] In a second aspect, the present invention provides a low-dielectric fluorinated graphene composite film, and the low-dielectric fluorinated graphene composite film is obtained by using the preparation method described in the first aspect.

[0032] Preferably, the thickness of the low-dielectric fluorinated graphene composite film is 40 μm, and the dielectric constant is (2.18 @ 10 MHz).

[0033] Preferably, the low-dielectric fluorinated graphene composite film is applicable to the interlayer dielectric of a flexible printed circuit board.

[0034] Preferably, the low-dielectric fluorinated graphene composite film has advantages such as good thermal stability, relatively high hydrophobicity, and high tensile strength.

[0035] The numerical ranges described in the present invention not only include the point values exemplified above, but also include any point values between the above numerical ranges not exemplified. Due to space limitations and for the sake of brevity, the specific point values included in the ranges of the present invention are not exhaustively exemplified herein.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] 1. The composite film prepared by the present invention has an extremely low dielectric constant, which can well reduce the signal transmission delay time and is of great significance for high-frequency and high-speed communication.

[0038] 2. The composite film prepared by the present invention has good thermal stability and dimensional stability, which helps to reduce deformation in a later higher-temperature environment and improve the service life.

[0039] 3. The composite film prepared by the present invention has good mechanical strength and relatively high hydrophobic properties, which helps to improve durability and increase the reliability of the device. Description of the Drawings

[0040] Figure 1 are SEM images of different fluorinated graphene / fluorinated polyimide composite films;

[0041] Figure 2 are Fourier transform infrared spectra of different fluorinated graphene / fluorinated polyimide composite films;

[0042] Figure 3 are graphs showing the variation of the dielectric constant of different fluorinated graphene / fluorinated polyimide composite films with frequency; Explanation of the reference numerals in the drawings:

[0043] Among them, FG1-PI: the fluorination temperature of fluorinated graphene is 100 °C, and the addition amount is 0.5 wt%;

[0044] FG2-PI: the fluorination temperature of fluorinated graphene is 140 °C, and the addition amount is 0.5 wt%;

[0045] FG3-PI: The fluorination temperature of graphene fluoride is 180 °C and the addition amount is 0.5 wt%.

[0046] FG4-PI: The fluorination temperature of graphene fluoride is 220 °C and the addition amount is 0.5 wt%.

[0047] PI: No doping treatment. Detailed implementation manners

[0048] The present invention will be described in detail below with reference to the drawings and embodiments:

[0049] Example 1

[0050] Step 1: Take 200 mg of graphene and put it into a fluorination reactor. Evacuate the air in the cavity, slowly heat it to 100 °C, and introduce F 2 F with a volume fraction of 30% 2 / N 2 mixed gas, and carry out fluorination reaction for 4 h. After the reaction is completed, turn off the heating device to obtain a fluorinated product with a fluorine-carbon ratio of 0.93.

[0051] Step 2: Take 0.5 wt% of the fluorinated product obtained in Step 1, add a solvent and ultrasonicate for 30 min, then add 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and add hexafluorodiacid anhydride in batches while mechanically stirring, and carry out polymerization reaction for 6 h to obtain a polyamic acid solution.

[0052] Step 3: Spin-coat the polyamic acid solution obtained in Step 2 into a film, coat it on glass, then put it into an oven at 80 °C and dry it for 2 h, and then transfer it to a muffle furnace and heat it at 100 °C, 150 °C, 200 °C, 250 °C, and 300 °C for 1 h respectively to obtain a series of graphene fluoride composite films.

[0053] As shown in the attached Figure 1 figure, after adding graphene fluoride, the cross-section still remains smooth and complete, indicating that graphene fluoride is well dispersed in the matrix when the doping amount is 0.5 wt%.

[0054] As shown in the attached Figure 2 figure, the absorption peaks near 718 cm -1 and 1375 cm -1 correspond to C=O bending and C-N stretching respectively, and the peaks near 1720 cm -1 and 1784 cm -1 can be attributed to C=O stretching vibration and asymmetric stretching. The FTIR results prove the successful synthesis of graphene fluoride / fluorinated polyimide composite films.

[0055] As shown in the attached Figure 3As shown, the dielectric constant of the fluorinated graphene composite film decreases significantly, and it has good frequency stability of the dielectric constant. The intrinsic dielectric constant of fluorinated graphene is about 1.3. The C-F bond has a low polarizability, and the nanosheets have a large surface area and can be well dispersed in the matrix. The interaction between the two hinders the movement of the polyimide molecular chains, increases the free volume, reduces the dipole density, and results in a lower dielectric constant.

[0056] Example 2

[0057] Step 1: Take 200 mg of graphene and put it into a fluorination reaction kettle. Evacuate the air in the cavity, slowly heat it to 100 °C, and introduce F 2 F with a volume fraction of 30% 2 / N 2 mixed gas, carry out fluorination reaction for 4 h. After the reaction is completed, turn off the heating device to obtain a fluorinated product with a fluorine-carbon ratio of 1.17.

[0058] Step 2: Take 0.5 wt% of the fluorinated product obtained in Step 1, add a solvent and ultrasonicate for 30 min. Then add 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and add hexafluorodiacid in batches while mechanically stirring. Carry out polymerization reaction for 6 h to obtain a polyamic acid solution.

[0059] Step 3: Spin-coat the polyamic acid solution obtained in Step 2 into a film, coat it on glass, then put it into an oven at 80 °C and dry for 2 h. Then transfer it to a muffle furnace and heat it at 100 °C, 150 °C, 200 °C, 250 °C, and 300 °C for 1 h respectively to obtain a series of fluorinated graphene composite films.

[0060] As shown in the appendix Figure 1 As shown, after adding fluorinated graphene, the cross-section still remains smooth and complete, indicating that fluorinated graphene is well dispersed in the matrix when the doping amount is 0.5 wt%.

[0061] As shown in the appendix Figure 2 As shown, the absorption peaks near 718 cm -1 and 1375 cm -1 correspond to C=O bending and C-N stretching respectively. The peaks near 1720 cm -1 and 1784 cm -1 can be attributed to C=O stretching vibration and asymmetric stretching. The FTIR results prove the successful synthesis of the fluorinated graphene / fluorinated polyimide composite film.

[0062] As shown in the appendix Figure 3As shown, the dielectric constant of the fluorinated graphene composite film decreases significantly, and it has good frequency stability of the dielectric constant. The intrinsic dielectric constant of fluorinated graphene is about 1.3. The C-F bond has a low polarizability, and the nanosheets have a large surface area and can be well dispersed in the matrix. The interaction between the two hinders the movement of the polyimide molecular chains, increases the free volume, reduces the dipole density, and results in a lower dielectric constant.

[0063] Example 3

[0064] Step 1: Take 200 mg of graphene and put it into a fluorination reactor. Evacuate the air in the cavity, slowly heat it to 100 °C, and introduce F 2 F with a volume fraction of 30% 2 / N 2 mixed gas, carry out fluorination reaction for 4 h. After the reaction is completed, turn off the heating device to obtain a fluorinated product with a fluorine-carbon ratio of 1.32.

[0065] Step 2: Take 0.5 wt% of the fluorinated product obtained in Step 1, add a solvent and ultrasonicate for 30 min, then add 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and add hexafluorodiacid in batches while mechanically stirring. Carry out polymerization reaction for 6 h to obtain a polyamic acid solution.

[0066] Step 3: Spin-coat the polyamic acid solution obtained in Step 2 into a film, coat it on glass, then put it into an oven at 80 °C and dry for 2 h, and then transfer it to a muffle furnace and heat it at 100 °C, 150 °C, 200 °C, 250 °C, and 300 °C for 1 h respectively to obtain a series of fluorinated graphene composite films.

[0067] As shown in the appendix Figure 1 As shown, after adding fluorinated graphene, the cross-section still remains smooth and complete, indicating that fluorinated graphene is well dispersed in the matrix when the doping amount is 0.5 wt%.

[0068] As shown in the appendix Figure 2 As shown, the absorption peaks near 718 cm -1 and 1375 cm -1 correspond to C=O bending and C-N stretching respectively. The peaks near 1720 cm -1 and 1784 cm -1 can be attributed to C=O stretching vibration and asymmetric stretching. The FTIR results prove the successful synthesis of the fluorinated graphene / fluorinated polyimide composite film.

[0069] As shown in the appendix Figure 3As shown, the dielectric constant of the fluorinated graphene composite film decreases significantly and has good frequency stability of the dielectric constant. The intrinsic dielectric constant of fluorinated graphene is about 1.3. The polarizability of the C-F bond is low, and the nanosheets have a large surface area and can be well dispersed in the matrix. The interaction between the two hinders the movement of the polyimide molecular chains, increases the free volume, reduces the dipole density, and results in a lower dielectric constant.

[0070] Example 4

[0071] Step 1: Take 200 mg of graphene and put it into a fluorination reaction kettle. Evacuate the air in the cavity, slowly heat it to 100 °C, and introduce F 2 F with a volume fraction of 30% 2 / N 2 mixed gas, carry out fluorination reaction for 4 h. After the reaction is completed, turn off the heating device to obtain a fluorinated product with a fluorine-carbon ratio of 1.19.

[0072] Step 2: Take 0.5 wt% of the fluorinated product obtained in Step 1, add a solvent and ultrasonicate for 30 min, then add 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and add hexafluorodiacid anhydride in batches while mechanically stirring. Carry out a polymerization reaction for 6 h to obtain a polyamic acid solution.

[0073] Step 3: Spin-coat the polyamic acid solution obtained in Step 2 into a film, coat it on glass, then put it into an oven at 80 °C and dry for 2 h, and then transfer it to a muffle furnace and heat it at 100 °C, 150 °C, 200 °C, 250 °C, and 300 °C for 1 h respectively to obtain a series of fluorinated graphene composite films.

[0074] As shown in the appendix Figure 1 As shown, after adding fluorinated graphene, the cross-section still remains smooth and complete, indicating that fluorinated graphene is well dispersed in the matrix when the doping amount is 0.5 wt%.

[0075] As shown in the appendix Figure 2 As shown, the absorption peaks near 718 cm -1 and 1375 cm -1 correspond to C=O bending and C-N stretching respectively. The peaks near 1720 cm -1 and 1784 cm -1 can be attributed to C=O stretching vibration and asymmetric stretching. The FTIR results prove the successful synthesis of the fluorinated graphene / fluorinated polyimide composite film.

[0076] As shown in the appendix Figure 3As shown, the dielectric constant of the fluorinated graphene composite film decreases significantly and has good dielectric constant frequency stability. The intrinsic dielectric constant of fluorinated graphene is about 1.3. The C-F bond has a low polarizability, and the nanosheets have a large surface area and can be well dispersed in the matrix. The interaction between the two hinders the movement of the polyimide molecular chains, increases the free volume, reduces the dipole density, and results in a lower dielectric constant.

[0077] Example 5

[0078] Preparation of a fluorinated polyimide film without doping treatment under the same experimental process.

[0079] Step 1: Add 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and add hexafluorodiacid anhydride in batches while mechanically stirring. Polymerize for 6 h to obtain a polyamic acid solution.

[0080] Step 2: Spin-coat the polyamic acid solution obtained in Step 2 into a film, coat it on glass, then place it in an oven at 80 °C and dry for 2 h, and then transfer it to a muffle furnace and heat it at 100 °C, 150 °C, 200 °C, 250 °C, and 300 °C for 1 h respectively to obtain a fluorinated polyimide film.

[0081] As shown in the appendix Figure 1 As shown, the cross-section of the fluorinated polyimide film without doping treatment is smooth and complete, and has a specific orientation due to the amorphous nature of the polyimide.

[0082] As shown in the appendix Figure 2 As shown, the absorption peaks near 718 cm -1 and 1375 cm -1 correspond to C=O bending and C-N stretching respectively. The peaks near 1720 cm -1 and 1784 cm -1 can be attributed to the stretching vibration of C=O and asymmetric stretching. The FTIR results prove the successful synthesis of the fluorinated polyimide composite film.

[0083] As shown in the appendix Figure 3 As shown, the intrinsic dielectric constant of the fluorinated polyimide is about 3.19@10 MHz and has good dielectric constant frequency stability. The low polarizability of the C-F bond and the increased free volume caused by the large side groups result in a lower dielectric constant.

Claims

1. A method for preparing a low dielectric fluorinated graphene composite film, characterized in that: The preparation method is prepared according to the following steps: Step 1: Place a certain amount of graphene in a fluorination reactor, evacuate the air, heat to a set temperature, and then introduce a certain volume fraction of F2 / N2 mixed gas to react for a period of time to obtain a fluorinated graphene product. Step 2: Take a certain amount of the fluorinated graphene product described in step 1, add a solvent and perform ultrasound for a period of time, then add a diamine monomer, add a dianhydride monomer in portions while mechanically stirring, and perform in-situ polymerization for a period of time to obtain a polyamic acid solution. Step 3: The polyamic acid solution in step 2 is coated on the glass using a film-forming process, and then transferred to an oven, heated at a set temperature for a period of time to remove excess solvent, and then the glass plate is placed in a muffle furnace for heating treatment to obtain a fluorinated graphene / fluorinated polyimide composite film.

2. The preparation method according to claim 1, characterized in that: The graphene raw material described in step 1 can be single-layer graphene, graphene oxide, reduced graphene oxide, sponge graphite or other modified graphite, preferably single-layer graphene. Preferably, the amount of graphene in step 1 is 100-500 mg, for example, 100 mg, 300 mg, 450 mg or 500 mg, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

3. The preparation method according to claim 1-2, characterized in that: The fluorinating agent described in step 1 is a F2 / N2 mixed gas with an F2 volume fraction of 10% to 50%, which can be 10%, 20%, 30%, 40% or 50%, preferably a 30% F2 / N2 mixed gas. Preferably, the flow rate of the mixed gas in step 1 is 1 to 5 m 3 / min, for example, 1m 3 / min,2m 3 / min,3m 3 / min or 5m 3 / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

4. The preparation method according to claims 1-3, characterized in that: The set temperature in step 1 is 100°C to 400°C, for example, it can be 100°C, 200°C, 300°C, 400°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. Preferably, the reaction time in step 1 is 2 to 6 hours, for example, 2 hours, 4 hours or 6 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. Preferably, the fluorine-carbon ratio of the fluorinated graphene product in step 1 is 0.8 to 1.4, for example, 0.9, 1.0, 1.2 or 1.4, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

5. The preparation method according to claims 1-4, characterized in that: The addition amount of the fluorinated graphene product described in step 2 is 0.5wt% to 3wt%, for example, it can be 0.5wt%, 0.75wt%, 1.0wt%, 2.0wt% or 3.0wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

6. The preparation method according to claims 1-5, characterized in that: The solvent in step 2 can be N-methylpyrrolidone, dimethylacetamide, N,N-dimethylformamide, propionitrile, acetamide, preferably N-methylpyrrolidone. Preferably, the ultrasonic time in step 2 is 30 to 60 minutes, for example, 30 minutes, 40 minutes or 60 minutes, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. Preferably, the diamine monomer described in step 2 includes 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, preferably 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. Preferably, the dianhydride monomer in step 2 includes 3,3,4,4-dibenzophenonetetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, pyromellitic anhydride, hexafluoro dianhydride, preferably hexafluoro dianhydride. Preferably, the in-situ polymerization time in step 2 is 4 to 12 hours, for example, 4 hours, 8 hours or 12 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

7. The preparation method according to claims 1-6, characterized in that: The film forming process described in step three can be a spin coating film forming process, a cast film forming process, a scraping film forming process or a hot pressing film forming process, preferably a spin coating film forming process.

8. The preparation method according to claims 1-7, characterized in that: The set temperature in step three is 60-100° C., for example, 60° C., 70° C., 80° C. or 100° C., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. Preferably, the heating time in step three is 2 to 5 hours, for example, 2 hours, 3 hours or 5 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. Preferably, the temperature treatment in step three can be 100°C, 150°C, 200°C, 250°C, 300°C for 1h or 2h respectively, or 100°C, 200°C, 300°C for 1.5h or 2h respectively, preferably 100°C, 150°C, 200°C, 250°C, 300°C for 1h respectively.

Images